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/fsnotify.h>
36 #include <linux/lockdep.h>
37 #include <linux/user_namespace.h>
41 static LIST_HEAD(super_blocks
);
42 static DEFINE_SPINLOCK(sb_lock
);
44 static char *sb_writers_name
[SB_FREEZE_LEVELS
] = {
51 * One thing we have to be careful of with a per-sb shrinker is that we don't
52 * drop the last active reference to the superblock from within the shrinker.
53 * If that happens we could trigger unregistering the shrinker from within the
54 * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
55 * take a passive reference to the superblock to avoid this from occurring.
57 static unsigned long super_cache_scan(struct shrinker
*shrink
,
58 struct shrink_control
*sc
)
60 struct super_block
*sb
;
67 sb
= container_of(shrink
, struct super_block
, s_shrink
);
70 * Deadlock avoidance. We may hold various FS locks, and we don't want
71 * to recurse into the FS that called us in clear_inode() and friends..
73 if (!(sc
->gfp_mask
& __GFP_FS
))
76 if (!trylock_super(sb
))
79 if (sb
->s_op
->nr_cached_objects
)
80 fs_objects
= sb
->s_op
->nr_cached_objects(sb
, sc
);
82 inodes
= list_lru_shrink_count(&sb
->s_inode_lru
, sc
);
83 dentries
= list_lru_shrink_count(&sb
->s_dentry_lru
, sc
);
84 total_objects
= dentries
+ inodes
+ fs_objects
+ 1;
88 /* proportion the scan between the caches */
89 dentries
= mult_frac(sc
->nr_to_scan
, dentries
, total_objects
);
90 inodes
= mult_frac(sc
->nr_to_scan
, inodes
, total_objects
);
91 fs_objects
= mult_frac(sc
->nr_to_scan
, fs_objects
, total_objects
);
94 * prune the dcache first as the icache is pinned by it, then
95 * prune the icache, followed by the filesystem specific caches
97 * Ensure that we always scan at least one object - memcg kmem
98 * accounting uses this to fully empty the caches.
100 sc
->nr_to_scan
= dentries
+ 1;
101 freed
= prune_dcache_sb(sb
, sc
);
102 sc
->nr_to_scan
= inodes
+ 1;
103 freed
+= prune_icache_sb(sb
, sc
);
106 sc
->nr_to_scan
= fs_objects
+ 1;
107 freed
+= sb
->s_op
->free_cached_objects(sb
, sc
);
110 up_read(&sb
->s_umount
);
114 static unsigned long super_cache_count(struct shrinker
*shrink
,
115 struct shrink_control
*sc
)
117 struct super_block
*sb
;
118 long total_objects
= 0;
120 sb
= container_of(shrink
, struct super_block
, s_shrink
);
123 * We don't call trylock_super() here as it is a scalability bottleneck,
124 * so we're exposed to partial setup state. The shrinker rwsem does not
125 * protect filesystem operations backing list_lru_shrink_count() or
126 * s_op->nr_cached_objects(). Counts can change between
127 * super_cache_count and super_cache_scan, so we really don't need locks
130 * However, if we are currently mounting the superblock, the underlying
131 * filesystem might be in a state of partial construction and hence it
132 * is dangerous to access it. trylock_super() uses a SB_BORN check to
133 * avoid this situation, so do the same here. The memory barrier is
134 * matched with the one in mount_fs() as we don't hold locks here.
136 if (!(sb
->s_flags
& SB_BORN
))
140 if (sb
->s_op
&& sb
->s_op
->nr_cached_objects
)
141 total_objects
= sb
->s_op
->nr_cached_objects(sb
, sc
);
143 total_objects
+= list_lru_shrink_count(&sb
->s_dentry_lru
, sc
);
144 total_objects
+= list_lru_shrink_count(&sb
->s_inode_lru
, sc
);
146 total_objects
= vfs_pressure_ratio(total_objects
);
147 return total_objects
;
150 static void destroy_super_work(struct work_struct
*work
)
152 struct super_block
*s
= container_of(work
, struct super_block
,
156 for (i
= 0; i
< SB_FREEZE_LEVELS
; i
++)
157 percpu_free_rwsem(&s
->s_writers
.rw_sem
[i
]);
161 static void destroy_super_rcu(struct rcu_head
*head
)
163 struct super_block
*s
= container_of(head
, struct super_block
, rcu
);
164 INIT_WORK(&s
->destroy_work
, destroy_super_work
);
165 schedule_work(&s
->destroy_work
);
169 * destroy_super - frees a superblock
170 * @s: superblock to free
172 * Frees a superblock.
174 static void destroy_super(struct super_block
*s
)
176 list_lru_destroy(&s
->s_dentry_lru
);
177 list_lru_destroy(&s
->s_inode_lru
);
179 WARN_ON(!list_empty(&s
->s_mounts
));
180 put_user_ns(s
->s_user_ns
);
182 call_rcu(&s
->rcu
, destroy_super_rcu
);
186 * alloc_super - create new superblock
187 * @type: filesystem type superblock should belong to
188 * @flags: the mount flags
189 * @user_ns: User namespace for the super_block
191 * Allocates and initializes a new &struct super_block. alloc_super()
192 * returns a pointer new superblock or %NULL if allocation had failed.
