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/ratelimit.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/security.h>
28 #include <linux/seqlock.h>
29 #include <linux/bootmem.h>
30 #include <linux/bit_spinlock.h>
31 #include <linux/rculist_bl.h>
32 #include <linux/list_lru.h>
38 * dcache->d_inode->i_lock protects:
39 * - i_dentry, d_u.d_alias, d_inode of aliases
40 * dcache_hash_bucket lock protects:
41 * - the dcache hash table
42 * s_roots bl list spinlock protects:
43 * - the s_roots list (see __d_drop)
44 * dentry->d_sb->s_dentry_lru_lock protects:
45 * - the dcache lru lists and counters
52 * - d_parent and d_subdirs
53 * - childrens' d_child and d_parent
54 * - d_u.d_alias, d_inode
57 * dentry->d_inode->i_lock
59 * dentry->d_sb->s_dentry_lru_lock
60 * dcache_hash_bucket lock
63 * If there is an ancestor relationship:
64 * dentry->d_parent->...->d_parent->d_lock
66 * dentry->d_parent->d_lock
69 * If no ancestor relationship:
70 * arbitrary, since it's serialized on rename_lock
72 int sysctl_vfs_cache_pressure __read_mostly = 100;
73 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
75 __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
77 EXPORT_SYMBOL(rename_lock);
79 static struct kmem_cache *dentry_cache __read_mostly;
81 const struct qstr empty_name = QSTR_INIT("", 0);
82 EXPORT_SYMBOL(empty_name);
83 const struct qstr slash_name = QSTR_INIT("/", 1);
84 EXPORT_SYMBOL(slash_name);
87 * This is the single most critical data structure when it comes
88 * to the dcache: the hashtable for lookups. Somebody should try
89 * to make this good - I've just made it work.
91 * This hash-function tries to avoid losing too many bits of hash
92 * information, yet avoid using a prime hash-size or similar.
95 static unsigned int d_hash_shift __read_mostly;
97 static struct hlist_bl_head *dentry_hashtable __read_mostly;
99 static inline struct hlist_bl_head *d_hash(unsigned int hash)
101 return dentry_hashtable + (hash >> d_hash_shift);
104 #define IN_LOOKUP_SHIFT 10
105 static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT];
107 static inline struct hlist_bl_head *in_lookup_hash(const struct dentry *parent,
110 hash += (unsigned long) parent / L1_CACHE_BYTES;
111 return in_lookup_hashtable + hash_32(hash, IN_LOOKUP_SHIFT);
115 /* Statistics gathering. */
116 struct dentry_stat_t dentry_stat = {
120 static DEFINE_PER_CPU(long, nr_dentry);
121 static DEFINE_PER_CPU(long, nr_dentry_unused);
123 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
126 * Here we resort to our own counters instead of using generic per-cpu counters
127 * for consistency with what the vfs inode code does. We are expected to harvest
128 * better code and performance by having our own specialized counters.
130 * Please note that the loop is done over all possible CPUs, not over all online
131 * CPUs. The reason for this is that we don't want to play games with CPUs going
132 * on and off. If one of them goes off, we will just keep their counters.
134 * glommer: See cffbc8a for details, and if you ever intend to change this,
135 * please update all vfs counters to match.
137 static long get_nr_dentry(void)
141 for_each_possible_cpu(i)
142 sum += per_cpu(nr_dentry, i);
143 return sum < 0 ? 0 : sum;
146 static long get_nr_dentry_unused(void)
150 for_each_possible_cpu(i)
151 sum += per_cpu(nr_dentry_unused, i);
152 return sum < 0 ? 0 : sum;
155 int proc_nr_dentry(struct ctl_table *table, int write, void __user *buffer,
156 size_t *lenp, loff_t *ppos)
158 dentry_stat.nr_dentry = get_nr_dentry();
159 dentry_stat.nr_unused = get_nr_dentry_unused();
160 return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
165 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
166 * The strings are both count bytes long, and count is non-zero.
168 #ifdef CONFIG_DCACHE_WORD_ACCESS
170 #include <asm/word-at-a-time.h>
172 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
173 * aligned allocation for this particular component. We don't
174 * strictly need the load_unaligned_zeropad() safety, but it
175 * doesn't hurt either.
177 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
178 * need the careful unaligned handling.
180 static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
182 unsigned long a,b,mask;
185 a = read_word_at_a_time(cs);
186 b = load_unaligned_zeropad(ct);
187 if (tcount < sizeof(unsigned long))
189 if (unlikely(a != b))
191 cs += sizeof(unsigned long);
192 ct += sizeof(unsigned long);
193 tcount -= sizeof(unsigned long);
197 mask = bytemask_from_count(tcount);
198 return unlikely(!!((a ^ b) & mask));
203 static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
217 static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
220 * Be careful about RCU walk racing with rename:
221 * use 'READ_ONCE' to fetch the name pointer.
223 * NOTE! Even if a rename will mean that the length
224 * was not loaded atomically, we don't care. The
225 * RCU walk will check the sequence count eventually,
226 * and catch it. And we won't overrun the buffer,
227 * because we're reading the name pointer atomically,
228 * and a dentry name is guaranteed to be properly
229 * terminated with a NUL byte.
231 * End result: even if 'len' is wrong, we'll exit
232 * early because the data cannot match (there can
233 * be no NUL in the ct/tcount data)
235 const unsigned char *cs = READ_ONCE(dentry->d_name.name);
237 return dentry_string_cmp(cs, ct, tcount);
240 struct external_name {
243 struct rcu_head head;
245 unsigned char name[];
248 static inline struct external_name *external_name(struct dentry *dentry)
250 return container_of(dentry->d_name.name, struct external_name, name[0]);
253 static void __d_free(struct rcu_head *head)
255 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
257 kmem_cache_free(dentry_cache, dentry);
260 static void __d_free_external(struct rcu_head *head)
262 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
263 kfree(external_name(dentry));
264 kmem_cache_free(dentry_cache, dentry);
267 static inline int dname_external(const struct dentry *dentry)
269 return dentry->d_name.name != dentry->d_iname;
272 void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry)
274 spin_lock(&dentry->d_lock);
275 if (unlikely(dname_external(dentry))) {
276 struct external_name *p = external_name(dentry);
277 atomic_inc(&p->u.count);
278 spin_unlock(&dentry->d_lock);
279 name->name = p->name;
281 memcpy(name->inline_name, dentry->d_iname, DNAME_INLINE_LEN);
282 spin_unlock(&dentry->d_lock);
283 name->name = name->inline_name;
286 EXPORT_SYMBOL(take_dentry_name_snapshot);
288 void release_dentry_name_snapshot(struct name_snapshot *name)
290 if (unlikely(name->name != name->inline_name)) {
291 struct external_name *p;
292 p = container_of(name->name, struct external_name, name[0]);
293 if (unlikely(atomic_dec_and_test(&p->u.count)))
294 kfree_rcu(p, u.head);
297 EXPORT_SYMBOL(release_dentry_name_snapshot);
299 static inline void __d_set_inode_and_type(struct dentry *dentry,
305 dentry->d_inode = inode;
306 flags = READ_ONCE(dentry->d_flags);
307 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
309 WRITE_ONCE(dentry->d_flags, flags);
312 static inline void __d_clear_type_and_inode(struct dentry *dentry)
314 unsigned flags = READ_ONCE(dentry->d_flags);
316 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
317 WRITE_ONCE(dentry->d_flags, flags);
318 dentry->d_inode = NULL;
321 static void dentry_free(struct dentry *dentry)
323 WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias));
324 if (unlikely(dname_external(dentry))) {
325 struct external_name *p = external_name(dentry);
326 if (likely(atomic_dec_and_test(&p->u.count))) {
327 call_rcu(&dentry->d_u.d_rcu, __d_free_external);
331 /* if dentry was never visible to RCU, immediate free is OK */
332 if (!(dentry->d_flags & DCACHE_RCUACCESS))
333 __d_free(&dentry->d_u.d_rcu);
335 call_rcu(&dentry->d_u.d_rcu, __d_free);
339 * Release the dentry's inode, using the filesystem
340 * d_iput() operation if defined.
342 static void dentry_unlink_inode(struct dentry * dentry)
343 __releases(dentry->d_lock)
344 __releases(dentry->d_inode->i_lock)
346 struct inode *inode = dentry->d_inode;
347 bool hashed = !d_unhashed(dentry);
350 raw_write_seqcount_begin(&dentry->d_seq);
351 __d_clear_type_and_inode(dentry);
352 hlist_del_init(&dentry->d_u.d_alias);
354 raw_write_seqcount_end(&dentry->d_seq);
355 spin_unlock(&dentry->d_lock);
356 spin_unlock(&inode->i_lock);
358 fsnotify_inoderemove(inode);
359 if (dentry->d_op && dentry->d_op->d_iput)
360 dentry->d_op->d_iput(dentry, inode);
366 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
367 * is in use - which includes both the "real" per-superblock
368 * LRU list _and_ the DCACHE_SHRINK_LIST use.
370 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
371 * on the shrink list (ie not on the superblock LRU list).
373 * The per-cpu "nr_dentry_unused" counters are updated with
374 * the DCACHE_LRU_LIST bit.
376 * These helper functions make sure we always follow the
377 * rules. d_lock must be held by the caller.
379 #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
380 static void d_lru_add(struct dentry *dentry)
382 D_FLAG_VERIFY(dentry, 0);
383 dentry->d_flags |= DCACHE_LRU_LIST;
384 this_cpu_inc(nr_dentry_unused);
385 WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
388 static void d_lru_del(struct dentry *dentry)
390 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
391 dentry->d_flags &= ~DCACHE_LRU_LIST;
392 this_cpu_dec(nr_dentry_unused);
393 WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
396 static void d_shrink_del(struct dentry *dentry)
398 D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
399 list_del_init(&dentry->d_lru);
400 dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
401 this_cpu_dec(nr_dentry_unused);
404 static void d_shrink_add(struct dentry *dentry, struct list_head *list)
406 D_FLAG_VERIFY(dentry, 0);
407 list_add(&dentry->d_lru, list);
408 dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST;
409 this_cpu_inc(nr_dentry_unused);
413 * These can only be called under the global LRU lock, ie during the
414 * callback for freeing the LRU list. "isolate" removes it from the
415 * LRU lists entirely, while shrink_move moves it to the indicated
418 static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry)
420 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
421 dentry->d_flags &= ~DCACHE_LRU_LIST;
422 this_cpu_dec(nr_dentry_unused);
423 list_lru_isolate(lru, &dentry->d_lru);
426 static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
427 struct list_head *list)
429 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
430 dentry->d_flags |= DCACHE_SHRINK_LIST;
431 list_lru_isolate_move(lru, &dentry->d_lru, list);
435 * d_drop - drop a dentry
436 * @dentry: dentry to drop
438 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
439 * be found through a VFS lookup any more. Note that this is different from
440 * deleting the dentry - d_delete will try to mark the dentry negative if
441 * possible, giving a successful _negative_ lookup, while d_drop will
442 * just make the cache lookup fail.
