1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 1991, 1992 Linus Torvalds
7 * super.c contains code to handle: - mount structures
9 * - filesystem drivers list
11 * - umount system call
14 * GK 2/5/95 - Changed to support mounting the root fs via NFS
16 * Added kerneld support: Jacques Gelinas and Bjorn Ekwall
17 * Added change_root: Werner Almesberger & Hans Lermen, Feb '96
18 * Added options to /proc/mounts:
19 * Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
20 * Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
21 * Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
24 #include <linux/export.h>
25 #include <linux/slab.h>
26 #include <linux/blkdev.h>
27 #include <linux/mount.h>
28 #include <linux/security.h>
29 #include <linux/writeback.h> /* for the emergency remount stuff */
30 #include <linux/idr.h>
31 #include <linux/mutex.h>
32 #include <linux/backing-dev.h>
33 #include <linux/rculist_bl.h>
34 #include <linux/fscrypt.h>
35 #include <linux/fsnotify.h>
36 #include <linux/lockdep.h>
37 #include <linux/user_namespace.h>
38 #include <linux/fs_context.h>
39 #include <uapi/linux/mount.h>
42 static int thaw_super_locked(struct super_block *sb);
44 static LIST_HEAD(super_blocks);
45 static DEFINE_SPINLOCK(sb_lock);
47 static char *sb_writers_name[SB_FREEZE_LEVELS] = {
54 * One thing we have to be careful of with a per-sb shrinker is that we don't
55 * drop the last active reference to the superblock from within the shrinker.
56 * If that happens we could trigger unregistering the shrinker from within the
57 * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
58 * take a passive reference to the superblock to avoid this from occurring.
60 static unsigned long super_cache_scan(struct shrinker *shrink,
61 struct shrink_control *sc)
63 struct super_block *sb;
70 sb = container_of(shrink, struct super_block, s_shrink);
73 * Deadlock avoidance. We may hold various FS locks, and we don't want
74 * to recurse into the FS that called us in clear_inode() and friends..
76 if (!(sc->gfp_mask & __GFP_FS))
79 if (!trylock_super(sb))
82 if (sb->s_op->nr_cached_objects)
83 fs_objects = sb->s_op->nr_cached_objects(sb, sc);
85 inodes = list_lru_shrink_count(&sb->s_inode_lru, sc);
86 dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc);
87 total_objects = dentries + inodes + fs_objects + 1;
91 /* proportion the scan between the caches */
92 dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);
93 inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);
94 fs_objects = mult_frac(sc->nr_to_scan, fs_objects, total_objects);
97 * prune the dcache first as the icache is pinned by it, then
98 * prune the icache, followed by the filesystem specific caches
100 * Ensure that we always scan at least one object - memcg kmem
101 * accounting uses this to fully empty the caches.
103 sc->nr_to_scan = dentries + 1;
104 freed = prune_dcache_sb(sb, sc);
105 sc->nr_to_scan = inodes + 1;
106 freed += prune_icache_sb(sb, sc);
109 sc->nr_to_scan = fs_objects + 1;
110 freed += sb->s_op->free_cached_objects(sb, sc);
113 up_read(&sb->s_umount);
117 static unsigned long super_cache_count(struct shrinker *shrink,
118 struct shrink_control *sc)
120 struct super_block *sb;
121 long total_objects = 0;
123 sb = container_of(shrink, struct super_block, s_shrink);
126 * We don't call trylock_super() here as it is a scalability bottleneck,
127 * so we're exposed to partial setup state. The shrinker rwsem does not
128 * protect filesystem operations backing list_lru_shrink_count() or
129 * s_op->nr_cached_objects(). Counts can change between
130 * super_cache_count and super_cache_scan, so we really don't need locks
133 * However, if we are currently mounting the superblock, the underlying
134 * filesystem might be in a state of partial construction and hence it
135 * is dangerous to access it. trylock_super() uses a SB_BORN check to
136 * avoid this situation, so do the same here. The memory barrier is
137 * matched with the one in mount_fs() as we don't hold locks here.
139 if (!(sb->s_flags & SB_BORN))
143 if (sb->s_op && sb->s_op->nr_cached_objects)
144 total_objects = sb->s_op->nr_cached_objects(sb, sc);
146 total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc);
147 total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc);
152 total_objects = vfs_pressure_ratio(total_objects);
153 return total_objects;
156 static void destroy_super_work(struct work_struct *work)
158 struct super_block *s = container_of(work, struct super_block,
162 for (i = 0; i < SB_FREEZE_LEVELS; i++)
163 percpu_free_rwsem(&s->s_writers.rw_sem[i]);
167 static void destroy_super_rcu(struct rcu_head *head)
169 struct super_block *s = container_of(head, struct super_block, rcu);
170 INIT_WORK(&s->destroy_work, destroy_super_work);
171 schedule_work(&s->destroy_work);
174 /* Free a superblock that has never been seen by anyone */
175 static void destroy_unused_super(struct super_block *s)
179 up_write(&s->s_umount);
180 list_lru_destroy(&s->s_dentry_lru);
181 list_lru_destroy(&s->s_inode_lru);
183 put_user_ns(s->s_user_ns);
185 free_prealloced_shrinker(&s->s_shrink);
186 /* no delays needed */
187 destroy_super_work(&s->destroy_work);
191 * alloc_super - create new superblock
192 * @type: filesystem type superblock should belong to
193 * @flags: the mount flags
194 * @user_ns: User namespace for the super_block
196 * Allocates and initializes a new &struct super_block. alloc_super()
197 * returns a pointer new superblock or %NULL if allocation had failed.
199 static struct super_block *alloc_super(struct file_system_type *type, int flags,
200 struct user_namespace *user_ns)
202 struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
203 static const struct super_operations default_op;
209 INIT_LIST_HEAD(&s->s_mounts);
210 s->s_user_ns = get_user_ns(user_ns);
211 init_rwsem(&s->s_umount);
212 lockdep_set_class(&s->s_umount, &type->s_umount_key);
214 * sget() can have s_umount recursion.
