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>
40 #include <linux/list_lru.h>
41 #include <linux/kasan.h>
48 * dcache->d_inode->i_lock protects:
49 * - i_dentry, d_u.d_alias, d_inode of aliases
50 * dcache_hash_bucket lock protects:
51 * - the dcache hash table
52 * s_anon bl list spinlock protects:
53 * - the s_anon list (see __d_drop)
54 * dentry->d_sb->s_dentry_lru_lock protects:
55 * - the dcache lru lists and counters
62 * - d_parent and d_subdirs
63 * - childrens' d_child and d_parent
64 * - d_u.d_alias, d_inode
67 * dentry->d_inode->i_lock
69 * dentry->d_sb->s_dentry_lru_lock
70 * dcache_hash_bucket lock
73 * If there is an ancestor relationship:
74 * dentry->d_parent->...->d_parent->d_lock
76 * dentry->d_parent->d_lock
79 * If no ancestor relationship:
80 * if (dentry1 < dentry2)
84 int sysctl_vfs_cache_pressure __read_mostly
= 100;
85 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure
);
87 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(rename_lock
);
89 EXPORT_SYMBOL(rename_lock
);
91 static struct kmem_cache
*dentry_cache __read_mostly
;
94 * This is the single most critical data structure when it comes
95 * to the dcache: the hashtable for lookups. Somebody should try
96 * to make this good - I've just made it work.
98 * This hash-function tries to avoid losing too many bits of hash
99 * information, yet avoid using a prime hash-size or similar.
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 return dentry_hashtable
+ hash_32(hash
, d_hash_shift
);
114 /* Statistics gathering. */
115 struct dentry_stat_t dentry_stat
= {
119 static DEFINE_PER_CPU(long, nr_dentry
);
120 static DEFINE_PER_CPU(long, nr_dentry_unused
);
122 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
125 * Here we resort to our own counters instead of using generic per-cpu counters
126 * for consistency with what the vfs inode code does. We are expected to harvest
127 * better code and performance by having our own specialized counters.
129 * Please note that the loop is done over all possible CPUs, not over all online
130 * CPUs. The reason for this is that we don't want to play games with CPUs going
131 * on and off. If one of them goes off, we will just keep their counters.
133 * glommer: See cffbc8a for details, and if you ever intend to change this,
134 * please update all vfs counters to match.
136 static long get_nr_dentry(void)
140 for_each_possible_cpu(i
)
141 sum
+= per_cpu(nr_dentry
, i
);
142 return sum
< 0 ? 0 : sum
;
145 static long get_nr_dentry_unused(void)
149 for_each_possible_cpu(i
)
150 sum
+= per_cpu(nr_dentry_unused
, i
);
151 return sum
< 0 ? 0 : sum
;
154 int proc_nr_dentry(struct ctl_table
*table
, int write
, void __user
*buffer
,
155 size_t *lenp
, loff_t
*ppos
)
157 dentry_stat
.nr_dentry
= get_nr_dentry();
158 dentry_stat
.nr_unused
= get_nr_dentry_unused();
159 return proc_doulongvec_minmax(table
, write
, buffer
, lenp
, ppos
);
164 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
165 * The strings are both count bytes long, and count is non-zero.
167 #ifdef CONFIG_DCACHE_WORD_ACCESS
169 #include <asm/word-at-a-time.h>
171 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
172 * aligned allocation for this particular component. We don't
173 * strictly need the load_unaligned_zeropad() safety, but it
174 * doesn't hurt either.
176 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
177 * need the careful unaligned handling.
179 static inline int dentry_string_cmp(const unsigned char *cs
, const unsigned char *ct
, unsigned tcount
)
181 unsigned long a
,b
,mask
;
184 a
= *(unsigned long *)cs
;
185 b
= load_unaligned_zeropad(ct
);
186 if (tcount
< sizeof(unsigned long))
188 if (unlikely(a
!= b
))
190 cs
+= sizeof(unsigned long);
191 ct
+= sizeof(unsigned long);
192 tcount
-= sizeof(unsigned long);
196 mask
= bytemask_from_count(tcount
);
197 return unlikely(!!((a
^ b
) & mask
));
202 static inline int dentry_string_cmp(const unsigned char *cs
, const unsigned char *ct
, unsigned tcount
)
216 static inline int dentry_cmp(const struct dentry
*dentry
, const unsigned char *ct
, unsigned tcount
)
218 const unsigned char *cs
;
220 * Be careful about RCU walk racing with rename:
221 * use ACCESS_ONCE to fetch the name pointer.
223 * NOTE! Even if a rename will mean that the length
224 * was not loaded atomically, we don't care. The
225 * RCU walk will check the sequence count eventually,
226 * and catch it. And we won't overrun the buffer,
227 * because we're reading the name pointer atomically,
228 * and a dentry name is guaranteed to be properly
229 * terminated with a NUL byte.
231 * End result: even if 'len' is wrong, we'll exit
232 * early because the data cannot match (there can
233 * be no NUL in the ct/tcount data)
235 cs
= ACCESS_ONCE(dentry
->d_name
.name
);
236 smp_read_barrier_depends();
237 return dentry_string_cmp(cs
, ct
, tcount
);
240 struct external_name
{
243 struct rcu_head head
;
245 unsigned char name
[];
248 static inline struct external_name
*external_name(struct dentry
*dentry
)
250 return container_of(dentry
->d_name
.name
, struct external_name
, name
[0]);
253 static void __d_free(struct rcu_head
*head
)
255 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
257 kmem_cache_free(dentry_cache
, dentry
);
260 static void __d_free_external(struct rcu_head
*head
)
262 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
263 kfree(external_name(dentry
));
264 kmem_cache_free(dentry_cache
, dentry
);
267 static inline int dname_external(const struct dentry
*dentry
)
269 return dentry
->d_name
.name
!= dentry
->d_iname
;
272 static void dentry_free(struct dentry
*dentry
)
274 WARN_ON(!hlist_unhashed(&dentry
->d_u
.d_alias
));
275 if (unlikely(dname_external(dentry
))) {
276 struct external_name
*p
= external_name(dentry
);
277 if (likely(atomic_dec_and_test(&p
->u
.count
))) {
278 call_rcu(&dentry
->d_u
.d_rcu
, __d_free_external
);
282 /* if dentry was never visible to RCU, immediate free is OK */
283 if (!(dentry
->d_flags
& DCACHE_RCUACCESS
))
284 __d_free(&dentry
->d_u
.d_rcu
);
286 call_rcu(&dentry
->d_u
.d_rcu
, __d_free
);
290 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
291 * @dentry: the target dentry
292 * After this call, in-progress rcu-walk path lookup will fail. This
293 * should be called after unhashing, and after changing d_inode (if
294 * the dentry has not already been unhashed).
296 static inline void dentry_rcuwalk_barrier(struct dentry
*dentry
)
298 assert_spin_locked(&dentry
->d_lock
);
299 /* Go through a barrier */
300 write_seqcount_barrier(&dentry
->d_seq
);
304 * Release the dentry's inode, using the filesystem
305 * d_iput() operation if defined. Dentry has no refcount
308 static void dentry_iput(struct dentry
* dentry
)
309 __releases(dentry
->d_lock
)
310 __releases(dentry
->d_inode
->i_lock
)
312 struct inode
*inode
= dentry
->d_inode
;
314 dentry
->d_inode
= NULL
;
315 hlist_del_init(&dentry
->d_u
.d_alias
);
316 spin_unlock(&dentry
->d_lock
);
317 spin_unlock(&inode
->i_lock
);
319 fsnotify_inoderemove(inode
);
320 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
321 dentry
->d_op
->d_iput(dentry
, inode
);
325 spin_unlock(&dentry
->d_lock
);
330 * Release the dentry's inode, using the filesystem
331 * d_iput() operation if defined. dentry remains in-use.
333 static void dentry_unlink_inode(struct dentry
* dentry
)
334 __releases(dentry
->d_lock
)
335 __releases(dentry
->d_inode
->i_lock
)
337 struct inode
*inode
= dentry
->d_inode
;
338 __d_clear_type(dentry
);
339 dentry
->d_inode
= NULL
;
340 hlist_del_init(&dentry
->d_u
.d_alias
);
341 dentry_rcuwalk_barrier(dentry
);
342 spin_unlock(&dentry
->d_lock
);
343 spin_unlock(&inode
->i_lock
);
345 fsnotify_inoderemove(inode
);
346 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
347 dentry
->d_op
->d_iput(dentry
, inode
);
353 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
354 * is in use - which includes both the "real" per-superblock
355 * LRU list _and_ the DCACHE_SHRINK_LIST use.
357 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
358 * on the shrink list (ie not on the superblock LRU list).
360 * The per-cpu "nr_dentry_unused" counters are updated with
361 * the DCACHE_LRU_LIST bit.
363 * These helper functions make sure we always follow the
364 * rules. d_lock must be held by the caller.
366 #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
367 static void d_lru_add(struct dentry
*dentry
)
369 D_FLAG_VERIFY(dentry
, 0);
370 dentry
->d_flags
|= DCACHE_LRU_LIST
;
371 this_cpu_inc(nr_dentry_unused
);
372 WARN_ON_ONCE(!list_lru_add(&dentry
->d_sb
->s_dentry_lru
, &dentry
->d_lru
));
375 static void d_lru_del(struct dentry
*dentry
)
377 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
378 dentry
->d_flags
&= ~DCACHE_LRU_LIST
;
379 this_cpu_dec(nr_dentry_unused
);
380 WARN_ON_ONCE(!list_lru_del(&dentry
->d_sb
->s_dentry_lru
, &dentry
->d_lru
));
383 static void d_shrink_del(struct dentry
*dentry
)
385 D_FLAG_VERIFY(dentry
, DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
);
386 list_del_init(&dentry
->d_lru
);
387 dentry
->d_flags
&= ~(DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
);
388 this_cpu_dec(nr_dentry_unused
);
391 static void d_shrink_add(struct dentry
*dentry
, struct list_head
*list
)
393 D_FLAG_VERIFY(dentry
, 0);
394 list_add(&dentry
->d_lru
, list
);
395 dentry
->d_flags
|= DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
;
396 this_cpu_inc(nr_dentry_unused
);
400 * These can only be called under the global LRU lock, ie during the
401 * callback for freeing the LRU list. "isolate" removes it from the
402 * LRU lists entirely, while shrink_move moves it to the indicated
405 static void d_lru_isolate(struct list_lru_one
*lru
, struct dentry
*dentry
)
407 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
408 dentry
->d_flags
&= ~DCACHE_LRU_LIST
;
409 this_cpu_dec(nr_dentry_unused
);
410 list_lru_isolate(lru
, &dentry
->d_lru
);
413 static void d_lru_shrink_move(struct list_lru_one
*lru
, struct dentry
*dentry
,
414 struct list_head
*list
)
416 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
417 dentry
->d_flags
|= DCACHE_SHRINK_LIST
;
418 list_lru_isolate_move(lru
, &dentry
->d_lru
, list
);
422 * dentry_lru_(add|del)_list) must be called with d_lock held.
424 static void dentry_lru_add(struct dentry
*dentry
)
426 if (unlikely(!(dentry
->d_flags
& DCACHE_LRU_LIST
)))
431 * d_drop - drop a dentry
432 * @dentry: dentry to drop
434 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
435 * be found through a VFS lookup any more. Note that this is different from
436 * deleting the dentry - d_delete will try to mark the dentry negative if
437 * possible, giving a successful _negative_ lookup, while d_drop will
438 * just make the cache lookup fail.
440 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
441 * reason (NFS timeouts or autofs deletes).
443 * __d_drop requires dentry->d_lock.