444 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
445 * reason (NFS timeouts or autofs deletes).
447 * __d_drop requires dentry->d_lock
448 * ___d_drop doesn't mark dentry as "unhashed"
449 * (dentry->d_hash.pprev will be LIST_POISON2, not NULL).
451 static void ___d_drop(struct dentry *dentry)
453 struct hlist_bl_head *b;
455 * Hashed dentries are normally on the dentry hashtable,
456 * with the exception of those newly allocated by
457 * d_obtain_root, which are always IS_ROOT:
459 if (unlikely(IS_ROOT(dentry)))
460 b = &dentry->d_sb->s_roots;
462 b = d_hash(dentry->d_name.hash);
465 __hlist_bl_del(&dentry->d_hash);
469 void __d_drop(struct dentry *dentry)
471 if (!d_unhashed(dentry)) {
473 dentry->d_hash.pprev = NULL;
474 write_seqcount_invalidate(&dentry->d_seq);
477 EXPORT_SYMBOL(__d_drop);
479 void d_drop(struct dentry *dentry)
481 spin_lock(&dentry->d_lock);
483 spin_unlock(&dentry->d_lock);
485 EXPORT_SYMBOL(d_drop);
487 static inline void dentry_unlist(struct dentry *dentry, struct dentry *parent)
491 * Inform d_walk() and shrink_dentry_list() that we are no longer
492 * attached to the dentry tree
494 dentry->d_flags |= DCACHE_DENTRY_KILLED;
495 if (unlikely(list_empty(&dentry->d_child)))
497 __list_del_entry(&dentry->d_child);
499 * Cursors can move around the list of children. While we'd been
500 * a normal list member, it didn't matter - ->d_child.next would've
501 * been updated. However, from now on it won't be and for the
502 * things like d_walk() it might end up with a nasty surprise.
503 * Normally d_walk() doesn't care about cursors moving around -
504 * ->d_lock on parent prevents that and since a cursor has no children
505 * of its own, we get through it without ever unlocking the parent.
506 * There is one exception, though - if we ascend from a child that
507 * gets killed as soon as we unlock it, the next sibling is found
508 * using the value left in its ->d_child.next. And if _that_
509 * pointed to a cursor, and cursor got moved (e.g. by lseek())
510 * before d_walk() regains parent->d_lock, we'll end up skipping
511 * everything the cursor had been moved past.
513 * Solution: make sure that the pointer left behind in ->d_child.next
514 * points to something that won't be moving around. I.e. skip the
517 while (dentry->d_child.next != &parent->d_subdirs) {
518 next = list_entry(dentry->d_child.next, struct dentry, d_child);
519 if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR)))
521 dentry->d_child.next = next->d_child.next;
525 static void __dentry_kill(struct dentry *dentry)
527 struct dentry *parent = NULL;
528 bool can_free = true;
529 if (!IS_ROOT(dentry))
530 parent = dentry->d_parent;
533 * The dentry is now unrecoverably dead to the world.
535 lockref_mark_dead(&dentry->d_lockref);
538 * inform the fs via d_prune that this dentry is about to be
539 * unhashed and destroyed.
541 if (dentry->d_flags & DCACHE_OP_PRUNE)
542 dentry->d_op->d_prune(dentry);
544 if (dentry->d_flags & DCACHE_LRU_LIST) {
545 if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
548 /* if it was on the hash then remove it */
550 dentry_unlist(dentry, parent);
552 spin_unlock(&parent->d_lock);
554 dentry_unlink_inode(dentry);
556 spin_unlock(&dentry->d_lock);
557 this_cpu_dec(nr_dentry);
558 if (dentry->d_op && dentry->d_op->d_release)
559 dentry->d_op->d_release(dentry);
561 spin_lock(&dentry->d_lock);
562 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
563 dentry->d_flags |= DCACHE_MAY_FREE;
566 spin_unlock(&dentry->d_lock);
567 if (likely(can_free))
571 static struct dentry *__lock_parent(struct dentry *dentry)
573 struct dentry *parent;
575 spin_unlock(&dentry->d_lock);
577 parent = READ_ONCE(dentry->d_parent);
578 spin_lock(&parent->d_lock);
580 * We can't blindly lock dentry until we are sure
581 * that we won't violate the locking order.
582 * Any changes of dentry->d_parent must have
583 * been done with parent->d_lock held, so
584 * spin_lock() above is enough of a barrier
585 * for checking if it's still our child.
587 if (unlikely(parent != dentry->d_parent)) {
588 spin_unlock(&parent->d_lock);
592 if (parent != dentry)
593 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
599 static inline struct dentry *lock_parent(struct dentry *dentry)
601 struct dentry *parent = dentry->d_parent;
604 if (likely(spin_trylock(&parent->d_lock)))
606 return __lock_parent(dentry);
609 static inline bool retain_dentry(struct dentry *dentry)
611 WARN_ON(d_in_lookup(dentry));
613 /* Unreachable? Get rid of it */
614 if (unlikely(d_unhashed(dentry)))
617 if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
620 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) {
621 if (dentry->d_op->d_delete(dentry))
624 /* retain; LRU fodder */
625 dentry->d_lockref.count--;
626 if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
628 else if (unlikely(!(dentry->d_flags & DCACHE_REFERENCED)))
629 dentry->d_flags |= DCACHE_REFERENCED;
634 * Finish off a dentry we've decided to kill.
635 * dentry->d_lock must be held, returns with it unlocked.
636 * Returns dentry requiring refcount drop, or NULL if we're done.
638 static struct dentry *dentry_kill(struct dentry *dentry)
639 __releases(dentry->d_lock)
641 struct inode *inode = dentry->d_inode;
642 struct dentry *parent = NULL;
644 if (inode && unlikely(!spin_trylock(&inode->i_lock)))
647 if (!IS_ROOT(dentry)) {
648 parent = dentry->d_parent;
649 if (unlikely(!spin_trylock(&parent->d_lock))) {
650 parent = __lock_parent(dentry);
651 if (likely(inode || !dentry->d_inode))
653 /* negative that became positive */
655 spin_unlock(&parent->d_lock);
656 inode = dentry->d_inode;
660 __dentry_kill(dentry);
664 spin_unlock(&dentry->d_lock);
665 spin_lock(&inode->i_lock);
666 spin_lock(&dentry->d_lock);
667 parent = lock_parent(dentry);
669 if (unlikely(dentry->d_lockref.count != 1)) {
670 dentry->d_lockref.count--;
671 } else if (likely(!retain_dentry(dentry))) {
672 __dentry_kill(dentry);
675 /* we are keeping it, after all */
677 spin_unlock(&inode->i_lock);
679 spin_unlock(&parent->d_lock);
680 spin_unlock(&dentry->d_lock);
685 * Try to do a lockless dput(), and return whether that was successful.
687 * If unsuccessful, we return false, having already taken the dentry lock.
689 * The caller needs to hold the RCU read lock, so that the dentry is
690 * guaranteed to stay around even if the refcount goes down to zero!
692 static inline bool fast_dput(struct dentry *dentry)
695 unsigned int d_flags;
698 * If we have a d_op->d_delete() operation, we sould not
699 * let the dentry count go to zero, so use "put_or_lock".
701 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE))
702 return lockref_put_or_lock(&dentry->d_lockref);
705 * .. otherwise, we can try to just decrement the
706 * lockref optimistically.
708 ret = lockref_put_return(&dentry->d_lockref);
711 * If the lockref_put_return() failed due to the lock being held
712 * by somebody else, the fast path has failed. We will need to
713 * get the lock, and then check the count again.
715 if (unlikely(ret < 0)) {
716 spin_lock(&dentry->d_lock);
717 if (dentry->d_lockref.count > 1) {
718 dentry->d_lockref.count--;
719 spin_unlock(&dentry->d_lock);
726 * If we weren't the last ref, we're done.
732 * Careful, careful. The reference count went down
733 * to zero, but we don't hold the dentry lock, so
734 * somebody else could get it again, and do another
735 * dput(), and we need to not race with that.
737 * However, there is a very special and common case
738 * where we don't care, because there is nothing to
739 * do: the dentry is still hashed, it does not have
740 * a 'delete' op, and it's referenced and already on
743 * NOTE! Since we aren't locked, these values are
744 * not "stable". However, it is sufficient that at
745 * some point after we dropped the reference the
746 * dentry was hashed and the flags had the proper
747 * value. Other dentry users may have re-gotten
748 * a reference to the dentry and change that, but
749 * our work is done - we can leave the dentry
750 * around with a zero refcount.
753 d_flags = READ_ONCE(dentry->d_flags);
754 d_flags &= DCACHE_REFERENCED | DCACHE_LRU_LIST | DCACHE_DISCONNECTED;
756 /* Nothing to do? Dropping the reference was all we needed? */
757 if (d_flags == (DCACHE_REFERENCED | DCACHE_LRU_LIST) && !d_unhashed(dentry))
761 * Not the fast normal case? Get the lock. We've already decremented
762 * the refcount, but we'll need to re-check the situation after
765 spin_lock(&dentry->d_lock);
768 * Did somebody else grab a reference to it in the meantime, and
769 * we're no longer the last user after all? Alternatively, somebody
770 * else could have killed it and marked it dead. Either way, we
771 * don't need to do anything else.
