4 * Complete reimplementation
5 * (C) 1997 Thomas Schoebel-Theuer,
6 * with heavy changes by Linus Torvalds
10 * Notes on the allocation strategy:
12 * The dcache is a master of the icache - whenever a dcache entry
13 * exists, the inode will always exist. "iput()" is done either when
14 * the dcache entry is deleted or garbage collected.
17 #include <linux/syscalls.h>
18 #include <linux/string.h>
21 #include <linux/fsnotify.h>
22 #include <linux/slab.h>
23 #include <linux/init.h>
24 #include <linux/hash.h>
25 #include <linux/cache.h>
26 #include <linux/export.h>
27 #include <linux/mount.h>
28 #include <linux/file.h>
29 #include <asm/uaccess.h>
30 #include <linux/security.h>
31 #include <linux/seqlock.h>
32 #include <linux/swap.h>
33 #include <linux/bootmem.h>
34 #include <linux/fs_struct.h>
35 #include <linux/hardirq.h>
36 #include <linux/bit_spinlock.h>
37 #include <linux/rculist_bl.h>
38 #include <linux/prefetch.h>
39 #include <linux/ratelimit.h>
40 #include <linux/list_lru.h>
41 #include <linux/kasan.h>
48 * dcache->d_inode->i_lock protects:
49 * - i_dentry, d_u.d_alias, d_inode of aliases
50 * dcache_hash_bucket lock protects:
51 * - the dcache hash table
52 * s_anon bl list spinlock protects:
53 * - the s_anon list (see __d_drop)
54 * dentry->d_sb->s_dentry_lru_lock protects:
55 * - the dcache lru lists and counters
62 * - d_parent and d_subdirs
63 * - childrens' d_child and d_parent
64 * - d_u.d_alias, d_inode
67 * dentry->d_inode->i_lock
69 * dentry->d_sb->s_dentry_lru_lock
70 * dcache_hash_bucket lock
73 * If there is an ancestor relationship:
74 * dentry->d_parent->...->d_parent->d_lock
76 * dentry->d_parent->d_lock
79 * If no ancestor relationship:
80 * if (dentry1 < dentry2)
84 int sysctl_vfs_cache_pressure __read_mostly
= 100;
85 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure
);
87 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(rename_lock
);
89 EXPORT_SYMBOL(rename_lock
);
91 static struct kmem_cache
*dentry_cache __read_mostly
;
94 * This is the single most critical data structure when it comes
95 * to the dcache: the hashtable for lookups. Somebody should try
96 * to make this good - I've just made it work.
98 * This hash-function tries to avoid losing too many bits of hash
99 * information, yet avoid using a prime hash-size or similar.
102 static unsigned int d_hash_mask __read_mostly
;
103 static unsigned int d_hash_shift __read_mostly
;
105 static struct hlist_bl_head
*dentry_hashtable __read_mostly
;
107 static inline struct hlist_bl_head
*d_hash(const struct dentry
*parent
,
110 hash
+= (unsigned long) parent
/ L1_CACHE_BYTES
;
111 return dentry_hashtable
+ hash_32(hash
, d_hash_shift
);
114 #define IN_LOOKUP_SHIFT 10
115 static struct hlist_bl_head in_lookup_hashtable
[1 << IN_LOOKUP_SHIFT
];
117 static inline struct hlist_bl_head
*in_lookup_hash(const struct dentry
*parent
,
120 hash
+= (unsigned long) parent
/ L1_CACHE_BYTES
;
121 return in_lookup_hashtable
+ hash_32(hash
, IN_LOOKUP_SHIFT
);
125 /* Statistics gathering. */
126 struct dentry_stat_t dentry_stat
= {
130 static DEFINE_PER_CPU(long, nr_dentry
);
131 static DEFINE_PER_CPU(long, nr_dentry_unused
);
133 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
136 * Here we resort to our own counters instead of using generic per-cpu counters
137 * for consistency with what the vfs inode code does. We are expected to harvest
138 * better code and performance by having our own specialized counters.
140 * Please note that the loop is done over all possible CPUs, not over all online
141 * CPUs. The reason for this is that we don't want to play games with CPUs going
142 * on and off. If one of them goes off, we will just keep their counters.
144 * glommer: See cffbc8a for details, and if you ever intend to change this,
145 * please update all vfs counters to match.
147 static long get_nr_dentry(void)
151 for_each_possible_cpu(i
)
152 sum
+= per_cpu(nr_dentry
, i
);
153 return sum
< 0 ? 0 : sum
;
156 static long get_nr_dentry_unused(void)
160 for_each_possible_cpu(i
)
161 sum
+= per_cpu(nr_dentry_unused
, i
);
162 return sum
< 0 ? 0 : sum
;
165 int proc_nr_dentry(struct ctl_table
*table
, int write
, void __user
*buffer
,
166 size_t *lenp
, loff_t
*ppos
)
168 dentry_stat
.nr_dentry
= get_nr_dentry();
169 dentry_stat
.nr_unused
= get_nr_dentry_unused();
170 return proc_doulongvec_minmax(table
, write
, buffer
, lenp
, ppos
);
175 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
176 * The strings are both count bytes long, and count is non-zero.
178 #ifdef CONFIG_DCACHE_WORD_ACCESS
180 #include <asm/word-at-a-time.h>
182 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
183 * aligned allocation for this particular component. We don't
184 * strictly need the load_unaligned_zeropad() safety, but it
185 * doesn't hurt either.
187 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
188 * need the careful unaligned handling.
190 static inline int dentry_string_cmp(const unsigned char *cs
, const unsigned char *ct
, unsigned tcount
)
192 unsigned long a
,b
,mask
;
195 a
= *(unsigned long *)cs
;
196 b
= load_unaligned_zeropad(ct
);
197 if (tcount
< sizeof(unsigned long))
199 if (unlikely(a
!= b
))
201 cs
+= sizeof(unsigned long);
202 ct
+= sizeof(unsigned long);
203 tcount
-= sizeof(unsigned long);
207 mask
= bytemask_from_count(tcount
);
208 return unlikely(!!((a
^ b
) & mask
));
213 static inline int dentry_string_cmp(const unsigned char *cs
, const unsigned char *ct
, unsigned tcount
)
227 static inline int dentry_cmp(const struct dentry
*dentry
, const unsigned char *ct
, unsigned tcount
)
230 * Be careful about RCU walk racing with rename:
231 * use 'lockless_dereference' to fetch the name pointer.
233 * NOTE! Even if a rename will mean that the length
234 * was not loaded atomically, we don't care. The
235 * RCU walk will check the sequence count eventually,
236 * and catch it. And we won't overrun the buffer,
237 * because we're reading the name pointer atomically,
238 * and a dentry name is guaranteed to be properly
239 * terminated with a NUL byte.
241 * End result: even if 'len' is wrong, we'll exit
242 * early because the data cannot match (there can
243 * be no NUL in the ct/tcount data)
245 const unsigned char *cs
= lockless_dereference(dentry
->d_name
.name
);
247 return dentry_string_cmp(cs
, ct
, tcount
);
250 struct external_name
{
253 struct rcu_head head
;
255 unsigned char name
[];
258 static inline struct external_name
*external_name(struct dentry
*dentry
)
260 return container_of(dentry
->d_name
.name
, struct external_name
, name
[0]);
263 static void __d_free(struct rcu_head
*head
)
265 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
267 kmem_cache_free(dentry_cache
, dentry
);
270 static void __d_free_external(struct rcu_head
*head
)
272 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
273 kfree(external_name(dentry
));
274 kmem_cache_free(dentry_cache
, dentry
);
277 static inline int dname_external(const struct dentry
*dentry
)
279 return dentry
->d_name
.name
!= dentry
->d_iname
;
282 static inline void __d_set_inode_and_type(struct dentry
*dentry
,
288 dentry
->d_inode
= inode
;
289 flags
= READ_ONCE(dentry
->d_flags
);
290 flags
&= ~(DCACHE_ENTRY_TYPE
| DCACHE_FALLTHRU
);
292 WRITE_ONCE(dentry
->d_flags
, flags
);
295 static inline void __d_clear_type_and_inode(struct dentry
*dentry
)
297 unsigned flags
= READ_ONCE(dentry
->d_flags
);
299 flags
&= ~(DCACHE_ENTRY_TYPE
| DCACHE_FALLTHRU
);
300 WRITE_ONCE(dentry
->d_flags
, flags
);
301 dentry
->d_inode
= NULL
;
304 static void dentry_free(struct dentry
*dentry
)
306 WARN_ON(!hlist_unhashed(&dentry
->d_u
.d_alias
));
307 if (unlikely(dname_external(dentry
))) {
308 struct external_name
*p
= external_name(dentry
);
309 if (likely(atomic_dec_and_test(&p
->u
.count
))) {
310 call_rcu(&dentry
->d_u
.d_rcu
, __d_free_external
);
314 /* if dentry was never visible to RCU, immediate free is OK */
315 if (!(dentry
->d_flags
& DCACHE_RCUACCESS
))
316 __d_free(&dentry
->d_u
.d_rcu
);
318 call_rcu(&dentry
->d_u
.d_rcu
, __d_free
);
322 * dentry_rcuwalk_invalidate - invalidate in-progress rcu-walk lookups
323 * @dentry: the target dentry
324 * After this call, in-progress rcu-walk path lookup will fail. This
325 * should be called after unhashing, and after changing d_inode (if
326 * the dentry has not already been unhashed).
328 static inline void dentry_rcuwalk_invalidate(struct dentry
*dentry
)
330 lockdep_assert_held(&dentry
->d_lock
);
331 /* Go through am invalidation barrier */
332 write_seqcount_invalidate(&dentry
->d_seq
);
336 * Release the dentry's inode, using the filesystem
337 * d_iput() operation if defined. Dentry has no refcount
340 static void dentry_iput(struct dentry
* dentry
)
341 __releases(dentry
->d_lock
)
342 __releases(dentry
->d_inode
->i_lock
)
344 struct inode
*inode
= dentry
->d_inode
;
346 __d_clear_type_and_inode(dentry
);
347 hlist_del_init(&dentry
->d_u
.d_alias
);
348 spin_unlock(&dentry
->d_lock
);
349 spin_unlock(&inode
->i_lock
);
351 fsnotify_inoderemove(inode
);
352 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
353 dentry
->d_op
->d_iput(dentry
, inode
);
357 spin_unlock(&dentry
->d_lock
);
362 * Release the dentry's inode, using the filesystem
363 * d_iput() operation if defined. dentry remains in-use.
365 static void dentry_unlink_inode(struct dentry
* dentry
)
366 __releases(dentry
->d_lock
)
367 __releases(dentry
->d_inode
->i_lock
)
369 struct inode
*inode
= dentry
->d_inode
;
371 raw_write_seqcount_begin(&dentry
->d_seq
);
372 __d_clear_type_and_inode(dentry
);
373 hlist_del_init(&dentry
->d_u
.d_alias
);
374 raw_write_seqcount_end(&dentry
->d_seq
);
375 spin_unlock(&dentry
->d_lock
);
376 spin_unlock(&inode
->i_lock
);
378 fsnotify_inoderemove(inode
);
379 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
380 dentry
->d_op
->d_iput(dentry
, inode
);
386 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
387 * is in use - which includes both the "real" per-superblock
388 * LRU list _and_ the DCACHE_SHRINK_LIST use.
390 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
391 * on the shrink list (ie not on the superblock LRU list).
393 * The per-cpu "nr_dentry_unused" counters are updated with
394 * the DCACHE_LRU_LIST bit.
396 * These helper functions make sure we always follow the
397 * rules. d_lock must be held by the caller.
399 #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
400 static void d_lru_add(struct dentry
*dentry
)
402 D_FLAG_VERIFY(dentry
, 0);
403 dentry
->d_flags
|= DCACHE_LRU_LIST
;
404 this_cpu_inc(nr_dentry_unused
);
405 WARN_ON_ONCE(!list_lru_add(&dentry
->d_sb
->s_dentry_lru
, &dentry
->d_lru
));
408 static void d_lru_del(struct dentry
*dentry
)
410 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
411 dentry
->d_flags
&= ~DCACHE_LRU_LIST
;
412 this_cpu_dec(nr_dentry_unused
);
413 WARN_ON_ONCE(!list_lru_del(&dentry
->d_sb
->s_dentry_lru
, &dentry
->d_lru
));
416 static void d_shrink_del(struct dentry
*dentry
)
418 D_FLAG_VERIFY(dentry
, DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
);
419 list_del_init(&dentry
->d_lru
);
420 dentry
->d_flags
&= ~(DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
);
421 this_cpu_dec(nr_dentry_unused
);
424 static void d_shrink_add(struct dentry
*dentry
, struct list_head
*list
)
426 D_FLAG_VERIFY(dentry
, 0);
427 list_add(&dentry
->d_lru
, list
);
428 dentry
->d_flags
|= DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
;
429 this_cpu_inc(nr_dentry_unused
);
433 * These can only be called under the global LRU lock, ie during the
434 * callback for freeing the LRU list. "isolate" removes it from the
435 * LRU lists entirely, while shrink_move moves it to the indicated
438 static void d_lru_isolate(struct list_lru_one
*lru
, struct dentry
*dentry
)
440 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
441 dentry
->d_flags
&= ~DCACHE_LRU_LIST
;
442 this_cpu_dec(nr_dentry_unused
);
443 list_lru_isolate(lru
, &dentry
->d_lru
);
446 static void d_lru_shrink_move(struct list_lru_one
*lru
, struct dentry
*dentry
,
447 struct list_head
*list
)
449 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
450 dentry
->d_flags
|= DCACHE_SHRINK_LIST
;
451 list_lru_isolate_move(lru
, &dentry
->d_lru
, list
);
455 * dentry_lru_(add|del)_list) must be called with d_lock held.
