linux-stable/fs/super.c

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/*
* linux/fs/super.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* super.c contains code to handle: - mount structures
* - super-block tables
* - filesystem drivers list
* - mount system call
* - umount system call
* - ustat system call
*
* GK 2/5/95 - Changed to support mounting the root fs via NFS
*
* Added kerneld support: Jacques Gelinas and Bjorn Ekwall
* Added change_root: Werner Almesberger & Hans Lermen, Feb '96
* Added options to /proc/mounts:
* Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
* Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
* Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
*/
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/writeback.h> /* for the emergency remount stuff */
#include <linux/idr.h>
#include <linux/mutex.h>
#include <linux/backing-dev.h>
#include <linux/rculist_bl.h>
#include <linux/cleancache.h>
#include <linux/fsnotify.h>
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
#include <linux/lockdep.h>
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
#include <linux/user_namespace.h>
#include "internal.h"
static LIST_HEAD(super_blocks);
static DEFINE_SPINLOCK(sb_lock);
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
static char *sb_writers_name[SB_FREEZE_LEVELS] = {
"sb_writers",
"sb_pagefaults",
"sb_internal",
};
/*
* One thing we have to be careful of with a per-sb shrinker is that we don't
* drop the last active reference to the superblock from within the shrinker.
* If that happens we could trigger unregistering the shrinker from within the
* shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
* take a passive reference to the superblock to avoid this from occurring.
*/
shrinker: convert superblock shrinkers to new API Convert superblock shrinker to use the new count/scan API, and propagate the API changes through to the filesystem callouts. The filesystem callouts already use a count/scan API, so it's just changing counters to longs to match the VM API. This requires the dentry and inode shrinker callouts to be converted to the count/scan API. This is mainly a mechanical change. [glommer@openvz.org: use mult_frac for fractional proportions, build fixes] Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Glauber Costa <glommer@openvz.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:17:57 +00:00
static unsigned long super_cache_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
struct super_block *sb;
shrinker: convert superblock shrinkers to new API Convert superblock shrinker to use the new count/scan API, and propagate the API changes through to the filesystem callouts. The filesystem callouts already use a count/scan API, so it's just changing counters to longs to match the VM API. This requires the dentry and inode shrinker callouts to be converted to the count/scan API. This is mainly a mechanical change. [glommer@openvz.org: use mult_frac for fractional proportions, build fixes] Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Glauber Costa <glommer@openvz.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:17:57 +00:00
long fs_objects = 0;
long total_objects;
long freed = 0;
long dentries;
long inodes;
sb = container_of(shrink, struct super_block, s_shrink);
/*
* Deadlock avoidance. We may hold various FS locks, and we don't want
* to recurse into the FS that called us in clear_inode() and friends..
*/
shrinker: convert superblock shrinkers to new API Convert superblock shrinker to use the new count/scan API, and propagate the API changes through to the filesystem callouts. The filesystem callouts already use a count/scan API, so it's just changing counters to longs to match the VM API. This requires the dentry and inode shrinker callouts to be converted to the count/scan API. This is mainly a mechanical change. [glommer@openvz.org: use mult_frac for fractional proportions, build fixes] Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Glauber Costa <glommer@openvz.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:17:57 +00:00
if (!(sc->gfp_mask & __GFP_FS))
return SHRINK_STOP;
if (!trylock_super(sb))
shrinker: convert superblock shrinkers to new API Convert superblock shrinker to use the new count/scan API, and propagate the API changes through to the filesystem callouts. The filesystem callouts already use a count/scan API, so it's just changing counters to longs to match the VM API. This requires the dentry and inode shrinker callouts to be converted to the count/scan API. This is mainly a mechanical change. [glommer@openvz.org: use mult_frac for fractional proportions, build fixes] Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Glauber Costa <glommer@openvz.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:17:57 +00:00
return SHRINK_STOP;
if (sb->s_op->nr_cached_objects)
fs_objects = sb->s_op->nr_cached_objects(sb, sc);
list_lru: introduce list_lru_shrink_{count,walk} Kmem accounting of memcg is unusable now, because it lacks slab shrinker support. That means when we hit the limit we will get ENOMEM w/o any chance to recover. What we should do then is to call shrink_slab, which would reclaim old inode/dentry caches from this cgroup. This is what this patch set is intended to do. Basically, it does two things. First, it introduces the notion of per-memcg slab shrinker. A shrinker that wants to reclaim objects per cgroup should mark itself as SHRINKER_MEMCG_AWARE. Then it will be passed the memory cgroup to scan from in shrink_control->memcg. For such shrinkers shrink_slab iterates over the whole cgroup subtree under the target cgroup and calls the shrinker for each kmem-active memory cgroup. Secondly, this patch set makes the list_lru structure per-memcg. It's done transparently to list_lru users - everything they have to do is to tell list_lru_init that they want memcg-aware list_lru. Then the list_lru will automatically distribute objects among per-memcg lists basing on which cgroup the object is accounted to. This way to make FS shrinkers (icache, dcache) memcg-aware we only need to make them use memcg-aware list_lru, and this is what this patch set does. As before, this patch set only enables per-memcg kmem reclaim when the pressure goes from memory.limit, not from memory.kmem.limit. Handling memory.kmem.limit is going to be tricky due to GFP_NOFS allocations, and it is still unclear whether we will have this knob in the unified hierarchy. This patch (of 9): NUMA aware slab shrinkers use the list_lru structure to distribute objects coming from different NUMA nodes to different lists. Whenever such a shrinker needs to count or scan objects from a particular node, it issues commands like this: count = list_lru_count_node(lru, sc->nid); freed = list_lru_walk_node(lru, sc->nid, isolate_func, isolate_arg, &sc->nr_to_scan); where sc is an instance of the shrink_control structure passed to it from vmscan. To simplify this, let's add special list_lru functions to be used by shrinkers, list_lru_shrink_count() and list_lru_shrink_walk(), which consolidate the nid and nr_to_scan arguments in the shrink_control structure. This will also allow us to avoid patching shrinkers that use list_lru when we make shrink_slab() per-memcg - all we will have to do is extend the shrink_control structure to include the target memcg and make list_lru_shrink_{count,walk} handle this appropriately. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Suggested-by: Dave Chinner <david@fromorbit.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Glauber Costa <glommer@gmail.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-12 22:58:47 +00:00
inodes = list_lru_shrink_count(&sb->s_inode_lru, sc);
dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc);
total_objects = dentries + inodes + fs_objects + 1;
if (!total_objects)
total_objects = 1;
shrinker: convert superblock shrinkers to new API Convert superblock shrinker to use the new count/scan API, and propagate the API changes through to the filesystem callouts. The filesystem callouts already use a count/scan API, so it's just changing counters to longs to match the VM API. This requires the dentry and inode shrinker callouts to be converted to the count/scan API. This is mainly a mechanical change. [glommer@openvz.org: use mult_frac for fractional proportions, build fixes] Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Glauber Costa <glommer@openvz.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:17:57 +00:00
/* proportion the scan between the caches */
dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);
inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);
list_lru: introduce list_lru_shrink_{count,walk} Kmem accounting of memcg is unusable now, because it lacks slab shrinker support. That means when we hit the limit we will get ENOMEM w/o any chance to recover. What we should do then is to call shrink_slab, which would reclaim old inode/dentry caches from this cgroup. This is what this patch set is intended to do. Basically, it does two things. First, it introduces the notion of per-memcg slab shrinker. A shrinker that wants to reclaim objects per cgroup should mark itself as SHRINKER_MEMCG_AWARE. Then it will be passed the memory cgroup to scan from in shrink_control->memcg. For such shrinkers shrink_slab iterates over the whole cgroup subtree under the target cgroup and calls the shrinker for each kmem-active memory cgroup. Secondly, this patch set makes the list_lru structure per-memcg. It's done transparently to list_lru users - everything they have to do is to tell list_lru_init that they want memcg-aware list_lru. Then the list_lru will automatically distribute objects among per-memcg lists basing on which cgroup the object is accounted to. This way to make FS shrinkers (icache, dcache) memcg-aware we only need to make them use memcg-aware list_lru, and this is what this patch set does. As before, this patch set only enables per-memcg kmem reclaim when the pressure goes from memory.limit, not from memory.kmem.limit. Handling memory.kmem.limit is going to be tricky due to GFP_NOFS allocations, and it is still unclear whether we will have this knob in the unified hierarchy. This patch (of 9): NUMA aware slab shrinkers use the list_lru structure to distribute objects coming from different NUMA nodes to different lists. Whenever such a shrinker needs to count or scan objects from a particular node, it issues commands like this: count = list_lru_count_node(lru, sc->nid); freed = list_lru_walk_node(lru, sc->nid, isolate_func, isolate_arg, &sc->nr_to_scan); where sc is an instance of the shrink_control structure passed to it from vmscan. To simplify this, let's add special list_lru functions to be used by shrinkers, list_lru_shrink_count() and list_lru_shrink_walk(), which consolidate the nid and nr_to_scan arguments in the shrink_control structure. This will also allow us to avoid patching shrinkers that use list_lru when we make shrink_slab() per-memcg - all we will have to do is extend the shrink_control structure to include the target memcg and make list_lru_shrink_{count,walk} handle this appropriately. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Suggested-by: Dave Chinner <david@fromorbit.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Glauber Costa <glommer@gmail.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-12 22:58:47 +00:00
fs_objects = mult_frac(sc->nr_to_scan, fs_objects, total_objects);
shrinker: convert superblock shrinkers to new API Convert superblock shrinker to use the new count/scan API, and propagate the API changes through to the filesystem callouts. The filesystem callouts already use a count/scan API, so it's just changing counters to longs to match the VM API. This requires the dentry and inode shrinker callouts to be converted to the count/scan API. This is mainly a mechanical change. [glommer@openvz.org: use mult_frac for fractional proportions, build fixes] Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Glauber Costa <glommer@openvz.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:17:57 +00:00
/*
* prune the dcache first as the icache is pinned by it, then
* prune the icache, followed by the filesystem specific caches
*
* Ensure that we always scan at least one object - memcg kmem
* accounting uses this to fully empty the caches.
shrinker: convert superblock shrinkers to new API Convert superblock shrinker to use the new count/scan API, and propagate the API changes through to the filesystem callouts. The filesystem callouts already use a count/scan API, so it's just changing counters to longs to match the VM API. This requires the dentry and inode shrinker callouts to be converted to the count/scan API. This is mainly a mechanical change. [glommer@openvz.org: use mult_frac for fractional proportions, build fixes] Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Glauber Costa <glommer@openvz.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:17:57 +00:00
*/
sc->nr_to_scan = dentries + 1;
list_lru: introduce list_lru_shrink_{count,walk} Kmem accounting of memcg is unusable now, because it lacks slab shrinker support. That means when we hit the limit we will get ENOMEM w/o any chance to recover. What we should do then is to call shrink_slab, which would reclaim old inode/dentry caches from this cgroup. This is what this patch set is intended to do. Basically, it does two things. First, it introduces the notion of per-memcg slab shrinker. A shrinker that wants to reclaim objects per cgroup should mark itself as SHRINKER_MEMCG_AWARE. Then it will be passed the memory cgroup to scan from in shrink_control->memcg. For such shrinkers shrink_slab iterates over the whole cgroup subtree under the target cgroup and calls the shrinker for each kmem-active memory cgroup. Secondly, this patch set makes the list_lru structure per-memcg. It's done transparently to list_lru users - everything they have to do is to tell list_lru_init that they want memcg-aware list_lru. Then the list_lru will automatically distribute objects among per-memcg lists basing on which cgroup the object is accounted to. This way to make FS shrinkers (icache, dcache) memcg-aware we only need to make them use memcg-aware list_lru, and this is what this patch set does. As before, this patch set only enables per-memcg kmem reclaim when the pressure goes from memory.limit, not from memory.kmem.limit. Handling memory.kmem.limit is going to be tricky due to GFP_NOFS allocations, and it is still unclear whether we will have this knob in the unified hierarchy. This patch (of 9): NUMA aware slab shrinkers use the list_lru structure to distribute objects coming from different NUMA nodes to different lists. Whenever such a shrinker needs to count or scan objects from a particular node, it issues commands like this: count = list_lru_count_node(lru, sc->nid); freed = list_lru_walk_node(lru, sc->nid, isolate_func, isolate_arg, &sc->nr_to_scan); where sc is an instance of the shrink_control structure passed to it from vmscan. To simplify this, let's add special list_lru functions to be used by shrinkers, list_lru_shrink_count() and list_lru_shrink_walk(), which consolidate the nid and nr_to_scan arguments in the shrink_control structure. This will also allow us to avoid patching shrinkers that use list_lru when we make shrink_slab() per-memcg - all we will have to do is extend the shrink_control structure to include the target memcg and make list_lru_shrink_{count,walk} handle this appropriately. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Suggested-by: Dave Chinner <david@fromorbit.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Glauber Costa <glommer@gmail.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-12 22:58:47 +00:00
freed = prune_dcache_sb(sb, sc);
sc->nr_to_scan = inodes + 1;
list_lru: introduce list_lru_shrink_{count,walk} Kmem accounting of memcg is unusable now, because it lacks slab shrinker support. That means when we hit the limit we will get ENOMEM w/o any chance to recover. What we should do then is to call shrink_slab, which would reclaim old inode/dentry caches from this cgroup. This is what this patch set is intended to do. Basically, it does two things. First, it introduces the notion of per-memcg slab shrinker. A shrinker that wants to reclaim objects per cgroup should mark itself as SHRINKER_MEMCG_AWARE. Then it will be passed the memory cgroup to scan from in shrink_control->memcg. For such shrinkers shrink_slab iterates over the whole cgroup subtree under the target cgroup and calls the shrinker for each kmem-active memory cgroup. Secondly, this patch set makes the list_lru structure per-memcg. It's done transparently to list_lru users - everything they have to do is to tell list_lru_init that they want memcg-aware list_lru. Then the list_lru will automatically distribute objects among per-memcg lists basing on which cgroup the object is accounted to. This way to make FS shrinkers (icache, dcache) memcg-aware we only need to make them use memcg-aware list_lru, and this is what this patch set does. As before, this patch set only enables per-memcg kmem reclaim when the pressure goes from memory.limit, not from memory.kmem.limit. Handling memory.kmem.limit is going to be tricky due to GFP_NOFS allocations, and it is still unclear whether we will have this knob in the unified hierarchy. This patch (of 9): NUMA aware slab shrinkers use the list_lru structure to distribute objects coming from different NUMA nodes to different lists. Whenever such a shrinker needs to count or scan objects from a particular node, it issues commands like this: count = list_lru_count_node(lru, sc->nid); freed = list_lru_walk_node(lru, sc->nid, isolate_func, isolate_arg, &sc->nr_to_scan); where sc is an instance of the shrink_control structure passed to it from vmscan. To simplify this, let's add special list_lru functions to be used by shrinkers, list_lru_shrink_count() and list_lru_shrink_walk(), which consolidate the nid and nr_to_scan arguments in the shrink_control structure. This will also allow us to avoid patching shrinkers that use list_lru when we make shrink_slab() per-memcg - all we will have to do is extend the shrink_control structure to include the target memcg and make list_lru_shrink_{count,walk} handle this appropriately. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Suggested-by: Dave Chinner <david@fromorbit.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Glauber Costa <glommer@gmail.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-12 22:58:47 +00:00
