drm/i915: unbind unmappable objects on fault/pin
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / dcache.c
blob23702a9d4e6d130b6ef226d1157f1a484f93a282
1 /*
2 * fs/dcache.c
4 * Complete reimplementation
5 * (C) 1997 Thomas Schoebel-Theuer,
6 * with heavy changes by Linus Torvalds
7 */
9 /*
10 * Notes on the allocation strategy:
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.
17 #include <linux/syscalls.h>
18 #include <linux/string.h>
19 #include <linux/mm.h>
20 #include <linux/fs.h>
21 #include <linux/fsnotify.h>
22 #include <linux/slab.h>
23 #include <linux/init.h>
24 #include <linux/hash.h>
25 #include <linux/cache.h>
26 #include <linux/module.h>
27 #include <linux/mount.h>
28 #include <linux/file.h>
29 #include <asm/uaccess.h>
30 #include <linux/security.h>
31 #include <linux/seqlock.h>
32 #include <linux/swap.h>
33 #include <linux/bootmem.h>
34 #include <linux/fs_struct.h>
35 #include <linux/hardirq.h>
36 #include "internal.h"
38 int sysctl_vfs_cache_pressure __read_mostly = 100;
39 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
41 __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
42 __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
44 EXPORT_SYMBOL(dcache_lock);
46 static struct kmem_cache *dentry_cache __read_mostly;
48 #define DNAME_INLINE_LEN (sizeof(struct dentry)-offsetof(struct dentry,d_iname))
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.
55 * This hash-function tries to avoid losing too many bits of hash
56 * information, yet avoid using a prime hash-size or similar.
58 #define D_HASHBITS d_hash_shift
59 #define D_HASHMASK d_hash_mask
61 static unsigned int d_hash_mask __read_mostly;
62 static unsigned int d_hash_shift __read_mostly;
63 static struct hlist_head *dentry_hashtable __read_mostly;
65 /* Statistics gathering. */
66 struct dentry_stat_t dentry_stat = {
67 .age_limit = 45,
70 static struct percpu_counter nr_dentry __cacheline_aligned_in_smp;
71 static struct percpu_counter nr_dentry_unused __cacheline_aligned_in_smp;
73 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
74 int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
75 size_t *lenp, loff_t *ppos)
77 dentry_stat.nr_dentry = percpu_counter_sum_positive(&nr_dentry);
78 dentry_stat.nr_unused = percpu_counter_sum_positive(&nr_dentry_unused);
79 return proc_dointvec(table, write, buffer, lenp, ppos);
81 #endif
83 static void __d_free(struct rcu_head *head)
85 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
87 WARN_ON(!list_empty(&dentry->d_alias));
88 if (dname_external(dentry))
89 kfree(dentry->d_name.name);
90 kmem_cache_free(dentry_cache, dentry);
94 * no dcache_lock, please.
96 static void d_free(struct dentry *dentry)
98 percpu_counter_dec(&nr_dentry);
99 if (dentry->d_op && dentry->d_op->d_release)
100 dentry->d_op->d_release(dentry);
102 /* if dentry was never inserted into hash, immediate free is OK */
103 if (hlist_unhashed(&dentry->d_hash))
104 __d_free(&dentry->d_u.d_rcu);
105 else
106 call_rcu(&dentry->d_u.d_rcu, __d_free);
110 * Release the dentry's inode, using the filesystem
111 * d_iput() operation if defined.
113 static void dentry_iput(struct dentry * dentry)
114 __releases(dentry->d_lock)
115 __releases(dcache_lock)
117 struct inode *inode = dentry->d_inode;
118 if (inode) {
119 dentry->d_inode = NULL;
120 list_del_init(&dentry->d_alias);
121 spin_unlock(&dentry->d_lock);
122 spin_unlock(&dcache_lock);
123 if (!inode->i_nlink)
124 fsnotify_inoderemove(inode);
125 if (dentry->d_op && dentry->d_op->d_iput)
126 dentry->d_op->d_iput(dentry, inode);
127 else
128 iput(inode);
129 } else {
130 spin_unlock(&dentry->d_lock);
131 spin_unlock(&dcache_lock);
136 * dentry_lru_(add|del|move_tail) must be called with dcache_lock held.
138 static void dentry_lru_add(struct dentry *dentry)
140 if (list_empty(&dentry->d_lru)) {
141 list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
142 dentry->d_sb->s_nr_dentry_unused++;
143 percpu_counter_inc(&nr_dentry_unused);
147 static void dentry_lru_del(struct dentry *dentry)
149 if (!list_empty(&dentry->d_lru)) {
150 list_del_init(&dentry->d_lru);
151 dentry->d_sb->s_nr_dentry_unused--;
152 percpu_counter_dec(&nr_dentry_unused);
156 static void dentry_lru_move_tail(struct dentry *dentry)
158 if (list_empty(&dentry->d_lru)) {
159 list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
160 dentry->d_sb->s_nr_dentry_unused++;
161 percpu_counter_inc(&nr_dentry_unused);
162 } else {
163 list_move_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
168 * d_kill - kill dentry and return parent
169 * @dentry: dentry to kill
171 * The dentry must already be unhashed and removed from the LRU.
173 * If this is the root of the dentry tree, return NULL.
175 static struct dentry *d_kill(struct dentry *dentry)
176 __releases(dentry->d_lock)
177 __releases(dcache_lock)
179 struct dentry *parent;
181 list_del(&dentry->d_u.d_child);
182 /*drops the locks, at that point nobody can reach this dentry */
183 dentry_iput(dentry);
184 if (IS_ROOT(dentry))
185 parent = NULL;
186 else
187 parent = dentry->d_parent;
188 d_free(dentry);
189 return parent;
193 * This is dput
195 * This is complicated by the fact that we do not want to put
196 * dentries that are no longer on any hash chain on the unused
197 * list: we'd much rather just get rid of them immediately.
199 * However, that implies that we have to traverse the dentry
200 * tree upwards to the parents which might _also_ now be
201 * scheduled for deletion (it may have been only waiting for
202 * its last child to go away).
204 * This tail recursion is done by hand as we don't want to depend
205 * on the compiler to always get this right (gcc generally doesn't).
206 * Real recursion would eat up our stack space.
210 * dput - release a dentry
211 * @dentry: dentry to release
213 * Release a dentry. This will drop the usage count and if appropriate
214 * call the dentry unlink method as well as removing it from the queues and
215 * releasing its resources. If the parent dentries were scheduled for release
216 * they too may now get deleted.
218 * no dcache lock, please.
221 void dput(struct dentry *dentry)
223 if (!dentry)
224 return;
226 repeat:
227 if (atomic_read(&dentry->d_count) == 1)
228 might_sleep();
229 if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
230 return;
232 spin_lock(&dentry->d_lock);
233 if (atomic_read(&dentry->d_count)) {
234 spin_unlock(&dentry->d_lock);
235 spin_unlock(&dcache_lock);
236 return;
240 * AV: ->d_delete() is _NOT_ allowed to block now.
242 if (dentry->d_op && dentry->d_op->d_delete) {
243 if (dentry->d_op->d_delete(dentry))
244 goto unhash_it;
247 /* Unreachable? Get rid of it */
248 if (d_unhashed(dentry))
249 goto kill_it;
251 /* Otherwise leave it cached and ensure it's on the LRU */
252 dentry->d_flags |= DCACHE_REFERENCED;
253 dentry_lru_add(dentry);
255 spin_unlock(&dentry->d_lock);
256 spin_unlock(&dcache_lock);
257 return;
259 unhash_it:
260 __d_drop(dentry);
261 kill_it:
262 /* if dentry was on the d_lru list delete it from there */
263 dentry_lru_del(dentry);
264 dentry = d_kill(dentry);
265 if (dentry)
266 goto repeat;
268 EXPORT_SYMBOL(dput);
271 * d_invalidate - invalidate a dentry
272 * @dentry: dentry to invalidate
274 * Try to invalidate the dentry if it turns out to be
275 * possible. If there are other dentries that can be
276 * reached through this one we can't delete it and we
277 * return -EBUSY. On success we return 0.
279 * no dcache lock.
282 int d_invalidate(struct dentry * dentry)
285 * If it's already been dropped, return OK.
287 spin_lock(&dcache_lock);
288 if (d_unhashed(dentry)) {
289 spin_unlock(&dcache_lock);
290 return 0;
293 * Check whether to do a partial shrink_dcache
294 * to get rid of unused child entries.
296 if (!list_empty(&dentry->d_subdirs)) {
297 spin_unlock(&dcache_lock);
298 shrink_dcache_parent(dentry);
299 spin_lock(&dcache_lock);
303 * Somebody else still using it?
305 * If it's a directory, we can't drop it
306 * for fear of somebody re-populating it
307 * with children (even though dropping it
308 * would make it unreachable from the root,
309 * we might still populate it if it was a
310 * working directory or similar).
