]> git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - fs/dcache.c
Merge tag 'hwlock-v4.18' of git://github.com/andersson/remoteproc
[mirror_ubuntu-jammy-kernel.git] / fs / dcache.c
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/ratelimit.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/security.h>
28 #include <linux/seqlock.h>
29 #include <linux/bootmem.h>
30 #include <linux/bit_spinlock.h>
31 #include <linux/rculist_bl.h>
32 #include <linux/list_lru.h>
33 #include "internal.h"
34 #include "mount.h"
35
36 /*
37 * Usage:
38 * dcache->d_inode->i_lock protects:
39 * - i_dentry, d_u.d_alias, d_inode of aliases
40 * dcache_hash_bucket lock protects:
41 * - the dcache hash table
42 * s_roots bl list spinlock protects:
43 * - the s_roots list (see __d_drop)
44 * dentry->d_sb->s_dentry_lru_lock protects:
45 * - the dcache lru lists and counters
46 * d_lock protects:
47 * - d_flags
48 * - d_name
49 * - d_lru
50 * - d_count
51 * - d_unhashed()
52 * - d_parent and d_subdirs
53 * - childrens' d_child and d_parent
54 * - d_u.d_alias, d_inode
55 *
56 * Ordering:
57 * dentry->d_inode->i_lock
58 * dentry->d_lock
59 * dentry->d_sb->s_dentry_lru_lock
60 * dcache_hash_bucket lock
61 * s_roots lock
62 *
63 * If there is an ancestor relationship:
64 * dentry->d_parent->...->d_parent->d_lock
65 * ...
66 * dentry->d_parent->d_lock
67 * dentry->d_lock
68 *
69 * If no ancestor relationship:
70 * arbitrary, since it's serialized on rename_lock
71 */
72 int sysctl_vfs_cache_pressure __read_mostly = 100;
73 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
74
75 __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
76
77 EXPORT_SYMBOL(rename_lock);
78
79 static struct kmem_cache *dentry_cache __read_mostly;
80
81 const struct qstr empty_name = QSTR_INIT("", 0);
82 EXPORT_SYMBOL(empty_name);
83 const struct qstr slash_name = QSTR_INIT("/", 1);
84 EXPORT_SYMBOL(slash_name);
85
86 /*
87 * This is the single most critical data structure when it comes
88 * to the dcache: the hashtable for lookups. Somebody should try
89 * to make this good - I've just made it work.
90 *
91 * This hash-function tries to avoid losing too many bits of hash
92 * information, yet avoid using a prime hash-size or similar.
93 */
94
95 static unsigned int d_hash_shift __read_mostly;
96
97 static struct hlist_bl_head *dentry_hashtable __read_mostly;
98
99 static inline struct hlist_bl_head *d_hash(unsigned int hash)
100 {
101 return dentry_hashtable + (hash >> d_hash_shift);
102 }
103
104 #define IN_LOOKUP_SHIFT 10
105 static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT];
106
107 static inline struct hlist_bl_head *in_lookup_hash(const struct dentry *parent,
108 unsigned int hash)
109 {
110 hash += (unsigned long) parent / L1_CACHE_BYTES;
111 return in_lookup_hashtable + hash_32(hash, IN_LOOKUP_SHIFT);
112 }
113
114
115 /* Statistics gathering. */
116 struct dentry_stat_t dentry_stat = {
117 .age_limit = 45,
118 };
119
120 static DEFINE_PER_CPU(long, nr_dentry);
121 static DEFINE_PER_CPU(long, nr_dentry_unused);
122
123 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
124
125 /*
126 * Here we resort to our own counters instead of using generic per-cpu counters
127 * for consistency with what the vfs inode code does. We are expected to harvest
128 * better code and performance by having our own specialized counters.
129 *
130 * Please note that the loop is done over all possible CPUs, not over all online
131 * CPUs. The reason for this is that we don't want to play games with CPUs going
132 * on and off. If one of them goes off, we will just keep their counters.
133 *
134 * glommer: See cffbc8a for details, and if you ever intend to change this,
135 * please update all vfs counters to match.
136 */
137 static long get_nr_dentry(void)
138 {
139 int i;
140 long sum = 0;
141 for_each_possible_cpu(i)
142 sum += per_cpu(nr_dentry, i);
143 return sum < 0 ? 0 : sum;
144 }
145
146 static long get_nr_dentry_unused(void)
147 {
148 int i;
149 long sum = 0;
150 for_each_possible_cpu(i)
151 sum += per_cpu(nr_dentry_unused, i);
152 return sum < 0 ? 0 : sum;
153 }
154
155 int proc_nr_dentry(struct ctl_table *table, int write, void __user *buffer,
156 size_t *lenp, loff_t *ppos)
157 {
158 dentry_stat.nr_dentry = get_nr_dentry();
159 dentry_stat.nr_unused = get_nr_dentry_unused();
160 return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
161 }
162 #endif
163
164 /*
165 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
166 * The strings are both count bytes long, and count is non-zero.
167 */
168 #ifdef CONFIG_DCACHE_WORD_ACCESS
169
170 #include <asm/word-at-a-time.h>
171 /*
172 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
173 * aligned allocation for this particular component. We don't
174 * strictly need the load_unaligned_zeropad() safety, but it
175 * doesn't hurt either.
176 *
177 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
178 * need the careful unaligned handling.
179 */
180 static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
181 {
182 unsigned long a,b,mask;
183
184 for (;;) {
185 a = read_word_at_a_time(cs);
186 b = load_unaligned_zeropad(ct);
187 if (tcount < sizeof(unsigned long))
188 break;
189 if (unlikely(a != b))
190 return 1;
191 cs += sizeof(unsigned long);
192 ct += sizeof(unsigned long);
193 tcount -= sizeof(unsigned long);
194 if (!tcount)
195 return 0;
196 }
197 mask = bytemask_from_count(tcount);
198 return unlikely(!!((a ^ b) & mask));
199 }
200
201 #else
202
203 static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
204 {
205 do {
206 if (*cs != *ct)
207 return 1;
208 cs++;
209 ct++;
210 tcount--;
211 } while (tcount);
212 return 0;
213 }
214
215 #endif
216
217 static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
218 {
219 /*
220 * Be careful about RCU walk racing with rename:
221 * use 'READ_ONCE' to fetch the name pointer.
222 *
223 * NOTE! Even if a rename will mean that the length
224 * was not loaded atomically, we don't care. The
225 * RCU walk will check the sequence count eventually,
226 * and catch it. And we won't overrun the buffer,
227 * because we're reading the name pointer atomically,
228 * and a dentry name is guaranteed to be properly
229 * terminated with a NUL byte.
230 *
231 * End result: even if 'len' is wrong, we'll exit
232 * early because the data cannot match (there can
233 * be no NUL in the ct/tcount data)
234 */
235 const unsigned char *cs = READ_ONCE(dentry->d_name.name);
236
237 return dentry_string_cmp(cs, ct, tcount);
238 }
239
240 struct external_name {
241 union {
242 atomic_t count;
243 struct rcu_head head;
244 } u;
245 unsigned char name[];
246 };
247
248 static inline struct external_name *external_name(struct dentry *dentry)
249 {
250 return container_of(dentry->d_name.name, struct external_name, name[0]);
251 }
252
253 static void __d_free(struct rcu_head *head)
254 {
255 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
256
257 kmem_cache_free(dentry_cache, dentry);
258 }
259
260 static void __d_free_external_name(struct rcu_head *head)
261 {
262 struct external_name *name = container_of(head, struct external_name,
263 u.head);
264
265 mod_node_page_state(page_pgdat(virt_to_page(name)),
266 NR_INDIRECTLY_RECLAIMABLE_BYTES,
267 -ksize(name));
268
269 kfree(name);
270 }
271
272 static void __d_free_external(struct rcu_head *head)
273 {
274 struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
275
276 __d_free_external_name(&external_name(dentry)->u.head);
277
278 kmem_cache_free(dentry_cache, dentry);
279 }
280
281 static inline int dname_external(const struct dentry *dentry)
282 {
283 return dentry->d_name.name != dentry->d_iname;
284 }
285
286 void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry)
287 {
288 spin_lock(&dentry->d_lock);
289 if (unlikely(dname_external(dentry))) {
290 struct external_name *p = external_name(dentry);
291 atomic_inc(&p->u.count);
292 spin_unlock(&dentry->d_lock);
293 name->name = p->name;
294 } else {
295 memcpy(name->inline_name, dentry->d_iname, DNAME_INLINE_LEN);
296 spin_unlock(&dentry->d_lock);
297 name->name = name->inline_name;
298 }
299 }
300 EXPORT_SYMBOL(take_dentry_name_snapshot);
301
302 void release_dentry_name_snapshot(struct name_snapshot *name)
303 {
304 if (unlikely(name->name != name->inline_name)) {
305 struct external_name *p;
306 p = container_of(name->name, struct external_name, name[0]);
307 if (unlikely(atomic_dec_and_test(&p->u.count)))
308 call_rcu(&p->u.head, __d_free_external_name);
309 }
310 }
311 EXPORT_SYMBOL(release_dentry_name_snapshot);
312
313 static inline void __d_set_inode_and_type(struct dentry *dentry,
314 struct inode *inode,
315 unsigned type_flags)
316 {
317 unsigned flags;
318
319 dentry->d_inode = inode;
320 flags = READ_ONCE(dentry->d_flags);
321 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
322 flags |= type_flags;
323 WRITE_ONCE(dentry->d_flags, flags);
324 }
325
326 static inline void __d_clear_type_and_inode(struct dentry *dentry)
327 {
328 unsigned flags = READ_ONCE(dentry->d_flags);
329
330 flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
331 WRITE_ONCE(dentry->d_flags, flags);
332 dentry->d_inode = NULL;
333 }
334
335 static void dentry_free(struct dentry *dentry)
336 {
337 WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias));
338 if (unlikely(dname_external(dentry))) {
339 struct external_name *p = external_name(dentry);
340 if (likely(atomic_dec_and_test(&p->u.count))) {
341 call_rcu(&dentry->d_u.d_rcu, __d_free_external);
342 return;
343 }
344 }
345 /* if dentry was never visible to RCU, immediate free is OK */
346 if (!(dentry->d_flags & DCACHE_RCUACCESS))
347 __d_free(&dentry->d_u.d_rcu);
348 else
349 call_rcu(&dentry->d_u.d_rcu, __d_free);
350 }
351
352 /*
353 * Release the dentry's inode, using the filesystem
354 * d_iput() operation if defined.
355 */
356 static void dentry_unlink_inode(struct dentry * dentry)
357 __releases(dentry->d_lock)
358 __releases(dentry->d_inode->i_lock)
359 {
360 struct inode *inode = dentry->d_inode;
361 bool hashed = !d_unhashed(dentry);
362
363 if (hashed)
364 raw_write_seqcount_begin(&dentry->d_seq);
365 __d_clear_type_and_inode(dentry);
366 hlist_del_init(&dentry->d_u.d_alias);
367 if (hashed)
368 raw_write_seqcount_end(&dentry->d_seq);
369 spin_unlock(&dentry->d_lock);
370 spin_unlock(&inode->i_lock);
371 if (!inode->i_nlink)
372 fsnotify_inoderemove(inode);
373 if (dentry->d_op && dentry->d_op->d_iput)
374 dentry->d_op->d_iput(dentry, inode);
375 else
376 iput(inode);
377 }
378
379 /*
380 * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
381 * is in use - which includes both the "real" per-superblock
382 * LRU list _and_ the DCACHE_SHRINK_LIST use.
383 *
384 * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
385 * on the shrink list (ie not on the superblock LRU list).
386 *
387 * The per-cpu "nr_dentry_unused" counters are updated with
388 * the DCACHE_LRU_LIST bit.
389 *
390 * These helper functions make sure we always follow the
391 * rules. d_lock must be held by the caller.
392 */
393 #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
394 static void d_lru_add(struct dentry *dentry)
395 {
396 D_FLAG_VERIFY(dentry, 0);
397 dentry->d_flags |= DCACHE_LRU_LIST;
398 this_cpu_inc(nr_dentry_unused);
399 WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
400 }
401
402 static void d_lru_del(struct dentry *dentry)
403 {
404 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
405 dentry->d_flags &= ~DCACHE_LRU_LIST;
406 this_cpu_dec(nr_dentry_unused);
407 WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
408 }
409
410 static void d_shrink_del(struct dentry *dentry)
411 {
412 D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
413 list_del_init(&dentry->d_lru);
414 dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
415 this_cpu_dec(nr_dentry_unused);
416 }
417
418 static void d_shrink_add(struct dentry *dentry, struct list_head *list)
419 {
420 D_FLAG_VERIFY(dentry, 0);
421 list_add(&dentry->d_lru, list);
422 dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST;
423 this_cpu_inc(nr_dentry_unused);
424 }
425
426 /*
427 * These can only be called under the global LRU lock, ie during the
428 * callback for freeing the LRU list. "isolate" removes it from the
429 * LRU lists entirely, while shrink_move moves it to the indicated
430 * private list.
