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/export.h>
27 #include <linux/mount.h>
28 #include <linux/file.h>
29 #include <asm/uaccess.h>
30 #include <linux/security.h>
31 #include <linux/seqlock.h>
32 #include <linux/swap.h>
33 #include <linux/bootmem.h>
34 #include <linux/fs_struct.h>
35 #include <linux/hardirq.h>
36 #include <linux/bit_spinlock.h>
37 #include <linux/rculist_bl.h>
38 #include <linux/prefetch.h>
39 #include <linux/ratelimit.h>
45 * dcache->d_inode->i_lock protects:
46 * - i_dentry, d_alias, d_inode of aliases
47 * dcache_hash_bucket lock protects:
48 * - the dcache hash table
49 * s_anon bl list spinlock protects:
50 * - the s_anon list (see __d_drop)
51 * dcache_lru_lock protects:
52 * - the dcache lru lists and counters
59 * - d_parent and d_subdirs
60 * - childrens' d_child and d_parent
64 * dentry->d_inode->i_lock
67 * dcache_hash_bucket lock
70 * If there is an ancestor relationship:
71 * dentry->d_parent->...->d_parent->d_lock
73 * dentry->d_parent->d_lock
76 * If no ancestor relationship:
77 * if (dentry1 < dentry2)
81 int sysctl_vfs_cache_pressure __read_mostly
= 100;
82 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure
);
84 static __cacheline_aligned_in_smp
DEFINE_SPINLOCK(dcache_lru_lock
);
85 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(rename_lock
);
87 EXPORT_SYMBOL(rename_lock
);
89 static struct kmem_cache
*dentry_cache __read_mostly
;
92 * This is the single most critical data structure when it comes
93 * to the dcache: the hashtable for lookups. Somebody should try
94 * to make this good - I've just made it work.
96 * This hash-function tries to avoid losing too many bits of hash
97 * information, yet avoid using a prime hash-size or similar.
99 #define D_HASHBITS d_hash_shift
100 #define D_HASHMASK d_hash_mask
102 static unsigned int d_hash_mask __read_mostly
;
103 static unsigned int d_hash_shift __read_mostly
;
105 static struct hlist_bl_head
*dentry_hashtable __read_mostly
;
107 static inline struct hlist_bl_head
*d_hash(const struct dentry
*parent
,
110 hash
+= (unsigned long) parent
/ L1_CACHE_BYTES
;
111 hash
= hash
+ (hash
>> D_HASHBITS
);
112 return dentry_hashtable
+ (hash
& D_HASHMASK
);
115 /* Statistics gathering. */
116 struct dentry_stat_t dentry_stat
= {
120 static DEFINE_PER_CPU(unsigned int, nr_dentry
);
122 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
123 static int get_nr_dentry(void)
127 for_each_possible_cpu(i
)
128 sum
+= per_cpu(nr_dentry
, i
);
129 return sum
< 0 ? 0 : sum
;
132 int proc_nr_dentry(ctl_table
*table
, int write
, void __user
*buffer
,
133 size_t *lenp
, loff_t
*ppos
)
135 dentry_stat
.nr_dentry
= get_nr_dentry();
136 return proc_dointvec(table
, write
, buffer
, lenp
, ppos
);
141 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
142 * The strings are both count bytes long, and count is non-zero.
144 #ifdef CONFIG_DCACHE_WORD_ACCESS
146 #include <asm/word-at-a-time.h>
148 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
149 * aligned allocation for this particular component. We don't
150 * strictly need the load_unaligned_zeropad() safety, but it
151 * doesn't hurt either.
153 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
154 * need the careful unaligned handling.
156 static inline int dentry_string_cmp(const unsigned char *cs
, const unsigned char *ct
, unsigned tcount
)
158 unsigned long a
,b
,mask
;
161 a
= *(unsigned long *)cs
;
162 b
= load_unaligned_zeropad(ct
);
163 if (tcount
< sizeof(unsigned long))
165 if (unlikely(a
!= b
))
167 cs
+= sizeof(unsigned long);
168 ct
+= sizeof(unsigned long);
169 tcount
-= sizeof(unsigned long);
173 mask
= ~(~0ul << tcount
*8);
174 return unlikely(!!((a
^ b
) & mask
));
179 static inline int dentry_string_cmp(const unsigned char *cs
, const unsigned char *ct
, unsigned tcount
)
193 static inline int dentry_cmp(const struct dentry
*dentry
, const unsigned char *ct
, unsigned tcount
)
195 const unsigned char *cs
;
197 * Be careful about RCU walk racing with rename:
198 * use ACCESS_ONCE to fetch the name pointer.
200 * NOTE! Even if a rename will mean that the length
201 * was not loaded atomically, we don't care. The
202 * RCU walk will check the sequence count eventually,
203 * and catch it. And we won't overrun the buffer,
204 * because we're reading the name pointer atomically,
205 * and a dentry name is guaranteed to be properly
206 * terminated with a NUL byte.
208 * End result: even if 'len' is wrong, we'll exit
209 * early because the data cannot match (there can
210 * be no NUL in the ct/tcount data)
212 cs
= ACCESS_ONCE(dentry
->d_name
.name
);
213 smp_read_barrier_depends();
214 return dentry_string_cmp(cs
, ct
, tcount
);
217 static void __d_free(struct rcu_head
*head
)
219 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
221 WARN_ON(!list_empty(&dentry
->d_alias
));
222 if (dname_external(dentry
))
223 kfree(dentry
->d_name
.name
);
224 kmem_cache_free(dentry_cache
, dentry
);
230 static void d_free(struct dentry
*dentry
)
232 BUG_ON(dentry
->d_count
);
233 this_cpu_dec(nr_dentry
);
234 if (dentry
->d_op
&& dentry
->d_op
->d_release
)
235 dentry
->d_op
->d_release(dentry
);
237 /* if dentry was never visible to RCU, immediate free is OK */
238 if (!(dentry
->d_flags
& DCACHE_RCUACCESS
))
239 __d_free(&dentry
->d_u
.d_rcu
);
241 call_rcu(&dentry
->d_u
.d_rcu
, __d_free
);
245 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
246 * @dentry: the target dentry
247 * After this call, in-progress rcu-walk path lookup will fail. This
248 * should be called after unhashing, and after changing d_inode (if
249 * the dentry has not already been unhashed).
251 static inline void dentry_rcuwalk_barrier(struct dentry
*dentry
)
253 assert_spin_locked(&dentry
->d_lock
);
254 /* Go through a barrier */
255 write_seqcount_barrier(&dentry
->d_seq
);
259 * Release the dentry's inode, using the filesystem
260 * d_iput() operation if defined. Dentry has no refcount
263 static void dentry_iput(struct dentry
* dentry
)
264 __releases(dentry
->d_lock
)
265 __releases(dentry
->d_inode
->i_lock
)
267 struct inode
*inode
= dentry
->d_inode
;
269 dentry
->d_inode
= NULL
;
270 list_del_init(&dentry
->d_alias
);
271 spin_unlock(&dentry
->d_lock
);
272 spin_unlock(&inode
->i_lock
);
274 fsnotify_inoderemove(inode
);
275 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
276 dentry
->d_op
->d_iput(dentry
, inode
);
280 spin_unlock(&dentry
->d_lock
);
285 * Release the dentry's inode, using the filesystem
286 * d_iput() operation if defined. dentry remains in-use.
288 static void dentry_unlink_inode(struct dentry
* dentry
)
289 __releases(dentry
->d_lock
)
290 __releases(dentry
->d_inode
->i_lock
)
292 struct inode
*inode
= dentry
->d_inode
;
293 dentry
->d_inode
= NULL
;
294 list_del_init(&dentry
->d_alias
);
295 dentry_rcuwalk_barrier(dentry
);
296 spin_unlock(&dentry
->d_lock
);
297 spin_unlock(&inode
->i_lock
);
299 fsnotify_inoderemove(inode
);
300 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
301 dentry
->d_op
->d_iput(dentry
, inode
);
307 * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
309 static void dentry_lru_add(struct dentry
*dentry
)
311 if (list_empty(&dentry
->d_lru
)) {
312 spin_lock(&dcache_lru_lock
);
313 list_add(&dentry
->d_lru
, &dentry
->d_sb
->s_dentry_lru
);
314 dentry
->d_sb
->s_nr_dentry_unused
++;
315 dentry_stat
.nr_unused
++;
316 spin_unlock(&dcache_lru_lock
);
320 static void __dentry_lru_del(struct dentry
*dentry
)
322 list_del_init(&dentry
->d_lru
);
323 dentry
->d_flags
&= ~DCACHE_SHRINK_LIST
;
324 dentry
->d_sb
->s_nr_dentry_unused
--;
325 dentry_stat
.nr_unused
--;
329 * Remove a dentry with references from the LRU.
331 static void dentry_lru_del(struct dentry
*dentry
)
333 if (!list_empty(&dentry
->d_lru
)) {
334 spin_lock(&dcache_lru_lock
);
335 __dentry_lru_del(dentry
);
336 spin_unlock(&dcache_lru_lock
);
341 * Remove a dentry that is unreferenced and about to be pruned
342 * (unhashed and destroyed) from the LRU, and inform the file system.
343 * This wrapper should be called _prior_ to unhashing a victim dentry.
345 static void dentry_lru_prune(struct dentry
*dentry
)
347 if (!list_empty(&dentry
->d_lru
)) {
348 if (dentry
->d_flags
& DCACHE_OP_PRUNE
)
349 dentry
->d_op
->d_prune(dentry
);
351 spin_lock(&dcache_lru_lock
);
352 __dentry_lru_del(dentry
);
353 spin_unlock(&dcache_lru_lock
);
357 static void dentry_lru_move_list(struct dentry
*dentry
, struct list_head
*list
)
359 spin_lock(&dcache_lru_lock
);
360 if (list_empty(&dentry
->d_lru
)) {
361 list_add_tail(&dentry
->d_lru
, list
);
362 dentry
->d_sb
->s_nr_dentry_unused
++;
363 dentry_stat
.nr_unused
++;
365 list_move_tail(&dentry
->d_lru
, list
);
367 spin_unlock(&dcache_lru_lock
);
371 * d_kill - kill dentry and return parent
372 * @dentry: dentry to kill
373 * @parent: parent dentry
375 * The dentry must already be unhashed and removed from the LRU.
377 * If this is the root of the dentry tree, return NULL.
379 * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
382 static struct dentry
*d_kill(struct dentry
*dentry
, struct dentry
*parent
)
383 __releases(dentry
->d_lock
)
384 __releases(parent
->d_lock
)
385 __releases(dentry
->d_inode
->i_lock
)
387 list_del(&dentry
->d_u
.d_child
);
389 * Inform try_to_ascend() that we are no longer attached to the
392 dentry
->d_flags
|= DCACHE_DISCONNECTED
;
394 spin_unlock(&parent
->d_lock
);
397 * dentry_iput drops the locks, at which point nobody (except
398 * transient RCU lookups) can reach this dentry.
