blob: 86bdb93789c6629c60027fdba100e99aa2709610 [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
37/* #define DCACHE_DEBUG 1 */
38
39int sysctl_vfs_cache_pressure = 100;
40EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
41
42 __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
Adrian Bunk75c96f82005-05-05 16:16:09 -070043static seqlock_t rename_lock __cacheline_aligned_in_smp = SEQLOCK_UNLOCKED;
Linus Torvalds1da177e2005-04-16 15:20:36 -070044
45EXPORT_SYMBOL(dcache_lock);
46
47static kmem_cache_t *dentry_cache;
48
49#define DNAME_INLINE_LEN (sizeof(struct dentry)-offsetof(struct dentry,d_iname))
50
51/*
52 * This is the single most critical data structure when it comes
53 * to the dcache: the hashtable for lookups. Somebody should try
54 * to make this good - I've just made it work.
55 *
56 * This hash-function tries to avoid losing too many bits of hash
57 * information, yet avoid using a prime hash-size or similar.
58 */
59#define D_HASHBITS d_hash_shift
60#define D_HASHMASK d_hash_mask
61
62static unsigned int d_hash_mask;
63static unsigned int d_hash_shift;
64static struct hlist_head *dentry_hashtable;
65static LIST_HEAD(dentry_unused);
66
67/* Statistics gathering. */
68struct dentry_stat_t dentry_stat = {
69 .age_limit = 45,
70};
71
72static void d_callback(struct rcu_head *head)
73{
Eric Dumazet5160ee62006-01-08 01:03:32 -080074 struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
Linus Torvalds1da177e2005-04-16 15:20:36 -070075
76 if (dname_external(dentry))
77 kfree(dentry->d_name.name);
78 kmem_cache_free(dentry_cache, dentry);
79}
80
81/*
82 * no dcache_lock, please. The caller must decrement dentry_stat.nr_dentry
83 * inside dcache_lock.
84 */
85static void d_free(struct dentry *dentry)
86{
87 if (dentry->d_op && dentry->d_op->d_release)
88 dentry->d_op->d_release(dentry);
Eric Dumazet5160ee62006-01-08 01:03:32 -080089 call_rcu(&dentry->d_u.d_rcu, d_callback);
Linus Torvalds1da177e2005-04-16 15:20:36 -070090}
91
92/*
93 * Release the dentry's inode, using the filesystem
94 * d_iput() operation if defined.
95 * Called with dcache_lock and per dentry lock held, drops both.
96 */
Arjan van de Ven858119e2006-01-14 13:20:43 -080097static void dentry_iput(struct dentry * dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -070098{
99 struct inode *inode = dentry->d_inode;
100 if (inode) {
101 dentry->d_inode = NULL;
102 list_del_init(&dentry->d_alias);
103 spin_unlock(&dentry->d_lock);
104 spin_unlock(&dcache_lock);
Linus Torvaldsf805fbd2005-09-19 19:54:29 -0700105 if (!inode->i_nlink)
106 fsnotify_inoderemove(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107 if (dentry->d_op && dentry->d_op->d_iput)
108 dentry->d_op->d_iput(dentry, inode);
109 else
110 iput(inode);
111 } else {
112 spin_unlock(&dentry->d_lock);
113 spin_unlock(&dcache_lock);
114 }
115}
116
117/*
118 * This is dput
119 *
120 * This is complicated by the fact that we do not want to put
121 * dentries that are no longer on any hash chain on the unused
122 * list: we'd much rather just get rid of them immediately.
123 *
124 * However, that implies that we have to traverse the dentry
125 * tree upwards to the parents which might _also_ now be
126 * scheduled for deletion (it may have been only waiting for
127 * its last child to go away).
128 *
129 * This tail recursion is done by hand as we don't want to depend
130 * on the compiler to always get this right (gcc generally doesn't).
131 * Real recursion would eat up our stack space.
132 */
133
134/*
135 * dput - release a dentry
136 * @dentry: dentry to release
137 *
138 * Release a dentry. This will drop the usage count and if appropriate
139 * call the dentry unlink method as well as removing it from the queues and
140 * releasing its resources. If the parent dentries were scheduled for release
141 * they too may now get deleted.
142 *
143 * no dcache lock, please.
144 */
145
146void dput(struct dentry *dentry)
147{
148 if (!dentry)
149 return;
150
151repeat:
152 if (atomic_read(&dentry->d_count) == 1)
153 might_sleep();
154 if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
155 return;
156
157 spin_lock(&dentry->d_lock);
158 if (atomic_read(&dentry->d_count)) {
159 spin_unlock(&dentry->d_lock);
160 spin_unlock(&dcache_lock);
161 return;
162 }
163
164 /*
165 * AV: ->d_delete() is _NOT_ allowed to block now.
166 */
167 if (dentry->d_op && dentry->d_op->d_delete) {
168 if (dentry->d_op->d_delete(dentry))
169 goto unhash_it;
170 }
171 /* Unreachable? Get rid of it */
172 if (d_unhashed(dentry))
173 goto kill_it;
174 if (list_empty(&dentry->d_lru)) {
175 dentry->d_flags |= DCACHE_REFERENCED;
176 list_add(&dentry->d_lru, &dentry_unused);
177 dentry_stat.nr_unused++;
178 }
179 spin_unlock(&dentry->d_lock);
180 spin_unlock(&dcache_lock);
181 return;
182
183unhash_it:
184 __d_drop(dentry);
185
186kill_it: {
187 struct dentry *parent;
188
189 /* If dentry was on d_lru list
190 * delete it from there
191 */
192 if (!list_empty(&dentry->d_lru)) {
193 list_del(&dentry->d_lru);
194 dentry_stat.nr_unused--;
195 }
Eric Dumazet5160ee62006-01-08 01:03:32 -0800196 list_del(&dentry->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700197 dentry_stat.nr_dentry--; /* For d_free, below */
198 /*drops the locks, at that point nobody can reach this dentry */
199 dentry_iput(dentry);
200 parent = dentry->d_parent;
201 d_free(dentry);
202 if (dentry == parent)
203 return;
204 dentry = parent;
205 goto repeat;
206 }
207}
208
209/**
210 * d_invalidate - invalidate a dentry
211 * @dentry: dentry to invalidate
212 *
213 * Try to invalidate the dentry if it turns out to be
214 * possible. If there are other dentries that can be
215 * reached through this one we can't delete it and we
216 * return -EBUSY. On success we return 0.
217 *
218 * no dcache lock.
219 */
220
221int d_invalidate(struct dentry * dentry)
222{
223 /*
224 * If it's already been dropped, return OK.
225 */
226 spin_lock(&dcache_lock);
227 if (d_unhashed(dentry)) {
228 spin_unlock(&dcache_lock);
229 return 0;
230 }
231 /*
232 * Check whether to do a partial shrink_dcache
233 * to get rid of unused child entries.
234 */
235 if (!list_empty(&dentry->d_subdirs)) {
236 spin_unlock(&dcache_lock);
237 shrink_dcache_parent(dentry);
238 spin_lock(&dcache_lock);
239 }
240
241 /*
242 * Somebody else still using it?
243 *
244 * If it's a directory, we can't drop it
245 * for fear of somebody re-populating it
246 * with children (even though dropping it
247 * would make it unreachable from the root,
248 * we might still populate it if it was a
249 * working directory or similar).
