blob: 59dbc92c2079b88054c6f5852b5c7bd04cbd187c [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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/config.h>
18#include <linux/syscalls.h>
19#include <linux/string.h>
20#include <linux/mm.h>
21#include <linux/fs.h>
John McCutchan7a91bf72005-08-08 13:52:16 -040022#include <linux/fsnotify.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070023#include <linux/slab.h>
24#include <linux/init.h>
25#include <linux/smp_lock.h>
26#include <linux/hash.h>
27#include <linux/cache.h>
28#include <linux/module.h>
29#include <linux/mount.h>
30#include <linux/file.h>
31#include <asm/uaccess.h>
32#include <linux/security.h>
33#include <linux/seqlock.h>
34#include <linux/swap.h>
35#include <linux/bootmem.h>
36
Linus Torvalds1da177e2005-04-16 15:20:36 -070037
Eric Dumazetfa3536c2006-03-26 01:37:24 -080038int sysctl_vfs_cache_pressure __read_mostly = 100;
Linus Torvalds1da177e2005-04-16 15:20:36 -070039EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
40
41 __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
Adrian Bunk75c96f82005-05-05 16:16:09 -070042static seqlock_t rename_lock __cacheline_aligned_in_smp = SEQLOCK_UNLOCKED;
Linus Torvalds1da177e2005-04-16 15:20:36 -070043
44EXPORT_SYMBOL(dcache_lock);
45
Eric Dumazetfa3536c2006-03-26 01:37:24 -080046static kmem_cache_t *dentry_cache __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -070047
48#define DNAME_INLINE_LEN (sizeof(struct dentry)-offsetof(struct dentry,d_iname))
49
50/*
51 * This is the single most critical data structure when it comes
52 * to the dcache: the hashtable for lookups. Somebody should try
53 * to make this good - I've just made it work.
54 *
55 * This hash-function tries to avoid losing too many bits of hash
56 * information, yet avoid using a prime hash-size or similar.
57 */
58#define D_HASHBITS d_hash_shift
59#define D_HASHMASK d_hash_mask
60
Eric Dumazetfa3536c2006-03-26 01:37:24 -080061static unsigned int d_hash_mask __read_mostly;
62static unsigned int d_hash_shift __read_mostly;
63static struct hlist_head *dentry_hashtable __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -070064static LIST_HEAD(dentry_unused);
65
66/* Statistics gathering. */
67struct dentry_stat_t dentry_stat = {
68 .age_limit = 45,
69};
70
71static void d_callback(struct rcu_head *head)
72{
Eric Dumazet5160ee62006-01-08 01:03:32 -080073 struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
Linus Torvalds1da177e2005-04-16 15:20:36 -070074
75 if (dname_external(dentry))
76 kfree(dentry->d_name.name);
77 kmem_cache_free(dentry_cache, dentry);
78}
79
80/*
81 * no dcache_lock, please. The caller must decrement dentry_stat.nr_dentry
82 * inside dcache_lock.
83 */
84static void d_free(struct dentry *dentry)
85{
86 if (dentry->d_op && dentry->d_op->d_release)
87 dentry->d_op->d_release(dentry);
Eric Dumazet5160ee62006-01-08 01:03:32 -080088 call_rcu(&dentry->d_u.d_rcu, d_callback);
Linus Torvalds1da177e2005-04-16 15:20:36 -070089}
90
91/*
92 * Release the dentry's inode, using the filesystem
93 * d_iput() operation if defined.
94 * Called with dcache_lock and per dentry lock held, drops both.
95 */
Arjan van de Ven858119e2006-01-14 13:20:43 -080096static void dentry_iput(struct dentry * dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -070097{
98 struct inode *inode = dentry->d_inode;
99 if (inode) {
100 dentry->d_inode = NULL;
101 list_del_init(&dentry->d_alias);
102 spin_unlock(&dentry->d_lock);
103 spin_unlock(&dcache_lock);
Linus Torvaldsf805fbd2005-09-19 19:54:29 -0700104 if (!inode->i_nlink)
105 fsnotify_inoderemove(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106 if (dentry->d_op && dentry->d_op->d_iput)
107 dentry->d_op->d_iput(dentry, inode);
108 else
109 iput(inode);
110 } else {
111 spin_unlock(&dentry->d_lock);
112 spin_unlock(&dcache_lock);
113 }
114}
115
116/*
117 * This is dput
118 *
119 * This is complicated by the fact that we do not want to put
120 * dentries that are no longer on any hash chain on the unused
121 * list: we'd much rather just get rid of them immediately.
122 *
123 * However, that implies that we have to traverse the dentry
124 * tree upwards to the parents which might _also_ now be
125 * scheduled for deletion (it may have been only waiting for
126 * its last child to go away).
127 *
128 * This tail recursion is done by hand as we don't want to depend
129 * on the compiler to always get this right (gcc generally doesn't).
130 * Real recursion would eat up our stack space.
131 */
132
133/*
134 * dput - release a dentry
135 * @dentry: dentry to release
136 *
137 * Release a dentry. This will drop the usage count and if appropriate
138 * call the dentry unlink method as well as removing it from the queues and
139 * releasing its resources. If the parent dentries were scheduled for release
140 * they too may now get deleted.
141 *
142 * no dcache lock, please.
143 */
144
145void dput(struct dentry *dentry)
146{
147 if (!dentry)
148 return;
149
150repeat:
151 if (atomic_read(&dentry->d_count) == 1)
152 might_sleep();
153 if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
154 return;
155
156 spin_lock(&dentry->d_lock);
157 if (atomic_read(&dentry->d_count)) {
158 spin_unlock(&dentry->d_lock);
159 spin_unlock(&dcache_lock);
160 return;
161 }
162
163 /*
164 * AV: ->d_delete() is _NOT_ allowed to block now.
165 */
166 if (dentry->d_op && dentry->d_op->d_delete) {
167 if (dentry->d_op->d_delete(dentry))
168 goto unhash_it;
169 }
170 /* Unreachable? Get rid of it */
171 if (d_unhashed(dentry))
172 goto kill_it;
173 if (list_empty(&dentry->d_lru)) {
174 dentry->d_flags |= DCACHE_REFERENCED;
175 list_add(&dentry->d_lru, &dentry_unused);
176 dentry_stat.nr_unused++;
177 }
178 spin_unlock(&dentry->d_lock);
179 spin_unlock(&dcache_lock);
180 return;
181
182unhash_it:
183 __d_drop(dentry);
184
185kill_it: {
186 struct dentry *parent;
187
188 /* If dentry was on d_lru list
189 * delete it from there
190 */
191 if (!list_empty(&dentry->d_lru)) {
192 list_del(&dentry->d_lru);
193 dentry_stat.nr_unused--;
194 }
Eric Dumazet5160ee62006-01-08 01:03:32 -0800195 list_del(&dentry->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196 dentry_stat.nr_dentry--; /* For d_free, below */
197 /*drops the locks, at that point nobody can reach this dentry */
198 dentry_iput(dentry);
199 parent = dentry->d_parent;
200 d_free(dentry);
201 if (dentry == parent)
202 return;
203 dentry = parent;
204 goto repeat;
205 }
206}
207
208/**
209 * d_invalidate - invalidate a dentry
210 * @dentry: dentry to invalidate
211 *
212 * Try to invalidate the dentry if it turns out to be
213 * possible. If there are other dentries that can be
214 * reached through this one we can't delete it and we
215 * return -EBUSY. On success we return 0.
216 *
217 * no dcache lock.
218 */
219
220int d_invalidate(struct dentry * dentry)
221{
222 /*
223 * If it's already been dropped, return OK.
224 */
225 spin_lock(&dcache_lock);
226 if (d_unhashed(dentry)) {
227 spin_unlock(&dcache_lock);
228 return 0;
229 }
230 /*
231 * Check whether to do a partial shrink_dcache
232 * to get rid of unused child entries.
