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
, enum freeze_holder who
);
44 static LIST_HEAD(super_blocks
);
45 static DEFINE_SPINLOCK(sb_lock
);
47 static char *sb_writers_name
[SB_FREEZE_LEVELS
] = {
53 static inline void __super_lock(struct super_block
*sb
, bool excl
)
56 down_write(&sb
->s_umount
);
58 down_read(&sb
->s_umount
);
61 static inline void super_unlock(struct super_block
*sb
, bool excl
)
64 up_write(&sb
->s_umount
);
66 up_read(&sb
->s_umount
);
69 static inline void __super_lock_excl(struct super_block
*sb
)
71 __super_lock(sb
, true);
74 static inline void super_unlock_excl(struct super_block
*sb
)
76 super_unlock(sb
, true);
79 static inline void super_unlock_shared(struct super_block
*sb
)
81 super_unlock(sb
, false);
84 static inline bool wait_born(struct super_block
*sb
)
89 * Pairs with smp_store_release() in super_wake() and ensures
90 * that we see SB_BORN or SB_DYING after we're woken.
92 flags
= smp_load_acquire(&sb
->s_flags
);
93 return flags
& (SB_BORN
| SB_DYING
);
97 * super_lock - wait for superblock to become ready and lock it
98 * @sb: superblock to wait for
99 * @excl: whether exclusive access is required
101 * If the superblock has neither passed through vfs_get_tree() or
102 * generic_shutdown_super() yet wait for it to happen. Either superblock
103 * creation will succeed and SB_BORN is set by vfs_get_tree() or we're
104 * woken and we'll see SB_DYING.
106 * The caller must have acquired a temporary reference on @sb->s_count.
108 * Return: The function returns true if SB_BORN was set and with
109 * s_umount held. The function returns false if SB_DYING was
110 * set and without s_umount held.
112 static __must_check
bool super_lock(struct super_block
*sb
, bool excl
)
115 lockdep_assert_not_held(&sb
->s_umount
);
118 __super_lock(sb
, excl
);
121 * Has gone through generic_shutdown_super() in the meantime.
122 * @sb->s_root is NULL and @sb->s_active is 0. No one needs to
123 * grab a reference to this. Tell them so.
125 if (sb
->s_flags
& SB_DYING
) {
126 super_unlock(sb
, excl
);
130 /* Has called ->get_tree() successfully. */
131 if (sb
->s_flags
& SB_BORN
)
134 super_unlock(sb
, excl
);
136 /* wait until the superblock is ready or dying */
137 wait_var_event(&sb
->s_flags
, wait_born(sb
));
140 * Neither SB_BORN nor SB_DYING are ever unset so we never loop.
141 * Just reacquire @sb->s_umount for the caller.
146 /* wait and try to acquire read-side of @sb->s_umount */
147 static inline bool super_lock_shared(struct super_block
*sb
)
149 return super_lock(sb
, false);
152 /* wait and try to acquire write-side of @sb->s_umount */
153 static inline bool super_lock_excl(struct super_block
*sb
)
155 return super_lock(sb
, true);
159 #define SUPER_WAKE_FLAGS (SB_BORN | SB_DYING | SB_DEAD)
160 static void super_wake(struct super_block
*sb
, unsigned int flag
)
162 WARN_ON_ONCE((flag
& ~SUPER_WAKE_FLAGS
));
163 WARN_ON_ONCE(hweight32(flag
& SUPER_WAKE_FLAGS
) > 1);
166 * Pairs with smp_load_acquire() in super_lock() to make sure
167 * all initializations in the superblock are seen by the user
168 * seeing SB_BORN sent.
170 smp_store_release(&sb
->s_flags
, sb
->s_flags
| flag
);
172 * Pairs with the barrier in prepare_to_wait_event() to make sure
173 * ___wait_var_event() either sees SB_BORN set or
174 * waitqueue_active() check in wake_up_var() sees the waiter.
177 wake_up_var(&sb
->s_flags
);
181 * One thing we have to be careful of with a per-sb shrinker is that we don't
182 * drop the last active reference to the superblock from within the shrinker.
183 * If that happens we could trigger unregistering the shrinker from within the
184 * shrinker path and that leads to deadlock on the shrinker_mutex. Hence we
185 * take a passive reference to the superblock to avoid this from occurring.
187 static unsigned long super_cache_scan(struct shrinker
*shrink
,
188 struct shrink_control
*sc
)
190 struct super_block
*sb
;
197 sb
= shrink
->private_data
;
200 * Deadlock avoidance. We may hold various FS locks, and we don't want
201 * to recurse into the FS that called us in clear_inode() and friends..
203 if (!(sc
->gfp_mask
& __GFP_FS
))
206 if (!super_trylock_shared(sb
))
209 if (sb
->s_op
->nr_cached_objects
)
210 fs_objects
= sb
->s_op
->nr_cached_objects(sb
, sc
);
212 inodes
= list_lru_shrink_count(&sb
->s_inode_lru
, sc
);
213 dentries
= list_lru_shrink_count(&sb
->s_dentry_lru
, sc
);
214 total_objects
= dentries
+ inodes
+ fs_objects
+ 1;
218 /* proportion the scan between the caches */
219 dentries
= mult_frac(sc
->nr_to_scan
, dentries
, total_objects
);
220 inodes
= mult_frac(sc
->nr_to_scan
, inodes
, total_objects
);
221 fs_objects
= mult_frac(sc
->nr_to_scan
, fs_objects
, total_objects
);
224 * prune the dcache first as the icache is pinned by it, then
225 * prune the icache, followed by the filesystem specific caches
227 * Ensure that we always scan at least one object - memcg kmem
228 * accounting uses this to fully empty the caches.
230 sc
->nr_to_scan
= dentries
+ 1;
231 freed
= prune_dcache_sb(sb
, sc
);
232 sc
->nr_to_scan
= inodes
+ 1;
233 freed
+= prune_icache_sb(sb
, sc
);
236 sc
->nr_to_scan
= fs_objects
+ 1;
237 freed
+= sb
->s_op
->free_cached_objects(sb
, sc
);
240 super_unlock_shared(sb
);
244 static unsigned long super_cache_count(struct shrinker
*shrink
,
245 struct shrink_control
*sc
)
247 struct super_block
*sb
;
248 long total_objects
= 0;
250 sb
= shrink
->private_data
;
253 * We don't call super_trylock_shared() here as it is a scalability
254 * bottleneck, so we're exposed to partial setup state. The shrinker
255 * rwsem does not protect filesystem operations backing
256 * list_lru_shrink_count() or s_op->nr_cached_objects(). Counts can
257 * change between super_cache_count and super_cache_scan, so we really
258 * don't need locks here.
260 * However, if we are currently mounting the superblock, the underlying
261 * filesystem might be in a state of partial construction and hence it
262 * is dangerous to access it. super_trylock_shared() uses a SB_BORN check
263 * to avoid this situation, so do the same here. The memory barrier is
264 * matched with the one in mount_fs() as we don't hold locks here.
266 if (!(sb
->s_flags
& SB_BORN
))
270 if (sb
->s_op
&& sb
->s_op
->nr_cached_objects
)
271 total_objects
= sb
->s_op
->nr_cached_objects(sb
, sc
);
273 total_objects
+= list_lru_shrink_count(&sb
->s_dentry_lru
, sc
);
274 total_objects
+= list_lru_shrink_count(&sb
->s_inode_lru
, sc
);
279 total_objects
= vfs_pressure_ratio(total_objects
);
280 return total_objects
;
283 static void destroy_super_work(struct work_struct
*work
)
285 struct super_block
*s
= container_of(work
, struct super_block
,
289 for (i
= 0; i
< SB_FREEZE_LEVELS
; i
++)
290 percpu_free_rwsem(&s
->s_writers
.rw_sem
[i
]);
294 static void destroy_super_rcu(struct rcu_head
*head
)
296 struct super_block
*s
= container_of(head
, struct super_block
, rcu
);
297 INIT_WORK(&s
->destroy_work
, destroy_super_work
);
298 schedule_work(&s
->destroy_work
);
301 /* Free a superblock that has never been seen by anyone */
302 static void destroy_unused_super(struct super_block
*s
)
306 super_unlock_excl(s
);
307 list_lru_destroy(&s
->s_dentry_lru
);
308 list_lru_destroy(&s
->s_inode_lru
);
310 put_user_ns(s
->s_user_ns
);
312 shrinker_free(s
->s_shrink
);
313 /* no delays needed */
314 destroy_super_work(&s
->destroy_work
);
318 * alloc_super - create new superblock
319 * @type: filesystem type superblock should belong to
320 * @flags: the mount flags
321 * @user_ns: User namespace for the super_block
323 * Allocates and initializes a new &struct super_block. alloc_super()
324 * returns a pointer new superblock or %NULL if allocation had failed.