457 static void dentry_lru_add(struct dentry
*dentry
)
459 if (unlikely(!(dentry
->d_flags
& DCACHE_LRU_LIST
)))
464 * d_drop - drop a dentry
465 * @dentry: dentry to drop
467 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
468 * be found through a VFS lookup any more. Note that this is different from
469 * deleting the dentry - d_delete will try to mark the dentry negative if
470 * possible, giving a successful _negative_ lookup, while d_drop will
471 * just make the cache lookup fail.
473 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
474 * reason (NFS timeouts or autofs deletes).
476 * __d_drop requires dentry->d_lock.
478 void __d_drop(struct dentry
*dentry
)
480 if (!d_unhashed(dentry
)) {
481 struct hlist_bl_head
*b
;
483 * Hashed dentries are normally on the dentry hashtable,
484 * with the exception of those newly allocated by
485 * d_obtain_alias, which are always IS_ROOT:
487 if (unlikely(IS_ROOT(dentry
)))
488 b
= &dentry
->d_sb
->s_anon
;
490 b
= d_hash(dentry
->d_parent
, dentry
->d_name
.hash
);
493 __hlist_bl_del(&dentry
->d_hash
);
494 dentry
->d_hash
.pprev
= NULL
;
496 dentry_rcuwalk_invalidate(dentry
);
499 EXPORT_SYMBOL(__d_drop
);
501 void d_drop(struct dentry
*dentry
)
503 spin_lock(&dentry
->d_lock
);
505 spin_unlock(&dentry
->d_lock
);
507 EXPORT_SYMBOL(d_drop
);
509 static inline void dentry_unlist(struct dentry
*dentry
, struct dentry
*parent
)
513 * Inform d_walk() and shrink_dentry_list() that we are no longer
514 * attached to the dentry tree
516 dentry
->d_flags
|= DCACHE_DENTRY_KILLED
;
517 if (unlikely(list_empty(&dentry
->d_child
)))
519 __list_del_entry(&dentry
->d_child
);
521 * Cursors can move around the list of children. While we'd been
522 * a normal list member, it didn't matter - ->d_child.next would've
523 * been updated. However, from now on it won't be and for the
524 * things like d_walk() it might end up with a nasty surprise.
525 * Normally d_walk() doesn't care about cursors moving around -
526 * ->d_lock on parent prevents that and since a cursor has no children
527 * of its own, we get through it without ever unlocking the parent.
528 * There is one exception, though - if we ascend from a child that
529 * gets killed as soon as we unlock it, the next sibling is found
530 * using the value left in its ->d_child.next. And if _that_
531 * pointed to a cursor, and cursor got moved (e.g. by lseek())
532 * before d_walk() regains parent->d_lock, we'll end up skipping
533 * everything the cursor had been moved past.
535 * Solution: make sure that the pointer left behind in ->d_child.next
536 * points to something that won't be moving around. I.e. skip the
539 while (dentry
->d_child
.next
!= &parent
->d_subdirs
) {
540 next
= list_entry(dentry
->d_child
.next
, struct dentry
, d_child
);
541 if (likely(!(next
->d_flags
& DCACHE_DENTRY_CURSOR
)))
543 dentry
->d_child
.next
= next
->d_child
.next
;
547 static void __dentry_kill(struct dentry
*dentry
)
549 struct dentry
*parent
= NULL
;
550 bool can_free
= true;
551 if (!IS_ROOT(dentry
))
552 parent
= dentry
->d_parent
;
555 * The dentry is now unrecoverably dead to the world.
557 lockref_mark_dead(&dentry
->d_lockref
);
560 * inform the fs via d_prune that this dentry is about to be
561 * unhashed and destroyed.
563 if (dentry
->d_flags
& DCACHE_OP_PRUNE
)
564 dentry
->d_op
->d_prune(dentry
);
566 if (dentry
->d_flags
& DCACHE_LRU_LIST
) {
567 if (!(dentry
->d_flags
& DCACHE_SHRINK_LIST
))
570 /* if it was on the hash then remove it */
572 dentry_unlist(dentry
, parent
);
574 spin_unlock(&parent
->d_lock
);
577 * dentry_iput drops the locks, at which point nobody (except
578 * transient RCU lookups) can reach this dentry.
580 BUG_ON(dentry
->d_lockref
.count
> 0);
581 this_cpu_dec(nr_dentry
);
582 if (dentry
->d_op
&& dentry
->d_op
->d_release
)
583 dentry
->d_op
->d_release(dentry
);
585 spin_lock(&dentry
->d_lock
);
586 if (dentry
->d_flags
& DCACHE_SHRINK_LIST
) {
587 dentry
->d_flags
|= DCACHE_MAY_FREE
;
590 spin_unlock(&dentry
->d_lock
);
591 if (likely(can_free
))
596 * Finish off a dentry we've decided to kill.
597 * dentry->d_lock must be held, returns with it unlocked.
598 * If ref is non-zero, then decrement the refcount too.
599 * Returns dentry requiring refcount drop, or NULL if we're done.
601 static struct dentry
*dentry_kill(struct dentry
*dentry
)
602 __releases(dentry
->d_lock
)
604 struct inode
*inode
= dentry
->d_inode
;
605 struct dentry
*parent
= NULL
;
607 if (inode
&& unlikely(!spin_trylock(&inode
->i_lock
)))
610 if (!IS_ROOT(dentry
)) {
611 parent
= dentry
->d_parent
;
612 if (unlikely(!spin_trylock(&parent
->d_lock
))) {
614 spin_unlock(&inode
->i_lock
);
619 __dentry_kill(dentry
);
623 spin_unlock(&dentry
->d_lock
);
625 return dentry
; /* try again with same dentry */
628 static inline struct dentry
*lock_parent(struct dentry
*dentry
)
630 struct dentry
*parent
= dentry
->d_parent
;
633 if (unlikely(dentry
->d_lockref
.count
< 0))
635 if (likely(spin_trylock(&parent
->d_lock
)))
638 spin_unlock(&dentry
->d_lock
);
640 parent
= ACCESS_ONCE(dentry
->d_parent
);
641 spin_lock(&parent
->d_lock
);
643 * We can't blindly lock dentry until we are sure
644 * that we won't violate the locking order.
645 * Any changes of dentry->d_parent must have
646 * been done with parent->d_lock held, so
647 * spin_lock() above is enough of a barrier
648 * for checking if it's still our child.
650 if (unlikely(parent
!= dentry
->d_parent
)) {
651 spin_unlock(&parent
->d_lock
);
655 if (parent
!= dentry
)
656 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
663 * Try to do a lockless dput(), and return whether that was successful.
665 * If unsuccessful, we return false, having already taken the dentry lock.
667 * The caller needs to hold the RCU read lock, so that the dentry is
668 * guaranteed to stay around even if the refcount goes down to zero!
670 static inline bool fast_dput(struct dentry
*dentry
)
673 unsigned int d_flags
;
676 * If we have a d_op->d_delete() operation, we sould not
677 * let the dentry count go to zero, so use "put_or_lock".
679 if (unlikely(dentry
->d_flags
& DCACHE_OP_DELETE
))
680 return lockref_put_or_lock(&dentry
->d_lockref
);
683 * .. otherwise, we can try to just decrement the
684 * lockref optimistically.
686 ret
= lockref_put_return(&dentry
->d_lockref
);
689 * If the lockref_put_return() failed due to the lock being held
690 * by somebody else, the fast path has failed. We will need to
691 * get the lock, and then check the count again.
693 if (unlikely(ret
< 0)) {
694 spin_lock(&dentry
->d_lock
);
695 if (dentry
->d_lockref
.count
> 1) {
696 dentry
->d_lockref
.count
--;
697 spin_unlock(&dentry
->d_lock
);
704 * If we weren't the last ref, we're done.
710 * Careful, careful. The reference count went down
711 * to zero, but we don't hold the dentry lock, so
712 * somebody else could get it again, and do another
713 * dput(), and we need to not race with that.
715 * However, there is a very special and common case
716 * where we don't care, because there is nothing to
717 * do: the dentry is still hashed, it does not have
718 * a 'delete' op, and it's referenced and already on
721 * NOTE! Since we aren't locked, these values are
722 * not "stable". However, it is sufficient that at
723 * some point after we dropped the reference the
724 * dentry was hashed and the flags had the proper
725 * value. Other dentry users may have re-gotten
726 * a reference to the dentry and change that, but
727 * our work is done - we can leave the dentry
728 * around with a zero refcount.
731 d_flags
= ACCESS_ONCE(dentry
->d_flags
);
732 d_flags
&= DCACHE_REFERENCED
| DCACHE_LRU_LIST
| DCACHE_DISCONNECTED
;
734 /* Nothing to do? Dropping the reference was all we needed? */
735 if (d_flags
== (DCACHE_REFERENCED
| DCACHE_LRU_LIST
) && !d_unhashed(dentry
))
739 * Not the fast normal case? Get the lock. We've already decremented
740 * the refcount, but we'll need to re-check the situation after
743 spin_lock(&dentry
->d_lock
);
746 * Did somebody else grab a reference to it in the meantime, and
747 * we're no longer the last user after all? Alternatively, somebody
748 * else could have killed it and marked it dead. Either way, we
749 * don't need to do anything else.
751 if (dentry
->d_lockref
.count
) {
752 spin_unlock(&dentry
->d_lock
);
757 * Re-get the reference we optimistically dropped. We hold the
758 * lock, and we just tested that it was zero, so we can just
761 dentry
->d_lockref
.count
= 1;
769 * This is complicated by the fact that we do not want to put
770 * dentries that are no longer on any hash chain on the unused
771 * list: we'd much rather just get rid of them immediately.
773 * However, that implies that we have to traverse the dentry
774 * tree upwards to the parents which might _also_ now be
775 * scheduled for deletion (it may have been only waiting for
776 * its last child to go away).
778 * This tail recursion is done by hand as we don't want to depend
779 * on the compiler to always get this right (gcc generally doesn't).
780 * Real recursion would eat up our stack space.
784 * dput - release a dentry
785 * @dentry: dentry to release
787 * Release a dentry. This will drop the usage count and if appropriate
788 * call the dentry unlink method as well as removing it from the queues and
789 * releasing its resources. If the parent dentries were scheduled for release
790 * they too may now get deleted.
792 void dput(struct dentry
*dentry
)
794 if (unlikely(!dentry
))
799 if (likely(fast_dput(dentry
))) {
804 /* Slow case: now with the dentry lock held */
807 WARN_ON(d_in_lookup(dentry
));
809 /* Unreachable? Get rid of it */
810 if (unlikely(d_unhashed(dentry
)))
813 if (unlikely(dentry
->d_flags
& DCACHE_DISCONNECTED
))
816 if (unlikely(dentry
->d_flags
& DCACHE_OP_DELETE
)) {
817 if (dentry
->d_op
->d_delete(dentry
))
821 if (!(dentry
->d_flags
& DCACHE_REFERENCED
))
822 dentry
->d_flags
|= DCACHE_REFERENCED
;
823 dentry_lru_add(dentry
);
825 dentry
->d_lockref
.count
--;
826 spin_unlock(&dentry
->d_lock
);
830 dentry
= dentry_kill(dentry
);
837 /* This must be called with d_lock held */
838 static inline void __dget_dlock(struct dentry
*dentry
)
840 dentry
->d_lockref
.count
++;
843 static inline void __dget(struct dentry
*dentry
)
845 lockref_get(&dentry
->d_lockref
);
848 struct dentry
*dget_parent(struct dentry
*dentry
)
854 * Do optimistic parent lookup without any
858 ret
= ACCESS_ONCE(dentry
->d_parent
);
859 gotref
= lockref_get_not_zero(&ret
->d_lockref
);
861 if (likely(gotref
)) {
862 if (likely(ret
== ACCESS_ONCE(dentry
->d_parent
)))
869 * Don't need rcu_dereference because we re-check it was correct under
873 ret
= dentry
->d_parent
;
874 spin_lock(&ret
->d_lock
);
875 if (unlikely(ret
!= dentry
->d_parent
)) {
876 spin_unlock(&ret
->d_lock
);
881 BUG_ON(!ret
->d_lockref
.count
);
882 ret
->d_lockref
.count
++;
883 spin_unlock(&ret
->d_lock
);
886 EXPORT_SYMBOL(dget_parent
);
889 * d_find_alias - grab a hashed alias of inode
890 * @inode: inode in question
892 * If inode has a hashed alias, or is a directory and has any alias,
893 * acquire the reference to alias and return it. Otherwise return NULL.
894 * Notice that if inode is a directory there can be only one alias and
895 * it can be unhashed only if it has no children, or if it is the root
896 * of a filesystem, or if the directory was renamed and d_revalidate
897 * was the first vfs operation to notice.
899 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
900 * any other hashed alias over that one.
902 static struct dentry
*__d_find_alias(struct inode
*inode
)
904 struct dentry
*alias
, *discon_alias
;
908 hlist_for_each_entry(alias
, &inode
->i_dentry
, d_u
.d_alias
) {
909 spin_lock(&alias
->d_lock
);
910 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
911 if (IS_ROOT(alias
) &&
912 (alias
->d_flags
& DCACHE_DISCONNECTED
)) {
913 discon_alias
= alias
;
916 spin_unlock(&alias
->d_lock
);
920 spin_unlock(&alias
->d_lock
);
923 alias
= discon_alias
;
924 spin_lock(&alias
->d_lock
);
925 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
927 spin_unlock(&alias
->d_lock
);
930 spin_unlock(&alias
->d_lock
);
936 struct dentry
*d_find_alias(struct inode
*inode
)
938 struct dentry
*de
= NULL
;
940 if (!hlist_empty(&inode
->i_dentry
)) {
941 spin_lock(&inode
->i_lock
);
942 de
= __d_find_alias(inode
);
943 spin_unlock(&inode
->i_lock
);
947 EXPORT_SYMBOL(d_find_alias
);
950 * Try to kill dentries associated with this inode.
