4 * Complete reimplementation
5 * (C) 1997 Thomas Schoebel-Theuer,
6 * with heavy changes by Linus Torvalds
10 * Notes on the allocation strategy:
12 * The dcache is a master of the icache - whenever a dcache entry
13 * exists, the inode will always exist. "iput()" is done either when
14 * the dcache entry is deleted or garbage collected.
17 #include <linux/syscalls.h>
18 #include <linux/string.h>
21 #include <linux/fsnotify.h>
22 #include <linux/slab.h>
23 #include <linux/init.h>
24 #include <linux/hash.h>
25 #include <linux/cache.h>
26 #include <linux/export.h>
27 #include <linux/mount.h>
28 #include <linux/file.h>
29 #include <asm/uaccess.h>
30 #include <linux/security.h>
31 #include <linux/seqlock.h>
32 #include <linux/swap.h>
33 #include <linux/bootmem.h>
34 #include <linux/fs_struct.h>
35 #include <linux/hardirq.h>
36 #include <linux/bit_spinlock.h>
37 #include <linux/rculist_bl.h>
38 #include <linux/prefetch.h>
39 #include <linux/ratelimit.h>
45 * dcache->d_inode->i_lock protects:
46 * - i_dentry, d_alias, d_inode of aliases
47 * dcache_hash_bucket lock protects:
48 * - the dcache hash table
49 * s_anon bl list spinlock protects:
50 * - the s_anon list (see __d_drop)
51 * dcache_lru_lock protects:
52 * - the dcache lru lists and counters
59 * - d_parent and d_subdirs
60 * - childrens' d_child and d_parent
64 * dentry->d_inode->i_lock
67 * dcache_hash_bucket lock
70 * If there is an ancestor relationship:
71 * dentry->d_parent->...->d_parent->d_lock
73 * dentry->d_parent->d_lock
76 * If no ancestor relationship:
77 * if (dentry1 < dentry2)
81 int sysctl_vfs_cache_pressure __read_mostly = 100;
82 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
84 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
85 __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
87 EXPORT_SYMBOL(rename_lock);
89 static struct kmem_cache *dentry_cache __read_mostly;
92 * This is the single most critical data structure when it comes
93 * to the dcache: the hashtable for lookups. Somebody should try
94 * to make this good - I've just made it work.
96 * This hash-function tries to avoid losing too many bits of hash
97 * information, yet avoid using a prime hash-size or similar.
99 #define D_HASHBITS d_hash_shift
100 #define D_HASHMASK d_hash_mask
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(const struct dentry *parent,
110 hash += (unsigned long) parent / L1_CACHE_BYTES;
111 hash = hash + (hash >> D_HASHBITS);
112 return dentry_hashtable + (hash & D_HASHMASK);
115 /* Statistics gathering. */
116 struct dentry_stat_t dentry_stat = {
120 static DEFINE_PER_CPU(unsigned int, nr_dentry);
122 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
123 static int get_nr_dentry(void)
127 for_each_possible_cpu(i)
128 sum += per_cpu(nr_dentry, i);
129 return sum < 0 ? 0 : sum;
132 int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
133 size_t *lenp, loff_t *ppos)
135 dentry_stat.nr_dentry = get_nr_dentry();
136 return proc_dointvec(table, write, buffer, lenp, ppos);
141 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
142 * The strings are both count bytes long, and count is non-zero.
144 #ifdef CONFIG_DCACHE_WORD_ACCESS
146 #include <asm/word-at-a-time.h>
148 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
149 * aligned allocation for this particular component. We don't
150 * strictly need the load_unaligned_zeropad() safety, but it
151 * doesn't hurt either.
153 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
154 * need the careful unaligned handling.
156 static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
158 unsigned long a,b,mask;
161 a = *(unsigned long *)cs;
162 b = load_unaligned_zeropad(ct);
163 if (tcount < sizeof(unsigned long))
165 if (unlikely(a != b))
167 cs += sizeof(unsigned long);
168 ct += sizeof(unsigned long);
169 tcount -= sizeof(unsigned long);
173 mask = ~(~0ul << tcount*8);
174 return unlikely(!!((a ^ b) & mask));
179 static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
193 static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
195 const unsigned char *cs;
197 * Be careful about RCU walk racing with rename:
198 * use ACCESS_ONCE to fetch the name pointer.
200 * NOTE! Even if a rename will mean that the length
201 * was not loaded atomically, we don't care. The
202 * RCU walk will check the sequence count eventually,
203 * and catch it. And we won't overrun the buffer,
204 * because we're reading the name pointer atomically,
205 * and a dentry name is guaranteed to be properly
206 * terminated with a NUL byte.
208 * End result: even if 'len' is wrong, we'll exit
209 * early because the data cannot match (there can
210 * be no NUL in the ct/tcount data)
212 cs = ACCESS_ONCE(dentry->d_name.name);
213 smp_read_barrier_depends();
214 return dentry_string_cmp(cs, ct, tcount);
217 static void __d_free(struct rcu_head *head)
219 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
221 WARN_ON(!hlist_unhashed(&dentry->d_alias));
222 if (dname_external(dentry))
223 kfree(dentry->d_name.name);
224 kmem_cache_free(dentry_cache, dentry);
230 static void d_free(struct dentry *dentry)
232 BUG_ON(dentry->d_lockref.count);
233 this_cpu_dec(nr_dentry);
234 if (dentry->d_op && dentry->d_op->d_release)
235 dentry->d_op->d_release(dentry);
237 /* if dentry was never visible to RCU, immediate free is OK */
238 if (!(dentry->d_flags & DCACHE_RCUACCESS))
239 __d_free(&dentry->d_u.d_rcu);
241 call_rcu(&dentry->d_u.d_rcu, __d_free);
245 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
246 * @dentry: the target dentry
247 * After this call, in-progress rcu-walk path lookup will fail. This
248 * should be called after unhashing, and after changing d_inode (if
249 * the dentry has not already been unhashed).
251 static inline void dentry_rcuwalk_barrier(struct dentry *dentry)
253 assert_spin_locked(&dentry->d_lock);
254 /* Go through a barrier */
255 write_seqcount_barrier(&dentry->d_seq);
259 * Release the dentry's inode, using the filesystem
260 * d_iput() operation if defined. Dentry has no refcount
263 static void dentry_iput(struct dentry * dentry)
264 __releases(dentry->d_lock)
265 __releases(dentry->d_inode->i_lock)
267 struct inode *inode = dentry->d_inode;
269 dentry->d_inode = NULL;
270 hlist_del_init(&dentry->d_alias);
271 spin_unlock(&dentry->d_lock);
272 spin_unlock(&inode->i_lock);
274 fsnotify_inoderemove(inode);
275 if (dentry->d_op && dentry->d_op->d_iput)
276 dentry->d_op->d_iput(dentry, inode);
280 spin_unlock(&dentry->d_lock);
285 * Release the dentry's inode, using the filesystem
286 * d_iput() operation if defined. dentry remains in-use.
288 static void dentry_unlink_inode(struct dentry * dentry)
289 __releases(dentry->d_lock)
290 __releases(dentry->d_inode->i_lock)
292 struct inode *inode = dentry->d_inode;
293 dentry->d_inode = NULL;
294 hlist_del_init(&dentry->d_alias);
295 dentry_rcuwalk_barrier(dentry);
296 spin_unlock(&dentry->d_lock);
297 spin_unlock(&inode->i_lock);
299 fsnotify_inoderemove(inode);
300 if (dentry->d_op && dentry->d_op->d_iput)
301 dentry->d_op->d_iput(dentry, inode);
307 * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
309 static void dentry_lru_add(struct dentry *dentry)
311 if (list_empty(&dentry->d_lru)) {
312 spin_lock(&dcache_lru_lock);
313 list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
314 dentry->d_sb->s_nr_dentry_unused++;
315 dentry_stat.nr_unused++;
316 spin_unlock(&dcache_lru_lock);
320 static void __dentry_lru_del(struct dentry *dentry)
322 list_del_init(&dentry->d_lru);
323 dentry->d_flags &= ~DCACHE_SHRINK_LIST;
324 dentry->d_sb->s_nr_dentry_unused--;
325 dentry_stat.nr_unused--;
329 * Remove a dentry with references from the LRU.
331 static void dentry_lru_del(struct dentry *dentry)
333 if (!list_empty(&dentry->d_lru)) {
334 spin_lock(&dcache_lru_lock);
335 __dentry_lru_del(dentry);
336 spin_unlock(&dcache_lru_lock);
340 static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)
342 spin_lock(&dcache_lru_lock);
343 if (list_empty(&dentry->d_lru)) {
344 list_add_tail(&dentry->d_lru, list);
345 dentry->d_sb->s_nr_dentry_unused++;
346 dentry_stat.nr_unused++;
348 list_move_tail(&dentry->d_lru, list);
350 spin_unlock(&dcache_lru_lock);
354 * d_kill - kill dentry and return parent
355 * @dentry: dentry to kill
356 * @parent: parent dentry
358 * The dentry must already be unhashed and removed from the LRU.
360 * If this is the root of the dentry tree, return NULL.
362 * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
365 static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
366 __releases(dentry->d_lock)
367 __releases(parent->d_lock)
368 __releases(dentry->d_inode->i_lock)
370 list_del(&dentry->d_u.d_child);
372 * Inform try_to_ascend() that we are no longer attached to the
375 dentry->d_flags |= DCACHE_DENTRY_KILLED;
377 spin_unlock(&parent->d_lock);
380 * dentry_iput drops the locks, at which point nobody (except
381 * transient RCU lookups) can reach this dentry.
