1 // SPDX-License-Identifier: GPL-2.0-only
5 * Complete reimplementation
6 * (C) 1997 Thomas Schoebel-Theuer,
7 * with heavy changes by Linus Torvalds
11 * Notes on the allocation strategy:
13 * The dcache is a master of the icache - whenever a dcache entry
14 * exists, the inode will always exist. "iput()" is done either when
15 * the dcache entry is deleted or garbage collected.
18 #include <linux/ratelimit.h>
19 #include <linux/string.h>
22 #include <linux/fscrypt.h>
23 #include <linux/fsnotify.h>
24 #include <linux/slab.h>
25 #include <linux/init.h>
26 #include <linux/hash.h>
27 #include <linux/cache.h>
28 #include <linux/export.h>
29 #include <linux/security.h>
30 #include <linux/seqlock.h>
31 #include <linux/memblock.h>
32 #include <linux/bit_spinlock.h>
33 #include <linux/rculist_bl.h>
34 #include <linux/list_lru.h>
40 * dcache->d_inode->i_lock protects:
41 * - i_dentry, d_u.d_alias, d_inode of aliases
42 * dcache_hash_bucket lock protects:
43 * - the dcache hash table
44 * s_roots bl list spinlock protects:
45 * - the s_roots list (see __d_drop)
46 * dentry->d_sb->s_dentry_lru_lock protects:
47 * - the dcache lru lists and counters
54 * - d_parent and d_subdirs
55 * - childrens' d_child and d_parent
56 * - d_u.d_alias, d_inode
59 * dentry->d_inode->i_lock
61 * dentry->d_sb->s_dentry_lru_lock
62 * dcache_hash_bucket lock
65 * If there is an ancestor relationship:
66 * dentry->d_parent->...->d_parent->d_lock
68 * dentry->d_parent->d_lock
71 * If no ancestor relationship:
72 * arbitrary, since it's serialized on rename_lock
74 int sysctl_vfs_cache_pressure __read_mostly
= 100;
75 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure
);
77 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(rename_lock
);
79 EXPORT_SYMBOL(rename_lock
);
81 static struct kmem_cache
*dentry_cache __read_mostly
;
83 const struct qstr empty_name
= QSTR_INIT("", 0);
84 EXPORT_SYMBOL(empty_name
);
85 const struct qstr slash_name
= QSTR_INIT("/", 1);
86 EXPORT_SYMBOL(slash_name
);
89 * This is the single most critical data structure when it comes
90 * to the dcache: the hashtable for lookups. Somebody should try
91 * to make this good - I've just made it work.
93 * This hash-function tries to avoid losing too many bits of hash
94 * information, yet avoid using a prime hash-size or similar.
97 static unsigned int d_hash_shift __read_mostly
;
99 static struct hlist_bl_head
*dentry_hashtable __read_mostly
;
101 static inline struct hlist_bl_head
*d_hash(unsigned int hash
)
103 return dentry_hashtable
+ (hash
>> d_hash_shift
);
106 #define IN_LOOKUP_SHIFT 10
107 static struct hlist_bl_head in_lookup_hashtable
[1 << IN_LOOKUP_SHIFT
];
109 static inline struct hlist_bl_head
*in_lookup_hash(const struct dentry
*parent
,
112 hash
+= (unsigned long) parent
/ L1_CACHE_BYTES
;
113 return in_lookup_hashtable
+ hash_32(hash
, IN_LOOKUP_SHIFT
);
117 /* Statistics gathering. */
118 struct dentry_stat_t dentry_stat
= {
122 static DEFINE_PER_CPU(long, nr_dentry
);
123 static DEFINE_PER_CPU(long, nr_dentry_unused
);
124 static DEFINE_PER_CPU(long, nr_dentry_negative
);
126 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
129 * Here we resort to our own counters instead of using generic per-cpu counters
130 * for consistency with what the vfs inode code does. We are expected to harvest
131 * better code and performance by having our own specialized counters.
133 * Please note that the loop is done over all possible CPUs, not over all online
134 * CPUs. The reason for this is that we don't want to play games with CPUs going
135 * on and off. If one of them goes off, we will just keep their counters.
137 * glommer: See cffbc8a for details, and if you ever intend to change this,
138 * please update all vfs counters to match.
140 static long get_nr_dentry(void)
144 for_each_possible_cpu(i
)
145 sum
+= per_cpu(nr_dentry
, i
);
146 return sum
< 0 ? 0 : sum
;
149 static long get_nr_dentry_unused(void)
153 for_each_possible_cpu(i
)
154 sum
+= per_cpu(nr_dentry_unused
, i
);
155 return sum
< 0 ? 0 : sum
;
158 static long get_nr_dentry_negative(void)
163 for_each_possible_cpu(i
)
164 sum
+= per_cpu(nr_dentry_negative
, i
);
165 return sum
< 0 ? 0 : sum
;
168 int proc_nr_dentry(struct ctl_table
*table
, int write
, void __user
*buffer
,
169 size_t *lenp
, loff_t
*ppos
)
171 dentry_stat
.nr_dentry
= get_nr_dentry();
172 dentry_stat
.nr_unused
= get_nr_dentry_unused();
173 dentry_stat
.nr_negative
= get_nr_dentry_negative();
174 return proc_doulongvec_minmax(table
, write
, buffer
, lenp
, ppos
);
179 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
180 * The strings are both count bytes long, and count is non-zero.
182 #ifdef CONFIG_DCACHE_WORD_ACCESS
184 #include <asm/word-at-a-time.h>
186 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
187 * aligned allocation for this particular component. We don't
188 * strictly need the load_unaligned_zeropad() safety, but it
189 * doesn't hurt either.
191 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
192 * need the careful unaligned handling.
194 static inline int dentry_string_cmp(const unsigned char *cs
, const unsigned char *ct
, unsigned tcount
)
196 unsigned long a
,b
,mask
;
199 a
= read_word_at_a_time(cs
);
200 b
= load_unaligned_zeropad(ct
);
201 if (tcount
< sizeof(unsigned long))
203 if (unlikely(a
!= b
))
205 cs
+= sizeof(unsigned long);
206 ct
+= sizeof(unsigned long);
207 tcount
-= sizeof(unsigned long);
211 mask
= bytemask_from_count(tcount
);
212 return unlikely(!!((a
^ b
) & mask
));
217 static inline int dentry_string_cmp(const unsigned char *cs
, const unsigned char *ct
, unsigned tcount
)
231 static inline int dentry_cmp(const struct dentry
*dentry
, const unsigned char *ct
, unsigned tcount
)
234 * Be careful about RCU walk racing with rename:
235 * use 'READ_ONCE' to fetch the name pointer.
237 * NOTE! Even if a rename will mean that the length
238 * was not loaded atomically, we don't care. The
239 * RCU walk will check the sequence count eventually,
240 * and catch it. And we won't overrun the buffer,
241 * because we're reading the name pointer atomically,
242 * and a dentry name is guaranteed to be properly
243 * terminated with a NUL byte.
245 * End result: even if 'len' is wrong, we'll exit
246 * early because the data cannot match (there can
247 * be no NUL in the ct/tcount data)
249 const unsigned char *cs
= READ_ONCE(dentry
->d_name
.name
);
251 return dentry_string_cmp(cs
, ct
, tcount
);
254 struct external_name
{
257 struct rcu_head head
;
259 unsigned char name
[];
262 static inline struct external_name
*external_name(struct dentry
*dentry
)
264 return container_of(dentry
->d_name
.name
, struct external_name
, name
[0]);
267 static void __d_free(struct rcu_head
*head
)
269 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
271 kmem_cache_free(dentry_cache
, dentry
);
274 static void __d_free_external(struct rcu_head
*head
)
276 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
277 kfree(external_name(dentry
));
278 kmem_cache_free(dentry_cache
, dentry
);
281 static inline int dname_external(const struct dentry
*dentry
)
283 return dentry
->d_name
.name
!= dentry
->d_iname
;
286 void take_dentry_name_snapshot(struct name_snapshot
*name
, struct dentry
*dentry
)
288 spin_lock(&dentry
->d_lock
);
289 name
->name
= dentry
->d_name
;
290 if (unlikely(dname_external(dentry
))) {
291 atomic_inc(&external_name(dentry
)->u
.count
);
293 memcpy(name
->inline_name
, dentry
->d_iname
,
294 dentry
->d_name
.len
+ 1);
295 name
->name
.name
= name
->inline_name
;
297 spin_unlock(&dentry
->d_lock
);
299 EXPORT_SYMBOL(take_dentry_name_snapshot
);
301 void release_dentry_name_snapshot(struct name_snapshot
*name
)
303 if (unlikely(name
->name
.name
!= name
->inline_name
)) {
304 struct external_name
*p
;
305 p
= container_of(name
->name
.name
, struct external_name
, name
[0]);
306 if (unlikely(atomic_dec_and_test(&p
->u
.count
)))
307 kfree_rcu(p
, u
.head
);
310 EXPORT_SYMBOL(release_dentry_name_snapshot
);
312 static inline void __d_set_inode_and_type(struct dentry
*dentry
,
318 dentry
->d_inode
= inode
;
319 flags
= READ_ONCE(dentry
->d_flags
);
320 flags
&= ~(DCACHE_ENTRY_TYPE
| DCACHE_FALLTHRU
);
322 WRITE_ONCE(dentry
->d_flags
, flags
);
325 static inline void __d_clear_type_and_inode(struct dentry
*dentry
)
327 unsigned flags
= READ_ONCE(dentry
->d_flags
);
329 flags
&= ~(DCACHE_ENTRY_TYPE
| DCACHE_FALLTHRU
);
330 WRITE_ONCE(dentry
->d_flags
, flags
);
331 dentry
->d_inode
= NULL
;
332 if (dentry
->d_flags
& DCACHE_LRU_LIST
)
333 this_cpu_inc(nr_dentry_negative
);
336 static void dentry_free(struct dentry
*dentry
)
338 WARN_ON(!hlist_unhashed(&dentry
->d_u
.d_alias
));
339 if (unlikely(dname_external(dentry
))) {
340 struct external_name
*p
= external_name(dentry
);
341 if (likely(atomic_dec_and_test(&p
->u
.count
))) {
342 call_rcu(&dentry
->d_u
.d_rcu
, __d_free_external
);
346 /* if dentry was never visible to RCU, immediate free is OK */
347 if (dentry
->d_flags
& DCACHE_NORCU
)
348 __d_free(&dentry
->d_u
.d_rcu
);
350 call_rcu(&dentry
->d_u
.d_rcu
, __d_free
);
354 * Release the dentry's inode, using the filesystem
355 * d_iput() operation if defined.
357 static void dentry_unlink_inode(struct dentry
* dentry
)
358 __releases(dentry
->d_lock
)
359 __releases(dentry
->d_inode
->i_lock
)
361 struct inode
*inode
= dentry
->d_inode
;
363 raw_write_seqcount_begin(&dentry
->d_seq
);
364 __d_clear_type_and_inode(dentry
);
365 hlist_del_init(&dentry
->d_u
.d_alias
);
366 raw_write_seqcount_end(&dentry
->d_seq
);
367 spin_unlock(&dentry
->d_lock
);
368 spin_unlock(&inode
->i_lock
);
370 fsnotify_inoderemove(inode
);
371 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
372 dentry
->d_op
->d_iput(dentry
, inode
);
378 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
379 * is in use - which includes both the "real" per-superblock
380 * LRU list _and_ the DCACHE_SHRINK_LIST use.
382 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
383 * on the shrink list (ie not on the superblock LRU list).
385 * The per-cpu "nr_dentry_unused" counters are updated with
386 * the DCACHE_LRU_LIST bit.
388 * The per-cpu "nr_dentry_negative" counters are only updated
389 * when deleted from or added to the per-superblock LRU list, not
390 * from/to the shrink list. That is to avoid an unneeded dec/inc
391 * pair when moving from LRU to shrink list in select_collect().
