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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 "internal.h" |
40 | |
41 | /* |
42 | * Usage: |
43 | * dcache->d_inode->i_lock protects: |
44 | * - i_dentry, d_alias, d_inode of aliases |
45 | * dcache_hash_bucket lock protects: |
46 | * - the dcache hash table |
47 | * s_anon bl list spinlock protects: |
48 | * - the s_anon list (see __d_drop) |
49 | * dcache_lru_lock protects: |
50 | * - the dcache lru lists and counters |
51 | * d_lock protects: |
52 | * - d_flags |
53 | * - d_name |
54 | * - d_lru |
55 | * - d_count |
56 | * - d_unhashed() |
57 | * - d_parent and d_subdirs |
58 | * - childrens' d_child and d_parent |
59 | * - d_alias, d_inode |
60 | * |
61 | * Ordering: |
62 | * dentry->d_inode->i_lock |
63 | * dentry->d_lock |
64 | * dcache_lru_lock |
65 | * dcache_hash_bucket lock |
66 | * s_anon lock |
67 | * |
68 | * If there is an ancestor relationship: |
69 | * dentry->d_parent->...->d_parent->d_lock |
70 | * ... |
71 | * dentry->d_parent->d_lock |
72 | * dentry->d_lock |
73 | * |
74 | * If no ancestor relationship: |
75 | * if (dentry1 < dentry2) |
76 | * dentry1->d_lock |
77 | * dentry2->d_lock |
78 | */ |
79 | int sysctl_vfs_cache_pressure __read_mostly = 100; |
80 | EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure); |
81 | |
82 | static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock); |
83 | __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock); |
84 | |
85 | EXPORT_SYMBOL(rename_lock); |
86 | |
87 | static struct kmem_cache *dentry_cache __read_mostly; |
88 | |
89 | /* |
90 | * This is the single most critical data structure when it comes |
91 | * to the dcache: the hashtable for lookups. Somebody should try |
92 | * to make this good - I've just made it work. |
93 | * |
94 | * This hash-function tries to avoid losing too many bits of hash |
95 | * information, yet avoid using a prime hash-size or similar. |
96 | */ |
97 | #define D_HASHBITS d_hash_shift |
98 | #define D_HASHMASK d_hash_mask |
99 | |
100 | static unsigned int d_hash_mask __read_mostly; |
101 | static unsigned int d_hash_shift __read_mostly; |
102 | |
103 | static struct hlist_bl_head *dentry_hashtable __read_mostly; |
104 | |
105 | static inline struct hlist_bl_head *d_hash(struct dentry *parent, |
106 | unsigned long hash) |
107 | { |
108 | hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES; |
109 | hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS); |
110 | return dentry_hashtable + (hash & D_HASHMASK); |
111 | } |
112 | |
113 | /* Statistics gathering. */ |
114 | struct dentry_stat_t dentry_stat = { |
115 | .age_limit = 45, |
116 | }; |
117 | |
118 | static DEFINE_PER_CPU(unsigned int, nr_dentry); |
119 | |
120 | #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS) |
121 | static int get_nr_dentry(void) |
122 | { |
123 | int i; |
124 | int sum = 0; |
125 | for_each_possible_cpu(i) |
126 | sum += per_cpu(nr_dentry, i); |
127 | return sum < 0 ? 0 : sum; |
128 | } |
129 | |
130 | int proc_nr_dentry(ctl_table *table, int write, void __user *buffer, |
131 | size_t *lenp, loff_t *ppos) |
132 | { |
133 | dentry_stat.nr_dentry = get_nr_dentry(); |
134 | return proc_dointvec(table, write, buffer, lenp, ppos); |
135 | } |
136 | #endif |
137 | |
138 | static void __d_free(struct rcu_head *head) |
139 | { |
140 | struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu); |
141 | |
142 | WARN_ON(!list_empty(&dentry->d_alias)); |
143 | if (dname_external(dentry)) |
144 | kfree(dentry->d_name.name); |
145 | kmem_cache_free(dentry_cache, dentry); |
146 | } |
147 | |
148 | /* |
149 | * no locks, please. |
150 | */ |
151 | static void d_free(struct dentry *dentry) |
152 | { |
153 | BUG_ON(dentry->d_count); |
154 | this_cpu_dec(nr_dentry); |
155 | if (dentry->d_op && dentry->d_op->d_release) |
156 | dentry->d_op->d_release(dentry); |
157 | |
158 | /* if dentry was never visible to RCU, immediate free is OK */ |
159 | if (!(dentry->d_flags & DCACHE_RCUACCESS)) |
160 | __d_free(&dentry->d_u.d_rcu); |
161 | else |
162 | call_rcu(&dentry->d_u.d_rcu, __d_free); |
163 | } |
164 | |
165 | /** |
166 | * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups |
167 | * @dentry: the target dentry |
168 | * After this call, in-progress rcu-walk path lookup will fail. This |
169 | * should be called after unhashing, and after changing d_inode (if |
170 | * the dentry has not already been unhashed). |
171 | */ |
172 | static inline void dentry_rcuwalk_barrier(struct dentry *dentry) |
173 | { |
174 | assert_spin_locked(&dentry->d_lock); |
175 | /* Go through a barrier */ |
176 | write_seqcount_barrier(&dentry->d_seq); |
177 | } |
178 | |
179 | /* |
180 | * Release the dentry's inode, using the filesystem |
181 | * d_iput() operation if defined. Dentry has no refcount |
182 | * and is unhashed. |
183 | */ |
184 | static void dentry_iput(struct dentry * dentry) |
185 | __releases(dentry->d_lock) |
186 | __releases(dentry->d_inode->i_lock) |
187 | { |
188 | struct inode *inode = dentry->d_inode; |
189 | if (inode) { |
190 | dentry->d_inode = NULL; |
191 | list_del_init(&dentry->d_alias); |
192 | spin_unlock(&dentry->d_lock); |
193 | spin_unlock(&inode->i_lock); |
194 | if (!inode->i_nlink) |
195 | fsnotify_inoderemove(inode); |
196 | if (dentry->d_op && dentry->d_op->d_iput) |
197 | dentry->d_op->d_iput(dentry, inode); |
198 | else |
199 | iput(inode); |
200 | } else { |
201 | spin_unlock(&dentry->d_lock); |
202 | } |
203 | } |
204 | |
205 | /* |
206 | * Release the dentry's inode, using the filesystem |
207 | * d_iput() operation if defined. dentry remains in-use. |
208 | */ |
209 | static void dentry_unlink_inode(struct dentry * dentry) |
210 | __releases(dentry->d_lock) |
211 | __releases(dentry->d_inode->i_lock) |
212 | { |
213 | struct inode *inode = dentry->d_inode; |
214 | dentry->d_inode = NULL; |
215 | list_del_init(&dentry->d_alias); |
216 | dentry_rcuwalk_barrier(dentry); |
217 | spin_unlock(&dentry->d_lock); |
218 | spin_unlock(&inode->i_lock); |
219 | if (!inode->i_nlink) |
220 | fsnotify_inoderemove(inode); |
221 | if (dentry->d_op && dentry->d_op->d_iput) |
222 | dentry->d_op->d_iput(dentry, inode); |
223 | else |
224 | iput(inode); |
225 | } |
226 | |
227 | /* |
228 | * dentry_lru_(add|del|move_tail) must be called with d_lock held. |
229 | */ |
230 | static void dentry_lru_add(struct dentry *dentry) |
231 | { |
232 | if (list_empty(&dentry->d_lru)) { |
233 | spin_lock(&dcache_lru_lock); |
234 | list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru); |
235 | dentry->d_sb->s_nr_dentry_unused++; |
236 | dentry_stat.nr_unused++; |
237 | spin_unlock(&dcache_lru_lock); |
238 | } |
239 | } |
240 | |
241 | static void __dentry_lru_del(struct dentry *dentry) |
242 | { |
243 | list_del_init(&dentry->d_lru); |
244 | dentry->d_sb->s_nr_dentry_unused--; |
245 | dentry_stat.nr_unused--; |
246 | } |
247 | |
248 | static void dentry_lru_del(struct dentry *dentry) |
249 | { |
250 | if (!list_empty(&dentry->d_lru)) { |
251 | spin_lock(&dcache_lru_lock); |
252 | __dentry_lru_del(dentry); |
253 | spin_unlock(&dcache_lru_lock); |
254 | } |
255 | } |
256 | |
257 | static void dentry_lru_move_tail(struct dentry *dentry) |
258 | { |
259 | spin_lock(&dcache_lru_lock); |
260 | if (list_empty(&dentry->d_lru)) { |
261 | list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru); |
262 | dentry->d_sb->s_nr_dentry_unused++; |
263 | dentry_stat.nr_unused++; |
264 | } else { |
265 | list_move_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru); |
266 | } |
267 | spin_unlock(&dcache_lru_lock); |
268 | } |
269 | |
270 | /** |
271 | * d_kill - kill dentry and return parent |
272 | * @dentry: dentry to kill |
273 | * @parent: parent dentry |
274 | * |
275 | * The dentry must already be unhashed and removed from the LRU. |
276 | * |
277 | * If this is the root of the dentry tree, return NULL. |
278 | * |
279 | * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by |
280 | * d_kill. |
281 | */ |
282 | static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent) |
283 | __releases(dentry->d_lock) |
284 | __releases(parent->d_lock) |
285 | __releases(dentry->d_inode->i_lock) |
286 | { |
287 | list_del(&dentry->d_u.d_child); |
288 | /* |
289 | * Inform try_to_ascend() that we are no longer attached to the |
290 | * dentry tree |
291 | */ |
292 | dentry->d_flags |= DCACHE_DISCONNECTED; |
293 | if (parent) |
294 | spin_unlock(&parent->d_lock); |
295 | dentry_iput(dentry); |
296 | /* |
297 | * dentry_iput drops the locks, at which point nobody (except |
298 | * transient RCU lookups) can reach this dentry. |
299 | */ |
300 | d_free(dentry); |
301 | return parent; |
302 | } |
303 | |
304 | /* |
305 | * Unhash a dentry without inserting an RCU walk barrier or checking that |
306 | * dentry->d_lock is locked. The caller must take care of that, if |
307 | * appropriate. |
308 | */ |
309 | static void __d_shrink(struct dentry *dentry) |
310 | { |
311 | if (!d_unhashed(dentry)) { |
312 | struct hlist_bl_head *b; |
313 | if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED)) |
314 | b = &dentry->d_sb->s_anon; |
315 | else |
316 | b = d_hash(dentry->d_parent, dentry->d_name.hash); |
317 | |
318 | hlist_bl_lock(b); |
319 | __hlist_bl_del(&dentry->d_hash); |
320 | dentry->d_hash.pprev = NULL; |
321 | hlist_bl_unlock(b); |
322 | } |
323 | } |
324 | |
325 | /** |
326 | * d_drop - drop a dentry |
327 | * @dentry: dentry to drop |
328 | * |
329 | * d_drop() unhashes the entry from the parent dentry hashes, so that it won't |
330 | * be found through a VFS lookup any more. Note that this is different from |
331 | * deleting the dentry - d_delete will try to mark the dentry negative if |
332 | * possible, giving a successful _negative_ lookup, while d_drop will |
333 | * just make the cache lookup fail. |
334 | * |
335 | * d_drop() is used mainly for stuff that wants to invalidate a dentry for some |
336 | * reason (NFS timeouts or autofs deletes). |
337 | * |
338 | * __d_drop requires dentry->d_lock. |
339 | */ |
340 | void __d_drop(struct dentry *dentry) |
341 | { |
342 | if (!d_unhashed(dentry)) { |
343 | __d_shrink(dentry); |
344 | dentry_rcuwalk_barrier(dentry); |
345 | } |
346 | } |
347 | EXPORT_SYMBOL(__d_drop); |
348 | |
349 | void d_drop(struct dentry *dentry) |
350 | { |
351 | spin_lock(&dentry->d_lock); |
352 | __d_drop(dentry); |
353 | spin_unlock(&dentry->d_lock); |
354 | } |
355 | EXPORT_SYMBOL(d_drop); |
356 | |
357 | /* |
358 | * d_clear_need_lookup - drop a dentry from cache and clear the need lookup flag |
359 | * @dentry: dentry to drop |
360 | * |
361 | * This is called when we do a lookup on a placeholder dentry that needed to be |
362 | * looked up. The dentry should have been hashed in order for it to be found by |
363 | * the lookup code, but now needs to be unhashed while we do the actual lookup |
364 | * and clear the DCACHE_NEED_LOOKUP flag. |
365 | */ |
366 | void d_clear_need_lookup(struct dentry *dentry) |
367 | { |
368 | spin_lock(&dentry->d_lock); |
369 | __d_drop(dentry); |
370 | dentry->d_flags &= ~DCACHE_NEED_LOOKUP; |
371 | spin_unlock(&dentry->d_lock); |
372 | } |
373 | EXPORT_SYMBOL(d_clear_need_lookup); |
374 | |
375 | /* |
376 | * Finish off a dentry we've decided to kill. |
377 | * dentry->d_lock must be held, returns with it unlocked. |
378 | * If ref is non-zero, then decrement the refcount too. |
379 | * Returns dentry requiring refcount drop, or NULL if we're done. |
380 | */ |
381 | static inline struct dentry *dentry_kill(struct dentry *dentry, int ref) |
382 | __releases(dentry->d_lock) |
383 | { |
384 | struct inode *inode; |
385 | struct dentry *parent; |
386 | |
387 | inode = dentry->d_inode; |
388 | if (inode && !spin_trylock(&inode->i_lock)) { |
389 | relock: |
390 | spin_unlock(&dentry->d_lock); |
391 | cpu_relax(); |
392 | return dentry; /* try again with same dentry */ |
393 | } |
394 | if (IS_ROOT(dentry)) |
395 | parent = NULL; |
396 | else |
397 | parent = dentry->d_parent; |
398 | if (parent && !spin_trylock(&parent->d_lock)) { |
399 | if (inode) |
400 | spin_unlock(&inode->i_lock); |
401 | goto relock; |
402 | } |
403 | |
404 | if (ref) |
405 | dentry->d_count--; |
406 | /* if dentry was on the d_lru list delete it from there */ |
