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>
42 * dcache->d_inode->i_lock protects:
43 * - i_dentry, d_alias, d_inode of aliases
44 * dcache_hash_bucket lock protects:
45 * - the dcache hash table
46 * s_anon bl list spinlock protects:
47 * - the s_anon list (see __d_drop)
48 * dcache_lru_lock protects:
49 * - the dcache lru lists and counters
56 * - d_parent and d_subdirs
57 * - childrens' d_child and d_parent
61 * dentry->d_inode->i_lock
64 * dcache_hash_bucket lock
67 * If there is an ancestor relationship:
68 * dentry->d_parent->...->d_parent->d_lock
70 * dentry->d_parent->d_lock
73 * If no ancestor relationship:
74 * if (dentry1 < dentry2)
78 int sysctl_vfs_cache_pressure __read_mostly
= 100;
79 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure
);
81 static __cacheline_aligned_in_smp
DEFINE_SPINLOCK(dcache_lru_lock
);
82 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(rename_lock
);
84 EXPORT_SYMBOL(rename_lock
);
86 static struct kmem_cache
*dentry_cache __read_mostly
;
89 * This is the single most critical data structure when it comes
90 * to the dcache: the hashtable for lookups. Somebody should try
91 * to make this good - I've just made it work.
93 * This hash-function tries to avoid losing too many bits of hash
94 * information, yet avoid using a prime hash-size or similar.
96 #define D_HASHBITS d_hash_shift
97 #define D_HASHMASK d_hash_mask
99 static unsigned int d_hash_mask __read_mostly
;
100 static unsigned int d_hash_shift __read_mostly
;
102 static struct hlist_bl_head
*dentry_hashtable __read_mostly
;
104 static inline struct hlist_bl_head
*d_hash(struct dentry
*parent
,
107 hash
+= ((unsigned long) parent
^ GOLDEN_RATIO_PRIME
) / L1_CACHE_BYTES
;
108 hash
= hash
^ ((hash
^ GOLDEN_RATIO_PRIME
) >> D_HASHBITS
);
109 return dentry_hashtable
+ (hash
& D_HASHMASK
);
112 static inline void spin_lock_bucket(struct hlist_bl_head
*b
)
114 bit_spin_lock(0, (unsigned long *)&b
->first
);
117 static inline void spin_unlock_bucket(struct hlist_bl_head
*b
)
119 __bit_spin_unlock(0, (unsigned long *)&b
->first
);
122 /* Statistics gathering. */
123 struct dentry_stat_t dentry_stat
= {
127 static DEFINE_PER_CPU(unsigned int, nr_dentry
);
129 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
130 static int get_nr_dentry(void)
134 for_each_possible_cpu(i
)
135 sum
+= per_cpu(nr_dentry
, i
);
136 return sum
< 0 ? 0 : sum
;
139 int proc_nr_dentry(ctl_table
*table
, int write
, void __user
*buffer
,
140 size_t *lenp
, loff_t
*ppos
)
142 dentry_stat
.nr_dentry
= get_nr_dentry();
143 return proc_dointvec(table
, write
, buffer
, lenp
, ppos
);
147 static void __d_free(struct rcu_head
*head
)
149 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
151 WARN_ON(!list_empty(&dentry
->d_alias
));
152 if (dname_external(dentry
))
153 kfree(dentry
->d_name
.name
);
154 kmem_cache_free(dentry_cache
, dentry
);
160 static void d_free(struct dentry
*dentry
)
162 BUG_ON(dentry
->d_count
);
163 this_cpu_dec(nr_dentry
);
164 if (dentry
->d_op
&& dentry
->d_op
->d_release
)
165 dentry
->d_op
->d_release(dentry
);
167 /* if dentry was never inserted into hash, immediate free is OK */
168 if (hlist_bl_unhashed(&dentry
->d_hash
))
169 __d_free(&dentry
->d_u
.d_rcu
);
171 call_rcu(&dentry
->d_u
.d_rcu
, __d_free
);
175 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
176 * @dentry: the target dentry
177 * After this call, in-progress rcu-walk path lookup will fail. This
178 * should be called after unhashing, and after changing d_inode (if
179 * the dentry has not already been unhashed).
181 static inline void dentry_rcuwalk_barrier(struct dentry
*dentry
)
183 assert_spin_locked(&dentry
->d_lock
);
184 /* Go through a barrier */
185 write_seqcount_barrier(&dentry
->d_seq
);
189 * Release the dentry's inode, using the filesystem
190 * d_iput() operation if defined. Dentry has no refcount
193 static void dentry_iput(struct dentry
* dentry
)
194 __releases(dentry
->d_lock
)
195 __releases(dentry
->d_inode
->i_lock
)
197 struct inode
*inode
= dentry
->d_inode
;
199 dentry
->d_inode
= NULL
;
200 list_del_init(&dentry
->d_alias
);
201 spin_unlock(&dentry
->d_lock
);
202 spin_unlock(&inode
->i_lock
);
204 fsnotify_inoderemove(inode
);
205 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
206 dentry
->d_op
->d_iput(dentry
, inode
);
210 spin_unlock(&dentry
->d_lock
);
215 * Release the dentry's inode, using the filesystem
216 * d_iput() operation if defined. dentry remains in-use.
218 static void dentry_unlink_inode(struct dentry
* dentry
)
219 __releases(dentry
->d_lock
)
220 __releases(dentry
->d_inode
->i_lock
)
222 struct inode
*inode
= dentry
->d_inode
;
223 dentry
->d_inode
= NULL
;
224 list_del_init(&dentry
->d_alias
);
225 dentry_rcuwalk_barrier(dentry
);
226 spin_unlock(&dentry
->d_lock
);
227 spin_unlock(&inode
->i_lock
);
229 fsnotify_inoderemove(inode
);
230 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
231 dentry
->d_op
->d_iput(dentry
, inode
);
237 * dentry_lru_(add|del|move_tail) must be called with d_lock held.
239 static void dentry_lru_add(struct dentry
*dentry
)
241 if (list_empty(&dentry
->d_lru
)) {
242 spin_lock(&dcache_lru_lock
);
243 list_add(&dentry
->d_lru
, &dentry
->d_sb
->s_dentry_lru
);
244 dentry
->d_sb
->s_nr_dentry_unused
++;
245 dentry_stat
.nr_unused
++;
246 spin_unlock(&dcache_lru_lock
);
250 static void __dentry_lru_del(struct dentry
*dentry
)
252 list_del_init(&dentry
->d_lru
);
253 dentry
->d_sb
->s_nr_dentry_unused
--;
254 dentry_stat
.nr_unused
--;
257 static void dentry_lru_del(struct dentry
*dentry
)
259 if (!list_empty(&dentry
->d_lru
)) {
260 spin_lock(&dcache_lru_lock
);
261 __dentry_lru_del(dentry
);
262 spin_unlock(&dcache_lru_lock
);
266 static void dentry_lru_move_tail(struct dentry
*dentry
)
268 spin_lock(&dcache_lru_lock
);
269 if (list_empty(&dentry
->d_lru
)) {
270 list_add_tail(&dentry
->d_lru
, &dentry
->d_sb
->s_dentry_lru
);
271 dentry
->d_sb
->s_nr_dentry_unused
++;
272 dentry_stat
.nr_unused
++;
274 list_move_tail(&dentry
->d_lru
, &dentry
->d_sb
->s_dentry_lru
);
276 spin_unlock(&dcache_lru_lock
);
280 * d_kill - kill dentry and return parent
281 * @dentry: dentry to kill
282 * @parent: parent dentry
284 * The dentry must already be unhashed and removed from the LRU.
286 * If this is the root of the dentry tree, return NULL.
288 * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
291 static struct dentry
*d_kill(struct dentry
*dentry
, struct dentry
*parent
)
292 __releases(dentry
->d_lock
)
293 __releases(parent
->d_lock
)
294 __releases(dentry
->d_inode
->i_lock
)
296 list_del(&dentry
->d_u
.d_child
);
298 * Inform try_to_ascend() that we are no longer attached to the
301 dentry
->d_flags
|= DCACHE_DISCONNECTED
;
303 spin_unlock(&parent
->d_lock
);
306 * dentry_iput drops the locks, at which point nobody (except
307 * transient RCU lookups) can reach this dentry.
314 * d_drop - drop a dentry
315 * @dentry: dentry to drop
317 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
318 * be found through a VFS lookup any more. Note that this is different from
319 * deleting the dentry - d_delete will try to mark the dentry negative if
320 * possible, giving a successful _negative_ lookup, while d_drop will
321 * just make the cache lookup fail.
323 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
324 * reason (NFS timeouts or autofs deletes).
326 * __d_drop requires dentry->d_lock.
328 void __d_drop(struct dentry
*dentry
)
330 if (!(dentry
->d_flags
& DCACHE_UNHASHED
)) {
331 struct hlist_bl_head
*b
;
332 if (unlikely(dentry
->d_flags
& DCACHE_DISCONNECTED
)) {
333 b
= &dentry
->d_sb
->s_anon
;
335 dentry
->d_flags
|= DCACHE_UNHASHED
;
336 hlist_bl_del_init(&dentry
->d_hash
);
337 spin_unlock_bucket(b
);
339 struct hlist_bl_head
*b
;
340 b
= d_hash(dentry
->d_parent
, dentry
->d_name
.hash
);
343 * We may not actually need to put DCACHE_UNHASHED
344 * manipulations under the hash lock, but follow
345 * the principle of least surprise.
347 dentry
->d_flags
|= DCACHE_UNHASHED
;
348 hlist_bl_del_rcu(&dentry
->d_hash
);
349 spin_unlock_bucket(b
);
350 dentry_rcuwalk_barrier(dentry
);
354 EXPORT_SYMBOL(__d_drop
);
356 void d_drop(struct dentry
*dentry
)
358 spin_lock(&dentry
->d_lock
);
360 spin_unlock(&dentry
->d_lock
);
362 EXPORT_SYMBOL(d_drop
);
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
))
453 /* Otherwise leave it cached and ensure it's on the LRU */
454 dentry
->d_flags
|= DCACHE_REFERENCED
;
455 dentry_lru_add(dentry
);
458 spin_unlock(&dentry
->d_lock
);
462 dentry
= dentry_kill(dentry
, 1);
469 * d_invalidate - invalidate a dentry
470 * @dentry: dentry to invalidate
472 * Try to invalidate the dentry if it turns out to be
473 * possible. If there are other dentries that can be
474 * reached through this one we can't delete it and we
475 * return -EBUSY. On success we return 0.
480 int d_invalidate(struct dentry
* dentry
)
483 * If it's already been dropped, return OK.
