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 bool super_flags(const struct super_block
*sb
, unsigned int flags
)
87 * Pairs with smp_store_release() in super_wake() and ensures
88 * that we see @flags after we're woken.
90 return smp_load_acquire(&sb
->s_flags
) & flags
;
94 * super_lock - wait for superblock to become ready and lock it
95 * @sb: superblock to wait for
96 * @excl: whether exclusive access is required
98 * If the superblock has neither passed through vfs_get_tree() or
99 * generic_shutdown_super() yet wait for it to happen. Either superblock
100 * creation will succeed and SB_BORN is set by vfs_get_tree() or we're
101 * woken and we'll see SB_DYING.
103 * The caller must have acquired a temporary reference on @sb->s_count.
105 * Return: The function returns true if SB_BORN was set and with
106 * s_umount held. The function returns false if SB_DYING was
107 * set and without s_umount held.
109 static __must_check
bool super_lock(struct super_block
*sb
, bool excl
)
111 lockdep_assert_not_held(&sb
->s_umount
);
113 /* wait until the superblock is ready or dying */
114 wait_var_event(&sb
->s_flags
, super_flags(sb
, SB_BORN
| SB_DYING
));
116 /* Don't pointlessly acquire s_umount. */
117 if (super_flags(sb
, SB_DYING
))
120 __super_lock(sb
, excl
);
123 * Has gone through generic_shutdown_super() in the meantime.
124 * @sb->s_root is NULL and @sb->s_active is 0. No one needs to
125 * grab a reference to this. Tell them so.
127 if (sb
->s_flags
& SB_DYING
) {
128 super_unlock(sb
, excl
);
132 WARN_ON_ONCE(!(sb
->s_flags
& SB_BORN
));
136 /* wait and try to acquire read-side of @sb->s_umount */
137 static inline bool super_lock_shared(struct super_block
*sb
)
139 return super_lock(sb
, false);
142 /* wait and try to acquire write-side of @sb->s_umount */
143 static inline bool super_lock_excl(struct super_block
*sb
)
145 return super_lock(sb
, true);
149 #define SUPER_WAKE_FLAGS (SB_BORN | SB_DYING | SB_DEAD)
150 static void super_wake(struct super_block
*sb
, unsigned int flag
)
152 WARN_ON_ONCE((flag
& ~SUPER_WAKE_FLAGS
));
153 WARN_ON_ONCE(hweight32(flag
& SUPER_WAKE_FLAGS
) > 1);
156 * Pairs with smp_load_acquire() in super_lock() to make sure
157 * all initializations in the superblock are seen by the user
158 * seeing SB_BORN sent.
160 smp_store_release(&sb
->s_flags
, sb
->s_flags
| flag
);
162 * Pairs with the barrier in prepare_to_wait_event() to make sure
163 * ___wait_var_event() either sees SB_BORN set or
164 * waitqueue_active() check in wake_up_var() sees the waiter.
167 wake_up_var(&sb
->s_flags
);
171 * One thing we have to be careful of with a per-sb shrinker is that we don't
172 * drop the last active reference to the superblock from within the shrinker.
173 * If that happens we could trigger unregistering the shrinker from within the
174 * shrinker path and that leads to deadlock on the shrinker_mutex. Hence we
175 * take a passive reference to the superblock to avoid this from occurring.
177 static unsigned long super_cache_scan(struct shrinker
*shrink
,
178 struct shrink_control
*sc
)
180 struct super_block
*sb
;
187 sb
= shrink
->private_data
;
190 * Deadlock avoidance. We may hold various FS locks, and we don't want
191 * to recurse into the FS that called us in clear_inode() and friends..
193 if (!(sc
->gfp_mask
& __GFP_FS
))
196 if (!super_trylock_shared(sb
))
199 if (sb
->s_op
->nr_cached_objects
)
200 fs_objects
= sb
->s_op
->nr_cached_objects(sb
, sc
);
202 inodes
= list_lru_shrink_count(&sb
->s_inode_lru
, sc
);
203 dentries
= list_lru_shrink_count(&sb
->s_dentry_lru
, sc
);
204 total_objects
= dentries
+ inodes
+ fs_objects
+ 1;
208 /* proportion the scan between the caches */
209 dentries
= mult_frac(sc
->nr_to_scan
, dentries
, total_objects
);
210 inodes
= mult_frac(sc
->nr_to_scan
, inodes
, total_objects
);
211 fs_objects
= mult_frac(sc
->nr_to_scan
, fs_objects
, total_objects
);
214 * prune the dcache first as the icache is pinned by it, then
215 * prune the icache, followed by the filesystem specific caches
217 * Ensure that we always scan at least one object - memcg kmem
218 * accounting uses this to fully empty the caches.
220 sc
->nr_to_scan
= dentries
+ 1;
221 freed
= prune_dcache_sb(sb
, sc
);
222 sc
->nr_to_scan
= inodes
+ 1;
223 freed
+= prune_icache_sb(sb
, sc
);
226 sc
->nr_to_scan
= fs_objects
+ 1;
227 freed
+= sb
->s_op
->free_cached_objects(sb
, sc
);
230 super_unlock_shared(sb
);
234 static unsigned long super_cache_count(struct shrinker
*shrink
,
235 struct shrink_control
*sc
)
237 struct super_block
*sb
;
238 long total_objects
= 0;
240 sb
= shrink
->private_data
;
243 * We don't call super_trylock_shared() here as it is a scalability
244 * bottleneck, so we're exposed to partial setup state. The shrinker
245 * rwsem does not protect filesystem operations backing
246 * list_lru_shrink_count() or s_op->nr_cached_objects(). Counts can
247 * change between super_cache_count and super_cache_scan, so we really
248 * don't need locks here.
250 * However, if we are currently mounting the superblock, the underlying
251 * filesystem might be in a state of partial construction and hence it
252 * is dangerous to access it. super_trylock_shared() uses a SB_BORN check
253 * to avoid this situation, so do the same here. The memory barrier is
254 * matched with the one in mount_fs() as we don't hold locks here.
256 if (!(sb
->s_flags
& SB_BORN
))
260 if (sb
->s_op
&& sb
->s_op
->nr_cached_objects
)
261 total_objects
= sb
->s_op
->nr_cached_objects(sb
, sc
);
263 total_objects
+= list_lru_shrink_count(&sb
->s_dentry_lru
, sc
);
264 total_objects
+= list_lru_shrink_count(&sb
->s_inode_lru
, sc
);
269 total_objects
= vfs_pressure_ratio(total_objects
);
270 return total_objects
;
273 static void destroy_super_work(struct work_struct
*work
)
275 struct super_block
*s
= container_of(work
, struct super_block
,
278 put_user_ns(s
->s_user_ns
);
280 for (int i
= 0; i
< SB_FREEZE_LEVELS
; i
++)
281 percpu_free_rwsem(&s
->s_writers
.rw_sem
[i
]);
285 static void destroy_super_rcu(struct rcu_head
*head
)
287 struct super_block
*s
= container_of(head
, struct super_block
, rcu
);
288 INIT_WORK(&s
->destroy_work
, destroy_super_work
);
289 schedule_work(&s
->destroy_work
);
292 /* Free a superblock that has never been seen by anyone */
293 static void destroy_unused_super(struct super_block
*s
)
297 super_unlock_excl(s
);
298 list_lru_destroy(&s
->s_dentry_lru
);
299 list_lru_destroy(&s
->s_inode_lru
);
300 shrinker_free(s
->s_shrink
);
301 /* no delays needed */
302 destroy_super_work(&s
->destroy_work
);
306 * alloc_super - create new superblock
307 * @type: filesystem type superblock should belong to
308 * @flags: the mount flags
309 * @user_ns: User namespace for the super_block
311 * Allocates and initializes a new &struct super_block. alloc_super()
312 * returns a pointer new superblock or %NULL if allocation had failed.