312 spin_lock(&dentry->d_lock);
313 if (atomic_read(&dentry->d_count) > 1) {
314 if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
315 spin_unlock(&dentry->d_lock);
316 spin_unlock(&dcache_lock);
317 return -EBUSY;
321 __d_drop(dentry);
322 spin_unlock(&dentry->d_lock);
323 spin_unlock(&dcache_lock);
324 return 0;
326 EXPORT_SYMBOL(d_invalidate);
328 /* This should be called _only_ with dcache_lock held */
329 static inline struct dentry * __dget_locked(struct dentry *dentry)
331 atomic_inc(&dentry->d_count);
332 dentry_lru_del(dentry);
333 return dentry;
336 struct dentry * dget_locked(struct dentry *dentry)
338 return __dget_locked(dentry);
340 EXPORT_SYMBOL(dget_locked);
343 * d_find_alias - grab a hashed alias of inode
344 * @inode: inode in question
345 * @want_discon: flag, used by d_splice_alias, to request
346 * that only a DISCONNECTED alias be returned.
348 * If inode has a hashed alias, or is a directory and has any alias,
349 * acquire the reference to alias and return it. Otherwise return NULL.
350 * Notice that if inode is a directory there can be only one alias and
351 * it can be unhashed only if it has no children, or if it is the root
352 * of a filesystem.
354 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
355 * any other hashed alias over that one unless @want_discon is set,
356 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
359 static struct dentry * __d_find_alias(struct inode *inode, int want_discon)
361 struct list_head *head, *next, *tmp;
362 struct dentry *alias, *discon_alias=NULL;
364 head = &inode->i_dentry;
365 next = inode->i_dentry.next;
366 while (next != head) {
367 tmp = next;
368 next = tmp->next;
369 prefetch(next);
370 alias = list_entry(tmp, struct dentry, d_alias);
371 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
372 if (IS_ROOT(alias) &&
373 (alias->d_flags & DCACHE_DISCONNECTED))
374 discon_alias = alias;
375 else if (!want_discon) {
376 __dget_locked(alias);
377 return alias;
381 if (discon_alias)
382 __dget_locked(discon_alias);
383 return discon_alias;
386 struct dentry * d_find_alias(struct inode *inode)
388 struct dentry *de = NULL;
390 if (!list_empty(&inode->i_dentry)) {
391 spin_lock(&dcache_lock);
392 de = __d_find_alias(inode, 0);
393 spin_unlock(&dcache_lock);
395 return de;
397 EXPORT_SYMBOL(d_find_alias);
400 * Try to kill dentries associated with this inode.
401 * WARNING: you must own a reference to inode.
403 void d_prune_aliases(struct inode *inode)
405 struct dentry *dentry;
406 restart:
407 spin_lock(&dcache_lock);
408 list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
409 spin_lock(&dentry->d_lock);
410 if (!atomic_read(&dentry->d_count)) {
411 __dget_locked(dentry);
412 __d_drop(dentry);
413 spin_unlock(&dentry->d_lock);
414 spin_unlock(&dcache_lock);
415 dput(dentry);
416 goto restart;
418 spin_unlock(&dentry->d_lock);
420 spin_unlock(&dcache_lock);
422 EXPORT_SYMBOL(d_prune_aliases);
425 * Throw away a dentry - free the inode, dput the parent. This requires that
426 * the LRU list has already been removed.
428 * Try to prune ancestors as well. This is necessary to prevent
429 * quadratic behavior of shrink_dcache_parent(), but is also expected
430 * to be beneficial in reducing dentry cache fragmentation.
432 static void prune_one_dentry(struct dentry * dentry)
433 __releases(dentry->d_lock)
434 __releases(dcache_lock)
435 __acquires(dcache_lock)
437 __d_drop(dentry);
438 dentry = d_kill(dentry);
441 * Prune ancestors. Locking is simpler than in dput(),
442 * because dcache_lock needs to be taken anyway.
444 spin_lock(&dcache_lock);
445 while (dentry) {
446 if (!atomic_dec_and_lock(&dentry->d_count, &dentry->d_lock))
447 return;
449 if (dentry->d_op && dentry->d_op->d_delete)
450 dentry->d_op->d_delete(dentry);
451 dentry_lru_del(dentry);
452 __d_drop(dentry);
453 dentry = d_kill(dentry);
454 spin_lock(&dcache_lock);
458 static void shrink_dentry_list(struct list_head *list)
460 struct dentry *dentry;
462 while (!list_empty(list)) {
463 dentry = list_entry(list->prev, struct dentry, d_lru);
464 dentry_lru_del(dentry);
467 * We found an inuse dentry which was not removed from
468 * the LRU because of laziness during lookup. Do not free
469 * it - just keep it off the LRU list.
471 spin_lock(&dentry->d_lock);
472 if (atomic_read(&dentry->d_count)) {
473 spin_unlock(&dentry->d_lock);
474 continue;
476 prune_one_dentry(dentry);
477 /* dentry->d_lock was dropped in prune_one_dentry() */
478 cond_resched_lock(&dcache_lock);
483 * __shrink_dcache_sb - shrink the dentry LRU on a given superblock
484 * @sb: superblock to shrink dentry LRU.
485 * @count: number of entries to prune
486 * @flags: flags to control the dentry processing
488 * If flags contains DCACHE_REFERENCED reference dentries will not be pruned.
490 static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
492 /* called from prune_dcache() and shrink_dcache_parent() */
493 struct dentry *dentry;
494 LIST_HEAD(referenced);
495 LIST_HEAD(tmp);
496 int cnt = *count;
498 spin_lock(&dcache_lock);
499 while (!list_empty(&sb->s_dentry_lru)) {
500 dentry = list_entry(sb->s_dentry_lru.prev,
501 struct dentry, d_lru);
502 BUG_ON(dentry->d_sb != sb);
505 * If we are honouring the DCACHE_REFERENCED flag and the
506 * dentry has this flag set, don't free it. Clear the flag
507 * and put it back on the LRU.
509 if (flags & DCACHE_REFERENCED) {
510 spin_lock(&dentry->d_lock);
511 if (dentry->d_flags & DCACHE_REFERENCED) {
512 dentry->d_flags &= ~DCACHE_REFERENCED;
513 list_move(&dentry->d_lru, &referenced);
514 spin_unlock(&dentry->d_lock);
515 cond_resched_lock(&dcache_lock);
516 continue;
518 spin_unlock(&dentry->d_lock);
521 list_move_tail(&dentry->d_lru, &tmp);
522 if (!--cnt)
523 break;
524 cond_resched_lock(&dcache_lock);
527 *count = cnt;
528 shrink_dentry_list(&tmp);
530 if (!list_empty(&referenced))
531 list_splice(&referenced, &sb->s_dentry_lru);
532 spin_unlock(&dcache_lock);
537 * prune_dcache - shrink the dcache
538 * @count: number of entries to try to free
540 * Shrink the dcache. This is done when we need more memory, or simply when we
541 * need to unmount something (at which point we need to unuse all dentries).
543 * This function may fail to free any resources if all the dentries are in use.
545 static void prune_dcache(int count)
547 struct super_block *sb, *p = NULL;
548 int w_count;
549 int unused = percpu_counter_sum_positive(&nr_dentry_unused);
550 int prune_ratio;
551 int pruned;
553 if (unused == 0 || count == 0)
554 return;
555 spin_lock(&dcache_lock);
556 if (count >= unused)
557 prune_ratio = 1;
558 else
559 prune_ratio = unused / count;
560 spin_lock(&sb_lock);
561 list_for_each_entry(sb, &super_blocks, s_list) {
562 if (list_empty(&sb->s_instances))
563 continue;
564 if (sb->s_nr_dentry_unused == 0)
565 continue;
566 sb->s_count++;
567 /* Now, we reclaim unused dentrins with fairness.
568 * We reclaim them same percentage from each superblock.
569 * We calculate number of dentries to scan on this sb
570 * as follows, but the implementation is arranged to avoid
571 * overflows:
572 * number of dentries to scan on this sb =
573 * count * (number of dentries on this sb /
574 * number of dentries in the machine)
576 spin_unlock(&sb_lock);
577 if (prune_ratio != 1)
578 w_count = (sb->s_nr_dentry_unused / prune_ratio) + 1;
579 else
580 w_count = sb->s_nr_dentry_unused;
581 pruned = w_count;
583 * We need to be sure this filesystem isn't being unmounted,
584 * otherwise we could race with generic_shutdown_super(), and
585 * end up holding a reference to an inode while the filesystem
586 * is unmounted. So we try to get s_umount, and make sure
587 * s_root isn't NULL.
589 if (down_read_trylock(&sb->s_umount)) {
590 if ((sb->s_root != NULL) &&
591 (!list_empty(&sb->s_dentry_lru))) {
592 spin_unlock(&dcache_lock);
593 __shrink_dcache_sb(sb, &w_count,
594 DCACHE_REFERENCED);
595 pruned -= w_count;
596 spin_lock(&dcache_lock);
598 up_read(&sb->s_umount);
600 spin_lock(&sb_lock);
601 if (p)
602 __put_super(p);
603 count -= pruned;
604 p = sb;
605 /* more work left to do? */
606 if (count <= 0)
607 break;
609 if (p)
610 __put_super(p);
611 spin_unlock(&sb_lock);
612 spin_unlock(&dcache_lock);
616 * shrink_dcache_sb - shrink dcache for a superblock
617 * @sb: superblock
619 * Shrink the dcache for the specified super block. This is used to free
620 * the dcache before unmounting a file system.