216 * When it cannot find a suitable sb, it allocates a new
217 * one (this one), and tries again to find a suitable old
220 * In case that succeeds, it will acquire the s_umount
221 * lock of the old one. Since these are clearly distrinct
222 * locks, and this object isn't exposed yet, there's no
225 * Annotate this by putting this lock in a different
228 down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
230 if (security_sb_alloc(s))
233 for (i = 0; i < SB_FREEZE_LEVELS; i++) {
234 if (__percpu_init_rwsem(&s->s_writers.rw_sem[i],
236 &type->s_writers_key[i]))
239 init_waitqueue_head(&s->s_writers.wait_unfrozen);
240 s->s_bdi = &noop_backing_dev_info;
242 if (s->s_user_ns != &init_user_ns)
243 s->s_iflags |= SB_I_NODEV;
244 INIT_HLIST_NODE(&s->s_instances);
245 INIT_HLIST_BL_HEAD(&s->s_roots);
246 mutex_init(&s->s_sync_lock);
247 INIT_LIST_HEAD(&s->s_inodes);
248 spin_lock_init(&s->s_inode_list_lock);
249 INIT_LIST_HEAD(&s->s_inodes_wb);
250 spin_lock_init(&s->s_inode_wblist_lock);
253 atomic_set(&s->s_active, 1);
254 mutex_init(&s->s_vfs_rename_mutex);
255 lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
256 init_rwsem(&s->s_dquot.dqio_sem);
257 s->s_maxbytes = MAX_NON_LFS;
258 s->s_op = &default_op;
259 s->s_time_gran = 1000000000;
260 s->s_time_min = TIME64_MIN;
261 s->s_time_max = TIME64_MAX;
263 s->s_shrink.seeks = DEFAULT_SEEKS;
264 s->s_shrink.scan_objects = super_cache_scan;
265 s->s_shrink.count_objects = super_cache_count;
266 s->s_shrink.batch = 1024;
267 s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
268 if (prealloc_shrinker(&s->s_shrink, "sb-%s", type->name))
270 if (list_lru_init_memcg(&s->s_dentry_lru, &s->s_shrink))
272 if (list_lru_init_memcg(&s->s_inode_lru, &s->s_shrink))
277 destroy_unused_super(s);
281 /* Superblock refcounting */
284 * Drop a superblock's refcount. The caller must hold sb_lock.
286 static void __put_super(struct super_block *s)
289 list_del_init(&s->s_list);
290 WARN_ON(s->s_dentry_lru.node);
291 WARN_ON(s->s_inode_lru.node);
292 WARN_ON(!list_empty(&s->s_mounts));
294 fscrypt_destroy_keyring(s);
295 put_user_ns(s->s_user_ns);
297 call_rcu(&s->rcu, destroy_super_rcu);
302 * put_super - drop a temporary reference to superblock
303 * @sb: superblock in question
305 * Drops a temporary reference, frees superblock if there's no
308 void put_super(struct super_block *sb)
312 spin_unlock(&sb_lock);
317 * deactivate_locked_super - drop an active reference to superblock
318 * @s: superblock to deactivate
320 * Drops an active reference to superblock, converting it into a temporary
321 * one if there is no other active references left. In that case we
322 * tell fs driver to shut it down and drop the temporary reference we
325 * Caller holds exclusive lock on superblock; that lock is released.
327 void deactivate_locked_super(struct super_block *s)
329 struct file_system_type *fs = s->s_type;
330 if (atomic_dec_and_test(&s->s_active)) {
331 unregister_shrinker(&s->s_shrink);
335 * Since list_lru_destroy() may sleep, we cannot call it from
336 * put_super(), where we hold the sb_lock. Therefore we destroy
337 * the lru lists right now.
339 list_lru_destroy(&s->s_dentry_lru);
340 list_lru_destroy(&s->s_inode_lru);
345 up_write(&s->s_umount);
349 EXPORT_SYMBOL(deactivate_locked_super);
352 * deactivate_super - drop an active reference to superblock
353 * @s: superblock to deactivate
355 * Variant of deactivate_locked_super(), except that superblock is *not*
356 * locked by caller. If we are going to drop the final active reference,
357 * lock will be acquired prior to that.
359 void deactivate_super(struct super_block *s)
361 if (!atomic_add_unless(&s->s_active, -1, 1)) {
362 down_write(&s->s_umount);
363 deactivate_locked_super(s);
367 EXPORT_SYMBOL(deactivate_super);
370 * grab_super - acquire an active reference
371 * @s: reference we are trying to make active
373 * Tries to acquire an active reference. grab_super() is used when we
374 * had just found a superblock in super_blocks or fs_type->fs_supers
375 * and want to turn it into a full-blown active reference. grab_super()
376 * is called with sb_lock held and drops it. Returns 1 in case of
377 * success, 0 if we had failed (superblock contents was already dead or
378 * dying when grab_super() had been called). Note that this is only
379 * called for superblocks not in rundown mode (== ones still on ->fs_supers
380 * of their type), so increment of ->s_count is OK here.
382 static int grab_super(struct super_block *s) __releases(sb_lock)
385 spin_unlock(&sb_lock);
386 down_write(&s->s_umount);
387 if ((s->s_flags & SB_BORN) && atomic_inc_not_zero(&s->s_active)) {
391 up_write(&s->s_umount);
397 * trylock_super - try to grab ->s_umount shared
398 * @sb: reference we are trying to grab
400 * Try to prevent fs shutdown. This is used in places where we
401 * cannot take an active reference but we need to ensure that the
402 * filesystem is not shut down while we are working on it. It returns
403 * false if we cannot acquire s_umount or if we lose the race and
404 * filesystem already got into shutdown, and returns true with the s_umount
405 * lock held in read mode in case of success. On successful return,
406 * the caller must drop the s_umount lock when done.
408 * Note that unlike get_super() et.al. this one does *not* bump ->s_count.
409 * The reason why it's safe is that we are OK with doing trylock instead
410 * of down_read(). There's a couple of places that are OK with that, but
411 * it's very much not a general-purpose interface.
