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>
40 * dcache_inode_lock protects:
41 * - i_dentry, d_alias, d_inode
42 * dcache_hash_lock protects:
43 * - the dcache hash table, s_anon lists
44 * dcache_lru_lock protects:
45 * - the dcache lru lists and counters
52 * - d_parent and d_subdirs
53 * - childrens' d_child and d_parent
62 * If there is an ancestor relationship:
63 * dentry->d_parent->...->d_parent->d_lock
65 * dentry->d_parent->d_lock
68 * If no ancestor relationship:
69 * if (dentry1 < dentry2)
73 int sysctl_vfs_cache_pressure __read_mostly
= 100;
74 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure
);
76 __cacheline_aligned_in_smp
DEFINE_SPINLOCK(dcache_inode_lock
);
77 static __cacheline_aligned_in_smp
DEFINE_SPINLOCK(dcache_hash_lock
);
78 static __cacheline_aligned_in_smp
DEFINE_SPINLOCK(dcache_lru_lock
);
79 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(rename_lock
);
81 EXPORT_SYMBOL(rename_lock
);
82 EXPORT_SYMBOL(dcache_inode_lock
);
84 static struct kmem_cache
*dentry_cache __read_mostly
;
87 * This is the single most critical data structure when it comes
88 * to the dcache: the hashtable for lookups. Somebody should try
89 * to make this good - I've just made it work.
91 * This hash-function tries to avoid losing too many bits of hash
92 * information, yet avoid using a prime hash-size or similar.
94 #define D_HASHBITS d_hash_shift
95 #define D_HASHMASK d_hash_mask
97 static unsigned int d_hash_mask __read_mostly
;
98 static unsigned int d_hash_shift __read_mostly
;
99 static struct hlist_head
*dentry_hashtable __read_mostly
;
101 /* Statistics gathering. */
102 struct dentry_stat_t dentry_stat
= {
106 static DEFINE_PER_CPU(unsigned int, nr_dentry
);
108 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
109 static int get_nr_dentry(void)
113 for_each_possible_cpu(i
)
114 sum
+= per_cpu(nr_dentry
, i
);
115 return sum
< 0 ? 0 : sum
;
118 int proc_nr_dentry(ctl_table
*table
, int write
, void __user
*buffer
,
119 size_t *lenp
, loff_t
*ppos
)
121 dentry_stat
.nr_dentry
= get_nr_dentry();
122 return proc_dointvec(table
, write
, buffer
, lenp
, ppos
);
126 static void __d_free(struct rcu_head
*head
)
128 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
130 WARN_ON(!list_empty(&dentry
->d_alias
));
131 if (dname_external(dentry
))
132 kfree(dentry
->d_name
.name
);
133 kmem_cache_free(dentry_cache
, dentry
);
139 static void d_free(struct dentry
*dentry
)
141 BUG_ON(dentry
->d_count
);
142 this_cpu_dec(nr_dentry
);
143 if (dentry
->d_op
&& dentry
->d_op
->d_release
)
144 dentry
->d_op
->d_release(dentry
);
146 /* if dentry was never inserted into hash, immediate free is OK */
147 if (hlist_unhashed(&dentry
->d_hash
))
148 __d_free(&dentry
->d_u
.d_rcu
);
150 call_rcu(&dentry
->d_u
.d_rcu
, __d_free
);
154 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
155 * After this call, in-progress rcu-walk path lookup will fail. This
156 * should be called after unhashing, and after changing d_inode (if
157 * the dentry has not already been unhashed).
159 static inline void dentry_rcuwalk_barrier(struct dentry
*dentry
)
161 assert_spin_locked(&dentry
->d_lock
);
162 /* Go through a barrier */
163 write_seqcount_barrier(&dentry
->d_seq
);
167 * Release the dentry's inode, using the filesystem
168 * d_iput() operation if defined. Dentry has no refcount
171 static void dentry_iput(struct dentry
* dentry
)
172 __releases(dentry
->d_lock
)
173 __releases(dcache_inode_lock
)
175 struct inode
*inode
= dentry
->d_inode
;
177 dentry
->d_inode
= NULL
;
178 list_del_init(&dentry
->d_alias
);
179 spin_unlock(&dentry
->d_lock
);
180 spin_unlock(&dcache_inode_lock
);
182 fsnotify_inoderemove(inode
);
183 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
184 dentry
->d_op
->d_iput(dentry
, inode
);
188 spin_unlock(&dentry
->d_lock
);
189 spin_unlock(&dcache_inode_lock
);
194 * Release the dentry's inode, using the filesystem
195 * d_iput() operation if defined. dentry remains in-use.
197 static void dentry_unlink_inode(struct dentry
* dentry
)
198 __releases(dentry
->d_lock
)
199 __releases(dcache_inode_lock
)
201 struct inode
*inode
= dentry
->d_inode
;
202 dentry
->d_inode
= NULL
;
203 list_del_init(&dentry
->d_alias
);
204 dentry_rcuwalk_barrier(dentry
);
205 spin_unlock(&dentry
->d_lock
);
206 spin_unlock(&dcache_inode_lock
);
208 fsnotify_inoderemove(inode
);
209 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
210 dentry
->d_op
->d_iput(dentry
, inode
);
216 * dentry_lru_(add|del|move_tail) must be called with d_lock held.
218 static void dentry_lru_add(struct dentry
*dentry
)
220 if (list_empty(&dentry
->d_lru
)) {
221 spin_lock(&dcache_lru_lock
);
222 list_add(&dentry
->d_lru
, &dentry
->d_sb
->s_dentry_lru
);
223 dentry
->d_sb
->s_nr_dentry_unused
++;
224 dentry_stat
.nr_unused
++;
225 spin_unlock(&dcache_lru_lock
);
229 static void __dentry_lru_del(struct dentry
*dentry
)
231 list_del_init(&dentry
->d_lru
);
232 dentry
->d_sb
->s_nr_dentry_unused
--;
233 dentry_stat
.nr_unused
--;
236 static void dentry_lru_del(struct dentry
*dentry
)
238 if (!list_empty(&dentry
->d_lru
)) {
239 spin_lock(&dcache_lru_lock
);
240 __dentry_lru_del(dentry
);
241 spin_unlock(&dcache_lru_lock
);
245 static void dentry_lru_move_tail(struct dentry
*dentry
)
247 spin_lock(&dcache_lru_lock
);
248 if (list_empty(&dentry
->d_lru
)) {
249 list_add_tail(&dentry
->d_lru
, &dentry
->d_sb
->s_dentry_lru
);
250 dentry
->d_sb
->s_nr_dentry_unused
++;
251 dentry_stat
.nr_unused
++;
253 list_move_tail(&dentry
->d_lru
, &dentry
->d_sb
->s_dentry_lru
);
255 spin_unlock(&dcache_lru_lock
);
259 * d_kill - kill dentry and return parent
260 * @dentry: dentry to kill
262 * The dentry must already be unhashed and removed from the LRU.
264 * If this is the root of the dentry tree, return NULL.
266 * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
269 static struct dentry
*d_kill(struct dentry
*dentry
, struct dentry
*parent
)
270 __releases(dentry
->d_lock
)
271 __releases(parent
->d_lock
)
272 __releases(dcache_inode_lock
)
274 dentry
->d_parent
= NULL
;
275 list_del(&dentry
->d_u
.d_child
);
277 spin_unlock(&parent
->d_lock
);
280 * dentry_iput drops the locks, at which point nobody (except
281 * transient RCU lookups) can reach this dentry.
288 * d_drop - drop a dentry
289 * @dentry: dentry to drop
291 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
292 * be found through a VFS lookup any more. Note that this is different from
293 * deleting the dentry - d_delete will try to mark the dentry negative if
294 * possible, giving a successful _negative_ lookup, while d_drop will
295 * just make the cache lookup fail.
297 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
298 * reason (NFS timeouts or autofs deletes).
300 * __d_drop requires dentry->d_lock.
302 void __d_drop(struct dentry
*dentry
)
304 if (!(dentry
->d_flags
& DCACHE_UNHASHED
)) {
305 dentry
->d_flags
|= DCACHE_UNHASHED
;
306 spin_lock(&dcache_hash_lock
);
307 hlist_del_rcu(&dentry
->d_hash
);
308 spin_unlock(&dcache_hash_lock
);
309 dentry_rcuwalk_barrier(dentry
);
312 EXPORT_SYMBOL(__d_drop
);
314 void d_drop(struct dentry
*dentry
)
316 spin_lock(&dentry
->d_lock
);
318 spin_unlock(&dentry
->d_lock
);
320 EXPORT_SYMBOL(d_drop
);
323 * Finish off a dentry we've decided to kill.
324 * dentry->d_lock must be held, returns with it unlocked.
325 * If ref is non-zero, then decrement the refcount too.
326 * Returns dentry requiring refcount drop, or NULL if we're done.
328 static inline struct dentry
*dentry_kill(struct dentry
*dentry
, int ref
)
329 __releases(dentry
->d_lock
)
331 struct dentry
*parent
;
333 if (!spin_trylock(&dcache_inode_lock
)) {
335 spin_unlock(&dentry
->d_lock
);
337 return dentry
; /* try again with same dentry */
342 parent
= dentry
->d_parent
;
343 if (parent
&& !spin_trylock(&parent
->d_lock
)) {
344 spin_unlock(&dcache_inode_lock
);
350 /* if dentry was on the d_lru list delete it from there */
351 dentry_lru_del(dentry
);
352 /* if it was on the hash then remove it */
354 return d_kill(dentry
, parent
);
360 * This is complicated by the fact that we do not want to put
361 * dentries that are no longer on any hash chain on the unused
362 * list: we'd much rather just get rid of them immediately.
364 * However, that implies that we have to traverse the dentry
365 * tree upwards to the parents which might _also_ now be
366 * scheduled for deletion (it may have been only waiting for
367 * its last child to go away).
369 * This tail recursion is done by hand as we don't want to depend
370 * on the compiler to always get this right (gcc generally doesn't).
371 * Real recursion would eat up our stack space.
375 * dput - release a dentry
376 * @dentry: dentry to release
378 * Release a dentry. This will drop the usage count and if appropriate
379 * call the dentry unlink method as well as removing it from the queues and
380 * releasing its resources. If the parent dentries were scheduled for release
381 * they too may now get deleted.
