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>
45 * dcache->d_inode->i_lock protects:
46 * - i_dentry, d_alias, d_inode of aliases
47 * dcache_hash_bucket lock protects:
48 * - the dcache hash table
49 * s_anon bl list spinlock protects:
50 * - the s_anon list (see __d_drop)
51 * dcache_lru_lock protects:
52 * - the dcache lru lists and counters
59 * - d_parent and d_subdirs
60 * - childrens' d_child and d_parent
64 * dentry->d_inode->i_lock
67 * dcache_hash_bucket lock
70 * If there is an ancestor relationship:
71 * dentry->d_parent->...->d_parent->d_lock
73 * dentry->d_parent->d_lock
76 * If no ancestor relationship:
77 * if (dentry1 < dentry2)
81 int sysctl_vfs_cache_pressure __read_mostly
= 100;
82 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure
);
84 static __cacheline_aligned_in_smp
DEFINE_SPINLOCK(dcache_lru_lock
);
85 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(rename_lock
);
87 EXPORT_SYMBOL(rename_lock
);
89 static struct kmem_cache
*dentry_cache __read_mostly
;
92 * read_seqbegin_or_lock - begin a sequence number check or locking block
93 * @lock: sequence lock
94 * @seq : sequence number to be checked
96 * First try it once optimistically without taking the lock. If that fails,
97 * take the lock. The sequence number is also used as a marker for deciding
98 * whether to be a reader (even) or writer (odd).
99 * N.B. seq must be initialized to an even number to begin with.
101 static inline void read_seqbegin_or_lock(seqlock_t
*lock
, int *seq
)
103 if (!(*seq
& 1)) /* Even */
104 *seq
= read_seqbegin(lock
);
106 read_seqlock_excl(lock
);
109 static inline int need_seqretry(seqlock_t
*lock
, int seq
)
111 return !(seq
& 1) && read_seqretry(lock
, seq
);
114 static inline void done_seqretry(seqlock_t
*lock
, int seq
)
117 read_sequnlock_excl(lock
);
121 * This is the single most critical data structure when it comes
122 * to the dcache: the hashtable for lookups. Somebody should try
123 * to make this good - I've just made it work.
125 * This hash-function tries to avoid losing too many bits of hash
126 * information, yet avoid using a prime hash-size or similar.
128 #define D_HASHBITS d_hash_shift
129 #define D_HASHMASK d_hash_mask
131 static unsigned int d_hash_mask __read_mostly
;
132 static unsigned int d_hash_shift __read_mostly
;
134 static struct hlist_bl_head
*dentry_hashtable __read_mostly
;
136 static inline struct hlist_bl_head
*d_hash(const struct dentry
*parent
,
139 hash
+= (unsigned long) parent
/ L1_CACHE_BYTES
;
140 hash
= hash
+ (hash
>> D_HASHBITS
);
141 return dentry_hashtable
+ (hash
& D_HASHMASK
);
144 /* Statistics gathering. */
145 struct dentry_stat_t dentry_stat
= {
149 static DEFINE_PER_CPU(unsigned int, nr_dentry
);
151 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
152 static int get_nr_dentry(void)
156 for_each_possible_cpu(i
)
157 sum
+= per_cpu(nr_dentry
, i
);
158 return sum
< 0 ? 0 : sum
;
161 int proc_nr_dentry(ctl_table
*table
, int write
, void __user
*buffer
,
162 size_t *lenp
, loff_t
*ppos
)
164 dentry_stat
.nr_dentry
= get_nr_dentry();
165 return proc_dointvec(table
, write
, buffer
, lenp
, ppos
);
170 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
171 * The strings are both count bytes long, and count is non-zero.
173 #ifdef CONFIG_DCACHE_WORD_ACCESS
175 #include <asm/word-at-a-time.h>
177 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
178 * aligned allocation for this particular component. We don't
179 * strictly need the load_unaligned_zeropad() safety, but it
180 * doesn't hurt either.
182 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
183 * need the careful unaligned handling.
185 static inline int dentry_string_cmp(const unsigned char *cs
, const unsigned char *ct
, unsigned tcount
)
187 unsigned long a
,b
,mask
;
190 a
= *(unsigned long *)cs
;
191 b
= load_unaligned_zeropad(ct
);
192 if (tcount
< sizeof(unsigned long))
194 if (unlikely(a
!= b
))
196 cs
+= sizeof(unsigned long);
197 ct
+= sizeof(unsigned long);
198 tcount
-= sizeof(unsigned long);
202 mask
= ~(~0ul << tcount
*8);
203 return unlikely(!!((a
^ b
) & mask
));
208 static inline int dentry_string_cmp(const unsigned char *cs
, const unsigned char *ct
, unsigned tcount
)
222 static inline int dentry_cmp(const struct dentry
*dentry
, const unsigned char *ct
, unsigned tcount
)
224 const unsigned char *cs
;
226 * Be careful about RCU walk racing with rename:
227 * use ACCESS_ONCE to fetch the name pointer.
229 * NOTE! Even if a rename will mean that the length
230 * was not loaded atomically, we don't care. The
231 * RCU walk will check the sequence count eventually,
232 * and catch it. And we won't overrun the buffer,
233 * because we're reading the name pointer atomically,
234 * and a dentry name is guaranteed to be properly
235 * terminated with a NUL byte.
237 * End result: even if 'len' is wrong, we'll exit
238 * early because the data cannot match (there can
239 * be no NUL in the ct/tcount data)
241 cs
= ACCESS_ONCE(dentry
->d_name
.name
);
242 smp_read_barrier_depends();
243 return dentry_string_cmp(cs
, ct
, tcount
);
246 static void __d_free(struct rcu_head
*head
)
248 struct dentry
*dentry
= container_of(head
, struct dentry
, d_u
.d_rcu
);
250 WARN_ON(!hlist_unhashed(&dentry
->d_alias
));
251 if (dname_external(dentry
))
252 kfree(dentry
->d_name
.name
);
253 kmem_cache_free(dentry_cache
, dentry
);
259 static void d_free(struct dentry
*dentry
)
261 BUG_ON((int)dentry
->d_lockref
.count
> 0);
262 this_cpu_dec(nr_dentry
);
263 if (dentry
->d_op
&& dentry
->d_op
->d_release
)
264 dentry
->d_op
->d_release(dentry
);
266 /* if dentry was never visible to RCU, immediate free is OK */
267 if (!(dentry
->d_flags
& DCACHE_RCUACCESS
))
268 __d_free(&dentry
->d_u
.d_rcu
);
270 call_rcu(&dentry
->d_u
.d_rcu
, __d_free
);
274 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
275 * @dentry: the target dentry
276 * After this call, in-progress rcu-walk path lookup will fail. This
277 * should be called after unhashing, and after changing d_inode (if
278 * the dentry has not already been unhashed).
280 static inline void dentry_rcuwalk_barrier(struct dentry
*dentry
)
282 assert_spin_locked(&dentry
->d_lock
);
283 /* Go through a barrier */
284 write_seqcount_barrier(&dentry
->d_seq
);
288 * Release the dentry's inode, using the filesystem
289 * d_iput() operation if defined. Dentry has no refcount
292 static void dentry_iput(struct dentry
* dentry
)
293 __releases(dentry
->d_lock
)
294 __releases(dentry
->d_inode
->i_lock
)
296 struct inode
*inode
= dentry
->d_inode
;
298 dentry
->d_inode
= NULL
;
299 hlist_del_init(&dentry
->d_alias
);
300 spin_unlock(&dentry
->d_lock
);
301 spin_unlock(&inode
->i_lock
);
303 fsnotify_inoderemove(inode
);
304 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
305 dentry
->d_op
->d_iput(dentry
, inode
);
309 spin_unlock(&dentry
->d_lock
);
314 * Release the dentry's inode, using the filesystem
315 * d_iput() operation if defined. dentry remains in-use.
317 static void dentry_unlink_inode(struct dentry
* dentry
)
318 __releases(dentry
->d_lock
)
319 __releases(dentry
->d_inode
->i_lock
)
321 struct inode
*inode
= dentry
->d_inode
;
322 dentry
->d_inode
= NULL
;
323 hlist_del_init(&dentry
->d_alias
);
324 dentry_rcuwalk_barrier(dentry
);
325 spin_unlock(&dentry
->d_lock
);
326 spin_unlock(&inode
->i_lock
);
328 fsnotify_inoderemove(inode
);
329 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
330 dentry
->d_op
->d_iput(dentry
, inode
);
336 * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
338 static void dentry_lru_add(struct dentry
*dentry
)
340 if (unlikely(!(dentry
->d_flags
& DCACHE_LRU_LIST
))) {
341 spin_lock(&dcache_lru_lock
);
342 dentry
->d_flags
|= DCACHE_LRU_LIST
;
343 list_add(&dentry
->d_lru
, &dentry
->d_sb
->s_dentry_lru
);
344 dentry
->d_sb
->s_nr_dentry_unused
++;
345 dentry_stat
.nr_unused
++;
346 spin_unlock(&dcache_lru_lock
);
350 static void __dentry_lru_del(struct dentry
*dentry
)
352 list_del_init(&dentry
->d_lru
);
353 dentry
->d_flags
&= ~(DCACHE_SHRINK_LIST
| DCACHE_LRU_LIST
);
354 dentry
->d_sb
->s_nr_dentry_unused
--;
355 dentry_stat
.nr_unused
--;
359 * Remove a dentry with references from the LRU.
361 static void dentry_lru_del(struct dentry
*dentry
)
363 if (!list_empty(&dentry
->d_lru
)) {
364 spin_lock(&dcache_lru_lock
);
365 __dentry_lru_del(dentry
);
366 spin_unlock(&dcache_lru_lock
);
370 static void dentry_lru_move_list(struct dentry
*dentry
, struct list_head
*list
)
372 spin_lock(&dcache_lru_lock
);
373 if (list_empty(&dentry
->d_lru
)) {
374 dentry
->d_flags
|= DCACHE_LRU_LIST
;
375 list_add_tail(&dentry
->d_lru
, list
);
376 dentry
->d_sb
->s_nr_dentry_unused
++;
377 dentry_stat
.nr_unused
++;
379 list_move_tail(&dentry
->d_lru
, list
);
381 spin_unlock(&dcache_lru_lock
);
385 * d_kill - kill dentry and return parent
386 * @dentry: dentry to kill
387 * @parent: parent dentry
389 * The dentry must already be unhashed and removed from the LRU.
391 * If this is the root of the dentry tree, return NULL.
393 * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
396 static struct dentry
*d_kill(struct dentry
*dentry
, struct dentry
*parent
)
397 __releases(dentry
->d_lock
)
398 __releases(parent
->d_lock
)
399 __releases(dentry
->d_inode
->i_lock
)
401 list_del(&dentry
->d_u
.d_child
);
403 * Inform try_to_ascend() that we are no longer attached to the
406 dentry
->d_flags
|= DCACHE_DENTRY_KILLED
;
408 spin_unlock(&parent
->d_lock
);
411 * dentry_iput drops the locks, at which point nobody (except
412 * transient RCU lookups) can reach this dentry.
