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_name(struct rcu_head *head)
262 struct external_name *name = container_of(head, struct external_name,
265 mod_node_page_state(page_pgdat(virt_to_page(name)),
266 NR_INDIRECTLY_RECLAIMABLE_BYTES,
272 static void __d_free_external(struct rcu_head *head)
274 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
276 __d_free_external_name(&external_name(dentry)->u.head);
278 kmem_cache_free(dentry_cache, dentry);
281 static inline int dname_external(const struct dentry *dentry)
283 return dentry->d_name.name != dentry->d_iname;
286 void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry)
288 spin_lock(&dentry->d_lock);
289 if (unlikely(dname_external(dentry))) {
290 struct external_name *p = external_name(dentry);
291 atomic_inc(&p->u.count);
292 spin_unlock(&dentry->d_lock);
293 name->name = p->name;
295 memcpy(name->inline_name, dentry->d_iname,
296 dentry->d_name.len + 1);
297 spin_unlock(&dentry->d_lock);
298 name->name = name->inline_name;
301 EXPORT_SYMBOL(take_dentry_name_snapshot);
303 void release_dentry_name_snapshot(struct name_snapshot *name)
305 if (unlikely(name->name != name->inline_name)) {
306 struct external_name *p;
307 p = container_of(name->name, struct external_name, name[0]);
308 if (unlikely(atomic_dec_and_test(&p->u.count)))
309 call_rcu(&p->u.head, __d_free_external_name);
312 EXPORT_SYMBOL(release_dentry_name_snapshot);
314 static inline void __d_set_inode_and_type(struct dentry *dentry,
320 dentry->d_inode = inode;
321 flags = READ_ONCE(dentry->d_flags);
322 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
324 WRITE_ONCE(dentry->d_flags, flags);
327 static inline void __d_clear_type_and_inode(struct dentry *dentry)
329 unsigned flags = READ_ONCE(dentry->d_flags);
331 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
332 WRITE_ONCE(dentry->d_flags, flags);
333 dentry->d_inode = NULL;
336 static void dentry_free(struct dentry *dentry)
338 WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias));
339 if (unlikely(dname_external(dentry))) {
340 struct external_name *p = external_name(dentry);
341 if (likely(atomic_dec_and_test(&p->u.count))) {
342 call_rcu(&dentry->d_u.d_rcu, __d_free_external);
346 /* if dentry was never visible to RCU, immediate free is OK */
347 if (dentry->d_flags & DCACHE_NORCU)
348 __d_free(&dentry->d_u.d_rcu);
350 call_rcu(&dentry->d_u.d_rcu, __d_free);
354 * Release the dentry's inode, using the filesystem
355 * d_iput() operation if defined.
357 static void dentry_unlink_inode(struct dentry * dentry)
358 __releases(dentry->d_lock)
359 __releases(dentry->d_inode->i_lock)
361 struct inode *inode = dentry->d_inode;
363 raw_write_seqcount_begin(&dentry->d_seq);
364 __d_clear_type_and_inode(dentry);
365 hlist_del_init(&dentry->d_u.d_alias);
366 raw_write_seqcount_end(&dentry->d_seq);
367 spin_unlock(&dentry->d_lock);
368 spin_unlock(&inode->i_lock);
370 fsnotify_inoderemove(inode);
371 if (dentry->d_op && dentry->d_op->d_iput)
372 dentry->d_op->d_iput(dentry, inode);
378 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
379 * is in use - which includes both the "real" per-superblock
380 * LRU list _and_ the DCACHE_SHRINK_LIST use.
382 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
383 * on the shrink list (ie not on the superblock LRU list).
385 * The per-cpu "nr_dentry_unused" counters are updated with
386 * the DCACHE_LRU_LIST bit.
388 * These helper functions make sure we always follow the
389 * rules. d_lock must be held by the caller.
391 #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
392 static void d_lru_add(struct dentry *dentry)
394 D_FLAG_VERIFY(dentry, 0);
395 dentry->d_flags |= DCACHE_LRU_LIST;
396 this_cpu_inc(nr_dentry_unused);
397 WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
400 static void d_lru_del(struct dentry *dentry)
402 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
403 dentry->d_flags &= ~DCACHE_LRU_LIST;
404 this_cpu_dec(nr_dentry_unused);
405 WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
408 static void d_shrink_del(struct dentry *dentry)
410 D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
411 list_del_init(&dentry->d_lru);
412 dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
413 this_cpu_dec(nr_dentry_unused);
416 static void d_shrink_add(struct dentry *dentry, struct list_head *list)
418 D_FLAG_VERIFY(dentry, 0);
419 list_add(&dentry->d_lru, list);
420 dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST;
421 this_cpu_inc(nr_dentry_unused);
425 * These can only be called under the global LRU lock, ie during the
426 * callback for freeing the LRU list. "isolate" removes it from the
427 * LRU lists entirely, while shrink_move moves it to the indicated
430 static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry)
432 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
433 dentry->d_flags &= ~DCACHE_LRU_LIST;
434 this_cpu_dec(nr_dentry_unused);
435 list_lru_isolate(lru, &dentry->d_lru);
438 static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
439 struct list_head *list)
441 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
442 dentry->d_flags |= DCACHE_SHRINK_LIST;
443 list_lru_isolate_move(lru, &dentry->d_lru, list);
447 * d_drop - drop a dentry
448 * @dentry: dentry to drop
450 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
451 * be found through a VFS lookup any more. Note that this is different from
452 * deleting the dentry - d_delete will try to mark the dentry negative if
453 * possible, giving a successful _negative_ lookup, while d_drop will
454 * just make the cache lookup fail.
456 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
457 * reason (NFS timeouts or autofs deletes).
459 * __d_drop requires dentry->d_lock
460 * ___d_drop doesn't mark dentry as "unhashed"
461 * (dentry->d_hash.pprev will be LIST_POISON2, not NULL).
463 static void ___d_drop(struct dentry *dentry)
465 struct hlist_bl_head *b;
467 * Hashed dentries are normally on the dentry hashtable,
468 * with the exception of those newly allocated by
469 * d_obtain_root, which are always IS_ROOT:
471 if (unlikely(IS_ROOT(dentry)))
472 b = &dentry->d_sb->s_roots;
474 b = d_hash(dentry->d_name.hash);
477 __hlist_bl_del(&dentry->d_hash);
481 void __d_drop(struct dentry *dentry)
483 if (!d_unhashed(dentry)) {
485 dentry->d_hash.pprev = NULL;
486 write_seqcount_invalidate(&dentry->d_seq);
489 EXPORT_SYMBOL(__d_drop);
491 void d_drop(struct dentry *dentry)
493 spin_lock(&dentry->d_lock);
495 spin_unlock(&dentry->d_lock);
497 EXPORT_SYMBOL(d_drop);
499 static inline void dentry_unlist(struct dentry *dentry, struct dentry *parent)
503 * Inform d_walk() and shrink_dentry_list() that we are no longer
504 * attached to the dentry tree
506 dentry->d_flags |= DCACHE_DENTRY_KILLED;
507 if (unlikely(list_empty(&dentry->d_child)))
509 __list_del_entry(&dentry->d_child);
511 * Cursors can move around the list of children. While we'd been
512 * a normal list member, it didn't matter - ->d_child.next would've
513 * been updated. However, from now on it won't be and for the
514 * things like d_walk() it might end up with a nasty surprise.
515 * Normally d_walk() doesn't care about cursors moving around -
516 * ->d_lock on parent prevents that and since a cursor has no children
517 * of its own, we get through it without ever unlocking the parent.
518 * There is one exception, though - if we ascend from a child that
519 * gets killed as soon as we unlock it, the next sibling is found
520 * using the value left in its ->d_child.next. And if _that_
521 * pointed to a cursor, and cursor got moved (e.g. by lseek())
522 * before d_walk() regains parent->d_lock, we'll end up skipping
523 * everything the cursor had been moved past.
525 * Solution: make sure that the pointer left behind in ->d_child.next
526 * points to something that won't be moving around. I.e. skip the
529 while (dentry->d_child.next != &parent->d_subdirs) {
530 next = list_entry(dentry->d_child.next, struct dentry, d_child);
531 if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR)))
533 dentry->d_child.next = next->d_child.next;
537 static void __dentry_kill(struct dentry *dentry)
539 struct dentry *parent = NULL;
540 bool can_free = true;
541 if (!IS_ROOT(dentry))
542 parent = dentry->d_parent;
545 * The dentry is now unrecoverably dead to the world.
547 lockref_mark_dead(&dentry->d_lockref);
550 * inform the fs via d_prune that this dentry is about to be
551 * unhashed and destroyed.