383 void dput(struct dentry
*dentry
)
389 if (dentry
->d_count
== 1)
391 spin_lock(&dentry
->d_lock
);
392 BUG_ON(!dentry
->d_count
);
393 if (dentry
->d_count
> 1) {
395 spin_unlock(&dentry
->d_lock
);
399 if (dentry
->d_flags
& DCACHE_OP_DELETE
) {
400 if (dentry
->d_op
->d_delete(dentry
))
404 /* Unreachable? Get rid of it */
405 if (d_unhashed(dentry
))
408 /* Otherwise leave it cached and ensure it's on the LRU */
409 dentry
->d_flags
|= DCACHE_REFERENCED
;
410 dentry_lru_add(dentry
);
413 spin_unlock(&dentry
->d_lock
);
417 dentry
= dentry_kill(dentry
, 1);
424 * d_invalidate - invalidate a dentry
425 * @dentry: dentry to invalidate
427 * Try to invalidate the dentry if it turns out to be
428 * possible. If there are other dentries that can be
429 * reached through this one we can't delete it and we
430 * return -EBUSY. On success we return 0.
435 int d_invalidate(struct dentry
* dentry
)
438 * If it's already been dropped, return OK.
440 spin_lock(&dentry
->d_lock
);
441 if (d_unhashed(dentry
)) {
442 spin_unlock(&dentry
->d_lock
);
446 * Check whether to do a partial shrink_dcache
447 * to get rid of unused child entries.
449 if (!list_empty(&dentry
->d_subdirs
)) {
450 spin_unlock(&dentry
->d_lock
);
451 shrink_dcache_parent(dentry
);
452 spin_lock(&dentry
->d_lock
);
456 * Somebody else still using it?
458 * If it's a directory, we can't drop it
459 * for fear of somebody re-populating it
460 * with children (even though dropping it
461 * would make it unreachable from the root,
462 * we might still populate it if it was a
463 * working directory or similar).
465 if (dentry
->d_count
> 1) {
466 if (dentry
->d_inode
&& S_ISDIR(dentry
->d_inode
->i_mode
)) {
467 spin_unlock(&dentry
->d_lock
);
473 spin_unlock(&dentry
->d_lock
);
476 EXPORT_SYMBOL(d_invalidate
);
478 /* This must be called with d_lock held */
479 static inline void __dget_dlock(struct dentry
*dentry
)
484 static inline void __dget(struct dentry
*dentry
)
486 spin_lock(&dentry
->d_lock
);
487 __dget_dlock(dentry
);
488 spin_unlock(&dentry
->d_lock
);
491 struct dentry
*dget_parent(struct dentry
*dentry
)
497 * Don't need rcu_dereference because we re-check it was correct under
501 ret
= dentry
->d_parent
;
506 spin_lock(&ret
->d_lock
);
507 if (unlikely(ret
!= dentry
->d_parent
)) {
508 spin_unlock(&ret
->d_lock
);
513 BUG_ON(!ret
->d_count
);
515 spin_unlock(&ret
->d_lock
);
519 EXPORT_SYMBOL(dget_parent
);
522 * d_find_alias - grab a hashed alias of inode
523 * @inode: inode in question
524 * @want_discon: flag, used by d_splice_alias, to request
525 * that only a DISCONNECTED alias be returned.
527 * If inode has a hashed alias, or is a directory and has any alias,
528 * acquire the reference to alias and return it. Otherwise return NULL.
529 * Notice that if inode is a directory there can be only one alias and
530 * it can be unhashed only if it has no children, or if it is the root
533 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
534 * any other hashed alias over that one unless @want_discon is set,
535 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
537 static struct dentry
*__d_find_alias(struct inode
*inode
, int want_discon
)
539 struct dentry
*alias
, *discon_alias
;
543 list_for_each_entry(alias
, &inode
->i_dentry
, d_alias
) {
544 spin_lock(&alias
->d_lock
);
545 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
546 if (IS_ROOT(alias
) &&
547 (alias
->d_flags
& DCACHE_DISCONNECTED
)) {
548 discon_alias
= alias
;
549 } else if (!want_discon
) {
551 spin_unlock(&alias
->d_lock
);
555 spin_unlock(&alias
->d_lock
);
558 alias
= discon_alias
;
559 spin_lock(&alias
->d_lock
);
560 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
561 if (IS_ROOT(alias
) &&
562 (alias
->d_flags
& DCACHE_DISCONNECTED
)) {
564 spin_unlock(&alias
->d_lock
);
568 spin_unlock(&alias
->d_lock
);
574 struct dentry
*d_find_alias(struct inode
*inode
)
576 struct dentry
*de
= NULL
;
578 if (!list_empty(&inode
->i_dentry
)) {
579 spin_lock(&dcache_inode_lock
);
580 de
= __d_find_alias(inode
, 0);
581 spin_unlock(&dcache_inode_lock
);
585 EXPORT_SYMBOL(d_find_alias
);
588 * Try to kill dentries associated with this inode.
589 * WARNING: you must own a reference to inode.
591 void d_prune_aliases(struct inode
*inode
)
593 struct dentry
*dentry
;
595 spin_lock(&dcache_inode_lock
);
596 list_for_each_entry(dentry
, &inode
->i_dentry
, d_alias
) {
597 spin_lock(&dentry
->d_lock
);
598 if (!dentry
->d_count
) {
599 __dget_dlock(dentry
);
601 spin_unlock(&dentry
->d_lock
);
602 spin_unlock(&dcache_inode_lock
);
606 spin_unlock(&dentry
->d_lock
);
608 spin_unlock(&dcache_inode_lock
);
610 EXPORT_SYMBOL(d_prune_aliases
);
613 * Try to throw away a dentry - free the inode, dput the parent.
614 * Requires dentry->d_lock is held, and dentry->d_count == 0.
615 * Releases dentry->d_lock.
617 * This may fail if locks cannot be acquired no problem, just try again.
619 static void try_prune_one_dentry(struct dentry
*dentry
)
620 __releases(dentry
->d_lock
)
622 struct dentry
*parent
;
624 parent
= dentry_kill(dentry
, 0);
626 * If dentry_kill returns NULL, we have nothing more to do.
627 * if it returns the same dentry, trylocks failed. In either
628 * case, just loop again.
630 * Otherwise, we need to prune ancestors too. This is necessary
631 * to prevent quadratic behavior of shrink_dcache_parent(), but
632 * is also expected to be beneficial in reducing dentry cache
637 if (parent
== dentry
)
640 /* Prune ancestors. */
643 spin_lock(&dentry
->d_lock
);
644 if (dentry
->d_count
> 1) {
646 spin_unlock(&dentry
->d_lock
);
649 dentry
= dentry_kill(dentry
, 1);
653 static void shrink_dentry_list(struct list_head
*list
)
655 struct dentry
*dentry
;
659 dentry
= list_entry_rcu(list
->prev
, struct dentry
, d_lru
);
660 if (&dentry
->d_lru
== list
)
662 spin_lock(&dentry
->d_lock
);
663 if (dentry
!= list_entry(list
->prev
, struct dentry
, d_lru
)) {
664 spin_unlock(&dentry
->d_lock
);
669 * We found an inuse dentry which was not removed from
670 * the LRU because of laziness during lookup. Do not free
671 * it - just keep it off the LRU list.
673 if (dentry
->d_count
) {
674 dentry_lru_del(dentry
);
675 spin_unlock(&dentry
->d_lock
);
681 try_prune_one_dentry(dentry
);
689 * __shrink_dcache_sb - shrink the dentry LRU on a given superblock
690 * @sb: superblock to shrink dentry LRU.
691 * @count: number of entries to prune
692 * @flags: flags to control the dentry processing
694 * If flags contains DCACHE_REFERENCED reference dentries will not be pruned.
696 static void __shrink_dcache_sb(struct super_block
*sb
, int *count
, int flags
)
698 /* called from prune_dcache() and shrink_dcache_parent() */
699 struct dentry
*dentry
;
700 LIST_HEAD(referenced
);
705 spin_lock(&dcache_lru_lock
);
706 while (!list_empty(&sb
->s_dentry_lru
)) {
707 dentry
= list_entry(sb
->s_dentry_lru
.prev
,
708 struct dentry
, d_lru
);
709 BUG_ON(dentry
->d_sb
!= sb
);
711 if (!spin_trylock(&dentry
->d_lock
)) {
712 spin_unlock(&dcache_lru_lock
);
718 * If we are honouring the DCACHE_REFERENCED flag and the
719 * dentry has this flag set, don't free it. Clear the flag
720 * and put it back on the LRU.
722 if (flags
& DCACHE_REFERENCED
&&
723 dentry
->d_flags
& DCACHE_REFERENCED
) {
724 dentry
->d_flags
&= ~DCACHE_REFERENCED
;
725 list_move(&dentry
->d_lru
, &referenced
);
726 spin_unlock(&dentry
->d_lock
);
728 list_move_tail(&dentry
->d_lru
, &tmp
);
729 spin_unlock(&dentry
->d_lock
);
733 cond_resched_lock(&dcache_lru_lock
);
735 if (!list_empty(&referenced
))
736 list_splice(&referenced
, &sb
->s_dentry_lru
);
737 spin_unlock(&dcache_lru_lock
);
739 shrink_dentry_list(&tmp
);
745 * prune_dcache - shrink the dcache
746 * @count: number of entries to try to free
748 * Shrink the dcache. This is done when we need more memory, or simply when we
749 * need to unmount something (at which point we need to unuse all dentries).
751 * This function may fail to free any resources if all the dentries are in use.
753 static void prune_dcache(int count
)
755 struct super_block
*sb
, *p
= NULL
;
757 int unused
= dentry_stat
.nr_unused
;
761 if (unused
== 0 || count
== 0)
766 prune_ratio
= unused
/ count
;
768 list_for_each_entry(sb
, &super_blocks
, s_list
) {
769 if (list_empty(&sb
->s_instances
))
771 if (sb
->s_nr_dentry_unused
== 0)
774 /* Now, we reclaim unused dentrins with fairness.
775 * We reclaim them same percentage from each superblock.
776 * We calculate number of dentries to scan on this sb
777 * as follows, but the implementation is arranged to avoid
779 * number of dentries to scan on this sb =
780 * count * (number of dentries on this sb /
781 * number of dentries in the machine)
783 spin_unlock(&sb_lock
);
784 if (prune_ratio
!= 1)
785 w_count
= (sb
->s_nr_dentry_unused
/ prune_ratio
) + 1;
787 w_count
= sb
->s_nr_dentry_unused
;
790 * We need to be sure this filesystem isn't being unmounted,
791 * otherwise we could race with generic_shutdown_super(), and
792 * end up holding a reference to an inode while the filesystem
793 * is unmounted. So we try to get s_umount, and make sure
796 if (down_read_trylock(&sb
->s_umount
)) {
797 if ((sb
->s_root
!= NULL
) &&
798 (!list_empty(&sb
->s_dentry_lru
))) {
799 __shrink_dcache_sb(sb
, &w_count
,
803 up_read(&sb
->s_umount
);
810 /* more work left to do? */
816 spin_unlock(&sb_lock
);
820 * shrink_dcache_sb - shrink dcache for a superblock
823 * Shrink the dcache for the specified super block. This is used to free
824 * the dcache before unmounting a file system.
