4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * super.c contains code to handle: - mount structures
8 * - filesystem drivers list
10 * - umount system call
13 * GK 2/5/95 - Changed to support mounting the root fs via NFS
15 * Added kerneld support: Jacques Gelinas and Bjorn Ekwall
16 * Added change_root: Werner Almesberger & Hans Lermen, Feb '96
17 * Added options to /proc/mounts:
18 * Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
19 * Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
20 * Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
23 #include <linux/export.h>
24 #include <linux/slab.h>
25 #include <linux/blkdev.h>
26 #include <linux/mount.h>
27 #include <linux/security.h>
28 #include <linux/writeback.h> /* for the emergency remount stuff */
29 #include <linux/idr.h>
30 #include <linux/mutex.h>
31 #include <linux/backing-dev.h>
32 #include <linux/rculist_bl.h>
33 #include <linux/cleancache.h>
34 #include <linux/fsnotify.h>
35 #include <linux/lockdep.h>
39 LIST_HEAD(super_blocks
);
40 DEFINE_SPINLOCK(sb_lock
);
42 static char *sb_writers_name
[SB_FREEZE_LEVELS
] = {
49 * One thing we have to be careful of with a per-sb shrinker is that we don't
50 * drop the last active reference to the superblock from within the shrinker.
51 * If that happens we could trigger unregistering the shrinker from within the
52 * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
53 * take a passive reference to the superblock to avoid this from occurring.
55 static unsigned long super_cache_scan(struct shrinker
*shrink
,
56 struct shrink_control
*sc
)
58 struct super_block
*sb
;
65 sb
= container_of(shrink
, struct super_block
, s_shrink
);
68 * Deadlock avoidance. We may hold various FS locks, and we don't want
69 * to recurse into the FS that called us in clear_inode() and friends..
71 if (!(sc
->gfp_mask
& __GFP_FS
))
74 if (!grab_super_passive(sb
))
77 if (sb
->s_op
->nr_cached_objects
)
78 fs_objects
= sb
->s_op
->nr_cached_objects(sb
, sc
->nid
);
80 inodes
= list_lru_count_node(&sb
->s_inode_lru
, sc
->nid
);
81 dentries
= list_lru_count_node(&sb
->s_dentry_lru
, sc
->nid
);
82 total_objects
= dentries
+ inodes
+ fs_objects
+ 1;
84 /* proportion the scan between the caches */
85 dentries
= mult_frac(sc
->nr_to_scan
, dentries
, total_objects
);
86 inodes
= mult_frac(sc
->nr_to_scan
, inodes
, total_objects
);
89 * prune the dcache first as the icache is pinned by it, then
90 * prune the icache, followed by the filesystem specific caches
92 freed
= prune_dcache_sb(sb
, dentries
, sc
->nid
);
93 freed
+= prune_icache_sb(sb
, inodes
, sc
->nid
);
96 fs_objects
= mult_frac(sc
->nr_to_scan
, fs_objects
,
98 freed
+= sb
->s_op
->free_cached_objects(sb
, fs_objects
,
106 static unsigned long super_cache_count(struct shrinker
*shrink
,
107 struct shrink_control
*sc
)
109 struct super_block
*sb
;
110 long total_objects
= 0;
112 sb
= container_of(shrink
, struct super_block
, s_shrink
);
115 * Don't call grab_super_passive as it is a potential
116 * scalability bottleneck. The counts could get updated
117 * between super_cache_count and super_cache_scan anyway.
118 * Call to super_cache_count with shrinker_rwsem held
119 * ensures the safety of call to list_lru_count_node() and
120 * s_op->nr_cached_objects().
122 if (sb
->s_op
&& sb
->s_op
->nr_cached_objects
)
123 total_objects
= sb
->s_op
->nr_cached_objects(sb
,
126 total_objects
+= list_lru_count_node(&sb
->s_dentry_lru
,
128 total_objects
+= list_lru_count_node(&sb
->s_inode_lru
,
131 total_objects
= vfs_pressure_ratio(total_objects
);
132 return total_objects
;
136 * destroy_super - frees a superblock
137 * @s: superblock to free
139 * Frees a superblock.
141 static void destroy_super(struct super_block
*s
)
144 list_lru_destroy(&s
->s_dentry_lru
);
145 list_lru_destroy(&s
->s_inode_lru
);
146 for (i
= 0; i
< SB_FREEZE_LEVELS
; i
++)
147 percpu_counter_destroy(&s
->s_writers
.counter
[i
]);
149 WARN_ON(!list_empty(&s
->s_mounts
));
156 * alloc_super - create new superblock
157 * @type: filesystem type superblock should belong to
158 * @flags: the mount flags
160 * Allocates and initializes a new &struct super_block. alloc_super()
161 * returns a pointer new superblock or %NULL if allocation had failed.