freed += prune_icache_sb(sb, sc);
shrinker: convert superblock shrinkers to new API Convert superblock shrinker to use the new count/scan API, and propagate the API changes through to the filesystem callouts. The filesystem callouts already use a count/scan API, so it's just changing counters to longs to match the VM API. This requires the dentry and inode shrinker callouts to be converted to the count/scan API. This is mainly a mechanical change. [glommer@openvz.org: use mult_frac for fractional proportions, build fixes] Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Glauber Costa <glommer@openvz.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:17:57 +00:00
if (fs_objects) {
sc->nr_to_scan = fs_objects + 1;
freed += sb->s_op->free_cached_objects(sb, sc);
}
up_read(&sb->s_umount);
shrinker: convert superblock shrinkers to new API Convert superblock shrinker to use the new count/scan API, and propagate the API changes through to the filesystem callouts. The filesystem callouts already use a count/scan API, so it's just changing counters to longs to match the VM API. This requires the dentry and inode shrinker callouts to be converted to the count/scan API. This is mainly a mechanical change. [glommer@openvz.org: use mult_frac for fractional proportions, build fixes] Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Glauber Costa <glommer@openvz.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:17:57 +00:00
return freed;
}
static unsigned long super_cache_count(struct shrinker *shrink,
struct shrink_control *sc)
{
struct super_block *sb;
long total_objects = 0;
sb = container_of(shrink, struct super_block, s_shrink);
fs/superblock: avoid locking counting inodes and dentries before reclaiming them We remove the call to grab_super_passive in call to super_cache_count. This becomes a scalability bottleneck as multiple threads are trying to do memory reclamation, e.g. when we are doing large amount of file read and page cache is under pressure. The cached objects quickly got reclaimed down to 0 and we are aborting the cache_scan() reclaim. But counting creates a log jam acquiring the sb_lock. We are holding the shrinker_rwsem which ensures the safety of call to list_lru_count_node() and s_op->nr_cached_objects. The shrinker is unregistered now before ->kill_sb() so the operation is safe when we are doing unmount. The impact will depend heavily on the machine and the workload but for a small machine using postmark tuned to use 4xRAM size the results were 3.15.0-rc5 3.15.0-rc5 vanilla shrinker-v1r1 Ops/sec Transactions 21.00 ( 0.00%) 24.00 ( 14.29%) Ops/sec FilesCreate 39.00 ( 0.00%) 44.00 ( 12.82%) Ops/sec CreateTransact 10.00 ( 0.00%) 12.00 ( 20.00%) Ops/sec FilesDeleted 6202.00 ( 0.00%) 6202.00 ( 0.00%) Ops/sec DeleteTransact 11.00 ( 0.00%) 12.00 ( 9.09%) Ops/sec DataRead/MB 25.97 ( 0.00%) 29.10 ( 12.05%) Ops/sec DataWrite/MB 49.99 ( 0.00%) 56.02 ( 12.06%) ffsb running in a configuration that is meant to simulate a mail server showed 3.15.0-rc5 3.15.0-rc5 vanilla shrinker-v1r1 Ops/sec readall 9402.63 ( 0.00%) 9567.97 ( 1.76%) Ops/sec create 4695.45 ( 0.00%) 4735.00 ( 0.84%) Ops/sec delete 173.72 ( 0.00%) 179.83 ( 3.52%) Ops/sec Transactions 14271.80 ( 0.00%) 14482.81 ( 1.48%) Ops/sec Read 37.00 ( 0.00%) 37.60 ( 1.62%) Ops/sec Write 18.20 ( 0.00%) 18.30 ( 0.55%) Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Mel Gorman <mgorman@suse.de> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Chinner <david@fromorbit.com> Tested-by: Yuanhan Liu <yuanhan.liu@linux.intel.com> Cc: Bob Liu <bob.liu@oracle.com> Cc: Jan Kara <jack@suse.cz> Acked-by: Rik van Riel <riel@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04 23:10:47 +00:00
/*
* Don't call trylock_super as it is a potential
fs/superblock: avoid locking counting inodes and dentries before reclaiming them We remove the call to grab_super_passive in call to super_cache_count. This becomes a scalability bottleneck as multiple threads are trying to do memory reclamation, e.g. when we are doing large amount of file read and page cache is under pressure. The cached objects quickly got reclaimed down to 0 and we are aborting the cache_scan() reclaim. But counting creates a log jam acquiring the sb_lock. We are holding the shrinker_rwsem which ensures the safety of call to list_lru_count_node() and s_op->nr_cached_objects. The shrinker is unregistered now before ->kill_sb() so the operation is safe when we are doing unmount. The impact will depend heavily on the machine and the workload but for a small machine using postmark tuned to use 4xRAM size the results were 3.15.0-rc5 3.15.0-rc5 vanilla shrinker-v1r1 Ops/sec Transactions 21.00 ( 0.00%) 24.00 ( 14.29%) Ops/sec FilesCreate 39.00 ( 0.00%) 44.00 ( 12.82%) Ops/sec CreateTransact 10.00 ( 0.00%) 12.00 ( 20.00%) Ops/sec FilesDeleted 6202.00 ( 0.00%) 6202.00 ( 0.00%) Ops/sec DeleteTransact 11.00 ( 0.00%) 12.00 ( 9.09%) Ops/sec DataRead/MB 25.97 ( 0.00%) 29.10 ( 12.05%) Ops/sec DataWrite/MB 49.99 ( 0.00%) 56.02 ( 12.06%) ffsb running in a configuration that is meant to simulate a mail server showed 3.15.0-rc5 3.15.0-rc5 vanilla shrinker-v1r1 Ops/sec readall 9402.63 ( 0.00%) 9567.97 ( 1.76%) Ops/sec create 4695.45 ( 0.00%) 4735.00 ( 0.84%) Ops/sec delete 173.72 ( 0.00%) 179.83 ( 3.52%) Ops/sec Transactions 14271.80 ( 0.00%) 14482.81 ( 1.48%) Ops/sec Read 37.00 ( 0.00%) 37.60 ( 1.62%) Ops/sec Write 18.20 ( 0.00%) 18.30 ( 0.55%) Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Mel Gorman <mgorman@suse.de> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Chinner <david@fromorbit.com> Tested-by: Yuanhan Liu <yuanhan.liu@linux.intel.com> Cc: Bob Liu <bob.liu@oracle.com> Cc: Jan Kara <jack@suse.cz> Acked-by: Rik van Riel <riel@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04 23:10:47 +00:00
* scalability bottleneck. The counts could get updated
* between super_cache_count and super_cache_scan anyway.
* Call to super_cache_count with shrinker_rwsem held
list_lru: introduce list_lru_shrink_{count,walk} Kmem accounting of memcg is unusable now, because it lacks slab shrinker support. That means when we hit the limit we will get ENOMEM w/o any chance to recover. What we should do then is to call shrink_slab, which would reclaim old inode/dentry caches from this cgroup. This is what this patch set is intended to do. Basically, it does two things. First, it introduces the notion of per-memcg slab shrinker. A shrinker that wants to reclaim objects per cgroup should mark itself as SHRINKER_MEMCG_AWARE. Then it will be passed the memory cgroup to scan from in shrink_control->memcg. For such shrinkers shrink_slab iterates over the whole cgroup subtree under the target cgroup and calls the shrinker for each kmem-active memory cgroup. Secondly, this patch set makes the list_lru structure per-memcg. It's done transparently to list_lru users - everything they have to do is to tell list_lru_init that they want memcg-aware list_lru. Then the list_lru will automatically distribute objects among per-memcg lists basing on which cgroup the object is accounted to. This way to make FS shrinkers (icache, dcache) memcg-aware we only need to make them use memcg-aware list_lru, and this is what this patch set does. As before, this patch set only enables per-memcg kmem reclaim when the pressure goes from memory.limit, not from memory.kmem.limit. Handling memory.kmem.limit is going to be tricky due to GFP_NOFS allocations, and it is still unclear whether we will have this knob in the unified hierarchy. This patch (of 9): NUMA aware slab shrinkers use the list_lru structure to distribute objects coming from different NUMA nodes to different lists. Whenever such a shrinker needs to count or scan objects from a particular node, it issues commands like this: count = list_lru_count_node(lru, sc->nid); freed = list_lru_walk_node(lru, sc->nid, isolate_func, isolate_arg, &sc->nr_to_scan); where sc is an instance of the shrink_control structure passed to it from vmscan. To simplify this, let's add special list_lru functions to be used by shrinkers, list_lru_shrink_count() and list_lru_shrink_walk(), which consolidate the nid and nr_to_scan arguments in the shrink_control structure. This will also allow us to avoid patching shrinkers that use list_lru when we make shrink_slab() per-memcg - all we will have to do is extend the shrink_control structure to include the target memcg and make list_lru_shrink_{count,walk} handle this appropriately. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Suggested-by: Dave Chinner <david@fromorbit.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Glauber Costa <glommer@gmail.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-12 22:58:47 +00:00
* ensures the safety of call to list_lru_shrink_count() and
fs/superblock: avoid locking counting inodes and dentries before reclaiming them We remove the call to grab_super_passive in call to super_cache_count. This becomes a scalability bottleneck as multiple threads are trying to do memory reclamation, e.g. when we are doing large amount of file read and page cache is under pressure. The cached objects quickly got reclaimed down to 0 and we are aborting the cache_scan() reclaim. But counting creates a log jam acquiring the sb_lock. We are holding the shrinker_rwsem which ensures the safety of call to list_lru_count_node() and s_op->nr_cached_objects. The shrinker is unregistered now before ->kill_sb() so the operation is safe when we are doing unmount. The impact will depend heavily on the machine and the workload but for a small machine using postmark tuned to use 4xRAM size the results were 3.15.0-rc5 3.15.0-rc5 vanilla shrinker-v1r1 Ops/sec Transactions 21.00 ( 0.00%) 24.00 ( 14.29%) Ops/sec FilesCreate 39.00 ( 0.00%) 44.00 ( 12.82%) Ops/sec CreateTransact 10.00 ( 0.00%) 12.00 ( 20.00%) Ops/sec FilesDeleted 6202.00 ( 0.00%) 6202.00 ( 0.00%) Ops/sec DeleteTransact 11.00 ( 0.00%) 12.00 ( 9.09%) Ops/sec DataRead/MB 25.97 ( 0.00%) 29.10 ( 12.05%) Ops/sec DataWrite/MB 49.99 ( 0.00%) 56.02 ( 12.06%) ffsb running in a configuration that is meant to simulate a mail server showed 3.15.0-rc5 3.15.0-rc5 vanilla shrinker-v1r1 Ops/sec readall 9402.63 ( 0.00%) 9567.97 ( 1.76%) Ops/sec create 4695.45 ( 0.00%) 4735.00 ( 0.84%) Ops/sec delete 173.72 ( 0.00%) 179.83 ( 3.52%) Ops/sec Transactions 14271.80 ( 0.00%) 14482.81 ( 1.48%) Ops/sec Read 37.00 ( 0.00%) 37.60 ( 1.62%) Ops/sec Write 18.20 ( 0.00%) 18.30 ( 0.55%) Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Mel Gorman <mgorman@suse.de> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Chinner <david@fromorbit.com> Tested-by: Yuanhan Liu <yuanhan.liu@linux.intel.com> Cc: Bob Liu <bob.liu@oracle.com> Cc: Jan Kara <jack@suse.cz> Acked-by: Rik van Riel <riel@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04 23:10:47 +00:00
* s_op->nr_cached_objects().
*/
shrinker: convert superblock shrinkers to new API Convert superblock shrinker to use the new count/scan API, and propagate the API changes through to the filesystem callouts. The filesystem callouts already use a count/scan API, so it's just changing counters to longs to match the VM API. This requires the dentry and inode shrinker callouts to be converted to the count/scan API. This is mainly a mechanical change. [glommer@openvz.org: use mult_frac for fractional proportions, build fixes] Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Glauber Costa <glommer@openvz.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:17:57 +00:00
if (sb->s_op && sb->s_op->nr_cached_objects)
total_objects = sb->s_op->nr_cached_objects(sb, sc);
shrinker: convert superblock shrinkers to new API Convert superblock shrinker to use the new count/scan API, and propagate the API changes through to the filesystem callouts. The filesystem callouts already use a count/scan API, so it's just changing counters to longs to match the VM API. This requires the dentry and inode shrinker callouts to be converted to the count/scan API. This is mainly a mechanical change. [glommer@openvz.org: use mult_frac for fractional proportions, build fixes] Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Glauber Costa <glommer@openvz.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:17:57 +00:00
list_lru: introduce list_lru_shrink_{count,walk} Kmem accounting of memcg is unusable now, because it lacks slab shrinker support. That means when we hit the limit we will get ENOMEM w/o any chance to recover. What we should do then is to call shrink_slab, which would reclaim old inode/dentry caches from this cgroup. This is what this patch set is intended to do. Basically, it does two things. First, it introduces the notion of per-memcg slab shrinker. A shrinker that wants to reclaim objects per cgroup should mark itself as SHRINKER_MEMCG_AWARE. Then it will be passed the memory cgroup to scan from in shrink_control->memcg. For such shrinkers shrink_slab iterates over the whole cgroup subtree under the target cgroup and calls the shrinker for each kmem-active memory cgroup. Secondly, this patch set makes the list_lru structure per-memcg. It's done transparently to list_lru users - everything they have to do is to tell list_lru_init that they want memcg-aware list_lru. Then the list_lru will automatically distribute objects among per-memcg lists basing on which cgroup the object is accounted to. This way to make FS shrinkers (icache, dcache) memcg-aware we only need to make them use memcg-aware list_lru, and this is what this patch set does. As before, this patch set only enables per-memcg kmem reclaim when the pressure goes from memory.limit, not from memory.kmem.limit. Handling memory.kmem.limit is going to be tricky due to GFP_NOFS allocations, and it is still unclear whether we will have this knob in the unified hierarchy. This patch (of 9): NUMA aware slab shrinkers use the list_lru structure to distribute objects coming from different NUMA nodes to different lists. Whenever such a shrinker needs to count or scan objects from a particular node, it issues commands like this: count = list_lru_count_node(lru, sc->nid); freed = list_lru_walk_node(lru, sc->nid, isolate_func, isolate_arg, &sc->nr_to_scan); where sc is an instance of the shrink_control structure passed to it from vmscan. To simplify this, let's add special list_lru functions to be used by shrinkers, list_lru_shrink_count() and list_lru_shrink_walk(), which consolidate the nid and nr_to_scan arguments in the shrink_control structure. This will also allow us to avoid patching shrinkers that use list_lru when we make shrink_slab() per-memcg - all we will have to do is extend the shrink_control structure to include the target memcg and make list_lru_shrink_{count,walk} handle this appropriately. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Suggested-by: Dave Chinner <david@fromorbit.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Glauber Costa <glommer@gmail.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-02-12 22:58:47 +00:00
total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc);
total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc);
shrinker: convert superblock shrinkers to new API Convert superblock shrinker to use the new count/scan API, and propagate the API changes through to the filesystem callouts. The filesystem callouts already use a count/scan API, so it's just changing counters to longs to match the VM API. This requires the dentry and inode shrinker callouts to be converted to the count/scan API. This is mainly a mechanical change. [glommer@openvz.org: use mult_frac for fractional proportions, build fixes] Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Glauber Costa <glommer@openvz.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:17:57 +00:00
super: fix calculation of shrinkable objects for small numbers The sysctl knob sysctl_vfs_cache_pressure is used to determine which percentage of the shrinkable objects in our cache we should actively try to shrink. It works great in situations in which we have many objects (at least more than 100), because the aproximation errors will be negligible. But if this is not the case, specially when total_objects < 100, we may end up concluding that we have no objects at all (total / 100 = 0, if total < 100). This is certainly not the biggest killer in the world, but may matter in very low kernel memory situations. Signed-off-by: Glauber Costa <glommer@openvz.org> Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Dave Chinner <david@fromorbit.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:17:53 +00:00
total_objects = vfs_pressure_ratio(total_objects);
return total_objects;
}
static void destroy_super_work(struct work_struct *work)
{
struct super_block *s = container_of(work, struct super_block,
destroy_work);
int i;
for (i = 0; i < SB_FREEZE_LEVELS; i++)
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
percpu_free_rwsem(&s->s_writers.rw_sem[i]);
kfree(s);
}
static void destroy_super_rcu(struct rcu_head *head)
{
struct super_block *s = container_of(head, struct super_block, rcu);
INIT_WORK(&s->destroy_work, destroy_super_work);
schedule_work(&s->destroy_work);
}
/**
* destroy_super - frees a superblock
* @s: superblock to free
*
* Frees a superblock.
