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/cleancache.h>
35 #include <linux/fscrypt.h>
36 #include <linux/fsnotify.h>
37 #include <linux/lockdep.h>
38 #include <linux/user_namespace.h>
39 #include <linux/fs_context.h>
40 #include <uapi/linux/mount.h>
43 static int thaw_super_locked(struct super_block
*sb
);
45 static LIST_HEAD(super_blocks
);
46 static DEFINE_SPINLOCK(sb_lock
);
48 static char *sb_writers_name
[SB_FREEZE_LEVELS
] = {
55 * One thing we have to be careful of with a per-sb shrinker is that we don't
56 * drop the last active reference to the superblock from within the shrinker.
57 * If that happens we could trigger unregistering the shrinker from within the
58 * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
59 * take a passive reference to the superblock to avoid this from occurring.
61 static unsigned long super_cache_scan(struct shrinker
*shrink
,
62 struct shrink_control
*sc
)
64 struct super_block
*sb
;
71 sb
= container_of(shrink
, struct super_block
, s_shrink
);
74 * Deadlock avoidance. We may hold various FS locks, and we don't want
75 * to recurse into the FS that called us in clear_inode() and friends..
77 if (!(sc
->gfp_mask
& __GFP_FS
))
80 if (!trylock_super(sb
))
83 if (sb
->s_op
->nr_cached_objects
)
84 fs_objects
= sb
->s_op
->nr_cached_objects(sb
, sc
);
86 inodes
= list_lru_shrink_count(&sb
->s_inode_lru
, sc
);
87 dentries
= list_lru_shrink_count(&sb
->s_dentry_lru
, sc
);
88 total_objects
= dentries
+ inodes
+ fs_objects
+ 1;
92 /* proportion the scan between the caches */
93 dentries
= mult_frac(sc
->nr_to_scan
, dentries
, total_objects
);
94 inodes
= mult_frac(sc
->nr_to_scan
, inodes
, total_objects
);
95 fs_objects
= mult_frac(sc
->nr_to_scan
, fs_objects
, total_objects
);
98 * prune the dcache first as the icache is pinned by it, then
99 * prune the icache, followed by the filesystem specific caches
101 * Ensure that we always scan at least one object - memcg kmem
102 * accounting uses this to fully empty the caches.
104 sc
->nr_to_scan
= dentries
+ 1;
105 freed
= prune_dcache_sb(sb
, sc
);
106 sc
->nr_to_scan
= inodes
+ 1;
107 freed
+= prune_icache_sb(sb
, sc
);
110 sc
->nr_to_scan
= fs_objects
+ 1;
111 freed
+= sb
->s_op
->free_cached_objects(sb
, sc
);
114 up_read(&sb
->s_umount
);
118 static unsigned long super_cache_count(struct shrinker
*shrink
,
119 struct shrink_control
*sc
)
121 struct super_block
*sb
;
122 long total_objects
= 0;
124 sb
= container_of(shrink
, struct super_block
, s_shrink
);
127 * We don't call trylock_super() here as it is a scalability bottleneck,
128 * so we're exposed to partial setup state. The shrinker rwsem does not
129 * protect filesystem operations backing list_lru_shrink_count() or
130 * s_op->nr_cached_objects(). Counts can change between
131 * super_cache_count and super_cache_scan, so we really don't need locks
134 * However, if we are currently mounting the superblock, the underlying
135 * filesystem might be in a state of partial construction and hence it
136 * is dangerous to access it. trylock_super() uses a SB_BORN check to
137 * avoid this situation, so do the same here. The memory barrier is
138 * matched with the one in mount_fs() as we don't hold locks here.
140 if (!(sb
->s_flags
& SB_BORN
))
144 if (sb
->s_op
&& sb
->s_op
->nr_cached_objects
)
145 total_objects
= sb
->s_op
->nr_cached_objects(sb
, sc
);
147 total_objects
+= list_lru_shrink_count(&sb
->s_dentry_lru
, sc
);
148 total_objects
+= list_lru_shrink_count(&sb
->s_inode_lru
, sc
);
153 total_objects
= vfs_pressure_ratio(total_objects
);
154 return total_objects
;
157 static void destroy_super_work(struct work_struct
*work
)
159 struct super_block
*s
= container_of(work
, struct super_block
,
163 for (i
= 0; i
< SB_FREEZE_LEVELS
; i
++)
164 percpu_free_rwsem(&s
->s_writers
.rw_sem
[i
]);
168 static void destroy_super_rcu(struct rcu_head
*head
)
170 struct super_block
*s
= container_of(head
, struct super_block
, rcu
);
171 INIT_WORK(&s
->destroy_work
, destroy_super_work
);
172 schedule_work(&s
->destroy_work
);
175 /* Free a superblock that has never been seen by anyone */
176 static void destroy_unused_super(struct super_block
*s
)
180 up_write(&s
->s_umount
);
181 list_lru_destroy(&s
->s_dentry_lru
);
182 list_lru_destroy(&s
->s_inode_lru
);
184 put_user_ns(s
->s_user_ns
);
186 free_prealloced_shrinker(&s
->s_shrink
);
187 /* no delays needed */
188 destroy_super_work(&s
->destroy_work
);
192 * alloc_super - create new superblock
193 * @type: filesystem type superblock should belong to
194 * @flags: the mount flags
195 * @user_ns: User namespace for the super_block
197 * Allocates and initializes a new &struct super_block. alloc_super()
198 * returns a pointer new superblock or %NULL if allocation had failed.
200 static struct super_block
*alloc_super(struct file_system_type
*type
, int flags
,
201 struct user_namespace
*user_ns
)
203 struct super_block
*s
= kzalloc(sizeof(struct super_block
), GFP_USER
);
204 static const struct super_operations default_op
;
210 INIT_LIST_HEAD(&s
->s_mounts
);
211 s
->s_user_ns
= get_user_ns(user_ns
);
212 init_rwsem(&s
->s_umount
);
213 lockdep_set_class(&s
->s_umount
, &type
->s_umount_key
);
215 * sget() can have s_umount recursion.
