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![Linus Torvalds](/assets/img/avatar_default.png)
Pull namespace updates from Eric Biederman: "There is a lot here. A lot of these changes result in subtle user visible differences in kernel behavior. I don't expect anything will care but I will revert/fix things immediately if any regressions show up. From Seth Forshee there is a continuation of the work to make the vfs ready for unpriviled mounts. We had thought the previous changes prevented the creation of files outside of s_user_ns of a filesystem, but it turns we missed the O_CREAT path. Ooops. Pavel Tikhomirov and Oleg Nesterov worked together to fix a long standing bug in the implemenation of PR_SET_CHILD_SUBREAPER where only children that are forked after the prctl are considered and not children forked before the prctl. The only known user of this prctl systemd forks all children after the prctl. So no userspace regressions will occur. Holding earlier forked children to the same rules as later forked children creates a semantic that is sane enough to allow checkpoing of processes that use this feature. There is a long delayed change by Nikolay Borisov to limit inotify instances inside a user namespace. Michael Kerrisk extends the API for files used to maniuplate namespaces with two new trivial ioctls to allow discovery of the hierachy and properties of namespaces. Konstantin Khlebnikov with the help of Al Viro adds code that when a network namespace exits purges it's sysctl entries from the dcache. As in some circumstances this could use a lot of memory. Vivek Goyal fixed a bug with stacked filesystems where the permissions on the wrong inode were being checked. I continue previous work on ptracing across exec. Allowing a file to be setuid across exec while being ptraced if the tracer has enough credentials in the user namespace, and if the process has CAP_SETUID in it's own namespace. Proc files for setuid or otherwise undumpable executables are now owned by the root in the user namespace of their mm. Allowing debugging of setuid applications in containers to work better. A bug I introduced with permission checking and automount is now fixed. The big change is to mark the mounts that the kernel initiates as a result of an automount. This allows the permission checks in sget to be safely suppressed for this kind of mount. As the permission check happened when the original filesystem was mounted. Finally a special case in the mount namespace is removed preventing unbounded chains in the mount hash table, and making the semantics simpler which benefits CRIU. The vfs fix along with related work in ima and evm I believe makes us ready to finish developing and merge fully unprivileged mounts of the fuse filesystem. The cleanups of the mount namespace makes discussing how to fix the worst case complexity of umount. The stacked filesystem fixes pave the way for adding multiple mappings for the filesystem uids so that efficient and safer containers can be implemented" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: proc/sysctl: Don't grab i_lock under sysctl_lock. vfs: Use upper filesystem inode in bprm_fill_uid() proc/sysctl: prune stale dentries during unregistering mnt: Tuck mounts under others instead of creating shadow/side mounts. prctl: propagate has_child_subreaper flag to every descendant introduce the walk_process_tree() helper nsfs: Add an ioctl() to return owner UID of a userns fs: Better permission checking for submounts exit: fix the setns() && PR_SET_CHILD_SUBREAPER interaction vfs: open() with O_CREAT should not create inodes with unknown ids nsfs: Add an ioctl() to return the namespace type proc: Better ownership of files for non-dumpable tasks in user namespaces exec: Remove LSM_UNSAFE_PTRACE_CAP exec: Test the ptracer's saved cred to see if the tracee can gain caps exec: Don't reset euid and egid when the tracee has CAP_SETUID inotify: Convert to using per-namespace limits
1488 lines
38 KiB
C
1488 lines
38 KiB
C
/*
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* linux/fs/super.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* super.c contains code to handle: - mount structures
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* - super-block tables
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* - filesystem drivers list
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* - mount system call
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* - umount system call
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* - ustat system call
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*
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* GK 2/5/95 - Changed to support mounting the root fs via NFS
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*
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* Added kerneld support: Jacques Gelinas and Bjorn Ekwall
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* Added change_root: Werner Almesberger & Hans Lermen, Feb '96
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* Added options to /proc/mounts:
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* Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
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* Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
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* Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
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*/
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#include <linux/export.h>
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#include <linux/slab.h>
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#include <linux/blkdev.h>
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#include <linux/mount.h>
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#include <linux/security.h>
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#include <linux/writeback.h> /* for the emergency remount stuff */
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#include <linux/idr.h>
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#include <linux/mutex.h>
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#include <linux/backing-dev.h>
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#include <linux/rculist_bl.h>
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#include <linux/cleancache.h>
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#include <linux/fsnotify.h>
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#include <linux/lockdep.h>
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#include <linux/user_namespace.h>
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#include "internal.h"
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static LIST_HEAD(super_blocks);
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static DEFINE_SPINLOCK(sb_lock);
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static char *sb_writers_name[SB_FREEZE_LEVELS] = {
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"sb_writers",
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"sb_pagefaults",
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"sb_internal",
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};
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/*
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* One thing we have to be careful of with a per-sb shrinker is that we don't
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* drop the last active reference to the superblock from within the shrinker.