951 * WARNING: you must own a reference to inode.
953 void d_prune_aliases(struct inode
*inode
)
955 struct dentry
*dentry
;
957 spin_lock(&inode
->i_lock
);
958 hlist_for_each_entry(dentry
, &inode
->i_dentry
, d_u
.d_alias
) {
959 spin_lock(&dentry
->d_lock
);
960 if (!dentry
->d_lockref
.count
) {
961 struct dentry
*parent
= lock_parent(dentry
);
962 if (likely(!dentry
->d_lockref
.count
)) {
963 __dentry_kill(dentry
);
968 spin_unlock(&parent
->d_lock
);
970 spin_unlock(&dentry
->d_lock
);
972 spin_unlock(&inode
->i_lock
);
974 EXPORT_SYMBOL(d_prune_aliases
);
976 static void shrink_dentry_list(struct list_head
*list
)
978 struct dentry
*dentry
, *parent
;
980 while (!list_empty(list
)) {
982 dentry
= list_entry(list
->prev
, struct dentry
, d_lru
);
983 spin_lock(&dentry
->d_lock
);
984 parent
= lock_parent(dentry
);
987 * The dispose list is isolated and dentries are not accounted
988 * to the LRU here, so we can simply remove it from the list
989 * here regardless of whether it is referenced or not.
991 d_shrink_del(dentry
);
994 * We found an inuse dentry which was not removed from
995 * the LRU because of laziness during lookup. Do not free it.
997 if (dentry
->d_lockref
.count
> 0) {
998 spin_unlock(&dentry
->d_lock
);
1000 spin_unlock(&parent
->d_lock
);
1005 if (unlikely(dentry
->d_flags
& DCACHE_DENTRY_KILLED
)) {
1006 bool can_free
= dentry
->d_flags
& DCACHE_MAY_FREE
;
1007 spin_unlock(&dentry
->d_lock
);
1009 spin_unlock(&parent
->d_lock
);
1011 dentry_free(dentry
);
1015 inode
= dentry
->d_inode
;
1016 if (inode
&& unlikely(!spin_trylock(&inode
->i_lock
))) {
1017 d_shrink_add(dentry
, list
);
1018 spin_unlock(&dentry
->d_lock
);
1020 spin_unlock(&parent
->d_lock
);
1024 __dentry_kill(dentry
);
1027 * We need to prune ancestors too. This is necessary to prevent
1028 * quadratic behavior of shrink_dcache_parent(), but is also
1029 * expected to be beneficial in reducing dentry cache
1033 while (dentry
&& !lockref_put_or_lock(&dentry
->d_lockref
)) {
1034 parent
= lock_parent(dentry
);
1035 if (dentry
->d_lockref
.count
!= 1) {
1036 dentry
->d_lockref
.count
--;
1037 spin_unlock(&dentry
->d_lock
);
1039 spin_unlock(&parent
->d_lock
);
1042 inode
= dentry
->d_inode
; /* can't be NULL */
1043 if (unlikely(!spin_trylock(&inode
->i_lock
))) {
1044 spin_unlock(&dentry
->d_lock
);
1046 spin_unlock(&parent
->d_lock
);
1050 __dentry_kill(dentry
);
1056 static enum lru_status
dentry_lru_isolate(struct list_head
*item
,
1057 struct list_lru_one
*lru
, spinlock_t
*lru_lock
, void *arg
)
1059 struct list_head
*freeable
= arg
;
1060 struct dentry
*dentry
= container_of(item
, struct dentry
, d_lru
);
1064 * we are inverting the lru lock/dentry->d_lock here,
1065 * so use a trylock. If we fail to get the lock, just skip
1068 if (!spin_trylock(&dentry
->d_lock
))
1072 * Referenced dentries are still in use. If they have active
1073 * counts, just remove them from the LRU. Otherwise give them
1074 * another pass through the LRU.
1076 if (dentry
->d_lockref
.count
) {
1077 d_lru_isolate(lru
, dentry
);
1078 spin_unlock(&dentry
->d_lock
);
1082 if (dentry
->d_flags
& DCACHE_REFERENCED
) {
1083 dentry
->d_flags
&= ~DCACHE_REFERENCED
;
1084 spin_unlock(&dentry
->d_lock
);
1087 * The list move itself will be made by the common LRU code. At
1088 * this point, we've dropped the dentry->d_lock but keep the
1089 * lru lock. This is safe to do, since every list movement is
1090 * protected by the lru lock even if both locks are held.
1092 * This is guaranteed by the fact that all LRU management
1093 * functions are intermediated by the LRU API calls like
1094 * list_lru_add and list_lru_del. List movement in this file
1095 * only ever occur through this functions or through callbacks
1096 * like this one, that are called from the LRU API.
1098 * The only exceptions to this are functions like
1099 * shrink_dentry_list, and code that first checks for the
1100 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1101 * operating only with stack provided lists after they are
1102 * properly isolated from the main list. It is thus, always a
1108 d_lru_shrink_move(lru
, dentry
, freeable
);
1109 spin_unlock(&dentry
->d_lock
);
1115 * prune_dcache_sb - shrink the dcache
1117 * @sc: shrink control, passed to list_lru_shrink_walk()
1119 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1120 * is done when we need more memory and called from the superblock shrinker
1123 * This function may fail to free any resources if all the dentries are in
1126 long prune_dcache_sb(struct super_block
*sb
, struct shrink_control
*sc
)
1131 freed
= list_lru_shrink_walk(&sb
->s_dentry_lru
, sc
,
1132 dentry_lru_isolate
, &dispose
);
1133 shrink_dentry_list(&dispose
);
1137 static enum lru_status
dentry_lru_isolate_shrink(struct list_head
*item
,
1138 struct list_lru_one
*lru
, spinlock_t
*lru_lock
, void *arg
)
1140 struct list_head
*freeable
= arg
;
1141 struct dentry
*dentry
= container_of(item
, struct dentry
, d_lru
);
1144 * we are inverting the lru lock/dentry->d_lock here,
1145 * so use a trylock. If we fail to get the lock, just skip
1148 if (!spin_trylock(&dentry
->d_lock
))
1151 d_lru_shrink_move(lru
, dentry
, freeable
);
1152 spin_unlock(&dentry
->d_lock
);
1159 * shrink_dcache_sb - shrink dcache for a superblock
1162 * Shrink the dcache for the specified super block. This is used to free
1163 * the dcache before unmounting a file system.
1165 void shrink_dcache_sb(struct super_block
*sb
)
1172 freed
= list_lru_walk(&sb
->s_dentry_lru
,
1173 dentry_lru_isolate_shrink
, &dispose
, UINT_MAX
);
1175 this_cpu_sub(nr_dentry_unused
, freed
);
1176 shrink_dentry_list(&dispose
);
1177 } while (freed
> 0);
1179 EXPORT_SYMBOL(shrink_dcache_sb
);
1182 * enum d_walk_ret - action to talke during tree walk
1183 * @D_WALK_CONTINUE: contrinue walk
1184 * @D_WALK_QUIT: quit walk
1185 * @D_WALK_NORETRY: quit when retry is needed
1186 * @D_WALK_SKIP: skip this dentry and its children
1196 * d_walk - walk the dentry tree
1197 * @parent: start of walk
1198 * @data: data passed to @enter() and @finish()
1199 * @enter: callback when first entering the dentry
1200 * @finish: callback when successfully finished the walk
1202 * The @enter() and @finish() callbacks are called with d_lock held.
1204 static void d_walk(struct dentry
*parent
, void *data
,
1205 enum d_walk_ret (*enter
)(void *, struct dentry
*),
1206 void (*finish
)(void *))
1208 struct dentry
*this_parent
;
1209 struct list_head
*next
;
1211 enum d_walk_ret ret
;
1215 read_seqbegin_or_lock(&rename_lock
, &seq
);
1216 this_parent
= parent
;
1217 spin_lock(&this_parent
->d_lock
);
1219 ret
= enter(data
, this_parent
);
1221 case D_WALK_CONTINUE
:
1226 case D_WALK_NORETRY
:
1231 next
= this_parent
->d_subdirs
.next
;
1233 while (next
!= &this_parent
->d_subdirs
) {
1234 struct list_head
*tmp
= next
;
1235 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_child
);
1238 if (unlikely(dentry
->d_flags
& DCACHE_DENTRY_CURSOR
))
1241 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1243 ret
= enter(data
, dentry
);
1245 case D_WALK_CONTINUE
:
1248 spin_unlock(&dentry
->d_lock
);
1250 case D_WALK_NORETRY
:
1254 spin_unlock(&dentry
->d_lock
);
1258 if (!list_empty(&dentry
->d_subdirs
)) {
1259 spin_unlock(&this_parent
->d_lock
);
1260 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
1261 this_parent
= dentry
;
1262 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
1265 spin_unlock(&dentry
->d_lock
);
1268 * All done at this level ... ascend and resume the search.
1272 if (this_parent
!= parent
) {
1273 struct dentry
*child
= this_parent
;
1274 this_parent
= child
->d_parent
;
1276 spin_unlock(&child
->d_lock
);
1277 spin_lock(&this_parent
->d_lock
);
1279 /* might go back up the wrong parent if we have had a rename. */
1280 if (need_seqretry(&rename_lock
, seq
))
1282 /* go into the first sibling still alive */
1284 next
= child
->d_child
.next
;
1285 if (next
== &this_parent
->d_subdirs
)
1287 child
= list_entry(next
, struct dentry
, d_child
);
1288 } while (unlikely(child
->d_flags
& DCACHE_DENTRY_KILLED
));
1292 if (need_seqretry(&rename_lock
, seq
))
1299 spin_unlock(&this_parent
->d_lock
);
1300 done_seqretry(&rename_lock
, seq
);
1304 spin_unlock(&this_parent
->d_lock
);
1314 * Search for at least 1 mount point in the dentry's subdirs.
1315 * We descend to the next level whenever the d_subdirs
1316 * list is non-empty and continue searching.
1319 static enum d_walk_ret
check_mount(void *data
, struct dentry
*dentry
)
1322 if (d_mountpoint(dentry
)) {
1326 return D_WALK_CONTINUE
;
1330 * have_submounts - check for mounts over a dentry
1331 * @parent: dentry to check.
1333 * Return true if the parent or its subdirectories contain
1336 int have_submounts(struct dentry
*parent
)
1340 d_walk(parent
, &ret
, check_mount
, NULL
);
1344 EXPORT_SYMBOL(have_submounts
);
1347 * Called by mount code to set a mountpoint and check if the mountpoint is
1348 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1349 * subtree can become unreachable).
1351 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1352 * this reason take rename_lock and d_lock on dentry and ancestors.
1354 int d_set_mounted(struct dentry
*dentry
)
1358 write_seqlock(&rename_lock
);
1359 for (p
= dentry
->d_parent
; !IS_ROOT(p
); p
= p
->d_parent
) {
1360 /* Need exclusion wrt. d_invalidate() */
1361 spin_lock(&p
->d_lock
);
1362 if (unlikely(d_unhashed(p
))) {
1363 spin_unlock(&p
->d_lock
);
1366 spin_unlock(&p
->d_lock
);
1368 spin_lock(&dentry
->d_lock
);
1369 if (!d_unlinked(dentry
)) {
1370 dentry
->d_flags
|= DCACHE_MOUNTED
;
1373 spin_unlock(&dentry
->d_lock
);
1375 write_sequnlock(&rename_lock
);
1380 * Search the dentry child list of the specified parent,
1381 * and move any unused dentries to the end of the unused
1382 * list for prune_dcache(). We descend to the next level
1383 * whenever the d_subdirs list is non-empty and continue
1386 * It returns zero iff there are no unused children,
1387 * otherwise it returns the number of children moved to
1388 * the end of the unused list. This may not be the total
1389 * number of unused children, because select_parent can
1390 * drop the lock and return early due to latency
1394 struct select_data
{
1395 struct dentry
*start
;
1396 struct list_head dispose
;
1400 static enum d_walk_ret
select_collect(void *_data
, struct dentry
*dentry
)
1402 struct select_data
*data
= _data
;
1403 enum d_walk_ret ret
= D_WALK_CONTINUE
;
1405 if (data
->start
== dentry
)
1408 if (dentry
->d_flags
& DCACHE_SHRINK_LIST
) {
1411 if (dentry
->d_flags
& DCACHE_LRU_LIST
)
1413 if (!dentry
->d_lockref
.count
) {
1414 d_shrink_add(dentry
, &data
->dispose
);
1419 * We can return to the caller if we have found some (this
1420 * ensures forward progress). We'll be coming back to find
1423 if (!list_empty(&data
->dispose
))
1424 ret
= need_resched() ? D_WALK_QUIT
: D_WALK_NORETRY
;
1430 * shrink_dcache_parent - prune dcache
1431 * @parent: parent of entries to prune
1433 * Prune the dcache to remove unused children of the parent dentry.
