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1/*
2 * linux/fs/super.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
6 * super.c contains code to handle: - mount structures
7 * - super-block tables
8 * - filesystem drivers list
9 * - mount system call
10 * - umount system call
11 * - ustat system call
12 *
13 * GK 2/5/95 - Changed to support mounting the root fs via NFS
14 *
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
21 */
22
23#include <linux/module.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 "internal.h"
36
37
38LIST_HEAD(super_blocks);
39DEFINE_SPINLOCK(sb_lock);
40
41/*
42 * One thing we have to be careful of with a per-sb shrinker is that we don't
43 * drop the last active reference to the superblock from within the shrinker.
44 * If that happens we could trigger unregistering the shrinker from within the
45 * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
46 * take a passive reference to the superblock to avoid this from occurring.
47 */
48static int prune_super(struct shrinker *shrink, struct shrink_control *sc)
49{
50 struct super_block *sb;
51 int fs_objects = 0;
52 int total_objects;
53
54 sb = container_of(shrink, struct super_block, s_shrink);
55
56 /*
57 * Deadlock avoidance. We may hold various FS locks, and we don't want
58 * to recurse into the FS that called us in clear_inode() and friends..
59 */
60 if (sc->nr_to_scan && !(sc->gfp_mask & __GFP_FS))
61 return -1;
62
63 if (!grab_super_passive(sb))
64 return -1;
65
66 if (sb->s_op && sb->s_op->nr_cached_objects)
67 fs_objects = sb->s_op->nr_cached_objects(sb);
68
69 total_objects = sb->s_nr_dentry_unused +
70 sb->s_nr_inodes_unused + fs_objects + 1;
71
72 if (sc->nr_to_scan) {
73 int dentries;
74 int inodes;
75
76 /* proportion the scan between the caches */
77 dentries = (sc->nr_to_scan * sb->s_nr_dentry_unused) /
78 total_objects;
79 inodes = (sc->nr_to_scan * sb->s_nr_inodes_unused) /
80 total_objects;
81 if (fs_objects)
82 fs_objects = (sc->nr_to_scan * fs_objects) /
83 total_objects;
84 /*
85 * prune the dcache first as the icache is pinned by it, then
86 * prune the icache, followed by the filesystem specific caches
87 */
88 prune_dcache_sb(sb, dentries);
89 prune_icache_sb(sb, inodes);
90
91 if (fs_objects && sb->s_op->free_cached_objects) {
92 sb->s_op->free_cached_objects(sb, fs_objects);
93 fs_objects = sb->s_op->nr_cached_objects(sb);
94 }
95 total_objects = sb->s_nr_dentry_unused +
96 sb->s_nr_inodes_unused + fs_objects;
97 }
98
99 total_objects = (total_objects / 100) * sysctl_vfs_cache_pressure;
100 drop_super(sb);
101 return total_objects;
102}
103
104/**
105 * alloc_super - create new superblock
106 * @type: filesystem type superblock should belong to
107 *
108 * Allocates and initializes a new &struct super_block. alloc_super()
109 * returns a pointer new superblock or %NULL if allocation had failed.
110 */
111static struct super_block *alloc_super(struct file_system_type *type)
112{
113 struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
114 static const struct super_operations default_op;
115
116 if (s) {
117 if (security_sb_alloc(s)) {
118 kfree(s);
119 s = NULL;
120 goto out;
121 }
122#ifdef CONFIG_SMP
123 s->s_files = alloc_percpu(struct list_head);
124 if (!s->s_files) {
125 security_sb_free(s);
126 kfree(s);
127 s = NULL;
128 goto out;
129 } else {
130 int i;
131
132 for_each_possible_cpu(i)
133 INIT_LIST_HEAD(per_cpu_ptr(s->s_files, i));
134 }
135#else
136 INIT_LIST_HEAD(&s->s_files);
137#endif
138 s->s_bdi = &default_backing_dev_info;
139 INIT_LIST_HEAD(&s->s_instances);
140 INIT_HLIST_BL_HEAD(&s->s_anon);
141 INIT_LIST_HEAD(&s->s_inodes);
142 INIT_LIST_HEAD(&s->s_dentry_lru);
143 INIT_LIST_HEAD(&s->s_inode_lru);
144 spin_lock_init(&s->s_inode_lru_lock);
145 init_rwsem(&s->s_umount);
146 mutex_init(&s->s_lock);
147 lockdep_set_class(&s->s_umount, &type->s_umount_key);
148 /*
149 * The locking rules for s_lock are up to the
150 * filesystem. For example ext3fs has different
151 * lock ordering than usbfs:
152 */
153 lockdep_set_class(&s->s_lock, &type->s_lock_key);
154 /*
155 * sget() can have s_umount recursion.
156 *
157 * When it cannot find a suitable sb, it allocates a new
158 * one (this one), and tries again to find a suitable old
159 * one.
160 *
161 * In case that succeeds, it will acquire the s_umount
162 * lock of the old one. Since these are clearly distrinct
163 * locks, and this object isn't exposed yet, there's no
164 * risk of deadlocks.
165 *
166 * Annotate this by putting this lock in a different
167 * subclass.
168 */
169 down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
170 s->s_count = 1;
171 atomic_set(&s->s_active, 1);
172 mutex_init(&s->s_vfs_rename_mutex);
173 lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
174 mutex_init(&s->s_dquot.dqio_mutex);
175 mutex_init(&s->s_dquot.dqonoff_mutex);
176 init_rwsem(&s->s_dquot.dqptr_sem);
177 init_waitqueue_head(&s->s_wait_unfrozen);
178 s->s_maxbytes = MAX_NON_LFS;
179 s->s_op = &default_op;
180 s->s_time_gran = 1000000000;
181 s->cleancache_poolid = -1;
182
183 s->s_shrink.seeks = DEFAULT_SEEKS;
184 s->s_shrink.shrink = prune_super;
185 s->s_shrink.batch = 1024;
186 }
187out:
188 return s;
189}
190
191/**
192 * destroy_super - frees a superblock
193 * @s: superblock to free
194 *
195 * Frees a superblock.
196 */
197static inline void destroy_super(struct super_block *s)
198{
199#ifdef CONFIG_SMP
200 free_percpu(s->s_files);
201#endif
202 security_sb_free(s);
203 kfree(s->s_subtype);
204 kfree(s->s_options);
205 kfree(s);
206}
207
208/* Superblock refcounting */
209
210/*
211 * Drop a superblock's refcount. The caller must hold sb_lock.
212 */
213void __put_super(struct super_block *sb)
214{
215 if (!--sb->s_count) {
216 list_del_init(&sb->s_list);
217 destroy_super(sb);
218 }
219}
220
221/**
222 * put_super - drop a temporary reference to superblock
223 * @sb: superblock in question
224 *
225 * Drops a temporary reference, frees superblock if there's no
226 * references left.
227 */
228void put_super(struct super_block *sb)
229{
230 spin_lock(&sb_lock);
231 __put_super(sb);
232 spin_unlock(&sb_lock);
233}
234
235
236/**
237 * deactivate_locked_super - drop an active reference to superblock
238 * @s: superblock to deactivate
239 *
240 * Drops an active reference to superblock, converting it into a temprory
241 * one if there is no other active references left. In that case we
242 * tell fs driver to shut it down and drop the temporary reference we
243 * had just acquired.
244 *
245 * Caller holds exclusive lock on superblock; that lock is released.
246 */
247void deactivate_locked_super(struct super_block *s)
248{
249 struct file_system_type *fs = s->s_type;
250 if (atomic_dec_and_test(&s->s_active)) {
251 cleancache_flush_fs(s);
252 fs->kill_sb(s);
253
254 /* caches are now gone, we can safely kill the shrinker now */
255 unregister_shrinker(&s->s_shrink);
256
257 /*
258 * We need to call rcu_barrier so all the delayed rcu free
259 * inodes are flushed before we release the fs module.
260 */
261 rcu_barrier();
262 put_filesystem(fs);
263 put_super(s);
264 } else {
265 up_write(&s->s_umount);
266 }
267}
268
269EXPORT_SYMBOL(deactivate_locked_super);
270
271/**
272 * deactivate_super - drop an active reference to superblock
273 * @s: superblock to deactivate
274 *
275 * Variant of deactivate_locked_super(), except that superblock is *not*
276 * locked by caller. If we are going to drop the final active reference,
277 * lock will be acquired prior to that.
278 */
279void deactivate_super(struct super_block *s)
280{
281 if (!atomic_add_unless(&s->s_active, -1, 1)) {
282 down_write(&s->s_umount);
283 deactivate_locked_super(s);
284 }
285}
286
287EXPORT_SYMBOL(deactivate_super);
288
289/**
290 * grab_super - acquire an active reference
291 * @s: reference we are trying to make active
292 *
293 * Tries to acquire an active reference. grab_super() is used when we
294 * had just found a superblock in super_blocks or fs_type->fs_supers
295 * and want to turn it into a full-blown active reference. grab_super()
296 * is called with sb_lock held and drops it. Returns 1 in case of
297 * success, 0 if we had failed (superblock contents was already dead or
298 * dying when grab_super() had been called).
299 */
300static int grab_super(struct super_block *s) __releases(sb_lock)
301{
302 if (atomic_inc_not_zero(&s->s_active)) {
303 spin_unlock(&sb_lock);
304 return 1;
305 }
306 /* it's going away */
307 s->s_count++;
308 spin_unlock(&sb_lock);
309 /* wait for it to die */
310 down_write(&s->s_umount);
311 up_write(&s->s_umount);
312 put_super(s);
313 return 0;
314}
315
316/*
317 * grab_super_passive - acquire a passive reference
318 * @s: reference we are trying to grab
319 *
320 * Tries to acquire a passive reference. This is used in places where we
321 * cannot take an active reference but we need to ensure that the
322 * superblock does not go away while we are working on it. It returns
323 * false if a reference was not gained, and returns true with the s_umount
324 * lock held in read mode if a reference is gained. On successful return,
325 * the caller must drop the s_umount lock and the passive reference when
326 * done.
327 */
328bool grab_super_passive(struct super_block *sb)
329{
330 spin_lock(&sb_lock);
331 if (list_empty(&sb->s_instances)) {
332 spin_unlock(&sb_lock);
333 return false;
334 }
335
336 sb->s_count++;
337 spin_unlock(&sb_lock);
338
339 if (down_read_trylock(&sb->s_umount)) {
340 if (sb->s_root)
341 return true;
342 up_read(&sb->s_umount);
343 }
344
345 put_super(sb);
346 return false;
347}
348
349/*
350 * Superblock locking. We really ought to get rid of these two.
351 */
352void lock_super(struct super_block * sb)
353{
354 mutex_lock(&sb->s_lock);
355}
356
357void unlock_super(struct super_block * sb)
358{
359 mutex_unlock(&sb->s_lock);
360}
361
362EXPORT_SYMBOL(lock_super);
363EXPORT_SYMBOL(unlock_super);
364
365/**
366 * generic_shutdown_super - common helper for ->kill_sb()
367 * @sb: superblock to kill
368 *
369 * generic_shutdown_super() does all fs-independent work on superblock
370 * shutdown. Typical ->kill_sb() should pick all fs-specific objects
371 * that need destruction out of superblock, call generic_shutdown_super()
372 * and release aforementioned objects. Note: dentries and inodes _are_
373 * taken care of and do not need specific handling.
374 *
375 * Upon calling this function, the filesystem may no longer alter or
376 * rearrange the set of dentries belonging to this super_block, nor may it
377 * change the attachments of dentries to inodes.