388 * Unhash a dentry without inserting an RCU walk barrier or checking that
389 * dentry->d_lock is locked. The caller must take care of that, if
392 static void __d_shrink(struct dentry *dentry)
394 if (!d_unhashed(dentry)) {
395 struct hlist_bl_head *b;
396 if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
397 b = &dentry->d_sb->s_anon;
399 b = d_hash(dentry->d_parent, dentry->d_name.hash);
402 __hlist_bl_del(&dentry->d_hash);
403 dentry->d_hash.pprev = NULL;
409 * d_drop - drop a dentry
410 * @dentry: dentry to drop
412 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
413 * be found through a VFS lookup any more. Note that this is different from
414 * deleting the dentry - d_delete will try to mark the dentry negative if
415 * possible, giving a successful _negative_ lookup, while d_drop will
416 * just make the cache lookup fail.
418 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
419 * reason (NFS timeouts or autofs deletes).
421 * __d_drop requires dentry->d_lock.
423 void __d_drop(struct dentry *dentry)
425 if (!d_unhashed(dentry)) {
427 dentry_rcuwalk_barrier(dentry);
430 EXPORT_SYMBOL(__d_drop);
432 void d_drop(struct dentry *dentry)
434 spin_lock(&dentry->d_lock);
436 spin_unlock(&dentry->d_lock);
438 EXPORT_SYMBOL(d_drop);
441 * Finish off a dentry we've decided to kill.
442 * dentry->d_lock must be held, returns with it unlocked.
443 * If ref is non-zero, then decrement the refcount too.
444 * Returns dentry requiring refcount drop, or NULL if we're done.
446 static inline struct dentry *dentry_kill(struct dentry *dentry, int ref)
447 __releases(dentry->d_lock)
450 struct dentry *parent;
452 inode = dentry->d_inode;
453 if (inode && !spin_trylock(&inode->i_lock)) {
455 spin_unlock(&dentry->d_lock);
457 return dentry; /* try again with same dentry */
462 parent = dentry->d_parent;
463 if (parent && !spin_trylock(&parent->d_lock)) {
465 spin_unlock(&inode->i_lock);
470 dentry->d_lockref.count--;
472 * inform the fs via d_prune that this dentry is about to be
473 * unhashed and destroyed.
475 if ((dentry->d_flags & DCACHE_OP_PRUNE) && !d_unhashed(dentry))
476 dentry->d_op->d_prune(dentry);
478 dentry_lru_del(dentry);
479 /* if it was on the hash then remove it */
481 return d_kill(dentry, parent);
487 * This is complicated by the fact that we do not want to put
488 * dentries that are no longer on any hash chain on the unused
489 * list: we'd much rather just get rid of them immediately.
491 * However, that implies that we have to traverse the dentry
492 * tree upwards to the parents which might _also_ now be
493 * scheduled for deletion (it may have been only waiting for
494 * its last child to go away).
496 * This tail recursion is done by hand as we don't want to depend
497 * on the compiler to always get this right (gcc generally doesn't).
498 * Real recursion would eat up our stack space.
502 * dput - release a dentry
503 * @dentry: dentry to release
505 * Release a dentry. This will drop the usage count and if appropriate
506 * call the dentry unlink method as well as removing it from the queues and
507 * releasing its resources. If the parent dentries were scheduled for release
508 * they too may now get deleted.
510 void dput(struct dentry *dentry)
516 if (dentry->d_lockref.count == 1)
518 if (lockref_put_or_lock(&dentry->d_lockref))
521 if (dentry->d_flags & DCACHE_OP_DELETE) {
522 if (dentry->d_op->d_delete(dentry))
526 /* Unreachable? Get rid of it */
527 if (d_unhashed(dentry))
530 dentry->d_flags |= DCACHE_REFERENCED;
531 dentry_lru_add(dentry);
533 dentry->d_lockref.count--;
534 spin_unlock(&dentry->d_lock);
538 dentry = dentry_kill(dentry, 1);
545 * d_invalidate - invalidate a dentry
546 * @dentry: dentry to invalidate
548 * Try to invalidate the dentry if it turns out to be
549 * possible. If there are other dentries that can be
550 * reached through this one we can't delete it and we
551 * return -EBUSY. On success we return 0.
556 int d_invalidate(struct dentry * dentry)
559 * If it's already been dropped, return OK.
561 spin_lock(&dentry->d_lock);
562 if (d_unhashed(dentry)) {
563 spin_unlock(&dentry->d_lock);
567 * Check whether to do a partial shrink_dcache
568 * to get rid of unused child entries.
570 if (!list_empty(&dentry->d_subdirs)) {
571 spin_unlock(&dentry->d_lock);
572 shrink_dcache_parent(dentry);
573 spin_lock(&dentry->d_lock);
577 * Somebody else still using it?
579 * If it's a directory, we can't drop it
580 * for fear of somebody re-populating it
581 * with children (even though dropping it
582 * would make it unreachable from the root,
583 * we might still populate it if it was a
584 * working directory or similar).
585 * We also need to leave mountpoints alone,
588 if (dentry->d_lockref.count > 1 && dentry->d_inode) {
589 if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) {
590 spin_unlock(&dentry->d_lock);
596 spin_unlock(&dentry->d_lock);
599 EXPORT_SYMBOL(d_invalidate);
601 /* This must be called with d_lock held */
602 static inline void __dget_dlock(struct dentry *dentry)
604 dentry->d_lockref.count++;
607 static inline void __dget(struct dentry *dentry)
609 lockref_get(&dentry->d_lockref);
612 struct dentry *dget_parent(struct dentry *dentry)
618 * Do optimistic parent lookup without any
622 ret = ACCESS_ONCE(dentry->d_parent);
623 gotref = lockref_get_not_zero(&ret->d_lockref);
625 if (likely(gotref)) {
626 if (likely(ret == ACCESS_ONCE(dentry->d_parent)))
633 * Don't need rcu_dereference because we re-check it was correct under
637 ret = dentry->d_parent;
638 spin_lock(&ret->d_lock);
639 if (unlikely(ret != dentry->d_parent)) {
640 spin_unlock(&ret->d_lock);
645 BUG_ON(!ret->d_lockref.count);
646 ret->d_lockref.count++;
647 spin_unlock(&ret->d_lock);
650 EXPORT_SYMBOL(dget_parent);
653 * d_find_alias - grab a hashed alias of inode
654 * @inode: inode in question
655 * @want_discon: flag, used by d_splice_alias, to request
656 * that only a DISCONNECTED alias be returned.
658 * If inode has a hashed alias, or is a directory and has any alias,
659 * acquire the reference to alias and return it. Otherwise return NULL.
660 * Notice that if inode is a directory there can be only one alias and
661 * it can be unhashed only if it has no children, or if it is the root
664 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
665 * any other hashed alias over that one unless @want_discon is set,
666 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
668 static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
670 struct dentry *alias, *discon_alias;
674 hlist_for_each_entry(alias, &inode->i_dentry, d_alias) {
675 spin_lock(&alias->d_lock);
676 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
677 if (IS_ROOT(alias) &&
678 (alias->d_flags & DCACHE_DISCONNECTED)) {
679 discon_alias = alias;
680 } else if (!want_discon) {
682 spin_unlock(&alias->d_lock);
686 spin_unlock(&alias->d_lock);
689 alias = discon_alias;
690 spin_lock(&alias->d_lock);
691 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
692 if (IS_ROOT(alias) &&
693 (alias->d_flags & DCACHE_DISCONNECTED)) {
695 spin_unlock(&alias->d_lock);
699 spin_unlock(&alias->d_lock);
705 struct dentry *d_find_alias(struct inode *inode)
707 struct dentry *de = NULL;
709 if (!hlist_empty(&inode->i_dentry)) {
710 spin_lock(&inode->i_lock);
711 de = __d_find_alias(inode, 0);
712 spin_unlock(&inode->i_lock);
716 EXPORT_SYMBOL(d_find_alias);
719 * Try to kill dentries associated with this inode.
720 * WARNING: you must own a reference to inode.
722 void d_prune_aliases(struct inode *inode)
724 struct dentry *dentry;
726 spin_lock(&inode->i_lock);
727 hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
728 spin_lock(&dentry->d_lock);
729 if (!dentry->d_lockref.count) {
731 * inform the fs via d_prune that this dentry
732 * is about to be unhashed and destroyed.
734 if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
736 dentry->d_op->d_prune(dentry);
738 __dget_dlock(dentry);
740 spin_unlock(&dentry->d_lock);
741 spin_unlock(&inode->i_lock);
745 spin_unlock(&dentry->d_lock);
747 spin_unlock(&inode->i_lock);
749 EXPORT_SYMBOL(d_prune_aliases);
752 * Try to throw away a dentry - free the inode, dput the parent.
753 * Requires dentry->d_lock is held, and dentry->d_count == 0.
754 * Releases dentry->d_lock.
756 * This may fail if locks cannot be acquired no problem, just try again.
758 static void try_prune_one_dentry(struct dentry *dentry)
759 __releases(dentry->d_lock)
761 struct dentry *parent;
763 parent = dentry_kill(dentry, 0);
765 * If dentry_kill returns NULL, we have nothing more to do.
766 * if it returns the same dentry, trylocks failed. In either
767 * case, just loop again.
769 * Otherwise, we need to prune ancestors too. This is necessary
770 * to prevent quadratic behavior of shrink_dcache_parent(), but
771 * is also expected to be beneficial in reducing dentry cache
776 if (parent == dentry)
779 /* Prune ancestors. */
782 if (lockref_put_or_lock(&dentry->d_lockref))
784 dentry = dentry_kill(dentry, 1);
788 static void shrink_dentry_list(struct list_head *list)
790 struct dentry *dentry;
794 dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
795 if (&dentry->d_lru == list)
797 spin_lock(&dentry->d_lock);
798 if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
799 spin_unlock(&dentry->d_lock);
804 * We found an inuse dentry which was not removed from
805 * the LRU because of laziness during lookup. Do not free
806 * it - just keep it off the LRU list.