413 bool trylock_super(struct super_block *sb)
415 if (down_read_trylock(&sb->s_umount)) {
416 if (!hlist_unhashed(&sb->s_instances) &&
417 sb->s_root && (sb->s_flags & SB_BORN))
419 up_read(&sb->s_umount);
426 * retire_super - prevents superblock from being reused
427 * @sb: superblock to retire
429 * The function marks superblock to be ignored in superblock test, which
430 * prevents it from being reused for any new mounts. If the superblock has
431 * a private bdi, it also unregisters it, but doesn't reduce the refcount
432 * of the superblock to prevent potential races. The refcount is reduced
433 * by generic_shutdown_super(). The function can not be called
434 * concurrently with generic_shutdown_super(). It is safe to call the
435 * function multiple times, subsequent calls have no effect.
437 * The marker will affect the re-use only for block-device-based
438 * superblocks. Other superblocks will still get marked if this function
439 * is used, but that will not affect their reusability.
441 void retire_super(struct super_block *sb)
443 WARN_ON(!sb->s_bdev);
444 down_write(&sb->s_umount);
445 if (sb->s_iflags & SB_I_PERSB_BDI) {
446 bdi_unregister(sb->s_bdi);
447 sb->s_iflags &= ~SB_I_PERSB_BDI;
449 sb->s_iflags |= SB_I_RETIRED;
450 up_write(&sb->s_umount);
452 EXPORT_SYMBOL(retire_super);
455 * generic_shutdown_super - common helper for ->kill_sb()
456 * @sb: superblock to kill
458 * generic_shutdown_super() does all fs-independent work on superblock
459 * shutdown. Typical ->kill_sb() should pick all fs-specific objects
460 * that need destruction out of superblock, call generic_shutdown_super()
461 * and release aforementioned objects. Note: dentries and inodes _are_
462 * taken care of and do not need specific handling.
464 * Upon calling this function, the filesystem may no longer alter or
465 * rearrange the set of dentries belonging to this super_block, nor may it
466 * change the attachments of dentries to inodes.
468 void generic_shutdown_super(struct super_block *sb)
470 const struct super_operations *sop = sb->s_op;
473 shrink_dcache_for_umount(sb);
475 sb->s_flags &= ~SB_ACTIVE;
477 cgroup_writeback_umount();
479 /* Evict all inodes with zero refcount. */
483 * Clean up and evict any inodes that still have references due
484 * to fsnotify or the security policy.
486 fsnotify_sb_delete(sb);
487 security_sb_delete(sb);
490 * Now that all potentially-encrypted inodes have been evicted,
491 * the fscrypt keyring can be destroyed.
493 fscrypt_destroy_keyring(sb);
495 if (sb->s_dio_done_wq) {
496 destroy_workqueue(sb->s_dio_done_wq);
497 sb->s_dio_done_wq = NULL;
503 if (CHECK_DATA_CORRUPTION(!list_empty(&sb->s_inodes),
504 "VFS: Busy inodes after unmount of %s (%s)",
505 sb->s_id, sb->s_type->name)) {
507 * Adding a proper bailout path here would be hard, but
508 * we can at least make it more likely that a later
509 * iput_final() or such crashes cleanly.
513 spin_lock(&sb->s_inode_list_lock);
514 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
515 inode->i_op = VFS_PTR_POISON;
516 inode->i_sb = VFS_PTR_POISON;
517 inode->i_mapping = VFS_PTR_POISON;
519 spin_unlock(&sb->s_inode_list_lock);
523 /* should be initialized for __put_super_and_need_restart() */
524 hlist_del_init(&sb->s_instances);
525 spin_unlock(&sb_lock);
526 up_write(&sb->s_umount);
527 if (sb->s_bdi != &noop_backing_dev_info) {
528 if (sb->s_iflags & SB_I_PERSB_BDI)
529 bdi_unregister(sb->s_bdi);
531 sb->s_bdi = &noop_backing_dev_info;
535 EXPORT_SYMBOL(generic_shutdown_super);
537 bool mount_capable(struct fs_context *fc)
539 if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT))
540 return capable(CAP_SYS_ADMIN);
542 return ns_capable(fc->user_ns, CAP_SYS_ADMIN);
546 * sget_fc - Find or create a superblock
547 * @fc: Filesystem context.
548 * @test: Comparison callback
549 * @set: Setup callback
551 * Find or create a superblock using the parameters stored in the filesystem
552 * context and the two callback functions.
554 * If an extant superblock is matched, then that will be returned with an
555 * elevated reference count that the caller must transfer or discard.
557 * If no match is made, a new superblock will be allocated and basic
558 * initialisation will be performed (s_type, s_fs_info and s_id will be set and
559 * the set() callback will be invoked), the superblock will be published and it
560 * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE
563 struct super_block *sget_fc(struct fs_context *fc,
564 int (*test)(struct super_block *, struct fs_context *),
565 int (*set)(struct super_block *, struct fs_context *))
567 struct super_block *s = NULL;
568 struct super_block *old;
569 struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;
575 hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {
577 goto share_extant_sb;
581 spin_unlock(&sb_lock);
582 s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);
584 return ERR_PTR(-ENOMEM);
588 s->s_fs_info = fc->s_fs_info;
592 spin_unlock(&sb_lock);
593 destroy_unused_super(s);
596 fc->s_fs_info = NULL;
597 s->s_type = fc->fs_type;
598 s->s_iflags |= fc->s_iflags;
599 strlcpy(s->s_id, s->s_type->name, sizeof(s->s_id));
600 list_add_tail(&s->s_list, &super_blocks);
601 hlist_add_head(&s->s_instances, &s->s_type->fs_supers);
602 spin_unlock(&sb_lock);
603 get_filesystem(s->s_type);
604 register_shrinker_prepared(&s->s_shrink);
608 if (user_ns != old->s_user_ns) {
609 spin_unlock(&sb_lock);
610 destroy_unused_super(s);
611 return ERR_PTR(-EBUSY);
613 if (!grab_super(old))
615 destroy_unused_super(s);
618 EXPORT_SYMBOL(sget_fc);
621 * sget - find or create a superblock
622 * @type: filesystem type superblock should belong to
623 * @test: comparison callback
624 * @set: setup callback
625 * @flags: mount flags
626 * @data: argument to each of them
628 struct super_block *sget(struct file_system_type *type,
629 int (*test)(struct super_block *,void *),
630 int (*set)(struct super_block *,void *),
634 struct user_namespace *user_ns = current_user_ns();
635 struct super_block *s = NULL;
636 struct super_block *old;
639 /* We don't yet pass the user namespace of the parent
640 * mount through to here so always use &init_user_ns
641 * until that changes.
