4 * Complete reimplementation
5 * (C) 1997 Thomas Schoebel-Theuer,
6 * with heavy changes by Linus Torvalds
10 * Notes on the allocation strategy:
12 * The dcache is a master of the icache - whenever a dcache entry
13 * exists, the inode will always exist. "iput()" is done either when
14 * the dcache entry is deleted or garbage collected.
17 #include <linux/syscalls.h>
18 #include <linux/string.h>
21 #include <linux/fsnotify.h>
22 #include <linux/slab.h>
23 #include <linux/init.h>
24 #include <linux/hash.h>
25 #include <linux/cache.h>
26 #include <linux/export.h>
27 #include <linux/mount.h>
28 #include <linux/file.h>
29 #include <asm/uaccess.h>
30 #include <linux/security.h>
31 #include <linux/seqlock.h>
32 #include <linux/swap.h>
33 #include <linux/bootmem.h>
34 #include <linux/fs_struct.h>
35 #include <linux/hardirq.h>
36 #include <linux/bit_spinlock.h>
37 #include <linux/rculist_bl.h>
38 #include <linux/prefetch.h>
39 #include <linux/ratelimit.h>
40 #include <linux/list_lru.h>
41 #include <linux/kasan.h>
48 * dcache->d_inode->i_lock protects:
49 * - i_dentry, d_u.d_alias, d_inode of aliases
50 * dcache_hash_bucket lock protects:
51 * - the dcache hash table
52 * s_anon bl list spinlock protects:
53 * - the s_anon list (see __d_drop)
54 * dentry->d_sb->s_dentry_lru_lock protects:
55 * - the dcache lru lists and counters
62 * - d_parent and d_subdirs
63 * - childrens' d_child and d_parent
64 * - d_u.d_alias, d_inode
67 * dentry->d_inode->i_lock
69 * dentry->d_sb->s_dentry_lru_lock
70 * dcache_hash_bucket lock
73 * If there is an ancestor relationship:
74 * dentry->d_parent->...->d_parent->d_lock
76 * dentry->d_parent->d_lock
79 * If no ancestor relationship:
80 * if (dentry1 < dentry2)
84 int sysctl_vfs_cache_pressure __read_mostly = 100;
85 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
87 __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
89 EXPORT_SYMBOL(rename_lock);
91 static struct kmem_cache *dentry_cache __read_mostly;
94 * This is the single most critical data structure when it comes
95 * to the dcache: the hashtable for lookups. Somebody should try
96 * to make this good - I've just made it work.
98 * This hash-function tries to avoid losing too many bits of hash
99 * information, yet avoid using a prime hash-size or similar.
102 static unsigned int d_hash_mask __read_mostly;
103 static unsigned int d_hash_shift __read_mostly;
105 static struct hlist_bl_head *dentry_hashtable __read_mostly;
107 static inline struct hlist_bl_head *d_hash(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,
290 dentry->d_name.len + 1);
291 spin_unlock(&dentry->d_lock);
292 name->name = name->inline_name;
295 EXPORT_SYMBOL(take_dentry_name_snapshot);
297 void release_dentry_name_snapshot(struct name_snapshot *name)
299 if (unlikely(name->name != name->inline_name)) {
300 struct external_name *p;
301 p = container_of(name->name, struct external_name, name[0]);
302 if (unlikely(atomic_dec_and_test(&p->u.count)))
303 kfree_rcu(p, u.head);
306 EXPORT_SYMBOL(release_dentry_name_snapshot);
308 static inline void __d_set_inode_and_type(struct dentry *dentry,
314 dentry->d_inode = inode;
315 flags = READ_ONCE(dentry->d_flags);
316 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
318 WRITE_ONCE(dentry->d_flags, flags);
321 static inline void __d_clear_type_and_inode(struct dentry *dentry)
323 unsigned flags = READ_ONCE(dentry->d_flags);
325 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
326 WRITE_ONCE(dentry->d_flags, flags);
327 dentry->d_inode = NULL;
330 static void dentry_free(struct dentry *dentry)
332 WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias));
333 if (unlikely(dname_external(dentry))) {
334 struct external_name *p = external_name(dentry);
335 if (likely(atomic_dec_and_test(&p->u.count))) {
336 call_rcu(&dentry->d_u.d_rcu, __d_free_external);
340 /* if dentry was never visible to RCU, immediate free is OK */
341 if (!(dentry->d_flags & DCACHE_RCUACCESS))
342 __d_free(&dentry->d_u.d_rcu);
344 call_rcu(&dentry->d_u.d_rcu, __d_free);
348 * Release the dentry's inode, using the filesystem
349 * d_iput() operation if defined.
351 static void dentry_unlink_inode(struct dentry * dentry)
352 __releases(dentry->d_lock)
353 __releases(dentry->d_inode->i_lock)
355 struct inode *inode = dentry->d_inode;
357 raw_write_seqcount_begin(&dentry->d_seq);
358 __d_clear_type_and_inode(dentry);
359 hlist_del_init(&dentry->d_u.d_alias);
360 raw_write_seqcount_end(&dentry->d_seq);
361 spin_unlock(&dentry->d_lock);
362 spin_unlock(&inode->i_lock);
364 fsnotify_inoderemove(inode);
365 if (dentry->d_op && dentry->d_op->d_iput)
366 dentry->d_op->d_iput(dentry, inode);
372 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
373 * is in use - which includes both the "real" per-superblock
374 * LRU list _and_ the DCACHE_SHRINK_LIST use.
376 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
377 * on the shrink list (ie not on the superblock LRU list).
379 * The per-cpu "nr_dentry_unused" counters are updated with
380 * the DCACHE_LRU_LIST bit.
382 * These helper functions make sure we always follow the
383 * rules. d_lock must be held by the caller.
385 #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
386 static void d_lru_add(struct dentry *dentry)
388 D_FLAG_VERIFY(dentry, 0);
389 dentry->d_flags |= DCACHE_LRU_LIST;
390 this_cpu_inc(nr_dentry_unused);
391 WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
394 static void d_lru_del(struct dentry *dentry)
396 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
397 dentry->d_flags &= ~DCACHE_LRU_LIST;
398 this_cpu_dec(nr_dentry_unused);
399 WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
402 static void d_shrink_del(struct dentry *dentry)
404 D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
405 list_del_init(&dentry->d_lru);
406 dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
407 this_cpu_dec(nr_dentry_unused);
410 static void d_shrink_add(struct dentry *dentry, struct list_head *list)
412 D_FLAG_VERIFY(dentry, 0);
413 list_add(&dentry->d_lru, list);
414 dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST;
415 this_cpu_inc(nr_dentry_unused);
419 * These can only be called under the global LRU lock, ie during the
420 * callback for freeing the LRU list. "isolate" removes it from the
421 * LRU lists entirely, while shrink_move moves it to the indicated
424 static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry)
426 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
427 dentry->d_flags &= ~DCACHE_LRU_LIST;
428 this_cpu_dec(nr_dentry_unused);
429 list_lru_isolate(lru, &dentry->d_lru);
432 static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
433 struct list_head *list)
435 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
436 dentry->d_flags |= DCACHE_SHRINK_LIST;
437 list_lru_isolate_move(lru, &dentry->d_lru, list);
441 * dentry_lru_(add|del)_list) must be called with d_lock held.
443 static void dentry_lru_add(struct dentry *dentry)
445 if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
450 * d_drop - drop a dentry
451 * @dentry: dentry to drop
453 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
454 * be found through a VFS lookup any more. Note that this is different from
455 * deleting the dentry - d_delete will try to mark the dentry negative if
456 * possible, giving a successful _negative_ lookup, while d_drop will
457 * just make the cache lookup fail.
459 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
460 * reason (NFS timeouts or autofs deletes).
462 * __d_drop requires dentry->d_lock
463 * ___d_drop doesn't mark dentry as "unhashed"
464 * (dentry->d_hash.pprev will be LIST_POISON2, not NULL).
466 static void ___d_drop(struct dentry *dentry)
468 if (!d_unhashed(dentry)) {
469 struct hlist_bl_head *b;
471 * Hashed dentries are normally on the dentry hashtable,
472 * with the exception of those newly allocated by
473 * d_obtain_alias, which are always IS_ROOT:
475 if (unlikely(IS_ROOT(dentry)))
476 b = &dentry->d_sb->s_anon;
478 b = d_hash(dentry->d_name.hash);
481 __hlist_bl_del(&dentry->d_hash);
483 /* After this call, in-progress rcu-walk path lookup will fail. */
484 write_seqcount_invalidate(&dentry->d_seq);
488 void __d_drop(struct dentry *dentry)
491 dentry->d_hash.pprev = NULL;
493 EXPORT_SYMBOL(__d_drop);
495 void d_drop(struct dentry *dentry)
497 spin_lock(&dentry->d_lock);
499 spin_unlock(&dentry->d_lock);
501 EXPORT_SYMBOL(d_drop);
503 static inline void dentry_unlist(struct dentry *dentry, struct dentry *parent)
507 * Inform d_walk() and shrink_dentry_list() that we are no longer
508 * attached to the dentry tree
510 dentry->d_flags |= DCACHE_DENTRY_KILLED;
511 if (unlikely(list_empty(&dentry->d_child)))
513 __list_del_entry(&dentry->d_child);
515 * Cursors can move around the list of children. While we'd been
516 * a normal list member, it didn't matter - ->d_child.next would've
517 * been updated. However, from now on it won't be and for the
518 * things like d_walk() it might end up with a nasty surprise.
519 * Normally d_walk() doesn't care about cursors moving around -
520 * ->d_lock on parent prevents that and since a cursor has no children
521 * of its own, we get through it without ever unlocking the parent.
522 * There is one exception, though - if we ascend from a child that
523 * gets killed as soon as we unlock it, the next sibling is found
524 * using the value left in its ->d_child.next. And if _that_
525 * pointed to a cursor, and cursor got moved (e.g. by lseek())
526 * before d_walk() regains parent->d_lock, we'll end up skipping
527 * everything the cursor had been moved past.
529 * Solution: make sure that the pointer left behind in ->d_child.next
530 * points to something that won't be moving around. I.e. skip the
533 while (dentry->d_child.next != &parent->d_subdirs) {
534 next = list_entry(dentry->d_child.next, struct dentry, d_child);
535 if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR)))
537 dentry->d_child.next = next->d_child.next;
541 static void __dentry_kill(struct dentry *dentry)
543 struct dentry *parent = NULL;
544 bool can_free = true;
545 if (!IS_ROOT(dentry))
546 parent = dentry->d_parent;
549 * The dentry is now unrecoverably dead to the world.
551 lockref_mark_dead(&dentry->d_lockref);
554 * inform the fs via d_prune that this dentry is about to be
555 * unhashed and destroyed.
