4 * Complete reimplementation
5 * (C) 1997 Thomas Schoebel-Theuer,
6 * with heavy changes by Linus Torvalds
10 * Notes on the allocation strategy:
12 * The dcache is a master of the icache - whenever a dcache entry
13 * exists, the inode will always exist. "iput()" is done either when
14 * the dcache entry is deleted or garbage collected.
17 #include <linux/syscalls.h>
18 #include <linux/string.h>
21 #include <linux/fsnotify.h>
22 #include <linux/slab.h>
23 #include <linux/init.h>
24 #include <linux/hash.h>
25 #include <linux/cache.h>
26 #include <linux/export.h>
27 #include <linux/mount.h>
28 #include <linux/file.h>
29 #include <linux/uaccess.h>
30 #include <linux/security.h>
31 #include <linux/seqlock.h>
32 #include <linux/swap.h>
33 #include <linux/bootmem.h>
34 #include <linux/fs_struct.h>
35 #include <linux/hardirq.h>
36 #include <linux/bit_spinlock.h>
37 #include <linux/rculist_bl.h>
38 #include <linux/prefetch.h>
39 #include <linux/ratelimit.h>
40 #include <linux/list_lru.h>
41 #include <linux/kasan.h>
48 * dcache->d_inode->i_lock protects:
49 * - i_dentry, d_u.d_alias, d_inode of aliases
50 * dcache_hash_bucket lock protects:
51 * - the dcache hash table
52 * s_anon bl list spinlock protects:
53 * - the s_anon list (see __d_drop)
54 * dentry->d_sb->s_dentry_lru_lock protects:
55 * - the dcache lru lists and counters
62 * - d_parent and d_subdirs
63 * - childrens' d_child and d_parent
64 * - d_u.d_alias, d_inode
67 * dentry->d_inode->i_lock
69 * dentry->d_sb->s_dentry_lru_lock
70 * dcache_hash_bucket lock
73 * If there is an ancestor relationship:
74 * dentry->d_parent->...->d_parent->d_lock
76 * dentry->d_parent->d_lock
79 * If no ancestor relationship:
80 * if (dentry1 < dentry2)
84 int sysctl_vfs_cache_pressure __read_mostly = 100;
85 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
87 __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
89 EXPORT_SYMBOL(rename_lock);
91 static struct kmem_cache *dentry_cache __read_mostly;
94 * This is the single most critical data structure when it comes
95 * to the dcache: the hashtable for lookups. Somebody should try
96 * to make this good - I've just made it work.
98 * This hash-function tries to avoid losing too many bits of hash
99 * information, yet avoid using a prime hash-size or similar.
102 static unsigned int d_hash_mask __read_mostly;
103 static unsigned int d_hash_shift __read_mostly;
105 static struct hlist_bl_head *dentry_hashtable __read_mostly;
107 static inline struct hlist_bl_head *d_hash(unsigned int hash)
109 return dentry_hashtable + (hash >> (32 - d_hash_shift));
112 #define IN_LOOKUP_SHIFT 10
113 static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT];
115 static inline struct hlist_bl_head *in_lookup_hash(const struct dentry *parent,
118 hash += (unsigned long) parent / L1_CACHE_BYTES;
119 return in_lookup_hashtable + hash_32(hash, IN_LOOKUP_SHIFT);
123 /* Statistics gathering. */
124 struct dentry_stat_t dentry_stat = {
128 static DEFINE_PER_CPU(long, nr_dentry);
129 static DEFINE_PER_CPU(long, nr_dentry_unused);
131 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
134 * Here we resort to our own counters instead of using generic per-cpu counters
135 * for consistency with what the vfs inode code does. We are expected to harvest
136 * better code and performance by having our own specialized counters.
138 * Please note that the loop is done over all possible CPUs, not over all online
139 * CPUs. The reason for this is that we don't want to play games with CPUs going
140 * on and off. If one of them goes off, we will just keep their counters.
142 * glommer: See cffbc8a for details, and if you ever intend to change this,
143 * please update all vfs counters to match.
145 static long get_nr_dentry(void)
149 for_each_possible_cpu(i)
150 sum += per_cpu(nr_dentry, i);
151 return sum < 0 ? 0 : sum;
154 static long get_nr_dentry_unused(void)
158 for_each_possible_cpu(i)
159 sum += per_cpu(nr_dentry_unused, i);
160 return sum < 0 ? 0 : sum;
163 int proc_nr_dentry(struct ctl_table *table, int write, void __user *buffer,
164 size_t *lenp, loff_t *ppos)
166 dentry_stat.nr_dentry = get_nr_dentry();
167 dentry_stat.nr_unused = get_nr_dentry_unused();
168 return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
173 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
174 * The strings are both count bytes long, and count is non-zero.
176 #ifdef CONFIG_DCACHE_WORD_ACCESS
178 #include <asm/word-at-a-time.h>
180 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
181 * aligned allocation for this particular component. We don't
182 * strictly need the load_unaligned_zeropad() safety, but it
183 * doesn't hurt either.
185 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
186 * need the careful unaligned handling.
188 static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
190 unsigned long a,b,mask;
193 a = *(unsigned long *)cs;
194 b = load_unaligned_zeropad(ct);
195 if (tcount < sizeof(unsigned long))
197 if (unlikely(a != b))
199 cs += sizeof(unsigned long);
200 ct += sizeof(unsigned long);
201 tcount -= sizeof(unsigned long);
205 mask = bytemask_from_count(tcount);
206 return unlikely(!!((a ^ b) & mask));
211 static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
225 static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
228 * Be careful about RCU walk racing with rename:
229 * use 'lockless_dereference' to fetch the name pointer.
231 * NOTE! Even if a rename will mean that the length
232 * was not loaded atomically, we don't care. The
233 * RCU walk will check the sequence count eventually,
234 * and catch it. And we won't overrun the buffer,
235 * because we're reading the name pointer atomically,
236 * and a dentry name is guaranteed to be properly
237 * terminated with a NUL byte.
239 * End result: even if 'len' is wrong, we'll exit
240 * early because the data cannot match (there can
241 * be no NUL in the ct/tcount data)
243 const unsigned char *cs = lockless_dereference(dentry->d_name.name);
245 return dentry_string_cmp(cs, ct, tcount);
248 struct external_name {
251 struct rcu_head head;
253 unsigned char name[];
256 static inline struct external_name *external_name(struct dentry *dentry)
258 return container_of(dentry->d_name.name, struct external_name, name[0]);
261 static void __d_free(struct rcu_head *head)
263 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
265 kmem_cache_free(dentry_cache, dentry);
268 static void __d_free_external(struct rcu_head *head)
270 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
271 kfree(external_name(dentry));
272 kmem_cache_free(dentry_cache, dentry);
275 static inline int dname_external(const struct dentry *dentry)
277 return dentry->d_name.name != dentry->d_iname;
280 void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry)
282 spin_lock(&dentry->d_lock);
283 if (unlikely(dname_external(dentry))) {
284 struct external_name *p = external_name(dentry);
285 atomic_inc(&p->u.count);
286 spin_unlock(&dentry->d_lock);
287 name->name = p->name;
289 memcpy(name->inline_name, dentry->d_iname, DNAME_INLINE_LEN);
290 spin_unlock(&dentry->d_lock);
291 name->name = name->inline_name;
294 EXPORT_SYMBOL(take_dentry_name_snapshot);
296 void release_dentry_name_snapshot(struct name_snapshot *name)
298 if (unlikely(name->name != name->inline_name)) {
299 struct external_name *p;
300 p = container_of(name->name, struct external_name, name[0]);
301 if (unlikely(atomic_dec_and_test(&p->u.count)))
302 kfree_rcu(p, u.head);
305 EXPORT_SYMBOL(release_dentry_name_snapshot);
307 static inline void __d_set_inode_and_type(struct dentry *dentry,
313 dentry->d_inode = inode;
314 flags = READ_ONCE(dentry->d_flags);
315 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
317 WRITE_ONCE(dentry->d_flags, flags);
320 static inline void __d_clear_type_and_inode(struct dentry *dentry)
322 unsigned flags = READ_ONCE(dentry->d_flags);
324 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
325 WRITE_ONCE(dentry->d_flags, flags);
326 dentry->d_inode = NULL;
329 static void dentry_free(struct dentry *dentry)
331 WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias));
332 if (unlikely(dname_external(dentry))) {
333 struct external_name *p = external_name(dentry);
334 if (likely(atomic_dec_and_test(&p->u.count))) {
335 call_rcu(&dentry->d_u.d_rcu, __d_free_external);
339 /* if dentry was never visible to RCU, immediate free is OK */
340 if (!(dentry->d_flags & DCACHE_RCUACCESS))
341 __d_free(&dentry->d_u.d_rcu);
343 call_rcu(&dentry->d_u.d_rcu, __d_free);
347 * Release the dentry's inode, using the filesystem
348 * d_iput() operation if defined.
350 static void dentry_unlink_inode(struct dentry * dentry)
351 __releases(dentry->d_lock)
352 __releases(dentry->d_inode->i_lock)
354 struct inode *inode = dentry->d_inode;
355 bool hashed = !d_unhashed(dentry);
358 raw_write_seqcount_begin(&dentry->d_seq);
359 __d_clear_type_and_inode(dentry);
360 hlist_del_init(&dentry->d_u.d_alias);
362 raw_write_seqcount_end(&dentry->d_seq);
363 spin_unlock(&dentry->d_lock);
364 spin_unlock(&inode->i_lock);
366 fsnotify_inoderemove(inode);
367 if (dentry->d_op && dentry->d_op->d_iput)
368 dentry->d_op->d_iput(dentry, inode);
374 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
375 * is in use - which includes both the "real" per-superblock
376 * LRU list _and_ the DCACHE_SHRINK_LIST use.
378 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
379 * on the shrink list (ie not on the superblock LRU list).
381 * The per-cpu "nr_dentry_unused" counters are updated with
382 * the DCACHE_LRU_LIST bit.
384 * These helper functions make sure we always follow the
385 * rules. d_lock must be held by the caller.
387 #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
388 static void d_lru_add(struct dentry *dentry)
390 D_FLAG_VERIFY(dentry, 0);
391 dentry->d_flags |= DCACHE_LRU_LIST;
392 this_cpu_inc(nr_dentry_unused);
393 WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
396 static void d_lru_del(struct dentry *dentry)
398 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
399 dentry->d_flags &= ~DCACHE_LRU_LIST;
400 this_cpu_dec(nr_dentry_unused);
401 WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
404 static void d_shrink_del(struct dentry *dentry)
406 D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
407 list_del_init(&dentry->d_lru);
408 dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
409 this_cpu_dec(nr_dentry_unused);
412 static void d_shrink_add(struct dentry *dentry, struct list_head *list)
414 D_FLAG_VERIFY(dentry, 0);
415 list_add(&dentry->d_lru, list);
416 dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST;
417 this_cpu_inc(nr_dentry_unused);
421 * These can only be called under the global LRU lock, ie during the
422 * callback for freeing the LRU list. "isolate" removes it from the
423 * LRU lists entirely, while shrink_move moves it to the indicated
426 static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry)
428 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
429 dentry->d_flags &= ~DCACHE_LRU_LIST;
430 this_cpu_dec(nr_dentry_unused);
431 list_lru_isolate(lru, &dentry->d_lru);
434 static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
435 struct list_head *list)
437 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
438 dentry->d_flags |= DCACHE_SHRINK_LIST;
439 list_lru_isolate_move(lru, &dentry->d_lru, list);
443 * dentry_lru_(add|del)_list) must be called with d_lock held.