826 void shrink_dcache_sb(struct super_block
*sb
)
830 spin_lock(&dcache_lru_lock
);
831 while (!list_empty(&sb
->s_dentry_lru
)) {
832 list_splice_init(&sb
->s_dentry_lru
, &tmp
);
833 spin_unlock(&dcache_lru_lock
);
834 shrink_dentry_list(&tmp
);
835 spin_lock(&dcache_lru_lock
);
837 spin_unlock(&dcache_lru_lock
);
839 EXPORT_SYMBOL(shrink_dcache_sb
);
842 * destroy a single subtree of dentries for unmount
843 * - see the comments on shrink_dcache_for_umount() for a description of the
846 static void shrink_dcache_for_umount_subtree(struct dentry
*dentry
)
848 struct dentry
*parent
;
849 unsigned detached
= 0;
851 BUG_ON(!IS_ROOT(dentry
));
853 /* detach this root from the system */
854 spin_lock(&dentry
->d_lock
);
855 dentry_lru_del(dentry
);
857 spin_unlock(&dentry
->d_lock
);
860 /* descend to the first leaf in the current subtree */
861 while (!list_empty(&dentry
->d_subdirs
)) {
864 /* this is a branch with children - detach all of them
865 * from the system in one go */
866 spin_lock(&dentry
->d_lock
);
867 list_for_each_entry(loop
, &dentry
->d_subdirs
,
869 spin_lock_nested(&loop
->d_lock
,
870 DENTRY_D_LOCK_NESTED
);
871 dentry_lru_del(loop
);
873 spin_unlock(&loop
->d_lock
);
875 spin_unlock(&dentry
->d_lock
);
877 /* move to the first child */
878 dentry
= list_entry(dentry
->d_subdirs
.next
,
879 struct dentry
, d_u
.d_child
);
882 /* consume the dentries from this leaf up through its parents
883 * until we find one with children or run out altogether */
887 if (dentry
->d_count
!= 0) {
889 "BUG: Dentry %p{i=%lx,n=%s}"
891 " [unmount of %s %s]\n",
894 dentry
->d_inode
->i_ino
: 0UL,
897 dentry
->d_sb
->s_type
->name
,
902 if (IS_ROOT(dentry
)) {
904 list_del(&dentry
->d_u
.d_child
);
906 parent
= dentry
->d_parent
;
907 spin_lock(&parent
->d_lock
);
909 list_del(&dentry
->d_u
.d_child
);
910 spin_unlock(&parent
->d_lock
);
915 inode
= dentry
->d_inode
;
917 dentry
->d_inode
= NULL
;
918 list_del_init(&dentry
->d_alias
);
919 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
920 dentry
->d_op
->d_iput(dentry
, inode
);
927 /* finished when we fall off the top of the tree,
928 * otherwise we ascend to the parent and move to the
929 * next sibling if there is one */
933 } while (list_empty(&dentry
->d_subdirs
));
935 dentry
= list_entry(dentry
->d_subdirs
.next
,
936 struct dentry
, d_u
.d_child
);
941 * destroy the dentries attached to a superblock on unmounting
942 * - we don't need to use dentry->d_lock because:
943 * - the superblock is detached from all mountings and open files, so the
944 * dentry trees will not be rearranged by the VFS
945 * - s_umount is write-locked, so the memory pressure shrinker will ignore
946 * any dentries belonging to this superblock that it comes across
947 * - the filesystem itself is no longer permitted to rearrange the dentries
950 void shrink_dcache_for_umount(struct super_block
*sb
)
952 struct dentry
*dentry
;
954 if (down_read_trylock(&sb
->s_umount
))
959 spin_lock(&dentry
->d_lock
);
961 spin_unlock(&dentry
->d_lock
);
962 shrink_dcache_for_umount_subtree(dentry
);
964 while (!hlist_empty(&sb
->s_anon
)) {
965 dentry
= hlist_entry(sb
->s_anon
.first
, struct dentry
, d_hash
);
966 shrink_dcache_for_umount_subtree(dentry
);
971 * Search for at least 1 mount point in the dentry's subdirs.
972 * We descend to the next level whenever the d_subdirs
973 * list is non-empty and continue searching.
977 * have_submounts - check for mounts over a dentry
978 * @parent: dentry to check.
980 * Return true if the parent or its subdirectories contain
983 int have_submounts(struct dentry
*parent
)
985 struct dentry
*this_parent
;
986 struct list_head
*next
;
990 seq
= read_seqbegin(&rename_lock
);
992 this_parent
= parent
;
994 if (d_mountpoint(parent
))
996 spin_lock(&this_parent
->d_lock
);
998 next
= this_parent
->d_subdirs
.next
;
1000 while (next
!= &this_parent
->d_subdirs
) {
1001 struct list_head
*tmp
= next
;
1002 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_u
.d_child
);
1005 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1006 /* Have we found a mount point ? */
1007 if (d_mountpoint(dentry
)) {
1008 spin_unlock(&dentry
->d_lock
);
1009 spin_unlock(&this_parent
->d_lock
);
1012 if (!list_empty(&dentry
->d_subdirs
)) {
1013 spin_unlock(&this_parent
->d_lock
);
1014 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
1015 this_parent
= dentry
;
1016 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
1019 spin_unlock(&dentry
->d_lock
);
1022 * All done at this level ... ascend and resume the search.
1024 if (this_parent
!= parent
) {
1026 struct dentry
*child
;
1028 tmp
= this_parent
->d_parent
;
1030 spin_unlock(&this_parent
->d_lock
);
1031 child
= this_parent
;
1033 spin_lock(&this_parent
->d_lock
);
1034 /* might go back up the wrong parent if we have had a rename
1036 if (this_parent
!= child
->d_parent
||
1037 (!locked
&& read_seqretry(&rename_lock
, seq
))) {
1038 spin_unlock(&this_parent
->d_lock
);
1043 next
= child
->d_u
.d_child
.next
;
1046 spin_unlock(&this_parent
->d_lock
);
1047 if (!locked
&& read_seqretry(&rename_lock
, seq
))
1050 write_sequnlock(&rename_lock
);
1051 return 0; /* No mount points found in tree */
1053 if (!locked
&& read_seqretry(&rename_lock
, seq
))
1056 write_sequnlock(&rename_lock
);
1061 write_seqlock(&rename_lock
);
1064 EXPORT_SYMBOL(have_submounts
);
1067 * Search the dentry child list for the specified parent,
1068 * and move any unused dentries to the end of the unused
1069 * list for prune_dcache(). We descend to the next level
1070 * whenever the d_subdirs list is non-empty and continue
1073 * It returns zero iff there are no unused children,
1074 * otherwise it returns the number of children moved to
1075 * the end of the unused list. This may not be the total
1076 * number of unused children, because select_parent can
1077 * drop the lock and return early due to latency
1080 static int select_parent(struct dentry
* parent
)
1082 struct dentry
*this_parent
;
1083 struct list_head
*next
;
1088 seq
= read_seqbegin(&rename_lock
);
1090 this_parent
= parent
;
1091 spin_lock(&this_parent
->d_lock
);
1093 next
= this_parent
->d_subdirs
.next
;
1095 while (next
!= &this_parent
->d_subdirs
) {
1096 struct list_head
*tmp
= next
;
1097 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_u
.d_child
);
1100 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1103 * move only zero ref count dentries to the end
1104 * of the unused list for prune_dcache
1106 if (!dentry
->d_count
) {
1107 dentry_lru_move_tail(dentry
);
1110 dentry_lru_del(dentry
);
1114 * We can return to the caller if we have found some (this
1115 * ensures forward progress). We'll be coming back to find
1118 if (found
&& need_resched()) {
1119 spin_unlock(&dentry
->d_lock
);
1124 * Descend a level if the d_subdirs list is non-empty.
1126 if (!list_empty(&dentry
->d_subdirs
)) {
1127 spin_unlock(&this_parent
->d_lock
);
1128 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
1129 this_parent
= dentry
;
1130 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
1134 spin_unlock(&dentry
->d_lock
);
1137 * All done at this level ... ascend and resume the search.
1139 if (this_parent
!= parent
) {
1141 struct dentry
*child
;
1143 tmp
= this_parent
->d_parent
;
1145 spin_unlock(&this_parent
->d_lock
);
1146 child
= this_parent
;
1148 spin_lock(&this_parent
->d_lock
);
1149 /* might go back up the wrong parent if we have had a rename
1151 if (this_parent
!= child
->d_parent
||
1152 (!locked
&& read_seqretry(&rename_lock
, seq
))) {
1153 spin_unlock(&this_parent
->d_lock
);
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 * Scan `nr' dentries and return the number which remain.
1197 * We need to avoid reentering the filesystem if the caller is performing a
1198 * GFP_NOFS allocation attempt. One example deadlock is:
1200 * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
1201 * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
1202 * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
1204 * In this case we return -1 to tell the caller that we baled.
1206 static int shrink_dcache_memory(struct shrinker
*shrink
, int nr
, gfp_t gfp_mask
)
1209 if (!(gfp_mask
& __GFP_FS
))
1214 return (dentry_stat
.nr_unused
/ 100) * sysctl_vfs_cache_pressure
;
1217 static struct shrinker dcache_shrinker
= {
1218 .shrink
= shrink_dcache_memory
,
1219 .seeks
= DEFAULT_SEEKS
,
1223 * d_alloc - allocate a dcache entry
1224 * @parent: parent of entry to allocate
1225 * @name: qstr of the name
1227 * Allocates a dentry. It returns %NULL if there is insufficient memory
1228 * available. On a success the dentry is returned. The name passed in is
1229 * copied and the copy passed in may be reused after this call.
