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>
43 * dcache->d_inode->i_lock protects:
44 * - i_dentry, d_alias, d_inode of aliases
45 * dcache_hash_bucket lock protects:
46 * - the dcache hash table
47 * s_anon bl list spinlock protects:
48 * - the s_anon list (see __d_drop)
49 * dcache_lru_lock protects:
50 * - the dcache lru lists and counters
57 * - d_parent and d_subdirs
58 * - childrens' d_child and d_parent
62 * dentry->d_inode->i_lock
65 * dcache_hash_bucket lock
68 * If there is an ancestor relationship:
69 * dentry->d_parent->...->d_parent->d_lock
71 * dentry->d_parent->d_lock
74 * If no ancestor relationship:
75 * if (dentry1 < dentry2)
79 int sysctl_vfs_cache_pressure __read_mostly = 100;
80 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
82 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
83 __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
85 EXPORT_SYMBOL(rename_lock);
87 static struct kmem_cache *dentry_cache __read_mostly;
90 * This is the single most critical data structure when it comes
91 * to the dcache: the hashtable for lookups. Somebody should try
92 * to make this good - I've just made it work.
94 * This hash-function tries to avoid losing too many bits of hash
95 * information, yet avoid using a prime hash-size or similar.
97 #define D_HASHBITS d_hash_shift
98 #define D_HASHMASK d_hash_mask
100 static unsigned int d_hash_mask __read_mostly;
101 static unsigned int d_hash_shift __read_mostly;
103 static struct hlist_bl_head *dentry_hashtable __read_mostly;
105 static inline struct hlist_bl_head *d_hash(struct dentry *parent,
108 hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
109 hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
110 return dentry_hashtable + (hash & D_HASHMASK);
113 /* Statistics gathering. */
114 struct dentry_stat_t dentry_stat = {
118 static DEFINE_PER_CPU(unsigned int, nr_dentry);
120 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
121 static int get_nr_dentry(void)
125 for_each_possible_cpu(i)
126 sum += per_cpu(nr_dentry, i);
127 return sum < 0 ? 0 : sum;
130 int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
131 size_t *lenp, loff_t *ppos)
133 dentry_stat.nr_dentry = get_nr_dentry();
134 return proc_dointvec(table, write, buffer, lenp, ppos);
138 static void __d_free(struct rcu_head *head)
140 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
142 WARN_ON(!list_empty(&dentry->d_alias));
143 if (dname_external(dentry))
144 kfree(dentry->d_name.name);
145 kmem_cache_free(dentry_cache, dentry);
151 static void d_free(struct dentry *dentry)
153 BUG_ON(dentry->d_count);
154 this_cpu_dec(nr_dentry);
155 if (dentry->d_op && dentry->d_op->d_release)
156 dentry->d_op->d_release(dentry);
158 /* if dentry was never visible to RCU, immediate free is OK */
159 if (!(dentry->d_flags & DCACHE_RCUACCESS))
160 __d_free(&dentry->d_u.d_rcu);
162 call_rcu(&dentry->d_u.d_rcu, __d_free);
166 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
167 * @dentry: the target dentry
168 * After this call, in-progress rcu-walk path lookup will fail. This
169 * should be called after unhashing, and after changing d_inode (if
170 * the dentry has not already been unhashed).
172 static inline void dentry_rcuwalk_barrier(struct dentry *dentry)
174 assert_spin_locked(&dentry->d_lock);
175 /* Go through a barrier */
176 write_seqcount_barrier(&dentry->d_seq);
180 * Release the dentry's inode, using the filesystem
181 * d_iput() operation if defined. Dentry has no refcount
184 static void dentry_iput(struct dentry * dentry)
185 __releases(dentry->d_lock)
186 __releases(dentry->d_inode->i_lock)
188 struct inode *inode = dentry->d_inode;
190 dentry->d_inode = NULL;
191 list_del_init(&dentry->d_alias);
192 spin_unlock(&dentry->d_lock);
193 spin_unlock(&inode->i_lock);
195 fsnotify_inoderemove(inode);
196 if (dentry->d_op && dentry->d_op->d_iput)
197 dentry->d_op->d_iput(dentry, inode);
201 spin_unlock(&dentry->d_lock);
206 * Release the dentry's inode, using the filesystem
207 * d_iput() operation if defined. dentry remains in-use.
209 static void dentry_unlink_inode(struct dentry * dentry)
210 __releases(dentry->d_lock)
211 __releases(dentry->d_inode->i_lock)
213 struct inode *inode = dentry->d_inode;
214 dentry->d_inode = NULL;
215 list_del_init(&dentry->d_alias);
216 dentry_rcuwalk_barrier(dentry);
217 spin_unlock(&dentry->d_lock);
218 spin_unlock(&inode->i_lock);
220 fsnotify_inoderemove(inode);
221 if (dentry->d_op && dentry->d_op->d_iput)
222 dentry->d_op->d_iput(dentry, inode);
228 * dentry_lru_(add|del|move_tail) must be called with d_lock held.
230 static void dentry_lru_add(struct dentry *dentry)
232 if (list_empty(&dentry->d_lru)) {
233 spin_lock(&dcache_lru_lock);
234 list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
235 dentry->d_sb->s_nr_dentry_unused++;
236 dentry_stat.nr_unused++;
237 spin_unlock(&dcache_lru_lock);
241 static void __dentry_lru_del(struct dentry *dentry)
243 list_del_init(&dentry->d_lru);
244 dentry->d_sb->s_nr_dentry_unused--;
245 dentry_stat.nr_unused--;
248 static void dentry_lru_del(struct dentry *dentry)
250 if (!list_empty(&dentry->d_lru)) {
251 spin_lock(&dcache_lru_lock);
252 __dentry_lru_del(dentry);
253 spin_unlock(&dcache_lru_lock);
257 static void dentry_lru_move_tail(struct dentry *dentry)
259 spin_lock(&dcache_lru_lock);
260 if (list_empty(&dentry->d_lru)) {
261 list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
262 dentry->d_sb->s_nr_dentry_unused++;
263 dentry_stat.nr_unused++;
265 list_move_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
267 spin_unlock(&dcache_lru_lock);
271 * d_kill - kill dentry and return parent
272 * @dentry: dentry to kill
273 * @parent: parent dentry
275 * The dentry must already be unhashed and removed from the LRU.
277 * If this is the root of the dentry tree, return NULL.
279 * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
282 static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
283 __releases(dentry->d_lock)
284 __releases(parent->d_lock)
285 __releases(dentry->d_inode->i_lock)
287 list_del(&dentry->d_u.d_child);
289 * Inform try_to_ascend() that we are no longer attached to the
292 dentry->d_flags |= DCACHE_DISCONNECTED;
294 spin_unlock(&parent->d_lock);
297 * dentry_iput drops the locks, at which point nobody (except
298 * transient RCU lookups) can reach this dentry.
305 * d_drop - drop a dentry
306 * @dentry: dentry to drop
308 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
309 * be found through a VFS lookup any more. Note that this is different from
310 * deleting the dentry - d_delete will try to mark the dentry negative if
311 * possible, giving a successful _negative_ lookup, while d_drop will
312 * just make the cache lookup fail.
314 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
315 * reason (NFS timeouts or autofs deletes).
317 * __d_drop requires dentry->d_lock.
319 void __d_drop(struct dentry *dentry)
321 if (!d_unhashed(dentry)) {
322 struct hlist_bl_head *b;
323 if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
324 b = &dentry->d_sb->s_anon;
326 b = d_hash(dentry->d_parent, dentry->d_name.hash);
329 __hlist_bl_del(&dentry->d_hash);
330 dentry->d_hash.pprev = NULL;
333 dentry_rcuwalk_barrier(dentry);
336 EXPORT_SYMBOL(__d_drop);
338 void d_drop(struct dentry *dentry)
340 spin_lock(&dentry->d_lock);
342 spin_unlock(&dentry->d_lock);
344 EXPORT_SYMBOL(d_drop);
347 * d_clear_need_lookup - drop a dentry from cache and clear the need lookup flag
348 * @dentry: dentry to drop
350 * This is called when we do a lookup on a placeholder dentry that needed to be
351 * looked up. The dentry should have been hashed in order for it to be found by
352 * the lookup code, but now needs to be unhashed while we do the actual lookup
353 * and clear the DCACHE_NEED_LOOKUP flag.
355 void d_clear_need_lookup(struct dentry *dentry)
357 spin_lock(&dentry->d_lock);
359 dentry->d_flags &= ~DCACHE_NEED_LOOKUP;
360 spin_unlock(&dentry->d_lock);
362 EXPORT_SYMBOL(d_clear_need_lookup);
365 * Finish off a dentry we've decided to kill.
366 * dentry->d_lock must be held, returns with it unlocked.
367 * If ref is non-zero, then decrement the refcount too.
368 * Returns dentry requiring refcount drop, or NULL if we're done.
370 static inline struct dentry *dentry_kill(struct dentry *dentry, int ref)
371 __releases(dentry->d_lock)
374 struct dentry *parent;
376 inode = dentry->d_inode;
377 if (inode && !spin_trylock(&inode->i_lock)) {
379 spin_unlock(&dentry->d_lock);
381 return dentry; /* try again with same dentry */
386 parent = dentry->d_parent;
387 if (parent && !spin_trylock(&parent->d_lock)) {
389 spin_unlock(&inode->i_lock);
395 /* if dentry was on the d_lru list delete it from there */
396 dentry_lru_del(dentry);
397 /* if it was on the hash then remove it */
399 return d_kill(dentry, parent);
405 * This is complicated by the fact that we do not want to put
406 * dentries that are no longer on any hash chain on the unused
407 * list: we'd much rather just get rid of them immediately.