445 void __d_drop(struct dentry
*dentry
)
447 if (!d_unhashed(dentry
)) {
448 struct hlist_bl_head
*b
;
450 * Hashed dentries are normally on the dentry hashtable,
451 * with the exception of those newly allocated by
452 * d_obtain_alias, which are always IS_ROOT:
454 if (unlikely(IS_ROOT(dentry
)))
455 b
= &dentry
->d_sb
->s_anon
;
457 b
= d_hash(dentry
->d_parent
, dentry
->d_name
.hash
);
460 __hlist_bl_del(&dentry
->d_hash
);
461 dentry
->d_hash
.pprev
= NULL
;
463 dentry_rcuwalk_barrier(dentry
);
466 EXPORT_SYMBOL(__d_drop
);
468 void d_drop(struct dentry
*dentry
)
470 spin_lock(&dentry
->d_lock
);
472 spin_unlock(&dentry
->d_lock
);
474 EXPORT_SYMBOL(d_drop
);
476 static void __dentry_kill(struct dentry
*dentry
)
478 struct dentry
*parent
= NULL
;
479 bool can_free
= true;
480 if (!IS_ROOT(dentry
))
481 parent
= dentry
->d_parent
;
484 * The dentry is now unrecoverably dead to the world.
486 lockref_mark_dead(&dentry
->d_lockref
);
489 * inform the fs via d_prune that this dentry is about to be
490 * unhashed and destroyed.
492 if (dentry
->d_flags
& DCACHE_OP_PRUNE
)
493 dentry
->d_op
->d_prune(dentry
);
495 if (dentry
->d_flags
& DCACHE_LRU_LIST
) {
496 if (!(dentry
->d_flags
& DCACHE_SHRINK_LIST
))
499 /* if it was on the hash then remove it */
501 __list_del_entry(&dentry
->d_child
);
503 * Inform d_walk() that we are no longer attached to the
506 dentry
->d_flags
|= DCACHE_DENTRY_KILLED
;
508 spin_unlock(&parent
->d_lock
);
511 * dentry_iput drops the locks, at which point nobody (except
512 * transient RCU lookups) can reach this dentry.
514 BUG_ON((int)dentry
->d_lockref
.count
> 0);
515 this_cpu_dec(nr_dentry
);
516 if (dentry
->d_op
&& dentry
->d_op
->d_release
)
517 dentry
->d_op
->d_release(dentry
);
519 spin_lock(&dentry
->d_lock
);
520 if (dentry
->d_flags
& DCACHE_SHRINK_LIST
) {
521 dentry
->d_flags
|= DCACHE_MAY_FREE
;
524 spin_unlock(&dentry
->d_lock
);
525 if (likely(can_free
))
530 * Finish off a dentry we've decided to kill.
531 * dentry->d_lock must be held, returns with it unlocked.
532 * If ref is non-zero, then decrement the refcount too.
533 * Returns dentry requiring refcount drop, or NULL if we're done.
535 static struct dentry
*dentry_kill(struct dentry
*dentry
)
536 __releases(dentry
->d_lock
)
538 struct inode
*inode
= dentry
->d_inode
;
539 struct dentry
*parent
= NULL
;
541 if (inode
&& unlikely(!spin_trylock(&inode
->i_lock
)))
544 if (!IS_ROOT(dentry
)) {
545 parent
= dentry
->d_parent
;
546 if (unlikely(!spin_trylock(&parent
->d_lock
))) {
548 spin_unlock(&inode
->i_lock
);
553 __dentry_kill(dentry
);
557 spin_unlock(&dentry
->d_lock
);
559 return dentry
; /* try again with same dentry */
562 static inline struct dentry
*lock_parent(struct dentry
*dentry
)
564 struct dentry
*parent
= dentry
->d_parent
;
567 if (unlikely((int)dentry
->d_lockref
.count
< 0))
569 if (likely(spin_trylock(&parent
->d_lock
)))
572 spin_unlock(&dentry
->d_lock
);
574 parent
= ACCESS_ONCE(dentry
->d_parent
);
575 spin_lock(&parent
->d_lock
);
577 * We can't blindly lock dentry until we are sure
578 * that we won't violate the locking order.
579 * Any changes of dentry->d_parent must have
580 * been done with parent->d_lock held, so
581 * spin_lock() above is enough of a barrier
582 * for checking if it's still our child.
584 if (unlikely(parent
!= dentry
->d_parent
)) {
585 spin_unlock(&parent
->d_lock
);
589 if (parent
!= dentry
)
590 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
599 * This is complicated by the fact that we do not want to put
600 * dentries that are no longer on any hash chain on the unused
601 * list: we'd much rather just get rid of them immediately.
603 * However, that implies that we have to traverse the dentry
604 * tree upwards to the parents which might _also_ now be
605 * scheduled for deletion (it may have been only waiting for
606 * its last child to go away).
608 * This tail recursion is done by hand as we don't want to depend
609 * on the compiler to always get this right (gcc generally doesn't).
610 * Real recursion would eat up our stack space.
614 * dput - release a dentry
615 * @dentry: dentry to release
617 * Release a dentry. This will drop the usage count and if appropriate
618 * call the dentry unlink method as well as removing it from the queues and
619 * releasing its resources. If the parent dentries were scheduled for release
620 * they too may now get deleted.
622 void dput(struct dentry
*dentry
)
624 if (unlikely(!dentry
))
628 if (lockref_put_or_lock(&dentry
->d_lockref
))
631 /* Unreachable? Get rid of it */
632 if (unlikely(d_unhashed(dentry
)))
635 if (unlikely(dentry
->d_flags
& DCACHE_OP_DELETE
)) {
636 if (dentry
->d_op
->d_delete(dentry
))
640 if (!(dentry
->d_flags
& DCACHE_REFERENCED
))
641 dentry
->d_flags
|= DCACHE_REFERENCED
;
642 dentry_lru_add(dentry
);
644 dentry
->d_lockref
.count
--;
645 spin_unlock(&dentry
->d_lock
);
649 dentry
= dentry_kill(dentry
);
656 /* This must be called with d_lock held */
657 static inline void __dget_dlock(struct dentry
*dentry
)
659 dentry
->d_lockref
.count
++;
662 static inline void __dget(struct dentry
*dentry
)
664 lockref_get(&dentry
->d_lockref
);
667 struct dentry
*dget_parent(struct dentry
*dentry
)
673 * Do optimistic parent lookup without any
677 ret
= ACCESS_ONCE(dentry
->d_parent
);
678 gotref
= lockref_get_not_zero(&ret
->d_lockref
);
680 if (likely(gotref
)) {
681 if (likely(ret
== ACCESS_ONCE(dentry
->d_parent
)))
688 * Don't need rcu_dereference because we re-check it was correct under
692 ret
= dentry
->d_parent
;
693 spin_lock(&ret
->d_lock
);
694 if (unlikely(ret
!= dentry
->d_parent
)) {
695 spin_unlock(&ret
->d_lock
);
700 BUG_ON(!ret
->d_lockref
.count
);
701 ret
->d_lockref
.count
++;
702 spin_unlock(&ret
->d_lock
);
705 EXPORT_SYMBOL(dget_parent
);
708 * d_find_alias - grab a hashed alias of inode
709 * @inode: inode in question
711 * If inode has a hashed alias, or is a directory and has any alias,
712 * acquire the reference to alias and return it. Otherwise return NULL.
713 * Notice that if inode is a directory there can be only one alias and
714 * it can be unhashed only if it has no children, or if it is the root
715 * of a filesystem, or if the directory was renamed and d_revalidate
716 * was the first vfs operation to notice.
718 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
719 * any other hashed alias over that one.
721 static struct dentry
*__d_find_alias(struct inode
*inode
)
723 struct dentry
*alias
, *discon_alias
;
727 hlist_for_each_entry(alias
, &inode
->i_dentry
, d_u
.d_alias
) {
728 spin_lock(&alias
->d_lock
);
729 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
730 if (IS_ROOT(alias
) &&
731 (alias
->d_flags
& DCACHE_DISCONNECTED
)) {
732 discon_alias
= alias
;
735 spin_unlock(&alias
->d_lock
);
739 spin_unlock(&alias
->d_lock
);
742 alias
= discon_alias
;
743 spin_lock(&alias
->d_lock
);
744 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
746 spin_unlock(&alias
->d_lock
);
749 spin_unlock(&alias
->d_lock
);
755 struct dentry
*d_find_alias(struct inode
*inode
)
757 struct dentry
*de
= NULL
;
759 if (!hlist_empty(&inode
->i_dentry
)) {
760 spin_lock(&inode
->i_lock
);
761 de
= __d_find_alias(inode
);
762 spin_unlock(&inode
->i_lock
);
766 EXPORT_SYMBOL(d_find_alias
);
769 * Try to kill dentries associated with this inode.
770 * WARNING: you must own a reference to inode.
772 void d_prune_aliases(struct inode
*inode
)
774 struct dentry
*dentry
;
776 spin_lock(&inode
->i_lock
);
777 hlist_for_each_entry(dentry
, &inode
->i_dentry
, d_u
.d_alias
) {
778 spin_lock(&dentry
->d_lock
);
779 if (!dentry
->d_lockref
.count
) {
780 struct dentry
*parent
= lock_parent(dentry
);
781 if (likely(!dentry
->d_lockref
.count
)) {
782 __dentry_kill(dentry
);
787 spin_unlock(&parent
->d_lock
);
789 spin_unlock(&dentry
->d_lock
);
791 spin_unlock(&inode
->i_lock
);
793 EXPORT_SYMBOL(d_prune_aliases
);
795 static void shrink_dentry_list(struct list_head
*list
)
797 struct dentry
*dentry
, *parent
;
799 while (!list_empty(list
)) {
801 dentry
= list_entry(list
->prev
, struct dentry
, d_lru
);
802 spin_lock(&dentry
->d_lock
);
803 parent
= lock_parent(dentry
);
806 * The dispose list is isolated and dentries are not accounted
807 * to the LRU here, so we can simply remove it from the list
808 * here regardless of whether it is referenced or not.
810 d_shrink_del(dentry
);
813 * We found an inuse dentry which was not removed from
814 * the LRU because of laziness during lookup. Do not free it.
816 if ((int)dentry
->d_lockref
.count
> 0) {
817 spin_unlock(&dentry
->d_lock
);
819 spin_unlock(&parent
->d_lock
);
824 if (unlikely(dentry
->d_flags
& DCACHE_DENTRY_KILLED
)) {
825 bool can_free
= dentry
->d_flags
& DCACHE_MAY_FREE
;
826 spin_unlock(&dentry
->d_lock
);
828 spin_unlock(&parent
->d_lock
);
834 inode
= dentry
->d_inode
;
835 if (inode
&& unlikely(!spin_trylock(&inode
->i_lock
))) {
836 d_shrink_add(dentry
, list
);
837 spin_unlock(&dentry
->d_lock
);
839 spin_unlock(&parent
->d_lock
);
843 __dentry_kill(dentry
);
846 * We need to prune ancestors too. This is necessary to prevent
847 * quadratic behavior of shrink_dcache_parent(), but is also
848 * expected to be beneficial in reducing dentry cache
852 while (dentry
&& !lockref_put_or_lock(&dentry
->d_lockref
)) {
853 parent
= lock_parent(dentry
);
854 if (dentry
->d_lockref
.count
!= 1) {
855 dentry
->d_lockref
.count
--;
856 spin_unlock(&dentry
->d_lock
);
858 spin_unlock(&parent
->d_lock
);
861 inode
= dentry
->d_inode
; /* can't be NULL */
862 if (unlikely(!spin_trylock(&inode
->i_lock
))) {
863 spin_unlock(&dentry
->d_lock
);
865 spin_unlock(&parent
->d_lock
);
869 __dentry_kill(dentry
);
875 static enum lru_status
dentry_lru_isolate(struct list_head
*item
,
876 struct list_lru_one
*lru
, spinlock_t
*lru_lock
, void *arg
)
878 struct list_head
*freeable
= arg
;
879 struct dentry
*dentry
= container_of(item
, struct dentry
, d_lru
);
883 * we are inverting the lru lock/dentry->d_lock here,
884 * so use a trylock. If we fail to get the lock, just skip
887 if (!spin_trylock(&dentry
->d_lock
))
891 * Referenced dentries are still in use. If they have active
892 * counts, just remove them from the LRU. Otherwise give them
893 * another pass through the LRU.