217 * When it cannot find a suitable sb, it allocates a new
218 * one (this one), and tries again to find a suitable old
221 * In case that succeeds, it will acquire the s_umount
222 * lock of the old one. Since these are clearly distrinct
223 * locks, and this object isn't exposed yet, there's no
226 * Annotate this by putting this lock in a different
229 down_write_nested(&s
->s_umount
, SINGLE_DEPTH_NESTING
);
231 if (security_sb_alloc(s
))
234 for (i
= 0; i
< SB_FREEZE_LEVELS
; i
++) {
235 if (__percpu_init_rwsem(&s
->s_writers
.rw_sem
[i
],
237 &type
->s_writers_key
[i
]))
240 init_waitqueue_head(&s
->s_writers
.wait_unfrozen
);
241 s
->s_bdi
= &noop_backing_dev_info
;
243 if (s
->s_user_ns
!= &init_user_ns
)
244 s
->s_iflags
|= SB_I_NODEV
;
245 INIT_HLIST_NODE(&s
->s_instances
);
246 INIT_HLIST_BL_HEAD(&s
->s_roots
);
247 mutex_init(&s
->s_sync_lock
);
248 INIT_LIST_HEAD(&s
->s_inodes
);
249 spin_lock_init(&s
->s_inode_list_lock
);
250 INIT_LIST_HEAD(&s
->s_inodes_wb
);
251 spin_lock_init(&s
->s_inode_wblist_lock
);
254 atomic_set(&s
->s_active
, 1);
255 mutex_init(&s
->s_vfs_rename_mutex
);
256 lockdep_set_class(&s
->s_vfs_rename_mutex
, &type
->s_vfs_rename_key
);
257 init_rwsem(&s
->s_dquot
.dqio_sem
);
258 s
->s_maxbytes
= MAX_NON_LFS
;
259 s
->s_op
= &default_op
;
260 s
->s_time_gran
= 1000000000;
261 s
->s_time_min
= TIME64_MIN
;
262 s
->s_time_max
= TIME64_MAX
;
263 s
->cleancache_poolid
= CLEANCACHE_NO_POOL
;
265 s
->s_shrink
.seeks
= DEFAULT_SEEKS
;
266 s
->s_shrink
.scan_objects
= super_cache_scan
;
267 s
->s_shrink
.count_objects
= super_cache_count
;
268 s
->s_shrink
.batch
= 1024;
269 s
->s_shrink
.flags
= SHRINKER_NUMA_AWARE
| SHRINKER_MEMCG_AWARE
;
270 if (prealloc_shrinker(&s
->s_shrink
))
272 if (list_lru_init_memcg(&s
->s_dentry_lru
, &s
->s_shrink
))
274 if (list_lru_init_memcg(&s
->s_inode_lru
, &s
->s_shrink
))
279 destroy_unused_super(s
);
283 /* Superblock refcounting */
286 * Drop a superblock's refcount. The caller must hold sb_lock.
288 static void __put_super(struct super_block
*s
)
291 list_del_init(&s
->s_list
);
292 WARN_ON(s
->s_dentry_lru
.node
);
293 WARN_ON(s
->s_inode_lru
.node
);
294 WARN_ON(!list_empty(&s
->s_mounts
));
297 put_user_ns(s
->s_user_ns
);
299 call_rcu(&s
->rcu
, destroy_super_rcu
);
304 * put_super - drop a temporary reference to superblock
305 * @sb: superblock in question
307 * Drops a temporary reference, frees superblock if there's no
310 void put_super(struct super_block
*sb
)
314 spin_unlock(&sb_lock
);
319 * deactivate_locked_super - drop an active reference to superblock
320 * @s: superblock to deactivate
322 * Drops an active reference to superblock, converting it into a temporary
323 * one if there is no other active references left. In that case we
324 * tell fs driver to shut it down and drop the temporary reference we
327 * Caller holds exclusive lock on superblock; that lock is released.
329 void deactivate_locked_super(struct super_block
*s
)
331 struct file_system_type
*fs
= s
->s_type
;
332 if (atomic_dec_and_test(&s
->s_active
)) {
333 cleancache_invalidate_fs(s
);
334 unregister_shrinker(&s
->s_shrink
);
338 * Since list_lru_destroy() may sleep, we cannot call it from
339 * put_super(), where we hold the sb_lock. Therefore we destroy
340 * the lru lists right now.
342 list_lru_destroy(&s
->s_dentry_lru
);
343 list_lru_destroy(&s
->s_inode_lru
);
348 up_write(&s
->s_umount
);
352 EXPORT_SYMBOL(deactivate_locked_super
);
355 * deactivate_super - drop an active reference to superblock
356 * @s: superblock to deactivate
358 * Variant of deactivate_locked_super(), except that superblock is *not*
359 * locked by caller. If we are going to drop the final active reference,
360 * lock will be acquired prior to that.
362 void deactivate_super(struct super_block
*s
)
364 if (!atomic_add_unless(&s
->s_active
, -1, 1)) {
365 down_write(&s
->s_umount
);
366 deactivate_locked_super(s
);
370 EXPORT_SYMBOL(deactivate_super
);
373 * grab_super - acquire an active reference
374 * @s: reference we are trying to make active
376 * Tries to acquire an active reference. grab_super() is used when we
377 * had just found a superblock in super_blocks or fs_type->fs_supers
378 * and want to turn it into a full-blown active reference. grab_super()
379 * is called with sb_lock held and drops it. Returns 1 in case of
380 * success, 0 if we had failed (superblock contents was already dead or
381 * dying when grab_super() had been called). Note that this is only
382 * called for superblocks not in rundown mode (== ones still on ->fs_supers
383 * of their type), so increment of ->s_count is OK here.
385 static int grab_super(struct super_block
*s
) __releases(sb_lock
)
388 spin_unlock(&sb_lock
);
389 down_write(&s
->s_umount
);
390 if ((s
->s_flags
& SB_BORN
) && atomic_inc_not_zero(&s
->s_active
)) {
394 up_write(&s
->s_umount
);
400 * trylock_super - try to grab ->s_umount shared
401 * @sb: reference we are trying to grab
403 * Try to prevent fs shutdown. This is used in places where we
404 * cannot take an active reference but we need to ensure that the
405 * filesystem is not shut down while we are working on it. It returns
406 * false if we cannot acquire s_umount or if we lose the race and
407 * filesystem already got into shutdown, and returns true with the s_umount
408 * lock held in read mode in case of success. On successful return,
409 * the caller must drop the s_umount lock when done.
411 * Note that unlike get_super() et.al. this one does *not* bump ->s_count.
412 * The reason why it's safe is that we are OK with doing trylock instead
413 * of down_read(). There's a couple of places that are OK with that, but
414 * it's very much not a general-purpose interface.