419 * Unhash a dentry without inserting an RCU walk barrier or checking that
420 * dentry->d_lock is locked. The caller must take care of that, if
423 static void __d_shrink(struct dentry
*dentry
)
425 if (!d_unhashed(dentry
)) {
426 struct hlist_bl_head
*b
;
427 if (unlikely(dentry
->d_flags
& DCACHE_DISCONNECTED
))
428 b
= &dentry
->d_sb
->s_anon
;
430 b
= d_hash(dentry
->d_parent
, dentry
->d_name
.hash
);
433 __hlist_bl_del(&dentry
->d_hash
);
434 dentry
->d_hash
.pprev
= NULL
;
440 * d_drop - drop a dentry
441 * @dentry: dentry to drop
443 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
444 * be found through a VFS lookup any more. Note that this is different from
445 * deleting the dentry - d_delete will try to mark the dentry negative if
446 * possible, giving a successful _negative_ lookup, while d_drop will
447 * just make the cache lookup fail.
449 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
450 * reason (NFS timeouts or autofs deletes).
452 * __d_drop requires dentry->d_lock.
454 void __d_drop(struct dentry
*dentry
)
456 if (!d_unhashed(dentry
)) {
458 dentry_rcuwalk_barrier(dentry
);
461 EXPORT_SYMBOL(__d_drop
);
463 void d_drop(struct dentry
*dentry
)
465 spin_lock(&dentry
->d_lock
);
467 spin_unlock(&dentry
->d_lock
);
469 EXPORT_SYMBOL(d_drop
);
472 * Finish off a dentry we've decided to kill.
473 * dentry->d_lock must be held, returns with it unlocked.
474 * If ref is non-zero, then decrement the refcount too.
475 * Returns dentry requiring refcount drop, or NULL if we're done.
477 static inline struct dentry
*dentry_kill(struct dentry
*dentry
)
478 __releases(dentry
->d_lock
)
481 struct dentry
*parent
;
483 inode
= dentry
->d_inode
;
484 if (inode
&& !spin_trylock(&inode
->i_lock
)) {
486 spin_unlock(&dentry
->d_lock
);
488 return dentry
; /* try again with same dentry */
493 parent
= dentry
->d_parent
;
494 if (parent
&& !spin_trylock(&parent
->d_lock
)) {
496 spin_unlock(&inode
->i_lock
);
501 * The dentry is now unrecoverably dead to the world.
503 lockref_mark_dead(&dentry
->d_lockref
);
506 * inform the fs via d_prune that this dentry is about to be
507 * unhashed and destroyed.
509 if ((dentry
->d_flags
& DCACHE_OP_PRUNE
) && !d_unhashed(dentry
))
510 dentry
->d_op
->d_prune(dentry
);
512 dentry_lru_del(dentry
);
513 /* if it was on the hash then remove it */
515 return d_kill(dentry
, parent
);
521 * This is complicated by the fact that we do not want to put
522 * dentries that are no longer on any hash chain on the unused
523 * list: we'd much rather just get rid of them immediately.
525 * However, that implies that we have to traverse the dentry
526 * tree upwards to the parents which might _also_ now be
527 * scheduled for deletion (it may have been only waiting for
528 * its last child to go away).
530 * This tail recursion is done by hand as we don't want to depend
531 * on the compiler to always get this right (gcc generally doesn't).
532 * Real recursion would eat up our stack space.
536 * dput - release a dentry
537 * @dentry: dentry to release
539 * Release a dentry. This will drop the usage count and if appropriate
540 * call the dentry unlink method as well as removing it from the queues and
541 * releasing its resources. If the parent dentries were scheduled for release
542 * they too may now get deleted.
544 void dput(struct dentry
*dentry
)
546 if (unlikely(!dentry
))
550 if (lockref_put_or_lock(&dentry
->d_lockref
))
553 /* Unreachable? Get rid of it */
554 if (unlikely(d_unhashed(dentry
)))
557 if (unlikely(dentry
->d_flags
& DCACHE_OP_DELETE
)) {
558 if (dentry
->d_op
->d_delete(dentry
))
562 dentry
->d_flags
|= DCACHE_REFERENCED
;
563 dentry_lru_add(dentry
);
565 dentry
->d_lockref
.count
--;
566 spin_unlock(&dentry
->d_lock
);
570 dentry
= dentry_kill(dentry
);
577 * d_invalidate - invalidate a dentry
578 * @dentry: dentry to invalidate
580 * Try to invalidate the dentry if it turns out to be
581 * possible. If there are other dentries that can be
582 * reached through this one we can't delete it and we
583 * return -EBUSY. On success we return 0.
588 int d_invalidate(struct dentry
* dentry
)
591 * If it's already been dropped, return OK.
593 spin_lock(&dentry
->d_lock
);
594 if (d_unhashed(dentry
)) {
595 spin_unlock(&dentry
->d_lock
);
599 * Check whether to do a partial shrink_dcache
600 * to get rid of unused child entries.
602 if (!list_empty(&dentry
->d_subdirs
)) {
603 spin_unlock(&dentry
->d_lock
);
604 shrink_dcache_parent(dentry
);
605 spin_lock(&dentry
->d_lock
);
609 * Somebody else still using it?
611 * If it's a directory, we can't drop it
612 * for fear of somebody re-populating it
613 * with children (even though dropping it
614 * would make it unreachable from the root,
615 * we might still populate it if it was a
616 * working directory or similar).
617 * We also need to leave mountpoints alone,
620 if (dentry
->d_lockref
.count
> 1 && dentry
->d_inode
) {
621 if (S_ISDIR(dentry
->d_inode
->i_mode
) || d_mountpoint(dentry
)) {
622 spin_unlock(&dentry
->d_lock
);
628 spin_unlock(&dentry
->d_lock
);
631 EXPORT_SYMBOL(d_invalidate
);
633 /* This must be called with d_lock held */
634 static inline void __dget_dlock(struct dentry
*dentry
)
636 dentry
->d_lockref
.count
++;
639 static inline void __dget(struct dentry
*dentry
)
641 lockref_get(&dentry
->d_lockref
);
644 struct dentry
*dget_parent(struct dentry
*dentry
)
650 * Do optimistic parent lookup without any
654 ret
= ACCESS_ONCE(dentry
->d_parent
);
655 gotref
= lockref_get_not_zero(&ret
->d_lockref
);
657 if (likely(gotref
)) {
658 if (likely(ret
== ACCESS_ONCE(dentry
->d_parent
)))
665 * Don't need rcu_dereference because we re-check it was correct under
669 ret
= dentry
->d_parent
;
670 spin_lock(&ret
->d_lock
);
671 if (unlikely(ret
!= dentry
->d_parent
)) {
672 spin_unlock(&ret
->d_lock
);
677 BUG_ON(!ret
->d_lockref
.count
);
678 ret
->d_lockref
.count
++;
679 spin_unlock(&ret
->d_lock
);
682 EXPORT_SYMBOL(dget_parent
);
685 * d_find_alias - grab a hashed alias of inode
686 * @inode: inode in question
687 * @want_discon: flag, used by d_splice_alias, to request
688 * that only a DISCONNECTED alias be returned.
690 * If inode has a hashed alias, or is a directory and has any alias,
691 * acquire the reference to alias and return it. Otherwise return NULL.
692 * Notice that if inode is a directory there can be only one alias and
693 * it can be unhashed only if it has no children, or if it is the root
696 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
697 * any other hashed alias over that one unless @want_discon is set,
698 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
700 static struct dentry
*__d_find_alias(struct inode
*inode
, int want_discon
)
702 struct dentry
*alias
, *discon_alias
;
706 hlist_for_each_entry(alias
, &inode
->i_dentry
, d_alias
) {
707 spin_lock(&alias
->d_lock
);
708 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
709 if (IS_ROOT(alias
) &&
710 (alias
->d_flags
& DCACHE_DISCONNECTED
)) {
711 discon_alias
= alias
;
712 } else if (!want_discon
) {
714 spin_unlock(&alias
->d_lock
);
718 spin_unlock(&alias
->d_lock
);
721 alias
= discon_alias
;
722 spin_lock(&alias
->d_lock
);
723 if (S_ISDIR(inode
->i_mode
) || !d_unhashed(alias
)) {
724 if (IS_ROOT(alias
) &&
725 (alias
->d_flags
& DCACHE_DISCONNECTED
)) {
727 spin_unlock(&alias
->d_lock
);
731 spin_unlock(&alias
->d_lock
);
737 struct dentry
*d_find_alias(struct inode
*inode
)
739 struct dentry
*de
= NULL
;
741 if (!hlist_empty(&inode
->i_dentry
)) {
742 spin_lock(&inode
->i_lock
);
743 de
= __d_find_alias(inode
, 0);
744 spin_unlock(&inode
->i_lock
);
748 EXPORT_SYMBOL(d_find_alias
);
751 * Try to kill dentries associated with this inode.
752 * WARNING: you must own a reference to inode.
754 void d_prune_aliases(struct inode
*inode
)
756 struct dentry
*dentry
;
758 spin_lock(&inode
->i_lock
);
759 hlist_for_each_entry(dentry
, &inode
->i_dentry
, d_alias
) {
760 spin_lock(&dentry
->d_lock
);
761 if (!dentry
->d_lockref
.count
) {
763 * inform the fs via d_prune that this dentry
764 * is about to be unhashed and destroyed.
766 if ((dentry
->d_flags
& DCACHE_OP_PRUNE
) &&
768 dentry
->d_op
->d_prune(dentry
);
770 __dget_dlock(dentry
);
772 spin_unlock(&dentry
->d_lock
);
773 spin_unlock(&inode
->i_lock
);
777 spin_unlock(&dentry
->d_lock
);
779 spin_unlock(&inode
->i_lock
);
781 EXPORT_SYMBOL(d_prune_aliases
);
784 * Try to throw away a dentry - free the inode, dput the parent.
785 * Requires dentry->d_lock is held, and dentry->d_count == 0.
786 * Releases dentry->d_lock.
788 * This may fail if locks cannot be acquired no problem, just try again.
790 static void try_prune_one_dentry(struct dentry
*dentry
)
791 __releases(dentry
->d_lock
)
793 struct dentry
*parent
;
795 parent
= dentry_kill(dentry
);
797 * If dentry_kill returns NULL, we have nothing more to do.
798 * if it returns the same dentry, trylocks failed. In either
799 * case, just loop again.
801 * Otherwise, we need to prune ancestors too. This is necessary
802 * to prevent quadratic behavior of shrink_dcache_parent(), but
803 * is also expected to be beneficial in reducing dentry cache
808 if (parent
== dentry
)
811 /* Prune ancestors. */
814 if (lockref_put_or_lock(&dentry
->d_lockref
))
816 dentry
= dentry_kill(dentry
);
820 static void shrink_dentry_list(struct list_head
*list
)
822 struct dentry
*dentry
;
826 dentry
= list_entry_rcu(list
->prev
, struct dentry
, d_lru
);
827 if (&dentry
->d_lru
== list
)
829 spin_lock(&dentry
->d_lock
);
830 if (dentry
!= list_entry(list
->prev
, struct dentry
, d_lru
)) {
831 spin_unlock(&dentry
->d_lock
);
836 * We found an inuse dentry which was not removed from
837 * the LRU because of laziness during lookup. Do not free
838 * it - just keep it off the LRU list.