250 */
251 spin_lock(&dentry->d_lock);
252 if (atomic_read(&dentry->d_count) > 1) {
253 if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
254 spin_unlock(&dentry->d_lock);
255 spin_unlock(&dcache_lock);
256 return -EBUSY;
257 }
258 }
259
260 __d_drop(dentry);
261 spin_unlock(&dentry->d_lock);
262 spin_unlock(&dcache_lock);
263 return 0;
264}
265
266/* This should be called _only_ with dcache_lock held */
267
268static inline struct dentry * __dget_locked(struct dentry *dentry)
269{
270 atomic_inc(&dentry->d_count);
271 if (!list_empty(&dentry->d_lru)) {
272 dentry_stat.nr_unused--;
273 list_del_init(&dentry->d_lru);
274 }
275 return dentry;
276}
277
278struct dentry * dget_locked(struct dentry *dentry)
279{
280 return __dget_locked(dentry);
281}
282
283/**
284 * d_find_alias - grab a hashed alias of inode
285 * @inode: inode in question
286 * @want_discon: flag, used by d_splice_alias, to request
287 * that only a DISCONNECTED alias be returned.
288 *
289 * If inode has a hashed alias, or is a directory and has any alias,
290 * acquire the reference to alias and return it. Otherwise return NULL.
291 * Notice that if inode is a directory there can be only one alias and
292 * it can be unhashed only if it has no children, or if it is the root
293 * of a filesystem.
294 *
295 * If the inode has a DCACHE_DISCONNECTED alias, then prefer
296 * any other hashed alias over that one unless @want_discon is set,
297 * in which case only return a DCACHE_DISCONNECTED alias.
298 */
299
300static struct dentry * __d_find_alias(struct inode *inode, int want_discon)
301{
302 struct list_head *head, *next, *tmp;
303 struct dentry *alias, *discon_alias=NULL;
304
305 head = &inode->i_dentry;
306 next = inode->i_dentry.next;
307 while (next != head) {
308 tmp = next;
309 next = tmp->next;
310 prefetch(next);
311 alias = list_entry(tmp, struct dentry, d_alias);
312 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
313 if (alias->d_flags & DCACHE_DISCONNECTED)
314 discon_alias = alias;
315 else if (!want_discon) {
316 __dget_locked(alias);
317 return alias;
318 }
319 }
320 }
321 if (discon_alias)
322 __dget_locked(discon_alias);
323 return discon_alias;
324}
325
326struct dentry * d_find_alias(struct inode *inode)
327{
328 struct dentry *de;
329 spin_lock(&dcache_lock);
330 de = __d_find_alias(inode, 0);
331 spin_unlock(&dcache_lock);
332 return de;
333}
334
335/*
336 * Try to kill dentries associated with this inode.
337 * WARNING: you must own a reference to inode.
338 */
339void d_prune_aliases(struct inode *inode)
340{
Domen Puncer0cdca3f2005-09-10 00:27:07 -0700341 struct dentry *dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342restart:
343 spin_lock(&dcache_lock);
Domen Puncer0cdca3f2005-09-10 00:27:07 -0700344 list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700345 spin_lock(&dentry->d_lock);
346 if (!atomic_read(&dentry->d_count)) {
347 __dget_locked(dentry);
348 __d_drop(dentry);
349 spin_unlock(&dentry->d_lock);
350 spin_unlock(&dcache_lock);
351 dput(dentry);
352 goto restart;
353 }
354 spin_unlock(&dentry->d_lock);
355 }
356 spin_unlock(&dcache_lock);
357}
358
359/*
360 * Throw away a dentry - free the inode, dput the parent.
361 * This requires that the LRU list has already been
362 * removed.
363 * Called with dcache_lock, drops it and then regains.
364 */
365static inline void prune_one_dentry(struct dentry * dentry)
366{
367 struct dentry * parent;
368
369 __d_drop(dentry);
Eric Dumazet5160ee62006-01-08 01:03:32 -0800370 list_del(&dentry->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700371 dentry_stat.nr_dentry--; /* For d_free, below */
372 dentry_iput(dentry);
373 parent = dentry->d_parent;
374 d_free(dentry);
375 if (parent != dentry)
376 dput(parent);
377 spin_lock(&dcache_lock);
378}
379
380/**
381 * prune_dcache - shrink the dcache
382 * @count: number of entries to try and free
383 *
384 * Shrink the dcache. This is done when we need
385 * more memory, or simply when we need to unmount
386 * something (at which point we need to unuse
387 * all dentries).
388 *
389 * This function may fail to free any resources if
390 * all the dentries are in use.
391 */
392
393static void prune_dcache(int count)
394{
395 spin_lock(&dcache_lock);
396 for (; count ; count--) {
397 struct dentry *dentry;
398 struct list_head *tmp;
399
400 cond_resched_lock(&dcache_lock);
401
402 tmp = dentry_unused.prev;
403 if (tmp == &dentry_unused)
404 break;
405 list_del_init(tmp);
406 prefetch(dentry_unused.prev);
407 dentry_stat.nr_unused--;
408 dentry = list_entry(tmp, struct dentry, d_lru);
409
410 spin_lock(&dentry->d_lock);
411 /*
412 * We found an inuse dentry which was not removed from
413 * dentry_unused because of laziness during lookup. Do not free
414 * it - just keep it off the dentry_unused list.
415 */
416 if (atomic_read(&dentry->d_count)) {
417 spin_unlock(&dentry->d_lock);
418 continue;
419 }
420 /* If the dentry was recently referenced, don't free it. */
421 if (dentry->d_flags & DCACHE_REFERENCED) {
422 dentry->d_flags &= ~DCACHE_REFERENCED;
423 list_add(&dentry->d_lru, &dentry_unused);
424 dentry_stat.nr_unused++;
425 spin_unlock(&dentry->d_lock);
426 continue;
427 }
428 prune_one_dentry(dentry);
429 }
430 spin_unlock(&dcache_lock);
431}
432
433/*
434 * Shrink the dcache for the specified super block.
435 * This allows us to unmount a device without disturbing
436 * the dcache for the other devices.
437 *
438 * This implementation makes just two traversals of the
439 * unused list. On the first pass we move the selected
440 * dentries to the most recent end, and on the second
441 * pass we free them. The second pass must restart after
442 * each dput(), but since the target dentries are all at
443 * the end, it's really just a single traversal.
444 */
445
446/**
447 * shrink_dcache_sb - shrink dcache for a superblock
448 * @sb: superblock
449 *
450 * Shrink the dcache for the specified super block. This
451 * is used to free the dcache before unmounting a file
452 * system
453 */
454
455void shrink_dcache_sb(struct super_block * sb)
456{
457 struct list_head *tmp, *next;
458 struct dentry *dentry;
459
460 /*
461 * Pass one ... move the dentries for the specified
462 * superblock to the most recent end of the unused list.
463 */
464 spin_lock(&dcache_lock);
Domen Puncer0cdca3f2005-09-10 00:27:07 -0700465 list_for_each_safe(tmp, next, &dentry_unused) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700466 dentry = list_entry(tmp, struct dentry, d_lru);
467 if (dentry->d_sb != sb)
468 continue;
469 list_del(tmp);
470 list_add(tmp, &dentry_unused);
471 }
472
473 /*
474 * Pass two ... free the dentries for this superblock.
