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_chilren
55 * - childrens' d_sib 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 __ro_after_init
;
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
);
87 const struct qstr dotdot_name
= QSTR_INIT("..", 2);
88 EXPORT_SYMBOL(dotdot_name
);
91 * This is the single most critical data structure when it comes
92 * to the dcache: the hashtable for lookups. Somebody should try
93 * to make this good - I've just made it work.
95 * This hash-function tries to avoid losing too many bits of hash
96 * information, yet avoid using a prime hash-size or similar.
99 static unsigned int d_hash_shift __ro_after_init
;
101 static struct hlist_bl_head
*dentry_hashtable __ro_after_init
;
103 static inline struct hlist_bl_head
*d_hash(unsigned int hash
)
105 return dentry_hashtable
+ (hash
>> d_hash_shift
);
108 #define IN_LOOKUP_SHIFT 10
109 static struct hlist_bl_head in_lookup_hashtable
[1 << IN_LOOKUP_SHIFT
];
111 static inline struct hlist_bl_head
*in_lookup_hash(const struct dentry
*parent
,
114 hash
+= (unsigned long) parent
/ L1_CACHE_BYTES
;
115 return in_lookup_hashtable
+ hash_32(hash
, IN_LOOKUP_SHIFT
);
118 struct dentry_stat_t
{
121 long age_limit
; /* age in seconds */
122 long want_pages
; /* pages requested by system */
123 long nr_negative
; /* # of unused negative dentries */
124 long dummy
; /* Reserved for future use */
127 static DEFINE_PER_CPU(long, nr_dentry
);
128 static DEFINE_PER_CPU(long, nr_dentry_unused
);
129 static DEFINE_PER_CPU(long, nr_dentry_negative
);
131 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
132 /* Statistics gathering. */
133 static struct dentry_stat_t dentry_stat
= {
138 * Here we resort to our own counters instead of using generic per-cpu counters
139 * for consistency with what the vfs inode code does. We are expected to harvest
140 * better code and performance by having our own specialized counters.
142 * Please note that the loop is done over all possible CPUs, not over all online
143 * CPUs. The reason for this is that we don't want to play games with CPUs going
144 * on and off. If one of them goes off, we will just keep their counters.
146 * glommer: See cffbc8a for details, and if you ever intend to change this,
147 * please update all vfs counters to match.
149 static long get_nr_dentry(void)
153 for_each_possible_cpu(i
)
154 sum
+= per_cpu(nr_dentry
, i
);
155 return sum
< 0 ? 0 : sum
;
158 static long get_nr_dentry_unused(void)
162 for_each_possible_cpu(i
)
163 sum
+= per_cpu(nr_dentry_unused
, i
);
164 return sum
< 0 ? 0 : sum
;
167 static long get_nr_dentry_negative(void)
172 for_each_possible_cpu(i
)
173 sum
+= per_cpu(nr_dentry_negative
, i
);
174 return sum
< 0 ? 0 : sum
;
177 static int proc_nr_dentry(struct ctl_table
*table
, int write
, void *buffer
,
178 size_t *lenp
, loff_t
*ppos
)
180 dentry_stat
.nr_dentry
= get_nr_dentry();
181 dentry_stat
.nr_unused
= get_nr_dentry_unused();
182 dentry_stat
.nr_negative
= get_nr_dentry_negative();
183 return proc_doulongvec_minmax(table
, write
, buffer
, lenp
, ppos
);
186 static struct ctl_table fs_dcache_sysctls
[] = {
188 .procname
= "dentry-state",
189 .data
= &dentry_stat
,
190 .maxlen
= 6*sizeof(long),
192 .proc_handler
= proc_nr_dentry
,
196 static int __init
init_fs_dcache_sysctls(void)
198 register_sysctl_init("fs", fs_dcache_sysctls
);
201 fs_initcall(init_fs_dcache_sysctls
);
205 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
206 * The strings are both count bytes long, and count is non-zero.
208 #ifdef CONFIG_DCACHE_WORD_ACCESS
210 #include <asm/word-at-a-time.h>
212 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
213 * aligned allocation for this particular component. We don't
214 * strictly need the load_unaligned_zeropad() safety, but it
215 * doesn't hurt either.
217 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
218 * need the careful unaligned handling.
220 static inline int dentry_string_cmp(const unsigned char *cs
, const unsigned char *ct
, unsigned tcount
)
222 unsigned long a
,b
,mask
;
225 a
= read_word_at_a_time(cs
);
226 b
= load_unaligned_zeropad(ct
);
227 if (tcount
< sizeof(unsigned long))
229 if (unlikely(a
!= b
))
231 cs
+= sizeof(unsigned long);
232 ct
+= sizeof(unsigned long);
233 tcount
-= sizeof(unsigned long);
237 mask
= bytemask_from_count(tcount
);
238 return unlikely(!!((a
^ b
) & mask
));
243 static inline int dentry_string_cmp(const unsigned char *cs
, const unsigned char *ct
, unsigned tcount
)
257 static inline int dentry_cmp(const struct dentry
*dentry
, const unsigned char *ct
, unsigned tcount
)
260 * Be careful about RCU walk racing with rename:
261 * use 'READ_ONCE' to fetch the name pointer.
263 * NOTE! Even if a rename will mean that the length
264 * was not loaded atomically, we don't care. The
265 * RCU walk will check the sequence count eventually,
266 * and catch it. And we won't overrun the buffer,
267 * because we're reading the name pointer atomically,
268 * and a dentry name is guaranteed to be properly
269 * terminated with a NUL byte.
271 * End result: even if 'len' is wrong, we'll exit
272 * early because the data cannot match (there can
273 * be no NUL in the ct/tcount data)
275 const unsigned char *cs
= READ_ONCE(dentry
->d_name
.name
);
277 return dentry_string_cmp(cs
, ct
, tcount
);
280 struct external_name
{
283 struct rcu_head head
;
285 unsigned char name
[];
288 static inline struct external_name
*external_name(struct dentry
*dentry
)
290 return container_of(dentry
->d_name
.name
, struct external_name
, name
[0]);
293 static void __d_free(struct rcu_head
*head
)
295 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
297 kmem_cache_free(dentry_cache
, dentry
);
300 static void __d_free_external(struct rcu_head
*head
)
302 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
303 kfree(external_name(dentry
));
304 kmem_cache_free(dentry_cache
, dentry
);
307 static inline int dname_external(const struct dentry
*dentry
)
309 return dentry
->d_name
.name
!= dentry
->d_iname
;
312 void take_dentry_name_snapshot(struct name_snapshot
*name
, struct dentry
*dentry
)
314 spin_lock(&dentry
->d_lock
);
315 name
->name
= dentry
->d_name
;
316 if (unlikely(dname_external(dentry
))) {
317 atomic_inc(&external_name(dentry
)->u
.count
);
319 memcpy(name
->inline_name
, dentry
->d_iname
,
320 dentry
->d_name
.len
+ 1);
321 name
->name
.name
= name
->inline_name
;
323 spin_unlock(&dentry
->d_lock
);
325 EXPORT_SYMBOL(take_dentry_name_snapshot
);
327 void release_dentry_name_snapshot(struct name_snapshot
*name
)
329 if (unlikely(name
->name
.name
!= name
->inline_name
)) {
330 struct external_name
*p
;
331 p
= container_of(name
->name
.name
, struct external_name
, name
[0]);
332 if (unlikely(atomic_dec_and_test(&p
->u
.count
)))
333 kfree_rcu(p
, u
.head
);
336 EXPORT_SYMBOL(release_dentry_name_snapshot
);
338 static inline void __d_set_inode_and_type(struct dentry
*dentry
,
344 dentry
->d_inode
= inode
;
345 flags
= READ_ONCE(dentry
->d_flags
);
346 flags
&= ~DCACHE_ENTRY_TYPE
;
348 smp_store_release(&dentry
->d_flags
, flags
);
351 static inline void __d_clear_type_and_inode(struct dentry
*dentry
)
353 unsigned flags
= READ_ONCE(dentry
->d_flags
);
355 flags
&= ~DCACHE_ENTRY_TYPE
;
356 WRITE_ONCE(dentry
->d_flags
, flags
);
357 dentry
->d_inode
= NULL
;
358 if (dentry
->d_flags
& DCACHE_LRU_LIST
)
359 this_cpu_inc(nr_dentry_negative
);
362 static void dentry_free(struct dentry
*dentry
)
364 WARN_ON(!hlist_unhashed(&dentry
->d_u
.d_alias
));
365 if (unlikely(dname_external(dentry
))) {
366 struct external_name
*p
= external_name(dentry
);
367 if (likely(atomic_dec_and_test(&p
->u
.count
))) {
368 call_rcu(&dentry
->d_u
.d_rcu
, __d_free_external
);
372 /* if dentry was never visible to RCU, immediate free is OK */
373 if (dentry
->d_flags
& DCACHE_NORCU
)
374 __d_free(&dentry
->d_u
.d_rcu
);
376 call_rcu(&dentry
->d_u
.d_rcu
, __d_free
);
380 * Release the dentry's inode, using the filesystem
381 * d_iput() operation if defined.
383 static void dentry_unlink_inode(struct dentry
* dentry
)
384 __releases(dentry
->d_lock
)
385 __releases(dentry
->d_inode
->i_lock
)
387 struct inode
*inode
= dentry
->d_inode
;
389 raw_write_seqcount_begin(&dentry
->d_seq
);
390 __d_clear_type_and_inode(dentry
);
391 hlist_del_init(&dentry
->d_u
.d_alias
);
392 raw_write_seqcount_end(&dentry
->d_seq
);
393 spin_unlock(&dentry
->d_lock
);
394 spin_unlock(&inode
->i_lock
);
396 fsnotify_inoderemove(inode
);
397 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
398 dentry
->d_op
->d_iput(dentry
, inode
);
404 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
405 * is in use - which includes both the "real" per-superblock
406 * LRU list _and_ the DCACHE_SHRINK_LIST use.
408 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
409 * on the shrink list (ie not on the superblock LRU list).
411 * The per-cpu "nr_dentry_unused" counters are updated with
412 * the DCACHE_LRU_LIST bit.
414 * The per-cpu "nr_dentry_negative" counters are only updated
415 * when deleted from or added to the per-superblock LRU list, not
416 * from/to the shrink list. That is to avoid an unneeded dec/inc
417 * pair when moving from LRU to shrink list in select_collect().
419 * These helper functions make sure we always follow the
420 * rules. d_lock must be held by the caller.