314 static struct super_block
*alloc_super(struct file_system_type
*type
, int flags
,
315 struct user_namespace
*user_ns
)
317 struct super_block
*s
= kzalloc(sizeof(struct super_block
), GFP_KERNEL
);
318 static const struct super_operations default_op
;
324 INIT_LIST_HEAD(&s
->s_mounts
);
325 s
->s_user_ns
= get_user_ns(user_ns
);
326 init_rwsem(&s
->s_umount
);
327 lockdep_set_class(&s
->s_umount
, &type
->s_umount_key
);
329 * sget() can have s_umount recursion.
331 * When it cannot find a suitable sb, it allocates a new
332 * one (this one), and tries again to find a suitable old
335 * In case that succeeds, it will acquire the s_umount
336 * lock of the old one. Since these are clearly distrinct
337 * locks, and this object isn't exposed yet, there's no
340 * Annotate this by putting this lock in a different
343 down_write_nested(&s
->s_umount
, SINGLE_DEPTH_NESTING
);
345 if (security_sb_alloc(s
))
348 for (i
= 0; i
< SB_FREEZE_LEVELS
; i
++) {
349 if (__percpu_init_rwsem(&s
->s_writers
.rw_sem
[i
],
351 &type
->s_writers_key
[i
]))
354 s
->s_bdi
= &noop_backing_dev_info
;
356 if (s
->s_user_ns
!= &init_user_ns
)
357 s
->s_iflags
|= SB_I_NODEV
;
358 INIT_HLIST_NODE(&s
->s_instances
);
359 INIT_HLIST_BL_HEAD(&s
->s_roots
);
360 mutex_init(&s
->s_sync_lock
);
361 INIT_LIST_HEAD(&s
->s_inodes
);
362 spin_lock_init(&s
->s_inode_list_lock
);
363 INIT_LIST_HEAD(&s
->s_inodes_wb
);
364 spin_lock_init(&s
->s_inode_wblist_lock
);
367 atomic_set(&s
->s_active
, 1);
368 mutex_init(&s
->s_vfs_rename_mutex
);
369 lockdep_set_class(&s
->s_vfs_rename_mutex
, &type
->s_vfs_rename_key
);
370 init_rwsem(&s
->s_dquot
.dqio_sem
);
371 s
->s_maxbytes
= MAX_NON_LFS
;
372 s
->s_op
= &default_op
;
373 s
->s_time_gran
= 1000000000;
374 s
->s_time_min
= TIME64_MIN
;
375 s
->s_time_max
= TIME64_MAX
;
377 s
->s_shrink
= shrinker_alloc(SHRINKER_NUMA_AWARE
| SHRINKER_MEMCG_AWARE
,
378 "sb-%s", type
->name
);
382 s
->s_shrink
->scan_objects
= super_cache_scan
;
383 s
->s_shrink
->count_objects
= super_cache_count
;
384 s
->s_shrink
->batch
= 1024;
385 s
->s_shrink
->private_data
= s
;
387 if (list_lru_init_memcg(&s
->s_dentry_lru
, s
->s_shrink
))
389 if (list_lru_init_memcg(&s
->s_inode_lru
, s
->s_shrink
))
394 destroy_unused_super(s
);
398 /* Superblock refcounting */
401 * Drop a superblock's refcount. The caller must hold sb_lock.
403 static void __put_super(struct super_block
*s
)
406 list_del_init(&s
->s_list
);
407 WARN_ON(s
->s_dentry_lru
.node
);
408 WARN_ON(s
->s_inode_lru
.node
);
409 WARN_ON(!list_empty(&s
->s_mounts
));
410 call_rcu(&s
->rcu
, destroy_super_rcu
);
415 * put_super - drop a temporary reference to superblock
416 * @sb: superblock in question
418 * Drops a temporary reference, frees superblock if there's no
421 void put_super(struct super_block
*sb
)
425 spin_unlock(&sb_lock
);
428 static void kill_super_notify(struct super_block
*sb
)
430 lockdep_assert_not_held(&sb
->s_umount
);
432 /* already notified earlier */
433 if (sb
->s_flags
& SB_DEAD
)
437 * Remove it from @fs_supers so it isn't found by new
438 * sget{_fc}() walkers anymore. Any concurrent mounter still
439 * managing to grab a temporary reference is guaranteed to
440 * already see SB_DYING and will wait until we notify them about
444 hlist_del_init(&sb
->s_instances
);
445 spin_unlock(&sb_lock
);
448 * Let concurrent mounts know that this thing is really dead.
449 * We don't need @sb->s_umount here as every concurrent caller
450 * will see SB_DYING and either discard the superblock or wait
453 super_wake(sb
, SB_DEAD
);
457 * deactivate_locked_super - drop an active reference to superblock
458 * @s: superblock to deactivate
460 * Drops an active reference to superblock, converting it into a temporary
461 * one if there is no other active references left. In that case we
462 * tell fs driver to shut it down and drop the temporary reference we
465 * Caller holds exclusive lock on superblock; that lock is released.
467 void deactivate_locked_super(struct super_block
*s
)
469 struct file_system_type
*fs
= s
->s_type
;
470 if (atomic_dec_and_test(&s
->s_active
)) {
471 shrinker_free(s
->s_shrink
);
474 kill_super_notify(s
);
477 * Since list_lru_destroy() may sleep, we cannot call it from
478 * put_super(), where we hold the sb_lock. Therefore we destroy
479 * the lru lists right now.
481 list_lru_destroy(&s
->s_dentry_lru
);
482 list_lru_destroy(&s
->s_inode_lru
);
487 super_unlock_excl(s
);
491 EXPORT_SYMBOL(deactivate_locked_super
);
494 * deactivate_super - drop an active reference to superblock
495 * @s: superblock to deactivate
497 * Variant of deactivate_locked_super(), except that superblock is *not*
498 * locked by caller. If we are going to drop the final active reference,
499 * lock will be acquired prior to that.
501 void deactivate_super(struct super_block
*s
)
503 if (!atomic_add_unless(&s
->s_active
, -1, 1)) {
504 __super_lock_excl(s
);
505 deactivate_locked_super(s
);
509 EXPORT_SYMBOL(deactivate_super
);
512 * grab_super - acquire an active reference to a superblock
513 * @sb: superblock to acquire
515 * Acquire a temporary reference on a superblock and try to trade it for
516 * an active reference. This is used in sget{_fc}() to wait for a
517 * superblock to either become SB_BORN or for it to pass through
518 * sb->kill() and be marked as SB_DEAD.
520 * Return: This returns true if an active reference could be acquired,
523 static bool grab_super(struct super_block
*sb
)
528 spin_unlock(&sb_lock
);
529 locked
= super_lock_excl(sb
);
531 if (atomic_inc_not_zero(&sb
->s_active
)) {
535 super_unlock_excl(sb
);
537 wait_var_event(&sb
->s_flags
, super_flags(sb
, SB_DEAD
));
543 * super_trylock_shared - try to grab ->s_umount shared
544 * @sb: reference we are trying to grab
546 * Try to prevent fs shutdown. This is used in places where we
547 * cannot take an active reference but we need to ensure that the
548 * filesystem is not shut down while we are working on it. It returns
549 * false if we cannot acquire s_umount or if we lose the race and
550 * filesystem already got into shutdown, and returns true with the s_umount
551 * lock held in read mode in case of success. On successful return,
552 * the caller must drop the s_umount lock when done.
554 * Note that unlike get_super() et.al. this one does *not* bump ->s_count.
555 * The reason why it's safe is that we are OK with doing trylock instead
556 * of down_read(). There's a couple of places that are OK with that, but
557 * it's very much not a general-purpose interface.
559 bool super_trylock_shared(struct super_block
*sb
)
561 if (down_read_trylock(&sb
->s_umount
)) {
562 if (!(sb
->s_flags
& SB_DYING
) && sb
->s_root
&&
563 (sb
->s_flags
& SB_BORN
))
565 super_unlock_shared(sb
);
572 * retire_super - prevents superblock from being reused
573 * @sb: superblock to retire
575 * The function marks superblock to be ignored in superblock test, which
576 * prevents it from being reused for any new mounts. If the superblock has
577 * a private bdi, it also unregisters it, but doesn't reduce the refcount
578 * of the superblock to prevent potential races. The refcount is reduced
579 * by generic_shutdown_super(). The function can not be called
580 * concurrently with generic_shutdown_super(). It is safe to call the
581 * function multiple times, subsequent calls have no effect.