773 if (dentry->d_lockref.count) {
774 spin_unlock(&dentry->d_lock);
779 * Re-get the reference we optimistically dropped. We hold the
780 * lock, and we just tested that it was zero, so we can just
783 dentry->d_lockref.count = 1;
791 * This is complicated by the fact that we do not want to put
792 * dentries that are no longer on any hash chain on the unused
793 * list: we'd much rather just get rid of them immediately.
795 * However, that implies that we have to traverse the dentry
796 * tree upwards to the parents which might _also_ now be
797 * scheduled for deletion (it may have been only waiting for
798 * its last child to go away).
800 * This tail recursion is done by hand as we don't want to depend
801 * on the compiler to always get this right (gcc generally doesn't).
802 * Real recursion would eat up our stack space.
806 * dput - release a dentry
807 * @dentry: dentry to release
809 * Release a dentry. This will drop the usage count and if appropriate
810 * call the dentry unlink method as well as removing it from the queues and
811 * releasing its resources. If the parent dentries were scheduled for release
812 * they too may now get deleted.
814 void dput(struct dentry *dentry)
816 if (unlikely(!dentry))
823 if (likely(fast_dput(dentry))) {
828 /* Slow case: now with the dentry lock held */
831 if (likely(retain_dentry(dentry))) {
832 spin_unlock(&dentry->d_lock);
836 dentry = dentry_kill(dentry);
845 /* This must be called with d_lock held */
846 static inline void __dget_dlock(struct dentry *dentry)
848 dentry->d_lockref.count++;
851 static inline void __dget(struct dentry *dentry)
853 lockref_get(&dentry->d_lockref);
856 struct dentry *dget_parent(struct dentry *dentry)
862 * Do optimistic parent lookup without any
866 ret = READ_ONCE(dentry->d_parent);
867 gotref = lockref_get_not_zero(&ret->d_lockref);
869 if (likely(gotref)) {
870 if (likely(ret == READ_ONCE(dentry->d_parent)))
877 * Don't need rcu_dereference because we re-check it was correct under
881 ret = dentry->d_parent;
882 spin_lock(&ret->d_lock);
883 if (unlikely(ret != dentry->d_parent)) {
884 spin_unlock(&ret->d_lock);
889 BUG_ON(!ret->d_lockref.count);
890 ret->d_lockref.count++;
891 spin_unlock(&ret->d_lock);
894 EXPORT_SYMBOL(dget_parent);
897 * d_find_alias - grab a hashed alias of inode
898 * @inode: inode in question
900 * If inode has a hashed alias, or is a directory and has any alias,
901 * acquire the reference to alias and return it. Otherwise return NULL.
902 * Notice that if inode is a directory there can be only one alias and
903 * it can be unhashed only if it has no children, or if it is the root
904 * of a filesystem, or if the directory was renamed and d_revalidate
905 * was the first vfs operation to notice.
907 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
908 * any other hashed alias over that one.
910 static struct dentry *__d_find_alias(struct inode *inode)
912 struct dentry *alias, *discon_alias;
916 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
917 spin_lock(&alias->d_lock);
918 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
919 if (IS_ROOT(alias) &&
920 (alias->d_flags & DCACHE_DISCONNECTED)) {
921 discon_alias = alias;
924 spin_unlock(&alias->d_lock);
928 spin_unlock(&alias->d_lock);
931 alias = discon_alias;
932 spin_lock(&alias->d_lock);
933 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
935 spin_unlock(&alias->d_lock);
938 spin_unlock(&alias->d_lock);
944 struct dentry *d_find_alias(struct inode *inode)
946 struct dentry *de = NULL;
948 if (!hlist_empty(&inode->i_dentry)) {
949 spin_lock(&inode->i_lock);
950 de = __d_find_alias(inode);
951 spin_unlock(&inode->i_lock);
955 EXPORT_SYMBOL(d_find_alias);
958 * Try to kill dentries associated with this inode.
959 * WARNING: you must own a reference to inode.
961 void d_prune_aliases(struct inode *inode)
963 struct dentry *dentry;
965 spin_lock(&inode->i_lock);
966 hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
967 spin_lock(&dentry->d_lock);
968 if (!dentry->d_lockref.count) {
969 struct dentry *parent = lock_parent(dentry);
970 if (likely(!dentry->d_lockref.count)) {
971 __dentry_kill(dentry);
976 spin_unlock(&parent->d_lock);
978 spin_unlock(&dentry->d_lock);
980 spin_unlock(&inode->i_lock);
982 EXPORT_SYMBOL(d_prune_aliases);
985 * Lock a dentry from shrink list.
986 * Called under rcu_read_lock() and dentry->d_lock; the former
987 * guarantees that nothing we access will be freed under us.
988 * Note that dentry is *not* protected from concurrent dentry_kill(),
991 * Return false if dentry has been disrupted or grabbed, leaving
992 * the caller to kick it off-list. Otherwise, return true and have
993 * that dentry's inode and parent both locked.
995 static bool shrink_lock_dentry(struct dentry *dentry)
998 struct dentry *parent;
1000 if (dentry->d_lockref.count)
1003 inode = dentry->d_inode;
1004 if (inode && unlikely(!spin_trylock(&inode->i_lock))) {
1005 spin_unlock(&dentry->d_lock);
1006 spin_lock(&inode->i_lock);
1007 spin_lock(&dentry->d_lock);
1008 if (unlikely(dentry->d_lockref.count))
1010 /* changed inode means that somebody had grabbed it */
1011 if (unlikely(inode != dentry->d_inode))
1015 parent = dentry->d_parent;
1016 if (IS_ROOT(dentry) || likely(spin_trylock(&parent->d_lock)))
1019 spin_unlock(&dentry->d_lock);
1020 spin_lock(&parent->d_lock);
1021 if (unlikely(parent != dentry->d_parent)) {
1022 spin_unlock(&parent->d_lock);
1023 spin_lock(&dentry->d_lock);
1026 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1027 if (likely(!dentry->d_lockref.count))
1029 spin_unlock(&parent->d_lock);
1032 spin_unlock(&inode->i_lock);
1036 static void shrink_dentry_list(struct list_head *list)
1038 while (!list_empty(list)) {
1039 struct dentry *dentry, *parent;
1041 dentry = list_entry(list->prev, struct dentry, d_lru);
1042 spin_lock(&dentry->d_lock);
1044 if (!shrink_lock_dentry(dentry)) {
1045 bool can_free = false;
1047 d_shrink_del(dentry);
1048 if (dentry->d_lockref.count < 0)
1049 can_free = dentry->d_flags & DCACHE_MAY_FREE;
1050 spin_unlock(&dentry->d_lock);
1052 dentry_free(dentry);
1056 d_shrink_del(dentry);
1057 parent = dentry->d_parent;
1058 __dentry_kill(dentry);
1059 if (parent == dentry)
1062 * We need to prune ancestors too. This is necessary to prevent
1063 * quadratic behavior of shrink_dcache_parent(), but is also
1064 * expected to be beneficial in reducing dentry cache
1068 while (dentry && !lockref_put_or_lock(&dentry->d_lockref))
1069 dentry = dentry_kill(dentry);
1073 static enum lru_status dentry_lru_isolate(struct list_head *item,
1074 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1076 struct list_head *freeable = arg;
1077 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1081 * we are inverting the lru lock/dentry->d_lock here,
1082 * so use a trylock. If we fail to get the lock, just skip
1085 if (!spin_trylock(&dentry->d_lock))
1089 * Referenced dentries are still in use. If they have active
1090 * counts, just remove them from the LRU. Otherwise give them
1091 * another pass through the LRU.
1093 if (dentry->d_lockref.count) {
1094 d_lru_isolate(lru, dentry);
1095 spin_unlock(&dentry->d_lock);
1099 if (dentry->d_flags & DCACHE_REFERENCED) {
1100 dentry->d_flags &= ~DCACHE_REFERENCED;
1101 spin_unlock(&dentry->d_lock);
1104 * The list move itself will be made by the common LRU code. At
1105 * this point, we've dropped the dentry->d_lock but keep the
1106 * lru lock. This is safe to do, since every list movement is
1107 * protected by the lru lock even if both locks are held.
1109 * This is guaranteed by the fact that all LRU management
1110 * functions are intermediated by the LRU API calls like
1111 * list_lru_add and list_lru_del. List movement in this file
1112 * only ever occur through this functions or through callbacks
1113 * like this one, that are called from the LRU API.
1115 * The only exceptions to this are functions like
1116 * shrink_dentry_list, and code that first checks for the
1117 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1118 * operating only with stack provided lists after they are
1119 * properly isolated from the main list. It is thus, always a
1125 d_lru_shrink_move(lru, dentry, freeable);
1126 spin_unlock(&dentry->d_lock);
1132 * prune_dcache_sb - shrink the dcache
1134 * @sc: shrink control, passed to list_lru_shrink_walk()
1136 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1137 * is done when we need more memory and called from the superblock shrinker
1140 * This function may fail to free any resources if all the dentries are in
1143 long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc)
1148 freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc,
1149 dentry_lru_isolate, &dispose);
1150 shrink_dentry_list(&dispose);
1154 static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
1155 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1157 struct list_head *freeable = arg;
1158 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1161 * we are inverting the lru lock/dentry->d_lock here,
1162 * so use a trylock. If we fail to get the lock, just skip
1165 if (!spin_trylock(&dentry->d_lock))
1168 d_lru_shrink_move(lru, dentry, freeable);
1169 spin_unlock(&dentry->d_lock);
1176 * shrink_dcache_sb - shrink dcache for a superblock
1179 * Shrink the dcache for the specified super block. This is used to free
1180 * the dcache before unmounting a file system.
1182 void shrink_dcache_sb(struct super_block *sb)
1189 freed = list_lru_walk(&sb->s_dentry_lru,
1190 dentry_lru_isolate_shrink, &dispose, 1024);
1192 this_cpu_sub(nr_dentry_unused, freed);
1193 shrink_dentry_list(&dispose);
1195 } while (list_lru_count(&sb->s_dentry_lru) > 0);
1197 EXPORT_SYMBOL(shrink_dcache_sb);
1200 * enum d_walk_ret - action to talke during tree walk
1201 * @D_WALK_CONTINUE: contrinue walk
1202 * @D_WALK_QUIT: quit walk
1203 * @D_WALK_NORETRY: quit when retry is needed
1204 * @D_WALK_SKIP: skip this dentry and its children
1214 * d_walk - walk the dentry tree
1215 * @parent: start of walk
1216 * @data: data passed to @enter() and @finish()
1217 * @enter: callback when first entering the dentry
1218 * @finish: callback when successfully finished the walk
1220 * The @enter() and @finish() callbacks are called with d_lock held.
