1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/fs/super.c 4 * 5 * Copyright (C) 1991, 1992 Linus Torvalds 6 * 7 * super.c contains code to handle: - mount structures 8 * - super-block tables 9 * - filesystem drivers list 10 * - mount system call 11 * - umount system call 12 * - ustat system call 13 * 14 * GK 2/5/95 - Changed to support mounting the root fs via NFS 15 * 16 * Added kerneld support: Jacques Gelinas and Bjorn Ekwall 17 * Added change_root: Werner Almesberger & Hans Lermen, Feb '96 18 * Added options to /proc/mounts: 19 * Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996. 20 * Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998 21 * Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000 22 */ 23 24 #include <linux/export.h> 25 #include <linux/slab.h> 26 #include <linux/blkdev.h> 27 #include <linux/mount.h> 28 #include <linux/security.h> 29 #include <linux/writeback.h> /* for the emergency remount stuff */ 30 #include <linux/idr.h> 31 #include <linux/mutex.h> 32 #include <linux/backing-dev.h> 33 #include <linux/rculist_bl.h> 34 #include <linux/cleancache.h> 35 #include <linux/fscrypt.h> 36 #include <linux/fsnotify.h> 37 #include <linux/lockdep.h> 38 #include <linux/user_namespace.h> 39 #include <linux/fs_context.h> 40 #include <uapi/linux/mount.h> 41 #include "internal.h" 42 43 static int thaw_super_locked(struct super_block *sb); 44 45 static LIST_HEAD(super_blocks); 46 static DEFINE_SPINLOCK(sb_lock); 47 48 static char *sb_writers_name[SB_FREEZE_LEVELS] = { 49 "sb_writers", 50 "sb_pagefaults", 51 "sb_internal", 52 }; 53 54 /* 55 * One thing we have to be careful of with a per-sb shrinker is that we don't 56 * drop the last active reference to the superblock from within the shrinker. 57 * If that happens we could trigger unregistering the shrinker from within the 58 * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we 59 * take a passive reference to the superblock to avoid this from occurring. 60 */ 61 static unsigned long super_cache_scan(struct shrinker *shrink, 62 struct shrink_control *sc) 63 { 64 struct super_block *sb; 65 long fs_objects = 0; 66 long total_objects; 67 long freed = 0; 68 long dentries; 69 long inodes; 70 71 sb = container_of(shrink, struct super_block, s_shrink); 72 73 /* 74 * Deadlock avoidance. We may hold various FS locks, and we don't want 75 * to recurse into the FS that called us in clear_inode() and friends.. 76 */ 77 if (!(sc->gfp_mask & __GFP_FS)) 78 return SHRINK_STOP; 79 80 if (!trylock_super(sb)) 81 return SHRINK_STOP; 82 83 if (sb->s_op->nr_cached_objects) 84 fs_objects = sb->s_op->nr_cached_objects(sb, sc); 85 86 inodes = list_lru_shrink_count(&sb->s_inode_lru, sc); 87 dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc); 88 total_objects = dentries + inodes + fs_objects + 1; 89 if (!total_objects) 90 total_objects = 1; 91 92 /* proportion the scan between the caches */ 93 dentries = mult_frac(sc->nr_to_scan, dentries, total_objects); 94 inodes = mult_frac(sc->nr_to_scan, inodes, total_objects); 95 fs_objects = mult_frac(sc->nr_to_scan, fs_objects, total_objects); 96 97 /* 98 * prune the dcache first as the icache is pinned by it, then 99 * prune the icache, followed by the filesystem specific caches 100 * 101 * Ensure that we always scan at least one object - memcg kmem 102 * accounting uses this to fully empty the caches. 103 */ 104 sc->nr_to_scan = dentries + 1; 105 freed = prune_dcache_sb(sb, sc); 106 sc->nr_to_scan = inodes + 1; 107 freed += prune_icache_sb(sb, sc); 108 109 if (fs_objects) { 110 sc->nr_to_scan = fs_objects + 1; 111 freed += sb->s_op->free_cached_objects(sb, sc); 112 } 113 114 up_read(&sb->s_umount); 115 return freed; 116 } 117 118 static unsigned long super_cache_count(struct shrinker *shrink, 119 struct shrink_control *sc) 120 { 121 struct super_block *sb; 122 long total_objects = 0; 123 124 sb = container_of(shrink, struct super_block, s_shrink); 125 126 /* 127 * We don't call trylock_super() here as it is a scalability bottleneck, 128 * so we're exposed to partial setup state. The shrinker rwsem does not 129 * protect filesystem operations backing list_lru_shrink_count() or 130 * s_op->nr_cached_objects(). Counts can change between 131 * super_cache_count and super_cache_scan, so we really don't need locks 132 * here. 133 * 134 * However, if we are currently mounting the superblock, the underlying 135 * filesystem might be in a state of partial construction and hence it 136 * is dangerous to access it. trylock_super() uses a SB_BORN check to 137 * avoid this situation, so do the same here. The memory barrier is 138 * matched with the one in mount_fs() as we don't hold locks here. 139 */ 140 if (!(sb->s_flags & SB_BORN)) 141 return 0; 142 smp_rmb(); 143 144 if (sb->s_op && sb->s_op->nr_cached_objects) 145 total_objects = sb->s_op->nr_cached_objects(sb, sc); 146 147 total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc); 148 total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc); 149 150 if (!total_objects) 151 return SHRINK_EMPTY; 152 153 total_objects = vfs_pressure_ratio(total_objects); 154 return total_objects; 155 } 156 157 static void destroy_super_work(struct work_struct *work) 158 { 159 struct super_block *s = container_of(work, struct super_block, 160 destroy_work); 161 int i; 162 163 for (i = 0; i < SB_FREEZE_LEVELS; i++) 164 percpu_free_rwsem(&s->s_writers.rw_sem[i]); 165 kfree(s); 166 } 167 168 static void destroy_super_rcu(struct rcu_head *head) 169 { 170 struct super_block *s = container_of(head, struct super_block, rcu); 171 INIT_WORK(&s->destroy_work, destroy_super_work); 172 schedule_work(&s->destroy_work); 173 } 174 175 /* Free a superblock that has never been seen by anyone */ 176 static void destroy_unused_super(struct super_block *s) 177 { 178 if (!s) 179 return; 180 up_write(&s->s_umount); 181 list_lru_destroy(&s->s_dentry_lru); 182 list_lru_destroy(&s->s_inode_lru); 183 security_sb_free(s); 184 put_user_ns(s->s_user_ns); 185 kfree(s->s_subtype); 186 free_prealloced_shrinker(&s->s_shrink); 187 /* no delays needed */ 188 destroy_super_work(&s->destroy_work); 189 } 190 191 /** 192 * alloc_super - create new superblock 193 * @type: filesystem type superblock should belong to 194 * @flags: the mount flags 195 * @user_ns: User namespace for the super_block 196 * 197 * Allocates and initializes a new &struct super_block. alloc_super() 198 * returns a pointer new superblock or %NULL if allocation had failed. 199 */ 200 static struct super_block *alloc_super(struct file_system_type *type, int flags, 201 struct user_namespace *user_ns) 202 { 203 struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER); 204 static const struct super_operations default_op; 205 int i; 206 207 if (!s) 208 return NULL; 209 210 INIT_LIST_HEAD(&s->s_mounts); 211 s->s_user_ns = get_user_ns(user_ns); 212 init_rwsem(&s->s_umount); 213 lockdep_set_class(&s->s_umount, &type->s_umount_key); 214 /* 215 * sget() can have s_umount recursion. 