Loading...
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * fs/dcache.c
4 *
5 * Complete reimplementation
6 * (C) 1997 Thomas Schoebel-Theuer,
7 * with heavy changes by Linus Torvalds
8 */
9
10/*
11 * Notes on the allocation strategy:
12 *
13 * The dcache is a master of the icache - whenever a dcache entry
14 * exists, the inode will always exist. "iput()" is done either when
15 * the dcache entry is deleted or garbage collected.
16 */
17
18#include <linux/ratelimit.h>
19#include <linux/string.h>
20#include <linux/mm.h>
21#include <linux/fs.h>
22#include <linux/fscrypt.h>
23#include <linux/fsnotify.h>
24#include <linux/slab.h>
25#include <linux/init.h>
26#include <linux/hash.h>
27#include <linux/cache.h>
28#include <linux/export.h>
29#include <linux/security.h>
30#include <linux/seqlock.h>
31#include <linux/memblock.h>
32#include <linux/bit_spinlock.h>
33#include <linux/rculist_bl.h>
34#include <linux/list_lru.h>
35#include "internal.h"
36#include "mount.h"
37
38#include <asm/runtime-const.h>
39
40/*
41 * Usage:
42 * dcache->d_inode->i_lock protects:
43 * - i_dentry, d_u.d_alias, d_inode of aliases
44 * dcache_hash_bucket lock protects:
45 * - the dcache hash table
46 * s_roots bl list spinlock protects:
47 * - the s_roots list (see __d_drop)
48 * dentry->d_sb->s_dentry_lru_lock protects:
49 * - the dcache lru lists and counters
50 * d_lock protects:
51 * - d_flags
52 * - d_name
53 * - d_lru
54 * - d_count
55 * - d_unhashed()
56 * - d_parent and d_chilren
57 * - childrens' d_sib and d_parent
58 * - d_u.d_alias, d_inode
59 *
60 * Ordering:
61 * dentry->d_inode->i_lock
62 * dentry->d_lock
63 * dentry->d_sb->s_dentry_lru_lock
64 * dcache_hash_bucket lock
65 * s_roots lock
66 *
67 * If there is an ancestor relationship:
68 * dentry->d_parent->...->d_parent->d_lock
69 * ...
70 * dentry->d_parent->d_lock
71 * dentry->d_lock
72 *
73 * If no ancestor relationship:
74 * arbitrary, since it's serialized on rename_lock
75 */
76int sysctl_vfs_cache_pressure __read_mostly = 100;
77EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
78
79__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
80
81EXPORT_SYMBOL(rename_lock);
82
83static struct kmem_cache *dentry_cache __ro_after_init;
84
85const struct qstr empty_name = QSTR_INIT("", 0);
86EXPORT_SYMBOL(empty_name);
87const struct qstr slash_name = QSTR_INIT("/", 1);
88EXPORT_SYMBOL(slash_name);
89const struct qstr dotdot_name = QSTR_INIT("..", 2);
90EXPORT_SYMBOL(dotdot_name);
91
92/*
93 * This is the single most critical data structure when it comes
94 * to the dcache: the hashtable for lookups. Somebody should try
95 * to make this good - I've just made it work.
96 *
97 * This hash-function tries to avoid losing too many bits of hash
98 * information, yet avoid using a prime hash-size or similar.
99 *
100 * Marking the variables "used" ensures that the compiler doesn't
101 * optimize them away completely on architectures with runtime
102 * constant infrastructure, this allows debuggers to see their
103 * values. But updating these values has no effect on those arches.
104 */
105
106static unsigned int d_hash_shift __ro_after_init __used;
107
108static struct hlist_bl_head *dentry_hashtable __ro_after_init __used;
109
110static inline struct hlist_bl_head *d_hash(unsigned long hashlen)
111{
112 return runtime_const_ptr(dentry_hashtable) +
113 runtime_const_shift_right_32(hashlen, d_hash_shift);
114}
115
116#define IN_LOOKUP_SHIFT 10
117static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT];
118
119static inline struct hlist_bl_head *in_lookup_hash(const struct dentry *parent,
120 unsigned int hash)
121{
122 hash += (unsigned long) parent / L1_CACHE_BYTES;
123 return in_lookup_hashtable + hash_32(hash, IN_LOOKUP_SHIFT);
124}
125
126struct dentry_stat_t {
127 long nr_dentry;
128 long nr_unused;
129 long age_limit; /* age in seconds */
130 long want_pages; /* pages requested by system */
131 long nr_negative; /* # of unused negative dentries */
132 long dummy; /* Reserved for future use */
133};
134
135static DEFINE_PER_CPU(long, nr_dentry);
136static DEFINE_PER_CPU(long, nr_dentry_unused);
137static DEFINE_PER_CPU(long, nr_dentry_negative);
138static int dentry_negative_policy;
139
140#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
141/* Statistics gathering. */
142static struct dentry_stat_t dentry_stat = {
143 .age_limit = 45,
144};
145
146/*
147 * Here we resort to our own counters instead of using generic per-cpu counters
148 * for consistency with what the vfs inode code does. We are expected to harvest
149 * better code and performance by having our own specialized counters.
150 *
151 * Please note that the loop is done over all possible CPUs, not over all online
152 * CPUs. The reason for this is that we don't want to play games with CPUs going
153 * on and off. If one of them goes off, we will just keep their counters.
154 *
155 * glommer: See cffbc8a for details, and if you ever intend to change this,
156 * please update all vfs counters to match.
157 */
158static long get_nr_dentry(void)
159{
160 int i;
161 long sum = 0;
162 for_each_possible_cpu(i)
163 sum += per_cpu(nr_dentry, i);
164 return sum < 0 ? 0 : sum;
165}
166
167static long get_nr_dentry_unused(void)
168{
169 int i;
170 long sum = 0;
171 for_each_possible_cpu(i)
172 sum += per_cpu(nr_dentry_unused, i);
173 return sum < 0 ? 0 : sum;
174}
175
176static long get_nr_dentry_negative(void)
177{
178 int i;
179 long sum = 0;
180
181 for_each_possible_cpu(i)
182 sum += per_cpu(nr_dentry_negative, i);
183 return sum < 0 ? 0 : sum;
184}
185
186static int proc_nr_dentry(const struct ctl_table *table, int write, void *buffer,
187 size_t *lenp, loff_t *ppos)
188{
189 dentry_stat.nr_dentry = get_nr_dentry();
190 dentry_stat.nr_unused = get_nr_dentry_unused();
191 dentry_stat.nr_negative = get_nr_dentry_negative();
192 return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
193}
194
195static struct ctl_table fs_dcache_sysctls[] = {
196 {
197 .procname = "dentry-state",
198 .data = &dentry_stat,
199 .maxlen = 6*sizeof(long),
200 .mode = 0444,
201 .proc_handler = proc_nr_dentry,
202 },
203 {
204 .procname = "dentry-negative",
205 .data = &dentry_negative_policy,
206 .maxlen = sizeof(dentry_negative_policy),
207 .mode = 0644,
208 .proc_handler = proc_dointvec_minmax,
209 .extra1 = SYSCTL_ZERO,
210 .extra2 = SYSCTL_ONE,
211 },
212};
213
214static int __init init_fs_dcache_sysctls(void)
215{
216 register_sysctl_init("fs", fs_dcache_sysctls);
217 return 0;
218}
219fs_initcall(init_fs_dcache_sysctls);
220#endif
221
222/*
223 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
224 * The strings are both count bytes long, and count is non-zero.
225 */
226#ifdef CONFIG_DCACHE_WORD_ACCESS
227
228#include <asm/word-at-a-time.h>
229/*
230 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
231 * aligned allocation for this particular component. We don't
232 * strictly need the load_unaligned_zeropad() safety, but it
233 * doesn't hurt either.
234 *
235 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
236 * need the careful unaligned handling.
237 */
238static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
239{
240 unsigned long a,b,mask;
241
242 for (;;) {
243 a = read_word_at_a_time(cs);
244 b = load_unaligned_zeropad(ct);
245 if (tcount < sizeof(unsigned long))
246 break;
247 if (unlikely(a != b))
248 return 1;
249 cs += sizeof(unsigned long);
250 ct += sizeof(unsigned long);
251 tcount -= sizeof(unsigned long);
252 if (!tcount)
253 return 0;
254 }
255 mask = bytemask_from_count(tcount);
256 return unlikely(!!((a ^ b) & mask));
257}
258
259#else
260
261static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
262{
263 do {
264 if (*cs != *ct)
265 return 1;
266 cs++;
267 ct++;
268 tcount--;
269 } while (tcount);
270 return 0;
271}
272
273#endif
274
275static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
276{
277 /*
278 * Be careful about RCU walk racing with rename:
279 * use 'READ_ONCE' to fetch the name pointer.
280 *
281 * NOTE! Even if a rename will mean that the length
282 * was not loaded atomically, we don't care. The
283 * RCU walk will check the sequence count eventually,
284 * and catch it. And we won't overrun the buffer,
285 * because we're reading the name pointer atomically,
286 * and a dentry name is guaranteed to be properly
287 * terminated with a NUL byte.
288 *
289 * End result: even if 'len' is wrong, we'll exit
290 * early because the data cannot match (there can
291 * be no NUL in the ct/tcount data)
292 */
293 const unsigned char *cs = READ_ONCE(dentry->d_name.name);
294
295 return dentry_string_cmp(cs, ct, tcount);
296}
297
298struct external_name {
299 union {
300 atomic_t count;
301 struct rcu_head head;
302 } u;
303 unsigned char name[];
304};
305
306static inline struct external_name *external_name(struct dentry *dentry)
307{
308 return container_of(dentry->d_name.name, struct external_name, name[0]);
309}
310
311static void __d_free(struct rcu_head *head)
312{
313 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
314
315 kmem_cache_free(dentry_cache, dentry);
316}
317
318static void __d_free_external(struct rcu_head *head)
319{
320 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
321 kfree(external_name(dentry));
322 kmem_cache_free(dentry_cache, dentry);
323}
324
325static inline int dname_external(const struct dentry *dentry)
326{
327 return dentry->d_name.name != dentry->d_iname;
328}
329
330void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry)
331{
332 spin_lock(&dentry->d_lock);
333 name->name = dentry->d_name;
334 if (unlikely(dname_external(dentry))) {
335 atomic_inc(&external_name(dentry)->u.count);
336 } else {
337 memcpy(name->inline_name, dentry->d_iname,
338 dentry->d_name.len + 1);
339 name->name.name = name->inline_name;
340 }
341 spin_unlock(&dentry->d_lock);
342}
343EXPORT_SYMBOL(take_dentry_name_snapshot);
344
345void release_dentry_name_snapshot(struct name_snapshot *name)
346{
347 if (unlikely(name->name.name != name->inline_name)) {
348 struct external_name *p;
349 p = container_of(name->name.name, struct external_name, name[0]);
350 if (unlikely(atomic_dec_and_test(&p->u.count)))
351 kfree_rcu(p, u.head);
352 }
353}
354EXPORT_SYMBOL(release_dentry_name_snapshot);
355
356static inline void __d_set_inode_and_type(struct dentry *dentry,
357 struct inode *inode,
358 unsigned type_flags)
359{
360 unsigned flags;
361
362 dentry->d_inode = inode;
363 flags = READ_ONCE(dentry->d_flags);
364 flags &= ~DCACHE_ENTRY_TYPE;
365 flags |= type_flags;
366 smp_store_release(&dentry->d_flags, flags);
367}
368
369static inline void __d_clear_type_and_inode(struct dentry *dentry)
370{
371 unsigned flags = READ_ONCE(dentry->d_flags);
372
373 flags &= ~DCACHE_ENTRY_TYPE;
374 WRITE_ONCE(dentry->d_flags, flags);
375 dentry->d_inode = NULL;
376 /*
377 * The negative counter only tracks dentries on the LRU. Don't inc if
378 * d_lru is on another list.
379 */
380 if ((flags & (DCACHE_LRU_LIST|DCACHE_SHRINK_LIST)) == DCACHE_LRU_LIST)
381 this_cpu_inc(nr_dentry_negative);
382}
383
384static void dentry_free(struct dentry *dentry)
385{
386 WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias));
387 if (unlikely(dname_external(dentry))) {
388 struct external_name *p = external_name(dentry);
389 if (likely(atomic_dec_and_test(&p->u.count))) {
390 call_rcu(&dentry->d_u.d_rcu, __d_free_external);
391 return;
392 }
393 }
394 /* if dentry was never visible to RCU, immediate free is OK */
395 if (dentry->d_flags & DCACHE_NORCU)
396 __d_free(&dentry->d_u.d_rcu);
397 else
398 call_rcu(&dentry->d_u.d_rcu, __d_free);
399}
400
401/*
402 * Release the dentry's inode, using the filesystem
403 * d_iput() operation if defined.
404 */
405static void dentry_unlink_inode(struct dentry * dentry)
406 __releases(dentry->d_lock)
407 __releases(dentry->d_inode->i_lock)
408{
409 struct inode *inode = dentry->d_inode;
410
411 raw_write_seqcount_begin(&dentry->d_seq);
412 __d_clear_type_and_inode(dentry);
413 hlist_del_init(&dentry->d_u.d_alias);
414 raw_write_seqcount_end(&dentry->d_seq);
415 spin_unlock(&dentry->d_lock);
416 spin_unlock(&inode->i_lock);
417 if (!inode->i_nlink)
418 fsnotify_inoderemove(inode);
419 if (dentry->d_op && dentry->d_op->d_iput)
420 dentry->d_op->d_iput(dentry, inode);
421 else
422 iput(inode);
423}
424
425/*
426 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
427 * is in use - which includes both the "real" per-superblock
428 * LRU list _and_ the DCACHE_SHRINK_LIST use.
429 *
430 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
431 * on the shrink list (ie not on the superblock LRU list).
432 *
433 * The per-cpu "nr_dentry_unused" counters are updated with
434 * the DCACHE_LRU_LIST bit.
435 *
436 * The per-cpu "nr_dentry_negative" counters are only updated
437 * when deleted from or added to the per-superblock LRU list, not
438 * from/to the shrink list. That is to avoid an unneeded dec/inc
439 * pair when moving from LRU to shrink list in select_collect().
440 *
441 * These helper functions make sure we always follow the
442 * rules. d_lock must be held by the caller.
443 */
444#define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
445static void d_lru_add(struct dentry *dentry)
446{
447 D_FLAG_VERIFY(dentry, 0);
448 dentry->d_flags |= DCACHE_LRU_LIST;
449 this_cpu_inc(nr_dentry_unused);
450 if (d_is_negative(dentry))
451 this_cpu_inc(nr_dentry_negative);
452 WARN_ON_ONCE(!list_lru_add_obj(
453 &dentry->d_sb->s_dentry_lru, &dentry->d_lru));
454}
455
456static void d_lru_del(struct dentry *dentry)
457{
458 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
459 dentry->d_flags &= ~DCACHE_LRU_LIST;
460 this_cpu_dec(nr_dentry_unused);
461 if (d_is_negative(dentry))
462 this_cpu_dec(nr_dentry_negative);
463 WARN_ON_ONCE(!list_lru_del_obj(
464 &dentry->d_sb->s_dentry_lru, &dentry->d_lru));
465}
466
467static void d_shrink_del(struct dentry *dentry)
468{
469 D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
470 list_del_init(&dentry->d_lru);
471 dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
472 this_cpu_dec(nr_dentry_unused);
473}
474
475static void d_shrink_add(struct dentry *dentry, struct list_head *list)
476{
477 D_FLAG_VERIFY(dentry, 0);
478 list_add(&dentry->d_lru, list);
479 dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST;
480 this_cpu_inc(nr_dentry_unused);
481}
482
483/*
484 * These can only be called under the global LRU lock, ie during the
485 * callback for freeing the LRU list. "isolate" removes it from the
486 * LRU lists entirely, while shrink_move moves it to the indicated
487 * private list.
488 */
489static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry)
490{
491 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
492 dentry->d_flags &= ~DCACHE_LRU_LIST;
493 this_cpu_dec(nr_dentry_unused);
494 if (d_is_negative(dentry))
495 this_cpu_dec(nr_dentry_negative);
496 list_lru_isolate(lru, &dentry->d_lru);
497}
498
499static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
500 struct list_head *list)
501{
502 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
503 dentry->d_flags |= DCACHE_SHRINK_LIST;
504 if (d_is_negative(dentry))
505 this_cpu_dec(nr_dentry_negative);
506 list_lru_isolate_move(lru, &dentry->d_lru, list);
507}
508
509static void ___d_drop(struct dentry *dentry)
510{
511 struct hlist_bl_head *b;
512 /*
513 * Hashed dentries are normally on the dentry hashtable,
514 * with the exception of those newly allocated by
515 * d_obtain_root, which are always IS_ROOT:
516 */
517 if (unlikely(IS_ROOT(dentry)))
518 b = &dentry->d_sb->s_roots;
519 else
520 b = d_hash(dentry->d_name.hash);
521
522 hlist_bl_lock(b);
523 __hlist_bl_del(&dentry->d_hash);
524 hlist_bl_unlock(b);
525}
526
527void __d_drop(struct dentry *dentry)
528{
529 if (!d_unhashed(dentry)) {
530 ___d_drop(dentry);
531 dentry->d_hash.pprev = NULL;
532 write_seqcount_invalidate(&dentry->d_seq);
533 }
534}
535EXPORT_SYMBOL(__d_drop);
536
537/**
538 * d_drop - drop a dentry
539 * @dentry: dentry to drop
540 *
541 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
542 * be found through a VFS lookup any more. Note that this is different from
543 * deleting the dentry - d_delete will try to mark the dentry negative if
544 * possible, giving a successful _negative_ lookup, while d_drop will
545 * just make the cache lookup fail.
546 *
547 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
548 * reason (NFS timeouts or autofs deletes).
549 *
550 * __d_drop requires dentry->d_lock
551 *
552 * ___d_drop doesn't mark dentry as "unhashed"
553 * (dentry->d_hash.pprev will be LIST_POISON2, not NULL).
554 */
555void d_drop(struct dentry *dentry)
556{
557 spin_lock(&dentry->d_lock);
558 __d_drop(dentry);
559 spin_unlock(&dentry->d_lock);
560}
561EXPORT_SYMBOL(d_drop);
562
563static inline void dentry_unlist(struct dentry *dentry)
564{
565 struct dentry *next;
566 /*
567 * Inform d_walk() and shrink_dentry_list() that we are no longer
568 * attached to the dentry tree
569 */
570 dentry->d_flags |= DCACHE_DENTRY_KILLED;
571 if (unlikely(hlist_unhashed(&dentry->d_sib)))
572 return;
573 __hlist_del(&dentry->d_sib);
574 /*
575 * Cursors can move around the list of children. While we'd been
576 * a normal list member, it didn't matter - ->d_sib.next would've
577 * been updated. However, from now on it won't be and for the
578 * things like d_walk() it might end up with a nasty surprise.
579 * Normally d_walk() doesn't care about cursors moving around -
580 * ->d_lock on parent prevents that and since a cursor has no children
581 * of its own, we get through it without ever unlocking the parent.
582 * There is one exception, though - if we ascend from a child that
583 * gets killed as soon as we unlock it, the next sibling is found
584 * using the value left in its ->d_sib.next. And if _that_
585 * pointed to a cursor, and cursor got moved (e.g. by lseek())
586 * before d_walk() regains parent->d_lock, we'll end up skipping
587 * everything the cursor had been moved past.
588 *
589 * Solution: make sure that the pointer left behind in ->d_sib.next
590 * points to something that won't be moving around. I.e. skip the
591 * cursors.
592 */
593 while (dentry->d_sib.next) {
594 next = hlist_entry(dentry->d_sib.next, struct dentry, d_sib);
595 if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR)))
596 break;
597 dentry->d_sib.next = next->d_sib.next;
598 }
599}
600
601static struct dentry *__dentry_kill(struct dentry *dentry)
602{
603 struct dentry *parent = NULL;
604 bool can_free = true;
605
606 /*
607 * The dentry is now unrecoverably dead to the world.
608 */
609 lockref_mark_dead(&dentry->d_lockref);
610
611 /*
612 * inform the fs via d_prune that this dentry is about to be
613 * unhashed and destroyed.
614 */
615 if (dentry->d_flags & DCACHE_OP_PRUNE)
616 dentry->d_op->d_prune(dentry);
617
618 if (dentry->d_flags & DCACHE_LRU_LIST) {
619 if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
620 d_lru_del(dentry);
621 }
622 /* if it was on the hash then remove it */
623 __d_drop(dentry);
624 if (dentry->d_inode)
625 dentry_unlink_inode(dentry);
626 else
627 spin_unlock(&dentry->d_lock);
628 this_cpu_dec(nr_dentry);
629 if (dentry->d_op && dentry->d_op->d_release)
630 dentry->d_op->d_release(dentry);
631
632 cond_resched();
633 /* now that it's negative, ->d_parent is stable */
634 if (!IS_ROOT(dentry)) {
635 parent = dentry->d_parent;
636 spin_lock(&parent->d_lock);
637 }
638 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
639 dentry_unlist(dentry);
640 if (dentry->d_flags & DCACHE_SHRINK_LIST)
641 can_free = false;
642 spin_unlock(&dentry->d_lock);
643 if (likely(can_free))
644 dentry_free(dentry);
645 if (parent && --parent->d_lockref.count) {
646 spin_unlock(&parent->d_lock);
647 return NULL;
648 }
649 return parent;
650}
651
652/*
653 * Lock a dentry for feeding it to __dentry_kill().
654 * Called under rcu_read_lock() and dentry->d_lock; the former
655 * guarantees that nothing we access will be freed under us.
656 * Note that dentry is *not* protected from concurrent dentry_kill(),
657 * d_delete(), etc.
658 *
659 * Return false if dentry is busy. Otherwise, return true and have
660 * that dentry's inode locked.
661 */
662
663static bool lock_for_kill(struct dentry *dentry)
664{
665 struct inode *inode = dentry->d_inode;
666
667 if (unlikely(dentry->d_lockref.count))
668 return false;
669
670 if (!inode || likely(spin_trylock(&inode->i_lock)))
671 return true;
672
673 do {
674 spin_unlock(&dentry->d_lock);
675 spin_lock(&inode->i_lock);
676 spin_lock(&dentry->d_lock);
677 if (likely(inode == dentry->d_inode))
678 break;
679 spin_unlock(&inode->i_lock);
680 inode = dentry->d_inode;
681 } while (inode);
682 if (likely(!dentry->d_lockref.count))
683 return true;
684 if (inode)
685 spin_unlock(&inode->i_lock);
686 return false;
687}
688
689/*
690 * Decide if dentry is worth retaining. Usually this is called with dentry
691 * locked; if not locked, we are more limited and might not be able to tell
692 * without a lock. False in this case means "punt to locked path and recheck".
693 *
694 * In case we aren't locked, these predicates are not "stable". However, it is
695 * sufficient that at some point after we dropped the reference the dentry was
696 * hashed and the flags had the proper value. Other dentry users may have
697 * re-gotten a reference to the dentry and change that, but our work is done -
698 * we can leave the dentry around with a zero refcount.
699 */
700static inline bool retain_dentry(struct dentry *dentry, bool locked)
701{
702 unsigned int d_flags;
703
704 smp_rmb();
705 d_flags = READ_ONCE(dentry->d_flags);
706
707 // Unreachable? Nobody would be able to look it up, no point retaining
708 if (unlikely(d_unhashed(dentry)))
709 return false;
710
711 // Same if it's disconnected
712 if (unlikely(d_flags & DCACHE_DISCONNECTED))
713 return false;
714
715 // ->d_delete() might tell us not to bother, but that requires
716 // ->d_lock; can't decide without it
717 if (unlikely(d_flags & DCACHE_OP_DELETE)) {
718 if (!locked || dentry->d_op->d_delete(dentry))
719 return false;
720 }
721
722 // Explicitly told not to bother
723 if (unlikely(d_flags & DCACHE_DONTCACHE))
724 return false;
725
726 // At this point it looks like we ought to keep it. We also might
727 // need to do something - put it on LRU if it wasn't there already
728 // and mark it referenced if it was on LRU, but not marked yet.
729 // Unfortunately, both actions require ->d_lock, so in lockless
730 // case we'd have to punt rather than doing those.
731 if (unlikely(!(d_flags & DCACHE_LRU_LIST))) {
732 if (!locked)
733 return false;
734 d_lru_add(dentry);
735 } else if (unlikely(!(d_flags & DCACHE_REFERENCED))) {
736 if (!locked)
737 return false;
738 dentry->d_flags |= DCACHE_REFERENCED;
739 }
740 return true;
741}
742
743void d_mark_dontcache(struct inode *inode)
744{
745 struct dentry *de;
746
747 spin_lock(&inode->i_lock);
748 hlist_for_each_entry(de, &inode->i_dentry, d_u.d_alias) {
749 spin_lock(&de->d_lock);
750 de->d_flags |= DCACHE_DONTCACHE;
751 spin_unlock(&de->d_lock);
752 }
753 inode->i_state |= I_DONTCACHE;
754 spin_unlock(&inode->i_lock);
755}
756EXPORT_SYMBOL(d_mark_dontcache);
757
758/*
759 * Try to do a lockless dput(), and return whether that was successful.
760 *
761 * If unsuccessful, we return false, having already taken the dentry lock.
762 * In that case refcount is guaranteed to be zero and we have already
763 * decided that it's not worth keeping around.
764 *
765 * The caller needs to hold the RCU read lock, so that the dentry is
766 * guaranteed to stay around even if the refcount goes down to zero!
767 */
768static inline bool fast_dput(struct dentry *dentry)
769{
770 int ret;
771
772 /*
773 * try to decrement the lockref optimistically.
774 */
775 ret = lockref_put_return(&dentry->d_lockref);
776
777 /*
778 * If the lockref_put_return() failed due to the lock being held
779 * by somebody else, the fast path has failed. We will need to
780 * get the lock, and then check the count again.
781 */
782 if (unlikely(ret < 0)) {
783 spin_lock(&dentry->d_lock);
784 if (WARN_ON_ONCE(dentry->d_lockref.count <= 0)) {
785 spin_unlock(&dentry->d_lock);
786 return true;
787 }
788 dentry->d_lockref.count--;
789 goto locked;
790 }
791
792 /*
793 * If we weren't the last ref, we're done.
794 */
795 if (ret)
796 return true;
797
798 /*
799 * Can we decide that decrement of refcount is all we needed without
800 * taking the lock? There's a very common case when it's all we need -
801 * dentry looks like it ought to be retained and there's nothing else
802 * to do.
803 */
804 if (retain_dentry(dentry, false))
805 return true;
806
807 /*
808 * Either not worth retaining or we can't tell without the lock.
809 * Get the lock, then. We've already decremented the refcount to 0,
810 * but we'll need to re-check the situation after getting the lock.
811 */
812 spin_lock(&dentry->d_lock);
813
814 /*
815 * Did somebody else grab a reference to it in the meantime, and
816 * we're no longer the last user after all? Alternatively, somebody
817 * else could have killed it and marked it dead. Either way, we
818 * don't need to do anything else.
819 */
820locked:
821 if (dentry->d_lockref.count || retain_dentry(dentry, true)) {
822 spin_unlock(&dentry->d_lock);
823 return true;
824 }
825 return false;
826}
827
828
829/*
830 * This is dput
831 *
832 * This is complicated by the fact that we do not want to put
833 * dentries that are no longer on any hash chain on the unused
834 * list: we'd much rather just get rid of them immediately.
835 *
836 * However, that implies that we have to traverse the dentry
837 * tree upwards to the parents which might _also_ now be
838 * scheduled for deletion (it may have been only waiting for
839 * its last child to go away).
840 *
841 * This tail recursion is done by hand as we don't want to depend
842 * on the compiler to always get this right (gcc generally doesn't).
843 * Real recursion would eat up our stack space.