1232 struct dentry
*d_alloc(struct dentry
* parent
, const struct qstr
*name
)
1234 struct dentry
*dentry
;
1237 dentry
= kmem_cache_alloc(dentry_cache
, GFP_KERNEL
);
1241 if (name
->len
> DNAME_INLINE_LEN
-1) {
1242 dname
= kmalloc(name
->len
+ 1, GFP_KERNEL
);
1244 kmem_cache_free(dentry_cache
, dentry
);
1248 dname
= dentry
->d_iname
;
1250 dentry
->d_name
.name
= dname
;
1252 dentry
->d_name
.len
= name
->len
;
1253 dentry
->d_name
.hash
= name
->hash
;
1254 memcpy(dname
, name
->name
, name
->len
);
1255 dname
[name
->len
] = 0;
1257 dentry
->d_count
= 1;
1258 dentry
->d_flags
= DCACHE_UNHASHED
;
1259 spin_lock_init(&dentry
->d_lock
);
1260 seqcount_init(&dentry
->d_seq
);
1261 dentry
->d_inode
= NULL
;
1262 dentry
->d_parent
= NULL
;
1263 dentry
->d_sb
= NULL
;
1264 dentry
->d_op
= NULL
;
1265 dentry
->d_fsdata
= NULL
;
1266 INIT_HLIST_NODE(&dentry
->d_hash
);
1267 INIT_LIST_HEAD(&dentry
->d_lru
);
1268 INIT_LIST_HEAD(&dentry
->d_subdirs
);
1269 INIT_LIST_HEAD(&dentry
->d_alias
);
1270 INIT_LIST_HEAD(&dentry
->d_u
.d_child
);
1273 spin_lock(&parent
->d_lock
);
1275 * don't need child lock because it is not subject
1276 * to concurrency here
1278 __dget_dlock(parent
);
1279 dentry
->d_parent
= parent
;
1280 dentry
->d_sb
= parent
->d_sb
;
1281 list_add(&dentry
->d_u
.d_child
, &parent
->d_subdirs
);
1282 spin_unlock(&parent
->d_lock
);
1285 this_cpu_inc(nr_dentry
);
1289 EXPORT_SYMBOL(d_alloc
);
1291 struct dentry
*d_alloc_name(struct dentry
*parent
, const char *name
)
1296 q
.len
= strlen(name
);
1297 q
.hash
= full_name_hash(q
.name
, q
.len
);
1298 return d_alloc(parent
, &q
);
1300 EXPORT_SYMBOL(d_alloc_name
);
1302 void d_set_d_op(struct dentry
*dentry
, const struct dentry_operations
*op
)
1304 BUG_ON(dentry
->d_op
);
1305 BUG_ON(dentry
->d_flags
& (DCACHE_OP_HASH
|
1307 DCACHE_OP_REVALIDATE
|
1308 DCACHE_OP_DELETE
));
1313 dentry
->d_flags
|= DCACHE_OP_HASH
;
1315 dentry
->d_flags
|= DCACHE_OP_COMPARE
;
1316 if (op
->d_revalidate
)
1317 dentry
->d_flags
|= DCACHE_OP_REVALIDATE
;
1319 dentry
->d_flags
|= DCACHE_OP_DELETE
;
1322 EXPORT_SYMBOL(d_set_d_op
);
1324 static void __d_instantiate(struct dentry
*dentry
, struct inode
*inode
)
1326 spin_lock(&dentry
->d_lock
);
1328 list_add(&dentry
->d_alias
, &inode
->i_dentry
);
1329 dentry
->d_inode
= inode
;
1330 dentry_rcuwalk_barrier(dentry
);
1331 spin_unlock(&dentry
->d_lock
);
1332 fsnotify_d_instantiate(dentry
, inode
);
1336 * d_instantiate - fill in inode information for a dentry
1337 * @entry: dentry to complete
1338 * @inode: inode to attach to this dentry
1340 * Fill in inode information in the entry.
1342 * This turns negative dentries into productive full members
1345 * NOTE! This assumes that the inode count has been incremented
1346 * (or otherwise set) by the caller to indicate that it is now
1347 * in use by the dcache.
1350 void d_instantiate(struct dentry
*entry
, struct inode
* inode
)
1352 BUG_ON(!list_empty(&entry
->d_alias
));
1353 spin_lock(&dcache_inode_lock
);
1354 __d_instantiate(entry
, inode
);
1355 spin_unlock(&dcache_inode_lock
);
1356 security_d_instantiate(entry
, inode
);
1358 EXPORT_SYMBOL(d_instantiate
);
1361 * d_instantiate_unique - instantiate a non-aliased dentry
1362 * @entry: dentry to instantiate
1363 * @inode: inode to attach to this dentry
1365 * Fill in inode information in the entry. On success, it returns NULL.
1366 * If an unhashed alias of "entry" already exists, then we return the
1367 * aliased dentry instead and drop one reference to inode.
1369 * Note that in order to avoid conflicts with rename() etc, the caller
1370 * had better be holding the parent directory semaphore.
1372 * This also assumes that the inode count has been incremented
1373 * (or otherwise set) by the caller to indicate that it is now
1374 * in use by the dcache.
1376 static struct dentry
*__d_instantiate_unique(struct dentry
*entry
,
1377 struct inode
*inode
)
1379 struct dentry
*alias
;
1380 int len
= entry
->d_name
.len
;
1381 const char *name
= entry
->d_name
.name
;
1382 unsigned int hash
= entry
->d_name
.hash
;
1385 __d_instantiate(entry
, NULL
);
1389 list_for_each_entry(alias
, &inode
->i_dentry
, d_alias
) {
1390 struct qstr
*qstr
= &alias
->d_name
;
1393 * Don't need alias->d_lock here, because aliases with
1394 * d_parent == entry->d_parent are not subject to name or
1395 * parent changes, because the parent inode i_mutex is held.
1397 if (qstr
->hash
!= hash
)
1399 if (alias
->d_parent
!= entry
->d_parent
)
1401 if (qstr
->len
!= len
)
1403 if (memcmp(qstr
->name
, name
, len
))
1409 __d_instantiate(entry
, inode
);
1413 struct dentry
*d_instantiate_unique(struct dentry
*entry
, struct inode
*inode
)
1415 struct dentry
*result
;
1417 BUG_ON(!list_empty(&entry
->d_alias
));
1419 spin_lock(&dcache_inode_lock
);
1420 result
= __d_instantiate_unique(entry
, inode
);
1421 spin_unlock(&dcache_inode_lock
);
1424 security_d_instantiate(entry
, inode
);
1428 BUG_ON(!d_unhashed(result
));
1433 EXPORT_SYMBOL(d_instantiate_unique
);
1436 * d_alloc_root - allocate root dentry
1437 * @root_inode: inode to allocate the root for
1439 * Allocate a root ("/") dentry for the inode given. The inode is
1440 * instantiated and returned. %NULL is returned if there is insufficient
1441 * memory or the inode passed is %NULL.
1444 struct dentry
* d_alloc_root(struct inode
* root_inode
)
1446 struct dentry
*res
= NULL
;
1449 static const struct qstr name
= { .name
= "/", .len
= 1 };
1451 res
= d_alloc(NULL
, &name
);
1453 res
->d_sb
= root_inode
->i_sb
;
1454 res
->d_parent
= res
;
1455 d_instantiate(res
, root_inode
);
1460 EXPORT_SYMBOL(d_alloc_root
);
1462 static inline struct hlist_head
*d_hash(struct dentry
*parent
,
1465 hash
+= ((unsigned long) parent
^ GOLDEN_RATIO_PRIME
) / L1_CACHE_BYTES
;
1466 hash
= hash
^ ((hash
^ GOLDEN_RATIO_PRIME
) >> D_HASHBITS
);
1467 return dentry_hashtable
+ (hash
& D_HASHMASK
);
1471 * d_obtain_alias - find or allocate a dentry for a given inode
1472 * @inode: inode to allocate the dentry for
1474 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1475 * similar open by handle operations. The returned dentry may be anonymous,
1476 * or may have a full name (if the inode was already in the cache).
1478 * When called on a directory inode, we must ensure that the inode only ever
1479 * has one dentry. If a dentry is found, that is returned instead of
1480 * allocating a new one.
1482 * On successful return, the reference to the inode has been transferred
1483 * to the dentry. In case of an error the reference on the inode is released.
1484 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1485 * be passed in and will be the error will be propagate to the return value,
1486 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1488 struct dentry
*d_obtain_alias(struct inode
*inode
)
1490 static const struct qstr anonstring
= { .name
= "" };
1495 return ERR_PTR(-ESTALE
);
1497 return ERR_CAST(inode
);
1499 res
= d_find_alias(inode
);
1503 tmp
= d_alloc(NULL
, &anonstring
);
1505 res
= ERR_PTR(-ENOMEM
);
1508 tmp
->d_parent
= tmp
; /* make sure dput doesn't croak */
1511 spin_lock(&dcache_inode_lock
);
1512 res
= __d_find_alias(inode
, 0);
1514 spin_unlock(&dcache_inode_lock
);
1519 /* attach a disconnected dentry */
1520 spin_lock(&tmp
->d_lock
);
1521 tmp
->d_sb
= inode
->i_sb
;
1522 tmp
->d_inode
= inode
;
1523 tmp
->d_flags
|= DCACHE_DISCONNECTED
;
1524 tmp
->d_flags
&= ~DCACHE_UNHASHED
;
1525 list_add(&tmp
->d_alias
, &inode
->i_dentry
);
1526 spin_lock(&dcache_hash_lock
);
1527 hlist_add_head(&tmp
->d_hash
, &inode
->i_sb
->s_anon
);
1528 spin_unlock(&dcache_hash_lock
);
1529 spin_unlock(&tmp
->d_lock
);
1530 spin_unlock(&dcache_inode_lock
);
1538 EXPORT_SYMBOL(d_obtain_alias
);
1541 * d_splice_alias - splice a disconnected dentry into the tree if one exists
1542 * @inode: the inode which may have a disconnected dentry
1543 * @dentry: a negative dentry which we want to point to the inode.
1545 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1546 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1547 * and return it, else simply d_add the inode to the dentry and return NULL.
1549 * This is needed in the lookup routine of any filesystem that is exportable
1550 * (via knfsd) so that we can build dcache paths to directories effectively.
1552 * If a dentry was found and moved, then it is returned. Otherwise NULL
1553 * is returned. This matches the expected return value of ->lookup.
