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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * fs/dcache.c
4 *
5 * Complete reimplementation
6 * (C) 1997 Thomas Schoebel-Theuer,
7 * with heavy changes by Linus Torvalds
8 */
9
10/*
11 * Notes on the allocation strategy:
12 *
13 * The dcache is a master of the icache - whenever a dcache entry
14 * exists, the inode will always exist. "iput()" is done either when
15 * the dcache entry is deleted or garbage collected.
16 */
17
18#include <linux/ratelimit.h>
19#include <linux/string.h>
20#include <linux/mm.h>
21#include <linux/fs.h>
22#include <linux/fscrypt.h>
23#include <linux/fsnotify.h>
24#include <linux/slab.h>
25#include <linux/init.h>
26#include <linux/hash.h>
27#include <linux/cache.h>
28#include <linux/export.h>
29#include <linux/security.h>
30#include <linux/seqlock.h>
31#include <linux/memblock.h>
32#include <linux/bit_spinlock.h>
33#include <linux/rculist_bl.h>
34#include <linux/list_lru.h>
35#include "internal.h"
36#include "mount.h"
37
38#include <asm/runtime-const.h>
39
40/*
41 * Usage:
42 * dcache->d_inode->i_lock protects:
43 * - i_dentry, d_u.d_alias, d_inode of aliases
44 * dcache_hash_bucket lock protects:
45 * - the dcache hash table
46 * s_roots bl list spinlock protects:
47 * - the s_roots list (see __d_drop)
48 * dentry->d_sb->s_dentry_lru_lock protects:
49 * - the dcache lru lists and counters
50 * d_lock protects:
51 * - d_flags
52 * - d_name
53 * - d_lru
54 * - d_count
55 * - d_unhashed()
56 * - d_parent and d_chilren
57 * - childrens' d_sib and d_parent
58 * - d_u.d_alias, d_inode
59 *
60 * Ordering:
61 * dentry->d_inode->i_lock
62 * dentry->d_lock
63 * dentry->d_sb->s_dentry_lru_lock
64 * dcache_hash_bucket lock
65 * s_roots lock
66 *
67 * If there is an ancestor relationship:
68 * dentry->d_parent->...->d_parent->d_lock
69 * ...
70 * dentry->d_parent->d_lock
71 * dentry->d_lock
72 *
73 * If no ancestor relationship:
74 * arbitrary, since it's serialized on rename_lock
75 */
76int sysctl_vfs_cache_pressure __read_mostly = 100;
77EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
78
79__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
80
81EXPORT_SYMBOL(rename_lock);
82
83static struct kmem_cache *dentry_cache __ro_after_init;
84
85const struct qstr empty_name = QSTR_INIT("", 0);
86EXPORT_SYMBOL(empty_name);
87const struct qstr slash_name = QSTR_INIT("/", 1);
88EXPORT_SYMBOL(slash_name);
89const struct qstr dotdot_name = QSTR_INIT("..", 2);
90EXPORT_SYMBOL(dotdot_name);
91
92/*
93 * This is the single most critical data structure when it comes
94 * to the dcache: the hashtable for lookups. Somebody should try
95 * to make this good - I've just made it work.
96 *
97 * This hash-function tries to avoid losing too many bits of hash
98 * information, yet avoid using a prime hash-size or similar.
99 *
100 * Marking the variables "used" ensures that the compiler doesn't
101 * optimize them away completely on architectures with runtime
102 * constant infrastructure, this allows debuggers to see their
103 * values. But updating these values has no effect on those arches.
104 */
105
106static unsigned int d_hash_shift __ro_after_init __used;
107
108static struct hlist_bl_head *dentry_hashtable __ro_after_init __used;
109
110static inline struct hlist_bl_head *d_hash(unsigned long hashlen)
111{
112 return runtime_const_ptr(dentry_hashtable) +
113 runtime_const_shift_right_32(hashlen, d_hash_shift);
114}
115
116#define IN_LOOKUP_SHIFT 10
117static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT];
118
119static inline struct hlist_bl_head *in_lookup_hash(const struct dentry *parent,
120 unsigned int hash)
121{
122 hash += (unsigned long) parent / L1_CACHE_BYTES;
123 return in_lookup_hashtable + hash_32(hash, IN_LOOKUP_SHIFT);
124}
125
126struct dentry_stat_t {
127 long nr_dentry;
128 long nr_unused;
129 long age_limit; /* age in seconds */
130 long want_pages; /* pages requested by system */
131 long nr_negative; /* # of unused negative dentries */
132 long dummy; /* Reserved for future use */
133};
134
135static DEFINE_PER_CPU(long, nr_dentry);
136static DEFINE_PER_CPU(long, nr_dentry_unused);
137static DEFINE_PER_CPU(long, nr_dentry_negative);
138static int dentry_negative_policy;
139
140#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
141/* Statistics gathering. */
142static struct dentry_stat_t dentry_stat = {
143 .age_limit = 45,
144};
145
146/*
147 * Here we resort to our own counters instead of using generic per-cpu counters
148 * for consistency with what the vfs inode code does. We are expected to harvest
149 * better code and performance by having our own specialized counters.
150 *
151 * Please note that the loop is done over all possible CPUs, not over all online
152 * CPUs. The reason for this is that we don't want to play games with CPUs going
153 * on and off. If one of them goes off, we will just keep their counters.
154 *
155 * glommer: See cffbc8a for details, and if you ever intend to change this,
156 * please update all vfs counters to match.
157 */
158static long get_nr_dentry(void)
159{
160 int i;
161 long sum = 0;
162 for_each_possible_cpu(i)
163 sum += per_cpu(nr_dentry, i);
164 return sum < 0 ? 0 : sum;
165}
166
167static long get_nr_dentry_unused(void)
168{
169 int i;
170 long sum = 0;
171 for_each_possible_cpu(i)
172 sum += per_cpu(nr_dentry_unused, i);
173 return sum < 0 ? 0 : sum;
174}
175
176static long get_nr_dentry_negative(void)
177{
178 int i;
179 long sum = 0;
180
181 for_each_possible_cpu(i)
182 sum += per_cpu(nr_dentry_negative, i);
183 return sum < 0 ? 0 : sum;
184}
185
186static int proc_nr_dentry(const struct ctl_table *table, int write, void *buffer,
187 size_t *lenp, loff_t *ppos)
188{
189 dentry_stat.nr_dentry = get_nr_dentry();
190 dentry_stat.nr_unused = get_nr_dentry_unused();
191 dentry_stat.nr_negative = get_nr_dentry_negative();
192 return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
193}
194
195static struct ctl_table fs_dcache_sysctls[] = {
196 {
197 .procname = "dentry-state",
198 .data = &dentry_stat,
199 .maxlen = 6*sizeof(long),
200 .mode = 0444,
201 .proc_handler = proc_nr_dentry,
202 },
203 {
204 .procname = "dentry-negative",
205 .data = &dentry_negative_policy,
206 .maxlen = sizeof(dentry_negative_policy),
207 .mode = 0644,
208 .proc_handler = proc_dointvec_minmax,
209 .extra1 = SYSCTL_ZERO,
210 .extra2 = SYSCTL_ONE,
211 },
212};
213
214static int __init init_fs_dcache_sysctls(void)
215{
216 register_sysctl_init("fs", fs_dcache_sysctls);
217 return 0;
218}
219fs_initcall(init_fs_dcache_sysctls);
220#endif
221
222/*
223 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
224 * The strings are both count bytes long, and count is non-zero.
225 */
226#ifdef CONFIG_DCACHE_WORD_ACCESS
227
228#include <asm/word-at-a-time.h>
229/*
230 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
231 * aligned allocation for this particular component. We don't
232 * strictly need the load_unaligned_zeropad() safety, but it
233 * doesn't hurt either.
234 *
235 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
236 * need the careful unaligned handling.
237 */
238static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
239{
240 unsigned long a,b,mask;
241
242 for (;;) {
243 a = read_word_at_a_time(cs);
244 b = load_unaligned_zeropad(ct);
245 if (tcount < sizeof(unsigned long))
246 break;
247 if (unlikely(a != b))
248 return 1;
249 cs += sizeof(unsigned long);
250 ct += sizeof(unsigned long);
251 tcount -= sizeof(unsigned long);
252 if (!tcount)
253 return 0;
254 }
255 mask = bytemask_from_count(tcount);
256 return unlikely(!!((a ^ b) & mask));
257}
258
259#else
260
261static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
262{
263 do {
264 if (*cs != *ct)
265 return 1;
266 cs++;
267 ct++;
268 tcount--;
269 } while (tcount);
270 return 0;
271}
272
273#endif
274
275static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
276{
277 /*
278 * Be careful about RCU walk racing with rename:
279 * use 'READ_ONCE' to fetch the name pointer.
280 *
281 * NOTE! Even if a rename will mean that the length
282 * was not loaded atomically, we don't care. The
283 * RCU walk will check the sequence count eventually,
284 * and catch it. And we won't overrun the buffer,
285 * because we're reading the name pointer atomically,
286 * and a dentry name is guaranteed to be properly
287 * terminated with a NUL byte.
288 *
289 * End result: even if 'len' is wrong, we'll exit
290 * early because the data cannot match (there can
291 * be no NUL in the ct/tcount data)
292 */
293 const unsigned char *cs = READ_ONCE(dentry->d_name.name);
294
295 return dentry_string_cmp(cs, ct, tcount);
296}
297
298struct external_name {
299 union {
300 atomic_t count;
301 struct rcu_head head;
302 } u;
303 unsigned char name[];
304};
305
306static inline struct external_name *external_name(struct dentry *dentry)
307{
308 return container_of(dentry->d_name.name, struct external_name, name[0]);
309}
310
311static void __d_free(struct rcu_head *head)
312{
313 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
314
315 kmem_cache_free(dentry_cache, dentry);
316}
317
318static void __d_free_external(struct rcu_head *head)
319{
320 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
321 kfree(external_name(dentry));
322 kmem_cache_free(dentry_cache, dentry);
323}
324
325static inline int dname_external(const struct dentry *dentry)
326{
327 return dentry->d_name.name != dentry->d_iname;
328}
329
330void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry)
331{
332 spin_lock(&dentry->d_lock);
333 name->name = dentry->d_name;
334 if (unlikely(dname_external(dentry))) {
335 atomic_inc(&external_name(dentry)->u.count);
336 } else {
337 memcpy(name->inline_name, dentry->d_iname,
338 dentry->d_name.len + 1);
339 name->name.name = name->inline_name;
340 }
341 spin_unlock(&dentry->d_lock);
342}
343EXPORT_SYMBOL(take_dentry_name_snapshot);
344
345void release_dentry_name_snapshot(struct name_snapshot *name)
346{
347 if (unlikely(name->name.name != name->inline_name)) {
348 struct external_name *p;
349 p = container_of(name->name.name, struct external_name, name[0]);
350 if (unlikely(atomic_dec_and_test(&p->u.count)))
351 kfree_rcu(p, u.head);
352 }
353}
354EXPORT_SYMBOL(release_dentry_name_snapshot);
355
356static inline void __d_set_inode_and_type(struct dentry *dentry,
357 struct inode *inode,
358 unsigned type_flags)
359{
360 unsigned flags;
361
362 dentry->d_inode = inode;
363 flags = READ_ONCE(dentry->d_flags);
364 flags &= ~DCACHE_ENTRY_TYPE;
365 flags |= type_flags;
366 smp_store_release(&dentry->d_flags, flags);
367}
368
369static inline void __d_clear_type_and_inode(struct dentry *dentry)
370{
371 unsigned flags = READ_ONCE(dentry->d_flags);
372
373 flags &= ~DCACHE_ENTRY_TYPE;
374 WRITE_ONCE(dentry->d_flags, flags);
375 dentry->d_inode = NULL;
376 /*
377 * The negative counter only tracks dentries on the LRU. Don't inc if
378 * d_lru is on another list.
379 */
380 if ((flags & (DCACHE_LRU_LIST|DCACHE_SHRINK_LIST)) == DCACHE_LRU_LIST)
381 this_cpu_inc(nr_dentry_negative);
382}
383
384static void dentry_free(struct dentry *dentry)
385{
386 WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias));
387 if (unlikely(dname_external(dentry))) {
388 struct external_name *p = external_name(dentry);
389 if (likely(atomic_dec_and_test(&p->u.count))) {
390 call_rcu(&dentry->d_u.d_rcu, __d_free_external);
391 return;
392 }
393 }
394 /* if dentry was never visible to RCU, immediate free is OK */
395 if (dentry->d_flags & DCACHE_NORCU)
396 __d_free(&dentry->d_u.d_rcu);
397 else
398 call_rcu(&dentry->d_u.d_rcu, __d_free);
399}
400
401/*
402 * Release the dentry's inode, using the filesystem
403 * d_iput() operation if defined.
404 */
405static void dentry_unlink_inode(struct dentry * dentry)
406 __releases(dentry->d_lock)
407 __releases(dentry->d_inode->i_lock)
408{
409 struct inode *inode = dentry->d_inode;
410
411 raw_write_seqcount_begin(&dentry->d_seq);
412 __d_clear_type_and_inode(dentry);
413 hlist_del_init(&dentry->d_u.d_alias);
414 raw_write_seqcount_end(&dentry->d_seq);
415 spin_unlock(&dentry->d_lock);
416 spin_unlock(&inode->i_lock);
417 if (!inode->i_nlink)
418 fsnotify_inoderemove(inode);
419 if (dentry->d_op && dentry->d_op->d_iput)
420 dentry->d_op->d_iput(dentry, inode);
421 else
422 iput(inode);
423}
424
425/*
426 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
427 * is in use - which includes both the "real" per-superblock
428 * LRU list _and_ the DCACHE_SHRINK_LIST use.
429 *
430 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
431 * on the shrink list (ie not on the superblock LRU list).
432 *
433 * The per-cpu "nr_dentry_unused" counters are updated with
434 * the DCACHE_LRU_LIST bit.
435 *
436 * The per-cpu "nr_dentry_negative" counters are only updated
437 * when deleted from or added to the per-superblock LRU list, not
438 * from/to the shrink list. That is to avoid an unneeded dec/inc
439 * pair when moving from LRU to shrink list in select_collect().
440 *
441 * These helper functions make sure we always follow the
442 * rules. d_lock must be held by the caller.
443 */
444#define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
445static void d_lru_add(struct dentry *dentry)
446{
447 D_FLAG_VERIFY(dentry, 0);
448 dentry->d_flags |= DCACHE_LRU_LIST;
449 this_cpu_inc(nr_dentry_unused);
450 if (d_is_negative(dentry))
451 this_cpu_inc(nr_dentry_negative);
452 WARN_ON_ONCE(!list_lru_add_obj(
453 &dentry->d_sb->s_dentry_lru, &dentry->d_lru));
454}
455
456static void d_lru_del(struct dentry *dentry)
457{
458 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
459 dentry->d_flags &= ~DCACHE_LRU_LIST;
460 this_cpu_dec(nr_dentry_unused);
461 if (d_is_negative(dentry))
462 this_cpu_dec(nr_dentry_negative);
463 WARN_ON_ONCE(!list_lru_del_obj(
464 &dentry->d_sb->s_dentry_lru, &dentry->d_lru));
465}
466
467static void d_shrink_del(struct dentry *dentry)
468{
469 D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
470 list_del_init(&dentry->d_lru);
471 dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
472 this_cpu_dec(nr_dentry_unused);
473}
474
475static void d_shrink_add(struct dentry *dentry, struct list_head *list)
476{
477 D_FLAG_VERIFY(dentry, 0);
478 list_add(&dentry->d_lru, list);
479 dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST;
480 this_cpu_inc(nr_dentry_unused);
481}
482
483/*
484 * These can only be called under the global LRU lock, ie during the
485 * callback for freeing the LRU list. "isolate" removes it from the
486 * LRU lists entirely, while shrink_move moves it to the indicated
487 * private list.
488 */
489static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry)
490{
491 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
492 dentry->d_flags &= ~DCACHE_LRU_LIST;
493 this_cpu_dec(nr_dentry_unused);
494 if (d_is_negative(dentry))
495 this_cpu_dec(nr_dentry_negative);
496 list_lru_isolate(lru, &dentry->d_lru);
497}
498
499static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
500 struct list_head *list)
501{
502 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
503 dentry->d_flags |= DCACHE_SHRINK_LIST;
504 if (d_is_negative(dentry))
505 this_cpu_dec(nr_dentry_negative);
506 list_lru_isolate_move(lru, &dentry->d_lru, list);
507}
508
509static void ___d_drop(struct dentry *dentry)
510{
511 struct hlist_bl_head *b;
512 /*
513 * Hashed dentries are normally on the dentry hashtable,
514 * with the exception of those newly allocated by
515 * d_obtain_root, which are always IS_ROOT:
516 */
517 if (unlikely(IS_ROOT(dentry)))
518 b = &dentry->d_sb->s_roots;
519 else
520 b = d_hash(dentry->d_name.hash);
521
522 hlist_bl_lock(b);
523 __hlist_bl_del(&dentry->d_hash);
524 hlist_bl_unlock(b);
525}
526
527void __d_drop(struct dentry *dentry)
528{
529 if (!d_unhashed(dentry)) {
530 ___d_drop(dentry);
531 dentry->d_hash.pprev = NULL;
532 write_seqcount_invalidate(&dentry->d_seq);
533 }
534}
535EXPORT_SYMBOL(__d_drop);
536
537/**
538 * d_drop - drop a dentry
539 * @dentry: dentry to drop
540 *
541 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
542 * be found through a VFS lookup any more. Note that this is different from
543 * deleting the dentry - d_delete will try to mark the dentry negative if
544 * possible, giving a successful _negative_ lookup, while d_drop will
545 * just make the cache lookup fail.
546 *
547 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
548 * reason (NFS timeouts or autofs deletes).
549 *
550 * __d_drop requires dentry->d_lock
551 *
552 * ___d_drop doesn't mark dentry as "unhashed"
553 * (dentry->d_hash.pprev will be LIST_POISON2, not NULL).
554 */
555void d_drop(struct dentry *dentry)
556{
557 spin_lock(&dentry->d_lock);
558 __d_drop(dentry);
559 spin_unlock(&dentry->d_lock);
560}
561EXPORT_SYMBOL(d_drop);
562
563static inline void dentry_unlist(struct dentry *dentry)
564{
565 struct dentry *next;
566 /*
567 * Inform d_walk() and shrink_dentry_list() that we are no longer
568 * attached to the dentry tree
569 */
570 dentry->d_flags |= DCACHE_DENTRY_KILLED;
571 if (unlikely(hlist_unhashed(&dentry->d_sib)))
572 return;
573 __hlist_del(&dentry->d_sib);
574 /*
575 * Cursors can move around the list of children. While we'd been
576 * a normal list member, it didn't matter - ->d_sib.next would've
577 * been updated. However, from now on it won't be and for the
578 * things like d_walk() it might end up with a nasty surprise.
579 * Normally d_walk() doesn't care about cursors moving around -
580 * ->d_lock on parent prevents that and since a cursor has no children
581 * of its own, we get through it without ever unlocking the parent.
582 * There is one exception, though - if we ascend from a child that
583 * gets killed as soon as we unlock it, the next sibling is found
584 * using the value left in its ->d_sib.next. And if _that_
585 * pointed to a cursor, and cursor got moved (e.g. by lseek())
586 * before d_walk() regains parent->d_lock, we'll end up skipping
587 * everything the cursor had been moved past.
588 *
589 * Solution: make sure that the pointer left behind in ->d_sib.next
590 * points to something that won't be moving around. I.e. skip the
591 * cursors.
592 */
593 while (dentry->d_sib.next) {
594 next = hlist_entry(dentry->d_sib.next, struct dentry, d_sib);
595 if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR)))
596 break;
597 dentry->d_sib.next = next->d_sib.next;
598 }
599}
600
601static struct dentry *__dentry_kill(struct dentry *dentry)
602{
603 struct dentry *parent = NULL;
604 bool can_free = true;
605
606 /*
607 * The dentry is now unrecoverably dead to the world.
608 */
609 lockref_mark_dead(&dentry->d_lockref);
610
611 /*
612 * inform the fs via d_prune that this dentry is about to be
613 * unhashed and destroyed.
614 */
615 if (dentry->d_flags & DCACHE_OP_PRUNE)
616 dentry->d_op->d_prune(dentry);
617
618 if (dentry->d_flags & DCACHE_LRU_LIST) {
619 if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
620 d_lru_del(dentry);
621 }
622 /* if it was on the hash then remove it */
623 __d_drop(dentry);
624 if (dentry->d_inode)
625 dentry_unlink_inode(dentry);
626 else
627 spin_unlock(&dentry->d_lock);
628 this_cpu_dec(nr_dentry);
629 if (dentry->d_op && dentry->d_op->d_release)
630 dentry->d_op->d_release(dentry);
631
632 cond_resched();
633 /* now that it's negative, ->d_parent is stable */
634 if (!IS_ROOT(dentry)) {
635 parent = dentry->d_parent;
636 spin_lock(&parent->d_lock);
637 }
638 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
639 dentry_unlist(dentry);
640 if (dentry->d_flags & DCACHE_SHRINK_LIST)
641 can_free = false;
642 spin_unlock(&dentry->d_lock);
643 if (likely(can_free))
644 dentry_free(dentry);
645 if (parent && --parent->d_lockref.count) {
646 spin_unlock(&parent->d_lock);
647 return NULL;
648 }
649 return parent;
650}
651
652/*
653 * Lock a dentry for feeding it to __dentry_kill().
654 * Called under rcu_read_lock() and dentry->d_lock; the former
655 * guarantees that nothing we access will be freed under us.
656 * Note that dentry is *not* protected from concurrent dentry_kill(),
657 * d_delete(), etc.
658 *
659 * Return false if dentry is busy. Otherwise, return true and have
660 * that dentry's inode locked.
661 */
662
663static bool lock_for_kill(struct dentry *dentry)
664{
665 struct inode *inode = dentry->d_inode;
666
667 if (unlikely(dentry->d_lockref.count))
668 return false;
669
670 if (!inode || likely(spin_trylock(&inode->i_lock)))
671 return true;
672
673 do {
674 spin_unlock(&dentry->d_lock);
675 spin_lock(&inode->i_lock);
676 spin_lock(&dentry->d_lock);
677 if (likely(inode == dentry->d_inode))
678 break;
679 spin_unlock(&inode->i_lock);
680 inode = dentry->d_inode;
681 } while (inode);
682 if (likely(!dentry->d_lockref.count))
683 return true;
684 if (inode)
685 spin_unlock(&inode->i_lock);
686 return false;
687}
688
689/*
690 * Decide if dentry is worth retaining. Usually this is called with dentry
691 * locked; if not locked, we are more limited and might not be able to tell
692 * without a lock. False in this case means "punt to locked path and recheck".
693 *
694 * In case we aren't locked, these predicates are not "stable". However, it is
695 * sufficient that at some point after we dropped the reference the dentry was
696 * hashed and the flags had the proper value. Other dentry users may have
697 * re-gotten a reference to the dentry and change that, but our work is done -
698 * we can leave the dentry around with a zero refcount.
699 */
700static inline bool retain_dentry(struct dentry *dentry, bool locked)
701{
702 unsigned int d_flags;
703
704 smp_rmb();
705 d_flags = READ_ONCE(dentry->d_flags);
706
707 // Unreachable? Nobody would be able to look it up, no point retaining
708 if (unlikely(d_unhashed(dentry)))
709 return false;
710
711 // Same if it's disconnected
712 if (unlikely(d_flags & DCACHE_DISCONNECTED))
713 return false;
714
715 // ->d_delete() might tell us not to bother, but that requires
716 // ->d_lock; can't decide without it
717 if (unlikely(d_flags & DCACHE_OP_DELETE)) {
718 if (!locked || dentry->d_op->d_delete(dentry))
719 return false;
720 }
721
722 // Explicitly told not to bother
723 if (unlikely(d_flags & DCACHE_DONTCACHE))
724 return false;
725
726 // At this point it looks like we ought to keep it. We also might
727 // need to do something - put it on LRU if it wasn't there already
728 // and mark it referenced if it was on LRU, but not marked yet.
729 // Unfortunately, both actions require ->d_lock, so in lockless
730 // case we'd have to punt rather than doing those.
731 if (unlikely(!(d_flags & DCACHE_LRU_LIST))) {
732 if (!locked)
733 return false;
734 d_lru_add(dentry);
735 } else if (unlikely(!(d_flags & DCACHE_REFERENCED))) {
736 if (!locked)
737 return false;
738 dentry->d_flags |= DCACHE_REFERENCED;
739 }
740 return true;
741}
742
743void d_mark_dontcache(struct inode *inode)
744{
745 struct dentry *de;
746
747 spin_lock(&inode->i_lock);
748 hlist_for_each_entry(de, &inode->i_dentry, d_u.d_alias) {
749 spin_lock(&de->d_lock);
750 de->d_flags |= DCACHE_DONTCACHE;
751 spin_unlock(&de->d_lock);
752 }
753 inode->i_state |= I_DONTCACHE;
754 spin_unlock(&inode->i_lock);
755}
756EXPORT_SYMBOL(d_mark_dontcache);
757
758/*
759 * Try to do a lockless dput(), and return whether that was successful.