431 */
432 static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry)
433 {
434 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
435 dentry->d_flags &= ~DCACHE_LRU_LIST;
436 this_cpu_dec(nr_dentry_unused);
437 list_lru_isolate(lru, &dentry->d_lru);
438 }
439
440 static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
441 struct list_head *list)
442 {
443 D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
444 dentry->d_flags |= DCACHE_SHRINK_LIST;
445 list_lru_isolate_move(lru, &dentry->d_lru, list);
446 }
447
448 /**
449 * d_drop - drop a dentry
450 * @dentry: dentry to drop
451 *
452 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
453 * be found through a VFS lookup any more. Note that this is different from
454 * deleting the dentry - d_delete will try to mark the dentry negative if
455 * possible, giving a successful _negative_ lookup, while d_drop will
456 * just make the cache lookup fail.
457 *
458 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
459 * reason (NFS timeouts or autofs deletes).
460 *
461 * __d_drop requires dentry->d_lock
462 * ___d_drop doesn't mark dentry as "unhashed"
463 * (dentry->d_hash.pprev will be LIST_POISON2, not NULL).
464 */
465 static void ___d_drop(struct dentry *dentry)
466 {
467 struct hlist_bl_head *b;
468 /*
469 * Hashed dentries are normally on the dentry hashtable,
470 * with the exception of those newly allocated by
471 * d_obtain_root, which are always IS_ROOT:
472 */
473 if (unlikely(IS_ROOT(dentry)))
474 b = &dentry->d_sb->s_roots;
475 else
476 b = d_hash(dentry->d_name.hash);
477
478 hlist_bl_lock(b);
479 __hlist_bl_del(&dentry->d_hash);
480 hlist_bl_unlock(b);
481 }
482
483 void __d_drop(struct dentry *dentry)
484 {
485 if (!d_unhashed(dentry)) {
486 ___d_drop(dentry);
487 dentry->d_hash.pprev = NULL;
488 write_seqcount_invalidate(&dentry->d_seq);
489 }
490 }
491 EXPORT_SYMBOL(__d_drop);
492
493 void d_drop(struct dentry *dentry)
494 {
495 spin_lock(&dentry->d_lock);
496 __d_drop(dentry);
497 spin_unlock(&dentry->d_lock);
498 }
499 EXPORT_SYMBOL(d_drop);
500
501 static inline void dentry_unlist(struct dentry *dentry, struct dentry *parent)
502 {
503 struct dentry *next;
504 /*
505 * Inform d_walk() and shrink_dentry_list() that we are no longer
506 * attached to the dentry tree
507 */
508 dentry->d_flags |= DCACHE_DENTRY_KILLED;
509 if (unlikely(list_empty(&dentry->d_child)))
510 return;
511 __list_del_entry(&dentry->d_child);
512 /*
513 * Cursors can move around the list of children. While we'd been
514 * a normal list member, it didn't matter - ->d_child.next would've
515 * been updated. However, from now on it won't be and for the
516 * things like d_walk() it might end up with a nasty surprise.
517 * Normally d_walk() doesn't care about cursors moving around -
518 * ->d_lock on parent prevents that and since a cursor has no children
519 * of its own, we get through it without ever unlocking the parent.
520 * There is one exception, though - if we ascend from a child that
521 * gets killed as soon as we unlock it, the next sibling is found
522 * using the value left in its ->d_child.next. And if _that_
523 * pointed to a cursor, and cursor got moved (e.g. by lseek())
524 * before d_walk() regains parent->d_lock, we'll end up skipping
525 * everything the cursor had been moved past.
526 *
527 * Solution: make sure that the pointer left behind in ->d_child.next
528 * points to something that won't be moving around. I.e. skip the
529 * cursors.
530 */
531 while (dentry->d_child.next != &parent->d_subdirs) {
532 next = list_entry(dentry->d_child.next, struct dentry, d_child);
533 if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR)))
534 break;
535 dentry->d_child.next = next->d_child.next;
536 }
537 }
538
539 static void __dentry_kill(struct dentry *dentry)
540 {
541 struct dentry *parent = NULL;
542 bool can_free = true;
543 if (!IS_ROOT(dentry))
544 parent = dentry->d_parent;
545
546 /*
547 * The dentry is now unrecoverably dead to the world.
548 */
549 lockref_mark_dead(&dentry->d_lockref);
550
551 /*
552 * inform the fs via d_prune that this dentry is about to be
553 * unhashed and destroyed.
554 */
555 if (dentry->d_flags & DCACHE_OP_PRUNE)
556 dentry->d_op->d_prune(dentry);
557
558 if (dentry->d_flags & DCACHE_LRU_LIST) {
559 if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
560 d_lru_del(dentry);
561 }
562 /* if it was on the hash then remove it */
563 __d_drop(dentry);
564 dentry_unlist(dentry, parent);
565 if (parent)
566 spin_unlock(&parent->d_lock);
567 if (dentry->d_inode)
568 dentry_unlink_inode(dentry);
569 else
570 spin_unlock(&dentry->d_lock);
571 this_cpu_dec(nr_dentry);
572 if (dentry->d_op && dentry->d_op->d_release)
573 dentry->d_op->d_release(dentry);
574
575 spin_lock(&dentry->d_lock);
576 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
577 dentry->d_flags |= DCACHE_MAY_FREE;
578 can_free = false;
579 }
580 spin_unlock(&dentry->d_lock);
581 if (likely(can_free))
582 dentry_free(dentry);
583 cond_resched();
584 }
585
586 static struct dentry *__lock_parent(struct dentry *dentry)
587 {
588 struct dentry *parent;
589 rcu_read_lock();
590 spin_unlock(&dentry->d_lock);
591 again:
592 parent = READ_ONCE(dentry->d_parent);
593 spin_lock(&parent->d_lock);
594 /*
595 * We can't blindly lock dentry until we are sure
596 * that we won't violate the locking order.
597 * Any changes of dentry->d_parent must have
598 * been done with parent->d_lock held, so
599 * spin_lock() above is enough of a barrier
600 * for checking if it's still our child.
601 */
602 if (unlikely(parent != dentry->d_parent)) {
603 spin_unlock(&parent->d_lock);
604 goto again;
605 }
606 rcu_read_unlock();
607 if (parent != dentry)
608 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
609 else
610 parent = NULL;
611 return parent;
612 }
613
614 static inline struct dentry *lock_parent(struct dentry *dentry)
615 {
616 struct dentry *parent = dentry->d_parent;
617 if (IS_ROOT(dentry))
618 return NULL;
619 if (likely(spin_trylock(&parent->d_lock)))
620 return parent;
621 return __lock_parent(dentry);
622 }
623
624 static inline bool retain_dentry(struct dentry *dentry)
625 {
626 WARN_ON(d_in_lookup(dentry));
627
628 /* Unreachable? Get rid of it */
629 if (unlikely(d_unhashed(dentry)))
630 return false;
631
632 if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
633 return false;
634
635 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) {
636 if (dentry->d_op->d_delete(dentry))
637 return false;
638 }
639 /* retain; LRU fodder */
640 dentry->d_lockref.count--;
641 if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
642 d_lru_add(dentry);
643 else if (unlikely(!(dentry->d_flags & DCACHE_REFERENCED)))
644 dentry->d_flags |= DCACHE_REFERENCED;
645 return true;
646 }
647
648 /*
649 * Finish off a dentry we've decided to kill.
650 * dentry->d_lock must be held, returns with it unlocked.
651 * Returns dentry requiring refcount drop, or NULL if we're done.
652 */
653 static struct dentry *dentry_kill(struct dentry *dentry)
654 __releases(dentry->d_lock)
655 {
656 struct inode *inode = dentry->d_inode;
657 struct dentry *parent = NULL;
658
659 if (inode && unlikely(!spin_trylock(&inode->i_lock)))
660 goto slow_positive;
661
662 if (!IS_ROOT(dentry)) {
663 parent = dentry->d_parent;
664 if (unlikely(!spin_trylock(&parent->d_lock))) {
665 parent = __lock_parent(dentry);
666 if (likely(inode || !dentry->d_inode))
667 goto got_locks;
668 /* negative that became positive */
669 if (parent)
670 spin_unlock(&parent->d_lock);
671 inode = dentry->d_inode;
672 goto slow_positive;
673 }
674 }
675 __dentry_kill(dentry);
676 return parent;
677
678 slow_positive:
679 spin_unlock(&dentry->d_lock);
680 spin_lock(&inode->i_lock);
681 spin_lock(&dentry->d_lock);
682 parent = lock_parent(dentry);
683 got_locks:
684 if (unlikely(dentry->d_lockref.count != 1)) {
685 dentry->d_lockref.count--;
686 } else if (likely(!retain_dentry(dentry))) {
687 __dentry_kill(dentry);
688 return parent;
689 }
690 /* we are keeping it, after all */
691 if (inode)
692 spin_unlock(&inode->i_lock);
693 if (parent)
694 spin_unlock(&parent->d_lock);
695 spin_unlock(&dentry->d_lock);
696 return NULL;
697 }
698
699 /*
700 * Try to do a lockless dput(), and return whether that was successful.
701 *
702 * If unsuccessful, we return false, having already taken the dentry lock.
703 *
704 * The caller needs to hold the RCU read lock, so that the dentry is
705 * guaranteed to stay around even if the refcount goes down to zero!
706 */
707 static inline bool fast_dput(struct dentry *dentry)
708 {
709 int ret;
710 unsigned int d_flags;
711
712 /*
713 * If we have a d_op->d_delete() operation, we sould not
714 * let the dentry count go to zero, so use "put_or_lock".
715 */
716 if (unlikely(dentry->d_flags & DCACHE_OP_DELETE))
717 return lockref_put_or_lock(&dentry->d_lockref);
718
719 /*
720 * .. otherwise, we can try to just decrement the
721 * lockref optimistically.
722 */
723 ret = lockref_put_return(&dentry->d_lockref);
724
725 /*
726 * If the lockref_put_return() failed due to the lock being held
727 * by somebody else, the fast path has failed. We will need to
728 * get the lock, and then check the count again.
729 */
730 if (unlikely(ret < 0)) {
731 spin_lock(&dentry->d_lock);
732 if (dentry->d_lockref.count > 1) {
733 dentry->d_lockref.count--;
734 spin_unlock(&dentry->d_lock);
735 return 1;
736 }
737 return 0;
738 }
739
740 /*
741 * If we weren't the last ref, we're done.
742 */
743 if (ret)
744 return 1;
745
746 /*
747 * Careful, careful. The reference count went down
748 * to zero, but we don't hold the dentry lock, so
749 * somebody else could get it again, and do another
750 * dput(), and we need to not race with that.
751 *
752 * However, there is a very special and common case
753 * where we don't care, because there is nothing to
754 * do: the dentry is still hashed, it does not have
755 * a 'delete' op, and it's referenced and already on
756 * the LRU list.
757 *
758 * NOTE! Since we aren't locked, these values are
759 * not "stable". However, it is sufficient that at
760 * some point after we dropped the reference the
761 * dentry was hashed and the flags had the proper
762 * value. Other dentry users may have re-gotten
763 * a reference to the dentry and change that, but
764 * our work is done - we can leave the dentry
765 * around with a zero refcount.
766 */
767 smp_rmb();
768 d_flags = READ_ONCE(dentry->d_flags);
769 d_flags &= DCACHE_REFERENCED | DCACHE_LRU_LIST | DCACHE_DISCONNECTED;
770
771 /* Nothing to do? Dropping the reference was all we needed? */
772 if (d_flags == (DCACHE_REFERENCED | DCACHE_LRU_LIST) && !d_unhashed(dentry))
773 return 1;
774
775 /*
776 * Not the fast normal case? Get the lock. We've already decremented
777 * the refcount, but we'll need to re-check the situation after
778 * getting the lock.
779 */
780 spin_lock(&dentry->d_lock);
781
782 /*
783 * Did somebody else grab a reference to it in the meantime, and
784 * we're no longer the last user after all? Alternatively, somebody
785 * else could have killed it and marked it dead. Either way, we
786 * don't need to do anything else.
787 */
788 if (dentry->d_lockref.count) {
789 spin_unlock(&dentry->d_lock);
790 return 1;
791 }
792
793 /*
794 * Re-get the reference we optimistically dropped. We hold the
795 * lock, and we just tested that it was zero, so we can just
796 * set it to 1.
797 */
798 dentry->d_lockref.count = 1;
799 return 0;
800 }
801
802
803 /*
804 * This is dput
805 *
806 * This is complicated by the fact that we do not want to put
807 * dentries that are no longer on any hash chain on the unused
808 * list: we'd much rather just get rid of them immediately.
809 *
810 * However, that implies that we have to traverse the dentry
811 * tree upwards to the parents which might _also_ now be
812 * scheduled for deletion (it may have been only waiting for
813 * its last child to go away).
814 *
815 * This tail recursion is done by hand as we don't want to depend
816 * on the compiler to always get this right (gcc generally doesn't).
817 * Real recursion would eat up our stack space.
818 */
819
820 /*
821 * dput - release a dentry
822 * @dentry: dentry to release
823 *
824 * Release a dentry. This will drop the usage count and if appropriate
825 * call the dentry unlink method as well as removing it from the queues and
826 * releasing its resources. If the parent dentries were scheduled for release
827 * they too may now get deleted.