416 bool trylock_super(struct super_block
*sb
)
418 if (down_read_trylock(&sb
->s_umount
)) {
419 if (!hlist_unhashed(&sb
->s_instances
) &&
420 sb
->s_root
&& (sb
->s_flags
& SB_BORN
))
422 up_read(&sb
->s_umount
);
429 * generic_shutdown_super - common helper for ->kill_sb()
430 * @sb: superblock to kill
432 * generic_shutdown_super() does all fs-independent work on superblock
433 * shutdown. Typical ->kill_sb() should pick all fs-specific objects
434 * that need destruction out of superblock, call generic_shutdown_super()
435 * and release aforementioned objects. Note: dentries and inodes _are_
436 * taken care of and do not need specific handling.
438 * Upon calling this function, the filesystem may no longer alter or
439 * rearrange the set of dentries belonging to this super_block, nor may it
440 * change the attachments of dentries to inodes.
442 void generic_shutdown_super(struct super_block
*sb
)
444 const struct super_operations
*sop
= sb
->s_op
;
447 shrink_dcache_for_umount(sb
);
449 sb
->s_flags
&= ~SB_ACTIVE
;
451 cgroup_writeback_umount();
453 /* evict all inodes with zero refcount */
455 /* only nonzero refcount inodes can have marks */
456 fsnotify_sb_delete(sb
);
458 if (sb
->s_dio_done_wq
) {
459 destroy_workqueue(sb
->s_dio_done_wq
);
460 sb
->s_dio_done_wq
= NULL
;
466 if (!list_empty(&sb
->s_inodes
)) {
467 printk("VFS: Busy inodes after unmount of %s. "
468 "Self-destruct in 5 seconds. Have a nice day...\n",
473 /* should be initialized for __put_super_and_need_restart() */
474 hlist_del_init(&sb
->s_instances
);
475 spin_unlock(&sb_lock
);
476 up_write(&sb
->s_umount
);
477 if (sb
->s_bdi
!= &noop_backing_dev_info
) {
479 sb
->s_bdi
= &noop_backing_dev_info
;
483 EXPORT_SYMBOL(generic_shutdown_super
);
485 bool mount_capable(struct fs_context
*fc
)
487 if (!(fc
->fs_type
->fs_flags
& FS_USERNS_MOUNT
))
488 return capable(CAP_SYS_ADMIN
);
490 return ns_capable(fc
->user_ns
, CAP_SYS_ADMIN
);
494 * sget_fc - Find or create a superblock
495 * @fc: Filesystem context.
496 * @test: Comparison callback
497 * @set: Setup callback
499 * Find or create a superblock using the parameters stored in the filesystem
500 * context and the two callback functions.
502 * If an extant superblock is matched, then that will be returned with an
503 * elevated reference count that the caller must transfer or discard.
505 * If no match is made, a new superblock will be allocated and basic
506 * initialisation will be performed (s_type, s_fs_info and s_id will be set and
507 * the set() callback will be invoked), the superblock will be published and it
508 * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE
511 struct super_block
*sget_fc(struct fs_context
*fc
,
512 int (*test
)(struct super_block
*, struct fs_context
*),
513 int (*set
)(struct super_block
*, struct fs_context
*))
515 struct super_block
*s
= NULL
;
516 struct super_block
*old
;
517 struct user_namespace
*user_ns
= fc
->global
? &init_user_ns
: fc
->user_ns
;
523 hlist_for_each_entry(old
, &fc
->fs_type
->fs_supers
, s_instances
) {
525 goto share_extant_sb
;
529 spin_unlock(&sb_lock
);
530 s
= alloc_super(fc
->fs_type
, fc
->sb_flags
, user_ns
);
532 return ERR_PTR(-ENOMEM
);
536 s
->s_fs_info
= fc
->s_fs_info
;
540 spin_unlock(&sb_lock
);
541 destroy_unused_super(s
);
544 fc
->s_fs_info
= NULL
;
545 s
->s_type
= fc
->fs_type
;
546 s
->s_iflags
|= fc
->s_iflags
;
547 strlcpy(s
->s_id
, s
->s_type
->name
, sizeof(s
->s_id
));
548 list_add_tail(&s
->s_list
, &super_blocks
);
549 hlist_add_head(&s
->s_instances
, &s
->s_type
->fs_supers
);
550 spin_unlock(&sb_lock
);
551 get_filesystem(s
->s_type
);
552 register_shrinker_prepared(&s
->s_shrink
);
556 if (user_ns
!= old
->s_user_ns
) {
557 spin_unlock(&sb_lock
);
558 destroy_unused_super(s
);
559 return ERR_PTR(-EBUSY
);
561 if (!grab_super(old
))
563 destroy_unused_super(s
);
566 EXPORT_SYMBOL(sget_fc
);
569 * sget - find or create a superblock
570 * @type: filesystem type superblock should belong to
571 * @test: comparison callback
572 * @set: setup callback
573 * @flags: mount flags
574 * @data: argument to each of them
576 struct super_block
*sget(struct file_system_type
*type
,
577 int (*test
)(struct super_block
*,void *),
578 int (*set
)(struct super_block
*,void *),
582 struct user_namespace
*user_ns
= current_user_ns();
583 struct super_block
*s
= NULL
;
584 struct super_block
*old
;
587 /* We don't yet pass the user namespace of the parent
588 * mount through to here so always use &init_user_ns
589 * until that changes.
591 if (flags
& SB_SUBMOUNT
)
592 user_ns
= &init_user_ns
;
597 hlist_for_each_entry(old
, &type
->fs_supers
, s_instances
) {
598 if (!test(old
, data
))
600 if (user_ns
!= old
->s_user_ns
) {
601 spin_unlock(&sb_lock
);
602 destroy_unused_super(s
);
603 return ERR_PTR(-EBUSY
);
605 if (!grab_super(old
))
607 destroy_unused_super(s
);
612 spin_unlock(&sb_lock
);
613 s
= alloc_super(type
, (flags
& ~SB_SUBMOUNT
), user_ns
);
615 return ERR_PTR(-ENOMEM
);
621 spin_unlock(&sb_lock
);
622 destroy_unused_super(s
);
626 strlcpy(s
->s_id
, type
->name
, sizeof(s
->s_id
));
627 list_add_tail(&s
->s_list
, &super_blocks
);
628 hlist_add_head(&s
->s_instances
, &type
->fs_supers
);
629 spin_unlock(&sb_lock
);
630 get_filesystem(type
);
631 register_shrinker_prepared(&s
->s_shrink
);
636 void drop_super(struct super_block
*sb
)
638 up_read(&sb
->s_umount
);
642 EXPORT_SYMBOL(drop_super
);
644 void drop_super_exclusive(struct super_block
*sb
)
646 up_write(&sb
->s_umount
);
649 EXPORT_SYMBOL(drop_super_exclusive
);
651 static void __iterate_supers(void (*f
)(struct super_block
*))
653 struct super_block
*sb
, *p
= NULL
;
656 list_for_each_entry(sb
, &super_blocks
, s_list
) {
657 if (hlist_unhashed(&sb
->s_instances
))
660 spin_unlock(&sb_lock
);
671 spin_unlock(&sb_lock
);
674 * iterate_supers - call function for all active superblocks
675 * @f: function to call
676 * @arg: argument to pass to it
678 * Scans the superblock list and calls given function, passing it
679 * locked superblock and given argument.
