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 "internal.h" 40 41 /* 42 * Usage: 43 * dcache->d_inode->i_lock protects: 44 * - i_dentry, d_alias, d_inode of aliases 45 * dcache_hash_bucket lock protects: 46 * - the dcache hash table 47 * s_anon bl list spinlock protects: 48 * - the s_anon list (see __d_drop) 49 * dcache_lru_lock protects: 50 * - the dcache lru lists and counters 51 * d_lock protects: 52 * - d_flags 53 * - d_name 54 * - d_lru 55 * - d_count 56 * - d_unhashed() 57 * - d_parent and d_subdirs 58 * - childrens' d_child and d_parent 59 * - d_alias, d_inode 60 * 61 * Ordering: 62 * dentry->d_inode->i_lock 63 * dentry->d_lock 64 * dcache_lru_lock 65 * dcache_hash_bucket lock 66 * s_anon lock 67 * 68 * If there is an ancestor relationship: 69 * dentry->d_parent->...->d_parent->d_lock 70 * ... 71 * dentry->d_parent->d_lock 72 * dentry->d_lock 73 * 74 * If no ancestor relationship: 75 * if (dentry1 < dentry2) 76 * dentry1->d_lock 77 * dentry2->d_lock 78 */ 79 int sysctl_vfs_cache_pressure __read_mostly = 100; 80 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure); 81 82 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock); 83 __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock); 84 85 EXPORT_SYMBOL(rename_lock); 86 87 static struct kmem_cache *dentry_cache __read_mostly; 88 89 /* 90 * This is the single most critical data structure when it comes 91 * to the dcache: the hashtable for lookups. Somebody should try 92 * to make this good - I've just made it work. 93 * 94 * This hash-function tries to avoid losing too many bits of hash 95 * information, yet avoid using a prime hash-size or similar. 96 */ 97 #define D_HASHBITS d_hash_shift 98 #define D_HASHMASK d_hash_mask 99 100 static unsigned int d_hash_mask __read_mostly; 101 static unsigned int d_hash_shift __read_mostly; 102 103 static struct hlist_bl_head *dentry_hashtable __read_mostly; 104 105 static inline struct hlist_bl_head *d_hash(struct dentry *parent, 106 unsigned long hash) 107 { 108 hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES; 109 hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS); 110 return dentry_hashtable + (hash & D_HASHMASK); 111 } 112 113 /* Statistics gathering. */ 114 struct dentry_stat_t dentry_stat = { 115 .age_limit = 45, 116 }; 117 118 static DEFINE_PER_CPU(unsigned int, nr_dentry); 119 120 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS) 121 static int get_nr_dentry(void) 122 { 123 int i; 124 int sum = 0; 125 for_each_possible_cpu(i) 126 sum += per_cpu(nr_dentry, i); 127 return sum < 0 ? 0 : sum; 128 } 129 130 int proc_nr_dentry(ctl_table *table, int write, void __user *buffer, 131 size_t *lenp, loff_t *ppos) 132 { 133 dentry_stat.nr_dentry = get_nr_dentry(); 134 return proc_dointvec(table, write, buffer, lenp, ppos); 135 } 136 #endif 137 138 static void __d_free(struct rcu_head *head) 139 { 140 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu); 141 142 WARN_ON(!list_empty(&dentry->d_alias)); 143 if (dname_external(dentry)) 144 kfree(dentry->d_name.name); 145 kmem_cache_free(dentry_cache, dentry); 146 } 147 148 /* 149 * no locks, please. 150 */ 151 static void d_free(struct dentry *dentry) 152 { 153 BUG_ON(dentry->d_count); 154 this_cpu_dec(nr_dentry); 155 if (dentry->d_op && dentry->d_op->d_release) 156 dentry->d_op->d_release(dentry); 157 158 /* if dentry was never visible to RCU, immediate free is OK */ 159 if (!(dentry->d_flags & DCACHE_RCUACCESS)) 160 __d_free(&dentry->d_u.d_rcu); 161 else 162 call_rcu(&dentry->d_u.d_rcu, __d_free); 163 } 164 165 /** 166 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups 167 * @dentry: the target dentry 168 * After this call, in-progress rcu-walk path lookup will fail. This 169 * should be called after unhashing, and after changing d_inode (if 170 * the dentry has not already been unhashed). 171 */ 172 static inline void dentry_rcuwalk_barrier(struct dentry *dentry) 173 { 174 assert_spin_locked(&dentry->d_lock); 175 /* Go through a barrier */ 176 write_seqcount_barrier(&dentry->d_seq); 177 } 178 179 /* 180 * Release the dentry's inode, using the filesystem 181 * d_iput() operation if defined. Dentry has no refcount 182 * and is unhashed. 183 */ 184 static void dentry_iput(struct dentry * dentry) 185 __releases(dentry->d_lock) 186 __releases(dentry->d_inode->i_lock) 187 { 188 struct inode *inode = dentry->d_inode; 189 if (inode) { 190 dentry->d_inode = NULL; 191 list_del_init(&dentry->d_alias); 192 spin_unlock(&dentry->d_lock); 193 spin_unlock(&inode->i_lock); 194 if (!inode->i_nlink) 195 fsnotify_inoderemove(inode); 196 if (dentry->d_op && dentry->d_op->d_iput) 197 dentry->d_op->d_iput(dentry, inode); 198 else 199 iput(inode); 200 } else { 201 spin_unlock(&dentry->d_lock); 202 } 203 } 204 205 /* 206 * Release the dentry's inode, using the filesystem 207 * d_iput() operation if defined. dentry remains in-use. 208 */ 209 static void dentry_unlink_inode(struct dentry * dentry) 210 __releases(dentry->d_lock) 211 __releases(dentry->d_inode->i_lock) 212 { 213 struct inode *inode = dentry->d_inode; 214 dentry->d_inode = NULL; 215 list_del_init(&dentry->d_alias); 216 dentry_rcuwalk_barrier(dentry); 217 spin_unlock(&dentry->d_lock); 218 spin_unlock(&inode->i_lock); 219 if (!inode->i_nlink) 220 fsnotify_inoderemove(inode); 221 if (dentry->d_op && dentry->d_op->d_iput) 222 dentry->d_op->d_iput(dentry, inode); 223 else 224 iput(inode); 225 } 226 227 /* 228 * dentry_lru_(add|del|move_tail) must be called with d_lock held. 229 */ 230 static void dentry_lru_add(struct dentry *dentry) 231 { 232 if (list_empty(&dentry->d_lru)) { 233 spin_lock(&dcache_lru_lock); 234 list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru); 235 dentry->d_sb->s_nr_dentry_unused++; 236 dentry_stat.nr_unused++; 237 spin_unlock(&dcache_lru_lock); 238 } 239 } 240 241 static void __dentry_lru_del(struct dentry *dentry) 242 { 243 list_del_init(&dentry->d_lru); 244 dentry->d_sb->s_nr_dentry_unused--; 245 dentry_stat.nr_unused--; 246 } 247 248 static void dentry_lru_del(struct dentry *dentry) 249 { 250 if (!list_empty(&dentry->d_lru)) { 251 spin_lock(&dcache_lru_lock); 252 __dentry_lru_del(dentry); 253 spin_unlock(&dcache_lru_lock); 254 } 255 } 256 257 static void dentry_lru_move_tail(struct dentry *dentry) 258 { 259 spin_lock(&dcache_lru_lock); 260 if (list_empty(&dentry->d_lru)) { 261 list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru); 262 dentry->d_sb->s_nr_dentry_unused++; 263 dentry_stat.nr_unused++; 264 } else { 265 list_move_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru); 266 } 267 spin_unlock(&dcache_lru_lock); 268 } 269 270 /** 271 * d_kill - kill dentry and return parent 272 * @dentry: dentry to kill 273 * @parent: parent dentry 274 * 275 * The dentry must already be unhashed and removed from the LRU. 276 * 277 * If this is the root of the dentry tree, return NULL. 278 * 279 * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by 280 * d_kill. 281 */ 282 static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent) 283 __releases(dentry->d_lock) 284 __releases(parent->d_lock) 285 __releases(dentry->d_inode->i_lock) 286 { 287 list_del(&dentry->d_u.d_child); 288 /* 289 * Inform try_to_ascend() that we are no longer attached to the 290 * dentry tree 291 */ 292 dentry->d_flags |= DCACHE_DISCONNECTED; 293 if (parent) 294 spin_unlock(&parent->d_lock); 295 dentry_iput(dentry); 296 /* 297 * dentry_iput drops the locks, at which point nobody (except 298 * transient RCU lookups) can reach this dentry. 299 */ 300 d_free(dentry); 301 return parent; 302 } 303 304 /* 305 * Unhash a dentry without inserting an RCU walk barrier or checking that 306 * dentry->d_lock is locked. The caller must take care of that, if 307 * appropriate. 308 */ 309 static void __d_shrink(struct dentry *dentry) 310 { 311 if (!d_unhashed(dentry)) { 312 struct hlist_bl_head *b; 313 if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED)) 314 b = &dentry->d_sb->s_anon; 315 else 316 b = d_hash(dentry->d_parent, dentry->d_name.hash); 317 318 hlist_bl_lock(b); 319 __hlist_bl_del(&dentry->d_hash); 320 dentry->d_hash.pprev = NULL; 321 hlist_bl_unlock(b); 322 } 323 } 324 325 /** 326 * d_drop - drop a dentry 327 * @dentry: dentry to drop 328 * 329 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't 330 * be found through a VFS lookup any more. Note that this is different from 331 * deleting the dentry - d_delete will try to mark the dentry negative if 332 * possible, giving a successful _negative_ lookup, while d_drop will 333 * just make the cache lookup fail. 334 * 335 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some 336 * reason (NFS timeouts or autofs deletes). 337 * 338 * __d_drop requires dentry->d_lock. 339 */ 340 void __d_drop(struct dentry *dentry) 341 { 342 if (!d_unhashed(dentry)) { 343 __d_shrink(dentry); 344 dentry_rcuwalk_barrier(dentry); 345 } 346 } 347 EXPORT_SYMBOL(__d_drop); 348 349 void d_drop(struct dentry *dentry) 350 { 351 spin_lock(&dentry->d_lock); 352 __d_drop(dentry); 353 spin_unlock(&dentry->d_lock); 354 } 355 EXPORT_SYMBOL(d_drop); 356 357 /* 358 * d_clear_need_lookup - drop a dentry from cache and clear the need lookup flag 359 * @dentry: dentry to drop 360 * 361 * This is called when we do a lookup on a placeholder dentry that needed to be 362 * looked up. The dentry should have been hashed in order for it to be found by 363 * the lookup code, but now needs to be unhashed while we do the actual lookup 364 * and clear the DCACHE_NEED_LOOKUP flag. 365 */ 366 void d_clear_need_lookup(struct dentry *dentry) 367 { 368 spin_lock(&dentry->d_lock); 369 __d_drop(dentry); 370 dentry->d_flags &= ~DCACHE_NEED_LOOKUP; 371 spin_unlock(&dentry->d_lock); 372 } 373 EXPORT_SYMBOL(d_clear_need_lookup); 374 375 /* 376 * Finish off a dentry we've decided to kill. 377 * dentry->d_lock must be held, returns with it unlocked. 378 * If ref is non-zero, then decrement the refcount too. 379 * Returns dentry requiring refcount drop, or NULL if we're done. 380 */ 381 static inline struct dentry *dentry_kill(struct dentry *dentry, int ref) 382 __releases(dentry->d_lock) 383 { 384 struct inode *inode; 385 struct dentry *parent; 386 387 inode = dentry->d_inode; 388 if (inode && !spin_trylock(&inode->i_lock)) { 389 relock: 390 spin_unlock(&dentry->d_lock); 391 cpu_relax(); 392 return dentry; /* try again with same dentry */ 393 } 394 if (IS_ROOT(dentry)) 395 parent = NULL; 396 else 397 parent = dentry->d_parent; 398 if (parent && !spin_trylock(&parent->d_lock)) { 399 if (inode) 400 spin_unlock(&inode->i_lock); 401 goto relock; 402 } 403 404 if (ref) 405 dentry->d_count--; 406 /* if dentry was on the d_lru list delete it from there */ 407 dentry_lru_del(dentry); 408 /* if it was on the hash then remove it */ 409 __d_drop(dentry); 410 return d_kill(dentry, parent); 411 } 412 413 /* 414 * This is dput 415 * 416 * This is complicated by the fact that we do not want to put 417 * dentries that are no longer on any hash chain on the unused 418 * list: we'd much rather just get rid of them immediately. 