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 kmem_cache_t *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_callback(struct rcu_head *head)
73 struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
75 if (dname_external(dentry))
76 kfree(dentry->d_name.name);
77 kmem_cache_free(dentry_cache, dentry);
81 * no dcache_lock, please. The caller must decrement dentry_stat.nr_dentry
84 static void d_free(struct dentry *dentry)
86 if (dentry->d_op && dentry->d_op->d_release)
87 dentry->d_op->d_release(dentry);
88 call_rcu(&dentry->d_u.d_rcu, d_callback);
92 * Release the dentry's inode, using the filesystem
93 * d_iput() operation if defined.
94 * Called with dcache_lock and per dentry lock held, drops both.
96 static void dentry_iput(struct dentry * dentry)
98 struct inode *inode = dentry->d_inode;
100 dentry->d_inode = NULL;
101 list_del_init(&dentry->d_alias);
102 spin_unlock(&dentry->d_lock);
103 spin_unlock(&dcache_lock);
105 fsnotify_inoderemove(inode);
106 if (dentry->d_op && dentry->d_op->d_iput)
107 dentry->d_op->d_iput(dentry, inode);
111 spin_unlock(&dentry->d_lock);
112 spin_unlock(&dcache_lock);
119 * This is complicated by the fact that we do not want to put
120 * dentries that are no longer on any hash chain on the unused
121 * list: we'd much rather just get rid of them immediately.
123 * However, that implies that we have to traverse the dentry
124 * tree upwards to the parents which might _also_ now be
125 * scheduled for deletion (it may have been only waiting for
126 * its last child to go away).
128 * This tail recursion is done by hand as we don't want to depend
129 * on the compiler to always get this right (gcc generally doesn't).
130 * Real recursion would eat up our stack space.
134 * dput - release a dentry
135 * @dentry: dentry to release
137 * Release a dentry. This will drop the usage count and if appropriate
138 * call the dentry unlink method as well as removing it from the queues and
139 * releasing its resources. If the parent dentries were scheduled for release
140 * they too may now get deleted.
142 * no dcache lock, please.
145 void dput(struct dentry *dentry)
151 if (atomic_read(&dentry->d_count) == 1)
153 if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
156 spin_lock(&dentry->d_lock);
157 if (atomic_read(&dentry->d_count)) {
158 spin_unlock(&dentry->d_lock);
159 spin_unlock(&dcache_lock);
164 * AV: ->d_delete() is _NOT_ allowed to block now.
166 if (dentry->d_op && dentry->d_op->d_delete) {
167 if (dentry->d_op->d_delete(dentry))
170 /* Unreachable? Get rid of it */
171 if (d_unhashed(dentry))
173 if (list_empty(&dentry->d_lru)) {
174 dentry->d_flags |= DCACHE_REFERENCED;
175 list_add(&dentry->d_lru, &dentry_unused);
176 dentry_stat.nr_unused++;
178 spin_unlock(&dentry->d_lock);
179 spin_unlock(&dcache_lock);
186 struct dentry *parent;
188 /* If dentry was on d_lru list
189 * delete it from there
191 if (!list_empty(&dentry->d_lru)) {
192 list_del(&dentry->d_lru);
193 dentry_stat.nr_unused--;
195 list_del(&dentry->d_u.d_child);
196 dentry_stat.nr_dentry--; /* For d_free, below */
197 /*drops the locks, at that point nobody can reach this dentry */
199 parent = dentry->d_parent;
201 if (dentry == parent)
209 * d_invalidate - invalidate a dentry
210 * @dentry: dentry to invalidate
212 * Try to invalidate the dentry if it turns out to be
213 * possible. If there are other dentries that can be
214 * reached through this one we can't delete it and we
215 * return -EBUSY. On success we return 0.
220 int d_invalidate(struct dentry * dentry)
223 * If it's already been dropped, return OK.
225 spin_lock(&dcache_lock);
226 if (d_unhashed(dentry)) {
227 spin_unlock(&dcache_lock);
231 * Check whether to do a partial shrink_dcache
232 * to get rid of unused child entries.
234 if (!list_empty(&dentry->d_subdirs)) {
235 spin_unlock(&dcache_lock);
236 shrink_dcache_parent(dentry);
237 spin_lock(&dcache_lock);
241 * Somebody else still using it?
243 * If it's a directory, we can't drop it
244 * for fear of somebody re-populating it
245 * with children (even though dropping it
246 * would make it unreachable from the root,
247 * we might still populate it if it was a
248 * working directory or similar).
250 spin_lock(&dentry->d_lock);
251 if (atomic_read(&dentry->d_count) > 1) {
252 if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
253 spin_unlock(&dentry->d_lock);
254 spin_unlock(&dcache_lock);
260 spin_unlock(&dentry->d_lock);
261 spin_unlock(&dcache_lock);
265 /* This should be called _only_ with dcache_lock held */
267 static inline struct dentry * __dget_locked(struct dentry *dentry)
269 atomic_inc(&dentry->d_count);
270 if (!list_empty(&dentry->d_lru)) {
271 dentry_stat.nr_unused--;
272 list_del_init(&dentry->d_lru);
277 struct dentry * dget_locked(struct dentry *dentry)
279 return __dget_locked(dentry);
283 * d_find_alias - grab a hashed alias of inode
284 * @inode: inode in question
285 * @want_discon: flag, used by d_splice_alias, to request
286 * that only a DISCONNECTED alias be returned.
288 * If inode has a hashed alias, or is a directory and has any alias,
289 * acquire the reference to alias and return it. Otherwise return NULL.
290 * Notice that if inode is a directory there can be only one alias and
291 * it can be unhashed only if it has no children, or if it is the root
294 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
295 * any other hashed alias over that one unless @want_discon is set,
296 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
299 static struct dentry * __d_find_alias(struct inode *inode, int want_discon)
301 struct list_head *head, *next, *tmp;
302 struct dentry *alias, *discon_alias=NULL;
304 head = &inode->i_dentry;
305 next = inode->i_dentry.next;
306 while (next != head) {
310 alias = list_entry(tmp, struct dentry, d_alias);
311 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
312 if (IS_ROOT(alias) &&
313 (alias->d_flags & DCACHE_DISCONNECTED))
314 discon_alias = alias;
315 else if (!want_discon) {
316 __dget_locked(alias);
322 __dget_locked(discon_alias);
326 struct dentry * d_find_alias(struct inode *inode)
328 struct dentry *de = NULL;
330 if (!list_empty(&inode->i_dentry)) {
331 spin_lock(&dcache_lock);
332 de = __d_find_alias(inode, 0);
333 spin_unlock(&dcache_lock);
339 * Try to kill dentries associated with this inode.
