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/acct.h>
26 #include <linux/blkdev.h>
27 #include <linux/mount.h>
28 #include <linux/security.h>
29 #include <linux/writeback.h> /* for the emergency remount stuff */
30 #include <linux/idr.h>
31 #include <linux/mutex.h>
32 #include <linux/backing-dev.h>
33 #include <linux/rculist_bl.h>
34 #include <linux/cleancache.h>
35 #include <linux/fsnotify.h>
36 #include <linux/lockdep.h>
40 LIST_HEAD(super_blocks);
41 DEFINE_SPINLOCK(sb_lock);
43 static char *sb_writers_name[SB_FREEZE_LEVELS] = {
50 * One thing we have to be careful of with a per-sb shrinker is that we don't
51 * drop the last active reference to the superblock from within the shrinker.
52 * If that happens we could trigger unregistering the shrinker from within the
53 * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
54 * take a passive reference to the superblock to avoid this from occurring.
56 static unsigned long super_cache_scan(struct shrinker *shrink,
57 struct shrink_control *sc)
59 struct super_block *sb;
66 sb = container_of(shrink, struct super_block, s_shrink);
69 * Deadlock avoidance. We may hold various FS locks, and we don't want
70 * to recurse into the FS that called us in clear_inode() and friends..
72 if (!(sc->gfp_mask & __GFP_FS))
75 if (!grab_super_passive(sb))
78 if (sb->s_op && sb->s_op->nr_cached_objects)
79 fs_objects = sb->s_op->nr_cached_objects(sb);
81 inodes = list_lru_count(&sb->s_inode_lru);
82 total_objects = sb->s_nr_dentry_unused + inodes + fs_objects + 1;
84 /* proportion the scan between the caches */
85 dentries = mult_frac(sc->nr_to_scan, sb->s_nr_dentry_unused,
87 inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);
90 * prune the dcache first as the icache is pinned by it, then
91 * prune the icache, followed by the filesystem specific caches
93 freed = prune_dcache_sb(sb, dentries);
94 freed += prune_icache_sb(sb, inodes);
97 fs_objects = mult_frac(sc->nr_to_scan, fs_objects,
99 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);
114 if (!grab_super_passive(sb))
117 if (sb->s_op && sb->s_op->nr_cached_objects)
118 total_objects = sb->s_op->nr_cached_objects(sb);
120 total_objects += sb->s_nr_dentry_unused;
121 total_objects += list_lru_count(&sb->s_inode_lru);
123 total_objects = vfs_pressure_ratio(total_objects);
125 return total_objects;
128 static int init_sb_writers(struct super_block *s, struct file_system_type *type)
133 for (i = 0; i < SB_FREEZE_LEVELS; i++) {
134 err = percpu_counter_init(&s->s_writers.counter[i], 0);
137 lockdep_init_map(&s->s_writers.lock_map[i], sb_writers_name[i],
138 &type->s_writers_key[i], 0);
140 init_waitqueue_head(&s->s_writers.wait);
141 init_waitqueue_head(&s->s_writers.wait_unfrozen);
145 percpu_counter_destroy(&s->s_writers.counter[i]);
149 static void destroy_sb_writers(struct super_block *s)
153 for (i = 0; i < SB_FREEZE_LEVELS; i++)
154 percpu_counter_destroy(&s->s_writers.counter[i]);
158 * alloc_super - create new superblock
159 * @type: filesystem type superblock should belong to
160 * @flags: the mount flags
162 * Allocates and initializes a new &struct super_block. alloc_super()
163 * returns a pointer new superblock or %NULL if allocation had failed.
165 static struct super_block *alloc_super(struct file_system_type *type, int flags)
167 struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
168 static const struct super_operations default_op;
171 if (security_sb_alloc(s)) {
173 * We cannot call security_sb_free() without
174 * security_sb_alloc() succeeding. So bail out manually
181 s->s_files = alloc_percpu(struct list_head);
187 for_each_possible_cpu(i)
188 INIT_LIST_HEAD(per_cpu_ptr(s->s_files, i));
191 INIT_LIST_HEAD(&s->s_files);
193 if (init_sb_writers(s, type))
196 s->s_bdi = &default_backing_dev_info;
197 INIT_HLIST_NODE(&s->s_instances);
198 INIT_HLIST_BL_HEAD(&s->s_anon);
199 INIT_LIST_HEAD(&s->s_inodes);
200 INIT_LIST_HEAD(&s->s_dentry_lru);
201 spin_lock_init(&s->s_dentry_lru_lock);
202 list_lru_init(&s->s_inode_lru);
203 INIT_LIST_HEAD(&s->s_mounts);
204 init_rwsem(&s->s_umount);
205 lockdep_set_class(&s->s_umount, &type->s_umount_key);
207 * sget() can have s_umount recursion.