485 spin_lock(&dentry
->d_lock
);
486 if (d_unhashed(dentry
)) {
487 spin_unlock(&dentry
->d_lock
);
491 * Check whether to do a partial shrink_dcache
492 * to get rid of unused child entries.
494 if (!list_empty(&dentry
->d_subdirs
)) {
495 spin_unlock(&dentry
->d_lock
);
496 shrink_dcache_parent(dentry
);
497 spin_lock(&dentry
->d_lock
);
501 * Somebody else still using it?
503 * If it's a directory, we can't drop it
504 * for fear of somebody re-populating it
505 * with children (even though dropping it
506 * would make it unreachable from the root,
507 * we might still populate it if it was a
508 * working directory or similar).
510 if (dentry
->d_count
> 1) {
511 if (dentry
->d_inode
&& S_ISDIR(dentry
->d_inode
->i_mode
)) {
512 spin_unlock(&dentry
->d_lock
);
518 spin_unlock(&dentry
->d_lock
);
521 EXPORT_SYMBOL(d_invalidate
);
523 /* This must be called with d_lock held */
524 static inline void __dget_dlock(struct dentry
*dentry
)
529 static inline void __dget(struct dentry
*dentry
)
531 spin_lock(&dentry
->d_lock
);
532 __dget_dlock(dentry
);
533 spin_unlock(&dentry
->d_lock
);
536 struct dentry
*dget_parent(struct dentry
*dentry
)
542 * Don't need rcu_dereference because we re-check it was correct under
546 ret
= dentry
->d_parent
;
551 spin_lock(&ret
->d_lock
);
552 if (unlikely(ret
!= dentry
->d_parent
)) {
553 spin_unlock(&ret
->d_lock
);
558 BUG_ON(!ret
->d_count
);
560 spin_unlock(&ret
->d_lock
);
564 EXPORT_SYMBOL(dget_parent
);
567 * d_find_alias - grab a hashed alias of inode
568 * @inode: inode in question
569 * @want_discon: flag, used by d_splice_alias, to request
570 * that only a DISCONNECTED alias be returned.
572 * If inode has a hashed alias, or is a directory and has any alias,
573 * acquire the reference to alias and return it. Otherwise return NULL.
574 * Notice that if inode is a directory there can be only one alias and
575 * it can be unhashed only if it has no children, or if it is the root
578 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
579 * any other hashed alias over that one unless @want_discon is set,
580 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
582 static struct dentry
*__d_find_alias(struct inode
*inode
, int want_discon
)
584 struct dentry
*alias
, *discon_alias
;
588 list_for_each_entry(alias
, &inode
->i_dentry
, d_alias
) {
589 spin_lock(&alias
->d_lock
);
590 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
591 if (IS_ROOT(alias
) &&
592 (alias
->d_flags
& DCACHE_DISCONNECTED
)) {
593 discon_alias
= alias
;
594 } else if (!want_discon
) {
596 spin_unlock(&alias
->d_lock
);
600 spin_unlock(&alias
->d_lock
);
603 alias
= discon_alias
;
604 spin_lock(&alias
->d_lock
);
605 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
606 if (IS_ROOT(alias
) &&
607 (alias
->d_flags
& DCACHE_DISCONNECTED
)) {
609 spin_unlock(&alias
->d_lock
);
613 spin_unlock(&alias
->d_lock
);
619 struct dentry
*d_find_alias(struct inode
*inode
)
621 struct dentry
*de
= NULL
;
623 if (!list_empty(&inode
->i_dentry
)) {
624 spin_lock(&inode
->i_lock
);
625 de
= __d_find_alias(inode
, 0);
626 spin_unlock(&inode
->i_lock
);
630 EXPORT_SYMBOL(d_find_alias
);
633 * Try to kill dentries associated with this inode.
634 * WARNING: you must own a reference to inode.
636 void d_prune_aliases(struct inode
*inode
)
638 struct dentry
*dentry
;
640 spin_lock(&inode
->i_lock
);
641 list_for_each_entry(dentry
, &inode
->i_dentry
, d_alias
) {
642 spin_lock(&dentry
->d_lock
);
643 if (!dentry
->d_count
) {
644 __dget_dlock(dentry
);
646 spin_unlock(&dentry
->d_lock
);
647 spin_unlock(&inode
->i_lock
);
651 spin_unlock(&dentry
->d_lock
);
653 spin_unlock(&inode
->i_lock
);
655 EXPORT_SYMBOL(d_prune_aliases
);
658 * Try to throw away a dentry - free the inode, dput the parent.
659 * Requires dentry->d_lock is held, and dentry->d_count == 0.
660 * Releases dentry->d_lock.
662 * This may fail if locks cannot be acquired no problem, just try again.
664 static void try_prune_one_dentry(struct dentry
*dentry
)
665 __releases(dentry
->d_lock
)
667 struct dentry
*parent
;
669 parent
= dentry_kill(dentry
, 0);
671 * If dentry_kill returns NULL, we have nothing more to do.
672 * if it returns the same dentry, trylocks failed. In either
673 * case, just loop again.
675 * Otherwise, we need to prune ancestors too. This is necessary
676 * to prevent quadratic behavior of shrink_dcache_parent(), but
677 * is also expected to be beneficial in reducing dentry cache
682 if (parent
== dentry
)
685 /* Prune ancestors. */
688 spin_lock(&dentry
->d_lock
);
689 if (dentry
->d_count
> 1) {
691 spin_unlock(&dentry
->d_lock
);
694 dentry
= dentry_kill(dentry
, 1);
698 static void shrink_dentry_list(struct list_head
*list
)
700 struct dentry
*dentry
;
704 dentry
= list_entry_rcu(list
->prev
, struct dentry
, d_lru
);
705 if (&dentry
->d_lru
== list
)
707 spin_lock(&dentry
->d_lock
);
708 if (dentry
!= list_entry(list
->prev
, struct dentry
, d_lru
)) {
709 spin_unlock(&dentry
->d_lock
);
714 * We found an inuse dentry which was not removed from
715 * the LRU because of laziness during lookup. Do not free
716 * it - just keep it off the LRU list.
718 if (dentry
->d_count
) {
719 dentry_lru_del(dentry
);
720 spin_unlock(&dentry
->d_lock
);
726 try_prune_one_dentry(dentry
);
734 * __shrink_dcache_sb - shrink the dentry LRU on a given superblock
735 * @sb: superblock to shrink dentry LRU.
736 * @count: number of entries to prune
737 * @flags: flags to control the dentry processing
739 * If flags contains DCACHE_REFERENCED reference dentries will not be pruned.
741 static void __shrink_dcache_sb(struct super_block
*sb
, int *count
, int flags
)
743 /* called from prune_dcache() and shrink_dcache_parent() */
744 struct dentry
*dentry
;
745 LIST_HEAD(referenced
);
750 spin_lock(&dcache_lru_lock
);
751 while (!list_empty(&sb
->s_dentry_lru
)) {
752 dentry
= list_entry(sb
->s_dentry_lru
.prev
,
753 struct dentry
, d_lru
);
754 BUG_ON(dentry
->d_sb
!= sb
);
756 if (!spin_trylock(&dentry
->d_lock
)) {
757 spin_unlock(&dcache_lru_lock
);
763 * If we are honouring the DCACHE_REFERENCED flag and the
764 * dentry has this flag set, don't free it. Clear the flag
765 * and put it back on the LRU.
767 if (flags
& DCACHE_REFERENCED
&&
768 dentry
->d_flags
& DCACHE_REFERENCED
) {
769 dentry
->d_flags
&= ~DCACHE_REFERENCED
;
770 list_move(&dentry
->d_lru
, &referenced
);
771 spin_unlock(&dentry
->d_lock
);
773 list_move_tail(&dentry
->d_lru
, &tmp
);
774 spin_unlock(&dentry
->d_lock
);
778 cond_resched_lock(&dcache_lru_lock
);
780 if (!list_empty(&referenced
))
781 list_splice(&referenced
, &sb
->s_dentry_lru
);
782 spin_unlock(&dcache_lru_lock
);
784 shrink_dentry_list(&tmp
);
790 * prune_dcache - shrink the dcache
791 * @count: number of entries to try to free
793 * Shrink the dcache. This is done when we need more memory, or simply when we
794 * need to unmount something (at which point we need to unuse all dentries).
796 * This function may fail to free any resources if all the dentries are in use.
798 static void prune_dcache(int count
)
800 struct super_block
*sb
, *p
= NULL
;
802 int unused
= dentry_stat
.nr_unused
;
806 if (unused
== 0 || count
== 0)
811 prune_ratio
= unused
/ count
;
813 list_for_each_entry(sb
, &super_blocks
, s_list
) {
814 if (list_empty(&sb
->s_instances
))
816 if (sb
->s_nr_dentry_unused
== 0)
819 /* Now, we reclaim unused dentrins with fairness.
820 * We reclaim them same percentage from each superblock.
821 * We calculate number of dentries to scan on this sb
822 * as follows, but the implementation is arranged to avoid
824 * number of dentries to scan on this sb =
825 * count * (number of dentries on this sb /
826 * number of dentries in the machine)
828 spin_unlock(&sb_lock
);
829 if (prune_ratio
!= 1)
830 w_count
= (sb
->s_nr_dentry_unused
/ prune_ratio
) + 1;
832 w_count
= sb
->s_nr_dentry_unused
;
835 * We need to be sure this filesystem isn't being unmounted,
836 * otherwise we could race with generic_shutdown_super(), and
837 * end up holding a reference to an inode while the filesystem
838 * is unmounted. So we try to get s_umount, and make sure
841 if (down_read_trylock(&sb
->s_umount
)) {
842 if ((sb
->s_root
!= NULL
) &&
843 (!list_empty(&sb
->s_dentry_lru
))) {
844 __shrink_dcache_sb(sb
, &w_count
,
848 up_read(&sb
->s_umount
);
855 /* more work left to do? */
861 spin_unlock(&sb_lock
);
865 * shrink_dcache_sb - shrink dcache for a superblock
868 * Shrink the dcache for the specified super block. This is used to free
869 * the dcache before unmounting a file system.
