Merge tag 'ceph-for-6.1-rc1' of https://github.com/ceph/ceph-client
[platform/kernel/linux-starfive.git] / fs / dcache.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * fs/dcache.c
4  *
5  * Complete reimplementation
6  * (C) 1997 Thomas Schoebel-Theuer,
7  * with heavy changes by Linus Torvalds
8  */
9
10 /*
11  * Notes on the allocation strategy:
12  *
13  * The dcache is a master of the icache - whenever a dcache entry
14  * exists, the inode will always exist. "iput()" is done either when
15  * the dcache entry is deleted or garbage collected.
16  */
17
18 #include <linux/ratelimit.h>
19 #include <linux/string.h>
20 #include <linux/mm.h>
21 #include <linux/fs.h>
22 #include <linux/fscrypt.h>
23 #include <linux/fsnotify.h>
24 #include <linux/slab.h>
25 #include <linux/init.h>
26 #include <linux/hash.h>
27 #include <linux/cache.h>
28 #include <linux/export.h>
29 #include <linux/security.h>
30 #include <linux/seqlock.h>
31 #include <linux/memblock.h>
32 #include <linux/bit_spinlock.h>
33 #include <linux/rculist_bl.h>
34 #include <linux/list_lru.h>
35 #include "internal.h"
36 #include "mount.h"
37
38 /*
39  * Usage:
40  * dcache->d_inode->i_lock protects:
41  *   - i_dentry, d_u.d_alias, d_inode of aliases
42  * dcache_hash_bucket lock protects:
43  *   - the dcache hash table
44  * s_roots bl list spinlock protects:
45  *   - the s_roots list (see __d_drop)
46  * dentry->d_sb->s_dentry_lru_lock protects:
47  *   - the dcache lru lists and counters
48  * d_lock protects:
49  *   - d_flags
50  *   - d_name
51  *   - d_lru
52  *   - d_count
53  *   - d_unhashed()
54  *   - d_parent and d_subdirs
55  *   - childrens' d_child and d_parent
56  *   - d_u.d_alias, d_inode
57  *
58  * Ordering:
59  * dentry->d_inode->i_lock
60  *   dentry->d_lock
61  *     dentry->d_sb->s_dentry_lru_lock
62  *     dcache_hash_bucket lock
63  *     s_roots lock
64  *
65  * If there is an ancestor relationship:
66  * dentry->d_parent->...->d_parent->d_lock
67  *   ...
68  *     dentry->d_parent->d_lock
69  *       dentry->d_lock
70  *
71  * If no ancestor relationship:
72  * arbitrary, since it's serialized on rename_lock
73  */
74 int sysctl_vfs_cache_pressure __read_mostly = 100;
75 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
76
77 __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
78
79 EXPORT_SYMBOL(rename_lock);
80
81 static struct kmem_cache *dentry_cache __read_mostly;
82
83 const struct qstr empty_name = QSTR_INIT("", 0);
84 EXPORT_SYMBOL(empty_name);
85 const struct qstr slash_name = QSTR_INIT("/", 1);
86 EXPORT_SYMBOL(slash_name);
87 const struct qstr dotdot_name = QSTR_INIT("..", 2);
88 EXPORT_SYMBOL(dotdot_name);
89
90 /*
91  * This is the single most critical data structure when it comes
92  * to the dcache: the hashtable for lookups. Somebody should try
93  * to make this good - I've just made it work.
94  *
95  * This hash-function tries to avoid losing too many bits of hash
96  * information, yet avoid using a prime hash-size or similar.
97  */
98
99 static unsigned int d_hash_shift __read_mostly;
100
101 static struct hlist_bl_head *dentry_hashtable __read_mostly;
102
103 static inline struct hlist_bl_head *d_hash(unsigned int hash)
104 {
105         return dentry_hashtable + (hash >> d_hash_shift);
106 }
107
108 #define IN_LOOKUP_SHIFT 10
109 static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT];
110
111 static inline struct hlist_bl_head *in_lookup_hash(const struct dentry *parent,
112                                         unsigned int hash)
113 {
114         hash += (unsigned long) parent / L1_CACHE_BYTES;
115         return in_lookup_hashtable + hash_32(hash, IN_LOOKUP_SHIFT);
116 }
117
118 struct dentry_stat_t {
119         long nr_dentry;
120         long nr_unused;
121         long age_limit;         /* age in seconds */
122         long want_pages;        /* pages requested by system */
123         long nr_negative;       /* # of unused negative dentries */
124         long dummy;             /* Reserved for future use */
125 };
126
127 static DEFINE_PER_CPU(long, nr_dentry);
128 static DEFINE_PER_CPU(long, nr_dentry_unused);
129 static DEFINE_PER_CPU(long, nr_dentry_negative);
130
131 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
132 /* Statistics gathering. */
133 static struct dentry_stat_t dentry_stat = {
134         .age_limit = 45,
135 };
136
137 /*
138  * Here we resort to our own counters instead of using generic per-cpu counters
139  * for consistency with what the vfs inode code does. We are expected to harvest
140  * better code and performance by having our own specialized counters.