445 static void dentry_lru_add(struct dentry *dentry)
447 if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
449 else if (unlikely(!(dentry->d_flags & DCACHE_REFERENCED)))
450 dentry->d_flags |= DCACHE_REFERENCED;
454 * d_drop - drop a dentry
455 * @dentry: dentry to drop
457 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
458 * be found through a VFS lookup any more. Note that this is different from
459 * deleting the dentry - d_delete will try to mark the dentry negative if
460 * possible, giving a successful _negative_ lookup, while d_drop will
461 * just make the cache lookup fail.
463 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
464 * reason (NFS timeouts or autofs deletes).
466 * __d_drop requires dentry->d_lock.
468 void __d_drop(struct dentry *dentry)
470 if (!d_unhashed(dentry)) {
471 struct hlist_bl_head *b;
473 * Hashed dentries are normally on the dentry hashtable,
474 * with the exception of those newly allocated by
475 * d_obtain_alias, which are always IS_ROOT:
477 if (unlikely(IS_ROOT(dentry)))
478 b = &dentry->d_sb->s_anon;
480 b = d_hash(dentry->d_name.hash);
483 __hlist_bl_del(&dentry->d_hash);
484 dentry->d_hash.pprev = NULL;
486 /* After this call, in-progress rcu-walk path lookup will fail. */
487 write_seqcount_invalidate(&dentry->d_seq);
490 EXPORT_SYMBOL(__d_drop);
492 void d_drop(struct dentry *dentry)
494 spin_lock(&dentry->d_lock);
496 spin_unlock(&dentry->d_lock);
498 EXPORT_SYMBOL(d_drop);
500 static inline void dentry_unlist(struct dentry *dentry, struct dentry *parent)
504 * Inform d_walk() and shrink_dentry_list() that we are no longer
505 * attached to the dentry tree
507 dentry->d_flags |= DCACHE_DENTRY_KILLED;
508 if (unlikely(list_empty(&dentry->d_child)))
510 __list_del_entry(&dentry->d_child);
512 * Cursors can move around the list of children. While we'd been
513 * a normal list member, it didn't matter - ->d_child.next would've
514 * been updated. However, from now on it won't be and for the
515 * things like d_walk() it might end up with a nasty surprise.
516 * Normally d_walk() doesn't care about cursors moving around -
517 * ->d_lock on parent prevents that and since a cursor has no children
518 * of its own, we get through it without ever unlocking the parent.
519 * There is one exception, though - if we ascend from a child that
520 * gets killed as soon as we unlock it, the next sibling is found
521 * using the value left in its ->d_child.next. And if _that_
522 * pointed to a cursor, and cursor got moved (e.g. by lseek())
523 * before d_walk() regains parent->d_lock, we'll end up skipping
524 * everything the cursor had been moved past.
526 * Solution: make sure that the pointer left behind in ->d_child.next
527 * points to something that won't be moving around. I.e. skip the
530 while (dentry->d_child.next != &parent->d_subdirs) {
531 next = list_entry(dentry->d_child.next, struct dentry, d_child);
532 if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR)))
534 dentry->d_child.next = next->d_child.next;
538 static void __dentry_kill(struct dentry *dentry)
540 struct dentry *parent = NULL;
541 bool can_free = true;
542 if (!IS_ROOT(dentry))
543 parent = dentry->d_parent;
546 * The dentry is now unrecoverably dead to the world.
548 lockref_mark_dead(&dentry->d_lockref);
551 * inform the fs via d_prune that this dentry is about to be
552 * unhashed and destroyed.
554 if (dentry->d_flags & DCACHE_OP_PRUNE)
555 dentry->d_op->d_prune(dentry);
557 if (dentry->d_flags & DCACHE_LRU_LIST) {
558 if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
561 /* if it was on the hash then remove it */
563 dentry_unlist(dentry, parent);
565 spin_unlock(&parent->d_lock);
567 dentry_unlink_inode(dentry);
569 spin_unlock(&dentry->d_lock);
570 this_cpu_dec(nr_dentry);
571 if (dentry->d_op && dentry->d_op->d_release)
572 dentry->d_op->d_release(dentry);
574 spin_lock(&dentry->d_lock);
575 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
576 dentry->d_flags |= DCACHE_MAY_FREE;
579 spin_unlock(&dentry->d_lock);
580 if (likely(can_free))
585 * Finish off a dentry we've decided to kill.
586 * dentry->d_lock must be held, returns with it unlocked.
587 * If ref is non-zero, then decrement the refcount too.
588 * Returns dentry requiring refcount drop, or NULL if we're done.
590 static struct dentry *dentry_kill(struct dentry *dentry)
591 __releases(dentry->d_lock)
593 struct inode *inode = dentry->d_inode;
594 struct dentry *parent = NULL;
596 if (inode && unlikely(!spin_trylock(&inode->i_lock)))
599 if (!IS_ROOT(dentry)) {
600 parent = dentry->d_parent;
601 if (unlikely(!spin_trylock(&parent->d_lock))) {
603 spin_unlock(&inode->i_lock);
608 __dentry_kill(dentry);
612 spin_unlock(&dentry->d_lock);
613 return dentry; /* try again with same dentry */
616 static inline struct dentry *lock_parent(struct dentry *dentry)
618 struct dentry *parent = dentry->d_parent;
621 if (unlikely(dentry->d_lockref.count < 0))
623 if (likely(spin_trylock(&parent->d_lock)))
626 spin_unlock(&dentry->d_lock);
628 parent = ACCESS_ONCE(dentry->d_parent);
629 spin_lock(&parent->d_lock);
631 * We can't blindly lock dentry until we are sure
632 * that we won't violate the locking order.
633 * Any changes of dentry->d_parent must have
634 * been done with parent->d_lock held, so
635 * spin_lock() above is enough of a barrier
636 * for checking if it's still our child.
638 if (unlikely(parent != dentry->d_parent)) {
639 spin_unlock(&parent->d_lock);
643 if (parent != dentry)
644 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
651 * Try to do a lockless dput(), and return whether that was successful.
653 * If unsuccessful, we return false, having already taken the dentry lock.
655 * The caller needs to hold the RCU read lock, so that the dentry is
656 * guaranteed to stay around even if the refcount goes down to zero!
658 static inline bool fast_dput(struct dentry *dentry)
661 unsigned int d_flags;
664 * If we have a d_op->d_delete() operation, we sould not
665 * let the dentry count go to zero, so use "put_or_lock".
667 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE))
668 return lockref_put_or_lock(&dentry->d_lockref);
671 * .. otherwise, we can try to just decrement the
672 * lockref optimistically.
674 ret = lockref_put_return(&dentry->d_lockref);
677 * If the lockref_put_return() failed due to the lock being held
678 * by somebody else, the fast path has failed. We will need to
679 * get the lock, and then check the count again.
681 if (unlikely(ret < 0)) {
682 spin_lock(&dentry->d_lock);
683 if (dentry->d_lockref.count > 1) {
684 dentry->d_lockref.count--;
685 spin_unlock(&dentry->d_lock);
692 * If we weren't the last ref, we're done.
698 * Careful, careful. The reference count went down
699 * to zero, but we don't hold the dentry lock, so
700 * somebody else could get it again, and do another
701 * dput(), and we need to not race with that.
703 * However, there is a very special and common case
704 * where we don't care, because there is nothing to
705 * do: the dentry is still hashed, it does not have
706 * a 'delete' op, and it's referenced and already on
709 * NOTE! Since we aren't locked, these values are
710 * not "stable". However, it is sufficient that at
711 * some point after we dropped the reference the
712 * dentry was hashed and the flags had the proper
713 * value. Other dentry users may have re-gotten
714 * a reference to the dentry and change that, but
715 * our work is done - we can leave the dentry
716 * around with a zero refcount.
719 d_flags = ACCESS_ONCE(dentry->d_flags);
720 d_flags &= DCACHE_REFERENCED | DCACHE_LRU_LIST | DCACHE_DISCONNECTED;
722 /* Nothing to do? Dropping the reference was all we needed? */
723 if (d_flags == (DCACHE_REFERENCED | DCACHE_LRU_LIST) && !d_unhashed(dentry))
727 * Not the fast normal case? Get the lock. We've already decremented
728 * the refcount, but we'll need to re-check the situation after
731 spin_lock(&dentry->d_lock);
734 * Did somebody else grab a reference to it in the meantime, and
735 * we're no longer the last user after all? Alternatively, somebody
736 * else could have killed it and marked it dead. Either way, we
737 * don't need to do anything else.
739 if (dentry->d_lockref.count) {
740 spin_unlock(&dentry->d_lock);
745 * Re-get the reference we optimistically dropped. We hold the
746 * lock, and we just tested that it was zero, so we can just
749 dentry->d_lockref.count = 1;
757 * This is complicated by the fact that we do not want to put
758 * dentries that are no longer on any hash chain on the unused
759 * list: we'd much rather just get rid of them immediately.
761 * However, that implies that we have to traverse the dentry
762 * tree upwards to the parents which might _also_ now be
763 * scheduled for deletion (it may have been only waiting for
764 * its last child to go away).
766 * This tail recursion is done by hand as we don't want to depend
767 * on the compiler to always get this right (gcc generally doesn't).
768 * Real recursion would eat up our stack space.
772 * dput - release a dentry
773 * @dentry: dentry to release
775 * Release a dentry. This will drop the usage count and if appropriate
776 * call the dentry unlink method as well as removing it from the queues and
777 * releasing its resources. If the parent dentries were scheduled for release
778 * they too may now get deleted.
780 void dput(struct dentry *dentry)
782 if (unlikely(!dentry))
789 if (likely(fast_dput(dentry))) {
794 /* Slow case: now with the dentry lock held */
797 WARN_ON(d_in_lookup(dentry));
799 /* Unreachable? Get rid of it */
800 if (unlikely(d_unhashed(dentry)))
803 if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
806 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) {
807 if (dentry->d_op->d_delete(dentry))
811 dentry_lru_add(dentry);
813 dentry->d_lockref.count--;
814 spin_unlock(&dentry->d_lock);
818 dentry = dentry_kill(dentry);
827 /* This must be called with d_lock held */
828 static inline void __dget_dlock(struct dentry *dentry)
830 dentry->d_lockref.count++;
833 static inline void __dget(struct dentry *dentry)
835 lockref_get(&dentry->d_lockref);
838 struct dentry *dget_parent(struct dentry *dentry)
844 * Do optimistic parent lookup without any
848 ret = ACCESS_ONCE(dentry->d_parent);
849 gotref = lockref_get_not_zero(&ret->d_lockref);
851 if (likely(gotref)) {
852 if (likely(ret == ACCESS_ONCE(dentry->d_parent)))
859 * Don't need rcu_dereference because we re-check it was correct under
863 ret = dentry->d_parent;
864 spin_lock(&ret->d_lock);
865 if (unlikely(ret != dentry->d_parent)) {
866 spin_unlock(&ret->d_lock);
871 BUG_ON(!ret->d_lockref.count);
872 ret->d_lockref.count++;
873 spin_unlock(&ret->d_lock);
876 EXPORT_SYMBOL(dget_parent);
879 * d_find_alias - grab a hashed alias of inode
880 * @inode: inode in question
882 * If inode has a hashed alias, or is a directory and has any alias,
883 * acquire the reference to alias and return it. Otherwise return NULL.
