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
)
229 const unsigned char *cs
;
231 * Be careful about RCU walk racing with rename:
232 * use ACCESS_ONCE to fetch the name pointer.
234 * NOTE! Even if a rename will mean that the length
235 * was not loaded atomically, we don't care. The
236 * RCU walk will check the sequence count eventually,
237 * and catch it. And we won't overrun the buffer,
238 * because we're reading the name pointer atomically,
239 * and a dentry name is guaranteed to be properly
240 * terminated with a NUL byte.
242 * End result: even if 'len' is wrong, we'll exit
243 * early because the data cannot match (there can
244 * be no NUL in the ct/tcount data)
246 cs
= ACCESS_ONCE(dentry
->d_name
.name
);
247 smp_read_barrier_depends();
248 return dentry_string_cmp(cs
, ct
, tcount
);
251 struct external_name
{
254 struct rcu_head head
;
256 unsigned char name
[];
259 static inline struct external_name
*external_name(struct dentry
*dentry
)
261 return container_of(dentry
->d_name
.name
, struct external_name
, name
[0]);
264 static void __d_free(struct rcu_head
*head
)
266 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
268 kmem_cache_free(dentry_cache
, dentry
);
271 static void __d_free_external(struct rcu_head
*head
)
273 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
274 kfree(external_name(dentry
));
275 kmem_cache_free(dentry_cache
, dentry
);
278 static inline int dname_external(const struct dentry
*dentry
)
280 return dentry
->d_name
.name
!= dentry
->d_iname
;
283 static inline void __d_set_inode_and_type(struct dentry
*dentry
,
289 dentry
->d_inode
= inode
;
290 flags
= READ_ONCE(dentry
->d_flags
);
291 flags
&= ~(DCACHE_ENTRY_TYPE
| DCACHE_FALLTHRU
);
293 WRITE_ONCE(dentry
->d_flags
, flags
);
296 static inline void __d_clear_type_and_inode(struct dentry
*dentry
)
298 unsigned flags
= READ_ONCE(dentry
->d_flags
);
300 flags
&= ~(DCACHE_ENTRY_TYPE
| DCACHE_FALLTHRU
);
301 WRITE_ONCE(dentry
->d_flags
, flags
);
302 dentry
->d_inode
= NULL
;
305 static void dentry_free(struct dentry
*dentry
)
307 WARN_ON(!hlist_unhashed(&dentry
->d_u
.d_alias
));
308 if (unlikely(dname_external(dentry
))) {
309 struct external_name
*p
= external_name(dentry
);
310 if (likely(atomic_dec_and_test(&p
->u
.count
))) {
311 call_rcu(&dentry
->d_u
.d_rcu
, __d_free_external
);
315 /* if dentry was never visible to RCU, immediate free is OK */
316 if (!(dentry
->d_flags
& DCACHE_RCUACCESS
))
317 __d_free(&dentry
->d_u
.d_rcu
);
319 call_rcu(&dentry
->d_u
.d_rcu
, __d_free
);
323 * dentry_rcuwalk_invalidate - invalidate in-progress rcu-walk lookups
324 * @dentry: the target dentry
325 * After this call, in-progress rcu-walk path lookup will fail. This
326 * should be called after unhashing, and after changing d_inode (if
327 * the dentry has not already been unhashed).
329 static inline void dentry_rcuwalk_invalidate(struct dentry
*dentry
)
331 lockdep_assert_held(&dentry
->d_lock
);
332 /* Go through am invalidation barrier */
333 write_seqcount_invalidate(&dentry
->d_seq
);
337 * Release the dentry's inode, using the filesystem
338 * d_iput() operation if defined. Dentry has no refcount
341 static void dentry_iput(struct dentry
* dentry
)
342 __releases(dentry
->d_lock
)
343 __releases(dentry
->d_inode
->i_lock
)
345 struct inode
*inode
= dentry
->d_inode
;
347 __d_clear_type_and_inode(dentry
);
348 hlist_del_init(&dentry
->d_u
.d_alias
);
349 spin_unlock(&dentry
->d_lock
);
350 spin_unlock(&inode
->i_lock
);
352 fsnotify_inoderemove(inode
);
353 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
354 dentry
->d_op
->d_iput(dentry
, inode
);
358 spin_unlock(&dentry
->d_lock
);
363 * Release the dentry's inode, using the filesystem
364 * d_iput() operation if defined. dentry remains in-use.
366 static void dentry_unlink_inode(struct dentry
* dentry
)
367 __releases(dentry
->d_lock
)
368 __releases(dentry
->d_inode
->i_lock
)
370 struct inode
*inode
= dentry
->d_inode
;
372 raw_write_seqcount_begin(&dentry
->d_seq
);
373 __d_clear_type_and_inode(dentry
);
374 hlist_del_init(&dentry
->d_u
.d_alias
);
375 raw_write_seqcount_end(&dentry
->d_seq
);
376 spin_unlock(&dentry
->d_lock
);
377 spin_unlock(&inode
->i_lock
);
379 fsnotify_inoderemove(inode
);
380 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
381 dentry
->d_op
->d_iput(dentry
, inode
);
387 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
388 * is in use - which includes both the "real" per-superblock
389 * LRU list _and_ the DCACHE_SHRINK_LIST use.
391 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
392 * on the shrink list (ie not on the superblock LRU list).
394 * The per-cpu "nr_dentry_unused" counters are updated with
395 * the DCACHE_LRU_LIST bit.
397 * These helper functions make sure we always follow the
398 * rules. d_lock must be held by the caller.
400 #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
401 static void d_lru_add(struct dentry
*dentry
)
403 D_FLAG_VERIFY(dentry
, 0);
404 dentry
->d_flags
|= DCACHE_LRU_LIST
;
405 this_cpu_inc(nr_dentry_unused
);
406 WARN_ON_ONCE(!list_lru_add(&dentry
->d_sb
->s_dentry_lru
, &dentry
->d_lru
));
409 static void d_lru_del(struct dentry
*dentry
)
411 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
412 dentry
->d_flags
&= ~DCACHE_LRU_LIST
;
413 this_cpu_dec(nr_dentry_unused
);
414 WARN_ON_ONCE(!list_lru_del(&dentry
->d_sb
->s_dentry_lru
, &dentry
->d_lru
));
417 static void d_shrink_del(struct dentry
*dentry
)
419 D_FLAG_VERIFY(dentry
, DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
);
420 list_del_init(&dentry
->d_lru
);
421 dentry
->d_flags
&= ~(DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
);
422 this_cpu_dec(nr_dentry_unused
);
425 static void d_shrink_add(struct dentry
*dentry
, struct list_head
*list
)
427 D_FLAG_VERIFY(dentry
, 0);
428 list_add(&dentry
->d_lru
, list
);
429 dentry
->d_flags
|= DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
;
430 this_cpu_inc(nr_dentry_unused
);
434 * These can only be called under the global LRU lock, ie during the
435 * callback for freeing the LRU list. "isolate" removes it from the
436 * LRU lists entirely, while shrink_move moves it to the indicated
439 static void d_lru_isolate(struct list_lru_one
*lru
, struct dentry
*dentry
)
441 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
442 dentry
->d_flags
&= ~DCACHE_LRU_LIST
;
443 this_cpu_dec(nr_dentry_unused
);
444 list_lru_isolate(lru
, &dentry
->d_lru
);
447 static void d_lru_shrink_move(struct list_lru_one
*lru
, struct dentry
*dentry
,
448 struct list_head
*list
)
450 D_FLAG_VERIFY(dentry
, DCACHE_LRU_LIST
);
451 dentry
->d_flags
|= DCACHE_SHRINK_LIST
;
452 list_lru_isolate_move(lru
, &dentry
->d_lru
, list
);
456 * dentry_lru_(add|del)_list) must be called with d_lock held.
458 static void dentry_lru_add(struct dentry
*dentry
)
460 if (unlikely(!(dentry
->d_flags
& DCACHE_LRU_LIST
)))
465 * d_drop - drop a dentry
466 * @dentry: dentry to drop
468 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
469 * be found through a VFS lookup any more. Note that this is different from
470 * deleting the dentry - d_delete will try to mark the dentry negative if
471 * possible, giving a successful _negative_ lookup, while d_drop will
472 * just make the cache lookup fail.
474 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
475 * reason (NFS timeouts or autofs deletes).
477 * __d_drop requires dentry->d_lock.
479 void __d_drop(struct dentry
*dentry
)
481 if (!d_unhashed(dentry
)) {
482 struct hlist_bl_head
*b
;
484 * Hashed dentries are normally on the dentry hashtable,
485 * with the exception of those newly allocated by
486 * d_obtain_alias, which are always IS_ROOT:
488 if (unlikely(IS_ROOT(dentry
)))
489 b
= &dentry
->d_sb
->s_anon
;
491 b
= d_hash(dentry
->d_parent
, dentry
->d_name
.hash
);
494 __hlist_bl_del(&dentry
->d_hash
);
495 dentry
->d_hash
.pprev
= NULL
;
497 dentry_rcuwalk_invalidate(dentry
);
500 EXPORT_SYMBOL(__d_drop
);
502 void d_drop(struct dentry
*dentry
)
504 spin_lock(&dentry
->d_lock
);
506 spin_unlock(&dentry
->d_lock
);
508 EXPORT_SYMBOL(d_drop
);
510 static inline void dentry_unlist(struct dentry
*dentry
, struct dentry
*parent
)
514 * Inform d_walk() and shrink_dentry_list() that we are no longer
515 * attached to the dentry tree
517 dentry
->d_flags
|= DCACHE_DENTRY_KILLED
;
518 if (unlikely(list_empty(&dentry
->d_child
)))
520 __list_del_entry(&dentry
->d_child
);
522 * Cursors can move around the list of children. While we'd been
523 * a normal list member, it didn't matter - ->d_child.next would've
524 * been updated. However, from now on it won't be and for the
525 * things like d_walk() it might end up with a nasty surprise.
526 * Normally d_walk() doesn't care about cursors moving around -
527 * ->d_lock on parent prevents that and since a cursor has no children
528 * of its own, we get through it without ever unlocking the parent.
529 * There is one exception, though - if we ascend from a child that
530 * gets killed as soon as we unlock it, the next sibling is found
531 * using the value left in its ->d_child.next. And if _that_
532 * pointed to a cursor, and cursor got moved (e.g. by lseek())
533 * before d_walk() regains parent->d_lock, we'll end up skipping
534 * everything the cursor had been moved past.
536 * Solution: make sure that the pointer left behind in ->d_child.next
537 * points to something that won't be moving around. I.e. skip the
540 while (dentry
->d_child
.next
!= &parent
->d_subdirs
) {
541 next
= list_entry(dentry
->d_child
.next
, struct dentry
, d_child
);
542 if (likely(!(next
->d_flags
& DCACHE_DENTRY_CURSOR
)))
544 dentry
->d_child
.next
= next
->d_child
.next
;
548 static void __dentry_kill(struct dentry
*dentry
)
550 struct dentry
*parent
= NULL
;
551 bool can_free
= true;
552 if (!IS_ROOT(dentry
))
553 parent
= dentry
->d_parent
;
556 * The dentry is now unrecoverably dead to the world.
558 lockref_mark_dead(&dentry
->d_lockref
);
561 * inform the fs via d_prune that this dentry is about to be
562 * unhashed and destroyed.
564 if (dentry
->d_flags
& DCACHE_OP_PRUNE
)
565 dentry
->d_op
->d_prune(dentry
);
567 if (dentry
->d_flags
& DCACHE_LRU_LIST
) {
568 if (!(dentry
->d_flags
& DCACHE_SHRINK_LIST
))
571 /* if it was on the hash then remove it */
573 dentry_unlist(dentry
, parent
);
575 spin_unlock(&parent
->d_lock
);
578 * dentry_iput drops the locks, at which point nobody (except
579 * transient RCU lookups) can reach this dentry.
581 BUG_ON(dentry
->d_lockref
.count
> 0);
582 this_cpu_dec(nr_dentry
);
583 if (dentry
->d_op
&& dentry
->d_op
->d_release
)
584 dentry
->d_op
->d_release(dentry
);
586 spin_lock(&dentry
->d_lock
);
587 if (dentry
->d_flags
& DCACHE_SHRINK_LIST
) {
588 dentry
->d_flags
|= DCACHE_MAY_FREE
;
591 spin_unlock(&dentry
->d_lock
);
592 if (likely(can_free
))
597 * Finish off a dentry we've decided to kill.
598 * dentry->d_lock must be held, returns with it unlocked.
599 * If ref is non-zero, then decrement the refcount too.
600 * Returns dentry requiring refcount drop, or NULL if we're done.
