4 * Complete reimplementation
5 * (C) 1997 Thomas Schoebel-Theuer,
6 * with heavy changes by Linus Torvalds
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>
21 #include <linux/fsnotify.h>
22 #include <linux/slab.h>
23 #include <linux/init.h>
24 #include <linux/smp_lock.h>
25 #include <linux/hash.h>
26 #include <linux/cache.h>
27 #include <linux/module.h>
28 #include <linux/mount.h>
29 #include <linux/file.h>
30 #include <asm/uaccess.h>
31 #include <linux/security.h>
32 #include <linux/seqlock.h>
33 #include <linux/swap.h>
34 #include <linux/bootmem.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 static __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;
64 static LIST_HEAD(dentry_unused);
66 /* Statistics gathering. */
67 struct dentry_stat_t dentry_stat = {
71 static void __d_free(struct dentry *dentry)
73 if (dname_external(dentry))
74 kfree(dentry->d_name.name);
75 kmem_cache_free(dentry_cache, dentry);
78 static void d_callback(struct rcu_head *head)
80 struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
85 * no dcache_lock, please. The caller must decrement dentry_stat.nr_dentry
88 static void d_free(struct dentry *dentry)
90 if (dentry->d_op && dentry->d_op->d_release)
91 dentry->d_op->d_release(dentry);
92 /* if dentry was never inserted into hash, immediate free is OK */
93 if (dentry->d_hash.pprev == NULL)
96 call_rcu(&dentry->d_u.d_rcu, d_callback);
100 * Release the dentry's inode, using the filesystem
101 * d_iput() operation if defined.
102 * Called with dcache_lock and per dentry lock held, drops both.
104 static void dentry_iput(struct dentry * dentry)
106 struct inode *inode = dentry->d_inode;
108 dentry->d_inode = NULL;
109 list_del_init(&dentry->d_alias);
110 spin_unlock(&dentry->d_lock);
111 spin_unlock(&dcache_lock);
113 fsnotify_inoderemove(inode);
114 if (dentry->d_op && dentry->d_op->d_iput)
115 dentry->d_op->d_iput(dentry, inode);
119 spin_unlock(&dentry->d_lock);
120 spin_unlock(&dcache_lock);
127 * This is complicated by the fact that we do not want to put
128 * dentries that are no longer on any hash chain on the unused
129 * list: we'd much rather just get rid of them immediately.
131 * However, that implies that we have to traverse the dentry
132 * tree upwards to the parents which might _also_ now be
133 * scheduled for deletion (it may have been only waiting for
134 * its last child to go away).
136 * This tail recursion is done by hand as we don't want to depend
137 * on the compiler to always get this right (gcc generally doesn't).
138 * Real recursion would eat up our stack space.
142 * dput - release a dentry
143 * @dentry: dentry to release
145 * Release a dentry. This will drop the usage count and if appropriate
146 * call the dentry unlink method as well as removing it from the queues and
147 * releasing its resources. If the parent dentries were scheduled for release
148 * they too may now get deleted.
150 * no dcache lock, please.
153 void dput(struct dentry *dentry)
159 if (atomic_read(&dentry->d_count) == 1)
161 if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
164 spin_lock(&dentry->d_lock);
165 if (atomic_read(&dentry->d_count)) {
166 spin_unlock(&dentry->d_lock);
167 spin_unlock(&dcache_lock);
172 * AV: ->d_delete() is _NOT_ allowed to block now.
174 if (dentry->d_op && dentry->d_op->d_delete) {
175 if (dentry->d_op->d_delete(dentry))
178 /* Unreachable? Get rid of it */
179 if (d_unhashed(dentry))
181 if (list_empty(&dentry->d_lru)) {
182 dentry->d_flags |= DCACHE_REFERENCED;
183 list_add(&dentry->d_lru, &dentry_unused);
184 dentry_stat.nr_unused++;
186 spin_unlock(&dentry->d_lock);
187 spin_unlock(&dcache_lock);
194 struct dentry *parent;
196 /* If dentry was on d_lru list
197 * delete it from there
199 if (!list_empty(&dentry->d_lru)) {
200 list_del(&dentry->d_lru);
201 dentry_stat.nr_unused--;
203 list_del(&dentry->d_u.d_child);
204 dentry_stat.nr_dentry--; /* For d_free, below */
205 /*drops the locks, at that point nobody can reach this dentry */
207 parent = dentry->d_parent;
209 if (dentry == parent)
217 * d_invalidate - invalidate a dentry
218 * @dentry: dentry to invalidate
220 * Try to invalidate the dentry if it turns out to be
221 * possible. If there are other dentries that can be
222 * reached through this one we can't delete it and we
223 * return -EBUSY. On success we return 0.
228 int d_invalidate(struct dentry * dentry)
231 * If it's already been dropped, return OK.
233 spin_lock(&dcache_lock);
234 if (d_unhashed(dentry)) {
235 spin_unlock(&dcache_lock);
239 * Check whether to do a partial shrink_dcache
240 * to get rid of unused child entries.
242 if (!list_empty(&dentry->d_subdirs)) {
243 spin_unlock(&dcache_lock);
244 shrink_dcache_parent(dentry);
245 spin_lock(&dcache_lock);
249 * Somebody else still using it?
251 * If it's a directory, we can't drop it
252 * for fear of somebody re-populating it
253 * with children (even though dropping it
254 * would make it unreachable from the root,
255 * we might still populate it if it was a
256 * working directory or similar).
258 spin_lock(&dentry->d_lock);
259 if (atomic_read(&dentry->d_count) > 1) {
260 if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
261 spin_unlock(&dentry->d_lock);
262 spin_unlock(&dcache_lock);
268 spin_unlock(&dentry->d_lock);
269 spin_unlock(&dcache_lock);
273 /* This should be called _only_ with dcache_lock held */
275 static inline struct dentry * __dget_locked(struct dentry *dentry)
277 atomic_inc(&dentry->d_count);
278 if (!list_empty(&dentry->d_lru)) {
279 dentry_stat.nr_unused--;
280 list_del_init(&dentry->d_lru);
285 struct dentry * dget_locked(struct dentry *dentry)
287 return __dget_locked(dentry);
291 * d_find_alias - grab a hashed alias of inode
292 * @inode: inode in question
293 * @want_discon: flag, used by d_splice_alias, to request
294 * that only a DISCONNECTED alias be returned.
296 * If inode has a hashed alias, or is a directory and has any alias,
297 * acquire the reference to alias and return it. Otherwise return NULL.