760 *
761 * If unsuccessful, we return false, having already taken the dentry lock.
762 * In that case refcount is guaranteed to be zero and we have already
763 * decided that it's not worth keeping around.
764 *
765 * The caller needs to hold the RCU read lock, so that the dentry is
766 * guaranteed to stay around even if the refcount goes down to zero!
767 */
768static inline bool fast_dput(struct dentry *dentry)
769{
770 int ret;
771
772 /*
773 * try to decrement the lockref optimistically.
774 */
775 ret = lockref_put_return(&dentry->d_lockref);
776
777 /*
778 * If the lockref_put_return() failed due to the lock being held
779 * by somebody else, the fast path has failed. We will need to
780 * get the lock, and then check the count again.
781 */
782 if (unlikely(ret < 0)) {
783 spin_lock(&dentry->d_lock);
784 if (WARN_ON_ONCE(dentry->d_lockref.count <= 0)) {
785 spin_unlock(&dentry->d_lock);
786 return true;
787 }
788 dentry->d_lockref.count--;
789 goto locked;
790 }
791
792 /*
793 * If we weren't the last ref, we're done.
794 */
795 if (ret)
796 return true;
797
798 /*
799 * Can we decide that decrement of refcount is all we needed without
800 * taking the lock? There's a very common case when it's all we need -
801 * dentry looks like it ought to be retained and there's nothing else
802 * to do.
803 */
804 if (retain_dentry(dentry, false))
805 return true;
806
807 /*
808 * Either not worth retaining or we can't tell without the lock.
809 * Get the lock, then. We've already decremented the refcount to 0,
810 * but we'll need to re-check the situation after getting the lock.
811 */
812 spin_lock(&dentry->d_lock);
813
814 /*
815 * Did somebody else grab a reference to it in the meantime, and
816 * we're no longer the last user after all? Alternatively, somebody
817 * else could have killed it and marked it dead. Either way, we
818 * don't need to do anything else.
819 */
820locked:
821 if (dentry->d_lockref.count || retain_dentry(dentry, true)) {
822 spin_unlock(&dentry->d_lock);
823 return true;
824 }
825 return false;
826}
827
828
829/*
830 * This is dput
831 *
832 * This is complicated by the fact that we do not want to put
833 * dentries that are no longer on any hash chain on the unused
834 * list: we'd much rather just get rid of them immediately.
835 *
836 * However, that implies that we have to traverse the dentry
837 * tree upwards to the parents which might _also_ now be
838 * scheduled for deletion (it may have been only waiting for
839 * its last child to go away).
840 *
841 * This tail recursion is done by hand as we don't want to depend
842 * on the compiler to always get this right (gcc generally doesn't).
843 * Real recursion would eat up our stack space.
844 */
845
846/*
847 * dput - release a dentry
848 * @dentry: dentry to release
849 *
850 * Release a dentry. This will drop the usage count and if appropriate
851 * call the dentry unlink method as well as removing it from the queues and
852 * releasing its resources. If the parent dentries were scheduled for release
853 * they too may now get deleted.
854 */
855void dput(struct dentry *dentry)
856{
857 if (!dentry)
858 return;
859 might_sleep();
860 rcu_read_lock();
861 if (likely(fast_dput(dentry))) {
862 rcu_read_unlock();
863 return;
864 }
865 while (lock_for_kill(dentry)) {
866 rcu_read_unlock();
867 dentry = __dentry_kill(dentry);
868 if (!dentry)
869 return;
870 if (retain_dentry(dentry, true)) {
871 spin_unlock(&dentry->d_lock);
872 return;
873 }
874 rcu_read_lock();
875 }
876 rcu_read_unlock();
877 spin_unlock(&dentry->d_lock);
878}
879EXPORT_SYMBOL(dput);
880
881static void to_shrink_list(struct dentry *dentry, struct list_head *list)
882__must_hold(&dentry->d_lock)
883{
884 if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
885 if (dentry->d_flags & DCACHE_LRU_LIST)
886 d_lru_del(dentry);
887 d_shrink_add(dentry, list);
888 }
889}
890
891void dput_to_list(struct dentry *dentry, struct list_head *list)
892{
893 rcu_read_lock();
894 if (likely(fast_dput(dentry))) {
895 rcu_read_unlock();
896 return;
897 }
898 rcu_read_unlock();
899 to_shrink_list(dentry, list);
900 spin_unlock(&dentry->d_lock);
901}
902
903struct dentry *dget_parent(struct dentry *dentry)
904{
905 int gotref;
906 struct dentry *ret;
907 unsigned seq;
908
909 /*
910 * Do optimistic parent lookup without any
911 * locking.
912 */
913 rcu_read_lock();
914 seq = raw_seqcount_begin(&dentry->d_seq);
915 ret = READ_ONCE(dentry->d_parent);
916 gotref = lockref_get_not_zero(&ret->d_lockref);
917 rcu_read_unlock();
918 if (likely(gotref)) {
919 if (!read_seqcount_retry(&dentry->d_seq, seq))
920 return ret;
921 dput(ret);
922 }
923
924repeat:
925 /*
926 * Don't need rcu_dereference because we re-check it was correct under
927 * the lock.
928 */
929 rcu_read_lock();
930 ret = dentry->d_parent;
931 spin_lock(&ret->d_lock);
932 if (unlikely(ret != dentry->d_parent)) {
933 spin_unlock(&ret->d_lock);
934 rcu_read_unlock();
935 goto repeat;
936 }
937 rcu_read_unlock();
938 BUG_ON(!ret->d_lockref.count);
939 ret->d_lockref.count++;
940 spin_unlock(&ret->d_lock);
941 return ret;
942}
943EXPORT_SYMBOL(dget_parent);
944
945static struct dentry * __d_find_any_alias(struct inode *inode)
946{
947 struct dentry *alias;
948
949 if (hlist_empty(&inode->i_dentry))
950 return NULL;
951 alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
952 lockref_get(&alias->d_lockref);
953 return alias;
954}
955
956/**
957 * d_find_any_alias - find any alias for a given inode
958 * @inode: inode to find an alias for
959 *
960 * If any aliases exist for the given inode, take and return a
961 * reference for one of them. If no aliases exist, return %NULL.
962 */
963struct dentry *d_find_any_alias(struct inode *inode)
964{
965 struct dentry *de;
966
967 spin_lock(&inode->i_lock);
968 de = __d_find_any_alias(inode);
969 spin_unlock(&inode->i_lock);
970 return de;
971}
972EXPORT_SYMBOL(d_find_any_alias);
973
974static struct dentry *__d_find_alias(struct inode *inode)
975{
976 struct dentry *alias;
977
978 if (S_ISDIR(inode->i_mode))
979 return __d_find_any_alias(inode);
980
981 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
982 spin_lock(&alias->d_lock);
983 if (!d_unhashed(alias)) {
984 dget_dlock(alias);
985 spin_unlock(&alias->d_lock);
986 return alias;
987 }
988 spin_unlock(&alias->d_lock);
989 }
990 return NULL;
991}
992
993/**
994 * d_find_alias - grab a hashed alias of inode
995 * @inode: inode in question
996 *
997 * If inode has a hashed alias, or is a directory and has any alias,
998 * acquire the reference to alias and return it. Otherwise return NULL.
999 * Notice that if inode is a directory there can be only one alias and
1000 * it can be unhashed only if it has no children, or if it is the root
1001 * of a filesystem, or if the directory was renamed and d_revalidate
1002 * was the first vfs operation to notice.
1003 *
1004 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
1005 * any other hashed alias over that one.
1006 */
1007struct dentry *d_find_alias(struct inode *inode)
1008{
1009 struct dentry *de = NULL;
1010
1011 if (!hlist_empty(&inode->i_dentry)) {
1012 spin_lock(&inode->i_lock);
1013 de = __d_find_alias(inode);
1014 spin_unlock(&inode->i_lock);
1015 }
1016 return de;
1017}
1018EXPORT_SYMBOL(d_find_alias);
1019
1020/*
1021 * Caller MUST be holding rcu_read_lock() and be guaranteed
1022 * that inode won't get freed until rcu_read_unlock().
1023 */
1024struct dentry *d_find_alias_rcu(struct inode *inode)
1025{
1026 struct hlist_head *l = &inode->i_dentry;
1027 struct dentry *de = NULL;
1028
1029 spin_lock(&inode->i_lock);
1030 // ->i_dentry and ->i_rcu are colocated, but the latter won't be
1031 // used without having I_FREEING set, which means no aliases left
1032 if (likely(!(inode->i_state & I_FREEING) && !hlist_empty(l))) {
1033 if (S_ISDIR(inode->i_mode)) {
1034 de = hlist_entry(l->first, struct dentry, d_u.d_alias);
1035 } else {
1036 hlist_for_each_entry(de, l, d_u.d_alias)
1037 if (!d_unhashed(de))
1038 break;
1039 }
1040 }
1041 spin_unlock(&inode->i_lock);
1042 return de;
1043}
1044
1045/*
1046 * Try to kill dentries associated with this inode.
1047 * WARNING: you must own a reference to inode.
1048 */
1049void d_prune_aliases(struct inode *inode)
1050{
1051 LIST_HEAD(dispose);
1052 struct dentry *dentry;
1053
1054 spin_lock(&inode->i_lock);
1055 hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
1056 spin_lock(&dentry->d_lock);
1057 if (!dentry->d_lockref.count)
1058 to_shrink_list(dentry, &dispose);
1059 spin_unlock(&dentry->d_lock);
1060 }
1061 spin_unlock(&inode->i_lock);
1062 shrink_dentry_list(&dispose);
1063}
1064EXPORT_SYMBOL(d_prune_aliases);
1065
1066static inline void shrink_kill(struct dentry *victim)
1067{
1068 do {
1069 rcu_read_unlock();
1070 victim = __dentry_kill(victim);
1071 rcu_read_lock();
1072 } while (victim && lock_for_kill(victim));
1073 rcu_read_unlock();
1074 if (victim)
1075 spin_unlock(&victim->d_lock);
1076}
1077
1078void shrink_dentry_list(struct list_head *list)
1079{
1080 while (!list_empty(list)) {
1081 struct dentry *dentry;
1082
1083 dentry = list_entry(list->prev, struct dentry, d_lru);
1084 spin_lock(&dentry->d_lock);
1085 rcu_read_lock();
1086 if (!lock_for_kill(dentry)) {
1087 bool can_free;
1088 rcu_read_unlock();
1089 d_shrink_del(dentry);
1090 can_free = dentry->d_flags & DCACHE_DENTRY_KILLED;
1091 spin_unlock(&dentry->d_lock);
1092 if (can_free)
1093 dentry_free(dentry);
1094 continue;
1095 }
1096 d_shrink_del(dentry);
1097 shrink_kill(dentry);
1098 }
1099}
1100
1101static enum lru_status dentry_lru_isolate(struct list_head *item,
1102 struct list_lru_one *lru, void *arg)
1103{
1104 struct list_head *freeable = arg;
1105 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1106
1107
1108 /*
1109 * we are inverting the lru lock/dentry->d_lock here,
1110 * so use a trylock. If we fail to get the lock, just skip
1111 * it
1112 */
1113 if (!spin_trylock(&dentry->d_lock))
1114 return LRU_SKIP;
1115
1116 /*
1117 * Referenced dentries are still in use. If they have active
1118 * counts, just remove them from the LRU. Otherwise give them
1119 * another pass through the LRU.
1120 */
1121 if (dentry->d_lockref.count) {
1122 d_lru_isolate(lru, dentry);
1123 spin_unlock(&dentry->d_lock);
1124 return LRU_REMOVED;
1125 }
1126
1127 if (dentry->d_flags & DCACHE_REFERENCED) {
1128 dentry->d_flags &= ~DCACHE_REFERENCED;
1129 spin_unlock(&dentry->d_lock);
1130
1131 /*
1132 * The list move itself will be made by the common LRU code. At
1133 * this point, we've dropped the dentry->d_lock but keep the
1134 * lru lock. This is safe to do, since every list movement is
1135 * protected by the lru lock even if both locks are held.
1136 *
1137 * This is guaranteed by the fact that all LRU management
1138 * functions are intermediated by the LRU API calls like
1139 * list_lru_add_obj and list_lru_del_obj. List movement in this file
1140 * only ever occur through this functions or through callbacks
1141 * like this one, that are called from the LRU API.
1142 *
1143 * The only exceptions to this are functions like
1144 * shrink_dentry_list, and code that first checks for the
1145 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1146 * operating only with stack provided lists after they are
1147 * properly isolated from the main list. It is thus, always a
1148 * local access.
1149 */
1150 return LRU_ROTATE;
1151 }
1152
1153 d_lru_shrink_move(lru, dentry, freeable);
1154 spin_unlock(&dentry->d_lock);
1155
1156 return LRU_REMOVED;
1157}
1158
1159/**
1160 * prune_dcache_sb - shrink the dcache
1161 * @sb: superblock
1162 * @sc: shrink control, passed to list_lru_shrink_walk()
1163 *
1164 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1165 * is done when we need more memory and called from the superblock shrinker
1166 * function.
1167 *
1168 * This function may fail to free any resources if all the dentries are in
1169 * use.
1170 */
1171long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc)
1172{
1173 LIST_HEAD(dispose);
1174 long freed;
1175
1176 freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc,
1177 dentry_lru_isolate, &dispose);
1178 shrink_dentry_list(&dispose);
1179 return freed;
1180}
1181
1182static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
1183 struct list_lru_one *lru, void *arg)
1184{
1185 struct list_head *freeable = arg;
1186 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1187
1188 /*
1189 * we are inverting the lru lock/dentry->d_lock here,
1190 * so use a trylock. If we fail to get the lock, just skip
1191 * it
1192 */
1193 if (!spin_trylock(&dentry->d_lock))
1194 return LRU_SKIP;
1195
1196 d_lru_shrink_move(lru, dentry, freeable);
1197 spin_unlock(&dentry->d_lock);
1198
1199 return LRU_REMOVED;
1200}
1201
1202
1203/**
1204 * shrink_dcache_sb - shrink dcache for a superblock
1205 * @sb: superblock
1206 *
1207 * Shrink the dcache for the specified super block. This is used to free
1208 * the dcache before unmounting a file system.
1209 */
1210void shrink_dcache_sb(struct super_block *sb)
1211{
1212 do {
1213 LIST_HEAD(dispose);
1214
1215 list_lru_walk(&sb->s_dentry_lru,
1216 dentry_lru_isolate_shrink, &dispose, 1024);
1217 shrink_dentry_list(&dispose);
1218 } while (list_lru_count(&sb->s_dentry_lru) > 0);
1219}
1220EXPORT_SYMBOL(shrink_dcache_sb);
1221
1222/**
1223 * enum d_walk_ret - action to talke during tree walk
1224 * @D_WALK_CONTINUE: contrinue walk
1225 * @D_WALK_QUIT: quit walk
1226 * @D_WALK_NORETRY: quit when retry is needed
1227 * @D_WALK_SKIP: skip this dentry and its children
1228 */
1229enum d_walk_ret {
1230 D_WALK_CONTINUE,
1231 D_WALK_QUIT,
1232 D_WALK_NORETRY,
1233 D_WALK_SKIP,
1234};
1235
1236/**
1237 * d_walk - walk the dentry tree
1238 * @parent: start of walk
1239 * @data: data passed to @enter() and @finish()
1240 * @enter: callback when first entering the dentry
1241 *
1242 * The @enter() callbacks are called with d_lock held.
1243 */
1244static void d_walk(struct dentry *parent, void *data,
1245 enum d_walk_ret (*enter)(void *, struct dentry *))
1246{
1247 struct dentry *this_parent, *dentry;
1248 unsigned seq = 0;
1249 enum d_walk_ret ret;
1250 bool retry = true;
1251
1252again:
1253 read_seqbegin_or_lock(&rename_lock, &seq);
1254 this_parent = parent;
1255 spin_lock(&this_parent->d_lock);
1256
1257 ret = enter(data, this_parent);
1258 switch (ret) {
1259 case D_WALK_CONTINUE:
1260 break;
1261 case D_WALK_QUIT:
1262 case D_WALK_SKIP:
1263 goto out_unlock;
1264 case D_WALK_NORETRY:
1265 retry = false;
1266 break;
1267 }
1268repeat:
1269 dentry = d_first_child(this_parent);
1270resume:
1271 hlist_for_each_entry_from(dentry, d_sib) {
1272 if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR))
1273 continue;
1274
1275 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1276
1277 ret = enter(data, dentry);
1278 switch (ret) {
1279 case D_WALK_CONTINUE:
1280 break;
1281 case D_WALK_QUIT:
1282 spin_unlock(&dentry->d_lock);
1283 goto out_unlock;
1284 case D_WALK_NORETRY:
1285 retry = false;
1286 break;
1287 case D_WALK_SKIP:
1288 spin_unlock(&dentry->d_lock);
1289 continue;
1290 }
1291
1292 if (!hlist_empty(&dentry->d_children)) {
1293 spin_unlock(&this_parent->d_lock);
1294 spin_release(&dentry->d_lock.dep_map, _RET_IP_);
1295 this_parent = dentry;
1296 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1297 goto repeat;
1298 }
1299 spin_unlock(&dentry->d_lock);
1300 }
1301 /*
1302 * All done at this level ... ascend and resume the search.
1303 */
1304 rcu_read_lock();
1305ascend:
1306 if (this_parent != parent) {
1307 dentry = this_parent;
1308 this_parent = dentry->d_parent;
1309
1310 spin_unlock(&dentry->d_lock);
1311 spin_lock(&this_parent->d_lock);
1312
1313 /* might go back up the wrong parent if we have had a rename. */
1314 if (need_seqretry(&rename_lock, seq))
1315 goto rename_retry;
1316 /* go into the first sibling still alive */
1317 hlist_for_each_entry_continue(dentry, d_sib) {
1318 if (likely(!(dentry->d_flags & DCACHE_DENTRY_KILLED))) {
1319 rcu_read_unlock();
1320 goto resume;
1321 }
1322 }
1323 goto ascend;
1324 }
1325 if (need_seqretry(&rename_lock, seq))
1326 goto rename_retry;
1327 rcu_read_unlock();
1328
1329out_unlock:
1330 spin_unlock(&this_parent->d_lock);
1331 done_seqretry(&rename_lock, seq);
1332 return;
1333
1334rename_retry:
1335 spin_unlock(&this_parent->d_lock);
1336 rcu_read_unlock();
1337 BUG_ON(seq & 1);
1338 if (!retry)
1339 return;
1340 seq = 1;
1341 goto again;
1342}
1343
1344struct check_mount {
1345 struct vfsmount *mnt;
1346 unsigned int mounted;
1347};
1348
1349static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry)
1350{
1351 struct check_mount *info = data;
1352 struct path path = { .mnt = info->mnt, .dentry = dentry };
1353
1354 if (likely(!d_mountpoint(dentry)))
1355 return D_WALK_CONTINUE;
1356 if (__path_is_mountpoint(&path)) {
1357 info->mounted = 1;
1358 return D_WALK_QUIT;
1359 }
1360 return D_WALK_CONTINUE;
1361}
1362
1363/**
1364 * path_has_submounts - check for mounts over a dentry in the
1365 * current namespace.
1366 * @parent: path to check.
1367 *
1368 * Return true if the parent or its subdirectories contain
1369 * a mount point in the current namespace.
1370 */
1371int path_has_submounts(const struct path *parent)
1372{
1373 struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
1374
1375 read_seqlock_excl(&mount_lock);
1376 d_walk(parent->dentry, &data, path_check_mount);
1377 read_sequnlock_excl(&mount_lock);
1378
1379 return data.mounted;
1380}
1381EXPORT_SYMBOL(path_has_submounts);
1382
1383/*
1384 * Called by mount code to set a mountpoint and check if the mountpoint is
1385 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1386 * subtree can become unreachable).
1387 *
1388 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1389 * this reason take rename_lock and d_lock on dentry and ancestors.
1390 */
1391int d_set_mounted(struct dentry *dentry)
1392{
1393 struct dentry *p;
1394 int ret = -ENOENT;
1395 write_seqlock(&rename_lock);
1396 for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
1397 /* Need exclusion wrt. d_invalidate() */
1398 spin_lock(&p->d_lock);
1399 if (unlikely(d_unhashed(p))) {
1400 spin_unlock(&p->d_lock);
1401 goto out;
1402 }
1403 spin_unlock(&p->d_lock);
1404 }
1405 spin_lock(&dentry->d_lock);
1406 if (!d_unlinked(dentry)) {
1407 ret = -EBUSY;
1408 if (!d_mountpoint(dentry)) {
1409 dentry->d_flags |= DCACHE_MOUNTED;
1410 ret = 0;
1411 }
1412 }
1413 spin_unlock(&dentry->d_lock);
1414out:
1415 write_sequnlock(&rename_lock);
1416 return ret;
1417}
1418
1419/*
1420 * Search the dentry child list of the specified parent,
1421 * and move any unused dentries to the end of the unused
1422 * list for prune_dcache(). We descend to the next level
1423 * whenever the d_children list is non-empty and continue
1424 * searching.
1425 *
1426 * It returns zero iff there are no unused children,
1427 * otherwise it returns the number of children moved to
1428 * the end of the unused list. This may not be the total
1429 * number of unused children, because select_parent can
1430 * drop the lock and return early due to latency
1431 * constraints.
1432 */
1433
1434struct select_data {
1435 struct dentry *start;
1436 union {
1437 long found;
1438 struct dentry *victim;
1439 };
1440 struct list_head dispose;
1441};
1442
1443static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
1444{
1445 struct select_data *data = _data;
1446 enum d_walk_ret ret = D_WALK_CONTINUE;
1447
1448 if (data->start == dentry)
1449 goto out;
1450
1451 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1452 data->found++;
1453 } else if (!dentry->d_lockref.count) {
1454 to_shrink_list(dentry, &data->dispose);
1455 data->found++;
1456 } else if (dentry->d_lockref.count < 0) {
1457 data->found++;
1458 }
1459 /*
1460 * We can return to the caller if we have found some (this
1461 * ensures forward progress). We'll be coming back to find
1462 * the rest.
1463 */
1464 if (!list_empty(&data->dispose))
1465 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1466out:
1467 return ret;
1468}
1469
1470static enum d_walk_ret select_collect2(void *_data, struct dentry *dentry)
1471{
1472 struct select_data *data = _data;
1473 enum d_walk_ret ret = D_WALK_CONTINUE;
1474
1475 if (data->start == dentry)
1476 goto out;
1477
1478 if (!dentry->d_lockref.count) {
1479 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1480 rcu_read_lock();
1481 data->victim = dentry;
1482 return D_WALK_QUIT;
1483 }
1484 to_shrink_list(dentry, &data->dispose);
1485 }
1486 /*
1487 * We can return to the caller if we have found some (this
1488 * ensures forward progress). We'll be coming back to find
1489 * the rest.
1490 */
1491 if (!list_empty(&data->dispose))
1492 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1493out:
1494 return ret;
1495}
1496
1497/**
1498 * shrink_dcache_parent - prune dcache
1499 * @parent: parent of entries to prune
1500 *
1501 * Prune the dcache to remove unused children of the parent dentry.
1502 */
1503void shrink_dcache_parent(struct dentry *parent)
1504{
1505 for (;;) {
1506 struct select_data data = {.start = parent};
1507
1508 INIT_LIST_HEAD(&data.dispose);
1509 d_walk(parent, &data, select_collect);
1510
1511 if (!list_empty(&data.dispose)) {
1512 shrink_dentry_list(&data.dispose);
1513 continue;
1514 }
1515
1516 cond_resched();
1517 if (!data.found)
1518 break;
1519 data.victim = NULL;
1520 d_walk(parent, &data, select_collect2);
1521 if (data.victim) {
1522 spin_lock(&data.victim->d_lock);
1523 if (!lock_for_kill(data.victim)) {
1524 spin_unlock(&data.victim->d_lock);
1525 rcu_read_unlock();
1526 } else {
1527 shrink_kill(data.victim);
1528 }
1529 }
1530 if (!list_empty(&data.dispose))
1531 shrink_dentry_list(&data.dispose);
1532 }
1533}
1534EXPORT_SYMBOL(shrink_dcache_parent);
1535
1536static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
1537{
1538 /* it has busy descendents; complain about those instead */
1539 if (!hlist_empty(&dentry->d_children))
1540 return D_WALK_CONTINUE;
1541
1542 /* root with refcount 1 is fine */
1543 if (dentry == _data && dentry->d_lockref.count == 1)
1544 return D_WALK_CONTINUE;
1545
1546 WARN(1, "BUG: Dentry %p{i=%lx,n=%pd} "
1547 " still in use (%d) [unmount of %s %s]\n",
1548 dentry,
1549 dentry->d_inode ?