194 static struct super_block
*alloc_super(struct file_system_type
*type
, int flags
,
195 struct user_namespace
*user_ns
)
197 struct super_block
*s
= kzalloc(sizeof(struct super_block
), GFP_USER
);
198 static const struct super_operations default_op
;
204 INIT_LIST_HEAD(&s
->s_mounts
);
205 s
->s_user_ns
= get_user_ns(user_ns
);
207 if (security_sb_alloc(s
))
210 for (i
= 0; i
< SB_FREEZE_LEVELS
; i
++) {
211 if (__percpu_init_rwsem(&s
->s_writers
.rw_sem
[i
],
213 &type
->s_writers_key
[i
]))
216 init_waitqueue_head(&s
->s_writers
.wait_unfrozen
);
217 s
->s_bdi
= &noop_backing_dev_info
;
219 if (s
->s_user_ns
!= &init_user_ns
)
220 s
->s_iflags
|= SB_I_NODEV
;
221 INIT_HLIST_NODE(&s
->s_instances
);
222 INIT_HLIST_BL_HEAD(&s
->s_anon
);
223 mutex_init(&s
->s_sync_lock
);
224 INIT_LIST_HEAD(&s
->s_inodes
);
225 spin_lock_init(&s
->s_inode_list_lock
);
226 INIT_LIST_HEAD(&s
->s_inodes_wb
);
227 spin_lock_init(&s
->s_inode_wblist_lock
);
229 if (list_lru_init_memcg(&s
->s_dentry_lru
))
231 if (list_lru_init_memcg(&s
->s_inode_lru
))
234 init_rwsem(&s
->s_umount
);
235 lockdep_set_class(&s
->s_umount
, &type
->s_umount_key
);
237 * sget() can have s_umount recursion.
239 * When it cannot find a suitable sb, it allocates a new
240 * one (this one), and tries again to find a suitable old
243 * In case that succeeds, it will acquire the s_umount
244 * lock of the old one. Since these are clearly distrinct
245 * locks, and this object isn't exposed yet, there's no
248 * Annotate this by putting this lock in a different
251 down_write_nested(&s
->s_umount
, SINGLE_DEPTH_NESTING
);
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
->cleancache_poolid
= CLEANCACHE_NO_POOL
;
262 s
->s_shrink
.seeks
= DEFAULT_SEEKS
;
263 s
->s_shrink
.scan_objects
= super_cache_scan
;
264 s
->s_shrink
.count_objects
= super_cache_count
;
265 s
->s_shrink
.batch
= 1024;
266 s
->s_shrink
.flags
= SHRINKER_NUMA_AWARE
| SHRINKER_MEMCG_AWARE
;
274 /* Superblock refcounting */
277 * Drop a superblock's refcount. The caller must hold sb_lock.
279 static void __put_super(struct super_block
*sb
)
281 if (!--sb
->s_count
) {
282 list_del_init(&sb
->s_list
);
288 * put_super - drop a temporary reference to superblock
289 * @sb: superblock in question
291 * Drops a temporary reference, frees superblock if there's no
294 static void put_super(struct super_block
*sb
)
298 spin_unlock(&sb_lock
);
303 * deactivate_locked_super - drop an active reference to superblock
304 * @s: superblock to deactivate
306 * Drops an active reference to superblock, converting it into a temporary
307 * one if there is no other active references left. In that case we
308 * tell fs driver to shut it down and drop the temporary reference we
311 * Caller holds exclusive lock on superblock; that lock is released.
313 void deactivate_locked_super(struct super_block
*s
)
315 struct file_system_type
*fs
= s
->s_type
;
316 if (atomic_dec_and_test(&s
->s_active
)) {
317 cleancache_invalidate_fs(s
);
318 unregister_shrinker(&s
->s_shrink
);
322 * Since list_lru_destroy() may sleep, we cannot call it from
323 * put_super(), where we hold the sb_lock. Therefore we destroy
324 * the lru lists right now.
326 list_lru_destroy(&s
->s_dentry_lru
);
327 list_lru_destroy(&s
->s_inode_lru
);
332 up_write(&s
->s_umount
);
336 EXPORT_SYMBOL(deactivate_locked_super
);
339 * deactivate_super - drop an active reference to superblock
340 * @s: superblock to deactivate
342 * Variant of deactivate_locked_super(), except that superblock is *not*
343 * locked by caller. If we are going to drop the final active reference,
344 * lock will be acquired prior to that.
346 void deactivate_super(struct super_block
*s
)
348 if (!atomic_add_unless(&s
->s_active
, -1, 1)) {
349 down_write(&s
->s_umount
);
350 deactivate_locked_super(s
);
354 EXPORT_SYMBOL(deactivate_super
);
357 * grab_super - acquire an active reference
358 * @s: reference we are trying to make active
360 * Tries to acquire an active reference. grab_super() is used when we
361 * had just found a superblock in super_blocks or fs_type->fs_supers
362 * and want to turn it into a full-blown active reference. grab_super()
363 * is called with sb_lock held and drops it. Returns 1 in case of
364 * success, 0 if we had failed (superblock contents was already dead or
365 * dying when grab_super() had been called). Note that this is only
366 * called for superblocks not in rundown mode (== ones still on ->fs_supers
367 * of their type), so increment of ->s_count is OK here.
369 static int grab_super(struct super_block
*s
) __releases(sb_lock
)
372 spin_unlock(&sb_lock
);
373 down_write(&s
->s_umount
);
374 if ((s
->s_flags
& SB_BORN
) && atomic_inc_not_zero(&s
->s_active
)) {
378 up_write(&s
->s_umount
);
384 * trylock_super - try to grab ->s_umount shared
385 * @sb: reference we are trying to grab
387 * Try to prevent fs shutdown. This is used in places where we
388 * cannot take an active reference but we need to ensure that the
389 * filesystem is not shut down while we are working on it. It returns
390 * false if we cannot acquire s_umount or if we lose the race and
391 * filesystem already got into shutdown, and returns true with the s_umount
392 * lock held in read mode in case of success. On successful return,
393 * the caller must drop the s_umount lock when done.