895 if (dentry
->d_lockref
.count
) {
896 d_lru_isolate(lru
, dentry
);
897 spin_unlock(&dentry
->d_lock
);
901 if (dentry
->d_flags
& DCACHE_REFERENCED
) {
902 dentry
->d_flags
&= ~DCACHE_REFERENCED
;
903 spin_unlock(&dentry
->d_lock
);
906 * The list move itself will be made by the common LRU code. At
907 * this point, we've dropped the dentry->d_lock but keep the
908 * lru lock. This is safe to do, since every list movement is
909 * protected by the lru lock even if both locks are held.
911 * This is guaranteed by the fact that all LRU management
912 * functions are intermediated by the LRU API calls like
913 * list_lru_add and list_lru_del. List movement in this file
914 * only ever occur through this functions or through callbacks
915 * like this one, that are called from the LRU API.
917 * The only exceptions to this are functions like
918 * shrink_dentry_list, and code that first checks for the
919 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
920 * operating only with stack provided lists after they are
921 * properly isolated from the main list. It is thus, always a
927 d_lru_shrink_move(lru
, dentry
, freeable
);
928 spin_unlock(&dentry
->d_lock
);
934 * prune_dcache_sb - shrink the dcache
936 * @sc: shrink control, passed to list_lru_shrink_walk()
938 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
939 * is done when we need more memory and called from the superblock shrinker
942 * This function may fail to free any resources if all the dentries are in
945 long prune_dcache_sb(struct super_block
*sb
, struct shrink_control
*sc
)
950 freed
= list_lru_shrink_walk(&sb
->s_dentry_lru
, sc
,
951 dentry_lru_isolate
, &dispose
);
952 shrink_dentry_list(&dispose
);
956 static enum lru_status
dentry_lru_isolate_shrink(struct list_head
*item
,
957 struct list_lru_one
*lru
, spinlock_t
*lru_lock
, void *arg
)
959 struct list_head
*freeable
= arg
;
960 struct dentry
*dentry
= container_of(item
, struct dentry
, d_lru
);
963 * we are inverting the lru lock/dentry->d_lock here,
964 * so use a trylock. If we fail to get the lock, just skip
967 if (!spin_trylock(&dentry
->d_lock
))
970 d_lru_shrink_move(lru
, dentry
, freeable
);
971 spin_unlock(&dentry
->d_lock
);
978 * shrink_dcache_sb - shrink dcache for a superblock
981 * Shrink the dcache for the specified super block. This is used to free
982 * the dcache before unmounting a file system.
984 void shrink_dcache_sb(struct super_block
*sb
)
991 freed
= list_lru_walk(&sb
->s_dentry_lru
,
992 dentry_lru_isolate_shrink
, &dispose
, UINT_MAX
);
994 this_cpu_sub(nr_dentry_unused
, freed
);
995 shrink_dentry_list(&dispose
);
998 EXPORT_SYMBOL(shrink_dcache_sb
);
1001 * enum d_walk_ret - action to talke during tree walk
1002 * @D_WALK_CONTINUE: contrinue walk
1003 * @D_WALK_QUIT: quit walk
1004 * @D_WALK_NORETRY: quit when retry is needed
1005 * @D_WALK_SKIP: skip this dentry and its children
1015 * d_walk - walk the dentry tree
1016 * @parent: start of walk
1017 * @data: data passed to @enter() and @finish()
1018 * @enter: callback when first entering the dentry
1019 * @finish: callback when successfully finished the walk
1021 * The @enter() and @finish() callbacks are called with d_lock held.
1023 static void d_walk(struct dentry
*parent
, void *data
,
1024 enum d_walk_ret (*enter
)(void *, struct dentry
*),
1025 void (*finish
)(void *))
1027 struct dentry
*this_parent
;
1028 struct list_head
*next
;
1030 enum d_walk_ret ret
;
1034 read_seqbegin_or_lock(&rename_lock
, &seq
);
1035 this_parent
= parent
;
1036 spin_lock(&this_parent
->d_lock
);
1038 ret
= enter(data
, this_parent
);
1040 case D_WALK_CONTINUE
:
1045 case D_WALK_NORETRY
:
1050 next
= this_parent
->d_subdirs
.next
;
1052 while (next
!= &this_parent
->d_subdirs
) {
1053 struct list_head
*tmp
= next
;
1054 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_child
);
1057 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1059 ret
= enter(data
, dentry
);
1061 case D_WALK_CONTINUE
:
1064 spin_unlock(&dentry
->d_lock
);
1066 case D_WALK_NORETRY
:
1070 spin_unlock(&dentry
->d_lock
);
1074 if (!list_empty(&dentry
->d_subdirs
)) {
1075 spin_unlock(&this_parent
->d_lock
);
1076 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
1077 this_parent
= dentry
;
1078 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
1081 spin_unlock(&dentry
->d_lock
);
1084 * All done at this level ... ascend and resume the search.
1088 if (this_parent
!= parent
) {
1089 struct dentry
*child
= this_parent
;
1090 this_parent
= child
->d_parent
;
1092 spin_unlock(&child
->d_lock
);
1093 spin_lock(&this_parent
->d_lock
);
1095 /* might go back up the wrong parent if we have had a rename. */
1096 if (need_seqretry(&rename_lock
, seq
))
1098 next
= child
->d_child
.next
;
1099 while (unlikely(child
->d_flags
& DCACHE_DENTRY_KILLED
)) {
1100 if (next
== &this_parent
->d_subdirs
)
1102 child
= list_entry(next
, struct dentry
, d_child
);
1108 if (need_seqretry(&rename_lock
, seq
))
1115 spin_unlock(&this_parent
->d_lock
);
1116 done_seqretry(&rename_lock
, seq
);
1120 spin_unlock(&this_parent
->d_lock
);
1130 * Search for at least 1 mount point in the dentry's subdirs.
1131 * We descend to the next level whenever the d_subdirs
1132 * list is non-empty and continue searching.
1135 static enum d_walk_ret
check_mount(void *data
, struct dentry
*dentry
)
1138 if (d_mountpoint(dentry
)) {
1142 return D_WALK_CONTINUE
;
1146 * have_submounts - check for mounts over a dentry
1147 * @parent: dentry to check.
1149 * Return true if the parent or its subdirectories contain
1152 int have_submounts(struct dentry
*parent
)
1156 d_walk(parent
, &ret
, check_mount
, NULL
);
1160 EXPORT_SYMBOL(have_submounts
);
1163 * Called by mount code to set a mountpoint and check if the mountpoint is
1164 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1165 * subtree can become unreachable).
1167 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1168 * this reason take rename_lock and d_lock on dentry and ancestors.
1170 int d_set_mounted(struct dentry
*dentry
)
1174 write_seqlock(&rename_lock
);
1175 for (p
= dentry
->d_parent
; !IS_ROOT(p
); p
= p
->d_parent
) {
1176 /* Need exclusion wrt. d_invalidate() */
1177 spin_lock(&p
->d_lock
);
1178 if (unlikely(d_unhashed(p
))) {
1179 spin_unlock(&p
->d_lock
);
1182 spin_unlock(&p
->d_lock
);
1184 spin_lock(&dentry
->d_lock
);
1185 if (!d_unlinked(dentry
)) {
1186 dentry
->d_flags
|= DCACHE_MOUNTED
;
1189 spin_unlock(&dentry
->d_lock
);
1191 write_sequnlock(&rename_lock
);
1196 * Search the dentry child list of the specified parent,
1197 * and move any unused dentries to the end of the unused
1198 * list for prune_dcache(). We descend to the next level
1199 * whenever the d_subdirs list is non-empty and continue
1202 * It returns zero iff there are no unused children,
1203 * otherwise it returns the number of children moved to
1204 * the end of the unused list. This may not be the total
1205 * number of unused children, because select_parent can
1206 * drop the lock and return early due to latency
1210 struct select_data
{
1211 struct dentry
*start
;
1212 struct list_head dispose
;
1216 static enum d_walk_ret
select_collect(void *_data
, struct dentry
*dentry
)
1218 struct select_data
*data
= _data
;
1219 enum d_walk_ret ret
= D_WALK_CONTINUE
;
1221 if (data
->start
== dentry
)
1224 if (dentry
->d_flags
& DCACHE_SHRINK_LIST
) {
1227 if (dentry
->d_flags
& DCACHE_LRU_LIST
)
1229 if (!dentry
->d_lockref
.count
) {
1230 d_shrink_add(dentry
, &data
->dispose
);
1235 * We can return to the caller if we have found some (this
1236 * ensures forward progress). We'll be coming back to find
1239 if (!list_empty(&data
->dispose
))
1240 ret
= need_resched() ? D_WALK_QUIT
: D_WALK_NORETRY
;
1246 * shrink_dcache_parent - prune dcache
1247 * @parent: parent of entries to prune
1249 * Prune the dcache to remove unused children of the parent dentry.
1251 void shrink_dcache_parent(struct dentry
*parent
)
1254 struct select_data data
;
1256 INIT_LIST_HEAD(&data
.dispose
);
1257 data
.start
= parent
;
1260 d_walk(parent
, &data
, select_collect
, NULL
);
1264 shrink_dentry_list(&data
.dispose
);
1268 EXPORT_SYMBOL(shrink_dcache_parent
);
1270 static enum d_walk_ret
umount_check(void *_data
, struct dentry
*dentry
)
1272 /* it has busy descendents; complain about those instead */
1273 if (!list_empty(&dentry
->d_subdirs
))
1274 return D_WALK_CONTINUE
;
1276 /* root with refcount 1 is fine */
1277 if (dentry
== _data
&& dentry
->d_lockref
.count
== 1)
1278 return D_WALK_CONTINUE
;
1280 printk(KERN_ERR
"BUG: Dentry %p{i=%lx,n=%pd} "
1281 " still in use (%d) [unmount of %s %s]\n",
1284 dentry
->d_inode
->i_ino
: 0UL,
1286 dentry
->d_lockref
.count
,
1287 dentry
->d_sb
->s_type
->name
,
1288 dentry
->d_sb
->s_id
);
1290 return D_WALK_CONTINUE
;
1293 static void do_one_tree(struct dentry
*dentry
)
1295 shrink_dcache_parent(dentry
);
1296 d_walk(dentry
, dentry
, umount_check
, NULL
);
1302 * destroy the dentries attached to a superblock on unmounting
1304 void shrink_dcache_for_umount(struct super_block
*sb
)
1306 struct dentry
*dentry
;
1308 WARN(down_read_trylock(&sb
->s_umount
), "s_umount should've been locked");
1310 dentry
= sb
->s_root
;
1312 do_one_tree(dentry
);
1314 while (!hlist_bl_empty(&sb
->s_anon
)) {
1315 dentry
= dget(hlist_bl_entry(hlist_bl_first(&sb
->s_anon
), struct dentry
, d_hash
));
1316 do_one_tree(dentry
);
1320 struct detach_data
{
1321 struct select_data select
;
1322 struct dentry
*mountpoint
;
1324 static enum d_walk_ret
detach_and_collect(void *_data
, struct dentry
*dentry
)
1326 struct detach_data
*data
= _data
;
1328 if (d_mountpoint(dentry
)) {
1329 __dget_dlock(dentry
);
1330 data
->mountpoint
= dentry
;
1334 return select_collect(&data
->select
, dentry
);
1337 static void check_and_drop(void *_data
)
1339 struct detach_data
*data
= _data
;
1341 if (!data
->mountpoint
&& !data
->select
.found
)
1342 __d_drop(data
->select
.start
);
1346 * d_invalidate - detach submounts, prune dcache, and drop
1347 * @dentry: dentry to invalidate (aka detach, prune and drop)
1351 * The final d_drop is done as an atomic operation relative to
1352 * rename_lock ensuring there are no races with d_set_mounted. This
1353 * ensures there are no unhashed dentries on the path to a mountpoint.
