Line data Source code
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 :
42 : static int thaw_super_locked(struct super_block *sb);
43 :
44 : static LIST_HEAD(super_blocks);
45 : static DEFINE_SPINLOCK(sb_lock);
46 :
47 : static 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 : */
60 0 : static unsigned long super_cache_scan(struct shrinker *shrink,
61 : struct shrink_control *sc)
62 : {
63 : struct super_block *sb;
64 0 : long fs_objects = 0;
65 : long total_objects;
66 0 : long freed = 0;
67 : long dentries;
68 : long inodes;
69 :
70 0 : 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 0 : if (!(sc->gfp_mask & __GFP_FS))
77 : return SHRINK_STOP;
78 :
79 0 : if (!trylock_super(sb))
80 : return SHRINK_STOP;
81 :
82 0 : if (sb->s_op->nr_cached_objects)
83 0 : fs_objects = sb->s_op->nr_cached_objects(sb, sc);
84 :
85 0 : inodes = list_lru_shrink_count(&sb->s_inode_lru, sc);
86 0 : dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc);
87 0 : total_objects = dentries + inodes + fs_objects + 1;
88 0 : if (!total_objects)
89 0 : total_objects = 1;
90 :
91 : /* proportion the scan between the caches */
92 0 : dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);
93 0 : inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);
94 0 : 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 0 : sc->nr_to_scan = dentries + 1;
104 0 : freed = prune_dcache_sb(sb, sc);
105 0 : sc->nr_to_scan = inodes + 1;
106 0 : freed += prune_icache_sb(sb, sc);
107 :
108 0 : if (fs_objects) {
109 0 : sc->nr_to_scan = fs_objects + 1;
110 0 : freed += sb->s_op->free_cached_objects(sb, sc);
111 : }
112 :
113 0 : up_read(&sb->s_umount);
114 0 : return freed;
115 : }
116 :
117 0 : static unsigned long super_cache_count(struct shrinker *shrink,
118 : struct shrink_control *sc)
119 : {
120 : struct super_block *sb;
121 0 : long total_objects = 0;
122 :
123 0 : 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 0 : if (!(sb->s_flags & SB_BORN))
140 : return 0;
141 0 : smp_rmb();
142 :
143 0 : if (sb->s_op && sb->s_op->nr_cached_objects)
144 0 : total_objects = sb->s_op->nr_cached_objects(sb, sc);
145 :
146 0 : total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc);
147 0 : total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc);
148 :
149 0 : if (!total_objects)
150 : return SHRINK_EMPTY;
151 :
152 0 : total_objects = vfs_pressure_ratio(total_objects);
153 0 : return total_objects;
154 : }
155 :
156 0 : static void destroy_super_work(struct work_struct *work)
157 : {
158 0 : struct super_block *s = container_of(work, struct super_block,
159 : destroy_work);
160 : int i;
161 :
162 0 : for (i = 0; i < SB_FREEZE_LEVELS; i++)
163 0 : percpu_free_rwsem(&s->s_writers.rw_sem[i]);
164 0 : kfree(s);
165 0 : }
166 :
167 0 : static void destroy_super_rcu(struct rcu_head *head)
168 : {
169 0 : struct super_block *s = container_of(head, struct super_block, rcu);
170 0 : INIT_WORK(&s->destroy_work, destroy_super_work);
171 0 : schedule_work(&s->destroy_work);
172 0 : }
173 :
174 : /* Free a superblock that has never been seen by anyone */
175 0 : static void destroy_unused_super(struct super_block *s)
176 : {
177 0 : if (!s)
178 : return;
179 0 : up_write(&s->s_umount);
180 0 : list_lru_destroy(&s->s_dentry_lru);
181 0 : list_lru_destroy(&s->s_inode_lru);
182 0 : security_sb_free(s);
183 0 : put_user_ns(s->s_user_ns);
184 0 : kfree(s->s_subtype);
185 0 : free_prealloced_shrinker(&s->s_shrink);
186 : /* no delays needed */
187 0 : 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 : */
199 10 : static struct super_block *alloc_super(struct file_system_type *type, int flags,
200 : struct user_namespace *user_ns)
201 : {
202 10 : struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
203 : static const struct super_operations default_op;
204 : int i;
205 :
206 10 : if (!s)
207 : return NULL;
208 :
209 20 : INIT_LIST_HEAD(&s->s_mounts);
210 10 : s->s_user_ns = get_user_ns(user_ns);
211 10 : 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 10 : down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
229 :
230 10 : if (security_sb_alloc(s))
231 : goto fail;
232 :
233 40 : for (i = 0; i < SB_FREEZE_LEVELS; i++) {
234 60 : if (__percpu_init_rwsem(&s->s_writers.rw_sem[i],
235 30 : sb_writers_name[i],
236 : &type->s_writers_key[i]))
237 : goto fail;
238 : }
239 10 : init_waitqueue_head(&s->s_writers.wait_unfrozen);
240 10 : s->s_bdi = &noop_backing_dev_info;
241 10 : s->s_flags = flags;
242 10 : if (s->s_user_ns != &init_user_ns)
243 0 : s->s_iflags |= SB_I_NODEV;
244 20 : INIT_HLIST_NODE(&s->s_instances);
245 10 : INIT_HLIST_BL_HEAD(&s->s_roots);
246 10 : mutex_init(&s->s_sync_lock);
247 20 : INIT_LIST_HEAD(&s->s_inodes);
248 10 : spin_lock_init(&s->s_inode_list_lock);
249 20 : INIT_LIST_HEAD(&s->s_inodes_wb);
250 10 : spin_lock_init(&s->s_inode_wblist_lock);
251 :
252 10 : s->s_count = 1;
253 20 : atomic_set(&s->s_active, 1);
254 10 : mutex_init(&s->s_vfs_rename_mutex);
255 : lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
256 10 : init_rwsem(&s->s_dquot.dqio_sem);
257 10 : s->s_maxbytes = MAX_NON_LFS;
258 10 : s->s_op = &default_op;
259 10 : s->s_time_gran = 1000000000;
260 10 : s->s_time_min = TIME64_MIN;
261 10 : s->s_time_max = TIME64_MAX;
262 :
263 10 : s->s_shrink.seeks = DEFAULT_SEEKS;
264 10 : s->s_shrink.scan_objects = super_cache_scan;
265 10 : s->s_shrink.count_objects = super_cache_count;
266 10 : s->s_shrink.batch = 1024;
267 10 : s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
268 10 : if (prealloc_shrinker(&s->s_shrink))
269 : goto fail;
270 10 : if (list_lru_init_memcg(&s->s_dentry_lru, &s->s_shrink))
271 : goto fail;
272 10 : if (list_lru_init_memcg(&s->s_inode_lru, &s->s_shrink))
273 : goto fail;
274 : return s;
275 :
276 : fail:
277 0 : 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 : */
286 0 : static void __put_super(struct super_block *s)
287 : {
288 0 : if (!--s->s_count) {
289 0 : list_del_init(&s->s_list);
290 0 : WARN_ON(s->s_dentry_lru.node);
291 0 : WARN_ON(s->s_inode_lru.node);
292 0 : WARN_ON(!list_empty(&s->s_mounts));
293 0 : security_sb_free(s);
294 0 : fscrypt_sb_free(s);
295 0 : put_user_ns(s->s_user_ns);
296 0 : kfree(s->s_subtype);
297 0 : call_rcu(&s->rcu, destroy_super_rcu);
298 : }
299 0 : }
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 : */
308 0 : void put_super(struct super_block *sb)
309 : {
310 0 : spin_lock(&sb_lock);
311 0 : __put_super(sb);
312 0 : spin_unlock(&sb_lock);
313 0 : }
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 : */
327 0 : void deactivate_locked_super(struct super_block *s)
328 : {
329 0 : struct file_system_type *fs = s->s_type;
330 0 : if (atomic_dec_and_test(&s->s_active)) {
331 0 : unregister_shrinker(&s->s_shrink);
332 0 : 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 0 : list_lru_destroy(&s->s_dentry_lru);