871 void shrink_dcache_sb(struct super_block
*sb
)
875 spin_lock(&dcache_lru_lock
);
876 while (!list_empty(&sb
->s_dentry_lru
)) {
877 list_splice_init(&sb
->s_dentry_lru
, &tmp
);
878 spin_unlock(&dcache_lru_lock
);
879 shrink_dentry_list(&tmp
);
880 spin_lock(&dcache_lru_lock
);
882 spin_unlock(&dcache_lru_lock
);
884 EXPORT_SYMBOL(shrink_dcache_sb
);
887 * destroy a single subtree of dentries for unmount
888 * - see the comments on shrink_dcache_for_umount() for a description of the
891 static void shrink_dcache_for_umount_subtree(struct dentry
*dentry
)
893 struct dentry
*parent
;
894 unsigned detached
= 0;
896 BUG_ON(!IS_ROOT(dentry
));
898 /* detach this root from the system */
899 spin_lock(&dentry
->d_lock
);
900 dentry_lru_del(dentry
);
902 spin_unlock(&dentry
->d_lock
);
905 /* descend to the first leaf in the current subtree */
906 while (!list_empty(&dentry
->d_subdirs
)) {
909 /* this is a branch with children - detach all of them
910 * from the system in one go */
911 spin_lock(&dentry
->d_lock
);
912 list_for_each_entry(loop
, &dentry
->d_subdirs
,
914 spin_lock_nested(&loop
->d_lock
,
915 DENTRY_D_LOCK_NESTED
);
916 dentry_lru_del(loop
);
918 spin_unlock(&loop
->d_lock
);
920 spin_unlock(&dentry
->d_lock
);
922 /* move to the first child */
923 dentry
= list_entry(dentry
->d_subdirs
.next
,
924 struct dentry
, d_u
.d_child
);
927 /* consume the dentries from this leaf up through its parents
928 * until we find one with children or run out altogether */
932 if (dentry
->d_count
!= 0) {
934 "BUG: Dentry %p{i=%lx,n=%s}"
936 " [unmount of %s %s]\n",
939 dentry
->d_inode
->i_ino
: 0UL,
942 dentry
->d_sb
->s_type
->name
,
947 if (IS_ROOT(dentry
)) {
949 list_del(&dentry
->d_u
.d_child
);
951 parent
= dentry
->d_parent
;
952 spin_lock(&parent
->d_lock
);
954 list_del(&dentry
->d_u
.d_child
);
955 spin_unlock(&parent
->d_lock
);
960 inode
= dentry
->d_inode
;
962 dentry
->d_inode
= NULL
;
963 list_del_init(&dentry
->d_alias
);
964 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
965 dentry
->d_op
->d_iput(dentry
, inode
);
972 /* finished when we fall off the top of the tree,
973 * otherwise we ascend to the parent and move to the
974 * next sibling if there is one */
978 } while (list_empty(&dentry
->d_subdirs
));
980 dentry
= list_entry(dentry
->d_subdirs
.next
,
981 struct dentry
, d_u
.d_child
);
986 * destroy the dentries attached to a superblock on unmounting
987 * - we don't need to use dentry->d_lock because:
988 * - the superblock is detached from all mountings and open files, so the
989 * dentry trees will not be rearranged by the VFS
990 * - s_umount is write-locked, so the memory pressure shrinker will ignore
991 * any dentries belonging to this superblock that it comes across
992 * - the filesystem itself is no longer permitted to rearrange the dentries
995 void shrink_dcache_for_umount(struct super_block
*sb
)
997 struct dentry
*dentry
;
999 if (down_read_trylock(&sb
->s_umount
))
1002 dentry
= sb
->s_root
;
1004 spin_lock(&dentry
->d_lock
);
1006 spin_unlock(&dentry
->d_lock
);
1007 shrink_dcache_for_umount_subtree(dentry
);
1009 while (!hlist_bl_empty(&sb
->s_anon
)) {
1010 dentry
= hlist_bl_entry(hlist_bl_first(&sb
->s_anon
), struct dentry
, d_hash
);
1011 shrink_dcache_for_umount_subtree(dentry
);
1016 * This tries to ascend one level of parenthood, but
1017 * we can race with renaming, so we need to re-check
1018 * the parenthood after dropping the lock and check
1019 * that the sequence number still matches.
1021 static struct dentry
*try_to_ascend(struct dentry
*old
, int locked
, unsigned seq
)
1023 struct dentry
*new = old
->d_parent
;
1026 spin_unlock(&old
->d_lock
);
1027 spin_lock(&new->d_lock
);
1030 * might go back up the wrong parent if we have had a rename
1033 if (new != old
->d_parent
||
1034 (old
->d_flags
& DCACHE_DISCONNECTED
) ||
1035 (!locked
&& read_seqretry(&rename_lock
, seq
))) {
1036 spin_unlock(&new->d_lock
);
1045 * Search for at least 1 mount point in the dentry's subdirs.
1046 * We descend to the next level whenever the d_subdirs
1047 * list is non-empty and continue searching.
1051 * have_submounts - check for mounts over a dentry
1052 * @parent: dentry to check.
1054 * Return true if the parent or its subdirectories contain
1057 int have_submounts(struct dentry
*parent
)
1059 struct dentry
*this_parent
;
1060 struct list_head
*next
;
1064 seq
= read_seqbegin(&rename_lock
);
1066 this_parent
= parent
;
1068 if (d_mountpoint(parent
))
1070 spin_lock(&this_parent
->d_lock
);
1072 next
= this_parent
->d_subdirs
.next
;
1074 while (next
!= &this_parent
->d_subdirs
) {
1075 struct list_head
*tmp
= next
;
1076 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_u
.d_child
);
1079 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1080 /* Have we found a mount point ? */
1081 if (d_mountpoint(dentry
)) {
1082 spin_unlock(&dentry
->d_lock
);
1083 spin_unlock(&this_parent
->d_lock
);
1086 if (!list_empty(&dentry
->d_subdirs
)) {
1087 spin_unlock(&this_parent
->d_lock
);
1088 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
1089 this_parent
= dentry
;
1090 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
1093 spin_unlock(&dentry
->d_lock
);
1096 * All done at this level ... ascend and resume the search.
1098 if (this_parent
!= parent
) {
1099 struct dentry
*child
= this_parent
;
1100 this_parent
= try_to_ascend(this_parent
, locked
, seq
);
1103 next
= child
->d_u
.d_child
.next
;
1106 spin_unlock(&this_parent
->d_lock
);
1107 if (!locked
&& read_seqretry(&rename_lock
, seq
))
1110 write_sequnlock(&rename_lock
);
1111 return 0; /* No mount points found in tree */
1113 if (!locked
&& read_seqretry(&rename_lock
, seq
))
1116 write_sequnlock(&rename_lock
);
1121 write_seqlock(&rename_lock
);
1124 EXPORT_SYMBOL(have_submounts
);
1127 * Search the dentry child list for the specified parent,
1128 * and move any unused dentries to the end of the unused
1129 * list for prune_dcache(). We descend to the next level
1130 * whenever the d_subdirs list is non-empty and continue
1133 * It returns zero iff there are no unused children,
1134 * otherwise it returns the number of children moved to
1135 * the end of the unused list. This may not be the total
1136 * number of unused children, because select_parent can
1137 * drop the lock and return early due to latency
1140 static int select_parent(struct dentry
* parent
)
1142 struct dentry
*this_parent
;
1143 struct list_head
*next
;
1148 seq
= read_seqbegin(&rename_lock
);
1150 this_parent
= parent
;
1151 spin_lock(&this_parent
->d_lock
);
1153 next
= this_parent
->d_subdirs
.next
;
1155 while (next
!= &this_parent
->d_subdirs
) {
1156 struct list_head
*tmp
= next
;
1157 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_u
.d_child
);
1160 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1163 * move only zero ref count dentries to the end
1164 * of the unused list for prune_dcache
1166 if (!dentry
->d_count
) {
1167 dentry_lru_move_tail(dentry
);
1170 dentry_lru_del(dentry
);
1174 * We can return to the caller if we have found some (this
1175 * ensures forward progress). We'll be coming back to find
1178 if (found
&& need_resched()) {
1179 spin_unlock(&dentry
->d_lock
);
1184 * Descend a level if the d_subdirs list is non-empty.
1186 if (!list_empty(&dentry
->d_subdirs
)) {
1187 spin_unlock(&this_parent
->d_lock
);
1188 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
1189 this_parent
= dentry
;
1190 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
1194 spin_unlock(&dentry
->d_lock
);
1197 * All done at this level ... ascend and resume the search.
1199 if (this_parent
!= parent
) {
1200 struct dentry
*child
= this_parent
;
1201 this_parent
= try_to_ascend(this_parent
, locked
, seq
);
1204 next
= child
->d_u
.d_child
.next
;
1208 spin_unlock(&this_parent
->d_lock
);
1209 if (!locked
&& read_seqretry(&rename_lock
, seq
))
1212 write_sequnlock(&rename_lock
);
1219 write_seqlock(&rename_lock
);
1224 * shrink_dcache_parent - prune dcache
1225 * @parent: parent of entries to prune
1227 * Prune the dcache to remove unused children of the parent dentry.
1230 void shrink_dcache_parent(struct dentry
* parent
)
1232 struct super_block
*sb
= parent
->d_sb
;
1235 while ((found
= select_parent(parent
)) != 0)
1236 __shrink_dcache_sb(sb
, &found
, 0);
1238 EXPORT_SYMBOL(shrink_dcache_parent
);
1241 * Scan `nr' dentries and return the number which remain.
1243 * We need to avoid reentering the filesystem if the caller is performing a
1244 * GFP_NOFS allocation attempt. One example deadlock is:
1246 * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
1247 * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
1248 * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
1250 * In this case we return -1 to tell the caller that we baled.
1252 static int shrink_dcache_memory(struct shrinker
*shrink
, int nr
, gfp_t gfp_mask
)
1255 if (!(gfp_mask
& __GFP_FS
))
1260 return (dentry_stat
.nr_unused
/ 100) * sysctl_vfs_cache_pressure
;
1263 static struct shrinker dcache_shrinker
= {
1264 .shrink
= shrink_dcache_memory
,
1265 .seeks
= DEFAULT_SEEKS
,
1269 * d_alloc - allocate a dcache entry
1270 * @parent: parent of entry to allocate
1271 * @name: qstr of the name
1273 * Allocates a dentry. It returns %NULL if there is insufficient memory
1274 * available. On a success the dentry is returned. The name passed in is
1275 * copied and the copy passed in may be reused after this call.