622 void shrink_dcache_sb(struct super_block *sb)
624 LIST_HEAD(tmp);
626 spin_lock(&dcache_lock);
627 while (!list_empty(&sb->s_dentry_lru)) {
628 list_splice_init(&sb->s_dentry_lru, &tmp);
629 shrink_dentry_list(&tmp);
631 spin_unlock(&dcache_lock);
633 EXPORT_SYMBOL(shrink_dcache_sb);
636 * destroy a single subtree of dentries for unmount
637 * - see the comments on shrink_dcache_for_umount() for a description of the
638 * locking
640 static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
642 struct dentry *parent;
643 unsigned detached = 0;
645 BUG_ON(!IS_ROOT(dentry));
647 /* detach this root from the system */
648 spin_lock(&dcache_lock);
649 dentry_lru_del(dentry);
650 __d_drop(dentry);
651 spin_unlock(&dcache_lock);
653 for (;;) {
654 /* descend to the first leaf in the current subtree */
655 while (!list_empty(&dentry->d_subdirs)) {
656 struct dentry *loop;
658 /* this is a branch with children - detach all of them
659 * from the system in one go */
660 spin_lock(&dcache_lock);
661 list_for_each_entry(loop, &dentry->d_subdirs,
662 d_u.d_child) {
663 dentry_lru_del(loop);
664 __d_drop(loop);
665 cond_resched_lock(&dcache_lock);
667 spin_unlock(&dcache_lock);
669 /* move to the first child */
670 dentry = list_entry(dentry->d_subdirs.next,
671 struct dentry, d_u.d_child);
674 /* consume the dentries from this leaf up through its parents
675 * until we find one with children or run out altogether */
676 do {
677 struct inode *inode;
679 if (atomic_read(&dentry->d_count) != 0) {
680 printk(KERN_ERR
681 "BUG: Dentry %p{i=%lx,n=%s}"
682 " still in use (%d)"
683 " [unmount of %s %s]\n",
684 dentry,
685 dentry->d_inode ?
686 dentry->d_inode->i_ino : 0UL,
687 dentry->d_name.name,
688 atomic_read(&dentry->d_count),
689 dentry->d_sb->s_type->name,
690 dentry->d_sb->s_id);
691 BUG();
694 if (IS_ROOT(dentry))
695 parent = NULL;
696 else {
697 parent = dentry->d_parent;
698 atomic_dec(&parent->d_count);
701 list_del(&dentry->d_u.d_child);
702 detached++;
704 inode = dentry->d_inode;
705 if (inode) {
706 dentry->d_inode = NULL;
707 list_del_init(&dentry->d_alias);
708 if (dentry->d_op && dentry->d_op->d_iput)
709 dentry->d_op->d_iput(dentry, inode);
710 else
711 iput(inode);
714 d_free(dentry);
716 /* finished when we fall off the top of the tree,
717 * otherwise we ascend to the parent and move to the
718 * next sibling if there is one */
719 if (!parent)
720 return;
721 dentry = parent;
722 } while (list_empty(&dentry->d_subdirs));
724 dentry = list_entry(dentry->d_subdirs.next,
725 struct dentry, d_u.d_child);
730 * destroy the dentries attached to a superblock on unmounting
731 * - we don't need to use dentry->d_lock, and only need dcache_lock when
732 * removing the dentry from the system lists and hashes because:
733 * - the superblock is detached from all mountings and open files, so the
734 * dentry trees will not be rearranged by the VFS
735 * - s_umount is write-locked, so the memory pressure shrinker will ignore
736 * any dentries belonging to this superblock that it comes across
737 * - the filesystem itself is no longer permitted to rearrange the dentries
738 * in this superblock
740 void shrink_dcache_for_umount(struct super_block *sb)
742 struct dentry *dentry;
744 if (down_read_trylock(&sb->s_umount))
745 BUG();
747 dentry = sb->s_root;
748 sb->s_root = NULL;
749 atomic_dec(&dentry->d_count);
750 shrink_dcache_for_umount_subtree(dentry);
752 while (!hlist_empty(&sb->s_anon)) {
753 dentry = hlist_entry(sb->s_anon.first, struct dentry, d_hash);
754 shrink_dcache_for_umount_subtree(dentry);
759 * Search for at least 1 mount point in the dentry's subdirs.
760 * We descend to the next level whenever the d_subdirs
761 * list is non-empty and continue searching.
765 * have_submounts - check for mounts over a dentry
766 * @parent: dentry to check.
768 * Return true if the parent or its subdirectories contain
769 * a mount point
772 int have_submounts(struct dentry *parent)
774 struct dentry *this_parent = parent;
775 struct list_head *next;
777 spin_lock(&dcache_lock);
778 if (d_mountpoint(parent))
779 goto positive;
780 repeat:
781 next = this_parent->d_subdirs.next;
782 resume:
783 while (next != &this_parent->d_subdirs) {
784 struct list_head *tmp = next;
785 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
786 next = tmp->next;
787 /* Have we found a mount point ? */
788 if (d_mountpoint(dentry))
789 goto positive;
790 if (!list_empty(&dentry->d_subdirs)) {
791 this_parent = dentry;
792 goto repeat;
796 * All done at this level ... ascend and resume the search.
798 if (this_parent != parent) {
799 next = this_parent->d_u.d_child.next;
800 this_parent = this_parent->d_parent;
801 goto resume;
803 spin_unlock(&dcache_lock);
804 return 0; /* No mount points found in tree */
805 positive:
806 spin_unlock(&dcache_lock);
807 return 1;
809 EXPORT_SYMBOL(have_submounts);
812 * Search the dentry child list for the specified parent,
813 * and move any unused dentries to the end of the unused
814 * list for prune_dcache(). We descend to the next level
815 * whenever the d_subdirs list is non-empty and continue
816 * searching.
818 * It returns zero iff there are no unused children,
819 * otherwise it returns the number of children moved to
820 * the end of the unused list. This may not be the total
821 * number of unused children, because select_parent can
822 * drop the lock and return early due to latency
823 * constraints.
825 static int select_parent(struct dentry * parent)
827 struct dentry *this_parent = parent;
828 struct list_head *next;
829 int found = 0;
831 spin_lock(&dcache_lock);
832 repeat:
833 next = this_parent->d_subdirs.next;
834 resume:
835 while (next != &this_parent->d_subdirs) {
836 struct list_head *tmp = next;
837 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
838 next = tmp->next;
841 * move only zero ref count dentries to the end
842 * of the unused list for prune_dcache
844 if (!atomic_read(&dentry->d_count)) {
845 dentry_lru_move_tail(dentry);
846 found++;
847 } else {
848 dentry_lru_del(dentry);
852 * We can return to the caller if we have found some (this
853 * ensures forward progress). We'll be coming back to find
854 * the rest.
856 if (found && need_resched())
857 goto out;
860 * Descend a level if the d_subdirs list is non-empty.
862 if (!list_empty(&dentry->d_subdirs)) {
863 this_parent = dentry;
864 goto repeat;
868 * All done at this level ... ascend and resume the search.
870 if (this_parent != parent) {
871 next = this_parent->d_u.d_child.next;
872 this_parent = this_parent->d_parent;
873 goto resume;
875 out:
876 spin_unlock(&dcache_lock);
877 return found;
881 * shrink_dcache_parent - prune dcache
882 * @parent: parent of entries to prune
884 * Prune the dcache to remove unused children of the parent dentry.
887 void shrink_dcache_parent(struct dentry * parent)
889 struct super_block *sb = parent->d_sb;
890 int found;
892 while ((found = select_parent(parent)) != 0)
893 __shrink_dcache_sb(sb, &found, 0);
895 EXPORT_SYMBOL(shrink_dcache_parent);
898 * Scan `nr' dentries and return the number which remain.
900 * We need to avoid reentering the filesystem if the caller is performing a
901 * GFP_NOFS allocation attempt. One example deadlock is:
903 * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
904 * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
905 * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
907 * In this case we return -1 to tell the caller that we baled.
909 static int shrink_dcache_memory(struct shrinker *shrink, int nr, gfp_t gfp_mask)
911 int nr_unused;
913 if (nr) {
914 if (!(gfp_mask & __GFP_FS))
915 return -1;
916 prune_dcache(nr);
919 nr_unused = percpu_counter_sum_positive(&nr_dentry_unused);
920 return (nr_unused / 100) * sysctl_vfs_cache_pressure;
923 static struct shrinker dcache_shrinker = {
924 .shrink = shrink_dcache_memory,
925 .seeks = DEFAULT_SEEKS,
929 * d_alloc - allocate a dcache entry
930 * @parent: parent of entry to allocate
931 * @name: qstr of the name
933 * Allocates a dentry. It returns %NULL if there is insufficient memory
934 * available. On a success the dentry is returned. The name passed in is
935 * copied and the copy passed in may be reused after this call.