378 */
379void generic_shutdown_super(struct super_block *sb)
380{
381 const struct super_operations *sop = sb->s_op;
382
383 if (sb->s_root) {
384 shrink_dcache_for_umount(sb);
385 sync_filesystem(sb);
386 sb->s_flags &= ~MS_ACTIVE;
387
388 fsnotify_unmount_inodes(&sb->s_inodes);
389
390 evict_inodes(sb);
391
392 if (sop->put_super)
393 sop->put_super(sb);
394
395 if (!list_empty(&sb->s_inodes)) {
396 printk("VFS: Busy inodes after unmount of %s. "
397 "Self-destruct in 5 seconds. Have a nice day...\n",
398 sb->s_id);
399 }
400 }
401 spin_lock(&sb_lock);
402 /* should be initialized for __put_super_and_need_restart() */
403 list_del_init(&sb->s_instances);
404 spin_unlock(&sb_lock);
405 up_write(&sb->s_umount);
406}
407
408EXPORT_SYMBOL(generic_shutdown_super);
409
410/**
411 * sget - find or create a superblock
412 * @type: filesystem type superblock should belong to
413 * @test: comparison callback
414 * @set: setup callback
415 * @data: argument to each of them
416 */
417struct super_block *sget(struct file_system_type *type,
418 int (*test)(struct super_block *,void *),
419 int (*set)(struct super_block *,void *),
420 void *data)
421{
422 struct super_block *s = NULL;
423 struct super_block *old;
424 int err;
425
426retry:
427 spin_lock(&sb_lock);
428 if (test) {
429 list_for_each_entry(old, &type->fs_supers, s_instances) {
430 if (!test(old, data))
431 continue;
432 if (!grab_super(old))
433 goto retry;
434 if (s) {
435 up_write(&s->s_umount);
436 destroy_super(s);
437 s = NULL;
438 }
439 down_write(&old->s_umount);
440 if (unlikely(!(old->s_flags & MS_BORN))) {
441 deactivate_locked_super(old);
442 goto retry;
443 }
444 return old;
445 }
446 }
447 if (!s) {
448 spin_unlock(&sb_lock);
449 s = alloc_super(type);
450 if (!s)
451 return ERR_PTR(-ENOMEM);
452 goto retry;
453 }
454
455 err = set(s, data);
456 if (err) {
457 spin_unlock(&sb_lock);
458 up_write(&s->s_umount);
459 destroy_super(s);
460 return ERR_PTR(err);
461 }
462 s->s_type = type;
463 strlcpy(s->s_id, type->name, sizeof(s->s_id));
464 list_add_tail(&s->s_list, &super_blocks);
465 list_add(&s->s_instances, &type->fs_supers);
466 spin_unlock(&sb_lock);
467 get_filesystem(type);
468 register_shrinker(&s->s_shrink);
469 return s;
470}
471
472EXPORT_SYMBOL(sget);
473
474void drop_super(struct super_block *sb)
475{
476 up_read(&sb->s_umount);
477 put_super(sb);
478}
479
480EXPORT_SYMBOL(drop_super);
481
482/**
483 * sync_supers - helper for periodic superblock writeback
484 *
485 * Call the write_super method if present on all dirty superblocks in
486 * the system. This is for the periodic writeback used by most older
487 * filesystems. For data integrity superblock writeback use
488 * sync_filesystems() instead.
489 *
490 * Note: check the dirty flag before waiting, so we don't
491 * hold up the sync while mounting a device. (The newly
492 * mounted device won't need syncing.)
493 */
494void sync_supers(void)
495{
496 struct super_block *sb, *p = NULL;
497
498 spin_lock(&sb_lock);
499 list_for_each_entry(sb, &super_blocks, s_list) {
500 if (list_empty(&sb->s_instances))
501 continue;
502 if (sb->s_op->write_super && sb->s_dirt) {
503 sb->s_count++;
504 spin_unlock(&sb_lock);
505
506 down_read(&sb->s_umount);
507 if (sb->s_root && sb->s_dirt)
508 sb->s_op->write_super(sb);
509 up_read(&sb->s_umount);
510
511 spin_lock(&sb_lock);
512 if (p)
513 __put_super(p);
514 p = sb;
515 }
516 }
517 if (p)
518 __put_super(p);
519 spin_unlock(&sb_lock);
520}
521
522/**
523 * iterate_supers - call function for all active superblocks
524 * @f: function to call
525 * @arg: argument to pass to it
526 *
527 * Scans the superblock list and calls given function, passing it
528 * locked superblock and given argument.
529 */
530void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
531{
532 struct super_block *sb, *p = NULL;
533
534 spin_lock(&sb_lock);
535 list_for_each_entry(sb, &super_blocks, s_list) {
536 if (list_empty(&sb->s_instances))
537 continue;
538 sb->s_count++;
539 spin_unlock(&sb_lock);
540
541 down_read(&sb->s_umount);
542 if (sb->s_root)
543 f(sb, arg);
544 up_read(&sb->s_umount);
545
546 spin_lock(&sb_lock);
547 if (p)
548 __put_super(p);
549 p = sb;
550 }
551 if (p)
552 __put_super(p);
553 spin_unlock(&sb_lock);
554}
555
556/**
557 * iterate_supers_type - call function for superblocks of given type
558 * @type: fs type
559 * @f: function to call
560 * @arg: argument to pass to it
561 *
562 * Scans the superblock list and calls given function, passing it
563 * locked superblock and given argument.
564 */
565void iterate_supers_type(struct file_system_type *type,
566 void (*f)(struct super_block *, void *), void *arg)
567{
568 struct super_block *sb, *p = NULL;
569
570 spin_lock(&sb_lock);
571 list_for_each_entry(sb, &type->fs_supers, s_instances) {
572 sb->s_count++;
573 spin_unlock(&sb_lock);
574
575 down_read(&sb->s_umount);
576 if (sb->s_root)
577 f(sb, arg);
578 up_read(&sb->s_umount);
579
580 spin_lock(&sb_lock);
581 if (p)
582 __put_super(p);
583 p = sb;
584 }
585 if (p)
586 __put_super(p);
587 spin_unlock(&sb_lock);
588}
589
590EXPORT_SYMBOL(iterate_supers_type);
591
592/**
593 * get_super - get the superblock of a device
594 * @bdev: device to get the superblock for
595 *
596 * Scans the superblock list and finds the superblock of the file system
597 * mounted on the device given. %NULL is returned if no match is found.
598 */
599
600struct super_block *get_super(struct block_device *bdev)
601{
602 struct super_block *sb;
603
604 if (!bdev)
605 return NULL;
606
607 spin_lock(&sb_lock);
608rescan:
609 list_for_each_entry(sb, &super_blocks, s_list) {
610 if (list_empty(&sb->s_instances))
611 continue;
612 if (sb->s_bdev == bdev) {
613 sb->s_count++;
614 spin_unlock(&sb_lock);
615 down_read(&sb->s_umount);
616 /* still alive? */
617 if (sb->s_root)
618 return sb;
619 up_read(&sb->s_umount);
620 /* nope, got unmounted */
621 spin_lock(&sb_lock);
622 __put_super(sb);
623 goto rescan;
624 }
625 }
626 spin_unlock(&sb_lock);
627 return NULL;
628}
629
630EXPORT_SYMBOL(get_super);
631
632/**
633 * get_active_super - get an active reference to the superblock of a device
634 * @bdev: device to get the superblock for
635 *
636 * Scans the superblock list and finds the superblock of the file system
637 * mounted on the device given. Returns the superblock with an active
638 * reference or %NULL if none was found.
639 */
640struct super_block *get_active_super(struct block_device *bdev)
641{
642 struct super_block *sb;
643
644 if (!bdev)
645 return NULL;
646
647restart:
648 spin_lock(&sb_lock);
649 list_for_each_entry(sb, &super_blocks, s_list) {
650 if (list_empty(&sb->s_instances))
651 continue;
652 if (sb->s_bdev == bdev) {
653 if (grab_super(sb)) /* drops sb_lock */
654 return sb;
655 else
656 goto restart;
657 }
658 }
659 spin_unlock(&sb_lock);
660 return NULL;
661}
662
663struct super_block *user_get_super(dev_t dev)
664{
665 struct super_block *sb;
666
667 spin_lock(&sb_lock);
668rescan:
669 list_for_each_entry(sb, &super_blocks, s_list) {
670 if (list_empty(&sb->s_instances))
671 continue;
672 if (sb->s_dev == dev) {
673 sb->s_count++;
674 spin_unlock(&sb_lock);
675 down_read(&sb->s_umount);
676 /* still alive? */
677 if (sb->s_root)
678 return sb;
679 up_read(&sb->s_umount);
680 /* nope, got unmounted */
681 spin_lock(&sb_lock);
682 __put_super(sb);
683 goto rescan;
684 }
685 }
686 spin_unlock(&sb_lock);
687 return NULL;
688}
689
690/**
691 * do_remount_sb - asks filesystem to change mount options.
692 * @sb: superblock in question
693 * @flags: numeric part of options
694 * @data: the rest of options
695 * @force: whether or not to force the change
696 *
697 * Alters the mount options of a mounted file system.
698 */
699int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
700{
701 int retval;
702 int remount_ro;
703
704 if (sb->s_frozen != SB_UNFROZEN)
705 return -EBUSY;
706
707#ifdef CONFIG_BLOCK
708 if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
709 return -EACCES;
710#endif
711
712 if (flags & MS_RDONLY)
713 acct_auto_close(sb);
714 shrink_dcache_sb(sb);
715 sync_filesystem(sb);
716
717 remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY);
718
719 /* If we are remounting RDONLY and current sb is read/write,
720 make sure there are no rw files opened */
721 if (remount_ro) {
722 if (force)
723 mark_files_ro(sb);
724 else if (!fs_may_remount_ro(sb))
725 return -EBUSY;
726 }
727
728 if (sb->s_op->remount_fs) {
729 retval = sb->s_op->remount_fs(sb, &flags, data);
730 if (retval)
731 return retval;
732 }
733 sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
734
735 /*
736 * Some filesystems modify their metadata via some other path than the
737 * bdev buffer cache (eg. use a private mapping, or directories in
738 * pagecache, etc). Also file data modifications go via their own
739 * mappings. So If we try to mount readonly then copy the filesystem
740 * from bdev, we could get stale data, so invalidate it to give a best
741 * effort at coherency.
742 */
743 if (remount_ro && sb->s_bdev)
744 invalidate_bdev(sb->s_bdev);
745 return 0;
746}
747
748static void do_emergency_remount(struct work_struct *work)
749{
750 struct super_block *sb, *p = NULL;
751
752 spin_lock(&sb_lock);
753 list_for_each_entry(sb, &super_blocks, s_list) {
754 if (list_empty(&sb->s_instances))
755 continue;
756 sb->s_count++;
757 spin_unlock(&sb_lock);
758 down_write(&sb->s_umount);
759 if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
760 /*
761 * What lock protects sb->s_flags??
