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/hash.h>
25 #include <linux/cache.h>
26 #include <linux/module.h>
27 #include <linux/mount.h>
28 #include <linux/file.h>
29 #include <asm/uaccess.h>
30 #include <linux/security.h>
31 #include <linux/seqlock.h>
32 #include <linux/swap.h>
33 #include <linux/bootmem.h>
34 #include <linux/fs_struct.h>
35 #include <linux/hardirq.h>
36 #include <linux/bit_spinlock.h>
37 #include <linux/rculist_bl.h>
38 #include <linux/prefetch.h>
39 #include <linux/ratelimit.h>
44 * dcache->d_inode->i_lock protects:
45 * - i_dentry, d_alias, d_inode of aliases
46 * dcache_hash_bucket lock protects:
47 * - the dcache hash table
48 * s_anon bl list spinlock protects:
49 * - the s_anon list (see __d_drop)
50 * dcache_lru_lock protects:
51 * - the dcache lru lists and counters
58 * - d_parent and d_subdirs
59 * - childrens' d_child and d_parent
63 * dentry->d_inode->i_lock
66 * dcache_hash_bucket lock
69 * If there is an ancestor relationship:
70 * dentry->d_parent->...->d_parent->d_lock
72 * dentry->d_parent->d_lock
75 * If no ancestor relationship:
76 * if (dentry1 < dentry2)
80 int sysctl_vfs_cache_pressure __read_mostly = 100;
81 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
83 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
84 __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
86 EXPORT_SYMBOL(rename_lock);
88 static struct kmem_cache *dentry_cache __read_mostly;
91 * This is the single most critical data structure when it comes
92 * to the dcache: the hashtable for lookups. Somebody should try
93 * to make this good - I've just made it work.
95 * This hash-function tries to avoid losing too many bits of hash
96 * information, yet avoid using a prime hash-size or similar.
98 #define D_HASHBITS d_hash_shift
99 #define D_HASHMASK d_hash_mask
101 static unsigned int d_hash_mask __read_mostly;
102 static unsigned int d_hash_shift __read_mostly;
104 static struct hlist_bl_head *dentry_hashtable __read_mostly;
106 static inline struct hlist_bl_head *d_hash(struct dentry *parent,
109 hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
110 hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
111 return dentry_hashtable + (hash & D_HASHMASK);
114 /* Statistics gathering. */
115 struct dentry_stat_t dentry_stat = {
119 static DEFINE_PER_CPU(unsigned int, nr_dentry);
121 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
122 static int get_nr_dentry(void)
126 for_each_possible_cpu(i)
127 sum += per_cpu(nr_dentry, i);
128 return sum < 0 ? 0 : sum;
131 int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
132 size_t *lenp, loff_t *ppos)
134 dentry_stat.nr_dentry = get_nr_dentry();
135 return proc_dointvec(table, write, buffer, lenp, ppos);
139 static void __d_free(struct rcu_head *head)
141 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
143 WARN_ON(!list_empty(&dentry->d_alias));
144 if (dname_external(dentry))
145 kfree(dentry->d_name.name);
146 kmem_cache_free(dentry_cache, dentry);
152 static void d_free(struct dentry *dentry)
154 BUG_ON(dentry->d_count);
155 this_cpu_dec(nr_dentry);
156 if (dentry->d_op && dentry->d_op->d_release)
157 dentry->d_op->d_release(dentry);
159 /* if dentry was never visible to RCU, immediate free is OK */
160 if (!(dentry->d_flags & DCACHE_RCUACCESS))
161 __d_free(&dentry->d_u.d_rcu);
163 call_rcu(&dentry->d_u.d_rcu, __d_free);
167 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
168 * @dentry: the target dentry
169 * After this call, in-progress rcu-walk path lookup will fail. This
170 * should be called after unhashing, and after changing d_inode (if
171 * the dentry has not already been unhashed).
173 static inline void dentry_rcuwalk_barrier(struct dentry *dentry)
175 assert_spin_locked(&dentry->d_lock);
176 /* Go through a barrier */
177 write_seqcount_barrier(&dentry->d_seq);
181 * Release the dentry's inode, using the filesystem
182 * d_iput() operation if defined. Dentry has no refcount
185 static void dentry_iput(struct dentry * dentry)
186 __releases(dentry->d_lock)
187 __releases(dentry->d_inode->i_lock)
189 struct inode *inode = dentry->d_inode;
191 dentry->d_inode = NULL;
192 list_del_init(&dentry->d_alias);
193 spin_unlock(&dentry->d_lock);
194 spin_unlock(&inode->i_lock);
196 fsnotify_inoderemove(inode);
197 if (dentry->d_op && dentry->d_op->d_iput)
198 dentry->d_op->d_iput(dentry, inode);
202 spin_unlock(&dentry->d_lock);
207 * Release the dentry's inode, using the filesystem
208 * d_iput() operation if defined. dentry remains in-use.
210 static void dentry_unlink_inode(struct dentry * dentry)
211 __releases(dentry->d_lock)
212 __releases(dentry->d_inode->i_lock)
214 struct inode *inode = dentry->d_inode;
215 dentry->d_inode = NULL;
216 list_del_init(&dentry->d_alias);
217 dentry_rcuwalk_barrier(dentry);
218 spin_unlock(&dentry->d_lock);
219 spin_unlock(&inode->i_lock);
221 fsnotify_inoderemove(inode);
222 if (dentry->d_op && dentry->d_op->d_iput)
223 dentry->d_op->d_iput(dentry, inode);
229 * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
231 static void dentry_lru_add(struct dentry *dentry)
233 if (list_empty(&dentry->d_lru)) {
234 spin_lock(&dcache_lru_lock);
235 list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
236 dentry->d_sb->s_nr_dentry_unused++;
237 dentry_stat.nr_unused++;
238 spin_unlock(&dcache_lru_lock);
242 static void __dentry_lru_del(struct dentry *dentry)
244 list_del_init(&dentry->d_lru);
245 dentry->d_sb->s_nr_dentry_unused--;
246 dentry_stat.nr_unused--;
250 * Remove a dentry with references from the LRU.
252 static void dentry_lru_del(struct dentry *dentry)
254 if (!list_empty(&dentry->d_lru)) {
255 spin_lock(&dcache_lru_lock);
256 __dentry_lru_del(dentry);
257 spin_unlock(&dcache_lru_lock);
262 * Remove a dentry that is unreferenced and about to be pruned
263 * (unhashed and destroyed) from the LRU, and inform the file system.
264 * This wrapper should be called _prior_ to unhashing a victim dentry.
266 static void dentry_lru_prune(struct dentry *dentry)
268 if (!list_empty(&dentry->d_lru)) {
269 if (dentry->d_flags & DCACHE_OP_PRUNE)
270 dentry->d_op->d_prune(dentry);
272 spin_lock(&dcache_lru_lock);
273 __dentry_lru_del(dentry);
274 spin_unlock(&dcache_lru_lock);
278 static void dentry_lru_move_tail(struct dentry *dentry)
280 spin_lock(&dcache_lru_lock);
281 if (list_empty(&dentry->d_lru)) {
282 list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
283 dentry->d_sb->s_nr_dentry_unused++;
284 dentry_stat.nr_unused++;
286 list_move_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
288 spin_unlock(&dcache_lru_lock);
292 * d_kill - kill dentry and return parent
293 * @dentry: dentry to kill
294 * @parent: parent dentry
296 * The dentry must already be unhashed and removed from the LRU.
298 * If this is the root of the dentry tree, return NULL.
300 * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
303 static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
304 __releases(dentry->d_lock)
305 __releases(parent->d_lock)
306 __releases(dentry->d_inode->i_lock)
308 list_del(&dentry->d_u.d_child);
310 * Inform try_to_ascend() that we are no longer attached to the
313 dentry->d_flags |= DCACHE_DISCONNECTED;
315 spin_unlock(&parent->d_lock);
318 * dentry_iput drops the locks, at which point nobody (except
319 * transient RCU lookups) can reach this dentry.
326 * Unhash a dentry without inserting an RCU walk barrier or checking that
327 * dentry->d_lock is locked. The caller must take care of that, if
330 static void __d_shrink(struct dentry *dentry)
332 if (!d_unhashed(dentry)) {
333 struct hlist_bl_head *b;
334 if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
335 b = &dentry->d_sb->s_anon;
337 b = d_hash(dentry->d_parent, dentry->d_name.hash);
340 __hlist_bl_del(&dentry->d_hash);
341 dentry->d_hash.pprev = NULL;
347 * d_drop - drop a dentry
348 * @dentry: dentry to drop
350 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
351 * be found through a VFS lookup any more. Note that this is different from
352 * deleting the dentry - d_delete will try to mark the dentry negative if
353 * possible, giving a successful _negative_ lookup, while d_drop will
354 * just make the cache lookup fail.
356 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
357 * reason (NFS timeouts or autofs deletes).
359 * __d_drop requires dentry->d_lock.
361 void __d_drop(struct dentry *dentry)
363 if (!d_unhashed(dentry)) {
365 dentry_rcuwalk_barrier(dentry);
368 EXPORT_SYMBOL(__d_drop);
370 void d_drop(struct dentry *dentry)
372 spin_lock(&dentry->d_lock);
374 spin_unlock(&dentry->d_lock);
376 EXPORT_SYMBOL(d_drop);
379 * d_clear_need_lookup - drop a dentry from cache and clear the need lookup flag
380 * @dentry: dentry to drop
382 * This is called when we do a lookup on a placeholder dentry that needed to be
383 * looked up. The dentry should have been hashed in order for it to be found by
384 * the lookup code, but now needs to be unhashed while we do the actual lookup
385 * and clear the DCACHE_NEED_LOOKUP flag.