298 * Notice that if inode is a directory there can be only one alias and
299 * it can be unhashed only if it has no children, or if it is the root
302 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
303 * any other hashed alias over that one unless @want_discon is set,
304 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
307 static struct dentry * __d_find_alias(struct inode *inode, int want_discon)
309 struct list_head *head, *next, *tmp;
310 struct dentry *alias, *discon_alias=NULL;
312 head = &inode->i_dentry;
313 next = inode->i_dentry.next;
314 while (next != head) {
318 alias = list_entry(tmp, struct dentry, d_alias);
319 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
320 if (IS_ROOT(alias) &&
321 (alias->d_flags & DCACHE_DISCONNECTED))
322 discon_alias = alias;
323 else if (!want_discon) {
324 __dget_locked(alias);
330 __dget_locked(discon_alias);
334 struct dentry * d_find_alias(struct inode *inode)
336 struct dentry *de = NULL;
338 if (!list_empty(&inode->i_dentry)) {
339 spin_lock(&dcache_lock);
340 de = __d_find_alias(inode, 0);
341 spin_unlock(&dcache_lock);
347 * Try to kill dentries associated with this inode.
348 * WARNING: you must own a reference to inode.
350 void d_prune_aliases(struct inode *inode)
352 struct dentry *dentry;
354 spin_lock(&dcache_lock);
355 list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
356 spin_lock(&dentry->d_lock);
357 if (!atomic_read(&dentry->d_count)) {
358 __dget_locked(dentry);
360 spin_unlock(&dentry->d_lock);
361 spin_unlock(&dcache_lock);
365 spin_unlock(&dentry->d_lock);
367 spin_unlock(&dcache_lock);
371 * Throw away a dentry - free the inode, dput the parent. This requires that
372 * the LRU list has already been removed.
374 * Called with dcache_lock, drops it and then regains.
375 * Called with dentry->d_lock held, drops it.
377 static void prune_one_dentry(struct dentry * dentry)
379 struct dentry * parent;
382 list_del(&dentry->d_u.d_child);
383 dentry_stat.nr_dentry--; /* For d_free, below */
385 parent = dentry->d_parent;
387 if (parent != dentry)
389 spin_lock(&dcache_lock);
393 * prune_dcache - shrink the dcache
394 * @count: number of entries to try and free
395 * @sb: if given, ignore dentries for other superblocks
396 * which are being unmounted.
398 * Shrink the dcache. This is done when we need
399 * more memory, or simply when we need to unmount
400 * something (at which point we need to unuse
403 * This function may fail to free any resources if
404 * all the dentries are in use.
407 static void prune_dcache(int count, struct super_block *sb)
409 spin_lock(&dcache_lock);
410 for (; count ; count--) {
411 struct dentry *dentry;
412 struct list_head *tmp;
413 struct rw_semaphore *s_umount;
415 cond_resched_lock(&dcache_lock);
417 tmp = dentry_unused.prev;
419 /* Try to find a dentry for this sb, but don't try
420 * too hard, if they aren't near the tail they will
421 * be moved down again soon
424 while (skip && tmp != &dentry_unused &&
425 list_entry(tmp, struct dentry, d_lru)->d_sb != sb) {
430 if (tmp == &dentry_unused)
433 prefetch(dentry_unused.prev);
434 dentry_stat.nr_unused--;
435 dentry = list_entry(tmp, struct dentry, d_lru);
437 spin_lock(&dentry->d_lock);
439 * We found an inuse dentry which was not removed from
440 * dentry_unused because of laziness during lookup. Do not free
441 * it - just keep it off the dentry_unused list.
443 if (atomic_read(&dentry->d_count)) {
444 spin_unlock(&dentry->d_lock);
447 /* If the dentry was recently referenced, don't free it. */
448 if (dentry->d_flags & DCACHE_REFERENCED) {
449 dentry->d_flags &= ~DCACHE_REFERENCED;
450 list_add(&dentry->d_lru, &dentry_unused);
451 dentry_stat.nr_unused++;
452 spin_unlock(&dentry->d_lock);
456 * If the dentry is not DCACHED_REFERENCED, it is time
457 * to remove it from the dcache, provided the super block is
458 * NULL (which means we are trying to reclaim memory)
459 * or this dentry belongs to the same super block that
463 * If this dentry is for "my" filesystem, then I can prune it
464 * without taking the s_umount lock (I already hold it).
466 if (sb && dentry->d_sb == sb) {
467 prune_one_dentry(dentry);
471 * ...otherwise we need to be sure this filesystem isn't being
472 * unmounted, otherwise we could race with
473 * generic_shutdown_super(), and end up holding a reference to
474 * an inode while the filesystem is unmounted.
475 * So we try to get s_umount, and make sure s_root isn't NULL.
476 * (Take a local copy of s_umount to avoid a use-after-free of
479 s_umount = &dentry->d_sb->s_umount;
480 if (down_read_trylock(s_umount)) {
481 if (dentry->d_sb->s_root != NULL) {
482 prune_one_dentry(dentry);
488 spin_unlock(&dentry->d_lock);
490 * Insert dentry at the head of the list as inserting at the
491 * tail leads to a cycle.
493 list_add(&dentry->d_lru, &dentry_unused);
494 dentry_stat.nr_unused++;
496 spin_unlock(&dcache_lock);
500 * Shrink the dcache for the specified super block.
501 * This allows us to unmount a device without disturbing
502 * the dcache for the other devices.
504 * This implementation makes just two traversals of the
505 * unused list. On the first pass we move the selected
506 * dentries to the most recent end, and on the second
507 * pass we free them. The second pass must restart after
508 * each dput(), but since the target dentries are all at
509 * the end, it's really just a single traversal.
513 * shrink_dcache_sb - shrink dcache for a superblock
516 * Shrink the dcache for the specified super block. This
517 * is used to free the dcache before unmounting a file
521 void shrink_dcache_sb(struct super_block * sb)
523 struct list_head *tmp, *next;
524 struct dentry *dentry;
527 * Pass one ... move the dentries for the specified
528 * superblock to the most recent end of the unused list.
530 spin_lock(&dcache_lock);
531 list_for_each_safe(tmp, next, &dentry_unused) {
532 dentry = list_entry(tmp, struct dentry, d_lru);
533 if (dentry->d_sb != sb)
535 list_move(tmp, &dentry_unused);
539 * Pass two ... free the dentries for this superblock.