340 0 : list_lru_destroy(&s->s_inode_lru);
341 :
342 0 : put_filesystem(fs);
343 : put_super(s);
344 : } else {
345 0 : up_write(&s->s_umount);
346 : }
347 0 : }
348 :
349 : EXPORT_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 : */
359 10 : void deactivate_super(struct super_block *s)
360 : {
361 20 : if (!atomic_add_unless(&s->s_active, -1, 1)) {
362 0 : down_write(&s->s_umount);
363 0 : deactivate_locked_super(s);
364 : }
365 10 : }
366 :
367 : EXPORT_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 : */
382 0 : static int grab_super(struct super_block *s) __releases(sb_lock)
383 : {
384 0 : s->s_count++;
385 0 : spin_unlock(&sb_lock);
386 0 : down_write(&s->s_umount);
387 0 : if ((s->s_flags & SB_BORN) && atomic_inc_not_zero(&s->s_active)) {
388 0 : put_super(s);
389 0 : return 1;
390 : }
391 0 : up_write(&s->s_umount);
392 0 : put_super(s);
393 0 : 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 : */
413 0 : bool trylock_super(struct super_block *sb)
414 : {
415 0 : if (down_read_trylock(&sb->s_umount)) {
416 0 : if (!hlist_unhashed(&sb->s_instances) &&
417 0 : sb->s_root && (sb->s_flags & SB_BORN))
418 : return true;
419 0 : up_read(&sb->s_umount);
420 : }
421 :
422 : return false;
423 : }
424 :
425 : /**
426 : * generic_shutdown_super - common helper for ->kill_sb()
427 : * @sb: superblock to kill
428 : *
429 : * generic_shutdown_super() does all fs-independent work on superblock
430 : * shutdown. Typical ->kill_sb() should pick all fs-specific objects
431 : * that need destruction out of superblock, call generic_shutdown_super()
432 : * and release aforementioned objects. Note: dentries and inodes _are_
433 : * taken care of and do not need specific handling.
434 : *
435 : * Upon calling this function, the filesystem may no longer alter or
436 : * rearrange the set of dentries belonging to this super_block, nor may it
437 : * change the attachments of dentries to inodes.
438 : */
439 0 : void generic_shutdown_super(struct super_block *sb)
440 : {
441 0 : const struct super_operations *sop = sb->s_op;
442 :
443 0 : if (sb->s_root) {
444 0 : shrink_dcache_for_umount(sb);
445 0 : sync_filesystem(sb);
446 0 : sb->s_flags &= ~SB_ACTIVE;
447 :
448 : cgroup_writeback_umount();
449 :
450 : /* evict all inodes with zero refcount */
451 0 : evict_inodes(sb);
452 : /* only nonzero refcount inodes can have marks */
453 0 : fsnotify_sb_delete(sb);
454 0 : security_sb_delete(sb);
455 :
456 0 : if (sb->s_dio_done_wq) {
457 0 : destroy_workqueue(sb->s_dio_done_wq);
458 0 : sb->s_dio_done_wq = NULL;
459 : }
460 :
461 0 : if (sop->put_super)
462 0 : sop->put_super(sb);
463 :
464 0 : if (!list_empty(&sb->s_inodes)) {
465 0 : printk("VFS: Busy inodes after unmount of %s. "
466 : "Self-destruct in 5 seconds. Have a nice day...\n",
467 : sb->s_id);
468 : }
469 : }
470 0 : spin_lock(&sb_lock);
471 : /* should be initialized for __put_super_and_need_restart() */
472 0 : hlist_del_init(&sb->s_instances);
473 0 : spin_unlock(&sb_lock);
474 0 : up_write(&sb->s_umount);
475 0 : if (sb->s_bdi != &noop_backing_dev_info) {
476 0 : if (sb->s_iflags & SB_I_PERSB_BDI)
477 0 : bdi_unregister(sb->s_bdi);
478 0 : bdi_put(sb->s_bdi);
479 0 : sb->s_bdi = &noop_backing_dev_info;
480 : }
481 0 : }
482 :
483 : EXPORT_SYMBOL(generic_shutdown_super);
484 :
485 0 : bool mount_capable(struct fs_context *fc)
486 : {
487 0 : if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT))
488 0 : return capable(CAP_SYS_ADMIN);
489 : else
490 0 : return ns_capable(fc->user_ns, CAP_SYS_ADMIN);
491 : }
492 :
493 : /**
494 : * sget_fc - Find or create a superblock
495 : * @fc: Filesystem context.
496 : * @test: Comparison callback
497 : * @set: Setup callback
498 : *
499 : * Find or create a superblock using the parameters stored in the filesystem
500 : * context and the two callback functions.
501 : *
502 : * If an extant superblock is matched, then that will be returned with an
503 : * elevated reference count that the caller must transfer or discard.
504 : *
505 : * If no match is made, a new superblock will be allocated and basic
506 : * initialisation will be performed (s_type, s_fs_info and s_id will be set and
507 : * the set() callback will be invoked), the superblock will be published and it
508 : * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE
509 : * as yet unset.
510 : */
511 10 : struct super_block *sget_fc(struct fs_context *fc,
512 : int (*test)(struct super_block *, struct fs_context *),
513 : int (*set)(struct super_block *, struct fs_context *))
514 : {
515 10 : struct super_block *s = NULL;
516 : struct super_block *old;
517 10 : struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;
518 : int err;
519 :
520 : retry:
521 20 : spin_lock(&sb_lock);
522 20 : if (test) {
523 0 : hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {
524 0 : if (test(old, fc))
525 : goto share_extant_sb;
526 : }
527 : }
528 20 : if (!s) {
529 10 : spin_unlock(&sb_lock);
530 10 : s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);
531 10 : if (!s)
532 : return ERR_PTR(-ENOMEM);
533 : goto retry;
534 : }
535 :
536 10 : s->s_fs_info = fc->s_fs_info;
537 10 : err = set(s, fc);
538 10 : if (err) {
539 0 : s->s_fs_info = NULL;
540 0 : spin_unlock(&sb_lock);
541 0 : destroy_unused_super(s);
542 0 : return ERR_PTR(err);
543 : }
544 10 : fc->s_fs_info = NULL;
545 10 : s->s_type = fc->fs_type;
546 10 : s->s_iflags |= fc->s_iflags;
547 10 : strlcpy(s->s_id, s->s_type->name, sizeof(s->s_id));
548 20 : list_add_tail(&s->s_list, &super_blocks);
549 20 : hlist_add_head(&s->s_instances, &s->s_type->fs_supers);
550 10 : spin_unlock(&sb_lock);
551 10 : get_filesystem(s->s_type);
552 10 : register_shrinker_prepared(&s->s_shrink);
553 10 : return s;
554 :
555 : share_extant_sb:
556 0 : if (user_ns != old->s_user_ns) {
557 0 : spin_unlock(&sb_lock);
558 0 : destroy_unused_super(s);
559 0 : return ERR_PTR(-EBUSY);
560 : }
561 0 : if (!grab_super(old))
562 : goto retry;
563 0 : destroy_unused_super(s);
564 0 : return old;
565 : }
566 : EXPORT_SYMBOL(sget_fc);
567 :
568 : /**
569 : * sget - find or create a superblock
570 : * @type: filesystem type superblock should belong to
571 : * @test: comparison callback
572 : * @set: setup callback
573 : * @flags: mount flags
574 : * @data: argument to each of them
575 : */
576 0 : struct super_block *sget(struct file_system_type *type,
577 : int (*test)(struct super_block *,void *),
578 : int (*set)(struct super_block *,void *),
579 : int flags,
580 : void *data)
581 : {
582 0 : struct user_namespace *user_ns = current_user_ns();
583 0 : struct super_block *s = NULL;
584 : struct super_block *old;
585 : int err;
586 :
587 : /* We don't yet pass the user namespace of the parent
588 : * mount through to here so always use &init_user_ns
589 : * until that changes.