340 * WARNING: you must own a reference to inode.
342 void d_prune_aliases(struct inode *inode)
344 struct dentry *dentry;
346 spin_lock(&dcache_lock);
347 list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
348 spin_lock(&dentry->d_lock);
349 if (!atomic_read(&dentry->d_count)) {
350 __dget_locked(dentry);
352 spin_unlock(&dentry->d_lock);
353 spin_unlock(&dcache_lock);
357 spin_unlock(&dentry->d_lock);
359 spin_unlock(&dcache_lock);
363 * Throw away a dentry - free the inode, dput the parent. This requires that
364 * the LRU list has already been removed.
366 * Called with dcache_lock, drops it and then regains.
367 * Called with dentry->d_lock held, drops it.
369 static void prune_one_dentry(struct dentry * dentry)
371 struct dentry * parent;
374 list_del(&dentry->d_u.d_child);
375 dentry_stat.nr_dentry--; /* For d_free, below */
377 parent = dentry->d_parent;
379 if (parent != dentry)
381 spin_lock(&dcache_lock);
385 * prune_dcache - shrink the dcache
386 * @count: number of entries to try and free
387 * @sb: if given, ignore dentries for other superblocks
388 * which are being unmounted.
390 * Shrink the dcache. This is done when we need
391 * more memory, or simply when we need to unmount
392 * something (at which point we need to unuse
395 * This function may fail to free any resources if
396 * all the dentries are in use.
399 static void prune_dcache(int count, struct super_block *sb)
401 spin_lock(&dcache_lock);
402 for (; count ; count--) {
403 struct dentry *dentry;
404 struct list_head *tmp;
405 struct rw_semaphore *s_umount;
407 cond_resched_lock(&dcache_lock);
409 tmp = dentry_unused.prev;
411 /* Try to find a dentry for this sb, but don't try
412 * too hard, if they aren't near the tail they will
413 * be moved down again soon
416 while (skip && tmp != &dentry_unused &&
417 list_entry(tmp, struct dentry, d_lru)->d_sb != sb) {
422 if (tmp == &dentry_unused)
425 prefetch(dentry_unused.prev);
426 dentry_stat.nr_unused--;
427 dentry = list_entry(tmp, struct dentry, d_lru);
429 spin_lock(&dentry->d_lock);
431 * We found an inuse dentry which was not removed from
432 * dentry_unused because of laziness during lookup. Do not free
433 * it - just keep it off the dentry_unused list.
435 if (atomic_read(&dentry->d_count)) {
436 spin_unlock(&dentry->d_lock);
439 /* If the dentry was recently referenced, don't free it. */
440 if (dentry->d_flags & DCACHE_REFERENCED) {
441 dentry->d_flags &= ~DCACHE_REFERENCED;
442 list_add(&dentry->d_lru, &dentry_unused);
443 dentry_stat.nr_unused++;
444 spin_unlock(&dentry->d_lock);
448 * If the dentry is not DCACHED_REFERENCED, it is time
449 * to remove it from the dcache, provided the super block is
450 * NULL (which means we are trying to reclaim memory)
451 * or this dentry belongs to the same super block that
455 * If this dentry is for "my" filesystem, then I can prune it
456 * without taking the s_umount lock (I already hold it).
458 if (sb && dentry->d_sb == sb) {
459 prune_one_dentry(dentry);
463 * ...otherwise we need to be sure this filesystem isn't being
464 * unmounted, otherwise we could race with
465 * generic_shutdown_super(), and end up holding a reference to
466 * an inode while the filesystem is unmounted.
467 * So we try to get s_umount, and make sure s_root isn't NULL.
468 * (Take a local copy of s_umount to avoid a use-after-free of
471 s_umount = &dentry->d_sb->s_umount;
472 if (down_read_trylock(s_umount)) {
473 if (dentry->d_sb->s_root != NULL) {
474 prune_one_dentry(dentry);
480 spin_unlock(&dentry->d_lock);
482 * Insert dentry at the head of the list as inserting at the
483 * tail leads to a cycle.
485 list_add(&dentry->d_lru, &dentry_unused);
486 dentry_stat.nr_unused++;
488 spin_unlock(&dcache_lock);
492 * Shrink the dcache for the specified super block.
493 * This allows us to unmount a device without disturbing
494 * the dcache for the other devices.
496 * This implementation makes just two traversals of the
497 * unused list. On the first pass we move the selected
498 * dentries to the most recent end, and on the second
499 * pass we free them. The second pass must restart after
500 * each dput(), but since the target dentries are all at
501 * the end, it's really just a single traversal.
505 * shrink_dcache_sb - shrink dcache for a superblock
508 * Shrink the dcache for the specified super block. This
509 * is used to free the dcache before unmounting a file
513 void shrink_dcache_sb(struct super_block * sb)
515 struct list_head *tmp, *next;
516 struct dentry *dentry;
519 * Pass one ... move the dentries for the specified
520 * superblock to the most recent end of the unused list.
522 spin_lock(&dcache_lock);
523 list_for_each_safe(tmp, next, &dentry_unused) {
524 dentry = list_entry(tmp, struct dentry, d_lru);
525 if (dentry->d_sb != sb)
527 list_move(tmp, &dentry_unused);
531 * Pass two ... free the dentries for this superblock.