387 void d_clear_need_lookup(struct dentry *dentry)
389 spin_lock(&dentry->d_lock);
391 dentry->d_flags &= ~DCACHE_NEED_LOOKUP;
392 spin_unlock(&dentry->d_lock);
394 EXPORT_SYMBOL(d_clear_need_lookup);
397 * Finish off a dentry we've decided to kill.
398 * dentry->d_lock must be held, returns with it unlocked.
399 * If ref is non-zero, then decrement the refcount too.
400 * Returns dentry requiring refcount drop, or NULL if we're done.
402 static inline struct dentry *dentry_kill(struct dentry *dentry, int ref)
403 __releases(dentry->d_lock)
406 struct dentry *parent;
408 inode = dentry->d_inode;
409 if (inode && !spin_trylock(&inode->i_lock)) {
411 spin_unlock(&dentry->d_lock);
413 return dentry; /* try again with same dentry */
418 parent = dentry->d_parent;
419 if (parent && !spin_trylock(&parent->d_lock)) {
421 spin_unlock(&inode->i_lock);
428 * if dentry was on the d_lru list delete it from there.
429 * inform the fs via d_prune that this dentry is about to be
430 * unhashed and destroyed.
432 dentry_lru_prune(dentry);
433 /* if it was on the hash then remove it */
435 return d_kill(dentry, parent);
441 * This is complicated by the fact that we do not want to put
442 * dentries that are no longer on any hash chain on the unused
443 * list: we'd much rather just get rid of them immediately.
445 * However, that implies that we have to traverse the dentry
446 * tree upwards to the parents which might _also_ now be
447 * scheduled for deletion (it may have been only waiting for
448 * its last child to go away).
450 * This tail recursion is done by hand as we don't want to depend
451 * on the compiler to always get this right (gcc generally doesn't).
452 * Real recursion would eat up our stack space.
456 * dput - release a dentry
457 * @dentry: dentry to release
459 * Release a dentry. This will drop the usage count and if appropriate
460 * call the dentry unlink method as well as removing it from the queues and
461 * releasing its resources. If the parent dentries were scheduled for release
462 * they too may now get deleted.
464 void dput(struct dentry *dentry)
470 if (dentry->d_count == 1)
472 spin_lock(&dentry->d_lock);
473 BUG_ON(!dentry->d_count);
474 if (dentry->d_count > 1) {
476 spin_unlock(&dentry->d_lock);
480 if (dentry->d_flags & DCACHE_OP_DELETE) {
481 if (dentry->d_op->d_delete(dentry))
485 /* Unreachable? Get rid of it */
486 if (d_unhashed(dentry))
490 * If this dentry needs lookup, don't set the referenced flag so that it
491 * is more likely to be cleaned up by the dcache shrinker in case of
494 if (!d_need_lookup(dentry))
495 dentry->d_flags |= DCACHE_REFERENCED;
496 dentry_lru_add(dentry);
499 spin_unlock(&dentry->d_lock);
503 dentry = dentry_kill(dentry, 1);
510 * d_invalidate - invalidate a dentry
511 * @dentry: dentry to invalidate
513 * Try to invalidate the dentry if it turns out to be
514 * possible. If there are other dentries that can be
515 * reached through this one we can't delete it and we
516 * return -EBUSY. On success we return 0.
521 int d_invalidate(struct dentry * dentry)
524 * If it's already been dropped, return OK.
526 spin_lock(&dentry->d_lock);
527 if (d_unhashed(dentry)) {
528 spin_unlock(&dentry->d_lock);
532 * Check whether to do a partial shrink_dcache
533 * to get rid of unused child entries.
535 if (!list_empty(&dentry->d_subdirs)) {
536 spin_unlock(&dentry->d_lock);
537 shrink_dcache_parent(dentry);
538 spin_lock(&dentry->d_lock);
542 * Somebody else still using it?
544 * If it's a directory, we can't drop it
545 * for fear of somebody re-populating it
546 * with children (even though dropping it
547 * would make it unreachable from the root,
548 * we might still populate it if it was a
549 * working directory or similar).
550 * We also need to leave mountpoints alone,
553 if (dentry->d_count > 1 && dentry->d_inode) {
554 if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) {
555 spin_unlock(&dentry->d_lock);
561 spin_unlock(&dentry->d_lock);
564 EXPORT_SYMBOL(d_invalidate);
566 /* This must be called with d_lock held */
567 static inline void __dget_dlock(struct dentry *dentry)
572 static inline void __dget(struct dentry *dentry)
574 spin_lock(&dentry->d_lock);
575 __dget_dlock(dentry);
576 spin_unlock(&dentry->d_lock);
579 struct dentry *dget_parent(struct dentry *dentry)
585 * Don't need rcu_dereference because we re-check it was correct under
589 ret = dentry->d_parent;
590 spin_lock(&ret->d_lock);
591 if (unlikely(ret != dentry->d_parent)) {
592 spin_unlock(&ret->d_lock);
597 BUG_ON(!ret->d_count);
599 spin_unlock(&ret->d_lock);
602 EXPORT_SYMBOL(dget_parent);
605 * d_find_alias - grab a hashed alias of inode
606 * @inode: inode in question
607 * @want_discon: flag, used by d_splice_alias, to request
608 * that only a DISCONNECTED alias be returned.
610 * If inode has a hashed alias, or is a directory and has any alias,
611 * acquire the reference to alias and return it. Otherwise return NULL.
612 * Notice that if inode is a directory there can be only one alias and
613 * it can be unhashed only if it has no children, or if it is the root
616 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
617 * any other hashed alias over that one unless @want_discon is set,
618 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
620 static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
622 struct dentry *alias, *discon_alias;
626 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
627 spin_lock(&alias->d_lock);
628 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
629 if (IS_ROOT(alias) &&
630 (alias->d_flags & DCACHE_DISCONNECTED)) {
631 discon_alias = alias;
632 } else if (!want_discon) {
634 spin_unlock(&alias->d_lock);
638 spin_unlock(&alias->d_lock);
641 alias = discon_alias;
642 spin_lock(&alias->d_lock);
643 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
644 if (IS_ROOT(alias) &&
645 (alias->d_flags & DCACHE_DISCONNECTED)) {
647 spin_unlock(&alias->d_lock);
651 spin_unlock(&alias->d_lock);
657 struct dentry *d_find_alias(struct inode *inode)
659 struct dentry *de = NULL;
661 if (!list_empty(&inode->i_dentry)) {
662 spin_lock(&inode->i_lock);
663 de = __d_find_alias(inode, 0);
664 spin_unlock(&inode->i_lock);
668 EXPORT_SYMBOL(d_find_alias);
671 * Try to kill dentries associated with this inode.
672 * WARNING: you must own a reference to inode.
674 void d_prune_aliases(struct inode *inode)
676 struct dentry *dentry;
678 spin_lock(&inode->i_lock);
679 list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
680 spin_lock(&dentry->d_lock);
681 if (!dentry->d_count) {
682 __dget_dlock(dentry);
684 spin_unlock(&dentry->d_lock);
685 spin_unlock(&inode->i_lock);
689 spin_unlock(&dentry->d_lock);
691 spin_unlock(&inode->i_lock);
693 EXPORT_SYMBOL(d_prune_aliases);
696 * Try to throw away a dentry - free the inode, dput the parent.
697 * Requires dentry->d_lock is held, and dentry->d_count == 0.
698 * Releases dentry->d_lock.
700 * This may fail if locks cannot be acquired no problem, just try again.
702 static void try_prune_one_dentry(struct dentry *dentry)
703 __releases(dentry->d_lock)
705 struct dentry *parent;
707 parent = dentry_kill(dentry, 0);
709 * If dentry_kill returns NULL, we have nothing more to do.
710 * if it returns the same dentry, trylocks failed. In either
711 * case, just loop again.
713 * Otherwise, we need to prune ancestors too. This is necessary
714 * to prevent quadratic behavior of shrink_dcache_parent(), but
715 * is also expected to be beneficial in reducing dentry cache
720 if (parent == dentry)
723 /* Prune ancestors. */
726 spin_lock(&dentry->d_lock);
727 if (dentry->d_count > 1) {
729 spin_unlock(&dentry->d_lock);
732 dentry = dentry_kill(dentry, 1);
736 static void shrink_dentry_list(struct list_head *list)
738 struct dentry *dentry;
742 dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
743 if (&dentry->d_lru == list)
745 spin_lock(&dentry->d_lock);
746 if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
747 spin_unlock(&dentry->d_lock);
752 * We found an inuse dentry which was not removed from
753 * the LRU because of laziness during lookup. Do not free
754 * it - just keep it off the LRU list.
756 if (dentry->d_count) {
757 dentry_lru_del(dentry);
758 spin_unlock(&dentry->d_lock);
764 try_prune_one_dentry(dentry);
772 * __shrink_dcache_sb - shrink the dentry LRU on a given superblock
773 * @sb: superblock to shrink dentry LRU.
774 * @count: number of entries to prune
775 * @flags: flags to control the dentry processing
777 * If flags contains DCACHE_REFERENCED reference dentries will not be pruned.