557 if (dentry->d_flags & DCACHE_OP_PRUNE)
558 dentry->d_op->d_prune(dentry);
560 if (dentry->d_flags & DCACHE_LRU_LIST) {
561 if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
564 /* if it was on the hash then remove it */
566 dentry_unlist(dentry, parent);
568 spin_unlock(&parent->d_lock);
570 dentry_unlink_inode(dentry);
572 spin_unlock(&dentry->d_lock);
573 this_cpu_dec(nr_dentry);
574 if (dentry->d_op && dentry->d_op->d_release)
575 dentry->d_op->d_release(dentry);
577 spin_lock(&dentry->d_lock);
578 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
579 dentry->d_flags |= DCACHE_MAY_FREE;
582 spin_unlock(&dentry->d_lock);
583 if (likely(can_free))
588 * Finish off a dentry we've decided to kill.
589 * dentry->d_lock must be held, returns with it unlocked.
590 * If ref is non-zero, then decrement the refcount too.
591 * Returns dentry requiring refcount drop, or NULL if we're done.
593 static struct dentry *dentry_kill(struct dentry *dentry)
594 __releases(dentry->d_lock)
596 struct inode *inode = dentry->d_inode;
597 struct dentry *parent = NULL;
599 if (inode && unlikely(!spin_trylock(&inode->i_lock)))
602 if (!IS_ROOT(dentry)) {
603 parent = dentry->d_parent;
604 if (unlikely(!spin_trylock(&parent->d_lock))) {
606 spin_unlock(&inode->i_lock);
611 __dentry_kill(dentry);
615 spin_unlock(&dentry->d_lock);
616 return dentry; /* try again with same dentry */
619 static inline struct dentry *lock_parent(struct dentry *dentry)
621 struct dentry *parent = dentry->d_parent;
624 if (unlikely(dentry->d_lockref.count < 0))
626 if (likely(spin_trylock(&parent->d_lock)))
629 spin_unlock(&dentry->d_lock);
631 parent = ACCESS_ONCE(dentry->d_parent);
632 spin_lock(&parent->d_lock);
634 * We can't blindly lock dentry until we are sure
635 * that we won't violate the locking order.
636 * Any changes of dentry->d_parent must have
637 * been done with parent->d_lock held, so
638 * spin_lock() above is enough of a barrier
639 * for checking if it's still our child.
641 if (unlikely(parent != dentry->d_parent)) {
642 spin_unlock(&parent->d_lock);
645 if (parent != dentry) {
646 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
647 if (unlikely(dentry->d_lockref.count < 0)) {
648 spin_unlock(&parent->d_lock);
659 * Try to do a lockless dput(), and return whether that was successful.
661 * If unsuccessful, we return false, having already taken the dentry lock.
663 * The caller needs to hold the RCU read lock, so that the dentry is
664 * guaranteed to stay around even if the refcount goes down to zero!
666 static inline bool fast_dput(struct dentry *dentry)
669 unsigned int d_flags;
672 * If we have a d_op->d_delete() operation, we sould not
673 * let the dentry count go to zero, so use "put_or_lock".
675 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE))
676 return lockref_put_or_lock(&dentry->d_lockref);
679 * .. otherwise, we can try to just decrement the
680 * lockref optimistically.
682 ret = lockref_put_return(&dentry->d_lockref);
685 * If the lockref_put_return() failed due to the lock being held
686 * by somebody else, the fast path has failed. We will need to
687 * get the lock, and then check the count again.
689 if (unlikely(ret < 0)) {
690 spin_lock(&dentry->d_lock);
691 if (dentry->d_lockref.count > 1) {
692 dentry->d_lockref.count--;
693 spin_unlock(&dentry->d_lock);
700 * If we weren't the last ref, we're done.
706 * Careful, careful. The reference count went down
707 * to zero, but we don't hold the dentry lock, so
708 * somebody else could get it again, and do another
709 * dput(), and we need to not race with that.
711 * However, there is a very special and common case
712 * where we don't care, because there is nothing to
713 * do: the dentry is still hashed, it does not have
714 * a 'delete' op, and it's referenced and already on
717 * NOTE! Since we aren't locked, these values are
718 * not "stable". However, it is sufficient that at
719 * some point after we dropped the reference the
720 * dentry was hashed and the flags had the proper
721 * value. Other dentry users may have re-gotten
722 * a reference to the dentry and change that, but
723 * our work is done - we can leave the dentry
724 * around with a zero refcount.
727 d_flags = ACCESS_ONCE(dentry->d_flags);
728 d_flags &= DCACHE_REFERENCED | DCACHE_LRU_LIST | DCACHE_DISCONNECTED;
730 /* Nothing to do? Dropping the reference was all we needed? */
731 if (d_flags == (DCACHE_REFERENCED | DCACHE_LRU_LIST) && !d_unhashed(dentry))
735 * Not the fast normal case? Get the lock. We've already decremented
736 * the refcount, but we'll need to re-check the situation after
739 spin_lock(&dentry->d_lock);
742 * Did somebody else grab a reference to it in the meantime, and
743 * we're no longer the last user after all? Alternatively, somebody
744 * else could have killed it and marked it dead. Either way, we
745 * don't need to do anything else.
747 if (dentry->d_lockref.count) {
748 spin_unlock(&dentry->d_lock);
753 * Re-get the reference we optimistically dropped. We hold the
754 * lock, and we just tested that it was zero, so we can just
757 dentry->d_lockref.count = 1;
765 * This is complicated by the fact that we do not want to put
766 * dentries that are no longer on any hash chain on the unused
767 * list: we'd much rather just get rid of them immediately.
769 * However, that implies that we have to traverse the dentry
770 * tree upwards to the parents which might _also_ now be
771 * scheduled for deletion (it may have been only waiting for
772 * its last child to go away).
774 * This tail recursion is done by hand as we don't want to depend
775 * on the compiler to always get this right (gcc generally doesn't).
776 * Real recursion would eat up our stack space.
780 * dput - release a dentry
781 * @dentry: dentry to release
783 * Release a dentry. This will drop the usage count and if appropriate
784 * call the dentry unlink method as well as removing it from the queues and
785 * releasing its resources. If the parent dentries were scheduled for release
786 * they too may now get deleted.
788 void dput(struct dentry *dentry)
790 if (unlikely(!dentry))
797 if (likely(fast_dput(dentry))) {
802 /* Slow case: now with the dentry lock held */
805 WARN_ON(d_in_lookup(dentry));
807 /* Unreachable? Get rid of it */
808 if (unlikely(d_unhashed(dentry)))
811 if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
814 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) {
815 if (dentry->d_op->d_delete(dentry))
819 if (!(dentry->d_flags & DCACHE_REFERENCED))
820 dentry->d_flags |= DCACHE_REFERENCED;
821 dentry_lru_add(dentry);
823 dentry->d_lockref.count--;
824 spin_unlock(&dentry->d_lock);
828 dentry = dentry_kill(dentry);
837 /* This must be called with d_lock held */
838 static inline void __dget_dlock(struct dentry *dentry)
840 dentry->d_lockref.count++;
843 static inline void __dget(struct dentry *dentry)
845 lockref_get(&dentry->d_lockref);
848 struct dentry *dget_parent(struct dentry *dentry)
854 * Do optimistic parent lookup without any
858 ret = ACCESS_ONCE(dentry->d_parent);
859 gotref = lockref_get_not_zero(&ret->d_lockref);
861 if (likely(gotref)) {
862 if (likely(ret == ACCESS_ONCE(dentry->d_parent)))
869 * Don't need rcu_dereference because we re-check it was correct under
873 ret = dentry->d_parent;
874 spin_lock(&ret->d_lock);
875 if (unlikely(ret != dentry->d_parent)) {
876 spin_unlock(&ret->d_lock);
881 BUG_ON(!ret->d_lockref.count);
882 ret->d_lockref.count++;
883 spin_unlock(&ret->d_lock);
886 EXPORT_SYMBOL(dget_parent);
889 * d_find_alias - grab a hashed alias of inode
890 * @inode: inode in question
892 * If inode has a hashed alias, or is a directory and has any alias,
893 * acquire the reference to alias and return it. Otherwise return NULL.
894 * Notice that if inode is a directory there can be only one alias and
895 * it can be unhashed only if it has no children, or if it is the root
896 * of a filesystem, or if the directory was renamed and d_revalidate
897 * was the first vfs operation to notice.
899 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
900 * any other hashed alias over that one.
902 static struct dentry *__d_find_alias(struct inode *inode)
904 struct dentry *alias, *discon_alias;
908 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
909 spin_lock(&alias->d_lock);
910 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
911 if (IS_ROOT(alias) &&
912 (alias->d_flags & DCACHE_DISCONNECTED)) {
913 discon_alias = alias;
916 spin_unlock(&alias->d_lock);
920 spin_unlock(&alias->d_lock);
923 alias = discon_alias;
924 spin_lock(&alias->d_lock);
925 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
927 spin_unlock(&alias->d_lock);
930 spin_unlock(&alias->d_lock);
936 struct dentry *d_find_alias(struct inode *inode)
938 struct dentry *de = NULL;
940 if (!hlist_empty(&inode->i_dentry)) {
941 spin_lock(&inode->i_lock);
942 de = __d_find_alias(inode);
943 spin_unlock(&inode->i_lock);
947 EXPORT_SYMBOL(d_find_alias);
950 * Try to kill dentries associated with this inode.
951 * WARNING: you must own a reference to inode.
953 void d_prune_aliases(struct inode *inode)
955 struct dentry *dentry;
957 spin_lock(&inode->i_lock);
958 hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
959 spin_lock(&dentry->d_lock);
960 if (!dentry->d_lockref.count) {
961 struct dentry *parent = lock_parent(dentry);
962 if (likely(!dentry->d_lockref.count)) {
963 __dentry_kill(dentry);
968 spin_unlock(&parent->d_lock);
970 spin_unlock(&dentry->d_lock);
972 spin_unlock(&inode->i_lock);
974 EXPORT_SYMBOL(d_prune_aliases);
976 static void shrink_dentry_list(struct list_head *list)
978 struct dentry *dentry, *parent;
980 while (!list_empty(list)) {
982 dentry = list_entry(list->prev, struct dentry, d_lru);
983 spin_lock(&dentry->d_lock);
984 parent = lock_parent(dentry);
987 * The dispose list is isolated and dentries are not accounted
988 * to the LRU here, so we can simply remove it from the list
989 * here regardless of whether it is referenced or not.
991 d_shrink_del(dentry);
994 * We found an inuse dentry which was not removed from
995 * the LRU because of laziness during lookup. Do not free it.