1550 dentry->d_inode->i_ino : 0UL,
1551 dentry,
1552 dentry->d_lockref.count,
1553 dentry->d_sb->s_type->name,
1554 dentry->d_sb->s_id);
1555 return D_WALK_CONTINUE;
1556}
1557
1558static void do_one_tree(struct dentry *dentry)
1559{
1560 shrink_dcache_parent(dentry);
1561 d_walk(dentry, dentry, umount_check);
1562 d_drop(dentry);
1563 dput(dentry);
1564}
1565
1566/*
1567 * destroy the dentries attached to a superblock on unmounting
1568 */
1569void shrink_dcache_for_umount(struct super_block *sb)
1570{
1571 struct dentry *dentry;
1572
1573 rwsem_assert_held_write(&sb->s_umount);
1574
1575 dentry = sb->s_root;
1576 sb->s_root = NULL;
1577 do_one_tree(dentry);
1578
1579 while (!hlist_bl_empty(&sb->s_roots)) {
1580 dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_roots), struct dentry, d_hash));
1581 do_one_tree(dentry);
1582 }
1583}
1584
1585static enum d_walk_ret find_submount(void *_data, struct dentry *dentry)
1586{
1587 struct dentry **victim = _data;
1588 if (d_mountpoint(dentry)) {
1589 *victim = dget_dlock(dentry);
1590 return D_WALK_QUIT;
1591 }
1592 return D_WALK_CONTINUE;
1593}
1594
1595/**
1596 * d_invalidate - detach submounts, prune dcache, and drop
1597 * @dentry: dentry to invalidate (aka detach, prune and drop)
1598 */
1599void d_invalidate(struct dentry *dentry)
1600{
1601 bool had_submounts = false;
1602 spin_lock(&dentry->d_lock);
1603 if (d_unhashed(dentry)) {
1604 spin_unlock(&dentry->d_lock);
1605 return;
1606 }
1607 __d_drop(dentry);
1608 spin_unlock(&dentry->d_lock);
1609
1610 /* Negative dentries can be dropped without further checks */
1611 if (!dentry->d_inode)
1612 return;
1613
1614 shrink_dcache_parent(dentry);
1615 for (;;) {
1616 struct dentry *victim = NULL;
1617 d_walk(dentry, &victim, find_submount);
1618 if (!victim) {
1619 if (had_submounts)
1620 shrink_dcache_parent(dentry);
1621 return;
1622 }
1623 had_submounts = true;
1624 detach_mounts(victim);
1625 dput(victim);
1626 }
1627}
1628EXPORT_SYMBOL(d_invalidate);
1629
1630/**
1631 * __d_alloc - allocate a dcache entry
1632 * @sb: filesystem it will belong to
1633 * @name: qstr of the name
1634 *
1635 * Allocates a dentry. It returns %NULL if there is insufficient memory
1636 * available. On a success the dentry is returned. The name passed in is
1637 * copied and the copy passed in may be reused after this call.
1638 */
1639
1640static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1641{
1642 struct dentry *dentry;
1643 char *dname;
1644 int err;
1645
1646 dentry = kmem_cache_alloc_lru(dentry_cache, &sb->s_dentry_lru,
1647 GFP_KERNEL);
1648 if (!dentry)
1649 return NULL;
1650
1651 /*
1652 * We guarantee that the inline name is always NUL-terminated.
1653 * This way the memcpy() done by the name switching in rename
1654 * will still always have a NUL at the end, even if we might
1655 * be overwriting an internal NUL character
1656 */
1657 dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
1658 if (unlikely(!name)) {
1659 name = &slash_name;
1660 dname = dentry->d_iname;
1661 } else if (name->len > DNAME_INLINE_LEN-1) {
1662 size_t size = offsetof(struct external_name, name[1]);
1663 struct external_name *p = kmalloc(size + name->len,
1664 GFP_KERNEL_ACCOUNT |
1665 __GFP_RECLAIMABLE);
1666 if (!p) {
1667 kmem_cache_free(dentry_cache, dentry);
1668 return NULL;
1669 }
1670 atomic_set(&p->u.count, 1);
1671 dname = p->name;
1672 } else {
1673 dname = dentry->d_iname;
1674 }
1675
1676 dentry->d_name.len = name->len;
1677 dentry->d_name.hash = name->hash;
1678 memcpy(dname, name->name, name->len);
1679 dname[name->len] = 0;
1680
1681 /* Make sure we always see the terminating NUL character */
1682 smp_store_release(&dentry->d_name.name, dname); /* ^^^ */
1683
1684 dentry->d_lockref.count = 1;
1685 dentry->d_flags = 0;
1686 spin_lock_init(&dentry->d_lock);
1687 seqcount_spinlock_init(&dentry->d_seq, &dentry->d_lock);
1688 dentry->d_inode = NULL;
1689 dentry->d_parent = dentry;
1690 dentry->d_sb = sb;
1691 dentry->d_op = NULL;
1692 dentry->d_fsdata = NULL;
1693 INIT_HLIST_BL_NODE(&dentry->d_hash);
1694 INIT_LIST_HEAD(&dentry->d_lru);
1695 INIT_HLIST_HEAD(&dentry->d_children);
1696 INIT_HLIST_NODE(&dentry->d_u.d_alias);
1697 INIT_HLIST_NODE(&dentry->d_sib);
1698 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1699
1700 if (dentry->d_op && dentry->d_op->d_init) {
1701 err = dentry->d_op->d_init(dentry);
1702 if (err) {
1703 if (dname_external(dentry))
1704 kfree(external_name(dentry));
1705 kmem_cache_free(dentry_cache, dentry);
1706 return NULL;
1707 }
1708 }
1709
1710 this_cpu_inc(nr_dentry);
1711
1712 return dentry;
1713}
1714
1715/**
1716 * d_alloc - allocate a dcache entry
1717 * @parent: parent of entry to allocate
1718 * @name: qstr of the name
1719 *
1720 * Allocates a dentry. It returns %NULL if there is insufficient memory
1721 * available. On a success the dentry is returned. The name passed in is
1722 * copied and the copy passed in may be reused after this call.
1723 */
1724struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1725{
1726 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1727 if (!dentry)
1728 return NULL;
1729 spin_lock(&parent->d_lock);
1730 /*
1731 * don't need child lock because it is not subject
1732 * to concurrency here
1733 */
1734 dentry->d_parent = dget_dlock(parent);
1735 hlist_add_head(&dentry->d_sib, &parent->d_children);
1736 spin_unlock(&parent->d_lock);
1737
1738 return dentry;
1739}
1740EXPORT_SYMBOL(d_alloc);
1741
1742struct dentry *d_alloc_anon(struct super_block *sb)
1743{
1744 return __d_alloc(sb, NULL);
1745}
1746EXPORT_SYMBOL(d_alloc_anon);
1747
1748struct dentry *d_alloc_cursor(struct dentry * parent)
1749{
1750 struct dentry *dentry = d_alloc_anon(parent->d_sb);
1751 if (dentry) {
1752 dentry->d_flags |= DCACHE_DENTRY_CURSOR;
1753 dentry->d_parent = dget(parent);
1754 }
1755 return dentry;
1756}
1757
1758/**
1759 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1760 * @sb: the superblock
1761 * @name: qstr of the name
1762 *
1763 * For a filesystem that just pins its dentries in memory and never
1764 * performs lookups at all, return an unhashed IS_ROOT dentry.
1765 * This is used for pipes, sockets et.al. - the stuff that should
1766 * never be anyone's children or parents. Unlike all other
1767 * dentries, these will not have RCU delay between dropping the
1768 * last reference and freeing them.
1769 *
1770 * The only user is alloc_file_pseudo() and that's what should
1771 * be considered a public interface. Don't use directly.
1772 */
1773struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1774{
1775 static const struct dentry_operations anon_ops = {
1776 .d_dname = simple_dname
1777 };
1778 struct dentry *dentry = __d_alloc(sb, name);
1779 if (likely(dentry)) {
1780 dentry->d_flags |= DCACHE_NORCU;
1781 if (!sb->s_d_op)
1782 d_set_d_op(dentry, &anon_ops);
1783 }
1784 return dentry;
1785}
1786
1787struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1788{
1789 struct qstr q;
1790
1791 q.name = name;
1792 q.hash_len = hashlen_string(parent, name);
1793 return d_alloc(parent, &q);
1794}
1795EXPORT_SYMBOL(d_alloc_name);
1796
1797void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1798{
1799 WARN_ON_ONCE(dentry->d_op);
1800 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
1801 DCACHE_OP_COMPARE |
1802 DCACHE_OP_REVALIDATE |
1803 DCACHE_OP_WEAK_REVALIDATE |
1804 DCACHE_OP_DELETE |
1805 DCACHE_OP_REAL));
1806 dentry->d_op = op;
1807 if (!op)
1808 return;
1809 if (op->d_hash)
1810 dentry->d_flags |= DCACHE_OP_HASH;
1811 if (op->d_compare)
1812 dentry->d_flags |= DCACHE_OP_COMPARE;
1813 if (op->d_revalidate)
1814 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1815 if (op->d_weak_revalidate)
1816 dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
1817 if (op->d_delete)
1818 dentry->d_flags |= DCACHE_OP_DELETE;
1819 if (op->d_prune)
1820 dentry->d_flags |= DCACHE_OP_PRUNE;
1821 if (op->d_real)
1822 dentry->d_flags |= DCACHE_OP_REAL;
1823
1824}
1825EXPORT_SYMBOL(d_set_d_op);
1826
1827static unsigned d_flags_for_inode(struct inode *inode)
1828{
1829 unsigned add_flags = DCACHE_REGULAR_TYPE;
1830
1831 if (!inode)
1832 return DCACHE_MISS_TYPE;
1833
1834 if (S_ISDIR(inode->i_mode)) {
1835 add_flags = DCACHE_DIRECTORY_TYPE;
1836 if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) {
1837 if (unlikely(!inode->i_op->lookup))
1838 add_flags = DCACHE_AUTODIR_TYPE;
1839 else
1840 inode->i_opflags |= IOP_LOOKUP;
1841 }
1842 goto type_determined;
1843 }
1844
1845 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1846 if (unlikely(inode->i_op->get_link)) {
1847 add_flags = DCACHE_SYMLINK_TYPE;
1848 goto type_determined;
1849 }
1850 inode->i_opflags |= IOP_NOFOLLOW;
1851 }
1852
1853 if (unlikely(!S_ISREG(inode->i_mode)))
1854 add_flags = DCACHE_SPECIAL_TYPE;
1855
1856type_determined:
1857 if (unlikely(IS_AUTOMOUNT(inode)))
1858 add_flags |= DCACHE_NEED_AUTOMOUNT;
1859 return add_flags;
1860}
1861
1862static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1863{
1864 unsigned add_flags = d_flags_for_inode(inode);
1865 WARN_ON(d_in_lookup(dentry));
1866
1867 spin_lock(&dentry->d_lock);
1868 /*
1869 * The negative counter only tracks dentries on the LRU. Don't dec if
1870 * d_lru is on another list.
1871 */
1872 if ((dentry->d_flags &
1873 (DCACHE_LRU_LIST|DCACHE_SHRINK_LIST)) == DCACHE_LRU_LIST)
1874 this_cpu_dec(nr_dentry_negative);
1875 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
1876 raw_write_seqcount_begin(&dentry->d_seq);
1877 __d_set_inode_and_type(dentry, inode, add_flags);
1878 raw_write_seqcount_end(&dentry->d_seq);
1879 fsnotify_update_flags(dentry);
1880 spin_unlock(&dentry->d_lock);
1881}
1882
1883/**
1884 * d_instantiate - fill in inode information for a dentry
1885 * @entry: dentry to complete
1886 * @inode: inode to attach to this dentry
1887 *
1888 * Fill in inode information in the entry.
1889 *
1890 * This turns negative dentries into productive full members
1891 * of society.
1892 *
1893 * NOTE! This assumes that the inode count has been incremented
1894 * (or otherwise set) by the caller to indicate that it is now
1895 * in use by the dcache.
1896 */
1897
1898void d_instantiate(struct dentry *entry, struct inode * inode)
1899{
1900 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1901 if (inode) {
1902 security_d_instantiate(entry, inode);
1903 spin_lock(&inode->i_lock);
1904 __d_instantiate(entry, inode);
1905 spin_unlock(&inode->i_lock);
1906 }
1907}
1908EXPORT_SYMBOL(d_instantiate);
1909
1910/*
1911 * This should be equivalent to d_instantiate() + unlock_new_inode(),
1912 * with lockdep-related part of unlock_new_inode() done before
1913 * anything else. Use that instead of open-coding d_instantiate()/
1914 * unlock_new_inode() combinations.
1915 */
1916void d_instantiate_new(struct dentry *entry, struct inode *inode)
1917{
1918 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1919 BUG_ON(!inode);
1920 lockdep_annotate_inode_mutex_key(inode);
1921 security_d_instantiate(entry, inode);
1922 spin_lock(&inode->i_lock);
1923 __d_instantiate(entry, inode);
1924 WARN_ON(!(inode->i_state & I_NEW));
1925 inode->i_state &= ~I_NEW & ~I_CREATING;
1926 /*
1927 * Pairs with the barrier in prepare_to_wait_event() to make sure
1928 * ___wait_var_event() either sees the bit cleared or
1929 * waitqueue_active() check in wake_up_var() sees the waiter.
1930 */
1931 smp_mb();
1932 inode_wake_up_bit(inode, __I_NEW);
1933 spin_unlock(&inode->i_lock);
1934}
1935EXPORT_SYMBOL(d_instantiate_new);
1936
1937struct dentry *d_make_root(struct inode *root_inode)
1938{
1939 struct dentry *res = NULL;
1940
1941 if (root_inode) {
1942 res = d_alloc_anon(root_inode->i_sb);
1943 if (res)
1944 d_instantiate(res, root_inode);
1945 else
1946 iput(root_inode);
1947 }
1948 return res;
1949}
1950EXPORT_SYMBOL(d_make_root);
1951
1952static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected)
1953{
1954 struct super_block *sb;
1955 struct dentry *new, *res;
1956
1957 if (!inode)
1958 return ERR_PTR(-ESTALE);
1959 if (IS_ERR(inode))
1960 return ERR_CAST(inode);
1961
1962 sb = inode->i_sb;
1963
1964 res = d_find_any_alias(inode); /* existing alias? */
1965 if (res)
1966 goto out;
1967
1968 new = d_alloc_anon(sb);
1969 if (!new) {
1970 res = ERR_PTR(-ENOMEM);
1971 goto out;
1972 }
1973
1974 security_d_instantiate(new, inode);
1975 spin_lock(&inode->i_lock);
1976 res = __d_find_any_alias(inode); /* recheck under lock */
1977 if (likely(!res)) { /* still no alias, attach a disconnected dentry */
1978 unsigned add_flags = d_flags_for_inode(inode);
1979
1980 if (disconnected)
1981 add_flags |= DCACHE_DISCONNECTED;
1982
1983 spin_lock(&new->d_lock);
1984 __d_set_inode_and_type(new, inode, add_flags);
1985 hlist_add_head(&new->d_u.d_alias, &inode->i_dentry);
1986 if (!disconnected) {
1987 hlist_bl_lock(&sb->s_roots);
1988 hlist_bl_add_head(&new->d_hash, &sb->s_roots);
1989 hlist_bl_unlock(&sb->s_roots);
1990 }
1991 spin_unlock(&new->d_lock);
1992 spin_unlock(&inode->i_lock);
1993 inode = NULL; /* consumed by new->d_inode */
1994 res = new;
1995 } else {
1996 spin_unlock(&inode->i_lock);
1997 dput(new);
1998 }
1999
2000 out:
2001 iput(inode);
2002 return res;
2003}
2004
2005/**
2006 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
2007 * @inode: inode to allocate the dentry for
2008 *
2009 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
2010 * similar open by handle operations. The returned dentry may be anonymous,
2011 * or may have a full name (if the inode was already in the cache).
2012 *
2013 * When called on a directory inode, we must ensure that the inode only ever
2014 * has one dentry. If a dentry is found, that is returned instead of
2015 * allocating a new one.
2016 *
2017 * On successful return, the reference to the inode has been transferred
2018 * to the dentry. In case of an error the reference on the inode is released.
2019 * To make it easier to use in export operations a %NULL or IS_ERR inode may
2020 * be passed in and the error will be propagated to the return value,
2021 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
2022 */
2023struct dentry *d_obtain_alias(struct inode *inode)
2024{
2025 return __d_obtain_alias(inode, true);
2026}
2027EXPORT_SYMBOL(d_obtain_alias);
2028
2029/**
2030 * d_obtain_root - find or allocate a dentry for a given inode
2031 * @inode: inode to allocate the dentry for
2032 *
2033 * Obtain an IS_ROOT dentry for the root of a filesystem.
2034 *
2035 * We must ensure that directory inodes only ever have one dentry. If a
2036 * dentry is found, that is returned instead of allocating a new one.
2037 *
2038 * On successful return, the reference to the inode has been transferred
2039 * to the dentry. In case of an error the reference on the inode is
2040 * released. A %NULL or IS_ERR inode may be passed in and will be the
2041 * error will be propagate to the return value, with a %NULL @inode
2042 * replaced by ERR_PTR(-ESTALE).
2043 */
2044struct dentry *d_obtain_root(struct inode *inode)
2045{
2046 return __d_obtain_alias(inode, false);
2047}
2048EXPORT_SYMBOL(d_obtain_root);
2049
2050/**
2051 * d_add_ci - lookup or allocate new dentry with case-exact name
2052 * @dentry: the negative dentry that was passed to the parent's lookup func
2053 * @inode: the inode case-insensitive lookup has found
2054 * @name: the case-exact name to be associated with the returned dentry
2055 *
2056 * This is to avoid filling the dcache with case-insensitive names to the
2057 * same inode, only the actual correct case is stored in the dcache for
2058 * case-insensitive filesystems.
2059 *
2060 * For a case-insensitive lookup match and if the case-exact dentry
2061 * already exists in the dcache, use it and return it.
2062 *
2063 * If no entry exists with the exact case name, allocate new dentry with
2064 * the exact case, and return the spliced entry.
2065 */
2066struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
2067 struct qstr *name)
2068{
2069 struct dentry *found, *res;
2070
2071 /*
2072 * First check if a dentry matching the name already exists,
2073 * if not go ahead and create it now.
2074 */
2075 found = d_hash_and_lookup(dentry->d_parent, name);
2076 if (found) {
2077 iput(inode);
2078 return found;
2079 }
2080 if (d_in_lookup(dentry)) {
2081 found = d_alloc_parallel(dentry->d_parent, name,
2082 dentry->d_wait);
2083 if (IS_ERR(found) || !d_in_lookup(found)) {
2084 iput(inode);
2085 return found;
2086 }
2087 } else {
2088 found = d_alloc(dentry->d_parent, name);
2089 if (!found) {
2090 iput(inode);
2091 return ERR_PTR(-ENOMEM);
2092 }
2093 }
2094 res = d_splice_alias(inode, found);
2095 if (res) {
2096 d_lookup_done(found);
2097 dput(found);
2098 return res;
2099 }
2100 return found;
2101}
2102EXPORT_SYMBOL(d_add_ci);
2103
2104/**
2105 * d_same_name - compare dentry name with case-exact name
2106 * @dentry: the negative dentry that was passed to the parent's lookup func
2107 * @parent: parent dentry
2108 * @name: the case-exact name to be associated with the returned dentry
2109 *
2110 * Return: true if names are same, or false
2111 */
2112bool d_same_name(const struct dentry *dentry, const struct dentry *parent,
2113 const struct qstr *name)
2114{
2115 if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
2116 if (dentry->d_name.len != name->len)
2117 return false;
2118 return dentry_cmp(dentry, name->name, name->len) == 0;
2119 }
2120 return parent->d_op->d_compare(dentry,
2121 dentry->d_name.len, dentry->d_name.name,
2122 name) == 0;
2123}
2124EXPORT_SYMBOL_GPL(d_same_name);
2125
2126/*
2127 * This is __d_lookup_rcu() when the parent dentry has
2128 * DCACHE_OP_COMPARE, which makes things much nastier.
2129 */
2130static noinline struct dentry *__d_lookup_rcu_op_compare(
2131 const struct dentry *parent,
2132 const struct qstr *name,
2133 unsigned *seqp)
2134{
2135 u64 hashlen = name->hash_len;
2136 struct hlist_bl_head *b = d_hash(hashlen);
2137 struct hlist_bl_node *node;
2138 struct dentry *dentry;
2139
2140 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2141 int tlen;
2142 const char *tname;
2143 unsigned seq;
2144
2145seqretry:
2146 seq = raw_seqcount_begin(&dentry->d_seq);
2147 if (dentry->d_parent != parent)
2148 continue;
2149 if (d_unhashed(dentry))
2150 continue;
2151 if (dentry->d_name.hash != hashlen_hash(hashlen))
2152 continue;
2153 tlen = dentry->d_name.len;
2154 tname = dentry->d_name.name;
2155 /* we want a consistent (name,len) pair */
2156 if (read_seqcount_retry(&dentry->d_seq, seq)) {
2157 cpu_relax();
2158 goto seqretry;
2159 }
2160 if (parent->d_op->d_compare(dentry, tlen, tname, name) != 0)
2161 continue;
2162 *seqp = seq;
2163 return dentry;
2164 }
2165 return NULL;
2166}
2167
2168/**
2169 * __d_lookup_rcu - search for a dentry (racy, store-free)
2170 * @parent: parent dentry
2171 * @name: qstr of name we wish to find
2172 * @seqp: returns d_seq value at the point where the dentry was found
2173 * Returns: dentry, or NULL
2174 *
2175 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2176 * resolution (store-free path walking) design described in
2177 * Documentation/filesystems/path-lookup.txt.
2178 *
2179 * This is not to be used outside core vfs.
2180 *
2181 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2182 * held, and rcu_read_lock held. The returned dentry must not be stored into
2183 * without taking d_lock and checking d_seq sequence count against @seq
2184 * returned here.
2185 *
2186 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2187 * the returned dentry, so long as its parent's seqlock is checked after the
2188 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2189 * is formed, giving integrity down the path walk.
2190 *
2191 * NOTE! The caller *has* to check the resulting dentry against the sequence
2192 * number we've returned before using any of the resulting dentry state!
2193 */
2194struct dentry *__d_lookup_rcu(const struct dentry *parent,
2195 const struct qstr *name,
2196 unsigned *seqp)
2197{
2198 u64 hashlen = name->hash_len;
2199 const unsigned char *str = name->name;
2200 struct hlist_bl_head *b = d_hash(hashlen);
2201 struct hlist_bl_node *node;
2202 struct dentry *dentry;
2203
2204 /*
2205 * Note: There is significant duplication with __d_lookup_rcu which is
2206 * required to prevent single threaded performance regressions
2207 * especially on architectures where smp_rmb (in seqcounts) are costly.
2208 * Keep the two functions in sync.
2209 */
2210
2211 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE))
2212 return __d_lookup_rcu_op_compare(parent, name, seqp);
2213
2214 /*
2215 * The hash list is protected using RCU.
2216 *
2217 * Carefully use d_seq when comparing a candidate dentry, to avoid
2218 * races with d_move().
2219 *
2220 * It is possible that concurrent renames can mess up our list
2221 * walk here and result in missing our dentry, resulting in the
2222 * false-negative result. d_lookup() protects against concurrent
2223 * renames using rename_lock seqlock.
2224 *
2225 * See Documentation/filesystems/path-lookup.txt for more details.
2226 */
2227 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2228 unsigned seq;
2229
2230 /*
2231 * The dentry sequence count protects us from concurrent
2232 * renames, and thus protects parent and name fields.
2233 *
2234 * The caller must perform a seqcount check in order
2235 * to do anything useful with the returned dentry.
2236 *
2237 * NOTE! We do a "raw" seqcount_begin here. That means that
2238 * we don't wait for the sequence count to stabilize if it
2239 * is in the middle of a sequence change. If we do the slow
2240 * dentry compare, we will do seqretries until it is stable,
2241 * and if we end up with a successful lookup, we actually
2242 * want to exit RCU lookup anyway.
2243 *
2244 * Note that raw_seqcount_begin still *does* smp_rmb(), so
2245 * we are still guaranteed NUL-termination of ->d_name.name.
2246 */
2247 seq = raw_seqcount_begin(&dentry->d_seq);
2248 if (dentry->d_parent != parent)
2249 continue;
2250 if (d_unhashed(dentry))
2251 continue;
2252 if (dentry->d_name.hash_len != hashlen)
2253 continue;
2254 if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
2255 continue;
2256 *seqp = seq;
2257 return dentry;
2258 }
2259 return NULL;
2260}
2261
2262/**
2263 * d_lookup - search for a dentry
2264 * @parent: parent dentry
2265 * @name: qstr of name we wish to find
2266 * Returns: dentry, or NULL
2267 *
2268 * d_lookup searches the children of the parent dentry for the name in
2269 * question. If the dentry is found its reference count is incremented and the
2270 * dentry is returned. The caller must use dput to free the entry when it has
2271 * finished using it. %NULL is returned if the dentry does not exist.