779 static void __shrink_dcache_sb(struct super_block *sb, int count, int flags)
781 struct dentry *dentry;
782 LIST_HEAD(referenced);
786 spin_lock(&dcache_lru_lock);
787 while (!list_empty(&sb->s_dentry_lru)) {
788 dentry = list_entry(sb->s_dentry_lru.prev,
789 struct dentry, d_lru);
790 BUG_ON(dentry->d_sb != sb);
792 if (!spin_trylock(&dentry->d_lock)) {
793 spin_unlock(&dcache_lru_lock);
799 * If we are honouring the DCACHE_REFERENCED flag and the
800 * dentry has this flag set, don't free it. Clear the flag
801 * and put it back on the LRU.
803 if (flags & DCACHE_REFERENCED &&
804 dentry->d_flags & DCACHE_REFERENCED) {
805 dentry->d_flags &= ~DCACHE_REFERENCED;
806 list_move(&dentry->d_lru, &referenced);
807 spin_unlock(&dentry->d_lock);
809 list_move_tail(&dentry->d_lru, &tmp);
810 spin_unlock(&dentry->d_lock);
814 cond_resched_lock(&dcache_lru_lock);
816 if (!list_empty(&referenced))
817 list_splice(&referenced, &sb->s_dentry_lru);
818 spin_unlock(&dcache_lru_lock);
820 shrink_dentry_list(&tmp);
824 * prune_dcache_sb - shrink the dcache
826 * @nr_to_scan: number of entries to try to free
828 * Attempt to shrink the superblock dcache LRU by @nr_to_scan entries. This is
829 * done when we need more memory an called from the superblock shrinker
832 * This function may fail to free any resources if all the dentries are in
835 void prune_dcache_sb(struct super_block *sb, int nr_to_scan)
837 __shrink_dcache_sb(sb, nr_to_scan, DCACHE_REFERENCED);
841 * shrink_dcache_sb - shrink dcache for a superblock
844 * Shrink the dcache for the specified super block. This is used to free
845 * the dcache before unmounting a file system.
847 void shrink_dcache_sb(struct super_block *sb)
851 spin_lock(&dcache_lru_lock);
852 while (!list_empty(&sb->s_dentry_lru)) {
853 list_splice_init(&sb->s_dentry_lru, &tmp);
854 spin_unlock(&dcache_lru_lock);
855 shrink_dentry_list(&tmp);
856 spin_lock(&dcache_lru_lock);
858 spin_unlock(&dcache_lru_lock);
860 EXPORT_SYMBOL(shrink_dcache_sb);
863 * destroy a single subtree of dentries for unmount
864 * - see the comments on shrink_dcache_for_umount() for a description of the
867 static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
869 struct dentry *parent;
871 BUG_ON(!IS_ROOT(dentry));
874 /* descend to the first leaf in the current subtree */
875 while (!list_empty(&dentry->d_subdirs))
876 dentry = list_entry(dentry->d_subdirs.next,
877 struct dentry, d_u.d_child);
879 /* consume the dentries from this leaf up through its parents
880 * until we find one with children or run out altogether */
885 * remove the dentry from the lru, and inform
886 * the fs that this dentry is about to be
887 * unhashed and destroyed.
889 dentry_lru_prune(dentry);
892 if (dentry->d_count != 0) {
894 "BUG: Dentry %p{i=%lx,n=%s}"
896 " [unmount of %s %s]\n",
899 dentry->d_inode->i_ino : 0UL,
902 dentry->d_sb->s_type->name,
907 if (IS_ROOT(dentry)) {
909 list_del(&dentry->d_u.d_child);
911 parent = dentry->d_parent;
913 list_del(&dentry->d_u.d_child);
916 inode = dentry->d_inode;
918 dentry->d_inode = NULL;
919 list_del_init(&dentry->d_alias);
920 if (dentry->d_op && dentry->d_op->d_iput)
921 dentry->d_op->d_iput(dentry, inode);
928 /* finished when we fall off the top of the tree,
929 * otherwise we ascend to the parent and move to the
930 * next sibling if there is one */
934 } while (list_empty(&dentry->d_subdirs));
936 dentry = list_entry(dentry->d_subdirs.next,
937 struct dentry, d_u.d_child);
942 * destroy the dentries attached to a superblock on unmounting
943 * - we don't need to use dentry->d_lock because:
944 * - the superblock is detached from all mountings and open files, so the
945 * dentry trees will not be rearranged by the VFS
946 * - s_umount is write-locked, so the memory pressure shrinker will ignore
947 * any dentries belonging to this superblock that it comes across
948 * - the filesystem itself is no longer permitted to rearrange the dentries
951 void shrink_dcache_for_umount(struct super_block *sb)
953 struct dentry *dentry;
955 if (down_read_trylock(&sb->s_umount))
961 shrink_dcache_for_umount_subtree(dentry);
963 while (!hlist_bl_empty(&sb->s_anon)) {
964 dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
965 shrink_dcache_for_umount_subtree(dentry);
970 * This tries to ascend one level of parenthood, but
971 * we can race with renaming, so we need to re-check
972 * the parenthood after dropping the lock and check
973 * that the sequence number still matches.
975 static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq)
977 struct dentry *new = old->d_parent;
980 spin_unlock(&old->d_lock);
981 spin_lock(&new->d_lock);
984 * might go back up the wrong parent if we have had a rename
987 if (new != old->d_parent ||
988 (old->d_flags & DCACHE_DISCONNECTED) ||
989 (!locked && read_seqretry(&rename_lock, seq))) {
990 spin_unlock(&new->d_lock);
999 * Search for at least 1 mount point in the dentry's subdirs.
1000 * We descend to the next level whenever the d_subdirs
1001 * list is non-empty and continue searching.
1005 * have_submounts - check for mounts over a dentry
1006 * @parent: dentry to check.
1008 * Return true if the parent or its subdirectories contain
1011 int have_submounts(struct dentry *parent)
1013 struct dentry *this_parent;
1014 struct list_head *next;
1018 seq = read_seqbegin(&rename_lock);
1020 this_parent = parent;
1022 if (d_mountpoint(parent))
1024 spin_lock(&this_parent->d_lock);
1026 next = this_parent->d_subdirs.next;
1028 while (next != &this_parent->d_subdirs) {
1029 struct list_head *tmp = next;
1030 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
1033 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1034 /* Have we found a mount point ? */
1035 if (d_mountpoint(dentry)) {
1036 spin_unlock(&dentry->d_lock);
1037 spin_unlock(&this_parent->d_lock);
1040 if (!list_empty(&dentry->d_subdirs)) {
1041 spin_unlock(&this_parent->d_lock);
1042 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
1043 this_parent = dentry;
1044 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1047 spin_unlock(&dentry->d_lock);
1050 * All done at this level ... ascend and resume the search.
1052 if (this_parent != parent) {
1053 struct dentry *child = this_parent;
1054 this_parent = try_to_ascend(this_parent, locked, seq);
1057 next = child->d_u.d_child.next;
1060 spin_unlock(&this_parent->d_lock);
1061 if (!locked && read_seqretry(&rename_lock, seq))
1064 write_sequnlock(&rename_lock);
1065 return 0; /* No mount points found in tree */
1067 if (!locked && read_seqretry(&rename_lock, seq))
1070 write_sequnlock(&rename_lock);
1075 write_seqlock(&rename_lock);
1078 EXPORT_SYMBOL(have_submounts);
1081 * Search the dentry child list for the specified parent,
1082 * and move any unused dentries to the end of the unused
1083 * list for prune_dcache(). We descend to the next level
1084 * whenever the d_subdirs list is non-empty and continue
1087 * It returns zero iff there are no unused children,
1088 * otherwise it returns the number of children moved to
1089 * the end of the unused list. This may not be the total
1090 * number of unused children, because select_parent can
1091 * drop the lock and return early due to latency
1094 static int select_parent(struct dentry * parent)
1096 struct dentry *this_parent;
1097 struct list_head *next;
1102 seq = read_seqbegin(&rename_lock);
1104 this_parent = parent;
1105 spin_lock(&this_parent->d_lock);
1107 next = this_parent->d_subdirs.next;
1109 while (next != &this_parent->d_subdirs) {
1110 struct list_head *tmp = next;
1111 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
1114 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1117 * move only zero ref count dentries to the end
1118 * of the unused list for prune_dcache
1120 if (!dentry->d_count) {
1121 dentry_lru_move_tail(dentry);
1124 dentry_lru_del(dentry);
1128 * We can return to the caller if we have found some (this
1129 * ensures forward progress). We'll be coming back to find
1132 if (found && need_resched()) {
1133 spin_unlock(&dentry->d_lock);
1138 * Descend a level if the d_subdirs list is non-empty.
1140 if (!list_empty(&dentry->d_subdirs)) {
1141 spin_unlock(&this_parent->d_lock);
1142 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
1143 this_parent = dentry;
1144 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1148 spin_unlock(&dentry->d_lock);
1151 * All done at this level ... ascend and resume the search.
1153 if (this_parent != parent) {
1154 struct dentry *child = this_parent;
1155 this_parent = try_to_ascend(this_parent, locked, seq);
1158 next = child->d_u.d_child.next;
1162 spin_unlock(&this_parent->d_lock);
1163 if (!locked && read_seqretry(&rename_lock, seq))
1166 write_sequnlock(&rename_lock);
1173 write_seqlock(&rename_lock);
1178 * shrink_dcache_parent - prune dcache
1179 * @parent: parent of entries to prune
1181 * Prune the dcache to remove unused children of the parent dentry.