395 * Note that unlike get_super() et.al. this one does *not* bump ->s_count.
396 * The reason why it's safe is that we are OK with doing trylock instead
397 * of down_read(). There's a couple of places that are OK with that, but
398 * it's very much not a general-purpose interface.
400 bool trylock_super(struct super_block
*sb
)
402 if (down_read_trylock(&sb
->s_umount
)) {
403 if (!hlist_unhashed(&sb
->s_instances
) &&
404 sb
->s_root
&& (sb
->s_flags
& SB_BORN
))
406 up_read(&sb
->s_umount
);
413 * generic_shutdown_super - common helper for ->kill_sb()
414 * @sb: superblock to kill
416 * generic_shutdown_super() does all fs-independent work on superblock
417 * shutdown. Typical ->kill_sb() should pick all fs-specific objects
418 * that need destruction out of superblock, call generic_shutdown_super()
419 * and release aforementioned objects. Note: dentries and inodes _are_
420 * taken care of and do not need specific handling.
422 * Upon calling this function, the filesystem may no longer alter or
423 * rearrange the set of dentries belonging to this super_block, nor may it
424 * change the attachments of dentries to inodes.
426 void generic_shutdown_super(struct super_block
*sb
)
428 const struct super_operations
*sop
= sb
->s_op
;
431 shrink_dcache_for_umount(sb
);
433 sb
->s_flags
&= ~SB_ACTIVE
;
435 fsnotify_unmount_inodes(sb
);
436 cgroup_writeback_umount();
440 if (sb
->s_dio_done_wq
) {
441 destroy_workqueue(sb
->s_dio_done_wq
);
442 sb
->s_dio_done_wq
= NULL
;
448 if (!list_empty(&sb
->s_inodes
)) {
449 printk("VFS: Busy inodes after unmount of %s. "
450 "Self-destruct in 5 seconds. Have a nice day...\n",
455 /* should be initialized for __put_super_and_need_restart() */
456 hlist_del_init(&sb
->s_instances
);
457 spin_unlock(&sb_lock
);
458 up_write(&sb
->s_umount
);
459 if (sb
->s_bdi
!= &noop_backing_dev_info
) {
461 sb
->s_bdi
= &noop_backing_dev_info
;
465 EXPORT_SYMBOL(generic_shutdown_super
);
468 * sget_userns - find or create a superblock
469 * @type: filesystem type superblock should belong to
470 * @test: comparison callback
471 * @set: setup callback
472 * @flags: mount flags
473 * @user_ns: User namespace for the super_block
474 * @data: argument to each of them
476 struct super_block
*sget_userns(struct file_system_type
*type
,
477 int (*test
)(struct super_block
*,void *),
478 int (*set
)(struct super_block
*,void *),
479 int flags
, struct user_namespace
*user_ns
,
482 struct super_block
*s
= NULL
;
483 struct super_block
*old
;
486 if (!(flags
& (SB_KERNMOUNT
|SB_SUBMOUNT
)) &&
487 !(type
->fs_flags
& FS_USERNS_MOUNT
) &&
488 !capable(CAP_SYS_ADMIN
))
489 return ERR_PTR(-EPERM
);
493 hlist_for_each_entry(old
, &type
->fs_supers
, s_instances
) {
494 if (!test(old
, data
))
496 if (user_ns
!= old
->s_user_ns
) {
497 spin_unlock(&sb_lock
);
499 up_write(&s
->s_umount
);
502 return ERR_PTR(-EBUSY
);
504 if (!grab_super(old
))
507 up_write(&s
->s_umount
);
515 spin_unlock(&sb_lock
);
516 s
= alloc_super(type
, (flags
& ~SB_SUBMOUNT
), user_ns
);
518 return ERR_PTR(-ENOMEM
);
524 spin_unlock(&sb_lock
);
525 up_write(&s
->s_umount
);
530 strlcpy(s
->s_id
, type
->name
, sizeof(s
->s_id
));
531 list_add_tail(&s
->s_list
, &super_blocks
);
532 hlist_add_head(&s
->s_instances
, &type
->fs_supers
);
533 spin_unlock(&sb_lock
);
534 get_filesystem(type
);
535 err
= register_shrinker(&s
->s_shrink
);
537 deactivate_locked_super(s
);
543 EXPORT_SYMBOL(sget_userns
);
546 * sget - find or create a superblock
547 * @type: filesystem type superblock should belong to
548 * @test: comparison callback
549 * @set: setup callback
550 * @flags: mount flags
551 * @data: argument to each of them
553 struct super_block
*sget(struct file_system_type
*type
,
554 int (*test
)(struct super_block
*,void *),
555 int (*set
)(struct super_block
*,void *),
559 struct user_namespace
*user_ns
= current_user_ns();
561 /* We don't yet pass the user namespace of the parent
562 * mount through to here so always use &init_user_ns
563 * until that changes.
565 if (flags
& SB_SUBMOUNT
)
566 user_ns
= &init_user_ns
;
568 /* Ensure the requestor has permissions over the target filesystem */
569 if (!(flags
& (SB_KERNMOUNT
|SB_SUBMOUNT
)) && !ns_capable(user_ns
, CAP_SYS_ADMIN
))
570 return ERR_PTR(-EPERM
);
572 return sget_userns(type
, test
, set
, flags
, user_ns
, data
);
577 void drop_super(struct super_block
*sb
)
579 up_read(&sb
->s_umount
);
583 EXPORT_SYMBOL(drop_super
);
585 void drop_super_exclusive(struct super_block
*sb
)
587 up_write(&sb
->s_umount
);
590 EXPORT_SYMBOL(drop_super_exclusive
);
593 * iterate_supers - call function for all active superblocks
594 * @f: function to call
595 * @arg: argument to pass to it
597 * Scans the superblock list and calls given function, passing it
598 * locked superblock and given argument.