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* If that happens we could trigger unregistering the shrinker from within the
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* shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
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* take a passive reference to the superblock to avoid this from occurring.
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*/
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static unsigned long super_cache_scan(struct shrinker *shrink,
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struct shrink_control *sc)
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{
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struct super_block *sb;
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long fs_objects = 0;
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long total_objects;
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long freed = 0;
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long dentries;
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long inodes;
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sb = container_of(shrink, struct super_block, s_shrink);
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/*
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* Deadlock avoidance. We may hold various FS locks, and we don't want
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* to recurse into the FS that called us in clear_inode() and friends..
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*/
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if (!(sc->gfp_mask & __GFP_FS))
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return SHRINK_STOP;
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if (!trylock_super(sb))
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return SHRINK_STOP;
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if (sb->s_op->nr_cached_objects)
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fs_objects = sb->s_op->nr_cached_objects(sb, sc);
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inodes = list_lru_shrink_count(&sb->s_inode_lru, sc);
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dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc);
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total_objects = dentries + inodes + fs_objects + 1;
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if (!total_objects)
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total_objects = 1;
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/* proportion the scan between the caches */
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dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);
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inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);
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fs_objects = mult_frac(sc->nr_to_scan, fs_objects, total_objects);
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/*
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* prune the dcache first as the icache is pinned by it, then
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* prune the icache, followed by the filesystem specific caches
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*
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* Ensure that we always scan at least one object - memcg kmem
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* accounting uses this to fully empty the caches.
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*/
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sc->nr_to_scan = dentries + 1;
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freed = prune_dcache_sb(sb, sc);
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sc->nr_to_scan = inodes + 1;
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freed += prune_icache_sb(sb, sc);
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if (fs_objects) {
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sc->nr_to_scan = fs_objects + 1;
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freed += sb->s_op->free_cached_objects(sb, sc);
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}
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up_read(&sb->s_umount);
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return freed;
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}
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static unsigned long super_cache_count(struct shrinker *shrink,
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struct shrink_control *sc)
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{
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struct super_block *sb;
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long total_objects = 0;
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sb = container_of(shrink, struct super_block, s_shrink);
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/*
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* Don't call trylock_super as it is a potential
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* scalability bottleneck. The counts could get updated
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* between super_cache_count and super_cache_scan anyway.
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* Call to super_cache_count with shrinker_rwsem held
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* ensures the safety of call to list_lru_shrink_count() and
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* s_op->nr_cached_objects().
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*/
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if (sb->s_op && sb->s_op->nr_cached_objects)
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total_objects = sb->s_op->nr_cached_objects(sb, sc);
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total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc);
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total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc);
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total_objects = vfs_pressure_ratio(total_objects);
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return total_objects;
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}
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static void destroy_super_work(struct work_struct *work)
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{
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struct super_block *s = container_of(work, struct super_block,
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destroy_work);
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int i;
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for (i = 0; i < SB_FREEZE_LEVELS; i++)
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percpu_free_rwsem(&s->s_writers.rw_sem[i]);
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kfree(s);
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}
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static void destroy_super_rcu(struct rcu_head *head)
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{
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struct super_block *s = container_of(head, struct super_block, rcu);
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INIT_WORK(&s->destroy_work, destroy_super_work);
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schedule_work(&s->destroy_work);
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}
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/**
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* destroy_super - frees a superblock
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* @s: superblock to free
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*
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* Frees a superblock.
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*/
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static void destroy_super(struct super_block *s)
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{
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list_lru_destroy(&s->s_dentry_lru);
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list_lru_destroy(&s->s_inode_lru);
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security_sb_free(s);
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WARN_ON(!list_empty(&s->s_mounts));
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put_user_ns(s->s_user_ns);
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kfree(s->s_subtype);
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kfree(s->s_options);
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call_rcu(&s->rcu, destroy_super_rcu);
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}
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/**
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* alloc_super - create new superblock
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* @type: filesystem type superblock should belong to
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* @flags: the mount flags
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* @user_ns: User namespace for the super_block
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*
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* Allocates and initializes a new &struct super_block. alloc_super()
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* returns a pointer new superblock or %NULL if allocation had failed.