844 */
845
846/*
847 * dput - release a dentry
848 * @dentry: dentry to release
849 *
850 * Release a dentry. This will drop the usage count and if appropriate
851 * call the dentry unlink method as well as removing it from the queues and
852 * releasing its resources. If the parent dentries were scheduled for release
853 * they too may now get deleted.
854 */
855void dput(struct dentry *dentry)
856{
857 if (!dentry)
858 return;
859 might_sleep();
860 rcu_read_lock();
861 if (likely(fast_dput(dentry))) {
862 rcu_read_unlock();
863 return;
864 }
865 while (lock_for_kill(dentry)) {
866 rcu_read_unlock();
867 dentry = __dentry_kill(dentry);
868 if (!dentry)
869 return;
870 if (retain_dentry(dentry, true)) {
871 spin_unlock(&dentry->d_lock);
872 return;
873 }
874 rcu_read_lock();
875 }
876 rcu_read_unlock();
877 spin_unlock(&dentry->d_lock);
878}
879EXPORT_SYMBOL(dput);
880
881static void to_shrink_list(struct dentry *dentry, struct list_head *list)
882__must_hold(&dentry->d_lock)
883{
884 if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
885 if (dentry->d_flags & DCACHE_LRU_LIST)
886 d_lru_del(dentry);
887 d_shrink_add(dentry, list);
888 }
889}
890
891void dput_to_list(struct dentry *dentry, struct list_head *list)
892{
893 rcu_read_lock();
894 if (likely(fast_dput(dentry))) {
895 rcu_read_unlock();
896 return;
897 }
898 rcu_read_unlock();
899 to_shrink_list(dentry, list);
900 spin_unlock(&dentry->d_lock);
901}
902
903struct dentry *dget_parent(struct dentry *dentry)
904{
905 int gotref;
906 struct dentry *ret;
907 unsigned seq;
908
909 /*
910 * Do optimistic parent lookup without any
911 * locking.
912 */
913 rcu_read_lock();
914 seq = raw_seqcount_begin(&dentry->d_seq);
915 ret = READ_ONCE(dentry->d_parent);
916 gotref = lockref_get_not_zero(&ret->d_lockref);
917 rcu_read_unlock();
918 if (likely(gotref)) {
919 if (!read_seqcount_retry(&dentry->d_seq, seq))
920 return ret;
921 dput(ret);
922 }
923
924repeat:
925 /*
926 * Don't need rcu_dereference because we re-check it was correct under
927 * the lock.
928 */
929 rcu_read_lock();
930 ret = dentry->d_parent;
931 spin_lock(&ret->d_lock);
932 if (unlikely(ret != dentry->d_parent)) {
933 spin_unlock(&ret->d_lock);
934 rcu_read_unlock();
935 goto repeat;
936 }
937 rcu_read_unlock();
938 BUG_ON(!ret->d_lockref.count);
939 ret->d_lockref.count++;
940 spin_unlock(&ret->d_lock);
941 return ret;
942}
943EXPORT_SYMBOL(dget_parent);
944
945static struct dentry * __d_find_any_alias(struct inode *inode)
946{
947 struct dentry *alias;
948
949 if (hlist_empty(&inode->i_dentry))
950 return NULL;
951 alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
952 lockref_get(&alias->d_lockref);
953 return alias;
954}
955
956/**
957 * d_find_any_alias - find any alias for a given inode
958 * @inode: inode to find an alias for
959 *
960 * If any aliases exist for the given inode, take and return a
961 * reference for one of them. If no aliases exist, return %NULL.
962 */
963struct dentry *d_find_any_alias(struct inode *inode)
964{
965 struct dentry *de;
966
967 spin_lock(&inode->i_lock);
968 de = __d_find_any_alias(inode);
969 spin_unlock(&inode->i_lock);
970 return de;
971}
972EXPORT_SYMBOL(d_find_any_alias);
973
974static struct dentry *__d_find_alias(struct inode *inode)
975{
976 struct dentry *alias;
977
978 if (S_ISDIR(inode->i_mode))
979 return __d_find_any_alias(inode);
980
981 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
982 spin_lock(&alias->d_lock);
983 if (!d_unhashed(alias)) {
984 dget_dlock(alias);
985 spin_unlock(&alias->d_lock);
986 return alias;
987 }
988 spin_unlock(&alias->d_lock);
989 }
990 return NULL;
991}
992
993/**
994 * d_find_alias - grab a hashed alias of inode
995 * @inode: inode in question
996 *
997 * If inode has a hashed alias, or is a directory and has any alias,
998 * acquire the reference to alias and return it. Otherwise return NULL.
999 * Notice that if inode is a directory there can be only one alias and
1000 * it can be unhashed only if it has no children, or if it is the root
1001 * of a filesystem, or if the directory was renamed and d_revalidate
1002 * was the first vfs operation to notice.
1003 *
1004 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
1005 * any other hashed alias over that one.
1006 */
1007struct dentry *d_find_alias(struct inode *inode)
1008{
1009 struct dentry *de = NULL;
1010
1011 if (!hlist_empty(&inode->i_dentry)) {
1012 spin_lock(&inode->i_lock);
1013 de = __d_find_alias(inode);
1014 spin_unlock(&inode->i_lock);
1015 }
1016 return de;
1017}
1018EXPORT_SYMBOL(d_find_alias);
1019
1020/*
1021 * Caller MUST be holding rcu_read_lock() and be guaranteed
1022 * that inode won't get freed until rcu_read_unlock().
1023 */
1024struct dentry *d_find_alias_rcu(struct inode *inode)
1025{
1026 struct hlist_head *l = &inode->i_dentry;
1027 struct dentry *de = NULL;
1028
1029 spin_lock(&inode->i_lock);
1030 // ->i_dentry and ->i_rcu are colocated, but the latter won't be
1031 // used without having I_FREEING set, which means no aliases left
1032 if (likely(!(inode->i_state & I_FREEING) && !hlist_empty(l))) {
1033 if (S_ISDIR(inode->i_mode)) {
1034 de = hlist_entry(l->first, struct dentry, d_u.d_alias);
1035 } else {
1036 hlist_for_each_entry(de, l, d_u.d_alias)
1037 if (!d_unhashed(de))
1038 break;
1039 }
1040 }
1041 spin_unlock(&inode->i_lock);
1042 return de;
1043}
1044
1045/*
1046 * Try to kill dentries associated with this inode.
1047 * WARNING: you must own a reference to inode.
1048 */
1049void d_prune_aliases(struct inode *inode)
1050{
1051 LIST_HEAD(dispose);
1052 struct dentry *dentry;
1053
1054 spin_lock(&inode->i_lock);
1055 hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
1056 spin_lock(&dentry->d_lock);
1057 if (!dentry->d_lockref.count)
1058 to_shrink_list(dentry, &dispose);
1059 spin_unlock(&dentry->d_lock);
1060 }
1061 spin_unlock(&inode->i_lock);
1062 shrink_dentry_list(&dispose);
1063}
1064EXPORT_SYMBOL(d_prune_aliases);
1065
1066static inline void shrink_kill(struct dentry *victim)
1067{
1068 do {
1069 rcu_read_unlock();
1070 victim = __dentry_kill(victim);
1071 rcu_read_lock();
1072 } while (victim && lock_for_kill(victim));
1073 rcu_read_unlock();
1074 if (victim)
1075 spin_unlock(&victim->d_lock);
1076}
1077
1078void shrink_dentry_list(struct list_head *list)
1079{
1080 while (!list_empty(list)) {
1081 struct dentry *dentry;
1082
1083 dentry = list_entry(list->prev, struct dentry, d_lru);
1084 spin_lock(&dentry->d_lock);
1085 rcu_read_lock();
1086 if (!lock_for_kill(dentry)) {
1087 bool can_free;
1088 rcu_read_unlock();
1089 d_shrink_del(dentry);
1090 can_free = dentry->d_flags & DCACHE_DENTRY_KILLED;
1091 spin_unlock(&dentry->d_lock);
1092 if (can_free)
1093 dentry_free(dentry);
1094 continue;
1095 }
1096 d_shrink_del(dentry);
1097 shrink_kill(dentry);
1098 }
1099}
1100
1101static enum lru_status dentry_lru_isolate(struct list_head *item,
1102 struct list_lru_one *lru, void *arg)
1103{
1104 struct list_head *freeable = arg;
1105 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1106
1107
1108 /*
1109 * we are inverting the lru lock/dentry->d_lock here,
1110 * so use a trylock. If we fail to get the lock, just skip
1111 * it
1112 */
1113 if (!spin_trylock(&dentry->d_lock))
1114 return LRU_SKIP;
1115
1116 /*
1117 * Referenced dentries are still in use. If they have active
1118 * counts, just remove them from the LRU. Otherwise give them
1119 * another pass through the LRU.
1120 */
1121 if (dentry->d_lockref.count) {
1122 d_lru_isolate(lru, dentry);
1123 spin_unlock(&dentry->d_lock);
1124 return LRU_REMOVED;
1125 }
1126
1127 if (dentry->d_flags & DCACHE_REFERENCED) {
1128 dentry->d_flags &= ~DCACHE_REFERENCED;
1129 spin_unlock(&dentry->d_lock);
1130
1131 /*
1132 * The list move itself will be made by the common LRU code. At
1133 * this point, we've dropped the dentry->d_lock but keep the
1134 * lru lock. This is safe to do, since every list movement is
1135 * protected by the lru lock even if both locks are held.
1136 *
1137 * This is guaranteed by the fact that all LRU management
1138 * functions are intermediated by the LRU API calls like
1139 * list_lru_add_obj and list_lru_del_obj. List movement in this file
1140 * only ever occur through this functions or through callbacks
1141 * like this one, that are called from the LRU API.
1142 *
1143 * The only exceptions to this are functions like
1144 * shrink_dentry_list, and code that first checks for the
1145 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1146 * operating only with stack provided lists after they are
1147 * properly isolated from the main list. It is thus, always a
1148 * local access.
1149 */
1150 return LRU_ROTATE;
1151 }
1152
1153 d_lru_shrink_move(lru, dentry, freeable);
1154 spin_unlock(&dentry->d_lock);
1155
1156 return LRU_REMOVED;
1157}
1158
1159/**
1160 * prune_dcache_sb - shrink the dcache
1161 * @sb: superblock
1162 * @sc: shrink control, passed to list_lru_shrink_walk()
1163 *
1164 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1165 * is done when we need more memory and called from the superblock shrinker
1166 * function.
1167 *
1168 * This function may fail to free any resources if all the dentries are in
1169 * use.
1170 */
1171long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc)
1172{
1173 LIST_HEAD(dispose);
1174 long freed;
1175
1176 freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc,
1177 dentry_lru_isolate, &dispose);
1178 shrink_dentry_list(&dispose);
1179 return freed;
1180}
1181
1182static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
1183 struct list_lru_one *lru, void *arg)
1184{
1185 struct list_head *freeable = arg;
1186 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1187
1188 /*
1189 * we are inverting the lru lock/dentry->d_lock here,
1190 * so use a trylock. If we fail to get the lock, just skip
1191 * it
1192 */
1193 if (!spin_trylock(&dentry->d_lock))
1194 return LRU_SKIP;
1195
1196 d_lru_shrink_move(lru, dentry, freeable);
1197 spin_unlock(&dentry->d_lock);
1198
1199 return LRU_REMOVED;
1200}
1201
1202
1203/**
1204 * shrink_dcache_sb - shrink dcache for a superblock
1205 * @sb: superblock
1206 *
1207 * Shrink the dcache for the specified super block. This is used to free
1208 * the dcache before unmounting a file system.
1209 */
1210void shrink_dcache_sb(struct super_block *sb)
1211{
1212 do {
1213 LIST_HEAD(dispose);
1214
1215 list_lru_walk(&sb->s_dentry_lru,
1216 dentry_lru_isolate_shrink, &dispose, 1024);
1217 shrink_dentry_list(&dispose);
1218 } while (list_lru_count(&sb->s_dentry_lru) > 0);
1219}
1220EXPORT_SYMBOL(shrink_dcache_sb);
1221
1222/**
1223 * enum d_walk_ret - action to talke during tree walk
1224 * @D_WALK_CONTINUE: contrinue walk
1225 * @D_WALK_QUIT: quit walk
1226 * @D_WALK_NORETRY: quit when retry is needed
1227 * @D_WALK_SKIP: skip this dentry and its children
1228 */
1229enum d_walk_ret {
1230 D_WALK_CONTINUE,
1231 D_WALK_QUIT,
1232 D_WALK_NORETRY,
1233 D_WALK_SKIP,
1234};
1235
1236/**
1237 * d_walk - walk the dentry tree
1238 * @parent: start of walk
1239 * @data: data passed to @enter() and @finish()
1240 * @enter: callback when first entering the dentry
1241 *
1242 * The @enter() callbacks are called with d_lock held.
1243 */
1244static void d_walk(struct dentry *parent, void *data,
1245 enum d_walk_ret (*enter)(void *, struct dentry *))
1246{
1247 struct dentry *this_parent, *dentry;
1248 unsigned seq = 0;
1249 enum d_walk_ret ret;
1250 bool retry = true;
1251
1252again:
1253 read_seqbegin_or_lock(&rename_lock, &seq);
1254 this_parent = parent;
1255 spin_lock(&this_parent->d_lock);
1256
1257 ret = enter(data, this_parent);
1258 switch (ret) {
1259 case D_WALK_CONTINUE:
1260 break;
1261 case D_WALK_QUIT:
1262 case D_WALK_SKIP:
1263 goto out_unlock;
1264 case D_WALK_NORETRY:
1265 retry = false;
1266 break;
1267 }
1268repeat:
1269 dentry = d_first_child(this_parent);
1270resume:
1271 hlist_for_each_entry_from(dentry, d_sib) {
1272 if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR))
1273 continue;
1274
1275 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1276
1277 ret = enter(data, dentry);
1278 switch (ret) {
1279 case D_WALK_CONTINUE:
1280 break;
1281 case D_WALK_QUIT:
1282 spin_unlock(&dentry->d_lock);
1283 goto out_unlock;
1284 case D_WALK_NORETRY:
1285 retry = false;
1286 break;
1287 case D_WALK_SKIP:
1288 spin_unlock(&dentry->d_lock);
1289 continue;
1290 }
1291
1292 if (!hlist_empty(&dentry->d_children)) {
1293 spin_unlock(&this_parent->d_lock);
1294 spin_release(&dentry->d_lock.dep_map, _RET_IP_);
1295 this_parent = dentry;
1296 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1297 goto repeat;
1298 }
1299 spin_unlock(&dentry->d_lock);
1300 }
1301 /*
1302 * All done at this level ... ascend and resume the search.
1303 */
1304 rcu_read_lock();
1305ascend:
1306 if (this_parent != parent) {
1307 dentry = this_parent;
1308 this_parent = dentry->d_parent;
1309
1310 spin_unlock(&dentry->d_lock);
1311 spin_lock(&this_parent->d_lock);
1312
1313 /* might go back up the wrong parent if we have had a rename. */
1314 if (need_seqretry(&rename_lock, seq))
1315 goto rename_retry;
1316 /* go into the first sibling still alive */
1317 hlist_for_each_entry_continue(dentry, d_sib) {
1318 if (likely(!(dentry->d_flags & DCACHE_DENTRY_KILLED))) {
1319 rcu_read_unlock();
1320 goto resume;
1321 }
1322 }
1323 goto ascend;
1324 }
1325 if (need_seqretry(&rename_lock, seq))
1326 goto rename_retry;
1327 rcu_read_unlock();
1328
1329out_unlock:
1330 spin_unlock(&this_parent->d_lock);
1331 done_seqretry(&rename_lock, seq);
1332 return;
1333
1334rename_retry:
1335 spin_unlock(&this_parent->d_lock);
1336 rcu_read_unlock();
1337 BUG_ON(seq & 1);
1338 if (!retry)
1339 return;
1340 seq = 1;
1341 goto again;
1342}
1343
1344struct check_mount {
1345 struct vfsmount *mnt;
1346 unsigned int mounted;
1347};
1348
1349static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry)
1350{
1351 struct check_mount *info = data;
1352 struct path path = { .mnt = info->mnt, .dentry = dentry };
1353
1354 if (likely(!d_mountpoint(dentry)))
1355 return D_WALK_CONTINUE;
1356 if (__path_is_mountpoint(&path)) {
1357 info->mounted = 1;
1358 return D_WALK_QUIT;
1359 }
1360 return D_WALK_CONTINUE;
1361}
1362
1363/**
1364 * path_has_submounts - check for mounts over a dentry in the
1365 * current namespace.
1366 * @parent: path to check.
1367 *
1368 * Return true if the parent or its subdirectories contain
1369 * a mount point in the current namespace.
1370 */
1371int path_has_submounts(const struct path *parent)
1372{
1373 struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
1374
1375 read_seqlock_excl(&mount_lock);
1376 d_walk(parent->dentry, &data, path_check_mount);
1377 read_sequnlock_excl(&mount_lock);
1378
1379 return data.mounted;
1380}
1381EXPORT_SYMBOL(path_has_submounts);
1382
1383/*
1384 * Called by mount code to set a mountpoint and check if the mountpoint is
1385 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1386 * subtree can become unreachable).
1387 *
1388 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1389 * this reason take rename_lock and d_lock on dentry and ancestors.
1390 */
1391int d_set_mounted(struct dentry *dentry)
1392{
1393 struct dentry *p;
1394 int ret = -ENOENT;
1395 write_seqlock(&rename_lock);
1396 for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
1397 /* Need exclusion wrt. d_invalidate() */
1398 spin_lock(&p->d_lock);
1399 if (unlikely(d_unhashed(p))) {
1400 spin_unlock(&p->d_lock);
1401 goto out;
1402 }
1403 spin_unlock(&p->d_lock);
1404 }
1405 spin_lock(&dentry->d_lock);
1406 if (!d_unlinked(dentry)) {
1407 ret = -EBUSY;
1408 if (!d_mountpoint(dentry)) {
1409 dentry->d_flags |= DCACHE_MOUNTED;
1410 ret = 0;
1411 }
1412 }
1413 spin_unlock(&dentry->d_lock);
1414out:
1415 write_sequnlock(&rename_lock);
1416 return ret;
1417}
1418
1419/*
1420 * Search the dentry child list of the specified parent,
1421 * and move any unused dentries to the end of the unused
1422 * list for prune_dcache(). We descend to the next level
1423 * whenever the d_children list is non-empty and continue
1424 * searching.
1425 *
1426 * It returns zero iff there are no unused children,
1427 * otherwise it returns the number of children moved to
1428 * the end of the unused list. This may not be the total
1429 * number of unused children, because select_parent can
1430 * drop the lock and return early due to latency
1431 * constraints.
1432 */
1433
1434struct select_data {
1435 struct dentry *start;
1436 union {
1437 long found;
1438 struct dentry *victim;
1439 };
1440 struct list_head dispose;
1441};
1442
1443static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
1444{
1445 struct select_data *data = _data;
1446 enum d_walk_ret ret = D_WALK_CONTINUE;
1447
1448 if (data->start == dentry)
1449 goto out;
1450
1451 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1452 data->found++;
1453 } else if (!dentry->d_lockref.count) {
1454 to_shrink_list(dentry, &data->dispose);
1455 data->found++;
1456 } else if (dentry->d_lockref.count < 0) {
1457 data->found++;
1458 }
1459 /*
1460 * We can return to the caller if we have found some (this
1461 * ensures forward progress). We'll be coming back to find
1462 * the rest.
1463 */
1464 if (!list_empty(&data->dispose))
1465 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1466out:
1467 return ret;
1468}
1469
1470static enum d_walk_ret select_collect2(void *_data, struct dentry *dentry)
1471{
1472 struct select_data *data = _data;
1473 enum d_walk_ret ret = D_WALK_CONTINUE;
1474
1475 if (data->start == dentry)
1476 goto out;
1477
1478 if (!dentry->d_lockref.count) {
1479 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1480 rcu_read_lock();
1481 data->victim = dentry;
1482 return D_WALK_QUIT;
1483 }
1484 to_shrink_list(dentry, &data->dispose);
1485 }
1486 /*
1487 * We can return to the caller if we have found some (this
1488 * ensures forward progress). We'll be coming back to find
1489 * the rest.
1490 */
1491 if (!list_empty(&data->dispose))
1492 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1493out:
1494 return ret;
1495}
1496
1497/**
1498 * shrink_dcache_parent - prune dcache
1499 * @parent: parent of entries to prune
1500 *
1501 * Prune the dcache to remove unused children of the parent dentry.
1502 */
1503void shrink_dcache_parent(struct dentry *parent)
1504{
1505 for (;;) {
1506 struct select_data data = {.start = parent};
1507
1508 INIT_LIST_HEAD(&data.dispose);
1509 d_walk(parent, &data, select_collect);
1510
1511 if (!list_empty(&data.dispose)) {
1512 shrink_dentry_list(&data.dispose);
1513 continue;
1514 }
1515
1516 cond_resched();
1517 if (!data.found)
1518 break;
1519 data.victim = NULL;
1520 d_walk(parent, &data, select_collect2);
1521 if (data.victim) {
1522 spin_lock(&data.victim->d_lock);
1523 if (!lock_for_kill(data.victim)) {
1524 spin_unlock(&data.victim->d_lock);
1525 rcu_read_unlock();
1526 } else {
1527 shrink_kill(data.victim);
1528 }
1529 }
1530 if (!list_empty(&data.dispose))
1531 shrink_dentry_list(&data.dispose);
1532 }
1533}
1534EXPORT_SYMBOL(shrink_dcache_parent);
1535
1536static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
1537{
1538 /* it has busy descendents; complain about those instead */
1539 if (!hlist_empty(&dentry->d_children))
1540 return D_WALK_CONTINUE;
1541
1542 /* root with refcount 1 is fine */
1543 if (dentry == _data && dentry->d_lockref.count == 1)
1544 return D_WALK_CONTINUE;
1545
1546 WARN(1, "BUG: Dentry %p{i=%lx,n=%pd} "
1547 " still in use (%d) [unmount of %s %s]\n",
1548 dentry,
1549 dentry->d_inode ?
1550 dentry->d_inode->i_ino : 0UL,
1551 dentry,
1552 dentry->d_lockref.count,
1553 dentry->d_sb->s_type->name,
1554 dentry->d_sb->s_id);
1555 return D_WALK_CONTINUE;
1556}
1557
1558static void do_one_tree(struct dentry *dentry)
1559{
1560 shrink_dcache_parent(dentry);
1561 d_walk(dentry, dentry, umount_check);
1562 d_drop(dentry);
1563 dput(dentry);
1564}
1565
1566/*
1567 * destroy the dentries attached to a superblock on unmounting
1568 */
1569void shrink_dcache_for_umount(struct super_block *sb)
1570{
1571 struct dentry *dentry;
1572
1573 rwsem_assert_held_write(&sb->s_umount);
1574
1575 dentry = sb->s_root;
1576 sb->s_root = NULL;
1577 do_one_tree(dentry);
1578
1579 while (!hlist_bl_empty(&sb->s_roots)) {
1580 dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_roots), struct dentry, d_hash));
1581 do_one_tree(dentry);
1582 }
1583}
1584
1585static enum d_walk_ret find_submount(void *_data, struct dentry *dentry)
1586{
1587 struct dentry **victim = _data;
1588 if (d_mountpoint(dentry)) {
1589 *victim = dget_dlock(dentry);
1590 return D_WALK_QUIT;
1591 }
1592 return D_WALK_CONTINUE;
1593}
1594
1595/**
1596 * d_invalidate - detach submounts, prune dcache, and drop
1597 * @dentry: dentry to invalidate (aka detach, prune and drop)
1598 */
1599void d_invalidate(struct dentry *dentry)
1600{
1601 bool had_submounts = false;
1602 spin_lock(&dentry->d_lock);
1603 if (d_unhashed(dentry)) {
1604 spin_unlock(&dentry->d_lock);
1605 return;
1606 }
1607 __d_drop(dentry);
1608 spin_unlock(&dentry->d_lock);
1609
1610 /* Negative dentries can be dropped without further checks */
1611 if (!dentry->d_inode)
1612 return;
1613
1614 shrink_dcache_parent(dentry);
1615 for (;;) {
1616 struct dentry *victim = NULL;
1617 d_walk(dentry, &victim, find_submount);
1618 if (!victim) {
1619 if (had_submounts)
1620 shrink_dcache_parent(dentry);
1621 return;
1622 }
1623 had_submounts = true;
1624 detach_mounts(victim);
1625 dput(victim);
1626 }
1627}
1628EXPORT_SYMBOL(d_invalidate);
1629
1630/**
1631 * __d_alloc - allocate a dcache entry
1632 * @sb: filesystem it will belong to
1633 * @name: qstr of the name
1634 *
1635 * Allocates a dentry. It returns %NULL if there is insufficient memory
1636 * available. On a success the dentry is returned. The name passed in is
1637 * copied and the copy passed in may be reused after this call.
1638 */
1639
1640static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1641{
1642 struct dentry *dentry;
1643 char *dname;
1644 int err;
1645
1646 dentry = kmem_cache_alloc_lru(dentry_cache, &sb->s_dentry_lru,
1647 GFP_KERNEL);
1648 if (!dentry)
1649 return NULL;
1650
1651 /*
1652 * We guarantee that the inline name is always NUL-terminated.
1653 * This way the memcpy() done by the name switching in rename
1654 * will still always have a NUL at the end, even if we might
1655 * be overwriting an internal NUL character
1656 */
1657 dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
1658 if (unlikely(!name)) {
1659 name = &slash_name;
1660 dname = dentry->d_iname;
1661 } else if (name->len > DNAME_INLINE_LEN-1) {
1662 size_t size = offsetof(struct external_name, name[1]);
1663 struct external_name *p = kmalloc(size + name->len,
1664 GFP_KERNEL_ACCOUNT |
1665 __GFP_RECLAIMABLE);
1666 if (!p) {
1667 kmem_cache_free(dentry_cache, dentry);
1668 return NULL;
1669 }
1670 atomic_set(&p->u.count, 1);
1671 dname = p->name;
1672 } else {
1673 dname = dentry->d_iname;
1674 }
1675
1676 dentry->d_name.len = name->len;
1677 dentry->d_name.hash = name->hash;
1678 memcpy(dname, name->name, name->len);
1679 dname[name->len] = 0;
1680
1681 /* Make sure we always see the terminating NUL character */
1682 smp_store_release(&dentry->d_name.name, dname); /* ^^^ */
1683
1684 dentry->d_lockref.count = 1;
1685 dentry->d_flags = 0;
1686 spin_lock_init(&dentry->d_lock);
1687 seqcount_spinlock_init(&dentry->d_seq, &dentry->d_lock);
1688 dentry->d_inode = NULL;
1689 dentry->d_parent = dentry;
1690 dentry->d_sb = sb;
1691 dentry->d_op = NULL;
1692 dentry->d_fsdata = NULL;
1693 INIT_HLIST_BL_NODE(&dentry->d_hash);
1694 INIT_LIST_HEAD(&dentry->d_lru);
1695 INIT_HLIST_HEAD(&dentry->d_children);
1696 INIT_HLIST_NODE(&dentry->d_u.d_alias);
1697 INIT_HLIST_NODE(&dentry->d_sib);
1698 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1699
1700 if (dentry->d_op && dentry->d_op->d_init) {
1701 err = dentry->d_op->d_init(dentry);
1702 if (err) {
1703 if (dname_external(dentry))
1704 kfree(external_name(dentry));
1705 kmem_cache_free(dentry_cache, dentry);
1706 return NULL;
1707 }
1708 }
1709
1710 this_cpu_inc(nr_dentry);
1711
1712 return dentry;
1713}
1714
1715/**
1716 * d_alloc - allocate a dcache entry
1717 * @parent: parent of entry to allocate
1718 * @name: qstr of the name
1719 *
1720 * Allocates a dentry. It returns %NULL if there is insufficient memory
1721 * available. On a success the dentry is returned. The name passed in is
1722 * copied and the copy passed in may be reused after this call.
