1 /* 2 * fs/dcache.c 3 * 4 * Complete reimplementation 5 * (C) 1997 Thomas Schoebel-Theuer, 6 * with heavy changes by Linus Torvalds 7 */ 8 9 /* 10 * Notes on the allocation strategy: 11 * 12 * The dcache is a master of the icache - whenever a dcache entry 13 * exists, the inode will always exist. "iput()" is done either when 14 * the dcache entry is deleted or garbage collected. 15 */ 16 17 #include <linux/syscalls.h> 18 #include <linux/string.h> 19 #include <linux/mm.h> 20 #include <linux/fs.h> 21 #include <linux/fsnotify.h> 22 #include <linux/slab.h> 23 #include <linux/init.h> 24 #include <linux/hash.h> 25 #include <linux/cache.h> 26 #include <linux/module.h> 27 #include <linux/mount.h> 28 #include <linux/file.h> 29 #include <asm/uaccess.h> 30 #include <linux/security.h> 31 #include <linux/seqlock.h> 32 #include <linux/swap.h> 33 #include <linux/bootmem.h> 34 #include <linux/fs_struct.h> 35 #include <linux/hardirq.h> 36 #include <linux/bit_spinlock.h> 37 #include <linux/rculist_bl.h> 38 #include <linux/prefetch.h> 39 #include <linux/ratelimit.h> 40 #include "internal.h" 41 #include "mount.h" 42 43 /* 44 * Usage: 45 * dcache->d_inode->i_lock protects: 46 * - i_dentry, d_alias, d_inode of aliases 47 * dcache_hash_bucket lock protects: 48 * - the dcache hash table 49 * s_anon bl list spinlock protects: 50 * - the s_anon list (see __d_drop) 51 * dcache_lru_lock protects: 52 * - the dcache lru lists and counters 53 * d_lock protects: 54 * - d_flags 55 * - d_name 56 * - d_lru 57 * - d_count 58 * - d_unhashed() 59 * - d_parent and d_subdirs 60 * - childrens' d_child and d_parent 61 * - d_alias, d_inode 62 * 63 * Ordering: 64 * dentry->d_inode->i_lock 65 * dentry->d_lock 66 * dcache_lru_lock 67 * dcache_hash_bucket lock 68 * s_anon lock 69 * 70 * If there is an ancestor relationship: 71 * dentry->d_parent->...->d_parent->d_lock 72 * ... 73 * dentry->d_parent->d_lock 74 * dentry->d_lock 75 * 76 * If no ancestor relationship: 77 * if (dentry1 < dentry2) 78 * dentry1->d_lock 79 * dentry2->d_lock 80 */ 81 int sysctl_vfs_cache_pressure __read_mostly = 100; 82 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure); 83 84 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock); 85 __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock); 86 87 EXPORT_SYMBOL(rename_lock); 88 89 static struct kmem_cache *dentry_cache __read_mostly; 90 91 /* 92 * This is the single most critical data structure when it comes 93 * to the dcache: the hashtable for lookups. Somebody should try 94 * to make this good - I've just made it work. 95 * 96 * This hash-function tries to avoid losing too many bits of hash 97 * information, yet avoid using a prime hash-size or similar. 98 */ 99 #define D_HASHBITS d_hash_shift 100 #define D_HASHMASK d_hash_mask 101 102 static unsigned int d_hash_mask __read_mostly; 103 static unsigned int d_hash_shift __read_mostly; 104 105 static struct hlist_bl_head *dentry_hashtable __read_mostly; 106 107 static inline struct hlist_bl_head *d_hash(const struct dentry *parent, 108 unsigned long hash) 109 { 110 hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES; 111 hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS); 112 return dentry_hashtable + (hash & D_HASHMASK); 113 } 114 115 /* Statistics gathering. */ 116 struct dentry_stat_t dentry_stat = { 117 .age_limit = 45, 118 }; 119 120 static DEFINE_PER_CPU(unsigned int, nr_dentry); 121 122 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS) 123 static int get_nr_dentry(void) 124 { 125 int i; 126 int sum = 0; 127 for_each_possible_cpu(i) 128 sum += per_cpu(nr_dentry, i); 129 return sum < 0 ? 0 : sum; 130 } 131 132 int proc_nr_dentry(ctl_table *table, int write, void __user *buffer, 133 size_t *lenp, loff_t *ppos) 134 { 135 dentry_stat.nr_dentry = get_nr_dentry(); 136 return proc_dointvec(table, write, buffer, lenp, ppos); 137 } 138 #endif 139 140 /* 141 * Compare 2 name strings, return 0 if they match, otherwise non-zero. 142 * The strings are both count bytes long, and count is non-zero. 143 */ 144 static inline int dentry_cmp(const unsigned char *cs, size_t scount, 145 const unsigned char *ct, size_t tcount) 146 { 147 if (scount != tcount) 148 return 1; 149 150 do { 151 if (*cs != *ct) 152 return 1; 153 cs++; 154 ct++; 155 tcount--; 156 } while (tcount); 157 return 0; 158 } 159 160 static void __d_free(struct rcu_head *head) 161 { 162 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu); 163 164 WARN_ON(!list_empty(&dentry->d_alias)); 165 if (dname_external(dentry)) 166 kfree(dentry->d_name.name); 167 kmem_cache_free(dentry_cache, dentry); 168 } 169 170 /* 171 * no locks, please. 172 */ 173 static void d_free(struct dentry *dentry) 174 { 175 BUG_ON(dentry->d_count); 176 this_cpu_dec(nr_dentry); 177 if (dentry->d_op && dentry->d_op->d_release) 178 dentry->d_op->d_release(dentry); 179 180 /* if dentry was never visible to RCU, immediate free is OK */ 181 if (!(dentry->d_flags & DCACHE_RCUACCESS)) 182 __d_free(&dentry->d_u.d_rcu); 183 else 184 call_rcu(&dentry->d_u.d_rcu, __d_free); 185 } 186 187 /** 188 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups 189 * @dentry: the target dentry 190 * After this call, in-progress rcu-walk path lookup will fail. This 191 * should be called after unhashing, and after changing d_inode (if 192 * the dentry has not already been unhashed). 193 */ 194 static inline void dentry_rcuwalk_barrier(struct dentry *dentry) 195 { 196 assert_spin_locked(&dentry->d_lock); 197 /* Go through a barrier */ 198 write_seqcount_barrier(&dentry->d_seq); 199 } 200 201 /* 202 * Release the dentry's inode, using the filesystem 203 * d_iput() operation if defined. Dentry has no refcount 204 * and is unhashed. 205 */ 206 static void dentry_iput(struct dentry * dentry) 207 __releases(dentry->d_lock) 208 __releases(dentry->d_inode->i_lock) 209 { 210 struct inode *inode = dentry->d_inode; 211 if (inode) { 212 dentry->d_inode = NULL; 213 list_del_init(&dentry->d_alias); 214 spin_unlock(&dentry->d_lock); 215 spin_unlock(&inode->i_lock); 216 if (!inode->i_nlink) 217 fsnotify_inoderemove(inode); 218 if (dentry->d_op && dentry->d_op->d_iput) 219 dentry->d_op->d_iput(dentry, inode); 220 else 221 iput(inode); 222 } else { 223 spin_unlock(&dentry->d_lock); 224 } 225 } 226 227 /* 228 * Release the dentry's inode, using the filesystem 229 * d_iput() operation if defined. dentry remains in-use. 230 */ 231 static void dentry_unlink_inode(struct dentry * dentry) 232 __releases(dentry->d_lock) 233 __releases(dentry->d_inode->i_lock) 234 { 235 struct inode *inode = dentry->d_inode; 236 dentry->d_inode = NULL; 237 list_del_init(&dentry->d_alias); 238 dentry_rcuwalk_barrier(dentry); 239 spin_unlock(&dentry->d_lock); 240 spin_unlock(&inode->i_lock); 241 if (!inode->i_nlink) 242 fsnotify_inoderemove(inode); 243 if (dentry->d_op && dentry->d_op->d_iput) 244 dentry->d_op->d_iput(dentry, inode); 245 else 246 iput(inode); 247 } 248 249 /* 250 * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held. 251 */ 252 static void dentry_lru_add(struct dentry *dentry) 253 { 254 if (list_empty(&dentry->d_lru)) { 255 spin_lock(&dcache_lru_lock); 256 list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru); 257 dentry->d_sb->s_nr_dentry_unused++; 258 dentry_stat.nr_unused++; 259 spin_unlock(&dcache_lru_lock); 260 } 261 } 262 263 static void __dentry_lru_del(struct dentry *dentry) 264 { 265 list_del_init(&dentry->d_lru); 266 dentry->d_flags &= ~DCACHE_SHRINK_LIST; 267 dentry->d_sb->s_nr_dentry_unused--; 268 dentry_stat.nr_unused--; 269 } 270 271 /* 272 * Remove a dentry with references from the LRU. 273 */ 274 static void dentry_lru_del(struct dentry *dentry) 275 { 276 if (!list_empty(&dentry->d_lru)) { 277 spin_lock(&dcache_lru_lock); 278 __dentry_lru_del(dentry); 279 spin_unlock(&dcache_lru_lock); 280 } 281 } 282 283 /* 284 * Remove a dentry that is unreferenced and about to be pruned 285 * (unhashed and destroyed) from the LRU, and inform the file system. 286 * This wrapper should be called _prior_ to unhashing a victim dentry. 287 */ 288 static void dentry_lru_prune(struct dentry *dentry) 289 { 290 if (!list_empty(&dentry->d_lru)) { 291 if (dentry->d_flags & DCACHE_OP_PRUNE) 292 dentry->d_op->d_prune(dentry); 293 294 spin_lock(&dcache_lru_lock); 295 __dentry_lru_del(dentry); 296 spin_unlock(&dcache_lru_lock); 297 } 298 } 299 300 static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list) 301 { 302 spin_lock(&dcache_lru_lock); 303 if (list_empty(&dentry->d_lru)) { 304 list_add_tail(&dentry->d_lru, list); 305 dentry->d_sb->s_nr_dentry_unused++; 306 dentry_stat.nr_unused++; 307 } else { 308 list_move_tail(&dentry->d_lru, list); 309 } 310 spin_unlock(&dcache_lru_lock); 311 } 312 313 /** 314 * d_kill - kill dentry and return parent 315 * @dentry: dentry to kill 316 * @parent: parent dentry 317 * 318 * The dentry must already be unhashed and removed from the LRU. 319 * 320 * If this is the root of the dentry tree, return NULL. 321 * 322 * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by 323 * d_kill. 324 */ 325 static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent) 326 __releases(dentry->d_lock) 327 __releases(parent->d_lock) 328 __releases(dentry->d_inode->i_lock) 329 { 330 list_del(&dentry->d_u.d_child); 331 /* 332 * Inform try_to_ascend() that we are no longer attached to the 333 * dentry tree 334 */ 335 dentry->d_flags |= DCACHE_DISCONNECTED; 336 if (parent) 337 spin_unlock(&parent->d_lock); 338 dentry_iput(dentry); 339 /* 340 * dentry_iput drops the locks, at which point nobody (except 341 * transient RCU lookups) can reach this dentry. 342 */ 343 d_free(dentry); 344 return parent; 345 } 346 347 /* 348 * Unhash a dentry without inserting an RCU walk barrier or checking that 349 * dentry->d_lock is locked. The caller must take care of that, if 350 * appropriate. 351 */ 352 static void __d_shrink(struct dentry *dentry) 353 { 354 if (!d_unhashed(dentry)) { 355 struct hlist_bl_head *b; 356 if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED)) 357 b = &dentry->d_sb->s_anon; 358 else 359 b = d_hash(dentry->d_parent, dentry->d_name.hash); 360 361 hlist_bl_lock(b); 362 __hlist_bl_del(&dentry->d_hash); 363 dentry->d_hash.pprev = NULL; 364 hlist_bl_unlock(b); 365 } 366 } 367 368 /** 369 * d_drop - drop a dentry 370 * @dentry: dentry to drop 371 * 372 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't 373 * be found through a VFS lookup any more. Note that this is different from 374 * deleting the dentry - d_delete will try to mark the dentry negative if 375 * possible, giving a successful _negative_ lookup, while d_drop will 376 * just make the cache lookup fail. 377 * 378 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some 379 * reason (NFS timeouts or autofs deletes). 