808 if (dentry->d_lockref.count) {
809 dentry_lru_del(dentry);
810 spin_unlock(&dentry->d_lock);
816 try_prune_one_dentry(dentry);
824 * prune_dcache_sb - shrink the dcache
826 * @count: number of entries to try to free
828 * Attempt to shrink the superblock dcache LRU by @count entries. This is
829 * done when we need more memory an called from the superblock shrinker
832 * This function may fail to free any resources if all the dentries are in
835 void prune_dcache_sb(struct super_block *sb, int count)
837 struct dentry *dentry;
838 LIST_HEAD(referenced);
842 spin_lock(&dcache_lru_lock);
843 while (!list_empty(&sb->s_dentry_lru)) {
844 dentry = list_entry(sb->s_dentry_lru.prev,
845 struct dentry, d_lru);
846 BUG_ON(dentry->d_sb != sb);
848 if (!spin_trylock(&dentry->d_lock)) {
849 spin_unlock(&dcache_lru_lock);
854 if (dentry->d_flags & DCACHE_REFERENCED) {
855 dentry->d_flags &= ~DCACHE_REFERENCED;
856 list_move(&dentry->d_lru, &referenced);
857 spin_unlock(&dentry->d_lock);
859 list_move_tail(&dentry->d_lru, &tmp);
860 dentry->d_flags |= DCACHE_SHRINK_LIST;
861 spin_unlock(&dentry->d_lock);
865 cond_resched_lock(&dcache_lru_lock);
867 if (!list_empty(&referenced))
868 list_splice(&referenced, &sb->s_dentry_lru);
869 spin_unlock(&dcache_lru_lock);
871 shrink_dentry_list(&tmp);
875 * shrink_dcache_sb - shrink dcache for a superblock
878 * Shrink the dcache for the specified super block. This is used to free
879 * the dcache before unmounting a file system.
881 void shrink_dcache_sb(struct super_block *sb)
885 spin_lock(&dcache_lru_lock);
886 while (!list_empty(&sb->s_dentry_lru)) {
887 list_splice_init(&sb->s_dentry_lru, &tmp);
888 spin_unlock(&dcache_lru_lock);
889 shrink_dentry_list(&tmp);
890 spin_lock(&dcache_lru_lock);
892 spin_unlock(&dcache_lru_lock);
894 EXPORT_SYMBOL(shrink_dcache_sb);
897 * destroy a single subtree of dentries for unmount
898 * - see the comments on shrink_dcache_for_umount() for a description of the
901 static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
903 struct dentry *parent;
905 BUG_ON(!IS_ROOT(dentry));
908 /* descend to the first leaf in the current subtree */
909 while (!list_empty(&dentry->d_subdirs))
910 dentry = list_entry(dentry->d_subdirs.next,
911 struct dentry, d_u.d_child);
913 /* consume the dentries from this leaf up through its parents
914 * until we find one with children or run out altogether */
919 * inform the fs that this dentry is about to be
920 * unhashed and destroyed.
922 if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
924 dentry->d_op->d_prune(dentry);
926 dentry_lru_del(dentry);
929 if (dentry->d_lockref.count != 0) {
931 "BUG: Dentry %p{i=%lx,n=%s}"
933 " [unmount of %s %s]\n",
936 dentry->d_inode->i_ino : 0UL,
938 dentry->d_lockref.count,
939 dentry->d_sb->s_type->name,
944 if (IS_ROOT(dentry)) {
946 list_del(&dentry->d_u.d_child);
948 parent = dentry->d_parent;
949 parent->d_lockref.count--;
950 list_del(&dentry->d_u.d_child);
953 inode = dentry->d_inode;
955 dentry->d_inode = NULL;
956 hlist_del_init(&dentry->d_alias);
957 if (dentry->d_op && dentry->d_op->d_iput)
958 dentry->d_op->d_iput(dentry, inode);
965 /* finished when we fall off the top of the tree,
966 * otherwise we ascend to the parent and move to the
967 * next sibling if there is one */
971 } while (list_empty(&dentry->d_subdirs));
973 dentry = list_entry(dentry->d_subdirs.next,
974 struct dentry, d_u.d_child);
979 * destroy the dentries attached to a superblock on unmounting
980 * - we don't need to use dentry->d_lock because:
981 * - the superblock is detached from all mountings and open files, so the
982 * dentry trees will not be rearranged by the VFS
983 * - s_umount is write-locked, so the memory pressure shrinker will ignore
984 * any dentries belonging to this superblock that it comes across
985 * - the filesystem itself is no longer permitted to rearrange the dentries
988 void shrink_dcache_for_umount(struct super_block *sb)
990 struct dentry *dentry;
992 if (down_read_trylock(&sb->s_umount))
997 dentry->d_lockref.count--;
998 shrink_dcache_for_umount_subtree(dentry);
1000 while (!hlist_bl_empty(&sb->s_anon)) {
1001 dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
1002 shrink_dcache_for_umount_subtree(dentry);
1007 * This tries to ascend one level of parenthood, but
1008 * we can race with renaming, so we need to re-check
1009 * the parenthood after dropping the lock and check
1010 * that the sequence number still matches.
1012 static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq)
1014 struct dentry *new = old->d_parent;
1017 spin_unlock(&old->d_lock);
1018 spin_lock(&new->d_lock);
1021 * might go back up the wrong parent if we have had a rename
1024 if (new != old->d_parent ||
1025 (old->d_flags & DCACHE_DENTRY_KILLED) ||
1026 (!locked && read_seqretry(&rename_lock, seq))) {
1027 spin_unlock(&new->d_lock);
1035 * enum d_walk_ret - action to talke during tree walk
1036 * @D_WALK_CONTINUE: contrinue walk
1037 * @D_WALK_QUIT: quit walk
1038 * @D_WALK_NORETRY: quit when retry is needed
1039 * @D_WALK_SKIP: skip this dentry and its children
1049 * d_walk - walk the dentry tree
1050 * @parent: start of walk
1051 * @data: data passed to @enter() and @finish()
1052 * @enter: callback when first entering the dentry
1053 * @finish: callback when successfully finished the walk
1055 * The @enter() and @finish() callbacks are called with d_lock held.
1057 static void d_walk(struct dentry *parent, void *data,
1058 enum d_walk_ret (*enter)(void *, struct dentry *),
1059 void (*finish)(void *))
1061 struct dentry *this_parent;
1062 struct list_head *next;
1065 enum d_walk_ret ret;
1068 seq = read_seqbegin(&rename_lock);
1070 this_parent = parent;
1071 spin_lock(&this_parent->d_lock);
1073 ret = enter(data, this_parent);
1075 case D_WALK_CONTINUE:
1080 case D_WALK_NORETRY:
1085 next = this_parent->d_subdirs.next;
1087 while (next != &this_parent->d_subdirs) {
1088 struct list_head *tmp = next;
1089 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
1092 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1094 ret = enter(data, dentry);
1096 case D_WALK_CONTINUE:
1099 spin_unlock(&dentry->d_lock);
1101 case D_WALK_NORETRY:
1105 spin_unlock(&dentry->d_lock);
1109 if (!list_empty(&dentry->d_subdirs)) {
1110 spin_unlock(&this_parent->d_lock);
1111 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
1112 this_parent = dentry;
1113 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1116 spin_unlock(&dentry->d_lock);
1119 * All done at this level ... ascend and resume the search.
1121 if (this_parent != parent) {
1122 struct dentry *child = this_parent;
1123 this_parent = try_to_ascend(this_parent, locked, seq);
1126 next = child->d_u.d_child.next;
1129 if (!locked && read_seqretry(&rename_lock, seq)) {
1130 spin_unlock(&this_parent->d_lock);
1137 spin_unlock(&this_parent->d_lock);
1139 write_sequnlock(&rename_lock);
1148 write_seqlock(&rename_lock);
1153 * Search for at least 1 mount point in the dentry's subdirs.
1154 * We descend to the next level whenever the d_subdirs
1155 * list is non-empty and continue searching.
1159 * have_submounts - check for mounts over a dentry
1160 * @parent: dentry to check.
1162 * Return true if the parent or its subdirectories contain
1166 static enum d_walk_ret check_mount(void *data, struct dentry *dentry)
1169 if (d_mountpoint(dentry)) {
1173 return D_WALK_CONTINUE;
1176 int have_submounts(struct dentry *parent)
1180 d_walk(parent, &ret, check_mount, NULL);
1184 EXPORT_SYMBOL(have_submounts);
1187 * Search the dentry child list of the specified parent,
1188 * and move any unused dentries to the end of the unused
1189 * list for prune_dcache(). We descend to the next level
1190 * whenever the d_subdirs list is non-empty and continue
1193 * It returns zero iff there are no unused children,
1194 * otherwise it returns the number of children moved to
1195 * the end of the unused list. This may not be the total
1196 * number of unused children, because select_parent can
1197 * drop the lock and return early due to latency
1201 struct select_data {
1202 struct dentry *start;
1203 struct list_head dispose;
1207 static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
1209 struct select_data *data = _data;
1210 enum d_walk_ret ret = D_WALK_CONTINUE;
1212 if (data->start == dentry)
1216 * move only zero ref count dentries to the dispose list.