422 #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
423 static void d_lru_add(struct dentry
*dentry
)
425 D_FLAG_VERIFY(dentry
, 0);
426 dentry
->d_flags
|= DCACHE_LRU_LIST
;
427 this_cpu_inc(nr_dentry_unused
);
428 if (d_is_negative(dentry
))
429 this_cpu_inc(nr_dentry_negative
);
430 WARN_ON_ONCE(!list_lru_add_obj(
431 &dentry
->d_sb
->s_dentry_lru
, &dentry
->d_lru
));
434 static void d_lru_del(struct dentry
*dentry
)
436 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
437 dentry
->d_flags
&= ~DCACHE_LRU_LIST
;
438 this_cpu_dec(nr_dentry_unused
);
439 if (d_is_negative(dentry
))
440 this_cpu_dec(nr_dentry_negative
);
441 WARN_ON_ONCE(!list_lru_del_obj(
442 &dentry
->d_sb
->s_dentry_lru
, &dentry
->d_lru
));
445 static void d_shrink_del(struct dentry
*dentry
)
447 D_FLAG_VERIFY(dentry
, DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
);
448 list_del_init(&dentry
->d_lru
);
449 dentry
->d_flags
&= ~(DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
);
450 this_cpu_dec(nr_dentry_unused
);
453 static void d_shrink_add(struct dentry
*dentry
, struct list_head
*list
)
455 D_FLAG_VERIFY(dentry
, 0);
456 list_add(&dentry
->d_lru
, list
);
457 dentry
->d_flags
|= DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
;
458 this_cpu_inc(nr_dentry_unused
);
462 * These can only be called under the global LRU lock, ie during the
463 * callback for freeing the LRU list. "isolate" removes it from the
464 * LRU lists entirely, while shrink_move moves it to the indicated
467 static void d_lru_isolate(struct list_lru_one
*lru
, struct dentry
*dentry
)
469 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
470 dentry
->d_flags
&= ~DCACHE_LRU_LIST
;
471 this_cpu_dec(nr_dentry_unused
);
472 if (d_is_negative(dentry
))
473 this_cpu_dec(nr_dentry_negative
);
474 list_lru_isolate(lru
, &dentry
->d_lru
);
477 static void d_lru_shrink_move(struct list_lru_one
*lru
, struct dentry
*dentry
,
478 struct list_head
*list
)
480 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
481 dentry
->d_flags
|= DCACHE_SHRINK_LIST
;
482 if (d_is_negative(dentry
))
483 this_cpu_dec(nr_dentry_negative
);
484 list_lru_isolate_move(lru
, &dentry
->d_lru
, list
);
487 static void ___d_drop(struct dentry
*dentry
)
489 struct hlist_bl_head
*b
;
491 * Hashed dentries are normally on the dentry hashtable,
492 * with the exception of those newly allocated by
493 * d_obtain_root, which are always IS_ROOT:
495 if (unlikely(IS_ROOT(dentry
)))
496 b
= &dentry
->d_sb
->s_roots
;
498 b
= d_hash(dentry
->d_name
.hash
);
501 __hlist_bl_del(&dentry
->d_hash
);
505 void __d_drop(struct dentry
*dentry
)
507 if (!d_unhashed(dentry
)) {
509 dentry
->d_hash
.pprev
= NULL
;
510 write_seqcount_invalidate(&dentry
->d_seq
);
513 EXPORT_SYMBOL(__d_drop
);
516 * d_drop - drop a dentry
517 * @dentry: dentry to drop
519 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
520 * be found through a VFS lookup any more. Note that this is different from
521 * deleting the dentry - d_delete will try to mark the dentry negative if
522 * possible, giving a successful _negative_ lookup, while d_drop will
523 * just make the cache lookup fail.
525 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
526 * reason (NFS timeouts or autofs deletes).
528 * __d_drop requires dentry->d_lock
530 * ___d_drop doesn't mark dentry as "unhashed"
531 * (dentry->d_hash.pprev will be LIST_POISON2, not NULL).
533 void d_drop(struct dentry
*dentry
)
535 spin_lock(&dentry
->d_lock
);
537 spin_unlock(&dentry
->d_lock
);
539 EXPORT_SYMBOL(d_drop
);
541 static inline void dentry_unlist(struct dentry
*dentry
)
545 * Inform d_walk() and shrink_dentry_list() that we are no longer
546 * attached to the dentry tree
548 dentry
->d_flags
|= DCACHE_DENTRY_KILLED
;
549 if (unlikely(hlist_unhashed(&dentry
->d_sib
)))
551 __hlist_del(&dentry
->d_sib
);
553 * Cursors can move around the list of children. While we'd been
554 * a normal list member, it didn't matter - ->d_sib.next would've
555 * been updated. However, from now on it won't be and for the
556 * things like d_walk() it might end up with a nasty surprise.
557 * Normally d_walk() doesn't care about cursors moving around -
558 * ->d_lock on parent prevents that and since a cursor has no children
559 * of its own, we get through it without ever unlocking the parent.
560 * There is one exception, though - if we ascend from a child that
561 * gets killed as soon as we unlock it, the next sibling is found
562 * using the value left in its ->d_sib.next. And if _that_
563 * pointed to a cursor, and cursor got moved (e.g. by lseek())
564 * before d_walk() regains parent->d_lock, we'll end up skipping
565 * everything the cursor had been moved past.
567 * Solution: make sure that the pointer left behind in ->d_sib.next
568 * points to something that won't be moving around. I.e. skip the
571 while (dentry
->d_sib
.next
) {
572 next
= hlist_entry(dentry
->d_sib
.next
, struct dentry
, d_sib
);
573 if (likely(!(next
->d_flags
& DCACHE_DENTRY_CURSOR
)))
575 dentry
->d_sib
.next
= next
->d_sib
.next
;
579 static struct dentry
*__dentry_kill(struct dentry
*dentry
)
581 struct dentry
*parent
= NULL
;
582 bool can_free
= true;
585 * The dentry is now unrecoverably dead to the world.
587 lockref_mark_dead(&dentry
->d_lockref
);
590 * inform the fs via d_prune that this dentry is about to be
591 * unhashed and destroyed.
593 if (dentry
->d_flags
& DCACHE_OP_PRUNE
)
594 dentry
->d_op
->d_prune(dentry
);
596 if (dentry
->d_flags
& DCACHE_LRU_LIST
) {
597 if (!(dentry
->d_flags
& DCACHE_SHRINK_LIST
))
600 /* if it was on the hash then remove it */
603 dentry_unlink_inode(dentry
);
605 spin_unlock(&dentry
->d_lock
);
606 this_cpu_dec(nr_dentry
);
607 if (dentry
->d_op
&& dentry
->d_op
->d_release
)
608 dentry
->d_op
->d_release(dentry
);
611 /* now that it's negative, ->d_parent is stable */
612 if (!IS_ROOT(dentry
)) {
613 parent
= dentry
->d_parent
;
614 spin_lock(&parent
->d_lock
);
616 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
617 dentry_unlist(dentry
);
618 if (dentry
->d_flags
& DCACHE_SHRINK_LIST
)
620 spin_unlock(&dentry
->d_lock
);
621 if (likely(can_free
))
623 if (parent
&& --parent
->d_lockref
.count
) {
624 spin_unlock(&parent
->d_lock
);
631 * Lock a dentry for feeding it to __dentry_kill().
632 * Called under rcu_read_lock() and dentry->d_lock; the former
633 * guarantees that nothing we access will be freed under us.
634 * Note that dentry is *not* protected from concurrent dentry_kill(),
637 * Return false if dentry is busy. Otherwise, return true and have
638 * that dentry's inode locked.
641 static bool lock_for_kill(struct dentry
*dentry
)
643 struct inode
*inode
= dentry
->d_inode
;
645 if (unlikely(dentry
->d_lockref
.count
))
648 if (!inode
|| likely(spin_trylock(&inode
->i_lock
)))
652 spin_unlock(&dentry
->d_lock
);
653 spin_lock(&inode
->i_lock
);
654 spin_lock(&dentry
->d_lock
);
655 if (likely(inode
== dentry
->d_inode
))
657 spin_unlock(&inode
->i_lock
);
658 inode
= dentry
->d_inode
;
660 if (likely(!dentry
->d_lockref
.count
))
663 spin_unlock(&inode
->i_lock
);
668 * Decide if dentry is worth retaining. Usually this is called with dentry
669 * locked; if not locked, we are more limited and might not be able to tell
670 * without a lock. False in this case means "punt to locked path and recheck".
672 * In case we aren't locked, these predicates are not "stable". However, it is
673 * sufficient that at some point after we dropped the reference the dentry was
674 * hashed and the flags had the proper value. Other dentry users may have
675 * re-gotten a reference to the dentry and change that, but our work is done -
676 * we can leave the dentry around with a zero refcount.
678 static inline bool retain_dentry(struct dentry
*dentry
, bool locked
)
680 unsigned int d_flags
;
683 d_flags
= READ_ONCE(dentry
->d_flags
);
685 // Unreachable? Nobody would be able to look it up, no point retaining
686 if (unlikely(d_unhashed(dentry
)))
689 // Same if it's disconnected
690 if (unlikely(d_flags
& DCACHE_DISCONNECTED
))
693 // ->d_delete() might tell us not to bother, but that requires
694 // ->d_lock; can't decide without it
695 if (unlikely(d_flags
& DCACHE_OP_DELETE
)) {
696 if (!locked
|| dentry
->d_op
->d_delete(dentry
))
700 // Explicitly told not to bother
701 if (unlikely(d_flags
& DCACHE_DONTCACHE
))
704 // At this point it looks like we ought to keep it. We also might
705 // need to do something - put it on LRU if it wasn't there already
706 // and mark it referenced if it was on LRU, but not marked yet.
707 // Unfortunately, both actions require ->d_lock, so in lockless
708 // case we'd have to punt rather than doing those.
709 if (unlikely(!(d_flags
& DCACHE_LRU_LIST
))) {
713 } else if (unlikely(!(d_flags
& DCACHE_REFERENCED
))) {
716 dentry
->d_flags
|= DCACHE_REFERENCED
;
721 void d_mark_dontcache(struct inode
*inode
)
725 spin_lock(&inode
->i_lock
);
726 hlist_for_each_entry(de
, &inode
->i_dentry
, d_u
.d_alias
) {
727 spin_lock(&de
->d_lock
);
728 de
->d_flags
|= DCACHE_DONTCACHE
;
729 spin_unlock(&de
->d_lock
);
731 inode
->i_state
|= I_DONTCACHE
;
732 spin_unlock(&inode
->i_lock
);
734 EXPORT_SYMBOL(d_mark_dontcache
);
737 * Try to do a lockless dput(), and return whether that was successful.
739 * If unsuccessful, we return false, having already taken the dentry lock.
740 * In that case refcount is guaranteed to be zero and we have already
741 * decided that it's not worth keeping around.
743 * The caller needs to hold the RCU read lock, so that the dentry is
744 * guaranteed to stay around even if the refcount goes down to zero!
746 static inline bool fast_dput(struct dentry
*dentry
)
751 * try to decrement the lockref optimistically.
753 ret
= lockref_put_return(&dentry
->d_lockref
);
756 * If the lockref_put_return() failed due to the lock being held
757 * by somebody else, the fast path has failed. We will need to
758 * get the lock, and then check the count again.
760 if (unlikely(ret
< 0)) {
761 spin_lock(&dentry
->d_lock
);
762 if (WARN_ON_ONCE(dentry
->d_lockref
.count
<= 0)) {
763 spin_unlock(&dentry
->d_lock
);
766 dentry
->d_lockref
.count
--;
771 * If we weren't the last ref, we're done.
777 * Can we decide that decrement of refcount is all we needed without
778 * taking the lock? There's a very common case when it's all we need -
779 * dentry looks like it ought to be retained and there's nothing else
782 if (retain_dentry(dentry
, false))
786 * Either not worth retaining or we can't tell without the lock.
787 * Get the lock, then. We've already decremented the refcount to 0,
788 * but we'll need to re-check the situation after getting the lock.
790 spin_lock(&dentry
->d_lock
);
793 * Did somebody else grab a reference to it in the meantime, and
794 * we're no longer the last user after all? Alternatively, somebody
795 * else could have killed it and marked it dead. Either way, we
796 * don't need to do anything else.
799 if (dentry
->d_lockref
.count
|| retain_dentry(dentry
, true)) {
800 spin_unlock(&dentry
->d_lock
);
810 * This is complicated by the fact that we do not want to put
811 * dentries that are no longer on any hash chain on the unused
812 * list: we'd much rather just get rid of them immediately.
814 * However, that implies that we have to traverse the dentry
815 * tree upwards to the parents which might _also_ now be
816 * scheduled for deletion (it may have been only waiting for
817 * its last child to go away).
819 * This tail recursion is done by hand as we don't want to depend
820 * on the compiler to always get this right (gcc generally doesn't).
821 * Real recursion would eat up our stack space.
825 * dput - release a dentry
826 * @dentry: dentry to release
828 * Release a dentry. This will drop the usage count and if appropriate
829 * call the dentry unlink method as well as removing it from the queues and
830 * releasing its resources. If the parent dentries were scheduled for release
831 * they too may now get deleted.