602 static struct dentry
*dentry_kill(struct dentry
*dentry
)
603 __releases(dentry
->d_lock
)
605 struct inode
*inode
= dentry
->d_inode
;
606 struct dentry
*parent
= NULL
;
608 if (inode
&& unlikely(!spin_trylock(&inode
->i_lock
)))
611 if (!IS_ROOT(dentry
)) {
612 parent
= dentry
->d_parent
;
613 if (unlikely(!spin_trylock(&parent
->d_lock
))) {
615 spin_unlock(&inode
->i_lock
);
620 __dentry_kill(dentry
);
624 spin_unlock(&dentry
->d_lock
);
626 return dentry
; /* try again with same dentry */
629 static inline struct dentry
*lock_parent(struct dentry
*dentry
)
631 struct dentry
*parent
= dentry
->d_parent
;
634 if (unlikely(dentry
->d_lockref
.count
< 0))
636 if (likely(spin_trylock(&parent
->d_lock
)))
639 spin_unlock(&dentry
->d_lock
);
641 parent
= ACCESS_ONCE(dentry
->d_parent
);
642 spin_lock(&parent
->d_lock
);
644 * We can't blindly lock dentry until we are sure
645 * that we won't violate the locking order.
646 * Any changes of dentry->d_parent must have
647 * been done with parent->d_lock held, so
648 * spin_lock() above is enough of a barrier
649 * for checking if it's still our child.
651 if (unlikely(parent
!= dentry
->d_parent
)) {
652 spin_unlock(&parent
->d_lock
);
656 if (parent
!= dentry
)
657 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
664 * Try to do a lockless dput(), and return whether that was successful.
666 * If unsuccessful, we return false, having already taken the dentry lock.
668 * The caller needs to hold the RCU read lock, so that the dentry is
669 * guaranteed to stay around even if the refcount goes down to zero!
671 static inline bool fast_dput(struct dentry
*dentry
)
674 unsigned int d_flags
;
677 * If we have a d_op->d_delete() operation, we sould not
678 * let the dentry count go to zero, so use "put_or_lock".
680 if (unlikely(dentry
->d_flags
& DCACHE_OP_DELETE
))
681 return lockref_put_or_lock(&dentry
->d_lockref
);
684 * .. otherwise, we can try to just decrement the
685 * lockref optimistically.
687 ret
= lockref_put_return(&dentry
->d_lockref
);
690 * If the lockref_put_return() failed due to the lock being held
691 * by somebody else, the fast path has failed. We will need to
692 * get the lock, and then check the count again.
694 if (unlikely(ret
< 0)) {
695 spin_lock(&dentry
->d_lock
);
696 if (dentry
->d_lockref
.count
> 1) {
697 dentry
->d_lockref
.count
--;
698 spin_unlock(&dentry
->d_lock
);
705 * If we weren't the last ref, we're done.
711 * Careful, careful. The reference count went down
712 * to zero, but we don't hold the dentry lock, so
713 * somebody else could get it again, and do another
714 * dput(), and we need to not race with that.
716 * However, there is a very special and common case
717 * where we don't care, because there is nothing to
718 * do: the dentry is still hashed, it does not have
719 * a 'delete' op, and it's referenced and already on
722 * NOTE! Since we aren't locked, these values are
723 * not "stable". However, it is sufficient that at
724 * some point after we dropped the reference the
725 * dentry was hashed and the flags had the proper
726 * value. Other dentry users may have re-gotten
727 * a reference to the dentry and change that, but
728 * our work is done - we can leave the dentry
729 * around with a zero refcount.
732 d_flags
= ACCESS_ONCE(dentry
->d_flags
);
733 d_flags
&= DCACHE_REFERENCED
| DCACHE_LRU_LIST
| DCACHE_DISCONNECTED
;
735 /* Nothing to do? Dropping the reference was all we needed? */
736 if (d_flags
== (DCACHE_REFERENCED
| DCACHE_LRU_LIST
) && !d_unhashed(dentry
))
740 * Not the fast normal case? Get the lock. We've already decremented
741 * the refcount, but we'll need to re-check the situation after
744 spin_lock(&dentry
->d_lock
);
747 * Did somebody else grab a reference to it in the meantime, and
748 * we're no longer the last user after all? Alternatively, somebody
749 * else could have killed it and marked it dead. Either way, we
750 * don't need to do anything else.
752 if (dentry
->d_lockref
.count
) {
753 spin_unlock(&dentry
->d_lock
);
758 * Re-get the reference we optimistically dropped. We hold the
759 * lock, and we just tested that it was zero, so we can just
762 dentry
->d_lockref
.count
= 1;
770 * This is complicated by the fact that we do not want to put
771 * dentries that are no longer on any hash chain on the unused
772 * list: we'd much rather just get rid of them immediately.
774 * However, that implies that we have to traverse the dentry
775 * tree upwards to the parents which might _also_ now be
776 * scheduled for deletion (it may have been only waiting for
777 * its last child to go away).
779 * This tail recursion is done by hand as we don't want to depend
780 * on the compiler to always get this right (gcc generally doesn't).
781 * Real recursion would eat up our stack space.
785 * dput - release a dentry
786 * @dentry: dentry to release
788 * Release a dentry. This will drop the usage count and if appropriate
789 * call the dentry unlink method as well as removing it from the queues and
790 * releasing its resources. If the parent dentries were scheduled for release
791 * they too may now get deleted.
793 void dput(struct dentry
*dentry
)
795 if (unlikely(!dentry
))
800 if (likely(fast_dput(dentry
))) {
805 /* Slow case: now with the dentry lock held */
808 WARN_ON(d_in_lookup(dentry
));
810 /* Unreachable? Get rid of it */
811 if (unlikely(d_unhashed(dentry
)))
814 if (unlikely(dentry
->d_flags
& DCACHE_DISCONNECTED
))
817 if (unlikely(dentry
->d_flags
& DCACHE_OP_DELETE
)) {
818 if (dentry
->d_op
->d_delete(dentry
))
822 if (!(dentry
->d_flags
& DCACHE_REFERENCED
))
823 dentry
->d_flags
|= DCACHE_REFERENCED
;
824 dentry_lru_add(dentry
);
826 dentry
->d_lockref
.count
--;
827 spin_unlock(&dentry
->d_lock
);
831 dentry
= dentry_kill(dentry
);
838 /* This must be called with d_lock held */
839 static inline void __dget_dlock(struct dentry
*dentry
)
841 dentry
->d_lockref
.count
++;
844 static inline void __dget(struct dentry
*dentry
)
846 lockref_get(&dentry
->d_lockref
);
849 struct dentry
*dget_parent(struct dentry
*dentry
)
855 * Do optimistic parent lookup without any
859 ret
= ACCESS_ONCE(dentry
->d_parent
);
860 gotref
= lockref_get_not_zero(&ret
->d_lockref
);
862 if (likely(gotref
)) {
863 if (likely(ret
== ACCESS_ONCE(dentry
->d_parent
)))
870 * Don't need rcu_dereference because we re-check it was correct under
874 ret
= dentry
->d_parent
;
875 spin_lock(&ret
->d_lock
);
876 if (unlikely(ret
!= dentry
->d_parent
)) {
877 spin_unlock(&ret
->d_lock
);
882 BUG_ON(!ret
->d_lockref
.count
);
883 ret
->d_lockref
.count
++;
884 spin_unlock(&ret
->d_lock
);
887 EXPORT_SYMBOL(dget_parent
);
890 * d_find_alias - grab a hashed alias of inode
891 * @inode: inode in question
893 * If inode has a hashed alias, or is a directory and has any alias,
894 * acquire the reference to alias and return it. Otherwise return NULL.
895 * Notice that if inode is a directory there can be only one alias and
896 * it can be unhashed only if it has no children, or if it is the root
897 * of a filesystem, or if the directory was renamed and d_revalidate
898 * was the first vfs operation to notice.
900 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
901 * any other hashed alias over that one.
903 static struct dentry
*__d_find_alias(struct inode
*inode
)
905 struct dentry
*alias
, *discon_alias
;
909 hlist_for_each_entry(alias
, &inode
->i_dentry
, d_u
.d_alias
) {
910 spin_lock(&alias
->d_lock
);
911 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
912 if (IS_ROOT(alias
) &&
913 (alias
->d_flags
& DCACHE_DISCONNECTED
)) {
914 discon_alias
= alias
;
917 spin_unlock(&alias
->d_lock
);
921 spin_unlock(&alias
->d_lock
);
924 alias
= discon_alias
;
925 spin_lock(&alias
->d_lock
);
926 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
928 spin_unlock(&alias
->d_lock
);
931 spin_unlock(&alias
->d_lock
);
937 struct dentry
*d_find_alias(struct inode
*inode
)
939 struct dentry
*de
= NULL
;
941 if (!hlist_empty(&inode
->i_dentry
)) {
942 spin_lock(&inode
->i_lock
);
943 de
= __d_find_alias(inode
);
944 spin_unlock(&inode
->i_lock
);
948 EXPORT_SYMBOL(d_find_alias
);
951 * Try to kill dentries associated with this inode.
952 * WARNING: you must own a reference to inode.
954 void d_prune_aliases(struct inode
*inode
)
956 struct dentry
*dentry
;
958 spin_lock(&inode
->i_lock
);
959 hlist_for_each_entry(dentry
, &inode
->i_dentry
, d_u
.d_alias
) {
960 spin_lock(&dentry
->d_lock
);
961 if (!dentry
->d_lockref
.count
) {
962 struct dentry
*parent
= lock_parent(dentry
);
963 if (likely(!dentry
->d_lockref
.count
)) {
964 __dentry_kill(dentry
);
969 spin_unlock(&parent
->d_lock
);
971 spin_unlock(&dentry
->d_lock
);
973 spin_unlock(&inode
->i_lock
);
975 EXPORT_SYMBOL(d_prune_aliases
);
977 static void shrink_dentry_list(struct list_head
*list
)
979 struct dentry
*dentry
, *parent
;
981 while (!list_empty(list
)) {
983 dentry
= list_entry(list
->prev
, struct dentry
, d_lru
);
984 spin_lock(&dentry
->d_lock
);
985 parent
= lock_parent(dentry
);
988 * The dispose list is isolated and dentries are not accounted
989 * to the LRU here, so we can simply remove it from the list
990 * here regardless of whether it is referenced or not.
992 d_shrink_del(dentry
);
995 * We found an inuse dentry which was not removed from
996 * the LRU because of laziness during lookup. Do not free it.
998 if (dentry
->d_lockref
.count
> 0) {
999 spin_unlock(&dentry
->d_lock
);
1001 spin_unlock(&parent
->d_lock
);
1006 if (unlikely(dentry
->d_flags
& DCACHE_DENTRY_KILLED
)) {
1007 bool can_free
= dentry
->d_flags
& DCACHE_MAY_FREE
;
1008 spin_unlock(&dentry
->d_lock
);
1010 spin_unlock(&parent
->d_lock
);
1012 dentry_free(dentry
);
1016 inode
= dentry
->d_inode
;
1017 if (inode
&& unlikely(!spin_trylock(&inode
->i_lock
))) {
1018 d_shrink_add(dentry
, list
);
1019 spin_unlock(&dentry
->d_lock
);
1021 spin_unlock(&parent
->d_lock
);
1025 __dentry_kill(dentry
);
1028 * We need to prune ancestors too. This is necessary to prevent
1029 * quadratic behavior of shrink_dcache_parent(), but is also
1030 * expected to be beneficial in reducing dentry cache
1034 while (dentry
&& !lockref_put_or_lock(&dentry
->d_lockref
)) {
1035 parent
= lock_parent(dentry
);
1036 if (dentry
->d_lockref
.count
!= 1) {
1037 dentry
->d_lockref
.count
--;
1038 spin_unlock(&dentry
->d_lock
);
1040 spin_unlock(&parent
->d_lock
);
1043 inode
= dentry
->d_inode
; /* can't be NULL */
1044 if (unlikely(!spin_trylock(&inode
->i_lock
))) {
1045 spin_unlock(&dentry
->d_lock
);
1047 spin_unlock(&parent
->d_lock
);
1051 __dentry_kill(dentry
);
1057 static enum lru_status
dentry_lru_isolate(struct list_head
*item
,
1058 struct list_lru_one
*lru
, spinlock_t
*lru_lock
, void *arg
)
1060 struct list_head
*freeable
= arg
;
1061 struct dentry
*dentry
= container_of(item
, struct dentry
, d_lru
);
1065 * we are inverting the lru lock/dentry->d_lock here,
1066 * so use a trylock. If we fail to get the lock, just skip
1069 if (!spin_trylock(&dentry
->d_lock
))
1073 * Referenced dentries are still in use. If they have active
1074 * counts, just remove them from the LRU. Otherwise give them
1075 * another pass through the LRU.
