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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 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9