409 * However, that implies that we have to traverse the dentry
410 * tree upwards to the parents which might _also_ now be
411 * scheduled for deletion (it may have been only waiting for
412 * its last child to go away).
414 * This tail recursion is done by hand as we don't want to depend
415 * on the compiler to always get this right (gcc generally doesn't).
416 * Real recursion would eat up our stack space.
420 * dput - release a dentry
421 * @dentry: dentry to release
423 * Release a dentry. This will drop the usage count and if appropriate
424 * call the dentry unlink method as well as removing it from the queues and
425 * releasing its resources. If the parent dentries were scheduled for release
426 * they too may now get deleted.
428 void dput(struct dentry *dentry)
434 if (dentry->d_count == 1)
436 spin_lock(&dentry->d_lock);
437 BUG_ON(!dentry->d_count);
438 if (dentry->d_count > 1) {
440 spin_unlock(&dentry->d_lock);
444 if (dentry->d_flags & DCACHE_OP_DELETE) {
445 if (dentry->d_op->d_delete(dentry))
449 /* Unreachable? Get rid of it */
450 if (d_unhashed(dentry))
454 * If this dentry needs lookup, don't set the referenced flag so that it
455 * is more likely to be cleaned up by the dcache shrinker in case of
458 if (!d_need_lookup(dentry))
459 dentry->d_flags |= DCACHE_REFERENCED;
460 dentry_lru_add(dentry);
463 spin_unlock(&dentry->d_lock);
467 dentry = dentry_kill(dentry, 1);
474 * d_invalidate - invalidate a dentry
475 * @dentry: dentry to invalidate
477 * Try to invalidate the dentry if it turns out to be
478 * possible. If there are other dentries that can be
479 * reached through this one we can't delete it and we
480 * return -EBUSY. On success we return 0.
485 int d_invalidate(struct dentry * dentry)
488 * If it's already been dropped, return OK.
490 spin_lock(&dentry->d_lock);
491 if (d_unhashed(dentry)) {
492 spin_unlock(&dentry->d_lock);
496 * Check whether to do a partial shrink_dcache
497 * to get rid of unused child entries.
499 if (!list_empty(&dentry->d_subdirs)) {
500 spin_unlock(&dentry->d_lock);
501 shrink_dcache_parent(dentry);
502 spin_lock(&dentry->d_lock);
506 * Somebody else still using it?
508 * If it's a directory, we can't drop it
509 * for fear of somebody re-populating it
510 * with children (even though dropping it
511 * would make it unreachable from the root,
512 * we might still populate it if it was a
513 * working directory or similar).
515 if (dentry->d_count > 1) {
516 if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
517 spin_unlock(&dentry->d_lock);
523 spin_unlock(&dentry->d_lock);
526 EXPORT_SYMBOL(d_invalidate);
528 /* This must be called with d_lock held */
529 static inline void __dget_dlock(struct dentry *dentry)
534 static inline void __dget(struct dentry *dentry)
536 spin_lock(&dentry->d_lock);
537 __dget_dlock(dentry);
538 spin_unlock(&dentry->d_lock);
541 struct dentry *dget_parent(struct dentry *dentry)
547 * Don't need rcu_dereference because we re-check it was correct under
551 ret = dentry->d_parent;
556 spin_lock(&ret->d_lock);
557 if (unlikely(ret != dentry->d_parent)) {
558 spin_unlock(&ret->d_lock);
563 BUG_ON(!ret->d_count);
565 spin_unlock(&ret->d_lock);
569 EXPORT_SYMBOL(dget_parent);
572 * d_find_alias - grab a hashed alias of inode
573 * @inode: inode in question
574 * @want_discon: flag, used by d_splice_alias, to request
575 * that only a DISCONNECTED alias be returned.
577 * If inode has a hashed alias, or is a directory and has any alias,
578 * acquire the reference to alias and return it. Otherwise return NULL.
579 * Notice that if inode is a directory there can be only one alias and
580 * it can be unhashed only if it has no children, or if it is the root
583 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
584 * any other hashed alias over that one unless @want_discon is set,
585 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
587 static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
589 struct dentry *alias, *discon_alias;
593 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
594 spin_lock(&alias->d_lock);
595 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
596 if (IS_ROOT(alias) &&
597 (alias->d_flags & DCACHE_DISCONNECTED)) {
598 discon_alias = alias;
599 } else if (!want_discon) {
601 spin_unlock(&alias->d_lock);
605 spin_unlock(&alias->d_lock);
608 alias = discon_alias;
609 spin_lock(&alias->d_lock);
610 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
611 if (IS_ROOT(alias) &&
612 (alias->d_flags & DCACHE_DISCONNECTED)) {
614 spin_unlock(&alias->d_lock);
618 spin_unlock(&alias->d_lock);
624 struct dentry *d_find_alias(struct inode *inode)
626 struct dentry *de = NULL;
628 if (!list_empty(&inode->i_dentry)) {
629 spin_lock(&inode->i_lock);
630 de = __d_find_alias(inode, 0);
631 spin_unlock(&inode->i_lock);
635 EXPORT_SYMBOL(d_find_alias);
638 * Try to kill dentries associated with this inode.
639 * WARNING: you must own a reference to inode.
641 void d_prune_aliases(struct inode *inode)
643 struct dentry *dentry;
645 spin_lock(&inode->i_lock);
646 list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
647 spin_lock(&dentry->d_lock);
648 if (!dentry->d_count) {
649 __dget_dlock(dentry);
651 spin_unlock(&dentry->d_lock);
652 spin_unlock(&inode->i_lock);
656 spin_unlock(&dentry->d_lock);
658 spin_unlock(&inode->i_lock);
660 EXPORT_SYMBOL(d_prune_aliases);
663 * Try to throw away a dentry - free the inode, dput the parent.
664 * Requires dentry->d_lock is held, and dentry->d_count == 0.
665 * Releases dentry->d_lock.
667 * This may fail if locks cannot be acquired no problem, just try again.
669 static void try_prune_one_dentry(struct dentry *dentry)
670 __releases(dentry->d_lock)
672 struct dentry *parent;
674 parent = dentry_kill(dentry, 0);
676 * If dentry_kill returns NULL, we have nothing more to do.
677 * if it returns the same dentry, trylocks failed. In either
678 * case, just loop again.
680 * Otherwise, we need to prune ancestors too. This is necessary
681 * to prevent quadratic behavior of shrink_dcache_parent(), but
682 * is also expected to be beneficial in reducing dentry cache
687 if (parent == dentry)
690 /* Prune ancestors. */
693 spin_lock(&dentry->d_lock);
694 if (dentry->d_count > 1) {
696 spin_unlock(&dentry->d_lock);
699 dentry = dentry_kill(dentry, 1);
703 static void shrink_dentry_list(struct list_head *list)
705 struct dentry *dentry;
709 dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
710 if (&dentry->d_lru == list)
712 spin_lock(&dentry->d_lock);
713 if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
714 spin_unlock(&dentry->d_lock);
719 * We found an inuse dentry which was not removed from
720 * the LRU because of laziness during lookup. Do not free
721 * it - just keep it off the LRU list.
723 if (dentry->d_count) {
724 dentry_lru_del(dentry);
725 spin_unlock(&dentry->d_lock);
731 try_prune_one_dentry(dentry);
739 * __shrink_dcache_sb - shrink the dentry LRU on a given superblock
740 * @sb: superblock to shrink dentry LRU.
741 * @count: number of entries to prune
742 * @flags: flags to control the dentry processing
744 * If flags contains DCACHE_REFERENCED reference dentries will not be pruned.
746 static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
748 /* called from prune_dcache() and shrink_dcache_parent() */
749 struct dentry *dentry;
750 LIST_HEAD(referenced);
755 spin_lock(&dcache_lru_lock);
756 while (!list_empty(&sb->s_dentry_lru)) {
757 dentry = list_entry(sb->s_dentry_lru.prev,
758 struct dentry, d_lru);
759 BUG_ON(dentry->d_sb != sb);
761 if (!spin_trylock(&dentry->d_lock)) {
762 spin_unlock(&dcache_lru_lock);
768 * If we are honouring the DCACHE_REFERENCED flag and the
769 * dentry has this flag set, don't free it. Clear the flag
770 * and put it back on the LRU.
772 if (flags & DCACHE_REFERENCED &&
773 dentry->d_flags & DCACHE_REFERENCED) {
774 dentry->d_flags &= ~DCACHE_REFERENCED;
775 list_move(&dentry->d_lru, &referenced);
776 spin_unlock(&dentry->d_lock);
778 list_move_tail(&dentry->d_lru, &tmp);
779 spin_unlock(&dentry->d_lock);
783 cond_resched_lock(&dcache_lru_lock);
785 if (!list_empty(&referenced))
786 list_splice(&referenced, &sb->s_dentry_lru);
787 spin_unlock(&dcache_lru_lock);
789 shrink_dentry_list(&tmp);
795 * prune_dcache - shrink the dcache
796 * @count: number of entries to try to free
798 * Shrink the dcache. This is done when we need more memory, or simply when we
799 * need to unmount something (at which point we need to unuse all dentries).
801 * This function may fail to free any resources if all the dentries are in use.