590 : */
591 : if (flags & SB_SUBMOUNT)
592 : user_ns = &init_user_ns;
593 :
594 : retry:
595 0 : spin_lock(&sb_lock);
596 0 : if (test) {
597 0 : hlist_for_each_entry(old, &type->fs_supers, s_instances) {
598 0 : if (!test(old, data))
599 0 : continue;
600 0 : if (user_ns != old->s_user_ns) {
601 0 : spin_unlock(&sb_lock);
602 0 : destroy_unused_super(s);
603 0 : return ERR_PTR(-EBUSY);
604 : }
605 0 : if (!grab_super(old))
606 : goto retry;
607 0 : destroy_unused_super(s);
608 0 : return old;
609 : }
610 : }
611 0 : if (!s) {
612 0 : spin_unlock(&sb_lock);
613 0 : s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
614 0 : if (!s)
615 : return ERR_PTR(-ENOMEM);
616 : goto retry;
617 : }
618 :
619 0 : err = set(s, data);
620 0 : if (err) {
621 0 : spin_unlock(&sb_lock);
622 0 : destroy_unused_super(s);
623 0 : return ERR_PTR(err);
624 : }
625 0 : s->s_type = type;
626 0 : strlcpy(s->s_id, type->name, sizeof(s->s_id));
627 0 : list_add_tail(&s->s_list, &super_blocks);
628 0 : hlist_add_head(&s->s_instances, &type->fs_supers);
629 0 : spin_unlock(&sb_lock);
630 0 : get_filesystem(type);
631 0 : register_shrinker_prepared(&s->s_shrink);
632 0 : return s;
633 : }
634 : EXPORT_SYMBOL(sget);
635 :
636 0 : void drop_super(struct super_block *sb)
637 : {
638 0 : up_read(&sb->s_umount);
639 0 : put_super(sb);
640 0 : }
641 :
642 : EXPORT_SYMBOL(drop_super);
643 :
644 0 : void drop_super_exclusive(struct super_block *sb)
645 : {
646 0 : up_write(&sb->s_umount);
647 0 : put_super(sb);
648 0 : }
649 : EXPORT_SYMBOL(drop_super_exclusive);
650 :
651 0 : static void __iterate_supers(void (*f)(struct super_block *))
652 : {
653 0 : struct super_block *sb, *p = NULL;
654 :
655 0 : spin_lock(&sb_lock);
656 0 : list_for_each_entry(sb, &super_blocks, s_list) {
657 0 : if (hlist_unhashed(&sb->s_instances))
658 0 : continue;
659 0 : sb->s_count++;
660 0 : spin_unlock(&sb_lock);
661 :
662 0 : f(sb);
663 :
664 0 : spin_lock(&sb_lock);
665 0 : if (p)
666 0 : __put_super(p);
667 : p = sb;
668 : }
669 0 : if (p)
670 0 : __put_super(p);
671 0 : spin_unlock(&sb_lock);
672 0 : }
673 : /**
674 : * iterate_supers - call function for all active superblocks
675 : * @f: function to call
676 : * @arg: argument to pass to it
677 : *
678 : * Scans the superblock list and calls given function, passing it
679 : * locked superblock and given argument.
680 : */
681 0 : void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
682 : {
683 0 : struct super_block *sb, *p = NULL;
684 :
685 0 : spin_lock(&sb_lock);
686 0 : list_for_each_entry(sb, &super_blocks, s_list) {
687 0 : if (hlist_unhashed(&sb->s_instances))
688 0 : continue;
689 0 : sb->s_count++;
690 0 : spin_unlock(&sb_lock);
691 :
692 0 : down_read(&sb->s_umount);
693 0 : if (sb->s_root && (sb->s_flags & SB_BORN))
694 0 : f(sb, arg);
695 0 : up_read(&sb->s_umount);
696 :
697 0 : spin_lock(&sb_lock);
698 0 : if (p)
699 0 : __put_super(p);
700 : p = sb;
701 : }
702 0 : if (p)
703 0 : __put_super(p);
704 0 : spin_unlock(&sb_lock);
705 0 : }
706 :
707 : /**
708 : * iterate_supers_type - call function for superblocks of given type
709 : * @type: fs type
710 : * @f: function to call
711 : * @arg: argument to pass to it
712 : *
713 : * Scans the superblock list and calls given function, passing it
714 : * locked superblock and given argument.
715 : */
716 0 : void iterate_supers_type(struct file_system_type *type,
717 : void (*f)(struct super_block *, void *), void *arg)
718 : {
719 0 : struct super_block *sb, *p = NULL;
720 :
721 0 : spin_lock(&sb_lock);
722 0 : hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
723 0 : sb->s_count++;
724 0 : spin_unlock(&sb_lock);
725 :
726 0 : down_read(&sb->s_umount);
727 0 : if (sb->s_root && (sb->s_flags & SB_BORN))
728 0 : f(sb, arg);
729 0 : up_read(&sb->s_umount);
730 :
731 0 : spin_lock(&sb_lock);
732 0 : if (p)
733 0 : __put_super(p);
734 0 : p = sb;
735 : }
736 0 : if (p)
737 0 : __put_super(p);
738 0 : spin_unlock(&sb_lock);
739 0 : }
740 :
741 : EXPORT_SYMBOL(iterate_supers_type);
742 :
743 : /**
744 : * get_super - get the superblock of a device
745 : * @bdev: device to get the superblock for
746 : *
747 : * Scans the superblock list and finds the superblock of the file system
748 : * mounted on the device given. %NULL is returned if no match is found.
749 : */
750 0 : struct super_block *get_super(struct block_device *bdev)
751 : {
752 : struct super_block *sb;
753 :
754 0 : if (!bdev)
755 : return NULL;
756 :
757 : spin_lock(&sb_lock);
758 : rescan:
759 0 : list_for_each_entry(sb, &super_blocks, s_list) {
760 0 : if (hlist_unhashed(&sb->s_instances))
761 0 : continue;
762 0 : if (sb->s_bdev == bdev) {
763 0 : sb->s_count++;
764 0 : spin_unlock(&sb_lock);
765 0 : down_read(&sb->s_umount);
766 : /* still alive? */
767 0 : if (sb->s_root && (sb->s_flags & SB_BORN))
768 : return sb;
769 0 : up_read(&sb->s_umount);
770 : /* nope, got unmounted */
771 0 : spin_lock(&sb_lock);
772 0 : __put_super(sb);
773 0 : goto rescan;
774 : }
775 : }
776 0 : spin_unlock(&sb_lock);
777 0 : return NULL;
778 : }
779 :
780 : /**
781 : * get_active_super - get an active reference to the superblock of a device
782 : * @bdev: device to get the superblock for
783 : *
784 : * Scans the superblock list and finds the superblock of the file system
785 : * mounted on the device given. Returns the superblock with an active
786 : * reference or %NULL if none was found.