419 * 420 * However, that implies that we have to traverse the dentry 421 * tree upwards to the parents which might _also_ now be 422 * scheduled for deletion (it may have been only waiting for 423 * its last child to go away). 424 * 425 * This tail recursion is done by hand as we don't want to depend 426 * on the compiler to always get this right (gcc generally doesn't). 427 * Real recursion would eat up our stack space. 428 */ 429 430 /* 431 * dput - release a dentry 432 * @dentry: dentry to release 433 * 434 * Release a dentry. This will drop the usage count and if appropriate 435 * call the dentry unlink method as well as removing it from the queues and 436 * releasing its resources. If the parent dentries were scheduled for release 437 * they too may now get deleted. 438 */ 439 void dput(struct dentry *dentry) 440 { 441 if (!dentry) 442 return; 443 444 repeat: 445 if (dentry->d_count == 1) 446 might_sleep(); 447 spin_lock(&dentry->d_lock); 448 BUG_ON(!dentry->d_count); 449 if (dentry->d_count > 1) { 450 dentry->d_count--; 451 spin_unlock(&dentry->d_lock); 452 return; 453 } 454 455 if (dentry->d_flags & DCACHE_OP_DELETE) { 456 if (dentry->d_op->d_delete(dentry)) 457 goto kill_it; 458 } 459 460 /* Unreachable? Get rid of it */ 461 if (d_unhashed(dentry)) 462 goto kill_it; 463 464 /* 465 * If this dentry needs lookup, don't set the referenced flag so that it 466 * is more likely to be cleaned up by the dcache shrinker in case of 467 * memory pressure. 468 */ 469 if (!d_need_lookup(dentry)) 470 dentry->d_flags |= DCACHE_REFERENCED; 471 dentry_lru_add(dentry); 472 473 dentry->d_count--; 474 spin_unlock(&dentry->d_lock); 475 return; 476 477 kill_it: 478 dentry = dentry_kill(dentry, 1); 479 if (dentry) 480 goto repeat; 481 } 482 EXPORT_SYMBOL(dput); 483 484 /** 485 * d_invalidate - invalidate a dentry 486 * @dentry: dentry to invalidate 487 * 488 * Try to invalidate the dentry if it turns out to be 489 * possible. If there are other dentries that can be 490 * reached through this one we can't delete it and we 491 * return -EBUSY. On success we return 0. 492 * 493 * no dcache lock. 494 */ 495 496 int d_invalidate(struct dentry * dentry) 497 { 498 /* 499 * If it's already been dropped, return OK. 500 */ 501 spin_lock(&dentry->d_lock); 502 if (d_unhashed(dentry)) { 503 spin_unlock(&dentry->d_lock); 504 return 0; 505 } 506 /* 507 * Check whether to do a partial shrink_dcache 508 * to get rid of unused child entries. 509 */ 510 if (!list_empty(&dentry->d_subdirs)) { 511 spin_unlock(&dentry->d_lock); 512 shrink_dcache_parent(dentry); 513 spin_lock(&dentry->d_lock); 514 } 515 516 /* 517 * Somebody else still using it? 518 * 519 * If it's a directory, we can't drop it 520 * for fear of somebody re-populating it 521 * with children (even though dropping it 522 * would make it unreachable from the root, 523 * we might still populate it if it was a 524 * working directory or similar). 525 */ 526 if (dentry->d_count > 1) { 527 if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) { 528 spin_unlock(&dentry->d_lock); 529 return -EBUSY; 530 } 531 } 532 533 __d_drop(dentry); 534 spin_unlock(&dentry->d_lock); 535 return 0; 536 } 537 EXPORT_SYMBOL(d_invalidate); 538 539 /* This must be called with d_lock held */ 540 static inline void __dget_dlock(struct dentry *dentry) 541 { 542 dentry->d_count++; 543 } 544 545 static inline void __dget(struct dentry *dentry) 546 { 547 spin_lock(&dentry->d_lock); 548 __dget_dlock(dentry); 549 spin_unlock(&dentry->d_lock); 550 } 551 552 struct dentry *dget_parent(struct dentry *dentry) 553 { 554 struct dentry *ret; 555 556 repeat: 557 /* 558 * Don't need rcu_dereference because we re-check it was correct under 559 * the lock. 560 */ 561 rcu_read_lock(); 562 ret = dentry->d_parent; 563 spin_lock(&ret->d_lock); 564 if (unlikely(ret != dentry->d_parent)) { 565 spin_unlock(&ret->d_lock); 566 rcu_read_unlock(); 567 goto repeat; 568 } 569 rcu_read_unlock(); 570 BUG_ON(!ret->d_count); 571 ret->d_count++; 572 spin_unlock(&ret->d_lock); 573 return ret; 574 } 575 EXPORT_SYMBOL(dget_parent); 576 577 /** 578 * d_find_alias - grab a hashed alias of inode 579 * @inode: inode in question 580 * @want_discon: flag, used by d_splice_alias, to request 581 * that only a DISCONNECTED alias be returned. 582 * 583 * If inode has a hashed alias, or is a directory and has any alias, 584 * acquire the reference to alias and return it. Otherwise return NULL. 585 * Notice that if inode is a directory there can be only one alias and 586 * it can be unhashed only if it has no children, or if it is the root 587 * of a filesystem. 588 * 589 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer 590 * any other hashed alias over that one unless @want_discon is set, 591 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias. 592 */ 593 static struct dentry *__d_find_alias(struct inode *inode, int want_discon) 594 { 595 struct dentry *alias, *discon_alias; 596 597 again: 598 discon_alias = NULL; 599 list_for_each_entry(alias, &inode->i_dentry, d_alias) { 600 spin_lock(&alias->d_lock); 601 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) { 602 if (IS_ROOT(alias) && 603 (alias->d_flags & DCACHE_DISCONNECTED)) { 604 discon_alias = alias; 605 } else if (!want_discon) { 606 __dget_dlock(alias); 607 spin_unlock(&alias->d_lock); 608 return alias; 609 } 610 } 611 spin_unlock(&alias->d_lock); 612 } 613 if (discon_alias) { 614 alias = discon_alias; 615 spin_lock(&alias->d_lock); 616 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) { 617 if (IS_ROOT(alias) && 618 (alias->d_flags & DCACHE_DISCONNECTED)) { 619 __dget_dlock(alias); 620 spin_unlock(&alias->d_lock); 621 return alias; 622 } 623 } 624 spin_unlock(&alias->d_lock); 625 goto again; 626 } 627 return NULL; 628 } 629 630 struct dentry *d_find_alias(struct inode *inode) 631 { 632 struct dentry *de = NULL; 633 634 if (!list_empty(&inode->i_dentry)) { 635 spin_lock(&inode->i_lock); 636 de = __d_find_alias(inode, 0); 637 spin_unlock(&inode->i_lock); 638 } 639 return de; 640 } 641 EXPORT_SYMBOL(d_find_alias); 642 643 /* 644 * Try to kill dentries associated with this inode. 645 * WARNING: you must own a reference to inode. 646 */ 647 void d_prune_aliases(struct inode *inode) 648 { 649 struct dentry *dentry; 650 restart: 651 spin_lock(&inode->i_lock); 652 list_for_each_entry(dentry, &inode->i_dentry, d_alias) { 653 spin_lock(&dentry->d_lock); 654 if (!dentry->d_count) { 655 __dget_dlock(dentry); 656 __d_drop(dentry); 657 spin_unlock(&dentry->d_lock); 658 spin_unlock(&inode->i_lock); 659 dput(dentry); 660 goto restart; 661 } 662 spin_unlock(&dentry->d_lock); 663 } 664 spin_unlock(&inode->i_lock); 665 } 666 EXPORT_SYMBOL(d_prune_aliases); 667 668 /* 669 * Try to throw away a dentry - free the inode, dput the parent. 670 * Requires dentry->d_lock is held, and dentry->d_count == 0. 671 * Releases dentry->d_lock. 672 * 673 * This may fail if locks cannot be acquired no problem, just try again. 674 */ 675 static void try_prune_one_dentry(struct dentry *dentry) 676 __releases(dentry->d_lock) 677 { 678 struct dentry *parent; 679 680 parent = dentry_kill(dentry, 0); 681 /* 682 * If dentry_kill returns NULL, we have nothing more to do. 683 * if it returns the same dentry, trylocks failed. In either 684 * case, just loop again. 685 * 686 * Otherwise, we need to prune ancestors too. This is necessary 687 * to prevent quadratic behavior of shrink_dcache_parent(), but 688 * is also expected to be beneficial in reducing dentry cache 689 * fragmentation. 690 */ 691 if (!parent) 692 return; 693 if (parent == dentry) 694 return; 695 696 /* Prune ancestors. */ 697 dentry = parent; 698 while (dentry) { 699 spin_lock(&dentry->d_lock); 700 if (dentry->d_count > 1) { 701 dentry->d_count--; 702 spin_unlock(&dentry->d_lock); 703 return; 704 } 705 dentry = dentry_kill(dentry, 1); 706 } 707 } 708 709 static void shrink_dentry_list(struct list_head *list) 710 { 711 struct dentry *dentry; 712 713 rcu_read_lock(); 714 for (;;) { 715 dentry = list_entry_rcu(list->prev, struct dentry, d_lru); 716 if (&dentry->d_lru == list) 717 break; /* empty */ 718 spin_lock(&dentry->d_lock); 719 if (dentry != list_entry(list->prev, struct dentry, d_lru)) { 720 spin_unlock(&dentry->d_lock); 721 continue; 722 } 723 724 /* 725 * We found an inuse dentry which was not removed from 726 * the LRU because of laziness during lookup. Do not free 727 * it - just keep it off the LRU list. 728 */ 729 if (dentry->d_count) { 730 dentry_lru_del(dentry); 731 spin_unlock(&dentry->d_lock); 732 continue; 733 } 734 735 rcu_read_unlock(); 736 737 try_prune_one_dentry(dentry); 738 739 rcu_read_lock(); 740 } 741 rcu_read_unlock(); 742 } 743 744 /** 745 * __shrink_dcache_sb - shrink the dentry LRU on a given superblock 746 * @sb: superblock to shrink dentry LRU. 747 * @count: number of entries to prune 748 * @flags: flags to control the dentry processing 749 * 750 * If flags contains DCACHE_REFERENCED reference dentries will not be pruned. 751 */ 752 static void __shrink_dcache_sb(struct super_block *sb, int count, int flags) 753 { 754 struct dentry *dentry; 755 LIST_HEAD(referenced); 756 LIST_HEAD(tmp); 757 758 relock: 759 spin_lock(&dcache_lru_lock); 760 while (!list_empty(&sb->s_dentry_lru)) { 761 dentry = list_entry(sb->s_dentry_lru.prev, 762 struct dentry, d_lru); 763 BUG_ON(dentry->d_sb != sb); 764 765 if (!spin_trylock(&dentry->d_lock)) { 766 spin_unlock(&dcache_lru_lock); 767 cpu_relax(); 768 goto relock; 769 } 770 771 /* 772 * If we are honouring the DCACHE_REFERENCED flag and the 773 * dentry has this flag set, don't free it. Clear the flag 774 * and put it back on the LRU. 775 */ 776 if (flags & DCACHE_REFERENCED && 777 dentry->d_flags & DCACHE_REFERENCED) { 778 dentry->d_flags &= ~DCACHE_REFERENCED; 779 list_move(&dentry->d_lru, &referenced); 780 spin_unlock(&dentry->d_lock); 781 } else { 782 list_move_tail(&dentry->d_lru, &tmp); 783 spin_unlock(&dentry->d_lock); 784 if (!--count) 785 break; 786 } 787 cond_resched_lock(&dcache_lru_lock); 788 } 789 if (!list_empty(&referenced)) 790 list_splice(&referenced, &sb->s_dentry_lru); 791 spin_unlock(&dcache_lru_lock); 792 793 shrink_dentry_list(&tmp); 794 } 795 796 /** 797 * prune_dcache_sb - shrink the dcache 798 * @sb: superblock 799 * @nr_to_scan: number of entries to try to free 800 * 801 * Attempt to shrink the superblock dcache LRU by @nr_to_scan entries. This is 802 * done when we need more memory an called from the superblock shrinker 803 * function. 