475 */
476repeat:
Domen Puncer0cdca3f2005-09-10 00:27:07 -0700477 list_for_each_safe(tmp, next, &dentry_unused) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700478 dentry = list_entry(tmp, struct dentry, d_lru);
479 if (dentry->d_sb != sb)
480 continue;
481 dentry_stat.nr_unused--;
482 list_del_init(tmp);
483 spin_lock(&dentry->d_lock);
484 if (atomic_read(&dentry->d_count)) {
485 spin_unlock(&dentry->d_lock);
486 continue;
487 }
488 prune_one_dentry(dentry);
489 goto repeat;
490 }
491 spin_unlock(&dcache_lock);
492}
493
494/*
495 * Search for at least 1 mount point in the dentry's subdirs.
496 * We descend to the next level whenever the d_subdirs
497 * list is non-empty and continue searching.
498 */
499
500/**
501 * have_submounts - check for mounts over a dentry
502 * @parent: dentry to check.
503 *
504 * Return true if the parent or its subdirectories contain
505 * a mount point
506 */
507
508int have_submounts(struct dentry *parent)
509{
510 struct dentry *this_parent = parent;
511 struct list_head *next;
512
513 spin_lock(&dcache_lock);
514 if (d_mountpoint(parent))
515 goto positive;
516repeat:
517 next = this_parent->d_subdirs.next;
518resume:
519 while (next != &this_parent->d_subdirs) {
520 struct list_head *tmp = next;
Eric Dumazet5160ee62006-01-08 01:03:32 -0800521 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522 next = tmp->next;
523 /* Have we found a mount point ? */
524 if (d_mountpoint(dentry))
525 goto positive;
526 if (!list_empty(&dentry->d_subdirs)) {
527 this_parent = dentry;
528 goto repeat;
529 }
530 }
531 /*
532 * All done at this level ... ascend and resume the search.
533 */
534 if (this_parent != parent) {
Eric Dumazet5160ee62006-01-08 01:03:32 -0800535 next = this_parent->d_u.d_child.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700536 this_parent = this_parent->d_parent;
537 goto resume;
538 }
539 spin_unlock(&dcache_lock);
540 return 0; /* No mount points found in tree */
541positive:
542 spin_unlock(&dcache_lock);
543 return 1;
544}
545
546/*
547 * Search the dentry child list for the specified parent,
548 * and move any unused dentries to the end of the unused
549 * list for prune_dcache(). We descend to the next level
550 * whenever the d_subdirs list is non-empty and continue
551 * searching.
552 *
553 * It returns zero iff there are no unused children,
554 * otherwise it returns the number of children moved to
555 * the end of the unused list. This may not be the total
556 * number of unused children, because select_parent can
557 * drop the lock and return early due to latency
558 * constraints.
559 */
560static int select_parent(struct dentry * parent)
561{
562 struct dentry *this_parent = parent;
563 struct list_head *next;
564 int found = 0;
565
566 spin_lock(&dcache_lock);
567repeat:
568 next = this_parent->d_subdirs.next;
569resume:
570 while (next != &this_parent->d_subdirs) {
571 struct list_head *tmp = next;
Eric Dumazet5160ee62006-01-08 01:03:32 -0800572 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700573 next = tmp->next;
574
575 if (!list_empty(&dentry->d_lru)) {
576 dentry_stat.nr_unused--;
577 list_del_init(&dentry->d_lru);
578 }
579 /*
580 * move only zero ref count dentries to the end
581 * of the unused list for prune_dcache
582 */
583 if (!atomic_read(&dentry->d_count)) {
584 list_add(&dentry->d_lru, dentry_unused.prev);
585 dentry_stat.nr_unused++;
586 found++;
587 }
588
589 /*
590 * We can return to the caller if we have found some (this
591 * ensures forward progress). We'll be coming back to find
592 * the rest.
593 */
594 if (found && need_resched())
595 goto out;
596
597 /*
598 * Descend a level if the d_subdirs list is non-empty.
599 */
600 if (!list_empty(&dentry->d_subdirs)) {
601 this_parent = dentry;
602#ifdef DCACHE_DEBUG
603printk(KERN_DEBUG "select_parent: descending to %s/%s, found=%d\n",
604dentry->d_parent->d_name.name, dentry->d_name.name, found);
605#endif
606 goto repeat;
607 }
608 }
609 /*
610 * All done at this level ... ascend and resume the search.
611 */
612 if (this_parent != parent) {
Eric Dumazet5160ee62006-01-08 01:03:32 -0800613 next = this_parent->d_u.d_child.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700614 this_parent = this_parent->d_parent;
615#ifdef DCACHE_DEBUG
616printk(KERN_DEBUG "select_parent: ascending to %s/%s, found=%d\n",
617this_parent->d_parent->d_name.name, this_parent->d_name.name, found);
618#endif
619 goto resume;
620 }
621out:
622 spin_unlock(&dcache_lock);
623 return found;
624}
625
626/**
627 * shrink_dcache_parent - prune dcache
628 * @parent: parent of entries to prune
629 *
630 * Prune the dcache to remove unused children of the parent dentry.
631 */
632
633void shrink_dcache_parent(struct dentry * parent)
634{
635 int found;
636
637 while ((found = select_parent(parent)) != 0)
638 prune_dcache(found);
639}
640
641/**
642 * shrink_dcache_anon - further prune the cache
643 * @head: head of d_hash list of dentries to prune
644 *
645 * Prune the dentries that are anonymous
646 *
Paul E. McKenney665a7582005-11-07 00:59:17 -0800647 * parsing d_hash list does not hlist_for_each_entry_rcu() as it
Linus Torvalds1da177e2005-04-16 15:20:36 -0700648 * done under dcache_lock.
649 *
650 */
651void shrink_dcache_anon(struct hlist_head *head)
652{
653 struct hlist_node *lp;
654 int found;
655 do {
656 found = 0;
657 spin_lock(&dcache_lock);
658 hlist_for_each(lp, head) {
659 struct dentry *this = hlist_entry(lp, struct dentry, d_hash);
660 if (!list_empty(&this->d_lru)) {
661 dentry_stat.nr_unused--;
662 list_del_init(&this->d_lru);
663 }
664
665 /*
666 * move only zero ref count dentries to the end
667 * of the unused list for prune_dcache
668 */
669 if (!atomic_read(&this->d_count)) {
670 list_add_tail(&this->d_lru, &dentry_unused);
671 dentry_stat.nr_unused++;
672 found++;
673 }
674 }
675 spin_unlock(&dcache_lock);
676 prune_dcache(found);
677 } while(found);
678}
679
680/*
681 * Scan `nr' dentries and return the number which remain.
682 *
683 * We need to avoid reentering the filesystem if the caller is performing a
684 * GFP_NOFS allocation attempt. One example deadlock is:
685 *
686 * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
687 * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
688 * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
689 *
690 * In this case we return -1 to tell the caller that we baled.