1723 */
1724struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1725{
1726 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1727 if (!dentry)
1728 return NULL;
1729 spin_lock(&parent->d_lock);
1730 /*
1731 * don't need child lock because it is not subject
1732 * to concurrency here
1733 */
1734 dentry->d_parent = dget_dlock(parent);
1735 hlist_add_head(&dentry->d_sib, &parent->d_children);
1736 spin_unlock(&parent->d_lock);
1737
1738 return dentry;
1739}
1740EXPORT_SYMBOL(d_alloc);
1741
1742struct dentry *d_alloc_anon(struct super_block *sb)
1743{
1744 return __d_alloc(sb, NULL);
1745}
1746EXPORT_SYMBOL(d_alloc_anon);
1747
1748struct dentry *d_alloc_cursor(struct dentry * parent)
1749{
1750 struct dentry *dentry = d_alloc_anon(parent->d_sb);
1751 if (dentry) {
1752 dentry->d_flags |= DCACHE_DENTRY_CURSOR;
1753 dentry->d_parent = dget(parent);
1754 }
1755 return dentry;
1756}
1757
1758/**
1759 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1760 * @sb: the superblock
1761 * @name: qstr of the name
1762 *
1763 * For a filesystem that just pins its dentries in memory and never
1764 * performs lookups at all, return an unhashed IS_ROOT dentry.
1765 * This is used for pipes, sockets et.al. - the stuff that should
1766 * never be anyone's children or parents. Unlike all other
1767 * dentries, these will not have RCU delay between dropping the
1768 * last reference and freeing them.
1769 *
1770 * The only user is alloc_file_pseudo() and that's what should
1771 * be considered a public interface. Don't use directly.
1772 */
1773struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1774{
1775 static const struct dentry_operations anon_ops = {
1776 .d_dname = simple_dname
1777 };
1778 struct dentry *dentry = __d_alloc(sb, name);
1779 if (likely(dentry)) {
1780 dentry->d_flags |= DCACHE_NORCU;
1781 if (!sb->s_d_op)
1782 d_set_d_op(dentry, &anon_ops);
1783 }
1784 return dentry;
1785}
1786
1787struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1788{
1789 struct qstr q;
1790
1791 q.name = name;
1792 q.hash_len = hashlen_string(parent, name);
1793 return d_alloc(parent, &q);
1794}
1795EXPORT_SYMBOL(d_alloc_name);
1796
1797void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1798{
1799 WARN_ON_ONCE(dentry->d_op);
1800 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
1801 DCACHE_OP_COMPARE |
1802 DCACHE_OP_REVALIDATE |
1803 DCACHE_OP_WEAK_REVALIDATE |
1804 DCACHE_OP_DELETE |
1805 DCACHE_OP_REAL));
1806 dentry->d_op = op;
1807 if (!op)
1808 return;
1809 if (op->d_hash)
1810 dentry->d_flags |= DCACHE_OP_HASH;
1811 if (op->d_compare)
1812 dentry->d_flags |= DCACHE_OP_COMPARE;
1813 if (op->d_revalidate)
1814 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1815 if (op->d_weak_revalidate)
1816 dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
1817 if (op->d_delete)
1818 dentry->d_flags |= DCACHE_OP_DELETE;
1819 if (op->d_prune)
1820 dentry->d_flags |= DCACHE_OP_PRUNE;
1821 if (op->d_real)
1822 dentry->d_flags |= DCACHE_OP_REAL;
1823
1824}
1825EXPORT_SYMBOL(d_set_d_op);
1826
1827static unsigned d_flags_for_inode(struct inode *inode)
1828{
1829 unsigned add_flags = DCACHE_REGULAR_TYPE;
1830
1831 if (!inode)
1832 return DCACHE_MISS_TYPE;
1833
1834 if (S_ISDIR(inode->i_mode)) {
1835 add_flags = DCACHE_DIRECTORY_TYPE;
1836 if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) {
1837 if (unlikely(!inode->i_op->lookup))
1838 add_flags = DCACHE_AUTODIR_TYPE;
1839 else
1840 inode->i_opflags |= IOP_LOOKUP;
1841 }
1842 goto type_determined;
1843 }
1844
1845 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1846 if (unlikely(inode->i_op->get_link)) {
1847 add_flags = DCACHE_SYMLINK_TYPE;
1848 goto type_determined;
1849 }
1850 inode->i_opflags |= IOP_NOFOLLOW;
1851 }
1852
1853 if (unlikely(!S_ISREG(inode->i_mode)))
1854 add_flags = DCACHE_SPECIAL_TYPE;
1855
1856type_determined:
1857 if (unlikely(IS_AUTOMOUNT(inode)))
1858 add_flags |= DCACHE_NEED_AUTOMOUNT;
1859 return add_flags;
1860}
1861
1862static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1863{
1864 unsigned add_flags = d_flags_for_inode(inode);
1865 WARN_ON(d_in_lookup(dentry));
1866
1867 spin_lock(&dentry->d_lock);
1868 /*
1869 * The negative counter only tracks dentries on the LRU. Don't dec if
1870 * d_lru is on another list.
1871 */
1872 if ((dentry->d_flags &
1873 (DCACHE_LRU_LIST|DCACHE_SHRINK_LIST)) == DCACHE_LRU_LIST)
1874 this_cpu_dec(nr_dentry_negative);
1875 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
1876 raw_write_seqcount_begin(&dentry->d_seq);
1877 __d_set_inode_and_type(dentry, inode, add_flags);
1878 raw_write_seqcount_end(&dentry->d_seq);
1879 fsnotify_update_flags(dentry);
1880 spin_unlock(&dentry->d_lock);
1881}
1882
1883/**
1884 * d_instantiate - fill in inode information for a dentry
1885 * @entry: dentry to complete
1886 * @inode: inode to attach to this dentry
1887 *
1888 * Fill in inode information in the entry.
1889 *
1890 * This turns negative dentries into productive full members
1891 * of society.
1892 *
1893 * NOTE! This assumes that the inode count has been incremented
1894 * (or otherwise set) by the caller to indicate that it is now
1895 * in use by the dcache.
1896 */
1897
1898void d_instantiate(struct dentry *entry, struct inode * inode)
1899{
1900 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1901 if (inode) {
1902 security_d_instantiate(entry, inode);
1903 spin_lock(&inode->i_lock);
1904 __d_instantiate(entry, inode);
1905 spin_unlock(&inode->i_lock);
1906 }
1907}
1908EXPORT_SYMBOL(d_instantiate);
1909
1910/*
1911 * This should be equivalent to d_instantiate() + unlock_new_inode(),
1912 * with lockdep-related part of unlock_new_inode() done before
1913 * anything else. Use that instead of open-coding d_instantiate()/
1914 * unlock_new_inode() combinations.
1915 */
1916void d_instantiate_new(struct dentry *entry, struct inode *inode)
1917{
1918 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1919 BUG_ON(!inode);
1920 lockdep_annotate_inode_mutex_key(inode);
1921 security_d_instantiate(entry, inode);
1922 spin_lock(&inode->i_lock);
1923 __d_instantiate(entry, inode);
1924 WARN_ON(!(inode->i_state & I_NEW));
1925 inode->i_state &= ~I_NEW & ~I_CREATING;
1926 /*
1927 * Pairs with the barrier in prepare_to_wait_event() to make sure
1928 * ___wait_var_event() either sees the bit cleared or
1929 * waitqueue_active() check in wake_up_var() sees the waiter.
1930 */
1931 smp_mb();
1932 inode_wake_up_bit(inode, __I_NEW);
1933 spin_unlock(&inode->i_lock);
1934}
1935EXPORT_SYMBOL(d_instantiate_new);
1936
1937struct dentry *d_make_root(struct inode *root_inode)
1938{
1939 struct dentry *res = NULL;
1940
1941 if (root_inode) {
1942 res = d_alloc_anon(root_inode->i_sb);
1943 if (res)
1944 d_instantiate(res, root_inode);
1945 else
1946 iput(root_inode);
1947 }
1948 return res;
1949}
1950EXPORT_SYMBOL(d_make_root);
1951
1952static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected)
1953{
1954 struct super_block *sb;
1955 struct dentry *new, *res;
1956
1957 if (!inode)
1958 return ERR_PTR(-ESTALE);
1959 if (IS_ERR(inode))
1960 return ERR_CAST(inode);
1961
1962 sb = inode->i_sb;
1963
1964 res = d_find_any_alias(inode); /* existing alias? */
1965 if (res)
1966 goto out;
1967
1968 new = d_alloc_anon(sb);
1969 if (!new) {
1970 res = ERR_PTR(-ENOMEM);
1971 goto out;
1972 }
1973
1974 security_d_instantiate(new, inode);
1975 spin_lock(&inode->i_lock);
1976 res = __d_find_any_alias(inode); /* recheck under lock */
1977 if (likely(!res)) { /* still no alias, attach a disconnected dentry */
1978 unsigned add_flags = d_flags_for_inode(inode);
1979
1980 if (disconnected)
1981 add_flags |= DCACHE_DISCONNECTED;
1982
1983 spin_lock(&new->d_lock);
1984 __d_set_inode_and_type(new, inode, add_flags);
1985 hlist_add_head(&new->d_u.d_alias, &inode->i_dentry);
1986 if (!disconnected) {
1987 hlist_bl_lock(&sb->s_roots);
1988 hlist_bl_add_head(&new->d_hash, &sb->s_roots);
1989 hlist_bl_unlock(&sb->s_roots);
1990 }
1991 spin_unlock(&new->d_lock);
1992 spin_unlock(&inode->i_lock);
1993 inode = NULL; /* consumed by new->d_inode */
1994 res = new;
1995 } else {
1996 spin_unlock(&inode->i_lock);
1997 dput(new);
1998 }
1999
2000 out:
2001 iput(inode);
2002 return res;
2003}
2004
2005/**
2006 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
2007 * @inode: inode to allocate the dentry for
2008 *
2009 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
2010 * similar open by handle operations. The returned dentry may be anonymous,
2011 * or may have a full name (if the inode was already in the cache).
2012 *
2013 * When called on a directory inode, we must ensure that the inode only ever
2014 * has one dentry. If a dentry is found, that is returned instead of
2015 * allocating a new one.
2016 *
2017 * On successful return, the reference to the inode has been transferred
2018 * to the dentry. In case of an error the reference on the inode is released.
2019 * To make it easier to use in export operations a %NULL or IS_ERR inode may
2020 * be passed in and the error will be propagated to the return value,
2021 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
2022 */
2023struct dentry *d_obtain_alias(struct inode *inode)
2024{
2025 return __d_obtain_alias(inode, true);
2026}
2027EXPORT_SYMBOL(d_obtain_alias);
2028
2029/**
2030 * d_obtain_root - find or allocate a dentry for a given inode
2031 * @inode: inode to allocate the dentry for
2032 *
2033 * Obtain an IS_ROOT dentry for the root of a filesystem.
2034 *
2035 * We must ensure that directory inodes only ever have one dentry. If a
2036 * dentry is found, that is returned instead of allocating a new one.
2037 *
2038 * On successful return, the reference to the inode has been transferred
2039 * to the dentry. In case of an error the reference on the inode is
2040 * released. A %NULL or IS_ERR inode may be passed in and will be the
2041 * error will be propagate to the return value, with a %NULL @inode
2042 * replaced by ERR_PTR(-ESTALE).
2043 */
2044struct dentry *d_obtain_root(struct inode *inode)
2045{
2046 return __d_obtain_alias(inode, false);
2047}
2048EXPORT_SYMBOL(d_obtain_root);
2049
2050/**
2051 * d_add_ci - lookup or allocate new dentry with case-exact name
2052 * @dentry: the negative dentry that was passed to the parent's lookup func
2053 * @inode: the inode case-insensitive lookup has found
2054 * @name: the case-exact name to be associated with the returned dentry
2055 *
2056 * This is to avoid filling the dcache with case-insensitive names to the
2057 * same inode, only the actual correct case is stored in the dcache for
2058 * case-insensitive filesystems.
2059 *
2060 * For a case-insensitive lookup match and if the case-exact dentry
2061 * already exists in the dcache, use it and return it.
2062 *
2063 * If no entry exists with the exact case name, allocate new dentry with
2064 * the exact case, and return the spliced entry.
2065 */
2066struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
2067 struct qstr *name)
2068{
2069 struct dentry *found, *res;
2070
2071 /*
2072 * First check if a dentry matching the name already exists,
2073 * if not go ahead and create it now.
2074 */
2075 found = d_hash_and_lookup(dentry->d_parent, name);
2076 if (found) {
2077 iput(inode);
2078 return found;
2079 }
2080 if (d_in_lookup(dentry)) {
2081 found = d_alloc_parallel(dentry->d_parent, name,
2082 dentry->d_wait);
2083 if (IS_ERR(found) || !d_in_lookup(found)) {
2084 iput(inode);
2085 return found;
2086 }
2087 } else {
2088 found = d_alloc(dentry->d_parent, name);
2089 if (!found) {
2090 iput(inode);
2091 return ERR_PTR(-ENOMEM);
2092 }
2093 }
2094 res = d_splice_alias(inode, found);
2095 if (res) {
2096 d_lookup_done(found);
2097 dput(found);
2098 return res;
2099 }
2100 return found;
2101}
2102EXPORT_SYMBOL(d_add_ci);
2103
2104/**
2105 * d_same_name - compare dentry name with case-exact name
2106 * @dentry: the negative dentry that was passed to the parent's lookup func
2107 * @parent: parent dentry
2108 * @name: the case-exact name to be associated with the returned dentry
2109 *
2110 * Return: true if names are same, or false
2111 */
2112bool d_same_name(const struct dentry *dentry, const struct dentry *parent,
2113 const struct qstr *name)
2114{
2115 if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
2116 if (dentry->d_name.len != name->len)
2117 return false;
2118 return dentry_cmp(dentry, name->name, name->len) == 0;
2119 }
2120 return parent->d_op->d_compare(dentry,
2121 dentry->d_name.len, dentry->d_name.name,
2122 name) == 0;
2123}
2124EXPORT_SYMBOL_GPL(d_same_name);
2125
2126/*
2127 * This is __d_lookup_rcu() when the parent dentry has
2128 * DCACHE_OP_COMPARE, which makes things much nastier.
2129 */
2130static noinline struct dentry *__d_lookup_rcu_op_compare(
2131 const struct dentry *parent,
2132 const struct qstr *name,
2133 unsigned *seqp)
2134{
2135 u64 hashlen = name->hash_len;
2136 struct hlist_bl_head *b = d_hash(hashlen);
2137 struct hlist_bl_node *node;
2138 struct dentry *dentry;
2139
2140 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2141 int tlen;
2142 const char *tname;
2143 unsigned seq;
2144
2145seqretry:
2146 seq = raw_seqcount_begin(&dentry->d_seq);
2147 if (dentry->d_parent != parent)
2148 continue;
2149 if (d_unhashed(dentry))
2150 continue;
2151 if (dentry->d_name.hash != hashlen_hash(hashlen))
2152 continue;
2153 tlen = dentry->d_name.len;
2154 tname = dentry->d_name.name;
2155 /* we want a consistent (name,len) pair */
2156 if (read_seqcount_retry(&dentry->d_seq, seq)) {
2157 cpu_relax();
2158 goto seqretry;
2159 }
2160 if (parent->d_op->d_compare(dentry, tlen, tname, name) != 0)
2161 continue;
2162 *seqp = seq;
2163 return dentry;
2164 }
2165 return NULL;
2166}
2167
2168/**
2169 * __d_lookup_rcu - search for a dentry (racy, store-free)
2170 * @parent: parent dentry
2171 * @name: qstr of name we wish to find
2172 * @seqp: returns d_seq value at the point where the dentry was found
2173 * Returns: dentry, or NULL
2174 *
2175 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2176 * resolution (store-free path walking) design described in
2177 * Documentation/filesystems/path-lookup.txt.
2178 *
2179 * This is not to be used outside core vfs.
2180 *
2181 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2182 * held, and rcu_read_lock held. The returned dentry must not be stored into
2183 * without taking d_lock and checking d_seq sequence count against @seq
2184 * returned here.
2185 *
2186 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2187 * the returned dentry, so long as its parent's seqlock is checked after the
2188 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2189 * is formed, giving integrity down the path walk.
2190 *
2191 * NOTE! The caller *has* to check the resulting dentry against the sequence
2192 * number we've returned before using any of the resulting dentry state!
2193 */
2194struct dentry *__d_lookup_rcu(const struct dentry *parent,
2195 const struct qstr *name,
2196 unsigned *seqp)
2197{
2198 u64 hashlen = name->hash_len;
2199 const unsigned char *str = name->name;
2200 struct hlist_bl_head *b = d_hash(hashlen);
2201 struct hlist_bl_node *node;
2202 struct dentry *dentry;
2203
2204 /*
2205 * Note: There is significant duplication with __d_lookup_rcu which is
2206 * required to prevent single threaded performance regressions
2207 * especially on architectures where smp_rmb (in seqcounts) are costly.
2208 * Keep the two functions in sync.
2209 */
2210
2211 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE))
2212 return __d_lookup_rcu_op_compare(parent, name, seqp);
2213
2214 /*
2215 * The hash list is protected using RCU.
2216 *
2217 * Carefully use d_seq when comparing a candidate dentry, to avoid
2218 * races with d_move().
2219 *
2220 * It is possible that concurrent renames can mess up our list
2221 * walk here and result in missing our dentry, resulting in the
2222 * false-negative result. d_lookup() protects against concurrent
2223 * renames using rename_lock seqlock.
2224 *
2225 * See Documentation/filesystems/path-lookup.txt for more details.
2226 */
2227 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2228 unsigned seq;
2229
2230 /*
2231 * The dentry sequence count protects us from concurrent
2232 * renames, and thus protects parent and name fields.
2233 *
2234 * The caller must perform a seqcount check in order
2235 * to do anything useful with the returned dentry.
2236 *
2237 * NOTE! We do a "raw" seqcount_begin here. That means that
2238 * we don't wait for the sequence count to stabilize if it
2239 * is in the middle of a sequence change. If we do the slow
2240 * dentry compare, we will do seqretries until it is stable,
2241 * and if we end up with a successful lookup, we actually
2242 * want to exit RCU lookup anyway.
2243 *
2244 * Note that raw_seqcount_begin still *does* smp_rmb(), so
2245 * we are still guaranteed NUL-termination of ->d_name.name.
2246 */
2247 seq = raw_seqcount_begin(&dentry->d_seq);
2248 if (dentry->d_parent != parent)
2249 continue;
2250 if (d_unhashed(dentry))
2251 continue;
2252 if (dentry->d_name.hash_len != hashlen)
2253 continue;
2254 if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
2255 continue;
2256 *seqp = seq;
2257 return dentry;
2258 }
2259 return NULL;
2260}
2261
2262/**
2263 * d_lookup - search for a dentry
2264 * @parent: parent dentry
2265 * @name: qstr of name we wish to find
2266 * Returns: dentry, or NULL
2267 *
2268 * d_lookup searches the children of the parent dentry for the name in
2269 * question. If the dentry is found its reference count is incremented and the
2270 * dentry is returned. The caller must use dput to free the entry when it has
2271 * finished using it. %NULL is returned if the dentry does not exist.
2272 */
2273struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
2274{
2275 struct dentry *dentry;
2276 unsigned seq;
2277
2278 do {
2279 seq = read_seqbegin(&rename_lock);
2280 dentry = __d_lookup(parent, name);
2281 if (dentry)
2282 break;
2283 } while (read_seqretry(&rename_lock, seq));
2284 return dentry;
2285}
2286EXPORT_SYMBOL(d_lookup);
2287
2288/**
2289 * __d_lookup - search for a dentry (racy)
2290 * @parent: parent dentry
2291 * @name: qstr of name we wish to find
2292 * Returns: dentry, or NULL
2293 *
2294 * __d_lookup is like d_lookup, however it may (rarely) return a
2295 * false-negative result due to unrelated rename activity.
2296 *
2297 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2298 * however it must be used carefully, eg. with a following d_lookup in
2299 * the case of failure.
2300 *
2301 * __d_lookup callers must be commented.
2302 */
2303struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
2304{
2305 unsigned int hash = name->hash;
2306 struct hlist_bl_head *b = d_hash(hash);
2307 struct hlist_bl_node *node;
2308 struct dentry *found = NULL;
2309 struct dentry *dentry;
2310
2311 /*
2312 * Note: There is significant duplication with __d_lookup_rcu which is
2313 * required to prevent single threaded performance regressions
2314 * especially on architectures where smp_rmb (in seqcounts) are costly.
2315 * Keep the two functions in sync.
2316 */
2317
2318 /*
2319 * The hash list is protected using RCU.
2320 *
2321 * Take d_lock when comparing a candidate dentry, to avoid races
2322 * with d_move().
2323 *
2324 * It is possible that concurrent renames can mess up our list
2325 * walk here and result in missing our dentry, resulting in the
2326 * false-negative result. d_lookup() protects against concurrent
2327 * renames using rename_lock seqlock.
2328 *
2329 * See Documentation/filesystems/path-lookup.txt for more details.
2330 */
2331 rcu_read_lock();
2332
2333 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2334
2335 if (dentry->d_name.hash != hash)
2336 continue;
2337
2338 spin_lock(&dentry->d_lock);
2339 if (dentry->d_parent != parent)
2340 goto next;
2341 if (d_unhashed(dentry))
2342 goto next;
2343
2344 if (!d_same_name(dentry, parent, name))
2345 goto next;
2346
2347 dentry->d_lockref.count++;
2348 found = dentry;
2349 spin_unlock(&dentry->d_lock);
2350 break;
2351next:
2352 spin_unlock(&dentry->d_lock);
2353 }
2354 rcu_read_unlock();
2355
2356 return found;
2357}
2358
2359/**
2360 * d_hash_and_lookup - hash the qstr then search for a dentry
2361 * @dir: Directory to search in
2362 * @name: qstr of name we wish to find
2363 *
2364 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2365 */
2366struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2367{
2368 /*
2369 * Check for a fs-specific hash function. Note that we must
2370 * calculate the standard hash first, as the d_op->d_hash()
2371 * routine may choose to leave the hash value unchanged.
2372 */
2373 name->hash = full_name_hash(dir, name->name, name->len);
2374 if (dir->d_flags & DCACHE_OP_HASH) {
2375 int err = dir->d_op->d_hash(dir, name);
2376 if (unlikely(err < 0))
2377 return ERR_PTR(err);
2378 }
2379 return d_lookup(dir, name);
2380}
2381EXPORT_SYMBOL(d_hash_and_lookup);
2382
2383/*
2384 * When a file is deleted, we have two options:
2385 * - turn this dentry into a negative dentry
2386 * - unhash this dentry and free it.
2387 *
2388 * Usually, we want to just turn this into
2389 * a negative dentry, but if anybody else is
2390 * currently using the dentry or the inode
2391 * we can't do that and we fall back on removing
2392 * it from the hash queues and waiting for
2393 * it to be deleted later when it has no users
2394 */
2395
2396/**
2397 * d_delete - delete a dentry
2398 * @dentry: The dentry to delete
2399 *
2400 * Turn the dentry into a negative dentry if possible, otherwise
2401 * remove it from the hash queues so it can be deleted later
2402 */
2403
2404void d_delete(struct dentry * dentry)
2405{
2406 struct inode *inode = dentry->d_inode;
2407
2408 spin_lock(&inode->i_lock);
2409 spin_lock(&dentry->d_lock);
2410 /*
2411 * Are we the only user?
2412 */
2413 if (dentry->d_lockref.count == 1) {
2414 if (dentry_negative_policy)
2415 __d_drop(dentry);
2416 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2417 dentry_unlink_inode(dentry);
2418 } else {
2419 __d_drop(dentry);
2420 spin_unlock(&dentry->d_lock);
2421 spin_unlock(&inode->i_lock);
2422 }
2423}
2424EXPORT_SYMBOL(d_delete);
2425
2426static void __d_rehash(struct dentry *entry)
2427{
2428 struct hlist_bl_head *b = d_hash(entry->d_name.hash);
2429
2430 hlist_bl_lock(b);
2431 hlist_bl_add_head_rcu(&entry->d_hash, b);
2432 hlist_bl_unlock(b);
2433}
2434
2435/**
2436 * d_rehash - add an entry back to the hash
2437 * @entry: dentry to add to the hash
2438 *
2439 * Adds a dentry to the hash according to its name.
2440 */
2441
2442void d_rehash(struct dentry * entry)
2443{
2444 spin_lock(&entry->d_lock);
2445 __d_rehash(entry);
2446 spin_unlock(&entry->d_lock);
2447}
2448EXPORT_SYMBOL(d_rehash);
2449
2450static inline unsigned start_dir_add(struct inode *dir)
2451{
2452 preempt_disable_nested();
2453 for (;;) {
2454 unsigned n = dir->i_dir_seq;
2455 if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
2456 return n;
2457 cpu_relax();
2458 }
2459}
2460
2461static inline void end_dir_add(struct inode *dir, unsigned int n,
2462 wait_queue_head_t *d_wait)
2463{
2464 smp_store_release(&dir->i_dir_seq, n + 2);
2465 preempt_enable_nested();
2466 wake_up_all(d_wait);
2467}
2468
2469static void d_wait_lookup(struct dentry *dentry)
2470{
2471 if (d_in_lookup(dentry)) {
2472 DECLARE_WAITQUEUE(wait, current);
2473 add_wait_queue(dentry->d_wait, &wait);
2474 do {
2475 set_current_state(TASK_UNINTERRUPTIBLE);
2476 spin_unlock(&dentry->d_lock);
2477 schedule();
2478 spin_lock(&dentry->d_lock);
2479 } while (d_in_lookup(dentry));
2480 }
2481}
2482
2483struct dentry *d_alloc_parallel(struct dentry *parent,
2484 const struct qstr *name,
2485 wait_queue_head_t *wq)
2486{
2487 unsigned int hash = name->hash;
2488 struct hlist_bl_head *b = in_lookup_hash(parent, hash);
2489 struct hlist_bl_node *node;
2490 struct dentry *new = d_alloc(parent, name);
2491 struct dentry *dentry;
2492 unsigned seq, r_seq, d_seq;
2493
2494 if (unlikely(!new))
2495 return ERR_PTR(-ENOMEM);
2496
2497retry:
2498 rcu_read_lock();
2499 seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
2500 r_seq = read_seqbegin(&rename_lock);
2501 dentry = __d_lookup_rcu(parent, name, &d_seq);
2502 if (unlikely(dentry)) {
2503 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2504 rcu_read_unlock();
2505 goto retry;
2506 }
2507 if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
2508 rcu_read_unlock();
2509 dput(dentry);
2510 goto retry;
2511 }
2512 rcu_read_unlock();
2513 dput(new);
2514 return dentry;
2515 }
2516 if (unlikely(read_seqretry(&rename_lock, r_seq))) {
2517 rcu_read_unlock();
2518 goto retry;
2519 }
2520
2521 if (unlikely(seq & 1)) {
2522 rcu_read_unlock();
2523 goto retry;
2524 }
2525
2526 hlist_bl_lock(b);
2527 if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
2528 hlist_bl_unlock(b);
2529 rcu_read_unlock();
2530 goto retry;
2531 }
2532 /*
2533 * No changes for the parent since the beginning of d_lookup().
2534 * Since all removals from the chain happen with hlist_bl_lock(),
2535 * any potential in-lookup matches are going to stay here until
2536 * we unlock the chain. All fields are stable in everything
2537 * we encounter.