209 * When it cannot find a suitable sb, it allocates a new
210 * one (this one), and tries again to find a suitable old
213 * In case that succeeds, it will acquire the s_umount
214 * lock of the old one. Since these are clearly distrinct
215 * locks, and this object isn't exposed yet, there's no
218 * Annotate this by putting this lock in a different
221 down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
223 atomic_set(&s->s_active, 1);
224 mutex_init(&s->s_vfs_rename_mutex);
225 lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
226 mutex_init(&s->s_dquot.dqio_mutex);
227 mutex_init(&s->s_dquot.dqonoff_mutex);
228 init_rwsem(&s->s_dquot.dqptr_sem);
229 s->s_maxbytes = MAX_NON_LFS;
230 s->s_op = &default_op;
231 s->s_time_gran = 1000000000;
232 s->cleancache_poolid = -1;
234 s->s_shrink.seeks = DEFAULT_SEEKS;
235 s->s_shrink.scan_objects = super_cache_scan;
236 s->s_shrink.count_objects = super_cache_count;
237 s->s_shrink.batch = 1024;
245 free_percpu(s->s_files);
247 destroy_sb_writers(s);
254 * destroy_super - frees a superblock
255 * @s: superblock to free
257 * Frees a superblock.
259 static inline void destroy_super(struct super_block *s)
262 free_percpu(s->s_files);
264 destroy_sb_writers(s);
266 WARN_ON(!list_empty(&s->s_mounts));
272 /* Superblock refcounting */
275 * Drop a superblock's refcount. The caller must hold sb_lock.
277 static void __put_super(struct super_block *sb)
279 if (!--sb->s_count) {
280 list_del_init(&sb->s_list);
286 * put_super - drop a temporary reference to superblock
287 * @sb: superblock in question
289 * Drops a temporary reference, frees superblock if there's no
292 static void put_super(struct super_block *sb)
296 spin_unlock(&sb_lock);
301 * deactivate_locked_super - drop an active reference to superblock
302 * @s: superblock to deactivate
304 * Drops an active reference to superblock, converting it into a temprory
305 * one if there is no other active references left. In that case we
306 * tell fs driver to shut it down and drop the temporary reference we
309 * Caller holds exclusive lock on superblock; that lock is released.
311 void deactivate_locked_super(struct super_block *s)
313 struct file_system_type *fs = s->s_type;
314 if (atomic_dec_and_test(&s->s_active)) {
315 cleancache_invalidate_fs(s);
318 /* caches are now gone, we can safely kill the shrinker now */
319 unregister_shrinker(&s->s_shrink);
323 up_write(&s->s_umount);
327 EXPORT_SYMBOL(deactivate_locked_super);
330 * deactivate_super - drop an active reference to superblock
331 * @s: superblock to deactivate
333 * Variant of deactivate_locked_super(), except that superblock is *not*
334 * locked by caller. If we are going to drop the final active reference,
335 * lock will be acquired prior to that.
337 void deactivate_super(struct super_block *s)
339 if (!atomic_add_unless(&s->s_active, -1, 1)) {
340 down_write(&s->s_umount);
341 deactivate_locked_super(s);
345 EXPORT_SYMBOL(deactivate_super);
348 * grab_super - acquire an active reference
349 * @s: reference we are trying to make active
351 * Tries to acquire an active reference. grab_super() is used when we
352 * had just found a superblock in super_blocks or fs_type->fs_supers
353 * and want to turn it into a full-blown active reference. grab_super()
354 * is called with sb_lock held and drops it. Returns 1 in case of
355 * success, 0 if we had failed (superblock contents was already dead or
356 * dying when grab_super() had been called). Note that this is only
357 * called for superblocks not in rundown mode (== ones still on ->fs_supers
358 * of their type), so increment of ->s_count is OK here.