141  *
142  * Please note that the loop is done over all possible CPUs, not over all online
143  * CPUs. The reason for this is that we don't want to play games with CPUs going
144  * on and off. If one of them goes off, we will just keep their counters.
145  *
146  * glommer: See cffbc8a for details, and if you ever intend to change this,
147  * please update all vfs counters to match.
148  */
149 static long get_nr_dentry(void)
150 {
151         int i;
152         long sum = 0;
153         for_each_possible_cpu(i)
154                 sum += per_cpu(nr_dentry, i);
155         return sum < 0 ? 0 : sum;
156 }
157
158 static long get_nr_dentry_unused(void)
159 {
160         int i;
161         long sum = 0;
162         for_each_possible_cpu(i)
163                 sum += per_cpu(nr_dentry_unused, i);
164         return sum < 0 ? 0 : sum;
165 }
166
167 static long get_nr_dentry_negative(void)
168 {
169         int i;
170         long sum = 0;
171
172         for_each_possible_cpu(i)
173                 sum += per_cpu(nr_dentry_negative, i);
174         return sum < 0 ? 0 : sum;
175 }
176
177 static int proc_nr_dentry(struct ctl_table *table, int write, void *buffer,
178                           size_t *lenp, loff_t *ppos)
179 {
180         dentry_stat.nr_dentry = get_nr_dentry();
181         dentry_stat.nr_unused = get_nr_dentry_unused();
182         dentry_stat.nr_negative = get_nr_dentry_negative();
183         return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
184 }
185
186 static struct ctl_table fs_dcache_sysctls[] = {
187         {
188                 .procname       = "dentry-state",
189                 .data           = &dentry_stat,
190                 .maxlen         = 6*sizeof(long),
191                 .mode           = 0444,
192                 .proc_handler   = proc_nr_dentry,
193         },
194         { }
195 };
196
197 static int __init init_fs_dcache_sysctls(void)
198 {
199         register_sysctl_init("fs", fs_dcache_sysctls);
200         return 0;
201 }
202 fs_initcall(init_fs_dcache_sysctls);
203 #endif
204
205 /*
206  * Compare 2 name strings, return 0 if they match, otherwise non-zero.
207  * The strings are both count bytes long, and count is non-zero.
208  */
209 #ifdef CONFIG_DCACHE_WORD_ACCESS
210
211 #include <asm/word-at-a-time.h>
212 /*
213  * NOTE! 'cs' and 'scount' come from a dentry, so it has a
214  * aligned allocation for this particular component. We don't
215  * strictly need the load_unaligned_zeropad() safety, but it
216  * doesn't hurt either.
217  *
218  * In contrast, 'ct' and 'tcount' can be from a pathname, and do
219  * need the careful unaligned handling.
220  */
221 static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
222 {
223         unsigned long a,b,mask;
224
225         for (;;) {
226                 a = read_word_at_a_time(cs);
227                 b = load_unaligned_zeropad(ct);
228                 if (tcount < sizeof(unsigned long))
229                         break;
230                 if (unlikely(a != b))
231                         return 1;
232                 cs += sizeof(unsigned long);
233                 ct += sizeof(unsigned long);
234                 tcount -= sizeof(unsigned long);
235                 if (!tcount)
236                         return 0;
237         }
238         mask = bytemask_from_count(tcount);
239         return unlikely(!!((a ^ b) & mask));
240 }
241
242 #else
243
244 static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
245 {
246         do {
247                 if (*cs != *ct)
248                         return 1;
249                 cs++;
250                 ct++;
251                 tcount--;
252         } while (tcount);
253         return 0;
254 }
255
256 #endif
257
258 static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
259 {
260         /*
261          * Be careful about RCU walk racing with rename:
262          * use 'READ_ONCE' to fetch the name pointer.
