Loading...
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/*
39 * Usage:
40 * dcache->d_inode->i_lock protects:
41 * - i_dentry, d_u.d_alias, d_inode of aliases
42 * dcache_hash_bucket lock protects:
43 * - the dcache hash table
44 * s_roots bl list spinlock protects:
45 * - the s_roots list (see __d_drop)
46 * dentry->d_sb->s_dentry_lru_lock protects:
47 * - the dcache lru lists and counters
48 * d_lock protects:
49 * - d_flags
50 * - d_name
51 * - d_lru
52 * - d_count
53 * - d_unhashed()
54 * - d_parent and d_chilren
55 * - childrens' d_sib and d_parent
56 * - d_u.d_alias, d_inode
57 *
58 * Ordering:
59 * dentry->d_inode->i_lock
60 * dentry->d_lock
61 * dentry->d_sb->s_dentry_lru_lock
62 * dcache_hash_bucket lock
63 * s_roots lock
64 *
65 * If there is an ancestor relationship:
66 * dentry->d_parent->...->d_parent->d_lock
67 * ...
68 * dentry->d_parent->d_lock
69 * dentry->d_lock
70 *
71 * If no ancestor relationship:
72 * arbitrary, since it's serialized on rename_lock
73 */
74int sysctl_vfs_cache_pressure __read_mostly = 100;
75EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
76
77__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
78
79EXPORT_SYMBOL(rename_lock);
80
81static struct kmem_cache *dentry_cache __ro_after_init;
82
83const struct qstr empty_name = QSTR_INIT("", 0);
84EXPORT_SYMBOL(empty_name);
85const struct qstr slash_name = QSTR_INIT("/", 1);
86EXPORT_SYMBOL(slash_name);
87const struct qstr dotdot_name = QSTR_INIT("..", 2);
88EXPORT_SYMBOL(dotdot_name);
89
90/*
91 * This is the single most critical data structure when it comes
92 * to the dcache: the hashtable for lookups. Somebody should try
93 * to make this good - I've just made it work.
94 *
95 * This hash-function tries to avoid losing too many bits of hash
96 * information, yet avoid using a prime hash-size or similar.
97 */
98
99static unsigned int d_hash_shift __ro_after_init;
100
101static struct hlist_bl_head *dentry_hashtable __ro_after_init;
102
103static inline struct hlist_bl_head *d_hash(unsigned int hash)
104{
105 return dentry_hashtable + (hash >> d_hash_shift);
106}
107
108#define IN_LOOKUP_SHIFT 10
109static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT];
110
111static inline struct hlist_bl_head *in_lookup_hash(const struct dentry *parent,
112 unsigned int hash)
113{
114 hash += (unsigned long) parent / L1_CACHE_BYTES;
115 return in_lookup_hashtable + hash_32(hash, IN_LOOKUP_SHIFT);
116}
117
118struct dentry_stat_t {
119 long nr_dentry;
120 long nr_unused;
121 long age_limit; /* age in seconds */
122 long want_pages; /* pages requested by system */
123 long nr_negative; /* # of unused negative dentries */
124 long dummy; /* Reserved for future use */
125};
126
127static DEFINE_PER_CPU(long, nr_dentry);
128static DEFINE_PER_CPU(long, nr_dentry_unused);
129static DEFINE_PER_CPU(long, nr_dentry_negative);
130
131#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
132/* Statistics gathering. */
133static struct dentry_stat_t dentry_stat = {
134 .age_limit = 45,
135};
136
137/*
138 * Here we resort to our own counters instead of using generic per-cpu counters
139 * for consistency with what the vfs inode code does. We are expected to harvest
140 * better code and performance by having our own specialized counters.
141 *
142 * Please note that the loop is done over all possible CPUs, not over all online
143 * CPUs. The reason for this is that we don't want to play games with CPUs going
144 * on and off. If one of them goes off, we will just keep their counters.
145 *
146 * glommer: See cffbc8a for details, and if you ever intend to change this,
147 * please update all vfs counters to match.
148 */
149static long get_nr_dentry(void)
150{
151 int i;
152 long sum = 0;
153 for_each_possible_cpu(i)
154 sum += per_cpu(nr_dentry, i);
155 return sum < 0 ? 0 : sum;
156}
157
158static long get_nr_dentry_unused(void)
159{
160 int i;
161 long sum = 0;
162 for_each_possible_cpu(i)
163 sum += per_cpu(nr_dentry_unused, i);
164 return sum < 0 ? 0 : sum;
165}
166
167static long get_nr_dentry_negative(void)
168{
169 int i;
170 long sum = 0;
171
172 for_each_possible_cpu(i)
173 sum += per_cpu(nr_dentry_negative, i);
174 return sum < 0 ? 0 : sum;
175}
176
177static int proc_nr_dentry(struct ctl_table *table, int write, void *buffer,
178 size_t *lenp, loff_t *ppos)
179{
180 dentry_stat.nr_dentry = get_nr_dentry();
181 dentry_stat.nr_unused = get_nr_dentry_unused();
182 dentry_stat.nr_negative = get_nr_dentry_negative();
183 return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
184}
185
186static struct ctl_table fs_dcache_sysctls[] = {
187 {
188 .procname = "dentry-state",
189 .data = &dentry_stat,
190 .maxlen = 6*sizeof(long),
191 .mode = 0444,
192 .proc_handler = proc_nr_dentry,
193 },
194};
195
196static int __init init_fs_dcache_sysctls(void)
197{
198 register_sysctl_init("fs", fs_dcache_sysctls);
199 return 0;
200}
201fs_initcall(init_fs_dcache_sysctls);
202#endif
203
204/*
205 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
206 * The strings are both count bytes long, and count is non-zero.
207 */
208#ifdef CONFIG_DCACHE_WORD_ACCESS
209
210#include <asm/word-at-a-time.h>
211/*
212 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
213 * aligned allocation for this particular component. We don't
214 * strictly need the load_unaligned_zeropad() safety, but it
215 * doesn't hurt either.
216 *
217 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
218 * need the careful unaligned handling.
219 */
220static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
221{
222 unsigned long a,b,mask;
223
224 for (;;) {
225 a = read_word_at_a_time(cs);
226 b = load_unaligned_zeropad(ct);
227 if (tcount < sizeof(unsigned long))
228 break;
229 if (unlikely(a != b))
230 return 1;
231 cs += sizeof(unsigned long);
232 ct += sizeof(unsigned long);
233 tcount -= sizeof(unsigned long);
234 if (!tcount)
235 return 0;
236 }
237 mask = bytemask_from_count(tcount);
238 return unlikely(!!((a ^ b) & mask));
239}
240
241#else
242
243static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
244{
245 do {
246 if (*cs != *ct)
247 return 1;
248 cs++;
249 ct++;
250 tcount--;
251 } while (tcount);
252 return 0;
253}
254
255#endif
256
257static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
258{
259 /*
260 * Be careful about RCU walk racing with rename:
261 * use 'READ_ONCE' to fetch the name pointer.
262 *
263 * NOTE! Even if a rename will mean that the length
264 * was not loaded atomically, we don't care. The
265 * RCU walk will check the sequence count eventually,
266 * and catch it. And we won't overrun the buffer,
267 * because we're reading the name pointer atomically,
268 * and a dentry name is guaranteed to be properly
269 * terminated with a NUL byte.
270 *
271 * End result: even if 'len' is wrong, we'll exit
272 * early because the data cannot match (there can
273 * be no NUL in the ct/tcount data)
274 */
275 const unsigned char *cs = READ_ONCE(dentry->d_name.name);
276
277 return dentry_string_cmp(cs, ct, tcount);
278}
279
280struct external_name {
281 union {
282 atomic_t count;
283 struct rcu_head head;
284 } u;
285 unsigned char name[];
286};
287
288static inline struct external_name *external_name(struct dentry *dentry)
289{
290 return container_of(dentry->d_name.name, struct external_name, name[0]);
291}
292
293static void __d_free(struct rcu_head *head)
294{
295 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
296
297 kmem_cache_free(dentry_cache, dentry);
298}
299
300static void __d_free_external(struct rcu_head *head)
301{
302 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
303 kfree(external_name(dentry));
304 kmem_cache_free(dentry_cache, dentry);
305}
306
307static inline int dname_external(const struct dentry *dentry)
308{
309 return dentry->d_name.name != dentry->d_iname;
310}
311
312void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry)
313{
314 spin_lock(&dentry->d_lock);
315 name->name = dentry->d_name;
316 if (unlikely(dname_external(dentry))) {
317 atomic_inc(&external_name(dentry)->u.count);
318 } else {
319 memcpy(name->inline_name, dentry->d_iname,
320 dentry->d_name.len + 1);
321 name->name.name = name->inline_name;
322 }
323 spin_unlock(&dentry->d_lock);
324}
325EXPORT_SYMBOL(take_dentry_name_snapshot);
326
327void release_dentry_name_snapshot(struct name_snapshot *name)
328{
329 if (unlikely(name->name.name != name->inline_name)) {
330 struct external_name *p;
331 p = container_of(name->name.name, struct external_name, name[0]);
332 if (unlikely(atomic_dec_and_test(&p->u.count)))
333 kfree_rcu(p, u.head);
334 }
335}
336EXPORT_SYMBOL(release_dentry_name_snapshot);
337
338static inline void __d_set_inode_and_type(struct dentry *dentry,
339 struct inode *inode,
340 unsigned type_flags)
341{
342 unsigned flags;
343
344 dentry->d_inode = inode;
345 flags = READ_ONCE(dentry->d_flags);
346 flags &= ~DCACHE_ENTRY_TYPE;
347 flags |= type_flags;
348 smp_store_release(&dentry->d_flags, flags);
349}
350
351static inline void __d_clear_type_and_inode(struct dentry *dentry)
352{
353 unsigned flags = READ_ONCE(dentry->d_flags);
354
355 flags &= ~DCACHE_ENTRY_TYPE;
356 WRITE_ONCE(dentry->d_flags, flags);
357 dentry->d_inode = NULL;
358 if (dentry->d_flags & DCACHE_LRU_LIST)
359 this_cpu_inc(nr_dentry_negative);
360}
361
362static void dentry_free(struct dentry *dentry)
363{
364 WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias));
365 if (unlikely(dname_external(dentry))) {
366 struct external_name *p = external_name(dentry);
367 if (likely(atomic_dec_and_test(&p->u.count))) {
368 call_rcu(&dentry->d_u.d_rcu, __d_free_external);
369 return;
370 }
371 }
372 /* if dentry was never visible to RCU, immediate free is OK */
373 if (dentry->d_flags & DCACHE_NORCU)
374 __d_free(&dentry->d_u.d_rcu);
375 else
376 call_rcu(&dentry->d_u.d_rcu, __d_free);
377}
378
379/*
380 * Release the dentry's inode, using the filesystem
381 * d_iput() operation if defined.
382 */
383static void dentry_unlink_inode(struct dentry * dentry)
384 __releases(dentry->d_lock)
385 __releases(dentry->d_inode->i_lock)
386{
387 struct inode *inode = dentry->d_inode;
388
389 raw_write_seqcount_begin(&dentry->d_seq);
390 __d_clear_type_and_inode(dentry);
391 hlist_del_init(&dentry->d_u.d_alias);
392 raw_write_seqcount_end(&dentry->d_seq);
393 spin_unlock(&dentry->d_lock);
394 spin_unlock(&inode->i_lock);
395 if (!inode->i_nlink)
396 fsnotify_inoderemove(inode);
397 if (dentry->d_op && dentry->d_op->d_iput)
398 dentry->d_op->d_iput(dentry, inode);
399 else
400 iput(inode);
401}
402
403/*
404 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
405 * is in use - which includes both the "real" per-superblock
406 * LRU list _and_ the DCACHE_SHRINK_LIST use.
407 *
408 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
409 * on the shrink list (ie not on the superblock LRU list).
410 *
411 * The per-cpu "nr_dentry_unused" counters are updated with
412 * the DCACHE_LRU_LIST bit.
413 *
414 * The per-cpu "nr_dentry_negative" counters are only updated
415 * when deleted from or added to the per-superblock LRU list, not
416 * from/to the shrink list. That is to avoid an unneeded dec/inc
417 * pair when moving from LRU to shrink list in select_collect().
418 *
419 * These helper functions make sure we always follow the
420 * rules. d_lock must be held by the caller.
421 */
422#define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
423static void d_lru_add(struct dentry *dentry)
424{
425 D_FLAG_VERIFY(dentry, 0);
426 dentry->d_flags |= DCACHE_LRU_LIST;
427 this_cpu_inc(nr_dentry_unused);
428 if (d_is_negative(dentry))
429 this_cpu_inc(nr_dentry_negative);
430 WARN_ON_ONCE(!list_lru_add_obj(
431 &dentry->d_sb->s_dentry_lru, &dentry->d_lru));
432}
433
434static void d_lru_del(struct dentry *dentry)
435{
436 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
437 dentry->d_flags &= ~DCACHE_LRU_LIST;
438 this_cpu_dec(nr_dentry_unused);
439 if (d_is_negative(dentry))
440 this_cpu_dec(nr_dentry_negative);
441 WARN_ON_ONCE(!list_lru_del_obj(
442 &dentry->d_sb->s_dentry_lru, &dentry->d_lru));
443}
444
445static void d_shrink_del(struct dentry *dentry)
446{
447 D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
448 list_del_init(&dentry->d_lru);
449 dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
450 this_cpu_dec(nr_dentry_unused);
451}
452
453static void d_shrink_add(struct dentry *dentry, struct list_head *list)
454{
455 D_FLAG_VERIFY(dentry, 0);
456 list_add(&dentry->d_lru, list);
457 dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST;
458 this_cpu_inc(nr_dentry_unused);
459}
460
461/*
462 * These can only be called under the global LRU lock, ie during the
463 * callback for freeing the LRU list. "isolate" removes it from the
464 * LRU lists entirely, while shrink_move moves it to the indicated
465 * private list.
466 */
467static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry)
468{
469 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
470 dentry->d_flags &= ~DCACHE_LRU_LIST;
471 this_cpu_dec(nr_dentry_unused);
472 if (d_is_negative(dentry))
473 this_cpu_dec(nr_dentry_negative);
474 list_lru_isolate(lru, &dentry->d_lru);
475}
476
477static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
478 struct list_head *list)
479{
480 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
481 dentry->d_flags |= DCACHE_SHRINK_LIST;
482 if (d_is_negative(dentry))
483 this_cpu_dec(nr_dentry_negative);
484 list_lru_isolate_move(lru, &dentry->d_lru, list);
485}
486
487static void ___d_drop(struct dentry *dentry)
488{
489 struct hlist_bl_head *b;
490 /*
491 * Hashed dentries are normally on the dentry hashtable,
492 * with the exception of those newly allocated by
493 * d_obtain_root, which are always IS_ROOT:
494 */
495 if (unlikely(IS_ROOT(dentry)))
496 b = &dentry->d_sb->s_roots;
497 else
498 b = d_hash(dentry->d_name.hash);
499
500 hlist_bl_lock(b);
501 __hlist_bl_del(&dentry->d_hash);
502 hlist_bl_unlock(b);
503}
504
505void __d_drop(struct dentry *dentry)
506{
507 if (!d_unhashed(dentry)) {
508 ___d_drop(dentry);
509 dentry->d_hash.pprev = NULL;
510 write_seqcount_invalidate(&dentry->d_seq);
511 }
512}
513EXPORT_SYMBOL(__d_drop);
514
515/**
516 * d_drop - drop a dentry
517 * @dentry: dentry to drop
518 *
519 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
520 * be found through a VFS lookup any more. Note that this is different from
521 * deleting the dentry - d_delete will try to mark the dentry negative if
522 * possible, giving a successful _negative_ lookup, while d_drop will
523 * just make the cache lookup fail.
524 *
525 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
526 * reason (NFS timeouts or autofs deletes).
527 *
528 * __d_drop requires dentry->d_lock
529 *
530 * ___d_drop doesn't mark dentry as "unhashed"
531 * (dentry->d_hash.pprev will be LIST_POISON2, not NULL).
532 */
533void d_drop(struct dentry *dentry)
534{
535 spin_lock(&dentry->d_lock);
536 __d_drop(dentry);
537 spin_unlock(&dentry->d_lock);
538}
539EXPORT_SYMBOL(d_drop);
540
541static inline void dentry_unlist(struct dentry *dentry)
542{
543 struct dentry *next;
544 /*
545 * Inform d_walk() and shrink_dentry_list() that we are no longer
546 * attached to the dentry tree
547 */
548 dentry->d_flags |= DCACHE_DENTRY_KILLED;
549 if (unlikely(hlist_unhashed(&dentry->d_sib)))
550 return;
551 __hlist_del(&dentry->d_sib);
552 /*
553 * Cursors can move around the list of children. While we'd been
554 * a normal list member, it didn't matter - ->d_sib.next would've
555 * been updated. However, from now on it won't be and for the
556 * things like d_walk() it might end up with a nasty surprise.
557 * Normally d_walk() doesn't care about cursors moving around -
558 * ->d_lock on parent prevents that and since a cursor has no children
559 * of its own, we get through it without ever unlocking the parent.
560 * There is one exception, though - if we ascend from a child that
561 * gets killed as soon as we unlock it, the next sibling is found
562 * using the value left in its ->d_sib.next. And if _that_
563 * pointed to a cursor, and cursor got moved (e.g. by lseek())
564 * before d_walk() regains parent->d_lock, we'll end up skipping
565 * everything the cursor had been moved past.
566 *
567 * Solution: make sure that the pointer left behind in ->d_sib.next
568 * points to something that won't be moving around. I.e. skip the
569 * cursors.
570 */
571 while (dentry->d_sib.next) {
572 next = hlist_entry(dentry->d_sib.next, struct dentry, d_sib);
573 if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR)))
574 break;
575 dentry->d_sib.next = next->d_sib.next;
576 }
577}
578
579static struct dentry *__dentry_kill(struct dentry *dentry)
580{
581 struct dentry *parent = NULL;
582 bool can_free = true;
583
584 /*
585 * The dentry is now unrecoverably dead to the world.
586 */
587 lockref_mark_dead(&dentry->d_lockref);
588
589 /*
590 * inform the fs via d_prune that this dentry is about to be
591 * unhashed and destroyed.
592 */
593 if (dentry->d_flags & DCACHE_OP_PRUNE)
594 dentry->d_op->d_prune(dentry);
595
596 if (dentry->d_flags & DCACHE_LRU_LIST) {
597 if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
598 d_lru_del(dentry);
599 }
600 /* if it was on the hash then remove it */
601 __d_drop(dentry);
602 if (dentry->d_inode)
603 dentry_unlink_inode(dentry);
604 else
605 spin_unlock(&dentry->d_lock);
606 this_cpu_dec(nr_dentry);
607 if (dentry->d_op && dentry->d_op->d_release)
608 dentry->d_op->d_release(dentry);
609
610 cond_resched();
611 /* now that it's negative, ->d_parent is stable */
612 if (!IS_ROOT(dentry)) {
613 parent = dentry->d_parent;
614 spin_lock(&parent->d_lock);
615 }
616 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
617 dentry_unlist(dentry);
618 if (dentry->d_flags & DCACHE_SHRINK_LIST)
619 can_free = false;
620 spin_unlock(&dentry->d_lock);
621 if (likely(can_free))
622 dentry_free(dentry);
623 if (parent && --parent->d_lockref.count) {
624 spin_unlock(&parent->d_lock);
625 return NULL;
626 }
627 return parent;
628}
629
630/*
631 * Lock a dentry for feeding it to __dentry_kill().
632 * Called under rcu_read_lock() and dentry->d_lock; the former
633 * guarantees that nothing we access will be freed under us.
634 * Note that dentry is *not* protected from concurrent dentry_kill(),
635 * d_delete(), etc.
636 *
637 * Return false if dentry is busy. Otherwise, return true and have
638 * that dentry's inode locked.
639 */
640
641static bool lock_for_kill(struct dentry *dentry)
642{
643 struct inode *inode = dentry->d_inode;
644
645 if (unlikely(dentry->d_lockref.count))
646 return false;
647
648 if (!inode || likely(spin_trylock(&inode->i_lock)))
649 return true;
650
651 do {
652 spin_unlock(&dentry->d_lock);
653 spin_lock(&inode->i_lock);
654 spin_lock(&dentry->d_lock);
655 if (likely(inode == dentry->d_inode))
656 break;
657 spin_unlock(&inode->i_lock);
658 inode = dentry->d_inode;
659 } while (inode);
660 if (likely(!dentry->d_lockref.count))
661 return true;
662 if (inode)
663 spin_unlock(&inode->i_lock);
664 return false;
665}
666
667/*
668 * Decide if dentry is worth retaining. Usually this is called with dentry
669 * locked; if not locked, we are more limited and might not be able to tell
670 * without a lock. False in this case means "punt to locked path and recheck".
671 *
672 * In case we aren't locked, these predicates are not "stable". However, it is
673 * sufficient that at some point after we dropped the reference the dentry was
674 * hashed and the flags had the proper value. Other dentry users may have
675 * re-gotten a reference to the dentry and change that, but our work is done -
676 * we can leave the dentry around with a zero refcount.
677 */
678static inline bool retain_dentry(struct dentry *dentry, bool locked)
679{
680 unsigned int d_flags;
681
682 smp_rmb();
683 d_flags = READ_ONCE(dentry->d_flags);
684
685 // Unreachable? Nobody would be able to look it up, no point retaining
686 if (unlikely(d_unhashed(dentry)))
687 return false;
688
689 // Same if it's disconnected
690 if (unlikely(d_flags & DCACHE_DISCONNECTED))
691 return false;
692
693 // ->d_delete() might tell us not to bother, but that requires
694 // ->d_lock; can't decide without it
695 if (unlikely(d_flags & DCACHE_OP_DELETE)) {
696 if (!locked || dentry->d_op->d_delete(dentry))
697 return false;
698 }
699
700 // Explicitly told not to bother
701 if (unlikely(d_flags & DCACHE_DONTCACHE))
702 return false;
703
704 // At this point it looks like we ought to keep it. We also might
705 // need to do something - put it on LRU if it wasn't there already
706 // and mark it referenced if it was on LRU, but not marked yet.
707 // Unfortunately, both actions require ->d_lock, so in lockless
708 // case we'd have to punt rather than doing those.
709 if (unlikely(!(d_flags & DCACHE_LRU_LIST))) {
710 if (!locked)
711 return false;
712 d_lru_add(dentry);
713 } else if (unlikely(!(d_flags & DCACHE_REFERENCED))) {
714 if (!locked)
715 return false;
716 dentry->d_flags |= DCACHE_REFERENCED;
717 }
718 return true;
719}
720
721void d_mark_dontcache(struct inode *inode)
722{
723 struct dentry *de;
724
725 spin_lock(&inode->i_lock);
726 hlist_for_each_entry(de, &inode->i_dentry, d_u.d_alias) {
727 spin_lock(&de->d_lock);
728 de->d_flags |= DCACHE_DONTCACHE;
729 spin_unlock(&de->d_lock);
730 }
731 inode->i_state |= I_DONTCACHE;
732 spin_unlock(&inode->i_lock);
733}
734EXPORT_SYMBOL(d_mark_dontcache);
735
736/*
737 * Try to do a lockless dput(), and return whether that was successful.
738 *
739 * If unsuccessful, we return false, having already taken the dentry lock.
740 * In that case refcount is guaranteed to be zero and we have already
741 * decided that it's not worth keeping around.
742 *
743 * The caller needs to hold the RCU read lock, so that the dentry is
744 * guaranteed to stay around even if the refcount goes down to zero!
745 */
746static inline bool fast_dput(struct dentry *dentry)
747{
748 int ret;
749
750 /*
751 * try to decrement the lockref optimistically.
752 */
753 ret = lockref_put_return(&dentry->d_lockref);
754
755 /*
756 * If the lockref_put_return() failed due to the lock being held
757 * by somebody else, the fast path has failed. We will need to
758 * get the lock, and then check the count again.
759 */
760 if (unlikely(ret < 0)) {
761 spin_lock(&dentry->d_lock);
762 if (WARN_ON_ONCE(dentry->d_lockref.count <= 0)) {
763 spin_unlock(&dentry->d_lock);
764 return true;
765 }
766 dentry->d_lockref.count--;
767 goto locked;
768 }
769
770 /*
771 * If we weren't the last ref, we're done.
772 */
773 if (ret)
774 return true;
775
776 /*
777 * Can we decide that decrement of refcount is all we needed without
778 * taking the lock? There's a very common case when it's all we need -
779 * dentry looks like it ought to be retained and there's nothing else
780 * to do.
781 */
782 if (retain_dentry(dentry, false))
783 return true;
784
785 /*
786 * Either not worth retaining or we can't tell without the lock.
787 * Get the lock, then. We've already decremented the refcount to 0,
788 * but we'll need to re-check the situation after getting the lock.
789 */
790 spin_lock(&dentry->d_lock);
791
792 /*
793 * Did somebody else grab a reference to it in the meantime, and
794 * we're no longer the last user after all? Alternatively, somebody
795 * else could have killed it and marked it dead. Either way, we
796 * don't need to do anything else.
797 */
798locked:
799 if (dentry->d_lockref.count || retain_dentry(dentry, true)) {
800 spin_unlock(&dentry->d_lock);
801 return true;
802 }
803 return false;
804}
805
806
807/*
808 * This is dput
809 *
810 * This is complicated by the fact that we do not want to put
811 * dentries that are no longer on any hash chain on the unused
812 * list: we'd much rather just get rid of them immediately.
813 *
814 * However, that implies that we have to traverse the dentry
815 * tree upwards to the parents which might _also_ now be
816 * scheduled for deletion (it may have been only waiting for
817 * its last child to go away).
818 *
819 * This tail recursion is done by hand as we don't want to depend
820 * on the compiler to always get this right (gcc generally doesn't).
821 * Real recursion would eat up our stack space.
822 */
823
824/*
825 * dput - release a dentry
826 * @dentry: dentry to release
827 *
828 * Release a dentry. This will drop the usage count and if appropriate
829 * call the dentry unlink method as well as removing it from the queues and
830 * releasing its resources. If the parent dentries were scheduled for release
831 * they too may now get deleted.