787 : */
788 0 : struct super_block *get_active_super(struct block_device *bdev)
789 : {
790 : struct super_block *sb;
791 :
792 0 : if (!bdev)
793 : return NULL;
794 :
795 : restart:
796 0 : spin_lock(&sb_lock);
797 0 : list_for_each_entry(sb, &super_blocks, s_list) {
798 0 : if (hlist_unhashed(&sb->s_instances))
799 0 : continue;
800 0 : if (sb->s_bdev == bdev) {
801 0 : if (!grab_super(sb))
802 : goto restart;
803 0 : up_write(&sb->s_umount);
804 0 : return sb;
805 : }
806 : }
807 0 : spin_unlock(&sb_lock);
808 0 : return NULL;
809 : }
810 :
811 0 : struct super_block *user_get_super(dev_t dev, bool excl)
812 : {
813 : struct super_block *sb;
814 :
815 : spin_lock(&sb_lock);
816 : rescan:
817 0 : list_for_each_entry(sb, &super_blocks, s_list) {
818 0 : if (hlist_unhashed(&sb->s_instances))
819 0 : continue;
820 0 : if (sb->s_dev == dev) {
821 0 : sb->s_count++;
822 0 : spin_unlock(&sb_lock);
823 0 : if (excl)
824 0 : down_write(&sb->s_umount);
825 : else
826 0 : down_read(&sb->s_umount);
827 : /* still alive? */
828 0 : if (sb->s_root && (sb->s_flags & SB_BORN))
829 : return sb;
830 0 : if (excl)
831 0 : up_write(&sb->s_umount);
832 : else
833 0 : up_read(&sb->s_umount);
834 : /* nope, got unmounted */
835 0 : spin_lock(&sb_lock);
836 0 : __put_super(sb);
837 0 : goto rescan;
838 : }
839 : }
840 0 : spin_unlock(&sb_lock);
841 0 : return NULL;
842 : }
843 :
844 : /**
845 : * reconfigure_super - asks filesystem to change superblock parameters
846 : * @fc: The superblock and configuration
847 : *
848 : * Alters the configuration parameters of a live superblock.
849 : */
850 0 : int reconfigure_super(struct fs_context *fc)
851 : {
852 0 : struct super_block *sb = fc->root->d_sb;
853 : int retval;
854 0 : bool remount_ro = false;
855 0 : bool force = fc->sb_flags & SB_FORCE;
856 :
857 0 : if (fc->sb_flags_mask & ~MS_RMT_MASK)
858 : return -EINVAL;
859 0 : if (sb->s_writers.frozen != SB_UNFROZEN)
860 : return -EBUSY;
861 :
862 0 : retval = security_sb_remount(sb, fc->security);
863 : if (retval)
864 : return retval;
865 :
866 0 : if (fc->sb_flags_mask & SB_RDONLY) {
867 : #ifdef CONFIG_BLOCK
868 0 : if (!(fc->sb_flags & SB_RDONLY) && sb->s_bdev &&
869 0 : bdev_read_only(sb->s_bdev))
870 : return -EACCES;
871 : #endif
872 :
873 0 : remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb);
874 : }
875 :
876 0 : if (remount_ro) {
877 0 : if (!hlist_empty(&sb->s_pins)) {
878 0 : up_write(&sb->s_umount);
879 0 : group_pin_kill(&sb->s_pins);
880 0 : down_write(&sb->s_umount);
881 0 : if (!sb->s_root)
882 : return 0;
883 0 : if (sb->s_writers.frozen != SB_UNFROZEN)
884 : return -EBUSY;
885 0 : remount_ro = !sb_rdonly(sb);
886 : }
887 : }
888 0 : shrink_dcache_sb(sb);
889 :
890 : /* If we are reconfiguring to RDONLY and current sb is read/write,
891 : * make sure there are no files open for writing.
892 : */
893 0 : if (remount_ro) {
894 0 : if (force) {
895 0 : sb->s_readonly_remount = 1;
896 0 : smp_wmb();
897 : } else {
898 0 : retval = sb_prepare_remount_readonly(sb);
899 0 : if (retval)
900 : return retval;
901 : }
902 : }
903 :
904 0 : if (fc->ops->reconfigure) {
905 0 : retval = fc->ops->reconfigure(fc);
906 0 : if (retval) {
907 0 : if (!force)
908 : goto cancel_readonly;
909 : /* If forced remount, go ahead despite any errors */
910 0 : WARN(1, "forced remount of a %s fs returned %i\n",
911 : sb->s_type->name, retval);
912 : }
913 : }
914 :
915 0 : WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) |
916 : (fc->sb_flags & fc->sb_flags_mask)));
917 : /* Needs to be ordered wrt mnt_is_readonly() */
918 0 : smp_wmb();
919 0 : sb->s_readonly_remount = 0;
920 :
921 : /*
922 : * Some filesystems modify their metadata via some other path than the
923 : * bdev buffer cache (eg. use a private mapping, or directories in
924 : * pagecache, etc). Also file data modifications go via their own
925 : * mappings. So If we try to mount readonly then copy the filesystem
926 : * from bdev, we could get stale data, so invalidate it to give a best
927 : * effort at coherency.
928 : */
929 0 : if (remount_ro && sb->s_bdev)
930 0 : invalidate_bdev(sb->s_bdev);
931 : return 0;
932 :
933 : cancel_readonly:
934 0 : sb->s_readonly_remount = 0;
935 0 : return retval;
936 : }
937 :
938 0 : static void do_emergency_remount_callback(struct super_block *sb)
939 : {
940 0 : down_write(&sb->s_umount);
941 0 : if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) &&
942 0 : !sb_rdonly(sb)) {
943 : struct fs_context *fc;
944 :
945 0 : fc = fs_context_for_reconfigure(sb->s_root,
946 : SB_RDONLY | SB_FORCE, SB_RDONLY);
947 0 : if (!IS_ERR(fc)) {
948 0 : if (parse_monolithic_mount_data(fc, NULL) == 0)
949 0 : (void)reconfigure_super(fc);
950 0 : put_fs_context(fc);
951 : }
952 : }
953 0 : up_write(&sb->s_umount);
954 0 : }
955 :
956 0 : static void do_emergency_remount(struct work_struct *work)
957 : {
958 0 : __iterate_supers(do_emergency_remount_callback);
959 0 : kfree(work);
960 0 : printk("Emergency Remount complete\n");
961 0 : }
962 :
963 0 : void emergency_remount(void)
964 : {
965 : struct work_struct *work;
966 :
967 0 : work = kmalloc(sizeof(*work), GFP_ATOMIC);
968 0 : if (work) {
969 0 : INIT_WORK(work, do_emergency_remount);
970 : schedule_work(work);
971 : }
972 0 : }
973 :
974 0 : static void do_thaw_all_callback(struct super_block *sb)
975 : {
976 0 : down_write(&sb->s_umount);
977 0 : if (sb->s_root && sb->s_flags & SB_BORN) {
978 0 : emergency_thaw_bdev(sb);
979 0 : thaw_super_locked(sb);
980 : } else {
981 0 : up_write(&sb->s_umount);
982 : }
983 0 : }
984 :
985 0 : static void do_thaw_all(struct work_struct *work)
986 : {
987 0 : __iterate_supers(do_thaw_all_callback);
988 0 : kfree(work);
989 0 : printk(KERN_WARNING "Emergency Thaw complete\n");
990 0 : }
991 :
992 : /**
993 : * emergency_thaw_all -- forcibly thaw every frozen filesystem
994 : *
995 : * Used for emergency unfreeze of all filesystems via SysRq
996 : */
997 0 : void emergency_thaw_all(void)
998 : {
999 : struct work_struct *work;
1000 :
1001 0 : work = kmalloc(sizeof(*work), GFP_ATOMIC);
1002 0 : if (work) {
1003 0 : INIT_WORK(work, do_thaw_all);
1004 : schedule_work(work);
1005 : }
1006 0 : }
1007 :
1008 : static DEFINE_IDA(unnamed_dev_ida);
1009 :
1010 : /**
1011 : * get_anon_bdev - Allocate a block device for filesystems which don't have one.