583 * The marker will affect the re-use only for block-device-based
584 * superblocks. Other superblocks will still get marked if this function
585 * is used, but that will not affect their reusability.
587 void retire_super(struct super_block
*sb
)
589 WARN_ON(!sb
->s_bdev
);
590 __super_lock_excl(sb
);
591 if (sb
->s_iflags
& SB_I_PERSB_BDI
) {
592 bdi_unregister(sb
->s_bdi
);
593 sb
->s_iflags
&= ~SB_I_PERSB_BDI
;
595 sb
->s_iflags
|= SB_I_RETIRED
;
596 super_unlock_excl(sb
);
598 EXPORT_SYMBOL(retire_super
);
601 * generic_shutdown_super - common helper for ->kill_sb()
602 * @sb: superblock to kill
604 * generic_shutdown_super() does all fs-independent work on superblock
605 * shutdown. Typical ->kill_sb() should pick all fs-specific objects
606 * that need destruction out of superblock, call generic_shutdown_super()
607 * and release aforementioned objects. Note: dentries and inodes _are_
608 * taken care of and do not need specific handling.
610 * Upon calling this function, the filesystem may no longer alter or
611 * rearrange the set of dentries belonging to this super_block, nor may it
612 * change the attachments of dentries to inodes.
614 void generic_shutdown_super(struct super_block
*sb
)
616 const struct super_operations
*sop
= sb
->s_op
;
619 shrink_dcache_for_umount(sb
);
621 sb
->s_flags
&= ~SB_ACTIVE
;
623 cgroup_writeback_umount();
625 /* Evict all inodes with zero refcount. */
629 * Clean up and evict any inodes that still have references due
630 * to fsnotify or the security policy.
632 fsnotify_sb_delete(sb
);
633 security_sb_delete(sb
);
635 if (sb
->s_dio_done_wq
) {
636 destroy_workqueue(sb
->s_dio_done_wq
);
637 sb
->s_dio_done_wq
= NULL
;
644 * Now that all potentially-encrypted inodes have been evicted,
645 * the fscrypt keyring can be destroyed.
647 fscrypt_destroy_keyring(sb
);
649 if (CHECK_DATA_CORRUPTION(!list_empty(&sb
->s_inodes
),
650 "VFS: Busy inodes after unmount of %s (%s)",
651 sb
->s_id
, sb
->s_type
->name
)) {
653 * Adding a proper bailout path here would be hard, but
654 * we can at least make it more likely that a later
655 * iput_final() or such crashes cleanly.
659 spin_lock(&sb
->s_inode_list_lock
);
660 list_for_each_entry(inode
, &sb
->s_inodes
, i_sb_list
) {
661 inode
->i_op
= VFS_PTR_POISON
;
662 inode
->i_sb
= VFS_PTR_POISON
;
663 inode
->i_mapping
= VFS_PTR_POISON
;
665 spin_unlock(&sb
->s_inode_list_lock
);
669 * Broadcast to everyone that grabbed a temporary reference to this
670 * superblock before we removed it from @fs_supers that the superblock
671 * is dying. Every walker of @fs_supers outside of sget{_fc}() will now
672 * discard this superblock and treat it as dead.
674 * We leave the superblock on @fs_supers so it can be found by
675 * sget{_fc}() until we passed sb->kill_sb().
677 super_wake(sb
, SB_DYING
);
678 super_unlock_excl(sb
);
679 if (sb
->s_bdi
!= &noop_backing_dev_info
) {
680 if (sb
->s_iflags
& SB_I_PERSB_BDI
)
681 bdi_unregister(sb
->s_bdi
);
683 sb
->s_bdi
= &noop_backing_dev_info
;
687 EXPORT_SYMBOL(generic_shutdown_super
);
689 bool mount_capable(struct fs_context
*fc
)
691 if (!(fc
->fs_type
->fs_flags
& FS_USERNS_MOUNT
))
692 return capable(CAP_SYS_ADMIN
);
694 return ns_capable(fc
->user_ns
, CAP_SYS_ADMIN
);
698 * sget_fc - Find or create a superblock
699 * @fc: Filesystem context.
700 * @test: Comparison callback
701 * @set: Setup callback
703 * Create a new superblock or find an existing one.
705 * The @test callback is used to find a matching existing superblock.
706 * Whether or not the requested parameters in @fc are taken into account
707 * is specific to the @test callback that is used. They may even be
708 * completely ignored.
710 * If an extant superblock is matched, it will be returned unless:
712 * (1) the namespace the filesystem context @fc and the extant
713 * superblock's namespace differ
715 * (2) the filesystem context @fc has requested that reusing an extant
716 * superblock is not allowed
718 * In both cases EBUSY will be returned.
720 * If no match is made, a new superblock will be allocated and basic
721 * initialisation will be performed (s_type, s_fs_info and s_id will be
722 * set and the @set callback will be invoked), the superblock will be
723 * published and it will be returned in a partially constructed state
724 * with SB_BORN and SB_ACTIVE as yet unset.
726 * Return: On success, an extant or newly created superblock is
727 * returned. On failure an error pointer is returned.
729 struct super_block
*sget_fc(struct fs_context
*fc
,
730 int (*test
)(struct super_block
*, struct fs_context
*),
731 int (*set
)(struct super_block
*, struct fs_context
*))
733 struct super_block
*s
= NULL
;
734 struct super_block
*old
;
735 struct user_namespace
*user_ns
= fc
->global
? &init_user_ns
: fc
->user_ns
;
741 hlist_for_each_entry(old
, &fc
->fs_type
->fs_supers
, s_instances
) {
743 goto share_extant_sb
;
747 spin_unlock(&sb_lock
);
748 s
= alloc_super(fc
->fs_type
, fc
->sb_flags
, user_ns
);
750 return ERR_PTR(-ENOMEM
);
754 s
->s_fs_info
= fc
->s_fs_info
;
758 spin_unlock(&sb_lock
);
759 destroy_unused_super(s
);
762 fc
->s_fs_info
= NULL
;
763 s
->s_type
= fc
->fs_type
;
764 s
->s_iflags
|= fc
->s_iflags
;
765 strscpy(s
->s_id
, s
->s_type
->name
, sizeof(s
->s_id
));
767 * Make the superblock visible on @super_blocks and @fs_supers.
768 * It's in a nascent state and users should wait on SB_BORN or
769 * SB_DYING to be set.
771 list_add_tail(&s
->s_list
, &super_blocks
);
772 hlist_add_head(&s
->s_instances
, &s
->s_type
->fs_supers
);
773 spin_unlock(&sb_lock
);
774 get_filesystem(s
->s_type
);
775 shrinker_register(s
->s_shrink
);
779 if (user_ns
!= old
->s_user_ns
|| fc
->exclusive
) {
780 spin_unlock(&sb_lock
);
781 destroy_unused_super(s
);
783 warnfc(fc
, "reusing existing filesystem not allowed");
785 warnfc(fc
, "reusing existing filesystem in another namespace not allowed");
786 return ERR_PTR(-EBUSY
);
788 if (!grab_super(old
))
790 destroy_unused_super(s
);
793 EXPORT_SYMBOL(sget_fc
);
796 * sget - find or create a superblock
797 * @type: filesystem type superblock should belong to
798 * @test: comparison callback
799 * @set: setup callback
800 * @flags: mount flags
801 * @data: argument to each of them
803 struct super_block
*sget(struct file_system_type
*type
,
804 int (*test
)(struct super_block
*,void *),
805 int (*set
)(struct super_block
*,void *),
809 struct user_namespace
*user_ns
= current_user_ns();
810 struct super_block
*s
= NULL
;
811 struct super_block
*old
;
814 /* We don't yet pass the user namespace of the parent
815 * mount through to here so always use &init_user_ns
816 * until that changes.