263          *
264          * NOTE! Even if a rename will mean that the length
265          * was not loaded atomically, we don't care. The
266          * RCU walk will check the sequence count eventually,
267          * and catch it. And we won't overrun the buffer,
268          * because we're reading the name pointer atomically,
269          * and a dentry name is guaranteed to be properly
270          * terminated with a NUL byte.
271          *
272          * End result: even if 'len' is wrong, we'll exit
273          * early because the data cannot match (there can
274          * be no NUL in the ct/tcount data)
275          */
276         const unsigned char *cs = READ_ONCE(dentry->d_name.name);
277
278         return dentry_string_cmp(cs, ct, tcount);
279 }
280
281 struct external_name {
282         union {
283                 atomic_t count;
284                 struct rcu_head head;
285         } u;
286         unsigned char name[];
287 };
288
289 static inline struct external_name *external_name(struct dentry *dentry)
290 {
291         return container_of(dentry->d_name.name, struct external_name, name[0]);
292 }
293
294 static void __d_free(struct rcu_head *head)
295 {
296         struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
297
298         kmem_cache_free(dentry_cache, dentry); 
299 }
300
301 static void __d_free_external(struct rcu_head *head)
302 {
303         struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
304         kfree(external_name(dentry));
305         kmem_cache_free(dentry_cache, dentry);
306 }
307
308 static inline int dname_external(const struct dentry *dentry)
309 {
310         return dentry->d_name.name != dentry->d_iname;
311 }
312
313 void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry)
314 {
315         spin_lock(&dentry->d_lock);
316         name->name = dentry->d_name;
317         if (unlikely(dname_external(dentry))) {
318                 atomic_inc(&external_name(dentry)->u.count);
319         } else {
320                 memcpy(name->inline_name, dentry->d_iname,
321                        dentry->d_name.len + 1);
322                 name->name.name = name->inline_name;
323         }
324         spin_unlock(&dentry->d_lock);
325 }
326 EXPORT_SYMBOL(take_dentry_name_snapshot);
327
328 void release_dentry_name_snapshot(struct name_snapshot *name)
329 {
330         if (unlikely(name->name.name != name->inline_name)) {
331                 struct external_name *p;
332                 p = container_of(name->name.name, struct external_name, name[0]);
333                 if (unlikely(atomic_dec_and_test(&p->u.count)))
334                         kfree_rcu(p, u.head);
335         }
336 }
337 EXPORT_SYMBOL(release_dentry_name_snapshot);
338
339 static inline void __d_set_inode_and_type(struct dentry *dentry,
340                                           struct inode *inode,
341                                           unsigned type_flags)
342 {
343         unsigned flags;
344
345         dentry->d_inode = inode;
346         flags = READ_ONCE(dentry->d_flags);
347         flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
348         flags |= type_flags;
349         smp_store_release(&dentry->d_flags, flags);
350 }
351
352 static inline void __d_clear_type_and_inode(struct dentry *dentry)
353 {
354         unsigned flags = READ_ONCE(dentry->d_flags);
355
356         flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
357         WRITE_ONCE(dentry->d_flags, flags);
358         dentry->d_inode = NULL;
359         if (dentry->d_flags & DCACHE_LRU_LIST)
360                 this_cpu_inc(nr_dentry_negative);
361 }
362
363 static void dentry_free(struct dentry *dentry)
364 {
365         WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias));
366         if (unlikely(dname_external(dentry))) {
367                 struct external_name *p = external_name(dentry);
368                 if (likely(atomic_dec_and_test(&p->u.count))) {
369                         call_rcu(&dentry->d_u.d_rcu, __d_free_external);
370                         return;
371                 }
372         }
373         /* if dentry was never visible to RCU, immediate free is OK */
374         if (dentry->d_flags & DCACHE_NORCU)
375                 __d_free(&dentry->d_u.d_rcu);
376         else
377                 call_rcu(&dentry->d_u.d_rcu, __d_free);
378 }
379
380 /*
381  * Release the dentry's inode, using the filesystem
382  * d_iput() operation if defined.