216 * 217 * When it cannot find a suitable sb, it allocates a new 218 * one (this one), and tries again to find a suitable old 219 * one. 220 * 221 * In case that succeeds, it will acquire the s_umount 222 * lock of the old one. Since these are clearly distrinct 223 * locks, and this object isn't exposed yet, there's no 224 * risk of deadlocks. 225 * 226 * Annotate this by putting this lock in a different 227 * subclass. 228 */ 229 down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING); 230 231 if (security_sb_alloc(s)) 232 goto fail; 233 234 for (i = 0; i < SB_FREEZE_LEVELS; i++) { 235 if (__percpu_init_rwsem(&s->s_writers.rw_sem[i], 236 sb_writers_name[i], 237 &type->s_writers_key[i])) 238 goto fail; 239 } 240 init_waitqueue_head(&s->s_writers.wait_unfrozen); 241 s->s_bdi = &noop_backing_dev_info; 242 s->s_flags = flags; 243 if (s->s_user_ns != &init_user_ns) 244 s->s_iflags |= SB_I_NODEV; 245 INIT_HLIST_NODE(&s->s_instances); 246 INIT_HLIST_BL_HEAD(&s->s_roots); 247 mutex_init(&s->s_sync_lock); 248 INIT_LIST_HEAD(&s->s_inodes); 249 spin_lock_init(&s->s_inode_list_lock); 250 INIT_LIST_HEAD(&s->s_inodes_wb); 251 spin_lock_init(&s->s_inode_wblist_lock); 252 253 s->s_count = 1; 254 atomic_set(&s->s_active, 1); 255 mutex_init(&s->s_vfs_rename_mutex); 256 lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key); 257 init_rwsem(&s->s_dquot.dqio_sem); 258 s->s_maxbytes = MAX_NON_LFS; 259 s->s_op = &default_op; 260 s->s_time_gran = 1000000000; 261 s->s_time_min = TIME64_MIN; 262 s->s_time_max = TIME64_MAX; 263 s->cleancache_poolid = CLEANCACHE_NO_POOL; 264 265 s->s_shrink.seeks = DEFAULT_SEEKS; 266 s->s_shrink.scan_objects = super_cache_scan; 267 s->s_shrink.count_objects = super_cache_count; 268 s->s_shrink.batch = 1024; 269 s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE; 270 if (prealloc_shrinker(&s->s_shrink)) 271 goto fail; 272 if (list_lru_init_memcg(&s->s_dentry_lru, &s->s_shrink)) 273 goto fail; 274 if (list_lru_init_memcg(&s->s_inode_lru, &s->s_shrink)) 275 goto fail; 276 return s; 277 278 fail: 279 destroy_unused_super(s); 280 return NULL; 281 } 282 283 /* Superblock refcounting */ 284 285 /* 286 * Drop a superblock's refcount. The caller must hold sb_lock. 287 */ 288 static void __put_super(struct super_block *s) 289 { 290 if (!--s->s_count) { 291 list_del_init(&s->s_list); 292 WARN_ON(s->s_dentry_lru.node); 293 WARN_ON(s->s_inode_lru.node); 294 WARN_ON(!list_empty(&s->s_mounts)); 295 security_sb_free(s); 296 fscrypt_sb_free(s); 297 put_user_ns(s->s_user_ns); 298 kfree(s->s_subtype); 299 call_rcu(&s->rcu, destroy_super_rcu); 300 } 301 } 302 303 /** 304 * put_super - drop a temporary reference to superblock 305 * @sb: superblock in question 306 * 307 * Drops a temporary reference, frees superblock if there's no 308 * references left. 309 */ 310 static void put_super(struct super_block *sb) 311 { 312 spin_lock(&sb_lock); 313 __put_super(sb); 314 spin_unlock(&sb_lock); 315 } 316 317 318 /** 319 * deactivate_locked_super - drop an active reference to superblock 320 * @s: superblock to deactivate 321 * 322 * Drops an active reference to superblock, converting it into a temporary 323 * one if there is no other active references left. In that case we 324 * tell fs driver to shut it down and drop the temporary reference we 325 * had just acquired. 326 * 327 * Caller holds exclusive lock on superblock; that lock is released. 328 */ 329 void deactivate_locked_super(struct super_block *s) 330 { 331 struct file_system_type *fs = s->s_type; 332 if (atomic_dec_and_test(&s->s_active)) { 333 cleancache_invalidate_fs(s); 334 unregister_shrinker(&s->s_shrink); 335 fs->kill_sb(s); 336 337 /* 338 * Since list_lru_destroy() may sleep, we cannot call it from 339 * put_super(), where we hold the sb_lock. Therefore we destroy 340 * the lru lists right now. 341 */ 342 list_lru_destroy(&s->s_dentry_lru); 343 list_lru_destroy(&s->s_inode_lru); 344 345 put_filesystem(fs); 346 put_super(s); 347 } else { 348 up_write(&s->s_umount); 349 } 350 } 351 352 EXPORT_SYMBOL(deactivate_locked_super); 353 354 /** 355 * deactivate_super - drop an active reference to superblock 356 * @s: superblock to deactivate 357 * 358 * Variant of deactivate_locked_super(), except that superblock is *not* 359 * locked by caller. If we are going to drop the final active reference, 360 * lock will be acquired prior to that. 361 */ 362 void deactivate_super(struct super_block *s) 363 { 364 if (!atomic_add_unless(&s->s_active, -1, 1)) { 365 down_write(&s->s_umount); 366 deactivate_locked_super(s); 367 } 368 } 369 370 EXPORT_SYMBOL(deactivate_super); 371 372 /** 373 * grab_super - acquire an active reference 374 * @s: reference we are trying to make active 375 * 376 * Tries to acquire an active reference. grab_super() is used when we 377 * had just found a superblock in super_blocks or fs_type->fs_supers 378 * and want to turn it into a full-blown active reference. grab_super() 379 * is called with sb_lock held and drops it. Returns 1 in case of 380 * success, 0 if we had failed (superblock contents was already dead or 381 * dying when grab_super() had been called). Note that this is only 382 * called for superblocks not in rundown mode (== ones still on ->fs_supers 383 * of their type), so increment of ->s_count is OK here. 384 */ 385 static int grab_super(struct super_block *s) __releases(sb_lock) 386 { 387 s->s_count++; 388 spin_unlock(&sb_lock); 389 down_write(&s->s_umount); 390 if ((s->s_flags & SB_BORN) && atomic_inc_not_zero(&s->s_active)) { 391 put_super(s); 392 return 1; 393 } 394 up_write(&s->s_umount); 395 put_super(s); 396 return 0; 397 } 398 399 /* 400 * trylock_super - try to grab ->s_umount shared 401 * @sb: reference we are trying to grab 402 * 403 * Try to prevent fs shutdown. This is used in places where we 404 * cannot take an active reference but we need to ensure that the 405 * filesystem is not shut down while we are working on it. It returns 406 * false if we cannot acquire s_umount or if we lose the race and 407 * filesystem already got into shutdown, and returns true with the s_umount 408 * lock held in read mode in case of success. On successful return, 409 * the caller must drop the s_umount lock when done. 410 * 411 * Note that unlike get_super() et.al. this one does *not* bump ->s_count. 412 * The reason why it's safe is that we are OK with doing trylock instead 413 * of down_read(). There's a couple of places that are OK with that, but 414 * it's very much not a general-purpose interface. 