326 static struct super_block
*alloc_super(struct file_system_type
*type
, int flags
,
327 struct user_namespace
*user_ns
)
329 struct super_block
*s
= kzalloc(sizeof(struct super_block
), GFP_USER
);
330 static const struct super_operations default_op
;
336 INIT_LIST_HEAD(&s
->s_mounts
);
337 s
->s_user_ns
= get_user_ns(user_ns
);
338 init_rwsem(&s
->s_umount
);
339 lockdep_set_class(&s
->s_umount
, &type
->s_umount_key
);
341 * sget() can have s_umount recursion.
343 * When it cannot find a suitable sb, it allocates a new
344 * one (this one), and tries again to find a suitable old
347 * In case that succeeds, it will acquire the s_umount
348 * lock of the old one. Since these are clearly distrinct
349 * locks, and this object isn't exposed yet, there's no
352 * Annotate this by putting this lock in a different
355 down_write_nested(&s
->s_umount
, SINGLE_DEPTH_NESTING
);
357 if (security_sb_alloc(s
))
360 for (i
= 0; i
< SB_FREEZE_LEVELS
; i
++) {
361 if (__percpu_init_rwsem(&s
->s_writers
.rw_sem
[i
],
363 &type
->s_writers_key
[i
]))
366 s
->s_bdi
= &noop_backing_dev_info
;
368 if (s
->s_user_ns
!= &init_user_ns
)
369 s
->s_iflags
|= SB_I_NODEV
;
370 INIT_HLIST_NODE(&s
->s_instances
);
371 INIT_HLIST_BL_HEAD(&s
->s_roots
);
372 mutex_init(&s
->s_sync_lock
);
373 INIT_LIST_HEAD(&s
->s_inodes
);
374 spin_lock_init(&s
->s_inode_list_lock
);
375 INIT_LIST_HEAD(&s
->s_inodes_wb
);
376 spin_lock_init(&s
->s_inode_wblist_lock
);
379 atomic_set(&s
->s_active
, 1);
380 mutex_init(&s
->s_vfs_rename_mutex
);
381 lockdep_set_class(&s
->s_vfs_rename_mutex
, &type
->s_vfs_rename_key
);
382 init_rwsem(&s
->s_dquot
.dqio_sem
);
383 s
->s_maxbytes
= MAX_NON_LFS
;
384 s
->s_op
= &default_op
;
385 s
->s_time_gran
= 1000000000;
386 s
->s_time_min
= TIME64_MIN
;
387 s
->s_time_max
= TIME64_MAX
;
389 s
->s_shrink
= shrinker_alloc(SHRINKER_NUMA_AWARE
| SHRINKER_MEMCG_AWARE
,
390 "sb-%s", type
->name
);
394 s
->s_shrink
->scan_objects
= super_cache_scan
;
395 s
->s_shrink
->count_objects
= super_cache_count
;
396 s
->s_shrink
->batch
= 1024;
397 s
->s_shrink
->private_data
= s
;
399 if (list_lru_init_memcg(&s
->s_dentry_lru
, s
->s_shrink
))
401 if (list_lru_init_memcg(&s
->s_inode_lru
, s
->s_shrink
))
406 destroy_unused_super(s
);
410 /* Superblock refcounting */
413 * Drop a superblock's refcount. The caller must hold sb_lock.
415 static void __put_super(struct super_block
*s
)
418 list_del_init(&s
->s_list
);
419 WARN_ON(s
->s_dentry_lru
.node
);
420 WARN_ON(s
->s_inode_lru
.node
);
421 WARN_ON(!list_empty(&s
->s_mounts
));
423 put_user_ns(s
->s_user_ns
);
425 call_rcu(&s
->rcu
, destroy_super_rcu
);
430 * put_super - drop a temporary reference to superblock
431 * @sb: superblock in question
433 * Drops a temporary reference, frees superblock if there's no
436 void put_super(struct super_block
*sb
)
440 spin_unlock(&sb_lock
);
443 static void kill_super_notify(struct super_block
*sb
)
445 lockdep_assert_not_held(&sb
->s_umount
);
447 /* already notified earlier */
448 if (sb
->s_flags
& SB_DEAD
)
452 * Remove it from @fs_supers so it isn't found by new
453 * sget{_fc}() walkers anymore. Any concurrent mounter still
454 * managing to grab a temporary reference is guaranteed to
455 * already see SB_DYING and will wait until we notify them about
459 hlist_del_init(&sb
->s_instances
);
460 spin_unlock(&sb_lock
);
463 * Let concurrent mounts know that this thing is really dead.
464 * We don't need @sb->s_umount here as every concurrent caller
465 * will see SB_DYING and either discard the superblock or wait
468 super_wake(sb
, SB_DEAD
);
472 * deactivate_locked_super - drop an active reference to superblock
473 * @s: superblock to deactivate
475 * Drops an active reference to superblock, converting it into a temporary
476 * one if there is no other active references left. In that case we
477 * tell fs driver to shut it down and drop the temporary reference we
480 * Caller holds exclusive lock on superblock; that lock is released.
482 void deactivate_locked_super(struct super_block
*s
)
484 struct file_system_type
*fs
= s
->s_type
;
485 if (atomic_dec_and_test(&s
->s_active
)) {
486 shrinker_free(s
->s_shrink
);
489 kill_super_notify(s
);
492 * Since list_lru_destroy() may sleep, we cannot call it from
493 * put_super(), where we hold the sb_lock. Therefore we destroy
494 * the lru lists right now.
496 list_lru_destroy(&s
->s_dentry_lru
);
497 list_lru_destroy(&s
->s_inode_lru
);
502 super_unlock_excl(s
);
506 EXPORT_SYMBOL(deactivate_locked_super
);
509 * deactivate_super - drop an active reference to superblock
510 * @s: superblock to deactivate
512 * Variant of deactivate_locked_super(), except that superblock is *not*
513 * locked by caller. If we are going to drop the final active reference,
514 * lock will be acquired prior to that.
516 void deactivate_super(struct super_block
*s
)
518 if (!atomic_add_unless(&s
->s_active
, -1, 1)) {
519 __super_lock_excl(s
);
520 deactivate_locked_super(s
);
524 EXPORT_SYMBOL(deactivate_super
);
526 static inline bool wait_dead(struct super_block
*sb
)
531 * Pairs with memory barrier in super_wake() and ensures
532 * that we see SB_DEAD after we're woken.
534 flags
= smp_load_acquire(&sb
->s_flags
);
535 return flags
& SB_DEAD
;
539 * grab_super - acquire an active reference to a superblock
540 * @sb: superblock to acquire
542 * Acquire a temporary reference on a superblock and try to trade it for
543 * an active reference. This is used in sget{_fc}() to wait for a
544 * superblock to either become SB_BORN or for it to pass through
545 * sb->kill() and be marked as SB_DEAD.
547 * Return: This returns true if an active reference could be acquired,
550 static bool grab_super(struct super_block
*sb
)
555 spin_unlock(&sb_lock
);
556 locked
= super_lock_excl(sb
);
558 if (atomic_inc_not_zero(&sb
->s_active
)) {
562 super_unlock_excl(sb
);
564 wait_var_event(&sb
->s_flags
, wait_dead(sb
));
570 * super_trylock_shared - try to grab ->s_umount shared
571 * @sb: reference we are trying to grab
573 * Try to prevent fs shutdown. This is used in places where we
574 * cannot take an active reference but we need to ensure that the
575 * filesystem is not shut down while we are working on it. It returns
576 * false if we cannot acquire s_umount or if we lose the race and
577 * filesystem already got into shutdown, and returns true with the s_umount
578 * lock held in read mode in case of success. On successful return,
579 * the caller must drop the s_umount lock when done.