233 */
234 if (!list_empty(&dentry->d_subdirs)) {
235 spin_unlock(&dcache_lock);
236 shrink_dcache_parent(dentry);
237 spin_lock(&dcache_lock);
238 }
239
240 /*
241 * Somebody else still using it?
242 *
243 * If it's a directory, we can't drop it
244 * for fear of somebody re-populating it
245 * with children (even though dropping it
246 * would make it unreachable from the root,
247 * we might still populate it if it was a
248 * working directory or similar).
249 */
250 spin_lock(&dentry->d_lock);
251 if (atomic_read(&dentry->d_count) > 1) {
252 if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
253 spin_unlock(&dentry->d_lock);
254 spin_unlock(&dcache_lock);
255 return -EBUSY;
256 }
257 }
258
259 __d_drop(dentry);
260 spin_unlock(&dentry->d_lock);
261 spin_unlock(&dcache_lock);
262 return 0;
263}
264
265/* This should be called _only_ with dcache_lock held */
266
267static inline struct dentry * __dget_locked(struct dentry *dentry)
268{
269 atomic_inc(&dentry->d_count);
270 if (!list_empty(&dentry->d_lru)) {
271 dentry_stat.nr_unused--;
272 list_del_init(&dentry->d_lru);
273 }
274 return dentry;
275}
276
277struct dentry * dget_locked(struct dentry *dentry)
278{
279 return __dget_locked(dentry);
280}
281
282/**
283 * d_find_alias - grab a hashed alias of inode
284 * @inode: inode in question
285 * @want_discon: flag, used by d_splice_alias, to request
286 * that only a DISCONNECTED alias be returned.
287 *
288 * If inode has a hashed alias, or is a directory and has any alias,
289 * acquire the reference to alias and return it. Otherwise return NULL.
290 * Notice that if inode is a directory there can be only one alias and
291 * it can be unhashed only if it has no children, or if it is the root
292 * of a filesystem.
293 *
294 * If the inode has a DCACHE_DISCONNECTED alias, then prefer
295 * any other hashed alias over that one unless @want_discon is set,
296 * in which case only return a DCACHE_DISCONNECTED alias.
297 */
298
299static struct dentry * __d_find_alias(struct inode *inode, int want_discon)
300{
301 struct list_head *head, *next, *tmp;
302 struct dentry *alias, *discon_alias=NULL;
303
304 head = &inode->i_dentry;
305 next = inode->i_dentry.next;
306 while (next != head) {
307 tmp = next;
308 next = tmp->next;
309 prefetch(next);
310 alias = list_entry(tmp, struct dentry, d_alias);
311 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
312 if (alias->d_flags & DCACHE_DISCONNECTED)
313 discon_alias = alias;
314 else if (!want_discon) {
315 __dget_locked(alias);
316 return alias;
317 }
318 }
319 }
320 if (discon_alias)
321 __dget_locked(discon_alias);
322 return discon_alias;
323}
324
325struct dentry * d_find_alias(struct inode *inode)
326{
David Howells214fda12006-03-25 03:06:36 -0800327 struct dentry *de = NULL;
328
329 if (!list_empty(&inode->i_dentry)) {
330 spin_lock(&dcache_lock);
331 de = __d_find_alias(inode, 0);
332 spin_unlock(&dcache_lock);
333 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700334 return de;
335}
336
337/*
338 * Try to kill dentries associated with this inode.
339 * WARNING: you must own a reference to inode.
340 */
341void d_prune_aliases(struct inode *inode)
342{
Domen Puncer0cdca3f2005-09-10 00:27:07 -0700343 struct dentry *dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344restart:
345 spin_lock(&dcache_lock);
Domen Puncer0cdca3f2005-09-10 00:27:07 -0700346 list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700347 spin_lock(&dentry->d_lock);
348 if (!atomic_read(&dentry->d_count)) {
349 __dget_locked(dentry);
350 __d_drop(dentry);
351 spin_unlock(&dentry->d_lock);
352 spin_unlock(&dcache_lock);
353 dput(dentry);
354 goto restart;
355 }
356 spin_unlock(&dentry->d_lock);
357 }
358 spin_unlock(&dcache_lock);
359}
360
361/*
Andrew Mortond702ccb2006-06-22 14:47:31 -0700362 * Throw away a dentry - free the inode, dput the parent. This requires that
363 * the LRU list has already been removed.
364 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700365 * Called with dcache_lock, drops it and then regains.
Andrew Mortond702ccb2006-06-22 14:47:31 -0700366 * Called with dentry->d_lock held, drops it.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 */
Andrew Mortond702ccb2006-06-22 14:47:31 -0700368static void prune_one_dentry(struct dentry * dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700369{
370 struct dentry * parent;
371
372 __d_drop(dentry);
Eric Dumazet5160ee62006-01-08 01:03:32 -0800373 list_del(&dentry->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700374 dentry_stat.nr_dentry--; /* For d_free, below */
375 dentry_iput(dentry);
376 parent = dentry->d_parent;
377 d_free(dentry);
378 if (parent != dentry)
379 dput(parent);
380 spin_lock(&dcache_lock);
381}
382
383/**
384 * prune_dcache - shrink the dcache
385 * @count: number of entries to try and free
NeilBrown0feae5c2006-06-22 14:47:28 -0700386 * @sb: if given, ignore dentries for other superblocks
387 * which are being unmounted.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700388 *
389 * Shrink the dcache. This is done when we need
390 * more memory, or simply when we need to unmount
391 * something (at which point we need to unuse
392 * all dentries).
393 *
394 * This function may fail to free any resources if
395 * all the dentries are in use.
396 */
397
NeilBrown0feae5c2006-06-22 14:47:28 -0700398static void prune_dcache(int count, struct super_block *sb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399{
400 spin_lock(&dcache_lock);
401 for (; count ; count--) {
402 struct dentry *dentry;
403 struct list_head *tmp;
NeilBrown0feae5c2006-06-22 14:47:28 -0700404 struct rw_semaphore *s_umount;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700405
406 cond_resched_lock(&dcache_lock);
407
408 tmp = dentry_unused.prev;
NeilBrown0feae5c2006-06-22 14:47:28 -0700409 if (unlikely(sb)) {
410 /* Try to find a dentry for this sb, but don't try
411 * too hard, if they aren't near the tail they will
412 * be moved down again soon
413 */
414 int skip = count;
415 while (skip && tmp != &dentry_unused &&
416 list_entry(tmp, struct dentry, d_lru)->d_sb != sb) {
417 skip--;
418 tmp = tmp->prev;
419 }
420 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700421 if (tmp == &dentry_unused)
422 break;
423 list_del_init(tmp);
424 prefetch(dentry_unused.prev);
425 dentry_stat.nr_unused--;
426 dentry = list_entry(tmp, struct dentry, d_lru);
427
428 spin_lock(&dentry->d_lock);
429 /*
430 * We found an inuse dentry which was not removed from
431 * dentry_unused because of laziness during lookup. Do not free
432 * it - just keep it off the dentry_unused list.
433 */
434 if (atomic_read(&dentry->d_count)) {
435 spin_unlock(&dentry->d_lock);
436 continue;
437 }
438 /* If the dentry was recently referenced, don't free it. */
439 if (dentry->d_flags & DCACHE_REFERENCED) {
440 dentry->d_flags &= ~DCACHE_REFERENCED;
441 list_add(&dentry->d_lru, &dentry_unused);
442 dentry_stat.nr_unused++;
443 spin_unlock(&dentry->d_lock);
444 continue;
445 }
NeilBrown0feae5c2006-06-22 14:47:28 -0700446 /*
447 * If the dentry is not DCACHED_REFERENCED, it is time
448 * to remove it from the dcache, provided the super block is
449 * NULL (which means we are trying to reclaim memory)
450 * or this dentry belongs to the same super block that
451 * we want to shrink.
452 */
453 /*
454 * If this dentry is for "my" filesystem, then I can prune it
455 * without taking the s_umount lock (I already hold it).