407 | dentry_lru_del(dentry); |
408 | /* if it was on the hash then remove it */ |
409 | __d_drop(dentry); |
410 | return d_kill(dentry, parent); |
411 | } |
412 | |
413 | /* |
414 | * This is dput |
415 | * |
416 | * This is complicated by the fact that we do not want to put |
417 | * dentries that are no longer on any hash chain on the unused |
418 | * list: we'd much rather just get rid of them immediately. |
419 | * |
420 | * However, that implies that we have to traverse the dentry |
421 | * tree upwards to the parents which might _also_ now be |
422 | * scheduled for deletion (it may have been only waiting for |
423 | * its last child to go away). |
424 | * |
425 | * This tail recursion is done by hand as we don't want to depend |
426 | * on the compiler to always get this right (gcc generally doesn't). |
427 | * Real recursion would eat up our stack space. |
428 | */ |
429 | |
430 | /* |
431 | * dput - release a dentry |
432 | * @dentry: dentry to release |
433 | * |
434 | * Release a dentry. This will drop the usage count and if appropriate |
435 | * call the dentry unlink method as well as removing it from the queues and |
436 | * releasing its resources. If the parent dentries were scheduled for release |
437 | * they too may now get deleted. |
438 | */ |
439 | void dput(struct dentry *dentry) |
440 | { |
441 | if (!dentry) |
442 | return; |
443 | |
444 | repeat: |
445 | if (dentry->d_count == 1) |
446 | might_sleep(); |
447 | spin_lock(&dentry->d_lock); |
448 | BUG_ON(!dentry->d_count); |
449 | if (dentry->d_count > 1) { |
450 | dentry->d_count--; |
451 | spin_unlock(&dentry->d_lock); |
452 | return; |
453 | } |
454 | |
455 | if (dentry->d_flags & DCACHE_OP_DELETE) { |
456 | if (dentry->d_op->d_delete(dentry)) |
457 | goto kill_it; |
458 | } |
459 | |
460 | /* Unreachable? Get rid of it */ |
461 | if (d_unhashed(dentry)) |
462 | goto kill_it; |
463 | |
464 | /* |
465 | * If this dentry needs lookup, don't set the referenced flag so that it |
466 | * is more likely to be cleaned up by the dcache shrinker in case of |
467 | * memory pressure. |
468 | */ |
469 | if (!d_need_lookup(dentry)) |
470 | dentry->d_flags |= DCACHE_REFERENCED; |
471 | dentry_lru_add(dentry); |
472 | |
473 | dentry->d_count--; |
474 | spin_unlock(&dentry->d_lock); |
475 | return; |
476 | |
477 | kill_it: |
478 | dentry = dentry_kill(dentry, 1); |
479 | if (dentry) |
480 | goto repeat; |
481 | } |
482 | EXPORT_SYMBOL(dput); |
483 | |
484 | /** |
485 | * d_invalidate - invalidate a dentry |
486 | * @dentry: dentry to invalidate |
487 | * |
488 | * Try to invalidate the dentry if it turns out to be |
489 | * possible. If there are other dentries that can be |
490 | * reached through this one we can't delete it and we |
491 | * return -EBUSY. On success we return 0. |
492 | * |
493 | * no dcache lock. |
494 | */ |
495 | |
496 | int d_invalidate(struct dentry * dentry) |
497 | { |
498 | /* |
499 | * If it's already been dropped, return OK. |
500 | */ |
501 | spin_lock(&dentry->d_lock); |
502 | if (d_unhashed(dentry)) { |
503 | spin_unlock(&dentry->d_lock); |
504 | return 0; |
505 | } |
506 | /* |
507 | * Check whether to do a partial shrink_dcache |
508 | * to get rid of unused child entries. |
509 | */ |
510 | if (!list_empty(&dentry->d_subdirs)) { |
511 | spin_unlock(&dentry->d_lock); |
512 | shrink_dcache_parent(dentry); |
513 | spin_lock(&dentry->d_lock); |
514 | } |
515 | |
516 | /* |
517 | * Somebody else still using it? |
518 | * |
519 | * If it's a directory, we can't drop it |
520 | * for fear of somebody re-populating it |
521 | * with children (even though dropping it |
522 | * would make it unreachable from the root, |
523 | * we might still populate it if it was a |
524 | * working directory or similar). |
525 | */ |
526 | if (dentry->d_count > 1) { |
527 | if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) { |
528 | spin_unlock(&dentry->d_lock); |
529 | return -EBUSY; |
530 | } |
531 | } |
532 | |
533 | __d_drop(dentry); |
534 | spin_unlock(&dentry->d_lock); |
535 | return 0; |
536 | } |
537 | EXPORT_SYMBOL(d_invalidate); |
538 | |
539 | /* This must be called with d_lock held */ |
540 | static inline void __dget_dlock(struct dentry *dentry) |
541 | { |
542 | dentry->d_count++; |
543 | } |
544 | |
545 | static inline void __dget(struct dentry *dentry) |
546 | { |
547 | spin_lock(&dentry->d_lock); |
548 | __dget_dlock(dentry); |
549 | spin_unlock(&dentry->d_lock); |
550 | } |
551 | |
552 | struct dentry *dget_parent(struct dentry *dentry) |
553 | { |
554 | struct dentry *ret; |
555 | |
556 | repeat: |
557 | /* |
558 | * Don't need rcu_dereference because we re-check it was correct under |
559 | * the lock. |
560 | */ |
561 | rcu_read_lock(); |
562 | ret = dentry->d_parent; |
563 | spin_lock(&ret->d_lock); |
564 | if (unlikely(ret != dentry->d_parent)) { |
565 | spin_unlock(&ret->d_lock); |
566 | rcu_read_unlock(); |
567 | goto repeat; |
568 | } |
569 | rcu_read_unlock(); |
570 | BUG_ON(!ret->d_count); |
571 | ret->d_count++; |
572 | spin_unlock(&ret->d_lock); |
573 | return ret; |
574 | } |
575 | EXPORT_SYMBOL(dget_parent); |
576 | |
577 | /** |
578 | * d_find_alias - grab a hashed alias of inode |
579 | * @inode: inode in question |
580 | * @want_discon: flag, used by d_splice_alias, to request |
581 | * that only a DISCONNECTED alias be returned. |
582 | * |
583 | * If inode has a hashed alias, or is a directory and has any alias, |
584 | * acquire the reference to alias and return it. Otherwise return NULL. |
585 | * Notice that if inode is a directory there can be only one alias and |
586 | * it can be unhashed only if it has no children, or if it is the root |
587 | * of a filesystem. |
588 | * |
589 | * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer |
590 | * any other hashed alias over that one unless @want_discon is set, |
591 | * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias. |
592 | */ |
593 | static struct dentry *__d_find_alias(struct inode *inode, int want_discon) |
594 | { |
595 | struct dentry *alias, *discon_alias; |
596 | |
597 | again: |
598 | discon_alias = NULL; |
599 | list_for_each_entry(alias, &inode->i_dentry, d_alias) { |
600 | spin_lock(&alias->d_lock); |
601 | if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) { |
602 | if (IS_ROOT(alias) && |
603 | (alias->d_flags & DCACHE_DISCONNECTED)) { |
604 | discon_alias = alias; |
605 | } else if (!want_discon) { |
606 | __dget_dlock(alias); |
607 | spin_unlock(&alias->d_lock); |
608 | return alias; |
609 | } |
610 | } |
611 | spin_unlock(&alias->d_lock); |
612 | } |
613 | if (discon_alias) { |
614 | alias = discon_alias; |
615 | spin_lock(&alias->d_lock); |
616 | if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) { |
617 | if (IS_ROOT(alias) && |
618 | (alias->d_flags & DCACHE_DISCONNECTED)) { |
619 | __dget_dlock(alias); |
620 | spin_unlock(&alias->d_lock); |
621 | return alias; |
622 | } |
623 | } |
624 | spin_unlock(&alias->d_lock); |
625 | goto again; |
626 | } |
627 | return NULL; |
628 | } |
629 | |
630 | struct dentry *d_find_alias(struct inode *inode) |
631 | { |
632 | struct dentry *de = NULL; |
633 | |
634 | if (!list_empty(&inode->i_dentry)) { |
635 | spin_lock(&inode->i_lock); |
636 | de = __d_find_alias(inode, 0); |
637 | spin_unlock(&inode->i_lock); |
638 | } |
639 | return de; |
640 | } |
641 | EXPORT_SYMBOL(d_find_alias); |
642 | |
643 | /* |
644 | * Try to kill dentries associated with this inode. |
645 | * WARNING: you must own a reference to inode. |
646 | */ |
647 | void d_prune_aliases(struct inode *inode) |
648 | { |
649 | struct dentry *dentry; |
650 | restart: |
651 | spin_lock(&inode->i_lock); |
652 | list_for_each_entry(dentry, &inode->i_dentry, d_alias) { |
653 | spin_lock(&dentry->d_lock); |
654 | if (!dentry->d_count) { |
655 | __dget_dlock(dentry); |
656 | __d_drop(dentry); |
657 | spin_unlock(&dentry->d_lock); |
658 | spin_unlock(&inode->i_lock); |
659 | dput(dentry); |
660 | goto restart; |
661 | } |
662 | spin_unlock(&dentry->d_lock); |
663 | } |
664 | spin_unlock(&inode->i_lock); |
665 | } |
666 | EXPORT_SYMBOL(d_prune_aliases); |
667 | |
668 | /* |
669 | * Try to throw away a dentry - free the inode, dput the parent. |
670 | * Requires dentry->d_lock is held, and dentry->d_count == 0. |
671 | * Releases dentry->d_lock. |
672 | * |
673 | * This may fail if locks cannot be acquired no problem, just try again. |
674 | */ |
675 | static void try_prune_one_dentry(struct dentry *dentry) |
676 | __releases(dentry->d_lock) |
677 | { |
678 | struct dentry *parent; |
679 | |
680 | parent = dentry_kill(dentry, 0); |
681 | /* |
682 | * If dentry_kill returns NULL, we have nothing more to do. |
683 | * if it returns the same dentry, trylocks failed. In either |
684 | * case, just loop again. |
685 | * |
686 | * Otherwise, we need to prune ancestors too. This is necessary |
687 | * to prevent quadratic behavior of shrink_dcache_parent(), but |
688 | * is also expected to be beneficial in reducing dentry cache |
689 | * fragmentation. |
690 | */ |
691 | if (!parent) |
692 | return; |
693 | if (parent == dentry) |
694 | return; |
695 | |
696 | /* Prune ancestors. */ |
697 | dentry = parent; |
698 | while (dentry) { |
699 | spin_lock(&dentry->d_lock); |
700 | if (dentry->d_count > 1) { |
701 | dentry->d_count--; |
702 | spin_unlock(&dentry->d_lock); |
703 | return; |
704 | } |
705 | dentry = dentry_kill(dentry, 1); |
706 | } |
707 | } |
708 | |
709 | static void shrink_dentry_list(struct list_head *list) |
710 | { |
711 | struct dentry *dentry; |
712 | |
713 | rcu_read_lock(); |
714 | for (;;) { |
715 | dentry = list_entry_rcu(list->prev, struct dentry, d_lru); |
716 | if (&dentry->d_lru == list) |
717 | break; /* empty */ |
718 | spin_lock(&dentry->d_lock); |
719 | if (dentry != list_entry(list->prev, struct dentry, d_lru)) { |
720 | spin_unlock(&dentry->d_lock); |
721 | continue; |
722 | } |
723 | |
724 | /* |
725 | * We found an inuse dentry which was not removed from |
726 | * the LRU because of laziness during lookup. Do not free |
727 | * it - just keep it off the LRU list. |
728 | */ |
729 | if (dentry->d_count) { |
730 | dentry_lru_del(dentry); |
731 | spin_unlock(&dentry->d_lock); |
732 | continue; |
733 | } |
734 | |
735 | rcu_read_unlock(); |
736 | |
737 | try_prune_one_dentry(dentry); |
738 | |
739 | rcu_read_lock(); |
740 | } |
741 | rcu_read_unlock(); |
742 | } |
743 | |
744 | /** |
745 | * __shrink_dcache_sb - shrink the dentry LRU on a given superblock |
746 | * @sb: superblock to shrink dentry LRU. |
747 | * @count: number of entries to prune |
748 | * @flags: flags to control the dentry processing |
749 | * |
750 | * If flags contains DCACHE_REFERENCED reference dentries will not be pruned. |
751 | */ |
752 | static void __shrink_dcache_sb(struct super_block *sb, int count, int flags) |
753 | { |
754 | struct dentry *dentry; |
755 | LIST_HEAD(referenced); |
756 | LIST_HEAD(tmp); |
757 | |
758 | relock: |
759 | spin_lock(&dcache_lru_lock); |
760 | while (!list_empty(&sb->s_dentry_lru)) { |
761 | dentry = list_entry(sb->s_dentry_lru.prev, |
762 | struct dentry, d_lru); |
763 | BUG_ON(dentry->d_sb != sb); |
764 | |
765 | if (!spin_trylock(&dentry->d_lock)) { |
766 | spin_unlock(&dcache_lru_lock); |
767 | cpu_relax(); |
768 | goto relock; |
769 | } |
770 | |
771 | /* |
772 | * If we are honouring the DCACHE_REFERENCED flag and the |
773 | * dentry has this flag set, don't free it. Clear the flag |
774 | * and put it back on the LRU. |
775 | */ |
776 | if (flags & DCACHE_REFERENCED && |
777 | dentry->d_flags & DCACHE_REFERENCED) { |
778 | dentry->d_flags &= ~DCACHE_REFERENCED; |
779 | list_move(&dentry->d_lru, &referenced); |
780 | spin_unlock(&dentry->d_lock); |
781 | } else { |
782 | list_move_tail(&dentry->d_lru, &tmp); |
783 | spin_unlock(&dentry->d_lock); |
784 | if (!--count) |
785 | break; |
786 | } |
787 | cond_resched_lock(&dcache_lru_lock); |
788 | } |
789 | if (!list_empty(&referenced)) |
790 | list_splice(&referenced, &sb->s_dentry_lru); |
791 | spin_unlock(&dcache_lru_lock); |
792 | |
793 | shrink_dentry_list(&tmp); |
794 | } |
795 | |
796 | /** |
797 | * prune_dcache_sb - shrink the dcache |
798 | * @sb: superblock |
799 | * @nr_to_scan: number of entries to try to free |
800 | * |