405 * Unhash a dentry without inserting an RCU walk barrier or checking that
406 * dentry->d_lock is locked. The caller must take care of that, if
409 static void __d_shrink(struct dentry
*dentry
)
411 if (!d_unhashed(dentry
)) {
412 struct hlist_bl_head
*b
;
413 if (unlikely(dentry
->d_flags
& DCACHE_DISCONNECTED
))
414 b
= &dentry
->d_sb
->s_anon
;
416 b
= d_hash(dentry
->d_parent
, dentry
->d_name
.hash
);
419 __hlist_bl_del(&dentry
->d_hash
);
420 dentry
->d_hash
.pprev
= NULL
;
426 * d_drop - drop a dentry
427 * @dentry: dentry to drop
429 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
430 * be found through a VFS lookup any more. Note that this is different from
431 * deleting the dentry - d_delete will try to mark the dentry negative if
432 * possible, giving a successful _negative_ lookup, while d_drop will
433 * just make the cache lookup fail.
435 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
436 * reason (NFS timeouts or autofs deletes).
438 * __d_drop requires dentry->d_lock.
440 void __d_drop(struct dentry
*dentry
)
442 if (!d_unhashed(dentry
)) {
444 dentry_rcuwalk_barrier(dentry
);
447 EXPORT_SYMBOL(__d_drop
);
449 void d_drop(struct dentry
*dentry
)
451 spin_lock(&dentry
->d_lock
);
453 spin_unlock(&dentry
->d_lock
);
455 EXPORT_SYMBOL(d_drop
);
458 * d_clear_need_lookup - drop a dentry from cache and clear the need lookup flag
459 * @dentry: dentry to drop
461 * This is called when we do a lookup on a placeholder dentry that needed to be
462 * looked up. The dentry should have been hashed in order for it to be found by
463 * the lookup code, but now needs to be unhashed while we do the actual lookup
464 * and clear the DCACHE_NEED_LOOKUP flag.
466 void d_clear_need_lookup(struct dentry
*dentry
)
468 spin_lock(&dentry
->d_lock
);
470 dentry
->d_flags
&= ~DCACHE_NEED_LOOKUP
;
471 spin_unlock(&dentry
->d_lock
);
473 EXPORT_SYMBOL(d_clear_need_lookup
);
476 * Finish off a dentry we've decided to kill.
477 * dentry->d_lock must be held, returns with it unlocked.
478 * If ref is non-zero, then decrement the refcount too.
479 * Returns dentry requiring refcount drop, or NULL if we're done.
481 static inline struct dentry
*dentry_kill(struct dentry
*dentry
, int ref
)
482 __releases(dentry
->d_lock
)
485 struct dentry
*parent
;
487 inode
= dentry
->d_inode
;
488 if (inode
&& !spin_trylock(&inode
->i_lock
)) {
490 spin_unlock(&dentry
->d_lock
);
492 return dentry
; /* try again with same dentry */
497 parent
= dentry
->d_parent
;
498 if (parent
&& !spin_trylock(&parent
->d_lock
)) {
500 spin_unlock(&inode
->i_lock
);
507 * if dentry was on the d_lru list delete it from there.
508 * inform the fs via d_prune that this dentry is about to be
509 * unhashed and destroyed.
511 dentry_lru_prune(dentry
);
512 /* if it was on the hash then remove it */
514 return d_kill(dentry
, parent
);
520 * This is complicated by the fact that we do not want to put
521 * dentries that are no longer on any hash chain on the unused
522 * list: we'd much rather just get rid of them immediately.
524 * However, that implies that we have to traverse the dentry
525 * tree upwards to the parents which might _also_ now be
526 * scheduled for deletion (it may have been only waiting for
527 * its last child to go away).
529 * This tail recursion is done by hand as we don't want to depend
530 * on the compiler to always get this right (gcc generally doesn't).
531 * Real recursion would eat up our stack space.
535 * dput - release a dentry
536 * @dentry: dentry to release
538 * Release a dentry. This will drop the usage count and if appropriate
539 * call the dentry unlink method as well as removing it from the queues and
540 * releasing its resources. If the parent dentries were scheduled for release
541 * they too may now get deleted.
543 void dput(struct dentry
*dentry
)
549 if (dentry
->d_count
== 1)
551 spin_lock(&dentry
->d_lock
);
552 BUG_ON(!dentry
->d_count
);
553 if (dentry
->d_count
> 1) {
555 spin_unlock(&dentry
->d_lock
);
559 if (dentry
->d_flags
& DCACHE_OP_DELETE
) {
560 if (dentry
->d_op
->d_delete(dentry
))
564 /* Unreachable? Get rid of it */
565 if (d_unhashed(dentry
))
569 * If this dentry needs lookup, don't set the referenced flag so that it
570 * is more likely to be cleaned up by the dcache shrinker in case of
573 if (!d_need_lookup(dentry
))
574 dentry
->d_flags
|= DCACHE_REFERENCED
;
575 dentry_lru_add(dentry
);
578 spin_unlock(&dentry
->d_lock
);
582 dentry
= dentry_kill(dentry
, 1);
589 * d_invalidate - invalidate a dentry
590 * @dentry: dentry to invalidate
592 * Try to invalidate the dentry if it turns out to be
593 * possible. If there are other dentries that can be
594 * reached through this one we can't delete it and we
595 * return -EBUSY. On success we return 0.
600 int d_invalidate(struct dentry
* dentry
)
603 * If it's already been dropped, return OK.
605 spin_lock(&dentry
->d_lock
);
606 if (d_unhashed(dentry
)) {
607 spin_unlock(&dentry
->d_lock
);
611 * Check whether to do a partial shrink_dcache
612 * to get rid of unused child entries.
614 if (!list_empty(&dentry
->d_subdirs
)) {
615 spin_unlock(&dentry
->d_lock
);
616 shrink_dcache_parent(dentry
);
617 spin_lock(&dentry
->d_lock
);
621 * Somebody else still using it?
623 * If it's a directory, we can't drop it
624 * for fear of somebody re-populating it
625 * with children (even though dropping it
626 * would make it unreachable from the root,
627 * we might still populate it if it was a
628 * working directory or similar).
629 * We also need to leave mountpoints alone,
632 if (dentry
->d_count
> 1 && dentry
->d_inode
) {
633 if (S_ISDIR(dentry
->d_inode
->i_mode
) || d_mountpoint(dentry
)) {
634 spin_unlock(&dentry
->d_lock
);
640 spin_unlock(&dentry
->d_lock
);
643 EXPORT_SYMBOL(d_invalidate
);
645 /* This must be called with d_lock held */
646 static inline void __dget_dlock(struct dentry
*dentry
)
651 static inline void __dget(struct dentry
*dentry
)
653 spin_lock(&dentry
->d_lock
);
654 __dget_dlock(dentry
);
655 spin_unlock(&dentry
->d_lock
);
658 struct dentry
*dget_parent(struct dentry
*dentry
)
664 * Don't need rcu_dereference because we re-check it was correct under
668 ret
= dentry
->d_parent
;
669 spin_lock(&ret
->d_lock
);
670 if (unlikely(ret
!= dentry
->d_parent
)) {
671 spin_unlock(&ret
->d_lock
);
676 BUG_ON(!ret
->d_count
);
678 spin_unlock(&ret
->d_lock
);
681 EXPORT_SYMBOL(dget_parent
);
684 * d_find_alias - grab a hashed alias of inode
685 * @inode: inode in question
686 * @want_discon: flag, used by d_splice_alias, to request
687 * that only a DISCONNECTED alias be returned.
689 * If inode has a hashed alias, or is a directory and has any alias,
690 * acquire the reference to alias and return it. Otherwise return NULL.
691 * Notice that if inode is a directory there can be only one alias and
692 * it can be unhashed only if it has no children, or if it is the root
695 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
696 * any other hashed alias over that one unless @want_discon is set,
697 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
699 static struct dentry
*__d_find_alias(struct inode
*inode
, int want_discon
)
701 struct dentry
*alias
, *discon_alias
;
705 list_for_each_entry(alias
, &inode
->i_dentry
, d_alias
) {
706 spin_lock(&alias
->d_lock
);
707 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
708 if (IS_ROOT(alias
) &&
709 (alias
->d_flags
& DCACHE_DISCONNECTED
)) {
710 discon_alias
= alias
;
711 } else if (!want_discon
) {
713 spin_unlock(&alias
->d_lock
);
717 spin_unlock(&alias
->d_lock
);
720 alias
= discon_alias
;
721 spin_lock(&alias
->d_lock
);
722 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
723 if (IS_ROOT(alias
) &&
724 (alias
->d_flags
& DCACHE_DISCONNECTED
)) {
726 spin_unlock(&alias
->d_lock
);
730 spin_unlock(&alias
->d_lock
);
736 struct dentry
*d_find_alias(struct inode
*inode
)
738 struct dentry
*de
= NULL
;
740 if (!list_empty(&inode
->i_dentry
)) {
741 spin_lock(&inode
->i_lock
);
742 de
= __d_find_alias(inode
, 0);
743 spin_unlock(&inode
->i_lock
);
747 EXPORT_SYMBOL(d_find_alias
);
750 * Try to kill dentries associated with this inode.
751 * WARNING: you must own a reference to inode.
753 void d_prune_aliases(struct inode
*inode
)
755 struct dentry
*dentry
;
757 spin_lock(&inode
->i_lock
);
758 list_for_each_entry(dentry
, &inode
->i_dentry
, d_alias
) {
759 spin_lock(&dentry
->d_lock
);
760 if (!dentry
->d_count
) {
761 __dget_dlock(dentry
);
763 spin_unlock(&dentry
->d_lock
);
764 spin_unlock(&inode
->i_lock
);
768 spin_unlock(&dentry
->d_lock
);
770 spin_unlock(&inode
->i_lock
);
772 EXPORT_SYMBOL(d_prune_aliases
);
775 * Try to throw away a dentry - free the inode, dput the parent.
776 * Requires dentry->d_lock is held, and dentry->d_count == 0.
777 * Releases dentry->d_lock.
779 * This may fail if locks cannot be acquired no problem, just try again.
781 static void try_prune_one_dentry(struct dentry
*dentry
)
782 __releases(dentry
->d_lock
)
784 struct dentry
*parent
;
786 parent
= dentry_kill(dentry
, 0);
788 * If dentry_kill returns NULL, we have nothing more to do.
789 * if it returns the same dentry, trylocks failed. In either
790 * case, just loop again.
792 * Otherwise, we need to prune ancestors too. This is necessary
793 * to prevent quadratic behavior of shrink_dcache_parent(), but
794 * is also expected to be beneficial in reducing dentry cache
799 if (parent
== dentry
)
802 /* Prune ancestors. */
805 spin_lock(&dentry
->d_lock
);
806 if (dentry
->d_count
> 1) {
808 spin_unlock(&dentry
->d_lock
);
811 dentry
= dentry_kill(dentry
, 1);
815 static void shrink_dentry_list(struct list_head
*list
)
817 struct dentry
*dentry
;
821 dentry
= list_entry_rcu(list
->prev
, struct dentry
, d_lru
);
822 if (&dentry
->d_lru
== list
)
824 spin_lock(&dentry
->d_lock
);
825 if (dentry
!= list_entry(list
->prev
, struct dentry
, d_lru
)) {
826 spin_unlock(&dentry
->d_lock
);
831 * We found an inuse dentry which was not removed from
832 * the LRU because of laziness during lookup. Do not free
833 * it - just keep it off the LRU list.