415 */ 416 bool trylock_super(struct super_block *sb) 417 { 418 if (down_read_trylock(&sb->s_umount)) { 419 if (!hlist_unhashed(&sb->s_instances) && 420 sb->s_root && (sb->s_flags & SB_BORN)) 421 return true; 422 up_read(&sb->s_umount); 423 } 424 425 return false; 426 } 427 428 /** 429 * generic_shutdown_super - common helper for ->kill_sb() 430 * @sb: superblock to kill 431 * 432 * generic_shutdown_super() does all fs-independent work on superblock 433 * shutdown. Typical ->kill_sb() should pick all fs-specific objects 434 * that need destruction out of superblock, call generic_shutdown_super() 435 * and release aforementioned objects. Note: dentries and inodes _are_ 436 * taken care of and do not need specific handling. 437 * 438 * Upon calling this function, the filesystem may no longer alter or 439 * rearrange the set of dentries belonging to this super_block, nor may it 440 * change the attachments of dentries to inodes. 441 */ 442 void generic_shutdown_super(struct super_block *sb) 443 { 444 const struct super_operations *sop = sb->s_op; 445 446 if (sb->s_root) { 447 shrink_dcache_for_umount(sb); 448 sync_filesystem(sb); 449 sb->s_flags &= ~SB_ACTIVE; 450 451 fsnotify_sb_delete(sb); 452 cgroup_writeback_umount(); 453 454 evict_inodes(sb); 455 456 if (sb->s_dio_done_wq) { 457 destroy_workqueue(sb->s_dio_done_wq); 458 sb->s_dio_done_wq = NULL; 459 } 460 461 if (sop->put_super) 462 sop->put_super(sb); 463 464 if (!list_empty(&sb->s_inodes)) { 465 printk("VFS: Busy inodes after unmount of %s. " 466 "Self-destruct in 5 seconds. Have a nice day...\n", 467 sb->s_id); 468 } 469 } 470 spin_lock(&sb_lock); 471 /* should be initialized for __put_super_and_need_restart() */ 472 hlist_del_init(&sb->s_instances); 473 spin_unlock(&sb_lock); 474 up_write(&sb->s_umount); 475 if (sb->s_bdi != &noop_backing_dev_info) { 476 bdi_put(sb->s_bdi); 477 sb->s_bdi = &noop_backing_dev_info; 478 } 479 } 480 481 EXPORT_SYMBOL(generic_shutdown_super); 482 483 bool mount_capable(struct fs_context *fc) 484 { 485 if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT)) 486 return capable(CAP_SYS_ADMIN); 487 else 488 return ns_capable(fc->user_ns, CAP_SYS_ADMIN); 489 } 490 491 /** 492 * sget_fc - Find or create a superblock 493 * @fc: Filesystem context. 494 * @test: Comparison callback 495 * @set: Setup callback 496 * 497 * Find or create a superblock using the parameters stored in the filesystem 498 * context and the two callback functions. 499 * 500 * If an extant superblock is matched, then that will be returned with an 501 * elevated reference count that the caller must transfer or discard. 502 * 503 * If no match is made, a new superblock will be allocated and basic 504 * initialisation will be performed (s_type, s_fs_info and s_id will be set and 505 * the set() callback will be invoked), the superblock will be published and it 506 * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE 507 * as yet unset. 508 */ 509 struct super_block *sget_fc(struct fs_context *fc, 510 int (*test)(struct super_block *, struct fs_context *), 511 int (*set)(struct super_block *, struct fs_context *)) 512 { 513 struct super_block *s = NULL; 514 struct super_block *old; 515 struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns; 516 int err; 517 518 retry: 519 spin_lock(&sb_lock); 520 if (test) { 521 hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) { 522 if (test(old, fc)) 523 goto share_extant_sb; 524 } 525 } 526 if (!s) { 527 spin_unlock(&sb_lock); 528 s = alloc_super(fc->fs_type, fc->sb_flags, user_ns); 529 if (!s) 530 return ERR_PTR(-ENOMEM); 531 goto retry; 532 } 533 534 s->s_fs_info = fc->s_fs_info; 535 err = set(s, fc); 536 if (err) { 537 s->s_fs_info = NULL; 538 spin_unlock(&sb_lock); 539 destroy_unused_super(s); 540 return ERR_PTR(err); 541 } 542 fc->s_fs_info = NULL; 543 s->s_type = fc->fs_type; 544 s->s_iflags |= fc->s_iflags; 545 strlcpy(s->s_id, s->s_type->name, sizeof(s->s_id)); 546 list_add_tail(&s->s_list, &super_blocks); 547 hlist_add_head(&s->s_instances, &s->s_type->fs_supers); 548 spin_unlock(&sb_lock); 549 get_filesystem(s->s_type); 550 register_shrinker_prepared(&s->s_shrink); 551 return s; 552 553 share_extant_sb: 554 if (user_ns != old->s_user_ns) { 555 spin_unlock(&sb_lock); 556 destroy_unused_super(s); 557 return ERR_PTR(-EBUSY); 558 } 559 if (!grab_super(old)) 560 goto retry; 561 destroy_unused_super(s); 562 return old; 563 } 564 EXPORT_SYMBOL(sget_fc); 565 566 /** 567 * sget - find or create a superblock 568 * @type: filesystem type superblock should belong to 569 * @test: comparison callback 570 * @set: setup callback 571 * @flags: mount flags 572 * @data: argument to each of them 573 */ 574 struct super_block *sget(struct file_system_type *type, 575 int (*test)(struct super_block *,void *), 576 int (*set)(struct super_block *,void *), 577 int flags, 578 void *data) 579 { 580 struct user_namespace *user_ns = current_user_ns(); 581 struct super_block *s = NULL; 582 struct super_block *old; 583 int err; 584 585 /* We don't yet pass the user namespace of the parent 586 * mount through to here so always use &init_user_ns 587 * until that changes. 588 */ 589 if (flags & SB_SUBMOUNT) 590 user_ns = &init_user_ns; 591 592 retry: 593 spin_lock(&sb_lock); 594 if (test) { 595 hlist_for_each_entry(old, &type->fs_supers, s_instances) { 596 if (!test(old, data)) 597 continue; 598 if (user_ns != old->s_user_ns) { 599 spin_unlock(&sb_lock); 600 destroy_unused_super(s); 601 return ERR_PTR(-EBUSY); 602 } 603 if (!grab_super(old)) 604 goto retry; 605 destroy_unused_super(s); 606 return old; 607 } 608 } 609 if (!s) { 610 spin_unlock(&sb_lock); 611 s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns); 612 if (!s) 613 return ERR_PTR(-ENOMEM); 614 goto retry; 615 } 616 617 err = set(s, data); 618 if (err) { 619 spin_unlock(&sb_lock); 620 destroy_unused_super(s); 621 return ERR_PTR(err); 622 } 623 s->s_type = type; 624 strlcpy(s->s_id, type->name, sizeof(s->s_id)); 625 list_add_tail(&s->s_list, &super_blocks); 626 hlist_add_head(&s->s_instances, &type->fs_supers); 627 spin_unlock(&sb_lock); 628 get_filesystem(type); 629 register_shrinker_prepared(&s->s_shrink); 630 return s; 631 } 632 EXPORT_SYMBOL(sget); 633 634 void drop_super(struct super_block *sb) 635 { 636 up_read(&sb->s_umount); 637 put_super(sb); 638 } 639 640 EXPORT_SYMBOL(drop_super); 641 642 void drop_super_exclusive(struct super_block *sb) 643 { 644 up_write(&sb->s_umount); 645 put_super(sb); 646 } 647 EXPORT_SYMBOL(drop_super_exclusive); 648 649 static void __iterate_supers(void (*f)(struct super_block *)) 650 { 651 struct super_block *sb, *p = NULL; 652 653 spin_lock(&sb_lock); 654 list_for_each_entry(sb, &super_blocks, s_list) { 655 if (hlist_unhashed(&sb->s_instances)) 656 continue; 657 sb->s_count++; 658 spin_unlock(&sb_lock); 659 660 f(sb); 661 662 spin_lock(&sb_lock); 663 if (p) 664 __put_super(p); 665 p = sb; 666 } 667 if (p) 668 __put_super(p); 669 spin_unlock(&sb_lock); 670 } 671 /** 672 * iterate_supers - call function for all active superblocks 673 * @f: function to call 674 * @arg: argument to pass to it 675 * 676 * Scans the superblock list and calls given function, passing it 677 * locked superblock and given argument. 