163 static struct super_block
*alloc_super(struct file_system_type
*type
, int flags
)
165 struct super_block
*s
= kzalloc(sizeof(struct super_block
), GFP_USER
);
166 static const struct super_operations default_op
;
172 INIT_LIST_HEAD(&s
->s_mounts
);
174 if (security_sb_alloc(s
))
177 for (i
= 0; i
< SB_FREEZE_LEVELS
; i
++) {
178 if (percpu_counter_init(&s
->s_writers
.counter
[i
], 0) < 0)
180 lockdep_init_map(&s
->s_writers
.lock_map
[i
], sb_writers_name
[i
],
181 &type
->s_writers_key
[i
], 0);
183 init_waitqueue_head(&s
->s_writers
.wait
);
184 init_waitqueue_head(&s
->s_writers
.wait_unfrozen
);
186 s
->s_bdi
= &default_backing_dev_info
;
187 INIT_HLIST_NODE(&s
->s_instances
);
188 INIT_HLIST_BL_HEAD(&s
->s_anon
);
189 INIT_LIST_HEAD(&s
->s_inodes
);
191 if (list_lru_init(&s
->s_dentry_lru
))
193 if (list_lru_init(&s
->s_inode_lru
))
196 init_rwsem(&s
->s_umount
);
197 lockdep_set_class(&s
->s_umount
, &type
->s_umount_key
);
199 * sget() can have s_umount recursion.
201 * When it cannot find a suitable sb, it allocates a new
202 * one (this one), and tries again to find a suitable old
205 * In case that succeeds, it will acquire the s_umount
206 * lock of the old one. Since these are clearly distrinct
207 * locks, and this object isn't exposed yet, there's no
210 * Annotate this by putting this lock in a different
213 down_write_nested(&s
->s_umount
, SINGLE_DEPTH_NESTING
);
215 atomic_set(&s
->s_active
, 1);
216 mutex_init(&s
->s_vfs_rename_mutex
);
217 lockdep_set_class(&s
->s_vfs_rename_mutex
, &type
->s_vfs_rename_key
);
218 mutex_init(&s
->s_dquot
.dqio_mutex
);
219 mutex_init(&s
->s_dquot
.dqonoff_mutex
);
220 s
->s_maxbytes
= MAX_NON_LFS
;
221 s
->s_op
= &default_op
;
222 s
->s_time_gran
= 1000000000;
223 s
->cleancache_poolid
= -1;
225 s
->s_shrink
.seeks
= DEFAULT_SEEKS
;
226 s
->s_shrink
.scan_objects
= super_cache_scan
;
227 s
->s_shrink
.count_objects
= super_cache_count
;
228 s
->s_shrink
.batch
= 1024;
229 s
->s_shrink
.flags
= SHRINKER_NUMA_AWARE
;
237 /* Superblock refcounting */
240 * Drop a superblock's refcount. The caller must hold sb_lock.
242 static void __put_super(struct super_block
*sb
)
244 if (!--sb
->s_count
) {
245 list_del_init(&sb
->s_list
);
251 * put_super - drop a temporary reference to superblock
252 * @sb: superblock in question
254 * Drops a temporary reference, frees superblock if there's no
257 static void put_super(struct super_block
*sb
)
261 spin_unlock(&sb_lock
);
266 * deactivate_locked_super - drop an active reference to superblock
267 * @s: superblock to deactivate
269 * Drops an active reference to superblock, converting it into a temprory
270 * one if there is no other active references left. In that case we
271 * tell fs driver to shut it down and drop the temporary reference we
274 * Caller holds exclusive lock on superblock; that lock is released.
276 void deactivate_locked_super(struct super_block
*s
)
278 struct file_system_type
*fs
= s
->s_type
;
279 if (atomic_dec_and_test(&s
->s_active
)) {
280 cleancache_invalidate_fs(s
);
281 unregister_shrinker(&s
->s_shrink
);
287 up_write(&s
->s_umount
);
291 EXPORT_SYMBOL(deactivate_locked_super
);
294 * deactivate_super - drop an active reference to superblock
295 * @s: superblock to deactivate
297 * Variant of deactivate_locked_super(), except that superblock is *not*
298 * locked by caller. If we are going to drop the final active reference,
299 * lock will be acquired prior to that.
301 void deactivate_super(struct super_block
*s
)
303 if (!atomic_add_unless(&s
->s_active
, -1, 1)) {
304 down_write(&s
->s_umount
);
305 deactivate_locked_super(s
);
309 EXPORT_SYMBOL(deactivate_super
);
312 * grab_super - acquire an active reference
313 * @s: reference we are trying to make active
315 * Tries to acquire an active reference. grab_super() is used when we
316 * had just found a superblock in super_blocks or fs_type->fs_supers
317 * and want to turn it into a full-blown active reference. grab_super()
318 * is called with sb_lock held and drops it. Returns 1 in case of
319 * success, 0 if we had failed (superblock contents was already dead or
320 * dying when grab_super() had been called). Note that this is only
321 * called for superblocks not in rundown mode (== ones still on ->fs_supers
322 * of their type), so increment of ->s_count is OK here.