542 list_for_each_safe(tmp, next, &dentry_unused) {
543 dentry = list_entry(tmp, struct dentry, d_lru);
544 if (dentry->d_sb != sb)
546 dentry_stat.nr_unused--;
548 spin_lock(&dentry->d_lock);
549 if (atomic_read(&dentry->d_count)) {
550 spin_unlock(&dentry->d_lock);
553 prune_one_dentry(dentry);
554 cond_resched_lock(&dcache_lock);
557 spin_unlock(&dcache_lock);
561 * destroy a single subtree of dentries for unmount
562 * - see the comments on shrink_dcache_for_umount() for a description of the
565 static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
567 struct dentry *parent;
568 unsigned detached = 0;
570 BUG_ON(!IS_ROOT(dentry));
572 /* detach this root from the system */
573 spin_lock(&dcache_lock);
574 if (!list_empty(&dentry->d_lru)) {
575 dentry_stat.nr_unused--;
576 list_del_init(&dentry->d_lru);
579 spin_unlock(&dcache_lock);
582 /* descend to the first leaf in the current subtree */
583 while (!list_empty(&dentry->d_subdirs)) {
586 /* this is a branch with children - detach all of them
587 * from the system in one go */
588 spin_lock(&dcache_lock);
589 list_for_each_entry(loop, &dentry->d_subdirs,
591 if (!list_empty(&loop->d_lru)) {
592 dentry_stat.nr_unused--;
593 list_del_init(&loop->d_lru);
597 cond_resched_lock(&dcache_lock);
599 spin_unlock(&dcache_lock);
601 /* move to the first child */
602 dentry = list_entry(dentry->d_subdirs.next,
603 struct dentry, d_u.d_child);
606 /* consume the dentries from this leaf up through its parents
607 * until we find one with children or run out altogether */
611 if (atomic_read(&dentry->d_count) != 0) {
613 "BUG: Dentry %p{i=%lx,n=%s}"
615 " [unmount of %s %s]\n",
618 dentry->d_inode->i_ino : 0UL,
620 atomic_read(&dentry->d_count),
621 dentry->d_sb->s_type->name,
626 parent = dentry->d_parent;
627 if (parent == dentry)
630 atomic_dec(&parent->d_count);
632 list_del(&dentry->d_u.d_child);
635 inode = dentry->d_inode;
637 dentry->d_inode = NULL;
638 list_del_init(&dentry->d_alias);
639 if (dentry->d_op && dentry->d_op->d_iput)
640 dentry->d_op->d_iput(dentry, inode);
647 /* finished when we fall off the top of the tree,
648 * otherwise we ascend to the parent and move to the
649 * next sibling if there is one */
655 } while (list_empty(&dentry->d_subdirs));
657 dentry = list_entry(dentry->d_subdirs.next,
658 struct dentry, d_u.d_child);
661 /* several dentries were freed, need to correct nr_dentry */
662 spin_lock(&dcache_lock);
663 dentry_stat.nr_dentry -= detached;
664 spin_unlock(&dcache_lock);
668 * destroy the dentries attached to a superblock on unmounting
669 * - we don't need to use dentry->d_lock, and only need dcache_lock when
670 * removing the dentry from the system lists and hashes because:
671 * - the superblock is detached from all mountings and open files, so the
672 * dentry trees will not be rearranged by the VFS
673 * - s_umount is write-locked, so the memory pressure shrinker will ignore
674 * any dentries belonging to this superblock that it comes across
675 * - the filesystem itself is no longer permitted to rearrange the dentries
678 void shrink_dcache_for_umount(struct super_block *sb)
680 struct dentry *dentry;
682 if (down_read_trylock(&sb->s_umount))
687 atomic_dec(&dentry->d_count);
688 shrink_dcache_for_umount_subtree(dentry);
690 while (!hlist_empty(&sb->s_anon)) {
691 dentry = hlist_entry(sb->s_anon.first, struct dentry, d_hash);
692 shrink_dcache_for_umount_subtree(dentry);
697 * Search for at least 1 mount point in the dentry's subdirs.
698 * We descend to the next level whenever the d_subdirs
699 * list is non-empty and continue searching.
703 * have_submounts - check for mounts over a dentry
704 * @parent: dentry to check.
706 * Return true if the parent or its subdirectories contain
710 int have_submounts(struct dentry *parent)
712 struct dentry *this_parent = parent;
713 struct list_head *next;
715 spin_lock(&dcache_lock);
716 if (d_mountpoint(parent))
719 next = this_parent->d_subdirs.next;
721 while (next != &this_parent->d_subdirs) {
722 struct list_head *tmp = next;
723 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
725 /* Have we found a mount point ? */
726 if (d_mountpoint(dentry))
728 if (!list_empty(&dentry->d_subdirs)) {
729 this_parent = dentry;
734 * All done at this level ... ascend and resume the search.
736 if (this_parent != parent) {
737 next = this_parent->d_u.d_child.next;
738 this_parent = this_parent->d_parent;
741 spin_unlock(&dcache_lock);
742 return 0; /* No mount points found in tree */
744 spin_unlock(&dcache_lock);
749 * Search the dentry child list for the specified parent,
750 * and move any unused dentries to the end of the unused
751 * list for prune_dcache(). We descend to the next level
752 * whenever the d_subdirs list is non-empty and continue
755 * It returns zero iff there are no unused children,
756 * otherwise it returns the number of children moved to
757 * the end of the unused list. This may not be the total
758 * number of unused children, because select_parent can
759 * drop the lock and return early due to latency
762 static int select_parent(struct dentry * parent)
764 struct dentry *this_parent = parent;
765 struct list_head *next;
768 spin_lock(&dcache_lock);
770 next = this_parent->d_subdirs.next;
772 while (next != &this_parent->d_subdirs) {
773 struct list_head *tmp = next;
774 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
777 if (!list_empty(&dentry->d_lru)) {
778 dentry_stat.nr_unused--;
779 list_del_init(&dentry->d_lru);
782 * move only zero ref count dentries to the end
783 * of the unused list for prune_dcache
785 if (!atomic_read(&dentry->d_count)) {
786 list_add_tail(&dentry->d_lru, &dentry_unused);
787 dentry_stat.nr_unused++;
792 * We can return to the caller if we have found some (this
793 * ensures forward progress). We'll be coming back to find
796 if (found && need_resched())
800 * Descend a level if the d_subdirs list is non-empty.
802 if (!list_empty(&dentry->d_subdirs)) {
803 this_parent = dentry;
808 * All done at this level ... ascend and resume the search.
810 if (this_parent != parent) {
811 next = this_parent->d_u.d_child.next;
812 this_parent = this_parent->d_parent;
816 spin_unlock(&dcache_lock);
821 * shrink_dcache_parent - prune dcache
822 * @parent: parent of entries to prune
824 * Prune the dcache to remove unused children of the parent dentry.
