linux-stable/fs/notify/inode_mark.c
Tejun Heo 5a0e3ad6af include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files.  percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.

percpu.h -> slab.h dependency is about to be removed.  Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability.  As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.

  http://userweb.kernel.org/~tj/misc/slabh-sweep.py

The script does the followings.

* Scan files for gfp and slab usages and update includes such that
  only the necessary includes are there.  ie. if only gfp is used,
  gfp.h, if slab is used, slab.h.

* When the script inserts a new include, it looks at the include
  blocks and try to put the new include such that its order conforms
  to its surrounding.  It's put in the include block which contains
  core kernel includes, in the same order that the rest are ordered -
  alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
  doesn't seem to be any matching order.

* If the script can't find a place to put a new include (mostly
  because the file doesn't have fitting include block), it prints out
  an error message indicating which .h file needs to be added to the
  file.

The conversion was done in the following steps.

1. The initial automatic conversion of all .c files updated slightly
   over 4000 files, deleting around 700 includes and adding ~480 gfp.h
   and ~3000 slab.h inclusions.  The script emitted errors for ~400
   files.

2. Each error was manually checked.  Some didn't need the inclusion,
   some needed manual addition while adding it to implementation .h or
   embedding .c file was more appropriate for others.  This step added
   inclusions to around 150 files.

3. The script was run again and the output was compared to the edits
   from #2 to make sure no file was left behind.

4. Several build tests were done and a couple of problems were fixed.
   e.g. lib/decompress_*.c used malloc/free() wrappers around slab
   APIs requiring slab.h to be added manually.

5. The script was run on all .h files but without automatically
   editing them as sprinkling gfp.h and slab.h inclusions around .h
   files could easily lead to inclusion dependency hell.  Most gfp.h
   inclusion directives were ignored as stuff from gfp.h was usually
   wildly available and often used in preprocessor macros.  Each
   slab.h inclusion directive was examined and added manually as
   necessary.

6. percpu.h was updated not to include slab.h.

7. Build test were done on the following configurations and failures
   were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
   distributed build env didn't work with gcov compiles) and a few
   more options had to be turned off depending on archs to make things
   build (like ipr on powerpc/64 which failed due to missing writeq).

   * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
   * powerpc and powerpc64 SMP allmodconfig
   * sparc and sparc64 SMP allmodconfig
   * ia64 SMP allmodconfig
   * s390 SMP allmodconfig
   * alpha SMP allmodconfig
   * um on x86_64 SMP allmodconfig

8. percpu.h modifications were reverted so that it could be applied as
   a separate patch and serve as bisection point.

Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-30 22:02:32 +09:00

425 lines
13 KiB
C

/*
* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
* fsnotify inode mark locking/lifetime/and refcnting
*
* REFCNT:
* The mark->refcnt tells how many "things" in the kernel currently are
* referencing this object. The object typically will live inside the kernel
* with a refcnt of 2, one for each list it is on (i_list, g_list). Any task
* which can find this object holding the appropriete locks, can take a reference
* and the object itself is guarenteed to survive until the reference is dropped.
*
* LOCKING:
* There are 3 spinlocks involved with fsnotify inode marks and they MUST
* be taken in order as follows:
*
* entry->lock
* group->mark_lock
* inode->i_lock
*
* entry->lock protects 2 things, entry->group and entry->inode. You must hold
* that lock to dereference either of these things (they could be NULL even with
* the lock)
*
* group->mark_lock protects the mark_entries list anchored inside a given group
* and each entry is hooked via the g_list. It also sorta protects the
* free_g_list, which when used is anchored by a private list on the stack of the
* task which held the group->mark_lock.
*
* inode->i_lock protects the i_fsnotify_mark_entries list anchored inside a
* given inode and each entry is hooked via the i_list. (and sorta the
* free_i_list)
*
*
* LIFETIME:
* Inode marks survive between when they are added to an inode and when their
* refcnt==0.
*
* The inode mark can be cleared for a number of different reasons including:
* - The inode is unlinked for the last time. (fsnotify_inode_remove)
* - The inode is being evicted from cache. (fsnotify_inode_delete)
* - The fs the inode is on is unmounted. (fsnotify_inode_delete/fsnotify_unmount_inodes)
* - Something explicitly requests that it be removed. (fsnotify_destroy_mark_by_entry)
* - The fsnotify_group associated with the mark is going away and all such marks
* need to be cleaned up. (fsnotify_clear_marks_by_group)
*
* Worst case we are given an inode and need to clean up all the marks on that
* inode. We take i_lock and walk the i_fsnotify_mark_entries safely. For each
* mark on the list we take a reference (so the mark can't disappear under us).
* We remove that mark form the inode's list of marks and we add this mark to a
* private list anchored on the stack using i_free_list; At this point we no
* longer fear anything finding the mark using the inode's list of marks.
*
* We can safely and locklessly run the private list on the stack of everything
* we just unattached from the original inode. For each mark on the private list
* we grab the mark-> and can thus dereference mark->group and mark->inode. If
* we see the group and inode are not NULL we take those locks. Now holding all
* 3 locks we can completely remove the mark from other tasks finding it in the
* future. Remember, 10 things might already be referencing this mark, but they
* better be holding a ref. We drop our reference we took before we unhooked it
* from the inode. When the ref hits 0 we can free the mark.
*
* Very similarly for freeing by group, except we use free_g_list.
*
* This has the very interesting property of being able to run concurrently with
* any (or all) other directions.
*/
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/writeback.h> /* for inode_lock */
#include <asm/atomic.h>
#include <linux/fsnotify_backend.h>
#include "fsnotify.h"
void fsnotify_get_mark(struct fsnotify_mark_entry *entry)
{
atomic_inc(&entry->refcnt);
}
void fsnotify_put_mark(struct fsnotify_mark_entry *entry)
{
if (atomic_dec_and_test(&entry->refcnt))
entry->free_mark(entry);
}
/*
* Recalculate the mask of events relevant to a given inode locked.
*/
static void fsnotify_recalc_inode_mask_locked(struct inode *inode)
{
struct fsnotify_mark_entry *entry;
struct hlist_node *pos;
__u32 new_mask = 0;
assert_spin_locked(&inode->i_lock);
hlist_for_each_entry(entry, pos, &inode->i_fsnotify_mark_entries, i_list)
new_mask |= entry->mask;
inode->i_fsnotify_mask = new_mask;
}
/*
* Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
* any notifier is interested in hearing for this inode.
*/
void fsnotify_recalc_inode_mask(struct inode *inode)
{
spin_lock(&inode->i_lock);
fsnotify_recalc_inode_mask_locked(inode);
spin_unlock(&inode->i_lock);
__fsnotify_update_child_dentry_flags(inode);
}
/*
* Any time a mark is getting freed we end up here.
* The caller had better be holding a reference to this mark so we don't actually
* do the final put under the entry->lock
*/
void fsnotify_destroy_mark_by_entry(struct fsnotify_mark_entry *entry)
{
struct fsnotify_group *group;
struct inode *inode;
spin_lock(&entry->lock);
group = entry->group;
inode = entry->inode;
BUG_ON(group && !inode);
BUG_ON(!group && inode);
/* if !group something else already marked this to die */
if (!group) {
spin_unlock(&entry->lock);
return;
}
/* 1 from caller and 1 for being on i_list/g_list */
BUG_ON(atomic_read(&entry->refcnt) < 2);
spin_lock(&group->mark_lock);
spin_lock(&inode->i_lock);
hlist_del_init(&entry->i_list);
entry->inode = NULL;
list_del_init(&entry->g_list);
entry->group = NULL;
fsnotify_put_mark(entry); /* for i_list and g_list */
/*
* this mark is now off the inode->i_fsnotify_mark_entries list and we
* hold the inode->i_lock, so this is the perfect time to update the
* inode->i_fsnotify_mask
*/
fsnotify_recalc_inode_mask_locked(inode);
spin_unlock(&inode->i_lock);
spin_unlock(&group->mark_lock);
spin_unlock(&entry->lock);
/*
* Some groups like to know that marks are being freed. This is a
* callback to the group function to let it know that this entry
* is being freed.
*/
if (group->ops->freeing_mark)
group->ops->freeing_mark(entry, group);
/*
* __fsnotify_update_child_dentry_flags(inode);
*