393 * These helper functions make sure we always follow the
394 * rules. d_lock must be held by the caller.
396 #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
397 static void d_lru_add(struct dentry
*dentry
)
399 D_FLAG_VERIFY(dentry
, 0);
400 dentry
->d_flags
|= DCACHE_LRU_LIST
;
401 this_cpu_inc(nr_dentry_unused
);
402 if (d_is_negative(dentry
))
403 this_cpu_inc(nr_dentry_negative
);
404 WARN_ON_ONCE(!list_lru_add(&dentry
->d_sb
->s_dentry_lru
, &dentry
->d_lru
));
407 static void d_lru_del(struct dentry
*dentry
)
409 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
410 dentry
->d_flags
&= ~DCACHE_LRU_LIST
;
411 this_cpu_dec(nr_dentry_unused
);
412 if (d_is_negative(dentry
))
413 this_cpu_dec(nr_dentry_negative
);
414 WARN_ON_ONCE(!list_lru_del(&dentry
->d_sb
->s_dentry_lru
, &dentry
->d_lru
));
417 static void d_shrink_del(struct dentry
*dentry
)
419 D_FLAG_VERIFY(dentry
, DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
);
420 list_del_init(&dentry
->d_lru
);
421 dentry
->d_flags
&= ~(DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
);
422 this_cpu_dec(nr_dentry_unused
);
425 static void d_shrink_add(struct dentry
*dentry
, struct list_head
*list
)
427 D_FLAG_VERIFY(dentry
, 0);
428 list_add(&dentry
->d_lru
, list
);
429 dentry
->d_flags
|= DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
;
430 this_cpu_inc(nr_dentry_unused
);
434 * These can only be called under the global LRU lock, ie during the
435 * callback for freeing the LRU list. "isolate" removes it from the
436 * LRU lists entirely, while shrink_move moves it to the indicated
439 static void d_lru_isolate(struct list_lru_one
*lru
, struct dentry
*dentry
)
441 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
442 dentry
->d_flags
&= ~DCACHE_LRU_LIST
;
443 this_cpu_dec(nr_dentry_unused
);
444 if (d_is_negative(dentry
))
445 this_cpu_dec(nr_dentry_negative
);
446 list_lru_isolate(lru
, &dentry
->d_lru
);
449 static void d_lru_shrink_move(struct list_lru_one
*lru
, struct dentry
*dentry
,
450 struct list_head
*list
)
452 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
453 dentry
->d_flags
|= DCACHE_SHRINK_LIST
;
454 if (d_is_negative(dentry
))
455 this_cpu_dec(nr_dentry_negative
);
456 list_lru_isolate_move(lru
, &dentry
->d_lru
, list
);
460 * d_drop - drop a dentry
461 * @dentry: dentry to drop
463 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
464 * be found through a VFS lookup any more. Note that this is different from
465 * deleting the dentry - d_delete will try to mark the dentry negative if
466 * possible, giving a successful _negative_ lookup, while d_drop will
467 * just make the cache lookup fail.
469 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
470 * reason (NFS timeouts or autofs deletes).
472 * __d_drop requires dentry->d_lock
473 * ___d_drop doesn't mark dentry as "unhashed"
474 * (dentry->d_hash.pprev will be LIST_POISON2, not NULL).
476 static void ___d_drop(struct dentry
*dentry
)
478 struct hlist_bl_head
*b
;
480 * Hashed dentries are normally on the dentry hashtable,
481 * with the exception of those newly allocated by
482 * d_obtain_root, which are always IS_ROOT:
484 if (unlikely(IS_ROOT(dentry
)))
485 b
= &dentry
->d_sb
->s_roots
;
487 b
= d_hash(dentry
->d_name
.hash
);
490 __hlist_bl_del(&dentry
->d_hash
);
494 void __d_drop(struct dentry
*dentry
)
496 if (!d_unhashed(dentry
)) {
498 dentry
->d_hash
.pprev
= NULL
;
499 write_seqcount_invalidate(&dentry
->d_seq
);
502 EXPORT_SYMBOL(__d_drop
);
504 void d_drop(struct dentry
*dentry
)
506 spin_lock(&dentry
->d_lock
);
508 spin_unlock(&dentry
->d_lock
);
510 EXPORT_SYMBOL(d_drop
);
512 static inline void dentry_unlist(struct dentry
*dentry
, struct dentry
*parent
)
516 * Inform d_walk() and shrink_dentry_list() that we are no longer
517 * attached to the dentry tree
519 dentry
->d_flags
|= DCACHE_DENTRY_KILLED
;
520 if (unlikely(list_empty(&dentry
->d_child
)))
522 __list_del_entry(&dentry
->d_child
);
524 * Cursors can move around the list of children. While we'd been
525 * a normal list member, it didn't matter - ->d_child.next would've
526 * been updated. However, from now on it won't be and for the
527 * things like d_walk() it might end up with a nasty surprise.
528 * Normally d_walk() doesn't care about cursors moving around -
529 * ->d_lock on parent prevents that and since a cursor has no children
530 * of its own, we get through it without ever unlocking the parent.
531 * There is one exception, though - if we ascend from a child that
532 * gets killed as soon as we unlock it, the next sibling is found
533 * using the value left in its ->d_child.next. And if _that_
534 * pointed to a cursor, and cursor got moved (e.g. by lseek())
535 * before d_walk() regains parent->d_lock, we'll end up skipping
536 * everything the cursor had been moved past.
538 * Solution: make sure that the pointer left behind in ->d_child.next
539 * points to something that won't be moving around. I.e. skip the
542 while (dentry
->d_child
.next
!= &parent
->d_subdirs
) {
543 next
= list_entry(dentry
->d_child
.next
, struct dentry
, d_child
);
544 if (likely(!(next
->d_flags
& DCACHE_DENTRY_CURSOR
)))
546 dentry
->d_child
.next
= next
->d_child
.next
;
550 static void __dentry_kill(struct dentry
*dentry
)
552 struct dentry
*parent
= NULL
;
553 bool can_free
= true;
554 if (!IS_ROOT(dentry
))
555 parent
= dentry
->d_parent
;
558 * The dentry is now unrecoverably dead to the world.
560 lockref_mark_dead(&dentry
->d_lockref
);
563 * inform the fs via d_prune that this dentry is about to be
564 * unhashed and destroyed.
566 if (dentry
->d_flags
& DCACHE_OP_PRUNE
)
567 dentry
->d_op
->d_prune(dentry
);
569 if (dentry
->d_flags
& DCACHE_LRU_LIST
) {
570 if (!(dentry
->d_flags
& DCACHE_SHRINK_LIST
))
573 /* if it was on the hash then remove it */
575 dentry_unlist(dentry
, parent
);
577 spin_unlock(&parent
->d_lock
);
579 dentry_unlink_inode(dentry
);
581 spin_unlock(&dentry
->d_lock
);
582 this_cpu_dec(nr_dentry
);
583 if (dentry
->d_op
&& dentry
->d_op
->d_release
)
584 dentry
->d_op
->d_release(dentry
);
586 spin_lock(&dentry
->d_lock
);
587 if (dentry
->d_flags
& DCACHE_SHRINK_LIST
) {
588 dentry
->d_flags
|= DCACHE_MAY_FREE
;
591 spin_unlock(&dentry
->d_lock
);
592 if (likely(can_free
))
597 static struct dentry
*__lock_parent(struct dentry
*dentry
)
599 struct dentry
*parent
;
601 spin_unlock(&dentry
->d_lock
);
603 parent
= READ_ONCE(dentry
->d_parent
);
604 spin_lock(&parent
->d_lock
);
606 * We can't blindly lock dentry until we are sure
607 * that we won't violate the locking order.
608 * Any changes of dentry->d_parent must have
609 * been done with parent->d_lock held, so
610 * spin_lock() above is enough of a barrier
611 * for checking if it's still our child.
613 if (unlikely(parent
!= dentry
->d_parent
)) {
614 spin_unlock(&parent
->d_lock
);
618 if (parent
!= dentry
)
619 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
625 static inline struct dentry
*lock_parent(struct dentry
*dentry
)
627 struct dentry
*parent
= dentry
->d_parent
;
630 if (likely(spin_trylock(&parent
->d_lock
)))
632 return __lock_parent(dentry
);
635 static inline bool retain_dentry(struct dentry
*dentry
)
637 WARN_ON(d_in_lookup(dentry
));
639 /* Unreachable? Get rid of it */
640 if (unlikely(d_unhashed(dentry
)))
643 if (unlikely(dentry
->d_flags
& DCACHE_DISCONNECTED
))
646 if (unlikely(dentry
->d_flags
& DCACHE_OP_DELETE
)) {
647 if (dentry
->d_op
->d_delete(dentry
))
650 /* retain; LRU fodder */
651 dentry
->d_lockref
.count
--;
652 if (unlikely(!(dentry
->d_flags
& DCACHE_LRU_LIST
)))
654 else if (unlikely(!(dentry
->d_flags
& DCACHE_REFERENCED
)))
655 dentry
->d_flags
|= DCACHE_REFERENCED
;
660 * Finish off a dentry we've decided to kill.
661 * dentry->d_lock must be held, returns with it unlocked.
662 * Returns dentry requiring refcount drop, or NULL if we're done.
664 static struct dentry
*dentry_kill(struct dentry
*dentry
)
665 __releases(dentry
->d_lock
)
667 struct inode
*inode
= dentry
->d_inode
;
668 struct dentry
*parent
= NULL
;
670 if (inode
&& unlikely(!spin_trylock(&inode
->i_lock
)))
673 if (!IS_ROOT(dentry
)) {
674 parent
= dentry
->d_parent
;
675 if (unlikely(!spin_trylock(&parent
->d_lock
))) {
676 parent
= __lock_parent(dentry
);
677 if (likely(inode
|| !dentry
->d_inode
))
679 /* negative that became positive */
681 spin_unlock(&parent
->d_lock
);
682 inode
= dentry
->d_inode
;
686 __dentry_kill(dentry
);
690 spin_unlock(&dentry
->d_lock
);
691 spin_lock(&inode
->i_lock
);
692 spin_lock(&dentry
->d_lock
);
693 parent
= lock_parent(dentry
);
695 if (unlikely(dentry
->d_lockref
.count
!= 1)) {
696 dentry
->d_lockref
.count
--;
697 } else if (likely(!retain_dentry(dentry
))) {
698 __dentry_kill(dentry
);
701 /* we are keeping it, after all */
703 spin_unlock(&inode
->i_lock
);
705 spin_unlock(&parent
->d_lock
);
706 spin_unlock(&dentry
->d_lock
);
711 * Try to do a lockless dput(), and return whether that was successful.
713 * If unsuccessful, we return false, having already taken the dentry lock.
715 * The caller needs to hold the RCU read lock, so that the dentry is
716 * guaranteed to stay around even if the refcount goes down to zero!
718 static inline bool fast_dput(struct dentry
*dentry
)
721 unsigned int d_flags
;
724 * If we have a d_op->d_delete() operation, we sould not
725 * let the dentry count go to zero, so use "put_or_lock".
727 if (unlikely(dentry
->d_flags
& DCACHE_OP_DELETE
))
728 return lockref_put_or_lock(&dentry
->d_lockref
);
731 * .. otherwise, we can try to just decrement the
732 * lockref optimistically.
734 ret
= lockref_put_return(&dentry
->d_lockref
);
737 * If the lockref_put_return() failed due to the lock being held
738 * by somebody else, the fast path has failed. We will need to
739 * get the lock, and then check the count again.
741 if (unlikely(ret
< 0)) {
742 spin_lock(&dentry
->d_lock
);
743 if (dentry
->d_lockref
.count
> 1) {
744 dentry
->d_lockref
.count
--;
745 spin_unlock(&dentry
->d_lock
);
752 * If we weren't the last ref, we're done.