691 */
Al Viro27496a82005-10-21 03:20:48 -0400692static int shrink_dcache_memory(int nr, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700693{
694 if (nr) {
695 if (!(gfp_mask & __GFP_FS))
696 return -1;
697 prune_dcache(nr);
698 }
699 return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
700}
701
702/**
703 * d_alloc - allocate a dcache entry
704 * @parent: parent of entry to allocate
705 * @name: qstr of the name
706 *
707 * Allocates a dentry. It returns %NULL if there is insufficient memory
708 * available. On a success the dentry is returned. The name passed in is
709 * copied and the copy passed in may be reused after this call.
710 */
711
712struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
713{
714 struct dentry *dentry;
715 char *dname;
716
717 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
718 if (!dentry)
719 return NULL;
720
721 if (name->len > DNAME_INLINE_LEN-1) {
722 dname = kmalloc(name->len + 1, GFP_KERNEL);
723 if (!dname) {
724 kmem_cache_free(dentry_cache, dentry);
725 return NULL;
726 }
727 } else {
728 dname = dentry->d_iname;
729 }
730 dentry->d_name.name = dname;
731
732 dentry->d_name.len = name->len;
733 dentry->d_name.hash = name->hash;
734 memcpy(dname, name->name, name->len);
735 dname[name->len] = 0;
736
737 atomic_set(&dentry->d_count, 1);
738 dentry->d_flags = DCACHE_UNHASHED;
739 spin_lock_init(&dentry->d_lock);
740 dentry->d_inode = NULL;
741 dentry->d_parent = NULL;
742 dentry->d_sb = NULL;
743 dentry->d_op = NULL;
744 dentry->d_fsdata = NULL;
745 dentry->d_mounted = 0;
746 dentry->d_cookie = NULL;
747 INIT_HLIST_NODE(&dentry->d_hash);
748 INIT_LIST_HEAD(&dentry->d_lru);
749 INIT_LIST_HEAD(&dentry->d_subdirs);
750 INIT_LIST_HEAD(&dentry->d_alias);
751
752 if (parent) {
753 dentry->d_parent = dget(parent);
754 dentry->d_sb = parent->d_sb;
755 } else {
Eric Dumazet5160ee62006-01-08 01:03:32 -0800756 INIT_LIST_HEAD(&dentry->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700757 }
758
759 spin_lock(&dcache_lock);
760 if (parent)
Eric Dumazet5160ee62006-01-08 01:03:32 -0800761 list_add(&dentry->d_u.d_child, &parent->d_subdirs);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700762 dentry_stat.nr_dentry++;
763 spin_unlock(&dcache_lock);
764
765 return dentry;
766}
767
768struct dentry *d_alloc_name(struct dentry *parent, const char *name)
769{
770 struct qstr q;
771
772 q.name = name;
773 q.len = strlen(name);
774 q.hash = full_name_hash(q.name, q.len);
775 return d_alloc(parent, &q);
776}
777
778/**
779 * d_instantiate - fill in inode information for a dentry
780 * @entry: dentry to complete
781 * @inode: inode to attach to this dentry
782 *
783 * Fill in inode information in the entry.
784 *
785 * This turns negative dentries into productive full members
786 * of society.
787 *
788 * NOTE! This assumes that the inode count has been incremented
789 * (or otherwise set) by the caller to indicate that it is now
790 * in use by the dcache.
791 */
792
793void d_instantiate(struct dentry *entry, struct inode * inode)
794{
795 if (!list_empty(&entry->d_alias)) BUG();
796 spin_lock(&dcache_lock);
797 if (inode)
798 list_add(&entry->d_alias, &inode->i_dentry);
799 entry->d_inode = inode;
800 spin_unlock(&dcache_lock);
801 security_d_instantiate(entry, inode);
802}
803
804/**
805 * d_instantiate_unique - instantiate a non-aliased dentry
806 * @entry: dentry to instantiate
807 * @inode: inode to attach to this dentry
808 *
809 * Fill in inode information in the entry. On success, it returns NULL.
810 * If an unhashed alias of "entry" already exists, then we return the
Oleg Drokine866cfa2006-01-09 20:52:51 -0800811 * aliased dentry instead and drop one reference to inode.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700812 *
813 * Note that in order to avoid conflicts with rename() etc, the caller
814 * had better be holding the parent directory semaphore.
Oleg Drokine866cfa2006-01-09 20:52:51 -0800815 *
816 * This also assumes that the inode count has been incremented
817 * (or otherwise set) by the caller to indicate that it is now
818 * in use by the dcache.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700819 */
820struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
821{
822 struct dentry *alias;
823 int len = entry->d_name.len;
824 const char *name = entry->d_name.name;
825 unsigned int hash = entry->d_name.hash;
826
827 BUG_ON(!list_empty(&entry->d_alias));
828 spin_lock(&dcache_lock);
829 if (!inode)
830 goto do_negative;
831 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
832 struct qstr *qstr = &alias->d_name;
833
834 if (qstr->hash != hash)
835 continue;
836 if (alias->d_parent != entry->d_parent)
837 continue;
838 if (qstr->len != len)
839 continue;
840 if (memcmp(qstr->name, name, len))
841 continue;
842 dget_locked(alias);
843 spin_unlock(&dcache_lock);
844 BUG_ON(!d_unhashed(alias));
Oleg Drokine866cfa2006-01-09 20:52:51 -0800845 iput(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700846 return alias;
847 }
848 list_add(&entry->d_alias, &inode->i_dentry);
849do_negative:
850 entry->d_inode = inode;
851 spin_unlock(&dcache_lock);
852 security_d_instantiate(entry, inode);
853 return NULL;
854}
855EXPORT_SYMBOL(d_instantiate_unique);
856
857/**
858 * d_alloc_root - allocate root dentry
859 * @root_inode: inode to allocate the root for
860 *
861 * Allocate a root ("/") dentry for the inode given. The inode is
862 * instantiated and returned. %NULL is returned if there is insufficient
863 * memory or the inode passed is %NULL.
864 */
865
866struct dentry * d_alloc_root(struct inode * root_inode)
867{
868 struct dentry *res = NULL;
869
870 if (root_inode) {
871 static const struct qstr name = { .name = "/", .len = 1 };
872
873 res = d_alloc(NULL, &name);
874 if (res) {
875 res->d_sb = root_inode->i_sb;
876 res->d_parent = res;
877 d_instantiate(res, root_inode);
878 }
879 }
880 return res;
881}
882
883static inline struct hlist_head *d_hash(struct dentry *parent,
884 unsigned long hash)
885{
886 hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
887 hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
888 return dentry_hashtable + (hash & D_HASHMASK);
889}
890
891/**
892 * d_alloc_anon - allocate an anonymous dentry
893 * @inode: inode to allocate the dentry for
894 *
895 * This is similar to d_alloc_root. It is used by filesystems when
896 * creating a dentry for a given inode, often in the process of
897 * mapping a filehandle to a dentry. The returned dentry may be
898 * anonymous, or may have a full name (if the inode was already
899 * in the cache). The file system may need to make further
900 * efforts to connect this dentry into the dcache properly.
901 *
902 * When called on a directory inode, we must ensure that
903 * the inode only ever has one dentry. If a dentry is
904 * found, that is returned instead of allocating a new one.
905 *
906 * On successful return, the reference to the inode has been transferred
907 * to the dentry. If %NULL is returned (indicating kmalloc failure),
908 * the reference on the inode has not been released.