884 * Notice that if inode is a directory there can be only one alias and
885 * it can be unhashed only if it has no children, or if it is the root
886 * of a filesystem, or if the directory was renamed and d_revalidate
887 * was the first vfs operation to notice.
889 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
890 * any other hashed alias over that one.
892 static struct dentry *__d_find_alias(struct inode *inode)
894 struct dentry *alias, *discon_alias;
898 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
899 spin_lock(&alias->d_lock);
900 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
901 if (IS_ROOT(alias) &&
902 (alias->d_flags & DCACHE_DISCONNECTED)) {
903 discon_alias = alias;
906 spin_unlock(&alias->d_lock);
910 spin_unlock(&alias->d_lock);
913 alias = discon_alias;
914 spin_lock(&alias->d_lock);
915 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
917 spin_unlock(&alias->d_lock);
920 spin_unlock(&alias->d_lock);
926 struct dentry *d_find_alias(struct inode *inode)
928 struct dentry *de = NULL;
930 if (!hlist_empty(&inode->i_dentry)) {
931 spin_lock(&inode->i_lock);
932 de = __d_find_alias(inode);
933 spin_unlock(&inode->i_lock);
937 EXPORT_SYMBOL(d_find_alias);
940 * Try to kill dentries associated with this inode.
941 * WARNING: you must own a reference to inode.
943 void d_prune_aliases(struct inode *inode)
945 struct dentry *dentry;
947 spin_lock(&inode->i_lock);
948 hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
949 spin_lock(&dentry->d_lock);
950 if (!dentry->d_lockref.count) {
951 struct dentry *parent = lock_parent(dentry);
952 if (likely(!dentry->d_lockref.count)) {
953 __dentry_kill(dentry);
958 spin_unlock(&parent->d_lock);
960 spin_unlock(&dentry->d_lock);
962 spin_unlock(&inode->i_lock);
964 EXPORT_SYMBOL(d_prune_aliases);
966 static void shrink_dentry_list(struct list_head *list)
968 struct dentry *dentry, *parent;
970 while (!list_empty(list)) {
972 dentry = list_entry(list->prev, struct dentry, d_lru);
973 spin_lock(&dentry->d_lock);
974 parent = lock_parent(dentry);
977 * The dispose list is isolated and dentries are not accounted
978 * to the LRU here, so we can simply remove it from the list
979 * here regardless of whether it is referenced or not.
981 d_shrink_del(dentry);
984 * We found an inuse dentry which was not removed from
985 * the LRU because of laziness during lookup. Do not free it.
987 if (dentry->d_lockref.count > 0) {
988 spin_unlock(&dentry->d_lock);
990 spin_unlock(&parent->d_lock);
995 if (unlikely(dentry->d_flags & DCACHE_DENTRY_KILLED)) {
996 bool can_free = dentry->d_flags & DCACHE_MAY_FREE;
997 spin_unlock(&dentry->d_lock);
999 spin_unlock(&parent->d_lock);
1001 dentry_free(dentry);
1005 inode = dentry->d_inode;
1006 if (inode && unlikely(!spin_trylock(&inode->i_lock))) {
1007 d_shrink_add(dentry, list);
1008 spin_unlock(&dentry->d_lock);
1010 spin_unlock(&parent->d_lock);
1014 __dentry_kill(dentry);
1017 * We need to prune ancestors too. This is necessary to prevent
1018 * quadratic behavior of shrink_dcache_parent(), but is also
1019 * expected to be beneficial in reducing dentry cache
1023 while (dentry && !lockref_put_or_lock(&dentry->d_lockref)) {
1024 parent = lock_parent(dentry);
1025 if (dentry->d_lockref.count != 1) {
1026 dentry->d_lockref.count--;
1027 spin_unlock(&dentry->d_lock);
1029 spin_unlock(&parent->d_lock);
1032 inode = dentry->d_inode; /* can't be NULL */
1033 if (unlikely(!spin_trylock(&inode->i_lock))) {
1034 spin_unlock(&dentry->d_lock);
1036 spin_unlock(&parent->d_lock);
1040 __dentry_kill(dentry);
1046 static enum lru_status dentry_lru_isolate(struct list_head *item,
1047 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1049 struct list_head *freeable = arg;
1050 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1054 * we are inverting the lru lock/dentry->d_lock here,
1055 * so use a trylock. If we fail to get the lock, just skip
1058 if (!spin_trylock(&dentry->d_lock))
1062 * Referenced dentries are still in use. If they have active
1063 * counts, just remove them from the LRU. Otherwise give them
1064 * another pass through the LRU.
1066 if (dentry->d_lockref.count) {
1067 d_lru_isolate(lru, dentry);
1068 spin_unlock(&dentry->d_lock);
1072 if (dentry->d_flags & DCACHE_REFERENCED) {
1073 dentry->d_flags &= ~DCACHE_REFERENCED;
1074 spin_unlock(&dentry->d_lock);
1077 * The list move itself will be made by the common LRU code. At
1078 * this point, we've dropped the dentry->d_lock but keep the
1079 * lru lock. This is safe to do, since every list movement is
1080 * protected by the lru lock even if both locks are held.
1082 * This is guaranteed by the fact that all LRU management
1083 * functions are intermediated by the LRU API calls like
1084 * list_lru_add and list_lru_del. List movement in this file
1085 * only ever occur through this functions or through callbacks
1086 * like this one, that are called from the LRU API.
1088 * The only exceptions to this are functions like
1089 * shrink_dentry_list, and code that first checks for the
1090 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1091 * operating only with stack provided lists after they are
1092 * properly isolated from the main list. It is thus, always a
1098 d_lru_shrink_move(lru, dentry, freeable);
1099 spin_unlock(&dentry->d_lock);
1105 * prune_dcache_sb - shrink the dcache
1107 * @sc: shrink control, passed to list_lru_shrink_walk()
1109 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1110 * is done when we need more memory and called from the superblock shrinker
1113 * This function may fail to free any resources if all the dentries are in
1116 long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc)
1121 freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc,
1122 dentry_lru_isolate, &dispose);
1123 shrink_dentry_list(&dispose);
1127 static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
1128 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1130 struct list_head *freeable = arg;
1131 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1134 * we are inverting the lru lock/dentry->d_lock here,
1135 * so use a trylock. If we fail to get the lock, just skip
1138 if (!spin_trylock(&dentry->d_lock))
1141 d_lru_shrink_move(lru, dentry, freeable);
1142 spin_unlock(&dentry->d_lock);
1149 * shrink_dcache_sb - shrink dcache for a superblock
1152 * Shrink the dcache for the specified super block. This is used to free
1153 * the dcache before unmounting a file system.
1155 void shrink_dcache_sb(struct super_block *sb)
1162 freed = list_lru_walk(&sb->s_dentry_lru,
1163 dentry_lru_isolate_shrink, &dispose, UINT_MAX);
1165 this_cpu_sub(nr_dentry_unused, freed);
1166 shrink_dentry_list(&dispose);
1167 } while (freed > 0);
1169 EXPORT_SYMBOL(shrink_dcache_sb);
1172 * enum d_walk_ret - action to talke during tree walk
1173 * @D_WALK_CONTINUE: contrinue walk
1174 * @D_WALK_QUIT: quit walk
1175 * @D_WALK_NORETRY: quit when retry is needed
1176 * @D_WALK_SKIP: skip this dentry and its children
1186 * d_walk - walk the dentry tree
1187 * @parent: start of walk
1188 * @data: data passed to @enter() and @finish()
1189 * @enter: callback when first entering the dentry
1190 * @finish: callback when successfully finished the walk
1192 * The @enter() and @finish() callbacks are called with d_lock held.
1194 static void d_walk(struct dentry *parent, void *data,
1195 enum d_walk_ret (*enter)(void *, struct dentry *),
1196 void (*finish)(void *))
1198 struct dentry *this_parent;
1199 struct list_head *next;
1201 enum d_walk_ret ret;
1205 read_seqbegin_or_lock(&rename_lock, &seq);
1206 this_parent = parent;
1207 spin_lock(&this_parent->d_lock);
1209 ret = enter(data, this_parent);
1211 case D_WALK_CONTINUE:
1216 case D_WALK_NORETRY:
1221 next = this_parent->d_subdirs.next;
1223 while (next != &this_parent->d_subdirs) {
1224 struct list_head *tmp = next;
1225 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
1228 if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR))
1231 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1233 ret = enter(data, dentry);
1235 case D_WALK_CONTINUE:
1238 spin_unlock(&dentry->d_lock);
1240 case D_WALK_NORETRY:
1244 spin_unlock(&dentry->d_lock);
1248 if (!list_empty(&dentry->d_subdirs)) {
1249 spin_unlock(&this_parent->d_lock);
1250 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
1251 this_parent = dentry;
1252 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1255 spin_unlock(&dentry->d_lock);
1258 * All done at this level ... ascend and resume the search.
1262 if (this_parent != parent) {
1263 struct dentry *child = this_parent;
1264 this_parent = child->d_parent;
1266 spin_unlock(&child->d_lock);
1267 spin_lock(&this_parent->d_lock);
1269 /* might go back up the wrong parent if we have had a rename. */
1270 if (need_seqretry(&rename_lock, seq))
1272 /* go into the first sibling still alive */
1274 next = child->d_child.next;
1275 if (next == &this_parent->d_subdirs)
1277 child = list_entry(next, struct dentry, d_child);
1278 } while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
1282 if (need_seqretry(&rename_lock, seq))
1289 spin_unlock(&this_parent->d_lock);
1290 done_seqretry(&rename_lock, seq);
1294 spin_unlock(&this_parent->d_lock);
1303 struct check_mount {
1304 struct vfsmount *mnt;
1305 unsigned int mounted;
1308 static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry)
1310 struct check_mount *info = data;
1311 struct path path = { .mnt = info->mnt, .dentry = dentry };
1313 if (likely(!d_mountpoint(dentry)))
1314 return D_WALK_CONTINUE;
1315 if (__path_is_mountpoint(&path)) {
1319 return D_WALK_CONTINUE;
1323 * path_has_submounts - check for mounts over a dentry in the
1324 * current namespace.
1325 * @parent: path to check.
1327 * Return true if the parent or its subdirectories contain
1328 * a mount point in the current namespace.
1330 int path_has_submounts(const struct path *parent)
1332 struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
1334 read_seqlock_excl(&mount_lock);
1335 d_walk(parent->dentry, &data, path_check_mount, NULL);
1336 read_sequnlock_excl(&mount_lock);
1338 return data.mounted;
1340 EXPORT_SYMBOL(path_has_submounts);
1343 * Called by mount code to set a mountpoint and check if the mountpoint is
1344 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1345 * subtree can become unreachable).
1347 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1348 * this reason take rename_lock and d_lock on dentry and ancestors.