600 void iterate_supers(void (*f
)(struct super_block
*, void *), void *arg
)
602 struct super_block
*sb
, *p
= NULL
;
605 list_for_each_entry(sb
, &super_blocks
, s_list
) {
606 if (hlist_unhashed(&sb
->s_instances
))
609 spin_unlock(&sb_lock
);
611 down_read(&sb
->s_umount
);
612 if (sb
->s_root
&& (sb
->s_flags
& SB_BORN
))
614 up_read(&sb
->s_umount
);
623 spin_unlock(&sb_lock
);
627 * iterate_supers_type - call function for superblocks of given type
629 * @f: function to call
630 * @arg: argument to pass to it
632 * Scans the superblock list and calls given function, passing it
633 * locked superblock and given argument.
635 void iterate_supers_type(struct file_system_type
*type
,
636 void (*f
)(struct super_block
*, void *), void *arg
)
638 struct super_block
*sb
, *p
= NULL
;
641 hlist_for_each_entry(sb
, &type
->fs_supers
, s_instances
) {
643 spin_unlock(&sb_lock
);
645 down_read(&sb
->s_umount
);
646 if (sb
->s_root
&& (sb
->s_flags
& SB_BORN
))
648 up_read(&sb
->s_umount
);
657 spin_unlock(&sb_lock
);
660 EXPORT_SYMBOL(iterate_supers_type
);
662 static struct super_block
*__get_super(struct block_device
*bdev
, bool excl
)
664 struct super_block
*sb
;
671 list_for_each_entry(sb
, &super_blocks
, s_list
) {
672 if (hlist_unhashed(&sb
->s_instances
))
674 if (sb
->s_bdev
== bdev
) {
676 spin_unlock(&sb_lock
);
678 down_read(&sb
->s_umount
);
680 down_write(&sb
->s_umount
);
682 if (sb
->s_root
&& (sb
->s_flags
& SB_BORN
))
685 up_read(&sb
->s_umount
);
687 up_write(&sb
->s_umount
);
688 /* nope, got unmounted */
694 spin_unlock(&sb_lock
);
699 * get_super - get the superblock of a device
700 * @bdev: device to get the superblock for
702 * Scans the superblock list and finds the superblock of the file system
703 * mounted on the device given. %NULL is returned if no match is found.
705 struct super_block
*get_super(struct block_device
*bdev
)
707 return __get_super(bdev
, false);
709 EXPORT_SYMBOL(get_super
);
711 static struct super_block
*__get_super_thawed(struct block_device
*bdev
,
715 struct super_block
*s
= __get_super(bdev
, excl
);
716 if (!s
|| s
->s_writers
.frozen
== SB_UNFROZEN
)
719 up_read(&s
->s_umount
);
721 up_write(&s
->s_umount
);
722 wait_event(s
->s_writers
.wait_unfrozen
,
723 s
->s_writers
.frozen
== SB_UNFROZEN
);
729 * get_super_thawed - get thawed superblock of a device
730 * @bdev: device to get the superblock for
732 * Scans the superblock list and finds the superblock of the file system
733 * mounted on the device. The superblock is returned once it is thawed
734 * (or immediately if it was not frozen). %NULL is returned if no match
737 struct super_block
*get_super_thawed(struct block_device
*bdev
)
739 return __get_super_thawed(bdev
, false);
741 EXPORT_SYMBOL(get_super_thawed
);
744 * get_super_exclusive_thawed - get thawed 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. The superblock is returned once it is thawed
749 * (or immediately if it was not frozen) and s_umount semaphore is held
750 * in exclusive mode. %NULL is returned if no match is found.
752 struct super_block
*get_super_exclusive_thawed(struct block_device
*bdev
)
754 return __get_super_thawed(bdev
, true);
756 EXPORT_SYMBOL(get_super_exclusive_thawed
);
759 * get_active_super - get an active reference to the superblock of a device
760 * @bdev: device to get the superblock for
762 * Scans the superblock list and finds the superblock of the file system
763 * mounted on the device given. Returns the superblock with an active
764 * reference or %NULL if none was found.
766 struct super_block
*get_active_super(struct block_device
*bdev
)
768 struct super_block
*sb
;
775 list_for_each_entry(sb
, &super_blocks
, s_list
) {
776 if (hlist_unhashed(&sb
->s_instances
))
778 if (sb
->s_bdev
== bdev
) {
781 up_write(&sb
->s_umount
);
785 spin_unlock(&sb_lock
);
789 struct super_block
*user_get_super(dev_t dev
)
791 struct super_block
*sb
;
795 list_for_each_entry(sb
, &super_blocks
, s_list
) {
796 if (hlist_unhashed(&sb
->s_instances
))
798 if (sb
->s_dev
== dev
) {
800 spin_unlock(&sb_lock
);
801 down_read(&sb
->s_umount
);
803 if (sb
->s_root
&& (sb
->s_flags
& SB_BORN
))
805 up_read(&sb
->s_umount
);
806 /* nope, got unmounted */
812 spin_unlock(&sb_lock
);
817 * do_remount_sb2 - asks filesystem to change mount options.
818 * @mnt: mount we are looking at
819 * @sb: superblock in question
820 * @sb_flags: revised superblock flags
821 * @data: the rest of options
822 * @force: whether or not to force the change
824 * Alters the mount options of a mounted file system.