997 if (dentry->d_lockref.count > 0) {
998 spin_unlock(&dentry->d_lock);
1000 spin_unlock(&parent->d_lock);
1005 if (unlikely(dentry->d_flags & DCACHE_DENTRY_KILLED)) {
1006 bool can_free = dentry->d_flags & DCACHE_MAY_FREE;
1007 spin_unlock(&dentry->d_lock);
1009 spin_unlock(&parent->d_lock);
1011 dentry_free(dentry);
1015 inode = dentry->d_inode;
1016 if (inode && unlikely(!spin_trylock(&inode->i_lock))) {
1017 d_shrink_add(dentry, list);
1018 spin_unlock(&dentry->d_lock);
1020 spin_unlock(&parent->d_lock);
1024 __dentry_kill(dentry);
1027 * We need to prune ancestors too. This is necessary to prevent
1028 * quadratic behavior of shrink_dcache_parent(), but is also
1029 * expected to be beneficial in reducing dentry cache
1033 while (dentry && !lockref_put_or_lock(&dentry->d_lockref)) {
1034 parent = lock_parent(dentry);
1035 if (dentry->d_lockref.count != 1) {
1036 dentry->d_lockref.count--;
1037 spin_unlock(&dentry->d_lock);
1039 spin_unlock(&parent->d_lock);
1042 inode = dentry->d_inode; /* can't be NULL */
1043 if (unlikely(!spin_trylock(&inode->i_lock))) {
1044 spin_unlock(&dentry->d_lock);
1046 spin_unlock(&parent->d_lock);
1050 __dentry_kill(dentry);
1056 static enum lru_status dentry_lru_isolate(struct list_head *item,
1057 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1059 struct list_head *freeable = arg;
1060 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1064 * we are inverting the lru lock/dentry->d_lock here,
1065 * so use a trylock. If we fail to get the lock, just skip
1068 if (!spin_trylock(&dentry->d_lock))
1072 * Referenced dentries are still in use. If they have active
1073 * counts, just remove them from the LRU. Otherwise give them
1074 * another pass through the LRU.
1076 if (dentry->d_lockref.count) {
1077 d_lru_isolate(lru, dentry);
1078 spin_unlock(&dentry->d_lock);
1082 if (dentry->d_flags & DCACHE_REFERENCED) {
1083 dentry->d_flags &= ~DCACHE_REFERENCED;
1084 spin_unlock(&dentry->d_lock);
1087 * The list move itself will be made by the common LRU code. At
1088 * this point, we've dropped the dentry->d_lock but keep the
1089 * lru lock. This is safe to do, since every list movement is
1090 * protected by the lru lock even if both locks are held.
1092 * This is guaranteed by the fact that all LRU management
1093 * functions are intermediated by the LRU API calls like
1094 * list_lru_add and list_lru_del. List movement in this file
1095 * only ever occur through this functions or through callbacks
1096 * like this one, that are called from the LRU API.
1098 * The only exceptions to this are functions like
1099 * shrink_dentry_list, and code that first checks for the
1100 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1101 * operating only with stack provided lists after they are
1102 * properly isolated from the main list. It is thus, always a
1108 d_lru_shrink_move(lru, dentry, freeable);
1109 spin_unlock(&dentry->d_lock);
1115 * prune_dcache_sb - shrink the dcache
1117 * @sc: shrink control, passed to list_lru_shrink_walk()
1119 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1120 * is done when we need more memory and called from the superblock shrinker
1123 * This function may fail to free any resources if all the dentries are in
1126 long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc)
1131 freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc,
1132 dentry_lru_isolate, &dispose);
1133 shrink_dentry_list(&dispose);
1137 static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
1138 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1140 struct list_head *freeable = arg;
1141 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1144 * we are inverting the lru lock/dentry->d_lock here,
1145 * so use a trylock. If we fail to get the lock, just skip
1148 if (!spin_trylock(&dentry->d_lock))
1151 d_lru_shrink_move(lru, dentry, freeable);
1152 spin_unlock(&dentry->d_lock);
1159 * shrink_dcache_sb - shrink dcache for a superblock
1162 * Shrink the dcache for the specified super block. This is used to free
1163 * the dcache before unmounting a file system.
1165 void shrink_dcache_sb(struct super_block *sb)
1170 list_lru_walk(&sb->s_dentry_lru,
1171 dentry_lru_isolate_shrink, &dispose, 1024);
1172 shrink_dentry_list(&dispose);
1174 } while (list_lru_count(&sb->s_dentry_lru) > 0);
1176 EXPORT_SYMBOL(shrink_dcache_sb);
1179 * enum d_walk_ret - action to talke during tree walk
1180 * @D_WALK_CONTINUE: contrinue walk
1181 * @D_WALK_QUIT: quit walk
1182 * @D_WALK_NORETRY: quit when retry is needed
1183 * @D_WALK_SKIP: skip this dentry and its children
1193 * d_walk - walk the dentry tree
1194 * @parent: start of walk
1195 * @data: data passed to @enter() and @finish()
1196 * @enter: callback when first entering the dentry
1197 * @finish: callback when successfully finished the walk
1199 * The @enter() and @finish() callbacks are called with d_lock held.
1201 static void d_walk(struct dentry *parent, void *data,
1202 enum d_walk_ret (*enter)(void *, struct dentry *),
1203 void (*finish)(void *))
1205 struct dentry *this_parent;
1206 struct list_head *next;
1208 enum d_walk_ret ret;
1212 read_seqbegin_or_lock(&rename_lock, &seq);
1213 this_parent = parent;
1214 spin_lock(&this_parent->d_lock);
1216 ret = enter(data, this_parent);
1218 case D_WALK_CONTINUE:
1223 case D_WALK_NORETRY:
1228 next = this_parent->d_subdirs.next;
1230 while (next != &this_parent->d_subdirs) {
1231 struct list_head *tmp = next;
1232 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
1235 if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR))
1238 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1240 ret = enter(data, dentry);
1242 case D_WALK_CONTINUE:
1245 spin_unlock(&dentry->d_lock);
1247 case D_WALK_NORETRY:
1251 spin_unlock(&dentry->d_lock);
1255 if (!list_empty(&dentry->d_subdirs)) {
1256 spin_unlock(&this_parent->d_lock);
1257 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
1258 this_parent = dentry;
1259 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1262 spin_unlock(&dentry->d_lock);
1265 * All done at this level ... ascend and resume the search.
1269 if (this_parent != parent) {
1270 struct dentry *child = this_parent;
1271 this_parent = child->d_parent;
1273 spin_unlock(&child->d_lock);
1274 spin_lock(&this_parent->d_lock);
1276 /* might go back up the wrong parent if we have had a rename. */
1277 if (need_seqretry(&rename_lock, seq))
1279 /* go into the first sibling still alive */
1281 next = child->d_child.next;
1282 if (next == &this_parent->d_subdirs)
1284 child = list_entry(next, struct dentry, d_child);
1285 } while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
1289 if (need_seqretry(&rename_lock, seq))
1296 spin_unlock(&this_parent->d_lock);
1297 done_seqretry(&rename_lock, seq);
1301 spin_unlock(&this_parent->d_lock);
1311 * Search for at least 1 mount point in the dentry's subdirs.
1312 * We descend to the next level whenever the d_subdirs
1313 * list is non-empty and continue searching.
1316 static enum d_walk_ret check_mount(void *data, struct dentry *dentry)
1319 if (d_mountpoint(dentry)) {
1323 return D_WALK_CONTINUE;
1327 * have_submounts - check for mounts over a dentry
1328 * @parent: dentry to check.
1330 * Return true if the parent or its subdirectories contain
1333 int have_submounts(struct dentry *parent)
1337 d_walk(parent, &ret, check_mount, NULL);
1341 EXPORT_SYMBOL(have_submounts);
1344 * Called by mount code to set a mountpoint and check if the mountpoint is
1345 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1346 * subtree can become unreachable).
1348 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1349 * this reason take rename_lock and d_lock on dentry and ancestors.
1351 int d_set_mounted(struct dentry *dentry)
1355 write_seqlock(&rename_lock);
1356 for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
1357 /* Need exclusion wrt. d_invalidate() */
1358 spin_lock(&p->d_lock);
1359 if (unlikely(d_unhashed(p))) {
1360 spin_unlock(&p->d_lock);
1363 spin_unlock(&p->d_lock);
1365 spin_lock(&dentry->d_lock);
1366 if (!d_unlinked(dentry)) {
1368 if (!d_mountpoint(dentry)) {
1369 dentry->d_flags |= DCACHE_MOUNTED;
1373 spin_unlock(&dentry->d_lock);
1375 write_sequnlock(&rename_lock);
1380 * Search the dentry child list of the specified parent,
1381 * and move any unused dentries to the end of the unused
1382 * list for prune_dcache(). We descend to the next level
1383 * whenever the d_subdirs list is non-empty and continue
1386 * It returns zero iff there are no unused children,
1387 * otherwise it returns the number of children moved to
1388 * the end of the unused list. This may not be the total
1389 * number of unused children, because select_parent can
1390 * drop the lock and return early due to latency
1394 struct select_data {
1395 struct dentry *start;
1396 struct list_head dispose;
1400 static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
1402 struct select_data *data = _data;
1403 enum d_walk_ret ret = D_WALK_CONTINUE;
1405 if (data->start == dentry)
1408 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1411 if (dentry->d_flags & DCACHE_LRU_LIST)
1413 if (!dentry->d_lockref.count) {
1414 d_shrink_add(dentry, &data->dispose);
1419 * We can return to the caller if we have found some (this
1420 * ensures forward progress). We'll be coming back to find
1423 if (!list_empty(&data->dispose))
1424 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1430 * shrink_dcache_parent - prune dcache
1431 * @parent: parent of entries to prune
1433 * Prune the dcache to remove unused children of the parent dentry.
1435 void shrink_dcache_parent(struct dentry *parent)
1438 struct select_data data;
1440 INIT_LIST_HEAD(&data.dispose);
1441 data.start = parent;
1444 d_walk(parent, &data, select_collect, NULL);
1448 shrink_dentry_list(&data.dispose);
1452 EXPORT_SYMBOL(shrink_dcache_parent);
1454 static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
1456 /* it has busy descendents; complain about those instead */
1457 if (!list_empty(&dentry->d_subdirs))
1458 return D_WALK_CONTINUE;
1460 /* root with refcount 1 is fine */
1461 if (dentry == _data && dentry->d_lockref.count == 1)
1462 return D_WALK_CONTINUE;
1464 printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%pd} "
1465 " still in use (%d) [unmount of %s %s]\n",
1468 dentry->d_inode->i_ino : 0UL,
1470 dentry->d_lockref.count,
1471 dentry->d_sb->s_type->name,
1472 dentry->d_sb->s_id);
1474 return D_WALK_CONTINUE;
1477 static void do_one_tree(struct dentry *dentry)
1479 shrink_dcache_parent(dentry);
1480 d_walk(dentry, dentry, umount_check, NULL);
1486 * destroy the dentries attached to a superblock on unmounting
1488 void shrink_dcache_for_umount(struct super_block *sb)
1490 struct dentry *dentry;
1492 WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked");
1494 dentry = sb->s_root;
1496 do_one_tree(dentry);
1498 while (!hlist_bl_empty(&sb->s_anon)) {
1499 dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash));
1500 do_one_tree(dentry);
1504 struct detach_data {
1505 struct select_data select;
1506 struct dentry *mountpoint;
1508 static enum d_walk_ret detach_and_collect(void *_data, struct dentry *dentry)
1510 struct detach_data *data = _data;
1512 if (d_mountpoint(dentry)) {
1513 __dget_dlock(dentry);
1514 data->mountpoint = dentry;
1518 return select_collect(&data->select, dentry);
1521 static void check_and_drop(void *_data)
1523 struct detach_data *data = _data;
1525 if (!data->mountpoint && list_empty(&data->select.dispose))
1526 __d_drop(data->select.start);
1530 * d_invalidate - detach submounts, prune dcache, and drop
1531 * @dentry: dentry to invalidate (aka detach, prune and drop)
1535 * The final d_drop is done as an atomic operation relative to
1536 * rename_lock ensuring there are no races with d_set_mounted. This
1537 * ensures there are no unhashed dentries on the path to a mountpoint.