681 void iterate_supers(void (*f
)(struct super_block
*, void *), void *arg
)
683 struct super_block
*sb
, *p
= NULL
;
686 list_for_each_entry(sb
, &super_blocks
, s_list
) {
687 if (hlist_unhashed(&sb
->s_instances
))
690 spin_unlock(&sb_lock
);
692 down_read(&sb
->s_umount
);
693 if (sb
->s_root
&& (sb
->s_flags
& SB_BORN
))
695 up_read(&sb
->s_umount
);
704 spin_unlock(&sb_lock
);
708 * iterate_supers_type - call function for superblocks of given type
710 * @f: function to call
711 * @arg: argument to pass to it
713 * Scans the superblock list and calls given function, passing it
714 * locked superblock and given argument.
716 void iterate_supers_type(struct file_system_type
*type
,
717 void (*f
)(struct super_block
*, void *), void *arg
)
719 struct super_block
*sb
, *p
= NULL
;
722 hlist_for_each_entry(sb
, &type
->fs_supers
, s_instances
) {
724 spin_unlock(&sb_lock
);
726 down_read(&sb
->s_umount
);
727 if (sb
->s_root
&& (sb
->s_flags
& SB_BORN
))
729 up_read(&sb
->s_umount
);
738 spin_unlock(&sb_lock
);
741 EXPORT_SYMBOL(iterate_supers_type
);
744 * get_super - get the superblock of a device
745 * @bdev: device to get the superblock for
747 * Scans the superblock list and finds the superblock of the file system
748 * mounted on the device given. %NULL is returned if no match is found.
750 struct super_block
*get_super(struct block_device
*bdev
)
752 struct super_block
*sb
;
759 list_for_each_entry(sb
, &super_blocks
, s_list
) {
760 if (hlist_unhashed(&sb
->s_instances
))
762 if (sb
->s_bdev
== bdev
) {
764 spin_unlock(&sb_lock
);
765 down_read(&sb
->s_umount
);
767 if (sb
->s_root
&& (sb
->s_flags
& SB_BORN
))
769 up_read(&sb
->s_umount
);
770 /* nope, got unmounted */
776 spin_unlock(&sb_lock
);
781 * get_active_super - get an active reference to the superblock of a device
782 * @bdev: device to get the superblock for
784 * Scans the superblock list and finds the superblock of the file system
785 * mounted on the device given. Returns the superblock with an active
786 * reference or %NULL if none was found.
788 struct super_block
*get_active_super(struct block_device
*bdev
)
790 struct super_block
*sb
;
797 list_for_each_entry(sb
, &super_blocks
, s_list
) {
798 if (hlist_unhashed(&sb
->s_instances
))
800 if (sb
->s_bdev
== bdev
) {
803 up_write(&sb
->s_umount
);
807 spin_unlock(&sb_lock
);
811 struct super_block
*user_get_super(dev_t dev
, bool excl
)
813 struct super_block
*sb
;
817 list_for_each_entry(sb
, &super_blocks
, s_list
) {
818 if (hlist_unhashed(&sb
->s_instances
))
820 if (sb
->s_dev
== dev
) {
822 spin_unlock(&sb_lock
);
824 down_write(&sb
->s_umount
);
826 down_read(&sb
->s_umount
);
828 if (sb
->s_root
&& (sb
->s_flags
& SB_BORN
))
831 up_write(&sb
->s_umount
);
833 up_read(&sb
->s_umount
);
834 /* nope, got unmounted */
840 spin_unlock(&sb_lock
);
845 * reconfigure_super - asks filesystem to change superblock parameters
846 * @fc: The superblock and configuration
848 * Alters the configuration parameters of a live superblock.
850 int reconfigure_super(struct fs_context
*fc
)
852 struct super_block
*sb
= fc
->root
->d_sb
;
854 bool remount_ro
= false;
855 bool force
= fc
->sb_flags
& SB_FORCE
;
857 if (fc
->sb_flags_mask
& ~MS_RMT_MASK
)
859 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
)
862 retval
= security_sb_remount(sb
, fc
->security
);
866 if (fc
->sb_flags_mask
& SB_RDONLY
) {
868 if (!(fc
->sb_flags
& SB_RDONLY
) && sb
->s_bdev
&&
869 bdev_read_only(sb
->s_bdev
))
873 remount_ro
= (fc
->sb_flags
& SB_RDONLY
) && !sb_rdonly(sb
);
877 if (!hlist_empty(&sb
->s_pins
)) {
878 up_write(&sb
->s_umount
);
879 group_pin_kill(&sb
->s_pins
);
880 down_write(&sb
->s_umount
);
883 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
)
885 remount_ro
= !sb_rdonly(sb
);
888 shrink_dcache_sb(sb
);
890 /* If we are reconfiguring to RDONLY and current sb is read/write,
891 * make sure there are no files open for writing.
895 sb
->s_readonly_remount
= 1;
898 retval
= sb_prepare_remount_readonly(sb
);
904 if (fc
->ops
->reconfigure
) {
905 retval
= fc
->ops
->reconfigure(fc
);
908 goto cancel_readonly
;
909 /* If forced remount, go ahead despite any errors */
910 WARN(1, "forced remount of a %s fs returned %i\n",
911 sb
->s_type
->name
, retval
);
915 WRITE_ONCE(sb
->s_flags
, ((sb
->s_flags
& ~fc
->sb_flags_mask
) |
916 (fc
->sb_flags
& fc
->sb_flags_mask
)));
917 /* Needs to be ordered wrt mnt_is_readonly() */
919 sb
->s_readonly_remount
= 0;
922 * Some filesystems modify their metadata via some other path than the
923 * bdev buffer cache (eg. use a private mapping, or directories in
924 * pagecache, etc). Also file data modifications go via their own
925 * mappings. So If we try to mount readonly then copy the filesystem
926 * from bdev, we could get stale data, so invalidate it to give a best
927 * effort at coherency.