835 if (dentry
->d_count
) {
836 dentry_lru_del(dentry
);
837 spin_unlock(&dentry
->d_lock
);
843 try_prune_one_dentry(dentry
);
851 * prune_dcache_sb - shrink the dcache
853 * @count: number of entries to try to free
855 * Attempt to shrink the superblock dcache LRU by @count entries. This is
856 * done when we need more memory an called from the superblock shrinker
859 * This function may fail to free any resources if all the dentries are in
862 void prune_dcache_sb(struct super_block
*sb
, int count
)
864 struct dentry
*dentry
;
865 LIST_HEAD(referenced
);
869 spin_lock(&dcache_lru_lock
);
870 while (!list_empty(&sb
->s_dentry_lru
)) {
871 dentry
= list_entry(sb
->s_dentry_lru
.prev
,
872 struct dentry
, d_lru
);
873 BUG_ON(dentry
->d_sb
!= sb
);
875 if (!spin_trylock(&dentry
->d_lock
)) {
876 spin_unlock(&dcache_lru_lock
);
881 if (dentry
->d_flags
& DCACHE_REFERENCED
) {
882 dentry
->d_flags
&= ~DCACHE_REFERENCED
;
883 list_move(&dentry
->d_lru
, &referenced
);
884 spin_unlock(&dentry
->d_lock
);
886 list_move_tail(&dentry
->d_lru
, &tmp
);
887 dentry
->d_flags
|= DCACHE_SHRINK_LIST
;
888 spin_unlock(&dentry
->d_lock
);
892 cond_resched_lock(&dcache_lru_lock
);
894 if (!list_empty(&referenced
))
895 list_splice(&referenced
, &sb
->s_dentry_lru
);
896 spin_unlock(&dcache_lru_lock
);
898 shrink_dentry_list(&tmp
);
902 * shrink_dcache_sb - shrink dcache for a superblock
905 * Shrink the dcache for the specified super block. This is used to free
906 * the dcache before unmounting a file system.
908 void shrink_dcache_sb(struct super_block
*sb
)
912 spin_lock(&dcache_lru_lock
);
913 while (!list_empty(&sb
->s_dentry_lru
)) {
914 list_splice_init(&sb
->s_dentry_lru
, &tmp
);
915 spin_unlock(&dcache_lru_lock
);
916 shrink_dentry_list(&tmp
);
917 spin_lock(&dcache_lru_lock
);
919 spin_unlock(&dcache_lru_lock
);
921 EXPORT_SYMBOL(shrink_dcache_sb
);
924 * destroy a single subtree of dentries for unmount
925 * - see the comments on shrink_dcache_for_umount() for a description of the
928 static void shrink_dcache_for_umount_subtree(struct dentry
*dentry
)
930 struct dentry
*parent
;
932 BUG_ON(!IS_ROOT(dentry
));
935 /* descend to the first leaf in the current subtree */
936 while (!list_empty(&dentry
->d_subdirs
))
937 dentry
= list_entry(dentry
->d_subdirs
.next
,
938 struct dentry
, d_u
.d_child
);
940 /* consume the dentries from this leaf up through its parents
941 * until we find one with children or run out altogether */
946 * remove the dentry from the lru, and inform
947 * the fs that this dentry is about to be
948 * unhashed and destroyed.
950 dentry_lru_prune(dentry
);
953 if (dentry
->d_count
!= 0) {
955 "BUG: Dentry %p{i=%lx,n=%s}"
957 " [unmount of %s %s]\n",
960 dentry
->d_inode
->i_ino
: 0UL,
963 dentry
->d_sb
->s_type
->name
,
968 if (IS_ROOT(dentry
)) {
970 list_del(&dentry
->d_u
.d_child
);
972 parent
= dentry
->d_parent
;
974 list_del(&dentry
->d_u
.d_child
);
977 inode
= dentry
->d_inode
;
979 dentry
->d_inode
= NULL
;
980 list_del_init(&dentry
->d_alias
);
981 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
982 dentry
->d_op
->d_iput(dentry
, inode
);
989 /* finished when we fall off the top of the tree,
990 * otherwise we ascend to the parent and move to the
991 * next sibling if there is one */
995 } while (list_empty(&dentry
->d_subdirs
));
997 dentry
= list_entry(dentry
->d_subdirs
.next
,
998 struct dentry
, d_u
.d_child
);
1003 * destroy the dentries attached to a superblock on unmounting
1004 * - we don't need to use dentry->d_lock because:
1005 * - the superblock is detached from all mountings and open files, so the
1006 * dentry trees will not be rearranged by the VFS
1007 * - s_umount is write-locked, so the memory pressure shrinker will ignore
1008 * any dentries belonging to this superblock that it comes across
1009 * - the filesystem itself is no longer permitted to rearrange the dentries
1010 * in this superblock
1012 void shrink_dcache_for_umount(struct super_block
*sb
)
1014 struct dentry
*dentry
;
1016 if (down_read_trylock(&sb
->s_umount
))
1019 dentry
= sb
->s_root
;
1022 shrink_dcache_for_umount_subtree(dentry
);
1024 while (!hlist_bl_empty(&sb
->s_anon
)) {
1025 dentry
= hlist_bl_entry(hlist_bl_first(&sb
->s_anon
), struct dentry
, d_hash
);
1026 shrink_dcache_for_umount_subtree(dentry
);
1031 * This tries to ascend one level of parenthood, but
1032 * we can race with renaming, so we need to re-check
1033 * the parenthood after dropping the lock and check
1034 * that the sequence number still matches.
1036 static struct dentry
*try_to_ascend(struct dentry
*old
, int locked
, unsigned seq
)
1038 struct dentry
*new = old
->d_parent
;
1041 spin_unlock(&old
->d_lock
);
1042 spin_lock(&new->d_lock
);
1045 * might go back up the wrong parent if we have had a rename
1048 if (new != old
->d_parent
||
1049 (old
->d_flags
& DCACHE_DISCONNECTED
) ||
1050 (!locked
&& read_seqretry(&rename_lock
, seq
))) {
1051 spin_unlock(&new->d_lock
);
1060 * Search for at least 1 mount point in the dentry's subdirs.
1061 * We descend to the next level whenever the d_subdirs
1062 * list is non-empty and continue searching.
1066 * have_submounts - check for mounts over a dentry
1067 * @parent: dentry to check.
1069 * Return true if the parent or its subdirectories contain
1072 int have_submounts(struct dentry
*parent
)
1074 struct dentry
*this_parent
;
1075 struct list_head
*next
;
1079 seq
= read_seqbegin(&rename_lock
);
1081 this_parent
= parent
;
1083 if (d_mountpoint(parent
))
1085 spin_lock(&this_parent
->d_lock
);
1087 next
= this_parent
->d_subdirs
.next
;
1089 while (next
!= &this_parent
->d_subdirs
) {
1090 struct list_head
*tmp
= next
;
1091 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_u
.d_child
);
1094 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1095 /* Have we found a mount point ? */
1096 if (d_mountpoint(dentry
)) {
1097 spin_unlock(&dentry
->d_lock
);
1098 spin_unlock(&this_parent
->d_lock
);
1101 if (!list_empty(&dentry
->d_subdirs
)) {
1102 spin_unlock(&this_parent
->d_lock
);
1103 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
1104 this_parent
= dentry
;
1105 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
1108 spin_unlock(&dentry
->d_lock
);
1111 * All done at this level ... ascend and resume the search.
1113 if (this_parent
!= parent
) {
1114 struct dentry
*child
= this_parent
;
1115 this_parent
= try_to_ascend(this_parent
, locked
, seq
);
1118 next
= child
->d_u
.d_child
.next
;
1121 spin_unlock(&this_parent
->d_lock
);
1122 if (!locked
&& read_seqretry(&rename_lock
, seq
))
1125 write_sequnlock(&rename_lock
);
1126 return 0; /* No mount points found in tree */
1128 if (!locked
&& read_seqretry(&rename_lock
, seq
))
1131 write_sequnlock(&rename_lock
);
1136 write_seqlock(&rename_lock
);
1139 EXPORT_SYMBOL(have_submounts
);
1142 * Search the dentry child list for the specified parent,
1143 * and move any unused dentries to the end of the unused
1144 * list for prune_dcache(). We descend to the next level
1145 * whenever the d_subdirs list is non-empty and continue
1148 * It returns zero iff there are no unused children,
1149 * otherwise it returns the number of children moved to
1150 * the end of the unused list. This may not be the total
1151 * number of unused children, because select_parent can
1152 * drop the lock and return early due to latency
1155 static int select_parent(struct dentry
*parent
, struct list_head
*dispose
)
1157 struct dentry
*this_parent
;
1158 struct list_head
*next
;
1163 seq
= read_seqbegin(&rename_lock
);
1165 this_parent
= parent
;
1166 spin_lock(&this_parent
->d_lock
);
1168 next
= this_parent
->d_subdirs
.next
;
1170 while (next
!= &this_parent
->d_subdirs
) {
1171 struct list_head
*tmp
= next
;
1172 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_u
.d_child
);
1175 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1178 * move only zero ref count dentries to the dispose list.
1180 * Those which are presently on the shrink list, being processed
1181 * by shrink_dentry_list(), shouldn't be moved. Otherwise the
1182 * loop in shrink_dcache_parent() might not make any progress
1185 if (dentry
->d_count
) {
1186 dentry_lru_del(dentry
);
1187 } else if (!(dentry
->d_flags
& DCACHE_SHRINK_LIST
)) {
1188 dentry_lru_move_list(dentry
, dispose
);
1189 dentry
->d_flags
|= DCACHE_SHRINK_LIST
;
1193 * We can return to the caller if we have found some (this
1194 * ensures forward progress). We'll be coming back to find
1197 if (found
&& need_resched()) {
1198 spin_unlock(&dentry
->d_lock
);
1203 * Descend a level if the d_subdirs list is non-empty.
1205 if (!list_empty(&dentry
->d_subdirs
)) {
1206 spin_unlock(&this_parent
->d_lock
);
1207 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
1208 this_parent
= dentry
;
1209 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
1213 spin_unlock(&dentry
->d_lock
);
1216 * All done at this level ... ascend and resume the search.
1218 if (this_parent
!= parent
) {
1219 struct dentry
*child
= this_parent
;
1220 this_parent
= try_to_ascend(this_parent
, locked
, seq
);
1223 next
= child
->d_u
.d_child
.next
;
1227 spin_unlock(&this_parent
->d_lock
);
1228 if (!locked
&& read_seqretry(&rename_lock
, seq
))
1231 write_sequnlock(&rename_lock
);
1238 write_seqlock(&rename_lock
);
1243 * shrink_dcache_parent - prune dcache
1244 * @parent: parent of entries to prune
1246 * Prune the dcache to remove unused children of the parent dentry.