1218 * Those which are presently on the shrink list, being processed
1219 * by shrink_dentry_list(), shouldn't be moved. Otherwise the
1220 * loop in shrink_dcache_parent() might not make any progress
1223 if (dentry->d_lockref.count) {
1224 dentry_lru_del(dentry);
1225 } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
1226 dentry_lru_move_list(dentry, &data->dispose);
1227 dentry->d_flags |= DCACHE_SHRINK_LIST;
1229 ret = D_WALK_NORETRY;
1232 * We can return to the caller if we have found some (this
1233 * ensures forward progress). We'll be coming back to find
1236 if (data->found && need_resched())
1243 * shrink_dcache_parent - prune dcache
1244 * @parent: parent of entries to prune
1246 * Prune the dcache to remove unused children of the parent dentry.
1248 void shrink_dcache_parent(struct dentry *parent)
1251 struct select_data data;
1253 INIT_LIST_HEAD(&data.dispose);
1254 data.start = parent;
1257 d_walk(parent, &data, select_collect, NULL);
1261 shrink_dentry_list(&data.dispose);
1265 EXPORT_SYMBOL(shrink_dcache_parent);
1267 static enum d_walk_ret check_and_collect(void *_data, struct dentry *dentry)
1269 struct select_data *data = _data;
1271 if (d_mountpoint(dentry)) {
1272 data->found = -EBUSY;
1276 return select_collect(_data, dentry);
1279 static void check_and_drop(void *_data)
1281 struct select_data *data = _data;
1283 if (d_mountpoint(data->start))
1284 data->found = -EBUSY;
1286 __d_drop(data->start);
1290 * check_submounts_and_drop - prune dcache, check for submounts and drop
1292 * All done as a single atomic operation relative to has_unlinked_ancestor().
1293 * Returns 0 if successfully unhashed @parent. If there were submounts then
1296 * @dentry: dentry to prune and drop
1298 int check_submounts_and_drop(struct dentry *dentry)
1302 /* Negative dentries can be dropped without further checks */
1303 if (!dentry->d_inode) {
1309 struct select_data data;
1311 INIT_LIST_HEAD(&data.dispose);
1312 data.start = dentry;
1315 d_walk(dentry, &data, check_and_collect, check_and_drop);
1318 if (!list_empty(&data.dispose))
1319 shrink_dentry_list(&data.dispose);
1330 EXPORT_SYMBOL(check_submounts_and_drop);
1333 * __d_alloc - allocate a dcache entry
1334 * @sb: filesystem it will belong to
1335 * @name: qstr of the name
1337 * Allocates a dentry. It returns %NULL if there is insufficient memory
1338 * available. On a success the dentry is returned. The name passed in is
1339 * copied and the copy passed in may be reused after this call.
1342 struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1344 struct dentry *dentry;
1347 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
1352 * We guarantee that the inline name is always NUL-terminated.
1353 * This way the memcpy() done by the name switching in rename
1354 * will still always have a NUL at the end, even if we might
1355 * be overwriting an internal NUL character
1357 dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
1358 if (name->len > DNAME_INLINE_LEN-1) {
1359 dname = kmalloc(name->len + 1, GFP_KERNEL);
1361 kmem_cache_free(dentry_cache, dentry);
1365 dname = dentry->d_iname;
1368 dentry->d_name.len = name->len;
1369 dentry->d_name.hash = name->hash;
1370 memcpy(dname, name->name, name->len);
1371 dname[name->len] = 0;
1373 /* Make sure we always see the terminating NUL character */
1375 dentry->d_name.name = dname;
1377 dentry->d_lockref.count = 1;
1378 dentry->d_flags = 0;
1379 spin_lock_init(&dentry->d_lock);
1380 seqcount_init(&dentry->d_seq);
1381 dentry->d_inode = NULL;
1382 dentry->d_parent = dentry;
1384 dentry->d_op = NULL;
1385 dentry->d_fsdata = NULL;
1386 INIT_HLIST_BL_NODE(&dentry->d_hash);
1387 INIT_LIST_HEAD(&dentry->d_lru);
1388 INIT_LIST_HEAD(&dentry->d_subdirs);
1389 INIT_HLIST_NODE(&dentry->d_alias);
1390 INIT_LIST_HEAD(&dentry->d_u.d_child);
1391 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1393 this_cpu_inc(nr_dentry);
1399 * d_alloc - allocate a dcache entry
1400 * @parent: parent of entry to allocate
1401 * @name: qstr of the name
1403 * Allocates a dentry. It returns %NULL if there is insufficient memory
1404 * available. On a success the dentry is returned. The name passed in is
1405 * copied and the copy passed in may be reused after this call.
1407 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1409 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1413 spin_lock(&parent->d_lock);
1415 * don't need child lock because it is not subject
1416 * to concurrency here
1418 __dget_dlock(parent);
1419 dentry->d_parent = parent;
1420 list_add(&dentry->d_u.d_child, &parent->d_subdirs);
1421 spin_unlock(&parent->d_lock);
1425 EXPORT_SYMBOL(d_alloc);
1427 struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1429 struct dentry *dentry = __d_alloc(sb, name);
1431 dentry->d_flags |= DCACHE_DISCONNECTED;
1434 EXPORT_SYMBOL(d_alloc_pseudo);
1436 struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1441 q.len = strlen(name);
1442 q.hash = full_name_hash(q.name, q.len);
1443 return d_alloc(parent, &q);
1445 EXPORT_SYMBOL(d_alloc_name);
1447 void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1449 WARN_ON_ONCE(dentry->d_op);
1450 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
1452 DCACHE_OP_REVALIDATE |
1453 DCACHE_OP_WEAK_REVALIDATE |
1454 DCACHE_OP_DELETE ));
1459 dentry->d_flags |= DCACHE_OP_HASH;
1461 dentry->d_flags |= DCACHE_OP_COMPARE;
1462 if (op->d_revalidate)
1463 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1464 if (op->d_weak_revalidate)
1465 dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
1467 dentry->d_flags |= DCACHE_OP_DELETE;
1469 dentry->d_flags |= DCACHE_OP_PRUNE;
1472 EXPORT_SYMBOL(d_set_d_op);
1474 static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1476 spin_lock(&dentry->d_lock);
1478 if (unlikely(IS_AUTOMOUNT(inode)))
1479 dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
1480 hlist_add_head(&dentry->d_alias, &inode->i_dentry);
1482 dentry->d_inode = inode;
1483 dentry_rcuwalk_barrier(dentry);
1484 spin_unlock(&dentry->d_lock);
1485 fsnotify_d_instantiate(dentry, inode);
1489 * d_instantiate - fill in inode information for a dentry
1490 * @entry: dentry to complete
1491 * @inode: inode to attach to this dentry
1493 * Fill in inode information in the entry.
1495 * This turns negative dentries into productive full members
1498 * NOTE! This assumes that the inode count has been incremented
1499 * (or otherwise set) by the caller to indicate that it is now
1500 * in use by the dcache.
1503 void d_instantiate(struct dentry *entry, struct inode * inode)
1505 BUG_ON(!hlist_unhashed(&entry->d_alias));
1507 spin_lock(&inode->i_lock);
1508 __d_instantiate(entry, inode);
1510 spin_unlock(&inode->i_lock);
1511 security_d_instantiate(entry, inode);
1513 EXPORT_SYMBOL(d_instantiate);
1516 * d_instantiate_unique - instantiate a non-aliased dentry
1517 * @entry: dentry to instantiate
1518 * @inode: inode to attach to this dentry
1520 * Fill in inode information in the entry. On success, it returns NULL.
1521 * If an unhashed alias of "entry" already exists, then we return the
1522 * aliased dentry instead and drop one reference to inode.
1524 * Note that in order to avoid conflicts with rename() etc, the caller
1525 * had better be holding the parent directory semaphore.
1527 * This also assumes that the inode count has been incremented
1528 * (or otherwise set) by the caller to indicate that it is now
1529 * in use by the dcache.
1531 static struct dentry *__d_instantiate_unique(struct dentry *entry,
1532 struct inode *inode)
1534 struct dentry *alias;
1535 int len = entry->d_name.len;
1536 const char *name = entry->d_name.name;
1537 unsigned int hash = entry->d_name.hash;
1540 __d_instantiate(entry, NULL);
1544 hlist_for_each_entry(alias, &inode->i_dentry, d_alias) {
1546 * Don't need alias->d_lock here, because aliases with
1547 * d_parent == entry->d_parent are not subject to name or
1548 * parent changes, because the parent inode i_mutex is held.
1550 if (alias->d_name.hash != hash)
1552 if (alias->d_parent != entry->d_parent)
1554 if (alias->d_name.len != len)
1556 if (dentry_cmp(alias, name, len))
1562 __d_instantiate(entry, inode);
1566 struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
1568 struct dentry *result;
1570 BUG_ON(!hlist_unhashed(&entry->d_alias));
1573 spin_lock(&inode->i_lock);
1574 result = __d_instantiate_unique(entry, inode);
1576 spin_unlock(&inode->i_lock);
1579 security_d_instantiate(entry, inode);
1583 BUG_ON(!d_unhashed(result));
1588 EXPORT_SYMBOL(d_instantiate_unique);
1590 struct dentry *d_make_root(struct inode *root_inode)
1592 struct dentry *res = NULL;
1595 static const struct qstr name = QSTR_INIT("/", 1);
1597 res = __d_alloc(root_inode->i_sb, &name);
1599 d_instantiate(res, root_inode);
1605 EXPORT_SYMBOL(d_make_root);
1607 static struct dentry * __d_find_any_alias(struct inode *inode)
1609 struct dentry *alias;
1611 if (hlist_empty(&inode->i_dentry))
1613 alias = hlist_entry(inode->i_dentry.first, struct dentry, d_alias);
1619 * d_find_any_alias - find any alias for a given inode
1620 * @inode: inode to find an alias for
1622 * If any aliases exist for the given inode, take and return a
1623 * reference for one of them. If no aliases exist, return %NULL.