383  */
384 static void dentry_unlink_inode(struct dentry * dentry)
385         __releases(dentry->d_lock)
386         __releases(dentry->d_inode->i_lock)
387 {
388         struct inode *inode = dentry->d_inode;
389
390         raw_write_seqcount_begin(&dentry->d_seq);
391         __d_clear_type_and_inode(dentry);
392         hlist_del_init(&dentry->d_u.d_alias);
393         raw_write_seqcount_end(&dentry->d_seq);
394         spin_unlock(&dentry->d_lock);
395         spin_unlock(&inode->i_lock);
396         if (!inode->i_nlink)
397                 fsnotify_inoderemove(inode);
398         if (dentry->d_op && dentry->d_op->d_iput)
399                 dentry->d_op->d_iput(dentry, inode);
400         else
401                 iput(inode);
402 }
403
404 /*
405  * The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
406  * is in use - which includes both the "real" per-superblock
407  * LRU list _and_ the DCACHE_SHRINK_LIST use.
408  *
409  * The DCACHE_SHRINK_LIST bit is set whenever the dentry is
410  * on the shrink list (ie not on the superblock LRU list).
411  *
412  * The per-cpu "nr_dentry_unused" counters are updated with
413  * the DCACHE_LRU_LIST bit.
414  *
415  * The per-cpu "nr_dentry_negative" counters are only updated
416  * when deleted from or added to the per-superblock LRU list, not
417  * from/to the shrink list. That is to avoid an unneeded dec/inc
418  * pair when moving from LRU to shrink list in select_collect().
419  *
420  * These helper functions make sure we always follow the
421  * rules. d_lock must be held by the caller.
422  */
423 #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
424 static void d_lru_add(struct dentry *dentry)
425 {
426         D_FLAG_VERIFY(dentry, 0);
427         dentry->d_flags |= DCACHE_LRU_LIST;
428         this_cpu_inc(nr_dentry_unused);
429         if (d_is_negative(dentry))
430                 this_cpu_inc(nr_dentry_negative);
431         WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
432 }
433
434 static void d_lru_del(struct dentry *dentry)
435 {
436         D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
437         dentry->d_flags &= ~DCACHE_LRU_LIST;
438         this_cpu_dec(nr_dentry_unused);
439         if (d_is_negative(dentry))
440                 this_cpu_dec(nr_dentry_negative);
441         WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
442 }
443
444 static void d_shrink_del(struct dentry *dentry)
445 {
446         D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
447         list_del_init(&dentry->d_lru);
448         dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
449         this_cpu_dec(nr_dentry_unused);
450 }
451
452 static void d_shrink_add(struct dentry *dentry, struct list_head *list)
453 {
454         D_FLAG_VERIFY(dentry, 0);
455         list_add(&dentry->d_lru, list);
456         dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST;
457         this_cpu_inc(nr_dentry_unused);
458 }
459
460 /*
461  * These can only be called under the global LRU lock, ie during the
462  * callback for freeing the LRU list. "isolate" removes it from the
463  * LRU lists entirely, while shrink_move moves it to the indicated
464  * private list.
465  */
466 static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry)
467 {
468         D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
469         dentry->d_flags &= ~DCACHE_LRU_LIST;
470         this_cpu_dec(nr_dentry_unused);
471         if (d_is_negative(dentry))
472                 this_cpu_dec(nr_dentry_negative);
473         list_lru_isolate(lru, &dentry->d_lru);
474 }
475
476 static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
477                               struct list_head *list)
478 {
479         D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
480         dentry->d_flags |= DCACHE_SHRINK_LIST;
481         if (d_is_negative(dentry))
482                 this_cpu_dec(nr_dentry_negative);
483         list_lru_isolate_move(lru, &dentry->d_lru, list);
484 }
485
486 static void ___d_drop(struct dentry *dentry)
487 {
488         struct hlist_bl_head *b;
489         /*
490          * Hashed dentries are normally on the dentry hashtable,
491          * with the exception of those newly allocated by
492          * d_obtain_root, which are always IS_ROOT:
493          */
494         if (unlikely(IS_ROOT(dentry)))
495                 b = &dentry->d_sb->s_roots;
496         else
497                 b = d_hash(dentry->d_name.hash);
498
499         hlist_bl_lock(b);
500         __hlist_bl_del(&dentry->d_hash);
501         hlist_bl_unlock(b);
502 }
503
504 void __d_drop(struct dentry *dentry)
505 {
506         if (!d_unhashed(dentry)) {
507                 ___d_drop(dentry);
508                 dentry->d_hash.pprev = NULL;
509                 write_seqcount_invalidate(&dentry->d_seq);
510         }
511 }
512 EXPORT_SYMBOL(__d_drop);
513
514 /**
515  * d_drop - drop a dentry
516  * @dentry: dentry to drop
517  *
518  * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
519  * be found through a VFS lookup any more. Note that this is different from
520  * deleting the dentry - d_delete will try to mark the dentry negative if
521  * possible, giving a successful _negative_ lookup, while d_drop will
522  * just make the cache lookup fail.