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*/
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static struct super_block *alloc_super(struct file_system_type *type, int flags,
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struct user_namespace *user_ns)
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{
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struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
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static const struct super_operations default_op;
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int i;
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if (!s)
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return NULL;
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INIT_LIST_HEAD(&s->s_mounts);
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s->s_user_ns = get_user_ns(user_ns);
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if (security_sb_alloc(s))
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goto fail;
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for (i = 0; i < SB_FREEZE_LEVELS; i++) {
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if (__percpu_init_rwsem(&s->s_writers.rw_sem[i],
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sb_writers_name[i],
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&type->s_writers_key[i]))
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goto fail;
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}
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init_waitqueue_head(&s->s_writers.wait_unfrozen);
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s->s_bdi = &noop_backing_dev_info;
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s->s_flags = flags;
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if (s->s_user_ns != &init_user_ns)
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s->s_iflags |= SB_I_NODEV;
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INIT_HLIST_NODE(&s->s_instances);
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INIT_HLIST_BL_HEAD(&s->s_anon);
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mutex_init(&s->s_sync_lock);
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INIT_LIST_HEAD(&s->s_inodes);
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spin_lock_init(&s->s_inode_list_lock);
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INIT_LIST_HEAD(&s->s_inodes_wb);
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spin_lock_init(&s->s_inode_wblist_lock);
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if (list_lru_init_memcg(&s->s_dentry_lru))
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goto fail;
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if (list_lru_init_memcg(&s->s_inode_lru))
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goto fail;
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init_rwsem(&s->s_umount);
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lockdep_set_class(&s->s_umount, &type->s_umount_key);
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/*
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* sget() can have s_umount recursion.
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*
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* When it cannot find a suitable sb, it allocates a new
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* one (this one), and tries again to find a suitable old
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* one.
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*
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* In case that succeeds, it will acquire the s_umount
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* lock of the old one. Since these are clearly distrinct
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* locks, and this object isn't exposed yet, there's no
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* risk of deadlocks.
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*
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* Annotate this by putting this lock in a different
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* subclass.
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*/
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down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
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s->s_count = 1;
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atomic_set(&s->s_active, 1);
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mutex_init(&s->s_vfs_rename_mutex);
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lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
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mutex_init(&s->s_dquot.dqio_mutex);
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s->s_maxbytes = MAX_NON_LFS;
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s->s_op = &default_op;
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s->s_time_gran = 1000000000;
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s->cleancache_poolid = CLEANCACHE_NO_POOL;
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s->s_shrink.seeks = DEFAULT_SEEKS;
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s->s_shrink.scan_objects = super_cache_scan;
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s->s_shrink.count_objects = super_cache_count;
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s->s_shrink.batch = 1024;
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s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
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return s;
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fail:
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destroy_super(s);
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return NULL;
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}
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/* Superblock refcounting */
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/*
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* Drop a superblock's refcount. The caller must hold sb_lock.
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*/
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static void __put_super(struct super_block *sb)
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{
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if (!--sb->s_count) {
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list_del_init(&sb->s_list);
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destroy_super(sb);
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}
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}
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/**
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* put_super - drop a temporary reference to superblock
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* @sb: superblock in question
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*
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* Drops a temporary reference, frees superblock if there's no
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* references left.
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*/
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static void put_super(struct super_block *sb)
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{
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spin_lock(&sb_lock);
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__put_super(sb);
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spin_unlock(&sb_lock);
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}
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/**
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* deactivate_locked_super - drop an active reference to superblock
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* @s: superblock to deactivate
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*
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* Drops an active reference to superblock, converting it into a temporary
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* one if there is no other active references left. In that case we
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* tell fs driver to shut it down and drop the temporary reference we
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* had just acquired.
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*
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* Caller holds exclusive lock on superblock; that lock is released.
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*/
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void deactivate_locked_super(struct super_block *s)
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{
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struct file_system_type *fs = s->s_type;
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if (atomic_dec_and_test(&s->s_active)) {
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cleancache_invalidate_fs(s);
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unregister_shrinker(&s->s_shrink);
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fs->kill_sb(s);
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/*
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* Since list_lru_destroy() may sleep, we cannot call it from
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* put_super(), where we hold the sb_lock. Therefore we destroy
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* the lru lists right now.