1278 struct dentry
*d_alloc(struct dentry
* parent
, const struct qstr
*name
)
1280 struct dentry
*dentry
;
1283 dentry
= kmem_cache_alloc(dentry_cache
, GFP_KERNEL
);
1287 if (name
->len
> DNAME_INLINE_LEN
-1) {
1288 dname
= kmalloc(name
->len
+ 1, GFP_KERNEL
);
1290 kmem_cache_free(dentry_cache
, dentry
);
1294 dname
= dentry
->d_iname
;
1296 dentry
->d_name
.name
= dname
;
1298 dentry
->d_name
.len
= name
->len
;
1299 dentry
->d_name
.hash
= name
->hash
;
1300 memcpy(dname
, name
->name
, name
->len
);
1301 dname
[name
->len
] = 0;
1303 dentry
->d_count
= 1;
1304 dentry
->d_flags
= DCACHE_UNHASHED
;
1305 spin_lock_init(&dentry
->d_lock
);
1306 seqcount_init(&dentry
->d_seq
);
1307 dentry
->d_inode
= NULL
;
1308 dentry
->d_parent
= NULL
;
1309 dentry
->d_sb
= NULL
;
1310 dentry
->d_op
= NULL
;
1311 dentry
->d_fsdata
= NULL
;
1312 INIT_HLIST_BL_NODE(&dentry
->d_hash
);
1313 INIT_LIST_HEAD(&dentry
->d_lru
);
1314 INIT_LIST_HEAD(&dentry
->d_subdirs
);
1315 INIT_LIST_HEAD(&dentry
->d_alias
);
1316 INIT_LIST_HEAD(&dentry
->d_u
.d_child
);
1319 spin_lock(&parent
->d_lock
);
1321 * don't need child lock because it is not subject
1322 * to concurrency here
1324 __dget_dlock(parent
);
1325 dentry
->d_parent
= parent
;
1326 dentry
->d_sb
= parent
->d_sb
;
1327 d_set_d_op(dentry
, dentry
->d_sb
->s_d_op
);
1328 list_add(&dentry
->d_u
.d_child
, &parent
->d_subdirs
);
1329 spin_unlock(&parent
->d_lock
);
1332 this_cpu_inc(nr_dentry
);
1336 EXPORT_SYMBOL(d_alloc
);
1338 struct dentry
*d_alloc_pseudo(struct super_block
*sb
, const struct qstr
*name
)
1340 struct dentry
*dentry
= d_alloc(NULL
, name
);
1343 d_set_d_op(dentry
, dentry
->d_sb
->s_d_op
);
1344 dentry
->d_parent
= dentry
;
1345 dentry
->d_flags
|= DCACHE_DISCONNECTED
;
1349 EXPORT_SYMBOL(d_alloc_pseudo
);
1351 struct dentry
*d_alloc_name(struct dentry
*parent
, const char *name
)
1356 q
.len
= strlen(name
);
1357 q
.hash
= full_name_hash(q
.name
, q
.len
);
1358 return d_alloc(parent
, &q
);
1360 EXPORT_SYMBOL(d_alloc_name
);
1362 void d_set_d_op(struct dentry
*dentry
, const struct dentry_operations
*op
)
1364 WARN_ON_ONCE(dentry
->d_op
);
1365 WARN_ON_ONCE(dentry
->d_flags
& (DCACHE_OP_HASH
|
1367 DCACHE_OP_REVALIDATE
|
1368 DCACHE_OP_DELETE
));
1373 dentry
->d_flags
|= DCACHE_OP_HASH
;
1375 dentry
->d_flags
|= DCACHE_OP_COMPARE
;
1376 if (op
->d_revalidate
)
1377 dentry
->d_flags
|= DCACHE_OP_REVALIDATE
;
1379 dentry
->d_flags
|= DCACHE_OP_DELETE
;
1382 EXPORT_SYMBOL(d_set_d_op
);
1384 static void __d_instantiate(struct dentry
*dentry
, struct inode
*inode
)
1386 spin_lock(&dentry
->d_lock
);
1388 if (unlikely(IS_AUTOMOUNT(inode
)))
1389 dentry
->d_flags
|= DCACHE_NEED_AUTOMOUNT
;
1390 list_add(&dentry
->d_alias
, &inode
->i_dentry
);
1392 dentry
->d_inode
= inode
;
1393 dentry_rcuwalk_barrier(dentry
);
1394 spin_unlock(&dentry
->d_lock
);
1395 fsnotify_d_instantiate(dentry
, inode
);
1399 * d_instantiate - fill in inode information for a dentry
1400 * @entry: dentry to complete
1401 * @inode: inode to attach to this dentry
1403 * Fill in inode information in the entry.
1405 * This turns negative dentries into productive full members
1408 * NOTE! This assumes that the inode count has been incremented
1409 * (or otherwise set) by the caller to indicate that it is now
1410 * in use by the dcache.
1413 void d_instantiate(struct dentry
*entry
, struct inode
* inode
)
1415 BUG_ON(!list_empty(&entry
->d_alias
));
1417 spin_lock(&inode
->i_lock
);
1418 __d_instantiate(entry
, inode
);
1420 spin_unlock(&inode
->i_lock
);
1421 security_d_instantiate(entry
, inode
);
1423 EXPORT_SYMBOL(d_instantiate
);
1426 * d_instantiate_unique - instantiate a non-aliased dentry
1427 * @entry: dentry to instantiate
1428 * @inode: inode to attach to this dentry
1430 * Fill in inode information in the entry. On success, it returns NULL.
1431 * If an unhashed alias of "entry" already exists, then we return the
1432 * aliased dentry instead and drop one reference to inode.
1434 * Note that in order to avoid conflicts with rename() etc, the caller
1435 * had better be holding the parent directory semaphore.
1437 * This also assumes that the inode count has been incremented
1438 * (or otherwise set) by the caller to indicate that it is now
1439 * in use by the dcache.
1441 static struct dentry
*__d_instantiate_unique(struct dentry
*entry
,
1442 struct inode
*inode
)
1444 struct dentry
*alias
;
1445 int len
= entry
->d_name
.len
;
1446 const char *name
= entry
->d_name
.name
;
1447 unsigned int hash
= entry
->d_name
.hash
;
1450 __d_instantiate(entry
, NULL
);
1454 list_for_each_entry(alias
, &inode
->i_dentry
, d_alias
) {
1455 struct qstr
*qstr
= &alias
->d_name
;
1458 * Don't need alias->d_lock here, because aliases with
1459 * d_parent == entry->d_parent are not subject to name or
1460 * parent changes, because the parent inode i_mutex is held.
1462 if (qstr
->hash
!= hash
)
1464 if (alias
->d_parent
!= entry
->d_parent
)
1466 if (dentry_cmp(qstr
->name
, qstr
->len
, name
, len
))
1472 __d_instantiate(entry
, inode
);
1476 struct dentry
*d_instantiate_unique(struct dentry
*entry
, struct inode
*inode
)
1478 struct dentry
*result
;
1480 BUG_ON(!list_empty(&entry
->d_alias
));
1483 spin_lock(&inode
->i_lock
);
1484 result
= __d_instantiate_unique(entry
, inode
);
1486 spin_unlock(&inode
->i_lock
);
1489 security_d_instantiate(entry
, inode
);
1493 BUG_ON(!d_unhashed(result
));
1498 EXPORT_SYMBOL(d_instantiate_unique
);
1501 * d_alloc_root - allocate root dentry
1502 * @root_inode: inode to allocate the root for
1504 * Allocate a root ("/") dentry for the inode given. The inode is
1505 * instantiated and returned. %NULL is returned if there is insufficient
1506 * memory or the inode passed is %NULL.
1509 struct dentry
* d_alloc_root(struct inode
* root_inode
)
1511 struct dentry
*res
= NULL
;
1514 static const struct qstr name
= { .name
= "/", .len
= 1 };
1516 res
= d_alloc(NULL
, &name
);
1518 res
->d_sb
= root_inode
->i_sb
;
1519 d_set_d_op(res
, res
->d_sb
->s_d_op
);
1520 res
->d_parent
= res
;
1521 d_instantiate(res
, root_inode
);
1526 EXPORT_SYMBOL(d_alloc_root
);
1528 static struct dentry
* __d_find_any_alias(struct inode
*inode
)
1530 struct dentry
*alias
;
1532 if (list_empty(&inode
->i_dentry
))
1534 alias
= list_first_entry(&inode
->i_dentry
, struct dentry
, d_alias
);
1539 static struct dentry
* d_find_any_alias(struct inode
*inode
)
1543 spin_lock(&inode
->i_lock
);
1544 de
= __d_find_any_alias(inode
);
1545 spin_unlock(&inode
->i_lock
);
1551 * d_obtain_alias - find or allocate a dentry for a given inode
1552 * @inode: inode to allocate the dentry for
1554 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1555 * similar open by handle operations. The returned dentry may be anonymous,
1556 * or may have a full name (if the inode was already in the cache).
1558 * When called on a directory inode, we must ensure that the inode only ever
1559 * has one dentry. If a dentry is found, that is returned instead of
1560 * allocating a new one.
1562 * On successful return, the reference to the inode has been transferred
1563 * to the dentry. In case of an error the reference on the inode is released.
1564 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1565 * be passed in and will be the error will be propagate to the return value,
1566 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1568 struct dentry
*d_obtain_alias(struct inode
*inode
)
1570 static const struct qstr anonstring
= { .name
= "" };
1575 return ERR_PTR(-ESTALE
);
1577 return ERR_CAST(inode
);
1579 res
= d_find_any_alias(inode
);
1583 tmp
= d_alloc(NULL
, &anonstring
);
1585 res
= ERR_PTR(-ENOMEM
);
1588 tmp
->d_parent
= tmp
; /* make sure dput doesn't croak */
1591 spin_lock(&inode
->i_lock
);
1592 res
= __d_find_any_alias(inode
);
1594 spin_unlock(&inode
->i_lock
);
1599 /* attach a disconnected dentry */
1600 spin_lock(&tmp
->d_lock
);
1601 tmp
->d_sb
= inode
->i_sb
;
1602 d_set_d_op(tmp
, tmp
->d_sb
->s_d_op
);
1603 tmp
->d_inode
= inode
;
1604 tmp
->d_flags
|= DCACHE_DISCONNECTED
;
1605 list_add(&tmp
->d_alias
, &inode
->i_dentry
);
1606 bit_spin_lock(0, (unsigned long *)&tmp
->d_sb
->s_anon
.first
);
1607 tmp
->d_flags
&= ~DCACHE_UNHASHED
;
1608 hlist_bl_add_head(&tmp
->d_hash
, &tmp
->d_sb
->s_anon
);
1609 __bit_spin_unlock(0, (unsigned long *)&tmp
->d_sb
->s_anon
.first
);
1610 spin_unlock(&tmp
->d_lock
);
1611 spin_unlock(&inode
->i_lock
);
1612 security_d_instantiate(tmp
, inode
);
1617 if (res
&& !IS_ERR(res
))
1618 security_d_instantiate(res
, inode
);
1622 EXPORT_SYMBOL(d_obtain_alias
);
1625 * d_splice_alias - splice a disconnected dentry into the tree if one exists
1626 * @inode: the inode which may have a disconnected dentry
1627 * @dentry: a negative dentry which we want to point to the inode.