832 */
833void dput(struct dentry *dentry)
834{
835 if (!dentry)
836 return;
837 might_sleep();
838 rcu_read_lock();
839 if (likely(fast_dput(dentry))) {
840 rcu_read_unlock();
841 return;
842 }
843 while (lock_for_kill(dentry)) {
844 rcu_read_unlock();
845 dentry = __dentry_kill(dentry);
846 if (!dentry)
847 return;
848 if (retain_dentry(dentry, true)) {
849 spin_unlock(&dentry->d_lock);
850 return;
851 }
852 rcu_read_lock();
853 }
854 rcu_read_unlock();
855 spin_unlock(&dentry->d_lock);
856}
857EXPORT_SYMBOL(dput);
858
859static void to_shrink_list(struct dentry *dentry, struct list_head *list)
860__must_hold(&dentry->d_lock)
861{
862 if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
863 if (dentry->d_flags & DCACHE_LRU_LIST)
864 d_lru_del(dentry);
865 d_shrink_add(dentry, list);
866 }
867}
868
869void dput_to_list(struct dentry *dentry, struct list_head *list)
870{
871 rcu_read_lock();
872 if (likely(fast_dput(dentry))) {
873 rcu_read_unlock();
874 return;
875 }
876 rcu_read_unlock();
877 to_shrink_list(dentry, list);
878 spin_unlock(&dentry->d_lock);
879}
880
881struct dentry *dget_parent(struct dentry *dentry)
882{
883 int gotref;
884 struct dentry *ret;
885 unsigned seq;
886
887 /*
888 * Do optimistic parent lookup without any
889 * locking.
890 */
891 rcu_read_lock();
892 seq = raw_seqcount_begin(&dentry->d_seq);
893 ret = READ_ONCE(dentry->d_parent);
894 gotref = lockref_get_not_zero(&ret->d_lockref);
895 rcu_read_unlock();
896 if (likely(gotref)) {
897 if (!read_seqcount_retry(&dentry->d_seq, seq))
898 return ret;
899 dput(ret);
900 }
901
902repeat:
903 /*
904 * Don't need rcu_dereference because we re-check it was correct under
905 * the lock.
906 */
907 rcu_read_lock();
908 ret = dentry->d_parent;
909 spin_lock(&ret->d_lock);
910 if (unlikely(ret != dentry->d_parent)) {
911 spin_unlock(&ret->d_lock);
912 rcu_read_unlock();
913 goto repeat;
914 }
915 rcu_read_unlock();
916 BUG_ON(!ret->d_lockref.count);
917 ret->d_lockref.count++;
918 spin_unlock(&ret->d_lock);
919 return ret;
920}
921EXPORT_SYMBOL(dget_parent);
922
923static struct dentry * __d_find_any_alias(struct inode *inode)
924{
925 struct dentry *alias;
926
927 if (hlist_empty(&inode->i_dentry))
928 return NULL;
929 alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
930 lockref_get(&alias->d_lockref);
931 return alias;
932}
933
934/**
935 * d_find_any_alias - find any alias for a given inode
936 * @inode: inode to find an alias for
937 *
938 * If any aliases exist for the given inode, take and return a
939 * reference for one of them. If no aliases exist, return %NULL.
940 */
941struct dentry *d_find_any_alias(struct inode *inode)
942{
943 struct dentry *de;
944
945 spin_lock(&inode->i_lock);
946 de = __d_find_any_alias(inode);
947 spin_unlock(&inode->i_lock);
948 return de;
949}
950EXPORT_SYMBOL(d_find_any_alias);
951
952static struct dentry *__d_find_alias(struct inode *inode)
953{
954 struct dentry *alias;
955
956 if (S_ISDIR(inode->i_mode))
957 return __d_find_any_alias(inode);
958
959 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
960 spin_lock(&alias->d_lock);
961 if (!d_unhashed(alias)) {
962 dget_dlock(alias);
963 spin_unlock(&alias->d_lock);
964 return alias;
965 }
966 spin_unlock(&alias->d_lock);
967 }
968 return NULL;
969}
970
971/**
972 * d_find_alias - grab a hashed alias of inode
973 * @inode: inode in question
974 *
975 * If inode has a hashed alias, or is a directory and has any alias,
976 * acquire the reference to alias and return it. Otherwise return NULL.
977 * Notice that if inode is a directory there can be only one alias and
978 * it can be unhashed only if it has no children, or if it is the root
979 * of a filesystem, or if the directory was renamed and d_revalidate
980 * was the first vfs operation to notice.
981 *
982 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
983 * any other hashed alias over that one.
984 */
985struct dentry *d_find_alias(struct inode *inode)
986{
987 struct dentry *de = NULL;
988
989 if (!hlist_empty(&inode->i_dentry)) {
990 spin_lock(&inode->i_lock);
991 de = __d_find_alias(inode);
992 spin_unlock(&inode->i_lock);
993 }
994 return de;
995}
996EXPORT_SYMBOL(d_find_alias);
997
998/*
999 * Caller MUST be holding rcu_read_lock() and be guaranteed
1000 * that inode won't get freed until rcu_read_unlock().
1001 */
1002struct dentry *d_find_alias_rcu(struct inode *inode)
1003{
1004 struct hlist_head *l = &inode->i_dentry;
1005 struct dentry *de = NULL;
1006
1007 spin_lock(&inode->i_lock);
1008 // ->i_dentry and ->i_rcu are colocated, but the latter won't be
1009 // used without having I_FREEING set, which means no aliases left
1010 if (likely(!(inode->i_state & I_FREEING) && !hlist_empty(l))) {
1011 if (S_ISDIR(inode->i_mode)) {
1012 de = hlist_entry(l->first, struct dentry, d_u.d_alias);
1013 } else {
1014 hlist_for_each_entry(de, l, d_u.d_alias)
1015 if (!d_unhashed(de))
1016 break;
1017 }
1018 }
1019 spin_unlock(&inode->i_lock);
1020 return de;
1021}
1022
1023/*
1024 * Try to kill dentries associated with this inode.
1025 * WARNING: you must own a reference to inode.
1026 */
1027void d_prune_aliases(struct inode *inode)
1028{
1029 LIST_HEAD(dispose);
1030 struct dentry *dentry;
1031
1032 spin_lock(&inode->i_lock);
1033 hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
1034 spin_lock(&dentry->d_lock);
1035 if (!dentry->d_lockref.count)
1036 to_shrink_list(dentry, &dispose);
1037 spin_unlock(&dentry->d_lock);
1038 }
1039 spin_unlock(&inode->i_lock);
1040 shrink_dentry_list(&dispose);
1041}
1042EXPORT_SYMBOL(d_prune_aliases);
1043
1044static inline void shrink_kill(struct dentry *victim)
1045{
1046 do {
1047 rcu_read_unlock();
1048 victim = __dentry_kill(victim);
1049 rcu_read_lock();
1050 } while (victim && lock_for_kill(victim));
1051 rcu_read_unlock();
1052 if (victim)
1053 spin_unlock(&victim->d_lock);
1054}
1055
1056void shrink_dentry_list(struct list_head *list)
1057{
1058 while (!list_empty(list)) {
1059 struct dentry *dentry;
1060
1061 dentry = list_entry(list->prev, struct dentry, d_lru);
1062 spin_lock(&dentry->d_lock);
1063 rcu_read_lock();
1064 if (!lock_for_kill(dentry)) {
1065 bool can_free;
1066 rcu_read_unlock();
1067 d_shrink_del(dentry);
1068 can_free = dentry->d_flags & DCACHE_DENTRY_KILLED;
1069 spin_unlock(&dentry->d_lock);
1070 if (can_free)
1071 dentry_free(dentry);
1072 continue;
1073 }
1074 d_shrink_del(dentry);
1075 shrink_kill(dentry);
1076 }
1077}
1078
1079static enum lru_status dentry_lru_isolate(struct list_head *item,
1080 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1081{
1082 struct list_head *freeable = arg;
1083 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1084
1085
1086 /*
1087 * we are inverting the lru lock/dentry->d_lock here,
1088 * so use a trylock. If we fail to get the lock, just skip
1089 * it
1090 */
1091 if (!spin_trylock(&dentry->d_lock))
1092 return LRU_SKIP;
1093
1094 /*
1095 * Referenced dentries are still in use. If they have active
1096 * counts, just remove them from the LRU. Otherwise give them
1097 * another pass through the LRU.
1098 */
1099 if (dentry->d_lockref.count) {
1100 d_lru_isolate(lru, dentry);
1101 spin_unlock(&dentry->d_lock);
1102 return LRU_REMOVED;
1103 }
1104
1105 if (dentry->d_flags & DCACHE_REFERENCED) {
1106 dentry->d_flags &= ~DCACHE_REFERENCED;
1107 spin_unlock(&dentry->d_lock);
1108
1109 /*
1110 * The list move itself will be made by the common LRU code. At
1111 * this point, we've dropped the dentry->d_lock but keep the
1112 * lru lock. This is safe to do, since every list movement is
1113 * protected by the lru lock even if both locks are held.
1114 *
1115 * This is guaranteed by the fact that all LRU management
1116 * functions are intermediated by the LRU API calls like
1117 * list_lru_add_obj and list_lru_del_obj. List movement in this file
1118 * only ever occur through this functions or through callbacks
1119 * like this one, that are called from the LRU API.
1120 *
1121 * The only exceptions to this are functions like
1122 * shrink_dentry_list, and code that first checks for the
1123 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1124 * operating only with stack provided lists after they are
1125 * properly isolated from the main list. It is thus, always a
1126 * local access.
1127 */
1128 return LRU_ROTATE;
1129 }
1130
1131 d_lru_shrink_move(lru, dentry, freeable);
1132 spin_unlock(&dentry->d_lock);
1133
1134 return LRU_REMOVED;
1135}
1136
1137/**
1138 * prune_dcache_sb - shrink the dcache
1139 * @sb: superblock
1140 * @sc: shrink control, passed to list_lru_shrink_walk()
1141 *
1142 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1143 * is done when we need more memory and called from the superblock shrinker
1144 * function.
1145 *
1146 * This function may fail to free any resources if all the dentries are in
1147 * use.
1148 */
1149long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc)
1150{
1151 LIST_HEAD(dispose);
1152 long freed;
1153
1154 freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc,
1155 dentry_lru_isolate, &dispose);
1156 shrink_dentry_list(&dispose);
1157 return freed;
1158}
1159
1160static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
1161 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1162{
1163 struct list_head *freeable = arg;
1164 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1165
1166 /*
1167 * we are inverting the lru lock/dentry->d_lock here,
1168 * so use a trylock. If we fail to get the lock, just skip
1169 * it
1170 */
1171 if (!spin_trylock(&dentry->d_lock))
1172 return LRU_SKIP;
1173
1174 d_lru_shrink_move(lru, dentry, freeable);
1175 spin_unlock(&dentry->d_lock);
1176
1177 return LRU_REMOVED;
1178}
1179
1180
1181/**
1182 * shrink_dcache_sb - shrink dcache for a superblock
1183 * @sb: superblock
1184 *
1185 * Shrink the dcache for the specified super block. This is used to free
1186 * the dcache before unmounting a file system.
1187 */
1188void shrink_dcache_sb(struct super_block *sb)
1189{
1190 do {
1191 LIST_HEAD(dispose);
1192
1193 list_lru_walk(&sb->s_dentry_lru,
1194 dentry_lru_isolate_shrink, &dispose, 1024);
1195 shrink_dentry_list(&dispose);
1196 } while (list_lru_count(&sb->s_dentry_lru) > 0);
1197}
1198EXPORT_SYMBOL(shrink_dcache_sb);
1199
1200/**
1201 * enum d_walk_ret - action to talke during tree walk
1202 * @D_WALK_CONTINUE: contrinue walk
1203 * @D_WALK_QUIT: quit walk
1204 * @D_WALK_NORETRY: quit when retry is needed
1205 * @D_WALK_SKIP: skip this dentry and its children
1206 */
1207enum d_walk_ret {
1208 D_WALK_CONTINUE,
1209 D_WALK_QUIT,
1210 D_WALK_NORETRY,
1211 D_WALK_SKIP,
1212};
1213
1214/**
1215 * d_walk - walk the dentry tree
1216 * @parent: start of walk
1217 * @data: data passed to @enter() and @finish()
1218 * @enter: callback when first entering the dentry
1219 *
1220 * The @enter() callbacks are called with d_lock held.
1221 */
1222static void d_walk(struct dentry *parent, void *data,
1223 enum d_walk_ret (*enter)(void *, struct dentry *))
1224{
1225 struct dentry *this_parent, *dentry;
1226 unsigned seq = 0;
1227 enum d_walk_ret ret;
1228 bool retry = true;
1229
1230again:
1231 read_seqbegin_or_lock(&rename_lock, &seq);
1232 this_parent = parent;
1233 spin_lock(&this_parent->d_lock);
1234
1235 ret = enter(data, this_parent);
1236 switch (ret) {
1237 case D_WALK_CONTINUE:
1238 break;
1239 case D_WALK_QUIT:
1240 case D_WALK_SKIP:
1241 goto out_unlock;
1242 case D_WALK_NORETRY:
1243 retry = false;
1244 break;
1245 }
1246repeat:
1247 dentry = d_first_child(this_parent);
1248resume:
1249 hlist_for_each_entry_from(dentry, d_sib) {
1250 if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR))
1251 continue;
1252
1253 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1254
1255 ret = enter(data, dentry);
1256 switch (ret) {
1257 case D_WALK_CONTINUE:
1258 break;
1259 case D_WALK_QUIT:
1260 spin_unlock(&dentry->d_lock);
1261 goto out_unlock;
1262 case D_WALK_NORETRY:
1263 retry = false;
1264 break;
1265 case D_WALK_SKIP:
1266 spin_unlock(&dentry->d_lock);
1267 continue;
1268 }
1269
1270 if (!hlist_empty(&dentry->d_children)) {
1271 spin_unlock(&this_parent->d_lock);
1272 spin_release(&dentry->d_lock.dep_map, _RET_IP_);
1273 this_parent = dentry;
1274 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1275 goto repeat;
1276 }
1277 spin_unlock(&dentry->d_lock);
1278 }
1279 /*
1280 * All done at this level ... ascend and resume the search.
1281 */
1282 rcu_read_lock();
1283ascend:
1284 if (this_parent != parent) {
1285 dentry = this_parent;
1286 this_parent = dentry->d_parent;
1287
1288 spin_unlock(&dentry->d_lock);
1289 spin_lock(&this_parent->d_lock);
1290
1291 /* might go back up the wrong parent if we have had a rename. */
1292 if (need_seqretry(&rename_lock, seq))
1293 goto rename_retry;
1294 /* go into the first sibling still alive */
1295 hlist_for_each_entry_continue(dentry, d_sib) {
1296 if (likely(!(dentry->d_flags & DCACHE_DENTRY_KILLED))) {
1297 rcu_read_unlock();
1298 goto resume;
1299 }
1300 }
1301 goto ascend;
1302 }
1303 if (need_seqretry(&rename_lock, seq))
1304 goto rename_retry;
1305 rcu_read_unlock();
1306
1307out_unlock:
1308 spin_unlock(&this_parent->d_lock);
1309 done_seqretry(&rename_lock, seq);
1310 return;
1311
1312rename_retry:
1313 spin_unlock(&this_parent->d_lock);
1314 rcu_read_unlock();
1315 BUG_ON(seq & 1);
1316 if (!retry)
1317 return;
1318 seq = 1;
1319 goto again;
1320}
1321
1322struct check_mount {
1323 struct vfsmount *mnt;
1324 unsigned int mounted;
1325};
1326
1327static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry)
1328{
1329 struct check_mount *info = data;
1330 struct path path = { .mnt = info->mnt, .dentry = dentry };
1331
1332 if (likely(!d_mountpoint(dentry)))
1333 return D_WALK_CONTINUE;
1334 if (__path_is_mountpoint(&path)) {
1335 info->mounted = 1;
1336 return D_WALK_QUIT;
1337 }
1338 return D_WALK_CONTINUE;
1339}
1340
1341/**
1342 * path_has_submounts - check for mounts over a dentry in the
1343 * current namespace.
1344 * @parent: path to check.
1345 *
1346 * Return true if the parent or its subdirectories contain
1347 * a mount point in the current namespace.
1348 */
1349int path_has_submounts(const struct path *parent)
1350{
1351 struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
1352
1353 read_seqlock_excl(&mount_lock);
1354 d_walk(parent->dentry, &data, path_check_mount);
1355 read_sequnlock_excl(&mount_lock);
1356
1357 return data.mounted;
1358}
1359EXPORT_SYMBOL(path_has_submounts);
1360
1361/*
1362 * Called by mount code to set a mountpoint and check if the mountpoint is
1363 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1364 * subtree can become unreachable).
1365 *
1366 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1367 * this reason take rename_lock and d_lock on dentry and ancestors.
1368 */
1369int d_set_mounted(struct dentry *dentry)
1370{
1371 struct dentry *p;
1372 int ret = -ENOENT;
1373 write_seqlock(&rename_lock);
1374 for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
1375 /* Need exclusion wrt. d_invalidate() */
1376 spin_lock(&p->d_lock);
1377 if (unlikely(d_unhashed(p))) {
1378 spin_unlock(&p->d_lock);
1379 goto out;
1380 }
1381 spin_unlock(&p->d_lock);
1382 }
1383 spin_lock(&dentry->d_lock);
1384 if (!d_unlinked(dentry)) {
1385 ret = -EBUSY;
1386 if (!d_mountpoint(dentry)) {
1387 dentry->d_flags |= DCACHE_MOUNTED;
1388 ret = 0;
1389 }
1390 }
1391 spin_unlock(&dentry->d_lock);
1392out:
1393 write_sequnlock(&rename_lock);
1394 return ret;
1395}
1396
1397/*
1398 * Search the dentry child list of the specified parent,
1399 * and move any unused dentries to the end of the unused
1400 * list for prune_dcache(). We descend to the next level
1401 * whenever the d_children list is non-empty and continue
1402 * searching.
1403 *
1404 * It returns zero iff there are no unused children,
1405 * otherwise it returns the number of children moved to
1406 * the end of the unused list. This may not be the total
1407 * number of unused children, because select_parent can
1408 * drop the lock and return early due to latency
1409 * constraints.
1410 */
1411
1412struct select_data {
1413 struct dentry *start;
1414 union {
1415 long found;
1416 struct dentry *victim;
1417 };
1418 struct list_head dispose;
1419};
1420
1421static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
1422{
1423 struct select_data *data = _data;
1424 enum d_walk_ret ret = D_WALK_CONTINUE;
1425
1426 if (data->start == dentry)
1427 goto out;
1428
1429 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1430 data->found++;
1431 } else if (!dentry->d_lockref.count) {
1432 to_shrink_list(dentry, &data->dispose);
1433 data->found++;
1434 } else if (dentry->d_lockref.count < 0) {
1435 data->found++;
1436 }
1437 /*
1438 * We can return to the caller if we have found some (this
1439 * ensures forward progress). We'll be coming back to find
1440 * the rest.
1441 */
1442 if (!list_empty(&data->dispose))
1443 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1444out:
1445 return ret;
1446}
1447
1448static enum d_walk_ret select_collect2(void *_data, struct dentry *dentry)
1449{
1450 struct select_data *data = _data;
1451 enum d_walk_ret ret = D_WALK_CONTINUE;
1452
1453 if (data->start == dentry)
1454 goto out;
1455
1456 if (!dentry->d_lockref.count) {
1457 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1458 rcu_read_lock();
1459 data->victim = dentry;
1460 return D_WALK_QUIT;
1461 }
1462 to_shrink_list(dentry, &data->dispose);
1463 }
1464 /*
1465 * We can return to the caller if we have found some (this
1466 * ensures forward progress). We'll be coming back to find
1467 * the rest.
1468 */
1469 if (!list_empty(&data->dispose))
1470 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1471out:
1472 return ret;
1473}
1474
1475/**
1476 * shrink_dcache_parent - prune dcache
1477 * @parent: parent of entries to prune
1478 *
1479 * Prune the dcache to remove unused children of the parent dentry.
1480 */
1481void shrink_dcache_parent(struct dentry *parent)
1482{
1483 for (;;) {
1484 struct select_data data = {.start = parent};
1485
1486 INIT_LIST_HEAD(&data.dispose);
1487 d_walk(parent, &data, select_collect);
1488
1489 if (!list_empty(&data.dispose)) {
1490 shrink_dentry_list(&data.dispose);
1491 continue;
1492 }
1493
1494 cond_resched();
1495 if (!data.found)
1496 break;
1497 data.victim = NULL;
1498 d_walk(parent, &data, select_collect2);
1499 if (data.victim) {
1500 spin_lock(&data.victim->d_lock);
1501 if (!lock_for_kill(data.victim)) {
1502 spin_unlock(&data.victim->d_lock);
1503 rcu_read_unlock();
1504 } else {
1505 shrink_kill(data.victim);
1506 }
1507 }
1508 if (!list_empty(&data.dispose))
1509 shrink_dentry_list(&data.dispose);
1510 }
1511}
1512EXPORT_SYMBOL(shrink_dcache_parent);
1513
1514static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
1515{
1516 /* it has busy descendents; complain about those instead */
1517 if (!hlist_empty(&dentry->d_children))
1518 return D_WALK_CONTINUE;
1519
1520 /* root with refcount 1 is fine */
1521 if (dentry == _data && dentry->d_lockref.count == 1)
1522 return D_WALK_CONTINUE;
1523
1524 WARN(1, "BUG: Dentry %p{i=%lx,n=%pd} "
1525 " still in use (%d) [unmount of %s %s]\n",
1526 dentry,
1527 dentry->d_inode ?
1528 dentry->d_inode->i_ino : 0UL,
1529 dentry,
1530 dentry->d_lockref.count,
1531 dentry->d_sb->s_type->name,
1532 dentry->d_sb->s_id);
1533 return D_WALK_CONTINUE;
1534}
1535
1536static void do_one_tree(struct dentry *dentry)
1537{
1538 shrink_dcache_parent(dentry);
1539 d_walk(dentry, dentry, umount_check);
1540 d_drop(dentry);
1541 dput(dentry);
1542}
1543
1544/*
1545 * destroy the dentries attached to a superblock on unmounting
1546 */
1547void shrink_dcache_for_umount(struct super_block *sb)
1548{
1549 struct dentry *dentry;
1550
1551 WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked");
1552
1553 dentry = sb->s_root;
1554 sb->s_root = NULL;
1555 do_one_tree(dentry);
1556
1557 while (!hlist_bl_empty(&sb->s_roots)) {
1558 dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_roots), struct dentry, d_hash));
1559 do_one_tree(dentry);
1560 }
1561}
1562
1563static enum d_walk_ret find_submount(void *_data, struct dentry *dentry)
1564{
1565 struct dentry **victim = _data;
1566 if (d_mountpoint(dentry)) {
1567 *victim = dget_dlock(dentry);
1568 return D_WALK_QUIT;
1569 }
1570 return D_WALK_CONTINUE;
1571}
1572
1573/**
1574 * d_invalidate - detach submounts, prune dcache, and drop
1575 * @dentry: dentry to invalidate (aka detach, prune and drop)
1576 */
1577void d_invalidate(struct dentry *dentry)
1578{
1579 bool had_submounts = false;
1580 spin_lock(&dentry->d_lock);
1581 if (d_unhashed(dentry)) {
1582 spin_unlock(&dentry->d_lock);
1583 return;
1584 }
1585 __d_drop(dentry);
1586 spin_unlock(&dentry->d_lock);
1587
1588 /* Negative dentries can be dropped without further checks */
1589 if (!dentry->d_inode)
1590 return;
1591
1592 shrink_dcache_parent(dentry);
1593 for (;;) {
1594 struct dentry *victim = NULL;
1595 d_walk(dentry, &victim, find_submount);
1596 if (!victim) {
1597 if (had_submounts)
1598 shrink_dcache_parent(dentry);
1599 return;
1600 }
1601 had_submounts = true;
1602 detach_mounts(victim);
1603 dput(victim);
1604 }
1605}
1606EXPORT_SYMBOL(d_invalidate);
1607
1608/**
1609 * __d_alloc - allocate a dcache entry
1610 * @sb: filesystem it will belong to
1611 * @name: qstr of the name
1612 *
1613 * Allocates a dentry. It returns %NULL if there is insufficient memory
1614 * available. On a success the dentry is returned. The name passed in is
1615 * copied and the copy passed in may be reused after this call.
1616 */
1617
1618static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1619{
1620 struct dentry *dentry;
1621 char *dname;
1622 int err;
1623
1624 dentry = kmem_cache_alloc_lru(dentry_cache, &sb->s_dentry_lru,
1625 GFP_KERNEL);
1626 if (!dentry)
1627 return NULL;
1628
1629 /*
1630 * We guarantee that the inline name is always NUL-terminated.