1248 void shrink_dcache_parent(struct dentry
* parent
)
1253 while ((found
= select_parent(parent
, &dispose
)) != 0)
1254 shrink_dentry_list(&dispose
);
1256 EXPORT_SYMBOL(shrink_dcache_parent
);
1259 * __d_alloc - allocate a dcache entry
1260 * @sb: filesystem it will belong to
1261 * @name: qstr of the name
1263 * Allocates a dentry. It returns %NULL if there is insufficient memory
1264 * available. On a success the dentry is returned. The name passed in is
1265 * copied and the copy passed in may be reused after this call.
1268 struct dentry
*__d_alloc(struct super_block
*sb
, const struct qstr
*name
)
1270 struct dentry
*dentry
;
1273 dentry
= kmem_cache_alloc(dentry_cache
, GFP_KERNEL
);
1278 * We guarantee that the inline name is always NUL-terminated.
1279 * This way the memcpy() done by the name switching in rename
1280 * will still always have a NUL at the end, even if we might
1281 * be overwriting an internal NUL character
1283 dentry
->d_iname
[DNAME_INLINE_LEN
-1] = 0;
1284 if (name
->len
> DNAME_INLINE_LEN
-1) {
1285 dname
= kmalloc(name
->len
+ 1, GFP_KERNEL
);
1287 kmem_cache_free(dentry_cache
, dentry
);
1291 dname
= dentry
->d_iname
;
1294 dentry
->d_name
.len
= name
->len
;
1295 dentry
->d_name
.hash
= name
->hash
;
1296 memcpy(dname
, name
->name
, name
->len
);
1297 dname
[name
->len
] = 0;
1299 /* Make sure we always see the terminating NUL character */
1301 dentry
->d_name
.name
= dname
;
1303 dentry
->d_count
= 1;
1304 dentry
->d_flags
= 0;
1305 spin_lock_init(&dentry
->d_lock
);
1306 seqcount_init(&dentry
->d_seq
);
1307 dentry
->d_inode
= NULL
;
1308 dentry
->d_parent
= dentry
;
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
);
1317 d_set_d_op(dentry
, dentry
->d_sb
->s_d_op
);
1319 this_cpu_inc(nr_dentry
);
1325 * d_alloc - allocate a dcache entry
1326 * @parent: parent of entry to allocate
1327 * @name: qstr of the name
1329 * Allocates a dentry. It returns %NULL if there is insufficient memory
1330 * available. On a success the dentry is returned. The name passed in is
1331 * copied and the copy passed in may be reused after this call.
1333 struct dentry
*d_alloc(struct dentry
* parent
, const struct qstr
*name
)
1335 struct dentry
*dentry
= __d_alloc(parent
->d_sb
, name
);
1339 spin_lock(&parent
->d_lock
);
1341 * don't need child lock because it is not subject
1342 * to concurrency here
1344 __dget_dlock(parent
);
1345 dentry
->d_parent
= parent
;
1346 list_add(&dentry
->d_u
.d_child
, &parent
->d_subdirs
);
1347 spin_unlock(&parent
->d_lock
);
1351 EXPORT_SYMBOL(d_alloc
);
1353 struct dentry
*d_alloc_pseudo(struct super_block
*sb
, const struct qstr
*name
)
1355 struct dentry
*dentry
= __d_alloc(sb
, name
);
1357 dentry
->d_flags
|= DCACHE_DISCONNECTED
;
1360 EXPORT_SYMBOL(d_alloc_pseudo
);
1362 struct dentry
*d_alloc_name(struct dentry
*parent
, const char *name
)
1367 q
.len
= strlen(name
);
1368 q
.hash
= full_name_hash(q
.name
, q
.len
);
1369 return d_alloc(parent
, &q
);
1371 EXPORT_SYMBOL(d_alloc_name
);
1373 void d_set_d_op(struct dentry
*dentry
, const struct dentry_operations
*op
)
1375 WARN_ON_ONCE(dentry
->d_op
);
1376 WARN_ON_ONCE(dentry
->d_flags
& (DCACHE_OP_HASH
|
1378 DCACHE_OP_REVALIDATE
|
1379 DCACHE_OP_DELETE
));
1384 dentry
->d_flags
|= DCACHE_OP_HASH
;
1386 dentry
->d_flags
|= DCACHE_OP_COMPARE
;
1387 if (op
->d_revalidate
)
1388 dentry
->d_flags
|= DCACHE_OP_REVALIDATE
;
1390 dentry
->d_flags
|= DCACHE_OP_DELETE
;
1392 dentry
->d_flags
|= DCACHE_OP_PRUNE
;
1395 EXPORT_SYMBOL(d_set_d_op
);
1397 static void __d_instantiate(struct dentry
*dentry
, struct inode
*inode
)
1399 spin_lock(&dentry
->d_lock
);
1401 if (unlikely(IS_AUTOMOUNT(inode
)))
1402 dentry
->d_flags
|= DCACHE_NEED_AUTOMOUNT
;
1403 list_add(&dentry
->d_alias
, &inode
->i_dentry
);
1405 dentry
->d_inode
= inode
;
1406 dentry_rcuwalk_barrier(dentry
);
1407 spin_unlock(&dentry
->d_lock
);
1408 fsnotify_d_instantiate(dentry
, inode
);
1412 * d_instantiate - fill in inode information for a dentry
1413 * @entry: dentry to complete
1414 * @inode: inode to attach to this dentry
1416 * Fill in inode information in the entry.
1418 * This turns negative dentries into productive full members
1421 * NOTE! This assumes that the inode count has been incremented
1422 * (or otherwise set) by the caller to indicate that it is now
1423 * in use by the dcache.
1426 void d_instantiate(struct dentry
*entry
, struct inode
* inode
)
1428 BUG_ON(!list_empty(&entry
->d_alias
));
1430 spin_lock(&inode
->i_lock
);
1431 __d_instantiate(entry
, inode
);
1433 spin_unlock(&inode
->i_lock
);
1434 security_d_instantiate(entry
, inode
);
1436 EXPORT_SYMBOL(d_instantiate
);
1439 * d_instantiate_unique - instantiate a non-aliased dentry
1440 * @entry: dentry to instantiate
1441 * @inode: inode to attach to this dentry
1443 * Fill in inode information in the entry. On success, it returns NULL.
1444 * If an unhashed alias of "entry" already exists, then we return the
1445 * aliased dentry instead and drop one reference to inode.
1447 * Note that in order to avoid conflicts with rename() etc, the caller
1448 * had better be holding the parent directory semaphore.
1450 * This also assumes that the inode count has been incremented
1451 * (or otherwise set) by the caller to indicate that it is now
1452 * in use by the dcache.
1454 static struct dentry
*__d_instantiate_unique(struct dentry
*entry
,
1455 struct inode
*inode
)
1457 struct dentry
*alias
;
1458 int len
= entry
->d_name
.len
;
1459 const char *name
= entry
->d_name
.name
;
1460 unsigned int hash
= entry
->d_name
.hash
;
1463 __d_instantiate(entry
, NULL
);
1467 list_for_each_entry(alias
, &inode
->i_dentry
, d_alias
) {
1469 * Don't need alias->d_lock here, because aliases with
1470 * d_parent == entry->d_parent are not subject to name or
1471 * parent changes, because the parent inode i_mutex is held.
1473 if (alias
->d_name
.hash
!= hash
)
1475 if (alias
->d_parent
!= entry
->d_parent
)
1477 if (alias
->d_name
.len
!= len
)
1479 if (dentry_cmp(alias
, name
, len
))
1485 __d_instantiate(entry
, inode
);
1489 struct dentry
*d_instantiate_unique(struct dentry
*entry
, struct inode
*inode
)
1491 struct dentry
*result
;
1493 BUG_ON(!list_empty(&entry
->d_alias
));
1496 spin_lock(&inode
->i_lock
);
1497 result
= __d_instantiate_unique(entry
, inode
);
1499 spin_unlock(&inode
->i_lock
);
1502 security_d_instantiate(entry
, inode
);
1506 BUG_ON(!d_unhashed(result
));
1511 EXPORT_SYMBOL(d_instantiate_unique
);
1513 struct dentry
*d_make_root(struct inode
*root_inode
)
1515 struct dentry
*res
= NULL
;
1518 static const struct qstr name
= QSTR_INIT("/", 1);
1520 res
= __d_alloc(root_inode
->i_sb
, &name
);
1522 d_instantiate(res
, root_inode
);
1528 EXPORT_SYMBOL(d_make_root
);
1530 static struct dentry
* __d_find_any_alias(struct inode
*inode
)
1532 struct dentry
*alias
;
1534 if (list_empty(&inode
->i_dentry
))
1536 alias
= list_first_entry(&inode
->i_dentry
, struct dentry
, d_alias
);
1542 * d_find_any_alias - find any alias for a given inode
1543 * @inode: inode to find an alias for
1545 * If any aliases exist for the given inode, take and return a
1546 * reference for one of them. If no aliases exist, return %NULL.
1548 struct dentry
*d_find_any_alias(struct inode
*inode
)
1552 spin_lock(&inode
->i_lock
);
1553 de
= __d_find_any_alias(inode
);
1554 spin_unlock(&inode
->i_lock
);
1557 EXPORT_SYMBOL(d_find_any_alias
);
1560 * d_obtain_alias - find or allocate a dentry for a given inode
1561 * @inode: inode to allocate the dentry for
1563 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1564 * similar open by handle operations. The returned dentry may be anonymous,
1565 * or may have a full name (if the inode was already in the cache).
1567 * When called on a directory inode, we must ensure that the inode only ever
1568 * has one dentry. If a dentry is found, that is returned instead of
1569 * allocating a new one.
1571 * On successful return, the reference to the inode has been transferred
1572 * to the dentry. In case of an error the reference on the inode is released.
1573 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1574 * be passed in and will be the error will be propagate to the return value,
1575 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1577 struct dentry
*d_obtain_alias(struct inode
*inode
)
1579 static const struct qstr anonstring
= { .name
= "" };
1584 return ERR_PTR(-ESTALE
);
1586 return ERR_CAST(inode
);
1588 res
= d_find_any_alias(inode
);
1592 tmp
= __d_alloc(inode
->i_sb
, &anonstring
);
1594 res
= ERR_PTR(-ENOMEM
);
1598 spin_lock(&inode
->i_lock
);
1599 res
= __d_find_any_alias(inode
);
1601 spin_unlock(&inode
->i_lock
);
1606 /* attach a disconnected dentry */
1607 spin_lock(&tmp
->d_lock
);
1608 tmp
->d_inode
= inode
;
1609 tmp
->d_flags
|= DCACHE_DISCONNECTED
;
1610 list_add(&tmp
->d_alias
, &inode
->i_dentry
);
1611 hlist_bl_lock(&tmp
->d_sb
->s_anon
);
1612 hlist_bl_add_head(&tmp
->d_hash
, &tmp
->d_sb
->s_anon
);
1613 hlist_bl_unlock(&tmp
->d_sb
->s_anon
);
1614 spin_unlock(&tmp
->d_lock
);
1615 spin_unlock(&inode
->i_lock
);
1616 security_d_instantiate(tmp
, inode
);
1621 if (res
&& !IS_ERR(res
))
1622 security_d_instantiate(res
, inode
);
1626 EXPORT_SYMBOL(d_obtain_alias
);
1629 * d_splice_alias - splice a disconnected dentry into the tree if one exists
1630 * @inode: the inode which may have a disconnected dentry
1631 * @dentry: a negative dentry which we want to point to the inode.
