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