827 void shrink_dcache_parent(struct dentry * parent)
831 while ((found = select_parent(parent)) != 0)
832 prune_dcache(found, parent->d_sb);
836 * Scan `nr' dentries and return the number which remain.
838 * We need to avoid reentering the filesystem if the caller is performing a
839 * GFP_NOFS allocation attempt. One example deadlock is:
841 * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
842 * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
843 * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
845 * In this case we return -1 to tell the caller that we baled.
847 static int shrink_dcache_memory(int nr, gfp_t gfp_mask)
850 if (!(gfp_mask & __GFP_FS))
852 prune_dcache(nr, NULL);
854 return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
858 * d_alloc - allocate a dcache entry
859 * @parent: parent of entry to allocate
860 * @name: qstr of the name
862 * Allocates a dentry. It returns %NULL if there is insufficient memory
863 * available. On a success the dentry is returned. The name passed in is
864 * copied and the copy passed in may be reused after this call.
867 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
869 struct dentry *dentry;
872 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
876 if (name->len > DNAME_INLINE_LEN-1) {
877 dname = kmalloc(name->len + 1, GFP_KERNEL);
879 kmem_cache_free(dentry_cache, dentry);
883 dname = dentry->d_iname;
885 dentry->d_name.name = dname;
887 dentry->d_name.len = name->len;
888 dentry->d_name.hash = name->hash;
889 memcpy(dname, name->name, name->len);
890 dname[name->len] = 0;
892 atomic_set(&dentry->d_count, 1);
893 dentry->d_flags = DCACHE_UNHASHED;
894 spin_lock_init(&dentry->d_lock);
895 dentry->d_inode = NULL;
896 dentry->d_parent = NULL;
899 dentry->d_fsdata = NULL;
900 dentry->d_mounted = 0;
901 #ifdef CONFIG_PROFILING
902 dentry->d_cookie = NULL;
904 INIT_HLIST_NODE(&dentry->d_hash);
905 INIT_LIST_HEAD(&dentry->d_lru);
906 INIT_LIST_HEAD(&dentry->d_subdirs);
907 INIT_LIST_HEAD(&dentry->d_alias);
910 dentry->d_parent = dget(parent);
911 dentry->d_sb = parent->d_sb;
913 INIT_LIST_HEAD(&dentry->d_u.d_child);
916 spin_lock(&dcache_lock);
918 list_add(&dentry->d_u.d_child, &parent->d_subdirs);
919 dentry_stat.nr_dentry++;
920 spin_unlock(&dcache_lock);
925 struct dentry *d_alloc_name(struct dentry *parent, const char *name)
930 q.len = strlen(name);
931 q.hash = full_name_hash(q.name, q.len);
932 return d_alloc(parent, &q);
936 * d_instantiate - fill in inode information for a dentry
937 * @entry: dentry to complete
938 * @inode: inode to attach to this dentry
940 * Fill in inode information in the entry.
942 * This turns negative dentries into productive full members
945 * NOTE! This assumes that the inode count has been incremented
946 * (or otherwise set) by the caller to indicate that it is now
947 * in use by the dcache.
950 void d_instantiate(struct dentry *entry, struct inode * inode)
952 BUG_ON(!list_empty(&entry->d_alias));
953 spin_lock(&dcache_lock);
955 list_add(&entry->d_alias, &inode->i_dentry);
956 entry->d_inode = inode;
957 fsnotify_d_instantiate(entry, inode);
958 spin_unlock(&dcache_lock);
959 security_d_instantiate(entry, inode);
963 * d_instantiate_unique - instantiate a non-aliased dentry
964 * @entry: dentry to instantiate
965 * @inode: inode to attach to this dentry
967 * Fill in inode information in the entry. On success, it returns NULL.
968 * If an unhashed alias of "entry" already exists, then we return the
969 * aliased dentry instead and drop one reference to inode.
971 * Note that in order to avoid conflicts with rename() etc, the caller
972 * had better be holding the parent directory semaphore.
974 * This also assumes that the inode count has been incremented
975 * (or otherwise set) by the caller to indicate that it is now
976 * in use by the dcache.
978 static struct dentry *__d_instantiate_unique(struct dentry *entry,
981 struct dentry *alias;
982 int len = entry->d_name.len;
983 const char *name = entry->d_name.name;
984 unsigned int hash = entry->d_name.hash;
987 entry->d_inode = NULL;
991 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
992 struct qstr *qstr = &alias->d_name;
994 if (qstr->hash != hash)
996 if (alias->d_parent != entry->d_parent)
998 if (qstr->len != len)
1000 if (memcmp(qstr->name, name, len))
1006 list_add(&entry->d_alias, &inode->i_dentry);
1007 entry->d_inode = inode;
1008 fsnotify_d_instantiate(entry, inode);
1012 struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
1014 struct dentry *result;
1016 BUG_ON(!list_empty(&entry->d_alias));
1018 spin_lock(&dcache_lock);
1019 result = __d_instantiate_unique(entry, inode);
1020 spin_unlock(&dcache_lock);
1023 security_d_instantiate(entry, inode);
1027 BUG_ON(!d_unhashed(result));
1032 EXPORT_SYMBOL(d_instantiate_unique);
1035 * d_alloc_root - allocate root dentry
1036 * @root_inode: inode to allocate the root for
1038 * Allocate a root ("/") dentry for the inode given. The inode is
1039 * instantiated and returned. %NULL is returned if there is insufficient
1040 * memory or the inode passed is %NULL.
1043 struct dentry * d_alloc_root(struct inode * root_inode)
1045 struct dentry *res = NULL;
1048 static const struct qstr name = { .name = "/", .len = 1 };
1050 res = d_alloc(NULL, &name);
1052 res->d_sb = root_inode->i_sb;
1053 res->d_parent = res;
1054 d_instantiate(res, root_inode);
1060 static inline struct hlist_head *d_hash(struct dentry *parent,
1063 hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
1064 hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
1065 return dentry_hashtable + (hash & D_HASHMASK);
1069 * d_alloc_anon - allocate an anonymous dentry
1070 * @inode: inode to allocate the dentry for
1072 * This is similar to d_alloc_root. It is used by filesystems when
1073 * creating a dentry for a given inode, often in the process of
1074 * mapping a filehandle to a dentry. The returned dentry may be
1075 * anonymous, or may have a full name (if the inode was already
1076 * in the cache). The file system may need to make further
1077 * efforts to connect this dentry into the dcache properly.
1079 * When called on a directory inode, we must ensure that
1080 * the inode only ever has one dentry. If a dentry is
1081 * found, that is returned instead of allocating a new one.
1083 * On successful return, the reference to the inode has been transferred
1084 * to the dentry. If %NULL is returned (indicating kmalloc failure),
1085 * the reference on the inode has not been released.