1012 : * @p: Pointer to a dev_t.
1013 : *
1014 : * Filesystems which don't use real block devices can call this function
1015 : * to allocate a virtual block device.
1016 : *
1017 : * Context: Any context. Frequently called while holding sb_lock.
1018 : * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
1019 : * or -ENOMEM if memory allocation failed.
1020 : */
1021 10 : int get_anon_bdev(dev_t *p)
1022 : {
1023 : int dev;
1024 :
1025 : /*
1026 : * Many userspace utilities consider an FSID of 0 invalid.
1027 : * Always return at least 1 from get_anon_bdev.
1028 : */
1029 10 : dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
1030 : GFP_ATOMIC);
1031 10 : if (dev == -ENOSPC)
1032 0 : dev = -EMFILE;
1033 10 : if (dev < 0)
1034 : return dev;
1035 :
1036 10 : *p = MKDEV(0, dev);
1037 10 : return 0;
1038 : }
1039 : EXPORT_SYMBOL(get_anon_bdev);
1040 :
1041 0 : void free_anon_bdev(dev_t dev)
1042 : {
1043 0 : ida_free(&unnamed_dev_ida, MINOR(dev));
1044 0 : }
1045 : EXPORT_SYMBOL(free_anon_bdev);
1046 :
1047 0 : int set_anon_super(struct super_block *s, void *data)
1048 : {
1049 10 : return get_anon_bdev(&s->s_dev);
1050 : }
1051 : EXPORT_SYMBOL(set_anon_super);
1052 :
1053 0 : void kill_anon_super(struct super_block *sb)
1054 : {
1055 0 : dev_t dev = sb->s_dev;
1056 0 : generic_shutdown_super(sb);
1057 0 : free_anon_bdev(dev);
1058 0 : }
1059 : EXPORT_SYMBOL(kill_anon_super);
1060 :
1061 0 : void kill_litter_super(struct super_block *sb)
1062 : {
1063 0 : if (sb->s_root)
1064 0 : d_genocide(sb->s_root);
1065 0 : kill_anon_super(sb);
1066 0 : }
1067 : EXPORT_SYMBOL(kill_litter_super);
1068 :
1069 10 : int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)
1070 : {
1071 10 : return set_anon_super(sb, NULL);
1072 : }
1073 : EXPORT_SYMBOL(set_anon_super_fc);
1074 :
1075 0 : static int test_keyed_super(struct super_block *sb, struct fs_context *fc)
1076 : {
1077 0 : return sb->s_fs_info == fc->s_fs_info;
1078 : }
1079 :
1080 0 : static int test_single_super(struct super_block *s, struct fs_context *fc)
1081 : {
1082 0 : return 1;
1083 : }
1084 :
1085 : /**
1086 : * vfs_get_super - Get a superblock with a search key set in s_fs_info.
1087 : * @fc: The filesystem context holding the parameters
1088 : * @keying: How to distinguish superblocks
1089 : * @fill_super: Helper to initialise a new superblock
1090 : *
1091 : * Search for a superblock and create a new one if not found. The search
1092 : * criterion is controlled by @keying. If the search fails, a new superblock
1093 : * is created and @fill_super() is called to initialise it.
1094 : *
1095 : * @keying can take one of a number of values:
1096 : *
1097 : * (1) vfs_get_single_super - Only one superblock of this type may exist on the
1098 : * system. This is typically used for special system filesystems.
1099 : *
1100 : * (2) vfs_get_keyed_super - Multiple superblocks may exist, but they must have
1101 : * distinct keys (where the key is in s_fs_info). Searching for the same
1102 : * key again will turn up the superblock for that key.
1103 : *
1104 : * (3) vfs_get_independent_super - Multiple superblocks may exist and are
1105 : * unkeyed. Each call will get a new superblock.
1106 : *
1107 : * A permissions check is made by sget_fc() unless we're getting a superblock
1108 : * for a kernel-internal mount or a submount.
1109 : */
1110 10 : int vfs_get_super(struct fs_context *fc,
1111 : enum vfs_get_super_keying keying,
1112 : int (*fill_super)(struct super_block *sb,
1113 : struct fs_context *fc))
1114 : {
1115 : int (*test)(struct super_block *, struct fs_context *);
1116 : struct super_block *sb;
1117 : int err;
1118 :
1119 10 : switch (keying) {
1120 : case vfs_get_single_super:
1121 : case vfs_get_single_reconf_super:
1122 : test = test_single_super;
1123 : break;
1124 : case vfs_get_keyed_super:
1125 0 : test = test_keyed_super;
1126 0 : break;
1127 : case vfs_get_independent_super:
1128 10 : test = NULL;
1129 10 : break;
1130 : default:
1131 0 : BUG();
1132 : }
1133 :
1134 10 : sb = sget_fc(fc, test, set_anon_super_fc);
1135 10 : if (IS_ERR(sb))
1136 0 : return PTR_ERR(sb);
1137 :
1138 10 : if (!sb->s_root) {
1139 10 : err = fill_super(sb, fc);
1140 10 : if (err)
1141 : goto error;
1142 :
1143 10 : sb->s_flags |= SB_ACTIVE;
1144 20 : fc->root = dget(sb->s_root);
1145 : } else {
1146 0 : fc->root = dget(sb->s_root);
1147 0 : if (keying == vfs_get_single_reconf_super) {
1148 0 : err = reconfigure_super(fc);
1149 0 : if (err < 0) {
1150 0 : dput(fc->root);
1151 0 : fc->root = NULL;
1152 0 : goto error;
1153 : }
1154 : }
1155 : }
1156 :
1157 : return 0;
1158 :
1159 : error:
1160 0 : deactivate_locked_super(sb);
1161 0 : return err;
1162 : }
1163 : EXPORT_SYMBOL(vfs_get_super);
1164 :
1165 10 : int get_tree_nodev(struct fs_context *fc,
1166 : int (*fill_super)(struct super_block *sb,
1167 : struct fs_context *fc))
1168 : {
1169 10 : return vfs_get_super(fc, vfs_get_independent_super, fill_super);
1170 : }
1171 : EXPORT_SYMBOL(get_tree_nodev);
1172 :
1173 0 : int get_tree_single(struct fs_context *fc,
1174 : int (*fill_super)(struct super_block *sb,
1175 : struct fs_context *fc))
1176 : {
1177 0 : return vfs_get_super(fc, vfs_get_single_super, fill_super);
1178 : }
1179 : EXPORT_SYMBOL(get_tree_single);
1180 :
1181 0 : int get_tree_single_reconf(struct fs_context *fc,
1182 : int (*fill_super)(struct super_block *sb,
1183 : struct fs_context *fc))
1184 : {
1185 0 : return vfs_get_super(fc, vfs_get_single_reconf_super, fill_super);
1186 : }