1355 void d_invalidate(struct dentry
*dentry
)
1358 * If it's already been dropped, return OK.
1360 spin_lock(&dentry
->d_lock
);
1361 if (d_unhashed(dentry
)) {
1362 spin_unlock(&dentry
->d_lock
);
1365 spin_unlock(&dentry
->d_lock
);
1367 /* Negative dentries can be dropped without further checks */
1368 if (!dentry
->d_inode
) {
1374 struct detach_data data
;
1376 data
.mountpoint
= NULL
;
1377 INIT_LIST_HEAD(&data
.select
.dispose
);
1378 data
.select
.start
= dentry
;
1379 data
.select
.found
= 0;
1381 d_walk(dentry
, &data
, detach_and_collect
, check_and_drop
);
1383 if (data
.select
.found
)
1384 shrink_dentry_list(&data
.select
.dispose
);
1386 if (data
.mountpoint
) {
1387 detach_mounts(data
.mountpoint
);
1388 dput(data
.mountpoint
);
1391 if (!data
.mountpoint
&& !data
.select
.found
)
1397 EXPORT_SYMBOL(d_invalidate
);
1400 * __d_alloc - allocate a dcache entry
1401 * @sb: filesystem it will belong to
1402 * @name: qstr of the name
1404 * Allocates a dentry. It returns %NULL if there is insufficient memory
1405 * available. On a success the dentry is returned. The name passed in is
1406 * copied and the copy passed in may be reused after this call.
1409 struct dentry
*__d_alloc(struct super_block
*sb
, const struct qstr
*name
)
1411 struct dentry
*dentry
;
1414 dentry
= kmem_cache_alloc(dentry_cache
, GFP_KERNEL
);
1419 * We guarantee that the inline name is always NUL-terminated.
1420 * This way the memcpy() done by the name switching in rename
1421 * will still always have a NUL at the end, even if we might
1422 * be overwriting an internal NUL character
1424 dentry
->d_iname
[DNAME_INLINE_LEN
-1] = 0;
1425 if (name
->len
> DNAME_INLINE_LEN
-1) {
1426 size_t size
= offsetof(struct external_name
, name
[1]);
1427 struct external_name
*p
= kmalloc(size
+ name
->len
, GFP_KERNEL
);
1429 kmem_cache_free(dentry_cache
, dentry
);
1432 atomic_set(&p
->u
.count
, 1);
1434 if (IS_ENABLED(CONFIG_DCACHE_WORD_ACCESS
))
1435 kasan_unpoison_shadow(dname
,
1436 round_up(name
->len
+ 1, sizeof(unsigned long)));
1438 dname
= dentry
->d_iname
;
1441 dentry
->d_name
.len
= name
->len
;
1442 dentry
->d_name
.hash
= name
->hash
;
1443 memcpy(dname
, name
->name
, name
->len
);
1444 dname
[name
->len
] = 0;
1446 /* Make sure we always see the terminating NUL character */
1448 dentry
->d_name
.name
= dname
;
1450 dentry
->d_lockref
.count
= 1;
1451 dentry
->d_flags
= 0;
1452 spin_lock_init(&dentry
->d_lock
);
1453 seqcount_init(&dentry
->d_seq
);
1454 dentry
->d_inode
= NULL
;
1455 dentry
->d_parent
= dentry
;
1457 dentry
->d_op
= NULL
;
1458 dentry
->d_fsdata
= NULL
;
1459 INIT_HLIST_BL_NODE(&dentry
->d_hash
);
1460 INIT_LIST_HEAD(&dentry
->d_lru
);
1461 INIT_LIST_HEAD(&dentry
->d_subdirs
);
1462 INIT_HLIST_NODE(&dentry
->d_u
.d_alias
);
1463 INIT_LIST_HEAD(&dentry
->d_child
);
1464 d_set_d_op(dentry
, dentry
->d_sb
->s_d_op
);
1466 this_cpu_inc(nr_dentry
);
1472 * d_alloc - allocate a dcache entry
1473 * @parent: parent of entry to allocate
1474 * @name: qstr of the name
1476 * Allocates a dentry. It returns %NULL if there is insufficient memory
1477 * available. On a success the dentry is returned. The name passed in is
1478 * copied and the copy passed in may be reused after this call.
1480 struct dentry
*d_alloc(struct dentry
* parent
, const struct qstr
*name
)
1482 struct dentry
*dentry
= __d_alloc(parent
->d_sb
, name
);
1486 spin_lock(&parent
->d_lock
);
1488 * don't need child lock because it is not subject
1489 * to concurrency here
1491 __dget_dlock(parent
);
1492 dentry
->d_parent
= parent
;
1493 list_add(&dentry
->d_child
, &parent
->d_subdirs
);
1494 spin_unlock(&parent
->d_lock
);
1498 EXPORT_SYMBOL(d_alloc
);
1501 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1502 * @sb: the superblock
1503 * @name: qstr of the name
1505 * For a filesystem that just pins its dentries in memory and never
1506 * performs lookups at all, return an unhashed IS_ROOT dentry.
1508 struct dentry
*d_alloc_pseudo(struct super_block
*sb
, const struct qstr
*name
)
1510 return __d_alloc(sb
, name
);
1512 EXPORT_SYMBOL(d_alloc_pseudo
);
1514 struct dentry
*d_alloc_name(struct dentry
*parent
, const char *name
)
1519 q
.len
= strlen(name
);
1520 q
.hash
= full_name_hash(q
.name
, q
.len
);
1521 return d_alloc(parent
, &q
);
1523 EXPORT_SYMBOL(d_alloc_name
);
1525 void d_set_d_op(struct dentry
*dentry
, const struct dentry_operations
*op
)
1527 WARN_ON_ONCE(dentry
->d_op
);
1528 WARN_ON_ONCE(dentry
->d_flags
& (DCACHE_OP_HASH
|
1530 DCACHE_OP_REVALIDATE
|
1531 DCACHE_OP_WEAK_REVALIDATE
|
1532 DCACHE_OP_DELETE
));
1537 dentry
->d_flags
|= DCACHE_OP_HASH
;
1539 dentry
->d_flags
|= DCACHE_OP_COMPARE
;
1540 if (op
->d_revalidate
)
1541 dentry
->d_flags
|= DCACHE_OP_REVALIDATE
;
1542 if (op
->d_weak_revalidate
)
1543 dentry
->d_flags
|= DCACHE_OP_WEAK_REVALIDATE
;
1545 dentry
->d_flags
|= DCACHE_OP_DELETE
;
1547 dentry
->d_flags
|= DCACHE_OP_PRUNE
;
1550 EXPORT_SYMBOL(d_set_d_op
);
1552 static unsigned d_flags_for_inode(struct inode
*inode
)
1554 unsigned add_flags
= DCACHE_FILE_TYPE
;
1557 return DCACHE_MISS_TYPE
;
1559 if (S_ISDIR(inode
->i_mode
)) {
1560 add_flags
= DCACHE_DIRECTORY_TYPE
;
1561 if (unlikely(!(inode
->i_opflags
& IOP_LOOKUP
))) {
1562 if (unlikely(!inode
->i_op
->lookup
))
1563 add_flags
= DCACHE_AUTODIR_TYPE
;
1565 inode
->i_opflags
|= IOP_LOOKUP
;
1567 } else if (unlikely(!(inode
->i_opflags
& IOP_NOFOLLOW
))) {
1568 if (unlikely(inode
->i_op
->follow_link
))
1569 add_flags
= DCACHE_SYMLINK_TYPE
;
1571 inode
->i_opflags
|= IOP_NOFOLLOW
;
1574 if (unlikely(IS_AUTOMOUNT(inode
)))
1575 add_flags
|= DCACHE_NEED_AUTOMOUNT
;
1579 static void __d_instantiate(struct dentry
*dentry
, struct inode
*inode
)
1581 unsigned add_flags
= d_flags_for_inode(inode
);
1583 spin_lock(&dentry
->d_lock
);
1584 __d_set_type(dentry
, add_flags
);
1586 hlist_add_head(&dentry
->d_u
.d_alias
, &inode
->i_dentry
);
1587 dentry
->d_inode
= inode
;
1588 dentry_rcuwalk_barrier(dentry
);
1589 spin_unlock(&dentry
->d_lock
);
1590 fsnotify_d_instantiate(dentry
, inode
);
1594 * d_instantiate - fill in inode information for a dentry
1595 * @entry: dentry to complete
1596 * @inode: inode to attach to this dentry
1598 * Fill in inode information in the entry.
1600 * This turns negative dentries into productive full members
1603 * NOTE! This assumes that the inode count has been incremented
1604 * (or otherwise set) by the caller to indicate that it is now
1605 * in use by the dcache.
1608 void d_instantiate(struct dentry
*entry
, struct inode
* inode
)
1610 BUG_ON(!hlist_unhashed(&entry
->d_u
.d_alias
));
1612 spin_lock(&inode
->i_lock
);
1613 __d_instantiate(entry
, inode
);
1615 spin_unlock(&inode
->i_lock
);
1616 security_d_instantiate(entry
, inode
);
1618 EXPORT_SYMBOL(d_instantiate
);
1621 * d_instantiate_unique - instantiate a non-aliased dentry
1622 * @entry: dentry to instantiate
1623 * @inode: inode to attach to this dentry
1625 * Fill in inode information in the entry. On success, it returns NULL.
1626 * If an unhashed alias of "entry" already exists, then we return the
1627 * aliased dentry instead and drop one reference to inode.
1629 * Note that in order to avoid conflicts with rename() etc, the caller
1630 * had better be holding the parent directory semaphore.
1632 * This also assumes that the inode count has been incremented
1633 * (or otherwise set) by the caller to indicate that it is now
1634 * in use by the dcache.
1636 static struct dentry
*__d_instantiate_unique(struct dentry
*entry
,
1637 struct inode
*inode
)
1639 struct dentry
*alias
;
1640 int len
= entry
->d_name
.len
;
1641 const char *name
= entry
->d_name
.name
;
1642 unsigned int hash
= entry
->d_name
.hash
;
1645 __d_instantiate(entry
, NULL
);
1649 hlist_for_each_entry(alias
, &inode
->i_dentry
, d_u
.d_alias
) {
1651 * Don't need alias->d_lock here, because aliases with
1652 * d_parent == entry->d_parent are not subject to name or
1653 * parent changes, because the parent inode i_mutex is held.
1655 if (alias
->d_name
.hash
!= hash
)
1657 if (alias
->d_parent
!= entry
->d_parent
)
1659 if (alias
->d_name
.len
!= len
)
1661 if (dentry_cmp(alias
, name
, len
))
1667 __d_instantiate(entry
, inode
);
1671 struct dentry
*d_instantiate_unique(struct dentry
*entry
, struct inode
*inode
)
1673 struct dentry
*result
;
1675 BUG_ON(!hlist_unhashed(&entry
->d_u
.d_alias
));
1678 spin_lock(&inode
->i_lock
);
1679 result
= __d_instantiate_unique(entry
, inode
);
1681 spin_unlock(&inode
->i_lock
);
1684 security_d_instantiate(entry
, inode
);
1688 BUG_ON(!d_unhashed(result
));
1693 EXPORT_SYMBOL(d_instantiate_unique
);
1696 * d_instantiate_no_diralias - instantiate a non-aliased dentry
1697 * @entry: dentry to complete
1698 * @inode: inode to attach to this dentry
1700 * Fill in inode information in the entry. If a directory alias is found, then
1701 * return an error (and drop inode). Together with d_materialise_unique() this
1702 * guarantees that a directory inode may never have more than one alias.