1435 void shrink_dcache_parent(struct dentry
*parent
)
1438 struct select_data data
;
1440 INIT_LIST_HEAD(&data
.dispose
);
1441 data
.start
= parent
;
1444 d_walk(parent
, &data
, select_collect
, NULL
);
1448 shrink_dentry_list(&data
.dispose
);
1452 EXPORT_SYMBOL(shrink_dcache_parent
);
1454 static enum d_walk_ret
umount_check(void *_data
, struct dentry
*dentry
)
1456 /* it has busy descendents; complain about those instead */
1457 if (!list_empty(&dentry
->d_subdirs
))
1458 return D_WALK_CONTINUE
;
1460 /* root with refcount 1 is fine */
1461 if (dentry
== _data
&& dentry
->d_lockref
.count
== 1)
1462 return D_WALK_CONTINUE
;
1464 printk(KERN_ERR
"BUG: Dentry %p{i=%lx,n=%pd} "
1465 " still in use (%d) [unmount of %s %s]\n",
1468 dentry
->d_inode
->i_ino
: 0UL,
1470 dentry
->d_lockref
.count
,
1471 dentry
->d_sb
->s_type
->name
,
1472 dentry
->d_sb
->s_id
);
1474 return D_WALK_CONTINUE
;
1477 static void do_one_tree(struct dentry
*dentry
)
1479 shrink_dcache_parent(dentry
);
1480 d_walk(dentry
, dentry
, umount_check
, NULL
);
1486 * destroy the dentries attached to a superblock on unmounting
1488 void shrink_dcache_for_umount(struct super_block
*sb
)
1490 struct dentry
*dentry
;
1492 WARN(down_read_trylock(&sb
->s_umount
), "s_umount should've been locked");
1494 dentry
= sb
->s_root
;
1496 do_one_tree(dentry
);
1498 while (!hlist_bl_empty(&sb
->s_anon
)) {
1499 dentry
= dget(hlist_bl_entry(hlist_bl_first(&sb
->s_anon
), struct dentry
, d_hash
));
1500 do_one_tree(dentry
);
1504 struct detach_data
{
1505 struct select_data select
;
1506 struct dentry
*mountpoint
;
1508 static enum d_walk_ret
detach_and_collect(void *_data
, struct dentry
*dentry
)
1510 struct detach_data
*data
= _data
;
1512 if (d_mountpoint(dentry
)) {
1513 __dget_dlock(dentry
);
1514 data
->mountpoint
= dentry
;
1518 return select_collect(&data
->select
, dentry
);
1521 static void check_and_drop(void *_data
)
1523 struct detach_data
*data
= _data
;
1525 if (!data
->mountpoint
&& !data
->select
.found
)
1526 __d_drop(data
->select
.start
);
1530 * d_invalidate - detach submounts, prune dcache, and drop
1531 * @dentry: dentry to invalidate (aka detach, prune and drop)
1535 * The final d_drop is done as an atomic operation relative to
1536 * rename_lock ensuring there are no races with d_set_mounted. This
1537 * ensures there are no unhashed dentries on the path to a mountpoint.
1539 void d_invalidate(struct dentry
*dentry
)
1542 * If it's already been dropped, return OK.
1544 spin_lock(&dentry
->d_lock
);
1545 if (d_unhashed(dentry
)) {
1546 spin_unlock(&dentry
->d_lock
);
1549 spin_unlock(&dentry
->d_lock
);
1551 /* Negative dentries can be dropped without further checks */
1552 if (!dentry
->d_inode
) {
1558 struct detach_data data
;
1560 data
.mountpoint
= NULL
;
1561 INIT_LIST_HEAD(&data
.select
.dispose
);
1562 data
.select
.start
= dentry
;
1563 data
.select
.found
= 0;
1565 d_walk(dentry
, &data
, detach_and_collect
, check_and_drop
);
1567 if (data
.select
.found
)
1568 shrink_dentry_list(&data
.select
.dispose
);
1570 if (data
.mountpoint
) {
1571 detach_mounts(data
.mountpoint
);
1572 dput(data
.mountpoint
);
1575 if (!data
.mountpoint
&& !data
.select
.found
)
1581 EXPORT_SYMBOL(d_invalidate
);
1584 * __d_alloc - allocate a dcache entry
1585 * @sb: filesystem it will belong to
1586 * @name: qstr of the name
1588 * Allocates a dentry. It returns %NULL if there is insufficient memory
1589 * available. On a success the dentry is returned. The name passed in is
1590 * copied and the copy passed in may be reused after this call.
1593 struct dentry
*__d_alloc(struct super_block
*sb
, const struct qstr
*name
)
1595 struct dentry
*dentry
;
1598 dentry
= kmem_cache_alloc(dentry_cache
, GFP_KERNEL
);
1603 * We guarantee that the inline name is always NUL-terminated.
1604 * This way the memcpy() done by the name switching in rename
1605 * will still always have a NUL at the end, even if we might
1606 * be overwriting an internal NUL character
1608 dentry
->d_iname
[DNAME_INLINE_LEN
-1] = 0;
1609 if (unlikely(!name
)) {
1610 static const struct qstr anon
= QSTR_INIT("/", 1);
1612 dname
= dentry
->d_iname
;
1613 } else if (name
->len
> DNAME_INLINE_LEN
-1) {
1614 size_t size
= offsetof(struct external_name
, name
[1]);
1615 struct external_name
*p
= kmalloc(size
+ name
->len
,
1616 GFP_KERNEL_ACCOUNT
);
1618 kmem_cache_free(dentry_cache
, dentry
);
1621 atomic_set(&p
->u
.count
, 1);
1623 if (IS_ENABLED(CONFIG_DCACHE_WORD_ACCESS
))
1624 kasan_unpoison_shadow(dname
,
1625 round_up(name
->len
+ 1, sizeof(unsigned long)));
1627 dname
= dentry
->d_iname
;
1630 dentry
->d_name
.len
= name
->len
;
1631 dentry
->d_name
.hash
= name
->hash
;
1632 memcpy(dname
, name
->name
, name
->len
);
1633 dname
[name
->len
] = 0;
1635 /* Make sure we always see the terminating NUL character */
1637 dentry
->d_name
.name
= dname
;
1639 dentry
->d_lockref
.count
= 1;
1640 dentry
->d_flags
= 0;
1641 spin_lock_init(&dentry
->d_lock
);
1642 seqcount_init(&dentry
->d_seq
);
1643 dentry
->d_inode
= NULL
;
1644 dentry
->d_parent
= dentry
;
1646 dentry
->d_op
= NULL
;
1647 dentry
->d_fsdata
= NULL
;
1648 INIT_HLIST_BL_NODE(&dentry
->d_hash
);
1649 INIT_LIST_HEAD(&dentry
->d_lru
);
1650 INIT_LIST_HEAD(&dentry
->d_subdirs
);
1651 INIT_HLIST_NODE(&dentry
->d_u
.d_alias
);
1652 INIT_LIST_HEAD(&dentry
->d_child
);
1653 d_set_d_op(dentry
, dentry
->d_sb
->s_d_op
);
1655 this_cpu_inc(nr_dentry
);
1661 * d_alloc - allocate a dcache entry
1662 * @parent: parent of entry to allocate
1663 * @name: qstr of the name
1665 * Allocates a dentry. It returns %NULL if there is insufficient memory
1666 * available. On a success the dentry is returned. The name passed in is
1667 * copied and the copy passed in may be reused after this call.
1669 struct dentry
*d_alloc(struct dentry
* parent
, const struct qstr
*name
)
1671 struct dentry
*dentry
= __d_alloc(parent
->d_sb
, name
);
1674 dentry
->d_flags
|= DCACHE_RCUACCESS
;
1675 spin_lock(&parent
->d_lock
);
1677 * don't need child lock because it is not subject
1678 * to concurrency here
1680 __dget_dlock(parent
);
1681 dentry
->d_parent
= parent
;
1682 list_add(&dentry
->d_child
, &parent
->d_subdirs
);
1683 spin_unlock(&parent
->d_lock
);
1687 EXPORT_SYMBOL(d_alloc
);
1689 struct dentry
*d_alloc_cursor(struct dentry
* parent
)
1691 struct dentry
*dentry
= __d_alloc(parent
->d_sb
, NULL
);
1693 dentry
->d_flags
|= DCACHE_RCUACCESS
| DCACHE_DENTRY_CURSOR
;
1694 dentry
->d_parent
= dget(parent
);
1700 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1701 * @sb: the superblock
1702 * @name: qstr of the name
1704 * For a filesystem that just pins its dentries in memory and never
1705 * performs lookups at all, return an unhashed IS_ROOT dentry.
1707 struct dentry
*d_alloc_pseudo(struct super_block
*sb
, const struct qstr
*name
)
1709 return __d_alloc(sb
, name
);
1711 EXPORT_SYMBOL(d_alloc_pseudo
);
1713 struct dentry
*d_alloc_name(struct dentry
*parent
, const char *name
)
1718 q
.hash_len
= hashlen_string(name
);
1719 return d_alloc(parent
, &q
);
1721 EXPORT_SYMBOL(d_alloc_name
);
1723 void d_set_d_op(struct dentry
*dentry
, const struct dentry_operations
*op
)
1725 WARN_ON_ONCE(dentry
->d_op
);
1726 WARN_ON_ONCE(dentry
->d_flags
& (DCACHE_OP_HASH
|
1728 DCACHE_OP_REVALIDATE
|
1729 DCACHE_OP_WEAK_REVALIDATE
|
1731 DCACHE_OP_SELECT_INODE
|
1737 dentry
->d_flags
|= DCACHE_OP_HASH
;
1739 dentry
->d_flags
|= DCACHE_OP_COMPARE
;
1740 if (op
->d_revalidate
)
1741 dentry
->d_flags
|= DCACHE_OP_REVALIDATE
;
1742 if (op
->d_weak_revalidate
)
1743 dentry
->d_flags
|= DCACHE_OP_WEAK_REVALIDATE
;
1745 dentry
->d_flags
|= DCACHE_OP_DELETE
;
1747 dentry
->d_flags
|= DCACHE_OP_PRUNE
;
1748 if (op
->d_select_inode
)
1749 dentry
->d_flags
|= DCACHE_OP_SELECT_INODE
;
1751 dentry
->d_flags
|= DCACHE_OP_REAL
;
1754 EXPORT_SYMBOL(d_set_d_op
);
1758 * d_set_fallthru - Mark a dentry as falling through to a lower layer
1759 * @dentry - The dentry to mark
1761 * Mark a dentry as falling through to the lower layer (as set with
1762 * d_pin_lower()). This flag may be recorded on the medium.
1764 void d_set_fallthru(struct dentry
*dentry
)
1766 spin_lock(&dentry
->d_lock
);
1767 dentry
->d_flags
|= DCACHE_FALLTHRU
;
1768 spin_unlock(&dentry
->d_lock
);
1770 EXPORT_SYMBOL(d_set_fallthru
);
1772 static unsigned d_flags_for_inode(struct inode
*inode
)
1774 unsigned add_flags
= DCACHE_REGULAR_TYPE
;
1777 return DCACHE_MISS_TYPE
;
1779 if (S_ISDIR(inode
->i_mode
)) {
1780 add_flags
= DCACHE_DIRECTORY_TYPE
;
1781 if (unlikely(!(inode
->i_opflags
& IOP_LOOKUP
))) {
1782 if (unlikely(!inode
->i_op
->lookup
))
1783 add_flags
= DCACHE_AUTODIR_TYPE
;
1785 inode
->i_opflags
|= IOP_LOOKUP
;
1787 goto type_determined
;
1790 if (unlikely(!(inode
->i_opflags
& IOP_NOFOLLOW
))) {
1791 if (unlikely(inode
->i_op
->get_link
)) {
1792 add_flags
= DCACHE_SYMLINK_TYPE
;
1793 goto type_determined
;
1795 inode
->i_opflags
|= IOP_NOFOLLOW
;
1798 if (unlikely(!S_ISREG(inode
->i_mode
)))
1799 add_flags
= DCACHE_SPECIAL_TYPE
;
1802 if (unlikely(IS_AUTOMOUNT(inode
)))
1803 add_flags
|= DCACHE_NEED_AUTOMOUNT
;
1807 static void __d_instantiate(struct dentry
*dentry
, struct inode
*inode
)
1809 unsigned add_flags
= d_flags_for_inode(inode
);
1810 WARN_ON(d_in_lookup(dentry
));
1812 spin_lock(&dentry
->d_lock
);
1813 hlist_add_head(&dentry
->d_u
.d_alias
, &inode
->i_dentry
);
1814 raw_write_seqcount_begin(&dentry
->d_seq
);
1815 __d_set_inode_and_type(dentry
, inode
, add_flags
);
1816 raw_write_seqcount_end(&dentry
->d_seq
);
1817 fsnotify_update_flags(dentry
);
1818 spin_unlock(&dentry
->d_lock
);
1822 * d_instantiate - fill in inode information for a dentry
1823 * @entry: dentry to complete
1824 * @inode: inode to attach to this dentry
1826 * Fill in inode information in the entry.
1828 * This turns negative dentries into productive full members
1831 * NOTE! This assumes that the inode count has been incremented
1832 * (or otherwise set) by the caller to indicate that it is now
1833 * in use by the dcache.
1836 void d_instantiate(struct dentry
*entry
, struct inode
* inode
)
1838 BUG_ON(!hlist_unhashed(&entry
->d_u
.d_alias
));
1840 security_d_instantiate(entry
, inode
);
1841 spin_lock(&inode
->i_lock
);
1842 __d_instantiate(entry
, inode
);
1843 spin_unlock(&inode
->i_lock
);
1846 EXPORT_SYMBOL(d_instantiate
);
1849 * d_instantiate_no_diralias - instantiate a non-aliased dentry
1850 * @entry: dentry to complete
1851 * @inode: inode to attach to this dentry
1853 * Fill in inode information in the entry. If a directory alias is found, then
1854 * return an error (and drop inode). Together with d_materialise_unique() this
1855 * guarantees that a directory inode may never have more than one alias.