833 void dput(struct dentry
*dentry
)
839 if (likely(fast_dput(dentry
))) {
843 while (lock_for_kill(dentry
)) {
845 dentry
= __dentry_kill(dentry
);
848 if (retain_dentry(dentry
, true)) {
849 spin_unlock(&dentry
->d_lock
);
855 spin_unlock(&dentry
->d_lock
);
859 static void to_shrink_list(struct dentry
*dentry
, struct list_head
*list
)
860 __must_hold(&dentry
->d_lock
)
862 if (!(dentry
->d_flags
& DCACHE_SHRINK_LIST
)) {
863 if (dentry
->d_flags
& DCACHE_LRU_LIST
)
865 d_shrink_add(dentry
, list
);
869 void dput_to_list(struct dentry
*dentry
, struct list_head
*list
)
872 if (likely(fast_dput(dentry
))) {
877 to_shrink_list(dentry
, list
);
878 spin_unlock(&dentry
->d_lock
);
881 struct dentry
*dget_parent(struct dentry
*dentry
)
888 * Do optimistic parent lookup without any
892 seq
= raw_seqcount_begin(&dentry
->d_seq
);
893 ret
= READ_ONCE(dentry
->d_parent
);
894 gotref
= lockref_get_not_zero(&ret
->d_lockref
);
896 if (likely(gotref
)) {
897 if (!read_seqcount_retry(&dentry
->d_seq
, seq
))
904 * Don't need rcu_dereference because we re-check it was correct under
908 ret
= dentry
->d_parent
;
909 spin_lock(&ret
->d_lock
);
910 if (unlikely(ret
!= dentry
->d_parent
)) {
911 spin_unlock(&ret
->d_lock
);
916 BUG_ON(!ret
->d_lockref
.count
);
917 ret
->d_lockref
.count
++;
918 spin_unlock(&ret
->d_lock
);
921 EXPORT_SYMBOL(dget_parent
);
923 static struct dentry
* __d_find_any_alias(struct inode
*inode
)
925 struct dentry
*alias
;
927 if (hlist_empty(&inode
->i_dentry
))
929 alias
= hlist_entry(inode
->i_dentry
.first
, struct dentry
, d_u
.d_alias
);
930 lockref_get(&alias
->d_lockref
);
935 * d_find_any_alias - find any alias for a given inode
936 * @inode: inode to find an alias for
938 * If any aliases exist for the given inode, take and return a
939 * reference for one of them. If no aliases exist, return %NULL.
941 struct dentry
*d_find_any_alias(struct inode
*inode
)
945 spin_lock(&inode
->i_lock
);
946 de
= __d_find_any_alias(inode
);
947 spin_unlock(&inode
->i_lock
);
950 EXPORT_SYMBOL(d_find_any_alias
);
952 static struct dentry
*__d_find_alias(struct inode
*inode
)
954 struct dentry
*alias
;
956 if (S_ISDIR(inode
->i_mode
))
957 return __d_find_any_alias(inode
);
959 hlist_for_each_entry(alias
, &inode
->i_dentry
, d_u
.d_alias
) {
960 spin_lock(&alias
->d_lock
);
961 if (!d_unhashed(alias
)) {
963 spin_unlock(&alias
->d_lock
);
966 spin_unlock(&alias
->d_lock
);
972 * d_find_alias - grab a hashed alias of inode
973 * @inode: inode in question
975 * If inode has a hashed alias, or is a directory and has any alias,
976 * acquire the reference to alias and return it. Otherwise return NULL.
977 * Notice that if inode is a directory there can be only one alias and
978 * it can be unhashed only if it has no children, or if it is the root
979 * of a filesystem, or if the directory was renamed and d_revalidate
980 * was the first vfs operation to notice.
982 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
983 * any other hashed alias over that one.
985 struct dentry
*d_find_alias(struct inode
*inode
)
987 struct dentry
*de
= NULL
;
989 if (!hlist_empty(&inode
->i_dentry
)) {
990 spin_lock(&inode
->i_lock
);
991 de
= __d_find_alias(inode
);
992 spin_unlock(&inode
->i_lock
);
996 EXPORT_SYMBOL(d_find_alias
);
999 * Caller MUST be holding rcu_read_lock() and be guaranteed
1000 * that inode won't get freed until rcu_read_unlock().
1002 struct dentry
*d_find_alias_rcu(struct inode
*inode
)
1004 struct hlist_head
*l
= &inode
->i_dentry
;
1005 struct dentry
*de
= NULL
;
1007 spin_lock(&inode
->i_lock
);
1008 // ->i_dentry and ->i_rcu are colocated, but the latter won't be
1009 // used without having I_FREEING set, which means no aliases left
1010 if (likely(!(inode
->i_state
& I_FREEING
) && !hlist_empty(l
))) {
1011 if (S_ISDIR(inode
->i_mode
)) {
1012 de
= hlist_entry(l
->first
, struct dentry
, d_u
.d_alias
);
1014 hlist_for_each_entry(de
, l
, d_u
.d_alias
)
1015 if (!d_unhashed(de
))
1019 spin_unlock(&inode
->i_lock
);
1024 * Try to kill dentries associated with this inode.
1025 * WARNING: you must own a reference to inode.
1027 void d_prune_aliases(struct inode
*inode
)
1030 struct dentry
*dentry
;
1032 spin_lock(&inode
->i_lock
);
1033 hlist_for_each_entry(dentry
, &inode
->i_dentry
, d_u
.d_alias
) {
1034 spin_lock(&dentry
->d_lock
);
1035 if (!dentry
->d_lockref
.count
)
1036 to_shrink_list(dentry
, &dispose
);
1037 spin_unlock(&dentry
->d_lock
);
1039 spin_unlock(&inode
->i_lock
);
1040 shrink_dentry_list(&dispose
);
1042 EXPORT_SYMBOL(d_prune_aliases
);
1044 static inline void shrink_kill(struct dentry
*victim
)
1048 victim
= __dentry_kill(victim
);
1050 } while (victim
&& lock_for_kill(victim
));
1053 spin_unlock(&victim
->d_lock
);
1056 void shrink_dentry_list(struct list_head
*list
)
1058 while (!list_empty(list
)) {
1059 struct dentry
*dentry
;
1061 dentry
= list_entry(list
->prev
, struct dentry
, d_lru
);
1062 spin_lock(&dentry
->d_lock
);
1064 if (!lock_for_kill(dentry
)) {
1067 d_shrink_del(dentry
);
1068 can_free
= dentry
->d_flags
& DCACHE_DENTRY_KILLED
;
1069 spin_unlock(&dentry
->d_lock
);
1071 dentry_free(dentry
);
1074 d_shrink_del(dentry
);
1075 shrink_kill(dentry
);
1079 static enum lru_status
dentry_lru_isolate(struct list_head
*item
,
1080 struct list_lru_one
*lru
, spinlock_t
*lru_lock
, void *arg
)
1082 struct list_head
*freeable
= arg
;
1083 struct dentry
*dentry
= container_of(item
, struct dentry
, d_lru
);
1087 * we are inverting the lru lock/dentry->d_lock here,
1088 * so use a trylock. If we fail to get the lock, just skip
1091 if (!spin_trylock(&dentry
->d_lock
))
1095 * Referenced dentries are still in use. If they have active
1096 * counts, just remove them from the LRU. Otherwise give them
1097 * another pass through the LRU.
1099 if (dentry
->d_lockref
.count
) {
1100 d_lru_isolate(lru
, dentry
);
1101 spin_unlock(&dentry
->d_lock
);
1105 if (dentry
->d_flags
& DCACHE_REFERENCED
) {
1106 dentry
->d_flags
&= ~DCACHE_REFERENCED
;
1107 spin_unlock(&dentry
->d_lock
);
1110 * The list move itself will be made by the common LRU code. At
1111 * this point, we've dropped the dentry->d_lock but keep the
1112 * lru lock. This is safe to do, since every list movement is
1113 * protected by the lru lock even if both locks are held.
1115 * This is guaranteed by the fact that all LRU management
1116 * functions are intermediated by the LRU API calls like
1117 * list_lru_add_obj and list_lru_del_obj. List movement in this file
1118 * only ever occur through this functions or through callbacks
1119 * like this one, that are called from the LRU API.
1121 * The only exceptions to this are functions like
1122 * shrink_dentry_list, and code that first checks for the
1123 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1124 * operating only with stack provided lists after they are
1125 * properly isolated from the main list. It is thus, always a
1131 d_lru_shrink_move(lru
, dentry
, freeable
);
1132 spin_unlock(&dentry
->d_lock
);
1138 * prune_dcache_sb - shrink the dcache
1140 * @sc: shrink control, passed to list_lru_shrink_walk()
1142 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1143 * is done when we need more memory and called from the superblock shrinker
1146 * This function may fail to free any resources if all the dentries are in
1149 long prune_dcache_sb(struct super_block
*sb
, struct shrink_control
*sc
)
1154 freed
= list_lru_shrink_walk(&sb
->s_dentry_lru
, sc
,
1155 dentry_lru_isolate
, &dispose
);
1156 shrink_dentry_list(&dispose
);
1160 static enum lru_status
dentry_lru_isolate_shrink(struct list_head
*item
,
1161 struct list_lru_one
*lru
, spinlock_t
*lru_lock
, void *arg
)
1163 struct list_head
*freeable
= arg
;
1164 struct dentry
*dentry
= container_of(item
, struct dentry
, d_lru
);
1167 * we are inverting the lru lock/dentry->d_lock here,
1168 * so use a trylock. If we fail to get the lock, just skip
1171 if (!spin_trylock(&dentry
->d_lock
))
1174 d_lru_shrink_move(lru
, dentry
, freeable
);
1175 spin_unlock(&dentry
->d_lock
);
1182 * shrink_dcache_sb - shrink dcache for a superblock
1185 * Shrink the dcache for the specified super block. This is used to free
1186 * the dcache before unmounting a file system.
1188 void shrink_dcache_sb(struct super_block
*sb
)
1193 list_lru_walk(&sb
->s_dentry_lru
,
1194 dentry_lru_isolate_shrink
, &dispose
, 1024);
1195 shrink_dentry_list(&dispose
);
1196 } while (list_lru_count(&sb
->s_dentry_lru
) > 0);
1198 EXPORT_SYMBOL(shrink_dcache_sb
);
1201 * enum d_walk_ret - action to talke during tree walk
1202 * @D_WALK_CONTINUE: contrinue walk
1203 * @D_WALK_QUIT: quit walk
1204 * @D_WALK_NORETRY: quit when retry is needed
1205 * @D_WALK_SKIP: skip this dentry and its children
1215 * d_walk - walk the dentry tree
1216 * @parent: start of walk
1217 * @data: data passed to @enter() and @finish()
1218 * @enter: callback when first entering the dentry
1220 * The @enter() callbacks are called with d_lock held.
1222 static void d_walk(struct dentry
*parent
, void *data
,
1223 enum d_walk_ret (*enter
)(void *, struct dentry
*))
1225 struct dentry
*this_parent
, *dentry
;
1227 enum d_walk_ret ret
;
1231 read_seqbegin_or_lock(&rename_lock
, &seq
);
1232 this_parent
= parent
;
1233 spin_lock(&this_parent
->d_lock
);
1235 ret
= enter(data
, this_parent
);
1237 case D_WALK_CONTINUE
:
1242 case D_WALK_NORETRY
:
1247 dentry
= d_first_child(this_parent
);
1249 hlist_for_each_entry_from(dentry
, d_sib
) {
1250 if (unlikely(dentry
->d_flags
& DCACHE_DENTRY_CURSOR
))
1253 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1255 ret
= enter(data
, dentry
);
1257 case D_WALK_CONTINUE
:
1260 spin_unlock(&dentry
->d_lock
);
1262 case D_WALK_NORETRY
:
1266 spin_unlock(&dentry
->d_lock
);
1270 if (!hlist_empty(&dentry
->d_children
)) {
1271 spin_unlock(&this_parent
->d_lock
);
1272 spin_release(&dentry
->d_lock
.dep_map
, _RET_IP_
);
1273 this_parent
= dentry
;
1274 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
1277 spin_unlock(&dentry
->d_lock
);
1280 * All done at this level ... ascend and resume the search.