1633 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1634 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1635 * and return it, else simply d_add the inode to the dentry and return NULL.
1637 * This is needed in the lookup routine of any filesystem that is exportable
1638 * (via knfsd) so that we can build dcache paths to directories effectively.
1640 * If a dentry was found and moved, then it is returned. Otherwise NULL
1641 * is returned. This matches the expected return value of ->lookup.
1644 struct dentry
*d_splice_alias(struct inode
*inode
, struct dentry
*dentry
)
1646 struct dentry
*new = NULL
;
1649 return ERR_CAST(inode
);
1651 if (inode
&& S_ISDIR(inode
->i_mode
)) {
1652 spin_lock(&inode
->i_lock
);
1653 new = __d_find_any_alias(inode
);
1655 spin_unlock(&inode
->i_lock
);
1656 security_d_instantiate(new, inode
);
1657 d_move(new, dentry
);
1660 /* already taking inode->i_lock, so d_add() by hand */
1661 __d_instantiate(dentry
, inode
);
1662 spin_unlock(&inode
->i_lock
);
1663 security_d_instantiate(dentry
, inode
);
1667 d_add(dentry
, inode
);
1670 EXPORT_SYMBOL(d_splice_alias
);
1673 * d_add_ci - lookup or allocate new dentry with case-exact name
1674 * @inode: the inode case-insensitive lookup has found
1675 * @dentry: the negative dentry that was passed to the parent's lookup func
1676 * @name: the case-exact name to be associated with the returned dentry
1678 * This is to avoid filling the dcache with case-insensitive names to the
1679 * same inode, only the actual correct case is stored in the dcache for
1680 * case-insensitive filesystems.
1682 * For a case-insensitive lookup match and if the the case-exact dentry
1683 * already exists in in the dcache, use it and return it.
1685 * If no entry exists with the exact case name, allocate new dentry with
1686 * the exact case, and return the spliced entry.
1688 struct dentry
*d_add_ci(struct dentry
*dentry
, struct inode
*inode
,
1692 struct dentry
*found
;
1696 * First check if a dentry matching the name already exists,
1697 * if not go ahead and create it now.
1699 found
= d_hash_and_lookup(dentry
->d_parent
, name
);
1701 new = d_alloc(dentry
->d_parent
, name
);
1707 found
= d_splice_alias(inode
, new);
1716 * If a matching dentry exists, and it's not negative use it.
1718 * Decrement the reference count to balance the iget() done
1721 if (found
->d_inode
) {
1722 if (unlikely(found
->d_inode
!= inode
)) {
1723 /* This can't happen because bad inodes are unhashed. */
1724 BUG_ON(!is_bad_inode(inode
));
1725 BUG_ON(!is_bad_inode(found
->d_inode
));
1732 * We are going to instantiate this dentry, unhash it and clear the
1733 * lookup flag so we can do that.
1735 if (unlikely(d_need_lookup(found
)))
1736 d_clear_need_lookup(found
);
1739 * Negative dentry: instantiate it unless the inode is a directory and
1740 * already has a dentry.
1742 new = d_splice_alias(inode
, found
);
1751 return ERR_PTR(error
);
1753 EXPORT_SYMBOL(d_add_ci
);
1756 * Do the slow-case of the dentry name compare.
1758 * Unlike the dentry_cmp() function, we need to atomically
1759 * load the name, length and inode information, so that the
1760 * filesystem can rely on them, and can use the 'name' and
1761 * 'len' information without worrying about walking off the
1762 * end of memory etc.
1764 * Thus the read_seqcount_retry() and the "duplicate" info
1765 * in arguments (the low-level filesystem should not look
1766 * at the dentry inode or name contents directly, since
1767 * rename can change them while we're in RCU mode).
1769 enum slow_d_compare
{
1775 static noinline
enum slow_d_compare
slow_dentry_cmp(
1776 const struct dentry
*parent
,
1777 struct inode
*inode
,
1778 struct dentry
*dentry
,
1780 const struct qstr
*name
)
1782 int tlen
= dentry
->d_name
.len
;
1783 const char *tname
= dentry
->d_name
.name
;
1784 struct inode
*i
= dentry
->d_inode
;
1786 if (read_seqcount_retry(&dentry
->d_seq
, seq
)) {
1788 return D_COMP_SEQRETRY
;
1790 if (parent
->d_op
->d_compare(parent
, inode
,
1793 return D_COMP_NOMATCH
;
1798 * __d_lookup_rcu - search for a dentry (racy, store-free)
1799 * @parent: parent dentry
1800 * @name: qstr of name we wish to find
1801 * @seqp: returns d_seq value at the point where the dentry was found
1802 * @inode: returns dentry->d_inode when the inode was found valid.
1803 * Returns: dentry, or NULL
1805 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
1806 * resolution (store-free path walking) design described in
1807 * Documentation/filesystems/path-lookup.txt.
1809 * This is not to be used outside core vfs.
1811 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
1812 * held, and rcu_read_lock held. The returned dentry must not be stored into
1813 * without taking d_lock and checking d_seq sequence count against @seq
1816 * A refcount may be taken on the found dentry with the __d_rcu_to_refcount
1819 * Alternatively, __d_lookup_rcu may be called again to look up the child of
1820 * the returned dentry, so long as its parent's seqlock is checked after the
1821 * child is looked up. Thus, an interlocking stepping of sequence lock checks
1822 * is formed, giving integrity down the path walk.
1824 * NOTE! The caller *has* to check the resulting dentry against the sequence
1825 * number we've returned before using any of the resulting dentry state!
1827 struct dentry
*__d_lookup_rcu(const struct dentry
*parent
,
1828 const struct qstr
*name
,
1829 unsigned *seqp
, struct inode
*inode
)
1831 u64 hashlen
= name
->hash_len
;
1832 const unsigned char *str
= name
->name
;
1833 struct hlist_bl_head
*b
= d_hash(parent
, hashlen_hash(hashlen
));
1834 struct hlist_bl_node
*node
;
1835 struct dentry
*dentry
;
1838 * Note: There is significant duplication with __d_lookup_rcu which is
1839 * required to prevent single threaded performance regressions
1840 * especially on architectures where smp_rmb (in seqcounts) are costly.
1841 * Keep the two functions in sync.
1845 * The hash list is protected using RCU.
1847 * Carefully use d_seq when comparing a candidate dentry, to avoid
1848 * races with d_move().
1850 * It is possible that concurrent renames can mess up our list
1851 * walk here and result in missing our dentry, resulting in the
1852 * false-negative result. d_lookup() protects against concurrent
1853 * renames using rename_lock seqlock.
1855 * See Documentation/filesystems/path-lookup.txt for more details.
1857 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
1862 * The dentry sequence count protects us from concurrent
1863 * renames, and thus protects inode, parent and name fields.
1865 * The caller must perform a seqcount check in order
1866 * to do anything useful with the returned dentry,
1867 * including using the 'd_inode' pointer.
1869 * NOTE! We do a "raw" seqcount_begin here. That means that
1870 * we don't wait for the sequence count to stabilize if it
1871 * is in the middle of a sequence change. If we do the slow
1872 * dentry compare, we will do seqretries until it is stable,
1873 * and if we end up with a successful lookup, we actually
1874 * want to exit RCU lookup anyway.
1876 seq
= raw_seqcount_begin(&dentry
->d_seq
);
1877 if (dentry
->d_parent
!= parent
)
1879 if (d_unhashed(dentry
))
1883 if (unlikely(parent
->d_flags
& DCACHE_OP_COMPARE
)) {
1884 if (dentry
->d_name
.hash
!= hashlen_hash(hashlen
))
1886 switch (slow_dentry_cmp(parent
, inode
, dentry
, seq
, name
)) {
1889 case D_COMP_NOMATCH
:
1896 if (dentry
->d_name
.hash_len
!= hashlen
)
1898 if (!dentry_cmp(dentry
, str
, hashlen_len(hashlen
)))
1905 * d_lookup - search for a dentry
1906 * @parent: parent dentry
1907 * @name: qstr of name we wish to find
1908 * Returns: dentry, or NULL
1910 * d_lookup searches the children of the parent dentry for the name in
1911 * question. If the dentry is found its reference count is incremented and the
1912 * dentry is returned. The caller must use dput to free the entry when it has
1913 * finished using it. %NULL is returned if the dentry does not exist.
1915 struct dentry
*d_lookup(struct dentry
*parent
, struct qstr
*name
)
1917 struct dentry
*dentry
;
1921 seq
= read_seqbegin(&rename_lock
);
1922 dentry
= __d_lookup(parent
, name
);
1925 } while (read_seqretry(&rename_lock
, seq
));
1928 EXPORT_SYMBOL(d_lookup
);
1931 * __d_lookup - search for a dentry (racy)
1932 * @parent: parent dentry
1933 * @name: qstr of name we wish to find
1934 * Returns: dentry, or NULL
1936 * __d_lookup is like d_lookup, however it may (rarely) return a
1937 * false-negative result due to unrelated rename activity.
1939 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
1940 * however it must be used carefully, eg. with a following d_lookup in
1941 * the case of failure.
1943 * __d_lookup callers must be commented.
1945 struct dentry
*__d_lookup(struct dentry
*parent
, struct qstr
*name
)
1947 unsigned int len
= name
->len
;
1948 unsigned int hash
= name
->hash
;
1949 const unsigned char *str
= name
->name
;
1950 struct hlist_bl_head
*b
= d_hash(parent
, hash
);
1951 struct hlist_bl_node
*node
;
1952 struct dentry
*found
= NULL
;
1953 struct dentry
*dentry
;
1956 * Note: There is significant duplication with __d_lookup_rcu which is
1957 * required to prevent single threaded performance regressions
1958 * especially on architectures where smp_rmb (in seqcounts) are costly.
1959 * Keep the two functions in sync.
1963 * The hash list is protected using RCU.
1965 * Take d_lock when comparing a candidate dentry, to avoid races
1968 * It is possible that concurrent renames can mess up our list
1969 * walk here and result in missing our dentry, resulting in the
1970 * false-negative result. d_lookup() protects against concurrent
1971 * renames using rename_lock seqlock.
1973 * See Documentation/filesystems/path-lookup.txt for more details.
1977 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
1979 if (dentry
->d_name
.hash
!= hash
)
1982 spin_lock(&dentry
->d_lock
);
1983 if (dentry
->d_parent
!= parent
)
1985 if (d_unhashed(dentry
))
1989 * It is safe to compare names since d_move() cannot
1990 * change the qstr (protected by d_lock).