840 if (dentry
->d_lockref
.count
) {
841 dentry_lru_del(dentry
);
842 spin_unlock(&dentry
->d_lock
);
848 try_prune_one_dentry(dentry
);
856 * prune_dcache_sb - shrink the dcache
858 * @count: number of entries to try to free
860 * Attempt to shrink the superblock dcache LRU by @count entries. This is
861 * done when we need more memory an called from the superblock shrinker
864 * This function may fail to free any resources if all the dentries are in
867 void prune_dcache_sb(struct super_block
*sb
, int count
)
869 struct dentry
*dentry
;
870 LIST_HEAD(referenced
);
874 spin_lock(&dcache_lru_lock
);
875 while (!list_empty(&sb
->s_dentry_lru
)) {
876 dentry
= list_entry(sb
->s_dentry_lru
.prev
,
877 struct dentry
, d_lru
);
878 BUG_ON(dentry
->d_sb
!= sb
);
880 if (!spin_trylock(&dentry
->d_lock
)) {
881 spin_unlock(&dcache_lru_lock
);
886 if (dentry
->d_flags
& DCACHE_REFERENCED
) {
887 dentry
->d_flags
&= ~DCACHE_REFERENCED
;
888 list_move(&dentry
->d_lru
, &referenced
);
889 spin_unlock(&dentry
->d_lock
);
891 list_move_tail(&dentry
->d_lru
, &tmp
);
892 dentry
->d_flags
|= DCACHE_SHRINK_LIST
;
893 spin_unlock(&dentry
->d_lock
);
897 cond_resched_lock(&dcache_lru_lock
);
899 if (!list_empty(&referenced
))
900 list_splice(&referenced
, &sb
->s_dentry_lru
);
901 spin_unlock(&dcache_lru_lock
);
903 shrink_dentry_list(&tmp
);
907 * shrink_dcache_sb - shrink dcache for a superblock
910 * Shrink the dcache for the specified super block. This is used to free
911 * the dcache before unmounting a file system.
913 void shrink_dcache_sb(struct super_block
*sb
)
917 spin_lock(&dcache_lru_lock
);
918 while (!list_empty(&sb
->s_dentry_lru
)) {
919 list_splice_init(&sb
->s_dentry_lru
, &tmp
);
920 spin_unlock(&dcache_lru_lock
);
921 shrink_dentry_list(&tmp
);
922 spin_lock(&dcache_lru_lock
);
924 spin_unlock(&dcache_lru_lock
);
926 EXPORT_SYMBOL(shrink_dcache_sb
);
929 * destroy a single subtree of dentries for unmount
930 * - see the comments on shrink_dcache_for_umount() for a description of the
933 static void shrink_dcache_for_umount_subtree(struct dentry
*dentry
)
935 struct dentry
*parent
;
937 BUG_ON(!IS_ROOT(dentry
));
940 /* descend to the first leaf in the current subtree */
941 while (!list_empty(&dentry
->d_subdirs
))
942 dentry
= list_entry(dentry
->d_subdirs
.next
,
943 struct dentry
, d_u
.d_child
);
945 /* consume the dentries from this leaf up through its parents
946 * until we find one with children or run out altogether */
951 * inform the fs that this dentry is about to be
952 * unhashed and destroyed.
954 if ((dentry
->d_flags
& DCACHE_OP_PRUNE
) &&
956 dentry
->d_op
->d_prune(dentry
);
958 dentry_lru_del(dentry
);
961 if (dentry
->d_lockref
.count
!= 0) {
963 "BUG: Dentry %p{i=%lx,n=%s}"
965 " [unmount of %s %s]\n",
968 dentry
->d_inode
->i_ino
: 0UL,
970 dentry
->d_lockref
.count
,
971 dentry
->d_sb
->s_type
->name
,
976 if (IS_ROOT(dentry
)) {
978 list_del(&dentry
->d_u
.d_child
);
980 parent
= dentry
->d_parent
;
981 parent
->d_lockref
.count
--;
982 list_del(&dentry
->d_u
.d_child
);
985 inode
= dentry
->d_inode
;
987 dentry
->d_inode
= NULL
;
988 hlist_del_init(&dentry
->d_alias
);
989 if (dentry
->d_op
&& dentry
->d_op
->d_iput
)
990 dentry
->d_op
->d_iput(dentry
, inode
);
997 /* finished when we fall off the top of the tree,
998 * otherwise we ascend to the parent and move to the
999 * next sibling if there is one */
1003 } while (list_empty(&dentry
->d_subdirs
));
1005 dentry
= list_entry(dentry
->d_subdirs
.next
,
1006 struct dentry
, d_u
.d_child
);
1011 * destroy the dentries attached to a superblock on unmounting
1012 * - we don't need to use dentry->d_lock because:
1013 * - the superblock is detached from all mountings and open files, so the
1014 * dentry trees will not be rearranged by the VFS
1015 * - s_umount is write-locked, so the memory pressure shrinker will ignore
1016 * any dentries belonging to this superblock that it comes across
1017 * - the filesystem itself is no longer permitted to rearrange the dentries
1018 * in this superblock
1020 void shrink_dcache_for_umount(struct super_block
*sb
)
1022 struct dentry
*dentry
;
1024 if (down_read_trylock(&sb
->s_umount
))
1027 dentry
= sb
->s_root
;
1029 dentry
->d_lockref
.count
--;
1030 shrink_dcache_for_umount_subtree(dentry
);
1032 while (!hlist_bl_empty(&sb
->s_anon
)) {
1033 dentry
= hlist_bl_entry(hlist_bl_first(&sb
->s_anon
), struct dentry
, d_hash
);
1034 shrink_dcache_for_umount_subtree(dentry
);
1039 * This tries to ascend one level of parenthood, but
1040 * we can race with renaming, so we need to re-check
1041 * the parenthood after dropping the lock and check
1042 * that the sequence number still matches.
1044 static struct dentry
*try_to_ascend(struct dentry
*old
, unsigned seq
)
1046 struct dentry
*new = old
->d_parent
;
1049 spin_unlock(&old
->d_lock
);
1050 spin_lock(&new->d_lock
);
1053 * might go back up the wrong parent if we have had a rename
1056 if (new != old
->d_parent
||
1057 (old
->d_flags
& DCACHE_DENTRY_KILLED
) ||
1058 need_seqretry(&rename_lock
, seq
)) {
1059 spin_unlock(&new->d_lock
);
1067 * enum d_walk_ret - action to talke during tree walk
1068 * @D_WALK_CONTINUE: contrinue walk
1069 * @D_WALK_QUIT: quit walk
1070 * @D_WALK_NORETRY: quit when retry is needed
1071 * @D_WALK_SKIP: skip this dentry and its children
1081 * d_walk - walk the dentry tree
1082 * @parent: start of walk
1083 * @data: data passed to @enter() and @finish()
1084 * @enter: callback when first entering the dentry
1085 * @finish: callback when successfully finished the walk
1087 * The @enter() and @finish() callbacks are called with d_lock held.
1089 static void d_walk(struct dentry
*parent
, void *data
,
1090 enum d_walk_ret (*enter
)(void *, struct dentry
*),
1091 void (*finish
)(void *))
1093 struct dentry
*this_parent
;
1094 struct list_head
*next
;
1096 enum d_walk_ret ret
;
1100 read_seqbegin_or_lock(&rename_lock
, &seq
);
1101 this_parent
= parent
;
1102 spin_lock(&this_parent
->d_lock
);
1104 ret
= enter(data
, this_parent
);
1106 case D_WALK_CONTINUE
:
1111 case D_WALK_NORETRY
:
1116 next
= this_parent
->d_subdirs
.next
;
1118 while (next
!= &this_parent
->d_subdirs
) {
1119 struct list_head
*tmp
= next
;
1120 struct dentry
*dentry
= list_entry(tmp
, struct dentry
, d_u
.d_child
);
1123 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
1125 ret
= enter(data
, dentry
);
1127 case D_WALK_CONTINUE
:
1130 spin_unlock(&dentry
->d_lock
);
1132 case D_WALK_NORETRY
:
1136 spin_unlock(&dentry
->d_lock
);
1140 if (!list_empty(&dentry
->d_subdirs
)) {
1141 spin_unlock(&this_parent
->d_lock
);
1142 spin_release(&dentry
->d_lock
.dep_map
, 1, _RET_IP_
);
1143 this_parent
= dentry
;
1144 spin_acquire(&this_parent
->d_lock
.dep_map
, 0, 1, _RET_IP_
);
1147 spin_unlock(&dentry
->d_lock
);
1150 * All done at this level ... ascend and resume the search.
1152 if (this_parent
!= parent
) {
1153 struct dentry
*child
= this_parent
;
1154 this_parent
= try_to_ascend(this_parent
, seq
);
1157 next
= child
->d_u
.d_child
.next
;
1160 if (need_seqretry(&rename_lock
, seq
)) {
1161 spin_unlock(&this_parent
->d_lock
);
1168 spin_unlock(&this_parent
->d_lock
);
1169 done_seqretry(&rename_lock
, seq
);
1180 * Search for at least 1 mount point in the dentry's subdirs.
1181 * We descend to the next level whenever the d_subdirs
1182 * list is non-empty and continue searching.
1186 * have_submounts - check for mounts over a dentry
1187 * @parent: dentry to check.
1189 * Return true if the parent or its subdirectories contain
1193 static enum d_walk_ret
check_mount(void *data
, struct dentry
*dentry
)
1196 if (d_mountpoint(dentry
)) {
1200 return D_WALK_CONTINUE
;
1203 int have_submounts(struct dentry
*parent
)
1207 d_walk(parent
, &ret
, check_mount
, NULL
);
1211 EXPORT_SYMBOL(have_submounts
);
1214 * Called by mount code to set a mountpoint and check if the mountpoint is
1215 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1216 * subtree can become unreachable).
1218 * Only one of check_submounts_and_drop() and d_set_mounted() must succeed. For
1219 * this reason take rename_lock and d_lock on dentry and ancestors.
1221 int d_set_mounted(struct dentry
*dentry
)
1225 write_seqlock(&rename_lock
);
1226 for (p
= dentry
->d_parent
; !IS_ROOT(p
); p
= p
->d_parent
) {
1227 /* Need exclusion wrt. check_submounts_and_drop() */
1228 spin_lock(&p
->d_lock
);
1229 if (unlikely(d_unhashed(p
))) {
1230 spin_unlock(&p
->d_lock
);
1233 spin_unlock(&p
->d_lock
);
1235 spin_lock(&dentry
->d_lock
);
1236 if (!d_unlinked(dentry
)) {
1237 dentry
->d_flags
|= DCACHE_MOUNTED
;
1240 spin_unlock(&dentry
->d_lock
);
1242 write_sequnlock(&rename_lock
);
1247 * Search the dentry child list of the specified parent,
1248 * and move any unused dentries to the end of the unused
1249 * list for prune_dcache(). We descend to the next level
1250 * whenever the d_subdirs list is non-empty and continue
1253 * It returns zero iff there are no unused children,
1254 * otherwise it returns the number of children moved to
1255 * the end of the unused list. This may not be the total
1256 * number of unused children, because select_parent can
1257 * drop the lock and return early due to latency
1261 struct select_data
{
1262 struct dentry
*start
;
1263 struct list_head dispose
;
1267 static enum d_walk_ret
select_collect(void *_data
, struct dentry
*dentry
)
1269 struct select_data
*data
= _data
;
1270 enum d_walk_ret ret
= D_WALK_CONTINUE
;
1272 if (data
->start
== dentry
)
1276 * move only zero ref count dentries to the dispose list.
1278 * Those which are presently on the shrink list, being processed
1279 * by shrink_dentry_list(), shouldn't be moved. Otherwise the
1280 * loop in shrink_dcache_parent() might not make any progress
1283 if (dentry
->d_lockref
.count
) {
1284 dentry_lru_del(dentry
);
1285 } else if (!(dentry
->d_flags
& DCACHE_SHRINK_LIST
)) {
1286 dentry_lru_move_list(dentry
, &data
->dispose
);
1287 dentry
->d_flags
|= DCACHE_SHRINK_LIST
;
1289 ret
= D_WALK_NORETRY
;
1292 * We can return to the caller if we have found some (this
1293 * ensures forward progress). We'll be coming back to find
1296 if (data
->found
&& need_resched())
1303 * shrink_dcache_parent - prune dcache
1304 * @parent: parent of entries to prune
1306 * Prune the dcache to remove unused children of the parent dentry.