456 */
457 if (sb && dentry->d_sb == sb) {
458 prune_one_dentry(dentry);
459 continue;
460 }
461 /*
462 * ...otherwise we need to be sure this filesystem isn't being
463 * unmounted, otherwise we could race with
464 * generic_shutdown_super(), and end up holding a reference to
465 * an inode while the filesystem is unmounted.
466 * So we try to get s_umount, and make sure s_root isn't NULL.
467 * (Take a local copy of s_umount to avoid a use-after-free of
468 * `dentry').
469 */
470 s_umount = &dentry->d_sb->s_umount;
471 if (down_read_trylock(s_umount)) {
472 if (dentry->d_sb->s_root != NULL) {
473 prune_one_dentry(dentry);
474 up_read(s_umount);
475 continue;
476 }
477 up_read(s_umount);
478 }
479 spin_unlock(&dentry->d_lock);
480 /* Cannot remove the first dentry, and it isn't appropriate
481 * to move it to the head of the list, so give up, and try
482 * later
483 */
484 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700485 }
486 spin_unlock(&dcache_lock);
487}
488
489/*
490 * Shrink the dcache for the specified super block.
491 * This allows us to unmount a device without disturbing
492 * the dcache for the other devices.
493 *
494 * This implementation makes just two traversals of the
495 * unused list. On the first pass we move the selected
496 * dentries to the most recent end, and on the second
497 * pass we free them. The second pass must restart after
498 * each dput(), but since the target dentries are all at
499 * the end, it's really just a single traversal.
500 */
501
502/**
503 * shrink_dcache_sb - shrink dcache for a superblock
504 * @sb: superblock
505 *
506 * Shrink the dcache for the specified super block. This
507 * is used to free the dcache before unmounting a file
508 * system
509 */
510
511void shrink_dcache_sb(struct super_block * sb)
512{
513 struct list_head *tmp, *next;
514 struct dentry *dentry;
515
516 /*
517 * Pass one ... move the dentries for the specified
518 * superblock to the most recent end of the unused list.
519 */
520 spin_lock(&dcache_lock);
Domen Puncer0cdca3f2005-09-10 00:27:07 -0700521 list_for_each_safe(tmp, next, &dentry_unused) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522 dentry = list_entry(tmp, struct dentry, d_lru);
523 if (dentry->d_sb != sb)
524 continue;
525 list_del(tmp);
526 list_add(tmp, &dentry_unused);
527 }
528
529 /*
530 * Pass two ... free the dentries for this superblock.
531 */
532repeat:
Domen Puncer0cdca3f2005-09-10 00:27:07 -0700533 list_for_each_safe(tmp, next, &dentry_unused) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700534 dentry = list_entry(tmp, struct dentry, d_lru);
535 if (dentry->d_sb != sb)
536 continue;
537 dentry_stat.nr_unused--;
538 list_del_init(tmp);
539 spin_lock(&dentry->d_lock);
540 if (atomic_read(&dentry->d_count)) {
541 spin_unlock(&dentry->d_lock);
542 continue;
543 }
544 prune_one_dentry(dentry);
Kirill Korotaev2ab13462006-03-25 03:07:45 -0800545 cond_resched_lock(&dcache_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700546 goto repeat;
547 }
548 spin_unlock(&dcache_lock);
549}
550
551/*
552 * Search for at least 1 mount point in the dentry's subdirs.
553 * We descend to the next level whenever the d_subdirs
554 * list is non-empty and continue searching.
555 */
556
557/**
558 * have_submounts - check for mounts over a dentry
559 * @parent: dentry to check.
560 *
561 * Return true if the parent or its subdirectories contain
562 * a mount point
563 */
564
565int have_submounts(struct dentry *parent)
566{
567 struct dentry *this_parent = parent;
568 struct list_head *next;
569
570 spin_lock(&dcache_lock);
571 if (d_mountpoint(parent))
572 goto positive;
573repeat:
574 next = this_parent->d_subdirs.next;
575resume:
576 while (next != &this_parent->d_subdirs) {
577 struct list_head *tmp = next;
Eric Dumazet5160ee62006-01-08 01:03:32 -0800578 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700579 next = tmp->next;
580 /* Have we found a mount point ? */
581 if (d_mountpoint(dentry))
582 goto positive;
583 if (!list_empty(&dentry->d_subdirs)) {
584 this_parent = dentry;
585 goto repeat;
586 }
587 }
588 /*
589 * All done at this level ... ascend and resume the search.
590 */
591 if (this_parent != parent) {
Eric Dumazet5160ee62006-01-08 01:03:32 -0800592 next = this_parent->d_u.d_child.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593 this_parent = this_parent->d_parent;
594 goto resume;
595 }
596 spin_unlock(&dcache_lock);
597 return 0; /* No mount points found in tree */
598positive:
599 spin_unlock(&dcache_lock);
600 return 1;
601}
602
603/*
604 * Search the dentry child list for the specified parent,
605 * and move any unused dentries to the end of the unused
606 * list for prune_dcache(). We descend to the next level
607 * whenever the d_subdirs list is non-empty and continue
608 * searching.
609 *
610 * It returns zero iff there are no unused children,
611 * otherwise it returns the number of children moved to
612 * the end of the unused list. This may not be the total
613 * number of unused children, because select_parent can
614 * drop the lock and return early due to latency
615 * constraints.
616 */
617static int select_parent(struct dentry * parent)
618{
619 struct dentry *this_parent = parent;
620 struct list_head *next;
621 int found = 0;
622
623 spin_lock(&dcache_lock);
624repeat:
625 next = this_parent->d_subdirs.next;
626resume:
627 while (next != &this_parent->d_subdirs) {
628 struct list_head *tmp = next;
Eric Dumazet5160ee62006-01-08 01:03:32 -0800629 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700630 next = tmp->next;
631
632 if (!list_empty(&dentry->d_lru)) {
633 dentry_stat.nr_unused--;
634 list_del_init(&dentry->d_lru);
635 }
636 /*
637 * move only zero ref count dentries to the end
638 * of the unused list for prune_dcache
639 */
640 if (!atomic_read(&dentry->d_count)) {
641 list_add(&dentry->d_lru, dentry_unused.prev);
642 dentry_stat.nr_unused++;
643 found++;
644 }
645
646 /*
647 * We can return to the caller if we have found some (this
648 * ensures forward progress). We'll be coming back to find
649 * the rest.
650 */
651 if (found && need_resched())
652 goto out;
653
654 /*
655 * Descend a level if the d_subdirs list is non-empty.
656 */
657 if (!list_empty(&dentry->d_subdirs)) {
658 this_parent = dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700659 goto repeat;
660 }
661 }
662 /*
663 * All done at this level ... ascend and resume the search.
664 */
665 if (this_parent != parent) {
Eric Dumazet5160ee62006-01-08 01:03:32 -0800666 next = this_parent->d_u.d_child.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667 this_parent = this_parent->d_parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700668 goto resume;
669 }
670out:
671 spin_unlock(&dcache_lock);
672 return found;
673}
674
675/**
676 * shrink_dcache_parent - prune dcache
677 * @parent: parent of entries to prune
678 *
679 * Prune the dcache to remove unused children of the parent dentry.
680 */
681
682void shrink_dcache_parent(struct dentry * parent)
683{
684 int found;
685
686 while ((found = select_parent(parent)) != 0)
NeilBrown0feae5c2006-06-22 14:47:28 -0700687 prune_dcache(found, parent->d_sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700688}
689
690/**
691 * shrink_dcache_anon - further prune the cache
692 * @head: head of d_hash list of dentries to prune
693 *
694 * Prune the dentries that are anonymous
695 *
Paul E. McKenney665a7582005-11-07 00:59:17 -0800696 * parsing d_hash list does not hlist_for_each_entry_rcu() as it
Linus Torvalds1da177e2005-04-16 15:20:36 -0700697 * done under dcache_lock.