1187 : EXPORT_SYMBOL(get_tree_single_reconf);
1188 :
1189 0 : int get_tree_keyed(struct fs_context *fc,
1190 : int (*fill_super)(struct super_block *sb,
1191 : struct fs_context *fc),
1192 : void *key)
1193 : {
1194 0 : fc->s_fs_info = key;
1195 0 : return vfs_get_super(fc, vfs_get_keyed_super, fill_super);
1196 : }
1197 : EXPORT_SYMBOL(get_tree_keyed);
1198 :
1199 : #ifdef CONFIG_BLOCK
1200 :
1201 0 : static int set_bdev_super(struct super_block *s, void *data)
1202 : {
1203 0 : s->s_bdev = data;
1204 0 : s->s_dev = s->s_bdev->bd_dev;
1205 0 : s->s_bdi = bdi_get(s->s_bdev->bd_disk->bdi);
1206 :
1207 0 : if (blk_queue_stable_writes(s->s_bdev->bd_disk->queue))
1208 0 : s->s_iflags |= SB_I_STABLE_WRITES;
1209 0 : return 0;
1210 : }
1211 :
1212 0 : static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1213 : {
1214 0 : return set_bdev_super(s, fc->sget_key);
1215 : }
1216 :
1217 0 : static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1218 : {
1219 0 : return s->s_bdev == fc->sget_key;
1220 : }
1221 :
1222 : /**
1223 : * get_tree_bdev - Get a superblock based on a single block device
1224 : * @fc: The filesystem context holding the parameters
1225 : * @fill_super: Helper to initialise a new superblock
1226 : */
1227 0 : int get_tree_bdev(struct fs_context *fc,
1228 : int (*fill_super)(struct super_block *,
1229 : struct fs_context *))
1230 : {
1231 : struct block_device *bdev;
1232 : struct super_block *s;
1233 0 : fmode_t mode = FMODE_READ | FMODE_EXCL;
1234 0 : int error = 0;
1235 :
1236 0 : if (!(fc->sb_flags & SB_RDONLY))
1237 0 : mode |= FMODE_WRITE;
1238 :
1239 0 : if (!fc->source)
1240 0 : return invalf(fc, "No source specified");
1241 :
1242 0 : bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type);
1243 0 : if (IS_ERR(bdev)) {
1244 0 : errorf(fc, "%s: Can't open blockdev", fc->source);
1245 0 : return PTR_ERR(bdev);
1246 : }
1247 :
1248 : /* Once the superblock is inserted into the list by sget_fc(), s_umount
1249 : * will protect the lockfs code from trying to start a snapshot while
1250 : * we are mounting
1251 : */
1252 0 : mutex_lock(&bdev->bd_fsfreeze_mutex);
1253 0 : if (bdev->bd_fsfreeze_count > 0) {
1254 0 : mutex_unlock(&bdev->bd_fsfreeze_mutex);
1255 0 : warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
1256 0 : blkdev_put(bdev, mode);
1257 0 : return -EBUSY;
1258 : }
1259 :
1260 0 : fc->sb_flags |= SB_NOSEC;
1261 0 : fc->sget_key = bdev;
1262 0 : s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc);
1263 0 : mutex_unlock(&bdev->bd_fsfreeze_mutex);
1264 0 : if (IS_ERR(s)) {
1265 0 : blkdev_put(bdev, mode);
1266 0 : return PTR_ERR(s);
1267 : }
1268 :
1269 0 : if (s->s_root) {
1270 : /* Don't summarily change the RO/RW state. */
1271 0 : if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
1272 0 : warnf(fc, "%pg: Can't mount, would change RO state", bdev);
1273 0 : deactivate_locked_super(s);
1274 0 : blkdev_put(bdev, mode);
1275 0 : return -EBUSY;
1276 : }
1277 :
1278 : /*
1279 : * s_umount nests inside open_mutex during
1280 : * __invalidate_device(). blkdev_put() acquires
1281 : * open_mutex and can't be called under s_umount. Drop
1282 : * s_umount temporarily. This is safe as we're
1283 : * holding an active reference.
1284 : */
1285 0 : up_write(&s->s_umount);
1286 0 : blkdev_put(bdev, mode);
1287 0 : down_write(&s->s_umount);
1288 : } else {
1289 0 : s->s_mode = mode;
1290 0 : snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1291 0 : sb_set_blocksize(s, block_size(bdev));
1292 0 : error = fill_super(s, fc);
1293 0 : if (error) {
1294 0 : deactivate_locked_super(s);
1295 0 : return error;
1296 : }
1297 :
1298 0 : s->s_flags |= SB_ACTIVE;
1299 0 : bdev->bd_super = s;
1300 : }
1301 :
1302 0 : BUG_ON(fc->root);
1303 0 : fc->root = dget(s->s_root);
1304 0 : return 0;
1305 : }
1306 : EXPORT_SYMBOL(get_tree_bdev);
1307 :
1308 0 : static int test_bdev_super(struct super_block *s, void *data)
1309 : {
1310 0 : return (void *)s->s_bdev == data;
1311 : }
1312 :
1313 0 : struct dentry *mount_bdev(struct file_system_type *fs_type,
1314 : int flags, const char *dev_name, void *data,
1315 : int (*fill_super)(struct super_block *, void *, int))
1316 : {
1317 : struct block_device *bdev;
1318 : struct super_block *s;
1319 0 : fmode_t mode = FMODE_READ | FMODE_EXCL;
1320 0 : int error = 0;
1321 :
1322 0 : if (!(flags & SB_RDONLY))
1323 0 : mode |= FMODE_WRITE;
1324 :
1325 0 : bdev = blkdev_get_by_path(dev_name, mode, fs_type);
1326 0 : if (IS_ERR(bdev))
1327 : return ERR_CAST(bdev);
1328 :
1329 : /*
1330 : * once the super is inserted into the list by sget, s_umount
1331 : * will protect the lockfs code from trying to start a snapshot
1332 : * while we are mounting
1333 : */
1334 0 : mutex_lock(&bdev->bd_fsfreeze_mutex);
1335 0 : if (bdev->bd_fsfreeze_count > 0) {
1336 0 : mutex_unlock(&bdev->bd_fsfreeze_mutex);
1337 0 : error = -EBUSY;
1338 0 : goto error_bdev;
1339 : }
1340 0 : s = sget(fs_type, test_bdev_super, set_bdev_super, flags | SB_NOSEC,
1341 : bdev);
1342 0 : mutex_unlock(&bdev->bd_fsfreeze_mutex);
1343 0 : if (IS_ERR(s))
1344 : goto error_s;
1345 :
1346 0 : if (s->s_root) {
1347 0 : if ((flags ^ s->s_flags) & SB_RDONLY) {
1348 0 : deactivate_locked_super(s);
1349 0 : error = -EBUSY;
1350 0 : goto error_bdev;
1351 : }
1352 :
1353 : /*
1354 : * s_umount nests inside open_mutex during
1355 : * __invalidate_device(). blkdev_put() acquires
1356 : * open_mutex and can't be called under s_umount. Drop
1357 : * s_umount temporarily. This is safe as we're
1358 : * holding an active reference.