803 static void prune_dcache(int count)
805 struct super_block *sb, *p = NULL;
807 int unused = dentry_stat.nr_unused;
811 if (unused == 0 || count == 0)
816 prune_ratio = unused / count;
818 list_for_each_entry(sb, &super_blocks, s_list) {
819 if (list_empty(&sb->s_instances))
821 if (sb->s_nr_dentry_unused == 0)
824 /* Now, we reclaim unused dentrins with fairness.
825 * We reclaim them same percentage from each superblock.
826 * We calculate number of dentries to scan on this sb
827 * as follows, but the implementation is arranged to avoid
829 * number of dentries to scan on this sb =
830 * count * (number of dentries on this sb /
831 * number of dentries in the machine)
833 spin_unlock(&sb_lock);
834 if (prune_ratio != 1)
835 w_count = (sb->s_nr_dentry_unused / prune_ratio) + 1;
837 w_count = sb->s_nr_dentry_unused;
840 * We need to be sure this filesystem isn't being unmounted,
841 * otherwise we could race with generic_shutdown_super(), and
842 * end up holding a reference to an inode while the filesystem
843 * is unmounted. So we try to get s_umount, and make sure
846 if (down_read_trylock(&sb->s_umount)) {
847 if ((sb->s_root != NULL) &&
848 (!list_empty(&sb->s_dentry_lru))) {
849 __shrink_dcache_sb(sb, &w_count,
853 up_read(&sb->s_umount);
860 /* more work left to do? */
866 spin_unlock(&sb_lock);
870 * shrink_dcache_sb - shrink dcache for a superblock
873 * Shrink the dcache for the specified super block. This is used to free
874 * the dcache before unmounting a file system.
876 void shrink_dcache_sb(struct super_block *sb)
880 spin_lock(&dcache_lru_lock);
881 while (!list_empty(&sb->s_dentry_lru)) {
882 list_splice_init(&sb->s_dentry_lru, &tmp);
883 spin_unlock(&dcache_lru_lock);
884 shrink_dentry_list(&tmp);
885 spin_lock(&dcache_lru_lock);
887 spin_unlock(&dcache_lru_lock);
889 EXPORT_SYMBOL(shrink_dcache_sb);
892 * destroy a single subtree of dentries for unmount
893 * - see the comments on shrink_dcache_for_umount() for a description of the
896 static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
898 struct dentry *parent;
899 unsigned detached = 0;
901 BUG_ON(!IS_ROOT(dentry));
903 /* detach this root from the system */
904 spin_lock(&dentry->d_lock);
905 dentry_lru_del(dentry);
907 spin_unlock(&dentry->d_lock);
910 /* descend to the first leaf in the current subtree */
911 while (!list_empty(&dentry->d_subdirs)) {
914 /* this is a branch with children - detach all of them
915 * from the system in one go */
916 spin_lock(&dentry->d_lock);
917 list_for_each_entry(loop, &dentry->d_subdirs,
919 spin_lock_nested(&loop->d_lock,
920 DENTRY_D_LOCK_NESTED);
921 dentry_lru_del(loop);
923 spin_unlock(&loop->d_lock);
925 spin_unlock(&dentry->d_lock);
927 /* move to the first child */
928 dentry = list_entry(dentry->d_subdirs.next,
929 struct dentry, d_u.d_child);
932 /* consume the dentries from this leaf up through its parents
933 * until we find one with children or run out altogether */
937 if (dentry->d_count != 0) {
939 "BUG: Dentry %p{i=%lx,n=%s}"
941 " [unmount of %s %s]\n",
944 dentry->d_inode->i_ino : 0UL,
947 dentry->d_sb->s_type->name,
952 if (IS_ROOT(dentry)) {
954 list_del(&dentry->d_u.d_child);
956 parent = dentry->d_parent;
957 spin_lock(&parent->d_lock);
959 list_del(&dentry->d_u.d_child);
960 spin_unlock(&parent->d_lock);
965 inode = dentry->d_inode;
967 dentry->d_inode = NULL;
968 list_del_init(&dentry->d_alias);
969 if (dentry->d_op && dentry->d_op->d_iput)
970 dentry->d_op->d_iput(dentry, inode);
977 /* finished when we fall off the top of the tree,
978 * otherwise we ascend to the parent and move to the
979 * next sibling if there is one */
983 } while (list_empty(&dentry->d_subdirs));
985 dentry = list_entry(dentry->d_subdirs.next,
986 struct dentry, d_u.d_child);
991 * destroy the dentries attached to a superblock on unmounting
992 * - we don't need to use dentry->d_lock because:
993 * - the superblock is detached from all mountings and open files, so the
994 * dentry trees will not be rearranged by the VFS
995 * - s_umount is write-locked, so the memory pressure shrinker will ignore
996 * any dentries belonging to this superblock that it comes across
997 * - the filesystem itself is no longer permitted to rearrange the dentries
1000 void shrink_dcache_for_umount(struct super_block *sb)
1002 struct dentry *dentry;
1004 if (down_read_trylock(&sb->s_umount))
1007 dentry = sb->s_root;
1009 spin_lock(&dentry->d_lock);
1011 spin_unlock(&dentry->d_lock);
1012 shrink_dcache_for_umount_subtree(dentry);
1014 while (!hlist_bl_empty(&sb->s_anon)) {
1015 dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
1016 shrink_dcache_for_umount_subtree(dentry);
1021 * This tries to ascend one level of parenthood, but
1022 * we can race with renaming, so we need to re-check
1023 * the parenthood after dropping the lock and check
1024 * that the sequence number still matches.
1026 static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq)
1028 struct dentry *new = old->d_parent;
1031 spin_unlock(&old->d_lock);
1032 spin_lock(&new->d_lock);
1035 * might go back up the wrong parent if we have had a rename
1038 if (new != old->d_parent ||
1039 (old->d_flags & DCACHE_DISCONNECTED) ||
1040 (!locked && read_seqretry(&rename_lock, seq))) {
1041 spin_unlock(&new->d_lock);
1050 * Search for at least 1 mount point in the dentry's subdirs.
1051 * We descend to the next level whenever the d_subdirs
1052 * list is non-empty and continue searching.
1056 * have_submounts - check for mounts over a dentry
1057 * @parent: dentry to check.
1059 * Return true if the parent or its subdirectories contain
1062 int have_submounts(struct dentry *parent)
1064 struct dentry *this_parent;
1065 struct list_head *next;
1069 seq = read_seqbegin(&rename_lock);
1071 this_parent = parent;
1073 if (d_mountpoint(parent))
1075 spin_lock(&this_parent->d_lock);
1077 next = this_parent->d_subdirs.next;
1079 while (next != &this_parent->d_subdirs) {
1080 struct list_head *tmp = next;
1081 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
1084 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1085 /* Have we found a mount point ? */
1086 if (d_mountpoint(dentry)) {
1087 spin_unlock(&dentry->d_lock);
1088 spin_unlock(&this_parent->d_lock);
1091 if (!list_empty(&dentry->d_subdirs)) {
1092 spin_unlock(&this_parent->d_lock);
1093 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
1094 this_parent = dentry;
1095 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1098 spin_unlock(&dentry->d_lock);
1101 * All done at this level ... ascend and resume the search.
1103 if (this_parent != parent) {
1104 struct dentry *child = this_parent;
1105 this_parent = try_to_ascend(this_parent, locked, seq);
1108 next = child->d_u.d_child.next;
1111 spin_unlock(&this_parent->d_lock);
1112 if (!locked && read_seqretry(&rename_lock, seq))
1115 write_sequnlock(&rename_lock);
1116 return 0; /* No mount points found in tree */
1118 if (!locked && read_seqretry(&rename_lock, seq))
1121 write_sequnlock(&rename_lock);
1126 write_seqlock(&rename_lock);
1129 EXPORT_SYMBOL(have_submounts);
1132 * Search the dentry child list for the specified parent,
1133 * and move any unused dentries to the end of the unused
1134 * list for prune_dcache(). We descend to the next level
1135 * whenever the d_subdirs list is non-empty and continue
1138 * It returns zero iff there are no unused children,
1139 * otherwise it returns the number of children moved to
1140 * the end of the unused list. This may not be the total
1141 * number of unused children, because select_parent can
1142 * drop the lock and return early due to latency
1145 static int select_parent(struct dentry * parent)
1147 struct dentry *this_parent;
1148 struct list_head *next;
1153 seq = read_seqbegin(&rename_lock);
1155 this_parent = parent;
1156 spin_lock(&this_parent->d_lock);
1158 next = this_parent->d_subdirs.next;
1160 while (next != &this_parent->d_subdirs) {
1161 struct list_head *tmp = next;
1162 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
1165 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1168 * move only zero ref count dentries to the end
1169 * of the unused list for prune_dcache
1171 if (!dentry->d_count) {
1172 dentry_lru_move_tail(dentry);
1175 dentry_lru_del(dentry);
1179 * We can return to the caller if we have found some (this
1180 * ensures forward progress). We'll be coming back to find
1183 if (found && need_resched()) {
1184 spin_unlock(&dentry->d_lock);
1189 * Descend a level if the d_subdirs list is non-empty.
1191 if (!list_empty(&dentry->d_subdirs)) {
1192 spin_unlock(&this_parent->d_lock);
1193 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
1194 this_parent = dentry;
1195 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1199 spin_unlock(&dentry->d_lock);
1202 * All done at this level ... ascend and resume the search.