1857 int d_instantiate_no_diralias(struct dentry
*entry
, struct inode
*inode
)
1859 BUG_ON(!hlist_unhashed(&entry
->d_u
.d_alias
));
1861 security_d_instantiate(entry
, inode
);
1862 spin_lock(&inode
->i_lock
);
1863 if (S_ISDIR(inode
->i_mode
) && !hlist_empty(&inode
->i_dentry
)) {
1864 spin_unlock(&inode
->i_lock
);
1868 __d_instantiate(entry
, inode
);
1869 spin_unlock(&inode
->i_lock
);
1873 EXPORT_SYMBOL(d_instantiate_no_diralias
);
1875 struct dentry
*d_make_root(struct inode
*root_inode
)
1877 struct dentry
*res
= NULL
;
1880 res
= __d_alloc(root_inode
->i_sb
, NULL
);
1882 d_instantiate(res
, root_inode
);
1888 EXPORT_SYMBOL(d_make_root
);
1890 static struct dentry
* __d_find_any_alias(struct inode
*inode
)
1892 struct dentry
*alias
;
1894 if (hlist_empty(&inode
->i_dentry
))
1896 alias
= hlist_entry(inode
->i_dentry
.first
, struct dentry
, d_u
.d_alias
);
1902 * d_find_any_alias - find any alias for a given inode
1903 * @inode: inode to find an alias for
1905 * If any aliases exist for the given inode, take and return a
1906 * reference for one of them. If no aliases exist, return %NULL.
1908 struct dentry
*d_find_any_alias(struct inode
*inode
)
1912 spin_lock(&inode
->i_lock
);
1913 de
= __d_find_any_alias(inode
);
1914 spin_unlock(&inode
->i_lock
);
1917 EXPORT_SYMBOL(d_find_any_alias
);
1919 static struct dentry
*__d_obtain_alias(struct inode
*inode
, int disconnected
)
1926 return ERR_PTR(-ESTALE
);
1928 return ERR_CAST(inode
);
1930 res
= d_find_any_alias(inode
);
1934 tmp
= __d_alloc(inode
->i_sb
, NULL
);
1936 res
= ERR_PTR(-ENOMEM
);
1940 security_d_instantiate(tmp
, inode
);
1941 spin_lock(&inode
->i_lock
);
1942 res
= __d_find_any_alias(inode
);
1944 spin_unlock(&inode
->i_lock
);
1949 /* attach a disconnected dentry */
1950 add_flags
= d_flags_for_inode(inode
);
1953 add_flags
|= DCACHE_DISCONNECTED
;
1955 spin_lock(&tmp
->d_lock
);
1956 __d_set_inode_and_type(tmp
, inode
, add_flags
);
1957 hlist_add_head(&tmp
->d_u
.d_alias
, &inode
->i_dentry
);
1958 hlist_bl_lock(&tmp
->d_sb
->s_anon
);
1959 hlist_bl_add_head(&tmp
->d_hash
, &tmp
->d_sb
->s_anon
);
1960 hlist_bl_unlock(&tmp
->d_sb
->s_anon
);
1961 spin_unlock(&tmp
->d_lock
);
1962 spin_unlock(&inode
->i_lock
);
1972 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
1973 * @inode: inode to allocate the dentry for
1975 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1976 * similar open by handle operations. The returned dentry may be anonymous,
1977 * or may have a full name (if the inode was already in the cache).
1979 * When called on a directory inode, we must ensure that the inode only ever
1980 * has one dentry. If a dentry is found, that is returned instead of
1981 * allocating a new one.
1983 * On successful return, the reference to the inode has been transferred
1984 * to the dentry. In case of an error the reference on the inode is released.
1985 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1986 * be passed in and the error will be propagated to the return value,
1987 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1989 struct dentry
*d_obtain_alias(struct inode
*inode
)
1991 return __d_obtain_alias(inode
, 1);
1993 EXPORT_SYMBOL(d_obtain_alias
);
1996 * d_obtain_root - find or allocate a dentry for a given inode
1997 * @inode: inode to allocate the dentry for
1999 * Obtain an IS_ROOT dentry for the root of a filesystem.
2001 * We must ensure that directory inodes only ever have one dentry. If a
2002 * dentry is found, that is returned instead of allocating a new one.
2004 * On successful return, the reference to the inode has been transferred
2005 * to the dentry. In case of an error the reference on the inode is
2006 * released. A %NULL or IS_ERR inode may be passed in and will be the
2007 * error will be propagate to the return value, with a %NULL @inode
2008 * replaced by ERR_PTR(-ESTALE).
2010 struct dentry
*d_obtain_root(struct inode
*inode
)
2012 return __d_obtain_alias(inode
, 0);
2014 EXPORT_SYMBOL(d_obtain_root
);
2017 * d_add_ci - lookup or allocate new dentry with case-exact name
2018 * @inode: the inode case-insensitive lookup has found
2019 * @dentry: the negative dentry that was passed to the parent's lookup func
2020 * @name: the case-exact name to be associated with the returned dentry
2022 * This is to avoid filling the dcache with case-insensitive names to the
2023 * same inode, only the actual correct case is stored in the dcache for
2024 * case-insensitive filesystems.
2026 * For a case-insensitive lookup match and if the the case-exact dentry
2027 * already exists in in the dcache, use it and return it.
2029 * If no entry exists with the exact case name, allocate new dentry with
2030 * the exact case, and return the spliced entry.
2032 struct dentry
*d_add_ci(struct dentry
*dentry
, struct inode
*inode
,
2035 struct dentry
*found
, *res
;
2038 * First check if a dentry matching the name already exists,
2039 * if not go ahead and create it now.
2041 found
= d_hash_and_lookup(dentry
->d_parent
, name
);
2046 if (d_in_lookup(dentry
)) {
2047 found
= d_alloc_parallel(dentry
->d_parent
, name
,
2049 if (IS_ERR(found
) || !d_in_lookup(found
)) {
2054 found
= d_alloc(dentry
->d_parent
, name
);
2057 return ERR_PTR(-ENOMEM
);
2060 res
= d_splice_alias(inode
, found
);
2067 EXPORT_SYMBOL(d_add_ci
);
2070 * Do the slow-case of the dentry name compare.
2072 * Unlike the dentry_cmp() function, we need to atomically
2073 * load the name and length information, so that the
2074 * filesystem can rely on them, and can use the 'name' and
2075 * 'len' information without worrying about walking off the
2076 * end of memory etc.
2078 * Thus the read_seqcount_retry() and the "duplicate" info
2079 * in arguments (the low-level filesystem should not look
2080 * at the dentry inode or name contents directly, since
2081 * rename can change them while we're in RCU mode).
2083 enum slow_d_compare
{
2089 static noinline
enum slow_d_compare
slow_dentry_cmp(
2090 const struct dentry
*parent
,
2091 struct dentry
*dentry
,
2093 const struct qstr
*name
)
2095 int tlen
= dentry
->d_name
.len
;
2096 const char *tname
= dentry
->d_name
.name
;
2098 if (read_seqcount_retry(&dentry
->d_seq
, seq
)) {
2100 return D_COMP_SEQRETRY
;
2102 if (parent
->d_op
->d_compare(parent
, dentry
, tlen
, tname
, name
))
2103 return D_COMP_NOMATCH
;
2108 * __d_lookup_rcu - search for a dentry (racy, store-free)
2109 * @parent: parent dentry
2110 * @name: qstr of name we wish to find
2111 * @seqp: returns d_seq value at the point where the dentry was found
2112 * Returns: dentry, or NULL
2114 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2115 * resolution (store-free path walking) design described in
2116 * Documentation/filesystems/path-lookup.txt.
2118 * This is not to be used outside core vfs.
2120 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2121 * held, and rcu_read_lock held. The returned dentry must not be stored into
2122 * without taking d_lock and checking d_seq sequence count against @seq
2125 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2128 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2129 * the returned dentry, so long as its parent's seqlock is checked after the
2130 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2131 * is formed, giving integrity down the path walk.
2133 * NOTE! The caller *has* to check the resulting dentry against the sequence
2134 * number we've returned before using any of the resulting dentry state!
2136 struct dentry
*__d_lookup_rcu(const struct dentry
*parent
,
2137 const struct qstr
*name
,
2140 u64 hashlen
= name
->hash_len
;
2141 const unsigned char *str
= name
->name
;
2142 struct hlist_bl_head
*b
= d_hash(parent
, hashlen_hash(hashlen
));
2143 struct hlist_bl_node
*node
;
2144 struct dentry
*dentry
;
2147 * Note: There is significant duplication with __d_lookup_rcu which is
2148 * required to prevent single threaded performance regressions
2149 * especially on architectures where smp_rmb (in seqcounts) are costly.
2150 * Keep the two functions in sync.
2154 * The hash list is protected using RCU.
2156 * Carefully use d_seq when comparing a candidate dentry, to avoid
2157 * races with d_move().
2159 * It is possible that concurrent renames can mess up our list
2160 * walk here and result in missing our dentry, resulting in the
2161 * false-negative result. d_lookup() protects against concurrent
2162 * renames using rename_lock seqlock.
2164 * See Documentation/filesystems/path-lookup.txt for more details.
2166 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
2171 * The dentry sequence count protects us from concurrent
2172 * renames, and thus protects parent and name fields.
2174 * The caller must perform a seqcount check in order
2175 * to do anything useful with the returned dentry.
2177 * NOTE! We do a "raw" seqcount_begin here. That means that
2178 * we don't wait for the sequence count to stabilize if it
2179 * is in the middle of a sequence change. If we do the slow
2180 * dentry compare, we will do seqretries until it is stable,
2181 * and if we end up with a successful lookup, we actually
2182 * want to exit RCU lookup anyway.
2184 seq
= raw_seqcount_begin(&dentry
->d_seq
);
2185 if (dentry
->d_parent
!= parent
)
2187 if (d_unhashed(dentry
))
2190 if (unlikely(parent
->d_flags
& DCACHE_OP_COMPARE
)) {
2191 if (dentry
->d_name
.hash
!= hashlen_hash(hashlen
))
2194 switch (slow_dentry_cmp(parent
, dentry
, seq
, name
)) {
2197 case D_COMP_NOMATCH
:
2204 if (dentry
->d_name
.hash_len
!= hashlen
)
2207 if (!dentry_cmp(dentry
, str
, hashlen_len(hashlen
)))
2214 * d_lookup - search for a dentry
2215 * @parent: parent dentry
2216 * @name: qstr of name we wish to find
2217 * Returns: dentry, or NULL
2219 * d_lookup searches the children of the parent dentry for the name in
2220 * question. If the dentry is found its reference count is incremented and the
2221 * dentry is returned. The caller must use dput to free the entry when it has
2222 * finished using it. %NULL is returned if the dentry does not exist.
2224 struct dentry
*d_lookup(const struct dentry
*parent
, const struct qstr
*name
)
2226 struct dentry
*dentry
;
2230 seq
= read_seqbegin(&rename_lock
);
2231 dentry
= __d_lookup(parent
, name
);
2234 } while (read_seqretry(&rename_lock
, seq
));
2237 EXPORT_SYMBOL(d_lookup
);
2240 * __d_lookup - search for a dentry (racy)
2241 * @parent: parent dentry
2242 * @name: qstr of name we wish to find
2243 * Returns: dentry, or NULL
2245 * __d_lookup is like d_lookup, however it may (rarely) return a
2246 * false-negative result due to unrelated rename activity.
2248 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2249 * however it must be used carefully, eg. with a following d_lookup in
2250 * the case of failure.
2252 * __d_lookup callers must be commented.
2254 struct dentry
*__d_lookup(const struct dentry
*parent
, const struct qstr
*name
)
2256 unsigned int len
= name
->len
;
2257 unsigned int hash
= name
->hash
;
2258 const unsigned char *str
= name
->name
;
2259 struct hlist_bl_head
*b
= d_hash(parent
, hash
);
2260 struct hlist_bl_node
*node
;
2261 struct dentry
*found
= NULL
;
2262 struct dentry
*dentry
;
2265 * Note: There is significant duplication with __d_lookup_rcu which is
2266 * required to prevent single threaded performance regressions
2267 * especially on architectures where smp_rmb (in seqcounts) are costly.
2268 * Keep the two functions in sync.
2272 * The hash list is protected using RCU.
2274 * Take d_lock when comparing a candidate dentry, to avoid races
2277 * It is possible that concurrent renames can mess up our list
2278 * walk here and result in missing our dentry, resulting in the
2279 * false-negative result. d_lookup() protects against concurrent
2280 * renames using rename_lock seqlock.
2282 * See Documentation/filesystems/path-lookup.txt for more details.
2286 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
2288 if (dentry
->d_name
.hash
!= hash
)
2291 spin_lock(&dentry
->d_lock
);
2292 if (dentry
->d_parent
!= parent
)
2294 if (d_unhashed(dentry
))
2298 * It is safe to compare names since d_move() cannot
2299 * change the qstr (protected by d_lock).