1992 if (parent
->d_flags
& DCACHE_OP_COMPARE
) {
1993 int tlen
= dentry
->d_name
.len
;
1994 const char *tname
= dentry
->d_name
.name
;
1995 if (parent
->d_op
->d_compare(parent
, parent
->d_inode
,
1996 dentry
, dentry
->d_inode
,
2000 if (dentry
->d_name
.len
!= len
)
2002 if (dentry_cmp(dentry
, str
, len
))
2008 spin_unlock(&dentry
->d_lock
);
2011 spin_unlock(&dentry
->d_lock
);
2019 * d_hash_and_lookup - hash the qstr then search for a dentry
2020 * @dir: Directory to search in
2021 * @name: qstr of name we wish to find
2023 * On hash failure or on lookup failure NULL is returned.
2025 struct dentry
*d_hash_and_lookup(struct dentry
*dir
, struct qstr
*name
)
2027 struct dentry
*dentry
= NULL
;
2030 * Check for a fs-specific hash function. Note that we must
2031 * calculate the standard hash first, as the d_op->d_hash()
2032 * routine may choose to leave the hash value unchanged.
2034 name
->hash
= full_name_hash(name
->name
, name
->len
);
2035 if (dir
->d_flags
& DCACHE_OP_HASH
) {
2036 if (dir
->d_op
->d_hash(dir
, dir
->d_inode
, name
) < 0)
2039 dentry
= d_lookup(dir
, name
);
2045 * d_validate - verify dentry provided from insecure source (deprecated)
2046 * @dentry: The dentry alleged to be valid child of @dparent
2047 * @dparent: The parent dentry (known to be valid)
2049 * An insecure source has sent us a dentry, here we verify it and dget() it.
2050 * This is used by ncpfs in its readdir implementation.
2051 * Zero is returned in the dentry is invalid.
2053 * This function is slow for big directories, and deprecated, do not use it.
2055 int d_validate(struct dentry
*dentry
, struct dentry
*dparent
)
2057 struct dentry
*child
;
2059 spin_lock(&dparent
->d_lock
);
2060 list_for_each_entry(child
, &dparent
->d_subdirs
, d_u
.d_child
) {
2061 if (dentry
== child
) {
2062 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
2063 __dget_dlock(dentry
);
2064 spin_unlock(&dentry
->d_lock
);
2065 spin_unlock(&dparent
->d_lock
);
2069 spin_unlock(&dparent
->d_lock
);
2073 EXPORT_SYMBOL(d_validate
);
2076 * When a file is deleted, we have two options:
2077 * - turn this dentry into a negative dentry
2078 * - unhash this dentry and free it.
2080 * Usually, we want to just turn this into
2081 * a negative dentry, but if anybody else is
2082 * currently using the dentry or the inode
2083 * we can't do that and we fall back on removing
2084 * it from the hash queues and waiting for
2085 * it to be deleted later when it has no users
2089 * d_delete - delete a dentry
2090 * @dentry: The dentry to delete
2092 * Turn the dentry into a negative dentry if possible, otherwise
2093 * remove it from the hash queues so it can be deleted later
2096 void d_delete(struct dentry
* dentry
)
2098 struct inode
*inode
;
2101 * Are we the only user?
2104 spin_lock(&dentry
->d_lock
);
2105 inode
= dentry
->d_inode
;
2106 isdir
= S_ISDIR(inode
->i_mode
);
2107 if (dentry
->d_count
== 1) {
2108 if (inode
&& !spin_trylock(&inode
->i_lock
)) {
2109 spin_unlock(&dentry
->d_lock
);
2113 dentry
->d_flags
&= ~DCACHE_CANT_MOUNT
;
2114 dentry_unlink_inode(dentry
);
2115 fsnotify_nameremove(dentry
, isdir
);
2119 if (!d_unhashed(dentry
))
2122 spin_unlock(&dentry
->d_lock
);
2124 fsnotify_nameremove(dentry
, isdir
);
2126 EXPORT_SYMBOL(d_delete
);
2128 static void __d_rehash(struct dentry
* entry
, struct hlist_bl_head
*b
)
2130 BUG_ON(!d_unhashed(entry
));
2132 entry
->d_flags
|= DCACHE_RCUACCESS
;
2133 hlist_bl_add_head_rcu(&entry
->d_hash
, b
);
2137 static void _d_rehash(struct dentry
* entry
)
2139 __d_rehash(entry
, d_hash(entry
->d_parent
, entry
->d_name
.hash
));
2143 * d_rehash - add an entry back to the hash
2144 * @entry: dentry to add to the hash
2146 * Adds a dentry to the hash according to its name.
2149 void d_rehash(struct dentry
* entry
)
2151 spin_lock(&entry
->d_lock
);
2153 spin_unlock(&entry
->d_lock
);
2155 EXPORT_SYMBOL(d_rehash
);
2158 * dentry_update_name_case - update case insensitive dentry with a new name
2159 * @dentry: dentry to be updated
2162 * Update a case insensitive dentry with new case of name.
2164 * dentry must have been returned by d_lookup with name @name. Old and new
2165 * name lengths must match (ie. no d_compare which allows mismatched name
2168 * Parent inode i_mutex must be held over d_lookup and into this call (to
2169 * keep renames and concurrent inserts, and readdir(2) away).
2171 void dentry_update_name_case(struct dentry
*dentry
, struct qstr
*name
)
2173 BUG_ON(!mutex_is_locked(&dentry
->d_parent
->d_inode
->i_mutex
));
2174 BUG_ON(dentry
->d_name
.len
!= name
->len
); /* d_lookup gives this */
2176 spin_lock(&dentry
->d_lock
);
2177 write_seqcount_begin(&dentry
->d_seq
);
2178 memcpy((unsigned char *)dentry
->d_name
.name
, name
->name
, name
->len
);
2179 write_seqcount_end(&dentry
->d_seq
);
2180 spin_unlock(&dentry
->d_lock
);
2182 EXPORT_SYMBOL(dentry_update_name_case
);
2184 static void switch_names(struct dentry
*dentry
, struct dentry
*target
)
2186 if (dname_external(target
)) {
2187 if (dname_external(dentry
)) {
2189 * Both external: swap the pointers
2191 swap(target
->d_name
.name
, dentry
->d_name
.name
);
2194 * dentry:internal, target:external. Steal target's
2195 * storage and make target internal.
2197 memcpy(target
->d_iname
, dentry
->d_name
.name
,
2198 dentry
->d_name
.len
+ 1);
2199 dentry
->d_name
.name
= target
->d_name
.name
;
2200 target
->d_name
.name
= target
->d_iname
;
2203 if (dname_external(dentry
)) {
2205 * dentry:external, target:internal. Give dentry's
2206 * storage to target and make dentry internal
2208 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2209 target
->d_name
.len
+ 1);
2210 target
->d_name
.name
= dentry
->d_name
.name
;
2211 dentry
->d_name
.name
= dentry
->d_iname
;
2214 * Both are internal. Just copy target to dentry
2216 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2217 target
->d_name
.len
+ 1);
2218 dentry
->d_name
.len
= target
->d_name
.len
;
2222 swap(dentry
->d_name
.len
, target
->d_name
.len
);
2225 static void dentry_lock_for_move(struct dentry
*dentry
, struct dentry
*target
)
2228 * XXXX: do we really need to take target->d_lock?
2230 if (IS_ROOT(dentry
) || dentry
->d_parent
== target
->d_parent
)
2231 spin_lock(&target
->d_parent
->d_lock
);
2233 if (d_ancestor(dentry
->d_parent
, target
->d_parent
)) {
2234 spin_lock(&dentry
->d_parent
->d_lock
);
2235 spin_lock_nested(&target
->d_parent
->d_lock
,
2236 DENTRY_D_LOCK_NESTED
);
2238 spin_lock(&target
->d_parent
->d_lock
);
2239 spin_lock_nested(&dentry
->d_parent
->d_lock
,
2240 DENTRY_D_LOCK_NESTED
);
2243 if (target
< dentry
) {
2244 spin_lock_nested(&target
->d_lock
, 2);
2245 spin_lock_nested(&dentry
->d_lock
, 3);
2247 spin_lock_nested(&dentry
->d_lock
, 2);
2248 spin_lock_nested(&target
->d_lock
, 3);
2252 static void dentry_unlock_parents_for_move(struct dentry
*dentry
,
2253 struct dentry
*target
)
2255 if (target
->d_parent
!= dentry
->d_parent
)
2256 spin_unlock(&dentry
->d_parent
->d_lock
);
2257 if (target
->d_parent
!= target
)
2258 spin_unlock(&target
->d_parent
->d_lock
);
2262 * When switching names, the actual string doesn't strictly have to
2263 * be preserved in the target - because we're dropping the target
2264 * anyway. As such, we can just do a simple memcpy() to copy over
2265 * the new name before we switch.
2267 * Note that we have to be a lot more careful about getting the hash
2268 * switched - we have to switch the hash value properly even if it
2269 * then no longer matches the actual (corrupted) string of the target.
2270 * The hash value has to match the hash queue that the dentry is on..
2273 * __d_move - move a dentry
2274 * @dentry: entry to move
2275 * @target: new dentry
2277 * Update the dcache to reflect the move of a file name. Negative
2278 * dcache entries should not be moved in this way. Caller must hold
2279 * rename_lock, the i_mutex of the source and target directories,
2280 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2282 static void __d_move(struct dentry
* dentry
, struct dentry
* target
)
2284 if (!dentry
->d_inode
)
2285 printk(KERN_WARNING
"VFS: moving negative dcache entry\n");
2287 BUG_ON(d_ancestor(dentry
, target
));
2288 BUG_ON(d_ancestor(target
, dentry
));
2290 dentry_lock_for_move(dentry
, target
);
2292 write_seqcount_begin(&dentry
->d_seq
);
2293 write_seqcount_begin(&target
->d_seq
);
2295 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
2298 * Move the dentry to the target hash queue. Don't bother checking
2299 * for the same hash queue because of how unlikely it is.
2302 __d_rehash(dentry
, d_hash(target
->d_parent
, target
->d_name
.hash
));
2304 /* Unhash the target: dput() will then get rid of it */
2307 list_del(&dentry
->d_u
.d_child
);
2308 list_del(&target
->d_u
.d_child
);
2310 /* Switch the names.. */
2311 switch_names(dentry
, target
);
2312 swap(dentry
->d_name
.hash
, target
->d_name
.hash
);
2314 /* ... and switch the parents */
2315 if (IS_ROOT(dentry
)) {
2316 dentry
->d_parent
= target
->d_parent
;
2317 target
->d_parent
= target
;
2318 INIT_LIST_HEAD(&target
->d_u
.d_child
);
2320 swap(dentry
->d_parent
, target
->d_parent
);
2322 /* And add them back to the (new) parent lists */
2323 list_add(&target
->d_u
.d_child
, &target
->d_parent
->d_subdirs
);
2326 list_add(&dentry
->d_u
.d_child
, &dentry
->d_parent
->d_subdirs
);
2328 write_seqcount_end(&target
->d_seq
);
2329 write_seqcount_end(&dentry
->d_seq
);
2331 dentry_unlock_parents_for_move(dentry
, target
);
2332 spin_unlock(&target
->d_lock
);
2333 fsnotify_d_move(dentry
);
2334 spin_unlock(&dentry
->d_lock
);
2338 * d_move - move a dentry
2339 * @dentry: entry to move
2340 * @target: new dentry
2342 * Update the dcache to reflect the move of a file name. Negative
2343 * dcache entries should not be moved in this way. See the locking
2344 * requirements for __d_move.