2538 */
2539 hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
2540 if (dentry->d_name.hash != hash)
2541 continue;
2542 if (dentry->d_parent != parent)
2543 continue;
2544 if (!d_same_name(dentry, parent, name))
2545 continue;
2546 hlist_bl_unlock(b);
2547 /* now we can try to grab a reference */
2548 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2549 rcu_read_unlock();
2550 goto retry;
2551 }
2552
2553 rcu_read_unlock();
2554 /*
2555 * somebody is likely to be still doing lookup for it;
2556 * wait for them to finish
2557 */
2558 spin_lock(&dentry->d_lock);
2559 d_wait_lookup(dentry);
2560 /*
2561 * it's not in-lookup anymore; in principle we should repeat
2562 * everything from dcache lookup, but it's likely to be what
2563 * d_lookup() would've found anyway. If it is, just return it;
2564 * otherwise we really have to repeat the whole thing.
2565 */
2566 if (unlikely(dentry->d_name.hash != hash))
2567 goto mismatch;
2568 if (unlikely(dentry->d_parent != parent))
2569 goto mismatch;
2570 if (unlikely(d_unhashed(dentry)))
2571 goto mismatch;
2572 if (unlikely(!d_same_name(dentry, parent, name)))
2573 goto mismatch;
2574 /* OK, it *is* a hashed match; return it */
2575 spin_unlock(&dentry->d_lock);
2576 dput(new);
2577 return dentry;
2578 }
2579 rcu_read_unlock();
2580 /* we can't take ->d_lock here; it's OK, though. */
2581 new->d_flags |= DCACHE_PAR_LOOKUP;
2582 new->d_wait = wq;
2583 hlist_bl_add_head(&new->d_u.d_in_lookup_hash, b);
2584 hlist_bl_unlock(b);
2585 return new;
2586mismatch:
2587 spin_unlock(&dentry->d_lock);
2588 dput(dentry);
2589 goto retry;
2590}
2591EXPORT_SYMBOL(d_alloc_parallel);
2592
2593/*
2594 * - Unhash the dentry
2595 * - Retrieve and clear the waitqueue head in dentry
2596 * - Return the waitqueue head
2597 */
2598static wait_queue_head_t *__d_lookup_unhash(struct dentry *dentry)
2599{
2600 wait_queue_head_t *d_wait;
2601 struct hlist_bl_head *b;
2602
2603 lockdep_assert_held(&dentry->d_lock);
2604
2605 b = in_lookup_hash(dentry->d_parent, dentry->d_name.hash);
2606 hlist_bl_lock(b);
2607 dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
2608 __hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
2609 d_wait = dentry->d_wait;
2610 dentry->d_wait = NULL;
2611 hlist_bl_unlock(b);
2612 INIT_HLIST_NODE(&dentry->d_u.d_alias);
2613 INIT_LIST_HEAD(&dentry->d_lru);
2614 return d_wait;
2615}
2616
2617void __d_lookup_unhash_wake(struct dentry *dentry)
2618{
2619 spin_lock(&dentry->d_lock);
2620 wake_up_all(__d_lookup_unhash(dentry));
2621 spin_unlock(&dentry->d_lock);
2622}
2623EXPORT_SYMBOL(__d_lookup_unhash_wake);
2624
2625/* inode->i_lock held if inode is non-NULL */
2626
2627static inline void __d_add(struct dentry *dentry, struct inode *inode)
2628{
2629 wait_queue_head_t *d_wait;
2630 struct inode *dir = NULL;
2631 unsigned n;
2632 spin_lock(&dentry->d_lock);
2633 if (unlikely(d_in_lookup(dentry))) {
2634 dir = dentry->d_parent->d_inode;
2635 n = start_dir_add(dir);
2636 d_wait = __d_lookup_unhash(dentry);
2637 }
2638 if (inode) {
2639 unsigned add_flags = d_flags_for_inode(inode);
2640 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2641 raw_write_seqcount_begin(&dentry->d_seq);
2642 __d_set_inode_and_type(dentry, inode, add_flags);
2643 raw_write_seqcount_end(&dentry->d_seq);
2644 fsnotify_update_flags(dentry);
2645 }
2646 __d_rehash(dentry);
2647 if (dir)
2648 end_dir_add(dir, n, d_wait);
2649 spin_unlock(&dentry->d_lock);
2650 if (inode)
2651 spin_unlock(&inode->i_lock);
2652}
2653
2654/**
2655 * d_add - add dentry to hash queues
2656 * @entry: dentry to add
2657 * @inode: The inode to attach to this dentry
2658 *
2659 * This adds the entry to the hash queues and initializes @inode.
2660 * The entry was actually filled in earlier during d_alloc().
2661 */
2662
2663void d_add(struct dentry *entry, struct inode *inode)
2664{
2665 if (inode) {
2666 security_d_instantiate(entry, inode);
2667 spin_lock(&inode->i_lock);
2668 }
2669 __d_add(entry, inode);
2670}
2671EXPORT_SYMBOL(d_add);
2672
2673/**
2674 * d_exact_alias - find and hash an exact unhashed alias
2675 * @entry: dentry to add
2676 * @inode: The inode to go with this dentry
2677 *
2678 * If an unhashed dentry with the same name/parent and desired
2679 * inode already exists, hash and return it. Otherwise, return
2680 * NULL.
2681 *
2682 * Parent directory should be locked.
2683 */
2684struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
2685{
2686 struct dentry *alias;
2687 unsigned int hash = entry->d_name.hash;
2688
2689 spin_lock(&inode->i_lock);
2690 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
2691 /*
2692 * Don't need alias->d_lock here, because aliases with
2693 * d_parent == entry->d_parent are not subject to name or
2694 * parent changes, because the parent inode i_mutex is held.
2695 */
2696 if (alias->d_name.hash != hash)
2697 continue;
2698 if (alias->d_parent != entry->d_parent)
2699 continue;
2700 if (!d_same_name(alias, entry->d_parent, &entry->d_name))
2701 continue;
2702 spin_lock(&alias->d_lock);
2703 if (!d_unhashed(alias)) {
2704 spin_unlock(&alias->d_lock);
2705 alias = NULL;
2706 } else {
2707 dget_dlock(alias);
2708 __d_rehash(alias);
2709 spin_unlock(&alias->d_lock);
2710 }
2711 spin_unlock(&inode->i_lock);
2712 return alias;
2713 }
2714 spin_unlock(&inode->i_lock);
2715 return NULL;
2716}
2717EXPORT_SYMBOL(d_exact_alias);
2718
2719static void swap_names(struct dentry *dentry, struct dentry *target)
2720{
2721 if (unlikely(dname_external(target))) {
2722 if (unlikely(dname_external(dentry))) {
2723 /*
2724 * Both external: swap the pointers
2725 */
2726 swap(target->d_name.name, dentry->d_name.name);
2727 } else {
2728 /*
2729 * dentry:internal, target:external. Steal target's
2730 * storage and make target internal.
2731 */
2732 memcpy(target->d_iname, dentry->d_name.name,
2733 dentry->d_name.len + 1);
2734 dentry->d_name.name = target->d_name.name;
2735 target->d_name.name = target->d_iname;
2736 }
2737 } else {
2738 if (unlikely(dname_external(dentry))) {
2739 /*
2740 * dentry:external, target:internal. Give dentry's
2741 * storage to target and make dentry internal
2742 */
2743 memcpy(dentry->d_iname, target->d_name.name,
2744 target->d_name.len + 1);
2745 target->d_name.name = dentry->d_name.name;
2746 dentry->d_name.name = dentry->d_iname;
2747 } else {
2748 /*
2749 * Both are internal.
2750 */
2751 unsigned int i;
2752 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
2753 for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
2754 swap(((long *) &dentry->d_iname)[i],
2755 ((long *) &target->d_iname)[i]);
2756 }
2757 }
2758 }
2759 swap(dentry->d_name.hash_len, target->d_name.hash_len);
2760}
2761
2762static void copy_name(struct dentry *dentry, struct dentry *target)
2763{
2764 struct external_name *old_name = NULL;
2765 if (unlikely(dname_external(dentry)))
2766 old_name = external_name(dentry);
2767 if (unlikely(dname_external(target))) {
2768 atomic_inc(&external_name(target)->u.count);
2769 dentry->d_name = target->d_name;
2770 } else {
2771 memcpy(dentry->d_iname, target->d_name.name,
2772 target->d_name.len + 1);
2773 dentry->d_name.name = dentry->d_iname;
2774 dentry->d_name.hash_len = target->d_name.hash_len;
2775 }
2776 if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
2777 kfree_rcu(old_name, u.head);
2778}
2779
2780/*
2781 * __d_move - move a dentry
2782 * @dentry: entry to move
2783 * @target: new dentry
2784 * @exchange: exchange the two dentries
2785 *
2786 * Update the dcache to reflect the move of a file name. Negative
2787 * dcache entries should not be moved in this way. Caller must hold
2788 * rename_lock, the i_mutex of the source and target directories,
2789 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2790 */
2791static void __d_move(struct dentry *dentry, struct dentry *target,
2792 bool exchange)
2793{
2794 struct dentry *old_parent, *p;
2795 wait_queue_head_t *d_wait;
2796 struct inode *dir = NULL;
2797 unsigned n;
2798
2799 WARN_ON(!dentry->d_inode);
2800 if (WARN_ON(dentry == target))
2801 return;
2802
2803 BUG_ON(d_ancestor(target, dentry));
2804 old_parent = dentry->d_parent;
2805 p = d_ancestor(old_parent, target);
2806 if (IS_ROOT(dentry)) {
2807 BUG_ON(p);
2808 spin_lock(&target->d_parent->d_lock);
2809 } else if (!p) {
2810 /* target is not a descendent of dentry->d_parent */
2811 spin_lock(&target->d_parent->d_lock);
2812 spin_lock_nested(&old_parent->d_lock, DENTRY_D_LOCK_NESTED);
2813 } else {
2814 BUG_ON(p == dentry);
2815 spin_lock(&old_parent->d_lock);
2816 if (p != target)
2817 spin_lock_nested(&target->d_parent->d_lock,
2818 DENTRY_D_LOCK_NESTED);
2819 }
2820 spin_lock_nested(&dentry->d_lock, 2);
2821 spin_lock_nested(&target->d_lock, 3);
2822
2823 if (unlikely(d_in_lookup(target))) {
2824 dir = target->d_parent->d_inode;
2825 n = start_dir_add(dir);
2826 d_wait = __d_lookup_unhash(target);
2827 }
2828
2829 write_seqcount_begin(&dentry->d_seq);
2830 write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
2831
2832 /* unhash both */
2833 if (!d_unhashed(dentry))
2834 ___d_drop(dentry);
2835 if (!d_unhashed(target))
2836 ___d_drop(target);
2837
2838 /* ... and switch them in the tree */
2839 dentry->d_parent = target->d_parent;
2840 if (!exchange) {
2841 copy_name(dentry, target);
2842 target->d_hash.pprev = NULL;
2843 dentry->d_parent->d_lockref.count++;
2844 if (dentry != old_parent) /* wasn't IS_ROOT */
2845 WARN_ON(!--old_parent->d_lockref.count);
2846 } else {
2847 target->d_parent = old_parent;
2848 swap_names(dentry, target);
2849 if (!hlist_unhashed(&target->d_sib))
2850 __hlist_del(&target->d_sib);
2851 hlist_add_head(&target->d_sib, &target->d_parent->d_children);
2852 __d_rehash(target);
2853 fsnotify_update_flags(target);
2854 }
2855 if (!hlist_unhashed(&dentry->d_sib))
2856 __hlist_del(&dentry->d_sib);
2857 hlist_add_head(&dentry->d_sib, &dentry->d_parent->d_children);
2858 __d_rehash(dentry);
2859 fsnotify_update_flags(dentry);
2860 fscrypt_handle_d_move(dentry);
2861
2862 write_seqcount_end(&target->d_seq);
2863 write_seqcount_end(&dentry->d_seq);
2864
2865 if (dir)
2866 end_dir_add(dir, n, d_wait);
2867
2868 if (dentry->d_parent != old_parent)
2869 spin_unlock(&dentry->d_parent->d_lock);
2870 if (dentry != old_parent)
2871 spin_unlock(&old_parent->d_lock);
2872 spin_unlock(&target->d_lock);
2873 spin_unlock(&dentry->d_lock);
2874}
2875
2876/*
2877 * d_move - move a dentry
2878 * @dentry: entry to move
2879 * @target: new dentry
2880 *
2881 * Update the dcache to reflect the move of a file name. Negative
2882 * dcache entries should not be moved in this way. See the locking
2883 * requirements for __d_move.
2884 */
2885void d_move(struct dentry *dentry, struct dentry *target)
2886{
2887 write_seqlock(&rename_lock);
2888 __d_move(dentry, target, false);
2889 write_sequnlock(&rename_lock);
2890}
2891EXPORT_SYMBOL(d_move);
2892
2893/*
2894 * d_exchange - exchange two dentries
2895 * @dentry1: first dentry
2896 * @dentry2: second dentry
2897 */
2898void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
2899{
2900 write_seqlock(&rename_lock);
2901
2902 WARN_ON(!dentry1->d_inode);
2903 WARN_ON(!dentry2->d_inode);
2904 WARN_ON(IS_ROOT(dentry1));
2905 WARN_ON(IS_ROOT(dentry2));
2906
2907 __d_move(dentry1, dentry2, true);
2908
2909 write_sequnlock(&rename_lock);
2910}
2911
2912/**
2913 * d_ancestor - search for an ancestor
2914 * @p1: ancestor dentry
2915 * @p2: child dentry
2916 *
2917 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2918 * an ancestor of p2, else NULL.
2919 */
2920struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2921{
2922 struct dentry *p;
2923
2924 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2925 if (p->d_parent == p1)
2926 return p;
2927 }
2928 return NULL;
2929}
2930
2931/*
2932 * This helper attempts to cope with remotely renamed directories
2933 *
2934 * It assumes that the caller is already holding
2935 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2936 *
2937 * Note: If ever the locking in lock_rename() changes, then please
2938 * remember to update this too...
2939 */
2940static int __d_unalias(struct dentry *dentry, struct dentry *alias)
2941{
2942 struct mutex *m1 = NULL;
2943 struct rw_semaphore *m2 = NULL;
2944 int ret = -ESTALE;
2945
2946 /* If alias and dentry share a parent, then no extra locks required */
2947 if (alias->d_parent == dentry->d_parent)
2948 goto out_unalias;
2949
2950 /* See lock_rename() */
2951 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
2952 goto out_err;
2953 m1 = &dentry->d_sb->s_vfs_rename_mutex;
2954 if (!inode_trylock_shared(alias->d_parent->d_inode))
2955 goto out_err;
2956 m2 = &alias->d_parent->d_inode->i_rwsem;
2957out_unalias:
2958 __d_move(alias, dentry, false);
2959 ret = 0;
2960out_err:
2961 if (m2)
2962 up_read(m2);
2963 if (m1)
2964 mutex_unlock(m1);
2965 return ret;
2966}
2967
2968/**
2969 * d_splice_alias - splice a disconnected dentry into the tree if one exists
2970 * @inode: the inode which may have a disconnected dentry
2971 * @dentry: a negative dentry which we want to point to the inode.
2972 *
2973 * If inode is a directory and has an IS_ROOT alias, then d_move that in
2974 * place of the given dentry and return it, else simply d_add the inode
2975 * to the dentry and return NULL.
2976 *
2977 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
2978 * we should error out: directories can't have multiple aliases.
2979 *
2980 * This is needed in the lookup routine of any filesystem that is exportable
2981 * (via knfsd) so that we can build dcache paths to directories effectively.
2982 *
2983 * If a dentry was found and moved, then it is returned. Otherwise NULL
2984 * is returned. This matches the expected return value of ->lookup.
2985 *
2986 * Cluster filesystems may call this function with a negative, hashed dentry.
2987 * In that case, we know that the inode will be a regular file, and also this
2988 * will only occur during atomic_open. So we need to check for the dentry
2989 * being already hashed only in the final case.
2990 */
2991struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
2992{
2993 if (IS_ERR(inode))
2994 return ERR_CAST(inode);
2995
2996 BUG_ON(!d_unhashed(dentry));
2997
2998 if (!inode)
2999 goto out;
3000
3001 security_d_instantiate(dentry, inode);
3002 spin_lock(&inode->i_lock);
3003 if (S_ISDIR(inode->i_mode)) {
3004 struct dentry *new = __d_find_any_alias(inode);
3005 if (unlikely(new)) {
3006 /* The reference to new ensures it remains an alias */
3007 spin_unlock(&inode->i_lock);
3008 write_seqlock(&rename_lock);
3009 if (unlikely(d_ancestor(new, dentry))) {
3010 write_sequnlock(&rename_lock);
3011 dput(new);
3012 new = ERR_PTR(-ELOOP);
3013 pr_warn_ratelimited(
3014 "VFS: Lookup of '%s' in %s %s"
3015 " would have caused loop\n",
3016 dentry->d_name.name,
3017 inode->i_sb->s_type->name,
3018 inode->i_sb->s_id);
3019 } else if (!IS_ROOT(new)) {
3020 struct dentry *old_parent = dget(new->d_parent);
3021 int err = __d_unalias(dentry, new);
3022 write_sequnlock(&rename_lock);
3023 if (err) {
3024 dput(new);
3025 new = ERR_PTR(err);
3026 }
3027 dput(old_parent);
3028 } else {
3029 __d_move(new, dentry, false);
3030 write_sequnlock(&rename_lock);
3031 }
3032 iput(inode);
3033 return new;
3034 }
3035 }
3036out:
3037 __d_add(dentry, inode);
3038 return NULL;
3039}
3040EXPORT_SYMBOL(d_splice_alias);
3041
3042/*
3043 * Test whether new_dentry is a subdirectory of old_dentry.
3044 *
3045 * Trivially implemented using the dcache structure
3046 */
3047
3048/**
3049 * is_subdir - is new dentry a subdirectory of old_dentry
3050 * @new_dentry: new dentry
3051 * @old_dentry: old dentry
3052 *
3053 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3054 * Returns false otherwise.
3055 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3056 */
3057
3058bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
3059{
3060 bool subdir;
3061 unsigned seq;
3062
3063 if (new_dentry == old_dentry)
3064 return true;
3065
3066 /* Access d_parent under rcu as d_move() may change it. */
3067 rcu_read_lock();
3068 seq = read_seqbegin(&rename_lock);
3069 subdir = d_ancestor(old_dentry, new_dentry);
3070 /* Try lockless once... */
3071 if (read_seqretry(&rename_lock, seq)) {
3072 /* ...else acquire lock for progress even on deep chains. */
3073 read_seqlock_excl(&rename_lock);
3074 subdir = d_ancestor(old_dentry, new_dentry);
3075 read_sequnlock_excl(&rename_lock);
3076 }
3077 rcu_read_unlock();
3078 return subdir;
3079}
3080EXPORT_SYMBOL(is_subdir);
3081
3082static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
3083{
3084 struct dentry *root = data;
3085 if (dentry != root) {
3086 if (d_unhashed(dentry) || !dentry->d_inode)
3087 return D_WALK_SKIP;
3088
3089 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
3090 dentry->d_flags |= DCACHE_GENOCIDE;
3091 dentry->d_lockref.count--;
3092 }
3093 }
3094 return D_WALK_CONTINUE;
3095}
3096
3097void d_genocide(struct dentry *parent)
3098{
3099 d_walk(parent, parent, d_genocide_kill);
3100}
3101
3102void d_mark_tmpfile(struct file *file, struct inode *inode)
3103{
3104 struct dentry *dentry = file->f_path.dentry;
3105
3106 BUG_ON(dentry->d_name.name != dentry->d_iname ||
3107 !hlist_unhashed(&dentry->d_u.d_alias) ||
3108 !d_unlinked(dentry));
3109 spin_lock(&dentry->d_parent->d_lock);
3110 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
3111 dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
3112 (unsigned long long)inode->i_ino);
3113 spin_unlock(&dentry->d_lock);
3114 spin_unlock(&dentry->d_parent->d_lock);
3115}
3116EXPORT_SYMBOL(d_mark_tmpfile);
3117
3118void d_tmpfile(struct file *file, struct inode *inode)
3119{
3120 struct dentry *dentry = file->f_path.dentry;
3121
3122 inode_dec_link_count(inode);
3123 d_mark_tmpfile(file, inode);
3124 d_instantiate(dentry, inode);
3125}
3126EXPORT_SYMBOL(d_tmpfile);
3127
3128/*
3129 * Obtain inode number of the parent dentry.
3130 */
3131ino_t d_parent_ino(struct dentry *dentry)
3132{
3133 struct dentry *parent;
3134 struct inode *iparent;
3135 unsigned seq;
3136 ino_t ret;
3137
3138 scoped_guard(rcu) {
3139 seq = raw_seqcount_begin(&dentry->d_seq);
3140 parent = READ_ONCE(dentry->d_parent);
3141 iparent = d_inode_rcu(parent);
3142 if (likely(iparent)) {
3143 ret = iparent->i_ino;
3144 if (!read_seqcount_retry(&dentry->d_seq, seq))
3145 return ret;
3146 }
3147 }
3148
3149 spin_lock(&dentry->d_lock);
3150 ret = dentry->d_parent->d_inode->i_ino;
3151 spin_unlock(&dentry->d_lock);
3152 return ret;
3153}
3154EXPORT_SYMBOL(d_parent_ino);
3155
3156static __initdata unsigned long dhash_entries;
3157static int __init set_dhash_entries(char *str)
3158{
3159 if (!str)
3160 return 0;
3161 dhash_entries = simple_strtoul(str, &str, 0);
3162 return 1;
3163}
3164__setup("dhash_entries=", set_dhash_entries);
3165
3166static void __init dcache_init_early(void)
3167{
3168 /* If hashes are distributed across NUMA nodes, defer
3169 * hash allocation until vmalloc space is available.
3170 */
3171 if (hashdist)
3172 return;
3173
3174 dentry_hashtable =
3175 alloc_large_system_hash("Dentry cache",
3176 sizeof(struct hlist_bl_head),
3177 dhash_entries,
3178 13,
3179 HASH_EARLY | HASH_ZERO,
3180 &d_hash_shift,
3181 NULL,
3182 0,
3183 0);
3184 d_hash_shift = 32 - d_hash_shift;
3185
3186 runtime_const_init(shift, d_hash_shift);
3187 runtime_const_init(ptr, dentry_hashtable);
3188}
3189
3190static void __init dcache_init(void)
3191{
3192 /*
3193 * A constructor could be added for stable state like the lists,
3194 * but it is probably not worth it because of the cache nature
3195 * of the dcache.
3196 */
3197 dentry_cache = KMEM_CACHE_USERCOPY(dentry,
3198 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_ACCOUNT,
3199 d_iname);
3200
3201 /* Hash may have been set up in dcache_init_early */
3202 if (!hashdist)
3203 return;
3204
3205 dentry_hashtable =
3206 alloc_large_system_hash("Dentry cache",
3207 sizeof(struct hlist_bl_head),
3208 dhash_entries,
3209 13,
3210 HASH_ZERO,
3211 &d_hash_shift,
3212 NULL,
3213 0,
3214 0);
3215 d_hash_shift = 32 - d_hash_shift;
3216
3217 runtime_const_init(shift, d_hash_shift);
3218 runtime_const_init(ptr, dentry_hashtable);
3219}
3220
3221/* SLAB cache for __getname() consumers */
3222struct kmem_cache *names_cachep __ro_after_init;
3223EXPORT_SYMBOL(names_cachep);
3224
3225void __init vfs_caches_init_early(void)
3226{
3227 int i;
3228
3229 for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++)
3230 INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]);
3231
3232 dcache_init_early();
3233 inode_init_early();
3234}
3235
3236void __init vfs_caches_init(void)
3237{
3238 names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0,
3239 SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL);
3240
3241 dcache_init();
3242 inode_init();
3243 files_init();
3244 files_maxfiles_init();
3245 mnt_init();
3246 bdev_cache_init();
3247 chrdev_init();
3248}
1/*
2 * fs/dcache.c
3 *
4 * Complete reimplementation
5 * (C) 1997 Thomas Schoebel-Theuer,
6 * with heavy changes by Linus Torvalds
7 */
8
9/*
10 * Notes on the allocation strategy:
11 *
12 * The dcache is a master of the icache - whenever a dcache entry
13 * exists, the inode will always exist. "iput()" is done either when
14 * the dcache entry is deleted or garbage collected.
15 */
16
17#include <linux/syscalls.h>
18#include <linux/string.h>
19#include <linux/mm.h>
20#include <linux/fs.h>
21#include <linux/fsnotify.h>
22#include <linux/slab.h>
23#include <linux/init.h>
24#include <linux/hash.h>
25#include <linux/cache.h>
26#include <linux/export.h>
27#include <linux/mount.h>
28#include <linux/file.h>
29#include <linux/uaccess.h>
30#include <linux/security.h>
31#include <linux/seqlock.h>
32#include <linux/swap.h>
33#include <linux/bootmem.h>
34#include <linux/fs_struct.h>
35#include <linux/hardirq.h>
36#include <linux/bit_spinlock.h>
37#include <linux/rculist_bl.h>
38#include <linux/prefetch.h>
39#include <linux/ratelimit.h>
40#include <linux/list_lru.h>
41#include <linux/kasan.h>
42
43#include "internal.h"
44#include "mount.h"
45
46/*
47 * Usage:
48 * dcache->d_inode->i_lock protects:
49 * - i_dentry, d_u.d_alias, d_inode of aliases
50 * dcache_hash_bucket lock protects:
51 * - the dcache hash table
52 * s_anon bl list spinlock protects:
53 * - the s_anon list (see __d_drop)
54 * dentry->d_sb->s_dentry_lru_lock protects:
55 * - the dcache lru lists and counters
56 * d_lock protects:
57 * - d_flags
58 * - d_name
59 * - d_lru
60 * - d_count
61 * - d_unhashed()
62 * - d_parent and d_subdirs
63 * - childrens' d_child and d_parent
64 * - d_u.d_alias, d_inode
65 *
66 * Ordering:
67 * dentry->d_inode->i_lock
68 * dentry->d_lock
69 * dentry->d_sb->s_dentry_lru_lock
70 * dcache_hash_bucket lock
71 * s_anon lock
72 *
73 * If there is an ancestor relationship:
74 * dentry->d_parent->...->d_parent->d_lock
75 * ...
76 * dentry->d_parent->d_lock
77 * dentry->d_lock
78 *
79 * If no ancestor relationship:
80 * if (dentry1 < dentry2)
81 * dentry1->d_lock
82 * dentry2->d_lock
83 */
84int sysctl_vfs_cache_pressure __read_mostly = 100;
85EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
86
87__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
88
89EXPORT_SYMBOL(rename_lock);
90
91static struct kmem_cache *dentry_cache __read_mostly;
92
93/*
94 * This is the single most critical data structure when it comes
95 * to the dcache: the hashtable for lookups. Somebody should try
96 * to make this good - I've just made it work.
97 *
98 * This hash-function tries to avoid losing too many bits of hash
99 * information, yet avoid using a prime hash-size or similar.
100 */
101
102static unsigned int d_hash_mask __read_mostly;
103static unsigned int d_hash_shift __read_mostly;
104
105static struct hlist_bl_head *dentry_hashtable __read_mostly;
106
107static inline struct hlist_bl_head *d_hash(unsigned int hash)
108{
109 return dentry_hashtable + (hash >> (32 - d_hash_shift));
110}
111
112#define IN_LOOKUP_SHIFT 10
113static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT];
114
115static inline struct hlist_bl_head *in_lookup_hash(const struct dentry *parent,
116 unsigned int hash)
117{
118 hash += (unsigned long) parent / L1_CACHE_BYTES;
119 return in_lookup_hashtable + hash_32(hash, IN_LOOKUP_SHIFT);
120}
121
122
123/* Statistics gathering. */
124struct dentry_stat_t dentry_stat = {
125 .age_limit = 45,
126};
127
128static DEFINE_PER_CPU(long, nr_dentry);
129static DEFINE_PER_CPU(long, nr_dentry_unused);
130
131#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
132
133/*
134 * Here we resort to our own counters instead of using generic per-cpu counters
135 * for consistency with what the vfs inode code does. We are expected to harvest
136 * better code and performance by having our own specialized counters.