826 int do_remount_sb2(struct vfsmount
*mnt
, struct super_block
*sb
, int sb_flags
, void *data
, int force
)
831 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
)
835 if (!(sb_flags
& SB_RDONLY
) && bdev_read_only(sb
->s_bdev
))
839 remount_ro
= (sb_flags
& SB_RDONLY
) && !sb_rdonly(sb
);
842 if (!hlist_empty(&sb
->s_pins
)) {
843 up_write(&sb
->s_umount
);
844 group_pin_kill(&sb
->s_pins
);
845 down_write(&sb
->s_umount
);
848 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
)
850 remount_ro
= (sb_flags
& SB_RDONLY
) && !sb_rdonly(sb
);
853 shrink_dcache_sb(sb
);
855 /* If we are remounting RDONLY and current sb is read/write,
856 make sure there are no rw files opened */
859 sb
->s_readonly_remount
= 1;
862 retval
= sb_prepare_remount_readonly(sb
);
868 if (mnt
&& sb
->s_op
->remount_fs2
) {
869 retval
= sb
->s_op
->remount_fs2(mnt
, sb
, &sb_flags
, data
);
872 goto cancel_readonly
;
873 /* If forced remount, go ahead despite any errors */
874 WARN(1, "forced remount of a %s fs returned %i\n",
875 sb
->s_type
->name
, retval
);
877 } else if (sb
->s_op
->remount_fs
) {
878 retval
= sb
->s_op
->remount_fs(sb
, &sb_flags
, data
);
881 goto cancel_readonly
;
882 /* If forced remount, go ahead despite any errors */
883 WARN(1, "forced remount of a %s fs returned %i\n",
884 sb
->s_type
->name
, retval
);
887 sb
->s_flags
= (sb
->s_flags
& ~MS_RMT_MASK
) | (sb_flags
& MS_RMT_MASK
);
888 /* Needs to be ordered wrt mnt_is_readonly() */
890 sb
->s_readonly_remount
= 0;
893 * Some filesystems modify their metadata via some other path than the
894 * bdev buffer cache (eg. use a private mapping, or directories in
895 * pagecache, etc). Also file data modifications go via their own
896 * mappings. So If we try to mount readonly then copy the filesystem
897 * from bdev, we could get stale data, so invalidate it to give a best
898 * effort at coherency.
900 if (remount_ro
&& sb
->s_bdev
)
901 invalidate_bdev(sb
->s_bdev
);
905 sb
->s_readonly_remount
= 0;
909 int do_remount_sb(struct super_block
*sb
, int flags
, void *data
, int force
)
911 return do_remount_sb2(NULL
, sb
, flags
, data
, force
);
914 static void do_emergency_remount(struct work_struct
*work
)
916 struct super_block
*sb
, *p
= NULL
;
919 list_for_each_entry_reverse(sb
, &super_blocks
, s_list
) {
920 if (hlist_unhashed(&sb
->s_instances
))
923 spin_unlock(&sb_lock
);
924 down_write(&sb
->s_umount
);
925 if (sb
->s_root
&& sb
->s_bdev
&& (sb
->s_flags
& SB_BORN
) &&
928 * What lock protects sb->s_flags??
930 do_remount_sb(sb
, SB_RDONLY
, NULL
, 1);
932 up_write(&sb
->s_umount
);
940 spin_unlock(&sb_lock
);
942 printk("Emergency Remount complete\n");
945 void emergency_remount(void)
947 struct work_struct
*work
;
949 work
= kmalloc(sizeof(*work
), GFP_ATOMIC
);
951 INIT_WORK(work
, do_emergency_remount
);
957 * Unnamed block devices are dummy devices used by virtual
958 * filesystems which don't use real block-devices. -- jrs
961 static DEFINE_IDA(unnamed_dev_ida
);
962 static DEFINE_SPINLOCK(unnamed_dev_lock
);/* protects the above */
963 /* Many userspace utilities consider an FSID of 0 invalid.
964 * Always return at least 1 from get_anon_bdev.
966 static int unnamed_dev_start
= 1;
968 int get_anon_bdev(dev_t
*p
)
974 if (ida_pre_get(&unnamed_dev_ida
, GFP_ATOMIC
) == 0)
976 spin_lock(&unnamed_dev_lock
);
977 error
= ida_get_new_above(&unnamed_dev_ida
, unnamed_dev_start
, &dev
);
979 unnamed_dev_start
= dev
+ 1;
980 spin_unlock(&unnamed_dev_lock
);
981 if (error
== -EAGAIN
)
982 /* We raced and lost with another CPU. */
987 if (dev
>= (1 << MINORBITS
)) {
988 spin_lock(&unnamed_dev_lock
);
989 ida_remove(&unnamed_dev_ida
, dev
);
990 if (unnamed_dev_start
> dev
)
991 unnamed_dev_start
= dev
;
992 spin_unlock(&unnamed_dev_lock
);
995 *p
= MKDEV(0, dev
& MINORMASK
);
998 EXPORT_SYMBOL(get_anon_bdev
);
1000 void free_anon_bdev(dev_t dev
)
1002 int slot
= MINOR(dev
);
1003 spin_lock(&unnamed_dev_lock
);
1004 ida_remove(&unnamed_dev_ida
, slot
);
1005 if (slot
< unnamed_dev_start
)
1006 unnamed_dev_start
= slot
;
1007 spin_unlock(&unnamed_dev_lock
);
1009 EXPORT_SYMBOL(free_anon_bdev
);
1011 int set_anon_super(struct super_block
*s
, void *data
)
1013 return get_anon_bdev(&s
->s_dev
);
1016 EXPORT_SYMBOL(set_anon_super
);
1018 void kill_anon_super(struct super_block
*sb
)
1020 dev_t dev
= sb
->s_dev
;
1021 generic_shutdown_super(sb
);
1022 free_anon_bdev(dev
);
1025 EXPORT_SYMBOL(kill_anon_super
);
1027 void kill_litter_super(struct super_block
*sb
)
1030 d_genocide(sb
->s_root
);
1031 kill_anon_super(sb
);
1034 EXPORT_SYMBOL(kill_litter_super
);
1036 static int ns_test_super(struct super_block
*sb
, void *data
)
1038 return sb
->s_fs_info
== data
;
1041 static int ns_set_super(struct super_block
*sb
, void *data
)
1043 sb
->s_fs_info
= data
;
1044 return set_anon_super(sb
, NULL
);
1047 struct dentry
*mount_ns(struct file_system_type
*fs_type
,
1048 int flags
, void *data
, void *ns
, struct user_namespace
*user_ns
,
1049 int (*fill_super
)(struct super_block
*, void *, int))
1051 struct super_block
*sb
;
1053 /* Don't allow mounting unless the caller has CAP_SYS_ADMIN
1054 * over the namespace.