1556 struct dentry
*d_splice_alias(struct inode
*inode
, struct dentry
*dentry
)
1558 struct dentry
*new = NULL
;
1560 if (inode
&& S_ISDIR(inode
->i_mode
)) {
1561 spin_lock(&dcache_inode_lock
);
1562 new = __d_find_alias(inode
, 1);
1564 BUG_ON(!(new->d_flags
& DCACHE_DISCONNECTED
));
1565 spin_unlock(&dcache_inode_lock
);
1566 security_d_instantiate(new, inode
);
1567 d_move(new, dentry
);
1570 /* already taking dcache_inode_lock, so d_add() by hand */
1571 __d_instantiate(dentry
, inode
);
1572 spin_unlock(&dcache_inode_lock
);
1573 security_d_instantiate(dentry
, inode
);
1577 d_add(dentry
, inode
);
1580 EXPORT_SYMBOL(d_splice_alias
);
1583 * d_add_ci - lookup or allocate new dentry with case-exact name
1584 * @inode: the inode case-insensitive lookup has found
1585 * @dentry: the negative dentry that was passed to the parent's lookup func
1586 * @name: the case-exact name to be associated with the returned dentry
1588 * This is to avoid filling the dcache with case-insensitive names to the
1589 * same inode, only the actual correct case is stored in the dcache for
1590 * case-insensitive filesystems.
1592 * For a case-insensitive lookup match and if the the case-exact dentry
1593 * already exists in in the dcache, use it and return it.
1595 * If no entry exists with the exact case name, allocate new dentry with
1596 * the exact case, and return the spliced entry.
1598 struct dentry
*d_add_ci(struct dentry
*dentry
, struct inode
*inode
,
1602 struct dentry
*found
;
1606 * First check if a dentry matching the name already exists,
1607 * if not go ahead and create it now.
1609 found
= d_hash_and_lookup(dentry
->d_parent
, name
);
1611 new = d_alloc(dentry
->d_parent
, name
);
1617 found
= d_splice_alias(inode
, new);
1626 * If a matching dentry exists, and it's not negative use it.
1628 * Decrement the reference count to balance the iget() done
1631 if (found
->d_inode
) {
1632 if (unlikely(found
->d_inode
!= inode
)) {
1633 /* This can't happen because bad inodes are unhashed. */
1634 BUG_ON(!is_bad_inode(inode
));
1635 BUG_ON(!is_bad_inode(found
->d_inode
));
1642 * Negative dentry: instantiate it unless the inode is a directory and
1643 * already has a dentry.
1645 spin_lock(&dcache_inode_lock
);
1646 if (!S_ISDIR(inode
->i_mode
) || list_empty(&inode
->i_dentry
)) {
1647 __d_instantiate(found
, inode
);
1648 spin_unlock(&dcache_inode_lock
);
1649 security_d_instantiate(found
, inode
);
1654 * In case a directory already has a (disconnected) entry grab a
1655 * reference to it, move it in place and use it.
1657 new = list_entry(inode
->i_dentry
.next
, struct dentry
, d_alias
);
1659 spin_unlock(&dcache_inode_lock
);
1660 security_d_instantiate(found
, inode
);
1668 return ERR_PTR(error
);
1670 EXPORT_SYMBOL(d_add_ci
);
1673 * __d_lookup_rcu - search for a dentry (racy, store-free)
1674 * @parent: parent dentry
1675 * @name: qstr of name we wish to find
1676 * @seq: returns d_seq value at the point where the dentry was found
1677 * @inode: returns dentry->d_inode when the inode was found valid.
1678 * Returns: dentry, or NULL
1680 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
1681 * resolution (store-free path walking) design described in
1682 * Documentation/filesystems/path-lookup.txt.
1684 * This is not to be used outside core vfs.
1686 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
1687 * held, and rcu_read_lock held. The returned dentry must not be stored into
1688 * without taking d_lock and checking d_seq sequence count against @seq
1691 * A refcount may be taken on the found dentry with the __d_rcu_to_refcount
1694 * Alternatively, __d_lookup_rcu may be called again to look up the child of
1695 * the returned dentry, so long as its parent's seqlock is checked after the
1696 * child is looked up. Thus, an interlocking stepping of sequence lock checks
1697 * is formed, giving integrity down the path walk.
1699 struct dentry
*__d_lookup_rcu(struct dentry
*parent
, struct qstr
*name
,
1700 unsigned *seq
, struct inode
**inode
)
1702 unsigned int len
= name
->len
;
1703 unsigned int hash
= name
->hash
;
1704 const unsigned char *str
= name
->name
;
1705 struct hlist_head
*head
= d_hash(parent
, hash
);
1706 struct hlist_node
*node
;
1707 struct dentry
*dentry
;
1710 * Note: There is significant duplication with __d_lookup_rcu which is
1711 * required to prevent single threaded performance regressions
1712 * especially on architectures where smp_rmb (in seqcounts) are costly.
1713 * Keep the two functions in sync.
1717 * The hash list is protected using RCU.
1719 * Carefully use d_seq when comparing a candidate dentry, to avoid
1720 * races with d_move().
1722 * It is possible that concurrent renames can mess up our list
1723 * walk here and result in missing our dentry, resulting in the
1724 * false-negative result. d_lookup() protects against concurrent
1725 * renames using rename_lock seqlock.
1727 * See Documentation/vfs/dcache-locking.txt for more details.
1729 hlist_for_each_entry_rcu(dentry
, node
, head
, d_hash
) {
1734 if (dentry
->d_name
.hash
!= hash
)
1738 *seq
= read_seqcount_begin(&dentry
->d_seq
);
1739 if (dentry
->d_parent
!= parent
)
1741 if (d_unhashed(dentry
))
1743 tlen
= dentry
->d_name
.len
;
1744 tname
= dentry
->d_name
.name
;
1745 i
= dentry
->d_inode
;
1747 * This seqcount check is required to ensure name and
1748 * len are loaded atomically, so as not to walk off the
1749 * edge of memory when walking. If we could load this
1750 * atomically some other way, we could drop this check.
1752 if (read_seqcount_retry(&dentry
->d_seq
, *seq
))
1754 if (parent
->d_flags
& DCACHE_OP_COMPARE
) {
1755 if (parent
->d_op
->d_compare(parent
, *inode
,
1762 if (memcmp(tname
, str
, tlen
))
1766 * No extra seqcount check is required after the name
1767 * compare. The caller must perform a seqcount check in
1768 * order to do anything useful with the returned dentry
1778 * d_lookup - search for a dentry
1779 * @parent: parent dentry
1780 * @name: qstr of name we wish to find
1781 * Returns: dentry, or NULL
1783 * d_lookup searches the children of the parent dentry for the name in
1784 * question. If the dentry is found its reference count is incremented and the
1785 * dentry is returned. The caller must use dput to free the entry when it has
1786 * finished using it. %NULL is returned if the dentry does not exist.
1788 struct dentry
*d_lookup(struct dentry
*parent
, struct qstr
*name
)
1790 struct dentry
*dentry
;
1794 seq
= read_seqbegin(&rename_lock
);
1795 dentry
= __d_lookup(parent
, name
);
1798 } while (read_seqretry(&rename_lock
, seq
));
1801 EXPORT_SYMBOL(d_lookup
);
1804 * __d_lookup - search for a dentry (racy)
1805 * @parent: parent dentry
1806 * @name: qstr of name we wish to find
1807 * Returns: dentry, or NULL
1809 * __d_lookup is like d_lookup, however it may (rarely) return a
1810 * false-negative result due to unrelated rename activity.
1812 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
1813 * however it must be used carefully, eg. with a following d_lookup in
1814 * the case of failure.
1816 * __d_lookup callers must be commented.
1818 struct dentry
*__d_lookup(struct dentry
*parent
, struct qstr
*name
)
1820 unsigned int len
= name
->len
;
1821 unsigned int hash
= name
->hash
;
1822 const unsigned char *str
= name
->name
;
1823 struct hlist_head
*head
= d_hash(parent
,hash
);
1824 struct hlist_node
*node
;
1825 struct dentry
*found
= NULL
;
1826 struct dentry
*dentry
;
1829 * Note: There is significant duplication with __d_lookup_rcu which is
1830 * required to prevent single threaded performance regressions
1831 * especially on architectures where smp_rmb (in seqcounts) are costly.
1832 * Keep the two functions in sync.
1836 * The hash list is protected using RCU.
1838 * Take d_lock when comparing a candidate dentry, to avoid races
1841 * It is possible that concurrent renames can mess up our list
1842 * walk here and result in missing our dentry, resulting in the
1843 * false-negative result. d_lookup() protects against concurrent
1844 * renames using rename_lock seqlock.
1846 * See Documentation/vfs/dcache-locking.txt for more details.
1850 hlist_for_each_entry_rcu(dentry
, node
, head
, d_hash
) {
1854 if (dentry
->d_name
.hash
!= hash
)
1857 spin_lock(&dentry
->d_lock
);
1858 if (dentry
->d_parent
!= parent
)
1860 if (d_unhashed(dentry
))
1864 * It is safe to compare names since d_move() cannot
1865 * change the qstr (protected by d_lock).
1867 tlen
= dentry
->d_name
.len
;
1868 tname
= dentry
->d_name
.name
;
1869 if (parent
->d_flags
& DCACHE_OP_COMPARE
) {
1870 if (parent
->d_op
->d_compare(parent
, parent
->d_inode
,
1871 dentry
, dentry
->d_inode
,
1877 if (memcmp(tname
, str
, tlen
))
1883 spin_unlock(&dentry
->d_lock
);
1886 spin_unlock(&dentry
->d_lock
);
1894 * d_hash_and_lookup - hash the qstr then search for a dentry
1895 * @dir: Directory to search in
1896 * @name: qstr of name we wish to find
1898 * On hash failure or on lookup failure NULL is returned.
1900 struct dentry
*d_hash_and_lookup(struct dentry
*dir
, struct qstr
*name
)
1902 struct dentry
*dentry
= NULL
;
1905 * Check for a fs-specific hash function. Note that we must
1906 * calculate the standard hash first, as the d_op->d_hash()
1907 * routine may choose to leave the hash value unchanged.
1909 name
->hash
= full_name_hash(name
->name
, name
->len
);
1910 if (dir
->d_flags
& DCACHE_OP_HASH
) {
1911 if (dir
->d_op
->d_hash(dir
, dir
->d_inode
, name
) < 0)
1914 dentry
= d_lookup(dir
, name
);
1920 * d_validate - verify dentry provided from insecure source (deprecated)
1921 * @dentry: The dentry alleged to be valid child of @dparent
1922 * @dparent: The parent dentry (known to be valid)
1924 * An insecure source has sent us a dentry, here we verify it and dget() it.
1925 * This is used by ncpfs in its readdir implementation.
1926 * Zero is returned in the dentry is invalid.
1928 * This function is slow for big directories, and deprecated, do not use it.