1204 if (this_parent != parent) {
1205 struct dentry *child = this_parent;
1206 this_parent = try_to_ascend(this_parent, locked, seq);
1209 next = child->d_u.d_child.next;
1213 spin_unlock(&this_parent->d_lock);
1214 if (!locked && read_seqretry(&rename_lock, seq))
1217 write_sequnlock(&rename_lock);
1224 write_seqlock(&rename_lock);
1229 * shrink_dcache_parent - prune dcache
1230 * @parent: parent of entries to prune
1232 * Prune the dcache to remove unused children of the parent dentry.
1235 void shrink_dcache_parent(struct dentry * parent)
1237 struct super_block *sb = parent->d_sb;
1240 while ((found = select_parent(parent)) != 0)
1241 __shrink_dcache_sb(sb, &found, 0);
1243 EXPORT_SYMBOL(shrink_dcache_parent);
1246 * Scan `sc->nr_slab_to_reclaim' dentries and return the number which remain.
1248 * We need to avoid reentering the filesystem if the caller is performing a
1249 * GFP_NOFS allocation attempt. One example deadlock is:
1251 * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
1252 * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
1253 * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
1255 * In this case we return -1 to tell the caller that we baled.
1257 static int shrink_dcache_memory(struct shrinker *shrink,
1258 struct shrink_control *sc)
1260 int nr = sc->nr_to_scan;
1261 gfp_t gfp_mask = sc->gfp_mask;
1264 if (!(gfp_mask & __GFP_FS))
1269 return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
1272 static struct shrinker dcache_shrinker = {
1273 .shrink = shrink_dcache_memory,
1274 .seeks = DEFAULT_SEEKS,
1278 * __d_alloc - allocate a dcache entry
1279 * @sb: filesystem it will belong to
1280 * @name: qstr of the name
1282 * Allocates a dentry. It returns %NULL if there is insufficient memory
1283 * available. On a success the dentry is returned. The name passed in is
1284 * copied and the copy passed in may be reused after this call.
1287 struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1289 struct dentry *dentry;
1292 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
1296 if (name->len > DNAME_INLINE_LEN-1) {
1297 dname = kmalloc(name->len + 1, GFP_KERNEL);
1299 kmem_cache_free(dentry_cache, dentry);
1303 dname = dentry->d_iname;
1305 dentry->d_name.name = dname;
1307 dentry->d_name.len = name->len;
1308 dentry->d_name.hash = name->hash;
1309 memcpy(dname, name->name, name->len);
1310 dname[name->len] = 0;
1312 dentry->d_count = 1;
1313 dentry->d_flags = 0;
1314 spin_lock_init(&dentry->d_lock);
1315 seqcount_init(&dentry->d_seq);
1316 dentry->d_inode = NULL;
1317 dentry->d_parent = dentry;
1319 dentry->d_op = NULL;
1320 dentry->d_fsdata = NULL;
1321 INIT_HLIST_BL_NODE(&dentry->d_hash);
1322 INIT_LIST_HEAD(&dentry->d_lru);
1323 INIT_LIST_HEAD(&dentry->d_subdirs);
1324 INIT_LIST_HEAD(&dentry->d_alias);
1325 INIT_LIST_HEAD(&dentry->d_u.d_child);
1326 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1328 this_cpu_inc(nr_dentry);
1334 * d_alloc - allocate a dcache entry
1335 * @parent: parent of entry to allocate
1336 * @name: qstr of the name
1338 * Allocates a dentry. It returns %NULL if there is insufficient memory
1339 * available. On a success the dentry is returned. The name passed in is
1340 * copied and the copy passed in may be reused after this call.
1342 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1344 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1348 spin_lock(&parent->d_lock);
1350 * don't need child lock because it is not subject
1351 * to concurrency here
1353 __dget_dlock(parent);
1354 dentry->d_parent = parent;
1355 list_add(&dentry->d_u.d_child, &parent->d_subdirs);
1356 spin_unlock(&parent->d_lock);
1360 EXPORT_SYMBOL(d_alloc);
1362 struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1364 struct dentry *dentry = __d_alloc(sb, name);
1366 dentry->d_flags |= DCACHE_DISCONNECTED;
1369 EXPORT_SYMBOL(d_alloc_pseudo);
1371 struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1376 q.len = strlen(name);
1377 q.hash = full_name_hash(q.name, q.len);
1378 return d_alloc(parent, &q);
1380 EXPORT_SYMBOL(d_alloc_name);
1382 void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1384 WARN_ON_ONCE(dentry->d_op);
1385 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
1387 DCACHE_OP_REVALIDATE |
1388 DCACHE_OP_DELETE ));
1393 dentry->d_flags |= DCACHE_OP_HASH;
1395 dentry->d_flags |= DCACHE_OP_COMPARE;
1396 if (op->d_revalidate)
1397 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1399 dentry->d_flags |= DCACHE_OP_DELETE;
1402 EXPORT_SYMBOL(d_set_d_op);
1404 static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1406 spin_lock(&dentry->d_lock);
1408 if (unlikely(IS_AUTOMOUNT(inode)))
1409 dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
1410 list_add(&dentry->d_alias, &inode->i_dentry);
1412 dentry->d_inode = inode;
1413 dentry_rcuwalk_barrier(dentry);
1414 spin_unlock(&dentry->d_lock);
1415 fsnotify_d_instantiate(dentry, inode);
1419 * d_instantiate - fill in inode information for a dentry
1420 * @entry: dentry to complete
1421 * @inode: inode to attach to this dentry
1423 * Fill in inode information in the entry.
1425 * This turns negative dentries into productive full members
1428 * NOTE! This assumes that the inode count has been incremented
1429 * (or otherwise set) by the caller to indicate that it is now
1430 * in use by the dcache.
1433 void d_instantiate(struct dentry *entry, struct inode * inode)
1435 BUG_ON(!list_empty(&entry->d_alias));
1437 spin_lock(&inode->i_lock);
1438 __d_instantiate(entry, inode);
1440 spin_unlock(&inode->i_lock);
1441 security_d_instantiate(entry, inode);
1443 EXPORT_SYMBOL(d_instantiate);
1446 * d_instantiate_unique - instantiate a non-aliased dentry
1447 * @entry: dentry to instantiate
1448 * @inode: inode to attach to this dentry
1450 * Fill in inode information in the entry. On success, it returns NULL.
1451 * If an unhashed alias of "entry" already exists, then we return the
1452 * aliased dentry instead and drop one reference to inode.
1454 * Note that in order to avoid conflicts with rename() etc, the caller
1455 * had better be holding the parent directory semaphore.
1457 * This also assumes that the inode count has been incremented
1458 * (or otherwise set) by the caller to indicate that it is now
1459 * in use by the dcache.
1461 static struct dentry *__d_instantiate_unique(struct dentry *entry,
1462 struct inode *inode)
1464 struct dentry *alias;
1465 int len = entry->d_name.len;
1466 const char *name = entry->d_name.name;
1467 unsigned int hash = entry->d_name.hash;
1470 __d_instantiate(entry, NULL);
1474 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
1475 struct qstr *qstr = &alias->d_name;
1478 * Don't need alias->d_lock here, because aliases with
1479 * d_parent == entry->d_parent are not subject to name or
1480 * parent changes, because the parent inode i_mutex is held.
1482 if (qstr->hash != hash)
1484 if (alias->d_parent != entry->d_parent)
1486 if (dentry_cmp(qstr->name, qstr->len, name, len))
1492 __d_instantiate(entry, inode);
1496 struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
1498 struct dentry *result;
1500 BUG_ON(!list_empty(&entry->d_alias));
1503 spin_lock(&inode->i_lock);
1504 result = __d_instantiate_unique(entry, inode);
1506 spin_unlock(&inode->i_lock);
1509 security_d_instantiate(entry, inode);
1513 BUG_ON(!d_unhashed(result));
1518 EXPORT_SYMBOL(d_instantiate_unique);
1521 * d_alloc_root - allocate root dentry
1522 * @root_inode: inode to allocate the root for
1524 * Allocate a root ("/") dentry for the inode given. The inode is
1525 * instantiated and returned. %NULL is returned if there is insufficient
1526 * memory or the inode passed is %NULL.
1529 struct dentry * d_alloc_root(struct inode * root_inode)
1531 struct dentry *res = NULL;
1534 static const struct qstr name = { .name = "/", .len = 1 };
1536 res = __d_alloc(root_inode->i_sb, &name);
1538 d_instantiate(res, root_inode);
1542 EXPORT_SYMBOL(d_alloc_root);
1544 static struct dentry * __d_find_any_alias(struct inode *inode)
1546 struct dentry *alias;
1548 if (list_empty(&inode->i_dentry))
1550 alias = list_first_entry(&inode->i_dentry, struct dentry, d_alias);
1555 static struct dentry * d_find_any_alias(struct inode *inode)
1559 spin_lock(&inode->i_lock);
1560 de = __d_find_any_alias(inode);
1561 spin_unlock(&inode->i_lock);
1567 * d_obtain_alias - find or allocate a dentry for a given inode
1568 * @inode: inode to allocate the dentry for
1570 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1571 * similar open by handle operations. The returned dentry may be anonymous,
1572 * or may have a full name (if the inode was already in the cache).
1574 * When called on a directory inode, we must ensure that the inode only ever
1575 * has one dentry. If a dentry is found, that is returned instead of
1576 * allocating a new one.
1578 * On successful return, the reference to the inode has been transferred
1579 * to the dentry. In case of an error the reference on the inode is released.