324 static int grab_super(struct super_block
*s
) __releases(sb_lock
)
327 spin_unlock(&sb_lock
);
328 down_write(&s
->s_umount
);
329 if ((s
->s_flags
& MS_BORN
) && atomic_inc_not_zero(&s
->s_active
)) {
333 up_write(&s
->s_umount
);
339 * grab_super_passive - acquire a passive reference
340 * @sb: reference we are trying to grab
342 * Tries to acquire a passive reference. This is used in places where we
343 * cannot take an active reference but we need to ensure that the
344 * superblock does not go away while we are working on it. It returns
345 * false if a reference was not gained, and returns true with the s_umount
346 * lock held in read mode if a reference is gained. On successful return,
347 * the caller must drop the s_umount lock and the passive reference when
350 bool grab_super_passive(struct super_block
*sb
)
353 if (hlist_unhashed(&sb
->s_instances
)) {
354 spin_unlock(&sb_lock
);
359 spin_unlock(&sb_lock
);
361 if (down_read_trylock(&sb
->s_umount
)) {
362 if (sb
->s_root
&& (sb
->s_flags
& MS_BORN
))
364 up_read(&sb
->s_umount
);
372 * generic_shutdown_super - common helper for ->kill_sb()
373 * @sb: superblock to kill
375 * generic_shutdown_super() does all fs-independent work on superblock
376 * shutdown. Typical ->kill_sb() should pick all fs-specific objects
377 * that need destruction out of superblock, call generic_shutdown_super()
378 * and release aforementioned objects. Note: dentries and inodes _are_
379 * taken care of and do not need specific handling.
381 * Upon calling this function, the filesystem may no longer alter or
382 * rearrange the set of dentries belonging to this super_block, nor may it
383 * change the attachments of dentries to inodes.
385 void generic_shutdown_super(struct super_block
*sb
)
387 const struct super_operations
*sop
= sb
->s_op
;
390 shrink_dcache_for_umount(sb
);
392 sb
->s_flags
&= ~MS_ACTIVE
;
394 fsnotify_unmount_inodes(&sb
->s_inodes
);
398 if (sb
->s_dio_done_wq
) {
399 destroy_workqueue(sb
->s_dio_done_wq
);
400 sb
->s_dio_done_wq
= NULL
;
406 if (!list_empty(&sb
->s_inodes
)) {
407 printk("VFS: Busy inodes after unmount of %s. "
408 "Self-destruct in 5 seconds. Have a nice day...\n",
413 /* should be initialized for __put_super_and_need_restart() */
414 hlist_del_init(&sb
->s_instances
);
415 spin_unlock(&sb_lock
);
416 up_write(&sb
->s_umount
);
419 EXPORT_SYMBOL(generic_shutdown_super
);
422 * sget - find or create a superblock
423 * @type: filesystem type superblock should belong to
424 * @test: comparison callback
425 * @set: setup callback
426 * @flags: mount flags
427 * @data: argument to each of them
429 struct super_block
*sget(struct file_system_type
*type
,
430 int (*test
)(struct super_block
*,void *),
431 int (*set
)(struct super_block
*,void *),
435 struct super_block
*s
= NULL
;
436 struct super_block
*old
;
442 hlist_for_each_entry(old
, &type
->fs_supers
, s_instances
) {
443 if (!test(old
, data
))
445 if (!grab_super(old
))
448 up_write(&s
->s_umount
);
456 spin_unlock(&sb_lock
);
457 s
= alloc_super(type
, flags
);
459 return ERR_PTR(-ENOMEM
);
465 spin_unlock(&sb_lock
);
466 up_write(&s
->s_umount
);
471 strlcpy(s
->s_id
, type
->name
, sizeof(s
->s_id
));
472 list_add_tail(&s
->s_list
, &super_blocks
);
473 hlist_add_head(&s
->s_instances
, &type
->fs_supers
);
474 spin_unlock(&sb_lock
);
475 get_filesystem(type
);
476 register_shrinker(&s
->s_shrink
);
482 void drop_super(struct super_block
*sb
)
484 up_read(&sb
->s_umount
);
488 EXPORT_SYMBOL(drop_super
);
491 * iterate_supers - call function for all active superblocks
492 * @f: function to call
493 * @arg: argument to pass to it
495 * Scans the superblock list and calls given function, passing it
496 * locked superblock and given argument.
498 void iterate_supers(void (*f
)(struct super_block
*, void *), void *arg
)
500 struct super_block
*sb
, *p
= NULL
;
503 list_for_each_entry(sb
, &super_blocks
, s_list
) {
504 if (hlist_unhashed(&sb
->s_instances
))
507 spin_unlock(&sb_lock
);
509 down_read(&sb
->s_umount
);
510 if (sb
->s_root
&& (sb
->s_flags
& MS_BORN
))
512 up_read(&sb
->s_umount
);
521 spin_unlock(&sb_lock
);
525 * iterate_supers_type - call function for superblocks of given type
527 * @f: function to call
528 * @arg: argument to pass to it
530 * Scans the superblock list and calls given function, passing it
531 * locked superblock and given argument.