380 * 381 * __d_drop requires dentry->d_lock. 382 */ 383 void __d_drop(struct dentry *dentry) 384 { 385 if (!d_unhashed(dentry)) { 386 __d_shrink(dentry); 387 dentry_rcuwalk_barrier(dentry); 388 } 389 } 390 EXPORT_SYMBOL(__d_drop); 391 392 void d_drop(struct dentry *dentry) 393 { 394 spin_lock(&dentry->d_lock); 395 __d_drop(dentry); 396 spin_unlock(&dentry->d_lock); 397 } 398 EXPORT_SYMBOL(d_drop); 399 400 /* 401 * d_clear_need_lookup - drop a dentry from cache and clear the need lookup flag 402 * @dentry: dentry to drop 403 * 404 * This is called when we do a lookup on a placeholder dentry that needed to be 405 * looked up. The dentry should have been hashed in order for it to be found by 406 * the lookup code, but now needs to be unhashed while we do the actual lookup 407 * and clear the DCACHE_NEED_LOOKUP flag. 408 */ 409 void d_clear_need_lookup(struct dentry *dentry) 410 { 411 spin_lock(&dentry->d_lock); 412 __d_drop(dentry); 413 dentry->d_flags &= ~DCACHE_NEED_LOOKUP; 414 spin_unlock(&dentry->d_lock); 415 } 416 EXPORT_SYMBOL(d_clear_need_lookup); 417 418 /* 419 * Finish off a dentry we've decided to kill. 420 * dentry->d_lock must be held, returns with it unlocked. 421 * If ref is non-zero, then decrement the refcount too. 422 * Returns dentry requiring refcount drop, or NULL if we're done. 423 */ 424 static inline struct dentry *dentry_kill(struct dentry *dentry, int ref) 425 __releases(dentry->d_lock) 426 { 427 struct inode *inode; 428 struct dentry *parent; 429 430 inode = dentry->d_inode; 431 if (inode && !spin_trylock(&inode->i_lock)) { 432 relock: 433 spin_unlock(&dentry->d_lock); 434 cpu_relax(); 435 return dentry; /* try again with same dentry */ 436 } 437 if (IS_ROOT(dentry)) 438 parent = NULL; 439 else 440 parent = dentry->d_parent; 441 if (parent && !spin_trylock(&parent->d_lock)) { 442 if (inode) 443 spin_unlock(&inode->i_lock); 444 goto relock; 445 } 446 447 if (ref) 448 dentry->d_count--; 449 /* 450 * if dentry was on the d_lru list delete it from there. 451 * inform the fs via d_prune that this dentry is about to be 452 * unhashed and destroyed. 453 */ 454 dentry_lru_prune(dentry); 455 /* if it was on the hash then remove it */ 456 __d_drop(dentry); 457 return d_kill(dentry, parent); 458 } 459 460 /* 461 * This is dput 462 * 463 * This is complicated by the fact that we do not want to put 464 * dentries that are no longer on any hash chain on the unused 465 * list: we'd much rather just get rid of them immediately. 466 * 467 * However, that implies that we have to traverse the dentry 468 * tree upwards to the parents which might _also_ now be 469 * scheduled for deletion (it may have been only waiting for 470 * its last child to go away). 471 * 472 * This tail recursion is done by hand as we don't want to depend 473 * on the compiler to always get this right (gcc generally doesn't). 474 * Real recursion would eat up our stack space. 475 */ 476 477 /* 478 * dput - release a dentry 479 * @dentry: dentry to release 480 * 481 * Release a dentry. This will drop the usage count and if appropriate 482 * call the dentry unlink method as well as removing it from the queues and 483 * releasing its resources. If the parent dentries were scheduled for release 484 * they too may now get deleted. 485 */ 486 void dput(struct dentry *dentry) 487 { 488 if (!dentry) 489 return; 490 491 repeat: 492 if (dentry->d_count == 1) 493 might_sleep(); 494 spin_lock(&dentry->d_lock); 495 BUG_ON(!dentry->d_count); 496 if (dentry->d_count > 1) { 497 dentry->d_count--; 498 spin_unlock(&dentry->d_lock); 499 return; 500 } 501 502 if (dentry->d_flags & DCACHE_OP_DELETE) { 503 if (dentry->d_op->d_delete(dentry)) 504 goto kill_it; 505 } 506 507 /* Unreachable? Get rid of it */ 508 if (d_unhashed(dentry)) 509 goto kill_it; 510 511 /* 512 * If this dentry needs lookup, don't set the referenced flag so that it 513 * is more likely to be cleaned up by the dcache shrinker in case of 514 * memory pressure. 515 */ 516 if (!d_need_lookup(dentry)) 517 dentry->d_flags |= DCACHE_REFERENCED; 518 dentry_lru_add(dentry); 519 520 dentry->d_count--; 521 spin_unlock(&dentry->d_lock); 522 return; 523 524 kill_it: 525 dentry = dentry_kill(dentry, 1); 526 if (dentry) 527 goto repeat; 528 } 529 EXPORT_SYMBOL(dput); 530 531 /** 532 * d_invalidate - invalidate a dentry 533 * @dentry: dentry to invalidate 534 * 535 * Try to invalidate the dentry if it turns out to be 536 * possible. If there are other dentries that can be 537 * reached through this one we can't delete it and we 538 * return -EBUSY. On success we return 0. 539 * 540 * no dcache lock. 541 */ 542 543 int d_invalidate(struct dentry * dentry) 544 { 545 /* 546 * If it's already been dropped, return OK. 547 */ 548 spin_lock(&dentry->d_lock); 549 if (d_unhashed(dentry)) { 550 spin_unlock(&dentry->d_lock); 551 return 0; 552 } 553 /* 554 * Check whether to do a partial shrink_dcache 555 * to get rid of unused child entries. 556 */ 557 if (!list_empty(&dentry->d_subdirs)) { 558 spin_unlock(&dentry->d_lock); 559 shrink_dcache_parent(dentry); 560 spin_lock(&dentry->d_lock); 561 } 562 563 /* 564 * Somebody else still using it? 565 * 566 * If it's a directory, we can't drop it 567 * for fear of somebody re-populating it 568 * with children (even though dropping it 569 * would make it unreachable from the root, 570 * we might still populate it if it was a 571 * working directory or similar). 572 * We also need to leave mountpoints alone, 573 * directory or not. 574 */ 575 if (dentry->d_count > 1 && dentry->d_inode) { 576 if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) { 577 spin_unlock(&dentry->d_lock); 578 return -EBUSY; 579 } 580 } 581 582 __d_drop(dentry); 583 spin_unlock(&dentry->d_lock); 584 return 0; 585 } 586 EXPORT_SYMBOL(d_invalidate); 587 588 /* This must be called with d_lock held */ 589 static inline void __dget_dlock(struct dentry *dentry) 590 { 591 dentry->d_count++; 592 } 593 594 static inline void __dget(struct dentry *dentry) 595 { 596 spin_lock(&dentry->d_lock); 597 __dget_dlock(dentry); 598 spin_unlock(&dentry->d_lock); 599 } 600 601 struct dentry *dget_parent(struct dentry *dentry) 602 { 603 struct dentry *ret; 604 605 repeat: 606 /* 607 * Don't need rcu_dereference because we re-check it was correct under 608 * the lock. 609 */ 610 rcu_read_lock(); 611 ret = dentry->d_parent; 612 spin_lock(&ret->d_lock); 613 if (unlikely(ret != dentry->d_parent)) { 614 spin_unlock(&ret->d_lock); 615 rcu_read_unlock(); 616 goto repeat; 617 } 618 rcu_read_unlock(); 619 BUG_ON(!ret->d_count); 620 ret->d_count++; 621 spin_unlock(&ret->d_lock); 622 return ret; 623 } 624 EXPORT_SYMBOL(dget_parent); 625 626 /** 627 * d_find_alias - grab a hashed alias of inode 628 * @inode: inode in question 629 * @want_discon: flag, used by d_splice_alias, to request 630 * that only a DISCONNECTED alias be returned. 631 * 632 * If inode has a hashed alias, or is a directory and has any alias, 633 * acquire the reference to alias and return it. Otherwise return NULL. 634 * Notice that if inode is a directory there can be only one alias and 635 * it can be unhashed only if it has no children, or if it is the root 636 * of a filesystem. 637 * 638 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer 639 * any other hashed alias over that one unless @want_discon is set, 640 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias. 641 */ 642 static struct dentry *__d_find_alias(struct inode *inode, int want_discon) 643 { 644 struct dentry *alias, *discon_alias; 645 646 again: 647 discon_alias = NULL; 648 list_for_each_entry(alias, &inode->i_dentry, d_alias) { 649 spin_lock(&alias->d_lock); 650 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) { 651 if (IS_ROOT(alias) && 652 (alias->d_flags & DCACHE_DISCONNECTED)) { 653 discon_alias = alias; 654 } else if (!want_discon) { 655 __dget_dlock(alias); 656 spin_unlock(&alias->d_lock); 657 return alias; 658 } 659 } 660 spin_unlock(&alias->d_lock); 661 } 662 if (discon_alias) { 663 alias = discon_alias; 664 spin_lock(&alias->d_lock); 665 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) { 666 if (IS_ROOT(alias) && 667 (alias->d_flags & DCACHE_DISCONNECTED)) { 668 __dget_dlock(alias); 669 spin_unlock(&alias->d_lock); 670 return alias; 671 } 672 } 673 spin_unlock(&alias->d_lock); 674 goto again; 675 } 676 return NULL; 677 } 678 679 struct dentry *d_find_alias(struct inode *inode) 680 { 681 struct dentry *de = NULL; 682 683 if (!list_empty(&inode->i_dentry)) { 684 spin_lock(&inode->i_lock); 685 de = __d_find_alias(inode, 0); 686 spin_unlock(&inode->i_lock); 687 } 688 return de; 689 } 690 EXPORT_SYMBOL(d_find_alias); 691 692 /* 693 * Try to kill dentries associated with this inode. 694 * WARNING: you must own a reference to inode. 695 */ 696 void d_prune_aliases(struct inode *inode) 697 { 698 struct dentry *dentry; 699 restart: 700 spin_lock(&inode->i_lock); 701 list_for_each_entry(dentry, &inode->i_dentry, d_alias) { 702 spin_lock(&dentry->d_lock); 703 if (!dentry->d_count) { 704 __dget_dlock(dentry); 705 __d_drop(dentry); 706 spin_unlock(&dentry->d_lock); 707 spin_unlock(&inode->i_lock); 708 dput(dentry); 709 goto restart; 710 } 711 spin_unlock(&dentry->d_lock); 712 } 713 spin_unlock(&inode->i_lock); 714 } 715 EXPORT_SYMBOL(d_prune_aliases); 716 717 /* 718 * Try to throw away a dentry - free the inode, dput the parent. 719 * Requires dentry->d_lock is held, and dentry->d_count == 0. 720 * Releases dentry->d_lock. 721 * 722 * This may fail if locks cannot be acquired no problem, just try again. 723 */ 724 static void try_prune_one_dentry(struct dentry *dentry) 725 __releases(dentry->d_lock) 726 { 727 struct dentry *parent; 728 729 parent = dentry_kill(dentry, 0); 730 /* 731 * If dentry_kill returns NULL, we have nothing more to do. 732 * if it returns the same dentry, trylocks failed. In either 733 * case, just loop again. 734 * 735 * Otherwise, we need to prune ancestors too. This is necessary 736 * to prevent quadratic behavior of shrink_dcache_parent(), but 737 * is also expected to be beneficial in reducing dentry cache 738 * fragmentation. 739 */ 740 if (!parent) 741 return; 742 if (parent == dentry) 743 return; 744 745 /* Prune ancestors. */ 746 dentry = parent; 747 while (dentry) { 748 spin_lock(&dentry->d_lock); 749 if (dentry->d_count > 1) { 750 dentry->d_count--; 751 spin_unlock(&dentry->d_lock); 752 return; 753 } 754 dentry = dentry_kill(dentry, 1); 755 } 756 } 757 758 static void shrink_dentry_list(struct list_head *list) 759 { 760 struct dentry *dentry; 761 762 rcu_read_lock(); 763 for (;;) { 764 dentry = list_entry_rcu(list->prev, struct dentry, d_lru); 765 if (&dentry->d_lru == list) 766 break; /* empty */ 767 spin_lock(&dentry->d_lock); 768 if (dentry != list_entry(list->prev, struct dentry, d_lru)) { 769 spin_unlock(&dentry->d_lock); 770 continue; 771 } 772 773 /* 774 * We found an inuse dentry which was not removed from 775 * the LRU because of laziness during lookup. Do not free 776 * it - just keep it off the LRU list. 777 */ 778 if (dentry->d_count) { 779 dentry_lru_del(dentry); 780 spin_unlock(&dentry->d_lock); 781 continue; 782 } 783 784 rcu_read_unlock(); 785 786 try_prune_one_dentry(dentry); 787 788 rcu_read_lock(); 789 } 790 rcu_read_unlock(); 791 } 792 793 /** 794 * prune_dcache_sb - shrink the dcache 795 * @sb: superblock 796 * @count: number of entries to try to free 797 * 798 * Attempt to shrink the superblock dcache LRU by @count entries. This is 799 * done when we need more memory an called from the superblock shrinker 800 * function. 