929 if (remount_ro
&& sb
->s_bdev
)
930 invalidate_bdev(sb
->s_bdev
);
934 sb
->s_readonly_remount
= 0;
938 static void do_emergency_remount_callback(struct super_block
*sb
)
940 down_write(&sb
->s_umount
);
941 if (sb
->s_root
&& sb
->s_bdev
&& (sb
->s_flags
& SB_BORN
) &&
943 struct fs_context
*fc
;
945 fc
= fs_context_for_reconfigure(sb
->s_root
,
946 SB_RDONLY
| SB_FORCE
, SB_RDONLY
);
948 if (parse_monolithic_mount_data(fc
, NULL
) == 0)
949 (void)reconfigure_super(fc
);
953 up_write(&sb
->s_umount
);
956 static void do_emergency_remount(struct work_struct
*work
)
958 __iterate_supers(do_emergency_remount_callback
);
960 printk("Emergency Remount complete\n");
963 void emergency_remount(void)
965 struct work_struct
*work
;
967 work
= kmalloc(sizeof(*work
), GFP_ATOMIC
);
969 INIT_WORK(work
, do_emergency_remount
);
974 static void do_thaw_all_callback(struct super_block
*sb
)
976 down_write(&sb
->s_umount
);
977 if (sb
->s_root
&& sb
->s_flags
& SB_BORN
) {
978 emergency_thaw_bdev(sb
);
979 thaw_super_locked(sb
);
981 up_write(&sb
->s_umount
);
985 static void do_thaw_all(struct work_struct
*work
)
987 __iterate_supers(do_thaw_all_callback
);
989 printk(KERN_WARNING
"Emergency Thaw complete\n");
993 * emergency_thaw_all -- forcibly thaw every frozen filesystem
995 * Used for emergency unfreeze of all filesystems via SysRq
997 void emergency_thaw_all(void)
999 struct work_struct
*work
;
1001 work
= kmalloc(sizeof(*work
), GFP_ATOMIC
);
1003 INIT_WORK(work
, do_thaw_all
);
1004 schedule_work(work
);
1008 static DEFINE_IDA(unnamed_dev_ida
);
1011 * get_anon_bdev - Allocate a block device for filesystems which don't have one.
1012 * @p: Pointer to a dev_t.
1014 * Filesystems which don't use real block devices can call this function
1015 * to allocate a virtual block device.
1017 * Context: Any context. Frequently called while holding sb_lock.
1018 * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
1019 * or -ENOMEM if memory allocation failed.
1021 int get_anon_bdev(dev_t
*p
)
1026 * Many userspace utilities consider an FSID of 0 invalid.
1027 * Always return at least 1 from get_anon_bdev.
1029 dev
= ida_alloc_range(&unnamed_dev_ida
, 1, (1 << MINORBITS
) - 1,
1039 EXPORT_SYMBOL(get_anon_bdev
);
1041 void free_anon_bdev(dev_t dev
)
1043 ida_free(&unnamed_dev_ida
, MINOR(dev
));
1045 EXPORT_SYMBOL(free_anon_bdev
);
1047 int set_anon_super(struct super_block
*s
, void *data
)
1049 return get_anon_bdev(&s
->s_dev
);
1051 EXPORT_SYMBOL(set_anon_super
);
1053 void kill_anon_super(struct super_block
*sb
)
1055 dev_t dev
= sb
->s_dev
;
1056 generic_shutdown_super(sb
);
1057 free_anon_bdev(dev
);
1059 EXPORT_SYMBOL(kill_anon_super
);
1061 void kill_litter_super(struct super_block
*sb
)
1064 d_genocide(sb
->s_root
);
1065 kill_anon_super(sb
);
1067 EXPORT_SYMBOL(kill_litter_super
);
1069 int set_anon_super_fc(struct super_block
*sb
, struct fs_context
*fc
)
1071 return set_anon_super(sb
, NULL
);
1073 EXPORT_SYMBOL(set_anon_super_fc
);
1075 static int test_keyed_super(struct super_block
*sb
, struct fs_context
*fc
)
1077 return sb
->s_fs_info
== fc
->s_fs_info
;
1080 static int test_single_super(struct super_block
*s
, struct fs_context
*fc
)
1086 * vfs_get_super - Get a superblock with a search key set in s_fs_info.
1087 * @fc: The filesystem context holding the parameters
1088 * @keying: How to distinguish superblocks
1089 * @fill_super: Helper to initialise a new superblock
1091 * Search for a superblock and create a new one if not found. The search
1092 * criterion is controlled by @keying. If the search fails, a new superblock
1093 * is created and @fill_super() is called to initialise it.
1095 * @keying can take one of a number of values:
1097 * (1) vfs_get_single_super - Only one superblock of this type may exist on the
1098 * system. This is typically used for special system filesystems.
1100 * (2) vfs_get_keyed_super - Multiple superblocks may exist, but they must have
1101 * distinct keys (where the key is in s_fs_info). Searching for the same
1102 * key again will turn up the superblock for that key.
1104 * (3) vfs_get_independent_super - Multiple superblocks may exist and are
1105 * unkeyed. Each call will get a new superblock.
1107 * A permissions check is made by sget_fc() unless we're getting a superblock
1108 * for a kernel-internal mount or a submount.