762 */
763 do_remount_sb(sb, MS_RDONLY, NULL, 1);
764 }
765 up_write(&sb->s_umount);
766 spin_lock(&sb_lock);
767 if (p)
768 __put_super(p);
769 p = sb;
770 }
771 if (p)
772 __put_super(p);
773 spin_unlock(&sb_lock);
774 kfree(work);
775 printk("Emergency Remount complete\n");
776}
777
778void emergency_remount(void)
779{
780 struct work_struct *work;
781
782 work = kmalloc(sizeof(*work), GFP_ATOMIC);
783 if (work) {
784 INIT_WORK(work, do_emergency_remount);
785 schedule_work(work);
786 }
787}
788
789/*
790 * Unnamed block devices are dummy devices used by virtual
791 * filesystems which don't use real block-devices. -- jrs
792 */
793
794static DEFINE_IDA(unnamed_dev_ida);
795static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
796static int unnamed_dev_start = 0; /* don't bother trying below it */
797
798int get_anon_bdev(dev_t *p)
799{
800 int dev;
801 int error;
802
803 retry:
804 if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
805 return -ENOMEM;
806 spin_lock(&unnamed_dev_lock);
807 error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);
808 if (!error)
809 unnamed_dev_start = dev + 1;
810 spin_unlock(&unnamed_dev_lock);
811 if (error == -EAGAIN)
812 /* We raced and lost with another CPU. */
813 goto retry;
814 else if (error)
815 return -EAGAIN;
816
817 if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
818 spin_lock(&unnamed_dev_lock);
819 ida_remove(&unnamed_dev_ida, dev);
820 if (unnamed_dev_start > dev)
821 unnamed_dev_start = dev;
822 spin_unlock(&unnamed_dev_lock);
823 return -EMFILE;
824 }
825 *p = MKDEV(0, dev & MINORMASK);
826 return 0;
827}
828EXPORT_SYMBOL(get_anon_bdev);
829
830void free_anon_bdev(dev_t dev)
831{
832 int slot = MINOR(dev);
833 spin_lock(&unnamed_dev_lock);
834 ida_remove(&unnamed_dev_ida, slot);
835 if (slot < unnamed_dev_start)
836 unnamed_dev_start = slot;
837 spin_unlock(&unnamed_dev_lock);
838}
839EXPORT_SYMBOL(free_anon_bdev);
840
841int set_anon_super(struct super_block *s, void *data)
842{
843 int error = get_anon_bdev(&s->s_dev);
844 if (!error)
845 s->s_bdi = &noop_backing_dev_info;
846 return error;
847}
848
849EXPORT_SYMBOL(set_anon_super);
850
851void kill_anon_super(struct super_block *sb)
852{
853 dev_t dev = sb->s_dev;
854 generic_shutdown_super(sb);
855 free_anon_bdev(dev);
856}
857
858EXPORT_SYMBOL(kill_anon_super);
859
860void kill_litter_super(struct super_block *sb)
861{
862 if (sb->s_root)
863 d_genocide(sb->s_root);
864 kill_anon_super(sb);
865}
866
867EXPORT_SYMBOL(kill_litter_super);
868
869static int ns_test_super(struct super_block *sb, void *data)
870{
871 return sb->s_fs_info == data;
872}
873
874static int ns_set_super(struct super_block *sb, void *data)
875{
876 sb->s_fs_info = data;
877 return set_anon_super(sb, NULL);
878}
879
880struct dentry *mount_ns(struct file_system_type *fs_type, int flags,
881 void *data, int (*fill_super)(struct super_block *, void *, int))
882{
883 struct super_block *sb;
884
885 sb = sget(fs_type, ns_test_super, ns_set_super, data);
886 if (IS_ERR(sb))
887 return ERR_CAST(sb);
888
889 if (!sb->s_root) {
890 int err;
891 sb->s_flags = flags;
892 err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
893 if (err) {
894 deactivate_locked_super(sb);
895 return ERR_PTR(err);
896 }
897
898 sb->s_flags |= MS_ACTIVE;
899 }
900
901 return dget(sb->s_root);
902}
903
904EXPORT_SYMBOL(mount_ns);
905
906#ifdef CONFIG_BLOCK
907static int set_bdev_super(struct super_block *s, void *data)
908{
909 s->s_bdev = data;
910 s->s_dev = s->s_bdev->bd_dev;
911
912 /*
913 * We set the bdi here to the queue backing, file systems can
914 * overwrite this in ->fill_super()
915 */
916 s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info;
917 return 0;
918}
919
920static int test_bdev_super(struct super_block *s, void *data)
921{
922 return (void *)s->s_bdev == data;
923}
924
925struct dentry *mount_bdev(struct file_system_type *fs_type,
926 int flags, const char *dev_name, void *data,
927 int (*fill_super)(struct super_block *, void *, int))
928{
929 struct block_device *bdev;
930 struct super_block *s;
931 fmode_t mode = FMODE_READ | FMODE_EXCL;
932 int error = 0;
933
934 if (!(flags & MS_RDONLY))
935 mode |= FMODE_WRITE;
936
937 bdev = blkdev_get_by_path(dev_name, mode, fs_type);
938 if (IS_ERR(bdev))
939 return ERR_CAST(bdev);
940
941 /*
942 * once the super is inserted into the list by sget, s_umount
943 * will protect the lockfs code from trying to start a snapshot
944 * while we are mounting
945 */
946 mutex_lock(&bdev->bd_fsfreeze_mutex);
947 if (bdev->bd_fsfreeze_count > 0) {
948 mutex_unlock(&bdev->bd_fsfreeze_mutex);
949 error = -EBUSY;
950 goto error_bdev;
951 }
952 s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
953 mutex_unlock(&bdev->bd_fsfreeze_mutex);
954 if (IS_ERR(s))
955 goto error_s;
956
957 if (s->s_root) {
958 if ((flags ^ s->s_flags) & MS_RDONLY) {
959 deactivate_locked_super(s);
960 error = -EBUSY;
961 goto error_bdev;
962 }
963
964 /*
965 * s_umount nests inside bd_mutex during
966 * __invalidate_device(). blkdev_put() acquires
967 * bd_mutex and can't be called under s_umount. Drop
968 * s_umount temporarily. This is safe as we're
969 * holding an active reference.
970 */
971 up_write(&s->s_umount);
972 blkdev_put(bdev, mode);
973 down_write(&s->s_umount);
974 } else {
975 char b[BDEVNAME_SIZE];
976
977 s->s_flags = flags | MS_NOSEC;
978 s->s_mode = mode;
979 strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
980 sb_set_blocksize(s, block_size(bdev));
981 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
982 if (error) {
983 deactivate_locked_super(s);
984 goto error;
985 }
986
987 s->s_flags |= MS_ACTIVE;
988 bdev->bd_super = s;
989 }
990
991 return dget(s->s_root);
992
993error_s:
994 error = PTR_ERR(s);
995error_bdev:
996 blkdev_put(bdev, mode);
997error:
998 return ERR_PTR(error);
999}
1000EXPORT_SYMBOL(mount_bdev);
1001
1002void kill_block_super(struct super_block *sb)
1003{
1004 struct block_device *bdev = sb->s_bdev;
1005 fmode_t mode = sb->s_mode;
1006
1007 bdev->bd_super = NULL;
1008 generic_shutdown_super(sb);
1009 sync_blockdev(bdev);
1010 WARN_ON_ONCE(!(mode & FMODE_EXCL));
1011 blkdev_put(bdev, mode | FMODE_EXCL);
1012}
1013
1014EXPORT_SYMBOL(kill_block_super);
1015#endif
1016
1017struct dentry *mount_nodev(struct file_system_type *fs_type,
1018 int flags, void *data,
1019 int (*fill_super)(struct super_block *, void *, int))
1020{
1021 int error;
1022 struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
1023
1024 if (IS_ERR(s))
1025 return ERR_CAST(s);
1026
1027 s->s_flags = flags;
1028
1029 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
1030 if (error) {
1031 deactivate_locked_super(s);
1032 return ERR_PTR(error);
1033 }
1034 s->s_flags |= MS_ACTIVE;
1035 return dget(s->s_root);
1036}
1037EXPORT_SYMBOL(mount_nodev);
1038
1039static int compare_single(struct super_block *s, void *p)
1040{
1041 return 1;
1042}
1043
1044struct dentry *mount_single(struct file_system_type *fs_type,
1045 int flags, void *data,
1046 int (*fill_super)(struct super_block *, void *, int))
1047{
1048 struct super_block *s;
1049 int error;
1050
1051 s = sget(fs_type, compare_single, set_anon_super, NULL);
1052 if (IS_ERR(s))
1053 return ERR_CAST(s);
1054 if (!s->s_root) {
1055 s->s_flags = flags;
1056 error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
1057 if (error) {
1058 deactivate_locked_super(s);
1059 return ERR_PTR(error);
1060 }
1061 s->s_flags |= MS_ACTIVE;
1062 } else {
1063 do_remount_sb(s, flags, data, 0);
1064 }
1065 return dget(s->s_root);
1066}
1067EXPORT_SYMBOL(mount_single);
1068
1069struct dentry *
1070mount_fs(struct file_system_type *type, int flags, const char *name, void *data)
1071{
1072 struct dentry *root;
1073 struct super_block *sb;
1074 char *secdata = NULL;
1075 int error = -ENOMEM;
1076
1077 if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
1078 secdata = alloc_secdata();
1079 if (!secdata)
1080 goto out;
1081
1082 error = security_sb_copy_data(data, secdata);
1083 if (error)
1084 goto out_free_secdata;
1085 }
1086
1087 root = type->mount(type, flags, name, data);
1088 if (IS_ERR(root)) {
1089 error = PTR_ERR(root);
1090 goto out_free_secdata;
1091 }
1092 sb = root->d_sb;
1093 BUG_ON(!sb);
1094 WARN_ON(!sb->s_bdi);
1095 WARN_ON(sb->s_bdi == &default_backing_dev_info);
1096 sb->s_flags |= MS_BORN;
1097
1098 error = security_sb_kern_mount(sb, flags, secdata);
1099 if (error)
1100 goto out_sb;
1101
1102 /*
1103 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1104 * but s_maxbytes was an unsigned long long for many releases. Throw
1105 * this warning for a little while to try and catch filesystems that
1106 * violate this rule.
1107 */
1108 WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
1109 "negative value (%lld)\n", type->name, sb->s_maxbytes);
1110
1111 up_write(&sb->s_umount);
1112 free_secdata(secdata);
1113 return root;
1114out_sb:
1115 dput(root);
1116 deactivate_locked_super(sb);
1117out_free_secdata:
1118 free_secdata(secdata);
1119out:
1120 return ERR_PTR(error);
1121}
1122
1123/**
1124 * freeze_super - lock the filesystem and force it into a consistent state
1125 * @sb: the super to lock
1126 *
1127 * Syncs the super to make sure the filesystem is consistent and calls the fs's
1128 * freeze_fs. Subsequent calls to this without first thawing the fs will return
1129 * -EBUSY.
1130 */
1131int freeze_super(struct super_block *sb)
1132{
1133 int ret;
1134
1135 atomic_inc(&sb->s_active);
1136 down_write(&sb->s_umount);
1137 if (sb->s_frozen) {
1138 deactivate_locked_super(sb);
1139 return -EBUSY;
1140 }
1141
1142 if (sb->s_flags & MS_RDONLY) {
1143 sb->s_frozen = SB_FREEZE_TRANS;
1144 smp_wmb();
1145 up_write(&sb->s_umount);
1146 return 0;
1147 }
1148
1149 sb->s_frozen = SB_FREEZE_WRITE;
1150 smp_wmb();
1151
1152 sync_filesystem(sb);
1153
1154 sb->s_frozen = SB_FREEZE_TRANS;
1155 smp_wmb();
1156
1157 sync_blockdev(sb->s_bdev);
1158 if (sb->s_op->freeze_fs) {
1159 ret = sb->s_op->freeze_fs(sb);
1160 if (ret) {
1161 printk(KERN_ERR
1162 "VFS:Filesystem freeze failed\n");
1163 sb->s_frozen = SB_UNFROZEN;
1164 deactivate_locked_super(sb);
1165 return ret;
1166 }
1167 }
1168 up_write(&sb->s_umount);
1169 return 0;
1170}
1171EXPORT_SYMBOL(freeze_super);
1172
1173/**
1174 * thaw_super -- unlock filesystem
1175 * @sb: the super to thaw
1176 *
1177 * Unlocks the filesystem and marks it writeable again after freeze_super().