1077 if (dentry
->d_lockref
.count
) {
1078 d_lru_isolate(lru
, dentry
);
1079 spin_unlock(&dentry
->d_lock
);
1083 if (dentry
->d_flags
& DCACHE_REFERENCED
) {
1084 dentry
->d_flags
&= ~DCACHE_REFERENCED
;
1085 spin_unlock(&dentry
->d_lock
);
1088 * The list move itself will be made by the common LRU code. At
1089 * this point, we've dropped the dentry->d_lock but keep the
1090 * lru lock. This is safe to do, since every list movement is
1091 * protected by the lru lock even if both locks are held.
1093 * This is guaranteed by the fact that all LRU management
1094 * functions are intermediated by the LRU API calls like
1095 * list_lru_add and list_lru_del. List movement in this file
1096 * only ever occur through this functions or through callbacks
1097 * like this one, that are called from the LRU API.
1099 * The only exceptions to this are functions like
1100 * shrink_dentry_list, and code that first checks for the
1101 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1102 * operating only with stack provided lists after they are
1103 * properly isolated from the main list. It is thus, always a
1109 d_lru_shrink_move(lru
, dentry
, freeable
);
1110 spin_unlock(&dentry
->d_lock
);
1116 * prune_dcache_sb - shrink the dcache
1118 * @sc: shrink control, passed to list_lru_shrink_walk()
1120 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1121 * is done when we need more memory and called from the superblock shrinker
1124 * This function may fail to free any resources if all the dentries are in
1127 long prune_dcache_sb(struct super_block
*sb
, struct shrink_control
*sc
)
1132 freed
= list_lru_shrink_walk(&sb
->s_dentry_lru
, sc
,
1133 dentry_lru_isolate
, &dispose
);
1134 shrink_dentry_list(&dispose
);
1138 static enum lru_status
dentry_lru_isolate_shrink(struct list_head
*item
,
1139 struct list_lru_one
*lru
, spinlock_t
*lru_lock
, void *arg
)
1141 struct list_head
*freeable
= arg
;
1142 struct dentry
*dentry
= container_of(item
, struct dentry
, d_lru
);
1145 * we are inverting the lru lock/dentry->d_lock here,
1146 * so use a trylock. If we fail to get the lock, just skip
1149 if (!spin_trylock(&dentry
->d_lock
))
1152 d_lru_shrink_move(lru
, dentry
, freeable
);
1153 spin_unlock(&dentry
->d_lock
);
1160 * shrink_dcache_sb - shrink dcache for a superblock
1163 * Shrink the dcache for the specified super block. This is used to free
1164 * the dcache before unmounting a file system.
1166 void shrink_dcache_sb(struct super_block
*sb
)
1173 freed
= list_lru_walk(&sb
->s_dentry_lru
,
1174 dentry_lru_isolate_shrink
, &dispose
, UINT_MAX
);
1176 this_cpu_sub(nr_dentry_unused
, freed
);
1177 shrink_dentry_list(&dispose
);
1178 } while (freed
> 0);
1180 EXPORT_SYMBOL(shrink_dcache_sb
);
1183 * enum d_walk_ret - action to talke during tree walk
1184 * @D_WALK_CONTINUE: contrinue walk
1185 * @D_WALK_QUIT: quit walk
1186 * @D_WALK_NORETRY: quit when retry is needed
1187 * @D_WALK_SKIP: skip this dentry and its children
1197 * d_walk - walk the dentry tree
1198 * @parent: start of walk
1199 * @data: data passed to @enter() and @finish()
1200 * @enter: callback when first entering the dentry
1201 * @finish: callback when successfully finished the walk
1203 * The @enter() and @finish() callbacks are called with d_lock held.
1205 static void d_walk(struct dentry
*parent
, void *data
,
1206 enum d_walk_ret (*enter
)(void *, struct dentry
*),
1207 void (*finish
)(void *))
1209 struct dentry
*this_parent
;
1210 struct list_head
*next
;
1212 enum d_walk_ret ret
;
1216 read_seqbegin_or_lock(&rename_lock
, &seq
);
1217 this_parent
= parent
;
1218 spin_lock(&this_parent
->d_lock
);
1220 ret
= enter(data
, this_parent
);
1222 case D_WALK_CONTINUE
:
1227 case D_WALK_NORETRY
:
1232 next
= this_parent
->d_subdirs
.next
;
1234 while (next
!= &this_parent
->d_subdirs
) {
1235 struct list_head
*tmp
= next
;
1236 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_child
);
1239 if (unlikely(dentry
->d_flags
& DCACHE_DENTRY_CURSOR
))
1242 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1244 ret
= enter(data
, dentry
);
1246 case D_WALK_CONTINUE
:
1249 spin_unlock(&dentry
->d_lock
);
1251 case D_WALK_NORETRY
:
1255 spin_unlock(&dentry
->d_lock
);
1259 if (!list_empty(&dentry
->d_subdirs
)) {
1260 spin_unlock(&this_parent
->d_lock
);
1261 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
1262 this_parent
= dentry
;
1263 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
1266 spin_unlock(&dentry
->d_lock
);
1269 * All done at this level ... ascend and resume the search.
1273 if (this_parent
!= parent
) {
1274 struct dentry
*child
= this_parent
;
1275 this_parent
= child
->d_parent
;
1277 spin_unlock(&child
->d_lock
);
1278 spin_lock(&this_parent
->d_lock
);
1280 /* might go back up the wrong parent if we have had a rename. */
1281 if (need_seqretry(&rename_lock
, seq
))
1283 /* go into the first sibling still alive */
1285 next
= child
->d_child
.next
;
1286 if (next
== &this_parent
->d_subdirs
)
1288 child
= list_entry(next
, struct dentry
, d_child
);
1289 } while (unlikely(child
->d_flags
& DCACHE_DENTRY_KILLED
));
1293 if (need_seqretry(&rename_lock
, seq
))
1300 spin_unlock(&this_parent
->d_lock
);
1301 done_seqretry(&rename_lock
, seq
);
1305 spin_unlock(&this_parent
->d_lock
);
1315 * Search for at least 1 mount point in the dentry's subdirs.
1316 * We descend to the next level whenever the d_subdirs
1317 * list is non-empty and continue searching.
1320 static enum d_walk_ret
check_mount(void *data
, struct dentry
*dentry
)
1323 if (d_mountpoint(dentry
)) {
1327 return D_WALK_CONTINUE
;
1331 * have_submounts - check for mounts over a dentry
1332 * @parent: dentry to check.
1334 * Return true if the parent or its subdirectories contain
1337 int have_submounts(struct dentry
*parent
)
1341 d_walk(parent
, &ret
, check_mount
, NULL
);
1345 EXPORT_SYMBOL(have_submounts
);
1348 * Called by mount code to set a mountpoint and check if the mountpoint is
1349 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1350 * subtree can become unreachable).
1352 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1353 * this reason take rename_lock and d_lock on dentry and ancestors.
1355 int d_set_mounted(struct dentry
*dentry
)
1359 write_seqlock(&rename_lock
);
1360 for (p
= dentry
->d_parent
; !IS_ROOT(p
); p
= p
->d_parent
) {
1361 /* Need exclusion wrt. d_invalidate() */
1362 spin_lock(&p
->d_lock
);
1363 if (unlikely(d_unhashed(p
))) {
1364 spin_unlock(&p
->d_lock
);
1367 spin_unlock(&p
->d_lock
);
1369 spin_lock(&dentry
->d_lock
);
1370 if (!d_unlinked(dentry
)) {
1371 dentry
->d_flags
|= DCACHE_MOUNTED
;
1374 spin_unlock(&dentry
->d_lock
);
1376 write_sequnlock(&rename_lock
);
1381 * Search the dentry child list of the specified parent,
1382 * and move any unused dentries to the end of the unused
1383 * list for prune_dcache(). We descend to the next level
1384 * whenever the d_subdirs list is non-empty and continue
1387 * It returns zero iff there are no unused children,
1388 * otherwise it returns the number of children moved to
1389 * the end of the unused list. This may not be the total
1390 * number of unused children, because select_parent can
1391 * drop the lock and return early due to latency
1395 struct select_data
{
1396 struct dentry
*start
;
1397 struct list_head dispose
;
1401 static enum d_walk_ret
select_collect(void *_data
, struct dentry
*dentry
)
1403 struct select_data
*data
= _data
;
1404 enum d_walk_ret ret
= D_WALK_CONTINUE
;
1406 if (data
->start
== dentry
)
1409 if (dentry
->d_flags
& DCACHE_SHRINK_LIST
) {
1412 if (dentry
->d_flags
& DCACHE_LRU_LIST
)
1414 if (!dentry
->d_lockref
.count
) {
1415 d_shrink_add(dentry
, &data
->dispose
);
1420 * We can return to the caller if we have found some (this
1421 * ensures forward progress). We'll be coming back to find
1424 if (!list_empty(&data
->dispose
))
1425 ret
= need_resched() ? D_WALK_QUIT
: D_WALK_NORETRY
;
1431 * shrink_dcache_parent - prune dcache
1432 * @parent: parent of entries to prune
1434 * Prune the dcache to remove unused children of the parent dentry.
1436 void shrink_dcache_parent(struct dentry
*parent
)
1439 struct select_data data
;
1441 INIT_LIST_HEAD(&data
.dispose
);
1442 data
.start
= parent
;
1445 d_walk(parent
, &data
, select_collect
, NULL
);
1449 shrink_dentry_list(&data
.dispose
);
1453 EXPORT_SYMBOL(shrink_dcache_parent
);
1455 static enum d_walk_ret
umount_check(void *_data
, struct dentry
*dentry
)
1457 /* it has busy descendents; complain about those instead */
1458 if (!list_empty(&dentry
->d_subdirs
))
1459 return D_WALK_CONTINUE
;
1461 /* root with refcount 1 is fine */
1462 if (dentry
== _data
&& dentry
->d_lockref
.count
== 1)
1463 return D_WALK_CONTINUE
;
1465 printk(KERN_ERR
"BUG: Dentry %p{i=%lx,n=%pd} "
1466 " still in use (%d) [unmount of %s %s]\n",
1469 dentry
->d_inode
->i_ino
: 0UL,
1471 dentry
->d_lockref
.count
,
1472 dentry
->d_sb
->s_type
->name
,
1473 dentry
->d_sb
->s_id
);
1475 return D_WALK_CONTINUE
;
1478 static void do_one_tree(struct dentry
*dentry
)
1480 shrink_dcache_parent(dentry
);
1481 d_walk(dentry
, dentry
, umount_check
, NULL
);
1487 * destroy the dentries attached to a superblock on unmounting
1489 void shrink_dcache_for_umount(struct super_block
*sb
)
1491 struct dentry
*dentry
;
1493 WARN(down_read_trylock(&sb
->s_umount
), "s_umount should've been locked");
1495 dentry
= sb
->s_root
;
1497 do_one_tree(dentry
);
1499 while (!hlist_bl_empty(&sb
->s_anon
)) {
1500 dentry
= dget(hlist_bl_entry(hlist_bl_first(&sb
->s_anon
), struct dentry
, d_hash
));
1501 do_one_tree(dentry
);
1505 struct detach_data
{
1506 struct select_data select
;
1507 struct dentry
*mountpoint
;
1509 static enum d_walk_ret
detach_and_collect(void *_data
, struct dentry
*dentry
)
1511 struct detach_data
*data
= _data
;
1513 if (d_mountpoint(dentry
)) {
1514 __dget_dlock(dentry
);
1515 data
->mountpoint
= dentry
;
1519 return select_collect(&data
->select
, dentry
);
1522 static void check_and_drop(void *_data
)
1524 struct detach_data
*data
= _data
;
1526 if (!data
->mountpoint
&& !data
->select
.found
)
1527 __d_drop(data
->select
.start
);
1531 * d_invalidate - detach submounts, prune dcache, and drop
1532 * @dentry: dentry to invalidate (aka detach, prune and drop)
1536 * The final d_drop is done as an atomic operation relative to
1537 * rename_lock ensuring there are no races with d_set_mounted. This
1538 * ensures there are no unhashed dentries on the path to a mountpoint.
1540 void d_invalidate(struct dentry
*dentry
)
1543 * If it's already been dropped, return OK.
1545 spin_lock(&dentry
->d_lock
);
1546 if (d_unhashed(dentry
)) {
1547 spin_unlock(&dentry
->d_lock
);
1550 spin_unlock(&dentry
->d_lock
);
1552 /* Negative dentries can be dropped without further checks */
1553 if (!dentry
->d_inode
) {
1559 struct detach_data data
;
1561 data
.mountpoint
= NULL
;
1562 INIT_LIST_HEAD(&data
.select
.dispose
);
1563 data
.select
.start
= dentry
;
1564 data
.select
.found
= 0;
1566 d_walk(dentry
, &data
, detach_and_collect
, check_and_drop
);
1568 if (data
.select
.found
)
1569 shrink_dentry_list(&data
.select
.dispose
);
1571 if (data
.mountpoint
) {
1572 detach_mounts(data
.mountpoint
);
1573 dput(data
.mountpoint
);
1576 if (!data
.mountpoint
&& !data
.select
.found
)
1582 EXPORT_SYMBOL(d_invalidate
);
1585 * __d_alloc - allocate a dcache entry
1586 * @sb: filesystem it will belong to
1587 * @name: qstr of the name
1589 * Allocates a dentry. It returns %NULL if there is insufficient memory
1590 * available. On a success the dentry is returned. The name passed in is
1591 * copied and the copy passed in may be reused after this call.