1631 * This way the memcpy() done by the name switching in rename
1632 * will still always have a NUL at the end, even if we might
1633 * be overwriting an internal NUL character
1634 */
1635 dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
1636 if (unlikely(!name)) {
1637 name = &slash_name;
1638 dname = dentry->d_iname;
1639 } else if (name->len > DNAME_INLINE_LEN-1) {
1640 size_t size = offsetof(struct external_name, name[1]);
1641 struct external_name *p = kmalloc(size + name->len,
1642 GFP_KERNEL_ACCOUNT |
1643 __GFP_RECLAIMABLE);
1644 if (!p) {
1645 kmem_cache_free(dentry_cache, dentry);
1646 return NULL;
1647 }
1648 atomic_set(&p->u.count, 1);
1649 dname = p->name;
1650 } else {
1651 dname = dentry->d_iname;
1652 }
1653
1654 dentry->d_name.len = name->len;
1655 dentry->d_name.hash = name->hash;
1656 memcpy(dname, name->name, name->len);
1657 dname[name->len] = 0;
1658
1659 /* Make sure we always see the terminating NUL character */
1660 smp_store_release(&dentry->d_name.name, dname); /* ^^^ */
1661
1662 dentry->d_lockref.count = 1;
1663 dentry->d_flags = 0;
1664 spin_lock_init(&dentry->d_lock);
1665 seqcount_spinlock_init(&dentry->d_seq, &dentry->d_lock);
1666 dentry->d_inode = NULL;
1667 dentry->d_parent = dentry;
1668 dentry->d_sb = sb;
1669 dentry->d_op = NULL;
1670 dentry->d_fsdata = NULL;
1671 INIT_HLIST_BL_NODE(&dentry->d_hash);
1672 INIT_LIST_HEAD(&dentry->d_lru);
1673 INIT_HLIST_HEAD(&dentry->d_children);
1674 INIT_HLIST_NODE(&dentry->d_u.d_alias);
1675 INIT_HLIST_NODE(&dentry->d_sib);
1676 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1677
1678 if (dentry->d_op && dentry->d_op->d_init) {
1679 err = dentry->d_op->d_init(dentry);
1680 if (err) {
1681 if (dname_external(dentry))
1682 kfree(external_name(dentry));
1683 kmem_cache_free(dentry_cache, dentry);
1684 return NULL;
1685 }
1686 }
1687
1688 this_cpu_inc(nr_dentry);
1689
1690 return dentry;
1691}
1692
1693/**
1694 * d_alloc - allocate a dcache entry
1695 * @parent: parent of entry to allocate
1696 * @name: qstr of the name
1697 *
1698 * Allocates a dentry. It returns %NULL if there is insufficient memory
1699 * available. On a success the dentry is returned. The name passed in is
1700 * copied and the copy passed in may be reused after this call.
1701 */
1702struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1703{
1704 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1705 if (!dentry)
1706 return NULL;
1707 spin_lock(&parent->d_lock);
1708 /*
1709 * don't need child lock because it is not subject
1710 * to concurrency here
1711 */
1712 dentry->d_parent = dget_dlock(parent);
1713 hlist_add_head(&dentry->d_sib, &parent->d_children);
1714 spin_unlock(&parent->d_lock);
1715
1716 return dentry;
1717}
1718EXPORT_SYMBOL(d_alloc);
1719
1720struct dentry *d_alloc_anon(struct super_block *sb)
1721{
1722 return __d_alloc(sb, NULL);
1723}
1724EXPORT_SYMBOL(d_alloc_anon);
1725
1726struct dentry *d_alloc_cursor(struct dentry * parent)
1727{
1728 struct dentry *dentry = d_alloc_anon(parent->d_sb);
1729 if (dentry) {
1730 dentry->d_flags |= DCACHE_DENTRY_CURSOR;
1731 dentry->d_parent = dget(parent);
1732 }
1733 return dentry;
1734}
1735
1736/**
1737 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1738 * @sb: the superblock
1739 * @name: qstr of the name
1740 *
1741 * For a filesystem that just pins its dentries in memory and never
1742 * performs lookups at all, return an unhashed IS_ROOT dentry.
1743 * This is used for pipes, sockets et.al. - the stuff that should
1744 * never be anyone's children or parents. Unlike all other
1745 * dentries, these will not have RCU delay between dropping the
1746 * last reference and freeing them.
1747 *
1748 * The only user is alloc_file_pseudo() and that's what should
1749 * be considered a public interface. Don't use directly.
1750 */
1751struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1752{
1753 static const struct dentry_operations anon_ops = {
1754 .d_dname = simple_dname
1755 };
1756 struct dentry *dentry = __d_alloc(sb, name);
1757 if (likely(dentry)) {
1758 dentry->d_flags |= DCACHE_NORCU;
1759 if (!sb->s_d_op)
1760 d_set_d_op(dentry, &anon_ops);
1761 }
1762 return dentry;
1763}
1764
1765struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1766{
1767 struct qstr q;
1768
1769 q.name = name;
1770 q.hash_len = hashlen_string(parent, name);
1771 return d_alloc(parent, &q);
1772}
1773EXPORT_SYMBOL(d_alloc_name);
1774
1775void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1776{
1777 WARN_ON_ONCE(dentry->d_op);
1778 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
1779 DCACHE_OP_COMPARE |
1780 DCACHE_OP_REVALIDATE |
1781 DCACHE_OP_WEAK_REVALIDATE |
1782 DCACHE_OP_DELETE |
1783 DCACHE_OP_REAL));
1784 dentry->d_op = op;
1785 if (!op)
1786 return;
1787 if (op->d_hash)
1788 dentry->d_flags |= DCACHE_OP_HASH;
1789 if (op->d_compare)
1790 dentry->d_flags |= DCACHE_OP_COMPARE;
1791 if (op->d_revalidate)
1792 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1793 if (op->d_weak_revalidate)
1794 dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
1795 if (op->d_delete)
1796 dentry->d_flags |= DCACHE_OP_DELETE;
1797 if (op->d_prune)
1798 dentry->d_flags |= DCACHE_OP_PRUNE;
1799 if (op->d_real)
1800 dentry->d_flags |= DCACHE_OP_REAL;
1801
1802}
1803EXPORT_SYMBOL(d_set_d_op);
1804
1805static unsigned d_flags_for_inode(struct inode *inode)
1806{
1807 unsigned add_flags = DCACHE_REGULAR_TYPE;
1808
1809 if (!inode)
1810 return DCACHE_MISS_TYPE;
1811
1812 if (S_ISDIR(inode->i_mode)) {
1813 add_flags = DCACHE_DIRECTORY_TYPE;
1814 if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) {
1815 if (unlikely(!inode->i_op->lookup))
1816 add_flags = DCACHE_AUTODIR_TYPE;
1817 else
1818 inode->i_opflags |= IOP_LOOKUP;
1819 }
1820 goto type_determined;
1821 }
1822
1823 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1824 if (unlikely(inode->i_op->get_link)) {
1825 add_flags = DCACHE_SYMLINK_TYPE;
1826 goto type_determined;
1827 }
1828 inode->i_opflags |= IOP_NOFOLLOW;
1829 }
1830
1831 if (unlikely(!S_ISREG(inode->i_mode)))
1832 add_flags = DCACHE_SPECIAL_TYPE;
1833
1834type_determined:
1835 if (unlikely(IS_AUTOMOUNT(inode)))
1836 add_flags |= DCACHE_NEED_AUTOMOUNT;
1837 return add_flags;
1838}
1839
1840static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1841{
1842 unsigned add_flags = d_flags_for_inode(inode);
1843 WARN_ON(d_in_lookup(dentry));
1844
1845 spin_lock(&dentry->d_lock);
1846 /*
1847 * Decrement negative dentry count if it was in the LRU list.
1848 */
1849 if (dentry->d_flags & DCACHE_LRU_LIST)
1850 this_cpu_dec(nr_dentry_negative);
1851 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
1852 raw_write_seqcount_begin(&dentry->d_seq);
1853 __d_set_inode_and_type(dentry, inode, add_flags);
1854 raw_write_seqcount_end(&dentry->d_seq);
1855 fsnotify_update_flags(dentry);
1856 spin_unlock(&dentry->d_lock);
1857}
1858
1859/**
1860 * d_instantiate - fill in inode information for a dentry
1861 * @entry: dentry to complete
1862 * @inode: inode to attach to this dentry
1863 *
1864 * Fill in inode information in the entry.
1865 *
1866 * This turns negative dentries into productive full members
1867 * of society.
1868 *
1869 * NOTE! This assumes that the inode count has been incremented
1870 * (or otherwise set) by the caller to indicate that it is now
1871 * in use by the dcache.
1872 */
1873
1874void d_instantiate(struct dentry *entry, struct inode * inode)
1875{
1876 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1877 if (inode) {
1878 security_d_instantiate(entry, inode);
1879 spin_lock(&inode->i_lock);
1880 __d_instantiate(entry, inode);
1881 spin_unlock(&inode->i_lock);
1882 }
1883}
1884EXPORT_SYMBOL(d_instantiate);
1885
1886/*
1887 * This should be equivalent to d_instantiate() + unlock_new_inode(),
1888 * with lockdep-related part of unlock_new_inode() done before
1889 * anything else. Use that instead of open-coding d_instantiate()/
1890 * unlock_new_inode() combinations.
1891 */
1892void d_instantiate_new(struct dentry *entry, struct inode *inode)
1893{
1894 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1895 BUG_ON(!inode);
1896 lockdep_annotate_inode_mutex_key(inode);
1897 security_d_instantiate(entry, inode);
1898 spin_lock(&inode->i_lock);
1899 __d_instantiate(entry, inode);
1900 WARN_ON(!(inode->i_state & I_NEW));
1901 inode->i_state &= ~I_NEW & ~I_CREATING;
1902 smp_mb();
1903 wake_up_bit(&inode->i_state, __I_NEW);
1904 spin_unlock(&inode->i_lock);
1905}
1906EXPORT_SYMBOL(d_instantiate_new);
1907
1908struct dentry *d_make_root(struct inode *root_inode)
1909{
1910 struct dentry *res = NULL;
1911
1912 if (root_inode) {
1913 res = d_alloc_anon(root_inode->i_sb);
1914 if (res)
1915 d_instantiate(res, root_inode);
1916 else
1917 iput(root_inode);
1918 }
1919 return res;
1920}
1921EXPORT_SYMBOL(d_make_root);
1922
1923static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected)
1924{
1925 struct super_block *sb;
1926 struct dentry *new, *res;
1927
1928 if (!inode)
1929 return ERR_PTR(-ESTALE);
1930 if (IS_ERR(inode))
1931 return ERR_CAST(inode);
1932
1933 sb = inode->i_sb;
1934
1935 res = d_find_any_alias(inode); /* existing alias? */
1936 if (res)
1937 goto out;
1938
1939 new = d_alloc_anon(sb);
1940 if (!new) {
1941 res = ERR_PTR(-ENOMEM);
1942 goto out;
1943 }
1944
1945 security_d_instantiate(new, inode);
1946 spin_lock(&inode->i_lock);
1947 res = __d_find_any_alias(inode); /* recheck under lock */
1948 if (likely(!res)) { /* still no alias, attach a disconnected dentry */
1949 unsigned add_flags = d_flags_for_inode(inode);
1950
1951 if (disconnected)
1952 add_flags |= DCACHE_DISCONNECTED;
1953
1954 spin_lock(&new->d_lock);
1955 __d_set_inode_and_type(new, inode, add_flags);
1956 hlist_add_head(&new->d_u.d_alias, &inode->i_dentry);
1957 if (!disconnected) {
1958 hlist_bl_lock(&sb->s_roots);
1959 hlist_bl_add_head(&new->d_hash, &sb->s_roots);
1960 hlist_bl_unlock(&sb->s_roots);
1961 }
1962 spin_unlock(&new->d_lock);
1963 spin_unlock(&inode->i_lock);
1964 inode = NULL; /* consumed by new->d_inode */
1965 res = new;
1966 } else {
1967 spin_unlock(&inode->i_lock);
1968 dput(new);
1969 }
1970
1971 out:
1972 iput(inode);
1973 return res;
1974}
1975
1976/**
1977 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
1978 * @inode: inode to allocate the dentry for
1979 *
1980 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1981 * similar open by handle operations. The returned dentry may be anonymous,
1982 * or may have a full name (if the inode was already in the cache).
1983 *
1984 * When called on a directory inode, we must ensure that the inode only ever
1985 * has one dentry. If a dentry is found, that is returned instead of
1986 * allocating a new one.
1987 *
1988 * On successful return, the reference to the inode has been transferred
1989 * to the dentry. In case of an error the reference on the inode is released.
1990 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1991 * be passed in and the error will be propagated to the return value,
1992 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1993 */
1994struct dentry *d_obtain_alias(struct inode *inode)
1995{
1996 return __d_obtain_alias(inode, true);
1997}
1998EXPORT_SYMBOL(d_obtain_alias);
1999
2000/**
2001 * d_obtain_root - find or allocate a dentry for a given inode
2002 * @inode: inode to allocate the dentry for
2003 *
2004 * Obtain an IS_ROOT dentry for the root of a filesystem.
2005 *
2006 * We must ensure that directory inodes only ever have one dentry. If a
2007 * dentry is found, that is returned instead of allocating a new one.
2008 *
2009 * On successful return, the reference to the inode has been transferred
2010 * to the dentry. In case of an error the reference on the inode is
2011 * released. A %NULL or IS_ERR inode may be passed in and will be the
2012 * error will be propagate to the return value, with a %NULL @inode
2013 * replaced by ERR_PTR(-ESTALE).
2014 */
2015struct dentry *d_obtain_root(struct inode *inode)
2016{
2017 return __d_obtain_alias(inode, false);
2018}
2019EXPORT_SYMBOL(d_obtain_root);
2020
2021/**
2022 * d_add_ci - lookup or allocate new dentry with case-exact name
2023 * @inode: the inode case-insensitive lookup has found
2024 * @dentry: the negative dentry that was passed to the parent's lookup func
2025 * @name: the case-exact name to be associated with the returned dentry
2026 *
2027 * This is to avoid filling the dcache with case-insensitive names to the
2028 * same inode, only the actual correct case is stored in the dcache for
2029 * case-insensitive filesystems.
2030 *
2031 * For a case-insensitive lookup match and if the case-exact dentry
2032 * already exists in the dcache, use it and return it.
2033 *
2034 * If no entry exists with the exact case name, allocate new dentry with
2035 * the exact case, and return the spliced entry.
2036 */
2037struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
2038 struct qstr *name)
2039{
2040 struct dentry *found, *res;
2041
2042 /*
2043 * First check if a dentry matching the name already exists,
2044 * if not go ahead and create it now.
2045 */
2046 found = d_hash_and_lookup(dentry->d_parent, name);
2047 if (found) {
2048 iput(inode);
2049 return found;
2050 }
2051 if (d_in_lookup(dentry)) {
2052 found = d_alloc_parallel(dentry->d_parent, name,
2053 dentry->d_wait);
2054 if (IS_ERR(found) || !d_in_lookup(found)) {
2055 iput(inode);
2056 return found;
2057 }
2058 } else {
2059 found = d_alloc(dentry->d_parent, name);
2060 if (!found) {
2061 iput(inode);
2062 return ERR_PTR(-ENOMEM);
2063 }
2064 }
2065 res = d_splice_alias(inode, found);
2066 if (res) {
2067 d_lookup_done(found);
2068 dput(found);
2069 return res;
2070 }
2071 return found;
2072}
2073EXPORT_SYMBOL(d_add_ci);
2074
2075/**
2076 * d_same_name - compare dentry name with case-exact name
2077 * @parent: parent dentry
2078 * @dentry: the negative dentry that was passed to the parent's lookup func
2079 * @name: the case-exact name to be associated with the returned dentry
2080 *
2081 * Return: true if names are same, or false
2082 */
2083bool d_same_name(const struct dentry *dentry, const struct dentry *parent,
2084 const struct qstr *name)
2085{
2086 if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
2087 if (dentry->d_name.len != name->len)
2088 return false;
2089 return dentry_cmp(dentry, name->name, name->len) == 0;
2090 }
2091 return parent->d_op->d_compare(dentry,
2092 dentry->d_name.len, dentry->d_name.name,
2093 name) == 0;
2094}
2095EXPORT_SYMBOL_GPL(d_same_name);
2096
2097/*
2098 * This is __d_lookup_rcu() when the parent dentry has
2099 * DCACHE_OP_COMPARE, which makes things much nastier.
2100 */
2101static noinline struct dentry *__d_lookup_rcu_op_compare(
2102 const struct dentry *parent,
2103 const struct qstr *name,
2104 unsigned *seqp)
2105{
2106 u64 hashlen = name->hash_len;
2107 struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
2108 struct hlist_bl_node *node;
2109 struct dentry *dentry;
2110
2111 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2112 int tlen;
2113 const char *tname;
2114 unsigned seq;
2115
2116seqretry:
2117 seq = raw_seqcount_begin(&dentry->d_seq);
2118 if (dentry->d_parent != parent)
2119 continue;
2120 if (d_unhashed(dentry))
2121 continue;
2122 if (dentry->d_name.hash != hashlen_hash(hashlen))
2123 continue;
2124 tlen = dentry->d_name.len;
2125 tname = dentry->d_name.name;
2126 /* we want a consistent (name,len) pair */
2127 if (read_seqcount_retry(&dentry->d_seq, seq)) {
2128 cpu_relax();
2129 goto seqretry;
2130 }
2131 if (parent->d_op->d_compare(dentry, tlen, tname, name) != 0)
2132 continue;
2133 *seqp = seq;
2134 return dentry;
2135 }
2136 return NULL;
2137}
2138
2139/**
2140 * __d_lookup_rcu - search for a dentry (racy, store-free)
2141 * @parent: parent dentry
2142 * @name: qstr of name we wish to find
2143 * @seqp: returns d_seq value at the point where the dentry was found
2144 * Returns: dentry, or NULL
2145 *
2146 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2147 * resolution (store-free path walking) design described in
2148 * Documentation/filesystems/path-lookup.txt.
2149 *
2150 * This is not to be used outside core vfs.
2151 *
2152 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2153 * held, and rcu_read_lock held. The returned dentry must not be stored into
2154 * without taking d_lock and checking d_seq sequence count against @seq
2155 * returned here.
2156 *
2157 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2158 * function.
2159 *
2160 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2161 * the returned dentry, so long as its parent's seqlock is checked after the
2162 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2163 * is formed, giving integrity down the path walk.
2164 *
2165 * NOTE! The caller *has* to check the resulting dentry against the sequence
2166 * number we've returned before using any of the resulting dentry state!
2167 */
2168struct dentry *__d_lookup_rcu(const struct dentry *parent,
2169 const struct qstr *name,
2170 unsigned *seqp)
2171{
2172 u64 hashlen = name->hash_len;
2173 const unsigned char *str = name->name;
2174 struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
2175 struct hlist_bl_node *node;
2176 struct dentry *dentry;
2177
2178 /*
2179 * Note: There is significant duplication with __d_lookup_rcu which is
2180 * required to prevent single threaded performance regressions
2181 * especially on architectures where smp_rmb (in seqcounts) are costly.
2182 * Keep the two functions in sync.
2183 */
2184
2185 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE))
2186 return __d_lookup_rcu_op_compare(parent, name, seqp);
2187
2188 /*
2189 * The hash list is protected using RCU.
2190 *
2191 * Carefully use d_seq when comparing a candidate dentry, to avoid
2192 * races with d_move().
2193 *
2194 * It is possible that concurrent renames can mess up our list
2195 * walk here and result in missing our dentry, resulting in the
2196 * false-negative result. d_lookup() protects against concurrent
2197 * renames using rename_lock seqlock.
2198 *
2199 * See Documentation/filesystems/path-lookup.txt for more details.
2200 */
2201 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2202 unsigned seq;
2203
2204 /*
2205 * The dentry sequence count protects us from concurrent
2206 * renames, and thus protects parent and name fields.
2207 *
2208 * The caller must perform a seqcount check in order
2209 * to do anything useful with the returned dentry.
2210 *
2211 * NOTE! We do a "raw" seqcount_begin here. That means that
2212 * we don't wait for the sequence count to stabilize if it
2213 * is in the middle of a sequence change. If we do the slow
2214 * dentry compare, we will do seqretries until it is stable,
2215 * and if we end up with a successful lookup, we actually
2216 * want to exit RCU lookup anyway.
2217 *
2218 * Note that raw_seqcount_begin still *does* smp_rmb(), so
2219 * we are still guaranteed NUL-termination of ->d_name.name.
2220 */
2221 seq = raw_seqcount_begin(&dentry->d_seq);
2222 if (dentry->d_parent != parent)
2223 continue;
2224 if (d_unhashed(dentry))
2225 continue;
2226 if (dentry->d_name.hash_len != hashlen)
2227 continue;
2228 if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
2229 continue;
2230 *seqp = seq;
2231 return dentry;
2232 }
2233 return NULL;
2234}
2235
2236/**
2237 * d_lookup - search for a dentry
2238 * @parent: parent dentry
2239 * @name: qstr of name we wish to find
2240 * Returns: dentry, or NULL
2241 *
2242 * d_lookup searches the children of the parent dentry for the name in
2243 * question. If the dentry is found its reference count is incremented and the
2244 * dentry is returned. The caller must use dput to free the entry when it has
2245 * finished using it. %NULL is returned if the dentry does not exist.
2246 */
2247struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
2248{
2249 struct dentry *dentry;
2250 unsigned seq;
2251
2252 do {
2253 seq = read_seqbegin(&rename_lock);
2254 dentry = __d_lookup(parent, name);
2255 if (dentry)
2256 break;
2257 } while (read_seqretry(&rename_lock, seq));
2258 return dentry;
2259}
2260EXPORT_SYMBOL(d_lookup);
2261
2262/**
2263 * __d_lookup - search for a dentry (racy)
2264 * @parent: parent dentry
2265 * @name: qstr of name we wish to find
2266 * Returns: dentry, or NULL
2267 *
2268 * __d_lookup is like d_lookup, however it may (rarely) return a
2269 * false-negative result due to unrelated rename activity.
2270 *
2271 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2272 * however it must be used carefully, eg. with a following d_lookup in
2273 * the case of failure.
2274 *
2275 * __d_lookup callers must be commented.
2276 */
2277struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
2278{
2279 unsigned int hash = name->hash;
2280 struct hlist_bl_head *b = d_hash(hash);
2281 struct hlist_bl_node *node;
2282 struct dentry *found = NULL;
2283 struct dentry *dentry;
2284
2285 /*
2286 * Note: There is significant duplication with __d_lookup_rcu which is
2287 * required to prevent single threaded performance regressions
2288 * especially on architectures where smp_rmb (in seqcounts) are costly.
2289 * Keep the two functions in sync.
2290 */
2291
2292 /*
2293 * The hash list is protected using RCU.
2294 *
2295 * Take d_lock when comparing a candidate dentry, to avoid races
2296 * with d_move().
2297 *
2298 * It is possible that concurrent renames can mess up our list
2299 * walk here and result in missing our dentry, resulting in the
2300 * false-negative result. d_lookup() protects against concurrent
2301 * renames using rename_lock seqlock.
2302 *
2303 * See Documentation/filesystems/path-lookup.txt for more details.
2304 */
2305 rcu_read_lock();
2306
2307 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2308
2309 if (dentry->d_name.hash != hash)
2310 continue;
2311
2312 spin_lock(&dentry->d_lock);
2313 if (dentry->d_parent != parent)
2314 goto next;
2315 if (d_unhashed(dentry))
2316 goto next;
2317
2318 if (!d_same_name(dentry, parent, name))
2319 goto next;
2320
2321 dentry->d_lockref.count++;
2322 found = dentry;
2323 spin_unlock(&dentry->d_lock);
2324 break;
2325next:
2326 spin_unlock(&dentry->d_lock);
2327 }
2328 rcu_read_unlock();
2329
2330 return found;
2331}
2332
2333/**
2334 * d_hash_and_lookup - hash the qstr then search for a dentry
2335 * @dir: Directory to search in
2336 * @name: qstr of name we wish to find
2337 *
2338 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2339 */
2340struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2341{
2342 /*
2343 * Check for a fs-specific hash function. Note that we must
2344 * calculate the standard hash first, as the d_op->d_hash()
2345 * routine may choose to leave the hash value unchanged.
2346 */
2347 name->hash = full_name_hash(dir, name->name, name->len);
2348 if (dir->d_flags & DCACHE_OP_HASH) {
2349 int err = dir->d_op->d_hash(dir, name);
2350 if (unlikely(err < 0))
2351 return ERR_PTR(err);
2352 }
2353 return d_lookup(dir, name);
2354}
2355EXPORT_SYMBOL(d_hash_and_lookup);
2356
2357/*
2358 * When a file is deleted, we have two options:
2359 * - turn this dentry into a negative dentry
2360 * - unhash this dentry and free it.
2361 *
2362 * Usually, we want to just turn this into
2363 * a negative dentry, but if anybody else is
2364 * currently using the dentry or the inode
2365 * we can't do that and we fall back on removing
2366 * it from the hash queues and waiting for
2367 * it to be deleted later when it has no users
2368 */
2369
2370/**
2371 * d_delete - delete a dentry
2372 * @dentry: The dentry to delete
2373 *
2374 * Turn the dentry into a negative dentry if possible, otherwise
2375 * remove it from the hash queues so it can be deleted later
2376 */
2377
2378void d_delete(struct dentry * dentry)
2379{
2380 struct inode *inode = dentry->d_inode;
2381
2382 spin_lock(&inode->i_lock);
2383 spin_lock(&dentry->d_lock);
2384 /*
2385 * Are we the only user?
2386 */
2387 if (dentry->d_lockref.count == 1) {
2388 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2389 dentry_unlink_inode(dentry);
2390 } else {
2391 __d_drop(dentry);
2392 spin_unlock(&dentry->d_lock);
2393 spin_unlock(&inode->i_lock);
2394 }
2395}
2396EXPORT_SYMBOL(d_delete);
2397
2398static void __d_rehash(struct dentry *entry)
2399{
2400 struct hlist_bl_head *b = d_hash(entry->d_name.hash);
2401
2402 hlist_bl_lock(b);
2403 hlist_bl_add_head_rcu(&entry->d_hash, b);
2404 hlist_bl_unlock(b);
2405}
2406
2407/**
2408 * d_rehash - add an entry back to the hash
2409 * @entry: dentry to add to the hash
2410 *
2411 * Adds a dentry to the hash according to its name.