1178 */
1179int thaw_super(struct super_block *sb)
1180{
1181 int error;
1182
1183 down_write(&sb->s_umount);
1184 if (sb->s_frozen == SB_UNFROZEN) {
1185 up_write(&sb->s_umount);
1186 return -EINVAL;
1187 }
1188
1189 if (sb->s_flags & MS_RDONLY)
1190 goto out;
1191
1192 if (sb->s_op->unfreeze_fs) {
1193 error = sb->s_op->unfreeze_fs(sb);
1194 if (error) {
1195 printk(KERN_ERR
1196 "VFS:Filesystem thaw failed\n");
1197 sb->s_frozen = SB_FREEZE_TRANS;
1198 up_write(&sb->s_umount);
1199 return error;
1200 }
1201 }
1202
1203out:
1204 sb->s_frozen = SB_UNFROZEN;
1205 smp_wmb();
1206 wake_up(&sb->s_wait_unfrozen);
1207 deactivate_locked_super(sb);
1208
1209 return 0;
1210}
1211EXPORT_SYMBOL(thaw_super);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/fs/super.c
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 *
7 * super.c contains code to handle: - mount structures
8 * - super-block tables
9 * - filesystem drivers list
10 * - mount system call
11 * - umount system call
12 * - ustat system call
13 *
14 * GK 2/5/95 - Changed to support mounting the root fs via NFS
15 *
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
22 */
23
24#include <linux/export.h>
25#include <linux/slab.h>
26#include <linux/blkdev.h>
27#include <linux/mount.h>
28#include <linux/security.h>
29#include <linux/writeback.h> /* for the emergency remount stuff */
30#include <linux/idr.h>
31#include <linux/mutex.h>
32#include <linux/backing-dev.h>
33#include <linux/rculist_bl.h>
34#include <linux/cleancache.h>
35#include <linux/fscrypt.h>
36#include <linux/fsnotify.h>
37#include <linux/lockdep.h>
38#include <linux/user_namespace.h>
39#include <linux/fs_context.h>
40#include <uapi/linux/mount.h>
41#include "internal.h"
42
43static int thaw_super_locked(struct super_block *sb);
44
45static LIST_HEAD(super_blocks);
46static DEFINE_SPINLOCK(sb_lock);
47
48static char *sb_writers_name[SB_FREEZE_LEVELS] = {
49 "sb_writers",
50 "sb_pagefaults",
51 "sb_internal",
52};
53
54/*
55 * One thing we have to be careful of with a per-sb shrinker is that we don't
56 * drop the last active reference to the superblock from within the shrinker.
57 * If that happens we could trigger unregistering the shrinker from within the
58 * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
59 * take a passive reference to the superblock to avoid this from occurring.
60 */
61static unsigned long super_cache_scan(struct shrinker *shrink,
62 struct shrink_control *sc)
63{
64 struct super_block *sb;
65 long fs_objects = 0;
66 long total_objects;
67 long freed = 0;
68 long dentries;
69 long inodes;
70
71 sb = container_of(shrink, struct super_block, s_shrink);
72
73 /*
74 * Deadlock avoidance. We may hold various FS locks, and we don't want
75 * to recurse into the FS that called us in clear_inode() and friends..
76 */
77 if (!(sc->gfp_mask & __GFP_FS))
78 return SHRINK_STOP;
79
80 if (!trylock_super(sb))
81 return SHRINK_STOP;
82
83 if (sb->s_op->nr_cached_objects)
84 fs_objects = sb->s_op->nr_cached_objects(sb, sc);
85
86 inodes = list_lru_shrink_count(&sb->s_inode_lru, sc);
87 dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc);
88 total_objects = dentries + inodes + fs_objects + 1;
89 if (!total_objects)
90 total_objects = 1;
91
92 /* proportion the scan between the caches */
93 dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);
94 inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);
95 fs_objects = mult_frac(sc->nr_to_scan, fs_objects, total_objects);
96
97 /*
98 * prune the dcache first as the icache is pinned by it, then
99 * prune the icache, followed by the filesystem specific caches
100 *
101 * Ensure that we always scan at least one object - memcg kmem
102 * accounting uses this to fully empty the caches.
103 */
104 sc->nr_to_scan = dentries + 1;
105 freed = prune_dcache_sb(sb, sc);
106 sc->nr_to_scan = inodes + 1;
107 freed += prune_icache_sb(sb, sc);
108
109 if (fs_objects) {
110 sc->nr_to_scan = fs_objects + 1;
111 freed += sb->s_op->free_cached_objects(sb, sc);
112 }
113
114 up_read(&sb->s_umount);
115 return freed;
116}
117
118static unsigned long super_cache_count(struct shrinker *shrink,
119 struct shrink_control *sc)
120{
121 struct super_block *sb;
122 long total_objects = 0;
123
124 sb = container_of(shrink, struct super_block, s_shrink);
125
126 /*
127 * We don't call trylock_super() here as it is a scalability bottleneck,
128 * so we're exposed to partial setup state. The shrinker rwsem does not
129 * protect filesystem operations backing list_lru_shrink_count() or
130 * s_op->nr_cached_objects(). Counts can change between
131 * super_cache_count and super_cache_scan, so we really don't need locks
132 * here.
133 *
134 * However, if we are currently mounting the superblock, the underlying
135 * filesystem might be in a state of partial construction and hence it
136 * is dangerous to access it. trylock_super() uses a SB_BORN check to
137 * avoid this situation, so do the same here. The memory barrier is
138 * matched with the one in mount_fs() as we don't hold locks here.
139 */
140 if (!(sb->s_flags & SB_BORN))
141 return 0;
142 smp_rmb();
143
144 if (sb->s_op && sb->s_op->nr_cached_objects)
145 total_objects = sb->s_op->nr_cached_objects(sb, sc);
146
147 total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc);
148 total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc);
149
150 if (!total_objects)
151 return SHRINK_EMPTY;
152
153 total_objects = vfs_pressure_ratio(total_objects);
154 return total_objects;
155}
156
157static void destroy_super_work(struct work_struct *work)
158{
159 struct super_block *s = container_of(work, struct super_block,
160 destroy_work);
161 int i;
162
163 for (i = 0; i < SB_FREEZE_LEVELS; i++)
164 percpu_free_rwsem(&s->s_writers.rw_sem[i]);
165 kfree(s);
166}
167
168static void destroy_super_rcu(struct rcu_head *head)
169{
170 struct super_block *s = container_of(head, struct super_block, rcu);
171 INIT_WORK(&s->destroy_work, destroy_super_work);
172 schedule_work(&s->destroy_work);
173}
174
175/* Free a superblock that has never been seen by anyone */
176static void destroy_unused_super(struct super_block *s)
177{
178 if (!s)
179 return;
180 up_write(&s->s_umount);
181 list_lru_destroy(&s->s_dentry_lru);
182 list_lru_destroy(&s->s_inode_lru);
183 security_sb_free(s);
184 put_user_ns(s->s_user_ns);
185 kfree(s->s_subtype);
186 free_prealloced_shrinker(&s->s_shrink);
187 /* no delays needed */
188 destroy_super_work(&s->destroy_work);
189}
190
191/**
192 * alloc_super - create new superblock
193 * @type: filesystem type superblock should belong to
194 * @flags: the mount flags
195 * @user_ns: User namespace for the super_block
196 *
197 * Allocates and initializes a new &struct super_block. alloc_super()
198 * returns a pointer new superblock or %NULL if allocation had failed.
199 */
200static struct super_block *alloc_super(struct file_system_type *type, int flags,
201 struct user_namespace *user_ns)
202{
203 struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
204 static const struct super_operations default_op;
205 int i;
206
207 if (!s)
208 return NULL;
209
210 INIT_LIST_HEAD(&s->s_mounts);
211 s->s_user_ns = get_user_ns(user_ns);
212 init_rwsem(&s->s_umount);
213 lockdep_set_class(&s->s_umount, &type->s_umount_key);
214 /*
215 * sget() can have s_umount recursion.
216 *
217 * When it cannot find a suitable sb, it allocates a new
218 * one (this one), and tries again to find a suitable old
219 * one.
220 *
221 * In case that succeeds, it will acquire the s_umount
222 * lock of the old one. Since these are clearly distrinct
223 * locks, and this object isn't exposed yet, there's no
224 * risk of deadlocks.
225 *
226 * Annotate this by putting this lock in a different
227 * subclass.
228 */
229 down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
230
231 if (security_sb_alloc(s))
232 goto fail;
233
234 for (i = 0; i < SB_FREEZE_LEVELS; i++) {
235 if (__percpu_init_rwsem(&s->s_writers.rw_sem[i],
236 sb_writers_name[i],
237 &type->s_writers_key[i]))
238 goto fail;
239 }
240 init_waitqueue_head(&s->s_writers.wait_unfrozen);
241 s->s_bdi = &noop_backing_dev_info;
242 s->s_flags = flags;
243 if (s->s_user_ns != &init_user_ns)
244 s->s_iflags |= SB_I_NODEV;
245 INIT_HLIST_NODE(&s->s_instances);
246 INIT_HLIST_BL_HEAD(&s->s_roots);
247 mutex_init(&s->s_sync_lock);
248 INIT_LIST_HEAD(&s->s_inodes);
249 spin_lock_init(&s->s_inode_list_lock);
250 INIT_LIST_HEAD(&s->s_inodes_wb);
251 spin_lock_init(&s->s_inode_wblist_lock);
252
253 s->s_count = 1;
254 atomic_set(&s->s_active, 1);
255 mutex_init(&s->s_vfs_rename_mutex);
256 lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
257 init_rwsem(&s->s_dquot.dqio_sem);
258 s->s_maxbytes = MAX_NON_LFS;
259 s->s_op = &default_op;
260 s->s_time_gran = 1000000000;
261 s->s_time_min = TIME64_MIN;
262 s->s_time_max = TIME64_MAX;
263 s->cleancache_poolid = CLEANCACHE_NO_POOL;
264
265 s->s_shrink.seeks = DEFAULT_SEEKS;
266 s->s_shrink.scan_objects = super_cache_scan;
267 s->s_shrink.count_objects = super_cache_count;
268 s->s_shrink.batch = 1024;
269 s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
270 if (prealloc_shrinker(&s->s_shrink))
271 goto fail;
272 if (list_lru_init_memcg(&s->s_dentry_lru, &s->s_shrink))
273 goto fail;
274 if (list_lru_init_memcg(&s->s_inode_lru, &s->s_shrink))
275 goto fail;
276 return s;
277
278fail:
279 destroy_unused_super(s);
280 return NULL;
281}
282
283/* Superblock refcounting */
284
285/*
286 * Drop a superblock's refcount. The caller must hold sb_lock.
287 */
288static void __put_super(struct super_block *s)
289{
290 if (!--s->s_count) {
291 list_del_init(&s->s_list);
292 WARN_ON(s->s_dentry_lru.node);
293 WARN_ON(s->s_inode_lru.node);
294 WARN_ON(!list_empty(&s->s_mounts));
295 security_sb_free(s);
296 fscrypt_sb_free(s);
297 put_user_ns(s->s_user_ns);
298 kfree(s->s_subtype);
299 call_rcu(&s->rcu, destroy_super_rcu);
300 }
301}
302
303/**
304 * put_super - drop a temporary reference to superblock
305 * @sb: superblock in question
306 *
307 * Drops a temporary reference, frees superblock if there's no
308 * references left.
309 */
310static void put_super(struct super_block *sb)
311{
312 spin_lock(&sb_lock);
313 __put_super(sb);
314 spin_unlock(&sb_lock);
315}
316
317
318/**
319 * deactivate_locked_super - drop an active reference to superblock
320 * @s: superblock to deactivate
321 *
322 * Drops an active reference to superblock, converting it into a temporary
323 * one if there is no other active references left. In that case we
324 * tell fs driver to shut it down and drop the temporary reference we
325 * had just acquired.
326 *
327 * Caller holds exclusive lock on superblock; that lock is released.
328 */
329void deactivate_locked_super(struct super_block *s)
330{
331 struct file_system_type *fs = s->s_type;
332 if (atomic_dec_and_test(&s->s_active)) {
333 cleancache_invalidate_fs(s);
334 unregister_shrinker(&s->s_shrink);
335 fs->kill_sb(s);
336
337 /*
338 * Since list_lru_destroy() may sleep, we cannot call it from
339 * put_super(), where we hold the sb_lock. Therefore we destroy
340 * the lru lists right now.
341 */
342 list_lru_destroy(&s->s_dentry_lru);
343 list_lru_destroy(&s->s_inode_lru);
344
345 put_filesystem(fs);
346 put_super(s);
347 } else {
348 up_write(&s->s_umount);
349 }
350}
351
352EXPORT_SYMBOL(deactivate_locked_super);
353
354/**
355 * deactivate_super - drop an active reference to superblock
356 * @s: superblock to deactivate
357 *
358 * Variant of deactivate_locked_super(), except that superblock is *not*
359 * locked by caller. If we are going to drop the final active reference,
360 * lock will be acquired prior to that.
