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1 | /* | |
2 | * linux/fs/super.c | |
3 | * | |
4 | * Copyright (C) 1991, 1992 Linus Torvalds | |
5 | * | |
6 | * super.c contains code to handle: - mount structures | |
7 | * - super-block tables | |
8 | * - filesystem drivers list | |
9 | * - mount system call | |
10 | * - umount system call | |
11 | * - ustat system call | |
12 | * | |
13 | * GK 2/5/95 - Changed to support mounting the root fs via NFS | |
14 | * | |
15 | * Added kerneld support: Jacques Gelinas and Bjorn Ekwall | |
16 | * Added change_root: Werner Almesberger & Hans Lermen, Feb '96 | |
17 | * Added options to /proc/mounts: | |
18 | * Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996. | |
19 | * Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998 | |
20 | * Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000 | |
21 | */ | |
22 | ||
23 | #include <linux/export.h> | |
24 | #include <linux/slab.h> | |
25 | #include <linux/blkdev.h> | |
26 | #include <linux/mount.h> | |
27 | #include <linux/security.h> | |
28 | #include <linux/writeback.h> /* for the emergency remount stuff */ | |
29 | #include <linux/idr.h> | |
30 | #include <linux/mutex.h> | |
31 | #include <linux/backing-dev.h> | |
32 | #include <linux/rculist_bl.h> | |
33 | #include <linux/cleancache.h> | |
34 | #include <linux/fsnotify.h> | |
35 | #include <linux/lockdep.h> | |
36 | #include <linux/user_namespace.h> | |
37 | #include "internal.h" | |
38 | ||
39 | ||
40 | static LIST_HEAD(super_blocks); | |
41 | static DEFINE_SPINLOCK(sb_lock); | |
42 | ||
43 | static char *sb_writers_name[SB_FREEZE_LEVELS] = { | |
44 | "sb_writers", | |
45 | "sb_pagefaults", | |
46 | "sb_internal", | |
47 | }; | |
48 | ||
49 | /* | |
50 | * One thing we have to be careful of with a per-sb shrinker is that we don't | |
51 | * drop the last active reference to the superblock from within the shrinker. | |
52 | * If that happens we could trigger unregistering the shrinker from within the | |
53 | * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we | |
54 | * take a passive reference to the superblock to avoid this from occurring. | |
55 | */ | |
56 | static unsigned long super_cache_scan(struct shrinker *shrink, | |
57 | struct shrink_control *sc) | |
58 | { | |
59 | struct super_block *sb; | |
60 | long fs_objects = 0; | |
61 | long total_objects; | |
62 | long freed = 0; | |
63 | long dentries; | |
64 | long inodes; | |
65 | ||
66 | sb = container_of(shrink, struct super_block, s_shrink); | |
67 | ||
68 | /* | |
69 | * Deadlock avoidance. We may hold various FS locks, and we don't want | |
70 | * to recurse into the FS that called us in clear_inode() and friends.. | |
71 | */ | |
72 | if (!(sc->gfp_mask & __GFP_FS)) | |
73 | return SHRINK_STOP; | |
74 | ||
75 | if (!trylock_super(sb)) | |
76 | return SHRINK_STOP; | |
77 | ||
78 | if (sb->s_op->nr_cached_objects) | |
79 | fs_objects = sb->s_op->nr_cached_objects(sb, sc); | |
80 | ||
81 | inodes = list_lru_shrink_count(&sb->s_inode_lru, sc); | |
82 | dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc); | |
83 | total_objects = dentries + inodes + fs_objects + 1; | |
84 | if (!total_objects) | |
85 | total_objects = 1; | |
86 | ||
87 | /* proportion the scan between the caches */ | |
88 | dentries = mult_frac(sc->nr_to_scan, dentries, total_objects); | |
89 | inodes = mult_frac(sc->nr_to_scan, inodes, total_objects); | |
90 | fs_objects = mult_frac(sc->nr_to_scan, fs_objects, total_objects); | |
91 | ||
92 | /* | |
93 | * prune the dcache first as the icache is pinned by it, then | |
94 | * prune the icache, followed by the filesystem specific caches | |
95 | * | |
96 | * Ensure that we always scan at least one object - memcg kmem | |
97 | * accounting uses this to fully empty the caches. | |
98 | */ | |
99 | sc->nr_to_scan = dentries + 1; | |
100 | freed = prune_dcache_sb(sb, sc); | |
101 | sc->nr_to_scan = inodes + 1; | |
102 | freed += prune_icache_sb(sb, sc); | |
103 | ||
104 | if (fs_objects) { | |
105 | sc->nr_to_scan = fs_objects + 1; | |
106 | freed += sb->s_op->free_cached_objects(sb, sc); | |
107 | } | |
108 | ||
109 | up_read(&sb->s_umount); | |
110 | return freed; | |
111 | } | |
112 | ||
113 | static unsigned long super_cache_count(struct shrinker *shrink, | |
114 | struct shrink_control *sc) | |
115 | { | |
116 | struct super_block *sb; | |
117 | long total_objects = 0; | |
118 | ||
119 | sb = container_of(shrink, struct super_block, s_shrink); | |
120 | ||
121 | /* | |
122 | * Don't call trylock_super as it is a potential | |
123 | * scalability bottleneck. The counts could get updated | |
124 | * between super_cache_count and super_cache_scan anyway. | |
125 | * Call to super_cache_count with shrinker_rwsem held | |
126 | * ensures the safety of call to list_lru_shrink_count() and | |
127 | * s_op->nr_cached_objects(). | |
128 | */ | |
129 | if (sb->s_op && sb->s_op->nr_cached_objects) | |
130 | total_objects = sb->s_op->nr_cached_objects(sb, sc); | |
131 | ||
132 | total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc); | |
133 | total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc); | |
134 | ||
135 | total_objects = vfs_pressure_ratio(total_objects); | |
136 | return total_objects; | |
137 | } | |
138 | ||
139 | static void destroy_super_work(struct work_struct *work) | |
140 | { | |
141 | struct super_block *s = container_of(work, struct super_block, | |
142 | destroy_work); | |
143 | int i; | |
144 | ||
145 | for (i = 0; i < SB_FREEZE_LEVELS; i++) | |
146 | percpu_free_rwsem(&s->s_writers.rw_sem[i]); | |
147 | kfree(s); | |
148 | } | |
149 | ||
150 | static void destroy_super_rcu(struct rcu_head *head) | |
151 | { | |
152 | struct super_block *s = container_of(head, struct super_block, rcu); | |
153 | INIT_WORK(&s->destroy_work, destroy_super_work); | |
154 | schedule_work(&s->destroy_work); | |
155 | } | |
156 | ||
157 | /** | |
158 | * destroy_super - frees a superblock | |
159 | * @s: superblock to free | |
160 | * | |
161 | * Frees a superblock. | |
162 | */ | |
163 | static void destroy_super(struct super_block *s) | |
164 | { | |
165 | list_lru_destroy(&s->s_dentry_lru); | |
166 | list_lru_destroy(&s->s_inode_lru); | |
167 | security_sb_free(s); | |
168 | WARN_ON(!list_empty(&s->s_mounts)); | |
169 | put_user_ns(s->s_user_ns); | |
170 | kfree(s->s_subtype); | |
171 | call_rcu(&s->rcu, destroy_super_rcu); | |
172 | } | |
173 | ||
174 | /** | |
175 | * alloc_super - create new superblock | |
176 | * @type: filesystem type superblock should belong to | |
177 | * @flags: the mount flags | |
178 | * @user_ns: User namespace for the super_block | |