1539 void d_invalidate(struct dentry *dentry)
1542 * If it's already been dropped, return OK.
1544 spin_lock(&dentry->d_lock);
1545 if (d_unhashed(dentry)) {
1546 spin_unlock(&dentry->d_lock);
1549 spin_unlock(&dentry->d_lock);
1551 /* Negative dentries can be dropped without further checks */
1552 if (!dentry->d_inode) {
1558 struct detach_data data;
1560 data.mountpoint = NULL;
1561 INIT_LIST_HEAD(&data.select.dispose);
1562 data.select.start = dentry;
1563 data.select.found = 0;
1565 d_walk(dentry, &data, detach_and_collect, check_and_drop);
1567 if (!list_empty(&data.select.dispose))
1568 shrink_dentry_list(&data.select.dispose);
1569 else if (!data.mountpoint)
1572 if (data.mountpoint) {
1573 detach_mounts(data.mountpoint);
1574 dput(data.mountpoint);
1579 EXPORT_SYMBOL(d_invalidate);
1582 * __d_alloc - allocate a dcache entry
1583 * @sb: filesystem it will belong to
1584 * @name: qstr of the name
1586 * Allocates a dentry. It returns %NULL if there is insufficient memory
1587 * available. On a success the dentry is returned. The name passed in is
1588 * copied and the copy passed in may be reused after this call.
1591 struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1593 struct dentry *dentry;
1597 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
1602 * We guarantee that the inline name is always NUL-terminated.
1603 * This way the memcpy() done by the name switching in rename
1604 * will still always have a NUL at the end, even if we might
1605 * be overwriting an internal NUL character
1607 dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
1608 if (unlikely(!name)) {
1609 static const struct qstr anon = QSTR_INIT("/", 1);
1611 dname = dentry->d_iname;
1612 } else if (name->len > DNAME_INLINE_LEN-1) {
1613 size_t size = offsetof(struct external_name, name[1]);
1614 struct external_name *p = kmalloc(size + name->len,
1615 GFP_KERNEL_ACCOUNT);
1617 kmem_cache_free(dentry_cache, dentry);
1620 atomic_set(&p->u.count, 1);
1622 if (IS_ENABLED(CONFIG_DCACHE_WORD_ACCESS))
1623 kasan_unpoison_shadow(dname,
1624 round_up(name->len + 1, sizeof(unsigned long)));
1626 dname = dentry->d_iname;
1629 dentry->d_name.len = name->len;
1630 dentry->d_name.hash = name->hash;
1631 memcpy(dname, name->name, name->len);
1632 dname[name->len] = 0;
1634 /* Make sure we always see the terminating NUL character */
1636 dentry->d_name.name = dname;
1638 dentry->d_lockref.count = 1;
1639 dentry->d_flags = 0;
1640 spin_lock_init(&dentry->d_lock);
1641 seqcount_init(&dentry->d_seq);
1642 dentry->d_inode = NULL;
1643 dentry->d_parent = dentry;
1645 dentry->d_op = NULL;
1646 dentry->d_fsdata = NULL;
1647 INIT_HLIST_BL_NODE(&dentry->d_hash);
1648 INIT_LIST_HEAD(&dentry->d_lru);
1649 INIT_LIST_HEAD(&dentry->d_subdirs);
1650 INIT_HLIST_NODE(&dentry->d_u.d_alias);
1651 INIT_LIST_HEAD(&dentry->d_child);
1652 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1654 if (dentry->d_op && dentry->d_op->d_init) {
1655 err = dentry->d_op->d_init(dentry);
1657 if (dname_external(dentry))
1658 kfree(external_name(dentry));
1659 kmem_cache_free(dentry_cache, dentry);
1664 this_cpu_inc(nr_dentry);
1670 * d_alloc - allocate a dcache entry
1671 * @parent: parent of entry to allocate
1672 * @name: qstr of the name
1674 * Allocates a dentry. It returns %NULL if there is insufficient memory
1675 * available. On a success the dentry is returned. The name passed in is
1676 * copied and the copy passed in may be reused after this call.
1678 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1680 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1683 dentry->d_flags |= DCACHE_RCUACCESS;
1684 spin_lock(&parent->d_lock);
1686 * don't need child lock because it is not subject
1687 * to concurrency here
1689 __dget_dlock(parent);
1690 dentry->d_parent = parent;
1691 list_add(&dentry->d_child, &parent->d_subdirs);
1692 spin_unlock(&parent->d_lock);
1696 EXPORT_SYMBOL(d_alloc);
1698 struct dentry *d_alloc_cursor(struct dentry * parent)
1700 struct dentry *dentry = __d_alloc(parent->d_sb, NULL);
1702 dentry->d_flags |= DCACHE_RCUACCESS | DCACHE_DENTRY_CURSOR;
1703 dentry->d_parent = dget(parent);
1709 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1710 * @sb: the superblock
1711 * @name: qstr of the name
1713 * For a filesystem that just pins its dentries in memory and never
1714 * performs lookups at all, return an unhashed IS_ROOT dentry.
1716 struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1718 return __d_alloc(sb, name);
1720 EXPORT_SYMBOL(d_alloc_pseudo);
1722 struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1727 q.hash_len = hashlen_string(parent, name);
1728 return d_alloc(parent, &q);
1730 EXPORT_SYMBOL(d_alloc_name);
1732 void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1734 WARN_ON_ONCE(dentry->d_op);
1735 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
1737 DCACHE_OP_REVALIDATE |
1738 DCACHE_OP_WEAK_REVALIDATE |
1745 dentry->d_flags |= DCACHE_OP_HASH;
1747 dentry->d_flags |= DCACHE_OP_COMPARE;
1748 if (op->d_revalidate)
1749 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1750 if (op->d_weak_revalidate)
1751 dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
1753 dentry->d_flags |= DCACHE_OP_DELETE;
1755 dentry->d_flags |= DCACHE_OP_PRUNE;
1757 dentry->d_flags |= DCACHE_OP_REAL;
1760 EXPORT_SYMBOL(d_set_d_op);
1764 * d_set_fallthru - Mark a dentry as falling through to a lower layer
1765 * @dentry - The dentry to mark
1767 * Mark a dentry as falling through to the lower layer (as set with
1768 * d_pin_lower()). This flag may be recorded on the medium.
1770 void d_set_fallthru(struct dentry *dentry)
1772 spin_lock(&dentry->d_lock);
1773 dentry->d_flags |= DCACHE_FALLTHRU;
1774 spin_unlock(&dentry->d_lock);
1776 EXPORT_SYMBOL(d_set_fallthru);
1778 static unsigned d_flags_for_inode(struct inode *inode)
1780 unsigned add_flags = DCACHE_REGULAR_TYPE;
1783 return DCACHE_MISS_TYPE;
1785 if (S_ISDIR(inode->i_mode)) {
1786 add_flags = DCACHE_DIRECTORY_TYPE;
1787 if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) {
1788 if (unlikely(!inode->i_op->lookup))
1789 add_flags = DCACHE_AUTODIR_TYPE;
1791 inode->i_opflags |= IOP_LOOKUP;
1793 goto type_determined;
1796 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1797 if (unlikely(inode->i_op->get_link)) {
1798 add_flags = DCACHE_SYMLINK_TYPE;
1799 goto type_determined;
1801 inode->i_opflags |= IOP_NOFOLLOW;
1804 if (unlikely(!S_ISREG(inode->i_mode)))
1805 add_flags = DCACHE_SPECIAL_TYPE;
1808 if (unlikely(IS_AUTOMOUNT(inode)))
1809 add_flags |= DCACHE_NEED_AUTOMOUNT;
1813 static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1815 unsigned add_flags = d_flags_for_inode(inode);
1816 WARN_ON(d_in_lookup(dentry));
1818 spin_lock(&dentry->d_lock);
1819 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
1820 raw_write_seqcount_begin(&dentry->d_seq);
1821 __d_set_inode_and_type(dentry, inode, add_flags);
1822 raw_write_seqcount_end(&dentry->d_seq);
1823 fsnotify_update_flags(dentry);
1824 spin_unlock(&dentry->d_lock);
1828 * d_instantiate - fill in inode information for a dentry
1829 * @entry: dentry to complete
1830 * @inode: inode to attach to this dentry
1832 * Fill in inode information in the entry.
1834 * This turns negative dentries into productive full members
1837 * NOTE! This assumes that the inode count has been incremented
1838 * (or otherwise set) by the caller to indicate that it is now
1839 * in use by the dcache.
1842 void d_instantiate(struct dentry *entry, struct inode * inode)
1844 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1846 security_d_instantiate(entry, inode);
1847 spin_lock(&inode->i_lock);
1848 __d_instantiate(entry, inode);
1849 spin_unlock(&inode->i_lock);
1852 EXPORT_SYMBOL(d_instantiate);
1855 * This should be equivalent to d_instantiate() + unlock_new_inode(),
1856 * with lockdep-related part of unlock_new_inode() done before
1857 * anything else. Use that instead of open-coding d_instantiate()/
1858 * unlock_new_inode() combinations.
1860 void d_instantiate_new(struct dentry *entry, struct inode *inode)
1862 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1864 lockdep_annotate_inode_mutex_key(inode);
1865 security_d_instantiate(entry, inode);
1866 spin_lock(&inode->i_lock);
1867 __d_instantiate(entry, inode);
1868 WARN_ON(!(inode->i_state & I_NEW));
1869 inode->i_state &= ~I_NEW;
1871 wake_up_bit(&inode->i_state, __I_NEW);
1872 spin_unlock(&inode->i_lock);
1874 EXPORT_SYMBOL(d_instantiate_new);
1877 * d_instantiate_no_diralias - instantiate a non-aliased dentry
1878 * @entry: dentry to complete
1879 * @inode: inode to attach to this dentry
1881 * Fill in inode information in the entry. If a directory alias is found, then
1882 * return an error (and drop inode). Together with d_materialise_unique() this
1883 * guarantees that a directory inode may never have more than one alias.