1222 static void d_walk(struct dentry *parent, void *data,
1223 enum d_walk_ret (*enter)(void *, struct dentry *),
1224 void (*finish)(void *))
1226 struct dentry *this_parent;
1227 struct list_head *next;
1229 enum d_walk_ret ret;
1233 read_seqbegin_or_lock(&rename_lock, &seq);
1234 this_parent = parent;
1235 spin_lock(&this_parent->d_lock);
1237 ret = enter(data, this_parent);
1239 case D_WALK_CONTINUE:
1244 case D_WALK_NORETRY:
1249 next = this_parent->d_subdirs.next;
1251 while (next != &this_parent->d_subdirs) {
1252 struct list_head *tmp = next;
1253 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
1256 if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR))
1259 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1261 ret = enter(data, dentry);
1263 case D_WALK_CONTINUE:
1266 spin_unlock(&dentry->d_lock);
1268 case D_WALK_NORETRY:
1272 spin_unlock(&dentry->d_lock);
1276 if (!list_empty(&dentry->d_subdirs)) {
1277 spin_unlock(&this_parent->d_lock);
1278 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
1279 this_parent = dentry;
1280 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1283 spin_unlock(&dentry->d_lock);
1286 * All done at this level ... ascend and resume the search.
1290 if (this_parent != parent) {
1291 struct dentry *child = this_parent;
1292 this_parent = child->d_parent;
1294 spin_unlock(&child->d_lock);
1295 spin_lock(&this_parent->d_lock);
1297 /* might go back up the wrong parent if we have had a rename. */
1298 if (need_seqretry(&rename_lock, seq))
1300 /* go into the first sibling still alive */
1302 next = child->d_child.next;
1303 if (next == &this_parent->d_subdirs)
1305 child = list_entry(next, struct dentry, d_child);
1306 } while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
1310 if (need_seqretry(&rename_lock, seq))
1317 spin_unlock(&this_parent->d_lock);
1318 done_seqretry(&rename_lock, seq);
1322 spin_unlock(&this_parent->d_lock);
1331 struct check_mount {
1332 struct vfsmount *mnt;
1333 unsigned int mounted;
1336 static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry)
1338 struct check_mount *info = data;
1339 struct path path = { .mnt = info->mnt, .dentry = dentry };
1341 if (likely(!d_mountpoint(dentry)))
1342 return D_WALK_CONTINUE;
1343 if (__path_is_mountpoint(&path)) {
1347 return D_WALK_CONTINUE;
1351 * path_has_submounts - check for mounts over a dentry in the
1352 * current namespace.
1353 * @parent: path to check.
1355 * Return true if the parent or its subdirectories contain
1356 * a mount point in the current namespace.
1358 int path_has_submounts(const struct path *parent)
1360 struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
1362 read_seqlock_excl(&mount_lock);
1363 d_walk(parent->dentry, &data, path_check_mount, NULL);
1364 read_sequnlock_excl(&mount_lock);
1366 return data.mounted;
1368 EXPORT_SYMBOL(path_has_submounts);
1371 * Called by mount code to set a mountpoint and check if the mountpoint is
1372 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1373 * subtree can become unreachable).
1375 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1376 * this reason take rename_lock and d_lock on dentry and ancestors.
1378 int d_set_mounted(struct dentry *dentry)
1382 write_seqlock(&rename_lock);
1383 for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
1384 /* Need exclusion wrt. d_invalidate() */
1385 spin_lock(&p->d_lock);
1386 if (unlikely(d_unhashed(p))) {
1387 spin_unlock(&p->d_lock);
1390 spin_unlock(&p->d_lock);
1392 spin_lock(&dentry->d_lock);
1393 if (!d_unlinked(dentry)) {
1395 if (!d_mountpoint(dentry)) {
1396 dentry->d_flags |= DCACHE_MOUNTED;
1400 spin_unlock(&dentry->d_lock);
1402 write_sequnlock(&rename_lock);
1407 * Search the dentry child list of the specified parent,
1408 * and move any unused dentries to the end of the unused
1409 * list for prune_dcache(). We descend to the next level
1410 * whenever the d_subdirs list is non-empty and continue
1413 * It returns zero iff there are no unused children,
1414 * otherwise it returns the number of children moved to
1415 * the end of the unused list. This may not be the total
1416 * number of unused children, because select_parent can
1417 * drop the lock and return early due to latency
1421 struct select_data {
1422 struct dentry *start;
1423 struct list_head dispose;
1427 static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
1429 struct select_data *data = _data;
1430 enum d_walk_ret ret = D_WALK_CONTINUE;
1432 if (data->start == dentry)
1435 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1438 if (dentry->d_flags & DCACHE_LRU_LIST)
1440 if (!dentry->d_lockref.count) {
1441 d_shrink_add(dentry, &data->dispose);
1446 * We can return to the caller if we have found some (this
1447 * ensures forward progress). We'll be coming back to find
1450 if (!list_empty(&data->dispose))
1451 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1457 * shrink_dcache_parent - prune dcache
1458 * @parent: parent of entries to prune
1460 * Prune the dcache to remove unused children of the parent dentry.
1462 void shrink_dcache_parent(struct dentry *parent)
1465 struct select_data data;
1467 INIT_LIST_HEAD(&data.dispose);
1468 data.start = parent;
1471 d_walk(parent, &data, select_collect, NULL);
1475 shrink_dentry_list(&data.dispose);
1479 EXPORT_SYMBOL(shrink_dcache_parent);
1481 static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
1483 /* it has busy descendents; complain about those instead */
1484 if (!list_empty(&dentry->d_subdirs))
1485 return D_WALK_CONTINUE;
1487 /* root with refcount 1 is fine */
1488 if (dentry == _data && dentry->d_lockref.count == 1)
1489 return D_WALK_CONTINUE;
1491 printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%pd} "
1492 " still in use (%d) [unmount of %s %s]\n",
1495 dentry->d_inode->i_ino : 0UL,
1497 dentry->d_lockref.count,
1498 dentry->d_sb->s_type->name,
1499 dentry->d_sb->s_id);
1501 return D_WALK_CONTINUE;
1504 static void do_one_tree(struct dentry *dentry)
1506 shrink_dcache_parent(dentry);
1507 d_walk(dentry, dentry, umount_check, NULL);
1513 * destroy the dentries attached to a superblock on unmounting
1515 void shrink_dcache_for_umount(struct super_block *sb)
1517 struct dentry *dentry;
1519 WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked");
1521 dentry = sb->s_root;
1523 do_one_tree(dentry);
1525 while (!hlist_bl_empty(&sb->s_roots)) {
1526 dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_roots), struct dentry, d_hash));
1527 do_one_tree(dentry);
1531 struct detach_data {
1532 struct select_data select;
1533 struct dentry *mountpoint;
1535 static enum d_walk_ret detach_and_collect(void *_data, struct dentry *dentry)
1537 struct detach_data *data = _data;
1539 if (d_mountpoint(dentry)) {
1540 __dget_dlock(dentry);
1541 data->mountpoint = dentry;
1545 return select_collect(&data->select, dentry);
1548 static void check_and_drop(void *_data)
1550 struct detach_data *data = _data;
1552 if (!data->mountpoint && list_empty(&data->select.dispose))
1553 __d_drop(data->select.start);
1557 * d_invalidate - detach submounts, prune dcache, and drop
1558 * @dentry: dentry to invalidate (aka detach, prune and drop)
1562 * The final d_drop is done as an atomic operation relative to
1563 * rename_lock ensuring there are no races with d_set_mounted. This
1564 * ensures there are no unhashed dentries on the path to a mountpoint.
1566 void d_invalidate(struct dentry *dentry)
1569 * If it's already been dropped, return OK.
1571 spin_lock(&dentry->d_lock);
1572 if (d_unhashed(dentry)) {
1573 spin_unlock(&dentry->d_lock);
1576 spin_unlock(&dentry->d_lock);
1578 /* Negative dentries can be dropped without further checks */
1579 if (!dentry->d_inode) {
1585 struct detach_data data;
1587 data.mountpoint = NULL;
1588 INIT_LIST_HEAD(&data.select.dispose);
1589 data.select.start = dentry;
1590 data.select.found = 0;
1592 d_walk(dentry, &data, detach_and_collect, check_and_drop);
1594 if (!list_empty(&data.select.dispose))
1595 shrink_dentry_list(&data.select.dispose);
1596 else if (!data.mountpoint)
1599 if (data.mountpoint) {
1600 detach_mounts(data.mountpoint);
1601 dput(data.mountpoint);
1606 EXPORT_SYMBOL(d_invalidate);
1609 * __d_alloc - allocate a dcache entry
1610 * @sb: filesystem it will belong to
1611 * @name: qstr of the name
1613 * Allocates a dentry. It returns %NULL if there is insufficient memory
1614 * available. On a success the dentry is returned. The name passed in is
1615 * copied and the copy passed in may be reused after this call.
1618 struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1620 struct dentry *dentry;
1624 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
1629 * We guarantee that the inline name is always NUL-terminated.