938 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
940 struct dentry *dentry;
941 char *dname;
943 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
944 if (!dentry)
945 return NULL;
947 if (name->len > DNAME_INLINE_LEN-1) {
948 dname = kmalloc(name->len + 1, GFP_KERNEL);
949 if (!dname) {
950 kmem_cache_free(dentry_cache, dentry);
951 return NULL;
953 } else {
954 dname = dentry->d_iname;
956 dentry->d_name.name = dname;
958 dentry->d_name.len = name->len;
959 dentry->d_name.hash = name->hash;
960 memcpy(dname, name->name, name->len);
961 dname[name->len] = 0;
963 atomic_set(&dentry->d_count, 1);
964 dentry->d_flags = DCACHE_UNHASHED;
965 spin_lock_init(&dentry->d_lock);
966 dentry->d_inode = NULL;
967 dentry->d_parent = NULL;
968 dentry->d_sb = NULL;
969 dentry->d_op = NULL;
970 dentry->d_fsdata = NULL;
971 dentry->d_mounted = 0;
972 INIT_HLIST_NODE(&dentry->d_hash);
973 INIT_LIST_HEAD(&dentry->d_lru);
974 INIT_LIST_HEAD(&dentry->d_subdirs);
975 INIT_LIST_HEAD(&dentry->d_alias);
977 if (parent) {
978 dentry->d_parent = dget(parent);
979 dentry->d_sb = parent->d_sb;
980 } else {
981 INIT_LIST_HEAD(&dentry->d_u.d_child);
984 spin_lock(&dcache_lock);
985 if (parent)
986 list_add(&dentry->d_u.d_child, &parent->d_subdirs);
987 spin_unlock(&dcache_lock);
989 percpu_counter_inc(&nr_dentry);
991 return dentry;
993 EXPORT_SYMBOL(d_alloc);
995 struct dentry *d_alloc_name(struct dentry *parent, const char *name)
997 struct qstr q;
999 q.name = name;
1000 q.len = strlen(name);
1001 q.hash = full_name_hash(q.name, q.len);
1002 return d_alloc(parent, &q);
1004 EXPORT_SYMBOL(d_alloc_name);
1006 /* the caller must hold dcache_lock */
1007 static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1009 if (inode)
1010 list_add(&dentry->d_alias, &inode->i_dentry);
1011 dentry->d_inode = inode;
1012 fsnotify_d_instantiate(dentry, inode);
1016 * d_instantiate - fill in inode information for a dentry
1017 * @entry: dentry to complete
1018 * @inode: inode to attach to this dentry
1020 * Fill in inode information in the entry.
1022 * This turns negative dentries into productive full members
1023 * of society.
1025 * NOTE! This assumes that the inode count has been incremented
1026 * (or otherwise set) by the caller to indicate that it is now
1027 * in use by the dcache.
1030 void d_instantiate(struct dentry *entry, struct inode * inode)
1032 BUG_ON(!list_empty(&entry->d_alias));
1033 spin_lock(&dcache_lock);
1034 __d_instantiate(entry, inode);
1035 spin_unlock(&dcache_lock);
1036 security_d_instantiate(entry, inode);
1038 EXPORT_SYMBOL(d_instantiate);
1041 * d_instantiate_unique - instantiate a non-aliased dentry
1042 * @entry: dentry to instantiate
1043 * @inode: inode to attach to this dentry
1045 * Fill in inode information in the entry. On success, it returns NULL.
1046 * If an unhashed alias of "entry" already exists, then we return the
1047 * aliased dentry instead and drop one reference to inode.
1049 * Note that in order to avoid conflicts with rename() etc, the caller
1050 * had better be holding the parent directory semaphore.
1052 * This also assumes that the inode count has been incremented
1053 * (or otherwise set) by the caller to indicate that it is now
1054 * in use by the dcache.
1056 static struct dentry *__d_instantiate_unique(struct dentry *entry,
1057 struct inode *inode)
1059 struct dentry *alias;
1060 int len = entry->d_name.len;
1061 const char *name = entry->d_name.name;
1062 unsigned int hash = entry->d_name.hash;
1064 if (!inode) {
1065 __d_instantiate(entry, NULL);
1066 return NULL;
1069 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
1070 struct qstr *qstr = &alias->d_name;
1072 if (qstr->hash != hash)
1073 continue;
1074 if (alias->d_parent != entry->d_parent)
1075 continue;
1076 if (qstr->len != len)
1077 continue;
1078 if (memcmp(qstr->name, name, len))
1079 continue;
1080 dget_locked(alias);
1081 return alias;
1084 __d_instantiate(entry, inode);
1085 return NULL;
1088 struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
1090 struct dentry *result;
1092 BUG_ON(!list_empty(&entry->d_alias));
1094 spin_lock(&dcache_lock);
1095 result = __d_instantiate_unique(entry, inode);
1096 spin_unlock(&dcache_lock);
1098 if (!result) {
1099 security_d_instantiate(entry, inode);
1100 return NULL;
1103 BUG_ON(!d_unhashed(result));
1104 iput(inode);
1105 return result;
1108 EXPORT_SYMBOL(d_instantiate_unique);
1111 * d_alloc_root - allocate root dentry
1112 * @root_inode: inode to allocate the root for
1114 * Allocate a root ("/") dentry for the inode given. The inode is
1115 * instantiated and returned. %NULL is returned if there is insufficient
1116 * memory or the inode passed is %NULL.
1119 struct dentry * d_alloc_root(struct inode * root_inode)
1121 struct dentry *res = NULL;
1123 if (root_inode) {
1124 static const struct qstr name = { .name = "/", .len = 1 };
1126 res = d_alloc(NULL, &name);
1127 if (res) {
1128 res->d_sb = root_inode->i_sb;
1129 res->d_parent = res;
1130 d_instantiate(res, root_inode);
1133 return res;
1135 EXPORT_SYMBOL(d_alloc_root);
1137 static inline struct hlist_head *d_hash(struct dentry *parent,
1138 unsigned long hash)
1140 hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
1141 hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
1142 return dentry_hashtable + (hash & D_HASHMASK);
1146 * d_obtain_alias - find or allocate a dentry for a given inode
1147 * @inode: inode to allocate the dentry for
1149 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1150 * similar open by handle operations. The returned dentry may be anonymous,
1151 * or may have a full name (if the inode was already in the cache).
1153 * When called on a directory inode, we must ensure that the inode only ever
1154 * has one dentry. If a dentry is found, that is returned instead of
1155 * allocating a new one.
1157 * On successful return, the reference to the inode has been transferred
1158 * to the dentry. In case of an error the reference on the inode is released.
1159 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1160 * be passed in and will be the error will be propagate to the return value,
1161 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1163 struct dentry *d_obtain_alias(struct inode *inode)
1165 static const struct qstr anonstring = { .name = "" };
1166 struct dentry *tmp;
1167 struct dentry *res;
1169 if (!inode)
1170 return ERR_PTR(-ESTALE);
1171 if (IS_ERR(inode))
1172 return ERR_CAST(inode);
1174 res = d_find_alias(inode);
1175 if (res)
1176 goto out_iput;
1178 tmp = d_alloc(NULL, &anonstring);
1179 if (!tmp) {
1180 res = ERR_PTR(-ENOMEM);
1181 goto out_iput;
1183 tmp->d_parent = tmp; /* make sure dput doesn't croak */
1185 spin_lock(&dcache_lock);
1186 res = __d_find_alias(inode, 0);
1187 if (res) {
1188 spin_unlock(&dcache_lock);
1189 dput(tmp);
1190 goto out_iput;
1193 /* attach a disconnected dentry */
1194 spin_lock(&tmp->d_lock);
1195 tmp->d_sb = inode->i_sb;
1196 tmp->d_inode = inode;
1197 tmp->d_flags |= DCACHE_DISCONNECTED;
1198 tmp->d_flags &= ~DCACHE_UNHASHED;
1199 list_add(&tmp->d_alias, &inode->i_dentry);
1200 hlist_add_head(&tmp->d_hash, &inode->i_sb->s_anon);
1201 spin_unlock(&tmp->d_lock);
1203 spin_unlock(&dcache_lock);
1204 return tmp;
1206 out_iput:
1207 iput(inode);
1208 return res;
1210 EXPORT_SYMBOL(d_obtain_alias);
1213 * d_splice_alias - splice a disconnected dentry into the tree if one exists
1214 * @inode: the inode which may have a disconnected dentry
1215 * @dentry: a negative dentry which we want to point to the inode.
1217 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1218 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1219 * and return it, else simply d_add the inode to the dentry and return NULL.
1221 * This is needed in the lookup routine of any filesystem that is exportable
1222 * (via knfsd) so that we can build dcache paths to directories effectively.
1224 * If a dentry was found and moved, then it is returned. Otherwise NULL
1225 * is returned. This matches the expected return value of ->lookup.