2301 if (parent
->d_flags
& DCACHE_OP_COMPARE
) {
2302 int tlen
= dentry
->d_name
.len
;
2303 const char *tname
= dentry
->d_name
.name
;
2304 if (parent
->d_op
->d_compare(parent
, dentry
, tlen
, tname
, name
))
2307 if (dentry
->d_name
.len
!= len
)
2309 if (dentry_cmp(dentry
, str
, len
))
2313 dentry
->d_lockref
.count
++;
2315 spin_unlock(&dentry
->d_lock
);
2318 spin_unlock(&dentry
->d_lock
);
2326 * d_hash_and_lookup - hash the qstr then search for a dentry
2327 * @dir: Directory to search in
2328 * @name: qstr of name we wish to find
2330 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2332 struct dentry
*d_hash_and_lookup(struct dentry
*dir
, struct qstr
*name
)
2335 * Check for a fs-specific hash function. Note that we must
2336 * calculate the standard hash first, as the d_op->d_hash()
2337 * routine may choose to leave the hash value unchanged.
2339 name
->hash
= full_name_hash(name
->name
, name
->len
);
2340 if (dir
->d_flags
& DCACHE_OP_HASH
) {
2341 int err
= dir
->d_op
->d_hash(dir
, name
);
2342 if (unlikely(err
< 0))
2343 return ERR_PTR(err
);
2345 return d_lookup(dir
, name
);
2347 EXPORT_SYMBOL(d_hash_and_lookup
);
2350 * When a file is deleted, we have two options:
2351 * - turn this dentry into a negative dentry
2352 * - unhash this dentry and free it.
2354 * Usually, we want to just turn this into
2355 * a negative dentry, but if anybody else is
2356 * currently using the dentry or the inode
2357 * we can't do that and we fall back on removing
2358 * it from the hash queues and waiting for
2359 * it to be deleted later when it has no users
2363 * d_delete - delete a dentry
2364 * @dentry: The dentry to delete
2366 * Turn the dentry into a negative dentry if possible, otherwise
2367 * remove it from the hash queues so it can be deleted later
2370 void d_delete(struct dentry
* dentry
)
2372 struct inode
*inode
;
2375 * Are we the only user?
2378 spin_lock(&dentry
->d_lock
);
2379 inode
= dentry
->d_inode
;
2380 isdir
= S_ISDIR(inode
->i_mode
);
2381 if (dentry
->d_lockref
.count
== 1) {
2382 if (!spin_trylock(&inode
->i_lock
)) {
2383 spin_unlock(&dentry
->d_lock
);
2387 dentry
->d_flags
&= ~DCACHE_CANT_MOUNT
;
2388 dentry_unlink_inode(dentry
);
2389 fsnotify_nameremove(dentry
, isdir
);
2393 if (!d_unhashed(dentry
))
2396 spin_unlock(&dentry
->d_lock
);
2398 fsnotify_nameremove(dentry
, isdir
);
2400 EXPORT_SYMBOL(d_delete
);
2402 static void __d_rehash(struct dentry
* entry
, struct hlist_bl_head
*b
)
2404 BUG_ON(!d_unhashed(entry
));
2406 hlist_bl_add_head_rcu(&entry
->d_hash
, b
);
2410 static void _d_rehash(struct dentry
* entry
)
2412 __d_rehash(entry
, d_hash(entry
->d_parent
, entry
->d_name
.hash
));
2416 * d_rehash - add an entry back to the hash
2417 * @entry: dentry to add to the hash
2419 * Adds a dentry to the hash according to its name.
2422 void d_rehash(struct dentry
* entry
)
2424 spin_lock(&entry
->d_lock
);
2426 spin_unlock(&entry
->d_lock
);
2428 EXPORT_SYMBOL(d_rehash
);
2430 static inline unsigned start_dir_add(struct inode
*dir
)
2434 unsigned n
= dir
->i_dir_seq
;
2435 if (!(n
& 1) && cmpxchg(&dir
->i_dir_seq
, n
, n
+ 1) == n
)
2441 static inline void end_dir_add(struct inode
*dir
, unsigned n
)
2443 smp_store_release(&dir
->i_dir_seq
, n
+ 2);
2446 static void d_wait_lookup(struct dentry
*dentry
)
2448 if (d_in_lookup(dentry
)) {
2449 DECLARE_WAITQUEUE(wait
, current
);
2450 add_wait_queue(dentry
->d_wait
, &wait
);
2452 set_current_state(TASK_UNINTERRUPTIBLE
);
2453 spin_unlock(&dentry
->d_lock
);
2455 spin_lock(&dentry
->d_lock
);
2456 } while (d_in_lookup(dentry
));
2460 struct dentry
*d_alloc_parallel(struct dentry
*parent
,
2461 const struct qstr
*name
,
2462 wait_queue_head_t
*wq
)
2464 unsigned int len
= name
->len
;
2465 unsigned int hash
= name
->hash
;
2466 const unsigned char *str
= name
->name
;
2467 struct hlist_bl_head
*b
= in_lookup_hash(parent
, hash
);
2468 struct hlist_bl_node
*node
;
2469 struct dentry
*new = d_alloc(parent
, name
);
2470 struct dentry
*dentry
;
2471 unsigned seq
, r_seq
, d_seq
;
2474 return ERR_PTR(-ENOMEM
);
2478 seq
= smp_load_acquire(&parent
->d_inode
->i_dir_seq
) & ~1;
2479 r_seq
= read_seqbegin(&rename_lock
);
2480 dentry
= __d_lookup_rcu(parent
, name
, &d_seq
);
2481 if (unlikely(dentry
)) {
2482 if (!lockref_get_not_dead(&dentry
->d_lockref
)) {
2486 if (read_seqcount_retry(&dentry
->d_seq
, d_seq
)) {
2495 if (unlikely(read_seqretry(&rename_lock
, r_seq
))) {
2500 if (unlikely(parent
->d_inode
->i_dir_seq
!= seq
)) {
2506 * No changes for the parent since the beginning of d_lookup().
2507 * Since all removals from the chain happen with hlist_bl_lock(),
2508 * any potential in-lookup matches are going to stay here until
2509 * we unlock the chain. All fields are stable in everything
2512 hlist_bl_for_each_entry(dentry
, node
, b
, d_u
.d_in_lookup_hash
) {
2513 if (dentry
->d_name
.hash
!= hash
)
2515 if (dentry
->d_parent
!= parent
)
2517 if (parent
->d_flags
& DCACHE_OP_COMPARE
) {
2518 int tlen
= dentry
->d_name
.len
;
2519 const char *tname
= dentry
->d_name
.name
;
2520 if (parent
->d_op
->d_compare(parent
, dentry
, tlen
, tname
, name
))
2523 if (dentry
->d_name
.len
!= len
)
2525 if (dentry_cmp(dentry
, str
, len
))
2529 /* now we can try to grab a reference */
2530 if (!lockref_get_not_dead(&dentry
->d_lockref
)) {
2537 * somebody is likely to be still doing lookup for it;
2538 * wait for them to finish
2540 spin_lock(&dentry
->d_lock
);
2541 d_wait_lookup(dentry
);
2543 * it's not in-lookup anymore; in principle we should repeat
2544 * everything from dcache lookup, but it's likely to be what
2545 * d_lookup() would've found anyway. If it is, just return it;
2546 * otherwise we really have to repeat the whole thing.
2548 if (unlikely(dentry
->d_name
.hash
!= hash
))
2550 if (unlikely(dentry
->d_parent
!= parent
))
2552 if (unlikely(d_unhashed(dentry
)))
2554 if (parent
->d_flags
& DCACHE_OP_COMPARE
) {
2555 int tlen
= dentry
->d_name
.len
;
2556 const char *tname
= dentry
->d_name
.name
;
2557 if (parent
->d_op
->d_compare(parent
, dentry
, tlen
, tname
, name
))
2560 if (unlikely(dentry
->d_name
.len
!= len
))
2562 if (unlikely(dentry_cmp(dentry
, str
, len
)))
2565 /* OK, it *is* a hashed match; return it */
2566 spin_unlock(&dentry
->d_lock
);
2571 /* we can't take ->d_lock here; it's OK, though. */
2572 new->d_flags
|= DCACHE_PAR_LOOKUP
;
2574 hlist_bl_add_head_rcu(&new->d_u
.d_in_lookup_hash
, b
);
2578 spin_unlock(&dentry
->d_lock
);
2582 EXPORT_SYMBOL(d_alloc_parallel
);
2584 void __d_lookup_done(struct dentry
*dentry
)
2586 struct hlist_bl_head
*b
= in_lookup_hash(dentry
->d_parent
,
2587 dentry
->d_name
.hash
);
2589 dentry
->d_flags
&= ~DCACHE_PAR_LOOKUP
;
2590 __hlist_bl_del(&dentry
->d_u
.d_in_lookup_hash
);
2591 wake_up_all(dentry
->d_wait
);
2592 dentry
->d_wait
= NULL
;
2594 INIT_HLIST_NODE(&dentry
->d_u
.d_alias
);
2595 INIT_LIST_HEAD(&dentry
->d_lru
);
2597 EXPORT_SYMBOL(__d_lookup_done
);
2599 /* inode->i_lock held if inode is non-NULL */
2601 static inline void __d_add(struct dentry
*dentry
, struct inode
*inode
)
2603 struct inode
*dir
= NULL
;
2605 spin_lock(&dentry
->d_lock
);
2606 if (unlikely(d_in_lookup(dentry
))) {
2607 dir
= dentry
->d_parent
->d_inode
;
2608 n
= start_dir_add(dir
);
2609 __d_lookup_done(dentry
);
2612 unsigned add_flags
= d_flags_for_inode(inode
);
2613 hlist_add_head(&dentry
->d_u
.d_alias
, &inode
->i_dentry
);
2614 raw_write_seqcount_begin(&dentry
->d_seq
);
2615 __d_set_inode_and_type(dentry
, inode
, add_flags
);
2616 raw_write_seqcount_end(&dentry
->d_seq
);
2617 fsnotify_update_flags(dentry
);
2621 end_dir_add(dir
, n
);
2622 spin_unlock(&dentry
->d_lock
);
2624 spin_unlock(&inode
->i_lock
);
2628 * d_add - add dentry to hash queues
2629 * @entry: dentry to add
2630 * @inode: The inode to attach to this dentry
2632 * This adds the entry to the hash queues and initializes @inode.
2633 * The entry was actually filled in earlier during d_alloc().
2636 void d_add(struct dentry
*entry
, struct inode
*inode
)
2639 security_d_instantiate(entry
, inode
);
2640 spin_lock(&inode
->i_lock
);
2642 __d_add(entry
, inode
);
2644 EXPORT_SYMBOL(d_add
);
2647 * d_exact_alias - find and hash an exact unhashed alias
2648 * @entry: dentry to add
2649 * @inode: The inode to go with this dentry
2651 * If an unhashed dentry with the same name/parent and desired
2652 * inode already exists, hash and return it. Otherwise, return
2655 * Parent directory should be locked.
2657 struct dentry
*d_exact_alias(struct dentry
*entry
, struct inode
*inode
)
2659 struct dentry
*alias
;
2660 int len
= entry
->d_name
.len
;
2661 const char *name
= entry
->d_name
.name
;
2662 unsigned int hash
= entry
->d_name
.hash
;
2664 spin_lock(&inode
->i_lock
);
2665 hlist_for_each_entry(alias
, &inode
->i_dentry
, d_u
.d_alias
) {
2667 * Don't need alias->d_lock here, because aliases with
2668 * d_parent == entry->d_parent are not subject to name or
2669 * parent changes, because the parent inode i_mutex is held.
2671 if (alias
->d_name
.hash
!= hash
)
2673 if (alias
->d_parent
!= entry
->d_parent
)
2675 if (alias
->d_name
.len
!= len
)
2677 if (dentry_cmp(alias
, name
, len
))
2679 spin_lock(&alias
->d_lock
);
2680 if (!d_unhashed(alias
)) {
2681 spin_unlock(&alias
->d_lock
);
2684 __dget_dlock(alias
);
2686 spin_unlock(&alias
->d_lock
);
2688 spin_unlock(&inode
->i_lock
);
2691 spin_unlock(&inode
->i_lock
);
2694 EXPORT_SYMBOL(d_exact_alias
);
2697 * dentry_update_name_case - update case insensitive dentry with a new name
2698 * @dentry: dentry to be updated
2701 * Update a case insensitive dentry with new case of name.
2703 * dentry must have been returned by d_lookup with name @name. Old and new
2704 * name lengths must match (ie. no d_compare which allows mismatched name
2707 * Parent inode i_mutex must be held over d_lookup and into this call (to
2708 * keep renames and concurrent inserts, and readdir(2) away).
2710 void dentry_update_name_case(struct dentry
*dentry
, struct qstr
*name
)
2712 BUG_ON(!inode_is_locked(dentry
->d_parent
->d_inode
));
2713 BUG_ON(dentry
->d_name
.len
!= name
->len
); /* d_lookup gives this */
2715 spin_lock(&dentry
->d_lock
);
2716 write_seqcount_begin(&dentry
->d_seq
);
2717 memcpy((unsigned char *)dentry
->d_name
.name
, name
->name
, name
->len
);
2718 write_seqcount_end(&dentry
->d_seq
);
2719 spin_unlock(&dentry
->d_lock
);
2721 EXPORT_SYMBOL(dentry_update_name_case
);
2723 static void swap_names(struct dentry
*dentry
, struct dentry
*target
)
2725 if (unlikely(dname_external(target
))) {
2726 if (unlikely(dname_external(dentry
))) {
2728 * Both external: swap the pointers
2730 swap(target
->d_name
.name
, dentry
->d_name
.name
);
2733 * dentry:internal, target:external. Steal target's
2734 * storage and make target internal.