804 * 805 * This function may fail to free any resources if all the dentries are in 806 * use. 807 */ 808 void prune_dcache_sb(struct super_block *sb, int nr_to_scan) 809 { 810 __shrink_dcache_sb(sb, nr_to_scan, DCACHE_REFERENCED); 811 } 812 813 /** 814 * shrink_dcache_sb - shrink dcache for a superblock 815 * @sb: superblock 816 * 817 * Shrink the dcache for the specified super block. This is used to free 818 * the dcache before unmounting a file system. 819 */ 820 void shrink_dcache_sb(struct super_block *sb) 821 { 822 LIST_HEAD(tmp); 823 824 spin_lock(&dcache_lru_lock); 825 while (!list_empty(&sb->s_dentry_lru)) { 826 list_splice_init(&sb->s_dentry_lru, &tmp); 827 spin_unlock(&dcache_lru_lock); 828 shrink_dentry_list(&tmp); 829 spin_lock(&dcache_lru_lock); 830 } 831 spin_unlock(&dcache_lru_lock); 832 } 833 EXPORT_SYMBOL(shrink_dcache_sb); 834 835 /* 836 * destroy a single subtree of dentries for unmount 837 * - see the comments on shrink_dcache_for_umount() for a description of the 838 * locking 839 */ 840 static void shrink_dcache_for_umount_subtree(struct dentry *dentry) 841 { 842 struct dentry *parent; 843 844 BUG_ON(!IS_ROOT(dentry)); 845 846 for (;;) { 847 /* descend to the first leaf in the current subtree */ 848 while (!list_empty(&dentry->d_subdirs)) 849 dentry = list_entry(dentry->d_subdirs.next, 850 struct dentry, d_u.d_child); 851 852 /* consume the dentries from this leaf up through its parents 853 * until we find one with children or run out altogether */ 854 do { 855 struct inode *inode; 856 857 /* detach from the system */ 858 dentry_lru_del(dentry); 859 __d_shrink(dentry); 860 861 if (dentry->d_count != 0) { 862 printk(KERN_ERR 863 "BUG: Dentry %p{i=%lx,n=%s}" 864 " still in use (%d)" 865 " [unmount of %s %s]\n", 866 dentry, 867 dentry->d_inode ? 868 dentry->d_inode->i_ino : 0UL, 869 dentry->d_name.name, 870 dentry->d_count, 871 dentry->d_sb->s_type->name, 872 dentry->d_sb->s_id); 873 BUG(); 874 } 875 876 if (IS_ROOT(dentry)) { 877 parent = NULL; 878 list_del(&dentry->d_u.d_child); 879 } else { 880 parent = dentry->d_parent; 881 parent->d_count--; 882 list_del(&dentry->d_u.d_child); 883 } 884 885 inode = dentry->d_inode; 886 if (inode) { 887 dentry->d_inode = NULL; 888 list_del_init(&dentry->d_alias); 889 if (dentry->d_op && dentry->d_op->d_iput) 890 dentry->d_op->d_iput(dentry, inode); 891 else 892 iput(inode); 893 } 894 895 d_free(dentry); 896 897 /* finished when we fall off the top of the tree, 898 * otherwise we ascend to the parent and move to the 899 * next sibling if there is one */ 900 if (!parent) 901 return; 902 dentry = parent; 903 } while (list_empty(&dentry->d_subdirs)); 904 905 dentry = list_entry(dentry->d_subdirs.next, 906 struct dentry, d_u.d_child); 907 } 908 } 909 910 /* 911 * destroy the dentries attached to a superblock on unmounting 912 * - we don't need to use dentry->d_lock because: 913 * - the superblock is detached from all mountings and open files, so the 914 * dentry trees will not be rearranged by the VFS 915 * - s_umount is write-locked, so the memory pressure shrinker will ignore 916 * any dentries belonging to this superblock that it comes across 917 * - the filesystem itself is no longer permitted to rearrange the dentries 918 * in this superblock 919 */ 920 void shrink_dcache_for_umount(struct super_block *sb) 921 { 922 struct dentry *dentry; 923 924 if (down_read_trylock(&sb->s_umount)) 925 BUG(); 926 927 dentry = sb->s_root; 928 sb->s_root = NULL; 929 dentry->d_count--; 930 shrink_dcache_for_umount_subtree(dentry); 931 932 while (!hlist_bl_empty(&sb->s_anon)) { 933 dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash); 934 shrink_dcache_for_umount_subtree(dentry); 935 } 936 } 937 938 /* 939 * This tries to ascend one level of parenthood, but 940 * we can race with renaming, so we need to re-check 941 * the parenthood after dropping the lock and check 942 * that the sequence number still matches. 943 */ 944 static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq) 945 { 946 struct dentry *new = old->d_parent; 947 948 rcu_read_lock(); 949 spin_unlock(&old->d_lock); 950 spin_lock(&new->d_lock); 951 952 /* 953 * might go back up the wrong parent if we have had a rename 954 * or deletion 955 */ 956 if (new != old->d_parent || 957 (old->d_flags & DCACHE_DISCONNECTED) || 958 (!locked && read_seqretry(&rename_lock, seq))) { 959 spin_unlock(&new->d_lock); 960 new = NULL; 961 } 962 rcu_read_unlock(); 963 return new; 964 } 965 966 967 /* 968 * Search for at least 1 mount point in the dentry's subdirs. 969 * We descend to the next level whenever the d_subdirs 970 * list is non-empty and continue searching. 971 */ 972 973 /** 974 * have_submounts - check for mounts over a dentry 975 * @parent: dentry to check. 976 * 977 * Return true if the parent or its subdirectories contain 978 * a mount point 979 */ 980 int have_submounts(struct dentry *parent) 981 { 982 struct dentry *this_parent; 983 struct list_head *next; 984 unsigned seq; 985 int locked = 0; 986 987 seq = read_seqbegin(&rename_lock); 988 again: 989 this_parent = parent; 990 991 if (d_mountpoint(parent)) 992 goto positive; 993 spin_lock(&this_parent->d_lock); 994 repeat: 995 next = this_parent->d_subdirs.next; 996 resume: 997 while (next != &this_parent->d_subdirs) { 998 struct list_head *tmp = next; 999 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); 1000 next = tmp->next; 1001 1002 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); 1003 /* Have we found a mount point ? */ 1004 if (d_mountpoint(dentry)) { 1005 spin_unlock(&dentry->d_lock); 1006 spin_unlock(&this_parent->d_lock); 1007 goto positive; 1008 } 1009 if (!list_empty(&dentry->d_subdirs)) { 1010 spin_unlock(&this_parent->d_lock); 1011 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_); 1012 this_parent = dentry; 1013 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); 1014 goto repeat; 1015 } 1016 spin_unlock(&dentry->d_lock); 1017 } 1018 /* 1019 * All done at this level ... ascend and resume the search. 1020 */ 1021 if (this_parent != parent) { 1022 struct dentry *child = this_parent; 1023 this_parent = try_to_ascend(this_parent, locked, seq); 1024 if (!this_parent) 1025 goto rename_retry; 1026 next = child->d_u.d_child.next; 1027 goto resume; 1028 } 1029 spin_unlock(&this_parent->d_lock); 1030 if (!locked && read_seqretry(&rename_lock, seq)) 1031 goto rename_retry; 1032 if (locked) 1033 write_sequnlock(&rename_lock); 1034 return 0; /* No mount points found in tree */ 1035 positive: 1036 if (!locked && read_seqretry(&rename_lock, seq)) 1037 goto rename_retry; 1038 if (locked) 1039 write_sequnlock(&rename_lock); 1040 return 1; 1041 1042 rename_retry: 1043 locked = 1; 1044 write_seqlock(&rename_lock); 1045 goto again; 1046 } 1047 EXPORT_SYMBOL(have_submounts); 1048 1049 /* 1050 * Search the dentry child list for the specified parent, 1051 * and move any unused dentries to the end of the unused 1052 * list for prune_dcache(). We descend to the next level 1053 * whenever the d_subdirs list is non-empty and continue 1054 * searching. 1055 * 1056 * It returns zero iff there are no unused children, 1057 * otherwise it returns the number of children moved to 1058 * the end of the unused list. This may not be the total 1059 * number of unused children, because select_parent can 1060 * drop the lock and return early due to latency 1061 * constraints. 1062 */ 1063 static int select_parent(struct dentry * parent) 1064 { 1065 struct dentry *this_parent; 1066 struct list_head *next; 1067 unsigned seq; 1068 int found = 0; 1069 int locked = 0; 1070 1071 seq = read_seqbegin(&rename_lock); 1072 again: 1073 this_parent = parent; 1074 spin_lock(&this_parent->d_lock); 1075 repeat: 1076 next = this_parent->d_subdirs.next; 1077 resume: 1078 while (next != &this_parent->d_subdirs) { 1079 struct list_head *tmp = next; 1080 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); 1081 next = tmp->next; 1082 1083 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); 1084 1085 /* 1086 * move only zero ref count dentries to the end 1087 * of the unused list for prune_dcache 1088 */ 1089 if (!dentry->d_count) { 1090 dentry_lru_move_tail(dentry); 1091 found++; 1092 } else { 1093 dentry_lru_del(dentry); 1094 } 1095 1096 /* 1097 * We can return to the caller if we have found some (this 1098 * ensures forward progress). We'll be coming back to find 1099 * the rest. 1100 */ 1101 if (found && need_resched()) { 1102 spin_unlock(&dentry->d_lock); 1103 goto out; 1104 } 1105 1106 /* 1107 * Descend a level if the d_subdirs list is non-empty. 1108 */ 1109 if (!list_empty(&dentry->d_subdirs)) { 1110 spin_unlock(&this_parent->d_lock); 1111 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_); 1112 this_parent = dentry; 1113 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); 1114 goto repeat; 1115 } 1116 1117 spin_unlock(&dentry->d_lock); 1118 } 1119 /* 1120 * All done at this level ... ascend and resume the search. 1121 */ 1122 if (this_parent != parent) { 1123 struct dentry *child = this_parent; 1124 this_parent = try_to_ascend(this_parent, locked, seq); 1125 if (!this_parent) 1126 goto rename_retry; 1127 next = child->d_u.d_child.next; 1128 goto resume; 1129 } 1130 out: 1131 spin_unlock(&this_parent->d_lock); 1132 if (!locked && read_seqretry(&rename_lock, seq)) 1133 goto rename_retry; 1134 if (locked) 1135 write_sequnlock(&rename_lock); 1136 return found; 1137 1138 rename_retry: 1139 if (found) 1140 return found; 1141 locked = 1; 1142 write_seqlock(&rename_lock); 1143 goto again; 1144 } 1145 1146 /** 1147 * shrink_dcache_parent - prune dcache 1148 * @parent: parent of entries to prune 1149 * 1150 * Prune the dcache to remove unused children of the parent dentry. 