361 */
362void deactivate_super(struct super_block *s)
363{
364 if (!atomic_add_unless(&s->s_active, -1, 1)) {
365 down_write(&s->s_umount);
366 deactivate_locked_super(s);
367 }
368}
369
370EXPORT_SYMBOL(deactivate_super);
371
372/**
373 * grab_super - acquire an active reference
374 * @s: reference we are trying to make active
375 *
376 * Tries to acquire an active reference. grab_super() is used when we
377 * had just found a superblock in super_blocks or fs_type->fs_supers
378 * and want to turn it into a full-blown active reference. grab_super()
379 * is called with sb_lock held and drops it. Returns 1 in case of
380 * success, 0 if we had failed (superblock contents was already dead or
381 * dying when grab_super() had been called). Note that this is only
382 * called for superblocks not in rundown mode (== ones still on ->fs_supers
383 * of their type), so increment of ->s_count is OK here.
384 */
385static int grab_super(struct super_block *s) __releases(sb_lock)
386{
387 s->s_count++;
388 spin_unlock(&sb_lock);
389 down_write(&s->s_umount);
390 if ((s->s_flags & SB_BORN) && atomic_inc_not_zero(&s->s_active)) {
391 put_super(s);
392 return 1;
393 }
394 up_write(&s->s_umount);
395 put_super(s);
396 return 0;
397}
398
399/*
400 * trylock_super - try to grab ->s_umount shared
401 * @sb: reference we are trying to grab
402 *
403 * Try to prevent fs shutdown. This is used in places where we
404 * cannot take an active reference but we need to ensure that the
405 * filesystem is not shut down while we are working on it. It returns
406 * false if we cannot acquire s_umount or if we lose the race and
407 * filesystem already got into shutdown, and returns true with the s_umount
408 * lock held in read mode in case of success. On successful return,
409 * the caller must drop the s_umount lock when done.
410 *
411 * Note that unlike get_super() et.al. this one does *not* bump ->s_count.
412 * The reason why it's safe is that we are OK with doing trylock instead
413 * of down_read(). There's a couple of places that are OK with that, but
414 * it's very much not a general-purpose interface.
415 */
416bool trylock_super(struct super_block *sb)
417{
418 if (down_read_trylock(&sb->s_umount)) {
419 if (!hlist_unhashed(&sb->s_instances) &&
420 sb->s_root && (sb->s_flags & SB_BORN))
421 return true;
422 up_read(&sb->s_umount);
423 }
424
425 return false;
426}
427
428/**
429 * generic_shutdown_super - common helper for ->kill_sb()
430 * @sb: superblock to kill
431 *
432 * generic_shutdown_super() does all fs-independent work on superblock
433 * shutdown. Typical ->kill_sb() should pick all fs-specific objects
434 * that need destruction out of superblock, call generic_shutdown_super()
435 * and release aforementioned objects. Note: dentries and inodes _are_
436 * taken care of and do not need specific handling.
437 *
438 * Upon calling this function, the filesystem may no longer alter or
439 * rearrange the set of dentries belonging to this super_block, nor may it
440 * change the attachments of dentries to inodes.
441 */
442void generic_shutdown_super(struct super_block *sb)
443{
444 const struct super_operations *sop = sb->s_op;
445
446 if (sb->s_root) {
447 shrink_dcache_for_umount(sb);
448 sync_filesystem(sb);
449 sb->s_flags &= ~SB_ACTIVE;
450
451 fsnotify_sb_delete(sb);
452 cgroup_writeback_umount();
453
454 evict_inodes(sb);
455
456 if (sb->s_dio_done_wq) {
457 destroy_workqueue(sb->s_dio_done_wq);
458 sb->s_dio_done_wq = NULL;
459 }
460
461 if (sop->put_super)
462 sop->put_super(sb);
463
464 if (!list_empty(&sb->s_inodes)) {
465 printk("VFS: Busy inodes after unmount of %s. "
466 "Self-destruct in 5 seconds. Have a nice day...\n",
467 sb->s_id);
468 }
469 }
470 spin_lock(&sb_lock);
471 /* should be initialized for __put_super_and_need_restart() */
472 hlist_del_init(&sb->s_instances);
473 spin_unlock(&sb_lock);
474 up_write(&sb->s_umount);
475 if (sb->s_bdi != &noop_backing_dev_info) {
476 bdi_put(sb->s_bdi);
477 sb->s_bdi = &noop_backing_dev_info;
478 }
479}
480
481EXPORT_SYMBOL(generic_shutdown_super);
482
483bool mount_capable(struct fs_context *fc)
484{
485 if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT))
486 return capable(CAP_SYS_ADMIN);
487 else
488 return ns_capable(fc->user_ns, CAP_SYS_ADMIN);
489}
490
491/**
492 * sget_fc - Find or create a superblock
493 * @fc: Filesystem context.
494 * @test: Comparison callback
495 * @set: Setup callback
496 *
497 * Find or create a superblock using the parameters stored in the filesystem
498 * context and the two callback functions.
499 *
500 * If an extant superblock is matched, then that will be returned with an
501 * elevated reference count that the caller must transfer or discard.
502 *
503 * If no match is made, a new superblock will be allocated and basic
504 * initialisation will be performed (s_type, s_fs_info and s_id will be set and
505 * the set() callback will be invoked), the superblock will be published and it
506 * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE
507 * as yet unset.
508 */
509struct super_block *sget_fc(struct fs_context *fc,
510 int (*test)(struct super_block *, struct fs_context *),
511 int (*set)(struct super_block *, struct fs_context *))
512{
513 struct super_block *s = NULL;
514 struct super_block *old;
515 struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;
516 int err;
517
518retry:
519 spin_lock(&sb_lock);
520 if (test) {
521 hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {
522 if (test(old, fc))
523 goto share_extant_sb;
524 }
525 }
526 if (!s) {
527 spin_unlock(&sb_lock);
528 s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);
529 if (!s)
530 return ERR_PTR(-ENOMEM);
531 goto retry;
532 }
533
534 s->s_fs_info = fc->s_fs_info;
535 err = set(s, fc);
536 if (err) {
537 s->s_fs_info = NULL;
538 spin_unlock(&sb_lock);
539 destroy_unused_super(s);
540 return ERR_PTR(err);
541 }
542 fc->s_fs_info = NULL;
543 s->s_type = fc->fs_type;
544 s->s_iflags |= fc->s_iflags;
545 strlcpy(s->s_id, s->s_type->name, sizeof(s->s_id));
546 list_add_tail(&s->s_list, &super_blocks);
547 hlist_add_head(&s->s_instances, &s->s_type->fs_supers);
548 spin_unlock(&sb_lock);
549 get_filesystem(s->s_type);
550 register_shrinker_prepared(&s->s_shrink);
551 return s;
552
553share_extant_sb:
554 if (user_ns != old->s_user_ns) {
555 spin_unlock(&sb_lock);
556 destroy_unused_super(s);
557 return ERR_PTR(-EBUSY);
558 }
559 if (!grab_super(old))
560 goto retry;
561 destroy_unused_super(s);
562 return old;
563}
564EXPORT_SYMBOL(sget_fc);
565
566/**
567 * sget - find or create a superblock
568 * @type: filesystem type superblock should belong to
569 * @test: comparison callback
570 * @set: setup callback
571 * @flags: mount flags
572 * @data: argument to each of them
573 */
574struct super_block *sget(struct file_system_type *type,
575 int (*test)(struct super_block *,void *),
576 int (*set)(struct super_block *,void *),
577 int flags,
578 void *data)
579{
580 struct user_namespace *user_ns = current_user_ns();
581 struct super_block *s = NULL;
582 struct super_block *old;
583 int err;
584
585 /* We don't yet pass the user namespace of the parent
586 * mount through to here so always use &init_user_ns
587 * until that changes.
588 */
589 if (flags & SB_SUBMOUNT)
590 user_ns = &init_user_ns;
591
592retry:
593 spin_lock(&sb_lock);
594 if (test) {
595 hlist_for_each_entry(old, &type->fs_supers, s_instances) {
596 if (!test(old, data))
597 continue;
598 if (user_ns != old->s_user_ns) {
599 spin_unlock(&sb_lock);
600 destroy_unused_super(s);
601 return ERR_PTR(-EBUSY);
602 }
603 if (!grab_super(old))
604 goto retry;
605 destroy_unused_super(s);
606 return old;
607 }
608 }
609 if (!s) {
610 spin_unlock(&sb_lock);
611 s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
612 if (!s)
613 return ERR_PTR(-ENOMEM);
614 goto retry;
615 }
616
617 err = set(s, data);
618 if (err) {
619 spin_unlock(&sb_lock);
620 destroy_unused_super(s);
621 return ERR_PTR(err);
622 }
623 s->s_type = type;
624 strlcpy(s->s_id, type->name, sizeof(s->s_id));
625 list_add_tail(&s->s_list, &super_blocks);
626 hlist_add_head(&s->s_instances, &type->fs_supers);
627 spin_unlock(&sb_lock);
628 get_filesystem(type);
629 register_shrinker_prepared(&s->s_shrink);
630 return s;
631}
632EXPORT_SYMBOL(sget);
633
634void drop_super(struct super_block *sb)
635{
636 up_read(&sb->s_umount);
637 put_super(sb);
638}
639
640EXPORT_SYMBOL(drop_super);
641
642void drop_super_exclusive(struct super_block *sb)
643{
644 up_write(&sb->s_umount);
645 put_super(sb);
646}
647EXPORT_SYMBOL(drop_super_exclusive);
648
649static void __iterate_supers(void (*f)(struct super_block *))
650{
651 struct super_block *sb, *p = NULL;
652
653 spin_lock(&sb_lock);
654 list_for_each_entry(sb, &super_blocks, s_list) {
655 if (hlist_unhashed(&sb->s_instances))
656 continue;
657 sb->s_count++;
658 spin_unlock(&sb_lock);
659
660 f(sb);
661
662 spin_lock(&sb_lock);
663 if (p)
664 __put_super(p);
665 p = sb;
666 }
667 if (p)
668 __put_super(p);
669 spin_unlock(&sb_lock);
670}
671/**
672 * iterate_supers - call function for all active superblocks
673 * @f: function to call
674 * @arg: argument to pass to it
675 *
676 * Scans the superblock list and calls given function, passing it
677 * locked superblock and given argument.
678 */
679void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
680{
681 struct super_block *sb, *p = NULL;
682
683 spin_lock(&sb_lock);
684 list_for_each_entry(sb, &super_blocks, s_list) {
685 if (hlist_unhashed(&sb->s_instances))
686 continue;
687 sb->s_count++;
688 spin_unlock(&sb_lock);
689
690 down_read(&sb->s_umount);
691 if (sb->s_root && (sb->s_flags & SB_BORN))
692 f(sb, arg);
693 up_read(&sb->s_umount);
694
695 spin_lock(&sb_lock);
696 if (p)
697 __put_super(p);
698 p = sb;
699 }
700 if (p)
701 __put_super(p);
702 spin_unlock(&sb_lock);
703}
704
705/**
706 * iterate_supers_type - call function for superblocks of given type
707 * @type: fs type
708 * @f: function to call
709 * @arg: argument to pass to it
710 *
711 * Scans the superblock list and calls given function, passing it
712 * locked superblock and given argument.