1594 struct dentry
*__d_alloc(struct super_block
*sb
, const struct qstr
*name
)
1596 struct dentry
*dentry
;
1599 dentry
= kmem_cache_alloc(dentry_cache
, GFP_KERNEL
);
1604 * We guarantee that the inline name is always NUL-terminated.
1605 * This way the memcpy() done by the name switching in rename
1606 * will still always have a NUL at the end, even if we might
1607 * be overwriting an internal NUL character
1609 dentry
->d_iname
[DNAME_INLINE_LEN
-1] = 0;
1610 if (unlikely(!name
)) {
1611 static const struct qstr anon
= QSTR_INIT("/", 1);
1613 dname
= dentry
->d_iname
;
1614 } else if (name
->len
> DNAME_INLINE_LEN
-1) {
1615 size_t size
= offsetof(struct external_name
, name
[1]);
1616 struct external_name
*p
= kmalloc(size
+ name
->len
,
1617 GFP_KERNEL_ACCOUNT
);
1619 kmem_cache_free(dentry_cache
, dentry
);
1622 atomic_set(&p
->u
.count
, 1);
1624 if (IS_ENABLED(CONFIG_DCACHE_WORD_ACCESS
))
1625 kasan_unpoison_shadow(dname
,
1626 round_up(name
->len
+ 1, sizeof(unsigned long)));
1628 dname
= dentry
->d_iname
;
1631 dentry
->d_name
.len
= name
->len
;
1632 dentry
->d_name
.hash
= name
->hash
;
1633 memcpy(dname
, name
->name
, name
->len
);
1634 dname
[name
->len
] = 0;
1636 /* Make sure we always see the terminating NUL character */
1638 dentry
->d_name
.name
= dname
;
1640 dentry
->d_lockref
.count
= 1;
1641 dentry
->d_flags
= 0;
1642 spin_lock_init(&dentry
->d_lock
);
1643 seqcount_init(&dentry
->d_seq
);
1644 dentry
->d_inode
= NULL
;
1645 dentry
->d_parent
= dentry
;
1647 dentry
->d_op
= NULL
;
1648 dentry
->d_fsdata
= NULL
;
1649 INIT_HLIST_BL_NODE(&dentry
->d_hash
);
1650 INIT_LIST_HEAD(&dentry
->d_lru
);
1651 INIT_LIST_HEAD(&dentry
->d_subdirs
);
1652 INIT_HLIST_NODE(&dentry
->d_u
.d_alias
);
1653 INIT_LIST_HEAD(&dentry
->d_child
);
1654 d_set_d_op(dentry
, dentry
->d_sb
->s_d_op
);
1656 this_cpu_inc(nr_dentry
);
1662 * d_alloc - allocate a dcache entry
1663 * @parent: parent of entry to allocate
1664 * @name: qstr of the name
1666 * Allocates a dentry. It returns %NULL if there is insufficient memory
1667 * available. On a success the dentry is returned. The name passed in is
1668 * copied and the copy passed in may be reused after this call.
1670 struct dentry
*d_alloc(struct dentry
* parent
, const struct qstr
*name
)
1672 struct dentry
*dentry
= __d_alloc(parent
->d_sb
, name
);
1675 dentry
->d_flags
|= DCACHE_RCUACCESS
;
1676 spin_lock(&parent
->d_lock
);
1678 * don't need child lock because it is not subject
1679 * to concurrency here
1681 __dget_dlock(parent
);
1682 dentry
->d_parent
= parent
;
1683 list_add(&dentry
->d_child
, &parent
->d_subdirs
);
1684 spin_unlock(&parent
->d_lock
);
1688 EXPORT_SYMBOL(d_alloc
);
1690 struct dentry
*d_alloc_cursor(struct dentry
* parent
)
1692 struct dentry
*dentry
= __d_alloc(parent
->d_sb
, NULL
);
1694 dentry
->d_flags
|= DCACHE_RCUACCESS
| DCACHE_DENTRY_CURSOR
;
1695 dentry
->d_parent
= dget(parent
);
1701 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1702 * @sb: the superblock
1703 * @name: qstr of the name
1705 * For a filesystem that just pins its dentries in memory and never
1706 * performs lookups at all, return an unhashed IS_ROOT dentry.
1708 struct dentry
*d_alloc_pseudo(struct super_block
*sb
, const struct qstr
*name
)
1710 return __d_alloc(sb
, name
);
1712 EXPORT_SYMBOL(d_alloc_pseudo
);
1714 struct dentry
*d_alloc_name(struct dentry
*parent
, const char *name
)
1719 q
.hash_len
= hashlen_string(name
);
1720 return d_alloc(parent
, &q
);
1722 EXPORT_SYMBOL(d_alloc_name
);
1724 void d_set_d_op(struct dentry
*dentry
, const struct dentry_operations
*op
)
1726 WARN_ON_ONCE(dentry
->d_op
);
1727 WARN_ON_ONCE(dentry
->d_flags
& (DCACHE_OP_HASH
|
1729 DCACHE_OP_REVALIDATE
|
1730 DCACHE_OP_WEAK_REVALIDATE
|
1732 DCACHE_OP_SELECT_INODE
|
1738 dentry
->d_flags
|= DCACHE_OP_HASH
;
1740 dentry
->d_flags
|= DCACHE_OP_COMPARE
;
1741 if (op
->d_revalidate
)
1742 dentry
->d_flags
|= DCACHE_OP_REVALIDATE
;
1743 if (op
->d_weak_revalidate
)
1744 dentry
->d_flags
|= DCACHE_OP_WEAK_REVALIDATE
;
1746 dentry
->d_flags
|= DCACHE_OP_DELETE
;
1748 dentry
->d_flags
|= DCACHE_OP_PRUNE
;
1749 if (op
->d_select_inode
)
1750 dentry
->d_flags
|= DCACHE_OP_SELECT_INODE
;
1752 dentry
->d_flags
|= DCACHE_OP_REAL
;
1755 EXPORT_SYMBOL(d_set_d_op
);
1759 * d_set_fallthru - Mark a dentry as falling through to a lower layer
1760 * @dentry - The dentry to mark
1762 * Mark a dentry as falling through to the lower layer (as set with
1763 * d_pin_lower()). This flag may be recorded on the medium.
1765 void d_set_fallthru(struct dentry
*dentry
)
1767 spin_lock(&dentry
->d_lock
);
1768 dentry
->d_flags
|= DCACHE_FALLTHRU
;
1769 spin_unlock(&dentry
->d_lock
);
1771 EXPORT_SYMBOL(d_set_fallthru
);
1773 static unsigned d_flags_for_inode(struct inode
*inode
)
1775 unsigned add_flags
= DCACHE_REGULAR_TYPE
;
1778 return DCACHE_MISS_TYPE
;
1780 if (S_ISDIR(inode
->i_mode
)) {
1781 add_flags
= DCACHE_DIRECTORY_TYPE
;
1782 if (unlikely(!(inode
->i_opflags
& IOP_LOOKUP
))) {
1783 if (unlikely(!inode
->i_op
->lookup
))
1784 add_flags
= DCACHE_AUTODIR_TYPE
;
1786 inode
->i_opflags
|= IOP_LOOKUP
;
1788 goto type_determined
;
1791 if (unlikely(!(inode
->i_opflags
& IOP_NOFOLLOW
))) {
1792 if (unlikely(inode
->i_op
->get_link
)) {
1793 add_flags
= DCACHE_SYMLINK_TYPE
;
1794 goto type_determined
;
1796 inode
->i_opflags
|= IOP_NOFOLLOW
;
1799 if (unlikely(!S_ISREG(inode
->i_mode
)))
1800 add_flags
= DCACHE_SPECIAL_TYPE
;
1803 if (unlikely(IS_AUTOMOUNT(inode
)))
1804 add_flags
|= DCACHE_NEED_AUTOMOUNT
;
1808 static void __d_instantiate(struct dentry
*dentry
, struct inode
*inode
)
1810 unsigned add_flags
= d_flags_for_inode(inode
);
1811 WARN_ON(d_in_lookup(dentry
));
1813 spin_lock(&dentry
->d_lock
);
1814 hlist_add_head(&dentry
->d_u
.d_alias
, &inode
->i_dentry
);
1815 raw_write_seqcount_begin(&dentry
->d_seq
);
1816 __d_set_inode_and_type(dentry
, inode
, add_flags
);
1817 raw_write_seqcount_end(&dentry
->d_seq
);
1818 __fsnotify_d_instantiate(dentry
);
1819 spin_unlock(&dentry
->d_lock
);
1823 * d_instantiate - fill in inode information for a dentry
1824 * @entry: dentry to complete
1825 * @inode: inode to attach to this dentry
1827 * Fill in inode information in the entry.
1829 * This turns negative dentries into productive full members
1832 * NOTE! This assumes that the inode count has been incremented
1833 * (or otherwise set) by the caller to indicate that it is now
1834 * in use by the dcache.
1837 void d_instantiate(struct dentry
*entry
, struct inode
* inode
)
1839 BUG_ON(!hlist_unhashed(&entry
->d_u
.d_alias
));
1841 security_d_instantiate(entry
, inode
);
1842 spin_lock(&inode
->i_lock
);
1843 __d_instantiate(entry
, inode
);
1844 spin_unlock(&inode
->i_lock
);
1847 EXPORT_SYMBOL(d_instantiate
);
1850 * d_instantiate_no_diralias - instantiate a non-aliased dentry
1851 * @entry: dentry to complete
1852 * @inode: inode to attach to this dentry
1854 * Fill in inode information in the entry. If a directory alias is found, then
1855 * return an error (and drop inode). Together with d_materialise_unique() this
1856 * guarantees that a directory inode may never have more than one alias.
1858 int d_instantiate_no_diralias(struct dentry
*entry
, struct inode
*inode
)
1860 BUG_ON(!hlist_unhashed(&entry
->d_u
.d_alias
));
1862 security_d_instantiate(entry
, inode
);
1863 spin_lock(&inode
->i_lock
);
1864 if (S_ISDIR(inode
->i_mode
) && !hlist_empty(&inode
->i_dentry
)) {
1865 spin_unlock(&inode
->i_lock
);
1869 __d_instantiate(entry
, inode
);
1870 spin_unlock(&inode
->i_lock
);
1874 EXPORT_SYMBOL(d_instantiate_no_diralias
);
1876 struct dentry
*d_make_root(struct inode
*root_inode
)
1878 struct dentry
*res
= NULL
;
1881 res
= __d_alloc(root_inode
->i_sb
, NULL
);
1883 d_instantiate(res
, root_inode
);
1889 EXPORT_SYMBOL(d_make_root
);
1891 static struct dentry
* __d_find_any_alias(struct inode
*inode
)
1893 struct dentry
*alias
;
1895 if (hlist_empty(&inode
->i_dentry
))
1897 alias
= hlist_entry(inode
->i_dentry
.first
, struct dentry
, d_u
.d_alias
);
1903 * d_find_any_alias - find any alias for a given inode
1904 * @inode: inode to find an alias for
1906 * If any aliases exist for the given inode, take and return a
1907 * reference for one of them. If no aliases exist, return %NULL.
1909 struct dentry
*d_find_any_alias(struct inode
*inode
)
1913 spin_lock(&inode
->i_lock
);
1914 de
= __d_find_any_alias(inode
);
1915 spin_unlock(&inode
->i_lock
);
1918 EXPORT_SYMBOL(d_find_any_alias
);
1920 static struct dentry
*__d_obtain_alias(struct inode
*inode
, int disconnected
)
1927 return ERR_PTR(-ESTALE
);
1929 return ERR_CAST(inode
);
1931 res
= d_find_any_alias(inode
);
1935 tmp
= __d_alloc(inode
->i_sb
, NULL
);
1937 res
= ERR_PTR(-ENOMEM
);
1941 security_d_instantiate(tmp
, inode
);
1942 spin_lock(&inode
->i_lock
);
1943 res
= __d_find_any_alias(inode
);
1945 spin_unlock(&inode
->i_lock
);
1950 /* attach a disconnected dentry */
1951 add_flags
= d_flags_for_inode(inode
);
1954 add_flags
|= DCACHE_DISCONNECTED
;
1956 spin_lock(&tmp
->d_lock
);
1957 __d_set_inode_and_type(tmp
, inode
, add_flags
);
1958 hlist_add_head(&tmp
->d_u
.d_alias
, &inode
->i_dentry
);
1959 hlist_bl_lock(&tmp
->d_sb
->s_anon
);
1960 hlist_bl_add_head(&tmp
->d_hash
, &tmp
->d_sb
->s_anon
);
1961 hlist_bl_unlock(&tmp
->d_sb
->s_anon
);
1962 spin_unlock(&tmp
->d_lock
);
1963 spin_unlock(&inode
->i_lock
);
1973 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
1974 * @inode: inode to allocate the dentry for
1976 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1977 * similar open by handle operations. The returned dentry may be anonymous,
1978 * or may have a full name (if the inode was already in the cache).