2412 */
2413
2414void d_rehash(struct dentry * entry)
2415{
2416 spin_lock(&entry->d_lock);
2417 __d_rehash(entry);
2418 spin_unlock(&entry->d_lock);
2419}
2420EXPORT_SYMBOL(d_rehash);
2421
2422static inline unsigned start_dir_add(struct inode *dir)
2423{
2424 preempt_disable_nested();
2425 for (;;) {
2426 unsigned n = dir->i_dir_seq;
2427 if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
2428 return n;
2429 cpu_relax();
2430 }
2431}
2432
2433static inline void end_dir_add(struct inode *dir, unsigned int n,
2434 wait_queue_head_t *d_wait)
2435{
2436 smp_store_release(&dir->i_dir_seq, n + 2);
2437 preempt_enable_nested();
2438 wake_up_all(d_wait);
2439}
2440
2441static void d_wait_lookup(struct dentry *dentry)
2442{
2443 if (d_in_lookup(dentry)) {
2444 DECLARE_WAITQUEUE(wait, current);
2445 add_wait_queue(dentry->d_wait, &wait);
2446 do {
2447 set_current_state(TASK_UNINTERRUPTIBLE);
2448 spin_unlock(&dentry->d_lock);
2449 schedule();
2450 spin_lock(&dentry->d_lock);
2451 } while (d_in_lookup(dentry));
2452 }
2453}
2454
2455struct dentry *d_alloc_parallel(struct dentry *parent,
2456 const struct qstr *name,
2457 wait_queue_head_t *wq)
2458{
2459 unsigned int hash = name->hash;
2460 struct hlist_bl_head *b = in_lookup_hash(parent, hash);
2461 struct hlist_bl_node *node;
2462 struct dentry *new = d_alloc(parent, name);
2463 struct dentry *dentry;
2464 unsigned seq, r_seq, d_seq;
2465
2466 if (unlikely(!new))
2467 return ERR_PTR(-ENOMEM);
2468
2469retry:
2470 rcu_read_lock();
2471 seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
2472 r_seq = read_seqbegin(&rename_lock);
2473 dentry = __d_lookup_rcu(parent, name, &d_seq);
2474 if (unlikely(dentry)) {
2475 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2476 rcu_read_unlock();
2477 goto retry;
2478 }
2479 if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
2480 rcu_read_unlock();
2481 dput(dentry);
2482 goto retry;
2483 }
2484 rcu_read_unlock();
2485 dput(new);
2486 return dentry;
2487 }
2488 if (unlikely(read_seqretry(&rename_lock, r_seq))) {
2489 rcu_read_unlock();
2490 goto retry;
2491 }
2492
2493 if (unlikely(seq & 1)) {
2494 rcu_read_unlock();
2495 goto retry;
2496 }
2497
2498 hlist_bl_lock(b);
2499 if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
2500 hlist_bl_unlock(b);
2501 rcu_read_unlock();
2502 goto retry;
2503 }
2504 /*
2505 * No changes for the parent since the beginning of d_lookup().
2506 * Since all removals from the chain happen with hlist_bl_lock(),
2507 * any potential in-lookup matches are going to stay here until
2508 * we unlock the chain. All fields are stable in everything
2509 * we encounter.
2510 */
2511 hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
2512 if (dentry->d_name.hash != hash)
2513 continue;
2514 if (dentry->d_parent != parent)
2515 continue;
2516 if (!d_same_name(dentry, parent, name))
2517 continue;
2518 hlist_bl_unlock(b);
2519 /* now we can try to grab a reference */
2520 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2521 rcu_read_unlock();
2522 goto retry;
2523 }
2524
2525 rcu_read_unlock();
2526 /*
2527 * somebody is likely to be still doing lookup for it;
2528 * wait for them to finish
2529 */
2530 spin_lock(&dentry->d_lock);
2531 d_wait_lookup(dentry);
2532 /*
2533 * it's not in-lookup anymore; in principle we should repeat
2534 * everything from dcache lookup, but it's likely to be what
2535 * d_lookup() would've found anyway. If it is, just return it;
2536 * otherwise we really have to repeat the whole thing.
2537 */
2538 if (unlikely(dentry->d_name.hash != hash))
2539 goto mismatch;
2540 if (unlikely(dentry->d_parent != parent))
2541 goto mismatch;
2542 if (unlikely(d_unhashed(dentry)))
2543 goto mismatch;
2544 if (unlikely(!d_same_name(dentry, parent, name)))
2545 goto mismatch;
2546 /* OK, it *is* a hashed match; return it */
2547 spin_unlock(&dentry->d_lock);
2548 dput(new);
2549 return dentry;
2550 }
2551 rcu_read_unlock();
2552 /* we can't take ->d_lock here; it's OK, though. */
2553 new->d_flags |= DCACHE_PAR_LOOKUP;
2554 new->d_wait = wq;
2555 hlist_bl_add_head(&new->d_u.d_in_lookup_hash, b);
2556 hlist_bl_unlock(b);
2557 return new;
2558mismatch:
2559 spin_unlock(&dentry->d_lock);
2560 dput(dentry);
2561 goto retry;
2562}
2563EXPORT_SYMBOL(d_alloc_parallel);
2564
2565/*
2566 * - Unhash the dentry
2567 * - Retrieve and clear the waitqueue head in dentry
2568 * - Return the waitqueue head
2569 */
2570static wait_queue_head_t *__d_lookup_unhash(struct dentry *dentry)
2571{
2572 wait_queue_head_t *d_wait;
2573 struct hlist_bl_head *b;
2574
2575 lockdep_assert_held(&dentry->d_lock);
2576
2577 b = in_lookup_hash(dentry->d_parent, dentry->d_name.hash);
2578 hlist_bl_lock(b);
2579 dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
2580 __hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
2581 d_wait = dentry->d_wait;
2582 dentry->d_wait = NULL;
2583 hlist_bl_unlock(b);
2584 INIT_HLIST_NODE(&dentry->d_u.d_alias);
2585 INIT_LIST_HEAD(&dentry->d_lru);
2586 return d_wait;
2587}
2588
2589void __d_lookup_unhash_wake(struct dentry *dentry)
2590{
2591 spin_lock(&dentry->d_lock);
2592 wake_up_all(__d_lookup_unhash(dentry));
2593 spin_unlock(&dentry->d_lock);
2594}
2595EXPORT_SYMBOL(__d_lookup_unhash_wake);
2596
2597/* inode->i_lock held if inode is non-NULL */
2598
2599static inline void __d_add(struct dentry *dentry, struct inode *inode)
2600{
2601 wait_queue_head_t *d_wait;
2602 struct inode *dir = NULL;
2603 unsigned n;
2604 spin_lock(&dentry->d_lock);
2605 if (unlikely(d_in_lookup(dentry))) {
2606 dir = dentry->d_parent->d_inode;
2607 n = start_dir_add(dir);
2608 d_wait = __d_lookup_unhash(dentry);
2609 }
2610 if (inode) {
2611 unsigned add_flags = d_flags_for_inode(inode);
2612 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2613 raw_write_seqcount_begin(&dentry->d_seq);
2614 __d_set_inode_and_type(dentry, inode, add_flags);
2615 raw_write_seqcount_end(&dentry->d_seq);
2616 fsnotify_update_flags(dentry);
2617 }
2618 __d_rehash(dentry);
2619 if (dir)
2620 end_dir_add(dir, n, d_wait);
2621 spin_unlock(&dentry->d_lock);
2622 if (inode)
2623 spin_unlock(&inode->i_lock);
2624}
2625
2626/**
2627 * d_add - add dentry to hash queues
2628 * @entry: dentry to add
2629 * @inode: The inode to attach to this dentry
2630 *
2631 * This adds the entry to the hash queues and initializes @inode.
2632 * The entry was actually filled in earlier during d_alloc().
2633 */
2634
2635void d_add(struct dentry *entry, struct inode *inode)
2636{
2637 if (inode) {
2638 security_d_instantiate(entry, inode);
2639 spin_lock(&inode->i_lock);
2640 }
2641 __d_add(entry, inode);
2642}
2643EXPORT_SYMBOL(d_add);
2644
2645/**
2646 * d_exact_alias - find and hash an exact unhashed alias
2647 * @entry: dentry to add
2648 * @inode: The inode to go with this dentry
2649 *
2650 * If an unhashed dentry with the same name/parent and desired
2651 * inode already exists, hash and return it. Otherwise, return
2652 * NULL.
2653 *
2654 * Parent directory should be locked.
2655 */
2656struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
2657{
2658 struct dentry *alias;
2659 unsigned int hash = entry->d_name.hash;
2660
2661 spin_lock(&inode->i_lock);
2662 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
2663 /*
2664 * Don't need alias->d_lock here, because aliases with
2665 * d_parent == entry->d_parent are not subject to name or
2666 * parent changes, because the parent inode i_mutex is held.
2667 */
2668 if (alias->d_name.hash != hash)
2669 continue;
2670 if (alias->d_parent != entry->d_parent)
2671 continue;
2672 if (!d_same_name(alias, entry->d_parent, &entry->d_name))
2673 continue;
2674 spin_lock(&alias->d_lock);
2675 if (!d_unhashed(alias)) {
2676 spin_unlock(&alias->d_lock);
2677 alias = NULL;
2678 } else {
2679 dget_dlock(alias);
2680 __d_rehash(alias);
2681 spin_unlock(&alias->d_lock);
2682 }
2683 spin_unlock(&inode->i_lock);
2684 return alias;
2685 }
2686 spin_unlock(&inode->i_lock);
2687 return NULL;
2688}
2689EXPORT_SYMBOL(d_exact_alias);
2690
2691static void swap_names(struct dentry *dentry, struct dentry *target)
2692{
2693 if (unlikely(dname_external(target))) {
2694 if (unlikely(dname_external(dentry))) {
2695 /*
2696 * Both external: swap the pointers
2697 */
2698 swap(target->d_name.name, dentry->d_name.name);
2699 } else {
2700 /*
2701 * dentry:internal, target:external. Steal target's
2702 * storage and make target internal.
2703 */
2704 memcpy(target->d_iname, dentry->d_name.name,
2705 dentry->d_name.len + 1);
2706 dentry->d_name.name = target->d_name.name;
2707 target->d_name.name = target->d_iname;
2708 }
2709 } else {
2710 if (unlikely(dname_external(dentry))) {
2711 /*
2712 * dentry:external, target:internal. Give dentry's
2713 * storage to target and make dentry internal
2714 */
2715 memcpy(dentry->d_iname, target->d_name.name,
2716 target->d_name.len + 1);
2717 target->d_name.name = dentry->d_name.name;
2718 dentry->d_name.name = dentry->d_iname;
2719 } else {
2720 /*
2721 * Both are internal.
2722 */
2723 unsigned int i;
2724 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
2725 for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
2726 swap(((long *) &dentry->d_iname)[i],
2727 ((long *) &target->d_iname)[i]);
2728 }
2729 }
2730 }
2731 swap(dentry->d_name.hash_len, target->d_name.hash_len);
2732}
2733
2734static void copy_name(struct dentry *dentry, struct dentry *target)
2735{
2736 struct external_name *old_name = NULL;
2737 if (unlikely(dname_external(dentry)))
2738 old_name = external_name(dentry);
2739 if (unlikely(dname_external(target))) {
2740 atomic_inc(&external_name(target)->u.count);
2741 dentry->d_name = target->d_name;
2742 } else {
2743 memcpy(dentry->d_iname, target->d_name.name,
2744 target->d_name.len + 1);
2745 dentry->d_name.name = dentry->d_iname;
2746 dentry->d_name.hash_len = target->d_name.hash_len;
2747 }
2748 if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
2749 kfree_rcu(old_name, u.head);
2750}
2751
2752/*
2753 * __d_move - move a dentry
2754 * @dentry: entry to move
2755 * @target: new dentry
2756 * @exchange: exchange the two dentries
2757 *
2758 * Update the dcache to reflect the move of a file name. Negative
2759 * dcache entries should not be moved in this way. Caller must hold
2760 * rename_lock, the i_mutex of the source and target directories,
2761 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2762 */
2763static void __d_move(struct dentry *dentry, struct dentry *target,
2764 bool exchange)
2765{
2766 struct dentry *old_parent, *p;
2767 wait_queue_head_t *d_wait;
2768 struct inode *dir = NULL;
2769 unsigned n;
2770
2771 WARN_ON(!dentry->d_inode);
2772 if (WARN_ON(dentry == target))
2773 return;
2774
2775 BUG_ON(d_ancestor(target, dentry));
2776 old_parent = dentry->d_parent;
2777 p = d_ancestor(old_parent, target);
2778 if (IS_ROOT(dentry)) {
2779 BUG_ON(p);
2780 spin_lock(&target->d_parent->d_lock);
2781 } else if (!p) {
2782 /* target is not a descendent of dentry->d_parent */
2783 spin_lock(&target->d_parent->d_lock);
2784 spin_lock_nested(&old_parent->d_lock, DENTRY_D_LOCK_NESTED);
2785 } else {
2786 BUG_ON(p == dentry);
2787 spin_lock(&old_parent->d_lock);
2788 if (p != target)
2789 spin_lock_nested(&target->d_parent->d_lock,
2790 DENTRY_D_LOCK_NESTED);
2791 }
2792 spin_lock_nested(&dentry->d_lock, 2);
2793 spin_lock_nested(&target->d_lock, 3);
2794
2795 if (unlikely(d_in_lookup(target))) {
2796 dir = target->d_parent->d_inode;
2797 n = start_dir_add(dir);
2798 d_wait = __d_lookup_unhash(target);
2799 }
2800
2801 write_seqcount_begin(&dentry->d_seq);
2802 write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
2803
2804 /* unhash both */
2805 if (!d_unhashed(dentry))
2806 ___d_drop(dentry);
2807 if (!d_unhashed(target))
2808 ___d_drop(target);
2809
2810 /* ... and switch them in the tree */
2811 dentry->d_parent = target->d_parent;
2812 if (!exchange) {
2813 copy_name(dentry, target);
2814 target->d_hash.pprev = NULL;
2815 dentry->d_parent->d_lockref.count++;
2816 if (dentry != old_parent) /* wasn't IS_ROOT */
2817 WARN_ON(!--old_parent->d_lockref.count);
2818 } else {
2819 target->d_parent = old_parent;
2820 swap_names(dentry, target);
2821 if (!hlist_unhashed(&target->d_sib))
2822 __hlist_del(&target->d_sib);
2823 hlist_add_head(&target->d_sib, &target->d_parent->d_children);
2824 __d_rehash(target);
2825 fsnotify_update_flags(target);
2826 }
2827 if (!hlist_unhashed(&dentry->d_sib))
2828 __hlist_del(&dentry->d_sib);
2829 hlist_add_head(&dentry->d_sib, &dentry->d_parent->d_children);
2830 __d_rehash(dentry);
2831 fsnotify_update_flags(dentry);
2832 fscrypt_handle_d_move(dentry);
2833
2834 write_seqcount_end(&target->d_seq);
2835 write_seqcount_end(&dentry->d_seq);
2836
2837 if (dir)
2838 end_dir_add(dir, n, d_wait);
2839
2840 if (dentry->d_parent != old_parent)
2841 spin_unlock(&dentry->d_parent->d_lock);
2842 if (dentry != old_parent)
2843 spin_unlock(&old_parent->d_lock);
2844 spin_unlock(&target->d_lock);
2845 spin_unlock(&dentry->d_lock);
2846}
2847
2848/*
2849 * d_move - move a dentry
2850 * @dentry: entry to move
2851 * @target: new dentry
2852 *
2853 * Update the dcache to reflect the move of a file name. Negative
2854 * dcache entries should not be moved in this way. See the locking
2855 * requirements for __d_move.
2856 */
2857void d_move(struct dentry *dentry, struct dentry *target)
2858{
2859 write_seqlock(&rename_lock);
2860 __d_move(dentry, target, false);
2861 write_sequnlock(&rename_lock);
2862}
2863EXPORT_SYMBOL(d_move);
2864
2865/*
2866 * d_exchange - exchange two dentries
2867 * @dentry1: first dentry
2868 * @dentry2: second dentry
2869 */
2870void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
2871{
2872 write_seqlock(&rename_lock);
2873
2874 WARN_ON(!dentry1->d_inode);
2875 WARN_ON(!dentry2->d_inode);
2876 WARN_ON(IS_ROOT(dentry1));
2877 WARN_ON(IS_ROOT(dentry2));
2878
2879 __d_move(dentry1, dentry2, true);
2880
2881 write_sequnlock(&rename_lock);
2882}
2883
2884/**
2885 * d_ancestor - search for an ancestor
2886 * @p1: ancestor dentry
2887 * @p2: child dentry
2888 *
2889 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2890 * an ancestor of p2, else NULL.
2891 */
2892struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2893{
2894 struct dentry *p;
2895
2896 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2897 if (p->d_parent == p1)
2898 return p;
2899 }
2900 return NULL;
2901}
2902
2903/*
2904 * This helper attempts to cope with remotely renamed directories
2905 *
2906 * It assumes that the caller is already holding
2907 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2908 *
2909 * Note: If ever the locking in lock_rename() changes, then please
2910 * remember to update this too...
2911 */
2912static int __d_unalias(struct dentry *dentry, struct dentry *alias)
2913{
2914 struct mutex *m1 = NULL;
2915 struct rw_semaphore *m2 = NULL;
2916 int ret = -ESTALE;
2917
2918 /* If alias and dentry share a parent, then no extra locks required */
2919 if (alias->d_parent == dentry->d_parent)
2920 goto out_unalias;
2921
2922 /* See lock_rename() */
2923 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
2924 goto out_err;
2925 m1 = &dentry->d_sb->s_vfs_rename_mutex;
2926 if (!inode_trylock_shared(alias->d_parent->d_inode))
2927 goto out_err;
2928 m2 = &alias->d_parent->d_inode->i_rwsem;
2929out_unalias:
2930 __d_move(alias, dentry, false);
2931 ret = 0;
2932out_err:
2933 if (m2)
2934 up_read(m2);
2935 if (m1)
2936 mutex_unlock(m1);
2937 return ret;
2938}
2939
2940/**
2941 * d_splice_alias - splice a disconnected dentry into the tree if one exists
2942 * @inode: the inode which may have a disconnected dentry
2943 * @dentry: a negative dentry which we want to point to the inode.
2944 *
2945 * If inode is a directory and has an IS_ROOT alias, then d_move that in
2946 * place of the given dentry and return it, else simply d_add the inode
2947 * to the dentry and return NULL.
2948 *
2949 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
2950 * we should error out: directories can't have multiple aliases.
2951 *
2952 * This is needed in the lookup routine of any filesystem that is exportable
2953 * (via knfsd) so that we can build dcache paths to directories effectively.
2954 *
2955 * If a dentry was found and moved, then it is returned. Otherwise NULL
2956 * is returned. This matches the expected return value of ->lookup.
2957 *
2958 * Cluster filesystems may call this function with a negative, hashed dentry.
2959 * In that case, we know that the inode will be a regular file, and also this
2960 * will only occur during atomic_open. So we need to check for the dentry
2961 * being already hashed only in the final case.
2962 */
2963struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
2964{
2965 if (IS_ERR(inode))
2966 return ERR_CAST(inode);
2967
2968 BUG_ON(!d_unhashed(dentry));
2969
2970 if (!inode)
2971 goto out;
2972
2973 security_d_instantiate(dentry, inode);
2974 spin_lock(&inode->i_lock);
2975 if (S_ISDIR(inode->i_mode)) {
2976 struct dentry *new = __d_find_any_alias(inode);
2977 if (unlikely(new)) {
2978 /* The reference to new ensures it remains an alias */
2979 spin_unlock(&inode->i_lock);
2980 write_seqlock(&rename_lock);
2981 if (unlikely(d_ancestor(new, dentry))) {
2982 write_sequnlock(&rename_lock);
2983 dput(new);
2984 new = ERR_PTR(-ELOOP);
2985 pr_warn_ratelimited(
2986 "VFS: Lookup of '%s' in %s %s"
2987 " would have caused loop\n",
2988 dentry->d_name.name,
2989 inode->i_sb->s_type->name,
2990 inode->i_sb->s_id);
2991 } else if (!IS_ROOT(new)) {
2992 struct dentry *old_parent = dget(new->d_parent);
2993 int err = __d_unalias(dentry, new);
2994 write_sequnlock(&rename_lock);
2995 if (err) {
2996 dput(new);
2997 new = ERR_PTR(err);
2998 }
2999 dput(old_parent);
3000 } else {
3001 __d_move(new, dentry, false);
3002 write_sequnlock(&rename_lock);
3003 }
3004 iput(inode);
3005 return new;
3006 }
3007 }
3008out:
3009 __d_add(dentry, inode);
3010 return NULL;
3011}
3012EXPORT_SYMBOL(d_splice_alias);
3013
3014/*
3015 * Test whether new_dentry is a subdirectory of old_dentry.
3016 *
3017 * Trivially implemented using the dcache structure
3018 */
3019
3020/**
3021 * is_subdir - is new dentry a subdirectory of old_dentry
3022 * @new_dentry: new dentry
3023 * @old_dentry: old dentry
3024 *
3025 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3026 * Returns false otherwise.
3027 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3028 */
3029
3030bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
3031{
3032 bool result;
3033 unsigned seq;
3034
3035 if (new_dentry == old_dentry)
3036 return true;
3037
3038 do {
3039 /* for restarting inner loop in case of seq retry */
3040 seq = read_seqbegin(&rename_lock);
3041 /*
3042 * Need rcu_readlock to protect against the d_parent trashing
3043 * due to d_move
3044 */
3045 rcu_read_lock();
3046 if (d_ancestor(old_dentry, new_dentry))
3047 result = true;
3048 else
3049 result = false;
3050 rcu_read_unlock();
3051 } while (read_seqretry(&rename_lock, seq));
3052
3053 return result;
3054}
3055EXPORT_SYMBOL(is_subdir);
3056
3057static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
3058{
3059 struct dentry *root = data;
3060 if (dentry != root) {
3061 if (d_unhashed(dentry) || !dentry->d_inode)
3062 return D_WALK_SKIP;
3063
3064 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
3065 dentry->d_flags |= DCACHE_GENOCIDE;
3066 dentry->d_lockref.count--;
3067 }
3068 }
3069 return D_WALK_CONTINUE;
3070}
3071
3072void d_genocide(struct dentry *parent)
3073{
3074 d_walk(parent, parent, d_genocide_kill);
3075}
3076
3077void d_mark_tmpfile(struct file *file, struct inode *inode)
3078{
3079 struct dentry *dentry = file->f_path.dentry;
3080
3081 BUG_ON(dentry->d_name.name != dentry->d_iname ||
3082 !hlist_unhashed(&dentry->d_u.d_alias) ||
3083 !d_unlinked(dentry));
3084 spin_lock(&dentry->d_parent->d_lock);
3085 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
3086 dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
3087 (unsigned long long)inode->i_ino);
3088 spin_unlock(&dentry->d_lock);
3089 spin_unlock(&dentry->d_parent->d_lock);
3090}
3091EXPORT_SYMBOL(d_mark_tmpfile);
3092
3093void d_tmpfile(struct file *file, struct inode *inode)
3094{
3095 struct dentry *dentry = file->f_path.dentry;
3096
3097 inode_dec_link_count(inode);
3098 d_mark_tmpfile(file, inode);
3099 d_instantiate(dentry, inode);
3100}
3101EXPORT_SYMBOL(d_tmpfile);
3102
3103static __initdata unsigned long dhash_entries;
3104static int __init set_dhash_entries(char *str)
3105{
3106 if (!str)
3107 return 0;
3108 dhash_entries = simple_strtoul(str, &str, 0);
3109 return 1;
3110}
3111__setup("dhash_entries=", set_dhash_entries);
3112
3113static void __init dcache_init_early(void)
3114{
3115 /* If hashes are distributed across NUMA nodes, defer
3116 * hash allocation until vmalloc space is available.
3117 */
3118 if (hashdist)
3119 return;
3120
3121 dentry_hashtable =
3122 alloc_large_system_hash("Dentry cache",
3123 sizeof(struct hlist_bl_head),
3124 dhash_entries,
3125 13,
3126 HASH_EARLY | HASH_ZERO,
3127 &d_hash_shift,
3128 NULL,
3129 0,
3130 0);
3131 d_hash_shift = 32 - d_hash_shift;
3132}
3133
3134static void __init dcache_init(void)
3135{
3136 /*
3137 * A constructor could be added for stable state like the lists,
3138 * but it is probably not worth it because of the cache nature
3139 * of the dcache.
3140 */
3141 dentry_cache = KMEM_CACHE_USERCOPY(dentry,
3142 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_ACCOUNT,
3143 d_iname);
3144
3145 /* Hash may have been set up in dcache_init_early */
3146 if (!hashdist)
3147 return;
3148
3149 dentry_hashtable =
3150 alloc_large_system_hash("Dentry cache",
3151 sizeof(struct hlist_bl_head),
3152 dhash_entries,
3153 13,
3154 HASH_ZERO,
3155 &d_hash_shift,
3156 NULL,
3157 0,
3158 0);
3159 d_hash_shift = 32 - d_hash_shift;
3160}
3161
3162/* SLAB cache for __getname() consumers */
3163struct kmem_cache *names_cachep __ro_after_init;
3164EXPORT_SYMBOL(names_cachep);
3165
3166void __init vfs_caches_init_early(void)
3167{
3168 int i;
3169
3170 for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++)
3171 INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]);
3172
3173 dcache_init_early();
3174 inode_init_early();
3175}
3176
3177void __init vfs_caches_init(void)
3178{
3179 names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0,
3180 SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL);
3181
3182 dcache_init();
3183 inode_init();
3184 files_init();
3185 files_maxfiles_init();
3186 mnt_init();
3187 bdev_cache_init();
3188 chrdev_init();
3189}
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/*
39 * Usage:
40 * dcache->d_inode->i_lock protects:
41 * - i_dentry, d_u.d_alias, d_inode of aliases
42 * dcache_hash_bucket lock protects:
43 * - the dcache hash table
44 * s_roots bl list spinlock protects:
45 * - the s_roots list (see __d_drop)
46 * dentry->d_sb->s_dentry_lru_lock protects:
47 * - the dcache lru lists and counters
48 * d_lock protects:
49 * - d_flags
50 * - d_name
51 * - d_lru
52 * - d_count
53 * - d_unhashed()
54 * - d_parent and d_subdirs
55 * - childrens' d_child and d_parent
56 * - d_u.d_alias, d_inode
57 *
58 * Ordering:
59 * dentry->d_inode->i_lock
60 * dentry->d_lock
61 * dentry->d_sb->s_dentry_lru_lock
62 * dcache_hash_bucket lock
63 * s_roots lock
64 *
65 * If there is an ancestor relationship:
66 * dentry->d_parent->...->d_parent->d_lock
67 * ...