2272 */
2273struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
2274{
2275 struct dentry *dentry;
2276 unsigned seq;
2277
2278 do {
2279 seq = read_seqbegin(&rename_lock);
2280 dentry = __d_lookup(parent, name);
2281 if (dentry)
2282 break;
2283 } while (read_seqretry(&rename_lock, seq));
2284 return dentry;
2285}
2286EXPORT_SYMBOL(d_lookup);
2287
2288/**
2289 * __d_lookup - search for a dentry (racy)
2290 * @parent: parent dentry
2291 * @name: qstr of name we wish to find
2292 * Returns: dentry, or NULL
2293 *
2294 * __d_lookup is like d_lookup, however it may (rarely) return a
2295 * false-negative result due to unrelated rename activity.
2296 *
2297 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2298 * however it must be used carefully, eg. with a following d_lookup in
2299 * the case of failure.
2300 *
2301 * __d_lookup callers must be commented.
2302 */
2303struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
2304{
2305 unsigned int hash = name->hash;
2306 struct hlist_bl_head *b = d_hash(hash);
2307 struct hlist_bl_node *node;
2308 struct dentry *found = NULL;
2309 struct dentry *dentry;
2310
2311 /*
2312 * Note: There is significant duplication with __d_lookup_rcu which is
2313 * required to prevent single threaded performance regressions
2314 * especially on architectures where smp_rmb (in seqcounts) are costly.
2315 * Keep the two functions in sync.
2316 */
2317
2318 /*
2319 * The hash list is protected using RCU.
2320 *
2321 * Take d_lock when comparing a candidate dentry, to avoid races
2322 * with d_move().
2323 *
2324 * It is possible that concurrent renames can mess up our list
2325 * walk here and result in missing our dentry, resulting in the
2326 * false-negative result. d_lookup() protects against concurrent
2327 * renames using rename_lock seqlock.
2328 *
2329 * See Documentation/filesystems/path-lookup.txt for more details.
2330 */
2331 rcu_read_lock();
2332
2333 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2334
2335 if (dentry->d_name.hash != hash)
2336 continue;
2337
2338 spin_lock(&dentry->d_lock);
2339 if (dentry->d_parent != parent)
2340 goto next;
2341 if (d_unhashed(dentry))
2342 goto next;
2343
2344 if (!d_same_name(dentry, parent, name))
2345 goto next;
2346
2347 dentry->d_lockref.count++;
2348 found = dentry;
2349 spin_unlock(&dentry->d_lock);
2350 break;
2351next:
2352 spin_unlock(&dentry->d_lock);
2353 }
2354 rcu_read_unlock();
2355
2356 return found;
2357}
2358
2359/**
2360 * d_hash_and_lookup - hash the qstr then search for a dentry
2361 * @dir: Directory to search in
2362 * @name: qstr of name we wish to find
2363 *
2364 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2365 */
2366struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2367{
2368 /*
2369 * Check for a fs-specific hash function. Note that we must
2370 * calculate the standard hash first, as the d_op->d_hash()
2371 * routine may choose to leave the hash value unchanged.
2372 */
2373 name->hash = full_name_hash(dir, name->name, name->len);
2374 if (dir->d_flags & DCACHE_OP_HASH) {
2375 int err = dir->d_op->d_hash(dir, name);
2376 if (unlikely(err < 0))
2377 return ERR_PTR(err);
2378 }
2379 return d_lookup(dir, name);
2380}
2381EXPORT_SYMBOL(d_hash_and_lookup);
2382
2383/*
2384 * When a file is deleted, we have two options:
2385 * - turn this dentry into a negative dentry
2386 * - unhash this dentry and free it.
2387 *
2388 * Usually, we want to just turn this into
2389 * a negative dentry, but if anybody else is
2390 * currently using the dentry or the inode
2391 * we can't do that and we fall back on removing
2392 * it from the hash queues and waiting for
2393 * it to be deleted later when it has no users
2394 */
2395
2396/**
2397 * d_delete - delete a dentry
2398 * @dentry: The dentry to delete
2399 *
2400 * Turn the dentry into a negative dentry if possible, otherwise
2401 * remove it from the hash queues so it can be deleted later
2402 */
2403
2404void d_delete(struct dentry * dentry)
2405{
2406 struct inode *inode = dentry->d_inode;
2407
2408 spin_lock(&inode->i_lock);
2409 spin_lock(&dentry->d_lock);
2410 /*
2411 * Are we the only user?
2412 */
2413 if (dentry->d_lockref.count == 1) {
2414 if (dentry_negative_policy)
2415 __d_drop(dentry);
2416 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2417 dentry_unlink_inode(dentry);
2418 } else {
2419 __d_drop(dentry);
2420 spin_unlock(&dentry->d_lock);
2421 spin_unlock(&inode->i_lock);
2422 }
2423}
2424EXPORT_SYMBOL(d_delete);
2425
2426static void __d_rehash(struct dentry *entry)
2427{
2428 struct hlist_bl_head *b = d_hash(entry->d_name.hash);
2429
2430 hlist_bl_lock(b);
2431 hlist_bl_add_head_rcu(&entry->d_hash, b);
2432 hlist_bl_unlock(b);
2433}
2434
2435/**
2436 * d_rehash - add an entry back to the hash
2437 * @entry: dentry to add to the hash
2438 *
2439 * Adds a dentry to the hash according to its name.
2440 */
2441
2442void d_rehash(struct dentry * entry)
2443{
2444 spin_lock(&entry->d_lock);
2445 __d_rehash(entry);
2446 spin_unlock(&entry->d_lock);
2447}
2448EXPORT_SYMBOL(d_rehash);
2449
2450static inline unsigned start_dir_add(struct inode *dir)
2451{
2452 preempt_disable_nested();
2453 for (;;) {
2454 unsigned n = dir->i_dir_seq;
2455 if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
2456 return n;
2457 cpu_relax();
2458 }
2459}
2460
2461static inline void end_dir_add(struct inode *dir, unsigned int n,
2462 wait_queue_head_t *d_wait)
2463{
2464 smp_store_release(&dir->i_dir_seq, n + 2);
2465 preempt_enable_nested();
2466 wake_up_all(d_wait);
2467}
2468
2469static void d_wait_lookup(struct dentry *dentry)
2470{
2471 if (d_in_lookup(dentry)) {
2472 DECLARE_WAITQUEUE(wait, current);
2473 add_wait_queue(dentry->d_wait, &wait);
2474 do {
2475 set_current_state(TASK_UNINTERRUPTIBLE);
2476 spin_unlock(&dentry->d_lock);
2477 schedule();
2478 spin_lock(&dentry->d_lock);
2479 } while (d_in_lookup(dentry));
2480 }
2481}
2482
2483struct dentry *d_alloc_parallel(struct dentry *parent,
2484 const struct qstr *name,
2485 wait_queue_head_t *wq)
2486{
2487 unsigned int hash = name->hash;
2488 struct hlist_bl_head *b = in_lookup_hash(parent, hash);
2489 struct hlist_bl_node *node;
2490 struct dentry *new = d_alloc(parent, name);
2491 struct dentry *dentry;
2492 unsigned seq, r_seq, d_seq;
2493
2494 if (unlikely(!new))
2495 return ERR_PTR(-ENOMEM);
2496
2497retry:
2498 rcu_read_lock();
2499 seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
2500 r_seq = read_seqbegin(&rename_lock);
2501 dentry = __d_lookup_rcu(parent, name, &d_seq);
2502 if (unlikely(dentry)) {
2503 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2504 rcu_read_unlock();
2505 goto retry;
2506 }
2507 if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
2508 rcu_read_unlock();
2509 dput(dentry);
2510 goto retry;
2511 }
2512 rcu_read_unlock();
2513 dput(new);
2514 return dentry;
2515 }
2516 if (unlikely(read_seqretry(&rename_lock, r_seq))) {
2517 rcu_read_unlock();
2518 goto retry;
2519 }
2520
2521 if (unlikely(seq & 1)) {
2522 rcu_read_unlock();
2523 goto retry;
2524 }
2525
2526 hlist_bl_lock(b);
2527 if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
2528 hlist_bl_unlock(b);
2529 rcu_read_unlock();
2530 goto retry;
2531 }
2532 /*
2533 * No changes for the parent since the beginning of d_lookup().
2534 * Since all removals from the chain happen with hlist_bl_lock(),
2535 * any potential in-lookup matches are going to stay here until
2536 * we unlock the chain. All fields are stable in everything
2537 * we encounter.
2538 */
2539 hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
2540 if (dentry->d_name.hash != hash)
2541 continue;
2542 if (dentry->d_parent != parent)
2543 continue;
2544 if (!d_same_name(dentry, parent, name))
2545 continue;
2546 hlist_bl_unlock(b);
2547 /* now we can try to grab a reference */
2548 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2549 rcu_read_unlock();
2550 goto retry;
2551 }
2552
2553 rcu_read_unlock();
2554 /*
2555 * somebody is likely to be still doing lookup for it;
2556 * wait for them to finish
2557 */
2558 spin_lock(&dentry->d_lock);
2559 d_wait_lookup(dentry);
2560 /*
2561 * it's not in-lookup anymore; in principle we should repeat
2562 * everything from dcache lookup, but it's likely to be what
2563 * d_lookup() would've found anyway. If it is, just return it;
2564 * otherwise we really have to repeat the whole thing.
2565 */
2566 if (unlikely(dentry->d_name.hash != hash))
2567 goto mismatch;
2568 if (unlikely(dentry->d_parent != parent))
2569 goto mismatch;
2570 if (unlikely(d_unhashed(dentry)))
2571 goto mismatch;
2572 if (unlikely(!d_same_name(dentry, parent, name)))
2573 goto mismatch;
2574 /* OK, it *is* a hashed match; return it */
2575 spin_unlock(&dentry->d_lock);
2576 dput(new);
2577 return dentry;
2578 }
2579 rcu_read_unlock();
2580 /* we can't take ->d_lock here; it's OK, though. */
2581 new->d_flags |= DCACHE_PAR_LOOKUP;
2582 new->d_wait = wq;
2583 hlist_bl_add_head(&new->d_u.d_in_lookup_hash, b);
2584 hlist_bl_unlock(b);
2585 return new;
2586mismatch:
2587 spin_unlock(&dentry->d_lock);
2588 dput(dentry);
2589 goto retry;
2590}
2591EXPORT_SYMBOL(d_alloc_parallel);
2592
2593/*
2594 * - Unhash the dentry
2595 * - Retrieve and clear the waitqueue head in dentry
2596 * - Return the waitqueue head
2597 */
2598static wait_queue_head_t *__d_lookup_unhash(struct dentry *dentry)
2599{
2600 wait_queue_head_t *d_wait;
2601 struct hlist_bl_head *b;
2602
2603 lockdep_assert_held(&dentry->d_lock);
2604
2605 b = in_lookup_hash(dentry->d_parent, dentry->d_name.hash);
2606 hlist_bl_lock(b);
2607 dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
2608 __hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
2609 d_wait = dentry->d_wait;
2610 dentry->d_wait = NULL;
2611 hlist_bl_unlock(b);
2612 INIT_HLIST_NODE(&dentry->d_u.d_alias);
2613 INIT_LIST_HEAD(&dentry->d_lru);
2614 return d_wait;
2615}
2616
2617void __d_lookup_unhash_wake(struct dentry *dentry)
2618{
2619 spin_lock(&dentry->d_lock);
2620 wake_up_all(__d_lookup_unhash(dentry));
2621 spin_unlock(&dentry->d_lock);
2622}
2623EXPORT_SYMBOL(__d_lookup_unhash_wake);
2624
2625/* inode->i_lock held if inode is non-NULL */
2626
2627static inline void __d_add(struct dentry *dentry, struct inode *inode)
2628{
2629 wait_queue_head_t *d_wait;
2630 struct inode *dir = NULL;
2631 unsigned n;
2632 spin_lock(&dentry->d_lock);
2633 if (unlikely(d_in_lookup(dentry))) {
2634 dir = dentry->d_parent->d_inode;
2635 n = start_dir_add(dir);
2636 d_wait = __d_lookup_unhash(dentry);
2637 }
2638 if (inode) {
2639 unsigned add_flags = d_flags_for_inode(inode);
2640 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2641 raw_write_seqcount_begin(&dentry->d_seq);
2642 __d_set_inode_and_type(dentry, inode, add_flags);
2643 raw_write_seqcount_end(&dentry->d_seq);
2644 fsnotify_update_flags(dentry);
2645 }
2646 __d_rehash(dentry);
2647 if (dir)
2648 end_dir_add(dir, n, d_wait);
2649 spin_unlock(&dentry->d_lock);
2650 if (inode)
2651 spin_unlock(&inode->i_lock);
2652}
2653
2654/**
2655 * d_add - add dentry to hash queues
2656 * @entry: dentry to add
2657 * @inode: The inode to attach to this dentry
2658 *
2659 * This adds the entry to the hash queues and initializes @inode.
2660 * The entry was actually filled in earlier during d_alloc().
2661 */
2662
2663void d_add(struct dentry *entry, struct inode *inode)
2664{
2665 if (inode) {
2666 security_d_instantiate(entry, inode);
2667 spin_lock(&inode->i_lock);
2668 }
2669 __d_add(entry, inode);
2670}
2671EXPORT_SYMBOL(d_add);
2672
2673/**
2674 * d_exact_alias - find and hash an exact unhashed alias
2675 * @entry: dentry to add
2676 * @inode: The inode to go with this dentry
2677 *
2678 * If an unhashed dentry with the same name/parent and desired
2679 * inode already exists, hash and return it. Otherwise, return
2680 * NULL.
2681 *
2682 * Parent directory should be locked.
2683 */
2684struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
2685{
2686 struct dentry *alias;
2687 unsigned int hash = entry->d_name.hash;
2688
2689 spin_lock(&inode->i_lock);
2690 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
2691 /*
2692 * Don't need alias->d_lock here, because aliases with
2693 * d_parent == entry->d_parent are not subject to name or
2694 * parent changes, because the parent inode i_mutex is held.
2695 */
2696 if (alias->d_name.hash != hash)
2697 continue;
2698 if (alias->d_parent != entry->d_parent)
2699 continue;
2700 if (!d_same_name(alias, entry->d_parent, &entry->d_name))
2701 continue;
2702 spin_lock(&alias->d_lock);
2703 if (!d_unhashed(alias)) {
2704 spin_unlock(&alias->d_lock);
2705 alias = NULL;
2706 } else {
2707 dget_dlock(alias);
2708 __d_rehash(alias);
2709 spin_unlock(&alias->d_lock);
2710 }
2711 spin_unlock(&inode->i_lock);
2712 return alias;
2713 }
2714 spin_unlock(&inode->i_lock);
2715 return NULL;
2716}
2717EXPORT_SYMBOL(d_exact_alias);
2718
2719static void swap_names(struct dentry *dentry, struct dentry *target)
2720{
2721 if (unlikely(dname_external(target))) {
2722 if (unlikely(dname_external(dentry))) {
2723 /*
2724 * Both external: swap the pointers
2725 */
2726 swap(target->d_name.name, dentry->d_name.name);
2727 } else {
2728 /*
2729 * dentry:internal, target:external. Steal target's
2730 * storage and make target internal.
2731 */
2732 memcpy(target->d_iname, dentry->d_name.name,
2733 dentry->d_name.len + 1);
2734 dentry->d_name.name = target->d_name.name;
2735 target->d_name.name = target->d_iname;
2736 }
2737 } else {
2738 if (unlikely(dname_external(dentry))) {
2739 /*
2740 * dentry:external, target:internal. Give dentry's
2741 * storage to target and make dentry internal
2742 */
2743 memcpy(dentry->d_iname, target->d_name.name,
2744 target->d_name.len + 1);
2745 target->d_name.name = dentry->d_name.name;
2746 dentry->d_name.name = dentry->d_iname;
2747 } else {
2748 /*
2749 * Both are internal.
2750 */
2751 unsigned int i;
2752 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
2753 for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
2754 swap(((long *) &dentry->d_iname)[i],
2755 ((long *) &target->d_iname)[i]);
2756 }
2757 }
2758 }
2759 swap(dentry->d_name.hash_len, target->d_name.hash_len);
2760}
2761
2762static void copy_name(struct dentry *dentry, struct dentry *target)
2763{
2764 struct external_name *old_name = NULL;
2765 if (unlikely(dname_external(dentry)))
2766 old_name = external_name(dentry);
2767 if (unlikely(dname_external(target))) {
2768 atomic_inc(&external_name(target)->u.count);
2769 dentry->d_name = target->d_name;
2770 } else {
2771 memcpy(dentry->d_iname, target->d_name.name,
2772 target->d_name.len + 1);
2773 dentry->d_name.name = dentry->d_iname;
2774 dentry->d_name.hash_len = target->d_name.hash_len;
2775 }
2776 if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
2777 kfree_rcu(old_name, u.head);
2778}
2779
2780/*
2781 * __d_move - move a dentry
2782 * @dentry: entry to move
2783 * @target: new dentry
2784 * @exchange: exchange the two dentries
2785 *
2786 * Update the dcache to reflect the move of a file name. Negative
2787 * dcache entries should not be moved in this way. Caller must hold
2788 * rename_lock, the i_mutex of the source and target directories,
2789 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2790 */
2791static void __d_move(struct dentry *dentry, struct dentry *target,
2792 bool exchange)
2793{
2794 struct dentry *old_parent, *p;
2795 wait_queue_head_t *d_wait;
2796 struct inode *dir = NULL;
2797 unsigned n;
2798
2799 WARN_ON(!dentry->d_inode);
2800 if (WARN_ON(dentry == target))
2801 return;
2802
2803 BUG_ON(d_ancestor(target, dentry));
2804 old_parent = dentry->d_parent;
2805 p = d_ancestor(old_parent, target);
2806 if (IS_ROOT(dentry)) {
2807 BUG_ON(p);
2808 spin_lock(&target->d_parent->d_lock);
2809 } else if (!p) {
2810 /* target is not a descendent of dentry->d_parent */
2811 spin_lock(&target->d_parent->d_lock);
2812 spin_lock_nested(&old_parent->d_lock, DENTRY_D_LOCK_NESTED);
2813 } else {
2814 BUG_ON(p == dentry);
2815 spin_lock(&old_parent->d_lock);
2816 if (p != target)
2817 spin_lock_nested(&target->d_parent->d_lock,
2818 DENTRY_D_LOCK_NESTED);
2819 }
2820 spin_lock_nested(&dentry->d_lock, 2);
2821 spin_lock_nested(&target->d_lock, 3);
2822
2823 if (unlikely(d_in_lookup(target))) {
2824 dir = target->d_parent->d_inode;
2825 n = start_dir_add(dir);
2826 d_wait = __d_lookup_unhash(target);
2827 }
2828
2829 write_seqcount_begin(&dentry->d_seq);
2830 write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
2831
2832 /* unhash both */
2833 if (!d_unhashed(dentry))
2834 ___d_drop(dentry);
2835 if (!d_unhashed(target))
2836 ___d_drop(target);
2837
2838 /* ... and switch them in the tree */
2839 dentry->d_parent = target->d_parent;
2840 if (!exchange) {
2841 copy_name(dentry, target);
2842 target->d_hash.pprev = NULL;
2843 dentry->d_parent->d_lockref.count++;
2844 if (dentry != old_parent) /* wasn't IS_ROOT */
2845 WARN_ON(!--old_parent->d_lockref.count);
2846 } else {
2847 target->d_parent = old_parent;
2848 swap_names(dentry, target);
2849 if (!hlist_unhashed(&target->d_sib))
2850 __hlist_del(&target->d_sib);
2851 hlist_add_head(&target->d_sib, &target->d_parent->d_children);
2852 __d_rehash(target);
2853 fsnotify_update_flags(target);
2854 }
2855 if (!hlist_unhashed(&dentry->d_sib))
2856 __hlist_del(&dentry->d_sib);
2857 hlist_add_head(&dentry->d_sib, &dentry->d_parent->d_children);
2858 __d_rehash(dentry);
2859 fsnotify_update_flags(dentry);
2860 fscrypt_handle_d_move(dentry);
2861
2862 write_seqcount_end(&target->d_seq);
2863 write_seqcount_end(&dentry->d_seq);
2864
2865 if (dir)
2866 end_dir_add(dir, n, d_wait);
2867
2868 if (dentry->d_parent != old_parent)
2869 spin_unlock(&dentry->d_parent->d_lock);
2870 if (dentry != old_parent)
2871 spin_unlock(&old_parent->d_lock);
2872 spin_unlock(&target->d_lock);
2873 spin_unlock(&dentry->d_lock);
2874}
2875
2876/*
2877 * d_move - move a dentry
2878 * @dentry: entry to move
2879 * @target: new dentry
2880 *
2881 * Update the dcache to reflect the move of a file name. Negative
2882 * dcache entries should not be moved in this way. See the locking
2883 * requirements for __d_move.
2884 */
2885void d_move(struct dentry *dentry, struct dentry *target)
2886{
2887 write_seqlock(&rename_lock);
2888 __d_move(dentry, target, false);
2889 write_sequnlock(&rename_lock);
2890}
2891EXPORT_SYMBOL(d_move);
2892
2893/*
2894 * d_exchange - exchange two dentries
2895 * @dentry1: first dentry
2896 * @dentry2: second dentry
2897 */
2898void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
2899{
2900 write_seqlock(&rename_lock);
2901
2902 WARN_ON(!dentry1->d_inode);
2903 WARN_ON(!dentry2->d_inode);
2904 WARN_ON(IS_ROOT(dentry1));
2905 WARN_ON(IS_ROOT(dentry2));
2906
2907 __d_move(dentry1, dentry2, true);
2908
2909 write_sequnlock(&rename_lock);
2910}
2911
2912/**
2913 * d_ancestor - search for an ancestor
2914 * @p1: ancestor dentry
2915 * @p2: child dentry
2916 *
2917 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2918 * an ancestor of p2, else NULL.
2919 */
2920struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2921{
2922 struct dentry *p;
2923
2924 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2925 if (p->d_parent == p1)
2926 return p;
2927 }
2928 return NULL;
2929}
2930
2931/*
2932 * This helper attempts to cope with remotely renamed directories
2933 *
2934 * It assumes that the caller is already holding
2935 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2936 *
2937 * Note: If ever the locking in lock_rename() changes, then please
2938 * remember to update this too...
2939 */
2940static int __d_unalias(struct dentry *dentry, struct dentry *alias)
2941{
2942 struct mutex *m1 = NULL;
2943 struct rw_semaphore *m2 = NULL;
2944 int ret = -ESTALE;
2945
2946 /* If alias and dentry share a parent, then no extra locks required */
2947 if (alias->d_parent == dentry->d_parent)
2948 goto out_unalias;
2949
2950 /* See lock_rename() */
2951 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
2952 goto out_err;
2953 m1 = &dentry->d_sb->s_vfs_rename_mutex;
2954 if (!inode_trylock_shared(alias->d_parent->d_inode))
2955 goto out_err;
2956 m2 = &alias->d_parent->d_inode->i_rwsem;
2957out_unalias:
2958 __d_move(alias, dentry, false);
2959 ret = 0;
2960out_err:
2961 if (m2)
2962 up_read(m2);
2963 if (m1)
2964 mutex_unlock(m1);
2965 return ret;
2966}
2967
2968/**
2969 * d_splice_alias - splice a disconnected dentry into the tree if one exists
2970 * @inode: the inode which may have a disconnected dentry
2971 * @dentry: a negative dentry which we want to point to the inode.
2972 *
2973 * If inode is a directory and has an IS_ROOT alias, then d_move that in
2974 * place of the given dentry and return it, else simply d_add the inode
2975 * to the dentry and return NULL.
2976 *
2977 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
2978 * we should error out: directories can't have multiple aliases.
2979 *
2980 * This is needed in the lookup routine of any filesystem that is exportable
2981 * (via knfsd) so that we can build dcache paths to directories effectively.
2982 *
2983 * If a dentry was found and moved, then it is returned. Otherwise NULL
2984 * is returned. This matches the expected return value of ->lookup.
2985 *
2986 * Cluster filesystems may call this function with a negative, hashed dentry.
2987 * In that case, we know that the inode will be a regular file, and also this
2988 * will only occur during atomic_open. So we need to check for the dentry
2989 * being already hashed only in the final case.
2990 */
2991struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
2992{
2993 if (IS_ERR(inode))
2994 return ERR_CAST(inode);
2995
2996 BUG_ON(!d_unhashed(dentry));
2997
2998 if (!inode)
2999 goto out;
3000
3001 security_d_instantiate(dentry, inode);
3002 spin_lock(&inode->i_lock);
3003 if (S_ISDIR(inode->i_mode)) {
3004 struct dentry *new = __d_find_any_alias(inode);
3005 if (unlikely(new)) {
3006 /* The reference to new ensures it remains an alias */
3007 spin_unlock(&inode->i_lock);
3008 write_seqlock(&rename_lock);
3009 if (unlikely(d_ancestor(new, dentry))) {
3010 write_sequnlock(&rename_lock);
3011 dput(new);
3012 new = ERR_PTR(-ELOOP);
3013 pr_warn_ratelimited(
3014 "VFS: Lookup of '%s' in %s %s"
3015 " would have caused loop\n",
3016 dentry->d_name.name,
3017 inode->i_sb->s_type->name,
3018 inode->i_sb->s_id);
3019 } else if (!IS_ROOT(new)) {
3020 struct dentry *old_parent = dget(new->d_parent);
3021 int err = __d_unalias(dentry, new);
3022 write_sequnlock(&rename_lock);
3023 if (err) {
3024 dput(new);
3025 new = ERR_PTR(err);
3026 }
3027 dput(old_parent);
3028 } else {
3029 __d_move(new, dentry, false);
3030 write_sequnlock(&rename_lock);
3031 }
3032 iput(inode);
3033 return new;
3034 }
3035 }
3036out:
3037 __d_add(dentry, inode);
3038 return NULL;
3039}
3040EXPORT_SYMBOL(d_splice_alias);
3041
3042/*
3043 * Test whether new_dentry is a subdirectory of old_dentry.