1110 int vfs_get_super(struct fs_context
*fc
,
1111 enum vfs_get_super_keying keying
,
1112 int (*fill_super
)(struct super_block
*sb
,
1113 struct fs_context
*fc
))
1115 int (*test
)(struct super_block
*, struct fs_context
*);
1116 struct super_block
*sb
;
1120 case vfs_get_single_super
:
1121 case vfs_get_single_reconf_super
:
1122 test
= test_single_super
;
1124 case vfs_get_keyed_super
:
1125 test
= test_keyed_super
;
1127 case vfs_get_independent_super
:
1134 sb
= sget_fc(fc
, test
, set_anon_super_fc
);
1139 err
= fill_super(sb
, fc
);
1143 sb
->s_flags
|= SB_ACTIVE
;
1144 fc
->root
= dget(sb
->s_root
);
1146 fc
->root
= dget(sb
->s_root
);
1147 if (keying
== vfs_get_single_reconf_super
) {
1148 err
= reconfigure_super(fc
);
1160 deactivate_locked_super(sb
);
1163 EXPORT_SYMBOL(vfs_get_super
);
1165 int get_tree_nodev(struct fs_context
*fc
,
1166 int (*fill_super
)(struct super_block
*sb
,
1167 struct fs_context
*fc
))
1169 return vfs_get_super(fc
, vfs_get_independent_super
, fill_super
);
1171 EXPORT_SYMBOL(get_tree_nodev
);
1173 int get_tree_single(struct fs_context
*fc
,
1174 int (*fill_super
)(struct super_block
*sb
,
1175 struct fs_context
*fc
))
1177 return vfs_get_super(fc
, vfs_get_single_super
, fill_super
);
1179 EXPORT_SYMBOL(get_tree_single
);
1181 int get_tree_single_reconf(struct fs_context
*fc
,
1182 int (*fill_super
)(struct super_block
*sb
,
1183 struct fs_context
*fc
))
1185 return vfs_get_super(fc
, vfs_get_single_reconf_super
, fill_super
);
1187 EXPORT_SYMBOL(get_tree_single_reconf
);
1189 int get_tree_keyed(struct fs_context
*fc
,
1190 int (*fill_super
)(struct super_block
*sb
,
1191 struct fs_context
*fc
),
1194 fc
->s_fs_info
= key
;
1195 return vfs_get_super(fc
, vfs_get_keyed_super
, fill_super
);
1197 EXPORT_SYMBOL(get_tree_keyed
);
1201 static int set_bdev_super(struct super_block
*s
, void *data
)
1204 s
->s_dev
= s
->s_bdev
->bd_dev
;
1205 s
->s_bdi
= bdi_get(s
->s_bdev
->bd_bdi
);
1207 if (blk_queue_stable_writes(s
->s_bdev
->bd_disk
->queue
))
1208 s
->s_iflags
|= SB_I_STABLE_WRITES
;
1212 static int set_bdev_super_fc(struct super_block
*s
, struct fs_context
*fc
)
1214 return set_bdev_super(s
, fc
->sget_key
);
1217 static int test_bdev_super_fc(struct super_block
*s
, struct fs_context
*fc
)
1219 return s
->s_bdev
== fc
->sget_key
;
1223 * get_tree_bdev - Get a superblock based on a single block device
1224 * @fc: The filesystem context holding the parameters
1225 * @fill_super: Helper to initialise a new superblock
1227 int get_tree_bdev(struct fs_context
*fc
,
1228 int (*fill_super
)(struct super_block
*,
1229 struct fs_context
*))
1231 struct block_device
*bdev
;
1232 struct super_block
*s
;
1233 fmode_t mode
= FMODE_READ
| FMODE_EXCL
;
1236 if (!(fc
->sb_flags
& SB_RDONLY
))
1237 mode
|= FMODE_WRITE
;
1240 return invalf(fc
, "No source specified");
1242 bdev
= blkdev_get_by_path(fc
->source
, mode
, fc
->fs_type
);
1244 errorf(fc
, "%s: Can't open blockdev", fc
->source
);
1245 return PTR_ERR(bdev
);
1248 /* Once the superblock is inserted into the list by sget_fc(), s_umount
1249 * will protect the lockfs code from trying to start a snapshot while
1252 mutex_lock(&bdev
->bd_fsfreeze_mutex
);
1253 if (bdev
->bd_fsfreeze_count
> 0) {
1254 mutex_unlock(&bdev
->bd_fsfreeze_mutex
);
1255 warnf(fc
, "%pg: Can't mount, blockdev is frozen", bdev
);
1256 blkdev_put(bdev
, mode
);
1260 fc
->sb_flags
|= SB_NOSEC
;
1261 fc
->sget_key
= bdev
;
1262 s
= sget_fc(fc
, test_bdev_super_fc
, set_bdev_super_fc
);
1263 mutex_unlock(&bdev
->bd_fsfreeze_mutex
);
1265 blkdev_put(bdev
, mode
);
1270 /* Don't summarily change the RO/RW state. */
1271 if ((fc
->sb_flags
^ s
->s_flags
) & SB_RDONLY
) {
1272 warnf(fc
, "%pg: Can't mount, would change RO state", bdev
);
1273 deactivate_locked_super(s
);
1274 blkdev_put(bdev
, mode
);
1279 * s_umount nests inside bd_mutex during
1280 * __invalidate_device(). blkdev_put() acquires
1281 * bd_mutex and can't be called under s_umount. Drop
1282 * s_umount temporarily. This is safe as we're
1283 * holding an active reference.
1285 up_write(&s
->s_umount
);
1286 blkdev_put(bdev
, mode
);
1287 down_write(&s
->s_umount
);
1290 snprintf(s
->s_id
, sizeof(s
->s_id
), "%pg", bdev
);
1291 sb_set_blocksize(s
, block_size(bdev
));
1292 error
= fill_super(s
, fc
);
1294 deactivate_locked_super(s
);
1298 s
->s_flags
|= SB_ACTIVE
;
1303 fc
->root
= dget(s
->s_root
);
1306 EXPORT_SYMBOL(get_tree_bdev
);
1308 static int test_bdev_super(struct super_block
*s
, void *data
)
1310 return (void *)s
->s_bdev
== data
;
1313 struct dentry
*mount_bdev(struct file_system_type
*fs_type
,
1314 int flags
, const char *dev_name
, void *data
,
1315 int (*fill_super
)(struct super_block
*, void *, int))
1317 struct block_device
*bdev
;
1318 struct super_block
*s
;
1319 fmode_t mode
= FMODE_READ
| FMODE_EXCL
;
1322 if (!(flags
& SB_RDONLY
))
1323 mode
|= FMODE_WRITE
;
1325 bdev
= blkdev_get_by_path(dev_name
, mode
, fs_type
);
1327 return ERR_CAST(bdev
);
1330 * once the super is inserted into the list by sget, s_umount
1331 * will protect the lockfs code from trying to start a snapshot
1332 * while we are mounting
1334 mutex_lock(&bdev
->bd_fsfreeze_mutex
);
1335 if (bdev
->bd_fsfreeze_count
> 0) {
1336 mutex_unlock(&bdev
->bd_fsfreeze_mutex
);
1340 s
= sget(fs_type
, test_bdev_super
, set_bdev_super
, flags
| SB_NOSEC
,
1342 mutex_unlock(&bdev
->bd_fsfreeze_mutex
);
1347 if ((flags
^ s
->s_flags
) & SB_RDONLY
) {
1348 deactivate_locked_super(s
);
1354 * s_umount nests inside bd_mutex during
1355 * __invalidate_device(). blkdev_put() acquires
1356 * bd_mutex and can't be called under s_umount. Drop
1357 * s_umount temporarily. This is safe as we're
1358 * holding an active reference.