1228 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
1230 struct dentry *new = NULL;
1232 if (inode && S_ISDIR(inode->i_mode)) {
1233 spin_lock(&dcache_lock);
1234 new = __d_find_alias(inode, 1);
1235 if (new) {
1236 BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
1237 spin_unlock(&dcache_lock);
1238 security_d_instantiate(new, inode);
1239 d_move(new, dentry);
1240 iput(inode);
1241 } else {
1242 /* already taking dcache_lock, so d_add() by hand */
1243 __d_instantiate(dentry, inode);
1244 spin_unlock(&dcache_lock);
1245 security_d_instantiate(dentry, inode);
1246 d_rehash(dentry);
1248 } else
1249 d_add(dentry, inode);
1250 return new;
1252 EXPORT_SYMBOL(d_splice_alias);
1255 * d_add_ci - lookup or allocate new dentry with case-exact name
1256 * @inode: the inode case-insensitive lookup has found
1257 * @dentry: the negative dentry that was passed to the parent's lookup func
1258 * @name: the case-exact name to be associated with the returned dentry
1260 * This is to avoid filling the dcache with case-insensitive names to the
1261 * same inode, only the actual correct case is stored in the dcache for
1262 * case-insensitive filesystems.
1264 * For a case-insensitive lookup match and if the the case-exact dentry
1265 * already exists in in the dcache, use it and return it.
1267 * If no entry exists with the exact case name, allocate new dentry with
1268 * the exact case, and return the spliced entry.
1270 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
1271 struct qstr *name)
1273 int error;
1274 struct dentry *found;
1275 struct dentry *new;
1278 * First check if a dentry matching the name already exists,
1279 * if not go ahead and create it now.
1281 found = d_hash_and_lookup(dentry->d_parent, name);
1282 if (!found) {
1283 new = d_alloc(dentry->d_parent, name);
1284 if (!new) {
1285 error = -ENOMEM;
1286 goto err_out;
1289 found = d_splice_alias(inode, new);
1290 if (found) {
1291 dput(new);
1292 return found;
1294 return new;
1298 * If a matching dentry exists, and it's not negative use it.
1300 * Decrement the reference count to balance the iget() done
1301 * earlier on.
1303 if (found->d_inode) {
1304 if (unlikely(found->d_inode != inode)) {
1305 /* This can't happen because bad inodes are unhashed. */
1306 BUG_ON(!is_bad_inode(inode));
1307 BUG_ON(!is_bad_inode(found->d_inode));
1309 iput(inode);
1310 return found;
1314 * Negative dentry: instantiate it unless the inode is a directory and
1315 * already has a dentry.
1317 spin_lock(&dcache_lock);
1318 if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) {
1319 __d_instantiate(found, inode);
1320 spin_unlock(&dcache_lock);
1321 security_d_instantiate(found, inode);
1322 return found;
1326 * In case a directory already has a (disconnected) entry grab a
1327 * reference to it, move it in place and use it.
1329 new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
1330 dget_locked(new);
1331 spin_unlock(&dcache_lock);
1332 security_d_instantiate(found, inode);
1333 d_move(new, found);
1334 iput(inode);
1335 dput(found);
1336 return new;
1338 err_out:
1339 iput(inode);
1340 return ERR_PTR(error);
1342 EXPORT_SYMBOL(d_add_ci);
1345 * d_lookup - search for a dentry
1346 * @parent: parent dentry
1347 * @name: qstr of name we wish to find
1348 * Returns: dentry, or NULL
1350 * d_lookup searches the children of the parent dentry for the name in
1351 * question. If the dentry is found its reference count is incremented and the
1352 * dentry is returned. The caller must use dput to free the entry when it has
1353 * finished using it. %NULL is returned if the dentry does not exist.
1355 struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
1357 struct dentry * dentry = NULL;
1358 unsigned long seq;
1360 do {
1361 seq = read_seqbegin(&rename_lock);
1362 dentry = __d_lookup(parent, name);
1363 if (dentry)
1364 break;
1365 } while (read_seqretry(&rename_lock, seq));
1366 return dentry;
1368 EXPORT_SYMBOL(d_lookup);
1371 * __d_lookup - search for a dentry (racy)
1372 * @parent: parent dentry
1373 * @name: qstr of name we wish to find
1374 * Returns: dentry, or NULL
1376 * __d_lookup is like d_lookup, however it may (rarely) return a
1377 * false-negative result due to unrelated rename activity.
1379 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
1380 * however it must be used carefully, eg. with a following d_lookup in
1381 * the case of failure.
1383 * __d_lookup callers must be commented.
1385 struct dentry * __d_lookup(struct dentry * parent, struct qstr * name)
1387 unsigned int len = name->len;
1388 unsigned int hash = name->hash;
1389 const unsigned char *str = name->name;
1390 struct hlist_head *head = d_hash(parent,hash);
1391 struct dentry *found = NULL;
1392 struct hlist_node *node;
1393 struct dentry *dentry;
1396 * The hash list is protected using RCU.
1398 * Take d_lock when comparing a candidate dentry, to avoid races
1399 * with d_move().
1401 * It is possible that concurrent renames can mess up our list
1402 * walk here and result in missing our dentry, resulting in the
1403 * false-negative result. d_lookup() protects against concurrent
1404 * renames using rename_lock seqlock.
1406 * See Documentation/vfs/dcache-locking.txt for more details.
1408 rcu_read_lock();
1410 hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
1411 struct qstr *qstr;
1413 if (dentry->d_name.hash != hash)
1414 continue;
1415 if (dentry->d_parent != parent)
1416 continue;
1418 spin_lock(&dentry->d_lock);
1421 * Recheck the dentry after taking the lock - d_move may have
1422 * changed things. Don't bother checking the hash because
1423 * we're about to compare the whole name anyway.
1425 if (dentry->d_parent != parent)
1426 goto next;
1428 /* non-existing due to RCU? */
1429 if (d_unhashed(dentry))
1430 goto next;
1433 * It is safe to compare names since d_move() cannot
1434 * change the qstr (protected by d_lock).
1436 qstr = &dentry->d_name;
1437 if (parent->d_op && parent->d_op->d_compare) {
1438 if (parent->d_op->d_compare(parent, qstr, name))
1439 goto next;
1440 } else {
1441 if (qstr->len != len)
1442 goto next;
1443 if (memcmp(qstr->name, str, len))
1444 goto next;
1447 atomic_inc(&dentry->d_count);
1448 found = dentry;
1449 spin_unlock(&dentry->d_lock);
1450 break;
1451 next:
1452 spin_unlock(&dentry->d_lock);
1454 rcu_read_unlock();
1456 return found;
1460 * d_hash_and_lookup - hash the qstr then search for a dentry
1461 * @dir: Directory to search in
1462 * @name: qstr of name we wish to find
1464 * On hash failure or on lookup failure NULL is returned.
1466 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
1468 struct dentry *dentry = NULL;
1471 * Check for a fs-specific hash function. Note that we must
1472 * calculate the standard hash first, as the d_op->d_hash()
1473 * routine may choose to leave the hash value unchanged.
1475 name->hash = full_name_hash(name->name, name->len);
1476 if (dir->d_op && dir->d_op->d_hash) {
1477 if (dir->d_op->d_hash(dir, name) < 0)
1478 goto out;
1480 dentry = d_lookup(dir, name);
1481 out:
1482 return dentry;
1486 * d_validate - verify dentry provided from insecure source
1487 * @dentry: The dentry alleged to be valid child of @dparent
1488 * @dparent: The parent dentry (known to be valid)
1490 * An insecure source has sent us a dentry, here we verify it and dget() it.
1491 * This is used by ncpfs in its readdir implementation.
1492 * Zero is returned in the dentry is invalid.
1494 int d_validate(struct dentry *dentry, struct dentry *parent)
1496 struct hlist_head *head = d_hash(parent, dentry->d_name.hash);
1497 struct hlist_node *node;
1498 struct dentry *d;
1500 /* Check whether the ptr might be valid at all.. */
1501 if (!kmem_ptr_validate(dentry_cache, dentry))
1502 return 0;
1503 if (dentry->d_parent != parent)
1504 return 0;
1506 rcu_read_lock();
1507 hlist_for_each_entry_rcu(d, node, head, d_hash) {
1508 if (d == dentry) {
1509 dget(dentry);
1510 return 1;
1513 rcu_read_unlock();
1514 return 0;
1516 EXPORT_SYMBOL(d_validate);
1519 * When a file is deleted, we have two options:
1520 * - turn this dentry into a negative dentry
1521 * - unhash this dentry and free it.
1523 * Usually, we want to just turn this into
1524 * a negative dentry, but if anybody else is
1525 * currently using the dentry or the inode
1526 * we can't do that and we fall back on removing
1527 * it from the hash queues and waiting for
1528 * it to be deleted later when it has no users
1532 * d_delete - delete a dentry
1533 * @dentry: The dentry to delete
1535 * Turn the dentry into a negative dentry if possible, otherwise
1536 * remove it from the hash queues so it can be deleted later
1539 void d_delete(struct dentry * dentry)
1541 int isdir = 0;
1543 * Are we the only user?