534 list_for_each_safe(tmp, next, &dentry_unused) {
535 dentry = list_entry(tmp, struct dentry, d_lru);
536 if (dentry->d_sb != sb)
538 dentry_stat.nr_unused--;
540 spin_lock(&dentry->d_lock);
541 if (atomic_read(&dentry->d_count)) {
542 spin_unlock(&dentry->d_lock);
545 prune_one_dentry(dentry);
546 cond_resched_lock(&dcache_lock);
549 spin_unlock(&dcache_lock);
553 * destroy a single subtree of dentries for unmount
554 * - see the comments on shrink_dcache_for_umount() for a description of the
557 static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
559 struct dentry *parent;
561 BUG_ON(!IS_ROOT(dentry));
563 /* detach this root from the system */
564 spin_lock(&dcache_lock);
565 if (!list_empty(&dentry->d_lru)) {
566 dentry_stat.nr_unused--;
567 list_del_init(&dentry->d_lru);
570 spin_unlock(&dcache_lock);
573 /* descend to the first leaf in the current subtree */
574 while (!list_empty(&dentry->d_subdirs)) {
577 /* this is a branch with children - detach all of them
578 * from the system in one go */
579 spin_lock(&dcache_lock);
580 list_for_each_entry(loop, &dentry->d_subdirs,
582 if (!list_empty(&loop->d_lru)) {
583 dentry_stat.nr_unused--;
584 list_del_init(&loop->d_lru);
588 cond_resched_lock(&dcache_lock);
590 spin_unlock(&dcache_lock);
592 /* move to the first child */
593 dentry = list_entry(dentry->d_subdirs.next,
594 struct dentry, d_u.d_child);
597 /* consume the dentries from this leaf up through its parents
598 * until we find one with children or run out altogether */
602 if (atomic_read(&dentry->d_count) != 0) {
604 "BUG: Dentry %p{i=%lx,n=%s}"
606 " [unmount of %s %s]\n",
609 dentry->d_inode->i_ino : 0UL,
611 atomic_read(&dentry->d_count),
612 dentry->d_sb->s_type->name,
617 parent = dentry->d_parent;
618 if (parent == dentry)
621 atomic_dec(&parent->d_count);
623 list_del(&dentry->d_u.d_child);
624 dentry_stat.nr_dentry--; /* For d_free, below */
626 inode = dentry->d_inode;
628 dentry->d_inode = NULL;
629 list_del_init(&dentry->d_alias);
630 if (dentry->d_op && dentry->d_op->d_iput)
631 dentry->d_op->d_iput(dentry, inode);
638 /* finished when we fall off the top of the tree,
639 * otherwise we ascend to the parent and move to the
640 * next sibling if there is one */
646 } while (list_empty(&dentry->d_subdirs));
648 dentry = list_entry(dentry->d_subdirs.next,
649 struct dentry, d_u.d_child);
654 * destroy the dentries attached to a superblock on unmounting
655 * - we don't need to use dentry->d_lock, and only need dcache_lock when
656 * removing the dentry from the system lists and hashes because:
657 * - the superblock is detached from all mountings and open files, so the
658 * dentry trees will not be rearranged by the VFS
659 * - s_umount is write-locked, so the memory pressure shrinker will ignore
660 * any dentries belonging to this superblock that it comes across
661 * - the filesystem itself is no longer permitted to rearrange the dentries
664 void shrink_dcache_for_umount(struct super_block *sb)
666 struct dentry *dentry;
668 if (down_read_trylock(&sb->s_umount))
673 atomic_dec(&dentry->d_count);
674 shrink_dcache_for_umount_subtree(dentry);
676 while (!hlist_empty(&sb->s_anon)) {
677 dentry = hlist_entry(sb->s_anon.first, struct dentry, d_hash);
678 shrink_dcache_for_umount_subtree(dentry);
683 * Search for at least 1 mount point in the dentry's subdirs.
684 * We descend to the next level whenever the d_subdirs
685 * list is non-empty and continue searching.
689 * have_submounts - check for mounts over a dentry
690 * @parent: dentry to check.
692 * Return true if the parent or its subdirectories contain
696 int have_submounts(struct dentry *parent)
698 struct dentry *this_parent = parent;
699 struct list_head *next;
701 spin_lock(&dcache_lock);
702 if (d_mountpoint(parent))
705 next = this_parent->d_subdirs.next;
707 while (next != &this_parent->d_subdirs) {
708 struct list_head *tmp = next;
709 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
711 /* Have we found a mount point ? */
712 if (d_mountpoint(dentry))
714 if (!list_empty(&dentry->d_subdirs)) {
715 this_parent = dentry;
720 * All done at this level ... ascend and resume the search.
722 if (this_parent != parent) {
723 next = this_parent->d_u.d_child.next;
724 this_parent = this_parent->d_parent;
727 spin_unlock(&dcache_lock);
728 return 0; /* No mount points found in tree */
730 spin_unlock(&dcache_lock);
735 * Search the dentry child list for the specified parent,
736 * and move any unused dentries to the end of the unused
737 * list for prune_dcache(). We descend to the next level
738 * whenever the d_subdirs list is non-empty and continue
741 * It returns zero iff there are no unused children,
742 * otherwise it returns the number of children moved to
743 * the end of the unused list. This may not be the total
744 * number of unused children, because select_parent can
745 * drop the lock and return early due to latency
748 static int select_parent(struct dentry * parent)
750 struct dentry *this_parent = parent;
751 struct list_head *next;
754 spin_lock(&dcache_lock);
756 next = this_parent->d_subdirs.next;
758 while (next != &this_parent->d_subdirs) {
759 struct list_head *tmp = next;
760 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
763 if (!list_empty(&dentry->d_lru)) {
764 dentry_stat.nr_unused--;
765 list_del_init(&dentry->d_lru);
768 * move only zero ref count dentries to the end
769 * of the unused list for prune_dcache
771 if (!atomic_read(&dentry->d_count)) {
772 list_add_tail(&dentry->d_lru, &dentry_unused);
773 dentry_stat.nr_unused++;
778 * We can return to the caller if we have found some (this
779 * ensures forward progress). We'll be coming back to find
782 if (found && need_resched())
786 * Descend a level if the d_subdirs list is non-empty.
788 if (!list_empty(&dentry->d_subdirs)) {
789 this_parent = dentry;
794 * All done at this level ... ascend and resume the search.
796 if (this_parent != parent) {
797 next = this_parent->d_u.d_child.next;
798 this_parent = this_parent->d_parent;
802 spin_unlock(&dcache_lock);
807 * shrink_dcache_parent - prune dcache
808 * @parent: parent of entries to prune
810 * Prune the dcache to remove unused children of the parent dentry.
813 void shrink_dcache_parent(struct dentry * parent)
817 while ((found = select_parent(parent)) != 0)
818 prune_dcache(found, parent->d_sb);
822 * Scan `nr' dentries and return the number which remain.
824 * We need to avoid reentering the filesystem if the caller is performing a
825 * GFP_NOFS allocation attempt. One example deadlock is:
827 * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
828 * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
829 * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
831 * In this case we return -1 to tell the caller that we baled.
833 static int shrink_dcache_memory(int nr, gfp_t gfp_mask)
836 if (!(gfp_mask & __GFP_FS))
838 prune_dcache(nr, NULL);
840 return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
844 * d_alloc - allocate a dcache entry
845 * @parent: parent of entry to allocate
846 * @name: qstr of the name
848 * Allocates a dentry. It returns %NULL if there is insufficient memory
849 * available. On a success the dentry is returned. The name passed in is
850 * copied and the copy passed in may be reused after this call.