360 static int grab_super(struct super_block *s) __releases(sb_lock)
363 spin_unlock(&sb_lock);
364 down_write(&s->s_umount);
365 if ((s->s_flags & MS_BORN) && atomic_inc_not_zero(&s->s_active)) {
369 up_write(&s->s_umount);
375 * grab_super_passive - acquire a passive reference
376 * @sb: reference we are trying to grab
378 * Tries to acquire a passive reference. This is used in places where we
379 * cannot take an active reference but we need to ensure that the
380 * superblock does not go away while we are working on it. It returns
381 * false if a reference was not gained, and returns true with the s_umount
382 * lock held in read mode if a reference is gained. On successful return,
383 * the caller must drop the s_umount lock and the passive reference when
386 bool grab_super_passive(struct super_block *sb)
389 if (hlist_unhashed(&sb->s_instances)) {
390 spin_unlock(&sb_lock);
395 spin_unlock(&sb_lock);
397 if (down_read_trylock(&sb->s_umount)) {
398 if (sb->s_root && (sb->s_flags & MS_BORN))
400 up_read(&sb->s_umount);
408 * generic_shutdown_super - common helper for ->kill_sb()
409 * @sb: superblock to kill
411 * generic_shutdown_super() does all fs-independent work on superblock
412 * shutdown. Typical ->kill_sb() should pick all fs-specific objects
413 * that need destruction out of superblock, call generic_shutdown_super()
414 * and release aforementioned objects. Note: dentries and inodes _are_
415 * taken care of and do not need specific handling.
417 * Upon calling this function, the filesystem may no longer alter or
418 * rearrange the set of dentries belonging to this super_block, nor may it
419 * change the attachments of dentries to inodes.
421 void generic_shutdown_super(struct super_block *sb)
423 const struct super_operations *sop = sb->s_op;
426 shrink_dcache_for_umount(sb);
428 sb->s_flags &= ~MS_ACTIVE;
430 fsnotify_unmount_inodes(&sb->s_inodes);
437 if (!list_empty(&sb->s_inodes)) {
438 printk("VFS: Busy inodes after unmount of %s. "
439 "Self-destruct in 5 seconds. Have a nice day...\n",
444 /* should be initialized for __put_super_and_need_restart() */
445 hlist_del_init(&sb->s_instances);
446 spin_unlock(&sb_lock);
447 up_write(&sb->s_umount);
450 EXPORT_SYMBOL(generic_shutdown_super);
453 * sget - find or create a superblock
454 * @type: filesystem type superblock should belong to
455 * @test: comparison callback
456 * @set: setup callback
457 * @flags: mount flags
458 * @data: argument to each of them
460 struct super_block *sget(struct file_system_type *type,
461 int (*test)(struct super_block *,void *),
462 int (*set)(struct super_block *,void *),
466 struct super_block *s = NULL;
467 struct super_block *old;
473 hlist_for_each_entry(old, &type->fs_supers, s_instances) {
474 if (!test(old, data))
476 if (!grab_super(old))
479 up_write(&s->s_umount);
487 spin_unlock(&sb_lock);
488 s = alloc_super(type, flags);
490 return ERR_PTR(-ENOMEM);
496 spin_unlock(&sb_lock);
497 up_write(&s->s_umount);
502 strlcpy(s->s_id, type->name, sizeof(s->s_id));
503 list_add_tail(&s->s_list, &super_blocks);
504 hlist_add_head(&s->s_instances, &type->fs_supers);
505 spin_unlock(&sb_lock);
506 get_filesystem(type);
507 register_shrinker(&s->s_shrink);
513 void drop_super(struct super_block *sb)
515 up_read(&sb->s_umount);
519 EXPORT_SYMBOL(drop_super);
522 * iterate_supers - call function for all active superblocks
523 * @f: function to call
524 * @arg: argument to pass to it
526 * Scans the superblock list and calls given function, passing it
527 * locked superblock and given argument.