818 if (flags
& SB_SUBMOUNT
)
819 user_ns
= &init_user_ns
;
824 hlist_for_each_entry(old
, &type
->fs_supers
, s_instances
) {
825 if (!test(old
, data
))
827 if (user_ns
!= old
->s_user_ns
) {
828 spin_unlock(&sb_lock
);
829 destroy_unused_super(s
);
830 return ERR_PTR(-EBUSY
);
832 if (!grab_super(old
))
834 destroy_unused_super(s
);
839 spin_unlock(&sb_lock
);
840 s
= alloc_super(type
, (flags
& ~SB_SUBMOUNT
), user_ns
);
842 return ERR_PTR(-ENOMEM
);
848 spin_unlock(&sb_lock
);
849 destroy_unused_super(s
);
853 strscpy(s
->s_id
, type
->name
, sizeof(s
->s_id
));
854 list_add_tail(&s
->s_list
, &super_blocks
);
855 hlist_add_head(&s
->s_instances
, &type
->fs_supers
);
856 spin_unlock(&sb_lock
);
857 get_filesystem(type
);
858 shrinker_register(s
->s_shrink
);
863 void drop_super(struct super_block
*sb
)
865 super_unlock_shared(sb
);
869 EXPORT_SYMBOL(drop_super
);
871 void drop_super_exclusive(struct super_block
*sb
)
873 super_unlock_excl(sb
);
876 EXPORT_SYMBOL(drop_super_exclusive
);
878 static void __iterate_supers(void (*f
)(struct super_block
*))
880 struct super_block
*sb
, *p
= NULL
;
883 list_for_each_entry(sb
, &super_blocks
, s_list
) {
884 if (super_flags(sb
, SB_DYING
))
887 spin_unlock(&sb_lock
);
898 spin_unlock(&sb_lock
);
901 * iterate_supers - call function for all active superblocks
902 * @f: function to call
903 * @arg: argument to pass to it
905 * Scans the superblock list and calls given function, passing it
906 * locked superblock and given argument.
908 void iterate_supers(void (*f
)(struct super_block
*, void *), void *arg
)
910 struct super_block
*sb
, *p
= NULL
;
913 list_for_each_entry(sb
, &super_blocks
, s_list
) {
917 spin_unlock(&sb_lock
);
919 locked
= super_lock_shared(sb
);
923 super_unlock_shared(sb
);
933 spin_unlock(&sb_lock
);
937 * iterate_supers_type - call function for superblocks of given type
939 * @f: function to call
940 * @arg: argument to pass to it
942 * Scans the superblock list and calls given function, passing it
943 * locked superblock and given argument.
945 void iterate_supers_type(struct file_system_type
*type
,
946 void (*f
)(struct super_block
*, void *), void *arg
)
948 struct super_block
*sb
, *p
= NULL
;
951 hlist_for_each_entry(sb
, &type
->fs_supers
, s_instances
) {
955 spin_unlock(&sb_lock
);
957 locked
= super_lock_shared(sb
);
961 super_unlock_shared(sb
);
971 spin_unlock(&sb_lock
);
974 EXPORT_SYMBOL(iterate_supers_type
);
976 struct super_block
*user_get_super(dev_t dev
, bool excl
)
978 struct super_block
*sb
;
981 list_for_each_entry(sb
, &super_blocks
, s_list
) {
982 if (sb
->s_dev
== dev
) {
986 spin_unlock(&sb_lock
);
988 locked
= super_lock(sb
, excl
);
992 super_unlock(sb
, excl
);
994 /* nope, got unmounted */
1000 spin_unlock(&sb_lock
);
1005 * reconfigure_super - asks filesystem to change superblock parameters
1006 * @fc: The superblock and configuration
1008 * Alters the configuration parameters of a live superblock.
1010 int reconfigure_super(struct fs_context
*fc
)
1012 struct super_block
*sb
= fc
->root
->d_sb
;
1014 bool remount_ro
= false;
1015 bool remount_rw
= false;
1016 bool force
= fc
->sb_flags
& SB_FORCE
;
1018 if (fc
->sb_flags_mask
& ~MS_RMT_MASK
)
1020 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
)
1023 retval
= security_sb_remount(sb
, fc
->security
);
1027 if (fc
->sb_flags_mask
& SB_RDONLY
) {
1029 if (!(fc
->sb_flags
& SB_RDONLY
) && sb
->s_bdev
&&
1030 bdev_read_only(sb
->s_bdev
))
1033 remount_rw
= !(fc
->sb_flags
& SB_RDONLY
) && sb_rdonly(sb
);
1034 remount_ro
= (fc
->sb_flags
& SB_RDONLY
) && !sb_rdonly(sb
);
1038 if (!hlist_empty(&sb
->s_pins
)) {
1039 super_unlock_excl(sb
);
1040 group_pin_kill(&sb
->s_pins
);
1041 __super_lock_excl(sb
);
1044 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
)
1046 remount_ro
= !sb_rdonly(sb
);
1049 shrink_dcache_sb(sb
);
1051 /* If we are reconfiguring to RDONLY and current sb is read/write,
1052 * make sure there are no files open for writing.
1056 sb_start_ro_state_change(sb
);
1058 retval
= sb_prepare_remount_readonly(sb
);
1062 } else if (remount_rw
) {
1064 * Protect filesystem's reconfigure code from writes from
1065 * userspace until reconfigure finishes.
1067 sb_start_ro_state_change(sb
);
1070 if (fc
->ops
->reconfigure
) {
1071 retval
= fc
->ops
->reconfigure(fc
);
1074 goto cancel_readonly
;
1075 /* If forced remount, go ahead despite any errors */
1076 WARN(1, "forced remount of a %s fs returned %i\n",
1077 sb
->s_type
->name
, retval
);
1081 WRITE_ONCE(sb
->s_flags
, ((sb
->s_flags
& ~fc
->sb_flags_mask
) |
1082 (fc
->sb_flags
& fc
->sb_flags_mask
)));
1083 sb_end_ro_state_change(sb
);
1086 * Some filesystems modify their metadata via some other path than the
1087 * bdev buffer cache (eg. use a private mapping, or directories in
1088 * pagecache, etc). Also file data modifications go via their own
1089 * mappings. So If we try to mount readonly then copy the filesystem
1090 * from bdev, we could get stale data, so invalidate it to give a best
1091 * effort at coherency.
1093 if (remount_ro
&& sb
->s_bdev
)
1094 invalidate_bdev(sb
->s_bdev
);
1098 sb_end_ro_state_change(sb
);
1102 static void do_emergency_remount_callback(struct super_block
*sb
)
1104 bool locked
= super_lock_excl(sb
);
1106 if (locked
&& sb
->s_root
&& sb
->s_bdev
&& !sb_rdonly(sb
)) {
1107 struct fs_context
*fc
;
1109 fc
= fs_context_for_reconfigure(sb
->s_root
,
1110 SB_RDONLY
| SB_FORCE
, SB_RDONLY
);
1112 if (parse_monolithic_mount_data(fc
, NULL
) == 0)
1113 (void)reconfigure_super(fc
);
1118 super_unlock_excl(sb
);
1121 static void do_emergency_remount(struct work_struct
*work
)
1123 __iterate_supers(do_emergency_remount_callback
);
1125 printk("Emergency Remount complete\n");
1128 void emergency_remount(void)
1130 struct work_struct
*work
;
1132 work
= kmalloc(sizeof(*work
), GFP_ATOMIC
);
1134 INIT_WORK(work
, do_emergency_remount
);
1135 schedule_work(work
);
1139 static void do_thaw_all_callback(struct super_block
*sb
)
1141 bool locked
= super_lock_excl(sb
);
1143 if (locked
&& sb
->s_root
) {
1144 if (IS_ENABLED(CONFIG_BLOCK
))
1145 while (sb
->s_bdev
&& !bdev_thaw(sb
->s_bdev
))
1146 pr_warn("Emergency Thaw on %pg\n", sb
->s_bdev
);
1147 thaw_super_locked(sb
, FREEZE_HOLDER_USERSPACE
);
1151 super_unlock_excl(sb
);
1154 static void do_thaw_all(struct work_struct
*work
)
1156 __iterate_supers(do_thaw_all_callback
);
1158 printk(KERN_WARNING
"Emergency Thaw complete\n");
1162 * emergency_thaw_all -- forcibly thaw every frozen filesystem
1164 * Used for emergency unfreeze of all filesystems via SysRq
1166 void emergency_thaw_all(void)
1168 struct work_struct
*work
;
1170 work
= kmalloc(sizeof(*work
), GFP_ATOMIC
);
1172 INIT_WORK(work
, do_thaw_all
);
1173 schedule_work(work
);
1177 static DEFINE_IDA(unnamed_dev_ida
);
1180 * get_anon_bdev - Allocate a block device for filesystems which don't have one.