1625 struct dentry *d_find_any_alias(struct inode *inode)
1629 spin_lock(&inode->i_lock);
1630 de = __d_find_any_alias(inode);
1631 spin_unlock(&inode->i_lock);
1634 EXPORT_SYMBOL(d_find_any_alias);
1637 * d_obtain_alias - find or allocate a dentry for a given inode
1638 * @inode: inode to allocate the dentry for
1640 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1641 * similar open by handle operations. The returned dentry may be anonymous,
1642 * or may have a full name (if the inode was already in the cache).
1644 * When called on a directory inode, we must ensure that the inode only ever
1645 * has one dentry. If a dentry is found, that is returned instead of
1646 * allocating a new one.
1648 * On successful return, the reference to the inode has been transferred
1649 * to the dentry. In case of an error the reference on the inode is released.
1650 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1651 * be passed in and will be the error will be propagate to the return value,
1652 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1654 struct dentry *d_obtain_alias(struct inode *inode)
1656 static const struct qstr anonstring = QSTR_INIT("/", 1);
1661 return ERR_PTR(-ESTALE);
1663 return ERR_CAST(inode);
1665 res = d_find_any_alias(inode);
1669 tmp = __d_alloc(inode->i_sb, &anonstring);
1671 res = ERR_PTR(-ENOMEM);
1675 spin_lock(&inode->i_lock);
1676 res = __d_find_any_alias(inode);
1678 spin_unlock(&inode->i_lock);
1683 /* attach a disconnected dentry */
1684 spin_lock(&tmp->d_lock);
1685 tmp->d_inode = inode;
1686 tmp->d_flags |= DCACHE_DISCONNECTED;
1687 hlist_add_head(&tmp->d_alias, &inode->i_dentry);
1688 hlist_bl_lock(&tmp->d_sb->s_anon);
1689 hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
1690 hlist_bl_unlock(&tmp->d_sb->s_anon);
1691 spin_unlock(&tmp->d_lock);
1692 spin_unlock(&inode->i_lock);
1693 security_d_instantiate(tmp, inode);
1698 if (res && !IS_ERR(res))
1699 security_d_instantiate(res, inode);
1703 EXPORT_SYMBOL(d_obtain_alias);
1706 * d_splice_alias - splice a disconnected dentry into the tree if one exists
1707 * @inode: the inode which may have a disconnected dentry
1708 * @dentry: a negative dentry which we want to point to the inode.
1710 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1711 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1712 * and return it, else simply d_add the inode to the dentry and return NULL.
1714 * This is needed in the lookup routine of any filesystem that is exportable
1715 * (via knfsd) so that we can build dcache paths to directories effectively.
1717 * If a dentry was found and moved, then it is returned. Otherwise NULL
1718 * is returned. This matches the expected return value of ->lookup.
1720 * Cluster filesystems may call this function with a negative, hashed dentry.
1721 * In that case, we know that the inode will be a regular file, and also this
1722 * will only occur during atomic_open. So we need to check for the dentry
1723 * being already hashed only in the final case.
1725 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
1727 struct dentry *new = NULL;
1730 return ERR_CAST(inode);
1732 if (inode && S_ISDIR(inode->i_mode)) {
1733 spin_lock(&inode->i_lock);
1734 new = __d_find_alias(inode, 1);
1736 BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
1737 spin_unlock(&inode->i_lock);
1738 security_d_instantiate(new, inode);
1739 d_move(new, dentry);
1742 /* already taking inode->i_lock, so d_add() by hand */
1743 __d_instantiate(dentry, inode);
1744 spin_unlock(&inode->i_lock);
1745 security_d_instantiate(dentry, inode);
1749 d_instantiate(dentry, inode);
1750 if (d_unhashed(dentry))
1755 EXPORT_SYMBOL(d_splice_alias);
1758 * d_add_ci - lookup or allocate new dentry with case-exact name
1759 * @inode: the inode case-insensitive lookup has found
1760 * @dentry: the negative dentry that was passed to the parent's lookup func
1761 * @name: the case-exact name to be associated with the returned dentry
1763 * This is to avoid filling the dcache with case-insensitive names to the
1764 * same inode, only the actual correct case is stored in the dcache for
1765 * case-insensitive filesystems.
1767 * For a case-insensitive lookup match and if the the case-exact dentry
1768 * already exists in in the dcache, use it and return it.
1770 * If no entry exists with the exact case name, allocate new dentry with
1771 * the exact case, and return the spliced entry.
1773 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
1776 struct dentry *found;
1780 * First check if a dentry matching the name already exists,
1781 * if not go ahead and create it now.
1783 found = d_hash_and_lookup(dentry->d_parent, name);
1784 if (unlikely(IS_ERR(found)))
1787 new = d_alloc(dentry->d_parent, name);
1789 found = ERR_PTR(-ENOMEM);
1793 found = d_splice_alias(inode, new);
1802 * If a matching dentry exists, and it's not negative use it.
1804 * Decrement the reference count to balance the iget() done
1807 if (found->d_inode) {
1808 if (unlikely(found->d_inode != inode)) {
1809 /* This can't happen because bad inodes are unhashed. */
1810 BUG_ON(!is_bad_inode(inode));
1811 BUG_ON(!is_bad_inode(found->d_inode));
1818 * Negative dentry: instantiate it unless the inode is a directory and
1819 * already has a dentry.
1821 new = d_splice_alias(inode, found);
1832 EXPORT_SYMBOL(d_add_ci);
1835 * Do the slow-case of the dentry name compare.
1837 * Unlike the dentry_cmp() function, we need to atomically
1838 * load the name and length information, so that the
1839 * filesystem can rely on them, and can use the 'name' and
1840 * 'len' information without worrying about walking off the
1841 * end of memory etc.
1843 * Thus the read_seqcount_retry() and the "duplicate" info
1844 * in arguments (the low-level filesystem should not look
1845 * at the dentry inode or name contents directly, since
1846 * rename can change them while we're in RCU mode).
1848 enum slow_d_compare {
1854 static noinline enum slow_d_compare slow_dentry_cmp(
1855 const struct dentry *parent,
1856 struct dentry *dentry,
1858 const struct qstr *name)
1860 int tlen = dentry->d_name.len;
1861 const char *tname = dentry->d_name.name;
1863 if (read_seqcount_retry(&dentry->d_seq, seq)) {
1865 return D_COMP_SEQRETRY;
1867 if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
1868 return D_COMP_NOMATCH;
1873 * __d_lookup_rcu - search for a dentry (racy, store-free)
1874 * @parent: parent dentry
1875 * @name: qstr of name we wish to find
1876 * @seqp: returns d_seq value at the point where the dentry was found
1877 * Returns: dentry, or NULL
1879 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
1880 * resolution (store-free path walking) design described in
1881 * Documentation/filesystems/path-lookup.txt.
1883 * This is not to be used outside core vfs.
1885 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
1886 * held, and rcu_read_lock held. The returned dentry must not be stored into
1887 * without taking d_lock and checking d_seq sequence count against @seq
1890 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
1893 * Alternatively, __d_lookup_rcu may be called again to look up the child of
1894 * the returned dentry, so long as its parent's seqlock is checked after the
1895 * child is looked up. Thus, an interlocking stepping of sequence lock checks
1896 * is formed, giving integrity down the path walk.
1898 * NOTE! The caller *has* to check the resulting dentry against the sequence
1899 * number we've returned before using any of the resulting dentry state!
1901 struct dentry *__d_lookup_rcu(const struct dentry *parent,
1902 const struct qstr *name,
1905 u64 hashlen = name->hash_len;
1906 const unsigned char *str = name->name;
1907 struct hlist_bl_head *b = d_hash(parent, hashlen_hash(hashlen));
1908 struct hlist_bl_node *node;
1909 struct dentry *dentry;
1912 * Note: There is significant duplication with __d_lookup_rcu which is
1913 * required to prevent single threaded performance regressions
1914 * especially on architectures where smp_rmb (in seqcounts) are costly.
1915 * Keep the two functions in sync.
1919 * The hash list is protected using RCU.
1921 * Carefully use d_seq when comparing a candidate dentry, to avoid
1922 * races with d_move().
1924 * It is possible that concurrent renames can mess up our list
1925 * walk here and result in missing our dentry, resulting in the
1926 * false-negative result. d_lookup() protects against concurrent
1927 * renames using rename_lock seqlock.
1929 * See Documentation/filesystems/path-lookup.txt for more details.
1931 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
1936 * The dentry sequence count protects us from concurrent
1937 * renames, and thus protects parent and name fields.
1939 * The caller must perform a seqcount check in order
1940 * to do anything useful with the returned dentry.
1942 * NOTE! We do a "raw" seqcount_begin here. That means that
1943 * we don't wait for the sequence count to stabilize if it
1944 * is in the middle of a sequence change. If we do the slow
1945 * dentry compare, we will do seqretries until it is stable,
1946 * and if we end up with a successful lookup, we actually
1947 * want to exit RCU lookup anyway.
1949 seq = raw_seqcount_begin(&dentry->d_seq);
1950 if (dentry->d_parent != parent)
1952 if (d_unhashed(dentry))
1955 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
1956 if (dentry->d_name.hash != hashlen_hash(hashlen))
1959 switch (slow_dentry_cmp(parent, dentry, seq, name)) {
1962 case D_COMP_NOMATCH:
1969 if (dentry->d_name.hash_len != hashlen)
1972 if (!dentry_cmp(dentry, str, hashlen_len(hashlen)))
1979 * d_lookup - search for a dentry
1980 * @parent: parent dentry
1981 * @name: qstr of name we wish to find
1982 * Returns: dentry, or NULL
1984 * d_lookup searches the children of the parent dentry for the name in
1985 * question. If the dentry is found its reference count is incremented and the
1986 * dentry is returned. The caller must use dput to free the entry when it has
1987 * finished using it. %NULL is returned if the dentry does not exist.