1359 : */
1360 0 : up_write(&s->s_umount);
1361 0 : blkdev_put(bdev, mode);
1362 0 : down_write(&s->s_umount);
1363 : } else {
1364 0 : s->s_mode = mode;
1365 0 : snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1366 0 : sb_set_blocksize(s, block_size(bdev));
1367 0 : error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1368 0 : if (error) {
1369 0 : deactivate_locked_super(s);
1370 0 : goto error;
1371 : }
1372 :
1373 0 : s->s_flags |= SB_ACTIVE;
1374 0 : bdev->bd_super = s;
1375 : }
1376 :
1377 0 : return dget(s->s_root);
1378 :
1379 : error_s:
1380 0 : error = PTR_ERR(s);
1381 : error_bdev:
1382 0 : blkdev_put(bdev, mode);
1383 : error:
1384 0 : return ERR_PTR(error);
1385 : }
1386 : EXPORT_SYMBOL(mount_bdev);
1387 :
1388 0 : void kill_block_super(struct super_block *sb)
1389 : {
1390 0 : struct block_device *bdev = sb->s_bdev;
1391 0 : fmode_t mode = sb->s_mode;
1392 :
1393 0 : bdev->bd_super = NULL;
1394 0 : generic_shutdown_super(sb);
1395 0 : sync_blockdev(bdev);
1396 0 : WARN_ON_ONCE(!(mode & FMODE_EXCL));
1397 0 : blkdev_put(bdev, mode | FMODE_EXCL);
1398 0 : }
1399 :
1400 : EXPORT_SYMBOL(kill_block_super);
1401 : #endif
1402 :
1403 0 : struct dentry *mount_nodev(struct file_system_type *fs_type,
1404 : int flags, void *data,
1405 : int (*fill_super)(struct super_block *, void *, int))
1406 : {
1407 : int error;
1408 0 : struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
1409 :
1410 0 : if (IS_ERR(s))
1411 : return ERR_CAST(s);
1412 :
1413 0 : error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1414 0 : if (error) {
1415 0 : deactivate_locked_super(s);
1416 0 : return ERR_PTR(error);
1417 : }
1418 0 : s->s_flags |= SB_ACTIVE;
1419 0 : return dget(s->s_root);
1420 : }
1421 : EXPORT_SYMBOL(mount_nodev);
1422 :
1423 0 : int reconfigure_single(struct super_block *s,
1424 : int flags, void *data)
1425 : {
1426 : struct fs_context *fc;
1427 : int ret;
1428 :
1429 : /* The caller really need to be passing fc down into mount_single(),
1430 : * then a chunk of this can be removed. [Bollocks -- AV]
1431 : * Better yet, reconfiguration shouldn't happen, but rather the second
1432 : * mount should be rejected if the parameters are not compatible.
1433 : */
1434 0 : fc = fs_context_for_reconfigure(s->s_root, flags, MS_RMT_MASK);
1435 0 : if (IS_ERR(fc))
1436 0 : return PTR_ERR(fc);
1437 :
1438 0 : ret = parse_monolithic_mount_data(fc, data);
1439 0 : if (ret < 0)
1440 : goto out;
1441 :
1442 0 : ret = reconfigure_super(fc);
1443 : out:
1444 0 : put_fs_context(fc);
1445 0 : return ret;
1446 : }
1447 :
1448 0 : static int compare_single(struct super_block *s, void *p)
1449 : {
1450 0 : return 1;
1451 : }
1452 :
1453 0 : struct dentry *mount_single(struct file_system_type *fs_type,
1454 : int flags, void *data,
1455 : int (*fill_super)(struct super_block *, void *, int))
1456 : {
1457 : struct super_block *s;
1458 : int error;
1459 :
1460 0 : s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
1461 0 : if (IS_ERR(s))
1462 : return ERR_CAST(s);
1463 0 : if (!s->s_root) {
1464 0 : error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1465 0 : if (!error)
1466 0 : s->s_flags |= SB_ACTIVE;
1467 : } else {
1468 0 : error = reconfigure_single(s, flags, data);
1469 : }
1470 0 : if (unlikely(error)) {
1471 0 : deactivate_locked_super(s);
1472 0 : return ERR_PTR(error);
1473 : }
1474 0 : return dget(s->s_root);
1475 : }
1476 : EXPORT_SYMBOL(mount_single);
1477 :
1478 : /**
1479 : * vfs_get_tree - Get the mountable root
1480 : * @fc: The superblock configuration context.
1481 : *
1482 : * The filesystem is invoked to get or create a superblock which can then later
1483 : * be used for mounting. The filesystem places a pointer to the root to be
1484 : * used for mounting in @fc->root.
1485 : */
1486 10 : int vfs_get_tree(struct fs_context *fc)
1487 : {
1488 : struct super_block *sb;
1489 : int error;
1490 :
1491 10 : if (fc->root)
1492 : return -EBUSY;
1493 :
1494 : /* Get the mountable root in fc->root, with a ref on the root and a ref
1495 : * on the superblock.
1496 : */
1497 10 : error = fc->ops->get_tree(fc);
1498 10 : if (error < 0)
1499 : return error;
1500 :
1501 10 : if (!fc->root) {
1502 0 : pr_err("Filesystem %s get_tree() didn't set fc->root\n",
1503 : fc->fs_type->name);
1504 : /* We don't know what the locking state of the superblock is -
1505 : * if there is a superblock.
1506 : */
1507 0 : BUG();
1508 : }
1509 :
1510 10 : sb = fc->root->d_sb;
1511 10 : WARN_ON(!sb->s_bdi);
1512 :
1513 : /*
1514 : * Write barrier is for super_cache_count(). We place it before setting
1515 : * SB_BORN as the data dependency between the two functions is the
1516 : * superblock structure contents that we just set up, not the SB_BORN
1517 : * flag.
1518 : */
1519 10 : smp_wmb();
1520 10 : sb->s_flags |= SB_BORN;
1521 :
1522 10 : error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL);
1523 : if (unlikely(error)) {
1524 : fc_drop_locked(fc);
1525 : return error;
1526 : }
1527 :
1528 : /*
1529 : * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1530 : * but s_maxbytes was an unsigned long long for many releases. Throw
1531 : * this warning for a little while to try and catch filesystems that
1532 : * violate this rule.
1533 : */
1534 10 : WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
1535 : "negative value (%lld)\n", fc->fs_type->name, sb->s_maxbytes);
1536 :
1537 : return 0;
1538 : }
1539 : EXPORT_SYMBOL(vfs_get_tree);
1540 :
1541 : /*
1542 : * Setup private BDI for given superblock. It gets automatically cleaned up
1543 : * in generic_shutdown_super().
1544 : */
1545 0 : int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)
1546 : {
1547 : struct backing_dev_info *bdi;
1548 : int err;
1549 : va_list args;
1550 :
1551 0 : bdi = bdi_alloc(NUMA_NO_NODE);
1552 0 : if (!bdi)
1553 : return -ENOMEM;
1554 :
1555 0 : va_start(args, fmt);
1556 0 : err = bdi_register_va(bdi, fmt, args);
1557 0 : va_end(args);
1558 0 : if (err) {
1559 0 : bdi_put(bdi);
1560 0 : return err;
1561 : }
1562 0 : WARN_ON(sb->s_bdi != &noop_backing_dev_info);
1563 0 : sb->s_bdi = bdi;
1564 0 : sb->s_iflags |= SB_I_PERSB_BDI;
1565 :
1566 0 : return 0;
1567 : }
1568 : EXPORT_SYMBOL(super_setup_bdi_name);
1569 :
1570 : /*
1571 : * Setup private BDI for given superblock. I gets automatically cleaned up
1572 : * in generic_shutdown_super().
1573 : */
1574 0 : int super_setup_bdi(struct super_block *sb)
1575 : {
1576 : static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
1577 :
1578 0 : return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,
1579 : atomic_long_inc_return(&bdi_seq));
1580 : }
1581 : EXPORT_SYMBOL(super_setup_bdi);
1582 :
1583 : /**
1584 : * sb_wait_write - wait until all writers to given file system finish
1585 : * @sb: the super for which we wait
1586 : * @level: type of writers we wait for (normal vs page fault)
1587 : *
1588 : * This function waits until there are no writers of given type to given file
1589 : * system.