* I really want to call that, but we can't, we have no idea if the inode
* still exists the second we drop the entry->lock.
*
* The next time an event arrive to this inode from one of it's children
* __fsnotify_parent will see that the inode doesn't care about it's
* children and will update all of these flags then. So really this
* is just a lazy update (and could be a perf win...)
*/
iput(inode);
/*
* it's possible that this group tried to destroy itself, but this
* this mark was simultaneously being freed by inode. If that's the
* case, we finish freeing the group here.
*/
if (unlikely(atomic_dec_and_test(&group->num_marks)))
fsnotify_final_destroy_group(group);
}
/*
* Given a group, destroy all of the marks associated with that group.
*/
void fsnotify_clear_marks_by_group(struct fsnotify_group *group)
{
struct fsnotify_mark_entry *lentry, *entry;
LIST_HEAD(free_list);
spin_lock(&group->mark_lock);
list_for_each_entry_safe(entry, lentry, &group->mark_entries, g_list) {
list_add(&entry->free_g_list, &free_list);
list_del_init(&entry->g_list);
fsnotify_get_mark(entry);
}
spin_unlock(&group->mark_lock);
list_for_each_entry_safe(entry, lentry, &free_list, free_g_list) {
fsnotify_destroy_mark_by_entry(entry);
fsnotify_put_mark(entry);
}
}
/*
* Given an inode, destroy all of the marks associated with that inode.
*/
void fsnotify_clear_marks_by_inode(struct inode *inode)
{
struct fsnotify_mark_entry *entry, *lentry;
struct hlist_node *pos, *n;
LIST_HEAD(free_list);
spin_lock(&inode->i_lock);
hlist_for_each_entry_safe(entry, pos, n, &inode->i_fsnotify_mark_entries, i_list) {
list_add(&entry->free_i_list, &free_list);
hlist_del_init(&entry->i_list);
fsnotify_get_mark(entry);
}
spin_unlock(&inode->i_lock);
list_for_each_entry_safe(entry, lentry, &free_list, free_i_list) {
fsnotify_destroy_mark_by_entry(entry);
fsnotify_put_mark(entry);
}
}
/*
* given a group and inode, find the mark associated with that combination.
* if found take a reference to that mark and return it, else return NULL
*/
struct fsnotify_mark_entry *fsnotify_find_mark_entry(struct fsnotify_group *group,
struct inode *inode)
{
struct fsnotify_mark_entry *entry;
struct hlist_node *pos;
assert_spin_locked(&inode->i_lock);
hlist_for_each_entry(entry, pos, &inode->i_fsnotify_mark_entries, i_list) {
if (entry->group == group) {
fsnotify_get_mark(entry);
return entry;
}
}
return NULL;
}
/*
* Nothing fancy, just initialize lists and locks and counters.
*/
void fsnotify_init_mark(struct fsnotify_mark_entry *entry,
void (*free_mark)(struct fsnotify_mark_entry *entry))
{
spin_lock_init(&entry->lock);
atomic_set(&entry->refcnt, 1);
INIT_HLIST_NODE(&entry->i_list);
entry->group = NULL;
entry->mask = 0;
entry->inode = NULL;
entry->free_mark = free_mark;
}
/*
* Attach an initialized mark entry to a given group and inode.
* These marks may be used for the fsnotify backend to determine which
* event types should be delivered to which group and for which inodes.
*/
int fsnotify_add_mark(struct fsnotify_mark_entry *entry,
struct fsnotify_group *group, struct inode *inode)
{
struct fsnotify_mark_entry *lentry;
int ret = 0;
inode = igrab(inode);
if (unlikely(!inode))
return -EINVAL;
/*
* LOCKING ORDER!!!!
* entry->lock
* group->mark_lock
* inode->i_lock
*/
spin_lock(&entry->lock);
spin_lock(&group->mark_lock);
spin_lock(&inode->i_lock);
lentry = fsnotify_find_mark_entry(group, inode);
if (!lentry) {
entry->group = group;
entry->inode = inode;
hlist_add_head(&entry->i_list, &inode->i_fsnotify_mark_entries);
list_add(&entry->g_list, &group->mark_entries);
fsnotify_get_mark(entry); /* for i_list and g_list */
atomic_inc(&group->num_marks);
fsnotify_recalc_inode_mask_locked(inode);
}
spin_unlock(&inode->i_lock);
spin_unlock(&group->mark_lock);
spin_unlock(&entry->lock);
if (lentry) {
ret = -EEXIST;
iput(inode);
fsnotify_put_mark(lentry);
} else {
__fsnotify_update_child_dentry_flags(inode);
}
return ret;
}
/**
* fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
* @list: list of inodes being unmounted (sb->s_inodes)
*
* Called with inode_lock held, protecting the unmounting super block's list
* of inodes, and with iprune_mutex held, keeping shrink_icache_memory() at bay.
* We temporarily drop inode_lock, however, and CAN block.
*/
void fsnotify_unmount_inodes(struct list_head *list)
{
struct inode *inode, *next_i, *need_iput = NULL;
list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
struct inode *need_iput_tmp;
/*
* We cannot __iget() an inode in state I_CLEAR, I_FREEING,
* I_WILL_FREE, or I_NEW which is fine because by that point
* the inode cannot have any associated watches.
*/
if (inode->i_state & (I_CLEAR|I_FREEING|I_WILL_FREE|I_NEW))
continue;
/*
* If i_count is zero, the inode cannot have any watches and
* doing an __iget/iput with MS_ACTIVE clear would actually
* evict all inodes with zero i_count from icache which is
* unnecessarily violent and may in fact be illegal to do.
*/
if (!atomic_read(&inode->i_count))
continue;
need_iput_tmp = need_iput;
need_iput = NULL;
/* In case fsnotify_inode_delete() drops a reference. */
if (inode != need_iput_tmp)
__iget(inode);
else
need_iput_tmp = NULL;
/* In case the dropping of a reference would nuke next_i. */
if ((&next_i->i_sb_list != list) &&
atomic_read(&next_i->i_count) &&
!(next_i->i_state & (I_CLEAR | I_FREEING | I_WILL_FREE))) {
__iget(next_i);
need_iput = next_i;
}
/*
* We can safely drop inode_lock here because we hold
* references on both inode and next_i. Also no new inodes
* will be added since the umount has begun. Finally,
* iprune_mutex keeps shrink_icache_memory() away.
*/
spin_unlock(&inode_lock);
if (need_iput_tmp)
iput(need_iput_tmp);
/* for each watch, send FS_UNMOUNT and then remove it */
fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
fsnotify_inode_delete(inode);
iput(inode);
spin_lock(&inode_lock);
}
}