533 void iterate_supers_type(struct file_system_type
*type
,
534 void (*f
)(struct super_block
*, void *), void *arg
)
536 struct super_block
*sb
, *p
= NULL
;
539 hlist_for_each_entry(sb
, &type
->fs_supers
, s_instances
) {
541 spin_unlock(&sb_lock
);
543 down_read(&sb
->s_umount
);
544 if (sb
->s_root
&& (sb
->s_flags
& MS_BORN
))
546 up_read(&sb
->s_umount
);
555 spin_unlock(&sb_lock
);
558 EXPORT_SYMBOL(iterate_supers_type
);
561 * get_super - get the superblock of a device
562 * @bdev: device to get the superblock for
564 * Scans the superblock list and finds the superblock of the file system
565 * mounted on the device given. %NULL is returned if no match is found.
568 struct super_block
*get_super(struct block_device
*bdev
)
570 struct super_block
*sb
;
577 list_for_each_entry(sb
, &super_blocks
, s_list
) {
578 if (hlist_unhashed(&sb
->s_instances
))
580 if (sb
->s_bdev
== bdev
) {
582 spin_unlock(&sb_lock
);
583 down_read(&sb
->s_umount
);
585 if (sb
->s_root
&& (sb
->s_flags
& MS_BORN
))
587 up_read(&sb
->s_umount
);
588 /* nope, got unmounted */
594 spin_unlock(&sb_lock
);
598 EXPORT_SYMBOL(get_super
);
601 * get_super_thawed - get thawed superblock of a device
602 * @bdev: device to get the superblock for
604 * Scans the superblock list and finds the superblock of the file system
605 * mounted on the device. The superblock is returned once it is thawed
606 * (or immediately if it was not frozen). %NULL is returned if no match
609 struct super_block
*get_super_thawed(struct block_device
*bdev
)
612 struct super_block
*s
= get_super(bdev
);
613 if (!s
|| s
->s_writers
.frozen
== SB_UNFROZEN
)
615 up_read(&s
->s_umount
);
616 wait_event(s
->s_writers
.wait_unfrozen
,
617 s
->s_writers
.frozen
== SB_UNFROZEN
);
621 EXPORT_SYMBOL(get_super_thawed
);
624 * get_active_super - get an active reference to the superblock of a device
625 * @bdev: device to get the superblock for
627 * Scans the superblock list and finds the superblock of the file system
628 * mounted on the device given. Returns the superblock with an active
629 * reference or %NULL if none was found.
631 struct super_block
*get_active_super(struct block_device
*bdev
)
633 struct super_block
*sb
;
640 list_for_each_entry(sb
, &super_blocks
, s_list
) {
641 if (hlist_unhashed(&sb
->s_instances
))
643 if (sb
->s_bdev
== bdev
) {
646 up_write(&sb
->s_umount
);
650 spin_unlock(&sb_lock
);
654 struct super_block
*user_get_super(dev_t dev
)
656 struct super_block
*sb
;
660 list_for_each_entry(sb
, &super_blocks
, s_list
) {
661 if (hlist_unhashed(&sb
->s_instances
))
663 if (sb
->s_dev
== dev
) {
665 spin_unlock(&sb_lock
);
666 down_read(&sb
->s_umount
);
668 if (sb
->s_root
&& (sb
->s_flags
& MS_BORN
))
670 up_read(&sb
->s_umount
);
671 /* nope, got unmounted */
677 spin_unlock(&sb_lock
);
682 * do_remount_sb - asks filesystem to change mount options.
683 * @sb: superblock in question
684 * @flags: numeric part of options
685 * @data: the rest of options
686 * @force: whether or not to force the change
688 * Alters the mount options of a mounted file system.
690 int do_remount_sb(struct super_block
*sb
, int flags
, void *data
, int force
)
695 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
)
699 if (!(flags
& MS_RDONLY
) && bdev_read_only(sb
->s_bdev
))
703 remount_ro
= (flags
& MS_RDONLY
) && !(sb
->s_flags
& MS_RDONLY
);
706 if (sb
->s_pins
.first
) {
707 up_write(&sb
->s_umount
);
709 down_write(&sb
->s_umount
);
712 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
)
714 remount_ro
= (flags
& MS_RDONLY
) && !(sb
->s_flags
& MS_RDONLY
);
717 shrink_dcache_sb(sb
);
719 /* If we are remounting RDONLY and current sb is read/write,
720 make sure there are no rw files opened */
723 sb
->s_readonly_remount
= 1;
726 retval
= sb_prepare_remount_readonly(sb
);
732 if (sb
->s_op
->remount_fs
) {
733 retval
= sb
->s_op
->remount_fs(sb
, &flags
, data
);
736 goto cancel_readonly
;
737 /* If forced remount, go ahead despite any errors */
738 WARN(1, "forced remount of a %s fs returned %i\n",
739 sb
->s_type
->name
, retval
);
742 sb
->s_flags
= (sb
->s_flags
& ~MS_RMT_MASK
) | (flags
& MS_RMT_MASK
);
743 /* Needs to be ordered wrt mnt_is_readonly() */
745 sb
->s_readonly_remount
= 0;
748 * Some filesystems modify their metadata via some other path than the
749 * bdev buffer cache (eg. use a private mapping, or directories in
750 * pagecache, etc). Also file data modifications go via their own
751 * mappings. So If we try to mount readonly then copy the filesystem
752 * from bdev, we could get stale data, so invalidate it to give a best
753 * effort at coherency.