179 | * | |
180 | * Allocates and initializes a new &struct super_block. alloc_super() | |
181 | * returns a pointer new superblock or %NULL if allocation had failed. | |
182 | */ | |
183 | static struct super_block *alloc_super(struct file_system_type *type, int flags, | |
184 | struct user_namespace *user_ns) | |
185 | { | |
186 | struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER); | |
187 | static const struct super_operations default_op; | |
188 | int i; | |
189 | ||
190 | if (!s) | |
191 | return NULL; | |
192 | ||
193 | INIT_LIST_HEAD(&s->s_mounts); | |
194 | s->s_user_ns = get_user_ns(user_ns); | |
195 | ||
196 | if (security_sb_alloc(s)) | |
197 | goto fail; | |
198 | ||
199 | for (i = 0; i < SB_FREEZE_LEVELS; i++) { | |
200 | if (__percpu_init_rwsem(&s->s_writers.rw_sem[i], | |
201 | sb_writers_name[i], | |
202 | &type->s_writers_key[i])) | |
203 | goto fail; | |
204 | } | |
205 | init_waitqueue_head(&s->s_writers.wait_unfrozen); | |
206 | s->s_bdi = &noop_backing_dev_info; | |
207 | s->s_flags = flags; | |
208 | if (s->s_user_ns != &init_user_ns) | |
209 | s->s_iflags |= SB_I_NODEV; | |
210 | INIT_HLIST_NODE(&s->s_instances); | |
211 | INIT_HLIST_BL_HEAD(&s->s_anon); | |
212 | mutex_init(&s->s_sync_lock); | |
213 | INIT_LIST_HEAD(&s->s_inodes); | |
214 | spin_lock_init(&s->s_inode_list_lock); | |
215 | INIT_LIST_HEAD(&s->s_inodes_wb); | |
216 | spin_lock_init(&s->s_inode_wblist_lock); | |
217 | ||
218 | if (list_lru_init_memcg(&s->s_dentry_lru)) | |
219 | goto fail; | |
220 | if (list_lru_init_memcg(&s->s_inode_lru)) | |
221 | goto fail; | |
222 | ||
223 | init_rwsem(&s->s_umount); | |
224 | lockdep_set_class(&s->s_umount, &type->s_umount_key); | |
225 | /* | |
226 | * sget() can have s_umount recursion. | |
227 | * | |
228 | * When it cannot find a suitable sb, it allocates a new | |
229 | * one (this one), and tries again to find a suitable old | |
230 | * one. | |
231 | * | |
232 | * In case that succeeds, it will acquire the s_umount | |
233 | * lock of the old one. Since these are clearly distrinct | |
234 | * locks, and this object isn't exposed yet, there's no | |
235 | * risk of deadlocks. | |
236 | * | |
237 | * Annotate this by putting this lock in a different | |
238 | * subclass. | |
239 | */ | |
240 | down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING); | |
241 | s->s_count = 1; | |
242 | atomic_set(&s->s_active, 1); | |
243 | mutex_init(&s->s_vfs_rename_mutex); | |
244 | lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key); | |
245 | init_rwsem(&s->s_dquot.dqio_sem); | |
246 | s->s_maxbytes = MAX_NON_LFS; | |
247 | s->s_op = &default_op; | |
248 | s->s_time_gran = 1000000000; | |
249 | s->cleancache_poolid = CLEANCACHE_NO_POOL; | |
250 | ||
251 | s->s_shrink.seeks = DEFAULT_SEEKS; | |
252 | s->s_shrink.scan_objects = super_cache_scan; | |
253 | s->s_shrink.count_objects = super_cache_count; | |
254 | s->s_shrink.batch = 1024; | |
255 | s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE; | |
256 | return s; | |
257 | ||
258 | fail: | |
259 | destroy_super(s); | |
260 | return NULL; | |
261 | } | |
262 | ||
263 | /* Superblock refcounting */ | |
264 | ||
265 | /* | |
266 | * Drop a superblock's refcount. The caller must hold sb_lock. | |
267 | */ | |
268 | static void __put_super(struct super_block *sb) | |
269 | { | |
270 | if (!--sb->s_count) { | |
271 | list_del_init(&sb->s_list); | |
272 | destroy_super(sb); | |
273 | } | |
274 | } | |
275 | ||
276 | /** | |
277 | * put_super - drop a temporary reference to superblock | |
278 | * @sb: superblock in question | |
279 | * | |
280 | * Drops a temporary reference, frees superblock if there's no | |
281 | * references left. | |
282 | */ | |
283 | static void put_super(struct super_block *sb) | |
284 | { | |
285 | spin_lock(&sb_lock); | |
286 | __put_super(sb); | |
287 | spin_unlock(&sb_lock); | |
288 | } | |
289 | ||
290 | ||
291 | /** | |
292 | * deactivate_locked_super - drop an active reference to superblock | |
293 | * @s: superblock to deactivate | |
294 | * | |
295 | * Drops an active reference to superblock, converting it into a temporary | |
296 | * one if there is no other active references left. In that case we | |
297 | * tell fs driver to shut it down and drop the temporary reference we | |
298 | * had just acquired. | |
299 | * | |
300 | * Caller holds exclusive lock on superblock; that lock is released. | |
301 | */ | |
302 | void deactivate_locked_super(struct super_block *s) | |
303 | { | |
304 | struct file_system_type *fs = s->s_type; | |
305 | if (atomic_dec_and_test(&s->s_active)) { | |
306 | cleancache_invalidate_fs(s); | |
307 | unregister_shrinker(&s->s_shrink); | |
308 | fs->kill_sb(s); | |
309 | ||
310 | /* | |
311 | * Since list_lru_destroy() may sleep, we cannot call it from | |
312 | * put_super(), where we hold the sb_lock. Therefore we destroy | |
313 | * the lru lists right now. | |
314 | */ | |
315 | list_lru_destroy(&s->s_dentry_lru); | |
316 | list_lru_destroy(&s->s_inode_lru); | |
317 | ||
318 | put_filesystem(fs); | |
319 | put_super(s); | |
320 | } else { | |
321 | up_write(&s->s_umount); | |
322 | } | |
323 | } | |
324 | ||
325 | EXPORT_SYMBOL(deactivate_locked_super); | |
326 | ||
327 | /** | |
328 | * deactivate_super - drop an active reference to superblock | |
329 | * @s: superblock to deactivate | |
330 | * | |
331 | * Variant of deactivate_locked_super(), except that superblock is *not* | |
332 | * locked by caller. If we are going to drop the final active reference, | |
333 | * lock will be acquired prior to that. | |
334 | */ | |
335 | void deactivate_super(struct super_block *s) | |
336 | { | |
337 | if (!atomic_add_unless(&s->s_active, -1, 1)) { | |
338 | down_write(&s->s_umount); | |
339 | deactivate_locked_super(s); | |
340 | } | |
341 | } | |
342 | ||
343 | EXPORT_SYMBOL(deactivate_super); | |
344 | ||
345 | /** | |
346 | * grab_super - acquire an active reference | |
347 | * @s: reference we are trying to make active | |
348 | * | |
349 | * Tries to acquire an active reference. grab_super() is used when we | |
350 | * had just found a superblock in super_blocks or fs_type->fs_supers | |
351 | * and want to turn it into a full-blown active reference. grab_super() | |
352 | * is called with sb_lock held and drops it. Returns 1 in case of | |
353 | * success, 0 if we had failed (superblock contents was already dead or | |
354 | * dying when grab_super() had been called). Note that this is only | |
355 | * called for superblocks not in rundown mode (== ones still on ->fs_supers | |
356 | * of their type), so increment of ->s_count is OK here. | |