1885 int d_instantiate_no_diralias(struct dentry *entry, struct inode *inode)
1887 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1889 security_d_instantiate(entry, inode);
1890 spin_lock(&inode->i_lock);
1891 if (S_ISDIR(inode->i_mode) && !hlist_empty(&inode->i_dentry)) {
1892 spin_unlock(&inode->i_lock);
1896 __d_instantiate(entry, inode);
1897 spin_unlock(&inode->i_lock);
1901 EXPORT_SYMBOL(d_instantiate_no_diralias);
1903 struct dentry *d_make_root(struct inode *root_inode)
1905 struct dentry *res = NULL;
1908 res = __d_alloc(root_inode->i_sb, NULL);
1910 res->d_flags |= DCACHE_RCUACCESS;
1911 d_instantiate(res, root_inode);
1918 EXPORT_SYMBOL(d_make_root);
1920 static struct dentry * __d_find_any_alias(struct inode *inode)
1922 struct dentry *alias;
1924 if (hlist_empty(&inode->i_dentry))
1926 alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
1932 * d_find_any_alias - find any alias for a given inode
1933 * @inode: inode to find an alias for
1935 * If any aliases exist for the given inode, take and return a
1936 * reference for one of them. If no aliases exist, return %NULL.
1938 struct dentry *d_find_any_alias(struct inode *inode)
1942 spin_lock(&inode->i_lock);
1943 de = __d_find_any_alias(inode);
1944 spin_unlock(&inode->i_lock);
1947 EXPORT_SYMBOL(d_find_any_alias);
1949 static struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
1956 return ERR_PTR(-ESTALE);
1958 return ERR_CAST(inode);
1960 res = d_find_any_alias(inode);
1964 tmp = __d_alloc(inode->i_sb, NULL);
1966 res = ERR_PTR(-ENOMEM);
1970 security_d_instantiate(tmp, inode);
1971 spin_lock(&inode->i_lock);
1972 res = __d_find_any_alias(inode);
1974 spin_unlock(&inode->i_lock);
1979 /* attach a disconnected dentry */
1980 add_flags = d_flags_for_inode(inode);
1983 add_flags |= DCACHE_DISCONNECTED;
1985 spin_lock(&tmp->d_lock);
1986 __d_set_inode_and_type(tmp, inode, add_flags);
1987 hlist_add_head(&tmp->d_u.d_alias, &inode->i_dentry);
1988 hlist_bl_lock(&tmp->d_sb->s_anon);
1989 hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
1990 hlist_bl_unlock(&tmp->d_sb->s_anon);
1991 spin_unlock(&tmp->d_lock);
1992 spin_unlock(&inode->i_lock);
2002 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
2003 * @inode: inode to allocate the dentry for
2005 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
2006 * similar open by handle operations. The returned dentry may be anonymous,
2007 * or may have a full name (if the inode was already in the cache).
2009 * When called on a directory inode, we must ensure that the inode only ever
2010 * has one dentry. If a dentry is found, that is returned instead of
2011 * allocating a new one.
2013 * On successful return, the reference to the inode has been transferred
2014 * to the dentry. In case of an error the reference on the inode is released.
2015 * To make it easier to use in export operations a %NULL or IS_ERR inode may
2016 * be passed in and the error will be propagated to the return value,
2017 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
2019 struct dentry *d_obtain_alias(struct inode *inode)
2021 return __d_obtain_alias(inode, 1);
2023 EXPORT_SYMBOL(d_obtain_alias);
2026 * d_obtain_root - find or allocate a dentry for a given inode
2027 * @inode: inode to allocate the dentry for
2029 * Obtain an IS_ROOT dentry for the root of a filesystem.
2031 * We must ensure that directory inodes only ever have one dentry. If a
2032 * dentry is found, that is returned instead of allocating a new one.
2034 * On successful return, the reference to the inode has been transferred
2035 * to the dentry. In case of an error the reference on the inode is
2036 * released. A %NULL or IS_ERR inode may be passed in and will be the
2037 * error will be propagate to the return value, with a %NULL @inode
2038 * replaced by ERR_PTR(-ESTALE).
2040 struct dentry *d_obtain_root(struct inode *inode)
2042 return __d_obtain_alias(inode, 0);
2044 EXPORT_SYMBOL(d_obtain_root);
2047 * d_add_ci - lookup or allocate new dentry with case-exact name
2048 * @inode: the inode case-insensitive lookup has found
2049 * @dentry: the negative dentry that was passed to the parent's lookup func
2050 * @name: the case-exact name to be associated with the returned dentry
2052 * This is to avoid filling the dcache with case-insensitive names to the
2053 * same inode, only the actual correct case is stored in the dcache for
2054 * case-insensitive filesystems.
2056 * For a case-insensitive lookup match and if the the case-exact dentry
2057 * already exists in in the dcache, use it and return it.
2059 * If no entry exists with the exact case name, allocate new dentry with
2060 * the exact case, and return the spliced entry.
2062 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
2065 struct dentry *found, *res;
2068 * First check if a dentry matching the name already exists,
2069 * if not go ahead and create it now.
2071 found = d_hash_and_lookup(dentry->d_parent, name);
2076 if (d_in_lookup(dentry)) {
2077 found = d_alloc_parallel(dentry->d_parent, name,
2079 if (IS_ERR(found) || !d_in_lookup(found)) {
2084 found = d_alloc(dentry->d_parent, name);
2087 return ERR_PTR(-ENOMEM);
2090 res = d_splice_alias(inode, found);
2097 EXPORT_SYMBOL(d_add_ci);
2100 static inline bool d_same_name(const struct dentry *dentry,
2101 const struct dentry *parent,
2102 const struct qstr *name)
2104 if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
2105 if (dentry->d_name.len != name->len)
2107 return dentry_cmp(dentry, name->name, name->len) == 0;
2109 return parent->d_op->d_compare(dentry,
2110 dentry->d_name.len, dentry->d_name.name,
2115 * __d_lookup_rcu - search for a dentry (racy, store-free)
2116 * @parent: parent dentry
2117 * @name: qstr of name we wish to find
2118 * @seqp: returns d_seq value at the point where the dentry was found
2119 * Returns: dentry, or NULL
2121 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2122 * resolution (store-free path walking) design described in
2123 * Documentation/filesystems/path-lookup.txt.
2125 * This is not to be used outside core vfs.
2127 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2128 * held, and rcu_read_lock held. The returned dentry must not be stored into
2129 * without taking d_lock and checking d_seq sequence count against @seq
2132 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2135 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2136 * the returned dentry, so long as its parent's seqlock is checked after the
2137 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2138 * is formed, giving integrity down the path walk.
2140 * NOTE! The caller *has* to check the resulting dentry against the sequence
2141 * number we've returned before using any of the resulting dentry state!
2143 struct dentry *__d_lookup_rcu(const struct dentry *parent,
2144 const struct qstr *name,
2147 u64 hashlen = name->hash_len;
2148 const unsigned char *str = name->name;
2149 struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
2150 struct hlist_bl_node *node;
2151 struct dentry *dentry;
2154 * Note: There is significant duplication with __d_lookup_rcu which is
2155 * required to prevent single threaded performance regressions
2156 * especially on architectures where smp_rmb (in seqcounts) are costly.
2157 * Keep the two functions in sync.
2161 * The hash list is protected using RCU.
2163 * Carefully use d_seq when comparing a candidate dentry, to avoid
2164 * races with d_move().
2166 * It is possible that concurrent renames can mess up our list
2167 * walk here and result in missing our dentry, resulting in the
2168 * false-negative result. d_lookup() protects against concurrent
2169 * renames using rename_lock seqlock.
2171 * See Documentation/filesystems/path-lookup.txt for more details.
2173 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2178 * The dentry sequence count protects us from concurrent
2179 * renames, and thus protects parent and name fields.
2181 * The caller must perform a seqcount check in order
2182 * to do anything useful with the returned dentry.
2184 * NOTE! We do a "raw" seqcount_begin here. That means that
2185 * we don't wait for the sequence count to stabilize if it
2186 * is in the middle of a sequence change. If we do the slow
2187 * dentry compare, we will do seqretries until it is stable,
2188 * and if we end up with a successful lookup, we actually
2189 * want to exit RCU lookup anyway.
2191 * Note that raw_seqcount_begin still *does* smp_rmb(), so
2192 * we are still guaranteed NUL-termination of ->d_name.name.
2194 seq = raw_seqcount_begin(&dentry->d_seq);
2195 if (dentry->d_parent != parent)
2197 if (d_unhashed(dentry))
2200 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
2203 if (dentry->d_name.hash != hashlen_hash(hashlen))
2205 tlen = dentry->d_name.len;
2206 tname = dentry->d_name.name;
2207 /* we want a consistent (name,len) pair */
2208 if (read_seqcount_retry(&dentry->d_seq, seq)) {
2212 if (parent->d_op->d_compare(dentry,
2213 tlen, tname, name) != 0)
2216 if (dentry->d_name.hash_len != hashlen)
2218 if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
2228 * d_lookup - search for a dentry
2229 * @parent: parent dentry
2230 * @name: qstr of name we wish to find
2231 * Returns: dentry, or NULL
2233 * d_lookup searches the children of the parent dentry for the name in
2234 * question. If the dentry is found its reference count is incremented and the
2235 * dentry is returned. The caller must use dput to free the entry when it has
2236 * finished using it. %NULL is returned if the dentry does not exist.
2238 struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
2240 struct dentry *dentry;
2244 seq = read_seqbegin(&rename_lock);
2245 dentry = __d_lookup(parent, name);
2248 } while (read_seqretry(&rename_lock, seq));
2251 EXPORT_SYMBOL(d_lookup);
2254 * __d_lookup - search for a dentry (racy)
2255 * @parent: parent dentry
2256 * @name: qstr of name we wish to find
2257 * Returns: dentry, or NULL
2259 * __d_lookup is like d_lookup, however it may (rarely) return a
2260 * false-negative result due to unrelated rename activity.
2262 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2263 * however it must be used carefully, eg. with a following d_lookup in
2264 * the case of failure.
2266 * __d_lookup callers must be commented.
2268 struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
2270 unsigned int hash = name->hash;
2271 struct hlist_bl_head *b = d_hash(hash);
2272 struct hlist_bl_node *node;
2273 struct dentry *found = NULL;
2274 struct dentry *dentry;
2277 * Note: There is significant duplication with __d_lookup_rcu which is
2278 * required to prevent single threaded performance regressions
2279 * especially on architectures where smp_rmb (in seqcounts) are costly.
2280 * Keep the two functions in sync.
2284 * The hash list is protected using RCU.
2286 * Take d_lock when comparing a candidate dentry, to avoid races
2289 * It is possible that concurrent renames can mess up our list
2290 * walk here and result in missing our dentry, resulting in the
2291 * false-negative result. d_lookup() protects against concurrent
2292 * renames using rename_lock seqlock.
2294 * See Documentation/filesystems/path-lookup.txt for more details.
2298 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2300 if (dentry->d_name.hash != hash)
2303 spin_lock(&dentry->d_lock);
2304 if (dentry->d_parent != parent)
2306 if (d_unhashed(dentry))
2309 if (!d_same_name(dentry, parent, name))
2312 dentry->d_lockref.count++;
2314 spin_unlock(&dentry->d_lock);
2317 spin_unlock(&dentry->d_lock);
2325 * d_hash_and_lookup - hash the qstr then search for a dentry
2326 * @dir: Directory to search in
2327 * @name: qstr of name we wish to find
2329 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2331 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2334 * Check for a fs-specific hash function. Note that we must
2335 * calculate the standard hash first, as the d_op->d_hash()
2336 * routine may choose to leave the hash value unchanged.