2736 memcpy(target
->d_iname
, dentry
->d_name
.name
,
2737 dentry
->d_name
.len
+ 1);
2738 dentry
->d_name
.name
= target
->d_name
.name
;
2739 target
->d_name
.name
= target
->d_iname
;
2742 if (unlikely(dname_external(dentry
))) {
2744 * dentry:external, target:internal. Give dentry's
2745 * storage to target and make dentry internal
2747 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2748 target
->d_name
.len
+ 1);
2749 target
->d_name
.name
= dentry
->d_name
.name
;
2750 dentry
->d_name
.name
= dentry
->d_iname
;
2753 * Both are internal.
2756 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN
, sizeof(long)));
2757 kmemcheck_mark_initialized(dentry
->d_iname
, DNAME_INLINE_LEN
);
2758 kmemcheck_mark_initialized(target
->d_iname
, DNAME_INLINE_LEN
);
2759 for (i
= 0; i
< DNAME_INLINE_LEN
/ sizeof(long); i
++) {
2760 swap(((long *) &dentry
->d_iname
)[i
],
2761 ((long *) &target
->d_iname
)[i
]);
2765 swap(dentry
->d_name
.hash_len
, target
->d_name
.hash_len
);
2768 static void copy_name(struct dentry
*dentry
, struct dentry
*target
)
2770 struct external_name
*old_name
= NULL
;
2771 if (unlikely(dname_external(dentry
)))
2772 old_name
= external_name(dentry
);
2773 if (unlikely(dname_external(target
))) {
2774 atomic_inc(&external_name(target
)->u
.count
);
2775 dentry
->d_name
= target
->d_name
;
2777 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2778 target
->d_name
.len
+ 1);
2779 dentry
->d_name
.name
= dentry
->d_iname
;
2780 dentry
->d_name
.hash_len
= target
->d_name
.hash_len
;
2782 if (old_name
&& likely(atomic_dec_and_test(&old_name
->u
.count
)))
2783 kfree_rcu(old_name
, u
.head
);
2786 static void dentry_lock_for_move(struct dentry
*dentry
, struct dentry
*target
)
2789 * XXXX: do we really need to take target->d_lock?
2791 if (IS_ROOT(dentry
) || dentry
->d_parent
== target
->d_parent
)
2792 spin_lock(&target
->d_parent
->d_lock
);
2794 if (d_ancestor(dentry
->d_parent
, target
->d_parent
)) {
2795 spin_lock(&dentry
->d_parent
->d_lock
);
2796 spin_lock_nested(&target
->d_parent
->d_lock
,
2797 DENTRY_D_LOCK_NESTED
);
2799 spin_lock(&target
->d_parent
->d_lock
);
2800 spin_lock_nested(&dentry
->d_parent
->d_lock
,
2801 DENTRY_D_LOCK_NESTED
);
2804 if (target
< dentry
) {
2805 spin_lock_nested(&target
->d_lock
, 2);
2806 spin_lock_nested(&dentry
->d_lock
, 3);
2808 spin_lock_nested(&dentry
->d_lock
, 2);
2809 spin_lock_nested(&target
->d_lock
, 3);
2813 static void dentry_unlock_for_move(struct dentry
*dentry
, struct dentry
*target
)
2815 if (target
->d_parent
!= dentry
->d_parent
)
2816 spin_unlock(&dentry
->d_parent
->d_lock
);
2817 if (target
->d_parent
!= target
)
2818 spin_unlock(&target
->d_parent
->d_lock
);
2819 spin_unlock(&target
->d_lock
);
2820 spin_unlock(&dentry
->d_lock
);
2824 * When switching names, the actual string doesn't strictly have to
2825 * be preserved in the target - because we're dropping the target
2826 * anyway. As such, we can just do a simple memcpy() to copy over
2827 * the new name before we switch, unless we are going to rehash
2828 * it. Note that if we *do* unhash the target, we are not allowed
2829 * to rehash it without giving it a new name/hash key - whether
2830 * we swap or overwrite the names here, resulting name won't match
2831 * the reality in filesystem; it's only there for d_path() purposes.
2832 * Note that all of this is happening under rename_lock, so the
2833 * any hash lookup seeing it in the middle of manipulations will
2834 * be discarded anyway. So we do not care what happens to the hash
2838 * __d_move - move a dentry
2839 * @dentry: entry to move
2840 * @target: new dentry
2841 * @exchange: exchange the two dentries
2843 * Update the dcache to reflect the move of a file name. Negative
2844 * dcache entries should not be moved in this way. Caller must hold
2845 * rename_lock, the i_mutex of the source and target directories,
2846 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2848 static void __d_move(struct dentry
*dentry
, struct dentry
*target
,
2851 struct inode
*dir
= NULL
;
2853 if (!dentry
->d_inode
)
2854 printk(KERN_WARNING
"VFS: moving negative dcache entry\n");
2856 BUG_ON(d_ancestor(dentry
, target
));
2857 BUG_ON(d_ancestor(target
, dentry
));
2859 dentry_lock_for_move(dentry
, target
);
2860 if (unlikely(d_in_lookup(target
))) {
2861 dir
= target
->d_parent
->d_inode
;
2862 n
= start_dir_add(dir
);
2863 __d_lookup_done(target
);
2866 write_seqcount_begin(&dentry
->d_seq
);
2867 write_seqcount_begin_nested(&target
->d_seq
, DENTRY_D_LOCK_NESTED
);
2869 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
2872 * Move the dentry to the target hash queue. Don't bother checking
2873 * for the same hash queue because of how unlikely it is.
2876 __d_rehash(dentry
, d_hash(target
->d_parent
, target
->d_name
.hash
));
2879 * Unhash the target (d_delete() is not usable here). If exchanging
2880 * the two dentries, then rehash onto the other's hash queue.
2885 d_hash(dentry
->d_parent
, dentry
->d_name
.hash
));
2888 /* Switch the names.. */
2890 swap_names(dentry
, target
);
2892 copy_name(dentry
, target
);
2894 /* ... and switch them in the tree */
2895 if (IS_ROOT(dentry
)) {
2896 /* splicing a tree */
2897 dentry
->d_flags
|= DCACHE_RCUACCESS
;
2898 dentry
->d_parent
= target
->d_parent
;
2899 target
->d_parent
= target
;
2900 list_del_init(&target
->d_child
);
2901 list_move(&dentry
->d_child
, &dentry
->d_parent
->d_subdirs
);
2903 /* swapping two dentries */
2904 swap(dentry
->d_parent
, target
->d_parent
);
2905 list_move(&target
->d_child
, &target
->d_parent
->d_subdirs
);
2906 list_move(&dentry
->d_child
, &dentry
->d_parent
->d_subdirs
);
2908 fsnotify_update_flags(target
);
2909 fsnotify_update_flags(dentry
);
2912 write_seqcount_end(&target
->d_seq
);
2913 write_seqcount_end(&dentry
->d_seq
);
2916 end_dir_add(dir
, n
);
2917 dentry_unlock_for_move(dentry
, target
);
2921 * d_move - move a dentry
2922 * @dentry: entry to move
2923 * @target: new dentry
2925 * Update the dcache to reflect the move of a file name. Negative
2926 * dcache entries should not be moved in this way. See the locking
2927 * requirements for __d_move.
2929 void d_move(struct dentry
*dentry
, struct dentry
*target
)
2931 write_seqlock(&rename_lock
);
2932 __d_move(dentry
, target
, false);
2933 write_sequnlock(&rename_lock
);
2935 EXPORT_SYMBOL(d_move
);
2938 * d_exchange - exchange two dentries
2939 * @dentry1: first dentry
2940 * @dentry2: second dentry
2942 void d_exchange(struct dentry
*dentry1
, struct dentry
*dentry2
)
2944 write_seqlock(&rename_lock
);
2946 WARN_ON(!dentry1
->d_inode
);
2947 WARN_ON(!dentry2
->d_inode
);
2948 WARN_ON(IS_ROOT(dentry1
));
2949 WARN_ON(IS_ROOT(dentry2
));
2951 __d_move(dentry1
, dentry2
, true);
2953 write_sequnlock(&rename_lock
);
2957 * d_ancestor - search for an ancestor
2958 * @p1: ancestor dentry
2961 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2962 * an ancestor of p2, else NULL.
2964 struct dentry
*d_ancestor(struct dentry
*p1
, struct dentry
*p2
)
2968 for (p
= p2
; !IS_ROOT(p
); p
= p
->d_parent
) {
2969 if (p
->d_parent
== p1
)
2976 * This helper attempts to cope with remotely renamed directories
2978 * It assumes that the caller is already holding
2979 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2981 * Note: If ever the locking in lock_rename() changes, then please
2982 * remember to update this too...
2984 static int __d_unalias(struct inode
*inode
,
2985 struct dentry
*dentry
, struct dentry
*alias
)
2987 struct mutex
*m1
= NULL
;
2988 struct rw_semaphore
*m2
= NULL
;
2991 /* If alias and dentry share a parent, then no extra locks required */
2992 if (alias
->d_parent
== dentry
->d_parent
)
2995 /* See lock_rename() */
2996 if (!mutex_trylock(&dentry
->d_sb
->s_vfs_rename_mutex
))
2998 m1
= &dentry
->d_sb
->s_vfs_rename_mutex
;
2999 if (!inode_trylock_shared(alias
->d_parent
->d_inode
))
3001 m2
= &alias
->d_parent
->d_inode
->i_rwsem
;
3003 __d_move(alias
, dentry
, false);
3014 * d_splice_alias - splice a disconnected dentry into the tree if one exists
3015 * @inode: the inode which may have a disconnected dentry
3016 * @dentry: a negative dentry which we want to point to the inode.
3018 * If inode is a directory and has an IS_ROOT alias, then d_move that in
3019 * place of the given dentry and return it, else simply d_add the inode
3020 * to the dentry and return NULL.
3022 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
3023 * we should error out: directories can't have multiple aliases.
3025 * This is needed in the lookup routine of any filesystem that is exportable
3026 * (via knfsd) so that we can build dcache paths to directories effectively.
3028 * If a dentry was found and moved, then it is returned. Otherwise NULL
3029 * is returned. This matches the expected return value of ->lookup.
3031 * Cluster filesystems may call this function with a negative, hashed dentry.
3032 * In that case, we know that the inode will be a regular file, and also this
3033 * will only occur during atomic_open. So we need to check for the dentry
3034 * being already hashed only in the final case.
3036 struct dentry
*d_splice_alias(struct inode
*inode
, struct dentry
*dentry
)
3039 return ERR_CAST(inode
);
3041 BUG_ON(!d_unhashed(dentry
));
3046 security_d_instantiate(dentry
, inode
);
3047 spin_lock(&inode
->i_lock
);
3048 if (S_ISDIR(inode
->i_mode
)) {
3049 struct dentry
*new = __d_find_any_alias(inode
);
3050 if (unlikely(new)) {
3051 /* The reference to new ensures it remains an alias */
3052 spin_unlock(&inode
->i_lock
);
3053 write_seqlock(&rename_lock
);
3054 if (unlikely(d_ancestor(new, dentry
))) {
3055 write_sequnlock(&rename_lock
);
3057 new = ERR_PTR(-ELOOP
);
3058 pr_warn_ratelimited(
3059 "VFS: Lookup of '%s' in %s %s"
3060 " would have caused loop\n",
3061 dentry
->d_name
.name
,
3062 inode
->i_sb
->s_type
->name
,
3064 } else if (!IS_ROOT(new)) {
3065 int err
= __d_unalias(inode
, dentry
, new);
3066 write_sequnlock(&rename_lock
);
3072 __d_move(new, dentry
, false);
3073 write_sequnlock(&rename_lock
);
3080 __d_add(dentry
, inode
);
3083 EXPORT_SYMBOL(d_splice_alias
);
3085 static int prepend(char **buffer
, int *buflen
, const char *str
, int namelen
)
3089 return -ENAMETOOLONG
;
3091 memcpy(*buffer
, str
, namelen
);
3096 * prepend_name - prepend a pathname in front of current buffer pointer
3097 * @buffer: buffer pointer
3098 * @buflen: allocated length of the buffer
3099 * @name: name string and length qstr structure
3101 * With RCU path tracing, it may race with d_move(). Use ACCESS_ONCE() to
3102 * make sure that either the old or the new name pointer and length are
3103 * fetched. However, there may be mismatch between length and pointer.
3104 * The length cannot be trusted, we need to copy it byte-by-byte until
3105 * the length is reached or a null byte is found. It also prepends "/" at
3106 * the beginning of the name. The sequence number check at the caller will
3107 * retry it again when a d_move() does happen. So any garbage in the buffer
3108 * due to mismatched pointer and length will be discarded.
3110 * Data dependency barrier is needed to make sure that we see that terminating
3111 * NUL. Alpha strikes again, film at 11...
3113 static int prepend_name(char **buffer
, int *buflen
, struct qstr
*name
)
3115 const char *dname
= ACCESS_ONCE(name
->name
);
3116 u32 dlen
= ACCESS_ONCE(name
->len
);
3119 smp_read_barrier_depends();
3121 *buflen
-= dlen
+ 1;
3123 return -ENAMETOOLONG
;
3124 p
= *buffer
-= dlen
+ 1;
3136 * prepend_path - Prepend path string to a buffer
3137 * @path: the dentry/vfsmount to report
3138 * @root: root vfsmnt/dentry
3139 * @buffer: pointer to the end of the buffer
3140 * @buflen: pointer to buffer length
3142 * The function will first try to write out the pathname without taking any
3143 * lock other than the RCU read lock to make sure that dentries won't go away.
3144 * It only checks the sequence number of the global rename_lock as any change
3145 * in the dentry's d_seq will be preceded by changes in the rename_lock
3146 * sequence number. If the sequence number had been changed, it will restart
3147 * the whole pathname back-tracing sequence again by taking the rename_lock.