1151 */ 1152 1153 void shrink_dcache_parent(struct dentry * parent) 1154 { 1155 struct super_block *sb = parent->d_sb; 1156 int found; 1157 1158 while ((found = select_parent(parent)) != 0) 1159 __shrink_dcache_sb(sb, found, 0); 1160 } 1161 EXPORT_SYMBOL(shrink_dcache_parent); 1162 1163 /** 1164 * __d_alloc - allocate a dcache entry 1165 * @sb: filesystem it will belong to 1166 * @name: qstr of the name 1167 * 1168 * Allocates a dentry. It returns %NULL if there is insufficient memory 1169 * available. On a success the dentry is returned. The name passed in is 1170 * copied and the copy passed in may be reused after this call. 1171 */ 1172 1173 struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name) 1174 { 1175 struct dentry *dentry; 1176 char *dname; 1177 1178 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL); 1179 if (!dentry) 1180 return NULL; 1181 1182 if (name->len > DNAME_INLINE_LEN-1) { 1183 dname = kmalloc(name->len + 1, GFP_KERNEL); 1184 if (!dname) { 1185 kmem_cache_free(dentry_cache, dentry); 1186 return NULL; 1187 } 1188 } else { 1189 dname = dentry->d_iname; 1190 } 1191 dentry->d_name.name = dname; 1192 1193 dentry->d_name.len = name->len; 1194 dentry->d_name.hash = name->hash; 1195 memcpy(dname, name->name, name->len); 1196 dname[name->len] = 0; 1197 1198 dentry->d_count = 1; 1199 dentry->d_flags = 0; 1200 spin_lock_init(&dentry->d_lock); 1201 seqcount_init(&dentry->d_seq); 1202 dentry->d_inode = NULL; 1203 dentry->d_parent = dentry; 1204 dentry->d_sb = sb; 1205 dentry->d_op = NULL; 1206 dentry->d_fsdata = NULL; 1207 INIT_HLIST_BL_NODE(&dentry->d_hash); 1208 INIT_LIST_HEAD(&dentry->d_lru); 1209 INIT_LIST_HEAD(&dentry->d_subdirs); 1210 INIT_LIST_HEAD(&dentry->d_alias); 1211 INIT_LIST_HEAD(&dentry->d_u.d_child); 1212 d_set_d_op(dentry, dentry->d_sb->s_d_op); 1213 1214 this_cpu_inc(nr_dentry); 1215 1216 return dentry; 1217 } 1218 1219 /** 1220 * d_alloc - allocate a dcache entry 1221 * @parent: parent of entry to allocate 1222 * @name: qstr of the name 1223 * 1224 * Allocates a dentry. It returns %NULL if there is insufficient memory 1225 * available. On a success the dentry is returned. The name passed in is 1226 * copied and the copy passed in may be reused after this call. 1227 */ 1228 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name) 1229 { 1230 struct dentry *dentry = __d_alloc(parent->d_sb, name); 1231 if (!dentry) 1232 return NULL; 1233 1234 spin_lock(&parent->d_lock); 1235 /* 1236 * don't need child lock because it is not subject 1237 * to concurrency here 1238 */ 1239 __dget_dlock(parent); 1240 dentry->d_parent = parent; 1241 list_add(&dentry->d_u.d_child, &parent->d_subdirs); 1242 spin_unlock(&parent->d_lock); 1243 1244 return dentry; 1245 } 1246 EXPORT_SYMBOL(d_alloc); 1247 1248 struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name) 1249 { 1250 struct dentry *dentry = __d_alloc(sb, name); 1251 if (dentry) 1252 dentry->d_flags |= DCACHE_DISCONNECTED; 1253 return dentry; 1254 } 1255 EXPORT_SYMBOL(d_alloc_pseudo); 1256 1257 struct dentry *d_alloc_name(struct dentry *parent, const char *name) 1258 { 1259 struct qstr q; 1260 1261 q.name = name; 1262 q.len = strlen(name); 1263 q.hash = full_name_hash(q.name, q.len); 1264 return d_alloc(parent, &q); 1265 } 1266 EXPORT_SYMBOL(d_alloc_name); 1267 1268 void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op) 1269 { 1270 WARN_ON_ONCE(dentry->d_op); 1271 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH | 1272 DCACHE_OP_COMPARE | 1273 DCACHE_OP_REVALIDATE | 1274 DCACHE_OP_DELETE )); 1275 dentry->d_op = op; 1276 if (!op) 1277 return; 1278 if (op->d_hash) 1279 dentry->d_flags |= DCACHE_OP_HASH; 1280 if (op->d_compare) 1281 dentry->d_flags |= DCACHE_OP_COMPARE; 1282 if (op->d_revalidate) 1283 dentry->d_flags |= DCACHE_OP_REVALIDATE; 1284 if (op->d_delete) 1285 dentry->d_flags |= DCACHE_OP_DELETE; 1286 1287 } 1288 EXPORT_SYMBOL(d_set_d_op); 1289 1290 static void __d_instantiate(struct dentry *dentry, struct inode *inode) 1291 { 1292 spin_lock(&dentry->d_lock); 1293 if (inode) { 1294 if (unlikely(IS_AUTOMOUNT(inode))) 1295 dentry->d_flags |= DCACHE_NEED_AUTOMOUNT; 1296 list_add(&dentry->d_alias, &inode->i_dentry); 1297 } 1298 dentry->d_inode = inode; 1299 dentry_rcuwalk_barrier(dentry); 1300 spin_unlock(&dentry->d_lock); 1301 fsnotify_d_instantiate(dentry, inode); 1302 } 1303 1304 /** 1305 * d_instantiate - fill in inode information for a dentry 1306 * @entry: dentry to complete 1307 * @inode: inode to attach to this dentry 1308 * 1309 * Fill in inode information in the entry. 1310 * 1311 * This turns negative dentries into productive full members 1312 * of society. 1313 * 1314 * NOTE! This assumes that the inode count has been incremented 1315 * (or otherwise set) by the caller to indicate that it is now 1316 * in use by the dcache. 1317 */ 1318 1319 void d_instantiate(struct dentry *entry, struct inode * inode) 1320 { 1321 BUG_ON(!list_empty(&entry->d_alias)); 1322 if (inode) 1323 spin_lock(&inode->i_lock); 1324 __d_instantiate(entry, inode); 1325 if (inode) 1326 spin_unlock(&inode->i_lock); 1327 security_d_instantiate(entry, inode); 1328 } 1329 EXPORT_SYMBOL(d_instantiate); 1330 1331 /** 1332 * d_instantiate_unique - instantiate a non-aliased dentry 1333 * @entry: dentry to instantiate 1334 * @inode: inode to attach to this dentry 1335 * 1336 * Fill in inode information in the entry. On success, it returns NULL. 1337 * If an unhashed alias of "entry" already exists, then we return the 1338 * aliased dentry instead and drop one reference to inode. 1339 * 1340 * Note that in order to avoid conflicts with rename() etc, the caller 1341 * had better be holding the parent directory semaphore. 1342 * 1343 * This also assumes that the inode count has been incremented 1344 * (or otherwise set) by the caller to indicate that it is now 1345 * in use by the dcache. 1346 */ 1347 static struct dentry *__d_instantiate_unique(struct dentry *entry, 1348 struct inode *inode) 1349 { 1350 struct dentry *alias; 1351 int len = entry->d_name.len; 1352 const char *name = entry->d_name.name; 1353 unsigned int hash = entry->d_name.hash; 1354 1355 if (!inode) { 1356 __d_instantiate(entry, NULL); 1357 return NULL; 1358 } 1359 1360 list_for_each_entry(alias, &inode->i_dentry, d_alias) { 1361 struct qstr *qstr = &alias->d_name; 1362 1363 /* 1364 * Don't need alias->d_lock here, because aliases with 1365 * d_parent == entry->d_parent are not subject to name or 1366 * parent changes, because the parent inode i_mutex is held. 1367 */ 1368 if (qstr->hash != hash) 1369 continue; 1370 if (alias->d_parent != entry->d_parent) 1371 continue; 1372 if (dentry_cmp(qstr->name, qstr->len, name, len)) 1373 continue; 1374 __dget(alias); 1375 return alias; 1376 } 1377 1378 __d_instantiate(entry, inode); 1379 return NULL; 1380 } 1381 1382 struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode) 1383 { 1384 struct dentry *result; 1385 1386 BUG_ON(!list_empty(&entry->d_alias)); 1387 1388 if (inode) 1389 spin_lock(&inode->i_lock); 1390 result = __d_instantiate_unique(entry, inode); 1391 if (inode) 1392 spin_unlock(&inode->i_lock); 1393 1394 if (!result) { 1395 security_d_instantiate(entry, inode); 1396 return NULL; 1397 } 1398 1399 BUG_ON(!d_unhashed(result)); 1400 iput(inode); 1401 return result; 1402 } 1403 1404 EXPORT_SYMBOL(d_instantiate_unique); 1405 1406 /** 1407 * d_alloc_root - allocate root dentry 1408 * @root_inode: inode to allocate the root for 1409 * 1410 * Allocate a root ("/") dentry for the inode given. The inode is 1411 * instantiated and returned. %NULL is returned if there is insufficient 1412 * memory or the inode passed is %NULL. 1413 */ 1414 1415 struct dentry * d_alloc_root(struct inode * root_inode) 1416 { 1417 struct dentry *res = NULL; 1418 1419 if (root_inode) { 1420 static const struct qstr name = { .name = "/", .len = 1 }; 1421 1422 res = __d_alloc(root_inode->i_sb, &name); 1423 if (res) 1424 d_instantiate(res, root_inode); 1425 } 1426 return res; 1427 } 1428 EXPORT_SYMBOL(d_alloc_root); 1429 1430 static struct dentry * __d_find_any_alias(struct inode *inode) 1431 { 1432 struct dentry *alias; 1433 1434 if (list_empty(&inode->i_dentry)) 1435 return NULL; 1436 alias = list_first_entry(&inode->i_dentry, struct dentry, d_alias); 1437 __dget(alias); 1438 return alias; 1439 } 1440 1441 static struct dentry * d_find_any_alias(struct inode *inode) 1442 { 1443 struct dentry *de; 1444 1445 spin_lock(&inode->i_lock); 1446 de = __d_find_any_alias(inode); 1447 spin_unlock(&inode->i_lock); 1448 return de; 1449 } 1450 1451 1452 /** 1453 * d_obtain_alias - find or allocate a dentry for a given inode 1454 * @inode: inode to allocate the dentry for 1455 * 1456 * Obtain a dentry for an inode resulting from NFS filehandle conversion or 1457 * similar open by handle operations. The returned dentry may be anonymous, 1458 * or may have a full name (if the inode was already in the cache). 1459 * 1460 * When called on a directory inode, we must ensure that the inode only ever 1461 * has one dentry. If a dentry is found, that is returned instead of 1462 * allocating a new one. 1463 * 1464 * On successful return, the reference to the inode has been transferred 1465 * to the dentry. In case of an error the reference on the inode is released. 1466 * To make it easier to use in export operations a %NULL or IS_ERR inode may 1467 * be passed in and will be the error will be propagate to the return value, 1468 * with a %NULL @inode replaced by ERR_PTR(-ESTALE). 1469 */ 1470 struct dentry *d_obtain_alias(struct inode *inode) 1471 { 1472 static const struct qstr anonstring = { .name = "" }; 1473 struct dentry *tmp; 1474 struct dentry *res; 1475 1476 if (!inode) 1477 return ERR_PTR(-ESTALE); 1478 if (IS_ERR(inode)) 1479 return ERR_CAST(inode); 1480 1481 res = d_find_any_alias(inode); 1482 if (res) 1483 goto out_iput; 1484 1485 tmp = __d_alloc(inode->i_sb, &anonstring); 1486 if (!tmp) { 1487 res = ERR_PTR(-ENOMEM); 1488 goto out_iput; 1489 } 1490 1491 spin_lock(&inode->i_lock); 1492 res = __d_find_any_alias(inode); 1493 if (res) { 1494 spin_unlock(&inode->i_lock); 1495 dput(tmp); 1496 goto out_iput; 1497 } 1498 1499 /* attach a disconnected dentry */ 1500 spin_lock(&tmp->d_lock); 1501 tmp->d_inode = inode; 1502 tmp->d_flags |= DCACHE_DISCONNECTED; 1503 list_add(&tmp->d_alias, &inode->i_dentry); 1504 hlist_bl_lock(&tmp->d_sb->s_anon); 1505 hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon); 1506 hlist_bl_unlock(&tmp->d_sb->s_anon); 1507 spin_unlock(&tmp->d_lock); 1508 spin_unlock(&inode->i_lock); 1509 security_d_instantiate(tmp, inode); 1510 1511 return tmp; 1512 1513 out_iput: 1514 if (res && !IS_ERR(res)) 1515 security_d_instantiate(res, inode); 1516 iput(inode); 1517 return res; 1518 } 1519 EXPORT_SYMBOL(d_obtain_alias); 1520 1521 /** 1522 * d_splice_alias - splice a disconnected dentry into the tree if one exists 1523 * @inode: the inode which may have a disconnected dentry 1524 * @dentry: a negative dentry which we want to point to the inode. 1525 * 1526 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and 1527 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry 1528 * and return it, else simply d_add the inode to the dentry and return NULL. 1529 * 1530 * This is needed in the lookup routine of any filesystem that is exportable 1531 * (via knfsd) so that we can build dcache paths to directories effectively. 1532 * 1533 * If a dentry was found and moved, then it is returned. Otherwise NULL 1534 * is returned. This matches the expected return value of ->lookup. 