581 * Note that unlike get_super() et.al. this one does *not* bump ->s_count.
582 * The reason why it's safe is that we are OK with doing trylock instead
583 * of down_read(). There's a couple of places that are OK with that, but
584 * it's very much not a general-purpose interface.
586 bool super_trylock_shared(struct super_block
*sb
)
588 if (down_read_trylock(&sb
->s_umount
)) {
589 if (!(sb
->s_flags
& SB_DYING
) && sb
->s_root
&&
590 (sb
->s_flags
& SB_BORN
))
592 super_unlock_shared(sb
);
599 * retire_super - prevents superblock from being reused
600 * @sb: superblock to retire
602 * The function marks superblock to be ignored in superblock test, which
603 * prevents it from being reused for any new mounts. If the superblock has
604 * a private bdi, it also unregisters it, but doesn't reduce the refcount
605 * of the superblock to prevent potential races. The refcount is reduced
606 * by generic_shutdown_super(). The function can not be called
607 * concurrently with generic_shutdown_super(). It is safe to call the
608 * function multiple times, subsequent calls have no effect.
610 * The marker will affect the re-use only for block-device-based
611 * superblocks. Other superblocks will still get marked if this function
612 * is used, but that will not affect their reusability.
614 void retire_super(struct super_block
*sb
)
616 WARN_ON(!sb
->s_bdev
);
617 __super_lock_excl(sb
);
618 if (sb
->s_iflags
& SB_I_PERSB_BDI
) {
619 bdi_unregister(sb
->s_bdi
);
620 sb
->s_iflags
&= ~SB_I_PERSB_BDI
;
622 sb
->s_iflags
|= SB_I_RETIRED
;
623 super_unlock_excl(sb
);
625 EXPORT_SYMBOL(retire_super
);
628 * generic_shutdown_super - common helper for ->kill_sb()
629 * @sb: superblock to kill
631 * generic_shutdown_super() does all fs-independent work on superblock
632 * shutdown. Typical ->kill_sb() should pick all fs-specific objects
633 * that need destruction out of superblock, call generic_shutdown_super()
634 * and release aforementioned objects. Note: dentries and inodes _are_
635 * taken care of and do not need specific handling.
637 * Upon calling this function, the filesystem may no longer alter or
638 * rearrange the set of dentries belonging to this super_block, nor may it
639 * change the attachments of dentries to inodes.
641 void generic_shutdown_super(struct super_block
*sb
)
643 const struct super_operations
*sop
= sb
->s_op
;
646 shrink_dcache_for_umount(sb
);
648 sb
->s_flags
&= ~SB_ACTIVE
;
650 cgroup_writeback_umount();
652 /* Evict all inodes with zero refcount. */
656 * Clean up and evict any inodes that still have references due
657 * to fsnotify or the security policy.
659 fsnotify_sb_delete(sb
);
660 security_sb_delete(sb
);
663 * Now that all potentially-encrypted inodes have been evicted,
664 * the fscrypt keyring can be destroyed.
666 fscrypt_destroy_keyring(sb
);
668 if (sb
->s_dio_done_wq
) {
669 destroy_workqueue(sb
->s_dio_done_wq
);
670 sb
->s_dio_done_wq
= NULL
;
676 if (CHECK_DATA_CORRUPTION(!list_empty(&sb
->s_inodes
),
677 "VFS: Busy inodes after unmount of %s (%s)",
678 sb
->s_id
, sb
->s_type
->name
)) {
680 * Adding a proper bailout path here would be hard, but
681 * we can at least make it more likely that a later
682 * iput_final() or such crashes cleanly.
686 spin_lock(&sb
->s_inode_list_lock
);
687 list_for_each_entry(inode
, &sb
->s_inodes
, i_sb_list
) {
688 inode
->i_op
= VFS_PTR_POISON
;
689 inode
->i_sb
= VFS_PTR_POISON
;
690 inode
->i_mapping
= VFS_PTR_POISON
;
692 spin_unlock(&sb
->s_inode_list_lock
);
696 * Broadcast to everyone that grabbed a temporary reference to this
697 * superblock before we removed it from @fs_supers that the superblock
698 * is dying. Every walker of @fs_supers outside of sget{_fc}() will now
699 * discard this superblock and treat it as dead.
701 * We leave the superblock on @fs_supers so it can be found by
702 * sget{_fc}() until we passed sb->kill_sb().
704 super_wake(sb
, SB_DYING
);
705 super_unlock_excl(sb
);
706 if (sb
->s_bdi
!= &noop_backing_dev_info
) {
707 if (sb
->s_iflags
& SB_I_PERSB_BDI
)
708 bdi_unregister(sb
->s_bdi
);
710 sb
->s_bdi
= &noop_backing_dev_info
;
714 EXPORT_SYMBOL(generic_shutdown_super
);
716 bool mount_capable(struct fs_context
*fc
)
718 if (!(fc
->fs_type
->fs_flags
& FS_USERNS_MOUNT
))
719 return capable(CAP_SYS_ADMIN
);
721 return ns_capable(fc
->user_ns
, CAP_SYS_ADMIN
);
725 * sget_fc - Find or create a superblock
726 * @fc: Filesystem context.
727 * @test: Comparison callback
728 * @set: Setup callback
730 * Create a new superblock or find an existing one.
732 * The @test callback is used to find a matching existing superblock.
733 * Whether or not the requested parameters in @fc are taken into account
734 * is specific to the @test callback that is used. They may even be
735 * completely ignored.
737 * If an extant superblock is matched, it will be returned unless:
739 * (1) the namespace the filesystem context @fc and the extant
740 * superblock's namespace differ
742 * (2) the filesystem context @fc has requested that reusing an extant
743 * superblock is not allowed
745 * In both cases EBUSY will be returned.
747 * If no match is made, a new superblock will be allocated and basic
748 * initialisation will be performed (s_type, s_fs_info and s_id will be
749 * set and the @set callback will be invoked), the superblock will be
750 * published and it will be returned in a partially constructed state
751 * with SB_BORN and SB_ACTIVE as yet unset.
753 * Return: On success, an extant or newly created superblock is
754 * returned. On failure an error pointer is returned.
756 struct super_block
*sget_fc(struct fs_context
*fc
,
757 int (*test
)(struct super_block
*, struct fs_context
*),
758 int (*set
)(struct super_block
*, struct fs_context
*))
760 struct super_block
*s
= NULL
;
761 struct super_block
*old
;
762 struct user_namespace
*user_ns
= fc
->global
? &init_user_ns
: fc
->user_ns
;
768 hlist_for_each_entry(old
, &fc
->fs_type
->fs_supers
, s_instances
) {
770 goto share_extant_sb
;
774 spin_unlock(&sb_lock
);
775 s
= alloc_super(fc
->fs_type
, fc
->sb_flags
, user_ns
);
777 return ERR_PTR(-ENOMEM
);
781 s
->s_fs_info
= fc
->s_fs_info
;
785 spin_unlock(&sb_lock
);
786 destroy_unused_super(s
);
789 fc
->s_fs_info
= NULL
;
790 s
->s_type
= fc
->fs_type
;
791 s
->s_iflags
|= fc
->s_iflags
;
792 strscpy(s
->s_id
, s
->s_type
->name
, sizeof(s
->s_id
));
794 * Make the superblock visible on @super_blocks and @fs_supers.
795 * It's in a nascent state and users should wait on SB_BORN or
796 * SB_DYING to be set.