529 void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
531 struct super_block *sb, *p = NULL;
534 list_for_each_entry(sb, &super_blocks, s_list) {
535 if (hlist_unhashed(&sb->s_instances))
538 spin_unlock(&sb_lock);
540 down_read(&sb->s_umount);
541 if (sb->s_root && (sb->s_flags & MS_BORN))
543 up_read(&sb->s_umount);
552 spin_unlock(&sb_lock);
556 * iterate_supers_type - call function for superblocks of given type
558 * @f: function to call
559 * @arg: argument to pass to it
561 * Scans the superblock list and calls given function, passing it
562 * locked superblock and given argument.
564 void iterate_supers_type(struct file_system_type *type,
565 void (*f)(struct super_block *, void *), void *arg)
567 struct super_block *sb, *p = NULL;
570 hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
572 spin_unlock(&sb_lock);
574 down_read(&sb->s_umount);
575 if (sb->s_root && (sb->s_flags & MS_BORN))
577 up_read(&sb->s_umount);
586 spin_unlock(&sb_lock);
589 EXPORT_SYMBOL(iterate_supers_type);
592 * get_super - get the superblock of a device
593 * @bdev: device to get the superblock for
595 * Scans the superblock list and finds the superblock of the file system
596 * mounted on the device given. %NULL is returned if no match is found.
599 struct super_block *get_super(struct block_device *bdev)
601 struct super_block *sb;
608 list_for_each_entry(sb, &super_blocks, s_list) {
609 if (hlist_unhashed(&sb->s_instances))
611 if (sb->s_bdev == bdev) {
613 spin_unlock(&sb_lock);
614 down_read(&sb->s_umount);
616 if (sb->s_root && (sb->s_flags & MS_BORN))
618 up_read(&sb->s_umount);
619 /* nope, got unmounted */
625 spin_unlock(&sb_lock);
629 EXPORT_SYMBOL(get_super);
632 * get_super_thawed - get thawed superblock of a device
633 * @bdev: device to get the superblock for
635 * Scans the superblock list and finds the superblock of the file system
636 * mounted on the device. The superblock is returned once it is thawed
637 * (or immediately if it was not frozen). %NULL is returned if no match
640 struct super_block *get_super_thawed(struct block_device *bdev)
643 struct super_block *s = get_super(bdev);
644 if (!s || s->s_writers.frozen == SB_UNFROZEN)
646 up_read(&s->s_umount);
647 wait_event(s->s_writers.wait_unfrozen,
648 s->s_writers.frozen == SB_UNFROZEN);
652 EXPORT_SYMBOL(get_super_thawed);
655 * get_active_super - get an active reference to the superblock of a device
656 * @bdev: device to get the superblock for
658 * Scans the superblock list and finds the superblock of the file system
659 * mounted on the device given. Returns the superblock with an active
660 * reference or %NULL if none was found.
662 struct super_block *get_active_super(struct block_device *bdev)
664 struct super_block *sb;
671 list_for_each_entry(sb, &super_blocks, s_list) {
672 if (hlist_unhashed(&sb->s_instances))
674 if (sb->s_bdev == bdev) {
677 up_write(&sb->s_umount);
681 spin_unlock(&sb_lock);
685 struct super_block *user_get_super(dev_t dev)
687 struct super_block *sb;
691 list_for_each_entry(sb, &super_blocks, s_list) {
692 if (hlist_unhashed(&sb->s_instances))
694 if (sb->s_dev == dev) {
696 spin_unlock(&sb_lock);
697 down_read(&sb->s_umount);
699 if (sb->s_root && (sb->s_flags & MS_BORN))
701 up_read(&sb->s_umount);
702 /* nope, got unmounted */
708 spin_unlock(&sb_lock);
713 * do_remount_sb - asks filesystem to change mount options.
714 * @sb: superblock in question
715 * @flags: numeric part of options
716 * @data: the rest of options
717 * @force: whether or not to force the change
719 * Alters the mount options of a mounted file system.