1360 up_write(&s
->s_umount
);
1361 blkdev_put(bdev
, mode
);
1362 down_write(&s
->s_umount
);
1365 snprintf(s
->s_id
, sizeof(s
->s_id
), "%pg", bdev
);
1366 sb_set_blocksize(s
, block_size(bdev
));
1367 error
= fill_super(s
, data
, flags
& SB_SILENT
? 1 : 0);
1369 deactivate_locked_super(s
);
1373 s
->s_flags
|= SB_ACTIVE
;
1377 return dget(s
->s_root
);
1382 blkdev_put(bdev
, mode
);
1384 return ERR_PTR(error
);
1386 EXPORT_SYMBOL(mount_bdev
);
1388 void kill_block_super(struct super_block
*sb
)
1390 struct block_device
*bdev
= sb
->s_bdev
;
1391 fmode_t mode
= sb
->s_mode
;
1393 bdev
->bd_super
= NULL
;
1394 generic_shutdown_super(sb
);
1395 sync_blockdev(bdev
);
1396 WARN_ON_ONCE(!(mode
& FMODE_EXCL
));
1397 blkdev_put(bdev
, mode
| FMODE_EXCL
);
1400 EXPORT_SYMBOL(kill_block_super
);
1403 struct dentry
*mount_nodev(struct file_system_type
*fs_type
,
1404 int flags
, void *data
,
1405 int (*fill_super
)(struct super_block
*, void *, int))
1408 struct super_block
*s
= sget(fs_type
, NULL
, set_anon_super
, flags
, NULL
);
1413 error
= fill_super(s
, data
, flags
& SB_SILENT
? 1 : 0);
1415 deactivate_locked_super(s
);
1416 return ERR_PTR(error
);
1418 s
->s_flags
|= SB_ACTIVE
;
1419 return dget(s
->s_root
);
1421 EXPORT_SYMBOL(mount_nodev
);
1423 static int reconfigure_single(struct super_block
*s
,
1424 int flags
, void *data
)
1426 struct fs_context
*fc
;
1429 /* The caller really need to be passing fc down into mount_single(),
1430 * then a chunk of this can be removed. [Bollocks -- AV]
1431 * Better yet, reconfiguration shouldn't happen, but rather the second
1432 * mount should be rejected if the parameters are not compatible.
1434 fc
= fs_context_for_reconfigure(s
->s_root
, flags
, MS_RMT_MASK
);
1438 ret
= parse_monolithic_mount_data(fc
, data
);
1442 ret
= reconfigure_super(fc
);
1448 static int compare_single(struct super_block
*s
, void *p
)
1453 struct dentry
*mount_single(struct file_system_type
*fs_type
,
1454 int flags
, void *data
,
1455 int (*fill_super
)(struct super_block
*, void *, int))
1457 struct super_block
*s
;
1460 s
= sget(fs_type
, compare_single
, set_anon_super
, flags
, NULL
);
1464 error
= fill_super(s
, data
, flags
& SB_SILENT
? 1 : 0);
1466 s
->s_flags
|= SB_ACTIVE
;
1468 error
= reconfigure_single(s
, flags
, data
);
1470 if (unlikely(error
)) {
1471 deactivate_locked_super(s
);
1472 return ERR_PTR(error
);
1474 return dget(s
->s_root
);
1476 EXPORT_SYMBOL(mount_single
);
1479 * vfs_get_tree - Get the mountable root
1480 * @fc: The superblock configuration context.
1482 * The filesystem is invoked to get or create a superblock which can then later
1483 * be used for mounting. The filesystem places a pointer to the root to be
1484 * used for mounting in @fc->root.
1486 int vfs_get_tree(struct fs_context
*fc
)
1488 struct super_block
*sb
;
1494 /* Get the mountable root in fc->root, with a ref on the root and a ref
1495 * on the superblock.
1497 error
= fc
->ops
->get_tree(fc
);
1502 pr_err("Filesystem %s get_tree() didn't set fc->root\n",
1504 /* We don't know what the locking state of the superblock is -
1505 * if there is a superblock.
1510 sb
= fc
->root
->d_sb
;
1511 WARN_ON(!sb
->s_bdi
);
1514 * Write barrier is for super_cache_count(). We place it before setting
1515 * SB_BORN as the data dependency between the two functions is the
1516 * superblock structure contents that we just set up, not the SB_BORN
1520 sb
->s_flags
|= SB_BORN
;
1522 error
= security_sb_set_mnt_opts(sb
, fc
->security
, 0, NULL
);
1523 if (unlikely(error
)) {
1529 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1530 * but s_maxbytes was an unsigned long long for many releases. Throw
1531 * this warning for a little while to try and catch filesystems that
1532 * violate this rule.
1534 WARN((sb
->s_maxbytes
< 0), "%s set sb->s_maxbytes to "
1535 "negative value (%lld)\n", fc
->fs_type
->name
, sb
->s_maxbytes
);
1539 EXPORT_SYMBOL(vfs_get_tree
);
1542 * Setup private BDI for given superblock. It gets automatically cleaned up
1543 * in generic_shutdown_super().
1545 int super_setup_bdi_name(struct super_block
*sb
, char *fmt
, ...)
1547 struct backing_dev_info
*bdi
;
1551 bdi
= bdi_alloc(NUMA_NO_NODE
);
1555 va_start(args
, fmt
);
1556 err
= bdi_register_va(bdi
, fmt
, args
);
1562 WARN_ON(sb
->s_bdi
!= &noop_backing_dev_info
);
1567 EXPORT_SYMBOL(super_setup_bdi_name
);
1570 * Setup private BDI for given superblock. I gets automatically cleaned up
1571 * in generic_shutdown_super().