1184 void shrink_dcache_parent(struct dentry * parent)
1186 struct super_block *sb = parent->d_sb;
1189 while ((found = select_parent(parent)) != 0)
1190 __shrink_dcache_sb(sb, found, 0);
1192 EXPORT_SYMBOL(shrink_dcache_parent);
1195 * __d_alloc - allocate a dcache entry
1196 * @sb: filesystem it will belong to
1197 * @name: qstr of the name
1199 * Allocates a dentry. It returns %NULL if there is insufficient memory
1200 * available. On a success the dentry is returned. The name passed in is
1201 * copied and the copy passed in may be reused after this call.
1204 struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1206 struct dentry *dentry;
1209 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
1213 if (name->len > DNAME_INLINE_LEN-1) {
1214 dname = kmalloc(name->len + 1, GFP_KERNEL);
1216 kmem_cache_free(dentry_cache, dentry);
1220 dname = dentry->d_iname;
1222 dentry->d_name.name = dname;
1224 dentry->d_name.len = name->len;
1225 dentry->d_name.hash = name->hash;
1226 memcpy(dname, name->name, name->len);
1227 dname[name->len] = 0;
1229 dentry->d_count = 1;
1230 dentry->d_flags = 0;
1231 spin_lock_init(&dentry->d_lock);
1232 seqcount_init(&dentry->d_seq);
1233 dentry->d_inode = NULL;
1234 dentry->d_parent = dentry;
1236 dentry->d_op = NULL;
1237 dentry->d_fsdata = NULL;
1238 INIT_HLIST_BL_NODE(&dentry->d_hash);
1239 INIT_LIST_HEAD(&dentry->d_lru);
1240 INIT_LIST_HEAD(&dentry->d_subdirs);
1241 INIT_LIST_HEAD(&dentry->d_alias);
1242 INIT_LIST_HEAD(&dentry->d_u.d_child);
1243 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1245 this_cpu_inc(nr_dentry);
1251 * d_alloc - allocate a dcache entry
1252 * @parent: parent of entry to allocate
1253 * @name: qstr of the name
1255 * Allocates a dentry. It returns %NULL if there is insufficient memory
1256 * available. On a success the dentry is returned. The name passed in is
1257 * copied and the copy passed in may be reused after this call.
1259 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1261 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1265 spin_lock(&parent->d_lock);
1267 * don't need child lock because it is not subject
1268 * to concurrency here
1270 __dget_dlock(parent);
1271 dentry->d_parent = parent;
1272 list_add(&dentry->d_u.d_child, &parent->d_subdirs);
1273 spin_unlock(&parent->d_lock);
1277 EXPORT_SYMBOL(d_alloc);
1279 struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1281 struct dentry *dentry = __d_alloc(sb, name);
1283 dentry->d_flags |= DCACHE_DISCONNECTED;
1286 EXPORT_SYMBOL(d_alloc_pseudo);
1288 struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1293 q.len = strlen(name);
1294 q.hash = full_name_hash(q.name, q.len);
1295 return d_alloc(parent, &q);
1297 EXPORT_SYMBOL(d_alloc_name);
1299 void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1301 WARN_ON_ONCE(dentry->d_op);
1302 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
1304 DCACHE_OP_REVALIDATE |
1305 DCACHE_OP_DELETE ));
1310 dentry->d_flags |= DCACHE_OP_HASH;
1312 dentry->d_flags |= DCACHE_OP_COMPARE;
1313 if (op->d_revalidate)
1314 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1316 dentry->d_flags |= DCACHE_OP_DELETE;
1318 dentry->d_flags |= DCACHE_OP_PRUNE;
1321 EXPORT_SYMBOL(d_set_d_op);
1323 static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1325 spin_lock(&dentry->d_lock);
1327 if (unlikely(IS_AUTOMOUNT(inode)))
1328 dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
1329 list_add(&dentry->d_alias, &inode->i_dentry);
1331 dentry->d_inode = inode;
1332 dentry_rcuwalk_barrier(dentry);
1333 spin_unlock(&dentry->d_lock);
1334 fsnotify_d_instantiate(dentry, inode);
1338 * d_instantiate - fill in inode information for a dentry
1339 * @entry: dentry to complete
1340 * @inode: inode to attach to this dentry
1342 * Fill in inode information in the entry.
1344 * This turns negative dentries into productive full members
1347 * NOTE! This assumes that the inode count has been incremented
1348 * (or otherwise set) by the caller to indicate that it is now
1349 * in use by the dcache.
1352 void d_instantiate(struct dentry *entry, struct inode * inode)
1354 BUG_ON(!list_empty(&entry->d_alias));
1356 spin_lock(&inode->i_lock);
1357 __d_instantiate(entry, inode);
1359 spin_unlock(&inode->i_lock);
1360 security_d_instantiate(entry, inode);
1362 EXPORT_SYMBOL(d_instantiate);
1365 * d_instantiate_unique - instantiate a non-aliased dentry
1366 * @entry: dentry to instantiate
1367 * @inode: inode to attach to this dentry
1369 * Fill in inode information in the entry. On success, it returns NULL.
1370 * If an unhashed alias of "entry" already exists, then we return the
1371 * aliased dentry instead and drop one reference to inode.
1373 * Note that in order to avoid conflicts with rename() etc, the caller
1374 * had better be holding the parent directory semaphore.
1376 * This also assumes that the inode count has been incremented
1377 * (or otherwise set) by the caller to indicate that it is now
1378 * in use by the dcache.
1380 static struct dentry *__d_instantiate_unique(struct dentry *entry,
1381 struct inode *inode)
1383 struct dentry *alias;
1384 int len = entry->d_name.len;
1385 const char *name = entry->d_name.name;
1386 unsigned int hash = entry->d_name.hash;
1389 __d_instantiate(entry, NULL);
1393 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
1394 struct qstr *qstr = &alias->d_name;
1397 * Don't need alias->d_lock here, because aliases with
1398 * d_parent == entry->d_parent are not subject to name or
1399 * parent changes, because the parent inode i_mutex is held.
1401 if (qstr->hash != hash)
1403 if (alias->d_parent != entry->d_parent)
1405 if (dentry_cmp(qstr->name, qstr->len, name, len))
1411 __d_instantiate(entry, inode);
1415 struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
1417 struct dentry *result;
1419 BUG_ON(!list_empty(&entry->d_alias));
1422 spin_lock(&inode->i_lock);
1423 result = __d_instantiate_unique(entry, inode);
1425 spin_unlock(&inode->i_lock);
1428 security_d_instantiate(entry, inode);
1432 BUG_ON(!d_unhashed(result));
1437 EXPORT_SYMBOL(d_instantiate_unique);
1440 * d_alloc_root - allocate root dentry
1441 * @root_inode: inode to allocate the root for
1443 * Allocate a root ("/") dentry for the inode given. The inode is
1444 * instantiated and returned. %NULL is returned if there is insufficient
1445 * memory or the inode passed is %NULL.
1448 struct dentry * d_alloc_root(struct inode * root_inode)
1450 struct dentry *res = NULL;
1453 static const struct qstr name = { .name = "/", .len = 1 };
1455 res = __d_alloc(root_inode->i_sb, &name);
1457 d_instantiate(res, root_inode);
1461 EXPORT_SYMBOL(d_alloc_root);
1463 static struct dentry * __d_find_any_alias(struct inode *inode)
1465 struct dentry *alias;
1467 if (list_empty(&inode->i_dentry))
1469 alias = list_first_entry(&inode->i_dentry, struct dentry, d_alias);
1475 * d_find_any_alias - find any alias for a given inode
1476 * @inode: inode to find an alias for
1478 * If any aliases exist for the given inode, take and return a
1479 * reference for one of them. If no aliases exist, return %NULL.
1481 struct dentry *d_find_any_alias(struct inode *inode)
1485 spin_lock(&inode->i_lock);
1486 de = __d_find_any_alias(inode);
1487 spin_unlock(&inode->i_lock);
1490 EXPORT_SYMBOL(d_find_any_alias);
1493 * d_obtain_alias - find or allocate a dentry for a given inode
1494 * @inode: inode to allocate the dentry for
1496 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1497 * similar open by handle operations. The returned dentry may be anonymous,
1498 * or may have a full name (if the inode was already in the cache).
1500 * When called on a directory inode, we must ensure that the inode only ever
1501 * has one dentry. If a dentry is found, that is returned instead of
1502 * allocating a new one.
1504 * On successful return, the reference to the inode has been transferred
1505 * to the dentry. In case of an error the reference on the inode is released.