828 */
829 void dput(struct dentry *dentry)
830 {
831 while (dentry) {
832 might_sleep();
833
834 rcu_read_lock();
835 if (likely(fast_dput(dentry))) {
836 rcu_read_unlock();
837 return;
838 }
839
840 /* Slow case: now with the dentry lock held */
841 rcu_read_unlock();
842
843 if (likely(retain_dentry(dentry))) {
844 spin_unlock(&dentry->d_lock);
845 return;
846 }
847
848 dentry = dentry_kill(dentry);
849 }
850 }
851 EXPORT_SYMBOL(dput);
852
853
854 /* This must be called with d_lock held */
855 static inline void __dget_dlock(struct dentry *dentry)
856 {
857 dentry->d_lockref.count++;
858 }
859
860 static inline void __dget(struct dentry *dentry)
861 {
862 lockref_get(&dentry->d_lockref);
863 }
864
865 struct dentry *dget_parent(struct dentry *dentry)
866 {
867 int gotref;
868 struct dentry *ret;
869
870 /*
871 * Do optimistic parent lookup without any
872 * locking.
873 */
874 rcu_read_lock();
875 ret = READ_ONCE(dentry->d_parent);
876 gotref = lockref_get_not_zero(&ret->d_lockref);
877 rcu_read_unlock();
878 if (likely(gotref)) {
879 if (likely(ret == READ_ONCE(dentry->d_parent)))
880 return ret;
881 dput(ret);
882 }
883
884 repeat:
885 /*
886 * Don't need rcu_dereference because we re-check it was correct under
887 * the lock.
888 */
889 rcu_read_lock();
890 ret = dentry->d_parent;
891 spin_lock(&ret->d_lock);
892 if (unlikely(ret != dentry->d_parent)) {
893 spin_unlock(&ret->d_lock);
894 rcu_read_unlock();
895 goto repeat;
896 }
897 rcu_read_unlock();
898 BUG_ON(!ret->d_lockref.count);
899 ret->d_lockref.count++;
900 spin_unlock(&ret->d_lock);
901 return ret;
902 }
903 EXPORT_SYMBOL(dget_parent);
904
905 static struct dentry * __d_find_any_alias(struct inode *inode)
906 {
907 struct dentry *alias;
908
909 if (hlist_empty(&inode->i_dentry))
910 return NULL;
911 alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
912 __dget(alias);
913 return alias;
914 }
915
916 /**
917 * d_find_any_alias - find any alias for a given inode
918 * @inode: inode to find an alias for
919 *
920 * If any aliases exist for the given inode, take and return a
921 * reference for one of them. If no aliases exist, return %NULL.
922 */
923 struct dentry *d_find_any_alias(struct inode *inode)
924 {
925 struct dentry *de;
926
927 spin_lock(&inode->i_lock);
928 de = __d_find_any_alias(inode);
929 spin_unlock(&inode->i_lock);
930 return de;
931 }
932 EXPORT_SYMBOL(d_find_any_alias);
933
934 /**
935 * d_find_alias - grab a hashed alias of inode
936 * @inode: inode in question
937 *
938 * If inode has a hashed alias, or is a directory and has any alias,
939 * acquire the reference to alias and return it. Otherwise return NULL.
940 * Notice that if inode is a directory there can be only one alias and
941 * it can be unhashed only if it has no children, or if it is the root
942 * of a filesystem, or if the directory was renamed and d_revalidate
943 * was the first vfs operation to notice.
944 *
945 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
946 * any other hashed alias over that one.
947 */
948 static struct dentry *__d_find_alias(struct inode *inode)
949 {
950 struct dentry *alias;
951
952 if (S_ISDIR(inode->i_mode))
953 return __d_find_any_alias(inode);
954
955 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
956 spin_lock(&alias->d_lock);
957 if (!d_unhashed(alias)) {
958 __dget_dlock(alias);
959 spin_unlock(&alias->d_lock);
960 return alias;
961 }
962 spin_unlock(&alias->d_lock);
963 }
964 return NULL;
965 }
966
967 struct dentry *d_find_alias(struct inode *inode)
968 {
969 struct dentry *de = NULL;
970
971 if (!hlist_empty(&inode->i_dentry)) {
972 spin_lock(&inode->i_lock);
973 de = __d_find_alias(inode);
974 spin_unlock(&inode->i_lock);
975 }
976 return de;
977 }
978 EXPORT_SYMBOL(d_find_alias);
979
980 /*
981 * Try to kill dentries associated with this inode.
982 * WARNING: you must own a reference to inode.
983 */
984 void d_prune_aliases(struct inode *inode)
985 {
986 struct dentry *dentry;
987 restart:
988 spin_lock(&inode->i_lock);
989 hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
990 spin_lock(&dentry->d_lock);
991 if (!dentry->d_lockref.count) {
992 struct dentry *parent = lock_parent(dentry);
993 if (likely(!dentry->d_lockref.count)) {
994 __dentry_kill(dentry);
995 dput(parent);
996 goto restart;
997 }
998 if (parent)
999 spin_unlock(&parent->d_lock);
1000 }
1001 spin_unlock(&dentry->d_lock);
1002 }
1003 spin_unlock(&inode->i_lock);
1004 }
1005 EXPORT_SYMBOL(d_prune_aliases);
1006
1007 /*
1008 * Lock a dentry from shrink list.
1009 * Called under rcu_read_lock() and dentry->d_lock; the former
1010 * guarantees that nothing we access will be freed under us.
1011 * Note that dentry is *not* protected from concurrent dentry_kill(),
1012 * d_delete(), etc.
1013 *
1014 * Return false if dentry has been disrupted or grabbed, leaving
1015 * the caller to kick it off-list. Otherwise, return true and have
1016 * that dentry's inode and parent both locked.
1017 */
1018 static bool shrink_lock_dentry(struct dentry *dentry)
1019 {
1020 struct inode *inode;
1021 struct dentry *parent;
1022
1023 if (dentry->d_lockref.count)
1024 return false;
1025
1026 inode = dentry->d_inode;
1027 if (inode && unlikely(!spin_trylock(&inode->i_lock))) {
1028 spin_unlock(&dentry->d_lock);
1029 spin_lock(&inode->i_lock);
1030 spin_lock(&dentry->d_lock);
1031 if (unlikely(dentry->d_lockref.count))
1032 goto out;
1033 /* changed inode means that somebody had grabbed it */
1034 if (unlikely(inode != dentry->d_inode))
1035 goto out;
1036 }
1037
1038 parent = dentry->d_parent;
1039 if (IS_ROOT(dentry) || likely(spin_trylock(&parent->d_lock)))
1040 return true;
1041
1042 spin_unlock(&dentry->d_lock);
1043 spin_lock(&parent->d_lock);
1044 if (unlikely(parent != dentry->d_parent)) {
1045 spin_unlock(&parent->d_lock);
1046 spin_lock(&dentry->d_lock);
1047 goto out;
1048 }
1049 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1050 if (likely(!dentry->d_lockref.count))
1051 return true;
1052 spin_unlock(&parent->d_lock);
1053 out:
1054 if (inode)
1055 spin_unlock(&inode->i_lock);
1056 return false;
1057 }
1058
1059 static void shrink_dentry_list(struct list_head *list)
1060 {
1061 while (!list_empty(list)) {
1062 struct dentry *dentry, *parent;
1063
1064 dentry = list_entry(list->prev, struct dentry, d_lru);
1065 spin_lock(&dentry->d_lock);
1066 rcu_read_lock();
1067 if (!shrink_lock_dentry(dentry)) {
1068 bool can_free = false;
1069 rcu_read_unlock();
1070 d_shrink_del(dentry);
1071 if (dentry->d_lockref.count < 0)
1072 can_free = dentry->d_flags & DCACHE_MAY_FREE;
1073 spin_unlock(&dentry->d_lock);
1074 if (can_free)
1075 dentry_free(dentry);
1076 continue;
1077 }
1078 rcu_read_unlock();
1079 d_shrink_del(dentry);
1080 parent = dentry->d_parent;
1081 __dentry_kill(dentry);
1082 if (parent == dentry)
1083 continue;
1084 /*
1085 * We need to prune ancestors too. This is necessary to prevent
1086 * quadratic behavior of shrink_dcache_parent(), but is also
1087 * expected to be beneficial in reducing dentry cache
1088 * fragmentation.
1089 */
1090 dentry = parent;
1091 while (dentry && !lockref_put_or_lock(&dentry->d_lockref))
1092 dentry = dentry_kill(dentry);
1093 }
1094 }
1095
1096 static enum lru_status dentry_lru_isolate(struct list_head *item,
1097 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1098 {
1099 struct list_head *freeable = arg;
1100 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1101
1102
1103 /*
1104 * we are inverting the lru lock/dentry->d_lock here,
1105 * so use a trylock. If we fail to get the lock, just skip
1106 * it
1107 */
1108 if (!spin_trylock(&dentry->d_lock))
1109 return LRU_SKIP;
1110
1111 /*
1112 * Referenced dentries are still in use. If they have active
1113 * counts, just remove them from the LRU. Otherwise give them
1114 * another pass through the LRU.
1115 */
1116 if (dentry->d_lockref.count) {
1117 d_lru_isolate(lru, dentry);
1118 spin_unlock(&dentry->d_lock);
1119 return LRU_REMOVED;
1120 }
1121
1122 if (dentry->d_flags & DCACHE_REFERENCED) {
1123 dentry->d_flags &= ~DCACHE_REFERENCED;
1124 spin_unlock(&dentry->d_lock);
1125
1126 /*
1127 * The list move itself will be made by the common LRU code. At
1128 * this point, we've dropped the dentry->d_lock but keep the
1129 * lru lock. This is safe to do, since every list movement is
1130 * protected by the lru lock even if both locks are held.
1131 *
1132 * This is guaranteed by the fact that all LRU management
1133 * functions are intermediated by the LRU API calls like
1134 * list_lru_add and list_lru_del. List movement in this file
1135 * only ever occur through this functions or through callbacks
1136 * like this one, that are called from the LRU API.
1137 *
1138 * The only exceptions to this are functions like
1139 * shrink_dentry_list, and code that first checks for the
1140 * DCACHE_SHRINK_LIST flag. Those are guaranteed to be
1141 * operating only with stack provided lists after they are
1142 * properly isolated from the main list. It is thus, always a
1143 * local access.
1144 */
1145 return LRU_ROTATE;
1146 }
1147
1148 d_lru_shrink_move(lru, dentry, freeable);
1149 spin_unlock(&dentry->d_lock);
1150
1151 return LRU_REMOVED;
1152 }
1153
1154 /**
1155 * prune_dcache_sb - shrink the dcache
1156 * @sb: superblock
1157 * @sc: shrink control, passed to list_lru_shrink_walk()
1158 *
1159 * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1160 * is done when we need more memory and called from the superblock shrinker
1161 * function.
1162 *
1163 * This function may fail to free any resources if all the dentries are in
1164 * use.
1165 */
1166 long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc)
1167 {
1168 LIST_HEAD(dispose);
1169 long freed;
1170
1171 freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc,
1172 dentry_lru_isolate, &dispose);
1173 shrink_dentry_list(&dispose);
1174 return freed;
1175 }
1176
1177 static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
1178 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1179 {
1180 struct list_head *freeable = arg;
1181 struct dentry *dentry = container_of(item, struct dentry, d_lru);
1182
1183 /*
1184 * we are inverting the lru lock/dentry->d_lock here,
1185 * so use a trylock. If we fail to get the lock, just skip
1186 * it
1187 */
1188 if (!spin_trylock(&dentry->d_lock))
1189 return LRU_SKIP;
1190
1191 d_lru_shrink_move(lru, dentry, freeable);
1192 spin_unlock(&dentry->d_lock);
1193
1194 return LRU_REMOVED;
1195 }
1196
1197
1198 /**
1199 * shrink_dcache_sb - shrink dcache for a superblock
1200 * @sb: superblock
1201 *
1202 * Shrink the dcache for the specified super block. This is used to free
1203 * the dcache before unmounting a file system.
1204 */
1205 void shrink_dcache_sb(struct super_block *sb)
1206 {
1207 long freed;
1208
1209 do {
1210 LIST_HEAD(dispose);
1211
1212 freed = list_lru_walk(&sb->s_dentry_lru,
1213 dentry_lru_isolate_shrink, &dispose, 1024);
1214
1215 this_cpu_sub(nr_dentry_unused, freed);
1216 shrink_dentry_list(&dispose);
1217 } while (list_lru_count(&sb->s_dentry_lru) > 0);
1218 }
1219 EXPORT_SYMBOL(shrink_dcache_sb);
1220
1221 /**
1222 * enum d_walk_ret - action to talke during tree walk
1223 * @D_WALK_CONTINUE: contrinue walk
1224 * @D_WALK_QUIT: quit walk
1225 * @D_WALK_NORETRY: quit when retry is needed
1226 * @D_WALK_SKIP: skip this dentry and its children
1227 */
1228 enum d_walk_ret {
1229 D_WALK_CONTINUE,
1230 D_WALK_QUIT,
1231 D_WALK_NORETRY,
1232 D_WALK_SKIP,
1233 };
1234
1235 /**
1236 * d_walk - walk the dentry tree
1237 * @parent: start of walk
1238 * @data: data passed to @enter() and @finish()
1239 * @enter: callback when first entering the dentry
1240 *
1241 * The @enter() callbacks are called with d_lock held.