1580 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1581 * be passed in and will be the error will be propagate to the return value,
1582 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1584 struct dentry *d_obtain_alias(struct inode *inode)
1586 static const struct qstr anonstring = { .name = "" };
1591 return ERR_PTR(-ESTALE);
1593 return ERR_CAST(inode);
1595 res = d_find_any_alias(inode);
1599 tmp = __d_alloc(inode->i_sb, &anonstring);
1601 res = ERR_PTR(-ENOMEM);
1605 spin_lock(&inode->i_lock);
1606 res = __d_find_any_alias(inode);
1608 spin_unlock(&inode->i_lock);
1613 /* attach a disconnected dentry */
1614 spin_lock(&tmp->d_lock);
1615 tmp->d_inode = inode;
1616 tmp->d_flags |= DCACHE_DISCONNECTED;
1617 list_add(&tmp->d_alias, &inode->i_dentry);
1618 hlist_bl_lock(&tmp->d_sb->s_anon);
1619 hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
1620 hlist_bl_unlock(&tmp->d_sb->s_anon);
1621 spin_unlock(&tmp->d_lock);
1622 spin_unlock(&inode->i_lock);
1623 security_d_instantiate(tmp, inode);
1628 if (res && !IS_ERR(res))
1629 security_d_instantiate(res, inode);
1633 EXPORT_SYMBOL(d_obtain_alias);
1636 * d_splice_alias - splice a disconnected dentry into the tree if one exists
1637 * @inode: the inode which may have a disconnected dentry
1638 * @dentry: a negative dentry which we want to point to the inode.
1640 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1641 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1642 * and return it, else simply d_add the inode to the dentry and return NULL.
1644 * This is needed in the lookup routine of any filesystem that is exportable
1645 * (via knfsd) so that we can build dcache paths to directories effectively.
1647 * If a dentry was found and moved, then it is returned. Otherwise NULL
1648 * is returned. This matches the expected return value of ->lookup.
1651 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
1653 struct dentry *new = NULL;
1656 return ERR_CAST(inode);
1658 if (inode && S_ISDIR(inode->i_mode)) {
1659 spin_lock(&inode->i_lock);
1660 new = __d_find_alias(inode, 1);
1662 BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
1663 spin_unlock(&inode->i_lock);
1664 security_d_instantiate(new, inode);
1665 d_move(new, dentry);
1668 /* already taking inode->i_lock, so d_add() by hand */
1669 __d_instantiate(dentry, inode);
1670 spin_unlock(&inode->i_lock);
1671 security_d_instantiate(dentry, inode);
1675 d_add(dentry, inode);
1678 EXPORT_SYMBOL(d_splice_alias);
1681 * d_add_ci - lookup or allocate new dentry with case-exact name
1682 * @inode: the inode case-insensitive lookup has found
1683 * @dentry: the negative dentry that was passed to the parent's lookup func
1684 * @name: the case-exact name to be associated with the returned dentry
1686 * This is to avoid filling the dcache with case-insensitive names to the
1687 * same inode, only the actual correct case is stored in the dcache for
1688 * case-insensitive filesystems.
1690 * For a case-insensitive lookup match and if the the case-exact dentry
1691 * already exists in in the dcache, use it and return it.
1693 * If no entry exists with the exact case name, allocate new dentry with
1694 * the exact case, and return the spliced entry.
1696 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
1700 struct dentry *found;
1704 * First check if a dentry matching the name already exists,
1705 * if not go ahead and create it now.
1707 found = d_hash_and_lookup(dentry->d_parent, name);
1709 new = d_alloc(dentry->d_parent, name);
1715 found = d_splice_alias(inode, new);
1724 * If a matching dentry exists, and it's not negative use it.
1726 * Decrement the reference count to balance the iget() done
1729 if (found->d_inode) {
1730 if (unlikely(found->d_inode != inode)) {
1731 /* This can't happen because bad inodes are unhashed. */
1732 BUG_ON(!is_bad_inode(inode));
1733 BUG_ON(!is_bad_inode(found->d_inode));
1740 * We are going to instantiate this dentry, unhash it and clear the
1741 * lookup flag so we can do that.
1743 if (unlikely(d_need_lookup(found)))
1744 d_clear_need_lookup(found);
1747 * Negative dentry: instantiate it unless the inode is a directory and
1748 * already has a dentry.
1750 spin_lock(&inode->i_lock);
1751 if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) {
1752 __d_instantiate(found, inode);
1753 spin_unlock(&inode->i_lock);
1754 security_d_instantiate(found, inode);
1759 * In case a directory already has a (disconnected) entry grab a
1760 * reference to it, move it in place and use it.
1762 new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
1764 spin_unlock(&inode->i_lock);
1765 security_d_instantiate(found, inode);
1773 return ERR_PTR(error);
1775 EXPORT_SYMBOL(d_add_ci);
1778 * __d_lookup_rcu - search for a dentry (racy, store-free)
1779 * @parent: parent dentry
1780 * @name: qstr of name we wish to find
1781 * @seq: returns d_seq value at the point where the dentry was found
1782 * @inode: returns dentry->d_inode when the inode was found valid.
1783 * Returns: dentry, or NULL
1785 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
1786 * resolution (store-free path walking) design described in
1787 * Documentation/filesystems/path-lookup.txt.
1789 * This is not to be used outside core vfs.
1791 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
1792 * held, and rcu_read_lock held. The returned dentry must not be stored into
1793 * without taking d_lock and checking d_seq sequence count against @seq
1796 * A refcount may be taken on the found dentry with the __d_rcu_to_refcount
1799 * Alternatively, __d_lookup_rcu may be called again to look up the child of
1800 * the returned dentry, so long as its parent's seqlock is checked after the
1801 * child is looked up. Thus, an interlocking stepping of sequence lock checks
1802 * is formed, giving integrity down the path walk.
1804 struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
1805 unsigned *seq, struct inode **inode)
1807 unsigned int len = name->len;
1808 unsigned int hash = name->hash;
1809 const unsigned char *str = name->name;
1810 struct hlist_bl_head *b = d_hash(parent, hash);
1811 struct hlist_bl_node *node;
1812 struct dentry *dentry;
1815 * Note: There is significant duplication with __d_lookup_rcu which is
1816 * required to prevent single threaded performance regressions
1817 * especially on architectures where smp_rmb (in seqcounts) are costly.
1818 * Keep the two functions in sync.
1822 * The hash list is protected using RCU.
1824 * Carefully use d_seq when comparing a candidate dentry, to avoid
1825 * races with d_move().
1827 * It is possible that concurrent renames can mess up our list
1828 * walk here and result in missing our dentry, resulting in the
1829 * false-negative result. d_lookup() protects against concurrent
1830 * renames using rename_lock seqlock.
1832 * See Documentation/filesystems/path-lookup.txt for more details.
1834 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
1839 if (dentry->d_name.hash != hash)
1843 *seq = read_seqcount_begin(&dentry->d_seq);
1844 if (dentry->d_parent != parent)
1846 if (d_unhashed(dentry))
1848 tlen = dentry->d_name.len;
1849 tname = dentry->d_name.name;
1850 i = dentry->d_inode;
1855 * This seqcount check is required to ensure name and
1856 * len are loaded atomically, so as not to walk off the
1857 * edge of memory when walking. If we could load this
1858 * atomically some other way, we could drop this check.
1860 if (read_seqcount_retry(&dentry->d_seq, *seq))
1862 if (parent->d_flags & DCACHE_OP_COMPARE) {
1863 if (parent->d_op->d_compare(parent, *inode,
1868 if (dentry_cmp(tname, tlen, str, len))
1872 * No extra seqcount check is required after the name
1873 * compare. The caller must perform a seqcount check in
1874 * order to do anything useful with the returned dentry
1884 * d_lookup - search for a dentry
1885 * @parent: parent dentry
1886 * @name: qstr of name we wish to find
1887 * Returns: dentry, or NULL
1889 * d_lookup searches the children of the parent dentry for the name in
1890 * question. If the dentry is found its reference count is incremented and the
1891 * dentry is returned. The caller must use dput to free the entry when it has
1892 * finished using it. %NULL is returned if the dentry does not exist.
1894 struct dentry *d_lookup(struct dentry *parent, struct qstr *name)
1896 struct dentry *dentry;
1900 seq = read_seqbegin(&rename_lock);
1901 dentry = __d_lookup(parent, name);
1904 } while (read_seqretry(&rename_lock, seq));
1907 EXPORT_SYMBOL(d_lookup);
1910 * __d_lookup - search for a dentry (racy)
1911 * @parent: parent dentry
1912 * @name: qstr of name we wish to find
1913 * Returns: dentry, or NULL
1915 * __d_lookup is like d_lookup, however it may (rarely) return a
1916 * false-negative result due to unrelated rename activity.
1918 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
1919 * however it must be used carefully, eg. with a following d_lookup in
1920 * the case of failure.
1922 * __d_lookup callers must be commented.
1924 struct dentry *__d_lookup(struct dentry *parent, struct qstr *name)
1926 unsigned int len = name->len;
1927 unsigned int hash = name->hash;
1928 const unsigned char *str = name->name;
1929 struct hlist_bl_head *b = d_hash(parent, hash);
1930 struct hlist_bl_node *node;
1931 struct dentry *found = NULL;
1932 struct dentry *dentry;
1935 * Note: There is significant duplication with __d_lookup_rcu which is
1936 * required to prevent single threaded performance regressions
1937 * especially on architectures where smp_rmb (in seqcounts) are costly.
1938 * Keep the two functions in sync.
1942 * The hash list is protected using RCU.