678 */ 679 void iterate_supers(void (*f)(struct super_block *, void *), void *arg) 680 { 681 struct super_block *sb, *p = NULL; 682 683 spin_lock(&sb_lock); 684 list_for_each_entry(sb, &super_blocks, s_list) { 685 if (hlist_unhashed(&sb->s_instances)) 686 continue; 687 sb->s_count++; 688 spin_unlock(&sb_lock); 689 690 down_read(&sb->s_umount); 691 if (sb->s_root && (sb->s_flags & SB_BORN)) 692 f(sb, arg); 693 up_read(&sb->s_umount); 694 695 spin_lock(&sb_lock); 696 if (p) 697 __put_super(p); 698 p = sb; 699 } 700 if (p) 701 __put_super(p); 702 spin_unlock(&sb_lock); 703 } 704 705 /** 706 * iterate_supers_type - call function for superblocks of given type 707 * @type: fs type 708 * @f: function to call 709 * @arg: argument to pass to it 710 * 711 * Scans the superblock list and calls given function, passing it 712 * locked superblock and given argument. 713 */ 714 void iterate_supers_type(struct file_system_type *type, 715 void (*f)(struct super_block *, void *), void *arg) 716 { 717 struct super_block *sb, *p = NULL; 718 719 spin_lock(&sb_lock); 720 hlist_for_each_entry(sb, &type->fs_supers, s_instances) { 721 sb->s_count++; 722 spin_unlock(&sb_lock); 723 724 down_read(&sb->s_umount); 725 if (sb->s_root && (sb->s_flags & SB_BORN)) 726 f(sb, arg); 727 up_read(&sb->s_umount); 728 729 spin_lock(&sb_lock); 730 if (p) 731 __put_super(p); 732 p = sb; 733 } 734 if (p) 735 __put_super(p); 736 spin_unlock(&sb_lock); 737 } 738 739 EXPORT_SYMBOL(iterate_supers_type); 740 741 static struct super_block *__get_super(struct block_device *bdev, bool excl) 742 { 743 struct super_block *sb; 744 745 if (!bdev) 746 return NULL; 747 748 spin_lock(&sb_lock); 749 rescan: 750 list_for_each_entry(sb, &super_blocks, s_list) { 751 if (hlist_unhashed(&sb->s_instances)) 752 continue; 753 if (sb->s_bdev == bdev) { 754 sb->s_count++; 755 spin_unlock(&sb_lock); 756 if (!excl) 757 down_read(&sb->s_umount); 758 else 759 down_write(&sb->s_umount); 760 /* still alive? */ 761 if (sb->s_root && (sb->s_flags & SB_BORN)) 762 return sb; 763 if (!excl) 764 up_read(&sb->s_umount); 765 else 766 up_write(&sb->s_umount); 767 /* nope, got unmounted */ 768 spin_lock(&sb_lock); 769 __put_super(sb); 770 goto rescan; 771 } 772 } 773 spin_unlock(&sb_lock); 774 return NULL; 775 } 776 777 /** 778 * get_super - get the superblock of a device 779 * @bdev: device to get the superblock for 780 * 781 * Scans the superblock list and finds the superblock of the file system 782 * mounted on the device given. %NULL is returned if no match is found. 783 */ 784 struct super_block *get_super(struct block_device *bdev) 785 { 786 return __get_super(bdev, false); 787 } 788 EXPORT_SYMBOL(get_super); 789 790 static struct super_block *__get_super_thawed(struct block_device *bdev, 791 bool excl) 792 { 793 while (1) { 794 struct super_block *s = __get_super(bdev, excl); 795 if (!s || s->s_writers.frozen == SB_UNFROZEN) 796 return s; 797 if (!excl) 798 up_read(&s->s_umount); 799 else 800 up_write(&s->s_umount); 801 wait_event(s->s_writers.wait_unfrozen, 802 s->s_writers.frozen == SB_UNFROZEN); 803 put_super(s); 804 } 805 } 806 807 /** 808 * get_super_thawed - get thawed superblock of a device 809 * @bdev: device to get the superblock for 810 * 811 * Scans the superblock list and finds the superblock of the file system 812 * mounted on the device. The superblock is returned once it is thawed 813 * (or immediately if it was not frozen). %NULL is returned if no match 814 * is found. 815 */ 816 struct super_block *get_super_thawed(struct block_device *bdev) 817 { 818 return __get_super_thawed(bdev, false); 819 } 820 EXPORT_SYMBOL(get_super_thawed); 821 822 /** 823 * get_super_exclusive_thawed - get thawed superblock of a device 824 * @bdev: device to get the superblock for 825 * 826 * Scans the superblock list and finds the superblock of the file system 827 * mounted on the device. The superblock is returned once it is thawed 828 * (or immediately if it was not frozen) and s_umount semaphore is held 829 * in exclusive mode. %NULL is returned if no match is found. 830 */ 831 struct super_block *get_super_exclusive_thawed(struct block_device *bdev) 832 { 833 return __get_super_thawed(bdev, true); 834 } 835 EXPORT_SYMBOL(get_super_exclusive_thawed); 836 837 /** 838 * get_active_super - get an active reference to the superblock of a device 839 * @bdev: device to get the superblock for 840 * 841 * Scans the superblock list and finds the superblock of the file system 842 * mounted on the device given. Returns the superblock with an active 843 * reference or %NULL if none was found. 844 */ 845 struct super_block *get_active_super(struct block_device *bdev) 846 { 847 struct super_block *sb; 848 849 if (!bdev) 850 return NULL; 851 852 restart: 853 spin_lock(&sb_lock); 854 list_for_each_entry(sb, &super_blocks, s_list) { 855 if (hlist_unhashed(&sb->s_instances)) 856 continue; 857 if (sb->s_bdev == bdev) { 858 if (!grab_super(sb)) 859 goto restart; 860 up_write(&sb->s_umount); 861 return sb; 862 } 863 } 864 spin_unlock(&sb_lock); 865 return NULL; 866 } 867 868 struct super_block *user_get_super(dev_t dev) 869 { 870 struct super_block *sb; 871 872 spin_lock(&sb_lock); 873 rescan: 874 list_for_each_entry(sb, &super_blocks, s_list) { 875 if (hlist_unhashed(&sb->s_instances)) 876 continue; 877 if (sb->s_dev == dev) { 878 sb->s_count++; 879 spin_unlock(&sb_lock); 880 down_read(&sb->s_umount); 881 /* still alive? */ 882 if (sb->s_root && (sb->s_flags & SB_BORN)) 883 return sb; 884 up_read(&sb->s_umount); 885 /* nope, got unmounted */ 886 spin_lock(&sb_lock); 887 __put_super(sb); 888 goto rescan; 889 } 890 } 891 spin_unlock(&sb_lock); 892 return NULL; 893 } 894 895 /** 896 * reconfigure_super - asks filesystem to change superblock parameters 897 * @fc: The superblock and configuration 898 * 899 * Alters the configuration parameters of a live superblock. 900 */ 901 int reconfigure_super(struct fs_context *fc) 902 { 903 struct super_block *sb = fc->root->d_sb; 904 int retval; 905 bool remount_ro = false; 906 bool force = fc->sb_flags & SB_FORCE; 907 908 if (fc->sb_flags_mask & ~MS_RMT_MASK) 909 return -EINVAL; 910 if (sb->s_writers.frozen != SB_UNFROZEN) 911 return -EBUSY; 912 913 retval = security_sb_remount(sb, fc->security); 914 if (retval) 915 return retval; 916 917 if (fc->sb_flags_mask & SB_RDONLY) { 918 #ifdef CONFIG_BLOCK 919 if (!