1989 struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
1991 struct dentry *dentry;
1995 seq = read_seqbegin(&rename_lock);
1996 dentry = __d_lookup(parent, name);
1999 } while (read_seqretry(&rename_lock, seq));
2002 EXPORT_SYMBOL(d_lookup);
2005 * __d_lookup - search for a dentry (racy)
2006 * @parent: parent dentry
2007 * @name: qstr of name we wish to find
2008 * Returns: dentry, or NULL
2010 * __d_lookup is like d_lookup, however it may (rarely) return a
2011 * false-negative result due to unrelated rename activity.
2013 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2014 * however it must be used carefully, eg. with a following d_lookup in
2015 * the case of failure.
2017 * __d_lookup callers must be commented.
2019 struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
2021 unsigned int len = name->len;
2022 unsigned int hash = name->hash;
2023 const unsigned char *str = name->name;
2024 struct hlist_bl_head *b = d_hash(parent, hash);
2025 struct hlist_bl_node *node;
2026 struct dentry *found = NULL;
2027 struct dentry *dentry;
2030 * Note: There is significant duplication with __d_lookup_rcu which is
2031 * required to prevent single threaded performance regressions
2032 * especially on architectures where smp_rmb (in seqcounts) are costly.
2033 * Keep the two functions in sync.
2037 * The hash list is protected using RCU.
2039 * Take d_lock when comparing a candidate dentry, to avoid races
2042 * It is possible that concurrent renames can mess up our list
2043 * walk here and result in missing our dentry, resulting in the
2044 * false-negative result. d_lookup() protects against concurrent
2045 * renames using rename_lock seqlock.
2047 * See Documentation/filesystems/path-lookup.txt for more details.
2051 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2053 if (dentry->d_name.hash != hash)
2056 spin_lock(&dentry->d_lock);
2057 if (dentry->d_parent != parent)
2059 if (d_unhashed(dentry))
2063 * It is safe to compare names since d_move() cannot
2064 * change the qstr (protected by d_lock).
2066 if (parent->d_flags & DCACHE_OP_COMPARE) {
2067 int tlen = dentry->d_name.len;
2068 const char *tname = dentry->d_name.name;
2069 if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
2072 if (dentry->d_name.len != len)
2074 if (dentry_cmp(dentry, str, len))
2078 dentry->d_lockref.count++;
2080 spin_unlock(&dentry->d_lock);
2083 spin_unlock(&dentry->d_lock);
2091 * d_hash_and_lookup - hash the qstr then search for a dentry
2092 * @dir: Directory to search in
2093 * @name: qstr of name we wish to find
2095 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2097 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2100 * Check for a fs-specific hash function. Note that we must
2101 * calculate the standard hash first, as the d_op->d_hash()
2102 * routine may choose to leave the hash value unchanged.
2104 name->hash = full_name_hash(name->name, name->len);
2105 if (dir->d_flags & DCACHE_OP_HASH) {
2106 int err = dir->d_op->d_hash(dir, name);
2107 if (unlikely(err < 0))
2108 return ERR_PTR(err);
2110 return d_lookup(dir, name);
2112 EXPORT_SYMBOL(d_hash_and_lookup);
2115 * d_validate - verify dentry provided from insecure source (deprecated)
2116 * @dentry: The dentry alleged to be valid child of @dparent
2117 * @dparent: The parent dentry (known to be valid)
2119 * An insecure source has sent us a dentry, here we verify it and dget() it.
2120 * This is used by ncpfs in its readdir implementation.
2121 * Zero is returned in the dentry is invalid.
2123 * This function is slow for big directories, and deprecated, do not use it.
2125 int d_validate(struct dentry *dentry, struct dentry *dparent)
2127 struct dentry *child;
2129 spin_lock(&dparent->d_lock);
2130 list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
2131 if (dentry == child) {
2132 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
2133 __dget_dlock(dentry);
2134 spin_unlock(&dentry->d_lock);
2135 spin_unlock(&dparent->d_lock);
2139 spin_unlock(&dparent->d_lock);
2143 EXPORT_SYMBOL(d_validate);
2146 * When a file is deleted, we have two options:
2147 * - turn this dentry into a negative dentry
2148 * - unhash this dentry and free it.
2150 * Usually, we want to just turn this into
2151 * a negative dentry, but if anybody else is
2152 * currently using the dentry or the inode
2153 * we can't do that and we fall back on removing
2154 * it from the hash queues and waiting for
2155 * it to be deleted later when it has no users
2159 * d_delete - delete a dentry
2160 * @dentry: The dentry to delete
2162 * Turn the dentry into a negative dentry if possible, otherwise
2163 * remove it from the hash queues so it can be deleted later
2166 void d_delete(struct dentry * dentry)
2168 struct inode *inode;
2171 * Are we the only user?
2174 spin_lock(&dentry->d_lock);
2175 inode = dentry->d_inode;
2176 isdir = S_ISDIR(inode->i_mode);
2177 if (dentry->d_lockref.count == 1) {
2178 if (!spin_trylock(&inode->i_lock)) {
2179 spin_unlock(&dentry->d_lock);
2183 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2184 dentry_unlink_inode(dentry);
2185 fsnotify_nameremove(dentry, isdir);
2189 if (!d_unhashed(dentry))
2192 spin_unlock(&dentry->d_lock);
2194 fsnotify_nameremove(dentry, isdir);
2196 EXPORT_SYMBOL(d_delete);
2198 static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
2200 BUG_ON(!d_unhashed(entry));
2202 entry->d_flags |= DCACHE_RCUACCESS;
2203 hlist_bl_add_head_rcu(&entry->d_hash, b);
2207 static void _d_rehash(struct dentry * entry)
2209 __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
2213 * d_rehash - add an entry back to the hash
2214 * @entry: dentry to add to the hash
2216 * Adds a dentry to the hash according to its name.
2219 void d_rehash(struct dentry * entry)
2221 spin_lock(&entry->d_lock);
2223 spin_unlock(&entry->d_lock);
2225 EXPORT_SYMBOL(d_rehash);
2228 * dentry_update_name_case - update case insensitive dentry with a new name
2229 * @dentry: dentry to be updated
2232 * Update a case insensitive dentry with new case of name.
2234 * dentry must have been returned by d_lookup with name @name. Old and new
2235 * name lengths must match (ie. no d_compare which allows mismatched name
2238 * Parent inode i_mutex must be held over d_lookup and into this call (to
2239 * keep renames and concurrent inserts, and readdir(2) away).
2241 void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
2243 BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));
2244 BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
2246 spin_lock(&dentry->d_lock);
2247 write_seqcount_begin(&dentry->d_seq);
2248 memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
2249 write_seqcount_end(&dentry->d_seq);
2250 spin_unlock(&dentry->d_lock);
2252 EXPORT_SYMBOL(dentry_update_name_case);
2254 static void switch_names(struct dentry *dentry, struct dentry *target)
2256 if (dname_external(target)) {
2257 if (dname_external(dentry)) {
2259 * Both external: swap the pointers
2261 swap(target->d_name.name, dentry->d_name.name);
2264 * dentry:internal, target:external. Steal target's
2265 * storage and make target internal.
2267 memcpy(target->d_iname, dentry->d_name.name,
2268 dentry->d_name.len + 1);
2269 dentry->d_name.name = target->d_name.name;
2270 target->d_name.name = target->d_iname;
2273 if (dname_external(dentry)) {
2275 * dentry:external, target:internal. Give dentry's
2276 * storage to target and make dentry internal
2278 memcpy(dentry->d_iname, target->d_name.name,
2279 target->d_name.len + 1);
2280 target->d_name.name = dentry->d_name.name;
2281 dentry->d_name.name = dentry->d_iname;
2284 * Both are internal. Just copy target to dentry
2286 memcpy(dentry->d_iname, target->d_name.name,
2287 target->d_name.len + 1);
2288 dentry->d_name.len = target->d_name.len;
2292 swap(dentry->d_name.len, target->d_name.len);
2295 static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
2298 * XXXX: do we really need to take target->d_lock?
2300 if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent)
2301 spin_lock(&target->d_parent->d_lock);
2303 if (d_ancestor(dentry->d_parent, target->d_parent)) {
2304 spin_lock(&dentry->d_parent->d_lock);
2305 spin_lock_nested(&target->d_parent->d_lock,
2306 DENTRY_D_LOCK_NESTED);
2308 spin_lock(&target->d_parent->d_lock);
2309 spin_lock_nested(&dentry->d_parent->d_lock,
2310 DENTRY_D_LOCK_NESTED);
2313 if (target < dentry) {
2314 spin_lock_nested(&target->d_lock, 2);
2315 spin_lock_nested(&dentry->d_lock, 3);
2317 spin_lock_nested(&dentry->d_lock, 2);
2318 spin_lock_nested(&target->d_lock, 3);
2322 static void dentry_unlock_parents_for_move(struct dentry *dentry,
2323 struct dentry *target)
2325 if (target->d_parent != dentry->d_parent)
2326 spin_unlock(&dentry->d_parent->d_lock);
2327 if (target->d_parent != target)
2328 spin_unlock(&target->d_parent->d_lock);
2332 * When switching names, the actual string doesn't strictly have to
2333 * be preserved in the target - because we're dropping the target
2334 * anyway. As such, we can just do a simple memcpy() to copy over
2335 * the new name before we switch.