3044 *
3045 * Trivially implemented using the dcache structure
3046 */
3047
3048/**
3049 * is_subdir - is new dentry a subdirectory of old_dentry
3050 * @new_dentry: new dentry
3051 * @old_dentry: old dentry
3052 *
3053 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3054 * Returns false otherwise.
3055 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3056 */
3057
3058bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
3059{
3060 bool subdir;
3061 unsigned seq;
3062
3063 if (new_dentry == old_dentry)
3064 return true;
3065
3066 /* Access d_parent under rcu as d_move() may change it. */
3067 rcu_read_lock();
3068 seq = read_seqbegin(&rename_lock);
3069 subdir = d_ancestor(old_dentry, new_dentry);
3070 /* Try lockless once... */
3071 if (read_seqretry(&rename_lock, seq)) {
3072 /* ...else acquire lock for progress even on deep chains. */
3073 read_seqlock_excl(&rename_lock);
3074 subdir = d_ancestor(old_dentry, new_dentry);
3075 read_sequnlock_excl(&rename_lock);
3076 }
3077 rcu_read_unlock();
3078 return subdir;
3079}
3080EXPORT_SYMBOL(is_subdir);
3081
3082static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
3083{
3084 struct dentry *root = data;
3085 if (dentry != root) {
3086 if (d_unhashed(dentry) || !dentry->d_inode)
3087 return D_WALK_SKIP;
3088
3089 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
3090 dentry->d_flags |= DCACHE_GENOCIDE;
3091 dentry->d_lockref.count--;
3092 }
3093 }
3094 return D_WALK_CONTINUE;
3095}
3096
3097void d_genocide(struct dentry *parent)
3098{
3099 d_walk(parent, parent, d_genocide_kill);
3100}
3101
3102void d_mark_tmpfile(struct file *file, struct inode *inode)
3103{
3104 struct dentry *dentry = file->f_path.dentry;
3105
3106 BUG_ON(dentry->d_name.name != dentry->d_iname ||
3107 !hlist_unhashed(&dentry->d_u.d_alias) ||
3108 !d_unlinked(dentry));
3109 spin_lock(&dentry->d_parent->d_lock);
3110 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
3111 dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
3112 (unsigned long long)inode->i_ino);
3113 spin_unlock(&dentry->d_lock);
3114 spin_unlock(&dentry->d_parent->d_lock);
3115}
3116EXPORT_SYMBOL(d_mark_tmpfile);
3117
3118void d_tmpfile(struct file *file, struct inode *inode)
3119{
3120 struct dentry *dentry = file->f_path.dentry;
3121
3122 inode_dec_link_count(inode);
3123 d_mark_tmpfile(file, inode);
3124 d_instantiate(dentry, inode);
3125}
3126EXPORT_SYMBOL(d_tmpfile);
3127
3128/*
3129 * Obtain inode number of the parent dentry.
3130 */
3131ino_t d_parent_ino(struct dentry *dentry)
3132{
3133 struct dentry *parent;
3134 struct inode *iparent;
3135 unsigned seq;
3136 ino_t ret;
3137
3138 scoped_guard(rcu) {
3139 seq = raw_seqcount_begin(&dentry->d_seq);
3140 parent = READ_ONCE(dentry->d_parent);
3141 iparent = d_inode_rcu(parent);
3142 if (likely(iparent)) {
3143 ret = iparent->i_ino;
3144 if (!read_seqcount_retry(&dentry->d_seq, seq))
3145 return ret;
3146 }
3147 }
3148
3149 spin_lock(&dentry->d_lock);
3150 ret = dentry->d_parent->d_inode->i_ino;
3151 spin_unlock(&dentry->d_lock);
3152 return ret;
3153}
3154EXPORT_SYMBOL(d_parent_ino);
3155
3156static __initdata unsigned long dhash_entries;
3157static int __init set_dhash_entries(char *str)
3158{
3159 if (!str)
3160 return 0;
3161 dhash_entries = simple_strtoul(str, &str, 0);
3162 return 1;
3163}
3164__setup("dhash_entries=", set_dhash_entries);
3165
3166static void __init dcache_init_early(void)
3167{
3168 /* If hashes are distributed across NUMA nodes, defer
3169 * hash allocation until vmalloc space is available.
3170 */
3171 if (hashdist)
3172 return;
3173
3174 dentry_hashtable =
3175 alloc_large_system_hash("Dentry cache",
3176 sizeof(struct hlist_bl_head),
3177 dhash_entries,
3178 13,
3179 HASH_EARLY | HASH_ZERO,
3180 &d_hash_shift,
3181 NULL,
3182 0,
3183 0);
3184 d_hash_shift = 32 - d_hash_shift;
3185
3186 runtime_const_init(shift, d_hash_shift);
3187 runtime_const_init(ptr, dentry_hashtable);
3188}
3189
3190static void __init dcache_init(void)
3191{
3192 /*
3193 * A constructor could be added for stable state like the lists,
3194 * but it is probably not worth it because of the cache nature
3195 * of the dcache.
3196 */
3197 dentry_cache = KMEM_CACHE_USERCOPY(dentry,
3198 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_ACCOUNT,
3199 d_iname);
3200
3201 /* Hash may have been set up in dcache_init_early */
3202 if (!hashdist)
3203 return;
3204
3205 dentry_hashtable =
3206 alloc_large_system_hash("Dentry cache",
3207 sizeof(struct hlist_bl_head),
3208 dhash_entries,
3209 13,
3210 HASH_ZERO,
3211 &d_hash_shift,
3212 NULL,
3213 0,
3214 0);
3215 d_hash_shift = 32 - d_hash_shift;
3216
3217 runtime_const_init(shift, d_hash_shift);
3218 runtime_const_init(ptr, dentry_hashtable);
3219}
3220
3221/* SLAB cache for __getname() consumers */
3222struct kmem_cache *names_cachep __ro_after_init;
3223EXPORT_SYMBOL(names_cachep);
3224
3225void __init vfs_caches_init_early(void)
3226{
3227 int i;
3228
3229 for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++)
3230 INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]);
3231
3232 dcache_init_early();
3233 inode_init_early();
3234}
3235
3236void __init vfs_caches_init(void)
3237{
3238 names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0,
3239 SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL);
3240
3241 dcache_init();
3242 inode_init();
3243 files_init();
3244 files_maxfiles_init();
3245 mnt_init();
3246 bdev_cache_init();
3247 chrdev_init();
3248}
1/*
2 * fs/dcache.c
3 *
4 * Complete reimplementation
5 * (C) 1997 Thomas Schoebel-Theuer,
6 * with heavy changes by Linus Torvalds
7 */
8
9/*
10 * Notes on the allocation strategy:
11 *
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.
15 */
16
17#include <linux/syscalls.h>
18#include <linux/string.h>
19#include <linux/mm.h>
20#include <linux/fs.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/module.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 "internal.h"
40
41/*
42 * Usage:
43 * dcache->d_inode->i_lock protects:
44 * - i_dentry, d_alias, d_inode of aliases
45 * dcache_hash_bucket lock protects:
46 * - the dcache hash table
47 * s_anon bl list spinlock protects:
48 * - the s_anon list (see __d_drop)
49 * dcache_lru_lock protects:
50 * - the dcache lru lists and counters
51 * d_lock protects:
52 * - d_flags
53 * - d_name
54 * - d_lru
55 * - d_count
56 * - d_unhashed()
57 * - d_parent and d_subdirs
58 * - childrens' d_child and d_parent
59 * - d_alias, d_inode
60 *
61 * Ordering:
62 * dentry->d_inode->i_lock
63 * dentry->d_lock
64 * dcache_lru_lock
65 * dcache_hash_bucket lock
66 * s_anon lock
67 *
68 * If there is an ancestor relationship:
69 * dentry->d_parent->...->d_parent->d_lock
70 * ...
71 * dentry->d_parent->d_lock
72 * dentry->d_lock
73 *
74 * If no ancestor relationship:
75 * if (dentry1 < dentry2)
76 * dentry1->d_lock
77 * dentry2->d_lock
78 */
79int sysctl_vfs_cache_pressure __read_mostly = 100;
80EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
81
82static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
83__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
84
85EXPORT_SYMBOL(rename_lock);
86
87static struct kmem_cache *dentry_cache __read_mostly;
88
89/*
90 * This is the single most critical data structure when it comes
91 * to the dcache: the hashtable for lookups. Somebody should try
92 * to make this good - I've just made it work.
93 *
94 * This hash-function tries to avoid losing too many bits of hash
95 * information, yet avoid using a prime hash-size or similar.
96 */
97#define D_HASHBITS d_hash_shift
98#define D_HASHMASK d_hash_mask
99
100static unsigned int d_hash_mask __read_mostly;
101static unsigned int d_hash_shift __read_mostly;
102
103static struct hlist_bl_head *dentry_hashtable __read_mostly;
104
105static inline struct hlist_bl_head *d_hash(struct dentry *parent,
106 unsigned long hash)
107{
108 hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
109 hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
110 return dentry_hashtable + (hash & D_HASHMASK);
111}
112
113/* Statistics gathering. */
114struct dentry_stat_t dentry_stat = {
115 .age_limit = 45,
116};
117
118static DEFINE_PER_CPU(unsigned int, nr_dentry);
119
120#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
121static int get_nr_dentry(void)
122{
123 int i;
124 int sum = 0;
125 for_each_possible_cpu(i)
126 sum += per_cpu(nr_dentry, i);
127 return sum < 0 ? 0 : sum;
128}
129
130int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
131 size_t *lenp, loff_t *ppos)
132{
133 dentry_stat.nr_dentry = get_nr_dentry();
134 return proc_dointvec(table, write, buffer, lenp, ppos);
135}
136#endif
137
138static void __d_free(struct rcu_head *head)
139{
140 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
141
142 WARN_ON(!list_empty(&dentry->d_alias));
143 if (dname_external(dentry))
144 kfree(dentry->d_name.name);
145 kmem_cache_free(dentry_cache, dentry);
146}
147
148/*
149 * no locks, please.
150 */
151static void d_free(struct dentry *dentry)
152{
153 BUG_ON(dentry->d_count);
154 this_cpu_dec(nr_dentry);
155 if (dentry->d_op && dentry->d_op->d_release)
156 dentry->d_op->d_release(dentry);
157
158 /* if dentry was never visible to RCU, immediate free is OK */
159 if (!(dentry->d_flags & DCACHE_RCUACCESS))
160 __d_free(&dentry->d_u.d_rcu);
161 else
162 call_rcu(&dentry->d_u.d_rcu, __d_free);
163}
164
165/**
166 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
167 * @dentry: the target dentry
168 * After this call, in-progress rcu-walk path lookup will fail. This
169 * should be called after unhashing, and after changing d_inode (if
170 * the dentry has not already been unhashed).
171 */
172static inline void dentry_rcuwalk_barrier(struct dentry *dentry)
173{
174 assert_spin_locked(&dentry->d_lock);
175 /* Go through a barrier */
176 write_seqcount_barrier(&dentry->d_seq);
177}
178
179/*
180 * Release the dentry's inode, using the filesystem
181 * d_iput() operation if defined. Dentry has no refcount
182 * and is unhashed.
183 */
184static void dentry_iput(struct dentry * dentry)
185 __releases(dentry->d_lock)
186 __releases(dentry->d_inode->i_lock)
187{
188 struct inode *inode = dentry->d_inode;
189 if (inode) {
190 dentry->d_inode = NULL;
191 list_del_init(&dentry->d_alias);
192 spin_unlock(&dentry->d_lock);
193 spin_unlock(&inode->i_lock);
194 if (!inode->i_nlink)
195 fsnotify_inoderemove(inode);
196 if (dentry->d_op && dentry->d_op->d_iput)
197 dentry->d_op->d_iput(dentry, inode);
198 else
199 iput(inode);
200 } else {
201 spin_unlock(&dentry->d_lock);
202 }
203}
204
205/*
206 * Release the dentry's inode, using the filesystem
207 * d_iput() operation if defined. dentry remains in-use.
208 */
209static void dentry_unlink_inode(struct dentry * dentry)
210 __releases(dentry->d_lock)
211 __releases(dentry->d_inode->i_lock)
212{
213 struct inode *inode = dentry->d_inode;
214 dentry->d_inode = NULL;
215 list_del_init(&dentry->d_alias);
216 dentry_rcuwalk_barrier(dentry);
217 spin_unlock(&dentry->d_lock);
218 spin_unlock(&inode->i_lock);
219 if (!inode->i_nlink)
220 fsnotify_inoderemove(inode);
221 if (dentry->d_op && dentry->d_op->d_iput)
222 dentry->d_op->d_iput(dentry, inode);
223 else
224 iput(inode);
225}
226
227/*
228 * dentry_lru_(add|del|move_tail) must be called with d_lock held.
229 */
230static void dentry_lru_add(struct dentry *dentry)
231{
232 if (list_empty(&dentry->d_lru)) {
233 spin_lock(&dcache_lru_lock);
234 list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
235 dentry->d_sb->s_nr_dentry_unused++;
236 dentry_stat.nr_unused++;
237 spin_unlock(&dcache_lru_lock);
238 }
239}
240
241static void __dentry_lru_del(struct dentry *dentry)
242{
243 list_del_init(&dentry->d_lru);
244 dentry->d_sb->s_nr_dentry_unused--;
245 dentry_stat.nr_unused--;
246}
247
248static void dentry_lru_del(struct dentry *dentry)
249{
250 if (!list_empty(&dentry->d_lru)) {
251 spin_lock(&dcache_lru_lock);
252 __dentry_lru_del(dentry);
253 spin_unlock(&dcache_lru_lock);
254 }
255}
256
257static void dentry_lru_move_tail(struct dentry *dentry)
258{
259 spin_lock(&dcache_lru_lock);
260 if (list_empty(&dentry->d_lru)) {
261 list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
262 dentry->d_sb->s_nr_dentry_unused++;
263 dentry_stat.nr_unused++;
264 } else {
265 list_move_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
266 }
267 spin_unlock(&dcache_lru_lock);
268}
269
270/**
271 * d_kill - kill dentry and return parent
272 * @dentry: dentry to kill
273 * @parent: parent dentry
274 *
275 * The dentry must already be unhashed and removed from the LRU.
276 *
277 * If this is the root of the dentry tree, return NULL.
278 *
279 * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
280 * d_kill.
281 */
282static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
283 __releases(dentry->d_lock)
284 __releases(parent->d_lock)
285 __releases(dentry->d_inode->i_lock)
286{
287 list_del(&dentry->d_u.d_child);
288 /*
289 * Inform try_to_ascend() that we are no longer attached to the
290 * dentry tree
291 */
292 dentry->d_flags |= DCACHE_DISCONNECTED;
293 if (parent)
294 spin_unlock(&parent->d_lock);
295 dentry_iput(dentry);
296 /*
297 * dentry_iput drops the locks, at which point nobody (except
298 * transient RCU lookups) can reach this dentry.
299 */
300 d_free(dentry);
301 return parent;
302}
303
304/*
305 * Unhash a dentry without inserting an RCU walk barrier or checking that
306 * dentry->d_lock is locked. The caller must take care of that, if
307 * appropriate.
308 */
309static void __d_shrink(struct dentry *dentry)
310{
311 if (!d_unhashed(dentry)) {
312 struct hlist_bl_head *b;
313 if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
314 b = &dentry->d_sb->s_anon;
315 else
316 b = d_hash(dentry->d_parent, dentry->d_name.hash);
317
318 hlist_bl_lock(b);
319 __hlist_bl_del(&dentry->d_hash);
320 dentry->d_hash.pprev = NULL;
321 hlist_bl_unlock(b);
322 }
323}
324
325/**
326 * d_drop - drop a dentry
327 * @dentry: dentry to drop
328 *
329 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
330 * be found through a VFS lookup any more. Note that this is different from
331 * deleting the dentry - d_delete will try to mark the dentry negative if
332 * possible, giving a successful _negative_ lookup, while d_drop will
333 * just make the cache lookup fail.
334 *
335 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
336 * reason (NFS timeouts or autofs deletes).
337 *
338 * __d_drop requires dentry->d_lock.
339 */
340void __d_drop(struct dentry *dentry)
341{
342 if (!d_unhashed(dentry)) {
343 __d_shrink(dentry);
344 dentry_rcuwalk_barrier(dentry);
345 }
346}
347EXPORT_SYMBOL(__d_drop);
348
349void d_drop(struct dentry *dentry)
350{
351 spin_lock(&dentry->d_lock);
352 __d_drop(dentry);
353 spin_unlock(&dentry->d_lock);
354}
355EXPORT_SYMBOL(d_drop);
356
357/*
358 * d_clear_need_lookup - drop a dentry from cache and clear the need lookup flag
359 * @dentry: dentry to drop
360 *
361 * This is called when we do a lookup on a placeholder dentry that needed to be
362 * looked up. The dentry should have been hashed in order for it to be found by
363 * the lookup code, but now needs to be unhashed while we do the actual lookup
364 * and clear the DCACHE_NEED_LOOKUP flag.
365 */
366void d_clear_need_lookup(struct dentry *dentry)
367{
368 spin_lock(&dentry->d_lock);
369 __d_drop(dentry);
370 dentry->d_flags &= ~DCACHE_NEED_LOOKUP;
371 spin_unlock(&dentry->d_lock);
372}
373EXPORT_SYMBOL(d_clear_need_lookup);
374
375/*
376 * Finish off a dentry we've decided to kill.
377 * dentry->d_lock must be held, returns with it unlocked.
378 * If ref is non-zero, then decrement the refcount too.
379 * Returns dentry requiring refcount drop, or NULL if we're done.
380 */
381static inline struct dentry *dentry_kill(struct dentry *dentry, int ref)
382 __releases(dentry->d_lock)
383{
384 struct inode *inode;
385 struct dentry *parent;
386
387 inode = dentry->d_inode;
388 if (inode && !spin_trylock(&inode->i_lock)) {
389relock:
390 spin_unlock(&dentry->d_lock);
391 cpu_relax();
392 return dentry; /* try again with same dentry */
393 }
394 if (IS_ROOT(dentry))
395 parent = NULL;
396 else
397 parent = dentry->d_parent;
398 if (parent && !spin_trylock(&parent->d_lock)) {
399 if (inode)
400 spin_unlock(&inode->i_lock);
401 goto relock;
402 }
403
404 if (ref)
405 dentry->d_count--;
406 /* if dentry was on the d_lru list delete it from there */
407 dentry_lru_del(dentry);
408 /* if it was on the hash then remove it */
409 __d_drop(dentry);
410 return d_kill(dentry, parent);
411}
412
413/*
414 * This is dput
415 *
416 * This is complicated by the fact that we do not want to put
417 * dentries that are no longer on any hash chain on the unused
418 * list: we'd much rather just get rid of them immediately.
419 *
420 * However, that implies that we have to traverse the dentry
421 * tree upwards to the parents which might _also_ now be
422 * scheduled for deletion (it may have been only waiting for
423 * its last child to go away).
424 *
425 * This tail recursion is done by hand as we don't want to depend
426 * on the compiler to always get this right (gcc generally doesn't).
427 * Real recursion would eat up our stack space.
428 */
429
430/*
431 * dput - release a dentry
432 * @dentry: dentry to release
433 *
434 * Release a dentry. This will drop the usage count and if appropriate
435 * call the dentry unlink method as well as removing it from the queues and
436 * releasing its resources. If the parent dentries were scheduled for release
437 * they too may now get deleted.
438 */
439void dput(struct dentry *dentry)
440{
441 if (!dentry)
442 return;
443
444repeat:
445 if (dentry->d_count == 1)
446 might_sleep();
447 spin_lock(&dentry->d_lock);
448 BUG_ON(!dentry->d_count);
449 if (dentry->d_count > 1) {
450 dentry->d_count--;
451 spin_unlock(&dentry->d_lock);
452 return;
453 }
454
455 if (dentry->d_flags & DCACHE_OP_DELETE) {
456 if (dentry->d_op->d_delete(dentry))
457 goto kill_it;
458 }
459
460 /* Unreachable? Get rid of it */
461 if (d_unhashed(dentry))
462 goto kill_it;
463
464 /*
465 * If this dentry needs lookup, don't set the referenced flag so that it
466 * is more likely to be cleaned up by the dcache shrinker in case of
467 * memory pressure.
468 */
469 if (!d_need_lookup(dentry))
470 dentry->d_flags |= DCACHE_REFERENCED;
471 dentry_lru_add(dentry);
472
473 dentry->d_count--;
474 spin_unlock(&dentry->d_lock);
475 return;
476
477kill_it:
478 dentry = dentry_kill(dentry, 1);
479 if (dentry)
480 goto repeat;
481}
482EXPORT_SYMBOL(dput);
483
484/**
485 * d_invalidate - invalidate a dentry
486 * @dentry: dentry to invalidate
487 *
488 * Try to invalidate the dentry if it turns out to be
489 * possible. If there are other dentries that can be
490 * reached through this one we can't delete it and we
491 * return -EBUSY. On success we return 0.
492 *
493 * no dcache lock.
494 */
495
496int d_invalidate(struct dentry * dentry)
497{
498 /*
499 * If it's already been dropped, return OK.
500 */
501 spin_lock(&dentry->d_lock);
502 if (d_unhashed(dentry)) {
503 spin_unlock(&dentry->d_lock);
504 return 0;
505 }
506 /*
507 * Check whether to do a partial shrink_dcache
508 * to get rid of unused child entries.
509 */
510 if (!list_empty(&dentry->d_subdirs)) {
511 spin_unlock(&dentry->d_lock);
512 shrink_dcache_parent(dentry);
513 spin_lock(&dentry->d_lock);
514 }
515
516 /*
517 * Somebody else still using it?
518 *
519 * If it's a directory, we can't drop it
520 * for fear of somebody re-populating it
521 * with children (even though dropping it
522 * would make it unreachable from the root,
523 * we might still populate it if it was a
524 * working directory or similar).
525 */
526 if (dentry->d_count > 1) {
527 if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
528 spin_unlock(&dentry->d_lock);
529 return -EBUSY;
530 }
531 }
532
533 __d_drop(dentry);
534 spin_unlock(&dentry->d_lock);
535 return 0;
536}
537EXPORT_SYMBOL(d_invalidate);
538
539/* This must be called with d_lock held */
540static inline void __dget_dlock(struct dentry *dentry)
541{
542 dentry->d_count++;
543}
544
545static inline void __dget(struct dentry *dentry)
546{
547 spin_lock(&dentry->d_lock);
548 __dget_dlock(dentry);
549 spin_unlock(&dentry->d_lock);
550}
551
552struct dentry *dget_parent(struct dentry *dentry)
553{
554 struct dentry *ret;
555
556repeat:
557 /*
558 * Don't need rcu_dereference because we re-check it was correct under
559 * the lock.
560 */
561 rcu_read_lock();
562 ret = dentry->d_parent;
563 spin_lock(&ret->d_lock);
564 if (unlikely(ret != dentry->d_parent)) {
565 spin_unlock(&ret->d_lock);
566 rcu_read_unlock();
567 goto repeat;
568 }
569 rcu_read_unlock();
570 BUG_ON(!ret->d_count);
571 ret->d_count++;
572 spin_unlock(&ret->d_lock);
573 return ret;
574}
575EXPORT_SYMBOL(dget_parent);
576
577/**
578 * d_find_alias - grab a hashed alias of inode
579 * @inode: inode in question
580 * @want_discon: flag, used by d_splice_alias, to request
581 * that only a DISCONNECTED alias be returned.
582 *
583 * If inode has a hashed alias, or is a directory and has any alias,
584 * acquire the reference to alias and return it. Otherwise return NULL.
585 * Notice that if inode is a directory there can be only one alias and
586 * it can be unhashed only if it has no children, or if it is the root
587 * of a filesystem.