801 * 802 * This function may fail to free any resources if all the dentries are in 803 * use. 804 */ 805 void prune_dcache_sb(struct super_block *sb, int count) 806 { 807 struct dentry *dentry; 808 LIST_HEAD(referenced); 809 LIST_HEAD(tmp); 810 811 relock: 812 spin_lock(&dcache_lru_lock); 813 while (!list_empty(&sb->s_dentry_lru)) { 814 dentry = list_entry(sb->s_dentry_lru.prev, 815 struct dentry, d_lru); 816 BUG_ON(dentry->d_sb != sb); 817 818 if (!spin_trylock(&dentry->d_lock)) { 819 spin_unlock(&dcache_lru_lock); 820 cpu_relax(); 821 goto relock; 822 } 823 824 if (dentry->d_flags & DCACHE_REFERENCED) { 825 dentry->d_flags &= ~DCACHE_REFERENCED; 826 list_move(&dentry->d_lru, &referenced); 827 spin_unlock(&dentry->d_lock); 828 } else { 829 list_move_tail(&dentry->d_lru, &tmp); 830 dentry->d_flags |= DCACHE_SHRINK_LIST; 831 spin_unlock(&dentry->d_lock); 832 if (!--count) 833 break; 834 } 835 cond_resched_lock(&dcache_lru_lock); 836 } 837 if (!list_empty(&referenced)) 838 list_splice(&referenced, &sb->s_dentry_lru); 839 spin_unlock(&dcache_lru_lock); 840 841 shrink_dentry_list(&tmp); 842 } 843 844 /** 845 * shrink_dcache_sb - shrink dcache for a superblock 846 * @sb: superblock 847 * 848 * Shrink the dcache for the specified super block. This is used to free 849 * the dcache before unmounting a file system. 850 */ 851 void shrink_dcache_sb(struct super_block *sb) 852 { 853 LIST_HEAD(tmp); 854 855 spin_lock(&dcache_lru_lock); 856 while (!list_empty(&sb->s_dentry_lru)) { 857 list_splice_init(&sb->s_dentry_lru, &tmp); 858 spin_unlock(&dcache_lru_lock); 859 shrink_dentry_list(&tmp); 860 spin_lock(&dcache_lru_lock); 861 } 862 spin_unlock(&dcache_lru_lock); 863 } 864 EXPORT_SYMBOL(shrink_dcache_sb); 865 866 /* 867 * destroy a single subtree of dentries for unmount 868 * - see the comments on shrink_dcache_for_umount() for a description of the 869 * locking 870 */ 871 static void shrink_dcache_for_umount_subtree(struct dentry *dentry) 872 { 873 struct dentry *parent; 874 875 BUG_ON(!IS_ROOT(dentry)); 876 877 for (;;) { 878 /* descend to the first leaf in the current subtree */ 879 while (!list_empty(&dentry->d_subdirs)) 880 dentry = list_entry(dentry->d_subdirs.next, 881 struct dentry, d_u.d_child); 882 883 /* consume the dentries from this leaf up through its parents 884 * until we find one with children or run out altogether */ 885 do { 886 struct inode *inode; 887 888 /* 889 * remove the dentry from the lru, and inform 890 * the fs that this dentry is about to be 891 * unhashed and destroyed. 892 */ 893 dentry_lru_prune(dentry); 894 __d_shrink(dentry); 895 896 if (dentry->d_count != 0) { 897 printk(KERN_ERR 898 "BUG: Dentry %p{i=%lx,n=%s}" 899 " still in use (%d)" 900 " [unmount of %s %s]\n", 901 dentry, 902 dentry->d_inode ? 903 dentry->d_inode->i_ino : 0UL, 904 dentry->d_name.name, 905 dentry->d_count, 906 dentry->d_sb->s_type->name, 907 dentry->d_sb->s_id); 908 BUG(); 909 } 910 911 if (IS_ROOT(dentry)) { 912 parent = NULL; 913 list_del(&dentry->d_u.d_child); 914 } else { 915 parent = dentry->d_parent; 916 parent->d_count--; 917 list_del(&dentry->d_u.d_child); 918 } 919 920 inode = dentry->d_inode; 921 if (inode) { 922 dentry->d_inode = NULL; 923 list_del_init(&dentry->d_alias); 924 if (dentry->d_op && dentry->d_op->d_iput) 925 dentry->d_op->d_iput(dentry, inode); 926 else 927 iput(inode); 928 } 929 930 d_free(dentry); 931 932 /* finished when we fall off the top of the tree, 933 * otherwise we ascend to the parent and move to the 934 * next sibling if there is one */ 935 if (!parent) 936 return; 937 dentry = parent; 938 } while (list_empty(&dentry->d_subdirs)); 939 940 dentry = list_entry(dentry->d_subdirs.next, 941 struct dentry, d_u.d_child); 942 } 943 } 944 945 /* 946 * destroy the dentries attached to a superblock on unmounting 947 * - we don't need to use dentry->d_lock because: 948 * - the superblock is detached from all mountings and open files, so the 949 * dentry trees will not be rearranged by the VFS 950 * - s_umount is write-locked, so the memory pressure shrinker will ignore 951 * any dentries belonging to this superblock that it comes across 952 * - the filesystem itself is no longer permitted to rearrange the dentries 953 * in this superblock 954 */ 955 void shrink_dcache_for_umount(struct super_block *sb) 956 { 957 struct dentry *dentry; 958 959 if (down_read_trylock(&sb->s_umount)) 960 BUG(); 961 962 dentry = sb->s_root; 963 sb->s_root = NULL; 964 dentry->d_count--; 965 shrink_dcache_for_umount_subtree(dentry); 966 967 while (!hlist_bl_empty(&sb->s_anon)) { 968 dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash); 969 shrink_dcache_for_umount_subtree(dentry); 970 } 971 } 972 973 /* 974 * This tries to ascend one level of parenthood, but 975 * we can race with renaming, so we need to re-check 976 * the parenthood after dropping the lock and check 977 * that the sequence number still matches. 978 */ 979 static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq) 980 { 981 struct dentry *new = old->d_parent; 982 983 rcu_read_lock(); 984 spin_unlock(&old->d_lock); 985 spin_lock(&new->d_lock); 986 987 /* 988 * might go back up the wrong parent if we have had a rename 989 * or deletion 990 */ 991 if (new != old->d_parent || 992 (old->d_flags & DCACHE_DISCONNECTED) || 993 (!locked && read_seqretry(&rename_lock, seq))) { 994 spin_unlock(&new->d_lock); 995 new = NULL; 996 } 997 rcu_read_unlock(); 998 return new; 999 } 1000 1001 1002 /* 1003 * Search for at least 1 mount point in the dentry's subdirs. 1004 * We descend to the next level whenever the d_subdirs 1005 * list is non-empty and continue searching. 1006 */ 1007 1008 /** 1009 * have_submounts - check for mounts over a dentry 1010 * @parent: dentry to check. 1011 * 1012 * Return true if the parent or its subdirectories contain 1013 * a mount point 1014 */ 1015 int have_submounts(struct dentry *parent) 1016 { 1017 struct dentry *this_parent; 1018 struct list_head *next; 1019 unsigned seq; 1020 int locked = 0; 1021 1022 seq = read_seqbegin(&rename_lock); 1023 again: 1024 this_parent = parent; 1025 1026 if (d_mountpoint(parent)) 1027 goto positive; 1028 spin_lock(&this_parent->d_lock); 1029 repeat: 1030 next = this_parent->d_subdirs.next; 1031 resume: 1032 while (next != &this_parent->d_subdirs) { 1033 struct list_head *tmp = next; 1034 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); 1035 next = tmp->next; 1036 1037 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); 1038 /* Have we found a mount point ? */ 1039 if (d_mountpoint(dentry)) { 1040 spin_unlock(&dentry->d_lock); 1041 spin_unlock(&this_parent->d_lock); 1042 goto positive; 1043 } 1044 if (!list_empty(&dentry->d_subdirs)) { 1045 spin_unlock(&this_parent->d_lock); 1046 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_); 1047 this_parent = dentry; 1048 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); 1049 goto repeat; 1050 } 1051 spin_unlock(&dentry->d_lock); 1052 } 1053 /* 1054 * All done at this level ... ascend and resume the search. 1055 */ 1056 if (this_parent != parent) { 1057 struct dentry *child = this_parent; 1058 this_parent = try_to_ascend(this_parent, locked, seq); 1059 if (!this_parent) 1060 goto rename_retry; 1061 next = child->d_u.d_child.next; 1062 goto resume; 1063 } 1064 spin_unlock(&this_parent->d_lock); 1065 if (!locked && read_seqretry(&rename_lock, seq)) 1066 goto rename_retry; 1067 if (locked) 1068 write_sequnlock(&rename_lock); 1069 return 0; /* No mount points found in tree */ 1070 positive: 1071 if (!locked && read_seqretry(&rename_lock, seq)) 1072 goto rename_retry; 1073 if (locked) 1074 write_sequnlock(&rename_lock); 1075 return 1; 1076 1077 rename_retry: 1078 locked = 1; 1079 write_seqlock(&rename_lock); 1080 goto again; 1081 } 1082 EXPORT_SYMBOL(have_submounts); 1083 1084 /* 1085 * Search the dentry child list for the specified parent, 1086 * and move any unused dentries to the end of the unused 1087 * list for prune_dcache(). We descend to the next level 1088 * whenever the d_subdirs list is non-empty and continue 1089 * searching. 1090 * 1091 * It returns zero iff there are no unused children, 1092 * otherwise it returns the number of children moved to 1093 * the end of the unused list. This may not be the total 1094 * number of unused children, because select_parent can 1095 * drop the lock and return early due to latency 1096 * constraints. 1097 */ 1098 static int select_parent(struct dentry *parent, struct list_head *dispose) 1099 { 1100 struct dentry *this_parent; 1101 struct list_head *next; 1102 unsigned seq; 1103 int found = 0; 1104 int locked = 0; 1105 1106 seq = read_seqbegin(&rename_lock); 1107 again: 1108 this_parent = parent; 1109 spin_lock(&this_parent->d_lock); 1110 repeat: 1111 next = this_parent->d_subdirs.next; 1112 resume: 1113 while (next != &this_parent->d_subdirs) { 1114 struct list_head *tmp = next; 1115 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); 1116 next = tmp->next; 1117 1118 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); 1119 1120 /* 1121 * move only zero ref count dentries to the dispose list. 1122 * 1123 * Those which are presently on the shrink list, being processed 1124 * by shrink_dentry_list(), shouldn't be moved. Otherwise the 1125 * loop in shrink_dcache_parent() might not make any progress 1126 * and loop forever. 1127 */ 1128 if (dentry->d_count) { 1129 dentry_lru_del(dentry); 1130 } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) { 1131 dentry_lru_move_list(dentry, dispose); 1132 dentry->d_flags |= DCACHE_SHRINK_LIST; 1133 found++; 1134 } 1135 /* 1136 * We can return to the caller if we have found some (this 1137 * ensures forward progress). We'll be coming back to find 1138 * the rest. 1139 */ 1140 if (found && need_resched()) { 1141 spin_unlock(&dentry->d_lock); 1142 goto out; 1143 } 1144 1145 /* 1146 * Descend a level if the d_subdirs list is non-empty. 1147 */ 1148 if (!list_empty(&dentry->d_subdirs)) { 1149 spin_unlock(&this_parent->d_lock); 1150 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_); 1151 this_parent = dentry; 1152 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); 1153 goto repeat; 1154 } 1155 1156 spin_unlock(&dentry->d_lock); 1157 } 1158 /* 1159 * All done at this level ... ascend and resume the search. 1160 */ 1161 if (this_parent != parent) { 1162 struct dentry *child = this_parent; 1163 this_parent = try_to_ascend(this_parent, locked, seq); 1164 if (!this_parent) 1165 goto rename_retry; 1166 next = child->d_u.d_child.next; 1167 goto resume; 1168 } 1169 out: 1170 spin_unlock(&this_parent->d_lock); 1171 if (!locked && read_seqretry(&rename_lock, seq)) 1172 goto rename_retry; 1173 if (locked) 1174 write_sequnlock(&rename_lock); 1175 return found; 1176 1177 rename_retry: 1178 if (found) 1179 return found; 1180 locked = 1; 1181 write_seqlock(&rename_lock); 1182 goto again; 1183 } 1184 1185 /** 1186 * shrink_dcache_parent - prune dcache 1187 * @parent: parent of entries to prune 1188 * 1189 * Prune the dcache to remove unused children of the parent dentry. 