357 | */ | |
358 | static int grab_super(struct super_block *s) __releases(sb_lock) | |
359 | { | |
360 | s->s_count++; | |
361 | spin_unlock(&sb_lock); | |
362 | down_write(&s->s_umount); | |
363 | if ((s->s_flags & SB_BORN) && atomic_inc_not_zero(&s->s_active)) { | |
364 | put_super(s); | |
365 | return 1; | |
366 | } | |
367 | up_write(&s->s_umount); | |
368 | put_super(s); | |
369 | return 0; | |
370 | } | |
371 | ||
372 | /* | |
373 | * trylock_super - try to grab ->s_umount shared | |
374 | * @sb: reference we are trying to grab | |
375 | * | |
376 | * Try to prevent fs shutdown. This is used in places where we | |
377 | * cannot take an active reference but we need to ensure that the | |
378 | * filesystem is not shut down while we are working on it. It returns | |
379 | * false if we cannot acquire s_umount or if we lose the race and | |
380 | * filesystem already got into shutdown, and returns true with the s_umount | |
381 | * lock held in read mode in case of success. On successful return, | |
382 | * the caller must drop the s_umount lock when done. | |
383 | * | |
384 | * Note that unlike get_super() et.al. this one does *not* bump ->s_count. | |
385 | * The reason why it's safe is that we are OK with doing trylock instead | |
386 | * of down_read(). There's a couple of places that are OK with that, but | |
387 | * it's very much not a general-purpose interface. | |
388 | */ | |
389 | bool trylock_super(struct super_block *sb) | |
390 | { | |
391 | if (down_read_trylock(&sb->s_umount)) { | |
392 | if (!hlist_unhashed(&sb->s_instances) && | |
393 | sb->s_root && (sb->s_flags & SB_BORN)) | |
394 | return true; | |
395 | up_read(&sb->s_umount); | |
396 | } | |
397 | ||
398 | return false; | |
399 | } | |
400 | ||
401 | /** | |
402 | * generic_shutdown_super - common helper for ->kill_sb() | |
403 | * @sb: superblock to kill | |
404 | * | |
405 | * generic_shutdown_super() does all fs-independent work on superblock | |
406 | * shutdown. Typical ->kill_sb() should pick all fs-specific objects | |
407 | * that need destruction out of superblock, call generic_shutdown_super() | |
408 | * and release aforementioned objects. Note: dentries and inodes _are_ | |
409 | * taken care of and do not need specific handling. | |
410 | * | |
411 | * Upon calling this function, the filesystem may no longer alter or | |
412 | * rearrange the set of dentries belonging to this super_block, nor may it | |
413 | * change the attachments of dentries to inodes. | |
414 | */ | |
415 | void generic_shutdown_super(struct super_block *sb) | |
416 | { | |
417 | const struct super_operations *sop = sb->s_op; | |
418 | ||
419 | if (sb->s_root) { | |
420 | shrink_dcache_for_umount(sb); | |
421 | sync_filesystem(sb); | |
422 | sb->s_flags &= ~SB_ACTIVE; | |
423 | ||
424 | fsnotify_unmount_inodes(sb); | |
425 | cgroup_writeback_umount(); | |
426 | ||
427 | evict_inodes(sb); | |
428 | ||
429 | if (sb->s_dio_done_wq) { | |
430 | destroy_workqueue(sb->s_dio_done_wq); | |
431 | sb->s_dio_done_wq = NULL; | |
432 | } | |
433 | ||
434 | if (sop->put_super) | |
435 | sop->put_super(sb); | |
436 | ||
437 | if (!list_empty(&sb->s_inodes)) { | |
438 | printk("VFS: Busy inodes after unmount of %s. " | |
439 | "Self-destruct in 5 seconds. Have a nice day...\n", | |
440 | sb->s_id); | |
441 | } | |
442 | } | |
443 | spin_lock(&sb_lock); | |
444 | /* should be initialized for __put_super_and_need_restart() */ | |
445 | hlist_del_init(&sb->s_instances); | |
446 | spin_unlock(&sb_lock); | |
447 | up_write(&sb->s_umount); | |
448 | if (sb->s_bdi != &noop_backing_dev_info) { | |
449 | bdi_put(sb->s_bdi); | |
450 | sb->s_bdi = &noop_backing_dev_info; | |
451 | } | |
452 | } | |
453 | ||
454 | EXPORT_SYMBOL(generic_shutdown_super); | |
455 | ||
456 | /** | |
457 | * sget_userns - find or create a superblock | |
458 | * @type: filesystem type superblock should belong to | |
459 | * @test: comparison callback | |
460 | * @set: setup callback | |
461 | * @flags: mount flags | |
462 | * @user_ns: User namespace for the super_block | |
463 | * @data: argument to each of them | |
464 | */ | |
465 | struct super_block *sget_userns(struct file_system_type *type, | |
466 | int (*test)(struct super_block *,void *), | |
467 | int (*set)(struct super_block *,void *), | |
468 | int flags, struct user_namespace *user_ns, | |
469 | void *data) | |
470 | { | |
471 | struct super_block *s = NULL; | |
472 | struct super_block *old; | |
473 | int err; | |
474 | ||
475 | if (!(flags & (SB_KERNMOUNT|SB_SUBMOUNT)) && | |
476 | !(type->fs_flags & FS_USERNS_MOUNT) && | |
477 | !capable(CAP_SYS_ADMIN)) | |
478 | return ERR_PTR(-EPERM); | |
479 | retry: | |
480 | spin_lock(&sb_lock); | |
481 | if (test) { | |
482 | hlist_for_each_entry(old, &type->fs_supers, s_instances) { | |
483 | if (!test(old, data)) | |
484 | continue; | |
485 | if (user_ns != old->s_user_ns) { | |
486 | spin_unlock(&sb_lock); | |
487 | if (s) { | |
488 | up_write(&s->s_umount); | |
489 | destroy_super(s); | |
490 | } | |
491 | return ERR_PTR(-EBUSY); | |
492 | } | |
493 | if (!grab_super(old)) | |
494 | goto retry; | |
495 | if (s) { | |
496 | up_write(&s->s_umount); | |
497 | destroy_super(s); | |
498 | s = NULL; | |
499 | } | |
500 | return old; | |
501 | } | |
502 | } | |
503 | if (!s) { | |
504 | spin_unlock(&sb_lock); | |
505 | s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns); | |
506 | if (!s) | |
507 | return ERR_PTR(-ENOMEM); | |
508 | goto retry; | |
509 | } | |
510 | ||
511 | err = set(s, data); | |
512 | if (err) { | |
513 | spin_unlock(&sb_lock); | |
514 | up_write(&s->s_umount); | |
515 | destroy_super(s); | |
516 | return ERR_PTR(err); | |
517 | } | |
518 | s->s_type = type; | |
519 | strlcpy(s->s_id, type->name, sizeof(s->s_id)); | |
520 | list_add_tail(&s->s_list, &super_blocks); | |
521 | hlist_add_head(&s->s_instances, &type->fs_supers); | |
522 | spin_unlock(&sb_lock); | |
523 | get_filesystem(type); | |
524 | register_shrinker(&s->s_shrink); | |
525 | return s; | |
526 | } | |
527 | ||
528 | EXPORT_SYMBOL(sget_userns); | |
529 | ||
530 | /** | |
531 | * sget - find or create a superblock | |
532 | * @type: filesystem type superblock should belong to | |
533 | * @test: comparison callback | |
534 | * @set: setup callback | |
535 | * @flags: mount flags | |
536 | * @data: argument to each of them | |
537 | */ | |
538 | struct super_block *sget(struct file_system_type *type, | |
539 | int (*test)(struct super_block *,void *), | |
540 | int (*set)(struct super_block *,void *), | |
541 | int flags, | |
542 | void *data) | |
543 | { | |