1181 * @p: Pointer to a dev_t.
1183 * Filesystems which don't use real block devices can call this function
1184 * to allocate a virtual block device.
1186 * Context: Any context. Frequently called while holding sb_lock.
1187 * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
1188 * or -ENOMEM if memory allocation failed.
1190 int get_anon_bdev(dev_t
*p
)
1195 * Many userspace utilities consider an FSID of 0 invalid.
1196 * Always return at least 1 from get_anon_bdev.
1198 dev
= ida_alloc_range(&unnamed_dev_ida
, 1, (1 << MINORBITS
) - 1,
1208 EXPORT_SYMBOL(get_anon_bdev
);
1210 void free_anon_bdev(dev_t dev
)
1212 ida_free(&unnamed_dev_ida
, MINOR(dev
));
1214 EXPORT_SYMBOL(free_anon_bdev
);
1216 int set_anon_super(struct super_block
*s
, void *data
)
1218 return get_anon_bdev(&s
->s_dev
);
1220 EXPORT_SYMBOL(set_anon_super
);
1222 void kill_anon_super(struct super_block
*sb
)
1224 dev_t dev
= sb
->s_dev
;
1225 generic_shutdown_super(sb
);
1226 kill_super_notify(sb
);
1227 free_anon_bdev(dev
);
1229 EXPORT_SYMBOL(kill_anon_super
);
1231 void kill_litter_super(struct super_block
*sb
)
1234 d_genocide(sb
->s_root
);
1235 kill_anon_super(sb
);
1237 EXPORT_SYMBOL(kill_litter_super
);
1239 int set_anon_super_fc(struct super_block
*sb
, struct fs_context
*fc
)
1241 return set_anon_super(sb
, NULL
);
1243 EXPORT_SYMBOL(set_anon_super_fc
);
1245 static int test_keyed_super(struct super_block
*sb
, struct fs_context
*fc
)
1247 return sb
->s_fs_info
== fc
->s_fs_info
;
1250 static int test_single_super(struct super_block
*s
, struct fs_context
*fc
)
1255 static int vfs_get_super(struct fs_context
*fc
,
1256 int (*test
)(struct super_block
*, struct fs_context
*),
1257 int (*fill_super
)(struct super_block
*sb
,
1258 struct fs_context
*fc
))
1260 struct super_block
*sb
;
1263 sb
= sget_fc(fc
, test
, set_anon_super_fc
);
1268 err
= fill_super(sb
, fc
);
1272 sb
->s_flags
|= SB_ACTIVE
;
1275 fc
->root
= dget(sb
->s_root
);
1279 deactivate_locked_super(sb
);
1283 int get_tree_nodev(struct fs_context
*fc
,
1284 int (*fill_super
)(struct super_block
*sb
,
1285 struct fs_context
*fc
))
1287 return vfs_get_super(fc
, NULL
, fill_super
);
1289 EXPORT_SYMBOL(get_tree_nodev
);
1291 int get_tree_single(struct fs_context
*fc
,
1292 int (*fill_super
)(struct super_block
*sb
,
1293 struct fs_context
*fc
))
1295 return vfs_get_super(fc
, test_single_super
, fill_super
);
1297 EXPORT_SYMBOL(get_tree_single
);
1299 int get_tree_keyed(struct fs_context
*fc
,
1300 int (*fill_super
)(struct super_block
*sb
,
1301 struct fs_context
*fc
),
1304 fc
->s_fs_info
= key
;
1305 return vfs_get_super(fc
, test_keyed_super
, fill_super
);
1307 EXPORT_SYMBOL(get_tree_keyed
);
1309 static int set_bdev_super(struct super_block
*s
, void *data
)
1311 s
->s_dev
= *(dev_t
*)data
;
1315 static int super_s_dev_set(struct super_block
*s
, struct fs_context
*fc
)
1317 return set_bdev_super(s
, fc
->sget_key
);
1320 static int super_s_dev_test(struct super_block
*s
, struct fs_context
*fc
)
1322 return !(s
->s_iflags
& SB_I_RETIRED
) &&
1323 s
->s_dev
== *(dev_t
*)fc
->sget_key
;
1327 * sget_dev - Find or create a superblock by device number
1328 * @fc: Filesystem context.
1329 * @dev: device number
1331 * Find or create a superblock using the provided device number that
1332 * will be stored in fc->sget_key.
1334 * If an extant superblock is matched, then that will be returned with
1335 * an elevated reference count that the caller must transfer or discard.
1337 * If no match is made, a new superblock will be allocated and basic
1338 * initialisation will be performed (s_type, s_fs_info, s_id, s_dev will
1339 * be set). The superblock will be published and it will be returned in
1340 * a partially constructed state with SB_BORN and SB_ACTIVE as yet
1343 * Return: an existing or newly created superblock on success, an error
1344 * pointer on failure.
1346 struct super_block
*sget_dev(struct fs_context
*fc
, dev_t dev
)
1348 fc
->sget_key
= &dev
;
1349 return sget_fc(fc
, super_s_dev_test
, super_s_dev_set
);
1351 EXPORT_SYMBOL(sget_dev
);
1355 * Lock the superblock that is holder of the bdev. Returns the superblock
1356 * pointer if we successfully locked the superblock and it is alive. Otherwise
1357 * we return NULL and just unlock bdev->bd_holder_lock.
1359 * The function must be called with bdev->bd_holder_lock and releases it.
1361 static struct super_block
*bdev_super_lock(struct block_device
*bdev
, bool excl
)
1362 __releases(&bdev
->bd_holder_lock
)
1364 struct super_block
*sb
= bdev
->bd_holder
;
1367 lockdep_assert_held(&bdev
->bd_holder_lock
);
1368 lockdep_assert_not_held(&sb
->s_umount
);
1369 lockdep_assert_not_held(&bdev
->bd_disk
->open_mutex
);
1371 /* Make sure sb doesn't go away from under us */
1372 spin_lock(&sb_lock
);
1374 spin_unlock(&sb_lock
);
1376 mutex_unlock(&bdev
->bd_holder_lock
);
1378 locked
= super_lock(sb
, excl
);
1381 * If the superblock wasn't already SB_DYING then we hold
1382 * s_umount and can safely drop our temporary reference.
1389 if (!sb
->s_root
|| !(sb
->s_flags
& SB_ACTIVE
)) {
1390 super_unlock(sb
, excl
);
1397 static void fs_bdev_mark_dead(struct block_device
*bdev
, bool surprise
)
1399 struct super_block
*sb
;
1401 sb
= bdev_super_lock(bdev
, false);
1406 sync_filesystem(sb
);
1407 shrink_dcache_sb(sb
);
1408 invalidate_inodes(sb
);
1409 if (sb
->s_op
->shutdown
)
1410 sb
->s_op
->shutdown(sb
);
1412 super_unlock_shared(sb
);
1415 static void fs_bdev_sync(struct block_device
*bdev
)
1417 struct super_block
*sb
;
1419 sb
= bdev_super_lock(bdev
, false);
1423 sync_filesystem(sb
);
1424 super_unlock_shared(sb
);
1427 static struct super_block
*get_bdev_super(struct block_device
*bdev
)
1429 bool active
= false;
1430 struct super_block
*sb
;
1432 sb
= bdev_super_lock(bdev
, true);
1434 active
= atomic_inc_not_zero(&sb
->s_active
);
1435 super_unlock_excl(sb
);
1443 * fs_bdev_freeze - freeze owning filesystem of block device
1444 * @bdev: block device
1446 * Freeze the filesystem that owns this block device if it is still
1449 * A filesystem that owns multiple block devices may be frozen from each
1450 * block device and won't be unfrozen until all block devices are
1451 * unfrozen. Each block device can only freeze the filesystem once as we
1452 * nest freezes for block devices in the block layer.