755 if (remount_ro
&& sb
->s_bdev
)
756 invalidate_bdev(sb
->s_bdev
);
760 sb
->s_readonly_remount
= 0;
764 static void do_emergency_remount(struct work_struct
*work
)
766 struct super_block
*sb
, *p
= NULL
;
769 list_for_each_entry(sb
, &super_blocks
, s_list
) {
770 if (hlist_unhashed(&sb
->s_instances
))
773 spin_unlock(&sb_lock
);
774 down_write(&sb
->s_umount
);
775 if (sb
->s_root
&& sb
->s_bdev
&& (sb
->s_flags
& MS_BORN
) &&
776 !(sb
->s_flags
& MS_RDONLY
)) {
778 * What lock protects sb->s_flags??
780 do_remount_sb(sb
, MS_RDONLY
, NULL
, 1);
782 up_write(&sb
->s_umount
);
790 spin_unlock(&sb_lock
);
792 printk("Emergency Remount complete\n");
795 void emergency_remount(void)
797 struct work_struct
*work
;
799 work
= kmalloc(sizeof(*work
), GFP_ATOMIC
);
801 INIT_WORK(work
, do_emergency_remount
);
807 * Unnamed block devices are dummy devices used by virtual
808 * filesystems which don't use real block-devices. -- jrs
811 static DEFINE_IDA(unnamed_dev_ida
);
812 static DEFINE_SPINLOCK(unnamed_dev_lock
);/* protects the above */
813 /* Many userspace utilities consider an FSID of 0 invalid.
814 * Always return at least 1 from get_anon_bdev.
816 static int unnamed_dev_start
= 1;
818 int get_anon_bdev(dev_t
*p
)
824 if (ida_pre_get(&unnamed_dev_ida
, GFP_ATOMIC
) == 0)
826 spin_lock(&unnamed_dev_lock
);
827 error
= ida_get_new_above(&unnamed_dev_ida
, unnamed_dev_start
, &dev
);
829 unnamed_dev_start
= dev
+ 1;
830 spin_unlock(&unnamed_dev_lock
);
831 if (error
== -EAGAIN
)
832 /* We raced and lost with another CPU. */
837 if (dev
== (1 << MINORBITS
)) {
838 spin_lock(&unnamed_dev_lock
);
839 ida_remove(&unnamed_dev_ida
, dev
);
840 if (unnamed_dev_start
> dev
)
841 unnamed_dev_start
= dev
;
842 spin_unlock(&unnamed_dev_lock
);
845 *p
= MKDEV(0, dev
& MINORMASK
);
848 EXPORT_SYMBOL(get_anon_bdev
);
850 void free_anon_bdev(dev_t dev
)
852 int slot
= MINOR(dev
);
853 spin_lock(&unnamed_dev_lock
);
854 ida_remove(&unnamed_dev_ida
, slot
);
855 if (slot
< unnamed_dev_start
)
856 unnamed_dev_start
= slot
;
857 spin_unlock(&unnamed_dev_lock
);
859 EXPORT_SYMBOL(free_anon_bdev
);
861 int set_anon_super(struct super_block
*s
, void *data
)
863 int error
= get_anon_bdev(&s
->s_dev
);
865 s
->s_bdi
= &noop_backing_dev_info
;
869 EXPORT_SYMBOL(set_anon_super
);
871 void kill_anon_super(struct super_block
*sb
)
873 dev_t dev
= sb
->s_dev
;
874 generic_shutdown_super(sb
);
878 EXPORT_SYMBOL(kill_anon_super
);
880 void kill_litter_super(struct super_block
*sb
)
883 d_genocide(sb
->s_root
);
887 EXPORT_SYMBOL(kill_litter_super
);
889 static int ns_test_super(struct super_block
*sb
, void *data
)
891 return sb
->s_fs_info
== data
;
894 static int ns_set_super(struct super_block
*sb
, void *data
)
896 sb
->s_fs_info
= data
;
897 return set_anon_super(sb
, NULL
);
900 struct dentry
*mount_ns(struct file_system_type
*fs_type
, int flags
,
901 void *data
, int (*fill_super
)(struct super_block
*, void *, int))
903 struct super_block
*sb
;
905 sb
= sget(fs_type
, ns_test_super
, ns_set_super
, flags
, data
);
911 err
= fill_super(sb
, data
, flags
& MS_SILENT
? 1 : 0);
913 deactivate_locked_super(sb
);
917 sb
->s_flags
|= MS_ACTIVE
;
920 return dget(sb
->s_root
);
923 EXPORT_SYMBOL(mount_ns
);
926 static int set_bdev_super(struct super_block
*s
, void *data
)
929 s
->s_dev
= s
->s_bdev
->bd_dev
;
932 * We set the bdi here to the queue backing, file systems can
933 * overwrite this in ->fill_super()
935 s
->s_bdi
= &bdev_get_queue(s
->s_bdev
)->backing_dev_info
;
939 static int test_bdev_super(struct super_block
*s
, void *data
)
941 return (void *)s
->s_bdev
== data
;
944 struct dentry
*mount_bdev(struct file_system_type
*fs_type
,
945 int flags
, const char *dev_name
, void *data
,
946 int (*fill_super