553 if (dentry->d_flags & DCACHE_OP_PRUNE)
554 dentry->d_op->d_prune(dentry);
556 if (dentry->d_flags & DCACHE_LRU_LIST) {
557 if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
560 /* if it was on the hash then remove it */
562 dentry_unlist(dentry, parent);
564 spin_unlock(&parent->d_lock);
566 dentry_unlink_inode(dentry);
568 spin_unlock(&dentry->d_lock);
569 this_cpu_dec(nr_dentry);
570 if (dentry->d_op && dentry->d_op->d_release)
571 dentry->d_op->d_release(dentry);
573 spin_lock(&dentry->d_lock);
574 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
575 dentry->d_flags |= DCACHE_MAY_FREE;
578 spin_unlock(&dentry->d_lock);
579 if (likely(can_free))
584 static struct dentry *__lock_parent(struct dentry *dentry)
586 struct dentry *parent;
588 spin_unlock(&dentry->d_lock);
590 parent = READ_ONCE(dentry->d_parent);
591 spin_lock(&parent->d_lock);
593 * We can't blindly lock dentry until we are sure
594 * that we won't violate the locking order.
595 * Any changes of dentry->d_parent must have
596 * been done with parent->d_lock held, so
597 * spin_lock() above is enough of a barrier
598 * for checking if it's still our child.
600 if (unlikely(parent != dentry->d_parent)) {
601 spin_unlock(&parent->d_lock);
605 if (parent != dentry)
606 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
612 static inline struct dentry *lock_parent(struct dentry *dentry)
614 struct dentry *parent = dentry->d_parent;
617 if (likely(spin_trylock(&parent->d_lock)))
619 return __lock_parent(dentry);
622 static inline bool retain_dentry(struct dentry *dentry)
624 WARN_ON(d_in_lookup(dentry));
626 /* Unreachable? Get rid of it */
627 if (unlikely(d_unhashed(dentry)))
630 if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
633 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) {
634 if (dentry->d_op->d_delete(dentry))
637 /* retain; LRU fodder */
638 dentry->d_lockref.count--;
639 if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
641 else if (unlikely(!(dentry->d_flags & DCACHE_REFERENCED)))
642 dentry->d_flags |= DCACHE_REFERENCED;
647 * Finish off a dentry we've decided to kill.
648 * dentry->d_lock must be held, returns with it unlocked.
649 * Returns dentry requiring refcount drop, or NULL if we're done.
651 static struct dentry *dentry_kill(struct dentry *dentry)
652 __releases(dentry->d_lock)
654 struct inode *inode = dentry->d_inode;
655 struct dentry *parent = NULL;
657 if (inode && unlikely(!spin_trylock(&inode->i_lock)))
660 if (!IS_ROOT(dentry)) {
661 parent = dentry->d_parent;
662 if (unlikely(!spin_trylock(&parent->d_lock))) {
663 parent = __lock_parent(dentry);
664 if (likely(inode || !dentry->d_inode))
666 /* negative that became positive */
668 spin_unlock(&parent->d_lock);
669 inode = dentry->d_inode;
673 __dentry_kill(dentry);
677 spin_unlock(&dentry->d_lock);
678 spin_lock(&inode->i_lock);
679 spin_lock(&dentry->d_lock);
680 parent = lock_parent(dentry);
682 if (unlikely(dentry->d_lockref.count != 1)) {
683 dentry->d_lockref.count--;
684 } else if (likely(!retain_dentry(dentry))) {
685 __dentry_kill(dentry);
688 /* we are keeping it, after all */
690 spin_unlock(&inode->i_lock);
692 spin_unlock(&parent->d_lock);
693 spin_unlock(&dentry->d_lock);
698 * Try to do a lockless dput(), and return whether that was successful.
700 * If unsuccessful, we return false, having already taken the dentry lock.
702 * The caller needs to hold the RCU read lock, so that the dentry is
703 * guaranteed to stay around even if the refcount goes down to zero!
705 static inline bool fast_dput(struct dentry *dentry)
708 unsigned int d_flags;
711 * If we have a d_op->d_delete() operation, we sould not
712 * let the dentry count go to zero, so use "put_or_lock".
714 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE))
715 return lockref_put_or_lock(&dentry->d_lockref);
718 * .. otherwise, we can try to just decrement the
719 * lockref optimistically.
721 ret = lockref_put_return(&dentry->d_lockref);
724 * If the lockref_put_return() failed due to the lock being held
725 * by somebody else, the fast path has failed. We will need to
726 * get the lock, and then check the count again.
728 if (unlikely(ret < 0)) {
729 spin_lock(&dentry->d_lock);
730 if (dentry->d_lockref.count > 1) {
731 dentry->d_lockref.count--;
732 spin_unlock(&dentry->d_lock);
739 * If we weren't the last ref, we're done.
745 * Careful, careful. The reference count went down
746 * to zero, but we don't hold the dentry lock, so
747 * somebody else could get it again, and do another
748 * dput(), and we need to not race with that.
750 * However, there is a very special and common case
751 * where we don't care, because there is nothing to
752 * do: the dentry is still hashed, it does not have
753 * a 'delete' op, and it's referenced and already on
756 * NOTE! Since we aren't locked, these values are
757 * not "stable". However, it is sufficient that at
758 * some point after we dropped the reference the
759 * dentry was hashed and the flags had the proper
760 * value. Other dentry users may have re-gotten
761 * a reference to the dentry and change that, but
762 * our work is done - we can leave the dentry
763 * around with a zero refcount.
766 d_flags = READ_ONCE(dentry->d_flags);
767 d_flags &= DCACHE_REFERENCED | DCACHE_LRU_LIST | DCACHE_DISCONNECTED;
769 /* Nothing to do? Dropping the reference was all we needed? */
770 if (d_flags == (DCACHE_REFERENCED | DCACHE_LRU_LIST) && !d_unhashed(dentry))
774 * Not the fast normal case? Get the lock. We've already decremented
775 * the refcount, but we'll need to re-check the situation after
778 spin_lock(&dentry->d_lock);
781 * Did somebody else grab a reference to it in the meantime, and
782 * we're no longer the last user after all? Alternatively, somebody
783 * else could have killed it and marked it dead. Either way, we
784 * don't need to do anything else.
786 if (dentry->d_lockref.count) {
787 spin_unlock(&dentry->d_lock);
792 * Re-get the reference we optimistically dropped. We hold the
793 * lock, and we just tested that it was zero, so we can just
796 dentry->d_lockref.count = 1;
804 * This is complicated by the fact that we do not want to put
805 * dentries that are no longer on any hash chain on the unused
806 * list: we'd much rather just get rid of them immediately.
808 * However, that implies that we have to traverse the dentry
809 * tree upwards to the parents which might _also_ now be
810 * scheduled for deletion (it may have been only waiting for
811 * its last child to go away).
813 * This tail recursion is done by hand as we don't want to depend
814 * on the compiler to always get this right (gcc generally doesn't).
815 * Real recursion would eat up our stack space.
819 * dput - release a dentry
820 * @dentry: dentry to release
822 * Release a dentry. This will drop the usage count and if appropriate
823 * call the dentry unlink method as well as removing it from the queues and
824 * releasing its resources. If the parent dentries were scheduled for release
825 * they too may now get deleted.
827 void dput(struct dentry *dentry)
833 if (likely(fast_dput(dentry))) {
838 /* Slow case: now with the dentry lock held */
841 if (likely(retain_dentry(dentry))) {
842 spin_unlock(&dentry->d_lock);
846 dentry = dentry_kill(dentry);
852 /* This must be called with d_lock held */
853 static inline void __dget_dlock(struct dentry *dentry)
855 dentry->d_lockref.count++;
858 static inline void __dget(struct dentry *dentry)
860 lockref_get(&dentry->d_lockref);
863 struct dentry *dget_parent(struct dentry *dentry)
870 * Do optimistic parent lookup without any
874 seq = raw_seqcount_begin(&dentry->d_seq);
875 ret = READ_ONCE(dentry->d_parent);
876 gotref = lockref_get_not_zero(&ret->d_lockref);
878 if (likely(gotref)) {
879 if (!read_seqcount_retry(&dentry->d_seq, seq))
886 * Don't need rcu_dereference because we re-check it was correct under
890 ret = dentry->d_parent;
891 spin_lock(&ret->d_lock);
892 if (unlikely(ret != dentry->d_parent)) {
893 spin_unlock(&ret->d_lock);
898 BUG_ON(!ret->d_lockref.count);
899 ret->d_lockref.count++;
900 spin_unlock(&ret->d_lock);
903 EXPORT_SYMBOL(dget_parent);
905 static struct dentry * __d_find_any_alias(struct inode *inode)
907 struct dentry *alias;
909 if (hlist_empty(&inode->i_dentry))
911 alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
917 * d_find_any_alias - find any alias for a given inode
918 * @inode: inode to find an alias for
920 * If any aliases exist for the given inode, take and return a
921 * reference for one of them. If no aliases exist, return %NULL.