1284 if (this_parent
!= parent
) {
1285 dentry
= this_parent
;
1286 this_parent
= dentry
->d_parent
;
1288 spin_unlock(&dentry
->d_lock
);
1289 spin_lock(&this_parent
->d_lock
);
1291 /* might go back up the wrong parent if we have had a rename. */
1292 if (need_seqretry(&rename_lock
, seq
))
1294 /* go into the first sibling still alive */
1295 hlist_for_each_entry_continue(dentry
, d_sib
) {
1296 if (likely(!(dentry
->d_flags
& DCACHE_DENTRY_KILLED
))) {
1303 if (need_seqretry(&rename_lock
, seq
))
1308 spin_unlock(&this_parent
->d_lock
);
1309 done_seqretry(&rename_lock
, seq
);
1313 spin_unlock(&this_parent
->d_lock
);
1322 struct check_mount
{
1323 struct vfsmount
*mnt
;
1324 unsigned int mounted
;
1327 static enum d_walk_ret
path_check_mount(void *data
, struct dentry
*dentry
)
1329 struct check_mount
*info
= data
;
1330 struct path path
= { .mnt
= info
->mnt
, .dentry
= dentry
};
1332 if (likely(!d_mountpoint(dentry
)))
1333 return D_WALK_CONTINUE
;
1334 if (__path_is_mountpoint(&path
)) {
1338 return D_WALK_CONTINUE
;
1342 * path_has_submounts - check for mounts over a dentry in the
1343 * current namespace.
1344 * @parent: path to check.
1346 * Return true if the parent or its subdirectories contain
1347 * a mount point in the current namespace.
1349 int path_has_submounts(const struct path
*parent
)
1351 struct check_mount data
= { .mnt
= parent
->mnt
, .mounted
= 0 };
1353 read_seqlock_excl(&mount_lock
);
1354 d_walk(parent
->dentry
, &data
, path_check_mount
);
1355 read_sequnlock_excl(&mount_lock
);
1357 return data
.mounted
;
1359 EXPORT_SYMBOL(path_has_submounts
);
1362 * Called by mount code to set a mountpoint and check if the mountpoint is
1363 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1364 * subtree can become unreachable).
1366 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1367 * this reason take rename_lock and d_lock on dentry and ancestors.
1369 int d_set_mounted(struct dentry
*dentry
)
1373 write_seqlock(&rename_lock
);
1374 for (p
= dentry
->d_parent
; !IS_ROOT(p
); p
= p
->d_parent
) {
1375 /* Need exclusion wrt. d_invalidate() */
1376 spin_lock(&p
->d_lock
);
1377 if (unlikely(d_unhashed(p
))) {
1378 spin_unlock(&p
->d_lock
);
1381 spin_unlock(&p
->d_lock
);
1383 spin_lock(&dentry
->d_lock
);
1384 if (!d_unlinked(dentry
)) {
1386 if (!d_mountpoint(dentry
)) {
1387 dentry
->d_flags
|= DCACHE_MOUNTED
;
1391 spin_unlock(&dentry
->d_lock
);
1393 write_sequnlock(&rename_lock
);
1398 * Search the dentry child list of the specified parent,
1399 * and move any unused dentries to the end of the unused
1400 * list for prune_dcache(). We descend to the next level
1401 * whenever the d_children list is non-empty and continue
1404 * It returns zero iff there are no unused children,
1405 * otherwise it returns the number of children moved to
1406 * the end of the unused list. This may not be the total
1407 * number of unused children, because select_parent can
1408 * drop the lock and return early due to latency
1412 struct select_data
{
1413 struct dentry
*start
;
1416 struct dentry
*victim
;
1418 struct list_head dispose
;
1421 static enum d_walk_ret
select_collect(void *_data
, struct dentry
*dentry
)
1423 struct select_data
*data
= _data
;
1424 enum d_walk_ret ret
= D_WALK_CONTINUE
;
1426 if (data
->start
== dentry
)
1429 if (dentry
->d_flags
& DCACHE_SHRINK_LIST
) {
1431 } else if (!dentry
->d_lockref
.count
) {
1432 to_shrink_list(dentry
, &data
->dispose
);
1434 } else if (dentry
->d_lockref
.count
< 0) {
1438 * We can return to the caller if we have found some (this
1439 * ensures forward progress). We'll be coming back to find
1442 if (!list_empty(&data
->dispose
))
1443 ret
= need_resched() ? D_WALK_QUIT
: D_WALK_NORETRY
;
1448 static enum d_walk_ret
select_collect2(void *_data
, struct dentry
*dentry
)
1450 struct select_data
*data
= _data
;
1451 enum d_walk_ret ret
= D_WALK_CONTINUE
;
1453 if (data
->start
== dentry
)
1456 if (!dentry
->d_lockref
.count
) {
1457 if (dentry
->d_flags
& DCACHE_SHRINK_LIST
) {
1459 data
->victim
= dentry
;
1462 to_shrink_list(dentry
, &data
->dispose
);
1465 * We can return to the caller if we have found some (this
1466 * ensures forward progress). We'll be coming back to find
1469 if (!list_empty(&data
->dispose
))
1470 ret
= need_resched() ? D_WALK_QUIT
: D_WALK_NORETRY
;
1476 * shrink_dcache_parent - prune dcache
1477 * @parent: parent of entries to prune
1479 * Prune the dcache to remove unused children of the parent dentry.
1481 void shrink_dcache_parent(struct dentry
*parent
)
1484 struct select_data data
= {.start
= parent
};
1486 INIT_LIST_HEAD(&data
.dispose
);
1487 d_walk(parent
, &data
, select_collect
);
1489 if (!list_empty(&data
.dispose
)) {
1490 shrink_dentry_list(&data
.dispose
);
1498 d_walk(parent
, &data
, select_collect2
);
1500 spin_lock(&data
.victim
->d_lock
);
1501 if (!lock_for_kill(data
.victim
)) {
1502 spin_unlock(&data
.victim
->d_lock
);
1505 shrink_kill(data
.victim
);
1508 if (!list_empty(&data
.dispose
))
1509 shrink_dentry_list(&data
.dispose
);
1512 EXPORT_SYMBOL(shrink_dcache_parent
);
1514 static enum d_walk_ret
umount_check(void *_data
, struct dentry
*dentry
)
1516 /* it has busy descendents; complain about those instead */
1517 if (!hlist_empty(&dentry
->d_children
))
1518 return D_WALK_CONTINUE
;
1520 /* root with refcount 1 is fine */
1521 if (dentry
== _data
&& dentry
->d_lockref
.count
== 1)
1522 return D_WALK_CONTINUE
;
1524 WARN(1, "BUG: Dentry %p{i=%lx,n=%pd} "
1525 " still in use (%d) [unmount of %s %s]\n",
1528 dentry
->d_inode
->i_ino
: 0UL,
1530 dentry
->d_lockref
.count
,
1531 dentry
->d_sb
->s_type
->name
,
1532 dentry
->d_sb
->s_id
);
1533 return D_WALK_CONTINUE
;
1536 static void do_one_tree(struct dentry
*dentry
)
1538 shrink_dcache_parent(dentry
);
1539 d_walk(dentry
, dentry
, umount_check
);
1545 * destroy the dentries attached to a superblock on unmounting
1547 void shrink_dcache_for_umount(struct super_block
*sb
)
1549 struct dentry
*dentry
;
1551 WARN(down_read_trylock(&sb
->s_umount
), "s_umount should've been locked");
1553 dentry
= sb
->s_root
;
1555 do_one_tree(dentry
);
1557 while (!hlist_bl_empty(&sb
->s_roots
)) {
1558 dentry
= dget(hlist_bl_entry(hlist_bl_first(&sb
->s_roots
), struct dentry
, d_hash
));
1559 do_one_tree(dentry
);
1563 static enum d_walk_ret
find_submount(void *_data
, struct dentry
*dentry
)
1565 struct dentry
**victim
= _data
;
1566 if (d_mountpoint(dentry
)) {
1567 *victim
= dget_dlock(dentry
);
1570 return D_WALK_CONTINUE
;
1574 * d_invalidate - detach submounts, prune dcache, and drop
1575 * @dentry: dentry to invalidate (aka detach, prune and drop)
1577 void d_invalidate(struct dentry
*dentry
)
1579 bool had_submounts
= false;
1580 spin_lock(&dentry
->d_lock
);
1581 if (d_unhashed(dentry
)) {
1582 spin_unlock(&dentry
->d_lock
);
1586 spin_unlock(&dentry
->d_lock
);
1588 /* Negative dentries can be dropped without further checks */
1589 if (!dentry
->d_inode
)
1592 shrink_dcache_parent(dentry
);
1594 struct dentry
*victim
= NULL
;
1595 d_walk(dentry
, &victim
, find_submount
);
1598 shrink_dcache_parent(dentry
);
1601 had_submounts
= true;
1602 detach_mounts(victim
);
1606 EXPORT_SYMBOL(d_invalidate
);
1609 * __d_alloc - allocate a dcache entry
1610 * @sb: filesystem it will belong to
1611 * @name: qstr of the name
1613 * Allocates a dentry. It returns %NULL if there is insufficient memory
1614 * available. On a success the dentry is returned. The name passed in is
1615 * copied and the copy passed in may be reused after this call.
1618 static struct dentry
*__d_alloc(struct super_block
*sb
, const struct qstr
*name
)
1620 struct dentry
*dentry
;
1624 dentry
= kmem_cache_alloc_lru(dentry_cache
, &sb
->s_dentry_lru
,
1630 * We guarantee that the inline name is always NUL-terminated.
1631 * This way the memcpy() done by the name switching in rename
1632 * will still always have a NUL at the end, even if we might
1633 * be overwriting an internal NUL character
1635 dentry
->d_iname
[DNAME_INLINE_LEN
-1] = 0;
1636 if (unlikely(!name
)) {
1638 dname
= dentry
->d_iname
;
1639 } else if (name
->len
> DNAME_INLINE_LEN
-1) {
1640 size_t size
= offsetof(struct external_name
, name
[1]);
1641 struct external_name
*p
= kmalloc(size
+ name
->len
,
1642 GFP_KERNEL_ACCOUNT
|
1645 kmem_cache_free(dentry_cache
, dentry
);
1648 atomic_set(&p
->u
.count
, 1);
1651 dname
= dentry
->d_iname
;
1654 dentry
->d_name
.len
= name
->len
;
1655 dentry
->d_name
.hash
= name
->hash
;
1656 memcpy(dname
, name
->name
, name
->len
);
1657 dname
[name
->len
] = 0;
1659 /* Make sure we always see the terminating NUL character */
1660 smp_store_release(&dentry
->d_name
.name
, dname
); /* ^^^ */
1662 dentry
->d_lockref
.count
= 1;
1663 dentry
->d_flags
= 0;
1664 spin_lock_init(&dentry
->d_lock
);
1665 seqcount_spinlock_init(&dentry
->d_seq
, &dentry
->d_lock
);
1666 dentry
->d_inode
= NULL
;
1667 dentry
->d_parent
= dentry
;
1669 dentry
->d_op
= NULL
;
1670 dentry
->d_fsdata
= NULL
;
1671 INIT_HLIST_BL_NODE(&dentry
->d_hash
);
1672 INIT_LIST_HEAD(&dentry
->d_lru
);
1673 INIT_HLIST_HEAD(&dentry
->d_children
);
1674 INIT_HLIST_NODE(&dentry
->d_u
.d_alias
);
1675 INIT_HLIST_NODE(&dentry
->d_sib
);
1676 d_set_d_op(dentry
, dentry
->d_sb
->s_d_op
);
1678 if (dentry
->d_op
&& dentry
->d_op
->d_init
) {
1679 err
= dentry
->d_op
->d_init(dentry
);
1681 if (dname_external(dentry
))
1682 kfree(external_name(dentry
));
1683 kmem_cache_free(dentry_cache
, dentry
);
1688 this_cpu_inc(nr_dentry
);
1694 * d_alloc - allocate a dcache entry
1695 * @parent: parent of entry to allocate
1696 * @name: qstr of the name
1698 * Allocates a dentry. It returns %NULL if there is insufficient memory
1699 * available. On a success the dentry is returned. The name passed in is
1700 * copied and the copy passed in may be reused after this call.