801 | * Attempt to shrink the superblock dcache LRU by @nr_to_scan entries. This is |
802 | * done when we need more memory an called from the superblock shrinker |
803 | * function. |
804 | * |
805 | * This function may fail to free any resources if all the dentries are in |
806 | * use. |
807 | */ |
808 | void prune_dcache_sb(struct super_block *sb, int nr_to_scan) |
809 | { |
810 | __shrink_dcache_sb(sb, nr_to_scan, DCACHE_REFERENCED); |
811 | } |
812 | |
813 | /** |
814 | * shrink_dcache_sb - shrink dcache for a superblock |
815 | * @sb: superblock |
816 | * |
817 | * Shrink the dcache for the specified super block. This is used to free |
818 | * the dcache before unmounting a file system. |
819 | */ |
820 | void shrink_dcache_sb(struct super_block *sb) |
821 | { |
822 | LIST_HEAD(tmp); |
823 | |
824 | spin_lock(&dcache_lru_lock); |
825 | while (!list_empty(&sb->s_dentry_lru)) { |
826 | list_splice_init(&sb->s_dentry_lru, &tmp); |
827 | spin_unlock(&dcache_lru_lock); |
828 | shrink_dentry_list(&tmp); |
829 | spin_lock(&dcache_lru_lock); |
830 | } |
831 | spin_unlock(&dcache_lru_lock); |
832 | } |
833 | EXPORT_SYMBOL(shrink_dcache_sb); |
834 | |
835 | /* |
836 | * destroy a single subtree of dentries for unmount |
837 | * - see the comments on shrink_dcache_for_umount() for a description of the |
838 | * locking |
839 | */ |
840 | static void shrink_dcache_for_umount_subtree(struct dentry *dentry) |
841 | { |
842 | struct dentry *parent; |
843 | |
844 | BUG_ON(!IS_ROOT(dentry)); |
845 | |
846 | for (;;) { |
847 | /* descend to the first leaf in the current subtree */ |
848 | while (!list_empty(&dentry->d_subdirs)) |
849 | dentry = list_entry(dentry->d_subdirs.next, |
850 | struct dentry, d_u.d_child); |
851 | |
852 | /* consume the dentries from this leaf up through its parents |
853 | * until we find one with children or run out altogether */ |
854 | do { |
855 | struct inode *inode; |
856 | |
857 | /* detach from the system */ |
858 | dentry_lru_del(dentry); |
859 | __d_shrink(dentry); |
860 | |
861 | if (dentry->d_count != 0) { |
862 | printk(KERN_ERR |
863 | "BUG: Dentry %p{i=%lx,n=%s}" |
864 | " still in use (%d)" |
865 | " [unmount of %s %s]\n", |
866 | dentry, |
867 | dentry->d_inode ? |
868 | dentry->d_inode->i_ino : 0UL, |
869 | dentry->d_name.name, |
870 | dentry->d_count, |
871 | dentry->d_sb->s_type->name, |
872 | dentry->d_sb->s_id); |
873 | BUG(); |
874 | } |
875 | |
876 | if (IS_ROOT(dentry)) { |
877 | parent = NULL; |
878 | list_del(&dentry->d_u.d_child); |
879 | } else { |
880 | parent = dentry->d_parent; |
881 | parent->d_count--; |
882 | list_del(&dentry->d_u.d_child); |
883 | } |
884 | |
885 | inode = dentry->d_inode; |
886 | if (inode) { |
887 | dentry->d_inode = NULL; |
888 | list_del_init(&dentry->d_alias); |
889 | if (dentry->d_op && dentry->d_op->d_iput) |
890 | dentry->d_op->d_iput(dentry, inode); |
891 | else |
892 | iput(inode); |
893 | } |
894 | |
895 | d_free(dentry); |
896 | |
897 | /* finished when we fall off the top of the tree, |
898 | * otherwise we ascend to the parent and move to the |
899 | * next sibling if there is one */ |
900 | if (!parent) |
901 | return; |
902 | dentry = parent; |
903 | } while (list_empty(&dentry->d_subdirs)); |
904 | |
905 | dentry = list_entry(dentry->d_subdirs.next, |
906 | struct dentry, d_u.d_child); |
907 | } |
908 | } |
909 | |
910 | /* |
911 | * destroy the dentries attached to a superblock on unmounting |
912 | * - we don't need to use dentry->d_lock because: |
913 | * - the superblock is detached from all mountings and open files, so the |
914 | * dentry trees will not be rearranged by the VFS |
915 | * - s_umount is write-locked, so the memory pressure shrinker will ignore |
916 | * any dentries belonging to this superblock that it comes across |
917 | * - the filesystem itself is no longer permitted to rearrange the dentries |
918 | * in this superblock |
919 | */ |
920 | void shrink_dcache_for_umount(struct super_block *sb) |
921 | { |
922 | struct dentry *dentry; |
923 | |
924 | if (down_read_trylock(&sb->s_umount)) |
925 | BUG(); |
926 | |
927 | dentry = sb->s_root; |
928 | sb->s_root = NULL; |
929 | dentry->d_count--; |
930 | shrink_dcache_for_umount_subtree(dentry); |
931 | |
932 | while (!hlist_bl_empty(&sb->s_anon)) { |
933 | dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash); |
934 | shrink_dcache_for_umount_subtree(dentry); |
935 | } |
936 | } |
937 | |
938 | /* |
939 | * This tries to ascend one level of parenthood, but |
940 | * we can race with renaming, so we need to re-check |
941 | * the parenthood after dropping the lock and check |
942 | * that the sequence number still matches. |
943 | */ |
944 | static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq) |
945 | { |
946 | struct dentry *new = old->d_parent; |
947 | |
948 | rcu_read_lock(); |
949 | spin_unlock(&old->d_lock); |
950 | spin_lock(&new->d_lock); |
951 | |
952 | /* |
953 | * might go back up the wrong parent if we have had a rename |
954 | * or deletion |
955 | */ |
956 | if (new != old->d_parent || |
957 | (old->d_flags & DCACHE_DISCONNECTED) || |
958 | (!locked && read_seqretry(&rename_lock, seq))) { |
959 | spin_unlock(&new->d_lock); |
960 | new = NULL; |
961 | } |
962 | rcu_read_unlock(); |
963 | return new; |
964 | } |
965 | |
966 | |
967 | /* |
968 | * Search for at least 1 mount point in the dentry's subdirs. |
969 | * We descend to the next level whenever the d_subdirs |
970 | * list is non-empty and continue searching. |
971 | */ |
972 | |
973 | /** |
974 | * have_submounts - check for mounts over a dentry |
975 | * @parent: dentry to check. |
976 | * |
977 | * Return true if the parent or its subdirectories contain |
978 | * a mount point |
979 | */ |
980 | int have_submounts(struct dentry *parent) |
981 | { |
982 | struct dentry *this_parent; |
983 | struct list_head *next; |
984 | unsigned seq; |
985 | int locked = 0; |
986 | |
987 | seq = read_seqbegin(&rename_lock); |
988 | again: |
989 | this_parent = parent; |
990 | |
991 | if (d_mountpoint(parent)) |
992 | goto positive; |
993 | spin_lock(&this_parent->d_lock); |
994 | repeat: |
995 | next = this_parent->d_subdirs.next; |
996 | resume: |
997 | while (next != &this_parent->d_subdirs) { |
998 | struct list_head *tmp = next; |
999 | struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); |
1000 | next = tmp->next; |
1001 | |
1002 | spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
1003 | /* Have we found a mount point ? */ |
1004 | if (d_mountpoint(dentry)) { |
1005 | spin_unlock(&dentry->d_lock); |
1006 | spin_unlock(&this_parent->d_lock); |
1007 | goto positive; |
1008 | } |
1009 | if (!list_empty(&dentry->d_subdirs)) { |
1010 | spin_unlock(&this_parent->d_lock); |
1011 | spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_); |
1012 | this_parent = dentry; |
1013 | spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); |
1014 | goto repeat; |
1015 | } |
1016 | spin_unlock(&dentry->d_lock); |
1017 | } |
1018 | /* |
1019 | * All done at this level ... ascend and resume the search. |
1020 | */ |
1021 | if (this_parent != parent) { |
1022 | struct dentry *child = this_parent; |
1023 | this_parent = try_to_ascend(this_parent, locked, seq); |
1024 | if (!this_parent) |
1025 | goto rename_retry; |
1026 | next = child->d_u.d_child.next; |
1027 | goto resume; |
1028 | } |
1029 | spin_unlock(&this_parent->d_lock); |
1030 | if (!locked && read_seqretry(&rename_lock, seq)) |
1031 | goto rename_retry; |
1032 | if (locked) |
1033 | write_sequnlock(&rename_lock); |
1034 | return 0; /* No mount points found in tree */ |
1035 | positive: |
1036 | if (!locked && read_seqretry(&rename_lock, seq)) |
1037 | goto rename_retry; |
1038 | if (locked) |
1039 | write_sequnlock(&rename_lock); |
1040 | return 1; |
1041 | |
1042 | rename_retry: |
1043 | locked = 1; |
1044 | write_seqlock(&rename_lock); |
1045 | goto again; |
1046 | } |
1047 | EXPORT_SYMBOL(have_submounts); |
1048 | |
1049 | /* |
1050 | * Search the dentry child list for the specified parent, |
1051 | * and move any unused dentries to the end of the unused |
1052 | * list for prune_dcache(). We descend to the next level |
1053 | * whenever the d_subdirs list is non-empty and continue |
1054 | * searching. |
1055 | * |
1056 | * It returns zero iff there are no unused children, |
1057 | * otherwise it returns the number of children moved to |
1058 | * the end of the unused list. This may not be the total |
1059 | * number of unused children, because select_parent can |
1060 | * drop the lock and return early due to latency |
1061 | * constraints. |
1062 | */ |
1063 | static int select_parent(struct dentry * parent) |
1064 | { |
1065 | struct dentry *this_parent; |
1066 | struct list_head *next; |
1067 | unsigned seq; |
1068 | int found = 0; |
1069 | int locked = 0; |
1070 | |
1071 | seq = read_seqbegin(&rename_lock); |
1072 | again: |
1073 | this_parent = parent; |
1074 | spin_lock(&this_parent->d_lock); |
1075 | repeat: |
1076 | next = this_parent->d_subdirs.next; |
1077 | resume: |
1078 | while (next != &this_parent->d_subdirs) { |
1079 | struct list_head *tmp = next; |
1080 | struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); |
1081 | next = tmp->next; |
1082 | |
1083 | spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
1084 | |
1085 | /* |
1086 | * move only zero ref count dentries to the end |
1087 | * of the unused list for prune_dcache |
1088 | */ |
1089 | if (!dentry->d_count) { |
1090 | dentry_lru_move_tail(dentry); |
1091 | found++; |
1092 | } else { |
1093 | dentry_lru_del(dentry); |
1094 | } |
1095 | |
1096 | /* |
1097 | * We can return to the caller if we have found some (this |
1098 | * ensures forward progress). We'll be coming back to find |
1099 | * the rest. |
1100 | */ |
1101 | if (found && need_resched()) { |
1102 | spin_unlock(&dentry->d_lock); |
1103 | goto out; |
1104 | } |
1105 | |
1106 | /* |
1107 | * Descend a level if the d_subdirs list is non-empty. |
1108 | */ |
1109 | if (!list_empty(&dentry->d_subdirs)) { |
1110 | spin_unlock(&this_parent->d_lock); |
1111 | spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_); |
1112 | this_parent = dentry; |
1113 | spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); |
1114 | goto repeat; |
1115 | } |
1116 | |
1117 | spin_unlock(&dentry->d_lock); |
1118 | } |
1119 | /* |
1120 | * All done at this level ... ascend and resume the search. |
1121 | */ |
1122 | if (this_parent != parent) { |
1123 | struct dentry *child = this_parent; |
1124 | this_parent = try_to_ascend(this_parent, locked, seq); |
1125 | if (!this_parent) |
1126 | goto rename_retry; |
1127 | next = child->d_u.d_child.next; |
1128 | goto resume; |
1129 | } |
1130 | out: |
1131 | spin_unlock(&this_parent->d_lock); |
1132 | if (!locked && read_seqretry(&rename_lock, seq)) |
1133 | goto rename_retry; |
1134 | if (locked) |
1135 | write_sequnlock(&rename_lock); |
1136 | return found; |
1137 | |
1138 | rename_retry: |
1139 | if (found) |
1140 | return found; |
1141 | locked = 1; |
1142 | write_seqlock(&rename_lock); |
1143 | goto again; |
1144 | } |
1145 | |
1146 | /** |
1147 | * shrink_dcache_parent - prune dcache |
1148 | * @parent: parent of entries to prune |
1149 | * |
1150 | * Prune the dcache to remove unused children of the parent dentry. |
1151 | */ |
1152 | |
1153 | void shrink_dcache_parent(struct dentry * parent) |
1154 | { |
1155 | struct super_block *sb = parent->d_sb; |
1156 | int found; |
1157 | |
1158 | while ((found = select_parent(parent)) != 0) |
1159 | __shrink_dcache_sb(sb, found, 0); |
1160 | } |
1161 | EXPORT_SYMBOL(shrink_dcache_parent); |
1162 | |
1163 | /** |
1164 | * __d_alloc - allocate a dcache entry |
1165 | * @sb: filesystem it will belong to |
1166 | * @name: qstr of the name |
1167 | * |
1168 | * Allocates a dentry. It returns %NULL if there is insufficient memory |
1169 | * available. On a success the dentry is returned. The name passed in is |
1170 | * copied and the copy passed in may be reused after this call. |
1171 | */ |
1172 | |
1173 | struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name) |
1174 | { |
1175 | struct dentry *dentry; |
1176 | char *dname; |
1177 | |
1178 | dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL); |
1179 | if (!dentry) |
1180 | return NULL; |
1181 | |