909 */
910
911struct dentry * d_alloc_anon(struct inode *inode)
912{
913 static const struct qstr anonstring = { .name = "" };
914 struct dentry *tmp;
915 struct dentry *res;
916
917 if ((res = d_find_alias(inode))) {
918 iput(inode);
919 return res;
920 }
921
922 tmp = d_alloc(NULL, &anonstring);
923 if (!tmp)
924 return NULL;
925
926 tmp->d_parent = tmp; /* make sure dput doesn't croak */
927
928 spin_lock(&dcache_lock);
929 res = __d_find_alias(inode, 0);
930 if (!res) {
931 /* attach a disconnected dentry */
932 res = tmp;
933 tmp = NULL;
934 spin_lock(&res->d_lock);
935 res->d_sb = inode->i_sb;
936 res->d_parent = res;
937 res->d_inode = inode;
938 res->d_flags |= DCACHE_DISCONNECTED;
939 res->d_flags &= ~DCACHE_UNHASHED;
940 list_add(&res->d_alias, &inode->i_dentry);
941 hlist_add_head(&res->d_hash, &inode->i_sb->s_anon);
942 spin_unlock(&res->d_lock);
943
944 inode = NULL; /* don't drop reference */
945 }
946 spin_unlock(&dcache_lock);
947
948 if (inode)
949 iput(inode);
950 if (tmp)
951 dput(tmp);
952 return res;
953}
954
955
956/**
957 * d_splice_alias - splice a disconnected dentry into the tree if one exists
958 * @inode: the inode which may have a disconnected dentry
959 * @dentry: a negative dentry which we want to point to the inode.
960 *
961 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
962 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
963 * and return it, else simply d_add the inode to the dentry and return NULL.
964 *
965 * This is needed in the lookup routine of any filesystem that is exportable
966 * (via knfsd) so that we can build dcache paths to directories effectively.
967 *
968 * If a dentry was found and moved, then it is returned. Otherwise NULL
969 * is returned. This matches the expected return value of ->lookup.
970 *
971 */
972struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
973{
974 struct dentry *new = NULL;
975
976 if (inode) {
977 spin_lock(&dcache_lock);
978 new = __d_find_alias(inode, 1);
979 if (new) {
980 BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
981 spin_unlock(&dcache_lock);
982 security_d_instantiate(new, inode);
983 d_rehash(dentry);
984 d_move(new, dentry);
985 iput(inode);
986 } else {
987 /* d_instantiate takes dcache_lock, so we do it by hand */
988 list_add(&dentry->d_alias, &inode->i_dentry);
989 dentry->d_inode = inode;
990 spin_unlock(&dcache_lock);
991 security_d_instantiate(dentry, inode);
992 d_rehash(dentry);
993 }
994 } else
995 d_add(dentry, inode);
996 return new;
997}
998
999
1000/**
1001 * d_lookup - search for a dentry
1002 * @parent: parent dentry
1003 * @name: qstr of name we wish to find
1004 *
1005 * Searches the children of the parent dentry for the name in question. If
1006 * the dentry is found its reference count is incremented and the dentry
1007 * is returned. The caller must use d_put to free the entry when it has
1008 * finished using it. %NULL is returned on failure.
1009 *
1010 * __d_lookup is dcache_lock free. The hash list is protected using RCU.
1011 * Memory barriers are used while updating and doing lockless traversal.
1012 * To avoid races with d_move while rename is happening, d_lock is used.
1013 *
1014 * Overflows in memcmp(), while d_move, are avoided by keeping the length
1015 * and name pointer in one structure pointed by d_qstr.
1016 *
1017 * rcu_read_lock() and rcu_read_unlock() are used to disable preemption while
1018 * lookup is going on.
1019 *
1020 * dentry_unused list is not updated even if lookup finds the required dentry
1021 * in there. It is updated in places such as prune_dcache, shrink_dcache_sb,
1022 * select_parent and __dget_locked. This laziness saves lookup from dcache_lock
1023 * acquisition.
1024 *
1025 * d_lookup() is protected against the concurrent renames in some unrelated
1026 * directory using the seqlockt_t rename_lock.
1027 */
1028
1029struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
1030{
1031 struct dentry * dentry = NULL;
1032 unsigned long seq;
1033
1034 do {
1035 seq = read_seqbegin(&rename_lock);
1036 dentry = __d_lookup(parent, name);
1037 if (dentry)
1038 break;
1039 } while (read_seqretry(&rename_lock, seq));
1040 return dentry;
1041}
1042
1043struct dentry * __d_lookup(struct dentry * parent, struct qstr * name)
1044{
1045 unsigned int len = name->len;
1046 unsigned int hash = name->hash;
1047 const unsigned char *str = name->name;
1048 struct hlist_head *head = d_hash(parent,hash);
1049 struct dentry *found = NULL;
1050 struct hlist_node *node;
Paul E. McKenney665a7582005-11-07 00:59:17 -08001051 struct dentry *dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001052
1053 rcu_read_lock();
1054
Paul E. McKenney665a7582005-11-07 00:59:17 -08001055 hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001056 struct qstr *qstr;
1057
Linus Torvalds1da177e2005-04-16 15:20:36 -07001058 if (dentry->d_name.hash != hash)
1059 continue;
1060 if (dentry->d_parent != parent)
1061 continue;
1062
1063 spin_lock(&dentry->d_lock);
1064
1065 /*
1066 * Recheck the dentry after taking the lock - d_move may have
1067 * changed things. Don't bother checking the hash because we're
1068 * about to compare the whole name anyway.
1069 */
1070 if (dentry->d_parent != parent)
1071 goto next;
1072
1073 /*
1074 * It is safe to compare names since d_move() cannot
1075 * change the qstr (protected by d_lock).
1076 */
1077 qstr = &dentry->d_name;
1078 if (parent->d_op && parent->d_op->d_compare) {
1079 if (parent->d_op->d_compare(parent, qstr, name))
1080 goto next;
1081 } else {
1082 if (qstr->len != len)
1083 goto next;
1084 if (memcmp(qstr->name, str, len))
1085 goto next;
1086 }
1087
1088 if (!d_unhashed(dentry)) {
1089 atomic_inc(&dentry->d_count);
1090 found = dentry;
1091 }
1092 spin_unlock(&dentry->d_lock);
1093 break;
1094next:
1095 spin_unlock(&dentry->d_lock);
1096 }
1097 rcu_read_unlock();
1098
1099 return found;
1100}
1101
1102/**
1103 * d_validate - verify dentry provided from insecure source
1104 * @dentry: The dentry alleged to be valid child of @dparent
1105 * @dparent: The parent dentry (known to be valid)
1106 * @hash: Hash of the dentry
1107 * @len: Length of the name
1108 *
1109 * An insecure source has sent us a dentry, here we verify it and dget() it.
1110 * This is used by ncpfs in its readdir implementation.
1111 * Zero is returned in the dentry is invalid.