1242 */
1243 static void d_walk(struct dentry *parent, void *data,
1244 enum d_walk_ret (*enter)(void *, struct dentry *))
1245 {
1246 struct dentry *this_parent;
1247 struct list_head *next;
1248 unsigned seq = 0;
1249 enum d_walk_ret ret;
1250 bool retry = true;
1251
1252 again:
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 }
1268 repeat:
1269 next = this_parent->d_subdirs.next;
1270 resume:
1271 while (next != &this_parent->d_subdirs) {
1272 struct list_head *tmp = next;
1273 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
1274 next = tmp->next;
1275
1276 if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR))
1277 continue;
1278
1279 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1280
1281 ret = enter(data, dentry);
1282 switch (ret) {
1283 case D_WALK_CONTINUE:
1284 break;
1285 case D_WALK_QUIT:
1286 spin_unlock(&dentry->d_lock);
1287 goto out_unlock;
1288 case D_WALK_NORETRY:
1289 retry = false;
1290 break;
1291 case D_WALK_SKIP:
1292 spin_unlock(&dentry->d_lock);
1293 continue;
1294 }
1295
1296 if (!list_empty(&dentry->d_subdirs)) {
1297 spin_unlock(&this_parent->d_lock);
1298 spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
1299 this_parent = dentry;
1300 spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1301 goto repeat;
1302 }
1303 spin_unlock(&dentry->d_lock);
1304 }
1305 /*
1306 * All done at this level ... ascend and resume the search.
1307 */
1308 rcu_read_lock();
1309 ascend:
1310 if (this_parent != parent) {
1311 struct dentry *child = this_parent;
1312 this_parent = child->d_parent;
1313
1314 spin_unlock(&child->d_lock);
1315 spin_lock(&this_parent->d_lock);
1316
1317 /* might go back up the wrong parent if we have had a rename. */
1318 if (need_seqretry(&rename_lock, seq))
1319 goto rename_retry;
1320 /* go into the first sibling still alive */
1321 do {
1322 next = child->d_child.next;
1323 if (next == &this_parent->d_subdirs)
1324 goto ascend;
1325 child = list_entry(next, struct dentry, d_child);
1326 } while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
1327 rcu_read_unlock();
1328 goto resume;
1329 }
1330 if (need_seqretry(&rename_lock, seq))
1331 goto rename_retry;
1332 rcu_read_unlock();
1333
1334 out_unlock:
1335 spin_unlock(&this_parent->d_lock);
1336 done_seqretry(&rename_lock, seq);
1337 return;
1338
1339 rename_retry:
1340 spin_unlock(&this_parent->d_lock);
1341 rcu_read_unlock();
1342 BUG_ON(seq & 1);
1343 if (!retry)
1344 return;
1345 seq = 1;
1346 goto again;
1347 }
1348
1349 struct check_mount {
1350 struct vfsmount *mnt;
1351 unsigned int mounted;
1352 };
1353
1354 static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry)
1355 {
1356 struct check_mount *info = data;
1357 struct path path = { .mnt = info->mnt, .dentry = dentry };
1358
1359 if (likely(!d_mountpoint(dentry)))
1360 return D_WALK_CONTINUE;
1361 if (__path_is_mountpoint(&path)) {
1362 info->mounted = 1;
1363 return D_WALK_QUIT;
1364 }
1365 return D_WALK_CONTINUE;
1366 }
1367
1368 /**
1369 * path_has_submounts - check for mounts over a dentry in the
1370 * current namespace.
1371 * @parent: path to check.
1372 *
1373 * Return true if the parent or its subdirectories contain
1374 * a mount point in the current namespace.
1375 */
1376 int path_has_submounts(const struct path *parent)
1377 {
1378 struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
1379
1380 read_seqlock_excl(&mount_lock);
1381 d_walk(parent->dentry, &data, path_check_mount);
1382 read_sequnlock_excl(&mount_lock);
1383
1384 return data.mounted;
1385 }
1386 EXPORT_SYMBOL(path_has_submounts);
1387
1388 /*
1389 * Called by mount code to set a mountpoint and check if the mountpoint is
1390 * reachable (e.g. NFS can unhash a directory dentry and then the complete
1391 * subtree can become unreachable).
1392 *
1393 * Only one of d_invalidate() and d_set_mounted() must succeed. For
1394 * this reason take rename_lock and d_lock on dentry and ancestors.
1395 */
1396 int d_set_mounted(struct dentry *dentry)
1397 {
1398 struct dentry *p;
1399 int ret = -ENOENT;
1400 write_seqlock(&rename_lock);
1401 for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
1402 /* Need exclusion wrt. d_invalidate() */
1403 spin_lock(&p->d_lock);
1404 if (unlikely(d_unhashed(p))) {
1405 spin_unlock(&p->d_lock);
1406 goto out;
1407 }
1408 spin_unlock(&p->d_lock);
1409 }
1410 spin_lock(&dentry->d_lock);
1411 if (!d_unlinked(dentry)) {
1412 ret = -EBUSY;
1413 if (!d_mountpoint(dentry)) {
1414 dentry->d_flags |= DCACHE_MOUNTED;
1415 ret = 0;
1416 }
1417 }
1418 spin_unlock(&dentry->d_lock);
1419 out:
1420 write_sequnlock(&rename_lock);
1421 return ret;
1422 }
1423
1424 /*
1425 * Search the dentry child list of the specified parent,
1426 * and move any unused dentries to the end of the unused
1427 * list for prune_dcache(). We descend to the next level
1428 * whenever the d_subdirs list is non-empty and continue
1429 * searching.
1430 *
1431 * It returns zero iff there are no unused children,
1432 * otherwise it returns the number of children moved to
1433 * the end of the unused list. This may not be the total
1434 * number of unused children, because select_parent can
1435 * drop the lock and return early due to latency
1436 * constraints.
1437 */
1438
1439 struct select_data {
1440 struct dentry *start;
1441 struct list_head dispose;
1442 int found;
1443 };
1444
1445 static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
1446 {
1447 struct select_data *data = _data;
1448 enum d_walk_ret ret = D_WALK_CONTINUE;
1449
1450 if (data->start == dentry)
1451 goto out;
1452
1453 if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1454 data->found++;
1455 } else {
1456 if (dentry->d_flags & DCACHE_LRU_LIST)
1457 d_lru_del(dentry);
1458 if (!dentry->d_lockref.count) {
1459 d_shrink_add(dentry, &data->dispose);
1460 data->found++;
1461 }
1462 }
1463 /*
1464 * We can return to the caller if we have found some (this
1465 * ensures forward progress). We'll be coming back to find
1466 * the rest.
1467 */
1468 if (!list_empty(&data->dispose))
1469 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1470 out:
1471 return ret;
1472 }
1473
1474 /**
1475 * shrink_dcache_parent - prune dcache
1476 * @parent: parent of entries to prune
1477 *
1478 * Prune the dcache to remove unused children of the parent dentry.
1479 */
1480 void shrink_dcache_parent(struct dentry *parent)
1481 {
1482 for (;;) {
1483 struct select_data data;
1484
1485 INIT_LIST_HEAD(&data.dispose);
1486 data.start = parent;
1487 data.found = 0;
1488
1489 d_walk(parent, &data, select_collect);
1490
1491 if (!list_empty(&data.dispose)) {
1492 shrink_dentry_list(&data.dispose);
1493 continue;
1494 }
1495
1496 cond_resched();
1497 if (!data.found)
1498 break;
1499 }
1500 }
1501 EXPORT_SYMBOL(shrink_dcache_parent);
1502
1503 static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
1504 {
1505 /* it has busy descendents; complain about those instead */
1506 if (!list_empty(&dentry->d_subdirs))
1507 return D_WALK_CONTINUE;
1508
1509 /* root with refcount 1 is fine */
1510 if (dentry == _data && dentry->d_lockref.count == 1)
1511 return D_WALK_CONTINUE;
1512
1513 printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%pd} "
1514 " still in use (%d) [unmount of %s %s]\n",
1515 dentry,
1516 dentry->d_inode ?
1517 dentry->d_inode->i_ino : 0UL,
1518 dentry,
1519 dentry->d_lockref.count,
1520 dentry->d_sb->s_type->name,
1521 dentry->d_sb->s_id);
1522 WARN_ON(1);
1523 return D_WALK_CONTINUE;
1524 }
1525
1526 static void do_one_tree(struct dentry *dentry)
1527 {
1528 shrink_dcache_parent(dentry);
1529 d_walk(dentry, dentry, umount_check);
1530 d_drop(dentry);
1531 dput(dentry);
1532 }
1533
1534 /*
1535 * destroy the dentries attached to a superblock on unmounting
1536 */
1537 void shrink_dcache_for_umount(struct super_block *sb)
1538 {
1539 struct dentry *dentry;
1540
1541 WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked");
1542
1543 dentry = sb->s_root;
1544 sb->s_root = NULL;
1545 do_one_tree(dentry);
1546
1547 while (!hlist_bl_empty(&sb->s_roots)) {
1548 dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_roots), struct dentry, d_hash));
1549 do_one_tree(dentry);
1550 }
1551 }
1552
1553 static enum d_walk_ret find_submount(void *_data, struct dentry *dentry)
1554 {
1555 struct dentry **victim = _data;
1556 if (d_mountpoint(dentry)) {
1557 __dget_dlock(dentry);
1558 *victim = dentry;
1559 return D_WALK_QUIT;
1560 }
1561 return D_WALK_CONTINUE;
1562 }
1563
1564 /**
1565 * d_invalidate - detach submounts, prune dcache, and drop
1566 * @dentry: dentry to invalidate (aka detach, prune and drop)
1567 */
1568 void d_invalidate(struct dentry *dentry)
1569 {
1570 bool had_submounts = false;
1571 spin_lock(&dentry->d_lock);
1572 if (d_unhashed(dentry)) {
1573 spin_unlock(&dentry->d_lock);
1574 return;
1575 }
1576 __d_drop(dentry);
1577 spin_unlock(&dentry->d_lock);
1578
1579 /* Negative dentries can be dropped without further checks */
1580 if (!dentry->d_inode)
1581 return;
1582
1583 shrink_dcache_parent(dentry);
1584 for (;;) {
1585 struct dentry *victim = NULL;
1586 d_walk(dentry, &victim, find_submount);
1587 if (!victim) {
1588 if (had_submounts)
1589 shrink_dcache_parent(dentry);
1590 return;
1591 }
1592 had_submounts = true;
1593 detach_mounts(victim);
1594 dput(victim);
1595 }
1596 }
1597 EXPORT_SYMBOL(d_invalidate);
1598
1599 /**
1600 * __d_alloc - allocate a dcache entry
1601 * @sb: filesystem it will belong to
1602 * @name: qstr of the name
1603 *
1604 * Allocates a dentry. It returns %NULL if there is insufficient memory
1605 * available. On a success the dentry is returned. The name passed in is
1606 * copied and the copy passed in may be reused after this call.
1607 */
1608
1609 struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1610 {
1611 struct external_name *ext = NULL;
1612 struct dentry *dentry;
1613 char *dname;
1614 int err;
1615
1616 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
1617 if (!dentry)
1618 return NULL;
1619
1620 /*
1621 * We guarantee that the inline name is always NUL-terminated.