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*/
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list_lru_destroy(&s->s_dentry_lru);
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list_lru_destroy(&s->s_inode_lru);
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put_filesystem(fs);
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put_super(s);
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} else {
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up_write(&s->s_umount);
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}
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}
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EXPORT_SYMBOL(deactivate_locked_super);
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/**
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* deactivate_super - drop an active reference to superblock
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* @s: superblock to deactivate
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*
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* Variant of deactivate_locked_super(), except that superblock is *not*
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* locked by caller. If we are going to drop the final active reference,
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* lock will be acquired prior to that.
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*/
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void deactivate_super(struct super_block *s)
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{
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if (!atomic_add_unless(&s->s_active, -1, 1)) {
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down_write(&s->s_umount);
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deactivate_locked_super(s);
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}
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}
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EXPORT_SYMBOL(deactivate_super);
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/**
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* grab_super - acquire an active reference
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* @s: reference we are trying to make active
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*
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* Tries to acquire an active reference. grab_super() is used when we
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* had just found a superblock in super_blocks or fs_type->fs_supers
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* and want to turn it into a full-blown active reference. grab_super()
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* is called with sb_lock held and drops it. Returns 1 in case of
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* success, 0 if we had failed (superblock contents was already dead or
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* dying when grab_super() had been called). Note that this is only
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* called for superblocks not in rundown mode (== ones still on ->fs_supers
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* of their type), so increment of ->s_count is OK here.
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*/
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static int grab_super(struct super_block *s) __releases(sb_lock)
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{
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s->s_count++;
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spin_unlock(&sb_lock);
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down_write(&s->s_umount);
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if ((s->s_flags & MS_BORN) && atomic_inc_not_zero(&s->s_active)) {
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put_super(s);
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return 1;
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}
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up_write(&s->s_umount);
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put_super(s);
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return 0;
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}
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|
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/*
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* trylock_super - try to grab ->s_umount shared
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* @sb: reference we are trying to grab
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*
|
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* Try to prevent fs shutdown. This is used in places where we
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* cannot take an active reference but we need to ensure that the
|
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* filesystem is not shut down while we are working on it. It returns
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* false if we cannot acquire s_umount or if we lose the race and
|
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* filesystem already got into shutdown, and returns true with the s_umount
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* lock held in read mode in case of success. On successful return,
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* the caller must drop the s_umount lock when done.
|
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*
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* Note that unlike get_super() et.al. this one does *not* bump ->s_count.
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* The reason why it's safe is that we are OK with doing trylock instead
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* of down_read(). There's a couple of places that are OK with that, but
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* it's very much not a general-purpose interface.
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*/
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bool trylock_super(struct super_block *sb)
|