1506 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1507 * be passed in and will be the error will be propagate to the return value,
1508 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1510 struct dentry *d_obtain_alias(struct inode *inode)
1512 static const struct qstr anonstring = { .name = "" };
1517 return ERR_PTR(-ESTALE);
1519 return ERR_CAST(inode);
1521 res = d_find_any_alias(inode);
1525 tmp = __d_alloc(inode->i_sb, &anonstring);
1527 res = ERR_PTR(-ENOMEM);
1531 spin_lock(&inode->i_lock);
1532 res = __d_find_any_alias(inode);
1534 spin_unlock(&inode->i_lock);
1539 /* attach a disconnected dentry */
1540 spin_lock(&tmp->d_lock);
1541 tmp->d_inode = inode;
1542 tmp->d_flags |= DCACHE_DISCONNECTED;
1543 list_add(&tmp->d_alias, &inode->i_dentry);
1544 hlist_bl_lock(&tmp->d_sb->s_anon);
1545 hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
1546 hlist_bl_unlock(&tmp->d_sb->s_anon);
1547 spin_unlock(&tmp->d_lock);
1548 spin_unlock(&inode->i_lock);
1549 security_d_instantiate(tmp, inode);
1554 if (res && !IS_ERR(res))
1555 security_d_instantiate(res, inode);
1559 EXPORT_SYMBOL(d_obtain_alias);
1562 * d_splice_alias - splice a disconnected dentry into the tree if one exists
1563 * @inode: the inode which may have a disconnected dentry
1564 * @dentry: a negative dentry which we want to point to the inode.
1566 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1567 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1568 * and return it, else simply d_add the inode to the dentry and return NULL.
1570 * This is needed in the lookup routine of any filesystem that is exportable
1571 * (via knfsd) so that we can build dcache paths to directories effectively.
1573 * If a dentry was found and moved, then it is returned. Otherwise NULL
1574 * is returned. This matches the expected return value of ->lookup.
1577 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
1579 struct dentry *new = NULL;
1582 return ERR_CAST(inode);
1584 if (inode && S_ISDIR(inode->i_mode)) {
1585 spin_lock(&inode->i_lock);
1586 new = __d_find_alias(inode, 1);
1588 BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
1589 spin_unlock(&inode->i_lock);
1590 security_d_instantiate(new, inode);
1591 d_move(new, dentry);
1594 /* already taking inode->i_lock, so d_add() by hand */
1595 __d_instantiate(dentry, inode);
1596 spin_unlock(&inode->i_lock);
1597 security_d_instantiate(dentry, inode);
1601 d_add(dentry, inode);
1604 EXPORT_SYMBOL(d_splice_alias);
1607 * d_add_ci - lookup or allocate new dentry with case-exact name
1608 * @inode: the inode case-insensitive lookup has found
1609 * @dentry: the negative dentry that was passed to the parent's lookup func
1610 * @name: the case-exact name to be associated with the returned dentry
1612 * This is to avoid filling the dcache with case-insensitive names to the
1613 * same inode, only the actual correct case is stored in the dcache for
1614 * case-insensitive filesystems.
1616 * For a case-insensitive lookup match and if the the case-exact dentry
1617 * already exists in in the dcache, use it and return it.
1619 * If no entry exists with the exact case name, allocate new dentry with
1620 * the exact case, and return the spliced entry.
1622 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
1626 struct dentry *found;
1630 * First check if a dentry matching the name already exists,
1631 * if not go ahead and create it now.
1633 found = d_hash_and_lookup(dentry->d_parent, name);
1635 new = d_alloc(dentry->d_parent, name);
1641 found = d_splice_alias(inode, new);
1650 * If a matching dentry exists, and it's not negative use it.
1652 * Decrement the reference count to balance the iget() done
1655 if (found->d_inode) {
1656 if (unlikely(found->d_inode != inode)) {
1657 /* This can't happen because bad inodes are unhashed. */
1658 BUG_ON(!is_bad_inode(inode));
1659 BUG_ON(!is_bad_inode(found->d_inode));
1666 * We are going to instantiate this dentry, unhash it and clear the
1667 * lookup flag so we can do that.
1669 if (unlikely(d_need_lookup(found)))
1670 d_clear_need_lookup(found);
1673 * Negative dentry: instantiate it unless the inode is a directory and
1674 * already has a dentry.
1676 new = d_splice_alias(inode, found);
1685 return ERR_PTR(error);
1687 EXPORT_SYMBOL(d_add_ci);
1690 * __d_lookup_rcu - search for a dentry (racy, store-free)
1691 * @parent: parent dentry
1692 * @name: qstr of name we wish to find
1693 * @seq: returns d_seq value at the point where the dentry was found
1694 * @inode: returns dentry->d_inode when the inode was found valid.
1695 * Returns: dentry, or NULL
1697 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
1698 * resolution (store-free path walking) design described in
1699 * Documentation/filesystems/path-lookup.txt.
1701 * This is not to be used outside core vfs.
1703 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
1704 * held, and rcu_read_lock held. The returned dentry must not be stored into
1705 * without taking d_lock and checking d_seq sequence count against @seq
1708 * A refcount may be taken on the found dentry with the __d_rcu_to_refcount
1711 * Alternatively, __d_lookup_rcu may be called again to look up the child of
1712 * the returned dentry, so long as its parent's seqlock is checked after the
1713 * child is looked up. Thus, an interlocking stepping of sequence lock checks
1714 * is formed, giving integrity down the path walk.
1716 struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
1717 unsigned *seq, struct inode **inode)
1719 unsigned int len = name->len;
1720 unsigned int hash = name->hash;
1721 const unsigned char *str = name->name;
1722 struct hlist_bl_head *b = d_hash(parent, hash);
1723 struct hlist_bl_node *node;
1724 struct dentry *dentry;
1727 * Note: There is significant duplication with __d_lookup_rcu which is
1728 * required to prevent single threaded performance regressions
1729 * especially on architectures where smp_rmb (in seqcounts) are costly.
1730 * Keep the two functions in sync.
1734 * The hash list is protected using RCU.
1736 * Carefully use d_seq when comparing a candidate dentry, to avoid
1737 * races with d_move().
1739 * It is possible that concurrent renames can mess up our list
1740 * walk here and result in missing our dentry, resulting in the
1741 * false-negative result. d_lookup() protects against concurrent
1742 * renames using rename_lock seqlock.
1744 * See Documentation/filesystems/path-lookup.txt for more details.
1746 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
1751 if (dentry->d_name.hash != hash)
1755 *seq = read_seqcount_begin(&dentry->d_seq);
1756 if (dentry->d_parent != parent)
1758 if (d_unhashed(dentry))
1760 tlen = dentry->d_name.len;
1761 tname = dentry->d_name.name;
1762 i = dentry->d_inode;
1765 * This seqcount check is required to ensure name and
1766 * len are loaded atomically, so as not to walk off the
1767 * edge of memory when walking. If we could load this
1768 * atomically some other way, we could drop this check.
1770 if (read_seqcount_retry(&dentry->d_seq, *seq))
1772 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
1773 if (parent->d_op->d_compare(parent, *inode,
1778 if (dentry_cmp(tname, tlen, str, len))
1782 * No extra seqcount check is required after the name
1783 * compare. The caller must perform a seqcount check in
1784 * order to do anything useful with the returned dentry
1794 * d_lookup - search for a dentry
1795 * @parent: parent dentry
1796 * @name: qstr of name we wish to find
1797 * Returns: dentry, or NULL
1799 * d_lookup searches the children of the parent dentry for the name in
1800 * question. If the dentry is found its reference count is incremented and the
1801 * dentry is returned. The caller must use dput to free the entry when it has
1802 * finished using it. %NULL is returned if the dentry does not exist.
1804 struct dentry *d_lookup(struct dentry *parent, struct qstr *name)
1806 struct dentry *dentry;
1810 seq = read_seqbegin(&rename_lock);
1811 dentry = __d_lookup(parent, name);
1814 } while (read_seqretry(&rename_lock, seq));
1817 EXPORT_SYMBOL(d_lookup);
1820 * __d_lookup - search for a dentry (racy)
1821 * @parent: parent dentry
1822 * @name: qstr of name we wish to find
1823 * Returns: dentry, or NULL
1825 * __d_lookup is like d_lookup, however it may (rarely) return a
1826 * false-negative result due to unrelated rename activity.
1828 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
1829 * however it must be used carefully, eg. with a following d_lookup in
1830 * the case of failure.
1832 * __d_lookup callers must be commented.
1834 struct dentry *__d_lookup(struct dentry *parent, struct qstr *name)
1836 unsigned int len = name->len;
1837 unsigned int hash = name->hash;
1838 const unsigned char *str = name->name;
1839 struct hlist_bl_head *b = d_hash(parent, hash);
1840 struct hlist_bl_node *node;
1841 struct dentry *found = NULL;
1842 struct dentry *dentry;
1845 * Note: There is significant duplication with __d_lookup_rcu which is
1846 * required to prevent single threaded performance regressions
1847 * especially on architectures where smp_rmb (in seqcounts) are costly.
1848 * Keep the two functions in sync.
1852 * The hash list is protected using RCU.
1854 * Take d_lock when comparing a candidate dentry, to avoid races
1857 * It is possible that concurrent renames can mess up our list
1858 * walk here and result in missing our dentry, resulting in the
1859 * false-negative result. d_lookup() protects against concurrent
1860 * renames using rename_lock seqlock.
1862 * See Documentation/filesystems/path-lookup.txt for more details.
1866 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
1870 if (dentry->d_name.hash != hash)
1873 spin_lock(&dentry->d_lock);
1874 if (dentry->d_parent != parent)
1876 if (d_unhashed(dentry))
1880 * It is safe to compare names since d_move() cannot
1881 * change the qstr (protected by d_lock).