1622 * This way the memcpy() done by the name switching in rename
1623 * will still always have a NUL at the end, even if we might
1624 * be overwriting an internal NUL character
1625 */
1626 dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
1627 if (unlikely(!name)) {
1628 name = &slash_name;
1629 dname = dentry->d_iname;
1630 } else if (name->len > DNAME_INLINE_LEN-1) {
1631 size_t size = offsetof(struct external_name, name[1]);
1632
1633 ext = kmalloc(size + name->len, GFP_KERNEL_ACCOUNT);
1634 if (!ext) {
1635 kmem_cache_free(dentry_cache, dentry);
1636 return NULL;
1637 }
1638 atomic_set(&ext->u.count, 1);
1639 dname = ext->name;
1640 } else {
1641 dname = dentry->d_iname;
1642 }
1643
1644 dentry->d_name.len = name->len;
1645 dentry->d_name.hash = name->hash;
1646 memcpy(dname, name->name, name->len);
1647 dname[name->len] = 0;
1648
1649 /* Make sure we always see the terminating NUL character */
1650 smp_store_release(&dentry->d_name.name, dname); /* ^^^ */
1651
1652 dentry->d_lockref.count = 1;
1653 dentry->d_flags = 0;
1654 spin_lock_init(&dentry->d_lock);
1655 seqcount_init(&dentry->d_seq);
1656 dentry->d_inode = NULL;
1657 dentry->d_parent = dentry;
1658 dentry->d_sb = sb;
1659 dentry->d_op = NULL;
1660 dentry->d_fsdata = NULL;
1661 INIT_HLIST_BL_NODE(&dentry->d_hash);
1662 INIT_LIST_HEAD(&dentry->d_lru);
1663 INIT_LIST_HEAD(&dentry->d_subdirs);
1664 INIT_HLIST_NODE(&dentry->d_u.d_alias);
1665 INIT_LIST_HEAD(&dentry->d_child);
1666 d_set_d_op(dentry, dentry->d_sb->s_d_op);
1667
1668 if (dentry->d_op && dentry->d_op->d_init) {
1669 err = dentry->d_op->d_init(dentry);
1670 if (err) {
1671 if (dname_external(dentry))
1672 kfree(external_name(dentry));
1673 kmem_cache_free(dentry_cache, dentry);
1674 return NULL;
1675 }
1676 }
1677
1678 if (unlikely(ext)) {
1679 pg_data_t *pgdat = page_pgdat(virt_to_page(ext));
1680 mod_node_page_state(pgdat, NR_INDIRECTLY_RECLAIMABLE_BYTES,
1681 ksize(ext));
1682 }
1683
1684 this_cpu_inc(nr_dentry);
1685
1686 return dentry;
1687 }
1688
1689 /**
1690 * d_alloc - allocate a dcache entry
1691 * @parent: parent of entry to allocate
1692 * @name: qstr of the name
1693 *
1694 * Allocates a dentry. It returns %NULL if there is insufficient memory
1695 * available. On a success the dentry is returned. The name passed in is
1696 * copied and the copy passed in may be reused after this call.
1697 */
1698 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1699 {
1700 struct dentry *dentry = __d_alloc(parent->d_sb, name);
1701 if (!dentry)
1702 return NULL;
1703 dentry->d_flags |= DCACHE_RCUACCESS;
1704 spin_lock(&parent->d_lock);
1705 /*
1706 * don't need child lock because it is not subject
1707 * to concurrency here
1708 */
1709 __dget_dlock(parent);
1710 dentry->d_parent = parent;
1711 list_add(&dentry->d_child, &parent->d_subdirs);
1712 spin_unlock(&parent->d_lock);
1713
1714 return dentry;
1715 }
1716 EXPORT_SYMBOL(d_alloc);
1717
1718 struct dentry *d_alloc_anon(struct super_block *sb)
1719 {
1720 return __d_alloc(sb, NULL);
1721 }
1722 EXPORT_SYMBOL(d_alloc_anon);
1723
1724 struct dentry *d_alloc_cursor(struct dentry * parent)
1725 {
1726 struct dentry *dentry = d_alloc_anon(parent->d_sb);
1727 if (dentry) {
1728 dentry->d_flags |= DCACHE_RCUACCESS | DCACHE_DENTRY_CURSOR;
1729 dentry->d_parent = dget(parent);
1730 }
1731 return dentry;
1732 }
1733
1734 /**
1735 * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1736 * @sb: the superblock
1737 * @name: qstr of the name
1738 *
1739 * For a filesystem that just pins its dentries in memory and never
1740 * performs lookups at all, return an unhashed IS_ROOT dentry.
1741 */
1742 struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1743 {
1744 return __d_alloc(sb, name);
1745 }
1746 EXPORT_SYMBOL(d_alloc_pseudo);
1747
1748 struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1749 {
1750 struct qstr q;
1751
1752 q.name = name;
1753 q.hash_len = hashlen_string(parent, name);
1754 return d_alloc(parent, &q);
1755 }
1756 EXPORT_SYMBOL(d_alloc_name);
1757
1758 void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1759 {
1760 WARN_ON_ONCE(dentry->d_op);
1761 WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
1762 DCACHE_OP_COMPARE |
1763 DCACHE_OP_REVALIDATE |
1764 DCACHE_OP_WEAK_REVALIDATE |
1765 DCACHE_OP_DELETE |
1766 DCACHE_OP_REAL));
1767 dentry->d_op = op;
1768 if (!op)
1769 return;
1770 if (op->d_hash)
1771 dentry->d_flags |= DCACHE_OP_HASH;
1772 if (op->d_compare)
1773 dentry->d_flags |= DCACHE_OP_COMPARE;
1774 if (op->d_revalidate)
1775 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1776 if (op->d_weak_revalidate)
1777 dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
1778 if (op->d_delete)
1779 dentry->d_flags |= DCACHE_OP_DELETE;
1780 if (op->d_prune)
1781 dentry->d_flags |= DCACHE_OP_PRUNE;
1782 if (op->d_real)
1783 dentry->d_flags |= DCACHE_OP_REAL;
1784
1785 }
1786 EXPORT_SYMBOL(d_set_d_op);
1787
1788
1789 /*
1790 * d_set_fallthru - Mark a dentry as falling through to a lower layer
1791 * @dentry - The dentry to mark
1792 *
1793 * Mark a dentry as falling through to the lower layer (as set with
1794 * d_pin_lower()). This flag may be recorded on the medium.
1795 */
1796 void d_set_fallthru(struct dentry *dentry)
1797 {
1798 spin_lock(&dentry->d_lock);
1799 dentry->d_flags |= DCACHE_FALLTHRU;
1800 spin_unlock(&dentry->d_lock);
1801 }
1802 EXPORT_SYMBOL(d_set_fallthru);
1803
1804 static unsigned d_flags_for_inode(struct inode *inode)
1805 {
1806 unsigned add_flags = DCACHE_REGULAR_TYPE;
1807
1808 if (!inode)
1809 return DCACHE_MISS_TYPE;
1810
1811 if (S_ISDIR(inode->i_mode)) {
1812 add_flags = DCACHE_DIRECTORY_TYPE;
1813 if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) {
1814 if (unlikely(!inode->i_op->lookup))
1815 add_flags = DCACHE_AUTODIR_TYPE;
1816 else
1817 inode->i_opflags |= IOP_LOOKUP;
1818 }
1819 goto type_determined;
1820 }
1821
1822 if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1823 if (unlikely(inode->i_op->get_link)) {
1824 add_flags = DCACHE_SYMLINK_TYPE;
1825 goto type_determined;
1826 }
1827 inode->i_opflags |= IOP_NOFOLLOW;
1828 }
1829
1830 if (unlikely(!S_ISREG(inode->i_mode)))
1831 add_flags = DCACHE_SPECIAL_TYPE;
1832
1833 type_determined:
1834 if (unlikely(IS_AUTOMOUNT(inode)))
1835 add_flags |= DCACHE_NEED_AUTOMOUNT;
1836 return add_flags;
1837 }
1838
1839 static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1840 {
1841 unsigned add_flags = d_flags_for_inode(inode);
1842 WARN_ON(d_in_lookup(dentry));
1843
1844 spin_lock(&dentry->d_lock);
1845 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
1846 raw_write_seqcount_begin(&dentry->d_seq);
1847 __d_set_inode_and_type(dentry, inode, add_flags);
1848 raw_write_seqcount_end(&dentry->d_seq);
1849 fsnotify_update_flags(dentry);
1850 spin_unlock(&dentry->d_lock);
1851 }
1852
1853 /**
1854 * d_instantiate - fill in inode information for a dentry
1855 * @entry: dentry to complete
1856 * @inode: inode to attach to this dentry
1857 *
1858 * Fill in inode information in the entry.
1859 *
1860 * This turns negative dentries into productive full members
1861 * of society.
1862 *
1863 * NOTE! This assumes that the inode count has been incremented
1864 * (or otherwise set) by the caller to indicate that it is now
1865 * in use by the dcache.
1866 */
1867
1868 void d_instantiate(struct dentry *entry, struct inode * inode)
1869 {
1870 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1871 if (inode) {
1872 security_d_instantiate(entry, inode);
1873 spin_lock(&inode->i_lock);
1874 __d_instantiate(entry, inode);
1875 spin_unlock(&inode->i_lock);
1876 }
1877 }
1878 EXPORT_SYMBOL(d_instantiate);
1879
1880 /*
1881 * This should be equivalent to d_instantiate() + unlock_new_inode(),
1882 * with lockdep-related part of unlock_new_inode() done before
1883 * anything else. Use that instead of open-coding d_instantiate()/
1884 * unlock_new_inode() combinations.
1885 */
1886 void d_instantiate_new(struct dentry *entry, struct inode *inode)
1887 {
1888 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1889 BUG_ON(!inode);
1890 lockdep_annotate_inode_mutex_key(inode);
1891 security_d_instantiate(entry, inode);
1892 spin_lock(&inode->i_lock);
1893 __d_instantiate(entry, inode);
1894 WARN_ON(!(inode->i_state & I_NEW));
1895 inode->i_state &= ~I_NEW;
1896 smp_mb();
1897 wake_up_bit(&inode->i_state, __I_NEW);
1898 spin_unlock(&inode->i_lock);
1899 }
1900 EXPORT_SYMBOL(d_instantiate_new);
1901
1902 /**
1903 * d_instantiate_no_diralias - instantiate a non-aliased dentry
1904 * @entry: dentry to complete
1905 * @inode: inode to attach to this dentry
1906 *
1907 * Fill in inode information in the entry. If a directory alias is found, then
1908 * return an error (and drop inode). Together with d_materialise_unique() this
1909 * guarantees that a directory inode may never have more than one alias.
1910 */
1911 int d_instantiate_no_diralias(struct dentry *entry, struct inode *inode)
1912 {
1913 BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
1914
1915 security_d_instantiate(entry, inode);
1916 spin_lock(&inode->i_lock);
1917 if (S_ISDIR(inode->i_mode) && !hlist_empty(&inode->i_dentry)) {
1918 spin_unlock(&inode->i_lock);
1919 iput(inode);
1920 return -EBUSY;
1921 }
1922 __d_instantiate(entry, inode);
1923 spin_unlock(&inode->i_lock);
1924
1925 return 0;
1926 }
1927 EXPORT_SYMBOL(d_instantiate_no_diralias);
1928
1929 struct dentry *d_make_root(struct inode *root_inode)
1930 {
1931 struct dentry *res = NULL;
1932
1933 if (root_inode) {
1934 res = d_alloc_anon(root_inode->i_sb);
1935 if (res)
1936 d_instantiate(res, root_inode);
1937 else
1938 iput(root_inode);
1939 }
1940 return res;
1941 }
1942 EXPORT_SYMBOL(d_make_root);
1943
1944 static struct dentry *__d_instantiate_anon(struct dentry *dentry,
1945 struct inode *inode,
1946 bool disconnected)
1947 {
1948 struct dentry *res;
1949 unsigned add_flags;
1950
1951 security_d_instantiate(dentry, inode);
1952 spin_lock(&inode->i_lock);
1953 res = __d_find_any_alias(inode);
1954 if (res) {
1955 spin_unlock(&inode->i_lock);
1956 dput(dentry);
1957 goto out_iput;
1958 }
1959
1960 /* attach a disconnected dentry */
1961 add_flags = d_flags_for_inode(inode);
1962
1963 if (disconnected)
1964 add_flags |= DCACHE_DISCONNECTED;
1965
1966 spin_lock(&dentry->d_lock);
1967 __d_set_inode_and_type(dentry, inode, add_flags);
1968 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
1969 if (!disconnected) {
1970 hlist_bl_lock(&dentry->d_sb->s_roots);
1971 hlist_bl_add_head(&dentry->d_hash, &dentry->d_sb->s_roots);
1972 hlist_bl_unlock(&dentry->d_sb->s_roots);
1973 }
1974 spin_unlock(&dentry->d_lock);
1975 spin_unlock(&inode->i_lock);
1976
1977 return dentry;
1978
1979 out_iput:
1980 iput(inode);
1981 return res;
1982 }
1983
1984 struct dentry *d_instantiate_anon(struct dentry *dentry, struct inode *inode)
1985 {
1986 return __d_instantiate_anon(dentry, inode, true);
1987 }
1988 EXPORT_SYMBOL(d_instantiate_anon);
1989
1990 static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected)
1991 {
1992 struct dentry *tmp;
1993 struct dentry *res;
1994
1995 if (!inode)
1996 return ERR_PTR(-ESTALE);
1997 if (IS_ERR(inode))
1998 return ERR_CAST(inode);
1999
2000 res = d_find_any_alias(inode);
2001 if (res)
2002 goto out_iput;
2003
2004 tmp = d_alloc_anon(inode->i_sb);
2005 if (!tmp) {
2006 res = ERR_PTR(-ENOMEM);
2007 goto out_iput;
2008 }
2009
2010 return __d_instantiate_anon(tmp, inode, disconnected);
2011
2012 out_iput:
2013 iput(inode);
2014 return res;
2015 }
2016
2017 /**
2018 * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
2019 * @inode: inode to allocate the dentry for
2020 *
2021 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
2022 * similar open by handle operations. The returned dentry may be anonymous,
2023 * or may have a full name (if the inode was already in the cache).
2024 *
2025 * When called on a directory inode, we must ensure that the inode only ever
2026 * has one dentry. If a dentry is found, that is returned instead of
2027 * allocating a new one.
2028 *
2029 * On successful return, the reference to the inode has been transferred
2030 * to the dentry. In case of an error the reference on the inode is released.