1190 */ 1191 void shrink_dcache_parent(struct dentry * parent) 1192 { 1193 LIST_HEAD(dispose); 1194 int found; 1195 1196 while ((found = select_parent(parent, &dispose)) != 0) 1197 shrink_dentry_list(&dispose); 1198 } 1199 EXPORT_SYMBOL(shrink_dcache_parent); 1200 1201 /** 1202 * __d_alloc - allocate a dcache entry 1203 * @sb: filesystem it will belong to 1204 * @name: qstr of the name 1205 * 1206 * Allocates a dentry. It returns %NULL if there is insufficient memory 1207 * available. On a success the dentry is returned. The name passed in is 1208 * copied and the copy passed in may be reused after this call. 1209 */ 1210 1211 struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name) 1212 { 1213 struct dentry *dentry; 1214 char *dname; 1215 1216 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL); 1217 if (!dentry) 1218 return NULL; 1219 1220 if (name->len > DNAME_INLINE_LEN-1) { 1221 dname = kmalloc(name->len + 1, GFP_KERNEL); 1222 if (!dname) { 1223 kmem_cache_free(dentry_cache, dentry); 1224 return NULL; 1225 } 1226 } else { 1227 dname = dentry->d_iname; 1228 } 1229 dentry->d_name.name = dname; 1230 1231 dentry->d_name.len = name->len; 1232 dentry->d_name.hash = name->hash; 1233 memcpy(dname, name->name, name->len); 1234 dname[name->len] = 0; 1235 1236 dentry->d_count = 1; 1237 dentry->d_flags = 0; 1238 spin_lock_init(&dentry->d_lock); 1239 seqcount_init(&dentry->d_seq); 1240 dentry->d_inode = NULL; 1241 dentry->d_parent = dentry; 1242 dentry->d_sb = sb; 1243 dentry->d_op = NULL; 1244 dentry->d_fsdata = NULL; 1245 INIT_HLIST_BL_NODE(&dentry->d_hash); 1246 INIT_LIST_HEAD(&dentry->d_lru); 1247 INIT_LIST_HEAD(&dentry->d_subdirs); 1248 INIT_LIST_HEAD(&dentry->d_alias); 1249 INIT_LIST_HEAD(&dentry->d_u.d_child); 1250 d_set_d_op(dentry, dentry->d_sb->s_d_op); 1251 1252 this_cpu_inc(nr_dentry); 1253 1254 return dentry; 1255 } 1256 1257 /** 1258 * d_alloc - allocate a dcache entry 1259 * @parent: parent of entry to allocate 1260 * @name: qstr of the name 1261 * 1262 * Allocates a dentry. It returns %NULL if there is insufficient memory 1263 * available. On a success the dentry is returned. The name passed in is 1264 * copied and the copy passed in may be reused after this call. 1265 */ 1266 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name) 1267 { 1268 struct dentry *dentry = __d_alloc(parent->d_sb, name); 1269 if (!dentry) 1270 return NULL; 1271 1272 spin_lock(&parent->d_lock); 1273 /* 1274 * don't need child lock because it is not subject 1275 * to concurrency here 1276 */ 1277 __dget_dlock(parent); 1278 dentry->d_parent = parent; 1279 list_add(&dentry->d_u.d_child, &parent->d_subdirs); 1280 spin_unlock(&parent->d_lock); 1281 1282 return dentry; 1283 } 1284 EXPORT_SYMBOL(d_alloc); 1285 1286 struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name) 1287 { 1288 struct dentry *dentry = __d_alloc(sb, name); 1289 if (dentry) 1290 dentry->d_flags |= DCACHE_DISCONNECTED; 1291 return dentry; 1292 } 1293 EXPORT_SYMBOL(d_alloc_pseudo); 1294 1295 struct dentry *d_alloc_name(struct dentry *parent, const char *name) 1296 { 1297 struct qstr q; 1298 1299 q.name = name; 1300 q.len = strlen(name); 1301 q.hash = full_name_hash(q.name, q.len); 1302 return d_alloc(parent, &q); 1303 } 1304 EXPORT_SYMBOL(d_alloc_name); 1305 1306 void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op) 1307 { 1308 WARN_ON_ONCE(dentry->d_op); 1309 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH | 1310 DCACHE_OP_COMPARE | 1311 DCACHE_OP_REVALIDATE | 1312 DCACHE_OP_DELETE )); 1313 dentry->d_op = op; 1314 if (!op) 1315 return; 1316 if (op->d_hash) 1317 dentry->d_flags |= DCACHE_OP_HASH; 1318 if (op->d_compare) 1319 dentry->d_flags |= DCACHE_OP_COMPARE; 1320 if (op->d_revalidate) 1321 dentry->d_flags |= DCACHE_OP_REVALIDATE; 1322 if (op->d_delete) 1323 dentry->d_flags |= DCACHE_OP_DELETE; 1324 if (op->d_prune) 1325 dentry->d_flags |= DCACHE_OP_PRUNE; 1326 1327 } 1328 EXPORT_SYMBOL(d_set_d_op); 1329 1330 static void __d_instantiate(struct dentry *dentry, struct inode *inode) 1331 { 1332 spin_lock(&dentry->d_lock); 1333 if (inode) { 1334 if (unlikely(IS_AUTOMOUNT(inode))) 1335 dentry->d_flags |= DCACHE_NEED_AUTOMOUNT; 1336 list_add(&dentry->d_alias, &inode->i_dentry); 1337 } 1338 dentry->d_inode = inode; 1339 dentry_rcuwalk_barrier(dentry); 1340 spin_unlock(&dentry->d_lock); 1341 fsnotify_d_instantiate(dentry, inode); 1342 } 1343 1344 /** 1345 * d_instantiate - fill in inode information for a dentry 1346 * @entry: dentry to complete 1347 * @inode: inode to attach to this dentry 1348 * 1349 * Fill in inode information in the entry. 1350 * 1351 * This turns negative dentries into productive full members 1352 * of society. 1353 * 1354 * NOTE! This assumes that the inode count has been incremented 1355 * (or otherwise set) by the caller to indicate that it is now 1356 * in use by the dcache. 1357 */ 1358 1359 void d_instantiate(struct dentry *entry, struct inode * inode) 1360 { 1361 BUG_ON(!list_empty(&entry->d_alias)); 1362 if (inode) 1363 spin_lock(&inode->i_lock); 1364 __d_instantiate(entry, inode); 1365 if (inode) 1366 spin_unlock(&inode->i_lock); 1367 security_d_instantiate(entry, inode); 1368 } 1369 EXPORT_SYMBOL(d_instantiate); 1370 1371 /** 1372 * d_instantiate_unique - instantiate a non-aliased dentry 1373 * @entry: dentry to instantiate 1374 * @inode: inode to attach to this dentry 1375 * 1376 * Fill in inode information in the entry. On success, it returns NULL. 1377 * If an unhashed alias of "entry" already exists, then we return the 1378 * aliased dentry instead and drop one reference to inode. 1379 * 1380 * Note that in order to avoid conflicts with rename() etc, the caller 1381 * had better be holding the parent directory semaphore. 1382 * 1383 * This also assumes that the inode count has been incremented 1384 * (or otherwise set) by the caller to indicate that it is now 1385 * in use by the dcache. 1386 */ 1387 static struct dentry *__d_instantiate_unique(struct dentry *entry, 1388 struct inode *inode) 1389 { 1390 struct dentry *alias; 1391 int len = entry->d_name.len; 1392 const char *name = entry->d_name.name; 1393 unsigned int hash = entry->d_name.hash; 1394 1395 if (!inode) { 1396 __d_instantiate(entry, NULL); 1397 return NULL; 1398 } 1399 1400 list_for_each_entry(alias, &inode->i_dentry, d_alias) { 1401 struct qstr *qstr = &alias->d_name; 1402 1403 /* 1404 * Don't need alias->d_lock here, because aliases with 1405 * d_parent == entry->d_parent are not subject to name or 1406 * parent changes, because the parent inode i_mutex is held. 1407 */ 1408 if (qstr->hash != hash) 1409 continue; 1410 if (alias->d_parent != entry->d_parent) 1411 continue; 1412 if (dentry_cmp(qstr->name, qstr->len, name, len)) 1413 continue; 1414 __dget(alias); 1415 return alias; 1416 } 1417 1418 __d_instantiate(entry, inode); 1419 return NULL; 1420 } 1421 1422 struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode) 1423 { 1424 struct dentry *result; 1425 1426 BUG_ON(!list_empty(&entry->d_alias)); 1427 1428 if (inode) 1429 spin_lock(&inode->i_lock); 1430 result = __d_instantiate_unique(entry, inode); 1431 if (inode) 1432 spin_unlock(&inode->i_lock); 1433 1434 if (!result) { 1435 security_d_instantiate(entry, inode); 1436 return NULL; 1437 } 1438 1439 BUG_ON(!d_unhashed(result)); 1440 iput(inode); 1441 return result; 1442 } 1443 1444 EXPORT_SYMBOL(d_instantiate_unique); 1445 1446 /** 1447 * d_alloc_root - allocate root dentry 1448 * @root_inode: inode to allocate the root for 1449 * 1450 * Allocate a root ("/") dentry for the inode given. The inode is 1451 * instantiated and returned. %NULL is returned if there is insufficient 1452 * memory or the inode passed is %NULL. 1453 */ 1454 1455 struct dentry * d_alloc_root(struct inode * root_inode) 1456 { 1457 struct dentry *res = NULL; 1458 1459 if (root_inode) { 1460 static const struct qstr name = { .name = "/", .len = 1 }; 1461 1462 res = __d_alloc(root_inode->i_sb, &name); 1463 if (res) 1464 d_instantiate(res, root_inode); 1465 } 1466 return res; 1467 } 1468 EXPORT_SYMBOL(d_alloc_root); 1469 1470 struct dentry *d_make_root(struct inode *root_inode) 1471 { 1472 struct dentry *res = NULL; 1473 1474 if (root_inode) { 1475 static const struct qstr name = { .name = "/", .len = 1 }; 1476 1477 res = __d_alloc(root_inode->i_sb, &name); 1478 if (res) 1479 d_instantiate(res, root_inode); 1480 else 1481 iput(root_inode); 1482 } 1483 return res; 1484 } 1485 EXPORT_SYMBOL(d_make_root); 1486 1487 static struct dentry * __d_find_any_alias(struct inode *inode) 1488 { 1489 struct dentry *alias; 1490 1491 if (list_empty(&inode->i_dentry)) 1492 return NULL; 1493 alias = list_first_entry(&inode->i_dentry, struct dentry, d_alias); 1494 __dget(alias); 1495 return alias; 1496 } 1497 1498 /** 1499 * d_find_any_alias - find any alias for a given inode 1500 * @inode: inode to find an alias for 1501 * 1502 * If any aliases exist for the given inode, take and return a 1503 * reference for one of them. If no aliases exist, return %NULL. 1504 */ 1505 struct dentry *d_find_any_alias(struct inode *inode) 1506 { 1507 struct dentry *de; 1508 1509 spin_lock(&inode->i_lock); 1510 de = __d_find_any_alias(inode); 1511 spin_unlock(&inode->i_lock); 1512 return de; 1513 } 1514 EXPORT_SYMBOL(d_find_any_alias); 1515 1516 /** 1517 * d_obtain_alias - find or allocate a dentry for a given inode 1518 * @inode: inode to allocate the dentry for 1519 * 1520 * Obtain a dentry for an inode resulting from NFS filehandle conversion or 1521 * similar open by handle operations. The returned dentry may be anonymous, 1522 * or may have a full name (if the inode was already in the cache). 1523 * 1524 * When called on a directory inode, we must ensure that the inode only ever 1525 * has one dentry. If a dentry is found, that is returned instead of 1526 * allocating a new one. 1527 * 1528 * On successful return, the reference to the inode has been transferred 1529 * to the dentry. In case of an error the reference on the inode is released. 1530 * To make it easier to use in export operations a %NULL or IS_ERR inode may 1531 * be passed in and will be the error will be propagate to the return value, 1532 * with a %NULL @inode replaced by ERR_PTR(-ESTALE). 1533 */ 1534 struct dentry *d_obtain_alias(struct inode *inode) 1535 { 1536 static const struct qstr anonstring = { .name = "" }; 1537 struct dentry *tmp; 1538 struct dentry *res; 1539 1540 if (!inode) 1541 return ERR_PTR(-ESTALE); 1542 if (IS_ERR(inode)) 1543 return ERR_CAST(inode); 1544 1545 res = d_find_any_alias(inode); 1546 if (res) 1547 goto out_iput; 1548 1549 tmp = __d_alloc(inode->i_sb, &anonstring); 1550 if (!tmp) { 1551 res = ERR_PTR(-ENOMEM); 1552 goto out_iput; 1553 } 1554 1555 spin_lock(&inode->i_lock); 1556 res = __d_find_any_alias(inode); 1557 if (res) { 1558 spin_unlock(&inode->i_lock); 1559 dput(tmp); 1560 goto out_iput; 1561 } 1562 1563 /* attach a disconnected dentry */ 1564 spin_lock(&tmp->d_lock); 1565 tmp->d_inode = inode; 1566 tmp->d_flags |= DCACHE_DISCONNECTED; 1567 list_add(&tmp->d_alias, &inode->i_dentry); 1568 hlist_bl_lock(&tmp->d_sb->s_anon); 1569 hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon); 1570 hlist_bl_unlock(&tmp->d_sb->s_anon); 1571 spin_unlock(&tmp->d_lock); 1572 spin_unlock(&inode->i_lock); 1573 security_d_instantiate(tmp, inode); 1574 1575 return tmp; 1576 1577 out_iput: 1578 if (res && !IS_ERR(res)) 1579 security_d_instantiate(res, inode); 1580 iput(inode); 1581 return res; 1582 } 1583 EXPORT_SYMBOL(d_obtain_alias); 1584 1585 /** 1586 * d_splice_alias - splice a disconnected dentry into the tree if one exists 1587 * @inode: the inode which may have a disconnected dentry 1588 * @dentry: a negative dentry which we want to point to the inode. 