1704 int d_instantiate_no_diralias(struct dentry
*entry
, struct inode
*inode
)
1706 BUG_ON(!hlist_unhashed(&entry
->d_u
.d_alias
));
1708 spin_lock(&inode
->i_lock
);
1709 if (S_ISDIR(inode
->i_mode
) && !hlist_empty(&inode
->i_dentry
)) {
1710 spin_unlock(&inode
->i_lock
);
1714 __d_instantiate(entry
, inode
);
1715 spin_unlock(&inode
->i_lock
);
1716 security_d_instantiate(entry
, inode
);
1720 EXPORT_SYMBOL(d_instantiate_no_diralias
);
1722 struct dentry
*d_make_root(struct inode
*root_inode
)
1724 struct dentry
*res
= NULL
;
1727 static const struct qstr name
= QSTR_INIT("/", 1);
1729 res
= __d_alloc(root_inode
->i_sb
, &name
);
1731 d_instantiate(res
, root_inode
);
1737 EXPORT_SYMBOL(d_make_root
);
1739 static struct dentry
* __d_find_any_alias(struct inode
*inode
)
1741 struct dentry
*alias
;
1743 if (hlist_empty(&inode
->i_dentry
))
1745 alias
= hlist_entry(inode
->i_dentry
.first
, struct dentry
, d_u
.d_alias
);
1751 * d_find_any_alias - find any alias for a given inode
1752 * @inode: inode to find an alias for
1754 * If any aliases exist for the given inode, take and return a
1755 * reference for one of them. If no aliases exist, return %NULL.
1757 struct dentry
*d_find_any_alias(struct inode
*inode
)
1761 spin_lock(&inode
->i_lock
);
1762 de
= __d_find_any_alias(inode
);
1763 spin_unlock(&inode
->i_lock
);
1766 EXPORT_SYMBOL(d_find_any_alias
);
1768 static struct dentry
*__d_obtain_alias(struct inode
*inode
, int disconnected
)
1770 static const struct qstr anonstring
= QSTR_INIT("/", 1);
1776 return ERR_PTR(-ESTALE
);
1778 return ERR_CAST(inode
);
1780 res
= d_find_any_alias(inode
);
1784 tmp
= __d_alloc(inode
->i_sb
, &anonstring
);
1786 res
= ERR_PTR(-ENOMEM
);
1790 spin_lock(&inode
->i_lock
);
1791 res
= __d_find_any_alias(inode
);
1793 spin_unlock(&inode
->i_lock
);
1798 /* attach a disconnected dentry */
1799 add_flags
= d_flags_for_inode(inode
);
1802 add_flags
|= DCACHE_DISCONNECTED
;
1804 spin_lock(&tmp
->d_lock
);
1805 tmp
->d_inode
= inode
;
1806 tmp
->d_flags
|= add_flags
;
1807 hlist_add_head(&tmp
->d_u
.d_alias
, &inode
->i_dentry
);
1808 hlist_bl_lock(&tmp
->d_sb
->s_anon
);
1809 hlist_bl_add_head(&tmp
->d_hash
, &tmp
->d_sb
->s_anon
);
1810 hlist_bl_unlock(&tmp
->d_sb
->s_anon
);
1811 spin_unlock(&tmp
->d_lock
);
1812 spin_unlock(&inode
->i_lock
);
1813 security_d_instantiate(tmp
, inode
);
1818 if (res
&& !IS_ERR(res
))
1819 security_d_instantiate(res
, inode
);
1825 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
1826 * @inode: inode to allocate the dentry for
1828 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1829 * similar open by handle operations. The returned dentry may be anonymous,
1830 * or may have a full name (if the inode was already in the cache).
1832 * When called on a directory inode, we must ensure that the inode only ever
1833 * has one dentry. If a dentry is found, that is returned instead of
1834 * allocating a new one.
1836 * On successful return, the reference to the inode has been transferred
1837 * to the dentry. In case of an error the reference on the inode is released.
1838 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1839 * be passed in and the error will be propagated to the return value,
1840 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1842 struct dentry
*d_obtain_alias(struct inode
*inode
)
1844 return __d_obtain_alias(inode
, 1);
1846 EXPORT_SYMBOL(d_obtain_alias
);
1849 * d_obtain_root - find or allocate a dentry for a given inode
1850 * @inode: inode to allocate the dentry for
1852 * Obtain an IS_ROOT dentry for the root of a filesystem.
1854 * We must ensure that directory inodes only ever have one dentry. If a
1855 * dentry is found, that is returned instead of allocating a new one.
1857 * On successful return, the reference to the inode has been transferred
1858 * to the dentry. In case of an error the reference on the inode is
1859 * released. A %NULL or IS_ERR inode may be passed in and will be the
1860 * error will be propagate to the return value, with a %NULL @inode
1861 * replaced by ERR_PTR(-ESTALE).
1863 struct dentry
*d_obtain_root(struct inode
*inode
)
1865 return __d_obtain_alias(inode
, 0);
1867 EXPORT_SYMBOL(d_obtain_root
);
1870 * d_add_ci - lookup or allocate new dentry with case-exact name
1871 * @inode: the inode case-insensitive lookup has found
1872 * @dentry: the negative dentry that was passed to the parent's lookup func
1873 * @name: the case-exact name to be associated with the returned dentry
1875 * This is to avoid filling the dcache with case-insensitive names to the
1876 * same inode, only the actual correct case is stored in the dcache for
1877 * case-insensitive filesystems.
1879 * For a case-insensitive lookup match and if the the case-exact dentry
1880 * already exists in in the dcache, use it and return it.
1882 * If no entry exists with the exact case name, allocate new dentry with
1883 * the exact case, and return the spliced entry.
1885 struct dentry
*d_add_ci(struct dentry
*dentry
, struct inode
*inode
,
1888 struct dentry
*found
;
1892 * First check if a dentry matching the name already exists,
1893 * if not go ahead and create it now.
1895 found
= d_hash_and_lookup(dentry
->d_parent
, name
);
1897 new = d_alloc(dentry
->d_parent
, name
);
1899 found
= ERR_PTR(-ENOMEM
);
1901 found
= d_splice_alias(inode
, new);
1912 EXPORT_SYMBOL(d_add_ci
);
1915 * Do the slow-case of the dentry name compare.
1917 * Unlike the dentry_cmp() function, we need to atomically
1918 * load the name and length information, so that the
1919 * filesystem can rely on them, and can use the 'name' and
1920 * 'len' information without worrying about walking off the
1921 * end of memory etc.
1923 * Thus the read_seqcount_retry() and the "duplicate" info
1924 * in arguments (the low-level filesystem should not look
1925 * at the dentry inode or name contents directly, since
1926 * rename can change them while we're in RCU mode).
1928 enum slow_d_compare
{
1934 static noinline
enum slow_d_compare
slow_dentry_cmp(
1935 const struct dentry
*parent
,
1936 struct dentry
*dentry
,
1938 const struct qstr
*name
)
1940 int tlen
= dentry
->d_name
.len
;
1941 const char *tname
= dentry
->d_name
.name
;
1943 if (read_seqcount_retry(&dentry
->d_seq
, seq
)) {
1945 return D_COMP_SEQRETRY
;
1947 if (parent
->d_op
->d_compare(parent
, dentry
, tlen
, tname
, name
))
1948 return D_COMP_NOMATCH
;
1953 * __d_lookup_rcu - search for a dentry (racy, store-free)
1954 * @parent: parent dentry
1955 * @name: qstr of name we wish to find
1956 * @seqp: returns d_seq value at the point where the dentry was found
1957 * Returns: dentry, or NULL
1959 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
1960 * resolution (store-free path walking) design described in
1961 * Documentation/filesystems/path-lookup.txt.
1963 * This is not to be used outside core vfs.
1965 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
1966 * held, and rcu_read_lock held. The returned dentry must not be stored into
1967 * without taking d_lock and checking d_seq sequence count against @seq
1970 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
1973 * Alternatively, __d_lookup_rcu may be called again to look up the child of
1974 * the returned dentry, so long as its parent's seqlock is checked after the
1975 * child is looked up. Thus, an interlocking stepping of sequence lock checks
1976 * is formed, giving integrity down the path walk.
1978 * NOTE! The caller *has* to check the resulting dentry against the sequence
1979 * number we've returned before using any of the resulting dentry state!
1981 struct dentry
*__d_lookup_rcu(const struct dentry
*parent
,
1982 const struct qstr
*name
,
1985 u64 hashlen
= name
->hash_len
;
1986 const unsigned char *str
= name
->name
;
1987 struct hlist_bl_head
*b
= d_hash(parent
, hashlen_hash(hashlen
));
1988 struct hlist_bl_node
*node
;
1989 struct dentry
*dentry
;
1992 * Note: There is significant duplication with __d_lookup_rcu which is
1993 * required to prevent single threaded performance regressions
1994 * especially on architectures where smp_rmb (in seqcounts) are costly.
1995 * Keep the two functions in sync.
1999 * The hash list is protected using RCU.
2001 * Carefully use d_seq when comparing a candidate dentry, to avoid
2002 * races with d_move().
2004 * It is possible that concurrent renames can mess up our list
2005 * walk here and result in missing our dentry, resulting in the
2006 * false-negative result. d_lookup() protects against concurrent
2007 * renames using rename_lock seqlock.
2009 * See Documentation/filesystems/path-lookup.txt for more details.
2011 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
2016 * The dentry sequence count protects us from concurrent
2017 * renames, and thus protects parent and name fields.
2019 * The caller must perform a seqcount check in order
2020 * to do anything useful with the returned dentry.
2022 * NOTE! We do a "raw" seqcount_begin here. That means that
2023 * we don't wait for the sequence count to stabilize if it
2024 * is in the middle of a sequence change. If we do the slow
2025 * dentry compare, we will do seqretries until it is stable,
2026 * and if we end up with a successful lookup, we actually
2027 * want to exit RCU lookup anyway.
2029 seq
= raw_seqcount_begin(&dentry
->d_seq
);
2030 if (dentry
->d_parent
!= parent
)
2032 if (d_unhashed(dentry
))
2035 if (unlikely(parent
->d_flags
& DCACHE_OP_COMPARE
)) {
2036 if (dentry
->d_name
.hash
!= hashlen_hash(hashlen
))
2039 switch (slow_dentry_cmp(parent
, dentry
, seq
, name
)) {
2042 case D_COMP_NOMATCH
:
2049 if (dentry
->d_name
.hash_len
!= hashlen
)
2052 if (!dentry_cmp(dentry
, str
, hashlen_len(hashlen
)))
2059 * d_lookup - search for a dentry
2060 * @parent: parent dentry
2061 * @name: qstr of name we wish to find
2062 * Returns: dentry, or NULL
2064 * d_lookup searches the children of the parent dentry for the name in
2065 * question. If the dentry is found its reference count is incremented and the
2066 * dentry is returned. The caller must use dput to free the entry when it has
2067 * finished using it. %NULL is returned if the dentry does not exist.
2069 struct dentry
*d_lookup(const struct dentry
*parent
, const struct qstr
*name
)
2071 struct dentry
*dentry
;
2075 seq
= read_seqbegin(&rename_lock
);
2076 dentry
= __d_lookup(parent
, name
);
2079 } while (read_seqretry(&rename_lock
, seq
));
2082 EXPORT_SYMBOL(d_lookup
);
2085 * __d_lookup - search for a dentry (racy)
2086 * @parent: parent dentry
2087 * @name: qstr of name we wish to find
2088 * Returns: dentry, or NULL
2090 * __d_lookup is like d_lookup, however it may (rarely) return a
2091 * false-negative result due to unrelated rename activity.
2093 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2094 * however it must be used carefully, eg. with a following d_lookup in
2095 * the case of failure.
2097 * __d_lookup callers must be commented.