758 * Careful, careful. The reference count went down
759 * to zero, but we don't hold the dentry lock, so
760 * somebody else could get it again, and do another
761 * dput(), and we need to not race with that.
763 * However, there is a very special and common case
764 * where we don't care, because there is nothing to
765 * do: the dentry is still hashed, it does not have
766 * a 'delete' op, and it's referenced and already on
769 * NOTE! Since we aren't locked, these values are
770 * not "stable". However, it is sufficient that at
771 * some point after we dropped the reference the
772 * dentry was hashed and the flags had the proper
773 * value. Other dentry users may have re-gotten
774 * a reference to the dentry and change that, but
775 * our work is done - we can leave the dentry
776 * around with a zero refcount.
779 d_flags
= READ_ONCE(dentry
->d_flags
);
780 d_flags
&= DCACHE_REFERENCED
| DCACHE_LRU_LIST
| DCACHE_DISCONNECTED
;
782 /* Nothing to do? Dropping the reference was all we needed? */
783 if (d_flags
== (DCACHE_REFERENCED
| DCACHE_LRU_LIST
) && !d_unhashed(dentry
))
787 * Not the fast normal case? Get the lock. We've already decremented
788 * the refcount, but we'll need to re-check the situation after
791 spin_lock(&dentry
->d_lock
);
794 * Did somebody else grab a reference to it in the meantime, and
795 * we're no longer the last user after all? Alternatively, somebody
796 * else could have killed it and marked it dead. Either way, we
797 * don't need to do anything else.
799 if (dentry
->d_lockref
.count
) {
800 spin_unlock(&dentry
->d_lock
);
805 * Re-get the reference we optimistically dropped. We hold the
806 * lock, and we just tested that it was zero, so we can just
809 dentry
->d_lockref
.count
= 1;
817 * This is complicated by the fact that we do not want to put
818 * dentries that are no longer on any hash chain on the unused
819 * list: we'd much rather just get rid of them immediately.
821 * However, that implies that we have to traverse the dentry
822 * tree upwards to the parents which might _also_ now be
823 * scheduled for deletion (it may have been only waiting for
824 * its last child to go away).
826 * This tail recursion is done by hand as we don't want to depend
827 * on the compiler to always get this right (gcc generally doesn't).
828 * Real recursion would eat up our stack space.
832 * dput - release a dentry
833 * @dentry: dentry to release
835 * Release a dentry. This will drop the usage count and if appropriate
836 * call the dentry unlink method as well as removing it from the queues and
837 * releasing its resources. If the parent dentries were scheduled for release
838 * they too may now get deleted.
840 void dput(struct dentry
*dentry
)
846 if (likely(fast_dput(dentry
))) {
851 /* Slow case: now with the dentry lock held */
854 if (likely(retain_dentry(dentry
))) {
855 spin_unlock(&dentry
->d_lock
);
859 dentry
= dentry_kill(dentry
);
865 /* This must be called with d_lock held */
866 static inline void __dget_dlock(struct dentry
*dentry
)
868 dentry
->d_lockref
.count
++;
871 static inline void __dget(struct dentry
*dentry
)
873 lockref_get(&dentry
->d_lockref
);
876 struct dentry
*dget_parent(struct dentry
*dentry
)
882 * Do optimistic parent lookup without any
886 ret
= READ_ONCE(dentry
->d_parent
);
887 gotref
= lockref_get_not_zero(&ret
->d_lockref
);
889 if (likely(gotref
)) {
890 if (likely(ret
== READ_ONCE(dentry
->d_parent
)))
897 * Don't need rcu_dereference because we re-check it was correct under
901 ret
= dentry
->d_parent
;
902 spin_lock(&ret
->d_lock
);
903 if (unlikely(ret
!= dentry
->d_parent
)) {
904 spin_unlock(&ret
->d_lock
);
909 BUG_ON(!ret
->d_lockref
.count
);
910 ret
->d_lockref
.count
++;
911 spin_unlock(&ret
->d_lock
);
914 EXPORT_SYMBOL(dget_parent
);
916 static struct dentry
* __d_find_any_alias(struct inode
*inode
)
918 struct dentry
*alias
;
920 if (hlist_empty(&inode
->i_dentry
))
922 alias
= hlist_entry(inode
->i_dentry
.first
, struct dentry
, d_u
.d_alias
);
928 * d_find_any_alias - find any alias for a given inode
929 * @inode: inode to find an alias for
931 * If any aliases exist for the given inode, take and return a
932 * reference for one of them. If no aliases exist, return %NULL.
934 struct dentry
*d_find_any_alias(struct inode
*inode
)
938 spin_lock(&inode
->i_lock
);
939 de
= __d_find_any_alias(inode
);
940 spin_unlock(&inode
->i_lock
);
943 EXPORT_SYMBOL(d_find_any_alias
);
946 * d_find_alias - grab a hashed alias of inode
947 * @inode: inode in question
949 * If inode has a hashed alias, or is a directory and has any alias,
950 * acquire the reference to alias and return it. Otherwise return NULL.
951 * Notice that if inode is a directory there can be only one alias and
952 * it can be unhashed only if it has no children, or if it is the root
953 * of a filesystem, or if the directory was renamed and d_revalidate
954 * was the first vfs operation to notice.
956 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
957 * any other hashed alias over that one.
959 static struct dentry
*__d_find_alias(struct inode
*inode
)
961 struct dentry
*alias
;
963 if (S_ISDIR(inode
->i_mode
))
964 return __d_find_any_alias(inode
);
966 hlist_for_each_entry(alias
, &inode
->i_dentry
, d_u
.d_alias
) {
967 spin_lock(&alias
->d_lock
);
968 if (!d_unhashed(alias
)) {
970 spin_unlock(&alias
->d_lock
);
973 spin_unlock(&alias
->d_lock
);
978 struct dentry
*d_find_alias(struct inode
*inode
)
980 struct dentry
*de
= NULL
;
982 if (!hlist_empty(&inode
->i_dentry
)) {
983 spin_lock(&inode
->i_lock
);
984 de
= __d_find_alias(inode
);
985 spin_unlock(&inode
->i_lock
);
989 EXPORT_SYMBOL(d_find_alias
);
992 * Try to kill dentries associated with this inode.
993 * WARNING: you must own a reference to inode.
995 void d_prune_aliases(struct inode
*inode
)
997 struct dentry
*dentry
;
999 spin_lock(&inode
->i_lock
);
1000 hlist_for_each_entry(dentry
, &inode
->i_dentry
, d_u
.d_alias
) {
1001 spin_lock(&dentry
->d_lock
);
1002 if (!dentry
->d_lockref
.count
) {
1003 struct dentry
*parent
= lock_parent(dentry
);
1004 if (likely(!dentry
->d_lockref
.count
)) {
1005 __dentry_kill(dentry
);
1010 spin_unlock(&parent
->d_lock
);
1012 spin_unlock(&dentry
->d_lock
);
1014 spin_unlock(&inode
->i_lock
);
1016 EXPORT_SYMBOL(d_prune_aliases
);
1019 * Lock a dentry from shrink list.
1020 * Called under rcu_read_lock() and dentry->d_lock; the former
1021 * guarantees that nothing we access will be freed under us.
1022 * Note that dentry is *not* protected from concurrent dentry_kill(),
1025 * Return false if dentry has been disrupted or grabbed, leaving
1026 * the caller to kick it off-list. Otherwise, return true and have
1027 * that dentry's inode and parent both locked.
1029 static bool shrink_lock_dentry(struct dentry
*dentry
)
1031 struct inode
*inode
;
1032 struct dentry
*parent
;
1034 if (dentry
->d_lockref
.count
)
1037 inode
= dentry
->d_inode
;
1038 if (inode
&& unlikely(!spin_trylock(&inode
->i_lock
))) {
1039 spin_unlock(&dentry
->d_lock
);
1040 spin_lock(&inode
->i_lock
);
1041 spin_lock(&dentry
->d_lock
);
1042 if (unlikely(dentry
->d_lockref
.count
))
1044 /* changed inode means that somebody had grabbed it */
1045 if (unlikely(inode
!= dentry
->d_inode
))
1049 parent
= dentry
->d_parent
;
1050 if (IS_ROOT(dentry
) || likely(spin_trylock(&parent
->d_lock
)))
1053 spin_unlock(&dentry
->d_lock
);
1054 spin_lock(&parent
->d_lock
);
1055 if (unlikely(parent
!= dentry
->d_parent
)) {
1056 spin_unlock(&parent
->d_lock
);
1057 spin_lock(&dentry
->d_lock
);
1060 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1061 if (likely(!dentry
->d_lockref
.count
))
1063 spin_unlock(&parent
->d_lock
);
1066 spin_unlock(&inode
->i_lock
);
1070 static void shrink_dentry_list(struct list_head
*list
)
1072 while (!list_empty(list
)) {
1073 struct dentry
*dentry
, *parent
;
1075 dentry
= list_entry(list
->prev
, struct dentry
, d_lru
);
1076 spin_lock(&dentry
->d_lock
);
1078 if (!shrink_lock_dentry(dentry
)) {
1079 bool can_free
= false;
1081 d_shrink_del(dentry
);
1082 if (dentry
->d_lockref
.count
< 0)
1083 can_free
= dentry
->d_flags
& DCACHE_MAY_FREE
;
1084 spin_unlock(&dentry
->d_lock
);
1086 dentry_free(dentry
);
1090 d_shrink_del(dentry
);
1091 parent
= dentry
->d_parent
;
1092 __dentry_kill(dentry
);
1093 if (parent
== dentry
)
1096 * We need to prune ancestors too. This is necessary to prevent
1097 * quadratic behavior of shrink_dcache_parent(), but is also
1098 * expected to be beneficial in reducing dentry cache
1102 while (dentry
&& !lockref_put_or_lock(&dentry
->d_lockref
))
1103 dentry
= dentry_kill(dentry
);
1107 static enum lru_status
dentry_lru_isolate(struct list_head
*item
,
1108 struct list_lru_one
*lru
, spinlock_t
*lru_lock
, void *arg
)
1110 struct list_head
*freeable
= arg
;
1111 struct dentry
*dentry
= container_of(item
, struct dentry
, d_lru
);
1115 * we are inverting the lru lock/dentry->d_lock here,
1116 * so use a trylock. If we fail to get the lock, just skip
1119 if (!spin_trylock(&dentry
->d_lock
))
1123 * Referenced dentries are still in use. If they have active
1124 * counts, just remove them from the LRU. Otherwise give them
1125 * another pass through the LRU.
1127 if (dentry
->d_lockref
.count
) {
1128 d_lru_isolate(lru
, dentry
);
1129 spin_unlock(&dentry
->d_lock
);
1133 if (dentry
->d_flags
& DCACHE_REFERENCED
) {
1134 dentry
->d_flags
&= ~DCACHE_REFERENCED
;
1135 spin_unlock(&dentry
->d_lock
);
1138 * The list move itself will be made by the common LRU code. At
1139 * this point, we've dropped the dentry->d_lock but keep the
1140 * lru lock. This is safe to do, since every list movement is
1141 * protected by the lru lock even if both locks are held.
1143 * This is guaranteed by the fact that all LRU management
1144 * functions are intermediated by the LRU API calls like
1145 * list_lru_add and list_lru_del. List movement in this file
1146 * only ever occur through this functions or through callbacks
1147 * like this one, that are called from the LRU API.