1629 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1630 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1631 * and return it, else simply d_add the inode to the dentry and return NULL.
1633 * This is needed in the lookup routine of any filesystem that is exportable
1634 * (via knfsd) so that we can build dcache paths to directories effectively.
1636 * If a dentry was found and moved, then it is returned. Otherwise NULL
1637 * is returned. This matches the expected return value of ->lookup.
1640 struct dentry
*d_splice_alias(struct inode
*inode
, struct dentry
*dentry
)
1642 struct dentry
*new = NULL
;
1644 if (inode
&& S_ISDIR(inode
->i_mode
)) {
1645 spin_lock(&inode
->i_lock
);
1646 new = __d_find_alias(inode
, 1);
1648 BUG_ON(!(new->d_flags
& DCACHE_DISCONNECTED
));
1649 spin_unlock(&inode
->i_lock
);
1650 security_d_instantiate(new, inode
);
1651 d_move(new, dentry
);
1654 /* already taking inode->i_lock, so d_add() by hand */
1655 __d_instantiate(dentry
, inode
);
1656 spin_unlock(&inode
->i_lock
);
1657 security_d_instantiate(dentry
, inode
);
1661 d_add(dentry
, inode
);
1664 EXPORT_SYMBOL(d_splice_alias
);
1667 * d_add_ci - lookup or allocate new dentry with case-exact name
1668 * @inode: the inode case-insensitive lookup has found
1669 * @dentry: the negative dentry that was passed to the parent's lookup func
1670 * @name: the case-exact name to be associated with the returned dentry
1672 * This is to avoid filling the dcache with case-insensitive names to the
1673 * same inode, only the actual correct case is stored in the dcache for
1674 * case-insensitive filesystems.
1676 * For a case-insensitive lookup match and if the the case-exact dentry
1677 * already exists in in the dcache, use it and return it.
1679 * If no entry exists with the exact case name, allocate new dentry with
1680 * the exact case, and return the spliced entry.
1682 struct dentry
*d_add_ci(struct dentry
*dentry
, struct inode
*inode
,
1686 struct dentry
*found
;
1690 * First check if a dentry matching the name already exists,
1691 * if not go ahead and create it now.
1693 found
= d_hash_and_lookup(dentry
->d_parent
, name
);
1695 new = d_alloc(dentry
->d_parent
, name
);
1701 found
= d_splice_alias(inode
, new);
1710 * If a matching dentry exists, and it's not negative use it.
1712 * Decrement the reference count to balance the iget() done
1715 if (found
->d_inode
) {
1716 if (unlikely(found
->d_inode
!= inode
)) {
1717 /* This can't happen because bad inodes are unhashed. */
1718 BUG_ON(!is_bad_inode(inode
));
1719 BUG_ON(!is_bad_inode(found
->d_inode
));
1726 * Negative dentry: instantiate it unless the inode is a directory and
1727 * already has a dentry.
1729 spin_lock(&inode
->i_lock
);
1730 if (!S_ISDIR(inode
->i_mode
) || list_empty(&inode
->i_dentry
)) {
1731 __d_instantiate(found
, inode
);
1732 spin_unlock(&inode
->i_lock
);
1733 security_d_instantiate(found
, inode
);
1738 * In case a directory already has a (disconnected) entry grab a
1739 * reference to it, move it in place and use it.
1741 new = list_entry(inode
->i_dentry
.next
, struct dentry
, d_alias
);
1743 spin_unlock(&inode
->i_lock
);
1744 security_d_instantiate(found
, inode
);
1752 return ERR_PTR(error
);
1754 EXPORT_SYMBOL(d_add_ci
);
1757 * __d_lookup_rcu - search for a dentry (racy, store-free)
1758 * @parent: parent dentry
1759 * @name: qstr of name we wish to find
1760 * @seq: returns d_seq value at the point where the dentry was found
1761 * @inode: returns dentry->d_inode when the inode was found valid.
1762 * Returns: dentry, or NULL
1764 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
1765 * resolution (store-free path walking) design described in
1766 * Documentation/filesystems/path-lookup.txt.
1768 * This is not to be used outside core vfs.
1770 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
1771 * held, and rcu_read_lock held. The returned dentry must not be stored into
1772 * without taking d_lock and checking d_seq sequence count against @seq
1775 * A refcount may be taken on the found dentry with the __d_rcu_to_refcount
1778 * Alternatively, __d_lookup_rcu may be called again to look up the child of
1779 * the returned dentry, so long as its parent's seqlock is checked after the
1780 * child is looked up. Thus, an interlocking stepping of sequence lock checks
1781 * is formed, giving integrity down the path walk.
1783 struct dentry
*__d_lookup_rcu(struct dentry
*parent
, struct qstr
*name
,
1784 unsigned *seq
, struct inode
**inode
)
1786 unsigned int len
= name
->len
;
1787 unsigned int hash
= name
->hash
;
1788 const unsigned char *str
= name
->name
;
1789 struct hlist_bl_head
*b
= d_hash(parent
, hash
);
1790 struct hlist_bl_node
*node
;
1791 struct dentry
*dentry
;
1794 * Note: There is significant duplication with __d_lookup_rcu which is
1795 * required to prevent single threaded performance regressions
1796 * especially on architectures where smp_rmb (in seqcounts) are costly.
1797 * Keep the two functions in sync.
1801 * The hash list is protected using RCU.
1803 * Carefully use d_seq when comparing a candidate dentry, to avoid
1804 * races with d_move().
1806 * It is possible that concurrent renames can mess up our list
1807 * walk here and result in missing our dentry, resulting in the
1808 * false-negative result. d_lookup() protects against concurrent
1809 * renames using rename_lock seqlock.
1811 * See Documentation/filesystems/path-lookup.txt for more details.
1813 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
1818 if (dentry
->d_name
.hash
!= hash
)
1822 *seq
= read_seqcount_begin(&dentry
->d_seq
);
1823 if (dentry
->d_parent
!= parent
)
1825 if (d_unhashed(dentry
))
1827 tlen
= dentry
->d_name
.len
;
1828 tname
= dentry
->d_name
.name
;
1829 i
= dentry
->d_inode
;
1834 * This seqcount check is required to ensure name and
1835 * len are loaded atomically, so as not to walk off the
1836 * edge of memory when walking. If we could load this
1837 * atomically some other way, we could drop this check.
1839 if (read_seqcount_retry(&dentry
->d_seq
, *seq
))
1841 if (parent
->d_flags
& DCACHE_OP_COMPARE
) {
1842 if (parent
->d_op
->d_compare(parent
, *inode
,
1847 if (dentry_cmp(tname
, tlen
, str
, len
))
1851 * No extra seqcount check is required after the name
1852 * compare. The caller must perform a seqcount check in
1853 * order to do anything useful with the returned dentry
1863 * d_lookup - search for a dentry
1864 * @parent: parent dentry
1865 * @name: qstr of name we wish to find
1866 * Returns: dentry, or NULL
1868 * d_lookup searches the children of the parent dentry for the name in
1869 * question. If the dentry is found its reference count is incremented and the
1870 * dentry is returned. The caller must use dput to free the entry when it has
1871 * finished using it. %NULL is returned if the dentry does not exist.
1873 struct dentry
*d_lookup(struct dentry
*parent
, struct qstr
*name
)
1875 struct dentry
*dentry
;
1879 seq
= read_seqbegin(&rename_lock
);
1880 dentry
= __d_lookup(parent
, name
);
1883 } while (read_seqretry(&rename_lock
, seq
));
1886 EXPORT_SYMBOL(d_lookup
);
1889 * __d_lookup - search for a dentry (racy)
1890 * @parent: parent dentry
1891 * @name: qstr of name we wish to find
1892 * Returns: dentry, or NULL
1894 * __d_lookup is like d_lookup, however it may (rarely) return a
1895 * false-negative result due to unrelated rename activity.
1897 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
1898 * however it must be used carefully, eg. with a following d_lookup in
1899 * the case of failure.
1901 * __d_lookup callers must be commented.
1903 struct dentry
*__d_lookup(struct dentry
*parent
, struct qstr
*name
)
1905 unsigned int len
= name
->len
;
1906 unsigned int hash
= name
->hash
;
1907 const unsigned char *str
= name
->name
;
1908 struct hlist_bl_head
*b
= d_hash(parent
, hash
);
1909 struct hlist_bl_node
*node
;
1910 struct dentry
*found
= NULL
;
1911 struct dentry
*dentry
;
1914 * Note: There is significant duplication with __d_lookup_rcu which is
1915 * required to prevent single threaded performance regressions
1916 * especially on architectures where smp_rmb (in seqcounts) are costly.
1917 * Keep the two functions in sync.
1921 * The hash list is protected using RCU.
1923 * Take d_lock when comparing a candidate dentry, to avoid races
1926 * It is possible that concurrent renames can mess up our list
1927 * walk here and result in missing our dentry, resulting in the
1928 * false-negative result. d_lookup() protects against concurrent
1929 * renames using rename_lock seqlock.
1931 * See Documentation/filesystems/path-lookup.txt for more details.
1935 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
1939 if (dentry
->d_name
.hash
!= hash
)
1942 spin_lock(&dentry
->d_lock
);
1943 if (dentry
->d_parent
!= parent
)
1945 if (d_unhashed(dentry
))
1949 * It is safe to compare names since d_move() cannot
1950 * change the qstr (protected by d_lock).
1952 tlen
= dentry
->d_name
.len
;
1953 tname
= dentry
->d_name
.name
;
1954 if (parent
->d_flags
& DCACHE_OP_COMPARE
) {
1955 if (parent
->d_op
->d_compare(parent
, parent
->d_inode
,
1956 dentry
, dentry
->d_inode
,
1960 if (dentry_cmp(tname
, tlen
, str
, len
))
1966 spin_unlock(&dentry
->d_lock
);
1969 spin_unlock(&dentry
->d_lock
);
1977 * d_hash_and_lookup - hash the qstr then search for a dentry
1978 * @dir: Directory to search in
1979 * @name: qstr of name we wish to find
1981 * On hash failure or on lookup failure NULL is returned.
1983 struct dentry
*d_hash_and_lookup(struct dentry
*dir
, struct qstr
*name
)
1985 struct dentry
*dentry
= NULL
;
1988 * Check for a fs-specific hash function. Note that we must
1989 * calculate the standard hash first, as the d_op->d_hash()
1990 * routine may choose to leave the hash value unchanged.