2346 void d_move(struct dentry
*dentry
, struct dentry
*target
)
2348 write_seqlock(&rename_lock
);
2349 __d_move(dentry
, target
);
2350 write_sequnlock(&rename_lock
);
2352 EXPORT_SYMBOL(d_move
);
2355 * d_ancestor - search for an ancestor
2356 * @p1: ancestor dentry
2359 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2360 * an ancestor of p2, else NULL.
2362 struct dentry
*d_ancestor(struct dentry
*p1
, struct dentry
*p2
)
2366 for (p
= p2
; !IS_ROOT(p
); p
= p
->d_parent
) {
2367 if (p
->d_parent
== p1
)
2374 * This helper attempts to cope with remotely renamed directories
2376 * It assumes that the caller is already holding
2377 * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
2379 * Note: If ever the locking in lock_rename() changes, then please
2380 * remember to update this too...
2382 static struct dentry
*__d_unalias(struct inode
*inode
,
2383 struct dentry
*dentry
, struct dentry
*alias
)
2385 struct mutex
*m1
= NULL
, *m2
= NULL
;
2388 /* If alias and dentry share a parent, then no extra locks required */
2389 if (alias
->d_parent
== dentry
->d_parent
)
2392 /* See lock_rename() */
2393 ret
= ERR_PTR(-EBUSY
);
2394 if (!mutex_trylock(&dentry
->d_sb
->s_vfs_rename_mutex
))
2396 m1
= &dentry
->d_sb
->s_vfs_rename_mutex
;
2397 if (!mutex_trylock(&alias
->d_parent
->d_inode
->i_mutex
))
2399 m2
= &alias
->d_parent
->d_inode
->i_mutex
;
2401 __d_move(alias
, dentry
);
2404 spin_unlock(&inode
->i_lock
);
2413 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
2414 * named dentry in place of the dentry to be replaced.
2415 * returns with anon->d_lock held!
2417 static void __d_materialise_dentry(struct dentry
*dentry
, struct dentry
*anon
)
2419 struct dentry
*dparent
, *aparent
;
2421 dentry_lock_for_move(anon
, dentry
);
2423 write_seqcount_begin(&dentry
->d_seq
);
2424 write_seqcount_begin(&anon
->d_seq
);
2426 dparent
= dentry
->d_parent
;
2427 aparent
= anon
->d_parent
;
2429 switch_names(dentry
, anon
);
2430 swap(dentry
->d_name
.hash
, anon
->d_name
.hash
);
2432 dentry
->d_parent
= (aparent
== anon
) ? dentry
: aparent
;
2433 list_del(&dentry
->d_u
.d_child
);
2434 if (!IS_ROOT(dentry
))
2435 list_add(&dentry
->d_u
.d_child
, &dentry
->d_parent
->d_subdirs
);
2437 INIT_LIST_HEAD(&dentry
->d_u
.d_child
);
2439 anon
->d_parent
= (dparent
== dentry
) ? anon
: dparent
;
2440 list_del(&anon
->d_u
.d_child
);
2442 list_add(&anon
->d_u
.d_child
, &anon
->d_parent
->d_subdirs
);
2444 INIT_LIST_HEAD(&anon
->d_u
.d_child
);
2446 write_seqcount_end(&dentry
->d_seq
);
2447 write_seqcount_end(&anon
->d_seq
);
2449 dentry_unlock_parents_for_move(anon
, dentry
);
2450 spin_unlock(&dentry
->d_lock
);
2452 /* anon->d_lock still locked, returns locked */
2453 anon
->d_flags
&= ~DCACHE_DISCONNECTED
;
2457 * d_materialise_unique - introduce an inode into the tree
2458 * @dentry: candidate dentry
2459 * @inode: inode to bind to the dentry, to which aliases may be attached
2461 * Introduces an dentry into the tree, substituting an extant disconnected
2462 * root directory alias in its place if there is one. Caller must hold the
2463 * i_mutex of the parent directory.
2465 struct dentry
*d_materialise_unique(struct dentry
*dentry
, struct inode
*inode
)
2467 struct dentry
*actual
;
2469 BUG_ON(!d_unhashed(dentry
));
2473 __d_instantiate(dentry
, NULL
);
2478 spin_lock(&inode
->i_lock
);
2480 if (S_ISDIR(inode
->i_mode
)) {
2481 struct dentry
*alias
;
2483 /* Does an aliased dentry already exist? */
2484 alias
= __d_find_alias(inode
, 0);
2487 write_seqlock(&rename_lock
);
2489 if (d_ancestor(alias
, dentry
)) {
2490 /* Check for loops */
2491 actual
= ERR_PTR(-ELOOP
);
2492 spin_unlock(&inode
->i_lock
);
2493 } else if (IS_ROOT(alias
)) {
2494 /* Is this an anonymous mountpoint that we
2495 * could splice into our tree? */
2496 __d_materialise_dentry(dentry
, alias
);
2497 write_sequnlock(&rename_lock
);
2501 /* Nope, but we must(!) avoid directory
2502 * aliasing. This drops inode->i_lock */
2503 actual
= __d_unalias(inode
, dentry
, alias
);
2505 write_sequnlock(&rename_lock
);
2506 if (IS_ERR(actual
)) {
2507 if (PTR_ERR(actual
) == -ELOOP
)
2508 pr_warn_ratelimited(
2509 "VFS: Lookup of '%s' in %s %s"
2510 " would have caused loop\n",
2511 dentry
->d_name
.name
,
2512 inode
->i_sb
->s_type
->name
,
2520 /* Add a unique reference */
2521 actual
= __d_instantiate_unique(dentry
, inode
);
2525 BUG_ON(!d_unhashed(actual
));
2527 spin_lock(&actual
->d_lock
);
2530 spin_unlock(&actual
->d_lock
);
2531 spin_unlock(&inode
->i_lock
);
2533 if (actual
== dentry
) {
2534 security_d_instantiate(dentry
, inode
);
2541 EXPORT_SYMBOL_GPL(d_materialise_unique
);
2543 static int prepend(char **buffer
, int *buflen
, const char *str
, int namelen
)
2547 return -ENAMETOOLONG
;
2549 memcpy(*buffer
, str
, namelen
);
2553 static int prepend_name(char **buffer
, int *buflen
, struct qstr
*name
)
2555 return prepend(buffer
, buflen
, name
->name
, name
->len
);
2559 * prepend_path - Prepend path string to a buffer
2560 * @path: the dentry/vfsmount to report
2561 * @root: root vfsmnt/dentry
2562 * @buffer: pointer to the end of the buffer
2563 * @buflen: pointer to buffer length
2565 * Caller holds the rename_lock.
2567 static int prepend_path(const struct path
*path
,
2568 const struct path
*root
,
2569 char **buffer
, int *buflen
)
2571 struct dentry
*dentry
= path
->dentry
;
2572 struct vfsmount
*vfsmnt
= path
->mnt
;
2573 struct mount
*mnt
= real_mount(vfsmnt
);
2577 br_read_lock(&vfsmount_lock
);
2578 while (dentry
!= root
->dentry
|| vfsmnt
!= root
->mnt
) {
2579 struct dentry
* parent
;
2581 if (dentry
== vfsmnt
->mnt_root
|| IS_ROOT(dentry
)) {
2583 if (!mnt_has_parent(mnt
))
2585 dentry
= mnt
->mnt_mountpoint
;
2586 mnt
= mnt
->mnt_parent
;
2590 parent
= dentry
->d_parent
;
2592 spin_lock(&dentry
->d_lock
);
2593 error
= prepend_name(buffer
, buflen
, &dentry
->d_name
);
2594 spin_unlock(&dentry
->d_lock
);
2596 error
= prepend(buffer
, buflen
, "/", 1);
2604 if (!error
&& !slash
)
2605 error
= prepend(buffer
, buflen
, "/", 1);
2608 br_read_unlock(&vfsmount_lock
);
2613 * Filesystems needing to implement special "root names"
2614 * should do so with ->d_dname()
2616 if (IS_ROOT(dentry
) &&
2617 (dentry
->d_name
.len
!= 1 || dentry
->d_name
.name
[0] != '/')) {
2618 WARN(1, "Root dentry has weird name <%.*s>\n",
2619 (int) dentry
->d_name
.len
, dentry
->d_name
.name
);
2622 error
= prepend(buffer
, buflen
, "/", 1);
2624 error
= real_mount(vfsmnt
)->mnt_ns
? 1 : 2;
2629 * __d_path - return the path of a dentry
2630 * @path: the dentry/vfsmount to report
2631 * @root: root vfsmnt/dentry
2632 * @buf: buffer to return value in
2633 * @buflen: buffer length
2635 * Convert a dentry into an ASCII path name.
2637 * Returns a pointer into the buffer or an error code if the
2638 * path was too long.
2640 * "buflen" should be positive.
2642 * If the path is not reachable from the supplied root, return %NULL.
2644 char *__d_path(const struct path
*path
,
2645 const struct path
*root
,
2646 char *buf
, int buflen
)
2648 char *res
= buf
+ buflen
;
2651 prepend(&res
, &buflen
, "\0", 1);
2652 write_seqlock(&rename_lock
);
2653 error
= prepend_path(path
, root
, &res
, &buflen
);
2654 write_sequnlock(&rename_lock
);
2657 return ERR_PTR(error
);
2663 char *d_absolute_path(const struct path
*path
,
2664 char *buf
, int buflen
)
2666 struct path root
= {};
2667 char *res
= buf
+ buflen
;
2670 prepend(&res
, &buflen
, "\0", 1);
2671 write_seqlock(&rename_lock
);
2672 error
= prepend_path(path
, &root
, &res
, &buflen
);
2673 write_sequnlock(&rename_lock
);
2678 return ERR_PTR(error
);
2683 * same as __d_path but appends "(deleted)" for unlinked files.
2685 static int path_with_deleted(const struct path
*path
,
2686 const struct path
*root
,
2687 char **buf
, int *buflen
)
2689 prepend(buf
, buflen
, "\0", 1);
2690 if (d_unlinked(path
->dentry
)) {
2691 int error
= prepend(buf
, buflen
, " (deleted)", 10);
2696 return prepend_path(path
, root
, buf
, buflen
);
2699 static int prepend_unreachable(char **buffer
, int *buflen
)
2701 return prepend(buffer
, buflen
, "(unreachable)", 13);
2705 * d_path - return the path of a dentry
2706 * @path: path to report
2707 * @buf: buffer to return value in
2708 * @buflen: buffer length
2710 * Convert a dentry into an ASCII path name. If the entry has been deleted
2711 * the string " (deleted)" is appended. Note that this is ambiguous.