798 list_add_tail(&s
->s_list
, &super_blocks
);
799 hlist_add_head(&s
->s_instances
, &s
->s_type
->fs_supers
);
800 spin_unlock(&sb_lock
);
801 get_filesystem(s
->s_type
);
802 shrinker_register(s
->s_shrink
);
806 if (user_ns
!= old
->s_user_ns
|| fc
->exclusive
) {
807 spin_unlock(&sb_lock
);
808 destroy_unused_super(s
);
810 warnfc(fc
, "reusing existing filesystem not allowed");
812 warnfc(fc
, "reusing existing filesystem in another namespace not allowed");
813 return ERR_PTR(-EBUSY
);
815 if (!grab_super(old
))
817 destroy_unused_super(s
);
820 EXPORT_SYMBOL(sget_fc
);
823 * sget - find or create a superblock
824 * @type: filesystem type superblock should belong to
825 * @test: comparison callback
826 * @set: setup callback
827 * @flags: mount flags
828 * @data: argument to each of them
830 struct super_block
*sget(struct file_system_type
*type
,
831 int (*test
)(struct super_block
*,void *),
832 int (*set
)(struct super_block
*,void *),
836 struct user_namespace
*user_ns
= current_user_ns();
837 struct super_block
*s
= NULL
;
838 struct super_block
*old
;
841 /* We don't yet pass the user namespace of the parent
842 * mount through to here so always use &init_user_ns
843 * until that changes.
845 if (flags
& SB_SUBMOUNT
)
846 user_ns
= &init_user_ns
;
851 hlist_for_each_entry(old
, &type
->fs_supers
, s_instances
) {
852 if (!test(old
, data
))
854 if (user_ns
!= old
->s_user_ns
) {
855 spin_unlock(&sb_lock
);
856 destroy_unused_super(s
);
857 return ERR_PTR(-EBUSY
);
859 if (!grab_super(old
))
861 destroy_unused_super(s
);
866 spin_unlock(&sb_lock
);
867 s
= alloc_super(type
, (flags
& ~SB_SUBMOUNT
), user_ns
);
869 return ERR_PTR(-ENOMEM
);
875 spin_unlock(&sb_lock
);
876 destroy_unused_super(s
);
880 strscpy(s
->s_id
, type
->name
, sizeof(s
->s_id
));
881 list_add_tail(&s
->s_list
, &super_blocks
);
882 hlist_add_head(&s
->s_instances
, &type
->fs_supers
);
883 spin_unlock(&sb_lock
);
884 get_filesystem(type
);
885 shrinker_register(s
->s_shrink
);
890 void drop_super(struct super_block
*sb
)
892 super_unlock_shared(sb
);
896 EXPORT_SYMBOL(drop_super
);
898 void drop_super_exclusive(struct super_block
*sb
)
900 super_unlock_excl(sb
);
903 EXPORT_SYMBOL(drop_super_exclusive
);
905 static void __iterate_supers(void (*f
)(struct super_block
*))
907 struct super_block
*sb
, *p
= NULL
;
910 list_for_each_entry(sb
, &super_blocks
, s_list
) {
911 /* Pairs with memory marrier in super_wake(). */
912 if (smp_load_acquire(&sb
->s_flags
) & SB_DYING
)
915 spin_unlock(&sb_lock
);
926 spin_unlock(&sb_lock
);
929 * iterate_supers - call function for all active superblocks
930 * @f: function to call
931 * @arg: argument to pass to it
933 * Scans the superblock list and calls given function, passing it
934 * locked superblock and given argument.
936 void iterate_supers(void (*f
)(struct super_block
*, void *), void *arg
)
938 struct super_block
*sb
, *p
= NULL
;
941 list_for_each_entry(sb
, &super_blocks
, s_list
) {
945 spin_unlock(&sb_lock
);
947 locked
= super_lock_shared(sb
);
951 super_unlock_shared(sb
);
961 spin_unlock(&sb_lock
);
965 * iterate_supers_type - call function for superblocks of given type
967 * @f: function to call
968 * @arg: argument to pass to it
970 * Scans the superblock list and calls given function, passing it
971 * locked superblock and given argument.
973 void iterate_supers_type(struct file_system_type
*type
,
974 void (*f
)(struct super_block
*, void *), void *arg
)
976 struct super_block
*sb
, *p
= NULL
;
979 hlist_for_each_entry(sb
, &type
->fs_supers
, s_instances
) {
983 spin_unlock(&sb_lock
);
985 locked
= super_lock_shared(sb
);
989 super_unlock_shared(sb
);
999 spin_unlock(&sb_lock
);
1002 EXPORT_SYMBOL(iterate_supers_type
);
1004 struct super_block
*user_get_super(dev_t dev
, bool excl
)
1006 struct super_block
*sb
;
1008 spin_lock(&sb_lock
);
1009 list_for_each_entry(sb
, &super_blocks
, s_list
) {
1010 if (sb
->s_dev
== dev
) {
1014 spin_unlock(&sb_lock
);
1016 locked
= super_lock(sb
, excl
);
1020 super_unlock(sb
, excl
);
1022 /* nope, got unmounted */
1023 spin_lock(&sb_lock
);
1028 spin_unlock(&sb_lock
);
1033 * reconfigure_super - asks filesystem to change superblock parameters
1034 * @fc: The superblock and configuration
1036 * Alters the configuration parameters of a live superblock.
1038 int reconfigure_super(struct fs_context
*fc
)
1040 struct super_block
*sb
= fc
->root
->d_sb
;
1042 bool remount_ro
= false;
1043 bool remount_rw
= false;
1044 bool force
= fc
->sb_flags
& SB_FORCE
;
1046 if (fc
->sb_flags_mask
& ~MS_RMT_MASK
)
1048 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
)
1051 retval
= security_sb_remount(sb
, fc
->security
);
1055 if (fc
->sb_flags_mask
& SB_RDONLY
) {
1057 if (!(fc
->sb_flags
& SB_RDONLY
) && sb
->s_bdev
&&
1058 bdev_read_only(sb
->s_bdev
))
1061 remount_rw
= !(fc
->sb_flags
& SB_RDONLY
) && sb_rdonly(sb
);
1062 remount_ro
= (fc
->sb_flags
& SB_RDONLY
) && !sb_rdonly(sb
);
1066 if (!hlist_empty(&sb
->s_pins
)) {
1067 super_unlock_excl(sb
);
1068 group_pin_kill(&sb
->s_pins
);
1069 __super_lock_excl(sb
);
1072 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
)
1074 remount_ro
= !sb_rdonly(sb
);
1077 shrink_dcache_sb(sb
);
1079 /* If we are reconfiguring to RDONLY and current sb is read/write,
1080 * make sure there are no files open for writing.
1084 sb_start_ro_state_change(sb
);
1086 retval
= sb_prepare_remount_readonly(sb
);
1090 } else if (remount_rw
) {
1092 * Protect filesystem's reconfigure code from writes from
1093 * userspace until reconfigure finishes.
1095 sb_start_ro_state_change(sb
);
1098 if (fc
->ops
->reconfigure
) {
1099 retval
= fc
->ops
->reconfigure(fc
);
1102 goto cancel_readonly
;
1103 /* If forced remount, go ahead despite any errors */
1104 WARN(1, "forced remount of a %s fs returned %i\n",
1105 sb
->s_type
->name
, retval
);
1109 WRITE_ONCE(sb
->s_flags
, ((sb
->s_flags
& ~fc
->sb_flags_mask
) |
1110 (fc
->sb_flags
& fc
->sb_flags_mask
)));
1111 sb_end_ro_state_change(sb
);
1114 * Some filesystems modify their metadata via some other path than the
1115 * bdev buffer cache (eg. use a private mapping, or directories in
1116 * pagecache, etc). Also file data modifications go via their own
1117 * mappings. So If we try to mount readonly then copy the filesystem
1118 * from bdev, we could get stale data, so invalidate it to give a best
1119 * effort at coherency.