(fc->sb_flags & SB_RDONLY) && bdev_read_only(sb->s_bdev)) 920 return -EACCES; 921 #endif 922 923 remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb); 924 } 925 926 if (remount_ro) { 927 if (!hlist_empty(&sb->s_pins)) { 928 up_write(&sb->s_umount); 929 group_pin_kill(&sb->s_pins); 930 down_write(&sb->s_umount); 931 if (!sb->s_root) 932 return 0; 933 if (sb->s_writers.frozen != SB_UNFROZEN) 934 return -EBUSY; 935 remount_ro = !sb_rdonly(sb); 936 } 937 } 938 shrink_dcache_sb(sb); 939 940 /* If we are reconfiguring to RDONLY and current sb is read/write, 941 * make sure there are no files open for writing. 942 */ 943 if (remount_ro) { 944 if (force) { 945 sb->s_readonly_remount = 1; 946 smp_wmb(); 947 } else { 948 retval = sb_prepare_remount_readonly(sb); 949 if (retval) 950 return retval; 951 } 952 } 953 954 if (fc->ops->reconfigure) { 955 retval = fc->ops->reconfigure(fc); 956 if (retval) { 957 if (!force) 958 goto cancel_readonly; 959 /* If forced remount, go ahead despite any errors */ 960 WARN(1, "forced remount of a %s fs returned %i\n", 961 sb->s_type->name, retval); 962 } 963 } 964 965 WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) | 966 (fc->sb_flags & fc->sb_flags_mask))); 967 /* Needs to be ordered wrt mnt_is_readonly() */ 968 smp_wmb(); 969 sb->s_readonly_remount = 0; 970 971 /* 972 * Some filesystems modify their metadata via some other path than the 973 * bdev buffer cache (eg. use a private mapping, or directories in 974 * pagecache, etc). Also file data modifications go via their own 975 * mappings. So If we try to mount readonly then copy the filesystem 976 * from bdev, we could get stale data, so invalidate it to give a best 977 * effort at coherency. 978 */ 979 if (remount_ro && sb->s_bdev) 980 invalidate_bdev(sb->s_bdev); 981 return 0; 982 983 cancel_readonly: 984 sb->s_readonly_remount = 0; 985 return retval; 986 } 987 988 static void do_emergency_remount_callback(struct super_block *sb) 989 { 990 down_write(&sb->s_umount); 991 if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) && 992 !sb_rdonly(sb)) { 993 struct fs_context *fc; 994 995 fc = fs_context_for_reconfigure(sb->s_root, 996 SB_RDONLY | SB_FORCE, SB_RDONLY); 997 if (!IS_ERR(fc)) { 998 if (parse_monolithic_mount_data(fc, NULL) == 0) 999 (void)reconfigure_super(fc); 1000 put_fs_context(fc); 1001 } 1002 } 1003 up_write(&sb->s_umount); 1004 } 1005 1006 static void do_emergency_remount(struct work_struct *work) 1007 { 1008 __iterate_supers(do_emergency_remount_callback); 1009 kfree(work); 1010 printk("Emergency Remount complete\n"); 1011 } 1012 1013 void emergency_remount(void) 1014 { 1015 struct work_struct *work; 1016 1017 work = kmalloc(sizeof(*work), GFP_ATOMIC); 1018 if (work) { 1019 INIT_WORK(work, do_emergency_remount); 1020 schedule_work(work); 1021 } 1022 } 1023 1024 static void do_thaw_all_callback(struct super_block *sb) 1025 { 1026 down_write(&sb->s_umount); 1027 if (sb->s_root && sb->s_flags & SB_BORN) { 1028 emergency_thaw_bdev(sb); 1029 thaw_super_locked(sb); 1030 } else { 1031 up_write(&sb->s_umount); 1032 } 1033 } 1034 1035 static void do_thaw_all(struct work_struct *work) 1036 { 1037 __iterate_supers(do_thaw_all_callback); 1038 kfree(work); 1039 printk(KERN_WARNING "Emergency Thaw complete\n"); 1040 } 1041 1042 /** 1043 * emergency_thaw_all -- forcibly thaw every frozen filesystem 1044 * 1045 * Used for emergency unfreeze of all filesystems via SysRq 1046 */ 1047 void emergency_thaw_all(void) 1048 { 1049 struct work_struct *work; 1050 1051 work = kmalloc(sizeof(*work), GFP_ATOMIC); 1052 if (work) { 1053 INIT_WORK(work, do_thaw_all); 1054 schedule_work(work); 1055 } 1056 } 1057 1058 static DEFINE_IDA(unnamed_dev_ida); 1059 1060 /** 1061 * get_anon_bdev - Allocate a block device for filesystems which don't have one. 1062 * @p: Pointer to a dev_t. 1063 * 1064 * Filesystems which don't use real block devices can call this function 1065 * to allocate a virtual block device. 1066 * 1067 * Context: Any context. Frequently called while holding sb_lock. 1068 * Return: 0 on success, -EMFILE if there are no anonymous bdevs left 1069 * or -ENOMEM if memory allocation failed. 1070 */ 1071 int get_anon_bdev(dev_t *p) 1072 { 1073 int dev; 1074 1075 /* 1076 * Many userspace utilities consider an FSID of 0 invalid. 1077 * Always return at least 1 from get_anon_bdev. 1078 */ 1079 dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1, 1080 GFP_ATOMIC); 1081 if (dev == -ENOSPC) 1082 dev = -EMFILE; 1083 if (dev < 0) 1084 return dev; 1085 1086 *p = MKDEV(0, dev); 1087 return 0; 1088 } 1089 EXPORT_SYMBOL(get_anon_bdev); 1090 1091 void free_anon_bdev(dev_t dev) 1092 { 1093 ida_free(&unnamed_dev_ida, MINOR(dev)); 1094 } 1095 EXPORT_SYMBOL(free_anon_bdev); 1096 1097 int set_anon_super(struct super_block *s, void *data) 1098 { 1099 return get_anon_bdev(&s->s_dev); 1100 } 1101 EXPORT_SYMBOL(set_anon_super); 1102 1103 void kill_anon_super(struct super_block *sb) 1104 { 1105 dev_t dev = sb->s_dev; 1106 generic_shutdown_super(sb); 1107 free_anon_bdev(dev); 1108 } 1109 EXPORT_SYMBOL(kill_anon_super); 1110 1111 void kill_litter_super(struct super_block *sb) 1112 { 1113 if (sb->s_root) 1114 d_genocide(sb->s_root); 1115 kill_anon_super(sb); 1116 } 1117 EXPORT_SYMBOL(kill_litter_super); 1118 1119 int set_anon_super_fc(struct super_block *sb, struct fs_context *fc) 1120 { 1121 return set_anon_super(sb, NULL); 1122 } 1123 EXPORT_SYMBOL(set_anon_super_fc); 1124 1125 static int test_keyed_super(struct super_block *sb, struct fs_context *fc) 1126 { 1127 return sb->s_fs_info == fc->s_fs_info; 1128 } 1129 1130 static int test_single_super(struct super_block *s, struct fs_context *fc) 1131 { 1132 return 1; 1133 } 1134 1135 /** 1136 * vfs_get_super - Get a superblock with a search key set in s_fs_info. 1137 * @fc: The filesystem context holding the parameters 1138 * @keying: How to distinguish superblocks 1139 * @fill_super: Helper to initialise a new superblock 1140 * 1141 * Search for a superblock and create a new one if not found. The search 1142 * criterion is controlled by @keying. If the search fails, a new superblock 1143 * is created and @fill_super() is called to initialise it. 1144 * 1145 * @keying can take one of a number of values: 1146 * 1147 * (1) vfs_get_single_super - Only one superblock of this type may exist on the 1148 * system. This is typically used for special system filesystems. 1149 * 1150 * (2) vfs_get_keyed_super - Multiple superblocks may exist, but they must have 1151 * distinct keys (where the key is in s_fs_info). Searching for the same 1152 * key again will turn up the superblock for that key. 1153 * 1154 * (3) vfs_get_independent_super - Multiple superblocks may exist and are 1155 * unkeyed. Each call will get a new superblock. 1156 * 1157 * A permissions check is made by sget_fc() unless we're getting a superblock 1158 * for a kernel-internal mount or a submount. 