137 *
138 * Please note that the loop is done over all possible CPUs, not over all online
139 * CPUs. The reason for this is that we don't want to play games with CPUs going
140 * on and off. If one of them goes off, we will just keep their counters.
141 *
142 * glommer: See cffbc8a for details, and if you ever intend to change this,
143 * please update all vfs counters to match.
144 */
145static long get_nr_dentry(void)
146{
147 int i;
148 long sum = 0;
149 for_each_possible_cpu(i)
150 sum += per_cpu(nr_dentry, i);
151 return sum < 0 ? 0 : sum;
152}
153
154static long get_nr_dentry_unused(void)
155{
156 int i;
157 long sum = 0;
158 for_each_possible_cpu(i)
159 sum += per_cpu(nr_dentry_unused, i);
160 return sum < 0 ? 0 : sum;
161}
162
163int proc_nr_dentry(struct ctl_table *table, int write, void __user *buffer,
164 size_t *lenp, loff_t *ppos)
165{
166 dentry_stat.nr_dentry = get_nr_dentry();
167 dentry_stat.nr_unused = get_nr_dentry_unused();
168 return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
169}
170#endif
171
172/*
173 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
174 * The strings are both count bytes long, and count is non-zero.
175 */
176#ifdef CONFIG_DCACHE_WORD_ACCESS
177
178#include <asm/word-at-a-time.h>
179/*
180 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
181 * aligned allocation for this particular component. We don't
182 * strictly need the load_unaligned_zeropad() safety, but it
183 * doesn't hurt either.
184 *
185 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
186 * need the careful unaligned handling.
187 */
188static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
189{
190 unsigned long a,b,mask;
191
192 for (;;) {
193 a = *(unsigned long *)cs;
194 b = load_unaligned_zeropad(ct);
195 if (tcount < sizeof(unsigned long))
196 break;
197 if (unlikely(a != b))
198 return 1;
199 cs += sizeof(unsigned long);
200 ct += sizeof(unsigned long);
201 tcount -= sizeof(unsigned long);
202 if (!tcount)
203 return 0;
204 }
205 mask = bytemask_from_count(tcount);
206 return unlikely(!!((a ^ b) & mask));
207}
208
209#else
210
211static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
212{
213 do {
214 if (*cs != *ct)
215 return 1;
216 cs++;
217 ct++;
218 tcount--;
219 } while (tcount);
220 return 0;
221}
222
223#endif
224
225static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
226{
227 /*
228 * Be careful about RCU walk racing with rename:
229 * use 'lockless_dereference' to fetch the name pointer.
230 *
231 * NOTE! Even if a rename will mean that the length
232 * was not loaded atomically, we don't care. The
233 * RCU walk will check the sequence count eventually,
234 * and catch it. And we won't overrun the buffer,
235 * because we're reading the name pointer atomically,
236 * and a dentry name is guaranteed to be properly
237 * terminated with a NUL byte.
238 *
239 * End result: even if 'len' is wrong, we'll exit
240 * early because the data cannot match (there can
241 * be no NUL in the ct/tcount data)
242 */
243 const unsigned char *cs = lockless_dereference(dentry->d_name.name);
244
245 return dentry_string_cmp(cs, ct, tcount);
246}
247
248struct external_name {
249 union {
250 atomic_t count;
251 struct rcu_head head;
252 } u;
253 unsigned char name[];
254};
255
256static inline struct external_name *external_name(struct dentry *dentry)
257{
258 return container_of(dentry->d_name.name, struct external_name, name[0]);
259}
260
261static void __d_free(struct rcu_head *head)
262{
263 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
264
265 kmem_cache_free(dentry_cache, dentry);
266}
267
268static void __d_free_external(struct rcu_head *head)
269{
270 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
271 kfree(external_name(dentry));
272 kmem_cache_free(dentry_cache, dentry);
273}
274
275static inline int dname_external(const struct dentry *dentry)
276{
277 return dentry->d_name.name != dentry->d_iname;
278}
279
280static inline void __d_set_inode_and_type(struct dentry *dentry,
281 struct inode *inode,
282 unsigned type_flags)
283{
284 unsigned flags;
285
286 dentry->d_inode = inode;
287 flags = READ_ONCE(dentry->d_flags);
288 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
289 flags |= type_flags;
290 WRITE_ONCE(dentry->d_flags, flags);
291}
292
293static inline void __d_clear_type_and_inode(struct dentry *dentry)
294{
295 unsigned flags = READ_ONCE(dentry->d_flags);
296
297 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
298 WRITE_ONCE(dentry->d_flags, flags);
299 dentry->d_inode = NULL;
300}
301
302static void dentry_free(struct dentry *dentry)
303{
304 WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias));
305 if (unlikely(dname_external(dentry))) {
306 struct external_name *p = external_name(dentry);
307 if (likely(atomic_dec_and_test(&p->u.count))) {
308 call_rcu(&dentry->d_u.d_rcu, __d_free_external);
309 return;
310 }
311 }
312 /* if dentry was never visible to RCU, immediate free is OK */
313 if (!(dentry->d_flags & DCACHE_RCUACCESS))
314 __d_free(&dentry->d_u.d_rcu);
315 else
316 call_rcu(&dentry->d_u.d_rcu, __d_free);
317}
318
319/*
320 * Release the dentry's inode, using the filesystem
321 * d_iput() operation if defined.
322 */
323static void dentry_unlink_inode(struct dentry * dentry)
324 __releases(dentry->d_lock)
325 __releases(dentry->d_inode->i_lock)
326{
327 struct inode *inode = dentry->d_inode;
328 bool hashed = !d_unhashed(dentry);
329
330 if (hashed)
331 raw_write_seqcount_begin(&dentry->d_seq);
332 __d_clear_type_and_inode(dentry);
333 hlist_del_init(&dentry->d_u.d_alias);
334 if (hashed)
335 raw_write_seqcount_end(&dentry->d_seq);
336 spin_unlock(&dentry->d_lock);
337 spin_unlock(&inode->i_lock);
338 if (!inode->i_nlink)
339 fsnotify_inoderemove(inode);
340 if (dentry->d_op && dentry->d_op->d_iput)
341 dentry->d_op->d_iput(dentry, inode);
342 else
343 iput(inode);
344}
345
346/*
347 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
348 * is in use - which includes both the "real" per-superblock
349 * LRU list _and_ the DCACHE_SHRINK_LIST use.
350 *
351 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
352 * on the shrink list (ie not on the superblock LRU list).
353 *
354 * The per-cpu "nr_dentry_unused" counters are updated with
355 * the DCACHE_LRU_LIST bit.
356 *
357 * These helper functions make sure we always follow the
358 * rules. d_lock must be held by the caller.
359 */
360#define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
361static void d_lru_add(struct dentry *dentry)
362{
363 D_FLAG_VERIFY(dentry, 0);
364 dentry->d_flags |= DCACHE_LRU_LIST;
365 this_cpu_inc(nr_dentry_unused);
366 WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
367}
368
369static void d_lru_del(struct dentry *dentry)
370{
371 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
372 dentry->d_flags &= ~DCACHE_LRU_LIST;
373 this_cpu_dec(nr_dentry_unused);
374 WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
375}
376
377static void d_shrink_del(struct dentry *dentry)
378{
379 D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
380 list_del_init(&dentry->d_lru);
381 dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
382 this_cpu_dec(nr_dentry_unused);
383}
384
385static void d_shrink_add(struct dentry *dentry, struct list_head *list)
386{
387 D_FLAG_VERIFY(dentry, 0);
388 list_add(&dentry->d_lru, list);
389 dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST;
390 this_cpu_inc(nr_dentry_unused);
391}
392
393/*
394 * These can only be called under the global LRU lock, ie during the
395 * callback for freeing the LRU list. "isolate" removes it from the
396 * LRU lists entirely, while shrink_move moves it to the indicated
397 * private list.
398 */
399static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry)
400{
401 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
402 dentry->d_flags &= ~DCACHE_LRU_LIST;
403 this_cpu_dec(nr_dentry_unused);
404 list_lru_isolate(lru, &dentry->d_lru);
405}
406
407static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
408 struct list_head *list)
409{
410 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
411 dentry->d_flags |= DCACHE_SHRINK_LIST;
412 list_lru_isolate_move(lru, &dentry->d_lru, list);
413}
414
415/*
416 * dentry_lru_(add|del)_list) must be called with d_lock held.
417 */
418static void dentry_lru_add(struct dentry *dentry)
419{
420 if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
421 d_lru_add(dentry);
422}
423
424/**
425 * d_drop - drop a dentry
426 * @dentry: dentry to drop
427 *
428 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
429 * be found through a VFS lookup any more. Note that this is different from
430 * deleting the dentry - d_delete will try to mark the dentry negative if
431 * possible, giving a successful _negative_ lookup, while d_drop will
432 * just make the cache lookup fail.
433 *
434 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
435 * reason (NFS timeouts or autofs deletes).
436 *
437 * __d_drop requires dentry->d_lock.
438 */
439void __d_drop(struct dentry *dentry)
440{
441 if (!d_unhashed(dentry)) {
442 struct hlist_bl_head *b;
443 /*
444 * Hashed dentries are normally on the dentry hashtable,
445 * with the exception of those newly allocated by
446 * d_obtain_alias, which are always IS_ROOT:
447 */
448 if (unlikely(IS_ROOT(dentry)))
449 b = &dentry->d_sb->s_anon;
450 else
451 b = d_hash(dentry->d_name.hash);
452
453 hlist_bl_lock(b);
454 __hlist_bl_del(&dentry->d_hash);
455 dentry->d_hash.pprev = NULL;
456 hlist_bl_unlock(b);
457 /* After this call, in-progress rcu-walk path lookup will fail. */
458 write_seqcount_invalidate(&dentry->d_seq);
459 }
460}
461EXPORT_SYMBOL(__d_drop);
462
463void d_drop(struct dentry *dentry)
464{
465 spin_lock(&dentry->d_lock);
466 __d_drop(dentry);
467 spin_unlock(&dentry->d_lock);
468}
469EXPORT_SYMBOL(d_drop);
470
471static inline void dentry_unlist(struct dentry *dentry, struct dentry *parent)
472{
473 struct dentry *next;
474 /*
475 * Inform d_walk() and shrink_dentry_list() that we are no longer
476 * attached to the dentry tree
477 */
478 dentry->d_flags |= DCACHE_DENTRY_KILLED;
479 if (unlikely(list_empty(&dentry->d_child)))
480 return;
481 __list_del_entry(&dentry->d_child);
482 /*
483 * Cursors can move around the list of children. While we'd been
484 * a normal list member, it didn't matter - ->d_child.next would've
485 * been updated. However, from now on it won't be and for the
486 * things like d_walk() it might end up with a nasty surprise.
487 * Normally d_walk() doesn't care about cursors moving around -
488 * ->d_lock on parent prevents that and since a cursor has no children
489 * of its own, we get through it without ever unlocking the parent.
490 * There is one exception, though - if we ascend from a child that
491 * gets killed as soon as we unlock it, the next sibling is found
492 * using the value left in its ->d_child.next. And if _that_
493 * pointed to a cursor, and cursor got moved (e.g. by lseek())
494 * before d_walk() regains parent->d_lock, we'll end up skipping
495 * everything the cursor had been moved past.
496 *
497 * Solution: make sure that the pointer left behind in ->d_child.next
498 * points to something that won't be moving around. I.e. skip the
499 * cursors.
500 */
501 while (dentry->d_child.next != &parent->d_subdirs) {
502 next = list_entry(dentry->d_child.next, struct dentry, d_child);
503 if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR)))
504 break;
505 dentry->d_child.next = next->d_child.next;
506 }
507}
508
509static void __dentry_kill(struct dentry *dentry)
510{
511 struct dentry *parent = NULL;
512 bool can_free = true;
513 if (!IS_ROOT(dentry))
514 parent = dentry->d_parent;
515
516 /*
517 * The dentry is now unrecoverably dead to the world.
518 */
519 lockref_mark_dead(&dentry->d_lockref);
520
521 /*
522 * inform the fs via d_prune that this dentry is about to be
523 * unhashed and destroyed.
524 */
525 if (dentry->d_flags & DCACHE_OP_PRUNE)
526 dentry->d_op->d_prune(dentry);
527
528 if (dentry->d_flags & DCACHE_LRU_LIST) {
529 if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
530 d_lru_del(dentry);
531 }
532 /* if it was on the hash then remove it */
533 __d_drop(dentry);
534 dentry_unlist(dentry, parent);
535 if (parent)
536 spin_unlock(&parent->d_lock);
537 if (dentry->d_inode)
538 dentry_unlink_inode(dentry);
539 else
540 spin_unlock(&dentry->d_lock);
541 this_cpu_dec(nr_dentry);
542 if (dentry->d_op && dentry->d_op->d_release)
543 dentry->d_op->d_release(dentry);
544
545 spin_lock(&dentry->d_lock);
546 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
547 dentry->d_flags |= DCACHE_MAY_FREE;
548 can_free = false;
549 }
550 spin_unlock(&dentry->d_lock);
551 if (likely(can_free))
552 dentry_free(dentry);
553}
554
555/*
556 * Finish off a dentry we've decided to kill.
557 * dentry->d_lock must be held, returns with it unlocked.
558 * If ref is non-zero, then decrement the refcount too.
559 * Returns dentry requiring refcount drop, or NULL if we're done.
560 */
561static struct dentry *dentry_kill(struct dentry *dentry)
562 __releases(dentry->d_lock)
563{
564 struct inode *inode = dentry->d_inode;
565 struct dentry *parent = NULL;
566
567 if (inode && unlikely(!spin_trylock(&inode->i_lock)))
568 goto failed;
569
570 if (!IS_ROOT(dentry)) {
571 parent = dentry->d_parent;
572 if (unlikely(!spin_trylock(&parent->d_lock))) {
573 if (inode)
574 spin_unlock(&inode->i_lock);
575 goto failed;
576 }
577 }
578
579 __dentry_kill(dentry);
580 return parent;
581
582failed:
583 spin_unlock(&dentry->d_lock);
584 return dentry; /* try again with same dentry */
585}
586
587static inline struct dentry *lock_parent(struct dentry *dentry)
588{
589 struct dentry *parent = dentry->d_parent;
590 if (IS_ROOT(dentry))
591 return NULL;
592 if (unlikely(dentry->d_lockref.count < 0))
593 return NULL;
594 if (likely(spin_trylock(&parent->d_lock)))
595 return parent;
596 rcu_read_lock();
597 spin_unlock(&dentry->d_lock);
598again:
599 parent = ACCESS_ONCE(dentry->d_parent);
600 spin_lock(&parent->d_lock);
601 /*
602 * We can't blindly lock dentry until we are sure
603 * that we won't violate the locking order.
604 * Any changes of dentry->d_parent must have
605 * been done with parent->d_lock held, so
606 * spin_lock() above is enough of a barrier
607 * for checking if it's still our child.
608 */
609 if (unlikely(parent != dentry->d_parent)) {
610 spin_unlock(&parent->d_lock);
611 goto again;
612 }
613 rcu_read_unlock();
614 if (parent != dentry)
615 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
616 else
617 parent = NULL;
618 return parent;
619}
620
621/*
622 * Try to do a lockless dput(), and return whether that was successful.
623 *
624 * If unsuccessful, we return false, having already taken the dentry lock.
625 *
626 * The caller needs to hold the RCU read lock, so that the dentry is
627 * guaranteed to stay around even if the refcount goes down to zero!
628 */
629static inline bool fast_dput(struct dentry *dentry)
630{
631 int ret;
632 unsigned int d_flags;
633
634 /*
635 * If we have a d_op->d_delete() operation, we sould not
636 * let the dentry count go to zero, so use "put_or_lock".
637 */
638 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE))
639 return lockref_put_or_lock(&dentry->d_lockref);
640
641 /*
642 * .. otherwise, we can try to just decrement the
643 * lockref optimistically.
644 */
645 ret = lockref_put_return(&dentry->d_lockref);
646
647 /*
648 * If the lockref_put_return() failed due to the lock being held
649 * by somebody else, the fast path has failed. We will need to
650 * get the lock, and then check the count again.
651 */
652 if (unlikely(ret < 0)) {
653 spin_lock(&dentry->d_lock);
654 if (dentry->d_lockref.count > 1) {
655 dentry->d_lockref.count--;
656 spin_unlock(&dentry->d_lock);
657 return 1;
658 }
659 return 0;
660 }
661
662 /*
663 * If we weren't the last ref, we're done.
664 */
665 if (ret)
666 return 1;
667
668 /*
669 * Careful, careful. The reference count went down
670 * to zero, but we don't hold the dentry lock, so
671 * somebody else could get it again, and do another
672 * dput(), and we need to not race with that.
673 *
674 * However, there is a very special and common case
675 * where we don't care, because there is nothing to
676 * do: the dentry is still hashed, it does not have
677 * a 'delete' op, and it's referenced and already on
678 * the LRU list.
679 *
680 * NOTE! Since we aren't locked, these values are
681 * not "stable". However, it is sufficient that at
682 * some point after we dropped the reference the
683 * dentry was hashed and the flags had the proper
684 * value. Other dentry users may have re-gotten
685 * a reference to the dentry and change that, but
686 * our work is done - we can leave the dentry
687 * around with a zero refcount.
688 */
689 smp_rmb();
690 d_flags = ACCESS_ONCE(dentry->d_flags);
691 d_flags &= DCACHE_REFERENCED | DCACHE_LRU_LIST | DCACHE_DISCONNECTED;
692
693 /* Nothing to do? Dropping the reference was all we needed? */
694 if (d_flags == (DCACHE_REFERENCED | DCACHE_LRU_LIST) && !d_unhashed(dentry))
695 return 1;
696
697 /*
698 * Not the fast normal case? Get the lock. We've already decremented
699 * the refcount, but we'll need to re-check the situation after
700 * getting the lock.
701 */
702 spin_lock(&dentry->d_lock);
703
704 /*
705 * Did somebody else grab a reference to it in the meantime, and
706 * we're no longer the last user after all? Alternatively, somebody
707 * else could have killed it and marked it dead. Either way, we
708 * don't need to do anything else.
709 */
710 if (dentry->d_lockref.count) {
711 spin_unlock(&dentry->d_lock);
712 return 1;
713 }
714
715 /*
716 * Re-get the reference we optimistically dropped. We hold the
717 * lock, and we just tested that it was zero, so we can just
718 * set it to 1.
719 */
720 dentry->d_lockref.count = 1;
721 return 0;
722}
723
724
725/*
726 * This is dput
727 *
728 * This is complicated by the fact that we do not want to put
729 * dentries that are no longer on any hash chain on the unused
730 * list: we'd much rather just get rid of them immediately.
731 *
732 * However, that implies that we have to traverse the dentry
733 * tree upwards to the parents which might _also_ now be
734 * scheduled for deletion (it may have been only waiting for
735 * its last child to go away).
736 *
737 * This tail recursion is done by hand as we don't want to depend
738 * on the compiler to always get this right (gcc generally doesn't).
739 * Real recursion would eat up our stack space.
740 */
741
742/*
743 * dput - release a dentry
744 * @dentry: dentry to release
745 *
746 * Release a dentry. This will drop the usage count and if appropriate
747 * call the dentry unlink method as well as removing it from the queues and
748 * releasing its resources. If the parent dentries were scheduled for release
749 * they too may now get deleted.
750 */
751void dput(struct dentry *dentry)
752{
753 if (unlikely(!dentry))
754 return;
755
756repeat:
757 might_sleep();
758
759 rcu_read_lock();
760 if (likely(fast_dput(dentry))) {
761 rcu_read_unlock();
762 return;
763 }
764
765 /* Slow case: now with the dentry lock held */
766 rcu_read_unlock();
767
768 WARN_ON(d_in_lookup(dentry));
769
770 /* Unreachable? Get rid of it */
771 if (unlikely(d_unhashed(dentry)))
772 goto kill_it;
773
774 if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
775 goto kill_it;
776
777 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) {
778 if (dentry->d_op->d_delete(dentry))
779 goto kill_it;
780 }
781
782 if (!(dentry->d_flags & DCACHE_REFERENCED))
783 dentry->d_flags |= DCACHE_REFERENCED;
784 dentry_lru_add(dentry);
785
786 dentry->d_lockref.count--;
787 spin_unlock(&dentry->d_lock);
788 return;
789
790kill_it:
791 dentry = dentry_kill(dentry);
792 if (dentry) {
793 cond_resched();
794 goto repeat;
795 }
796}
797EXPORT_SYMBOL(dput);
798
799
800/* This must be called with d_lock held */
801static inline void __dget_dlock(struct dentry *dentry)
802{
803 dentry->d_lockref.count++;
804}
805
806static inline void __dget(struct dentry *dentry)
807{
808 lockref_get(&dentry->d_lockref);
809}
810
811struct dentry *dget_parent(struct dentry *dentry)
812{
813 int gotref;
814 struct dentry *ret;
815
816 /*
817 * Do optimistic parent lookup without any
818 * locking.
819 */
820 rcu_read_lock();
821 ret = ACCESS_ONCE(dentry->d_parent);
822 gotref = lockref_get_not_zero(&ret->d_lockref);
823 rcu_read_unlock();
824 if (likely(gotref)) {
825 if (likely(ret == ACCESS_ONCE(dentry->d_parent)))
826 return ret;
827 dput(ret);
828 }
829
830repeat:
831 /*
832 * Don't need rcu_dereference because we re-check it was correct under
833 * the lock.
834 */
835 rcu_read_lock();
836 ret = dentry->d_parent;
837 spin_lock(&ret->d_lock);
838 if (unlikely(ret != dentry->d_parent)) {
839 spin_unlock(&ret->d_lock);
840 rcu_read_unlock();
841 goto repeat;
842 }
843 rcu_read_unlock();
844 BUG_ON(!ret->d_lockref.count);
845 ret->d_lockref.count++;
846 spin_unlock(&ret->d_lock);
847 return ret;
848}
849EXPORT_SYMBOL(dget_parent);
850
851/**
852 * d_find_alias - grab a hashed alias of inode
853 * @inode: inode in question
854 *
855 * If inode has a hashed alias, or is a directory and has any alias,
856 * acquire the reference to alias and return it. Otherwise return NULL.
857 * Notice that if inode is a directory there can be only one alias and
858 * it can be unhashed only if it has no children, or if it is the root
859 * of a filesystem, or if the directory was renamed and d_revalidate
860 * was the first vfs operation to notice.
861 *
862 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
863 * any other hashed alias over that one.
864 */
865static struct dentry *__d_find_alias(struct inode *inode)
866{
867 struct dentry *alias, *discon_alias;
868
869again:
870 discon_alias = NULL;
871 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
872 spin_lock(&alias->d_lock);
873 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
874 if (IS_ROOT(alias) &&
875 (alias->d_flags & DCACHE_DISCONNECTED)) {
876 discon_alias = alias;
877 } else {
878 __dget_dlock(alias);
879 spin_unlock(&alias->d_lock);
880 return alias;
881 }
882 }
883 spin_unlock(&alias->d_lock);
884 }
885 if (discon_alias) {
886 alias = discon_alias;
887 spin_lock(&alias->d_lock);
888 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
889 __dget_dlock(alias);
890 spin_unlock(&alias->d_lock);
891 return alias;
892 }
893 spin_unlock(&alias->d_lock);
894 goto again;
895 }
896 return NULL;
897}
898
899struct dentry *d_find_alias(struct inode *inode)
900{
901 struct dentry *de = NULL;
902
903 if (!hlist_empty(&inode->i_dentry)) {
904 spin_lock(&inode->i_lock);
905 de = __d_find_alias(inode);
906 spin_unlock(&inode->i_lock);
907 }
908 return de;
909}
910EXPORT_SYMBOL(d_find_alias);
911
912/*
913 * Try to kill dentries associated with this inode.
914 * WARNING: you must own a reference to inode.
915 */
916void d_prune_aliases(struct inode *inode)
917{
918 struct dentry *dentry;
919restart:
920 spin_lock(&inode->i_lock);
921 hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
922 spin_lock(&dentry->d_lock);
923 if (!dentry->d_lockref.count) {
924 struct dentry *parent = lock_parent(dentry);
925 if (likely(!dentry->d_lockref.count)) {
926 __dentry_kill(dentry);
927 dput(parent);
928 goto restart;
929 }
930 if (parent)
931 spin_unlock(&parent->d_lock);
932 }
933 spin_unlock(&dentry->d_lock);
934 }
935 spin_unlock(&inode->i_lock);
936}
937EXPORT_SYMBOL(d_prune_aliases);
938
939static void shrink_dentry_list(struct list_head *list)
940{
941 struct dentry *dentry, *parent;
942
943 while (!list_empty(list)) {
944 struct inode *inode;
945 dentry = list_entry(list->prev, struct dentry, d_lru);
946 spin_lock(&dentry->d_lock);
947 parent = lock_parent(dentry);
948
949 /*
950 * The dispose list is isolated and dentries are not accounted
951 * to the LRU here, so we can simply remove it from the list
952 * here regardless of whether it is referenced or not.
953 */
954 d_shrink_del(dentry);
955
956 /*
957 * We found an inuse dentry which was not removed from
958 * the LRU because of laziness during lookup. Do not free it.
959 */
960 if (dentry->d_lockref.count > 0) {
961 spin_unlock(&dentry->d_lock);
962 if (parent)
963 spin_unlock(&parent->d_lock);
964 continue;
965 }
966
967
968 if (unlikely(dentry->d_flags & DCACHE_DENTRY_KILLED)) {
969 bool can_free = dentry->d_flags & DCACHE_MAY_FREE;
970 spin_unlock(&dentry->d_lock);
971 if (parent)
972 spin_unlock(&parent->d_lock);
973 if (can_free)
974 dentry_free(dentry);
975 continue;
976 }
977
978 inode = dentry->d_inode;
979 if (inode && unlikely(!spin_trylock(&inode->i_lock))) {
980 d_shrink_add(dentry, list);
981 spin_unlock(&dentry->d_lock);
982 if (parent)
983 spin_unlock(&parent->d_lock);
984 continue;
985 }
986
987 __dentry_kill(dentry);
988
989 /*
990 * We need to prune ancestors too. This is necessary to prevent
991 * quadratic behavior of shrink_dcache_parent(), but is also
992 * expected to be beneficial in reducing dentry cache
993 * fragmentation.
994 */
995 dentry = parent;
996 while (dentry && !lockref_put_or_lock(&dentry->d_lockref)) {
997 parent = lock_parent(dentry);
998 if (dentry->d_lockref.count != 1) {
999 dentry->d_lockref.count--;
1000 spin_unlock(&dentry->d_lock);
1001 if (parent)
1002 spin_unlock(&parent->d_lock);
1003 break;
1004 }
1005 inode = dentry->d_inode; /* can't be NULL */
1006 if (unlikely(!spin_trylock(&inode->i_lock))) {
1007 spin_unlock(&dentry->d_lock);
1008 if (parent)
1009 spin_unlock(&parent->d_lock);
1010 cpu_relax();
1011 continue;
1012 }
1013 __dentry_kill(dentry);
1014 dentry = parent;
1015 }
1016 }
1017}
1018
1019static enum lru_status dentry_lru_isolate(struct list_head *item,
1020 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1021{
1022 struct list_head *freeable = arg;
1023 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1024
1025
1026 /*
1027 * we are inverting the lru lock/dentry->d_lock here,
1028 * so use a trylock. If we fail to get the lock, just skip
1029 * it
1030 */
1031 if (!spin_trylock(&dentry->d_lock))
1032 return LRU_SKIP;
1033
1034 /*
1035 * Referenced dentries are still in use. If they have active
1036 * counts, just remove them from the LRU. Otherwise give them
1037 * another pass through the LRU.