1308 void shrink_dcache_parent(struct dentry
*parent
)
1311 struct select_data data
;
1313 INIT_LIST_HEAD(&data
.dispose
);
1314 data
.start
= parent
;
1317 d_walk(parent
, &data
, select_collect
, NULL
);
1321 shrink_dentry_list(&data
.dispose
);
1325 EXPORT_SYMBOL(shrink_dcache_parent
);
1327 static enum d_walk_ret
check_and_collect(void *_data
, struct dentry
*dentry
)
1329 struct select_data
*data
= _data
;
1331 if (d_mountpoint(dentry
)) {
1332 data
->found
= -EBUSY
;
1336 return select_collect(_data
, dentry
);
1339 static void check_and_drop(void *_data
)
1341 struct select_data
*data
= _data
;
1343 if (d_mountpoint(data
->start
))
1344 data
->found
= -EBUSY
;
1346 __d_drop(data
->start
);
1350 * check_submounts_and_drop - prune dcache, check for submounts and drop
1352 * All done as a single atomic operation relative to has_unlinked_ancestor().
1353 * Returns 0 if successfully unhashed @parent. If there were submounts then
1356 * @dentry: dentry to prune and drop
1358 int check_submounts_and_drop(struct dentry
*dentry
)
1362 /* Negative dentries can be dropped without further checks */
1363 if (!dentry
->d_inode
) {
1369 struct select_data data
;
1371 INIT_LIST_HEAD(&data
.dispose
);
1372 data
.start
= dentry
;
1375 d_walk(dentry
, &data
, check_and_collect
, check_and_drop
);
1378 if (!list_empty(&data
.dispose
))
1379 shrink_dentry_list(&data
.dispose
);
1390 EXPORT_SYMBOL(check_submounts_and_drop
);
1393 * __d_alloc - allocate a dcache entry
1394 * @sb: filesystem it will belong to
1395 * @name: qstr of the name
1397 * Allocates a dentry. It returns %NULL if there is insufficient memory
1398 * available. On a success the dentry is returned. The name passed in is
1399 * copied and the copy passed in may be reused after this call.
1402 struct dentry
*__d_alloc(struct super_block
*sb
, const struct qstr
*name
)
1404 struct dentry
*dentry
;
1407 dentry
= kmem_cache_alloc(dentry_cache
, GFP_KERNEL
);
1412 * We guarantee that the inline name is always NUL-terminated.
1413 * This way the memcpy() done by the name switching in rename
1414 * will still always have a NUL at the end, even if we might
1415 * be overwriting an internal NUL character
1417 dentry
->d_iname
[DNAME_INLINE_LEN
-1] = 0;
1418 if (name
->len
> DNAME_INLINE_LEN
-1) {
1419 dname
= kmalloc(name
->len
+ 1, GFP_KERNEL
);
1421 kmem_cache_free(dentry_cache
, dentry
);
1425 dname
= dentry
->d_iname
;
1428 dentry
->d_name
.len
= name
->len
;
1429 dentry
->d_name
.hash
= name
->hash
;
1430 memcpy(dname
, name
->name
, name
->len
);
1431 dname
[name
->len
] = 0;
1433 /* Make sure we always see the terminating NUL character */
1435 dentry
->d_name
.name
= dname
;
1437 dentry
->d_lockref
.count
= 1;
1438 dentry
->d_flags
= 0;
1439 spin_lock_init(&dentry
->d_lock
);
1440 seqcount_init(&dentry
->d_seq
);
1441 dentry
->d_inode
= NULL
;
1442 dentry
->d_parent
= dentry
;
1444 dentry
->d_op
= NULL
;
1445 dentry
->d_fsdata
= NULL
;
1446 INIT_HLIST_BL_NODE(&dentry
->d_hash
);
1447 INIT_LIST_HEAD(&dentry
->d_lru
);
1448 INIT_LIST_HEAD(&dentry
->d_subdirs
);
1449 INIT_HLIST_NODE(&dentry
->d_alias
);
1450 INIT_LIST_HEAD(&dentry
->d_u
.d_child
);
1451 d_set_d_op(dentry
, dentry
->d_sb
->s_d_op
);
1453 this_cpu_inc(nr_dentry
);
1459 * d_alloc - allocate a dcache entry
1460 * @parent: parent of entry to allocate
1461 * @name: qstr of the name
1463 * Allocates a dentry. It returns %NULL if there is insufficient memory
1464 * available. On a success the dentry is returned. The name passed in is
1465 * copied and the copy passed in may be reused after this call.
1467 struct dentry
*d_alloc(struct dentry
* parent
, const struct qstr
*name
)
1469 struct dentry
*dentry
= __d_alloc(parent
->d_sb
, name
);
1473 spin_lock(&parent
->d_lock
);
1475 * don't need child lock because it is not subject
1476 * to concurrency here
1478 __dget_dlock(parent
);
1479 dentry
->d_parent
= parent
;
1480 list_add(&dentry
->d_u
.d_child
, &parent
->d_subdirs
);
1481 spin_unlock(&parent
->d_lock
);
1485 EXPORT_SYMBOL(d_alloc
);
1487 struct dentry
*d_alloc_pseudo(struct super_block
*sb
, const struct qstr
*name
)
1489 struct dentry
*dentry
= __d_alloc(sb
, name
);
1491 dentry
->d_flags
|= DCACHE_DISCONNECTED
;
1494 EXPORT_SYMBOL(d_alloc_pseudo
);
1496 struct dentry
*d_alloc_name(struct dentry
*parent
, const char *name
)
1501 q
.len
= strlen(name
);
1502 q
.hash
= full_name_hash(q
.name
, q
.len
);
1503 return d_alloc(parent
, &q
);
1505 EXPORT_SYMBOL(d_alloc_name
);
1507 void d_set_d_op(struct dentry
*dentry
, const struct dentry_operations
*op
)
1509 WARN_ON_ONCE(dentry
->d_op
);
1510 WARN_ON_ONCE(dentry
->d_flags
& (DCACHE_OP_HASH
|
1512 DCACHE_OP_REVALIDATE
|
1513 DCACHE_OP_WEAK_REVALIDATE
|
1514 DCACHE_OP_DELETE
));
1519 dentry
->d_flags
|= DCACHE_OP_HASH
;
1521 dentry
->d_flags
|= DCACHE_OP_COMPARE
;
1522 if (op
->d_revalidate
)
1523 dentry
->d_flags
|= DCACHE_OP_REVALIDATE
;
1524 if (op
->d_weak_revalidate
)
1525 dentry
->d_flags
|= DCACHE_OP_WEAK_REVALIDATE
;
1527 dentry
->d_flags
|= DCACHE_OP_DELETE
;
1529 dentry
->d_flags
|= DCACHE_OP_PRUNE
;
1532 EXPORT_SYMBOL(d_set_d_op
);
1534 static void __d_instantiate(struct dentry
*dentry
, struct inode
*inode
)
1536 spin_lock(&dentry
->d_lock
);
1538 if (unlikely(IS_AUTOMOUNT(inode
)))
1539 dentry
->d_flags
|= DCACHE_NEED_AUTOMOUNT
;
1540 hlist_add_head(&dentry
->d_alias
, &inode
->i_dentry
);
1542 dentry
->d_inode
= inode
;
1543 dentry_rcuwalk_barrier(dentry
);
1544 spin_unlock(&dentry
->d_lock
);
1545 fsnotify_d_instantiate(dentry
, inode
);
1549 * d_instantiate - fill in inode information for a dentry
1550 * @entry: dentry to complete
1551 * @inode: inode to attach to this dentry
1553 * Fill in inode information in the entry.
1555 * This turns negative dentries into productive full members
1558 * NOTE! This assumes that the inode count has been incremented
1559 * (or otherwise set) by the caller to indicate that it is now
1560 * in use by the dcache.
1563 void d_instantiate(struct dentry
*entry
, struct inode
* inode
)
1565 BUG_ON(!hlist_unhashed(&entry
->d_alias
));
1567 spin_lock(&inode
->i_lock
);
1568 __d_instantiate(entry
, inode
);
1570 spin_unlock(&inode
->i_lock
);
1571 security_d_instantiate(entry
, inode
);
1573 EXPORT_SYMBOL(d_instantiate
);
1576 * d_instantiate_unique - instantiate a non-aliased dentry
1577 * @entry: dentry to instantiate
1578 * @inode: inode to attach to this dentry
1580 * Fill in inode information in the entry. On success, it returns NULL.
1581 * If an unhashed alias of "entry" already exists, then we return the
1582 * aliased dentry instead and drop one reference to inode.
1584 * Note that in order to avoid conflicts with rename() etc, the caller
1585 * had better be holding the parent directory semaphore.
1587 * This also assumes that the inode count has been incremented
1588 * (or otherwise set) by the caller to indicate that it is now
1589 * in use by the dcache.
1591 static struct dentry
*__d_instantiate_unique(struct dentry
*entry
,
1592 struct inode
*inode
)
1594 struct dentry
*alias
;
1595 int len
= entry
->d_name
.len
;
1596 const char *name
= entry
->d_name
.name
;
1597 unsigned int hash
= entry
->d_name
.hash
;
1600 __d_instantiate(entry
, NULL
);
1604 hlist_for_each_entry(alias
, &inode
->i_dentry
, d_alias
) {
1606 * Don't need alias->d_lock here, because aliases with
1607 * d_parent == entry->d_parent are not subject to name or
1608 * parent changes, because the parent inode i_mutex is held.
1610 if (alias
->d_name
.hash
!= hash
)
1612 if (alias
->d_parent
!= entry
->d_parent
)
1614 if (alias
->d_name
.len
!= len
)
1616 if (dentry_cmp(alias
, name
, len
))
1622 __d_instantiate(entry
, inode
);
1626 struct dentry
*d_instantiate_unique(struct dentry
*entry
, struct inode
*inode
)
1628 struct dentry
*result
;
1630 BUG_ON(!hlist_unhashed(&entry
->d_alias
));
1633 spin_lock(&inode
->i_lock
);
1634 result
= __d_instantiate_unique(entry
, inode
);
1636 spin_unlock(&inode
->i_lock
);
1639 security_d_instantiate(entry
, inode
);
1643 BUG_ON(!d_unhashed(result
));
1648 EXPORT_SYMBOL(d_instantiate_unique
);
1650 struct dentry
*d_make_root(struct inode
*root_inode
)
1652 struct dentry
*res
= NULL
;
1655 static const struct qstr name
= QSTR_INIT("/", 1);
1657 res
= __d_alloc(root_inode
->i_sb
, &name
);
1659 d_instantiate(res
, root_inode
);
1665 EXPORT_SYMBOL(d_make_root
);
1667 static struct dentry
* __d_find_any_alias(struct inode
*inode
)
1669 struct dentry
*alias
;
1671 if (hlist_empty(&inode
->i_dentry
))
1673 alias
= hlist_entry(inode
->i_dentry
.first
, struct dentry
, d_alias
);
1679 * d_find_any_alias - find any alias for a given inode
1680 * @inode: inode to find an alias for
1682 * If any aliases exist for the given inode, take and return a
1683 * reference for one of them. If no aliases exist, return %NULL.