2031 * To make it easier to use in export operations a %NULL or IS_ERR inode may
2032 * be passed in and the error will be propagated to the return value,
2033 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
2034 */
2035 struct dentry *d_obtain_alias(struct inode *inode)
2036 {
2037 return __d_obtain_alias(inode, true);
2038 }
2039 EXPORT_SYMBOL(d_obtain_alias);
2040
2041 /**
2042 * d_obtain_root - find or allocate a dentry for a given inode
2043 * @inode: inode to allocate the dentry for
2044 *
2045 * Obtain an IS_ROOT dentry for the root of a filesystem.
2046 *
2047 * We must ensure that directory inodes only ever have one dentry. If a
2048 * dentry is found, that is returned instead of allocating a new one.
2049 *
2050 * On successful return, the reference to the inode has been transferred
2051 * to the dentry. In case of an error the reference on the inode is
2052 * released. A %NULL or IS_ERR inode may be passed in and will be the
2053 * error will be propagate to the return value, with a %NULL @inode
2054 * replaced by ERR_PTR(-ESTALE).
2055 */
2056 struct dentry *d_obtain_root(struct inode *inode)
2057 {
2058 return __d_obtain_alias(inode, false);
2059 }
2060 EXPORT_SYMBOL(d_obtain_root);
2061
2062 /**
2063 * d_add_ci - lookup or allocate new dentry with case-exact name
2064 * @inode: the inode case-insensitive lookup has found
2065 * @dentry: the negative dentry that was passed to the parent's lookup func
2066 * @name: the case-exact name to be associated with the returned dentry
2067 *
2068 * This is to avoid filling the dcache with case-insensitive names to the
2069 * same inode, only the actual correct case is stored in the dcache for
2070 * case-insensitive filesystems.
2071 *
2072 * For a case-insensitive lookup match and if the the case-exact dentry
2073 * already exists in in the dcache, use it and return it.
2074 *
2075 * If no entry exists with the exact case name, allocate new dentry with
2076 * the exact case, and return the spliced entry.
2077 */
2078 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
2079 struct qstr *name)
2080 {
2081 struct dentry *found, *res;
2082
2083 /*
2084 * First check if a dentry matching the name already exists,
2085 * if not go ahead and create it now.
2086 */
2087 found = d_hash_and_lookup(dentry->d_parent, name);
2088 if (found) {
2089 iput(inode);
2090 return found;
2091 }
2092 if (d_in_lookup(dentry)) {
2093 found = d_alloc_parallel(dentry->d_parent, name,
2094 dentry->d_wait);
2095 if (IS_ERR(found) || !d_in_lookup(found)) {
2096 iput(inode);
2097 return found;
2098 }
2099 } else {
2100 found = d_alloc(dentry->d_parent, name);
2101 if (!found) {
2102 iput(inode);
2103 return ERR_PTR(-ENOMEM);
2104 }
2105 }
2106 res = d_splice_alias(inode, found);
2107 if (res) {
2108 dput(found);
2109 return res;
2110 }
2111 return found;
2112 }
2113 EXPORT_SYMBOL(d_add_ci);
2114
2115
2116 static inline bool d_same_name(const struct dentry *dentry,
2117 const struct dentry *parent,
2118 const struct qstr *name)
2119 {
2120 if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
2121 if (dentry->d_name.len != name->len)
2122 return false;
2123 return dentry_cmp(dentry, name->name, name->len) == 0;
2124 }
2125 return parent->d_op->d_compare(dentry,
2126 dentry->d_name.len, dentry->d_name.name,
2127 name) == 0;
2128 }
2129
2130 /**
2131 * __d_lookup_rcu - search for a dentry (racy, store-free)
2132 * @parent: parent dentry
2133 * @name: qstr of name we wish to find
2134 * @seqp: returns d_seq value at the point where the dentry was found
2135 * Returns: dentry, or NULL
2136 *
2137 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2138 * resolution (store-free path walking) design described in
2139 * Documentation/filesystems/path-lookup.txt.
2140 *
2141 * This is not to be used outside core vfs.
2142 *
2143 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2144 * held, and rcu_read_lock held. The returned dentry must not be stored into
2145 * without taking d_lock and checking d_seq sequence count against @seq
2146 * returned here.
2147 *
2148 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2149 * function.
2150 *
2151 * Alternatively, __d_lookup_rcu may be called again to look up the child of
2152 * the returned dentry, so long as its parent's seqlock is checked after the
2153 * child is looked up. Thus, an interlocking stepping of sequence lock checks
2154 * is formed, giving integrity down the path walk.
2155 *
2156 * NOTE! The caller *has* to check the resulting dentry against the sequence
2157 * number we've returned before using any of the resulting dentry state!
2158 */
2159 struct dentry *__d_lookup_rcu(const struct dentry *parent,
2160 const struct qstr *name,
2161 unsigned *seqp)
2162 {
2163 u64 hashlen = name->hash_len;
2164 const unsigned char *str = name->name;
2165 struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
2166 struct hlist_bl_node *node;
2167 struct dentry *dentry;
2168
2169 /*
2170 * Note: There is significant duplication with __d_lookup_rcu which is
2171 * required to prevent single threaded performance regressions
2172 * especially on architectures where smp_rmb (in seqcounts) are costly.
2173 * Keep the two functions in sync.
2174 */
2175
2176 /*
2177 * The hash list is protected using RCU.
2178 *
2179 * Carefully use d_seq when comparing a candidate dentry, to avoid
2180 * races with d_move().
2181 *
2182 * It is possible that concurrent renames can mess up our list
2183 * walk here and result in missing our dentry, resulting in the
2184 * false-negative result. d_lookup() protects against concurrent
2185 * renames using rename_lock seqlock.
2186 *
2187 * See Documentation/filesystems/path-lookup.txt for more details.
2188 */
2189 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2190 unsigned seq;
2191
2192 seqretry:
2193 /*
2194 * The dentry sequence count protects us from concurrent
2195 * renames, and thus protects parent and name fields.
2196 *
2197 * The caller must perform a seqcount check in order
2198 * to do anything useful with the returned dentry.
2199 *
2200 * NOTE! We do a "raw" seqcount_begin here. That means that
2201 * we don't wait for the sequence count to stabilize if it
2202 * is in the middle of a sequence change. If we do the slow
2203 * dentry compare, we will do seqretries until it is stable,
2204 * and if we end up with a successful lookup, we actually
2205 * want to exit RCU lookup anyway.
2206 *
2207 * Note that raw_seqcount_begin still *does* smp_rmb(), so
2208 * we are still guaranteed NUL-termination of ->d_name.name.
2209 */
2210 seq = raw_seqcount_begin(&dentry->d_seq);
2211 if (dentry->d_parent != parent)
2212 continue;
2213 if (d_unhashed(dentry))
2214 continue;
2215
2216 if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
2217 int tlen;
2218 const char *tname;
2219 if (dentry->d_name.hash != hashlen_hash(hashlen))
2220 continue;
2221 tlen = dentry->d_name.len;
2222 tname = dentry->d_name.name;
2223 /* we want a consistent (name,len) pair */
2224 if (read_seqcount_retry(&dentry->d_seq, seq)) {
2225 cpu_relax();
2226 goto seqretry;
2227 }
2228 if (parent->d_op->d_compare(dentry,
2229 tlen, tname, name) != 0)
2230 continue;
2231 } else {
2232 if (dentry->d_name.hash_len != hashlen)
2233 continue;
2234 if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
2235 continue;
2236 }
2237 *seqp = seq;
2238 return dentry;
2239 }
2240 return NULL;
2241 }
2242
2243 /**
2244 * d_lookup - search for a dentry
2245 * @parent: parent dentry
2246 * @name: qstr of name we wish to find
2247 * Returns: dentry, or NULL
2248 *
2249 * d_lookup searches the children of the parent dentry for the name in
2250 * question. If the dentry is found its reference count is incremented and the
2251 * dentry is returned. The caller must use dput to free the entry when it has
2252 * finished using it. %NULL is returned if the dentry does not exist.
2253 */
2254 struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
2255 {
2256 struct dentry *dentry;
2257 unsigned seq;
2258
2259 do {
2260 seq = read_seqbegin(&rename_lock);
2261 dentry = __d_lookup(parent, name);
2262 if (dentry)
2263 break;
2264 } while (read_seqretry(&rename_lock, seq));
2265 return dentry;
2266 }
2267 EXPORT_SYMBOL(d_lookup);
2268
2269 /**
2270 * __d_lookup - search for a dentry (racy)
2271 * @parent: parent dentry
2272 * @name: qstr of name we wish to find
2273 * Returns: dentry, or NULL
2274 *
2275 * __d_lookup is like d_lookup, however it may (rarely) return a
2276 * false-negative result due to unrelated rename activity.
2277 *
2278 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2279 * however it must be used carefully, eg. with a following d_lookup in
2280 * the case of failure.
2281 *
2282 * __d_lookup callers must be commented.
2283 */
2284 struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
2285 {
2286 unsigned int hash = name->hash;
2287 struct hlist_bl_head *b = d_hash(hash);
2288 struct hlist_bl_node *node;
2289 struct dentry *found = NULL;
2290 struct dentry *dentry;
2291
2292 /*
2293 * Note: There is significant duplication with __d_lookup_rcu which is
2294 * required to prevent single threaded performance regressions
2295 * especially on architectures where smp_rmb (in seqcounts) are costly.
2296 * Keep the two functions in sync.
2297 */
2298
2299 /*
2300 * The hash list is protected using RCU.
2301 *
2302 * Take d_lock when comparing a candidate dentry, to avoid races
2303 * with d_move().
2304 *
2305 * It is possible that concurrent renames can mess up our list
2306 * walk here and result in missing our dentry, resulting in the
2307 * false-negative result. d_lookup() protects against concurrent
2308 * renames using rename_lock seqlock.
2309 *
2310 * See Documentation/filesystems/path-lookup.txt for more details.
2311 */
2312 rcu_read_lock();
2313
2314 hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2315
2316 if (dentry->d_name.hash != hash)
2317 continue;
2318
2319 spin_lock(&dentry->d_lock);
2320 if (dentry->d_parent != parent)
2321 goto next;
2322 if (d_unhashed(dentry))
2323 goto next;
2324
2325 if (!d_same_name(dentry, parent, name))
2326 goto next;
2327
2328 dentry->d_lockref.count++;
2329 found = dentry;
2330 spin_unlock(&dentry->d_lock);
2331 break;
2332 next:
2333 spin_unlock(&dentry->d_lock);
2334 }
2335 rcu_read_unlock();
2336
2337 return found;
2338 }
2339
2340 /**
2341 * d_hash_and_lookup - hash the qstr then search for a dentry
2342 * @dir: Directory to search in
2343 * @name: qstr of name we wish to find
2344 *
2345 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2346 */
2347 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2348 {
2349 /*
2350 * Check for a fs-specific hash function. Note that we must
2351 * calculate the standard hash first, as the d_op->d_hash()
2352 * routine may choose to leave the hash value unchanged.
2353 */
2354 name->hash = full_name_hash(dir, name->name, name->len);
2355 if (dir->d_flags & DCACHE_OP_HASH) {
2356 int err = dir->d_op->d_hash(dir, name);
2357 if (unlikely(err < 0))
2358 return ERR_PTR(err);
2359 }
2360 return d_lookup(dir, name);
2361 }
2362 EXPORT_SYMBOL(d_hash_and_lookup);
2363
2364 /*
2365 * When a file is deleted, we have two options:
2366 * - turn this dentry into a negative dentry
2367 * - unhash this dentry and free it.
2368 *
2369 * Usually, we want to just turn this into
2370 * a negative dentry, but if anybody else is
2371 * currently using the dentry or the inode
2372 * we can't do that and we fall back on removing
2373 * it from the hash queues and waiting for
2374 * it to be deleted later when it has no users
2375 */
2376
2377 /**
2378 * d_delete - delete a dentry
2379 * @dentry: The dentry to delete
2380 *
2381 * Turn the dentry into a negative dentry if possible, otherwise
2382 * remove it from the hash queues so it can be deleted later
2383 */
2384
2385 void d_delete(struct dentry * dentry)
2386 {
2387 struct inode *inode = dentry->d_inode;
2388 int isdir = d_is_dir(dentry);
2389
2390 spin_lock(&inode->i_lock);
2391 spin_lock(&dentry->d_lock);
2392 /*
2393 * Are we the only user?
2394 */
2395 if (dentry->d_lockref.count == 1) {
2396 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2397 dentry_unlink_inode(dentry);
2398 } else {
2399 __d_drop(dentry);
2400 spin_unlock(&dentry->d_lock);
2401 spin_unlock(&inode->i_lock);
2402 }
2403 fsnotify_nameremove(dentry, isdir);
2404 }
2405 EXPORT_SYMBOL(d_delete);
2406
2407 static void __d_rehash(struct dentry *entry)
2408 {
2409 struct hlist_bl_head *b = d_hash(entry->d_name.hash);
2410
2411 hlist_bl_lock(b);
2412 hlist_bl_add_head_rcu(&entry->d_hash, b);
2413 hlist_bl_unlock(b);
2414 }
2415
2416 /**
2417 * d_rehash - add an entry back to the hash
2418 * @entry: dentry to add to the hash
2419 *
2420 * Adds a dentry to the hash according to its name.