*/
static void destroy_super(struct super_block *s)
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
{
list_lru_destroy(&s->s_dentry_lru);
list_lru_destroy(&s->s_inode_lru);
security_sb_free(s);
WARN_ON(!list_empty(&s->s_mounts));
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
put_user_ns(s->s_user_ns);
kfree(s->s_subtype);
kfree(s->s_options);
call_rcu(&s->rcu, destroy_super_rcu);
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
}
/**
* alloc_super - create new superblock
* @type: filesystem type superblock should belong to
* @flags: the mount flags
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
* @user_ns: User namespace for the super_block
*
* Allocates and initializes a new &struct super_block. alloc_super()
* returns a pointer new superblock or %NULL if allocation had failed.
*/
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
static struct super_block *alloc_super(struct file_system_type *type, int flags,
struct user_namespace *user_ns)
{
struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
static const struct super_operations default_op;
int i;
if (!s)
return NULL;
INIT_LIST_HEAD(&s->s_mounts);
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
s->s_user_ns = get_user_ns(user_ns);
if (security_sb_alloc(s))
goto fail;
for (i = 0; i < SB_FREEZE_LEVELS; i++) {
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
if (__percpu_init_rwsem(&s->s_writers.rw_sem[i],
sb_writers_name[i],
&type->s_writers_key[i]))
goto fail;
}
init_waitqueue_head(&s->s_writers.wait_unfrozen);
s->s_bdi = &noop_backing_dev_info;
s->s_flags = flags;
if (s->s_user_ns != &init_user_ns)
s->s_iflags |= SB_I_NODEV;
INIT_HLIST_NODE(&s->s_instances);
INIT_HLIST_BL_HEAD(&s->s_anon);
mutex_init(&s->s_sync_lock);
INIT_LIST_HEAD(&s->s_inodes);
spin_lock_init(&s->s_inode_list_lock);
fs/fs-writeback.c: add a new writeback list for sync wait_sb_inodes() currently does a walk of all inodes in the filesystem to find dirty one to wait on during sync. This is highly inefficient and wastes a lot of CPU when there are lots of clean cached inodes that we don't need to wait on. To avoid this "all inode" walk, we need to track inodes that are currently under writeback that we need to wait for. We do this by adding inodes to a writeback list on the sb when the mapping is first tagged as having pages under writeback. wait_sb_inodes() can then walk this list of "inodes under IO" and wait specifically just for the inodes that the current sync(2) needs to wait for. Define a couple helpers to add/remove an inode from the writeback list and call them when the overall mapping is tagged for or cleared from writeback. Update wait_sb_inodes() to walk only the inodes under writeback due to the sync. With this change, filesystem sync times are significantly reduced for fs' with largely populated inode caches and otherwise no other work to do. For example, on a 16xcpu 2GHz x86-64 server, 10TB XFS filesystem with a ~10m entry inode cache, sync times are reduced from ~7.3s to less than 0.1s when the filesystem is fully clean. Link: http://lkml.kernel.org/r/1466594593-6757-2-git-send-email-bfoster@redhat.com Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Jan Kara <jack@suse.cz> Tested-by: Holger Hoffstätte <holger.hoffstaette@applied-asynchrony.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-07-26 22:21:50 +00:00
INIT_LIST_HEAD(&s->s_inodes_wb);
spin_lock_init(&s->s_inode_wblist_lock);
if (list_lru_init_memcg(&s->s_dentry_lru))
goto fail;
if (list_lru_init_memcg(&s->s_inode_lru))
goto fail;
init_rwsem(&s->s_umount);
lockdep_set_class(&s->s_umount, &type->s_umount_key);
/*
* sget() can have s_umount recursion.
*
* When it cannot find a suitable sb, it allocates a new
* one (this one), and tries again to find a suitable old
* one.
*
* In case that succeeds, it will acquire the s_umount
* lock of the old one. Since these are clearly distrinct
* locks, and this object isn't exposed yet, there's no
* risk of deadlocks.
*
* Annotate this by putting this lock in a different
* subclass.
*/
down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
s->s_count = 1;
atomic_set(&s->s_active, 1);
mutex_init(&s->s_vfs_rename_mutex);
lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
mutex_init(&s->s_dquot.dqio_mutex);
s->s_maxbytes = MAX_NON_LFS;
s->s_op = &default_op;
s->s_time_gran = 1000000000;
cleancache: remove limit on the number of cleancache enabled filesystems The limit equals 32 and is imposed by the number of entries in the fs_poolid_map and shared_fs_poolid_map. Nowadays it is insufficient, because with containers on board a Linux host can have hundreds of active fs mounts. These maps were introduced by commit 49a9ab815acb8 ("mm: cleancache: lazy initialization to allow tmem backends to build/run as modules") in order to allow compiling cleancache drivers as modules. Real pool ids are stored in these maps while super_block->cleancache_poolid points to an entry in the map, so that on cleancache registration we can walk over all (if there are <= 32 of them, of course) cleancache-enabled super blocks and assign real pool ids. Actually, there is absolutely no need in these maps, because we can iterate over all super blocks immediately using iterate_supers. This is not racy, because cleancache_init_ops is called from mount_fs with super_block->s_umount held for writing, while iterate_supers takes this semaphore for reading, so if we call iterate_supers after setting cleancache_ops, all super blocks that had been created before cleancache_register_ops was called will be assigned pool ids by the action function of iterate_supers while all newer super blocks will receive it in cleancache_init_fs. This patch therefore removes the maps and hence the artificial limit on the number of cleancache enabled filesystems. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: David Vrabel <david.vrabel@citrix.com> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Stefan Hengelein <ilendir@googlemail.com> Cc: Florian Schmaus <fschmaus@gmail.com> Cc: Andor Daam <andor.daam@googlemail.com> Cc: Dan Magenheimer <dan.magenheimer@oracle.com> Cc: Bob Liu <lliubbo@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-14 22:46:48 +00:00
s->cleancache_poolid = CLEANCACHE_NO_POOL;
s->s_shrink.seeks = DEFAULT_SEEKS;
s->s_shrink.scan_objects = super_cache_scan;
s->s_shrink.count_objects = super_cache_count;
s->s_shrink.batch = 1024;
s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
return s;
list_lru: dynamically adjust node arrays We currently use a compile-time constant to size the node array for the list_lru structure. Due to this, we don't need to allocate any memory at initialization time. But as a consequence, the structures that contain embedded list_lru lists can become way too big (the superblock for instance contains two of them). This patch aims at ameliorating this situation by dynamically allocating the node arrays with the firmware provided nr_node_ids. Signed-off-by: Glauber Costa <glommer@openvz.org> Cc: Dave Chinner <dchinner@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Carlos Maiolino <cmaiolino@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chuck Lever <chuck.lever@oracle.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: David Rientjes <rientjes@google.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Greg Thelen <gthelen@google.com> Cc: J. Bruce Fields <bfields@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Kent Overstreet <koverstreet@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Thomas Hellstrom <thellstrom@vmware.com> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-08-28 00:18:18 +00:00
fail:
destroy_super(s);
return NULL;
}
/* Superblock refcounting */
/*
* Drop a superblock's refcount. The caller must hold sb_lock.
*/
static void __put_super(struct super_block *sb)
{
if (!--sb->s_count) {
list_del_init(&sb->s_list);
destroy_super(sb);
}
}
/**
* put_super - drop a temporary reference to superblock
* @sb: superblock in question
*
* Drops a temporary reference, frees superblock if there's no
* references left.
*/
static void put_super(struct super_block *sb)
{
spin_lock(&sb_lock);
__put_super(sb);
spin_unlock(&sb_lock);
}
/**
* deactivate_locked_super - drop an active reference to superblock
* @s: superblock to deactivate
*
* Drops an active reference to superblock, converting it into a temporary
* one if there is no other active references left. In that case we
* tell fs driver to shut it down and drop the temporary reference we
* had just acquired.
*
* Caller holds exclusive lock on superblock; that lock is released.
*/
void deactivate_locked_super(struct super_block *s)
{
struct file_system_type *fs = s->s_type;
if (atomic_dec_and_test(&s->s_active)) {
cleancache_invalidate_fs(s);
unregister_shrinker(&s->s_shrink);
fs/superblock: unregister sb shrinker before ->kill_sb() This series is aimed at regressions noticed during reclaim activity. The first two patches are shrinker patches that were posted ages ago but never merged for reasons that are unclear to me. I'm posting them again to see if there was a reason they were dropped or if they just got lost. Dave? Time? The last patch adjusts proportional reclaim. Yuanhan Liu, can you retest the vm scalability test cases on a larger machine? Hugh, does this work for you on the memcg test cases? Based on ext4, I get the following results but unfortunately my larger test machines are all unavailable so this is based on a relatively small machine. postmark 3.15.0-rc5 3.15.0-rc5 vanilla proportion-v1r4 Ops/sec Transactions 21.00 ( 0.00%) 25.00 ( 19.05%) Ops/sec FilesCreate 39.00 ( 0.00%) 45.00 ( 15.38%) Ops/sec CreateTransact 10.00 ( 0.00%) 12.00 ( 20.00%) Ops/sec FilesDeleted 6202.00 ( 0.00%) 6202.00 ( 0.00%) Ops/sec DeleteTransact 11.00 ( 0.00%) 12.00 ( 9.09%) Ops/sec DataRead/MB 25.97 ( 0.00%) 30.02 ( 15.59%) Ops/sec DataWrite/MB 49.99 ( 0.00%) 57.78 ( 15.58%) ffsb (mail server simulator) 3.15.0-rc5 3.15.0-rc5 vanilla proportion-v1r4 Ops/sec readall 9402.63 ( 0.00%) 9805.74 ( 4.29%) Ops/sec create 4695.45 ( 0.00%) 4781.39 ( 1.83%) Ops/sec delete 173.72 ( 0.00%) 177.23 ( 2.02%) Ops/sec Transactions 14271.80 ( 0.00%) 14764.37 ( 3.45%) Ops/sec Read 37.00 ( 0.00%) 38.50 ( 4.05%) Ops/sec Write 18.20 ( 0.00%) 18.50 ( 1.65%) dd of a large file 3.15.0-rc5 3.15.0-rc5 vanilla proportion-v1r4 WallTime DownloadTar 75.00 ( 0.00%) 61.00 ( 18.67%) WallTime DD 423.00 ( 0.00%) 401.00 ( 5.20%) WallTime Delete 2.00 ( 0.00%) 5.00 (-150.00%) stutter (times mmap latency during large amounts of IO) 3.15.0-rc5 3.15.0-rc5 vanilla proportion-v1r4 Unit >5ms Delays 80252.0000 ( 0.00%) 81523.0000 ( -1.58%) Unit Mmap min 8.2118 ( 0.00%) 8.3206 ( -1.33%) Unit Mmap mean 17.4614 ( 0.00%) 17.2868 ( 1.00%) Unit Mmap stddev 24.9059 ( 0.00%) 34.6771 (-39.23%) Unit Mmap max 2811.6433 ( 0.00%) 2645.1398 ( 5.92%) Unit Mmap 90% 20.5098 ( 0.00%) 18.3105 ( 10.72%) Unit Mmap 93% 22.9180 ( 0.00%) 20.1751 ( 11.97%) Unit Mmap 95% 25.2114 ( 0.00%) 22.4988 ( 10.76%) Unit Mmap 99% 46.1430 ( 0.00%) 43.5952 ( 5.52%) Unit Ideal Tput 85.2623 ( 0.00%) 78.8906 ( 7.47%) Unit Tput min 44.0666 ( 0.00%) 43.9609 ( 0.24%) Unit Tput mean 45.5646 ( 0.00%) 45.2009 ( 0.80%) Unit Tput stddev 0.9318 ( 0.00%) 1.1084 (-18.95%) Unit Tput max 46.7375 ( 0.00%) 46.7539 ( -0.04%) This patch (of 3): We will like to unregister the sb shrinker before ->kill_sb(). This will allow cached objects to be counted without call to grab_super_passive() to update ref count on sb. We want to avoid locking during memory reclamation especially when we are skipping the memory reclaim when we are out of cached objects. This is safe because grab_super_passive does a try-lock on the sb->s_umount now, and so if we are in the unmount process, it won't ever block. That means what used to be a deadlock and races we were avoiding by using grab_super_passive() is now: shrinker umount down_read(shrinker_rwsem) down_write(sb->s_umount) shrinker_unregister down_write(shrinker_rwsem) <blocks> grab_super_passive(sb) down_read_trylock(sb->s_umount) <fails> <shrinker aborts> .... <shrinkers finish running> up_read(shrinker_rwsem) <unblocks> <removes shrinker> up_write(shrinker_rwsem) ->kill_sb() .... So it is safe to deregister the shrinker before ->kill_sb(). Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Mel Gorman <mgorman@suse.de> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Chinner <david@fromorbit.com> Tested-by: Yuanhan Liu <yuanhan.liu@linux.intel.com> Cc: Bob Liu <bob.liu@oracle.com> Cc: Jan Kara <jack@suse.cz> Acked-by: Rik van Riel <riel@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04 23:10:46 +00:00
fs->kill_sb(s);
/*
* Since list_lru_destroy() may sleep, we cannot call it from
* put_super(), where we hold the sb_lock. Therefore we destroy
* the lru lists right now.
*/
list_lru_destroy(&s->s_dentry_lru);
list_lru_destroy(&s->s_inode_lru);
put_filesystem(fs);
put_super(s);
} else {
up_write(&s->s_umount);
}
}
EXPORT_SYMBOL(deactivate_locked_super);
/**
* deactivate_super - drop an active reference to superblock
* @s: superblock to deactivate
*
* Variant of deactivate_locked_super(), except that superblock is *not*
* locked by caller. If we are going to drop the final active reference,
* lock will be acquired prior to that.