713 */
714void iterate_supers_type(struct file_system_type *type,
715 void (*f)(struct super_block *, void *), void *arg)
716{
717 struct super_block *sb, *p = NULL;
718
719 spin_lock(&sb_lock);
720 hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
721 sb->s_count++;
722 spin_unlock(&sb_lock);
723
724 down_read(&sb->s_umount);
725 if (sb->s_root && (sb->s_flags & SB_BORN))
726 f(sb, arg);
727 up_read(&sb->s_umount);
728
729 spin_lock(&sb_lock);
730 if (p)
731 __put_super(p);
732 p = sb;
733 }
734 if (p)
735 __put_super(p);
736 spin_unlock(&sb_lock);
737}
738
739EXPORT_SYMBOL(iterate_supers_type);
740
741static struct super_block *__get_super(struct block_device *bdev, bool excl)
742{
743 struct super_block *sb;
744
745 if (!bdev)
746 return NULL;
747
748 spin_lock(&sb_lock);
749rescan:
750 list_for_each_entry(sb, &super_blocks, s_list) {
751 if (hlist_unhashed(&sb->s_instances))
752 continue;
753 if (sb->s_bdev == bdev) {
754 sb->s_count++;
755 spin_unlock(&sb_lock);
756 if (!excl)
757 down_read(&sb->s_umount);
758 else
759 down_write(&sb->s_umount);
760 /* still alive? */
761 if (sb->s_root && (sb->s_flags & SB_BORN))
762 return sb;
763 if (!excl)
764 up_read(&sb->s_umount);
765 else
766 up_write(&sb->s_umount);
767 /* nope, got unmounted */
768 spin_lock(&sb_lock);
769 __put_super(sb);
770 goto rescan;
771 }
772 }
773 spin_unlock(&sb_lock);
774 return NULL;
775}
776
777/**
778 * get_super - get the superblock of a device
779 * @bdev: device to get the superblock for
780 *
781 * Scans the superblock list and finds the superblock of the file system
782 * mounted on the device given. %NULL is returned if no match is found.
783 */
784struct super_block *get_super(struct block_device *bdev)
785{
786 return __get_super(bdev, false);
787}
788EXPORT_SYMBOL(get_super);
789
790static struct super_block *__get_super_thawed(struct block_device *bdev,
791 bool excl)
792{
793 while (1) {
794 struct super_block *s = __get_super(bdev, excl);
795 if (!s || s->s_writers.frozen == SB_UNFROZEN)
796 return s;
797 if (!excl)
798 up_read(&s->s_umount);
799 else
800 up_write(&s->s_umount);
801 wait_event(s->s_writers.wait_unfrozen,
802 s->s_writers.frozen == SB_UNFROZEN);
803 put_super(s);
804 }
805}
806
807/**
808 * get_super_thawed - get thawed superblock of a device
809 * @bdev: device to get the superblock for
810 *
811 * Scans the superblock list and finds the superblock of the file system
812 * mounted on the device. The superblock is returned once it is thawed
813 * (or immediately if it was not frozen). %NULL is returned if no match
814 * is found.
815 */
816struct super_block *get_super_thawed(struct block_device *bdev)
817{
818 return __get_super_thawed(bdev, false);
819}
820EXPORT_SYMBOL(get_super_thawed);
821
822/**
823 * get_super_exclusive_thawed - get thawed superblock of a device
824 * @bdev: device to get the superblock for
825 *
826 * Scans the superblock list and finds the superblock of the file system
827 * mounted on the device. The superblock is returned once it is thawed
828 * (or immediately if it was not frozen) and s_umount semaphore is held
829 * in exclusive mode. %NULL is returned if no match is found.
830 */
831struct super_block *get_super_exclusive_thawed(struct block_device *bdev)
832{
833 return __get_super_thawed(bdev, true);
834}
835EXPORT_SYMBOL(get_super_exclusive_thawed);
836
837/**
838 * get_active_super - get an active reference to the superblock of a device
839 * @bdev: device to get the superblock for
840 *
841 * Scans the superblock list and finds the superblock of the file system
842 * mounted on the device given. Returns the superblock with an active
843 * reference or %NULL if none was found.
844 */
845struct super_block *get_active_super(struct block_device *bdev)
846{
847 struct super_block *sb;
848
849 if (!bdev)
850 return NULL;
851
852restart:
853 spin_lock(&sb_lock);
854 list_for_each_entry(sb, &super_blocks, s_list) {
855 if (hlist_unhashed(&sb->s_instances))
856 continue;
857 if (sb->s_bdev == bdev) {
858 if (!grab_super(sb))
859 goto restart;
860 up_write(&sb->s_umount);
861 return sb;
862 }
863 }
864 spin_unlock(&sb_lock);
865 return NULL;
866}
867
868struct super_block *user_get_super(dev_t dev)
869{
870 struct super_block *sb;
871
872 spin_lock(&sb_lock);
873rescan:
874 list_for_each_entry(sb, &super_blocks, s_list) {
875 if (hlist_unhashed(&sb->s_instances))
876 continue;
877 if (sb->s_dev == dev) {
878 sb->s_count++;
879 spin_unlock(&sb_lock);
880 down_read(&sb->s_umount);
881 /* still alive? */
882 if (sb->s_root && (sb->s_flags & SB_BORN))
883 return sb;
884 up_read(&sb->s_umount);
885 /* nope, got unmounted */
886 spin_lock(&sb_lock);
887 __put_super(sb);
888 goto rescan;
889 }
890 }
891 spin_unlock(&sb_lock);
892 return NULL;
893}
894
895/**
896 * reconfigure_super - asks filesystem to change superblock parameters
897 * @fc: The superblock and configuration
898 *
899 * Alters the configuration parameters of a live superblock.
900 */
901int reconfigure_super(struct fs_context *fc)
902{
903 struct super_block *sb = fc->root->d_sb;
904 int retval;
905 bool remount_ro = false;
906 bool force = fc->sb_flags & SB_FORCE;
907
908 if (fc->sb_flags_mask & ~MS_RMT_MASK)
909 return -EINVAL;
910 if (sb->s_writers.frozen != SB_UNFROZEN)
911 return -EBUSY;
912
913 retval = security_sb_remount(sb, fc->security);
914 if (retval)
915 return retval;
916
917 if (fc->sb_flags_mask & SB_RDONLY) {
918#ifdef CONFIG_BLOCK
919 if (!(fc->sb_flags & SB_RDONLY) && bdev_read_only(sb->s_bdev))
920 return -EACCES;
921#endif
922
923 remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb);
924 }
925
926 if (remount_ro) {
927 if (!hlist_empty(&sb->s_pins)) {
928 up_write(&sb->s_umount);
929 group_pin_kill(&sb->s_pins);
930 down_write(&sb->s_umount);
931 if (!sb->s_root)
932 return 0;
933 if (sb->s_writers.frozen != SB_UNFROZEN)
934 return -EBUSY;
935 remount_ro = !sb_rdonly(sb);
936 }
937 }
938 shrink_dcache_sb(sb);
939
940 /* If we are reconfiguring to RDONLY and current sb is read/write,
941 * make sure there are no files open for writing.
942 */
943 if (remount_ro) {
944 if (force) {
945 sb->s_readonly_remount = 1;
946 smp_wmb();
947 } else {
948 retval = sb_prepare_remount_readonly(sb);
949 if (retval)
950 return retval;
951 }
952 }
953
954 if (fc->ops->reconfigure) {
955 retval = fc->ops->reconfigure(fc);
956 if (retval) {
957 if (!force)
958 goto cancel_readonly;
959 /* If forced remount, go ahead despite any errors */
960 WARN(1, "forced remount of a %s fs returned %i\n",
961 sb->s_type->name, retval);
962 }
963 }
964
965 WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) |
966 (fc->sb_flags & fc->sb_flags_mask)));
967 /* Needs to be ordered wrt mnt_is_readonly() */
968 smp_wmb();
969 sb->s_readonly_remount = 0;
970
971 /*
972 * Some filesystems modify their metadata via some other path than the
973 * bdev buffer cache (eg. use a private mapping, or directories in
974 * pagecache, etc). Also file data modifications go via their own
975 * mappings. So If we try to mount readonly then copy the filesystem
976 * from bdev, we could get stale data, so invalidate it to give a best
977 * effort at coherency.
978 */
979 if (remount_ro && sb->s_bdev)
980 invalidate_bdev(sb->s_bdev);
981 return 0;
982
983cancel_readonly:
984 sb->s_readonly_remount = 0;
985 return retval;
986}
987
988static void do_emergency_remount_callback(struct super_block *sb)
989{
990 down_write(&sb->s_umount);
991 if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) &&
992 !sb_rdonly(sb)) {
993 struct fs_context *fc;
994
995 fc = fs_context_for_reconfigure(sb->s_root,
996 SB_RDONLY | SB_FORCE, SB_RDONLY);
997 if (!IS_ERR(fc)) {
998 if (parse_monolithic_mount_data(fc, NULL) == 0)
999 (void)reconfigure_super(fc);
1000 put_fs_context(fc);
1001 }
1002 }
1003 up_write(&sb->s_umount);
1004}
1005
1006static void do_emergency_remount(struct work_struct *work)
1007{
1008 __iterate_supers(do_emergency_remount_callback);
1009 kfree(work);
1010 printk("Emergency Remount complete\n");
1011}
1012
1013void emergency_remount(void)
1014{
1015 struct work_struct *work;
1016
1017 work = kmalloc(sizeof(*work), GFP_ATOMIC);
1018 if (work) {
1019 INIT_WORK(work, do_emergency_remount);
1020 schedule_work(work);
1021 }
1022}
1023
1024static void do_thaw_all_callback(struct super_block *sb)
1025{
1026 down_write(&sb->s_umount);
1027 if (sb->s_root && sb->s_flags & SB_BORN) {
1028 emergency_thaw_bdev(sb);
1029 thaw_super_locked(sb);
1030 } else {
1031 up_write(&sb->s_umount);
1032 }
1033}
1034
1035static void do_thaw_all(struct work_struct *work)
1036{
1037 __iterate_supers(do_thaw_all_callback);
1038 kfree(work);
1039 printk(KERN_WARNING "Emergency Thaw complete\n");
1040}
1041
1042/**
1043 * emergency_thaw_all -- forcibly thaw every frozen filesystem
1044 *
1045 * Used for emergency unfreeze of all filesystems via SysRq
1046 */
1047void emergency_thaw_all(void)
1048{
1049 struct work_struct *work;
1050
1051 work = kmalloc(sizeof(*work), GFP_ATOMIC);
1052 if (work) {
1053 INIT_WORK(work, do_thaw_all);
1054 schedule_work(work);
1055 }
1056}
1057
1058static DEFINE_IDA(unnamed_dev_ida);
1059
1060/**
1061 * get_anon_bdev - Allocate a block device for filesystems which don't have one.
1062 * @p: Pointer to a dev_t.
1063 *
1064 * Filesystems which don't use real block devices can call this function
1065 * to allocate a virtual block device.
1066 *
1067 * Context: Any context. Frequently called while holding sb_lock.
1068 * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
1069 * or -ENOMEM if memory allocation failed.
1070 */
1071int get_anon_bdev(dev_t *p)
1072{
1073 int dev;
1074
1075 /*
1076 * Many userspace utilities consider an FSID of 0 invalid.
1077 * Always return at least 1 from get_anon_bdev.
1078 */
1079 dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
1080 GFP_ATOMIC);
1081 if (dev == -ENOSPC)
1082 dev = -EMFILE;
1083 if (dev < 0)
1084 return dev;
1085
1086 *p = MKDEV(0, dev);
1087 return 0;
1088}
1089EXPORT_SYMBOL(get_anon_bdev);
1090
1091void free_anon_bdev(dev_t dev)
1092{
1093 ida_free(&unnamed_dev_ida, MINOR(dev));
1094}
1095EXPORT_SYMBOL(free_anon_bdev);
1096
1097int set_anon_super(struct super_block *s, void *data)
1098{
1099 return get_anon_bdev(&s->s_dev);
1100}
1101EXPORT_SYMBOL(set_anon_super);
1102
1103void kill_anon_super(struct super_block *sb)
1104{
1105 dev_t dev = sb->s_dev;
1106 generic_shutdown_super(sb);
1107 free_anon_bdev(dev);
1108}
1109EXPORT_SYMBOL(kill_anon_super);
1110
1111void kill_litter_super(struct super_block *sb)
1112{
1113 if (sb->s_root)
1114 d_genocide(sb->s_root);
1115 kill_anon_super(sb);
1116}
1117EXPORT_SYMBOL(kill_litter_super);
1118
1119int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)
1120{
1121 return set_anon_super(sb, NULL);
1122}
1123EXPORT_SYMBOL(set_anon_super_fc);
1124
1125static int test_keyed_super(struct super_block *sb, struct fs_context *fc)
1126{
1127 return sb->s_fs_info == fc->s_fs_info;
1128}
1129
1130static int test_single_super(struct super_block *s, struct fs_context *fc)
1131{
1132 return 1;
1133}
1134
1135/**
1136 * vfs_get_super - Get a superblock with a search key set in s_fs_info.