1149 * The only exceptions to this are functions like
1150 * shrink_dentry_list, and code that first checks for the
1151 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1152 * operating only with stack provided lists after they are
1153 * properly isolated from the main list. It is thus, always a
1159 d_lru_shrink_move(lru
, dentry
, freeable
);
1160 spin_unlock(&dentry
->d_lock
);
1166 * prune_dcache_sb - shrink the dcache
1168 * @sc: shrink control, passed to list_lru_shrink_walk()
1170 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1171 * is done when we need more memory and called from the superblock shrinker
1174 * This function may fail to free any resources if all the dentries are in
1177 long prune_dcache_sb(struct super_block
*sb
, struct shrink_control
*sc
)
1182 freed
= list_lru_shrink_walk(&sb
->s_dentry_lru
, sc
,
1183 dentry_lru_isolate
, &dispose
);
1184 shrink_dentry_list(&dispose
);
1188 static enum lru_status
dentry_lru_isolate_shrink(struct list_head
*item
,
1189 struct list_lru_one
*lru
, spinlock_t
*lru_lock
, void *arg
)
1191 struct list_head
*freeable
= arg
;
1192 struct dentry
*dentry
= container_of(item
, struct dentry
, d_lru
);
1195 * we are inverting the lru lock/dentry->d_lock here,
1196 * so use a trylock. If we fail to get the lock, just skip
1199 if (!spin_trylock(&dentry
->d_lock
))
1202 d_lru_shrink_move(lru
, dentry
, freeable
);
1203 spin_unlock(&dentry
->d_lock
);
1210 * shrink_dcache_sb - shrink dcache for a superblock
1213 * Shrink the dcache for the specified super block. This is used to free
1214 * the dcache before unmounting a file system.
1216 void shrink_dcache_sb(struct super_block
*sb
)
1221 list_lru_walk(&sb
->s_dentry_lru
,
1222 dentry_lru_isolate_shrink
, &dispose
, 1024);
1223 shrink_dentry_list(&dispose
);
1224 } while (list_lru_count(&sb
->s_dentry_lru
) > 0);
1226 EXPORT_SYMBOL(shrink_dcache_sb
);
1229 * enum d_walk_ret - action to talke during tree walk
1230 * @D_WALK_CONTINUE: contrinue walk
1231 * @D_WALK_QUIT: quit walk
1232 * @D_WALK_NORETRY: quit when retry is needed
1233 * @D_WALK_SKIP: skip this dentry and its children
1243 * d_walk - walk the dentry tree
1244 * @parent: start of walk
1245 * @data: data passed to @enter() and @finish()
1246 * @enter: callback when first entering the dentry
1248 * The @enter() callbacks are called with d_lock held.
1250 static void d_walk(struct dentry
*parent
, void *data
,
1251 enum d_walk_ret (*enter
)(void *, struct dentry
*))
1253 struct dentry
*this_parent
;
1254 struct list_head
*next
;
1256 enum d_walk_ret ret
;
1260 read_seqbegin_or_lock(&rename_lock
, &seq
);
1261 this_parent
= parent
;
1262 spin_lock(&this_parent
->d_lock
);
1264 ret
= enter(data
, this_parent
);
1266 case D_WALK_CONTINUE
:
1271 case D_WALK_NORETRY
:
1276 next
= this_parent
->d_subdirs
.next
;
1278 while (next
!= &this_parent
->d_subdirs
) {
1279 struct list_head
*tmp
= next
;
1280 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_child
);
1283 if (unlikely(dentry
->d_flags
& DCACHE_DENTRY_CURSOR
))
1286 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1288 ret
= enter(data
, dentry
);
1290 case D_WALK_CONTINUE
:
1293 spin_unlock(&dentry
->d_lock
);
1295 case D_WALK_NORETRY
:
1299 spin_unlock(&dentry
->d_lock
);
1303 if (!list_empty(&dentry
->d_subdirs
)) {
1304 spin_unlock(&this_parent
->d_lock
);
1305 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
1306 this_parent
= dentry
;
1307 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
1310 spin_unlock(&dentry
->d_lock
);
1313 * All done at this level ... ascend and resume the search.
1317 if (this_parent
!= parent
) {
1318 struct dentry
*child
= this_parent
;
1319 this_parent
= child
->d_parent
;
1321 spin_unlock(&child
->d_lock
);
1322 spin_lock(&this_parent
->d_lock
);
1324 /* might go back up the wrong parent if we have had a rename. */
1325 if (need_seqretry(&rename_lock
, seq
))
1327 /* go into the first sibling still alive */
1329 next
= child
->d_child
.next
;
1330 if (next
== &this_parent
->d_subdirs
)
1332 child
= list_entry(next
, struct dentry
, d_child
);
1333 } while (unlikely(child
->d_flags
& DCACHE_DENTRY_KILLED
));
1337 if (need_seqretry(&rename_lock
, seq
))
1342 spin_unlock(&this_parent
->d_lock
);
1343 done_seqretry(&rename_lock
, seq
);
1347 spin_unlock(&this_parent
->d_lock
);
1356 struct check_mount
{
1357 struct vfsmount
*mnt
;
1358 unsigned int mounted
;
1361 static enum d_walk_ret
path_check_mount(void *data
, struct dentry
*dentry
)
1363 struct check_mount
*info
= data
;
1364 struct path path
= { .mnt
= info
->mnt
, .dentry
= dentry
};
1366 if (likely(!d_mountpoint(dentry
)))
1367 return D_WALK_CONTINUE
;
1368 if (__path_is_mountpoint(&path
)) {
1372 return D_WALK_CONTINUE
;
1376 * path_has_submounts - check for mounts over a dentry in the
1377 * current namespace.
1378 * @parent: path to check.
1380 * Return true if the parent or its subdirectories contain
1381 * a mount point in the current namespace.
1383 int path_has_submounts(const struct path
*parent
)
1385 struct check_mount data
= { .mnt
= parent
->mnt
, .mounted
= 0 };
1387 read_seqlock_excl(&mount_lock
);
1388 d_walk(parent
->dentry
, &data
, path_check_mount
);
1389 read_sequnlock_excl(&mount_lock
);
1391 return data
.mounted
;
1393 EXPORT_SYMBOL(path_has_submounts
);
1396 * Called by mount code to set a mountpoint and check if the mountpoint is
1397 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1398 * subtree can become unreachable).
1400 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1401 * this reason take rename_lock and d_lock on dentry and ancestors.
1403 int d_set_mounted(struct dentry
*dentry
)
1407 write_seqlock(&rename_lock
);
1408 for (p
= dentry
->d_parent
; !IS_ROOT(p
); p
= p
->d_parent
) {
1409 /* Need exclusion wrt. d_invalidate() */
1410 spin_lock(&p
->d_lock
);
1411 if (unlikely(d_unhashed(p
))) {
1412 spin_unlock(&p
->d_lock
);
1415 spin_unlock(&p
->d_lock
);
1417 spin_lock(&dentry
->d_lock
);
1418 if (!d_unlinked(dentry
)) {
1420 if (!d_mountpoint(dentry
)) {
1421 dentry
->d_flags
|= DCACHE_MOUNTED
;
1425 spin_unlock(&dentry
->d_lock
);
1427 write_sequnlock(&rename_lock
);
1432 * Search the dentry child list of the specified parent,
1433 * and move any unused dentries to the end of the unused
1434 * list for prune_dcache(). We descend to the next level
1435 * whenever the d_subdirs list is non-empty and continue
1438 * It returns zero iff there are no unused children,
1439 * otherwise it returns the number of children moved to
1440 * the end of the unused list. This may not be the total
1441 * number of unused children, because select_parent can
1442 * drop the lock and return early due to latency
1446 struct select_data
{
1447 struct dentry
*start
;
1448 struct list_head dispose
;
1452 static enum d_walk_ret
select_collect(void *_data
, struct dentry
*dentry
)
1454 struct select_data
*data
= _data
;
1455 enum d_walk_ret ret
= D_WALK_CONTINUE
;
1457 if (data
->start
== dentry
)
1460 if (dentry
->d_flags
& DCACHE_SHRINK_LIST
) {
1463 if (dentry
->d_flags
& DCACHE_LRU_LIST
)
1465 if (!dentry
->d_lockref
.count
) {
1466 d_shrink_add(dentry
, &data
->dispose
);
1471 * We can return to the caller if we have found some (this
1472 * ensures forward progress). We'll be coming back to find
1475 if (!list_empty(&data
->dispose
))
1476 ret
= need_resched() ? D_WALK_QUIT
: D_WALK_NORETRY
;
1482 * shrink_dcache_parent - prune dcache
1483 * @parent: parent of entries to prune
1485 * Prune the dcache to remove unused children of the parent dentry.
1487 void shrink_dcache_parent(struct dentry
*parent
)
1490 struct select_data data
;
1492 INIT_LIST_HEAD(&data
.dispose
);
1493 data
.start
= parent
;
1496 d_walk(parent
, &data
, select_collect
);
1498 if (!list_empty(&data
.dispose
)) {
1499 shrink_dentry_list(&data
.dispose
);
1508 EXPORT_SYMBOL(shrink_dcache_parent
);
1510 static enum d_walk_ret
umount_check(void *_data
, struct dentry
*dentry
)
1512 /* it has busy descendents; complain about those instead */
1513 if (!list_empty(&dentry
->d_subdirs
))
1514 return D_WALK_CONTINUE
;
1516 /* root with refcount 1 is fine */
1517 if (dentry
== _data
&& dentry
->d_lockref
.count
== 1)
1518 return D_WALK_CONTINUE
;
1520 printk(KERN_ERR
"BUG: Dentry %p{i=%lx,n=%pd} "
1521 " still in use (%d) [unmount of %s %s]\n",
1524 dentry
->d_inode
->i_ino
: 0UL,
1526 dentry
->d_lockref
.count
,
1527 dentry
->d_sb
->s_type
->name
,
1528 dentry
->d_sb
->s_id
);
1530 return D_WALK_CONTINUE
;
1533 static void do_one_tree(struct dentry
*dentry
)
1535 shrink_dcache_parent(dentry
);
1536 d_walk(dentry
, dentry
, umount_check
);
1542 * destroy the dentries attached to a superblock on unmounting
1544 void shrink_dcache_for_umount(struct super_block
*sb
)
1546 struct dentry
*dentry
;
1548 WARN(down_read_trylock(&sb
->s_umount
), "s_umount should've been locked");
1550 dentry
= sb
->s_root
;
1552 do_one_tree(dentry
);
1554 while (!hlist_bl_empty(&sb
->s_roots
)) {
1555 dentry
= dget(hlist_bl_entry(hlist_bl_first(&sb
->s_roots
), struct dentry
, d_hash
));
1556 do_one_tree(dentry
);
1560 static enum d_walk_ret
find_submount(void *_data
, struct dentry
*dentry
)
1562 struct dentry
**victim
= _data
;
1563 if (d_mountpoint(dentry
)) {
1564 __dget_dlock(dentry
);
1568 return D_WALK_CONTINUE
;
1572 * d_invalidate - detach submounts, prune dcache, and drop
1573 * @dentry: dentry to invalidate (aka detach, prune and drop)
1575 void d_invalidate(struct dentry
*dentry
)
1577 bool had_submounts
= false;
1578 spin_lock(&dentry
->d_lock
);
1579 if (d_unhashed(dentry
)) {
1580 spin_unlock(&dentry
->d_lock
);
1584 spin_unlock(&dentry
->d_lock
);
1586 /* Negative dentries can be dropped without further checks */
1587 if (!dentry
->d_inode
)
1590 shrink_dcache_parent(dentry
);
1592 struct dentry
*victim
= NULL
;
1593 d_walk(dentry
, &victim
, find_submount
);
1596 shrink_dcache_parent(dentry
);
1599 had_submounts
= true;
1600 detach_mounts(victim
);
1604 EXPORT_SYMBOL(d_invalidate
);
1607 * __d_alloc - allocate a dcache entry
1608 * @sb: filesystem it will belong to
1609 * @name: qstr of the name
1611 * Allocates a dentry. It returns %NULL if there is insufficient memory
1612 * available. On a success the dentry is returned. The name passed in is
1613 * copied and the copy passed in may be reused after this call.
1616 struct dentry
*__d_alloc(struct super_block
*sb
, const struct qstr
*name
)
1618 struct dentry
*dentry
;
1622 dentry
= kmem_cache_alloc(dentry_cache
, GFP_KERNEL
);
1627 * We guarantee that the inline name is always NUL-terminated.