853 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
855 struct dentry *dentry;
858 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
862 if (name->len > DNAME_INLINE_LEN-1) {
863 dname = kmalloc(name->len + 1, GFP_KERNEL);
865 kmem_cache_free(dentry_cache, dentry);
869 dname = dentry->d_iname;
871 dentry->d_name.name = dname;
873 dentry->d_name.len = name->len;
874 dentry->d_name.hash = name->hash;
875 memcpy(dname, name->name, name->len);
876 dname[name->len] = 0;
878 atomic_set(&dentry->d_count, 1);
879 dentry->d_flags = DCACHE_UNHASHED;
880 spin_lock_init(&dentry->d_lock);
881 dentry->d_inode = NULL;
882 dentry->d_parent = NULL;
885 dentry->d_fsdata = NULL;
886 dentry->d_mounted = 0;
887 #ifdef CONFIG_PROFILING
888 dentry->d_cookie = NULL;
890 INIT_HLIST_NODE(&dentry->d_hash);
891 INIT_LIST_HEAD(&dentry->d_lru);
892 INIT_LIST_HEAD(&dentry->d_subdirs);
893 INIT_LIST_HEAD(&dentry->d_alias);
896 dentry->d_parent = dget(parent);
897 dentry->d_sb = parent->d_sb;
899 INIT_LIST_HEAD(&dentry->d_u.d_child);
902 spin_lock(&dcache_lock);
904 list_add(&dentry->d_u.d_child, &parent->d_subdirs);
905 dentry_stat.nr_dentry++;
906 spin_unlock(&dcache_lock);
911 struct dentry *d_alloc_name(struct dentry *parent, const char *name)
916 q.len = strlen(name);
917 q.hash = full_name_hash(q.name, q.len);
918 return d_alloc(parent, &q);
922 * d_instantiate - fill in inode information for a dentry
923 * @entry: dentry to complete
924 * @inode: inode to attach to this dentry
926 * Fill in inode information in the entry.
928 * This turns negative dentries into productive full members
931 * NOTE! This assumes that the inode count has been incremented
932 * (or otherwise set) by the caller to indicate that it is now
933 * in use by the dcache.
936 void d_instantiate(struct dentry *entry, struct inode * inode)
938 BUG_ON(!list_empty(&entry->d_alias));
939 spin_lock(&dcache_lock);
941 list_add(&entry->d_alias, &inode->i_dentry);
942 entry->d_inode = inode;
943 fsnotify_d_instantiate(entry, inode);
944 spin_unlock(&dcache_lock);
945 security_d_instantiate(entry, inode);
949 * d_instantiate_unique - instantiate a non-aliased dentry
950 * @entry: dentry to instantiate
951 * @inode: inode to attach to this dentry
953 * Fill in inode information in the entry. On success, it returns NULL.
954 * If an unhashed alias of "entry" already exists, then we return the
955 * aliased dentry instead and drop one reference to inode.
957 * Note that in order to avoid conflicts with rename() etc, the caller
958 * had better be holding the parent directory semaphore.
960 * This also assumes that the inode count has been incremented
961 * (or otherwise set) by the caller to indicate that it is now
962 * in use by the dcache.
964 static struct dentry *__d_instantiate_unique(struct dentry *entry,
967 struct dentry *alias;
968 int len = entry->d_name.len;
969 const char *name = entry->d_name.name;
970 unsigned int hash = entry->d_name.hash;
973 entry->d_inode = NULL;
977 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
978 struct qstr *qstr = &alias->d_name;
980 if (qstr->hash != hash)
982 if (alias->d_parent != entry->d_parent)
984 if (qstr->len != len)
986 if (memcmp(qstr->name, name, len))
992 list_add(&entry->d_alias, &inode->i_dentry);
993 entry->d_inode = inode;
994 fsnotify_d_instantiate(entry, inode);
998 struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
1000 struct dentry *result;
1002 BUG_ON(!list_empty(&entry->d_alias));
1004 spin_lock(&dcache_lock);
1005 result = __d_instantiate_unique(entry, inode);
1006 spin_unlock(&dcache_lock);
1009 security_d_instantiate(entry, inode);
1013 BUG_ON(!d_unhashed(result));
1018 EXPORT_SYMBOL(d_instantiate_unique);
1021 * d_alloc_root - allocate root dentry
1022 * @root_inode: inode to allocate the root for
1024 * Allocate a root ("/") dentry for the inode given. The inode is
1025 * instantiated and returned. %NULL is returned if there is insufficient
1026 * memory or the inode passed is %NULL.
1029 struct dentry * d_alloc_root(struct inode * root_inode)
1031 struct dentry *res = NULL;
1034 static const struct qstr name = { .name = "/", .len = 1 };
1036 res = d_alloc(NULL, &name);
1038 res->d_sb = root_inode->i_sb;
1039 res->d_parent = res;
1040 d_instantiate(res, root_inode);
1046 static inline struct hlist_head *d_hash(struct dentry *parent,
1049 hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
1050 hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
1051 return dentry_hashtable + (hash & D_HASHMASK);
1055 * d_alloc_anon - allocate an anonymous dentry
1056 * @inode: inode to allocate the dentry for
1058 * This is similar to d_alloc_root. It is used by filesystems when
1059 * creating a dentry for a given inode, often in the process of
1060 * mapping a filehandle to a dentry. The returned dentry may be
1061 * anonymous, or may have a full name (if the inode was already
1062 * in the cache). The file system may need to make further
1063 * efforts to connect this dentry into the dcache properly.
1065 * When called on a directory inode, we must ensure that
1066 * the inode only ever has one dentry. If a dentry is
1067 * found, that is returned instead of allocating a new one.
1069 * On successful return, the reference to the inode has been transferred
1070 * to the dentry. If %NULL is returned (indicating kmalloc failure),
1071 * the reference on the inode has not been released.