1137 * @fc: The filesystem context holding the parameters
1138 * @keying: How to distinguish superblocks
1139 * @fill_super: Helper to initialise a new superblock
1140 *
1141 * Search for a superblock and create a new one if not found. The search
1142 * criterion is controlled by @keying. If the search fails, a new superblock
1143 * is created and @fill_super() is called to initialise it.
1144 *
1145 * @keying can take one of a number of values:
1146 *
1147 * (1) vfs_get_single_super - Only one superblock of this type may exist on the
1148 * system. This is typically used for special system filesystems.
1149 *
1150 * (2) vfs_get_keyed_super - Multiple superblocks may exist, but they must have
1151 * distinct keys (where the key is in s_fs_info). Searching for the same
1152 * key again will turn up the superblock for that key.
1153 *
1154 * (3) vfs_get_independent_super - Multiple superblocks may exist and are
1155 * unkeyed. Each call will get a new superblock.
1156 *
1157 * A permissions check is made by sget_fc() unless we're getting a superblock
1158 * for a kernel-internal mount or a submount.
1159 */
1160int vfs_get_super(struct fs_context *fc,
1161 enum vfs_get_super_keying keying,
1162 int (*fill_super)(struct super_block *sb,
1163 struct fs_context *fc))
1164{
1165 int (*test)(struct super_block *, struct fs_context *);
1166 struct super_block *sb;
1167 int err;
1168
1169 switch (keying) {
1170 case vfs_get_single_super:
1171 case vfs_get_single_reconf_super:
1172 test = test_single_super;
1173 break;
1174 case vfs_get_keyed_super:
1175 test = test_keyed_super;
1176 break;
1177 case vfs_get_independent_super:
1178 test = NULL;
1179 break;
1180 default:
1181 BUG();
1182 }
1183
1184 sb = sget_fc(fc, test, set_anon_super_fc);
1185 if (IS_ERR(sb))
1186 return PTR_ERR(sb);
1187
1188 if (!sb->s_root) {
1189 err = fill_super(sb, fc);
1190 if (err)
1191 goto error;
1192
1193 sb->s_flags |= SB_ACTIVE;
1194 fc->root = dget(sb->s_root);
1195 } else {
1196 fc->root = dget(sb->s_root);
1197 if (keying == vfs_get_single_reconf_super) {
1198 err = reconfigure_super(fc);
1199 if (err < 0) {
1200 dput(fc->root);
1201 fc->root = NULL;
1202 goto error;
1203 }
1204 }
1205 }
1206
1207 return 0;
1208
1209error:
1210 deactivate_locked_super(sb);
1211 return err;
1212}
1213EXPORT_SYMBOL(vfs_get_super);
1214
1215int get_tree_nodev(struct fs_context *fc,
1216 int (*fill_super)(struct super_block *sb,
1217 struct fs_context *fc))
1218{
1219 return vfs_get_super(fc, vfs_get_independent_super, fill_super);
1220}
1221EXPORT_SYMBOL(get_tree_nodev);
1222
1223int get_tree_single(struct fs_context *fc,
1224 int (*fill_super)(struct super_block *sb,
1225 struct fs_context *fc))
1226{
1227 return vfs_get_super(fc, vfs_get_single_super, fill_super);
1228}
1229EXPORT_SYMBOL(get_tree_single);
1230
1231int get_tree_single_reconf(struct fs_context *fc,
1232 int (*fill_super)(struct super_block *sb,
1233 struct fs_context *fc))
1234{
1235 return vfs_get_super(fc, vfs_get_single_reconf_super, fill_super);
1236}
1237EXPORT_SYMBOL(get_tree_single_reconf);
1238
1239int get_tree_keyed(struct fs_context *fc,
1240 int (*fill_super)(struct super_block *sb,
1241 struct fs_context *fc),
1242 void *key)
1243{
1244 fc->s_fs_info = key;
1245 return vfs_get_super(fc, vfs_get_keyed_super, fill_super);
1246}
1247EXPORT_SYMBOL(get_tree_keyed);
1248
1249#ifdef CONFIG_BLOCK
1250
1251static int set_bdev_super(struct super_block *s, void *data)
1252{
1253 s->s_bdev = data;
1254 s->s_dev = s->s_bdev->bd_dev;
1255 s->s_bdi = bdi_get(s->s_bdev->bd_bdi);
1256
1257 return 0;
1258}
1259
1260static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1261{
1262 return set_bdev_super(s, fc->sget_key);
1263}
1264
1265static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1266{
1267 return s->s_bdev == fc->sget_key;
1268}
1269
1270/**
1271 * get_tree_bdev - Get a superblock based on a single block device
1272 * @fc: The filesystem context holding the parameters
1273 * @fill_super: Helper to initialise a new superblock
1274 */
1275int get_tree_bdev(struct fs_context *fc,
1276 int (*fill_super)(struct super_block *,
1277 struct fs_context *))
1278{
1279 struct block_device *bdev;
1280 struct super_block *s;
1281 fmode_t mode = FMODE_READ | FMODE_EXCL;
1282 int error = 0;
1283
1284 if (!(fc->sb_flags & SB_RDONLY))
1285 mode |= FMODE_WRITE;
1286
1287 if (!fc->source)
1288 return invalf(fc, "No source specified");
1289
1290 bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type);
1291 if (IS_ERR(bdev)) {
1292 errorf(fc, "%s: Can't open blockdev", fc->source);
1293 return PTR_ERR(bdev);
1294 }
1295
1296 /* Once the superblock is inserted into the list by sget_fc(), s_umount
1297 * will protect the lockfs code from trying to start a snapshot while
1298 * we are mounting
1299 */
1300 mutex_lock(&bdev->bd_fsfreeze_mutex);
1301 if (bdev->bd_fsfreeze_count > 0) {
1302 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1303 blkdev_put(bdev, mode);
1304 warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
1305 return -EBUSY;
1306 }
1307
1308 fc->sb_flags |= SB_NOSEC;
1309 fc->sget_key = bdev;
1310 s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc);
1311 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1312 if (IS_ERR(s)) {
1313 blkdev_put(bdev, mode);
1314 return PTR_ERR(s);
1315 }
1316
1317 if (s->s_root) {
1318 /* Don't summarily change the RO/RW state. */
1319 if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
1320 warnf(fc, "%pg: Can't mount, would change RO state", bdev);
1321 deactivate_locked_super(s);
1322 blkdev_put(bdev, mode);
1323 return -EBUSY;
1324 }
1325
1326 /*
1327 * s_umount nests inside bd_mutex during
1328 * __invalidate_device(). blkdev_put() acquires
1329 * bd_mutex and can't be called under s_umount. Drop
1330 * s_umount temporarily. This is safe as we're
1331 * holding an active reference.
1332 */
1333 up_write(&s->s_umount);
1334 blkdev_put(bdev, mode);
1335 down_write(&s->s_umount);
1336 } else {
1337 s->s_mode = mode;
1338 snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1339 sb_set_blocksize(s, block_size(bdev));
1340 error = fill_super(s, fc);
1341 if (error) {
1342 deactivate_locked_super(s);
1343 return error;
1344 }
1345
1346 s->s_flags |= SB_ACTIVE;
1347 bdev->bd_super = s;
1348 }
1349
1350 BUG_ON(fc->root);
1351 fc->root = dget(s->s_root);
1352 return 0;
1353}
1354EXPORT_SYMBOL(get_tree_bdev);
1355
1356static int test_bdev_super(struct super_block *s, void *data)
1357{
1358 return (void *)s->s_bdev == data;
1359}
1360
1361struct dentry *mount_bdev(struct file_system_type *fs_type,
1362 int flags, const char *dev_name, void *data,
1363 int (*fill_super)(struct super_block *, void *, int))
1364{
1365 struct block_device *bdev;
1366 struct super_block *s;
1367 fmode_t mode = FMODE_READ | FMODE_EXCL;
1368 int error = 0;
1369
1370 if (!(flags & SB_RDONLY))
1371 mode |= FMODE_WRITE;
1372
1373 bdev = blkdev_get_by_path(dev_name, mode, fs_type);
1374 if (IS_ERR(bdev))
1375 return ERR_CAST(bdev);
1376
1377 /*
1378 * once the super is inserted into the list by sget, s_umount
1379 * will protect the lockfs code from trying to start a snapshot
1380 * while we are mounting
1381 */
1382 mutex_lock(&bdev->bd_fsfreeze_mutex);
1383 if (bdev->bd_fsfreeze_count > 0) {
1384 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1385 error = -EBUSY;
1386 goto error_bdev;
1387 }
1388 s = sget(fs_type, test_bdev_super, set_bdev_super, flags | SB_NOSEC,
1389 bdev);
1390 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1391 if (IS_ERR(s))
1392 goto error_s;
1393
1394 if (s->s_root) {
1395 if ((flags ^ s->s_flags) & SB_RDONLY) {
1396 deactivate_locked_super(s);
1397 error = -EBUSY;
1398 goto error_bdev;
1399 }
1400
1401 /*
1402 * s_umount nests inside bd_mutex during
1403 * __invalidate_device(). blkdev_put() acquires
1404 * bd_mutex and can't be called under s_umount. Drop
1405 * s_umount temporarily. This is safe as we're
1406 * holding an active reference.
1407 */
1408 up_write(&s->s_umount);
1409 blkdev_put(bdev, mode);
1410 down_write(&s->s_umount);
1411 } else {
1412 s->s_mode = mode;
1413 snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1414 sb_set_blocksize(s, block_size(bdev));
1415 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1416 if (error) {
1417 deactivate_locked_super(s);
1418 goto error;
1419 }
1420
1421 s->s_flags |= SB_ACTIVE;
1422 bdev->bd_super = s;
1423 }
1424
1425 return dget(s->s_root);
1426
1427error_s:
1428 error = PTR_ERR(s);
1429error_bdev:
1430 blkdev_put(bdev, mode);
1431error:
1432 return ERR_PTR(error);
1433}
1434EXPORT_SYMBOL(mount_bdev);
1435
1436void kill_block_super(struct super_block *sb)
1437{
1438 struct block_device *bdev = sb->s_bdev;
1439 fmode_t mode = sb->s_mode;
1440
1441 bdev->bd_super = NULL;
1442 generic_shutdown_super(sb);
1443 sync_blockdev(bdev);
1444 WARN_ON_ONCE(!(mode & FMODE_EXCL));
1445 blkdev_put(bdev, mode | FMODE_EXCL);
1446}
1447
1448EXPORT_SYMBOL(kill_block_super);
1449#endif
1450
1451struct dentry *mount_nodev(struct file_system_type *fs_type,
1452 int flags, void *data,
1453 int (*fill_super)(struct super_block *, void *, int))
1454{
1455 int error;
1456 struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
1457
1458 if (IS_ERR(s))
1459 return ERR_CAST(s);
1460
1461 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1462 if (error) {
1463 deactivate_locked_super(s);
1464 return ERR_PTR(error);
1465 }
1466 s->s_flags |= SB_ACTIVE;
1467 return dget(s->s_root);
1468}
1469EXPORT_SYMBOL(mount_nodev);
1470
1471static int reconfigure_single(struct super_block *s,
1472 int flags, void *data)
1473{
1474 struct fs_context *fc;
1475 int ret;
1476
1477 /* The caller really need to be passing fc down into mount_single(),
1478 * then a chunk of this can be removed. [Bollocks -- AV]
1479 * Better yet, reconfiguration shouldn't happen, but rather the second
1480 * mount should be rejected if the parameters are not compatible.