1159 */ 1160 int vfs_get_super(struct fs_context *fc, 1161 enum vfs_get_super_keying keying, 1162 int (*fill_super)(struct super_block *sb, 1163 struct fs_context *fc)) 1164 { 1165 int (*test)(struct super_block *, struct fs_context *); 1166 struct super_block *sb; 1167 int err; 1168 1169 switch (keying) { 1170 case vfs_get_single_super: 1171 case vfs_get_single_reconf_super: 1172 test = test_single_super; 1173 break; 1174 case vfs_get_keyed_super: 1175 test = test_keyed_super; 1176 break; 1177 case vfs_get_independent_super: 1178 test = NULL; 1179 break; 1180 default: 1181 BUG(); 1182 } 1183 1184 sb = sget_fc(fc, test, set_anon_super_fc); 1185 if (IS_ERR(sb)) 1186 return PTR_ERR(sb); 1187 1188 if (!sb->s_root) { 1189 err = fill_super(sb, fc); 1190 if (err) 1191 goto error; 1192 1193 sb->s_flags |= SB_ACTIVE; 1194 fc->root = dget(sb->s_root); 1195 } else { 1196 fc->root = dget(sb->s_root); 1197 if (keying == vfs_get_single_reconf_super) { 1198 err = reconfigure_super(fc); 1199 if (err < 0) { 1200 dput(fc->root); 1201 fc->root = NULL; 1202 goto error; 1203 } 1204 } 1205 } 1206 1207 return 0; 1208 1209 error: 1210 deactivate_locked_super(sb); 1211 return err; 1212 } 1213 EXPORT_SYMBOL(vfs_get_super); 1214 1215 int get_tree_nodev(struct fs_context *fc, 1216 int (*fill_super)(struct super_block *sb, 1217 struct fs_context *fc)) 1218 { 1219 return vfs_get_super(fc, vfs_get_independent_super, fill_super); 1220 } 1221 EXPORT_SYMBOL(get_tree_nodev); 1222 1223 int get_tree_single(struct fs_context *fc, 1224 int (*fill_super)(struct super_block *sb, 1225 struct fs_context *fc)) 1226 { 1227 return vfs_get_super(fc, vfs_get_single_super, fill_super); 1228 } 1229 EXPORT_SYMBOL(get_tree_single); 1230 1231 int get_tree_single_reconf(struct fs_context *fc, 1232 int (*fill_super)(struct super_block *sb, 1233 struct fs_context *fc)) 1234 { 1235 return vfs_get_super(fc, vfs_get_single_reconf_super, fill_super); 1236 } 1237 EXPORT_SYMBOL(get_tree_single_reconf); 1238 1239 int get_tree_keyed(struct fs_context *fc, 1240 int (*fill_super)(struct super_block *sb, 1241 struct fs_context *fc), 1242 void *key) 1243 { 1244 fc->s_fs_info = key; 1245 return vfs_get_super(fc, vfs_get_keyed_super, fill_super); 1246 } 1247 EXPORT_SYMBOL(get_tree_keyed); 1248 1249 #ifdef CONFIG_BLOCK 1250 1251 static int set_bdev_super(struct super_block *s, void *data) 1252 { 1253 s->s_bdev = data; 1254 s->s_dev = s->s_bdev->bd_dev; 1255 s->s_bdi = bdi_get(s->s_bdev->bd_bdi); 1256 1257 return 0; 1258 } 1259 1260 static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc) 1261 { 1262 return set_bdev_super(s, fc->sget_key); 1263 } 1264 1265 static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc) 1266 { 1267 return s->s_bdev == fc->sget_key; 1268 } 1269 1270 /** 1271 * get_tree_bdev - Get a superblock based on a single block device 1272 * @fc: The filesystem context holding the parameters 1273 * @fill_super: Helper to initialise a new superblock 1274 */ 1275 int get_tree_bdev(struct fs_context *fc, 1276 int (*fill_super)(struct super_block *, 1277 struct fs_context *)) 1278 { 1279 struct block_device *bdev; 1280 struct super_block *s; 1281 fmode_t mode = FMODE_READ | FMODE_EXCL; 1282 int error = 0; 1283 1284 if (!(fc->sb_flags & SB_RDONLY)) 1285 mode |= FMODE_WRITE; 1286 1287 if (!fc->source) 1288 return invalf(fc, "No source specified"); 1289 1290 bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type); 1291 if (IS_ERR(bdev)) { 1292 errorf(fc, "%s: Can't open blockdev", fc->source); 1293 return PTR_ERR(bdev); 1294 } 1295 1296 /* Once the superblock is inserted into the list by sget_fc(), s_umount 1297 * will protect the lockfs code from trying to start a snapshot while 1298 * we are mounting 1299 */ 1300 mutex_lock(&bdev->bd_fsfreeze_mutex); 1301 if (bdev->bd_fsfreeze_count > 0) { 1302 mutex_unlock(&bdev->bd_fsfreeze_mutex); 1303 warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev); 1304 return -EBUSY; 1305 } 1306 1307 fc->sb_flags |= SB_NOSEC; 1308 fc->sget_key = bdev; 1309 s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc); 1310 mutex_unlock(&bdev->bd_fsfreeze_mutex); 1311 if (IS_ERR(s)) 1312 return PTR_ERR(s); 1313 1314 if (s->s_root) { 1315 /* Don't summarily change the RO/RW state. */ 1316 if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) { 1317 warnf(fc, "%pg: Can't mount, would change RO state", bdev); 1318 deactivate_locked_super(s); 1319 blkdev_put(bdev, mode); 1320 return -EBUSY; 1321 } 1322 1323 /* 1324 * s_umount nests inside bd_mutex during 1325 * __invalidate_device(). blkdev_put() acquires 1326 * bd_mutex and can't be called under s_umount. Drop 1327 * s_umount temporarily. This is safe as we're 1328 * holding an active reference. 1329 */ 1330 up_write(&s->s_umount); 1331 blkdev_put(bdev, mode); 1332 down_write(&s->s_umount); 1333 } else { 1334 s->s_mode = mode; 1335 snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev); 1336 sb_set_blocksize(s, block_size(bdev)); 1337 error = fill_super(s, fc); 1338 if (error) { 1339 deactivate_locked_super(s); 1340 return error; 1341 } 1342 1343 s->s_flags |= SB_ACTIVE; 1344 bdev->bd_super = s; 1345 } 1346 1347 BUG_ON(fc->root); 1348 fc->root = dget(s->s_root); 1349 return 0; 1350 } 1351 EXPORT_SYMBOL(get_tree_bdev); 1352 1353 static int test_bdev_super(struct super_block *s, void *data) 1354 { 1355 return (void *)s->s_bdev == data; 1356 } 1357 1358 struct dentry *mount_bdev(struct file_system_type *fs_type, 1359 int flags, const char *dev_name, void *data, 1360 int (*fill_super)(struct super_block *, void *, int)) 1361 { 1362 struct block_device *bdev; 1363 struct super_block *s; 1364 fmode_t mode = FMODE_READ | FMODE_EXCL; 1365 int error = 0; 1366 1367 if (!(flags & SB_RDONLY)) 1368 mode |= FMODE_WRITE; 1369 1370 bdev = blkdev_get_by_path(dev_name, mode, fs_type); 1371 if (IS_ERR(bdev)) 1372 return ERR_CAST(bdev); 1373 1374 /* 1375 * once the super is inserted into the list by sget, s_umount 1376 * will protect the lockfs code from trying to start a snapshot 1377 * while we are mounting 1378 */ 1379 mutex_lock(&bdev->bd_fsfreeze_mutex); 1380 if (bdev->bd_fsfreeze_count > 0) { 1381 mutex_unlock(&bdev->bd_fsfreeze_mutex); 1382 error = -EBUSY; 1383 goto error_bdev; 1384 } 1385 s = sget(fs_type, test_bdev_super, set_bdev_super, flags | SB_NOSEC, 1386 bdev); 1387 mutex_unlock(&bdev->bd_fsfreeze_mutex); 1388 if (IS_ERR(s)) 1389 goto error_s; 1390 1391 if (s->s_root) { 1392 if ((flags ^ s->s_flags) & SB_RDONLY) { 1393 deactivate_locked_super(s); 1394 error = -EBUSY; 1395 goto error_bdev; 1396 } 1397 1398 /* 1399 * s_umount nests inside bd_mutex during 1400 * __invalidate_device(). blkdev_put() acquires 1401 * bd_mutex and can't be called under s_umount. Drop 1402 * s_umount temporarily. This is safe as we're 1403 * holding an active reference. 