*/
void deactivate_super(struct super_block *s)
{
if (!atomic_add_unless(&s->s_active, -1, 1)) {
down_write(&s->s_umount);
deactivate_locked_super(s);
}
}
EXPORT_SYMBOL(deactivate_super);
/**
* grab_super - acquire an active reference
* @s: reference we are trying to make active
*
* Tries to acquire an active reference. grab_super() is used when we
* had just found a superblock in super_blocks or fs_type->fs_supers
* and want to turn it into a full-blown active reference. grab_super()
* is called with sb_lock held and drops it. Returns 1 in case of
* success, 0 if we had failed (superblock contents was already dead or
livelock avoidance in sget() Eric Sandeen has found a nasty livelock in sget() - take a mount(2) about to fail. The superblock is on ->fs_supers, ->s_umount is held exclusive, ->s_active is 1. Along comes two more processes, trying to mount the same thing; sget() in each is picking that superblock, bumping ->s_count and trying to grab ->s_umount. ->s_active is 3 now. Original mount(2) finally gets to deactivate_locked_super() on failure; ->s_active is 2, superblock is still ->fs_supers because shutdown will *not* happen until ->s_active hits 0. ->s_umount is dropped and now we have two processes chasing each other: s_active = 2, A acquired ->s_umount, B blocked A sees that the damn thing is stillborn, does deactivate_locked_super() s_active = 1, A drops ->s_umount, B gets it A restarts the search and finds the same superblock. And bumps it ->s_active. s_active = 2, B holds ->s_umount, A blocked on trying to get it ... and we are in the earlier situation with A and B switched places. The root cause, of course, is that ->s_active should not grow until we'd got MS_BORN. Then failing ->mount() will have deactivate_locked_super() shut the damn thing down. Fortunately, it's easy to do - the key point is that grab_super() is called only for superblocks currently on ->fs_supers, so it can bump ->s_count and grab ->s_umount first, then check MS_BORN and bump ->s_active; we must never increment ->s_count for superblocks past ->kill_sb(), but grab_super() is never called for those. The bug is pretty old; we would've caught it by now, if not for accidental exclusion between sget() for block filesystems; the things like cgroup or e.g. mtd-based filesystems don't have anything of that sort, so they get bitten. The right way to deal with that is obviously to fix sget()... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-07-19 23:13:55 +00:00
* dying when grab_super() had been called). Note that this is only
* called for superblocks not in rundown mode (== ones still on ->fs_supers
* of their type), so increment of ->s_count is OK here.
*/
static int grab_super(struct super_block *s) __releases(sb_lock)
{
s->s_count++;
spin_unlock(&sb_lock);
down_write(&s->s_umount);
livelock avoidance in sget() Eric Sandeen has found a nasty livelock in sget() - take a mount(2) about to fail. The superblock is on ->fs_supers, ->s_umount is held exclusive, ->s_active is 1. Along comes two more processes, trying to mount the same thing; sget() in each is picking that superblock, bumping ->s_count and trying to grab ->s_umount. ->s_active is 3 now. Original mount(2) finally gets to deactivate_locked_super() on failure; ->s_active is 2, superblock is still ->fs_supers because shutdown will *not* happen until ->s_active hits 0. ->s_umount is dropped and now we have two processes chasing each other: s_active = 2, A acquired ->s_umount, B blocked A sees that the damn thing is stillborn, does deactivate_locked_super() s_active = 1, A drops ->s_umount, B gets it A restarts the search and finds the same superblock. And bumps it ->s_active. s_active = 2, B holds ->s_umount, A blocked on trying to get it ... and we are in the earlier situation with A and B switched places. The root cause, of course, is that ->s_active should not grow until we'd got MS_BORN. Then failing ->mount() will have deactivate_locked_super() shut the damn thing down. Fortunately, it's easy to do - the key point is that grab_super() is called only for superblocks currently on ->fs_supers, so it can bump ->s_count and grab ->s_umount first, then check MS_BORN and bump ->s_active; we must never increment ->s_count for superblocks past ->kill_sb(), but grab_super() is never called for those. The bug is pretty old; we would've caught it by now, if not for accidental exclusion between sget() for block filesystems; the things like cgroup or e.g. mtd-based filesystems don't have anything of that sort, so they get bitten. The right way to deal with that is obviously to fix sget()... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-07-19 23:13:55 +00:00
if ((s->s_flags & MS_BORN) && atomic_inc_not_zero(&s->s_active)) {
put_super(s);
return 1;
}
up_write(&s->s_umount);
put_super(s);
return 0;
}
/*
* trylock_super - try to grab ->s_umount shared
* @sb: reference we are trying to grab
*
* Try to prevent fs shutdown. This is used in places where we
* cannot take an active reference but we need to ensure that the
* filesystem is not shut down while we are working on it. It returns
* false if we cannot acquire s_umount or if we lose the race and
* filesystem already got into shutdown, and returns true with the s_umount
* lock held in read mode in case of success. On successful return,
* the caller must drop the s_umount lock when done.
*
* Note that unlike get_super() et.al. this one does *not* bump ->s_count.
* The reason why it's safe is that we are OK with doing trylock instead
* of down_read(). There's a couple of places that are OK with that, but
* it's very much not a general-purpose interface.
*/
bool trylock_super(struct super_block *sb)
{
if (down_read_trylock(&sb->s_umount)) {
if (!hlist_unhashed(&sb->s_instances) &&
sb->s_root && (sb->s_flags & MS_BORN))
return true;
up_read(&sb->s_umount);
}
return false;
}
/**
* generic_shutdown_super - common helper for ->kill_sb()
* @sb: superblock to kill
*
* generic_shutdown_super() does all fs-independent work on superblock
* shutdown. Typical ->kill_sb() should pick all fs-specific objects
* that need destruction out of superblock, call generic_shutdown_super()
* and release aforementioned objects. Note: dentries and inodes _are_
* taken care of and do not need specific handling.
[PATCH] VFS: Destroy the dentries contributed by a superblock on unmounting The attached patch destroys all the dentries attached to a superblock in one go by: (1) Destroying the tree rooted at s_root. (2) Destroying every entry in the anon list, one at a time. (3) Each entry in the anon list has its subtree consumed from the leaves inwards. This reduces the amount of work generic_shutdown_super() does, and avoids iterating through the dentry_unused list. Note that locking is almost entirely absent in the shrink_dcache_for_umount*() functions added by this patch. This is because: (1) at the point the filesystem calls generic_shutdown_super(), it is not permitted to further touch the superblock's set of dentries, and nor may it remove aliases from inodes; (2) the dcache memory shrinker now skips dentries that are being unmounted; and (3) the superblock no longer has any external references through which the VFS can reach it. Given these points, the only locking we need to do is when we remove dentries from the unused list and the name hashes, which we do a directory's worth at a time. We also don't need to guard against reference counts going to zero unexpectedly and removing bits of the tree we're working on as nothing else can call dput(). A cut down version of dentry_iput() has been folded into shrink_dcache_for_umount_subtree() function. Apart from not needing to unlock things, it also doesn't need to check for inotify watches. In this version of the patch, the complaint about a dentry still being in use has been expanded from a single BUG_ON() and now gives much more information. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: NeilBrown <neilb@suse.de> Acked-by: Ian Kent <raven@themaw.net> Cc: Trond Myklebust <trond.myklebust@fys.uio.no> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-11 08:22:19 +00:00
*
* Upon calling this function, the filesystem may no longer alter or
* rearrange the set of dentries belonging to this super_block, nor may it
* change the attachments of dentries to inodes.
*/
void generic_shutdown_super(struct super_block *sb)
{
const struct super_operations *sop = sb->s_op;
[PATCH] VFS: Destroy the dentries contributed by a superblock on unmounting The attached patch destroys all the dentries attached to a superblock in one go by: (1) Destroying the tree rooted at s_root. (2) Destroying every entry in the anon list, one at a time. (3) Each entry in the anon list has its subtree consumed from the leaves inwards. This reduces the amount of work generic_shutdown_super() does, and avoids iterating through the dentry_unused list. Note that locking is almost entirely absent in the shrink_dcache_for_umount*() functions added by this patch. This is because: (1) at the point the filesystem calls generic_shutdown_super(), it is not permitted to further touch the superblock's set of dentries, and nor may it remove aliases from inodes; (2) the dcache memory shrinker now skips dentries that are being unmounted; and (3) the superblock no longer has any external references through which the VFS can reach it. Given these points, the only locking we need to do is when we remove dentries from the unused list and the name hashes, which we do a directory's worth at a time. We also don't need to guard against reference counts going to zero unexpectedly and removing bits of the tree we're working on as nothing else can call dput(). A cut down version of dentry_iput() has been folded into shrink_dcache_for_umount_subtree() function. Apart from not needing to unlock things, it also doesn't need to check for inotify watches. In this version of the patch, the complaint about a dentry still being in use has been expanded from a single BUG_ON() and now gives much more information. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: NeilBrown <neilb@suse.de> Acked-by: Ian Kent <raven@themaw.net> Cc: Trond Myklebust <trond.myklebust@fys.uio.no> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-11 08:22:19 +00:00
if (sb->s_root) {
shrink_dcache_for_umount(sb);
sync_filesystem(sb);
sb->s_flags &= ~MS_ACTIVE;
fsnotify_unmount_inodes(sb);
writeback: flush inode cgroup wb switches instead of pinning super_block If cgroup writeback is in use, inodes can be scheduled for asynchronous wb switching. Before 5ff8eaac1636 ("writeback: keep superblock pinned during cgroup writeback association switches"), this could race with umount leading to super_block being destroyed while inodes are pinned for wb switching. 5ff8eaac1636 fixed it by bumping s_active while wb switches are in flight; however, this allowed in-flight wb switches to make umounts asynchronous when the userland expected synchronosity - e.g. fsck immediately following umount may fail because the device is still busy. This patch removes the problematic super_block pinning and instead makes generic_shutdown_super() flush in-flight wb switches. wb switches are now executed on a dedicated isw_wq so that they can be flushed and isw_nr_in_flight keeps track of the number of in-flight wb switches so that flushing can be avoided in most cases. v2: Move cgroup_writeback_umount() further below and add MS_ACTIVE check in inode_switch_wbs() as Jan an Al suggested. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Tahsin Erdogan <tahsin@google.com> Cc: Jan Kara <jack@suse.cz> Cc: Al Viro <viro@ZenIV.linux.org.uk> Link: http://lkml.kernel.org/g/CAAeU0aNCq7LGODvVGRU-oU_o-6enii5ey0p1c26D1ZzYwkDc5A@mail.gmail.com Fixes: 5ff8eaac1636 ("writeback: keep superblock pinned during cgroup writeback association switches") Cc: stable@vger.kernel.org #v4.5 Reviewed-by: Jan Kara <jack@suse.cz> Tested-by: Tahsin Erdogan <tahsin@google.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-02-29 23:28:53 +00:00
cgroup_writeback_umount();
evict_inodes(sb);
if (sb->s_dio_done_wq) {
destroy_workqueue(sb->s_dio_done_wq);
sb->s_dio_done_wq = NULL;
}
if (sop->put_super)
sop->put_super(sb);
if (!list_empty(&sb->s_inodes)) {
printk("VFS: Busy inodes after unmount of %s. "
"Self-destruct in 5 seconds. Have a nice day...\n",
sb->s_id);
}
}
spin_lock(&sb_lock);
/* should be initialized for __put_super_and_need_restart() */
hlist_del_init(&sb->s_instances);
spin_unlock(&sb_lock);
up_write(&sb->s_umount);
}
EXPORT_SYMBOL(generic_shutdown_super);
/**
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
* sget_userns - find or create a superblock
* @type: filesystem type superblock should belong to
* @test: comparison callback
* @set: setup callback
* @flags: mount flags
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
* @user_ns: User namespace for the super_block
* @data: argument to each of them
*/
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
struct super_block *sget_userns(struct file_system_type *type,
int (*test)(struct super_block *,void *),
int (*set)(struct super_block *,void *),
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
int flags, struct user_namespace *user_ns,
void *data)
{
struct super_block *s = NULL;
struct super_block *old;
int err;
fs: Better permission checking for submounts To support unprivileged users mounting filesystems two permission checks have to be performed: a test to see if the user allowed to create a mount in the mount namespace, and a test to see if the user is allowed to access the specified filesystem. The automount case is special in that mounting the original filesystem grants permission to mount the sub-filesystems, to any user who happens to stumble across the their mountpoint and satisfies the ordinary filesystem permission checks. Attempting to handle the automount case by using override_creds almost works. It preserves the idea that permission to mount the original filesystem is permission to mount the sub-filesystem. Unfortunately using override_creds messes up the filesystems ordinary permission checks. Solve this by being explicit that a mount is a submount by introducing vfs_submount, and using it where appropriate. vfs_submount uses a new mount internal mount flags MS_SUBMOUNT, to let sget and friends know that a mount is a submount so they can take appropriate action. sget and sget_userns are modified to not perform any permission checks on submounts. follow_automount is modified to stop using override_creds as that has proven problemantic. do_mount is modified to always remove the new MS_SUBMOUNT flag so that we know userspace will never by able to specify it. autofs4 is modified to stop using current_real_cred that was put in there to handle the previous version of submount permission checking. cifs is modified to pass the mountpoint all of the way down to vfs_submount. debugfs is modified to pass the mountpoint all of the way down to trace_automount by adding a new parameter. To make this change easier a new typedef debugfs_automount_t is introduced to capture the type of the debugfs automount function. Cc: stable@vger.kernel.org Fixes: 069d5ac9ae0d ("autofs: Fix automounts by using current_real_cred()->uid") Fixes: aeaa4a79ff6a ("fs: Call d_automount with the filesystems creds") Reviewed-by: Trond Myklebust <trond.myklebust@primarydata.com> Reviewed-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-01-31 17:06:16 +00:00
if (!(flags & (MS_KERNMOUNT|MS_SUBMOUNT)) &&
!(type->fs_flags & FS_USERNS_MOUNT) &&
!capable(CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);
retry:
spin_lock(&sb_lock);
if (test) {