1088 struct dentry * d_alloc_anon(struct inode *inode)
1090 static const struct qstr anonstring = { .name = "" };
1094 if ((res = d_find_alias(inode))) {
1099 tmp = d_alloc(NULL, &anonstring);
1103 tmp->d_parent = tmp; /* make sure dput doesn't croak */
1105 spin_lock(&dcache_lock);
1106 res = __d_find_alias(inode, 0);
1108 /* attach a disconnected dentry */
1111 spin_lock(&res->d_lock);
1112 res->d_sb = inode->i_sb;
1113 res->d_parent = res;
1114 res->d_inode = inode;
1115 res->d_flags |= DCACHE_DISCONNECTED;
1116 res->d_flags &= ~DCACHE_UNHASHED;
1117 list_add(&res->d_alias, &inode->i_dentry);
1118 hlist_add_head(&res->d_hash, &inode->i_sb->s_anon);
1119 spin_unlock(&res->d_lock);
1121 inode = NULL; /* don't drop reference */
1123 spin_unlock(&dcache_lock);
1134 * d_splice_alias - splice a disconnected dentry into the tree if one exists
1135 * @inode: the inode which may have a disconnected dentry
1136 * @dentry: a negative dentry which we want to point to the inode.
1138 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1139 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1140 * and return it, else simply d_add the inode to the dentry and return NULL.
1142 * This is needed in the lookup routine of any filesystem that is exportable
1143 * (via knfsd) so that we can build dcache paths to directories effectively.
1145 * If a dentry was found and moved, then it is returned. Otherwise NULL
1146 * is returned. This matches the expected return value of ->lookup.
1149 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
1151 struct dentry *new = NULL;
1153 if (inode && S_ISDIR(inode->i_mode)) {
1154 spin_lock(&dcache_lock);
1155 new = __d_find_alias(inode, 1);
1157 BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
1158 fsnotify_d_instantiate(new, inode);
1159 spin_unlock(&dcache_lock);
1160 security_d_instantiate(new, inode);
1162 d_move(new, dentry);
1165 /* d_instantiate takes dcache_lock, so we do it by hand */
1166 list_add(&dentry->d_alias, &inode->i_dentry);
1167 dentry->d_inode = inode;
1168 fsnotify_d_instantiate(dentry, inode);
1169 spin_unlock(&dcache_lock);
1170 security_d_instantiate(dentry, inode);
1174 d_add(dentry, inode);
1180 * d_lookup - search for a dentry
1181 * @parent: parent dentry
1182 * @name: qstr of name we wish to find
1184 * Searches the children of the parent dentry for the name in question. If
1185 * the dentry is found its reference count is incremented and the dentry
1186 * is returned. The caller must use d_put to free the entry when it has
1187 * finished using it. %NULL is returned on failure.
1189 * __d_lookup is dcache_lock free. The hash list is protected using RCU.
1190 * Memory barriers are used while updating and doing lockless traversal.
1191 * To avoid races with d_move while rename is happening, d_lock is used.
1193 * Overflows in memcmp(), while d_move, are avoided by keeping the length
1194 * and name pointer in one structure pointed by d_qstr.
1196 * rcu_read_lock() and rcu_read_unlock() are used to disable preemption while
1197 * lookup is going on.
1199 * dentry_unused list is not updated even if lookup finds the required dentry
1200 * in there. It is updated in places such as prune_dcache, shrink_dcache_sb,
1201 * select_parent and __dget_locked. This laziness saves lookup from dcache_lock
1204 * d_lookup() is protected against the concurrent renames in some unrelated
1205 * directory using the seqlockt_t rename_lock.
1208 struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
1210 struct dentry * dentry = NULL;
1214 seq = read_seqbegin(&rename_lock);
1215 dentry = __d_lookup(parent, name);
1218 } while (read_seqretry(&rename_lock, seq));
1222 struct dentry * __d_lookup(struct dentry * parent, struct qstr * name)
1224 unsigned int len = name->len;
1225 unsigned int hash = name->hash;
1226 const unsigned char *str = name->name;
1227 struct hlist_head *head = d_hash(parent,hash);
1228 struct dentry *found = NULL;
1229 struct hlist_node *node;
1230 struct dentry *dentry;
1234 hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
1237 if (dentry->d_name.hash != hash)
1239 if (dentry->d_parent != parent)
1242 spin_lock(&dentry->d_lock);
1245 * Recheck the dentry after taking the lock - d_move may have
1246 * changed things. Don't bother checking the hash because we're
1247 * about to compare the whole name anyway.
1249 if (dentry->d_parent != parent)
1253 * It is safe to compare names since d_move() cannot
1254 * change the qstr (protected by d_lock).
1256 qstr = &dentry->d_name;
1257 if (parent->d_op && parent->d_op->d_compare) {
1258 if (parent->d_op->d_compare(parent, qstr, name))
1261 if (qstr->len != len)
1263 if (memcmp(qstr->name, str, len))
1267 if (!d_unhashed(dentry)) {
1268 atomic_inc(&dentry->d_count);
1271 spin_unlock(&dentry->d_lock);
1274 spin_unlock(&dentry->d_lock);
1282 * d_hash_and_lookup - hash the qstr then search for a dentry
1283 * @dir: Directory to search in
1284 * @name: qstr of name we wish to find
1286 * On hash failure or on lookup failure NULL is returned.
1288 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
1290 struct dentry *dentry = NULL;
1293 * Check for a fs-specific hash function. Note that we must
1294 * calculate the standard hash first, as the d_op->d_hash()
1295 * routine may choose to leave the hash value unchanged.
1297 name->hash = full_name_hash(name->name, name->len);
1298 if (dir->d_op && dir->d_op->d_hash) {
1299 if (dir->d_op->d_hash(dir, name) < 0)
1302 dentry = d_lookup(dir, name);
1308 * d_validate - verify dentry provided from insecure source
1309 * @dentry: The dentry alleged to be valid child of @dparent
1310 * @dparent: The parent dentry (known to be valid)
1311 * @hash: Hash of the dentry
1312 * @len: Length of the name
1314 * An insecure source has sent us a dentry, here we verify it and dget() it.
1315 * This is used by ncpfs in its readdir implementation.
1316 * Zero is returned in the dentry is invalid.