698 *
699 */
NeilBrown0feae5c2006-06-22 14:47:28 -0700700void shrink_dcache_anon(struct super_block *sb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700701{
702 struct hlist_node *lp;
NeilBrown0feae5c2006-06-22 14:47:28 -0700703 struct hlist_head *head = &sb->s_anon;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700704 int found;
705 do {
706 found = 0;
707 spin_lock(&dcache_lock);
708 hlist_for_each(lp, head) {
709 struct dentry *this = hlist_entry(lp, struct dentry, d_hash);
710 if (!list_empty(&this->d_lru)) {
711 dentry_stat.nr_unused--;
712 list_del_init(&this->d_lru);
713 }
714
715 /*
716 * move only zero ref count dentries to the end
717 * of the unused list for prune_dcache
718 */
719 if (!atomic_read(&this->d_count)) {
720 list_add_tail(&this->d_lru, &dentry_unused);
721 dentry_stat.nr_unused++;
722 found++;
723 }
724 }
725 spin_unlock(&dcache_lock);
NeilBrown0feae5c2006-06-22 14:47:28 -0700726 prune_dcache(found, sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700727 } while(found);
728}
729
730/*
731 * Scan `nr' dentries and return the number which remain.
732 *
733 * We need to avoid reentering the filesystem if the caller is performing a
734 * GFP_NOFS allocation attempt. One example deadlock is:
735 *
736 * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
737 * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
738 * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
739 *
740 * In this case we return -1 to tell the caller that we baled.
741 */
Al Viro27496a82005-10-21 03:20:48 -0400742static int shrink_dcache_memory(int nr, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700743{
744 if (nr) {
745 if (!(gfp_mask & __GFP_FS))
746 return -1;
NeilBrown0feae5c2006-06-22 14:47:28 -0700747 prune_dcache(nr, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748 }
749 return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
750}
751
752/**
753 * d_alloc - allocate a dcache entry
754 * @parent: parent of entry to allocate
755 * @name: qstr of the name
756 *
757 * Allocates a dentry. It returns %NULL if there is insufficient memory
758 * available. On a success the dentry is returned. The name passed in is
759 * copied and the copy passed in may be reused after this call.
760 */
761
762struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
763{
764 struct dentry *dentry;
765 char *dname;
766
767 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
768 if (!dentry)
769 return NULL;
770
771 if (name->len > DNAME_INLINE_LEN-1) {
772 dname = kmalloc(name->len + 1, GFP_KERNEL);
773 if (!dname) {
774 kmem_cache_free(dentry_cache, dentry);
775 return NULL;
776 }
777 } else {
778 dname = dentry->d_iname;
779 }
780 dentry->d_name.name = dname;
781
782 dentry->d_name.len = name->len;
783 dentry->d_name.hash = name->hash;
784 memcpy(dname, name->name, name->len);
785 dname[name->len] = 0;
786
787 atomic_set(&dentry->d_count, 1);
788 dentry->d_flags = DCACHE_UNHASHED;
789 spin_lock_init(&dentry->d_lock);
790 dentry->d_inode = NULL;
791 dentry->d_parent = NULL;
792 dentry->d_sb = NULL;
793 dentry->d_op = NULL;
794 dentry->d_fsdata = NULL;
795 dentry->d_mounted = 0;
Marcelo Tosatti47ba87e2006-02-03 03:04:06 -0800796#ifdef CONFIG_PROFILING
Linus Torvalds1da177e2005-04-16 15:20:36 -0700797 dentry->d_cookie = NULL;
Marcelo Tosatti47ba87e2006-02-03 03:04:06 -0800798#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700799 INIT_HLIST_NODE(&dentry->d_hash);
800 INIT_LIST_HEAD(&dentry->d_lru);
801 INIT_LIST_HEAD(&dentry->d_subdirs);
802 INIT_LIST_HEAD(&dentry->d_alias);
803
804 if (parent) {
805 dentry->d_parent = dget(parent);
806 dentry->d_sb = parent->d_sb;
807 } else {
Eric Dumazet5160ee62006-01-08 01:03:32 -0800808 INIT_LIST_HEAD(&dentry->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700809 }
810
811 spin_lock(&dcache_lock);
812 if (parent)
Eric Dumazet5160ee62006-01-08 01:03:32 -0800813 list_add(&dentry->d_u.d_child, &parent->d_subdirs);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700814 dentry_stat.nr_dentry++;
815 spin_unlock(&dcache_lock);
816
817 return dentry;
818}
819
820struct dentry *d_alloc_name(struct dentry *parent, const char *name)
821{
822 struct qstr q;
823
824 q.name = name;
825 q.len = strlen(name);
826 q.hash = full_name_hash(q.name, q.len);
827 return d_alloc(parent, &q);
828}
829
830/**
831 * d_instantiate - fill in inode information for a dentry
832 * @entry: dentry to complete
833 * @inode: inode to attach to this dentry
834 *
835 * Fill in inode information in the entry.
836 *
837 * This turns negative dentries into productive full members
838 * of society.
839 *
840 * NOTE! This assumes that the inode count has been incremented
841 * (or otherwise set) by the caller to indicate that it is now
842 * in use by the dcache.
843 */
844
845void d_instantiate(struct dentry *entry, struct inode * inode)
846{
Eric Sesterhenn28133c72006-03-26 18:25:39 +0200847 BUG_ON(!list_empty(&entry->d_alias));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700848 spin_lock(&dcache_lock);
849 if (inode)
850 list_add(&entry->d_alias, &inode->i_dentry);
851 entry->d_inode = inode;
Nick Pigginc32ccd82006-03-25 03:07:09 -0800852 fsnotify_d_instantiate(entry, inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700853 spin_unlock(&dcache_lock);
854 security_d_instantiate(entry, inode);
855}
856
857/**
858 * d_instantiate_unique - instantiate a non-aliased dentry
859 * @entry: dentry to instantiate
860 * @inode: inode to attach to this dentry
861 *
862 * Fill in inode information in the entry. On success, it returns NULL.
863 * If an unhashed alias of "entry" already exists, then we return the
Oleg Drokine866cfa2006-01-09 20:52:51 -0800864 * aliased dentry instead and drop one reference to inode.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700865 *
866 * Note that in order to avoid conflicts with rename() etc, the caller
867 * had better be holding the parent directory semaphore.
Oleg Drokine866cfa2006-01-09 20:52:51 -0800868 *
869 * This also assumes that the inode count has been incremented
870 * (or otherwise set) by the caller to indicate that it is now
871 * in use by the dcache.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700872 */
873struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
874{
875 struct dentry *alias;
876 int len = entry->d_name.len;
877 const char *name = entry->d_name.name;
878 unsigned int hash = entry->d_name.hash;
879
880 BUG_ON(!list_empty(&entry->d_alias));
881 spin_lock(&dcache_lock);
882 if (!inode)
883 goto do_negative;
884 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
885 struct qstr *qstr = &alias->d_name;
886
887 if (qstr->hash != hash)
888 continue;
889 if (alias->d_parent != entry->d_parent)
890 continue;
891 if (qstr->len != len)
892 continue;
893 if (memcmp(qstr->name, name, len))
894 continue;
895 dget_locked(alias);
896 spin_unlock(&dcache_lock);
897 BUG_ON(!d_unhashed(alias));
Oleg Drokine866cfa2006-01-09 20:52:51 -0800898 iput(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700899 return alias;
900 }
901 list_add(&entry->d_alias, &inode->i_dentry);
902do_negative:
903 entry->d_inode = inode;
Nick Pigginc32ccd82006-03-25 03:07:09 -0800904 fsnotify_d_instantiate(entry, inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700905 spin_unlock(&dcache_lock);
906 security_d_instantiate(entry, inode);
907 return NULL;
908}
909EXPORT_SYMBOL(d_instantiate_unique);
910
911/**
912 * d_alloc_root - allocate root dentry
913 * @root_inode: inode to allocate the root for
914 *
915 * Allocate a root ("/") dentry for the inode given. The inode is
916 * instantiated and returned. %NULL is returned if there is insufficient
917 * memory or the inode passed is %NULL.