1630 * This way the memcpy() done by the name switching in rename
1631 * will still always have a NUL at the end, even if we might
1632 * be overwriting an internal NUL character
1634 dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
1635 if (unlikely(!name)) {
1637 dname = dentry->d_iname;
1638 } else if (name->len > DNAME_INLINE_LEN-1) {
1639 size_t size = offsetof(struct external_name, name[1]);
1640 struct external_name *p = kmalloc(size + name->len,
1641 GFP_KERNEL_ACCOUNT);
1643 kmem_cache_free(dentry_cache, dentry);
1646 atomic_set(&p->u.count, 1);
1649 dname = dentry->d_iname;
1652 dentry->d_name.len = name->len;
1653 dentry->d_name.hash = name->hash;
1654 memcpy(dname, name->name, name->len);
1655 dname[name->len] = 0;
1657 /* Make sure we always see the terminating NUL character */
1658 smp_store_release(&dentry->d_name.name, dname); /* ^^^ */
1660 dentry->d_lockref.count = 1;
1661 dentry->d_flags = 0;
1662 spin_lock_init(&dentry->d_lock);
1663 seqcount_init(&dentry->d_seq);
1664 dentry->d_inode = NULL;
1665 dentry->d_parent = dentry;
1667 dentry->d_op = NULL;
1668 dentry->d_fsdata = NULL;
1669 INIT_HLIST_BL_NODE(&dentry->d_hash);
1670 INIT_LIST_HEAD(&dentry->d_lru);
1671 INIT_LIST_HEAD(&dentry->d_subdirs);
1672 INIT_HLIST_NODE(&dentry->d_u.d_alias);
1673 INIT_LIST_HEAD(&dentry->d_child);
1674 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1676 if (dentry->d_op && dentry->d_op->d_init) {
1677 err = dentry->d_op->d_init(dentry);
1679 if (dname_external(dentry))
1680 kfree(external_name(dentry));
1681 kmem_cache_free(dentry_cache, dentry);
1686 this_cpu_inc(nr_dentry);
1692 * d_alloc - allocate a dcache entry
1693 * @parent: parent of entry to allocate
1694 * @name: qstr of the name
1696 * Allocates a dentry. It returns %NULL if there is insufficient memory
1697 * available. On a success the dentry is returned. The name passed in is
1698 * copied and the copy passed in may be reused after this call.
1700 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1702 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1705 dentry->d_flags |= DCACHE_RCUACCESS;
1706 spin_lock(&parent->d_lock);
1708 * don't need child lock because it is not subject
1709 * to concurrency here
1711 __dget_dlock(parent);
1712 dentry->d_parent = parent;
1713 list_add(&dentry->d_child, &parent->d_subdirs);
1714 spin_unlock(&parent->d_lock);
1718 EXPORT_SYMBOL(d_alloc);
1720 struct dentry *d_alloc_anon(struct super_block *sb)
1722 return __d_alloc(sb, NULL);
1724 EXPORT_SYMBOL(d_alloc_anon);
1726 struct dentry *d_alloc_cursor(struct dentry * parent)
1728 struct dentry *dentry = d_alloc_anon(parent->d_sb);
1730 dentry->d_flags |= DCACHE_RCUACCESS | DCACHE_DENTRY_CURSOR;
1731 dentry->d_parent = dget(parent);
1737 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1738 * @sb: the superblock
1739 * @name: qstr of the name
1741 * For a filesystem that just pins its dentries in memory and never
1742 * performs lookups at all, return an unhashed IS_ROOT dentry.
1744 struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1746 return __d_alloc(sb, name);
1748 EXPORT_SYMBOL(d_alloc_pseudo);
1750 struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1755 q.hash_len = hashlen_string(parent, name);
1756 return d_alloc(parent, &q);
1758 EXPORT_SYMBOL(d_alloc_name);
1760 void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1762 WARN_ON_ONCE(dentry->d_op);
1763 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
1765 DCACHE_OP_REVALIDATE |
1766 DCACHE_OP_WEAK_REVALIDATE |
1773 dentry->d_flags |= DCACHE_OP_HASH;
1775 dentry->d_flags |= DCACHE_OP_COMPARE;
1776 if (op->d_revalidate)
1777 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1778 if (op->d_weak_revalidate)
1779 dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
1781 dentry->d_flags |= DCACHE_OP_DELETE;
1783 dentry->d_flags |= DCACHE_OP_PRUNE;
1785 dentry->d_flags |= DCACHE_OP_REAL;
1788 EXPORT_SYMBOL(d_set_d_op);
1792 * d_set_fallthru - Mark a dentry as falling through to a lower layer
1793 * @dentry - The dentry to mark
1795 * Mark a dentry as falling through to the lower layer (as set with
1796 * d_pin_lower()). This flag may be recorded on the medium.
1798 void d_set_fallthru(struct dentry *dentry)
1800 spin_lock(&dentry->d_lock);
1801 dentry->d_flags |= DCACHE_FALLTHRU;
1802 spin_unlock(&dentry->d_lock);
1804 EXPORT_SYMBOL(d_set_fallthru);
1806 static unsigned d_flags_for_inode(struct inode *inode)
1808 unsigned add_flags = DCACHE_REGULAR_TYPE;
1811 return DCACHE_MISS_TYPE;
1813 if (S_ISDIR(inode->i_mode)) {
1814 add_flags = DCACHE_DIRECTORY_TYPE;
1815 if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) {
1816 if (unlikely(!inode->i_op->lookup))
1817 add_flags = DCACHE_AUTODIR_TYPE;
1819 inode->i_opflags |= IOP_LOOKUP;
1821 goto type_determined;
1824 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1825 if (unlikely(inode->i_op->get_link)) {
1826 add_flags = DCACHE_SYMLINK_TYPE;
1827 goto type_determined;
1829 inode->i_opflags |= IOP_NOFOLLOW;
1832 if (unlikely(!S_ISREG(inode->i_mode)))
1833 add_flags = DCACHE_SPECIAL_TYPE;
1836 if (unlikely(IS_AUTOMOUNT(inode)))
1837 add_flags |= DCACHE_NEED_AUTOMOUNT;
1841 static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1843 unsigned add_flags = d_flags_for_inode(inode);
1844 WARN_ON(d_in_lookup(dentry));
1846 spin_lock(&dentry->d_lock);
1847 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
1848 raw_write_seqcount_begin(&dentry->d_seq);
1849 __d_set_inode_and_type(dentry, inode, add_flags);
1850 raw_write_seqcount_end(&dentry->d_seq);
1851 fsnotify_update_flags(dentry);
1852 spin_unlock(&dentry->d_lock);
1856 * d_instantiate - fill in inode information for a dentry
1857 * @entry: dentry to complete
1858 * @inode: inode to attach to this dentry
1860 * Fill in inode information in the entry.
1862 * This turns negative dentries into productive full members
1865 * NOTE! This assumes that the inode count has been incremented
1866 * (or otherwise set) by the caller to indicate that it is now
1867 * in use by the dcache.
1870 void d_instantiate(struct dentry *entry, struct inode * inode)
1872 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1874 security_d_instantiate(entry, inode);
1875 spin_lock(&inode->i_lock);
1876 __d_instantiate(entry, inode);
1877 spin_unlock(&inode->i_lock);
1880 EXPORT_SYMBOL(d_instantiate);
1883 * d_instantiate_no_diralias - instantiate a non-aliased dentry
1884 * @entry: dentry to complete
1885 * @inode: inode to attach to this dentry
1887 * Fill in inode information in the entry. If a directory alias is found, then
1888 * return an error (and drop inode). Together with d_materialise_unique() this
1889 * guarantees that a directory inode may never have more than one alias.
1891 int d_instantiate_no_diralias(struct dentry *entry, struct inode *inode)
1893 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1895 security_d_instantiate(entry, inode);
1896 spin_lock(&inode->i_lock);
1897 if (S_ISDIR(inode->i_mode) && !hlist_empty(&inode->i_dentry)) {
1898 spin_unlock(&inode->i_lock);
1902 __d_instantiate(entry, inode);
1903 spin_unlock(&inode->i_lock);
1907 EXPORT_SYMBOL(d_instantiate_no_diralias);
1909 struct dentry *d_make_root(struct inode *root_inode)
1911 struct dentry *res = NULL;
1914 res = d_alloc_anon(root_inode->i_sb);
1916 d_instantiate(res, root_inode);
1922 EXPORT_SYMBOL(d_make_root);
1924 static struct dentry * __d_find_any_alias(struct inode *inode)
1926 struct dentry *alias;
1928 if (hlist_empty(&inode->i_dentry))
1930 alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
1936 * d_find_any_alias - find any alias for a given inode
1937 * @inode: inode to find an alias for
1939 * If any aliases exist for the given inode, take and return a
1940 * reference for one of them. If no aliases exist, return %NULL.
1942 struct dentry *d_find_any_alias(struct inode *inode)
1946 spin_lock(&inode->i_lock);
1947 de = __d_find_any_alias(inode);
1948 spin_unlock(&inode->i_lock);
1951 EXPORT_SYMBOL(d_find_any_alias);
1953 static struct dentry *__d_instantiate_anon(struct dentry *dentry,
1954 struct inode *inode,
1960 security_d_instantiate(dentry, inode);
1961 spin_lock(&inode->i_lock);
1962 res = __d_find_any_alias(inode);
1964 spin_unlock(&inode->i_lock);
1969 /* attach a disconnected dentry */
1970 add_flags = d_flags_for_inode(inode);
1973 add_flags |= DCACHE_DISCONNECTED;
1975 spin_lock(&dentry->d_lock);
1976 __d_set_inode_and_type(dentry, inode, add_flags);
1977 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
1978 if (!disconnected) {
1979 hlist_bl_lock(&dentry->d_sb->s_roots);
1980 hlist_bl_add_head(&dentry->d_hash, &dentry->d_sb->s_roots);
1981 hlist_bl_unlock(&dentry->d_sb->s_roots);
1983 spin_unlock(&dentry->d_lock);
1984 spin_unlock(&inode->i_lock);
1993 struct dentry *d_instantiate_anon(struct dentry *dentry, struct inode *inode)
1995 return __d_instantiate_anon(dentry, inode, true);
1997 EXPORT_SYMBOL(d_instantiate_anon);
1999 static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected)
2005 return ERR_PTR(-ESTALE);
2007 return ERR_CAST(inode);
2009 res = d_find_any_alias(inode);
2013 tmp = d_alloc_anon(inode->i_sb);
2015 res = ERR_PTR(-ENOMEM);
2019 return __d_instantiate_anon(tmp, inode, disconnected);
2027 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
2028 * @inode: inode to allocate the dentry for
2030 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
2031 * similar open by handle operations. The returned dentry may be anonymous,
2032 * or may have a full name (if the inode was already in the cache).