1883 tlen = dentry->d_name.len;
1884 tname = dentry->d_name.name;
1885 if (parent->d_flags & DCACHE_OP_COMPARE) {
1886 if (parent->d_op->d_compare(parent, parent->d_inode,
1887 dentry, dentry->d_inode,
1891 if (dentry_cmp(tname, tlen, str, len))
1897 spin_unlock(&dentry->d_lock);
1900 spin_unlock(&dentry->d_lock);
1908 * d_hash_and_lookup - hash the qstr then search for a dentry
1909 * @dir: Directory to search in
1910 * @name: qstr of name we wish to find
1912 * On hash failure or on lookup failure NULL is returned.
1914 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
1916 struct dentry *dentry = NULL;
1919 * Check for a fs-specific hash function. Note that we must
1920 * calculate the standard hash first, as the d_op->d_hash()
1921 * routine may choose to leave the hash value unchanged.
1923 name->hash = full_name_hash(name->name, name->len);
1924 if (dir->d_flags & DCACHE_OP_HASH) {
1925 if (dir->d_op->d_hash(dir, dir->d_inode, name) < 0)
1928 dentry = d_lookup(dir, name);
1934 * d_validate - verify dentry provided from insecure source (deprecated)
1935 * @dentry: The dentry alleged to be valid child of @dparent
1936 * @dparent: The parent dentry (known to be valid)
1938 * An insecure source has sent us a dentry, here we verify it and dget() it.
1939 * This is used by ncpfs in its readdir implementation.
1940 * Zero is returned in the dentry is invalid.
1942 * This function is slow for big directories, and deprecated, do not use it.
1944 int d_validate(struct dentry *dentry, struct dentry *dparent)
1946 struct dentry *child;
1948 spin_lock(&dparent->d_lock);
1949 list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
1950 if (dentry == child) {
1951 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1952 __dget_dlock(dentry);
1953 spin_unlock(&dentry->d_lock);
1954 spin_unlock(&dparent->d_lock);
1958 spin_unlock(&dparent->d_lock);
1962 EXPORT_SYMBOL(d_validate);
1965 * When a file is deleted, we have two options:
1966 * - turn this dentry into a negative dentry
1967 * - unhash this dentry and free it.
1969 * Usually, we want to just turn this into
1970 * a negative dentry, but if anybody else is
1971 * currently using the dentry or the inode
1972 * we can't do that and we fall back on removing
1973 * it from the hash queues and waiting for
1974 * it to be deleted later when it has no users
1978 * d_delete - delete a dentry
1979 * @dentry: The dentry to delete
1981 * Turn the dentry into a negative dentry if possible, otherwise
1982 * remove it from the hash queues so it can be deleted later
1985 void d_delete(struct dentry * dentry)
1987 struct inode *inode;
1990 * Are we the only user?
1993 spin_lock(&dentry->d_lock);
1994 inode = dentry->d_inode;
1995 isdir = S_ISDIR(inode->i_mode);
1996 if (dentry->d_count == 1) {
1997 if (inode && !spin_trylock(&inode->i_lock)) {
1998 spin_unlock(&dentry->d_lock);
2002 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2003 dentry_unlink_inode(dentry);
2004 fsnotify_nameremove(dentry, isdir);
2008 if (!d_unhashed(dentry))
2011 spin_unlock(&dentry->d_lock);
2013 fsnotify_nameremove(dentry, isdir);
2015 EXPORT_SYMBOL(d_delete);
2017 static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
2019 BUG_ON(!d_unhashed(entry));
2021 entry->d_flags |= DCACHE_RCUACCESS;
2022 hlist_bl_add_head_rcu(&entry->d_hash, b);
2026 static void _d_rehash(struct dentry * entry)
2028 __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
2032 * d_rehash - add an entry back to the hash
2033 * @entry: dentry to add to the hash
2035 * Adds a dentry to the hash according to its name.
2038 void d_rehash(struct dentry * entry)
2040 spin_lock(&entry->d_lock);
2042 spin_unlock(&entry->d_lock);
2044 EXPORT_SYMBOL(d_rehash);
2047 * dentry_update_name_case - update case insensitive dentry with a new name
2048 * @dentry: dentry to be updated
2051 * Update a case insensitive dentry with new case of name.
2053 * dentry must have been returned by d_lookup with name @name. Old and new
2054 * name lengths must match (ie. no d_compare which allows mismatched name
2057 * Parent inode i_mutex must be held over d_lookup and into this call (to
2058 * keep renames and concurrent inserts, and readdir(2) away).
2060 void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
2062 BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));
2063 BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
2065 spin_lock(&dentry->d_lock);
2066 write_seqcount_begin(&dentry->d_seq);
2067 memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
2068 write_seqcount_end(&dentry->d_seq);
2069 spin_unlock(&dentry->d_lock);
2071 EXPORT_SYMBOL(dentry_update_name_case);
2073 static void switch_names(struct dentry *dentry, struct dentry *target)
2075 if (dname_external(target)) {
2076 if (dname_external(dentry)) {
2078 * Both external: swap the pointers
2080 swap(target->d_name.name, dentry->d_name.name);
2083 * dentry:internal, target:external. Steal target's
2084 * storage and make target internal.
2086 memcpy(target->d_iname, dentry->d_name.name,
2087 dentry->d_name.len + 1);
2088 dentry->d_name.name = target->d_name.name;
2089 target->d_name.name = target->d_iname;
2092 if (dname_external(dentry)) {
2094 * dentry:external, target:internal. Give dentry's
2095 * storage to target and make dentry internal
2097 memcpy(dentry->d_iname, target->d_name.name,
2098 target->d_name.len + 1);
2099 target->d_name.name = dentry->d_name.name;
2100 dentry->d_name.name = dentry->d_iname;
2103 * Both are internal. Just copy target to dentry
2105 memcpy(dentry->d_iname, target->d_name.name,
2106 target->d_name.len + 1);
2107 dentry->d_name.len = target->d_name.len;
2111 swap(dentry->d_name.len, target->d_name.len);
2114 static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
2117 * XXXX: do we really need to take target->d_lock?
2119 if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent)
2120 spin_lock(&target->d_parent->d_lock);
2122 if (d_ancestor(dentry->d_parent, target->d_parent)) {
2123 spin_lock(&dentry->d_parent->d_lock);
2124 spin_lock_nested(&target->d_parent->d_lock,
2125 DENTRY_D_LOCK_NESTED);
2127 spin_lock(&target->d_parent->d_lock);
2128 spin_lock_nested(&dentry->d_parent->d_lock,
2129 DENTRY_D_LOCK_NESTED);
2132 if (target < dentry) {
2133 spin_lock_nested(&target->d_lock, 2);
2134 spin_lock_nested(&dentry->d_lock, 3);
2136 spin_lock_nested(&dentry->d_lock, 2);
2137 spin_lock_nested(&target->d_lock, 3);
2141 static void dentry_unlock_parents_for_move(struct dentry *dentry,
2142 struct dentry *target)
2144 if (target->d_parent != dentry->d_parent)
2145 spin_unlock(&dentry->d_parent->d_lock);
2146 if (target->d_parent != target)
2147 spin_unlock(&target->d_parent->d_lock);
2151 * When switching names, the actual string doesn't strictly have to
2152 * be preserved in the target - because we're dropping the target
2153 * anyway. As such, we can just do a simple memcpy() to copy over
2154 * the new name before we switch.
2156 * Note that we have to be a lot more careful about getting the hash
2157 * switched - we have to switch the hash value properly even if it
2158 * then no longer matches the actual (corrupted) string of the target.
2159 * The hash value has to match the hash queue that the dentry is on..
2162 * __d_move - move a dentry
2163 * @dentry: entry to move
2164 * @target: new dentry
2166 * Update the dcache to reflect the move of a file name. Negative
2167 * dcache entries should not be moved in this way. Caller must hold
2168 * rename_lock, the i_mutex of the source and target directories,
2169 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2171 static void __d_move(struct dentry * dentry, struct dentry * target)
2173 if (!dentry->d_inode)
2174 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
2176 BUG_ON(d_ancestor(dentry, target));
2177 BUG_ON(d_ancestor(target, dentry));
2179 dentry_lock_for_move(dentry, target);
2181 write_seqcount_begin(&dentry->d_seq);
2182 write_seqcount_begin(&target->d_seq);
2184 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
2187 * Move the dentry to the target hash queue. Don't bother checking
2188 * for the same hash queue because of how unlikely it is.
2191 __d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
2193 /* Unhash the target: dput() will then get rid of it */
2196 list_del(&dentry->d_u.d_child);
2197 list_del(&target->d_u.d_child);
2199 /* Switch the names.. */
2200 switch_names(dentry, target);
2201 swap(dentry->d_name.hash, target->d_name.hash);
2203 /* ... and switch the parents */
2204 if (IS_ROOT(dentry)) {
2205 dentry->d_parent = target->d_parent;
2206 target->d_parent = target;
2207 INIT_LIST_HEAD(&target->d_u.d_child);
2209 swap(dentry->d_parent, target->d_parent);
2211 /* And add them back to the (new) parent lists */
2212 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
2215 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
2217 write_seqcount_end(&target->d_seq);
2218 write_seqcount_end(&dentry->d_seq);
2220 dentry_unlock_parents_for_move(dentry, target);
2221 spin_unlock(&target->d_lock);
2222 fsnotify_d_move(dentry);
2223 spin_unlock(&dentry->d_lock);
2227 * d_move - move a dentry
2228 * @dentry: entry to move
2229 * @target: new dentry
2231 * Update the dcache to reflect the move of a file name. Negative
2232 * dcache entries should not be moved in this way. See the locking
2233 * requirements for __d_move.