1074 struct dentry * d_alloc_anon(struct inode *inode)
1076 static const struct qstr anonstring = { .name = "" };
1080 if ((res = d_find_alias(inode))) {
1085 tmp = d_alloc(NULL, &anonstring);
1089 tmp->d_parent = tmp; /* make sure dput doesn't croak */
1091 spin_lock(&dcache_lock);
1092 res = __d_find_alias(inode, 0);
1094 /* attach a disconnected dentry */
1097 spin_lock(&res->d_lock);
1098 res->d_sb = inode->i_sb;
1099 res->d_parent = res;
1100 res->d_inode = inode;
1101 res->d_flags |= DCACHE_DISCONNECTED;
1102 res->d_flags &= ~DCACHE_UNHASHED;
1103 list_add(&res->d_alias, &inode->i_dentry);
1104 hlist_add_head(&res->d_hash, &inode->i_sb->s_anon);
1105 spin_unlock(&res->d_lock);
1107 inode = NULL; /* don't drop reference */
1109 spin_unlock(&dcache_lock);
1120 * d_splice_alias - splice a disconnected dentry into the tree if one exists
1121 * @inode: the inode which may have a disconnected dentry
1122 * @dentry: a negative dentry which we want to point to the inode.
1124 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1125 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1126 * and return it, else simply d_add the inode to the dentry and return NULL.
1128 * This is needed in the lookup routine of any filesystem that is exportable
1129 * (via knfsd) so that we can build dcache paths to directories effectively.
1131 * If a dentry was found and moved, then it is returned. Otherwise NULL
1132 * is returned. This matches the expected return value of ->lookup.
1135 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
1137 struct dentry *new = NULL;
1139 if (inode && S_ISDIR(inode->i_mode)) {
1140 spin_lock(&dcache_lock);
1141 new = __d_find_alias(inode, 1);
1143 BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
1144 fsnotify_d_instantiate(new, inode);
1145 spin_unlock(&dcache_lock);
1146 security_d_instantiate(new, inode);
1148 d_move(new, dentry);
1151 /* d_instantiate takes dcache_lock, so we do it by hand */
1152 list_add(&dentry->d_alias, &inode->i_dentry);
1153 dentry->d_inode = inode;
1154 fsnotify_d_instantiate(dentry, inode);
1155 spin_unlock(&dcache_lock);
1156 security_d_instantiate(dentry, inode);
1160 d_add(dentry, inode);
1166 * d_lookup - search for a dentry
1167 * @parent: parent dentry
1168 * @name: qstr of name we wish to find
1170 * Searches the children of the parent dentry for the name in question. If
1171 * the dentry is found its reference count is incremented and the dentry
1172 * is returned. The caller must use d_put to free the entry when it has
1173 * finished using it. %NULL is returned on failure.
1175 * __d_lookup is dcache_lock free. The hash list is protected using RCU.
1176 * Memory barriers are used while updating and doing lockless traversal.
1177 * To avoid races with d_move while rename is happening, d_lock is used.
1179 * Overflows in memcmp(), while d_move, are avoided by keeping the length
1180 * and name pointer in one structure pointed by d_qstr.
1182 * rcu_read_lock() and rcu_read_unlock() are used to disable preemption while
1183 * lookup is going on.
1185 * dentry_unused list is not updated even if lookup finds the required dentry
1186 * in there. It is updated in places such as prune_dcache, shrink_dcache_sb,
1187 * select_parent and __dget_locked. This laziness saves lookup from dcache_lock
1190 * d_lookup() is protected against the concurrent renames in some unrelated
1191 * directory using the seqlockt_t rename_lock.
1194 struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
1196 struct dentry * dentry = NULL;
1200 seq = read_seqbegin(&rename_lock);
1201 dentry = __d_lookup(parent, name);
1204 } while (read_seqretry(&rename_lock, seq));
1208 struct dentry * __d_lookup(struct dentry * parent, struct qstr * name)
1210 unsigned int len = name->len;
1211 unsigned int hash = name->hash;
1212 const unsigned char *str = name->name;
1213 struct hlist_head *head = d_hash(parent,hash);
1214 struct dentry *found = NULL;
1215 struct hlist_node *node;
1216 struct dentry *dentry;
1220 hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
1223 if (dentry->d_name.hash != hash)
1225 if (dentry->d_parent != parent)
1228 spin_lock(&dentry->d_lock);
1231 * Recheck the dentry after taking the lock - d_move may have
1232 * changed things. Don't bother checking the hash because we're
1233 * about to compare the whole name anyway.
1235 if (dentry->d_parent != parent)
1239 * It is safe to compare names since d_move() cannot
1240 * change the qstr (protected by d_lock).
1242 qstr = &dentry->d_name;
1243 if (parent->d_op && parent->d_op->d_compare) {
1244 if (parent->d_op->d_compare(parent, qstr, name))
1247 if (qstr->len != len)
1249 if (memcmp(qstr->name, str, len))
1253 if (!d_unhashed(dentry)) {
1254 atomic_inc(&dentry->d_count);
1257 spin_unlock(&dentry->d_lock);
1260 spin_unlock(&dentry->d_lock);
1268 * d_hash_and_lookup - hash the qstr then search for a dentry
1269 * @dir: Directory to search in
1270 * @name: qstr of name we wish to find
1272 * On hash failure or on lookup failure NULL is returned.
1274 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
1276 struct dentry *dentry = NULL;
1279 * Check for a fs-specific hash function. Note that we must
1280 * calculate the standard hash first, as the d_op->d_hash()
1281 * routine may choose to leave the hash value unchanged.
1283 name->hash = full_name_hash(name->name, name->len);
1284 if (dir->d_op && dir->d_op->d_hash) {
1285 if (dir->d_op->d_hash(dir, name) < 0)
1288 dentry = d_lookup(dir, name);
1294 * d_validate - verify dentry provided from insecure source
1295 * @dentry: The dentry alleged to be valid child of @dparent
1296 * @dparent: The parent dentry (known to be valid)
1297 * @hash: Hash of the dentry
1298 * @len: Length of the name
1300 * An insecure source has sent us a dentry, here we verify it and dget() it.
1301 * This is used by ncpfs in its readdir implementation.
1302 * Zero is returned in the dentry is invalid.
1305 int d_validate(struct dentry *dentry, struct dentry *dparent)
1307 struct hlist_head *base;
1308 struct hlist_node *lhp;
1310 /* Check whether the ptr might be valid at all.. */
1311 if (!kmem_ptr_validate(dentry_cache, dentry))
1314 if (dentry->d_parent != dparent)
1317 spin_lock(&dcache_lock);
1318 base = d_hash(dparent, dentry->d_name.hash);
1319 hlist_for_each(lhp,base) {
1320 /* hlist_for_each_entry_rcu() not required for d_hash list
1321 * as it is parsed under dcache_lock
1323 if (dentry == hlist_entry(lhp, struct dentry, d_hash)) {
1324 __dget_locked(dentry);
1325 spin_unlock(&dcache_lock);
1329 spin_unlock(&dcache_lock);
1335 * When a file is deleted, we have two options:
1336 * - turn this dentry into a negative dentry
1337 * - unhash this dentry and free it.