68 * dentry->d_parent->d_lock
69 * dentry->d_lock
70 *
71 * If no ancestor relationship:
72 * arbitrary, since it's serialized on rename_lock
73 */
74int sysctl_vfs_cache_pressure __read_mostly = 100;
75EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
76
77__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
78
79EXPORT_SYMBOL(rename_lock);
80
81static struct kmem_cache *dentry_cache __read_mostly;
82
83const struct qstr empty_name = QSTR_INIT("", 0);
84EXPORT_SYMBOL(empty_name);
85const struct qstr slash_name = QSTR_INIT("/", 1);
86EXPORT_SYMBOL(slash_name);
87const struct qstr dotdot_name = QSTR_INIT("..", 2);
88EXPORT_SYMBOL(dotdot_name);
89
90/*
91 * This is the single most critical data structure when it comes
92 * to the dcache: the hashtable for lookups. Somebody should try
93 * to make this good - I've just made it work.
94 *
95 * This hash-function tries to avoid losing too many bits of hash
96 * information, yet avoid using a prime hash-size or similar.
97 */
98
99static unsigned int d_hash_shift __read_mostly;
100
101static struct hlist_bl_head *dentry_hashtable __read_mostly;
102
103static inline struct hlist_bl_head *d_hash(unsigned int hash)
104{
105 return dentry_hashtable + (hash >> d_hash_shift);
106}
107
108#define IN_LOOKUP_SHIFT 10
109static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT];
110
111static inline struct hlist_bl_head *in_lookup_hash(const struct dentry *parent,
112 unsigned int hash)
113{
114 hash += (unsigned long) parent / L1_CACHE_BYTES;
115 return in_lookup_hashtable + hash_32(hash, IN_LOOKUP_SHIFT);
116}
117
118
119/* Statistics gathering. */
120struct dentry_stat_t dentry_stat = {
121 .age_limit = 45,
122};
123
124static DEFINE_PER_CPU(long, nr_dentry);
125static DEFINE_PER_CPU(long, nr_dentry_unused);
126static DEFINE_PER_CPU(long, nr_dentry_negative);
127
128#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
129
130/*
131 * Here we resort to our own counters instead of using generic per-cpu counters
132 * for consistency with what the vfs inode code does. We are expected to harvest
133 * better code and performance by having our own specialized counters.
134 *
135 * Please note that the loop is done over all possible CPUs, not over all online
136 * CPUs. The reason for this is that we don't want to play games with CPUs going
137 * on and off. If one of them goes off, we will just keep their counters.
138 *
139 * glommer: See cffbc8a for details, and if you ever intend to change this,
140 * please update all vfs counters to match.
141 */
142static long get_nr_dentry(void)
143{
144 int i;
145 long sum = 0;
146 for_each_possible_cpu(i)
147 sum += per_cpu(nr_dentry, i);
148 return sum < 0 ? 0 : sum;
149}
150
151static long get_nr_dentry_unused(void)
152{
153 int i;
154 long sum = 0;
155 for_each_possible_cpu(i)
156 sum += per_cpu(nr_dentry_unused, i);
157 return sum < 0 ? 0 : sum;
158}
159
160static long get_nr_dentry_negative(void)
161{
162 int i;
163 long sum = 0;
164
165 for_each_possible_cpu(i)
166 sum += per_cpu(nr_dentry_negative, i);
167 return sum < 0 ? 0 : sum;
168}
169
170int proc_nr_dentry(struct ctl_table *table, int write, void *buffer,
171 size_t *lenp, loff_t *ppos)
172{
173 dentry_stat.nr_dentry = get_nr_dentry();
174 dentry_stat.nr_unused = get_nr_dentry_unused();
175 dentry_stat.nr_negative = get_nr_dentry_negative();
176 return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
177}
178#endif
179
180/*
181 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
182 * The strings are both count bytes long, and count is non-zero.
183 */
184#ifdef CONFIG_DCACHE_WORD_ACCESS
185
186#include <asm/word-at-a-time.h>
187/*
188 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
189 * aligned allocation for this particular component. We don't
190 * strictly need the load_unaligned_zeropad() safety, but it
191 * doesn't hurt either.
192 *
193 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
194 * need the careful unaligned handling.
195 */
196static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
197{
198 unsigned long a,b,mask;
199
200 for (;;) {
201 a = read_word_at_a_time(cs);
202 b = load_unaligned_zeropad(ct);
203 if (tcount < sizeof(unsigned long))
204 break;
205 if (unlikely(a != b))
206 return 1;
207 cs += sizeof(unsigned long);
208 ct += sizeof(unsigned long);
209 tcount -= sizeof(unsigned long);
210 if (!tcount)
211 return 0;
212 }
213 mask = bytemask_from_count(tcount);
214 return unlikely(!!((a ^ b) & mask));
215}
216
217#else
218
219static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
220{
221 do {
222 if (*cs != *ct)
223 return 1;
224 cs++;
225 ct++;
226 tcount--;
227 } while (tcount);
228 return 0;
229}
230
231#endif
232
233static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
234{
235 /*
236 * Be careful about RCU walk racing with rename:
237 * use 'READ_ONCE' to fetch the name pointer.
238 *
239 * NOTE! Even if a rename will mean that the length
240 * was not loaded atomically, we don't care. The
241 * RCU walk will check the sequence count eventually,
242 * and catch it. And we won't overrun the buffer,
243 * because we're reading the name pointer atomically,
244 * and a dentry name is guaranteed to be properly
245 * terminated with a NUL byte.
246 *
247 * End result: even if 'len' is wrong, we'll exit
248 * early because the data cannot match (there can
249 * be no NUL in the ct/tcount data)
250 */
251 const unsigned char *cs = READ_ONCE(dentry->d_name.name);
252
253 return dentry_string_cmp(cs, ct, tcount);
254}
255
256struct external_name {
257 union {
258 atomic_t count;
259 struct rcu_head head;
260 } u;
261 unsigned char name[];
262};
263
264static inline struct external_name *external_name(struct dentry *dentry)
265{
266 return container_of(dentry->d_name.name, struct external_name, name[0]);
267}
268
269static void __d_free(struct rcu_head *head)
270{
271 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
272
273 kmem_cache_free(dentry_cache, dentry);
274}
275
276static void __d_free_external(struct rcu_head *head)
277{
278 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
279 kfree(external_name(dentry));
280 kmem_cache_free(dentry_cache, dentry);
281}
282
283static inline int dname_external(const struct dentry *dentry)
284{
285 return dentry->d_name.name != dentry->d_iname;
286}
287
288void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry)
289{
290 spin_lock(&dentry->d_lock);
291 name->name = dentry->d_name;
292 if (unlikely(dname_external(dentry))) {
293 atomic_inc(&external_name(dentry)->u.count);
294 } else {
295 memcpy(name->inline_name, dentry->d_iname,
296 dentry->d_name.len + 1);
297 name->name.name = name->inline_name;
298 }
299 spin_unlock(&dentry->d_lock);
300}
301EXPORT_SYMBOL(take_dentry_name_snapshot);
302
303void release_dentry_name_snapshot(struct name_snapshot *name)
304{
305 if (unlikely(name->name.name != name->inline_name)) {
306 struct external_name *p;
307 p = container_of(name->name.name, struct external_name, name[0]);
308 if (unlikely(atomic_dec_and_test(&p->u.count)))
309 kfree_rcu(p, u.head);
310 }
311}
312EXPORT_SYMBOL(release_dentry_name_snapshot);
313
314static inline void __d_set_inode_and_type(struct dentry *dentry,
315 struct inode *inode,
316 unsigned type_flags)
317{
318 unsigned flags;
319
320 dentry->d_inode = inode;
321 flags = READ_ONCE(dentry->d_flags);
322 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
323 flags |= type_flags;
324 smp_store_release(&dentry->d_flags, flags);
325}
326
327static inline void __d_clear_type_and_inode(struct dentry *dentry)
328{
329 unsigned flags = READ_ONCE(dentry->d_flags);
330
331 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
332 WRITE_ONCE(dentry->d_flags, flags);
333 dentry->d_inode = NULL;
334 if (dentry->d_flags & DCACHE_LRU_LIST)
335 this_cpu_inc(nr_dentry_negative);
336}
337
338static void dentry_free(struct dentry *dentry)
339{
340 WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias));
341 if (unlikely(dname_external(dentry))) {
342 struct external_name *p = external_name(dentry);
343 if (likely(atomic_dec_and_test(&p->u.count))) {
344 call_rcu(&dentry->d_u.d_rcu, __d_free_external);
345 return;
346 }
347 }
348 /* if dentry was never visible to RCU, immediate free is OK */
349 if (dentry->d_flags & DCACHE_NORCU)
350 __d_free(&dentry->d_u.d_rcu);
351 else
352 call_rcu(&dentry->d_u.d_rcu, __d_free);
353}
354
355/*
356 * Release the dentry's inode, using the filesystem
357 * d_iput() operation if defined.
358 */
359static void dentry_unlink_inode(struct dentry * dentry)
360 __releases(dentry->d_lock)
361 __releases(dentry->d_inode->i_lock)
362{
363 struct inode *inode = dentry->d_inode;
364
365 raw_write_seqcount_begin(&dentry->d_seq);
366 __d_clear_type_and_inode(dentry);
367 hlist_del_init(&dentry->d_u.d_alias);
368 raw_write_seqcount_end(&dentry->d_seq);
369 spin_unlock(&dentry->d_lock);
370 spin_unlock(&inode->i_lock);
371 if (!inode->i_nlink)
372 fsnotify_inoderemove(inode);
373 if (dentry->d_op && dentry->d_op->d_iput)
374 dentry->d_op->d_iput(dentry, inode);
375 else
376 iput(inode);
377}
378
379/*
380 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
381 * is in use - which includes both the "real" per-superblock
382 * LRU list _and_ the DCACHE_SHRINK_LIST use.
383 *
384 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
385 * on the shrink list (ie not on the superblock LRU list).
386 *
387 * The per-cpu "nr_dentry_unused" counters are updated with
388 * the DCACHE_LRU_LIST bit.
389 *
390 * The per-cpu "nr_dentry_negative" counters are only updated
391 * when deleted from or added to the per-superblock LRU list, not
392 * from/to the shrink list. That is to avoid an unneeded dec/inc
393 * pair when moving from LRU to shrink list in select_collect().
394 *
395 * These helper functions make sure we always follow the
396 * rules. d_lock must be held by the caller.
397 */
398#define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
399static void d_lru_add(struct dentry *dentry)
400{
401 D_FLAG_VERIFY(dentry, 0);
402 dentry->d_flags |= DCACHE_LRU_LIST;
403 this_cpu_inc(nr_dentry_unused);
404 if (d_is_negative(dentry))
405 this_cpu_inc(nr_dentry_negative);
406 WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
407}
408
409static void d_lru_del(struct dentry *dentry)
410{
411 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
412 dentry->d_flags &= ~DCACHE_LRU_LIST;
413 this_cpu_dec(nr_dentry_unused);
414 if (d_is_negative(dentry))
415 this_cpu_dec(nr_dentry_negative);
416 WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
417}
418
419static void d_shrink_del(struct dentry *dentry)
420{
421 D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
422 list_del_init(&dentry->d_lru);
423 dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
424 this_cpu_dec(nr_dentry_unused);
425}
426
427static void d_shrink_add(struct dentry *dentry, struct list_head *list)
428{
429 D_FLAG_VERIFY(dentry, 0);
430 list_add(&dentry->d_lru, list);
431 dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST;
432 this_cpu_inc(nr_dentry_unused);
433}
434
435/*
436 * These can only be called under the global LRU lock, ie during the
437 * callback for freeing the LRU list. "isolate" removes it from the
438 * LRU lists entirely, while shrink_move moves it to the indicated
439 * private list.
440 */
441static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry)
442{
443 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
444 dentry->d_flags &= ~DCACHE_LRU_LIST;
445 this_cpu_dec(nr_dentry_unused);
446 if (d_is_negative(dentry))
447 this_cpu_dec(nr_dentry_negative);
448 list_lru_isolate(lru, &dentry->d_lru);
449}
450
451static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
452 struct list_head *list)
453{
454 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
455 dentry->d_flags |= DCACHE_SHRINK_LIST;
456 if (d_is_negative(dentry))
457 this_cpu_dec(nr_dentry_negative);
458 list_lru_isolate_move(lru, &dentry->d_lru, list);
459}
460
461static void ___d_drop(struct dentry *dentry)
462{
463 struct hlist_bl_head *b;
464 /*
465 * Hashed dentries are normally on the dentry hashtable,
466 * with the exception of those newly allocated by
467 * d_obtain_root, which are always IS_ROOT:
468 */
469 if (unlikely(IS_ROOT(dentry)))
470 b = &dentry->d_sb->s_roots;
471 else
472 b = d_hash(dentry->d_name.hash);
473
474 hlist_bl_lock(b);
475 __hlist_bl_del(&dentry->d_hash);
476 hlist_bl_unlock(b);
477}
478
479void __d_drop(struct dentry *dentry)
480{
481 if (!d_unhashed(dentry)) {
482 ___d_drop(dentry);
483 dentry->d_hash.pprev = NULL;
484 write_seqcount_invalidate(&dentry->d_seq);
485 }
486}
487EXPORT_SYMBOL(__d_drop);
488
489/**
490 * d_drop - drop a dentry
491 * @dentry: dentry to drop
492 *
493 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
494 * be found through a VFS lookup any more. Note that this is different from
495 * deleting the dentry - d_delete will try to mark the dentry negative if
496 * possible, giving a successful _negative_ lookup, while d_drop will
497 * just make the cache lookup fail.
498 *
499 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
500 * reason (NFS timeouts or autofs deletes).
501 *
502 * __d_drop requires dentry->d_lock
503 *
504 * ___d_drop doesn't mark dentry as "unhashed"
505 * (dentry->d_hash.pprev will be LIST_POISON2, not NULL).
506 */
507void d_drop(struct dentry *dentry)
508{
509 spin_lock(&dentry->d_lock);
510 __d_drop(dentry);
511 spin_unlock(&dentry->d_lock);
512}
513EXPORT_SYMBOL(d_drop);
514
515static inline void dentry_unlist(struct dentry *dentry, struct dentry *parent)
516{
517 struct dentry *next;
518 /*
519 * Inform d_walk() and shrink_dentry_list() that we are no longer
520 * attached to the dentry tree
521 */
522 dentry->d_flags |= DCACHE_DENTRY_KILLED;
523 if (unlikely(list_empty(&dentry->d_child)))
524 return;
525 __list_del_entry(&dentry->d_child);
526 /*
527 * Cursors can move around the list of children. While we'd been
528 * a normal list member, it didn't matter - ->d_child.next would've
529 * been updated. However, from now on it won't be and for the
530 * things like d_walk() it might end up with a nasty surprise.
531 * Normally d_walk() doesn't care about cursors moving around -
532 * ->d_lock on parent prevents that and since a cursor has no children
533 * of its own, we get through it without ever unlocking the parent.
534 * There is one exception, though - if we ascend from a child that
535 * gets killed as soon as we unlock it, the next sibling is found
536 * using the value left in its ->d_child.next. And if _that_
537 * pointed to a cursor, and cursor got moved (e.g. by lseek())
538 * before d_walk() regains parent->d_lock, we'll end up skipping
539 * everything the cursor had been moved past.
540 *
541 * Solution: make sure that the pointer left behind in ->d_child.next
542 * points to something that won't be moving around. I.e. skip the
543 * cursors.
544 */
545 while (dentry->d_child.next != &parent->d_subdirs) {
546 next = list_entry(dentry->d_child.next, struct dentry, d_child);
547 if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR)))
548 break;
549 dentry->d_child.next = next->d_child.next;
550 }
551}
552
553static void __dentry_kill(struct dentry *dentry)
554{
555 struct dentry *parent = NULL;
556 bool can_free = true;
557 if (!IS_ROOT(dentry))
558 parent = dentry->d_parent;
559
560 /*
561 * The dentry is now unrecoverably dead to the world.
562 */
563 lockref_mark_dead(&dentry->d_lockref);
564
565 /*
566 * inform the fs via d_prune that this dentry is about to be
567 * unhashed and destroyed.
568 */
569 if (dentry->d_flags & DCACHE_OP_PRUNE)
570 dentry->d_op->d_prune(dentry);
571
572 if (dentry->d_flags & DCACHE_LRU_LIST) {
573 if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
574 d_lru_del(dentry);
575 }
576 /* if it was on the hash then remove it */
577 __d_drop(dentry);
578 dentry_unlist(dentry, parent);
579 if (parent)
580 spin_unlock(&parent->d_lock);
581 if (dentry->d_inode)
582 dentry_unlink_inode(dentry);
583 else
584 spin_unlock(&dentry->d_lock);
585 this_cpu_dec(nr_dentry);
586 if (dentry->d_op && dentry->d_op->d_release)
587 dentry->d_op->d_release(dentry);
588
589 spin_lock(&dentry->d_lock);
590 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
591 dentry->d_flags |= DCACHE_MAY_FREE;
592 can_free = false;
593 }
594 spin_unlock(&dentry->d_lock);
595 if (likely(can_free))
596 dentry_free(dentry);
597 cond_resched();
598}
599
600static struct dentry *__lock_parent(struct dentry *dentry)
601{
602 struct dentry *parent;
603 rcu_read_lock();
604 spin_unlock(&dentry->d_lock);
605again:
606 parent = READ_ONCE(dentry->d_parent);
607 spin_lock(&parent->d_lock);
608 /*
609 * We can't blindly lock dentry until we are sure
610 * that we won't violate the locking order.
611 * Any changes of dentry->d_parent must have
612 * been done with parent->d_lock held, so
613 * spin_lock() above is enough of a barrier
614 * for checking if it's still our child.
615 */
616 if (unlikely(parent != dentry->d_parent)) {
617 spin_unlock(&parent->d_lock);
618 goto again;
619 }
620 rcu_read_unlock();
621 if (parent != dentry)
622 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
623 else
624 parent = NULL;
625 return parent;
626}
627
628static inline struct dentry *lock_parent(struct dentry *dentry)
629{
630 struct dentry *parent = dentry->d_parent;
631 if (IS_ROOT(dentry))
632 return NULL;
633 if (likely(spin_trylock(&parent->d_lock)))
634 return parent;
635 return __lock_parent(dentry);
636}
637
638static inline bool retain_dentry(struct dentry *dentry)
639{
640 WARN_ON(d_in_lookup(dentry));
641
642 /* Unreachable? Get rid of it */
643 if (unlikely(d_unhashed(dentry)))
644 return false;
645
646 if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
647 return false;
648
649 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) {
650 if (dentry->d_op->d_delete(dentry))
651 return false;
652 }
653
654 if (unlikely(dentry->d_flags & DCACHE_DONTCACHE))
655 return false;
656
657 /* retain; LRU fodder */
658 dentry->d_lockref.count--;
659 if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
660 d_lru_add(dentry);
661 else if (unlikely(!(dentry->d_flags & DCACHE_REFERENCED)))
662 dentry->d_flags |= DCACHE_REFERENCED;
663 return true;
664}
665
666void d_mark_dontcache(struct inode *inode)
667{
668 struct dentry *de;
669
670 spin_lock(&inode->i_lock);
671 hlist_for_each_entry(de, &inode->i_dentry, d_u.d_alias) {
672 spin_lock(&de->d_lock);
673 de->d_flags |= DCACHE_DONTCACHE;
674 spin_unlock(&de->d_lock);
675 }
676 inode->i_state |= I_DONTCACHE;
677 spin_unlock(&inode->i_lock);
678}
679EXPORT_SYMBOL(d_mark_dontcache);
680
681/*
682 * Finish off a dentry we've decided to kill.
683 * dentry->d_lock must be held, returns with it unlocked.
684 * Returns dentry requiring refcount drop, or NULL if we're done.
685 */
686static struct dentry *dentry_kill(struct dentry *dentry)
687 __releases(dentry->d_lock)
688{
689 struct inode *inode = dentry->d_inode;
690 struct dentry *parent = NULL;
691
692 if (inode && unlikely(!spin_trylock(&inode->i_lock)))
693 goto slow_positive;
694
695 if (!IS_ROOT(dentry)) {
696 parent = dentry->d_parent;
697 if (unlikely(!spin_trylock(&parent->d_lock))) {
698 parent = __lock_parent(dentry);
699 if (likely(inode || !dentry->d_inode))
700 goto got_locks;
701 /* negative that became positive */
702 if (parent)
703 spin_unlock(&parent->d_lock);
704 inode = dentry->d_inode;
705 goto slow_positive;
706 }
707 }
708 __dentry_kill(dentry);
709 return parent;
710
711slow_positive:
712 spin_unlock(&dentry->d_lock);
713 spin_lock(&inode->i_lock);
714 spin_lock(&dentry->d_lock);
715 parent = lock_parent(dentry);
716got_locks:
717 if (unlikely(dentry->d_lockref.count != 1)) {
718 dentry->d_lockref.count--;
719 } else if (likely(!retain_dentry(dentry))) {
720 __dentry_kill(dentry);
721 return parent;
722 }
723 /* we are keeping it, after all */
724 if (inode)
725 spin_unlock(&inode->i_lock);
726 if (parent)
727 spin_unlock(&parent->d_lock);
728 spin_unlock(&dentry->d_lock);
729 return NULL;
730}
731
732/*
733 * Try to do a lockless dput(), and return whether that was successful.
734 *
735 * If unsuccessful, we return false, having already taken the dentry lock.
736 *
737 * The caller needs to hold the RCU read lock, so that the dentry is
738 * guaranteed to stay around even if the refcount goes down to zero!
739 */
740static inline bool fast_dput(struct dentry *dentry)
741{
742 int ret;
743 unsigned int d_flags;
744
745 /*
746 * If we have a d_op->d_delete() operation, we sould not
747 * let the dentry count go to zero, so use "put_or_lock".
748 */
749 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE))
750 return lockref_put_or_lock(&dentry->d_lockref);
751
752 /*
753 * .. otherwise, we can try to just decrement the
754 * lockref optimistically.
755 */
756 ret = lockref_put_return(&dentry->d_lockref);
757
758 /*
759 * If the lockref_put_return() failed due to the lock being held
760 * by somebody else, the fast path has failed. We will need to
761 * get the lock, and then check the count again.
762 */
763 if (unlikely(ret < 0)) {
764 spin_lock(&dentry->d_lock);
765 if (dentry->d_lockref.count > 1) {
766 dentry->d_lockref.count--;
767 spin_unlock(&dentry->d_lock);
768 return true;
769 }
770 return false;
771 }
772
773 /*
774 * If we weren't the last ref, we're done.
775 */
776 if (ret)
777 return true;
778
779 /*
780 * Careful, careful. The reference count went down
781 * to zero, but we don't hold the dentry lock, so
782 * somebody else could get it again, and do another
783 * dput(), and we need to not race with that.
784 *
785 * However, there is a very special and common case
786 * where we don't care, because there is nothing to
787 * do: the dentry is still hashed, it does not have
788 * a 'delete' op, and it's referenced and already on
789 * the LRU list.
790 *
791 * NOTE! Since we aren't locked, these values are
792 * not "stable". However, it is sufficient that at
793 * some point after we dropped the reference the
794 * dentry was hashed and the flags had the proper
795 * value. Other dentry users may have re-gotten
796 * a reference to the dentry and change that, but
797 * our work is done - we can leave the dentry
798 * around with a zero refcount.
799 *
800 * Nevertheless, there are two cases that we should kill
801 * the dentry anyway.
802 * 1. free disconnected dentries as soon as their refcount
803 * reached zero.
804 * 2. free dentries if they should not be cached.
805 */
806 smp_rmb();
807 d_flags = READ_ONCE(dentry->d_flags);
808 d_flags &= DCACHE_REFERENCED | DCACHE_LRU_LIST |
809 DCACHE_DISCONNECTED | DCACHE_DONTCACHE;
810
811 /* Nothing to do? Dropping the reference was all we needed? */
812 if (d_flags == (DCACHE_REFERENCED | DCACHE_LRU_LIST) && !d_unhashed(dentry))
813 return true;
814
815 /*
816 * Not the fast normal case? Get the lock. We've already decremented
817 * the refcount, but we'll need to re-check the situation after
818 * getting the lock.
819 */
820 spin_lock(&dentry->d_lock);
821
822 /*
823 * Did somebody else grab a reference to it in the meantime, and
824 * we're no longer the last user after all? Alternatively, somebody
825 * else could have killed it and marked it dead. Either way, we
826 * don't need to do anything else.
827 */
828 if (dentry->d_lockref.count) {
829 spin_unlock(&dentry->d_lock);
830 return true;
831 }
832
833 /*
834 * Re-get the reference we optimistically dropped. We hold the
835 * lock, and we just tested that it was zero, so we can just
836 * set it to 1.
837 */
838 dentry->d_lockref.count = 1;
839 return false;
840}
841
842
843/*
844 * This is dput
845 *
846 * This is complicated by the fact that we do not want to put
847 * dentries that are no longer on any hash chain on the unused
848 * list: we'd much rather just get rid of them immediately.
849 *
850 * However, that implies that we have to traverse the dentry
851 * tree upwards to the parents which might _also_ now be
852 * scheduled for deletion (it may have been only waiting for
853 * its last child to go away).
854 *
855 * This tail recursion is done by hand as we don't want to depend
856 * on the compiler to always get this right (gcc generally doesn't).
857 * Real recursion would eat up our stack space.
858 */
859
860/*
861 * dput - release a dentry
862 * @dentry: dentry to release
863 *
864 * Release a dentry. This will drop the usage count and if appropriate
865 * call the dentry unlink method as well as removing it from the queues and
866 * releasing its resources. If the parent dentries were scheduled for release
867 * they too may now get deleted.