1350 int d_set_mounted(struct dentry *dentry)
1354 write_seqlock(&rename_lock);
1355 for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
1356 /* Need exclusion wrt. d_invalidate() */
1357 spin_lock(&p->d_lock);
1358 if (unlikely(d_unhashed(p))) {
1359 spin_unlock(&p->d_lock);
1362 spin_unlock(&p->d_lock);
1364 spin_lock(&dentry->d_lock);
1365 if (!d_unlinked(dentry)) {
1367 if (!d_mountpoint(dentry)) {
1368 dentry->d_flags |= DCACHE_MOUNTED;
1372 spin_unlock(&dentry->d_lock);
1374 write_sequnlock(&rename_lock);
1379 * Search the dentry child list of the specified parent,
1380 * and move any unused dentries to the end of the unused
1381 * list for prune_dcache(). We descend to the next level
1382 * whenever the d_subdirs list is non-empty and continue
1385 * It returns zero iff there are no unused children,
1386 * otherwise it returns the number of children moved to
1387 * the end of the unused list. This may not be the total
1388 * number of unused children, because select_parent can
1389 * drop the lock and return early due to latency
1393 struct select_data {
1394 struct dentry *start;
1395 struct list_head dispose;
1399 static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
1401 struct select_data *data = _data;
1402 enum d_walk_ret ret = D_WALK_CONTINUE;
1404 if (data->start == dentry)
1407 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1410 if (dentry->d_flags & DCACHE_LRU_LIST)
1412 if (!dentry->d_lockref.count) {
1413 d_shrink_add(dentry, &data->dispose);
1418 * We can return to the caller if we have found some (this
1419 * ensures forward progress). We'll be coming back to find
1422 if (!list_empty(&data->dispose))
1423 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1429 * shrink_dcache_parent - prune dcache
1430 * @parent: parent of entries to prune
1432 * Prune the dcache to remove unused children of the parent dentry.
1434 void shrink_dcache_parent(struct dentry *parent)
1437 struct select_data data;
1439 INIT_LIST_HEAD(&data.dispose);
1440 data.start = parent;
1443 d_walk(parent, &data, select_collect, NULL);
1447 shrink_dentry_list(&data.dispose);
1451 EXPORT_SYMBOL(shrink_dcache_parent);
1453 static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
1455 /* it has busy descendents; complain about those instead */
1456 if (!list_empty(&dentry->d_subdirs))
1457 return D_WALK_CONTINUE;
1459 /* root with refcount 1 is fine */
1460 if (dentry == _data && dentry->d_lockref.count == 1)
1461 return D_WALK_CONTINUE;
1463 printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%pd} "
1464 " still in use (%d) [unmount of %s %s]\n",
1467 dentry->d_inode->i_ino : 0UL,
1469 dentry->d_lockref.count,
1470 dentry->d_sb->s_type->name,
1471 dentry->d_sb->s_id);
1473 return D_WALK_CONTINUE;
1476 static void do_one_tree(struct dentry *dentry)
1478 shrink_dcache_parent(dentry);
1479 d_walk(dentry, dentry, umount_check, NULL);
1485 * destroy the dentries attached to a superblock on unmounting
1487 void shrink_dcache_for_umount(struct super_block *sb)
1489 struct dentry *dentry;
1491 WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked");
1493 dentry = sb->s_root;
1495 do_one_tree(dentry);
1497 while (!hlist_bl_empty(&sb->s_anon)) {
1498 dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash));
1499 do_one_tree(dentry);
1503 struct detach_data {
1504 struct select_data select;
1505 struct dentry *mountpoint;
1507 static enum d_walk_ret detach_and_collect(void *_data, struct dentry *dentry)
1509 struct detach_data *data = _data;
1511 if (d_mountpoint(dentry)) {
1512 __dget_dlock(dentry);
1513 data->mountpoint = dentry;
1517 return select_collect(&data->select, dentry);
1520 static void check_and_drop(void *_data)
1522 struct detach_data *data = _data;
1524 if (!data->mountpoint && list_empty(&data->select.dispose))
1525 __d_drop(data->select.start);
1529 * d_invalidate - detach submounts, prune dcache, and drop
1530 * @dentry: dentry to invalidate (aka detach, prune and drop)
1534 * The final d_drop is done as an atomic operation relative to
1535 * rename_lock ensuring there are no races with d_set_mounted. This
1536 * ensures there are no unhashed dentries on the path to a mountpoint.
1538 void d_invalidate(struct dentry *dentry)
1541 * If it's already been dropped, return OK.
1543 spin_lock(&dentry->d_lock);
1544 if (d_unhashed(dentry)) {
1545 spin_unlock(&dentry->d_lock);
1548 spin_unlock(&dentry->d_lock);
1550 /* Negative dentries can be dropped without further checks */
1551 if (!dentry->d_inode) {
1557 struct detach_data data;
1559 data.mountpoint = NULL;
1560 INIT_LIST_HEAD(&data.select.dispose);
1561 data.select.start = dentry;
1562 data.select.found = 0;
1564 d_walk(dentry, &data, detach_and_collect, check_and_drop);
1566 if (!list_empty(&data.select.dispose))
1567 shrink_dentry_list(&data.select.dispose);
1568 else if (!data.mountpoint)
1571 if (data.mountpoint) {
1572 detach_mounts(data.mountpoint);
1573 dput(data.mountpoint);
1578 EXPORT_SYMBOL(d_invalidate);
1581 * __d_alloc - allocate a dcache entry
1582 * @sb: filesystem it will belong to
1583 * @name: qstr of the name
1585 * Allocates a dentry. It returns %NULL if there is insufficient memory
1586 * available. On a success the dentry is returned. The name passed in is
1587 * copied and the copy passed in may be reused after this call.
1590 struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1592 struct dentry *dentry;
1596 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
1601 * We guarantee that the inline name is always NUL-terminated.
1602 * This way the memcpy() done by the name switching in rename
1603 * will still always have a NUL at the end, even if we might
1604 * be overwriting an internal NUL character
1606 dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
1607 if (unlikely(!name)) {
1608 static const struct qstr anon = QSTR_INIT("/", 1);
1610 dname = dentry->d_iname;
1611 } else if (name->len > DNAME_INLINE_LEN-1) {
1612 size_t size = offsetof(struct external_name, name[1]);
1613 struct external_name *p = kmalloc(size + name->len,
1614 GFP_KERNEL_ACCOUNT);
1616 kmem_cache_free(dentry_cache, dentry);
1619 atomic_set(&p->u.count, 1);
1621 if (IS_ENABLED(CONFIG_DCACHE_WORD_ACCESS))
1622 kasan_unpoison_shadow(dname,
1623 round_up(name->len + 1, sizeof(unsigned long)));
1625 dname = dentry->d_iname;
1628 dentry->d_name.len = name->len;
1629 dentry->d_name.hash = name->hash;
1630 memcpy(dname, name->name, name->len);
1631 dname[name->len] = 0;
1633 /* Make sure we always see the terminating NUL character */
1635 dentry->d_name.name = dname;
1637 dentry->d_lockref.count = 1;
1638 dentry->d_flags = 0;
1639 spin_lock_init(&dentry->d_lock);
1640 seqcount_init(&dentry->d_seq);
1641 dentry->d_inode = NULL;
1642 dentry->d_parent = dentry;
1644 dentry->d_op = NULL;
1645 dentry->d_fsdata = NULL;
1646 INIT_HLIST_BL_NODE(&dentry->d_hash);
1647 INIT_LIST_HEAD(&dentry->d_lru);
1648 INIT_LIST_HEAD(&dentry->d_subdirs);
1649 INIT_HLIST_NODE(&dentry->d_u.d_alias);
1650 INIT_LIST_HEAD(&dentry->d_child);
1651 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1653 if (dentry->d_op && dentry->d_op->d_init) {
1654 err = dentry->d_op->d_init(dentry);
1656 if (dname_external(dentry))
1657 kfree(external_name(dentry));
1658 kmem_cache_free(dentry_cache, dentry);
1663 this_cpu_inc(nr_dentry);
1669 * d_alloc - allocate a dcache entry
1670 * @parent: parent of entry to allocate
1671 * @name: qstr of the name
1673 * Allocates a dentry. It returns %NULL if there is insufficient memory
1674 * available. On a success the dentry is returned. The name passed in is
1675 * copied and the copy passed in may be reused after this call.
1677 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1679 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1682 dentry->d_flags |= DCACHE_RCUACCESS;
1683 spin_lock(&parent->d_lock);
1685 * don't need child lock because it is not subject
1686 * to concurrency here
1688 __dget_dlock(parent);
1689 dentry->d_parent = parent;
1690 list_add(&dentry->d_child, &parent->d_subdirs);
1691 spin_unlock(&parent->d_lock);
1695 EXPORT_SYMBOL(d_alloc);
1697 struct dentry *d_alloc_cursor(struct dentry * parent)
1699 struct dentry *dentry = __d_alloc(parent->d_sb, NULL);
1701 dentry->d_flags |= DCACHE_RCUACCESS | DCACHE_DENTRY_CURSOR;
1702 dentry->d_parent = dget(parent);
1708 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1709 * @sb: the superblock
1710 * @name: qstr of the name
1712 * For a filesystem that just pins its dentries in memory and never
1713 * performs lookups at all, return an unhashed IS_ROOT dentry.
1715 struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1717 return __d_alloc(sb, name);
1719 EXPORT_SYMBOL(d_alloc_pseudo);
1721 struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1726 q.hash_len = hashlen_string(parent, name);
1727 return d_alloc(parent, &q);
1729 EXPORT_SYMBOL(d_alloc_name);
1731 void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1733 WARN_ON_ONCE(dentry->d_op);
1734 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
1736 DCACHE_OP_REVALIDATE |
1737 DCACHE_OP_WEAK_REVALIDATE |
1744 dentry->d_flags |= DCACHE_OP_HASH;
1746 dentry->d_flags |= DCACHE_OP_COMPARE;
1747 if (op->d_revalidate)
1748 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1749 if (op->d_weak_revalidate)
1750 dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
1752 dentry->d_flags |= DCACHE_OP_DELETE;
1754 dentry->d_flags |= DCACHE_OP_PRUNE;
1756 dentry->d_flags |= DCACHE_OP_REAL;
1759 EXPORT_SYMBOL(d_set_d_op);
1763 * d_set_fallthru - Mark a dentry as falling through to a lower layer
1764 * @dentry - The dentry to mark
1766 * Mark a dentry as falling through to the lower layer (as set with
1767 * d_pin_lower()). This flag may be recorded on the medium.
1769 void d_set_fallthru(struct dentry *dentry)
1771 spin_lock(&dentry->d_lock);
1772 dentry->d_flags |= DCACHE_FALLTHRU;
1773 spin_unlock(&dentry->d_lock);
1775 EXPORT_SYMBOL(d_set_fallthru);
1777 static unsigned d_flags_for_inode(struct inode *inode)
1779 unsigned add_flags = DCACHE_REGULAR_TYPE;
1782 return DCACHE_MISS_TYPE;
1784 if (S_ISDIR(inode->i_mode)) {
1785 add_flags = DCACHE_DIRECTORY_TYPE;
1786 if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) {
1787 if (unlikely(!inode->i_op->lookup))
1788 add_flags = DCACHE_AUTODIR_TYPE;
1790 inode->i_opflags |= IOP_LOOKUP;
1792 goto type_determined;
1795 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1796 if (unlikely(inode->i_op->get_link)) {
1797 add_flags = DCACHE_SYMLINK_TYPE;
1798 goto type_determined;
1800 inode->i_opflags |= IOP_NOFOLLOW;
1803 if (unlikely(!S_ISREG(inode->i_mode)))
1804 add_flags = DCACHE_SPECIAL_TYPE;
1807 if (unlikely(IS_AUTOMOUNT(inode)))
1808 add_flags |= DCACHE_NEED_AUTOMOUNT;
1812 static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1814 unsigned add_flags = d_flags_for_inode(inode);
1815 WARN_ON(d_in_lookup(dentry));
1817 spin_lock(&dentry->d_lock);
1818 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
1819 raw_write_seqcount_begin(&dentry->d_seq);
1820 __d_set_inode_and_type(dentry, inode, add_flags);
1821 raw_write_seqcount_end(&dentry->d_seq);
1822 fsnotify_update_flags(dentry);
1823 spin_unlock(&dentry->d_lock);
1827 * d_instantiate - fill in inode information for a dentry
1828 * @entry: dentry to complete
1829 * @inode: inode to attach to this dentry
1831 * Fill in inode information in the entry.