923 struct dentry *d_find_any_alias(struct inode *inode)
927 spin_lock(&inode->i_lock);
928 de = __d_find_any_alias(inode);
929 spin_unlock(&inode->i_lock);
932 EXPORT_SYMBOL(d_find_any_alias);
935 * d_find_alias - grab a hashed alias of inode
936 * @inode: inode in question
938 * If inode has a hashed alias, or is a directory and has any alias,
939 * acquire the reference to alias and return it. Otherwise return NULL.
940 * Notice that if inode is a directory there can be only one alias and
941 * it can be unhashed only if it has no children, or if it is the root
942 * of a filesystem, or if the directory was renamed and d_revalidate
943 * was the first vfs operation to notice.
945 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
946 * any other hashed alias over that one.
948 static struct dentry *__d_find_alias(struct inode *inode)
950 struct dentry *alias;
952 if (S_ISDIR(inode->i_mode))
953 return __d_find_any_alias(inode);
955 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
956 spin_lock(&alias->d_lock);
957 if (!d_unhashed(alias)) {
959 spin_unlock(&alias->d_lock);
962 spin_unlock(&alias->d_lock);
967 struct dentry *d_find_alias(struct inode *inode)
969 struct dentry *de = NULL;
971 if (!hlist_empty(&inode->i_dentry)) {
972 spin_lock(&inode->i_lock);
973 de = __d_find_alias(inode);
974 spin_unlock(&inode->i_lock);
978 EXPORT_SYMBOL(d_find_alias);
981 * Try to kill dentries associated with this inode.
982 * WARNING: you must own a reference to inode.
984 void d_prune_aliases(struct inode *inode)
986 struct dentry *dentry;
988 spin_lock(&inode->i_lock);
989 hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
990 spin_lock(&dentry->d_lock);
991 if (!dentry->d_lockref.count) {
992 struct dentry *parent = lock_parent(dentry);
993 if (likely(!dentry->d_lockref.count)) {
994 __dentry_kill(dentry);
999 spin_unlock(&parent->d_lock);
1001 spin_unlock(&dentry->d_lock);
1003 spin_unlock(&inode->i_lock);
1005 EXPORT_SYMBOL(d_prune_aliases);
1008 * Lock a dentry from shrink list.
1009 * Called under rcu_read_lock() and dentry->d_lock; the former
1010 * guarantees that nothing we access will be freed under us.
1011 * Note that dentry is *not* protected from concurrent dentry_kill(),
1014 * Return false if dentry has been disrupted or grabbed, leaving
1015 * the caller to kick it off-list. Otherwise, return true and have
1016 * that dentry's inode and parent both locked.
1018 static bool shrink_lock_dentry(struct dentry *dentry)
1020 struct inode *inode;
1021 struct dentry *parent;
1023 if (dentry->d_lockref.count)
1026 inode = dentry->d_inode;
1027 if (inode && unlikely(!spin_trylock(&inode->i_lock))) {
1028 spin_unlock(&dentry->d_lock);
1029 spin_lock(&inode->i_lock);
1030 spin_lock(&dentry->d_lock);
1031 if (unlikely(dentry->d_lockref.count))
1033 /* changed inode means that somebody had grabbed it */
1034 if (unlikely(inode != dentry->d_inode))
1038 parent = dentry->d_parent;
1039 if (IS_ROOT(dentry) || likely(spin_trylock(&parent->d_lock)))
1042 spin_unlock(&dentry->d_lock);
1043 spin_lock(&parent->d_lock);
1044 if (unlikely(parent != dentry->d_parent)) {
1045 spin_unlock(&parent->d_lock);
1046 spin_lock(&dentry->d_lock);
1049 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1050 if (likely(!dentry->d_lockref.count))
1052 spin_unlock(&parent->d_lock);
1055 spin_unlock(&inode->i_lock);
1059 static void shrink_dentry_list(struct list_head *list)
1061 while (!list_empty(list)) {
1062 struct dentry *dentry, *parent;
1064 dentry = list_entry(list->prev, struct dentry, d_lru);
1065 spin_lock(&dentry->d_lock);
1067 if (!shrink_lock_dentry(dentry)) {
1068 bool can_free = false;
1070 d_shrink_del(dentry);
1071 if (dentry->d_lockref.count < 0)
1072 can_free = dentry->d_flags & DCACHE_MAY_FREE;
1073 spin_unlock(&dentry->d_lock);
1075 dentry_free(dentry);
1079 d_shrink_del(dentry);
1080 parent = dentry->d_parent;
1081 __dentry_kill(dentry);
1082 if (parent == dentry)
1085 * We need to prune ancestors too. This is necessary to prevent
1086 * quadratic behavior of shrink_dcache_parent(), but is also
1087 * expected to be beneficial in reducing dentry cache
1091 while (dentry && !lockref_put_or_lock(&dentry->d_lockref))
1092 dentry = dentry_kill(dentry);
1096 static enum lru_status dentry_lru_isolate(struct list_head *item,
1097 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1099 struct list_head *freeable = arg;
1100 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1104 * we are inverting the lru lock/dentry->d_lock here,
1105 * so use a trylock. If we fail to get the lock, just skip
1108 if (!spin_trylock(&dentry->d_lock))
1112 * Referenced dentries are still in use. If they have active
1113 * counts, just remove them from the LRU. Otherwise give them
1114 * another pass through the LRU.
1116 if (dentry->d_lockref.count) {
1117 d_lru_isolate(lru, dentry);
1118 spin_unlock(&dentry->d_lock);
1122 if (dentry->d_flags & DCACHE_REFERENCED) {
1123 dentry->d_flags &= ~DCACHE_REFERENCED;
1124 spin_unlock(&dentry->d_lock);
1127 * The list move itself will be made by the common LRU code. At
1128 * this point, we've dropped the dentry->d_lock but keep the
1129 * lru lock. This is safe to do, since every list movement is
1130 * protected by the lru lock even if both locks are held.
1132 * This is guaranteed by the fact that all LRU management
1133 * functions are intermediated by the LRU API calls like
1134 * list_lru_add and list_lru_del. List movement in this file
1135 * only ever occur through this functions or through callbacks
1136 * like this one, that are called from the LRU API.
1138 * The only exceptions to this are functions like
1139 * shrink_dentry_list, and code that first checks for the
1140 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1141 * operating only with stack provided lists after they are
1142 * properly isolated from the main list. It is thus, always a
1148 d_lru_shrink_move(lru, dentry, freeable);
1149 spin_unlock(&dentry->d_lock);
1155 * prune_dcache_sb - shrink the dcache
1157 * @sc: shrink control, passed to list_lru_shrink_walk()
1159 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1160 * is done when we need more memory and called from the superblock shrinker
1163 * This function may fail to free any resources if all the dentries are in
1166 long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc)
1171 freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc,
1172 dentry_lru_isolate, &dispose);
1173 shrink_dentry_list(&dispose);
1177 static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
1178 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1180 struct list_head *freeable = arg;
1181 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1184 * we are inverting the lru lock/dentry->d_lock here,
1185 * so use a trylock. If we fail to get the lock, just skip
1188 if (!spin_trylock(&dentry->d_lock))
1191 d_lru_shrink_move(lru, dentry, freeable);
1192 spin_unlock(&dentry->d_lock);
1199 * shrink_dcache_sb - shrink dcache for a superblock
1202 * Shrink the dcache for the specified super block. This is used to free
1203 * the dcache before unmounting a file system.
1205 void shrink_dcache_sb(struct super_block *sb)
1210 list_lru_walk(&sb->s_dentry_lru,
1211 dentry_lru_isolate_shrink, &dispose, 1024);
1212 shrink_dentry_list(&dispose);
1213 } while (list_lru_count(&sb->s_dentry_lru) > 0);
1215 EXPORT_SYMBOL(shrink_dcache_sb);
1218 * enum d_walk_ret - action to talke during tree walk
1219 * @D_WALK_CONTINUE: contrinue walk
1220 * @D_WALK_QUIT: quit walk
1221 * @D_WALK_NORETRY: quit when retry is needed
1222 * @D_WALK_SKIP: skip this dentry and its children
1232 * d_walk - walk the dentry tree
1233 * @parent: start of walk
1234 * @data: data passed to @enter() and @finish()
1235 * @enter: callback when first entering the dentry
1237 * The @enter() callbacks are called with d_lock held.
1239 static void d_walk(struct dentry *parent, void *data,
1240 enum d_walk_ret (*enter)(void *, struct dentry *))
1242 struct dentry *this_parent;
1243 struct list_head *next;
1245 enum d_walk_ret ret;
1249 read_seqbegin_or_lock(&rename_lock, &seq);
1250 this_parent = parent;
1251 spin_lock(&this_parent->d_lock);
1253 ret = enter(data, this_parent);
1255 case D_WALK_CONTINUE:
1260 case D_WALK_NORETRY:
1265 next = this_parent->d_subdirs.next;
1267 while (next != &this_parent->d_subdirs) {
1268 struct list_head *tmp = next;
1269 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
1272 if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR))
1275 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1277 ret = enter(data, dentry);
1279 case D_WALK_CONTINUE:
1282 spin_unlock(&dentry->d_lock);
1284 case D_WALK_NORETRY:
1288 spin_unlock(&dentry->d_lock);
1292 if (!list_empty(&dentry->d_subdirs)) {
1293 spin_unlock(&this_parent->d_lock);
1294 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
1295 this_parent = dentry;
1296 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1299 spin_unlock(&dentry->d_lock);
1302 * All done at this level ... ascend and resume the search.