1944 * Take d_lock when comparing a candidate dentry, to avoid races
1947 * It is possible that concurrent renames can mess up our list
1948 * walk here and result in missing our dentry, resulting in the
1949 * false-negative result. d_lookup() protects against concurrent
1950 * renames using rename_lock seqlock.
1952 * See Documentation/filesystems/path-lookup.txt for more details.
1956 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
1960 if (dentry->d_name.hash != hash)
1963 spin_lock(&dentry->d_lock);
1964 if (dentry->d_parent != parent)
1966 if (d_unhashed(dentry))
1970 * It is safe to compare names since d_move() cannot
1971 * change the qstr (protected by d_lock).
1973 tlen = dentry->d_name.len;
1974 tname = dentry->d_name.name;
1975 if (parent->d_flags & DCACHE_OP_COMPARE) {
1976 if (parent->d_op->d_compare(parent, parent->d_inode,
1977 dentry, dentry->d_inode,
1981 if (dentry_cmp(tname, tlen, str, len))
1987 spin_unlock(&dentry->d_lock);
1990 spin_unlock(&dentry->d_lock);
1998 * d_hash_and_lookup - hash the qstr then search for a dentry
1999 * @dir: Directory to search in
2000 * @name: qstr of name we wish to find
2002 * On hash failure or on lookup failure NULL is returned.
2004 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2006 struct dentry *dentry = NULL;
2009 * Check for a fs-specific hash function. Note that we must
2010 * calculate the standard hash first, as the d_op->d_hash()
2011 * routine may choose to leave the hash value unchanged.
2013 name->hash = full_name_hash(name->name, name->len);
2014 if (dir->d_flags & DCACHE_OP_HASH) {
2015 if (dir->d_op->d_hash(dir, dir->d_inode, name) < 0)
2018 dentry = d_lookup(dir, name);
2024 * d_validate - verify dentry provided from insecure source (deprecated)
2025 * @dentry: The dentry alleged to be valid child of @dparent
2026 * @dparent: The parent dentry (known to be valid)
2028 * An insecure source has sent us a dentry, here we verify it and dget() it.
2029 * This is used by ncpfs in its readdir implementation.
2030 * Zero is returned in the dentry is invalid.
2032 * This function is slow for big directories, and deprecated, do not use it.
2034 int d_validate(struct dentry *dentry, struct dentry *dparent)
2036 struct dentry *child;
2038 spin_lock(&dparent->d_lock);
2039 list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
2040 if (dentry == child) {
2041 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
2042 __dget_dlock(dentry);
2043 spin_unlock(&dentry->d_lock);
2044 spin_unlock(&dparent->d_lock);
2048 spin_unlock(&dparent->d_lock);
2052 EXPORT_SYMBOL(d_validate);
2055 * When a file is deleted, we have two options:
2056 * - turn this dentry into a negative dentry
2057 * - unhash this dentry and free it.
2059 * Usually, we want to just turn this into
2060 * a negative dentry, but if anybody else is
2061 * currently using the dentry or the inode
2062 * we can't do that and we fall back on removing
2063 * it from the hash queues and waiting for
2064 * it to be deleted later when it has no users
2068 * d_delete - delete a dentry
2069 * @dentry: The dentry to delete
2071 * Turn the dentry into a negative dentry if possible, otherwise
2072 * remove it from the hash queues so it can be deleted later
2075 void d_delete(struct dentry * dentry)
2077 struct inode *inode;
2080 * Are we the only user?
2083 spin_lock(&dentry->d_lock);
2084 inode = dentry->d_inode;
2085 isdir = S_ISDIR(inode->i_mode);
2086 if (dentry->d_count == 1) {
2087 if (inode && !spin_trylock(&inode->i_lock)) {
2088 spin_unlock(&dentry->d_lock);
2092 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2093 dentry_unlink_inode(dentry);
2094 fsnotify_nameremove(dentry, isdir);
2098 if (!d_unhashed(dentry))
2101 spin_unlock(&dentry->d_lock);
2103 fsnotify_nameremove(dentry, isdir);
2105 EXPORT_SYMBOL(d_delete);
2107 static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
2109 BUG_ON(!d_unhashed(entry));
2111 entry->d_flags |= DCACHE_RCUACCESS;
2112 hlist_bl_add_head_rcu(&entry->d_hash, b);
2116 static void _d_rehash(struct dentry * entry)
2118 __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
2122 * d_rehash - add an entry back to the hash
2123 * @entry: dentry to add to the hash
2125 * Adds a dentry to the hash according to its name.
2128 void d_rehash(struct dentry * entry)
2130 spin_lock(&entry->d_lock);
2132 spin_unlock(&entry->d_lock);
2134 EXPORT_SYMBOL(d_rehash);
2137 * dentry_update_name_case - update case insensitive dentry with a new name
2138 * @dentry: dentry to be updated
2141 * Update a case insensitive dentry with new case of name.
2143 * dentry must have been returned by d_lookup with name @name. Old and new
2144 * name lengths must match (ie. no d_compare which allows mismatched name
2147 * Parent inode i_mutex must be held over d_lookup and into this call (to
2148 * keep renames and concurrent inserts, and readdir(2) away).
2150 void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
2152 BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));
2153 BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
2155 spin_lock(&dentry->d_lock);
2156 write_seqcount_begin(&dentry->d_seq);
2157 memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
2158 write_seqcount_end(&dentry->d_seq);
2159 spin_unlock(&dentry->d_lock);
2161 EXPORT_SYMBOL(dentry_update_name_case);
2163 static void switch_names(struct dentry *dentry, struct dentry *target)
2165 if (dname_external(target)) {
2166 if (dname_external(dentry)) {
2168 * Both external: swap the pointers
2170 swap(target->d_name.name, dentry->d_name.name);
2173 * dentry:internal, target:external. Steal target's
2174 * storage and make target internal.
2176 memcpy(target->d_iname, dentry->d_name.name,
2177 dentry->d_name.len + 1);
2178 dentry->d_name.name = target->d_name.name;
2179 target->d_name.name = target->d_iname;
2182 if (dname_external(dentry)) {
2184 * dentry:external, target:internal. Give dentry's
2185 * storage to target and make dentry internal
2187 memcpy(dentry->d_iname, target->d_name.name,
2188 target->d_name.len + 1);
2189 target->d_name.name = dentry->d_name.name;
2190 dentry->d_name.name = dentry->d_iname;
2193 * Both are internal. Just copy target to dentry
2195 memcpy(dentry->d_iname, target->d_name.name,
2196 target->d_name.len + 1);
2197 dentry->d_name.len = target->d_name.len;
2201 swap(dentry->d_name.len, target->d_name.len);
2204 static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
2207 * XXXX: do we really need to take target->d_lock?
2209 if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent)
2210 spin_lock(&target->d_parent->d_lock);
2212 if (d_ancestor(dentry->d_parent, target->d_parent)) {
2213 spin_lock(&dentry->d_parent->d_lock);
2214 spin_lock_nested(&target->d_parent->d_lock,
2215 DENTRY_D_LOCK_NESTED);
2217 spin_lock(&target->d_parent->d_lock);
2218 spin_lock_nested(&dentry->d_parent->d_lock,
2219 DENTRY_D_LOCK_NESTED);
2222 if (target < dentry) {
2223 spin_lock_nested(&target->d_lock, 2);
2224 spin_lock_nested(&dentry->d_lock, 3);
2226 spin_lock_nested(&dentry->d_lock, 2);
2227 spin_lock_nested(&target->d_lock, 3);
2231 static void dentry_unlock_parents_for_move(struct dentry *dentry,
2232 struct dentry *target)
2234 if (target->d_parent != dentry->d_parent)
2235 spin_unlock(&dentry->d_parent->d_lock);
2236 if (target->d_parent != target)
2237 spin_unlock(&target->d_parent->d_lock);
2241 * When switching names, the actual string doesn't strictly have to
2242 * be preserved in the target - because we're dropping the target
2243 * anyway. As such, we can just do a simple memcpy() to copy over
2244 * the new name before we switch.
2246 * Note that we have to be a lot more careful about getting the hash
2247 * switched - we have to switch the hash value properly even if it
2248 * then no longer matches the actual (corrupted) string of the target.
2249 * The hash value has to match the hash queue that the dentry is on..
2252 * __d_move - move a dentry
2253 * @dentry: entry to move
2254 * @target: new dentry
2256 * Update the dcache to reflect the move of a file name. Negative
2257 * dcache entries should not be moved in this way. Caller hold
2260 static void __d_move(struct dentry * dentry, struct dentry * target)
2262 if (!dentry->d_inode)
2263 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
2265 BUG_ON(d_ancestor(dentry, target));
2266 BUG_ON(d_ancestor(target, dentry));
2268 dentry_lock_for_move(dentry, target);
2270 write_seqcount_begin(&dentry->d_seq);
2271 write_seqcount_begin(&target->d_seq);
2273 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
2276 * Move the dentry to the target hash queue. Don't bother checking
2277 * for the same hash queue because of how unlikely it is.