721 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
726 if (sb->s_writers.frozen != SB_UNFROZEN)
730 if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
734 if (flags & MS_RDONLY)
736 shrink_dcache_sb(sb);
739 remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY);
741 /* If we are remounting RDONLY and current sb is read/write,
742 make sure there are no rw files opened */
747 retval = sb_prepare_remount_readonly(sb);
753 if (sb->s_op->remount_fs) {
754 retval = sb->s_op->remount_fs(sb, &flags, data);
757 goto cancel_readonly;
758 /* If forced remount, go ahead despite any errors */
759 WARN(1, "forced remount of a %s fs returned %i\n",
760 sb->s_type->name, retval);
763 sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
764 /* Needs to be ordered wrt mnt_is_readonly() */
766 sb->s_readonly_remount = 0;
769 * Some filesystems modify their metadata via some other path than the
770 * bdev buffer cache (eg. use a private mapping, or directories in
771 * pagecache, etc). Also file data modifications go via their own
772 * mappings. So If we try to mount readonly then copy the filesystem
773 * from bdev, we could get stale data, so invalidate it to give a best
774 * effort at coherency.
776 if (remount_ro && sb->s_bdev)
777 invalidate_bdev(sb->s_bdev);
781 sb->s_readonly_remount = 0;
785 static void do_emergency_remount(struct work_struct *work)
787 struct super_block *sb, *p = NULL;
790 list_for_each_entry(sb, &super_blocks, s_list) {
791 if (hlist_unhashed(&sb->s_instances))
794 spin_unlock(&sb_lock);
795 down_write(&sb->s_umount);
796 if (sb->s_root && sb->s_bdev && (sb->s_flags & MS_BORN) &&
797 !(sb->s_flags & MS_RDONLY)) {
799 * What lock protects sb->s_flags??
801 do_remount_sb(sb, MS_RDONLY, NULL, 1);
803 up_write(&sb->s_umount);
811 spin_unlock(&sb_lock);
813 printk("Emergency Remount complete\n");
816 void emergency_remount(void)
818 struct work_struct *work;
820 work = kmalloc(sizeof(*work), GFP_ATOMIC);
822 INIT_WORK(work, do_emergency_remount);
828 * Unnamed block devices are dummy devices used by virtual
829 * filesystems which don't use real block-devices. -- jrs
832 static DEFINE_IDA(unnamed_dev_ida);
833 static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
834 static int unnamed_dev_start = 0; /* don't bother trying below it */
836 int get_anon_bdev(dev_t *p)
842 if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
844 spin_lock(&unnamed_dev_lock);
845 error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);
847 unnamed_dev_start = dev + 1;
848 spin_unlock(&unnamed_dev_lock);
849 if (error == -EAGAIN)
850 /* We raced and lost with another CPU. */
855 if (dev == (1 << MINORBITS)) {
856 spin_lock(&unnamed_dev_lock);
857 ida_remove(&unnamed_dev_ida, dev);
858 if (unnamed_dev_start > dev)
859 unnamed_dev_start = dev;
860 spin_unlock(&unnamed_dev_lock);
863 *p = MKDEV(0, dev & MINORMASK);
866 EXPORT_SYMBOL(get_anon_bdev);
868 void free_anon_bdev(dev_t dev)
870 int slot = MINOR(dev);
871 spin_lock(&unnamed_dev_lock);
872 ida_remove(&unnamed_dev_ida, slot);
873 if (slot < unnamed_dev_start)
874 unnamed_dev_start = slot;
875 spin_unlock(&unnamed_dev_lock);
877 EXPORT_SYMBOL(free_anon_bdev);
879 int set_anon_super(struct super_block *s, void *data)
881 int error = get_anon_bdev(&s->s_dev);
883 s->s_bdi = &noop_backing_dev_info;
887 EXPORT_SYMBOL(set_anon_super);
889 void kill_anon_super(struct super_block *sb)
891 dev_t dev = sb->s_dev;
892 generic_shutdown_super(sb);
896 EXPORT_SYMBOL(kill_anon_super);
898 void kill_litter_super(struct super_block *sb)
901 d_genocide(sb->s_root);
905 EXPORT_SYMBOL(kill_litter_super);
907 static int ns_test_super(struct super_block *sb, void *data)
909 return sb->s_fs_info == data;
912 static int ns_set_super(struct super_block *sb, void *data)
914 sb->s_fs_info = data;
915 return set_anon_super(sb, NULL);
918 struct dentry *mount_ns(struct file_system_type *fs_type, int flags,
919 void *data, int (*fill_super)(struct super_block *, void *, int))
921 struct super_block *sb;
923 sb = sget(fs_type, ns_test_super, ns_set_super, flags, data);
929 err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
931 deactivate_locked_super(sb);
935 sb->s_flags |= MS_ACTIVE;