1685 struct dentry
*d_find_any_alias(struct inode
*inode
)
1689 spin_lock(&inode
->i_lock
);
1690 de
= __d_find_any_alias(inode
);
1691 spin_unlock(&inode
->i_lock
);
1694 EXPORT_SYMBOL(d_find_any_alias
);
1697 * d_obtain_alias - find or allocate a dentry for a given inode
1698 * @inode: inode to allocate the dentry for
1700 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1701 * similar open by handle operations. The returned dentry may be anonymous,
1702 * or may have a full name (if the inode was already in the cache).
1704 * When called on a directory inode, we must ensure that the inode only ever
1705 * has one dentry. If a dentry is found, that is returned instead of
1706 * allocating a new one.
1708 * On successful return, the reference to the inode has been transferred
1709 * to the dentry. In case of an error the reference on the inode is released.
1710 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1711 * be passed in and will be the error will be propagate to the return value,
1712 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1714 struct dentry
*d_obtain_alias(struct inode
*inode
)
1716 static const struct qstr anonstring
= QSTR_INIT("/", 1);
1721 return ERR_PTR(-ESTALE
);
1723 return ERR_CAST(inode
);
1725 res
= d_find_any_alias(inode
);
1729 tmp
= __d_alloc(inode
->i_sb
, &anonstring
);
1731 res
= ERR_PTR(-ENOMEM
);
1735 spin_lock(&inode
->i_lock
);
1736 res
= __d_find_any_alias(inode
);
1738 spin_unlock(&inode
->i_lock
);
1743 /* attach a disconnected dentry */
1744 spin_lock(&tmp
->d_lock
);
1745 tmp
->d_inode
= inode
;
1746 tmp
->d_flags
|= DCACHE_DISCONNECTED
;
1747 hlist_add_head(&tmp
->d_alias
, &inode
->i_dentry
);
1748 hlist_bl_lock(&tmp
->d_sb
->s_anon
);
1749 hlist_bl_add_head(&tmp
->d_hash
, &tmp
->d_sb
->s_anon
);
1750 hlist_bl_unlock(&tmp
->d_sb
->s_anon
);
1751 spin_unlock(&tmp
->d_lock
);
1752 spin_unlock(&inode
->i_lock
);
1753 security_d_instantiate(tmp
, inode
);
1758 if (res
&& !IS_ERR(res
))
1759 security_d_instantiate(res
, inode
);
1763 EXPORT_SYMBOL(d_obtain_alias
);
1766 * d_splice_alias - splice a disconnected dentry into the tree if one exists
1767 * @inode: the inode which may have a disconnected dentry
1768 * @dentry: a negative dentry which we want to point to the inode.
1770 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1771 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1772 * and return it, else simply d_add the inode to the dentry and return NULL.
1774 * This is needed in the lookup routine of any filesystem that is exportable
1775 * (via knfsd) so that we can build dcache paths to directories effectively.
1777 * If a dentry was found and moved, then it is returned. Otherwise NULL
1778 * is returned. This matches the expected return value of ->lookup.
1780 * Cluster filesystems may call this function with a negative, hashed dentry.
1781 * In that case, we know that the inode will be a regular file, and also this
1782 * will only occur during atomic_open. So we need to check for the dentry
1783 * being already hashed only in the final case.
1785 struct dentry
*d_splice_alias(struct inode
*inode
, struct dentry
*dentry
)
1787 struct dentry
*new = NULL
;
1790 return ERR_CAST(inode
);
1792 if (inode
&& S_ISDIR(inode
->i_mode
)) {
1793 spin_lock(&inode
->i_lock
);
1794 new = __d_find_alias(inode
, 1);
1796 BUG_ON(!(new->d_flags
& DCACHE_DISCONNECTED
));
1797 spin_unlock(&inode
->i_lock
);
1798 security_d_instantiate(new, inode
);
1799 d_move(new, dentry
);
1802 /* already taking inode->i_lock, so d_add() by hand */
1803 __d_instantiate(dentry
, inode
);
1804 spin_unlock(&inode
->i_lock
);
1805 security_d_instantiate(dentry
, inode
);
1809 d_instantiate(dentry
, inode
);
1810 if (d_unhashed(dentry
))
1815 EXPORT_SYMBOL(d_splice_alias
);
1818 * d_add_ci - lookup or allocate new dentry with case-exact name
1819 * @inode: the inode case-insensitive lookup has found
1820 * @dentry: the negative dentry that was passed to the parent's lookup func
1821 * @name: the case-exact name to be associated with the returned dentry
1823 * This is to avoid filling the dcache with case-insensitive names to the
1824 * same inode, only the actual correct case is stored in the dcache for
1825 * case-insensitive filesystems.
1827 * For a case-insensitive lookup match and if the the case-exact dentry
1828 * already exists in in the dcache, use it and return it.
1830 * If no entry exists with the exact case name, allocate new dentry with
1831 * the exact case, and return the spliced entry.
1833 struct dentry
*d_add_ci(struct dentry
*dentry
, struct inode
*inode
,
1836 struct dentry
*found
;
1840 * First check if a dentry matching the name already exists,
1841 * if not go ahead and create it now.
1843 found
= d_hash_and_lookup(dentry
->d_parent
, name
);
1844 if (unlikely(IS_ERR(found
)))
1847 new = d_alloc(dentry
->d_parent
, name
);
1849 found
= ERR_PTR(-ENOMEM
);
1853 found
= d_splice_alias(inode
, new);
1862 * If a matching dentry exists, and it's not negative use it.
1864 * Decrement the reference count to balance the iget() done
1867 if (found
->d_inode
) {
1868 if (unlikely(found
->d_inode
!= inode
)) {
1869 /* This can't happen because bad inodes are unhashed. */
1870 BUG_ON(!is_bad_inode(inode
));
1871 BUG_ON(!is_bad_inode(found
->d_inode
));
1878 * Negative dentry: instantiate it unless the inode is a directory and
1879 * already has a dentry.
1881 new = d_splice_alias(inode
, found
);
1892 EXPORT_SYMBOL(d_add_ci
);
1895 * Do the slow-case of the dentry name compare.
1897 * Unlike the dentry_cmp() function, we need to atomically
1898 * load the name and length information, so that the
1899 * filesystem can rely on them, and can use the 'name' and
1900 * 'len' information without worrying about walking off the
1901 * end of memory etc.
1903 * Thus the read_seqcount_retry() and the "duplicate" info
1904 * in arguments (the low-level filesystem should not look
1905 * at the dentry inode or name contents directly, since
1906 * rename can change them while we're in RCU mode).
1908 enum slow_d_compare
{
1914 static noinline
enum slow_d_compare
slow_dentry_cmp(
1915 const struct dentry
*parent
,
1916 struct dentry
*dentry
,
1918 const struct qstr
*name
)
1920 int tlen
= dentry
->d_name
.len
;
1921 const char *tname
= dentry
->d_name
.name
;
1923 if (read_seqcount_retry(&dentry
->d_seq
, seq
)) {
1925 return D_COMP_SEQRETRY
;
1927 if (parent
->d_op
->d_compare(parent
, dentry
, tlen
, tname
, name
))
1928 return D_COMP_NOMATCH
;
1933 * __d_lookup_rcu - search for a dentry (racy, store-free)
1934 * @parent: parent dentry
1935 * @name: qstr of name we wish to find
1936 * @seqp: returns d_seq value at the point where the dentry was found
1937 * Returns: dentry, or NULL
1939 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
1940 * resolution (store-free path walking) design described in
1941 * Documentation/filesystems/path-lookup.txt.
1943 * This is not to be used outside core vfs.
1945 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
1946 * held, and rcu_read_lock held. The returned dentry must not be stored into
1947 * without taking d_lock and checking d_seq sequence count against @seq
1950 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
1953 * Alternatively, __d_lookup_rcu may be called again to look up the child of
1954 * the returned dentry, so long as its parent's seqlock is checked after the
1955 * child is looked up. Thus, an interlocking stepping of sequence lock checks
1956 * is formed, giving integrity down the path walk.
1958 * NOTE! The caller *has* to check the resulting dentry against the sequence
1959 * number we've returned before using any of the resulting dentry state!
1961 struct dentry
*__d_lookup_rcu(const struct dentry
*parent
,
1962 const struct qstr
*name
,
1965 u64 hashlen
= name
->hash_len
;
1966 const unsigned char *str
= name
->name
;
1967 struct hlist_bl_head
*b
= d_hash(parent
, hashlen_hash(hashlen
));
1968 struct hlist_bl_node
*node
;
1969 struct dentry
*dentry
;
1972 * Note: There is significant duplication with __d_lookup_rcu which is
1973 * required to prevent single threaded performance regressions
1974 * especially on architectures where smp_rmb (in seqcounts) are costly.
1975 * Keep the two functions in sync.
1979 * The hash list is protected using RCU.
1981 * Carefully use d_seq when comparing a candidate dentry, to avoid
1982 * races with d_move().
1984 * It is possible that concurrent renames can mess up our list
1985 * walk here and result in missing our dentry, resulting in the
1986 * false-negative result. d_lookup() protects against concurrent
1987 * renames using rename_lock seqlock.
1989 * See Documentation/filesystems/path-lookup.txt for more details.
1991 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
1996 * The dentry sequence count protects us from concurrent
1997 * renames, and thus protects parent and name fields.
1999 * The caller must perform a seqcount check in order
2000 * to do anything useful with the returned dentry.
2002 * NOTE! We do a "raw" seqcount_begin here. That means that
2003 * we don't wait for the sequence count to stabilize if it
2004 * is in the middle of a sequence change. If we do the slow
2005 * dentry compare, we will do seqretries until it is stable,
2006 * and if we end up with a successful lookup, we actually
2007 * want to exit RCU lookup anyway.
2009 seq
= raw_seqcount_begin(&dentry
->d_seq
);
2010 if (dentry
->d_parent
!= parent
)
2012 if (d_unhashed(dentry
))
2015 if (unlikely(parent
->d_flags
& DCACHE_OP_COMPARE
)) {
2016 if (dentry
->d_name
.hash
!= hashlen_hash(hashlen
))
2019 switch (slow_dentry_cmp(parent
, dentry
, seq
, name
)) {
2022 case D_COMP_NOMATCH
:
2029 if (dentry
->d_name
.hash_len
!= hashlen
)
2032 if (!dentry_cmp(dentry
, str
, hashlen_len(hashlen
)))
2039 * d_lookup - search for a dentry
2040 * @parent: parent dentry
2041 * @name: qstr of name we wish to find
2042 * Returns: dentry, or NULL
2044 * d_lookup searches the children of the parent dentry for the name in
2045 * question. If the dentry is found its reference count is incremented and the
2046 * dentry is returned. The caller must use dput to free the entry when it has
2047 * finished using it. %NULL is returned if the dentry does not exist.
2049 struct dentry
*d_lookup(const struct dentry
*parent
, const struct qstr
*name
)
2051 struct dentry
*dentry
;
2055 seq
= read_seqbegin(&rename_lock
);
2056 dentry
= __d_lookup(parent
, name
);
2059 } while (read_seqretry(&rename_lock
, seq
));
2062 EXPORT_SYMBOL(d_lookup
);
2065 * __d_lookup - search for a dentry (racy)
2066 * @parent: parent dentry
2067 * @name: qstr of name we wish to find
2068 * Returns: dentry, or NULL
2070 * __d_lookup is like d_lookup, however it may (rarely) return a
2071 * false-negative result due to unrelated rename activity.
2073 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2074 * however it must be used carefully, eg. with a following d_lookup in
2075 * the case of failure.