1980 * When called on a directory inode, we must ensure that the inode only ever
1981 * has one dentry. If a dentry is found, that is returned instead of
1982 * allocating a new one.
1984 * On successful return, the reference to the inode has been transferred
1985 * to the dentry. In case of an error the reference on the inode is released.
1986 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1987 * be passed in and the error will be propagated to the return value,
1988 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1990 struct dentry
*d_obtain_alias(struct inode
*inode
)
1992 return __d_obtain_alias(inode
, 1);
1994 EXPORT_SYMBOL(d_obtain_alias
);
1997 * d_obtain_root - find or allocate a dentry for a given inode
1998 * @inode: inode to allocate the dentry for
2000 * Obtain an IS_ROOT dentry for the root of a filesystem.
2002 * We must ensure that directory inodes only ever have one dentry. If a
2003 * dentry is found, that is returned instead of allocating a new one.
2005 * On successful return, the reference to the inode has been transferred
2006 * to the dentry. In case of an error the reference on the inode is
2007 * released. A %NULL or IS_ERR inode may be passed in and will be the
2008 * error will be propagate to the return value, with a %NULL @inode
2009 * replaced by ERR_PTR(-ESTALE).
2011 struct dentry
*d_obtain_root(struct inode
*inode
)
2013 return __d_obtain_alias(inode
, 0);
2015 EXPORT_SYMBOL(d_obtain_root
);
2018 * d_add_ci - lookup or allocate new dentry with case-exact name
2019 * @inode: the inode case-insensitive lookup has found
2020 * @dentry: the negative dentry that was passed to the parent's lookup func
2021 * @name: the case-exact name to be associated with the returned dentry
2023 * This is to avoid filling the dcache with case-insensitive names to the
2024 * same inode, only the actual correct case is stored in the dcache for
2025 * case-insensitive filesystems.
2027 * For a case-insensitive lookup match and if the the case-exact dentry
2028 * already exists in in the dcache, use it and return it.
2030 * If no entry exists with the exact case name, allocate new dentry with
2031 * the exact case, and return the spliced entry.
2033 struct dentry
*d_add_ci(struct dentry
*dentry
, struct inode
*inode
,
2036 struct dentry
*found
, *res
;
2039 * First check if a dentry matching the name already exists,
2040 * if not go ahead and create it now.
2042 found
= d_hash_and_lookup(dentry
->d_parent
, name
);
2047 if (d_in_lookup(dentry
)) {
2048 found
= d_alloc_parallel(dentry
->d_parent
, name
,
2050 if (IS_ERR(found
) || !d_in_lookup(found
)) {
2055 found
= d_alloc(dentry
->d_parent
, name
);
2058 return ERR_PTR(-ENOMEM
);
2061 res
= d_splice_alias(inode
, found
);
2068 EXPORT_SYMBOL(d_add_ci
);
2071 * Do the slow-case of the dentry name compare.
2073 * Unlike the dentry_cmp() function, we need to atomically
2074 * load the name and length information, so that the
2075 * filesystem can rely on them, and can use the 'name' and
2076 * 'len' information without worrying about walking off the
2077 * end of memory etc.
2079 * Thus the read_seqcount_retry() and the "duplicate" info
2080 * in arguments (the low-level filesystem should not look
2081 * at the dentry inode or name contents directly, since
2082 * rename can change them while we're in RCU mode).
2084 enum slow_d_compare
{
2090 static noinline
enum slow_d_compare
slow_dentry_cmp(
2091 const struct dentry
*parent
,
2092 struct dentry
*dentry
,
2094 const struct qstr
*name
)
2096 int tlen
= dentry
->d_name
.len
;
2097 const char *tname
= dentry
->d_name
.name
;
2099 if (read_seqcount_retry(&dentry
->d_seq
, seq
)) {
2101 return D_COMP_SEQRETRY
;
2103 if (parent
->d_op
->d_compare(parent
, dentry
, tlen
, tname
, name
))
2104 return D_COMP_NOMATCH
;
2109 * __d_lookup_rcu - search for a dentry (racy, store-free)
2110 * @parent: parent dentry
2111 * @name: qstr of name we wish to find
2112 * @seqp: returns d_seq value at the point where the dentry was found
2113 * Returns: dentry, or NULL
2115 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2116 * resolution (store-free path walking) design described in
2117 * Documentation/filesystems/path-lookup.txt.
2119 * This is not to be used outside core vfs.
2121 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2122 * held, and rcu_read_lock held. The returned dentry must not be stored into
2123 * without taking d_lock and checking d_seq sequence count against @seq
2126 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2129 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2130 * the returned dentry, so long as its parent's seqlock is checked after the
2131 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2132 * is formed, giving integrity down the path walk.
2134 * NOTE! The caller *has* to check the resulting dentry against the sequence
2135 * number we've returned before using any of the resulting dentry state!
2137 struct dentry
*__d_lookup_rcu(const struct dentry
*parent
,
2138 const struct qstr
*name
,
2141 u64 hashlen
= name
->hash_len
;
2142 const unsigned char *str
= name
->name
;
2143 struct hlist_bl_head
*b
= d_hash(parent
, hashlen_hash(hashlen
));
2144 struct hlist_bl_node
*node
;
2145 struct dentry
*dentry
;
2148 * Note: There is significant duplication with __d_lookup_rcu which is
2149 * required to prevent single threaded performance regressions
2150 * especially on architectures where smp_rmb (in seqcounts) are costly.
2151 * Keep the two functions in sync.
2155 * The hash list is protected using RCU.
2157 * Carefully use d_seq when comparing a candidate dentry, to avoid
2158 * races with d_move().
2160 * It is possible that concurrent renames can mess up our list
2161 * walk here and result in missing our dentry, resulting in the
2162 * false-negative result. d_lookup() protects against concurrent
2163 * renames using rename_lock seqlock.
2165 * See Documentation/filesystems/path-lookup.txt for more details.
2167 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
2172 * The dentry sequence count protects us from concurrent
2173 * renames, and thus protects parent and name fields.
2175 * The caller must perform a seqcount check in order
2176 * to do anything useful with the returned dentry.
2178 * NOTE! We do a "raw" seqcount_begin here. That means that
2179 * we don't wait for the sequence count to stabilize if it
2180 * is in the middle of a sequence change. If we do the slow
2181 * dentry compare, we will do seqretries until it is stable,
2182 * and if we end up with a successful lookup, we actually
2183 * want to exit RCU lookup anyway.
2185 seq
= raw_seqcount_begin(&dentry
->d_seq
);
2186 if (dentry
->d_parent
!= parent
)
2188 if (d_unhashed(dentry
))
2191 if (unlikely(parent
->d_flags
& DCACHE_OP_COMPARE
)) {
2192 if (dentry
->d_name
.hash
!= hashlen_hash(hashlen
))
2195 switch (slow_dentry_cmp(parent
, dentry
, seq
, name
)) {
2198 case D_COMP_NOMATCH
:
2205 if (dentry
->d_name
.hash_len
!= hashlen
)
2208 if (!dentry_cmp(dentry
, str
, hashlen_len(hashlen
)))
2215 * d_lookup - search for a dentry
2216 * @parent: parent dentry
2217 * @name: qstr of name we wish to find
2218 * Returns: dentry, or NULL
2220 * d_lookup searches the children of the parent dentry for the name in
2221 * question. If the dentry is found its reference count is incremented and the
2222 * dentry is returned. The caller must use dput to free the entry when it has
2223 * finished using it. %NULL is returned if the dentry does not exist.
2225 struct dentry
*d_lookup(const struct dentry
*parent
, const struct qstr
*name
)
2227 struct dentry
*dentry
;
2231 seq
= read_seqbegin(&rename_lock
);
2232 dentry
= __d_lookup(parent
, name
);
2235 } while (read_seqretry(&rename_lock
, seq
));
2238 EXPORT_SYMBOL(d_lookup
);
2241 * __d_lookup - search for a dentry (racy)
2242 * @parent: parent dentry
2243 * @name: qstr of name we wish to find
2244 * Returns: dentry, or NULL
2246 * __d_lookup is like d_lookup, however it may (rarely) return a
2247 * false-negative result due to unrelated rename activity.
2249 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2250 * however it must be used carefully, eg. with a following d_lookup in
2251 * the case of failure.
2253 * __d_lookup callers must be commented.
2255 struct dentry
*__d_lookup(const struct dentry
*parent
, const struct qstr
*name
)
2257 unsigned int len
= name
->len
;
2258 unsigned int hash
= name
->hash
;
2259 const unsigned char *str
= name
->name
;
2260 struct hlist_bl_head
*b
= d_hash(parent
, hash
);
2261 struct hlist_bl_node
*node
;
2262 struct dentry
*found
= NULL
;
2263 struct dentry
*dentry
;
2266 * Note: There is significant duplication with __d_lookup_rcu which is
2267 * required to prevent single threaded performance regressions
2268 * especially on architectures where smp_rmb (in seqcounts) are costly.
2269 * Keep the two functions in sync.
2273 * The hash list is protected using RCU.
2275 * Take d_lock when comparing a candidate dentry, to avoid races
2278 * It is possible that concurrent renames can mess up our list
2279 * walk here and result in missing our dentry, resulting in the
2280 * false-negative result. d_lookup() protects against concurrent
2281 * renames using rename_lock seqlock.
2283 * See Documentation/filesystems/path-lookup.txt for more details.
2287 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
2289 if (dentry
->d_name
.hash
!= hash
)
2292 spin_lock(&dentry
->d_lock
);
2293 if (dentry
->d_parent
!= parent
)
2295 if (d_unhashed(dentry
))
2299 * It is safe to compare names since d_move() cannot
2300 * change the qstr (protected by d_lock).
2302 if (parent
->d_flags
& DCACHE_OP_COMPARE
) {
2303 int tlen
= dentry
->d_name
.len
;
2304 const char *tname
= dentry
->d_name
.name
;
2305 if (parent
->d_op
->d_compare(parent
, dentry
, tlen
, tname
, name
))
2308 if (dentry
->d_name
.len
!= len
)
2310 if (dentry_cmp(dentry
, str
, len
))
2314 dentry
->d_lockref
.count
++;
2316 spin_unlock(&dentry
->d_lock
);
2319 spin_unlock(&dentry
->d_lock
);
2327 * d_hash_and_lookup - hash the qstr then search for a dentry
2328 * @dir: Directory to search in
2329 * @name: qstr of name we wish to find
2331 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2333 struct dentry
*d_hash_and_lookup(struct dentry
*dir
, struct qstr
*name
)
2336 * Check for a fs-specific hash function. Note that we must
2337 * calculate the standard hash first, as the d_op->d_hash()
2338 * routine may choose to leave the hash value unchanged.
2340 name
->hash
= full_name_hash(name
->name
, name
->len
);
2341 if (dir
->d_flags
& DCACHE_OP_HASH
) {
2342 int err
= dir
->d_op
->d_hash(dir
, name
);
2343 if (unlikely(err
< 0))
2344 return ERR_PTR(err
);
2346 return d_lookup(dir
, name
);
2348 EXPORT_SYMBOL(d_hash_and_lookup
);
2351 * When a file is deleted, we have two options:
2352 * - turn this dentry into a negative dentry
2353 * - unhash this dentry and free it.
2355 * Usually, we want to just turn this into
2356 * a negative dentry, but if anybody else is
2357 * currently using the dentry or the inode
2358 * we can't do that and we fall back on removing
2359 * it from the hash queues and waiting for
2360 * it to be deleted later when it has no users
2364 * d_delete - delete a dentry
2365 * @dentry: The dentry to delete
2367 * Turn the dentry into a negative dentry if possible, otherwise
2368 * remove it from the hash queues so it can be deleted later
2371 void d_delete(struct dentry
* dentry
)
2373 struct inode
*inode
;
2376 * Are we the only user?