1833 * This turns negative dentries into productive full members
1836 * NOTE! This assumes that the inode count has been incremented
1837 * (or otherwise set) by the caller to indicate that it is now
1838 * in use by the dcache.
1841 void d_instantiate(struct dentry *entry, struct inode * inode)
1843 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1845 security_d_instantiate(entry, inode);
1846 spin_lock(&inode->i_lock);
1847 __d_instantiate(entry, inode);
1848 spin_unlock(&inode->i_lock);
1851 EXPORT_SYMBOL(d_instantiate);
1854 * d_instantiate_no_diralias - instantiate a non-aliased dentry
1855 * @entry: dentry to complete
1856 * @inode: inode to attach to this dentry
1858 * Fill in inode information in the entry. If a directory alias is found, then
1859 * return an error (and drop inode). Together with d_materialise_unique() this
1860 * guarantees that a directory inode may never have more than one alias.
1862 int d_instantiate_no_diralias(struct dentry *entry, struct inode *inode)
1864 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1866 security_d_instantiate(entry, inode);
1867 spin_lock(&inode->i_lock);
1868 if (S_ISDIR(inode->i_mode) && !hlist_empty(&inode->i_dentry)) {
1869 spin_unlock(&inode->i_lock);
1873 __d_instantiate(entry, inode);
1874 spin_unlock(&inode->i_lock);
1878 EXPORT_SYMBOL(d_instantiate_no_diralias);
1880 struct dentry *d_make_root(struct inode *root_inode)
1882 struct dentry *res = NULL;
1885 res = __d_alloc(root_inode->i_sb, NULL);
1887 d_instantiate(res, root_inode);
1893 EXPORT_SYMBOL(d_make_root);
1895 static struct dentry * __d_find_any_alias(struct inode *inode)
1897 struct dentry *alias;
1899 if (hlist_empty(&inode->i_dentry))
1901 alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
1907 * d_find_any_alias - find any alias for a given inode
1908 * @inode: inode to find an alias for
1910 * If any aliases exist for the given inode, take and return a
1911 * reference for one of them. If no aliases exist, return %NULL.
1913 struct dentry *d_find_any_alias(struct inode *inode)
1917 spin_lock(&inode->i_lock);
1918 de = __d_find_any_alias(inode);
1919 spin_unlock(&inode->i_lock);
1922 EXPORT_SYMBOL(d_find_any_alias);
1924 static struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
1931 return ERR_PTR(-ESTALE);
1933 return ERR_CAST(inode);
1935 res = d_find_any_alias(inode);
1939 tmp = __d_alloc(inode->i_sb, NULL);
1941 res = ERR_PTR(-ENOMEM);
1945 security_d_instantiate(tmp, inode);
1946 spin_lock(&inode->i_lock);
1947 res = __d_find_any_alias(inode);
1949 spin_unlock(&inode->i_lock);
1954 /* attach a disconnected dentry */
1955 add_flags = d_flags_for_inode(inode);
1958 add_flags |= DCACHE_DISCONNECTED;
1960 spin_lock(&tmp->d_lock);
1961 __d_set_inode_and_type(tmp, inode, add_flags);
1962 hlist_add_head(&tmp->d_u.d_alias, &inode->i_dentry);
1963 hlist_bl_lock(&tmp->d_sb->s_anon);
1964 hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
1965 hlist_bl_unlock(&tmp->d_sb->s_anon);
1966 spin_unlock(&tmp->d_lock);
1967 spin_unlock(&inode->i_lock);
1977 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
1978 * @inode: inode to allocate the dentry for
1980 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1981 * similar open by handle operations. The returned dentry may be anonymous,
1982 * or may have a full name (if the inode was already in the cache).
1984 * When called on a directory inode, we must ensure that the inode only ever
1985 * has one dentry. If a dentry is found, that is returned instead of
1986 * allocating a new one.
1988 * On successful return, the reference to the inode has been transferred
1989 * to the dentry. In case of an error the reference on the inode is released.
1990 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1991 * be passed in and the error will be propagated to the return value,
1992 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1994 struct dentry *d_obtain_alias(struct inode *inode)
1996 return __d_obtain_alias(inode, 1);
1998 EXPORT_SYMBOL(d_obtain_alias);
2001 * d_obtain_root - find or allocate a dentry for a given inode
2002 * @inode: inode to allocate the dentry for
2004 * Obtain an IS_ROOT dentry for the root of a filesystem.
2006 * We must ensure that directory inodes only ever have one dentry. If a
2007 * dentry is found, that is returned instead of allocating a new one.
2009 * On successful return, the reference to the inode has been transferred
2010 * to the dentry. In case of an error the reference on the inode is
2011 * released. A %NULL or IS_ERR inode may be passed in and will be the
2012 * error will be propagate to the return value, with a %NULL @inode
2013 * replaced by ERR_PTR(-ESTALE).
2015 struct dentry *d_obtain_root(struct inode *inode)
2017 return __d_obtain_alias(inode, 0);
2019 EXPORT_SYMBOL(d_obtain_root);
2022 * d_add_ci - lookup or allocate new dentry with case-exact name
2023 * @inode: the inode case-insensitive lookup has found
2024 * @dentry: the negative dentry that was passed to the parent's lookup func
2025 * @name: the case-exact name to be associated with the returned dentry
2027 * This is to avoid filling the dcache with case-insensitive names to the
2028 * same inode, only the actual correct case is stored in the dcache for
2029 * case-insensitive filesystems.
2031 * For a case-insensitive lookup match and if the the case-exact dentry
2032 * already exists in in the dcache, use it and return it.
2034 * If no entry exists with the exact case name, allocate new dentry with
2035 * the exact case, and return the spliced entry.
2037 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
2040 struct dentry *found, *res;
2043 * First check if a dentry matching the name already exists,
2044 * if not go ahead and create it now.
2046 found = d_hash_and_lookup(dentry->d_parent, name);
2051 if (d_in_lookup(dentry)) {
2052 found = d_alloc_parallel(dentry->d_parent, name,
2054 if (IS_ERR(found) || !d_in_lookup(found)) {
2059 found = d_alloc(dentry->d_parent, name);
2062 return ERR_PTR(-ENOMEM);
2065 res = d_splice_alias(inode, found);
2072 EXPORT_SYMBOL(d_add_ci);
2075 static inline bool d_same_name(const struct dentry *dentry,
2076 const struct dentry *parent,
2077 const struct qstr *name)
2079 if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
2080 if (dentry->d_name.len != name->len)
2082 return dentry_cmp(dentry, name->name, name->len) == 0;
2084 return parent->d_op->d_compare(dentry,
2085 dentry->d_name.len, dentry->d_name.name,
2090 * __d_lookup_rcu - search for a dentry (racy, store-free)
2091 * @parent: parent dentry
2092 * @name: qstr of name we wish to find
2093 * @seqp: returns d_seq value at the point where the dentry was found
2094 * Returns: dentry, or NULL
2096 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2097 * resolution (store-free path walking) design described in
2098 * Documentation/filesystems/path-lookup.txt.
2100 * This is not to be used outside core vfs.
2102 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2103 * held, and rcu_read_lock held. The returned dentry must not be stored into
2104 * without taking d_lock and checking d_seq sequence count against @seq
2107 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2110 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2111 * the returned dentry, so long as its parent's seqlock is checked after the
2112 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2113 * is formed, giving integrity down the path walk.
2115 * NOTE! The caller *has* to check the resulting dentry against the sequence
2116 * number we've returned before using any of the resulting dentry state!
2118 struct dentry *__d_lookup_rcu(const struct dentry *parent,
2119 const struct qstr *name,
2122 u64 hashlen = name->hash_len;
2123 const unsigned char *str = name->name;
2124 struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
2125 struct hlist_bl_node *node;
2126 struct dentry *dentry;
2129 * Note: There is significant duplication with __d_lookup_rcu which is
2130 * required to prevent single threaded performance regressions
2131 * especially on architectures where smp_rmb (in seqcounts) are costly.
2132 * Keep the two functions in sync.
2136 * The hash list is protected using RCU.
2138 * Carefully use d_seq when comparing a candidate dentry, to avoid
2139 * races with d_move().
2141 * It is possible that concurrent renames can mess up our list
2142 * walk here and result in missing our dentry, resulting in the
2143 * false-negative result. d_lookup() protects against concurrent
2144 * renames using rename_lock seqlock.
2146 * See Documentation/filesystems/path-lookup.txt for more details.
2148 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2153 * The dentry sequence count protects us from concurrent
2154 * renames, and thus protects parent and name fields.
2156 * The caller must perform a seqcount check in order
2157 * to do anything useful with the returned dentry.
2159 * NOTE! We do a "raw" seqcount_begin here. That means that
2160 * we don't wait for the sequence count to stabilize if it
2161 * is in the middle of a sequence change. If we do the slow
2162 * dentry compare, we will do seqretries until it is stable,
2163 * and if we end up with a successful lookup, we actually
2164 * want to exit RCU lookup anyway.
2166 * Note that raw_seqcount_begin still *does* smp_rmb(), so
2167 * we are still guaranteed NUL-termination of ->d_name.name.
2169 seq = raw_seqcount_begin(&dentry->d_seq);
2170 if (dentry->d_parent != parent)
2172 if (d_unhashed(dentry))
2175 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
2178 if (dentry->d_name.hash != hashlen_hash(hashlen))
2180 tlen = dentry->d_name.len;
2181 tname = dentry->d_name.name;
2182 /* we want a consistent (name,len) pair */
2183 if (read_seqcount_retry(&dentry->d_seq, seq)) {
2187 if (parent->d_op->d_compare(dentry,
2188 tlen, tname, name) != 0)
2191 if (dentry->d_name.hash_len != hashlen)
2193 if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
2203 * d_lookup - search for a dentry
2204 * @parent: parent dentry
2205 * @name: qstr of name we wish to find
2206 * Returns: dentry, or NULL
2208 * d_lookup searches the children of the parent dentry for the name in
2209 * question. If the dentry is found its reference count is incremented and the
2210 * dentry is returned. The caller must use dput to free the entry when it has
2211 * finished using it. %NULL is returned if the dentry does not exist.
2213 struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
2215 struct dentry *dentry;
2219 seq = read_seqbegin(&rename_lock);
2220 dentry = __d_lookup(parent, name);
2223 } while (read_seqretry(&rename_lock, seq));
2226 EXPORT_SYMBOL(d_lookup);
2229 * __d_lookup - search for a dentry (racy)
2230 * @parent: parent dentry
2231 * @name: qstr of name we wish to find
2232 * Returns: dentry, or NULL
2234 * __d_lookup is like d_lookup, however it may (rarely) return a
2235 * false-negative result due to unrelated rename activity.
2237 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2238 * however it must be used carefully, eg. with a following d_lookup in
2239 * the case of failure.
2241 * __d_lookup callers must be commented.