2338 name->hash = full_name_hash(dir, name->name, name->len);
2339 if (dir->d_flags & DCACHE_OP_HASH) {
2340 int err = dir->d_op->d_hash(dir, name);
2341 if (unlikely(err < 0))
2342 return ERR_PTR(err);
2344 return d_lookup(dir, name);
2346 EXPORT_SYMBOL(d_hash_and_lookup);
2349 * When a file is deleted, we have two options:
2350 * - turn this dentry into a negative dentry
2351 * - unhash this dentry and free it.
2353 * Usually, we want to just turn this into
2354 * a negative dentry, but if anybody else is
2355 * currently using the dentry or the inode
2356 * we can't do that and we fall back on removing
2357 * it from the hash queues and waiting for
2358 * it to be deleted later when it has no users
2362 * d_delete - delete a dentry
2363 * @dentry: The dentry to delete
2365 * Turn the dentry into a negative dentry if possible, otherwise
2366 * remove it from the hash queues so it can be deleted later
2369 void d_delete(struct dentry * dentry)
2371 struct inode *inode;
2374 * Are we the only user?
2377 spin_lock(&dentry->d_lock);
2378 inode = dentry->d_inode;
2379 isdir = S_ISDIR(inode->i_mode);
2380 if (dentry->d_lockref.count == 1) {
2381 if (!spin_trylock(&inode->i_lock)) {
2382 spin_unlock(&dentry->d_lock);
2386 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2387 dentry_unlink_inode(dentry);
2388 fsnotify_nameremove(dentry, isdir);
2392 if (!d_unhashed(dentry))
2395 spin_unlock(&dentry->d_lock);
2397 fsnotify_nameremove(dentry, isdir);
2399 EXPORT_SYMBOL(d_delete);
2401 static void __d_rehash(struct dentry *entry)
2403 struct hlist_bl_head *b = d_hash(entry->d_name.hash);
2406 hlist_bl_add_head_rcu(&entry->d_hash, b);
2411 * d_rehash - add an entry back to the hash
2412 * @entry: dentry to add to the hash
2414 * Adds a dentry to the hash according to its name.
2417 void d_rehash(struct dentry * entry)
2419 spin_lock(&entry->d_lock);
2421 spin_unlock(&entry->d_lock);
2423 EXPORT_SYMBOL(d_rehash);
2425 static inline unsigned start_dir_add(struct inode *dir)
2429 unsigned n = dir->i_dir_seq;
2430 if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
2436 static inline void end_dir_add(struct inode *dir, unsigned n)
2438 smp_store_release(&dir->i_dir_seq, n + 2);
2441 static void d_wait_lookup(struct dentry *dentry)
2443 if (d_in_lookup(dentry)) {
2444 DECLARE_WAITQUEUE(wait, current);
2445 add_wait_queue(dentry->d_wait, &wait);
2447 set_current_state(TASK_UNINTERRUPTIBLE);
2448 spin_unlock(&dentry->d_lock);
2450 spin_lock(&dentry->d_lock);
2451 } while (d_in_lookup(dentry));
2455 struct dentry *d_alloc_parallel(struct dentry *parent,
2456 const struct qstr *name,
2457 wait_queue_head_t *wq)
2459 unsigned int hash = name->hash;
2460 struct hlist_bl_head *b = in_lookup_hash(parent, hash);
2461 struct hlist_bl_node *node;
2462 struct dentry *new = d_alloc(parent, name);
2463 struct dentry *dentry;
2464 unsigned seq, r_seq, d_seq;
2467 return ERR_PTR(-ENOMEM);
2471 seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
2472 r_seq = read_seqbegin(&rename_lock);
2473 dentry = __d_lookup_rcu(parent, name, &d_seq);
2474 if (unlikely(dentry)) {
2475 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2479 if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
2488 if (unlikely(read_seqretry(&rename_lock, r_seq))) {
2493 if (unlikely(seq & 1)) {
2499 if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
2505 * No changes for the parent since the beginning of d_lookup().
2506 * Since all removals from the chain happen with hlist_bl_lock(),
2507 * any potential in-lookup matches are going to stay here until
2508 * we unlock the chain. All fields are stable in everything
2511 hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
2512 if (dentry->d_name.hash != hash)
2514 if (dentry->d_parent != parent)
2516 if (!d_same_name(dentry, parent, name))
2519 /* now we can try to grab a reference */
2520 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2527 * somebody is likely to be still doing lookup for it;
2528 * wait for them to finish
2530 spin_lock(&dentry->d_lock);
2531 d_wait_lookup(dentry);
2533 * it's not in-lookup anymore; in principle we should repeat
2534 * everything from dcache lookup, but it's likely to be what
2535 * d_lookup() would've found anyway. If it is, just return it;
2536 * otherwise we really have to repeat the whole thing.
2538 if (unlikely(dentry->d_name.hash != hash))
2540 if (unlikely(dentry->d_parent != parent))
2542 if (unlikely(d_unhashed(dentry)))
2544 if (unlikely(!d_same_name(dentry, parent, name)))
2546 /* OK, it *is* a hashed match; return it */
2547 spin_unlock(&dentry->d_lock);
2552 /* we can't take ->d_lock here; it's OK, though. */
2553 new->d_flags |= DCACHE_PAR_LOOKUP;
2555 hlist_bl_add_head_rcu(&new->d_u.d_in_lookup_hash, b);
2559 spin_unlock(&dentry->d_lock);
2563 EXPORT_SYMBOL(d_alloc_parallel);
2565 void __d_lookup_done(struct dentry *dentry)
2567 struct hlist_bl_head *b = in_lookup_hash(dentry->d_parent,
2568 dentry->d_name.hash);
2570 dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
2571 __hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
2572 wake_up_all(dentry->d_wait);
2573 dentry->d_wait = NULL;
2575 INIT_HLIST_NODE(&dentry->d_u.d_alias);
2576 INIT_LIST_HEAD(&dentry->d_lru);
2578 EXPORT_SYMBOL(__d_lookup_done);
2580 /* inode->i_lock held if inode is non-NULL */
2582 static inline void __d_add(struct dentry *dentry, struct inode *inode)
2584 struct inode *dir = NULL;
2586 spin_lock(&dentry->d_lock);
2587 if (unlikely(d_in_lookup(dentry))) {
2588 dir = dentry->d_parent->d_inode;
2589 n = start_dir_add(dir);
2590 __d_lookup_done(dentry);
2593 unsigned add_flags = d_flags_for_inode(inode);
2594 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2595 raw_write_seqcount_begin(&dentry->d_seq);
2596 __d_set_inode_and_type(dentry, inode, add_flags);
2597 raw_write_seqcount_end(&dentry->d_seq);
2598 fsnotify_update_flags(dentry);
2602 end_dir_add(dir, n);
2603 spin_unlock(&dentry->d_lock);
2605 spin_unlock(&inode->i_lock);
2609 * d_add - add dentry to hash queues
2610 * @entry: dentry to add
2611 * @inode: The inode to attach to this dentry
2613 * This adds the entry to the hash queues and initializes @inode.
2614 * The entry was actually filled in earlier during d_alloc().
2617 void d_add(struct dentry *entry, struct inode *inode)
2620 security_d_instantiate(entry, inode);
2621 spin_lock(&inode->i_lock);
2623 __d_add(entry, inode);
2625 EXPORT_SYMBOL(d_add);
2628 * d_exact_alias - find and hash an exact unhashed alias
2629 * @entry: dentry to add
2630 * @inode: The inode to go with this dentry
2632 * If an unhashed dentry with the same name/parent and desired
2633 * inode already exists, hash and return it. Otherwise, return
2636 * Parent directory should be locked.
2638 struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
2640 struct dentry *alias;
2641 unsigned int hash = entry->d_name.hash;
2643 spin_lock(&inode->i_lock);
2644 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
2646 * Don't need alias->d_lock here, because aliases with
2647 * d_parent == entry->d_parent are not subject to name or
2648 * parent changes, because the parent inode i_mutex is held.
2650 if (alias->d_name.hash != hash)
2652 if (alias->d_parent != entry->d_parent)
2654 if (!d_same_name(alias, entry->d_parent, &entry->d_name))
2656 spin_lock(&alias->d_lock);
2657 if (!d_unhashed(alias)) {
2658 spin_unlock(&alias->d_lock);
2661 __dget_dlock(alias);
2663 spin_unlock(&alias->d_lock);
2665 spin_unlock(&inode->i_lock);
2668 spin_unlock(&inode->i_lock);
2671 EXPORT_SYMBOL(d_exact_alias);
2674 * dentry_update_name_case - update case insensitive dentry with a new name
2675 * @dentry: dentry to be updated
2678 * Update a case insensitive dentry with new case of name.
2680 * dentry must have been returned by d_lookup with name @name. Old and new
2681 * name lengths must match (ie. no d_compare which allows mismatched name
2684 * Parent inode i_mutex must be held over d_lookup and into this call (to
2685 * keep renames and concurrent inserts, and readdir(2) away).
2687 void dentry_update_name_case(struct dentry *dentry, const struct qstr *name)
2689 BUG_ON(!inode_is_locked(dentry->d_parent->d_inode));
2690 BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
2692 spin_lock(&dentry->d_lock);
2693 write_seqcount_begin(&dentry->d_seq);
2694 memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
2695 write_seqcount_end(&dentry->d_seq);
2696 spin_unlock(&dentry->d_lock);
2698 EXPORT_SYMBOL(dentry_update_name_case);
2700 static void swap_names(struct dentry *dentry, struct dentry *target)
2702 if (unlikely(dname_external(target))) {
2703 if (unlikely(dname_external(dentry))) {
2705 * Both external: swap the pointers
2707 swap(target->d_name.name, dentry->d_name.name);
2710 * dentry:internal, target:external. Steal target's
2711 * storage and make target internal.
2713 memcpy(target->d_iname, dentry->d_name.name,
2714 dentry->d_name.len + 1);
2715 dentry->d_name.name = target->d_name.name;
2716 target->d_name.name = target->d_iname;
2719 if (unlikely(dname_external(dentry))) {
2721 * dentry:external, target:internal. Give dentry's
2722 * storage to target and make dentry internal
2724 memcpy(dentry->d_iname, target->d_name.name,
2725 target->d_name.len + 1);
2726 target->d_name.name = dentry->d_name.name;
2727 dentry->d_name.name = dentry->d_iname;
2730 * Both are internal.