2337 * Note that we have to be a lot more careful about getting the hash
2338 * switched - we have to switch the hash value properly even if it
2339 * then no longer matches the actual (corrupted) string of the target.
2340 * The hash value has to match the hash queue that the dentry is on..
2343 * __d_move - move a dentry
2344 * @dentry: entry to move
2345 * @target: new dentry
2347 * Update the dcache to reflect the move of a file name. Negative
2348 * dcache entries should not be moved in this way. Caller must hold
2349 * rename_lock, the i_mutex of the source and target directories,
2350 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2352 static void __d_move(struct dentry * dentry, struct dentry * target)
2354 if (!dentry->d_inode)
2355 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
2357 BUG_ON(d_ancestor(dentry, target));
2358 BUG_ON(d_ancestor(target, dentry));
2360 dentry_lock_for_move(dentry, target);
2362 write_seqcount_begin(&dentry->d_seq);
2363 write_seqcount_begin(&target->d_seq);
2365 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
2368 * Move the dentry to the target hash queue. Don't bother checking
2369 * for the same hash queue because of how unlikely it is.
2372 __d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
2374 /* Unhash the target: dput() will then get rid of it */
2377 list_del(&dentry->d_u.d_child);
2378 list_del(&target->d_u.d_child);
2380 /* Switch the names.. */
2381 switch_names(dentry, target);
2382 swap(dentry->d_name.hash, target->d_name.hash);
2384 /* ... and switch the parents */
2385 if (IS_ROOT(dentry)) {
2386 dentry->d_parent = target->d_parent;
2387 target->d_parent = target;
2388 INIT_LIST_HEAD(&target->d_u.d_child);
2390 swap(dentry->d_parent, target->d_parent);
2392 /* And add them back to the (new) parent lists */
2393 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
2396 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
2398 write_seqcount_end(&target->d_seq);
2399 write_seqcount_end(&dentry->d_seq);
2401 dentry_unlock_parents_for_move(dentry, target);
2402 spin_unlock(&target->d_lock);
2403 fsnotify_d_move(dentry);
2404 spin_unlock(&dentry->d_lock);
2408 * d_move - move a dentry
2409 * @dentry: entry to move
2410 * @target: new dentry
2412 * Update the dcache to reflect the move of a file name. Negative
2413 * dcache entries should not be moved in this way. See the locking
2414 * requirements for __d_move.
2416 void d_move(struct dentry *dentry, struct dentry *target)
2418 write_seqlock(&rename_lock);
2419 __d_move(dentry, target);
2420 write_sequnlock(&rename_lock);
2422 EXPORT_SYMBOL(d_move);
2425 * d_ancestor - search for an ancestor
2426 * @p1: ancestor dentry
2429 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2430 * an ancestor of p2, else NULL.
2432 struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2436 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2437 if (p->d_parent == p1)
2444 * This helper attempts to cope with remotely renamed directories
2446 * It assumes that the caller is already holding
2447 * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
2449 * Note: If ever the locking in lock_rename() changes, then please
2450 * remember to update this too...
2452 static struct dentry *__d_unalias(struct inode *inode,
2453 struct dentry *dentry, struct dentry *alias)
2455 struct mutex *m1 = NULL, *m2 = NULL;
2456 struct dentry *ret = ERR_PTR(-EBUSY);
2458 /* If alias and dentry share a parent, then no extra locks required */
2459 if (alias->d_parent == dentry->d_parent)
2462 /* See lock_rename() */
2463 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
2465 m1 = &dentry->d_sb->s_vfs_rename_mutex;
2466 if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
2468 m2 = &alias->d_parent->d_inode->i_mutex;
2470 if (likely(!d_mountpoint(alias))) {
2471 __d_move(alias, dentry);
2475 spin_unlock(&inode->i_lock);
2484 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
2485 * named dentry in place of the dentry to be replaced.
2486 * returns with anon->d_lock held!
2488 static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
2490 struct dentry *dparent;
2492 dentry_lock_for_move(anon, dentry);
2494 write_seqcount_begin(&dentry->d_seq);
2495 write_seqcount_begin(&anon->d_seq);
2497 dparent = dentry->d_parent;
2499 switch_names(dentry, anon);
2500 swap(dentry->d_name.hash, anon->d_name.hash);
2502 dentry->d_parent = dentry;
2503 list_del_init(&dentry->d_u.d_child);
2504 anon->d_parent = dparent;
2505 list_move(&anon->d_u.d_child, &dparent->d_subdirs);
2507 write_seqcount_end(&dentry->d_seq);
2508 write_seqcount_end(&anon->d_seq);
2510 dentry_unlock_parents_for_move(anon, dentry);
2511 spin_unlock(&dentry->d_lock);
2513 /* anon->d_lock still locked, returns locked */
2514 anon->d_flags &= ~DCACHE_DISCONNECTED;
2518 * d_materialise_unique - introduce an inode into the tree
2519 * @dentry: candidate dentry
2520 * @inode: inode to bind to the dentry, to which aliases may be attached
2522 * Introduces an dentry into the tree, substituting an extant disconnected
2523 * root directory alias in its place if there is one. Caller must hold the
2524 * i_mutex of the parent directory.
2526 struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
2528 struct dentry *actual;
2530 BUG_ON(!d_unhashed(dentry));
2534 __d_instantiate(dentry, NULL);
2539 spin_lock(&inode->i_lock);
2541 if (S_ISDIR(inode->i_mode)) {
2542 struct dentry *alias;
2544 /* Does an aliased dentry already exist? */
2545 alias = __d_find_alias(inode, 0);
2548 write_seqlock(&rename_lock);
2550 if (d_ancestor(alias, dentry)) {
2551 /* Check for loops */
2552 actual = ERR_PTR(-ELOOP);
2553 spin_unlock(&inode->i_lock);
2554 } else if (IS_ROOT(alias)) {
2555 /* Is this an anonymous mountpoint that we
2556 * could splice into our tree? */
2557 __d_materialise_dentry(dentry, alias);
2558 write_sequnlock(&rename_lock);
2562 /* Nope, but we must(!) avoid directory
2563 * aliasing. This drops inode->i_lock */
2564 actual = __d_unalias(inode, dentry, alias);
2566 write_sequnlock(&rename_lock);
2567 if (IS_ERR(actual)) {
2568 if (PTR_ERR(actual) == -ELOOP)
2569 pr_warn_ratelimited(
2570 "VFS: Lookup of '%s' in %s %s"
2571 " would have caused loop\n",
2572 dentry->d_name.name,
2573 inode->i_sb->s_type->name,
2581 /* Add a unique reference */
2582 actual = __d_instantiate_unique(dentry, inode);
2586 BUG_ON(!d_unhashed(actual));
2588 spin_lock(&actual->d_lock);
2591 spin_unlock(&actual->d_lock);
2592 spin_unlock(&inode->i_lock);
2594 if (actual == dentry) {
2595 security_d_instantiate(dentry, inode);
2602 EXPORT_SYMBOL_GPL(d_materialise_unique);
2604 static int prepend(char **buffer, int *buflen, const char *str, int namelen)
2608 return -ENAMETOOLONG;
2610 memcpy(*buffer, str, namelen);
2614 static int prepend_name(char **buffer, int *buflen, struct qstr *name)
2616 return prepend(buffer, buflen, name->name, name->len);
2620 * prepend_path - Prepend path string to a buffer
2621 * @path: the dentry/vfsmount to report
2622 * @root: root vfsmnt/dentry
2623 * @buffer: pointer to the end of the buffer
2624 * @buflen: pointer to buffer length
2626 * Caller holds the rename_lock.
2628 static int prepend_path(const struct path *path,
2629 const struct path *root,
2630 char **buffer, int *buflen)
2632 struct dentry *dentry = path->dentry;
2633 struct vfsmount *vfsmnt = path->mnt;
2634 struct mount *mnt = real_mount(vfsmnt);
2638 while (dentry != root->dentry || vfsmnt != root->mnt) {
2639 struct dentry * parent;
2641 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
2643 if (!mnt_has_parent(mnt))
2645 dentry = mnt->mnt_mountpoint;
2646 mnt = mnt->mnt_parent;
2650 parent = dentry->d_parent;
2652 spin_lock(&dentry->d_lock);
2653 error = prepend_name(buffer, buflen, &dentry->d_name);
2654 spin_unlock(&dentry->d_lock);
2656 error = prepend(buffer, buflen, "/", 1);
2664 if (!error && !slash)
2665 error = prepend(buffer, buflen, "/", 1);
2671 * Filesystems needing to implement special "root names"
2672 * should do so with ->d_dname()
2674 if (IS_ROOT(dentry) &&
2675 (dentry->d_name.len != 1 || dentry->d_name.name[0] != '/')) {
2676 WARN(1, "Root dentry has weird name <%.*s>\n",
2677 (int) dentry->d_name.len, dentry->d_name.name);
2680 error = prepend(buffer, buflen, "/", 1);
2682 error = is_mounted(vfsmnt) ? 1 : 2;
2687 * __d_path - return the path of a dentry
2688 * @path: the dentry/vfsmount to report
2689 * @root: root vfsmnt/dentry
2690 * @buf: buffer to return value in
2691 * @buflen: buffer length
2693 * Convert a dentry into an ASCII path name.
2695 * Returns a pointer into the buffer or an error code if the
2696 * path was too long.
2698 * "buflen" should be positive.
2700 * If the path is not reachable from the supplied root, return %NULL.