1454 * Return: If the freeze was successful zero is returned. If the freeze
1455 * failed a negative error code is returned.
1457 static int fs_bdev_freeze(struct block_device
*bdev
)
1459 struct super_block
*sb
;
1462 lockdep_assert_held(&bdev
->bd_fsfreeze_mutex
);
1464 sb
= get_bdev_super(bdev
);
1468 if (sb
->s_op
->freeze_super
)
1469 error
= sb
->s_op
->freeze_super(sb
,
1470 FREEZE_MAY_NEST
| FREEZE_HOLDER_USERSPACE
);
1472 error
= freeze_super(sb
,
1473 FREEZE_MAY_NEST
| FREEZE_HOLDER_USERSPACE
);
1475 error
= sync_blockdev(bdev
);
1476 deactivate_super(sb
);
1481 * fs_bdev_thaw - thaw owning filesystem of block device
1482 * @bdev: block device
1484 * Thaw the filesystem that owns this block device.
1486 * A filesystem that owns multiple block devices may be frozen from each
1487 * block device and won't be unfrozen until all block devices are
1488 * unfrozen. Each block device can only freeze the filesystem once as we
1489 * nest freezes for block devices in the block layer.
1491 * Return: If the thaw was successful zero is returned. If the thaw
1492 * failed a negative error code is returned. If this function
1493 * returns zero it doesn't mean that the filesystem is unfrozen
1494 * as it may have been frozen multiple times (kernel may hold a
1495 * freeze or might be frozen from other block devices).
1497 static int fs_bdev_thaw(struct block_device
*bdev
)
1499 struct super_block
*sb
;
1502 lockdep_assert_held(&bdev
->bd_fsfreeze_mutex
);
1504 sb
= get_bdev_super(bdev
);
1505 if (WARN_ON_ONCE(!sb
))
1508 if (sb
->s_op
->thaw_super
)
1509 error
= sb
->s_op
->thaw_super(sb
,
1510 FREEZE_MAY_NEST
| FREEZE_HOLDER_USERSPACE
);
1512 error
= thaw_super(sb
,
1513 FREEZE_MAY_NEST
| FREEZE_HOLDER_USERSPACE
);
1514 deactivate_super(sb
);
1518 const struct blk_holder_ops fs_holder_ops
= {
1519 .mark_dead
= fs_bdev_mark_dead
,
1520 .sync
= fs_bdev_sync
,
1521 .freeze
= fs_bdev_freeze
,
1522 .thaw
= fs_bdev_thaw
,
1524 EXPORT_SYMBOL_GPL(fs_holder_ops
);
1526 int setup_bdev_super(struct super_block
*sb
, int sb_flags
,
1527 struct fs_context
*fc
)
1529 blk_mode_t mode
= sb_open_mode(sb_flags
);
1530 struct file
*bdev_file
;
1531 struct block_device
*bdev
;
1533 bdev_file
= bdev_file_open_by_dev(sb
->s_dev
, mode
, sb
, &fs_holder_ops
);
1534 if (IS_ERR(bdev_file
)) {
1536 errorf(fc
, "%s: Can't open blockdev", fc
->source
);
1537 return PTR_ERR(bdev_file
);
1539 bdev
= file_bdev(bdev_file
);
1542 * This really should be in blkdev_get_by_dev, but right now can't due
1543 * to legacy issues that require us to allow opening a block device node
1544 * writable from userspace even for a read-only block device.
1546 if ((mode
& BLK_OPEN_WRITE
) && bdev_read_only(bdev
)) {
1552 * It is enough to check bdev was not frozen before we set
1553 * s_bdev as freezing will wait until SB_BORN is set.
1555 if (atomic_read(&bdev
->bd_fsfreeze_count
) > 0) {
1557 warnf(fc
, "%pg: Can't mount, blockdev is frozen", bdev
);
1561 spin_lock(&sb_lock
);
1562 sb
->s_bdev_file
= bdev_file
;
1564 sb
->s_bdi
= bdi_get(bdev
->bd_disk
->bdi
);
1565 if (bdev_stable_writes(bdev
))
1566 sb
->s_iflags
|= SB_I_STABLE_WRITES
;
1567 spin_unlock(&sb_lock
);
1569 snprintf(sb
->s_id
, sizeof(sb
->s_id
), "%pg", bdev
);
1570 shrinker_debugfs_rename(sb
->s_shrink
, "sb-%s:%s", sb
->s_type
->name
,
1572 sb_set_blocksize(sb
, block_size(bdev
));
1575 EXPORT_SYMBOL_GPL(setup_bdev_super
);
1578 * get_tree_bdev - Get a superblock based on a single block device
1579 * @fc: The filesystem context holding the parameters
1580 * @fill_super: Helper to initialise a new superblock
1582 int get_tree_bdev(struct fs_context
*fc
,
1583 int (*fill_super
)(struct super_block
*,
1584 struct fs_context
*))
1586 struct super_block
*s
;
1591 return invalf(fc
, "No source specified");
1593 error
= lookup_bdev(fc
->source
, &dev
);
1595 errorf(fc
, "%s: Can't lookup blockdev", fc
->source
);
1599 fc
->sb_flags
|= SB_NOSEC
;
1600 s
= sget_dev(fc
, dev
);
1605 /* Don't summarily change the RO/RW state. */
1606 if ((fc
->sb_flags
^ s
->s_flags
) & SB_RDONLY
) {
1607 warnf(fc
, "%pg: Can't mount, would change RO state", s
->s_bdev
);
1608 deactivate_locked_super(s
);
1612 error
= setup_bdev_super(s
, fc
->sb_flags
, fc
);
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
);
1656 error
= setup_bdev_super(s
, flags
, NULL
);
1658 error
= fill_super(s
, data
, flags
& SB_SILENT
? 1 : 0);
1660 deactivate_locked_super(s
);
1661 return ERR_PTR(error
);
1664 s
->s_flags
|= SB_ACTIVE
;
1667 return dget(s
->s_root
);
1669 EXPORT_SYMBOL(mount_bdev
);
1671 void kill_block_super(struct super_block
*sb
)
1673 struct block_device
*bdev
= sb
->s_bdev
;
1675 generic_shutdown_super(sb
);
1677 sync_blockdev(bdev
);
1678 fput(sb
->s_bdev_file
);
1682 EXPORT_SYMBOL(kill_block_super
);
1685 struct dentry
*mount_nodev(struct file_system_type
*fs_type
,
1686 int flags
, void *data
,
1687 int (*fill_super
)(struct super_block
*, void *, int))
1690 struct super_block
*s
= sget(fs_type
, NULL
, set_anon_super
, flags
, NULL
);
1695 error
= fill_super(s
, data
, flags
& SB_SILENT
? 1 : 0);
1697 deactivate_locked_super(s
);
1698 return ERR_PTR(error
);
1700 s
->s_flags
|= SB_ACTIVE
;
1701 return dget(s
->s_root
);
1703 EXPORT_SYMBOL(mount_nodev
);
1705 int reconfigure_single(struct super_block
*s
,
1706 int flags
, void *data
)
1708 struct fs_context
*fc
;
1711 /* The caller really need to be passing fc down into mount_single(),
1712 * then a chunk of this can be removed. [Bollocks -- AV]
1713 * Better yet, reconfiguration shouldn't happen, but rather the second
1714 * mount should be rejected if the parameters are not compatible.
1716 fc
= fs_context_for_reconfigure(s
->s_root
, flags
, MS_RMT_MASK
);
1720 ret
= parse_monolithic_mount_data(fc
, data
);
1724 ret
= reconfigure_super(fc
);
1730 static int compare_single(struct super_block
*s
, void *p
)
1735 struct dentry
*mount_single(struct file_system_type
*fs_type
,
1736 int flags
, void *data
,
1737 int (*fill_super
)(struct super_block
*, void *, int))
1739 struct super_block
*s
;
1742 s
= sget(fs_type
, compare_single
, set_anon_super
, flags
, NULL
);
1746 error
= fill_super(s
, data
, flags
& SB_SILENT
? 1 : 0);
1748 s
->s_flags
|= SB_ACTIVE
;
1750 error
= reconfigure_single(s
, flags
, data
);
1752 if (unlikely(error
)) {
1753 deactivate_locked_super(s
);
1754 return ERR_PTR(error
);
1756 return dget(s
->s_root
);
1758 EXPORT_SYMBOL(mount_single
);
1761 * vfs_get_tree - Get the mountable root
1762 * @fc: The superblock configuration context.