2077 * __d_lookup callers must be commented.
2079 struct dentry
*__d_lookup(const struct dentry
*parent
, const struct qstr
*name
)
2081 unsigned int len
= name
->len
;
2082 unsigned int hash
= name
->hash
;
2083 const unsigned char *str
= name
->name
;
2084 struct hlist_bl_head
*b
= d_hash(parent
, hash
);
2085 struct hlist_bl_node
*node
;
2086 struct dentry
*found
= NULL
;
2087 struct dentry
*dentry
;
2090 * Note: There is significant duplication with __d_lookup_rcu which is
2091 * required to prevent single threaded performance regressions
2092 * especially on architectures where smp_rmb (in seqcounts) are costly.
2093 * Keep the two functions in sync.
2097 * The hash list is protected using RCU.
2099 * Take d_lock when comparing a candidate dentry, to avoid races
2102 * It is possible that concurrent renames can mess up our list
2103 * walk here and result in missing our dentry, resulting in the
2104 * false-negative result. d_lookup() protects against concurrent
2105 * renames using rename_lock seqlock.
2107 * See Documentation/filesystems/path-lookup.txt for more details.
2111 hlist_bl_for_each_entry_rcu(dentry
, node
, b
, d_hash
) {
2113 if (dentry
->d_name
.hash
!= hash
)
2116 spin_lock(&dentry
->d_lock
);
2117 if (dentry
->d_parent
!= parent
)
2119 if (d_unhashed(dentry
))
2123 * It is safe to compare names since d_move() cannot
2124 * change the qstr (protected by d_lock).
2126 if (parent
->d_flags
& DCACHE_OP_COMPARE
) {
2127 int tlen
= dentry
->d_name
.len
;
2128 const char *tname
= dentry
->d_name
.name
;
2129 if (parent
->d_op
->d_compare(parent
, dentry
, tlen
, tname
, name
))
2132 if (dentry
->d_name
.len
!= len
)
2134 if (dentry_cmp(dentry
, str
, len
))
2138 dentry
->d_lockref
.count
++;
2140 spin_unlock(&dentry
->d_lock
);
2143 spin_unlock(&dentry
->d_lock
);
2151 * d_hash_and_lookup - hash the qstr then search for a dentry
2152 * @dir: Directory to search in
2153 * @name: qstr of name we wish to find
2155 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2157 struct dentry
*d_hash_and_lookup(struct dentry
*dir
, struct qstr
*name
)
2160 * Check for a fs-specific hash function. Note that we must
2161 * calculate the standard hash first, as the d_op->d_hash()
2162 * routine may choose to leave the hash value unchanged.
2164 name
->hash
= full_name_hash(name
->name
, name
->len
);
2165 if (dir
->d_flags
& DCACHE_OP_HASH
) {
2166 int err
= dir
->d_op
->d_hash(dir
, name
);
2167 if (unlikely(err
< 0))
2168 return ERR_PTR(err
);
2170 return d_lookup(dir
, name
);
2172 EXPORT_SYMBOL(d_hash_and_lookup
);
2175 * d_validate - verify dentry provided from insecure source (deprecated)
2176 * @dentry: The dentry alleged to be valid child of @dparent
2177 * @dparent: The parent dentry (known to be valid)
2179 * An insecure source has sent us a dentry, here we verify it and dget() it.
2180 * This is used by ncpfs in its readdir implementation.
2181 * Zero is returned in the dentry is invalid.
2183 * This function is slow for big directories, and deprecated, do not use it.
2185 int d_validate(struct dentry
*dentry
, struct dentry
*dparent
)
2187 struct dentry
*child
;
2189 spin_lock(&dparent
->d_lock
);
2190 list_for_each_entry(child
, &dparent
->d_subdirs
, d_u
.d_child
) {
2191 if (dentry
== child
) {
2192 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
2193 __dget_dlock(dentry
);
2194 spin_unlock(&dentry
->d_lock
);
2195 spin_unlock(&dparent
->d_lock
);
2199 spin_unlock(&dparent
->d_lock
);
2203 EXPORT_SYMBOL(d_validate
);
2206 * When a file is deleted, we have two options:
2207 * - turn this dentry into a negative dentry
2208 * - unhash this dentry and free it.
2210 * Usually, we want to just turn this into
2211 * a negative dentry, but if anybody else is
2212 * currently using the dentry or the inode
2213 * we can't do that and we fall back on removing
2214 * it from the hash queues and waiting for
2215 * it to be deleted later when it has no users
2219 * d_delete - delete a dentry
2220 * @dentry: The dentry to delete
2222 * Turn the dentry into a negative dentry if possible, otherwise
2223 * remove it from the hash queues so it can be deleted later
2226 void d_delete(struct dentry
* dentry
)
2228 struct inode
*inode
;
2231 * Are we the only user?
2234 spin_lock(&dentry
->d_lock
);
2235 inode
= dentry
->d_inode
;
2236 isdir
= S_ISDIR(inode
->i_mode
);
2237 if (dentry
->d_lockref
.count
== 1) {
2238 if (!spin_trylock(&inode
->i_lock
)) {
2239 spin_unlock(&dentry
->d_lock
);
2243 dentry
->d_flags
&= ~DCACHE_CANT_MOUNT
;
2244 dentry_unlink_inode(dentry
);
2245 fsnotify_nameremove(dentry
, isdir
);
2249 if (!d_unhashed(dentry
))
2252 spin_unlock(&dentry
->d_lock
);
2254 fsnotify_nameremove(dentry
, isdir
);
2256 EXPORT_SYMBOL(d_delete
);
2258 static void __d_rehash(struct dentry
* entry
, struct hlist_bl_head
*b
)
2260 BUG_ON(!d_unhashed(entry
));
2262 entry
->d_flags
|= DCACHE_RCUACCESS
;
2263 hlist_bl_add_head_rcu(&entry
->d_hash
, b
);
2267 static void _d_rehash(struct dentry
* entry
)
2269 __d_rehash(entry
, d_hash(entry
->d_parent
, entry
->d_name
.hash
));
2273 * d_rehash - add an entry back to the hash
2274 * @entry: dentry to add to the hash
2276 * Adds a dentry to the hash according to its name.
2279 void d_rehash(struct dentry
* entry
)
2281 spin_lock(&entry
->d_lock
);
2283 spin_unlock(&entry
->d_lock
);
2285 EXPORT_SYMBOL(d_rehash
);
2288 * dentry_update_name_case - update case insensitive dentry with a new name
2289 * @dentry: dentry to be updated
2292 * Update a case insensitive dentry with new case of name.
2294 * dentry must have been returned by d_lookup with name @name. Old and new
2295 * name lengths must match (ie. no d_compare which allows mismatched name
2298 * Parent inode i_mutex must be held over d_lookup and into this call (to
2299 * keep renames and concurrent inserts, and readdir(2) away).
2301 void dentry_update_name_case(struct dentry
*dentry
, struct qstr
*name
)
2303 BUG_ON(!mutex_is_locked(&dentry
->d_parent
->d_inode
->i_mutex
));
2304 BUG_ON(dentry
->d_name
.len
!= name
->len
); /* d_lookup gives this */
2306 spin_lock(&dentry
->d_lock
);
2307 write_seqcount_begin(&dentry
->d_seq
);
2308 memcpy((unsigned char *)dentry
->d_name
.name
, name
->name
, name
->len
);
2309 write_seqcount_end(&dentry
->d_seq
);
2310 spin_unlock(&dentry
->d_lock
);
2312 EXPORT_SYMBOL(dentry_update_name_case
);
2314 static void switch_names(struct dentry
*dentry
, struct dentry
*target
)
2316 if (dname_external(target
)) {
2317 if (dname_external(dentry
)) {
2319 * Both external: swap the pointers
2321 swap(target
->d_name
.name
, dentry
->d_name
.name
);
2324 * dentry:internal, target:external. Steal target's
2325 * storage and make target internal.
2327 memcpy(target
->d_iname
, dentry
->d_name
.name
,
2328 dentry
->d_name
.len
+ 1);
2329 dentry
->d_name
.name
= target
->d_name
.name
;
2330 target
->d_name
.name
= target
->d_iname
;
2333 if (dname_external(dentry
)) {
2335 * dentry:external, target:internal. Give dentry's
2336 * storage to target and make dentry internal
2338 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2339 target
->d_name
.len
+ 1);
2340 target
->d_name
.name
= dentry
->d_name
.name
;
2341 dentry
->d_name
.name
= dentry
->d_iname
;
2344 * Both are internal. Just copy target to dentry
2346 memcpy(dentry
->d_iname
, target
->d_name
.name
,
2347 target
->d_name
.len
+ 1);
2348 dentry
->d_name
.len
= target
->d_name
.len
;
2352 swap(dentry
->d_name
.len
, target
->d_name
.len
);
2355 static void dentry_lock_for_move(struct dentry
*dentry
, struct dentry
*target
)
2358 * XXXX: do we really need to take target->d_lock?
2360 if (IS_ROOT(dentry
) || dentry
->d_parent
== target
->d_parent
)
2361 spin_lock(&target
->d_parent
->d_lock
);
2363 if (d_ancestor(dentry
->d_parent
, target
->d_parent
)) {
2364 spin_lock(&dentry
->d_parent
->d_lock
);
2365 spin_lock_nested(&target
->d_parent
->d_lock
,
2366 DENTRY_D_LOCK_NESTED
);
2368 spin_lock(&target
->d_parent
->d_lock
);
2369 spin_lock_nested(&dentry
->d_parent
->d_lock
,
2370 DENTRY_D_LOCK_NESTED
);
2373 if (target
< dentry
) {
2374 spin_lock_nested(&target
->d_lock
, 2);
2375 spin_lock_nested(&dentry
->d_lock
, 3);
2377 spin_lock_nested(&dentry
->d_lock
, 2);
2378 spin_lock_nested(&target
->d_lock
, 3);
2382 static void dentry_unlock_parents_for_move(struct dentry
*dentry
,
2383 struct dentry
*target
)
2385 if (target
->d_parent
!= dentry
->d_parent
)
2386 spin_unlock(&dentry
->d_parent
->d_lock
);
2387 if (target
->d_parent
!= target
)
2388 spin_unlock(&target
->d_parent
->d_lock
);
2392 * When switching names, the actual string doesn't strictly have to
2393 * be preserved in the target - because we're dropping the target
2394 * anyway. As such, we can just do a simple memcpy() to copy over
2395 * the new name before we switch.
2397 * Note that we have to be a lot more careful about getting the hash
2398 * switched - we have to switch the hash value properly even if it
2399 * then no longer matches the actual (corrupted) string of the target.
2400 * The hash value has to match the hash queue that the dentry is on..
2403 * __d_move - move a dentry
2404 * @dentry: entry to move
2405 * @target: new dentry
2407 * Update the dcache to reflect the move of a file name. Negative
2408 * dcache entries should not be moved in this way. Caller must hold
2409 * rename_lock, the i_mutex of the source and target directories,
2410 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2412 static void __d_move(struct dentry
* dentry
, struct dentry
* target
)
2414 if (!dentry
->d_inode
)
2415 printk(KERN_WARNING
"VFS: moving negative dcache entry\n");
2417 BUG_ON(d_ancestor(dentry
, target
));
2418 BUG_ON(d_ancestor(target
, dentry
));
2420 dentry_lock_for_move(dentry
, target
);
2422 write_seqcount_begin(&dentry
->d_seq
);
2423 write_seqcount_begin(&target
->d_seq
);
2425 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
2428 * Move the dentry to the target hash queue. Don't bother checking
2429 * for the same hash queue because of how unlikely it is.