2099 struct dentry
*__d_lookup(const struct dentry
*parent
, const struct qstr
*name
)
2101 unsigned int len
= name
->len
;
2102 unsigned int hash
= name
->hash
;
2103 const unsigned char *str
= name
->name
;
2104 struct hlist_bl_head
*b
= d_hash(parent
, hash
);
2105 struct hlist_bl_node
*node
;
2106 struct dentry
*found
= NULL
;
2107 struct dentry
*dentry
;
2110 * Note: There is significant duplication with __d_lookup_rcu which is
2111 * required to prevent single threaded performance regressions
2112 * especially on architectures where smp_rmb (in seqcounts) are costly.
2113 * Keep the two functions in sync.
2117 * The hash list is protected using RCU.
2119 * Take d_lock when comparing a candidate dentry, to avoid races
2122 * It is possible that concurrent renames can mess up our list
2123 * walk here and result in missing our dentry, resulting in the
2124 * false-negative result. d_lookup() protects against concurrent
2125 * renames using rename_lock seqlock.
2127 * See Documentation/filesystems/path-lookup.txt for more details.
2131 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
2133 if (dentry
->d_name
.hash
!= hash
)
2136 spin_lock(&dentry
->d_lock
);
2137 if (dentry
->d_parent
!= parent
)
2139 if (d_unhashed(dentry
))
2143 * It is safe to compare names since d_move() cannot
2144 * change the qstr (protected by d_lock).
2146 if (parent
->d_flags
& DCACHE_OP_COMPARE
) {
2147 int tlen
= dentry
->d_name
.len
;
2148 const char *tname
= dentry
->d_name
.name
;
2149 if (parent
->d_op
->d_compare(parent
, dentry
, tlen
, tname
, name
))
2152 if (dentry
->d_name
.len
!= len
)
2154 if (dentry_cmp(dentry
, str
, len
))
2158 dentry
->d_lockref
.count
++;
2160 spin_unlock(&dentry
->d_lock
);
2163 spin_unlock(&dentry
->d_lock
);
2171 * d_hash_and_lookup - hash the qstr then search for a dentry
2172 * @dir: Directory to search in
2173 * @name: qstr of name we wish to find
2175 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2177 struct dentry
*d_hash_and_lookup(struct dentry
*dir
, struct qstr
*name
)
2180 * Check for a fs-specific hash function. Note that we must
2181 * calculate the standard hash first, as the d_op->d_hash()
2182 * routine may choose to leave the hash value unchanged.
2184 name
->hash
= full_name_hash(name
->name
, name
->len
);
2185 if (dir
->d_flags
& DCACHE_OP_HASH
) {
2186 int err
= dir
->d_op
->d_hash(dir
, name
);
2187 if (unlikely(err
< 0))
2188 return ERR_PTR(err
);
2190 return d_lookup(dir
, name
);
2192 EXPORT_SYMBOL(d_hash_and_lookup
);
2195 * d_validate - verify dentry provided from insecure source (deprecated)
2196 * @dentry: The dentry alleged to be valid child of @dparent
2197 * @dparent: The parent dentry (known to be valid)
2199 * An insecure source has sent us a dentry, here we verify it and dget() it.
2200 * This is used by ncpfs in its readdir implementation.
2201 * Zero is returned in the dentry is invalid.
2203 * This function is slow for big directories, and deprecated, do not use it.
2205 int d_validate(struct dentry
*dentry
, struct dentry
*dparent
)
2207 struct dentry
*child
;
2209 spin_lock(&dparent
->d_lock
);
2210 list_for_each_entry(child
, &dparent
->d_subdirs
, d_child
) {
2211 if (dentry
== child
) {
2212 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
2213 __dget_dlock(dentry
);
2214 spin_unlock(&dentry
->d_lock
);
2215 spin_unlock(&dparent
->d_lock
);
2219 spin_unlock(&dparent
->d_lock
);
2223 EXPORT_SYMBOL(d_validate
);
2226 * When a file is deleted, we have two options:
2227 * - turn this dentry into a negative dentry
2228 * - unhash this dentry and free it.
2230 * Usually, we want to just turn this into
2231 * a negative dentry, but if anybody else is
2232 * currently using the dentry or the inode
2233 * we can't do that and we fall back on removing
2234 * it from the hash queues and waiting for
2235 * it to be deleted later when it has no users
2239 * d_delete - delete a dentry
2240 * @dentry: The dentry to delete
2242 * Turn the dentry into a negative dentry if possible, otherwise
2243 * remove it from the hash queues so it can be deleted later
2246 void d_delete(struct dentry
* dentry
)
2248 struct inode
*inode
;
2251 * Are we the only user?
2254 spin_lock(&dentry
->d_lock
);
2255 inode
= dentry
->d_inode
;
2256 isdir
= S_ISDIR(inode
->i_mode
);
2257 if (dentry
->d_lockref
.count
== 1) {
2258 if (!spin_trylock(&inode
->i_lock
)) {
2259 spin_unlock(&dentry
->d_lock
);
2263 dentry
->d_flags
&= ~DCACHE_CANT_MOUNT
;
2264 dentry_unlink_inode(dentry
);
2265 fsnotify_nameremove(dentry
, isdir
);
2269 if (!d_unhashed(dentry
))
2272 spin_unlock(&dentry
->d_lock
);
2274 fsnotify_nameremove(dentry
, isdir
);
2276 EXPORT_SYMBOL(d_delete
);
2278 static void __d_rehash(struct dentry
* entry
, struct hlist_bl_head
*b
)
2280 BUG_ON(!d_unhashed(entry
));
2282 entry
->d_flags
|= DCACHE_RCUACCESS
;
2283 hlist_bl_add_head_rcu(&entry
->d_hash
, b
);
2287 static void _d_rehash(struct dentry
* entry
)
2289 __d_rehash(entry
, d_hash(entry
->d_parent
, entry
->d_name
.hash
));
2293 * d_rehash - add an entry back to the hash
2294 * @entry: dentry to add to the hash
2296 * Adds a dentry to the hash according to its name.
2299 void d_rehash(struct dentry
* entry
)
2301 spin_lock(&entry
->d_lock
);
2303 spin_unlock(&entry
->d_lock
);
2305 EXPORT_SYMBOL(d_rehash
);
2308 * dentry_update_name_case - update case insensitive dentry with a new name
2309 * @dentry: dentry to be updated
2312 * Update a case insensitive dentry with new case of name.
2314 * dentry must have been returned by d_lookup with name @name. Old and new
2315 * name lengths must match (ie. no d_compare which allows mismatched name
2318 * Parent inode i_mutex must be held over d_lookup and into this call (to
2319 * keep renames and concurrent inserts, and readdir(2) away).
2321 void dentry_update_name_case(struct dentry
*dentry
, struct qstr
*name
)
2323 BUG_ON(!mutex_is_locked(&dentry
->d_parent
->d_inode
->i_mutex
));
2324 BUG_ON(dentry
->d_name
.len
!= name
->len
); /* d_lookup gives this */
2326 spin_lock(&dentry
->d_lock
);
2327 write_seqcount_begin(&dentry
->d_seq
);
2328 memcpy((unsigned char *)dentry
->d_name
.name
, name
->name
, name
->len
);
2329 write_seqcount_end(&dentry
->d_seq
);
2330 spin_unlock(&dentry
->d_lock
);
2332 EXPORT_SYMBOL(dentry_update_name_case
);
2334 static void swap_names(struct dentry
*dentry
, struct dentry
*target
)
2336 if (unlikely(dname_external(target
))) {
2337 if (unlikely(dname_external(dentry
))) {
2339 * Both external: swap the pointers
2341 swap(target
->d_name
.name
, dentry
->d_name
.name
);
2344 * dentry:internal, target:external. Steal target's
2345 * storage and make target internal.
2347 memcpy(target
->d_iname
, dentry
->d_name
.name
,
2348 dentry
->d_name
.len
+ 1);
2349 dentry
->d_name
.name
= target
->d_name
.name
;
2350 target
->d_name
.name
= target
->d_iname
;
2353 if (unlikely(dname_external(dentry
))) {
2355 * dentry:external, target:internal. Give dentry's
2356 * storage to target and make dentry internal
2358 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2359 target
->d_name
.len
+ 1);
2360 target
->d_name
.name
= dentry
->d_name
.name
;
2361 dentry
->d_name
.name
= dentry
->d_iname
;
2364 * Both are internal.
2367 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN
, sizeof(long)));
2368 kmemcheck_mark_initialized(dentry
->d_iname
, DNAME_INLINE_LEN
);
2369 kmemcheck_mark_initialized(target
->d_iname
, DNAME_INLINE_LEN
);
2370 for (i
= 0; i
< DNAME_INLINE_LEN
/ sizeof(long); i
++) {
2371 swap(((long *) &dentry
->d_iname
)[i
],
2372 ((long *) &target
->d_iname
)[i
]);
2376 swap(dentry
->d_name
.hash_len
, target
->d_name
.hash_len
);
2379 static void copy_name(struct dentry
*dentry
, struct dentry
*target
)
2381 struct external_name
*old_name
= NULL
;
2382 if (unlikely(dname_external(dentry
)))
2383 old_name
= external_name(dentry
);
2384 if (unlikely(dname_external(target
))) {
2385 atomic_inc(&external_name(target
)->u
.count
);
2386 dentry
->d_name
= target
->d_name
;
2388 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2389 target
->d_name
.len
+ 1);
2390 dentry
->d_name
.name
= dentry
->d_iname
;
2391 dentry
->d_name
.hash_len
= target
->d_name
.hash_len
;
2393 if (old_name
&& likely(atomic_dec_and_test(&old_name
->u
.count
)))
2394 kfree_rcu(old_name
, u
.head
);
2397 static void dentry_lock_for_move(struct dentry
*dentry
, struct dentry
*target
)
2400 * XXXX: do we really need to take target->d_lock?
2402 if (IS_ROOT(dentry
) || dentry
->d_parent
== target
->d_parent
)
2403 spin_lock(&target
->d_parent
->d_lock
);
2405 if (d_ancestor(dentry
->d_parent
, target
->d_parent
)) {
2406 spin_lock(&dentry
->d_parent
->d_lock
);
2407 spin_lock_nested(&target
->d_parent
->d_lock
,
2408 DENTRY_D_LOCK_NESTED
);
2410 spin_lock(&target
->d_parent
->d_lock
);
2411 spin_lock_nested(&dentry
->d_parent
->d_lock
,
2412 DENTRY_D_LOCK_NESTED
);
2415 if (target
< dentry
) {
2416 spin_lock_nested(&target
->d_lock
, 2);
2417 spin_lock_nested(&dentry
->d_lock
, 3);
2419 spin_lock_nested(&dentry
->d_lock
, 2);
2420 spin_lock_nested(&target
->d_lock
, 3);
2424 static void dentry_unlock_for_move(struct dentry
*dentry
, struct dentry
*target
)
2426 if (target
->d_parent
!= dentry
->d_parent
)
2427 spin_unlock(&dentry
->d_parent
->d_lock
);
2428 if (target
->d_parent
!= target
)
2429 spin_unlock(&target
->d_parent
->d_lock
);
2430 spin_unlock(&target
->d_lock
);
2431 spin_unlock(&dentry
->d_lock
);
2435 * When switching names, the actual string doesn't strictly have to
2436 * be preserved in the target - because we're dropping the target
2437 * anyway. As such, we can just do a simple memcpy() to copy over
2438 * the new name before we switch, unless we are going to rehash
2439 * it. Note that if we *do* unhash the target, we are not allowed
2440 * to rehash it without giving it a new name/hash key - whether
2441 * we swap or overwrite the names here, resulting name won't match
2442 * the reality in filesystem; it's only there for d_path() purposes.