1764 * The filesystem is invoked to get or create a superblock which can then later
1765 * be used for mounting. The filesystem places a pointer to the root to be
1766 * used for mounting in @fc->root.
1768 int vfs_get_tree(struct fs_context
*fc
)
1770 struct super_block
*sb
;
1776 /* Get the mountable root in fc->root, with a ref on the root and a ref
1777 * on the superblock.
1779 error
= fc
->ops
->get_tree(fc
);
1784 pr_err("Filesystem %s get_tree() didn't set fc->root\n",
1786 /* We don't know what the locking state of the superblock is -
1787 * if there is a superblock.
1792 sb
= fc
->root
->d_sb
;
1793 WARN_ON(!sb
->s_bdi
);
1796 * super_wake() contains a memory barrier which also care of
1797 * ordering for super_cache_count(). We place it before setting
1798 * SB_BORN as the data dependency between the two functions is
1799 * the superblock structure contents that we just set up, not
1802 super_wake(sb
, SB_BORN
);
1804 error
= security_sb_set_mnt_opts(sb
, fc
->security
, 0, NULL
);
1805 if (unlikely(error
)) {
1811 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1812 * but s_maxbytes was an unsigned long long for many releases. Throw
1813 * this warning for a little while to try and catch filesystems that
1814 * violate this rule.
1816 WARN((sb
->s_maxbytes
< 0), "%s set sb->s_maxbytes to "
1817 "negative value (%lld)\n", fc
->fs_type
->name
, sb
->s_maxbytes
);
1821 EXPORT_SYMBOL(vfs_get_tree
);
1824 * Setup private BDI for given superblock. It gets automatically cleaned up
1825 * in generic_shutdown_super().
1827 int super_setup_bdi_name(struct super_block
*sb
, char *fmt
, ...)
1829 struct backing_dev_info
*bdi
;
1833 bdi
= bdi_alloc(NUMA_NO_NODE
);
1837 va_start(args
, fmt
);
1838 err
= bdi_register_va(bdi
, fmt
, args
);
1844 WARN_ON(sb
->s_bdi
!= &noop_backing_dev_info
);
1846 sb
->s_iflags
|= SB_I_PERSB_BDI
;
1850 EXPORT_SYMBOL(super_setup_bdi_name
);
1853 * Setup private BDI for given superblock. I gets automatically cleaned up
1854 * in generic_shutdown_super().
1856 int super_setup_bdi(struct super_block
*sb
)
1858 static atomic_long_t bdi_seq
= ATOMIC_LONG_INIT(0);
1860 return super_setup_bdi_name(sb
, "%.28s-%ld", sb
->s_type
->name
,
1861 atomic_long_inc_return(&bdi_seq
));
1863 EXPORT_SYMBOL(super_setup_bdi
);
1866 * sb_wait_write - wait until all writers to given file system finish
1867 * @sb: the super for which we wait
1868 * @level: type of writers we wait for (normal vs page fault)
1870 * This function waits until there are no writers of given type to given file
1873 static void sb_wait_write(struct super_block
*sb
, int level
)
1875 percpu_down_write(sb
->s_writers
.rw_sem
+ level
-1);
1879 * We are going to return to userspace and forget about these locks, the
1880 * ownership goes to the caller of thaw_super() which does unlock().
1882 static void lockdep_sb_freeze_release(struct super_block
*sb
)
1886 for (level
= SB_FREEZE_LEVELS
- 1; level
>= 0; level
--)
1887 percpu_rwsem_release(sb
->s_writers
.rw_sem
+ level
, 0, _THIS_IP_
);
1891 * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
1893 static void lockdep_sb_freeze_acquire(struct super_block
*sb
)
1897 for (level
= 0; level
< SB_FREEZE_LEVELS
; ++level
)
1898 percpu_rwsem_acquire(sb
->s_writers
.rw_sem
+ level
, 0, _THIS_IP_
);
1901 static void sb_freeze_unlock(struct super_block
*sb
, int level
)
1903 for (level
--; level
>= 0; level
--)
1904 percpu_up_write(sb
->s_writers
.rw_sem
+ level
);
1907 static int wait_for_partially_frozen(struct super_block
*sb
)
1912 unsigned short old
= sb
->s_writers
.frozen
;
1914 up_write(&sb
->s_umount
);
1915 ret
= wait_var_event_killable(&sb
->s_writers
.frozen
,
1916 sb
->s_writers
.frozen
!= old
);
1917 down_write(&sb
->s_umount
);
1918 } while (ret
== 0 &&
1919 sb
->s_writers
.frozen
!= SB_UNFROZEN
&&
1920 sb
->s_writers
.frozen
!= SB_FREEZE_COMPLETE
);
1925 #define FREEZE_HOLDERS (FREEZE_HOLDER_KERNEL | FREEZE_HOLDER_USERSPACE)
1926 #define FREEZE_FLAGS (FREEZE_HOLDERS | FREEZE_MAY_NEST)
1928 static inline int freeze_inc(struct super_block
*sb
, enum freeze_holder who
)
1930 WARN_ON_ONCE((who
& ~FREEZE_FLAGS
));
1931 WARN_ON_ONCE(hweight32(who
& FREEZE_HOLDERS
) > 1);
1933 if (who
& FREEZE_HOLDER_KERNEL
)
1934 ++sb
->s_writers
.freeze_kcount
;
1935 if (who
& FREEZE_HOLDER_USERSPACE
)
1936 ++sb
->s_writers
.freeze_ucount
;
1937 return sb
->s_writers
.freeze_kcount
+ sb
->s_writers
.freeze_ucount
;
1940 static inline int freeze_dec(struct super_block
*sb
, enum freeze_holder who
)
1942 WARN_ON_ONCE((who
& ~FREEZE_FLAGS
));
1943 WARN_ON_ONCE(hweight32(who
& FREEZE_HOLDERS
) > 1);
1945 if ((who
& FREEZE_HOLDER_KERNEL
) && sb
->s_writers
.freeze_kcount
)
1946 --sb
->s_writers
.freeze_kcount
;
1947 if ((who
& FREEZE_HOLDER_USERSPACE
) && sb
->s_writers
.freeze_ucount
)
1948 --sb
->s_writers
.freeze_ucount
;
1949 return sb
->s_writers
.freeze_kcount
+ sb
->s_writers
.freeze_ucount
;
1952 static inline bool may_freeze(struct super_block
*sb
, enum freeze_holder who
)
1954 WARN_ON_ONCE((who
& ~FREEZE_FLAGS
));
1955 WARN_ON_ONCE(hweight32(who
& FREEZE_HOLDERS
) > 1);
1957 if (who
& FREEZE_HOLDER_KERNEL
)
1958 return (who
& FREEZE_MAY_NEST
) ||
1959 sb
->s_writers
.freeze_kcount
== 0;
1960 if (who
& FREEZE_HOLDER_USERSPACE
)
1961 return (who
& FREEZE_MAY_NEST
) ||
1962 sb
->s_writers
.freeze_ucount
== 0;
1967 * freeze_super - lock the filesystem and force it into a consistent state
1968 * @sb: the super to lock
1969 * @who: context that wants to freeze
1971 * Syncs the super to make sure the filesystem is consistent and calls the fs's
1972 * freeze_fs. Subsequent calls to this without first thawing the fs may return
1976 * * %FREEZE_HOLDER_USERSPACE if userspace wants to freeze the fs;
1977 * * %FREEZE_HOLDER_KERNEL if the kernel wants to freeze the fs.
1978 * * %FREEZE_MAY_NEST whether nesting freeze and thaw requests is allowed.
1980 * The @who argument distinguishes between the kernel and userspace trying to
1981 * freeze the filesystem. Although there cannot be multiple kernel freezes or
1982 * multiple userspace freezes in effect at any given time, the kernel and
1983 * userspace can both hold a filesystem frozen. The filesystem remains frozen
1984 * until there are no kernel or userspace freezes in effect.