hlist: drop the node parameter from iterators I'm not sure why, but the hlist for each entry iterators were conceived list_for_each_entry(pos, head, member) The hlist ones were greedy and wanted an extra parameter: hlist_for_each_entry(tpos, pos, head, member) Why did they need an extra pos parameter? I'm not quite sure. Not only they don't really need it, it also prevents the iterator from looking exactly like the list iterator, which is unfortunate. Besides the semantic patch, there was some manual work required: - Fix up the actual hlist iterators in linux/list.h - Fix up the declaration of other iterators based on the hlist ones. - A very small amount of places were using the 'node' parameter, this was modified to use 'obj->member' instead. - Coccinelle didn't handle the hlist_for_each_entry_safe iterator properly, so those had to be fixed up manually. The semantic patch which is mostly the work of Peter Senna Tschudin is here: @@ iterator name hlist_for_each_entry, hlist_for_each_entry_continue, hlist_for_each_entry_from, hlist_for_each_entry_rcu, hlist_for_each_entry_rcu_bh, hlist_for_each_entry_continue_rcu_bh, for_each_busy_worker, ax25_uid_for_each, ax25_for_each, inet_bind_bucket_for_each, sctp_for_each_hentry, sk_for_each, sk_for_each_rcu, sk_for_each_from, sk_for_each_safe, sk_for_each_bound, hlist_for_each_entry_safe, hlist_for_each_entry_continue_rcu, nr_neigh_for_each, nr_neigh_for_each_safe, nr_node_for_each, nr_node_for_each_safe, for_each_gfn_indirect_valid_sp, for_each_gfn_sp, for_each_host; type T; expression a,c,d,e; identifier b; statement S; @@ -T b; <+... when != b ( hlist_for_each_entry(a, - b, c, d) S | hlist_for_each_entry_continue(a, - b, c) S | hlist_for_each_entry_from(a, - b, c) S | hlist_for_each_entry_rcu(a, - b, c, d) S | hlist_for_each_entry_rcu_bh(a, - b, c, d) S | hlist_for_each_entry_continue_rcu_bh(a, - b, c) S | for_each_busy_worker(a, c, - b, d) S | ax25_uid_for_each(a, - b, c) S | ax25_for_each(a, - b, c) S | inet_bind_bucket_for_each(a, - b, c) S | sctp_for_each_hentry(a, - b, c) S | sk_for_each(a, - b, c) S | sk_for_each_rcu(a, - b, c) S | sk_for_each_from -(a, b) +(a) S + sk_for_each_from(a) S | sk_for_each_safe(a, - b, c, d) S | sk_for_each_bound(a, - b, c) S | hlist_for_each_entry_safe(a, - b, c, d, e) S | hlist_for_each_entry_continue_rcu(a, - b, c) S | nr_neigh_for_each(a, - b, c) S | nr_neigh_for_each_safe(a, - b, c, d) S | nr_node_for_each(a, - b, c) S | nr_node_for_each_safe(a, - b, c, d) S | - for_each_gfn_sp(a, c, d, b) S + for_each_gfn_sp(a, c, d) S | - for_each_gfn_indirect_valid_sp(a, c, d, b) S + for_each_gfn_indirect_valid_sp(a, c, d) S | for_each_host(a, - b, c) S | for_each_host_safe(a, - b, c, d) S | for_each_mesh_entry(a, - b, c, d) S ) ...+> [akpm@linux-foundation.org: drop bogus change from net/ipv4/raw.c] [akpm@linux-foundation.org: drop bogus hunk from net/ipv6/raw.c] [akpm@linux-foundation.org: checkpatch fixes] [akpm@linux-foundation.org: fix warnings] [akpm@linux-foudnation.org: redo intrusive kvm changes] Tested-by: Peter Senna Tschudin <peter.senna@gmail.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Sasha Levin <sasha.levin@oracle.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Gleb Natapov <gleb@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-28 01:06:00 +00:00
hlist_for_each_entry(old, &type->fs_supers, s_instances) {
if (!test(old, data))
continue;
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
if (user_ns != old->s_user_ns) {
spin_unlock(&sb_lock);
if (s) {
up_write(&s->s_umount);
destroy_super(s);
}
return ERR_PTR(-EBUSY);
}
if (!grab_super(old))
goto retry;
if (s) {
up_write(&s->s_umount);
destroy_super(s);
s = NULL;
}
return old;
}
}
if (!s) {
spin_unlock(&sb_lock);
fs: Better permission checking for submounts To support unprivileged users mounting filesystems two permission checks have to be performed: a test to see if the user allowed to create a mount in the mount namespace, and a test to see if the user is allowed to access the specified filesystem. The automount case is special in that mounting the original filesystem grants permission to mount the sub-filesystems, to any user who happens to stumble across the their mountpoint and satisfies the ordinary filesystem permission checks. Attempting to handle the automount case by using override_creds almost works. It preserves the idea that permission to mount the original filesystem is permission to mount the sub-filesystem. Unfortunately using override_creds messes up the filesystems ordinary permission checks. Solve this by being explicit that a mount is a submount by introducing vfs_submount, and using it where appropriate. vfs_submount uses a new mount internal mount flags MS_SUBMOUNT, to let sget and friends know that a mount is a submount so they can take appropriate action. sget and sget_userns are modified to not perform any permission checks on submounts. follow_automount is modified to stop using override_creds as that has proven problemantic. do_mount is modified to always remove the new MS_SUBMOUNT flag so that we know userspace will never by able to specify it. autofs4 is modified to stop using current_real_cred that was put in there to handle the previous version of submount permission checking. cifs is modified to pass the mountpoint all of the way down to vfs_submount. debugfs is modified to pass the mountpoint all of the way down to trace_automount by adding a new parameter. To make this change easier a new typedef debugfs_automount_t is introduced to capture the type of the debugfs automount function. Cc: stable@vger.kernel.org Fixes: 069d5ac9ae0d ("autofs: Fix automounts by using current_real_cred()->uid") Fixes: aeaa4a79ff6a ("fs: Call d_automount with the filesystems creds") Reviewed-by: Trond Myklebust <trond.myklebust@primarydata.com> Reviewed-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-01-31 17:06:16 +00:00
s = alloc_super(type, (flags & ~MS_SUBMOUNT), user_ns);
if (!s)
return ERR_PTR(-ENOMEM);
goto retry;
}
err = set(s, data);
if (err) {
spin_unlock(&sb_lock);
up_write(&s->s_umount);
destroy_super(s);
return ERR_PTR(err);
}
s->s_type = type;
strlcpy(s->s_id, type->name, sizeof(s->s_id));
list_add_tail(&s->s_list, &super_blocks);
hlist_add_head(&s->s_instances, &type->fs_supers);
spin_unlock(&sb_lock);
get_filesystem(type);
register_shrinker(&s->s_shrink);
return s;
}
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
EXPORT_SYMBOL(sget_userns);
/**
* sget - find or create a superblock
* @type: filesystem type superblock should belong to
* @test: comparison callback
* @set: setup callback
* @flags: mount flags
* @data: argument to each of them
*/
struct super_block *sget(struct file_system_type *type,
int (*test)(struct super_block *,void *),
int (*set)(struct super_block *,void *),
int flags,
void *data)
{
struct user_namespace *user_ns = current_user_ns();
fs: Better permission checking for submounts To support unprivileged users mounting filesystems two permission checks have to be performed: a test to see if the user allowed to create a mount in the mount namespace, and a test to see if the user is allowed to access the specified filesystem. The automount case is special in that mounting the original filesystem grants permission to mount the sub-filesystems, to any user who happens to stumble across the their mountpoint and satisfies the ordinary filesystem permission checks. Attempting to handle the automount case by using override_creds almost works. It preserves the idea that permission to mount the original filesystem is permission to mount the sub-filesystem. Unfortunately using override_creds messes up the filesystems ordinary permission checks. Solve this by being explicit that a mount is a submount by introducing vfs_submount, and using it where appropriate. vfs_submount uses a new mount internal mount flags MS_SUBMOUNT, to let sget and friends know that a mount is a submount so they can take appropriate action. sget and sget_userns are modified to not perform any permission checks on submounts. follow_automount is modified to stop using override_creds as that has proven problemantic. do_mount is modified to always remove the new MS_SUBMOUNT flag so that we know userspace will never by able to specify it. autofs4 is modified to stop using current_real_cred that was put in there to handle the previous version of submount permission checking. cifs is modified to pass the mountpoint all of the way down to vfs_submount. debugfs is modified to pass the mountpoint all of the way down to trace_automount by adding a new parameter. To make this change easier a new typedef debugfs_automount_t is introduced to capture the type of the debugfs automount function. Cc: stable@vger.kernel.org Fixes: 069d5ac9ae0d ("autofs: Fix automounts by using current_real_cred()->uid") Fixes: aeaa4a79ff6a ("fs: Call d_automount with the filesystems creds") Reviewed-by: Trond Myklebust <trond.myklebust@primarydata.com> Reviewed-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-01-31 17:06:16 +00:00
/* We don't yet pass the user namespace of the parent
* mount through to here so always use &init_user_ns
* until that changes.
*/
if (flags & MS_SUBMOUNT)
user_ns = &init_user_ns;
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
/* Ensure the requestor has permissions over the target filesystem */
fs: Better permission checking for submounts To support unprivileged users mounting filesystems two permission checks have to be performed: a test to see if the user allowed to create a mount in the mount namespace, and a test to see if the user is allowed to access the specified filesystem. The automount case is special in that mounting the original filesystem grants permission to mount the sub-filesystems, to any user who happens to stumble across the their mountpoint and satisfies the ordinary filesystem permission checks. Attempting to handle the automount case by using override_creds almost works. It preserves the idea that permission to mount the original filesystem is permission to mount the sub-filesystem. Unfortunately using override_creds messes up the filesystems ordinary permission checks. Solve this by being explicit that a mount is a submount by introducing vfs_submount, and using it where appropriate. vfs_submount uses a new mount internal mount flags MS_SUBMOUNT, to let sget and friends know that a mount is a submount so they can take appropriate action. sget and sget_userns are modified to not perform any permission checks on submounts. follow_automount is modified to stop using override_creds as that has proven problemantic. do_mount is modified to always remove the new MS_SUBMOUNT flag so that we know userspace will never by able to specify it. autofs4 is modified to stop using current_real_cred that was put in there to handle the previous version of submount permission checking. cifs is modified to pass the mountpoint all of the way down to vfs_submount. debugfs is modified to pass the mountpoint all of the way down to trace_automount by adding a new parameter. To make this change easier a new typedef debugfs_automount_t is introduced to capture the type of the debugfs automount function. Cc: stable@vger.kernel.org Fixes: 069d5ac9ae0d ("autofs: Fix automounts by using current_real_cred()->uid") Fixes: aeaa4a79ff6a ("fs: Call d_automount with the filesystems creds") Reviewed-by: Trond Myklebust <trond.myklebust@primarydata.com> Reviewed-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-01-31 17:06:16 +00:00
if (!(flags & (MS_KERNMOUNT|MS_SUBMOUNT)) && !ns_capable(user_ns, CAP_SYS_ADMIN))
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
return ERR_PTR(-EPERM);
return sget_userns(type, test, set, flags, user_ns, data);
}
EXPORT_SYMBOL(sget);
void drop_super(struct super_block *sb)
{
up_read(&sb->s_umount);
put_super(sb);
}
EXPORT_SYMBOL(drop_super);
void drop_super_exclusive(struct super_block *sb)
{
up_write(&sb->s_umount);
put_super(sb);
}
EXPORT_SYMBOL(drop_super_exclusive);
/**
* iterate_supers - call function for all active superblocks
* @f: function to call
* @arg: argument to pass to it
*
* Scans the superblock list and calls given function, passing it
* locked superblock and given argument.
*/
void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
{
struct super_block *sb, *p = NULL;
spin_lock(&sb_lock);
list_for_each_entry(sb, &super_blocks, s_list) {
if (hlist_unhashed(&sb->s_instances))
continue;
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
if (sb->s_root && (sb->s_flags & MS_BORN))
f(sb, arg);
up_read(&sb->s_umount);
spin_lock(&sb_lock);
if (p)
__put_super(p);
p = sb;
}
if (p)
__put_super(p);
spin_unlock(&sb_lock);
}
/**
* iterate_supers_type - call function for superblocks of given type
* @type: fs type
* @f: function to call
* @arg: argument to pass to it
*
* Scans the superblock list and calls given function, passing it
* locked superblock and given argument.
*/
void iterate_supers_type(struct file_system_type *type,
void (*f)(struct super_block *, void *), void *arg)
{
struct super_block *sb, *p = NULL;
spin_lock(&sb_lock);
hlist: drop the node parameter from iterators I'm not sure why, but the hlist for each entry iterators were conceived list_for_each_entry(pos, head, member) The hlist ones were greedy and wanted an extra parameter: hlist_for_each_entry(tpos, pos, head, member) Why did they need an extra pos parameter? I'm not quite sure. Not only they don't really need it, it also prevents the iterator from looking exactly like the list iterator, which is unfortunate. Besides the semantic patch, there was some manual work required: - Fix up the actual hlist iterators in linux/list.h - Fix up the declaration of other iterators based on the hlist ones. - A very small amount of places were using the 'node' parameter, this was modified to use 'obj->member' instead. - Coccinelle didn't handle the hlist_for_each_entry_safe iterator properly, so those had to be fixed up manually. The semantic patch which is mostly the work of Peter Senna Tschudin is here: @@ iterator name hlist_for_each_entry, hlist_for_each_entry_continue, hlist_for_each_entry_from, hlist_for_each_entry_rcu, hlist_for_each_entry_rcu_bh, hlist_for_each_entry_continue_rcu_bh, for_each_busy_worker, ax25_uid_for_each, ax25_for_each, inet_bind_bucket_for_each, sctp_for_each_hentry, sk_for_each, sk_for_each_rcu, sk_for_each_from, sk_for_each_safe, sk_for_each_bound, hlist_for_each_entry_safe, hlist_for_each_entry_continue_rcu, nr_neigh_for_each, nr_neigh_for_each_safe, nr_node_for_each, nr_node_for_each_safe, for_each_gfn_indirect_valid_sp, for_each_gfn_sp, for_each_host; type T; expression a,c,d,e; identifier b; statement S; @@ -T b; <+... when != b ( hlist_for_each_entry(a, - b, c, d) S | hlist_for_each_entry_continue(a, - b, c) S | hlist_for_each_entry_from(a, - b, c) S | hlist_for_each_entry_rcu(a, - b, c, d) S | hlist_for_each_entry_rcu_bh(a, - b, c, d) S | hlist_for_each_entry_continue_rcu_bh(a, - b, c) S | for_each_busy_worker(a, c, - b, d) S | ax25_uid_for_each(a, - b, c) S | ax25_for_each(a, - b, c) S | inet_bind_bucket_for_each(a, - b, c) S | sctp_for_each_hentry(a, - b, c) S | sk_for_each(a, - b, c) S | sk_for_each_rcu(a, - b, c) S | sk_for_each_from -(a, b) +(a) S + sk_for_each_from(a) S | sk_for_each_safe(a, - b, c, d) S | sk_for_each_bound(a, - b, c) S | hlist_for_each_entry_safe(a, - b, c, d, e) S | hlist_for_each_entry_continue_rcu(a, - b, c) S | nr_neigh_for_each(a, - b, c) S | nr_neigh_for_each_safe(a, - b, c, d) S | nr_node_for_each(a, - b, c) S | nr_node_for_each_safe(a, - b, c, d) S | - for_each_gfn_sp(a, c, d, b) S + for_each_gfn_sp(a, c, d) S | - for_each_gfn_indirect_valid_sp(a, c, d, b) S + for_each_gfn_indirect_valid_sp(a, c, d) S | for_each_host(a, - b, c) S | for_each_host_safe(a, - b, c, d) S | for_each_mesh_entry(a, - b, c, d) S ) ...+> [akpm@linux-foundation.org: drop bogus change from net/ipv4/raw.c] [akpm@linux-foundation.org: drop bogus hunk from net/ipv6/raw.c] [akpm@linux-foundation.org: checkpatch fixes] [akpm@linux-foundation.org: fix warnings] [akpm@linux-foudnation.org: redo intrusive kvm changes] Tested-by: Peter Senna Tschudin <peter.senna@gmail.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Sasha Levin <sasha.levin@oracle.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Gleb Natapov <gleb@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-02-28 01:06:00 +00:00
hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
if (sb->s_root && (sb->s_flags & MS_BORN))
f(sb, arg);
up_read(&sb->s_umount);
spin_lock(&sb_lock);
if (p)
__put_super(p);
p = sb;
}
if (p)
__put_super(p);
spin_unlock(&sb_lock);
}
EXPORT_SYMBOL(iterate_supers_type);
static struct super_block *__get_super(struct block_device *bdev, bool excl)
{
struct super_block *sb;
if (!bdev)
return NULL;
spin_lock(&sb_lock);
rescan:
list_for_each_entry(sb, &super_blocks, s_list) {
if (hlist_unhashed(&sb->s_instances))
continue;
if (sb->s_bdev == bdev) {
sb->s_count++;
spin_unlock(&sb_lock);
if (!excl)
down_read(&sb->s_umount);
else
down_write(&sb->s_umount);
/* still alive? */
if (sb->s_root && (sb->s_flags & MS_BORN))
return sb;
if (!excl)
up_read(&sb->s_umount);
else
up_write(&sb->s_umount);
/* nope, got unmounted */
spin_lock(&sb_lock);
__put_super(sb);
goto rescan;
}
}
spin_unlock(&sb_lock);
return NULL;
}
/**
* get_super - get the superblock of a device
* @bdev: device to get the superblock for
*
* Scans the superblock list and finds the superblock of the file system
* mounted on the device given. %NULL is returned if no match is found.