2421 */
2422
2423 void d_rehash(struct dentry * entry)
2424 {
2425 spin_lock(&entry->d_lock);
2426 __d_rehash(entry);
2427 spin_unlock(&entry->d_lock);
2428 }
2429 EXPORT_SYMBOL(d_rehash);
2430
2431 static inline unsigned start_dir_add(struct inode *dir)
2432 {
2433
2434 for (;;) {
2435 unsigned n = dir->i_dir_seq;
2436 if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
2437 return n;
2438 cpu_relax();
2439 }
2440 }
2441
2442 static inline void end_dir_add(struct inode *dir, unsigned n)
2443 {
2444 smp_store_release(&dir->i_dir_seq, n + 2);
2445 }
2446
2447 static void d_wait_lookup(struct dentry *dentry)
2448 {
2449 if (d_in_lookup(dentry)) {
2450 DECLARE_WAITQUEUE(wait, current);
2451 add_wait_queue(dentry->d_wait, &wait);
2452 do {
2453 set_current_state(TASK_UNINTERRUPTIBLE);
2454 spin_unlock(&dentry->d_lock);
2455 schedule();
2456 spin_lock(&dentry->d_lock);
2457 } while (d_in_lookup(dentry));
2458 }
2459 }
2460
2461 struct dentry *d_alloc_parallel(struct dentry *parent,
2462 const struct qstr *name,
2463 wait_queue_head_t *wq)
2464 {
2465 unsigned int hash = name->hash;
2466 struct hlist_bl_head *b = in_lookup_hash(parent, hash);
2467 struct hlist_bl_node *node;
2468 struct dentry *new = d_alloc(parent, name);
2469 struct dentry *dentry;
2470 unsigned seq, r_seq, d_seq;
2471
2472 if (unlikely(!new))
2473 return ERR_PTR(-ENOMEM);
2474
2475 retry:
2476 rcu_read_lock();
2477 seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
2478 r_seq = read_seqbegin(&rename_lock);
2479 dentry = __d_lookup_rcu(parent, name, &d_seq);
2480 if (unlikely(dentry)) {
2481 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2482 rcu_read_unlock();
2483 goto retry;
2484 }
2485 if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
2486 rcu_read_unlock();
2487 dput(dentry);
2488 goto retry;
2489 }
2490 rcu_read_unlock();
2491 dput(new);
2492 return dentry;
2493 }
2494 if (unlikely(read_seqretry(&rename_lock, r_seq))) {
2495 rcu_read_unlock();
2496 goto retry;
2497 }
2498
2499 if (unlikely(seq & 1)) {
2500 rcu_read_unlock();
2501 goto retry;
2502 }
2503
2504 hlist_bl_lock(b);
2505 if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
2506 hlist_bl_unlock(b);
2507 rcu_read_unlock();
2508 goto retry;
2509 }
2510 /*
2511 * No changes for the parent since the beginning of d_lookup().
2512 * Since all removals from the chain happen with hlist_bl_lock(),
2513 * any potential in-lookup matches are going to stay here until
2514 * we unlock the chain. All fields are stable in everything
2515 * we encounter.
2516 */
2517 hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
2518 if (dentry->d_name.hash != hash)
2519 continue;
2520 if (dentry->d_parent != parent)
2521 continue;
2522 if (!d_same_name(dentry, parent, name))
2523 continue;
2524 hlist_bl_unlock(b);
2525 /* now we can try to grab a reference */
2526 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2527 rcu_read_unlock();
2528 goto retry;
2529 }
2530
2531 rcu_read_unlock();
2532 /*
2533 * somebody is likely to be still doing lookup for it;
2534 * wait for them to finish
2535 */
2536 spin_lock(&dentry->d_lock);
2537 d_wait_lookup(dentry);
2538 /*
2539 * it's not in-lookup anymore; in principle we should repeat
2540 * everything from dcache lookup, but it's likely to be what
2541 * d_lookup() would've found anyway. If it is, just return it;
2542 * otherwise we really have to repeat the whole thing.
2543 */
2544 if (unlikely(dentry->d_name.hash != hash))
2545 goto mismatch;
2546 if (unlikely(dentry->d_parent != parent))
2547 goto mismatch;
2548 if (unlikely(d_unhashed(dentry)))
2549 goto mismatch;
2550 if (unlikely(!d_same_name(dentry, parent, name)))
2551 goto mismatch;
2552 /* OK, it *is* a hashed match; return it */
2553 spin_unlock(&dentry->d_lock);
2554 dput(new);
2555 return dentry;
2556 }
2557 rcu_read_unlock();
2558 /* we can't take ->d_lock here; it's OK, though. */
2559 new->d_flags |= DCACHE_PAR_LOOKUP;
2560 new->d_wait = wq;
2561 hlist_bl_add_head_rcu(&new->d_u.d_in_lookup_hash, b);
2562 hlist_bl_unlock(b);
2563 return new;
2564 mismatch:
2565 spin_unlock(&dentry->d_lock);
2566 dput(dentry);
2567 goto retry;
2568 }
2569 EXPORT_SYMBOL(d_alloc_parallel);
2570
2571 void __d_lookup_done(struct dentry *dentry)
2572 {
2573 struct hlist_bl_head *b = in_lookup_hash(dentry->d_parent,
2574 dentry->d_name.hash);
2575 hlist_bl_lock(b);
2576 dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
2577 __hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
2578 wake_up_all(dentry->d_wait);
2579 dentry->d_wait = NULL;
2580 hlist_bl_unlock(b);
2581 INIT_HLIST_NODE(&dentry->d_u.d_alias);
2582 INIT_LIST_HEAD(&dentry->d_lru);
2583 }
2584 EXPORT_SYMBOL(__d_lookup_done);
2585
2586 /* inode->i_lock held if inode is non-NULL */
2587
2588 static inline void __d_add(struct dentry *dentry, struct inode *inode)
2589 {
2590 struct inode *dir = NULL;
2591 unsigned n;
2592 spin_lock(&dentry->d_lock);
2593 if (unlikely(d_in_lookup(dentry))) {
2594 dir = dentry->d_parent->d_inode;
2595 n = start_dir_add(dir);
2596 __d_lookup_done(dentry);
2597 }
2598 if (inode) {
2599 unsigned add_flags = d_flags_for_inode(inode);
2600 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2601 raw_write_seqcount_begin(&dentry->d_seq);
2602 __d_set_inode_and_type(dentry, inode, add_flags);
2603 raw_write_seqcount_end(&dentry->d_seq);
2604 fsnotify_update_flags(dentry);
2605 }
2606 __d_rehash(dentry);
2607 if (dir)
2608 end_dir_add(dir, n);
2609 spin_unlock(&dentry->d_lock);
2610 if (inode)
2611 spin_unlock(&inode->i_lock);
2612 }
2613
2614 /**
2615 * d_add - add dentry to hash queues
2616 * @entry: dentry to add
2617 * @inode: The inode to attach to this dentry
2618 *
2619 * This adds the entry to the hash queues and initializes @inode.
2620 * The entry was actually filled in earlier during d_alloc().
2621 */
2622
2623 void d_add(struct dentry *entry, struct inode *inode)
2624 {
2625 if (inode) {
2626 security_d_instantiate(entry, inode);
2627 spin_lock(&inode->i_lock);
2628 }
2629 __d_add(entry, inode);
2630 }
2631 EXPORT_SYMBOL(d_add);
2632
2633 /**
2634 * d_exact_alias - find and hash an exact unhashed alias
2635 * @entry: dentry to add
2636 * @inode: The inode to go with this dentry
2637 *
2638 * If an unhashed dentry with the same name/parent and desired
2639 * inode already exists, hash and return it. Otherwise, return
2640 * NULL.
2641 *
2642 * Parent directory should be locked.
2643 */
2644 struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
2645 {
2646 struct dentry *alias;
2647 unsigned int hash = entry->d_name.hash;
2648
2649 spin_lock(&inode->i_lock);
2650 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
2651 /*
2652 * Don't need alias->d_lock here, because aliases with
2653 * d_parent == entry->d_parent are not subject to name or
2654 * parent changes, because the parent inode i_mutex is held.
2655 */
2656 if (alias->d_name.hash != hash)
2657 continue;
2658 if (alias->d_parent != entry->d_parent)
2659 continue;
2660 if (!d_same_name(alias, entry->d_parent, &entry->d_name))
2661 continue;
2662 spin_lock(&alias->d_lock);
2663 if (!d_unhashed(alias)) {
2664 spin_unlock(&alias->d_lock);
2665 alias = NULL;
2666 } else {
2667 __dget_dlock(alias);
2668 __d_rehash(alias);
2669 spin_unlock(&alias->d_lock);
2670 }
2671 spin_unlock(&inode->i_lock);
2672 return alias;
2673 }
2674 spin_unlock(&inode->i_lock);
2675 return NULL;
2676 }
2677 EXPORT_SYMBOL(d_exact_alias);
2678
2679 /**
2680 * dentry_update_name_case - update case insensitive dentry with a new name
2681 * @dentry: dentry to be updated
2682 * @name: new name
2683 *
2684 * Update a case insensitive dentry with new case of name.
2685 *
2686 * dentry must have been returned by d_lookup with name @name. Old and new
2687 * name lengths must match (ie. no d_compare which allows mismatched name
2688 * lengths).
2689 *
2690 * Parent inode i_mutex must be held over d_lookup and into this call (to
2691 * keep renames and concurrent inserts, and readdir(2) away).
2692 */
2693 void dentry_update_name_case(struct dentry *dentry, const struct qstr *name)
2694 {
2695 BUG_ON(!inode_is_locked(dentry->d_parent->d_inode));
2696 BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
2697
2698 spin_lock(&dentry->d_lock);
2699 write_seqcount_begin(&dentry->d_seq);
2700 memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
2701 write_seqcount_end(&dentry->d_seq);
2702 spin_unlock(&dentry->d_lock);
2703 }
2704 EXPORT_SYMBOL(dentry_update_name_case);
2705
2706 static void swap_names(struct dentry *dentry, struct dentry *target)
2707 {
2708 if (unlikely(dname_external(target))) {
2709 if (unlikely(dname_external(dentry))) {
2710 /*
2711 * Both external: swap the pointers
2712 */
2713 swap(target->d_name.name, dentry->d_name.name);
2714 } else {
2715 /*
2716 * dentry:internal, target:external. Steal target's
2717 * storage and make target internal.
2718 */
2719 memcpy(target->d_iname, dentry->d_name.name,
2720 dentry->d_name.len + 1);
2721 dentry->d_name.name = target->d_name.name;
2722 target->d_name.name = target->d_iname;
2723 }
2724 } else {
2725 if (unlikely(dname_external(dentry))) {
2726 /*
2727 * dentry:external, target:internal. Give dentry's
2728 * storage to target and make dentry internal
2729 */
2730 memcpy(dentry->d_iname, target->d_name.name,
2731 target->d_name.len + 1);
2732 target->d_name.name = dentry->d_name.name;
2733 dentry->d_name.name = dentry->d_iname;
2734 } else {
2735 /*
2736 * Both are internal.