544 | struct user_namespace *user_ns = current_user_ns(); | |
545 | ||
546 | /* We don't yet pass the user namespace of the parent | |
547 | * mount through to here so always use &init_user_ns | |
548 | * until that changes. | |
549 | */ | |
550 | if (flags & SB_SUBMOUNT) | |
551 | user_ns = &init_user_ns; | |
552 | ||
553 | /* Ensure the requestor has permissions over the target filesystem */ | |
554 | if (!(flags & (SB_KERNMOUNT|SB_SUBMOUNT)) && !ns_capable(user_ns, CAP_SYS_ADMIN)) | |
555 | return ERR_PTR(-EPERM); | |
556 | ||
557 | return sget_userns(type, test, set, flags, user_ns, data); | |
558 | } | |
559 | ||
560 | EXPORT_SYMBOL(sget); | |
561 | ||
562 | void drop_super(struct super_block *sb) | |
563 | { | |
564 | up_read(&sb->s_umount); | |
565 | put_super(sb); | |
566 | } | |
567 | ||
568 | EXPORT_SYMBOL(drop_super); | |
569 | ||
570 | void drop_super_exclusive(struct super_block *sb) | |
571 | { | |
572 | up_write(&sb->s_umount); | |
573 | put_super(sb); | |
574 | } | |
575 | EXPORT_SYMBOL(drop_super_exclusive); | |
576 | ||
577 | /** | |
578 | * iterate_supers - call function for all active superblocks | |
579 | * @f: function to call | |
580 | * @arg: argument to pass to it | |
581 | * | |
582 | * Scans the superblock list and calls given function, passing it | |
583 | * locked superblock and given argument. | |
584 | */ | |
585 | void iterate_supers(void (*f)(struct super_block *, void *), void *arg) | |
586 | { | |
587 | struct super_block *sb, *p = NULL; | |
588 | ||
589 | spin_lock(&sb_lock); | |
590 | list_for_each_entry(sb, &super_blocks, s_list) { | |
591 | if (hlist_unhashed(&sb->s_instances)) | |
592 | continue; | |
593 | sb->s_count++; | |
594 | spin_unlock(&sb_lock); | |
595 | ||
596 | down_read(&sb->s_umount); | |
597 | if (sb->s_root && (sb->s_flags & SB_BORN)) | |
598 | f(sb, arg); | |
599 | up_read(&sb->s_umount); | |
600 | ||
601 | spin_lock(&sb_lock); | |
602 | if (p) | |
603 | __put_super(p); | |
604 | p = sb; | |
605 | } | |
606 | if (p) | |
607 | __put_super(p); | |
608 | spin_unlock(&sb_lock); | |
609 | } | |
610 | ||
611 | /** | |
612 | * iterate_supers_type - call function for superblocks of given type | |
613 | * @type: fs type | |
614 | * @f: function to call | |
615 | * @arg: argument to pass to it | |
616 | * | |
617 | * Scans the superblock list and calls given function, passing it | |
618 | * locked superblock and given argument. | |
619 | */ | |
620 | void iterate_supers_type(struct file_system_type *type, | |
621 | void (*f)(struct super_block *, void *), void *arg) | |
622 | { | |
623 | struct super_block *sb, *p = NULL; | |
624 | ||
625 | spin_lock(&sb_lock); | |
626 | hlist_for_each_entry(sb, &type->fs_supers, s_instances) { | |
627 | sb->s_count++; | |
628 | spin_unlock(&sb_lock); | |
629 | ||
630 | down_read(&sb->s_umount); | |
631 | if (sb->s_root && (sb->s_flags & SB_BORN)) | |
632 | f(sb, arg); | |
633 | up_read(&sb->s_umount); | |
634 | ||
635 | spin_lock(&sb_lock); | |
636 | if (p) | |
637 | __put_super(p); | |
638 | p = sb; | |
639 | } | |
640 | if (p) | |
641 | __put_super(p); | |
642 | spin_unlock(&sb_lock); | |
643 | } | |
644 | ||
645 | EXPORT_SYMBOL(iterate_supers_type); | |
646 | ||
647 | static struct super_block *__get_super(struct block_device *bdev, bool excl) | |
648 | { | |
649 | struct super_block *sb; | |
650 | ||
651 | if (!bdev) | |
652 | return NULL; | |
653 | ||
654 | spin_lock(&sb_lock); | |
655 | rescan: | |
656 | list_for_each_entry(sb, &super_blocks, s_list) { | |
657 | if (hlist_unhashed(&sb->s_instances)) | |
658 | continue; | |
659 | if (sb->s_bdev == bdev) { | |
660 | sb->s_count++; | |
661 | spin_unlock(&sb_lock); | |
662 | if (!excl) | |
663 | down_read(&sb->s_umount); | |
664 | else | |
665 | down_write(&sb->s_umount); | |
666 | /* still alive? */ | |
667 | if (sb->s_root && (sb->s_flags & SB_BORN)) | |
668 | return sb; | |
669 | if (!excl) | |
670 | up_read(&sb->s_umount); | |
671 | else | |
672 | up_write(&sb->s_umount); | |
673 | /* nope, got unmounted */ | |
674 | spin_lock(&sb_lock); | |
675 | __put_super(sb); | |
676 | goto rescan; | |
677 | } | |
678 | } | |
679 | spin_unlock(&sb_lock); | |
680 | return NULL; | |
681 | } | |
682 | ||
683 | /** | |
684 | * get_super - get the superblock of a device | |
685 | * @bdev: device to get the superblock for | |
686 | * | |
687 | * Scans the superblock list and finds the superblock of the file system | |
688 | * mounted on the device given. %NULL is returned if no match is found. | |
689 | */ | |
690 | struct super_block *get_super(struct block_device *bdev) | |
691 | { | |
692 | return __get_super(bdev, false); | |
693 | } | |
694 | EXPORT_SYMBOL(get_super); | |
695 | ||
696 | static struct super_block *__get_super_thawed(struct block_device *bdev, | |
697 | bool excl) | |
698 | { | |
699 | while (1) { | |
700 | struct super_block *s = __get_super(bdev, excl); | |
701 | if (!s || s->s_writers.frozen == SB_UNFROZEN) | |
702 | return s; | |
703 | if (!excl) | |
704 | up_read(&s->s_umount); | |
705 | else | |
706 | up_write(&s->s_umount); | |
707 | wait_event(s->s_writers.wait_unfrozen, | |
708 | s->s_writers.frozen == SB_UNFROZEN); | |
709 | put_super(s); | |
710 | } | |
711 | } | |
712 | ||
713 | /** | |
714 | * get_super_thawed - get thawed superblock of a device | |
715 | * @bdev: device to get the superblock for | |
716 | * | |
717 | * Scans the superblock list and finds the superblock of the file system | |
718 | * mounted on the device. The superblock is returned once it is thawed | |
719 | * (or immediately if it was not frozen). %NULL is returned if no match | |
720 | * is found. | |
721 | */ | |
722 | struct super_block *get_super_thawed(struct block_device *bdev) | |
723 | { | |
724 | return __get_super_thawed(bdev, false); | |
725 | } | |
726 | EXPORT_SYMBOL(get_super_thawed); | |
727 | ||
728 | /** | |
729 | * get_super_exclusive_thawed - get thawed superblock of a device | |
730 | * @bdev: device to get the superblock for | |
731 | * | |
732 | * Scans the superblock list and finds the superblock of the file system | |
733 | * mounted on the device. The superblock is returned once it is thawed | |
734 | * (or immediately if it was not frozen) and s_umount semaphore is held | |
735 | * in exclusive mode. %NULL is returned if no match is found. | |
736 | */ | |
737 | struct super_block *get_super_exclusive_thawed(struct block_device *bdev) | |
738 | { | |
739 | return __get_super_thawed(bdev, true); | |
740 | } | |
741 | EXPORT_SYMBOL(get_super_exclusive_thawed); | |
742 | ||
743 | /** | |