918 */
919
920struct dentry * d_alloc_root(struct inode * root_inode)
921{
922 struct dentry *res = NULL;
923
924 if (root_inode) {
925 static const struct qstr name = { .name = "/", .len = 1 };
926
927 res = d_alloc(NULL, &name);
928 if (res) {
929 res->d_sb = root_inode->i_sb;
930 res->d_parent = res;
931 d_instantiate(res, root_inode);
932 }
933 }
934 return res;
935}
936
937static inline struct hlist_head *d_hash(struct dentry *parent,
938 unsigned long hash)
939{
940 hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
941 hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
942 return dentry_hashtable + (hash & D_HASHMASK);
943}
944
945/**
946 * d_alloc_anon - allocate an anonymous dentry
947 * @inode: inode to allocate the dentry for
948 *
949 * This is similar to d_alloc_root. It is used by filesystems when
950 * creating a dentry for a given inode, often in the process of
951 * mapping a filehandle to a dentry. The returned dentry may be
952 * anonymous, or may have a full name (if the inode was already
953 * in the cache). The file system may need to make further
954 * efforts to connect this dentry into the dcache properly.
955 *
956 * When called on a directory inode, we must ensure that
957 * the inode only ever has one dentry. If a dentry is
958 * found, that is returned instead of allocating a new one.
959 *
960 * On successful return, the reference to the inode has been transferred
961 * to the dentry. If %NULL is returned (indicating kmalloc failure),
962 * the reference on the inode has not been released.
963 */
964
965struct dentry * d_alloc_anon(struct inode *inode)
966{
967 static const struct qstr anonstring = { .name = "" };
968 struct dentry *tmp;
969 struct dentry *res;
970
971 if ((res = d_find_alias(inode))) {
972 iput(inode);
973 return res;
974 }
975
976 tmp = d_alloc(NULL, &anonstring);
977 if (!tmp)
978 return NULL;
979
980 tmp->d_parent = tmp; /* make sure dput doesn't croak */
981
982 spin_lock(&dcache_lock);
983 res = __d_find_alias(inode, 0);
984 if (!res) {
985 /* attach a disconnected dentry */
986 res = tmp;
987 tmp = NULL;
988 spin_lock(&res->d_lock);
989 res->d_sb = inode->i_sb;
990 res->d_parent = res;
991 res->d_inode = inode;
992 res->d_flags |= DCACHE_DISCONNECTED;
993 res->d_flags &= ~DCACHE_UNHASHED;
994 list_add(&res->d_alias, &inode->i_dentry);
995 hlist_add_head(&res->d_hash, &inode->i_sb->s_anon);
996 spin_unlock(&res->d_lock);
997
998 inode = NULL; /* don't drop reference */
999 }
1000 spin_unlock(&dcache_lock);
1001
1002 if (inode)
1003 iput(inode);
1004 if (tmp)
1005 dput(tmp);
1006 return res;
1007}
1008
1009
1010/**
1011 * d_splice_alias - splice a disconnected dentry into the tree if one exists
1012 * @inode: the inode which may have a disconnected dentry
1013 * @dentry: a negative dentry which we want to point to the inode.
1014 *
1015 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1016 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1017 * and return it, else simply d_add the inode to the dentry and return NULL.
1018 *
1019 * This is needed in the lookup routine of any filesystem that is exportable
1020 * (via knfsd) so that we can build dcache paths to directories effectively.
1021 *
1022 * If a dentry was found and moved, then it is returned. Otherwise NULL
1023 * is returned. This matches the expected return value of ->lookup.
1024 *
1025 */
1026struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
1027{
1028 struct dentry *new = NULL;
1029
1030 if (inode) {
1031 spin_lock(&dcache_lock);
1032 new = __d_find_alias(inode, 1);
1033 if (new) {
1034 BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
Nick Pigginc32ccd82006-03-25 03:07:09 -08001035 fsnotify_d_instantiate(new, inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001036 spin_unlock(&dcache_lock);
1037 security_d_instantiate(new, inode);
1038 d_rehash(dentry);
1039 d_move(new, dentry);
1040 iput(inode);
1041 } else {
1042 /* d_instantiate takes dcache_lock, so we do it by hand */
1043 list_add(&dentry->d_alias, &inode->i_dentry);
1044 dentry->d_inode = inode;
Nick Pigginc32ccd82006-03-25 03:07:09 -08001045 fsnotify_d_instantiate(dentry, inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001046 spin_unlock(&dcache_lock);
1047 security_d_instantiate(dentry, inode);
1048 d_rehash(dentry);
1049 }
1050 } else
1051 d_add(dentry, inode);
1052 return new;
1053}
1054
1055
1056/**
1057 * d_lookup - search for a dentry
1058 * @parent: parent dentry
1059 * @name: qstr of name we wish to find
1060 *
1061 * Searches the children of the parent dentry for the name in question. If
1062 * the dentry is found its reference count is incremented and the dentry
1063 * is returned. The caller must use d_put to free the entry when it has
1064 * finished using it. %NULL is returned on failure.
1065 *
1066 * __d_lookup is dcache_lock free. The hash list is protected using RCU.
1067 * Memory barriers are used while updating and doing lockless traversal.
1068 * To avoid races with d_move while rename is happening, d_lock is used.
1069 *
1070 * Overflows in memcmp(), while d_move, are avoided by keeping the length
1071 * and name pointer in one structure pointed by d_qstr.
1072 *
1073 * rcu_read_lock() and rcu_read_unlock() are used to disable preemption while
1074 * lookup is going on.
1075 *
1076 * dentry_unused list is not updated even if lookup finds the required dentry
1077 * in there. It is updated in places such as prune_dcache, shrink_dcache_sb,
1078 * select_parent and __dget_locked. This laziness saves lookup from dcache_lock
1079 * acquisition.
1080 *
1081 * d_lookup() is protected against the concurrent renames in some unrelated
1082 * directory using the seqlockt_t rename_lock.
1083 */
1084
1085struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
1086{
1087 struct dentry * dentry = NULL;
1088 unsigned long seq;
1089
1090 do {
1091 seq = read_seqbegin(&rename_lock);
1092 dentry = __d_lookup(parent, name);
1093 if (dentry)
1094 break;
1095 } while (read_seqretry(&rename_lock, seq));
1096 return dentry;
1097}
1098
1099struct dentry * __d_lookup(struct dentry * parent, struct qstr * name)
1100{
1101 unsigned int len = name->len;
1102 unsigned int hash = name->hash;
1103 const unsigned char *str = name->name;
1104 struct hlist_head *head = d_hash(parent,hash);
1105 struct dentry *found = NULL;
1106 struct hlist_node *node;
Paul E. McKenney665a7582005-11-07 00:59:17 -08001107 struct dentry *dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001108
1109 rcu_read_lock();
1110
Paul E. McKenney665a7582005-11-07 00:59:17 -08001111 hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001112 struct qstr *qstr;
1113
Linus Torvalds1da177e2005-04-16 15:20:36 -07001114 if (dentry->d_name.hash != hash)
1115 continue;
1116 if (dentry->d_parent != parent)
1117 continue;
1118
1119 spin_lock(&dentry->d_lock);
1120
1121 /*
1122 * Recheck the dentry after taking the lock - d_move may have
1123 * changed things. Don't bother checking the hash because we're
1124 * about to compare the whole name anyway.
1125 */
1126 if (dentry->d_parent != parent)
1127 goto next;
1128
1129 /*
1130 * It is safe to compare names since d_move() cannot
1131 * change the qstr (protected by d_lock).
1132 */
1133 qstr = &dentry->d_name;
1134 if (parent->d_op && parent->d_op->d_compare) {
1135 if (parent->d_op->d_compare(parent, qstr, name))
1136 goto next;
1137 } else {
1138 if (qstr->len != len)
1139 goto next;
1140 if (memcmp(qstr->name, str, len))
1141 goto next;
1142 }
1143
1144 if (!d_unhashed(dentry)) {
1145 atomic_inc(&dentry->d_count);
1146 found = dentry;
1147 }
1148 spin_unlock(&dentry->d_lock);
1149 break;
1150next:
1151 spin_unlock(&dentry->d_lock);
1152 }
1153 rcu_read_unlock();
1154
1155 return found;
1156}
1157
1158/**
Eric W. Biederman3e7e2412006-03-31 02:31:43 -08001159 * d_hash_and_lookup - hash the qstr then search for a dentry
1160 * @dir: Directory to search in
1161 * @name: qstr of name we wish to find
1162 *
1163 * On hash failure or on lookup failure NULL is returned.