643 if (flags & SB_SUBMOUNT)
644 user_ns = &init_user_ns;
649 hlist_for_each_entry(old, &type->fs_supers, s_instances) {
650 if (!test(old, data))
652 if (user_ns != old->s_user_ns) {
653 spin_unlock(&sb_lock);
654 destroy_unused_super(s);
655 return ERR_PTR(-EBUSY);
657 if (!grab_super(old))
659 destroy_unused_super(s);
664 spin_unlock(&sb_lock);
665 s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
667 return ERR_PTR(-ENOMEM);
673 spin_unlock(&sb_lock);
674 destroy_unused_super(s);
678 strlcpy(s->s_id, type->name, sizeof(s->s_id));
679 list_add_tail(&s->s_list, &super_blocks);
680 hlist_add_head(&s->s_instances, &type->fs_supers);
681 spin_unlock(&sb_lock);
682 get_filesystem(type);
683 register_shrinker_prepared(&s->s_shrink);
688 void drop_super(struct super_block *sb)
690 up_read(&sb->s_umount);
694 EXPORT_SYMBOL(drop_super);
696 void drop_super_exclusive(struct super_block *sb)
698 up_write(&sb->s_umount);
701 EXPORT_SYMBOL(drop_super_exclusive);
703 static void __iterate_supers(void (*f)(struct super_block *))
705 struct super_block *sb, *p = NULL;
708 list_for_each_entry(sb, &super_blocks, s_list) {
709 if (hlist_unhashed(&sb->s_instances))
712 spin_unlock(&sb_lock);
723 spin_unlock(&sb_lock);
726 * iterate_supers - call function for all active superblocks
727 * @f: function to call
728 * @arg: argument to pass to it
730 * Scans the superblock list and calls given function, passing it
731 * locked superblock and given argument.
733 void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
735 struct super_block *sb, *p = NULL;
738 list_for_each_entry(sb, &super_blocks, s_list) {
739 if (hlist_unhashed(&sb->s_instances))
742 spin_unlock(&sb_lock);
744 down_read(&sb->s_umount);
745 if (sb->s_root && (sb->s_flags & SB_BORN))
747 up_read(&sb->s_umount);
756 spin_unlock(&sb_lock);
760 * iterate_supers_type - call function for superblocks of given type
762 * @f: function to call
763 * @arg: argument to pass to it
765 * Scans the superblock list and calls given function, passing it
766 * locked superblock and given argument.
768 void iterate_supers_type(struct file_system_type *type,
769 void (*f)(struct super_block *, void *), void *arg)
771 struct super_block *sb, *p = NULL;
774 hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
776 spin_unlock(&sb_lock);
778 down_read(&sb->s_umount);
779 if (sb->s_root && (sb->s_flags & SB_BORN))
781 up_read(&sb->s_umount);
790 spin_unlock(&sb_lock);
793 EXPORT_SYMBOL(iterate_supers_type);
796 * get_super - get the superblock of a device
797 * @bdev: device to get the superblock for
799 * Scans the superblock list and finds the superblock of the file system
800 * mounted on the device given. %NULL is returned if no match is found.
802 struct super_block *get_super(struct block_device *bdev)
804 struct super_block *sb;
811 list_for_each_entry(sb, &super_blocks, s_list) {
812 if (hlist_unhashed(&sb->s_instances))
814 if (sb->s_bdev == bdev) {
816 spin_unlock(&sb_lock);
817 down_read(&sb->s_umount);
819 if (sb->s_root && (sb->s_flags & SB_BORN))
821 up_read(&sb->s_umount);
822 /* nope, got unmounted */
828 spin_unlock(&sb_lock);
833 * get_active_super - get an active reference to the superblock of a device
834 * @bdev: device to get the superblock for
836 * Scans the superblock list and finds the superblock of the file system
837 * mounted on the device given. Returns the superblock with an active
838 * reference or %NULL if none was found.
840 struct super_block *get_active_super(struct block_device *bdev)
842 struct super_block *sb;
849 list_for_each_entry(sb, &super_blocks, s_list) {
850 if (hlist_unhashed(&sb->s_instances))
852 if (sb->s_bdev == bdev) {
855 up_write(&sb->s_umount);
859 spin_unlock(&sb_lock);
863 struct super_block *user_get_super(dev_t dev, bool excl)
865 struct super_block *sb;
869 list_for_each_entry(sb, &super_blocks, s_list) {
870 if (hlist_unhashed(&sb->s_instances))
872 if (sb->s_dev == dev) {
874 spin_unlock(&sb_lock);
876 down_write(&sb->s_umount);
878 down_read(&sb->s_umount);
880 if (sb->s_root && (sb->s_flags & SB_BORN))
883 up_write(&sb->s_umount);
885 up_read(&sb->s_umount);
886 /* nope, got unmounted */
892 spin_unlock(&sb_lock);
897 * reconfigure_super - asks filesystem to change superblock parameters
898 * @fc: The superblock and configuration
900 * Alters the configuration parameters of a live superblock.