2737 */
2738 unsigned int i;
2739 BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
2740 for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
2741 swap(((long *) &dentry->d_iname)[i],
2742 ((long *) &target->d_iname)[i]);
2743 }
2744 }
2745 }
2746 swap(dentry->d_name.hash_len, target->d_name.hash_len);
2747 }
2748
2749 static void copy_name(struct dentry *dentry, struct dentry *target)
2750 {
2751 struct external_name *old_name = NULL;
2752 if (unlikely(dname_external(dentry)))
2753 old_name = external_name(dentry);
2754 if (unlikely(dname_external(target))) {
2755 atomic_inc(&external_name(target)->u.count);
2756 dentry->d_name = target->d_name;
2757 } else {
2758 memcpy(dentry->d_iname, target->d_name.name,
2759 target->d_name.len + 1);
2760 dentry->d_name.name = dentry->d_iname;
2761 dentry->d_name.hash_len = target->d_name.hash_len;
2762 }
2763 if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
2764 call_rcu(&old_name->u.head, __d_free_external_name);
2765 }
2766
2767 /*
2768 * __d_move - move a dentry
2769 * @dentry: entry to move
2770 * @target: new dentry
2771 * @exchange: exchange the two dentries
2772 *
2773 * Update the dcache to reflect the move of a file name. Negative
2774 * dcache entries should not be moved in this way. Caller must hold
2775 * rename_lock, the i_mutex of the source and target directories,
2776 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2777 */
2778 static void __d_move(struct dentry *dentry, struct dentry *target,
2779 bool exchange)
2780 {
2781 struct dentry *old_parent, *p;
2782 struct inode *dir = NULL;
2783 unsigned n;
2784
2785 WARN_ON(!dentry->d_inode);
2786 if (WARN_ON(dentry == target))
2787 return;
2788
2789 BUG_ON(d_ancestor(target, dentry));
2790 old_parent = dentry->d_parent;
2791 p = d_ancestor(old_parent, target);
2792 if (IS_ROOT(dentry)) {
2793 BUG_ON(p);
2794 spin_lock(&target->d_parent->d_lock);
2795 } else if (!p) {
2796 /* target is not a descendent of dentry->d_parent */
2797 spin_lock(&target->d_parent->d_lock);
2798 spin_lock_nested(&old_parent->d_lock, DENTRY_D_LOCK_NESTED);
2799 } else {
2800 BUG_ON(p == dentry);
2801 spin_lock(&old_parent->d_lock);
2802 if (p != target)
2803 spin_lock_nested(&target->d_parent->d_lock,
2804 DENTRY_D_LOCK_NESTED);
2805 }
2806 spin_lock_nested(&dentry->d_lock, 2);
2807 spin_lock_nested(&target->d_lock, 3);
2808
2809 if (unlikely(d_in_lookup(target))) {
2810 dir = target->d_parent->d_inode;
2811 n = start_dir_add(dir);
2812 __d_lookup_done(target);
2813 }
2814
2815 write_seqcount_begin(&dentry->d_seq);
2816 write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
2817
2818 /* unhash both */
2819 if (!d_unhashed(dentry))
2820 ___d_drop(dentry);
2821 if (!d_unhashed(target))
2822 ___d_drop(target);
2823
2824 /* ... and switch them in the tree */
2825 dentry->d_parent = target->d_parent;
2826 if (!exchange) {
2827 copy_name(dentry, target);
2828 target->d_hash.pprev = NULL;
2829 dentry->d_parent->d_lockref.count++;
2830 if (dentry == old_parent)
2831 dentry->d_flags |= DCACHE_RCUACCESS;
2832 else
2833 WARN_ON(!--old_parent->d_lockref.count);
2834 } else {
2835 target->d_parent = old_parent;
2836 swap_names(dentry, target);
2837 list_move(&target->d_child, &target->d_parent->d_subdirs);
2838 __d_rehash(target);
2839 fsnotify_update_flags(target);
2840 }
2841 list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
2842 __d_rehash(dentry);
2843 fsnotify_update_flags(dentry);
2844
2845 write_seqcount_end(&target->d_seq);
2846 write_seqcount_end(&dentry->d_seq);
2847
2848 if (dir)
2849 end_dir_add(dir, n);
2850
2851 if (dentry->d_parent != old_parent)
2852 spin_unlock(&dentry->d_parent->d_lock);
2853 if (dentry != old_parent)
2854 spin_unlock(&old_parent->d_lock);
2855 spin_unlock(&target->d_lock);
2856 spin_unlock(&dentry->d_lock);
2857 }
2858
2859 /*
2860 * d_move - move a dentry
2861 * @dentry: entry to move
2862 * @target: new dentry
2863 *
2864 * Update the dcache to reflect the move of a file name. Negative
2865 * dcache entries should not be moved in this way. See the locking
2866 * requirements for __d_move.
2867 */
2868 void d_move(struct dentry *dentry, struct dentry *target)
2869 {
2870 write_seqlock(&rename_lock);
2871 __d_move(dentry, target, false);
2872 write_sequnlock(&rename_lock);
2873 }
2874 EXPORT_SYMBOL(d_move);
2875
2876 /*
2877 * d_exchange - exchange two dentries
2878 * @dentry1: first dentry
2879 * @dentry2: second dentry
2880 */
2881 void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
2882 {
2883 write_seqlock(&rename_lock);
2884
2885 WARN_ON(!dentry1->d_inode);
2886 WARN_ON(!dentry2->d_inode);
2887 WARN_ON(IS_ROOT(dentry1));
2888 WARN_ON(IS_ROOT(dentry2));
2889
2890 __d_move(dentry1, dentry2, true);
2891
2892 write_sequnlock(&rename_lock);
2893 }
2894
2895 /**
2896 * d_ancestor - search for an ancestor
2897 * @p1: ancestor dentry
2898 * @p2: child dentry
2899 *
2900 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
2901 * an ancestor of p2, else NULL.
2902 */
2903 struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2904 {
2905 struct dentry *p;
2906
2907 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2908 if (p->d_parent == p1)
2909 return p;
2910 }
2911 return NULL;
2912 }
2913
2914 /*
2915 * This helper attempts to cope with remotely renamed directories
2916 *
2917 * It assumes that the caller is already holding
2918 * dentry->d_parent->d_inode->i_mutex, and rename_lock
2919 *
2920 * Note: If ever the locking in lock_rename() changes, then please
2921 * remember to update this too...
2922 */
2923 static int __d_unalias(struct inode *inode,
2924 struct dentry *dentry, struct dentry *alias)
2925 {
2926 struct mutex *m1 = NULL;
2927 struct rw_semaphore *m2 = NULL;
2928 int ret = -ESTALE;
2929
2930 /* If alias and dentry share a parent, then no extra locks required */
2931 if (alias->d_parent == dentry->d_parent)
2932 goto out_unalias;
2933
2934 /* See lock_rename() */
2935 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
2936 goto out_err;
2937 m1 = &dentry->d_sb->s_vfs_rename_mutex;
2938 if (!inode_trylock_shared(alias->d_parent->d_inode))
2939 goto out_err;
2940 m2 = &alias->d_parent->d_inode->i_rwsem;
2941 out_unalias:
2942 __d_move(alias, dentry, false);
2943 ret = 0;
2944 out_err:
2945 if (m2)
2946 up_read(m2);
2947 if (m1)
2948 mutex_unlock(m1);
2949 return ret;
2950 }
2951
2952 /**
2953 * d_splice_alias - splice a disconnected dentry into the tree if one exists
2954 * @inode: the inode which may have a disconnected dentry
2955 * @dentry: a negative dentry which we want to point to the inode.
2956 *
2957 * If inode is a directory and has an IS_ROOT alias, then d_move that in
2958 * place of the given dentry and return it, else simply d_add the inode
2959 * to the dentry and return NULL.
2960 *
2961 * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
2962 * we should error out: directories can't have multiple aliases.
2963 *
2964 * This is needed in the lookup routine of any filesystem that is exportable
2965 * (via knfsd) so that we can build dcache paths to directories effectively.
2966 *
2967 * If a dentry was found and moved, then it is returned. Otherwise NULL
2968 * is returned. This matches the expected return value of ->lookup.
2969 *
2970 * Cluster filesystems may call this function with a negative, hashed dentry.
2971 * In that case, we know that the inode will be a regular file, and also this
2972 * will only occur during atomic_open. So we need to check for the dentry
2973 * being already hashed only in the final case.
2974 */
2975 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
2976 {
2977 if (IS_ERR(inode))
2978 return ERR_CAST(inode);
2979
2980 BUG_ON(!d_unhashed(dentry));
2981
2982 if (!inode)
2983 goto out;
2984
2985 security_d_instantiate(dentry, inode);
2986 spin_lock(&inode->i_lock);
2987 if (S_ISDIR(inode->i_mode)) {
2988 struct dentry *new = __d_find_any_alias(inode);
2989 if (unlikely(new)) {
2990 /* The reference to new ensures it remains an alias */
2991 spin_unlock(&inode->i_lock);
2992 write_seqlock(&rename_lock);
2993 if (unlikely(d_ancestor(new, dentry))) {
2994 write_sequnlock(&rename_lock);
2995 dput(new);
2996 new = ERR_PTR(-ELOOP);
2997 pr_warn_ratelimited(
2998 "VFS: Lookup of '%s' in %s %s"
2999 " would have caused loop\n",
3000 dentry->d_name.name,
3001 inode->i_sb->s_type->name,
3002 inode->i_sb->s_id);
3003 } else if (!IS_ROOT(new)) {
3004 struct dentry *old_parent = dget(new->d_parent);
3005 int err = __d_unalias(inode, dentry, new);
3006 write_sequnlock(&rename_lock);
3007 if (err) {
3008 dput(new);
3009 new = ERR_PTR(err);
3010 }
3011 dput(old_parent);
3012 } else {
3013 __d_move(new, dentry, false);
3014 write_sequnlock(&rename_lock);
3015 }
3016 iput(inode);
3017 return new;
3018 }
3019 }
3020 out:
3021 __d_add(dentry, inode);
3022 return NULL;
3023 }
3024 EXPORT_SYMBOL(d_splice_alias);
3025
3026 /*
3027 * Test whether new_dentry is a subdirectory of old_dentry.
3028 *
3029 * Trivially implemented using the dcache structure
3030 */
3031
3032 /**
3033 * is_subdir - is new dentry a subdirectory of old_dentry
3034 * @new_dentry: new dentry
3035 * @old_dentry: old dentry
3036 *
3037 * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3038 * Returns false otherwise.
3039 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3040 */
3041
3042 bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
3043 {
3044 bool result;
3045 unsigned seq;
3046
3047 if (new_dentry == old_dentry)
3048 return true;
3049
3050 do {
3051 /* for restarting inner loop in case of seq retry */
3052 seq = read_seqbegin(&rename_lock);
3053 /*
3054 * Need rcu_readlock to protect against the d_parent trashing
3055 * due to d_move
3056 */
3057 rcu_read_lock();
3058 if (d_ancestor(old_dentry, new_dentry))
3059 result = true;
3060 else
3061 result = false;
3062 rcu_read_unlock();
3063 } while (read_seqretry(&rename_lock, seq));
3064
3065 return result;
3066 }
3067 EXPORT_SYMBOL(is_subdir);
3068
3069 static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
3070 {
3071 struct dentry *root = data;
3072 if (dentry != root) {
3073 if (d_unhashed(dentry) || !dentry->d_inode)
3074 return D_WALK_SKIP;
3075
3076 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
3077 dentry->d_flags |= DCACHE_GENOCIDE;
3078 dentry->d_lockref.count--;
3079 }
3080 }
3081 return D_WALK_CONTINUE;
3082 }
3083
3084 void d_genocide(struct dentry *parent)
3085 {
3086 d_walk(parent, parent, d_genocide_kill);
3087 }
3088
3089 EXPORT_SYMBOL(d_genocide);
3090
3091 void d_tmpfile(struct dentry *dentry, struct inode *inode)
3092 {
3093 inode_dec_link_count(inode);
3094 BUG_ON(dentry->d_name.name != dentry->d_iname ||
3095 !hlist_unhashed(&dentry->d_u.d_alias) ||
3096 !d_unlinked(dentry));
3097 spin_lock(&dentry->d_parent->d_lock);
3098 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
3099 dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
3100 (unsigned long long)inode->i_ino);
3101 spin_unlock(&dentry->d_lock);
3102 spin_unlock(&dentry->d_parent->d_lock);
3103 d_instantiate(dentry, inode);
3104 }
3105 EXPORT_SYMBOL(d_tmpfile);
3106
3107 static __initdata unsigned long dhash_entries;
3108 static int __init set_dhash_entries(char *str)
3109 {
3110 if (!str)
3111 return 0;
3112 dhash_entries = simple_strtoul(str, &str, 0);
3113 return 1;
3114 }
3115 __setup("dhash_entries=", set_dhash_entries);
3116
3117 static void __init dcache_init_early(void)
3118 {
3119 /* If hashes are distributed across NUMA nodes, defer
3120 * hash allocation until vmalloc space is available.
3121 */
3122 if (hashdist)
3123 return;
3124
3125 dentry_hashtable =
3126 alloc_large_system_hash("Dentry cache",
3127 sizeof(struct hlist_bl_head),
3128 dhash_entries,
3129 13,
3130 HASH_EARLY | HASH_ZERO,
3131 &d_hash_shift,
3132 NULL,
3133 0,
3134 0);
3135 d_hash_shift = 32 - d_hash_shift;
3136 }
3137
3138 static void __init dcache_init(void)
3139 {
3140 /*
3141 * A constructor could be added for stable state like the lists,
3142 * but it is probably not worth it because of the cache nature
3143 * of the dcache.
3144 */
3145 dentry_cache = KMEM_CACHE_USERCOPY(dentry,
3146 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT,
3147 d_iname);
3148
3149 /* Hash may have been set up in dcache_init_early */
3150 if (!hashdist)
3151 return;
3152
3153 dentry_hashtable =
3154 alloc_large_system_hash("Dentry cache",
3155 sizeof(struct hlist_bl_head),
3156 dhash_entries,
3157 13,
3158 HASH_ZERO,
3159 &d_hash_shift,
3160 NULL,
3161 0,
3162 0);
3163 d_hash_shift = 32 - d_hash_shift;
3164 }
3165
3166 /* SLAB cache for __getname() consumers */
3167 struct kmem_cache *names_cachep __read_mostly;
3168 EXPORT_SYMBOL(names_cachep);
3169
3170 void __init vfs_caches_init_early(void)
3171 {
3172 int i;
3173
3174 for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++)
3175 INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]);
3176
3177 dcache_init_early();
3178 inode_init_early();
3179 }
3180
3181 void __init vfs_caches_init(void)
3182 {
3183 names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0,
3184 SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL);
3185
3186 dcache_init();
3187 inode_init();
3188 files_init();
3189 files_maxfiles_init();
3190 mnt_init();
3191 bdev_cache_init();
3192 chrdev_init();
3193 }