1164 */
1165struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
1166{
1167 struct dentry *dentry = NULL;
1168
1169 /*
1170 * Check for a fs-specific hash function. Note that we must
1171 * calculate the standard hash first, as the d_op->d_hash()
1172 * routine may choose to leave the hash value unchanged.
1173 */
1174 name->hash = full_name_hash(name->name, name->len);
1175 if (dir->d_op && dir->d_op->d_hash) {
1176 if (dir->d_op->d_hash(dir, name) < 0)
1177 goto out;
1178 }
1179 dentry = d_lookup(dir, name);
1180out:
1181 return dentry;
1182}
1183
1184/**
Linus Torvalds1da177e2005-04-16 15:20:36 -07001185 * d_validate - verify dentry provided from insecure source
1186 * @dentry: The dentry alleged to be valid child of @dparent
1187 * @dparent: The parent dentry (known to be valid)
1188 * @hash: Hash of the dentry
1189 * @len: Length of the name
1190 *
1191 * An insecure source has sent us a dentry, here we verify it and dget() it.
1192 * This is used by ncpfs in its readdir implementation.
1193 * Zero is returned in the dentry is invalid.
1194 */
1195
1196int d_validate(struct dentry *dentry, struct dentry *dparent)
1197{
1198 struct hlist_head *base;
1199 struct hlist_node *lhp;
1200
1201 /* Check whether the ptr might be valid at all.. */
1202 if (!kmem_ptr_validate(dentry_cache, dentry))
1203 goto out;
1204
1205 if (dentry->d_parent != dparent)
1206 goto out;
1207
1208 spin_lock(&dcache_lock);
1209 base = d_hash(dparent, dentry->d_name.hash);
1210 hlist_for_each(lhp,base) {
Paul E. McKenney665a7582005-11-07 00:59:17 -08001211 /* hlist_for_each_entry_rcu() not required for d_hash list
Linus Torvalds1da177e2005-04-16 15:20:36 -07001212 * as it is parsed under dcache_lock
1213 */
1214 if (dentry == hlist_entry(lhp, struct dentry, d_hash)) {
1215 __dget_locked(dentry);
1216 spin_unlock(&dcache_lock);
1217 return 1;
1218 }
1219 }
1220 spin_unlock(&dcache_lock);
1221out:
1222 return 0;
1223}
1224
1225/*
1226 * When a file is deleted, we have two options:
1227 * - turn this dentry into a negative dentry
1228 * - unhash this dentry and free it.
1229 *
1230 * Usually, we want to just turn this into
1231 * a negative dentry, but if anybody else is
1232 * currently using the dentry or the inode
1233 * we can't do that and we fall back on removing
1234 * it from the hash queues and waiting for
1235 * it to be deleted later when it has no users
1236 */
1237
1238/**
1239 * d_delete - delete a dentry
1240 * @dentry: The dentry to delete
1241 *
1242 * Turn the dentry into a negative dentry if possible, otherwise
1243 * remove it from the hash queues so it can be deleted later
1244 */
1245
1246void d_delete(struct dentry * dentry)
1247{
John McCutchan7a91bf72005-08-08 13:52:16 -04001248 int isdir = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001249 /*
1250 * Are we the only user?
1251 */
1252 spin_lock(&dcache_lock);
1253 spin_lock(&dentry->d_lock);
John McCutchan7a91bf72005-08-08 13:52:16 -04001254 isdir = S_ISDIR(dentry->d_inode->i_mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001255 if (atomic_read(&dentry->d_count) == 1) {
1256 dentry_iput(dentry);
John McCutchan7a91bf72005-08-08 13:52:16 -04001257 fsnotify_nameremove(dentry, isdir);
Amy Griffis7a2bd3f2006-03-31 02:30:54 -08001258
1259 /* remove this and other inotify debug checks after 2.6.18 */
1260 dentry->d_flags &= ~DCACHE_INOTIFY_PARENT_WATCHED;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001261 return;
1262 }
1263
1264 if (!d_unhashed(dentry))
1265 __d_drop(dentry);
1266
1267 spin_unlock(&dentry->d_lock);
1268 spin_unlock(&dcache_lock);
John McCutchan7a91bf72005-08-08 13:52:16 -04001269
1270 fsnotify_nameremove(dentry, isdir);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001271}
1272
1273static void __d_rehash(struct dentry * entry, struct hlist_head *list)
1274{
1275
1276 entry->d_flags &= ~DCACHE_UNHASHED;
1277 hlist_add_head_rcu(&entry->d_hash, list);
1278}
1279
1280/**
1281 * d_rehash - add an entry back to the hash
1282 * @entry: dentry to add to the hash
1283 *
1284 * Adds a dentry to the hash according to its name.
1285 */
1286
1287void d_rehash(struct dentry * entry)
1288{
1289 struct hlist_head *list = d_hash(entry->d_parent, entry->d_name.hash);
1290
1291 spin_lock(&dcache_lock);
1292 spin_lock(&entry->d_lock);
1293 __d_rehash(entry, list);
1294 spin_unlock(&entry->d_lock);
1295 spin_unlock(&dcache_lock);
1296}
1297
1298#define do_switch(x,y) do { \
1299 __typeof__ (x) __tmp = x; \
1300 x = y; y = __tmp; } while (0)
1301
1302/*
1303 * When switching names, the actual string doesn't strictly have to
1304 * be preserved in the target - because we're dropping the target
1305 * anyway. As such, we can just do a simple memcpy() to copy over
1306 * the new name before we switch.
1307 *
1308 * Note that we have to be a lot more careful about getting the hash
1309 * switched - we have to switch the hash value properly even if it
1310 * then no longer matches the actual (corrupted) string of the target.
1311 * The hash value has to match the hash queue that the dentry is on..
1312 */
1313static void switch_names(struct dentry *dentry, struct dentry *target)
1314{
1315 if (dname_external(target)) {
1316 if (dname_external(dentry)) {
1317 /*
1318 * Both external: swap the pointers
1319 */
1320 do_switch(target->d_name.name, dentry->d_name.name);
1321 } else {
1322 /*
1323 * dentry:internal, target:external. Steal target's
1324 * storage and make target internal.
1325 */
1326 dentry->d_name.name = target->d_name.name;
1327 target->d_name.name = target->d_iname;
1328 }
1329 } else {
1330 if (dname_external(dentry)) {
1331 /*
1332 * dentry:external, target:internal. Give dentry's
1333 * storage to target and make dentry internal
1334 */
1335 memcpy(dentry->d_iname, target->d_name.name,
1336 target->d_name.len + 1);
1337 target->d_name.name = dentry->d_name.name;
1338 dentry->d_name.name = dentry->d_iname;
1339 } else {
1340 /*
1341 * Both are internal. Just copy target to dentry
1342 */
1343 memcpy(dentry->d_iname, target->d_name.name,
1344 target->d_name.len + 1);
1345 }
1346 }
1347}
1348
1349/*
1350 * We cannibalize "target" when moving dentry on top of it,
1351 * because it's going to be thrown away anyway. We could be more
1352 * polite about it, though.
1353 *
1354 * This forceful removal will result in ugly /proc output if
1355 * somebody holds a file open that got deleted due to a rename.
1356 * We could be nicer about the deleted file, and let it show
1357 * up under the name it got deleted rather than the name that
1358 * deleted it.
1359 */
1360
1361/**
1362 * d_move - move a dentry
1363 * @dentry: entry to move
1364 * @target: new dentry
1365 *
1366 * Update the dcache to reflect the move of a file name. Negative
1367 * dcache entries should not be moved in this way.