2280 __d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
2282 /* Unhash the target: dput() will then get rid of it */
2285 list_del(&dentry->d_u.d_child);
2286 list_del(&target->d_u.d_child);
2288 /* Switch the names.. */
2289 switch_names(dentry, target);
2290 swap(dentry->d_name.hash, target->d_name.hash);
2292 /* ... and switch the parents */
2293 if (IS_ROOT(dentry)) {
2294 dentry->d_parent = target->d_parent;
2295 target->d_parent = target;
2296 INIT_LIST_HEAD(&target->d_u.d_child);
2298 swap(dentry->d_parent, target->d_parent);
2300 /* And add them back to the (new) parent lists */
2301 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
2304 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
2306 write_seqcount_end(&target->d_seq);
2307 write_seqcount_end(&dentry->d_seq);
2309 dentry_unlock_parents_for_move(dentry, target);
2310 spin_unlock(&target->d_lock);
2311 fsnotify_d_move(dentry);
2312 spin_unlock(&dentry->d_lock);
2316 * d_move - move a dentry
2317 * @dentry: entry to move
2318 * @target: new dentry
2320 * Update the dcache to reflect the move of a file name. Negative
2321 * dcache entries should not be moved in this way.
2323 void d_move(struct dentry *dentry, struct dentry *target)
2325 write_seqlock(&rename_lock);
2326 __d_move(dentry, target);
2327 write_sequnlock(&rename_lock);
2329 EXPORT_SYMBOL(d_move);
2332 * d_ancestor - search for an ancestor
2333 * @p1: ancestor dentry
2336 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2337 * an ancestor of p2, else NULL.
2339 struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2343 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2344 if (p->d_parent == p1)
2351 * This helper attempts to cope with remotely renamed directories
2353 * It assumes that the caller is already holding
2354 * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
2356 * Note: If ever the locking in lock_rename() changes, then please
2357 * remember to update this too...
2359 static struct dentry *__d_unalias(struct inode *inode,
2360 struct dentry *dentry, struct dentry *alias)
2362 struct mutex *m1 = NULL, *m2 = NULL;
2365 /* If alias and dentry share a parent, then no extra locks required */
2366 if (alias->d_parent == dentry->d_parent)
2369 /* See lock_rename() */
2370 ret = ERR_PTR(-EBUSY);
2371 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
2373 m1 = &dentry->d_sb->s_vfs_rename_mutex;
2374 if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
2376 m2 = &alias->d_parent->d_inode->i_mutex;
2378 __d_move(alias, dentry);
2381 spin_unlock(&inode->i_lock);
2390 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
2391 * named dentry in place of the dentry to be replaced.
2392 * returns with anon->d_lock held!
2394 static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
2396 struct dentry *dparent, *aparent;
2398 dentry_lock_for_move(anon, dentry);
2400 write_seqcount_begin(&dentry->d_seq);
2401 write_seqcount_begin(&anon->d_seq);
2403 dparent = dentry->d_parent;
2404 aparent = anon->d_parent;
2406 switch_names(dentry, anon);
2407 swap(dentry->d_name.hash, anon->d_name.hash);
2409 dentry->d_parent = (aparent == anon) ? dentry : aparent;
2410 list_del(&dentry->d_u.d_child);
2411 if (!IS_ROOT(dentry))
2412 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
2414 INIT_LIST_HEAD(&dentry->d_u.d_child);
2416 anon->d_parent = (dparent == dentry) ? anon : dparent;
2417 list_del(&anon->d_u.d_child);
2419 list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
2421 INIT_LIST_HEAD(&anon->d_u.d_child);
2423 write_seqcount_end(&dentry->d_seq);
2424 write_seqcount_end(&anon->d_seq);
2426 dentry_unlock_parents_for_move(anon, dentry);
2427 spin_unlock(&dentry->d_lock);
2429 /* anon->d_lock still locked, returns locked */
2430 anon->d_flags &= ~DCACHE_DISCONNECTED;
2434 * d_materialise_unique - introduce an inode into the tree
2435 * @dentry: candidate dentry
2436 * @inode: inode to bind to the dentry, to which aliases may be attached
2438 * Introduces an dentry into the tree, substituting an extant disconnected
2439 * root directory alias in its place if there is one
2441 struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
2443 struct dentry *actual;
2445 BUG_ON(!d_unhashed(dentry));
2449 __d_instantiate(dentry, NULL);
2454 spin_lock(&inode->i_lock);
2456 if (S_ISDIR(inode->i_mode)) {
2457 struct dentry *alias;
2459 /* Does an aliased dentry already exist? */
2460 alias = __d_find_alias(inode, 0);
2463 write_seqlock(&rename_lock);
2465 if (d_ancestor(alias, dentry)) {
2466 /* Check for loops */
2467 actual = ERR_PTR(-ELOOP);
2468 } else if (IS_ROOT(alias)) {
2469 /* Is this an anonymous mountpoint that we
2470 * could splice into our tree? */
2471 __d_materialise_dentry(dentry, alias);
2472 write_sequnlock(&rename_lock);
2476 /* Nope, but we must(!) avoid directory
2478 actual = __d_unalias(inode, dentry, alias);
2480 write_sequnlock(&rename_lock);
2487 /* Add a unique reference */
2488 actual = __d_instantiate_unique(dentry, inode);
2492 BUG_ON(!d_unhashed(actual));
2494 spin_lock(&actual->d_lock);
2497 spin_unlock(&actual->d_lock);
2498 spin_unlock(&inode->i_lock);
2500 if (actual == dentry) {
2501 security_d_instantiate(dentry, inode);
2508 EXPORT_SYMBOL_GPL(d_materialise_unique);
2510 static int prepend(char **buffer, int *buflen, const char *str, int namelen)
2514 return -ENAMETOOLONG;
2516 memcpy(*buffer, str, namelen);
2520 static int prepend_name(char **buffer, int *buflen, struct qstr *name)
2522 return prepend(buffer, buflen, name->name, name->len);
2526 * prepend_path - Prepend path string to a buffer
2527 * @path: the dentry/vfsmount to report
2528 * @root: root vfsmnt/dentry (may be modified by this function)
2529 * @buffer: pointer to the end of the buffer
2530 * @buflen: pointer to buffer length
2532 * Caller holds the rename_lock.
2534 * If path is not reachable from the supplied root, then the value of
2535 * root is changed (without modifying refcounts).
2537 static int prepend_path(const struct path *path, struct path *root,
2538 char **buffer, int *buflen)
2540 struct dentry *dentry = path->dentry;
2541 struct vfsmount *vfsmnt = path->mnt;
2545 br_read_lock(vfsmount_lock);
2546 while (dentry != root->dentry || vfsmnt != root->mnt) {
2547 struct dentry * parent;
2549 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
2551 if (vfsmnt->mnt_parent == vfsmnt) {
2554 dentry = vfsmnt->mnt_mountpoint;
2555 vfsmnt = vfsmnt->mnt_parent;
2558 parent = dentry->d_parent;
2560 spin_lock(&dentry->d_lock);
2561 error = prepend_name(buffer, buflen, &dentry->d_name);
2562 spin_unlock(&dentry->d_lock);
2564 error = prepend(buffer, buflen, "/", 1);
2573 if (!error && !slash)
2574 error = prepend(buffer, buflen, "/", 1);
2576 br_read_unlock(vfsmount_lock);
2581 * Filesystems needing to implement special "root names"
2582 * should do so with ->d_dname()
2584 if (IS_ROOT(dentry) &&
2585 (dentry->d_name.len != 1 || dentry->d_name.name[0] != '/')) {
2586 WARN(1, "Root dentry has weird name <%.*s>\n",
2587 (int) dentry->d_name.len, dentry->d_name.name);
2590 root->dentry = dentry;
2595 * __d_path - return the path of a dentry
2596 * @path: the dentry/vfsmount to report
2597 * @root: root vfsmnt/dentry (may be modified by this function)
2598 * @buf: buffer to return value in
2599 * @buflen: buffer length
2601 * Convert a dentry into an ASCII path name.
2603 * Returns a pointer into the buffer or an error code if the
2604 * path was too long.
2606 * "buflen" should be positive.
2608 * If path is not reachable from the supplied root, then the value of
2609 * root is changed (without modifying refcounts).
2611 char *__d_path(const struct path *path, struct path *root,
2612 char *buf, int buflen)
2614 char *res = buf + buflen;
2617 prepend(&res, &buflen, "\0", 1);
2618 write_seqlock(&rename_lock);
2619 error = prepend_path(path, root, &res, &buflen);
2620 write_sequnlock(&rename_lock);
2623 return ERR_PTR(error);
2628 * same as __d_path but appends "(deleted)" for unlinked files.
2630 static int path_with_deleted(const struct path *path, struct path *root,
2631 char **buf, int *buflen)
2633 prepend(buf, buflen, "\0", 1);
2634 if (d_unlinked(path->dentry)) {
2635 int error = prepend(buf, buflen, " (deleted)", 10);
2640 return prepend_path(path, root, buf, buflen);
2643 static int prepend_unreachable(char **buffer, int *buflen)
2645 return prepend(buffer, buflen, "(unreachable)", 13);
2649 * d_path - return the path of a dentry
2650 * @path: path to report
2651 * @buf: buffer to return value in
2652 * @buflen: buffer length
2654 * Convert a dentry into an ASCII path name. If the entry has been deleted
2655 * the string " (deleted)" is appended. Note that this is ambiguous.
2657 * Returns a pointer into the buffer or an error code if the path was
2658 * too long. Note: Callers should use the returned pointer, not the passed
2659 * in buffer, to use the name! The implementation often starts at an offset
2660 * into the buffer, and may leave 0 bytes at the start.
2662 * "buflen" should be positive.