1112 */
1113
1114int d_validate(struct dentry *dentry, struct dentry *dparent)
1115{
1116 struct hlist_head *base;
1117 struct hlist_node *lhp;
1118
1119 /* Check whether the ptr might be valid at all.. */
1120 if (!kmem_ptr_validate(dentry_cache, dentry))
1121 goto out;
1122
1123 if (dentry->d_parent != dparent)
1124 goto out;
1125
1126 spin_lock(&dcache_lock);
1127 base = d_hash(dparent, dentry->d_name.hash);
1128 hlist_for_each(lhp,base) {
Paul E. McKenney665a7582005-11-07 00:59:17 -08001129 /* hlist_for_each_entry_rcu() not required for d_hash list
Linus Torvalds1da177e2005-04-16 15:20:36 -07001130 * as it is parsed under dcache_lock
1131 */
1132 if (dentry == hlist_entry(lhp, struct dentry, d_hash)) {
1133 __dget_locked(dentry);
1134 spin_unlock(&dcache_lock);
1135 return 1;
1136 }
1137 }
1138 spin_unlock(&dcache_lock);
1139out:
1140 return 0;
1141}
1142
1143/*
1144 * When a file is deleted, we have two options:
1145 * - turn this dentry into a negative dentry
1146 * - unhash this dentry and free it.
1147 *
1148 * Usually, we want to just turn this into
1149 * a negative dentry, but if anybody else is
1150 * currently using the dentry or the inode
1151 * we can't do that and we fall back on removing
1152 * it from the hash queues and waiting for
1153 * it to be deleted later when it has no users
1154 */
1155
1156/**
1157 * d_delete - delete a dentry
1158 * @dentry: The dentry to delete
1159 *
1160 * Turn the dentry into a negative dentry if possible, otherwise
1161 * remove it from the hash queues so it can be deleted later
1162 */
1163
1164void d_delete(struct dentry * dentry)
1165{
John McCutchan7a91bf72005-08-08 13:52:16 -04001166 int isdir = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001167 /*
1168 * Are we the only user?
1169 */
1170 spin_lock(&dcache_lock);
1171 spin_lock(&dentry->d_lock);
John McCutchan7a91bf72005-08-08 13:52:16 -04001172 isdir = S_ISDIR(dentry->d_inode->i_mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001173 if (atomic_read(&dentry->d_count) == 1) {
1174 dentry_iput(dentry);
John McCutchan7a91bf72005-08-08 13:52:16 -04001175 fsnotify_nameremove(dentry, isdir);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001176 return;
1177 }
1178
1179 if (!d_unhashed(dentry))
1180 __d_drop(dentry);
1181
1182 spin_unlock(&dentry->d_lock);
1183 spin_unlock(&dcache_lock);
John McCutchan7a91bf72005-08-08 13:52:16 -04001184
1185 fsnotify_nameremove(dentry, isdir);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001186}
1187
1188static void __d_rehash(struct dentry * entry, struct hlist_head *list)
1189{
1190
1191 entry->d_flags &= ~DCACHE_UNHASHED;
1192 hlist_add_head_rcu(&entry->d_hash, list);
1193}
1194
1195/**
1196 * d_rehash - add an entry back to the hash
1197 * @entry: dentry to add to the hash
1198 *
1199 * Adds a dentry to the hash according to its name.
1200 */
1201
1202void d_rehash(struct dentry * entry)
1203{
1204 struct hlist_head *list = d_hash(entry->d_parent, entry->d_name.hash);
1205
1206 spin_lock(&dcache_lock);
1207 spin_lock(&entry->d_lock);
1208 __d_rehash(entry, list);
1209 spin_unlock(&entry->d_lock);
1210 spin_unlock(&dcache_lock);
1211}
1212
1213#define do_switch(x,y) do { \
1214 __typeof__ (x) __tmp = x; \
1215 x = y; y = __tmp; } while (0)
1216
1217/*
1218 * When switching names, the actual string doesn't strictly have to
1219 * be preserved in the target - because we're dropping the target
1220 * anyway. As such, we can just do a simple memcpy() to copy over
1221 * the new name before we switch.
1222 *
1223 * Note that we have to be a lot more careful about getting the hash
1224 * switched - we have to switch the hash value properly even if it
1225 * then no longer matches the actual (corrupted) string of the target.
1226 * The hash value has to match the hash queue that the dentry is on..
1227 */
1228static void switch_names(struct dentry *dentry, struct dentry *target)
1229{
1230 if (dname_external(target)) {
1231 if (dname_external(dentry)) {
1232 /*
1233 * Both external: swap the pointers
1234 */
1235 do_switch(target->d_name.name, dentry->d_name.name);
1236 } else {
1237 /*
1238 * dentry:internal, target:external. Steal target's
1239 * storage and make target internal.
1240 */
1241 dentry->d_name.name = target->d_name.name;
1242 target->d_name.name = target->d_iname;
1243 }
1244 } else {
1245 if (dname_external(dentry)) {
1246 /*
1247 * dentry:external, target:internal. Give dentry's
1248 * storage to target and make dentry internal
1249 */
1250 memcpy(dentry->d_iname, target->d_name.name,
1251 target->d_name.len + 1);
1252 target->d_name.name = dentry->d_name.name;
1253 dentry->d_name.name = dentry->d_iname;
1254 } else {
1255 /*
1256 * Both are internal. Just copy target to dentry
1257 */
1258 memcpy(dentry->d_iname, target->d_name.name,
1259 target->d_name.len + 1);
1260 }
1261 }
1262}
1263
1264/*
1265 * We cannibalize "target" when moving dentry on top of it,
1266 * because it's going to be thrown away anyway. We could be more
1267 * polite about it, though.
1268 *
1269 * This forceful removal will result in ugly /proc output if
1270 * somebody holds a file open that got deleted due to a rename.
1271 * We could be nicer about the deleted file, and let it show
1272 * up under the name it got deleted rather than the name that
1273 * deleted it.
1274 */
1275
1276/**
1277 * d_move - move a dentry
1278 * @dentry: entry to move
1279 * @target: new dentry
1280 *
1281 * Update the dcache to reflect the move of a file name. Negative
1282 * dcache entries should not be moved in this way.
1283 */
1284
1285void d_move(struct dentry * dentry, struct dentry * target)
1286{
1287 struct hlist_head *list;
1288
1289 if (!dentry->d_inode)
1290 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
1291
1292 spin_lock(&dcache_lock);
1293 write_seqlock(&rename_lock);
1294 /*
1295 * XXXX: do we really need to take target->d_lock?