1589 * 1590 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and 1591 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry 1592 * and return it, else simply d_add the inode to the dentry and return NULL. 1593 * 1594 * This is needed in the lookup routine of any filesystem that is exportable 1595 * (via knfsd) so that we can build dcache paths to directories effectively. 1596 * 1597 * If a dentry was found and moved, then it is returned. Otherwise NULL 1598 * is returned. This matches the expected return value of ->lookup. 1599 * 1600 */ 1601 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry) 1602 { 1603 struct dentry *new = NULL; 1604 1605 if (IS_ERR(inode)) 1606 return ERR_CAST(inode); 1607 1608 if (inode && S_ISDIR(inode->i_mode)) { 1609 spin_lock(&inode->i_lock); 1610 new = __d_find_alias(inode, 1); 1611 if (new) { 1612 BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED)); 1613 spin_unlock(&inode->i_lock); 1614 security_d_instantiate(new, inode); 1615 d_move(new, dentry); 1616 iput(inode); 1617 } else { 1618 /* already taking inode->i_lock, so d_add() by hand */ 1619 __d_instantiate(dentry, inode); 1620 spin_unlock(&inode->i_lock); 1621 security_d_instantiate(dentry, inode); 1622 d_rehash(dentry); 1623 } 1624 } else 1625 d_add(dentry, inode); 1626 return new; 1627 } 1628 EXPORT_SYMBOL(d_splice_alias); 1629 1630 /** 1631 * d_add_ci - lookup or allocate new dentry with case-exact name 1632 * @inode: the inode case-insensitive lookup has found 1633 * @dentry: the negative dentry that was passed to the parent's lookup func 1634 * @name: the case-exact name to be associated with the returned dentry 1635 * 1636 * This is to avoid filling the dcache with case-insensitive names to the 1637 * same inode, only the actual correct case is stored in the dcache for 1638 * case-insensitive filesystems. 1639 * 1640 * For a case-insensitive lookup match and if the the case-exact dentry 1641 * already exists in in the dcache, use it and return it. 1642 * 1643 * If no entry exists with the exact case name, allocate new dentry with 1644 * the exact case, and return the spliced entry. 1645 */ 1646 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode, 1647 struct qstr *name) 1648 { 1649 int error; 1650 struct dentry *found; 1651 struct dentry *new; 1652 1653 /* 1654 * First check if a dentry matching the name already exists, 1655 * if not go ahead and create it now. 1656 */ 1657 found = d_hash_and_lookup(dentry->d_parent, name); 1658 if (!found) { 1659 new = d_alloc(dentry->d_parent, name); 1660 if (!new) { 1661 error = -ENOMEM; 1662 goto err_out; 1663 } 1664 1665 found = d_splice_alias(inode, new); 1666 if (found) { 1667 dput(new); 1668 return found; 1669 } 1670 return new; 1671 } 1672 1673 /* 1674 * If a matching dentry exists, and it's not negative use it. 1675 * 1676 * Decrement the reference count to balance the iget() done 1677 * earlier on. 1678 */ 1679 if (found->d_inode) { 1680 if (unlikely(found->d_inode != inode)) { 1681 /* This can't happen because bad inodes are unhashed. */ 1682 BUG_ON(!is_bad_inode(inode)); 1683 BUG_ON(!is_bad_inode(found->d_inode)); 1684 } 1685 iput(inode); 1686 return found; 1687 } 1688 1689 /* 1690 * We are going to instantiate this dentry, unhash it and clear the 1691 * lookup flag so we can do that. 1692 */ 1693 if (unlikely(d_need_lookup(found))) 1694 d_clear_need_lookup(found); 1695 1696 /* 1697 * Negative dentry: instantiate it unless the inode is a directory and 1698 * already has a dentry. 1699 */ 1700 new = d_splice_alias(inode, found); 1701 if (new) { 1702 dput(found); 1703 found = new; 1704 } 1705 return found; 1706 1707 err_out: 1708 iput(inode); 1709 return ERR_PTR(error); 1710 } 1711 EXPORT_SYMBOL(d_add_ci); 1712 1713 /** 1714 * __d_lookup_rcu - search for a dentry (racy, store-free) 1715 * @parent: parent dentry 1716 * @name: qstr of name we wish to find 1717 * @seq: returns d_seq value at the point where the dentry was found 1718 * @inode: returns dentry->d_inode when the inode was found valid. 1719 * Returns: dentry, or NULL 1720 * 1721 * __d_lookup_rcu is the dcache lookup function for rcu-walk name 1722 * resolution (store-free path walking) design described in 1723 * Documentation/filesystems/path-lookup.txt. 1724 * 1725 * This is not to be used outside core vfs. 1726 * 1727 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock 1728 * held, and rcu_read_lock held. The returned dentry must not be stored into 1729 * without taking d_lock and checking d_seq sequence count against @seq 1730 * returned here. 1731 * 1732 * A refcount may be taken on the found dentry with the __d_rcu_to_refcount 1733 * function. 1734 * 1735 * Alternatively, __d_lookup_rcu may be called again to look up the child of 1736 * the returned dentry, so long as its parent's seqlock is checked after the 1737 * child is looked up. Thus, an interlocking stepping of sequence lock checks 1738 * is formed, giving integrity down the path walk. 1739 */ 1740 struct dentry *__d_lookup_rcu(const struct dentry *parent, 1741 const struct qstr *name, 1742 unsigned *seqp, struct inode **inode) 1743 { 1744 unsigned int len = name->len; 1745 unsigned int hash = name->hash; 1746 const unsigned char *str = name->name; 1747 struct hlist_bl_head *b = d_hash(parent, hash); 1748 struct hlist_bl_node *node; 1749 struct dentry *dentry; 1750 1751 /* 1752 * Note: There is significant duplication with __d_lookup_rcu which is 1753 * required to prevent single threaded performance regressions 1754 * especially on architectures where smp_rmb (in seqcounts) are costly. 1755 * Keep the two functions in sync. 1756 */ 1757 1758 /* 1759 * The hash list is protected using RCU. 1760 * 1761 * Carefully use d_seq when comparing a candidate dentry, to avoid 1762 * races with d_move(). 1763 * 1764 * It is possible that concurrent renames can mess up our list 1765 * walk here and result in missing our dentry, resulting in the 1766 * false-negative result. d_lookup() protects against concurrent 1767 * renames using rename_lock seqlock. 1768 * 1769 * See Documentation/filesystems/path-lookup.txt for more details. 1770 */ 1771 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { 1772 unsigned seq; 1773 struct inode *i; 1774 const char *tname; 1775 int tlen; 1776 1777 if (dentry->d_name.hash != hash) 1778 continue; 1779 1780 seqretry: 1781 seq = read_seqcount_begin(&dentry->d_seq); 1782 if (dentry->d_parent != parent) 1783 continue; 1784 if (d_unhashed(dentry)) 1785 continue; 1786 tlen = dentry->d_name.len; 1787 tname = dentry->d_name.name; 1788 i = dentry->d_inode; 1789 prefetch(tname); 1790 /* 1791 * This seqcount check is required to ensure name and 1792 * len are loaded atomically, so as not to walk off the 1793 * edge of memory when walking. If we could load this 1794 * atomically some other way, we could drop this check. 1795 */ 1796 if (read_seqcount_retry(&dentry->d_seq, seq)) 1797 goto seqretry; 1798 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) { 1799 if (parent->d_op->d_compare(parent, *inode, 1800 dentry, i, 1801 tlen, tname, name)) 1802 continue; 1803 } else { 1804 if (dentry_cmp(tname, tlen, str, len)) 1805 continue; 1806 } 1807 /* 1808 * No extra seqcount check is required after the name 1809 * compare. The caller must perform a seqcount check in 1810 * order to do anything useful with the returned dentry 1811 * anyway. 1812 */ 1813 *seqp = seq; 1814 *inode = i; 1815 return dentry; 1816 } 1817 return NULL; 1818 } 1819 1820 /** 1821 * d_lookup - search for a dentry 1822 * @parent: parent dentry 1823 * @name: qstr of name we wish to find 1824 * Returns: dentry, or NULL 1825 * 1826 * d_lookup searches the children of the parent dentry for the name in 1827 * question. If the dentry is found its reference count is incremented and the 1828 * dentry is returned. The caller must use dput to free the entry when it has 1829 * finished using it. %NULL is returned if the dentry does not exist. 1830 */ 1831 struct dentry *d_lookup(struct dentry *parent, struct qstr *name) 1832 { 1833 struct dentry *dentry; 1834 unsigned seq; 1835 1836 do { 1837 seq = read_seqbegin(&rename_lock); 1838 dentry = __d_lookup(parent, name); 1839 if (dentry) 1840 break; 1841 } while (read_seqretry(&rename_lock, seq)); 1842 return dentry; 1843 } 1844 EXPORT_SYMBOL(d_lookup); 1845 1846 /** 1847 * __d_lookup - search for a dentry (racy) 1848 * @parent: parent dentry 1849 * @name: qstr of name we wish to find 1850 * Returns: dentry, or NULL 1851 * 1852 * __d_lookup is like d_lookup, however it may (rarely) return a 1853 * false-negative result due to unrelated rename activity. 1854 * 1855 * __d_lookup is slightly faster by avoiding rename_lock read seqlock, 1856 * however it must be used carefully, eg. with a following d_lookup in 1857 * the case of failure. 1858 * 1859 * __d_lookup callers must be commented. 1860 */ 1861 struct dentry *__d_lookup(struct dentry *parent, struct qstr *name) 1862 { 1863 unsigned int len = name->len; 1864 unsigned int hash = name->hash; 1865 const unsigned char *str = name->name; 1866 struct hlist_bl_head *b = d_hash(parent, hash); 1867 struct hlist_bl_node *node; 1868 struct dentry *found = NULL; 1869 struct dentry *dentry; 1870 1871 /* 1872 * Note: There is significant duplication with __d_lookup_rcu which is 1873 * required to prevent single threaded performance regressions 1874 * especially on architectures where smp_rmb (in seqcounts) are costly. 1875 * Keep the two functions in sync. 1876 */ 1877 1878 /* 1879 * The hash list is protected using RCU. 1880 * 1881 * Take d_lock when comparing a candidate dentry, to avoid races 1882 * with d_move(). 1883 * 1884 * It is possible that concurrent renames can mess up our list 1885 * walk here and result in missing our dentry, resulting in the 1886 * false-negative result. d_lookup() protects against concurrent 1887 * renames using rename_lock seqlock. 1888 * 1889 * See Documentation/filesystems/path-lookup.txt for more details. 1890 */ 1891 rcu_read_lock(); 1892 1893 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { 1894 const char *tname; 1895 int tlen; 1896 1897 if (dentry->d_name.hash != hash) 1898 continue; 1899 1900 spin_lock(&dentry->d_lock); 1901 if (dentry->d_parent != parent) 1902 goto next; 1903 if (d_unhashed(dentry)) 1904 goto next; 1905 1906 /* 1907 * It is safe to compare names since d_move() cannot 1908 * change the qstr (protected by d_lock). 