1306 if (this_parent != parent) {
1307 struct dentry *child = this_parent;
1308 this_parent = child->d_parent;
1310 spin_unlock(&child->d_lock);
1311 spin_lock(&this_parent->d_lock);
1313 /* might go back up the wrong parent if we have had a rename. */
1314 if (need_seqretry(&rename_lock, seq))
1316 /* go into the first sibling still alive */
1318 next = child->d_child.next;
1319 if (next == &this_parent->d_subdirs)
1321 child = list_entry(next, struct dentry, d_child);
1322 } while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
1326 if (need_seqretry(&rename_lock, seq))
1331 spin_unlock(&this_parent->d_lock);
1332 done_seqretry(&rename_lock, seq);
1336 spin_unlock(&this_parent->d_lock);
1345 struct check_mount {
1346 struct vfsmount *mnt;
1347 unsigned int mounted;
1350 static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry)
1352 struct check_mount *info = data;
1353 struct path path = { .mnt = info->mnt, .dentry = dentry };
1355 if (likely(!d_mountpoint(dentry)))
1356 return D_WALK_CONTINUE;
1357 if (__path_is_mountpoint(&path)) {
1361 return D_WALK_CONTINUE;
1365 * path_has_submounts - check for mounts over a dentry in the
1366 * current namespace.
1367 * @parent: path to check.
1369 * Return true if the parent or its subdirectories contain
1370 * a mount point in the current namespace.
1372 int path_has_submounts(const struct path *parent)
1374 struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
1376 read_seqlock_excl(&mount_lock);
1377 d_walk(parent->dentry, &data, path_check_mount);
1378 read_sequnlock_excl(&mount_lock);
1380 return data.mounted;
1382 EXPORT_SYMBOL(path_has_submounts);
1385 * Called by mount code to set a mountpoint and check if the mountpoint is
1386 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1387 * subtree can become unreachable).
1389 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1390 * this reason take rename_lock and d_lock on dentry and ancestors.
1392 int d_set_mounted(struct dentry *dentry)
1396 write_seqlock(&rename_lock);
1397 for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
1398 /* Need exclusion wrt. d_invalidate() */
1399 spin_lock(&p->d_lock);
1400 if (unlikely(d_unhashed(p))) {
1401 spin_unlock(&p->d_lock);
1404 spin_unlock(&p->d_lock);
1406 spin_lock(&dentry->d_lock);
1407 if (!d_unlinked(dentry)) {
1409 if (!d_mountpoint(dentry)) {
1410 dentry->d_flags |= DCACHE_MOUNTED;
1414 spin_unlock(&dentry->d_lock);
1416 write_sequnlock(&rename_lock);
1421 * Search the dentry child list of the specified parent,
1422 * and move any unused dentries to the end of the unused
1423 * list for prune_dcache(). We descend to the next level
1424 * whenever the d_subdirs list is non-empty and continue
1427 * It returns zero iff there are no unused children,
1428 * otherwise it returns the number of children moved to
1429 * the end of the unused list. This may not be the total
1430 * number of unused children, because select_parent can
1431 * drop the lock and return early due to latency
1435 struct select_data {
1436 struct dentry *start;
1437 struct list_head dispose;
1441 static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
1443 struct select_data *data = _data;
1444 enum d_walk_ret ret = D_WALK_CONTINUE;
1446 if (data->start == dentry)
1449 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1452 if (dentry->d_flags & DCACHE_LRU_LIST)
1454 if (!dentry->d_lockref.count) {
1455 d_shrink_add(dentry, &data->dispose);
1460 * We can return to the caller if we have found some (this
1461 * ensures forward progress). We'll be coming back to find
1464 if (!list_empty(&data->dispose))
1465 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1471 * shrink_dcache_parent - prune dcache
1472 * @parent: parent of entries to prune
1474 * Prune the dcache to remove unused children of the parent dentry.
1476 void shrink_dcache_parent(struct dentry *parent)
1479 struct select_data data;
1481 INIT_LIST_HEAD(&data.dispose);
1482 data.start = parent;
1485 d_walk(parent, &data, select_collect);
1487 if (!list_empty(&data.dispose)) {
1488 shrink_dentry_list(&data.dispose);
1497 EXPORT_SYMBOL(shrink_dcache_parent);
1499 static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
1501 /* it has busy descendents; complain about those instead */
1502 if (!list_empty(&dentry->d_subdirs))
1503 return D_WALK_CONTINUE;
1505 /* root with refcount 1 is fine */
1506 if (dentry == _data && dentry->d_lockref.count == 1)
1507 return D_WALK_CONTINUE;
1509 printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%pd} "
1510 " still in use (%d) [unmount of %s %s]\n",
1513 dentry->d_inode->i_ino : 0UL,
1515 dentry->d_lockref.count,
1516 dentry->d_sb->s_type->name,
1517 dentry->d_sb->s_id);
1519 return D_WALK_CONTINUE;
1522 static void do_one_tree(struct dentry *dentry)
1524 shrink_dcache_parent(dentry);
1525 d_walk(dentry, dentry, umount_check);
1531 * destroy the dentries attached to a superblock on unmounting
1533 void shrink_dcache_for_umount(struct super_block *sb)
1535 struct dentry *dentry;
1537 WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked");
1539 dentry = sb->s_root;
1541 do_one_tree(dentry);
1543 while (!hlist_bl_empty(&sb->s_roots)) {
1544 dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_roots), struct dentry, d_hash));
1545 do_one_tree(dentry);
1549 static enum d_walk_ret find_submount(void *_data, struct dentry *dentry)
1551 struct dentry **victim = _data;
1552 if (d_mountpoint(dentry)) {
1553 __dget_dlock(dentry);
1557 return D_WALK_CONTINUE;
1561 * d_invalidate - detach submounts, prune dcache, and drop
1562 * @dentry: dentry to invalidate (aka detach, prune and drop)
1564 void d_invalidate(struct dentry *dentry)
1566 bool had_submounts = false;
1567 spin_lock(&dentry->d_lock);
1568 if (d_unhashed(dentry)) {
1569 spin_unlock(&dentry->d_lock);
1573 spin_unlock(&dentry->d_lock);
1575 /* Negative dentries can be dropped without further checks */
1576 if (!dentry->d_inode)
1579 shrink_dcache_parent(dentry);
1581 struct dentry *victim = NULL;
1582 d_walk(dentry, &victim, find_submount);
1585 shrink_dcache_parent(dentry);
1588 had_submounts = true;
1589 detach_mounts(victim);
1593 EXPORT_SYMBOL(d_invalidate);
1596 * __d_alloc - allocate a dcache entry
1597 * @sb: filesystem it will belong to
1598 * @name: qstr of the name
1600 * Allocates a dentry. It returns %NULL if there is insufficient memory
1601 * available. On a success the dentry is returned. The name passed in is
1602 * copied and the copy passed in may be reused after this call.
1605 struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1607 struct external_name *ext = NULL;
1608 struct dentry *dentry;
1612 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
1617 * We guarantee that the inline name is always NUL-terminated.
1618 * This way the memcpy() done by the name switching in rename
1619 * will still always have a NUL at the end, even if we might
1620 * be overwriting an internal NUL character
1622 dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
1623 if (unlikely(!name)) {
1625 dname = dentry->d_iname;
1626 } else if (name->len > DNAME_INLINE_LEN-1) {
1627 size_t size = offsetof(struct external_name, name[1]);
1629 ext = kmalloc(size + name->len, GFP_KERNEL_ACCOUNT);
1631 kmem_cache_free(dentry_cache, dentry);
1634 atomic_set(&ext->u.count, 1);
1637 dname = dentry->d_iname;
1640 dentry->d_name.len = name->len;
1641 dentry->d_name.hash = name->hash;
1642 memcpy(dname, name->name, name->len);
1643 dname[name->len] = 0;
1645 /* Make sure we always see the terminating NUL character */
1646 smp_store_release(&dentry->d_name.name, dname); /* ^^^ */
1648 dentry->d_lockref.count = 1;
1649 dentry->d_flags = 0;
1650 spin_lock_init(&dentry->d_lock);
1651 seqcount_init(&dentry->d_seq);
1652 dentry->d_inode = NULL;
1653 dentry->d_parent = dentry;
1655 dentry->d_op = NULL;
1656 dentry->d_fsdata = NULL;
1657 INIT_HLIST_BL_NODE(&dentry->d_hash);
1658 INIT_LIST_HEAD(&dentry->d_lru);
1659 INIT_LIST_HEAD(&dentry->d_subdirs);
1660 INIT_HLIST_NODE(&dentry->d_u.d_alias);
1661 INIT_LIST_HEAD(&dentry->d_child);
1662 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1664 if (dentry->d_op && dentry->d_op->d_init) {
1665 err = dentry->d_op->d_init(dentry);
1667 if (dname_external(dentry))
1668 kfree(external_name(dentry));
1669 kmem_cache_free(dentry_cache, dentry);
1674 if (unlikely(ext)) {
1675 pg_data_t *pgdat = page_pgdat(virt_to_page(ext));
1676 mod_node_page_state(pgdat, NR_INDIRECTLY_RECLAIMABLE_BYTES,
1680 this_cpu_inc(nr_dentry);
1686 * d_alloc - allocate a dcache entry
1687 * @parent: parent of entry to allocate
1688 * @name: qstr of the name
1690 * Allocates a dentry. It returns %NULL if there is insufficient memory
1691 * available. On a success the dentry is returned. The name passed in is
1692 * copied and the copy passed in may be reused after this call.