902 int reconfigure_super(struct fs_context *fc)
904 struct super_block *sb = fc->root->d_sb;
906 bool remount_ro = false;
907 bool remount_rw = false;
908 bool force = fc->sb_flags & SB_FORCE;
910 if (fc->sb_flags_mask & ~MS_RMT_MASK)
912 if (sb->s_writers.frozen != SB_UNFROZEN)
915 retval = security_sb_remount(sb, fc->security);
919 if (fc->sb_flags_mask & SB_RDONLY) {
921 if (!(fc->sb_flags & SB_RDONLY) && sb->s_bdev &&
922 bdev_read_only(sb->s_bdev))
925 remount_rw = !(fc->sb_flags & SB_RDONLY) && sb_rdonly(sb);
926 remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb);
930 if (!hlist_empty(&sb->s_pins)) {
931 up_write(&sb->s_umount);
932 group_pin_kill(&sb->s_pins);
933 down_write(&sb->s_umount);
936 if (sb->s_writers.frozen != SB_UNFROZEN)
938 remount_ro = !sb_rdonly(sb);
941 shrink_dcache_sb(sb);
943 /* If we are reconfiguring to RDONLY and current sb is read/write,
944 * make sure there are no files open for writing.
948 sb->s_readonly_remount = 1;
951 retval = sb_prepare_remount_readonly(sb);
955 } else if (remount_rw) {
957 * We set s_readonly_remount here to protect filesystem's
958 * reconfigure code from writes from userspace until
959 * reconfigure finishes.
961 sb->s_readonly_remount = 1;
965 if (fc->ops->reconfigure) {
966 retval = fc->ops->reconfigure(fc);
969 goto cancel_readonly;
970 /* If forced remount, go ahead despite any errors */
971 WARN(1, "forced remount of a %s fs returned %i\n",
972 sb->s_type->name, retval);
976 WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) |
977 (fc->sb_flags & fc->sb_flags_mask)));
978 /* Needs to be ordered wrt mnt_is_readonly() */
980 sb->s_readonly_remount = 0;
983 * Some filesystems modify their metadata via some other path than the
984 * bdev buffer cache (eg. use a private mapping, or directories in
985 * pagecache, etc). Also file data modifications go via their own
986 * mappings. So If we try to mount readonly then copy the filesystem
987 * from bdev, we could get stale data, so invalidate it to give a best
988 * effort at coherency.
990 if (remount_ro && sb->s_bdev)
991 invalidate_bdev(sb->s_bdev);
995 sb->s_readonly_remount = 0;
999 static void do_emergency_remount_callback(struct super_block *sb)
1001 down_write(&sb->s_umount);
1002 if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) &&
1004 struct fs_context *fc;
1006 fc = fs_context_for_reconfigure(sb->s_root,
1007 SB_RDONLY | SB_FORCE, SB_RDONLY);
1009 if (parse_monolithic_mount_data(fc, NULL) == 0)
1010 (void)reconfigure_super(fc);
1014 up_write(&sb->s_umount);
1017 static void do_emergency_remount(struct work_struct *work)
1019 __iterate_supers(do_emergency_remount_callback);
1021 printk("Emergency Remount complete\n");
1024 void emergency_remount(void)
1026 struct work_struct *work;
1028 work = kmalloc(sizeof(*work), GFP_ATOMIC);
1030 INIT_WORK(work, do_emergency_remount);
1031 schedule_work(work);
1035 static void do_thaw_all_callback(struct super_block *sb)
1037 down_write(&sb->s_umount);
1038 if (sb->s_root && sb->s_flags & SB_BORN) {
1039 emergency_thaw_bdev(sb);
1040 thaw_super_locked(sb);
1042 up_write(&sb->s_umount);
1046 static void do_thaw_all(struct work_struct *work)
1048 __iterate_supers(do_thaw_all_callback);
1050 printk(KERN_WARNING "Emergency Thaw complete\n");
1054 * emergency_thaw_all -- forcibly thaw every frozen filesystem
1056 * Used for emergency unfreeze of all filesystems via SysRq
1058 void emergency_thaw_all(void)
1060 struct work_struct *work;
1062 work = kmalloc(sizeof(*work), GFP_ATOMIC);
1064 INIT_WORK(work, do_thaw_all);
1065 schedule_work(work);
1069 static DEFINE_IDA(unnamed_dev_ida);
1072 * get_anon_bdev - Allocate a block device for filesystems which don't have one.
1073 * @p: Pointer to a dev_t.
1075 * Filesystems which don't use real block devices can call this function
1076 * to allocate a virtual block device.
1078 * Context: Any context. Frequently called while holding sb_lock.
1079 * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
1080 * or -ENOMEM if memory allocation failed.
1082 int get_anon_bdev(dev_t *p)
1087 * Many userspace utilities consider an FSID of 0 invalid.
1088 * Always return at least 1 from get_anon_bdev.
1090 dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
1100 EXPORT_SYMBOL(get_anon_bdev);
1102 void free_anon_bdev(dev_t dev)
1104 ida_free(&unnamed_dev_ida, MINOR(dev));
1106 EXPORT_SYMBOL(free_anon_bdev);
1108 int set_anon_super(struct super_block *s, void *data)
1110 return get_anon_bdev(&s->s_dev);
1112 EXPORT_SYMBOL(set_anon_super);
1114 void kill_anon_super(struct super_block *sb)
1116 dev_t dev = sb->s_dev;
1117 generic_shutdown_super(sb);
1118 free_anon_bdev(dev);
1120 EXPORT_SYMBOL(kill_anon_super);
1122 void kill_litter_super(struct super_block *sb)
1125 d_genocide(sb->s_root);
1126 kill_anon_super(sb);
1128 EXPORT_SYMBOL(kill_litter_super);
1130 int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)
1132 return set_anon_super(sb, NULL);
1134 EXPORT_SYMBOL(set_anon_super_fc);
1136 static int test_keyed_super(struct super_block *sb, struct fs_context *fc)
1138 return sb->s_fs_info == fc->s_fs_info;
1141 static int test_single_super(struct super_block *s, struct fs_context *fc)
1147 * vfs_get_super - Get a superblock with a search key set in s_fs_info.