1121 if (remount_ro
&& sb
->s_bdev
)
1122 invalidate_bdev(sb
->s_bdev
);
1126 sb_end_ro_state_change(sb
);
1130 static void do_emergency_remount_callback(struct super_block
*sb
)
1132 bool locked
= super_lock_excl(sb
);
1134 if (locked
&& sb
->s_root
&& sb
->s_bdev
&& !sb_rdonly(sb
)) {
1135 struct fs_context
*fc
;
1137 fc
= fs_context_for_reconfigure(sb
->s_root
,
1138 SB_RDONLY
| SB_FORCE
, SB_RDONLY
);
1140 if (parse_monolithic_mount_data(fc
, NULL
) == 0)
1141 (void)reconfigure_super(fc
);
1146 super_unlock_excl(sb
);
1149 static void do_emergency_remount(struct work_struct
*work
)
1151 __iterate_supers(do_emergency_remount_callback
);
1153 printk("Emergency Remount complete\n");
1156 void emergency_remount(void)
1158 struct work_struct
*work
;
1160 work
= kmalloc(sizeof(*work
), GFP_ATOMIC
);
1162 INIT_WORK(work
, do_emergency_remount
);
1163 schedule_work(work
);
1167 static void do_thaw_all_callback(struct super_block
*sb
)
1169 bool locked
= super_lock_excl(sb
);
1171 if (locked
&& sb
->s_root
) {
1172 if (IS_ENABLED(CONFIG_BLOCK
))
1173 while (sb
->s_bdev
&& !bdev_thaw(sb
->s_bdev
))
1174 pr_warn("Emergency Thaw on %pg\n", sb
->s_bdev
);
1175 thaw_super_locked(sb
, FREEZE_HOLDER_USERSPACE
);
1179 super_unlock_excl(sb
);
1182 static void do_thaw_all(struct work_struct
*work
)
1184 __iterate_supers(do_thaw_all_callback
);
1186 printk(KERN_WARNING
"Emergency Thaw complete\n");
1190 * emergency_thaw_all -- forcibly thaw every frozen filesystem
1192 * Used for emergency unfreeze of all filesystems via SysRq
1194 void emergency_thaw_all(void)
1196 struct work_struct
*work
;
1198 work
= kmalloc(sizeof(*work
), GFP_ATOMIC
);
1200 INIT_WORK(work
, do_thaw_all
);
1201 schedule_work(work
);
1205 static DEFINE_IDA(unnamed_dev_ida
);
1208 * get_anon_bdev - Allocate a block device for filesystems which don't have one.
1209 * @p: Pointer to a dev_t.
1211 * Filesystems which don't use real block devices can call this function
1212 * to allocate a virtual block device.
1214 * Context: Any context. Frequently called while holding sb_lock.
1215 * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
1216 * or -ENOMEM if memory allocation failed.
1218 int get_anon_bdev(dev_t
*p
)
1223 * Many userspace utilities consider an FSID of 0 invalid.
1224 * Always return at least 1 from get_anon_bdev.
1226 dev
= ida_alloc_range(&unnamed_dev_ida
, 1, (1 << MINORBITS
) - 1,
1236 EXPORT_SYMBOL(get_anon_bdev
);
1238 void free_anon_bdev(dev_t dev
)
1240 ida_free(&unnamed_dev_ida
, MINOR(dev
));
1242 EXPORT_SYMBOL(free_anon_bdev
);
1244 int set_anon_super(struct super_block
*s
, void *data
)
1246 return get_anon_bdev(&s
->s_dev
);
1248 EXPORT_SYMBOL(set_anon_super
);
1250 void kill_anon_super(struct super_block
*sb
)
1252 dev_t dev
= sb
->s_dev
;
1253 generic_shutdown_super(sb
);
1254 kill_super_notify(sb
);
1255 free_anon_bdev(dev
);
1257 EXPORT_SYMBOL(kill_anon_super
);
1259 void kill_litter_super(struct super_block
*sb
)
1262 d_genocide(sb
->s_root
);
1263 kill_anon_super(sb
);
1265 EXPORT_SYMBOL(kill_litter_super
);
1267 int set_anon_super_fc(struct super_block
*sb
, struct fs_context
*fc
)
1269 return set_anon_super(sb
, NULL
);
1271 EXPORT_SYMBOL(set_anon_super_fc
);
1273 static int test_keyed_super(struct super_block
*sb
, struct fs_context
*fc
)
1275 return sb
->s_fs_info
== fc
->s_fs_info
;
1278 static int test_single_super(struct super_block
*s
, struct fs_context
*fc
)
1283 static int vfs_get_super(struct fs_context
*fc
,
1284 int (*test
)(struct super_block
*, struct fs_context
*),
1285 int (*fill_super
)(struct super_block
*sb
,
1286 struct fs_context
*fc
))
1288 struct super_block
*sb
;
1291 sb
= sget_fc(fc
, test
, set_anon_super_fc
);
1296 err
= fill_super(sb
, fc
);
1300 sb
->s_flags
|= SB_ACTIVE
;
1303 fc
->root
= dget(sb
->s_root
);
1307 deactivate_locked_super(sb
);
1311 int get_tree_nodev(struct fs_context
*fc
,
1312 int (*fill_super
)(struct super_block
*sb
,
1313 struct fs_context
*fc
))
1315 return vfs_get_super(fc
, NULL
, fill_super
);
1317 EXPORT_SYMBOL(get_tree_nodev
);
1319 int get_tree_single(struct fs_context
*fc
,
1320 int (*fill_super
)(struct super_block
*sb
,
1321 struct fs_context
*fc
))
1323 return vfs_get_super(fc
, test_single_super
, fill_super
);
1325 EXPORT_SYMBOL(get_tree_single
);
1327 int get_tree_keyed(struct fs_context
*fc
,
1328 int (*fill_super
)(struct super_block
*sb
,
1329 struct fs_context
*fc
),
1332 fc
->s_fs_info
= key
;
1333 return vfs_get_super(fc
, test_keyed_super
, fill_super
);
1335 EXPORT_SYMBOL(get_tree_keyed
);
1337 static int set_bdev_super(struct super_block
*s
, void *data
)
1339 s
->s_dev
= *(dev_t
*)data
;
1343 static int super_s_dev_set(struct super_block
*s
, struct fs_context
*fc
)
1345 return set_bdev_super(s
, fc
->sget_key
);
1348 static int super_s_dev_test(struct super_block
*s
, struct fs_context
*fc
)
1350 return !(s
->s_iflags
& SB_I_RETIRED
) &&
1351 s
->s_dev
== *(dev_t
*)fc
->sget_key
;
1355 * sget_dev - Find or create a superblock by device number
1356 * @fc: Filesystem context.
1357 * @dev: device number
1359 * Find or create a superblock using the provided device number that
1360 * will be stored in fc->sget_key.
1362 * If an extant superblock is matched, then that will be returned with
1363 * an elevated reference count that the caller must transfer or discard.
1365 * If no match is made, a new superblock will be allocated and basic
1366 * initialisation will be performed (s_type, s_fs_info, s_id, s_dev will
1367 * be set). The superblock will be published and it will be returned in
1368 * a partially constructed state with SB_BORN and SB_ACTIVE as yet
1371 * Return: an existing or newly created superblock on success, an error
1372 * pointer on failure.
1374 struct super_block
*sget_dev(struct fs_context
*fc
, dev_t dev
)
1376 fc
->sget_key
= &dev
;
1377 return sget_fc(fc
, super_s_dev_test
, super_s_dev_set
);
1379 EXPORT_SYMBOL(sget_dev
);
1383 * Lock the superblock that is holder of the bdev. Returns the superblock
1384 * pointer if we successfully locked the superblock and it is alive. Otherwise
1385 * we return NULL and just unlock bdev->bd_holder_lock.
1387 * The function must be called with bdev->bd_holder_lock and releases it.
1389 static struct super_block
*bdev_super_lock(struct block_device
*bdev
, bool excl
)
1390 __releases(&bdev
->bd_holder_lock
)
1392 struct super_block
*sb
= bdev
->bd_holder
;
1395 lockdep_assert_held(&bdev
->bd_holder_lock
);
1396 lockdep_assert_not_held(&sb
->s_umount
);
1397 lockdep_assert_not_held(&bdev
->bd_disk
->open_mutex
);
1399 /* Make sure sb doesn't go away from under us */
1400 spin_lock(&sb_lock
);
1402 spin_unlock(&sb_lock
);
1404 mutex_unlock(&bdev
->bd_holder_lock
);
1406 locked
= super_lock(sb
, excl
);
1409 * If the superblock wasn't already SB_DYING then we hold
1410 * s_umount and can safely drop our temporary reference.