2379 spin_lock(&dentry
->d_lock
);
2380 inode
= dentry
->d_inode
;
2381 isdir
= S_ISDIR(inode
->i_mode
);
2382 if (dentry
->d_lockref
.count
== 1) {
2383 if (!spin_trylock(&inode
->i_lock
)) {
2384 spin_unlock(&dentry
->d_lock
);
2388 dentry
->d_flags
&= ~DCACHE_CANT_MOUNT
;
2389 dentry_unlink_inode(dentry
);
2390 fsnotify_nameremove(dentry
, isdir
);
2394 if (!d_unhashed(dentry
))
2397 spin_unlock(&dentry
->d_lock
);
2399 fsnotify_nameremove(dentry
, isdir
);
2401 EXPORT_SYMBOL(d_delete
);
2403 static void __d_rehash(struct dentry
* entry
, struct hlist_bl_head
*b
)
2405 BUG_ON(!d_unhashed(entry
));
2407 hlist_bl_add_head_rcu(&entry
->d_hash
, b
);
2411 static void _d_rehash(struct dentry
* entry
)
2413 __d_rehash(entry
, d_hash(entry
->d_parent
, entry
->d_name
.hash
));
2417 * d_rehash - add an entry back to the hash
2418 * @entry: dentry to add to the hash
2420 * Adds a dentry to the hash according to its name.
2423 void d_rehash(struct dentry
* entry
)
2425 spin_lock(&entry
->d_lock
);
2427 spin_unlock(&entry
->d_lock
);
2429 EXPORT_SYMBOL(d_rehash
);
2431 static inline unsigned start_dir_add(struct inode
*dir
)
2435 unsigned n
= dir
->i_dir_seq
;
2436 if (!(n
& 1) && cmpxchg(&dir
->i_dir_seq
, n
, n
+ 1) == n
)
2442 static inline void end_dir_add(struct inode
*dir
, unsigned n
)
2444 smp_store_release(&dir
->i_dir_seq
, n
+ 2);
2447 static void d_wait_lookup(struct dentry
*dentry
)
2449 if (d_in_lookup(dentry
)) {
2450 DECLARE_WAITQUEUE(wait
, current
);
2451 add_wait_queue(dentry
->d_wait
, &wait
);
2453 set_current_state(TASK_UNINTERRUPTIBLE
);
2454 spin_unlock(&dentry
->d_lock
);
2456 spin_lock(&dentry
->d_lock
);
2457 } while (d_in_lookup(dentry
));
2461 struct dentry
*d_alloc_parallel(struct dentry
*parent
,
2462 const struct qstr
*name
,
2463 wait_queue_head_t
*wq
)
2465 unsigned int len
= name
->len
;
2466 unsigned int hash
= name
->hash
;
2467 const unsigned char *str
= name
->name
;
2468 struct hlist_bl_head
*b
= in_lookup_hash(parent
, hash
);
2469 struct hlist_bl_node
*node
;
2470 struct dentry
*new = d_alloc(parent
, name
);
2471 struct dentry
*dentry
;
2472 unsigned seq
, r_seq
, d_seq
;
2475 return ERR_PTR(-ENOMEM
);
2479 seq
= smp_load_acquire(&parent
->d_inode
->i_dir_seq
) & ~1;
2480 r_seq
= read_seqbegin(&rename_lock
);
2481 dentry
= __d_lookup_rcu(parent
, name
, &d_seq
);
2482 if (unlikely(dentry
)) {
2483 if (!lockref_get_not_dead(&dentry
->d_lockref
)) {
2487 if (read_seqcount_retry(&dentry
->d_seq
, d_seq
)) {
2496 if (unlikely(read_seqretry(&rename_lock
, r_seq
))) {
2501 if (unlikely(parent
->d_inode
->i_dir_seq
!= seq
)) {
2507 * No changes for the parent since the beginning of d_lookup().
2508 * Since all removals from the chain happen with hlist_bl_lock(),
2509 * any potential in-lookup matches are going to stay here until
2510 * we unlock the chain. All fields are stable in everything
2513 hlist_bl_for_each_entry(dentry
, node
, b
, d_u
.d_in_lookup_hash
) {
2514 if (dentry
->d_name
.hash
!= hash
)
2516 if (dentry
->d_parent
!= parent
)
2518 if (parent
->d_flags
& DCACHE_OP_COMPARE
) {
2519 int tlen
= dentry
->d_name
.len
;
2520 const char *tname
= dentry
->d_name
.name
;
2521 if (parent
->d_op
->d_compare(parent
, dentry
, tlen
, tname
, name
))
2524 if (dentry
->d_name
.len
!= len
)
2526 if (dentry_cmp(dentry
, str
, len
))
2530 /* now we can try to grab a reference */
2531 if (!lockref_get_not_dead(&dentry
->d_lockref
)) {
2538 * somebody is likely to be still doing lookup for it;
2539 * wait for them to finish
2541 spin_lock(&dentry
->d_lock
);
2542 d_wait_lookup(dentry
);
2544 * it's not in-lookup anymore; in principle we should repeat
2545 * everything from dcache lookup, but it's likely to be what
2546 * d_lookup() would've found anyway. If it is, just return it;
2547 * otherwise we really have to repeat the whole thing.
2549 if (unlikely(dentry
->d_name
.hash
!= hash
))
2551 if (unlikely(dentry
->d_parent
!= parent
))
2553 if (unlikely(d_unhashed(dentry
)))
2555 if (parent
->d_flags
& DCACHE_OP_COMPARE
) {
2556 int tlen
= dentry
->d_name
.len
;
2557 const char *tname
= dentry
->d_name
.name
;
2558 if (parent
->d_op
->d_compare(parent
, dentry
, tlen
, tname
, name
))
2561 if (unlikely(dentry
->d_name
.len
!= len
))
2563 if (unlikely(dentry_cmp(dentry
, str
, len
)))
2566 /* OK, it *is* a hashed match; return it */
2567 spin_unlock(&dentry
->d_lock
);
2572 /* we can't take ->d_lock here; it's OK, though. */
2573 new->d_flags
|= DCACHE_PAR_LOOKUP
;
2575 hlist_bl_add_head_rcu(&new->d_u
.d_in_lookup_hash
, b
);
2579 spin_unlock(&dentry
->d_lock
);
2583 EXPORT_SYMBOL(d_alloc_parallel
);
2585 void __d_lookup_done(struct dentry
*dentry
)
2587 struct hlist_bl_head
*b
= in_lookup_hash(dentry
->d_parent
,
2588 dentry
->d_name
.hash
);
2590 dentry
->d_flags
&= ~DCACHE_PAR_LOOKUP
;
2591 __hlist_bl_del(&dentry
->d_u
.d_in_lookup_hash
);
2592 wake_up_all(dentry
->d_wait
);
2593 dentry
->d_wait
= NULL
;
2595 INIT_HLIST_NODE(&dentry
->d_u
.d_alias
);
2596 INIT_LIST_HEAD(&dentry
->d_lru
);
2598 EXPORT_SYMBOL(__d_lookup_done
);
2600 /* inode->i_lock held if inode is non-NULL */
2602 static inline void __d_add(struct dentry
*dentry
, struct inode
*inode
)
2604 struct inode
*dir
= NULL
;
2606 spin_lock(&dentry
->d_lock
);
2607 if (unlikely(d_in_lookup(dentry
))) {
2608 dir
= dentry
->d_parent
->d_inode
;
2609 n
= start_dir_add(dir
);
2610 __d_lookup_done(dentry
);
2613 unsigned add_flags
= d_flags_for_inode(inode
);
2614 hlist_add_head(&dentry
->d_u
.d_alias
, &inode
->i_dentry
);
2615 raw_write_seqcount_begin(&dentry
->d_seq
);
2616 __d_set_inode_and_type(dentry
, inode
, add_flags
);
2617 raw_write_seqcount_end(&dentry
->d_seq
);
2618 __fsnotify_d_instantiate(dentry
);
2622 end_dir_add(dir
, n
);
2623 spin_unlock(&dentry
->d_lock
);
2625 spin_unlock(&inode
->i_lock
);
2629 * d_add - add dentry to hash queues
2630 * @entry: dentry to add
2631 * @inode: The inode to attach to this dentry
2633 * This adds the entry to the hash queues and initializes @inode.
2634 * The entry was actually filled in earlier during d_alloc().
2637 void d_add(struct dentry
*entry
, struct inode
*inode
)
2640 security_d_instantiate(entry
, inode
);
2641 spin_lock(&inode
->i_lock
);
2643 __d_add(entry
, inode
);
2645 EXPORT_SYMBOL(d_add
);
2648 * d_exact_alias - find and hash an exact unhashed alias
2649 * @entry: dentry to add
2650 * @inode: The inode to go with this dentry
2652 * If an unhashed dentry with the same name/parent and desired
2653 * inode already exists, hash and return it. Otherwise, return
2656 * Parent directory should be locked.
2658 struct dentry
*d_exact_alias(struct dentry
*entry
, struct inode
*inode
)
2660 struct dentry
*alias
;
2661 int len
= entry
->d_name
.len
;
2662 const char *name
= entry
->d_name
.name
;
2663 unsigned int hash
= entry
->d_name
.hash
;
2665 spin_lock(&inode
->i_lock
);
2666 hlist_for_each_entry(alias
, &inode
->i_dentry
, d_u
.d_alias
) {
2668 * Don't need alias->d_lock here, because aliases with
2669 * d_parent == entry->d_parent are not subject to name or
2670 * parent changes, because the parent inode i_mutex is held.
2672 if (alias
->d_name
.hash
!= hash
)
2674 if (alias
->d_parent
!= entry
->d_parent
)
2676 if (alias
->d_name
.len
!= len
)
2678 if (dentry_cmp(alias
, name
, len
))
2680 spin_lock(&alias
->d_lock
);
2681 if (!d_unhashed(alias
)) {
2682 spin_unlock(&alias
->d_lock
);
2685 __dget_dlock(alias
);
2687 spin_unlock(&alias
->d_lock
);
2689 spin_unlock(&inode
->i_lock
);
2692 spin_unlock(&inode
->i_lock
);
2695 EXPORT_SYMBOL(d_exact_alias
);
2698 * dentry_update_name_case - update case insensitive dentry with a new name
2699 * @dentry: dentry to be updated
2702 * Update a case insensitive dentry with new case of name.
2704 * dentry must have been returned by d_lookup with name @name. Old and new
2705 * name lengths must match (ie. no d_compare which allows mismatched name
2708 * Parent inode i_mutex must be held over d_lookup and into this call (to
2709 * keep renames and concurrent inserts, and readdir(2) away).
2711 void dentry_update_name_case(struct dentry
*dentry
, struct qstr
*name
)
2713 BUG_ON(!inode_is_locked(dentry
->d_parent
->d_inode
));
2714 BUG_ON(dentry
->d_name
.len
!= name
->len
); /* d_lookup gives this */
2716 spin_lock(&dentry
->d_lock
);
2717 write_seqcount_begin(&dentry
->d_seq
);
2718 memcpy((unsigned char *)dentry
->d_name
.name
, name
->name
, name
->len
);
2719 write_seqcount_end(&dentry
->d_seq
);
2720 spin_unlock(&dentry
->d_lock
);
2722 EXPORT_SYMBOL(dentry_update_name_case
);
2724 static void swap_names(struct dentry
*dentry
, struct dentry
*target
)
2726 if (unlikely(dname_external(target
))) {
2727 if (unlikely(dname_external(dentry
))) {
2729 * Both external: swap the pointers
2731 swap(target
->d_name
.name
, dentry
->d_name
.name
);
2734 * dentry:internal, target:external. Steal target's
2735 * storage and make target internal.
2737 memcpy(target
->d_iname
, dentry
->d_name
.name
,
2738 dentry
->d_name
.len
+ 1);
2739 dentry
->d_name
.name
= target
->d_name
.name
;
2740 target
->d_name
.name
= target
->d_iname
;
2743 if (unlikely(dname_external(dentry
))) {
2745 * dentry:external, target:internal. Give dentry's
2746 * storage to target and make dentry internal
2748 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2749 target
->d_name
.len
+ 1);
2750 target
->d_name
.name
= dentry
->d_name
.name
;
2751 dentry
->d_name
.name
= dentry
->d_iname
;
2754 * Both are internal.
2757 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN
, sizeof(long)));
2758 kmemcheck_mark_initialized(dentry
->d_iname
, DNAME_INLINE_LEN
);
2759 kmemcheck_mark_initialized(target
->d_iname
, DNAME_INLINE_LEN
);
2760 for (i
= 0; i
< DNAME_INLINE_LEN
/ sizeof(long); i
++) {
2761 swap(((long *) &dentry
->d_iname
)[i
],
2762 ((long *) &target
->d_iname
)[i
]);
2766 swap(dentry
->d_name
.hash_len
, target
->d_name
.hash_len
);
2769 static void copy_name(struct dentry
*dentry
, struct dentry
*target
)
2771 struct external_name
*old_name
= NULL
;
2772 if (unlikely(dname_external(dentry
)))
2773 old_name
= external_name(dentry
);
2774 if (unlikely(dname_external(target
))) {
2775 atomic_inc(&external_name(target
)->u
.count
);
2776 dentry
->d_name
= target
->d_name
;
2778 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2779 target
->d_name
.len
+ 1);
2780 dentry
->d_name
.name
= dentry
->d_iname
;
2781 dentry
->d_name
.hash_len
= target
->d_name
.hash_len
;
2783 if (old_name
&& likely(atomic_dec_and_test(&old_name
->u
.count
)))
2784 kfree_rcu(old_name
, u
.head
);
2787 static void dentry_lock_for_move(struct dentry
*dentry
, struct dentry
*target
)
2790 * XXXX: do we really need to take target->d_lock?