1296 */
1297 if (target < dentry) {
1298 spin_lock(&target->d_lock);
1299 spin_lock(&dentry->d_lock);
1300 } else {
1301 spin_lock(&dentry->d_lock);
1302 spin_lock(&target->d_lock);
1303 }
1304
1305 /* Move the dentry to the target hash queue, if on different bucket */
1306 if (dentry->d_flags & DCACHE_UNHASHED)
1307 goto already_unhashed;
1308
1309 hlist_del_rcu(&dentry->d_hash);
1310
1311already_unhashed:
1312 list = d_hash(target->d_parent, target->d_name.hash);
1313 __d_rehash(dentry, list);
1314
1315 /* Unhash the target: dput() will then get rid of it */
1316 __d_drop(target);
1317
Eric Dumazet5160ee62006-01-08 01:03:32 -08001318 list_del(&dentry->d_u.d_child);
1319 list_del(&target->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001320
1321 /* Switch the names.. */
1322 switch_names(dentry, target);
1323 do_switch(dentry->d_name.len, target->d_name.len);
1324 do_switch(dentry->d_name.hash, target->d_name.hash);
1325
1326 /* ... and switch the parents */
1327 if (IS_ROOT(dentry)) {
1328 dentry->d_parent = target->d_parent;
1329 target->d_parent = target;
Eric Dumazet5160ee62006-01-08 01:03:32 -08001330 INIT_LIST_HEAD(&target->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001331 } else {
1332 do_switch(dentry->d_parent, target->d_parent);
1333
1334 /* And add them back to the (new) parent lists */
Eric Dumazet5160ee62006-01-08 01:03:32 -08001335 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001336 }
1337
Eric Dumazet5160ee62006-01-08 01:03:32 -08001338 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001339 spin_unlock(&target->d_lock);
1340 spin_unlock(&dentry->d_lock);
1341 write_sequnlock(&rename_lock);
1342 spin_unlock(&dcache_lock);
1343}
1344
1345/**
1346 * d_path - return the path of a dentry
1347 * @dentry: dentry to report
1348 * @vfsmnt: vfsmnt to which the dentry belongs
1349 * @root: root dentry
1350 * @rootmnt: vfsmnt to which the root dentry belongs
1351 * @buffer: buffer to return value in
1352 * @buflen: buffer length
1353 *
1354 * Convert a dentry into an ASCII path name. If the entry has been deleted
1355 * the string " (deleted)" is appended. Note that this is ambiguous.
1356 *
1357 * Returns the buffer or an error code if the path was too long.
1358 *
1359 * "buflen" should be positive. Caller holds the dcache_lock.
1360 */
1361static char * __d_path( struct dentry *dentry, struct vfsmount *vfsmnt,
1362 struct dentry *root, struct vfsmount *rootmnt,
1363 char *buffer, int buflen)
1364{
1365 char * end = buffer+buflen;
1366 char * retval;
1367 int namelen;
1368
1369 *--end = '\0';
1370 buflen--;
1371 if (!IS_ROOT(dentry) && d_unhashed(dentry)) {
1372 buflen -= 10;
1373 end -= 10;
1374 if (buflen < 0)
1375 goto Elong;
1376 memcpy(end, " (deleted)", 10);
1377 }
1378
1379 if (buflen < 1)
1380 goto Elong;
1381 /* Get '/' right */
1382 retval = end-1;
1383 *retval = '/';
1384
1385 for (;;) {
1386 struct dentry * parent;
1387
1388 if (dentry == root && vfsmnt == rootmnt)
1389 break;
1390 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
1391 /* Global root? */
1392 spin_lock(&vfsmount_lock);
1393 if (vfsmnt->mnt_parent == vfsmnt) {
1394 spin_unlock(&vfsmount_lock);
1395 goto global_root;
1396 }
1397 dentry = vfsmnt->mnt_mountpoint;
1398 vfsmnt = vfsmnt->mnt_parent;
1399 spin_unlock(&vfsmount_lock);
1400 continue;
1401 }
1402 parent = dentry->d_parent;
1403 prefetch(parent);
1404 namelen = dentry->d_name.len;
1405 buflen -= namelen + 1;
1406 if (buflen < 0)
1407 goto Elong;
1408 end -= namelen;
1409 memcpy(end, dentry->d_name.name, namelen);
1410 *--end = '/';
1411 retval = end;
1412 dentry = parent;
1413 }
1414
1415 return retval;
1416
1417global_root:
1418 namelen = dentry->d_name.len;
1419 buflen -= namelen;
1420 if (buflen < 0)
1421 goto Elong;
1422 retval -= namelen-1; /* hit the slash */
1423 memcpy(retval, dentry->d_name.name, namelen);
1424 return retval;
1425Elong:
1426 return ERR_PTR(-ENAMETOOLONG);
1427}
1428
1429/* write full pathname into buffer and return start of pathname */
1430char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
1431 char *buf, int buflen)
1432{
1433 char *res;
1434 struct vfsmount *rootmnt;
1435 struct dentry *root;
1436
1437 read_lock(&current->fs->lock);
1438 rootmnt = mntget(current->fs->rootmnt);
1439 root = dget(current->fs->root);
1440 read_unlock(&current->fs->lock);
1441 spin_lock(&dcache_lock);
1442 res = __d_path(dentry, vfsmnt, root, rootmnt, buf, buflen);
1443 spin_unlock(&dcache_lock);
1444 dput(root);
1445 mntput(rootmnt);
1446 return res;
1447}
1448
1449/*
1450 * NOTE! The user-level library version returns a
1451 * character pointer. The kernel system call just
1452 * returns the length of the buffer filled (which
1453 * includes the ending '\0' character), or a negative
1454 * error value. So libc would do something like
1455 *
1456 * char *getcwd(char * buf, size_t size)
1457 * {
1458 * int retval;
1459 *
1460 * retval = sys_getcwd(buf, size);
1461 * if (retval >= 0)
1462 * return buf;
1463 * errno = -retval;
1464 * return NULL;
1465 * }
1466 */
1467asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
1468{
1469 int error;
1470 struct vfsmount *pwdmnt, *rootmnt;
1471 struct dentry *pwd, *root;
1472 char *page = (char *) __get_free_page(GFP_USER);
1473
1474 if (!page)
1475 return -ENOMEM;
1476
1477 read_lock(&current->fs->lock);
1478 pwdmnt = mntget(current->fs->pwdmnt);
1479 pwd = dget(current->fs->pwd);
1480 rootmnt = mntget(current->fs->rootmnt);
1481 root = dget(current->fs->root);
1482 read_unlock(&current->fs->lock);
1483
1484 error = -ENOENT;
1485 /* Has the current directory has been unlinked? */
1486 spin_lock(&dcache_lock);
1487 if (pwd->d_parent == pwd || !d_unhashed(pwd)) {
1488 unsigned long len;
1489 char * cwd;
1490
1491 cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE);
1492 spin_unlock(&dcache_lock);
1493
1494 error = PTR_ERR(cwd);
1495 if (IS_ERR(cwd))
1496 goto out;
1497
1498 error = -ERANGE;
1499 len = PAGE_SIZE + page - cwd;
1500 if (len <= size) {
1501 error = len;
1502 if (copy_to_user(buf, cwd, len))
1503 error = -EFAULT;
1504 }
1505 } else
1506 spin_unlock(&dcache_lock);
1507
1508out:
1509 dput(pwd);
1510 mntput(pwdmnt);
1511 dput(root);
1512 mntput(rootmnt);
1513 free_page((unsigned long) page);
1514 return error;
1515}
1516
1517/*
1518 * Test whether new_dentry is a subdirectory of old_dentry.
1519 *
1520 * Trivially implemented using the dcache structure
1521 */
1522
1523/**
1524 * is_subdir - is new dentry a subdirectory of old_dentry
1525 * @new_dentry: new dentry
1526 * @old_dentry: old dentry
1527 *
1528 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
1529 * Returns 0 otherwise.