2432 __d_rehash(dentry
, d_hash(target
->d_parent
, target
->d_name
.hash
));
2434 /* Unhash the target: dput() will then get rid of it */
2437 list_del(&dentry
->d_u
.d_child
);
2438 list_del(&target
->d_u
.d_child
);
2440 /* Switch the names.. */
2441 switch_names(dentry
, target
);
2442 swap(dentry
->d_name
.hash
, target
->d_name
.hash
);
2444 /* ... and switch the parents */
2445 if (IS_ROOT(dentry
)) {
2446 dentry
->d_parent
= target
->d_parent
;
2447 target
->d_parent
= target
;
2448 INIT_LIST_HEAD(&target
->d_u
.d_child
);
2450 swap(dentry
->d_parent
, target
->d_parent
);
2452 /* And add them back to the (new) parent lists */
2453 list_add(&target
->d_u
.d_child
, &target
->d_parent
->d_subdirs
);
2456 list_add(&dentry
->d_u
.d_child
, &dentry
->d_parent
->d_subdirs
);
2458 write_seqcount_end(&target
->d_seq
);
2459 write_seqcount_end(&dentry
->d_seq
);
2461 dentry_unlock_parents_for_move(dentry
, target
);
2462 spin_unlock(&target
->d_lock
);
2463 fsnotify_d_move(dentry
);
2464 spin_unlock(&dentry
->d_lock
);
2468 * d_move - move a dentry
2469 * @dentry: entry to move
2470 * @target: new dentry
2472 * Update the dcache to reflect the move of a file name. Negative
2473 * dcache entries should not be moved in this way. See the locking
2474 * requirements for __d_move.
2476 void d_move(struct dentry
*dentry
, struct dentry
*target
)
2478 write_seqlock(&rename_lock
);
2479 __d_move(dentry
, target
);
2480 write_sequnlock(&rename_lock
);
2482 EXPORT_SYMBOL(d_move
);
2485 * d_ancestor - search for an ancestor
2486 * @p1: ancestor dentry
2489 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2490 * an ancestor of p2, else NULL.
2492 struct dentry
*d_ancestor(struct dentry
*p1
, struct dentry
*p2
)
2496 for (p
= p2
; !IS_ROOT(p
); p
= p
->d_parent
) {
2497 if (p
->d_parent
== p1
)
2504 * This helper attempts to cope with remotely renamed directories
2506 * It assumes that the caller is already holding
2507 * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
2509 * Note: If ever the locking in lock_rename() changes, then please
2510 * remember to update this too...
2512 static struct dentry
*__d_unalias(struct inode
*inode
,
2513 struct dentry
*dentry
, struct dentry
*alias
)
2515 struct mutex
*m1
= NULL
, *m2
= NULL
;
2516 struct dentry
*ret
= ERR_PTR(-EBUSY
);
2518 /* If alias and dentry share a parent, then no extra locks required */
2519 if (alias
->d_parent
== dentry
->d_parent
)
2522 /* See lock_rename() */
2523 if (!mutex_trylock(&dentry
->d_sb
->s_vfs_rename_mutex
))
2525 m1
= &dentry
->d_sb
->s_vfs_rename_mutex
;
2526 if (!mutex_trylock(&alias
->d_parent
->d_inode
->i_mutex
))
2528 m2
= &alias
->d_parent
->d_inode
->i_mutex
;
2530 if (likely(!d_mountpoint(alias
))) {
2531 __d_move(alias
, dentry
);
2535 spin_unlock(&inode
->i_lock
);
2544 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
2545 * named dentry in place of the dentry to be replaced.
2546 * returns with anon->d_lock held!
2548 static void __d_materialise_dentry(struct dentry
*dentry
, struct dentry
*anon
)
2550 struct dentry
*dparent
;
2552 dentry_lock_for_move(anon
, dentry
);
2554 write_seqcount_begin(&dentry
->d_seq
);
2555 write_seqcount_begin(&anon
->d_seq
);
2557 dparent
= dentry
->d_parent
;
2559 switch_names(dentry
, anon
);
2560 swap(dentry
->d_name
.hash
, anon
->d_name
.hash
);
2562 dentry
->d_parent
= dentry
;
2563 list_del_init(&dentry
->d_u
.d_child
);
2564 anon
->d_parent
= dparent
;
2565 list_move(&anon
->d_u
.d_child
, &dparent
->d_subdirs
);
2567 write_seqcount_end(&dentry
->d_seq
);
2568 write_seqcount_end(&anon
->d_seq
);
2570 dentry_unlock_parents_for_move(anon
, dentry
);
2571 spin_unlock(&dentry
->d_lock
);
2573 /* anon->d_lock still locked, returns locked */
2574 anon
->d_flags
&= ~DCACHE_DISCONNECTED
;
2578 * d_materialise_unique - introduce an inode into the tree
2579 * @dentry: candidate dentry
2580 * @inode: inode to bind to the dentry, to which aliases may be attached
2582 * Introduces an dentry into the tree, substituting an extant disconnected
2583 * root directory alias in its place if there is one. Caller must hold the
2584 * i_mutex of the parent directory.
2586 struct dentry
*d_materialise_unique(struct dentry
*dentry
, struct inode
*inode
)
2588 struct dentry
*actual
;
2590 BUG_ON(!d_unhashed(dentry
));
2594 __d_instantiate(dentry
, NULL
);
2599 spin_lock(&inode
->i_lock
);
2601 if (S_ISDIR(inode
->i_mode
)) {
2602 struct dentry
*alias
;
2604 /* Does an aliased dentry already exist? */
2605 alias
= __d_find_alias(inode
, 0);
2608 write_seqlock(&rename_lock
);
2610 if (d_ancestor(alias
, dentry
)) {
2611 /* Check for loops */
2612 actual
= ERR_PTR(-ELOOP
);
2613 spin_unlock(&inode
->i_lock
);
2614 } else if (IS_ROOT(alias
)) {
2615 /* Is this an anonymous mountpoint that we
2616 * could splice into our tree? */
2617 __d_materialise_dentry(dentry
, alias
);
2618 write_sequnlock(&rename_lock
);
2622 /* Nope, but we must(!) avoid directory
2623 * aliasing. This drops inode->i_lock */
2624 actual
= __d_unalias(inode
, dentry
, alias
);
2626 write_sequnlock(&rename_lock
);
2627 if (IS_ERR(actual
)) {
2628 if (PTR_ERR(actual
) == -ELOOP
)
2629 pr_warn_ratelimited(
2630 "VFS: Lookup of '%s' in %s %s"
2631 " would have caused loop\n",
2632 dentry
->d_name
.name
,
2633 inode
->i_sb
->s_type
->name
,
2641 /* Add a unique reference */
2642 actual
= __d_instantiate_unique(dentry
, inode
);
2646 BUG_ON(!d_unhashed(actual
));
2648 spin_lock(&actual
->d_lock
);
2651 spin_unlock(&actual
->d_lock
);
2652 spin_unlock(&inode
->i_lock
);
2654 if (actual
== dentry
) {
2655 security_d_instantiate(dentry
, inode
);
2662 EXPORT_SYMBOL_GPL(d_materialise_unique
);
2664 static int prepend(char **buffer
, int *buflen
, const char *str
, int namelen
)
2668 return -ENAMETOOLONG
;
2670 memcpy(*buffer
, str
, namelen
);
2675 * prepend_name - prepend a pathname in front of current buffer pointer
2676 * @buffer: buffer pointer
2677 * @buflen: allocated length of the buffer
2678 * @name: name string and length qstr structure
2680 * With RCU path tracing, it may race with d_move(). Use ACCESS_ONCE() to
2681 * make sure that either the old or the new name pointer and length are
2682 * fetched. However, there may be mismatch between length and pointer.
2683 * The length cannot be trusted, we need to copy it byte-by-byte until
2684 * the length is reached or a null byte is found. It also prepends "/" at
2685 * the beginning of the name. The sequence number check at the caller will
2686 * retry it again when a d_move() does happen. So any garbage in the buffer
2687 * due to mismatched pointer and length will be discarded.
2689 static int prepend_name(char **buffer
, int *buflen
, struct qstr
*name
)
2691 const char *dname
= ACCESS_ONCE(name
->name
);
2692 u32 dlen
= ACCESS_ONCE(name
->len
);
2695 if (*buflen
< dlen
+ 1)
2696 return -ENAMETOOLONG
;
2697 *buflen
-= dlen
+ 1;
2698 p
= *buffer
-= dlen
+ 1;
2710 * prepend_path - Prepend path string to a buffer
2711 * @path: the dentry/vfsmount to report
2712 * @root: root vfsmnt/dentry
2713 * @buffer: pointer to the end of the buffer
2714 * @buflen: pointer to buffer length
2716 * The function will first try to write out the pathname without taking any
2717 * lock other than the RCU read lock to make sure that dentries won't go away.
2718 * It only checks the sequence number of the global rename_lock as any change
2719 * in the dentry's d_seq will be preceded by changes in the rename_lock
2720 * sequence number. If the sequence number had been changed, it will restart
2721 * the whole pathname back-tracing sequence again by taking the rename_lock.
2722 * In this case, there is no need to take the RCU read lock as the recursive
2723 * parent pointer references will keep the dentry chain alive as long as no
2724 * rename operation is performed.
2726 static int prepend_path(const struct path
*path
,
2727 const struct path
*root
,
2728 char **buffer
, int *buflen
)
2730 struct dentry
*dentry
= path
->dentry
;
2731 struct vfsmount
*vfsmnt
= path
->mnt
;
2732 struct mount
*mnt
= real_mount(vfsmnt
);
2742 read_seqbegin_or_lock(&rename_lock
, &seq
);
2743 while (dentry
!= root
->dentry
|| vfsmnt
!= root
->mnt
) {
2744 struct dentry
* parent
;
2746 if (dentry
== vfsmnt
->mnt_root
|| IS_ROOT(dentry
)) {
2748 if (mnt_has_parent(mnt
)) {
2749 dentry
= mnt
->mnt_mountpoint
;
2750 mnt
= mnt
->mnt_parent
;
2755 * Filesystems needing to implement special "root names"
2756 * should do so with ->d_dname()
2758 if (IS_ROOT(dentry
) &&
2759 (dentry
->d_name
.len
!= 1 ||
2760 dentry
->d_name
.name
[0] != '/')) {
2761 WARN(1, "Root dentry has weird name <%.*s>\n",
2762 (int) dentry
->d_name
.len
,
2763 dentry
->d_name
.name
);
2766 error
= is_mounted(vfsmnt
) ? 1 : 2;
2769 parent
= dentry
->d_parent
;
2771 error
= prepend_name(&bptr
, &blen
, &dentry
->d_name
);
2779 if (need_seqretry(&rename_lock
, seq
)) {
2783 done_seqretry(&rename_lock
, seq
);
2785 if (error
>= 0 && bptr
== *buffer
) {
2787 error
= -ENAMETOOLONG
;
2797 * __d_path - return the path of a dentry
2798 * @path: the dentry/vfsmount to report
2799 * @root: root vfsmnt/dentry
2800 * @buf: buffer to return value in
2801 * @buflen: buffer length
2803 * Convert a dentry into an ASCII path name.
2805 * Returns a pointer into the buffer or an error code if the
2806 * path was too long.
2808 * "buflen" should be positive.
2810 * If the path is not reachable from the supplied root, return %NULL.