)(struct super_block
*, void *, int))
948 struct block_device
*bdev
;
949 struct super_block
*s
;
950 fmode_t mode
= FMODE_READ
| FMODE_EXCL
;
953 if (!(flags
& MS_RDONLY
))
956 bdev
= blkdev_get_by_path(dev_name
, mode
, fs_type
);
958 return ERR_CAST(bdev
);
961 * once the super is inserted into the list by sget, s_umount
962 * will protect the lockfs code from trying to start a snapshot
963 * while we are mounting
965 mutex_lock(&bdev
->bd_fsfreeze_mutex
);
966 if (bdev
->bd_fsfreeze_count
> 0) {
967 mutex_unlock(&bdev
->bd_fsfreeze_mutex
);
971 s
= sget(fs_type
, test_bdev_super
, set_bdev_super
, flags
| MS_NOSEC
,
973 mutex_unlock(&bdev
->bd_fsfreeze_mutex
);
978 if ((flags
^ s
->s_flags
) & MS_RDONLY
) {
979 deactivate_locked_super(s
);
985 * s_umount nests inside bd_mutex during
986 * __invalidate_device(). blkdev_put() acquires
987 * bd_mutex and can't be called under s_umount. Drop
988 * s_umount temporarily. This is safe as we're
989 * holding an active reference.
991 up_write(&s
->s_umount
);
992 blkdev_put(bdev
, mode
);
993 down_write(&s
->s_umount
);
995 char b
[BDEVNAME_SIZE
];
998 strlcpy(s
->s_id
, bdevname(bdev
, b
), sizeof(s
->s_id
));
999 sb_set_blocksize(s
, block_size(bdev
));
1000 error
= fill_super(s
, data
, flags
& MS_SILENT
? 1 : 0);
1002 deactivate_locked_super(s
);
1006 s
->s_flags
|= MS_ACTIVE
;
1010 return dget(s
->s_root
);
1015 blkdev_put(bdev
, mode
);
1017 return ERR_PTR(error
);
1019 EXPORT_SYMBOL(mount_bdev
);
1021 void kill_block_super(struct super_block
*sb
)
1023 struct block_device
*bdev
= sb
->s_bdev
;
1024 fmode_t mode
= sb
->s_mode
;
1026 bdev
->bd_super
= NULL
;
1027 generic_shutdown_super(sb
);
1028 sync_blockdev(bdev
);
1029 WARN_ON_ONCE(!(mode
& FMODE_EXCL
));
1030 blkdev_put(bdev
, mode
| FMODE_EXCL
);
1033 EXPORT_SYMBOL(kill_block_super
);
1036 struct dentry
*mount_nodev(struct file_system_type
*fs_type
,
1037 int flags
, void *data
,
1038 int (*fill_super
)(struct super_block
*, void *, int))
1041 struct super_block
*s
= sget(fs_type
, NULL
, set_anon_super
, flags
, NULL
);
1046 error
= fill_super(s
, data
, flags
& MS_SILENT
? 1 : 0);
1048 deactivate_locked_super(s
);
1049 return ERR_PTR(error
);
1051 s
->s_flags
|= MS_ACTIVE
;
1052 return dget(s
->s_root
);
1054 EXPORT_SYMBOL(mount_nodev
);
1056 static int compare_single(struct super_block
*s
, void *p
)
1061 struct dentry
*mount_single(struct file_system_type
*fs_type
,
1062 int flags
, void *data
,
1063 int (*fill_super
)(struct super_block
*, void *, int))
1065 struct super_block
*s
;
1068 s
= sget(fs_type
, compare_single
, set_anon_super
, flags
, NULL
);
1072 error
= fill_super(s
, data
, flags
& MS_SILENT
? 1 : 0);
1074 deactivate_locked_super(s
);
1075 return ERR_PTR(error
);
1077 s
->s_flags
|= MS_ACTIVE
;
1079 do_remount_sb(s
, flags
, data
, 0);
1081 return dget(s
->s_root
);
1083 EXPORT_SYMBOL(mount_single
);
1086 mount_fs(struct file_system_type
*type
, int flags
, const char *name
, void *data
)
1088 struct dentry
*root
;
1089 struct super_block
*sb
;
1090 char *secdata
= NULL
;
1091 int error
= -ENOMEM
;
1093 if (data
&& !(type
->fs_flags
& FS_BINARY_MOUNTDATA
)) {
1094 secdata
= alloc_secdata();
1098 error
= security_sb_copy_data(data
, secdata
);
1100 goto out_free_secdata
;
1103 root
= type
->mount(type
, flags
, name
, data
);
1105 error
= PTR_ERR(root
);
1106 goto out_free_secdata
;
1110 WARN_ON(!sb
->s_bdi
);
1111 WARN_ON(sb
->s_bdi
== &default_backing_dev_info
);
1112 sb
->s_flags
|= MS_BORN
;
1114 error
= security_sb_kern_mount(sb
, flags
, secdata
);
1119 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1120 * but s_maxbytes was an unsigned long long for many releases. Throw
1121 * this warning for a little while to try and catch filesystems that
1122 * violate this rule.