1404 */ 1405 up_write(&s->s_umount); 1406 blkdev_put(bdev, mode); 1407 down_write(&s->s_umount); 1408 } else { 1409 s->s_mode = mode; 1410 snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev); 1411 sb_set_blocksize(s, block_size(bdev)); 1412 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0); 1413 if (error) { 1414 deactivate_locked_super(s); 1415 goto error; 1416 } 1417 1418 s->s_flags |= SB_ACTIVE; 1419 bdev->bd_super = s; 1420 } 1421 1422 return dget(s->s_root); 1423 1424 error_s: 1425 error = PTR_ERR(s); 1426 error_bdev: 1427 blkdev_put(bdev, mode); 1428 error: 1429 return ERR_PTR(error); 1430 } 1431 EXPORT_SYMBOL(mount_bdev); 1432 1433 void kill_block_super(struct super_block *sb) 1434 { 1435 struct block_device *bdev = sb->s_bdev; 1436 fmode_t mode = sb->s_mode; 1437 1438 bdev->bd_super = NULL; 1439 generic_shutdown_super(sb); 1440 sync_blockdev(bdev); 1441 WARN_ON_ONCE(!(mode & FMODE_EXCL)); 1442 blkdev_put(bdev, mode | FMODE_EXCL); 1443 } 1444 1445 EXPORT_SYMBOL(kill_block_super); 1446 #endif 1447 1448 struct dentry *mount_nodev(struct file_system_type *fs_type, 1449 int flags, void *data, 1450 int (*fill_super)(struct super_block *, void *, int)) 1451 { 1452 int error; 1453 struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL); 1454 1455 if (IS_ERR(s)) 1456 return ERR_CAST(s); 1457 1458 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0); 1459 if (error) { 1460 deactivate_locked_super(s); 1461 return ERR_PTR(error); 1462 } 1463 s->s_flags |= SB_ACTIVE; 1464 return dget(s->s_root); 1465 } 1466 EXPORT_SYMBOL(mount_nodev); 1467 1468 static int reconfigure_single(struct super_block *s, 1469 int flags, void *data) 1470 { 1471 struct fs_context *fc; 1472 int ret; 1473 1474 /* The caller really need to be passing fc down into mount_single(), 1475 * then a chunk of this can be removed. [Bollocks -- AV] 1476 * Better yet, reconfiguration shouldn't happen, but rather the second 1477 * mount should be rejected if the parameters are not compatible. 1478 */ 1479 fc = fs_context_for_reconfigure(s->s_root, flags, MS_RMT_MASK); 1480 if (IS_ERR(fc)) 1481 return PTR_ERR(fc); 1482 1483 ret = parse_monolithic_mount_data(fc, data); 1484 if (ret < 0) 1485 goto out; 1486 1487 ret = reconfigure_super(fc); 1488 out: 1489 put_fs_context(fc); 1490 return ret; 1491 } 1492 1493 static int compare_single(struct super_block *s, void *p) 1494 { 1495 return 1; 1496 } 1497 1498 struct dentry *mount_single(struct file_system_type *fs_type, 1499 int flags, void *data, 1500 int (*fill_super)(struct super_block *, void *, int)) 1501 { 1502 struct super_block *s; 1503 int error; 1504 1505 s = sget(fs_type, compare_single, set_anon_super, flags, NULL); 1506 if (IS_ERR(s)) 1507 return ERR_CAST(s); 1508 if (!s->s_root) { 1509 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0); 1510 if (!error) 1511 s->s_flags |= SB_ACTIVE; 1512 } else { 1513 error = reconfigure_single(s, flags, data); 1514 } 1515 if (unlikely(error)) { 1516 deactivate_locked_super(s); 1517 return ERR_PTR(error); 1518 } 1519 return dget(s->s_root); 1520 } 1521 EXPORT_SYMBOL(mount_single); 1522 1523 /** 1524 * vfs_get_tree - Get the mountable root 1525 * @fc: The superblock configuration context. 1526 * 1527 * The filesystem is invoked to get or create a superblock which can then later 1528 * be used for mounting. The filesystem places a pointer to the root to be 1529 * used for mounting in @fc->root. 1530 */ 1531 int vfs_get_tree(struct fs_context *fc) 1532 { 1533 struct super_block *sb; 1534 int error; 1535 1536 if (fc->root) 1537 return -EBUSY; 1538 1539 /* Get the mountable root in fc->root, with a ref on the root and a ref 1540 * on the superblock. 1541 */ 1542 error = fc->ops->get_tree(fc); 1543 if (error < 0) 1544 return error; 1545 1546 if (!fc->root) { 1547 pr_err("Filesystem %s get_tree() didn't set fc->root\n", 1548 fc->fs_type->name); 1549 /* We don't know what the locking state of the superblock is - 1550 * if there is a superblock. 1551 */ 1552 BUG(); 1553 } 1554 1555 sb = fc->root->d_sb; 1556 WARN_ON(!sb->s_bdi); 1557 1558 /* 1559 * Write barrier is for super_cache_count(). We place it before setting 1560 * SB_BORN as the data dependency between the two functions is the 1561 * superblock structure contents that we just set up, not the SB_BORN 1562 * flag. 1563 */ 1564 smp_wmb(); 1565 sb->s_flags |= SB_BORN; 1566 1567 error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL); 1568 if (unlikely(error)) { 1569 fc_drop_locked(fc); 1570 return error; 1571 } 1572 1573 /* 1574 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE 1575 * but s_maxbytes was an unsigned long long for many releases. Throw 1576 * this warning for a little while to try and catch filesystems that 1577 * violate this rule. 1578 */ 1579 WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to " 1580 "negative value (%lld)\n", fc->fs_type->name, sb->s_maxbytes); 1581 1582 return 0; 1583 } 1584 EXPORT_SYMBOL(vfs_get_tree); 1585 1586 /* 1587 * Setup private BDI for given superblock. It gets automatically cleaned up 1588 * in generic_shutdown_super(). 1589 */ 1590 int super_setup_bdi_name(struct super_block *sb, char *fmt, ...) 1591 { 1592 struct backing_dev_info *bdi; 1593 int err; 1594 va_list args; 1595 1596 bdi = bdi_alloc(GFP_KERNEL); 1597 if (!bdi) 1598 return -ENOMEM; 1599 1600 bdi->name = sb->s_type->name; 1601 1602 va_start(args, fmt); 1603 err = bdi_register_va(bdi, fmt, args); 1604 va_end(args); 1605 if (err) { 1606 bdi_put(bdi); 1607 return err; 1608 } 1609 WARN_ON(sb->s_bdi != &noop_backing_dev_info); 1610 sb->s_bdi = bdi; 1611 1612 return 0; 1613 } 1614 EXPORT_SYMBOL(super_setup_bdi_name); 1615 1616 /* 1617 * Setup private BDI for given superblock. I gets automatically cleaned up 1618 * in generic_shutdown_super(). 1619 */ 1620 int super_setup_bdi(struct super_block *sb) 1621 { 1622 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0); 1623 1624 return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name, 1625 atomic_long_inc_return(&bdi_seq)); 1626 } 1627 EXPORT_SYMBOL(super_setup_bdi); 1628 1629 /* 1630 * This is an internal function, please use sb_end_{write,pagefault,intwrite} 1631 * instead. 1632 */ 1633 void __sb_end_write(struct super_block *sb, int level) 1634 { 1635 percpu_up_read(sb->s_writers.rw_sem + level-1); 1636 } 1637 EXPORT_SYMBOL(__sb_end_write); 1638 1639 /* 1640 * This is an internal function, please use sb_start_{write,pagefault,intwrite} 1641 * instead. 