1590 : */
1591 : static void sb_wait_write(struct super_block *sb, int level)
1592 : {
1593 0 : percpu_down_write(sb->s_writers.rw_sem + level-1);
1594 : }
1595 :
1596 : /*
1597 : * We are going to return to userspace and forget about these locks, the
1598 : * ownership goes to the caller of thaw_super() which does unlock().
1599 : */
1600 : static void lockdep_sb_freeze_release(struct super_block *sb)
1601 : {
1602 : int level;
1603 :
1604 0 : for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
1605 : percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1606 : }
1607 :
1608 : /*
1609 : * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
1610 : */
1611 : static void lockdep_sb_freeze_acquire(struct super_block *sb)
1612 : {
1613 : int level;
1614 :
1615 0 : for (level = 0; level < SB_FREEZE_LEVELS; ++level)
1616 : percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1617 : }
1618 :
1619 : static void sb_freeze_unlock(struct super_block *sb, int level)
1620 : {
1621 0 : for (level--; level >= 0; level--)
1622 0 : percpu_up_write(sb->s_writers.rw_sem + level);
1623 : }
1624 :
1625 : /**
1626 : * freeze_super - lock the filesystem and force it into a consistent state
1627 : * @sb: the super to lock
1628 : *
1629 : * Syncs the super to make sure the filesystem is consistent and calls the fs's
1630 : * freeze_fs. Subsequent calls to this without first thawing the fs will return
1631 : * -EBUSY.
1632 : *
1633 : * During this function, sb->s_writers.frozen goes through these values:
1634 : *
1635 : * SB_UNFROZEN: File system is normal, all writes progress as usual.
1636 : *
1637 : * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
1638 : * writes should be blocked, though page faults are still allowed. We wait for
1639 : * all writes to complete and then proceed to the next stage.
1640 : *
1641 : * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
1642 : * but internal fs threads can still modify the filesystem (although they
1643 : * should not dirty new pages or inodes), writeback can run etc. After waiting
1644 : * for all running page faults we sync the filesystem which will clean all
1645 : * dirty pages and inodes (no new dirty pages or inodes can be created when
1646 : * sync is running).
1647 : *
1648 : * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
1649 : * modification are blocked (e.g. XFS preallocation truncation on inode
1650 : * reclaim). This is usually implemented by blocking new transactions for
1651 : * filesystems that have them and need this additional guard. After all
1652 : * internal writers are finished we call ->freeze_fs() to finish filesystem
1653 : * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
1654 : * mostly auxiliary for filesystems to verify they do not modify frozen fs.
1655 : *
1656 : * sb->s_writers.frozen is protected by sb->s_umount.
1657 : */
1658 0 : int freeze_super(struct super_block *sb)
1659 : {
1660 : int ret;
1661 :
1662 0 : atomic_inc(&sb->s_active);
1663 0 : down_write(&sb->s_umount);
1664 0 : if (sb->s_writers.frozen != SB_UNFROZEN) {
1665 0 : deactivate_locked_super(sb);
1666 0 : return -EBUSY;
1667 : }
1668 :
1669 0 : if (!(sb->s_flags & SB_BORN)) {
1670 0 : up_write(&sb->s_umount);
1671 0 : return 0; /* sic - it's "nothing to do" */
1672 : }
1673 :
1674 0 : if (sb_rdonly(sb)) {
1675 : /* Nothing to do really... */
1676 0 : sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1677 0 : up_write(&sb->s_umount);
1678 0 : return 0;
1679 : }
1680 :
1681 0 : sb->s_writers.frozen = SB_FREEZE_WRITE;
1682 : /* Release s_umount to preserve sb_start_write -> s_umount ordering */
1683 0 : up_write(&sb->s_umount);
1684 0 : sb_wait_write(sb, SB_FREEZE_WRITE);
1685 0 : down_write(&sb->s_umount);
1686 :
1687 : /* Now we go and block page faults... */
1688 0 : sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
1689 0 : sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
1690 :
1691 : /* All writers are done so after syncing there won't be dirty data */
1692 0 : ret = sync_filesystem(sb);
1693 0 : if (ret) {
1694 0 : sb->s_writers.frozen = SB_UNFROZEN;
1695 0 : sb_freeze_unlock(sb, SB_FREEZE_PAGEFAULT);
1696 0 : wake_up(&sb->s_writers.wait_unfrozen);
1697 0 : deactivate_locked_super(sb);
1698 0 : return ret;
1699 : }
1700 :
1701 : /* Now wait for internal filesystem counter */
1702 0 : sb->s_writers.frozen = SB_FREEZE_FS;
1703 0 : sb_wait_write(sb, SB_FREEZE_FS);
1704 :
1705 0 : if (sb->s_op->freeze_fs) {
1706 0 : ret = sb->s_op->freeze_fs(sb);
1707 0 : if (ret) {
1708 0 : printk(KERN_ERR
1709 : "VFS:Filesystem freeze failed\n");
1710 0 : sb->s_writers.frozen = SB_UNFROZEN;
1711 0 : sb_freeze_unlock(sb, SB_FREEZE_FS);
1712 0 : wake_up(&sb->s_writers.wait_unfrozen);
1713 0 : deactivate_locked_super(sb);
1714 0 : return ret;
1715 : }
1716 : }
1717 : /*
1718 : * For debugging purposes so that fs can warn if it sees write activity
1719 : * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
1720 : */
1721 0 : sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1722 0 : lockdep_sb_freeze_release(sb);
1723 0 : up_write(&sb->s_umount);
1724 0 : return 0;
1725 : }
1726 : EXPORT_SYMBOL(freeze_super);
1727 :
1728 0 : static int thaw_super_locked(struct super_block *sb)
1729 : {
1730 : int error;
1731 :
1732 0 : if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) {
1733 0 : up_write(&sb->s_umount);
1734 0 : return -EINVAL;
1735 : }
1736 :
1737 0 : if (sb_rdonly(sb)) {
1738 0 : sb->s_writers.frozen = SB_UNFROZEN;
1739 0 : goto out;
1740 : }
1741 :
1742 0 : lockdep_sb_freeze_acquire(sb);
1743 :
1744 0 : if (sb->s_op->unfreeze_fs) {
1745 0 : error = sb->s_op->unfreeze_fs(sb);
1746 0 : if (error) {
1747 0 : printk(KERN_ERR
1748 : "VFS:Filesystem thaw failed\n");
1749 0 : lockdep_sb_freeze_release(sb);
1750 0 : up_write(&sb->s_umount);
1751 0 : return error;
1752 : }
1753 : }
1754 :
1755 0 : sb->s_writers.frozen = SB_UNFROZEN;
1756 : sb_freeze_unlock(sb, SB_FREEZE_FS);
1757 : out:
1758 0 : wake_up(&sb->s_writers.wait_unfrozen);
1759 0 : deactivate_locked_super(sb);
1760 0 : return 0;
1761 : }
1762 :
1763 : /**
1764 : * thaw_super -- unlock filesystem
1765 : * @sb: the super to thaw
1766 : *
1767 : * Unlocks the filesystem and marks it writeable again after freeze_super().
1768 : */
1769 0 : int thaw_super(struct super_block *sb)
1770 : {
1771 0 : down_write(&sb->s_umount);
1772 0 : return thaw_super_locked(sb);
1773 : }
1774 : EXPORT_SYMBOL(thaw_super);
|