744 | * get_active_super - get an active reference to 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. Returns the superblock with an active | |
749 | * reference or %NULL if none was found. | |
750 | */ | |
751 | struct super_block *get_active_super(struct block_device *bdev) | |
752 | { | |
753 | struct super_block *sb; | |
754 | ||
755 | if (!bdev) | |
756 | return NULL; | |
757 | ||
758 | restart: | |
759 | spin_lock(&sb_lock); | |
760 | list_for_each_entry(sb, &super_blocks, s_list) { | |
761 | if (hlist_unhashed(&sb->s_instances)) | |
762 | continue; | |
763 | if (sb->s_bdev == bdev) { | |
764 | if (!grab_super(sb)) | |
765 | goto restart; | |
766 | up_write(&sb->s_umount); | |
767 | return sb; | |
768 | } | |
769 | } | |
770 | spin_unlock(&sb_lock); | |
771 | return NULL; | |
772 | } | |
773 | ||
774 | struct super_block *user_get_super(dev_t dev) | |
775 | { | |
776 | struct super_block *sb; | |
777 | ||
778 | spin_lock(&sb_lock); | |
779 | rescan: | |
780 | list_for_each_entry(sb, &super_blocks, s_list) { | |
781 | if (hlist_unhashed(&sb->s_instances)) | |
782 | continue; | |
783 | if (sb->s_dev == dev) { | |
784 | sb->s_count++; | |
785 | spin_unlock(&sb_lock); | |
786 | down_read(&sb->s_umount); | |
787 | /* still alive? */ | |
788 | if (sb->s_root && (sb->s_flags & SB_BORN)) | |
789 | return sb; | |
790 | up_read(&sb->s_umount); | |
791 | /* nope, got unmounted */ | |
792 | spin_lock(&sb_lock); | |
793 | __put_super(sb); | |
794 | goto rescan; | |
795 | } | |
796 | } | |
797 | spin_unlock(&sb_lock); | |
798 | return NULL; | |
799 | } | |
800 | ||
801 | /** | |
802 | * do_remount_sb - asks filesystem to change mount options. | |
803 | * @sb: superblock in question | |
804 | * @sb_flags: revised superblock flags | |
805 | * @data: the rest of options | |
806 | * @force: whether or not to force the change | |
807 | * | |
808 | * Alters the mount options of a mounted file system. | |
809 | */ | |
810 | int do_remount_sb(struct super_block *sb, int sb_flags, void *data, int force) | |
811 | { | |
812 | int retval; | |
813 | int remount_ro; | |
814 | ||
815 | if (sb->s_writers.frozen != SB_UNFROZEN) | |
816 | return -EBUSY; | |
817 | ||
818 | #ifdef CONFIG_BLOCK | |
819 | if (!(sb_flags & SB_RDONLY) && bdev_read_only(sb->s_bdev)) | |
820 | return -EACCES; | |
821 | #endif | |
822 | ||
823 | remount_ro = (sb_flags & SB_RDONLY) && !sb_rdonly(sb); | |
824 | ||
825 | if (remount_ro) { | |
826 | if (!hlist_empty(&sb->s_pins)) { | |
827 | up_write(&sb->s_umount); | |
828 | group_pin_kill(&sb->s_pins); | |
829 | down_write(&sb->s_umount); | |
830 | if (!sb->s_root) | |
831 | return 0; | |
832 | if (sb->s_writers.frozen != SB_UNFROZEN) | |
833 | return -EBUSY; | |
834 | remount_ro = (sb_flags & SB_RDONLY) && !sb_rdonly(sb); | |
835 | } | |
836 | } | |
837 | shrink_dcache_sb(sb); | |
838 | ||
839 | /* If we are remounting RDONLY and current sb is read/write, | |
840 | make sure there are no rw files opened */ | |
841 | if (remount_ro) { | |
842 | if (force) { | |
843 | sb->s_readonly_remount = 1; | |
844 | smp_wmb(); | |
845 | } else { | |
846 | retval = sb_prepare_remount_readonly(sb); | |
847 | if (retval) | |
848 | return retval; | |
849 | } | |
850 | } | |
851 | ||
852 | if (sb->s_op->remount_fs) { | |
853 | retval = sb->s_op->remount_fs(sb, &sb_flags, data); | |
854 | if (retval) { | |
855 | if (!force) | |
856 | goto cancel_readonly; | |
857 | /* If forced remount, go ahead despite any errors */ | |
858 | WARN(1, "forced remount of a %s fs returned %i\n", | |
859 | sb->s_type->name, retval); | |
860 | } | |
861 | } | |
862 | sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (sb_flags & MS_RMT_MASK); | |
863 | /* Needs to be ordered wrt mnt_is_readonly() */ | |
864 | smp_wmb(); | |
865 | sb->s_readonly_remount = 0; | |
866 | ||
867 | /* | |
868 | * Some filesystems modify their metadata via some other path than the | |
869 | * bdev buffer cache (eg. use a private mapping, or directories in | |
870 | * pagecache, etc). Also file data modifications go via their own | |
871 | * mappings. So If we try to mount readonly then copy the filesystem | |
872 | * from bdev, we could get stale data, so invalidate it to give a best | |
873 | * effort at coherency. | |
874 | */ | |
875 | if (remount_ro && sb->s_bdev) | |
876 | invalidate_bdev(sb->s_bdev); | |
877 | return 0; | |
878 | ||
879 | cancel_readonly: | |
880 | sb->s_readonly_remount = 0; | |
881 | return retval; | |
882 | } | |
883 | ||
884 | static void do_emergency_remount(struct work_struct *work) | |
885 | { | |
886 | struct super_block *sb, *p = NULL; | |
887 | ||
888 | spin_lock(&sb_lock); | |
889 | list_for_each_entry(sb, &super_blocks, s_list) { | |
890 | if (hlist_unhashed(&sb->s_instances)) | |
891 | continue; | |
892 | sb->s_count++; | |
893 | spin_unlock(&sb_lock); | |
894 | down_write(&sb->s_umount); | |
895 | if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) && | |
896 | !sb_rdonly(sb)) { | |
897 | /* | |
898 | * What lock protects sb->s_flags?? | |
899 | */ | |
900 | do_remount_sb(sb, SB_RDONLY, NULL, 1); | |
901 | } | |
902 | up_write(&sb->s_umount); | |
903 | spin_lock(&sb_lock); | |
904 | if (p) | |
905 | __put_super(p); | |
906 | p = sb; | |
907 | } | |
908 | if (p) | |
909 | __put_super(p); | |
910 | spin_unlock(&sb_lock); | |
911 | kfree(work); | |
912 | printk("Emergency Remount complete\n"); | |
913 | } | |
914 | ||
915 | void emergency_remount(void) | |
916 | { | |
917 | struct work_struct *work; | |
918 | ||
919 | work = kmalloc(sizeof(*work), GFP_ATOMIC); | |
920 | if (work) { | |
921 | INIT_WORK(work, do_emergency_remount); | |
922 | schedule_work(work); | |
923 | } | |
924 | } | |
925 | ||
926 | /* | |
927 | * Unnamed block devices are dummy devices used by virtual | |
928 | * filesystems which don't use real block-devices. -- jrs | |
929 | */ | |
930 | ||
931 | static DEFINE_IDA(unnamed_dev_ida); | |
932 | static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */ | |
933 | /* Many userspace utilities consider an FSID of 0 invalid. | |
934 | * Always return at least 1 from get_anon_bdev. | |
935 | */ | |
936 | static int unnamed_dev_start = 1; | |
937 | ||
938 | int get_anon_bdev(dev_t *p) | |
939 | { | |
940 | int dev; | |
941 | int error; | |
942 | ||
943 | retry: | |
944 | if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0) | |
945 | return -ENOMEM; | |
946 | spin_lock(&unnamed_dev_lock); | |
947 | error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev); | |
948 | if (!error) | |
949 | unnamed_dev_start = dev + 1; | |
950 | spin_unlock(&unnamed_dev_lock); | |
951 | if (error == -EAGAIN) | |
952 | /* We raced and lost with another CPU. */ | |