1339 * Usually, we want to just turn this into
1340 * a negative dentry, but if anybody else is
1341 * currently using the dentry or the inode
1342 * we can't do that and we fall back on removing
1343 * it from the hash queues and waiting for
1344 * it to be deleted later when it has no users
1348 * d_delete - delete a dentry
1349 * @dentry: The dentry to delete
1351 * Turn the dentry into a negative dentry if possible, otherwise
1352 * remove it from the hash queues so it can be deleted later
1355 void d_delete(struct dentry * dentry)
1359 * Are we the only user?
1361 spin_lock(&dcache_lock);
1362 spin_lock(&dentry->d_lock);
1363 isdir = S_ISDIR(dentry->d_inode->i_mode);
1364 if (atomic_read(&dentry->d_count) == 1) {
1365 dentry_iput(dentry);
1366 fsnotify_nameremove(dentry, isdir);
1368 /* remove this and other inotify debug checks after 2.6.18 */
1369 dentry->d_flags &= ~DCACHE_INOTIFY_PARENT_WATCHED;
1373 if (!d_unhashed(dentry))
1376 spin_unlock(&dentry->d_lock);
1377 spin_unlock(&dcache_lock);
1379 fsnotify_nameremove(dentry, isdir);
1382 static void __d_rehash(struct dentry * entry, struct hlist_head *list)
1385 entry->d_flags &= ~DCACHE_UNHASHED;
1386 hlist_add_head_rcu(&entry->d_hash, list);
1389 static void _d_rehash(struct dentry * entry)
1391 __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
1395 * d_rehash - add an entry back to the hash
1396 * @entry: dentry to add to the hash
1398 * Adds a dentry to the hash according to its name.
1401 void d_rehash(struct dentry * entry)
1403 spin_lock(&dcache_lock);
1404 spin_lock(&entry->d_lock);
1406 spin_unlock(&entry->d_lock);
1407 spin_unlock(&dcache_lock);
1410 #define do_switch(x,y) do { \
1411 __typeof__ (x) __tmp = x; \
1412 x = y; y = __tmp; } while (0)
1415 * When switching names, the actual string doesn't strictly have to
1416 * be preserved in the target - because we're dropping the target
1417 * anyway. As such, we can just do a simple memcpy() to copy over
1418 * the new name before we switch.
1420 * Note that we have to be a lot more careful about getting the hash
1421 * switched - we have to switch the hash value properly even if it
1422 * then no longer matches the actual (corrupted) string of the target.
1423 * The hash value has to match the hash queue that the dentry is on..
1425 static void switch_names(struct dentry *dentry, struct dentry *target)
1427 if (dname_external(target)) {
1428 if (dname_external(dentry)) {
1430 * Both external: swap the pointers
1432 do_switch(target->d_name.name, dentry->d_name.name);
1435 * dentry:internal, target:external. Steal target's
1436 * storage and make target internal.
1438 dentry->d_name.name = target->d_name.name;
1439 target->d_name.name = target->d_iname;
1442 if (dname_external(dentry)) {
1444 * dentry:external, target:internal. Give dentry's
1445 * storage to target and make dentry internal
1447 memcpy(dentry->d_iname, target->d_name.name,
1448 target->d_name.len + 1);
1449 target->d_name.name = dentry->d_name.name;
1450 dentry->d_name.name = dentry->d_iname;
1453 * Both are internal. Just copy target to dentry
1455 memcpy(dentry->d_iname, target->d_name.name,
1456 target->d_name.len + 1);
1462 * We cannibalize "target" when moving dentry on top of it,
1463 * because it's going to be thrown away anyway. We could be more
1464 * polite about it, though.
1466 * This forceful removal will result in ugly /proc output if
1467 * somebody holds a file open that got deleted due to a rename.
1468 * We could be nicer about the deleted file, and let it show
1469 * up under the name it got deleted rather than the name that
1474 * d_move_locked - move a dentry
1475 * @dentry: entry to move
1476 * @target: new dentry
1478 * Update the dcache to reflect the move of a file name. Negative
1479 * dcache entries should not be moved in this way.
1481 static void d_move_locked(struct dentry * dentry, struct dentry * target)
1483 struct hlist_head *list;
1485 if (!dentry->d_inode)
1486 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
1488 write_seqlock(&rename_lock);
1490 * XXXX: do we really need to take target->d_lock?
1492 if (target < dentry) {
1493 spin_lock(&target->d_lock);
1494 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1496 spin_lock(&dentry->d_lock);
1497 spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
1500 /* Move the dentry to the target hash queue, if on different bucket */
1501 if (dentry->d_flags & DCACHE_UNHASHED)
1502 goto already_unhashed;
1504 hlist_del_rcu(&dentry->d_hash);
1507 list = d_hash(target->d_parent, target->d_name.hash);
1508 __d_rehash(dentry, list);
1510 /* Unhash the target: dput() will then get rid of it */
1513 list_del(&dentry->d_u.d_child);
1514 list_del(&target->d_u.d_child);
1516 /* Switch the names.. */
1517 switch_names(dentry, target);
1518 do_switch(dentry->d_name.len, target->d_name.len);
1519 do_switch(dentry->d_name.hash, target->d_name.hash);
1521 /* ... and switch the parents */
1522 if (IS_ROOT(dentry)) {
1523 dentry->d_parent = target->d_parent;
1524 target->d_parent = target;
1525 INIT_LIST_HEAD(&target->d_u.d_child);
1527 do_switch(dentry->d_parent, target->d_parent);
1529 /* And add them back to the (new) parent lists */
1530 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
1533 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
1534 spin_unlock(&target->d_lock);
1535 fsnotify_d_move(dentry);
1536 spin_unlock(&dentry->d_lock);
1537 write_sequnlock(&rename_lock);
1541 * d_move - move a dentry
1542 * @dentry: entry to move
1543 * @target: new dentry
1545 * Update the dcache to reflect the move of a file name. Negative
1546 * dcache entries should not be moved in this way.