1056 if (!(flags
& SB_KERNMOUNT
) && !ns_capable(user_ns
, CAP_SYS_ADMIN
))
1057 return ERR_PTR(-EPERM
);
1059 sb
= sget_userns(fs_type
, ns_test_super
, ns_set_super
, flags
,
1062 return ERR_CAST(sb
);
1066 err
= fill_super(sb
, data
, flags
& SB_SILENT
? 1 : 0);
1068 deactivate_locked_super(sb
);
1069 return ERR_PTR(err
);
1072 sb
->s_flags
|= SB_ACTIVE
;
1075 return dget(sb
->s_root
);
1078 EXPORT_SYMBOL(mount_ns
);
1081 static int set_bdev_super(struct super_block
*s
, void *data
)
1084 s
->s_dev
= s
->s_bdev
->bd_dev
;
1085 s
->s_bdi
= bdi_get(s
->s_bdev
->bd_bdi
);
1090 static int test_bdev_super(struct super_block
*s
, void *data
)
1092 return (void *)s
->s_bdev
== data
;
1095 struct dentry
*mount_bdev(struct file_system_type
*fs_type
,
1096 int flags
, const char *dev_name
, void *data
,
1097 int (*fill_super
)(struct super_block
*, void *, int))
1099 struct block_device
*bdev
;
1100 struct super_block
*s
;
1101 fmode_t mode
= FMODE_READ
| FMODE_EXCL
;
1104 if (!(flags
& SB_RDONLY
))
1105 mode
|= FMODE_WRITE
;
1107 bdev
= blkdev_get_by_path(dev_name
, mode
, fs_type
);
1109 return ERR_CAST(bdev
);
1112 * once the super is inserted into the list by sget, s_umount
1113 * will protect the lockfs code from trying to start a snapshot
1114 * while we are mounting
1116 mutex_lock(&bdev
->bd_fsfreeze_mutex
);
1117 if (bdev
->bd_fsfreeze_count
> 0) {
1118 mutex_unlock(&bdev
->bd_fsfreeze_mutex
);
1122 s
= sget(fs_type
, test_bdev_super
, set_bdev_super
, flags
| SB_NOSEC
,
1124 mutex_unlock(&bdev
->bd_fsfreeze_mutex
);
1129 if ((flags
^ s
->s_flags
) & SB_RDONLY
) {
1130 deactivate_locked_super(s
);
1136 * s_umount nests inside bd_mutex during
1137 * __invalidate_device(). blkdev_put() acquires
1138 * bd_mutex and can't be called under s_umount. Drop
1139 * s_umount temporarily. This is safe as we're
1140 * holding an active reference.
1142 up_write(&s
->s_umount
);
1143 blkdev_put(bdev
, mode
);
1144 down_write(&s
->s_umount
);
1147 snprintf(s
->s_id
, sizeof(s
->s_id
), "%pg", bdev
);
1148 sb_set_blocksize(s
, block_size(bdev
));
1149 error
= fill_super(s
, data
, flags
& SB_SILENT
? 1 : 0);
1151 deactivate_locked_super(s
);
1155 s
->s_flags
|= SB_ACTIVE
;
1159 return dget(s
->s_root
);
1164 blkdev_put(bdev
, mode
);
1166 return ERR_PTR(error
);
1168 EXPORT_SYMBOL(mount_bdev
);
1170 void kill_block_super(struct super_block
*sb
)
1172 struct block_device
*bdev
= sb
->s_bdev
;
1173 fmode_t mode
= sb
->s_mode
;
1175 bdev
->bd_super
= NULL
;
1176 generic_shutdown_super(sb
);
1177 sync_blockdev(bdev
);
1178 WARN_ON_ONCE(!(mode
& FMODE_EXCL
));
1179 blkdev_put(bdev
, mode
| FMODE_EXCL
);
1182 EXPORT_SYMBOL(kill_block_super
);
1185 struct dentry
*mount_nodev(struct file_system_type
*fs_type
,
1186 int flags
, void *data
,
1187 int (*fill_super
)(struct super_block
*, void *, int))
1190 struct super_block
*s
= sget(fs_type
, NULL
, set_anon_super
, flags
, NULL
);
1195 error
= fill_super(s
, data
, flags
& SB_SILENT
? 1 : 0);
1197 deactivate_locked_super(s
);
1198 return ERR_PTR(error
);
1200 s
->s_flags
|= SB_ACTIVE
;
1201 return dget(s
->s_root
);
1203 EXPORT_SYMBOL(mount_nodev
);
1205 static int compare_single(struct super_block
*s
, void *p
)
1210 struct dentry
*mount_single(struct file_system_type
*fs_type
,
1211 int flags
, void *data
,
1212 int (*fill_super
)(struct super_block
*, void *, int))
1214 struct super_block
*s
;
1217 s
= sget(fs_type
, compare_single
, set_anon_super
, flags
, NULL
);
1221 error
= fill_super(s
, data
, flags
& SB_SILENT
? 1 : 0);
1223 deactivate_locked_super(s
);
1224 return ERR_PTR(error
);
1226 s
->s_flags
|= SB_ACTIVE
;
1228 do_remount_sb(s
, flags
, data
, 0);
1230 return dget(s
->s_root
);
1232 EXPORT_SYMBOL(mount_single
);
1235 mount_fs(struct file_system_type
*type
, int flags
, const char *name
, struct vfsmount
*mnt
, void *data
)
1237 struct dentry
*root
;
1238 struct super_block
*sb
;
1239 char *secdata
= NULL
;