1368 */
1369
1370void d_move(struct dentry * dentry, struct dentry * target)
1371{
1372 struct hlist_head *list;
1373
1374 if (!dentry->d_inode)
1375 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
1376
1377 spin_lock(&dcache_lock);
1378 write_seqlock(&rename_lock);
1379 /*
1380 * XXXX: do we really need to take target->d_lock?
1381 */
1382 if (target < dentry) {
1383 spin_lock(&target->d_lock);
1384 spin_lock(&dentry->d_lock);
1385 } else {
1386 spin_lock(&dentry->d_lock);
1387 spin_lock(&target->d_lock);
1388 }
1389
1390 /* Move the dentry to the target hash queue, if on different bucket */
1391 if (dentry->d_flags & DCACHE_UNHASHED)
1392 goto already_unhashed;
1393
1394 hlist_del_rcu(&dentry->d_hash);
1395
1396already_unhashed:
1397 list = d_hash(target->d_parent, target->d_name.hash);
1398 __d_rehash(dentry, list);
1399
1400 /* Unhash the target: dput() will then get rid of it */
1401 __d_drop(target);
1402
Eric Dumazet5160ee62006-01-08 01:03:32 -08001403 list_del(&dentry->d_u.d_child);
1404 list_del(&target->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001405
1406 /* Switch the names.. */
1407 switch_names(dentry, target);
1408 do_switch(dentry->d_name.len, target->d_name.len);
1409 do_switch(dentry->d_name.hash, target->d_name.hash);
1410
1411 /* ... and switch the parents */
1412 if (IS_ROOT(dentry)) {
1413 dentry->d_parent = target->d_parent;
1414 target->d_parent = target;
Eric Dumazet5160ee62006-01-08 01:03:32 -08001415 INIT_LIST_HEAD(&target->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001416 } else {
1417 do_switch(dentry->d_parent, target->d_parent);
1418
1419 /* And add them back to the (new) parent lists */
Eric Dumazet5160ee62006-01-08 01:03:32 -08001420 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001421 }
1422
Eric Dumazet5160ee62006-01-08 01:03:32 -08001423 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001424 spin_unlock(&target->d_lock);
Nick Pigginc32ccd82006-03-25 03:07:09 -08001425 fsnotify_d_move(dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001426 spin_unlock(&dentry->d_lock);
1427 write_sequnlock(&rename_lock);
1428 spin_unlock(&dcache_lock);
1429}
1430
1431/**
1432 * d_path - return the path of a dentry
1433 * @dentry: dentry to report
1434 * @vfsmnt: vfsmnt to which the dentry belongs
1435 * @root: root dentry
1436 * @rootmnt: vfsmnt to which the root dentry belongs
1437 * @buffer: buffer to return value in
1438 * @buflen: buffer length
1439 *
1440 * Convert a dentry into an ASCII path name. If the entry has been deleted
1441 * the string " (deleted)" is appended. Note that this is ambiguous.
1442 *
1443 * Returns the buffer or an error code if the path was too long.
1444 *
1445 * "buflen" should be positive. Caller holds the dcache_lock.
1446 */
1447static char * __d_path( struct dentry *dentry, struct vfsmount *vfsmnt,
1448 struct dentry *root, struct vfsmount *rootmnt,
1449 char *buffer, int buflen)
1450{
1451 char * end = buffer+buflen;
1452 char * retval;
1453 int namelen;
1454
1455 *--end = '\0';
1456 buflen--;
1457 if (!IS_ROOT(dentry) && d_unhashed(dentry)) {
1458 buflen -= 10;
1459 end -= 10;
1460 if (buflen < 0)
1461 goto Elong;
1462 memcpy(end, " (deleted)", 10);
1463 }
1464
1465 if (buflen < 1)
1466 goto Elong;
1467 /* Get '/' right */
1468 retval = end-1;
1469 *retval = '/';
1470
1471 for (;;) {
1472 struct dentry * parent;
1473
1474 if (dentry == root && vfsmnt == rootmnt)
1475 break;
1476 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
1477 /* Global root? */
1478 spin_lock(&vfsmount_lock);
1479 if (vfsmnt->mnt_parent == vfsmnt) {
1480 spin_unlock(&vfsmount_lock);
1481 goto global_root;
1482 }
1483 dentry = vfsmnt->mnt_mountpoint;
1484 vfsmnt = vfsmnt->mnt_parent;
1485 spin_unlock(&vfsmount_lock);
1486 continue;
1487 }
1488 parent = dentry->d_parent;
1489 prefetch(parent);
1490 namelen = dentry->d_name.len;
1491 buflen -= namelen + 1;
1492 if (buflen < 0)
1493 goto Elong;
1494 end -= namelen;
1495 memcpy(end, dentry->d_name.name, namelen);
1496 *--end = '/';
1497 retval = end;
1498 dentry = parent;
1499 }
1500
1501 return retval;
1502
1503global_root:
1504 namelen = dentry->d_name.len;
1505 buflen -= namelen;
1506 if (buflen < 0)
1507 goto Elong;
1508 retval -= namelen-1; /* hit the slash */
1509 memcpy(retval, dentry->d_name.name, namelen);
1510 return retval;
1511Elong:
1512 return ERR_PTR(-ENAMETOOLONG);
1513}
1514
1515/* write full pathname into buffer and return start of pathname */
1516char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
1517 char *buf, int buflen)
1518{
1519 char *res;
1520 struct vfsmount *rootmnt;
1521 struct dentry *root;
1522
1523 read_lock(&current->fs->lock);
1524 rootmnt = mntget(current->fs->rootmnt);
1525 root = dget(current->fs->root);
1526 read_unlock(&current->fs->lock);
1527 spin_lock(&dcache_lock);
1528 res = __d_path(dentry, vfsmnt, root, rootmnt, buf, buflen);
1529 spin_unlock(&dcache_lock);
1530 dput(root);
1531 mntput(rootmnt);
1532 return res;
1533}
1534
1535/*
1536 * NOTE! The user-level library version returns a
1537 * character pointer. The kernel system call just
1538 * returns the length of the buffer filled (which
1539 * includes the ending '\0' character), or a negative
1540 * error value. So libc would do something like
1541 *
1542 * char *getcwd(char * buf, size_t size)
1543 * {
1544 * int retval;
1545 *
1546 * retval = sys_getcwd(buf, size);
1547 * if (retval >= 0)
1548 * return buf;
1549 * errno = -retval;
1550 * return NULL;
1551 * }
1552 */
1553asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
1554{
1555 int error;
1556 struct vfsmount *pwdmnt, *rootmnt;
1557 struct dentry *pwd, *root;
1558 char *page = (char *) __get_free_page(GFP_USER);
1559
1560 if (!page)
1561 return -ENOMEM;
1562
1563 read_lock(&current->fs->lock);
1564 pwdmnt = mntget(current->fs->pwdmnt);
1565 pwd = dget(current->fs->pwd);
1566 rootmnt = mntget(current->fs->rootmnt);
1567 root = dget(current->fs->root);
1568 read_unlock(&current->fs->lock);
1569
1570 error = -ENOENT;
1571 /* Has the current directory has been unlinked? */
1572 spin_lock(&dcache_lock);
1573 if (pwd->d_parent == pwd || !d_unhashed(pwd)) {
1574 unsigned long len;
1575 char * cwd;
1576
1577 cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE);
1578 spin_unlock(&dcache_lock);
1579
1580 error = PTR_ERR(cwd);
1581 if (IS_ERR(cwd))
1582 goto out;
1583
1584 error = -ERANGE;
1585 len = PAGE_SIZE + page - cwd;
1586 if (len <= size) {
1587 error = len;
1588 if (copy_to_user(buf, cwd, len))
1589 error = -EFAULT;
1590 }
1591 } else
1592 spin_unlock(&dcache_lock);
1593
1594out:
1595 dput(pwd);
1596 mntput(pwdmnt);
1597 dput(root);
1598 mntput(rootmnt);
1599 free_page((unsigned long) page);
1600 return error;
1601}
1602
1603/*
1604 * Test whether new_dentry is a subdirectory of old_dentry.