1417 if (!sb
->s_root
|| !(sb
->s_flags
& SB_ACTIVE
)) {
1418 super_unlock(sb
, excl
);
1425 static void fs_bdev_mark_dead(struct block_device
*bdev
, bool surprise
)
1427 struct super_block
*sb
;
1429 sb
= bdev_super_lock(bdev
, false);
1434 sync_filesystem(sb
);
1435 shrink_dcache_sb(sb
);
1436 invalidate_inodes(sb
);
1437 if (sb
->s_op
->shutdown
)
1438 sb
->s_op
->shutdown(sb
);
1440 super_unlock_shared(sb
);
1443 static void fs_bdev_sync(struct block_device
*bdev
)
1445 struct super_block
*sb
;
1447 sb
= bdev_super_lock(bdev
, false);
1451 sync_filesystem(sb
);
1452 super_unlock_shared(sb
);
1455 static struct super_block
*get_bdev_super(struct block_device
*bdev
)
1457 bool active
= false;
1458 struct super_block
*sb
;
1460 sb
= bdev_super_lock(bdev
, true);
1462 active
= atomic_inc_not_zero(&sb
->s_active
);
1463 super_unlock_excl(sb
);
1470 static int fs_bdev_freeze(struct block_device
*bdev
)
1472 struct super_block
*sb
;
1475 lockdep_assert_held(&bdev
->bd_fsfreeze_mutex
);
1477 sb
= get_bdev_super(bdev
);
1481 if (sb
->s_op
->freeze_super
)
1482 error
= sb
->s_op
->freeze_super(sb
, FREEZE_HOLDER_USERSPACE
);
1484 error
= freeze_super(sb
, FREEZE_HOLDER_USERSPACE
);
1486 error
= sync_blockdev(bdev
);
1487 deactivate_super(sb
);
1491 static int fs_bdev_thaw(struct block_device
*bdev
)
1493 struct super_block
*sb
;
1496 lockdep_assert_held(&bdev
->bd_fsfreeze_mutex
);
1498 sb
= get_bdev_super(bdev
);
1499 if (WARN_ON_ONCE(!sb
))
1502 if (sb
->s_op
->thaw_super
)
1503 error
= sb
->s_op
->thaw_super(sb
, FREEZE_HOLDER_USERSPACE
);
1505 error
= thaw_super(sb
, FREEZE_HOLDER_USERSPACE
);
1506 deactivate_super(sb
);
1510 const struct blk_holder_ops fs_holder_ops
= {
1511 .mark_dead
= fs_bdev_mark_dead
,
1512 .sync
= fs_bdev_sync
,
1513 .freeze
= fs_bdev_freeze
,
1514 .thaw
= fs_bdev_thaw
,
1516 EXPORT_SYMBOL_GPL(fs_holder_ops
);
1518 int setup_bdev_super(struct super_block
*sb
, int sb_flags
,
1519 struct fs_context
*fc
)
1521 blk_mode_t mode
= sb_open_mode(sb_flags
);
1522 struct bdev_handle
*bdev_handle
;
1523 struct block_device
*bdev
;
1525 bdev_handle
= bdev_open_by_dev(sb
->s_dev
, mode
, sb
, &fs_holder_ops
);
1526 if (IS_ERR(bdev_handle
)) {
1528 errorf(fc
, "%s: Can't open blockdev", fc
->source
);
1529 return PTR_ERR(bdev_handle
);
1531 bdev
= bdev_handle
->bdev
;
1534 * This really should be in blkdev_get_by_dev, but right now can't due
1535 * to legacy issues that require us to allow opening a block device node
1536 * writable from userspace even for a read-only block device.
1538 if ((mode
& BLK_OPEN_WRITE
) && bdev_read_only(bdev
)) {
1539 bdev_release(bdev_handle
);
1544 * It is enough to check bdev was not frozen before we set
1545 * s_bdev as freezing will wait until SB_BORN is set.
1547 if (atomic_read(&bdev
->bd_fsfreeze_count
) > 0) {
1549 warnf(fc
, "%pg: Can't mount, blockdev is frozen", bdev
);
1550 bdev_release(bdev_handle
);
1553 spin_lock(&sb_lock
);
1554 sb
->s_bdev_handle
= bdev_handle
;
1556 sb
->s_bdi
= bdi_get(bdev
->bd_disk
->bdi
);
1557 if (bdev_stable_writes(bdev
))
1558 sb
->s_iflags
|= SB_I_STABLE_WRITES
;
1559 spin_unlock(&sb_lock
);
1561 snprintf(sb
->s_id
, sizeof(sb
->s_id
), "%pg", bdev
);
1562 shrinker_debugfs_rename(sb
->s_shrink
, "sb-%s:%s", sb
->s_type
->name
,
1564 sb_set_blocksize(sb
, block_size(bdev
));
1567 EXPORT_SYMBOL_GPL(setup_bdev_super
);
1570 * get_tree_bdev - Get a superblock based on a single block device
1571 * @fc: The filesystem context holding the parameters
1572 * @fill_super: Helper to initialise a new superblock
1574 int get_tree_bdev(struct fs_context
*fc
,
1575 int (*fill_super
)(struct super_block
*,
1576 struct fs_context
*))
1578 struct super_block
*s
;
1583 return invalf(fc
, "No source specified");
1585 error
= lookup_bdev(fc
->source
, &dev
);
1587 errorf(fc
, "%s: Can't lookup blockdev", fc
->source
);
1591 fc
->sb_flags
|= SB_NOSEC
;
1592 s
= sget_dev(fc
, dev
);
1597 /* Don't summarily change the RO/RW state. */
1598 if ((fc
->sb_flags
^ s
->s_flags
) & SB_RDONLY
) {
1599 warnf(fc
, "%pg: Can't mount, would change RO state", s
->s_bdev
);
1600 deactivate_locked_super(s
);
1605 * We drop s_umount here because we need to open the bdev and
1606 * bdev->open_mutex ranks above s_umount (blkdev_put() ->
1607 * bdev_mark_dead()). It is safe because we have active sb
1608 * reference and SB_BORN is not set yet.
1610 super_unlock_excl(s
);
1611 error
= setup_bdev_super(s
, fc
->sb_flags
, fc
);
1612 __super_lock_excl(s
);
1614 error
= fill_super(s
, fc
);
1616 deactivate_locked_super(s
);
1619 s
->s_flags
|= SB_ACTIVE
;
1623 fc
->root
= dget(s
->s_root
);
1626 EXPORT_SYMBOL(get_tree_bdev
);
1628 static int test_bdev_super(struct super_block
*s
, void *data
)
1630 return !(s
->s_iflags
& SB_I_RETIRED
) && s
->s_dev
== *(dev_t
*)data
;
1633 struct dentry
*mount_bdev(struct file_system_type
*fs_type
,
1634 int flags
, const char *dev_name
, void *data
,
1635 int (*fill_super
)(struct super_block
*, void *, int))
1637 struct super_block
*s
;
1641 error
= lookup_bdev(dev_name
, &dev
);
1643 return ERR_PTR(error
);
1646 s
= sget(fs_type
, test_bdev_super
, set_bdev_super
, flags
, &dev
);
1651 if ((flags
^ s
->s_flags
) & SB_RDONLY
) {
1652 deactivate_locked_super(s
);
1653 return ERR_PTR(-EBUSY
);
1657 * We drop s_umount here because we need to open the bdev and
1658 * bdev->open_mutex ranks above s_umount (blkdev_put() ->
1659 * bdev_mark_dead()). It is safe because we have active sb
1660 * reference and SB_BORN is not set yet.