2713 * Returns a pointer into the buffer or an error code if the path was
2714 * too long. Note: Callers should use the returned pointer, not the passed
2715 * in buffer, to use the name! The implementation often starts at an offset
2716 * into the buffer, and may leave 0 bytes at the start.
2718 * "buflen" should be positive.
2720 char *d_path(const struct path
*path
, char *buf
, int buflen
)
2722 char *res
= buf
+ buflen
;
2727 * We have various synthetic filesystems that never get mounted. On
2728 * these filesystems dentries are never used for lookup purposes, and
2729 * thus don't need to be hashed. They also don't need a name until a
2730 * user wants to identify the object in /proc/pid/fd/. The little hack
2731 * below allows us to generate a name for these objects on demand:
2733 if (path
->dentry
->d_op
&& path
->dentry
->d_op
->d_dname
)
2734 return path
->dentry
->d_op
->d_dname(path
->dentry
, buf
, buflen
);
2736 get_fs_root(current
->fs
, &root
);
2737 write_seqlock(&rename_lock
);
2738 error
= path_with_deleted(path
, &root
, &res
, &buflen
);
2740 res
= ERR_PTR(error
);
2741 write_sequnlock(&rename_lock
);
2745 EXPORT_SYMBOL(d_path
);
2748 * d_path_with_unreachable - return the path of a dentry
2749 * @path: path to report
2750 * @buf: buffer to return value in
2751 * @buflen: buffer length
2753 * The difference from d_path() is that this prepends "(unreachable)"
2754 * to paths which are unreachable from the current process' root.
2756 char *d_path_with_unreachable(const struct path
*path
, char *buf
, int buflen
)
2758 char *res
= buf
+ buflen
;
2762 if (path
->dentry
->d_op
&& path
->dentry
->d_op
->d_dname
)
2763 return path
->dentry
->d_op
->d_dname(path
->dentry
, buf
, buflen
);
2765 get_fs_root(current
->fs
, &root
);
2766 write_seqlock(&rename_lock
);
2767 error
= path_with_deleted(path
, &root
, &res
, &buflen
);
2769 error
= prepend_unreachable(&res
, &buflen
);
2770 write_sequnlock(&rename_lock
);
2773 res
= ERR_PTR(error
);
2779 * Helper function for dentry_operations.d_dname() members
2781 char *dynamic_dname(struct dentry
*dentry
, char *buffer
, int buflen
,
2782 const char *fmt
, ...)
2788 va_start(args
, fmt
);
2789 sz
= vsnprintf(temp
, sizeof(temp
), fmt
, args
) + 1;
2792 if (sz
> sizeof(temp
) || sz
> buflen
)
2793 return ERR_PTR(-ENAMETOOLONG
);
2795 buffer
+= buflen
- sz
;
2796 return memcpy(buffer
, temp
, sz
);
2800 * Write full pathname from the root of the filesystem into the buffer.
2802 static char *__dentry_path(struct dentry
*dentry
, char *buf
, int buflen
)
2804 char *end
= buf
+ buflen
;
2807 prepend(&end
, &buflen
, "\0", 1);
2814 while (!IS_ROOT(dentry
)) {
2815 struct dentry
*parent
= dentry
->d_parent
;
2819 spin_lock(&dentry
->d_lock
);
2820 error
= prepend_name(&end
, &buflen
, &dentry
->d_name
);
2821 spin_unlock(&dentry
->d_lock
);
2822 if (error
!= 0 || prepend(&end
, &buflen
, "/", 1) != 0)
2830 return ERR_PTR(-ENAMETOOLONG
);
2833 char *dentry_path_raw(struct dentry
*dentry
, char *buf
, int buflen
)
2837 write_seqlock(&rename_lock
);
2838 retval
= __dentry_path(dentry
, buf
, buflen
);
2839 write_sequnlock(&rename_lock
);
2843 EXPORT_SYMBOL(dentry_path_raw
);
2845 char *dentry_path(struct dentry
*dentry
, char *buf
, int buflen
)
2850 write_seqlock(&rename_lock
);
2851 if (d_unlinked(dentry
)) {
2853 if (prepend(&p
, &buflen
, "//deleted", 10) != 0)
2857 retval
= __dentry_path(dentry
, buf
, buflen
);
2858 write_sequnlock(&rename_lock
);
2859 if (!IS_ERR(retval
) && p
)
2860 *p
= '/'; /* restore '/' overriden with '\0' */
2863 return ERR_PTR(-ENAMETOOLONG
);
2867 * NOTE! The user-level library version returns a
2868 * character pointer. The kernel system call just
2869 * returns the length of the buffer filled (which
2870 * includes the ending '\0' character), or a negative
2871 * error value. So libc would do something like
2873 * char *getcwd(char * buf, size_t size)
2877 * retval = sys_getcwd(buf, size);
2884 SYSCALL_DEFINE2(getcwd
, char __user
*, buf
, unsigned long, size
)
2887 struct path pwd
, root
;
2888 char *page
= (char *) __get_free_page(GFP_USER
);
2893 get_fs_root_and_pwd(current
->fs
, &root
, &pwd
);
2896 write_seqlock(&rename_lock
);
2897 if (!d_unlinked(pwd
.dentry
)) {
2899 char *cwd
= page
+ PAGE_SIZE
;
2900 int buflen
= PAGE_SIZE
;
2902 prepend(&cwd
, &buflen
, "\0", 1);
2903 error
= prepend_path(&pwd
, &root
, &cwd
, &buflen
);
2904 write_sequnlock(&rename_lock
);
2909 /* Unreachable from current root */
2911 error
= prepend_unreachable(&cwd
, &buflen
);
2917 len
= PAGE_SIZE
+ page
- cwd
;
2920 if (copy_to_user(buf
, cwd
, len
))
2924 write_sequnlock(&rename_lock
);
2930 free_page((unsigned long) page
);
2935 * Test whether new_dentry is a subdirectory of old_dentry.
2937 * Trivially implemented using the dcache structure
2941 * is_subdir - is new dentry a subdirectory of old_dentry
2942 * @new_dentry: new dentry
2943 * @old_dentry: old dentry
2945 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
2946 * Returns 0 otherwise.
2947 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
2950 int is_subdir(struct dentry
*new_dentry
, struct dentry
*old_dentry
)
2955 if (new_dentry
== old_dentry
)
2959 /* for restarting inner loop in case of seq retry */
2960 seq
= read_seqbegin(&rename_lock
);
2962 * Need rcu_readlock to protect against the d_parent trashing
2966 if (d_ancestor(old_dentry
, new_dentry
))
2971 } while (read_seqretry(&rename_lock
, seq
));
2976 void d_genocide(struct dentry
*root
)
2978 struct dentry
*this_parent
;
2979 struct list_head
*next
;
2983 seq
= read_seqbegin(&rename_lock
);
2986 spin_lock(&this_parent
->d_lock
);
2988 next
= this_parent
->d_subdirs
.next
;
2990 while (next
!= &this_parent
->d_subdirs
) {
2991 struct list_head
*tmp
= next
;
2992 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_u
.d_child
);
2995 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
2996 if (d_unhashed(dentry
) || !dentry
->d_inode
) {
2997 spin_unlock(&dentry
->d_lock
);
3000 if (!list_empty(&dentry
->d_subdirs
)) {
3001 spin_unlock(&this_parent
->d_lock
);
3002 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
3003 this_parent
= dentry
;
3004 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
3007 if (!(dentry
->d_flags
& DCACHE_GENOCIDE
)) {
3008 dentry
->d_flags
|= DCACHE_GENOCIDE
;
3011 spin_unlock(&dentry
->d_lock
);
3013 if (this_parent
!= root
) {
3014 struct dentry
*child
= this_parent
;
3015 if (!(this_parent
->d_flags
& DCACHE_GENOCIDE
)) {
3016 this_parent
->d_flags
|= DCACHE_GENOCIDE
;
3017 this_parent
->d_count
--;
3019 this_parent
= try_to_ascend(this_parent
, locked
, seq
);
3022 next
= child
->d_u
.d_child
.next
;
3025 spin_unlock(&this_parent
->d_lock
);
3026 if (!locked
&& read_seqretry(&rename_lock
, seq
))
3029 write_sequnlock(&rename_lock
);
3034 write_seqlock(&rename_lock
);
3039 * find_inode_number - check for dentry with name
3040 * @dir: directory to check
3041 * @name: Name to find.
3043 * Check whether a dentry already exists for the given name,
3044 * and return the inode number if it has an inode. Otherwise
3047 * This routine is used to post-process directory listings for
3048 * filesystems using synthetic inode numbers, and is necessary
3049 * to keep getcwd() working.
3052 ino_t
find_inode_number(struct dentry
*dir
, struct qstr
*name
)
3054 struct dentry
* dentry
;
3057 dentry
= d_hash_and_lookup(dir
, name
);
3059 if (dentry
->d_inode
)
3060 ino
= dentry
->d_inode
->i_ino
;
3065 EXPORT_SYMBOL(find_inode_number
);
3067 static __initdata
unsigned long dhash_entries
;
3068 static int __init
set_dhash_entries(char *str
)
3072 dhash_entries
= simple_strtoul(str
, &str
, 0);
3075 __setup("dhash_entries=", set_dhash_entries
);
3077 static void __init
dcache_init_early(void)
3081 /* If hashes are distributed across NUMA nodes, defer
3082 * hash allocation until vmalloc space is available.
3088 alloc_large_system_hash("Dentry cache",
3089 sizeof(struct hlist_bl_head
),
3098 for (loop
= 0; loop
< (1U << d_hash_shift
); loop
++)
3099 INIT_HLIST_BL_HEAD(dentry_hashtable
+ loop
);
3102 static void __init
dcache_init(void)
3107 * A constructor could be added for stable state like the lists,
3108 * but it is probably not worth it because of the cache nature
3111 dentry_cache
= KMEM_CACHE(dentry
,
3112 SLAB_RECLAIM_ACCOUNT
|SLAB_PANIC
|SLAB_MEM_SPREAD
);
3114 /* Hash may have been set up in dcache_init_early */
3119 alloc_large_system_hash("Dentry cache",
3120 sizeof(struct hlist_bl_head
),
3129 for (loop
= 0; loop
< (1U << d_hash_shift
); loop
++)
3130 INIT_HLIST_BL_HEAD(dentry_hashtable
+ loop
);
3133 /* SLAB cache for __getname() consumers */
3134 struct kmem_cache
*names_cachep __read_mostly
;
3135 EXPORT_SYMBOL(names_cachep
);
3137 EXPORT_SYMBOL(d_genocide
);
3139 void __init
vfs_caches_init_early(void)
3141 dcache_init_early();
3145 void __init
vfs_caches_init(unsigned long mempages
)
3147 unsigned long reserve
;
3149 /* Base hash sizes on available memory, with a reserve equal to
3150 150% of current kernel size */
3152 reserve
= min((mempages
- nr_free_pages()) * 3/2, mempages
- 1);
3153 mempages
-= reserve
;
3155 names_cachep
= kmem_cache_create("names_cache", PATH_MAX
, 0,
3156 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
);
3160 files_init(mempages
);