2243 struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
2245 unsigned int hash = name->hash;
2246 struct hlist_bl_head *b = d_hash(hash);
2247 struct hlist_bl_node *node;
2248 struct dentry *found = NULL;
2249 struct dentry *dentry;
2252 * Note: There is significant duplication with __d_lookup_rcu which is
2253 * required to prevent single threaded performance regressions
2254 * especially on architectures where smp_rmb (in seqcounts) are costly.
2255 * Keep the two functions in sync.
2259 * The hash list is protected using RCU.
2261 * Take d_lock when comparing a candidate dentry, to avoid races
2264 * It is possible that concurrent renames can mess up our list
2265 * walk here and result in missing our dentry, resulting in the
2266 * false-negative result. d_lookup() protects against concurrent
2267 * renames using rename_lock seqlock.
2269 * See Documentation/filesystems/path-lookup.txt for more details.
2273 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2275 if (dentry->d_name.hash != hash)
2278 spin_lock(&dentry->d_lock);
2279 if (dentry->d_parent != parent)
2281 if (d_unhashed(dentry))
2284 if (!d_same_name(dentry, parent, name))
2287 dentry->d_lockref.count++;
2289 spin_unlock(&dentry->d_lock);
2292 spin_unlock(&dentry->d_lock);
2300 * d_hash_and_lookup - hash the qstr then search for a dentry
2301 * @dir: Directory to search in
2302 * @name: qstr of name we wish to find
2304 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2306 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2309 * Check for a fs-specific hash function. Note that we must
2310 * calculate the standard hash first, as the d_op->d_hash()
2311 * routine may choose to leave the hash value unchanged.
2313 name->hash = full_name_hash(dir, name->name, name->len);
2314 if (dir->d_flags & DCACHE_OP_HASH) {
2315 int err = dir->d_op->d_hash(dir, name);
2316 if (unlikely(err < 0))
2317 return ERR_PTR(err);
2319 return d_lookup(dir, name);
2321 EXPORT_SYMBOL(d_hash_and_lookup);
2324 * When a file is deleted, we have two options:
2325 * - turn this dentry into a negative dentry
2326 * - unhash this dentry and free it.
2328 * Usually, we want to just turn this into
2329 * a negative dentry, but if anybody else is
2330 * currently using the dentry or the inode
2331 * we can't do that and we fall back on removing
2332 * it from the hash queues and waiting for
2333 * it to be deleted later when it has no users
2337 * d_delete - delete a dentry
2338 * @dentry: The dentry to delete
2340 * Turn the dentry into a negative dentry if possible, otherwise
2341 * remove it from the hash queues so it can be deleted later
2344 void d_delete(struct dentry * dentry)
2346 struct inode *inode;
2349 * Are we the only user?
2352 spin_lock(&dentry->d_lock);
2353 inode = dentry->d_inode;
2354 isdir = S_ISDIR(inode->i_mode);
2355 if (dentry->d_lockref.count == 1) {
2356 if (!spin_trylock(&inode->i_lock)) {
2357 spin_unlock(&dentry->d_lock);
2361 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2362 dentry_unlink_inode(dentry);
2363 fsnotify_nameremove(dentry, isdir);
2367 if (!d_unhashed(dentry))
2370 spin_unlock(&dentry->d_lock);
2372 fsnotify_nameremove(dentry, isdir);
2374 EXPORT_SYMBOL(d_delete);
2376 static void __d_rehash(struct dentry *entry)
2378 struct hlist_bl_head *b = d_hash(entry->d_name.hash);
2379 BUG_ON(!d_unhashed(entry));
2381 hlist_bl_add_head_rcu(&entry->d_hash, b);
2386 * d_rehash - add an entry back to the hash
2387 * @entry: dentry to add to the hash
2389 * Adds a dentry to the hash according to its name.
2392 void d_rehash(struct dentry * entry)
2394 spin_lock(&entry->d_lock);
2396 spin_unlock(&entry->d_lock);
2398 EXPORT_SYMBOL(d_rehash);
2400 static inline unsigned start_dir_add(struct inode *dir)
2404 unsigned n = dir->i_dir_seq;
2405 if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
2411 static inline void end_dir_add(struct inode *dir, unsigned n)
2413 smp_store_release(&dir->i_dir_seq, n + 2);
2416 static void d_wait_lookup(struct dentry *dentry)
2418 if (d_in_lookup(dentry)) {
2419 DECLARE_WAITQUEUE(wait, current);
2420 add_wait_queue(dentry->d_wait, &wait);
2422 set_current_state(TASK_UNINTERRUPTIBLE);
2423 spin_unlock(&dentry->d_lock);
2425 spin_lock(&dentry->d_lock);
2426 } while (d_in_lookup(dentry));
2430 struct dentry *d_alloc_parallel(struct dentry *parent,
2431 const struct qstr *name,
2432 wait_queue_head_t *wq)
2434 unsigned int hash = name->hash;
2435 struct hlist_bl_head *b = in_lookup_hash(parent, hash);
2436 struct hlist_bl_node *node;
2437 struct dentry *new = d_alloc(parent, name);
2438 struct dentry *dentry;
2439 unsigned seq, r_seq, d_seq;
2442 return ERR_PTR(-ENOMEM);
2446 seq = smp_load_acquire(&parent->d_inode->i_dir_seq) & ~1;
2447 r_seq = read_seqbegin(&rename_lock);
2448 dentry = __d_lookup_rcu(parent, name, &d_seq);
2449 if (unlikely(dentry)) {
2450 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2454 if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
2463 if (unlikely(read_seqretry(&rename_lock, r_seq))) {
2468 if (unlikely(parent->d_inode->i_dir_seq != seq)) {
2474 * No changes for the parent since the beginning of d_lookup().
2475 * Since all removals from the chain happen with hlist_bl_lock(),
2476 * any potential in-lookup matches are going to stay here until
2477 * we unlock the chain. All fields are stable in everything
2480 hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
2481 if (dentry->d_name.hash != hash)
2483 if (dentry->d_parent != parent)
2485 if (!d_same_name(dentry, parent, name))
2488 /* now we can try to grab a reference */
2489 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2496 * somebody is likely to be still doing lookup for it;
2497 * wait for them to finish
2499 spin_lock(&dentry->d_lock);
2500 d_wait_lookup(dentry);
2502 * it's not in-lookup anymore; in principle we should repeat
2503 * everything from dcache lookup, but it's likely to be what
2504 * d_lookup() would've found anyway. If it is, just return it;
2505 * otherwise we really have to repeat the whole thing.
2507 if (unlikely(dentry->d_name.hash != hash))
2509 if (unlikely(dentry->d_parent != parent))
2511 if (unlikely(d_unhashed(dentry)))
2513 if (unlikely(!d_same_name(dentry, parent, name)))
2515 /* OK, it *is* a hashed match; return it */
2516 spin_unlock(&dentry->d_lock);
2521 /* we can't take ->d_lock here; it's OK, though. */
2522 new->d_flags |= DCACHE_PAR_LOOKUP;
2524 hlist_bl_add_head_rcu(&new->d_u.d_in_lookup_hash, b);
2528 spin_unlock(&dentry->d_lock);
2532 EXPORT_SYMBOL(d_alloc_parallel);
2534 void __d_lookup_done(struct dentry *dentry)
2536 struct hlist_bl_head *b = in_lookup_hash(dentry->d_parent,
2537 dentry->d_name.hash);
2539 dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
2540 __hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
2541 wake_up_all(dentry->d_wait);
2542 dentry->d_wait = NULL;
2544 INIT_HLIST_NODE(&dentry->d_u.d_alias);
2545 INIT_LIST_HEAD(&dentry->d_lru);
2547 EXPORT_SYMBOL(__d_lookup_done);
2549 /* inode->i_lock held if inode is non-NULL */
2551 static inline void __d_add(struct dentry *dentry, struct inode *inode)
2553 struct inode *dir = NULL;
2555 spin_lock(&dentry->d_lock);
2556 if (unlikely(d_in_lookup(dentry))) {
2557 dir = dentry->d_parent->d_inode;
2558 n = start_dir_add(dir);
2559 __d_lookup_done(dentry);
2562 unsigned add_flags = d_flags_for_inode(inode);
2563 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2564 raw_write_seqcount_begin(&dentry->d_seq);
2565 __d_set_inode_and_type(dentry, inode, add_flags);
2566 raw_write_seqcount_end(&dentry->d_seq);
2567 fsnotify_update_flags(dentry);
2571 end_dir_add(dir, n);
2572 spin_unlock(&dentry->d_lock);
2574 spin_unlock(&inode->i_lock);
2578 * d_add - add dentry to hash queues
2579 * @entry: dentry to add
2580 * @inode: The inode to attach to this dentry
2582 * This adds the entry to the hash queues and initializes @inode.
2583 * The entry was actually filled in earlier during d_alloc().
2586 void d_add(struct dentry *entry, struct inode *inode)
2589 security_d_instantiate(entry, inode);
2590 spin_lock(&inode->i_lock);
2592 __d_add(entry, inode);
2594 EXPORT_SYMBOL(d_add);
2597 * d_exact_alias - find and hash an exact unhashed alias
2598 * @entry: dentry to add
2599 * @inode: The inode to go with this dentry
2601 * If an unhashed dentry with the same name/parent and desired
2602 * inode already exists, hash and return it. Otherwise, return
2605 * Parent directory should be locked.
2607 struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
2609 struct dentry *alias;
2610 unsigned int hash = entry->d_name.hash;
2612 spin_lock(&inode->i_lock);
2613 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
2615 * Don't need alias->d_lock here, because aliases with
2616 * d_parent == entry->d_parent are not subject to name or
2617 * parent changes, because the parent inode i_mutex is held.
2619 if (alias->d_name.hash != hash)
2621 if (alias->d_parent != entry->d_parent)
2623 if (!d_same_name(alias, entry->d_parent, &entry->d_name))
2625 spin_lock(&alias->d_lock);
2626 if (!d_unhashed(alias)) {
2627 spin_unlock(&alias->d_lock);
2630 __dget_dlock(alias);
2632 spin_unlock(&alias->d_lock);
2634 spin_unlock(&inode->i_lock);
2637 spin_unlock(&inode->i_lock);
2640 EXPORT_SYMBOL(d_exact_alias);
2643 * dentry_update_name_case - update case insensitive dentry with a new name
2644 * @dentry: dentry to be updated
2647 * Update a case insensitive dentry with new case of name.
2649 * dentry must have been returned by d_lookup with name @name. Old and new
2650 * name lengths must match (ie. no d_compare which allows mismatched name
2653 * Parent inode i_mutex must be held over d_lookup and into this call (to
2654 * keep renames and concurrent inserts, and readdir(2) away).
2656 void dentry_update_name_case(struct dentry *dentry, const struct qstr *name)
2658 BUG_ON(!inode_is_locked(dentry->d_parent->d_inode));
2659 BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
2661 spin_lock(&dentry->d_lock);
2662 write_seqcount_begin(&dentry->d_seq);
2663 memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
2664 write_seqcount_end(&dentry->d_seq);
2665 spin_unlock(&dentry->d_lock);
2667 EXPORT_SYMBOL(dentry_update_name_case);
2669 static void swap_names(struct dentry *dentry, struct dentry *target)
2671 if (unlikely(dname_external(target))) {
2672 if (unlikely(dname_external(dentry))) {
2674 * Both external: swap the pointers
2676 swap(target->d_name.name, dentry->d_name.name);
2679 * dentry:internal, target:external. Steal target's
2680 * storage and make target internal.