1319 int d_validate(struct dentry *dentry, struct dentry *dparent)
1321 struct hlist_head *base;
1322 struct hlist_node *lhp;
1324 /* Check whether the ptr might be valid at all.. */
1325 if (!kmem_ptr_validate(dentry_cache, dentry))
1328 if (dentry->d_parent != dparent)
1331 spin_lock(&dcache_lock);
1332 base = d_hash(dparent, dentry->d_name.hash);
1333 hlist_for_each(lhp,base) {
1334 /* hlist_for_each_entry_rcu() not required for d_hash list
1335 * as it is parsed under dcache_lock
1337 if (dentry == hlist_entry(lhp, struct dentry, d_hash)) {
1338 __dget_locked(dentry);
1339 spin_unlock(&dcache_lock);
1343 spin_unlock(&dcache_lock);
1349 * When a file is deleted, we have two options:
1350 * - turn this dentry into a negative dentry
1351 * - unhash this dentry and free it.
1353 * Usually, we want to just turn this into
1354 * a negative dentry, but if anybody else is
1355 * currently using the dentry or the inode
1356 * we can't do that and we fall back on removing
1357 * it from the hash queues and waiting for
1358 * it to be deleted later when it has no users
1362 * d_delete - delete a dentry
1363 * @dentry: The dentry to delete
1365 * Turn the dentry into a negative dentry if possible, otherwise
1366 * remove it from the hash queues so it can be deleted later
1369 void d_delete(struct dentry * dentry)
1373 * Are we the only user?
1375 spin_lock(&dcache_lock);
1376 spin_lock(&dentry->d_lock);
1377 isdir = S_ISDIR(dentry->d_inode->i_mode);
1378 if (atomic_read(&dentry->d_count) == 1) {
1379 dentry_iput(dentry);
1380 fsnotify_nameremove(dentry, isdir);
1382 /* remove this and other inotify debug checks after 2.6.18 */
1383 dentry->d_flags &= ~DCACHE_INOTIFY_PARENT_WATCHED;
1387 if (!d_unhashed(dentry))
1390 spin_unlock(&dentry->d_lock);
1391 spin_unlock(&dcache_lock);
1393 fsnotify_nameremove(dentry, isdir);
1396 static void __d_rehash(struct dentry * entry, struct hlist_head *list)
1399 entry->d_flags &= ~DCACHE_UNHASHED;
1400 hlist_add_head_rcu(&entry->d_hash, list);
1403 static void _d_rehash(struct dentry * entry)
1405 __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
1409 * d_rehash - add an entry back to the hash
1410 * @entry: dentry to add to the hash
1412 * Adds a dentry to the hash according to its name.
1415 void d_rehash(struct dentry * entry)
1417 spin_lock(&dcache_lock);
1418 spin_lock(&entry->d_lock);
1420 spin_unlock(&entry->d_lock);
1421 spin_unlock(&dcache_lock);
1424 #define do_switch(x,y) do { \
1425 __typeof__ (x) __tmp = x; \
1426 x = y; y = __tmp; } while (0)
1429 * When switching names, the actual string doesn't strictly have to
1430 * be preserved in the target - because we're dropping the target
1431 * anyway. As such, we can just do a simple memcpy() to copy over
1432 * the new name before we switch.
1434 * Note that we have to be a lot more careful about getting the hash
1435 * switched - we have to switch the hash value properly even if it
1436 * then no longer matches the actual (corrupted) string of the target.
1437 * The hash value has to match the hash queue that the dentry is on..
1439 static void switch_names(struct dentry *dentry, struct dentry *target)
1441 if (dname_external(target)) {
1442 if (dname_external(dentry)) {
1444 * Both external: swap the pointers
1446 do_switch(target->d_name.name, dentry->d_name.name);
1449 * dentry:internal, target:external. Steal target's
1450 * storage and make target internal.
1452 dentry->d_name.name = target->d_name.name;
1453 target->d_name.name = target->d_iname;
1456 if (dname_external(dentry)) {
1458 * dentry:external, target:internal. Give dentry's
1459 * storage to target and make dentry internal
1461 memcpy(dentry->d_iname, target->d_name.name,
1462 target->d_name.len + 1);
1463 target->d_name.name = dentry->d_name.name;
1464 dentry->d_name.name = dentry->d_iname;
1467 * Both are internal. Just copy target to dentry
1469 memcpy(dentry->d_iname, target->d_name.name,
1470 target->d_name.len + 1);
1476 * We cannibalize "target" when moving dentry on top of it,
1477 * because it's going to be thrown away anyway. We could be more
1478 * polite about it, though.
1480 * This forceful removal will result in ugly /proc output if
1481 * somebody holds a file open that got deleted due to a rename.
1482 * We could be nicer about the deleted file, and let it show
1483 * up under the name it got deleted rather than the name that
1488 * d_move_locked - move a dentry
1489 * @dentry: entry to move
1490 * @target: new dentry
1492 * Update the dcache to reflect the move of a file name. Negative
1493 * dcache entries should not be moved in this way.
1495 static void d_move_locked(struct dentry * dentry, struct dentry * target)
1497 struct hlist_head *list;
1499 if (!dentry->d_inode)
1500 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
1502 write_seqlock(&rename_lock);
1504 * XXXX: do we really need to take target->d_lock?
1506 if (target < dentry) {
1507 spin_lock(&target->d_lock);
1508 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1510 spin_lock(&dentry->d_lock);
1511 spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
1514 /* Move the dentry to the target hash queue, if on different bucket */
1515 if (dentry->d_flags & DCACHE_UNHASHED)
1516 goto already_unhashed;
1518 hlist_del_rcu(&dentry->d_hash);
1521 list = d_hash(target->d_parent, target->d_name.hash);
1522 __d_rehash(dentry, list);
1524 /* Unhash the target: dput() will then get rid of it */
1527 list_del(&dentry->d_u.d_child);
1528 list_del(&target->d_u.d_child);
1530 /* Switch the names.. */
1531 switch_names(dentry, target);
1532 do_switch(dentry->d_name.len, target->d_name.len);
1533 do_switch(dentry->d_name.hash, target->d_name.hash);
1535 /* ... and switch the parents */
1536 if (IS_ROOT(dentry)) {
1537 dentry->d_parent = target->d_parent;
1538 target->d_parent = target;
1539 INIT_LIST_HEAD(&target->d_u.d_child);
1541 do_switch(dentry->d_parent, target->d_parent);
1543 /* And add them back to the (new) parent lists */
1544 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
1547 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
1548 spin_unlock(&target->d_lock);
1549 fsnotify_d_move(dentry);
1550 spin_unlock(&dentry->d_lock);
1551 write_sequnlock(&rename_lock);
1555 * d_move - move a dentry
1556 * @dentry: entry to move
1557 * @target: new dentry
1559 * Update the dcache to reflect the move of a file name. Negative
1560 * dcache entries should not be moved in this way.