868 */
869void dput(struct dentry *dentry)
870{
871 while (dentry) {
872 might_sleep();
873
874 rcu_read_lock();
875 if (likely(fast_dput(dentry))) {
876 rcu_read_unlock();
877 return;
878 }
879
880 /* Slow case: now with the dentry lock held */
881 rcu_read_unlock();
882
883 if (likely(retain_dentry(dentry))) {
884 spin_unlock(&dentry->d_lock);
885 return;
886 }
887
888 dentry = dentry_kill(dentry);
889 }
890}
891EXPORT_SYMBOL(dput);
892
893static void __dput_to_list(struct dentry *dentry, struct list_head *list)
894__must_hold(&dentry->d_lock)
895{
896 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
897 /* let the owner of the list it's on deal with it */
898 --dentry->d_lockref.count;
899 } else {
900 if (dentry->d_flags & DCACHE_LRU_LIST)
901 d_lru_del(dentry);
902 if (!--dentry->d_lockref.count)
903 d_shrink_add(dentry, list);
904 }
905}
906
907void dput_to_list(struct dentry *dentry, struct list_head *list)
908{
909 rcu_read_lock();
910 if (likely(fast_dput(dentry))) {
911 rcu_read_unlock();
912 return;
913 }
914 rcu_read_unlock();
915 if (!retain_dentry(dentry))
916 __dput_to_list(dentry, list);
917 spin_unlock(&dentry->d_lock);
918}
919
920/* This must be called with d_lock held */
921static inline void __dget_dlock(struct dentry *dentry)
922{
923 dentry->d_lockref.count++;
924}
925
926static inline void __dget(struct dentry *dentry)
927{
928 lockref_get(&dentry->d_lockref);
929}
930
931struct dentry *dget_parent(struct dentry *dentry)
932{
933 int gotref;
934 struct dentry *ret;
935 unsigned seq;
936
937 /*
938 * Do optimistic parent lookup without any
939 * locking.
940 */
941 rcu_read_lock();
942 seq = raw_seqcount_begin(&dentry->d_seq);
943 ret = READ_ONCE(dentry->d_parent);
944 gotref = lockref_get_not_zero(&ret->d_lockref);
945 rcu_read_unlock();
946 if (likely(gotref)) {
947 if (!read_seqcount_retry(&dentry->d_seq, seq))
948 return ret;
949 dput(ret);
950 }
951
952repeat:
953 /*
954 * Don't need rcu_dereference because we re-check it was correct under
955 * the lock.
956 */
957 rcu_read_lock();
958 ret = dentry->d_parent;
959 spin_lock(&ret->d_lock);
960 if (unlikely(ret != dentry->d_parent)) {
961 spin_unlock(&ret->d_lock);
962 rcu_read_unlock();
963 goto repeat;
964 }
965 rcu_read_unlock();
966 BUG_ON(!ret->d_lockref.count);
967 ret->d_lockref.count++;
968 spin_unlock(&ret->d_lock);
969 return ret;
970}
971EXPORT_SYMBOL(dget_parent);
972
973static struct dentry * __d_find_any_alias(struct inode *inode)
974{
975 struct dentry *alias;
976
977 if (hlist_empty(&inode->i_dentry))
978 return NULL;
979 alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
980 __dget(alias);
981 return alias;
982}
983
984/**
985 * d_find_any_alias - find any alias for a given inode
986 * @inode: inode to find an alias for
987 *
988 * If any aliases exist for the given inode, take and return a
989 * reference for one of them. If no aliases exist, return %NULL.
990 */
991struct dentry *d_find_any_alias(struct inode *inode)
992{
993 struct dentry *de;
994
995 spin_lock(&inode->i_lock);
996 de = __d_find_any_alias(inode);
997 spin_unlock(&inode->i_lock);
998 return de;
999}
1000EXPORT_SYMBOL(d_find_any_alias);
1001
1002static struct dentry *__d_find_alias(struct inode *inode)
1003{
1004 struct dentry *alias;
1005
1006 if (S_ISDIR(inode->i_mode))
1007 return __d_find_any_alias(inode);
1008
1009 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
1010 spin_lock(&alias->d_lock);
1011 if (!d_unhashed(alias)) {
1012 __dget_dlock(alias);
1013 spin_unlock(&alias->d_lock);
1014 return alias;
1015 }
1016 spin_unlock(&alias->d_lock);
1017 }
1018 return NULL;
1019}
1020
1021/**
1022 * d_find_alias - grab a hashed alias of inode
1023 * @inode: inode in question
1024 *
1025 * If inode has a hashed alias, or is a directory and has any alias,
1026 * acquire the reference to alias and return it. Otherwise return NULL.
1027 * Notice that if inode is a directory there can be only one alias and
1028 * it can be unhashed only if it has no children, or if it is the root
1029 * of a filesystem, or if the directory was renamed and d_revalidate
1030 * was the first vfs operation to notice.
1031 *
1032 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
1033 * any other hashed alias over that one.
1034 */
1035struct dentry *d_find_alias(struct inode *inode)
1036{
1037 struct dentry *de = NULL;
1038
1039 if (!hlist_empty(&inode->i_dentry)) {
1040 spin_lock(&inode->i_lock);
1041 de = __d_find_alias(inode);
1042 spin_unlock(&inode->i_lock);
1043 }
1044 return de;
1045}
1046EXPORT_SYMBOL(d_find_alias);
1047
1048/*
1049 * Caller MUST be holding rcu_read_lock() and be guaranteed
1050 * that inode won't get freed until rcu_read_unlock().
1051 */
1052struct dentry *d_find_alias_rcu(struct inode *inode)
1053{
1054 struct hlist_head *l = &inode->i_dentry;
1055 struct dentry *de = NULL;
1056
1057 spin_lock(&inode->i_lock);
1058 // ->i_dentry and ->i_rcu are colocated, but the latter won't be
1059 // used without having I_FREEING set, which means no aliases left
1060 if (likely(!(inode->i_state & I_FREEING) && !hlist_empty(l))) {
1061 if (S_ISDIR(inode->i_mode)) {
1062 de = hlist_entry(l->first, struct dentry, d_u.d_alias);
1063 } else {
1064 hlist_for_each_entry(de, l, d_u.d_alias)
1065 if (!d_unhashed(de))
1066 break;
1067 }
1068 }
1069 spin_unlock(&inode->i_lock);
1070 return de;
1071}
1072
1073/*
1074 * Try to kill dentries associated with this inode.
1075 * WARNING: you must own a reference to inode.
1076 */
1077void d_prune_aliases(struct inode *inode)
1078{
1079 struct dentry *dentry;
1080restart:
1081 spin_lock(&inode->i_lock);
1082 hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
1083 spin_lock(&dentry->d_lock);
1084 if (!dentry->d_lockref.count) {
1085 struct dentry *parent = lock_parent(dentry);
1086 if (likely(!dentry->d_lockref.count)) {
1087 __dentry_kill(dentry);
1088 dput(parent);
1089 goto restart;
1090 }
1091 if (parent)
1092 spin_unlock(&parent->d_lock);
1093 }
1094 spin_unlock(&dentry->d_lock);
1095 }
1096 spin_unlock(&inode->i_lock);
1097}
1098EXPORT_SYMBOL(d_prune_aliases);
1099
1100/*
1101 * Lock a dentry from shrink list.
1102 * Called under rcu_read_lock() and dentry->d_lock; the former
1103 * guarantees that nothing we access will be freed under us.
1104 * Note that dentry is *not* protected from concurrent dentry_kill(),
1105 * d_delete(), etc.
1106 *
1107 * Return false if dentry has been disrupted or grabbed, leaving
1108 * the caller to kick it off-list. Otherwise, return true and have
1109 * that dentry's inode and parent both locked.
1110 */
1111static bool shrink_lock_dentry(struct dentry *dentry)
1112{
1113 struct inode *inode;
1114 struct dentry *parent;
1115
1116 if (dentry->d_lockref.count)
1117 return false;
1118
1119 inode = dentry->d_inode;
1120 if (inode && unlikely(!spin_trylock(&inode->i_lock))) {
1121 spin_unlock(&dentry->d_lock);
1122 spin_lock(&inode->i_lock);
1123 spin_lock(&dentry->d_lock);
1124 if (unlikely(dentry->d_lockref.count))
1125 goto out;
1126 /* changed inode means that somebody had grabbed it */
1127 if (unlikely(inode != dentry->d_inode))
1128 goto out;
1129 }
1130
1131 parent = dentry->d_parent;
1132 if (IS_ROOT(dentry) || likely(spin_trylock(&parent->d_lock)))
1133 return true;
1134
1135 spin_unlock(&dentry->d_lock);
1136 spin_lock(&parent->d_lock);
1137 if (unlikely(parent != dentry->d_parent)) {
1138 spin_unlock(&parent->d_lock);
1139 spin_lock(&dentry->d_lock);
1140 goto out;
1141 }
1142 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1143 if (likely(!dentry->d_lockref.count))
1144 return true;
1145 spin_unlock(&parent->d_lock);
1146out:
1147 if (inode)
1148 spin_unlock(&inode->i_lock);
1149 return false;
1150}
1151
1152void shrink_dentry_list(struct list_head *list)
1153{
1154 while (!list_empty(list)) {
1155 struct dentry *dentry, *parent;
1156
1157 dentry = list_entry(list->prev, struct dentry, d_lru);
1158 spin_lock(&dentry->d_lock);
1159 rcu_read_lock();
1160 if (!shrink_lock_dentry(dentry)) {
1161 bool can_free = false;
1162 rcu_read_unlock();
1163 d_shrink_del(dentry);
1164 if (dentry->d_lockref.count < 0)
1165 can_free = dentry->d_flags & DCACHE_MAY_FREE;
1166 spin_unlock(&dentry->d_lock);
1167 if (can_free)
1168 dentry_free(dentry);
1169 continue;
1170 }
1171 rcu_read_unlock();
1172 d_shrink_del(dentry);
1173 parent = dentry->d_parent;
1174 if (parent != dentry)
1175 __dput_to_list(parent, list);
1176 __dentry_kill(dentry);
1177 }
1178}
1179
1180static enum lru_status dentry_lru_isolate(struct list_head *item,
1181 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1182{
1183 struct list_head *freeable = arg;
1184 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1185
1186
1187 /*
1188 * we are inverting the lru lock/dentry->d_lock here,
1189 * so use a trylock. If we fail to get the lock, just skip
1190 * it
1191 */
1192 if (!spin_trylock(&dentry->d_lock))
1193 return LRU_SKIP;
1194
1195 /*
1196 * Referenced dentries are still in use. If they have active
1197 * counts, just remove them from the LRU. Otherwise give them
1198 * another pass through the LRU.
1199 */
1200 if (dentry->d_lockref.count) {
1201 d_lru_isolate(lru, dentry);
1202 spin_unlock(&dentry->d_lock);
1203 return LRU_REMOVED;
1204 }
1205
1206 if (dentry->d_flags & DCACHE_REFERENCED) {
1207 dentry->d_flags &= ~DCACHE_REFERENCED;
1208 spin_unlock(&dentry->d_lock);
1209
1210 /*
1211 * The list move itself will be made by the common LRU code. At
1212 * this point, we've dropped the dentry->d_lock but keep the
1213 * lru lock. This is safe to do, since every list movement is
1214 * protected by the lru lock even if both locks are held.
1215 *
1216 * This is guaranteed by the fact that all LRU management
1217 * functions are intermediated by the LRU API calls like
1218 * list_lru_add and list_lru_del. List movement in this file
1219 * only ever occur through this functions or through callbacks
1220 * like this one, that are called from the LRU API.
1221 *
1222 * The only exceptions to this are functions like
1223 * shrink_dentry_list, and code that first checks for the
1224 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1225 * operating only with stack provided lists after they are
1226 * properly isolated from the main list. It is thus, always a
1227 * local access.
1228 */
1229 return LRU_ROTATE;
1230 }
1231
1232 d_lru_shrink_move(lru, dentry, freeable);
1233 spin_unlock(&dentry->d_lock);
1234
1235 return LRU_REMOVED;
1236}
1237
1238/**
1239 * prune_dcache_sb - shrink the dcache
1240 * @sb: superblock
1241 * @sc: shrink control, passed to list_lru_shrink_walk()
1242 *
1243 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1244 * is done when we need more memory and called from the superblock shrinker
1245 * function.
1246 *
1247 * This function may fail to free any resources if all the dentries are in
1248 * use.
1249 */
1250long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc)
1251{
1252 LIST_HEAD(dispose);
1253 long freed;
1254
1255 freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc,
1256 dentry_lru_isolate, &dispose);
1257 shrink_dentry_list(&dispose);
1258 return freed;
1259}
1260
1261static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
1262 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1263{
1264 struct list_head *freeable = arg;
1265 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1266
1267 /*
1268 * we are inverting the lru lock/dentry->d_lock here,
1269 * so use a trylock. If we fail to get the lock, just skip
1270 * it
1271 */
1272 if (!spin_trylock(&dentry->d_lock))
1273 return LRU_SKIP;
1274
1275 d_lru_shrink_move(lru, dentry, freeable);
1276 spin_unlock(&dentry->d_lock);
1277
1278 return LRU_REMOVED;
1279}
1280
1281
1282/**
1283 * shrink_dcache_sb - shrink dcache for a superblock
1284 * @sb: superblock
1285 *
1286 * Shrink the dcache for the specified super block. This is used to free
1287 * the dcache before unmounting a file system.
1288 */
1289void shrink_dcache_sb(struct super_block *sb)
1290{
1291 do {
1292 LIST_HEAD(dispose);
1293
1294 list_lru_walk(&sb->s_dentry_lru,
1295 dentry_lru_isolate_shrink, &dispose, 1024);
1296 shrink_dentry_list(&dispose);
1297 } while (list_lru_count(&sb->s_dentry_lru) > 0);
1298}
1299EXPORT_SYMBOL(shrink_dcache_sb);
1300
1301/**
1302 * enum d_walk_ret - action to talke during tree walk
1303 * @D_WALK_CONTINUE: contrinue walk
1304 * @D_WALK_QUIT: quit walk
1305 * @D_WALK_NORETRY: quit when retry is needed
1306 * @D_WALK_SKIP: skip this dentry and its children
1307 */
1308enum d_walk_ret {
1309 D_WALK_CONTINUE,
1310 D_WALK_QUIT,
1311 D_WALK_NORETRY,
1312 D_WALK_SKIP,
1313};
1314
1315/**
1316 * d_walk - walk the dentry tree
1317 * @parent: start of walk
1318 * @data: data passed to @enter() and @finish()
1319 * @enter: callback when first entering the dentry
1320 *
1321 * The @enter() callbacks are called with d_lock held.
1322 */
1323static void d_walk(struct dentry *parent, void *data,
1324 enum d_walk_ret (*enter)(void *, struct dentry *))
1325{
1326 struct dentry *this_parent;
1327 struct list_head *next;
1328 unsigned seq = 0;
1329 enum d_walk_ret ret;
1330 bool retry = true;
1331
1332again:
1333 read_seqbegin_or_lock(&rename_lock, &seq);
1334 this_parent = parent;
1335 spin_lock(&this_parent->d_lock);
1336
1337 ret = enter(data, this_parent);
1338 switch (ret) {
1339 case D_WALK_CONTINUE:
1340 break;
1341 case D_WALK_QUIT:
1342 case D_WALK_SKIP:
1343 goto out_unlock;
1344 case D_WALK_NORETRY:
1345 retry = false;
1346 break;
1347 }
1348repeat:
1349 next = this_parent->d_subdirs.next;
1350resume:
1351 while (next != &this_parent->d_subdirs) {
1352 struct list_head *tmp = next;
1353 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
1354 next = tmp->next;
1355
1356 if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR))
1357 continue;
1358
1359 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1360
1361 ret = enter(data, dentry);
1362 switch (ret) {
1363 case D_WALK_CONTINUE:
1364 break;
1365 case D_WALK_QUIT:
1366 spin_unlock(&dentry->d_lock);
1367 goto out_unlock;
1368 case D_WALK_NORETRY:
1369 retry = false;
1370 break;
1371 case D_WALK_SKIP:
1372 spin_unlock(&dentry->d_lock);
1373 continue;
1374 }
1375
1376 if (!list_empty(&dentry->d_subdirs)) {
1377 spin_unlock(&this_parent->d_lock);
1378 spin_release(&dentry->d_lock.dep_map, _RET_IP_);
1379 this_parent = dentry;
1380 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1381 goto repeat;
1382 }
1383 spin_unlock(&dentry->d_lock);
1384 }
1385 /*
1386 * All done at this level ... ascend and resume the search.
1387 */
1388 rcu_read_lock();
1389ascend:
1390 if (this_parent != parent) {
1391 struct dentry *child = this_parent;
1392 this_parent = child->d_parent;
1393
1394 spin_unlock(&child->d_lock);
1395 spin_lock(&this_parent->d_lock);
1396
1397 /* might go back up the wrong parent if we have had a rename. */
1398 if (need_seqretry(&rename_lock, seq))
1399 goto rename_retry;
1400 /* go into the first sibling still alive */
1401 do {
1402 next = child->d_child.next;
1403 if (next == &this_parent->d_subdirs)
1404 goto ascend;
1405 child = list_entry(next, struct dentry, d_child);
1406 } while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
1407 rcu_read_unlock();
1408 goto resume;
1409 }
1410 if (need_seqretry(&rename_lock, seq))
1411 goto rename_retry;
1412 rcu_read_unlock();
1413
1414out_unlock:
1415 spin_unlock(&this_parent->d_lock);
1416 done_seqretry(&rename_lock, seq);
1417 return;
1418
1419rename_retry:
1420 spin_unlock(&this_parent->d_lock);
1421 rcu_read_unlock();
1422 BUG_ON(seq & 1);
1423 if (!retry)
1424 return;
1425 seq = 1;
1426 goto again;
1427}
1428
1429struct check_mount {
1430 struct vfsmount *mnt;
1431 unsigned int mounted;
1432};
1433
1434static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry)
1435{
1436 struct check_mount *info = data;
1437 struct path path = { .mnt = info->mnt, .dentry = dentry };
1438
1439 if (likely(!d_mountpoint(dentry)))
1440 return D_WALK_CONTINUE;
1441 if (__path_is_mountpoint(&path)) {
1442 info->mounted = 1;
1443 return D_WALK_QUIT;
1444 }
1445 return D_WALK_CONTINUE;
1446}
1447
1448/**
1449 * path_has_submounts - check for mounts over a dentry in the
1450 * current namespace.
1451 * @parent: path to check.
1452 *
1453 * Return true if the parent or its subdirectories contain
1454 * a mount point in the current namespace.
1455 */
1456int path_has_submounts(const struct path *parent)
1457{
1458 struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
1459
1460 read_seqlock_excl(&mount_lock);
1461 d_walk(parent->dentry, &data, path_check_mount);
1462 read_sequnlock_excl(&mount_lock);
1463
1464 return data.mounted;
1465}
1466EXPORT_SYMBOL(path_has_submounts);
1467
1468/*
1469 * Called by mount code to set a mountpoint and check if the mountpoint is
1470 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1471 * subtree can become unreachable).
1472 *
1473 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1474 * this reason take rename_lock and d_lock on dentry and ancestors.
1475 */
1476int d_set_mounted(struct dentry *dentry)
1477{
1478 struct dentry *p;
1479 int ret = -ENOENT;
1480 write_seqlock(&rename_lock);
1481 for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
1482 /* Need exclusion wrt. d_invalidate() */
1483 spin_lock(&p->d_lock);
1484 if (unlikely(d_unhashed(p))) {
1485 spin_unlock(&p->d_lock);
1486 goto out;
1487 }
1488 spin_unlock(&p->d_lock);
1489 }
1490 spin_lock(&dentry->d_lock);
1491 if (!d_unlinked(dentry)) {
1492 ret = -EBUSY;
1493 if (!d_mountpoint(dentry)) {
1494 dentry->d_flags |= DCACHE_MOUNTED;
1495 ret = 0;
1496 }
1497 }
1498 spin_unlock(&dentry->d_lock);
1499out:
1500 write_sequnlock(&rename_lock);
1501 return ret;
1502}
1503
1504/*
1505 * Search the dentry child list of the specified parent,
1506 * and move any unused dentries to the end of the unused
1507 * list for prune_dcache(). We descend to the next level
1508 * whenever the d_subdirs list is non-empty and continue
1509 * searching.
1510 *
1511 * It returns zero iff there are no unused children,
1512 * otherwise it returns the number of children moved to
1513 * the end of the unused list. This may not be the total
1514 * number of unused children, because select_parent can
1515 * drop the lock and return early due to latency
1516 * constraints.
1517 */
1518
1519struct select_data {
1520 struct dentry *start;
1521 union {
1522 long found;
1523 struct dentry *victim;
1524 };
1525 struct list_head dispose;
1526};
1527
1528static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
1529{
1530 struct select_data *data = _data;
1531 enum d_walk_ret ret = D_WALK_CONTINUE;
1532
1533 if (data->start == dentry)
1534 goto out;
1535
1536 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1537 data->found++;
1538 } else {
1539 if (dentry->d_flags & DCACHE_LRU_LIST)
1540 d_lru_del(dentry);
1541 if (!dentry->d_lockref.count) {
1542 d_shrink_add(dentry, &data->dispose);
1543 data->found++;
1544 }
1545 }
1546 /*
1547 * We can return to the caller if we have found some (this
1548 * ensures forward progress). We'll be coming back to find
1549 * the rest.
1550 */
1551 if (!list_empty(&data->dispose))
1552 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1553out:
1554 return ret;
1555}
1556
1557static enum d_walk_ret select_collect2(void *_data, struct dentry *dentry)
1558{
1559 struct select_data *data = _data;
1560 enum d_walk_ret ret = D_WALK_CONTINUE;
1561
1562 if (data->start == dentry)
1563 goto out;
1564
1565 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1566 if (!dentry->d_lockref.count) {
1567 rcu_read_lock();
1568 data->victim = dentry;
1569 return D_WALK_QUIT;
1570 }
1571 } else {
1572 if (dentry->d_flags & DCACHE_LRU_LIST)
1573 d_lru_del(dentry);
1574 if (!dentry->d_lockref.count)
1575 d_shrink_add(dentry, &data->dispose);
1576 }
1577 /*
1578 * We can return to the caller if we have found some (this
1579 * ensures forward progress). We'll be coming back to find
1580 * the rest.
1581 */
1582 if (!list_empty(&data->dispose))
1583 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1584out:
1585 return ret;
1586}
1587
1588/**
1589 * shrink_dcache_parent - prune dcache
1590 * @parent: parent of entries to prune
1591 *
1592 * Prune the dcache to remove unused children of the parent dentry.
1593 */
1594void shrink_dcache_parent(struct dentry *parent)
1595{
1596 for (;;) {
1597 struct select_data data = {.start = parent};
1598
1599 INIT_LIST_HEAD(&data.dispose);
1600 d_walk(parent, &data, select_collect);
1601
1602 if (!list_empty(&data.dispose)) {
1603 shrink_dentry_list(&data.dispose);
1604 continue;
1605 }
1606
1607 cond_resched();
1608 if (!data.found)
1609 break;
1610 data.victim = NULL;
1611 d_walk(parent, &data, select_collect2);
1612 if (data.victim) {
1613 struct dentry *parent;
1614 spin_lock(&data.victim->d_lock);
1615 if (!shrink_lock_dentry(data.victim)) {
1616 spin_unlock(&data.victim->d_lock);
1617 rcu_read_unlock();
1618 } else {
1619 rcu_read_unlock();
1620 parent = data.victim->d_parent;
1621 if (parent != data.victim)
1622 __dput_to_list(parent, &data.dispose);
1623 __dentry_kill(data.victim);
1624 }
1625 }
1626 if (!list_empty(&data.dispose))
1627 shrink_dentry_list(&data.dispose);
1628 }
1629}
1630EXPORT_SYMBOL(shrink_dcache_parent);
1631
1632static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
1633{
1634 /* it has busy descendents; complain about those instead */
1635 if (!list_empty(&dentry->d_subdirs))
1636 return D_WALK_CONTINUE;
1637
1638 /* root with refcount 1 is fine */
1639 if (dentry == _data && dentry->d_lockref.count == 1)
1640 return D_WALK_CONTINUE;
1641
1642 printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%pd} "
1643 " still in use (%d) [unmount of %s %s]\n",
1644 dentry,
1645 dentry->d_inode ?
1646 dentry->d_inode->i_ino : 0UL,
1647 dentry,
1648 dentry->d_lockref.count,
1649 dentry->d_sb->s_type->name,
1650 dentry->d_sb->s_id);
1651 WARN_ON(1);
1652 return D_WALK_CONTINUE;
1653}
1654
1655static void do_one_tree(struct dentry *dentry)
1656{
1657 shrink_dcache_parent(dentry);
1658 d_walk(dentry, dentry, umount_check);
1659 d_drop(dentry);
1660 dput(dentry);
1661}
1662
1663/*
1664 * destroy the dentries attached to a superblock on unmounting
1665 */
1666void shrink_dcache_for_umount(struct super_block *sb)
1667{
1668 struct dentry *dentry;
1669
1670 WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked");
1671
1672 dentry = sb->s_root;
1673 sb->s_root = NULL;
1674 do_one_tree(dentry);
1675
1676 while (!hlist_bl_empty(&sb->s_roots)) {
1677 dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_roots), struct dentry, d_hash));
1678 do_one_tree(dentry);
1679 }
1680}
1681
1682static enum d_walk_ret find_submount(void *_data, struct dentry *dentry)
1683{
1684 struct dentry **victim = _data;
1685 if (d_mountpoint(dentry)) {
1686 __dget_dlock(dentry);
1687 *victim = dentry;
1688 return D_WALK_QUIT;
1689 }
1690 return D_WALK_CONTINUE;
1691}
1692
1693/**
1694 * d_invalidate - detach submounts, prune dcache, and drop
1695 * @dentry: dentry to invalidate (aka detach, prune and drop)
1696 */
1697void d_invalidate(struct dentry *dentry)
1698{
1699 bool had_submounts = false;
1700 spin_lock(&dentry->d_lock);
1701 if (d_unhashed(dentry)) {
1702 spin_unlock(&dentry->d_lock);
1703 return;
1704 }
1705 __d_drop(dentry);
1706 spin_unlock(&dentry->d_lock);
1707
1708 /* Negative dentries can be dropped without further checks */
1709 if (!dentry->d_inode)
1710 return;
1711
1712 shrink_dcache_parent(dentry);
1713 for (;;) {
1714 struct dentry *victim = NULL;
1715 d_walk(dentry, &victim, find_submount);
1716 if (!victim) {
1717 if (had_submounts)
1718 shrink_dcache_parent(dentry);
1719 return;
1720 }
1721 had_submounts = true;
1722 detach_mounts(victim);
1723 dput(victim);
1724 }
1725}
1726EXPORT_SYMBOL(d_invalidate);
1727
1728/**
1729 * __d_alloc - allocate a dcache entry
1730 * @sb: filesystem it will belong to
1731 * @name: qstr of the name
1732 *
1733 * Allocates a dentry. It returns %NULL if there is insufficient memory
1734 * available. On a success the dentry is returned. The name passed in is
1735 * copied and the copy passed in may be reused after this call.