1182 | if (name->len > DNAME_INLINE_LEN-1) { |
1183 | dname = kmalloc(name->len + 1, GFP_KERNEL); |
1184 | if (!dname) { |
1185 | kmem_cache_free(dentry_cache, dentry); |
1186 | return NULL; |
1187 | } |
1188 | } else { |
1189 | dname = dentry->d_iname; |
1190 | } |
1191 | dentry->d_name.name = dname; |
1192 | |
1193 | dentry->d_name.len = name->len; |
1194 | dentry->d_name.hash = name->hash; |
1195 | memcpy(dname, name->name, name->len); |
1196 | dname[name->len] = 0; |
1197 | |
1198 | dentry->d_count = 1; |
1199 | dentry->d_flags = 0; |
1200 | spin_lock_init(&dentry->d_lock); |
1201 | seqcount_init(&dentry->d_seq); |
1202 | dentry->d_inode = NULL; |
1203 | dentry->d_parent = dentry; |
1204 | dentry->d_sb = sb; |
1205 | dentry->d_op = NULL; |
1206 | dentry->d_fsdata = NULL; |
1207 | INIT_HLIST_BL_NODE(&dentry->d_hash); |
1208 | INIT_LIST_HEAD(&dentry->d_lru); |
1209 | INIT_LIST_HEAD(&dentry->d_subdirs); |
1210 | INIT_LIST_HEAD(&dentry->d_alias); |
1211 | INIT_LIST_HEAD(&dentry->d_u.d_child); |
1212 | d_set_d_op(dentry, dentry->d_sb->s_d_op); |
1213 | |
1214 | this_cpu_inc(nr_dentry); |
1215 | |
1216 | return dentry; |
1217 | } |
1218 | |
1219 | /** |
1220 | * d_alloc - allocate a dcache entry |
1221 | * @parent: parent of entry to allocate |
1222 | * @name: qstr of the name |
1223 | * |
1224 | * Allocates a dentry. It returns %NULL if there is insufficient memory |
1225 | * available. On a success the dentry is returned. The name passed in is |
1226 | * copied and the copy passed in may be reused after this call. |
1227 | */ |
1228 | struct dentry *d_alloc(struct dentry * parent, const struct qstr *name) |
1229 | { |
1230 | struct dentry *dentry = __d_alloc(parent->d_sb, name); |
1231 | if (!dentry) |
1232 | return NULL; |
1233 | |
1234 | spin_lock(&parent->d_lock); |
1235 | /* |
1236 | * don't need child lock because it is not subject |
1237 | * to concurrency here |
1238 | */ |
1239 | __dget_dlock(parent); |
1240 | dentry->d_parent = parent; |
1241 | list_add(&dentry->d_u.d_child, &parent->d_subdirs); |
1242 | spin_unlock(&parent->d_lock); |
1243 | |
1244 | return dentry; |
1245 | } |
1246 | EXPORT_SYMBOL(d_alloc); |
1247 | |
1248 | struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name) |
1249 | { |
1250 | struct dentry *dentry = __d_alloc(sb, name); |
1251 | if (dentry) |
1252 | dentry->d_flags |= DCACHE_DISCONNECTED; |
1253 | return dentry; |
1254 | } |
1255 | EXPORT_SYMBOL(d_alloc_pseudo); |
1256 | |
1257 | struct dentry *d_alloc_name(struct dentry *parent, const char *name) |
1258 | { |
1259 | struct qstr q; |
1260 | |
1261 | q.name = name; |
1262 | q.len = strlen(name); |
1263 | q.hash = full_name_hash(q.name, q.len); |
1264 | return d_alloc(parent, &q); |
1265 | } |
1266 | EXPORT_SYMBOL(d_alloc_name); |
1267 | |
1268 | void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op) |
1269 | { |
1270 | WARN_ON_ONCE(dentry->d_op); |
1271 | WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH | |
1272 | DCACHE_OP_COMPARE | |
1273 | DCACHE_OP_REVALIDATE | |
1274 | DCACHE_OP_DELETE )); |
1275 | dentry->d_op = op; |
1276 | if (!op) |
1277 | return; |
1278 | if (op->d_hash) |
1279 | dentry->d_flags |= DCACHE_OP_HASH; |
1280 | if (op->d_compare) |
1281 | dentry->d_flags |= DCACHE_OP_COMPARE; |
1282 | if (op->d_revalidate) |
1283 | dentry->d_flags |= DCACHE_OP_REVALIDATE; |
1284 | if (op->d_delete) |
1285 | dentry->d_flags |= DCACHE_OP_DELETE; |
1286 | |
1287 | } |
1288 | EXPORT_SYMBOL(d_set_d_op); |
1289 | |
1290 | static void __d_instantiate(struct dentry *dentry, struct inode *inode) |
1291 | { |
1292 | spin_lock(&dentry->d_lock); |
1293 | if (inode) { |
1294 | if (unlikely(IS_AUTOMOUNT(inode))) |
1295 | dentry->d_flags |= DCACHE_NEED_AUTOMOUNT; |
1296 | list_add(&dentry->d_alias, &inode->i_dentry); |
1297 | } |
1298 | dentry->d_inode = inode; |
1299 | dentry_rcuwalk_barrier(dentry); |
1300 | spin_unlock(&dentry->d_lock); |
1301 | fsnotify_d_instantiate(dentry, inode); |
1302 | } |
1303 | |
1304 | /** |
1305 | * d_instantiate - fill in inode information for a dentry |
1306 | * @entry: dentry to complete |
1307 | * @inode: inode to attach to this dentry |
1308 | * |
1309 | * Fill in inode information in the entry. |
1310 | * |
1311 | * This turns negative dentries into productive full members |
1312 | * of society. |
1313 | * |
1314 | * NOTE! This assumes that the inode count has been incremented |
1315 | * (or otherwise set) by the caller to indicate that it is now |
1316 | * in use by the dcache. |
1317 | */ |
1318 | |
1319 | void d_instantiate(struct dentry *entry, struct inode * inode) |
1320 | { |
1321 | BUG_ON(!list_empty(&entry->d_alias)); |
1322 | if (inode) |
1323 | spin_lock(&inode->i_lock); |
1324 | __d_instantiate(entry, inode); |
1325 | if (inode) |
1326 | spin_unlock(&inode->i_lock); |
1327 | security_d_instantiate(entry, inode); |
1328 | } |
1329 | EXPORT_SYMBOL(d_instantiate); |
1330 | |
1331 | /** |
1332 | * d_instantiate_unique - instantiate a non-aliased dentry |
1333 | * @entry: dentry to instantiate |
1334 | * @inode: inode to attach to this dentry |
1335 | * |
1336 | * Fill in inode information in the entry. On success, it returns NULL. |
1337 | * If an unhashed alias of "entry" already exists, then we return the |
1338 | * aliased dentry instead and drop one reference to inode. |
1339 | * |
1340 | * Note that in order to avoid conflicts with rename() etc, the caller |
1341 | * had better be holding the parent directory semaphore. |
1342 | * |
1343 | * This also assumes that the inode count has been incremented |
1344 | * (or otherwise set) by the caller to indicate that it is now |
1345 | * in use by the dcache. |
1346 | */ |
1347 | static struct dentry *__d_instantiate_unique(struct dentry *entry, |
1348 | struct inode *inode) |
1349 | { |
1350 | struct dentry *alias; |
1351 | int len = entry->d_name.len; |
1352 | const char *name = entry->d_name.name; |
1353 | unsigned int hash = entry->d_name.hash; |
1354 | |
1355 | if (!inode) { |
1356 | __d_instantiate(entry, NULL); |
1357 | return NULL; |
1358 | } |
1359 | |
1360 | list_for_each_entry(alias, &inode->i_dentry, d_alias) { |
1361 | struct qstr *qstr = &alias->d_name; |
1362 | |
1363 | /* |
1364 | * Don't need alias->d_lock here, because aliases with |
1365 | * d_parent == entry->d_parent are not subject to name or |
1366 | * parent changes, because the parent inode i_mutex is held. |
1367 | */ |
1368 | if (qstr->hash != hash) |
1369 | continue; |
1370 | if (alias->d_parent != entry->d_parent) |
1371 | continue; |
1372 | if (dentry_cmp(qstr->name, qstr->len, name, len)) |
1373 | continue; |
1374 | __dget(alias); |
1375 | return alias; |
1376 | } |
1377 | |
1378 | __d_instantiate(entry, inode); |
1379 | return NULL; |
1380 | } |
1381 | |
1382 | struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode) |
1383 | { |
1384 | struct dentry *result; |
1385 | |
1386 | BUG_ON(!list_empty(&entry->d_alias)); |
1387 | |
1388 | if (inode) |
1389 | spin_lock(&inode->i_lock); |
1390 | result = __d_instantiate_unique(entry, inode); |
1391 | if (inode) |
1392 | spin_unlock(&inode->i_lock); |
1393 | |
1394 | if (!result) { |
1395 | security_d_instantiate(entry, inode); |
1396 | return NULL; |
1397 | } |
1398 | |
1399 | BUG_ON(!d_unhashed(result)); |
1400 | iput(inode); |
1401 | return result; |
1402 | } |
1403 | |
1404 | EXPORT_SYMBOL(d_instantiate_unique); |
1405 | |
1406 | /** |
1407 | * d_alloc_root - allocate root dentry |
1408 | * @root_inode: inode to allocate the root for |
1409 | * |
1410 | * Allocate a root ("/") dentry for the inode given. The inode is |
1411 | * instantiated and returned. %NULL is returned if there is insufficient |
1412 | * memory or the inode passed is %NULL. |
1413 | */ |
1414 | |
1415 | struct dentry * d_alloc_root(struct inode * root_inode) |
1416 | { |
1417 | struct dentry *res = NULL; |
1418 | |
1419 | if (root_inode) { |
1420 | static const struct qstr name = { .name = "/", .len = 1 }; |
1421 | |
1422 | res = __d_alloc(root_inode->i_sb, &name); |
1423 | if (res) |
1424 | d_instantiate(res, root_inode); |
1425 | } |
1426 | return res; |
1427 | } |
1428 | EXPORT_SYMBOL(d_alloc_root); |
1429 | |
1430 | static struct dentry * __d_find_any_alias(struct inode *inode) |
1431 | { |
1432 | struct dentry *alias; |
1433 | |
1434 | if (list_empty(&inode->i_dentry)) |
1435 | return NULL; |
1436 | alias = list_first_entry(&inode->i_dentry, struct dentry, d_alias); |
1437 | __dget(alias); |
1438 | return alias; |
1439 | } |
1440 | |
1441 | static struct dentry * d_find_any_alias(struct inode *inode) |
1442 | { |
1443 | struct dentry *de; |
1444 | |
1445 | spin_lock(&inode->i_lock); |
1446 | de = __d_find_any_alias(inode); |
1447 | spin_unlock(&inode->i_lock); |
1448 | return de; |
1449 | } |
1450 | |
1451 | |
1452 | /** |
1453 | * d_obtain_alias - find or allocate a dentry for a given inode |
1454 | * @inode: inode to allocate the dentry for |
1455 | * |
1456 | * Obtain a dentry for an inode resulting from NFS filehandle conversion or |
1457 | * similar open by handle operations. The returned dentry may be anonymous, |
1458 | * or may have a full name (if the inode was already in the cache). |
1459 | * |
1460 | * When called on a directory inode, we must ensure that the inode only ever |
1461 | * has one dentry. If a dentry is found, that is returned instead of |
1462 | * allocating a new one. |
1463 | * |
1464 | * On successful return, the reference to the inode has been transferred |
1465 | * to the dentry. In case of an error the reference on the inode is released. |
1466 | * To make it easier to use in export operations a %NULL or IS_ERR inode may |
1467 | * be passed in and will be the error will be propagate to the return value, |
1468 | * with a %NULL @inode replaced by ERR_PTR(-ESTALE). |
1469 | */ |
1470 | struct dentry *d_obtain_alias(struct inode *inode) |
1471 | { |
1472 | static const struct qstr anonstring = { .name = "" }; |
1473 | struct dentry *tmp; |
1474 | struct dentry *res; |
1475 | |
1476 | if (!inode) |
1477 | return ERR_PTR(-ESTALE); |
1478 | if (IS_ERR(inode)) |
1479 | return ERR_CAST(inode); |
1480 | |
1481 | res = d_find_any_alias(inode); |
1482 | if (res) |
1483 | goto out_iput; |
1484 | |
1485 | tmp = __d_alloc(inode->i_sb, &anonstring); |
1486 | if (!tmp) { |
1487 | res = ERR_PTR(-ENOMEM); |
1488 | goto out_iput; |
1489 | } |
1490 | |
1491 | spin_lock(&inode->i_lock); |
1492 | res = __d_find_any_alias(inode); |
1493 | if (res) { |
1494 | spin_unlock(&inode->i_lock); |
1495 | dput(tmp); |
1496 | goto out_iput; |
1497 | } |
1498 | |
1499 | /* attach a disconnected dentry */ |
1500 | spin_lock(&tmp->d_lock); |
1501 | tmp->d_inode = inode; |
1502 | tmp->d_flags |= DCACHE_DISCONNECTED; |
1503 | list_add(&tmp->d_alias, &inode->i_dentry); |
1504 | hlist_bl_lock(&tmp->d_sb->s_anon); |
1505 | hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon); |
1506 | hlist_bl_unlock(&tmp->d_sb->s_anon); |
1507 | spin_unlock(&tmp->d_lock); |
1508 | spin_unlock(&inode->i_lock); |
1509 | security_d_instantiate(tmp, inode); |
1510 | |
1511 | return tmp; |
1512 | |
1513 | out_iput: |
1514 | if (res && !IS_ERR(res)) |
1515 | security_d_instantiate(res, inode); |
1516 | iput(inode); |
1517 | return res; |
1518 | } |
1519 | EXPORT_SYMBOL(d_obtain_alias); |
1520 | |
1521 | /** |
1522 | * d_splice_alias - splice a disconnected dentry into the tree if one exists |
1523 | * @inode: the inode which may have a disconnected dentry |
1524 | * @dentry: a negative dentry which we want to point to the inode. |
1525 | * |
1526 | * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and |
1527 | * DCACHE_DISCONNECTED), then d_move that in place of the given dentry |
1528 | * and return it, else simply d_add the inode to the dentry and return NULL. |
1529 | * |
1530 | * This is needed in the lookup routine of any filesystem that is exportable |
1531 | * (via knfsd) so that we can build dcache paths to directories effectively. |
1532 | * |
1533 | * If a dentry was found and moved, then it is returned. Otherwise NULL |
1534 | * is returned. This matches the expected return value of ->lookup. |
1535 | * |
1536 | */ |
1537 | struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry) |
1538 | { |
1539 | struct dentry *new = NULL; |
1540 | |