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{
|
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if (down_read_trylock(&sb->s_umount)) {
|
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if (!hlist_unhashed(&sb->s_instances) &&
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sb->s_root && (sb->s_flags & MS_BORN))
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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_
|
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* taken care of and do not need specific handling.
|
|
*
|
|
* 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;
|
|
|
|
if (sb->s_root) {
|
|
shrink_dcache_for_umount(sb);
|
|
sync_filesystem(sb);
|
|
sb->s_flags &= ~MS_ACTIVE;
|
|
|
|
fsnotify_unmount_inodes(sb);
|
|
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);
|
|
|
|
/**
|
|
* sget_userns - find or create a superblock
|
|
* @type: filesystem type superblock should belong to
|
|
* @test: comparison callback
|
|
* @set: setup callback
|
|
* @flags: mount flags
|
|
* @user_ns: User namespace for the super_block
|
|
* @data: argument to each of them
|
|
*/
|
|
struct super_block *sget_userns(struct file_system_type *type,
|
|
int (*test)(struct super_block *,void *),
|
|
int (*set)(struct super_block *,void *),
|
|
int flags, struct user_namespace *user_ns,
|
|
void *data)
|
|
{
|
|
struct super_block *s = NULL;
|
|
struct super_block *old;
|
|
int err;
|
|
|
|
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_for_each_entry(old, &type->fs_supers, s_instances) {
|
|
if (!test(old, data))
|
|
continue;
|
|
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);
|
|
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;
|
|
}
|
|
|
|
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();
|
|
|
|
/* 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;
|
|
|
|
/* Ensure the requestor has permissions over the target filesystem */
|
|
if (!(flags & (MS_KERNMOUNT|MS_SUBMOUNT)) && !ns_capable(user_ns, CAP_SYS_ADMIN))
|
|
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_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);
|
|
if (!s || s->s_writers.frozen == SB_UNFROZEN)
|
|
return s;
|
|
if (!excl)
|
|
up_read(&s->s_umount);
|
|
else
|
|
up_write(&s->s_umount);
|
|
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) {
|
|
if (!grab_super(sb))
|
|
goto restart;
|
|
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;
|
|
|
|
if (sb->s_writers.frozen != SB_UNFROZEN)
|
|
return -EBUSY;
|
|
|
|
#ifdef CONFIG_BLOCK
|
|
if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
|
|
return -EACCES;
|
|
#endif
|
|
|
|
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 */
|
|
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;
|
|
|
|
/*
|
|
* 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);
|
|
|
|
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);
|
|
|
|
#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))
|
|
goto error_s;
|
|
|
|
if (s->s_root) {
|
|
if ((flags ^ s->s_flags) & MS_RDONLY) {
|
|
deactivate_locked_super(s);
|
|
error = -EBUSY;
|
|
goto error_bdev;
|
|
}
|
|
|
|
/*
|
|
* s_umount nests inside bd_mutex during
|
|
* __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);
|
|
goto error;
|
|
}
|
|
|
|
s->s_flags |= MS_ACTIVE;
|
|
bdev->bd_super = s;
|
|
}
|
|
|
|
return dget(s->s_root);
|
|
|
|
error_s:
|
|
error = PTR_ERR(s);
|
|
error_bdev:
|
|
blkdev_put(bdev, mode);
|
|
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));
|
|
blkdev_put(bdev, mode | FMODE_EXCL);
|
|
}
|
|
|
|
EXPORT_SYMBOL(kill_block_super);
|
|
#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();
|
|
if (!secdata)
|
|
goto out;
|
|
|
|
error = security_sb_copy_data(data, secdata);
|
|
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;
|
|
|
|
error = security_sb_kern_mount(sb, flags, secdata);
|
|
if (error)
|
|
goto out_sb;
|
|
|
|
/*
|
|
* 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:
|
|
return ERR_PTR(error);
|
|
}
|
|
|
|
/*
|
|
* This is an internal function, please use sb_end_{write,pagefault,intwrite}
|
|
* instead.
|
|
*/
|
|
void __sb_end_write(struct super_block *sb, int level)
|
|
{
|
|
percpu_up_read(sb->s_writers.rw_sem + level-1);
|
|
}
|
|
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;
|
|
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++)
|
|
if (percpu_rwsem_is_held(sb->s_writers.rw_sem + i)) {
|
|
force_trylock = true;
|
|
break;
|
|
}
|
|
}
|
|
#endif
|
|
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;
|
|
}
|
|
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
|
|
* system.
|
|
*/
|
|
static void sb_wait_write(struct super_block *sb, int level)
|
|
{
|
|
percpu_down_write(sb->s_writers.rw_sem + level-1);
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
int level;
|
|
|
|
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;
|
|
|
|
for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
|
|
percpu_up_write(sb->s_writers.rw_sem + level);
|
|
}
|
|
|
|
/**
|
|
* 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.
|
|
*
|
|
* 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);
|
|
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) {
|
|
/* Nothing to do really... */
|
|
sb->s_writers.frozen = SB_FREEZE_COMPLETE;
|
|
up_write(&sb->s_umount);
|
|
return 0;
|
|
}
|
|
|
|
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);
|
|
down_write(&sb->s_umount);
|
|
|
|
/* 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);
|
|
|
|
/* 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");
|
|
sb->s_writers.frozen = SB_UNFROZEN;
|
|
sb_freeze_unlock(sb);
|
|
wake_up(&sb->s_writers.wait_unfrozen);
|
|
deactivate_locked_super(sb);
|
|
return ret;
|
|
}
|
|
}
|
|
/*
|
|
* 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().
|
|
*/
|
|
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;
|
|
}
|
|
|
|
if (sb->s_flags & MS_RDONLY) {
|
|
sb->s_writers.frozen = SB_UNFROZEN;
|
|
goto out;
|
|
}
|
|
|
|
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;
|
|
}
|
|
}
|
|
|
|
sb->s_writers.frozen = SB_UNFROZEN;
|
|
sb_freeze_unlock(sb);
|
|
out:
|
|
wake_up(&sb->s_writers.wait_unfrozen);
|
|
deactivate_locked_super(sb);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(thaw_super);
|