2733 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
2734 kmemcheck_mark_initialized(dentry->d_iname, DNAME_INLINE_LEN);
2735 kmemcheck_mark_initialized(target->d_iname, DNAME_INLINE_LEN);
2736 for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
2737 swap(((long *) &dentry->d_iname)[i],
2738 ((long *) &target->d_iname)[i]);
2742 swap(dentry->d_name.hash_len, target->d_name.hash_len);
2745 static void copy_name(struct dentry *dentry, struct dentry *target)
2747 struct external_name *old_name = NULL;
2748 if (unlikely(dname_external(dentry)))
2749 old_name = external_name(dentry);
2750 if (unlikely(dname_external(target))) {
2751 atomic_inc(&external_name(target)->u.count);
2752 dentry->d_name = target->d_name;
2754 memcpy(dentry->d_iname, target->d_name.name,
2755 target->d_name.len + 1);
2756 dentry->d_name.name = dentry->d_iname;
2757 dentry->d_name.hash_len = target->d_name.hash_len;
2759 if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
2760 kfree_rcu(old_name, u.head);
2763 static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
2766 * XXXX: do we really need to take target->d_lock?
2768 if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent)
2769 spin_lock(&target->d_parent->d_lock);
2771 if (d_ancestor(dentry->d_parent, target->d_parent)) {
2772 spin_lock(&dentry->d_parent->d_lock);
2773 spin_lock_nested(&target->d_parent->d_lock,
2774 DENTRY_D_LOCK_NESTED);
2776 spin_lock(&target->d_parent->d_lock);
2777 spin_lock_nested(&dentry->d_parent->d_lock,
2778 DENTRY_D_LOCK_NESTED);
2781 if (target < dentry) {
2782 spin_lock_nested(&target->d_lock, 2);
2783 spin_lock_nested(&dentry->d_lock, 3);
2785 spin_lock_nested(&dentry->d_lock, 2);
2786 spin_lock_nested(&target->d_lock, 3);
2790 static void dentry_unlock_for_move(struct dentry *dentry, struct dentry *target)
2792 if (target->d_parent != dentry->d_parent)
2793 spin_unlock(&dentry->d_parent->d_lock);
2794 if (target->d_parent != target)
2795 spin_unlock(&target->d_parent->d_lock);
2796 spin_unlock(&target->d_lock);
2797 spin_unlock(&dentry->d_lock);
2801 * When switching names, the actual string doesn't strictly have to
2802 * be preserved in the target - because we're dropping the target
2803 * anyway. As such, we can just do a simple memcpy() to copy over
2804 * the new name before we switch, unless we are going to rehash
2805 * it. Note that if we *do* unhash the target, we are not allowed
2806 * to rehash it without giving it a new name/hash key - whether
2807 * we swap or overwrite the names here, resulting name won't match
2808 * the reality in filesystem; it's only there for d_path() purposes.
2809 * Note that all of this is happening under rename_lock, so the
2810 * any hash lookup seeing it in the middle of manipulations will
2811 * be discarded anyway. So we do not care what happens to the hash
2815 * __d_move - move a dentry
2816 * @dentry: entry to move
2817 * @target: new dentry
2818 * @exchange: exchange the two dentries
2820 * Update the dcache to reflect the move of a file name. Negative
2821 * dcache entries should not be moved in this way. Caller must hold
2822 * rename_lock, the i_mutex of the source and target directories,
2823 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2825 static void __d_move(struct dentry *dentry, struct dentry *target,
2828 struct inode *dir = NULL;
2830 if (!dentry->d_inode)
2831 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
2833 BUG_ON(d_ancestor(dentry, target));
2834 BUG_ON(d_ancestor(target, dentry));
2836 dentry_lock_for_move(dentry, target);
2837 if (unlikely(d_in_lookup(target))) {
2838 dir = target->d_parent->d_inode;
2839 n = start_dir_add(dir);
2840 __d_lookup_done(target);
2843 write_seqcount_begin(&dentry->d_seq);
2844 write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
2847 /* ___d_drop does write_seqcount_barrier, but they're OK to nest. */
2851 /* Switch the names.. */
2853 swap_names(dentry, target);
2855 copy_name(dentry, target);
2857 /* rehash in new place(s) */
2862 target->d_hash.pprev = NULL;
2864 /* ... and switch them in the tree */
2865 if (IS_ROOT(dentry)) {
2866 /* splicing a tree */
2867 dentry->d_flags |= DCACHE_RCUACCESS;
2868 dentry->d_parent = target->d_parent;
2869 target->d_parent = target;
2870 list_del_init(&target->d_child);
2871 list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
2873 /* swapping two dentries */
2874 swap(dentry->d_parent, target->d_parent);
2875 list_move(&target->d_child, &target->d_parent->d_subdirs);
2876 list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
2878 fsnotify_update_flags(target);
2879 fsnotify_update_flags(dentry);
2882 write_seqcount_end(&target->d_seq);
2883 write_seqcount_end(&dentry->d_seq);
2886 end_dir_add(dir, n);
2887 dentry_unlock_for_move(dentry, target);
2891 * d_move - move a dentry
2892 * @dentry: entry to move
2893 * @target: new dentry
2895 * Update the dcache to reflect the move of a file name. Negative
2896 * dcache entries should not be moved in this way. See the locking
2897 * requirements for __d_move.
2899 void d_move(struct dentry *dentry, struct dentry *target)
2901 write_seqlock(&rename_lock);
2902 __d_move(dentry, target, false);
2903 write_sequnlock(&rename_lock);
2905 EXPORT_SYMBOL(d_move);
2908 * d_exchange - exchange two dentries
2909 * @dentry1: first dentry
2910 * @dentry2: second dentry
2912 void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
2914 write_seqlock(&rename_lock);
2916 WARN_ON(!dentry1->d_inode);
2917 WARN_ON(!dentry2->d_inode);
2918 WARN_ON(IS_ROOT(dentry1));
2919 WARN_ON(IS_ROOT(dentry2));
2921 __d_move(dentry1, dentry2, true);
2923 write_sequnlock(&rename_lock);
2927 * d_ancestor - search for an ancestor
2928 * @p1: ancestor dentry
2931 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2932 * an ancestor of p2, else NULL.
2934 struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2938 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2939 if (p->d_parent == p1)
2946 * This helper attempts to cope with remotely renamed directories
2948 * It assumes that the caller is already holding
2949 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2951 * Note: If ever the locking in lock_rename() changes, then please
2952 * remember to update this too...
2954 static int __d_unalias(struct inode *inode,
2955 struct dentry *dentry, struct dentry *alias)
2957 struct mutex *m1 = NULL;
2958 struct rw_semaphore *m2 = NULL;
2961 /* If alias and dentry share a parent, then no extra locks required */
2962 if (alias->d_parent == dentry->d_parent)
2965 /* See lock_rename() */
2966 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
2968 m1 = &dentry->d_sb->s_vfs_rename_mutex;
2969 if (!inode_trylock_shared(alias->d_parent->d_inode))
2971 m2 = &alias->d_parent->d_inode->i_rwsem;
2973 __d_move(alias, dentry, false);
2984 * d_splice_alias - splice a disconnected dentry into the tree if one exists
2985 * @inode: the inode which may have a disconnected dentry
2986 * @dentry: a negative dentry which we want to point to the inode.
2988 * If inode is a directory and has an IS_ROOT alias, then d_move that in
2989 * place of the given dentry and return it, else simply d_add the inode
2990 * to the dentry and return NULL.
2992 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
2993 * we should error out: directories can't have multiple aliases.
2995 * This is needed in the lookup routine of any filesystem that is exportable
2996 * (via knfsd) so that we can build dcache paths to directories effectively.
2998 * If a dentry was found and moved, then it is returned. Otherwise NULL
2999 * is returned. This matches the expected return value of ->lookup.
3001 * Cluster filesystems may call this function with a negative, hashed dentry.
3002 * In that case, we know that the inode will be a regular file, and also this
3003 * will only occur during atomic_open. So we need to check for the dentry
3004 * being already hashed only in the final case.
3006 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
3009 return ERR_CAST(inode);
3011 BUG_ON(!d_unhashed(dentry));
3016 security_d_instantiate(dentry, inode);
3017 spin_lock(&inode->i_lock);
3018 if (S_ISDIR(inode->i_mode)) {
3019 struct dentry *new = __d_find_any_alias(inode);
3020 if (unlikely(new)) {
3021 /* The reference to new ensures it remains an alias */
3022 spin_unlock(&inode->i_lock);
3023 write_seqlock(&rename_lock);
3024 if (unlikely(d_ancestor(new, dentry))) {
3025 write_sequnlock(&rename_lock);
3027 new = ERR_PTR(-ELOOP);
3028 pr_warn_ratelimited(
3029 "VFS: Lookup of '%s' in %s %s"
3030 " would have caused loop\n",
3031 dentry->d_name.name,
3032 inode->i_sb->s_type->name,
3034 } else if (!IS_ROOT(new)) {
3035 int err = __d_unalias(inode, dentry, new);
3036 write_sequnlock(&rename_lock);
3042 __d_move(new, dentry, false);
3043 write_sequnlock(&rename_lock);
3050 __d_add(dentry, inode);
3053 EXPORT_SYMBOL(d_splice_alias);
3055 static int prepend(char **buffer, int *buflen, const char *str, int namelen)
3059 return -ENAMETOOLONG;
3061 memcpy(*buffer, str, namelen);
3066 * prepend_name - prepend a pathname in front of current buffer pointer
3067 * @buffer: buffer pointer
3068 * @buflen: allocated length of the buffer
3069 * @name: name string and length qstr structure
3071 * With RCU path tracing, it may race with d_move(). Use ACCESS_ONCE() to
3072 * make sure that either the old or the new name pointer and length are
3073 * fetched. However, there may be mismatch between length and pointer.
3074 * The length cannot be trusted, we need to copy it byte-by-byte until
3075 * the length is reached or a null byte is found. It also prepends "/" at
3076 * the beginning of the name. The sequence number check at the caller will
3077 * retry it again when a d_move() does happen. So any garbage in the buffer
3078 * due to mismatched pointer and length will be discarded.
3080 * Data dependency barrier is needed to make sure that we see that terminating
3081 * NUL. Alpha strikes again, film at 11...
3083 static int prepend_name(char **buffer, int *buflen, const struct qstr *name)
3085 const char *dname = ACCESS_ONCE(name->name);
3086 u32 dlen = ACCESS_ONCE(name->len);
3089 smp_read_barrier_depends();
3091 *buflen -= dlen + 1;
3093 return -ENAMETOOLONG;
3094 p = *buffer -= dlen + 1;
3106 * prepend_path - Prepend path string to a buffer
3107 * @path: the dentry/vfsmount to report
3108 * @root: root vfsmnt/dentry
3109 * @buffer: pointer to the end of the buffer
3110 * @buflen: pointer to buffer length
3112 * The function will first try to write out the pathname without taking any
3113 * lock other than the RCU read lock to make sure that dentries won't go away.
3114 * It only checks the sequence number of the global rename_lock as any change
3115 * in the dentry's d_seq will be preceded by changes in the rename_lock
3116 * sequence number. If the sequence number had been changed, it will restart
3117 * the whole pathname back-tracing sequence again by taking the rename_lock.
3118 * In this case, there is no need to take the RCU read lock as the recursive
3119 * parent pointer references will keep the dentry chain alive as long as no
3120 * rename operation is performed.