1148 * @fc: The filesystem context holding the parameters
1149 * @keying: How to distinguish superblocks
1150 * @fill_super: Helper to initialise a new superblock
1152 * Search for a superblock and create a new one if not found. The search
1153 * criterion is controlled by @keying. If the search fails, a new superblock
1154 * is created and @fill_super() is called to initialise it.
1156 * @keying can take one of a number of values:
1158 * (1) vfs_get_single_super - Only one superblock of this type may exist on the
1159 * system. This is typically used for special system filesystems.
1161 * (2) vfs_get_keyed_super - Multiple superblocks may exist, but they must have
1162 * distinct keys (where the key is in s_fs_info). Searching for the same
1163 * key again will turn up the superblock for that key.
1165 * (3) vfs_get_independent_super - Multiple superblocks may exist and are
1166 * unkeyed. Each call will get a new superblock.
1168 * A permissions check is made by sget_fc() unless we're getting a superblock
1169 * for a kernel-internal mount or a submount.
1171 int vfs_get_super(struct fs_context *fc,
1172 enum vfs_get_super_keying keying,
1173 int (*fill_super)(struct super_block *sb,
1174 struct fs_context *fc))
1176 int (*test)(struct super_block *, struct fs_context *);
1177 struct super_block *sb;
1181 case vfs_get_single_super:
1182 case vfs_get_single_reconf_super:
1183 test = test_single_super;
1185 case vfs_get_keyed_super:
1186 test = test_keyed_super;
1188 case vfs_get_independent_super:
1195 sb = sget_fc(fc, test, set_anon_super_fc);
1200 err = fill_super(sb, fc);
1204 sb->s_flags |= SB_ACTIVE;
1205 fc->root = dget(sb->s_root);
1207 fc->root = dget(sb->s_root);
1208 if (keying == vfs_get_single_reconf_super) {
1209 err = reconfigure_super(fc);
1221 deactivate_locked_super(sb);
1224 EXPORT_SYMBOL(vfs_get_super);
1226 int get_tree_nodev(struct fs_context *fc,
1227 int (*fill_super)(struct super_block *sb,
1228 struct fs_context *fc))
1230 return vfs_get_super(fc, vfs_get_independent_super, fill_super);
1232 EXPORT_SYMBOL(get_tree_nodev);
1234 int get_tree_single(struct fs_context *fc,
1235 int (*fill_super)(struct super_block *sb,
1236 struct fs_context *fc))
1238 return vfs_get_super(fc, vfs_get_single_super, fill_super);
1240 EXPORT_SYMBOL(get_tree_single);
1242 int get_tree_single_reconf(struct fs_context *fc,
1243 int (*fill_super)(struct super_block *sb,
1244 struct fs_context *fc))
1246 return vfs_get_super(fc, vfs_get_single_reconf_super, fill_super);
1248 EXPORT_SYMBOL(get_tree_single_reconf);
1250 int get_tree_keyed(struct fs_context *fc,
1251 int (*fill_super)(struct super_block *sb,
1252 struct fs_context *fc),
1255 fc->s_fs_info = key;
1256 return vfs_get_super(fc, vfs_get_keyed_super, fill_super);
1258 EXPORT_SYMBOL(get_tree_keyed);
1262 static int set_bdev_super(struct super_block *s, void *data)
1265 s->s_dev = s->s_bdev->bd_dev;
1266 s->s_bdi = bdi_get(s->s_bdev->bd_disk->bdi);
1268 if (bdev_stable_writes(s->s_bdev))
1269 s->s_iflags |= SB_I_STABLE_WRITES;
1273 static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1275 return set_bdev_super(s, fc->sget_key);
1278 static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1280 return !(s->s_iflags & SB_I_RETIRED) && s->s_bdev == fc->sget_key;
1284 * get_tree_bdev - Get a superblock based on a single block device
1285 * @fc: The filesystem context holding the parameters
1286 * @fill_super: Helper to initialise a new superblock
1288 int get_tree_bdev(struct fs_context *fc,
1289 int (*fill_super)(struct super_block *,
1290 struct fs_context *))
1292 struct block_device *bdev;
1293 struct super_block *s;
1294 fmode_t mode = FMODE_READ | FMODE_EXCL;
1297 if (!(fc->sb_flags & SB_RDONLY))
1298 mode |= FMODE_WRITE;
1301 return invalf(fc, "No source specified");
1303 bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type);
1305 errorf(fc, "%s: Can't open blockdev", fc->source);
1306 return PTR_ERR(bdev);
1309 /* Once the superblock is inserted into the list by sget_fc(), s_umount
1310 * will protect the lockfs code from trying to start a snapshot while
1313 mutex_lock(&bdev->bd_fsfreeze_mutex);
1314 if (bdev->bd_fsfreeze_count > 0) {
1315 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1316 warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
1317 blkdev_put(bdev, mode);
1321 fc->sb_flags |= SB_NOSEC;
1322 fc->sget_key = bdev;
1323 s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc);
1324 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1326 blkdev_put(bdev, mode);
1331 /* Don't summarily change the RO/RW state. */
1332 if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
1333 warnf(fc, "%pg: Can't mount, would change RO state", bdev);
1334 deactivate_locked_super(s);
1335 blkdev_put(bdev, mode);
1340 * s_umount nests inside open_mutex during
1341 * __invalidate_device(). blkdev_put() acquires
1342 * open_mutex and can't be called under s_umount. Drop
1343 * s_umount temporarily. This is safe as we're
1344 * holding an active reference.