1909 */ 1910 tlen = dentry->d_name.len; 1911 tname = dentry->d_name.name; 1912 if (parent->d_flags & DCACHE_OP_COMPARE) { 1913 if (parent->d_op->d_compare(parent, parent->d_inode, 1914 dentry, dentry->d_inode, 1915 tlen, tname, name)) 1916 goto next; 1917 } else { 1918 if (dentry_cmp(tname, tlen, str, len)) 1919 goto next; 1920 } 1921 1922 dentry->d_count++; 1923 found = dentry; 1924 spin_unlock(&dentry->d_lock); 1925 break; 1926 next: 1927 spin_unlock(&dentry->d_lock); 1928 } 1929 rcu_read_unlock(); 1930 1931 return found; 1932 } 1933 1934 /** 1935 * d_hash_and_lookup - hash the qstr then search for a dentry 1936 * @dir: Directory to search in 1937 * @name: qstr of name we wish to find 1938 * 1939 * On hash failure or on lookup failure NULL is returned. 1940 */ 1941 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name) 1942 { 1943 struct dentry *dentry = NULL; 1944 1945 /* 1946 * Check for a fs-specific hash function. Note that we must 1947 * calculate the standard hash first, as the d_op->d_hash() 1948 * routine may choose to leave the hash value unchanged. 1949 */ 1950 name->hash = full_name_hash(name->name, name->len); 1951 if (dir->d_flags & DCACHE_OP_HASH) { 1952 if (dir->d_op->d_hash(dir, dir->d_inode, name) < 0) 1953 goto out; 1954 } 1955 dentry = d_lookup(dir, name); 1956 out: 1957 return dentry; 1958 } 1959 1960 /** 1961 * d_validate - verify dentry provided from insecure source (deprecated) 1962 * @dentry: The dentry alleged to be valid child of @dparent 1963 * @dparent: The parent dentry (known to be valid) 1964 * 1965 * An insecure source has sent us a dentry, here we verify it and dget() it. 1966 * This is used by ncpfs in its readdir implementation. 1967 * Zero is returned in the dentry is invalid. 1968 * 1969 * This function is slow for big directories, and deprecated, do not use it. 1970 */ 1971 int d_validate(struct dentry *dentry, struct dentry *dparent) 1972 { 1973 struct dentry *child; 1974 1975 spin_lock(&dparent->d_lock); 1976 list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) { 1977 if (dentry == child) { 1978 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); 1979 __dget_dlock(dentry); 1980 spin_unlock(&dentry->d_lock); 1981 spin_unlock(&dparent->d_lock); 1982 return 1; 1983 } 1984 } 1985 spin_unlock(&dparent->d_lock); 1986 1987 return 0; 1988 } 1989 EXPORT_SYMBOL(d_validate); 1990 1991 /* 1992 * When a file is deleted, we have two options: 1993 * - turn this dentry into a negative dentry 1994 * - unhash this dentry and free it. 1995 * 1996 * Usually, we want to just turn this into 1997 * a negative dentry, but if anybody else is 1998 * currently using the dentry or the inode 1999 * we can't do that and we fall back on removing 2000 * it from the hash queues and waiting for 2001 * it to be deleted later when it has no users 2002 */ 2003 2004 /** 2005 * d_delete - delete a dentry 2006 * @dentry: The dentry to delete 2007 * 2008 * Turn the dentry into a negative dentry if possible, otherwise 2009 * remove it from the hash queues so it can be deleted later 2010 */ 2011 2012 void d_delete(struct dentry * dentry) 2013 { 2014 struct inode *inode; 2015 int isdir = 0; 2016 /* 2017 * Are we the only user? 2018 */ 2019 again: 2020 spin_lock(&dentry->d_lock); 2021 inode = dentry->d_inode; 2022 isdir = S_ISDIR(inode->i_mode); 2023 if (dentry->d_count == 1) { 2024 if (inode && !spin_trylock(&inode->i_lock)) { 2025 spin_unlock(&dentry->d_lock); 2026 cpu_relax(); 2027 goto again; 2028 } 2029 dentry->d_flags &= ~DCACHE_CANT_MOUNT; 2030 dentry_unlink_inode(dentry); 2031 fsnotify_nameremove(dentry, isdir); 2032 return; 2033 } 2034 2035 if (!d_unhashed(dentry)) 2036 __d_drop(dentry); 2037 2038 spin_unlock(&dentry->d_lock); 2039 2040 fsnotify_nameremove(dentry, isdir); 2041 } 2042 EXPORT_SYMBOL(d_delete); 2043 2044 static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b) 2045 { 2046 BUG_ON(!d_unhashed(entry)); 2047 hlist_bl_lock(b); 2048 entry->d_flags |= DCACHE_RCUACCESS; 2049 hlist_bl_add_head_rcu(&entry->d_hash, b); 2050 hlist_bl_unlock(b); 2051 } 2052 2053 static void _d_rehash(struct dentry * entry) 2054 { 2055 __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash)); 2056 } 2057 2058 /** 2059 * d_rehash - add an entry back to the hash 2060 * @entry: dentry to add to the hash 2061 * 2062 * Adds a dentry to the hash according to its name. 2063 */ 2064 2065 void d_rehash(struct dentry * entry) 2066 { 2067 spin_lock(&entry->d_lock); 2068 _d_rehash(entry); 2069 spin_unlock(&entry->d_lock); 2070 } 2071 EXPORT_SYMBOL(d_rehash); 2072 2073 /** 2074 * dentry_update_name_case - update case insensitive dentry with a new name 2075 * @dentry: dentry to be updated 2076 * @name: new name 2077 * 2078 * Update a case insensitive dentry with new case of name. 2079 * 2080 * dentry must have been returned by d_lookup with name @name. Old and new 2081 * name lengths must match (ie. no d_compare which allows mismatched name 2082 * lengths). 2083 * 2084 * Parent inode i_mutex must be held over d_lookup and into this call (to 2085 * keep renames and concurrent inserts, and readdir(2) away). 2086 */ 2087 void dentry_update_name_case(struct dentry *dentry, struct qstr *name) 2088 { 2089 BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex)); 2090 BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */ 2091 2092 spin_lock(&dentry->d_lock); 2093 write_seqcount_begin(&dentry->d_seq); 2094 memcpy((unsigned char *)dentry->d_name.name, name->name, name->len); 2095 write_seqcount_end(&dentry->d_seq); 2096 spin_unlock(&dentry->d_lock); 2097 } 2098 EXPORT_SYMBOL(dentry_update_name_case); 2099 2100 static void switch_names(struct dentry *dentry, struct dentry *target) 2101 { 2102 if (dname_external(target)) { 2103 if (dname_external(dentry)) { 2104 /* 2105 * Both external: swap the pointers 2106 */ 2107 swap(target->d_name.name, dentry->d_name.name); 2108 } else { 2109 /* 2110 * dentry:internal, target:external. Steal target's 2111 * storage and make target internal. 2112 */ 2113 memcpy(target->d_iname, dentry->d_name.name, 2114 dentry->d_name.len + 1); 2115 dentry->d_name.name = target->d_name.name; 2116 target->d_name.name = target->d_iname; 2117 } 2118 } else { 2119 if (dname_external(dentry)) { 2120 /* 2121 * dentry:external, target:internal. Give dentry's 2122 * storage to target and make dentry internal 2123 */ 2124 memcpy(dentry->d_iname, target->d_name.name, 2125 target->d_name.len + 1); 2126 target->d_name.name = dentry->d_name.name; 2127 dentry->d_name.name = dentry->d_iname; 2128 } else { 2129 /* 2130 * Both are internal. Just copy target to dentry 2131 */ 2132 memcpy(dentry->d_iname, target->d_name.name, 2133 target->d_name.len + 1); 2134 dentry->d_name.len = target->d_name.len; 2135 return; 2136 } 2137 } 2138 swap(dentry->d_name.len, target->d_name.len); 2139 } 2140 2141 static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target) 2142 { 2143 /* 2144 * XXXX: do we really need to take target->d_lock? 2145 */ 2146 if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent) 2147 spin_lock(&target->d_parent->d_lock); 2148 else { 2149 if (d_ancestor(dentry->d_parent, target->d_parent)) { 2150 spin_lock(&dentry->d_parent->d_lock); 2151 spin_lock_nested(&target->d_parent->d_lock, 2152 DENTRY_D_LOCK_NESTED); 2153 } else { 2154 spin_lock(&target->d_parent->d_lock); 2155 spin_lock_nested(&dentry->d_parent->d_lock, 2156 DENTRY_D_LOCK_NESTED); 2157 } 2158 } 2159 if (target < dentry) { 2160 spin_lock_nested(&target->d_lock, 2); 2161 spin_lock_nested(&dentry->d_lock, 3); 2162 } else { 2163 spin_lock_nested(&dentry->d_lock, 2); 2164 spin_lock_nested(&target->d_lock, 3); 2165 } 2166 } 2167 2168 static void dentry_unlock_parents_for_move(struct dentry *dentry, 2169 struct dentry *target) 2170 { 2171 if (target->d_parent != dentry->d_parent) 2172 spin_unlock(&dentry->d_parent->d_lock); 2173 if (target->d_parent != target) 2174 spin_unlock(&target->d_parent->d_lock); 2175 } 2176 2177 /* 2178 * When switching names, the actual string doesn't strictly have to 2179 * be preserved in the target - because we're dropping the target 2180 * anyway. As such, we can just do a simple memcpy() to copy over 2181 * the new name before we switch. 2182 * 2183 * Note that we have to be a lot more careful about getting the hash 2184 * switched - we have to switch the hash value properly even if it 2185 * then no longer matches the actual (corrupted) string of the target. 2186 * The hash value has to match the hash queue that the dentry is on.. 2187 */ 2188 /* 2189 * __d_move - move a dentry 2190 * @dentry: entry to move 2191 * @target: new dentry 2192 * 2193 * Update the dcache to reflect the move of a file name. Negative 2194 * dcache entries should not be moved in this way. Caller must hold 2195 * rename_lock, the i_mutex of the source and target directories, 2196 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename(). 2197 */ 2198 static void __d_move(struct dentry * dentry, struct dentry * target) 2199 { 2200 if (!dentry->d_inode) 2201 printk(KERN_WARNING "VFS: moving negative dcache entry\n"); 2202 2203 BUG_ON(d_ancestor(dentry, target)); 2204 BUG_ON(d_ancestor(target, dentry)); 2205 2206 dentry_lock_for_move(dentry, target); 2207 2208 write_seqcount_begin(&dentry->d_seq); 2209 write_seqcount_begin(&target->d_seq); 2210 2211 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */ 2212 2213 /* 2214 * Move the dentry to the target hash queue. Don't bother checking 2215 * for the same hash queue because of how unlikely it is. 2216 */ 2217 __d_drop(dentry); 2218 __d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash)); 2219 2220 /* Unhash the target: dput() will then get rid of it */ 2221 __d_drop(target); 2222 2223 list_del(&dentry->d_u.d_child); 2224 list_del(&target->d_u.d_child); 2225 2226 /* Switch the names.. */ 2227 switch_names(dentry, target); 2228 swap(dentry->d_name.hash, target->d_name.hash); 2229 2230 /* ... and switch the parents */ 2231 if (IS_ROOT(dentry)) { 2232 dentry->d_parent = target->d_parent; 2233 target->d_parent = target; 2234 INIT_LIST_HEAD(&target->d_u.d_child); 2235 } else { 2236 swap(dentry->d_parent, target->d_parent); 2237 2238 /* And add them back to the (new) parent lists */ 2239 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs); 2240 } 2241 2242 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs); 2243 2244 write_seqcount_end(&target->d_seq); 2245 write_seqcount_end(&dentry->d_seq); 2246 2247 dentry_unlock_parents_for_move(dentry, target); 2248 spin_unlock(&target->d_lock); 2249 fsnotify_d_move(dentry); 2250 spin_unlock(&dentry->d_lock); 2251 } 2252 2253 /* 2254 * d_move - move a dentry 2255 * @dentry: entry to move 2256 * @target: new dentry 2257 * 2258 * Update the dcache to reflect the move of a file name. Negative 2259 * dcache entries should not be moved in this way. See the locking 2260 * requirements for __d_move. 2261 */ 2262 void d_move(struct dentry *dentry, struct dentry *target) 2263 { 2264 write_seqlock(&rename_lock); 2265 __d_move(dentry, target); 2266 write_sequnlock(&rename_lock); 2267 } 2268 