1702 struct dentry
*d_alloc(struct dentry
* parent
, const struct qstr
*name
)
1704 struct dentry
*dentry
= __d_alloc(parent
->d_sb
, name
);
1707 spin_lock(&parent
->d_lock
);
1709 * don't need child lock because it is not subject
1710 * to concurrency here
1712 dentry
->d_parent
= dget_dlock(parent
);
1713 hlist_add_head(&dentry
->d_sib
, &parent
->d_children
);
1714 spin_unlock(&parent
->d_lock
);
1718 EXPORT_SYMBOL(d_alloc
);
1720 struct dentry
*d_alloc_anon(struct super_block
*sb
)
1722 return __d_alloc(sb
, NULL
);
1724 EXPORT_SYMBOL(d_alloc_anon
);
1726 struct dentry
*d_alloc_cursor(struct dentry
* parent
)
1728 struct dentry
*dentry
= d_alloc_anon(parent
->d_sb
);
1730 dentry
->d_flags
|= DCACHE_DENTRY_CURSOR
;
1731 dentry
->d_parent
= dget(parent
);
1737 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1738 * @sb: the superblock
1739 * @name: qstr of the name
1741 * For a filesystem that just pins its dentries in memory and never
1742 * performs lookups at all, return an unhashed IS_ROOT dentry.
1743 * This is used for pipes, sockets et.al. - the stuff that should
1744 * never be anyone's children or parents. Unlike all other
1745 * dentries, these will not have RCU delay between dropping the
1746 * last reference and freeing them.
1748 * The only user is alloc_file_pseudo() and that's what should
1749 * be considered a public interface. Don't use directly.
1751 struct dentry
*d_alloc_pseudo(struct super_block
*sb
, const struct qstr
*name
)
1753 static const struct dentry_operations anon_ops
= {
1754 .d_dname
= simple_dname
1756 struct dentry
*dentry
= __d_alloc(sb
, name
);
1757 if (likely(dentry
)) {
1758 dentry
->d_flags
|= DCACHE_NORCU
;
1760 d_set_d_op(dentry
, &anon_ops
);
1765 struct dentry
*d_alloc_name(struct dentry
*parent
, const char *name
)
1770 q
.hash_len
= hashlen_string(parent
, name
);
1771 return d_alloc(parent
, &q
);
1773 EXPORT_SYMBOL(d_alloc_name
);
1775 void d_set_d_op(struct dentry
*dentry
, const struct dentry_operations
*op
)
1777 WARN_ON_ONCE(dentry
->d_op
);
1778 WARN_ON_ONCE(dentry
->d_flags
& (DCACHE_OP_HASH
|
1780 DCACHE_OP_REVALIDATE
|
1781 DCACHE_OP_WEAK_REVALIDATE
|
1788 dentry
->d_flags
|= DCACHE_OP_HASH
;
1790 dentry
->d_flags
|= DCACHE_OP_COMPARE
;
1791 if (op
->d_revalidate
)
1792 dentry
->d_flags
|= DCACHE_OP_REVALIDATE
;
1793 if (op
->d_weak_revalidate
)
1794 dentry
->d_flags
|= DCACHE_OP_WEAK_REVALIDATE
;
1796 dentry
->d_flags
|= DCACHE_OP_DELETE
;
1798 dentry
->d_flags
|= DCACHE_OP_PRUNE
;
1800 dentry
->d_flags
|= DCACHE_OP_REAL
;
1803 EXPORT_SYMBOL(d_set_d_op
);
1805 static unsigned d_flags_for_inode(struct inode
*inode
)
1807 unsigned add_flags
= DCACHE_REGULAR_TYPE
;
1810 return DCACHE_MISS_TYPE
;
1812 if (S_ISDIR(inode
->i_mode
)) {
1813 add_flags
= DCACHE_DIRECTORY_TYPE
;
1814 if (unlikely(!(inode
->i_opflags
& IOP_LOOKUP
))) {
1815 if (unlikely(!inode
->i_op
->lookup
))
1816 add_flags
= DCACHE_AUTODIR_TYPE
;
1818 inode
->i_opflags
|= IOP_LOOKUP
;
1820 goto type_determined
;
1823 if (unlikely(!(inode
->i_opflags
& IOP_NOFOLLOW
))) {
1824 if (unlikely(inode
->i_op
->get_link
)) {
1825 add_flags
= DCACHE_SYMLINK_TYPE
;
1826 goto type_determined
;
1828 inode
->i_opflags
|= IOP_NOFOLLOW
;
1831 if (unlikely(!S_ISREG(inode
->i_mode
)))
1832 add_flags
= DCACHE_SPECIAL_TYPE
;
1835 if (unlikely(IS_AUTOMOUNT(inode
)))
1836 add_flags
|= DCACHE_NEED_AUTOMOUNT
;
1840 static void __d_instantiate(struct dentry
*dentry
, struct inode
*inode
)
1842 unsigned add_flags
= d_flags_for_inode(inode
);
1843 WARN_ON(d_in_lookup(dentry
));
1845 spin_lock(&dentry
->d_lock
);
1847 * Decrement negative dentry count if it was in the LRU list.
1849 if (dentry
->d_flags
& DCACHE_LRU_LIST
)
1850 this_cpu_dec(nr_dentry_negative
);
1851 hlist_add_head(&dentry
->d_u
.d_alias
, &inode
->i_dentry
);
1852 raw_write_seqcount_begin(&dentry
->d_seq
);
1853 __d_set_inode_and_type(dentry
, inode
, add_flags
);
1854 raw_write_seqcount_end(&dentry
->d_seq
);
1855 fsnotify_update_flags(dentry
);
1856 spin_unlock(&dentry
->d_lock
);
1860 * d_instantiate - fill in inode information for a dentry
1861 * @entry: dentry to complete
1862 * @inode: inode to attach to this dentry
1864 * Fill in inode information in the entry.
1866 * This turns negative dentries into productive full members
1869 * NOTE! This assumes that the inode count has been incremented
1870 * (or otherwise set) by the caller to indicate that it is now
1871 * in use by the dcache.
1874 void d_instantiate(struct dentry
*entry
, struct inode
* inode
)
1876 BUG_ON(!hlist_unhashed(&entry
->d_u
.d_alias
));
1878 security_d_instantiate(entry
, inode
);
1879 spin_lock(&inode
->i_lock
);
1880 __d_instantiate(entry
, inode
);
1881 spin_unlock(&inode
->i_lock
);
1884 EXPORT_SYMBOL(d_instantiate
);
1887 * This should be equivalent to d_instantiate() + unlock_new_inode(),
1888 * with lockdep-related part of unlock_new_inode() done before
1889 * anything else. Use that instead of open-coding d_instantiate()/
1890 * unlock_new_inode() combinations.
1892 void d_instantiate_new(struct dentry
*entry
, struct inode
*inode
)
1894 BUG_ON(!hlist_unhashed(&entry
->d_u
.d_alias
));
1896 lockdep_annotate_inode_mutex_key(inode
);
1897 security_d_instantiate(entry
, inode
);
1898 spin_lock(&inode
->i_lock
);
1899 __d_instantiate(entry
, inode
);
1900 WARN_ON(!(inode
->i_state
& I_NEW
));
1901 inode
->i_state
&= ~I_NEW
& ~I_CREATING
;
1903 wake_up_bit(&inode
->i_state
, __I_NEW
);
1904 spin_unlock(&inode
->i_lock
);
1906 EXPORT_SYMBOL(d_instantiate_new
);
1908 struct dentry
*d_make_root(struct inode
*root_inode
)
1910 struct dentry
*res
= NULL
;
1913 res
= d_alloc_anon(root_inode
->i_sb
);
1915 d_instantiate(res
, root_inode
);
1921 EXPORT_SYMBOL(d_make_root
);
1923 static struct dentry
*__d_obtain_alias(struct inode
*inode
, bool disconnected
)
1925 struct super_block
*sb
;
1926 struct dentry
*new, *res
;
1929 return ERR_PTR(-ESTALE
);
1931 return ERR_CAST(inode
);
1935 res
= d_find_any_alias(inode
); /* existing alias? */
1939 new = d_alloc_anon(sb
);
1941 res
= ERR_PTR(-ENOMEM
);
1945 security_d_instantiate(new, inode
);
1946 spin_lock(&inode
->i_lock
);
1947 res
= __d_find_any_alias(inode
); /* recheck under lock */
1948 if (likely(!res
)) { /* still no alias, attach a disconnected dentry */
1949 unsigned add_flags
= d_flags_for_inode(inode
);
1952 add_flags
|= DCACHE_DISCONNECTED
;
1954 spin_lock(&new->d_lock
);
1955 __d_set_inode_and_type(new, inode
, add_flags
);
1956 hlist_add_head(&new->d_u
.d_alias
, &inode
->i_dentry
);
1957 if (!disconnected
) {
1958 hlist_bl_lock(&sb
->s_roots
);
1959 hlist_bl_add_head(&new->d_hash
, &sb
->s_roots
);
1960 hlist_bl_unlock(&sb
->s_roots
);
1962 spin_unlock(&new->d_lock
);
1963 spin_unlock(&inode
->i_lock
);
1964 inode
= NULL
; /* consumed by new->d_inode */
1967 spin_unlock(&inode
->i_lock
);
1977 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
1978 * @inode: inode to allocate the dentry for
1980 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1981 * similar open by handle operations. The returned dentry may be anonymous,
1982 * or may have a full name (if the inode was already in the cache).
1984 * When called on a directory inode, we must ensure that the inode only ever
1985 * has one dentry. If a dentry is found, that is returned instead of
1986 * allocating a new one.
1988 * On successful return, the reference to the inode has been transferred
1989 * to the dentry. In case of an error the reference on the inode is released.
1990 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1991 * be passed in and the error will be propagated to the return value,
1992 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1994 struct dentry
*d_obtain_alias(struct inode
*inode
)
1996 return __d_obtain_alias(inode
, true);
1998 EXPORT_SYMBOL(d_obtain_alias
);
2001 * d_obtain_root - find or allocate a dentry for a given inode
2002 * @inode: inode to allocate the dentry for
2004 * Obtain an IS_ROOT dentry for the root of a filesystem.
2006 * We must ensure that directory inodes only ever have one dentry. If a
2007 * dentry is found, that is returned instead of allocating a new one.
2009 * On successful return, the reference to the inode has been transferred
2010 * to the dentry. In case of an error the reference on the inode is
2011 * released. A %NULL or IS_ERR inode may be passed in and will be the
2012 * error will be propagate to the return value, with a %NULL @inode
2013 * replaced by ERR_PTR(-ESTALE).