1694 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1696 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1699 spin_lock(&parent->d_lock);
1701 * don't need child lock because it is not subject
1702 * to concurrency here
1704 __dget_dlock(parent);
1705 dentry->d_parent = parent;
1706 list_add(&dentry->d_child, &parent->d_subdirs);
1707 spin_unlock(&parent->d_lock);
1711 EXPORT_SYMBOL(d_alloc);
1713 struct dentry *d_alloc_anon(struct super_block *sb)
1715 return __d_alloc(sb, NULL);
1717 EXPORT_SYMBOL(d_alloc_anon);
1719 struct dentry *d_alloc_cursor(struct dentry * parent)
1721 struct dentry *dentry = d_alloc_anon(parent->d_sb);
1723 dentry->d_flags |= DCACHE_DENTRY_CURSOR;
1724 dentry->d_parent = dget(parent);
1730 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1731 * @sb: the superblock
1732 * @name: qstr of the name
1734 * For a filesystem that just pins its dentries in memory and never
1735 * performs lookups at all, return an unhashed IS_ROOT dentry.
1736 * This is used for pipes, sockets et.al. - the stuff that should
1737 * never be anyone's children or parents. Unlike all other
1738 * dentries, these will not have RCU delay between dropping the
1739 * last reference and freeing them.
1741 struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1743 struct dentry *dentry = __d_alloc(sb, name);
1745 dentry->d_flags |= DCACHE_NORCU;
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 * This should be equivalent to d_instantiate() + unlock_new_inode(),
1884 * with lockdep-related part of unlock_new_inode() done before
1885 * anything else. Use that instead of open-coding d_instantiate()/
1886 * unlock_new_inode() combinations.
1888 void d_instantiate_new(struct dentry *entry, struct inode *inode)
1890 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1892 lockdep_annotate_inode_mutex_key(inode);
1893 security_d_instantiate(entry, inode);
1894 spin_lock(&inode->i_lock);
1895 __d_instantiate(entry, inode);
1896 WARN_ON(!(inode->i_state & I_NEW));
1897 inode->i_state &= ~I_NEW & ~I_CREATING;
1899 wake_up_bit(&inode->i_state, __I_NEW);
1900 spin_unlock(&inode->i_lock);
1902 EXPORT_SYMBOL(d_instantiate_new);
1904 struct dentry *d_make_root(struct inode *root_inode)
1906 struct dentry *res = NULL;
1909 res = d_alloc_anon(root_inode->i_sb);
1911 d_instantiate(res, root_inode);
1917 EXPORT_SYMBOL(d_make_root);
1919 static struct dentry *__d_instantiate_anon(struct dentry *dentry,
1920 struct inode *inode,
1926 security_d_instantiate(dentry, inode);
1927 spin_lock(&inode->i_lock);
1928 res = __d_find_any_alias(inode);
1930 spin_unlock(&inode->i_lock);
1935 /* attach a disconnected dentry */
1936 add_flags = d_flags_for_inode(inode);
1939 add_flags |= DCACHE_DISCONNECTED;
1941 spin_lock(&dentry->d_lock);
1942 __d_set_inode_and_type(dentry, inode, add_flags);
1943 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
1944 if (!disconnected) {
1945 hlist_bl_lock(&dentry->d_sb->s_roots);
1946 hlist_bl_add_head(&dentry->d_hash, &dentry->d_sb->s_roots);
1947 hlist_bl_unlock(&dentry->d_sb->s_roots);
1949 spin_unlock(&dentry->d_lock);
1950 spin_unlock(&inode->i_lock);
1959 struct dentry *d_instantiate_anon(struct dentry *dentry, struct inode *inode)
1961 return __d_instantiate_anon(dentry, inode, true);
1963 EXPORT_SYMBOL(d_instantiate_anon);
1965 static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected)
1971 return ERR_PTR(-ESTALE);
1973 return ERR_CAST(inode);
1975 res = d_find_any_alias(inode);
1979 tmp = d_alloc_anon(inode->i_sb);
1981 res = ERR_PTR(-ENOMEM);
1985 return __d_instantiate_anon(tmp, inode, disconnected);
1993 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
1994 * @inode: inode to allocate the dentry for
1996 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1997 * similar open by handle operations. The returned dentry may be anonymous,
1998 * or may have a full name (if the inode was already in the cache).
2000 * When called on a directory inode, we must ensure that the inode only ever
2001 * has one dentry. If a dentry is found, that is returned instead of
2002 * allocating a new one.
2004 * On successful return, the reference to the inode has been transferred
2005 * to the dentry. In case of an error the reference on the inode is released.
2006 * To make it easier to use in export operations a %NULL or IS_ERR inode may
2007 * be passed in and the error will be propagated to the return value,
2008 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
2010 struct dentry *d_obtain_alias(struct inode *inode)
2012 return __d_obtain_alias(inode, true);
2014 EXPORT_SYMBOL(d_obtain_alias);
2017 * d_obtain_root - find or allocate a dentry for a given inode
2018 * @inode: inode to allocate the dentry for
2020 * Obtain an IS_ROOT dentry for the root of a filesystem.
2022 * We must ensure that directory inodes only ever have one dentry. If a
2023 * dentry is found, that is returned instead of allocating a new one.
2025 * On successful return, the reference to the inode has been transferred
2026 * to the dentry. In case of an error the reference on the inode is
2027 * released. A %NULL or IS_ERR inode may be passed in and will be the
2028 * error will be propagate to the return value, with a %NULL @inode
2029 * replaced by ERR_PTR(-ESTALE).
2031 struct dentry *d_obtain_root(struct inode *inode)
2033 return __d_obtain_alias(inode, false);
2035 EXPORT_SYMBOL(d_obtain_root);
2038 * d_add_ci - lookup or allocate new dentry with case-exact name
2039 * @inode: the inode case-insensitive lookup has found
2040 * @dentry: the negative dentry that was passed to the parent's lookup func
2041 * @name: the case-exact name to be associated with the returned dentry
2043 * This is to avoid filling the dcache with case-insensitive names to the
2044 * same inode, only the actual correct case is stored in the dcache for
2045 * case-insensitive filesystems.
2047 * For a case-insensitive lookup match and if the the case-exact dentry
2048 * already exists in in the dcache, use it and return it.
2050 * If no entry exists with the exact case name, allocate new dentry with
2051 * the exact case, and return the spliced entry.
2053 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
2056 struct dentry *found, *res;
2059 * First check if a dentry matching the name already exists,
2060 * if not go ahead and create it now.
2062 found = d_hash_and_lookup(dentry->d_parent, name);
2067 if (d_in_lookup(dentry)) {
2068 found = d_alloc_parallel(dentry->d_parent, name,
2070 if (IS_ERR(found) || !d_in_lookup(found)) {
2075 found = d_alloc(dentry->d_parent, name);
2078 return ERR_PTR(-ENOMEM);
2081 res = d_splice_alias(inode, found);
2088 EXPORT_SYMBOL(d_add_ci);
2091 static inline bool d_same_name(const struct dentry *dentry,
2092 const struct dentry *parent,
2093 const struct qstr *name)
2095 if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
2096 if (dentry->d_name.len != name->len)
2098 return dentry_cmp(dentry, name->name, name->len) == 0;
2100 return parent->d_op->d_compare(dentry,
2101 dentry->d_name.len, dentry->d_name.name,
2106 * __d_lookup_rcu - search for a dentry (racy, store-free)
2107 * @parent: parent dentry
2108 * @name: qstr of name we wish to find
2109 * @seqp: returns d_seq value at the point where the dentry was found
2110 * Returns: dentry, or NULL
2112 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2113 * resolution (store-free path walking) design described in
2114 * Documentation/filesystems/path-lookup.txt.
2116 * This is not to be used outside core vfs.