2235 void d_move(struct dentry *dentry, struct dentry *target)
2237 write_seqlock(&rename_lock);
2238 __d_move(dentry, target);
2239 write_sequnlock(&rename_lock);
2241 EXPORT_SYMBOL(d_move);
2244 * d_ancestor - search for an ancestor
2245 * @p1: ancestor dentry
2248 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2249 * an ancestor of p2, else NULL.
2251 struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2255 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2256 if (p->d_parent == p1)
2263 * This helper attempts to cope with remotely renamed directories
2265 * It assumes that the caller is already holding
2266 * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
2268 * Note: If ever the locking in lock_rename() changes, then please
2269 * remember to update this too...
2271 static struct dentry *__d_unalias(struct inode *inode,
2272 struct dentry *dentry, struct dentry *alias)
2274 struct mutex *m1 = NULL, *m2 = NULL;
2277 /* If alias and dentry share a parent, then no extra locks required */
2278 if (alias->d_parent == dentry->d_parent)
2281 /* See lock_rename() */
2282 ret = ERR_PTR(-EBUSY);
2283 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
2285 m1 = &dentry->d_sb->s_vfs_rename_mutex;
2286 if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
2288 m2 = &alias->d_parent->d_inode->i_mutex;
2290 __d_move(alias, dentry);
2293 spin_unlock(&inode->i_lock);
2302 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
2303 * named dentry in place of the dentry to be replaced.
2304 * returns with anon->d_lock held!
2306 static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
2308 struct dentry *dparent, *aparent;
2310 dentry_lock_for_move(anon, dentry);
2312 write_seqcount_begin(&dentry->d_seq);
2313 write_seqcount_begin(&anon->d_seq);
2315 dparent = dentry->d_parent;
2316 aparent = anon->d_parent;
2318 switch_names(dentry, anon);
2319 swap(dentry->d_name.hash, anon->d_name.hash);
2321 dentry->d_parent = (aparent == anon) ? dentry : aparent;
2322 list_del(&dentry->d_u.d_child);
2323 if (!IS_ROOT(dentry))
2324 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
2326 INIT_LIST_HEAD(&dentry->d_u.d_child);
2328 anon->d_parent = (dparent == dentry) ? anon : dparent;
2329 list_del(&anon->d_u.d_child);
2331 list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
2333 INIT_LIST_HEAD(&anon->d_u.d_child);
2335 write_seqcount_end(&dentry->d_seq);
2336 write_seqcount_end(&anon->d_seq);
2338 dentry_unlock_parents_for_move(anon, dentry);
2339 spin_unlock(&dentry->d_lock);
2341 /* anon->d_lock still locked, returns locked */
2342 anon->d_flags &= ~DCACHE_DISCONNECTED;
2346 * d_materialise_unique - introduce an inode into the tree
2347 * @dentry: candidate dentry
2348 * @inode: inode to bind to the dentry, to which aliases may be attached
2350 * Introduces an dentry into the tree, substituting an extant disconnected
2351 * root directory alias in its place if there is one. Caller must hold the
2352 * i_mutex of the parent directory.
2354 struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
2356 struct dentry *actual;
2358 BUG_ON(!d_unhashed(dentry));
2362 __d_instantiate(dentry, NULL);
2367 spin_lock(&inode->i_lock);
2369 if (S_ISDIR(inode->i_mode)) {
2370 struct dentry *alias;
2372 /* Does an aliased dentry already exist? */
2373 alias = __d_find_alias(inode, 0);
2376 write_seqlock(&rename_lock);
2378 if (d_ancestor(alias, dentry)) {
2379 /* Check for loops */
2380 actual = ERR_PTR(-ELOOP);
2381 } else if (IS_ROOT(alias)) {
2382 /* Is this an anonymous mountpoint that we
2383 * could splice into our tree? */
2384 __d_materialise_dentry(dentry, alias);
2385 write_sequnlock(&rename_lock);
2389 /* Nope, but we must(!) avoid directory
2391 actual = __d_unalias(inode, dentry, alias);
2393 write_sequnlock(&rename_lock);
2394 if (IS_ERR(actual)) {
2395 if (PTR_ERR(actual) == -ELOOP)
2396 pr_warn_ratelimited(
2397 "VFS: Lookup of '%s' in %s %s"
2398 " would have caused loop\n",
2399 dentry->d_name.name,
2400 inode->i_sb->s_type->name,
2408 /* Add a unique reference */
2409 actual = __d_instantiate_unique(dentry, inode);
2413 BUG_ON(!d_unhashed(actual));
2415 spin_lock(&actual->d_lock);
2418 spin_unlock(&actual->d_lock);
2419 spin_unlock(&inode->i_lock);
2421 if (actual == dentry) {
2422 security_d_instantiate(dentry, inode);
2429 EXPORT_SYMBOL_GPL(d_materialise_unique);
2431 static int prepend(char **buffer, int *buflen, const char *str, int namelen)
2435 return -ENAMETOOLONG;
2437 memcpy(*buffer, str, namelen);
2441 static int prepend_name(char **buffer, int *buflen, struct qstr *name)
2443 return prepend(buffer, buflen, name->name, name->len);
2447 * prepend_path - Prepend path string to a buffer
2448 * @path: the dentry/vfsmount to report
2449 * @root: root vfsmnt/dentry
2450 * @buffer: pointer to the end of the buffer
2451 * @buflen: pointer to buffer length
2453 * Caller holds the rename_lock.
2455 static int prepend_path(const struct path *path,
2456 const struct path *root,
2457 char **buffer, int *buflen)
2459 struct dentry *dentry = path->dentry;
2460 struct vfsmount *vfsmnt = path->mnt;
2464 br_read_lock(vfsmount_lock);
2465 while (dentry != root->dentry || vfsmnt != root->mnt) {
2466 struct dentry * parent;
2468 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
2470 if (vfsmnt->mnt_parent == vfsmnt) {
2473 dentry = vfsmnt->mnt_mountpoint;
2474 vfsmnt = vfsmnt->mnt_parent;
2477 parent = dentry->d_parent;
2479 spin_lock(&dentry->d_lock);
2480 error = prepend_name(buffer, buflen, &dentry->d_name);
2481 spin_unlock(&dentry->d_lock);
2483 error = prepend(buffer, buflen, "/", 1);
2491 if (!error && !slash)
2492 error = prepend(buffer, buflen, "/", 1);
2495 br_read_unlock(vfsmount_lock);
2500 * Filesystems needing to implement special "root names"
2501 * should do so with ->d_dname()
2503 if (IS_ROOT(dentry) &&
2504 (dentry->d_name.len != 1 || dentry->d_name.name[0] != '/')) {
2505 WARN(1, "Root dentry has weird name <%.*s>\n",
2506 (int) dentry->d_name.len, dentry->d_name.name);
2509 error = prepend(buffer, buflen, "/", 1);
2511 error = vfsmnt->mnt_ns ? 1 : 2;
2516 * __d_path - return the path of a dentry
2517 * @path: the dentry/vfsmount to report
2518 * @root: root vfsmnt/dentry
2519 * @buf: buffer to return value in
2520 * @buflen: buffer length
2522 * Convert a dentry into an ASCII path name.
2524 * Returns a pointer into the buffer or an error code if the
2525 * path was too long.
2527 * "buflen" should be positive.
2529 * If the path is not reachable from the supplied root, return %NULL.
2531 char *__d_path(const struct path *path,
2532 const struct path *root,
2533 char *buf, int buflen)
2535 char *res = buf + buflen;
2538 prepend(&res, &buflen, "\0", 1);
2539 write_seqlock(&rename_lock);
2540 error = prepend_path(path, root, &res, &buflen);
2541 write_sequnlock(&rename_lock);
2544 return ERR_PTR(error);
2550 char *d_absolute_path(const struct path *path,
2551 char *buf, int buflen)
2553 struct path root = {};
2554 char *res = buf + buflen;
2557 prepend(&res, &buflen, "\0", 1);
2558 write_seqlock(&rename_lock);
2559 error = prepend_path(path, &root, &res, &buflen);
2560 write_sequnlock(&rename_lock);
2565 return ERR_PTR(error);
2570 * same as __d_path but appends "(deleted)" for unlinked files.
2572 static int path_with_deleted(const struct path *path,
2573 const struct path *root,
2574 char **buf, int *buflen)
2576 prepend(buf, buflen, "\0", 1);
2577 if (d_unlinked(path->dentry)) {
2578 int error = prepend(buf, buflen, " (deleted)", 10);
2583 return prepend_path(path, root, buf, buflen);
2586 static int prepend_unreachable(char **buffer, int *buflen)
2588 return prepend(buffer, buflen, "(unreachable)", 13);
2592 * d_path - return the path of a dentry
2593 * @path: path to report
2594 * @buf: buffer to return value in
2595 * @buflen: buffer length
2597 * Convert a dentry into an ASCII path name. If the entry has been deleted
2598 * the string " (deleted)" is appended. Note that this is ambiguous.
2600 * Returns a pointer into the buffer or an error code if the path was
2601 * too long. Note: Callers should use the returned pointer, not the passed
2602 * in buffer, to use the name! The implementation often starts at an offset
2603 * into the buffer, and may leave 0 bytes at the start.
2605 * "buflen" should be positive.