1541 | if (IS_ERR(inode)) |
1542 | return ERR_CAST(inode); |
1543 | |
1544 | if (inode && S_ISDIR(inode->i_mode)) { |
1545 | spin_lock(&inode->i_lock); |
1546 | new = __d_find_alias(inode, 1); |
1547 | if (new) { |
1548 | BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED)); |
1549 | spin_unlock(&inode->i_lock); |
1550 | security_d_instantiate(new, inode); |
1551 | d_move(new, dentry); |
1552 | iput(inode); |
1553 | } else { |
1554 | /* already taking inode->i_lock, so d_add() by hand */ |
1555 | __d_instantiate(dentry, inode); |
1556 | spin_unlock(&inode->i_lock); |
1557 | security_d_instantiate(dentry, inode); |
1558 | d_rehash(dentry); |
1559 | } |
1560 | } else |
1561 | d_add(dentry, inode); |
1562 | return new; |
1563 | } |
1564 | EXPORT_SYMBOL(d_splice_alias); |
1565 | |
1566 | /** |
1567 | * d_add_ci - lookup or allocate new dentry with case-exact name |
1568 | * @inode: the inode case-insensitive lookup has found |
1569 | * @dentry: the negative dentry that was passed to the parent's lookup func |
1570 | * @name: the case-exact name to be associated with the returned dentry |
1571 | * |
1572 | * This is to avoid filling the dcache with case-insensitive names to the |
1573 | * same inode, only the actual correct case is stored in the dcache for |
1574 | * case-insensitive filesystems. |
1575 | * |
1576 | * For a case-insensitive lookup match and if the the case-exact dentry |
1577 | * already exists in in the dcache, use it and return it. |
1578 | * |
1579 | * If no entry exists with the exact case name, allocate new dentry with |
1580 | * the exact case, and return the spliced entry. |
1581 | */ |
1582 | struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode, |
1583 | struct qstr *name) |
1584 | { |
1585 | int error; |
1586 | struct dentry *found; |
1587 | struct dentry *new; |
1588 | |
1589 | /* |
1590 | * First check if a dentry matching the name already exists, |
1591 | * if not go ahead and create it now. |
1592 | */ |
1593 | found = d_hash_and_lookup(dentry->d_parent, name); |
1594 | if (!found) { |
1595 | new = d_alloc(dentry->d_parent, name); |
1596 | if (!new) { |
1597 | error = -ENOMEM; |
1598 | goto err_out; |
1599 | } |
1600 | |
1601 | found = d_splice_alias(inode, new); |
1602 | if (found) { |
1603 | dput(new); |
1604 | return found; |
1605 | } |
1606 | return new; |
1607 | } |
1608 | |
1609 | /* |
1610 | * If a matching dentry exists, and it's not negative use it. |
1611 | * |
1612 | * Decrement the reference count to balance the iget() done |
1613 | * earlier on. |
1614 | */ |
1615 | if (found->d_inode) { |
1616 | if (unlikely(found->d_inode != inode)) { |
1617 | /* This can't happen because bad inodes are unhashed. */ |
1618 | BUG_ON(!is_bad_inode(inode)); |
1619 | BUG_ON(!is_bad_inode(found->d_inode)); |
1620 | } |
1621 | iput(inode); |
1622 | return found; |
1623 | } |
1624 | |
1625 | /* |
1626 | * We are going to instantiate this dentry, unhash it and clear the |
1627 | * lookup flag so we can do that. |
1628 | */ |
1629 | if (unlikely(d_need_lookup(found))) |
1630 | d_clear_need_lookup(found); |
1631 | |
1632 | /* |
1633 | * Negative dentry: instantiate it unless the inode is a directory and |
1634 | * already has a dentry. |
1635 | */ |
1636 | new = d_splice_alias(inode, found); |
1637 | if (new) { |
1638 | dput(found); |
1639 | found = new; |
1640 | } |
1641 | return found; |
1642 | |
1643 | err_out: |
1644 | iput(inode); |
1645 | return ERR_PTR(error); |
1646 | } |
1647 | EXPORT_SYMBOL(d_add_ci); |
1648 | |
1649 | /** |
1650 | * __d_lookup_rcu - search for a dentry (racy, store-free) |
1651 | * @parent: parent dentry |
1652 | * @name: qstr of name we wish to find |
1653 | * @seq: returns d_seq value at the point where the dentry was found |
1654 | * @inode: returns dentry->d_inode when the inode was found valid. |
1655 | * Returns: dentry, or NULL |
1656 | * |
1657 | * __d_lookup_rcu is the dcache lookup function for rcu-walk name |
1658 | * resolution (store-free path walking) design described in |
1659 | * Documentation/filesystems/path-lookup.txt. |
1660 | * |
1661 | * This is not to be used outside core vfs. |
1662 | * |
1663 | * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock |
1664 | * held, and rcu_read_lock held. The returned dentry must not be stored into |
1665 | * without taking d_lock and checking d_seq sequence count against @seq |
1666 | * returned here. |
1667 | * |
1668 | * A refcount may be taken on the found dentry with the __d_rcu_to_refcount |
1669 | * function. |
1670 | * |
1671 | * Alternatively, __d_lookup_rcu may be called again to look up the child of |
1672 | * the returned dentry, so long as its parent's seqlock is checked after the |
1673 | * child is looked up. Thus, an interlocking stepping of sequence lock checks |
1674 | * is formed, giving integrity down the path walk. |
1675 | */ |
1676 | struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name, |
1677 | unsigned *seq, struct inode **inode) |
1678 | { |
1679 | unsigned int len = name->len; |
1680 | unsigned int hash = name->hash; |
1681 | const unsigned char *str = name->name; |
1682 | struct hlist_bl_head *b = d_hash(parent, hash); |
1683 | struct hlist_bl_node *node; |
1684 | struct dentry *dentry; |
1685 | |
1686 | /* |
1687 | * Note: There is significant duplication with __d_lookup_rcu which is |
1688 | * required to prevent single threaded performance regressions |
1689 | * especially on architectures where smp_rmb (in seqcounts) are costly. |
1690 | * Keep the two functions in sync. |
1691 | */ |
1692 | |
1693 | /* |
1694 | * The hash list is protected using RCU. |
1695 | * |
1696 | * Carefully use d_seq when comparing a candidate dentry, to avoid |
1697 | * races with d_move(). |
1698 | * |
1699 | * It is possible that concurrent renames can mess up our list |
1700 | * walk here and result in missing our dentry, resulting in the |
1701 | * false-negative result. d_lookup() protects against concurrent |
1702 | * renames using rename_lock seqlock. |
1703 | * |
1704 | * See Documentation/filesystems/path-lookup.txt for more details. |
1705 | */ |
1706 | hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { |
1707 | struct inode *i; |
1708 | const char *tname; |
1709 | int tlen; |
1710 | |
1711 | if (dentry->d_name.hash != hash) |
1712 | continue; |
1713 | |
1714 | seqretry: |
1715 | *seq = read_seqcount_begin(&dentry->d_seq); |
1716 | if (dentry->d_parent != parent) |
1717 | continue; |
1718 | if (d_unhashed(dentry)) |
1719 | continue; |
1720 | tlen = dentry->d_name.len; |
1721 | tname = dentry->d_name.name; |
1722 | i = dentry->d_inode; |
1723 | prefetch(tname); |
1724 | /* |
1725 | * This seqcount check is required to ensure name and |
1726 | * len are loaded atomically, so as not to walk off the |
1727 | * edge of memory when walking. If we could load this |
1728 | * atomically some other way, we could drop this check. |
1729 | */ |
1730 | if (read_seqcount_retry(&dentry->d_seq, *seq)) |
1731 | goto seqretry; |
1732 | if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) { |
1733 | if (parent->d_op->d_compare(parent, *inode, |
1734 | dentry, i, |
1735 | tlen, tname, name)) |
1736 | continue; |
1737 | } else { |
1738 | if (dentry_cmp(tname, tlen, str, len)) |
1739 | continue; |
1740 | } |
1741 | /* |
1742 | * No extra seqcount check is required after the name |
1743 | * compare. The caller must perform a seqcount check in |
1744 | * order to do anything useful with the returned dentry |
1745 | * anyway. |
1746 | */ |
1747 | *inode = i; |
1748 | return dentry; |
1749 | } |
1750 | return NULL; |
1751 | } |
1752 | |
1753 | /** |
1754 | * d_lookup - search for a dentry |
1755 | * @parent: parent dentry |
1756 | * @name: qstr of name we wish to find |
1757 | * Returns: dentry, or NULL |
1758 | * |
1759 | * d_lookup searches the children of the parent dentry for the name in |
1760 | * question. If the dentry is found its reference count is incremented and the |
1761 | * dentry is returned. The caller must use dput to free the entry when it has |
1762 | * finished using it. %NULL is returned if the dentry does not exist. |
1763 | */ |
1764 | struct dentry *d_lookup(struct dentry *parent, struct qstr *name) |
1765 | { |
1766 | struct dentry *dentry; |
1767 | unsigned seq; |
1768 | |
1769 | do { |
1770 | seq = read_seqbegin(&rename_lock); |
1771 | dentry = __d_lookup(parent, name); |
1772 | if (dentry) |
1773 | break; |
1774 | } while (read_seqretry(&rename_lock, seq)); |
1775 | return dentry; |
1776 | } |
1777 | EXPORT_SYMBOL(d_lookup); |
1778 | |
1779 | /** |
1780 | * __d_lookup - search for a dentry (racy) |
1781 | * @parent: parent dentry |
1782 | * @name: qstr of name we wish to find |
1783 | * Returns: dentry, or NULL |
1784 | * |
1785 | * __d_lookup is like d_lookup, however it may (rarely) return a |
1786 | * false-negative result due to unrelated rename activity. |
1787 | * |
1788 | * __d_lookup is slightly faster by avoiding rename_lock read seqlock, |
1789 | * however it must be used carefully, eg. with a following d_lookup in |
1790 | * the case of failure. |
1791 | * |
1792 | * __d_lookup callers must be commented. |
1793 | */ |
1794 | struct dentry *__d_lookup(struct dentry *parent, struct qstr *name) |
1795 | { |
1796 | unsigned int len = name->len; |
1797 | unsigned int hash = name->hash; |
1798 | const unsigned char *str = name->name; |
1799 | struct hlist_bl_head *b = d_hash(parent, hash); |
1800 | struct hlist_bl_node *node; |
1801 | struct dentry *found = NULL; |
1802 | struct dentry *dentry; |
1803 | |
1804 | /* |
1805 | * Note: There is significant duplication with __d_lookup_rcu which is |
1806 | * required to prevent single threaded performance regressions |
1807 | * especially on architectures where smp_rmb (in seqcounts) are costly. |
1808 | * Keep the two functions in sync. |
1809 | */ |
1810 | |
1811 | /* |
1812 | * The hash list is protected using RCU. |
1813 | * |
1814 | * Take d_lock when comparing a candidate dentry, to avoid races |
1815 | * with d_move(). |
1816 | * |
1817 | * It is possible that concurrent renames can mess up our list |
1818 | * walk here and result in missing our dentry, resulting in the |
1819 | * false-negative result. d_lookup() protects against concurrent |
1820 | * renames using rename_lock seqlock. |
1821 | * |
1822 | * See Documentation/filesystems/path-lookup.txt for more details. |
1823 | */ |
1824 | rcu_read_lock(); |
1825 | |
1826 | hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { |
1827 | const char *tname; |
1828 | int tlen; |
1829 | |
1830 | if (dentry->d_name.hash != hash) |
1831 | continue; |
1832 | |
1833 | spin_lock(&dentry->d_lock); |
1834 | if (dentry->d_parent != parent) |
1835 | goto next; |
1836 | if (d_unhashed(dentry)) |
1837 | goto next; |
1838 | |
1839 | /* |
1840 | * It is safe to compare names since d_move() cannot |
1841 | * change the qstr (protected by d_lock). |
1842 | */ |
1843 | tlen = dentry->d_name.len; |
1844 | tname = dentry->d_name.name; |
1845 | if (parent->d_flags & DCACHE_OP_COMPARE) { |
1846 | if (parent->d_op->d_compare(parent, parent->d_inode, |
1847 | dentry, dentry->d_inode, |
1848 | tlen, tname, name)) |
1849 | goto next; |
1850 | } else { |
1851 | if (dentry_cmp(tname, tlen, str, len)) |
1852 | goto next; |
1853 | } |
1854 | |
1855 | dentry->d_count++; |
1856 | found = dentry; |
1857 | spin_unlock(&dentry->d_lock); |
1858 | break; |
1859 | next: |
1860 | spin_unlock(&dentry->d_lock); |
1861 | } |
1862 | rcu_read_unlock(); |
1863 | |
1864 | return found; |
1865 | } |
1866 | |
1867 | /** |
1868 | * d_hash_and_lookup - hash the qstr then search for a dentry |
1869 | * @dir: Directory to search in |
1870 | * @name: qstr of name we wish to find |
1871 | * |
1872 | * On hash failure or on lookup failure NULL is returned. |
1873 | */ |
1874 | struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name) |
1875 | { |
1876 | struct dentry *dentry = NULL; |
1877 | |
1878 | /* |
1879 | * Check for a fs-specific hash function. Note that we must |
1880 | * calculate the standard hash first, as the d_op->d_hash() |
1881 | * routine may choose to leave the hash value unchanged. |
1882 | */ |
1883 | name->hash = full_name_hash(name->name, name->len); |
1884 | if (dir->d_flags & DCACHE_OP_HASH) { |