1930 int d_validate(struct dentry
*dentry
, struct dentry
*dparent
)
1932 struct dentry
*child
;
1934 spin_lock(&dparent
->d_lock
);
1935 list_for_each_entry(child
, &dparent
->d_subdirs
, d_u
.d_child
) {
1936 if (dentry
== child
) {
1937 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1938 __dget_dlock(dentry
);
1939 spin_unlock(&dentry
->d_lock
);
1940 spin_unlock(&dparent
->d_lock
);
1944 spin_unlock(&dparent
->d_lock
);
1948 EXPORT_SYMBOL(d_validate
);
1951 * When a file is deleted, we have two options:
1952 * - turn this dentry into a negative dentry
1953 * - unhash this dentry and free it.
1955 * Usually, we want to just turn this into
1956 * a negative dentry, but if anybody else is
1957 * currently using the dentry or the inode
1958 * we can't do that and we fall back on removing
1959 * it from the hash queues and waiting for
1960 * it to be deleted later when it has no users
1964 * d_delete - delete a dentry
1965 * @dentry: The dentry to delete
1967 * Turn the dentry into a negative dentry if possible, otherwise
1968 * remove it from the hash queues so it can be deleted later
1971 void d_delete(struct dentry
* dentry
)
1975 * Are we the only user?
1978 spin_lock(&dentry
->d_lock
);
1979 isdir
= S_ISDIR(dentry
->d_inode
->i_mode
);
1980 if (dentry
->d_count
== 1) {
1981 if (!spin_trylock(&dcache_inode_lock
)) {
1982 spin_unlock(&dentry
->d_lock
);
1986 dentry
->d_flags
&= ~DCACHE_CANT_MOUNT
;
1987 dentry_unlink_inode(dentry
);
1988 fsnotify_nameremove(dentry
, isdir
);
1992 if (!d_unhashed(dentry
))
1995 spin_unlock(&dentry
->d_lock
);
1997 fsnotify_nameremove(dentry
, isdir
);
1999 EXPORT_SYMBOL(d_delete
);
2001 static void __d_rehash(struct dentry
* entry
, struct hlist_head
*list
)
2004 entry
->d_flags
&= ~DCACHE_UNHASHED
;
2005 hlist_add_head_rcu(&entry
->d_hash
, list
);
2008 static void _d_rehash(struct dentry
* entry
)
2010 __d_rehash(entry
, d_hash(entry
->d_parent
, entry
->d_name
.hash
));
2014 * d_rehash - add an entry back to the hash
2015 * @entry: dentry to add to the hash
2017 * Adds a dentry to the hash according to its name.
2020 void d_rehash(struct dentry
* entry
)
2022 spin_lock(&entry
->d_lock
);
2023 spin_lock(&dcache_hash_lock
);
2025 spin_unlock(&dcache_hash_lock
);
2026 spin_unlock(&entry
->d_lock
);
2028 EXPORT_SYMBOL(d_rehash
);
2031 * dentry_update_name_case - update case insensitive dentry with a new name
2032 * @dentry: dentry to be updated
2035 * Update a case insensitive dentry with new case of name.
2037 * dentry must have been returned by d_lookup with name @name. Old and new
2038 * name lengths must match (ie. no d_compare which allows mismatched name
2041 * Parent inode i_mutex must be held over d_lookup and into this call (to
2042 * keep renames and concurrent inserts, and readdir(2) away).
2044 void dentry_update_name_case(struct dentry
*dentry
, struct qstr
*name
)
2046 BUG_ON(!mutex_is_locked(&dentry
->d_inode
->i_mutex
));
2047 BUG_ON(dentry
->d_name
.len
!= name
->len
); /* d_lookup gives this */
2049 spin_lock(&dentry
->d_lock
);
2050 write_seqcount_begin(&dentry
->d_seq
);
2051 memcpy((unsigned char *)dentry
->d_name
.name
, name
->name
, name
->len
);
2052 write_seqcount_end(&dentry
->d_seq
);
2053 spin_unlock(&dentry
->d_lock
);
2055 EXPORT_SYMBOL(dentry_update_name_case
);
2057 static void switch_names(struct dentry
*dentry
, struct dentry
*target
)
2059 if (dname_external(target
)) {
2060 if (dname_external(dentry
)) {
2062 * Both external: swap the pointers
2064 swap(target
->d_name
.name
, dentry
->d_name
.name
);
2067 * dentry:internal, target:external. Steal target's
2068 * storage and make target internal.
2070 memcpy(target
->d_iname
, dentry
->d_name
.name
,
2071 dentry
->d_name
.len
+ 1);
2072 dentry
->d_name
.name
= target
->d_name
.name
;
2073 target
->d_name
.name
= target
->d_iname
;
2076 if (dname_external(dentry
)) {
2078 * dentry:external, target:internal. Give dentry's
2079 * storage to target and make dentry internal
2081 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2082 target
->d_name
.len
+ 1);
2083 target
->d_name
.name
= dentry
->d_name
.name
;
2084 dentry
->d_name
.name
= dentry
->d_iname
;
2087 * Both are internal. Just copy target to dentry
2089 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2090 target
->d_name
.len
+ 1);
2091 dentry
->d_name
.len
= target
->d_name
.len
;
2095 swap(dentry
->d_name
.len
, target
->d_name
.len
);
2098 static void dentry_lock_for_move(struct dentry
*dentry
, struct dentry
*target
)
2101 * XXXX: do we really need to take target->d_lock?
2103 if (IS_ROOT(dentry
) || dentry
->d_parent
== target
->d_parent
)
2104 spin_lock(&target
->d_parent
->d_lock
);
2106 if (d_ancestor(dentry
->d_parent
, target
->d_parent
)) {
2107 spin_lock(&dentry
->d_parent
->d_lock
);
2108 spin_lock_nested(&target
->d_parent
->d_lock
,
2109 DENTRY_D_LOCK_NESTED
);
2111 spin_lock(&target
->d_parent
->d_lock
);
2112 spin_lock_nested(&dentry
->d_parent
->d_lock
,
2113 DENTRY_D_LOCK_NESTED
);
2116 if (target
< dentry
) {
2117 spin_lock_nested(&target
->d_lock
, 2);
2118 spin_lock_nested(&dentry
->d_lock
, 3);
2120 spin_lock_nested(&dentry
->d_lock
, 2);
2121 spin_lock_nested(&target
->d_lock
, 3);
2125 static void dentry_unlock_parents_for_move(struct dentry
*dentry
,
2126 struct dentry
*target
)
2128 if (target
->d_parent
!= dentry
->d_parent
)
2129 spin_unlock(&dentry
->d_parent
->d_lock
);
2130 if (target
->d_parent
!= target
)
2131 spin_unlock(&target
->d_parent
->d_lock
);
2135 * When switching names, the actual string doesn't strictly have to
2136 * be preserved in the target - because we're dropping the target
2137 * anyway. As such, we can just do a simple memcpy() to copy over
2138 * the new name before we switch.
2140 * Note that we have to be a lot more careful about getting the hash
2141 * switched - we have to switch the hash value properly even if it
2142 * then no longer matches the actual (corrupted) string of the target.
2143 * The hash value has to match the hash queue that the dentry is on..
2146 * d_move - move a dentry
2147 * @dentry: entry to move
2148 * @target: new dentry
2150 * Update the dcache to reflect the move of a file name. Negative
2151 * dcache entries should not be moved in this way.
2153 void d_move(struct dentry
* dentry
, struct dentry
* target
)
2155 if (!dentry
->d_inode
)
2156 printk(KERN_WARNING
"VFS: moving negative dcache entry\n");
2158 BUG_ON(d_ancestor(dentry
, target
));
2159 BUG_ON(d_ancestor(target
, dentry
));
2161 write_seqlock(&rename_lock
);
2163 dentry_lock_for_move(dentry
, target
);
2165 write_seqcount_begin(&dentry
->d_seq
);
2166 write_seqcount_begin(&target
->d_seq
);
2168 /* Move the dentry to the target hash queue, if on different bucket */
2169 spin_lock(&dcache_hash_lock
);
2170 if (!d_unhashed(dentry
))
2171 hlist_del_rcu(&dentry
->d_hash
);
2172 __d_rehash(dentry
, d_hash(target
->d_parent
, target
->d_name
.hash
));
2173 spin_unlock(&dcache_hash_lock
);
2175 /* Unhash the target: dput() will then get rid of it */
2176 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
2179 list_del(&dentry
->d_u
.d_child
);
2180 list_del(&target
->d_u
.d_child
);
2182 /* Switch the names.. */
2183 switch_names(dentry
, target
);
2184 swap(dentry
->d_name
.hash
, target
->d_name
.hash
);
2186 /* ... and switch the parents */
2187 if (IS_ROOT(dentry
)) {
2188 dentry
->d_parent
= target
->d_parent
;
2189 target
->d_parent
= target
;
2190 INIT_LIST_HEAD(&target
->d_u
.d_child
);
2192 swap(dentry
->d_parent
, target
->d_parent
);
2194 /* And add them back to the (new) parent lists */
2195 list_add(&target
->d_u
.d_child
, &target
->d_parent
->d_subdirs
);
2198 list_add(&dentry
->d_u
.d_child
, &dentry
->d_parent
->d_subdirs
);
2200 write_seqcount_end(&target
->d_seq
);
2201 write_seqcount_end(&dentry
->d_seq
);
2203 dentry_unlock_parents_for_move(dentry
, target
);
2204 spin_unlock(&target
->d_lock
);
2205 fsnotify_d_move(dentry
);
2206 spin_unlock(&dentry
->d_lock
);
2207 write_sequnlock(&rename_lock
);
2209 EXPORT_SYMBOL(d_move
);
2212 * d_ancestor - search for an ancestor
2213 * @p1: ancestor dentry
2216 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2217 * an ancestor of p2, else NULL.
2219 struct dentry
*d_ancestor(struct dentry
*p1
, struct dentry
*p2
)
2223 for (p
= p2
; !IS_ROOT(p
); p
= p
->d_parent
) {
2224 if (p
->d_parent
== p1
)
2231 * This helper attempts to cope with remotely renamed directories
2233 * It assumes that the caller is already holding
2234 * dentry->d_parent->d_inode->i_mutex and the dcache_inode_lock
2236 * Note: If ever the locking in lock_rename() changes, then please
2237 * remember to update this too...