1563 void d_move(struct dentry * dentry, struct dentry * target)
1565 spin_lock(&dcache_lock);
1566 d_move_locked(dentry, target);
1567 spin_unlock(&dcache_lock);
1571 * Helper that returns 1 if p1 is a parent of p2, else 0
1573 static int d_isparent(struct dentry *p1, struct dentry *p2)
1577 for (p = p2; p->d_parent != p; p = p->d_parent) {
1578 if (p->d_parent == p1)
1585 * This helper attempts to cope with remotely renamed directories
1587 * It assumes that the caller is already holding
1588 * dentry->d_parent->d_inode->i_mutex and the dcache_lock
1590 * Note: If ever the locking in lock_rename() changes, then please
1591 * remember to update this too...
1593 * On return, dcache_lock will have been unlocked.
1595 static struct dentry *__d_unalias(struct dentry *dentry, struct dentry *alias)
1597 struct mutex *m1 = NULL, *m2 = NULL;
1600 /* If alias and dentry share a parent, then no extra locks required */
1601 if (alias->d_parent == dentry->d_parent)
1604 /* Check for loops */
1605 ret = ERR_PTR(-ELOOP);
1606 if (d_isparent(alias, dentry))
1609 /* See lock_rename() */
1610 ret = ERR_PTR(-EBUSY);
1611 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
1613 m1 = &dentry->d_sb->s_vfs_rename_mutex;
1614 if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
1616 m2 = &alias->d_parent->d_inode->i_mutex;
1618 d_move_locked(alias, dentry);
1621 spin_unlock(&dcache_lock);
1630 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
1631 * named dentry in place of the dentry to be replaced.
1633 static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
1635 struct dentry *dparent, *aparent;
1637 switch_names(dentry, anon);
1638 do_switch(dentry->d_name.len, anon->d_name.len);
1639 do_switch(dentry->d_name.hash, anon->d_name.hash);
1641 dparent = dentry->d_parent;
1642 aparent = anon->d_parent;
1644 dentry->d_parent = (aparent == anon) ? dentry : aparent;
1645 list_del(&dentry->d_u.d_child);
1646 if (!IS_ROOT(dentry))
1647 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
1649 INIT_LIST_HEAD(&dentry->d_u.d_child);
1651 anon->d_parent = (dparent == dentry) ? anon : dparent;
1652 list_del(&anon->d_u.d_child);
1654 list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
1656 INIT_LIST_HEAD(&anon->d_u.d_child);
1658 anon->d_flags &= ~DCACHE_DISCONNECTED;
1662 * d_materialise_unique - introduce an inode into the tree
1663 * @dentry: candidate dentry
1664 * @inode: inode to bind to the dentry, to which aliases may be attached
1666 * Introduces an dentry into the tree, substituting an extant disconnected
1667 * root directory alias in its place if there is one
1669 struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
1671 struct dentry *actual;
1673 BUG_ON(!d_unhashed(dentry));
1675 spin_lock(&dcache_lock);
1679 dentry->d_inode = NULL;
1683 if (S_ISDIR(inode->i_mode)) {
1684 struct dentry *alias;
1686 /* Does an aliased dentry already exist? */
1687 alias = __d_find_alias(inode, 0);
1690 /* Is this an anonymous mountpoint that we could splice
1692 if (IS_ROOT(alias)) {
1693 spin_lock(&alias->d_lock);
1694 __d_materialise_dentry(dentry, alias);
1698 /* Nope, but we must(!) avoid directory aliasing */
1699 actual = __d_unalias(dentry, alias);
1706 /* Add a unique reference */
1707 actual = __d_instantiate_unique(dentry, inode);
1710 else if (unlikely(!d_unhashed(actual)))
1711 goto shouldnt_be_hashed;
1714 spin_lock(&actual->d_lock);
1717 spin_unlock(&actual->d_lock);
1718 spin_unlock(&dcache_lock);
1720 if (actual == dentry) {
1721 security_d_instantiate(dentry, inode);
1729 spin_unlock(&dcache_lock);
1731 goto shouldnt_be_hashed;
1735 * d_path - return the path of a dentry
1736 * @dentry: dentry to report
1737 * @vfsmnt: vfsmnt to which the dentry belongs
1738 * @root: root dentry
1739 * @rootmnt: vfsmnt to which the root dentry belongs
1740 * @buffer: buffer to return value in
1741 * @buflen: buffer length
1743 * Convert a dentry into an ASCII path name. If the entry has been deleted
1744 * the string " (deleted)" is appended. Note that this is ambiguous.
1746 * Returns the buffer or an error code if the path was too long.
1748 * "buflen" should be positive. Caller holds the dcache_lock.
1750 static char * __d_path( struct dentry *dentry, struct vfsmount *vfsmnt,
1751 struct dentry *root, struct vfsmount *rootmnt,
1752 char *buffer, int buflen)
1754 char * end = buffer+buflen;
1760 if (!IS_ROOT(dentry) && d_unhashed(dentry)) {
1765 memcpy(end, " (deleted)", 10);
1775 struct dentry * parent;
1777 if (dentry == root && vfsmnt == rootmnt)
1779 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
1781 spin_lock(&vfsmount_lock);
1782 if (vfsmnt->mnt_parent == vfsmnt) {
1783 spin_unlock(&vfsmount_lock);
1786 dentry = vfsmnt->mnt_mountpoint;
1787 vfsmnt = vfsmnt->mnt_parent;
1788 spin_unlock(&vfsmount_lock);
1791 parent = dentry->d_parent;
1793 namelen = dentry->d_name.len;
1794 buflen -= namelen + 1;
1798 memcpy(end, dentry->d_name.name, namelen);
1807 namelen = dentry->d_name.len;
1811 retval -= namelen-1; /* hit the slash */
1812 memcpy(retval, dentry->d_name.name, namelen);
1815 return ERR_PTR(-ENAMETOOLONG);
1818 /* write full pathname into buffer and return start of pathname */
1819 char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
1820 char *buf, int buflen)
1823 struct vfsmount *rootmnt;
1824 struct dentry *root;
1826 read_lock(¤t->fs->lock);
1827 rootmnt = mntget(current->fs->rootmnt);
1828 root = dget(current->fs->root);
1829 read_unlock(¤t->fs->lock);
1830 spin_lock(&dcache_lock);
1831 res = __d_path(dentry, vfsmnt, root, rootmnt, buf, buflen);
1832 spin_unlock(&dcache_lock);
1839 * NOTE! The user-level library version returns a
1840 * character pointer. The kernel system call just
1841 * returns the length of the buffer filled (which
1842 * includes the ending '\0' character), or a negative
1843 * error value. So libc would do something like
1845 * char *getcwd(char * buf, size_t size)
1849 * retval = sys_getcwd(buf, size);
1856 asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
1859 struct vfsmount *pwdmnt, *rootmnt;
1860 struct dentry *pwd, *root;
1861 char *page = (char *) __get_free_page(GFP_USER);
1866 read_lock(¤t->fs->lock);
1867 pwdmnt = mntget(current->fs->pwdmnt);
1868 pwd = dget(current->fs->pwd);
1869 rootmnt = mntget(current->fs->rootmnt);
1870 root = dget(current->fs->root);
1871 read_unlock(¤t->fs->lock);
1874 /* Has the current directory has been unlinked? */
1875 spin_lock(&dcache_lock);
1876 if (pwd->d_parent == pwd || !d_unhashed(pwd)) {
1880 cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE);
1881 spin_unlock(&dcache_lock);
1883 error = PTR_ERR(cwd);
1888 len = PAGE_SIZE + page - cwd;
1891 if (copy_to_user(buf, cwd, len))
1895 spin_unlock(&dcache_lock);
1902 free_page((unsigned long) page);
1907 * Test whether new_dentry is a subdirectory of old_dentry.