953 | goto retry; | |
954 | else if (error) | |
955 | return -EAGAIN; | |
956 | ||
957 | if (dev >= (1 << MINORBITS)) { | |
958 | spin_lock(&unnamed_dev_lock); | |
959 | ida_remove(&unnamed_dev_ida, dev); | |
960 | if (unnamed_dev_start > dev) | |
961 | unnamed_dev_start = dev; | |
962 | spin_unlock(&unnamed_dev_lock); | |
963 | return -EMFILE; | |
964 | } | |
965 | *p = MKDEV(0, dev & MINORMASK); | |
966 | return 0; | |
967 | } | |
968 | EXPORT_SYMBOL(get_anon_bdev); | |
969 | ||
970 | void free_anon_bdev(dev_t dev) | |
971 | { | |
972 | int slot = MINOR(dev); | |
973 | spin_lock(&unnamed_dev_lock); | |
974 | ida_remove(&unnamed_dev_ida, slot); | |
975 | if (slot < unnamed_dev_start) | |
976 | unnamed_dev_start = slot; | |
977 | spin_unlock(&unnamed_dev_lock); | |
978 | } | |
979 | EXPORT_SYMBOL(free_anon_bdev); | |
980 | ||
981 | int set_anon_super(struct super_block *s, void *data) | |
982 | { | |
983 | return get_anon_bdev(&s->s_dev); | |
984 | } | |
985 | ||
986 | EXPORT_SYMBOL(set_anon_super); | |
987 | ||
988 | void kill_anon_super(struct super_block *sb) | |
989 | { | |
990 | dev_t dev = sb->s_dev; | |
991 | generic_shutdown_super(sb); | |
992 | free_anon_bdev(dev); | |
993 | } | |
994 | ||
995 | EXPORT_SYMBOL(kill_anon_super); | |
996 | ||
997 | void kill_litter_super(struct super_block *sb) | |
998 | { | |
999 | if (sb->s_root) | |
1000 | d_genocide(sb->s_root); | |
1001 | kill_anon_super(sb); | |
1002 | } | |
1003 | ||
1004 | EXPORT_SYMBOL(kill_litter_super); | |
1005 | ||
1006 | static int ns_test_super(struct super_block *sb, void *data) | |
1007 | { | |
1008 | return sb->s_fs_info == data; | |
1009 | } | |
1010 | ||
1011 | static int ns_set_super(struct super_block *sb, void *data) | |
1012 | { | |
1013 | sb->s_fs_info = data; | |
1014 | return set_anon_super(sb, NULL); | |
1015 | } | |
1016 | ||
1017 | struct dentry *mount_ns(struct file_system_type *fs_type, | |
1018 | int flags, void *data, void *ns, struct user_namespace *user_ns, | |
1019 | int (*fill_super)(struct super_block *, void *, int)) | |
1020 | { | |
1021 | struct super_block *sb; | |
1022 | ||
1023 | /* Don't allow mounting unless the caller has CAP_SYS_ADMIN | |
1024 | * over the namespace. | |
1025 | */ | |
1026 | if (!(flags & SB_KERNMOUNT) && !ns_capable(user_ns, CAP_SYS_ADMIN)) | |
1027 | return ERR_PTR(-EPERM); | |
1028 | ||
1029 | sb = sget_userns(fs_type, ns_test_super, ns_set_super, flags, | |
1030 | user_ns, ns); | |
1031 | if (IS_ERR(sb)) | |
1032 | return ERR_CAST(sb); | |
1033 | ||
1034 | if (!sb->s_root) { | |
1035 | int err; | |
1036 | err = fill_super(sb, data, flags & SB_SILENT ? 1 : 0); | |
1037 | if (err) { | |
1038 | deactivate_locked_super(sb); | |
1039 | return ERR_PTR(err); | |
1040 | } | |
1041 | ||
1042 | sb->s_flags |= SB_ACTIVE; | |
1043 | } | |
1044 | ||
1045 | return dget(sb->s_root); | |
1046 | } | |
1047 | ||
1048 | EXPORT_SYMBOL(mount_ns); | |
1049 | ||
1050 | #ifdef CONFIG_BLOCK | |
1051 | static int set_bdev_super(struct super_block *s, void *data) | |
1052 | { | |
1053 | s->s_bdev = data; | |
1054 | s->s_dev = s->s_bdev->bd_dev; | |
1055 | s->s_bdi = bdi_get(s->s_bdev->bd_bdi); | |
1056 | ||
1057 | return 0; | |
1058 | } | |
1059 | ||
1060 | static int test_bdev_super(struct super_block *s, void *data) | |
1061 | { | |
1062 | return (void *)s->s_bdev == data; | |
1063 | } | |
1064 | ||
1065 | struct dentry *mount_bdev(struct file_system_type *fs_type, | |
1066 | int flags, const char *dev_name, void *data, | |
1067 | int (*fill_super)(struct super_block *, void *, int)) | |
1068 | { | |
1069 | struct block_device *bdev; | |
1070 | struct super_block *s; | |
1071 | fmode_t mode = FMODE_READ | FMODE_EXCL; | |
1072 | int error = 0; | |
1073 | ||
1074 | if (!(flags & SB_RDONLY)) | |
1075 | mode |= FMODE_WRITE; | |
1076 | ||
1077 | bdev = blkdev_get_by_path(dev_name, mode, fs_type); | |
1078 | if (IS_ERR(bdev)) | |
1079 | return ERR_CAST(bdev); | |
1080 | ||
1081 | /* | |
1082 | * once the super is inserted into the list by sget, s_umount | |
1083 | * will protect the lockfs code from trying to start a snapshot | |
1084 | * while we are mounting | |
1085 | */ | |
1086 | mutex_lock(&bdev->bd_fsfreeze_mutex); | |
1087 | if (bdev->bd_fsfreeze_count > 0) { | |
1088 | mutex_unlock(&bdev->bd_fsfreeze_mutex); | |
1089 | error = -EBUSY; | |
1090 | goto error_bdev; | |
1091 | } | |
1092 | s = sget(fs_type, test_bdev_super, set_bdev_super, flags | SB_NOSEC, | |
1093 | bdev); | |
1094 | mutex_unlock(&bdev->bd_fsfreeze_mutex); | |
1095 | if (IS_ERR(s)) | |
1096 | goto error_s; | |
1097 | ||
1098 | if (s->s_root) { | |
1099 | if ((flags ^ s->s_flags) & SB_RDONLY) { | |
1100 | deactivate_locked_super(s); | |
1101 | error = -EBUSY; | |
1102 | goto error_bdev; | |
1103 | } | |
1104 | ||
1105 | /* | |
1106 | * s_umount nests inside bd_mutex during | |
1107 | * __invalidate_device(). blkdev_put() acquires | |
1108 | * bd_mutex and can't be called under s_umount. Drop | |
1109 | * s_umount temporarily. This is safe as we're | |
1110 | * holding an active reference. | |
1111 | */ | |
1112 | up_write(&s->s_umount); | |
1113 | blkdev_put(bdev, mode); | |
1114 | down_write(&s->s_umount); | |
1115 | } else { | |
1116 | s->s_mode = mode; | |
1117 | snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev); | |
1118 | sb_set_blocksize(s, block_size(bdev)); | |
1119 | error = fill_super(s, data, flags & SB_SILENT ? 1 : 0); | |
1120 | if (error) { | |
1121 | deactivate_locked_super(s); | |
1122 | goto error; | |
1123 | } | |
1124 | ||
1125 | s->s_flags |= SB_ACTIVE; | |
1126 | bdev->bd_super = s; | |
1127 | } | |
1128 | ||
1129 | return dget(s->s_root); | |
1130 | ||
1131 | error_s: | |
1132 | error = PTR_ERR(s); | |
1133 | error_bdev: | |
1134 | blkdev_put(bdev, mode); | |
1135 | error: | |
1136 | return ERR_PTR(error); | |
1137 | } | |
1138 | EXPORT_SYMBOL(mount_bdev); | |
1139 | ||
1140 | void kill_block_super(struct super_block *sb) | |
1141 | { | |
1142 | struct block_device *bdev = sb->s_bdev; | |
1143 | fmode_t mode = sb->s_mode; | |
1144 | ||
1145 | bdev->bd_super = NULL; | |
1146 | generic_shutdown_super(sb); | |
1147 | sync_blockdev(bdev); | |
1148 | WARN_ON_ONCE(!(mode & FMODE_EXCL)); | |
1149 | blkdev_put(bdev, mode | FMODE_EXCL); | |
1150 | } | |
1151 | ||
1152 | EXPORT_SYMBOL(kill_block_super); | |
1153 | #endif | |
1154 | ||
1155 | struct dentry *mount_nodev(struct file_system_type *fs_type, | |
1156 | int flags, void *data, | |
1157 | int (*fill_super)(struct super_block *, void *, int)) | |
1158 | { | |
1159 | int error; | |
1160 | struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL); | |