1038 */
1039 if (dentry->d_lockref.count) {
1040 d_lru_isolate(lru, dentry);
1041 spin_unlock(&dentry->d_lock);
1042 return LRU_REMOVED;
1043 }
1044
1045 if (dentry->d_flags & DCACHE_REFERENCED) {
1046 dentry->d_flags &= ~DCACHE_REFERENCED;
1047 spin_unlock(&dentry->d_lock);
1048
1049 /*
1050 * The list move itself will be made by the common LRU code. At
1051 * this point, we've dropped the dentry->d_lock but keep the
1052 * lru lock. This is safe to do, since every list movement is
1053 * protected by the lru lock even if both locks are held.
1054 *
1055 * This is guaranteed by the fact that all LRU management
1056 * functions are intermediated by the LRU API calls like
1057 * list_lru_add and list_lru_del. List movement in this file
1058 * only ever occur through this functions or through callbacks
1059 * like this one, that are called from the LRU API.
1060 *
1061 * The only exceptions to this are functions like
1062 * shrink_dentry_list, and code that first checks for the
1063 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1064 * operating only with stack provided lists after they are
1065 * properly isolated from the main list. It is thus, always a
1066 * local access.
1067 */
1068 return LRU_ROTATE;
1069 }
1070
1071 d_lru_shrink_move(lru, dentry, freeable);
1072 spin_unlock(&dentry->d_lock);
1073
1074 return LRU_REMOVED;
1075}
1076
1077/**
1078 * prune_dcache_sb - shrink the dcache
1079 * @sb: superblock
1080 * @sc: shrink control, passed to list_lru_shrink_walk()
1081 *
1082 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1083 * is done when we need more memory and called from the superblock shrinker
1084 * function.
1085 *
1086 * This function may fail to free any resources if all the dentries are in
1087 * use.
1088 */
1089long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc)
1090{
1091 LIST_HEAD(dispose);
1092 long freed;
1093
1094 freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc,
1095 dentry_lru_isolate, &dispose);
1096 shrink_dentry_list(&dispose);
1097 return freed;
1098}
1099
1100static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
1101 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1102{
1103 struct list_head *freeable = arg;
1104 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1105
1106 /*
1107 * we are inverting the lru lock/dentry->d_lock here,
1108 * so use a trylock. If we fail to get the lock, just skip
1109 * it
1110 */
1111 if (!spin_trylock(&dentry->d_lock))
1112 return LRU_SKIP;
1113
1114 d_lru_shrink_move(lru, dentry, freeable);
1115 spin_unlock(&dentry->d_lock);
1116
1117 return LRU_REMOVED;
1118}
1119
1120
1121/**
1122 * shrink_dcache_sb - shrink dcache for a superblock
1123 * @sb: superblock
1124 *
1125 * Shrink the dcache for the specified super block. This is used to free
1126 * the dcache before unmounting a file system.
1127 */
1128void shrink_dcache_sb(struct super_block *sb)
1129{
1130 long freed;
1131
1132 do {
1133 LIST_HEAD(dispose);
1134
1135 freed = list_lru_walk(&sb->s_dentry_lru,
1136 dentry_lru_isolate_shrink, &dispose, UINT_MAX);
1137
1138 this_cpu_sub(nr_dentry_unused, freed);
1139 shrink_dentry_list(&dispose);
1140 } while (freed > 0);
1141}
1142EXPORT_SYMBOL(shrink_dcache_sb);
1143
1144/**
1145 * enum d_walk_ret - action to talke during tree walk
1146 * @D_WALK_CONTINUE: contrinue walk
1147 * @D_WALK_QUIT: quit walk
1148 * @D_WALK_NORETRY: quit when retry is needed
1149 * @D_WALK_SKIP: skip this dentry and its children
1150 */
1151enum d_walk_ret {
1152 D_WALK_CONTINUE,
1153 D_WALK_QUIT,
1154 D_WALK_NORETRY,
1155 D_WALK_SKIP,
1156};
1157
1158/**
1159 * d_walk - walk the dentry tree
1160 * @parent: start of walk
1161 * @data: data passed to @enter() and @finish()
1162 * @enter: callback when first entering the dentry
1163 * @finish: callback when successfully finished the walk
1164 *
1165 * The @enter() and @finish() callbacks are called with d_lock held.
1166 */
1167static void d_walk(struct dentry *parent, void *data,
1168 enum d_walk_ret (*enter)(void *, struct dentry *),
1169 void (*finish)(void *))
1170{
1171 struct dentry *this_parent;
1172 struct list_head *next;
1173 unsigned seq = 0;
1174 enum d_walk_ret ret;
1175 bool retry = true;
1176
1177again:
1178 read_seqbegin_or_lock(&rename_lock, &seq);
1179 this_parent = parent;
1180 spin_lock(&this_parent->d_lock);
1181
1182 ret = enter(data, this_parent);
1183 switch (ret) {
1184 case D_WALK_CONTINUE:
1185 break;
1186 case D_WALK_QUIT:
1187 case D_WALK_SKIP:
1188 goto out_unlock;
1189 case D_WALK_NORETRY:
1190 retry = false;
1191 break;
1192 }
1193repeat:
1194 next = this_parent->d_subdirs.next;
1195resume:
1196 while (next != &this_parent->d_subdirs) {
1197 struct list_head *tmp = next;
1198 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
1199 next = tmp->next;
1200
1201 if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR))
1202 continue;
1203
1204 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1205
1206 ret = enter(data, dentry);
1207 switch (ret) {
1208 case D_WALK_CONTINUE:
1209 break;
1210 case D_WALK_QUIT:
1211 spin_unlock(&dentry->d_lock);
1212 goto out_unlock;
1213 case D_WALK_NORETRY:
1214 retry = false;
1215 break;
1216 case D_WALK_SKIP:
1217 spin_unlock(&dentry->d_lock);
1218 continue;
1219 }
1220
1221 if (!list_empty(&dentry->d_subdirs)) {
1222 spin_unlock(&this_parent->d_lock);
1223 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
1224 this_parent = dentry;
1225 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1226 goto repeat;
1227 }
1228 spin_unlock(&dentry->d_lock);
1229 }
1230 /*
1231 * All done at this level ... ascend and resume the search.
1232 */
1233 rcu_read_lock();
1234ascend:
1235 if (this_parent != parent) {
1236 struct dentry *child = this_parent;
1237 this_parent = child->d_parent;
1238
1239 spin_unlock(&child->d_lock);
1240 spin_lock(&this_parent->d_lock);
1241
1242 /* might go back up the wrong parent if we have had a rename. */
1243 if (need_seqretry(&rename_lock, seq))
1244 goto rename_retry;
1245 /* go into the first sibling still alive */
1246 do {
1247 next = child->d_child.next;
1248 if (next == &this_parent->d_subdirs)
1249 goto ascend;
1250 child = list_entry(next, struct dentry, d_child);
1251 } while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
1252 rcu_read_unlock();
1253 goto resume;
1254 }
1255 if (need_seqretry(&rename_lock, seq))
1256 goto rename_retry;
1257 rcu_read_unlock();
1258 if (finish)
1259 finish(data);
1260
1261out_unlock:
1262 spin_unlock(&this_parent->d_lock);
1263 done_seqretry(&rename_lock, seq);
1264 return;
1265
1266rename_retry:
1267 spin_unlock(&this_parent->d_lock);
1268 rcu_read_unlock();
1269 BUG_ON(seq & 1);
1270 if (!retry)
1271 return;
1272 seq = 1;
1273 goto again;
1274}
1275
1276struct check_mount {
1277 struct vfsmount *mnt;
1278 unsigned int mounted;
1279};
1280
1281static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry)
1282{
1283 struct check_mount *info = data;
1284 struct path path = { .mnt = info->mnt, .dentry = dentry };
1285
1286 if (likely(!d_mountpoint(dentry)))
1287 return D_WALK_CONTINUE;
1288 if (__path_is_mountpoint(&path)) {
1289 info->mounted = 1;
1290 return D_WALK_QUIT;
1291 }
1292 return D_WALK_CONTINUE;
1293}
1294
1295/**
1296 * path_has_submounts - check for mounts over a dentry in the
1297 * current namespace.
1298 * @parent: path to check.
1299 *
1300 * Return true if the parent or its subdirectories contain
1301 * a mount point in the current namespace.
1302 */
1303int path_has_submounts(const struct path *parent)
1304{
1305 struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
1306
1307 read_seqlock_excl(&mount_lock);
1308 d_walk(parent->dentry, &data, path_check_mount, NULL);
1309 read_sequnlock_excl(&mount_lock);
1310
1311 return data.mounted;
1312}
1313EXPORT_SYMBOL(path_has_submounts);
1314
1315/*
1316 * Called by mount code to set a mountpoint and check if the mountpoint is
1317 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1318 * subtree can become unreachable).
1319 *
1320 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1321 * this reason take rename_lock and d_lock on dentry and ancestors.
1322 */
1323int d_set_mounted(struct dentry *dentry)
1324{
1325 struct dentry *p;
1326 int ret = -ENOENT;
1327 write_seqlock(&rename_lock);
1328 for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
1329 /* Need exclusion wrt. d_invalidate() */
1330 spin_lock(&p->d_lock);
1331 if (unlikely(d_unhashed(p))) {
1332 spin_unlock(&p->d_lock);
1333 goto out;
1334 }
1335 spin_unlock(&p->d_lock);
1336 }
1337 spin_lock(&dentry->d_lock);
1338 if (!d_unlinked(dentry)) {
1339 ret = -EBUSY;
1340 if (!d_mountpoint(dentry)) {
1341 dentry->d_flags |= DCACHE_MOUNTED;
1342 ret = 0;
1343 }
1344 }
1345 spin_unlock(&dentry->d_lock);
1346out:
1347 write_sequnlock(&rename_lock);
1348 return ret;
1349}
1350
1351/*
1352 * Search the dentry child list of the specified parent,
1353 * and move any unused dentries to the end of the unused
1354 * list for prune_dcache(). We descend to the next level
1355 * whenever the d_subdirs list is non-empty and continue
1356 * searching.
1357 *
1358 * It returns zero iff there are no unused children,
1359 * otherwise it returns the number of children moved to
1360 * the end of the unused list. This may not be the total
1361 * number of unused children, because select_parent can
1362 * drop the lock and return early due to latency
1363 * constraints.
1364 */
1365
1366struct select_data {
1367 struct dentry *start;
1368 struct list_head dispose;
1369 int found;
1370};
1371
1372static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
1373{
1374 struct select_data *data = _data;
1375 enum d_walk_ret ret = D_WALK_CONTINUE;
1376
1377 if (data->start == dentry)
1378 goto out;
1379
1380 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1381 data->found++;
1382 } else {
1383 if (dentry->d_flags & DCACHE_LRU_LIST)
1384 d_lru_del(dentry);
1385 if (!dentry->d_lockref.count) {
1386 d_shrink_add(dentry, &data->dispose);
1387 data->found++;
1388 }
1389 }
1390 /*
1391 * We can return to the caller if we have found some (this
1392 * ensures forward progress). We'll be coming back to find
1393 * the rest.
1394 */
1395 if (!list_empty(&data->dispose))
1396 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1397out:
1398 return ret;
1399}
1400
1401/**
1402 * shrink_dcache_parent - prune dcache
1403 * @parent: parent of entries to prune
1404 *
1405 * Prune the dcache to remove unused children of the parent dentry.
1406 */
1407void shrink_dcache_parent(struct dentry *parent)
1408{
1409 for (;;) {
1410 struct select_data data;
1411
1412 INIT_LIST_HEAD(&data.dispose);
1413 data.start = parent;
1414 data.found = 0;
1415
1416 d_walk(parent, &data, select_collect, NULL);
1417 if (!data.found)
1418 break;
1419
1420 shrink_dentry_list(&data.dispose);
1421 cond_resched();
1422 }
1423}
1424EXPORT_SYMBOL(shrink_dcache_parent);
1425
1426static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
1427{
1428 /* it has busy descendents; complain about those instead */
1429 if (!list_empty(&dentry->d_subdirs))
1430 return D_WALK_CONTINUE;
1431
1432 /* root with refcount 1 is fine */
1433 if (dentry == _data && dentry->d_lockref.count == 1)
1434 return D_WALK_CONTINUE;
1435
1436 printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%pd} "
1437 " still in use (%d) [unmount of %s %s]\n",
1438 dentry,
1439 dentry->d_inode ?
1440 dentry->d_inode->i_ino : 0UL,
1441 dentry,
1442 dentry->d_lockref.count,
1443 dentry->d_sb->s_type->name,
1444 dentry->d_sb->s_id);
1445 WARN_ON(1);
1446 return D_WALK_CONTINUE;
1447}
1448
1449static void do_one_tree(struct dentry *dentry)
1450{
1451 shrink_dcache_parent(dentry);
1452 d_walk(dentry, dentry, umount_check, NULL);
1453 d_drop(dentry);
1454 dput(dentry);
1455}
1456
1457/*
1458 * destroy the dentries attached to a superblock on unmounting
1459 */
1460void shrink_dcache_for_umount(struct super_block *sb)
1461{
1462 struct dentry *dentry;
1463
1464 WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked");
1465
1466 dentry = sb->s_root;
1467 sb->s_root = NULL;
1468 do_one_tree(dentry);
1469
1470 while (!hlist_bl_empty(&sb->s_anon)) {
1471 dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash));
1472 do_one_tree(dentry);
1473 }
1474}
1475
1476struct detach_data {
1477 struct select_data select;
1478 struct dentry *mountpoint;
1479};
1480static enum d_walk_ret detach_and_collect(void *_data, struct dentry *dentry)
1481{
1482 struct detach_data *data = _data;
1483
1484 if (d_mountpoint(dentry)) {
1485 __dget_dlock(dentry);
1486 data->mountpoint = dentry;
1487 return D_WALK_QUIT;
1488 }
1489
1490 return select_collect(&data->select, dentry);
1491}
1492
1493static void check_and_drop(void *_data)
1494{
1495 struct detach_data *data = _data;
1496
1497 if (!data->mountpoint && !data->select.found)
1498 __d_drop(data->select.start);
1499}
1500
1501/**
1502 * d_invalidate - detach submounts, prune dcache, and drop
1503 * @dentry: dentry to invalidate (aka detach, prune and drop)
1504 *
1505 * no dcache lock.
1506 *
1507 * The final d_drop is done as an atomic operation relative to
1508 * rename_lock ensuring there are no races with d_set_mounted. This
1509 * ensures there are no unhashed dentries on the path to a mountpoint.
1510 */
1511void d_invalidate(struct dentry *dentry)
1512{
1513 /*
1514 * If it's already been dropped, return OK.
1515 */
1516 spin_lock(&dentry->d_lock);
1517 if (d_unhashed(dentry)) {
1518 spin_unlock(&dentry->d_lock);
1519 return;
1520 }
1521 spin_unlock(&dentry->d_lock);
1522
1523 /* Negative dentries can be dropped without further checks */
1524 if (!dentry->d_inode) {
1525 d_drop(dentry);
1526 return;
1527 }
1528
1529 for (;;) {
1530 struct detach_data data;
1531
1532 data.mountpoint = NULL;
1533 INIT_LIST_HEAD(&data.select.dispose);
1534 data.select.start = dentry;
1535 data.select.found = 0;
1536
1537 d_walk(dentry, &data, detach_and_collect, check_and_drop);
1538
1539 if (data.select.found)
1540 shrink_dentry_list(&data.select.dispose);
1541
1542 if (data.mountpoint) {
1543 detach_mounts(data.mountpoint);
1544 dput(data.mountpoint);
1545 }
1546
1547 if (!data.mountpoint && !data.select.found)
1548 break;
1549
1550 cond_resched();
1551 }
1552}
1553EXPORT_SYMBOL(d_invalidate);
1554
1555/**
1556 * __d_alloc - allocate a dcache entry
1557 * @sb: filesystem it will belong to
1558 * @name: qstr of the name
1559 *
1560 * Allocates a dentry. It returns %NULL if there is insufficient memory
1561 * available. On a success the dentry is returned. The name passed in is
1562 * copied and the copy passed in may be reused after this call.
1563 */
1564
1565struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1566{
1567 struct dentry *dentry;
1568 char *dname;
1569 int err;
1570
1571 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
1572 if (!dentry)
1573 return NULL;
1574
1575 /*
1576 * We guarantee that the inline name is always NUL-terminated.
1577 * This way the memcpy() done by the name switching in rename
1578 * will still always have a NUL at the end, even if we might
1579 * be overwriting an internal NUL character
1580 */
1581 dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
1582 if (unlikely(!name)) {
1583 static const struct qstr anon = QSTR_INIT("/", 1);
1584 name = &anon;
1585 dname = dentry->d_iname;
1586 } else if (name->len > DNAME_INLINE_LEN-1) {
1587 size_t size = offsetof(struct external_name, name[1]);
1588 struct external_name *p = kmalloc(size + name->len,
1589 GFP_KERNEL_ACCOUNT);
1590 if (!p) {
1591 kmem_cache_free(dentry_cache, dentry);
1592 return NULL;
1593 }
1594 atomic_set(&p->u.count, 1);
1595 dname = p->name;
1596 if (IS_ENABLED(CONFIG_DCACHE_WORD_ACCESS))
1597 kasan_unpoison_shadow(dname,
1598 round_up(name->len + 1, sizeof(unsigned long)));
1599 } else {
1600 dname = dentry->d_iname;
1601 }
1602
1603 dentry->d_name.len = name->len;
1604 dentry->d_name.hash = name->hash;
1605 memcpy(dname, name->name, name->len);
1606 dname[name->len] = 0;
1607
1608 /* Make sure we always see the terminating NUL character */
1609 smp_wmb();
1610 dentry->d_name.name = dname;
1611
1612 dentry->d_lockref.count = 1;
1613 dentry->d_flags = 0;
1614 spin_lock_init(&dentry->d_lock);
1615 seqcount_init(&dentry->d_seq);
1616 dentry->d_inode = NULL;
1617 dentry->d_parent = dentry;
1618 dentry->d_sb = sb;
1619 dentry->d_op = NULL;
1620 dentry->d_fsdata = NULL;
1621 INIT_HLIST_BL_NODE(&dentry->d_hash);
1622 INIT_LIST_HEAD(&dentry->d_lru);
1623 INIT_LIST_HEAD(&dentry->d_subdirs);
1624 INIT_HLIST_NODE(&dentry->d_u.d_alias);
1625 INIT_LIST_HEAD(&dentry->d_child);
1626 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1627
1628 if (dentry->d_op && dentry->d_op->d_init) {
1629 err = dentry->d_op->d_init(dentry);
1630 if (err) {
1631 if (dname_external(dentry))
1632 kfree(external_name(dentry));
1633 kmem_cache_free(dentry_cache, dentry);
1634 return NULL;
1635 }
1636 }
1637
1638 this_cpu_inc(nr_dentry);
1639
1640 return dentry;
1641}
1642
1643/**
1644 * d_alloc - allocate a dcache entry
1645 * @parent: parent of entry to allocate
1646 * @name: qstr of the name
1647 *
1648 * Allocates a dentry. It returns %NULL if there is insufficient memory
1649 * available. On a success the dentry is returned. The name passed in is
1650 * copied and the copy passed in may be reused after this call.
1651 */
1652struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1653{
1654 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1655 if (!dentry)
1656 return NULL;
1657 dentry->d_flags |= DCACHE_RCUACCESS;
1658 spin_lock(&parent->d_lock);
1659 /*
1660 * don't need child lock because it is not subject
1661 * to concurrency here
1662 */
1663 __dget_dlock(parent);
1664 dentry->d_parent = parent;
1665 list_add(&dentry->d_child, &parent->d_subdirs);
1666 spin_unlock(&parent->d_lock);
1667
1668 return dentry;
1669}
1670EXPORT_SYMBOL(d_alloc);
1671
1672struct dentry *d_alloc_cursor(struct dentry * parent)
1673{
1674 struct dentry *dentry = __d_alloc(parent->d_sb, NULL);
1675 if (dentry) {
1676 dentry->d_flags |= DCACHE_RCUACCESS | DCACHE_DENTRY_CURSOR;
1677 dentry->d_parent = dget(parent);
1678 }
1679 return dentry;
1680}
1681
1682/**
1683 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1684 * @sb: the superblock
1685 * @name: qstr of the name
1686 *
1687 * For a filesystem that just pins its dentries in memory and never
1688 * performs lookups at all, return an unhashed IS_ROOT dentry.
1689 */
1690struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1691{
1692 return __d_alloc(sb, name);
1693}
1694EXPORT_SYMBOL(d_alloc_pseudo);
1695
1696struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1697{
1698 struct qstr q;
1699
1700 q.name = name;
1701 q.hash_len = hashlen_string(parent, name);
1702 return d_alloc(parent, &q);
1703}
1704EXPORT_SYMBOL(d_alloc_name);
1705
1706void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1707{
1708 WARN_ON_ONCE(dentry->d_op);
1709 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
1710 DCACHE_OP_COMPARE |
1711 DCACHE_OP_REVALIDATE |
1712 DCACHE_OP_WEAK_REVALIDATE |
1713 DCACHE_OP_DELETE |
1714 DCACHE_OP_REAL));
1715 dentry->d_op = op;
1716 if (!op)
1717 return;
1718 if (op->d_hash)
1719 dentry->d_flags |= DCACHE_OP_HASH;
1720 if (op->d_compare)
1721 dentry->d_flags |= DCACHE_OP_COMPARE;
1722 if (op->d_revalidate)
1723 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1724 if (op->d_weak_revalidate)
1725 dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
1726 if (op->d_delete)
1727 dentry->d_flags |= DCACHE_OP_DELETE;
1728 if (op->d_prune)
1729 dentry->d_flags |= DCACHE_OP_PRUNE;
1730 if (op->d_real)
1731 dentry->d_flags |= DCACHE_OP_REAL;
1732
1733}
1734EXPORT_SYMBOL(d_set_d_op);
1735
1736
1737/*
1738 * d_set_fallthru - Mark a dentry as falling through to a lower layer
1739 * @dentry - The dentry to mark
1740 *
1741 * Mark a dentry as falling through to the lower layer (as set with
1742 * d_pin_lower()). This flag may be recorded on the medium.
1743 */
1744void d_set_fallthru(struct dentry *dentry)
1745{
1746 spin_lock(&dentry->d_lock);
1747 dentry->d_flags |= DCACHE_FALLTHRU;
1748 spin_unlock(&dentry->d_lock);
1749}
1750EXPORT_SYMBOL(d_set_fallthru);
1751
1752static unsigned d_flags_for_inode(struct inode *inode)
1753{
1754 unsigned add_flags = DCACHE_REGULAR_TYPE;
1755
1756 if (!inode)
1757 return DCACHE_MISS_TYPE;
1758
1759 if (S_ISDIR(inode->i_mode)) {
1760 add_flags = DCACHE_DIRECTORY_TYPE;
1761 if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) {
1762 if (unlikely(!inode->i_op->lookup))
1763 add_flags = DCACHE_AUTODIR_TYPE;
1764 else
1765 inode->i_opflags |= IOP_LOOKUP;
1766 }
1767 goto type_determined;
1768 }
1769
1770 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1771 if (unlikely(inode->i_op->get_link)) {
1772 add_flags = DCACHE_SYMLINK_TYPE;
1773 goto type_determined;
1774 }
1775 inode->i_opflags |= IOP_NOFOLLOW;
1776 }
1777
1778 if (unlikely(!S_ISREG(inode->i_mode)))
1779 add_flags = DCACHE_SPECIAL_TYPE;
1780
1781type_determined:
1782 if (unlikely(IS_AUTOMOUNT(inode)))
1783 add_flags |= DCACHE_NEED_AUTOMOUNT;
1784 return add_flags;
1785}
1786
1787static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1788{
1789 unsigned add_flags = d_flags_for_inode(inode);
1790 WARN_ON(d_in_lookup(dentry));
1791
1792 spin_lock(&dentry->d_lock);
1793 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
1794 raw_write_seqcount_begin(&dentry->d_seq);
1795 __d_set_inode_and_type(dentry, inode, add_flags);
1796 raw_write_seqcount_end(&dentry->d_seq);
1797 fsnotify_update_flags(dentry);
1798 spin_unlock(&dentry->d_lock);
1799}
1800
1801/**
1802 * d_instantiate - fill in inode information for a dentry
1803 * @entry: dentry to complete
1804 * @inode: inode to attach to this dentry
1805 *
1806 * Fill in inode information in the entry.
1807 *
1808 * This turns negative dentries into productive full members
1809 * of society.
1810 *
1811 * NOTE! This assumes that the inode count has been incremented
1812 * (or otherwise set) by the caller to indicate that it is now
1813 * in use by the dcache.
1814 */
1815
1816void d_instantiate(struct dentry *entry, struct inode * inode)
1817{
1818 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1819 if (inode) {
1820 security_d_instantiate(entry, inode);
1821 spin_lock(&inode->i_lock);
1822 __d_instantiate(entry, inode);
1823 spin_unlock(&inode->i_lock);
1824 }
1825}
1826EXPORT_SYMBOL(d_instantiate);
1827
1828/**
1829 * d_instantiate_no_diralias - instantiate a non-aliased dentry
1830 * @entry: dentry to complete
1831 * @inode: inode to attach to this dentry
1832 *
1833 * Fill in inode information in the entry. If a directory alias is found, then
1834 * return an error (and drop inode). Together with d_materialise_unique() this
1835 * guarantees that a directory inode may never have more than one alias.
1836 */
1837int d_instantiate_no_diralias(struct dentry *entry, struct inode *inode)
1838{
1839 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1840
1841 security_d_instantiate(entry, inode);
1842 spin_lock(&inode->i_lock);
1843 if (S_ISDIR(inode->i_mode) && !hlist_empty(&inode->i_dentry)) {
1844 spin_unlock(&inode->i_lock);
1845 iput(inode);
1846 return -EBUSY;
1847 }
1848 __d_instantiate(entry, inode);
1849 spin_unlock(&inode->i_lock);
1850
1851 return 0;
1852}
1853EXPORT_SYMBOL(d_instantiate_no_diralias);
1854
1855struct dentry *d_make_root(struct inode *root_inode)
1856{
1857 struct dentry *res = NULL;
1858
1859 if (root_inode) {
1860 res = __d_alloc(root_inode->i_sb, NULL);
1861 if (res)
1862 d_instantiate(res, root_inode);
1863 else
1864 iput(root_inode);
1865 }
1866 return res;
1867}
1868EXPORT_SYMBOL(d_make_root);
1869
1870static struct dentry * __d_find_any_alias(struct inode *inode)
1871{
1872 struct dentry *alias;
1873
1874 if (hlist_empty(&inode->i_dentry))
1875 return NULL;
1876 alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
1877 __dget(alias);
1878 return alias;
1879}
1880
1881/**
1882 * d_find_any_alias - find any alias for a given inode
1883 * @inode: inode to find an alias for
1884 *
1885 * If any aliases exist for the given inode, take and return a
1886 * reference for one of them. If no aliases exist, return %NULL.
1887 */
1888struct dentry *d_find_any_alias(struct inode *inode)
1889{
1890 struct dentry *de;
1891
1892 spin_lock(&inode->i_lock);
1893 de = __d_find_any_alias(inode);
1894 spin_unlock(&inode->i_lock);
1895 return de;
1896}
1897EXPORT_SYMBOL(d_find_any_alias);
1898
1899static struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
1900{
1901 struct dentry *tmp;
1902 struct dentry *res;
1903 unsigned add_flags;
1904
1905 if (!inode)
1906 return ERR_PTR(-ESTALE);
1907 if (IS_ERR(inode))
1908 return ERR_CAST(inode);
1909
1910 res = d_find_any_alias(inode);
1911 if (res)
1912 goto out_iput;
1913
1914 tmp = __d_alloc(inode->i_sb, NULL);
1915 if (!tmp) {
1916 res = ERR_PTR(-ENOMEM);
1917 goto out_iput;
1918 }
1919
1920 security_d_instantiate(tmp, inode);
1921 spin_lock(&inode->i_lock);
1922 res = __d_find_any_alias(inode);
1923 if (res) {
1924 spin_unlock(&inode->i_lock);
1925 dput(tmp);
1926 goto out_iput;
1927 }
1928
1929 /* attach a disconnected dentry */
1930 add_flags = d_flags_for_inode(inode);
1931
1932 if (disconnected)
1933 add_flags |= DCACHE_DISCONNECTED;
1934
1935 spin_lock(&tmp->d_lock);
1936 __d_set_inode_and_type(tmp, inode, add_flags);
1937 hlist_add_head(&tmp->d_u.d_alias, &inode->i_dentry);
1938 hlist_bl_lock(&tmp->d_sb->s_anon);
1939 hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
1940 hlist_bl_unlock(&tmp->d_sb->s_anon);
1941 spin_unlock(&tmp->d_lock);
1942 spin_unlock(&inode->i_lock);
1943
1944 return tmp;
1945
1946 out_iput:
1947 iput(inode);
1948 return res;
1949}
1950
1951/**
1952 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
1953 * @inode: inode to allocate the dentry for
1954 *
1955 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1956 * similar open by handle operations. The returned dentry may be anonymous,
1957 * or may have a full name (if the inode was already in the cache).