2443 * Note that all of this is happening under rename_lock, so the
2444 * any hash lookup seeing it in the middle of manipulations will
2445 * be discarded anyway. So we do not care what happens to the hash
2449 * __d_move - move a dentry
2450 * @dentry: entry to move
2451 * @target: new dentry
2452 * @exchange: exchange the two dentries
2454 * Update the dcache to reflect the move of a file name. Negative
2455 * dcache entries should not be moved in this way. Caller must hold
2456 * rename_lock, the i_mutex of the source and target directories,
2457 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2459 static void __d_move(struct dentry
*dentry
, struct dentry
*target
,
2462 if (!dentry
->d_inode
)
2463 printk(KERN_WARNING
"VFS: moving negative dcache entry\n");
2465 BUG_ON(d_ancestor(dentry
, target
));
2466 BUG_ON(d_ancestor(target
, dentry
));
2468 dentry_lock_for_move(dentry
, target
);
2470 write_seqcount_begin(&dentry
->d_seq
);
2471 write_seqcount_begin_nested(&target
->d_seq
, DENTRY_D_LOCK_NESTED
);
2473 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
2476 * Move the dentry to the target hash queue. Don't bother checking
2477 * for the same hash queue because of how unlikely it is.
2480 __d_rehash(dentry
, d_hash(target
->d_parent
, target
->d_name
.hash
));
2483 * Unhash the target (d_delete() is not usable here). If exchanging
2484 * the two dentries, then rehash onto the other's hash queue.
2489 d_hash(dentry
->d_parent
, dentry
->d_name
.hash
));
2492 /* Switch the names.. */
2494 swap_names(dentry
, target
);
2496 copy_name(dentry
, target
);
2498 /* ... and switch them in the tree */
2499 if (IS_ROOT(dentry
)) {
2500 /* splicing a tree */
2501 dentry
->d_parent
= target
->d_parent
;
2502 target
->d_parent
= target
;
2503 list_del_init(&target
->d_child
);
2504 list_move(&dentry
->d_child
, &dentry
->d_parent
->d_subdirs
);
2506 /* swapping two dentries */
2507 swap(dentry
->d_parent
, target
->d_parent
);
2508 list_move(&target
->d_child
, &target
->d_parent
->d_subdirs
);
2509 list_move(&dentry
->d_child
, &dentry
->d_parent
->d_subdirs
);
2511 fsnotify_d_move(target
);
2512 fsnotify_d_move(dentry
);
2515 write_seqcount_end(&target
->d_seq
);
2516 write_seqcount_end(&dentry
->d_seq
);
2518 dentry_unlock_for_move(dentry
, target
);
2522 * d_move - move a dentry
2523 * @dentry: entry to move
2524 * @target: new dentry
2526 * Update the dcache to reflect the move of a file name. Negative
2527 * dcache entries should not be moved in this way. See the locking
2528 * requirements for __d_move.
2530 void d_move(struct dentry
*dentry
, struct dentry
*target
)
2532 write_seqlock(&rename_lock
);
2533 __d_move(dentry
, target
, false);
2534 write_sequnlock(&rename_lock
);
2536 EXPORT_SYMBOL(d_move
);
2539 * d_exchange - exchange two dentries
2540 * @dentry1: first dentry
2541 * @dentry2: second dentry
2543 void d_exchange(struct dentry
*dentry1
, struct dentry
*dentry2
)
2545 write_seqlock(&rename_lock
);
2547 WARN_ON(!dentry1
->d_inode
);
2548 WARN_ON(!dentry2
->d_inode
);
2549 WARN_ON(IS_ROOT(dentry1
));
2550 WARN_ON(IS_ROOT(dentry2
));
2552 __d_move(dentry1
, dentry2
, true);
2554 write_sequnlock(&rename_lock
);
2558 * d_ancestor - search for an ancestor
2559 * @p1: ancestor dentry
2562 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2563 * an ancestor of p2, else NULL.
2565 struct dentry
*d_ancestor(struct dentry
*p1
, struct dentry
*p2
)
2569 for (p
= p2
; !IS_ROOT(p
); p
= p
->d_parent
) {
2570 if (p
->d_parent
== p1
)
2577 * This helper attempts to cope with remotely renamed directories
2579 * It assumes that the caller is already holding
2580 * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
2582 * Note: If ever the locking in lock_rename() changes, then please
2583 * remember to update this too...
2585 static int __d_unalias(struct inode
*inode
,
2586 struct dentry
*dentry
, struct dentry
*alias
)
2588 struct mutex
*m1
= NULL
, *m2
= NULL
;
2591 /* If alias and dentry share a parent, then no extra locks required */
2592 if (alias
->d_parent
== dentry
->d_parent
)
2595 /* See lock_rename() */
2596 if (!mutex_trylock(&dentry
->d_sb
->s_vfs_rename_mutex
))
2598 m1
= &dentry
->d_sb
->s_vfs_rename_mutex
;
2599 if (!mutex_trylock(&alias
->d_parent
->d_inode
->i_mutex
))
2601 m2
= &alias
->d_parent
->d_inode
->i_mutex
;
2603 __d_move(alias
, dentry
, false);
2606 spin_unlock(&inode
->i_lock
);
2615 * d_splice_alias - splice a disconnected dentry into the tree if one exists
2616 * @inode: the inode which may have a disconnected dentry
2617 * @dentry: a negative dentry which we want to point to the inode.
2619 * If inode is a directory and has an IS_ROOT alias, then d_move that in
2620 * place of the given dentry and return it, else simply d_add the inode
2621 * to the dentry and return NULL.
2623 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
2624 * we should error out: directories can't have multiple aliases.
2626 * This is needed in the lookup routine of any filesystem that is exportable
2627 * (via knfsd) so that we can build dcache paths to directories effectively.
2629 * If a dentry was found and moved, then it is returned. Otherwise NULL
2630 * is returned. This matches the expected return value of ->lookup.
2632 * Cluster filesystems may call this function with a negative, hashed dentry.
2633 * In that case, we know that the inode will be a regular file, and also this
2634 * will only occur during atomic_open. So we need to check for the dentry
2635 * being already hashed only in the final case.
2637 struct dentry
*d_splice_alias(struct inode
*inode
, struct dentry
*dentry
)
2640 return ERR_CAST(inode
);
2642 BUG_ON(!d_unhashed(dentry
));
2645 __d_instantiate(dentry
, NULL
);
2648 spin_lock(&inode
->i_lock
);
2649 if (S_ISDIR(inode
->i_mode
)) {
2650 struct dentry
*new = __d_find_any_alias(inode
);
2651 if (unlikely(new)) {
2652 write_seqlock(&rename_lock
);
2653 if (unlikely(d_ancestor(new, dentry
))) {
2654 write_sequnlock(&rename_lock
);
2655 spin_unlock(&inode
->i_lock
);
2657 new = ERR_PTR(-ELOOP
);
2658 pr_warn_ratelimited(
2659 "VFS: Lookup of '%s' in %s %s"
2660 " would have caused loop\n",
2661 dentry
->d_name
.name
,
2662 inode
->i_sb
->s_type
->name
,
2664 } else if (!IS_ROOT(new)) {
2665 int err
= __d_unalias(inode
, dentry
, new);
2666 write_sequnlock(&rename_lock
);
2672 __d_move(new, dentry
, false);
2673 write_sequnlock(&rename_lock
);
2674 spin_unlock(&inode
->i_lock
);
2675 security_d_instantiate(new, inode
);
2681 /* already taking inode->i_lock, so d_add() by hand */
2682 __d_instantiate(dentry
, inode
);
2683 spin_unlock(&inode
->i_lock
);
2685 security_d_instantiate(dentry
, inode
);
2689 EXPORT_SYMBOL(d_splice_alias
);
2691 static int prepend(char **buffer
, int *buflen
, const char *str
, int namelen
)
2695 return -ENAMETOOLONG
;
2697 memcpy(*buffer
, str
, namelen
);
2702 * prepend_name - prepend a pathname in front of current buffer pointer
2703 * @buffer: buffer pointer
2704 * @buflen: allocated length of the buffer
2705 * @name: name string and length qstr structure
2707 * With RCU path tracing, it may race with d_move(). Use ACCESS_ONCE() to
2708 * make sure that either the old or the new name pointer and length are
2709 * fetched. However, there may be mismatch between length and pointer.
2710 * The length cannot be trusted, we need to copy it byte-by-byte until
2711 * the length is reached or a null byte is found. It also prepends "/" at
2712 * the beginning of the name. The sequence number check at the caller will
2713 * retry it again when a d_move() does happen. So any garbage in the buffer
2714 * due to mismatched pointer and length will be discarded.
2716 * Data dependency barrier is needed to make sure that we see that terminating
2717 * NUL. Alpha strikes again, film at 11...
2719 static int prepend_name(char **buffer
, int *buflen
, struct qstr
*name
)
2721 const char *dname
= ACCESS_ONCE(name
->name
);
2722 u32 dlen
= ACCESS_ONCE(name
->len
);
2725 smp_read_barrier_depends();
2727 *buflen
-= dlen
+ 1;
2729 return -ENAMETOOLONG
;
2730 p
= *buffer
-= dlen
+ 1;
2742 * prepend_path - Prepend path string to a buffer
2743 * @path: the dentry/vfsmount to report
2744 * @root: root vfsmnt/dentry
2745 * @buffer: pointer to the end of the buffer
2746 * @buflen: pointer to buffer length
2748 * The function will first try to write out the pathname without taking any
2749 * lock other than the RCU read lock to make sure that dentries won't go away.
2750 * It only checks the sequence number of the global rename_lock as any change
2751 * in the dentry's d_seq will be preceded by changes in the rename_lock
2752 * sequence number. If the sequence number had been changed, it will restart
2753 * the whole pathname back-tracing sequence again by taking the rename_lock.
2754 * In this case, there is no need to take the RCU read lock as the recursive
2755 * parent pointer references will keep the dentry chain alive as long as no
2756 * rename operation is performed.
2758 static int prepend_path(const struct path
*path
,
2759 const struct path
*root
,
2760 char **buffer
, int *buflen
)
2762 struct dentry
*dentry
;
2763 struct vfsmount
*vfsmnt
;
2766 unsigned seq
, m_seq
= 0;
2772 read_seqbegin_or_lock(&mount_lock
, &m_seq
);
2779 dentry
= path
->dentry
;
2781 mnt
= real_mount(vfsmnt
);
2782 read_seqbegin_or_lock(&rename_lock
, &seq
);
2783 while (dentry
!= root
->dentry
|| vfsmnt
!= root
->mnt
) {
2784 struct dentry
* parent
;
2786 if (dentry
== vfsmnt
->mnt_root
|| IS_ROOT(dentry
)) {
2787 struct mount
*parent
= ACCESS_ONCE(mnt
->mnt_parent
);
2789 if (mnt
!= parent
) {
2790 dentry
= ACCESS_ONCE(mnt
->mnt_mountpoint
);
2796 * Filesystems needing to implement special "root names"
2797 * should do so with ->d_dname()
2799 if (IS_ROOT(dentry
) &&
2800 (dentry
->d_name
.len
!= 1 ||
2801 dentry
->d_name
.name
[0] != '/')) {
2802 WARN(1, "Root dentry has weird name <%.*s>\n",
2803 (int) dentry
->d_name
.len
,
2804 dentry
->d_name
.name
);
2807 error
= is_mounted(vfsmnt
) ? 1 : 2;
2810 parent
= dentry
->d_parent
;
2812 error
= prepend_name(&bptr
, &blen
, &dentry
->d_name
);
2820 if (need_seqretry(&rename_lock
, seq
)) {
2824 done_seqretry(&rename_lock
, seq
);
2828 if (need_seqretry(&mount_lock
, m_seq
)) {
2832 done_seqretry(&mount_lock
, m_seq
);
2834 if (error
>= 0 && bptr
== *buffer
) {
2836 error
= -ENAMETOOLONG
;
2846 * __d_path - return the path of a dentry
2847 * @path: the dentry/vfsmount to report
2848 * @root: root vfsmnt/dentry
2849 * @buf: buffer to return value in
2850 * @buflen: buffer length
2852 * Convert a dentry into an ASCII path name.