1986 * A filesystem may hold multiple devices and thus a filesystems may be
1987 * frozen through the block layer via multiple block devices. In this
1988 * case the request is marked as being allowed to nest by passing
1989 * FREEZE_MAY_NEST. The filesystem remains frozen until all block
1990 * devices are unfrozen. If multiple freezes are attempted without
1991 * FREEZE_MAY_NEST -EBUSY will be returned.
1993 * During this function, sb->s_writers.frozen goes through these values:
1995 * SB_UNFROZEN: File system is normal, all writes progress as usual.
1997 * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
1998 * writes should be blocked, though page faults are still allowed. We wait for
1999 * all writes to complete and then proceed to the next stage.
2001 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
2002 * but internal fs threads can still modify the filesystem (although they
2003 * should not dirty new pages or inodes), writeback can run etc. After waiting
2004 * for all running page faults we sync the filesystem which will clean all
2005 * dirty pages and inodes (no new dirty pages or inodes can be created when
2008 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
2009 * modification are blocked (e.g. XFS preallocation truncation on inode
2010 * reclaim). This is usually implemented by blocking new transactions for
2011 * filesystems that have them and need this additional guard. After all
2012 * internal writers are finished we call ->freeze_fs() to finish filesystem
2013 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
2014 * mostly auxiliary for filesystems to verify they do not modify frozen fs.
2016 * sb->s_writers.frozen is protected by sb->s_umount.
2018 * Return: If the freeze was successful zero is returned. If the freeze
2019 * failed a negative error code is returned.
2021 int freeze_super(struct super_block
*sb
, enum freeze_holder who
)
2025 if (!super_lock_excl(sb
)) {
2026 WARN_ON_ONCE("Dying superblock while freezing!");
2029 atomic_inc(&sb
->s_active
);
2032 if (sb
->s_writers
.frozen
== SB_FREEZE_COMPLETE
) {
2033 if (may_freeze(sb
, who
))
2034 ret
= !!WARN_ON_ONCE(freeze_inc(sb
, who
) == 1);
2037 /* All freezers share a single active reference. */
2038 deactivate_locked_super(sb
);
2042 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
) {
2043 ret
= wait_for_partially_frozen(sb
);
2045 deactivate_locked_super(sb
);
2052 if (sb_rdonly(sb
)) {
2053 /* Nothing to do really... */
2054 WARN_ON_ONCE(freeze_inc(sb
, who
) > 1);
2055 sb
->s_writers
.frozen
= SB_FREEZE_COMPLETE
;
2056 wake_up_var(&sb
->s_writers
.frozen
);
2057 super_unlock_excl(sb
);
2061 sb
->s_writers
.frozen
= SB_FREEZE_WRITE
;
2062 /* Release s_umount to preserve sb_start_write -> s_umount ordering */
2063 super_unlock_excl(sb
);
2064 sb_wait_write(sb
, SB_FREEZE_WRITE
);
2065 __super_lock_excl(sb
);
2067 /* Now we go and block page faults... */
2068 sb
->s_writers
.frozen
= SB_FREEZE_PAGEFAULT
;
2069 sb_wait_write(sb
, SB_FREEZE_PAGEFAULT
);
2071 /* All writers are done so after syncing there won't be dirty data */
2072 ret
= sync_filesystem(sb
);
2074 sb
->s_writers
.frozen
= SB_UNFROZEN
;
2075 sb_freeze_unlock(sb
, SB_FREEZE_PAGEFAULT
);
2076 wake_up_var(&sb
->s_writers
.frozen
);
2077 deactivate_locked_super(sb
);
2081 /* Now wait for internal filesystem counter */
2082 sb
->s_writers
.frozen
= SB_FREEZE_FS
;
2083 sb_wait_write(sb
, SB_FREEZE_FS
);
2085 if (sb
->s_op
->freeze_fs
) {
2086 ret
= sb
->s_op
->freeze_fs(sb
);
2089 "VFS:Filesystem freeze failed\n");
2090 sb
->s_writers
.frozen
= SB_UNFROZEN
;
2091 sb_freeze_unlock(sb
, SB_FREEZE_FS
);
2092 wake_up_var(&sb
->s_writers
.frozen
);
2093 deactivate_locked_super(sb
);
2098 * For debugging purposes so that fs can warn if it sees write activity
2099 * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
2101 WARN_ON_ONCE(freeze_inc(sb
, who
) > 1);
2102 sb
->s_writers
.frozen
= SB_FREEZE_COMPLETE
;
2103 wake_up_var(&sb
->s_writers
.frozen
);
2104 lockdep_sb_freeze_release(sb
);
2105 super_unlock_excl(sb
);
2108 EXPORT_SYMBOL(freeze_super
);
2111 * Undoes the effect of a freeze_super_locked call. If the filesystem is
2112 * frozen both by userspace and the kernel, a thaw call from either source
2113 * removes that state without releasing the other state or unlocking the
2116 static int thaw_super_locked(struct super_block
*sb
, enum freeze_holder who
)
2118 int error
= -EINVAL
;
2120 if (sb
->s_writers
.frozen
!= SB_FREEZE_COMPLETE
)
2124 * All freezers share a single active reference.
2125 * So just unlock in case there are any left.
2127 if (freeze_dec(sb
, who
))
2130 if (sb_rdonly(sb
)) {
2131 sb
->s_writers
.frozen
= SB_UNFROZEN
;
2132 wake_up_var(&sb
->s_writers
.frozen
);
2133 goto out_deactivate
;
2136 lockdep_sb_freeze_acquire(sb
);
2138 if (sb
->s_op
->unfreeze_fs
) {
2139 error
= sb
->s_op
->unfreeze_fs(sb
);
2141 pr_err("VFS: Filesystem thaw failed\n");
2142 freeze_inc(sb
, who
);
2143 lockdep_sb_freeze_release(sb
);
2148 sb
->s_writers
.frozen
= SB_UNFROZEN
;
2149 wake_up_var(&sb
->s_writers
.frozen
);
2150 sb_freeze_unlock(sb
, SB_FREEZE_FS
);
2152 deactivate_locked_super(sb
);
2156 super_unlock_excl(sb
);
2161 * thaw_super -- unlock filesystem
2162 * @sb: the super to thaw
2163 * @who: context that wants to freeze
2165 * Unlocks the filesystem and marks it writeable again after freeze_super()
2166 * if there are no remaining freezes on the filesystem.
2169 * * %FREEZE_HOLDER_USERSPACE if userspace wants to thaw the fs;
2170 * * %FREEZE_HOLDER_KERNEL if the kernel wants to thaw the fs.
2171 * * %FREEZE_MAY_NEST whether nesting freeze and thaw requests is allowed
2173 * A filesystem may hold multiple devices and thus a filesystems may
2174 * have been frozen through the block layer via multiple block devices.
2175 * The filesystem remains frozen until all block devices are unfrozen.
2177 int thaw_super(struct super_block
*sb
, enum freeze_holder who
)
2179 if (!super_lock_excl(sb
)) {
2180 WARN_ON_ONCE("Dying superblock while thawing!");
2183 return thaw_super_locked(sb
, who
);
2185 EXPORT_SYMBOL(thaw_super
);
2188 * Create workqueue for deferred direct IO completions. We allocate the
2189 * workqueue when it's first needed. This avoids creating workqueue for
2190 * filesystems that don't need it and also allows us to create the workqueue
2191 * late enough so the we can include s_id in the name of the workqueue.
2193 int sb_init_dio_done_wq(struct super_block
*sb
)
2195 struct workqueue_struct
*old
;
2196 struct workqueue_struct
*wq
= alloc_workqueue("dio/%s",
2202 * This has to be atomic as more DIOs can race to create the workqueue
2204 old
= cmpxchg(&sb
->s_dio_done_wq
, NULL
, wq
);
2205 /* Someone created workqueue before us? Free ours... */
2207 destroy_workqueue(wq
);
2210 EXPORT_SYMBOL_GPL(sb_init_dio_done_wq
);