1161 | ||
1162 | if (IS_ERR(s)) | |
1163 | return ERR_CAST(s); | |
1164 | ||
1165 | error = fill_super(s, data, flags & SB_SILENT ? 1 : 0); | |
1166 | if (error) { | |
1167 | deactivate_locked_super(s); | |
1168 | return ERR_PTR(error); | |
1169 | } | |
1170 | s->s_flags |= SB_ACTIVE; | |
1171 | return dget(s->s_root); | |
1172 | } | |
1173 | EXPORT_SYMBOL(mount_nodev); | |
1174 | ||
1175 | static int compare_single(struct super_block *s, void *p) | |
1176 | { | |
1177 | return 1; | |
1178 | } | |
1179 | ||
1180 | struct dentry *mount_single(struct file_system_type *fs_type, | |
1181 | int flags, void *data, | |
1182 | int (*fill_super)(struct super_block *, void *, int)) | |
1183 | { | |
1184 | struct super_block *s; | |
1185 | int error; | |
1186 | ||
1187 | s = sget(fs_type, compare_single, set_anon_super, flags, NULL); | |
1188 | if (IS_ERR(s)) | |
1189 | return ERR_CAST(s); | |
1190 | if (!s->s_root) { | |
1191 | error = fill_super(s, data, flags & SB_SILENT ? 1 : 0); | |
1192 | if (error) { | |
1193 | deactivate_locked_super(s); | |
1194 | return ERR_PTR(error); | |
1195 | } | |
1196 | s->s_flags |= SB_ACTIVE; | |
1197 | } else { | |
1198 | do_remount_sb(s, flags, data, 0); | |
1199 | } | |
1200 | return dget(s->s_root); | |
1201 | } | |
1202 | EXPORT_SYMBOL(mount_single); | |
1203 | ||
1204 | struct dentry * | |
1205 | mount_fs(struct file_system_type *type, int flags, const char *name, void *data) | |
1206 | { | |
1207 | struct dentry *root; | |
1208 | struct super_block *sb; | |
1209 | char *secdata = NULL; | |
1210 | int error = -ENOMEM; | |
1211 | ||
1212 | if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) { | |
1213 | secdata = alloc_secdata(); | |
1214 | if (!secdata) | |
1215 | goto out; | |
1216 | ||
1217 | error = security_sb_copy_data(data, secdata); | |
1218 | if (error) | |
1219 | goto out_free_secdata; | |
1220 | } | |
1221 | ||
1222 | root = type->mount(type, flags, name, data); | |
1223 | if (IS_ERR(root)) { | |
1224 | error = PTR_ERR(root); | |
1225 | goto out_free_secdata; | |
1226 | } | |
1227 | sb = root->d_sb; | |
1228 | BUG_ON(!sb); | |
1229 | WARN_ON(!sb->s_bdi); | |
1230 | sb->s_flags |= SB_BORN; | |
1231 | ||
1232 | error = security_sb_kern_mount(sb, flags, secdata); | |
1233 | if (error) | |
1234 | goto out_sb; | |
1235 | ||
1236 | /* | |
1237 | * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE | |
1238 | * but s_maxbytes was an unsigned long long for many releases. Throw | |
1239 | * this warning for a little while to try and catch filesystems that | |
1240 | * violate this rule. | |
1241 | */ | |
1242 | WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to " | |
1243 | "negative value (%lld)\n", type->name, sb->s_maxbytes); | |
1244 | ||
1245 | up_write(&sb->s_umount); | |
1246 | free_secdata(secdata); | |
1247 | return root; | |
1248 | out_sb: | |
1249 | dput(root); | |
1250 | deactivate_locked_super(sb); | |
1251 | out_free_secdata: | |
1252 | free_secdata(secdata); | |
1253 | out: | |
1254 | return ERR_PTR(error); | |
1255 | } | |
1256 | ||
1257 | /* | |
1258 | * Setup private BDI for given superblock. It gets automatically cleaned up | |
1259 | * in generic_shutdown_super(). | |
1260 | */ | |
1261 | int super_setup_bdi_name(struct super_block *sb, char *fmt, ...) | |
1262 | { | |
1263 | struct backing_dev_info *bdi; | |
1264 | int err; | |
1265 | va_list args; | |
1266 | ||
1267 | bdi = bdi_alloc(GFP_KERNEL); | |
1268 | if (!bdi) | |
1269 | return -ENOMEM; | |
1270 | ||
1271 | bdi->name = sb->s_type->name; | |
1272 | ||
1273 | va_start(args, fmt); | |
1274 | err = bdi_register_va(bdi, fmt, args); | |
1275 | va_end(args); | |
1276 | if (err) { | |
1277 | bdi_put(bdi); | |
1278 | return err; | |
1279 | } | |
1280 | WARN_ON(sb->s_bdi != &noop_backing_dev_info); | |
1281 | sb->s_bdi = bdi; | |
1282 | ||
1283 | return 0; | |
1284 | } | |
1285 | EXPORT_SYMBOL(super_setup_bdi_name); | |
1286 | ||
1287 | /* | |
1288 | * Setup private BDI for given superblock. I gets automatically cleaned up | |
1289 | * in generic_shutdown_super(). | |
1290 | */ | |
1291 | int super_setup_bdi(struct super_block *sb) | |
1292 | { | |
1293 | static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0); | |
1294 | ||
1295 | return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name, | |
1296 | atomic_long_inc_return(&bdi_seq)); | |
1297 | } | |
1298 | EXPORT_SYMBOL(super_setup_bdi); | |
1299 | ||
1300 | /* | |
1301 | * This is an internal function, please use sb_end_{write,pagefault,intwrite} | |
1302 | * instead. | |
1303 | */ | |
1304 | void __sb_end_write(struct super_block *sb, int level) | |
1305 | { | |
1306 | percpu_up_read(sb->s_writers.rw_sem + level-1); | |
1307 | } | |
1308 | EXPORT_SYMBOL(__sb_end_write); | |
1309 | ||
1310 | /* | |
1311 | * This is an internal function, please use sb_start_{write,pagefault,intwrite} | |
1312 | * instead. | |
1313 | */ | |
1314 | int __sb_start_write(struct super_block *sb, int level, bool wait) | |
1315 | { | |
1316 | bool force_trylock = false; | |
1317 | int ret = 1; | |
1318 | ||
1319 | #ifdef CONFIG_LOCKDEP | |
1320 | /* | |
1321 | * We want lockdep to tell us about possible deadlocks with freezing | |
1322 | * but it's it bit tricky to properly instrument it. Getting a freeze | |
1323 | * protection works as getting a read lock but there are subtle | |
1324 | * problems. XFS for example gets freeze protection on internal level | |
1325 | * twice in some cases, which is OK only because we already hold a | |
1326 | * freeze protection also on higher level. Due to these cases we have | |
1327 | * to use wait == F (trylock mode) which must not fail. | |
1328 | */ | |
1329 | if (wait) { | |
1330 | int i; | |
1331 | ||
1332 | for (i = 0; i < level - 1; i++) | |
1333 | if (percpu_rwsem_is_held(sb->s_writers.rw_sem + i)) { | |
1334 | force_trylock = true; | |
1335 | break; | |
1336 | } | |
1337 | } | |
1338 | #endif | |
1339 | if (wait && !force_trylock) | |
1340 | percpu_down_read(sb->s_writers.rw_sem + level-1); | |
1341 | else | |
1342 | ret = percpu_down_read_trylock(sb->s_writers.rw_sem + level-1); | |
1343 | ||
1344 | WARN_ON(force_trylock && !ret); | |
1345 | return ret; | |
1346 | } | |
1347 | EXPORT_SYMBOL(__sb_start_write); | |
1348 | ||
1349 | /** | |
1350 | * sb_wait_write - wait until all writers to given file system finish | |
1351 | * @sb: the super for which we wait | |
1352 | * @level: type of writers we wait for (normal vs page fault) | |
1353 | * | |
1354 | * This function waits until there are no writers of given type to given file | |
1355 | * system. | |
1356 | */ | |
