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