2118 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2119 * held, and rcu_read_lock held. The returned dentry must not be stored into
2120 * without taking d_lock and checking d_seq sequence count against @seq
2123 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2126 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2127 * the returned dentry, so long as its parent's seqlock is checked after the
2128 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2129 * is formed, giving integrity down the path walk.
2131 * NOTE! The caller *has* to check the resulting dentry against the sequence
2132 * number we've returned before using any of the resulting dentry state!
2134 struct dentry *__d_lookup_rcu(const struct dentry *parent,
2135 const struct qstr *name,
2138 u64 hashlen = name->hash_len;
2139 const unsigned char *str = name->name;
2140 struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
2141 struct hlist_bl_node *node;
2142 struct dentry *dentry;
2145 * Note: There is significant duplication with __d_lookup_rcu which is
2146 * required to prevent single threaded performance regressions
2147 * especially on architectures where smp_rmb (in seqcounts) are costly.
2148 * Keep the two functions in sync.
2152 * The hash list is protected using RCU.
2154 * Carefully use d_seq when comparing a candidate dentry, to avoid
2155 * races with d_move().
2157 * It is possible that concurrent renames can mess up our list
2158 * walk here and result in missing our dentry, resulting in the
2159 * false-negative result. d_lookup() protects against concurrent
2160 * renames using rename_lock seqlock.
2162 * See Documentation/filesystems/path-lookup.txt for more details.
2164 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2169 * The dentry sequence count protects us from concurrent
2170 * renames, and thus protects parent and name fields.
2172 * The caller must perform a seqcount check in order
2173 * to do anything useful with the returned dentry.
2175 * NOTE! We do a "raw" seqcount_begin here. That means that
2176 * we don't wait for the sequence count to stabilize if it
2177 * is in the middle of a sequence change. If we do the slow
2178 * dentry compare, we will do seqretries until it is stable,
2179 * and if we end up with a successful lookup, we actually
2180 * want to exit RCU lookup anyway.
2182 * Note that raw_seqcount_begin still *does* smp_rmb(), so
2183 * we are still guaranteed NUL-termination of ->d_name.name.
2185 seq = raw_seqcount_begin(&dentry->d_seq);
2186 if (dentry->d_parent != parent)
2188 if (d_unhashed(dentry))
2191 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
2194 if (dentry->d_name.hash != hashlen_hash(hashlen))
2196 tlen = dentry->d_name.len;
2197 tname = dentry->d_name.name;
2198 /* we want a consistent (name,len) pair */
2199 if (read_seqcount_retry(&dentry->d_seq, seq)) {
2203 if (parent->d_op->d_compare(dentry,
2204 tlen, tname, name) != 0)
2207 if (dentry->d_name.hash_len != hashlen)
2209 if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
2219 * d_lookup - search for a dentry
2220 * @parent: parent dentry
2221 * @name: qstr of name we wish to find
2222 * Returns: dentry, or NULL
2224 * d_lookup searches the children of the parent dentry for the name in
2225 * question. If the dentry is found its reference count is incremented and the
2226 * dentry is returned. The caller must use dput to free the entry when it has
2227 * finished using it. %NULL is returned if the dentry does not exist.
2229 struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
2231 struct dentry *dentry;
2235 seq = read_seqbegin(&rename_lock);
2236 dentry = __d_lookup(parent, name);
2239 } while (read_seqretry(&rename_lock, seq));
2242 EXPORT_SYMBOL(d_lookup);
2245 * __d_lookup - search for a dentry (racy)
2246 * @parent: parent dentry
2247 * @name: qstr of name we wish to find
2248 * Returns: dentry, or NULL
2250 * __d_lookup is like d_lookup, however it may (rarely) return a
2251 * false-negative result due to unrelated rename activity.
2253 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2254 * however it must be used carefully, eg. with a following d_lookup in
2255 * the case of failure.
2257 * __d_lookup callers must be commented.
2259 struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
2261 unsigned int hash = name->hash;
2262 struct hlist_bl_head *b = d_hash(hash);
2263 struct hlist_bl_node *node;
2264 struct dentry *found = NULL;
2265 struct dentry *dentry;
2268 * Note: There is significant duplication with __d_lookup_rcu which is
2269 * required to prevent single threaded performance regressions
2270 * especially on architectures where smp_rmb (in seqcounts) are costly.
2271 * Keep the two functions in sync.
2275 * The hash list is protected using RCU.
2277 * Take d_lock when comparing a candidate dentry, to avoid races
2280 * It is possible that concurrent renames can mess up our list
2281 * walk here and result in missing our dentry, resulting in the
2282 * false-negative result. d_lookup() protects against concurrent
2283 * renames using rename_lock seqlock.
2285 * See Documentation/filesystems/path-lookup.txt for more details.
2289 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2291 if (dentry->d_name.hash != hash)
2294 spin_lock(&dentry->d_lock);
2295 if (dentry->d_parent != parent)
2297 if (d_unhashed(dentry))
2300 if (!d_same_name(dentry, parent, name))
2303 dentry->d_lockref.count++;
2305 spin_unlock(&dentry->d_lock);
2308 spin_unlock(&dentry->d_lock);
2316 * d_hash_and_lookup - hash the qstr then search for a dentry
2317 * @dir: Directory to search in
2318 * @name: qstr of name we wish to find
2320 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2322 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2325 * Check for a fs-specific hash function. Note that we must
2326 * calculate the standard hash first, as the d_op->d_hash()
2327 * routine may choose to leave the hash value unchanged.
2329 name->hash = full_name_hash(dir, name->name, name->len);
2330 if (dir->d_flags & DCACHE_OP_HASH) {
2331 int err = dir->d_op->d_hash(dir, name);
2332 if (unlikely(err < 0))
2333 return ERR_PTR(err);
2335 return d_lookup(dir, name);
2337 EXPORT_SYMBOL(d_hash_and_lookup);
2340 * When a file is deleted, we have two options:
2341 * - turn this dentry into a negative dentry
2342 * - unhash this dentry and free it.
2344 * Usually, we want to just turn this into
2345 * a negative dentry, but if anybody else is
2346 * currently using the dentry or the inode
2347 * we can't do that and we fall back on removing
2348 * it from the hash queues and waiting for
2349 * it to be deleted later when it has no users
2353 * d_delete - delete a dentry
2354 * @dentry: The dentry to delete
2356 * Turn the dentry into a negative dentry if possible, otherwise
2357 * remove it from the hash queues so it can be deleted later
2360 void d_delete(struct dentry * dentry)
2362 struct inode *inode = dentry->d_inode;
2363 int isdir = d_is_dir(dentry);
2365 spin_lock(&inode->i_lock);
2366 spin_lock(&dentry->d_lock);
2368 * Are we the only user?
2370 if (dentry->d_lockref.count == 1) {
2371 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2372 dentry_unlink_inode(dentry);
2375 spin_unlock(&dentry->d_lock);
2376 spin_unlock(&inode->i_lock);
2378 fsnotify_nameremove(dentry, isdir);
2380 EXPORT_SYMBOL(d_delete);
2382 static void __d_rehash(struct dentry *entry)
2384 struct hlist_bl_head *b = d_hash(entry->d_name.hash);
2387 hlist_bl_add_head_rcu(&entry->d_hash, b);
2392 * d_rehash - add an entry back to the hash
2393 * @entry: dentry to add to the hash
2395 * Adds a dentry to the hash according to its name.
2398 void d_rehash(struct dentry * entry)
2400 spin_lock(&entry->d_lock);
2402 spin_unlock(&entry->d_lock);
2404 EXPORT_SYMBOL(d_rehash);
2406 static inline unsigned start_dir_add(struct inode *dir)
2410 unsigned n = dir->i_dir_seq;
2411 if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
2417 static inline void end_dir_add(struct inode *dir, unsigned n)
2419 smp_store_release(&dir->i_dir_seq, n + 2);
2422 static void d_wait_lookup(struct dentry *dentry)
2424 if (d_in_lookup(dentry)) {
2425 DECLARE_WAITQUEUE(wait, current);
2426 add_wait_queue(dentry->d_wait, &wait);
2428 set_current_state(TASK_UNINTERRUPTIBLE);
2429 spin_unlock(&dentry->d_lock);
2431 spin_lock(&dentry->d_lock);
2432 } while (d_in_lookup(dentry));
2436 struct dentry *d_alloc_parallel(struct dentry *parent,
2437 const struct qstr *name,
2438 wait_queue_head_t *wq)
2440 unsigned int hash = name->hash;
2441 struct hlist_bl_head *b = in_lookup_hash(parent, hash);
2442 struct hlist_bl_node *node;
2443 struct dentry *new = d_alloc(parent, name);
2444 struct dentry *dentry;
2445 unsigned seq, r_seq, d_seq;
2448 return ERR_PTR(-ENOMEM);
2452 seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
2453 r_seq = read_seqbegin(&rename_lock);
2454 dentry = __d_lookup_rcu(parent, name, &d_seq);
2455 if (unlikely(dentry)) {
2456 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2460 if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
2469 if (unlikely(read_seqretry(&rename_lock, r_seq))) {
2474 if (unlikely(seq & 1)) {
2480 if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
2486 * No changes for the parent since the beginning of d_lookup().