1549 void d_move(struct dentry * dentry, struct dentry * target)
1551 spin_lock(&dcache_lock);
1552 d_move_locked(dentry, target);
1553 spin_unlock(&dcache_lock);
1557 * Helper that returns 1 if p1 is a parent of p2, else 0
1559 static int d_isparent(struct dentry *p1, struct dentry *p2)
1563 for (p = p2; p->d_parent != p; p = p->d_parent) {
1564 if (p->d_parent == p1)
1571 * This helper attempts to cope with remotely renamed directories
1573 * It assumes that the caller is already holding
1574 * dentry->d_parent->d_inode->i_mutex and the dcache_lock
1576 * Note: If ever the locking in lock_rename() changes, then please
1577 * remember to update this too...
1579 * On return, dcache_lock will have been unlocked.
1581 static struct dentry *__d_unalias(struct dentry *dentry, struct dentry *alias)
1583 struct mutex *m1 = NULL, *m2 = NULL;
1586 /* If alias and dentry share a parent, then no extra locks required */
1587 if (alias->d_parent == dentry->d_parent)
1590 /* Check for loops */
1591 ret = ERR_PTR(-ELOOP);
1592 if (d_isparent(alias, dentry))
1595 /* See lock_rename() */
1596 ret = ERR_PTR(-EBUSY);
1597 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
1599 m1 = &dentry->d_sb->s_vfs_rename_mutex;
1600 if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
1602 m2 = &alias->d_parent->d_inode->i_mutex;
1604 d_move_locked(alias, dentry);
1607 spin_unlock(&dcache_lock);
1616 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
1617 * named dentry in place of the dentry to be replaced.
1619 static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
1621 struct dentry *dparent, *aparent;
1623 switch_names(dentry, anon);
1624 do_switch(dentry->d_name.len, anon->d_name.len);
1625 do_switch(dentry->d_name.hash, anon->d_name.hash);
1627 dparent = dentry->d_parent;
1628 aparent = anon->d_parent;
1630 dentry->d_parent = (aparent == anon) ? dentry : aparent;
1631 list_del(&dentry->d_u.d_child);
1632 if (!IS_ROOT(dentry))
1633 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
1635 INIT_LIST_HEAD(&dentry->d_u.d_child);
1637 anon->d_parent = (dparent == dentry) ? anon : dparent;
1638 list_del(&anon->d_u.d_child);
1640 list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
1642 INIT_LIST_HEAD(&anon->d_u.d_child);
1644 anon->d_flags &= ~DCACHE_DISCONNECTED;
1648 * d_materialise_unique - introduce an inode into the tree
1649 * @dentry: candidate dentry
1650 * @inode: inode to bind to the dentry, to which aliases may be attached
1652 * Introduces an dentry into the tree, substituting an extant disconnected
1653 * root directory alias in its place if there is one
1655 struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
1657 struct dentry *actual;
1659 BUG_ON(!d_unhashed(dentry));
1661 spin_lock(&dcache_lock);
1665 dentry->d_inode = NULL;
1669 if (S_ISDIR(inode->i_mode)) {
1670 struct dentry *alias;
1672 /* Does an aliased dentry already exist? */
1673 alias = __d_find_alias(inode, 0);
1676 /* Is this an anonymous mountpoint that we could splice
1678 if (IS_ROOT(alias)) {
1679 spin_lock(&alias->d_lock);
1680 __d_materialise_dentry(dentry, alias);
1684 /* Nope, but we must(!) avoid directory aliasing */
1685 actual = __d_unalias(dentry, alias);
1692 /* Add a unique reference */
1693 actual = __d_instantiate_unique(dentry, inode);
1696 else if (unlikely(!d_unhashed(actual)))
1697 goto shouldnt_be_hashed;
1700 spin_lock(&actual->d_lock);
1703 spin_unlock(&actual->d_lock);
1704 spin_unlock(&dcache_lock);
1706 if (actual == dentry) {
1707 security_d_instantiate(dentry, inode);
1715 spin_unlock(&dcache_lock);
1717 goto shouldnt_be_hashed;
1721 * d_path - return the path of a dentry
1722 * @dentry: dentry to report
1723 * @vfsmnt: vfsmnt to which the dentry belongs
1724 * @root: root dentry
1725 * @rootmnt: vfsmnt to which the root dentry belongs
1726 * @buffer: buffer to return value in
1727 * @buflen: buffer length
1729 * Convert a dentry into an ASCII path name. If the entry has been deleted
1730 * the string " (deleted)" is appended. Note that this is ambiguous.
1732 * Returns the buffer or an error code if the path was too long.
1734 * "buflen" should be positive. Caller holds the dcache_lock.
1736 static char * __d_path( struct dentry *dentry, struct vfsmount *vfsmnt,
1737 struct dentry *root, struct vfsmount *rootmnt,
1738 char *buffer, int buflen)
1740 char * end = buffer+buflen;
1746 if (!IS_ROOT(dentry) && d_unhashed(dentry)) {
1751 memcpy(end, " (deleted)", 10);
1761 struct dentry * parent;
1763 if (dentry == root && vfsmnt == rootmnt)
1765 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
1767 spin_lock(&vfsmount_lock);
1768 if (vfsmnt->mnt_parent == vfsmnt) {
1769 spin_unlock(&vfsmount_lock);
1772 dentry = vfsmnt->mnt_mountpoint;
1773 vfsmnt = vfsmnt->mnt_parent;
1774 spin_unlock(&vfsmount_lock);
1777 parent = dentry->d_parent;
1779 namelen = dentry->d_name.len;
1780 buflen -= namelen + 1;
1784 memcpy(end, dentry->d_name.name, namelen);
1793 namelen = dentry->d_name.len;
1797 retval -= namelen-1; /* hit the slash */
1798 memcpy(retval, dentry->d_name.name, namelen);
1801 return ERR_PTR(-ENAMETOOLONG);
1804 /* write full pathname into buffer and return start of pathname */
1805 char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
1806 char *buf, int buflen)
1809 struct vfsmount *rootmnt;
1810 struct dentry *root;
1812 read_lock(¤t->fs->lock);
1813 rootmnt = mntget(current->fs->rootmnt);
1814 root = dget(current->fs->root);
1815 read_unlock(¤t->fs->lock);
1816 spin_lock(&dcache_lock);
1817 res = __d_path(dentry, vfsmnt, root, rootmnt, buf, buflen);
1818 spin_unlock(&dcache_lock);
1825 * NOTE! The user-level library version returns a
1826 * character pointer. The kernel system call just
1827 * returns the length of the buffer filled (which
1828 * includes the ending '\0' character), or a negative
1829 * error value. So libc would do something like
1831 * char *getcwd(char * buf, size_t size)
1835 * retval = sys_getcwd(buf, size);
1842 asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
1845 struct vfsmount *pwdmnt, *rootmnt;
1846 struct dentry *pwd, *root;
1847 char *page = (char *) __get_free_page(GFP_USER);
1852 read_lock(¤t->fs->lock);
1853 pwdmnt = mntget(current->fs->pwdmnt);
1854 pwd = dget(current->fs->pwd);
1855 rootmnt = mntget(current->fs->rootmnt);
1856 root = dget(current->fs->root);
1857 read_unlock(¤t->fs->lock);
1860 /* Has the current directory has been unlinked? */
1861 spin_lock(&dcache_lock);
1862 if (pwd->d_parent == pwd || !d_unhashed(pwd)) {
1866 cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE);
1867 spin_unlock(&dcache_lock);
1869 error = PTR_ERR(cwd);
1874 len = PAGE_SIZE + page - cwd;
1877 if (copy_to_user(buf, cwd, len))
1881 spin_unlock(&dcache_lock);
1888 free_page((unsigned long) page);
1893 * Test whether new_dentry is a subdirectory of old_dentry.