1909 * Trivially implemented using the dcache structure
1913 * is_subdir - is new dentry a subdirectory of old_dentry
1914 * @new_dentry: new dentry
1915 * @old_dentry: old dentry
1917 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
1918 * Returns 0 otherwise.
1919 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
1922 int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
1925 struct dentry * saved = new_dentry;
1928 /* need rcu_readlock to protect against the d_parent trashing due to
1933 /* for restarting inner loop in case of seq retry */
1936 seq = read_seqbegin(&rename_lock);
1938 if (new_dentry != old_dentry) {
1939 struct dentry * parent = new_dentry->d_parent;
1940 if (parent == new_dentry)
1942 new_dentry = parent;
1948 } while (read_seqretry(&rename_lock, seq));
1954 void d_genocide(struct dentry *root)
1956 struct dentry *this_parent = root;
1957 struct list_head *next;
1959 spin_lock(&dcache_lock);
1961 next = this_parent->d_subdirs.next;
1963 while (next != &this_parent->d_subdirs) {
1964 struct list_head *tmp = next;
1965 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
1967 if (d_unhashed(dentry)||!dentry->d_inode)
1969 if (!list_empty(&dentry->d_subdirs)) {
1970 this_parent = dentry;
1973 atomic_dec(&dentry->d_count);
1975 if (this_parent != root) {
1976 next = this_parent->d_u.d_child.next;
1977 atomic_dec(&this_parent->d_count);
1978 this_parent = this_parent->d_parent;
1981 spin_unlock(&dcache_lock);
1985 * find_inode_number - check for dentry with name
1986 * @dir: directory to check
1987 * @name: Name to find.
1989 * Check whether a dentry already exists for the given name,
1990 * and return the inode number if it has an inode. Otherwise
1993 * This routine is used to post-process directory listings for
1994 * filesystems using synthetic inode numbers, and is necessary
1995 * to keep getcwd() working.
1998 ino_t find_inode_number(struct dentry *dir, struct qstr *name)
2000 struct dentry * dentry;
2003 dentry = d_hash_and_lookup(dir, name);
2005 if (dentry->d_inode)
2006 ino = dentry->d_inode->i_ino;
2012 static __initdata unsigned long dhash_entries;
2013 static int __init set_dhash_entries(char *str)
2017 dhash_entries = simple_strtoul(str, &str, 0);
2020 __setup("dhash_entries=", set_dhash_entries);
2022 static void __init dcache_init_early(void)
2026 /* If hashes are distributed across NUMA nodes, defer
2027 * hash allocation until vmalloc space is available.
2033 alloc_large_system_hash("Dentry cache",
2034 sizeof(struct hlist_head),
2042 for (loop = 0; loop < (1 << d_hash_shift); loop++)
2043 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
2046 static void __init dcache_init(unsigned long mempages)
2051 * A constructor could be added for stable state like the lists,
2052 * but it is probably not worth it because of the cache nature
2055 dentry_cache = kmem_cache_create("dentry_cache",
2056 sizeof(struct dentry),
2058 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
2062 set_shrinker(DEFAULT_SEEKS, shrink_dcache_memory);
2064 /* Hash may have been set up in dcache_init_early */
2069 alloc_large_system_hash("Dentry cache",
2070 sizeof(struct hlist_head),
2078 for (loop = 0; loop < (1 << d_hash_shift); loop++)
2079 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
2082 /* SLAB cache for __getname() consumers */
2083 struct kmem_cache *names_cachep __read_mostly;
2085 /* SLAB cache for file structures */
2086 struct kmem_cache *filp_cachep __read_mostly;
2088 EXPORT_SYMBOL(d_genocide);
2090 void __init vfs_caches_init_early(void)
2092 dcache_init_early();
2096 void __init vfs_caches_init(unsigned long mempages)
2098 unsigned long reserve;
2100 /* Base hash sizes on available memory, with a reserve equal to
2101 150% of current kernel size */
2103 reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
2104 mempages -= reserve;
2106 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
2107 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
2109 filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
2110 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
2112 dcache_init(mempages);
2113 inode_init(mempages);
2114 files_init(mempages);
2120 EXPORT_SYMBOL(d_alloc);
2121 EXPORT_SYMBOL(d_alloc_anon);
2122 EXPORT_SYMBOL(d_alloc_root);
2123 EXPORT_SYMBOL(d_delete);
2124 EXPORT_SYMBOL(d_find_alias);
2125 EXPORT_SYMBOL(d_instantiate);
2126 EXPORT_SYMBOL(d_invalidate);
2127 EXPORT_SYMBOL(d_lookup);
2128 EXPORT_SYMBOL(d_move);
2129 EXPORT_SYMBOL_GPL(d_materialise_unique);
2130 EXPORT_SYMBOL(d_path);
2131 EXPORT_SYMBOL(d_prune_aliases);
2132 EXPORT_SYMBOL(d_rehash);
2133 EXPORT_SYMBOL(d_splice_alias);
2134 EXPORT_SYMBOL(d_validate);
2135 EXPORT_SYMBOL(dget_locked);
2136 EXPORT_SYMBOL(dput);
2137 EXPORT_SYMBOL(find_inode_number);
2138 EXPORT_SYMBOL(have_submounts);
2139 EXPORT_SYMBOL(names_cachep);
2140 EXPORT_SYMBOL(shrink_dcache_parent);
2141 EXPORT_SYMBOL(shrink_dcache_sb);