1885 | if (dir->d_op->d_hash(dir, dir->d_inode, name) < 0) |
1886 | goto out; |
1887 | } |
1888 | dentry = d_lookup(dir, name); |
1889 | out: |
1890 | return dentry; |
1891 | } |
1892 | |
1893 | /** |
1894 | * d_validate - verify dentry provided from insecure source (deprecated) |
1895 | * @dentry: The dentry alleged to be valid child of @dparent |
1896 | * @dparent: The parent dentry (known to be valid) |
1897 | * |
1898 | * An insecure source has sent us a dentry, here we verify it and dget() it. |
1899 | * This is used by ncpfs in its readdir implementation. |
1900 | * Zero is returned in the dentry is invalid. |
1901 | * |
1902 | * This function is slow for big directories, and deprecated, do not use it. |
1903 | */ |
1904 | int d_validate(struct dentry *dentry, struct dentry *dparent) |
1905 | { |
1906 | struct dentry *child; |
1907 | |
1908 | spin_lock(&dparent->d_lock); |
1909 | list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) { |
1910 | if (dentry == child) { |
1911 | spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
1912 | __dget_dlock(dentry); |
1913 | spin_unlock(&dentry->d_lock); |
1914 | spin_unlock(&dparent->d_lock); |
1915 | return 1; |
1916 | } |
1917 | } |
1918 | spin_unlock(&dparent->d_lock); |
1919 | |
1920 | return 0; |
1921 | } |
1922 | EXPORT_SYMBOL(d_validate); |
1923 | |
1924 | /* |
1925 | * When a file is deleted, we have two options: |
1926 | * - turn this dentry into a negative dentry |
1927 | * - unhash this dentry and free it. |
1928 | * |
1929 | * Usually, we want to just turn this into |
1930 | * a negative dentry, but if anybody else is |
1931 | * currently using the dentry or the inode |
1932 | * we can't do that and we fall back on removing |
1933 | * it from the hash queues and waiting for |
1934 | * it to be deleted later when it has no users |
1935 | */ |
1936 | |
1937 | /** |
1938 | * d_delete - delete a dentry |
1939 | * @dentry: The dentry to delete |
1940 | * |
1941 | * Turn the dentry into a negative dentry if possible, otherwise |
1942 | * remove it from the hash queues so it can be deleted later |
1943 | */ |
1944 | |
1945 | void d_delete(struct dentry * dentry) |
1946 | { |
1947 | struct inode *inode; |
1948 | int isdir = 0; |
1949 | /* |
1950 | * Are we the only user? |
1951 | */ |
1952 | again: |
1953 | spin_lock(&dentry->d_lock); |
1954 | inode = dentry->d_inode; |
1955 | isdir = S_ISDIR(inode->i_mode); |
1956 | if (dentry->d_count == 1) { |
1957 | if (inode && !spin_trylock(&inode->i_lock)) { |
1958 | spin_unlock(&dentry->d_lock); |
1959 | cpu_relax(); |
1960 | goto again; |
1961 | } |
1962 | dentry->d_flags &= ~DCACHE_CANT_MOUNT; |
1963 | dentry_unlink_inode(dentry); |
1964 | fsnotify_nameremove(dentry, isdir); |
1965 | return; |
1966 | } |
1967 | |
1968 | if (!d_unhashed(dentry)) |
1969 | __d_drop(dentry); |
1970 | |
1971 | spin_unlock(&dentry->d_lock); |
1972 | |
1973 | fsnotify_nameremove(dentry, isdir); |
1974 | } |
1975 | EXPORT_SYMBOL(d_delete); |
1976 | |
1977 | static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b) |
1978 | { |
1979 | BUG_ON(!d_unhashed(entry)); |
1980 | hlist_bl_lock(b); |
1981 | entry->d_flags |= DCACHE_RCUACCESS; |
1982 | hlist_bl_add_head_rcu(&entry->d_hash, b); |
1983 | hlist_bl_unlock(b); |
1984 | } |
1985 | |
1986 | static void _d_rehash(struct dentry * entry) |
1987 | { |
1988 | __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash)); |
1989 | } |
1990 | |
1991 | /** |
1992 | * d_rehash - add an entry back to the hash |
1993 | * @entry: dentry to add to the hash |
1994 | * |
1995 | * Adds a dentry to the hash according to its name. |
1996 | */ |
1997 | |
1998 | void d_rehash(struct dentry * entry) |
1999 | { |
2000 | spin_lock(&entry->d_lock); |
2001 | _d_rehash(entry); |
2002 | spin_unlock(&entry->d_lock); |
2003 | } |
2004 | EXPORT_SYMBOL(d_rehash); |
2005 | |
2006 | /** |
2007 | * dentry_update_name_case - update case insensitive dentry with a new name |
2008 | * @dentry: dentry to be updated |
2009 | * @name: new name |
2010 | * |
2011 | * Update a case insensitive dentry with new case of name. |
2012 | * |
2013 | * dentry must have been returned by d_lookup with name @name. Old and new |
2014 | * name lengths must match (ie. no d_compare which allows mismatched name |
2015 | * lengths). |
2016 | * |
2017 | * Parent inode i_mutex must be held over d_lookup and into this call (to |
2018 | * keep renames and concurrent inserts, and readdir(2) away). |
2019 | */ |
2020 | void dentry_update_name_case(struct dentry *dentry, struct qstr *name) |
2021 | { |
2022 | BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex)); |
2023 | BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */ |
2024 | |
2025 | spin_lock(&dentry->d_lock); |
2026 | write_seqcount_begin(&dentry->d_seq); |
2027 | memcpy((unsigned char *)dentry->d_name.name, name->name, name->len); |
2028 | write_seqcount_end(&dentry->d_seq); |
2029 | spin_unlock(&dentry->d_lock); |
2030 | } |
2031 | EXPORT_SYMBOL(dentry_update_name_case); |
2032 | |
2033 | static void switch_names(struct dentry *dentry, struct dentry *target) |
2034 | { |
2035 | if (dname_external(target)) { |
2036 | if (dname_external(dentry)) { |
2037 | /* |
2038 | * Both external: swap the pointers |
2039 | */ |
2040 | swap(target->d_name.name, dentry->d_name.name); |
2041 | } else { |
2042 | /* |
2043 | * dentry:internal, target:external. Steal target's |
2044 | * storage and make target internal. |
2045 | */ |
2046 | memcpy(target->d_iname, dentry->d_name.name, |
2047 | dentry->d_name.len + 1); |
2048 | dentry->d_name.name = target->d_name.name; |
2049 | target->d_name.name = target->d_iname; |
2050 | } |
2051 | } else { |
2052 | if (dname_external(dentry)) { |
2053 | /* |
2054 | * dentry:external, target:internal. Give dentry's |
2055 | * storage to target and make dentry internal |
2056 | */ |
2057 | memcpy(dentry->d_iname, target->d_name.name, |
2058 | target->d_name.len + 1); |
2059 | target->d_name.name = dentry->d_name.name; |
2060 | dentry->d_name.name = dentry->d_iname; |
2061 | } else { |
2062 | /* |
2063 | * Both are internal. Just copy target to dentry |
2064 | */ |
2065 | memcpy(dentry->d_iname, target->d_name.name, |
2066 | target->d_name.len + 1); |
2067 | dentry->d_name.len = target->d_name.len; |
2068 | return; |
2069 | } |
2070 | } |
2071 | swap(dentry->d_name.len, target->d_name.len); |
2072 | } |
2073 | |
2074 | static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target) |
2075 | { |
2076 | /* |
2077 | * XXXX: do we really need to take target->d_lock? |
2078 | */ |
2079 | if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent) |
2080 | spin_lock(&target->d_parent->d_lock); |
2081 | else { |
2082 | if (d_ancestor(dentry->d_parent, target->d_parent)) { |
2083 | spin_lock(&dentry->d_parent->d_lock); |
2084 | spin_lock_nested(&target->d_parent->d_lock, |
2085 | DENTRY_D_LOCK_NESTED); |
2086 | } else { |
2087 | spin_lock(&target->d_parent->d_lock); |
2088 | spin_lock_nested(&dentry->d_parent->d_lock, |
2089 | DENTRY_D_LOCK_NESTED); |
2090 | } |
2091 | } |
2092 | if (target < dentry) { |
2093 | spin_lock_nested(&target->d_lock, 2); |
2094 | spin_lock_nested(&dentry->d_lock, 3); |
2095 | } else { |
2096 | spin_lock_nested(&dentry->d_lock, 2); |
2097 | spin_lock_nested(&target->d_lock, 3); |
2098 | } |
2099 | } |
2100 | |
2101 | static void dentry_unlock_parents_for_move(struct dentry *dentry, |
2102 | struct dentry *target) |
2103 | { |
2104 | if (target->d_parent != dentry->d_parent) |
2105 | spin_unlock(&dentry->d_parent->d_lock); |
2106 | if (target->d_parent != target) |
2107 | spin_unlock(&target->d_parent->d_lock); |
2108 | } |
2109 | |
2110 | /* |
2111 | * When switching names, the actual string doesn't strictly have to |
2112 | * be preserved in the target - because we're dropping the target |
2113 | * anyway. As such, we can just do a simple memcpy() to copy over |
2114 | * the new name before we switch. |
2115 | * |
2116 | * Note that we have to be a lot more careful about getting the hash |
2117 | * switched - we have to switch the hash value properly even if it |
2118 | * then no longer matches the actual (corrupted) string of the target. |
2119 | * The hash value has to match the hash queue that the dentry is on.. |
2120 | */ |
2121 | /* |
2122 | * __d_move - move a dentry |
2123 | * @dentry: entry to move |
2124 | * @target: new dentry |
2125 | * |
2126 | * Update the dcache to reflect the move of a file name. Negative |
2127 | * dcache entries should not be moved in this way. Caller must hold |
2128 | * rename_lock, the i_mutex of the source and target directories, |
2129 | * and the sb->s_vfs_rename_mutex if they differ. See lock_rename(). |
2130 | */ |
2131 | static void __d_move(struct dentry * dentry, struct dentry * target) |
2132 | { |
2133 | if (!dentry->d_inode) |
2134 | printk(KERN_WARNING "VFS: moving negative dcache entry\n"); |
2135 | |
2136 | BUG_ON(d_ancestor(dentry, target)); |
2137 | BUG_ON(d_ancestor(target, dentry)); |
2138 | |
2139 | dentry_lock_for_move(dentry, target); |
2140 | |
2141 | write_seqcount_begin(&dentry->d_seq); |
2142 | write_seqcount_begin(&target->d_seq); |
2143 | |
2144 | /* __d_drop does write_seqcount_barrier, but they're OK to nest. */ |
2145 | |
2146 | /* |
2147 | * Move the dentry to the target hash queue. Don't bother checking |
2148 | * for the same hash queue because of how unlikely it is. |
2149 | */ |
2150 | __d_drop(dentry); |
2151 | __d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash)); |
2152 | |
2153 | /* Unhash the target: dput() will then get rid of it */ |
2154 | __d_drop(target); |
2155 | |
2156 | list_del(&dentry->d_u.d_child); |
2157 | list_del(&target->d_u.d_child); |
2158 | |
2159 | /* Switch the names.. */ |
2160 | switch_names(dentry, target); |
2161 | swap(dentry->d_name.hash, target->d_name.hash); |
2162 | |
2163 | /* ... and switch the parents */ |
2164 | if (IS_ROOT(dentry)) { |
2165 | dentry->d_parent = target->d_parent; |
2166 | target->d_parent = target; |
2167 | INIT_LIST_HEAD(&target->d_u.d_child); |
2168 | } else { |
2169 | swap(dentry->d_parent, target->d_parent); |
2170 | |
2171 | /* And add them back to the (new) parent lists */ |
2172 | list_add(&target->d_u.d_child, &target->d_parent->d_subdirs); |
2173 | } |
2174 | |
2175 | list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs); |
2176 | |
2177 | write_seqcount_end(&target->d_seq); |
2178 | write_seqcount_end(&dentry->d_seq); |
2179 | |
2180 | dentry_unlock_parents_for_move(dentry, target); |
2181 | spin_unlock(&target->d_lock); |
2182 | fsnotify_d_move(dentry); |
2183 | spin_unlock(&dentry->d_lock); |
2184 | } |
2185 | |
2186 | /* |
2187 | * d_move - move a dentry |
2188 | * @dentry: entry to move |
2189 | * @target: new dentry |
2190 | * |
2191 | * Update the dcache to reflect the move of a file name. Negative |
2192 | * dcache entries should not be moved in this way. See the locking |
2193 | * requirements for __d_move. |
2194 | */ |
2195 | void d_move(struct dentry *dentry, struct dentry *target) |
2196 | { |
2197 | write_seqlock(&rename_lock); |
2198 | __d_move(dentry, target); |
2199 | write_sequnlock(&rename_lock); |
2200 | } |
2201 | EXPORT_SYMBOL(d_move); |
2202 | |
2203 | /** |
2204 | * d_ancestor - search for an ancestor |
2205 | * @p1: ancestor dentry |
2206 | * @p2: child dentry |
2207 | * |
2208 | * Returns the ancestor dentry of p2 which is a child of p1, if p1 is |
2209 | * an ancestor of p2, else NULL. |
2210 | */ |
2211 | struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2) |
2212 | { |
2213 | struct dentry *p; |
2214 | |
2215 | for (p = p2; !IS_ROOT(p); p = p->d_parent) { |
2216 | if (p->d_parent == p1) |
2217 | return p; |
2218 | } |
2219 | return NULL; |
2220 | } |
2221 | |
2222 | /* |
2223 | * This helper attempts to cope with remotely renamed directories |
2224 | * |
2225 | * It assumes that the caller is already holding |
2226 | * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock |
2227 | * |
2228 | * Note: If ever the locking in lock_rename() changes, then please |
2229 | * remember to update this too... |
2230 | */ |
2231 | static struct dentry *__d_unalias(struct inode *inode, |
2232 | struct dentry *dentry, struct dentry *alias) |
2233 | { |
2234 | struct mutex *m1 = NULL, *m2 = NULL; |