2487 * Since all removals from the chain happen with hlist_bl_lock(),
2488 * any potential in-lookup matches are going to stay here until
2489 * we unlock the chain. All fields are stable in everything
2492 hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
2493 if (dentry->d_name.hash != hash)
2495 if (dentry->d_parent != parent)
2497 if (!d_same_name(dentry, parent, name))
2500 /* now we can try to grab a reference */
2501 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2508 * somebody is likely to be still doing lookup for it;
2509 * wait for them to finish
2511 spin_lock(&dentry->d_lock);
2512 d_wait_lookup(dentry);
2514 * it's not in-lookup anymore; in principle we should repeat
2515 * everything from dcache lookup, but it's likely to be what
2516 * d_lookup() would've found anyway. If it is, just return it;
2517 * otherwise we really have to repeat the whole thing.
2519 if (unlikely(dentry->d_name.hash != hash))
2521 if (unlikely(dentry->d_parent != parent))
2523 if (unlikely(d_unhashed(dentry)))
2525 if (unlikely(!d_same_name(dentry, parent, name)))
2527 /* OK, it *is* a hashed match; return it */
2528 spin_unlock(&dentry->d_lock);
2533 /* we can't take ->d_lock here; it's OK, though. */
2534 new->d_flags |= DCACHE_PAR_LOOKUP;
2536 hlist_bl_add_head_rcu(&new->d_u.d_in_lookup_hash, b);
2540 spin_unlock(&dentry->d_lock);
2544 EXPORT_SYMBOL(d_alloc_parallel);
2546 void __d_lookup_done(struct dentry *dentry)
2548 struct hlist_bl_head *b = in_lookup_hash(dentry->d_parent,
2549 dentry->d_name.hash);
2551 dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
2552 __hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
2553 wake_up_all(dentry->d_wait);
2554 dentry->d_wait = NULL;
2556 INIT_HLIST_NODE(&dentry->d_u.d_alias);
2557 INIT_LIST_HEAD(&dentry->d_lru);
2559 EXPORT_SYMBOL(__d_lookup_done);
2561 /* inode->i_lock held if inode is non-NULL */
2563 static inline void __d_add(struct dentry *dentry, struct inode *inode)
2565 struct inode *dir = NULL;
2567 spin_lock(&dentry->d_lock);
2568 if (unlikely(d_in_lookup(dentry))) {
2569 dir = dentry->d_parent->d_inode;
2570 n = start_dir_add(dir);
2571 __d_lookup_done(dentry);
2574 unsigned add_flags = d_flags_for_inode(inode);
2575 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2576 raw_write_seqcount_begin(&dentry->d_seq);
2577 __d_set_inode_and_type(dentry, inode, add_flags);
2578 raw_write_seqcount_end(&dentry->d_seq);
2579 fsnotify_update_flags(dentry);
2583 end_dir_add(dir, n);
2584 spin_unlock(&dentry->d_lock);
2586 spin_unlock(&inode->i_lock);
2590 * d_add - add dentry to hash queues
2591 * @entry: dentry to add
2592 * @inode: The inode to attach to this dentry
2594 * This adds the entry to the hash queues and initializes @inode.
2595 * The entry was actually filled in earlier during d_alloc().
2598 void d_add(struct dentry *entry, struct inode *inode)
2601 security_d_instantiate(entry, inode);
2602 spin_lock(&inode->i_lock);
2604 __d_add(entry, inode);
2606 EXPORT_SYMBOL(d_add);
2609 * d_exact_alias - find and hash an exact unhashed alias
2610 * @entry: dentry to add
2611 * @inode: The inode to go with this dentry
2613 * If an unhashed dentry with the same name/parent and desired
2614 * inode already exists, hash and return it. Otherwise, return
2617 * Parent directory should be locked.
2619 struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
2621 struct dentry *alias;
2622 unsigned int hash = entry->d_name.hash;
2624 spin_lock(&inode->i_lock);
2625 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
2627 * Don't need alias->d_lock here, because aliases with
2628 * d_parent == entry->d_parent are not subject to name or
2629 * parent changes, because the parent inode i_mutex is held.
2631 if (alias->d_name.hash != hash)
2633 if (alias->d_parent != entry->d_parent)
2635 if (!d_same_name(alias, entry->d_parent, &entry->d_name))
2637 spin_lock(&alias->d_lock);
2638 if (!d_unhashed(alias)) {
2639 spin_unlock(&alias->d_lock);
2642 __dget_dlock(alias);
2644 spin_unlock(&alias->d_lock);
2646 spin_unlock(&inode->i_lock);
2649 spin_unlock(&inode->i_lock);
2652 EXPORT_SYMBOL(d_exact_alias);
2654 static void swap_names(struct dentry *dentry, struct dentry *target)
2656 if (unlikely(dname_external(target))) {
2657 if (unlikely(dname_external(dentry))) {
2659 * Both external: swap the pointers
2661 swap(target->d_name.name, dentry->d_name.name);
2664 * dentry:internal, target:external. Steal target's
2665 * storage and make target internal.
2667 memcpy(target->d_iname, dentry->d_name.name,
2668 dentry->d_name.len + 1);
2669 dentry->d_name.name = target->d_name.name;
2670 target->d_name.name = target->d_iname;
2673 if (unlikely(dname_external(dentry))) {
2675 * dentry:external, target:internal. Give dentry's
2676 * storage to target and make dentry internal
2678 memcpy(dentry->d_iname, target->d_name.name,
2679 target->d_name.len + 1);
2680 target->d_name.name = dentry->d_name.name;
2681 dentry->d_name.name = dentry->d_iname;
2684 * Both are internal.
2687 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
2688 for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
2689 swap(((long *) &dentry->d_iname)[i],
2690 ((long *) &target->d_iname)[i]);
2694 swap(dentry->d_name.hash_len, target->d_name.hash_len);
2697 static void copy_name(struct dentry *dentry, struct dentry *target)
2699 struct external_name *old_name = NULL;
2700 if (unlikely(dname_external(dentry)))
2701 old_name = external_name(dentry);
2702 if (unlikely(dname_external(target))) {
2703 atomic_inc(&external_name(target)->u.count);
2704 dentry->d_name = target->d_name;
2706 memcpy(dentry->d_iname, target->d_name.name,
2707 target->d_name.len + 1);
2708 dentry->d_name.name = dentry->d_iname;
2709 dentry->d_name.hash_len = target->d_name.hash_len;
2711 if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
2712 call_rcu(&old_name->u.head, __d_free_external_name);
2716 * When d_splice_alias() moves a directory's encrypted alias to its decrypted
2717 * alias as a result of the encryption key being added, DCACHE_ENCRYPTED_NAME
2718 * must be cleared. Note that we don't have to support arbitrary moves of this
2719 * flag because fscrypt doesn't allow encrypted aliases to be the source or
2720 * target of a rename().
2722 static inline void fscrypt_handle_d_move(struct dentry *dentry)
2724 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
2725 dentry->d_flags &= ~DCACHE_ENCRYPTED_NAME;
2730 * __d_move - move a dentry
2731 * @dentry: entry to move
2732 * @target: new dentry
2733 * @exchange: exchange the two dentries
2735 * Update the dcache to reflect the move of a file name. Negative
2736 * dcache entries should not be moved in this way. Caller must hold
2737 * rename_lock, the i_mutex of the source and target directories,
2738 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2740 static void __d_move(struct dentry *dentry, struct dentry *target,
2743 struct dentry *old_parent, *p;
2744 struct inode *dir = NULL;
2747 WARN_ON(!dentry->d_inode);
2748 if (WARN_ON(dentry == target))
2751 BUG_ON(d_ancestor(target, dentry));
2752 old_parent = dentry->d_parent;
2753 p = d_ancestor(old_parent, target);
2754 if (IS_ROOT(dentry)) {
2756 spin_lock(&target->d_parent->d_lock);
2758 /* target is not a descendent of dentry->d_parent */
2759 spin_lock(&target->d_parent->d_lock);
2760 spin_lock_nested(&old_parent->d_lock, DENTRY_D_LOCK_NESTED);
2762 BUG_ON(p == dentry);
2763 spin_lock(&old_parent->d_lock);
2765 spin_lock_nested(&target->d_parent->d_lock,
2766 DENTRY_D_LOCK_NESTED);
2768 spin_lock_nested(&dentry->d_lock, 2);
2769 spin_lock_nested(&target->d_lock, 3);
2771 if (unlikely(d_in_lookup(target))) {
2772 dir = target->d_parent->d_inode;
2773 n = start_dir_add(dir);
2774 __d_lookup_done(target);
2777 write_seqcount_begin(&dentry->d_seq);
2778 write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
2781 if (!d_unhashed(dentry))
2783 if (!d_unhashed(target))
2786 /* ... and switch them in the tree */
2787 dentry->d_parent = target->d_parent;
2789 copy_name(dentry, target);
2790 target->d_hash.pprev = NULL;
2791 dentry->d_parent->d_lockref.count++;
2792 if (dentry != old_parent) /* wasn't IS_ROOT */
2793 WARN_ON(!--old_parent->d_lockref.count);
2795 target->d_parent = old_parent;
2796 swap_names(dentry, target);
2797 list_move(&target->d_child, &target->d_parent->d_subdirs);
2799 fsnotify_update_flags(target);
2801 list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
2803 fsnotify_update_flags(dentry);
2804 fscrypt_handle_d_move(dentry);
2806 write_seqcount_end(&target->d_seq);
2807 write_seqcount_end(&dentry->d_seq);
2810 end_dir_add(dir, n);
2812 if (dentry->d_parent != old_parent)
2813 spin_unlock(&dentry->d_parent->d_lock);
2814 if (dentry != old_parent)
2815 spin_unlock(&old_parent->d_lock);
2816 spin_unlock(&target->d_lock);
2817 spin_unlock(&dentry->d_lock);
2821 * d_move - move a dentry
2822 * @dentry: entry to move
2823 * @target: new dentry
2825 * Update the dcache to reflect the move of a file name. Negative
2826 * dcache entries should not be moved in this way. See the locking
2827 * requirements for __d_move.