2812 char *__d_path(const struct path
*path
,
2813 const struct path
*root
,
2814 char *buf
, int buflen
)
2816 char *res
= buf
+ buflen
;
2819 prepend(&res
, &buflen
, "\0", 1);
2820 br_read_lock(&vfsmount_lock
);
2821 error
= prepend_path(path
, root
, &res
, &buflen
);
2822 br_read_unlock(&vfsmount_lock
);
2825 return ERR_PTR(error
);
2831 char *d_absolute_path(const struct path
*path
,
2832 char *buf
, int buflen
)
2834 struct path root
= {};
2835 char *res
= buf
+ buflen
;
2838 prepend(&res
, &buflen
, "\0", 1);
2839 br_read_lock(&vfsmount_lock
);
2840 error
= prepend_path(path
, &root
, &res
, &buflen
);
2841 br_read_unlock(&vfsmount_lock
);
2846 return ERR_PTR(error
);
2851 * same as __d_path but appends "(deleted)" for unlinked files.
2853 static int path_with_deleted(const struct path
*path
,
2854 const struct path
*root
,
2855 char **buf
, int *buflen
)
2857 prepend(buf
, buflen
, "\0", 1);
2858 if (d_unlinked(path
->dentry
)) {
2859 int error
= prepend(buf
, buflen
, " (deleted)", 10);
2864 return prepend_path(path
, root
, buf
, buflen
);
2867 static int prepend_unreachable(char **buffer
, int *buflen
)
2869 return prepend(buffer
, buflen
, "(unreachable)", 13);
2873 * d_path - return the path of a dentry
2874 * @path: path to report
2875 * @buf: buffer to return value in
2876 * @buflen: buffer length
2878 * Convert a dentry into an ASCII path name. If the entry has been deleted
2879 * the string " (deleted)" is appended. Note that this is ambiguous.
2881 * Returns a pointer into the buffer or an error code if the path was
2882 * too long. Note: Callers should use the returned pointer, not the passed
2883 * in buffer, to use the name! The implementation often starts at an offset
2884 * into the buffer, and may leave 0 bytes at the start.
2886 * "buflen" should be positive.
2888 char *d_path(const struct path
*path
, char *buf
, int buflen
)
2890 char *res
= buf
+ buflen
;
2895 * We have various synthetic filesystems that never get mounted. On
2896 * these filesystems dentries are never used for lookup purposes, and
2897 * thus don't need to be hashed. They also don't need a name until a
2898 * user wants to identify the object in /proc/pid/fd/. The little hack
2899 * below allows us to generate a name for these objects on demand:
2901 if (path
->dentry
->d_op
&& path
->dentry
->d_op
->d_dname
)
2902 return path
->dentry
->d_op
->d_dname(path
->dentry
, buf
, buflen
);
2904 get_fs_root(current
->fs
, &root
);
2905 br_read_lock(&vfsmount_lock
);
2906 error
= path_with_deleted(path
, &root
, &res
, &buflen
);
2907 br_read_unlock(&vfsmount_lock
);
2909 res
= ERR_PTR(error
);
2913 EXPORT_SYMBOL(d_path
);
2916 * Helper function for dentry_operations.d_dname() members
2918 char *dynamic_dname(struct dentry
*dentry
, char *buffer
, int buflen
,
2919 const char *fmt
, ...)
2925 va_start(args
, fmt
);
2926 sz
= vsnprintf(temp
, sizeof(temp
), fmt
, args
) + 1;
2929 if (sz
> sizeof(temp
) || sz
> buflen
)
2930 return ERR_PTR(-ENAMETOOLONG
);
2932 buffer
+= buflen
- sz
;
2933 return memcpy(buffer
, temp
, sz
);
2936 char *simple_dname(struct dentry
*dentry
, char *buffer
, int buflen
)
2938 char *end
= buffer
+ buflen
;
2939 /* these dentries are never renamed, so d_lock is not needed */
2940 if (prepend(&end
, &buflen
, " (deleted)", 11) ||
2941 prepend(&end
, &buflen
, dentry
->d_name
.name
, dentry
->d_name
.len
) ||
2942 prepend(&end
, &buflen
, "/", 1))
2943 end
= ERR_PTR(-ENAMETOOLONG
);
2948 * Write full pathname from the root of the filesystem into the buffer.
2950 static char *__dentry_path(struct dentry
*dentry
, char *buf
, int buflen
)
2960 prepend(&end
, &len
, "\0", 1);
2966 read_seqbegin_or_lock(&rename_lock
, &seq
);
2967 while (!IS_ROOT(dentry
)) {
2968 struct dentry
*parent
= dentry
->d_parent
;
2972 error
= prepend_name(&end
, &len
, &dentry
->d_name
);
2981 if (need_seqretry(&rename_lock
, seq
)) {
2985 done_seqretry(&rename_lock
, seq
);
2990 return ERR_PTR(-ENAMETOOLONG
);
2993 char *dentry_path_raw(struct dentry
*dentry
, char *buf
, int buflen
)
2995 return __dentry_path(dentry
, buf
, buflen
);
2997 EXPORT_SYMBOL(dentry_path_raw
);
2999 char *dentry_path(struct dentry
*dentry
, char *buf
, int buflen
)
3004 if (d_unlinked(dentry
)) {
3006 if (prepend(&p
, &buflen
, "//deleted", 10) != 0)
3010 retval
= __dentry_path(dentry
, buf
, buflen
);
3011 if (!IS_ERR(retval
) && p
)
3012 *p
= '/'; /* restore '/' overriden with '\0' */
3015 return ERR_PTR(-ENAMETOOLONG
);
3018 static void get_fs_root_and_pwd_rcu(struct fs_struct
*fs
, struct path
*root
,
3024 seq
= read_seqcount_begin(&fs
->seq
);
3027 } while (read_seqcount_retry(&fs
->seq
, seq
));
3031 * NOTE! The user-level library version returns a
3032 * character pointer. The kernel system call just
3033 * returns the length of the buffer filled (which
3034 * includes the ending '\0' character), or a negative
3035 * error value. So libc would do something like
3037 * char *getcwd(char * buf, size_t size)
3041 * retval = sys_getcwd(buf, size);
3048 SYSCALL_DEFINE2(getcwd
, char __user
*, buf
, unsigned long, size
)
3051 struct path pwd
, root
;
3052 char *page
= (char *) __get_free_page(GFP_USER
);
3058 get_fs_root_and_pwd_rcu(current
->fs
, &root
, &pwd
);
3061 br_read_lock(&vfsmount_lock
);
3062 if (!d_unlinked(pwd
.dentry
)) {
3064 char *cwd
= page
+ PAGE_SIZE
;
3065 int buflen
= PAGE_SIZE
;
3067 prepend(&cwd
, &buflen
, "\0", 1);
3068 error
= prepend_path(&pwd
, &root
, &cwd
, &buflen
);
3069 br_read_unlock(&vfsmount_lock
);
3074 /* Unreachable from current root */
3076 error
= prepend_unreachable(&cwd
, &buflen
);
3082 len
= PAGE_SIZE
+ page
- cwd
;
3085 if (copy_to_user(buf
, cwd
, len
))
3089 br_read_unlock(&vfsmount_lock
);
3094 free_page((unsigned long) page
);
3099 * Test whether new_dentry is a subdirectory of old_dentry.
3101 * Trivially implemented using the dcache structure
3105 * is_subdir - is new dentry a subdirectory of old_dentry
3106 * @new_dentry: new dentry
3107 * @old_dentry: old dentry
3109 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
3110 * Returns 0 otherwise.
3111 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3114 int is_subdir(struct dentry
*new_dentry
, struct dentry
*old_dentry
)
3119 if (new_dentry
== old_dentry
)
3123 /* for restarting inner loop in case of seq retry */
3124 seq
= read_seqbegin(&rename_lock
);
3126 * Need rcu_readlock to protect against the d_parent trashing
3130 if (d_ancestor(old_dentry
, new_dentry
))
3135 } while (read_seqretry(&rename_lock
, seq
));
3140 static enum d_walk_ret
d_genocide_kill(void *data
, struct dentry
*dentry
)
3142 struct dentry
*root
= data
;
3143 if (dentry
!= root
) {
3144 if (d_unhashed(dentry
) || !dentry
->d_inode
)
3147 if (!(dentry
->d_flags
& DCACHE_GENOCIDE
)) {
3148 dentry
->d_flags
|= DCACHE_GENOCIDE
;
3149 dentry
->d_lockref
.count
--;
3152 return D_WALK_CONTINUE
;
3155 void d_genocide(struct dentry
*parent
)
3157 d_walk(parent
, parent
, d_genocide_kill
, NULL
);
3160 void d_tmpfile(struct dentry
*dentry
, struct inode
*inode
)
3162 inode_dec_link_count(inode
);
3163 BUG_ON(dentry
->d_name
.name
!= dentry
->d_iname
||
3164 !hlist_unhashed(&dentry
->d_alias
) ||
3165 !d_unlinked(dentry
));
3166 spin_lock(&dentry
->d_parent
->d_lock
);
3167 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
3168 dentry
->d_name
.len
= sprintf(dentry
->d_iname
, "#%llu",
3169 (unsigned long long)inode
->i_ino
);
3170 spin_unlock(&dentry
->d_lock
);
3171 spin_unlock(&dentry
->d_parent
->d_lock
);
3172 d_instantiate(dentry
, inode
);
3174 EXPORT_SYMBOL(d_tmpfile
);
3176 static __initdata
unsigned long dhash_entries
;
3177 static int __init
set_dhash_entries(char *str
)
3181 dhash_entries
= simple_strtoul(str
, &str
, 0);
3184 __setup("dhash_entries=", set_dhash_entries
);
3186 static void __init
dcache_init_early(void)
3190 /* If hashes are distributed across NUMA nodes, defer
3191 * hash allocation until vmalloc space is available.
3197 alloc_large_system_hash("Dentry cache",
3198 sizeof(struct hlist_bl_head
),
3207 for (loop
= 0; loop
< (1U << d_hash_shift
); loop
++)
3208 INIT_HLIST_BL_HEAD(dentry_hashtable
+ loop
);
3211 static void __init
dcache_init(void)
3216 * A constructor could be added for stable state like the lists,
3217 * but it is probably not worth it because of the cache nature
3220 dentry_cache
= KMEM_CACHE(dentry
,
3221 SLAB_RECLAIM_ACCOUNT
|SLAB_PANIC
|SLAB_MEM_SPREAD
);
3223 /* Hash may have been set up in dcache_init_early */
3228 alloc_large_system_hash("Dentry cache",
3229 sizeof(struct hlist_bl_head
),
3238 for (loop
= 0; loop
< (1U << d_hash_shift
); loop
++)
3239 INIT_HLIST_BL_HEAD(dentry_hashtable
+ loop
);
3242 /* SLAB cache for __getname() consumers */
3243 struct kmem_cache
*names_cachep __read_mostly
;
3244 EXPORT_SYMBOL(names_cachep
);
3246 EXPORT_SYMBOL(d_genocide
);
3248 void __init
vfs_caches_init_early(void)
3250 dcache_init_early();
3254 void __init
vfs_caches_init(unsigned long mempages
)
3256 unsigned long reserve
;
3258 /* Base hash sizes on available memory, with a reserve equal to
3259 150% of current kernel size */
3261 reserve
= min((mempages
- nr_free_pages()) * 3/2, mempages
- 1);
3262 mempages
-= reserve
;
3264 names_cachep
= kmem_cache_create("names_cache", PATH_MAX
, 0,
3265 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
);
3269 files_init(mempages
);