2235 | struct dentry *ret; |
2236 | |
2237 | /* If alias and dentry share a parent, then no extra locks required */ |
2238 | if (alias->d_parent == dentry->d_parent) |
2239 | goto out_unalias; |
2240 | |
2241 | /* See lock_rename() */ |
2242 | ret = ERR_PTR(-EBUSY); |
2243 | if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex)) |
2244 | goto out_err; |
2245 | m1 = &dentry->d_sb->s_vfs_rename_mutex; |
2246 | if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex)) |
2247 | goto out_err; |
2248 | m2 = &alias->d_parent->d_inode->i_mutex; |
2249 | out_unalias: |
2250 | __d_move(alias, dentry); |
2251 | ret = alias; |
2252 | out_err: |
2253 | spin_unlock(&inode->i_lock); |
2254 | if (m2) |
2255 | mutex_unlock(m2); |
2256 | if (m1) |
2257 | mutex_unlock(m1); |
2258 | return ret; |
2259 | } |
2260 | |
2261 | /* |
2262 | * Prepare an anonymous dentry for life in the superblock's dentry tree as a |
2263 | * named dentry in place of the dentry to be replaced. |
2264 | * returns with anon->d_lock held! |
2265 | */ |
2266 | static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon) |
2267 | { |
2268 | struct dentry *dparent, *aparent; |
2269 | |
2270 | dentry_lock_for_move(anon, dentry); |
2271 | |
2272 | write_seqcount_begin(&dentry->d_seq); |
2273 | write_seqcount_begin(&anon->d_seq); |
2274 | |
2275 | dparent = dentry->d_parent; |
2276 | aparent = anon->d_parent; |
2277 | |
2278 | switch_names(dentry, anon); |
2279 | swap(dentry->d_name.hash, anon->d_name.hash); |
2280 | |
2281 | dentry->d_parent = (aparent == anon) ? dentry : aparent; |
2282 | list_del(&dentry->d_u.d_child); |
2283 | if (!IS_ROOT(dentry)) |
2284 | list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs); |
2285 | else |
2286 | INIT_LIST_HEAD(&dentry->d_u.d_child); |
2287 | |
2288 | anon->d_parent = (dparent == dentry) ? anon : dparent; |
2289 | list_del(&anon->d_u.d_child); |
2290 | if (!IS_ROOT(anon)) |
2291 | list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs); |
2292 | else |
2293 | INIT_LIST_HEAD(&anon->d_u.d_child); |
2294 | |
2295 | write_seqcount_end(&dentry->d_seq); |
2296 | write_seqcount_end(&anon->d_seq); |
2297 | |
2298 | dentry_unlock_parents_for_move(anon, dentry); |
2299 | spin_unlock(&dentry->d_lock); |
2300 | |
2301 | /* anon->d_lock still locked, returns locked */ |
2302 | anon->d_flags &= ~DCACHE_DISCONNECTED; |
2303 | } |
2304 | |
2305 | /** |
2306 | * d_materialise_unique - introduce an inode into the tree |
2307 | * @dentry: candidate dentry |
2308 | * @inode: inode to bind to the dentry, to which aliases may be attached |
2309 | * |
2310 | * Introduces an dentry into the tree, substituting an extant disconnected |
2311 | * root directory alias in its place if there is one. Caller must hold the |
2312 | * i_mutex of the parent directory. |
2313 | */ |
2314 | struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode) |
2315 | { |
2316 | struct dentry *actual; |
2317 | |
2318 | BUG_ON(!d_unhashed(dentry)); |
2319 | |
2320 | if (!inode) { |
2321 | actual = dentry; |
2322 | __d_instantiate(dentry, NULL); |
2323 | d_rehash(actual); |
2324 | goto out_nolock; |
2325 | } |
2326 | |
2327 | spin_lock(&inode->i_lock); |
2328 | |
2329 | if (S_ISDIR(inode->i_mode)) { |
2330 | struct dentry *alias; |
2331 | |
2332 | /* Does an aliased dentry already exist? */ |
2333 | alias = __d_find_alias(inode, 0); |
2334 | if (alias) { |
2335 | actual = alias; |
2336 | write_seqlock(&rename_lock); |
2337 | |
2338 | if (d_ancestor(alias, dentry)) { |
2339 | /* Check for loops */ |
2340 | actual = ERR_PTR(-ELOOP); |
2341 | } else if (IS_ROOT(alias)) { |
2342 | /* Is this an anonymous mountpoint that we |
2343 | * could splice into our tree? */ |
2344 | __d_materialise_dentry(dentry, alias); |
2345 | write_sequnlock(&rename_lock); |
2346 | __d_drop(alias); |
2347 | goto found; |
2348 | } else { |
2349 | /* Nope, but we must(!) avoid directory |
2350 | * aliasing */ |
2351 | actual = __d_unalias(inode, dentry, alias); |
2352 | } |
2353 | write_sequnlock(&rename_lock); |
2354 | if (IS_ERR(actual)) |
2355 | dput(alias); |
2356 | goto out_nolock; |
2357 | } |
2358 | } |
2359 | |
2360 | /* Add a unique reference */ |
2361 | actual = __d_instantiate_unique(dentry, inode); |
2362 | if (!actual) |
2363 | actual = dentry; |
2364 | else |
2365 | BUG_ON(!d_unhashed(actual)); |
2366 | |
2367 | spin_lock(&actual->d_lock); |
2368 | found: |
2369 | _d_rehash(actual); |
2370 | spin_unlock(&actual->d_lock); |
2371 | spin_unlock(&inode->i_lock); |
2372 | out_nolock: |
2373 | if (actual == dentry) { |
2374 | security_d_instantiate(dentry, inode); |
2375 | return NULL; |
2376 | } |
2377 | |
2378 | iput(inode); |
2379 | return actual; |
2380 | } |
2381 | EXPORT_SYMBOL_GPL(d_materialise_unique); |
2382 | |
2383 | static int prepend(char **buffer, int *buflen, const char *str, int namelen) |
2384 | { |
2385 | *buflen -= namelen; |
2386 | if (*buflen < 0) |
2387 | return -ENAMETOOLONG; |
2388 | *buffer -= namelen; |
2389 | memcpy(*buffer, str, namelen); |
2390 | return 0; |
2391 | } |
2392 | |
2393 | static int prepend_name(char **buffer, int *buflen, struct qstr *name) |
2394 | { |
2395 | return prepend(buffer, buflen, name->name, name->len); |
2396 | } |
2397 | |
2398 | /** |
2399 | * prepend_path - Prepend path string to a buffer |
2400 | * @path: the dentry/vfsmount to report |
2401 | * @root: root vfsmnt/dentry (may be modified by this function) |
2402 | * @buffer: pointer to the end of the buffer |
2403 | * @buflen: pointer to buffer length |
2404 | * |
2405 | * Caller holds the rename_lock. |
2406 | * |
2407 | * If path is not reachable from the supplied root, then the value of |
2408 | * root is changed (without modifying refcounts). |
2409 | */ |
2410 | static int prepend_path(const struct path *path, struct path *root, |
2411 | char **buffer, int *buflen) |
2412 | { |
2413 | struct dentry *dentry = path->dentry; |
2414 | struct vfsmount *vfsmnt = path->mnt; |
2415 | bool slash = false; |
2416 | int error = 0; |
2417 | |
2418 | br_read_lock(vfsmount_lock); |
2419 | while (dentry != root->dentry || vfsmnt != root->mnt) { |
2420 | struct dentry * parent; |
2421 | |
2422 | if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) { |
2423 | /* Global root? */ |
2424 | if (vfsmnt->mnt_parent == vfsmnt) { |
2425 | goto global_root; |
2426 | } |
2427 | dentry = vfsmnt->mnt_mountpoint; |
2428 | vfsmnt = vfsmnt->mnt_parent; |
2429 | continue; |
2430 | } |
2431 | parent = dentry->d_parent; |
2432 | prefetch(parent); |
2433 | spin_lock(&dentry->d_lock); |
2434 | error = prepend_name(buffer, buflen, &dentry->d_name); |
2435 | spin_unlock(&dentry->d_lock); |
2436 | if (!error) |
2437 | error = prepend(buffer, buflen, "/", 1); |
2438 | if (error) |
2439 | break; |
2440 | |
2441 | slash = true; |
2442 | dentry = parent; |
2443 | } |
2444 | |
2445 | out: |
2446 | if (!error && !slash) |
2447 | error = prepend(buffer, buflen, "/", 1); |
2448 | |
2449 | br_read_unlock(vfsmount_lock); |
2450 | return error; |
2451 | |
2452 | global_root: |
2453 | /* |
2454 | * Filesystems needing to implement special "root names" |
2455 | * should do so with ->d_dname() |
2456 | */ |
2457 | if (IS_ROOT(dentry) && |
2458 | (dentry->d_name.len != 1 || dentry->d_name.name[0] != '/')) { |
2459 | WARN(1, "Root dentry has weird name <%.*s>\n", |
2460 | (int) dentry->d_name.len, dentry->d_name.name); |
2461 | } |
2462 | root->mnt = vfsmnt; |
2463 | root->dentry = dentry; |
2464 | goto out; |
2465 | } |
2466 | |
2467 | /** |
2468 | * __d_path - return the path of a dentry |
2469 | * @path: the dentry/vfsmount to report |
2470 | * @root: root vfsmnt/dentry (may be modified by this function) |
2471 | * @buf: buffer to return value in |
2472 | * @buflen: buffer length |
2473 | * |
2474 | * Convert a dentry into an ASCII path name. |
2475 | * |
2476 | * Returns a pointer into the buffer or an error code if the |
2477 | * path was too long. |
2478 | * |
2479 | * "buflen" should be positive. |
2480 | * |
2481 | * If path is not reachable from the supplied root, then the value of |
2482 | * root is changed (without modifying refcounts). |
2483 | */ |
2484 | char *__d_path(const struct path *path, struct path *root, |
2485 | char *buf, int buflen) |
2486 | { |
2487 | char *res = buf + buflen; |
2488 | int error; |
2489 | |
2490 | prepend(&res, &buflen, "\0", 1); |
2491 | write_seqlock(&rename_lock); |
2492 | error = prepend_path(path, root, &res, &buflen); |
2493 | write_sequnlock(&rename_lock); |
2494 | |
2495 | if (error) |
2496 | return ERR_PTR(error); |
2497 | return res; |
2498 | } |
2499 | |
2500 | /* |
2501 | * same as __d_path but appends "(deleted)" for unlinked files. |
2502 | */ |
2503 | static int path_with_deleted(const struct path *path, struct path *root, |
2504 | char **buf, int *buflen) |
2505 | { |
2506 | prepend(buf, buflen, "\0", 1); |
2507 | if (d_unlinked(path->dentry)) { |
2508 | int error = prepend(buf, buflen, " (deleted)", 10); |
2509 | if (error) |
2510 | return error; |
2511 | } |
2512 | |
2513 | return prepend_path(path, root, buf, buflen); |
2514 | } |
2515 | |
2516 | static int prepend_unreachable(char **buffer, int *buflen) |
2517 | { |
2518 | return prepend(buffer, buflen, "(unreachable)", 13); |
2519 | } |
2520 | |
2521 | /** |
2522 | * d_path - return the path of a dentry |
2523 | * @path: path to report |
2524 | * @buf: buffer to return value in |
2525 | * @buflen: buffer length |
2526 | * |
2527 | * Convert a dentry into an ASCII path name. If the entry has been deleted |
2528 | * the string " (deleted)" is appended. Note that this is ambiguous. |
2529 | * |
2530 | * Returns a pointer into the buffer or an error code if the path was |
2531 | * too long. Note: Callers should use the returned pointer, not the passed |
2532 | * in buffer, to use the name! The implementation often starts at an offset |
2533 | * into the buffer, and may leave 0 bytes at the start. |
2534 | * |
2535 | * "buflen" should be positive. |
2536 | */ |
2537 | char *d_path(const struct path *path, char *buf, int buflen) |
2538 | { |
2539 | char *res = buf + buflen; |
2540 | struct path root; |
2541 | struct path tmp; |
2542 | int error; |
2543 | |
2544 | /* |
2545 | * We have various synthetic filesystems that never get mounted. On |
2546 | * these filesystems dentries are never used for lookup purposes, and |
2547 | * thus don't need to be hashed. They also don't need a name until a |
2548 | * user wants to identify the object in /proc/pid/fd/. The little hack |
2549 | * below allows us to generate a name for these objects on demand: |
2550 | */ |
2551 | if (path->dentry->d_op && path->dentry->d_op->d_dname) |
2552 | return path->dentry->d_op->d_dname(path->dentry, buf, buflen); |
2553 | |
2554 | get_fs_root(current->fs, &root); |
2555 | write_seqlock(&rename_lock); |
2556 | tmp = root; |
2557 | error = path_with_deleted(path, &tmp, &res, &buflen); |
2558 | if (error) |
2559 | res = ERR_PTR(error); |
2560 | write_sequnlock(&rename_lock); |
2561 | path_put(&root); |
2562 | return res; |
2563 | } |
2564 | EXPORT_SYMBOL(d_path); |
2565 | |
2566 | /** |
2567 | * d_path_with_unreachable - return the path of a dentry |
2568 | * @path: path to report |
2569 | * @buf: buffer to return value in |
2570 | * @buflen: buffer length |
2571 | * |
2572 | * The difference from d_path() is that this prepends "(unreachable)" |
2573 | * to paths which are unreachable from the current process' root. |
2574 | */ |
2575 | char *d_path_with_unreachable(const struct path *path, char *buf, int buflen) |
2576 | { |
2577 | char *res = buf + buflen; |
2578 | struct path root; |
2579 | struct path tmp; |
2580 | int error; |
2581 | |
2582 | if (path->dentry->d_op && path->dentry->d_op->d_dname) |
2583 | return path->dentry->d_op->d_dname(path->dentry, buf, buflen); |
2584 | |
2585 | get_fs_root(current->fs, &root); |
2586 | write_seqlock(&rename_lock); |
2587 | tmp = root; |
2588 | error = path_with_deleted(path, &tmp, &res, &buflen); |
2589 | if (!error && !path_equal(&tmp, &root)) |
2590 | error = prepend_unreachable(&res, &buflen); |
2591 | write_sequnlock(&rename_lock); |
2592 | path_put(&root); |
2593 | if (error) |
2594 | res = ERR_PTR(error); |
2595 | |
2596 | return res; |
2597 | } |
2598 | |
2599 | /* |
2600 | * Helper function for dentry_operations.d_dname() members |