1346 up_write(&s->s_umount);
1347 blkdev_put(bdev, mode);
1348 down_write(&s->s_umount);
1351 snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1352 shrinker_debugfs_rename(&s->s_shrink, "sb-%s:%s",
1353 fc->fs_type->name, s->s_id);
1354 sb_set_blocksize(s, block_size(bdev));
1355 error = fill_super(s, fc);
1357 deactivate_locked_super(s);
1361 s->s_flags |= SB_ACTIVE;
1366 fc->root = dget(s->s_root);
1369 EXPORT_SYMBOL(get_tree_bdev);
1371 static int test_bdev_super(struct super_block *s, void *data)
1373 return !(s->s_iflags & SB_I_RETIRED) && (void *)s->s_bdev == data;
1376 struct dentry *mount_bdev(struct file_system_type *fs_type,
1377 int flags, const char *dev_name, void *data,
1378 int (*fill_super)(struct super_block *, void *, int))
1380 struct block_device *bdev;
1381 struct super_block *s;
1382 fmode_t mode = FMODE_READ | FMODE_EXCL;
1385 if (!(flags & SB_RDONLY))
1386 mode |= FMODE_WRITE;
1388 bdev = blkdev_get_by_path(dev_name, mode, fs_type);
1390 return ERR_CAST(bdev);
1393 * once the super is inserted into the list by sget, s_umount
1394 * will protect the lockfs code from trying to start a snapshot
1395 * while we are mounting
1397 mutex_lock(&bdev->bd_fsfreeze_mutex);
1398 if (bdev->bd_fsfreeze_count > 0) {
1399 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1403 s = sget(fs_type, test_bdev_super, set_bdev_super, flags | SB_NOSEC,
1405 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1410 if ((flags ^ s->s_flags) & SB_RDONLY) {
1411 deactivate_locked_super(s);
1417 * s_umount nests inside open_mutex during
1418 * __invalidate_device(). blkdev_put() acquires
1419 * open_mutex and can't be called under s_umount. Drop
1420 * s_umount temporarily. This is safe as we're
1421 * holding an active reference.
1423 up_write(&s->s_umount);
1424 blkdev_put(bdev, mode);
1425 down_write(&s->s_umount);
1428 snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1429 shrinker_debugfs_rename(&s->s_shrink, "sb-%s:%s",
1430 fs_type->name, s->s_id);
1431 sb_set_blocksize(s, block_size(bdev));
1432 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1434 deactivate_locked_super(s);
1438 s->s_flags |= SB_ACTIVE;
1442 return dget(s->s_root);
1447 blkdev_put(bdev, mode);
1449 return ERR_PTR(error);
1451 EXPORT_SYMBOL(mount_bdev);
1453 void kill_block_super(struct super_block *sb)
1455 struct block_device *bdev = sb->s_bdev;
1456 fmode_t mode = sb->s_mode;
1458 bdev->bd_super = NULL;
1459 generic_shutdown_super(sb);
1460 sync_blockdev(bdev);
1461 WARN_ON_ONCE(!(mode & FMODE_EXCL));
1462 blkdev_put(bdev, mode | FMODE_EXCL);
1465 EXPORT_SYMBOL(kill_block_super);
1468 struct dentry *mount_nodev(struct file_system_type *fs_type,
1469 int flags, void *data,
1470 int (*fill_super)(struct super_block *, void *, int))
1473 struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
1478 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1480 deactivate_locked_super(s);
1481 return ERR_PTR(error);
1483 s->s_flags |= SB_ACTIVE;
1484 return dget(s->s_root);
1486 EXPORT_SYMBOL(mount_nodev);
1488 int reconfigure_single(struct super_block *s,
1489 int flags, void *data)
1491 struct fs_context *fc;
1494 /* The caller really need to be passing fc down into mount_single(),
1495 * then a chunk of this can be removed. [Bollocks -- AV]
1496 * Better yet, reconfiguration shouldn't happen, but rather the second
1497 * mount should be rejected if the parameters are not compatible.
1499 fc = fs_context_for_reconfigure(s->s_root, flags, MS_RMT_MASK);
1503 ret = parse_monolithic_mount_data(fc, data);
1507 ret = reconfigure_super(fc);
1513 static int compare_single(struct super_block *s, void *p)
1518 struct dentry *mount_single(struct file_system_type *fs_type,
1519 int flags, void *data,
1520 int (*fill_super)(struct super_block *, void *, int))
1522 struct super_block *s;
1525 s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
1529 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1531 s->s_flags |= SB_ACTIVE;
1533 error = reconfigure_single(s, flags, data);
1535 if (unlikely(error)) {
1536 deactivate_locked_super(s);
1537 return ERR_PTR(error);
1539 return dget(s->s_root);
1541 EXPORT_SYMBOL(mount_single);
1544 * vfs_get_tree - Get the mountable root
1545 * @fc: The superblock configuration context.
1547 * The filesystem is invoked to get or create a superblock which can then later
1548 * be used for mounting. The filesystem places a pointer to the root to be
1549 * used for mounting in @fc->root.
1551 int vfs_get_tree(struct fs_context *fc)
1553 struct super_block *sb;
1559 /* Get the mountable root in fc->root, with a ref on the root and a ref
1560 * on the superblock.
1562 error = fc->ops->get_tree(fc);
1567 pr_err("Filesystem %s get_tree() didn't set fc->root\n",
1569 /* We don't know what the locking state of the superblock is -
1570 * if there is a superblock.
1575 sb = fc->root->d_sb;
1576 WARN_ON(!sb->s_bdi);
1579 * Write barrier is for super_cache_count(). We place it before setting
1580 * SB_BORN as the data dependency between the two functions is the
1581 * superblock structure contents that we just set up, not the SB_BORN
1585 sb->s_flags |= SB_BORN;
1587 error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL);
1588 if (unlikely(error)) {
1594 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1595 * but s_maxbytes was an unsigned long long for many releases. Throw
1596 * this warning for a little while to try and catch filesystems that
1597 * violate this rule.
1599 WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
1600 "negative value (%lld)\n", fc->fs_type->name, sb->s_maxbytes);
1604 EXPORT_SYMBOL(vfs_get_tree);
1607 * Setup private BDI for given superblock. It gets automatically cleaned up
1608 * in generic_shutdown_super().
1610 int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)
1612 struct backing_dev_info *bdi;
1616 bdi = bdi_alloc(NUMA_NO_NODE);
1620 va_start(args, fmt);
1621 err = bdi_register_va(bdi, fmt, args);
1627 WARN_ON(sb->s_bdi != &noop_backing_dev_info);
1629 sb->s_iflags |= SB_I_PERSB_BDI;
1633 EXPORT_SYMBOL(super_setup_bdi_name);
1636 * Setup private BDI for given superblock. I gets automatically cleaned up
1637 * in generic_shutdown_super().