1662 super_unlock_excl(s
);
1663 error
= setup_bdev_super(s
, flags
, NULL
);
1664 __super_lock_excl(s
);
1666 error
= fill_super(s
, data
, flags
& SB_SILENT
? 1 : 0);
1668 deactivate_locked_super(s
);
1669 return ERR_PTR(error
);
1672 s
->s_flags
|= SB_ACTIVE
;
1675 return dget(s
->s_root
);
1677 EXPORT_SYMBOL(mount_bdev
);
1679 void kill_block_super(struct super_block
*sb
)
1681 struct block_device
*bdev
= sb
->s_bdev
;
1683 generic_shutdown_super(sb
);
1685 sync_blockdev(bdev
);
1686 bdev_release(sb
->s_bdev_handle
);
1690 EXPORT_SYMBOL(kill_block_super
);
1693 struct dentry
*mount_nodev(struct file_system_type
*fs_type
,
1694 int flags
, void *data
,
1695 int (*fill_super
)(struct super_block
*, void *, int))
1698 struct super_block
*s
= sget(fs_type
, NULL
, set_anon_super
, flags
, NULL
);
1703 error
= fill_super(s
, data
, flags
& SB_SILENT
? 1 : 0);
1705 deactivate_locked_super(s
);
1706 return ERR_PTR(error
);
1708 s
->s_flags
|= SB_ACTIVE
;
1709 return dget(s
->s_root
);
1711 EXPORT_SYMBOL(mount_nodev
);
1713 int reconfigure_single(struct super_block
*s
,
1714 int flags
, void *data
)
1716 struct fs_context
*fc
;
1719 /* The caller really need to be passing fc down into mount_single(),
1720 * then a chunk of this can be removed. [Bollocks -- AV]
1721 * Better yet, reconfiguration shouldn't happen, but rather the second
1722 * mount should be rejected if the parameters are not compatible.
1724 fc
= fs_context_for_reconfigure(s
->s_root
, flags
, MS_RMT_MASK
);
1728 ret
= parse_monolithic_mount_data(fc
, data
);
1732 ret
= reconfigure_super(fc
);
1738 static int compare_single(struct super_block
*s
, void *p
)
1743 struct dentry
*mount_single(struct file_system_type
*fs_type
,
1744 int flags
, void *data
,
1745 int (*fill_super
)(struct super_block
*, void *, int))
1747 struct super_block
*s
;
1750 s
= sget(fs_type
, compare_single
, set_anon_super
, flags
, NULL
);
1754 error
= fill_super(s
, data
, flags
& SB_SILENT
? 1 : 0);
1756 s
->s_flags
|= SB_ACTIVE
;
1758 error
= reconfigure_single(s
, flags
, data
);
1760 if (unlikely(error
)) {
1761 deactivate_locked_super(s
);
1762 return ERR_PTR(error
);
1764 return dget(s
->s_root
);
1766 EXPORT_SYMBOL(mount_single
);
1769 * vfs_get_tree - Get the mountable root
1770 * @fc: The superblock configuration context.
1772 * The filesystem is invoked to get or create a superblock which can then later
1773 * be used for mounting. The filesystem places a pointer to the root to be
1774 * used for mounting in @fc->root.
1776 int vfs_get_tree(struct fs_context
*fc
)
1778 struct super_block
*sb
;
1784 /* Get the mountable root in fc->root, with a ref on the root and a ref
1785 * on the superblock.
1787 error
= fc
->ops
->get_tree(fc
);
1792 pr_err("Filesystem %s get_tree() didn't set fc->root\n",
1794 /* We don't know what the locking state of the superblock is -
1795 * if there is a superblock.
1800 sb
= fc
->root
->d_sb
;
1801 WARN_ON(!sb
->s_bdi
);
1804 * super_wake() contains a memory barrier which also care of
1805 * ordering for super_cache_count(). We place it before setting
1806 * SB_BORN as the data dependency between the two functions is
1807 * the superblock structure contents that we just set up, not
1810 super_wake(sb
, SB_BORN
);
1812 error
= security_sb_set_mnt_opts(sb
, fc
->security
, 0, NULL
);
1813 if (unlikely(error
)) {
1819 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1820 * but s_maxbytes was an unsigned long long for many releases. Throw
1821 * this warning for a little while to try and catch filesystems that
1822 * violate this rule.
1824 WARN((sb
->s_maxbytes
< 0), "%s set sb->s_maxbytes to "
1825 "negative value (%lld)\n", fc
->fs_type
->name
, sb
->s_maxbytes
);
1829 EXPORT_SYMBOL(vfs_get_tree
);
1832 * Setup private BDI for given superblock. It gets automatically cleaned up
1833 * in generic_shutdown_super().
1835 int super_setup_bdi_name(struct super_block
*sb
, char *fmt
, ...)
1837 struct backing_dev_info
*bdi
;
1841 bdi
= bdi_alloc(NUMA_NO_NODE
);
1845 va_start(args
, fmt
);
1846 err
= bdi_register_va(bdi
, fmt
, args
);
1852 WARN_ON(sb
->s_bdi
!= &noop_backing_dev_info
);
1854 sb
->s_iflags
|= SB_I_PERSB_BDI
;
1858 EXPORT_SYMBOL(super_setup_bdi_name
);
1861 * Setup private BDI for given superblock. I gets automatically cleaned up
1862 * in generic_shutdown_super().
1864 int super_setup_bdi(struct super_block
*sb
)
1866 static atomic_long_t bdi_seq
= ATOMIC_LONG_INIT(0);
1868 return super_setup_bdi_name(sb
, "%.28s-%ld", sb
->s_type
->name
,
1869 atomic_long_inc_return(&bdi_seq
));
1871 EXPORT_SYMBOL(super_setup_bdi
);
1874 * sb_wait_write - wait until all writers to given file system finish
1875 * @sb: the super for which we wait
1876 * @level: type of writers we wait for (normal vs page fault)
1878 * This function waits until there are no writers of given type to given file
1881 static void sb_wait_write(struct super_block
*sb
, int level
)
1883 percpu_down_write(sb
->s_writers
.rw_sem
+ level
-1);
1887 * We are going to return to userspace and forget about these locks, the
1888 * ownership goes to the caller of thaw_super() which does unlock().
1890 static void lockdep_sb_freeze_release(struct super_block
*sb
)
1894 for (level
= SB_FREEZE_LEVELS
- 1; level
>= 0; level
--)
1895 percpu_rwsem_release(sb
->s_writers
.rw_sem
+ level
, 0, _THIS_IP_
);
1899 * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
1901 static void lockdep_sb_freeze_acquire(struct super_block
*sb
)
1905 for (level
= 0; level
< SB_FREEZE_LEVELS
; ++level
)
1906 percpu_rwsem_acquire(sb
->s_writers
.rw_sem
+ level
, 0, _THIS_IP_
);
1909 static void sb_freeze_unlock(struct super_block
*sb
, int level
)
1911 for (level
--; level
>= 0; level
--)
1912 percpu_up_write(sb
->s_writers
.rw_sem
+ level
);
1915 static int wait_for_partially_frozen(struct super_block
*sb
)
1920 unsigned short old
= sb
->s_writers
.frozen
;
1922 up_write(&sb
->s_umount
);
1923 ret
= wait_var_event_killable(&sb
->s_writers
.frozen
,
1924 sb
->s_writers
.frozen
!= old
);
1925 down_write(&sb
->s_umount
);
1926 } while (ret
== 0 &&
1927 sb
->s_writers
.frozen
!= SB_UNFROZEN
&&
1928 sb
->s_writers
.frozen
!= SB_FREEZE_COMPLETE
);
1934 * freeze_super - lock the filesystem and force it into a consistent state
1935 * @sb: the super to lock
1936 * @who: context that wants to freeze
1938 * Syncs the super to make sure the filesystem is consistent and calls the fs's
1939 * freeze_fs. Subsequent calls to this without first thawing the fs may return
1943 * * %FREEZE_HOLDER_USERSPACE if userspace wants to freeze the fs;
1944 * * %FREEZE_HOLDER_KERNEL if the kernel wants to freeze the fs.
1946 * The @who argument distinguishes between the kernel and userspace trying to
1947 * freeze the filesystem. Although there cannot be multiple kernel freezes or
1948 * multiple userspace freezes in effect at any given time, the kernel and
1949 * userspace can both hold a filesystem frozen. The filesystem remains frozen
1950 * until there are no kernel or userspace freezes in effect.