3122 static int prepend_path(const struct path *path,
3123 const struct path *root,
3124 char **buffer, int *buflen)
3126 struct dentry *dentry;
3127 struct vfsmount *vfsmnt;
3130 unsigned seq, m_seq = 0;
3136 read_seqbegin_or_lock(&mount_lock, &m_seq);
3143 dentry = path->dentry;
3145 mnt = real_mount(vfsmnt);
3146 read_seqbegin_or_lock(&rename_lock, &seq);
3147 while (dentry != root->dentry || vfsmnt != root->mnt) {
3148 struct dentry * parent;
3150 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
3151 struct mount *parent = ACCESS_ONCE(mnt->mnt_parent);
3153 if (dentry != vfsmnt->mnt_root) {
3160 if (mnt != parent) {
3161 dentry = ACCESS_ONCE(mnt->mnt_mountpoint);
3167 error = is_mounted(vfsmnt) ? 1 : 2;
3170 parent = dentry->d_parent;
3172 error = prepend_name(&bptr, &blen, &dentry->d_name);
3180 if (need_seqretry(&rename_lock, seq)) {
3184 done_seqretry(&rename_lock, seq);
3188 if (need_seqretry(&mount_lock, m_seq)) {
3192 done_seqretry(&mount_lock, m_seq);
3194 if (error >= 0 && bptr == *buffer) {
3196 error = -ENAMETOOLONG;
3206 * __d_path - return the path of a dentry
3207 * @path: the dentry/vfsmount to report
3208 * @root: root vfsmnt/dentry
3209 * @buf: buffer to return value in
3210 * @buflen: buffer length
3212 * Convert a dentry into an ASCII path name.
3214 * Returns a pointer into the buffer or an error code if the
3215 * path was too long.
3217 * "buflen" should be positive.
3219 * If the path is not reachable from the supplied root, return %NULL.
3221 char *__d_path(const struct path *path,
3222 const struct path *root,
3223 char *buf, int buflen)
3225 char *res = buf + buflen;
3228 prepend(&res, &buflen, "\0", 1);
3229 error = prepend_path(path, root, &res, &buflen);
3232 return ERR_PTR(error);
3238 char *d_absolute_path(const struct path *path,
3239 char *buf, int buflen)
3241 struct path root = {};
3242 char *res = buf + buflen;
3245 prepend(&res, &buflen, "\0", 1);
3246 error = prepend_path(path, &root, &res, &buflen);
3251 return ERR_PTR(error);
3256 * same as __d_path but appends "(deleted)" for unlinked files.
3258 static int path_with_deleted(const struct path *path,
3259 const struct path *root,
3260 char **buf, int *buflen)
3262 prepend(buf, buflen, "\0", 1);
3263 if (d_unlinked(path->dentry)) {
3264 int error = prepend(buf, buflen, " (deleted)", 10);
3269 return prepend_path(path, root, buf, buflen);
3272 static int prepend_unreachable(char **buffer, int *buflen)
3274 return prepend(buffer, buflen, "(unreachable)", 13);
3277 static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
3282 seq = read_seqcount_begin(&fs->seq);
3284 } while (read_seqcount_retry(&fs->seq, seq));
3288 * d_path - return the path of a dentry
3289 * @path: path to report
3290 * @buf: buffer to return value in
3291 * @buflen: buffer length
3293 * Convert a dentry into an ASCII path name. If the entry has been deleted
3294 * the string " (deleted)" is appended. Note that this is ambiguous.
3296 * Returns a pointer into the buffer or an error code if the path was
3297 * too long. Note: Callers should use the returned pointer, not the passed
3298 * in buffer, to use the name! The implementation often starts at an offset
3299 * into the buffer, and may leave 0 bytes at the start.
3301 * "buflen" should be positive.
3303 char *d_path(const struct path *path, char *buf, int buflen)
3305 char *res = buf + buflen;
3310 * We have various synthetic filesystems that never get mounted. On
3311 * these filesystems dentries are never used for lookup purposes, and
3312 * thus don't need to be hashed. They also don't need a name until a
3313 * user wants to identify the object in /proc/pid/fd/. The little hack
3314 * below allows us to generate a name for these objects on demand:
3316 * Some pseudo inodes are mountable. When they are mounted
3317 * path->dentry == path->mnt->mnt_root. In that case don't call d_dname
3318 * and instead have d_path return the mounted path.
3320 if (path->dentry->d_op && path->dentry->d_op->d_dname &&
3321 (!IS_ROOT(path->dentry) || path->dentry != path->mnt->mnt_root))
3322 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
3325 get_fs_root_rcu(current->fs, &root);
3326 error = path_with_deleted(path, &root, &res, &buflen);
3330 res = ERR_PTR(error);
3333 EXPORT_SYMBOL(d_path);
3336 * Helper function for dentry_operations.d_dname() members
3338 char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
3339 const char *fmt, ...)
3345 va_start(args, fmt);
3346 sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
3349 if (sz > sizeof(temp) || sz > buflen)
3350 return ERR_PTR(-ENAMETOOLONG);
3352 buffer += buflen - sz;
3353 return memcpy(buffer, temp, sz);
3356 char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
3358 char *end = buffer + buflen;
3359 /* these dentries are never renamed, so d_lock is not needed */
3360 if (prepend(&end, &buflen, " (deleted)", 11) ||
3361 prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len) ||
3362 prepend(&end, &buflen, "/", 1))
3363 end = ERR_PTR(-ENAMETOOLONG);
3366 EXPORT_SYMBOL(simple_dname);
3369 * Write full pathname from the root of the filesystem into the buffer.
3371 static char *__dentry_path(struct dentry *d, char *buf, int buflen)
3373 struct dentry *dentry;
3386 prepend(&end, &len, "\0", 1);
3390 read_seqbegin_or_lock(&rename_lock, &seq);
3391 while (!IS_ROOT(dentry)) {
3392 struct dentry *parent = dentry->d_parent;
3395 error = prepend_name(&end, &len, &dentry->d_name);
3404 if (need_seqretry(&rename_lock, seq)) {
3408 done_seqretry(&rename_lock, seq);
3413 return ERR_PTR(-ENAMETOOLONG);
3416 char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
3418 return __dentry_path(dentry, buf, buflen);
3420 EXPORT_SYMBOL(dentry_path_raw);
3422 char *dentry_path(struct dentry *dentry, char *buf, int buflen)
3427 if (d_unlinked(dentry)) {
3429 if (prepend(&p, &buflen, "//deleted", 10) != 0)
3433 retval = __dentry_path(dentry, buf, buflen);
3434 if (!IS_ERR(retval) && p)
3435 *p = '/'; /* restore '/' overriden with '\0' */
3438 return ERR_PTR(-ENAMETOOLONG);
3441 static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root,
3447 seq = read_seqcount_begin(&fs->seq);
3450 } while (read_seqcount_retry(&fs->seq, seq));
3454 * NOTE! The user-level library version returns a
3455 * character pointer. The kernel system call just
3456 * returns the length of the buffer filled (which
3457 * includes the ending '\0' character), or a negative
3458 * error value. So libc would do something like
3460 * char *getcwd(char * buf, size_t size)
3464 * retval = sys_getcwd(buf, size);
3471 SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
3474 struct path pwd, root;
3475 char *page = __getname();
3481 get_fs_root_and_pwd_rcu(current->fs, &root, &pwd);
3484 if (!d_unlinked(pwd.dentry)) {
3486 char *cwd = page + PATH_MAX;
3487 int buflen = PATH_MAX;
3489 prepend(&cwd, &buflen, "\0", 1);
3490 error = prepend_path(&pwd, &root, &cwd, &buflen);
3496 /* Unreachable from current root */
3498 error = prepend_unreachable(&cwd, &buflen);
3504 len = PATH_MAX + page - cwd;
3507 if (copy_to_user(buf, cwd, len))
3520 * Test whether new_dentry is a subdirectory of old_dentry.
3522 * Trivially implemented using the dcache structure
3526 * is_subdir - is new dentry a subdirectory of old_dentry
3527 * @new_dentry: new dentry
3528 * @old_dentry: old dentry
3530 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3531 * Returns false otherwise.
3532 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3535 bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
3540 if (new_dentry == old_dentry)
3544 /* for restarting inner loop in case of seq retry */
3545 seq = read_seqbegin(&rename_lock);
3547 * Need rcu_readlock to protect against the d_parent trashing
3551 if (d_ancestor(old_dentry, new_dentry))
3556 } while (read_seqretry(&rename_lock, seq));
3561 static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
3563 struct dentry *root = data;
3564 if (dentry != root) {
3565 if (d_unhashed(dentry) || !dentry->d_inode)
3568 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
3569 dentry->d_flags |= DCACHE_GENOCIDE;
3570 dentry->d_lockref.count--;
3573 return D_WALK_CONTINUE;
3576 void d_genocide(struct dentry *parent)
3578 d_walk(parent, parent, d_genocide_kill, NULL);
3581 void d_tmpfile(struct dentry *dentry, struct inode *inode)
3583 inode_dec_link_count(inode);
3584 BUG_ON(dentry->d_name.name != dentry->d_iname ||
3585 !hlist_unhashed(&dentry->d_u.d_alias) ||
3586 !d_unlinked(dentry));
3587 spin_lock(&dentry->d_parent->d_lock);
3588 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
3589 dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
3590 (unsigned long long)inode->i_ino);
3591 spin_unlock(&dentry->d_lock);
3592 spin_unlock(&dentry->d_parent->d_lock);
3593 d_instantiate(dentry, inode);
3595 EXPORT_SYMBOL(d_tmpfile);
3597 static __initdata unsigned long dhash_entries;
3598 static int __init set_dhash_entries(char *str)
3602 dhash_entries = simple_strtoul(str, &str, 0);
3605 __setup("dhash_entries=", set_dhash_entries);
3607 static void __init dcache_init_early(void)
3611 /* If hashes are distributed across NUMA nodes, defer
3612 * hash allocation until vmalloc space is available.
3618 alloc_large_system_hash("Dentry cache",
3619 sizeof(struct hlist_bl_head),
3628 for (loop = 0; loop < (1U << d_hash_shift); loop++)
3629 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
3632 static void __init dcache_init(void)
3637 * A constructor could be added for stable state like the lists,
3638 * but it is probably not worth it because of the cache nature
3641 dentry_cache = KMEM_CACHE(dentry,
3642 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT);
3644 /* Hash may have been set up in dcache_init_early */
3649 alloc_large_system_hash("Dentry cache",
3650 sizeof(struct hlist_bl_head),
3659 for (loop = 0; loop < (1U << d_hash_shift); loop++)
3660 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
3663 /* SLAB cache for __getname() consumers */
3664 struct kmem_cache *names_cachep __read_mostly;
3665 EXPORT_SYMBOL(names_cachep);
3667 EXPORT_SYMBOL(d_genocide);
3669 void __init vfs_caches_init_early(void)
3671 dcache_init_early();
3675 void __init vfs_caches_init(void)
3677 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
3678 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
3683 files_maxfiles_init();