2829 void d_move(struct dentry *dentry, struct dentry *target)
2831 write_seqlock(&rename_lock);
2832 __d_move(dentry, target, false);
2833 write_sequnlock(&rename_lock);
2835 EXPORT_SYMBOL(d_move);
2838 * d_exchange - exchange two dentries
2839 * @dentry1: first dentry
2840 * @dentry2: second dentry
2842 void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
2844 write_seqlock(&rename_lock);
2846 WARN_ON(!dentry1->d_inode);
2847 WARN_ON(!dentry2->d_inode);
2848 WARN_ON(IS_ROOT(dentry1));
2849 WARN_ON(IS_ROOT(dentry2));
2851 __d_move(dentry1, dentry2, true);
2853 write_sequnlock(&rename_lock);
2857 * d_ancestor - search for an ancestor
2858 * @p1: ancestor dentry
2861 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2862 * an ancestor of p2, else NULL.
2864 struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2868 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2869 if (p->d_parent == p1)
2876 * This helper attempts to cope with remotely renamed directories
2878 * It assumes that the caller is already holding
2879 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2881 * Note: If ever the locking in lock_rename() changes, then please
2882 * remember to update this too...
2884 static int __d_unalias(struct inode *inode,
2885 struct dentry *dentry, struct dentry *alias)
2887 struct mutex *m1 = NULL;
2888 struct rw_semaphore *m2 = NULL;
2891 /* If alias and dentry share a parent, then no extra locks required */
2892 if (alias->d_parent == dentry->d_parent)
2895 /* See lock_rename() */
2896 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
2898 m1 = &dentry->d_sb->s_vfs_rename_mutex;
2899 if (!inode_trylock_shared(alias->d_parent->d_inode))
2901 m2 = &alias->d_parent->d_inode->i_rwsem;
2903 __d_move(alias, dentry, false);
2914 * d_splice_alias - splice a disconnected dentry into the tree if one exists
2915 * @inode: the inode which may have a disconnected dentry
2916 * @dentry: a negative dentry which we want to point to the inode.
2918 * If inode is a directory and has an IS_ROOT alias, then d_move that in
2919 * place of the given dentry and return it, else simply d_add the inode
2920 * to the dentry and return NULL.
2922 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
2923 * we should error out: directories can't have multiple aliases.
2925 * This is needed in the lookup routine of any filesystem that is exportable
2926 * (via knfsd) so that we can build dcache paths to directories effectively.
2928 * If a dentry was found and moved, then it is returned. Otherwise NULL
2929 * is returned. This matches the expected return value of ->lookup.
2931 * Cluster filesystems may call this function with a negative, hashed dentry.
2932 * In that case, we know that the inode will be a regular file, and also this
2933 * will only occur during atomic_open. So we need to check for the dentry
2934 * being already hashed only in the final case.
2936 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
2939 return ERR_CAST(inode);
2941 BUG_ON(!d_unhashed(dentry));
2946 security_d_instantiate(dentry, inode);
2947 spin_lock(&inode->i_lock);
2948 if (S_ISDIR(inode->i_mode)) {
2949 struct dentry *new = __d_find_any_alias(inode);
2950 if (unlikely(new)) {
2951 /* The reference to new ensures it remains an alias */
2952 spin_unlock(&inode->i_lock);
2953 write_seqlock(&rename_lock);
2954 if (unlikely(d_ancestor(new, dentry))) {
2955 write_sequnlock(&rename_lock);
2957 new = ERR_PTR(-ELOOP);
2958 pr_warn_ratelimited(
2959 "VFS: Lookup of '%s' in %s %s"
2960 " would have caused loop\n",
2961 dentry->d_name.name,
2962 inode->i_sb->s_type->name,
2964 } else if (!IS_ROOT(new)) {
2965 struct dentry *old_parent = dget(new->d_parent);
2966 int err = __d_unalias(inode, dentry, new);
2967 write_sequnlock(&rename_lock);
2974 __d_move(new, dentry, false);
2975 write_sequnlock(&rename_lock);
2982 __d_add(dentry, inode);
2985 EXPORT_SYMBOL(d_splice_alias);
2988 * Test whether new_dentry is a subdirectory of old_dentry.
2990 * Trivially implemented using the dcache structure
2994 * is_subdir - is new dentry a subdirectory of old_dentry
2995 * @new_dentry: new dentry
2996 * @old_dentry: old dentry
2998 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
2999 * Returns false otherwise.
3000 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3003 bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
3008 if (new_dentry == old_dentry)
3012 /* for restarting inner loop in case of seq retry */
3013 seq = read_seqbegin(&rename_lock);
3015 * Need rcu_readlock to protect against the d_parent trashing
3019 if (d_ancestor(old_dentry, new_dentry))
3024 } while (read_seqretry(&rename_lock, seq));
3028 EXPORT_SYMBOL(is_subdir);
3030 static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
3032 struct dentry *root = data;
3033 if (dentry != root) {
3034 if (d_unhashed(dentry) || !dentry->d_inode)
3037 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
3038 dentry->d_flags |= DCACHE_GENOCIDE;
3039 dentry->d_lockref.count--;
3042 return D_WALK_CONTINUE;
3045 void d_genocide(struct dentry *parent)
3047 d_walk(parent, parent, d_genocide_kill);
3050 EXPORT_SYMBOL(d_genocide);
3052 void d_tmpfile(struct dentry *dentry, struct inode *inode)
3054 inode_dec_link_count(inode);
3055 BUG_ON(dentry->d_name.name != dentry->d_iname ||
3056 !hlist_unhashed(&dentry->d_u.d_alias) ||
3057 !d_unlinked(dentry));
3058 spin_lock(&dentry->d_parent->d_lock);
3059 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
3060 dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
3061 (unsigned long long)inode->i_ino);
3062 spin_unlock(&dentry->d_lock);
3063 spin_unlock(&dentry->d_parent->d_lock);
3064 d_instantiate(dentry, inode);
3066 EXPORT_SYMBOL(d_tmpfile);
3068 static __initdata unsigned long dhash_entries;
3069 static int __init set_dhash_entries(char *str)
3073 dhash_entries = simple_strtoul(str, &str, 0);
3076 __setup("dhash_entries=", set_dhash_entries);
3078 static void __init dcache_init_early(void)
3080 /* If hashes are distributed across NUMA nodes, defer
3081 * hash allocation until vmalloc space is available.
3087 alloc_large_system_hash("Dentry cache",
3088 sizeof(struct hlist_bl_head),
3091 HASH_EARLY | HASH_ZERO,
3096 d_hash_shift = 32 - d_hash_shift;
3099 static void __init dcache_init(void)
3102 * A constructor could be added for stable state like the lists,
3103 * but it is probably not worth it because of the cache nature
3106 dentry_cache = KMEM_CACHE_USERCOPY(dentry,
3107 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT,
3110 /* Hash may have been set up in dcache_init_early */
3115 alloc_large_system_hash("Dentry cache",
3116 sizeof(struct hlist_bl_head),
3124 d_hash_shift = 32 - d_hash_shift;
3127 /* SLAB cache for __getname() consumers */
3128 struct kmem_cache *names_cachep __read_mostly;
3129 EXPORT_SYMBOL(names_cachep);
3131 void __init vfs_caches_init_early(void)
3135 for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++)
3136 INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]);
3138 dcache_init_early();
3142 void __init vfs_caches_init(void)
3144 names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0,
3145 SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL);
3150 files_maxfiles_init();