1736 */
1737
1738static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1739{
1740 struct dentry *dentry;
1741 char *dname;
1742 int err;
1743
1744 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
1745 if (!dentry)
1746 return NULL;
1747
1748 /*
1749 * We guarantee that the inline name is always NUL-terminated.
1750 * This way the memcpy() done by the name switching in rename
1751 * will still always have a NUL at the end, even if we might
1752 * be overwriting an internal NUL character
1753 */
1754 dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
1755 if (unlikely(!name)) {
1756 name = &slash_name;
1757 dname = dentry->d_iname;
1758 } else if (name->len > DNAME_INLINE_LEN-1) {
1759 size_t size = offsetof(struct external_name, name[1]);
1760 struct external_name *p = kmalloc(size + name->len,
1761 GFP_KERNEL_ACCOUNT |
1762 __GFP_RECLAIMABLE);
1763 if (!p) {
1764 kmem_cache_free(dentry_cache, dentry);
1765 return NULL;
1766 }
1767 atomic_set(&p->u.count, 1);
1768 dname = p->name;
1769 } else {
1770 dname = dentry->d_iname;
1771 }
1772
1773 dentry->d_name.len = name->len;
1774 dentry->d_name.hash = name->hash;
1775 memcpy(dname, name->name, name->len);
1776 dname[name->len] = 0;
1777
1778 /* Make sure we always see the terminating NUL character */
1779 smp_store_release(&dentry->d_name.name, dname); /* ^^^ */
1780
1781 dentry->d_lockref.count = 1;
1782 dentry->d_flags = 0;
1783 spin_lock_init(&dentry->d_lock);
1784 seqcount_spinlock_init(&dentry->d_seq, &dentry->d_lock);
1785 dentry->d_inode = NULL;
1786 dentry->d_parent = dentry;
1787 dentry->d_sb = sb;
1788 dentry->d_op = NULL;
1789 dentry->d_fsdata = NULL;
1790 INIT_HLIST_BL_NODE(&dentry->d_hash);
1791 INIT_LIST_HEAD(&dentry->d_lru);
1792 INIT_LIST_HEAD(&dentry->d_subdirs);
1793 INIT_HLIST_NODE(&dentry->d_u.d_alias);
1794 INIT_LIST_HEAD(&dentry->d_child);
1795 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1796
1797 if (dentry->d_op && dentry->d_op->d_init) {
1798 err = dentry->d_op->d_init(dentry);
1799 if (err) {
1800 if (dname_external(dentry))
1801 kfree(external_name(dentry));
1802 kmem_cache_free(dentry_cache, dentry);
1803 return NULL;
1804 }
1805 }
1806
1807 this_cpu_inc(nr_dentry);
1808
1809 return dentry;
1810}
1811
1812/**
1813 * d_alloc - allocate a dcache entry
1814 * @parent: parent of entry to allocate
1815 * @name: qstr of the name
1816 *
1817 * Allocates a dentry. It returns %NULL if there is insufficient memory
1818 * available. On a success the dentry is returned. The name passed in is
1819 * copied and the copy passed in may be reused after this call.
1820 */
1821struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1822{
1823 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1824 if (!dentry)
1825 return NULL;
1826 spin_lock(&parent->d_lock);
1827 /*
1828 * don't need child lock because it is not subject
1829 * to concurrency here
1830 */
1831 __dget_dlock(parent);
1832 dentry->d_parent = parent;
1833 list_add(&dentry->d_child, &parent->d_subdirs);
1834 spin_unlock(&parent->d_lock);
1835
1836 return dentry;
1837}
1838EXPORT_SYMBOL(d_alloc);
1839
1840struct dentry *d_alloc_anon(struct super_block *sb)
1841{
1842 return __d_alloc(sb, NULL);
1843}
1844EXPORT_SYMBOL(d_alloc_anon);
1845
1846struct dentry *d_alloc_cursor(struct dentry * parent)
1847{
1848 struct dentry *dentry = d_alloc_anon(parent->d_sb);
1849 if (dentry) {
1850 dentry->d_flags |= DCACHE_DENTRY_CURSOR;
1851 dentry->d_parent = dget(parent);
1852 }
1853 return dentry;
1854}
1855
1856/**
1857 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1858 * @sb: the superblock
1859 * @name: qstr of the name
1860 *
1861 * For a filesystem that just pins its dentries in memory and never
1862 * performs lookups at all, return an unhashed IS_ROOT dentry.
1863 * This is used for pipes, sockets et.al. - the stuff that should
1864 * never be anyone's children or parents. Unlike all other
1865 * dentries, these will not have RCU delay between dropping the
1866 * last reference and freeing them.
1867 *
1868 * The only user is alloc_file_pseudo() and that's what should
1869 * be considered a public interface. Don't use directly.
1870 */
1871struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1872{
1873 struct dentry *dentry = __d_alloc(sb, name);
1874 if (likely(dentry))
1875 dentry->d_flags |= DCACHE_NORCU;
1876 return dentry;
1877}
1878
1879struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1880{
1881 struct qstr q;
1882
1883 q.name = name;
1884 q.hash_len = hashlen_string(parent, name);
1885 return d_alloc(parent, &q);
1886}
1887EXPORT_SYMBOL(d_alloc_name);
1888
1889void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1890{
1891 WARN_ON_ONCE(dentry->d_op);
1892 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
1893 DCACHE_OP_COMPARE |
1894 DCACHE_OP_REVALIDATE |
1895 DCACHE_OP_WEAK_REVALIDATE |
1896 DCACHE_OP_DELETE |
1897 DCACHE_OP_REAL));
1898 dentry->d_op = op;
1899 if (!op)
1900 return;
1901 if (op->d_hash)
1902 dentry->d_flags |= DCACHE_OP_HASH;
1903 if (op->d_compare)
1904 dentry->d_flags |= DCACHE_OP_COMPARE;
1905 if (op->d_revalidate)
1906 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1907 if (op->d_weak_revalidate)
1908 dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
1909 if (op->d_delete)
1910 dentry->d_flags |= DCACHE_OP_DELETE;
1911 if (op->d_prune)
1912 dentry->d_flags |= DCACHE_OP_PRUNE;
1913 if (op->d_real)
1914 dentry->d_flags |= DCACHE_OP_REAL;
1915
1916}
1917EXPORT_SYMBOL(d_set_d_op);
1918
1919
1920/*
1921 * d_set_fallthru - Mark a dentry as falling through to a lower layer
1922 * @dentry - The dentry to mark
1923 *
1924 * Mark a dentry as falling through to the lower layer (as set with
1925 * d_pin_lower()). This flag may be recorded on the medium.
1926 */
1927void d_set_fallthru(struct dentry *dentry)
1928{
1929 spin_lock(&dentry->d_lock);
1930 dentry->d_flags |= DCACHE_FALLTHRU;
1931 spin_unlock(&dentry->d_lock);
1932}
1933EXPORT_SYMBOL(d_set_fallthru);
1934
1935static unsigned d_flags_for_inode(struct inode *inode)
1936{
1937 unsigned add_flags = DCACHE_REGULAR_TYPE;
1938
1939 if (!inode)
1940 return DCACHE_MISS_TYPE;
1941
1942 if (S_ISDIR(inode->i_mode)) {
1943 add_flags = DCACHE_DIRECTORY_TYPE;
1944 if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) {
1945 if (unlikely(!inode->i_op->lookup))
1946 add_flags = DCACHE_AUTODIR_TYPE;
1947 else
1948 inode->i_opflags |= IOP_LOOKUP;
1949 }
1950 goto type_determined;
1951 }
1952
1953 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1954 if (unlikely(inode->i_op->get_link)) {
1955 add_flags = DCACHE_SYMLINK_TYPE;
1956 goto type_determined;
1957 }
1958 inode->i_opflags |= IOP_NOFOLLOW;
1959 }
1960
1961 if (unlikely(!S_ISREG(inode->i_mode)))
1962 add_flags = DCACHE_SPECIAL_TYPE;
1963
1964type_determined:
1965 if (unlikely(IS_AUTOMOUNT(inode)))
1966 add_flags |= DCACHE_NEED_AUTOMOUNT;
1967 return add_flags;
1968}
1969
1970static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1971{
1972 unsigned add_flags = d_flags_for_inode(inode);
1973 WARN_ON(d_in_lookup(dentry));
1974
1975 spin_lock(&dentry->d_lock);
1976 /*
1977 * Decrement negative dentry count if it was in the LRU list.
1978 */
1979 if (dentry->d_flags & DCACHE_LRU_LIST)
1980 this_cpu_dec(nr_dentry_negative);
1981 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
1982 raw_write_seqcount_begin(&dentry->d_seq);
1983 __d_set_inode_and_type(dentry, inode, add_flags);
1984 raw_write_seqcount_end(&dentry->d_seq);
1985 fsnotify_update_flags(dentry);
1986 spin_unlock(&dentry->d_lock);
1987}
1988
1989/**
1990 * d_instantiate - fill in inode information for a dentry
1991 * @entry: dentry to complete
1992 * @inode: inode to attach to this dentry
1993 *
1994 * Fill in inode information in the entry.
1995 *
1996 * This turns negative dentries into productive full members
1997 * of society.
1998 *
1999 * NOTE! This assumes that the inode count has been incremented
2000 * (or otherwise set) by the caller to indicate that it is now
2001 * in use by the dcache.
2002 */
2003
2004void d_instantiate(struct dentry *entry, struct inode * inode)
2005{
2006 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
2007 if (inode) {
2008 security_d_instantiate(entry, inode);
2009 spin_lock(&inode->i_lock);
2010 __d_instantiate(entry, inode);
2011 spin_unlock(&inode->i_lock);
2012 }
2013}
2014EXPORT_SYMBOL(d_instantiate);
2015
2016/*
2017 * This should be equivalent to d_instantiate() + unlock_new_inode(),
2018 * with lockdep-related part of unlock_new_inode() done before
2019 * anything else. Use that instead of open-coding d_instantiate()/
2020 * unlock_new_inode() combinations.
2021 */
2022void d_instantiate_new(struct dentry *entry, struct inode *inode)
2023{
2024 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
2025 BUG_ON(!inode);
2026 lockdep_annotate_inode_mutex_key(inode);
2027 security_d_instantiate(entry, inode);
2028 spin_lock(&inode->i_lock);
2029 __d_instantiate(entry, inode);
2030 WARN_ON(!(inode->i_state & I_NEW));
2031 inode->i_state &= ~I_NEW & ~I_CREATING;
2032 smp_mb();
2033 wake_up_bit(&inode->i_state, __I_NEW);
2034 spin_unlock(&inode->i_lock);
2035}
2036EXPORT_SYMBOL(d_instantiate_new);
2037
2038struct dentry *d_make_root(struct inode *root_inode)
2039{
2040 struct dentry *res = NULL;
2041
2042 if (root_inode) {
2043 res = d_alloc_anon(root_inode->i_sb);
2044 if (res)
2045 d_instantiate(res, root_inode);
2046 else
2047 iput(root_inode);
2048 }
2049 return res;
2050}
2051EXPORT_SYMBOL(d_make_root);
2052
2053static struct dentry *__d_instantiate_anon(struct dentry *dentry,
2054 struct inode *inode,
2055 bool disconnected)
2056{
2057 struct dentry *res;
2058 unsigned add_flags;
2059
2060 security_d_instantiate(dentry, inode);
2061 spin_lock(&inode->i_lock);
2062 res = __d_find_any_alias(inode);
2063 if (res) {
2064 spin_unlock(&inode->i_lock);
2065 dput(dentry);
2066 goto out_iput;
2067 }
2068
2069 /* attach a disconnected dentry */
2070 add_flags = d_flags_for_inode(inode);
2071
2072 if (disconnected)
2073 add_flags |= DCACHE_DISCONNECTED;
2074
2075 spin_lock(&dentry->d_lock);
2076 __d_set_inode_and_type(dentry, inode, add_flags);
2077 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2078 if (!disconnected) {
2079 hlist_bl_lock(&dentry->d_sb->s_roots);
2080 hlist_bl_add_head(&dentry->d_hash, &dentry->d_sb->s_roots);
2081 hlist_bl_unlock(&dentry->d_sb->s_roots);
2082 }
2083 spin_unlock(&dentry->d_lock);
2084 spin_unlock(&inode->i_lock);
2085
2086 return dentry;
2087
2088 out_iput:
2089 iput(inode);
2090 return res;
2091}
2092
2093struct dentry *d_instantiate_anon(struct dentry *dentry, struct inode *inode)
2094{
2095 return __d_instantiate_anon(dentry, inode, true);
2096}
2097EXPORT_SYMBOL(d_instantiate_anon);
2098
2099static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected)
2100{
2101 struct dentry *tmp;
2102 struct dentry *res;
2103
2104 if (!inode)
2105 return ERR_PTR(-ESTALE);
2106 if (IS_ERR(inode))
2107 return ERR_CAST(inode);
2108
2109 res = d_find_any_alias(inode);
2110 if (res)
2111 goto out_iput;
2112
2113 tmp = d_alloc_anon(inode->i_sb);
2114 if (!tmp) {
2115 res = ERR_PTR(-ENOMEM);
2116 goto out_iput;
2117 }
2118
2119 return __d_instantiate_anon(tmp, inode, disconnected);
2120
2121out_iput:
2122 iput(inode);
2123 return res;
2124}
2125
2126/**
2127 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
2128 * @inode: inode to allocate the dentry for
2129 *
2130 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
2131 * similar open by handle operations. The returned dentry may be anonymous,
2132 * or may have a full name (if the inode was already in the cache).
2133 *
2134 * When called on a directory inode, we must ensure that the inode only ever
2135 * has one dentry. If a dentry is found, that is returned instead of
2136 * allocating a new one.
2137 *
2138 * On successful return, the reference to the inode has been transferred
2139 * to the dentry. In case of an error the reference on the inode is released.
2140 * To make it easier to use in export operations a %NULL or IS_ERR inode may
2141 * be passed in and the error will be propagated to the return value,
2142 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
2143 */
2144struct dentry *d_obtain_alias(struct inode *inode)
2145{
2146 return __d_obtain_alias(inode, true);
2147}
2148EXPORT_SYMBOL(d_obtain_alias);
2149
2150/**
2151 * d_obtain_root - find or allocate a dentry for a given inode
2152 * @inode: inode to allocate the dentry for
2153 *
2154 * Obtain an IS_ROOT dentry for the root of a filesystem.
2155 *
2156 * We must ensure that directory inodes only ever have one dentry. If a
2157 * dentry is found, that is returned instead of allocating a new one.
2158 *
2159 * On successful return, the reference to the inode has been transferred
2160 * to the dentry. In case of an error the reference on the inode is
2161 * released. A %NULL or IS_ERR inode may be passed in and will be the
2162 * error will be propagate to the return value, with a %NULL @inode
2163 * replaced by ERR_PTR(-ESTALE).
2164 */
2165struct dentry *d_obtain_root(struct inode *inode)
2166{
2167 return __d_obtain_alias(inode, false);
2168}
2169EXPORT_SYMBOL(d_obtain_root);
2170
2171/**
2172 * d_add_ci - lookup or allocate new dentry with case-exact name
2173 * @inode: the inode case-insensitive lookup has found
2174 * @dentry: the negative dentry that was passed to the parent's lookup func
2175 * @name: the case-exact name to be associated with the returned dentry
2176 *
2177 * This is to avoid filling the dcache with case-insensitive names to the
2178 * same inode, only the actual correct case is stored in the dcache for
2179 * case-insensitive filesystems.
2180 *
2181 * For a case-insensitive lookup match and if the case-exact dentry
2182 * already exists in the dcache, use it and return it.
2183 *
2184 * If no entry exists with the exact case name, allocate new dentry with
2185 * the exact case, and return the spliced entry.
2186 */
2187struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
2188 struct qstr *name)
2189{
2190 struct dentry *found, *res;
2191
2192 /*
2193 * First check if a dentry matching the name already exists,
2194 * if not go ahead and create it now.
2195 */
2196 found = d_hash_and_lookup(dentry->d_parent, name);
2197 if (found) {
2198 iput(inode);
2199 return found;
2200 }
2201 if (d_in_lookup(dentry)) {
2202 found = d_alloc_parallel(dentry->d_parent, name,
2203 dentry->d_wait);
2204 if (IS_ERR(found) || !d_in_lookup(found)) {
2205 iput(inode);
2206 return found;
2207 }
2208 } else {
2209 found = d_alloc(dentry->d_parent, name);
2210 if (!found) {
2211 iput(inode);
2212 return ERR_PTR(-ENOMEM);
2213 }
2214 }
2215 res = d_splice_alias(inode, found);
2216 if (res) {
2217 dput(found);
2218 return res;
2219 }
2220 return found;
2221}
2222EXPORT_SYMBOL(d_add_ci);
2223
2224
2225static inline bool d_same_name(const struct dentry *dentry,
2226 const struct dentry *parent,
2227 const struct qstr *name)
2228{
2229 if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
2230 if (dentry->d_name.len != name->len)
2231 return false;
2232 return dentry_cmp(dentry, name->name, name->len) == 0;
2233 }
2234 return parent->d_op->d_compare(dentry,
2235 dentry->d_name.len, dentry->d_name.name,
2236 name) == 0;
2237}
2238
2239/**
2240 * __d_lookup_rcu - search for a dentry (racy, store-free)
2241 * @parent: parent dentry
2242 * @name: qstr of name we wish to find
2243 * @seqp: returns d_seq value at the point where the dentry was found
2244 * Returns: dentry, or NULL
2245 *
2246 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2247 * resolution (store-free path walking) design described in
2248 * Documentation/filesystems/path-lookup.txt.
2249 *
2250 * This is not to be used outside core vfs.
2251 *
2252 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2253 * held, and rcu_read_lock held. The returned dentry must not be stored into
2254 * without taking d_lock and checking d_seq sequence count against @seq
2255 * returned here.
2256 *
2257 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2258 * function.
2259 *
2260 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2261 * the returned dentry, so long as its parent's seqlock is checked after the
2262 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2263 * is formed, giving integrity down the path walk.
2264 *
2265 * NOTE! The caller *has* to check the resulting dentry against the sequence
2266 * number we've returned before using any of the resulting dentry state!
2267 */
2268struct dentry *__d_lookup_rcu(const struct dentry *parent,
2269 const struct qstr *name,
2270 unsigned *seqp)
2271{
2272 u64 hashlen = name->hash_len;
2273 const unsigned char *str = name->name;
2274 struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
2275 struct hlist_bl_node *node;
2276 struct dentry *dentry;
2277
2278 /*
2279 * Note: There is significant duplication with __d_lookup_rcu which is
2280 * required to prevent single threaded performance regressions
2281 * especially on architectures where smp_rmb (in seqcounts) are costly.
2282 * Keep the two functions in sync.
2283 */
2284
2285 /*
2286 * The hash list is protected using RCU.
2287 *
2288 * Carefully use d_seq when comparing a candidate dentry, to avoid
2289 * races with d_move().
2290 *
2291 * It is possible that concurrent renames can mess up our list
2292 * walk here and result in missing our dentry, resulting in the
2293 * false-negative result. d_lookup() protects against concurrent
2294 * renames using rename_lock seqlock.
2295 *
2296 * See Documentation/filesystems/path-lookup.txt for more details.
2297 */
2298 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2299 unsigned seq;
2300
2301seqretry:
2302 /*
2303 * The dentry sequence count protects us from concurrent
2304 * renames, and thus protects parent and name fields.
2305 *
2306 * The caller must perform a seqcount check in order
2307 * to do anything useful with the returned dentry.
2308 *
2309 * NOTE! We do a "raw" seqcount_begin here. That means that
2310 * we don't wait for the sequence count to stabilize if it
2311 * is in the middle of a sequence change. If we do the slow
2312 * dentry compare, we will do seqretries until it is stable,
2313 * and if we end up with a successful lookup, we actually
2314 * want to exit RCU lookup anyway.
2315 *
2316 * Note that raw_seqcount_begin still *does* smp_rmb(), so
2317 * we are still guaranteed NUL-termination of ->d_name.name.
2318 */
2319 seq = raw_seqcount_begin(&dentry->d_seq);
2320 if (dentry->d_parent != parent)
2321 continue;
2322 if (d_unhashed(dentry))
2323 continue;
2324
2325 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
2326 int tlen;
2327 const char *tname;
2328 if (dentry->d_name.hash != hashlen_hash(hashlen))
2329 continue;
2330 tlen = dentry->d_name.len;
2331 tname = dentry->d_name.name;
2332 /* we want a consistent (name,len) pair */
2333 if (read_seqcount_retry(&dentry->d_seq, seq)) {
2334 cpu_relax();
2335 goto seqretry;
2336 }
2337 if (parent->d_op->d_compare(dentry,
2338 tlen, tname, name) != 0)
2339 continue;
2340 } else {
2341 if (dentry->d_name.hash_len != hashlen)
2342 continue;
2343 if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
2344 continue;
2345 }
2346 *seqp = seq;
2347 return dentry;
2348 }
2349 return NULL;
2350}
2351
2352/**
2353 * d_lookup - search for a dentry
2354 * @parent: parent dentry
2355 * @name: qstr of name we wish to find
2356 * Returns: dentry, or NULL
2357 *
2358 * d_lookup searches the children of the parent dentry for the name in
2359 * question. If the dentry is found its reference count is incremented and the
2360 * dentry is returned. The caller must use dput to free the entry when it has
2361 * finished using it. %NULL is returned if the dentry does not exist.
2362 */
2363struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
2364{
2365 struct dentry *dentry;
2366 unsigned seq;
2367
2368 do {
2369 seq = read_seqbegin(&rename_lock);
2370 dentry = __d_lookup(parent, name);
2371 if (dentry)
2372 break;
2373 } while (read_seqretry(&rename_lock, seq));
2374 return dentry;
2375}
2376EXPORT_SYMBOL(d_lookup);
2377
2378/**
2379 * __d_lookup - search for a dentry (racy)
2380 * @parent: parent dentry
2381 * @name: qstr of name we wish to find
2382 * Returns: dentry, or NULL
2383 *
2384 * __d_lookup is like d_lookup, however it may (rarely) return a
2385 * false-negative result due to unrelated rename activity.
2386 *
2387 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2388 * however it must be used carefully, eg. with a following d_lookup in
2389 * the case of failure.
2390 *
2391 * __d_lookup callers must be commented.
2392 */
2393struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
2394{
2395 unsigned int hash = name->hash;
2396 struct hlist_bl_head *b = d_hash(hash);
2397 struct hlist_bl_node *node;
2398 struct dentry *found = NULL;
2399 struct dentry *dentry;
2400
2401 /*
2402 * Note: There is significant duplication with __d_lookup_rcu which is
2403 * required to prevent single threaded performance regressions
2404 * especially on architectures where smp_rmb (in seqcounts) are costly.
2405 * Keep the two functions in sync.
2406 */
2407
2408 /*
2409 * The hash list is protected using RCU.
2410 *
2411 * Take d_lock when comparing a candidate dentry, to avoid races
2412 * with d_move().
2413 *
2414 * It is possible that concurrent renames can mess up our list
2415 * walk here and result in missing our dentry, resulting in the
2416 * false-negative result. d_lookup() protects against concurrent
2417 * renames using rename_lock seqlock.
2418 *
2419 * See Documentation/filesystems/path-lookup.txt for more details.
2420 */
2421 rcu_read_lock();
2422
2423 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2424
2425 if (dentry->d_name.hash != hash)
2426 continue;
2427
2428 spin_lock(&dentry->d_lock);
2429 if (dentry->d_parent != parent)
2430 goto next;
2431 if (d_unhashed(dentry))
2432 goto next;
2433
2434 if (!d_same_name(dentry, parent, name))
2435 goto next;
2436
2437 dentry->d_lockref.count++;
2438 found = dentry;
2439 spin_unlock(&dentry->d_lock);
2440 break;
2441next:
2442 spin_unlock(&dentry->d_lock);
2443 }
2444 rcu_read_unlock();
2445
2446 return found;
2447}
2448
2449/**
2450 * d_hash_and_lookup - hash the qstr then search for a dentry
2451 * @dir: Directory to search in
2452 * @name: qstr of name we wish to find
2453 *
2454 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2455 */
2456struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2457{
2458 /*
2459 * Check for a fs-specific hash function. Note that we must
2460 * calculate the standard hash first, as the d_op->d_hash()
2461 * routine may choose to leave the hash value unchanged.
2462 */
2463 name->hash = full_name_hash(dir, name->name, name->len);
2464 if (dir->d_flags & DCACHE_OP_HASH) {
2465 int err = dir->d_op->d_hash(dir, name);
2466 if (unlikely(err < 0))
2467 return ERR_PTR(err);
2468 }
2469 return d_lookup(dir, name);
2470}
2471EXPORT_SYMBOL(d_hash_and_lookup);
2472
2473/*
2474 * When a file is deleted, we have two options:
2475 * - turn this dentry into a negative dentry
2476 * - unhash this dentry and free it.