2015 struct dentry
*d_obtain_root(struct inode
*inode
)
2017 return __d_obtain_alias(inode
, false);
2019 EXPORT_SYMBOL(d_obtain_root
);
2022 * d_add_ci - lookup or allocate new dentry with case-exact name
2023 * @inode: the inode case-insensitive lookup has found
2024 * @dentry: the negative dentry that was passed to the parent's lookup func
2025 * @name: the case-exact name to be associated with the returned dentry
2027 * This is to avoid filling the dcache with case-insensitive names to the
2028 * same inode, only the actual correct case is stored in the dcache for
2029 * case-insensitive filesystems.
2031 * For a case-insensitive lookup match and if the case-exact dentry
2032 * already exists in the dcache, use it and return it.
2034 * If no entry exists with the exact case name, allocate new dentry with
2035 * the exact case, and return the spliced entry.
2037 struct dentry
*d_add_ci(struct dentry
*dentry
, struct inode
*inode
,
2040 struct dentry
*found
, *res
;
2043 * First check if a dentry matching the name already exists,
2044 * if not go ahead and create it now.
2046 found
= d_hash_and_lookup(dentry
->d_parent
, name
);
2051 if (d_in_lookup(dentry
)) {
2052 found
= d_alloc_parallel(dentry
->d_parent
, name
,
2054 if (IS_ERR(found
) || !d_in_lookup(found
)) {
2059 found
= d_alloc(dentry
->d_parent
, name
);
2062 return ERR_PTR(-ENOMEM
);
2065 res
= d_splice_alias(inode
, found
);
2067 d_lookup_done(found
);
2073 EXPORT_SYMBOL(d_add_ci
);
2076 * d_same_name - compare dentry name with case-exact name
2077 * @parent: parent dentry
2078 * @dentry: the negative dentry that was passed to the parent's lookup func
2079 * @name: the case-exact name to be associated with the returned dentry
2081 * Return: true if names are same, or false
2083 bool d_same_name(const struct dentry
*dentry
, const struct dentry
*parent
,
2084 const struct qstr
*name
)
2086 if (likely(!(parent
->d_flags
& DCACHE_OP_COMPARE
))) {
2087 if (dentry
->d_name
.len
!= name
->len
)
2089 return dentry_cmp(dentry
, name
->name
, name
->len
) == 0;
2091 return parent
->d_op
->d_compare(dentry
,
2092 dentry
->d_name
.len
, dentry
->d_name
.name
,
2095 EXPORT_SYMBOL_GPL(d_same_name
);
2098 * This is __d_lookup_rcu() when the parent dentry has
2099 * DCACHE_OP_COMPARE, which makes things much nastier.
2101 static noinline
struct dentry
*__d_lookup_rcu_op_compare(
2102 const struct dentry
*parent
,
2103 const struct qstr
*name
,
2106 u64 hashlen
= name
->hash_len
;
2107 struct hlist_bl_head
*b
= d_hash(hashlen_hash(hashlen
));
2108 struct hlist_bl_node
*node
;
2109 struct dentry
*dentry
;
2111 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
2117 seq
= raw_seqcount_begin(&dentry
->d_seq
);
2118 if (dentry
->d_parent
!= parent
)
2120 if (d_unhashed(dentry
))
2122 if (dentry
->d_name
.hash
!= hashlen_hash(hashlen
))
2124 tlen
= dentry
->d_name
.len
;
2125 tname
= dentry
->d_name
.name
;
2126 /* we want a consistent (name,len) pair */
2127 if (read_seqcount_retry(&dentry
->d_seq
, seq
)) {
2131 if (parent
->d_op
->d_compare(dentry
, tlen
, tname
, name
) != 0)
2140 * __d_lookup_rcu - search for a dentry (racy, store-free)
2141 * @parent: parent dentry
2142 * @name: qstr of name we wish to find
2143 * @seqp: returns d_seq value at the point where the dentry was found
2144 * Returns: dentry, or NULL
2146 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2147 * resolution (store-free path walking) design described in
2148 * Documentation/filesystems/path-lookup.txt.
2150 * This is not to be used outside core vfs.
2152 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2153 * held, and rcu_read_lock held. The returned dentry must not be stored into
2154 * without taking d_lock and checking d_seq sequence count against @seq
2157 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2160 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2161 * the returned dentry, so long as its parent's seqlock is checked after the
2162 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2163 * is formed, giving integrity down the path walk.
2165 * NOTE! The caller *has* to check the resulting dentry against the sequence
2166 * number we've returned before using any of the resulting dentry state!
2168 struct dentry
*__d_lookup_rcu(const struct dentry
*parent
,
2169 const struct qstr
*name
,
2172 u64 hashlen
= name
->hash_len
;
2173 const unsigned char *str
= name
->name
;
2174 struct hlist_bl_head
*b
= d_hash(hashlen_hash(hashlen
));
2175 struct hlist_bl_node
*node
;
2176 struct dentry
*dentry
;
2179 * Note: There is significant duplication with __d_lookup_rcu which is
2180 * required to prevent single threaded performance regressions
2181 * especially on architectures where smp_rmb (in seqcounts) are costly.
2182 * Keep the two functions in sync.
2185 if (unlikely(parent
->d_flags
& DCACHE_OP_COMPARE
))
2186 return __d_lookup_rcu_op_compare(parent
, name
, seqp
);
2189 * The hash list is protected using RCU.
2191 * Carefully use d_seq when comparing a candidate dentry, to avoid
2192 * races with d_move().
2194 * It is possible that concurrent renames can mess up our list
2195 * walk here and result in missing our dentry, resulting in the
2196 * false-negative result. d_lookup() protects against concurrent
2197 * renames using rename_lock seqlock.
2199 * See Documentation/filesystems/path-lookup.txt for more details.
2201 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
2205 * The dentry sequence count protects us from concurrent
2206 * renames, and thus protects parent and name fields.
2208 * The caller must perform a seqcount check in order
2209 * to do anything useful with the returned dentry.
2211 * NOTE! We do a "raw" seqcount_begin here. That means that
2212 * we don't wait for the sequence count to stabilize if it
2213 * is in the middle of a sequence change. If we do the slow
2214 * dentry compare, we will do seqretries until it is stable,
2215 * and if we end up with a successful lookup, we actually
2216 * want to exit RCU lookup anyway.
2218 * Note that raw_seqcount_begin still *does* smp_rmb(), so
2219 * we are still guaranteed NUL-termination of ->d_name.name.
2221 seq
= raw_seqcount_begin(&dentry
->d_seq
);
2222 if (dentry
->d_parent
!= parent
)
2224 if (d_unhashed(dentry
))
2226 if (dentry
->d_name
.hash_len
!= hashlen
)
2228 if (dentry_cmp(dentry
, str
, hashlen_len(hashlen
)) != 0)
2237 * d_lookup - search for a dentry
2238 * @parent: parent dentry
2239 * @name: qstr of name we wish to find
2240 * Returns: dentry, or NULL
2242 * d_lookup searches the children of the parent dentry for the name in
2243 * question. If the dentry is found its reference count is incremented and the
2244 * dentry is returned. The caller must use dput to free the entry when it has
2245 * finished using it. %NULL is returned if the dentry does not exist.
2247 struct dentry
*d_lookup(const struct dentry
*parent
, const struct qstr
*name
)
2249 struct dentry
*dentry
;
2253 seq
= read_seqbegin(&rename_lock
);
2254 dentry
= __d_lookup(parent
, name
);
2257 } while (read_seqretry(&rename_lock
, seq
));
2260 EXPORT_SYMBOL(d_lookup
);
2263 * __d_lookup - search for a dentry (racy)
2264 * @parent: parent dentry
2265 * @name: qstr of name we wish to find
2266 * Returns: dentry, or NULL
2268 * __d_lookup is like d_lookup, however it may (rarely) return a
2269 * false-negative result due to unrelated rename activity.
2271 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2272 * however it must be used carefully, eg. with a following d_lookup in
2273 * the case of failure.
2275 * __d_lookup callers must be commented.
2277 struct dentry
*__d_lookup(const struct dentry
*parent
, const struct qstr
*name
)
2279 unsigned int hash
= name
->hash
;
2280 struct hlist_bl_head
*b
= d_hash(hash
);
2281 struct hlist_bl_node
*node
;
2282 struct dentry
*found
= NULL
;
2283 struct dentry
*dentry
;
2286 * Note: There is significant duplication with __d_lookup_rcu which is
2287 * required to prevent single threaded performance regressions
2288 * especially on architectures where smp_rmb (in seqcounts) are costly.
2289 * Keep the two functions in sync.
2293 * The hash list is protected using RCU.
2295 * Take d_lock when comparing a candidate dentry, to avoid races
2298 * It is possible that concurrent renames can mess up our list
2299 * walk here and result in missing our dentry, resulting in the
2300 * false-negative result. d_lookup() protects against concurrent
2301 * renames using rename_lock seqlock.
2303 * See Documentation/filesystems/path-lookup.txt for more details.
2307 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
2309 if (dentry
->d_name
.hash
!= hash
)
2312 spin_lock(&dentry
->d_lock
);
2313 if (dentry
->d_parent
!= parent
)
2315 if (d_unhashed(dentry
))
2318 if (!d_same_name(dentry
, parent
, name
))
2321 dentry
->d_lockref
.count
++;
2323 spin_unlock(&dentry
->d_lock
);
2326 spin_unlock(&dentry
->d_lock
);
2334 * d_hash_and_lookup - hash the qstr then search for a dentry
2335 * @dir: Directory to search in
2336 * @name: qstr of name we wish to find
2338 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2340 struct dentry
*d_hash_and_lookup(struct dentry
*dir
, struct qstr
*name
)
2343 * Check for a fs-specific hash function. Note that we must
2344 * calculate the standard hash first, as the d_op->d_hash()
2345 * routine may choose to leave the hash value unchanged.
2347 name
->hash
= full_name_hash(dir
, name
->name
, name
->len
);
2348 if (dir
->d_flags
& DCACHE_OP_HASH
) {
2349 int err
= dir
->d_op
->d_hash(dir
, name
);
2350 if (unlikely(err
< 0))
2351 return ERR_PTR(err
);
2353 return d_lookup(dir
, name
);
2355 EXPORT_SYMBOL(d_hash_and_lookup
);
2358 * When a file is deleted, we have two options:
2359 * - turn this dentry into a negative dentry
2360 * - unhash this dentry and free it.
2362 * Usually, we want to just turn this into
2363 * a negative dentry, but if anybody else is
2364 * currently using the dentry or the inode
2365 * we can't do that and we fall back on removing
2366 * it from the hash queues and waiting for
2367 * it to be deleted later when it has no users
2371 * d_delete - delete a dentry
2372 * @dentry: The dentry to delete
2374 * Turn the dentry into a negative dentry if possible, otherwise
2375 * remove it from the hash queues so it can be deleted later
2378 void d_delete(struct dentry
* dentry
)
2380 struct inode
*inode
= dentry
->d_inode
;
2382 spin_lock(&inode
->i_lock
);
2383 spin_lock(&dentry
->d_lock
);
2385 * Are we the only user?
2387 if (dentry
->d_lockref
.count
== 1) {
2388 dentry
->d_flags
&= ~DCACHE_CANT_MOUNT
;
2389 dentry_unlink_inode(dentry
);
2392 spin_unlock(&dentry
->d_lock
);
2393 spin_unlock(&inode
->i_lock
);
2396 EXPORT_SYMBOL(d_delete
);
2398 static void __d_rehash(struct dentry
*entry
)
2400 struct hlist_bl_head
*b
= d_hash(entry
->d_name
.hash
);
2403 hlist_bl_add_head_rcu(&entry
->d_hash
, b
);
2408 * d_rehash - add an entry back to the hash
2409 * @entry: dentry to add to the hash
2411 * Adds a dentry to the hash according to its name.