*/
struct super_block *get_super(struct block_device *bdev)
{
return __get_super(bdev, false);
}
EXPORT_SYMBOL(get_super);
static struct super_block *__get_super_thawed(struct block_device *bdev,
bool excl)
{
while (1) {
struct super_block *s = __get_super(bdev, excl);
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
if (!s || s->s_writers.frozen == SB_UNFROZEN)
return s;
if (!excl)
up_read(&s->s_umount);
else
up_write(&s->s_umount);
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
wait_event(s->s_writers.wait_unfrozen,
s->s_writers.frozen == SB_UNFROZEN);
put_super(s);
}
}
/**
* get_super_thawed - get thawed superblock of a device
* @bdev: device to get the superblock for
*
* Scans the superblock list and finds the superblock of the file system
* mounted on the device. The superblock is returned once it is thawed
* (or immediately if it was not frozen). %NULL is returned if no match
* is found.
*/
struct super_block *get_super_thawed(struct block_device *bdev)
{
return __get_super_thawed(bdev, false);
}
EXPORT_SYMBOL(get_super_thawed);
/**
* get_super_exclusive_thawed - get thawed superblock of a device
* @bdev: device to get the superblock for
*
* Scans the superblock list and finds the superblock of the file system
* mounted on the device. The superblock is returned once it is thawed
* (or immediately if it was not frozen) and s_umount semaphore is held
* in exclusive mode. %NULL is returned if no match is found.
*/
struct super_block *get_super_exclusive_thawed(struct block_device *bdev)
{
return __get_super_thawed(bdev, true);
}
EXPORT_SYMBOL(get_super_exclusive_thawed);
/**
* get_active_super - get an active reference to the superblock of a device
* @bdev: device to get the superblock for
*
* Scans the superblock list and finds the superblock of the file system
* mounted on the device given. Returns the superblock with an active
* reference or %NULL if none was found.
*/
struct super_block *get_active_super(struct block_device *bdev)
{
struct super_block *sb;
if (!bdev)
return NULL;
restart:
spin_lock(&sb_lock);
list_for_each_entry(sb, &super_blocks, s_list) {
if (hlist_unhashed(&sb->s_instances))
continue;
if (sb->s_bdev == bdev) {
livelock avoidance in sget() Eric Sandeen has found a nasty livelock in sget() - take a mount(2) about to fail. The superblock is on ->fs_supers, ->s_umount is held exclusive, ->s_active is 1. Along comes two more processes, trying to mount the same thing; sget() in each is picking that superblock, bumping ->s_count and trying to grab ->s_umount. ->s_active is 3 now. Original mount(2) finally gets to deactivate_locked_super() on failure; ->s_active is 2, superblock is still ->fs_supers because shutdown will *not* happen until ->s_active hits 0. ->s_umount is dropped and now we have two processes chasing each other: s_active = 2, A acquired ->s_umount, B blocked A sees that the damn thing is stillborn, does deactivate_locked_super() s_active = 1, A drops ->s_umount, B gets it A restarts the search and finds the same superblock. And bumps it ->s_active. s_active = 2, B holds ->s_umount, A blocked on trying to get it ... and we are in the earlier situation with A and B switched places. The root cause, of course, is that ->s_active should not grow until we'd got MS_BORN. Then failing ->mount() will have deactivate_locked_super() shut the damn thing down. Fortunately, it's easy to do - the key point is that grab_super() is called only for superblocks currently on ->fs_supers, so it can bump ->s_count and grab ->s_umount first, then check MS_BORN and bump ->s_active; we must never increment ->s_count for superblocks past ->kill_sb(), but grab_super() is never called for those. The bug is pretty old; we would've caught it by now, if not for accidental exclusion between sget() for block filesystems; the things like cgroup or e.g. mtd-based filesystems don't have anything of that sort, so they get bitten. The right way to deal with that is obviously to fix sget()... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-07-19 23:13:55 +00:00
if (!grab_super(sb))
goto restart;
livelock avoidance in sget() Eric Sandeen has found a nasty livelock in sget() - take a mount(2) about to fail. The superblock is on ->fs_supers, ->s_umount is held exclusive, ->s_active is 1. Along comes two more processes, trying to mount the same thing; sget() in each is picking that superblock, bumping ->s_count and trying to grab ->s_umount. ->s_active is 3 now. Original mount(2) finally gets to deactivate_locked_super() on failure; ->s_active is 2, superblock is still ->fs_supers because shutdown will *not* happen until ->s_active hits 0. ->s_umount is dropped and now we have two processes chasing each other: s_active = 2, A acquired ->s_umount, B blocked A sees that the damn thing is stillborn, does deactivate_locked_super() s_active = 1, A drops ->s_umount, B gets it A restarts the search and finds the same superblock. And bumps it ->s_active. s_active = 2, B holds ->s_umount, A blocked on trying to get it ... and we are in the earlier situation with A and B switched places. The root cause, of course, is that ->s_active should not grow until we'd got MS_BORN. Then failing ->mount() will have deactivate_locked_super() shut the damn thing down. Fortunately, it's easy to do - the key point is that grab_super() is called only for superblocks currently on ->fs_supers, so it can bump ->s_count and grab ->s_umount first, then check MS_BORN and bump ->s_active; we must never increment ->s_count for superblocks past ->kill_sb(), but grab_super() is never called for those. The bug is pretty old; we would've caught it by now, if not for accidental exclusion between sget() for block filesystems; the things like cgroup or e.g. mtd-based filesystems don't have anything of that sort, so they get bitten. The right way to deal with that is obviously to fix sget()... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-07-19 23:13:55 +00:00
up_write(&sb->s_umount);
return sb;
}
}
spin_unlock(&sb_lock);
return NULL;
}
struct super_block *user_get_super(dev_t dev)
{
struct super_block *sb;
spin_lock(&sb_lock);
rescan:
list_for_each_entry(sb, &super_blocks, s_list) {
if (hlist_unhashed(&sb->s_instances))
continue;
if (sb->s_dev == dev) {
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
/* still alive? */
if (sb->s_root && (sb->s_flags & MS_BORN))
return sb;
up_read(&sb->s_umount);
/* nope, got unmounted */
spin_lock(&sb_lock);
__put_super(sb);
goto rescan;
}
}
spin_unlock(&sb_lock);
return NULL;
}
/**
* do_remount_sb - asks filesystem to change mount options.
* @sb: superblock in question
* @flags: numeric part of options
* @data: the rest of options
* @force: whether or not to force the change
*
* Alters the mount options of a mounted file system.
*/
int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
{
int retval;
int remount_ro;
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
if (sb->s_writers.frozen != SB_UNFROZEN)
return -EBUSY;
[PATCH] BLOCK: Make it possible to disable the block layer [try #6] Make it possible to disable the block layer. Not all embedded devices require it, some can make do with just JFFS2, NFS, ramfs, etc - none of which require the block layer to be present. This patch does the following: (*) Introduces CONFIG_BLOCK to disable the block layer, buffering and blockdev support. (*) Adds dependencies on CONFIG_BLOCK to any configuration item that controls an item that uses the block layer. This includes: (*) Block I/O tracing. (*) Disk partition code. (*) All filesystems that are block based, eg: Ext3, ReiserFS, ISOFS. (*) The SCSI layer. As far as I can tell, even SCSI chardevs use the block layer to do scheduling. Some drivers that use SCSI facilities - such as USB storage - end up disabled indirectly from this. (*) Various block-based device drivers, such as IDE and the old CDROM drivers. (*) MTD blockdev handling and FTL. (*) JFFS - which uses set_bdev_super(), something it could avoid doing by taking a leaf out of JFFS2's book. (*) Makes most of the contents of linux/blkdev.h, linux/buffer_head.h and linux/elevator.h contingent on CONFIG_BLOCK being set. sector_div() is, however, still used in places, and so is still available. (*) Also made contingent are the contents of linux/mpage.h, linux/genhd.h and parts of linux/fs.h. (*) Makes a number of files in fs/ contingent on CONFIG_BLOCK. (*) Makes mm/bounce.c (bounce buffering) contingent on CONFIG_BLOCK. (*) set_page_dirty() doesn't call __set_page_dirty_buffers() if CONFIG_BLOCK is not enabled. (*) fs/no-block.c is created to hold out-of-line stubs and things that are required when CONFIG_BLOCK is not set: (*) Default blockdev file operations (to give error ENODEV on opening). (*) Makes some /proc changes: (*) /proc/devices does not list any blockdevs. (*) /proc/diskstats and /proc/partitions are contingent on CONFIG_BLOCK. (*) Makes some compat ioctl handling contingent on CONFIG_BLOCK. (*) If CONFIG_BLOCK is not defined, makes sys_quotactl() return -ENODEV if given command other than Q_SYNC or if a special device is specified. (*) In init/do_mounts.c, no reference is made to the blockdev routines if CONFIG_BLOCK is not defined. This does not prohibit NFS roots or JFFS2. (*) The bdflush, ioprio_set and ioprio_get syscalls can now be absent (return error ENOSYS by way of cond_syscall if so). (*) The seclvl_bd_claim() and seclvl_bd_release() security calls do nothing if CONFIG_BLOCK is not set, since they can't then happen. Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2006-09-30 18:45:40 +00:00
#ifdef CONFIG_BLOCK
if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
return -EACCES;
[PATCH] BLOCK: Make it possible to disable the block layer [try #6] Make it possible to disable the block layer. Not all embedded devices require it, some can make do with just JFFS2, NFS, ramfs, etc - none of which require the block layer to be present. This patch does the following: (*) Introduces CONFIG_BLOCK to disable the block layer, buffering and blockdev support. (*) Adds dependencies on CONFIG_BLOCK to any configuration item that controls an item that uses the block layer. This includes: (*) Block I/O tracing. (*) Disk partition code. (*) All filesystems that are block based, eg: Ext3, ReiserFS, ISOFS. (*) The SCSI layer. As far as I can tell, even SCSI chardevs use the block layer to do scheduling. Some drivers that use SCSI facilities - such as USB storage - end up disabled indirectly from this. (*) Various block-based device drivers, such as IDE and the old CDROM drivers. (*) MTD blockdev handling and FTL. (*) JFFS - which uses set_bdev_super(), something it could avoid doing by taking a leaf out of JFFS2's book. (*) Makes most of the contents of linux/blkdev.h, linux/buffer_head.h and linux/elevator.h contingent on CONFIG_BLOCK being set. sector_div() is, however, still used in places, and so is still available. (*) Also made contingent are the contents of linux/mpage.h, linux/genhd.h and parts of linux/fs.h. (*) Makes a number of files in fs/ contingent on CONFIG_BLOCK. (*) Makes mm/bounce.c (bounce buffering) contingent on CONFIG_BLOCK. (*) set_page_dirty() doesn't call __set_page_dirty_buffers() if CONFIG_BLOCK is not enabled. (*) fs/no-block.c is created to hold out-of-line stubs and things that are required when CONFIG_BLOCK is not set: (*) Default blockdev file operations (to give error ENODEV on opening). (*) Makes some /proc changes: (*) /proc/devices does not list any blockdevs. (*) /proc/diskstats and /proc/partitions are contingent on CONFIG_BLOCK. (*) Makes some compat ioctl handling contingent on CONFIG_BLOCK. (*) If CONFIG_BLOCK is not defined, makes sys_quotactl() return -ENODEV if given command other than Q_SYNC or if a special device is specified. (*) In init/do_mounts.c, no reference is made to the blockdev routines if CONFIG_BLOCK is not defined. This does not prohibit NFS roots or JFFS2. (*) The bdflush, ioprio_set and ioprio_get syscalls can now be absent (return error ENOSYS by way of cond_syscall if so). (*) The seclvl_bd_claim() and seclvl_bd_release() security calls do nothing if CONFIG_BLOCK is not set, since they can't then happen. Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2006-09-30 18:45:40 +00:00
#endif
2009-12-22 00:28:53 +00:00
remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY);
if (remount_ro) {
if (!hlist_empty(&sb->s_pins)) {
up_write(&sb->s_umount);
group_pin_kill(&sb->s_pins);
down_write(&sb->s_umount);
if (!sb->s_root)
return 0;
if (sb->s_writers.frozen != SB_UNFROZEN)
return -EBUSY;
remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY);
}
}
shrink_dcache_sb(sb);
/* If we are remounting RDONLY and current sb is read/write,
make sure there are no rw files opened */
2009-12-22 00:28:53 +00:00
if (remount_ro) {
if (force) {
sb->s_readonly_remount = 1;
smp_wmb();
} else {
retval = sb_prepare_remount_readonly(sb);
if (retval)
return retval;
}
}
if (sb->s_op->remount_fs) {
retval = sb->s_op->remount_fs(sb, &flags, data);
if (retval) {
if (!force)
goto cancel_readonly;
/* If forced remount, go ahead despite any errors */
WARN(1, "forced remount of a %s fs returned %i\n",
sb->s_type->name, retval);
}
}
sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
/* Needs to be ordered wrt mnt_is_readonly() */
smp_wmb();
sb->s_readonly_remount = 0;
2009-12-22 00:28:53 +00:00
/*
* Some filesystems modify their metadata via some other path than the
* bdev buffer cache (eg. use a private mapping, or directories in
* pagecache, etc). Also file data modifications go via their own
* mappings. So If we try to mount readonly then copy the filesystem
* from bdev, we could get stale data, so invalidate it to give a best
* effort at coherency.
*/
if (remount_ro && sb->s_bdev)
invalidate_bdev(sb->s_bdev);
return 0;
cancel_readonly:
sb->s_readonly_remount = 0;
return retval;
}
static void do_emergency_remount(struct work_struct *work)
{
struct super_block *sb, *p = NULL;
spin_lock(&sb_lock);
list_for_each_entry(sb, &super_blocks, s_list) {
if (hlist_unhashed(&sb->s_instances))
continue;
sb->s_count++;
spin_unlock(&sb_lock);
down_write(&sb->s_umount);
if (sb->s_root && sb->s_bdev && (sb->s_flags & MS_BORN) &&
!(sb->s_flags & MS_RDONLY)) {
/*
* What lock protects sb->s_flags??
*/
do_remount_sb(sb, MS_RDONLY, NULL, 1);
}
up_write(&sb->s_umount);
spin_lock(&sb_lock);
if (p)
__put_super(p);
p = sb;
}
if (p)
__put_super(p);
spin_unlock(&sb_lock);
kfree(work);
printk("Emergency Remount complete\n");
}
void emergency_remount(void)
{
struct work_struct *work;
work = kmalloc(sizeof(*work), GFP_ATOMIC);
if (work) {
INIT_WORK(work, do_emergency_remount);
schedule_work(work);
}
}
/*
* Unnamed block devices are dummy devices used by virtual
* filesystems which don't use real block-devices. -- jrs
*/
static DEFINE_IDA(unnamed_dev_ida);
static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
/* Many userspace utilities consider an FSID of 0 invalid.
* Always return at least 1 from get_anon_bdev.