1992 name
->hash
= full_name_hash(name
->name
, name
->len
);
1993 if (dir
->d_flags
& DCACHE_OP_HASH
) {
1994 if (dir
->d_op
->d_hash(dir
, dir
->d_inode
, name
) < 0)
1997 dentry
= d_lookup(dir
, name
);
2003 * d_validate - verify dentry provided from insecure source (deprecated)
2004 * @dentry: The dentry alleged to be valid child of @dparent
2005 * @dparent: The parent dentry (known to be valid)
2007 * An insecure source has sent us a dentry, here we verify it and dget() it.
2008 * This is used by ncpfs in its readdir implementation.
2009 * Zero is returned in the dentry is invalid.
2011 * This function is slow for big directories, and deprecated, do not use it.
2013 int d_validate(struct dentry
*dentry
, struct dentry
*dparent
)
2015 struct dentry
*child
;
2017 spin_lock(&dparent
->d_lock
);
2018 list_for_each_entry(child
, &dparent
->d_subdirs
, d_u
.d_child
) {
2019 if (dentry
== child
) {
2020 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
2021 __dget_dlock(dentry
);
2022 spin_unlock(&dentry
->d_lock
);
2023 spin_unlock(&dparent
->d_lock
);
2027 spin_unlock(&dparent
->d_lock
);
2031 EXPORT_SYMBOL(d_validate
);
2034 * When a file is deleted, we have two options:
2035 * - turn this dentry into a negative dentry
2036 * - unhash this dentry and free it.
2038 * Usually, we want to just turn this into
2039 * a negative dentry, but if anybody else is
2040 * currently using the dentry or the inode
2041 * we can't do that and we fall back on removing
2042 * it from the hash queues and waiting for
2043 * it to be deleted later when it has no users
2047 * d_delete - delete a dentry
2048 * @dentry: The dentry to delete
2050 * Turn the dentry into a negative dentry if possible, otherwise
2051 * remove it from the hash queues so it can be deleted later
2054 void d_delete(struct dentry
* dentry
)
2056 struct inode
*inode
;
2059 * Are we the only user?
2062 spin_lock(&dentry
->d_lock
);
2063 inode
= dentry
->d_inode
;
2064 isdir
= S_ISDIR(inode
->i_mode
);
2065 if (dentry
->d_count
== 1) {
2066 if (inode
&& !spin_trylock(&inode
->i_lock
)) {
2067 spin_unlock(&dentry
->d_lock
);
2071 dentry
->d_flags
&= ~DCACHE_CANT_MOUNT
;
2072 dentry_unlink_inode(dentry
);
2073 fsnotify_nameremove(dentry
, isdir
);
2077 if (!d_unhashed(dentry
))
2080 spin_unlock(&dentry
->d_lock
);
2082 fsnotify_nameremove(dentry
, isdir
);
2084 EXPORT_SYMBOL(d_delete
);
2086 static void __d_rehash(struct dentry
* entry
, struct hlist_bl_head
*b
)
2088 BUG_ON(!d_unhashed(entry
));
2089 spin_lock_bucket(b
);
2090 entry
->d_flags
&= ~DCACHE_UNHASHED
;
2091 hlist_bl_add_head_rcu(&entry
->d_hash
, b
);
2092 spin_unlock_bucket(b
);
2095 static void _d_rehash(struct dentry
* entry
)
2097 __d_rehash(entry
, d_hash(entry
->d_parent
, entry
->d_name
.hash
));
2101 * d_rehash - add an entry back to the hash
2102 * @entry: dentry to add to the hash
2104 * Adds a dentry to the hash according to its name.
2107 void d_rehash(struct dentry
* entry
)
2109 spin_lock(&entry
->d_lock
);
2111 spin_unlock(&entry
->d_lock
);
2113 EXPORT_SYMBOL(d_rehash
);
2116 * dentry_update_name_case - update case insensitive dentry with a new name
2117 * @dentry: dentry to be updated
2120 * Update a case insensitive dentry with new case of name.
2122 * dentry must have been returned by d_lookup with name @name. Old and new
2123 * name lengths must match (ie. no d_compare which allows mismatched name
2126 * Parent inode i_mutex must be held over d_lookup and into this call (to
2127 * keep renames and concurrent inserts, and readdir(2) away).
2129 void dentry_update_name_case(struct dentry
*dentry
, struct qstr
*name
)
2131 BUG_ON(!mutex_is_locked(&dentry
->d_parent
->d_inode
->i_mutex
));
2132 BUG_ON(dentry
->d_name
.len
!= name
->len
); /* d_lookup gives this */
2134 spin_lock(&dentry
->d_lock
);
2135 write_seqcount_begin(&dentry
->d_seq
);
2136 memcpy((unsigned char *)dentry
->d_name
.name
, name
->name
, name
->len
);
2137 write_seqcount_end(&dentry
->d_seq
);
2138 spin_unlock(&dentry
->d_lock
);
2140 EXPORT_SYMBOL(dentry_update_name_case
);
2142 static void switch_names(struct dentry
*dentry
, struct dentry
*target
)
2144 if (dname_external(target
)) {
2145 if (dname_external(dentry
)) {
2147 * Both external: swap the pointers
2149 swap(target
->d_name
.name
, dentry
->d_name
.name
);
2152 * dentry:internal, target:external. Steal target's
2153 * storage and make target internal.
2155 memcpy(target
->d_iname
, dentry
->d_name
.name
,
2156 dentry
->d_name
.len
+ 1);
2157 dentry
->d_name
.name
= target
->d_name
.name
;
2158 target
->d_name
.name
= target
->d_iname
;
2161 if (dname_external(dentry
)) {
2163 * dentry:external, target:internal. Give dentry's
2164 * storage to target and make dentry internal
2166 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2167 target
->d_name
.len
+ 1);
2168 target
->d_name
.name
= dentry
->d_name
.name
;
2169 dentry
->d_name
.name
= dentry
->d_iname
;
2172 * Both are internal. Just copy target to dentry
2174 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2175 target
->d_name
.len
+ 1);
2176 dentry
->d_name
.len
= target
->d_name
.len
;
2180 swap(dentry
->d_name
.len
, target
->d_name
.len
);
2183 static void dentry_lock_for_move(struct dentry
*dentry
, struct dentry
*target
)
2186 * XXXX: do we really need to take target->d_lock?
2188 if (IS_ROOT(dentry
) || dentry
->d_parent
== target
->d_parent
)
2189 spin_lock(&target
->d_parent
->d_lock
);
2191 if (d_ancestor(dentry
->d_parent
, target
->d_parent
)) {
2192 spin_lock(&dentry
->d_parent
->d_lock
);
2193 spin_lock_nested(&target
->d_parent
->d_lock
,
2194 DENTRY_D_LOCK_NESTED
);
2196 spin_lock(&target
->d_parent
->d_lock
);
2197 spin_lock_nested(&dentry
->d_parent
->d_lock
,
2198 DENTRY_D_LOCK_NESTED
);
2201 if (target
< dentry
) {
2202 spin_lock_nested(&target
->d_lock
, 2);
2203 spin_lock_nested(&dentry
->d_lock
, 3);
2205 spin_lock_nested(&dentry
->d_lock
, 2);
2206 spin_lock_nested(&target
->d_lock
, 3);
2210 static void dentry_unlock_parents_for_move(struct dentry
*dentry
,
2211 struct dentry
*target
)
2213 if (target
->d_parent
!= dentry
->d_parent
)
2214 spin_unlock(&dentry
->d_parent
->d_lock
);
2215 if (target
->d_parent
!= target
)
2216 spin_unlock(&target
->d_parent
->d_lock
);
2220 * When switching names, the actual string doesn't strictly have to
2221 * be preserved in the target - because we're dropping the target
2222 * anyway. As such, we can just do a simple memcpy() to copy over
2223 * the new name before we switch.
2225 * Note that we have to be a lot more careful about getting the hash
2226 * switched - we have to switch the hash value properly even if it
2227 * then no longer matches the actual (corrupted) string of the target.
2228 * The hash value has to match the hash queue that the dentry is on..
2231 * d_move - move a dentry
2232 * @dentry: entry to move
2233 * @target: new dentry
2235 * Update the dcache to reflect the move of a file name. Negative
2236 * dcache entries should not be moved in this way.
2238 void d_move(struct dentry
* dentry
, struct dentry
* target
)
2240 if (!dentry
->d_inode
)
2241 printk(KERN_WARNING
"VFS: moving negative dcache entry\n");
2243 BUG_ON(d_ancestor(dentry
, target
));
2244 BUG_ON(d_ancestor(target
, dentry
));
2246 write_seqlock(&rename_lock
);
2248 dentry_lock_for_move(dentry
, target
);
2250 write_seqcount_begin(&dentry
->d_seq
);
2251 write_seqcount_begin(&target
->d_seq
);
2253 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
2256 * Move the dentry to the target hash queue. Don't bother checking
2257 * for the same hash queue because of how unlikely it is.
2260 __d_rehash(dentry
, d_hash(target
->d_parent
, target
->d_name
.hash
));
2262 /* Unhash the target: dput() will then get rid of it */
2265 list_del(&dentry
->d_u
.d_child
);
2266 list_del(&target
->d_u
.d_child
);
2268 /* Switch the names.. */
2269 switch_names(dentry
, target
);
2270 swap(dentry
->d_name
.hash
, target
->d_name
.hash
);
2272 /* ... and switch the parents */
2273 if (IS_ROOT(dentry
)) {
2274 dentry
->d_parent
= target
->d_parent
;
2275 target
->d_parent
= target
;
2276 INIT_LIST_HEAD(&target
->d_u
.d_child
);
2278 swap(dentry
->d_parent
, target
->d_parent
);
2280 /* And add them back to the (new) parent lists */
2281 list_add(&target
->d_u
.d_child
, &target
->d_parent
->d_subdirs
);
2284 list_add(&dentry
->d_u
.d_child
, &dentry
->d_parent
->d_subdirs
);
2286 write_seqcount_end(&target
->d_seq
);
2287 write_seqcount_end(&dentry
->d_seq
);
2289 dentry_unlock_parents_for_move(dentry
, target
);
2290 spin_unlock(&target
->d_lock
);
2291 fsnotify_d_move(dentry
);
2292 spin_unlock(&dentry
->d_lock
);
2293 write_sequnlock(&rename_lock
);
2295 EXPORT_SYMBOL(d_move
);
2298 * d_ancestor - search for an ancestor
2299 * @p1: ancestor dentry
2302 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2303 * an ancestor of p2, else NULL.