1240 int error
= -ENOMEM
;
1242 if (data
&& !(type
->fs_flags
& FS_BINARY_MOUNTDATA
)) {
1243 secdata
= alloc_secdata();
1247 error
= security_sb_copy_data(data
, secdata
);
1249 goto out_free_secdata
;
1253 root
= type
->mount2(mnt
, type
, flags
, name
, data
);
1255 root
= type
->mount(type
, flags
, name
, data
);
1257 error
= PTR_ERR(root
);
1258 goto out_free_secdata
;
1262 WARN_ON(!sb
->s_bdi
);
1265 * Write barrier is for super_cache_count(). We place it before setting
1266 * SB_BORN as the data dependency between the two functions is the
1267 * superblock structure contents that we just set up, not the SB_BORN
1271 sb
->s_flags
|= SB_BORN
;
1273 error
= security_sb_kern_mount(sb
, flags
, secdata
);
1278 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1279 * but s_maxbytes was an unsigned long long for many releases. Throw
1280 * this warning for a little while to try and catch filesystems that
1281 * violate this rule.
1283 WARN((sb
->s_maxbytes
< 0), "%s set sb->s_maxbytes to "
1284 "negative value (%lld)\n", type
->name
, sb
->s_maxbytes
);
1286 up_write(&sb
->s_umount
);
1287 free_secdata(secdata
);
1291 deactivate_locked_super(sb
);
1293 free_secdata(secdata
);
1295 return ERR_PTR(error
);
1299 * Setup private BDI for given superblock. It gets automatically cleaned up
1300 * in generic_shutdown_super().
1302 int super_setup_bdi_name(struct super_block
*sb
, char *fmt
, ...)
1304 struct backing_dev_info
*bdi
;
1308 bdi
= bdi_alloc(GFP_KERNEL
);
1312 bdi
->name
= sb
->s_type
->name
;
1314 va_start(args
, fmt
);
1315 err
= bdi_register_va(bdi
, fmt
, args
);
1321 WARN_ON(sb
->s_bdi
!= &noop_backing_dev_info
);
1326 EXPORT_SYMBOL(super_setup_bdi_name
);
1329 * Setup private BDI for given superblock. I gets automatically cleaned up
1330 * in generic_shutdown_super().
1332 int super_setup_bdi(struct super_block
*sb
)
1334 static atomic_long_t bdi_seq
= ATOMIC_LONG_INIT(0);
1336 return super_setup_bdi_name(sb
, "%.28s-%ld", sb
->s_type
->name
,
1337 atomic_long_inc_return(&bdi_seq
));
1339 EXPORT_SYMBOL(super_setup_bdi
);
1342 * This is an internal function, please use sb_end_{write,pagefault,intwrite}
1345 void __sb_end_write(struct super_block
*sb
, int level
)
1347 percpu_up_read(sb
->s_writers
.rw_sem
+ level
-1);
1349 EXPORT_SYMBOL(__sb_end_write
);
1352 * This is an internal function, please use sb_start_{write,pagefault,intwrite}
1355 int __sb_start_write(struct super_block
*sb
, int level
, bool wait
)
1357 bool force_trylock
= false;
1360 #ifdef CONFIG_LOCKDEP
1362 * We want lockdep to tell us about possible deadlocks with freezing
1363 * but it's it bit tricky to properly instrument it. Getting a freeze
1364 * protection works as getting a read lock but there are subtle
1365 * problems. XFS for example gets freeze protection on internal level
1366 * twice in some cases, which is OK only because we already hold a
1367 * freeze protection also on higher level. Due to these cases we have
1368 * to use wait == F (trylock mode) which must not fail.
1373 for (i
= 0; i
< level
- 1; i
++)
1374 if (percpu_rwsem_is_held(sb
->s_writers
.rw_sem
+ i
)) {
1375 force_trylock
= true;
1380 if (wait
&& !force_trylock
)
1381 percpu_down_read(sb
->s_writers
.rw_sem
+ level
-1);
1383 ret
= percpu_down_read_trylock(sb
->s_writers
.rw_sem
+ level
-1);
1385 WARN_ON(force_trylock
&& !ret
);
1388 EXPORT_SYMBOL(__sb_start_write
);
1391 * sb_wait_write - wait until all writers to given file system finish
1392 * @sb: the super for which we wait
1393 * @level: type of writers we wait for (normal vs page fault)
1395 * This function waits until there are no writers of given type to given file
1398 static void sb_wait_write(struct super_block
*sb
, int level
)
1400 percpu_down_write(sb
->s_writers
.rw_sem
+ level
-1);
1404 * We are going to return to userspace and forget about these locks, the
1405 * ownership goes to the caller of thaw_super() which does unlock().