2414 void d_rehash(struct dentry
* entry
)
2416 spin_lock(&entry
->d_lock
);
2418 spin_unlock(&entry
->d_lock
);
2420 EXPORT_SYMBOL(d_rehash
);
2422 static inline unsigned start_dir_add(struct inode
*dir
)
2424 preempt_disable_nested();
2426 unsigned n
= dir
->i_dir_seq
;
2427 if (!(n
& 1) && cmpxchg(&dir
->i_dir_seq
, n
, n
+ 1) == n
)
2433 static inline void end_dir_add(struct inode
*dir
, unsigned int n
,
2434 wait_queue_head_t
*d_wait
)
2436 smp_store_release(&dir
->i_dir_seq
, n
+ 2);
2437 preempt_enable_nested();
2438 wake_up_all(d_wait
);
2441 static void d_wait_lookup(struct dentry
*dentry
)
2443 if (d_in_lookup(dentry
)) {
2444 DECLARE_WAITQUEUE(wait
, current
);
2445 add_wait_queue(dentry
->d_wait
, &wait
);
2447 set_current_state(TASK_UNINTERRUPTIBLE
);
2448 spin_unlock(&dentry
->d_lock
);
2450 spin_lock(&dentry
->d_lock
);
2451 } while (d_in_lookup(dentry
));
2455 struct dentry
*d_alloc_parallel(struct dentry
*parent
,
2456 const struct qstr
*name
,
2457 wait_queue_head_t
*wq
)
2459 unsigned int hash
= name
->hash
;
2460 struct hlist_bl_head
*b
= in_lookup_hash(parent
, hash
);
2461 struct hlist_bl_node
*node
;
2462 struct dentry
*new = d_alloc(parent
, name
);
2463 struct dentry
*dentry
;
2464 unsigned seq
, r_seq
, d_seq
;
2467 return ERR_PTR(-ENOMEM
);
2471 seq
= smp_load_acquire(&parent
->d_inode
->i_dir_seq
);
2472 r_seq
= read_seqbegin(&rename_lock
);
2473 dentry
= __d_lookup_rcu(parent
, name
, &d_seq
);
2474 if (unlikely(dentry
)) {
2475 if (!lockref_get_not_dead(&dentry
->d_lockref
)) {
2479 if (read_seqcount_retry(&dentry
->d_seq
, d_seq
)) {
2488 if (unlikely(read_seqretry(&rename_lock
, r_seq
))) {
2493 if (unlikely(seq
& 1)) {
2499 if (unlikely(READ_ONCE(parent
->d_inode
->i_dir_seq
) != seq
)) {
2505 * No changes for the parent since the beginning of d_lookup().
2506 * Since all removals from the chain happen with hlist_bl_lock(),
2507 * any potential in-lookup matches are going to stay here until
2508 * we unlock the chain. All fields are stable in everything
2511 hlist_bl_for_each_entry(dentry
, node
, b
, d_u
.d_in_lookup_hash
) {
2512 if (dentry
->d_name
.hash
!= hash
)
2514 if (dentry
->d_parent
!= parent
)
2516 if (!d_same_name(dentry
, parent
, name
))
2519 /* now we can try to grab a reference */
2520 if (!lockref_get_not_dead(&dentry
->d_lockref
)) {
2527 * somebody is likely to be still doing lookup for it;
2528 * wait for them to finish
2530 spin_lock(&dentry
->d_lock
);
2531 d_wait_lookup(dentry
);
2533 * it's not in-lookup anymore; in principle we should repeat
2534 * everything from dcache lookup, but it's likely to be what
2535 * d_lookup() would've found anyway. If it is, just return it;
2536 * otherwise we really have to repeat the whole thing.
2538 if (unlikely(dentry
->d_name
.hash
!= hash
))
2540 if (unlikely(dentry
->d_parent
!= parent
))
2542 if (unlikely(d_unhashed(dentry
)))
2544 if (unlikely(!d_same_name(dentry
, parent
, name
)))
2546 /* OK, it *is* a hashed match; return it */
2547 spin_unlock(&dentry
->d_lock
);
2552 /* we can't take ->d_lock here; it's OK, though. */
2553 new->d_flags
|= DCACHE_PAR_LOOKUP
;
2555 hlist_bl_add_head(&new->d_u
.d_in_lookup_hash
, b
);
2559 spin_unlock(&dentry
->d_lock
);
2563 EXPORT_SYMBOL(d_alloc_parallel
);
2566 * - Unhash the dentry
2567 * - Retrieve and clear the waitqueue head in dentry
2568 * - Return the waitqueue head
2570 static wait_queue_head_t
*__d_lookup_unhash(struct dentry
*dentry
)
2572 wait_queue_head_t
*d_wait
;
2573 struct hlist_bl_head
*b
;
2575 lockdep_assert_held(&dentry
->d_lock
);
2577 b
= in_lookup_hash(dentry
->d_parent
, dentry
->d_name
.hash
);
2579 dentry
->d_flags
&= ~DCACHE_PAR_LOOKUP
;
2580 __hlist_bl_del(&dentry
->d_u
.d_in_lookup_hash
);
2581 d_wait
= dentry
->d_wait
;
2582 dentry
->d_wait
= NULL
;
2584 INIT_HLIST_NODE(&dentry
->d_u
.d_alias
);
2585 INIT_LIST_HEAD(&dentry
->d_lru
);
2589 void __d_lookup_unhash_wake(struct dentry
*dentry
)
2591 spin_lock(&dentry
->d_lock
);
2592 wake_up_all(__d_lookup_unhash(dentry
));
2593 spin_unlock(&dentry
->d_lock
);
2595 EXPORT_SYMBOL(__d_lookup_unhash_wake
);
2597 /* inode->i_lock held if inode is non-NULL */
2599 static inline void __d_add(struct dentry
*dentry
, struct inode
*inode
)
2601 wait_queue_head_t
*d_wait
;
2602 struct inode
*dir
= NULL
;
2604 spin_lock(&dentry
->d_lock
);
2605 if (unlikely(d_in_lookup(dentry
))) {
2606 dir
= dentry
->d_parent
->d_inode
;
2607 n
= start_dir_add(dir
);
2608 d_wait
= __d_lookup_unhash(dentry
);
2611 unsigned add_flags
= d_flags_for_inode(inode
);
2612 hlist_add_head(&dentry
->d_u
.d_alias
, &inode
->i_dentry
);
2613 raw_write_seqcount_begin(&dentry
->d_seq
);
2614 __d_set_inode_and_type(dentry
, inode
, add_flags
);
2615 raw_write_seqcount_end(&dentry
->d_seq
);
2616 fsnotify_update_flags(dentry
);
2620 end_dir_add(dir
, n
, d_wait
);
2621 spin_unlock(&dentry
->d_lock
);
2623 spin_unlock(&inode
->i_lock
);
2627 * d_add - add dentry to hash queues
2628 * @entry: dentry to add
2629 * @inode: The inode to attach to this dentry
2631 * This adds the entry to the hash queues and initializes @inode.
2632 * The entry was actually filled in earlier during d_alloc().
2635 void d_add(struct dentry
*entry
, struct inode
*inode
)
2638 security_d_instantiate(entry
, inode
);
2639 spin_lock(&inode
->i_lock
);
2641 __d_add(entry
, inode
);
2643 EXPORT_SYMBOL(d_add
);
2646 * d_exact_alias - find and hash an exact unhashed alias
2647 * @entry: dentry to add
2648 * @inode: The inode to go with this dentry
2650 * If an unhashed dentry with the same name/parent and desired
2651 * inode already exists, hash and return it. Otherwise, return
2654 * Parent directory should be locked.
2656 struct dentry
*d_exact_alias(struct dentry
*entry
, struct inode
*inode
)
2658 struct dentry
*alias
;
2659 unsigned int hash
= entry
->d_name
.hash
;
2661 spin_lock(&inode
->i_lock
);
2662 hlist_for_each_entry(alias
, &inode
->i_dentry
, d_u
.d_alias
) {
2664 * Don't need alias->d_lock here, because aliases with
2665 * d_parent == entry->d_parent are not subject to name or
2666 * parent changes, because the parent inode i_mutex is held.
2668 if (alias
->d_name
.hash
!= hash
)
2670 if (alias
->d_parent
!= entry
->d_parent
)
2672 if (!d_same_name(alias
, entry
->d_parent
, &entry
->d_name
))
2674 spin_lock(&alias
->d_lock
);
2675 if (!d_unhashed(alias
)) {
2676 spin_unlock(&alias
->d_lock
);
2681 spin_unlock(&alias
->d_lock
);
2683 spin_unlock(&inode
->i_lock
);
2686 spin_unlock(&inode
->i_lock
);
2689 EXPORT_SYMBOL(d_exact_alias
);
2691 static void swap_names(struct dentry
*dentry
, struct dentry
*target
)
2693 if (unlikely(dname_external(target
))) {
2694 if (unlikely(dname_external(dentry
))) {
2696 * Both external: swap the pointers
2698 swap(target
->d_name
.name
, dentry
->d_name
.name
);
2701 * dentry:internal, target:external. Steal target's
2702 * storage and make target internal.
2704 memcpy(target
->d_iname
, dentry
->d_name
.name
,
2705 dentry
->d_name
.len
+ 1);
2706 dentry
->d_name
.name
= target
->d_name
.name
;
2707 target
->d_name
.name
= target
->d_iname
;
2710 if (unlikely(dname_external(dentry
))) {
2712 * dentry:external, target:internal. Give dentry's
2713 * storage to target and make dentry internal
2715 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2716 target
->d_name
.len
+ 1);
2717 target
->d_name
.name
= dentry
->d_name
.name
;
2718 dentry
->d_name
.name
= dentry
->d_iname
;
2721 * Both are internal.