1605 *
1606 * Trivially implemented using the dcache structure
1607 */
1608
1609/**
1610 * is_subdir - is new dentry a subdirectory of old_dentry
1611 * @new_dentry: new dentry
1612 * @old_dentry: old dentry
1613 *
1614 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
1615 * Returns 0 otherwise.
1616 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
1617 */
1618
1619int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
1620{
1621 int result;
1622 struct dentry * saved = new_dentry;
1623 unsigned long seq;
1624
1625 /* need rcu_readlock to protect against the d_parent trashing due to
1626 * d_move
1627 */
1628 rcu_read_lock();
1629 do {
1630 /* for restarting inner loop in case of seq retry */
1631 new_dentry = saved;
1632 result = 0;
1633 seq = read_seqbegin(&rename_lock);
1634 for (;;) {
1635 if (new_dentry != old_dentry) {
1636 struct dentry * parent = new_dentry->d_parent;
1637 if (parent == new_dentry)
1638 break;
1639 new_dentry = parent;
1640 continue;
1641 }
1642 result = 1;
1643 break;
1644 }
1645 } while (read_seqretry(&rename_lock, seq));
1646 rcu_read_unlock();
1647
1648 return result;
1649}
1650
1651void d_genocide(struct dentry *root)
1652{
1653 struct dentry *this_parent = root;
1654 struct list_head *next;
1655
1656 spin_lock(&dcache_lock);
1657repeat:
1658 next = this_parent->d_subdirs.next;
1659resume:
1660 while (next != &this_parent->d_subdirs) {
1661 struct list_head *tmp = next;
Eric Dumazet5160ee62006-01-08 01:03:32 -08001662 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001663 next = tmp->next;
1664 if (d_unhashed(dentry)||!dentry->d_inode)
1665 continue;
1666 if (!list_empty(&dentry->d_subdirs)) {
1667 this_parent = dentry;
1668 goto repeat;
1669 }
1670 atomic_dec(&dentry->d_count);
1671 }
1672 if (this_parent != root) {
Eric Dumazet5160ee62006-01-08 01:03:32 -08001673 next = this_parent->d_u.d_child.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001674 atomic_dec(&this_parent->d_count);
1675 this_parent = this_parent->d_parent;
1676 goto resume;
1677 }
1678 spin_unlock(&dcache_lock);
1679}
1680
1681/**
1682 * find_inode_number - check for dentry with name
1683 * @dir: directory to check
1684 * @name: Name to find.
1685 *
1686 * Check whether a dentry already exists for the given name,
1687 * and return the inode number if it has an inode. Otherwise
1688 * 0 is returned.
1689 *
1690 * This routine is used to post-process directory listings for
1691 * filesystems using synthetic inode numbers, and is necessary
1692 * to keep getcwd() working.
1693 */
1694
1695ino_t find_inode_number(struct dentry *dir, struct qstr *name)
1696{
1697 struct dentry * dentry;
1698 ino_t ino = 0;
1699
Eric W. Biederman3e7e2412006-03-31 02:31:43 -08001700 dentry = d_hash_and_lookup(dir, name);
1701 if (dentry) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001702 if (dentry->d_inode)
1703 ino = dentry->d_inode->i_ino;
1704 dput(dentry);
1705 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001706 return ino;
1707}
1708
1709static __initdata unsigned long dhash_entries;
1710static int __init set_dhash_entries(char *str)
1711{
1712 if (!str)
1713 return 0;
1714 dhash_entries = simple_strtoul(str, &str, 0);
1715 return 1;
1716}
1717__setup("dhash_entries=", set_dhash_entries);
1718
1719static void __init dcache_init_early(void)
1720{
1721 int loop;
1722
1723 /* If hashes are distributed across NUMA nodes, defer
1724 * hash allocation until vmalloc space is available.
1725 */
1726 if (hashdist)
1727 return;
1728
1729 dentry_hashtable =
1730 alloc_large_system_hash("Dentry cache",
1731 sizeof(struct hlist_head),
1732 dhash_entries,
1733 13,
1734 HASH_EARLY,
1735 &d_hash_shift,
1736 &d_hash_mask,
1737 0);
1738
1739 for (loop = 0; loop < (1 << d_hash_shift); loop++)
1740 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
1741}
1742
1743static void __init dcache_init(unsigned long mempages)
1744{
1745 int loop;
1746
1747 /*
1748 * A constructor could be added for stable state like the lists,
1749 * but it is probably not worth it because of the cache nature
1750 * of the dcache.
1751 */
1752 dentry_cache = kmem_cache_create("dentry_cache",
1753 sizeof(struct dentry),
1754 0,
Paul Jacksonb0196002006-03-24 03:16:09 -08001755 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
1756 SLAB_MEM_SPREAD),
Linus Torvalds1da177e2005-04-16 15:20:36 -07001757 NULL, NULL);
1758
1759 set_shrinker(DEFAULT_SEEKS, shrink_dcache_memory);
1760
1761 /* Hash may have been set up in dcache_init_early */
1762 if (!hashdist)
1763 return;
1764
1765 dentry_hashtable =
1766 alloc_large_system_hash("Dentry cache",
1767 sizeof(struct hlist_head),
1768 dhash_entries,
1769 13,
1770 0,
1771 &d_hash_shift,
1772 &d_hash_mask,
1773 0);
1774
1775 for (loop = 0; loop < (1 << d_hash_shift); loop++)
1776 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
1777}
1778
1779/* SLAB cache for __getname() consumers */
Eric Dumazetfa3536c2006-03-26 01:37:24 -08001780kmem_cache_t *names_cachep __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001781
1782/* SLAB cache for file structures */
Eric Dumazetfa3536c2006-03-26 01:37:24 -08001783kmem_cache_t *filp_cachep __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001784
1785EXPORT_SYMBOL(d_genocide);
1786
1787extern void bdev_cache_init(void);
1788extern void chrdev_init(void);
1789
1790void __init vfs_caches_init_early(void)
1791{
1792 dcache_init_early();
1793 inode_init_early();
1794}
1795
1796void __init vfs_caches_init(unsigned long mempages)
1797{
1798 unsigned long reserve;
1799
1800 /* Base hash sizes on available memory, with a reserve equal to
1801 150% of current kernel size */
1802
1803 reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
1804 mempages -= reserve;
1805
1806 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
1807 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1808
1809 filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
Dipankar Sarma529bf6b2006-03-07 21:55:35 -08001810 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001811
1812 dcache_init(mempages);
1813 inode_init(mempages);
1814 files_init(mempages);
1815 mnt_init(mempages);
1816 bdev_cache_init();
1817 chrdev_init();
1818}
1819
1820EXPORT_SYMBOL(d_alloc);
1821EXPORT_SYMBOL(d_alloc_anon);
1822EXPORT_SYMBOL(d_alloc_root);
1823EXPORT_SYMBOL(d_delete);
1824EXPORT_SYMBOL(d_find_alias);
1825EXPORT_SYMBOL(d_instantiate);
1826EXPORT_SYMBOL(d_invalidate);
1827EXPORT_SYMBOL(d_lookup);
1828EXPORT_SYMBOL(d_move);
1829EXPORT_SYMBOL(d_path);
1830EXPORT_SYMBOL(d_prune_aliases);
1831EXPORT_SYMBOL(d_rehash);
1832EXPORT_SYMBOL(d_splice_alias);
1833EXPORT_SYMBOL(d_validate);
1834EXPORT_SYMBOL(dget_locked);
1835EXPORT_SYMBOL(dput);
1836EXPORT_SYMBOL(find_inode_number);
1837EXPORT_SYMBOL(have_submounts);
1838EXPORT_SYMBOL(names_cachep);
1839EXPORT_SYMBOL(shrink_dcache_parent);
1840EXPORT_SYMBOL(shrink_dcache_sb);