2239 static struct dentry
*__d_unalias(struct dentry
*dentry
, struct dentry
*alias
)
2240 __releases(dcache_inode_lock
)
2242 struct mutex
*m1
= NULL
, *m2
= NULL
;
2245 /* If alias and dentry share a parent, then no extra locks required */
2246 if (alias
->d_parent
== dentry
->d_parent
)
2249 /* Check for loops */
2250 ret
= ERR_PTR(-ELOOP
);
2251 if (d_ancestor(alias
, dentry
))
2254 /* See lock_rename() */
2255 ret
= ERR_PTR(-EBUSY
);
2256 if (!mutex_trylock(&dentry
->d_sb
->s_vfs_rename_mutex
))
2258 m1
= &dentry
->d_sb
->s_vfs_rename_mutex
;
2259 if (!mutex_trylock(&alias
->d_parent
->d_inode
->i_mutex
))
2261 m2
= &alias
->d_parent
->d_inode
->i_mutex
;
2263 d_move(alias
, dentry
);
2266 spin_unlock(&dcache_inode_lock
);
2275 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
2276 * named dentry in place of the dentry to be replaced.
2277 * returns with anon->d_lock held!
2279 static void __d_materialise_dentry(struct dentry
*dentry
, struct dentry
*anon
)
2281 struct dentry
*dparent
, *aparent
;
2283 dentry_lock_for_move(anon
, dentry
);
2285 write_seqcount_begin(&dentry
->d_seq
);
2286 write_seqcount_begin(&anon
->d_seq
);
2288 dparent
= dentry
->d_parent
;
2289 aparent
= anon
->d_parent
;
2291 switch_names(dentry
, anon
);
2292 swap(dentry
->d_name
.hash
, anon
->d_name
.hash
);
2294 dentry
->d_parent
= (aparent
== anon
) ? dentry
: aparent
;
2295 list_del(&dentry
->d_u
.d_child
);
2296 if (!IS_ROOT(dentry
))
2297 list_add(&dentry
->d_u
.d_child
, &dentry
->d_parent
->d_subdirs
);
2299 INIT_LIST_HEAD(&dentry
->d_u
.d_child
);
2301 anon
->d_parent
= (dparent
== dentry
) ? anon
: dparent
;
2302 list_del(&anon
->d_u
.d_child
);
2304 list_add(&anon
->d_u
.d_child
, &anon
->d_parent
->d_subdirs
);
2306 INIT_LIST_HEAD(&anon
->d_u
.d_child
);
2308 write_seqcount_end(&dentry
->d_seq
);
2309 write_seqcount_end(&anon
->d_seq
);
2311 dentry_unlock_parents_for_move(anon
, dentry
);
2312 spin_unlock(&dentry
->d_lock
);
2314 /* anon->d_lock still locked, returns locked */
2315 anon
->d_flags
&= ~DCACHE_DISCONNECTED
;
2319 * d_materialise_unique - introduce an inode into the tree
2320 * @dentry: candidate dentry
2321 * @inode: inode to bind to the dentry, to which aliases may be attached
2323 * Introduces an dentry into the tree, substituting an extant disconnected
2324 * root directory alias in its place if there is one
2326 struct dentry
*d_materialise_unique(struct dentry
*dentry
, struct inode
*inode
)
2328 struct dentry
*actual
;
2330 BUG_ON(!d_unhashed(dentry
));
2334 __d_instantiate(dentry
, NULL
);
2339 spin_lock(&dcache_inode_lock
);
2341 if (S_ISDIR(inode
->i_mode
)) {
2342 struct dentry
*alias
;
2344 /* Does an aliased dentry already exist? */
2345 alias
= __d_find_alias(inode
, 0);
2348 /* Is this an anonymous mountpoint that we could splice
2350 if (IS_ROOT(alias
)) {
2351 __d_materialise_dentry(dentry
, alias
);
2355 /* Nope, but we must(!) avoid directory aliasing */
2356 actual
= __d_unalias(dentry
, alias
);
2363 /* Add a unique reference */
2364 actual
= __d_instantiate_unique(dentry
, inode
);
2368 BUG_ON(!d_unhashed(actual
));
2370 spin_lock(&actual
->d_lock
);
2372 spin_lock(&dcache_hash_lock
);
2374 spin_unlock(&dcache_hash_lock
);
2375 spin_unlock(&actual
->d_lock
);
2376 spin_unlock(&dcache_inode_lock
);
2378 if (actual
== dentry
) {
2379 security_d_instantiate(dentry
, inode
);
2386 EXPORT_SYMBOL_GPL(d_materialise_unique
);
2388 static int prepend(char **buffer
, int *buflen
, const char *str
, int namelen
)
2392 return -ENAMETOOLONG
;
2394 memcpy(*buffer
, str
, namelen
);
2398 static int prepend_name(char **buffer
, int *buflen
, struct qstr
*name
)
2400 return prepend(buffer
, buflen
, name
->name
, name
->len
);
2404 * Prepend path string to a buffer
2406 * @path: the dentry/vfsmount to report
2407 * @root: root vfsmnt/dentry (may be modified by this function)
2408 * @buffer: pointer to the end of the buffer
2409 * @buflen: pointer to buffer length
2411 * Caller holds the rename_lock.
2413 * If path is not reachable from the supplied root, then the value of
2414 * root is changed (without modifying refcounts).
2416 static int prepend_path(const struct path
*path
, struct path
*root
,
2417 char **buffer
, int *buflen
)
2419 struct dentry
*dentry
= path
->dentry
;
2420 struct vfsmount
*vfsmnt
= path
->mnt
;
2424 br_read_lock(vfsmount_lock
);
2425 while (dentry
!= root
->dentry
|| vfsmnt
!= root
->mnt
) {
2426 struct dentry
* parent
;
2428 if (dentry
== vfsmnt
->mnt_root
|| IS_ROOT(dentry
)) {
2430 if (vfsmnt
->mnt_parent
== vfsmnt
) {
2433 dentry
= vfsmnt
->mnt_mountpoint
;
2434 vfsmnt
= vfsmnt
->mnt_parent
;
2437 parent
= dentry
->d_parent
;
2439 spin_lock(&dentry
->d_lock
);
2440 error
= prepend_name(buffer
, buflen
, &dentry
->d_name
);
2441 spin_unlock(&dentry
->d_lock
);
2443 error
= prepend(buffer
, buflen
, "/", 1);
2452 if (!error
&& !slash
)
2453 error
= prepend(buffer
, buflen
, "/", 1);
2455 br_read_unlock(vfsmount_lock
);
2460 * Filesystems needing to implement special "root names"
2461 * should do so with ->d_dname()
2463 if (IS_ROOT(dentry
) &&
2464 (dentry
->d_name
.len
!= 1 || dentry
->d_name
.name
[0] != '/')) {
2465 WARN(1, "Root dentry has weird name <%.*s>\n",
2466 (int) dentry
->d_name
.len
, dentry
->d_name
.name
);
2469 root
->dentry
= dentry
;
2474 * __d_path - return the path of a dentry
2475 * @path: the dentry/vfsmount to report
2476 * @root: root vfsmnt/dentry (may be modified by this function)
2477 * @buf: buffer to return value in
2478 * @buflen: buffer length
2480 * Convert a dentry into an ASCII path name.
2482 * Returns a pointer into the buffer or an error code if the
2483 * path was too long.
2485 * "buflen" should be positive.
2487 * If path is not reachable from the supplied root, then the value of
2488 * root is changed (without modifying refcounts).
2490 char *__d_path(const struct path
*path
, struct path
*root
,
2491 char *buf
, int buflen
)
2493 char *res
= buf
+ buflen
;
2496 prepend(&res
, &buflen
, "\0", 1);
2497 write_seqlock(&rename_lock
);
2498 error
= prepend_path(path
, root
, &res
, &buflen
);
2499 write_sequnlock(&rename_lock
);
2502 return ERR_PTR(error
);
2507 * same as __d_path but appends "(deleted)" for unlinked files.
2509 static int path_with_deleted(const struct path
*path
, struct path
*root
,
2510 char **buf
, int *buflen
)
2512 prepend(buf
, buflen
, "\0", 1);
2513 if (d_unlinked(path
->dentry
)) {
2514 int error
= prepend(buf
, buflen
, " (deleted)", 10);
2519 return prepend_path(path
, root
, buf
, buflen
);
2522 static int prepend_unreachable(char **buffer
, int *buflen
)
2524 return prepend(buffer
, buflen
, "(unreachable)", 13);
2528 * d_path - return the path of a dentry
2529 * @path: path to report
2530 * @buf: buffer to return value in
2531 * @buflen: buffer length
2533 * Convert a dentry into an ASCII path name. If the entry has been deleted
2534 * the string " (deleted)" is appended. Note that this is ambiguous.
2536 * Returns a pointer into the buffer or an error code if the path was
2537 * too long. Note: Callers should use the returned pointer, not the passed
2538 * in buffer, to use the name! The implementation often starts at an offset
2539 * into the buffer, and may leave 0 bytes at the start.
2541 * "buflen" should be positive.
2543 char *d_path(const struct path
*path
, char *buf
, int buflen
)
2545 char *res
= buf
+ buflen
;
2551 * We have various synthetic filesystems that never get mounted. On
2552 * these filesystems dentries are never used for lookup purposes, and
2553 * thus don't need to be hashed. They also don't need a name until a
2554 * user wants to identify the object in /proc/pid/fd/. The little hack
2555 * below allows us to generate a name for these objects on demand:
2557 if (path
->dentry
->d_op
&& path
->dentry
->d_op
->d_dname
)
2558 return path
->dentry
->d_op
->d_dname(path
->dentry
, buf
, buflen
);
2560 get_fs_root(current
->fs
, &root
);
2561 write_seqlock(&rename_lock
);
2563 error
= path_with_deleted(path
, &tmp
, &res
, &buflen
);
2565 res
= ERR_PTR(error
);
2566 write_sequnlock(&rename_lock
);
2570 EXPORT_SYMBOL(d_path
);
2573 * d_path_with_unreachable - return the path of a dentry
2574 * @path: path to report
2575 * @buf: buffer to return value in
2576 * @buflen: buffer length
2578 * The difference from d_path() is that this prepends "(unreachable)"
2579 * to paths which are unreachable from the current process' root.