2477 *
2478 * Usually, we want to just turn this into
2479 * a negative dentry, but if anybody else is
2480 * currently using the dentry or the inode
2481 * we can't do that and we fall back on removing
2482 * it from the hash queues and waiting for
2483 * it to be deleted later when it has no users
2484 */
2485
2486/**
2487 * d_delete - delete a dentry
2488 * @dentry: The dentry to delete
2489 *
2490 * Turn the dentry into a negative dentry if possible, otherwise
2491 * remove it from the hash queues so it can be deleted later
2492 */
2493
2494void d_delete(struct dentry * dentry)
2495{
2496 struct inode *inode = dentry->d_inode;
2497
2498 spin_lock(&inode->i_lock);
2499 spin_lock(&dentry->d_lock);
2500 /*
2501 * Are we the only user?
2502 */
2503 if (dentry->d_lockref.count == 1) {
2504 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2505 dentry_unlink_inode(dentry);
2506 } else {
2507 __d_drop(dentry);
2508 spin_unlock(&dentry->d_lock);
2509 spin_unlock(&inode->i_lock);
2510 }
2511}
2512EXPORT_SYMBOL(d_delete);
2513
2514static void __d_rehash(struct dentry *entry)
2515{
2516 struct hlist_bl_head *b = d_hash(entry->d_name.hash);
2517
2518 hlist_bl_lock(b);
2519 hlist_bl_add_head_rcu(&entry->d_hash, b);
2520 hlist_bl_unlock(b);
2521}
2522
2523/**
2524 * d_rehash - add an entry back to the hash
2525 * @entry: dentry to add to the hash
2526 *
2527 * Adds a dentry to the hash according to its name.
2528 */
2529
2530void d_rehash(struct dentry * entry)
2531{
2532 spin_lock(&entry->d_lock);
2533 __d_rehash(entry);
2534 spin_unlock(&entry->d_lock);
2535}
2536EXPORT_SYMBOL(d_rehash);
2537
2538static inline unsigned start_dir_add(struct inode *dir)
2539{
2540
2541 for (;;) {
2542 unsigned n = dir->i_dir_seq;
2543 if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
2544 return n;
2545 cpu_relax();
2546 }
2547}
2548
2549static inline void end_dir_add(struct inode *dir, unsigned n)
2550{
2551 smp_store_release(&dir->i_dir_seq, n + 2);
2552}
2553
2554static void d_wait_lookup(struct dentry *dentry)
2555{
2556 if (d_in_lookup(dentry)) {
2557 DECLARE_WAITQUEUE(wait, current);
2558 add_wait_queue(dentry->d_wait, &wait);
2559 do {
2560 set_current_state(TASK_UNINTERRUPTIBLE);
2561 spin_unlock(&dentry->d_lock);
2562 schedule();
2563 spin_lock(&dentry->d_lock);
2564 } while (d_in_lookup(dentry));
2565 }
2566}
2567
2568struct dentry *d_alloc_parallel(struct dentry *parent,
2569 const struct qstr *name,
2570 wait_queue_head_t *wq)
2571{
2572 unsigned int hash = name->hash;
2573 struct hlist_bl_head *b = in_lookup_hash(parent, hash);
2574 struct hlist_bl_node *node;
2575 struct dentry *new = d_alloc(parent, name);
2576 struct dentry *dentry;
2577 unsigned seq, r_seq, d_seq;
2578
2579 if (unlikely(!new))
2580 return ERR_PTR(-ENOMEM);
2581
2582retry:
2583 rcu_read_lock();
2584 seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
2585 r_seq = read_seqbegin(&rename_lock);
2586 dentry = __d_lookup_rcu(parent, name, &d_seq);
2587 if (unlikely(dentry)) {
2588 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2589 rcu_read_unlock();
2590 goto retry;
2591 }
2592 if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
2593 rcu_read_unlock();
2594 dput(dentry);
2595 goto retry;
2596 }
2597 rcu_read_unlock();
2598 dput(new);
2599 return dentry;
2600 }
2601 if (unlikely(read_seqretry(&rename_lock, r_seq))) {
2602 rcu_read_unlock();
2603 goto retry;
2604 }
2605
2606 if (unlikely(seq & 1)) {
2607 rcu_read_unlock();
2608 goto retry;
2609 }
2610
2611 hlist_bl_lock(b);
2612 if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
2613 hlist_bl_unlock(b);
2614 rcu_read_unlock();
2615 goto retry;
2616 }
2617 /*
2618 * No changes for the parent since the beginning of d_lookup().
2619 * Since all removals from the chain happen with hlist_bl_lock(),
2620 * any potential in-lookup matches are going to stay here until
2621 * we unlock the chain. All fields are stable in everything
2622 * we encounter.
2623 */
2624 hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
2625 if (dentry->d_name.hash != hash)
2626 continue;
2627 if (dentry->d_parent != parent)
2628 continue;
2629 if (!d_same_name(dentry, parent, name))
2630 continue;
2631 hlist_bl_unlock(b);
2632 /* now we can try to grab a reference */
2633 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2634 rcu_read_unlock();
2635 goto retry;
2636 }
2637
2638 rcu_read_unlock();
2639 /*
2640 * somebody is likely to be still doing lookup for it;
2641 * wait for them to finish
2642 */
2643 spin_lock(&dentry->d_lock);
2644 d_wait_lookup(dentry);
2645 /*
2646 * it's not in-lookup anymore; in principle we should repeat
2647 * everything from dcache lookup, but it's likely to be what
2648 * d_lookup() would've found anyway. If it is, just return it;
2649 * otherwise we really have to repeat the whole thing.
2650 */
2651 if (unlikely(dentry->d_name.hash != hash))
2652 goto mismatch;
2653 if (unlikely(dentry->d_parent != parent))
2654 goto mismatch;
2655 if (unlikely(d_unhashed(dentry)))
2656 goto mismatch;
2657 if (unlikely(!d_same_name(dentry, parent, name)))
2658 goto mismatch;
2659 /* OK, it *is* a hashed match; return it */
2660 spin_unlock(&dentry->d_lock);
2661 dput(new);
2662 return dentry;
2663 }
2664 rcu_read_unlock();
2665 /* we can't take ->d_lock here; it's OK, though. */
2666 new->d_flags |= DCACHE_PAR_LOOKUP;
2667 new->d_wait = wq;
2668 hlist_bl_add_head_rcu(&new->d_u.d_in_lookup_hash, b);
2669 hlist_bl_unlock(b);
2670 return new;
2671mismatch:
2672 spin_unlock(&dentry->d_lock);
2673 dput(dentry);
2674 goto retry;
2675}
2676EXPORT_SYMBOL(d_alloc_parallel);
2677
2678void __d_lookup_done(struct dentry *dentry)
2679{
2680 struct hlist_bl_head *b = in_lookup_hash(dentry->d_parent,
2681 dentry->d_name.hash);
2682 hlist_bl_lock(b);
2683 dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
2684 __hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
2685 wake_up_all(dentry->d_wait);
2686 dentry->d_wait = NULL;
2687 hlist_bl_unlock(b);
2688 INIT_HLIST_NODE(&dentry->d_u.d_alias);
2689 INIT_LIST_HEAD(&dentry->d_lru);
2690}
2691EXPORT_SYMBOL(__d_lookup_done);
2692
2693/* inode->i_lock held if inode is non-NULL */
2694
2695static inline void __d_add(struct dentry *dentry, struct inode *inode)
2696{
2697 struct inode *dir = NULL;
2698 unsigned n;
2699 spin_lock(&dentry->d_lock);
2700 if (unlikely(d_in_lookup(dentry))) {
2701 dir = dentry->d_parent->d_inode;
2702 n = start_dir_add(dir);
2703 __d_lookup_done(dentry);
2704 }
2705 if (inode) {
2706 unsigned add_flags = d_flags_for_inode(inode);
2707 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2708 raw_write_seqcount_begin(&dentry->d_seq);
2709 __d_set_inode_and_type(dentry, inode, add_flags);
2710 raw_write_seqcount_end(&dentry->d_seq);
2711 fsnotify_update_flags(dentry);
2712 }
2713 __d_rehash(dentry);
2714 if (dir)
2715 end_dir_add(dir, n);
2716 spin_unlock(&dentry->d_lock);
2717 if (inode)
2718 spin_unlock(&inode->i_lock);
2719}
2720
2721/**
2722 * d_add - add dentry to hash queues
2723 * @entry: dentry to add
2724 * @inode: The inode to attach to this dentry
2725 *
2726 * This adds the entry to the hash queues and initializes @inode.
2727 * The entry was actually filled in earlier during d_alloc().
2728 */
2729
2730void d_add(struct dentry *entry, struct inode *inode)
2731{
2732 if (inode) {
2733 security_d_instantiate(entry, inode);
2734 spin_lock(&inode->i_lock);
2735 }
2736 __d_add(entry, inode);
2737}
2738EXPORT_SYMBOL(d_add);
2739
2740/**
2741 * d_exact_alias - find and hash an exact unhashed alias
2742 * @entry: dentry to add
2743 * @inode: The inode to go with this dentry
2744 *
2745 * If an unhashed dentry with the same name/parent and desired
2746 * inode already exists, hash and return it. Otherwise, return
2747 * NULL.
2748 *
2749 * Parent directory should be locked.
2750 */
2751struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
2752{
2753 struct dentry *alias;
2754 unsigned int hash = entry->d_name.hash;
2755
2756 spin_lock(&inode->i_lock);
2757 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
2758 /*
2759 * Don't need alias->d_lock here, because aliases with
2760 * d_parent == entry->d_parent are not subject to name or
2761 * parent changes, because the parent inode i_mutex is held.
2762 */
2763 if (alias->d_name.hash != hash)
2764 continue;
2765 if (alias->d_parent != entry->d_parent)
2766 continue;
2767 if (!d_same_name(alias, entry->d_parent, &entry->d_name))
2768 continue;
2769 spin_lock(&alias->d_lock);
2770 if (!d_unhashed(alias)) {
2771 spin_unlock(&alias->d_lock);
2772 alias = NULL;
2773 } else {
2774 __dget_dlock(alias);
2775 __d_rehash(alias);
2776 spin_unlock(&alias->d_lock);
2777 }
2778 spin_unlock(&inode->i_lock);
2779 return alias;
2780 }
2781 spin_unlock(&inode->i_lock);
2782 return NULL;
2783}
2784EXPORT_SYMBOL(d_exact_alias);
2785
2786static void swap_names(struct dentry *dentry, struct dentry *target)
2787{
2788 if (unlikely(dname_external(target))) {
2789 if (unlikely(dname_external(dentry))) {
2790 /*
2791 * Both external: swap the pointers
2792 */
2793 swap(target->d_name.name, dentry->d_name.name);
2794 } else {
2795 /*
2796 * dentry:internal, target:external. Steal target's
2797 * storage and make target internal.
2798 */
2799 memcpy(target->d_iname, dentry->d_name.name,
2800 dentry->d_name.len + 1);
2801 dentry->d_name.name = target->d_name.name;
2802 target->d_name.name = target->d_iname;
2803 }
2804 } else {
2805 if (unlikely(dname_external(dentry))) {
2806 /*
2807 * dentry:external, target:internal. Give dentry's
2808 * storage to target and make dentry internal
2809 */
2810 memcpy(dentry->d_iname, target->d_name.name,
2811 target->d_name.len + 1);
2812 target->d_name.name = dentry->d_name.name;
2813 dentry->d_name.name = dentry->d_iname;
2814 } else {
2815 /*
2816 * Both are internal.
2817 */
2818 unsigned int i;
2819 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
2820 for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
2821 swap(((long *) &dentry->d_iname)[i],
2822 ((long *) &target->d_iname)[i]);
2823 }
2824 }
2825 }
2826 swap(dentry->d_name.hash_len, target->d_name.hash_len);
2827}
2828
2829static void copy_name(struct dentry *dentry, struct dentry *target)
2830{
2831 struct external_name *old_name = NULL;
2832 if (unlikely(dname_external(dentry)))
2833 old_name = external_name(dentry);
2834 if (unlikely(dname_external(target))) {
2835 atomic_inc(&external_name(target)->u.count);
2836 dentry->d_name = target->d_name;
2837 } else {
2838 memcpy(dentry->d_iname, target->d_name.name,
2839 target->d_name.len + 1);
2840 dentry->d_name.name = dentry->d_iname;
2841 dentry->d_name.hash_len = target->d_name.hash_len;
2842 }
2843 if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
2844 kfree_rcu(old_name, u.head);
2845}
2846
2847/*
2848 * __d_move - move a dentry
2849 * @dentry: entry to move
2850 * @target: new dentry
2851 * @exchange: exchange the two dentries
2852 *
2853 * Update the dcache to reflect the move of a file name. Negative
2854 * dcache entries should not be moved in this way. Caller must hold
2855 * rename_lock, the i_mutex of the source and target directories,
2856 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2857 */
2858static void __d_move(struct dentry *dentry, struct dentry *target,
2859 bool exchange)
2860{
2861 struct dentry *old_parent, *p;
2862 struct inode *dir = NULL;
2863 unsigned n;
2864
2865 WARN_ON(!dentry->d_inode);
2866 if (WARN_ON(dentry == target))
2867 return;
2868
2869 BUG_ON(d_ancestor(target, dentry));
2870 old_parent = dentry->d_parent;
2871 p = d_ancestor(old_parent, target);
2872 if (IS_ROOT(dentry)) {
2873 BUG_ON(p);
2874 spin_lock(&target->d_parent->d_lock);
2875 } else if (!p) {
2876 /* target is not a descendent of dentry->d_parent */
2877 spin_lock(&target->d_parent->d_lock);
2878 spin_lock_nested(&old_parent->d_lock, DENTRY_D_LOCK_NESTED);
2879 } else {
2880 BUG_ON(p == dentry);
2881 spin_lock(&old_parent->d_lock);
2882 if (p != target)
2883 spin_lock_nested(&target->d_parent->d_lock,
2884 DENTRY_D_LOCK_NESTED);
2885 }
2886 spin_lock_nested(&dentry->d_lock, 2);
2887 spin_lock_nested(&target->d_lock, 3);
2888
2889 if (unlikely(d_in_lookup(target))) {
2890 dir = target->d_parent->d_inode;
2891 n = start_dir_add(dir);
2892 __d_lookup_done(target);
2893 }
2894
2895 write_seqcount_begin(&dentry->d_seq);
2896 write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
2897
2898 /* unhash both */
2899 if (!d_unhashed(dentry))
2900 ___d_drop(dentry);
2901 if (!d_unhashed(target))
2902 ___d_drop(target);
2903
2904 /* ... and switch them in the tree */
2905 dentry->d_parent = target->d_parent;
2906 if (!exchange) {
2907 copy_name(dentry, target);
2908 target->d_hash.pprev = NULL;
2909 dentry->d_parent->d_lockref.count++;
2910 if (dentry != old_parent) /* wasn't IS_ROOT */
2911 WARN_ON(!--old_parent->d_lockref.count);
2912 } else {
2913 target->d_parent = old_parent;
2914 swap_names(dentry, target);
2915 list_move(&target->d_child, &target->d_parent->d_subdirs);
2916 __d_rehash(target);
2917 fsnotify_update_flags(target);
2918 }
2919 list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
2920 __d_rehash(dentry);
2921 fsnotify_update_flags(dentry);
2922 fscrypt_handle_d_move(dentry);
2923
2924 write_seqcount_end(&target->d_seq);
2925 write_seqcount_end(&dentry->d_seq);
2926
2927 if (dir)
2928 end_dir_add(dir, n);
2929
2930 if (dentry->d_parent != old_parent)
2931 spin_unlock(&dentry->d_parent->d_lock);
2932 if (dentry != old_parent)
2933 spin_unlock(&old_parent->d_lock);
2934 spin_unlock(&target->d_lock);
2935 spin_unlock(&dentry->d_lock);
2936}
2937
2938/*
2939 * d_move - move a dentry
2940 * @dentry: entry to move
2941 * @target: new dentry
2942 *
2943 * Update the dcache to reflect the move of a file name. Negative
2944 * dcache entries should not be moved in this way. See the locking
2945 * requirements for __d_move.
2946 */
2947void d_move(struct dentry *dentry, struct dentry *target)
2948{
2949 write_seqlock(&rename_lock);
2950 __d_move(dentry, target, false);
2951 write_sequnlock(&rename_lock);
2952}
2953EXPORT_SYMBOL(d_move);
2954
2955/*
2956 * d_exchange - exchange two dentries
2957 * @dentry1: first dentry
2958 * @dentry2: second dentry
2959 */
2960void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
2961{
2962 write_seqlock(&rename_lock);
2963
2964 WARN_ON(!dentry1->d_inode);
2965 WARN_ON(!dentry2->d_inode);
2966 WARN_ON(IS_ROOT(dentry1));
2967 WARN_ON(IS_ROOT(dentry2));
2968
2969 __d_move(dentry1, dentry2, true);
2970
2971 write_sequnlock(&rename_lock);
2972}
2973
2974/**
2975 * d_ancestor - search for an ancestor
2976 * @p1: ancestor dentry
2977 * @p2: child dentry
2978 *
2979 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2980 * an ancestor of p2, else NULL.
2981 */
2982struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2983{
2984 struct dentry *p;
2985
2986 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2987 if (p->d_parent == p1)
2988 return p;
2989 }
2990 return NULL;
2991}
2992
2993/*
2994 * This helper attempts to cope with remotely renamed directories
2995 *
2996 * It assumes that the caller is already holding
2997 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2998 *
2999 * Note: If ever the locking in lock_rename() changes, then please
3000 * remember to update this too...
3001 */
3002static int __d_unalias(struct inode *inode,
3003 struct dentry *dentry, struct dentry *alias)
3004{
3005 struct mutex *m1 = NULL;
3006 struct rw_semaphore *m2 = NULL;
3007 int ret = -ESTALE;
3008
3009 /* If alias and dentry share a parent, then no extra locks required */
3010 if (alias->d_parent == dentry->d_parent)
3011 goto out_unalias;
3012
3013 /* See lock_rename() */
3014 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
3015 goto out_err;
3016 m1 = &dentry->d_sb->s_vfs_rename_mutex;
3017 if (!inode_trylock_shared(alias->d_parent->d_inode))
3018 goto out_err;
3019 m2 = &alias->d_parent->d_inode->i_rwsem;
3020out_unalias:
3021 __d_move(alias, dentry, false);
3022 ret = 0;
3023out_err:
3024 if (m2)
3025 up_read(m2);
3026 if (m1)
3027 mutex_unlock(m1);
3028 return ret;
3029}
3030
3031/**
3032 * d_splice_alias - splice a disconnected dentry into the tree if one exists
3033 * @inode: the inode which may have a disconnected dentry
3034 * @dentry: a negative dentry which we want to point to the inode.
3035 *
3036 * If inode is a directory and has an IS_ROOT alias, then d_move that in
3037 * place of the given dentry and return it, else simply d_add the inode
3038 * to the dentry and return NULL.
3039 *
3040 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
3041 * we should error out: directories can't have multiple aliases.
3042 *
3043 * This is needed in the lookup routine of any filesystem that is exportable
3044 * (via knfsd) so that we can build dcache paths to directories effectively.
3045 *
3046 * If a dentry was found and moved, then it is returned. Otherwise NULL
3047 * is returned. This matches the expected return value of ->lookup.
3048 *
3049 * Cluster filesystems may call this function with a negative, hashed dentry.
3050 * In that case, we know that the inode will be a regular file, and also this
3051 * will only occur during atomic_open. So we need to check for the dentry
3052 * being already hashed only in the final case.
3053 */
3054struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
3055{
3056 if (IS_ERR(inode))
3057 return ERR_CAST(inode);
3058
3059 BUG_ON(!d_unhashed(dentry));
3060
3061 if (!inode)
3062 goto out;
3063
3064 security_d_instantiate(dentry, inode);
3065 spin_lock(&inode->i_lock);
3066 if (S_ISDIR(inode->i_mode)) {
3067 struct dentry *new = __d_find_any_alias(inode);
3068 if (unlikely(new)) {
3069 /* The reference to new ensures it remains an alias */
3070 spin_unlock(&inode->i_lock);
3071 write_seqlock(&rename_lock);
3072 if (unlikely(d_ancestor(new, dentry))) {
3073 write_sequnlock(&rename_lock);
3074 dput(new);
3075 new = ERR_PTR(-ELOOP);
3076 pr_warn_ratelimited(
3077 "VFS: Lookup of '%s' in %s %s"
3078 " would have caused loop\n",
3079 dentry->d_name.name,
3080 inode->i_sb->s_type->name,
3081 inode->i_sb->s_id);
3082 } else if (!IS_ROOT(new)) {
3083 struct dentry *old_parent = dget(new->d_parent);
3084 int err = __d_unalias(inode, dentry, new);
3085 write_sequnlock(&rename_lock);
3086 if (err) {
3087 dput(new);
3088 new = ERR_PTR(err);
3089 }
3090 dput(old_parent);
3091 } else {
3092 __d_move(new, dentry, false);
3093 write_sequnlock(&rename_lock);
3094 }
3095 iput(inode);
3096 return new;
3097 }
3098 }
3099out:
3100 __d_add(dentry, inode);
3101 return NULL;
3102}
3103EXPORT_SYMBOL(d_splice_alias);
3104
3105/*
3106 * Test whether new_dentry is a subdirectory of old_dentry.
3107 *
3108 * Trivially implemented using the dcache structure
3109 */
3110
3111/**
3112 * is_subdir - is new dentry a subdirectory of old_dentry
3113 * @new_dentry: new dentry
3114 * @old_dentry: old dentry
3115 *
3116 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3117 * Returns false otherwise.
3118 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3119 */
3120
3121bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
3122{
3123 bool result;
3124 unsigned seq;
3125
3126 if (new_dentry == old_dentry)
3127 return true;
3128
3129 do {
3130 /* for restarting inner loop in case of seq retry */
3131 seq = read_seqbegin(&rename_lock);
3132 /*
3133 * Need rcu_readlock to protect against the d_parent trashing
3134 * due to d_move
3135 */
3136 rcu_read_lock();
3137 if (d_ancestor(old_dentry, new_dentry))
3138 result = true;
3139 else
3140 result = false;
3141 rcu_read_unlock();
3142 } while (read_seqretry(&rename_lock, seq));
3143
3144 return result;
3145}
3146EXPORT_SYMBOL(is_subdir);
3147
3148static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
3149{
3150 struct dentry *root = data;
3151 if (dentry != root) {
3152 if (d_unhashed(dentry) || !dentry->d_inode)
3153 return D_WALK_SKIP;
3154
3155 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
3156 dentry->d_flags |= DCACHE_GENOCIDE;
3157 dentry->d_lockref.count--;
3158 }
3159 }
3160 return D_WALK_CONTINUE;
3161}
3162
3163void d_genocide(struct dentry *parent)
3164{
3165 d_walk(parent, parent, d_genocide_kill);
3166}
3167
3168EXPORT_SYMBOL(d_genocide);
3169
3170void d_tmpfile(struct dentry *dentry, struct inode *inode)
3171{
3172 inode_dec_link_count(inode);
3173 BUG_ON(dentry->d_name.name != dentry->d_iname ||
3174 !hlist_unhashed(&dentry->d_u.d_alias) ||
3175 !d_unlinked(dentry));
3176 spin_lock(&dentry->d_parent->d_lock);
3177 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
3178 dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
3179 (unsigned long long)inode->i_ino);
3180 spin_unlock(&dentry->d_lock);
3181 spin_unlock(&dentry->d_parent->d_lock);
3182 d_instantiate(dentry, inode);
3183}
3184EXPORT_SYMBOL(d_tmpfile);
3185
3186static __initdata unsigned long dhash_entries;
3187static int __init set_dhash_entries(char *str)
3188{
3189 if (!str)
3190 return 0;
3191 dhash_entries = simple_strtoul(str, &str, 0);
3192 return 1;
3193}
3194__setup("dhash_entries=", set_dhash_entries);
3195
3196static void __init dcache_init_early(void)
3197{
3198 /* If hashes are distributed across NUMA nodes, defer
3199 * hash allocation until vmalloc space is available.
3200 */
3201 if (hashdist)
3202 return;
3203
3204 dentry_hashtable =
3205 alloc_large_system_hash("Dentry cache",
3206 sizeof(struct hlist_bl_head),
3207 dhash_entries,
3208 13,
3209 HASH_EARLY | HASH_ZERO,
3210 &d_hash_shift,
3211 NULL,
3212 0,
3213 0);
3214 d_hash_shift = 32 - d_hash_shift;
3215}
3216
3217static void __init dcache_init(void)
3218{
3219 /*
3220 * A constructor could be added for stable state like the lists,
3221 * but it is probably not worth it because of the cache nature
3222 * of the dcache.
3223 */
3224 dentry_cache = KMEM_CACHE_USERCOPY(dentry,
3225 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT,
3226 d_iname);
3227
3228 /* Hash may have been set up in dcache_init_early */
3229 if (!hashdist)
3230 return;
3231
3232 dentry_hashtable =
3233 alloc_large_system_hash("Dentry cache",
3234 sizeof(struct hlist_bl_head),
3235 dhash_entries,
3236 13,
3237 HASH_ZERO,
3238 &d_hash_shift,
3239 NULL,
3240 0,
3241 0);
3242 d_hash_shift = 32 - d_hash_shift;
3243}
3244
3245/* SLAB cache for __getname() consumers */
3246struct kmem_cache *names_cachep __read_mostly;
3247EXPORT_SYMBOL(names_cachep);
3248
3249void __init vfs_caches_init_early(void)
3250{
3251 int i;
3252
3253 for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++)
3254 INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]);
3255
3256 dcache_init_early();
3257 inode_init_early();
3258}
3259
3260void __init vfs_caches_init(void)
3261{
3262 names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0,
3263 SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL);
3264
3265 dcache_init();
3266 inode_init();
3267 files_init();
3268 files_maxfiles_init();
3269 mnt_init();
3270 bdev_cache_init();
3271 chrdev_init();
3272}