938 return dget(sb->s_root);
941 EXPORT_SYMBOL(mount_ns);
944 static int set_bdev_super(struct super_block *s, void *data)
947 s->s_dev = s->s_bdev->bd_dev;
950 * We set the bdi here to the queue backing, file systems can
951 * overwrite this in ->fill_super()
953 s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info;
957 static int test_bdev_super(struct super_block *s, void *data)
959 return (void *)s->s_bdev == data;
962 struct dentry *mount_bdev(struct file_system_type *fs_type,
963 int flags, const char *dev_name, void *data,
964 int (*fill_super)(struct super_block *, void *, int))
966 struct block_device *bdev;
967 struct super_block *s;
968 fmode_t mode = FMODE_READ | FMODE_EXCL;
971 if (!(flags & MS_RDONLY))
974 bdev = blkdev_get_by_path(dev_name, mode, fs_type);
976 return ERR_CAST(bdev);
979 * once the super is inserted into the list by sget, s_umount
980 * will protect the lockfs code from trying to start a snapshot
981 * while we are mounting
983 mutex_lock(&bdev->bd_fsfreeze_mutex);
984 if (bdev->bd_fsfreeze_count > 0) {
985 mutex_unlock(&bdev->bd_fsfreeze_mutex);
989 s = sget(fs_type, test_bdev_super, set_bdev_super, flags | MS_NOSEC,
991 mutex_unlock(&bdev->bd_fsfreeze_mutex);
996 if ((flags ^ s->s_flags) & MS_RDONLY) {
997 deactivate_locked_super(s);
1003 * s_umount nests inside bd_mutex during
1004 * __invalidate_device(). blkdev_put() acquires
1005 * bd_mutex and can't be called under s_umount. Drop
1006 * s_umount temporarily. This is safe as we're
1007 * holding an active reference.
1009 up_write(&s->s_umount);
1010 blkdev_put(bdev, mode);
1011 down_write(&s->s_umount);
1013 char b[BDEVNAME_SIZE];
1016 strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
1017 sb_set_blocksize(s, block_size(bdev));
1018 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
1020 deactivate_locked_super(s);
1024 s->s_flags |= MS_ACTIVE;
1028 return dget(s->s_root);
1033 blkdev_put(bdev, mode);
1035 return ERR_PTR(error);
1037 EXPORT_SYMBOL(mount_bdev);
1039 void kill_block_super(struct super_block *sb)
1041 struct block_device *bdev = sb->s_bdev;
1042 fmode_t mode = sb->s_mode;
1044 bdev->bd_super = NULL;
1045 generic_shutdown_super(sb);
1046 sync_blockdev(bdev);
1047 WARN_ON_ONCE(!(mode & FMODE_EXCL));
1048 blkdev_put(bdev, mode | FMODE_EXCL);
1051 EXPORT_SYMBOL(kill_block_super);
1054 struct dentry *mount_nodev(struct file_system_type *fs_type,
1055 int flags, void *data,
1056 int (*fill_super)(struct super_block *, void *, int))
1059 struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
1064 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
1066 deactivate_locked_super(s);
1067 return ERR_PTR(error);
1069 s->s_flags |= MS_ACTIVE;
1070 return dget(s->s_root);
1072 EXPORT_SYMBOL(mount_nodev);
1074 static int compare_single(struct super_block *s, void *p)
1079 struct dentry *mount_single(struct file_system_type *fs_type,
1080 int flags, void *data,
1081 int (*fill_super)(struct super_block *, void *, int))
1083 struct super_block *s;
1086 s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
1090 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
1092 deactivate_locked_super(s);
1093 return ERR_PTR(error);
1095 s->s_flags |= MS_ACTIVE;
1097 do_remount_sb(s, flags, data, 0);
1099 return dget(s->s_root);
1101 EXPORT_SYMBOL(mount_single);
1104 mount_fs(struct file_system_type *type, int flags, const char *name, void *data)
1106 struct dentry *root;
1107 struct super_block *sb;
1108 char *secdata = NULL;
1109 int error = -ENOMEM;
1111 if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
1112 secdata = alloc_secdata();
1116 error = security_sb_copy_data(data, secdata);
1118 goto out_free_secdata;
1121 root = type->mount(type, flags, name, data);
1123 error = PTR_ERR(root);
1124 goto out_free_secdata;
1128 WARN_ON(!sb->s_bdi);
1129 WARN_ON(sb->s_bdi == &default_backing_dev_info);
1130 sb->s_flags |= MS_BORN;
1132 error = security_sb_kern_mount(sb, flags, secdata);
1137 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1138 * but s_maxbytes was an unsigned long long for many releases. Throw
1139 * this warning for a little while to try and catch filesystems that
1140 * violate this rule.