1124 WARN((sb
->s_maxbytes
< 0), "%s set sb->s_maxbytes to "
1125 "negative value (%lld)\n", type
->name
, sb
->s_maxbytes
);
1127 up_write(&sb
->s_umount
);
1128 free_secdata(secdata
);
1132 deactivate_locked_super(sb
);
1134 free_secdata(secdata
);
1136 return ERR_PTR(error
);
1140 * This is an internal function, please use sb_end_{write,pagefault,intwrite}
1143 void __sb_end_write(struct super_block
*sb
, int level
)
1145 percpu_counter_dec(&sb
->s_writers
.counter
[level
-1]);
1147 * Make sure s_writers are updated before we wake up waiters in
1151 if (waitqueue_active(&sb
->s_writers
.wait
))
1152 wake_up(&sb
->s_writers
.wait
);
1153 rwsem_release(&sb
->s_writers
.lock_map
[level
-1], 1, _RET_IP_
);
1155 EXPORT_SYMBOL(__sb_end_write
);
1157 #ifdef CONFIG_LOCKDEP
1159 * We want lockdep to tell us about possible deadlocks with freezing but
1160 * it's it bit tricky to properly instrument it. Getting a freeze protection
1161 * works as getting a read lock but there are subtle problems. XFS for example
1162 * gets freeze protection on internal level twice in some cases, which is OK
1163 * only because we already hold a freeze protection also on higher level. Due
1164 * to these cases we have to tell lockdep we are doing trylock when we
1165 * already hold a freeze protection for a higher freeze level.
1167 static void acquire_freeze_lock(struct super_block
*sb
, int level
, bool trylock
,
1173 for (i
= 0; i
< level
- 1; i
++)
1174 if (lock_is_held(&sb
->s_writers
.lock_map
[i
])) {
1179 rwsem_acquire_read(&sb
->s_writers
.lock_map
[level
-1], 0, trylock
, ip
);
1184 * This is an internal function, please use sb_start_{write,pagefault,intwrite}
1187 int __sb_start_write(struct super_block
*sb
, int level
, bool wait
)
1190 if (unlikely(sb
->s_writers
.frozen
>= level
)) {
1193 wait_event(sb
->s_writers
.wait_unfrozen
,
1194 sb
->s_writers
.frozen
< level
);
1197 #ifdef CONFIG_LOCKDEP
1198 acquire_freeze_lock(sb
, level
, !wait
, _RET_IP_
);
1200 percpu_counter_inc(&sb
->s_writers
.counter
[level
-1]);
1202 * Make sure counter is updated before we check for frozen.
1203 * freeze_super() first sets frozen and then checks the counter.
1206 if (unlikely(sb
->s_writers
.frozen
>= level
)) {
1207 __sb_end_write(sb
, level
);
1212 EXPORT_SYMBOL(__sb_start_write
);
1215 * sb_wait_write - wait until all writers to given file system finish
1216 * @sb: the super for which we wait
1217 * @level: type of writers we wait for (normal vs page fault)
1219 * This function waits until there are no writers of given type to given file
1220 * system. Caller of this function should make sure there can be no new writers
1221 * of type @level before calling this function. Otherwise this function can
1224 static void sb_wait_write(struct super_block
*sb
, int level
)
1229 * We just cycle-through lockdep here so that it does not complain
1230 * about returning with lock to userspace
1232 rwsem_acquire(&sb
->s_writers
.lock_map
[level
-1], 0, 0, _THIS_IP_
);
1233 rwsem_release(&sb
->s_writers
.lock_map
[level
-1], 1, _THIS_IP_
);
1239 * We use a barrier in prepare_to_wait() to separate setting
1240 * of frozen and checking of the counter
1242 prepare_to_wait(&sb
->s_writers
.wait
, &wait
,
1243 TASK_UNINTERRUPTIBLE
);
1245 writers
= percpu_counter_sum(&sb
->s_writers
.counter
[level
-1]);
1249 finish_wait(&sb
->s_writers
.wait
, &wait
);
1254 * freeze_super - lock the filesystem and force it into a consistent state
1255 * @sb: the super to lock
1257 * Syncs the super to make sure the filesystem is consistent and calls the fs's
1258 * freeze_fs. Subsequent calls to this without first thawing the fs will return
1261 * During this function, sb->s_writers.frozen goes through these values:
1263 * SB_UNFROZEN: File system is normal, all writes progress as usual.