2305 struct dentry
*d_ancestor(struct dentry
*p1
, struct dentry
*p2
)
2309 for (p
= p2
; !IS_ROOT(p
); p
= p
->d_parent
) {
2310 if (p
->d_parent
== p1
)
2317 * This helper attempts to cope with remotely renamed directories
2319 * It assumes that the caller is already holding
2320 * dentry->d_parent->d_inode->i_mutex and the inode->i_lock
2322 * Note: If ever the locking in lock_rename() changes, then please
2323 * remember to update this too...
2325 static struct dentry
*__d_unalias(struct inode
*inode
,
2326 struct dentry
*dentry
, struct dentry
*alias
)
2328 struct mutex
*m1
= NULL
, *m2
= NULL
;
2331 /* If alias and dentry share a parent, then no extra locks required */
2332 if (alias
->d_parent
== dentry
->d_parent
)
2335 /* Check for loops */
2336 ret
= ERR_PTR(-ELOOP
);
2337 if (d_ancestor(alias
, dentry
))
2340 /* See lock_rename() */
2341 ret
= ERR_PTR(-EBUSY
);
2342 if (!mutex_trylock(&dentry
->d_sb
->s_vfs_rename_mutex
))
2344 m1
= &dentry
->d_sb
->s_vfs_rename_mutex
;
2345 if (!mutex_trylock(&alias
->d_parent
->d_inode
->i_mutex
))
2347 m2
= &alias
->d_parent
->d_inode
->i_mutex
;
2349 d_move(alias
, dentry
);
2352 spin_unlock(&inode
->i_lock
);
2361 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
2362 * named dentry in place of the dentry to be replaced.
2363 * returns with anon->d_lock held!
2365 static void __d_materialise_dentry(struct dentry
*dentry
, struct dentry
*anon
)
2367 struct dentry
*dparent
, *aparent
;
2369 dentry_lock_for_move(anon
, dentry
);
2371 write_seqcount_begin(&dentry
->d_seq
);
2372 write_seqcount_begin(&anon
->d_seq
);
2374 dparent
= dentry
->d_parent
;
2375 aparent
= anon
->d_parent
;
2377 switch_names(dentry
, anon
);
2378 swap(dentry
->d_name
.hash
, anon
->d_name
.hash
);
2380 dentry
->d_parent
= (aparent
== anon
) ? dentry
: aparent
;
2381 list_del(&dentry
->d_u
.d_child
);
2382 if (!IS_ROOT(dentry
))
2383 list_add(&dentry
->d_u
.d_child
, &dentry
->d_parent
->d_subdirs
);
2385 INIT_LIST_HEAD(&dentry
->d_u
.d_child
);
2387 anon
->d_parent
= (dparent
== dentry
) ? anon
: dparent
;
2388 list_del(&anon
->d_u
.d_child
);
2390 list_add(&anon
->d_u
.d_child
, &anon
->d_parent
->d_subdirs
);
2392 INIT_LIST_HEAD(&anon
->d_u
.d_child
);
2394 write_seqcount_end(&dentry
->d_seq
);
2395 write_seqcount_end(&anon
->d_seq
);
2397 dentry_unlock_parents_for_move(anon
, dentry
);
2398 spin_unlock(&dentry
->d_lock
);
2400 /* anon->d_lock still locked, returns locked */
2401 anon
->d_flags
&= ~DCACHE_DISCONNECTED
;
2405 * d_materialise_unique - introduce an inode into the tree
2406 * @dentry: candidate dentry
2407 * @inode: inode to bind to the dentry, to which aliases may be attached
2409 * Introduces an dentry into the tree, substituting an extant disconnected
2410 * root directory alias in its place if there is one
2412 struct dentry
*d_materialise_unique(struct dentry
*dentry
, struct inode
*inode
)
2414 struct dentry
*actual
;
2416 BUG_ON(!d_unhashed(dentry
));
2420 __d_instantiate(dentry
, NULL
);
2425 spin_lock(&inode
->i_lock
);
2427 if (S_ISDIR(inode
->i_mode
)) {
2428 struct dentry
*alias
;
2430 /* Does an aliased dentry already exist? */
2431 alias
= __d_find_alias(inode
, 0);
2434 /* Is this an anonymous mountpoint that we could splice
2436 if (IS_ROOT(alias
)) {
2437 __d_materialise_dentry(dentry
, alias
);
2441 /* Nope, but we must(!) avoid directory aliasing */
2442 actual
= __d_unalias(inode
, dentry
, alias
);
2449 /* Add a unique reference */
2450 actual
= __d_instantiate_unique(dentry
, inode
);
2454 BUG_ON(!d_unhashed(actual
));
2456 spin_lock(&actual
->d_lock
);
2459 spin_unlock(&actual
->d_lock
);
2460 spin_unlock(&inode
->i_lock
);
2462 if (actual
== dentry
) {
2463 security_d_instantiate(dentry
, inode
);
2470 EXPORT_SYMBOL_GPL(d_materialise_unique
);
2472 static int prepend(char **buffer
, int *buflen
, const char *str
, int namelen
)
2476 return -ENAMETOOLONG
;
2478 memcpy(*buffer
, str
, namelen
);
2482 static int prepend_name(char **buffer
, int *buflen
, struct qstr
*name
)
2484 return prepend(buffer
, buflen
, name
->name
, name
->len
);
2488 * prepend_path - Prepend path string to a buffer
2489 * @path: the dentry/vfsmount to report
2490 * @root: root vfsmnt/dentry (may be modified by this function)
2491 * @buffer: pointer to the end of the buffer
2492 * @buflen: pointer to buffer length
2494 * Caller holds the rename_lock.
2496 * If path is not reachable from the supplied root, then the value of
2497 * root is changed (without modifying refcounts).
2499 static int prepend_path(const struct path
*path
, struct path
*root
,
2500 char **buffer
, int *buflen
)
2502 struct dentry
*dentry
= path
->dentry
;
2503 struct vfsmount
*vfsmnt
= path
->mnt
;
2507 br_read_lock(vfsmount_lock
);
2508 while (dentry
!= root
->dentry
|| vfsmnt
!= root
->mnt
) {
2509 struct dentry
* parent
;
2511 if (dentry
== vfsmnt
->mnt_root
|| IS_ROOT(dentry
)) {
2513 if (vfsmnt
->mnt_parent
== vfsmnt
) {
2516 dentry
= vfsmnt
->mnt_mountpoint
;
2517 vfsmnt
= vfsmnt
->mnt_parent
;
2520 parent
= dentry
->d_parent
;
2522 spin_lock(&dentry
->d_lock
);
2523 error
= prepend_name(buffer
, buflen
, &dentry
->d_name
);
2524 spin_unlock(&dentry
->d_lock
);
2526 error
= prepend(buffer
, buflen
, "/", 1);
2535 if (!error
&& !slash
)
2536 error
= prepend(buffer
, buflen
, "/", 1);
2538 br_read_unlock(vfsmount_lock
);
2543 * Filesystems needing to implement special "root names"
2544 * should do so with ->d_dname()
2546 if (IS_ROOT(dentry
) &&
2547 (dentry
->d_name
.len
!= 1 || dentry
->d_name
.name
[0] != '/')) {
2548 WARN(1, "Root dentry has weird name <%.*s>\n",
2549 (int) dentry
->d_name
.len
, dentry
->d_name
.name
);
2552 root
->dentry
= dentry
;
2557 * __d_path - return the path of a dentry
2558 * @path: the dentry/vfsmount to report
2559 * @root: root vfsmnt/dentry (may be modified by this function)
2560 * @buf: buffer to return value in
2561 * @buflen: buffer length
2563 * Convert a dentry into an ASCII path name.
2565 * Returns a pointer into the buffer or an error code if the
2566 * path was too long.
2568 * "buflen" should be positive.
2570 * If path is not reachable from the supplied root, then the value of
2571 * root is changed (without modifying refcounts).
2573 char *__d_path(const struct path
*path
, struct path
*root
,
2574 char *buf
, int buflen
)
2576 char *res
= buf
+ buflen
;
2579 prepend(&res
, &buflen
, "\0", 1);
2580 write_seqlock(&rename_lock
);
2581 error
= prepend_path(path
, root
, &res
, &buflen
);
2582 write_sequnlock(&rename_lock
);
2585 return ERR_PTR(error
);
2590 * same as __d_path but appends "(deleted)" for unlinked files.
2592 static int path_with_deleted(const struct path
*path
, struct path
*root
,
2593 char **buf
, int *buflen
)
2595 prepend(buf
, buflen
, "\0", 1);
2596 if (d_unlinked(path
->dentry
)) {
2597 int error
= prepend(buf
, buflen
, " (deleted)", 10);
2602 return prepend_path(path
, root
, buf
, buflen
);
2605 static int prepend_unreachable(char **buffer
, int *buflen
)
2607 return prepend(buffer
, buflen
, "(unreachable)", 13);
2611 * d_path - return the path of a dentry
2612 * @path: path to report
2613 * @buf: buffer to return value in
2614 * @buflen: buffer length
2616 * Convert a dentry into an ASCII path name. If the entry has been deleted
2617 * the string " (deleted)" is appended. Note that this is ambiguous.
2619 * Returns a pointer into the buffer or an error code if the path was
2620 * too long. Note: Callers should use the returned pointer, not the passed
2621 * in buffer, to use the name! The implementation often starts at an offset
2622 * into the buffer, and may leave 0 bytes at the start.
2624 * "buflen" should be positive.
2626 char *d_path(const struct path
*path
, char *buf
, int buflen
)
2628 char *res
= buf
+ buflen
;
2634 * We have various synthetic filesystems that never get mounted. On
2635 * these filesystems dentries are never used for lookup purposes, and
2636 * thus don't need to be hashed. They also don't need a name until a
2637 * user wants to identify the object in /proc/pid/fd/. The little hack
2638 * below allows us to generate a name for these objects on demand:
2640 if (path
->dentry
->d_op
&& path
->dentry
->d_op
->d_dname
)
2641 return path
->dentry
->d_op
->d_dname(path
->dentry
, buf
, buflen
);
2643 get_fs_root(current
->fs
, &root
);
2644 write_seqlock(&rename_lock
);
2646 error
= path_with_deleted(path
, &tmp
, &res
, &buflen
);
2648 res
= ERR_PTR(error
);
2649 write_sequnlock(&rename_lock
);
2653 EXPORT_SYMBOL(d_path
);
2656 * d_path_with_unreachable - return the path of a dentry
2657 * @path: path to report
2658 * @buf: buffer to return value in
2659 * @buflen: buffer length
2661 * The difference from d_path() is that this prepends "(unreachable)"
2662 * to paths which are unreachable from the current process' root.