3148 * In this case, there is no need to take the RCU read lock as the recursive
3149 * parent pointer references will keep the dentry chain alive as long as no
3150 * rename operation is performed.
3152 static int prepend_path(const struct path
*path
,
3153 const struct path
*root
,
3154 char **buffer
, int *buflen
)
3156 struct dentry
*dentry
;
3157 struct vfsmount
*vfsmnt
;
3160 unsigned seq
, m_seq
= 0;
3166 read_seqbegin_or_lock(&mount_lock
, &m_seq
);
3173 dentry
= path
->dentry
;
3175 mnt
= real_mount(vfsmnt
);
3176 read_seqbegin_or_lock(&rename_lock
, &seq
);
3177 while (dentry
!= root
->dentry
|| vfsmnt
!= root
->mnt
) {
3178 struct dentry
* parent
;
3180 if (dentry
== vfsmnt
->mnt_root
|| IS_ROOT(dentry
)) {
3181 struct mount
*parent
= ACCESS_ONCE(mnt
->mnt_parent
);
3183 if (dentry
!= vfsmnt
->mnt_root
) {
3190 if (mnt
!= parent
) {
3191 dentry
= ACCESS_ONCE(mnt
->mnt_mountpoint
);
3197 error
= is_mounted(vfsmnt
) ? 1 : 2;
3200 parent
= dentry
->d_parent
;
3202 error
= prepend_name(&bptr
, &blen
, &dentry
->d_name
);
3210 if (need_seqretry(&rename_lock
, seq
)) {
3214 done_seqretry(&rename_lock
, seq
);
3218 if (need_seqretry(&mount_lock
, m_seq
)) {
3222 done_seqretry(&mount_lock
, m_seq
);
3224 if (error
>= 0 && bptr
== *buffer
) {
3226 error
= -ENAMETOOLONG
;
3236 * __d_path - return the path of a dentry
3237 * @path: the dentry/vfsmount to report
3238 * @root: root vfsmnt/dentry
3239 * @buf: buffer to return value in
3240 * @buflen: buffer length
3242 * Convert a dentry into an ASCII path name.
3244 * Returns a pointer into the buffer or an error code if the
3245 * path was too long.
3247 * "buflen" should be positive.
3249 * If the path is not reachable from the supplied root, return %NULL.
3251 char *__d_path(const struct path
*path
,
3252 const struct path
*root
,
3253 char *buf
, int buflen
)
3255 char *res
= buf
+ buflen
;
3258 prepend(&res
, &buflen
, "\0", 1);
3259 error
= prepend_path(path
, root
, &res
, &buflen
);
3262 return ERR_PTR(error
);
3268 char *d_absolute_path(const struct path
*path
,
3269 char *buf
, int buflen
)
3271 struct path root
= {};
3272 char *res
= buf
+ buflen
;
3275 prepend(&res
, &buflen
, "\0", 1);
3276 error
= prepend_path(path
, &root
, &res
, &buflen
);
3281 return ERR_PTR(error
);
3286 * same as __d_path but appends "(deleted)" for unlinked files.
3288 static int path_with_deleted(const struct path
*path
,
3289 const struct path
*root
,
3290 char **buf
, int *buflen
)
3292 prepend(buf
, buflen
, "\0", 1);
3293 if (d_unlinked(path
->dentry
)) {
3294 int error
= prepend(buf
, buflen
, " (deleted)", 10);
3299 return prepend_path(path
, root
, buf
, buflen
);
3302 static int prepend_unreachable(char **buffer
, int *buflen
)
3304 return prepend(buffer
, buflen
, "(unreachable)", 13);
3307 static void get_fs_root_rcu(struct fs_struct
*fs
, struct path
*root
)
3312 seq
= read_seqcount_begin(&fs
->seq
);
3314 } while (read_seqcount_retry(&fs
->seq
, seq
));
3318 * d_path - return the path of a dentry
3319 * @path: path to report
3320 * @buf: buffer to return value in
3321 * @buflen: buffer length
3323 * Convert a dentry into an ASCII path name. If the entry has been deleted
3324 * the string " (deleted)" is appended. Note that this is ambiguous.
3326 * Returns a pointer into the buffer or an error code if the path was
3327 * too long. Note: Callers should use the returned pointer, not the passed
3328 * in buffer, to use the name! The implementation often starts at an offset
3329 * into the buffer, and may leave 0 bytes at the start.
3331 * "buflen" should be positive.
3333 char *d_path(const struct path
*path
, char *buf
, int buflen
)
3335 char *res
= buf
+ buflen
;
3340 * We have various synthetic filesystems that never get mounted. On
3341 * these filesystems dentries are never used for lookup purposes, and
3342 * thus don't need to be hashed. They also don't need a name until a
3343 * user wants to identify the object in /proc/pid/fd/. The little hack
3344 * below allows us to generate a name for these objects on demand:
3346 * Some pseudo inodes are mountable. When they are mounted
3347 * path->dentry == path->mnt->mnt_root. In that case don't call d_dname
3348 * and instead have d_path return the mounted path.
3350 if (path
->dentry
->d_op
&& path
->dentry
->d_op
->d_dname
&&
3351 (!IS_ROOT(path
->dentry
) || path
->dentry
!= path
->mnt
->mnt_root
))
3352 return path
->dentry
->d_op
->d_dname(path
->dentry
, buf
, buflen
);
3355 get_fs_root_rcu(current
->fs
, &root
);
3356 error
= path_with_deleted(path
, &root
, &res
, &buflen
);
3360 res
= ERR_PTR(error
);
3363 EXPORT_SYMBOL(d_path
);
3366 * Helper function for dentry_operations.d_dname() members
3368 char *dynamic_dname(struct dentry
*dentry
, char *buffer
, int buflen
,
3369 const char *fmt
, ...)
3375 va_start(args
, fmt
);
3376 sz
= vsnprintf(temp
, sizeof(temp
), fmt
, args
) + 1;
3379 if (sz
> sizeof(temp
) || sz
> buflen
)
3380 return ERR_PTR(-ENAMETOOLONG
);
3382 buffer
+= buflen
- sz
;
3383 return memcpy(buffer
, temp
, sz
);
3386 char *simple_dname(struct dentry
*dentry
, char *buffer
, int buflen
)
3388 char *end
= buffer
+ buflen
;
3389 /* these dentries are never renamed, so d_lock is not needed */
3390 if (prepend(&end
, &buflen
, " (deleted)", 11) ||
3391 prepend(&end
, &buflen
, dentry
->d_name
.name
, dentry
->d_name
.len
) ||
3392 prepend(&end
, &buflen
, "/", 1))
3393 end
= ERR_PTR(-ENAMETOOLONG
);
3396 EXPORT_SYMBOL(simple_dname
);
3399 * Write full pathname from the root of the filesystem into the buffer.
3401 static char *__dentry_path(struct dentry
*d
, char *buf
, int buflen
)
3403 struct dentry
*dentry
;
3416 prepend(&end
, &len
, "\0", 1);
3420 read_seqbegin_or_lock(&rename_lock
, &seq
);
3421 while (!IS_ROOT(dentry
)) {
3422 struct dentry
*parent
= dentry
->d_parent
;
3425 error
= prepend_name(&end
, &len
, &dentry
->d_name
);
3434 if (need_seqretry(&rename_lock
, seq
)) {
3438 done_seqretry(&rename_lock
, seq
);
3443 return ERR_PTR(-ENAMETOOLONG
);
3446 char *dentry_path_raw(struct dentry
*dentry
, char *buf
, int buflen
)
3448 return __dentry_path(dentry
, buf
, buflen
);
3450 EXPORT_SYMBOL(dentry_path_raw
);
3452 char *dentry_path(struct dentry
*dentry
, char *buf
, int buflen
)
3457 if (d_unlinked(dentry
)) {
3459 if (prepend(&p
, &buflen
, "//deleted", 10) != 0)
3463 retval
= __dentry_path(dentry
, buf
, buflen
);
3464 if (!IS_ERR(retval
) && p
)
3465 *p
= '/'; /* restore '/' overriden with '\0' */
3468 return ERR_PTR(-ENAMETOOLONG
);
3471 static void get_fs_root_and_pwd_rcu(struct fs_struct
*fs
, struct path
*root
,
3477 seq
= read_seqcount_begin(&fs
->seq
);
3480 } while (read_seqcount_retry(&fs
->seq
, seq
));
3484 * NOTE! The user-level library version returns a
3485 * character pointer. The kernel system call just
3486 * returns the length of the buffer filled (which
3487 * includes the ending '\0' character), or a negative
3488 * error value. So libc would do something like
3490 * char *getcwd(char * buf, size_t size)
3494 * retval = sys_getcwd(buf, size);
3501 SYSCALL_DEFINE2(getcwd
, char __user
*, buf
, unsigned long, size
)
3504 struct path pwd
, root
;
3505 char *page
= __getname();
3511 get_fs_root_and_pwd_rcu(current
->fs
, &root
, &pwd
);
3514 if (!d_unlinked(pwd
.dentry
)) {
3516 char *cwd
= page
+ PATH_MAX
;
3517 int buflen
= PATH_MAX
;
3519 prepend(&cwd
, &buflen
, "\0", 1);
3520 error
= prepend_path(&pwd
, &root
, &cwd
, &buflen
);
3526 /* Unreachable from current root */
3528 error
= prepend_unreachable(&cwd
, &buflen
);
3534 len
= PATH_MAX
+ page
- cwd
;
3537 if (copy_to_user(buf
, cwd
, len
))
3550 * Test whether new_dentry is a subdirectory of old_dentry.
3552 * Trivially implemented using the dcache structure
3556 * is_subdir - is new dentry a subdirectory of old_dentry
3557 * @new_dentry: new dentry
3558 * @old_dentry: old dentry
3560 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3561 * Returns false otherwise.
3562 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3565 bool is_subdir(struct dentry
*new_dentry
, struct dentry
*old_dentry
)
3570 if (new_dentry
== old_dentry
)
3574 /* for restarting inner loop in case of seq retry */
3575 seq
= read_seqbegin(&rename_lock
);
3577 * Need rcu_readlock to protect against the d_parent trashing
3581 if (d_ancestor(old_dentry
, new_dentry
))
3586 } while (read_seqretry(&rename_lock
, seq
));
3591 static enum d_walk_ret
d_genocide_kill(void *data
, struct dentry
*dentry
)
3593 struct dentry
*root
= data
;
3594 if (dentry
!= root
) {
3595 if (d_unhashed(dentry
) || !dentry
->d_inode
)
3598 if (!(dentry
->d_flags
& DCACHE_GENOCIDE
)) {
3599 dentry
->d_flags
|= DCACHE_GENOCIDE
;
3600 dentry
->d_lockref
.count
--;
3603 return D_WALK_CONTINUE
;
3606 void d_genocide(struct dentry
*parent
)
3608 d_walk(parent
, parent
, d_genocide_kill
, NULL
);
3611 void d_tmpfile(struct dentry
*dentry
, struct inode
*inode
)
3613 inode_dec_link_count(inode
);
3614 BUG_ON(dentry
->d_name
.name
!= dentry
->d_iname
||
3615 !hlist_unhashed(&dentry
->d_u
.d_alias
) ||
3616 !d_unlinked(dentry
));
3617 spin_lock(&dentry
->d_parent
->d_lock
);
3618 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
3619 dentry
->d_name
.len
= sprintf(dentry
->d_iname
, "#%llu",
3620 (unsigned long long)inode
->i_ino
);
3621 spin_unlock(&dentry
->d_lock
);
3622 spin_unlock(&dentry
->d_parent
->d_lock
);
3623 d_instantiate(dentry
, inode
);
3625 EXPORT_SYMBOL(d_tmpfile
);
3627 static __initdata
unsigned long dhash_entries
;
3628 static int __init
set_dhash_entries(char *str
)
3632 dhash_entries
= simple_strtoul(str
, &str
, 0);
3635 __setup("dhash_entries=", set_dhash_entries
);
3637 static void __init
dcache_init_early(void)
3641 /* If hashes are distributed across NUMA nodes, defer
3642 * hash allocation until vmalloc space is available.
3648 alloc_large_system_hash("Dentry cache",
3649 sizeof(struct hlist_bl_head
),
3658 for (loop
= 0; loop
< (1U << d_hash_shift
); loop
++)
3659 INIT_HLIST_BL_HEAD(dentry_hashtable
+ loop
);
3662 static void __init
dcache_init(void)
3667 * A constructor could be added for stable state like the lists,
3668 * but it is probably not worth it because of the cache nature
3671 dentry_cache
= KMEM_CACHE(dentry
,
3672 SLAB_RECLAIM_ACCOUNT
|SLAB_PANIC
|SLAB_MEM_SPREAD
|SLAB_ACCOUNT
);
3674 /* Hash may have been set up in dcache_init_early */
3679 alloc_large_system_hash("Dentry cache",
3680 sizeof(struct hlist_bl_head
),
3689 for (loop
= 0; loop
< (1U << d_hash_shift
); loop
++)
3690 INIT_HLIST_BL_HEAD(dentry_hashtable
+ loop
);
3693 /* SLAB cache for __getname() consumers */
3694 struct kmem_cache
*names_cachep __read_mostly
;
3695 EXPORT_SYMBOL(names_cachep
);
3697 EXPORT_SYMBOL(d_genocide
);
3699 void __init
vfs_caches_init_early(void)
3701 dcache_init_early();
3705 void __init
vfs_caches_init(void)
3707 names_cachep
= kmem_cache_create("names_cache", PATH_MAX
, 0,
3708 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
);
3713 files_maxfiles_init();