1895 * Trivially implemented using the dcache structure
1899 * is_subdir - is new dentry a subdirectory of old_dentry
1900 * @new_dentry: new dentry
1901 * @old_dentry: old dentry
1903 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
1904 * Returns 0 otherwise.
1905 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
1908 int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
1911 struct dentry * saved = new_dentry;
1914 /* need rcu_readlock to protect against the d_parent trashing due to
1919 /* for restarting inner loop in case of seq retry */
1922 seq = read_seqbegin(&rename_lock);
1924 if (new_dentry != old_dentry) {
1925 struct dentry * parent = new_dentry->d_parent;
1926 if (parent == new_dentry)
1928 new_dentry = parent;
1934 } while (read_seqretry(&rename_lock, seq));
1940 void d_genocide(struct dentry *root)
1942 struct dentry *this_parent = root;
1943 struct list_head *next;
1945 spin_lock(&dcache_lock);
1947 next = this_parent->d_subdirs.next;
1949 while (next != &this_parent->d_subdirs) {
1950 struct list_head *tmp = next;
1951 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
1953 if (d_unhashed(dentry)||!dentry->d_inode)
1955 if (!list_empty(&dentry->d_subdirs)) {
1956 this_parent = dentry;
1959 atomic_dec(&dentry->d_count);
1961 if (this_parent != root) {
1962 next = this_parent->d_u.d_child.next;
1963 atomic_dec(&this_parent->d_count);
1964 this_parent = this_parent->d_parent;
1967 spin_unlock(&dcache_lock);
1971 * find_inode_number - check for dentry with name
1972 * @dir: directory to check
1973 * @name: Name to find.
1975 * Check whether a dentry already exists for the given name,
1976 * and return the inode number if it has an inode. Otherwise
1979 * This routine is used to post-process directory listings for
1980 * filesystems using synthetic inode numbers, and is necessary
1981 * to keep getcwd() working.
1984 ino_t find_inode_number(struct dentry *dir, struct qstr *name)
1986 struct dentry * dentry;
1989 dentry = d_hash_and_lookup(dir, name);
1991 if (dentry->d_inode)
1992 ino = dentry->d_inode->i_ino;
1998 static __initdata unsigned long dhash_entries;
1999 static int __init set_dhash_entries(char *str)
2003 dhash_entries = simple_strtoul(str, &str, 0);
2006 __setup("dhash_entries=", set_dhash_entries);
2008 static void __init dcache_init_early(void)
2012 /* If hashes are distributed across NUMA nodes, defer
2013 * hash allocation until vmalloc space is available.
2019 alloc_large_system_hash("Dentry cache",
2020 sizeof(struct hlist_head),
2028 for (loop = 0; loop < (1 << d_hash_shift); loop++)
2029 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
2032 static void __init dcache_init(unsigned long mempages)
2037 * A constructor could be added for stable state like the lists,
2038 * but it is probably not worth it because of the cache nature
2041 dentry_cache = kmem_cache_create("dentry_cache",
2042 sizeof(struct dentry),
2044 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
2048 set_shrinker(DEFAULT_SEEKS, shrink_dcache_memory);
2050 /* Hash may have been set up in dcache_init_early */
2055 alloc_large_system_hash("Dentry cache",
2056 sizeof(struct hlist_head),
2064 for (loop = 0; loop < (1 << d_hash_shift); loop++)
2065 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
2068 /* SLAB cache for __getname() consumers */
2069 kmem_cache_t *names_cachep __read_mostly;
2071 /* SLAB cache for file structures */
2072 kmem_cache_t *filp_cachep __read_mostly;
2074 EXPORT_SYMBOL(d_genocide);
2076 void __init vfs_caches_init_early(void)
2078 dcache_init_early();
2082 void __init vfs_caches_init(unsigned long mempages)
2084 unsigned long reserve;
2086 /* Base hash sizes on available memory, with a reserve equal to
2087 150% of current kernel size */
2089 reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
2090 mempages -= reserve;
2092 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
2093 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
2095 filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
2096 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
2098 dcache_init(mempages);
2099 inode_init(mempages);
2100 files_init(mempages);
2106 EXPORT_SYMBOL(d_alloc);
2107 EXPORT_SYMBOL(d_alloc_anon);
2108 EXPORT_SYMBOL(d_alloc_root);
2109 EXPORT_SYMBOL(d_delete);
2110 EXPORT_SYMBOL(d_find_alias);
2111 EXPORT_SYMBOL(d_instantiate);
2112 EXPORT_SYMBOL(d_invalidate);
2113 EXPORT_SYMBOL(d_lookup);
2114 EXPORT_SYMBOL(d_move);
2115 EXPORT_SYMBOL_GPL(d_materialise_unique);
2116 EXPORT_SYMBOL(d_path);
2117 EXPORT_SYMBOL(d_prune_aliases);
2118 EXPORT_SYMBOL(d_rehash);
2119 EXPORT_SYMBOL(d_splice_alias);
2120 EXPORT_SYMBOL(d_validate);
2121 EXPORT_SYMBOL(dget_locked);
2122 EXPORT_SYMBOL(dput);
2123 EXPORT_SYMBOL(find_inode_number);
2124 EXPORT_SYMBOL(have_submounts);
2125 EXPORT_SYMBOL(names_cachep);
2126 EXPORT_SYMBOL(shrink_dcache_parent);
2127 EXPORT_SYMBOL(shrink_dcache_sb);