2034 * When called on a directory inode, we must ensure that the inode only ever
2035 * has one dentry. If a dentry is found, that is returned instead of
2036 * allocating a new one.
2038 * On successful return, the reference to the inode has been transferred
2039 * to the dentry. In case of an error the reference on the inode is released.
2040 * To make it easier to use in export operations a %NULL or IS_ERR inode may
2041 * be passed in and the error will be propagated to the return value,
2042 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
2044 struct dentry *d_obtain_alias(struct inode *inode)
2046 return __d_obtain_alias(inode, true);
2048 EXPORT_SYMBOL(d_obtain_alias);
2051 * d_obtain_root - find or allocate a dentry for a given inode
2052 * @inode: inode to allocate the dentry for
2054 * Obtain an IS_ROOT dentry for the root of a filesystem.
2056 * We must ensure that directory inodes only ever have one dentry. If a
2057 * dentry is found, that is returned instead of allocating a new one.
2059 * On successful return, the reference to the inode has been transferred
2060 * to the dentry. In case of an error the reference on the inode is
2061 * released. A %NULL or IS_ERR inode may be passed in and will be the
2062 * error will be propagate to the return value, with a %NULL @inode
2063 * replaced by ERR_PTR(-ESTALE).
2065 struct dentry *d_obtain_root(struct inode *inode)
2067 return __d_obtain_alias(inode, false);
2069 EXPORT_SYMBOL(d_obtain_root);
2072 * d_add_ci - lookup or allocate new dentry with case-exact name
2073 * @inode: the inode case-insensitive lookup has found
2074 * @dentry: the negative dentry that was passed to the parent's lookup func
2075 * @name: the case-exact name to be associated with the returned dentry
2077 * This is to avoid filling the dcache with case-insensitive names to the
2078 * same inode, only the actual correct case is stored in the dcache for
2079 * case-insensitive filesystems.
2081 * For a case-insensitive lookup match and if the the case-exact dentry
2082 * already exists in in the dcache, use it and return it.
2084 * If no entry exists with the exact case name, allocate new dentry with
2085 * the exact case, and return the spliced entry.
2087 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
2090 struct dentry *found, *res;
2093 * First check if a dentry matching the name already exists,
2094 * if not go ahead and create it now.
2096 found = d_hash_and_lookup(dentry->d_parent, name);
2101 if (d_in_lookup(dentry)) {
2102 found = d_alloc_parallel(dentry->d_parent, name,
2104 if (IS_ERR(found) || !d_in_lookup(found)) {
2109 found = d_alloc(dentry->d_parent, name);
2112 return ERR_PTR(-ENOMEM);
2115 res = d_splice_alias(inode, found);
2122 EXPORT_SYMBOL(d_add_ci);
2125 static inline bool d_same_name(const struct dentry *dentry,
2126 const struct dentry *parent,
2127 const struct qstr *name)
2129 if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
2130 if (dentry->d_name.len != name->len)
2132 return dentry_cmp(dentry, name->name, name->len) == 0;
2134 return parent->d_op->d_compare(dentry,
2135 dentry->d_name.len, dentry->d_name.name,
2140 * __d_lookup_rcu - search for a dentry (racy, store-free)
2141 * @parent: parent dentry
2142 * @name: qstr of name we wish to find
2143 * @seqp: returns d_seq value at the point where the dentry was found
2144 * Returns: dentry, or NULL
2146 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2147 * resolution (store-free path walking) design described in
2148 * Documentation/filesystems/path-lookup.txt.
2150 * This is not to be used outside core vfs.
2152 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2153 * held, and rcu_read_lock held. The returned dentry must not be stored into
2154 * without taking d_lock and checking d_seq sequence count against @seq
2157 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2160 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2161 * the returned dentry, so long as its parent's seqlock is checked after the
2162 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2163 * is formed, giving integrity down the path walk.
2165 * NOTE! The caller *has* to check the resulting dentry against the sequence
2166 * number we've returned before using any of the resulting dentry state!
2168 struct dentry *__d_lookup_rcu(const struct dentry *parent,
2169 const struct qstr *name,
2172 u64 hashlen = name->hash_len;
2173 const unsigned char *str = name->name;
2174 struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
2175 struct hlist_bl_node *node;
2176 struct dentry *dentry;
2179 * Note: There is significant duplication with __d_lookup_rcu which is
2180 * required to prevent single threaded performance regressions
2181 * especially on architectures where smp_rmb (in seqcounts) are costly.
2182 * Keep the two functions in sync.
2186 * The hash list is protected using RCU.
2188 * Carefully use d_seq when comparing a candidate dentry, to avoid
2189 * races with d_move().
2191 * It is possible that concurrent renames can mess up our list
2192 * walk here and result in missing our dentry, resulting in the
2193 * false-negative result. d_lookup() protects against concurrent
2194 * renames using rename_lock seqlock.
2196 * See Documentation/filesystems/path-lookup.txt for more details.
2198 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2203 * The dentry sequence count protects us from concurrent
2204 * renames, and thus protects parent and name fields.
2206 * The caller must perform a seqcount check in order
2207 * to do anything useful with the returned dentry.
2209 * NOTE! We do a "raw" seqcount_begin here. That means that
2210 * we don't wait for the sequence count to stabilize if it
2211 * is in the middle of a sequence change. If we do the slow
2212 * dentry compare, we will do seqretries until it is stable,
2213 * and if we end up with a successful lookup, we actually
2214 * want to exit RCU lookup anyway.
2216 * Note that raw_seqcount_begin still *does* smp_rmb(), so
2217 * we are still guaranteed NUL-termination of ->d_name.name.
2219 seq = raw_seqcount_begin(&dentry->d_seq);
2220 if (dentry->d_parent != parent)
2222 if (d_unhashed(dentry))
2225 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
2228 if (dentry->d_name.hash != hashlen_hash(hashlen))
2230 tlen = dentry->d_name.len;
2231 tname = dentry->d_name.name;
2232 /* we want a consistent (name,len) pair */
2233 if (read_seqcount_retry(&dentry->d_seq, seq)) {
2237 if (parent->d_op->d_compare(dentry,
2238 tlen, tname, name) != 0)
2241 if (dentry->d_name.hash_len != hashlen)
2243 if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
2253 * d_lookup - search for a dentry
2254 * @parent: parent dentry
2255 * @name: qstr of name we wish to find
2256 * Returns: dentry, or NULL
2258 * d_lookup searches the children of the parent dentry for the name in
2259 * question. If the dentry is found its reference count is incremented and the
2260 * dentry is returned. The caller must use dput to free the entry when it has
2261 * finished using it. %NULL is returned if the dentry does not exist.
2263 struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
2265 struct dentry *dentry;
2269 seq = read_seqbegin(&rename_lock);
2270 dentry = __d_lookup(parent, name);
2273 } while (read_seqretry(&rename_lock, seq));
2276 EXPORT_SYMBOL(d_lookup);
2279 * __d_lookup - search for a dentry (racy)
2280 * @parent: parent dentry
2281 * @name: qstr of name we wish to find
2282 * Returns: dentry, or NULL
2284 * __d_lookup is like d_lookup, however it may (rarely) return a
2285 * false-negative result due to unrelated rename activity.
2287 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2288 * however it must be used carefully, eg. with a following d_lookup in
2289 * the case of failure.
2291 * __d_lookup callers must be commented.
2293 struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
2295 unsigned int hash = name->hash;
2296 struct hlist_bl_head *b = d_hash(hash);
2297 struct hlist_bl_node *node;
2298 struct dentry *found = NULL;
2299 struct dentry *dentry;
2302 * Note: There is significant duplication with __d_lookup_rcu which is
2303 * required to prevent single threaded performance regressions
2304 * especially on architectures where smp_rmb (in seqcounts) are costly.
2305 * Keep the two functions in sync.
2309 * The hash list is protected using RCU.
2311 * Take d_lock when comparing a candidate dentry, to avoid races
2314 * It is possible that concurrent renames can mess up our list
2315 * walk here and result in missing our dentry, resulting in the
2316 * false-negative result. d_lookup() protects against concurrent
2317 * renames using rename_lock seqlock.
2319 * See Documentation/filesystems/path-lookup.txt for more details.
2323 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2325 if (dentry->d_name.hash != hash)
2328 spin_lock(&dentry->d_lock);
2329 if (dentry->d_parent != parent)
2331 if (d_unhashed(dentry))
2334 if (!d_same_name(dentry, parent, name))
2337 dentry->d_lockref.count++;
2339 spin_unlock(&dentry->d_lock);
2342 spin_unlock(&dentry->d_lock);
2350 * d_hash_and_lookup - hash the qstr then search for a dentry
2351 * @dir: Directory to search in
2352 * @name: qstr of name we wish to find
2354 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2356 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2359 * Check for a fs-specific hash function. Note that we must
2360 * calculate the standard hash first, as the d_op->d_hash()
2361 * routine may choose to leave the hash value unchanged.
2363 name->hash = full_name_hash(dir, name->name, name->len);
2364 if (dir->d_flags & DCACHE_OP_HASH) {
2365 int err = dir->d_op->d_hash(dir, name);
2366 if (unlikely(err < 0))
2367 return ERR_PTR(err);
2369 return d_lookup(dir, name);
2371 EXPORT_SYMBOL(d_hash_and_lookup);
2374 * When a file is deleted, we have two options:
2375 * - turn this dentry into a negative dentry
2376 * - unhash this dentry and free it.
2378 * Usually, we want to just turn this into
2379 * a negative dentry, but if anybody else is
2380 * currently using the dentry or the inode
2381 * we can't do that and we fall back on removing
2382 * it from the hash queues and waiting for
2383 * it to be deleted later when it has no users
2387 * d_delete - delete a dentry
2388 * @dentry: The dentry to delete
2390 * Turn the dentry into a negative dentry if possible, otherwise
2391 * remove it from the hash queues so it can be deleted later
2394 void d_delete(struct dentry * dentry)
2396 struct inode *inode = dentry->d_inode;
2397 int isdir = d_is_dir(dentry);
2399 spin_lock(&inode->i_lock);
2400 spin_lock(&dentry->d_lock);
2402 * Are we the only user?