2607 char *d_path(const struct path *path, char *buf, int buflen)
2609 char *res = buf + buflen;
2614 * We have various synthetic filesystems that never get mounted. On
2615 * these filesystems dentries are never used for lookup purposes, and
2616 * thus don't need to be hashed. They also don't need a name until a
2617 * user wants to identify the object in /proc/pid/fd/. The little hack
2618 * below allows us to generate a name for these objects on demand:
2620 if (path->dentry->d_op && path->dentry->d_op->d_dname)
2621 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2623 get_fs_root(current->fs, &root);
2624 write_seqlock(&rename_lock);
2625 error = path_with_deleted(path, &root, &res, &buflen);
2627 res = ERR_PTR(error);
2628 write_sequnlock(&rename_lock);
2632 EXPORT_SYMBOL(d_path);
2635 * d_path_with_unreachable - return the path of a dentry
2636 * @path: path to report
2637 * @buf: buffer to return value in
2638 * @buflen: buffer length
2640 * The difference from d_path() is that this prepends "(unreachable)"
2641 * to paths which are unreachable from the current process' root.
2643 char *d_path_with_unreachable(const struct path *path, char *buf, int buflen)
2645 char *res = buf + buflen;
2649 if (path->dentry->d_op && path->dentry->d_op->d_dname)
2650 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2652 get_fs_root(current->fs, &root);
2653 write_seqlock(&rename_lock);
2654 error = path_with_deleted(path, &root, &res, &buflen);
2656 error = prepend_unreachable(&res, &buflen);
2657 write_sequnlock(&rename_lock);
2660 res = ERR_PTR(error);
2666 * Helper function for dentry_operations.d_dname() members
2668 char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
2669 const char *fmt, ...)
2675 va_start(args, fmt);
2676 sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
2679 if (sz > sizeof(temp) || sz > buflen)
2680 return ERR_PTR(-ENAMETOOLONG);
2682 buffer += buflen - sz;
2683 return memcpy(buffer, temp, sz);
2687 * Write full pathname from the root of the filesystem into the buffer.
2689 static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
2691 char *end = buf + buflen;
2694 prepend(&end, &buflen, "\0", 1);
2701 while (!IS_ROOT(dentry)) {
2702 struct dentry *parent = dentry->d_parent;
2706 spin_lock(&dentry->d_lock);
2707 error = prepend_name(&end, &buflen, &dentry->d_name);
2708 spin_unlock(&dentry->d_lock);
2709 if (error != 0 || prepend(&end, &buflen, "/", 1) != 0)
2717 return ERR_PTR(-ENAMETOOLONG);
2720 char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
2724 write_seqlock(&rename_lock);
2725 retval = __dentry_path(dentry, buf, buflen);
2726 write_sequnlock(&rename_lock);
2730 EXPORT_SYMBOL(dentry_path_raw);
2732 char *dentry_path(struct dentry *dentry, char *buf, int buflen)
2737 write_seqlock(&rename_lock);
2738 if (d_unlinked(dentry)) {
2740 if (prepend(&p, &buflen, "//deleted", 10) != 0)
2744 retval = __dentry_path(dentry, buf, buflen);
2745 write_sequnlock(&rename_lock);
2746 if (!IS_ERR(retval) && p)
2747 *p = '/'; /* restore '/' overriden with '\0' */
2750 return ERR_PTR(-ENAMETOOLONG);
2754 * NOTE! The user-level library version returns a
2755 * character pointer. The kernel system call just
2756 * returns the length of the buffer filled (which
2757 * includes the ending '\0' character), or a negative
2758 * error value. So libc would do something like
2760 * char *getcwd(char * buf, size_t size)
2764 * retval = sys_getcwd(buf, size);
2771 SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
2774 struct path pwd, root;
2775 char *page = (char *) __get_free_page(GFP_USER);
2780 get_fs_root_and_pwd(current->fs, &root, &pwd);
2783 write_seqlock(&rename_lock);
2784 if (!d_unlinked(pwd.dentry)) {
2786 char *cwd = page + PAGE_SIZE;
2787 int buflen = PAGE_SIZE;
2789 prepend(&cwd, &buflen, "\0", 1);
2790 error = prepend_path(&pwd, &root, &cwd, &buflen);
2791 write_sequnlock(&rename_lock);
2796 /* Unreachable from current root */
2798 error = prepend_unreachable(&cwd, &buflen);
2804 len = PAGE_SIZE + page - cwd;
2807 if (copy_to_user(buf, cwd, len))
2811 write_sequnlock(&rename_lock);
2817 free_page((unsigned long) page);
2822 * Test whether new_dentry is a subdirectory of old_dentry.
2824 * Trivially implemented using the dcache structure
2828 * is_subdir - is new dentry a subdirectory of old_dentry
2829 * @new_dentry: new dentry
2830 * @old_dentry: old dentry
2832 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
2833 * Returns 0 otherwise.
2834 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
2837 int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
2842 if (new_dentry == old_dentry)
2846 /* for restarting inner loop in case of seq retry */
2847 seq = read_seqbegin(&rename_lock);
2849 * Need rcu_readlock to protect against the d_parent trashing
2853 if (d_ancestor(old_dentry, new_dentry))
2858 } while (read_seqretry(&rename_lock, seq));
2863 int path_is_under(struct path *path1, struct path *path2)
2865 struct vfsmount *mnt = path1->mnt;
2866 struct dentry *dentry = path1->dentry;
2869 br_read_lock(vfsmount_lock);
2870 if (mnt != path2->mnt) {
2872 if (mnt->mnt_parent == mnt) {
2873 br_read_unlock(vfsmount_lock);
2876 if (mnt->mnt_parent == path2->mnt)
2878 mnt = mnt->mnt_parent;
2880 dentry = mnt->mnt_mountpoint;
2882 res = is_subdir(dentry, path2->dentry);
2883 br_read_unlock(vfsmount_lock);
2886 EXPORT_SYMBOL(path_is_under);
2888 void d_genocide(struct dentry *root)
2890 struct dentry *this_parent;
2891 struct list_head *next;
2895 seq = read_seqbegin(&rename_lock);
2898 spin_lock(&this_parent->d_lock);
2900 next = this_parent->d_subdirs.next;
2902 while (next != &this_parent->d_subdirs) {
2903 struct list_head *tmp = next;
2904 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
2907 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
2908 if (d_unhashed(dentry) || !dentry->d_inode) {
2909 spin_unlock(&dentry->d_lock);
2912 if (!list_empty(&dentry->d_subdirs)) {
2913 spin_unlock(&this_parent->d_lock);
2914 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
2915 this_parent = dentry;
2916 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
2919 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
2920 dentry->d_flags |= DCACHE_GENOCIDE;
2923 spin_unlock(&dentry->d_lock);
2925 if (this_parent != root) {
2926 struct dentry *child = this_parent;
2927 if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
2928 this_parent->d_flags |= DCACHE_GENOCIDE;
2929 this_parent->d_count--;
2931 this_parent = try_to_ascend(this_parent, locked, seq);
2934 next = child->d_u.d_child.next;
2937 spin_unlock(&this_parent->d_lock);
2938 if (!locked && read_seqretry(&rename_lock, seq))
2941 write_sequnlock(&rename_lock);
2946 write_seqlock(&rename_lock);
2951 * find_inode_number - check for dentry with name
2952 * @dir: directory to check
2953 * @name: Name to find.
2955 * Check whether a dentry already exists for the given name,
2956 * and return the inode number if it has an inode. Otherwise
2959 * This routine is used to post-process directory listings for
2960 * filesystems using synthetic inode numbers, and is necessary
2961 * to keep getcwd() working.
2964 ino_t find_inode_number(struct dentry *dir, struct qstr *name)
2966 struct dentry * dentry;
2969 dentry = d_hash_and_lookup(dir, name);
2971 if (dentry->d_inode)
2972 ino = dentry->d_inode->i_ino;
2977 EXPORT_SYMBOL(find_inode_number);
2979 static __initdata unsigned long dhash_entries;
2980 static int __init set_dhash_entries(char *str)
2984 dhash_entries = simple_strtoul(str, &str, 0);
2987 __setup("dhash_entries=", set_dhash_entries);
2989 static void __init dcache_init_early(void)
2993 /* If hashes are distributed across NUMA nodes, defer
2994 * hash allocation until vmalloc space is available.
3000 alloc_large_system_hash("Dentry cache",
3001 sizeof(struct hlist_bl_head),
3009 for (loop = 0; loop < (1 << d_hash_shift); loop++)
3010 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
3013 static void __init dcache_init(void)
3018 * A constructor could be added for stable state like the lists,
3019 * but it is probably not worth it because of the cache nature
3022 dentry_cache = KMEM_CACHE(dentry,
3023 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
3025 /* Hash may have been set up in dcache_init_early */
3030 alloc_large_system_hash("Dentry cache",
3031 sizeof(struct hlist_bl_head),
3039 for (loop = 0; loop < (1 << d_hash_shift); loop++)
3040 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
3043 /* SLAB cache for __getname() consumers */
3044 struct kmem_cache *names_cachep __read_mostly;
3045 EXPORT_SYMBOL(names_cachep);
3047 EXPORT_SYMBOL(d_genocide);
3049 void __init vfs_caches_init_early(void)
3051 dcache_init_early();
3055 void __init vfs_caches_init(unsigned long mempages)
3057 unsigned long reserve;
3059 /* Base hash sizes on available memory, with a reserve equal to
3060 150% of current kernel size */
3062 reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
3063 mempages -= reserve;
3065 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
3066 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
3070 files_init(mempages);