2792 if (IS_ROOT(dentry
) || dentry
->d_parent
== target
->d_parent
)
2793 spin_lock(&target
->d_parent
->d_lock
);
2795 if (d_ancestor(dentry
->d_parent
, target
->d_parent
)) {
2796 spin_lock(&dentry
->d_parent
->d_lock
);
2797 spin_lock_nested(&target
->d_parent
->d_lock
,
2798 DENTRY_D_LOCK_NESTED
);
2800 spin_lock(&target
->d_parent
->d_lock
);
2801 spin_lock_nested(&dentry
->d_parent
->d_lock
,
2802 DENTRY_D_LOCK_NESTED
);
2805 if (target
< dentry
) {
2806 spin_lock_nested(&target
->d_lock
, 2);
2807 spin_lock_nested(&dentry
->d_lock
, 3);
2809 spin_lock_nested(&dentry
->d_lock
, 2);
2810 spin_lock_nested(&target
->d_lock
, 3);
2814 static void dentry_unlock_for_move(struct dentry
*dentry
, struct dentry
*target
)
2816 if (target
->d_parent
!= dentry
->d_parent
)
2817 spin_unlock(&dentry
->d_parent
->d_lock
);
2818 if (target
->d_parent
!= target
)
2819 spin_unlock(&target
->d_parent
->d_lock
);
2820 spin_unlock(&target
->d_lock
);
2821 spin_unlock(&dentry
->d_lock
);
2825 * When switching names, the actual string doesn't strictly have to
2826 * be preserved in the target - because we're dropping the target
2827 * anyway. As such, we can just do a simple memcpy() to copy over
2828 * the new name before we switch, unless we are going to rehash
2829 * it. Note that if we *do* unhash the target, we are not allowed
2830 * to rehash it without giving it a new name/hash key - whether
2831 * we swap or overwrite the names here, resulting name won't match
2832 * the reality in filesystem; it's only there for d_path() purposes.
2833 * Note that all of this is happening under rename_lock, so the
2834 * any hash lookup seeing it in the middle of manipulations will
2835 * be discarded anyway. So we do not care what happens to the hash
2839 * __d_move - move a dentry
2840 * @dentry: entry to move
2841 * @target: new dentry
2842 * @exchange: exchange the two dentries
2844 * Update the dcache to reflect the move of a file name. Negative
2845 * dcache entries should not be moved in this way. Caller must hold
2846 * rename_lock, the i_mutex of the source and target directories,
2847 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2849 static void __d_move(struct dentry
*dentry
, struct dentry
*target
,
2852 struct inode
*dir
= NULL
;
2854 if (!dentry
->d_inode
)
2855 printk(KERN_WARNING
"VFS: moving negative dcache entry\n");
2857 BUG_ON(d_ancestor(dentry
, target
));
2858 BUG_ON(d_ancestor(target
, dentry
));
2860 dentry_lock_for_move(dentry
, target
);
2861 if (unlikely(d_in_lookup(target
))) {
2862 dir
= target
->d_parent
->d_inode
;
2863 n
= start_dir_add(dir
);
2864 __d_lookup_done(target
);
2867 write_seqcount_begin(&dentry
->d_seq
);
2868 write_seqcount_begin_nested(&target
->d_seq
, DENTRY_D_LOCK_NESTED
);
2870 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
2873 * Move the dentry to the target hash queue. Don't bother checking
2874 * for the same hash queue because of how unlikely it is.
2877 __d_rehash(dentry
, d_hash(target
->d_parent
, target
->d_name
.hash
));
2880 * Unhash the target (d_delete() is not usable here). If exchanging
2881 * the two dentries, then rehash onto the other's hash queue.
2886 d_hash(dentry
->d_parent
, dentry
->d_name
.hash
));
2889 /* Switch the names.. */
2891 swap_names(dentry
, target
);
2893 copy_name(dentry
, target
);
2895 /* ... and switch them in the tree */
2896 if (IS_ROOT(dentry
)) {
2897 /* splicing a tree */
2898 dentry
->d_flags
|= DCACHE_RCUACCESS
;
2899 dentry
->d_parent
= target
->d_parent
;
2900 target
->d_parent
= target
;
2901 list_del_init(&target
->d_child
);
2902 list_move(&dentry
->d_child
, &dentry
->d_parent
->d_subdirs
);
2904 /* swapping two dentries */
2905 swap(dentry
->d_parent
, target
->d_parent
);
2906 list_move(&target
->d_child
, &target
->d_parent
->d_subdirs
);
2907 list_move(&dentry
->d_child
, &dentry
->d_parent
->d_subdirs
);
2909 fsnotify_d_move(target
);
2910 fsnotify_d_move(dentry
);
2913 write_seqcount_end(&target
->d_seq
);
2914 write_seqcount_end(&dentry
->d_seq
);
2917 end_dir_add(dir
, n
);
2918 dentry_unlock_for_move(dentry
, target
);
2922 * d_move - move a dentry
2923 * @dentry: entry to move
2924 * @target: new dentry
2926 * Update the dcache to reflect the move of a file name. Negative
2927 * dcache entries should not be moved in this way. See the locking
2928 * requirements for __d_move.
2930 void d_move(struct dentry
*dentry
, struct dentry
*target
)
2932 write_seqlock(&rename_lock
);
2933 __d_move(dentry
, target
, false);
2934 write_sequnlock(&rename_lock
);
2936 EXPORT_SYMBOL(d_move
);
2939 * d_exchange - exchange two dentries
2940 * @dentry1: first dentry
2941 * @dentry2: second dentry
2943 void d_exchange(struct dentry
*dentry1
, struct dentry
*dentry2
)
2945 write_seqlock(&rename_lock
);
2947 WARN_ON(!dentry1
->d_inode
);
2948 WARN_ON(!dentry2
->d_inode
);
2949 WARN_ON(IS_ROOT(dentry1
));
2950 WARN_ON(IS_ROOT(dentry2
));
2952 __d_move(dentry1
, dentry2
, true);
2954 write_sequnlock(&rename_lock
);
2958 * d_ancestor - search for an ancestor
2959 * @p1: ancestor dentry
2962 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2963 * an ancestor of p2, else NULL.
2965 struct dentry
*d_ancestor(struct dentry
*p1
, struct dentry
*p2
)
2969 for (p
= p2
; !IS_ROOT(p
); p
= p
->d_parent
) {
2970 if (p
->d_parent
== p1
)
2977 * This helper attempts to cope with remotely renamed directories
2979 * It assumes that the caller is already holding
2980 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2982 * Note: If ever the locking in lock_rename() changes, then please
2983 * remember to update this too...
2985 static int __d_unalias(struct inode
*inode
,
2986 struct dentry
*dentry
, struct dentry
*alias
)
2988 struct mutex
*m1
= NULL
;
2989 struct rw_semaphore
*m2
= NULL
;
2992 /* If alias and dentry share a parent, then no extra locks required */
2993 if (alias
->d_parent
== dentry
->d_parent
)
2996 /* See lock_rename() */
2997 if (!mutex_trylock(&dentry
->d_sb
->s_vfs_rename_mutex
))
2999 m1
= &dentry
->d_sb
->s_vfs_rename_mutex
;
3000 if (!inode_trylock_shared(alias
->d_parent
->d_inode
))
3002 m2
= &alias
->d_parent
->d_inode
->i_rwsem
;
3004 __d_move(alias
, dentry
, false);
3015 * d_splice_alias - splice a disconnected dentry into the tree if one exists
3016 * @inode: the inode which may have a disconnected dentry
3017 * @dentry: a negative dentry which we want to point to the inode.
3019 * If inode is a directory and has an IS_ROOT alias, then d_move that in
3020 * place of the given dentry and return it, else simply d_add the inode
3021 * to the dentry and return NULL.
3023 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
3024 * we should error out: directories can't have multiple aliases.
3026 * This is needed in the lookup routine of any filesystem that is exportable
3027 * (via knfsd) so that we can build dcache paths to directories effectively.
3029 * If a dentry was found and moved, then it is returned. Otherwise NULL
3030 * is returned. This matches the expected return value of ->lookup.
3032 * Cluster filesystems may call this function with a negative, hashed dentry.
3033 * In that case, we know that the inode will be a regular file, and also this
3034 * will only occur during atomic_open. So we need to check for the dentry
3035 * being already hashed only in the final case.
3037 struct dentry
*d_splice_alias(struct inode
*inode
, struct dentry
*dentry
)
3040 return ERR_CAST(inode
);
3042 BUG_ON(!d_unhashed(dentry
));
3047 security_d_instantiate(dentry
, inode
);
3048 spin_lock(&inode
->i_lock
);
3049 if (S_ISDIR(inode
->i_mode
)) {
3050 struct dentry
*new = __d_find_any_alias(inode
);
3051 if (unlikely(new)) {
3052 /* The reference to new ensures it remains an alias */
3053 spin_unlock(&inode
->i_lock
);
3054 write_seqlock(&rename_lock
);
3055 if (unlikely(d_ancestor(new, dentry
))) {
3056 write_sequnlock(&rename_lock
);
3058 new = ERR_PTR(-ELOOP
);
3059 pr_warn_ratelimited(
3060 "VFS: Lookup of '%s' in %s %s"
3061 " would have caused loop\n",
3062 dentry
->d_name
.name
,
3063 inode
->i_sb
->s_type
->name
,
3065 } else if (!IS_ROOT(new)) {
3066 int err
= __d_unalias(inode
, dentry
, new);
3067 write_sequnlock(&rename_lock
);
3073 __d_move(new, dentry
, false);
3074 write_sequnlock(&rename_lock
);
3081 __d_add(dentry
, inode
);
3084 EXPORT_SYMBOL(d_splice_alias
);
3086 static int prepend(char **buffer
, int *buflen
, const char *str
, int namelen
)
3090 return -ENAMETOOLONG
;
3092 memcpy(*buffer
, str
, namelen
);
3097 * prepend_name - prepend a pathname in front of current buffer pointer
3098 * @buffer: buffer pointer
3099 * @buflen: allocated length of the buffer
3100 * @name: name string and length qstr structure
3102 * With RCU path tracing, it may race with d_move(). Use ACCESS_ONCE() to
3103 * make sure that either the old or the new name pointer and length are
3104 * fetched. However, there may be mismatch between length and pointer.
3105 * The length cannot be trusted, we need to copy it byte-by-byte until
3106 * the length is reached or a null byte is found. It also prepends "/" at
3107 * the beginning of the name. The sequence number check at the caller will
3108 * retry it again when a d_move() does happen. So any garbage in the buffer
3109 * due to mismatched pointer and length will be discarded.
3111 * Data dependency barrier is needed to make sure that we see that terminating
3112 * NUL. Alpha strikes again, film at 11...
3114 static int prepend_name(char **buffer
, int *buflen
, struct qstr
*name
)
3116 const char *dname
= ACCESS_ONCE(name
->name
);
3117 u32 dlen
= ACCESS_ONCE(name
->len
);
3120 smp_read_barrier_depends();
3122 *buflen
-= dlen
+ 1;
3124 return -ENAMETOOLONG
;
3125 p
= *buffer
-= dlen
+ 1;
3137 * prepend_path - Prepend path string to a buffer
3138 * @path: the dentry/vfsmount to report
3139 * @root: root vfsmnt/dentry
3140 * @buffer: pointer to the end of the buffer
3141 * @buflen: pointer to buffer length
3143 * The function will first try to write out the pathname without taking any
3144 * lock other than the RCU read lock to make sure that dentries won't go away.
3145 * It only checks the sequence number of the global rename_lock as any change
3146 * in the dentry's d_seq will be preceded by changes in the rename_lock
3147 * sequence number. If the sequence number had been changed, it will restart
3148 * the whole pathname back-tracing sequence again by taking the rename_lock.
3149 * In this case, there is no need to take the RCU read lock as the recursive
3150 * parent pointer references will keep the dentry chain alive as long as no
3151 * rename operation is performed.