2854 * Returns a pointer into the buffer or an error code if the
2855 * path was too long.
2857 * "buflen" should be positive.
2859 * If the path is not reachable from the supplied root, return %NULL.
2861 char *__d_path(const struct path
*path
,
2862 const struct path
*root
,
2863 char *buf
, int buflen
)
2865 char *res
= buf
+ buflen
;
2868 prepend(&res
, &buflen
, "\0", 1);
2869 error
= prepend_path(path
, root
, &res
, &buflen
);
2872 return ERR_PTR(error
);
2878 char *d_absolute_path(const struct path
*path
,
2879 char *buf
, int buflen
)
2881 struct path root
= {};
2882 char *res
= buf
+ buflen
;
2885 prepend(&res
, &buflen
, "\0", 1);
2886 error
= prepend_path(path
, &root
, &res
, &buflen
);
2891 return ERR_PTR(error
);
2896 * same as __d_path but appends "(deleted)" for unlinked files.
2898 static int path_with_deleted(const struct path
*path
,
2899 const struct path
*root
,
2900 char **buf
, int *buflen
)
2902 prepend(buf
, buflen
, "\0", 1);
2903 if (d_unlinked(path
->dentry
)) {
2904 int error
= prepend(buf
, buflen
, " (deleted)", 10);
2909 return prepend_path(path
, root
, buf
, buflen
);
2912 static int prepend_unreachable(char **buffer
, int *buflen
)
2914 return prepend(buffer
, buflen
, "(unreachable)", 13);
2917 static void get_fs_root_rcu(struct fs_struct
*fs
, struct path
*root
)
2922 seq
= read_seqcount_begin(&fs
->seq
);
2924 } while (read_seqcount_retry(&fs
->seq
, seq
));
2928 * d_path - return the path of a dentry
2929 * @path: path to report
2930 * @buf: buffer to return value in
2931 * @buflen: buffer length
2933 * Convert a dentry into an ASCII path name. If the entry has been deleted
2934 * the string " (deleted)" is appended. Note that this is ambiguous.
2936 * Returns a pointer into the buffer or an error code if the path was
2937 * too long. Note: Callers should use the returned pointer, not the passed
2938 * in buffer, to use the name! The implementation often starts at an offset
2939 * into the buffer, and may leave 0 bytes at the start.
2941 * "buflen" should be positive.
2943 char *d_path(const struct path
*path
, char *buf
, int buflen
)
2945 char *res
= buf
+ buflen
;
2950 * We have various synthetic filesystems that never get mounted. On
2951 * these filesystems dentries are never used for lookup purposes, and
2952 * thus don't need to be hashed. They also don't need a name until a
2953 * user wants to identify the object in /proc/pid/fd/. The little hack
2954 * below allows us to generate a name for these objects on demand:
2956 * Some pseudo inodes are mountable. When they are mounted
2957 * path->dentry == path->mnt->mnt_root. In that case don't call d_dname
2958 * and instead have d_path return the mounted path.
2960 if (path
->dentry
->d_op
&& path
->dentry
->d_op
->d_dname
&&
2961 (!IS_ROOT(path
->dentry
) || path
->dentry
!= path
->mnt
->mnt_root
))
2962 return path
->dentry
->d_op
->d_dname(path
->dentry
, buf
, buflen
);
2965 get_fs_root_rcu(current
->fs
, &root
);
2966 error
= path_with_deleted(path
, &root
, &res
, &buflen
);
2970 res
= ERR_PTR(error
);
2973 EXPORT_SYMBOL(d_path
);
2976 * Helper function for dentry_operations.d_dname() members
2978 char *dynamic_dname(struct dentry
*dentry
, char *buffer
, int buflen
,
2979 const char *fmt
, ...)
2985 va_start(args
, fmt
);
2986 sz
= vsnprintf(temp
, sizeof(temp
), fmt
, args
) + 1;
2989 if (sz
> sizeof(temp
) || sz
> buflen
)
2990 return ERR_PTR(-ENAMETOOLONG
);
2992 buffer
+= buflen
- sz
;
2993 return memcpy(buffer
, temp
, sz
);
2996 char *simple_dname(struct dentry
*dentry
, char *buffer
, int buflen
)
2998 char *end
= buffer
+ buflen
;
2999 /* these dentries are never renamed, so d_lock is not needed */
3000 if (prepend(&end
, &buflen
, " (deleted)", 11) ||
3001 prepend(&end
, &buflen
, dentry
->d_name
.name
, dentry
->d_name
.len
) ||
3002 prepend(&end
, &buflen
, "/", 1))
3003 end
= ERR_PTR(-ENAMETOOLONG
);
3006 EXPORT_SYMBOL(simple_dname
);
3009 * Write full pathname from the root of the filesystem into the buffer.
3011 static char *__dentry_path(struct dentry
*d
, char *buf
, int buflen
)
3013 struct dentry
*dentry
;
3026 prepend(&end
, &len
, "\0", 1);
3030 read_seqbegin_or_lock(&rename_lock
, &seq
);
3031 while (!IS_ROOT(dentry
)) {
3032 struct dentry
*parent
= dentry
->d_parent
;
3035 error
= prepend_name(&end
, &len
, &dentry
->d_name
);
3044 if (need_seqretry(&rename_lock
, seq
)) {
3048 done_seqretry(&rename_lock
, seq
);
3053 return ERR_PTR(-ENAMETOOLONG
);
3056 char *dentry_path_raw(struct dentry
*dentry
, char *buf
, int buflen
)
3058 return __dentry_path(dentry
, buf
, buflen
);
3060 EXPORT_SYMBOL(dentry_path_raw
);
3062 char *dentry_path(struct dentry
*dentry
, char *buf
, int buflen
)
3067 if (d_unlinked(dentry
)) {
3069 if (prepend(&p
, &buflen
, "//deleted", 10) != 0)
3073 retval
= __dentry_path(dentry
, buf
, buflen
);
3074 if (!IS_ERR(retval
) && p
)
3075 *p
= '/'; /* restore '/' overriden with '\0' */
3078 return ERR_PTR(-ENAMETOOLONG
);
3081 static void get_fs_root_and_pwd_rcu(struct fs_struct
*fs
, struct path
*root
,
3087 seq
= read_seqcount_begin(&fs
->seq
);
3090 } while (read_seqcount_retry(&fs
->seq
, seq
));
3094 * NOTE! The user-level library version returns a
3095 * character pointer. The kernel system call just
3096 * returns the length of the buffer filled (which
3097 * includes the ending '\0' character), or a negative
3098 * error value. So libc would do something like
3100 * char *getcwd(char * buf, size_t size)
3104 * retval = sys_getcwd(buf, size);
3111 SYSCALL_DEFINE2(getcwd
, char __user
*, buf
, unsigned long, size
)
3114 struct path pwd
, root
;
3115 char *page
= __getname();
3121 get_fs_root_and_pwd_rcu(current
->fs
, &root
, &pwd
);
3124 if (!d_unlinked(pwd
.dentry
)) {
3126 char *cwd
= page
+ PATH_MAX
;
3127 int buflen
= PATH_MAX
;
3129 prepend(&cwd
, &buflen
, "\0", 1);
3130 error
= prepend_path(&pwd
, &root
, &cwd
, &buflen
);
3136 /* Unreachable from current root */
3138 error
= prepend_unreachable(&cwd
, &buflen
);
3144 len
= PATH_MAX
+ page
- cwd
;
3147 if (copy_to_user(buf
, cwd
, len
))
3160 * Test whether new_dentry is a subdirectory of old_dentry.
3162 * Trivially implemented using the dcache structure
3166 * is_subdir - is new dentry a subdirectory of old_dentry
3167 * @new_dentry: new dentry
3168 * @old_dentry: old dentry
3170 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
3171 * Returns 0 otherwise.
3172 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3175 int is_subdir(struct dentry
*new_dentry
, struct dentry
*old_dentry
)
3180 if (new_dentry
== old_dentry
)
3184 /* for restarting inner loop in case of seq retry */
3185 seq
= read_seqbegin(&rename_lock
);
3187 * Need rcu_readlock to protect against the d_parent trashing
3191 if (d_ancestor(old_dentry
, new_dentry
))
3196 } while (read_seqretry(&rename_lock
, seq
));
3201 static enum d_walk_ret
d_genocide_kill(void *data
, struct dentry
*dentry
)
3203 struct dentry
*root
= data
;
3204 if (dentry
!= root
) {
3205 if (d_unhashed(dentry
) || !dentry
->d_inode
)
3208 if (!(dentry
->d_flags
& DCACHE_GENOCIDE
)) {
3209 dentry
->d_flags
|= DCACHE_GENOCIDE
;
3210 dentry
->d_lockref
.count
--;
3213 return D_WALK_CONTINUE
;
3216 void d_genocide(struct dentry
*parent
)
3218 d_walk(parent
, parent
, d_genocide_kill
, NULL
);
3221 void d_tmpfile(struct dentry
*dentry
, struct inode
*inode
)
3223 inode_dec_link_count(inode
);
3224 BUG_ON(dentry
->d_name
.name
!= dentry
->d_iname
||
3225 !hlist_unhashed(&dentry
->d_u
.d_alias
) ||
3226 !d_unlinked(dentry
));
3227 spin_lock(&dentry
->d_parent
->d_lock
);
3228 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
3229 dentry
->d_name
.len
= sprintf(dentry
->d_iname
, "#%llu",
3230 (unsigned long long)inode
->i_ino
);
3231 spin_unlock(&dentry
->d_lock
);
3232 spin_unlock(&dentry
->d_parent
->d_lock
);
3233 d_instantiate(dentry
, inode
);
3235 EXPORT_SYMBOL(d_tmpfile
);
3237 static __initdata
unsigned long dhash_entries
;
3238 static int __init
set_dhash_entries(char *str
)
3242 dhash_entries
= simple_strtoul(str
, &str
, 0);
3245 __setup("dhash_entries=", set_dhash_entries
);
3247 static void __init
dcache_init_early(void)
3251 /* If hashes are distributed across NUMA nodes, defer
3252 * hash allocation until vmalloc space is available.
3258 alloc_large_system_hash("Dentry cache",
3259 sizeof(struct hlist_bl_head
),
3268 for (loop
= 0; loop
< (1U << d_hash_shift
); loop
++)
3269 INIT_HLIST_BL_HEAD(dentry_hashtable
+ loop
);
3272 static void __init
dcache_init(void)
3277 * A constructor could be added for stable state like the lists,
3278 * but it is probably not worth it because of the cache nature
3281 dentry_cache
= KMEM_CACHE(dentry
,
3282 SLAB_RECLAIM_ACCOUNT
|SLAB_PANIC
|SLAB_MEM_SPREAD
);
3284 /* Hash may have been set up in dcache_init_early */
3289 alloc_large_system_hash("Dentry cache",
3290 sizeof(struct hlist_bl_head
),
3299 for (loop
= 0; loop
< (1U << d_hash_shift
); loop
++)
3300 INIT_HLIST_BL_HEAD(dentry_hashtable
+ loop
);
3303 /* SLAB cache for __getname() consumers */
3304 struct kmem_cache
*names_cachep __read_mostly
;
3305 EXPORT_SYMBOL(names_cachep
);
3307 EXPORT_SYMBOL(d_genocide
);
3309 void __init
vfs_caches_init_early(void)
3311 dcache_init_early();
3315 void __init
vfs_caches_init(unsigned long mempages
)
3317 unsigned long reserve
;
3319 /* Base hash sizes on available memory, with a reserve equal to
3320 150% of current kernel size */
3322 reserve
= min((mempages
- nr_free_pages()) * 3/2, mempages
- 1);
3323 mempages
-= reserve
;
3325 names_cachep
= kmem_cache_create("names_cache", PATH_MAX
, 0,
3326 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
);
3330 files_init(mempages
);