2664 char *d_path(const struct path *path, char *buf, int buflen)
2666 char *res = buf + buflen;
2672 * We have various synthetic filesystems that never get mounted. On
2673 * these filesystems dentries are never used for lookup purposes, and
2674 * thus don't need to be hashed. They also don't need a name until a
2675 * user wants to identify the object in /proc/pid/fd/. The little hack
2676 * below allows us to generate a name for these objects on demand:
2678 if (path->dentry->d_op && path->dentry->d_op->d_dname)
2679 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2681 get_fs_root(current->fs, &root);
2682 write_seqlock(&rename_lock);
2684 error = path_with_deleted(path, &tmp, &res, &buflen);
2686 res = ERR_PTR(error);
2687 write_sequnlock(&rename_lock);
2691 EXPORT_SYMBOL(d_path);
2694 * d_path_with_unreachable - return the path of a dentry
2695 * @path: path to report
2696 * @buf: buffer to return value in
2697 * @buflen: buffer length
2699 * The difference from d_path() is that this prepends "(unreachable)"
2700 * to paths which are unreachable from the current process' root.
2702 char *d_path_with_unreachable(const struct path *path, char *buf, int buflen)
2704 char *res = buf + buflen;
2709 if (path->dentry->d_op && path->dentry->d_op->d_dname)
2710 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2712 get_fs_root(current->fs, &root);
2713 write_seqlock(&rename_lock);
2715 error = path_with_deleted(path, &tmp, &res, &buflen);
2716 if (!error && !path_equal(&tmp, &root))
2717 error = prepend_unreachable(&res, &buflen);
2718 write_sequnlock(&rename_lock);
2721 res = ERR_PTR(error);
2727 * Helper function for dentry_operations.d_dname() members
2729 char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
2730 const char *fmt, ...)
2736 va_start(args, fmt);
2737 sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
2740 if (sz > sizeof(temp) || sz > buflen)
2741 return ERR_PTR(-ENAMETOOLONG);
2743 buffer += buflen - sz;
2744 return memcpy(buffer, temp, sz);
2748 * Write full pathname from the root of the filesystem into the buffer.
2750 static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
2752 char *end = buf + buflen;
2755 prepend(&end, &buflen, "\0", 1);
2762 while (!IS_ROOT(dentry)) {
2763 struct dentry *parent = dentry->d_parent;
2767 spin_lock(&dentry->d_lock);
2768 error = prepend_name(&end, &buflen, &dentry->d_name);
2769 spin_unlock(&dentry->d_lock);
2770 if (error != 0 || prepend(&end, &buflen, "/", 1) != 0)
2778 return ERR_PTR(-ENAMETOOLONG);
2781 char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
2785 write_seqlock(&rename_lock);
2786 retval = __dentry_path(dentry, buf, buflen);
2787 write_sequnlock(&rename_lock);
2791 EXPORT_SYMBOL(dentry_path_raw);
2793 char *dentry_path(struct dentry *dentry, char *buf, int buflen)
2798 write_seqlock(&rename_lock);
2799 if (d_unlinked(dentry)) {
2801 if (prepend(&p, &buflen, "//deleted", 10) != 0)
2805 retval = __dentry_path(dentry, buf, buflen);
2806 write_sequnlock(&rename_lock);
2807 if (!IS_ERR(retval) && p)
2808 *p = '/'; /* restore '/' overriden with '\0' */
2811 return ERR_PTR(-ENAMETOOLONG);
2815 * NOTE! The user-level library version returns a
2816 * character pointer. The kernel system call just
2817 * returns the length of the buffer filled (which
2818 * includes the ending '\0' character), or a negative
2819 * error value. So libc would do something like
2821 * char *getcwd(char * buf, size_t size)
2825 * retval = sys_getcwd(buf, size);
2832 SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
2835 struct path pwd, root;
2836 char *page = (char *) __get_free_page(GFP_USER);
2841 get_fs_root_and_pwd(current->fs, &root, &pwd);
2844 write_seqlock(&rename_lock);
2845 if (!d_unlinked(pwd.dentry)) {
2847 struct path tmp = root;
2848 char *cwd = page + PAGE_SIZE;
2849 int buflen = PAGE_SIZE;
2851 prepend(&cwd, &buflen, "\0", 1);
2852 error = prepend_path(&pwd, &tmp, &cwd, &buflen);
2853 write_sequnlock(&rename_lock);
2858 /* Unreachable from current root */
2859 if (!path_equal(&tmp, &root)) {
2860 error = prepend_unreachable(&cwd, &buflen);
2866 len = PAGE_SIZE + page - cwd;
2869 if (copy_to_user(buf, cwd, len))
2873 write_sequnlock(&rename_lock);
2879 free_page((unsigned long) page);
2884 * Test whether new_dentry is a subdirectory of old_dentry.
2886 * Trivially implemented using the dcache structure
2890 * is_subdir - is new dentry a subdirectory of old_dentry
2891 * @new_dentry: new dentry
2892 * @old_dentry: old dentry
2894 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
2895 * Returns 0 otherwise.
2896 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
2899 int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
2904 if (new_dentry == old_dentry)
2908 /* for restarting inner loop in case of seq retry */
2909 seq = read_seqbegin(&rename_lock);
2911 * Need rcu_readlock to protect against the d_parent trashing
2915 if (d_ancestor(old_dentry, new_dentry))
2920 } while (read_seqretry(&rename_lock, seq));
2925 int path_is_under(struct path *path1, struct path *path2)
2927 struct vfsmount *mnt = path1->mnt;
2928 struct dentry *dentry = path1->dentry;
2931 br_read_lock(vfsmount_lock);
2932 if (mnt != path2->mnt) {
2934 if (mnt->mnt_parent == mnt) {
2935 br_read_unlock(vfsmount_lock);
2938 if (mnt->mnt_parent == path2->mnt)
2940 mnt = mnt->mnt_parent;
2942 dentry = mnt->mnt_mountpoint;
2944 res = is_subdir(dentry, path2->dentry);
2945 br_read_unlock(vfsmount_lock);
2948 EXPORT_SYMBOL(path_is_under);
2950 void d_genocide(struct dentry *root)
2952 struct dentry *this_parent;
2953 struct list_head *next;
2957 seq = read_seqbegin(&rename_lock);
2960 spin_lock(&this_parent->d_lock);
2962 next = this_parent->d_subdirs.next;
2964 while (next != &this_parent->d_subdirs) {
2965 struct list_head *tmp = next;
2966 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
2969 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
2970 if (d_unhashed(dentry) || !dentry->d_inode) {
2971 spin_unlock(&dentry->d_lock);
2974 if (!list_empty(&dentry->d_subdirs)) {
2975 spin_unlock(&this_parent->d_lock);
2976 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
2977 this_parent = dentry;
2978 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
2981 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
2982 dentry->d_flags |= DCACHE_GENOCIDE;
2985 spin_unlock(&dentry->d_lock);
2987 if (this_parent != root) {
2988 struct dentry *child = this_parent;
2989 if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
2990 this_parent->d_flags |= DCACHE_GENOCIDE;
2991 this_parent->d_count--;
2993 this_parent = try_to_ascend(this_parent, locked, seq);
2996 next = child->d_u.d_child.next;
2999 spin_unlock(&this_parent->d_lock);
3000 if (!locked && read_seqretry(&rename_lock, seq))
3003 write_sequnlock(&rename_lock);
3008 write_seqlock(&rename_lock);
3013 * find_inode_number - check for dentry with name
3014 * @dir: directory to check
3015 * @name: Name to find.
3017 * Check whether a dentry already exists for the given name,
3018 * and return the inode number if it has an inode. Otherwise
3021 * This routine is used to post-process directory listings for
3022 * filesystems using synthetic inode numbers, and is necessary
3023 * to keep getcwd() working.
3026 ino_t find_inode_number(struct dentry *dir, struct qstr *name)
3028 struct dentry * dentry;
3031 dentry = d_hash_and_lookup(dir, name);
3033 if (dentry->d_inode)
3034 ino = dentry->d_inode->i_ino;
3039 EXPORT_SYMBOL(find_inode_number);
3041 static __initdata unsigned long dhash_entries;
3042 static int __init set_dhash_entries(char *str)
3046 dhash_entries = simple_strtoul(str, &str, 0);
3049 __setup("dhash_entries=", set_dhash_entries);
3051 static void __init dcache_init_early(void)
3055 /* If hashes are distributed across NUMA nodes, defer
3056 * hash allocation until vmalloc space is available.
3062 alloc_large_system_hash("Dentry cache",
3063 sizeof(struct hlist_bl_head),
3071 for (loop = 0; loop < (1 << d_hash_shift); loop++)
3072 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
3075 static void __init dcache_init(void)
3080 * A constructor could be added for stable state like the lists,
3081 * but it is probably not worth it because of the cache nature
3084 dentry_cache = KMEM_CACHE(dentry,
3085 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
3087 register_shrinker(&dcache_shrinker);
3089 /* Hash may have been set up in dcache_init_early */
3094 alloc_large_system_hash("Dentry cache",
3095 sizeof(struct hlist_bl_head),
3103 for (loop = 0; loop < (1 << d_hash_shift); loop++)
3104 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
3107 /* SLAB cache for __getname() consumers */
3108 struct kmem_cache *names_cachep __read_mostly;
3109 EXPORT_SYMBOL(names_cachep);
3111 EXPORT_SYMBOL(d_genocide);
3113 void __init vfs_caches_init_early(void)
3115 dcache_init_early();
3119 void __init vfs_caches_init(unsigned long mempages)
3121 unsigned long reserve;
3123 /* Base hash sizes on available memory, with a reserve equal to
3124 150% of current kernel size */
3126 reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
3127 mempages -= reserve;
3129 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
3130 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
3134 files_init(mempages);