1628 * This way the memcpy() done by the name switching in rename
1629 * will still always have a NUL at the end, even if we might
1630 * be overwriting an internal NUL character
1632 dentry
->d_iname
[DNAME_INLINE_LEN
-1] = 0;
1633 if (unlikely(!name
)) {
1635 dname
= dentry
->d_iname
;
1636 } else if (name
->len
> DNAME_INLINE_LEN
-1) {
1637 size_t size
= offsetof(struct external_name
, name
[1]);
1638 struct external_name
*p
= kmalloc(size
+ name
->len
,
1639 GFP_KERNEL_ACCOUNT
|
1642 kmem_cache_free(dentry_cache
, dentry
);
1645 atomic_set(&p
->u
.count
, 1);
1648 dname
= dentry
->d_iname
;
1651 dentry
->d_name
.len
= name
->len
;
1652 dentry
->d_name
.hash
= name
->hash
;
1653 memcpy(dname
, name
->name
, name
->len
);
1654 dname
[name
->len
] = 0;
1656 /* Make sure we always see the terminating NUL character */
1657 smp_store_release(&dentry
->d_name
.name
, dname
); /* ^^^ */
1659 dentry
->d_lockref
.count
= 1;
1660 dentry
->d_flags
= 0;
1661 spin_lock_init(&dentry
->d_lock
);
1662 seqcount_init(&dentry
->d_seq
);
1663 dentry
->d_inode
= NULL
;
1664 dentry
->d_parent
= dentry
;
1666 dentry
->d_op
= NULL
;
1667 dentry
->d_fsdata
= NULL
;
1668 INIT_HLIST_BL_NODE(&dentry
->d_hash
);
1669 INIT_LIST_HEAD(&dentry
->d_lru
);
1670 INIT_LIST_HEAD(&dentry
->d_subdirs
);
1671 INIT_HLIST_NODE(&dentry
->d_u
.d_alias
);
1672 INIT_LIST_HEAD(&dentry
->d_child
);
1673 d_set_d_op(dentry
, dentry
->d_sb
->s_d_op
);
1675 if (dentry
->d_op
&& dentry
->d_op
->d_init
) {
1676 err
= dentry
->d_op
->d_init(dentry
);
1678 if (dname_external(dentry
))
1679 kfree(external_name(dentry
));
1680 kmem_cache_free(dentry_cache
, dentry
);
1685 this_cpu_inc(nr_dentry
);
1691 * d_alloc - allocate a dcache entry
1692 * @parent: parent of entry to allocate
1693 * @name: qstr of the name
1695 * Allocates a dentry. It returns %NULL if there is insufficient memory
1696 * available. On a success the dentry is returned. The name passed in is
1697 * copied and the copy passed in may be reused after this call.
1699 struct dentry
*d_alloc(struct dentry
* parent
, const struct qstr
*name
)
1701 struct dentry
*dentry
= __d_alloc(parent
->d_sb
, name
);
1704 spin_lock(&parent
->d_lock
);
1706 * don't need child lock because it is not subject
1707 * to concurrency here
1709 __dget_dlock(parent
);
1710 dentry
->d_parent
= parent
;
1711 list_add(&dentry
->d_child
, &parent
->d_subdirs
);
1712 spin_unlock(&parent
->d_lock
);
1716 EXPORT_SYMBOL(d_alloc
);
1718 struct dentry
*d_alloc_anon(struct super_block
*sb
)
1720 return __d_alloc(sb
, NULL
);
1722 EXPORT_SYMBOL(d_alloc_anon
);
1724 struct dentry
*d_alloc_cursor(struct dentry
* parent
)
1726 struct dentry
*dentry
= d_alloc_anon(parent
->d_sb
);
1728 dentry
->d_flags
|= DCACHE_DENTRY_CURSOR
;
1729 dentry
->d_parent
= dget(parent
);
1735 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1736 * @sb: the superblock
1737 * @name: qstr of the name
1739 * For a filesystem that just pins its dentries in memory and never
1740 * performs lookups at all, return an unhashed IS_ROOT dentry.
1741 * This is used for pipes, sockets et.al. - the stuff that should
1742 * never be anyone's children or parents. Unlike all other
1743 * dentries, these will not have RCU delay between dropping the
1744 * last reference and freeing them.
1746 * The only user is alloc_file_pseudo() and that's what should
1747 * be considered a public interface. Don't use directly.
1749 struct dentry
*d_alloc_pseudo(struct super_block
*sb
, const struct qstr
*name
)
1751 struct dentry
*dentry
= __d_alloc(sb
, name
);
1753 dentry
->d_flags
|= DCACHE_NORCU
;
1757 struct dentry
*d_alloc_name(struct dentry
*parent
, const char *name
)
1762 q
.hash_len
= hashlen_string(parent
, name
);
1763 return d_alloc(parent
, &q
);
1765 EXPORT_SYMBOL(d_alloc_name
);
1767 void d_set_d_op(struct dentry
*dentry
, const struct dentry_operations
*op
)
1769 WARN_ON_ONCE(dentry
->d_op
);
1770 WARN_ON_ONCE(dentry
->d_flags
& (DCACHE_OP_HASH
|
1772 DCACHE_OP_REVALIDATE
|
1773 DCACHE_OP_WEAK_REVALIDATE
|
1780 dentry
->d_flags
|= DCACHE_OP_HASH
;
1782 dentry
->d_flags
|= DCACHE_OP_COMPARE
;
1783 if (op
->d_revalidate
)
1784 dentry
->d_flags
|= DCACHE_OP_REVALIDATE
;
1785 if (op
->d_weak_revalidate
)
1786 dentry
->d_flags
|= DCACHE_OP_WEAK_REVALIDATE
;
1788 dentry
->d_flags
|= DCACHE_OP_DELETE
;
1790 dentry
->d_flags
|= DCACHE_OP_PRUNE
;
1792 dentry
->d_flags
|= DCACHE_OP_REAL
;
1795 EXPORT_SYMBOL(d_set_d_op
);
1799 * d_set_fallthru - Mark a dentry as falling through to a lower layer
1800 * @dentry - The dentry to mark
1802 * Mark a dentry as falling through to the lower layer (as set with
1803 * d_pin_lower()). This flag may be recorded on the medium.
1805 void d_set_fallthru(struct dentry
*dentry
)
1807 spin_lock(&dentry
->d_lock
);
1808 dentry
->d_flags
|= DCACHE_FALLTHRU
;
1809 spin_unlock(&dentry
->d_lock
);
1811 EXPORT_SYMBOL(d_set_fallthru
);
1813 static unsigned d_flags_for_inode(struct inode
*inode
)
1815 unsigned add_flags
= DCACHE_REGULAR_TYPE
;
1818 return DCACHE_MISS_TYPE
;
1820 if (S_ISDIR(inode
->i_mode
)) {
1821 add_flags
= DCACHE_DIRECTORY_TYPE
;
1822 if (unlikely(!(inode
->i_opflags
& IOP_LOOKUP
))) {
1823 if (unlikely(!inode
->i_op
->lookup
))
1824 add_flags
= DCACHE_AUTODIR_TYPE
;
1826 inode
->i_opflags
|= IOP_LOOKUP
;
1828 goto type_determined
;
1831 if (unlikely(!(inode
->i_opflags
& IOP_NOFOLLOW
))) {
1832 if (unlikely(inode
->i_op
->get_link
)) {
1833 add_flags
= DCACHE_SYMLINK_TYPE
;
1834 goto type_determined
;
1836 inode
->i_opflags
|= IOP_NOFOLLOW
;
1839 if (unlikely(!S_ISREG(inode
->i_mode
)))
1840 add_flags
= DCACHE_SPECIAL_TYPE
;
1843 if (unlikely(IS_AUTOMOUNT(inode
)))
1844 add_flags
|= DCACHE_NEED_AUTOMOUNT
;
1848 static void __d_instantiate(struct dentry
*dentry
, struct inode
*inode
)
1850 unsigned add_flags
= d_flags_for_inode(inode
);
1851 WARN_ON(d_in_lookup(dentry
));
1853 spin_lock(&dentry
->d_lock
);
1855 * Decrement negative dentry count if it was in the LRU list.
1857 if (dentry
->d_flags
& DCACHE_LRU_LIST
)
1858 this_cpu_dec(nr_dentry_negative
);
1859 hlist_add_head(&dentry
->d_u
.d_alias
, &inode
->i_dentry
);
1860 raw_write_seqcount_begin(&dentry
->d_seq
);
1861 __d_set_inode_and_type(dentry
, inode
, add_flags
);
1862 raw_write_seqcount_end(&dentry
->d_seq
);
1863 fsnotify_update_flags(dentry
);
1864 spin_unlock(&dentry
->d_lock
);
1868 * d_instantiate - fill in inode information for a dentry
1869 * @entry: dentry to complete
1870 * @inode: inode to attach to this dentry
1872 * Fill in inode information in the entry.
1874 * This turns negative dentries into productive full members
1877 * NOTE! This assumes that the inode count has been incremented
1878 * (or otherwise set) by the caller to indicate that it is now
1879 * in use by the dcache.
1882 void d_instantiate(struct dentry
*entry
, struct inode
* inode
)
1884 BUG_ON(!hlist_unhashed(&entry
->d_u
.d_alias
));
1886 security_d_instantiate(entry
, inode
);
1887 spin_lock(&inode
->i_lock
);
1888 __d_instantiate(entry
, inode
);
1889 spin_unlock(&inode
->i_lock
);
1892 EXPORT_SYMBOL(d_instantiate
);
1895 * This should be equivalent to d_instantiate() + unlock_new_inode(),
1896 * with lockdep-related part of unlock_new_inode() done before
1897 * anything else. Use that instead of open-coding d_instantiate()/
1898 * unlock_new_inode() combinations.
1900 void d_instantiate_new(struct dentry
*entry
, struct inode
*inode
)
1902 BUG_ON(!hlist_unhashed(&entry
->d_u
.d_alias
));
1904 lockdep_annotate_inode_mutex_key(inode
);
1905 security_d_instantiate(entry
, inode
);
1906 spin_lock(&inode
->i_lock
);
1907 __d_instantiate(entry
, inode
);
1908 WARN_ON(!(inode
->i_state
& I_NEW
));
1909 inode
->i_state
&= ~I_NEW
& ~I_CREATING
;
1911 wake_up_bit(&inode
->i_state
, __I_NEW
);
1912 spin_unlock(&inode
->i_lock
);
1914 EXPORT_SYMBOL(d_instantiate_new
);
1916 struct dentry
*d_make_root(struct inode
*root_inode
)
1918 struct dentry
*res
= NULL
;
1921 res
= d_alloc_anon(root_inode
->i_sb
);
1923 d_instantiate(res
, root_inode
);
1929 EXPORT_SYMBOL(d_make_root
);
1931 static struct dentry
*__d_instantiate_anon(struct dentry
*dentry
,
1932 struct inode
*inode
,
1938 security_d_instantiate(dentry
, inode
);
1939 spin_lock(&inode
->i_lock
);
1940 res
= __d_find_any_alias(inode
);
1942 spin_unlock(&inode
->i_lock
);
1947 /* attach a disconnected dentry */
1948 add_flags
= d_flags_for_inode(inode
);
1951 add_flags
|= DCACHE_DISCONNECTED
;
1953 spin_lock(&dentry
->d_lock
);
1954 __d_set_inode_and_type(dentry
, inode
, add_flags
);
1955 hlist_add_head(&dentry
->d_u
.d_alias
, &inode
->i_dentry
);
1956 if (!disconnected
) {
1957 hlist_bl_lock(&dentry
->d_sb
->s_roots
);
1958 hlist_bl_add_head(&dentry
->d_hash
, &dentry
->d_sb
->s_roots
);
1959 hlist_bl_unlock(&dentry
->d_sb
->s_roots
);
1961 spin_unlock(&dentry
->d_lock
);
1962 spin_unlock(&inode
->i_lock
);
1971 struct dentry
*d_instantiate_anon(struct dentry
*dentry
, struct inode
*inode
)
1973 return __d_instantiate_anon(dentry
, inode
, true);
1975 EXPORT_SYMBOL(d_instantiate_anon
);
1977 static struct dentry
*__d_obtain_alias(struct inode
*inode
, bool disconnected
)
1983 return ERR_PTR(-ESTALE
);
1985 return ERR_CAST(inode
);
1987 res
= d_find_any_alias(inode
);
1991 tmp
= d_alloc_anon(inode
->i_sb
);
1993 res
= ERR_PTR(-ENOMEM
);
1997 return __d_instantiate_anon(tmp
, inode
, disconnected
);
2005 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
2006 * @inode: inode to allocate the dentry for
2008 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
2009 * similar open by handle operations. The returned dentry may be anonymous,
2010 * or may have a full name (if the inode was already in the cache).