1535 * 1536 */ 1537 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry) 1538 { 1539 struct dentry *new = NULL; 1540 1541 if (IS_ERR(inode)) 1542 return ERR_CAST(inode); 1543 1544 if (inode && S_ISDIR(inode->i_mode)) { 1545 spin_lock(&inode->i_lock); 1546 new = __d_find_alias(inode, 1); 1547 if (new) { 1548 BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED)); 1549 spin_unlock(&inode->i_lock); 1550 security_d_instantiate(new, inode); 1551 d_move(new, dentry); 1552 iput(inode); 1553 } else { 1554 /* already taking inode->i_lock, so d_add() by hand */ 1555 __d_instantiate(dentry, inode); 1556 spin_unlock(&inode->i_lock); 1557 security_d_instantiate(dentry, inode); 1558 d_rehash(dentry); 1559 } 1560 } else 1561 d_add(dentry, inode); 1562 return new; 1563 } 1564 EXPORT_SYMBOL(d_splice_alias); 1565 1566 /** 1567 * d_add_ci - lookup or allocate new dentry with case-exact name 1568 * @inode: the inode case-insensitive lookup has found 1569 * @dentry: the negative dentry that was passed to the parent's lookup func 1570 * @name: the case-exact name to be associated with the returned dentry 1571 * 1572 * This is to avoid filling the dcache with case-insensitive names to the 1573 * same inode, only the actual correct case is stored in the dcache for 1574 * case-insensitive filesystems. 1575 * 1576 * For a case-insensitive lookup match and if the the case-exact dentry 1577 * already exists in in the dcache, use it and return it. 1578 * 1579 * If no entry exists with the exact case name, allocate new dentry with 1580 * the exact case, and return the spliced entry. 1581 */ 1582 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode, 1583 struct qstr *name) 1584 { 1585 int error; 1586 struct dentry *found; 1587 struct dentry *new; 1588 1589 /* 1590 * First check if a dentry matching the name already exists, 1591 * if not go ahead and create it now. 1592 */ 1593 found = d_hash_and_lookup(dentry->d_parent, name); 1594 if (!found) { 1595 new = d_alloc(dentry->d_parent, name); 1596 if (!new) { 1597 error = -ENOMEM; 1598 goto err_out; 1599 } 1600 1601 found = d_splice_alias(inode, new); 1602 if (found) { 1603 dput(new); 1604 return found; 1605 } 1606 return new; 1607 } 1608 1609 /* 1610 * If a matching dentry exists, and it's not negative use it. 1611 * 1612 * Decrement the reference count to balance the iget() done 1613 * earlier on. 1614 */ 1615 if (found->d_inode) { 1616 if (unlikely(found->d_inode != inode)) { 1617 /* This can't happen because bad inodes are unhashed. */ 1618 BUG_ON(!is_bad_inode(inode)); 1619 BUG_ON(!is_bad_inode(found->d_inode)); 1620 } 1621 iput(inode); 1622 return found; 1623 } 1624 1625 /* 1626 * We are going to instantiate this dentry, unhash it and clear the 1627 * lookup flag so we can do that. 1628 */ 1629 if (unlikely(d_need_lookup(found))) 1630 d_clear_need_lookup(found); 1631 1632 /* 1633 * Negative dentry: instantiate it unless the inode is a directory and 1634 * already has a dentry. 1635 */ 1636 new = d_splice_alias(inode, found); 1637 if (new) { 1638 dput(found); 1639 found = new; 1640 } 1641 return found; 1642 1643 err_out: 1644 iput(inode); 1645 return ERR_PTR(error); 1646 } 1647 EXPORT_SYMBOL(d_add_ci); 1648 1649 /** 1650 * __d_lookup_rcu - search for a dentry (racy, store-free) 1651 * @parent: parent dentry 1652 * @name: qstr of name we wish to find 1653 * @seq: returns d_seq value at the point where the dentry was found 1654 * @inode: returns dentry->d_inode when the inode was found valid. 1655 * Returns: dentry, or NULL 1656 * 1657 * __d_lookup_rcu is the dcache lookup function for rcu-walk name 1658 * resolution (store-free path walking) design described in 1659 * Documentation/filesystems/path-lookup.txt. 1660 * 1661 * This is not to be used outside core vfs. 1662 * 1663 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock 1664 * held, and rcu_read_lock held. The returned dentry must not be stored into 1665 * without taking d_lock and checking d_seq sequence count against @seq 1666 * returned here. 1667 * 1668 * A refcount may be taken on the found dentry with the __d_rcu_to_refcount 1669 * function. 1670 * 1671 * Alternatively, __d_lookup_rcu may be called again to look up the child of 1672 * the returned dentry, so long as its parent's seqlock is checked after the 1673 * child is looked up. Thus, an interlocking stepping of sequence lock checks 1674 * is formed, giving integrity down the path walk. 1675 */ 1676 struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name, 1677 unsigned *seq, struct inode **inode) 1678 { 1679 unsigned int len = name->len; 1680 unsigned int hash = name->hash; 1681 const unsigned char *str = name->name; 1682 struct hlist_bl_head *b = d_hash(parent, hash); 1683 struct hlist_bl_node *node; 1684 struct dentry *dentry; 1685 1686 /* 1687 * Note: There is significant duplication with __d_lookup_rcu which is 1688 * required to prevent single threaded performance regressions 1689 * especially on architectures where smp_rmb (in seqcounts) are costly. 1690 * Keep the two functions in sync. 1691 */ 1692 1693 /* 1694 * The hash list is protected using RCU. 1695 * 1696 * Carefully use d_seq when comparing a candidate dentry, to avoid 1697 * races with d_move(). 1698 * 1699 * It is possible that concurrent renames can mess up our list 1700 * walk here and result in missing our dentry, resulting in the 1701 * false-negative result. d_lookup() protects against concurrent 1702 * renames using rename_lock seqlock. 1703 * 1704 * See Documentation/filesystems/path-lookup.txt for more details. 1705 */ 1706 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { 1707 struct inode *i; 1708 const char *tname; 1709 int tlen; 1710 1711 if (dentry->d_name.hash != hash) 1712 continue; 1713 1714 seqretry: 1715 *seq = read_seqcount_begin(&dentry->d_seq); 1716 if (dentry->d_parent != parent) 1717 continue; 1718 if (d_unhashed(dentry)) 1719 continue; 1720 tlen = dentry->d_name.len; 1721 tname = dentry->d_name.name; 1722 i = dentry->d_inode; 1723 prefetch(tname); 1724 /* 1725 * This seqcount check is required to ensure name and 1726 * len are loaded atomically, so as not to walk off the 1727 * edge of memory when walking. If we could load this 1728 * atomically some other way, we could drop this check. 1729 */ 1730 if (read_seqcount_retry(&dentry->d_seq, *seq)) 1731 goto seqretry; 1732 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) { 1733 if (parent->d_op->d_compare(parent, *inode, 1734 dentry, i, 1735 tlen, tname, name)) 1736 continue; 1737 } else { 1738 if (dentry_cmp(tname, tlen, str, len)) 1739 continue; 1740 } 1741 /* 1742 * No extra seqcount check is required after the name 1743 * compare. The caller must perform a seqcount check in 1744 * order to do anything useful with the returned dentry 1745 * anyway. 1746 */ 1747 *inode = i; 1748 return dentry; 1749 } 1750 return NULL; 1751 } 1752 1753 /** 1754 * d_lookup - search for a dentry 1755 * @parent: parent dentry 1756 * @name: qstr of name we wish to find 1757 * Returns: dentry, or NULL 1758 * 1759 * d_lookup searches the children of the parent dentry for the name in 1760 * question. If the dentry is found its reference count is incremented and the 1761 * dentry is returned. The caller must use dput to free the entry when it has 1762 * finished using it. %NULL is returned if the dentry does not exist. 1763 */ 1764 struct dentry *d_lookup(struct dentry *parent, struct qstr *name) 1765 { 1766 struct dentry *dentry; 1767 unsigned seq; 1768 1769 do { 1770 seq = read_seqbegin(&rename_lock); 1771 dentry = __d_lookup(parent, name); 1772 if (dentry) 1773 break; 1774 } while (read_seqretry(&rename_lock, seq)); 1775 return dentry; 1776 } 1777 EXPORT_SYMBOL(d_lookup); 1778 1779 /** 1780 * __d_lookup - search for a dentry (racy) 1781 * @parent: parent dentry 1782 * @name: qstr of name we wish to find 1783 * Returns: dentry, or NULL 1784 * 1785 * __d_lookup is like d_lookup, however it may (rarely) return a 1786 * false-negative result due to unrelated rename activity. 1787 * 1788 * __d_lookup is slightly faster by avoiding rename_lock read seqlock, 1789 * however it must be used carefully, eg. with a following d_lookup in 1790 * the case of failure. 1791 * 1792 * __d_lookup callers must be commented. 1793 */ 1794 struct dentry *__d_lookup(struct dentry *parent, struct qstr *name) 1795 { 1796 unsigned int len = name->len; 1797 unsigned int hash = name->hash; 1798 const unsigned char *str = name->name; 1799 struct hlist_bl_head *b = d_hash(parent, hash); 1800 struct hlist_bl_node *node; 1801 struct dentry *found = NULL; 1802 struct dentry *dentry; 1803 1804 /* 1805 * Note: There is significant duplication with __d_lookup_rcu which is 1806 * required to prevent single threaded performance regressions 1807 * especially on architectures where smp_rmb (in seqcounts) are costly. 1808 * Keep the two functions in sync. 1809 */ 1810 1811 /* 1812 * The hash list is protected using RCU. 1813 * 1814 * Take d_lock when comparing a candidate dentry, to avoid races 1815 * with d_move(). 1816 * 1817 * It is possible that concurrent renames can mess up our list 1818 * walk here and result in missing our dentry, resulting in the 1819 * false-negative result. d_lookup() protects against concurrent 1820 * renames using rename_lock seqlock. 1821 * 1822 * See Documentation/filesystems/path-lookup.txt for more details. 1823 */ 1824 rcu_read_lock(); 1825 1826 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { 1827 const char *tname; 1828 int tlen; 1829 1830 if (dentry->d_name.hash != hash) 1831 continue; 1832 1833 spin_lock(&dentry->d_lock); 1834 if (dentry->d_parent != parent) 1835 goto next; 1836 if (d_unhashed(dentry)) 1837 goto next; 1838 1839 /* 1840 * It is safe to compare names since d_move() cannot 1841 * change the qstr (protected by d_lock). 1842 */ 1843 tlen = dentry->d_name.len; 1844 tname = dentry->d_name.name; 1845 if (parent->d_flags & DCACHE_OP_COMPARE) { 1846 if (parent->d_op->d_compare(parent, parent->d_inode, 1847 dentry, dentry->d_inode, 1848 tlen, tname, name)) 1849 goto next; 1850 } else { 1851 if (dentry_cmp(tname, tlen, str, len)) 1852 goto next; 1853 } 1854 1855 dentry->d_count++; 1856 found = dentry; 1857 spin_unlock(&dentry->d_lock); 1858 break; 1859 next: 1860 spin_unlock(&dentry->d_lock); 1861 } 1862 rcu_read_unlock(); 1863 1864 return found; 1865 } 1866 1867 /** 1868 * d_hash_and_lookup - hash the qstr then search for a dentry 1869 * @dir: Directory to search in 1870 * @name: qstr of name we wish to find 1871 * 1872 * On hash failure or on lookup failure NULL is returned. 1873 */ 1874 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name) 1875 { 1876 struct dentry *dentry = NULL; 1877 1878 /* 1879 * Check for a fs-specific hash function. Note that we must 1880 * calculate the standard hash first, as the d_op->d_hash() 1881 * routine may choose to leave the hash value unchanged. 