1530 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
1531 */
1532
1533int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
1534{
1535 int result;
1536 struct dentry * saved = new_dentry;
1537 unsigned long seq;
1538
1539 /* need rcu_readlock to protect against the d_parent trashing due to
1540 * d_move
1541 */
1542 rcu_read_lock();
1543 do {
1544 /* for restarting inner loop in case of seq retry */
1545 new_dentry = saved;
1546 result = 0;
1547 seq = read_seqbegin(&rename_lock);
1548 for (;;) {
1549 if (new_dentry != old_dentry) {
1550 struct dentry * parent = new_dentry->d_parent;
1551 if (parent == new_dentry)
1552 break;
1553 new_dentry = parent;
1554 continue;
1555 }
1556 result = 1;
1557 break;
1558 }
1559 } while (read_seqretry(&rename_lock, seq));
1560 rcu_read_unlock();
1561
1562 return result;
1563}
1564
1565void d_genocide(struct dentry *root)
1566{
1567 struct dentry *this_parent = root;
1568 struct list_head *next;
1569
1570 spin_lock(&dcache_lock);
1571repeat:
1572 next = this_parent->d_subdirs.next;
1573resume:
1574 while (next != &this_parent->d_subdirs) {
1575 struct list_head *tmp = next;
Eric Dumazet5160ee62006-01-08 01:03:32 -08001576 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001577 next = tmp->next;
1578 if (d_unhashed(dentry)||!dentry->d_inode)
1579 continue;
1580 if (!list_empty(&dentry->d_subdirs)) {
1581 this_parent = dentry;
1582 goto repeat;
1583 }
1584 atomic_dec(&dentry->d_count);
1585 }
1586 if (this_parent != root) {
Eric Dumazet5160ee62006-01-08 01:03:32 -08001587 next = this_parent->d_u.d_child.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001588 atomic_dec(&this_parent->d_count);
1589 this_parent = this_parent->d_parent;
1590 goto resume;
1591 }
1592 spin_unlock(&dcache_lock);
1593}
1594
1595/**
1596 * find_inode_number - check for dentry with name
1597 * @dir: directory to check
1598 * @name: Name to find.
1599 *
1600 * Check whether a dentry already exists for the given name,
1601 * and return the inode number if it has an inode. Otherwise
1602 * 0 is returned.
1603 *
1604 * This routine is used to post-process directory listings for
1605 * filesystems using synthetic inode numbers, and is necessary
1606 * to keep getcwd() working.
1607 */
1608
1609ino_t find_inode_number(struct dentry *dir, struct qstr *name)
1610{
1611 struct dentry * dentry;
1612 ino_t ino = 0;
1613
1614 /*
1615 * Check for a fs-specific hash function. Note that we must
1616 * calculate the standard hash first, as the d_op->d_hash()
1617 * routine may choose to leave the hash value unchanged.
1618 */
1619 name->hash = full_name_hash(name->name, name->len);
1620 if (dir->d_op && dir->d_op->d_hash)
1621 {
1622 if (dir->d_op->d_hash(dir, name) != 0)
1623 goto out;
1624 }
1625
1626 dentry = d_lookup(dir, name);
1627 if (dentry)
1628 {
1629 if (dentry->d_inode)
1630 ino = dentry->d_inode->i_ino;
1631 dput(dentry);
1632 }
1633out:
1634 return ino;
1635}
1636
1637static __initdata unsigned long dhash_entries;
1638static int __init set_dhash_entries(char *str)
1639{
1640 if (!str)
1641 return 0;
1642 dhash_entries = simple_strtoul(str, &str, 0);
1643 return 1;
1644}
1645__setup("dhash_entries=", set_dhash_entries);
1646
1647static void __init dcache_init_early(void)
1648{
1649 int loop;
1650
1651 /* If hashes are distributed across NUMA nodes, defer
1652 * hash allocation until vmalloc space is available.
1653 */
1654 if (hashdist)
1655 return;
1656
1657 dentry_hashtable =
1658 alloc_large_system_hash("Dentry cache",
1659 sizeof(struct hlist_head),
1660 dhash_entries,
1661 13,
1662 HASH_EARLY,
1663 &d_hash_shift,
1664 &d_hash_mask,
1665 0);
1666
1667 for (loop = 0; loop < (1 << d_hash_shift); loop++)
1668 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
1669}
1670
1671static void __init dcache_init(unsigned long mempages)
1672{
1673 int loop;
1674
1675 /*
1676 * A constructor could be added for stable state like the lists,
1677 * but it is probably not worth it because of the cache nature
1678 * of the dcache.
1679 */
1680 dentry_cache = kmem_cache_create("dentry_cache",
1681 sizeof(struct dentry),
1682 0,
1683 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC,
1684 NULL, NULL);
1685
1686 set_shrinker(DEFAULT_SEEKS, shrink_dcache_memory);
1687
1688 /* Hash may have been set up in dcache_init_early */
1689 if (!hashdist)
1690 return;
1691
1692 dentry_hashtable =
1693 alloc_large_system_hash("Dentry cache",
1694 sizeof(struct hlist_head),
1695 dhash_entries,
1696 13,
1697 0,
1698 &d_hash_shift,
1699 &d_hash_mask,
1700 0);
1701
1702 for (loop = 0; loop < (1 << d_hash_shift); loop++)
1703 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
1704}
1705
1706/* SLAB cache for __getname() consumers */
1707kmem_cache_t *names_cachep;
1708
1709/* SLAB cache for file structures */
1710kmem_cache_t *filp_cachep;
1711
1712EXPORT_SYMBOL(d_genocide);
1713
1714extern void bdev_cache_init(void);
1715extern void chrdev_init(void);
1716
1717void __init vfs_caches_init_early(void)
1718{
1719 dcache_init_early();
1720 inode_init_early();
1721}
1722
1723void __init vfs_caches_init(unsigned long mempages)
1724{
1725 unsigned long reserve;
1726
1727 /* Base hash sizes on available memory, with a reserve equal to
1728 150% of current kernel size */
1729
1730 reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
1731 mempages -= reserve;
1732
1733 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
1734 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1735
1736 filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
1737 SLAB_HWCACHE_ALIGN|SLAB_PANIC, filp_ctor, filp_dtor);
1738
1739 dcache_init(mempages);
1740 inode_init(mempages);
1741 files_init(mempages);
1742 mnt_init(mempages);
1743 bdev_cache_init();
1744 chrdev_init();
1745}
1746
1747EXPORT_SYMBOL(d_alloc);
1748EXPORT_SYMBOL(d_alloc_anon);
1749EXPORT_SYMBOL(d_alloc_root);
1750EXPORT_SYMBOL(d_delete);
1751EXPORT_SYMBOL(d_find_alias);
1752EXPORT_SYMBOL(d_instantiate);
1753EXPORT_SYMBOL(d_invalidate);
1754EXPORT_SYMBOL(d_lookup);
1755EXPORT_SYMBOL(d_move);
1756EXPORT_SYMBOL(d_path);
1757EXPORT_SYMBOL(d_prune_aliases);
1758EXPORT_SYMBOL(d_rehash);
1759EXPORT_SYMBOL(d_splice_alias);
1760EXPORT_SYMBOL(d_validate);
1761EXPORT_SYMBOL(dget_locked);
1762EXPORT_SYMBOL(dput);
1763EXPORT_SYMBOL(find_inode_number);
1764EXPORT_SYMBOL(have_submounts);
1765EXPORT_SYMBOL(names_cachep);
1766EXPORT_SYMBOL(shrink_dcache_parent);
1767EXPORT_SYMBOL(shrink_dcache_sb);