2012 * When called on a directory inode, we must ensure that the inode only ever
2013 * has one dentry. If a dentry is found, that is returned instead of
2014 * allocating a new one.
2016 * On successful return, the reference to the inode has been transferred
2017 * to the dentry. In case of an error the reference on the inode is released.
2018 * To make it easier to use in export operations a %NULL or IS_ERR inode may
2019 * be passed in and the error will be propagated to the return value,
2020 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
2022 struct dentry
*d_obtain_alias(struct inode
*inode
)
2024 return __d_obtain_alias(inode
, true);
2026 EXPORT_SYMBOL(d_obtain_alias
);
2029 * d_obtain_root - find or allocate a dentry for a given inode
2030 * @inode: inode to allocate the dentry for
2032 * Obtain an IS_ROOT dentry for the root of a filesystem.
2034 * We must ensure that directory inodes only ever have one dentry. If a
2035 * dentry is found, that is returned instead of allocating a new one.
2037 * On successful return, the reference to the inode has been transferred
2038 * to the dentry. In case of an error the reference on the inode is
2039 * released. A %NULL or IS_ERR inode may be passed in and will be the
2040 * error will be propagate to the return value, with a %NULL @inode
2041 * replaced by ERR_PTR(-ESTALE).
2043 struct dentry
*d_obtain_root(struct inode
*inode
)
2045 return __d_obtain_alias(inode
, false);
2047 EXPORT_SYMBOL(d_obtain_root
);
2050 * d_add_ci - lookup or allocate new dentry with case-exact name
2051 * @inode: the inode case-insensitive lookup has found
2052 * @dentry: the negative dentry that was passed to the parent's lookup func
2053 * @name: the case-exact name to be associated with the returned dentry
2055 * This is to avoid filling the dcache with case-insensitive names to the
2056 * same inode, only the actual correct case is stored in the dcache for
2057 * case-insensitive filesystems.
2059 * For a case-insensitive lookup match and if the the case-exact dentry
2060 * already exists in in the dcache, use it and return it.
2062 * If no entry exists with the exact case name, allocate new dentry with
2063 * the exact case, and return the spliced entry.
2065 struct dentry
*d_add_ci(struct dentry
*dentry
, struct inode
*inode
,
2068 struct dentry
*found
, *res
;
2071 * First check if a dentry matching the name already exists,
2072 * if not go ahead and create it now.
2074 found
= d_hash_and_lookup(dentry
->d_parent
, name
);
2079 if (d_in_lookup(dentry
)) {
2080 found
= d_alloc_parallel(dentry
->d_parent
, name
,
2082 if (IS_ERR(found
) || !d_in_lookup(found
)) {
2087 found
= d_alloc(dentry
->d_parent
, name
);
2090 return ERR_PTR(-ENOMEM
);
2093 res
= d_splice_alias(inode
, found
);
2100 EXPORT_SYMBOL(d_add_ci
);
2103 static inline bool d_same_name(const struct dentry
*dentry
,
2104 const struct dentry
*parent
,
2105 const struct qstr
*name
)
2107 if (likely(!(parent
->d_flags
& DCACHE_OP_COMPARE
))) {
2108 if (dentry
->d_name
.len
!= name
->len
)
2110 return dentry_cmp(dentry
, name
->name
, name
->len
) == 0;
2112 return parent
->d_op
->d_compare(dentry
,
2113 dentry
->d_name
.len
, dentry
->d_name
.name
,
2118 * __d_lookup_rcu - search for a dentry (racy, store-free)
2119 * @parent: parent dentry
2120 * @name: qstr of name we wish to find
2121 * @seqp: returns d_seq value at the point where the dentry was found
2122 * Returns: dentry, or NULL
2124 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2125 * resolution (store-free path walking) design described in
2126 * Documentation/filesystems/path-lookup.txt.
2128 * This is not to be used outside core vfs.
2130 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2131 * held, and rcu_read_lock held. The returned dentry must not be stored into
2132 * without taking d_lock and checking d_seq sequence count against @seq
2135 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2138 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2139 * the returned dentry, so long as its parent's seqlock is checked after the
2140 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2141 * is formed, giving integrity down the path walk.
2143 * NOTE! The caller *has* to check the resulting dentry against the sequence
2144 * number we've returned before using any of the resulting dentry state!
2146 struct dentry
*__d_lookup_rcu(const struct dentry
*parent
,
2147 const struct qstr
*name
,
2150 u64 hashlen
= name
->hash_len
;
2151 const unsigned char *str
= name
->name
;
2152 struct hlist_bl_head
*b
= d_hash(hashlen_hash(hashlen
));
2153 struct hlist_bl_node
*node
;
2154 struct dentry
*dentry
;
2157 * Note: There is significant duplication with __d_lookup_rcu which is
2158 * required to prevent single threaded performance regressions
2159 * especially on architectures where smp_rmb (in seqcounts) are costly.
2160 * Keep the two functions in sync.
2164 * The hash list is protected using RCU.
2166 * Carefully use d_seq when comparing a candidate dentry, to avoid
2167 * races with d_move().
2169 * It is possible that concurrent renames can mess up our list
2170 * walk here and result in missing our dentry, resulting in the
2171 * false-negative result. d_lookup() protects against concurrent
2172 * renames using rename_lock seqlock.
2174 * See Documentation/filesystems/path-lookup.txt for more details.
2176 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
2181 * The dentry sequence count protects us from concurrent
2182 * renames, and thus protects parent and name fields.
2184 * The caller must perform a seqcount check in order
2185 * to do anything useful with the returned dentry.
2187 * NOTE! We do a "raw" seqcount_begin here. That means that
2188 * we don't wait for the sequence count to stabilize if it
2189 * is in the middle of a sequence change. If we do the slow
2190 * dentry compare, we will do seqretries until it is stable,
2191 * and if we end up with a successful lookup, we actually
2192 * want to exit RCU lookup anyway.
2194 * Note that raw_seqcount_begin still *does* smp_rmb(), so
2195 * we are still guaranteed NUL-termination of ->d_name.name.
2197 seq
= raw_seqcount_begin(&dentry
->d_seq
);
2198 if (dentry
->d_parent
!= parent
)
2200 if (d_unhashed(dentry
))
2203 if (unlikely(parent
->d_flags
& DCACHE_OP_COMPARE
)) {
2206 if (dentry
->d_name
.hash
!= hashlen_hash(hashlen
))
2208 tlen
= dentry
->d_name
.len
;
2209 tname
= dentry
->d_name
.name
;
2210 /* we want a consistent (name,len) pair */
2211 if (read_seqcount_retry(&dentry
->d_seq
, seq
)) {
2215 if (parent
->d_op
->d_compare(dentry
,
2216 tlen
, tname
, name
) != 0)
2219 if (dentry
->d_name
.hash_len
!= hashlen
)
2221 if (dentry_cmp(dentry
, str
, hashlen_len(hashlen
)) != 0)
2231 * d_lookup - search for a dentry
2232 * @parent: parent dentry
2233 * @name: qstr of name we wish to find
2234 * Returns: dentry, or NULL
2236 * d_lookup searches the children of the parent dentry for the name in
2237 * question. If the dentry is found its reference count is incremented and the
2238 * dentry is returned. The caller must use dput to free the entry when it has
2239 * finished using it. %NULL is returned if the dentry does not exist.
2241 struct dentry
*d_lookup(const struct dentry
*parent
, const struct qstr
*name
)
2243 struct dentry
*dentry
;
2247 seq
= read_seqbegin(&rename_lock
);
2248 dentry
= __d_lookup(parent
, name
);
2251 } while (read_seqretry(&rename_lock
, seq
));
2254 EXPORT_SYMBOL(d_lookup
);
2257 * __d_lookup - search for a dentry (racy)
2258 * @parent: parent dentry
2259 * @name: qstr of name we wish to find
2260 * Returns: dentry, or NULL
2262 * __d_lookup is like d_lookup, however it may (rarely) return a
2263 * false-negative result due to unrelated rename activity.
2265 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2266 * however it must be used carefully, eg. with a following d_lookup in
2267 * the case of failure.
2269 * __d_lookup callers must be commented.
2271 struct dentry
*__d_lookup(const struct dentry
*parent
, const struct qstr
*name
)
2273 unsigned int hash
= name
->hash
;
2274 struct hlist_bl_head
*b
= d_hash(hash
);
2275 struct hlist_bl_node
*node
;
2276 struct dentry
*found
= NULL
;
2277 struct dentry
*dentry
;
2280 * Note: There is significant duplication with __d_lookup_rcu which is
2281 * required to prevent single threaded performance regressions
2282 * especially on architectures where smp_rmb (in seqcounts) are costly.
2283 * Keep the two functions in sync.
2287 * The hash list is protected using RCU.
2289 * Take d_lock when comparing a candidate dentry, to avoid races
2292 * It is possible that concurrent renames can mess up our list
2293 * walk here and result in missing our dentry, resulting in the
2294 * false-negative result. d_lookup() protects against concurrent
2295 * renames using rename_lock seqlock.
2297 * See Documentation/filesystems/path-lookup.txt for more details.
2301 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
2303 if (dentry
->d_name
.hash
!= hash
)
2306 spin_lock(&dentry
->d_lock
);
2307 if (dentry
->d_parent
!= parent
)
2309 if (d_unhashed(dentry
))
2312 if (!d_same_name(dentry
, parent
, name
))
2315 dentry
->d_lockref
.count
++;
2317 spin_unlock(&dentry
->d_lock
);
2320 spin_unlock(&dentry
->d_lock
);
2328 * d_hash_and_lookup - hash the qstr then search for a dentry
2329 * @dir: Directory to search in
2330 * @name: qstr of name we wish to find
2332 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2334 struct dentry
*d_hash_and_lookup(struct dentry
*dir
, struct qstr
*name
)
2337 * Check for a fs-specific hash function. Note that we must
2338 * calculate the standard hash first, as the d_op->d_hash()
2339 * routine may choose to leave the hash value unchanged.
2341 name
->hash
= full_name_hash(dir
, name
->name
, name
->len
);
2342 if (dir
->d_flags
& DCACHE_OP_HASH
) {
2343 int err
= dir
->d_op
->d_hash(dir
, name
);
2344 if (unlikely(err
< 0))
2345 return ERR_PTR(err
);
2347 return d_lookup(dir
, name
);
2349 EXPORT_SYMBOL(d_hash_and_lookup
);
2352 * When a file is deleted, we have two options:
2353 * - turn this dentry into a negative dentry
2354 * - unhash this dentry and free it.
2356 * Usually, we want to just turn this into
2357 * a negative dentry, but if anybody else is
2358 * currently using the dentry or the inode
2359 * we can't do that and we fall back on removing
2360 * it from the hash queues and waiting for
2361 * it to be deleted later when it has no users
2365 * d_delete - delete a dentry
2366 * @dentry: The dentry to delete
2368 * Turn the dentry into a negative dentry if possible, otherwise
2369 * remove it from the hash queues so it can be deleted later
2372 void d_delete(struct dentry
* dentry
)
2374 struct inode
*inode
= dentry
->d_inode
;
2375 int isdir
= d_is_dir(dentry
);
2377 spin_lock(&inode
->i_lock
);
2378 spin_lock(&dentry
->d_lock
);
2380 * Are we the only user?