2404 if (dentry->d_lockref.count == 1) {
2405 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2406 dentry_unlink_inode(dentry);
2409 spin_unlock(&dentry->d_lock);
2410 spin_unlock(&inode->i_lock);
2412 fsnotify_nameremove(dentry, isdir);
2414 EXPORT_SYMBOL(d_delete);
2416 static void __d_rehash(struct dentry *entry)
2418 struct hlist_bl_head *b = d_hash(entry->d_name.hash);
2421 hlist_bl_add_head_rcu(&entry->d_hash, b);
2426 * d_rehash - add an entry back to the hash
2427 * @entry: dentry to add to the hash
2429 * Adds a dentry to the hash according to its name.
2432 void d_rehash(struct dentry * entry)
2434 spin_lock(&entry->d_lock);
2436 spin_unlock(&entry->d_lock);
2438 EXPORT_SYMBOL(d_rehash);
2440 static inline unsigned start_dir_add(struct inode *dir)
2444 unsigned n = dir->i_dir_seq;
2445 if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
2451 static inline void end_dir_add(struct inode *dir, unsigned n)
2453 smp_store_release(&dir->i_dir_seq, n + 2);
2456 static void d_wait_lookup(struct dentry *dentry)
2458 if (d_in_lookup(dentry)) {
2459 DECLARE_WAITQUEUE(wait, current);
2460 add_wait_queue(dentry->d_wait, &wait);
2462 set_current_state(TASK_UNINTERRUPTIBLE);
2463 spin_unlock(&dentry->d_lock);
2465 spin_lock(&dentry->d_lock);
2466 } while (d_in_lookup(dentry));
2470 struct dentry *d_alloc_parallel(struct dentry *parent,
2471 const struct qstr *name,
2472 wait_queue_head_t *wq)
2474 unsigned int hash = name->hash;
2475 struct hlist_bl_head *b = in_lookup_hash(parent, hash);
2476 struct hlist_bl_node *node;
2477 struct dentry *new = d_alloc(parent, name);
2478 struct dentry *dentry;
2479 unsigned seq, r_seq, d_seq;
2482 return ERR_PTR(-ENOMEM);
2486 seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
2487 r_seq = read_seqbegin(&rename_lock);
2488 dentry = __d_lookup_rcu(parent, name, &d_seq);
2489 if (unlikely(dentry)) {
2490 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2494 if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
2503 if (unlikely(read_seqretry(&rename_lock, r_seq))) {
2508 if (unlikely(seq & 1)) {
2514 if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
2520 * No changes for the parent since the beginning of d_lookup().
2521 * Since all removals from the chain happen with hlist_bl_lock(),
2522 * any potential in-lookup matches are going to stay here until
2523 * we unlock the chain. All fields are stable in everything
2526 hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
2527 if (dentry->d_name.hash != hash)
2529 if (dentry->d_parent != parent)
2531 if (!d_same_name(dentry, parent, name))
2534 /* now we can try to grab a reference */
2535 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2542 * somebody is likely to be still doing lookup for it;
2543 * wait for them to finish
2545 spin_lock(&dentry->d_lock);
2546 d_wait_lookup(dentry);
2548 * it's not in-lookup anymore; in principle we should repeat
2549 * everything from dcache lookup, but it's likely to be what
2550 * d_lookup() would've found anyway. If it is, just return it;
2551 * otherwise we really have to repeat the whole thing.
2553 if (unlikely(dentry->d_name.hash != hash))
2555 if (unlikely(dentry->d_parent != parent))
2557 if (unlikely(d_unhashed(dentry)))
2559 if (unlikely(!d_same_name(dentry, parent, name)))
2561 /* OK, it *is* a hashed match; return it */
2562 spin_unlock(&dentry->d_lock);
2567 /* we can't take ->d_lock here; it's OK, though. */
2568 new->d_flags |= DCACHE_PAR_LOOKUP;
2570 hlist_bl_add_head_rcu(&new->d_u.d_in_lookup_hash, b);
2574 spin_unlock(&dentry->d_lock);
2578 EXPORT_SYMBOL(d_alloc_parallel);
2580 void __d_lookup_done(struct dentry *dentry)
2582 struct hlist_bl_head *b = in_lookup_hash(dentry->d_parent,
2583 dentry->d_name.hash);
2585 dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
2586 __hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
2587 wake_up_all(dentry->d_wait);
2588 dentry->d_wait = NULL;
2590 INIT_HLIST_NODE(&dentry->d_u.d_alias);
2591 INIT_LIST_HEAD(&dentry->d_lru);
2593 EXPORT_SYMBOL(__d_lookup_done);
2595 /* inode->i_lock held if inode is non-NULL */
2597 static inline void __d_add(struct dentry *dentry, struct inode *inode)
2599 struct inode *dir = NULL;
2601 spin_lock(&dentry->d_lock);
2602 if (unlikely(d_in_lookup(dentry))) {
2603 dir = dentry->d_parent->d_inode;
2604 n = start_dir_add(dir);
2605 __d_lookup_done(dentry);
2608 unsigned add_flags = d_flags_for_inode(inode);
2609 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2610 raw_write_seqcount_begin(&dentry->d_seq);
2611 __d_set_inode_and_type(dentry, inode, add_flags);
2612 raw_write_seqcount_end(&dentry->d_seq);
2613 fsnotify_update_flags(dentry);
2617 end_dir_add(dir, n);
2618 spin_unlock(&dentry->d_lock);
2620 spin_unlock(&inode->i_lock);
2624 * d_add - add dentry to hash queues
2625 * @entry: dentry to add
2626 * @inode: The inode to attach to this dentry
2628 * This adds the entry to the hash queues and initializes @inode.
2629 * The entry was actually filled in earlier during d_alloc().
2632 void d_add(struct dentry *entry, struct inode *inode)
2635 security_d_instantiate(entry, inode);
2636 spin_lock(&inode->i_lock);
2638 __d_add(entry, inode);
2640 EXPORT_SYMBOL(d_add);
2643 * d_exact_alias - find and hash an exact unhashed alias
2644 * @entry: dentry to add
2645 * @inode: The inode to go with this dentry
2647 * If an unhashed dentry with the same name/parent and desired
2648 * inode already exists, hash and return it. Otherwise, return
2651 * Parent directory should be locked.
2653 struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
2655 struct dentry *alias;
2656 unsigned int hash = entry->d_name.hash;
2658 spin_lock(&inode->i_lock);
2659 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
2661 * Don't need alias->d_lock here, because aliases with
2662 * d_parent == entry->d_parent are not subject to name or
2663 * parent changes, because the parent inode i_mutex is held.
2665 if (alias->d_name.hash != hash)
2667 if (alias->d_parent != entry->d_parent)
2669 if (!d_same_name(alias, entry->d_parent, &entry->d_name))
2671 spin_lock(&alias->d_lock);
2672 if (!d_unhashed(alias)) {
2673 spin_unlock(&alias->d_lock);
2676 __dget_dlock(alias);
2678 spin_unlock(&alias->d_lock);
2680 spin_unlock(&inode->i_lock);
2683 spin_unlock(&inode->i_lock);
2686 EXPORT_SYMBOL(d_exact_alias);
2689 * dentry_update_name_case - update case insensitive dentry with a new name
2690 * @dentry: dentry to be updated
2693 * Update a case insensitive dentry with new case of name.
2695 * dentry must have been returned by d_lookup with name @name. Old and new
2696 * name lengths must match (ie. no d_compare which allows mismatched name
2699 * Parent inode i_mutex must be held over d_lookup and into this call (to
2700 * keep renames and concurrent inserts, and readdir(2) away).
2702 void dentry_update_name_case(struct dentry *dentry, const struct qstr *name)
2704 BUG_ON(!inode_is_locked(dentry->d_parent->d_inode));
2705 BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
2707 spin_lock(&dentry->d_lock);
2708 write_seqcount_begin(&dentry->d_seq);
2709 memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
2710 write_seqcount_end(&dentry->d_seq);
2711 spin_unlock(&dentry->d_lock);
2713 EXPORT_SYMBOL(dentry_update_name_case);
2715 static void swap_names(struct dentry *dentry, struct dentry *target)
2717 if (unlikely(dname_external(target))) {
2718 if (unlikely(dname_external(dentry))) {
2720 * Both external: swap the pointers
2722 swap(target->d_name.name, dentry->d_name.name);
2725 * dentry:internal, target:external. Steal target's
2726 * storage and make target internal.
2728 memcpy(target->d_iname, dentry->d_name.name,
2729 dentry->d_name.len + 1);
2730 dentry->d_name.name = target->d_name.name;
2731 target->d_name.name = target->d_iname;
2734 if (unlikely(dname_external(dentry))) {
2736 * dentry:external, target:internal. Give dentry's
2737 * storage to target and make dentry internal
2739 memcpy(dentry->d_iname, target->d_name.name,
2740 target->d_name.len + 1);
2741 target->d_name.name = dentry->d_name.name;
2742 dentry->d_name.name = dentry->d_iname;
2745 * Both are internal.