2581 char *d_path_with_unreachable(const struct path
*path
, char *buf
, int buflen
)
2583 char *res
= buf
+ buflen
;
2588 if (path
->dentry
->d_op
&& path
->dentry
->d_op
->d_dname
)
2589 return path
->dentry
->d_op
->d_dname(path
->dentry
, buf
, buflen
);
2591 get_fs_root(current
->fs
, &root
);
2592 write_seqlock(&rename_lock
);
2594 error
= path_with_deleted(path
, &tmp
, &res
, &buflen
);
2595 if (!error
&& !path_equal(&tmp
, &root
))
2596 error
= prepend_unreachable(&res
, &buflen
);
2597 write_sequnlock(&rename_lock
);
2600 res
= ERR_PTR(error
);
2606 * Helper function for dentry_operations.d_dname() members
2608 char *dynamic_dname(struct dentry
*dentry
, char *buffer
, int buflen
,
2609 const char *fmt
, ...)
2615 va_start(args
, fmt
);
2616 sz
= vsnprintf(temp
, sizeof(temp
), fmt
, args
) + 1;
2619 if (sz
> sizeof(temp
) || sz
> buflen
)
2620 return ERR_PTR(-ENAMETOOLONG
);
2622 buffer
+= buflen
- sz
;
2623 return memcpy(buffer
, temp
, sz
);
2627 * Write full pathname from the root of the filesystem into the buffer.
2629 static char *__dentry_path(struct dentry
*dentry
, char *buf
, int buflen
)
2631 char *end
= buf
+ buflen
;
2634 prepend(&end
, &buflen
, "\0", 1);
2641 while (!IS_ROOT(dentry
)) {
2642 struct dentry
*parent
= dentry
->d_parent
;
2646 spin_lock(&dentry
->d_lock
);
2647 error
= prepend_name(&end
, &buflen
, &dentry
->d_name
);
2648 spin_unlock(&dentry
->d_lock
);
2649 if (error
!= 0 || prepend(&end
, &buflen
, "/", 1) != 0)
2657 return ERR_PTR(-ENAMETOOLONG
);
2660 char *dentry_path_raw(struct dentry
*dentry
, char *buf
, int buflen
)
2664 write_seqlock(&rename_lock
);
2665 retval
= __dentry_path(dentry
, buf
, buflen
);
2666 write_sequnlock(&rename_lock
);
2670 EXPORT_SYMBOL(dentry_path_raw
);
2672 char *dentry_path(struct dentry
*dentry
, char *buf
, int buflen
)
2677 write_seqlock(&rename_lock
);
2678 if (d_unlinked(dentry
)) {
2680 if (prepend(&p
, &buflen
, "//deleted", 10) != 0)
2684 retval
= __dentry_path(dentry
, buf
, buflen
);
2685 write_sequnlock(&rename_lock
);
2686 if (!IS_ERR(retval
) && p
)
2687 *p
= '/'; /* restore '/' overriden with '\0' */
2690 return ERR_PTR(-ENAMETOOLONG
);
2694 * NOTE! The user-level library version returns a
2695 * character pointer. The kernel system call just
2696 * returns the length of the buffer filled (which
2697 * includes the ending '\0' character), or a negative
2698 * error value. So libc would do something like
2700 * char *getcwd(char * buf, size_t size)
2704 * retval = sys_getcwd(buf, size);
2711 SYSCALL_DEFINE2(getcwd
, char __user
*, buf
, unsigned long, size
)
2714 struct path pwd
, root
;
2715 char *page
= (char *) __get_free_page(GFP_USER
);
2720 get_fs_root_and_pwd(current
->fs
, &root
, &pwd
);
2723 write_seqlock(&rename_lock
);
2724 if (!d_unlinked(pwd
.dentry
)) {
2726 struct path tmp
= root
;
2727 char *cwd
= page
+ PAGE_SIZE
;
2728 int buflen
= PAGE_SIZE
;
2730 prepend(&cwd
, &buflen
, "\0", 1);
2731 error
= prepend_path(&pwd
, &tmp
, &cwd
, &buflen
);
2732 write_sequnlock(&rename_lock
);
2737 /* Unreachable from current root */
2738 if (!path_equal(&tmp
, &root
)) {
2739 error
= prepend_unreachable(&cwd
, &buflen
);
2745 len
= PAGE_SIZE
+ page
- cwd
;
2748 if (copy_to_user(buf
, cwd
, len
))
2752 write_sequnlock(&rename_lock
);
2758 free_page((unsigned long) page
);
2763 * Test whether new_dentry is a subdirectory of old_dentry.
2765 * Trivially implemented using the dcache structure
2769 * is_subdir - is new dentry a subdirectory of old_dentry
2770 * @new_dentry: new dentry
2771 * @old_dentry: old dentry
2773 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
2774 * Returns 0 otherwise.
2775 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
2778 int is_subdir(struct dentry
*new_dentry
, struct dentry
*old_dentry
)
2783 if (new_dentry
== old_dentry
)
2787 /* for restarting inner loop in case of seq retry */
2788 seq
= read_seqbegin(&rename_lock
);
2790 * Need rcu_readlock to protect against the d_parent trashing
2794 if (d_ancestor(old_dentry
, new_dentry
))
2799 } while (read_seqretry(&rename_lock
, seq
));
2804 int path_is_under(struct path
*path1
, struct path
*path2
)
2806 struct vfsmount
*mnt
= path1
->mnt
;
2807 struct dentry
*dentry
= path1
->dentry
;
2810 br_read_lock(vfsmount_lock
);
2811 if (mnt
!= path2
->mnt
) {
2813 if (mnt
->mnt_parent
== mnt
) {
2814 br_read_unlock(vfsmount_lock
);
2817 if (mnt
->mnt_parent
== path2
->mnt
)
2819 mnt
= mnt
->mnt_parent
;
2821 dentry
= mnt
->mnt_mountpoint
;
2823 res
= is_subdir(dentry
, path2
->dentry
);
2824 br_read_unlock(vfsmount_lock
);
2827 EXPORT_SYMBOL(path_is_under
);
2829 void d_genocide(struct dentry
*root
)
2831 struct dentry
*this_parent
;
2832 struct list_head
*next
;
2836 seq
= read_seqbegin(&rename_lock
);
2839 spin_lock(&this_parent
->d_lock
);
2841 next
= this_parent
->d_subdirs
.next
;
2843 while (next
!= &this_parent
->d_subdirs
) {
2844 struct list_head
*tmp
= next
;
2845 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_u
.d_child
);
2848 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
2849 if (d_unhashed(dentry
) || !dentry
->d_inode
) {
2850 spin_unlock(&dentry
->d_lock
);
2853 if (!list_empty(&dentry
->d_subdirs
)) {
2854 spin_unlock(&this_parent
->d_lock
);
2855 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
2856 this_parent
= dentry
;
2857 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
2860 if (!(dentry
->d_flags
& DCACHE_GENOCIDE
)) {
2861 dentry
->d_flags
|= DCACHE_GENOCIDE
;
2864 spin_unlock(&dentry
->d_lock
);
2866 if (this_parent
!= root
) {
2868 struct dentry
*child
;
2870 tmp
= this_parent
->d_parent
;
2871 if (!(this_parent
->d_flags
& DCACHE_GENOCIDE
)) {
2872 this_parent
->d_flags
|= DCACHE_GENOCIDE
;
2873 this_parent
->d_count
--;
2876 spin_unlock(&this_parent
->d_lock
);
2877 child
= this_parent
;
2879 spin_lock(&this_parent
->d_lock
);
2880 /* might go back up the wrong parent if we have had a rename
2882 if (this_parent
!= child
->d_parent
||
2883 (!locked
&& read_seqretry(&rename_lock
, seq
))) {
2884 spin_unlock(&this_parent
->d_lock
);
2889 next
= child
->d_u
.d_child
.next
;
2892 spin_unlock(&this_parent
->d_lock
);
2893 if (!locked
&& read_seqretry(&rename_lock
, seq
))
2896 write_sequnlock(&rename_lock
);
2901 write_seqlock(&rename_lock
);
2906 * find_inode_number - check for dentry with name
2907 * @dir: directory to check
2908 * @name: Name to find.
2910 * Check whether a dentry already exists for the given name,
2911 * and return the inode number if it has an inode. Otherwise
2914 * This routine is used to post-process directory listings for
2915 * filesystems using synthetic inode numbers, and is necessary
2916 * to keep getcwd() working.
2919 ino_t
find_inode_number(struct dentry
*dir
, struct qstr
*name
)
2921 struct dentry
* dentry
;
2924 dentry
= d_hash_and_lookup(dir
, name
);
2926 if (dentry
->d_inode
)
2927 ino
= dentry
->d_inode
->i_ino
;
2932 EXPORT_SYMBOL(find_inode_number
);
2934 static __initdata
unsigned long dhash_entries
;
2935 static int __init
set_dhash_entries(char *str
)
2939 dhash_entries
= simple_strtoul(str
, &str
, 0);
2942 __setup("dhash_entries=", set_dhash_entries
);
2944 static void __init
dcache_init_early(void)
2948 /* If hashes are distributed across NUMA nodes, defer
2949 * hash allocation until vmalloc space is available.
2955 alloc_large_system_hash("Dentry cache",
2956 sizeof(struct hlist_head
),
2964 for (loop
= 0; loop
< (1 << d_hash_shift
); loop
++)
2965 INIT_HLIST_HEAD(&dentry_hashtable
[loop
]);
2968 static void __init
dcache_init(void)
2973 * A constructor could be added for stable state like the lists,
2974 * but it is probably not worth it because of the cache nature
2977 dentry_cache
= KMEM_CACHE(dentry
,
2978 SLAB_RECLAIM_ACCOUNT
|SLAB_PANIC
|SLAB_MEM_SPREAD
);
2980 register_shrinker(&dcache_shrinker
);
2982 /* Hash may have been set up in dcache_init_early */
2987 alloc_large_system_hash("Dentry cache",
2988 sizeof(struct hlist_head
),
2996 for (loop
= 0; loop
< (1 << d_hash_shift
); loop
++)
2997 INIT_HLIST_HEAD(&dentry_hashtable
[loop
]);
3000 /* SLAB cache for __getname() consumers */
3001 struct kmem_cache
*names_cachep __read_mostly
;
3002 EXPORT_SYMBOL(names_cachep
);
3004 EXPORT_SYMBOL(d_genocide
);
3006 void __init
vfs_caches_init_early(void)
3008 dcache_init_early();
3012 void __init
vfs_caches_init(unsigned long mempages
)
3014 unsigned long reserve
;
3016 /* Base hash sizes on available memory, with a reserve equal to
3017 150% of current kernel size */
3019 reserve
= min((mempages
- nr_free_pages()) * 3/2, mempages
- 1);
3020 mempages
-= reserve
;
3022 names_cachep
= kmem_cache_create("names_cache", PATH_MAX
, 0,
3023 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
);
3027 files_init(mempages
);