1882 */ 1883 name->hash = full_name_hash(name->name, name->len); 1884 if (dir->d_flags & DCACHE_OP_HASH) { 1885 if (dir->d_op->d_hash(dir, dir->d_inode, name) < 0) 1886 goto out; 1887 } 1888 dentry = d_lookup(dir, name); 1889 out: 1890 return dentry; 1891 } 1892 1893 /** 1894 * d_validate - verify dentry provided from insecure source (deprecated) 1895 * @dentry: The dentry alleged to be valid child of @dparent 1896 * @dparent: The parent dentry (known to be valid) 1897 * 1898 * An insecure source has sent us a dentry, here we verify it and dget() it. 1899 * This is used by ncpfs in its readdir implementation. 1900 * Zero is returned in the dentry is invalid. 1901 * 1902 * This function is slow for big directories, and deprecated, do not use it. 1903 */ 1904 int d_validate(struct dentry *dentry, struct dentry *dparent) 1905 { 1906 struct dentry *child; 1907 1908 spin_lock(&dparent->d_lock); 1909 list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) { 1910 if (dentry == child) { 1911 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); 1912 __dget_dlock(dentry); 1913 spin_unlock(&dentry->d_lock); 1914 spin_unlock(&dparent->d_lock); 1915 return 1; 1916 } 1917 } 1918 spin_unlock(&dparent->d_lock); 1919 1920 return 0; 1921 } 1922 EXPORT_SYMBOL(d_validate); 1923 1924 /* 1925 * When a file is deleted, we have two options: 1926 * - turn this dentry into a negative dentry 1927 * - unhash this dentry and free it. 1928 * 1929 * Usually, we want to just turn this into 1930 * a negative dentry, but if anybody else is 1931 * currently using the dentry or the inode 1932 * we can't do that and we fall back on removing 1933 * it from the hash queues and waiting for 1934 * it to be deleted later when it has no users 1935 */ 1936 1937 /** 1938 * d_delete - delete a dentry 1939 * @dentry: The dentry to delete 1940 * 1941 * Turn the dentry into a negative dentry if possible, otherwise 1942 * remove it from the hash queues so it can be deleted later 1943 */ 1944 1945 void d_delete(struct dentry * dentry) 1946 { 1947 struct inode *inode; 1948 int isdir = 0; 1949 /* 1950 * Are we the only user? 1951 */ 1952 again: 1953 spin_lock(&dentry->d_lock); 1954 inode = dentry->d_inode; 1955 isdir = S_ISDIR(inode->i_mode); 1956 if (dentry->d_count == 1) { 1957 if (inode && !spin_trylock(&inode->i_lock)) { 1958 spin_unlock(&dentry->d_lock); 1959 cpu_relax(); 1960 goto again; 1961 } 1962 dentry->d_flags &= ~DCACHE_CANT_MOUNT; 1963 dentry_unlink_inode(dentry); 1964 fsnotify_nameremove(dentry, isdir); 1965 return; 1966 } 1967 1968 if (!d_unhashed(dentry)) 1969 __d_drop(dentry); 1970 1971 spin_unlock(&dentry->d_lock); 1972 1973 fsnotify_nameremove(dentry, isdir); 1974 } 1975 EXPORT_SYMBOL(d_delete); 1976 1977 static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b) 1978 { 1979 BUG_ON(!d_unhashed(entry)); 1980 hlist_bl_lock(b); 1981 entry->d_flags |= DCACHE_RCUACCESS; 1982 hlist_bl_add_head_rcu(&entry->d_hash, b); 1983 hlist_bl_unlock(b); 1984 } 1985 1986 static void _d_rehash(struct dentry * entry) 1987 { 1988 __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash)); 1989 } 1990 1991 /** 1992 * d_rehash - add an entry back to the hash 1993 * @entry: dentry to add to the hash 1994 * 1995 * Adds a dentry to the hash according to its name. 1996 */ 1997 1998 void d_rehash(struct dentry * entry) 1999 { 2000 spin_lock(&entry->d_lock); 2001 _d_rehash(entry); 2002 spin_unlock(&entry->d_lock); 2003 } 2004 EXPORT_SYMBOL(d_rehash); 2005 2006 /** 2007 * dentry_update_name_case - update case insensitive dentry with a new name 2008 * @dentry: dentry to be updated 2009 * @name: new name 2010 * 2011 * Update a case insensitive dentry with new case of name. 2012 * 2013 * dentry must have been returned by d_lookup with name @name. Old and new 2014 * name lengths must match (ie. no d_compare which allows mismatched name 2015 * lengths). 2016 * 2017 * Parent inode i_mutex must be held over d_lookup and into this call (to 2018 * keep renames and concurrent inserts, and readdir(2) away). 2019 */ 2020 void dentry_update_name_case(struct dentry *dentry, struct qstr *name) 2021 { 2022 BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex)); 2023 BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */ 2024 2025 spin_lock(&dentry->d_lock); 2026 write_seqcount_begin(&dentry->d_seq); 2027 memcpy((unsigned char *)dentry->d_name.name, name->name, name->len); 2028 write_seqcount_end(&dentry->d_seq); 2029 spin_unlock(&dentry->d_lock); 2030 } 2031 EXPORT_SYMBOL(dentry_update_name_case); 2032 2033 static void switch_names(struct dentry *dentry, struct dentry *target) 2034 { 2035 if (dname_external(target)) { 2036 if (dname_external(dentry)) { 2037 /* 2038 * Both external: swap the pointers 2039 */ 2040 swap(target->d_name.name, dentry->d_name.name); 2041 } else { 2042 /* 2043 * dentry:internal, target:external. Steal target's 2044 * storage and make target internal. 2045 */ 2046 memcpy(target->d_iname, dentry->d_name.name, 2047 dentry->d_name.len + 1); 2048 dentry->d_name.name = target->d_name.name; 2049 target->d_name.name = target->d_iname; 2050 } 2051 } else { 2052 if (dname_external(dentry)) { 2053 /* 2054 * dentry:external, target:internal. Give dentry's 2055 * storage to target and make dentry internal 2056 */ 2057 memcpy(dentry->d_iname, target->d_name.name, 2058 target->d_name.len + 1); 2059 target->d_name.name = dentry->d_name.name; 2060 dentry->d_name.name = dentry->d_iname; 2061 } else { 2062 /* 2063 * Both are internal. Just copy target to dentry 2064 */ 2065 memcpy(dentry->d_iname, target->d_name.name, 2066 target->d_name.len + 1); 2067 dentry->d_name.len = target->d_name.len; 2068 return; 2069 } 2070 } 2071 swap(dentry->d_name.len, target->d_name.len); 2072 } 2073 2074 static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target) 2075 { 2076 /* 2077 * XXXX: do we really need to take target->d_lock? 2078 */ 2079 if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent) 2080 spin_lock(&target->d_parent->d_lock); 2081 else { 2082 if (d_ancestor(dentry->d_parent, target->d_parent)) { 2083 spin_lock(&dentry->d_parent->d_lock); 2084 spin_lock_nested(&target->d_parent->d_lock, 2085 DENTRY_D_LOCK_NESTED); 2086 } else { 2087 spin_lock(&target->d_parent->d_lock); 2088 spin_lock_nested(&dentry->d_parent->d_lock, 2089 DENTRY_D_LOCK_NESTED); 2090 } 2091 } 2092 if (target < dentry) { 2093 spin_lock_nested(&target->d_lock, 2); 2094 spin_lock_nested(&dentry->d_lock, 3); 2095 } else { 2096 spin_lock_nested(&dentry->d_lock, 2); 2097 spin_lock_nested(&target->d_lock, 3); 2098 } 2099 } 2100 2101 static void dentry_unlock_parents_for_move(struct dentry *dentry, 2102 struct dentry *target) 2103 { 2104 if (target->d_parent != dentry->d_parent) 2105 spin_unlock(&dentry->d_parent->d_lock); 2106 if (target->d_parent != target) 2107 spin_unlock(&target->d_parent->d_lock); 2108 } 2109 2110 /* 2111 * When switching names, the actual string doesn't strictly have to 2112 * be preserved in the target - because we're dropping the target 2113 * anyway. As such, we can just do a simple memcpy() to copy over 2114 * the new name before we switch. 2115 * 2116 * Note that we have to be a lot more careful about getting the hash 2117 * switched - we have to switch the hash value properly even if it 2118 * then no longer matches the actual (corrupted) string of the target. 2119 * The hash value has to match the hash queue that the dentry is on.. 2120 */ 2121 /* 2122 * __d_move - move a dentry 2123 * @dentry: entry to move 2124 * @target: new dentry 2125 * 2126 * Update the dcache to reflect the move of a file name. Negative 2127 * dcache entries should not be moved in this way. Caller must hold 2128 * rename_lock, the i_mutex of the source and target directories, 2129 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename(). 2130 */ 2131 static void __d_move(struct dentry * dentry, struct dentry * target) 2132 { 2133 if (!dentry->d_inode) 2134 printk(KERN_WARNING "VFS: moving negative dcache entry\n"); 2135 2136 BUG_ON(d_ancestor(dentry, target)); 2137 BUG_ON(d_ancestor(target, dentry)); 2138 2139 dentry_lock_for_move(dentry, target); 2140 2141 write_seqcount_begin(&dentry->d_seq); 2142 write_seqcount_begin(&target->d_seq); 2143 2144 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */ 2145 2146 /* 2147 * Move the dentry to the target hash queue. Don't bother checking 2148 * for the same hash queue because of how unlikely it is. 2149 */ 2150 __d_drop(dentry); 2151 __d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash)); 2152 2153 /* Unhash the target: dput() will then get rid of it */ 2154 __d_drop(target); 2155 2156 list_del(&dentry->d_u.d_child); 2157 list_del(&target->d_u.d_child); 2158 2159 /* Switch the names.. */ 2160 switch_names(dentry, target); 2161 swap(dentry->d_name.hash, target->d_name.hash); 2162 2163 /* ... and switch the parents */ 2164 if (IS_ROOT(dentry)) { 2165 dentry->d_parent = target->d_parent; 2166 target->d_parent = target; 2167 INIT_LIST_HEAD(&target->d_u.d_child); 2168 } else { 2169 swap(dentry->d_parent, target->d_parent); 2170 2171 /* And add them back to the (new) parent lists */ 2172 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs); 2173 } 2174 2175 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs); 2176 2177 write_seqcount_end(&target->d_seq); 2178 write_seqcount_end(&dentry->d_seq); 2179 2180 dentry_unlock_parents_for_move(dentry, target); 2181 spin_unlock(&target->d_lock); 2182 fsnotify_d_move(dentry); 2183 spin_unlock(&dentry->d_lock); 2184 } 2185 2186 /* 2187 * d_move - move a dentry 2188 * @dentry: entry to move 2189 * @target: new dentry 2190 * 2191 * Update the dcache to reflect the move of a file name. Negative 2192 * dcache entries should not be moved in this way. See the locking 2193 * requirements for __d_move. 2194 */ 2195 void d_move(struct dentry *dentry, struct dentry *target) 2196 { 2197 write_seqlock(&rename_lock); 2198 __d_move(dentry, target); 2199 write_sequnlock(&rename_lock); 2200 } 2201 EXPORT_SYMBOL(d_move); 2202 2203 /** 2204 * d_ancestor - search for an ancestor 2205 * @p1: ancestor dentry 2206 * @p2: child dentry 2207 * 2208 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is 2209 * an ancestor of p2, else NULL. 2210 */ 2211 struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2) 2212 { 2213 struct dentry *p; 2214 2215 for (p = p2; !IS_ROOT(p); p = p->d_parent) { 2216 if (p->d_parent == p1) 2217 return p; 2218 } 2219 return NULL; 2220 } 2221 2222 /* 2223 * This helper attempts to cope with remotely renamed directories 2224 * 2225 * It assumes that the caller is already holding 2226 * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock 2227 * 2228 * Note: If ever the locking in lock_rename() changes, then please 2229 * remember to update this too... 2230 */ 2231 static struct dentry *__d_unalias(struct inode *inode, 2232 struct dentry *dentry, struct dentry *alias) 2233 { 2234 struct mutex *m1 = NULL, *m2 = NULL; 2235 struct dentry *ret; 2236 2237 /* If alias and dentry share a parent, then no extra locks required */ 2238 if (alias->d_parent == dentry->d_parent) 2239 goto out_unalias; 2240 2241 /* See lock_rename() */ 2242 ret = ERR_PTR(-EBUSY); 2243 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex)) 2244 goto out_err; 2245 m1 = &dentry->d_sb->s_vfs_rename_mutex; 2246 if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex)) 2247 goto out_err; 2248 m2 = &alias->d_parent->d_inode->i_mutex; 2249 out_unalias: 2250 __d_move(alias, dentry); 2251 ret = alias; 2252 out_err: 2253 spin_unlock(&inode->i_lock); 2254 if (m2) 2255 mutex_unlock(m2); 2256 if (m1) 2257 mutex_unlock(m1); 2258 return ret; 2259 } 2260 2261 /* 2262 * Prepare an anonymous dentry for life in the superblock's dentry tree as a 2263 * named dentry in place of the dentry to be replaced. 