1142 WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
1143 "negative value (%lld)\n", type->name, sb->s_maxbytes);
1145 up_write(&sb->s_umount);
1146 free_secdata(secdata);
1150 deactivate_locked_super(sb);
1152 free_secdata(secdata);
1154 return ERR_PTR(error);
1158 * This is an internal function, please use sb_end_{write,pagefault,intwrite}
1161 void __sb_end_write(struct super_block *sb, int level)
1163 percpu_counter_dec(&sb->s_writers.counter[level-1]);
1165 * Make sure s_writers are updated before we wake up waiters in
1169 if (waitqueue_active(&sb->s_writers.wait))
1170 wake_up(&sb->s_writers.wait);
1171 rwsem_release(&sb->s_writers.lock_map[level-1], 1, _RET_IP_);
1173 EXPORT_SYMBOL(__sb_end_write);
1175 #ifdef CONFIG_LOCKDEP
1177 * We want lockdep to tell us about possible deadlocks with freezing but
1178 * it's it bit tricky to properly instrument it. Getting a freeze protection
1179 * works as getting a read lock but there are subtle problems. XFS for example
1180 * gets freeze protection on internal level twice in some cases, which is OK
1181 * only because we already hold a freeze protection also on higher level. Due
1182 * to these cases we have to tell lockdep we are doing trylock when we
1183 * already hold a freeze protection for a higher freeze level.
1185 static void acquire_freeze_lock(struct super_block *sb, int level, bool trylock,
1191 for (i = 0; i < level - 1; i++)
1192 if (lock_is_held(&sb->s_writers.lock_map[i])) {
1197 rwsem_acquire_read(&sb->s_writers.lock_map[level-1], 0, trylock, ip);
1202 * This is an internal function, please use sb_start_{write,pagefault,intwrite}
1205 int __sb_start_write(struct super_block *sb, int level, bool wait)
1208 if (unlikely(sb->s_writers.frozen >= level)) {
1211 wait_event(sb->s_writers.wait_unfrozen,
1212 sb->s_writers.frozen < level);
1215 #ifdef CONFIG_LOCKDEP
1216 acquire_freeze_lock(sb, level, !wait, _RET_IP_);
1218 percpu_counter_inc(&sb->s_writers.counter[level-1]);
1220 * Make sure counter is updated before we check for frozen.
1221 * freeze_super() first sets frozen and then checks the counter.
1224 if (unlikely(sb->s_writers.frozen >= level)) {
1225 __sb_end_write(sb, level);
1230 EXPORT_SYMBOL(__sb_start_write);
1233 * sb_wait_write - wait until all writers to given file system finish
1234 * @sb: the super for which we wait
1235 * @level: type of writers we wait for (normal vs page fault)
1237 * This function waits until there are no writers of given type to given file
1238 * system. Caller of this function should make sure there can be no new writers
1239 * of type @level before calling this function. Otherwise this function can
1242 static void sb_wait_write(struct super_block *sb, int level)
1247 * We just cycle-through lockdep here so that it does not complain
1248 * about returning with lock to userspace
1250 rwsem_acquire(&sb->s_writers.lock_map[level-1], 0, 0, _THIS_IP_);
1251 rwsem_release(&sb->s_writers.lock_map[level-1], 1, _THIS_IP_);
1257 * We use a barrier in prepare_to_wait() to separate setting
1258 * of frozen and checking of the counter
1260 prepare_to_wait(&sb->s_writers.wait, &wait,
1261 TASK_UNINTERRUPTIBLE);
1263 writers = percpu_counter_sum(&sb->s_writers.counter[level-1]);
1267 finish_wait(&sb->s_writers.wait, &wait);
1272 * freeze_super - lock the filesystem and force it into a consistent state
1273 * @sb: the super to lock
1275 * Syncs the super to make sure the filesystem is consistent and calls the fs's
1276 * freeze_fs. Subsequent calls to this without first thawing the fs will return
1279 * During this function, sb->s_writers.frozen goes through these values:
1281 * SB_UNFROZEN: File system is normal, all writes progress as usual.