588 *
589 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
590 * any other hashed alias over that one unless @want_discon is set,
591 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
592 */
593static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
594{
595 struct dentry *alias, *discon_alias;
596
597again:
598 discon_alias = NULL;
599 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
600 spin_lock(&alias->d_lock);
601 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
602 if (IS_ROOT(alias) &&
603 (alias->d_flags & DCACHE_DISCONNECTED)) {
604 discon_alias = alias;
605 } else if (!want_discon) {
606 __dget_dlock(alias);
607 spin_unlock(&alias->d_lock);
608 return alias;
609 }
610 }
611 spin_unlock(&alias->d_lock);
612 }
613 if (discon_alias) {
614 alias = discon_alias;
615 spin_lock(&alias->d_lock);
616 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
617 if (IS_ROOT(alias) &&
618 (alias->d_flags & DCACHE_DISCONNECTED)) {
619 __dget_dlock(alias);
620 spin_unlock(&alias->d_lock);
621 return alias;
622 }
623 }
624 spin_unlock(&alias->d_lock);
625 goto again;
626 }
627 return NULL;
628}
629
630struct dentry *d_find_alias(struct inode *inode)
631{
632 struct dentry *de = NULL;
633
634 if (!list_empty(&inode->i_dentry)) {
635 spin_lock(&inode->i_lock);
636 de = __d_find_alias(inode, 0);
637 spin_unlock(&inode->i_lock);
638 }
639 return de;
640}
641EXPORT_SYMBOL(d_find_alias);
642
643/*
644 * Try to kill dentries associated with this inode.
645 * WARNING: you must own a reference to inode.
646 */
647void d_prune_aliases(struct inode *inode)
648{
649 struct dentry *dentry;
650restart:
651 spin_lock(&inode->i_lock);
652 list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
653 spin_lock(&dentry->d_lock);
654 if (!dentry->d_count) {
655 __dget_dlock(dentry);
656 __d_drop(dentry);
657 spin_unlock(&dentry->d_lock);
658 spin_unlock(&inode->i_lock);
659 dput(dentry);
660 goto restart;
661 }
662 spin_unlock(&dentry->d_lock);
663 }
664 spin_unlock(&inode->i_lock);
665}
666EXPORT_SYMBOL(d_prune_aliases);
667
668/*
669 * Try to throw away a dentry - free the inode, dput the parent.
670 * Requires dentry->d_lock is held, and dentry->d_count == 0.
671 * Releases dentry->d_lock.
672 *
673 * This may fail if locks cannot be acquired no problem, just try again.
674 */
675static void try_prune_one_dentry(struct dentry *dentry)
676 __releases(dentry->d_lock)
677{
678 struct dentry *parent;
679
680 parent = dentry_kill(dentry, 0);
681 /*
682 * If dentry_kill returns NULL, we have nothing more to do.
683 * if it returns the same dentry, trylocks failed. In either
684 * case, just loop again.
685 *
686 * Otherwise, we need to prune ancestors too. This is necessary
687 * to prevent quadratic behavior of shrink_dcache_parent(), but
688 * is also expected to be beneficial in reducing dentry cache
689 * fragmentation.
690 */
691 if (!parent)
692 return;
693 if (parent == dentry)
694 return;
695
696 /* Prune ancestors. */
697 dentry = parent;
698 while (dentry) {
699 spin_lock(&dentry->d_lock);
700 if (dentry->d_count > 1) {
701 dentry->d_count--;
702 spin_unlock(&dentry->d_lock);
703 return;
704 }
705 dentry = dentry_kill(dentry, 1);
706 }
707}
708
709static void shrink_dentry_list(struct list_head *list)
710{
711 struct dentry *dentry;
712
713 rcu_read_lock();
714 for (;;) {
715 dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
716 if (&dentry->d_lru == list)
717 break; /* empty */
718 spin_lock(&dentry->d_lock);
719 if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
720 spin_unlock(&dentry->d_lock);
721 continue;
722 }
723
724 /*
725 * We found an inuse dentry which was not removed from
726 * the LRU because of laziness during lookup. Do not free
727 * it - just keep it off the LRU list.
728 */
729 if (dentry->d_count) {
730 dentry_lru_del(dentry);
731 spin_unlock(&dentry->d_lock);
732 continue;
733 }
734
735 rcu_read_unlock();
736
737 try_prune_one_dentry(dentry);
738
739 rcu_read_lock();
740 }
741 rcu_read_unlock();
742}
743
744/**
745 * __shrink_dcache_sb - shrink the dentry LRU on a given superblock
746 * @sb: superblock to shrink dentry LRU.
747 * @count: number of entries to prune
748 * @flags: flags to control the dentry processing
749 *
750 * If flags contains DCACHE_REFERENCED reference dentries will not be pruned.
751 */
752static void __shrink_dcache_sb(struct super_block *sb, int count, int flags)
753{
754 struct dentry *dentry;
755 LIST_HEAD(referenced);
756 LIST_HEAD(tmp);
757
758relock:
759 spin_lock(&dcache_lru_lock);
760 while (!list_empty(&sb->s_dentry_lru)) {
761 dentry = list_entry(sb->s_dentry_lru.prev,
762 struct dentry, d_lru);
763 BUG_ON(dentry->d_sb != sb);
764
765 if (!spin_trylock(&dentry->d_lock)) {
766 spin_unlock(&dcache_lru_lock);
767 cpu_relax();
768 goto relock;
769 }
770
771 /*
772 * If we are honouring the DCACHE_REFERENCED flag and the
773 * dentry has this flag set, don't free it. Clear the flag
774 * and put it back on the LRU.
775 */
776 if (flags & DCACHE_REFERENCED &&
777 dentry->d_flags & DCACHE_REFERENCED) {
778 dentry->d_flags &= ~DCACHE_REFERENCED;
779 list_move(&dentry->d_lru, &referenced);
780 spin_unlock(&dentry->d_lock);
781 } else {
782 list_move_tail(&dentry->d_lru, &tmp);
783 spin_unlock(&dentry->d_lock);
784 if (!--count)
785 break;
786 }
787 cond_resched_lock(&dcache_lru_lock);
788 }
789 if (!list_empty(&referenced))
790 list_splice(&referenced, &sb->s_dentry_lru);
791 spin_unlock(&dcache_lru_lock);
792
793 shrink_dentry_list(&tmp);
794}
795
796/**
797 * prune_dcache_sb - shrink the dcache
798 * @sb: superblock
799 * @nr_to_scan: number of entries to try to free
800 *
801 * Attempt to shrink the superblock dcache LRU by @nr_to_scan entries. This is
802 * done when we need more memory an called from the superblock shrinker
803 * function.
804 *
805 * This function may fail to free any resources if all the dentries are in
806 * use.
807 */
808void prune_dcache_sb(struct super_block *sb, int nr_to_scan)
809{
810 __shrink_dcache_sb(sb, nr_to_scan, DCACHE_REFERENCED);
811}
812
813/**
814 * shrink_dcache_sb - shrink dcache for a superblock
815 * @sb: superblock
816 *
817 * Shrink the dcache for the specified super block. This is used to free
818 * the dcache before unmounting a file system.
819 */
820void shrink_dcache_sb(struct super_block *sb)
821{
822 LIST_HEAD(tmp);
823
824 spin_lock(&dcache_lru_lock);
825 while (!list_empty(&sb->s_dentry_lru)) {
826 list_splice_init(&sb->s_dentry_lru, &tmp);
827 spin_unlock(&dcache_lru_lock);
828 shrink_dentry_list(&tmp);
829 spin_lock(&dcache_lru_lock);
830 }
831 spin_unlock(&dcache_lru_lock);
832}
833EXPORT_SYMBOL(shrink_dcache_sb);
834
835/*
836 * destroy a single subtree of dentries for unmount
837 * - see the comments on shrink_dcache_for_umount() for a description of the
838 * locking
839 */
840static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
841{
842 struct dentry *parent;
843
844 BUG_ON(!IS_ROOT(dentry));
845
846 for (;;) {
847 /* descend to the first leaf in the current subtree */
848 while (!list_empty(&dentry->d_subdirs))
849 dentry = list_entry(dentry->d_subdirs.next,
850 struct dentry, d_u.d_child);
851
852 /* consume the dentries from this leaf up through its parents
853 * until we find one with children or run out altogether */
854 do {
855 struct inode *inode;
856
857 /* detach from the system */
858 dentry_lru_del(dentry);
859 __d_shrink(dentry);
860
861 if (dentry->d_count != 0) {
862 printk(KERN_ERR
863 "BUG: Dentry %p{i=%lx,n=%s}"
864 " still in use (%d)"
865 " [unmount of %s %s]\n",
866 dentry,
867 dentry->d_inode ?
868 dentry->d_inode->i_ino : 0UL,
869 dentry->d_name.name,
870 dentry->d_count,
871 dentry->d_sb->s_type->name,
872 dentry->d_sb->s_id);
873 BUG();
874 }
875
876 if (IS_ROOT(dentry)) {
877 parent = NULL;
878 list_del(&dentry->d_u.d_child);
879 } else {
880 parent = dentry->d_parent;
881 parent->d_count--;
882 list_del(&dentry->d_u.d_child);
883 }
884
885 inode = dentry->d_inode;
886 if (inode) {
887 dentry->d_inode = NULL;
888 list_del_init(&dentry->d_alias);
889 if (dentry->d_op && dentry->d_op->d_iput)
890 dentry->d_op->d_iput(dentry, inode);
891 else
892 iput(inode);
893 }
894
895 d_free(dentry);
896
897 /* finished when we fall off the top of the tree,
898 * otherwise we ascend to the parent and move to the
899 * next sibling if there is one */
900 if (!parent)
901 return;
902 dentry = parent;
903 } while (list_empty(&dentry->d_subdirs));
904
905 dentry = list_entry(dentry->d_subdirs.next,
906 struct dentry, d_u.d_child);
907 }
908}
909
910/*
911 * destroy the dentries attached to a superblock on unmounting
912 * - we don't need to use dentry->d_lock because:
913 * - the superblock is detached from all mountings and open files, so the
914 * dentry trees will not be rearranged by the VFS
915 * - s_umount is write-locked, so the memory pressure shrinker will ignore
916 * any dentries belonging to this superblock that it comes across
917 * - the filesystem itself is no longer permitted to rearrange the dentries
918 * in this superblock
919 */
920void shrink_dcache_for_umount(struct super_block *sb)
921{
922 struct dentry *dentry;
923
924 if (down_read_trylock(&sb->s_umount))
925 BUG();
926
927 dentry = sb->s_root;
928 sb->s_root = NULL;
929 dentry->d_count--;
930 shrink_dcache_for_umount_subtree(dentry);
931
932 while (!hlist_bl_empty(&sb->s_anon)) {
933 dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
934 shrink_dcache_for_umount_subtree(dentry);
935 }
936}
937
938/*
939 * This tries to ascend one level of parenthood, but
940 * we can race with renaming, so we need to re-check
941 * the parenthood after dropping the lock and check
942 * that the sequence number still matches.
943 */
944static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq)
945{
946 struct dentry *new = old->d_parent;
947
948 rcu_read_lock();
949 spin_unlock(&old->d_lock);
950 spin_lock(&new->d_lock);
951
952 /*
953 * might go back up the wrong parent if we have had a rename
954 * or deletion
955 */
956 if (new != old->d_parent ||
957 (old->d_flags & DCACHE_DISCONNECTED) ||
958 (!locked && read_seqretry(&rename_lock, seq))) {
959 spin_unlock(&new->d_lock);
960 new = NULL;
961 }
962 rcu_read_unlock();
963 return new;
964}
965
966
967/*
968 * Search for at least 1 mount point in the dentry's subdirs.
969 * We descend to the next level whenever the d_subdirs
970 * list is non-empty and continue searching.
971 */
972
973/**
974 * have_submounts - check for mounts over a dentry
975 * @parent: dentry to check.
976 *
977 * Return true if the parent or its subdirectories contain
978 * a mount point
979 */
980int have_submounts(struct dentry *parent)
981{
982 struct dentry *this_parent;
983 struct list_head *next;
984 unsigned seq;
985 int locked = 0;
986
987 seq = read_seqbegin(&rename_lock);
988again:
989 this_parent = parent;
990
991 if (d_mountpoint(parent))
992 goto positive;
993 spin_lock(&this_parent->d_lock);
994repeat:
995 next = this_parent->d_subdirs.next;
996resume:
997 while (next != &this_parent->d_subdirs) {
998 struct list_head *tmp = next;
999 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
1000 next = tmp->next;
1001
1002 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1003 /* Have we found a mount point ? */
1004 if (d_mountpoint(dentry)) {
1005 spin_unlock(&dentry->d_lock);
1006 spin_unlock(&this_parent->d_lock);
1007 goto positive;
1008 }
1009 if (!list_empty(&dentry->d_subdirs)) {
1010 spin_unlock(&this_parent->d_lock);
1011 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
1012 this_parent = dentry;
1013 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1014 goto repeat;
1015 }
1016 spin_unlock(&dentry->d_lock);
1017 }
1018 /*
1019 * All done at this level ... ascend and resume the search.
1020 */
1021 if (this_parent != parent) {
1022 struct dentry *child = this_parent;
1023 this_parent = try_to_ascend(this_parent, locked, seq);
1024 if (!this_parent)
1025 goto rename_retry;
1026 next = child->d_u.d_child.next;
1027 goto resume;
1028 }
1029 spin_unlock(&this_parent->d_lock);
1030 if (!locked && read_seqretry(&rename_lock, seq))
1031 goto rename_retry;
1032 if (locked)
1033 write_sequnlock(&rename_lock);
1034 return 0; /* No mount points found in tree */
1035positive:
1036 if (!locked && read_seqretry(&rename_lock, seq))
1037 goto rename_retry;
1038 if (locked)
1039 write_sequnlock(&rename_lock);
1040 return 1;
1041
1042rename_retry:
1043 locked = 1;
1044 write_seqlock(&rename_lock);
1045 goto again;
1046}
1047EXPORT_SYMBOL(have_submounts);
1048
1049/*
1050 * Search the dentry child list for the specified parent,
1051 * and move any unused dentries to the end of the unused
1052 * list for prune_dcache(). We descend to the next level
1053 * whenever the d_subdirs list is non-empty and continue
1054 * searching.
1055 *
1056 * It returns zero iff there are no unused children,
1057 * otherwise it returns the number of children moved to
1058 * the end of the unused list. This may not be the total
1059 * number of unused children, because select_parent can
1060 * drop the lock and return early due to latency
1061 * constraints.
1062 */
1063static int select_parent(struct dentry * parent)
1064{
1065 struct dentry *this_parent;
1066 struct list_head *next;
1067 unsigned seq;
1068 int found = 0;
1069 int locked = 0;
1070
1071 seq = read_seqbegin(&rename_lock);
1072again:
1073 this_parent = parent;
1074 spin_lock(&this_parent->d_lock);
1075repeat:
1076 next = this_parent->d_subdirs.next;
1077resume:
1078 while (next != &this_parent->d_subdirs) {
1079 struct list_head *tmp = next;
1080 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
1081 next = tmp->next;
1082
1083 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1084
1085 /*
1086 * move only zero ref count dentries to the end
1087 * of the unused list for prune_dcache
1088 */
1089 if (!dentry->d_count) {
1090 dentry_lru_move_tail(dentry);
1091 found++;
1092 } else {
1093 dentry_lru_del(dentry);
1094 }
1095
1096 /*
1097 * We can return to the caller if we have found some (this
1098 * ensures forward progress). We'll be coming back to find
1099 * the rest.
1100 */
1101 if (found && need_resched()) {
1102 spin_unlock(&dentry->d_lock);
1103 goto out;
1104 }
1105
1106 /*
1107 * Descend a level if the d_subdirs list is non-empty.
1108 */
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_);
1114 goto repeat;
1115 }
1116
1117 spin_unlock(&dentry->d_lock);
1118 }
1119 /*
1120 * All done at this level ... ascend and resume the search.
1121 */
1122 if (this_parent != parent) {
1123 struct dentry *child = this_parent;
1124 this_parent = try_to_ascend(this_parent, locked, seq);
1125 if (!this_parent)
1126 goto rename_retry;
1127 next = child->d_u.d_child.next;
1128 goto resume;
1129 }
1130out:
1131 spin_unlock(&this_parent->d_lock);
1132 if (!locked && read_seqretry(&rename_lock, seq))
1133 goto rename_retry;
1134 if (locked)
1135 write_sequnlock(&rename_lock);
1136 return found;
1137
1138rename_retry:
1139 if (found)
1140 return found;
1141 locked = 1;
1142 write_seqlock(&rename_lock);
1143 goto again;
1144}
1145
1146/**
1147 * shrink_dcache_parent - prune dcache
1148 * @parent: parent of entries to prune
1149 *
1150 * Prune the dcache to remove unused children of the parent dentry.
1151 */
1152
1153void shrink_dcache_parent(struct dentry * parent)
1154{
1155 struct super_block *sb = parent->d_sb;
1156 int found;
1157
1158 while ((found = select_parent(parent)) != 0)
1159 __shrink_dcache_sb(sb, found, 0);
1160}
1161EXPORT_SYMBOL(shrink_dcache_parent);
1162
1163/**
1164 * __d_alloc - allocate a dcache entry
1165 * @sb: filesystem it will belong to
1166 * @name: qstr of the name
1167 *
1168 * Allocates a dentry. It returns %NULL if there is insufficient memory
1169 * available. On a success the dentry is returned. The name passed in is
1170 * copied and the copy passed in may be reused after this call.
1171 */
1172
1173struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1174{
1175 struct dentry *dentry;
1176 char *dname;
1177
1178 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
1179 if (!dentry)
1180 return NULL;
1181
1182 if (name->len > DNAME_INLINE_LEN-1) {
1183 dname = kmalloc(name->len + 1, GFP_KERNEL);
1184 if (!dname) {
1185 kmem_cache_free(dentry_cache, dentry);
1186 return NULL;
1187 }
1188 } else {
1189 dname = dentry->d_iname;
1190 }
1191 dentry->d_name.name = dname;
1192
1193 dentry->d_name.len = name->len;
1194 dentry->d_name.hash = name->hash;
1195 memcpy(dname, name->name, name->len);
1196 dname[name->len] = 0;
1197
1198 dentry->d_count = 1;
1199 dentry->d_flags = 0;
1200 spin_lock_init(&dentry->d_lock);
1201 seqcount_init(&dentry->d_seq);
1202 dentry->d_inode = NULL;
1203 dentry->d_parent = dentry;
1204 dentry->d_sb = sb;
1205 dentry->d_op = NULL;
1206 dentry->d_fsdata = NULL;
1207 INIT_HLIST_BL_NODE(&dentry->d_hash);
1208 INIT_LIST_HEAD(&dentry->d_lru);
1209 INIT_LIST_HEAD(&dentry->d_subdirs);
1210 INIT_LIST_HEAD(&dentry->d_alias);
1211 INIT_LIST_HEAD(&dentry->d_u.d_child);
1212 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1213
1214 this_cpu_inc(nr_dentry);
1215
1216 return dentry;
1217}
1218
1219/**
1220 * d_alloc - allocate a dcache entry
1221 * @parent: parent of entry to allocate
1222 * @name: qstr of the name
1223 *
1224 * Allocates a dentry. It returns %NULL if there is insufficient memory
1225 * available. On a success the dentry is returned. The name passed in is
1226 * copied and the copy passed in may be reused after this call.
1227 */
1228struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1229{
1230 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1231 if (!dentry)
1232 return NULL;
1233
1234 spin_lock(&parent->d_lock);
1235 /*
1236 * don't need child lock because it is not subject
1237 * to concurrency here
1238 */
1239 __dget_dlock(parent);
1240 dentry->d_parent = parent;
1241 list_add(&dentry->d_u.d_child, &parent->d_subdirs);
1242 spin_unlock(&parent->d_lock);
1243
1244 return dentry;
1245}
1246EXPORT_SYMBOL(d_alloc);
1247
1248struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1249{
1250 struct dentry *dentry = __d_alloc(sb, name);
1251 if (dentry)
1252 dentry->d_flags |= DCACHE_DISCONNECTED;
1253 return dentry;
1254}
1255EXPORT_SYMBOL(d_alloc_pseudo);
1256
1257struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1258{
1259 struct qstr q;
1260
1261 q.name = name;
1262 q.len = strlen(name);
1263 q.hash = full_name_hash(q.name, q.len);
1264 return d_alloc(parent, &q);
1265}
1266EXPORT_SYMBOL(d_alloc_name);
1267
1268void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1269{
1270 WARN_ON_ONCE(dentry->d_op);
1271 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
1272 DCACHE_OP_COMPARE |
1273 DCACHE_OP_REVALIDATE |
1274 DCACHE_OP_DELETE ));
1275 dentry->d_op = op;
1276 if (!op)
1277 return;
1278 if (op->d_hash)
1279 dentry->d_flags |= DCACHE_OP_HASH;
1280 if (op->d_compare)
1281 dentry->d_flags |= DCACHE_OP_COMPARE;
1282 if (op->d_revalidate)
1283 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1284 if (op->d_delete)
1285 dentry->d_flags |= DCACHE_OP_DELETE;
1286
1287}
1288EXPORT_SYMBOL(d_set_d_op);
1289
1290static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1291{
1292 spin_lock(&dentry->d_lock);
1293 if (inode) {
1294 if (unlikely(IS_AUTOMOUNT(inode)))
1295 dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
1296 list_add(&dentry->d_alias, &inode->i_dentry);
1297 }
1298 dentry->d_inode = inode;
1299 dentry_rcuwalk_barrier(dentry);
1300 spin_unlock(&dentry->d_lock);
1301 fsnotify_d_instantiate(dentry, inode);
1302}
1303
1304/**
1305 * d_instantiate - fill in inode information for a dentry
1306 * @entry: dentry to complete
1307 * @inode: inode to attach to this dentry
1308 *
1309 * Fill in inode information in the entry.
1310 *
1311 * This turns negative dentries into productive full members
1312 * of society.
1313 *
1314 * NOTE! This assumes that the inode count has been incremented
1315 * (or otherwise set) by the caller to indicate that it is now
1316 * in use by the dcache.
1317 */
1318
1319void d_instantiate(struct dentry *entry, struct inode * inode)
1320{
1321 BUG_ON(!list_empty(&entry->d_alias));
1322 if (inode)
1323 spin_lock(&inode->i_lock);
1324 __d_instantiate(entry, inode);
1325 if (inode)
1326 spin_unlock(&inode->i_lock);
1327 security_d_instantiate(entry, inode);
1328}
1329EXPORT_SYMBOL(d_instantiate);
1330
1331/**
1332 * d_instantiate_unique - instantiate a non-aliased dentry
1333 * @entry: dentry to instantiate
1334 * @inode: inode to attach to this dentry
1335 *
1336 * Fill in inode information in the entry. On success, it returns NULL.
1337 * If an unhashed alias of "entry" already exists, then we return the
1338 * aliased dentry instead and drop one reference to inode.
1339 *
1340 * Note that in order to avoid conflicts with rename() etc, the caller
1341 * had better be holding the parent directory semaphore.
1342 *
1343 * This also assumes that the inode count has been incremented
1344 * (or otherwise set) by the caller to indicate that it is now
1345 * in use by the dcache.
1346 */
1347static struct dentry *__d_instantiate_unique(struct dentry *entry,
1348 struct inode *inode)
1349{
1350 struct dentry *alias;
1351 int len = entry->d_name.len;
1352 const char *name = entry->d_name.name;
1353 unsigned int hash = entry->d_name.hash;
1354
1355 if (!inode) {
1356 __d_instantiate(entry, NULL);
1357 return NULL;
1358 }
1359
1360 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
1361 struct qstr *qstr = &alias->d_name;
1362
1363 /*
1364 * Don't need alias->d_lock here, because aliases with
1365 * d_parent == entry->d_parent are not subject to name or
1366 * parent changes, because the parent inode i_mutex is held.
1367 */
1368 if (qstr->hash != hash)
1369 continue;
1370 if (alias->d_parent != entry->d_parent)
1371 continue;
1372 if (dentry_cmp(qstr->name, qstr->len, name, len))
1373 continue;
1374 __dget(alias);
1375 return alias;
1376 }
1377
1378 __d_instantiate(entry, inode);
1379 return NULL;
1380}
1381
1382struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
1383{
1384 struct dentry *result;
1385
1386 BUG_ON(!list_empty(&entry->d_alias));
1387
1388 if (inode)
1389 spin_lock(&inode->i_lock);
1390 result = __d_instantiate_unique(entry, inode);
1391 if (inode)
1392 spin_unlock(&inode->i_lock);
1393
1394 if (!result) {
1395 security_d_instantiate(entry, inode);
1396 return NULL;
1397 }
1398
1399 BUG_ON(!d_unhashed(result));
1400 iput(inode);
1401 return result;
1402}
1403
1404EXPORT_SYMBOL(d_instantiate_unique);
1405
1406/**
1407 * d_alloc_root - allocate root dentry
1408 * @root_inode: inode to allocate the root for
1409 *
1410 * Allocate a root ("/") dentry for the inode given. The inode is
1411 * instantiated and returned. %NULL is returned if there is insufficient
1412 * memory or the inode passed is %NULL.