1357 | static void sb_wait_write(struct super_block *sb, int level) | |
1358 | { | |
1359 | percpu_down_write(sb->s_writers.rw_sem + level-1); | |
1360 | } | |
1361 | ||
1362 | /* | |
1363 | * We are going to return to userspace and forget about these locks, the | |
1364 | * ownership goes to the caller of thaw_super() which does unlock(). | |
1365 | */ | |
1366 | static void lockdep_sb_freeze_release(struct super_block *sb) | |
1367 | { | |
1368 | int level; | |
1369 | ||
1370 | for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--) | |
1371 | percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_); | |
1372 | } | |
1373 | ||
1374 | /* | |
1375 | * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb). | |
1376 | */ | |
1377 | static void lockdep_sb_freeze_acquire(struct super_block *sb) | |
1378 | { | |
1379 | int level; | |
1380 | ||
1381 | for (level = 0; level < SB_FREEZE_LEVELS; ++level) | |
1382 | percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_); | |
1383 | } | |
1384 | ||
1385 | static void sb_freeze_unlock(struct super_block *sb) | |
1386 | { | |
1387 | int level; | |
1388 | ||
1389 | for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--) | |
1390 | percpu_up_write(sb->s_writers.rw_sem + level); | |
1391 | } | |
1392 | ||
1393 | /** | |
1394 | * freeze_super - lock the filesystem and force it into a consistent state | |
1395 | * @sb: the super to lock | |
1396 | * | |
1397 | * Syncs the super to make sure the filesystem is consistent and calls the fs's | |
1398 | * freeze_fs. Subsequent calls to this without first thawing the fs will return | |
1399 | * -EBUSY. | |
1400 | * | |
1401 | * During this function, sb->s_writers.frozen goes through these values: | |
1402 | * | |
1403 | * SB_UNFROZEN: File system is normal, all writes progress as usual. | |
1404 | * | |
1405 | * SB_FREEZE_WRITE: The file system is in the process of being frozen. New | |
1406 | * writes should be blocked, though page faults are still allowed. We wait for | |
1407 | * all writes to complete and then proceed to the next stage. | |
1408 | * | |
1409 | * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked | |
1410 | * but internal fs threads can still modify the filesystem (although they | |
1411 | * should not dirty new pages or inodes), writeback can run etc. After waiting | |
1412 | * for all running page faults we sync the filesystem which will clean all | |
1413 | * dirty pages and inodes (no new dirty pages or inodes can be created when | |
1414 | * sync is running). | |
1415 | * | |
1416 | * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs | |
1417 | * modification are blocked (e.g. XFS preallocation truncation on inode | |
1418 | * reclaim). This is usually implemented by blocking new transactions for | |
1419 | * filesystems that have them and need this additional guard. After all | |
1420 | * internal writers are finished we call ->freeze_fs() to finish filesystem | |
1421 | * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is | |
1422 | * mostly auxiliary for filesystems to verify they do not modify frozen fs. | |
1423 | * | |
1424 | * sb->s_writers.frozen is protected by sb->s_umount. | |
1425 | */ | |
1426 | int freeze_super(struct super_block *sb) | |
1427 | { | |
1428 | int ret; | |
1429 | ||
1430 | atomic_inc(&sb->s_active); | |
1431 | down_write(&sb->s_umount); | |
1432 | if (sb->s_writers.frozen != SB_UNFROZEN) { | |
1433 | deactivate_locked_super(sb); | |
1434 | return -EBUSY; | |
1435 | } | |
1436 | ||
1437 | if (!(sb->s_flags & SB_BORN)) { | |
1438 | up_write(&sb->s_umount); | |
1439 | return 0; /* sic - it's "nothing to do" */ | |
1440 | } | |
1441 | ||
1442 | if (sb_rdonly(sb)) { | |
1443 | /* Nothing to do really... */ | |
1444 | sb->s_writers.frozen = SB_FREEZE_COMPLETE; | |
1445 | up_write(&sb->s_umount); | |
1446 | return 0; | |
1447 | } | |
1448 | ||
1449 | sb->s_writers.frozen = SB_FREEZE_WRITE; | |
1450 | /* Release s_umount to preserve sb_start_write -> s_umount ordering */ | |
1451 | up_write(&sb->s_umount); | |
1452 | sb_wait_write(sb, SB_FREEZE_WRITE); | |
1453 | down_write(&sb->s_umount); | |
1454 | ||
1455 | /* Now we go and block page faults... */ | |
1456 | sb->s_writers.frozen = SB_FREEZE_PAGEFAULT; | |
1457 | sb_wait_write(sb, SB_FREEZE_PAGEFAULT); | |
1458 | ||
1459 | /* All writers are done so after syncing there won't be dirty data */ | |
1460 | sync_filesystem(sb); | |
1461 | ||
1462 | /* Now wait for internal filesystem counter */ | |
1463 | sb->s_writers.frozen = SB_FREEZE_FS; | |
1464 | sb_wait_write(sb, SB_FREEZE_FS); | |
1465 | ||
1466 | if (sb->s_op->freeze_fs) { | |
1467 | ret = sb->s_op->freeze_fs(sb); | |
1468 | if (ret) { | |
1469 | printk(KERN_ERR | |
1470 | "VFS:Filesystem freeze failed\n"); | |
1471 | sb->s_writers.frozen = SB_UNFROZEN; | |
1472 | sb_freeze_unlock(sb); | |
1473 | wake_up(&sb->s_writers.wait_unfrozen); | |
1474 | deactivate_locked_super(sb); | |
1475 | return ret; | |
1476 | } | |
1477 | } | |
1478 | /* | |
1479 | * For debugging purposes so that fs can warn if it sees write activity | |
1480 | * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super(). | |
1481 | */ | |
1482 | sb->s_writers.frozen = SB_FREEZE_COMPLETE; | |
1483 | lockdep_sb_freeze_release(sb); | |
1484 | up_write(&sb->s_umount); | |
1485 | return 0; | |
1486 | } | |
1487 | EXPORT_SYMBOL(freeze_super); | |
1488 | ||
1489 | /** | |
1490 | * thaw_super -- unlock filesystem | |
1491 | * @sb: the super to thaw | |
1492 | * | |
1493 | * Unlocks the filesystem and marks it writeable again after freeze_super(). | |
1494 | */ | |
1495 | int thaw_super(struct super_block *sb) | |
1496 | { | |
1497 | int error; | |
1498 | ||
1499 | down_write(&sb->s_umount); | |
1500 | if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) { | |
1501 | up_write(&sb->s_umount); | |
1502 | return -EINVAL; | |
1503 | } | |
1504 | ||
1505 | if (sb_rdonly(sb)) { | |
1506 | sb->s_writers.frozen = SB_UNFROZEN; | |
1507 | goto out; | |
1508 | } | |
1509 | ||
1510 | lockdep_sb_freeze_acquire(sb); | |
1511 | ||
1512 | if (sb->s_op->unfreeze_fs) { | |
1513 | error = sb->s_op->unfreeze_fs(sb); | |
1514 | if (error) { | |
1515 | printk(KERN_ERR | |
1516 | "VFS:Filesystem thaw failed\n"); | |
1517 | lockdep_sb_freeze_release(sb); | |
1518 | up_write(&sb->s_umount); | |
1519 | return error; | |
1520 | } | |
1521 | } | |
1522 | ||
1523 | sb->s_writers.frozen = SB_UNFROZEN; | |
1524 | sb_freeze_unlock(sb); | |
1525 | out: | |
1526 | wake_up(&sb->s_writers.wait_unfrozen); | |
1527 | deactivate_locked_super(sb); | |
1528 | return 0; | |
1529 | } | |
1530 | EXPORT_SYMBOL(thaw_super); |