1639 int super_setup_bdi(struct super_block *sb)
1641 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
1643 return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,
1644 atomic_long_inc_return(&bdi_seq));
1646 EXPORT_SYMBOL(super_setup_bdi);
1649 * sb_wait_write - wait until all writers to given file system finish
1650 * @sb: the super for which we wait
1651 * @level: type of writers we wait for (normal vs page fault)
1653 * This function waits until there are no writers of given type to given file
1656 static void sb_wait_write(struct super_block *sb, int level)
1658 percpu_down_write(sb->s_writers.rw_sem + level-1);
1662 * We are going to return to userspace and forget about these locks, the
1663 * ownership goes to the caller of thaw_super() which does unlock().
1665 static void lockdep_sb_freeze_release(struct super_block *sb)
1669 for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
1670 percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1674 * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
1676 static void lockdep_sb_freeze_acquire(struct super_block *sb)
1680 for (level = 0; level < SB_FREEZE_LEVELS; ++level)
1681 percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1684 static void sb_freeze_unlock(struct super_block *sb, int level)
1686 for (level--; level >= 0; level--)
1687 percpu_up_write(sb->s_writers.rw_sem + level);
1691 * freeze_super - lock the filesystem and force it into a consistent state
1692 * @sb: the super to lock
1694 * Syncs the super to make sure the filesystem is consistent and calls the fs's
1695 * freeze_fs. Subsequent calls to this without first thawing the fs will return
1698 * During this function, sb->s_writers.frozen goes through these values:
1700 * SB_UNFROZEN: File system is normal, all writes progress as usual.
1702 * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
1703 * writes should be blocked, though page faults are still allowed. We wait for
1704 * all writes to complete and then proceed to the next stage.
1706 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
1707 * but internal fs threads can still modify the filesystem (although they
1708 * should not dirty new pages or inodes), writeback can run etc. After waiting
1709 * for all running page faults we sync the filesystem which will clean all
1710 * dirty pages and inodes (no new dirty pages or inodes can be created when
1713 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
1714 * modification are blocked (e.g. XFS preallocation truncation on inode
1715 * reclaim). This is usually implemented by blocking new transactions for
1716 * filesystems that have them and need this additional guard. After all
1717 * internal writers are finished we call ->freeze_fs() to finish filesystem
1718 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
1719 * mostly auxiliary for filesystems to verify they do not modify frozen fs.
1721 * sb->s_writers.frozen is protected by sb->s_umount.
1723 int freeze_super(struct super_block *sb)
1727 atomic_inc(&sb->s_active);
1728 down_write(&sb->s_umount);
1729 if (sb->s_writers.frozen != SB_UNFROZEN) {
1730 deactivate_locked_super(sb);
1734 if (!(sb->s_flags & SB_BORN)) {
1735 up_write(&sb->s_umount);
1736 return 0; /* sic - it's "nothing to do" */
1739 if (sb_rdonly(sb)) {
1740 /* Nothing to do really... */
1741 sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1742 up_write(&sb->s_umount);
1746 sb->s_writers.frozen = SB_FREEZE_WRITE;
1747 /* Release s_umount to preserve sb_start_write -> s_umount ordering */
1748 up_write(&sb->s_umount);
1749 sb_wait_write(sb, SB_FREEZE_WRITE);
1750 down_write(&sb->s_umount);
1752 /* Now we go and block page faults... */
1753 sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
1754 sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
1756 /* All writers are done so after syncing there won't be dirty data */
1757 ret = sync_filesystem(sb);
1759 sb->s_writers.frozen = SB_UNFROZEN;
1760 sb_freeze_unlock(sb, SB_FREEZE_PAGEFAULT);
1761 wake_up(&sb->s_writers.wait_unfrozen);
1762 deactivate_locked_super(sb);
1766 /* Now wait for internal filesystem counter */
1767 sb->s_writers.frozen = SB_FREEZE_FS;
1768 sb_wait_write(sb, SB_FREEZE_FS);
1770 if (sb->s_op->freeze_fs) {
1771 ret = sb->s_op->freeze_fs(sb);
1774 "VFS:Filesystem freeze failed\n");
1775 sb->s_writers.frozen = SB_UNFROZEN;
1776 sb_freeze_unlock(sb, SB_FREEZE_FS);
1777 wake_up(&sb->s_writers.wait_unfrozen);
1778 deactivate_locked_super(sb);
1783 * For debugging purposes so that fs can warn if it sees write activity
1784 * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
1786 sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1787 lockdep_sb_freeze_release(sb);
1788 up_write(&sb->s_umount);
1791 EXPORT_SYMBOL(freeze_super);
1793 static int thaw_super_locked(struct super_block *sb)
1797 if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) {
1798 up_write(&sb->s_umount);
1802 if (sb_rdonly(sb)) {
1803 sb->s_writers.frozen = SB_UNFROZEN;
1807 lockdep_sb_freeze_acquire(sb);
1809 if (sb->s_op->unfreeze_fs) {
1810 error = sb->s_op->unfreeze_fs(sb);
1813 "VFS:Filesystem thaw failed\n");
1814 lockdep_sb_freeze_release(sb);
1815 up_write(&sb->s_umount);
1820 sb->s_writers.frozen = SB_UNFROZEN;
1821 sb_freeze_unlock(sb, SB_FREEZE_FS);
1823 wake_up(&sb->s_writers.wait_unfrozen);
1824 deactivate_locked_super(sb);
1829 * thaw_super -- unlock filesystem
1830 * @sb: the super to thaw
1832 * Unlocks the filesystem and marks it writeable again after freeze_super().
1834 int thaw_super(struct super_block *sb)
1836 down_write(&sb->s_umount);
1837 return thaw_super_locked(sb);
1839 EXPORT_SYMBOL(thaw_super);