2382 if (dentry
->d_lockref
.count
== 1) {
2383 dentry
->d_flags
&= ~DCACHE_CANT_MOUNT
;
2384 dentry_unlink_inode(dentry
);
2387 spin_unlock(&dentry
->d_lock
);
2388 spin_unlock(&inode
->i_lock
);
2390 fsnotify_nameremove(dentry
, isdir
);
2392 EXPORT_SYMBOL(d_delete
);
2394 static void __d_rehash(struct dentry
*entry
)
2396 struct hlist_bl_head
*b
= d_hash(entry
->d_name
.hash
);
2399 hlist_bl_add_head_rcu(&entry
->d_hash
, b
);
2404 * d_rehash - add an entry back to the hash
2405 * @entry: dentry to add to the hash
2407 * Adds a dentry to the hash according to its name.
2410 void d_rehash(struct dentry
* entry
)
2412 spin_lock(&entry
->d_lock
);
2414 spin_unlock(&entry
->d_lock
);
2416 EXPORT_SYMBOL(d_rehash
);
2418 static inline unsigned start_dir_add(struct inode
*dir
)
2422 unsigned n
= dir
->i_dir_seq
;
2423 if (!(n
& 1) && cmpxchg(&dir
->i_dir_seq
, n
, n
+ 1) == n
)
2429 static inline void end_dir_add(struct inode
*dir
, unsigned n
)
2431 smp_store_release(&dir
->i_dir_seq
, n
+ 2);
2434 static void d_wait_lookup(struct dentry
*dentry
)
2436 if (d_in_lookup(dentry
)) {
2437 DECLARE_WAITQUEUE(wait
, current
);
2438 add_wait_queue(dentry
->d_wait
, &wait
);
2440 set_current_state(TASK_UNINTERRUPTIBLE
);
2441 spin_unlock(&dentry
->d_lock
);
2443 spin_lock(&dentry
->d_lock
);
2444 } while (d_in_lookup(dentry
));
2448 struct dentry
*d_alloc_parallel(struct dentry
*parent
,
2449 const struct qstr
*name
,
2450 wait_queue_head_t
*wq
)
2452 unsigned int hash
= name
->hash
;
2453 struct hlist_bl_head
*b
= in_lookup_hash(parent
, hash
);
2454 struct hlist_bl_node
*node
;
2455 struct dentry
*new = d_alloc(parent
, name
);
2456 struct dentry
*dentry
;
2457 unsigned seq
, r_seq
, d_seq
;
2460 return ERR_PTR(-ENOMEM
);
2464 seq
= smp_load_acquire(&parent
->d_inode
->i_dir_seq
);
2465 r_seq
= read_seqbegin(&rename_lock
);
2466 dentry
= __d_lookup_rcu(parent
, name
, &d_seq
);
2467 if (unlikely(dentry
)) {
2468 if (!lockref_get_not_dead(&dentry
->d_lockref
)) {
2472 if (read_seqcount_retry(&dentry
->d_seq
, d_seq
)) {
2481 if (unlikely(read_seqretry(&rename_lock
, r_seq
))) {
2486 if (unlikely(seq
& 1)) {
2492 if (unlikely(READ_ONCE(parent
->d_inode
->i_dir_seq
) != seq
)) {
2498 * No changes for the parent since the beginning of d_lookup().
2499 * Since all removals from the chain happen with hlist_bl_lock(),
2500 * any potential in-lookup matches are going to stay here until
2501 * we unlock the chain. All fields are stable in everything
2504 hlist_bl_for_each_entry(dentry
, node
, b
, d_u
.d_in_lookup_hash
) {
2505 if (dentry
->d_name
.hash
!= hash
)
2507 if (dentry
->d_parent
!= parent
)
2509 if (!d_same_name(dentry
, parent
, name
))
2512 /* now we can try to grab a reference */
2513 if (!lockref_get_not_dead(&dentry
->d_lockref
)) {
2520 * somebody is likely to be still doing lookup for it;
2521 * wait for them to finish
2523 spin_lock(&dentry
->d_lock
);
2524 d_wait_lookup(dentry
);
2526 * it's not in-lookup anymore; in principle we should repeat
2527 * everything from dcache lookup, but it's likely to be what
2528 * d_lookup() would've found anyway. If it is, just return it;
2529 * otherwise we really have to repeat the whole thing.
2531 if (unlikely(dentry
->d_name
.hash
!= hash
))
2533 if (unlikely(dentry
->d_parent
!= parent
))
2535 if (unlikely(d_unhashed(dentry
)))
2537 if (unlikely(!d_same_name(dentry
, parent
, name
)))
2539 /* OK, it *is* a hashed match; return it */
2540 spin_unlock(&dentry
->d_lock
);
2545 /* we can't take ->d_lock here; it's OK, though. */
2546 new->d_flags
|= DCACHE_PAR_LOOKUP
;
2548 hlist_bl_add_head_rcu(&new->d_u
.d_in_lookup_hash
, b
);
2552 spin_unlock(&dentry
->d_lock
);
2556 EXPORT_SYMBOL(d_alloc_parallel
);
2558 void __d_lookup_done(struct dentry
*dentry
)
2560 struct hlist_bl_head
*b
= in_lookup_hash(dentry
->d_parent
,
2561 dentry
->d_name
.hash
);
2563 dentry
->d_flags
&= ~DCACHE_PAR_LOOKUP
;
2564 __hlist_bl_del(&dentry
->d_u
.d_in_lookup_hash
);
2565 wake_up_all(dentry
->d_wait
);
2566 dentry
->d_wait
= NULL
;
2568 INIT_HLIST_NODE(&dentry
->d_u
.d_alias
);
2569 INIT_LIST_HEAD(&dentry
->d_lru
);
2571 EXPORT_SYMBOL(__d_lookup_done
);
2573 /* inode->i_lock held if inode is non-NULL */
2575 static inline void __d_add(struct dentry
*dentry
, struct inode
*inode
)
2577 struct inode
*dir
= NULL
;
2579 spin_lock(&dentry
->d_lock
);
2580 if (unlikely(d_in_lookup(dentry
))) {
2581 dir
= dentry
->d_parent
->d_inode
;
2582 n
= start_dir_add(dir
);
2583 __d_lookup_done(dentry
);
2586 unsigned add_flags
= d_flags_for_inode(inode
);
2587 hlist_add_head(&dentry
->d_u
.d_alias
, &inode
->i_dentry
);
2588 raw_write_seqcount_begin(&dentry
->d_seq
);
2589 __d_set_inode_and_type(dentry
, inode
, add_flags
);
2590 raw_write_seqcount_end(&dentry
->d_seq
);
2591 fsnotify_update_flags(dentry
);
2595 end_dir_add(dir
, n
);
2596 spin_unlock(&dentry
->d_lock
);
2598 spin_unlock(&inode
->i_lock
);
2602 * d_add - add dentry to hash queues
2603 * @entry: dentry to add
2604 * @inode: The inode to attach to this dentry
2606 * This adds the entry to the hash queues and initializes @inode.
2607 * The entry was actually filled in earlier during d_alloc().
2610 void d_add(struct dentry
*entry
, struct inode
*inode
)
2613 security_d_instantiate(entry
, inode
);
2614 spin_lock(&inode
->i_lock
);
2616 __d_add(entry
, inode
);
2618 EXPORT_SYMBOL(d_add
);
2621 * d_exact_alias - find and hash an exact unhashed alias
2622 * @entry: dentry to add
2623 * @inode: The inode to go with this dentry
2625 * If an unhashed dentry with the same name/parent and desired
2626 * inode already exists, hash and return it. Otherwise, return
2629 * Parent directory should be locked.
2631 struct dentry
*d_exact_alias(struct dentry
*entry
, struct inode
*inode
)
2633 struct dentry
*alias
;
2634 unsigned int hash
= entry
->d_name
.hash
;
2636 spin_lock(&inode
->i_lock
);
2637 hlist_for_each_entry(alias
, &inode
->i_dentry
, d_u
.d_alias
) {
2639 * Don't need alias->d_lock here, because aliases with
2640 * d_parent == entry->d_parent are not subject to name or
2641 * parent changes, because the parent inode i_mutex is held.
2643 if (alias
->d_name
.hash
!= hash
)
2645 if (alias
->d_parent
!= entry
->d_parent
)
2647 if (!d_same_name(alias
, entry
->d_parent
, &entry
->d_name
))
2649 spin_lock(&alias
->d_lock
);
2650 if (!d_unhashed(alias
)) {
2651 spin_unlock(&alias
->d_lock
);
2654 __dget_dlock(alias
);
2656 spin_unlock(&alias
->d_lock
);
2658 spin_unlock(&inode
->i_lock
);
2661 spin_unlock(&inode
->i_lock
);
2664 EXPORT_SYMBOL(d_exact_alias
);
2666 static void swap_names(struct dentry
*dentry
, struct dentry
*target
)
2668 if (unlikely(dname_external(target
))) {
2669 if (unlikely(dname_external(dentry
))) {
2671 * Both external: swap the pointers
2673 swap(target
->d_name
.name
, dentry
->d_name
.name
);
2676 * dentry:internal, target:external. Steal target's
2677 * storage and make target internal.
2679 memcpy(target
->d_iname
, dentry
->d_name
.name
,
2680 dentry
->d_name
.len
+ 1);
2681 dentry
->d_name
.name
= target
->d_name
.name
;
2682 target
->d_name
.name
= target
->d_iname
;
2685 if (unlikely(dname_external(dentry
))) {
2687 * dentry:external, target:internal. Give dentry's
2688 * storage to target and make dentry internal
2690 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2691 target
->d_name
.len
+ 1);
2692 target
->d_name
.name
= dentry
->d_name
.name
;
2693 dentry
->d_name
.name
= dentry
->d_iname
;
2696 * Both are internal.