1413 */
1414
1415struct dentry * d_alloc_root(struct inode * root_inode)
1416{
1417 struct dentry *res = NULL;
1418
1419 if (root_inode) {
1420 static const struct qstr name = { .name = "/", .len = 1 };
1421
1422 res = __d_alloc(root_inode->i_sb, &name);
1423 if (res)
1424 d_instantiate(res, root_inode);
1425 }
1426 return res;
1427}
1428EXPORT_SYMBOL(d_alloc_root);
1429
1430static struct dentry * __d_find_any_alias(struct inode *inode)
1431{
1432 struct dentry *alias;
1433
1434 if (list_empty(&inode->i_dentry))
1435 return NULL;
1436 alias = list_first_entry(&inode->i_dentry, struct dentry, d_alias);
1437 __dget(alias);
1438 return alias;
1439}
1440
1441static struct dentry * d_find_any_alias(struct inode *inode)
1442{
1443 struct dentry *de;
1444
1445 spin_lock(&inode->i_lock);
1446 de = __d_find_any_alias(inode);
1447 spin_unlock(&inode->i_lock);
1448 return de;
1449}
1450
1451
1452/**
1453 * d_obtain_alias - find or allocate a dentry for a given inode
1454 * @inode: inode to allocate the dentry for
1455 *
1456 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1457 * similar open by handle operations. The returned dentry may be anonymous,
1458 * or may have a full name (if the inode was already in the cache).
1459 *
1460 * When called on a directory inode, we must ensure that the inode only ever
1461 * has one dentry. If a dentry is found, that is returned instead of
1462 * allocating a new one.
1463 *
1464 * On successful return, the reference to the inode has been transferred
1465 * to the dentry. In case of an error the reference on the inode is released.
1466 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1467 * be passed in and will be the error will be propagate to the return value,
1468 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1469 */
1470struct dentry *d_obtain_alias(struct inode *inode)
1471{
1472 static const struct qstr anonstring = { .name = "" };
1473 struct dentry *tmp;
1474 struct dentry *res;
1475
1476 if (!inode)
1477 return ERR_PTR(-ESTALE);
1478 if (IS_ERR(inode))
1479 return ERR_CAST(inode);
1480
1481 res = d_find_any_alias(inode);
1482 if (res)
1483 goto out_iput;
1484
1485 tmp = __d_alloc(inode->i_sb, &anonstring);
1486 if (!tmp) {
1487 res = ERR_PTR(-ENOMEM);
1488 goto out_iput;
1489 }
1490
1491 spin_lock(&inode->i_lock);
1492 res = __d_find_any_alias(inode);
1493 if (res) {
1494 spin_unlock(&inode->i_lock);
1495 dput(tmp);
1496 goto out_iput;
1497 }
1498
1499 /* attach a disconnected dentry */
1500 spin_lock(&tmp->d_lock);
1501 tmp->d_inode = inode;
1502 tmp->d_flags |= DCACHE_DISCONNECTED;
1503 list_add(&tmp->d_alias, &inode->i_dentry);
1504 hlist_bl_lock(&tmp->d_sb->s_anon);
1505 hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
1506 hlist_bl_unlock(&tmp->d_sb->s_anon);
1507 spin_unlock(&tmp->d_lock);
1508 spin_unlock(&inode->i_lock);
1509 security_d_instantiate(tmp, inode);
1510
1511 return tmp;
1512
1513 out_iput:
1514 if (res && !IS_ERR(res))
1515 security_d_instantiate(res, inode);
1516 iput(inode);
1517 return res;
1518}
1519EXPORT_SYMBOL(d_obtain_alias);
1520
1521/**
1522 * d_splice_alias - splice a disconnected dentry into the tree if one exists
1523 * @inode: the inode which may have a disconnected dentry
1524 * @dentry: a negative dentry which we want to point to the inode.
1525 *
1526 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1527 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1528 * and return it, else simply d_add the inode to the dentry and return NULL.
1529 *
1530 * This is needed in the lookup routine of any filesystem that is exportable
1531 * (via knfsd) so that we can build dcache paths to directories effectively.
1532 *
1533 * If a dentry was found and moved, then it is returned. Otherwise NULL
1534 * is returned. This matches the expected return value of ->lookup.
1535 *
1536 */
1537struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
1538{
1539 struct dentry *new = NULL;
1540
1541 if (IS_ERR(inode))
1542 return ERR_CAST(inode);
1543
1544 if (inode && S_ISDIR(inode->i_mode)) {
1545 spin_lock(&inode->i_lock);
1546 new = __d_find_alias(inode, 1);
1547 if (new) {
1548 BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
1549 spin_unlock(&inode->i_lock);
1550 security_d_instantiate(new, inode);
1551 d_move(new, dentry);
1552 iput(inode);
1553 } else {
1554 /* already taking inode->i_lock, so d_add() by hand */
1555 __d_instantiate(dentry, inode);
1556 spin_unlock(&inode->i_lock);
1557 security_d_instantiate(dentry, inode);
1558 d_rehash(dentry);
1559 }
1560 } else
1561 d_add(dentry, inode);
1562 return new;
1563}
1564EXPORT_SYMBOL(d_splice_alias);
1565
1566/**
1567 * d_add_ci - lookup or allocate new dentry with case-exact name
1568 * @inode: the inode case-insensitive lookup has found
1569 * @dentry: the negative dentry that was passed to the parent's lookup func
1570 * @name: the case-exact name to be associated with the returned dentry
1571 *
1572 * This is to avoid filling the dcache with case-insensitive names to the
1573 * same inode, only the actual correct case is stored in the dcache for
1574 * case-insensitive filesystems.
1575 *
1576 * For a case-insensitive lookup match and if the the case-exact dentry
1577 * already exists in in the dcache, use it and return it.
1578 *
1579 * If no entry exists with the exact case name, allocate new dentry with
1580 * the exact case, and return the spliced entry.
1581 */
1582struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
1583 struct qstr *name)
1584{
1585 int error;
1586 struct dentry *found;
1587 struct dentry *new;
1588
1589 /*
1590 * First check if a dentry matching the name already exists,
1591 * if not go ahead and create it now.
1592 */
1593 found = d_hash_and_lookup(dentry->d_parent, name);
1594 if (!found) {
1595 new = d_alloc(dentry->d_parent, name);
1596 if (!new) {
1597 error = -ENOMEM;
1598 goto err_out;
1599 }
1600
1601 found = d_splice_alias(inode, new);
1602 if (found) {
1603 dput(new);
1604 return found;
1605 }
1606 return new;
1607 }
1608
1609 /*
1610 * If a matching dentry exists, and it's not negative use it.
1611 *
1612 * Decrement the reference count to balance the iget() done
1613 * earlier on.
1614 */
1615 if (found->d_inode) {
1616 if (unlikely(found->d_inode != inode)) {
1617 /* This can't happen because bad inodes are unhashed. */
1618 BUG_ON(!is_bad_inode(inode));
1619 BUG_ON(!is_bad_inode(found->d_inode));
1620 }
1621 iput(inode);
1622 return found;
1623 }
1624
1625 /*
1626 * We are going to instantiate this dentry, unhash it and clear the
1627 * lookup flag so we can do that.
1628 */
1629 if (unlikely(d_need_lookup(found)))
1630 d_clear_need_lookup(found);
1631
1632 /*
1633 * Negative dentry: instantiate it unless the inode is a directory and
1634 * already has a dentry.
1635 */
1636 new = d_splice_alias(inode, found);
1637 if (new) {
1638 dput(found);
1639 found = new;
1640 }
1641 return found;
1642
1643err_out:
1644 iput(inode);
1645 return ERR_PTR(error);
1646}
1647EXPORT_SYMBOL(d_add_ci);
1648
1649/**
1650 * __d_lookup_rcu - search for a dentry (racy, store-free)
1651 * @parent: parent dentry
1652 * @name: qstr of name we wish to find
1653 * @seq: returns d_seq value at the point where the dentry was found
1654 * @inode: returns dentry->d_inode when the inode was found valid.
1655 * Returns: dentry, or NULL
1656 *
1657 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
1658 * resolution (store-free path walking) design described in
1659 * Documentation/filesystems/path-lookup.txt.
1660 *
1661 * This is not to be used outside core vfs.
1662 *
1663 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
1664 * held, and rcu_read_lock held. The returned dentry must not be stored into
1665 * without taking d_lock and checking d_seq sequence count against @seq
1666 * returned here.
1667 *
1668 * A refcount may be taken on the found dentry with the __d_rcu_to_refcount
1669 * function.
1670 *
1671 * Alternatively, __d_lookup_rcu may be called again to look up the child of
1672 * the returned dentry, so long as its parent's seqlock is checked after the
1673 * child is looked up. Thus, an interlocking stepping of sequence lock checks
1674 * is formed, giving integrity down the path walk.
1675 */
1676struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
1677 unsigned *seq, struct inode **inode)
1678{
1679 unsigned int len = name->len;
1680 unsigned int hash = name->hash;
1681 const unsigned char *str = name->name;
1682 struct hlist_bl_head *b = d_hash(parent, hash);
1683 struct hlist_bl_node *node;
1684 struct dentry *dentry;
1685
1686 /*
1687 * Note: There is significant duplication with __d_lookup_rcu which is
1688 * required to prevent single threaded performance regressions
1689 * especially on architectures where smp_rmb (in seqcounts) are costly.
1690 * Keep the two functions in sync.
1691 */
1692
1693 /*
1694 * The hash list is protected using RCU.
1695 *
1696 * Carefully use d_seq when comparing a candidate dentry, to avoid
1697 * races with d_move().
1698 *
1699 * It is possible that concurrent renames can mess up our list
1700 * walk here and result in missing our dentry, resulting in the
1701 * false-negative result. d_lookup() protects against concurrent
1702 * renames using rename_lock seqlock.
1703 *
1704 * See Documentation/filesystems/path-lookup.txt for more details.
1705 */
1706 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
1707 struct inode *i;
1708 const char *tname;
1709 int tlen;
1710
1711 if (dentry->d_name.hash != hash)
1712 continue;
1713
1714seqretry:
1715 *seq = read_seqcount_begin(&dentry->d_seq);
1716 if (dentry->d_parent != parent)
1717 continue;
1718 if (d_unhashed(dentry))
1719 continue;
1720 tlen = dentry->d_name.len;
1721 tname = dentry->d_name.name;
1722 i = dentry->d_inode;
1723 prefetch(tname);
1724 /*
1725 * This seqcount check is required to ensure name and
1726 * len are loaded atomically, so as not to walk off the
1727 * edge of memory when walking. If we could load this
1728 * atomically some other way, we could drop this check.
1729 */
1730 if (read_seqcount_retry(&dentry->d_seq, *seq))
1731 goto seqretry;
1732 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
1733 if (parent->d_op->d_compare(parent, *inode,
1734 dentry, i,
1735 tlen, tname, name))
1736 continue;
1737 } else {
1738 if (dentry_cmp(tname, tlen, str, len))
1739 continue;
1740 }
1741 /*
1742 * No extra seqcount check is required after the name
1743 * compare. The caller must perform a seqcount check in
1744 * order to do anything useful with the returned dentry
1745 * anyway.
1746 */
1747 *inode = i;
1748 return dentry;
1749 }
1750 return NULL;
1751}
1752
1753/**
1754 * d_lookup - search for a dentry
1755 * @parent: parent dentry
1756 * @name: qstr of name we wish to find
1757 * Returns: dentry, or NULL
1758 *
1759 * d_lookup searches the children of the parent dentry for the name in
1760 * question. If the dentry is found its reference count is incremented and the
1761 * dentry is returned. The caller must use dput to free the entry when it has
1762 * finished using it. %NULL is returned if the dentry does not exist.
1763 */
1764struct dentry *d_lookup(struct dentry *parent, struct qstr *name)
1765{
1766 struct dentry *dentry;
1767 unsigned seq;
1768
1769 do {
1770 seq = read_seqbegin(&rename_lock);
1771 dentry = __d_lookup(parent, name);
1772 if (dentry)
1773 break;
1774 } while (read_seqretry(&rename_lock, seq));
1775 return dentry;
1776}
1777EXPORT_SYMBOL(d_lookup);
1778
1779/**
1780 * __d_lookup - search for a dentry (racy)
1781 * @parent: parent dentry
1782 * @name: qstr of name we wish to find
1783 * Returns: dentry, or NULL
1784 *
1785 * __d_lookup is like d_lookup, however it may (rarely) return a
1786 * false-negative result due to unrelated rename activity.
1787 *
1788 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
1789 * however it must be used carefully, eg. with a following d_lookup in
1790 * the case of failure.
1791 *
1792 * __d_lookup callers must be commented.
1793 */
1794struct dentry *__d_lookup(struct dentry *parent, struct qstr *name)
1795{
1796 unsigned int len = name->len;
1797 unsigned int hash = name->hash;
1798 const unsigned char *str = name->name;
1799 struct hlist_bl_head *b = d_hash(parent, hash);
1800 struct hlist_bl_node *node;
1801 struct dentry *found = NULL;
1802 struct dentry *dentry;
1803
1804 /*
1805 * Note: There is significant duplication with __d_lookup_rcu which is
1806 * required to prevent single threaded performance regressions
1807 * especially on architectures where smp_rmb (in seqcounts) are costly.
1808 * Keep the two functions in sync.
1809 */
1810
1811 /*
1812 * The hash list is protected using RCU.
1813 *
1814 * Take d_lock when comparing a candidate dentry, to avoid races
1815 * with d_move().
1816 *
1817 * It is possible that concurrent renames can mess up our list
1818 * walk here and result in missing our dentry, resulting in the
1819 * false-negative result. d_lookup() protects against concurrent
1820 * renames using rename_lock seqlock.
1821 *
1822 * See Documentation/filesystems/path-lookup.txt for more details.
1823 */
1824 rcu_read_lock();
1825
1826 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
1827 const char *tname;
1828 int tlen;
1829
1830 if (dentry->d_name.hash != hash)
1831 continue;
1832
1833 spin_lock(&dentry->d_lock);
1834 if (dentry->d_parent != parent)
1835 goto next;
1836 if (d_unhashed(dentry))
1837 goto next;
1838
1839 /*
1840 * It is safe to compare names since d_move() cannot
1841 * change the qstr (protected by d_lock).
1842 */
1843 tlen = dentry->d_name.len;
1844 tname = dentry->d_name.name;
1845 if (parent->d_flags & DCACHE_OP_COMPARE) {
1846 if (parent->d_op->d_compare(parent, parent->d_inode,
1847 dentry, dentry->d_inode,
1848 tlen, tname, name))
1849 goto next;
1850 } else {
1851 if (dentry_cmp(tname, tlen, str, len))
1852 goto next;
1853 }
1854
1855 dentry->d_count++;
1856 found = dentry;
1857 spin_unlock(&dentry->d_lock);
1858 break;
1859next:
1860 spin_unlock(&dentry->d_lock);
1861 }
1862 rcu_read_unlock();
1863
1864 return found;
1865}
1866
1867/**
1868 * d_hash_and_lookup - hash the qstr then search for a dentry
1869 * @dir: Directory to search in
1870 * @name: qstr of name we wish to find
1871 *
1872 * On hash failure or on lookup failure NULL is returned.
1873 */
1874struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
1875{
1876 struct dentry *dentry = NULL;
1877
1878 /*
1879 * Check for a fs-specific hash function. Note that we must
1880 * calculate the standard hash first, as the d_op->d_hash()
1881 * routine may choose to leave the hash value unchanged.
1882 */
1883 name->hash = full_name_hash(name->name, name->len);
1884 if (dir->d_flags & DCACHE_OP_HASH) {
1885 if (dir->d_op->d_hash(dir, dir->d_inode, name) < 0)
1886 goto out;
1887 }
1888 dentry = d_lookup(dir, name);
1889out:
1890 return dentry;
1891}
1892
1893/**
1894 * d_validate - verify dentry provided from insecure source (deprecated)
1895 * @dentry: The dentry alleged to be valid child of @dparent
1896 * @dparent: The parent dentry (known to be valid)
1897 *
1898 * An insecure source has sent us a dentry, here we verify it and dget() it.
1899 * This is used by ncpfs in its readdir implementation.
1900 * Zero is returned in the dentry is invalid.
1901 *
1902 * This function is slow for big directories, and deprecated, do not use it.
1903 */
1904int d_validate(struct dentry *dentry, struct dentry *dparent)
1905{
1906 struct dentry *child;
1907
1908 spin_lock(&dparent->d_lock);
1909 list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
1910 if (dentry == child) {
1911 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1912 __dget_dlock(dentry);
1913 spin_unlock(&dentry->d_lock);
1914 spin_unlock(&dparent->d_lock);
1915 return 1;
1916 }
1917 }
1918 spin_unlock(&dparent->d_lock);
1919
1920 return 0;
1921}
1922EXPORT_SYMBOL(d_validate);
1923
1924/*
1925 * When a file is deleted, we have two options:
1926 * - turn this dentry into a negative dentry
1927 * - unhash this dentry and free it.
1928 *
1929 * Usually, we want to just turn this into
1930 * a negative dentry, but if anybody else is
1931 * currently using the dentry or the inode
1932 * we can't do that and we fall back on removing
1933 * it from the hash queues and waiting for
1934 * it to be deleted later when it has no users
1935 */
1936
1937/**
1938 * d_delete - delete a dentry
1939 * @dentry: The dentry to delete
1940 *
1941 * Turn the dentry into a negative dentry if possible, otherwise
1942 * remove it from the hash queues so it can be deleted later
1943 */
1944
1945void d_delete(struct dentry * dentry)
1946{
1947 struct inode *inode;
1948 int isdir = 0;
1949 /*
1950 * Are we the only user?
1951 */
1952again:
1953 spin_lock(&dentry->d_lock);
1954 inode = dentry->d_inode;
1955 isdir = S_ISDIR(inode->i_mode);
1956 if (dentry->d_count == 1) {
1957 if (inode && !spin_trylock(&inode->i_lock)) {
1958 spin_unlock(&dentry->d_lock);
1959 cpu_relax();
1960 goto again;
1961 }
1962 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
1963 dentry_unlink_inode(dentry);
1964 fsnotify_nameremove(dentry, isdir);
1965 return;
1966 }
1967
1968 if (!d_unhashed(dentry))
1969 __d_drop(dentry);
1970
1971 spin_unlock(&dentry->d_lock);
1972
1973 fsnotify_nameremove(dentry, isdir);
1974}
1975EXPORT_SYMBOL(d_delete);
1976
1977static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
1978{
1979 BUG_ON(!d_unhashed(entry));
1980 hlist_bl_lock(b);
1981 entry->d_flags |= DCACHE_RCUACCESS;
1982 hlist_bl_add_head_rcu(&entry->d_hash, b);
1983 hlist_bl_unlock(b);
1984}
1985
1986static void _d_rehash(struct dentry * entry)
1987{
1988 __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
1989}
1990
1991/**
1992 * d_rehash - add an entry back to the hash
1993 * @entry: dentry to add to the hash
1994 *
1995 * Adds a dentry to the hash according to its name.
1996 */
1997
1998void d_rehash(struct dentry * entry)
1999{
2000 spin_lock(&entry->d_lock);
2001 _d_rehash(entry);
2002 spin_unlock(&entry->d_lock);
2003}
2004EXPORT_SYMBOL(d_rehash);
2005
2006/**
2007 * dentry_update_name_case - update case insensitive dentry with a new name
2008 * @dentry: dentry to be updated
2009 * @name: new name
2010 *
2011 * Update a case insensitive dentry with new case of name.
2012 *
2013 * dentry must have been returned by d_lookup with name @name. Old and new
2014 * name lengths must match (ie. no d_compare which allows mismatched name
2015 * lengths).
2016 *
2017 * Parent inode i_mutex must be held over d_lookup and into this call (to
2018 * keep renames and concurrent inserts, and readdir(2) away).
2019 */
2020void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
2021{
2022 BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));
2023 BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
2024
2025 spin_lock(&dentry->d_lock);
2026 write_seqcount_begin(&dentry->d_seq);
2027 memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
2028 write_seqcount_end(&dentry->d_seq);
2029 spin_unlock(&dentry->d_lock);
2030}
2031EXPORT_SYMBOL(dentry_update_name_case);
2032
2033static void switch_names(struct dentry *dentry, struct dentry *target)
2034{
2035 if (dname_external(target)) {
2036 if (dname_external(dentry)) {
2037 /*
2038 * Both external: swap the pointers
2039 */
2040 swap(target->d_name.name, dentry->d_name.name);
2041 } else {
2042 /*
2043 * dentry:internal, target:external. Steal target's
2044 * storage and make target internal.
2045 */
2046 memcpy(target->d_iname, dentry->d_name.name,
2047 dentry->d_name.len + 1);
2048 dentry->d_name.name = target->d_name.name;
2049 target->d_name.name = target->d_iname;
2050 }
2051 } else {
2052 if (dname_external(dentry)) {
2053 /*
2054 * dentry:external, target:internal. Give dentry's
2055 * storage to target and make dentry internal
2056 */
2057 memcpy(dentry->d_iname, target->d_name.name,
2058 target->d_name.len + 1);
2059 target->d_name.name = dentry->d_name.name;
2060 dentry->d_name.name = dentry->d_iname;
2061 } else {
2062 /*
2063 * Both are internal. Just copy target to dentry
2064 */
2065 memcpy(dentry->d_iname, target->d_name.name,
2066 target->d_name.len + 1);
2067 dentry->d_name.len = target->d_name.len;
2068 return;
2069 }
2070 }
2071 swap(dentry->d_name.len, target->d_name.len);
2072}
2073
2074static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
2075{
2076 /*
2077 * XXXX: do we really need to take target->d_lock?
2078 */
2079 if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent)
2080 spin_lock(&target->d_parent->d_lock);
2081 else {
2082 if (d_ancestor(dentry->d_parent, target->d_parent)) {
2083 spin_lock(&dentry->d_parent->d_lock);
2084 spin_lock_nested(&target->d_parent->d_lock,
2085 DENTRY_D_LOCK_NESTED);
2086 } else {
2087 spin_lock(&target->d_parent->d_lock);
2088 spin_lock_nested(&dentry->d_parent->d_lock,
2089 DENTRY_D_LOCK_NESTED);
2090 }
2091 }
2092 if (target < dentry) {
2093 spin_lock_nested(&target->d_lock, 2);
2094 spin_lock_nested(&dentry->d_lock, 3);
2095 } else {
2096 spin_lock_nested(&dentry->d_lock, 2);
2097 spin_lock_nested(&target->d_lock, 3);
2098 }
2099}
2100
2101static void dentry_unlock_parents_for_move(struct dentry *dentry,
2102 struct dentry *target)
2103{
2104 if (target->d_parent != dentry->d_parent)
2105 spin_unlock(&dentry->d_parent->d_lock);
2106 if (target->d_parent != target)
2107 spin_unlock(&target->d_parent->d_lock);
2108}
2109
2110/*
2111 * When switching names, the actual string doesn't strictly have to
2112 * be preserved in the target - because we're dropping the target
2113 * anyway. As such, we can just do a simple memcpy() to copy over
2114 * the new name before we switch.
2115 *
2116 * Note that we have to be a lot more careful about getting the hash
2117 * switched - we have to switch the hash value properly even if it
2118 * then no longer matches the actual (corrupted) string of the target.
2119 * The hash value has to match the hash queue that the dentry is on..
2120 */
2121/*
2122 * __d_move - move a dentry
2123 * @dentry: entry to move
2124 * @target: new dentry
2125 *
2126 * Update the dcache to reflect the move of a file name. Negative
2127 * dcache entries should not be moved in this way. Caller must hold
2128 * rename_lock, the i_mutex of the source and target directories,
2129 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2130 */
2131static void __d_move(struct dentry * dentry, struct dentry * target)
2132{
2133 if (!dentry->d_inode)
2134 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
2135
2136 BUG_ON(d_ancestor(dentry, target));
2137 BUG_ON(d_ancestor(target, dentry));
2138
2139 dentry_lock_for_move(dentry, target);
2140
2141 write_seqcount_begin(&dentry->d_seq);
2142 write_seqcount_begin(&target->d_seq);
2143
2144 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
2145
2146 /*
2147 * Move the dentry to the target hash queue. Don't bother checking
2148 * for the same hash queue because of how unlikely it is.
2149 */
2150 __d_drop(dentry);
2151 __d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
2152
2153 /* Unhash the target: dput() will then get rid of it */
2154 __d_drop(target);
2155
2156 list_del(&dentry->d_u.d_child);
2157 list_del(&target->d_u.d_child);
2158
2159 /* Switch the names.. */
2160 switch_names(dentry, target);
2161 swap(dentry->d_name.hash, target->d_name.hash);
2162
2163 /* ... and switch the parents */
2164 if (IS_ROOT(dentry)) {
2165 dentry->d_parent = target->d_parent;
2166 target->d_parent = target;
2167 INIT_LIST_HEAD(&target->d_u.d_child);
2168 } else {
2169 swap(dentry->d_parent, target->d_parent);
2170
2171 /* And add them back to the (new) parent lists */
2172 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
2173 }
2174
2175 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
2176
2177 write_seqcount_end(&target->d_seq);
2178 write_seqcount_end(&dentry->d_seq);
2179
2180 dentry_unlock_parents_for_move(dentry, target);
2181 spin_unlock(&target->d_lock);
2182 fsnotify_d_move(dentry);
2183 spin_unlock(&dentry->d_lock);
2184}
2185
2186/*
2187 * d_move - move a dentry
2188 * @dentry: entry to move
2189 * @target: new dentry
2190 *
2191 * Update the dcache to reflect the move of a file name. Negative
2192 * dcache entries should not be moved in this way. See the locking
2193 * requirements for __d_move.