1958 *
1959 * When called on a directory inode, we must ensure that the inode only ever
1960 * has one dentry. If a dentry is found, that is returned instead of
1961 * allocating a new one.
1962 *
1963 * On successful return, the reference to the inode has been transferred
1964 * to the dentry. In case of an error the reference on the inode is released.
1965 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1966 * be passed in and the error will be propagated to the return value,
1967 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1968 */
1969struct dentry *d_obtain_alias(struct inode *inode)
1970{
1971 return __d_obtain_alias(inode, 1);
1972}
1973EXPORT_SYMBOL(d_obtain_alias);
1974
1975/**
1976 * d_obtain_root - find or allocate a dentry for a given inode
1977 * @inode: inode to allocate the dentry for
1978 *
1979 * Obtain an IS_ROOT dentry for the root of a filesystem.
1980 *
1981 * We must ensure that directory inodes only ever have one dentry. If a
1982 * dentry is found, that is returned instead of allocating a new one.
1983 *
1984 * On successful return, the reference to the inode has been transferred
1985 * to the dentry. In case of an error the reference on the inode is
1986 * released. A %NULL or IS_ERR inode may be passed in and will be the
1987 * error will be propagate to the return value, with a %NULL @inode
1988 * replaced by ERR_PTR(-ESTALE).
1989 */
1990struct dentry *d_obtain_root(struct inode *inode)
1991{
1992 return __d_obtain_alias(inode, 0);
1993}
1994EXPORT_SYMBOL(d_obtain_root);
1995
1996/**
1997 * d_add_ci - lookup or allocate new dentry with case-exact name
1998 * @inode: the inode case-insensitive lookup has found
1999 * @dentry: the negative dentry that was passed to the parent's lookup func
2000 * @name: the case-exact name to be associated with the returned dentry
2001 *
2002 * This is to avoid filling the dcache with case-insensitive names to the
2003 * same inode, only the actual correct case is stored in the dcache for
2004 * case-insensitive filesystems.
2005 *
2006 * For a case-insensitive lookup match and if the the case-exact dentry
2007 * already exists in in the dcache, use it and return it.
2008 *
2009 * If no entry exists with the exact case name, allocate new dentry with
2010 * the exact case, and return the spliced entry.
2011 */
2012struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
2013 struct qstr *name)
2014{
2015 struct dentry *found, *res;
2016
2017 /*
2018 * First check if a dentry matching the name already exists,
2019 * if not go ahead and create it now.
2020 */
2021 found = d_hash_and_lookup(dentry->d_parent, name);
2022 if (found) {
2023 iput(inode);
2024 return found;
2025 }
2026 if (d_in_lookup(dentry)) {
2027 found = d_alloc_parallel(dentry->d_parent, name,
2028 dentry->d_wait);
2029 if (IS_ERR(found) || !d_in_lookup(found)) {
2030 iput(inode);
2031 return found;
2032 }
2033 } else {
2034 found = d_alloc(dentry->d_parent, name);
2035 if (!found) {
2036 iput(inode);
2037 return ERR_PTR(-ENOMEM);
2038 }
2039 }
2040 res = d_splice_alias(inode, found);
2041 if (res) {
2042 dput(found);
2043 return res;
2044 }
2045 return found;
2046}
2047EXPORT_SYMBOL(d_add_ci);
2048
2049
2050static inline bool d_same_name(const struct dentry *dentry,
2051 const struct dentry *parent,
2052 const struct qstr *name)
2053{
2054 if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
2055 if (dentry->d_name.len != name->len)
2056 return false;
2057 return dentry_cmp(dentry, name->name, name->len) == 0;
2058 }
2059 return parent->d_op->d_compare(dentry,
2060 dentry->d_name.len, dentry->d_name.name,
2061 name) == 0;
2062}
2063
2064/**
2065 * __d_lookup_rcu - search for a dentry (racy, store-free)
2066 * @parent: parent dentry
2067 * @name: qstr of name we wish to find
2068 * @seqp: returns d_seq value at the point where the dentry was found
2069 * Returns: dentry, or NULL
2070 *
2071 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2072 * resolution (store-free path walking) design described in
2073 * Documentation/filesystems/path-lookup.txt.
2074 *
2075 * This is not to be used outside core vfs.
2076 *
2077 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2078 * held, and rcu_read_lock held. The returned dentry must not be stored into
2079 * without taking d_lock and checking d_seq sequence count against @seq
2080 * returned here.
2081 *
2082 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2083 * function.
2084 *
2085 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2086 * the returned dentry, so long as its parent's seqlock is checked after the
2087 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2088 * is formed, giving integrity down the path walk.
2089 *
2090 * NOTE! The caller *has* to check the resulting dentry against the sequence
2091 * number we've returned before using any of the resulting dentry state!
2092 */
2093struct dentry *__d_lookup_rcu(const struct dentry *parent,
2094 const struct qstr *name,
2095 unsigned *seqp)
2096{
2097 u64 hashlen = name->hash_len;
2098 const unsigned char *str = name->name;
2099 struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
2100 struct hlist_bl_node *node;
2101 struct dentry *dentry;
2102
2103 /*
2104 * Note: There is significant duplication with __d_lookup_rcu which is
2105 * required to prevent single threaded performance regressions
2106 * especially on architectures where smp_rmb (in seqcounts) are costly.
2107 * Keep the two functions in sync.
2108 */
2109
2110 /*
2111 * The hash list is protected using RCU.
2112 *
2113 * Carefully use d_seq when comparing a candidate dentry, to avoid
2114 * races with d_move().
2115 *
2116 * It is possible that concurrent renames can mess up our list
2117 * walk here and result in missing our dentry, resulting in the
2118 * false-negative result. d_lookup() protects against concurrent
2119 * renames using rename_lock seqlock.
2120 *
2121 * See Documentation/filesystems/path-lookup.txt for more details.
2122 */
2123 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2124 unsigned seq;
2125
2126seqretry:
2127 /*
2128 * The dentry sequence count protects us from concurrent
2129 * renames, and thus protects parent and name fields.
2130 *
2131 * The caller must perform a seqcount check in order
2132 * to do anything useful with the returned dentry.
2133 *
2134 * NOTE! We do a "raw" seqcount_begin here. That means that
2135 * we don't wait for the sequence count to stabilize if it
2136 * is in the middle of a sequence change. If we do the slow
2137 * dentry compare, we will do seqretries until it is stable,
2138 * and if we end up with a successful lookup, we actually
2139 * want to exit RCU lookup anyway.
2140 *
2141 * Note that raw_seqcount_begin still *does* smp_rmb(), so
2142 * we are still guaranteed NUL-termination of ->d_name.name.
2143 */
2144 seq = raw_seqcount_begin(&dentry->d_seq);
2145 if (dentry->d_parent != parent)
2146 continue;
2147 if (d_unhashed(dentry))
2148 continue;
2149
2150 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
2151 int tlen;
2152 const char *tname;
2153 if (dentry->d_name.hash != hashlen_hash(hashlen))
2154 continue;
2155 tlen = dentry->d_name.len;
2156 tname = dentry->d_name.name;
2157 /* we want a consistent (name,len) pair */
2158 if (read_seqcount_retry(&dentry->d_seq, seq)) {
2159 cpu_relax();
2160 goto seqretry;
2161 }
2162 if (parent->d_op->d_compare(dentry,
2163 tlen, tname, name) != 0)
2164 continue;
2165 } else {
2166 if (dentry->d_name.hash_len != hashlen)
2167 continue;
2168 if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
2169 continue;
2170 }
2171 *seqp = seq;
2172 return dentry;
2173 }
2174 return NULL;
2175}
2176
2177/**
2178 * d_lookup - search for a dentry
2179 * @parent: parent dentry
2180 * @name: qstr of name we wish to find
2181 * Returns: dentry, or NULL
2182 *
2183 * d_lookup searches the children of the parent dentry for the name in
2184 * question. If the dentry is found its reference count is incremented and the
2185 * dentry is returned. The caller must use dput to free the entry when it has
2186 * finished using it. %NULL is returned if the dentry does not exist.
2187 */
2188struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
2189{
2190 struct dentry *dentry;
2191 unsigned seq;
2192
2193 do {
2194 seq = read_seqbegin(&rename_lock);
2195 dentry = __d_lookup(parent, name);
2196 if (dentry)
2197 break;
2198 } while (read_seqretry(&rename_lock, seq));
2199 return dentry;
2200}
2201EXPORT_SYMBOL(d_lookup);
2202
2203/**
2204 * __d_lookup - search for a dentry (racy)
2205 * @parent: parent dentry
2206 * @name: qstr of name we wish to find
2207 * Returns: dentry, or NULL
2208 *
2209 * __d_lookup is like d_lookup, however it may (rarely) return a
2210 * false-negative result due to unrelated rename activity.
2211 *
2212 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2213 * however it must be used carefully, eg. with a following d_lookup in
2214 * the case of failure.
2215 *
2216 * __d_lookup callers must be commented.
2217 */
2218struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
2219{
2220 unsigned int hash = name->hash;
2221 struct hlist_bl_head *b = d_hash(hash);
2222 struct hlist_bl_node *node;
2223 struct dentry *found = NULL;
2224 struct dentry *dentry;
2225
2226 /*
2227 * Note: There is significant duplication with __d_lookup_rcu which is
2228 * required to prevent single threaded performance regressions
2229 * especially on architectures where smp_rmb (in seqcounts) are costly.
2230 * Keep the two functions in sync.
2231 */
2232
2233 /*
2234 * The hash list is protected using RCU.
2235 *
2236 * Take d_lock when comparing a candidate dentry, to avoid races
2237 * with d_move().
2238 *
2239 * It is possible that concurrent renames can mess up our list
2240 * walk here and result in missing our dentry, resulting in the
2241 * false-negative result. d_lookup() protects against concurrent
2242 * renames using rename_lock seqlock.
2243 *
2244 * See Documentation/filesystems/path-lookup.txt for more details.
2245 */
2246 rcu_read_lock();
2247
2248 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2249
2250 if (dentry->d_name.hash != hash)
2251 continue;
2252
2253 spin_lock(&dentry->d_lock);
2254 if (dentry->d_parent != parent)
2255 goto next;
2256 if (d_unhashed(dentry))
2257 goto next;
2258
2259 if (!d_same_name(dentry, parent, name))
2260 goto next;
2261
2262 dentry->d_lockref.count++;
2263 found = dentry;
2264 spin_unlock(&dentry->d_lock);
2265 break;
2266next:
2267 spin_unlock(&dentry->d_lock);
2268 }
2269 rcu_read_unlock();
2270
2271 return found;
2272}
2273
2274/**
2275 * d_hash_and_lookup - hash the qstr then search for a dentry
2276 * @dir: Directory to search in
2277 * @name: qstr of name we wish to find
2278 *
2279 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2280 */
2281struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2282{
2283 /*
2284 * Check for a fs-specific hash function. Note that we must
2285 * calculate the standard hash first, as the d_op->d_hash()
2286 * routine may choose to leave the hash value unchanged.
2287 */
2288 name->hash = full_name_hash(dir, name->name, name->len);
2289 if (dir->d_flags & DCACHE_OP_HASH) {
2290 int err = dir->d_op->d_hash(dir, name);
2291 if (unlikely(err < 0))
2292 return ERR_PTR(err);
2293 }
2294 return d_lookup(dir, name);
2295}
2296EXPORT_SYMBOL(d_hash_and_lookup);
2297
2298/*
2299 * When a file is deleted, we have two options:
2300 * - turn this dentry into a negative dentry
2301 * - unhash this dentry and free it.
2302 *
2303 * Usually, we want to just turn this into
2304 * a negative dentry, but if anybody else is
2305 * currently using the dentry or the inode
2306 * we can't do that and we fall back on removing
2307 * it from the hash queues and waiting for
2308 * it to be deleted later when it has no users
2309 */
2310
2311/**
2312 * d_delete - delete a dentry
2313 * @dentry: The dentry to delete
2314 *
2315 * Turn the dentry into a negative dentry if possible, otherwise
2316 * remove it from the hash queues so it can be deleted later
2317 */
2318
2319void d_delete(struct dentry * dentry)
2320{
2321 struct inode *inode;
2322 int isdir = 0;
2323 /*
2324 * Are we the only user?
2325 */
2326again:
2327 spin_lock(&dentry->d_lock);
2328 inode = dentry->d_inode;
2329 isdir = S_ISDIR(inode->i_mode);
2330 if (dentry->d_lockref.count == 1) {
2331 if (!spin_trylock(&inode->i_lock)) {
2332 spin_unlock(&dentry->d_lock);
2333 cpu_relax();
2334 goto again;
2335 }
2336 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2337 dentry_unlink_inode(dentry);
2338 fsnotify_nameremove(dentry, isdir);
2339 return;
2340 }
2341
2342 if (!d_unhashed(dentry))
2343 __d_drop(dentry);
2344
2345 spin_unlock(&dentry->d_lock);
2346
2347 fsnotify_nameremove(dentry, isdir);
2348}
2349EXPORT_SYMBOL(d_delete);
2350
2351static void __d_rehash(struct dentry *entry)
2352{
2353 struct hlist_bl_head *b = d_hash(entry->d_name.hash);
2354 BUG_ON(!d_unhashed(entry));
2355 hlist_bl_lock(b);
2356 hlist_bl_add_head_rcu(&entry->d_hash, b);
2357 hlist_bl_unlock(b);
2358}
2359
2360/**
2361 * d_rehash - add an entry back to the hash
2362 * @entry: dentry to add to the hash
2363 *
2364 * Adds a dentry to the hash according to its name.
2365 */
2366
2367void d_rehash(struct dentry * entry)
2368{
2369 spin_lock(&entry->d_lock);
2370 __d_rehash(entry);
2371 spin_unlock(&entry->d_lock);
2372}
2373EXPORT_SYMBOL(d_rehash);
2374
2375static inline unsigned start_dir_add(struct inode *dir)
2376{
2377
2378 for (;;) {
2379 unsigned n = dir->i_dir_seq;
2380 if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
2381 return n;
2382 cpu_relax();
2383 }
2384}
2385
2386static inline void end_dir_add(struct inode *dir, unsigned n)
2387{
2388 smp_store_release(&dir->i_dir_seq, n + 2);
2389}
2390
2391static void d_wait_lookup(struct dentry *dentry)
2392{
2393 if (d_in_lookup(dentry)) {
2394 DECLARE_WAITQUEUE(wait, current);
2395 add_wait_queue(dentry->d_wait, &wait);
2396 do {
2397 set_current_state(TASK_UNINTERRUPTIBLE);
2398 spin_unlock(&dentry->d_lock);
2399 schedule();
2400 spin_lock(&dentry->d_lock);
2401 } while (d_in_lookup(dentry));
2402 }
2403}
2404
2405struct dentry *d_alloc_parallel(struct dentry *parent,
2406 const struct qstr *name,
2407 wait_queue_head_t *wq)
2408{
2409 unsigned int hash = name->hash;
2410 struct hlist_bl_head *b = in_lookup_hash(parent, hash);
2411 struct hlist_bl_node *node;
2412 struct dentry *new = d_alloc(parent, name);
2413 struct dentry *dentry;
2414 unsigned seq, r_seq, d_seq;
2415
2416 if (unlikely(!new))
2417 return ERR_PTR(-ENOMEM);
2418
2419retry:
2420 rcu_read_lock();
2421 seq = smp_load_acquire(&parent->d_inode->i_dir_seq) & ~1;
2422 r_seq = read_seqbegin(&rename_lock);
2423 dentry = __d_lookup_rcu(parent, name, &d_seq);
2424 if (unlikely(dentry)) {
2425 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2426 rcu_read_unlock();
2427 goto retry;
2428 }
2429 if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
2430 rcu_read_unlock();
2431 dput(dentry);
2432 goto retry;
2433 }
2434 rcu_read_unlock();
2435 dput(new);
2436 return dentry;
2437 }
2438 if (unlikely(read_seqretry(&rename_lock, r_seq))) {
2439 rcu_read_unlock();
2440 goto retry;
2441 }
2442 hlist_bl_lock(b);
2443 if (unlikely(parent->d_inode->i_dir_seq != seq)) {
2444 hlist_bl_unlock(b);
2445 rcu_read_unlock();
2446 goto retry;
2447 }
2448 /*
2449 * No changes for the parent since the beginning of d_lookup().
2450 * Since all removals from the chain happen with hlist_bl_lock(),
2451 * any potential in-lookup matches are going to stay here until
2452 * we unlock the chain. All fields are stable in everything
2453 * we encounter.
2454 */
2455 hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
2456 if (dentry->d_name.hash != hash)
2457 continue;
2458 if (dentry->d_parent != parent)
2459 continue;
2460 if (!d_same_name(dentry, parent, name))
2461 continue;
2462 hlist_bl_unlock(b);
2463 /* now we can try to grab a reference */
2464 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2465 rcu_read_unlock();
2466 goto retry;
2467 }
2468
2469 rcu_read_unlock();
2470 /*
2471 * somebody is likely to be still doing lookup for it;
2472 * wait for them to finish
2473 */
2474 spin_lock(&dentry->d_lock);
2475 d_wait_lookup(dentry);
2476 /*
2477 * it's not in-lookup anymore; in principle we should repeat
2478 * everything from dcache lookup, but it's likely to be what
2479 * d_lookup() would've found anyway. If it is, just return it;
2480 * otherwise we really have to repeat the whole thing.
2481 */
2482 if (unlikely(dentry->d_name.hash != hash))
2483 goto mismatch;
2484 if (unlikely(dentry->d_parent != parent))
2485 goto mismatch;
2486 if (unlikely(d_unhashed(dentry)))
2487 goto mismatch;
2488 if (unlikely(!d_same_name(dentry, parent, name)))
2489 goto mismatch;
2490 /* OK, it *is* a hashed match; return it */
2491 spin_unlock(&dentry->d_lock);
2492 dput(new);
2493 return dentry;
2494 }
2495 rcu_read_unlock();
2496 /* we can't take ->d_lock here; it's OK, though. */
2497 new->d_flags |= DCACHE_PAR_LOOKUP;
2498 new->d_wait = wq;
2499 hlist_bl_add_head_rcu(&new->d_u.d_in_lookup_hash, b);
2500 hlist_bl_unlock(b);
2501 return new;
2502mismatch:
2503 spin_unlock(&dentry->d_lock);
2504 dput(dentry);
2505 goto retry;
2506}
2507EXPORT_SYMBOL(d_alloc_parallel);
2508
2509void __d_lookup_done(struct dentry *dentry)
2510{
2511 struct hlist_bl_head *b = in_lookup_hash(dentry->d_parent,
2512 dentry->d_name.hash);
2513 hlist_bl_lock(b);
2514 dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
2515 __hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
2516 wake_up_all(dentry->d_wait);
2517 dentry->d_wait = NULL;
2518 hlist_bl_unlock(b);
2519 INIT_HLIST_NODE(&dentry->d_u.d_alias);
2520 INIT_LIST_HEAD(&dentry->d_lru);
2521}
2522EXPORT_SYMBOL(__d_lookup_done);
2523
2524/* inode->i_lock held if inode is non-NULL */
2525
2526static inline void __d_add(struct dentry *dentry, struct inode *inode)
2527{
2528 struct inode *dir = NULL;
2529 unsigned n;
2530 spin_lock(&dentry->d_lock);
2531 if (unlikely(d_in_lookup(dentry))) {
2532 dir = dentry->d_parent->d_inode;
2533 n = start_dir_add(dir);
2534 __d_lookup_done(dentry);
2535 }
2536 if (inode) {
2537 unsigned add_flags = d_flags_for_inode(inode);
2538 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2539 raw_write_seqcount_begin(&dentry->d_seq);
2540 __d_set_inode_and_type(dentry, inode, add_flags);
2541 raw_write_seqcount_end(&dentry->d_seq);
2542 fsnotify_update_flags(dentry);
2543 }
2544 __d_rehash(dentry);
2545 if (dir)
2546 end_dir_add(dir, n);
2547 spin_unlock(&dentry->d_lock);
2548 if (inode)
2549 spin_unlock(&inode->i_lock);
2550}
2551
2552/**
2553 * d_add - add dentry to hash queues
2554 * @entry: dentry to add
2555 * @inode: The inode to attach to this dentry
2556 *
2557 * This adds the entry to the hash queues and initializes @inode.
2558 * The entry was actually filled in earlier during d_alloc().
2559 */
2560
2561void d_add(struct dentry *entry, struct inode *inode)
2562{
2563 if (inode) {
2564 security_d_instantiate(entry, inode);
2565 spin_lock(&inode->i_lock);
2566 }
2567 __d_add(entry, inode);
2568}
2569EXPORT_SYMBOL(d_add);
2570
2571/**
2572 * d_exact_alias - find and hash an exact unhashed alias
2573 * @entry: dentry to add
2574 * @inode: The inode to go with this dentry
2575 *
2576 * If an unhashed dentry with the same name/parent and desired
2577 * inode already exists, hash and return it. Otherwise, return
2578 * NULL.
2579 *
2580 * Parent directory should be locked.
2581 */
2582struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
2583{
2584 struct dentry *alias;
2585 unsigned int hash = entry->d_name.hash;
2586
2587 spin_lock(&inode->i_lock);
2588 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
2589 /*
2590 * Don't need alias->d_lock here, because aliases with
2591 * d_parent == entry->d_parent are not subject to name or
2592 * parent changes, because the parent inode i_mutex is held.
2593 */
2594 if (alias->d_name.hash != hash)
2595 continue;
2596 if (alias->d_parent != entry->d_parent)
2597 continue;
2598 if (!d_same_name(alias, entry->d_parent, &entry->d_name))
2599 continue;
2600 spin_lock(&alias->d_lock);
2601 if (!d_unhashed(alias)) {
2602 spin_unlock(&alias->d_lock);
2603 alias = NULL;
2604 } else {
2605 __dget_dlock(alias);
2606 __d_rehash(alias);
2607 spin_unlock(&alias->d_lock);
2608 }
2609 spin_unlock(&inode->i_lock);
2610 return alias;
2611 }
2612 spin_unlock(&inode->i_lock);
2613 return NULL;
2614}
2615EXPORT_SYMBOL(d_exact_alias);
2616
2617/**
2618 * dentry_update_name_case - update case insensitive dentry with a new name
2619 * @dentry: dentry to be updated
2620 * @name: new name
2621 *
2622 * Update a case insensitive dentry with new case of name.
2623 *
2624 * dentry must have been returned by d_lookup with name @name. Old and new
2625 * name lengths must match (ie. no d_compare which allows mismatched name
2626 * lengths).
2627 *
2628 * Parent inode i_mutex must be held over d_lookup and into this call (to
2629 * keep renames and concurrent inserts, and readdir(2) away).
2630 */
2631void dentry_update_name_case(struct dentry *dentry, const struct qstr *name)
2632{
2633 BUG_ON(!inode_is_locked(dentry->d_parent->d_inode));
2634 BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
2635
2636 spin_lock(&dentry->d_lock);
2637 write_seqcount_begin(&dentry->d_seq);
2638 memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
2639 write_seqcount_end(&dentry->d_seq);
2640 spin_unlock(&dentry->d_lock);
2641}
2642EXPORT_SYMBOL(dentry_update_name_case);
2643
2644static void swap_names(struct dentry *dentry, struct dentry *target)
2645{
2646 if (unlikely(dname_external(target))) {
2647 if (unlikely(dname_external(dentry))) {
2648 /*
2649 * Both external: swap the pointers
2650 */
2651 swap(target->d_name.name, dentry->d_name.name);
2652 } else {
2653 /*
2654 * dentry:internal, target:external. Steal target's
2655 * storage and make target internal.
2656 */
2657 memcpy(target->d_iname, dentry->d_name.name,
2658 dentry->d_name.len + 1);
2659 dentry->d_name.name = target->d_name.name;
2660 target->d_name.name = target->d_iname;
2661 }
2662 } else {
2663 if (unlikely(dname_external(dentry))) {
2664 /*
2665 * dentry:external, target:internal. Give dentry's
2666 * storage to target and make dentry internal
2667 */
2668 memcpy(dentry->d_iname, target->d_name.name,
2669 target->d_name.len + 1);
2670 target->d_name.name = dentry->d_name.name;
2671 dentry->d_name.name = dentry->d_iname;
2672 } else {
2673 /*
2674 * Both are internal.
2675 */
2676 unsigned int i;
2677 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
2678 kmemcheck_mark_initialized(dentry->d_iname, DNAME_INLINE_LEN);
2679 kmemcheck_mark_initialized(target->d_iname, DNAME_INLINE_LEN);
2680 for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
2681 swap(((long *) &dentry->d_iname)[i],
2682 ((long *) &target->d_iname)[i]);
2683 }
2684 }
2685 }
2686 swap(dentry->d_name.hash_len, target->d_name.hash_len);
2687}
2688
2689static void copy_name(struct dentry *dentry, struct dentry *target)
2690{
2691 struct external_name *old_name = NULL;
2692 if (unlikely(dname_external(dentry)))
2693 old_name = external_name(dentry);
2694 if (unlikely(dname_external(target))) {
2695 atomic_inc(&external_name(target)->u.count);
2696 dentry->d_name = target->d_name;
2697 } else {
2698 memcpy(dentry->d_iname, target->d_name.name,
2699 target->d_name.len + 1);
2700 dentry->d_name.name = dentry->d_iname;
2701 dentry->d_name.hash_len = target->d_name.hash_len;
2702 }
2703 if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
2704 kfree_rcu(old_name, u.head);
2705}
2706
2707static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
2708{
2709 /*
2710 * XXXX: do we really need to take target->d_lock?
2711 */
2712 if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent)
2713 spin_lock(&target->d_parent->d_lock);
2714 else {
2715 if (d_ancestor(dentry->d_parent, target->d_parent)) {
2716 spin_lock(&dentry->d_parent->d_lock);
2717 spin_lock_nested(&target->d_parent->d_lock,
2718 DENTRY_D_LOCK_NESTED);
2719 } else {
2720 spin_lock(&target->d_parent->d_lock);
2721 spin_lock_nested(&dentry->d_parent->d_lock,
2722 DENTRY_D_LOCK_NESTED);
2723 }
2724 }
2725 if (target < dentry) {
2726 spin_lock_nested(&target->d_lock, 2);
2727 spin_lock_nested(&dentry->d_lock, 3);
2728 } else {
2729 spin_lock_nested(&dentry->d_lock, 2);
2730 spin_lock_nested(&target->d_lock, 3);
2731 }
2732}
2733
2734static void dentry_unlock_for_move(struct dentry *dentry, struct dentry *target)
2735{
2736 if (target->d_parent != dentry->d_parent)
2737 spin_unlock(&dentry->d_parent->d_lock);
2738 if (target->d_parent != target)
2739 spin_unlock(&target->d_parent->d_lock);
2740 spin_unlock(&target->d_lock);
2741 spin_unlock(&dentry->d_lock);
2742}
2743
2744/*
2745 * When switching names, the actual string doesn't strictly have to
2746 * be preserved in the target - because we're dropping the target
2747 * anyway. As such, we can just do a simple memcpy() to copy over
2748 * the new name before we switch, unless we are going to rehash
2749 * it. Note that if we *do* unhash the target, we are not allowed
2750 * to rehash it without giving it a new name/hash key - whether
2751 * we swap or overwrite the names here, resulting name won't match
2752 * the reality in filesystem; it's only there for d_path() purposes.