1952 * During this function, sb->s_writers.frozen goes through these values:
1954 * SB_UNFROZEN: File system is normal, all writes progress as usual.
1956 * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
1957 * writes should be blocked, though page faults are still allowed. We wait for
1958 * all writes to complete and then proceed to the next stage.
1960 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
1961 * but internal fs threads can still modify the filesystem (although they
1962 * should not dirty new pages or inodes), writeback can run etc. After waiting
1963 * for all running page faults we sync the filesystem which will clean all
1964 * dirty pages and inodes (no new dirty pages or inodes can be created when
1967 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
1968 * modification are blocked (e.g. XFS preallocation truncation on inode
1969 * reclaim). This is usually implemented by blocking new transactions for
1970 * filesystems that have them and need this additional guard. After all
1971 * internal writers are finished we call ->freeze_fs() to finish filesystem
1972 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
1973 * mostly auxiliary for filesystems to verify they do not modify frozen fs.
1975 * sb->s_writers.frozen is protected by sb->s_umount.
1977 int freeze_super(struct super_block
*sb
, enum freeze_holder who
)
1981 if (!super_lock_excl(sb
)) {
1982 WARN_ON_ONCE("Dying superblock while freezing!");
1985 atomic_inc(&sb
->s_active
);
1988 if (sb
->s_writers
.frozen
== SB_FREEZE_COMPLETE
) {
1989 if (sb
->s_writers
.freeze_holders
& who
) {
1990 deactivate_locked_super(sb
);
1994 WARN_ON(sb
->s_writers
.freeze_holders
== 0);
1997 * Someone else already holds this type of freeze; share the
1998 * freeze and assign the active ref to the freeze.
2000 sb
->s_writers
.freeze_holders
|= who
;
2001 super_unlock_excl(sb
);
2005 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
) {
2006 ret
= wait_for_partially_frozen(sb
);
2008 deactivate_locked_super(sb
);
2015 if (!(sb
->s_flags
& SB_BORN
)) {
2016 super_unlock_excl(sb
);
2017 return 0; /* sic - it's "nothing to do" */
2020 if (sb_rdonly(sb
)) {
2021 /* Nothing to do really... */
2022 sb
->s_writers
.freeze_holders
|= who
;
2023 sb
->s_writers
.frozen
= SB_FREEZE_COMPLETE
;
2024 wake_up_var(&sb
->s_writers
.frozen
);
2025 super_unlock_excl(sb
);
2029 sb
->s_writers
.frozen
= SB_FREEZE_WRITE
;
2030 /* Release s_umount to preserve sb_start_write -> s_umount ordering */
2031 super_unlock_excl(sb
);
2032 sb_wait_write(sb
, SB_FREEZE_WRITE
);
2033 if (!super_lock_excl(sb
)) {
2034 WARN_ON_ONCE("Dying superblock while freezing!");
2038 /* Now we go and block page faults... */
2039 sb
->s_writers
.frozen
= SB_FREEZE_PAGEFAULT
;
2040 sb_wait_write(sb
, SB_FREEZE_PAGEFAULT
);
2042 /* All writers are done so after syncing there won't be dirty data */
2043 ret
= sync_filesystem(sb
);
2045 sb
->s_writers
.frozen
= SB_UNFROZEN
;
2046 sb_freeze_unlock(sb
, SB_FREEZE_PAGEFAULT
);
2047 wake_up_var(&sb
->s_writers
.frozen
);
2048 deactivate_locked_super(sb
);
2052 /* Now wait for internal filesystem counter */
2053 sb
->s_writers
.frozen
= SB_FREEZE_FS
;
2054 sb_wait_write(sb
, SB_FREEZE_FS
);
2056 if (sb
->s_op
->freeze_fs
) {
2057 ret
= sb
->s_op
->freeze_fs(sb
);
2060 "VFS:Filesystem freeze failed\n");
2061 sb
->s_writers
.frozen
= SB_UNFROZEN
;
2062 sb_freeze_unlock(sb
, SB_FREEZE_FS
);
2063 wake_up_var(&sb
->s_writers
.frozen
);
2064 deactivate_locked_super(sb
);
2069 * For debugging purposes so that fs can warn if it sees write activity
2070 * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
2072 sb
->s_writers
.freeze_holders
|= who
;
2073 sb
->s_writers
.frozen
= SB_FREEZE_COMPLETE
;
2074 wake_up_var(&sb
->s_writers
.frozen
);
2075 lockdep_sb_freeze_release(sb
);
2076 super_unlock_excl(sb
);
2079 EXPORT_SYMBOL(freeze_super
);
2082 * Undoes the effect of a freeze_super_locked call. If the filesystem is
2083 * frozen both by userspace and the kernel, a thaw call from either source
2084 * removes that state without releasing the other state or unlocking the
2087 static int thaw_super_locked(struct super_block
*sb
, enum freeze_holder who
)
2091 if (sb
->s_writers
.frozen
== SB_FREEZE_COMPLETE
) {
2092 if (!(sb
->s_writers
.freeze_holders
& who
)) {
2093 super_unlock_excl(sb
);
2098 * Freeze is shared with someone else. Release our hold and
2099 * drop the active ref that freeze_super assigned to the
2102 if (sb
->s_writers
.freeze_holders
& ~who
) {
2103 sb
->s_writers
.freeze_holders
&= ~who
;
2104 deactivate_locked_super(sb
);
2108 super_unlock_excl(sb
);
2112 if (sb_rdonly(sb
)) {
2113 sb
->s_writers
.freeze_holders
&= ~who
;
2114 sb
->s_writers
.frozen
= SB_UNFROZEN
;
2115 wake_up_var(&sb
->s_writers
.frozen
);
2119 lockdep_sb_freeze_acquire(sb
);
2121 if (sb
->s_op
->unfreeze_fs
) {
2122 error
= sb
->s_op
->unfreeze_fs(sb
);
2124 printk(KERN_ERR
"VFS:Filesystem thaw failed\n");
2125 lockdep_sb_freeze_release(sb
);
2126 super_unlock_excl(sb
);
2131 sb
->s_writers
.freeze_holders
&= ~who
;
2132 sb
->s_writers
.frozen
= SB_UNFROZEN
;
2133 wake_up_var(&sb
->s_writers
.frozen
);
2134 sb_freeze_unlock(sb
, SB_FREEZE_FS
);
2136 deactivate_locked_super(sb
);
2141 * thaw_super -- unlock filesystem
2142 * @sb: the super to thaw
2143 * @who: context that wants to freeze
2145 * Unlocks the filesystem and marks it writeable again after freeze_super()
2146 * if there are no remaining freezes on the filesystem.
2149 * * %FREEZE_HOLDER_USERSPACE if userspace wants to thaw the fs;
2150 * * %FREEZE_HOLDER_KERNEL if the kernel wants to thaw the fs.
2152 int thaw_super(struct super_block
*sb
, enum freeze_holder who
)
2154 if (!super_lock_excl(sb
)) {
2155 WARN_ON_ONCE("Dying superblock while thawing!");
2158 return thaw_super_locked(sb
, who
);
2160 EXPORT_SYMBOL(thaw_super
);
2163 * Create workqueue for deferred direct IO completions. We allocate the
2164 * workqueue when it's first needed. This avoids creating workqueue for
2165 * filesystems that don't need it and also allows us to create the workqueue
2166 * late enough so the we can include s_id in the name of the workqueue.
2168 int sb_init_dio_done_wq(struct super_block
*sb
)
2170 struct workqueue_struct
*old
;
2171 struct workqueue_struct
*wq
= alloc_workqueue("dio/%s",
2177 * This has to be atomic as more DIOs can race to create the workqueue
2179 old
= cmpxchg(&sb
->s_dio_done_wq
, NULL
, wq
);
2180 /* Someone created workqueue before us? Free ours... */
2182 destroy_workqueue(wq
);
2185 EXPORT_SYMBOL_GPL(sb_init_dio_done_wq
);