2682 memcpy(target->d_iname, dentry->d_name.name,
2683 dentry->d_name.len + 1);
2684 dentry->d_name.name = target->d_name.name;
2685 target->d_name.name = target->d_iname;
2688 if (unlikely(dname_external(dentry))) {
2690 * dentry:external, target:internal. Give dentry's
2691 * storage to target and make dentry internal
2693 memcpy(dentry->d_iname, target->d_name.name,
2694 target->d_name.len + 1);
2695 target->d_name.name = dentry->d_name.name;
2696 dentry->d_name.name = dentry->d_iname;
2699 * Both are internal.
2702 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
2703 kmemcheck_mark_initialized(dentry->d_iname, DNAME_INLINE_LEN);
2704 kmemcheck_mark_initialized(target->d_iname, DNAME_INLINE_LEN);
2705 for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
2706 swap(((long *) &dentry->d_iname)[i],
2707 ((long *) &target->d_iname)[i]);
2711 swap(dentry->d_name.hash_len, target->d_name.hash_len);
2714 static void copy_name(struct dentry *dentry, struct dentry *target)
2716 struct external_name *old_name = NULL;
2717 if (unlikely(dname_external(dentry)))
2718 old_name = external_name(dentry);
2719 if (unlikely(dname_external(target))) {
2720 atomic_inc(&external_name(target)->u.count);
2721 dentry->d_name = target->d_name;
2723 memcpy(dentry->d_iname, target->d_name.name,
2724 target->d_name.len + 1);
2725 dentry->d_name.name = dentry->d_iname;
2726 dentry->d_name.hash_len = target->d_name.hash_len;
2728 if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
2729 kfree_rcu(old_name, u.head);
2732 static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
2735 * XXXX: do we really need to take target->d_lock?
2737 if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent)
2738 spin_lock(&target->d_parent->d_lock);
2740 if (d_ancestor(dentry->d_parent, target->d_parent)) {
2741 spin_lock(&dentry->d_parent->d_lock);
2742 spin_lock_nested(&target->d_parent->d_lock,
2743 DENTRY_D_LOCK_NESTED);
2745 spin_lock(&target->d_parent->d_lock);
2746 spin_lock_nested(&dentry->d_parent->d_lock,
2747 DENTRY_D_LOCK_NESTED);
2750 if (target < dentry) {
2751 spin_lock_nested(&target->d_lock, 2);
2752 spin_lock_nested(&dentry->d_lock, 3);
2754 spin_lock_nested(&dentry->d_lock, 2);
2755 spin_lock_nested(&target->d_lock, 3);
2759 static void dentry_unlock_for_move(struct dentry *dentry, struct dentry *target)
2761 if (target->d_parent != dentry->d_parent)
2762 spin_unlock(&dentry->d_parent->d_lock);
2763 if (target->d_parent != target)
2764 spin_unlock(&target->d_parent->d_lock);
2765 spin_unlock(&target->d_lock);
2766 spin_unlock(&dentry->d_lock);
2770 * When switching names, the actual string doesn't strictly have to
2771 * be preserved in the target - because we're dropping the target
2772 * anyway. As such, we can just do a simple memcpy() to copy over
2773 * the new name before we switch, unless we are going to rehash
2774 * it. Note that if we *do* unhash the target, we are not allowed
2775 * to rehash it without giving it a new name/hash key - whether
2776 * we swap or overwrite the names here, resulting name won't match
2777 * the reality in filesystem; it's only there for d_path() purposes.
2778 * Note that all of this is happening under rename_lock, so the
2779 * any hash lookup seeing it in the middle of manipulations will
2780 * be discarded anyway. So we do not care what happens to the hash
2784 * __d_move - move a dentry
2785 * @dentry: entry to move
2786 * @target: new dentry
2787 * @exchange: exchange the two dentries
2789 * Update the dcache to reflect the move of a file name. Negative
2790 * dcache entries should not be moved in this way. Caller must hold
2791 * rename_lock, the i_mutex of the source and target directories,
2792 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2794 static void __d_move(struct dentry *dentry, struct dentry *target,
2797 struct inode *dir = NULL;
2799 if (!dentry->d_inode)
2800 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
2802 BUG_ON(d_ancestor(dentry, target));
2803 BUG_ON(d_ancestor(target, dentry));
2805 dentry_lock_for_move(dentry, target);
2806 if (unlikely(d_in_lookup(target))) {
2807 dir = target->d_parent->d_inode;
2808 n = start_dir_add(dir);
2809 __d_lookup_done(target);
2812 write_seqcount_begin(&dentry->d_seq);
2813 write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
2816 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
2820 /* Switch the names.. */
2822 swap_names(dentry, target);
2824 copy_name(dentry, target);
2826 /* rehash in new place(s) */
2831 /* ... and switch them in the tree */
2832 if (IS_ROOT(dentry)) {
2833 /* splicing a tree */
2834 dentry->d_flags |= DCACHE_RCUACCESS;
2835 dentry->d_parent = target->d_parent;
2836 target->d_parent = target;
2837 list_del_init(&target->d_child);
2838 list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
2840 /* swapping two dentries */
2841 swap(dentry->d_parent, target->d_parent);
2842 list_move(&target->d_child, &target->d_parent->d_subdirs);
2843 list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
2845 fsnotify_update_flags(target);
2846 fsnotify_update_flags(dentry);
2849 write_seqcount_end(&target->d_seq);
2850 write_seqcount_end(&dentry->d_seq);
2853 end_dir_add(dir, n);
2854 dentry_unlock_for_move(dentry, target);
2858 * d_move - move a dentry
2859 * @dentry: entry to move
2860 * @target: new dentry
2862 * Update the dcache to reflect the move of a file name. Negative
2863 * dcache entries should not be moved in this way. See the locking
2864 * requirements for __d_move.
2866 void d_move(struct dentry *dentry, struct dentry *target)
2868 write_seqlock(&rename_lock);
2869 __d_move(dentry, target, false);
2870 write_sequnlock(&rename_lock);
2872 EXPORT_SYMBOL(d_move);
2875 * d_exchange - exchange two dentries
2876 * @dentry1: first dentry
2877 * @dentry2: second dentry
2879 void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
2881 write_seqlock(&rename_lock);
2883 WARN_ON(!dentry1->d_inode);
2884 WARN_ON(!dentry2->d_inode);
2885 WARN_ON(IS_ROOT(dentry1));
2886 WARN_ON(IS_ROOT(dentry2));
2888 __d_move(dentry1, dentry2, true);
2890 write_sequnlock(&rename_lock);
2894 * d_ancestor - search for an ancestor
2895 * @p1: ancestor dentry
2898 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2899 * an ancestor of p2, else NULL.
2901 struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2905 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2906 if (p->d_parent == p1)
2913 * This helper attempts to cope with remotely renamed directories
2915 * It assumes that the caller is already holding
2916 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2918 * Note: If ever the locking in lock_rename() changes, then please
2919 * remember to update this too...
2921 static int __d_unalias(struct inode *inode,
2922 struct dentry *dentry, struct dentry *alias)
2924 struct mutex *m1 = NULL;
2925 struct rw_semaphore *m2 = NULL;
2928 /* If alias and dentry share a parent, then no extra locks required */
2929 if (alias->d_parent == dentry->d_parent)
2932 /* See lock_rename() */
2933 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
2935 m1 = &dentry->d_sb->s_vfs_rename_mutex;
2936 if (!inode_trylock_shared(alias->d_parent->d_inode))
2938 m2 = &alias->d_parent->d_inode->i_rwsem;
2940 __d_move(alias, dentry, false);
2951 * d_splice_alias - splice a disconnected dentry into the tree if one exists
2952 * @inode: the inode which may have a disconnected dentry
2953 * @dentry: a negative dentry which we want to point to the inode.
2955 * If inode is a directory and has an IS_ROOT alias, then d_move that in
2956 * place of the given dentry and return it, else simply d_add the inode
2957 * to the dentry and return NULL.
2959 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
2960 * we should error out: directories can't have multiple aliases.
2962 * This is needed in the lookup routine of any filesystem that is exportable
2963 * (via knfsd) so that we can build dcache paths to directories effectively.
2965 * If a dentry was found and moved, then it is returned. Otherwise NULL
2966 * is returned. This matches the expected return value of ->lookup.
2968 * Cluster filesystems may call this function with a negative, hashed dentry.
2969 * In that case, we know that the inode will be a regular file, and also this
2970 * will only occur during atomic_open. So we need to check for the dentry
2971 * being already hashed only in the final case.
2973 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
2976 return ERR_CAST(inode);
2978 BUG_ON(!d_unhashed(dentry));
2983 security_d_instantiate(dentry, inode);
2984 spin_lock(&inode->i_lock);
2985 if (S_ISDIR(inode->i_mode)) {
2986 struct dentry *new = __d_find_any_alias(inode);
2987 if (unlikely(new)) {
2988 /* The reference to new ensures it remains an alias */
2989 spin_unlock(&inode->i_lock);
2990 write_seqlock(&rename_lock);
2991 if (unlikely(d_ancestor(new, dentry))) {
2992 write_sequnlock(&rename_lock);
2994 new = ERR_PTR(-ELOOP);
2995 pr_warn_ratelimited(
2996 "VFS: Lookup of '%s' in %s %s"
2997 " would have caused loop\n",
2998 dentry->d_name.name,
2999 inode->i_sb->s_type->name,
3001 } else if (!IS_ROOT(new)) {
3002 int err = __d_unalias(inode, dentry, new);
3003 write_sequnlock(&rename_lock);
3009 __d_move(new, dentry, false);
3010 write_sequnlock(&rename_lock);
3017 __d_add(dentry, inode);
3020 EXPORT_SYMBOL(d_splice_alias);
3022 static int prepend(char **buffer, int *buflen, const char *str, int namelen)
3026 return -ENAMETOOLONG;
3028 memcpy(*buffer, str, namelen);
3033 * prepend_name - prepend a pathname in front of current buffer pointer
3034 * @buffer: buffer pointer
3035 * @buflen: allocated length of the buffer
3036 * @name: name string and length qstr structure
3038 * With RCU path tracing, it may race with d_move(). Use ACCESS_ONCE() to
3039 * make sure that either the old or the new name pointer and length are
3040 * fetched. However, there may be mismatch between length and pointer.
3041 * The length cannot be trusted, we need to copy it byte-by-byte until
3042 * the length is reached or a null byte is found. It also prepends "/" at
3043 * the beginning of the name. The sequence number check at the caller will
3044 * retry it again when a d_move() does happen. So any garbage in the buffer
3045 * due to mismatched pointer and length will be discarded.
3047 * Data dependency barrier is needed to make sure that we see that terminating
3048 * NUL. Alpha strikes again, film at 11...
3050 static int prepend_name(char **buffer, int *buflen, const struct qstr *name)
3052 const char *dname = ACCESS_ONCE(name->name);
3053 u32 dlen = ACCESS_ONCE(name->len);
3056 smp_read_barrier_depends();
3058 *buflen -= dlen + 1;
3060 return -ENAMETOOLONG;
3061 p = *buffer -= dlen + 1;
3073 * prepend_path - Prepend path string to a buffer
3074 * @path: the dentry/vfsmount to report
3075 * @root: root vfsmnt/dentry
3076 * @buffer: pointer to the end of the buffer
3077 * @buflen: pointer to buffer length
3079 * The function will first try to write out the pathname without taking any
3080 * lock other than the RCU read lock to make sure that dentries won't go away.