2753 * Note that all of this is happening under rename_lock, so the
2754 * any hash lookup seeing it in the middle of manipulations will
2755 * be discarded anyway. So we do not care what happens to the hash
2756 * key in that case.
2757 */
2758/*
2759 * __d_move - move a dentry
2760 * @dentry: entry to move
2761 * @target: new dentry
2762 * @exchange: exchange the two dentries
2763 *
2764 * Update the dcache to reflect the move of a file name. Negative
2765 * dcache entries should not be moved in this way. Caller must hold
2766 * rename_lock, the i_mutex of the source and target directories,
2767 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2768 */
2769static void __d_move(struct dentry *dentry, struct dentry *target,
2770 bool exchange)
2771{
2772 struct inode *dir = NULL;
2773 unsigned n;
2774 if (!dentry->d_inode)
2775 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
2776
2777 BUG_ON(d_ancestor(dentry, target));
2778 BUG_ON(d_ancestor(target, dentry));
2779
2780 dentry_lock_for_move(dentry, target);
2781 if (unlikely(d_in_lookup(target))) {
2782 dir = target->d_parent->d_inode;
2783 n = start_dir_add(dir);
2784 __d_lookup_done(target);
2785 }
2786
2787 write_seqcount_begin(&dentry->d_seq);
2788 write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
2789
2790 /* unhash both */
2791 /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
2792 __d_drop(dentry);
2793 __d_drop(target);
2794
2795 /* Switch the names.. */
2796 if (exchange)
2797 swap_names(dentry, target);
2798 else
2799 copy_name(dentry, target);
2800
2801 /* rehash in new place(s) */
2802 __d_rehash(dentry);
2803 if (exchange)
2804 __d_rehash(target);
2805
2806 /* ... and switch them in the tree */
2807 if (IS_ROOT(dentry)) {
2808 /* splicing a tree */
2809 dentry->d_flags |= DCACHE_RCUACCESS;
2810 dentry->d_parent = target->d_parent;
2811 target->d_parent = target;
2812 list_del_init(&target->d_child);
2813 list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
2814 } else {
2815 /* swapping two dentries */
2816 swap(dentry->d_parent, target->d_parent);
2817 list_move(&target->d_child, &target->d_parent->d_subdirs);
2818 list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
2819 if (exchange)
2820 fsnotify_update_flags(target);
2821 fsnotify_update_flags(dentry);
2822 }
2823
2824 write_seqcount_end(&target->d_seq);
2825 write_seqcount_end(&dentry->d_seq);
2826
2827 if (dir)
2828 end_dir_add(dir, n);
2829 dentry_unlock_for_move(dentry, target);
2830}
2831
2832/*
2833 * d_move - move a dentry
2834 * @dentry: entry to move
2835 * @target: new dentry
2836 *
2837 * Update the dcache to reflect the move of a file name. Negative
2838 * dcache entries should not be moved in this way. See the locking
2839 * requirements for __d_move.
2840 */
2841void d_move(struct dentry *dentry, struct dentry *target)
2842{
2843 write_seqlock(&rename_lock);
2844 __d_move(dentry, target, false);
2845 write_sequnlock(&rename_lock);
2846}
2847EXPORT_SYMBOL(d_move);
2848
2849/*
2850 * d_exchange - exchange two dentries
2851 * @dentry1: first dentry
2852 * @dentry2: second dentry
2853 */
2854void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
2855{
2856 write_seqlock(&rename_lock);
2857
2858 WARN_ON(!dentry1->d_inode);
2859 WARN_ON(!dentry2->d_inode);
2860 WARN_ON(IS_ROOT(dentry1));
2861 WARN_ON(IS_ROOT(dentry2));
2862
2863 __d_move(dentry1, dentry2, true);
2864
2865 write_sequnlock(&rename_lock);
2866}
2867
2868/**
2869 * d_ancestor - search for an ancestor
2870 * @p1: ancestor dentry
2871 * @p2: child dentry
2872 *
2873 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2874 * an ancestor of p2, else NULL.
2875 */
2876struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2877{
2878 struct dentry *p;
2879
2880 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2881 if (p->d_parent == p1)
2882 return p;
2883 }
2884 return NULL;
2885}
2886
2887/*
2888 * This helper attempts to cope with remotely renamed directories
2889 *
2890 * It assumes that the caller is already holding
2891 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2892 *
2893 * Note: If ever the locking in lock_rename() changes, then please
2894 * remember to update this too...
2895 */
2896static int __d_unalias(struct inode *inode,
2897 struct dentry *dentry, struct dentry *alias)
2898{
2899 struct mutex *m1 = NULL;
2900 struct rw_semaphore *m2 = NULL;
2901 int ret = -ESTALE;
2902
2903 /* If alias and dentry share a parent, then no extra locks required */
2904 if (alias->d_parent == dentry->d_parent)
2905 goto out_unalias;
2906
2907 /* See lock_rename() */
2908 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
2909 goto out_err;
2910 m1 = &dentry->d_sb->s_vfs_rename_mutex;
2911 if (!inode_trylock_shared(alias->d_parent->d_inode))
2912 goto out_err;
2913 m2 = &alias->d_parent->d_inode->i_rwsem;
2914out_unalias:
2915 __d_move(alias, dentry, false);
2916 ret = 0;
2917out_err:
2918 if (m2)
2919 up_read(m2);
2920 if (m1)
2921 mutex_unlock(m1);
2922 return ret;
2923}
2924
2925/**
2926 * d_splice_alias - splice a disconnected dentry into the tree if one exists
2927 * @inode: the inode which may have a disconnected dentry
2928 * @dentry: a negative dentry which we want to point to the inode.
2929 *
2930 * If inode is a directory and has an IS_ROOT alias, then d_move that in
2931 * place of the given dentry and return it, else simply d_add the inode
2932 * to the dentry and return NULL.
2933 *
2934 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
2935 * we should error out: directories can't have multiple aliases.
2936 *
2937 * This is needed in the lookup routine of any filesystem that is exportable
2938 * (via knfsd) so that we can build dcache paths to directories effectively.
2939 *
2940 * If a dentry was found and moved, then it is returned. Otherwise NULL
2941 * is returned. This matches the expected return value of ->lookup.
2942 *
2943 * Cluster filesystems may call this function with a negative, hashed dentry.
2944 * In that case, we know that the inode will be a regular file, and also this
2945 * will only occur during atomic_open. So we need to check for the dentry
2946 * being already hashed only in the final case.
2947 */
2948struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
2949{
2950 if (IS_ERR(inode))
2951 return ERR_CAST(inode);
2952
2953 BUG_ON(!d_unhashed(dentry));
2954
2955 if (!inode)
2956 goto out;
2957
2958 security_d_instantiate(dentry, inode);
2959 spin_lock(&inode->i_lock);
2960 if (S_ISDIR(inode->i_mode)) {
2961 struct dentry *new = __d_find_any_alias(inode);
2962 if (unlikely(new)) {
2963 /* The reference to new ensures it remains an alias */
2964 spin_unlock(&inode->i_lock);
2965 write_seqlock(&rename_lock);
2966 if (unlikely(d_ancestor(new, dentry))) {
2967 write_sequnlock(&rename_lock);
2968 dput(new);
2969 new = ERR_PTR(-ELOOP);
2970 pr_warn_ratelimited(
2971 "VFS: Lookup of '%s' in %s %s"
2972 " would have caused loop\n",
2973 dentry->d_name.name,
2974 inode->i_sb->s_type->name,
2975 inode->i_sb->s_id);
2976 } else if (!IS_ROOT(new)) {
2977 int err = __d_unalias(inode, dentry, new);
2978 write_sequnlock(&rename_lock);
2979 if (err) {
2980 dput(new);
2981 new = ERR_PTR(err);
2982 }
2983 } else {
2984 __d_move(new, dentry, false);
2985 write_sequnlock(&rename_lock);
2986 }
2987 iput(inode);
2988 return new;
2989 }
2990 }
2991out:
2992 __d_add(dentry, inode);
2993 return NULL;
2994}
2995EXPORT_SYMBOL(d_splice_alias);
2996
2997static int prepend(char **buffer, int *buflen, const char *str, int namelen)
2998{
2999 *buflen -= namelen;
3000 if (*buflen < 0)
3001 return -ENAMETOOLONG;
3002 *buffer -= namelen;
3003 memcpy(*buffer, str, namelen);
3004 return 0;
3005}
3006
3007/**
3008 * prepend_name - prepend a pathname in front of current buffer pointer
3009 * @buffer: buffer pointer
3010 * @buflen: allocated length of the buffer
3011 * @name: name string and length qstr structure
3012 *
3013 * With RCU path tracing, it may race with d_move(). Use ACCESS_ONCE() to
3014 * make sure that either the old or the new name pointer and length are
3015 * fetched. However, there may be mismatch between length and pointer.
3016 * The length cannot be trusted, we need to copy it byte-by-byte until
3017 * the length is reached or a null byte is found. It also prepends "/" at
3018 * the beginning of the name. The sequence number check at the caller will
3019 * retry it again when a d_move() does happen. So any garbage in the buffer
3020 * due to mismatched pointer and length will be discarded.
3021 *
3022 * Data dependency barrier is needed to make sure that we see that terminating
3023 * NUL. Alpha strikes again, film at 11...
3024 */
3025static int prepend_name(char **buffer, int *buflen, const struct qstr *name)
3026{
3027 const char *dname = ACCESS_ONCE(name->name);
3028 u32 dlen = ACCESS_ONCE(name->len);
3029 char *p;
3030
3031 smp_read_barrier_depends();
3032
3033 *buflen -= dlen + 1;
3034 if (*buflen < 0)
3035 return -ENAMETOOLONG;
3036 p = *buffer -= dlen + 1;
3037 *p++ = '/';
3038 while (dlen--) {
3039 char c = *dname++;
3040 if (!c)
3041 break;
3042 *p++ = c;
3043 }
3044 return 0;
3045}
3046
3047/**
3048 * prepend_path - Prepend path string to a buffer
3049 * @path: the dentry/vfsmount to report
3050 * @root: root vfsmnt/dentry
3051 * @buffer: pointer to the end of the buffer
3052 * @buflen: pointer to buffer length
3053 *
3054 * The function will first try to write out the pathname without taking any
3055 * lock other than the RCU read lock to make sure that dentries won't go away.
3056 * It only checks the sequence number of the global rename_lock as any change
3057 * in the dentry's d_seq will be preceded by changes in the rename_lock
3058 * sequence number. If the sequence number had been changed, it will restart
3059 * the whole pathname back-tracing sequence again by taking the rename_lock.
3060 * In this case, there is no need to take the RCU read lock as the recursive
3061 * parent pointer references will keep the dentry chain alive as long as no
3062 * rename operation is performed.
3063 */
3064static int prepend_path(const struct path *path,
3065 const struct path *root,
3066 char **buffer, int *buflen)
3067{
3068 struct dentry *dentry;
3069 struct vfsmount *vfsmnt;
3070 struct mount *mnt;
3071 int error = 0;
3072 unsigned seq, m_seq = 0;
3073 char *bptr;
3074 int blen;
3075
3076 rcu_read_lock();
3077restart_mnt:
3078 read_seqbegin_or_lock(&mount_lock, &m_seq);
3079 seq = 0;
3080 rcu_read_lock();
3081restart:
3082 bptr = *buffer;
3083 blen = *buflen;
3084 error = 0;
3085 dentry = path->dentry;
3086 vfsmnt = path->mnt;
3087 mnt = real_mount(vfsmnt);
3088 read_seqbegin_or_lock(&rename_lock, &seq);
3089 while (dentry != root->dentry || vfsmnt != root->mnt) {
3090 struct dentry * parent;
3091
3092 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
3093 struct mount *parent = ACCESS_ONCE(mnt->mnt_parent);
3094 /* Escaped? */
3095 if (dentry != vfsmnt->mnt_root) {
3096 bptr = *buffer;
3097 blen = *buflen;
3098 error = 3;
3099 break;
3100 }
3101 /* Global root? */
3102 if (mnt != parent) {
3103 dentry = ACCESS_ONCE(mnt->mnt_mountpoint);
3104 mnt = parent;
3105 vfsmnt = &mnt->mnt;
3106 continue;
3107 }
3108 if (!error)
3109 error = is_mounted(vfsmnt) ? 1 : 2;
3110 break;
3111 }
3112 parent = dentry->d_parent;
3113 prefetch(parent);
3114 error = prepend_name(&bptr, &blen, &dentry->d_name);
3115 if (error)
3116 break;
3117
3118 dentry = parent;
3119 }
3120 if (!(seq & 1))
3121 rcu_read_unlock();
3122 if (need_seqretry(&rename_lock, seq)) {
3123 seq = 1;
3124 goto restart;
3125 }
3126 done_seqretry(&rename_lock, seq);
3127
3128 if (!(m_seq & 1))
3129 rcu_read_unlock();
3130 if (need_seqretry(&mount_lock, m_seq)) {
3131 m_seq = 1;
3132 goto restart_mnt;
3133 }
3134 done_seqretry(&mount_lock, m_seq);
3135
3136 if (error >= 0 && bptr == *buffer) {
3137 if (--blen < 0)
3138 error = -ENAMETOOLONG;
3139 else
3140 *--bptr = '/';
3141 }
3142 *buffer = bptr;
3143 *buflen = blen;
3144 return error;
3145}
3146
3147/**
3148 * __d_path - return the path of a dentry
3149 * @path: the dentry/vfsmount to report
3150 * @root: root vfsmnt/dentry
3151 * @buf: buffer to return value in
3152 * @buflen: buffer length
3153 *
3154 * Convert a dentry into an ASCII path name.
3155 *
3156 * Returns a pointer into the buffer or an error code if the
3157 * path was too long.
3158 *
3159 * "buflen" should be positive.
3160 *
3161 * If the path is not reachable from the supplied root, return %NULL.
3162 */
3163char *__d_path(const struct path *path,
3164 const struct path *root,
3165 char *buf, int buflen)
3166{
3167 char *res = buf + buflen;
3168 int error;
3169
3170 prepend(&res, &buflen, "\0", 1);
3171 error = prepend_path(path, root, &res, &buflen);
3172
3173 if (error < 0)
3174 return ERR_PTR(error);
3175 if (error > 0)
3176 return NULL;
3177 return res;
3178}
3179
3180char *d_absolute_path(const struct path *path,
3181 char *buf, int buflen)
3182{
3183 struct path root = {};
3184 char *res = buf + buflen;
3185 int error;
3186
3187 prepend(&res, &buflen, "\0", 1);
3188 error = prepend_path(path, &root, &res, &buflen);
3189
3190 if (error > 1)
3191 error = -EINVAL;
3192 if (error < 0)
3193 return ERR_PTR(error);
3194 return res;
3195}
3196
3197/*
3198 * same as __d_path but appends "(deleted)" for unlinked files.
3199 */
3200static int path_with_deleted(const struct path *path,
3201 const struct path *root,
3202 char **buf, int *buflen)
3203{
3204 prepend(buf, buflen, "\0", 1);
3205 if (d_unlinked(path->dentry)) {
3206 int error = prepend(buf, buflen, " (deleted)", 10);
3207 if (error)
3208 return error;
3209 }
3210
3211 return prepend_path(path, root, buf, buflen);
3212}
3213
3214static int prepend_unreachable(char **buffer, int *buflen)
3215{
3216 return prepend(buffer, buflen, "(unreachable)", 13);
3217}
3218
3219static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
3220{
3221 unsigned seq;
3222
3223 do {
3224 seq = read_seqcount_begin(&fs->seq);
3225 *root = fs->root;
3226 } while (read_seqcount_retry(&fs->seq, seq));
3227}
3228
3229/**
3230 * d_path - return the path of a dentry
3231 * @path: path to report
3232 * @buf: buffer to return value in
3233 * @buflen: buffer length
3234 *
3235 * Convert a dentry into an ASCII path name. If the entry has been deleted
3236 * the string " (deleted)" is appended. Note that this is ambiguous.
3237 *
3238 * Returns a pointer into the buffer or an error code if the path was
3239 * too long. Note: Callers should use the returned pointer, not the passed
3240 * in buffer, to use the name! The implementation often starts at an offset
3241 * into the buffer, and may leave 0 bytes at the start.
3242 *
3243 * "buflen" should be positive.
3244 */
3245char *d_path(const struct path *path, char *buf, int buflen)
3246{
3247 char *res = buf + buflen;
3248 struct path root;
3249 int error;
3250
3251 /*
3252 * We have various synthetic filesystems that never get mounted. On
3253 * these filesystems dentries are never used for lookup purposes, and
3254 * thus don't need to be hashed. They also don't need a name until a
3255 * user wants to identify the object in /proc/pid/fd/. The little hack
3256 * below allows us to generate a name for these objects on demand:
3257 *
3258 * Some pseudo inodes are mountable. When they are mounted
3259 * path->dentry == path->mnt->mnt_root. In that case don't call d_dname
3260 * and instead have d_path return the mounted path.
3261 */
3262 if (path->dentry->d_op && path->dentry->d_op->d_dname &&
3263 (!IS_ROOT(path->dentry) || path->dentry != path->mnt->mnt_root))
3264 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
3265
3266 rcu_read_lock();
3267 get_fs_root_rcu(current->fs, &root);
3268 error = path_with_deleted(path, &root, &res, &buflen);
3269 rcu_read_unlock();
3270
3271 if (error < 0)
3272 res = ERR_PTR(error);
3273 return res;
3274}
3275EXPORT_SYMBOL(d_path);
3276
3277/*
3278 * Helper function for dentry_operations.d_dname() members
3279 */
3280char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
3281 const char *fmt, ...)
3282{
3283 va_list args;
3284 char temp[64];
3285 int sz;
3286
3287 va_start(args, fmt);
3288 sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
3289 va_end(args);
3290
3291 if (sz > sizeof(temp) || sz > buflen)
3292 return ERR_PTR(-ENAMETOOLONG);
3293
3294 buffer += buflen - sz;
3295 return memcpy(buffer, temp, sz);
3296}
3297
3298char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
3299{
3300 char *end = buffer + buflen;
3301 /* these dentries are never renamed, so d_lock is not needed */
3302 if (prepend(&end, &buflen, " (deleted)", 11) ||
3303 prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len) ||
3304 prepend(&end, &buflen, "/", 1))
3305 end = ERR_PTR(-ENAMETOOLONG);
3306 return end;
3307}
3308EXPORT_SYMBOL(simple_dname);
3309
3310/*
3311 * Write full pathname from the root of the filesystem into the buffer.
3312 */
3313static char *__dentry_path(struct dentry *d, char *buf, int buflen)
3314{
3315 struct dentry *dentry;
3316 char *end, *retval;
3317 int len, seq = 0;
3318 int error = 0;
3319
3320 if (buflen < 2)
3321 goto Elong;
3322
3323 rcu_read_lock();
3324restart:
3325 dentry = d;
3326 end = buf + buflen;
3327 len = buflen;
3328 prepend(&end, &len, "\0", 1);
3329 /* Get '/' right */
3330 retval = end-1;
3331 *retval = '/';
3332 read_seqbegin_or_lock(&rename_lock, &seq);
3333 while (!IS_ROOT(dentry)) {
3334 struct dentry *parent = dentry->d_parent;
3335
3336 prefetch(parent);
3337 error = prepend_name(&end, &len, &dentry->d_name);
3338 if (error)
3339 break;
3340
3341 retval = end;
3342 dentry = parent;
3343 }
3344 if (!(seq & 1))
3345 rcu_read_unlock();
3346 if (need_seqretry(&rename_lock, seq)) {
3347 seq = 1;
3348 goto restart;
3349 }
3350 done_seqretry(&rename_lock, seq);
3351 if (error)
3352 goto Elong;
3353 return retval;
3354Elong:
3355 return ERR_PTR(-ENAMETOOLONG);
3356}
3357
3358char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
3359{
3360 return __dentry_path(dentry, buf, buflen);
3361}
3362EXPORT_SYMBOL(dentry_path_raw);
3363
3364char *dentry_path(struct dentry *dentry, char *buf, int buflen)
3365{
3366 char *p = NULL;
3367 char *retval;
3368
3369 if (d_unlinked(dentry)) {
3370 p = buf + buflen;
3371 if (prepend(&p, &buflen, "//deleted", 10) != 0)
3372 goto Elong;
3373 buflen++;
3374 }
3375 retval = __dentry_path(dentry, buf, buflen);
3376 if (!IS_ERR(retval) && p)
3377 *p = '/'; /* restore '/' overriden with '\0' */
3378 return retval;
3379Elong:
3380 return ERR_PTR(-ENAMETOOLONG);
3381}
3382
3383static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root,
3384 struct path *pwd)
3385{
3386 unsigned seq;
3387
3388 do {
3389 seq = read_seqcount_begin(&fs->seq);
3390 *root = fs->root;
3391 *pwd = fs->pwd;
3392 } while (read_seqcount_retry(&fs->seq, seq));
3393}
3394
3395/*
3396 * NOTE! The user-level library version returns a
3397 * character pointer. The kernel system call just
3398 * returns the length of the buffer filled (which
3399 * includes the ending '\0' character), or a negative
3400 * error value. So libc would do something like
3401 *
3402 * char *getcwd(char * buf, size_t size)
3403 * {
3404 * int retval;
3405 *
3406 * retval = sys_getcwd(buf, size);
3407 * if (retval >= 0)
3408 * return buf;
3409 * errno = -retval;
3410 * return NULL;
3411 * }
3412 */
3413SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
3414{
3415 int error;
3416 struct path pwd, root;
3417 char *page = __getname();
3418
3419 if (!page)
3420 return -ENOMEM;
3421
3422 rcu_read_lock();
3423 get_fs_root_and_pwd_rcu(current->fs, &root, &pwd);
3424
3425 error = -ENOENT;
3426 if (!d_unlinked(pwd.dentry)) {
3427 unsigned long len;
3428 char *cwd = page + PATH_MAX;
3429 int buflen = PATH_MAX;
3430
3431 prepend(&cwd, &buflen, "\0", 1);
3432 error = prepend_path(&pwd, &root, &cwd, &buflen);
3433 rcu_read_unlock();
3434
3435 if (error < 0)
3436 goto out;
3437
3438 /* Unreachable from current root */
3439 if (error > 0) {
3440 error = prepend_unreachable(&cwd, &buflen);
3441 if (error)
3442 goto out;
3443 }
3444
3445 error = -ERANGE;
3446 len = PATH_MAX + page - cwd;
3447 if (len <= size) {
3448 error = len;
3449 if (copy_to_user(buf, cwd, len))
3450 error = -EFAULT;
3451 }
3452 } else {
3453 rcu_read_unlock();
3454 }
3455
3456out:
3457 __putname(page);
3458 return error;
3459}
3460
3461/*
3462 * Test whether new_dentry is a subdirectory of old_dentry.
3463 *
3464 * Trivially implemented using the dcache structure
3465 */
3466
3467/**
3468 * is_subdir - is new dentry a subdirectory of old_dentry
3469 * @new_dentry: new dentry
3470 * @old_dentry: old dentry
3471 *
3472 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3473 * Returns false otherwise.
3474 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3475 */
3476
3477bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
3478{
3479 bool result;
3480 unsigned seq;
3481
3482 if (new_dentry == old_dentry)
3483 return true;
3484
3485 do {
3486 /* for restarting inner loop in case of seq retry */
3487 seq = read_seqbegin(&rename_lock);
3488 /*
3489 * Need rcu_readlock to protect against the d_parent trashing
3490 * due to d_move
3491 */
3492 rcu_read_lock();
3493 if (d_ancestor(old_dentry, new_dentry))
3494 result = true;
3495 else
3496 result = false;
3497 rcu_read_unlock();
3498 } while (read_seqretry(&rename_lock, seq));
3499
3500 return result;
3501}
3502
3503static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
3504{
3505 struct dentry *root = data;
3506 if (dentry != root) {
3507 if (d_unhashed(dentry) || !dentry->d_inode)
3508 return D_WALK_SKIP;
3509
3510 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
3511 dentry->d_flags |= DCACHE_GENOCIDE;
3512 dentry->d_lockref.count--;
3513 }
3514 }
3515 return D_WALK_CONTINUE;
3516}
3517
3518void d_genocide(struct dentry *parent)
3519{
3520 d_walk(parent, parent, d_genocide_kill, NULL);
3521}
3522
3523void d_tmpfile(struct dentry *dentry, struct inode *inode)
3524{
3525 inode_dec_link_count(inode);
3526 BUG_ON(dentry->d_name.name != dentry->d_iname ||
3527 !hlist_unhashed(&dentry->d_u.d_alias) ||
3528 !d_unlinked(dentry));
3529 spin_lock(&dentry->d_parent->d_lock);
3530 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
3531 dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
3532 (unsigned long long)inode->i_ino);
3533 spin_unlock(&dentry->d_lock);
3534 spin_unlock(&dentry->d_parent->d_lock);
3535 d_instantiate(dentry, inode);
3536}
3537EXPORT_SYMBOL(d_tmpfile);
3538
3539static __initdata unsigned long dhash_entries;
3540static int __init set_dhash_entries(char *str)
3541{
3542 if (!str)
3543 return 0;
3544 dhash_entries = simple_strtoul(str, &str, 0);
3545 return 1;
3546}
3547__setup("dhash_entries=", set_dhash_entries);
3548
3549static void __init dcache_init_early(void)
3550{
3551 unsigned int loop;
3552
3553 /* If hashes are distributed across NUMA nodes, defer
3554 * hash allocation until vmalloc space is available.
3555 */
3556 if (hashdist)
3557 return;
3558
3559 dentry_hashtable =
3560 alloc_large_system_hash("Dentry cache",
3561 sizeof(struct hlist_bl_head),
3562 dhash_entries,
3563 13,
3564 HASH_EARLY,
3565 &d_hash_shift,
3566 &d_hash_mask,
3567 0,
3568 0);
3569
3570 for (loop = 0; loop < (1U << d_hash_shift); loop++)
3571 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
3572}
3573
3574static void __init dcache_init(void)
3575{
3576 unsigned int loop;
3577
3578 /*
3579 * A constructor could be added for stable state like the lists,
3580 * but it is probably not worth it because of the cache nature
3581 * of the dcache.
3582 */
3583 dentry_cache = KMEM_CACHE(dentry,
3584 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT);
3585
3586 /* Hash may have been set up in dcache_init_early */
3587 if (!hashdist)
3588 return;
3589
3590 dentry_hashtable =
3591 alloc_large_system_hash("Dentry cache",
3592 sizeof(struct hlist_bl_head),
3593 dhash_entries,
3594 13,
3595 0,
3596 &d_hash_shift,
3597 &d_hash_mask,
3598 0,
3599 0);
3600
3601 for (loop = 0; loop < (1U << d_hash_shift); loop++)
3602 INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
3603}
3604
3605/* SLAB cache for __getname() consumers */
3606struct kmem_cache *names_cachep __read_mostly;
3607EXPORT_SYMBOL(names_cachep);
3608
3609EXPORT_SYMBOL(d_genocide);
3610
3611void __init vfs_caches_init_early(void)
3612{
3613 dcache_init_early();
3614 inode_init_early();
3615}
3616
3617void __init vfs_caches_init(void)
3618{
3619 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
3620 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
3621
3622 dcache_init();
3623 inode_init();
3624 files_init();
3625 files_maxfiles_init();
3626 mnt_init();
3627 bdev_cache_init();
3628 chrdev_init();
3629}