EXPORT_SYMBOL(d_move); 2269 2270 /** 2271 * d_ancestor - search for an ancestor 2272 * @p1: ancestor dentry 2273 * @p2: child dentry 2274 * 2275 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is 2276 * an ancestor of p2, else NULL. 2277 */ 2278 struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2) 2279 { 2280 struct dentry *p; 2281 2282 for (p = p2; !IS_ROOT(p); p = p->d_parent) { 2283 if (p->d_parent == p1) 2284 return p; 2285 } 2286 return NULL; 2287 } 2288 2289 /* 2290 * This helper attempts to cope with remotely renamed directories 2291 * 2292 * It assumes that the caller is already holding 2293 * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock 2294 * 2295 * Note: If ever the locking in lock_rename() changes, then please 2296 * remember to update this too... 2297 */ 2298 static struct dentry *__d_unalias(struct inode *inode, 2299 struct dentry *dentry, struct dentry *alias) 2300 { 2301 struct mutex *m1 = NULL, *m2 = NULL; 2302 struct dentry *ret; 2303 2304 /* If alias and dentry share a parent, then no extra locks required */ 2305 if (alias->d_parent == dentry->d_parent) 2306 goto out_unalias; 2307 2308 /* See lock_rename() */ 2309 ret = ERR_PTR(-EBUSY); 2310 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex)) 2311 goto out_err; 2312 m1 = &dentry->d_sb->s_vfs_rename_mutex; 2313 if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex)) 2314 goto out_err; 2315 m2 = &alias->d_parent->d_inode->i_mutex; 2316 out_unalias: 2317 __d_move(alias, dentry); 2318 ret = alias; 2319 out_err: 2320 spin_unlock(&inode->i_lock); 2321 if (m2) 2322 mutex_unlock(m2); 2323 if (m1) 2324 mutex_unlock(m1); 2325 return ret; 2326 } 2327 2328 /* 2329 * Prepare an anonymous dentry for life in the superblock's dentry tree as a 2330 * named dentry in place of the dentry to be replaced. 2331 * returns with anon->d_lock held! 2332 */ 2333 static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon) 2334 { 2335 struct dentry *dparent, *aparent; 2336 2337 dentry_lock_for_move(anon, dentry); 2338 2339 write_seqcount_begin(&dentry->d_seq); 2340 write_seqcount_begin(&anon->d_seq); 2341 2342 dparent = dentry->d_parent; 2343 aparent = anon->d_parent; 2344 2345 switch_names(dentry, anon); 2346 swap(dentry->d_name.hash, anon->d_name.hash); 2347 2348 dentry->d_parent = (aparent == anon) ? dentry : aparent; 2349 list_del(&dentry->d_u.d_child); 2350 if (!IS_ROOT(dentry)) 2351 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs); 2352 else 2353 INIT_LIST_HEAD(&dentry->d_u.d_child); 2354 2355 anon->d_parent = (dparent == dentry) ? anon : dparent; 2356 list_del(&anon->d_u.d_child); 2357 if (!IS_ROOT(anon)) 2358 list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs); 2359 else 2360 INIT_LIST_HEAD(&anon->d_u.d_child); 2361 2362 write_seqcount_end(&dentry->d_seq); 2363 write_seqcount_end(&anon->d_seq); 2364 2365 dentry_unlock_parents_for_move(anon, dentry); 2366 spin_unlock(&dentry->d_lock); 2367 2368 /* anon->d_lock still locked, returns locked */ 2369 anon->d_flags &= ~DCACHE_DISCONNECTED; 2370 } 2371 2372 /** 2373 * d_materialise_unique - introduce an inode into the tree 2374 * @dentry: candidate dentry 2375 * @inode: inode to bind to the dentry, to which aliases may be attached 2376 * 2377 * Introduces an dentry into the tree, substituting an extant disconnected 2378 * root directory alias in its place if there is one. Caller must hold the 2379 * i_mutex of the parent directory. 2380 */ 2381 struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode) 2382 { 2383 struct dentry *actual; 2384 2385 BUG_ON(!d_unhashed(dentry)); 2386 2387 if (!inode) { 2388 actual = dentry; 2389 __d_instantiate(dentry, NULL); 2390 d_rehash(actual); 2391 goto out_nolock; 2392 } 2393 2394 spin_lock(&inode->i_lock); 2395 2396 if (S_ISDIR(inode->i_mode)) { 2397 struct dentry *alias; 2398 2399 /* Does an aliased dentry already exist? */ 2400 alias = __d_find_alias(inode, 0); 2401 if (alias) { 2402 actual = alias; 2403 write_seqlock(&rename_lock); 2404 2405 if (d_ancestor(alias, dentry)) { 2406 /* Check for loops */ 2407 actual = ERR_PTR(-ELOOP); 2408 } else if (IS_ROOT(alias)) { 2409 /* Is this an anonymous mountpoint that we 2410 * could splice into our tree? */ 2411 __d_materialise_dentry(dentry, alias); 2412 write_sequnlock(&rename_lock); 2413 __d_drop(alias); 2414 goto found; 2415 } else { 2416 /* Nope, but we must(!) avoid directory 2417 * aliasing */ 2418 actual = __d_unalias(inode, dentry, alias); 2419 } 2420 write_sequnlock(&rename_lock); 2421 if (IS_ERR(actual)) { 2422 if (PTR_ERR(actual) == -ELOOP) 2423 pr_warn_ratelimited( 2424 "VFS: Lookup of '%s' in %s %s" 2425 " would have caused loop\n", 2426 dentry->d_name.name, 2427 inode->i_sb->s_type->name, 2428 inode->i_sb->s_id); 2429 dput(alias); 2430 } 2431 goto out_nolock; 2432 } 2433 } 2434 2435 /* Add a unique reference */ 2436 actual = __d_instantiate_unique(dentry, inode); 2437 if (!actual) 2438 actual = dentry; 2439 else 2440 BUG_ON(!d_unhashed(actual)); 2441 2442 spin_lock(&actual->d_lock); 2443 found: 2444 _d_rehash(actual); 2445 spin_unlock(&actual->d_lock); 2446 spin_unlock(&inode->i_lock); 2447 out_nolock: 2448 if (actual == dentry) { 2449 security_d_instantiate(dentry, inode); 2450 return NULL; 2451 } 2452 2453 iput(inode); 2454 return actual; 2455 } 2456 EXPORT_SYMBOL_GPL(d_materialise_unique); 2457 2458 static int prepend(char **buffer, int *buflen, const char *str, int namelen) 2459 { 2460 *buflen -= namelen; 2461 if (*buflen < 0) 2462 return -ENAMETOOLONG; 2463 *buffer -= namelen; 2464 memcpy(*buffer, str, namelen); 2465 return 0; 2466 } 2467 2468 static int prepend_name(char **buffer, int *buflen, struct qstr *name) 2469 { 2470 return prepend(buffer, buflen, name->name, name->len); 2471 } 2472 2473 /** 2474 * prepend_path - Prepend path string to a buffer 2475 * @path: the dentry/vfsmount to report 2476 * @root: root vfsmnt/dentry 2477 * @buffer: pointer to the end of the buffer 2478 * @buflen: pointer to buffer length 2479 * 2480 * Caller holds the rename_lock. 2481 */ 2482 static int prepend_path(const struct path *path, 2483 const struct path *root, 2484 char **buffer, int *buflen) 2485 { 2486 struct dentry *dentry = path->dentry; 2487 struct vfsmount *vfsmnt = path->mnt; 2488 struct mount *mnt = real_mount(vfsmnt); 2489 bool slash = false; 2490 int error = 0; 2491 2492 br_read_lock(vfsmount_lock); 2493 while (dentry != root->dentry || vfsmnt != root->mnt) { 2494 struct dentry * parent; 2495 2496 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) { 2497 /* Global root? */ 2498 if (!mnt_has_parent(mnt)) 2499 goto global_root; 2500 dentry = mnt->mnt_mountpoint; 2501 mnt = mnt->mnt_parent; 2502 vfsmnt = &mnt->mnt; 2503 continue; 2504 } 2505 parent = dentry->d_parent; 2506 prefetch(parent); 2507 spin_lock(&dentry->d_lock); 2508 error = prepend_name(buffer, buflen, &dentry->d_name); 2509 spin_unlock(&dentry->d_lock); 2510 if (!error) 2511 error = prepend(buffer, buflen, "/", 1); 2512 if (error) 2513 break; 2514 2515 slash = true; 2516 dentry = parent; 2517 } 2518 2519 if (!error && !slash) 2520 error = prepend(buffer, buflen, "/", 1); 2521 2522 out: 2523 br_read_unlock(vfsmount_lock); 2524 return error; 2525 2526 global_root: 2527 /* 2528 * Filesystems needing to implement special "root names" 2529 * should do so with ->d_dname() 2530 */ 2531 if (IS_ROOT(dentry) && 2532 (dentry->d_name.len != 1 || dentry->d_name.name[0] != '/')) { 2533 WARN(1, "Root dentry has weird name <%.*s>\n", 2534 (int) dentry->d_name.len, dentry->d_name.name); 2535 } 2536 if (!slash) 2537 error = prepend(buffer, buflen, "/", 1); 2538 if (!error) 2539 error = real_mount(vfsmnt)->mnt_ns ? 1 : 2; 2540 goto out; 2541 } 2542 2543 /** 2544 * __d_path - return the path of a dentry 2545 * @path: the dentry/vfsmount to report 2546 * @root: root vfsmnt/dentry 2547 * @buf: buffer to return value in 2548 * @buflen: buffer length 2549 * 2550 * Convert a dentry into an ASCII path name. 2551 * 2552 * Returns a pointer into the buffer or an error code if the 2553 * path was too long. 2554 * 2555 * "buflen" should be positive. 2556 * 2557 * If the path is not reachable from the supplied root, return %NULL. 2558 */ 2559 char *__d_path(const struct path *path, 2560 const struct path *root, 2561 char *buf, int buflen) 2562 { 2563 char *res = buf + buflen; 2564 int error; 2565 2566 prepend(&res, &buflen, "\0", 1); 2567 write_seqlock(&rename_lock); 2568 error = prepend_path(path, root, &res, &buflen); 2569 write_sequnlock(&rename_lock); 2570 2571 if (error < 0) 2572 return ERR_PTR(error); 2573 if (error > 0) 2574 return NULL; 2575 return res; 2576 } 2577 2578 char *d_absolute_path(const struct path *path, 2579 char *buf, int buflen) 2580 { 2581 struct path root = {}; 2582 char *res = buf + buflen; 2583 int error; 2584 2585 prepend(&res, &buflen, "\0", 1); 2586 write_seqlock(&rename_lock); 2587 error = prepend_path(path, &root, &res, &buflen); 2588 write_sequnlock(&rename_lock); 2589 2590 if (error > 1) 2591 error = -EINVAL; 2592 if (error < 0) 2593 return ERR_PTR(error); 2594 return res; 2595 } 2596 2597 /* 2598 * same as __d_path but appends "(deleted)" for unlinked files. 2599 */ 2600 static int path_with_deleted(const struct path *path, 2601 const struct path *root, 2602 char **buf, int *buflen) 2603 { 2604 prepend(buf, buflen, "\0", 1); 2605 if (d_unlinked(path->dentry)) { 2606 int error = prepend(buf, buflen, " (deleted)", 10); 2607 if (error) 2608 return error; 2609 } 2610 2611 return prepend_path(path, root, buf, buflen); 2612 } 2613 2614 static int prepend_unreachable(char **buffer, int *buflen) 2615 { 2616 return prepend(buffer, buflen, "(unreachable)", 13); 2617 } 2618 2619 /** 2620 * d_path - return the path of a dentry 2621 * @path: path to report 2622 * @buf: buffer to return value in 2623 * @buflen: buffer length 2624 * 2625 * Convert a dentry into an ASCII path name. If the entry has been deleted 2626 * the string " (deleted)" is appended. Note that this is ambiguous. 2627 * 2628 * Returns a pointer into the buffer or an error code if the path was 2629 * too long. Note: Callers should use the returned pointer, not the passed 2630 * in buffer, to use the name! The implementation often starts at an offset 2631 * into the buffer, and may leave 0 bytes at the start. 2632 * 2633 * "buflen" should be positive. 