*/
static int unnamed_dev_start = 1;
int get_anon_bdev(dev_t *p)
{
int dev;
int error;
retry:
if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
return -ENOMEM;
spin_lock(&unnamed_dev_lock);
error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);
if (!error)
unnamed_dev_start = dev + 1;
spin_unlock(&unnamed_dev_lock);
if (error == -EAGAIN)
/* We raced and lost with another CPU. */
goto retry;
else if (error)
return -EAGAIN;
if (dev >= (1 << MINORBITS)) {
spin_lock(&unnamed_dev_lock);
ida_remove(&unnamed_dev_ida, dev);
if (unnamed_dev_start > dev)
unnamed_dev_start = dev;
spin_unlock(&unnamed_dev_lock);
return -EMFILE;
}
*p = MKDEV(0, dev & MINORMASK);
return 0;
}
EXPORT_SYMBOL(get_anon_bdev);
void free_anon_bdev(dev_t dev)
{
int slot = MINOR(dev);
spin_lock(&unnamed_dev_lock);
ida_remove(&unnamed_dev_ida, slot);
if (slot < unnamed_dev_start)
unnamed_dev_start = slot;
spin_unlock(&unnamed_dev_lock);
}
EXPORT_SYMBOL(free_anon_bdev);
int set_anon_super(struct super_block *s, void *data)
{
return get_anon_bdev(&s->s_dev);
}
EXPORT_SYMBOL(set_anon_super);
void kill_anon_super(struct super_block *sb)
{
dev_t dev = sb->s_dev;
generic_shutdown_super(sb);
free_anon_bdev(dev);
}
EXPORT_SYMBOL(kill_anon_super);
void kill_litter_super(struct super_block *sb)
{
if (sb->s_root)
d_genocide(sb->s_root);
kill_anon_super(sb);
}
EXPORT_SYMBOL(kill_litter_super);
static int ns_test_super(struct super_block *sb, void *data)
{
return sb->s_fs_info == data;
}
static int ns_set_super(struct super_block *sb, void *data)
{
sb->s_fs_info = data;
return set_anon_super(sb, NULL);
}
struct dentry *mount_ns(struct file_system_type *fs_type,
int flags, void *data, void *ns, struct user_namespace *user_ns,
int (*fill_super)(struct super_block *, void *, int))
{
struct super_block *sb;
/* Don't allow mounting unless the caller has CAP_SYS_ADMIN
* over the namespace.
*/
if (!(flags & MS_KERNMOUNT) && !ns_capable(user_ns, CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);
fs: Add user namespace member to struct super_block Start marking filesystems with a user namespace owner, s_user_ns. In this change this is only used for permission checks of who may mount a filesystem. Ultimately s_user_ns will be used for translating ids and checking capabilities for filesystems mounted from user namespaces. The default policy for setting s_user_ns is implemented in sget(), which arranges for s_user_ns to be set to current_user_ns() and to ensure that the mounter of the filesystem has CAP_SYS_ADMIN in that user_ns. The guts of sget are split out into another function sget_userns(). The function sget_userns calls alloc_super with the specified user namespace or it verifies the existing superblock that was found has the expected user namespace, and fails with EBUSY when it is not. This failing prevents users with the wrong privileges mounting a filesystem. The reason for the split of sget_userns from sget is that in some cases such as mount_ns and kernfs_mount_ns a different policy for permission checking of mounts and setting s_user_ns is necessary, and the existence of sget_userns() allows those policies to be implemented. The helper mount_ns is expected to be used for filesystems such as proc and mqueuefs which present per namespace information. The function mount_ns is modified to call sget_userns instead of sget to ensure the user namespace owner of the namespace whose information is presented by the filesystem is used on the superblock. For sysfs and cgroup the appropriate permission checks are already in place, and kernfs_mount_ns is modified to call sget_userns so that the init_user_ns is the only user namespace used. For the cgroup filesystem cgroup namespace mounts are bind mounts of a subset of the full cgroup filesystem and as such s_user_ns must be the same for all of them as there is only a single superblock. Mounts of sysfs that vary based on the network namespace could in principle change s_user_ns but it keeps the analysis and implementation of kernfs simpler if that is not supported, and at present there appear to be no benefits from supporting a different s_user_ns on any sysfs mount. Getting the details of setting s_user_ns correct has been a long process. Thanks to Pavel Tikhorirorv who spotted a leak in sget_userns. Thanks to Seth Forshee who has kept the work alive. Thanks-to: Seth Forshee <seth.forshee@canonical.com> Thanks-to: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Acked-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2016-05-24 14:29:01 +00:00
sb = sget_userns(fs_type, ns_test_super, ns_set_super, flags,
user_ns, ns);
if (IS_ERR(sb))
return ERR_CAST(sb);
if (!sb->s_root) {
int err;
err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
if (err) {
deactivate_locked_super(sb);
return ERR_PTR(err);
}
sb->s_flags |= MS_ACTIVE;
}
return dget(sb->s_root);
}
EXPORT_SYMBOL(mount_ns);
[PATCH] BLOCK: Make it possible to disable the block layer [try #6] Make it possible to disable the block layer. Not all embedded devices require it, some can make do with just JFFS2, NFS, ramfs, etc - none of which require the block layer to be present. This patch does the following: (*) Introduces CONFIG_BLOCK to disable the block layer, buffering and blockdev support. (*) Adds dependencies on CONFIG_BLOCK to any configuration item that controls an item that uses the block layer. This includes: (*) Block I/O tracing. (*) Disk partition code. (*) All filesystems that are block based, eg: Ext3, ReiserFS, ISOFS. (*) The SCSI layer. As far as I can tell, even SCSI chardevs use the block layer to do scheduling. Some drivers that use SCSI facilities - such as USB storage - end up disabled indirectly from this. (*) Various block-based device drivers, such as IDE and the old CDROM drivers. (*) MTD blockdev handling and FTL. (*) JFFS - which uses set_bdev_super(), something it could avoid doing by taking a leaf out of JFFS2's book. (*) Makes most of the contents of linux/blkdev.h, linux/buffer_head.h and linux/elevator.h contingent on CONFIG_BLOCK being set. sector_div() is, however, still used in places, and so is still available. (*) Also made contingent are the contents of linux/mpage.h, linux/genhd.h and parts of linux/fs.h. (*) Makes a number of files in fs/ contingent on CONFIG_BLOCK. (*) Makes mm/bounce.c (bounce buffering) contingent on CONFIG_BLOCK. (*) set_page_dirty() doesn't call __set_page_dirty_buffers() if CONFIG_BLOCK is not enabled. (*) fs/no-block.c is created to hold out-of-line stubs and things that are required when CONFIG_BLOCK is not set: (*) Default blockdev file operations (to give error ENODEV on opening). (*) Makes some /proc changes: (*) /proc/devices does not list any blockdevs. (*) /proc/diskstats and /proc/partitions are contingent on CONFIG_BLOCK. (*) Makes some compat ioctl handling contingent on CONFIG_BLOCK. (*) If CONFIG_BLOCK is not defined, makes sys_quotactl() return -ENODEV if given command other than Q_SYNC or if a special device is specified. (*) In init/do_mounts.c, no reference is made to the blockdev routines if CONFIG_BLOCK is not defined. This does not prohibit NFS roots or JFFS2. (*) The bdflush, ioprio_set and ioprio_get syscalls can now be absent (return error ENOSYS by way of cond_syscall if so). (*) The seclvl_bd_claim() and seclvl_bd_release() security calls do nothing if CONFIG_BLOCK is not set, since they can't then happen. Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2006-09-30 18:45:40 +00:00
#ifdef CONFIG_BLOCK
static int set_bdev_super(struct super_block *s, void *data)
{
s->s_bdev = data;
s->s_dev = s->s_bdev->bd_dev;
/*
* We set the bdi here to the queue backing, file systems can
* overwrite this in ->fill_super()
*/
s->s_bdi = bdev_get_queue(s->s_bdev)->backing_dev_info;
return 0;
}
static int test_bdev_super(struct super_block *s, void *data)
{
return (void *)s->s_bdev == data;
}
struct dentry *mount_bdev(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data,
int (*fill_super)(struct super_block *, void *, int))
{
struct block_device *bdev;
struct super_block *s;
fmode_t mode = FMODE_READ | FMODE_EXCL;
int error = 0;
if (!(flags & MS_RDONLY))
mode |= FMODE_WRITE;
bdev = blkdev_get_by_path(dev_name, mode, fs_type);
if (IS_ERR(bdev))
return ERR_CAST(bdev);
/*
* once the super is inserted into the list by sget, s_umount
* will protect the lockfs code from trying to start a snapshot
* while we are mounting
*/
mutex_lock(&bdev->bd_fsfreeze_mutex);
if (bdev->bd_fsfreeze_count > 0) {
mutex_unlock(&bdev->bd_fsfreeze_mutex);
error = -EBUSY;
goto error_bdev;
}
s = sget(fs_type, test_bdev_super, set_bdev_super, flags | MS_NOSEC,
bdev);
mutex_unlock(&bdev->bd_fsfreeze_mutex);
if (IS_ERR(s))
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
goto error_s;
if (s->s_root) {
if ((flags ^ s->s_flags) & MS_RDONLY) {
deactivate_locked_super(s);
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
error = -EBUSY;
goto error_bdev;
}
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
/*
* s_umount nests inside bd_mutex during
block: make blkdev_get/put() handle exclusive access Over time, block layer has accumulated a set of APIs dealing with bdev open, close, claim and release. * blkdev_get/put() are the primary open and close functions. * bd_claim/release() deal with exclusive open. * open/close_bdev_exclusive() are combination of open and claim and the other way around, respectively. * bd_link/unlink_disk_holder() to create and remove holder/slave symlinks. * open_by_devnum() wraps bdget() + blkdev_get(). The interface is a bit confusing and the decoupling of open and claim makes it impossible to properly guarantee exclusive access as in-kernel open + claim sequence can disturb the existing exclusive open even before the block layer knows the current open if for another exclusive access. Reorganize the interface such that, * blkdev_get() is extended to include exclusive access management. @holder argument is added and, if is @FMODE_EXCL specified, it will gain exclusive access atomically w.r.t. other exclusive accesses. * blkdev_put() is similarly extended. It now takes @mode argument and if @FMODE_EXCL is set, it releases an exclusive access. Also, when the last exclusive claim is released, the holder/slave symlinks are removed automatically. * bd_claim/release() and close_bdev_exclusive() are no longer necessary and either made static or removed. * bd_link_disk_holder() remains the same but bd_unlink_disk_holder() is no longer necessary and removed. * open_bdev_exclusive() becomes a simple wrapper around lookup_bdev() and blkdev_get(). It also has an unexpected extra bdev_read_only() test which probably should be moved into blkdev_get(). * open_by_devnum() is modified to take @holder argument and pass it to blkdev_get(). Most of bdev open/close operations are unified into blkdev_get/put() and most exclusive accesses are tested atomically at the open time (as it should). This cleans up code and removes some, both valid and invalid, but unnecessary all the same, corner cases. open_bdev_exclusive() and open_by_devnum() can use further cleanup - rename to blkdev_get_by_path() and blkdev_get_by_devt() and drop special features. Well, let's leave them for another day. Most conversions are straight-forward. drbd conversion is a bit more involved as there was some reordering, but the logic should stay the same. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Neil Brown <neilb@suse.de> Acked-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Acked-by: Mike Snitzer <snitzer@redhat.com> Acked-by: Philipp Reisner <philipp.reisner@linbit.com> Cc: Peter Osterlund <petero2@telia.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Jan Kara <jack@suse.cz> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andreas Dilger <adilger.kernel@dilger.ca> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <joel.becker@oracle.com> Cc: Alex Elder <aelder@sgi.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: dm-devel@redhat.com Cc: drbd-dev@lists.linbit.com Cc: Leo Chen <leochen@broadcom.com> Cc: Scott Branden <sbranden@broadcom.com> Cc: Chris Mason <chris.mason@oracle.com> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com> Cc: Joern Engel <joern@logfs.org> Cc: reiserfs-devel@vger.kernel.org Cc: Alexander Viro <viro@zeniv.linux.org.uk>
2010-11-13 10:55:17 +00:00
* __invalidate_device(). blkdev_put() acquires
* bd_mutex and can't be called under s_umount. Drop
* s_umount temporarily. This is safe as we're
* holding an active reference.