2724 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN
, sizeof(long)));
2725 for (i
= 0; i
< DNAME_INLINE_LEN
/ sizeof(long); i
++) {
2726 swap(((long *) &dentry
->d_iname
)[i
],
2727 ((long *) &target
->d_iname
)[i
]);
2731 swap(dentry
->d_name
.hash_len
, target
->d_name
.hash_len
);
2734 static void copy_name(struct dentry
*dentry
, struct dentry
*target
)
2736 struct external_name
*old_name
= NULL
;
2737 if (unlikely(dname_external(dentry
)))
2738 old_name
= external_name(dentry
);
2739 if (unlikely(dname_external(target
))) {
2740 atomic_inc(&external_name(target
)->u
.count
);
2741 dentry
->d_name
= target
->d_name
;
2743 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2744 target
->d_name
.len
+ 1);
2745 dentry
->d_name
.name
= dentry
->d_iname
;
2746 dentry
->d_name
.hash_len
= target
->d_name
.hash_len
;
2748 if (old_name
&& likely(atomic_dec_and_test(&old_name
->u
.count
)))
2749 kfree_rcu(old_name
, u
.head
);
2753 * __d_move - move a dentry
2754 * @dentry: entry to move
2755 * @target: new dentry
2756 * @exchange: exchange the two dentries
2758 * Update the dcache to reflect the move of a file name. Negative
2759 * dcache entries should not be moved in this way. Caller must hold
2760 * rename_lock, the i_mutex of the source and target directories,
2761 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2763 static void __d_move(struct dentry
*dentry
, struct dentry
*target
,
2766 struct dentry
*old_parent
, *p
;
2767 wait_queue_head_t
*d_wait
;
2768 struct inode
*dir
= NULL
;
2771 WARN_ON(!dentry
->d_inode
);
2772 if (WARN_ON(dentry
== target
))
2775 BUG_ON(d_ancestor(target
, dentry
));
2776 old_parent
= dentry
->d_parent
;
2777 p
= d_ancestor(old_parent
, target
);
2778 if (IS_ROOT(dentry
)) {
2780 spin_lock(&target
->d_parent
->d_lock
);
2782 /* target is not a descendent of dentry->d_parent */
2783 spin_lock(&target
->d_parent
->d_lock
);
2784 spin_lock_nested(&old_parent
->d_lock
, DENTRY_D_LOCK_NESTED
);
2786 BUG_ON(p
== dentry
);
2787 spin_lock(&old_parent
->d_lock
);
2789 spin_lock_nested(&target
->d_parent
->d_lock
,
2790 DENTRY_D_LOCK_NESTED
);
2792 spin_lock_nested(&dentry
->d_lock
, 2);
2793 spin_lock_nested(&target
->d_lock
, 3);
2795 if (unlikely(d_in_lookup(target
))) {
2796 dir
= target
->d_parent
->d_inode
;
2797 n
= start_dir_add(dir
);
2798 d_wait
= __d_lookup_unhash(target
);
2801 write_seqcount_begin(&dentry
->d_seq
);
2802 write_seqcount_begin_nested(&target
->d_seq
, DENTRY_D_LOCK_NESTED
);
2805 if (!d_unhashed(dentry
))
2807 if (!d_unhashed(target
))
2810 /* ... and switch them in the tree */
2811 dentry
->d_parent
= target
->d_parent
;
2813 copy_name(dentry
, target
);
2814 target
->d_hash
.pprev
= NULL
;
2815 dentry
->d_parent
->d_lockref
.count
++;
2816 if (dentry
!= old_parent
) /* wasn't IS_ROOT */
2817 WARN_ON(!--old_parent
->d_lockref
.count
);
2819 target
->d_parent
= old_parent
;
2820 swap_names(dentry
, target
);
2821 if (!hlist_unhashed(&target
->d_sib
))
2822 __hlist_del(&target
->d_sib
);
2823 hlist_add_head(&target
->d_sib
, &target
->d_parent
->d_children
);
2825 fsnotify_update_flags(target
);
2827 if (!hlist_unhashed(&dentry
->d_sib
))
2828 __hlist_del(&dentry
->d_sib
);
2829 hlist_add_head(&dentry
->d_sib
, &dentry
->d_parent
->d_children
);
2831 fsnotify_update_flags(dentry
);
2832 fscrypt_handle_d_move(dentry
);
2834 write_seqcount_end(&target
->d_seq
);
2835 write_seqcount_end(&dentry
->d_seq
);
2838 end_dir_add(dir
, n
, d_wait
);
2840 if (dentry
->d_parent
!= old_parent
)
2841 spin_unlock(&dentry
->d_parent
->d_lock
);
2842 if (dentry
!= old_parent
)
2843 spin_unlock(&old_parent
->d_lock
);
2844 spin_unlock(&target
->d_lock
);
2845 spin_unlock(&dentry
->d_lock
);
2849 * d_move - move a dentry
2850 * @dentry: entry to move
2851 * @target: new dentry
2853 * Update the dcache to reflect the move of a file name. Negative
2854 * dcache entries should not be moved in this way. See the locking
2855 * requirements for __d_move.
2857 void d_move(struct dentry
*dentry
, struct dentry
*target
)
2859 write_seqlock(&rename_lock
);
2860 __d_move(dentry
, target
, false);
2861 write_sequnlock(&rename_lock
);
2863 EXPORT_SYMBOL(d_move
);
2866 * d_exchange - exchange two dentries
2867 * @dentry1: first dentry
2868 * @dentry2: second dentry
2870 void d_exchange(struct dentry
*dentry1
, struct dentry
*dentry2
)
2872 write_seqlock(&rename_lock
);
2874 WARN_ON(!dentry1
->d_inode
);
2875 WARN_ON(!dentry2
->d_inode
);
2876 WARN_ON(IS_ROOT(dentry1
));
2877 WARN_ON(IS_ROOT(dentry2
));
2879 __d_move(dentry1
, dentry2
, true);
2881 write_sequnlock(&rename_lock
);
2885 * d_ancestor - search for an ancestor
2886 * @p1: ancestor dentry
2889 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2890 * an ancestor of p2, else NULL.
2892 struct dentry
*d_ancestor(struct dentry
*p1
, struct dentry
*p2
)
2896 for (p
= p2
; !IS_ROOT(p
); p
= p
->d_parent
) {
2897 if (p
->d_parent
== p1
)
2904 * This helper attempts to cope with remotely renamed directories
2906 * It assumes that the caller is already holding
2907 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2909 * Note: If ever the locking in lock_rename() changes, then please
2910 * remember to update this too...
2912 static int __d_unalias(struct dentry
*dentry
, struct dentry
*alias
)
2914 struct mutex
*m1
= NULL
;
2915 struct rw_semaphore
*m2
= NULL
;
2918 /* If alias and dentry share a parent, then no extra locks required */
2919 if (alias
->d_parent
== dentry
->d_parent
)
2922 /* See lock_rename() */
2923 if (!mutex_trylock(&dentry
->d_sb
->s_vfs_rename_mutex
))
2925 m1
= &dentry
->d_sb
->s_vfs_rename_mutex
;
2926 if (!inode_trylock_shared(alias
->d_parent
->d_inode
))
2928 m2
= &alias
->d_parent
->d_inode
->i_rwsem
;
2930 __d_move(alias
, dentry
, false);
2941 * d_splice_alias - splice a disconnected dentry into the tree if one exists
2942 * @inode: the inode which may have a disconnected dentry
2943 * @dentry: a negative dentry which we want to point to the inode.
2945 * If inode is a directory and has an IS_ROOT alias, then d_move that in
2946 * place of the given dentry and return it, else simply d_add the inode
2947 * to the dentry and return NULL.
2949 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
2950 * we should error out: directories can't have multiple aliases.
2952 * This is needed in the lookup routine of any filesystem that is exportable
2953 * (via knfsd) so that we can build dcache paths to directories effectively.
2955 * If a dentry was found and moved, then it is returned. Otherwise NULL
2956 * is returned. This matches the expected return value of ->lookup.
2958 * Cluster filesystems may call this function with a negative, hashed dentry.
2959 * In that case, we know that the inode will be a regular file, and also this
2960 * will only occur during atomic_open. So we need to check for the dentry
2961 * being already hashed only in the final case.
2963 struct dentry
*d_splice_alias(struct inode
*inode
, struct dentry
*dentry
)
2966 return ERR_CAST(inode
);
2968 BUG_ON(!d_unhashed(dentry
));
2973 security_d_instantiate(dentry
, inode
);
2974 spin_lock(&inode
->i_lock
);
2975 if (S_ISDIR(inode
->i_mode
)) {
2976 struct dentry
*new = __d_find_any_alias(inode
);
2977 if (unlikely(new)) {
2978 /* The reference to new ensures it remains an alias */
2979 spin_unlock(&inode
->i_lock
);
2980 write_seqlock(&rename_lock
);
2981 if (unlikely(d_ancestor(new, dentry
))) {
2982 write_sequnlock(&rename_lock
);
2984 new = ERR_PTR(-ELOOP
);
2985 pr_warn_ratelimited(
2986 "VFS: Lookup of '%s' in %s %s"
2987 " would have caused loop\n",
2988 dentry
->d_name
.name
,
2989 inode
->i_sb
->s_type
->name
,
2991 } else if (!IS_ROOT(new)) {
2992 struct dentry
*old_parent
= dget(new->d_parent
);
2993 int err
= __d_unalias(dentry
, new);
2994 write_sequnlock(&rename_lock
);
3001 __d_move(new, dentry
, false);
3002 write_sequnlock(&rename_lock
);
3009 __d_add(dentry
, inode
);
3012 EXPORT_SYMBOL(d_splice_alias
);
3015 * Test whether new_dentry is a subdirectory of old_dentry.
3017 * Trivially implemented using the dcache structure
3021 * is_subdir - is new dentry a subdirectory of old_dentry
3022 * @new_dentry: new dentry
3023 * @old_dentry: old dentry
3025 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3026 * Returns false otherwise.
3027 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3030 bool is_subdir(struct dentry
*new_dentry
, struct dentry
*old_dentry
)
3035 if (new_dentry
== old_dentry
)
3039 /* for restarting inner loop in case of seq retry */
3040 seq
= read_seqbegin(&rename_lock
);
3042 * Need rcu_readlock to protect against the d_parent trashing
3046 if (d_ancestor(old_dentry
, new_dentry
))
3051 } while (read_seqretry(&rename_lock
, seq
));
3055 EXPORT_SYMBOL(is_subdir
);
3057 static enum d_walk_ret
d_genocide_kill(void *data
, struct dentry
*dentry
)
3059 struct dentry
*root
= data
;
3060 if (dentry
!= root
) {
3061 if (d_unhashed(dentry
) || !dentry
->d_inode
)
3064 dentry
->d_lockref
.count
--;
3066 return D_WALK_CONTINUE
;
3069 void d_genocide(struct dentry
*parent
)
3071 d_walk(parent
, parent
, d_genocide_kill
);
3074 void d_mark_tmpfile(struct file
*file
, struct inode
*inode
)
3076 struct dentry
*dentry
= file
->f_path
.dentry
;
3078 BUG_ON(dentry
->d_name
.name
!= dentry
->d_iname
||
3079 !hlist_unhashed(&dentry
->d_u
.d_alias
) ||
3080 !d_unlinked(dentry
));
3081 spin_lock(&dentry
->d_parent
->d_lock
);
3082 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
3083 dentry
->d_name
.len
= sprintf(dentry
->d_iname
, "#%llu",
3084 (unsigned long long)inode
->i_ino
);
3085 spin_unlock(&dentry
->d_lock
);
3086 spin_unlock(&dentry
->d_parent
->d_lock
);
3088 EXPORT_SYMBOL(d_mark_tmpfile
);
3090 void d_tmpfile(struct file
*file
, struct inode
*inode
)
3092 struct dentry
*dentry
= file
->f_path
.dentry
;
3094 inode_dec_link_count(inode
);
3095 d_mark_tmpfile(file
, inode
);
3096 d_instantiate(dentry
, inode
);
3098 EXPORT_SYMBOL(d_tmpfile
);
3100 static __initdata
unsigned long dhash_entries
;
3101 static int __init
set_dhash_entries(char *str
)
3105 dhash_entries
= simple_strtoul(str
, &str
, 0);
3108 __setup("dhash_entries=", set_dhash_entries
);
3110 static void __init
dcache_init_early(void)
3112 /* If hashes are distributed across NUMA nodes, defer
3113 * hash allocation until vmalloc space is available.
3119 alloc_large_system_hash("Dentry cache",
3120 sizeof(struct hlist_bl_head
),
3123 HASH_EARLY
| HASH_ZERO
,
3128 d_hash_shift
= 32 - d_hash_shift
;
3131 static void __init
dcache_init(void)
3134 * A constructor could be added for stable state like the lists,
3135 * but it is probably not worth it because of the cache nature
3138 dentry_cache
= KMEM_CACHE_USERCOPY(dentry
,
3139 SLAB_RECLAIM_ACCOUNT
|SLAB_PANIC
|SLAB_MEM_SPREAD
|SLAB_ACCOUNT
,
3142 /* Hash may have been set up in dcache_init_early */
3147 alloc_large_system_hash("Dentry cache",
3148 sizeof(struct hlist_bl_head
),
3156 d_hash_shift
= 32 - d_hash_shift
;
3159 /* SLAB cache for __getname() consumers */
3160 struct kmem_cache
*names_cachep __ro_after_init
;
3161 EXPORT_SYMBOL(names_cachep
);
3163 void __init
vfs_caches_init_early(void)
3167 for (i
= 0; i
< ARRAY_SIZE(in_lookup_hashtable
); i
++)
3168 INIT_HLIST_BL_HEAD(&in_lookup_hashtable
[i
]);
3170 dcache_init_early();
3174 void __init
vfs_caches_init(void)
3176 names_cachep
= kmem_cache_create_usercopy("names_cache", PATH_MAX
, 0,
3177 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, 0, PATH_MAX
, NULL
);
3182 files_maxfiles_init();