2748 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
2749 for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
2750 swap(((long *) &dentry->d_iname)[i],
2751 ((long *) &target->d_iname)[i]);
2755 swap(dentry->d_name.hash_len, target->d_name.hash_len);
2758 static void copy_name(struct dentry *dentry, struct dentry *target)
2760 struct external_name *old_name = NULL;
2761 if (unlikely(dname_external(dentry)))
2762 old_name = external_name(dentry);
2763 if (unlikely(dname_external(target))) {
2764 atomic_inc(&external_name(target)->u.count);
2765 dentry->d_name = target->d_name;
2767 memcpy(dentry->d_iname, target->d_name.name,
2768 target->d_name.len + 1);
2769 dentry->d_name.name = dentry->d_iname;
2770 dentry->d_name.hash_len = target->d_name.hash_len;
2772 if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
2773 kfree_rcu(old_name, u.head);
2777 * __d_move - move a dentry
2778 * @dentry: entry to move
2779 * @target: new dentry
2780 * @exchange: exchange the two dentries
2782 * Update the dcache to reflect the move of a file name. Negative
2783 * dcache entries should not be moved in this way. Caller must hold
2784 * rename_lock, the i_mutex of the source and target directories,
2785 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2787 static void __d_move(struct dentry *dentry, struct dentry *target,
2790 struct dentry *old_parent, *p;
2791 struct inode *dir = NULL;
2794 WARN_ON(!dentry->d_inode);
2795 if (WARN_ON(dentry == target))
2798 BUG_ON(d_ancestor(target, dentry));
2799 old_parent = dentry->d_parent;
2800 p = d_ancestor(old_parent, target);
2801 if (IS_ROOT(dentry)) {
2803 spin_lock(&target->d_parent->d_lock);
2805 /* target is not a descendent of dentry->d_parent */
2806 spin_lock(&target->d_parent->d_lock);
2807 spin_lock_nested(&old_parent->d_lock, DENTRY_D_LOCK_NESTED);
2809 BUG_ON(p == dentry);
2810 spin_lock(&old_parent->d_lock);
2812 spin_lock_nested(&target->d_parent->d_lock,
2813 DENTRY_D_LOCK_NESTED);
2815 spin_lock_nested(&dentry->d_lock, 2);
2816 spin_lock_nested(&target->d_lock, 3);
2818 if (unlikely(d_in_lookup(target))) {
2819 dir = target->d_parent->d_inode;
2820 n = start_dir_add(dir);
2821 __d_lookup_done(target);
2824 write_seqcount_begin(&dentry->d_seq);
2825 write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
2828 if (!d_unhashed(dentry))
2830 if (!d_unhashed(target))
2833 /* ... and switch them in the tree */
2834 dentry->d_parent = target->d_parent;
2836 copy_name(dentry, target);
2837 target->d_hash.pprev = NULL;
2838 dentry->d_parent->d_lockref.count++;
2839 if (dentry == old_parent)
2840 dentry->d_flags |= DCACHE_RCUACCESS;
2842 WARN_ON(!--old_parent->d_lockref.count);
2844 target->d_parent = old_parent;
2845 swap_names(dentry, target);
2846 list_move(&target->d_child, &target->d_parent->d_subdirs);
2848 fsnotify_update_flags(target);
2850 list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
2852 fsnotify_update_flags(dentry);
2854 write_seqcount_end(&target->d_seq);
2855 write_seqcount_end(&dentry->d_seq);
2858 end_dir_add(dir, n);
2860 if (dentry->d_parent != old_parent)
2861 spin_unlock(&dentry->d_parent->d_lock);
2862 if (dentry != old_parent)
2863 spin_unlock(&old_parent->d_lock);
2864 spin_unlock(&target->d_lock);
2865 spin_unlock(&dentry->d_lock);
2869 * d_move - move a dentry
2870 * @dentry: entry to move
2871 * @target: new dentry
2873 * Update the dcache to reflect the move of a file name. Negative
2874 * dcache entries should not be moved in this way. See the locking
2875 * requirements for __d_move.
2877 void d_move(struct dentry *dentry, struct dentry *target)
2879 write_seqlock(&rename_lock);
2880 __d_move(dentry, target, false);
2881 write_sequnlock(&rename_lock);
2883 EXPORT_SYMBOL(d_move);
2886 * d_exchange - exchange two dentries
2887 * @dentry1: first dentry
2888 * @dentry2: second dentry
2890 void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
2892 write_seqlock(&rename_lock);
2894 WARN_ON(!dentry1->d_inode);
2895 WARN_ON(!dentry2->d_inode);
2896 WARN_ON(IS_ROOT(dentry1));
2897 WARN_ON(IS_ROOT(dentry2));
2899 __d_move(dentry1, dentry2, true);
2901 write_sequnlock(&rename_lock);
2905 * d_ancestor - search for an ancestor
2906 * @p1: ancestor dentry
2909 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2910 * an ancestor of p2, else NULL.
2912 struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2916 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2917 if (p->d_parent == p1)
2924 * This helper attempts to cope with remotely renamed directories
2926 * It assumes that the caller is already holding
2927 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2929 * Note: If ever the locking in lock_rename() changes, then please
2930 * remember to update this too...
2932 static int __d_unalias(struct inode *inode,
2933 struct dentry *dentry, struct dentry *alias)
2935 struct mutex *m1 = NULL;
2936 struct rw_semaphore *m2 = NULL;
2939 /* If alias and dentry share a parent, then no extra locks required */
2940 if (alias->d_parent == dentry->d_parent)
2943 /* See lock_rename() */
2944 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
2946 m1 = &dentry->d_sb->s_vfs_rename_mutex;
2947 if (!inode_trylock_shared(alias->d_parent->d_inode))
2949 m2 = &alias->d_parent->d_inode->i_rwsem;
2951 __d_move(alias, dentry, false);
2962 * d_splice_alias - splice a disconnected dentry into the tree if one exists
2963 * @inode: the inode which may have a disconnected dentry
2964 * @dentry: a negative dentry which we want to point to the inode.
2966 * If inode is a directory and has an IS_ROOT alias, then d_move that in
2967 * place of the given dentry and return it, else simply d_add the inode
2968 * to the dentry and return NULL.
2970 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
2971 * we should error out: directories can't have multiple aliases.
2973 * This is needed in the lookup routine of any filesystem that is exportable
2974 * (via knfsd) so that we can build dcache paths to directories effectively.
2976 * If a dentry was found and moved, then it is returned. Otherwise NULL
2977 * is returned. This matches the expected return value of ->lookup.
2979 * Cluster filesystems may call this function with a negative, hashed dentry.
2980 * In that case, we know that the inode will be a regular file, and also this
2981 * will only occur during atomic_open. So we need to check for the dentry
2982 * being already hashed only in the final case.
2984 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
2987 return ERR_CAST(inode);
2989 BUG_ON(!d_unhashed(dentry));
2994 security_d_instantiate(dentry, inode);
2995 spin_lock(&inode->i_lock);
2996 if (S_ISDIR(inode->i_mode)) {
2997 struct dentry *new = __d_find_any_alias(inode);
2998 if (unlikely(new)) {
2999 /* The reference to new ensures it remains an alias */
3000 spin_unlock(&inode->i_lock);
3001 write_seqlock(&rename_lock);
3002 if (unlikely(d_ancestor(new, dentry))) {
3003 write_sequnlock(&rename_lock);
3005 new = ERR_PTR(-ELOOP);
3006 pr_warn_ratelimited(
3007 "VFS: Lookup of '%s' in %s %s"
3008 " would have caused loop\n",
3009 dentry->d_name.name,
3010 inode->i_sb->s_type->name,
3012 } else if (!IS_ROOT(new)) {
3013 struct dentry *old_parent = dget(new->d_parent);
3014 int err = __d_unalias(inode, dentry, new);
3015 write_sequnlock(&rename_lock);
3022 __d_move(new, dentry, false);
3023 write_sequnlock(&rename_lock);
3030 __d_add(dentry, inode);
3033 EXPORT_SYMBOL(d_splice_alias);
3036 * Test whether new_dentry is a subdirectory of old_dentry.
3038 * Trivially implemented using the dcache structure
3042 * is_subdir - is new dentry a subdirectory of old_dentry
3043 * @new_dentry: new dentry
3044 * @old_dentry: old dentry
3046 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3047 * Returns false otherwise.
3048 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3051 bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
3056 if (new_dentry == old_dentry)
3060 /* for restarting inner loop in case of seq retry */
3061 seq = read_seqbegin(&rename_lock);
3063 * Need rcu_readlock to protect against the d_parent trashing
3067 if (d_ancestor(old_dentry, new_dentry))
3072 } while (read_seqretry(&rename_lock, seq));
3076 EXPORT_SYMBOL(is_subdir);
3078 static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
3080 struct dentry *root = data;
3081 if (dentry != root) {
3082 if (d_unhashed(dentry) || !dentry->d_inode)
3085 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
3086 dentry->d_flags |= DCACHE_GENOCIDE;
3087 dentry->d_lockref.count--;
3090 return D_WALK_CONTINUE;
3093 void d_genocide(struct dentry *parent)
3095 d_walk(parent, parent, d_genocide_kill, NULL);
3098 EXPORT_SYMBOL(d_genocide);
3100 void d_tmpfile(struct dentry *dentry, struct inode *inode)
3102 inode_dec_link_count(inode);
3103 BUG_ON(dentry->d_name.name != dentry->d_iname ||
3104 !hlist_unhashed(&dentry->d_u.d_alias) ||
3105 !d_unlinked(dentry));
3106 spin_lock(&dentry->d_parent->d_lock);
3107 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
3108 dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
3109 (unsigned long long)inode->i_ino);
3110 spin_unlock(&dentry->d_lock);
3111 spin_unlock(&dentry->d_parent->d_lock);
3112 d_instantiate(dentry, inode);
3114 EXPORT_SYMBOL(d_tmpfile);
3116 static __initdata unsigned long dhash_entries;
3117 static int __init set_dhash_entries(char *str)
3121 dhash_entries = simple_strtoul(str, &str, 0);
3124 __setup("dhash_entries=", set_dhash_entries);
3126 static void __init dcache_init_early(void)
3128 /* If hashes are distributed across NUMA nodes, defer
3129 * hash allocation until vmalloc space is available.
3135 alloc_large_system_hash("Dentry cache",
3136 sizeof(struct hlist_bl_head),
3139 HASH_EARLY | HASH_ZERO,
3144 d_hash_shift = 32 - d_hash_shift;
3147 static void __init dcache_init(void)
3150 * A constructor could be added for stable state like the lists,
3151 * but it is probably not worth it because of the cache nature
3154 dentry_cache = KMEM_CACHE_USERCOPY(dentry,
3155 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT,
3158 /* Hash may have been set up in dcache_init_early */
3163 alloc_large_system_hash("Dentry cache",
3164 sizeof(struct hlist_bl_head),
3172 d_hash_shift = 32 - d_hash_shift;
3175 /* SLAB cache for __getname() consumers */
3176 struct kmem_cache *names_cachep __read_mostly;
3177 EXPORT_SYMBOL(names_cachep);
3179 void __init vfs_caches_init_early(void)
3183 for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++)
3184 INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]);
3186 dcache_init_early();
3190 void __init vfs_caches_init(void)
3192 names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0,
3193 SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL);
3198 files_maxfiles_init();