1545 spin_lock(&dcache_lock);
1546 spin_lock(&dentry->d_lock);
1547 isdir = S_ISDIR(dentry->d_inode->i_mode);
1548 if (atomic_read(&dentry->d_count) == 1) {
1549 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
1550 dentry_iput(dentry);
1551 fsnotify_nameremove(dentry, isdir);
1552 return;
1555 if (!d_unhashed(dentry))
1556 __d_drop(dentry);
1558 spin_unlock(&dentry->d_lock);
1559 spin_unlock(&dcache_lock);
1561 fsnotify_nameremove(dentry, isdir);
1563 EXPORT_SYMBOL(d_delete);
1565 static void __d_rehash(struct dentry * entry, struct hlist_head *list)
1568 entry->d_flags &= ~DCACHE_UNHASHED;
1569 hlist_add_head_rcu(&entry->d_hash, list);
1572 static void _d_rehash(struct dentry * entry)
1574 __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
1578 * d_rehash - add an entry back to the hash
1579 * @entry: dentry to add to the hash
1581 * Adds a dentry to the hash according to its name.
1584 void d_rehash(struct dentry * entry)
1586 spin_lock(&dcache_lock);
1587 spin_lock(&entry->d_lock);
1588 _d_rehash(entry);
1589 spin_unlock(&entry->d_lock);
1590 spin_unlock(&dcache_lock);
1592 EXPORT_SYMBOL(d_rehash);
1595 * When switching names, the actual string doesn't strictly have to
1596 * be preserved in the target - because we're dropping the target
1597 * anyway. As such, we can just do a simple memcpy() to copy over
1598 * the new name before we switch.
1600 * Note that we have to be a lot more careful about getting the hash
1601 * switched - we have to switch the hash value properly even if it
1602 * then no longer matches the actual (corrupted) string of the target.
1603 * The hash value has to match the hash queue that the dentry is on..
1605 static void switch_names(struct dentry *dentry, struct dentry *target)
1607 if (dname_external(target)) {
1608 if (dname_external(dentry)) {
1610 * Both external: swap the pointers
1612 swap(target->d_name.name, dentry->d_name.name);
1613 } else {
1615 * dentry:internal, target:external. Steal target's
1616 * storage and make target internal.
1618 memcpy(target->d_iname, dentry->d_name.name,
1619 dentry->d_name.len + 1);
1620 dentry->d_name.name = target->d_name.name;
1621 target->d_name.name = target->d_iname;
1623 } else {
1624 if (dname_external(dentry)) {
1626 * dentry:external, target:internal. Give dentry's
1627 * storage to target and make dentry internal
1629 memcpy(dentry->d_iname, target->d_name.name,
1630 target->d_name.len + 1);
1631 target->d_name.name = dentry->d_name.name;
1632 dentry->d_name.name = dentry->d_iname;
1633 } else {
1635 * Both are internal. Just copy target to dentry
1637 memcpy(dentry->d_iname, target->d_name.name,
1638 target->d_name.len + 1);
1639 dentry->d_name.len = target->d_name.len;
1640 return;
1643 swap(dentry->d_name.len, target->d_name.len);
1647 * We cannibalize "target" when moving dentry on top of it,
1648 * because it's going to be thrown away anyway. We could be more
1649 * polite about it, though.
1651 * This forceful removal will result in ugly /proc output if
1652 * somebody holds a file open that got deleted due to a rename.
1653 * We could be nicer about the deleted file, and let it show
1654 * up under the name it had before it was deleted rather than
1655 * under the original name of the file that was moved on top of it.
1659 * d_move_locked - move a dentry
1660 * @dentry: entry to move
1661 * @target: new dentry
1663 * Update the dcache to reflect the move of a file name. Negative
1664 * dcache entries should not be moved in this way.
1666 static void d_move_locked(struct dentry * dentry, struct dentry * target)
1668 struct hlist_head *list;
1670 if (!dentry->d_inode)
1671 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
1673 write_seqlock(&rename_lock);
1675 * XXXX: do we really need to take target->d_lock?
1677 if (target < dentry) {
1678 spin_lock(&target->d_lock);
1679 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1680 } else {
1681 spin_lock(&dentry->d_lock);
1682 spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
1685 /* Move the dentry to the target hash queue, if on different bucket */
1686 if (d_unhashed(dentry))
1687 goto already_unhashed;
1689 hlist_del_rcu(&dentry->d_hash);
1691 already_unhashed:
1692 list = d_hash(target->d_parent, target->d_name.hash);
1693 __d_rehash(dentry, list);
1695 /* Unhash the target: dput() will then get rid of it */
1696 __d_drop(target);
1698 list_del(&dentry->d_u.d_child);
1699 list_del(&target->d_u.d_child);
1701 /* Switch the names.. */
1702 switch_names(dentry, target);
1703 swap(dentry->d_name.hash, target->d_name.hash);
1705 /* ... and switch the parents */
1706 if (IS_ROOT(dentry)) {
1707 dentry->d_parent = target->d_parent;
1708 target->d_parent = target;
1709 INIT_LIST_HEAD(&target->d_u.d_child);
1710 } else {
1711 swap(dentry->d_parent, target->d_parent);
1713 /* And add them back to the (new) parent lists */
1714 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
1717 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
1718 spin_unlock(&target->d_lock);
1719 fsnotify_d_move(dentry);
1720 spin_unlock(&dentry->d_lock);
1721 write_sequnlock(&rename_lock);
1725 * d_move - move a dentry
1726 * @dentry: entry to move
1727 * @target: new dentry
1729 * Update the dcache to reflect the move of a file name. Negative
1730 * dcache entries should not be moved in this way.
1733 void d_move(struct dentry * dentry, struct dentry * target)
1735 spin_lock(&dcache_lock);
1736 d_move_locked(dentry, target);
1737 spin_unlock(&dcache_lock);
1739 EXPORT_SYMBOL(d_move);
1742 * d_ancestor - search for an ancestor
1743 * @p1: ancestor dentry
1744 * @p2: child dentry
1746 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
1747 * an ancestor of p2, else NULL.
1749 struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
1751 struct dentry *p;
1753 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
1754 if (p->d_parent == p1)
1755 return p;
1757 return NULL;
1761 * This helper attempts to cope with remotely renamed directories
1763 * It assumes that the caller is already holding
1764 * dentry->d_parent->d_inode->i_mutex and the dcache_lock
1766 * Note: If ever the locking in lock_rename() changes, then please
1767 * remember to update this too...
1769 static struct dentry *__d_unalias(struct dentry *dentry, struct dentry *alias)
1770 __releases(dcache_lock)
1772 struct mutex *m1 = NULL, *m2 = NULL;
1773 struct dentry *ret;
1775 /* If alias and dentry share a parent, then no extra locks required */
1776 if (alias->d_parent == dentry->d_parent)
1777 goto out_unalias;
1779 /* Check for loops */
1780 ret = ERR_PTR(-ELOOP);
1781 if (d_ancestor(alias, dentry))
1782 goto out_err;
1784 /* See lock_rename() */
1785 ret = ERR_PTR(-EBUSY);
1786 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
1787 goto out_err;
1788 m1 = &dentry->d_sb->s_vfs_rename_mutex;
1789 if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
1790 goto out_err;
1791 m2 = &alias->d_parent->d_inode->i_mutex;
1792 out_unalias:
1793 d_move_locked(alias, dentry);
1794 ret = alias;
1795 out_err:
1796 spin_unlock(&dcache_lock);
1797 if (m2)
1798 mutex_unlock(m2);
1799 if (m1)
1800 mutex_unlock(m1);
1801 return ret;
1805 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
1806 * named dentry in place of the dentry to be replaced.
