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