2699 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN
, sizeof(long)));
2700 for (i
= 0; i
< DNAME_INLINE_LEN
/ sizeof(long); i
++) {
2701 swap(((long *) &dentry
->d_iname
)[i
],
2702 ((long *) &target
->d_iname
)[i
]);
2706 swap(dentry
->d_name
.hash_len
, target
->d_name
.hash_len
);
2709 static void copy_name(struct dentry
*dentry
, struct dentry
*target
)
2711 struct external_name
*old_name
= NULL
;
2712 if (unlikely(dname_external(dentry
)))
2713 old_name
= external_name(dentry
);
2714 if (unlikely(dname_external(target
))) {
2715 atomic_inc(&external_name(target
)->u
.count
);
2716 dentry
->d_name
= target
->d_name
;
2718 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2719 target
->d_name
.len
+ 1);
2720 dentry
->d_name
.name
= dentry
->d_iname
;
2721 dentry
->d_name
.hash_len
= target
->d_name
.hash_len
;
2723 if (old_name
&& likely(atomic_dec_and_test(&old_name
->u
.count
)))
2724 kfree_rcu(old_name
, u
.head
);
2728 * __d_move - move a dentry
2729 * @dentry: entry to move
2730 * @target: new dentry
2731 * @exchange: exchange the two dentries
2733 * Update the dcache to reflect the move of a file name. Negative
2734 * dcache entries should not be moved in this way. Caller must hold
2735 * rename_lock, the i_mutex of the source and target directories,
2736 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2738 static void __d_move(struct dentry
*dentry
, struct dentry
*target
,
2741 struct dentry
*old_parent
, *p
;
2742 struct inode
*dir
= NULL
;
2745 WARN_ON(!dentry
->d_inode
);
2746 if (WARN_ON(dentry
== target
))
2749 BUG_ON(d_ancestor(target
, dentry
));
2750 old_parent
= dentry
->d_parent
;
2751 p
= d_ancestor(old_parent
, target
);
2752 if (IS_ROOT(dentry
)) {
2754 spin_lock(&target
->d_parent
->d_lock
);
2756 /* target is not a descendent of dentry->d_parent */
2757 spin_lock(&target
->d_parent
->d_lock
);
2758 spin_lock_nested(&old_parent
->d_lock
, DENTRY_D_LOCK_NESTED
);
2760 BUG_ON(p
== dentry
);
2761 spin_lock(&old_parent
->d_lock
);
2763 spin_lock_nested(&target
->d_parent
->d_lock
,
2764 DENTRY_D_LOCK_NESTED
);
2766 spin_lock_nested(&dentry
->d_lock
, 2);
2767 spin_lock_nested(&target
->d_lock
, 3);
2769 if (unlikely(d_in_lookup(target
))) {
2770 dir
= target
->d_parent
->d_inode
;
2771 n
= start_dir_add(dir
);
2772 __d_lookup_done(target
);
2775 write_seqcount_begin(&dentry
->d_seq
);
2776 write_seqcount_begin_nested(&target
->d_seq
, DENTRY_D_LOCK_NESTED
);
2779 if (!d_unhashed(dentry
))
2781 if (!d_unhashed(target
))
2784 /* ... and switch them in the tree */
2785 dentry
->d_parent
= target
->d_parent
;
2787 copy_name(dentry
, target
);
2788 target
->d_hash
.pprev
= NULL
;
2789 dentry
->d_parent
->d_lockref
.count
++;
2790 if (dentry
!= old_parent
) /* wasn't IS_ROOT */
2791 WARN_ON(!--old_parent
->d_lockref
.count
);
2793 target
->d_parent
= old_parent
;
2794 swap_names(dentry
, target
);
2795 list_move(&target
->d_child
, &target
->d_parent
->d_subdirs
);
2797 fsnotify_update_flags(target
);
2799 list_move(&dentry
->d_child
, &dentry
->d_parent
->d_subdirs
);
2801 fsnotify_update_flags(dentry
);
2802 fscrypt_handle_d_move(dentry
);
2804 write_seqcount_end(&target
->d_seq
);
2805 write_seqcount_end(&dentry
->d_seq
);
2808 end_dir_add(dir
, n
);
2810 if (dentry
->d_parent
!= old_parent
)
2811 spin_unlock(&dentry
->d_parent
->d_lock
);
2812 if (dentry
!= old_parent
)
2813 spin_unlock(&old_parent
->d_lock
);
2814 spin_unlock(&target
->d_lock
);
2815 spin_unlock(&dentry
->d_lock
);
2819 * d_move - move a dentry
2820 * @dentry: entry to move
2821 * @target: new dentry
2823 * Update the dcache to reflect the move of a file name. Negative
2824 * dcache entries should not be moved in this way. See the locking
2825 * requirements for __d_move.
2827 void d_move(struct dentry
*dentry
, struct dentry
*target
)
2829 write_seqlock(&rename_lock
);
2830 __d_move(dentry
, target
, false);
2831 write_sequnlock(&rename_lock
);
2833 EXPORT_SYMBOL(d_move
);
2836 * d_exchange - exchange two dentries
2837 * @dentry1: first dentry
2838 * @dentry2: second dentry
2840 void d_exchange(struct dentry
*dentry1
, struct dentry
*dentry2
)
2842 write_seqlock(&rename_lock
);
2844 WARN_ON(!dentry1
->d_inode
);
2845 WARN_ON(!dentry2
->d_inode
);
2846 WARN_ON(IS_ROOT(dentry1
));
2847 WARN_ON(IS_ROOT(dentry2
));
2849 __d_move(dentry1
, dentry2
, true);
2851 write_sequnlock(&rename_lock
);
2855 * d_ancestor - search for an ancestor
2856 * @p1: ancestor dentry
2859 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2860 * an ancestor of p2, else NULL.
2862 struct dentry
*d_ancestor(struct dentry
*p1
, struct dentry
*p2
)
2866 for (p
= p2
; !IS_ROOT(p
); p
= p
->d_parent
) {
2867 if (p
->d_parent
== p1
)
2874 * This helper attempts to cope with remotely renamed directories
2876 * It assumes that the caller is already holding
2877 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2879 * Note: If ever the locking in lock_rename() changes, then please
2880 * remember to update this too...
2882 static int __d_unalias(struct inode
*inode
,
2883 struct dentry
*dentry
, struct dentry
*alias
)
2885 struct mutex
*m1
= NULL
;
2886 struct rw_semaphore
*m2
= NULL
;
2889 /* If alias and dentry share a parent, then no extra locks required */
2890 if (alias
->d_parent
== dentry
->d_parent
)
2893 /* See lock_rename() */
2894 if (!mutex_trylock(&dentry
->d_sb
->s_vfs_rename_mutex
))
2896 m1
= &dentry
->d_sb
->s_vfs_rename_mutex
;
2897 if (!inode_trylock_shared(alias
->d_parent
->d_inode
))
2899 m2
= &alias
->d_parent
->d_inode
->i_rwsem
;
2901 __d_move(alias
, dentry
, false);
2912 * d_splice_alias - splice a disconnected dentry into the tree if one exists
2913 * @inode: the inode which may have a disconnected dentry
2914 * @dentry: a negative dentry which we want to point to the inode.
2916 * If inode is a directory and has an IS_ROOT alias, then d_move that in
2917 * place of the given dentry and return it, else simply d_add the inode
2918 * to the dentry and return NULL.
2920 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
2921 * we should error out: directories can't have multiple aliases.
2923 * This is needed in the lookup routine of any filesystem that is exportable
2924 * (via knfsd) so that we can build dcache paths to directories effectively.
2926 * If a dentry was found and moved, then it is returned. Otherwise NULL
2927 * is returned. This matches the expected return value of ->lookup.
2929 * Cluster filesystems may call this function with a negative, hashed dentry.
2930 * In that case, we know that the inode will be a regular file, and also this
2931 * will only occur during atomic_open. So we need to check for the dentry
2932 * being already hashed only in the final case.
2934 struct dentry
*d_splice_alias(struct inode
*inode
, struct dentry
*dentry
)
2937 return ERR_CAST(inode
);
2939 BUG_ON(!d_unhashed(dentry
));
2944 security_d_instantiate(dentry
, inode
);
2945 spin_lock(&inode
->i_lock
);
2946 if (S_ISDIR(inode
->i_mode
)) {
2947 struct dentry
*new = __d_find_any_alias(inode
);
2948 if (unlikely(new)) {
2949 /* The reference to new ensures it remains an alias */
2950 spin_unlock(&inode
->i_lock
);
2951 write_seqlock(&rename_lock
);
2952 if (unlikely(d_ancestor(new, dentry
))) {
2953 write_sequnlock(&rename_lock
);
2955 new = ERR_PTR(-ELOOP
);
2956 pr_warn_ratelimited(
2957 "VFS: Lookup of '%s' in %s %s"
2958 " would have caused loop\n",
2959 dentry
->d_name
.name
,
2960 inode
->i_sb
->s_type
->name
,
2962 } else if (!IS_ROOT(new)) {
2963 struct dentry
*old_parent
= dget(new->d_parent
);
2964 int err
= __d_unalias(inode
, dentry
, new);
2965 write_sequnlock(&rename_lock
);
2972 __d_move(new, dentry
, false);
2973 write_sequnlock(&rename_lock
);
2980 __d_add(dentry
, inode
);
2983 EXPORT_SYMBOL(d_splice_alias
);
2986 * Test whether new_dentry is a subdirectory of old_dentry.
2988 * Trivially implemented using the dcache structure
2992 * is_subdir - is new dentry a subdirectory of old_dentry
2993 * @new_dentry: new dentry
2994 * @old_dentry: old dentry
2996 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
2997 * Returns false otherwise.
2998 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3001 bool is_subdir(struct dentry
*new_dentry
, struct dentry
*old_dentry
)
3006 if (new_dentry
== old_dentry
)
3010 /* for restarting inner loop in case of seq retry */
3011 seq
= read_seqbegin(&rename_lock
);
3013 * Need rcu_readlock to protect against the d_parent trashing
3017 if (d_ancestor(old_dentry
, new_dentry
))
3022 } while (read_seqretry(&rename_lock
, seq
));
3026 EXPORT_SYMBOL(is_subdir
);
3028 static enum d_walk_ret
d_genocide_kill(void *data
, struct dentry
*dentry
)
3030 struct dentry
*root
= data
;
3031 if (dentry
!= root
) {
3032 if (d_unhashed(dentry
) || !dentry
->d_inode
)
3035 if (!(dentry
->d_flags
& DCACHE_GENOCIDE
)) {
3036 dentry
->d_flags
|= DCACHE_GENOCIDE
;
3037 dentry
->d_lockref
.count
--;
3040 return D_WALK_CONTINUE
;
3043 void d_genocide(struct dentry
*parent
)
3045 d_walk(parent
, parent
, d_genocide_kill
);
3048 EXPORT_SYMBOL(d_genocide
);
3050 void d_tmpfile(struct dentry
*dentry
, struct inode
*inode
)
3052 inode_dec_link_count(inode
);
3053 BUG_ON(dentry
->d_name
.name
!= dentry
->d_iname
||
3054 !hlist_unhashed(&dentry
->d_u
.d_alias
) ||
3055 !d_unlinked(dentry
));
3056 spin_lock(&dentry
->d_parent
->d_lock
);
3057 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
3058 dentry
->d_name
.len
= sprintf(dentry
->d_iname
, "#%llu",
3059 (unsigned long long)inode
->i_ino
);
3060 spin_unlock(&dentry
->d_lock
);
3061 spin_unlock(&dentry
->d_parent
->d_lock
);
3062 d_instantiate(dentry
, inode
);
3064 EXPORT_SYMBOL(d_tmpfile
);
3066 static __initdata
unsigned long dhash_entries
;
3067 static int __init
set_dhash_entries(char *str
)
3071 dhash_entries
= simple_strtoul(str
, &str
, 0);
3074 __setup("dhash_entries=", set_dhash_entries
);
3076 static void __init
dcache_init_early(void)
3078 /* If hashes are distributed across NUMA nodes, defer
3079 * hash allocation until vmalloc space is available.
3085 alloc_large_system_hash("Dentry cache",
3086 sizeof(struct hlist_bl_head
),
3089 HASH_EARLY
| HASH_ZERO
,
3094 d_hash_shift
= 32 - d_hash_shift
;
3097 static void __init
dcache_init(void)
3100 * A constructor could be added for stable state like the lists,
3101 * but it is probably not worth it because of the cache nature
3104 dentry_cache
= KMEM_CACHE_USERCOPY(dentry
,
3105 SLAB_RECLAIM_ACCOUNT
|SLAB_PANIC
|SLAB_MEM_SPREAD
|SLAB_ACCOUNT
,
3108 /* Hash may have been set up in dcache_init_early */
3113 alloc_large_system_hash("Dentry cache",
3114 sizeof(struct hlist_bl_head
),
3122 d_hash_shift
= 32 - d_hash_shift
;
3125 /* SLAB cache for __getname() consumers */
3126 struct kmem_cache
*names_cachep __read_mostly
;
3127 EXPORT_SYMBOL(names_cachep
);
3129 void __init
vfs_caches_init_early(void)
3133 for (i
= 0; i
< ARRAY_SIZE(in_lookup_hashtable
); i
++)
3134 INIT_HLIST_BL_HEAD(&in_lookup_hashtable
[i
]);
3136 dcache_init_early();
3140 void __init
vfs_caches_init(void)
3142 names_cachep
= kmem_cache_create_usercopy("names_cache", PATH_MAX
, 0,
3143 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, 0, PATH_MAX
, NULL
);
3148 files_maxfiles_init();