2634 */ 2635 char *d_path(const struct path *path, char *buf, int buflen) 2636 { 2637 char *res = buf + buflen; 2638 struct path root; 2639 int error; 2640 2641 /* 2642 * We have various synthetic filesystems that never get mounted. On 2643 * these filesystems dentries are never used for lookup purposes, and 2644 * thus don't need to be hashed. They also don't need a name until a 2645 * user wants to identify the object in /proc/pid/fd/. The little hack 2646 * below allows us to generate a name for these objects on demand: 2647 */ 2648 if (path->dentry->d_op && path->dentry->d_op->d_dname) 2649 return path->dentry->d_op->d_dname(path->dentry, buf, buflen); 2650 2651 get_fs_root(current->fs, &root); 2652 write_seqlock(&rename_lock); 2653 error = path_with_deleted(path, &root, &res, &buflen); 2654 if (error < 0) 2655 res = ERR_PTR(error); 2656 write_sequnlock(&rename_lock); 2657 path_put(&root); 2658 return res; 2659 } 2660 EXPORT_SYMBOL(d_path); 2661 2662 /** 2663 * d_path_with_unreachable - return the path of a dentry 2664 * @path: path to report 2665 * @buf: buffer to return value in 2666 * @buflen: buffer length 2667 * 2668 * The difference from d_path() is that this prepends "(unreachable)" 2669 * to paths which are unreachable from the current process' root. 2670 */ 2671 char *d_path_with_unreachable(const struct path *path, char *buf, int buflen) 2672 { 2673 char *res = buf + buflen; 2674 struct path root; 2675 int error; 2676 2677 if (path->dentry->d_op && path->dentry->d_op->d_dname) 2678 return path->dentry->d_op->d_dname(path->dentry, buf, buflen); 2679 2680 get_fs_root(current->fs, &root); 2681 write_seqlock(&rename_lock); 2682 error = path_with_deleted(path, &root, &res, &buflen); 2683 if (error > 0) 2684 error = prepend_unreachable(&res, &buflen); 2685 write_sequnlock(&rename_lock); 2686 path_put(&root); 2687 if (error) 2688 res = ERR_PTR(error); 2689 2690 return res; 2691 } 2692 2693 /* 2694 * Helper function for dentry_operations.d_dname() members 2695 */ 2696 char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen, 2697 const char *fmt, ...) 2698 { 2699 va_list args; 2700 char temp[64]; 2701 int sz; 2702 2703 va_start(args, fmt); 2704 sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1; 2705 va_end(args); 2706 2707 if (sz > sizeof(temp) || sz > buflen) 2708 return ERR_PTR(-ENAMETOOLONG); 2709 2710 buffer += buflen - sz; 2711 return memcpy(buffer, temp, sz); 2712 } 2713 2714 /* 2715 * Write full pathname from the root of the filesystem into the buffer. 2716 */ 2717 static char *__dentry_path(struct dentry *dentry, char *buf, int buflen) 2718 { 2719 char *end = buf + buflen; 2720 char *retval; 2721 2722 prepend(&end, &buflen, "\0", 1); 2723 if (buflen < 1) 2724 goto Elong; 2725 /* Get '/' right */ 2726 retval = end-1; 2727 *retval = '/'; 2728 2729 while (!IS_ROOT(dentry)) { 2730 struct dentry *parent = dentry->d_parent; 2731 int error; 2732 2733 prefetch(parent); 2734 spin_lock(&dentry->d_lock); 2735 error = prepend_name(&end, &buflen, &dentry->d_name); 2736 spin_unlock(&dentry->d_lock); 2737 if (error != 0 || prepend(&end, &buflen, "/", 1) != 0) 2738 goto Elong; 2739 2740 retval = end; 2741 dentry = parent; 2742 } 2743 return retval; 2744 Elong: 2745 return ERR_PTR(-ENAMETOOLONG); 2746 } 2747 2748 char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen) 2749 { 2750 char *retval; 2751 2752 write_seqlock(&rename_lock); 2753 retval = __dentry_path(dentry, buf, buflen); 2754 write_sequnlock(&rename_lock); 2755 2756 return retval; 2757 } 2758 EXPORT_SYMBOL(dentry_path_raw); 2759 2760 char *dentry_path(struct dentry *dentry, char *buf, int buflen) 2761 { 2762 char *p = NULL; 2763 char *retval; 2764 2765 write_seqlock(&rename_lock); 2766 if (d_unlinked(dentry)) { 2767 p = buf + buflen; 2768 if (prepend(&p, &buflen, "//deleted", 10) != 0) 2769 goto Elong; 2770 buflen++; 2771 } 2772 retval = __dentry_path(dentry, buf, buflen); 2773 write_sequnlock(&rename_lock); 2774 if (!IS_ERR(retval) && p) 2775 *p = '/'; /* restore '/' overriden with '\0' */ 2776 return retval; 2777 Elong: 2778 return ERR_PTR(-ENAMETOOLONG); 2779 } 2780 2781 /* 2782 * NOTE! The user-level library version returns a 2783 * character pointer. The kernel system call just 2784 * returns the length of the buffer filled (which 2785 * includes the ending '\0' character), or a negative 2786 * error value. So libc would do something like 2787 * 2788 * char *getcwd(char * buf, size_t size) 2789 * { 2790 * int retval; 2791 * 2792 * retval = sys_getcwd(buf, size); 2793 * if (retval >= 0) 2794 * return buf; 2795 * errno = -retval; 2796 * return NULL; 2797 * } 2798 */ 2799 SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) 2800 { 2801 int error; 2802 struct path pwd, root; 2803 char *page = (char *) __get_free_page(GFP_USER); 2804 2805 if (!page) 2806 return -ENOMEM; 2807 2808 get_fs_root_and_pwd(current->fs, &root, &pwd); 2809 2810 error = -ENOENT; 2811 write_seqlock(&rename_lock); 2812 if (!d_unlinked(pwd.dentry)) { 2813 unsigned long len; 2814 char *cwd = page + PAGE_SIZE; 2815 int buflen = PAGE_SIZE; 2816 2817 prepend(&cwd, &buflen, "\0", 1); 2818 error = prepend_path(&pwd, &root, &cwd, &buflen); 2819 write_sequnlock(&rename_lock); 2820 2821 if (error < 0) 2822 goto out; 2823 2824 /* Unreachable from current root */ 2825 if (error > 0) { 2826 error = prepend_unreachable(&cwd, &buflen); 2827 if (error) 2828 goto out; 2829 } 2830 2831 error = -ERANGE; 2832 len = PAGE_SIZE + page - cwd; 2833 if (len <= size) { 2834 error = len; 2835 if (copy_to_user(buf, cwd, len)) 2836 error = -EFAULT; 2837 } 2838 } else { 2839 write_sequnlock(&rename_lock); 2840 } 2841 2842 out: 2843 path_put(&pwd); 2844 path_put(&root); 2845 free_page((unsigned long) page); 2846 return error; 2847 } 2848 2849 /* 2850 * Test whether new_dentry is a subdirectory of old_dentry. 2851 * 2852 * Trivially implemented using the dcache structure 2853 */ 2854 2855 /** 2856 * is_subdir - is new dentry a subdirectory of old_dentry 2857 * @new_dentry: new dentry 2858 * @old_dentry: old dentry 2859 * 2860 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth). 2861 * Returns 0 otherwise. 2862 * Caller must ensure that "new_dentry" is pinned before calling is_subdir() 2863 */ 2864 2865 int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry) 2866 { 2867 int result; 2868 unsigned seq; 2869 2870 if (new_dentry == old_dentry) 2871 return 1; 2872 2873 do { 2874 /* for restarting inner loop in case of seq retry */ 2875 seq = read_seqbegin(&rename_lock); 2876 /* 2877 * Need rcu_readlock to protect against the d_parent trashing 2878 * due to d_move 2879 */ 2880 rcu_read_lock(); 2881 if (d_ancestor(old_dentry, new_dentry)) 2882 result = 1; 2883 else 2884 result = 0; 2885 rcu_read_unlock(); 2886 } while (read_seqretry(&rename_lock, seq)); 2887 2888 return result; 2889 } 2890 2891 void d_genocide(struct dentry *root) 2892 { 2893 struct dentry *this_parent; 2894 struct list_head *next; 2895 unsigned seq; 2896 int locked = 0; 2897 2898 seq = read_seqbegin(&rename_lock); 2899 again: 2900 this_parent = root; 2901 spin_lock(&this_parent->d_lock); 2902 repeat: 2903 next = this_parent->d_subdirs.next; 2904 resume: 2905 while (next != &this_parent->d_subdirs) { 2906 struct list_head *tmp = next; 2907 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); 2908 next = tmp->next; 2909 2910 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); 2911 if (d_unhashed(dentry) || !dentry->d_inode) { 2912 spin_unlock(&dentry->d_lock); 2913 continue; 2914 } 2915 if (!list_empty(&dentry->d_subdirs)) { 2916 spin_unlock(&this_parent->d_lock); 2917 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_); 2918 this_parent = dentry; 2919 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); 2920 goto repeat; 2921 } 2922 if (!(dentry->d_flags & DCACHE_GENOCIDE)) { 2923 dentry->d_flags |= DCACHE_GENOCIDE; 2924 dentry->d_count--; 2925 } 2926 spin_unlock(&dentry->d_lock); 2927 } 2928 if (this_parent != root) { 2929 struct dentry *child = this_parent; 2930 if (!(this_parent->d_flags & DCACHE_GENOCIDE)) { 2931 this_parent->d_flags |= DCACHE_GENOCIDE; 2932 this_parent->d_count--; 2933 } 2934 this_parent = try_to_ascend(this_parent, locked, seq); 2935 if (!this_parent) 2936 goto rename_retry; 2937 next = child->d_u.d_child.next; 2938 goto resume; 2939 } 2940 spin_unlock(&this_parent->d_lock); 2941 if (!locked && read_seqretry(&rename_lock, seq)) 2942 goto rename_retry; 2943 if (locked) 2944 write_sequnlock(&rename_lock); 2945 return; 2946 2947 rename_retry: 2948 locked = 1; 2949 write_seqlock(&rename_lock); 2950 goto again; 2951 } 2952 2953 /** 2954 * find_inode_number - check for dentry with name 2955 * @dir: directory to check 2956 * @name: Name to find. 2957 * 2958 * Check whether a dentry already exists for the given name, 2959 * and return the inode number if it has an inode. Otherwise 2960 * 0 is returned. 2961 * 2962 * This routine is used to post-process directory listings for 2963 * filesystems using synthetic inode numbers, and is necessary 2964 * to keep getcwd() working. 2965 */ 2966 2967 ino_t find_inode_number(struct dentry *dir, struct qstr *name) 2968 { 2969 struct dentry * dentry; 2970 ino_t ino = 0; 2971 2972 dentry = d_hash_and_lookup(dir, name); 2973 if (dentry) { 2974 if (dentry->d_inode) 2975 ino = dentry->d_inode->i_ino; 2976 dput(dentry); 2977 } 2978 return ino; 2979 } 2980 EXPORT_SYMBOL(find_inode_number); 2981 2982 static __initdata unsigned long dhash_entries; 2983 static int __init set_dhash_entries(char *str) 2984 { 2985 if (!str) 2986 return 0; 2987 dhash_entries = simple_strtoul(str, &str, 0); 2988 return 1; 2989 } 2990 __setup("dhash_entries=", set_dhash_entries); 2991 2992 static void __init dcache_init_early(void) 2993 { 2994 unsigned int loop; 2995 2996 /* If hashes are distributed across NUMA nodes, defer 2997 * hash allocation until vmalloc space is available. 2998 */ 2999 if (hashdist) 3000 return; 3001 3002 dentry_hashtable = 3003 alloc_large_system_hash("Dentry cache", 3004 sizeof(struct hlist_bl_head), 3005 dhash_entries, 3006 13, 3007 HASH_EARLY, 3008 &d_hash_shift, 3009 &d_hash_mask, 3010 0); 3011 3012 for (loop = 0; loop < (1U << d_hash_shift); loop++) 3013 INIT_HLIST_BL_HEAD(dentry_hashtable + loop); 3014 } 3015 3016 static void __init dcache_init(void) 3017 { 3018 unsigned int loop; 3019 3020 /* 3021 * A constructor could be added for stable state like the lists, 3022 * but it is probably not worth it because of the cache nature 3023 * of the dcache. 3024 */ 3025 dentry_cache = KMEM_CACHE(dentry, 3026 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD); 3027 3028 /* Hash may have been set up in dcache_init_early */ 3029 if (!hashdist) 3030 return; 3031 3032 dentry_hashtable = 3033 alloc_large_system_hash("Dentry cache", 3034 sizeof(struct hlist_bl_head), 3035 dhash_entries, 3036 13, 3037 0, 3038 &d_hash_shift, 3039 &d_hash_mask, 3040 0); 3041 3042 for (loop = 0; loop < (1U << d_hash_shift); loop++) 3043 INIT_HLIST_BL_HEAD(dentry_hashtable + loop); 3044 } 3045 3046 /* SLAB cache for __getname() consumers */ 3047 struct kmem_cache *names_cachep __read_mostly; 3048 EXPORT_SYMBOL(names_cachep); 3049 3050 EXPORT_SYMBOL(d_genocide); 3051 3052 void __init vfs_caches_init_early(void) 3053 { 3054 dcache_init_early(); 3055 inode_init_early(); 3056 } 3057 3058 void __init vfs_caches_init(unsigned long mempages) 3059 { 3060 unsigned long reserve; 3061 3062 /* Base hash sizes on available memory, with a reserve equal to 3063 150% of current kernel size */ 3064 3065 reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1); 3066 mempages -= reserve; 3067 3068 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0, 3069 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 3070 3071 dcache_init(); 3072 inode_init(); 3073 files_init(mempages); 3074 mnt_init(); 3075 bdev_cache_init(); 3076 chrdev_init(); 3077 } 3078