1642 */ 1643 int __sb_start_write(struct super_block *sb, int level, bool wait) 1644 { 1645 bool force_trylock = false; 1646 int ret = 1; 1647 1648 #ifdef CONFIG_LOCKDEP 1649 /* 1650 * We want lockdep to tell us about possible deadlocks with freezing 1651 * but it's it bit tricky to properly instrument it. Getting a freeze 1652 * protection works as getting a read lock but there are subtle 1653 * problems. XFS for example gets freeze protection on internal level 1654 * twice in some cases, which is OK only because we already hold a 1655 * freeze protection also on higher level. Due to these cases we have 1656 * to use wait == F (trylock mode) which must not fail. 1657 */ 1658 if (wait) { 1659 int i; 1660 1661 for (i = 0; i < level - 1; i++) 1662 if (percpu_rwsem_is_held(sb->s_writers.rw_sem + i)) { 1663 force_trylock = true; 1664 break; 1665 } 1666 } 1667 #endif 1668 if (wait && !force_trylock) 1669 percpu_down_read(sb->s_writers.rw_sem + level-1); 1670 else 1671 ret = percpu_down_read_trylock(sb->s_writers.rw_sem + level-1); 1672 1673 WARN_ON(force_trylock && !ret); 1674 return ret; 1675 } 1676 EXPORT_SYMBOL(__sb_start_write); 1677 1678 /** 1679 * sb_wait_write - wait until all writers to given file system finish 1680 * @sb: the super for which we wait 1681 * @level: type of writers we wait for (normal vs page fault) 1682 * 1683 * This function waits until there are no writers of given type to given file 1684 * system. 1685 */ 1686 static void sb_wait_write(struct super_block *sb, int level) 1687 { 1688 percpu_down_write(sb->s_writers.rw_sem + level-1); 1689 } 1690 1691 /* 1692 * We are going to return to userspace and forget about these locks, the 1693 * ownership goes to the caller of thaw_super() which does unlock(). 1694 */ 1695 static void lockdep_sb_freeze_release(struct super_block *sb) 1696 { 1697 int level; 1698 1699 for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--) 1700 percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_); 1701 } 1702 1703 /* 1704 * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb). 1705 */ 1706 static void lockdep_sb_freeze_acquire(struct super_block *sb) 1707 { 1708 int level; 1709 1710 for (level = 0; level < SB_FREEZE_LEVELS; ++level) 1711 percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_); 1712 } 1713 1714 static void sb_freeze_unlock(struct super_block *sb) 1715 { 1716 int level; 1717 1718 for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--) 1719 percpu_up_write(sb->s_writers.rw_sem + level); 1720 } 1721 1722 /** 1723 * freeze_super - lock the filesystem and force it into a consistent state 1724 * @sb: the super to lock 1725 * 1726 * Syncs the super to make sure the filesystem is consistent and calls the fs's 1727 * freeze_fs. Subsequent calls to this without first thawing the fs will return 1728 * -EBUSY. 1729 * 1730 * During this function, sb->s_writers.frozen goes through these values: 1731 * 1732 * SB_UNFROZEN: File system is normal, all writes progress as usual. 1733 * 1734 * SB_FREEZE_WRITE: The file system is in the process of being frozen. New 1735 * writes should be blocked, though page faults are still allowed. We wait for 1736 * all writes to complete and then proceed to the next stage. 1737 * 1738 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked 1739 * but internal fs threads can still modify the filesystem (although they 1740 * should not dirty new pages or inodes), writeback can run etc. After waiting 1741 * for all running page faults we sync the filesystem which will clean all 1742 * dirty pages and inodes (no new dirty pages or inodes can be created when 1743 * sync is running). 1744 * 1745 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs 1746 * modification are blocked (e.g. XFS preallocation truncation on inode 1747 * reclaim). This is usually implemented by blocking new transactions for 1748 * filesystems that have them and need this additional guard. After all 1749 * internal writers are finished we call ->freeze_fs() to finish filesystem 1750 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is 1751 * mostly auxiliary for filesystems to verify they do not modify frozen fs. 1752 * 1753 * sb->s_writers.frozen is protected by sb->s_umount. 1754 */ 1755 int freeze_super(struct super_block *sb) 1756 { 1757 int ret; 1758 1759 atomic_inc(&sb->s_active); 1760 down_write(&sb->s_umount); 1761 if (sb->s_writers.frozen != SB_UNFROZEN) { 1762 deactivate_locked_super(sb); 1763 return -EBUSY; 1764 } 1765 1766 if (!(sb->s_flags & SB_BORN)) { 1767 up_write(&sb->s_umount); 1768 return 0; /* sic - it's "nothing to do" */ 1769 } 1770 1771 if (sb_rdonly(sb)) { 1772 /* Nothing to do really... */ 1773 sb->s_writers.frozen = SB_FREEZE_COMPLETE; 1774 up_write(&sb->s_umount); 1775 return 0; 1776 } 1777 1778 sb->s_writers.frozen = SB_FREEZE_WRITE; 1779 /* Release s_umount to preserve sb_start_write -> s_umount ordering */ 1780 up_write(&sb->s_umount); 1781 sb_wait_write(sb, SB_FREEZE_WRITE); 1782 down_write(&sb->s_umount); 1783 1784 /* Now we go and block page faults... */ 1785 sb->s_writers.frozen = SB_FREEZE_PAGEFAULT; 1786 sb_wait_write(sb, SB_FREEZE_PAGEFAULT); 1787 1788 /* All writers are done so after syncing there won't be dirty data */ 1789 sync_filesystem(sb); 1790 1791 /* Now wait for internal filesystem counter */ 1792 sb->s_writers.frozen = SB_FREEZE_FS; 1793 sb_wait_write(sb, SB_FREEZE_FS); 1794 1795 if (sb->s_op->freeze_fs) { 1796 ret = sb->s_op->freeze_fs(sb); 1797 if (ret) { 1798 printk(KERN_ERR 1799 "VFS:Filesystem freeze failed\n"); 1800 sb->s_writers.frozen = SB_UNFROZEN; 1801 sb_freeze_unlock(sb); 1802 wake_up(&sb->s_writers.wait_unfrozen); 1803 deactivate_locked_super(sb); 1804 return ret; 1805 } 1806 } 1807 /* 1808 * For debugging purposes so that fs can warn if it sees write activity 1809 * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super(). 1810 */ 1811 sb->s_writers.frozen = SB_FREEZE_COMPLETE; 1812 lockdep_sb_freeze_release(sb); 1813 up_write(&sb->s_umount); 1814 return 0; 1815 } 1816 EXPORT_SYMBOL(freeze_super); 1817 1818 /** 1819 * thaw_super -- unlock filesystem 1820 * @sb: the super to thaw 1821 * 1822 * Unlocks the filesystem and marks it writeable again after freeze_super(). 1823 */ 1824 static int thaw_super_locked(struct super_block *sb) 1825 { 1826 int error; 1827 1828 if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) { 1829 up_write(&sb->s_umount); 1830 return -EINVAL; 1831 } 1832 1833 if (sb_rdonly(sb)) { 1834 sb->s_writers.frozen = SB_UNFROZEN; 1835 goto out; 1836 } 1837 1838 lockdep_sb_freeze_acquire(sb); 1839 1840 if (sb->s_op->unfreeze_fs) { 1841 error = sb->s_op->unfreeze_fs(sb); 1842 if (error) { 1843 printk(KERN_ERR 1844 "VFS:Filesystem thaw failed\n"); 1845 lockdep_sb_freeze_release(sb); 1846 up_write(&sb->s_umount); 1847 return error; 1848 } 1849 } 1850 1851 sb->s_writers.frozen = SB_UNFROZEN; 1852 sb_freeze_unlock(sb); 1853 out: 1854 wake_up(&sb->s_writers.wait_unfrozen); 1855 deactivate_locked_super(sb); 1856 return 0; 1857 } 1858 1859 int thaw_super(struct super_block *sb) 1860 { 1861 down_write(&sb->s_umount); 1862 return thaw_super_locked(sb); 1863 } 1864 EXPORT_SYMBOL(thaw_super); 1865