2264 * returns with anon->d_lock held! 2265 */ 2266 static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon) 2267 { 2268 struct dentry *dparent, *aparent; 2269 2270 dentry_lock_for_move(anon, dentry); 2271 2272 write_seqcount_begin(&dentry->d_seq); 2273 write_seqcount_begin(&anon->d_seq); 2274 2275 dparent = dentry->d_parent; 2276 aparent = anon->d_parent; 2277 2278 switch_names(dentry, anon); 2279 swap(dentry->d_name.hash, anon->d_name.hash); 2280 2281 dentry->d_parent = (aparent == anon) ? dentry : aparent; 2282 list_del(&dentry->d_u.d_child); 2283 if (!IS_ROOT(dentry)) 2284 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs); 2285 else 2286 INIT_LIST_HEAD(&dentry->d_u.d_child); 2287 2288 anon->d_parent = (dparent == dentry) ? anon : dparent; 2289 list_del(&anon->d_u.d_child); 2290 if (!IS_ROOT(anon)) 2291 list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs); 2292 else 2293 INIT_LIST_HEAD(&anon->d_u.d_child); 2294 2295 write_seqcount_end(&dentry->d_seq); 2296 write_seqcount_end(&anon->d_seq); 2297 2298 dentry_unlock_parents_for_move(anon, dentry); 2299 spin_unlock(&dentry->d_lock); 2300 2301 /* anon->d_lock still locked, returns locked */ 2302 anon->d_flags &= ~DCACHE_DISCONNECTED; 2303 } 2304 2305 /** 2306 * d_materialise_unique - introduce an inode into the tree 2307 * @dentry: candidate dentry 2308 * @inode: inode to bind to the dentry, to which aliases may be attached 2309 * 2310 * Introduces an dentry into the tree, substituting an extant disconnected 2311 * root directory alias in its place if there is one. Caller must hold the 2312 * i_mutex of the parent directory. 2313 */ 2314 struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode) 2315 { 2316 struct dentry *actual; 2317 2318 BUG_ON(!d_unhashed(dentry)); 2319 2320 if (!inode) { 2321 actual = dentry; 2322 __d_instantiate(dentry, NULL); 2323 d_rehash(actual); 2324 goto out_nolock; 2325 } 2326 2327 spin_lock(&inode->i_lock); 2328 2329 if (S_ISDIR(inode->i_mode)) { 2330 struct dentry *alias; 2331 2332 /* Does an aliased dentry already exist? */ 2333 alias = __d_find_alias(inode, 0); 2334 if (alias) { 2335 actual = alias; 2336 write_seqlock(&rename_lock); 2337 2338 if (d_ancestor(alias, dentry)) { 2339 /* Check for loops */ 2340 actual = ERR_PTR(-ELOOP); 2341 } else if (IS_ROOT(alias)) { 2342 /* Is this an anonymous mountpoint that we 2343 * could splice into our tree? */ 2344 __d_materialise_dentry(dentry, alias); 2345 write_sequnlock(&rename_lock); 2346 __d_drop(alias); 2347 goto found; 2348 } else { 2349 /* Nope, but we must(!) avoid directory 2350 * aliasing */ 2351 actual = __d_unalias(inode, dentry, alias); 2352 } 2353 write_sequnlock(&rename_lock); 2354 if (IS_ERR(actual)) 2355 dput(alias); 2356 goto out_nolock; 2357 } 2358 } 2359 2360 /* Add a unique reference */ 2361 actual = __d_instantiate_unique(dentry, inode); 2362 if (!actual) 2363 actual = dentry; 2364 else 2365 BUG_ON(!d_unhashed(actual)); 2366 2367 spin_lock(&actual->d_lock); 2368 found: 2369 _d_rehash(actual); 2370 spin_unlock(&actual->d_lock); 2371 spin_unlock(&inode->i_lock); 2372 out_nolock: 2373 if (actual == dentry) { 2374 security_d_instantiate(dentry, inode); 2375 return NULL; 2376 } 2377 2378 iput(inode); 2379 return actual; 2380 } 2381 EXPORT_SYMBOL_GPL(d_materialise_unique); 2382 2383 static int prepend(char **buffer, int *buflen, const char *str, int namelen) 2384 { 2385 *buflen -= namelen; 2386 if (*buflen < 0) 2387 return -ENAMETOOLONG; 2388 *buffer -= namelen; 2389 memcpy(*buffer, str, namelen); 2390 return 0; 2391 } 2392 2393 static int prepend_name(char **buffer, int *buflen, struct qstr *name) 2394 { 2395 return prepend(buffer, buflen, name->name, name->len); 2396 } 2397 2398 /** 2399 * prepend_path - Prepend path string to a buffer 2400 * @path: the dentry/vfsmount to report 2401 * @root: root vfsmnt/dentry (may be modified by this function) 2402 * @buffer: pointer to the end of the buffer 2403 * @buflen: pointer to buffer length 2404 * 2405 * Caller holds the rename_lock. 2406 * 2407 * If path is not reachable from the supplied root, then the value of 2408 * root is changed (without modifying refcounts). 2409 */ 2410 static int prepend_path(const struct path *path, struct path *root, 2411 char **buffer, int *buflen) 2412 { 2413 struct dentry *dentry = path->dentry; 2414 struct vfsmount *vfsmnt = path->mnt; 2415 bool slash = false; 2416 int error = 0; 2417 2418 br_read_lock(vfsmount_lock); 2419 while (dentry != root->dentry || vfsmnt != root->mnt) { 2420 struct dentry * parent; 2421 2422 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) { 2423 /* Global root? */ 2424 if (vfsmnt->mnt_parent == vfsmnt) { 2425 goto global_root; 2426 } 2427 dentry = vfsmnt->mnt_mountpoint; 2428 vfsmnt = vfsmnt->mnt_parent; 2429 continue; 2430 } 2431 parent = dentry->d_parent; 2432 prefetch(parent); 2433 spin_lock(&dentry->d_lock); 2434 error = prepend_name(buffer, buflen, &dentry->d_name); 2435 spin_unlock(&dentry->d_lock); 2436 if (!error) 2437 error = prepend(buffer, buflen, "/", 1); 2438 if (error) 2439 break; 2440 2441 slash = true; 2442 dentry = parent; 2443 } 2444 2445 out: 2446 if (!error && !slash) 2447 error = prepend(buffer, buflen, "/", 1); 2448 2449 br_read_unlock(vfsmount_lock); 2450 return error; 2451 2452 global_root: 2453 /* 2454 * Filesystems needing to implement special "root names" 2455 * should do so with ->d_dname() 2456 */ 2457 if (IS_ROOT(dentry) && 2458 (dentry->d_name.len != 1 || dentry->d_name.name[0] != '/')) { 2459 WARN(1, "Root dentry has weird name <%.*s>\n", 2460 (int) dentry->d_name.len, dentry->d_name.name); 2461 } 2462 root->mnt = vfsmnt; 2463 root->dentry = dentry; 2464 goto out; 2465 } 2466 2467 /** 2468 * __d_path - return the path of a dentry 2469 * @path: the dentry/vfsmount to report 2470 * @root: root vfsmnt/dentry (may be modified by this function) 2471 * @buf: buffer to return value in 2472 * @buflen: buffer length 2473 * 2474 * Convert a dentry into an ASCII path name. 2475 * 2476 * Returns a pointer into the buffer or an error code if the 2477 * path was too long. 2478 * 2479 * "buflen" should be positive. 2480 * 2481 * If path is not reachable from the supplied root, then the value of 2482 * root is changed (without modifying refcounts). 2483 */ 2484 char *__d_path(const struct path *path, struct path *root, 2485 char *buf, int buflen) 2486 { 2487 char *res = buf + buflen; 2488 int error; 2489 2490 prepend(&res, &buflen, "\0", 1); 2491 write_seqlock(&rename_lock); 2492 error = prepend_path(path, root, &res, &buflen); 2493 write_sequnlock(&rename_lock); 2494 2495 if (error) 2496 return ERR_PTR(error); 2497 return res; 2498 } 2499 2500 /* 2501 * same as __d_path but appends "(deleted)" for unlinked files. 2502 */ 2503 static int path_with_deleted(const struct path *path, struct path *root, 2504 char **buf, int *buflen) 2505 { 2506 prepend(buf, buflen, "\0", 1); 2507 if (d_unlinked(path->dentry)) { 2508 int error = prepend(buf, buflen, " (deleted)", 10); 2509 if (error) 2510 return error; 2511 } 2512 2513 return prepend_path(path, root, buf, buflen); 2514 } 2515 2516 static int prepend_unreachable(char **buffer, int *buflen) 2517 { 2518 return prepend(buffer, buflen, "(unreachable)", 13); 2519 } 2520 2521 /** 2522 * d_path - return the path of a dentry 2523 * @path: path to report 2524 * @buf: buffer to return value in 2525 * @buflen: buffer length 2526 * 2527 * Convert a dentry into an ASCII path name. If the entry has been deleted 2528 * the string " (deleted)" is appended. Note that this is ambiguous. 2529 * 2530 * Returns a pointer into the buffer or an error code if the path was 2531 * too long. Note: Callers should use the returned pointer, not the passed 2532 * in buffer, to use the name! The implementation often starts at an offset 2533 * into the buffer, and may leave 0 bytes at the start. 2534 * 2535 * "buflen" should be positive. 2536 */ 2537 char *d_path(const struct path *path, char *buf, int buflen) 2538 { 2539 char *res = buf + buflen; 2540 struct path root; 2541 struct path tmp; 2542 int error; 2543 2544 /* 2545 * We have various synthetic filesystems that never get mounted. On 2546 * these filesystems dentries are never used for lookup purposes, and 2547 * thus don't need to be hashed. They also don't need a name until a 2548 * user wants to identify the object in /proc/pid/fd/. The little hack 2549 * below allows us to generate a name for these objects on demand: 2550 */ 2551 if (path->dentry->d_op && path->dentry->d_op->d_dname) 2552 return path->dentry->d_op->d_dname(path->dentry, buf, buflen); 2553 2554 get_fs_root(current->fs, &root); 2555 write_seqlock(&rename_lock); 2556 tmp = root; 2557 error = path_with_deleted(path, &tmp, &res, &buflen); 2558 if (error) 2559 res = ERR_PTR(error); 2560 write_sequnlock(&rename_lock); 2561 path_put(&root); 2562 return res; 2563 } 2564 EXPORT_SYMBOL(d_path); 2565 2566 /** 2567 * d_path_with_unreachable - return the path of a dentry 2568 * @path: path to report 2569 * @buf: buffer to return value in 2570 * @buflen: buffer length 2571 * 2572 * The difference from d_path() is that this prepends "(unreachable)" 2573 * to paths which are unreachable from the current process' root. 2574 */ 2575 char *d_path_with_unreachable(const struct path *path, char *buf, int buflen) 2576 { 2577 char *res = buf + buflen; 2578 struct path root; 2579 struct path tmp; 2580 int error; 2581 2582 if (path->dentry->d_op && path->dentry->d_op->d_dname) 2583 return path->dentry->d_op->d_dname(path->dentry, buf, buflen); 2584 2585 get_fs_root(current->fs, &root); 2586 write_seqlock(&rename_lock); 2587 tmp = root; 2588 error = path_with_deleted(path, &tmp, &res, &buflen); 2589 if (!error && !path_equal(&tmp, &root)) 2590 error = prepend_unreachable(&res, &buflen); 2591 write_sequnlock(&rename_lock); 2592 path_put(&root); 2593 if (error) 2594 res = ERR_PTR(error); 2595 2596 return res; 2597 } 2598 2599 /* 2600 * Helper function for dentry_operations.d_dname() members 2601 */ 2602 char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen, 2603 const char *fmt, ...) 