1573 int super_setup_bdi(struct super_block
*sb
)
1575 static atomic_long_t bdi_seq
= ATOMIC_LONG_INIT(0);
1577 return super_setup_bdi_name(sb
, "%.28s-%ld", sb
->s_type
->name
,
1578 atomic_long_inc_return(&bdi_seq
));
1580 EXPORT_SYMBOL(super_setup_bdi
);
1583 * sb_wait_write - wait until all writers to given file system finish
1584 * @sb: the super for which we wait
1585 * @level: type of writers we wait for (normal vs page fault)
1587 * This function waits until there are no writers of given type to given file
1590 static void sb_wait_write(struct super_block
*sb
, int level
)
1592 percpu_down_write(sb
->s_writers
.rw_sem
+ level
-1);
1596 * We are going to return to userspace and forget about these locks, the
1597 * ownership goes to the caller of thaw_super() which does unlock().
1599 static void lockdep_sb_freeze_release(struct super_block
*sb
)
1603 for (level
= SB_FREEZE_LEVELS
- 1; level
>= 0; level
--)
1604 percpu_rwsem_release(sb
->s_writers
.rw_sem
+ level
, 0, _THIS_IP_
);
1608 * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
1610 static void lockdep_sb_freeze_acquire(struct super_block
*sb
)
1614 for (level
= 0; level
< SB_FREEZE_LEVELS
; ++level
)
1615 percpu_rwsem_acquire(sb
->s_writers
.rw_sem
+ level
, 0, _THIS_IP_
);
1618 static void sb_freeze_unlock(struct super_block
*sb
)
1622 for (level
= SB_FREEZE_LEVELS
- 1; level
>= 0; level
--)
1623 percpu_up_write(sb
->s_writers
.rw_sem
+ level
);
1627 * freeze_super - lock the filesystem and force it into a consistent state
1628 * @sb: the super to lock
1630 * Syncs the super to make sure the filesystem is consistent and calls the fs's
1631 * freeze_fs. Subsequent calls to this without first thawing the fs will return
1634 * During this function, sb->s_writers.frozen goes through these values:
1636 * SB_UNFROZEN: File system is normal, all writes progress as usual.
1638 * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
1639 * writes should be blocked, though page faults are still allowed. We wait for
1640 * all writes to complete and then proceed to the next stage.
1642 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
1643 * but internal fs threads can still modify the filesystem (although they
1644 * should not dirty new pages or inodes), writeback can run etc. After waiting
1645 * for all running page faults we sync the filesystem which will clean all
1646 * dirty pages and inodes (no new dirty pages or inodes can be created when
1649 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
1650 * modification are blocked (e.g. XFS preallocation truncation on inode
1651 * reclaim). This is usually implemented by blocking new transactions for
1652 * filesystems that have them and need this additional guard. After all
1653 * internal writers are finished we call ->freeze_fs() to finish filesystem
1654 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
1655 * mostly auxiliary for filesystems to verify they do not modify frozen fs.
1657 * sb->s_writers.frozen is protected by sb->s_umount.
1659 int freeze_super(struct super_block
*sb
)
1663 atomic_inc(&sb
->s_active
);
1664 down_write(&sb
->s_umount
);
1665 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
) {
1666 deactivate_locked_super(sb
);
1670 if (!(sb
->s_flags
& SB_BORN
)) {
1671 up_write(&sb
->s_umount
);
1672 return 0; /* sic - it's "nothing to do" */
1675 if (sb_rdonly(sb
)) {
1676 /* Nothing to do really... */
1677 sb
->s_writers
.frozen
= SB_FREEZE_COMPLETE
;
1678 up_write(&sb
->s_umount
);
1682 sb
->s_writers
.frozen
= SB_FREEZE_WRITE
;
1683 /* Release s_umount to preserve sb_start_write -> s_umount ordering */
1684 up_write(&sb
->s_umount
);
1685 sb_wait_write(sb
, SB_FREEZE_WRITE
);
1686 down_write(&sb
->s_umount
);
1688 /* Now we go and block page faults... */
1689 sb
->s_writers
.frozen
= SB_FREEZE_PAGEFAULT
;
1690 sb_wait_write(sb
, SB_FREEZE_PAGEFAULT
);
1692 /* All writers are done so after syncing there won't be dirty data */
1693 sync_filesystem(sb
);
1695 /* Now wait for internal filesystem counter */
1696 sb
->s_writers
.frozen
= SB_FREEZE_FS
;
1697 sb_wait_write(sb
, SB_FREEZE_FS
);
1699 if (sb
->s_op
->freeze_fs
) {
1700 ret
= sb
->s_op
->freeze_fs(sb
);
1703 "VFS:Filesystem freeze failed\n");
1704 sb
->s_writers
.frozen
= SB_UNFROZEN
;
1705 sb_freeze_unlock(sb
);
1706 wake_up(&sb
->s_writers
.wait_unfrozen
);
1707 deactivate_locked_super(sb
);
1712 * For debugging purposes so that fs can warn if it sees write activity
1713 * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
1715 sb
->s_writers
.frozen
= SB_FREEZE_COMPLETE
;
1716 lockdep_sb_freeze_release(sb
);
1717 up_write(&sb
->s_umount
);
1720 EXPORT_SYMBOL(freeze_super
);
1722 static int thaw_super_locked(struct super_block
*sb
)
1726 if (sb
->s_writers
.frozen
!= SB_FREEZE_COMPLETE
) {
1727 up_write(&sb
->s_umount
);
1731 if (sb_rdonly(sb
)) {
1732 sb
->s_writers
.frozen
= SB_UNFROZEN
;
1736 lockdep_sb_freeze_acquire(sb
);
1738 if (sb
->s_op
->unfreeze_fs
) {
1739 error
= sb
->s_op
->unfreeze_fs(sb
);
1742 "VFS:Filesystem thaw failed\n");
1743 lockdep_sb_freeze_release(sb
);
1744 up_write(&sb
->s_umount
);
1749 sb
->s_writers
.frozen
= SB_UNFROZEN
;
1750 sb_freeze_unlock(sb
);
1752 wake_up(&sb
->s_writers
.wait_unfrozen
);
1753 deactivate_locked_super(sb
);
1758 * thaw_super -- unlock filesystem
1759 * @sb: the super to thaw
1761 * Unlocks the filesystem and marks it writeable again after freeze_super().
1763 int thaw_super(struct super_block
*sb
)
1765 down_write(&sb
->s_umount
);
1766 return thaw_super_locked(sb
);
1768 EXPORT_SYMBOL(thaw_super
);