2601 | */ |
2602 | char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen, |
2603 | const char *fmt, ...) |
2604 | { |
2605 | va_list args; |
2606 | char temp[64]; |
2607 | int sz; |
2608 | |
2609 | va_start(args, fmt); |
2610 | sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1; |
2611 | va_end(args); |
2612 | |
2613 | if (sz > sizeof(temp) || sz > buflen) |
2614 | return ERR_PTR(-ENAMETOOLONG); |
2615 | |
2616 | buffer += buflen - sz; |
2617 | return memcpy(buffer, temp, sz); |
2618 | } |
2619 | |
2620 | /* |
2621 | * Write full pathname from the root of the filesystem into the buffer. |
2622 | */ |
2623 | static char *__dentry_path(struct dentry *dentry, char *buf, int buflen) |
2624 | { |
2625 | char *end = buf + buflen; |
2626 | char *retval; |
2627 | |
2628 | prepend(&end, &buflen, "\0", 1); |
2629 | if (buflen < 1) |
2630 | goto Elong; |
2631 | /* Get '/' right */ |
2632 | retval = end-1; |
2633 | *retval = '/'; |
2634 | |
2635 | while (!IS_ROOT(dentry)) { |
2636 | struct dentry *parent = dentry->d_parent; |
2637 | int error; |
2638 | |
2639 | prefetch(parent); |
2640 | spin_lock(&dentry->d_lock); |
2641 | error = prepend_name(&end, &buflen, &dentry->d_name); |
2642 | spin_unlock(&dentry->d_lock); |
2643 | if (error != 0 || prepend(&end, &buflen, "/", 1) != 0) |
2644 | goto Elong; |
2645 | |
2646 | retval = end; |
2647 | dentry = parent; |
2648 | } |
2649 | return retval; |
2650 | Elong: |
2651 | return ERR_PTR(-ENAMETOOLONG); |
2652 | } |
2653 | |
2654 | char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen) |
2655 | { |
2656 | char *retval; |
2657 | |
2658 | write_seqlock(&rename_lock); |
2659 | retval = __dentry_path(dentry, buf, buflen); |
2660 | write_sequnlock(&rename_lock); |
2661 | |
2662 | return retval; |
2663 | } |
2664 | EXPORT_SYMBOL(dentry_path_raw); |
2665 | |
2666 | char *dentry_path(struct dentry *dentry, char *buf, int buflen) |
2667 | { |
2668 | char *p = NULL; |
2669 | char *retval; |
2670 | |
2671 | write_seqlock(&rename_lock); |
2672 | if (d_unlinked(dentry)) { |
2673 | p = buf + buflen; |
2674 | if (prepend(&p, &buflen, "//deleted", 10) != 0) |
2675 | goto Elong; |
2676 | buflen++; |
2677 | } |
2678 | retval = __dentry_path(dentry, buf, buflen); |
2679 | write_sequnlock(&rename_lock); |
2680 | if (!IS_ERR(retval) && p) |
2681 | *p = '/'; /* restore '/' overriden with '\0' */ |
2682 | return retval; |
2683 | Elong: |
2684 | return ERR_PTR(-ENAMETOOLONG); |
2685 | } |
2686 | |
2687 | /* |
2688 | * NOTE! The user-level library version returns a |
2689 | * character pointer. The kernel system call just |
2690 | * returns the length of the buffer filled (which |
2691 | * includes the ending '\0' character), or a negative |
2692 | * error value. So libc would do something like |
2693 | * |
2694 | * char *getcwd(char * buf, size_t size) |
2695 | * { |
2696 | * int retval; |
2697 | * |
2698 | * retval = sys_getcwd(buf, size); |
2699 | * if (retval >= 0) |
2700 | * return buf; |
2701 | * errno = -retval; |
2702 | * return NULL; |
2703 | * } |
2704 | */ |
2705 | SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) |
2706 | { |
2707 | int error; |
2708 | struct path pwd, root; |
2709 | char *page = (char *) __get_free_page(GFP_USER); |
2710 | |
2711 | if (!page) |
2712 | return -ENOMEM; |
2713 | |
2714 | get_fs_root_and_pwd(current->fs, &root, &pwd); |
2715 | |
2716 | error = -ENOENT; |
2717 | write_seqlock(&rename_lock); |
2718 | if (!d_unlinked(pwd.dentry)) { |
2719 | unsigned long len; |
2720 | struct path tmp = root; |
2721 | char *cwd = page + PAGE_SIZE; |
2722 | int buflen = PAGE_SIZE; |
2723 | |
2724 | prepend(&cwd, &buflen, "\0", 1); |
2725 | error = prepend_path(&pwd, &tmp, &cwd, &buflen); |
2726 | write_sequnlock(&rename_lock); |
2727 | |
2728 | if (error) |
2729 | goto out; |
2730 | |
2731 | /* Unreachable from current root */ |
2732 | if (!path_equal(&tmp, &root)) { |
2733 | error = prepend_unreachable(&cwd, &buflen); |
2734 | if (error) |
2735 | goto out; |
2736 | } |
2737 | |
2738 | error = -ERANGE; |
2739 | len = PAGE_SIZE + page - cwd; |
2740 | if (len <= size) { |
2741 | error = len; |
2742 | if (copy_to_user(buf, cwd, len)) |
2743 | error = -EFAULT; |
2744 | } |
2745 | } else { |
2746 | write_sequnlock(&rename_lock); |
2747 | } |
2748 | |
2749 | out: |
2750 | path_put(&pwd); |
2751 | path_put(&root); |
2752 | free_page((unsigned long) page); |
2753 | return error; |
2754 | } |
2755 | |
2756 | /* |
2757 | * Test whether new_dentry is a subdirectory of old_dentry. |
2758 | * |
2759 | * Trivially implemented using the dcache structure |
2760 | */ |
2761 | |
2762 | /** |
2763 | * is_subdir - is new dentry a subdirectory of old_dentry |
2764 | * @new_dentry: new dentry |
2765 | * @old_dentry: old dentry |
2766 | * |
2767 | * Returns 1 if new_dentry is a subdirectory of the parent (at any depth). |
2768 | * Returns 0 otherwise. |
2769 | * Caller must ensure that "new_dentry" is pinned before calling is_subdir() |
2770 | */ |
2771 | |
2772 | int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry) |
2773 | { |
2774 | int result; |
2775 | unsigned seq; |
2776 | |
2777 | if (new_dentry == old_dentry) |
2778 | return 1; |
2779 | |
2780 | do { |
2781 | /* for restarting inner loop in case of seq retry */ |
2782 | seq = read_seqbegin(&rename_lock); |
2783 | /* |
2784 | * Need rcu_readlock to protect against the d_parent trashing |
2785 | * due to d_move |
2786 | */ |
2787 | rcu_read_lock(); |
2788 | if (d_ancestor(old_dentry, new_dentry)) |
2789 | result = 1; |
2790 | else |
2791 | result = 0; |
2792 | rcu_read_unlock(); |
2793 | } while (read_seqretry(&rename_lock, seq)); |
2794 | |
2795 | return result; |
2796 | } |
2797 | |
2798 | int path_is_under(struct path *path1, struct path *path2) |
2799 | { |
2800 | struct vfsmount *mnt = path1->mnt; |
2801 | struct dentry *dentry = path1->dentry; |
2802 | int res; |
2803 | |
2804 | br_read_lock(vfsmount_lock); |
2805 | if (mnt != path2->mnt) { |
2806 | for (;;) { |
2807 | if (mnt->mnt_parent == mnt) { |
2808 | br_read_unlock(vfsmount_lock); |
2809 | return 0; |
2810 | } |
2811 | if (mnt->mnt_parent == path2->mnt) |
2812 | break; |
2813 | mnt = mnt->mnt_parent; |
2814 | } |
2815 | dentry = mnt->mnt_mountpoint; |
2816 | } |
2817 | res = is_subdir(dentry, path2->dentry); |
2818 | br_read_unlock(vfsmount_lock); |
2819 | return res; |
2820 | } |
2821 | EXPORT_SYMBOL(path_is_under); |
2822 | |
2823 | void d_genocide(struct dentry *root) |
2824 | { |
2825 | struct dentry *this_parent; |
2826 | struct list_head *next; |
2827 | unsigned seq; |
2828 | int locked = 0; |
2829 | |
2830 | seq = read_seqbegin(&rename_lock); |
2831 | again: |
2832 | this_parent = root; |
2833 | spin_lock(&this_parent->d_lock); |
2834 | repeat: |
2835 | next = this_parent->d_subdirs.next; |
2836 | resume: |
2837 | while (next != &this_parent->d_subdirs) { |
2838 | struct list_head *tmp = next; |
2839 | struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); |
2840 | next = tmp->next; |
2841 | |
2842 | spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
2843 | if (d_unhashed(dentry) || !dentry->d_inode) { |
2844 | spin_unlock(&dentry->d_lock); |
2845 | continue; |
2846 | } |
2847 | if (!list_empty(&dentry->d_subdirs)) { |
2848 | spin_unlock(&this_parent->d_lock); |
2849 | spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_); |
2850 | this_parent = dentry; |
2851 | spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); |
2852 | goto repeat; |
2853 | } |
2854 | if (!(dentry->d_flags & DCACHE_GENOCIDE)) { |
2855 | dentry->d_flags |= DCACHE_GENOCIDE; |
2856 | dentry->d_count--; |
2857 | } |
2858 | spin_unlock(&dentry->d_lock); |
2859 | } |
2860 | if (this_parent != root) { |
2861 | struct dentry *child = this_parent; |
2862 | if (!(this_parent->d_flags & DCACHE_GENOCIDE)) { |
2863 | this_parent->d_flags |= DCACHE_GENOCIDE; |
2864 | this_parent->d_count--; |
2865 | } |
2866 | this_parent = try_to_ascend(this_parent, locked, seq); |
2867 | if (!this_parent) |
2868 | goto rename_retry; |
2869 | next = child->d_u.d_child.next; |
2870 | goto resume; |
2871 | } |
2872 | spin_unlock(&this_parent->d_lock); |
2873 | if (!locked && read_seqretry(&rename_lock, seq)) |
2874 | goto rename_retry; |
2875 | if (locked) |
2876 | write_sequnlock(&rename_lock); |
2877 | return; |
2878 | |
2879 | rename_retry: |
2880 | locked = 1; |
2881 | write_seqlock(&rename_lock); |
2882 | goto again; |
2883 | } |
2884 | |
2885 | /** |
2886 | * find_inode_number - check for dentry with name |
2887 | * @dir: directory to check |
2888 | * @name: Name to find. |
2889 | * |
2890 | * Check whether a dentry already exists for the given name, |
2891 | * and return the inode number if it has an inode. Otherwise |
2892 | * 0 is returned. |
2893 | * |
2894 | * This routine is used to post-process directory listings for |
2895 | * filesystems using synthetic inode numbers, and is necessary |
2896 | * to keep getcwd() working. |
2897 | */ |
2898 | |
2899 | ino_t find_inode_number(struct dentry *dir, struct qstr *name) |
2900 | { |
2901 | struct dentry * dentry; |
2902 | ino_t ino = 0; |
2903 | |
2904 | dentry = d_hash_and_lookup(dir, name); |
2905 | if (dentry) { |
2906 | if (dentry->d_inode) |
2907 | ino = dentry->d_inode->i_ino; |
2908 | dput(dentry); |
2909 | } |
2910 | return ino; |
2911 | } |
2912 | EXPORT_SYMBOL(find_inode_number); |
2913 | |
2914 | static __initdata unsigned long dhash_entries; |
2915 | static int __init set_dhash_entries(char *str) |
2916 | { |
2917 | if (!str) |
2918 | return 0; |
2919 | dhash_entries = simple_strtoul(str, &str, 0); |
2920 | return 1; |
2921 | } |
2922 | __setup("dhash_entries=", set_dhash_entries); |
2923 | |
2924 | static void __init dcache_init_early(void) |
2925 | { |
2926 | int loop; |
2927 | |
2928 | /* If hashes are distributed across NUMA nodes, defer |
2929 | * hash allocation until vmalloc space is available. |
2930 | */ |
2931 | if (hashdist) |
2932 | return; |
2933 | |
2934 | dentry_hashtable = |
2935 | alloc_large_system_hash("Dentry cache", |
2936 | sizeof(struct hlist_bl_head), |
2937 | dhash_entries, |
2938 | 13, |
2939 | HASH_EARLY, |
2940 | &d_hash_shift, |
2941 | &d_hash_mask, |
2942 | 0); |
2943 | |
2944 | for (loop = 0; loop < (1 << d_hash_shift); loop++) |
2945 | INIT_HLIST_BL_HEAD(dentry_hashtable + loop); |
2946 | } |
2947 | |
2948 | static void __init dcache_init(void) |
2949 | { |
2950 | int loop; |
2951 | |
2952 | /* |
2953 | * A constructor could be added for stable state like the lists, |
2954 | * but it is probably not worth it because of the cache nature |
2955 | * of the dcache. |
2956 | */ |
2957 | dentry_cache = KMEM_CACHE(dentry, |
2958 | SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD); |
2959 | |
2960 | /* Hash may have been set up in dcache_init_early */ |
2961 | if (!hashdist) |
2962 | return; |
2963 | |
2964 | dentry_hashtable = |
2965 | alloc_large_system_hash("Dentry cache", |
2966 | sizeof(struct hlist_bl_head), |
2967 | dhash_entries, |
2968 | 13, |
2969 | 0, |
2970 | &d_hash_shift, |
2971 | &d_hash_mask, |
2972 | 0); |
2973 | |
2974 | for (loop = 0; loop < (1 << d_hash_shift); loop++) |
2975 | INIT_HLIST_BL_HEAD(dentry_hashtable + loop); |
2976 | } |
2977 | |
2978 | /* SLAB cache for __getname() consumers */ |
2979 | struct kmem_cache *names_cachep __read_mostly; |
2980 | EXPORT_SYMBOL(names_cachep); |
2981 | |
2982 | EXPORT_SYMBOL(d_genocide); |
2983 | |
2984 | void __init vfs_caches_init_early(void) |
2985 | { |
2986 | dcache_init_early(); |
2987 | inode_init_early(); |
2988 | } |
2989 | |
2990 | void __init vfs_caches_init(unsigned long mempages) |
2991 | { |
2992 | unsigned long reserve; |
2993 | |
2994 | /* Base hash sizes on available memory, with a reserve equal to |
2995 | 150% of current kernel size */ |
2996 | |
2997 | reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1); |
2998 | mempages -= reserve; |
2999 | |
3000 | names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0, |
3001 | SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); |
3002 | |
3003 | dcache_init(); |
3004 | inode_init(); |
3005 | files_init(mempages); |
3006 | mnt_init(); |
3007 | bdev_cache_init(); |
3008 | chrdev_init(); |
3009 | } |
3010 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9