*/
up_write(&s->s_umount);
blkdev_put(bdev, mode);
down_write(&s->s_umount);
} else {
s->s_mode = mode;
snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
sb_set_blocksize(s, block_size(bdev));
error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
if (error) {
deactivate_locked_super(s);
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
goto error;
}
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
s->s_flags |= MS_ACTIVE;
bdev->bd_super = s;
}
return dget(s->s_root);
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
error_s:
error = PTR_ERR(s);
error_bdev:
blkdev_put(bdev, mode);
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
error:
return ERR_PTR(error);
}
EXPORT_SYMBOL(mount_bdev);
void kill_block_super(struct super_block *sb)
{
struct block_device *bdev = sb->s_bdev;
fmode_t mode = sb->s_mode;
bdev->bd_super = NULL;
generic_shutdown_super(sb);
sync_blockdev(bdev);
WARN_ON_ONCE(!(mode & FMODE_EXCL));
block: make blkdev_get/put() handle exclusive access Over time, block layer has accumulated a set of APIs dealing with bdev open, close, claim and release. * blkdev_get/put() are the primary open and close functions. * bd_claim/release() deal with exclusive open. * open/close_bdev_exclusive() are combination of open and claim and the other way around, respectively. * bd_link/unlink_disk_holder() to create and remove holder/slave symlinks. * open_by_devnum() wraps bdget() + blkdev_get(). The interface is a bit confusing and the decoupling of open and claim makes it impossible to properly guarantee exclusive access as in-kernel open + claim sequence can disturb the existing exclusive open even before the block layer knows the current open if for another exclusive access. Reorganize the interface such that, * blkdev_get() is extended to include exclusive access management. @holder argument is added and, if is @FMODE_EXCL specified, it will gain exclusive access atomically w.r.t. other exclusive accesses. * blkdev_put() is similarly extended. It now takes @mode argument and if @FMODE_EXCL is set, it releases an exclusive access. Also, when the last exclusive claim is released, the holder/slave symlinks are removed automatically. * bd_claim/release() and close_bdev_exclusive() are no longer necessary and either made static or removed. * bd_link_disk_holder() remains the same but bd_unlink_disk_holder() is no longer necessary and removed. * open_bdev_exclusive() becomes a simple wrapper around lookup_bdev() and blkdev_get(). It also has an unexpected extra bdev_read_only() test which probably should be moved into blkdev_get(). * open_by_devnum() is modified to take @holder argument and pass it to blkdev_get(). Most of bdev open/close operations are unified into blkdev_get/put() and most exclusive accesses are tested atomically at the open time (as it should). This cleans up code and removes some, both valid and invalid, but unnecessary all the same, corner cases. open_bdev_exclusive() and open_by_devnum() can use further cleanup - rename to blkdev_get_by_path() and blkdev_get_by_devt() and drop special features. Well, let's leave them for another day. Most conversions are straight-forward. drbd conversion is a bit more involved as there was some reordering, but the logic should stay the same. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Neil Brown <neilb@suse.de> Acked-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Acked-by: Mike Snitzer <snitzer@redhat.com> Acked-by: Philipp Reisner <philipp.reisner@linbit.com> Cc: Peter Osterlund <petero2@telia.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Jan Kara <jack@suse.cz> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andreas Dilger <adilger.kernel@dilger.ca> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <joel.becker@oracle.com> Cc: Alex Elder <aelder@sgi.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: dm-devel@redhat.com Cc: drbd-dev@lists.linbit.com Cc: Leo Chen <leochen@broadcom.com> Cc: Scott Branden <sbranden@broadcom.com> Cc: Chris Mason <chris.mason@oracle.com> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com> Cc: Joern Engel <joern@logfs.org> Cc: reiserfs-devel@vger.kernel.org Cc: Alexander Viro <viro@zeniv.linux.org.uk>
2010-11-13 10:55:17 +00:00
blkdev_put(bdev, mode | FMODE_EXCL);
}
EXPORT_SYMBOL(kill_block_super);
[PATCH] BLOCK: Make it possible to disable the block layer [try #6] Make it possible to disable the block layer. Not all embedded devices require it, some can make do with just JFFS2, NFS, ramfs, etc - none of which require the block layer to be present. This patch does the following: (*) Introduces CONFIG_BLOCK to disable the block layer, buffering and blockdev support. (*) Adds dependencies on CONFIG_BLOCK to any configuration item that controls an item that uses the block layer. This includes: (*) Block I/O tracing. (*) Disk partition code. (*) All filesystems that are block based, eg: Ext3, ReiserFS, ISOFS. (*) The SCSI layer. As far as I can tell, even SCSI chardevs use the block layer to do scheduling. Some drivers that use SCSI facilities - such as USB storage - end up disabled indirectly from this. (*) Various block-based device drivers, such as IDE and the old CDROM drivers. (*) MTD blockdev handling and FTL. (*) JFFS - which uses set_bdev_super(), something it could avoid doing by taking a leaf out of JFFS2's book. (*) Makes most of the contents of linux/blkdev.h, linux/buffer_head.h and linux/elevator.h contingent on CONFIG_BLOCK being set. sector_div() is, however, still used in places, and so is still available. (*) Also made contingent are the contents of linux/mpage.h, linux/genhd.h and parts of linux/fs.h. (*) Makes a number of files in fs/ contingent on CONFIG_BLOCK. (*) Makes mm/bounce.c (bounce buffering) contingent on CONFIG_BLOCK. (*) set_page_dirty() doesn't call __set_page_dirty_buffers() if CONFIG_BLOCK is not enabled. (*) fs/no-block.c is created to hold out-of-line stubs and things that are required when CONFIG_BLOCK is not set: (*) Default blockdev file operations (to give error ENODEV on opening). (*) Makes some /proc changes: (*) /proc/devices does not list any blockdevs. (*) /proc/diskstats and /proc/partitions are contingent on CONFIG_BLOCK. (*) Makes some compat ioctl handling contingent on CONFIG_BLOCK. (*) If CONFIG_BLOCK is not defined, makes sys_quotactl() return -ENODEV if given command other than Q_SYNC or if a special device is specified. (*) In init/do_mounts.c, no reference is made to the blockdev routines if CONFIG_BLOCK is not defined. This does not prohibit NFS roots or JFFS2. (*) The bdflush, ioprio_set and ioprio_get syscalls can now be absent (return error ENOSYS by way of cond_syscall if so). (*) The seclvl_bd_claim() and seclvl_bd_release() security calls do nothing if CONFIG_BLOCK is not set, since they can't then happen. Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2006-09-30 18:45:40 +00:00
#endif
struct dentry *mount_nodev(struct file_system_type *fs_type,
int flags, void *data,
int (*fill_super)(struct super_block *, void *, int))
{
int error;
struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
if (IS_ERR(s))
return ERR_CAST(s);
error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
if (error) {
deactivate_locked_super(s);
return ERR_PTR(error);
}
s->s_flags |= MS_ACTIVE;
return dget(s->s_root);
}
EXPORT_SYMBOL(mount_nodev);
static int compare_single(struct super_block *s, void *p)
{
return 1;
}
struct dentry *mount_single(struct file_system_type *fs_type,
int flags, void *data,
int (*fill_super)(struct super_block *, void *, int))
{
struct super_block *s;
int error;
s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
if (IS_ERR(s))
return ERR_CAST(s);
if (!s->s_root) {
error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
if (error) {
deactivate_locked_super(s);
return ERR_PTR(error);
}
s->s_flags |= MS_ACTIVE;
} else {
do_remount_sb(s, flags, data, 0);
}
return dget(s->s_root);
}
EXPORT_SYMBOL(mount_single);
struct dentry *
mount_fs(struct file_system_type *type, int flags, const char *name, void *data)
{
struct dentry *root;
struct super_block *sb;
char *secdata = NULL;
int error = -ENOMEM;
if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
secdata = alloc_secdata();
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
if (!secdata)
goto out;
error = security_sb_copy_data(data, secdata);
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
if (error)
goto out_free_secdata;
}
root = type->mount(type, flags, name, data);
if (IS_ERR(root)) {
error = PTR_ERR(root);
goto out_free_secdata;
}
sb = root->d_sb;
BUG_ON(!sb);
WARN_ON(!sb->s_bdi);
sb->s_flags |= MS_BORN;
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
error = security_sb_kern_mount(sb, flags, secdata);
if (error)
goto out_sb;
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
/*
* filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
* but s_maxbytes was an unsigned long long for many releases. Throw
* this warning for a little while to try and catch filesystems that
* violate this rule.
*/
WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
"negative value (%lld)\n", type->name, sb->s_maxbytes);
up_write(&sb->s_umount);
free_secdata(secdata);
return root;
out_sb:
dput(root);
deactivate_locked_super(sb);
out_free_secdata:
free_secdata(secdata);
out:
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
return ERR_PTR(error);
}
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
/*
* This is an internal function, please use sb_end_{write,pagefault,intwrite}
* instead.
*/
void __sb_end_write(struct super_block *sb, int level)
{
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
percpu_up_read(sb->s_writers.rw_sem + level-1);
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
}
EXPORT_SYMBOL(__sb_end_write);
/*
* This is an internal function, please use sb_start_{write,pagefault,intwrite}
* instead.
*/
int __sb_start_write(struct super_block *sb, int level, bool wait)
{
bool force_trylock = false;
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
int ret = 1;
#ifdef CONFIG_LOCKDEP
/*
* We want lockdep to tell us about possible deadlocks with freezing
* but it's it bit tricky to properly instrument it. Getting a freeze
* protection works as getting a read lock but there are subtle
* problems. XFS for example gets freeze protection on internal level
* twice in some cases, which is OK only because we already hold a
* freeze protection also on higher level. Due to these cases we have
* to use wait == F (trylock mode) which must not fail.
*/
if (wait) {
int i;
for (i = 0; i < level - 1; i++)
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
if (percpu_rwsem_is_held(sb->s_writers.rw_sem + i)) {
force_trylock = true;
break;
}
}
#endif
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
if (wait && !force_trylock)
percpu_down_read(sb->s_writers.rw_sem + level-1);
else
ret = percpu_down_read_trylock(sb->s_writers.rw_sem + level-1);
WARN_ON(force_trylock && !ret);
return ret;
}
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
EXPORT_SYMBOL(__sb_start_write);
/**
* sb_wait_write - wait until all writers to given file system finish
* @sb: the super for which we wait
* @level: type of writers we wait for (normal vs page fault)
*
* This function waits until there are no writers of given type to given file
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
* system.
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
*/
static void sb_wait_write(struct super_block *sb, int level)
{
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
percpu_down_write(sb->s_writers.rw_sem + level-1);
}
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
/*
* We are going to return to userspace and forget about these locks, the
* ownership goes to the caller of thaw_super() which does unlock().
*/
static void lockdep_sb_freeze_release(struct super_block *sb)
{
int level;
for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
}
/*
* Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
*/
static void lockdep_sb_freeze_acquire(struct super_block *sb)
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
{
int level;
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
for (level = 0; level < SB_FREEZE_LEVELS; ++level)
percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
}
static void sb_freeze_unlock(struct super_block *sb)
{
int level;
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
percpu_up_write(sb->s_writers.rw_sem + level);
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
}
/**
* freeze_super - lock the filesystem and force it into a consistent state
* @sb: the super to lock
*
* Syncs the super to make sure the filesystem is consistent and calls the fs's
* freeze_fs. Subsequent calls to this without first thawing the fs will return
* -EBUSY.
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
*
* During this function, sb->s_writers.frozen goes through these values:
*
* SB_UNFROZEN: File system is normal, all writes progress as usual.
*
* SB_FREEZE_WRITE: The file system is in the process of being frozen. New
* writes should be blocked, though page faults are still allowed. We wait for
* all writes to complete and then proceed to the next stage.
*
* SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
* but internal fs threads can still modify the filesystem (although they
* should not dirty new pages or inodes), writeback can run etc. After waiting
* for all running page faults we sync the filesystem which will clean all
* dirty pages and inodes (no new dirty pages or inodes can be created when
* sync is running).
*
* SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
* modification are blocked (e.g. XFS preallocation truncation on inode
* reclaim). This is usually implemented by blocking new transactions for
* filesystems that have them and need this additional guard. After all
* internal writers are finished we call ->freeze_fs() to finish filesystem
* freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
* mostly auxiliary for filesystems to verify they do not modify frozen fs.
*
* sb->s_writers.frozen is protected by sb->s_umount.
*/
int freeze_super(struct super_block *sb)
{
int ret;
atomic_inc(&sb->s_active);
down_write(&sb->s_umount);
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
if (sb->s_writers.frozen != SB_UNFROZEN) {
deactivate_locked_super(sb);
return -EBUSY;
}
if (!(sb->s_flags & MS_BORN)) {
up_write(&sb->s_umount);
return 0; /* sic - it's "nothing to do" */
}
if (sb->s_flags & MS_RDONLY) {
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
/* Nothing to do really... */
sb->s_writers.frozen = SB_FREEZE_COMPLETE;
up_write(&sb->s_umount);
return 0;
}
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
sb->s_writers.frozen = SB_FREEZE_WRITE;
/* Release s_umount to preserve sb_start_write -> s_umount ordering */
up_write(&sb->s_umount);
sb_wait_write(sb, SB_FREEZE_WRITE);
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
down_write(&sb->s_umount);
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
/* Now we go and block page faults... */
sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
/* All writers are done so after syncing there won't be dirty data */
sync_filesystem(sb);
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
/* Now wait for internal filesystem counter */
sb->s_writers.frozen = SB_FREEZE_FS;
sb_wait_write(sb, SB_FREEZE_FS);
if (sb->s_op->freeze_fs) {
ret = sb->s_op->freeze_fs(sb);
if (ret) {
printk(KERN_ERR
"VFS:Filesystem freeze failed\n");
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
sb->s_writers.frozen = SB_UNFROZEN;
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
sb_freeze_unlock(sb);
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
wake_up(&sb->s_writers.wait_unfrozen);
deactivate_locked_super(sb);
return ret;
}
}
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
/*
* For debugging purposes so that fs can warn if it sees write activity
* when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
*/
sb->s_writers.frozen = SB_FREEZE_COMPLETE;
lockdep_sb_freeze_release(sb);
up_write(&sb->s_umount);
return 0;
}
EXPORT_SYMBOL(freeze_super);
/**
* thaw_super -- unlock filesystem
* @sb: the super to thaw
*
* Unlocks the filesystem and marks it writeable again after freeze_super().
*/
int thaw_super(struct super_block *sb)
{
int error;
down_write(&sb->s_umount);
if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) {
up_write(&sb->s_umount);
return -EINVAL;
}
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
if (sb->s_flags & MS_RDONLY) {
sb->s_writers.frozen = SB_UNFROZEN;
goto out;
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
}
lockdep_sb_freeze_acquire(sb);
if (sb->s_op->unfreeze_fs) {
error = sb->s_op->unfreeze_fs(sb);
if (error) {
printk(KERN_ERR
"VFS:Filesystem thaw failed\n");
lockdep_sb_freeze_release(sb);
up_write(&sb->s_umount);
return error;
}
}
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
sb->s_writers.frozen = SB_UNFROZEN;
change sb_writers to use percpu_rw_semaphore We can remove everything from struct sb_writers except frozen and add the array of percpu_rw_semaphore's instead. This patch doesn't remove sb_writers->wait_unfrozen yet, we keep it for get_super_thawed(). We will probably remove it later. This change tries to address the following problems: - Firstly, __sb_start_write() looks simply buggy. It does __sb_end_write() if it sees ->frozen, but if it migrates to another CPU before percpu_counter_dec(), sb_wait_write() can wrongly succeed if there is another task which holds the same "semaphore": sb_wait_write() can miss the result of the previous percpu_counter_inc() but see the result of this percpu_counter_dec(). - As Dave Hansen reports, it is suboptimal. The trivial microbenchmark that writes to a tmpfs file in a loop runs 12% faster if we change this code to rely on RCU and kill the memory barriers. - This code doesn't look simple. It would be better to rely on the generic locking code. According to Dave, this change adds the same performance improvement. Note: with this change both freeze_super() and thaw_super() will do synchronize_sched_expedited() 3 times. This is just ugly. But: - This will be "fixed" by the rcu_sync changes we are going to merge. After that freeze_super()->percpu_down_write() will use synchronize_sched(), and thaw_super() won't use synchronize() at all. This doesn't need any changes in fs/super.c. - Once we merge rcu_sync changes, we can also change super.c so that all wb_write->rw_sem's will share the single ->rss in struct sb_writes, then freeze_super() will need only one synchronize_sched(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Jan Kara <jack@suse.com>
2015-08-11 15:05:04 +00:00
sb_freeze_unlock(sb);
out:
fs: Improve filesystem freezing handling vfs_check_frozen() tests are racy since the filesystem can be frozen just after the test is performed. Thus in write paths we can end up marking some pages or inodes dirty even though the file system is already frozen. This creates problems with flusher thread hanging on frozen filesystem. Another problem is that exclusion between ->page_mkwrite() and filesystem freezing has been handled by setting page dirty and then verifying s_frozen. This guaranteed that either the freezing code sees the faulted page, writes it, and writeprotects it again or we see s_frozen set and bail out of page fault. This works to protect from page being marked writeable while filesystem freezing is running but has an unpleasant artefact of leaving dirty (although unmodified and writeprotected) pages on frozen filesystem resulting in similar problems with flusher thread as the first problem. This patch aims at providing exclusion between write paths and filesystem freezing. We implement a writer-freeze read-write semaphore in the superblock. Actually, there are three such semaphores because of lock ranking reasons - one for page fault handlers (->page_mkwrite), one for all other writers, and one of internal filesystem purposes (used e.g. to track running transactions). Write paths which should block freezing (e.g. directory operations, ->aio_write(), ->page_mkwrite) hold reader side of the semaphore. Code freezing the filesystem takes the writer side. Only that we don't really want to bounce cachelines of the semaphores between CPUs for each write happening. So we implement the reader side of the semaphore as a per-cpu counter and the writer side is implemented using s_writers.frozen superblock field. [AV: microoptimize sb_start_write(); we want it fast in normal case] BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa <kamal@canonical.com> Tested-by: Peter M. Petrakis <peter.petrakis@canonical.com> Tested-by: Dann Frazier <dann.frazier@canonical.com> Tested-by: Massimo Morana <massimo.morana@canonical.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-06-12 14:20:34 +00:00
wake_up(&sb->s_writers.wait_unfrozen);
deactivate_locked_super(sb);
return 0;
}
EXPORT_SYMBOL(thaw_super);