1808 static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
1810 struct dentry *dparent, *aparent;
1812 switch_names(dentry, anon);
1813 swap(dentry->d_name.hash, anon->d_name.hash);
1815 dparent = dentry->d_parent;
1816 aparent = anon->d_parent;
1818 dentry->d_parent = (aparent == anon) ? dentry : aparent;
1819 list_del(&dentry->d_u.d_child);
1820 if (!IS_ROOT(dentry))
1821 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
1822 else
1823 INIT_LIST_HEAD(&dentry->d_u.d_child);
1825 anon->d_parent = (dparent == dentry) ? anon : dparent;
1826 list_del(&anon->d_u.d_child);
1827 if (!IS_ROOT(anon))
1828 list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
1829 else
1830 INIT_LIST_HEAD(&anon->d_u.d_child);
1832 anon->d_flags &= ~DCACHE_DISCONNECTED;
1836 * d_materialise_unique - introduce an inode into the tree
1837 * @dentry: candidate dentry
1838 * @inode: inode to bind to the dentry, to which aliases may be attached
1840 * Introduces an dentry into the tree, substituting an extant disconnected
1841 * root directory alias in its place if there is one
1843 struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
1845 struct dentry *actual;
1847 BUG_ON(!d_unhashed(dentry));
1849 spin_lock(&dcache_lock);
1851 if (!inode) {
1852 actual = dentry;
1853 __d_instantiate(dentry, NULL);
1854 goto found_lock;
1857 if (S_ISDIR(inode->i_mode)) {
1858 struct dentry *alias;
1860 /* Does an aliased dentry already exist? */
1861 alias = __d_find_alias(inode, 0);
1862 if (alias) {
1863 actual = alias;
1864 /* Is this an anonymous mountpoint that we could splice
1865 * into our tree? */
1866 if (IS_ROOT(alias)) {
1867 spin_lock(&alias->d_lock);
1868 __d_materialise_dentry(dentry, alias);
1869 __d_drop(alias);
1870 goto found;
1872 /* Nope, but we must(!) avoid directory aliasing */
1873 actual = __d_unalias(dentry, alias);
1874 if (IS_ERR(actual))
1875 dput(alias);
1876 goto out_nolock;
1880 /* Add a unique reference */
1881 actual = __d_instantiate_unique(dentry, inode);
1882 if (!actual)
1883 actual = dentry;
1884 else if (unlikely(!d_unhashed(actual)))
1885 goto shouldnt_be_hashed;
1887 found_lock:
1888 spin_lock(&actual->d_lock);
1889 found:
1890 _d_rehash(actual);
1891 spin_unlock(&actual->d_lock);
1892 spin_unlock(&dcache_lock);
1893 out_nolock:
1894 if (actual == dentry) {
1895 security_d_instantiate(dentry, inode);
1896 return NULL;
1899 iput(inode);
1900 return actual;
1902 shouldnt_be_hashed:
1903 spin_unlock(&dcache_lock);
1904 BUG();
1906 EXPORT_SYMBOL_GPL(d_materialise_unique);
1908 static int prepend(char **buffer, int *buflen, const char *str, int namelen)
1910 *buflen -= namelen;
1911 if (*buflen < 0)
1912 return -ENAMETOOLONG;
1913 *buffer -= namelen;
1914 memcpy(*buffer, str, namelen);
1915 return 0;
1918 static int prepend_name(char **buffer, int *buflen, struct qstr *name)
1920 return prepend(buffer, buflen, name->name, name->len);
1924 * Prepend path string to a buffer
1926 * @path: the dentry/vfsmount to report
1927 * @root: root vfsmnt/dentry (may be modified by this function)
1928 * @buffer: pointer to the end of the buffer
1929 * @buflen: pointer to buffer length
1931 * Caller holds the dcache_lock.
1933 * If path is not reachable from the supplied root, then the value of
1934 * root is changed (without modifying refcounts).
1936 static int prepend_path(const struct path *path, struct path *root,
1937 char **buffer, int *buflen)
1939 struct dentry *dentry = path->dentry;
1940 struct vfsmount *vfsmnt = path->mnt;
1941 bool slash = false;
1942 int error = 0;
1944 br_read_lock(vfsmount_lock);
1945 while (dentry != root->dentry || vfsmnt != root->mnt) {
1946 struct dentry * parent;
1948 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
1949 /* Global root? */
1950 if (vfsmnt->mnt_parent == vfsmnt) {
1951 goto global_root;
1953 dentry = vfsmnt->mnt_mountpoint;
1954 vfsmnt = vfsmnt->mnt_parent;
1955 continue;
1957 parent = dentry->d_parent;
1958 prefetch(parent);
1959 error = prepend_name(buffer, buflen, &dentry->d_name);
1960 if (!error)
1961 error = prepend(buffer, buflen, "/", 1);
1962 if (error)
1963 break;
1965 slash = true;
1966 dentry = parent;
1969 out:
1970 if (!error && !slash)
1971 error = prepend(buffer, buflen, "/", 1);
1973 br_read_unlock(vfsmount_lock);
1974 return error;
1976 global_root:
1978 * Filesystems needing to implement special "root names"
1979 * should do so with ->d_dname()
1981 if (IS_ROOT(dentry) &&
1982 (dentry->d_name.len != 1 || dentry->d_name.name[0] != '/')) {
1983 WARN(1, "Root dentry has weird name <%.*s>\n",
1984 (int) dentry->d_name.len, dentry->d_name.name);
1986 root->mnt = vfsmnt;
1987 root->dentry = dentry;
1988 goto out;
1992 * __d_path - return the path of a dentry
1993 * @path: the dentry/vfsmount to report
1994 * @root: root vfsmnt/dentry (may be modified by this function)
1995 * @buf: buffer to return value in
1996 * @buflen: buffer length
1998 * Convert a dentry into an ASCII path name.
2000 * Returns a pointer into the buffer or an error code if the
2001 * path was too long.
2003 * "buflen" should be positive.
2005 * If path is not reachable from the supplied root, then the value of
2006 * root is changed (without modifying refcounts).
2008 char *__d_path(const struct path *path, struct path *root,
2009 char *buf, int buflen)
2011 char *res = buf + buflen;
2012 int error;
2014 prepend(&res, &buflen, "\0", 1);
2015 spin_lock(&dcache_lock);
2016 error = prepend_path(path, root, &res, &buflen);
2017 spin_unlock(&dcache_lock);
2019 if (error)
2020 return ERR_PTR(error);
2021 return res;
2025 * same as __d_path but appends "(deleted)" for unlinked files.
2027 static int path_with_deleted(const struct path *path, struct path *root,
2028 char **buf, int *buflen)
2030 prepend(buf, buflen, "\0", 1);
2031 if (d_unlinked(path->dentry)) {
2032 int error = prepend(buf, buflen, " (deleted)", 10);
2033 if (error)
2034 return error;
2037 return prepend_path(path, root, buf, buflen);
2040 static int prepend_unreachable(char **buffer, int *buflen)
2042 return prepend(buffer, buflen, "(unreachable)", 13);
2046 * d_path - return the path of a dentry
2047 * @path: path to report
2048 * @buf: buffer to return value in
2049 * @buflen: buffer length
2051 * Convert a dentry into an ASCII path name. If the entry has been deleted
2052 * the string " (deleted)" is appended. Note that this is ambiguous.
2054 * Returns a pointer into the buffer or an error code if the path was
2055 * too long. Note: Callers should use the returned pointer, not the passed
2056 * in buffer, to use the name! The implementation often starts at an offset
2057 * into the buffer, and may leave 0 bytes at the start.
2059 * "buflen" should be positive.
2061 char *d_path(const struct path *path, char *buf, int buflen)
2063 char *res = buf + buflen;
2064 struct path root;
2065 struct path tmp;
2066 int error;
2069 * We have various synthetic filesystems that never get mounted. On
2070 * these filesystems dentries are never used for lookup purposes, and
2071 * thus don't need to be hashed. They also don't need a name until a
2072 * user wants to identify the object in /proc/pid/fd/. The little hack
2073 * below allows us to generate a name for these objects on demand:
2075 if (path->dentry->d_op && path->dentry->d_op->d_dname)
2076 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2078 get_fs_root(current->fs, &root);
2079 spin_lock(&dcache_lock);
2080 tmp = root;
2081 error = path_with_deleted(path, &tmp, &res, &buflen);
2082 if (error)
2083 res = ERR_PTR(error);
2084 spin_unlock(&dcache_lock);
2085 path_put(&root);
2086 return res;
2088 EXPORT_SYMBOL(d_path);
2091 * d_path_with_unreachable - return the path of a dentry
2092 * @path: path to report
2093 * @buf: buffer to return value in
2094 * @buflen: buffer length
2096 * The difference from d_path() is that this prepends "(unreachable)"
2097 * to paths which are unreachable from the current process' root.
2099 char *d_path_with_unreachable(const struct path *path, char *buf, int buflen)
2101 char *res = buf + buflen;
2102 struct path root;
2103 struct path tmp;
2104 int error;
2106 if (path->dentry->d_op && path->dentry->d_op->d_dname)
2107 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2109 get_fs_root(current->fs, &root);
2110 spin_lock(&dcache_lock);
2111 tmp = root;
2112 error = path_with_deleted(path, &tmp, &res, &buflen);
2113 if (!error && !path_equal(&tmp, &root))
2114 error = prepend_unreachable(&res, &buflen);
2115 spin_unlock(&dcache_lock);
2116 path_put(&root);
2117 if (error)
2118 res = ERR_PTR(error);
2120 return res;
2124 * Helper function for dentry_operations.d_dname() members
2126 char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
2127 const char *fmt, ...)
2129 va_list args;
2130 char temp[64];
2131 int sz;
2133 va_start(args, fmt);
2134 sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
2135 va_end(args);
2137 if (sz > sizeof(temp) || sz > buflen)
2138 return ERR_PTR(-ENAMETOOLONG);
2140 buffer += buflen - sz;
2141 return memcpy(buffer, temp, sz);
2145 * Write full pathname from the root of the filesystem into the buffer.