1283 * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
1284 * writes should be blocked, though page faults are still allowed. We wait for
1285 * all writes to complete and then proceed to the next stage.
1287 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
1288 * but internal fs threads can still modify the filesystem (although they
1289 * should not dirty new pages or inodes), writeback can run etc. After waiting
1290 * for all running page faults we sync the filesystem which will clean all
1291 * dirty pages and inodes (no new dirty pages or inodes can be created when
1294 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
1295 * modification are blocked (e.g. XFS preallocation truncation on inode
1296 * reclaim). This is usually implemented by blocking new transactions for
1297 * filesystems that have them and need this additional guard. After all
1298 * internal writers are finished we call ->freeze_fs() to finish filesystem
1299 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
1300 * mostly auxiliary for filesystems to verify they do not modify frozen fs.
1302 * sb->s_writers.frozen is protected by sb->s_umount.
1304 int freeze_super(struct super_block *sb)
1308 atomic_inc(&sb->s_active);
1309 down_write(&sb->s_umount);
1310 if (sb->s_writers.frozen != SB_UNFROZEN) {
1311 deactivate_locked_super(sb);
1315 if (!(sb->s_flags & MS_BORN)) {
1316 up_write(&sb->s_umount);
1317 return 0; /* sic - it's "nothing to do" */
1320 if (sb->s_flags & MS_RDONLY) {
1321 /* Nothing to do really... */
1322 sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1323 up_write(&sb->s_umount);
1327 /* From now on, no new normal writers can start */
1328 sb->s_writers.frozen = SB_FREEZE_WRITE;
1331 /* Release s_umount to preserve sb_start_write -> s_umount ordering */
1332 up_write(&sb->s_umount);
1334 sb_wait_write(sb, SB_FREEZE_WRITE);
1336 /* Now we go and block page faults... */
1337 down_write(&sb->s_umount);
1338 sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
1341 sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
1343 /* All writers are done so after syncing there won't be dirty data */
1344 sync_filesystem(sb);
1346 /* Now wait for internal filesystem counter */
1347 sb->s_writers.frozen = SB_FREEZE_FS;
1349 sb_wait_write(sb, SB_FREEZE_FS);
1351 if (sb->s_op->freeze_fs) {
1352 ret = sb->s_op->freeze_fs(sb);
1355 "VFS:Filesystem freeze failed\n");
1356 sb->s_writers.frozen = SB_UNFROZEN;
1358 wake_up(&sb->s_writers.wait_unfrozen);
1359 deactivate_locked_super(sb);
1364 * This is just for debugging purposes so that fs can warn if it
1365 * sees write activity when frozen is set to SB_FREEZE_COMPLETE.
1367 sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1368 up_write(&sb->s_umount);
1371 EXPORT_SYMBOL(freeze_super);
1374 * thaw_super -- unlock filesystem
1375 * @sb: the super to thaw
1377 * Unlocks the filesystem and marks it writeable again after freeze_super().
1379 int thaw_super(struct super_block *sb)
1383 down_write(&sb->s_umount);
1384 if (sb->s_writers.frozen == SB_UNFROZEN) {
1385 up_write(&sb->s_umount);
1389 if (sb->s_flags & MS_RDONLY)
1392 if (sb->s_op->unfreeze_fs) {
1393 error = sb->s_op->unfreeze_fs(sb);
1396 "VFS:Filesystem thaw failed\n");
1397 up_write(&sb->s_umount);
1403 sb->s_writers.frozen = SB_UNFROZEN;
1405 wake_up(&sb->s_writers.wait_unfrozen);
1406 deactivate_locked_super(sb);
1410 EXPORT_SYMBOL(thaw_super);