2604 { 2605 va_list args; 2606 char temp[64]; 2607 int sz; 2608 2609 va_start(args, fmt); 2610 sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1; 2611 va_end(args); 2612 2613 if (sz > sizeof(temp) || sz > buflen) 2614 return ERR_PTR(-ENAMETOOLONG); 2615 2616 buffer += buflen - sz; 2617 return memcpy(buffer, temp, sz); 2618 } 2619 2620 /* 2621 * Write full pathname from the root of the filesystem into the buffer. 2622 */ 2623 static char *__dentry_path(struct dentry *dentry, char *buf, int buflen) 2624 { 2625 char *end = buf + buflen; 2626 char *retval; 2627 2628 prepend(&end, &buflen, "\0", 1); 2629 if (buflen < 1) 2630 goto Elong; 2631 /* Get '/' right */ 2632 retval = end-1; 2633 *retval = '/'; 2634 2635 while (!IS_ROOT(dentry)) { 2636 struct dentry *parent = dentry->d_parent; 2637 int error; 2638 2639 prefetch(parent); 2640 spin_lock(&dentry->d_lock); 2641 error = prepend_name(&end, &buflen, &dentry->d_name); 2642 spin_unlock(&dentry->d_lock); 2643 if (error != 0 || prepend(&end, &buflen, "/", 1) != 0) 2644 goto Elong; 2645 2646 retval = end; 2647 dentry = parent; 2648 } 2649 return retval; 2650 Elong: 2651 return ERR_PTR(-ENAMETOOLONG); 2652 } 2653 2654 char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen) 2655 { 2656 char *retval; 2657 2658 write_seqlock(&rename_lock); 2659 retval = __dentry_path(dentry, buf, buflen); 2660 write_sequnlock(&rename_lock); 2661 2662 return retval; 2663 } 2664 EXPORT_SYMBOL(dentry_path_raw); 2665 2666 char *dentry_path(struct dentry *dentry, char *buf, int buflen) 2667 { 2668 char *p = NULL; 2669 char *retval; 2670 2671 write_seqlock(&rename_lock); 2672 if (d_unlinked(dentry)) { 2673 p = buf + buflen; 2674 if (prepend(&p, &buflen, "//deleted", 10) != 0) 2675 goto Elong; 2676 buflen++; 2677 } 2678 retval = __dentry_path(dentry, buf, buflen); 2679 write_sequnlock(&rename_lock); 2680 if (!IS_ERR(retval) && p) 2681 *p = '/'; /* restore '/' overriden with '\0' */ 2682 return retval; 2683 Elong: 2684 return ERR_PTR(-ENAMETOOLONG); 2685 } 2686 2687 /* 2688 * NOTE! The user-level library version returns a 2689 * character pointer. The kernel system call just 2690 * returns the length of the buffer filled (which 2691 * includes the ending '\0' character), or a negative 2692 * error value. So libc would do something like 2693 * 2694 * char *getcwd(char * buf, size_t size) 2695 * { 2696 * int retval; 2697 * 2698 * retval = sys_getcwd(buf, size); 2699 * if (retval >= 0) 2700 * return buf; 2701 * errno = -retval; 2702 * return NULL; 2703 * } 2704 */ 2705 SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) 2706 { 2707 int error; 2708 struct path pwd, root; 2709 char *page = (char *) __get_free_page(GFP_USER); 2710 2711 if (!page) 2712 return -ENOMEM; 2713 2714 get_fs_root_and_pwd(current->fs, &root, &pwd); 2715 2716 error = -ENOENT; 2717 write_seqlock(&rename_lock); 2718 if (!d_unlinked(pwd.dentry)) { 2719 unsigned long len; 2720 struct path tmp = root; 2721 char *cwd = page + PAGE_SIZE; 2722 int buflen = PAGE_SIZE; 2723 2724 prepend(&cwd, &buflen, "\0", 1); 2725 error = prepend_path(&pwd, &tmp, &cwd, &buflen); 2726 write_sequnlock(&rename_lock); 2727 2728 if (error) 2729 goto out; 2730 2731 /* Unreachable from current root */ 2732 if (!path_equal(&tmp, &root)) { 2733 error = prepend_unreachable(&cwd, &buflen); 2734 if (error) 2735 goto out; 2736 } 2737 2738 error = -ERANGE; 2739 len = PAGE_SIZE + page - cwd; 2740 if (len <= size) { 2741 error = len; 2742 if (copy_to_user(buf, cwd, len)) 2743 error = -EFAULT; 2744 } 2745 } else { 2746 write_sequnlock(&rename_lock); 2747 } 2748 2749 out: 2750 path_put(&pwd); 2751 path_put(&root); 2752 free_page((unsigned long) page); 2753 return error; 2754 } 2755 2756 /* 2757 * Test whether new_dentry is a subdirectory of old_dentry. 2758 * 2759 * Trivially implemented using the dcache structure 2760 */ 2761 2762 /** 2763 * is_subdir - is new dentry a subdirectory of old_dentry 2764 * @new_dentry: new dentry 2765 * @old_dentry: old dentry 2766 * 2767 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth). 2768 * Returns 0 otherwise. 2769 * Caller must ensure that "new_dentry" is pinned before calling is_subdir() 2770 */ 2771 2772 int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry) 2773 { 2774 int result; 2775 unsigned seq; 2776 2777 if (new_dentry == old_dentry) 2778 return 1; 2779 2780 do { 2781 /* for restarting inner loop in case of seq retry */ 2782 seq = read_seqbegin(&rename_lock); 2783 /* 2784 * Need rcu_readlock to protect against the d_parent trashing 2785 * due to d_move 2786 */ 2787 rcu_read_lock(); 2788 if (d_ancestor(old_dentry, new_dentry)) 2789 result = 1; 2790 else 2791 result = 0; 2792 rcu_read_unlock(); 2793 } while (read_seqretry(&rename_lock, seq)); 2794 2795 return result; 2796 } 2797 2798 int path_is_under(struct path *path1, struct path *path2) 2799 { 2800 struct vfsmount *mnt = path1->mnt; 2801 struct dentry *dentry = path1->dentry; 2802 int res; 2803 2804 br_read_lock(vfsmount_lock); 2805 if (mnt != path2->mnt) { 2806 for (;;) { 2807 if (mnt->mnt_parent == mnt) { 2808 br_read_unlock(vfsmount_lock); 2809 return 0; 2810 } 2811 if (mnt->mnt_parent == path2->mnt) 2812 break; 2813 mnt = mnt->mnt_parent; 2814 } 2815 dentry = mnt->mnt_mountpoint; 2816 } 2817 res = is_subdir(dentry, path2->dentry); 2818 br_read_unlock(vfsmount_lock); 2819 return res; 2820 } 2821 EXPORT_SYMBOL(path_is_under); 2822 2823 void d_genocide(struct dentry *root) 2824 { 2825 struct dentry *this_parent; 2826 struct list_head *next; 2827 unsigned seq; 2828 int locked = 0; 2829 2830 seq = read_seqbegin(&rename_lock); 2831 again: 2832 this_parent = root; 2833 spin_lock(&this_parent->d_lock); 2834 repeat: 2835 next = this_parent->d_subdirs.next; 2836 resume: 2837 while (next != &this_parent->d_subdirs) { 2838 struct list_head *tmp = next; 2839 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); 2840 next = tmp->next; 2841 2842 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); 2843 if (d_unhashed(dentry) || !dentry->d_inode) { 2844 spin_unlock(&dentry->d_lock); 2845 continue; 2846 } 2847 if (!list_empty(&dentry->d_subdirs)) { 2848 spin_unlock(&this_parent->d_lock); 2849 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_); 2850 this_parent = dentry; 2851 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); 2852 goto repeat; 2853 } 2854 if (!(dentry->d_flags & DCACHE_GENOCIDE)) { 2855 dentry->d_flags |= DCACHE_GENOCIDE; 2856 dentry->d_count--; 2857 } 2858 spin_unlock(&dentry->d_lock); 2859 } 2860 if (this_parent != root) { 2861 struct dentry *child = this_parent; 2862 if (!(this_parent->d_flags & DCACHE_GENOCIDE)) { 2863 this_parent->d_flags |= DCACHE_GENOCIDE; 2864 this_parent->d_count--; 2865 } 2866 this_parent = try_to_ascend(this_parent, locked, seq); 2867 if (!this_parent) 2868 goto rename_retry; 2869 next = child->d_u.d_child.next; 2870 goto resume; 2871 } 2872 spin_unlock(&this_parent->d_lock); 2873 if (!locked && read_seqretry(&rename_lock, seq)) 2874 goto rename_retry; 2875 if (locked) 2876 write_sequnlock(&rename_lock); 2877 return; 2878 2879 rename_retry: 2880 locked = 1; 2881 write_seqlock(&rename_lock); 2882 goto again; 2883 } 2884 2885 /** 2886 * find_inode_number - check for dentry with name 2887 * @dir: directory to check 2888 * @name: Name to find. 2889 * 2890 * Check whether a dentry already exists for the given name, 2891 * and return the inode number if it has an inode. Otherwise 2892 * 0 is returned. 2893 * 2894 * This routine is used to post-process directory listings for 2895 * filesystems using synthetic inode numbers, and is necessary 2896 * to keep getcwd() working. 2897 */ 2898 2899 ino_t find_inode_number(struct dentry *dir, struct qstr *name) 2900 { 2901 struct dentry * dentry; 2902 ino_t ino = 0; 2903 2904 dentry = d_hash_and_lookup(dir, name); 2905 if (dentry) { 2906 if (dentry->d_inode) 2907 ino = dentry->d_inode->i_ino; 2908 dput(dentry); 2909 } 2910 return ino; 2911 } 2912 EXPORT_SYMBOL(find_inode_number); 2913 2914 static __initdata unsigned long dhash_entries; 2915 static int __init set_dhash_entries(char *str) 2916 { 2917 if (!str) 2918 return 0; 2919 dhash_entries = simple_strtoul(str, &str, 0); 2920 return 1; 2921 } 2922 __setup("dhash_entries=", set_dhash_entries); 2923 2924 static void __init dcache_init_early(void) 2925 { 2926 int loop; 2927 2928 /* If hashes are distributed across NUMA nodes, defer 2929 * hash allocation until vmalloc space is available. 2930 */ 2931 if (hashdist) 2932 return; 2933 2934 dentry_hashtable = 2935 alloc_large_system_hash("Dentry cache", 2936 sizeof(struct hlist_bl_head), 2937 dhash_entries, 2938 13, 2939 HASH_EARLY, 2940 &d_hash_shift, 2941 &d_hash_mask, 2942 0); 2943 2944 for (loop = 0; loop < (1 << d_hash_shift); loop++) 2945 INIT_HLIST_BL_HEAD(dentry_hashtable + loop); 2946 } 2947 2948 static void __init dcache_init(void) 2949 { 2950 int loop; 2951 2952 /* 2953 * A constructor could be added for stable state like the lists, 2954 * but it is probably not worth it because of the cache nature 2955 * of the dcache. 2956 */ 2957 dentry_cache = KMEM_CACHE(dentry, 2958 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD); 2959 2960 /* Hash may have been set up in dcache_init_early */ 2961 if (!hashdist) 2962 return; 2963 2964 dentry_hashtable = 2965 alloc_large_system_hash("Dentry cache", 2966 sizeof(struct hlist_bl_head), 2967 dhash_entries, 2968 13, 2969 0, 2970 &d_hash_shift, 2971 &d_hash_mask, 2972 0); 2973 2974 for (loop = 0; loop < (1 << d_hash_shift); loop++) 2975 INIT_HLIST_BL_HEAD(dentry_hashtable + loop); 2976 } 2977 2978 /* SLAB cache for __getname() consumers */ 2979 struct kmem_cache *names_cachep __read_mostly; 2980 EXPORT_SYMBOL(names_cachep); 2981 2982 EXPORT_SYMBOL(d_genocide); 2983 2984 void __init vfs_caches_init_early(void) 2985 { 2986 dcache_init_early(); 2987 inode_init_early(); 2988 } 2989 2990 void __init vfs_caches_init(unsigned long mempages) 2991 { 2992 unsigned long reserve; 2993 2994 /* Base hash sizes on available memory, with a reserve equal to 2995 150% of current kernel size */ 2996 2997 reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1); 2998 mempages -= reserve; 2999 3000 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0, 3001 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 3002 3003 dcache_init(); 3004 inode_init(); 3005 files_init(mempages); 3006 mnt_init(); 3007 bdev_cache_init(); 3008 chrdev_init(); 3009 } 3010