3153 static int prepend_path(const struct path
*path
,
3154 const struct path
*root
,
3155 char **buffer
, int *buflen
)
3157 struct dentry
*dentry
;
3158 struct vfsmount
*vfsmnt
;
3161 unsigned seq
, m_seq
= 0;
3167 read_seqbegin_or_lock(&mount_lock
, &m_seq
);
3174 dentry
= path
->dentry
;
3176 mnt
= real_mount(vfsmnt
);
3177 read_seqbegin_or_lock(&rename_lock
, &seq
);
3178 while (dentry
!= root
->dentry
|| vfsmnt
!= root
->mnt
) {
3179 struct dentry
* parent
;
3181 if (dentry
== vfsmnt
->mnt_root
|| IS_ROOT(dentry
)) {
3182 struct mount
*parent
= ACCESS_ONCE(mnt
->mnt_parent
);
3184 if (dentry
!= vfsmnt
->mnt_root
) {
3191 if (mnt
!= parent
) {
3192 dentry
= ACCESS_ONCE(mnt
->mnt_mountpoint
);
3198 error
= is_mounted(vfsmnt
) ? 1 : 2;
3201 parent
= dentry
->d_parent
;
3203 error
= prepend_name(&bptr
, &blen
, &dentry
->d_name
);
3211 if (need_seqretry(&rename_lock
, seq
)) {
3215 done_seqretry(&rename_lock
, seq
);
3219 if (need_seqretry(&mount_lock
, m_seq
)) {
3223 done_seqretry(&mount_lock
, m_seq
);
3225 if (error
>= 0 && bptr
== *buffer
) {
3227 error
= -ENAMETOOLONG
;
3237 * __d_path - return the path of a dentry
3238 * @path: the dentry/vfsmount to report
3239 * @root: root vfsmnt/dentry
3240 * @buf: buffer to return value in
3241 * @buflen: buffer length
3243 * Convert a dentry into an ASCII path name.
3245 * Returns a pointer into the buffer or an error code if the
3246 * path was too long.
3248 * "buflen" should be positive.
3250 * If the path is not reachable from the supplied root, return %NULL.
3252 char *__d_path(const struct path
*path
,
3253 const struct path
*root
,
3254 char *buf
, int buflen
)
3256 char *res
= buf
+ buflen
;
3259 prepend(&res
, &buflen
, "\0", 1);
3260 error
= prepend_path(path
, root
, &res
, &buflen
);
3263 return ERR_PTR(error
);
3269 char *d_absolute_path(const struct path
*path
,
3270 char *buf
, int buflen
)
3272 struct path root
= {};
3273 char *res
= buf
+ buflen
;
3276 prepend(&res
, &buflen
, "\0", 1);
3277 error
= prepend_path(path
, &root
, &res
, &buflen
);
3282 return ERR_PTR(error
);
3287 * same as __d_path but appends "(deleted)" for unlinked files.
3289 static int path_with_deleted(const struct path
*path
,
3290 const struct path
*root
,
3291 char **buf
, int *buflen
)
3293 prepend(buf
, buflen
, "\0", 1);
3294 if (d_unlinked(path
->dentry
)) {
3295 int error
= prepend(buf
, buflen
, " (deleted)", 10);
3300 return prepend_path(path
, root
, buf
, buflen
);
3303 static int prepend_unreachable(char **buffer
, int *buflen
)
3305 return prepend(buffer
, buflen
, "(unreachable)", 13);
3308 static void get_fs_root_rcu(struct fs_struct
*fs
, struct path
*root
)
3313 seq
= read_seqcount_begin(&fs
->seq
);
3315 } while (read_seqcount_retry(&fs
->seq
, seq
));
3319 * d_path - return the path of a dentry
3320 * @path: path to report
3321 * @buf: buffer to return value in
3322 * @buflen: buffer length
3324 * Convert a dentry into an ASCII path name. If the entry has been deleted
3325 * the string " (deleted)" is appended. Note that this is ambiguous.
3327 * Returns a pointer into the buffer or an error code if the path was
3328 * too long. Note: Callers should use the returned pointer, not the passed
3329 * in buffer, to use the name! The implementation often starts at an offset
3330 * into the buffer, and may leave 0 bytes at the start.
3332 * "buflen" should be positive.
3334 char *d_path(const struct path
*path
, char *buf
, int buflen
)
3336 char *res
= buf
+ buflen
;
3341 * We have various synthetic filesystems that never get mounted. On
3342 * these filesystems dentries are never used for lookup purposes, and
3343 * thus don't need to be hashed. They also don't need a name until a
3344 * user wants to identify the object in /proc/pid/fd/. The little hack
3345 * below allows us to generate a name for these objects on demand:
3347 * Some pseudo inodes are mountable. When they are mounted
3348 * path->dentry == path->mnt->mnt_root. In that case don't call d_dname
3349 * and instead have d_path return the mounted path.
3351 if (path
->dentry
->d_op
&& path
->dentry
->d_op
->d_dname
&&
3352 (!IS_ROOT(path
->dentry
) || path
->dentry
!= path
->mnt
->mnt_root
))
3353 return path
->dentry
->d_op
->d_dname(path
->dentry
, buf
, buflen
);
3356 get_fs_root_rcu(current
->fs
, &root
);
3357 error
= path_with_deleted(path
, &root
, &res
, &buflen
);
3361 res
= ERR_PTR(error
);
3364 EXPORT_SYMBOL(d_path
);
3367 * Helper function for dentry_operations.d_dname() members
3369 char *dynamic_dname(struct dentry
*dentry
, char *buffer
, int buflen
,
3370 const char *fmt
, ...)
3376 va_start(args
, fmt
);
3377 sz
= vsnprintf(temp
, sizeof(temp
), fmt
, args
) + 1;
3380 if (sz
> sizeof(temp
) || sz
> buflen
)
3381 return ERR_PTR(-ENAMETOOLONG
);
3383 buffer
+= buflen
- sz
;
3384 return memcpy(buffer
, temp
, sz
);
3387 char *simple_dname(struct dentry
*dentry
, char *buffer
, int buflen
)
3389 char *end
= buffer
+ buflen
;
3390 /* these dentries are never renamed, so d_lock is not needed */
3391 if (prepend(&end
, &buflen
, " (deleted)", 11) ||
3392 prepend(&end
, &buflen
, dentry
->d_name
.name
, dentry
->d_name
.len
) ||
3393 prepend(&end
, &buflen
, "/", 1))
3394 end
= ERR_PTR(-ENAMETOOLONG
);
3397 EXPORT_SYMBOL(simple_dname
);
3400 * Write full pathname from the root of the filesystem into the buffer.
3402 static char *__dentry_path(struct dentry
*d
, char *buf
, int buflen
)
3404 struct dentry
*dentry
;
3417 prepend(&end
, &len
, "\0", 1);
3421 read_seqbegin_or_lock(&rename_lock
, &seq
);
3422 while (!IS_ROOT(dentry
)) {
3423 struct dentry
*parent
= dentry
->d_parent
;
3426 error
= prepend_name(&end
, &len
, &dentry
->d_name
);
3435 if (need_seqretry(&rename_lock
, seq
)) {
3439 done_seqretry(&rename_lock
, seq
);
3444 return ERR_PTR(-ENAMETOOLONG
);
3447 char *dentry_path_raw(struct dentry
*dentry
, char *buf
, int buflen
)
3449 return __dentry_path(dentry
, buf
, buflen
);
3451 EXPORT_SYMBOL(dentry_path_raw
);
3453 char *dentry_path(struct dentry
*dentry
, char *buf
, int buflen
)
3458 if (d_unlinked(dentry
)) {
3460 if (prepend(&p
, &buflen
, "//deleted", 10) != 0)
3464 retval
= __dentry_path(dentry
, buf
, buflen
);
3465 if (!IS_ERR(retval
) && p
)
3466 *p
= '/'; /* restore '/' overriden with '\0' */
3469 return ERR_PTR(-ENAMETOOLONG
);
3472 static void get_fs_root_and_pwd_rcu(struct fs_struct
*fs
, struct path
*root
,
3478 seq
= read_seqcount_begin(&fs
->seq
);
3481 } while (read_seqcount_retry(&fs
->seq
, seq
));
3485 * NOTE! The user-level library version returns a
3486 * character pointer. The kernel system call just
3487 * returns the length of the buffer filled (which
3488 * includes the ending '\0' character), or a negative
3489 * error value. So libc would do something like
3491 * char *getcwd(char * buf, size_t size)
3495 * retval = sys_getcwd(buf, size);
3502 SYSCALL_DEFINE2(getcwd
, char __user
*, buf
, unsigned long, size
)
3505 struct path pwd
, root
;
3506 char *page
= __getname();
3512 get_fs_root_and_pwd_rcu(current
->fs
, &root
, &pwd
);
3515 if (!d_unlinked(pwd
.dentry
)) {
3517 char *cwd
= page
+ PATH_MAX
;
3518 int buflen
= PATH_MAX
;
3520 prepend(&cwd
, &buflen
, "\0", 1);
3521 error
= prepend_path(&pwd
, &root
, &cwd
, &buflen
);
3527 /* Unreachable from current root */
3529 error
= prepend_unreachable(&cwd
, &buflen
);
3535 len
= PATH_MAX
+ page
- cwd
;
3538 if (copy_to_user(buf
, cwd
, len
))
3551 * Test whether new_dentry is a subdirectory of old_dentry.
3553 * Trivially implemented using the dcache structure
3557 * is_subdir - is new dentry a subdirectory of old_dentry
3558 * @new_dentry: new dentry
3559 * @old_dentry: old dentry
3561 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3562 * Returns false otherwise.
3563 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3566 bool is_subdir(struct dentry
*new_dentry
, struct dentry
*old_dentry
)
3571 if (new_dentry
== old_dentry
)
3575 /* for restarting inner loop in case of seq retry */
3576 seq
= read_seqbegin(&rename_lock
);
3578 * Need rcu_readlock to protect against the d_parent trashing
3582 if (d_ancestor(old_dentry
, new_dentry
))
3587 } while (read_seqretry(&rename_lock
, seq
));
3592 static enum d_walk_ret
d_genocide_kill(void *data
, struct dentry
*dentry
)
3594 struct dentry
*root
= data
;
3595 if (dentry
!= root
) {
3596 if (d_unhashed(dentry
) || !dentry
->d_inode
)
3599 if (!(dentry
->d_flags
& DCACHE_GENOCIDE
)) {
3600 dentry
->d_flags
|= DCACHE_GENOCIDE
;
3601 dentry
->d_lockref
.count
--;
3604 return D_WALK_CONTINUE
;
3607 void d_genocide(struct dentry
*parent
)
3609 d_walk(parent
, parent
, d_genocide_kill
, NULL
);
3612 void d_tmpfile(struct dentry
*dentry
, struct inode
*inode
)
3614 inode_dec_link_count(inode
);
3615 BUG_ON(dentry
->d_name
.name
!= dentry
->d_iname
||
3616 !hlist_unhashed(&dentry
->d_u
.d_alias
) ||
3617 !d_unlinked(dentry
));
3618 spin_lock(&dentry
->d_parent
->d_lock
);
3619 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
3620 dentry
->d_name
.len
= sprintf(dentry
->d_iname
, "#%llu",
3621 (unsigned long long)inode
->i_ino
);
3622 spin_unlock(&dentry
->d_lock
);
3623 spin_unlock(&dentry
->d_parent
->d_lock
);
3624 d_instantiate(dentry
, inode
);
3626 EXPORT_SYMBOL(d_tmpfile
);
3628 static __initdata
unsigned long dhash_entries
;
3629 static int __init
set_dhash_entries(char *str
)
3633 dhash_entries
= simple_strtoul(str
, &str
, 0);
3636 __setup("dhash_entries=", set_dhash_entries
);
3638 static void __init
dcache_init_early(void)
3642 /* If hashes are distributed across NUMA nodes, defer
3643 * hash allocation until vmalloc space is available.
3649 alloc_large_system_hash("Dentry cache",
3650 sizeof(struct hlist_bl_head
),
3659 for (loop
= 0; loop
< (1U << d_hash_shift
); loop
++)
3660 INIT_HLIST_BL_HEAD(dentry_hashtable
+ loop
);
3663 static void __init
dcache_init(void)
3668 * A constructor could be added for stable state like the lists,
3669 * but it is probably not worth it because of the cache nature
3672 dentry_cache
= KMEM_CACHE(dentry
,
3673 SLAB_RECLAIM_ACCOUNT
|SLAB_PANIC
|SLAB_MEM_SPREAD
|SLAB_ACCOUNT
);
3675 /* Hash may have been set up in dcache_init_early */
3680 alloc_large_system_hash("Dentry cache",
3681 sizeof(struct hlist_bl_head
),
3690 for (loop
= 0; loop
< (1U << d_hash_shift
); loop
++)
3691 INIT_HLIST_BL_HEAD(dentry_hashtable
+ loop
);
3694 /* SLAB cache for __getname() consumers */
3695 struct kmem_cache
*names_cachep __read_mostly
;
3696 EXPORT_SYMBOL(names_cachep
);
3698 EXPORT_SYMBOL(d_genocide
);
3700 void __init
vfs_caches_init_early(void)
3702 dcache_init_early();
3706 void __init
vfs_caches_init(void)
3708 names_cachep
= kmem_cache_create("names_cache", PATH_MAX
, 0,
3709 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
);
3714 files_maxfiles_init();