2702 char *__d_path(const struct path *path,
2703 const struct path *root,
2704 char *buf, int buflen)
2706 char *res = buf + buflen;
2709 prepend(&res, &buflen, "\0", 1);
2710 br_read_lock(&vfsmount_lock);
2711 write_seqlock(&rename_lock);
2712 error = prepend_path(path, root, &res, &buflen);
2713 write_sequnlock(&rename_lock);
2714 br_read_unlock(&vfsmount_lock);
2717 return ERR_PTR(error);
2723 char *d_absolute_path(const struct path *path,
2724 char *buf, int buflen)
2726 struct path root = {};
2727 char *res = buf + buflen;
2730 prepend(&res, &buflen, "\0", 1);
2731 br_read_lock(&vfsmount_lock);
2732 write_seqlock(&rename_lock);
2733 error = prepend_path(path, &root, &res, &buflen);
2734 write_sequnlock(&rename_lock);
2735 br_read_unlock(&vfsmount_lock);
2740 return ERR_PTR(error);
2745 * same as __d_path but appends "(deleted)" for unlinked files.
2747 static int path_with_deleted(const struct path *path,
2748 const struct path *root,
2749 char **buf, int *buflen)
2751 prepend(buf, buflen, "\0", 1);
2752 if (d_unlinked(path->dentry)) {
2753 int error = prepend(buf, buflen, " (deleted)", 10);
2758 return prepend_path(path, root, buf, buflen);
2761 static int prepend_unreachable(char **buffer, int *buflen)
2763 return prepend(buffer, buflen, "(unreachable)", 13);
2767 * d_path - return the path of a dentry
2768 * @path: path to report
2769 * @buf: buffer to return value in
2770 * @buflen: buffer length
2772 * Convert a dentry into an ASCII path name. If the entry has been deleted
2773 * the string " (deleted)" is appended. Note that this is ambiguous.
2775 * Returns a pointer into the buffer or an error code if the path was
2776 * too long. Note: Callers should use the returned pointer, not the passed
2777 * in buffer, to use the name! The implementation often starts at an offset
2778 * into the buffer, and may leave 0 bytes at the start.
2780 * "buflen" should be positive.
2782 char *d_path(const struct path *path, char *buf, int buflen)
2784 char *res = buf + buflen;
2789 * We have various synthetic filesystems that never get mounted. On
2790 * these filesystems dentries are never used for lookup purposes, and
2791 * thus don't need to be hashed. They also don't need a name until a
2792 * user wants to identify the object in /proc/pid/fd/. The little hack
2793 * below allows us to generate a name for these objects on demand:
2795 if (path->dentry->d_op && path->dentry->d_op->d_dname)
2796 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2798 get_fs_root(current->fs, &root);
2799 br_read_lock(&vfsmount_lock);
2800 write_seqlock(&rename_lock);
2801 error = path_with_deleted(path, &root, &res, &buflen);
2802 write_sequnlock(&rename_lock);
2803 br_read_unlock(&vfsmount_lock);
2805 res = ERR_PTR(error);
2809 EXPORT_SYMBOL(d_path);
2812 * Helper function for dentry_operations.d_dname() members
2814 char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
2815 const char *fmt, ...)
2821 va_start(args, fmt);
2822 sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
2825 if (sz > sizeof(temp) || sz > buflen)
2826 return ERR_PTR(-ENAMETOOLONG);
2828 buffer += buflen - sz;
2829 return memcpy(buffer, temp, sz);
2832 char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
2834 char *end = buffer + buflen;
2835 /* these dentries are never renamed, so d_lock is not needed */
2836 if (prepend(&end, &buflen, " (deleted)", 11) ||
2837 prepend_name(&end, &buflen, &dentry->d_name) ||
2838 prepend(&end, &buflen, "/", 1))
2839 end = ERR_PTR(-ENAMETOOLONG);
2844 * Write full pathname from the root of the filesystem into the buffer.
2846 static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
2848 char *end = buf + buflen;
2851 prepend(&end, &buflen, "\0", 1);
2858 while (!IS_ROOT(dentry)) {
2859 struct dentry *parent = dentry->d_parent;
2863 spin_lock(&dentry->d_lock);
2864 error = prepend_name(&end, &buflen, &dentry->d_name);
2865 spin_unlock(&dentry->d_lock);
2866 if (error != 0 || prepend(&end, &buflen, "/", 1) != 0)
2874 return ERR_PTR(-ENAMETOOLONG);
2877 char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
2881 write_seqlock(&rename_lock);
2882 retval = __dentry_path(dentry, buf, buflen);
2883 write_sequnlock(&rename_lock);
2887 EXPORT_SYMBOL(dentry_path_raw);
2889 char *dentry_path(struct dentry *dentry, char *buf, int buflen)
2894 write_seqlock(&rename_lock);
2895 if (d_unlinked(dentry)) {
2897 if (prepend(&p, &buflen, "//deleted", 10) != 0)
2901 retval = __dentry_path(dentry, buf, buflen);
2902 write_sequnlock(&rename_lock);
2903 if (!IS_ERR(retval) && p)
2904 *p = '/'; /* restore '/' overriden with '\0' */
2907 return ERR_PTR(-ENAMETOOLONG);
2911 * NOTE! The user-level library version returns a
2912 * character pointer. The kernel system call just
2913 * returns the length of the buffer filled (which
2914 * includes the ending '\0' character), or a negative
2915 * error value. So libc would do something like
2917 * char *getcwd(char * buf, size_t size)
2921 * retval = sys_getcwd(buf, size);
2928 SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
2931 struct path pwd, root;
2932 char *page = (char *) __get_free_page(GFP_USER);
2937 get_fs_root_and_pwd(current->fs, &root, &pwd);
2940 br_read_lock(&vfsmount_lock);
2941 write_seqlock(&rename_lock);
2942 if (!d_unlinked(pwd.dentry)) {
2944 char *cwd = page + PAGE_SIZE;
2945 int buflen = PAGE_SIZE;
2947 prepend(&cwd, &buflen, "\0", 1);
2948 error = prepend_path(&pwd, &root, &cwd, &buflen);
2949 write_sequnlock(&rename_lock);
2950 br_read_unlock(&vfsmount_lock);
2955 /* Unreachable from current root */
2957 error = prepend_unreachable(&cwd, &buflen);
2963 len = PAGE_SIZE + page - cwd;
2966 if (copy_to_user(buf, cwd, len))
2970 write_sequnlock(&rename_lock);
2971 br_read_unlock(&vfsmount_lock);
2977 free_page((unsigned long) page);
2982 * Test whether new_dentry is a subdirectory of old_dentry.
2984 * Trivially implemented using the dcache structure
2988 * is_subdir - is new dentry a subdirectory of old_dentry
2989 * @new_dentry: new dentry
2990 * @old_dentry: old dentry
2992 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
2993 * Returns 0 otherwise.
2994 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
2997 int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
3002 if (new_dentry == old_dentry)
3006 /* for restarting inner loop in case of seq retry */
3007 seq = read_seqbegin(&rename_lock);
3009 * Need rcu_readlock to protect against the d_parent trashing
3013 if (d_ancestor(old_dentry, new_dentry))
3018 } while (read_seqretry(&rename_lock, seq));
3023 static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
3025 struct dentry *root = data;
3026 if (dentry != root) {
3027 if (d_unhashed(dentry) || !dentry->d_inode)
3030 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
3031 dentry->d_flags |= DCACHE_GENOCIDE;
3032 dentry->d_lockref.count--;
3035 return D_WALK_CONTINUE;
3038 void d_genocide(struct dentry *parent)
3040 d_walk(parent, parent, d_genocide_kill, NULL);
3043 void d_tmpfile(struct dentry *dentry, struct inode *inode)
3045 inode_dec_link_count(inode);
3046 BUG_ON(dentry->d_name.name != dentry->d_iname ||
3047 !hlist_unhashed(&dentry->d_alias) ||
3048 !d_unlinked(dentry));
3049 spin_lock(&dentry->d_parent->d_lock);
3050 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
3051 dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
3052 (unsigned long long)inode->i_ino);
3053 spin_unlock(&dentry->d_lock);
3054 spin_unlock(&dentry->d_parent->d_lock);
3055 d_instantiate(dentry, inode);
3057 EXPORT_SYMBOL(d_tmpfile);
3059 static __initdata unsigned long dhash_entries;
3060 static int __init set_dhash_entries(char *str)
3064 dhash_entries = simple_strtoul(str, &str, 0);
3067 __setup("dhash_entries=", set_dhash_entries);
3069 static void __init dcache_init_early(void)
3073 /* If hashes are distributed across NUMA nodes, defer
3074 * hash allocation until vmalloc space is available.
3080 alloc_large_system_hash("Dentry cache",
3081 sizeof(struct hlist_bl_head),
3090 for (loop = 0; loop < (1U << d_hash_shift); loop++)
3091 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
3094 static void __init dcache_init(void)
3099 * A constructor could be added for stable state like the lists,
3100 * but it is probably not worth it because of the cache nature
3103 dentry_cache = KMEM_CACHE(dentry,
3104 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
3106 /* Hash may have been set up in dcache_init_early */
3111 alloc_large_system_hash("Dentry cache",
3112 sizeof(struct hlist_bl_head),
3121 for (loop = 0; loop < (1U << d_hash_shift); loop++)
3122 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
3125 /* SLAB cache for __getname() consumers */
3126 struct kmem_cache *names_cachep __read_mostly;
3127 EXPORT_SYMBOL(names_cachep);
3129 EXPORT_SYMBOL(d_genocide);
3131 void __init vfs_caches_init_early(void)
3133 dcache_init_early();
3137 void __init vfs_caches_init(unsigned long mempages)
3139 unsigned long reserve;
3141 /* Base hash sizes on available memory, with a reserve equal to
3142 150% of current kernel size */
3144 reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
3145 mempages -= reserve;
3147 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
3148 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
3152 files_init(mempages);