2147 char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
2149 char *end = buf + buflen;
2150 char *retval;
2152 prepend(&end, &buflen, "\0", 1);
2153 if (buflen < 1)
2154 goto Elong;
2155 /* Get '/' right */
2156 retval = end-1;
2157 *retval = '/';
2159 while (!IS_ROOT(dentry)) {
2160 struct dentry *parent = dentry->d_parent;
2162 prefetch(parent);
2163 if ((prepend_name(&end, &buflen, &dentry->d_name) != 0) ||
2164 (prepend(&end, &buflen, "/", 1) != 0))
2165 goto Elong;
2167 retval = end;
2168 dentry = parent;
2170 return retval;
2171 Elong:
2172 return ERR_PTR(-ENAMETOOLONG);
2174 EXPORT_SYMBOL(__dentry_path);
2176 char *dentry_path(struct dentry *dentry, char *buf, int buflen)
2178 char *p = NULL;
2179 char *retval;
2181 spin_lock(&dcache_lock);
2182 if (d_unlinked(dentry)) {
2183 p = buf + buflen;
2184 if (prepend(&p, &buflen, "//deleted", 10) != 0)
2185 goto Elong;
2186 buflen++;
2188 retval = __dentry_path(dentry, buf, buflen);
2189 spin_unlock(&dcache_lock);
2190 if (!IS_ERR(retval) && p)
2191 *p = '/'; /* restore '/' overriden with '\0' */
2192 return retval;
2193 Elong:
2194 spin_unlock(&dcache_lock);
2195 return ERR_PTR(-ENAMETOOLONG);
2199 * NOTE! The user-level library version returns a
2200 * character pointer. The kernel system call just
2201 * returns the length of the buffer filled (which
2202 * includes the ending '\0' character), or a negative
2203 * error value. So libc would do something like
2205 * char *getcwd(char * buf, size_t size)
2207 * int retval;
2209 * retval = sys_getcwd(buf, size);
2210 * if (retval >= 0)
2211 * return buf;
2212 * errno = -retval;
2213 * return NULL;
2216 SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
2218 int error;
2219 struct path pwd, root;
2220 char *page = (char *) __get_free_page(GFP_USER);
2222 if (!page)
2223 return -ENOMEM;
2225 get_fs_root_and_pwd(current->fs, &root, &pwd);
2227 error = -ENOENT;
2228 spin_lock(&dcache_lock);
2229 if (!d_unlinked(pwd.dentry)) {
2230 unsigned long len;
2231 struct path tmp = root;
2232 char *cwd = page + PAGE_SIZE;
2233 int buflen = PAGE_SIZE;
2235 prepend(&cwd, &buflen, "\0", 1);
2236 error = prepend_path(&pwd, &tmp, &cwd, &buflen);
2237 spin_unlock(&dcache_lock);
2239 if (error)
2240 goto out;
2242 /* Unreachable from current root */
2243 if (!path_equal(&tmp, &root)) {
2244 error = prepend_unreachable(&cwd, &buflen);
2245 if (error)
2246 goto out;
2249 error = -ERANGE;
2250 len = PAGE_SIZE + page - cwd;
2251 if (len <= size) {
2252 error = len;
2253 if (copy_to_user(buf, cwd, len))
2254 error = -EFAULT;
2256 } else
2257 spin_unlock(&dcache_lock);
2259 out:
2260 path_put(&pwd);
2261 path_put(&root);
2262 free_page((unsigned long) page);
2263 return error;
2267 * Test whether new_dentry is a subdirectory of old_dentry.
2269 * Trivially implemented using the dcache structure
2273 * is_subdir - is new dentry a subdirectory of old_dentry
2274 * @new_dentry: new dentry
2275 * @old_dentry: old dentry
2277 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
2278 * Returns 0 otherwise.
2279 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
2282 int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
2284 int result;
2285 unsigned long seq;
2287 if (new_dentry == old_dentry)
2288 return 1;
2291 * Need rcu_readlock to protect against the d_parent trashing
2292 * due to d_move
2294 rcu_read_lock();
2295 do {
2296 /* for restarting inner loop in case of seq retry */
2297 seq = read_seqbegin(&rename_lock);
2298 if (d_ancestor(old_dentry, new_dentry))
2299 result = 1;
2300 else
2301 result = 0;
2302 } while (read_seqretry(&rename_lock, seq));
2303 rcu_read_unlock();
2305 return result;
2308 int path_is_under(struct path *path1, struct path *path2)
2310 struct vfsmount *mnt = path1->mnt;
2311 struct dentry *dentry = path1->dentry;
2312 int res;
2314 br_read_lock(vfsmount_lock);
2315 if (mnt != path2->mnt) {
2316 for (;;) {
2317 if (mnt->mnt_parent == mnt) {
2318 br_read_unlock(vfsmount_lock);
2319 return 0;
2321 if (mnt->mnt_parent == path2->mnt)
2322 break;
2323 mnt = mnt->mnt_parent;
2325 dentry = mnt->mnt_mountpoint;
2327 res = is_subdir(dentry, path2->dentry);
2328 br_read_unlock(vfsmount_lock);
2329 return res;
2331 EXPORT_SYMBOL(path_is_under);
2333 void d_genocide(struct dentry *root)
2335 struct dentry *this_parent = root;
2336 struct list_head *next;
2338 spin_lock(&dcache_lock);
2339 repeat:
2340 next = this_parent->d_subdirs.next;
2341 resume:
2342 while (next != &this_parent->d_subdirs) {
2343 struct list_head *tmp = next;
2344 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
2345 next = tmp->next;
2346 if (d_unhashed(dentry)||!dentry->d_inode)
2347 continue;
2348 if (!list_empty(&dentry->d_subdirs)) {
2349 this_parent = dentry;
2350 goto repeat;
2352 atomic_dec(&dentry->d_count);
2354 if (this_parent != root) {
2355 next = this_parent->d_u.d_child.next;
2356 atomic_dec(&this_parent->d_count);
2357 this_parent = this_parent->d_parent;
2358 goto resume;
2360 spin_unlock(&dcache_lock);
2364 * find_inode_number - check for dentry with name
2365 * @dir: directory to check
2366 * @name: Name to find.
2368 * Check whether a dentry already exists for the given name,
2369 * and return the inode number if it has an inode. Otherwise
2370 * 0 is returned.
2372 * This routine is used to post-process directory listings for
2373 * filesystems using synthetic inode numbers, and is necessary
2374 * to keep getcwd() working.
2377 ino_t find_inode_number(struct dentry *dir, struct qstr *name)
2379 struct dentry * dentry;
2380 ino_t ino = 0;
2382 dentry = d_hash_and_lookup(dir, name);
2383 if (dentry) {
2384 if (dentry->d_inode)
2385 ino = dentry->d_inode->i_ino;
2386 dput(dentry);
2388 return ino;
2390 EXPORT_SYMBOL(find_inode_number);
2392 static __initdata unsigned long dhash_entries;
2393 static int __init set_dhash_entries(char *str)
2395 if (!str)
2396 return 0;
2397 dhash_entries = simple_strtoul(str, &str, 0);
2398 return 1;
2400 __setup("dhash_entries=", set_dhash_entries);
2402 static void __init dcache_init_early(void)
2404 int loop;
2406 /* If hashes are distributed across NUMA nodes, defer
2407 * hash allocation until vmalloc space is available.
2409 if (hashdist)
2410 return;
2412 dentry_hashtable =
2413 alloc_large_system_hash("Dentry cache",
2414 sizeof(struct hlist_head),
2415 dhash_entries,
2417 HASH_EARLY,
2418 &d_hash_shift,
2419 &d_hash_mask,
2422 for (loop = 0; loop < (1 << d_hash_shift); loop++)
2423 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
2426 static void __init dcache_init(void)
2428 int loop;
2430 percpu_counter_init(&nr_dentry, 0);
2431 percpu_counter_init(&nr_dentry_unused, 0);
2434 * A constructor could be added for stable state like the lists,
2435 * but it is probably not worth it because of the cache nature
2436 * of the dcache.
2438 dentry_cache = KMEM_CACHE(dentry,
2439 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
2441 register_shrinker(&dcache_shrinker);
2443 /* Hash may have been set up in dcache_init_early */
2444 if (!hashdist)
2445 return;
2447 dentry_hashtable =
2448 alloc_large_system_hash("Dentry cache",
2449 sizeof(struct hlist_head),
2450 dhash_entries,
2453 &d_hash_shift,
2454 &d_hash_mask,
2457 for (loop = 0; loop < (1 << d_hash_shift); loop++)
2458 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
2461 /* SLAB cache for __getname() consumers */
2462 struct kmem_cache *names_cachep __read_mostly;
2463 EXPORT_SYMBOL(names_cachep);
2465 EXPORT_SYMBOL(d_genocide);
2467 void __init vfs_caches_init_early(void)
2469 dcache_init_early();
2470 inode_init_early();
2473 void __init vfs_caches_init(unsigned long mempages)
2475 unsigned long reserve;
2477 /* Base hash sizes on available memory, with a reserve equal to
2478 150% of current kernel size */
2480 reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
2481 mempages -= reserve;
2483 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
2484 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
2486 dcache_init();
2487 inode_init();
2488 files_init(mempages);
2489 mnt_init();
2490 bdev_cache_init();
2491 chrdev_init();