2664 char *d_path_with_unreachable(const struct path
*path
, char *buf
, int buflen
)
2666 char *res
= buf
+ buflen
;
2671 if (path
->dentry
->d_op
&& path
->dentry
->d_op
->d_dname
)
2672 return path
->dentry
->d_op
->d_dname(path
->dentry
, buf
, buflen
);
2674 get_fs_root(current
->fs
, &root
);
2675 write_seqlock(&rename_lock
);
2677 error
= path_with_deleted(path
, &tmp
, &res
, &buflen
);
2678 if (!error
&& !path_equal(&tmp
, &root
))
2679 error
= prepend_unreachable(&res
, &buflen
);
2680 write_sequnlock(&rename_lock
);
2683 res
= ERR_PTR(error
);
2689 * Helper function for dentry_operations.d_dname() members
2691 char *dynamic_dname(struct dentry
*dentry
, char *buffer
, int buflen
,
2692 const char *fmt
, ...)
2698 va_start(args
, fmt
);
2699 sz
= vsnprintf(temp
, sizeof(temp
), fmt
, args
) + 1;
2702 if (sz
> sizeof(temp
) || sz
> buflen
)
2703 return ERR_PTR(-ENAMETOOLONG
);
2705 buffer
+= buflen
- sz
;
2706 return memcpy(buffer
, temp
, sz
);
2710 * Write full pathname from the root of the filesystem into the buffer.
2712 static char *__dentry_path(struct dentry
*dentry
, char *buf
, int buflen
)
2714 char *end
= buf
+ buflen
;
2717 prepend(&end
, &buflen
, "\0", 1);
2724 while (!IS_ROOT(dentry
)) {
2725 struct dentry
*parent
= dentry
->d_parent
;
2729 spin_lock(&dentry
->d_lock
);
2730 error
= prepend_name(&end
, &buflen
, &dentry
->d_name
);
2731 spin_unlock(&dentry
->d_lock
);
2732 if (error
!= 0 || prepend(&end
, &buflen
, "/", 1) != 0)
2740 return ERR_PTR(-ENAMETOOLONG
);
2743 char *dentry_path_raw(struct dentry
*dentry
, char *buf
, int buflen
)
2747 write_seqlock(&rename_lock
);
2748 retval
= __dentry_path(dentry
, buf
, buflen
);
2749 write_sequnlock(&rename_lock
);
2753 EXPORT_SYMBOL(dentry_path_raw
);
2755 char *dentry_path(struct dentry
*dentry
, char *buf
, int buflen
)
2760 write_seqlock(&rename_lock
);
2761 if (d_unlinked(dentry
)) {
2763 if (prepend(&p
, &buflen
, "//deleted", 10) != 0)
2767 retval
= __dentry_path(dentry
, buf
, buflen
);
2768 write_sequnlock(&rename_lock
);
2769 if (!IS_ERR(retval
) && p
)
2770 *p
= '/'; /* restore '/' overriden with '\0' */
2773 return ERR_PTR(-ENAMETOOLONG
);
2777 * NOTE! The user-level library version returns a
2778 * character pointer. The kernel system call just
2779 * returns the length of the buffer filled (which
2780 * includes the ending '\0' character), or a negative
2781 * error value. So libc would do something like
2783 * char *getcwd(char * buf, size_t size)
2787 * retval = sys_getcwd(buf, size);
2794 SYSCALL_DEFINE2(getcwd
, char __user
*, buf
, unsigned long, size
)
2797 struct path pwd
, root
;
2798 char *page
= (char *) __get_free_page(GFP_USER
);
2803 get_fs_root_and_pwd(current
->fs
, &root
, &pwd
);
2806 write_seqlock(&rename_lock
);
2807 if (!d_unlinked(pwd
.dentry
)) {
2809 struct path tmp
= root
;
2810 char *cwd
= page
+ PAGE_SIZE
;
2811 int buflen
= PAGE_SIZE
;
2813 prepend(&cwd
, &buflen
, "\0", 1);
2814 error
= prepend_path(&pwd
, &tmp
, &cwd
, &buflen
);
2815 write_sequnlock(&rename_lock
);
2820 /* Unreachable from current root */
2821 if (!path_equal(&tmp
, &root
)) {
2822 error
= prepend_unreachable(&cwd
, &buflen
);
2828 len
= PAGE_SIZE
+ page
- cwd
;
2831 if (copy_to_user(buf
, cwd
, len
))
2835 write_sequnlock(&rename_lock
);
2841 free_page((unsigned long) page
);
2846 * Test whether new_dentry is a subdirectory of old_dentry.
2848 * Trivially implemented using the dcache structure
2852 * is_subdir - is new dentry a subdirectory of old_dentry
2853 * @new_dentry: new dentry
2854 * @old_dentry: old dentry
2856 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
2857 * Returns 0 otherwise.
2858 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
2861 int is_subdir(struct dentry
*new_dentry
, struct dentry
*old_dentry
)
2866 if (new_dentry
== old_dentry
)
2870 /* for restarting inner loop in case of seq retry */
2871 seq
= read_seqbegin(&rename_lock
);
2873 * Need rcu_readlock to protect against the d_parent trashing
2877 if (d_ancestor(old_dentry
, new_dentry
))
2882 } while (read_seqretry(&rename_lock
, seq
));
2887 int path_is_under(struct path
*path1
, struct path
*path2
)
2889 struct vfsmount
*mnt
= path1
->mnt
;
2890 struct dentry
*dentry
= path1
->dentry
;
2893 br_read_lock(vfsmount_lock
);
2894 if (mnt
!= path2
->mnt
) {
2896 if (mnt
->mnt_parent
== mnt
) {
2897 br_read_unlock(vfsmount_lock
);
2900 if (mnt
->mnt_parent
== path2
->mnt
)
2902 mnt
= mnt
->mnt_parent
;
2904 dentry
= mnt
->mnt_mountpoint
;
2906 res
= is_subdir(dentry
, path2
->dentry
);
2907 br_read_unlock(vfsmount_lock
);
2910 EXPORT_SYMBOL(path_is_under
);
2912 void d_genocide(struct dentry
*root
)
2914 struct dentry
*this_parent
;
2915 struct list_head
*next
;
2919 seq
= read_seqbegin(&rename_lock
);
2922 spin_lock(&this_parent
->d_lock
);
2924 next
= this_parent
->d_subdirs
.next
;
2926 while (next
!= &this_parent
->d_subdirs
) {
2927 struct list_head
*tmp
= next
;
2928 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_u
.d_child
);
2931 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
2932 if (d_unhashed(dentry
) || !dentry
->d_inode
) {
2933 spin_unlock(&dentry
->d_lock
);
2936 if (!list_empty(&dentry
->d_subdirs
)) {
2937 spin_unlock(&this_parent
->d_lock
);
2938 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
2939 this_parent
= dentry
;
2940 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
2943 if (!(dentry
->d_flags
& DCACHE_GENOCIDE
)) {
2944 dentry
->d_flags
|= DCACHE_GENOCIDE
;
2947 spin_unlock(&dentry
->d_lock
);
2949 if (this_parent
!= root
) {
2950 struct dentry
*child
= this_parent
;
2951 if (!(this_parent
->d_flags
& DCACHE_GENOCIDE
)) {
2952 this_parent
->d_flags
|= DCACHE_GENOCIDE
;
2953 this_parent
->d_count
--;
2955 this_parent
= try_to_ascend(this_parent
, locked
, seq
);
2958 next
= child
->d_u
.d_child
.next
;
2961 spin_unlock(&this_parent
->d_lock
);
2962 if (!locked
&& read_seqretry(&rename_lock
, seq
))
2965 write_sequnlock(&rename_lock
);
2970 write_seqlock(&rename_lock
);
2975 * find_inode_number - check for dentry with name
2976 * @dir: directory to check
2977 * @name: Name to find.
2979 * Check whether a dentry already exists for the given name,
2980 * and return the inode number if it has an inode. Otherwise
2983 * This routine is used to post-process directory listings for
2984 * filesystems using synthetic inode numbers, and is necessary
2985 * to keep getcwd() working.
2988 ino_t
find_inode_number(struct dentry
*dir
, struct qstr
*name
)
2990 struct dentry
* dentry
;
2993 dentry
= d_hash_and_lookup(dir
, name
);
2995 if (dentry
->d_inode
)
2996 ino
= dentry
->d_inode
->i_ino
;
3001 EXPORT_SYMBOL(find_inode_number
);
3003 static __initdata
unsigned long dhash_entries
;
3004 static int __init
set_dhash_entries(char *str
)
3008 dhash_entries
= simple_strtoul(str
, &str
, 0);
3011 __setup("dhash_entries=", set_dhash_entries
);
3013 static void __init
dcache_init_early(void)
3017 /* If hashes are distributed across NUMA nodes, defer
3018 * hash allocation until vmalloc space is available.
3024 alloc_large_system_hash("Dentry cache",
3025 sizeof(struct hlist_bl_head
),
3033 for (loop
= 0; loop
< (1 << d_hash_shift
); loop
++)
3034 INIT_HLIST_BL_HEAD(dentry_hashtable
+ loop
);
3037 static void __init
dcache_init(void)
3042 * A constructor could be added for stable state like the lists,
3043 * but it is probably not worth it because of the cache nature
3046 dentry_cache
= KMEM_CACHE(dentry
,
3047 SLAB_RECLAIM_ACCOUNT
|SLAB_PANIC
|SLAB_MEM_SPREAD
);
3049 register_shrinker(&dcache_shrinker
);
3051 /* Hash may have been set up in dcache_init_early */
3056 alloc_large_system_hash("Dentry cache",
3057 sizeof(struct hlist_bl_head
),
3065 for (loop
= 0; loop
< (1 << d_hash_shift
); loop
++)
3066 INIT_HLIST_BL_HEAD(dentry_hashtable
+ loop
);
3069 /* SLAB cache for __getname() consumers */
3070 struct kmem_cache
*names_cachep __read_mostly
;
3071 EXPORT_SYMBOL(names_cachep
);
3073 EXPORT_SYMBOL(d_genocide
);
3075 void __init
vfs_caches_init_early(void)
3077 dcache_init_early();
3081 void __init
vfs_caches_init(unsigned long mempages
)
3083 unsigned long reserve
;
3085 /* Base hash sizes on available memory, with a reserve equal to
3086 150% of current kernel size */
3088 reserve
= min((mempages
- nr_free_pages()) * 3/2, mempages
- 1);
3089 mempages
-= reserve
;
3091 names_cachep
= kmem_cache_create("names_cache", PATH_MAX
, 0,
3092 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
);
3096 files_init(mempages
);