1481 */
1482 fc = fs_context_for_reconfigure(s->s_root, flags, MS_RMT_MASK);
1483 if (IS_ERR(fc))
1484 return PTR_ERR(fc);
1485
1486 ret = parse_monolithic_mount_data(fc, data);
1487 if (ret < 0)
1488 goto out;
1489
1490 ret = reconfigure_super(fc);
1491out:
1492 put_fs_context(fc);
1493 return ret;
1494}
1495
1496static int compare_single(struct super_block *s, void *p)
1497{
1498 return 1;
1499}
1500
1501struct dentry *mount_single(struct file_system_type *fs_type,
1502 int flags, void *data,
1503 int (*fill_super)(struct super_block *, void *, int))
1504{
1505 struct super_block *s;
1506 int error;
1507
1508 s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
1509 if (IS_ERR(s))
1510 return ERR_CAST(s);
1511 if (!s->s_root) {
1512 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1513 if (!error)
1514 s->s_flags |= SB_ACTIVE;
1515 } else {
1516 error = reconfigure_single(s, flags, data);
1517 }
1518 if (unlikely(error)) {
1519 deactivate_locked_super(s);
1520 return ERR_PTR(error);
1521 }
1522 return dget(s->s_root);
1523}
1524EXPORT_SYMBOL(mount_single);
1525
1526/**
1527 * vfs_get_tree - Get the mountable root
1528 * @fc: The superblock configuration context.
1529 *
1530 * The filesystem is invoked to get or create a superblock which can then later
1531 * be used for mounting. The filesystem places a pointer to the root to be
1532 * used for mounting in @fc->root.
1533 */
1534int vfs_get_tree(struct fs_context *fc)
1535{
1536 struct super_block *sb;
1537 int error;
1538
1539 if (fc->root)
1540 return -EBUSY;
1541
1542 /* Get the mountable root in fc->root, with a ref on the root and a ref
1543 * on the superblock.
1544 */
1545 error = fc->ops->get_tree(fc);
1546 if (error < 0)
1547 return error;
1548
1549 if (!fc->root) {
1550 pr_err("Filesystem %s get_tree() didn't set fc->root\n",
1551 fc->fs_type->name);
1552 /* We don't know what the locking state of the superblock is -
1553 * if there is a superblock.
1554 */
1555 BUG();
1556 }
1557
1558 sb = fc->root->d_sb;
1559 WARN_ON(!sb->s_bdi);
1560
1561 /*
1562 * Write barrier is for super_cache_count(). We place it before setting
1563 * SB_BORN as the data dependency between the two functions is the
1564 * superblock structure contents that we just set up, not the SB_BORN
1565 * flag.
1566 */
1567 smp_wmb();
1568 sb->s_flags |= SB_BORN;
1569
1570 error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL);
1571 if (unlikely(error)) {
1572 fc_drop_locked(fc);
1573 return error;
1574 }
1575
1576 /*
1577 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1578 * but s_maxbytes was an unsigned long long for many releases. Throw
1579 * this warning for a little while to try and catch filesystems that
1580 * violate this rule.
1581 */
1582 WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
1583 "negative value (%lld)\n", fc->fs_type->name, sb->s_maxbytes);
1584
1585 return 0;
1586}
1587EXPORT_SYMBOL(vfs_get_tree);
1588
1589/*
1590 * Setup private BDI for given superblock. It gets automatically cleaned up
1591 * in generic_shutdown_super().
1592 */
1593int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)
1594{
1595 struct backing_dev_info *bdi;
1596 int err;
1597 va_list args;
1598
1599 bdi = bdi_alloc(GFP_KERNEL);
1600 if (!bdi)
1601 return -ENOMEM;
1602
1603 bdi->name = sb->s_type->name;
1604
1605 va_start(args, fmt);
1606 err = bdi_register_va(bdi, fmt, args);
1607 va_end(args);
1608 if (err) {
1609 bdi_put(bdi);
1610 return err;
1611 }
1612 WARN_ON(sb->s_bdi != &noop_backing_dev_info);
1613 sb->s_bdi = bdi;
1614
1615 return 0;
1616}
1617EXPORT_SYMBOL(super_setup_bdi_name);
1618
1619/*
1620 * Setup private BDI for given superblock. I gets automatically cleaned up
1621 * in generic_shutdown_super().
1622 */
1623int super_setup_bdi(struct super_block *sb)
1624{
1625 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
1626
1627 return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,
1628 atomic_long_inc_return(&bdi_seq));
1629}
1630EXPORT_SYMBOL(super_setup_bdi);
1631
1632/*
1633 * This is an internal function, please use sb_end_{write,pagefault,intwrite}
1634 * instead.
1635 */
1636void __sb_end_write(struct super_block *sb, int level)
1637{
1638 percpu_up_read(sb->s_writers.rw_sem + level-1);
1639}
1640EXPORT_SYMBOL(__sb_end_write);
1641
1642/*
1643 * This is an internal function, please use sb_start_{write,pagefault,intwrite}
1644 * instead.
1645 */
1646int __sb_start_write(struct super_block *sb, int level, bool wait)
1647{
1648 bool force_trylock = false;
1649 int ret = 1;
1650
1651#ifdef CONFIG_LOCKDEP
1652 /*
1653 * We want lockdep to tell us about possible deadlocks with freezing
1654 * but it's it bit tricky to properly instrument it. Getting a freeze
1655 * protection works as getting a read lock but there are subtle
1656 * problems. XFS for example gets freeze protection on internal level
1657 * twice in some cases, which is OK only because we already hold a
1658 * freeze protection also on higher level. Due to these cases we have
1659 * to use wait == F (trylock mode) which must not fail.
1660 */
1661 if (wait) {
1662 int i;
1663
1664 for (i = 0; i < level - 1; i++)
1665 if (percpu_rwsem_is_held(sb->s_writers.rw_sem + i)) {
1666 force_trylock = true;
1667 break;
1668 }
1669 }
1670#endif
1671 if (wait && !force_trylock)
1672 percpu_down_read(sb->s_writers.rw_sem + level-1);
1673 else
1674 ret = percpu_down_read_trylock(sb->s_writers.rw_sem + level-1);
1675
1676 WARN_ON(force_trylock && !ret);
1677 return ret;
1678}
1679EXPORT_SYMBOL(__sb_start_write);
1680
1681/**
1682 * sb_wait_write - wait until all writers to given file system finish
1683 * @sb: the super for which we wait
1684 * @level: type of writers we wait for (normal vs page fault)
1685 *
1686 * This function waits until there are no writers of given type to given file
1687 * system.
1688 */
1689static void sb_wait_write(struct super_block *sb, int level)
1690{
1691 percpu_down_write(sb->s_writers.rw_sem + level-1);
1692}
1693
1694/*
1695 * We are going to return to userspace and forget about these locks, the
1696 * ownership goes to the caller of thaw_super() which does unlock().
1697 */
1698static void lockdep_sb_freeze_release(struct super_block *sb)
1699{
1700 int level;
1701
1702 for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
1703 percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1704}
1705
1706/*
1707 * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
1708 */
1709static void lockdep_sb_freeze_acquire(struct super_block *sb)
1710{
1711 int level;
1712
1713 for (level = 0; level < SB_FREEZE_LEVELS; ++level)
1714 percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1715}
1716
1717static void sb_freeze_unlock(struct super_block *sb)
1718{
1719 int level;
1720
1721 for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
1722 percpu_up_write(sb->s_writers.rw_sem + level);
1723}
1724
1725/**
1726 * freeze_super - lock the filesystem and force it into a consistent state
1727 * @sb: the super to lock
1728 *
1729 * Syncs the super to make sure the filesystem is consistent and calls the fs's
1730 * freeze_fs. Subsequent calls to this without first thawing the fs will return
1731 * -EBUSY.
1732 *
1733 * During this function, sb->s_writers.frozen goes through these values:
1734 *
1735 * SB_UNFROZEN: File system is normal, all writes progress as usual.
1736 *
1737 * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
1738 * writes should be blocked, though page faults are still allowed. We wait for
1739 * all writes to complete and then proceed to the next stage.
1740 *
1741 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
1742 * but internal fs threads can still modify the filesystem (although they
1743 * should not dirty new pages or inodes), writeback can run etc. After waiting
1744 * for all running page faults we sync the filesystem which will clean all
1745 * dirty pages and inodes (no new dirty pages or inodes can be created when
1746 * sync is running).
1747 *
1748 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
1749 * modification are blocked (e.g. XFS preallocation truncation on inode
1750 * reclaim). This is usually implemented by blocking new transactions for
1751 * filesystems that have them and need this additional guard. After all
1752 * internal writers are finished we call ->freeze_fs() to finish filesystem
1753 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
1754 * mostly auxiliary for filesystems to verify they do not modify frozen fs.
1755 *
1756 * sb->s_writers.frozen is protected by sb->s_umount.
1757 */
1758int freeze_super(struct super_block *sb)
1759{
1760 int ret;
1761
1762 atomic_inc(&sb->s_active);
1763 down_write(&sb->s_umount);
1764 if (sb->s_writers.frozen != SB_UNFROZEN) {
1765 deactivate_locked_super(sb);
1766 return -EBUSY;
1767 }
1768
1769 if (!(sb->s_flags & SB_BORN)) {
1770 up_write(&sb->s_umount);
1771 return 0; /* sic - it's "nothing to do" */
1772 }
1773
1774 if (sb_rdonly(sb)) {
1775 /* Nothing to do really... */
1776 sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1777 up_write(&sb->s_umount);
1778 return 0;
1779 }
1780
1781 sb->s_writers.frozen = SB_FREEZE_WRITE;
1782 /* Release s_umount to preserve sb_start_write -> s_umount ordering */
1783 up_write(&sb->s_umount);
1784 sb_wait_write(sb, SB_FREEZE_WRITE);
1785 down_write(&sb->s_umount);
1786
1787 /* Now we go and block page faults... */
1788 sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
1789 sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
1790
1791 /* All writers are done so after syncing there won't be dirty data */
1792 sync_filesystem(sb);
1793
1794 /* Now wait for internal filesystem counter */
1795 sb->s_writers.frozen = SB_FREEZE_FS;
1796 sb_wait_write(sb, SB_FREEZE_FS);
1797
1798 if (sb->s_op->freeze_fs) {
1799 ret = sb->s_op->freeze_fs(sb);
1800 if (ret) {
1801 printk(KERN_ERR
1802 "VFS:Filesystem freeze failed\n");
1803 sb->s_writers.frozen = SB_UNFROZEN;
1804 sb_freeze_unlock(sb);
1805 wake_up(&sb->s_writers.wait_unfrozen);
1806 deactivate_locked_super(sb);
1807 return ret;
1808 }
1809 }
1810 /*
1811 * For debugging purposes so that fs can warn if it sees write activity
1812 * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
1813 */
1814 sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1815 lockdep_sb_freeze_release(sb);
1816 up_write(&sb->s_umount);
1817 return 0;
1818}
1819EXPORT_SYMBOL(freeze_super);
1820
1821/**
1822 * thaw_super -- unlock filesystem
1823 * @sb: the super to thaw
1824 *
1825 * Unlocks the filesystem and marks it writeable again after freeze_super().
1826 */
1827static int thaw_super_locked(struct super_block *sb)
1828{
1829 int error;
1830
1831 if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) {
1832 up_write(&sb->s_umount);
1833 return -EINVAL;
1834 }
1835
1836 if (sb_rdonly(sb)) {
1837 sb->s_writers.frozen = SB_UNFROZEN;
1838 goto out;
1839 }
1840
1841 lockdep_sb_freeze_acquire(sb);
1842
1843 if (sb->s_op->unfreeze_fs) {
1844 error = sb->s_op->unfreeze_fs(sb);
1845 if (error) {
1846 printk(KERN_ERR
1847 "VFS:Filesystem thaw failed\n");
1848 lockdep_sb_freeze_release(sb);
1849 up_write(&sb->s_umount);
1850 return error;
1851 }
1852 }
1853
1854 sb->s_writers.frozen = SB_UNFROZEN;
1855 sb_freeze_unlock(sb);
1856out:
1857 wake_up(&sb->s_writers.wait_unfrozen);
1858 deactivate_locked_super(sb);
1859 return 0;
1860}
1861
1862int thaw_super(struct super_block *sb)
1863{
1864 down_write(&sb->s_umount);
1865 return thaw_super_locked(sb);
1866}
1867EXPORT_SYMBOL(thaw_super);