1407 static void lockdep_sb_freeze_release(struct super_block
*sb
)
1411 for (level
= SB_FREEZE_LEVELS
- 1; level
>= 0; level
--)
1412 percpu_rwsem_release(sb
->s_writers
.rw_sem
+ level
, 0, _THIS_IP_
);
1416 * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
1418 static void lockdep_sb_freeze_acquire(struct super_block
*sb
)
1422 for (level
= 0; level
< SB_FREEZE_LEVELS
; ++level
)
1423 percpu_rwsem_acquire(sb
->s_writers
.rw_sem
+ level
, 0, _THIS_IP_
);
1426 static void sb_freeze_unlock(struct super_block
*sb
)
1430 for (level
= SB_FREEZE_LEVELS
- 1; level
>= 0; level
--)
1431 percpu_up_write(sb
->s_writers
.rw_sem
+ level
);
1435 * freeze_super - lock the filesystem and force it into a consistent state
1436 * @sb: the super to lock
1438 * Syncs the super to make sure the filesystem is consistent and calls the fs's
1439 * freeze_fs. Subsequent calls to this without first thawing the fs will return
1442 * During this function, sb->s_writers.frozen goes through these values:
1444 * SB_UNFROZEN: File system is normal, all writes progress as usual.
1446 * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
1447 * writes should be blocked, though page faults are still allowed. We wait for
1448 * all writes to complete and then proceed to the next stage.
1450 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
1451 * but internal fs threads can still modify the filesystem (although they
1452 * should not dirty new pages or inodes), writeback can run etc. After waiting
1453 * for all running page faults we sync the filesystem which will clean all
1454 * dirty pages and inodes (no new dirty pages or inodes can be created when
1457 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
1458 * modification are blocked (e.g. XFS preallocation truncation on inode
1459 * reclaim). This is usually implemented by blocking new transactions for
1460 * filesystems that have them and need this additional guard. After all
1461 * internal writers are finished we call ->freeze_fs() to finish filesystem
1462 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
1463 * mostly auxiliary for filesystems to verify they do not modify frozen fs.
1465 * sb->s_writers.frozen is protected by sb->s_umount.
1467 int freeze_super(struct super_block
*sb
)
1471 atomic_inc(&sb
->s_active
);
1472 down_write(&sb
->s_umount
);
1473 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
) {
1474 deactivate_locked_super(sb
);
1478 if (!(sb
->s_flags
& SB_BORN
)) {
1479 up_write(&sb
->s_umount
);
1480 return 0; /* sic - it's "nothing to do" */
1483 if (sb_rdonly(sb
)) {
1484 /* Nothing to do really... */
1485 sb
->s_writers
.frozen
= SB_FREEZE_COMPLETE
;
1486 up_write(&sb
->s_umount
);
1490 sb
->s_writers
.frozen
= SB_FREEZE_WRITE
;
1491 /* Release s_umount to preserve sb_start_write -> s_umount ordering */
1492 up_write(&sb
->s_umount
);
1493 sb_wait_write(sb
, SB_FREEZE_WRITE
);
1494 down_write(&sb
->s_umount
);
1496 /* Now we go and block page faults... */
1497 sb
->s_writers
.frozen
= SB_FREEZE_PAGEFAULT
;
1498 sb_wait_write(sb
, SB_FREEZE_PAGEFAULT
);
1500 /* All writers are done so after syncing there won't be dirty data */
1501 sync_filesystem(sb
);
1503 /* Now wait for internal filesystem counter */
1504 sb
->s_writers
.frozen
= SB_FREEZE_FS
;
1505 sb_wait_write(sb
, SB_FREEZE_FS
);
1507 if (sb
->s_op
->freeze_fs
) {
1508 ret
= sb
->s_op
->freeze_fs(sb
);
1511 "VFS:Filesystem freeze failed\n");
1512 sb
->s_writers
.frozen
= SB_UNFROZEN
;
1513 sb_freeze_unlock(sb
);
1514 wake_up(&sb
->s_writers
.wait_unfrozen
);
1515 deactivate_locked_super(sb
);
1520 * For debugging purposes so that fs can warn if it sees write activity
1521 * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
1523 sb
->s_writers
.frozen
= SB_FREEZE_COMPLETE
;
1524 lockdep_sb_freeze_release(sb
);
1525 up_write(&sb
->s_umount
);
1528 EXPORT_SYMBOL(freeze_super
);
1531 * thaw_super -- unlock filesystem
1532 * @sb: the super to thaw
1534 * Unlocks the filesystem and marks it writeable again after freeze_super().
1536 int thaw_super(struct super_block
*sb
)
1540 down_write(&sb
->s_umount
);
1541 if (sb
->s_writers
.frozen
!= SB_FREEZE_COMPLETE
) {
1542 up_write(&sb
->s_umount
);
1546 if (sb_rdonly(sb
)) {
1547 sb
->s_writers
.frozen
= SB_UNFROZEN
;
1551 lockdep_sb_freeze_acquire(sb
);
1553 if (sb
->s_op
->unfreeze_fs
) {
1554 error
= sb
->s_op
->unfreeze_fs(sb
);
1557 "VFS:Filesystem thaw failed\n");
1558 lockdep_sb_freeze_release(sb
);
1559 up_write(&sb
->s_umount
);
1564 sb
->s_writers
.frozen
= SB_UNFROZEN
;
1565 sb_freeze_unlock(sb
);
1567 wake_up(&sb
->s_writers
.wait_unfrozen
);
1568 deactivate_locked_super(sb
);
1571 EXPORT_SYMBOL(thaw_super
);