1265 * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
1266 * writes should be blocked, though page faults are still allowed. We wait for
1267 * all writes to complete and then proceed to the next stage.
1269 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
1270 * but internal fs threads can still modify the filesystem (although they
1271 * should not dirty new pages or inodes), writeback can run etc. After waiting
1272 * for all running page faults we sync the filesystem which will clean all
1273 * dirty pages and inodes (no new dirty pages or inodes can be created when
1276 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
1277 * modification are blocked (e.g. XFS preallocation truncation on inode
1278 * reclaim). This is usually implemented by blocking new transactions for
1279 * filesystems that have them and need this additional guard. After all
1280 * internal writers are finished we call ->freeze_fs() to finish filesystem
1281 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
1282 * mostly auxiliary for filesystems to verify they do not modify frozen fs.
1284 * sb->s_writers.frozen is protected by sb->s_umount.
1286 int freeze_super(struct super_block
*sb
)
1290 atomic_inc(&sb
->s_active
);
1291 down_write(&sb
->s_umount
);
1292 if (sb
->s_writers
.frozen
!= SB_UNFROZEN
) {
1293 deactivate_locked_super(sb
);
1297 if (!(sb
->s_flags
& MS_BORN
)) {
1298 up_write(&sb
->s_umount
);
1299 return 0; /* sic - it's "nothing to do" */
1302 if (sb
->s_flags
& MS_RDONLY
) {
1303 /* Nothing to do really... */
1304 sb
->s_writers
.frozen
= SB_FREEZE_COMPLETE
;
1305 up_write(&sb
->s_umount
);
1309 /* From now on, no new normal writers can start */
1310 sb
->s_writers
.frozen
= SB_FREEZE_WRITE
;
1313 /* Release s_umount to preserve sb_start_write -> s_umount ordering */
1314 up_write(&sb
->s_umount
);
1316 sb_wait_write(sb
, SB_FREEZE_WRITE
);
1318 /* Now we go and block page faults... */
1319 down_write(&sb
->s_umount
);
1320 sb
->s_writers
.frozen
= SB_FREEZE_PAGEFAULT
;
1323 sb_wait_write(sb
, SB_FREEZE_PAGEFAULT
);
1325 /* All writers are done so after syncing there won't be dirty data */
1326 sync_filesystem(sb
);
1328 /* Now wait for internal filesystem counter */
1329 sb
->s_writers
.frozen
= SB_FREEZE_FS
;
1331 sb_wait_write(sb
, SB_FREEZE_FS
);
1333 if (sb
->s_op
->freeze_fs
) {
1334 ret
= sb
->s_op
->freeze_fs(sb
);
1337 "VFS:Filesystem freeze failed\n");
1338 sb
->s_writers
.frozen
= SB_UNFROZEN
;
1340 wake_up(&sb
->s_writers
.wait_unfrozen
);
1341 deactivate_locked_super(sb
);
1346 * This is just for debugging purposes so that fs can warn if it
1347 * sees write activity when frozen is set to SB_FREEZE_COMPLETE.
1349 sb
->s_writers
.frozen
= SB_FREEZE_COMPLETE
;
1350 up_write(&sb
->s_umount
);
1353 EXPORT_SYMBOL(freeze_super
);
1356 * thaw_super -- unlock filesystem
1357 * @sb: the super to thaw
1359 * Unlocks the filesystem and marks it writeable again after freeze_super().
1361 int thaw_super(struct super_block
*sb
)
1365 down_write(&sb
->s_umount
);
1366 if (sb
->s_writers
.frozen
== SB_UNFROZEN
) {
1367 up_write(&sb
->s_umount
);
1371 if (sb
->s_flags
& MS_RDONLY
)
1374 if (sb
->s_op
->unfreeze_fs
) {
1375 error
= sb
->s_op
->unfreeze_fs(sb
);
1378 "VFS:Filesystem thaw failed\n");
1379 up_write(&sb
->s_umount
);
1385 sb
->s_writers
.frozen
= SB_UNFROZEN
;
1387 wake_up(&sb
->s_writers
.wait_unfrozen
);
1388 deactivate_locked_super(sb
);
1392 EXPORT_SYMBOL(thaw_super
);