3081 * It only checks the sequence number of the global rename_lock as any change
3082 * in the dentry's d_seq will be preceded by changes in the rename_lock
3083 * sequence number. If the sequence number had been changed, it will restart
3084 * the whole pathname back-tracing sequence again by taking the rename_lock.
3085 * In this case, there is no need to take the RCU read lock as the recursive
3086 * parent pointer references will keep the dentry chain alive as long as no
3087 * rename operation is performed.
3089 static int prepend_path(const struct path *path,
3090 const struct path *root,
3091 char **buffer, int *buflen)
3093 struct dentry *dentry;
3094 struct vfsmount *vfsmnt;
3097 unsigned seq, m_seq = 0;
3103 read_seqbegin_or_lock(&mount_lock, &m_seq);
3110 dentry = path->dentry;
3112 mnt = real_mount(vfsmnt);
3113 read_seqbegin_or_lock(&rename_lock, &seq);
3114 while (dentry != root->dentry || vfsmnt != root->mnt) {
3115 struct dentry * parent;
3117 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
3118 struct mount *parent = ACCESS_ONCE(mnt->mnt_parent);
3120 if (dentry != vfsmnt->mnt_root) {
3127 if (mnt != parent) {
3128 dentry = ACCESS_ONCE(mnt->mnt_mountpoint);
3134 error = is_mounted(vfsmnt) ? 1 : 2;
3137 parent = dentry->d_parent;
3139 error = prepend_name(&bptr, &blen, &dentry->d_name);
3147 if (need_seqretry(&rename_lock, seq)) {
3151 done_seqretry(&rename_lock, seq);
3155 if (need_seqretry(&mount_lock, m_seq)) {
3159 done_seqretry(&mount_lock, m_seq);
3161 if (error >= 0 && bptr == *buffer) {
3163 error = -ENAMETOOLONG;
3173 * __d_path - return the path of a dentry
3174 * @path: the dentry/vfsmount to report
3175 * @root: root vfsmnt/dentry
3176 * @buf: buffer to return value in
3177 * @buflen: buffer length
3179 * Convert a dentry into an ASCII path name.
3181 * Returns a pointer into the buffer or an error code if the
3182 * path was too long.
3184 * "buflen" should be positive.
3186 * If the path is not reachable from the supplied root, return %NULL.
3188 char *__d_path(const struct path *path,
3189 const struct path *root,
3190 char *buf, int buflen)
3192 char *res = buf + buflen;
3195 prepend(&res, &buflen, "\0", 1);
3196 error = prepend_path(path, root, &res, &buflen);
3199 return ERR_PTR(error);
3205 char *d_absolute_path(const struct path *path,
3206 char *buf, int buflen)
3208 struct path root = {};
3209 char *res = buf + buflen;
3212 prepend(&res, &buflen, "\0", 1);
3213 error = prepend_path(path, &root, &res, &buflen);
3218 return ERR_PTR(error);
3223 * same as __d_path but appends "(deleted)" for unlinked files.
3225 static int path_with_deleted(const struct path *path,
3226 const struct path *root,
3227 char **buf, int *buflen)
3229 prepend(buf, buflen, "\0", 1);
3230 if (d_unlinked(path->dentry)) {
3231 int error = prepend(buf, buflen, " (deleted)", 10);
3236 return prepend_path(path, root, buf, buflen);
3239 static int prepend_unreachable(char **buffer, int *buflen)
3241 return prepend(buffer, buflen, "(unreachable)", 13);
3244 static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
3249 seq = read_seqcount_begin(&fs->seq);
3251 } while (read_seqcount_retry(&fs->seq, seq));
3255 * d_path - return the path of a dentry
3256 * @path: path to report
3257 * @buf: buffer to return value in
3258 * @buflen: buffer length
3260 * Convert a dentry into an ASCII path name. If the entry has been deleted
3261 * the string " (deleted)" is appended. Note that this is ambiguous.
3263 * Returns a pointer into the buffer or an error code if the path was
3264 * too long. Note: Callers should use the returned pointer, not the passed
3265 * in buffer, to use the name! The implementation often starts at an offset
3266 * into the buffer, and may leave 0 bytes at the start.
3268 * "buflen" should be positive.
3270 char *d_path(const struct path *path, char *buf, int buflen)
3272 char *res = buf + buflen;
3277 * We have various synthetic filesystems that never get mounted. On
3278 * these filesystems dentries are never used for lookup purposes, and
3279 * thus don't need to be hashed. They also don't need a name until a
3280 * user wants to identify the object in /proc/pid/fd/. The little hack
3281 * below allows us to generate a name for these objects on demand:
3283 * Some pseudo inodes are mountable. When they are mounted
3284 * path->dentry == path->mnt->mnt_root. In that case don't call d_dname
3285 * and instead have d_path return the mounted path.
3287 if (path->dentry->d_op && path->dentry->d_op->d_dname &&
3288 (!IS_ROOT(path->dentry) || path->dentry != path->mnt->mnt_root))
3289 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
3292 get_fs_root_rcu(current->fs, &root);
3293 error = path_with_deleted(path, &root, &res, &buflen);
3297 res = ERR_PTR(error);
3300 EXPORT_SYMBOL(d_path);
3303 * Helper function for dentry_operations.d_dname() members
3305 char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
3306 const char *fmt, ...)
3312 va_start(args, fmt);
3313 sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
3316 if (sz > sizeof(temp) || sz > buflen)
3317 return ERR_PTR(-ENAMETOOLONG);
3319 buffer += buflen - sz;
3320 return memcpy(buffer, temp, sz);
3323 char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
3325 char *end = buffer + buflen;
3326 /* these dentries are never renamed, so d_lock is not needed */
3327 if (prepend(&end, &buflen, " (deleted)", 11) ||
3328 prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len) ||
3329 prepend(&end, &buflen, "/", 1))
3330 end = ERR_PTR(-ENAMETOOLONG);
3333 EXPORT_SYMBOL(simple_dname);
3336 * Write full pathname from the root of the filesystem into the buffer.
3338 static char *__dentry_path(struct dentry *d, char *buf, int buflen)
3340 struct dentry *dentry;
3353 prepend(&end, &len, "\0", 1);
3357 read_seqbegin_or_lock(&rename_lock, &seq);
3358 while (!IS_ROOT(dentry)) {
3359 struct dentry *parent = dentry->d_parent;
3362 error = prepend_name(&end, &len, &dentry->d_name);
3371 if (need_seqretry(&rename_lock, seq)) {
3375 done_seqretry(&rename_lock, seq);
3380 return ERR_PTR(-ENAMETOOLONG);
3383 char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
3385 return __dentry_path(dentry, buf, buflen);
3387 EXPORT_SYMBOL(dentry_path_raw);
3389 char *dentry_path(struct dentry *dentry, char *buf, int buflen)
3394 if (d_unlinked(dentry)) {
3396 if (prepend(&p, &buflen, "//deleted", 10) != 0)
3400 retval = __dentry_path(dentry, buf, buflen);
3401 if (!IS_ERR(retval) && p)
3402 *p = '/'; /* restore '/' overriden with '\0' */
3405 return ERR_PTR(-ENAMETOOLONG);
3408 static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root,
3414 seq = read_seqcount_begin(&fs->seq);
3417 } while (read_seqcount_retry(&fs->seq, seq));
3421 * NOTE! The user-level library version returns a
3422 * character pointer. The kernel system call just
3423 * returns the length of the buffer filled (which
3424 * includes the ending '\0' character), or a negative
3425 * error value. So libc would do something like
3427 * char *getcwd(char * buf, size_t size)
3431 * retval = sys_getcwd(buf, size);
3438 SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
3441 struct path pwd, root;
3442 char *page = __getname();
3448 get_fs_root_and_pwd_rcu(current->fs, &root, &pwd);
3451 if (!d_unlinked(pwd.dentry)) {
3453 char *cwd = page + PATH_MAX;
3454 int buflen = PATH_MAX;
3456 prepend(&cwd, &buflen, "\0", 1);
3457 error = prepend_path(&pwd, &root, &cwd, &buflen);
3463 /* Unreachable from current root */
3465 error = prepend_unreachable(&cwd, &buflen);
3471 len = PATH_MAX + page - cwd;
3474 if (copy_to_user(buf, cwd, len))
3487 * Test whether new_dentry is a subdirectory of old_dentry.
3489 * Trivially implemented using the dcache structure
3493 * is_subdir - is new dentry a subdirectory of old_dentry
3494 * @new_dentry: new dentry
3495 * @old_dentry: old dentry
3497 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3498 * Returns false otherwise.
3499 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3502 bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
3507 if (new_dentry == old_dentry)
3511 /* for restarting inner loop in case of seq retry */
3512 seq = read_seqbegin(&rename_lock);
3514 * Need rcu_readlock to protect against the d_parent trashing
3518 if (d_ancestor(old_dentry, new_dentry))
3523 } while (read_seqretry(&rename_lock, seq));
3528 static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
3530 struct dentry *root = data;
3531 if (dentry != root) {
3532 if (d_unhashed(dentry) || !dentry->d_inode)
3535 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
3536 dentry->d_flags |= DCACHE_GENOCIDE;
3537 dentry->d_lockref.count--;
3540 return D_WALK_CONTINUE;
3543 void d_genocide(struct dentry *parent)
3545 d_walk(parent, parent, d_genocide_kill, NULL);
3548 void d_tmpfile(struct dentry *dentry, struct inode *inode)
3550 inode_dec_link_count(inode);
3551 BUG_ON(dentry->d_name.name != dentry->d_iname ||
3552 !hlist_unhashed(&dentry->d_u.d_alias) ||
3553 !d_unlinked(dentry));
3554 spin_lock(&dentry->d_parent->d_lock);
3555 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
3556 dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
3557 (unsigned long long)inode->i_ino);
3558 spin_unlock(&dentry->d_lock);
3559 spin_unlock(&dentry->d_parent->d_lock);
3560 d_instantiate(dentry, inode);
3562 EXPORT_SYMBOL(d_tmpfile);
3564 static __initdata unsigned long dhash_entries;
3565 static int __init set_dhash_entries(char *str)
3569 dhash_entries = simple_strtoul(str, &str, 0);
3572 __setup("dhash_entries=", set_dhash_entries);
3574 static void __init dcache_init_early(void)
3578 /* If hashes are distributed across NUMA nodes, defer
3579 * hash allocation until vmalloc space is available.
3585 alloc_large_system_hash("Dentry cache",
3586 sizeof(struct hlist_bl_head),
3595 for (loop = 0; loop < (1U << d_hash_shift); loop++)
3596 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
3599 static void __init dcache_init(void)
3604 * A constructor could be added for stable state like the lists,
3605 * but it is probably not worth it because of the cache nature
3608 dentry_cache = KMEM_CACHE(dentry,
3609 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT);
3611 /* Hash may have been set up in dcache_init_early */
3616 alloc_large_system_hash("Dentry cache",
3617 sizeof(struct hlist_bl_head),
3626 for (loop = 0; loop < (1U << d_hash_shift); loop++)
3627 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
3630 /* SLAB cache for __getname() consumers */
3631 struct kmem_cache *names_cachep __read_mostly;
3632 EXPORT_SYMBOL(names_cachep);
3634 EXPORT_SYMBOL(d_genocide);
3636 void __init vfs_caches_init_early(void)
3640 for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++)
3641 INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]);
3643 dcache_init_early();
3647 void __init vfs_caches_init(void)
3649 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
3650 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
3655 files_maxfiles_init();