2194 */
2195void d_move(struct dentry *dentry, struct dentry *target)
2196{
2197 write_seqlock(&rename_lock);
2198 __d_move(dentry, target);
2199 write_sequnlock(&rename_lock);
2200}
2201EXPORT_SYMBOL(d_move);
2202
2203/**
2204 * d_ancestor - search for an ancestor
2205 * @p1: ancestor dentry
2206 * @p2: child dentry
2207 *
2208 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2209 * an ancestor of p2, else NULL.
2210 */
2211struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2212{
2213 struct dentry *p;
2214
2215 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2216 if (p->d_parent == p1)
2217 return p;
2218 }
2219 return NULL;
2220}
2221
2222/*
2223 * This helper attempts to cope with remotely renamed directories
2224 *
2225 * It assumes that the caller is already holding
2226 * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
2227 *
2228 * Note: If ever the locking in lock_rename() changes, then please
2229 * remember to update this too...
2230 */
2231static struct dentry *__d_unalias(struct inode *inode,
2232 struct dentry *dentry, struct dentry *alias)
2233{
2234 struct mutex *m1 = NULL, *m2 = NULL;
2235 struct dentry *ret;
2236
2237 /* If alias and dentry share a parent, then no extra locks required */
2238 if (alias->d_parent == dentry->d_parent)
2239 goto out_unalias;
2240
2241 /* See lock_rename() */
2242 ret = ERR_PTR(-EBUSY);
2243 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
2244 goto out_err;
2245 m1 = &dentry->d_sb->s_vfs_rename_mutex;
2246 if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
2247 goto out_err;
2248 m2 = &alias->d_parent->d_inode->i_mutex;
2249out_unalias:
2250 __d_move(alias, dentry);
2251 ret = alias;
2252out_err:
2253 spin_unlock(&inode->i_lock);
2254 if (m2)
2255 mutex_unlock(m2);
2256 if (m1)
2257 mutex_unlock(m1);
2258 return ret;
2259}
2260
2261/*
2262 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
2263 * named dentry in place of the dentry to be replaced.
2264 * returns with anon->d_lock held!
2265 */
2266static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
2267{
2268 struct dentry *dparent, *aparent;
2269
2270 dentry_lock_for_move(anon, dentry);
2271
2272 write_seqcount_begin(&dentry->d_seq);
2273 write_seqcount_begin(&anon->d_seq);
2274
2275 dparent = dentry->d_parent;
2276 aparent = anon->d_parent;
2277
2278 switch_names(dentry, anon);
2279 swap(dentry->d_name.hash, anon->d_name.hash);
2280
2281 dentry->d_parent = (aparent == anon) ? dentry : aparent;
2282 list_del(&dentry->d_u.d_child);
2283 if (!IS_ROOT(dentry))
2284 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
2285 else
2286 INIT_LIST_HEAD(&dentry->d_u.d_child);
2287
2288 anon->d_parent = (dparent == dentry) ? anon : dparent;
2289 list_del(&anon->d_u.d_child);
2290 if (!IS_ROOT(anon))
2291 list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
2292 else
2293 INIT_LIST_HEAD(&anon->d_u.d_child);
2294
2295 write_seqcount_end(&dentry->d_seq);
2296 write_seqcount_end(&anon->d_seq);
2297
2298 dentry_unlock_parents_for_move(anon, dentry);
2299 spin_unlock(&dentry->d_lock);
2300
2301 /* anon->d_lock still locked, returns locked */
2302 anon->d_flags &= ~DCACHE_DISCONNECTED;
2303}
2304
2305/**
2306 * d_materialise_unique - introduce an inode into the tree
2307 * @dentry: candidate dentry
2308 * @inode: inode to bind to the dentry, to which aliases may be attached
2309 *
2310 * Introduces an dentry into the tree, substituting an extant disconnected
2311 * root directory alias in its place if there is one. Caller must hold the
2312 * i_mutex of the parent directory.
2313 */
2314struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
2315{
2316 struct dentry *actual;
2317
2318 BUG_ON(!d_unhashed(dentry));
2319
2320 if (!inode) {
2321 actual = dentry;
2322 __d_instantiate(dentry, NULL);
2323 d_rehash(actual);
2324 goto out_nolock;
2325 }
2326
2327 spin_lock(&inode->i_lock);
2328
2329 if (S_ISDIR(inode->i_mode)) {
2330 struct dentry *alias;
2331
2332 /* Does an aliased dentry already exist? */
2333 alias = __d_find_alias(inode, 0);
2334 if (alias) {
2335 actual = alias;
2336 write_seqlock(&rename_lock);
2337
2338 if (d_ancestor(alias, dentry)) {
2339 /* Check for loops */
2340 actual = ERR_PTR(-ELOOP);
2341 } else if (IS_ROOT(alias)) {
2342 /* Is this an anonymous mountpoint that we
2343 * could splice into our tree? */
2344 __d_materialise_dentry(dentry, alias);
2345 write_sequnlock(&rename_lock);
2346 __d_drop(alias);
2347 goto found;
2348 } else {
2349 /* Nope, but we must(!) avoid directory
2350 * aliasing */
2351 actual = __d_unalias(inode, dentry, alias);
2352 }
2353 write_sequnlock(&rename_lock);
2354 if (IS_ERR(actual))
2355 dput(alias);
2356 goto out_nolock;
2357 }
2358 }
2359
2360 /* Add a unique reference */
2361 actual = __d_instantiate_unique(dentry, inode);
2362 if (!actual)
2363 actual = dentry;
2364 else
2365 BUG_ON(!d_unhashed(actual));
2366
2367 spin_lock(&actual->d_lock);
2368found:
2369 _d_rehash(actual);
2370 spin_unlock(&actual->d_lock);
2371 spin_unlock(&inode->i_lock);
2372out_nolock:
2373 if (actual == dentry) {
2374 security_d_instantiate(dentry, inode);
2375 return NULL;
2376 }
2377
2378 iput(inode);
2379 return actual;
2380}
2381EXPORT_SYMBOL_GPL(d_materialise_unique);
2382
2383static int prepend(char **buffer, int *buflen, const char *str, int namelen)
2384{
2385 *buflen -= namelen;
2386 if (*buflen < 0)
2387 return -ENAMETOOLONG;
2388 *buffer -= namelen;
2389 memcpy(*buffer, str, namelen);
2390 return 0;
2391}
2392
2393static int prepend_name(char **buffer, int *buflen, struct qstr *name)
2394{
2395 return prepend(buffer, buflen, name->name, name->len);
2396}
2397
2398/**
2399 * prepend_path - Prepend path string to a buffer
2400 * @path: the dentry/vfsmount to report
2401 * @root: root vfsmnt/dentry (may be modified by this function)
2402 * @buffer: pointer to the end of the buffer
2403 * @buflen: pointer to buffer length
2404 *
2405 * Caller holds the rename_lock.
2406 *
2407 * If path is not reachable from the supplied root, then the value of
2408 * root is changed (without modifying refcounts).
2409 */
2410static int prepend_path(const struct path *path, struct path *root,
2411 char **buffer, int *buflen)
2412{
2413 struct dentry *dentry = path->dentry;
2414 struct vfsmount *vfsmnt = path->mnt;
2415 bool slash = false;
2416 int error = 0;
2417
2418 br_read_lock(vfsmount_lock);
2419 while (dentry != root->dentry || vfsmnt != root->mnt) {
2420 struct dentry * parent;
2421
2422 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
2423 /* Global root? */
2424 if (vfsmnt->mnt_parent == vfsmnt) {
2425 goto global_root;
2426 }
2427 dentry = vfsmnt->mnt_mountpoint;
2428 vfsmnt = vfsmnt->mnt_parent;
2429 continue;
2430 }
2431 parent = dentry->d_parent;
2432 prefetch(parent);
2433 spin_lock(&dentry->d_lock);
2434 error = prepend_name(buffer, buflen, &dentry->d_name);
2435 spin_unlock(&dentry->d_lock);
2436 if (!error)
2437 error = prepend(buffer, buflen, "/", 1);
2438 if (error)
2439 break;
2440
2441 slash = true;
2442 dentry = parent;
2443 }
2444
2445out:
2446 if (!error && !slash)
2447 error = prepend(buffer, buflen, "/", 1);
2448
2449 br_read_unlock(vfsmount_lock);
2450 return error;
2451
2452global_root:
2453 /*
2454 * Filesystems needing to implement special "root names"
2455 * should do so with ->d_dname()
2456 */
2457 if (IS_ROOT(dentry) &&
2458 (dentry->d_name.len != 1 || dentry->d_name.name[0] != '/')) {
2459 WARN(1, "Root dentry has weird name <%.*s>\n",
2460 (int) dentry->d_name.len, dentry->d_name.name);
2461 }
2462 root->mnt = vfsmnt;
2463 root->dentry = dentry;
2464 goto out;
2465}
2466
2467/**
2468 * __d_path - return the path of a dentry
2469 * @path: the dentry/vfsmount to report
2470 * @root: root vfsmnt/dentry (may be modified by this function)
2471 * @buf: buffer to return value in
2472 * @buflen: buffer length
2473 *
2474 * Convert a dentry into an ASCII path name.
2475 *
2476 * Returns a pointer into the buffer or an error code if the
2477 * path was too long.
2478 *
2479 * "buflen" should be positive.
2480 *
2481 * If path is not reachable from the supplied root, then the value of
2482 * root is changed (without modifying refcounts).
2483 */
2484char *__d_path(const struct path *path, struct path *root,
2485 char *buf, int buflen)
2486{
2487 char *res = buf + buflen;
2488 int error;
2489
2490 prepend(&res, &buflen, "\0", 1);
2491 write_seqlock(&rename_lock);
2492 error = prepend_path(path, root, &res, &buflen);
2493 write_sequnlock(&rename_lock);
2494
2495 if (error)
2496 return ERR_PTR(error);
2497 return res;
2498}
2499
2500/*
2501 * same as __d_path but appends "(deleted)" for unlinked files.
2502 */
2503static int path_with_deleted(const struct path *path, struct path *root,
2504 char **buf, int *buflen)
2505{
2506 prepend(buf, buflen, "\0", 1);
2507 if (d_unlinked(path->dentry)) {
2508 int error = prepend(buf, buflen, " (deleted)", 10);
2509 if (error)
2510 return error;
2511 }
2512
2513 return prepend_path(path, root, buf, buflen);
2514}
2515
2516static int prepend_unreachable(char **buffer, int *buflen)
2517{
2518 return prepend(buffer, buflen, "(unreachable)", 13);
2519}
2520
2521/**
2522 * d_path - return the path of a dentry
2523 * @path: path to report
2524 * @buf: buffer to return value in
2525 * @buflen: buffer length
2526 *
2527 * Convert a dentry into an ASCII path name. If the entry has been deleted
2528 * the string " (deleted)" is appended. Note that this is ambiguous.
2529 *
2530 * Returns a pointer into the buffer or an error code if the path was
2531 * too long. Note: Callers should use the returned pointer, not the passed
2532 * in buffer, to use the name! The implementation often starts at an offset
2533 * into the buffer, and may leave 0 bytes at the start.
2534 *
2535 * "buflen" should be positive.
2536 */
2537char *d_path(const struct path *path, char *buf, int buflen)
2538{
2539 char *res = buf + buflen;
2540 struct path root;
2541 struct path tmp;
2542 int error;
2543
2544 /*
2545 * We have various synthetic filesystems that never get mounted. On
2546 * these filesystems dentries are never used for lookup purposes, and
2547 * thus don't need to be hashed. They also don't need a name until a
2548 * user wants to identify the object in /proc/pid/fd/. The little hack
2549 * below allows us to generate a name for these objects on demand:
2550 */
2551 if (path->dentry->d_op && path->dentry->d_op->d_dname)
2552 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2553
2554 get_fs_root(current->fs, &root);
2555 write_seqlock(&rename_lock);
2556 tmp = root;
2557 error = path_with_deleted(path, &tmp, &res, &buflen);
2558 if (error)
2559 res = ERR_PTR(error);
2560 write_sequnlock(&rename_lock);
2561 path_put(&root);
2562 return res;
2563}
2564EXPORT_SYMBOL(d_path);
2565
2566/**
2567 * d_path_with_unreachable - return the path of a dentry
2568 * @path: path to report
2569 * @buf: buffer to return value in
2570 * @buflen: buffer length
2571 *
2572 * The difference from d_path() is that this prepends "(unreachable)"
2573 * to paths which are unreachable from the current process' root.
2574 */
2575char *d_path_with_unreachable(const struct path *path, char *buf, int buflen)
2576{
2577 char *res = buf + buflen;
2578 struct path root;
2579 struct path tmp;
2580 int error;
2581
2582 if (path->dentry->d_op && path->dentry->d_op->d_dname)
2583 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2584
2585 get_fs_root(current->fs, &root);
2586 write_seqlock(&rename_lock);
2587 tmp = root;
2588 error = path_with_deleted(path, &tmp, &res, &buflen);
2589 if (!error && !path_equal(&tmp, &root))
2590 error = prepend_unreachable(&res, &buflen);
2591 write_sequnlock(&rename_lock);
2592 path_put(&root);
2593 if (error)
2594 res = ERR_PTR(error);
2595
2596 return res;
2597}
2598
2599/*
2600 * Helper function for dentry_operations.d_dname() members
2601 */
2602char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
2603 const char *fmt, ...)
2604{
2605 va_list args;
2606 char temp[64];
2607 int sz;
2608
2609 va_start(args, fmt);
2610 sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
2611 va_end(args);
2612
2613 if (sz > sizeof(temp) || sz > buflen)
2614 return ERR_PTR(-ENAMETOOLONG);
2615
2616 buffer += buflen - sz;
2617 return memcpy(buffer, temp, sz);
2618}
2619
2620/*
2621 * Write full pathname from the root of the filesystem into the buffer.
2622 */
2623static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
2624{
2625 char *end = buf + buflen;
2626 char *retval;
2627
2628 prepend(&end, &buflen, "\0", 1);
2629 if (buflen < 1)
2630 goto Elong;
2631 /* Get '/' right */
2632 retval = end-1;
2633 *retval = '/';
2634
2635 while (!IS_ROOT(dentry)) {
2636 struct dentry *parent = dentry->d_parent;
2637 int error;
2638
2639 prefetch(parent);
2640 spin_lock(&dentry->d_lock);
2641 error = prepend_name(&end, &buflen, &dentry->d_name);
2642 spin_unlock(&dentry->d_lock);
2643 if (error != 0 || prepend(&end, &buflen, "/", 1) != 0)
2644 goto Elong;
2645
2646 retval = end;
2647 dentry = parent;
2648 }
2649 return retval;
2650Elong:
2651 return ERR_PTR(-ENAMETOOLONG);
2652}
2653
2654char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
2655{
2656 char *retval;
2657
2658 write_seqlock(&rename_lock);
2659 retval = __dentry_path(dentry, buf, buflen);
2660 write_sequnlock(&rename_lock);
2661
2662 return retval;
2663}
2664EXPORT_SYMBOL(dentry_path_raw);
2665
2666char *dentry_path(struct dentry *dentry, char *buf, int buflen)
2667{
2668 char *p = NULL;
2669 char *retval;
2670
2671 write_seqlock(&rename_lock);
2672 if (d_unlinked(dentry)) {
2673 p = buf + buflen;
2674 if (prepend(&p, &buflen, "//deleted", 10) != 0)
2675 goto Elong;
2676 buflen++;
2677 }
2678 retval = __dentry_path(dentry, buf, buflen);
2679 write_sequnlock(&rename_lock);
2680 if (!IS_ERR(retval) && p)
2681 *p = '/'; /* restore '/' overriden with '\0' */
2682 return retval;
2683Elong:
2684 return ERR_PTR(-ENAMETOOLONG);
2685}
2686
2687/*
2688 * NOTE! The user-level library version returns a
2689 * character pointer. The kernel system call just
2690 * returns the length of the buffer filled (which
2691 * includes the ending '\0' character), or a negative
2692 * error value. So libc would do something like
2693 *
2694 * char *getcwd(char * buf, size_t size)
2695 * {
2696 * int retval;
2697 *
2698 * retval = sys_getcwd(buf, size);
2699 * if (retval >= 0)
2700 * return buf;
2701 * errno = -retval;
2702 * return NULL;
2703 * }
2704 */
2705SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
2706{
2707 int error;
2708 struct path pwd, root;
2709 char *page = (char *) __get_free_page(GFP_USER);
2710
2711 if (!page)
2712 return -ENOMEM;
2713
2714 get_fs_root_and_pwd(current->fs, &root, &pwd);
2715
2716 error = -ENOENT;
2717 write_seqlock(&rename_lock);
2718 if (!d_unlinked(pwd.dentry)) {
2719 unsigned long len;
2720 struct path tmp = root;
2721 char *cwd = page + PAGE_SIZE;
2722 int buflen = PAGE_SIZE;
2723
2724 prepend(&cwd, &buflen, "\0", 1);
2725 error = prepend_path(&pwd, &tmp, &cwd, &buflen);
2726 write_sequnlock(&rename_lock);
2727
2728 if (error)
2729 goto out;
2730
2731 /* Unreachable from current root */
2732 if (!path_equal(&tmp, &root)) {
2733 error = prepend_unreachable(&cwd, &buflen);
2734 if (error)
2735 goto out;
2736 }
2737
2738 error = -ERANGE;
2739 len = PAGE_SIZE + page - cwd;
2740 if (len <= size) {
2741 error = len;
2742 if (copy_to_user(buf, cwd, len))
2743 error = -EFAULT;
2744 }
2745 } else {
2746 write_sequnlock(&rename_lock);
2747 }
2748
2749out:
2750 path_put(&pwd);
2751 path_put(&root);
2752 free_page((unsigned long) page);
2753 return error;
2754}
2755
2756/*
2757 * Test whether new_dentry is a subdirectory of old_dentry.
2758 *
2759 * Trivially implemented using the dcache structure
2760 */
2761
2762/**
2763 * is_subdir - is new dentry a subdirectory of old_dentry
2764 * @new_dentry: new dentry
2765 * @old_dentry: old dentry
2766 *
2767 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
2768 * Returns 0 otherwise.
2769 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
2770 */
2771
2772int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
2773{
2774 int result;
2775 unsigned seq;
2776
2777 if (new_dentry == old_dentry)
2778 return 1;
2779
2780 do {
2781 /* for restarting inner loop in case of seq retry */
2782 seq = read_seqbegin(&rename_lock);
2783 /*
2784 * Need rcu_readlock to protect against the d_parent trashing
2785 * due to d_move
2786 */
2787 rcu_read_lock();
2788 if (d_ancestor(old_dentry, new_dentry))
2789 result = 1;
2790 else
2791 result = 0;
2792 rcu_read_unlock();
2793 } while (read_seqretry(&rename_lock, seq));
2794
2795 return result;
2796}
2797
2798int path_is_under(struct path *path1, struct path *path2)
2799{
2800 struct vfsmount *mnt = path1->mnt;
2801 struct dentry *dentry = path1->dentry;
2802 int res;
2803
2804 br_read_lock(vfsmount_lock);
2805 if (mnt != path2->mnt) {
2806 for (;;) {
2807 if (mnt->mnt_parent == mnt) {
2808 br_read_unlock(vfsmount_lock);
2809 return 0;
2810 }
2811 if (mnt->mnt_parent == path2->mnt)
2812 break;
2813 mnt = mnt->mnt_parent;
2814 }
2815 dentry = mnt->mnt_mountpoint;
2816 }
2817 res = is_subdir(dentry, path2->dentry);
2818 br_read_unlock(vfsmount_lock);
2819 return res;
2820}
2821EXPORT_SYMBOL(path_is_under);
2822
2823void d_genocide(struct dentry *root)
2824{
2825 struct dentry *this_parent;
2826 struct list_head *next;
2827 unsigned seq;
2828 int locked = 0;
2829
2830 seq = read_seqbegin(&rename_lock);
2831again:
2832 this_parent = root;
2833 spin_lock(&this_parent->d_lock);
2834repeat:
2835 next = this_parent->d_subdirs.next;
2836resume:
2837 while (next != &this_parent->d_subdirs) {
2838 struct list_head *tmp = next;
2839 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
2840 next = tmp->next;
2841
2842 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
2843 if (d_unhashed(dentry) || !dentry->d_inode) {
2844 spin_unlock(&dentry->d_lock);
2845 continue;
2846 }
2847 if (!list_empty(&dentry->d_subdirs)) {
2848 spin_unlock(&this_parent->d_lock);
2849 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
2850 this_parent = dentry;
2851 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
2852 goto repeat;
2853 }
2854 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
2855 dentry->d_flags |= DCACHE_GENOCIDE;
2856 dentry->d_count--;
2857 }
2858 spin_unlock(&dentry->d_lock);
2859 }
2860 if (this_parent != root) {
2861 struct dentry *child = this_parent;
2862 if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
2863 this_parent->d_flags |= DCACHE_GENOCIDE;
2864 this_parent->d_count--;
2865 }
2866 this_parent = try_to_ascend(this_parent, locked, seq);
2867 if (!this_parent)
2868 goto rename_retry;
2869 next = child->d_u.d_child.next;
2870 goto resume;
2871 }
2872 spin_unlock(&this_parent->d_lock);
2873 if (!locked && read_seqretry(&rename_lock, seq))
2874 goto rename_retry;
2875 if (locked)
2876 write_sequnlock(&rename_lock);
2877 return;
2878
2879rename_retry:
2880 locked = 1;
2881 write_seqlock(&rename_lock);
2882 goto again;
2883}
2884
2885/**
2886 * find_inode_number - check for dentry with name
2887 * @dir: directory to check
2888 * @name: Name to find.
2889 *
2890 * Check whether a dentry already exists for the given name,
2891 * and return the inode number if it has an inode. Otherwise
2892 * 0 is returned.
2893 *
2894 * This routine is used to post-process directory listings for
2895 * filesystems using synthetic inode numbers, and is necessary
2896 * to keep getcwd() working.
2897 */
2898
2899ino_t find_inode_number(struct dentry *dir, struct qstr *name)
2900{
2901 struct dentry * dentry;
2902 ino_t ino = 0;
2903
2904 dentry = d_hash_and_lookup(dir, name);
2905 if (dentry) {
2906 if (dentry->d_inode)
2907 ino = dentry->d_inode->i_ino;
2908 dput(dentry);
2909 }
2910 return ino;
2911}
2912EXPORT_SYMBOL(find_inode_number);
2913
2914static __initdata unsigned long dhash_entries;
2915static int __init set_dhash_entries(char *str)
2916{
2917 if (!str)
2918 return 0;
2919 dhash_entries = simple_strtoul(str, &str, 0);
2920 return 1;
2921}
2922__setup("dhash_entries=", set_dhash_entries);
2923
2924static void __init dcache_init_early(void)
2925{
2926 int loop;
2927
2928 /* If hashes are distributed across NUMA nodes, defer
2929 * hash allocation until vmalloc space is available.
2930 */
2931 if (hashdist)
2932 return;
2933
2934 dentry_hashtable =
2935 alloc_large_system_hash("Dentry cache",
2936 sizeof(struct hlist_bl_head),
2937 dhash_entries,
2938 13,
2939 HASH_EARLY,
2940 &d_hash_shift,
2941 &d_hash_mask,
2942 0);
2943
2944 for (loop = 0; loop < (1 << d_hash_shift); loop++)
2945 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
2946}
2947
2948static void __init dcache_init(void)
2949{
2950 int loop;
2951
2952 /*
2953 * A constructor could be added for stable state like the lists,
2954 * but it is probably not worth it because of the cache nature
2955 * of the dcache.
2956 */
2957 dentry_cache = KMEM_CACHE(dentry,
2958 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
2959
2960 /* Hash may have been set up in dcache_init_early */
2961 if (!hashdist)
2962 return;
2963
2964 dentry_hashtable =
2965 alloc_large_system_hash("Dentry cache",
2966 sizeof(struct hlist_bl_head),
2967 dhash_entries,
2968 13,
2969 0,
2970 &d_hash_shift,
2971 &d_hash_mask,
2972 0);
2973
2974 for (loop = 0; loop < (1 << d_hash_shift); loop++)
2975 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
2976}
2977
2978/* SLAB cache for __getname() consumers */
2979struct kmem_cache *names_cachep __read_mostly;
2980EXPORT_SYMBOL(names_cachep);
2981
2982EXPORT_SYMBOL(d_genocide);
2983
2984void __init vfs_caches_init_early(void)
2985{
2986 dcache_init_early();
2987 inode_init_early();
2988}
2989
2990void __init vfs_caches_init(unsigned long mempages)
2991{
2992 unsigned long reserve;
2993
2994 /* Base hash sizes on available memory, with a reserve equal to
2995 150% of current kernel size */
2996
2997 reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
2998 mempages -= reserve;
2999
3000 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
3001 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
3002
3003 dcache_init();
3004 inode_init();
3005 files_init(mempages);
3006 mnt_init();
3007 bdev_cache_init();
3008 chrdev_init();
3009}