523  *
524  * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
525  * reason (NFS timeouts or autofs deletes).
526  *
527  * __d_drop requires dentry->d_lock
528  *
529  * ___d_drop doesn't mark dentry as "unhashed"
530  * (dentry->d_hash.pprev will be LIST_POISON2, not NULL).
531  */
532 void d_drop(struct dentry *dentry)
533 {
534         spin_lock(&dentry->d_lock);
535         __d_drop(dentry);
536         spin_unlock(&dentry->d_lock);
537 }
538 EXPORT_SYMBOL(d_drop);
539
540 static inline void dentry_unlist(struct dentry *dentry, struct dentry *parent)
541 {
542         struct dentry *next;
543         /*
544          * Inform d_walk() and shrink_dentry_list() that we are no longer
545          * attached to the dentry tree
546          */
547         dentry->d_flags |= DCACHE_DENTRY_KILLED;
548         if (unlikely(list_empty(&dentry->d_child)))
549                 return;
550         __list_del_entry(&dentry->d_child);
551         /*
552          * Cursors can move around the list of children.  While we'd been
553          * a normal list member, it didn't matter - ->d_child.next would've
554          * been updated.  However, from now on it won't be and for the
555          * things like d_walk() it might end up with a nasty surprise.
556          * Normally d_walk() doesn't care about cursors moving around -
557          * ->d_lock on parent prevents that and since a cursor has no children
558          * of its own, we get through it without ever unlocking the parent.
559          * There is one exception, though - if we ascend from a child that
560          * gets killed as soon as we unlock it, the next sibling is found
561          * using the value left in its ->d_child.next.  And if _that_
562          * pointed to a cursor, and cursor got moved (e.g. by lseek())
563          * before d_walk() regains parent->d_lock, we'll end up skipping
564          * everything the cursor had been moved past.
565          *
566          * Solution: make sure that the pointer left behind in ->d_child.next
567          * points to something that won't be moving around.  I.e. skip the
568          * cursors.
569          */
570         while (dentry->d_child.next != &parent->d_subdirs) {
571                 next = list_entry(dentry->d_child.next, struct dentry, d_child);
572                 if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR)))
573                         break;
574                 dentry->d_child.next = next->d_child.next;
575         }
576 }
577
578 static void __dentry_kill(struct dentry *dentry)
579 {
580         struct dentry *parent = NULL;
581         bool can_free = true;
582         if (!IS_ROOT(dentry))
583                 parent = dentry->d_parent;
584
585         /*
586          * The dentry is now unrecoverably dead to the world.
587          */
588         lockref_mark_dead(&dentry->d_lockref);
589
590         /*
591          * inform the fs via d_prune that this dentry is about to be
592          * unhashed and destroyed.
593          */
594         if (dentry->d_flags & DCACHE_OP_PRUNE)
595                 dentry->d_op->d_prune(dentry);
596
597         if (dentry->d_flags & DCACHE_LRU_LIST) {
598                 if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
599                         d_lru_del(dentry);
600         }
601         /* if it was on the hash then remove it */
602         __d_drop(dentry);
603         dentry_unlist(dentry, parent);
604         if (parent)
605                 spin_unlock(&parent->d_lock);
606         if (dentry->d_inode)
607                 dentry_unlink_inode(dentry);
608         else
609                 spin_unlock(&dentry->d_lock);
610         this_cpu_dec(nr_dentry);
611         if (dentry->d_op && dentry->d_op->d_release)
612                 dentry->d_op->d_release(dentry);
613
614         spin_lock(&dentry->d_lock);
615         if (dentry->d_flags & DCACHE_SHRINK_LIST) {
616                 dentry->d_flags |= DCACHE_MAY_FREE;
617                 can_free = false;
618         }
619         spin_unlock(&dentry->d_lock);
620         if (likely(can_free))
621                 dentry_free(dentry);
622         cond_resched();
623 }
624
625 static struct dentry *__lock_parent(struct dentry *dentry)
626 {
627         struct dentry *parent;
628         rcu_read_lock();
629         spin_unlock(&dentry->d_lock);
630 again:
631         parent = READ_ONCE(dentry->d_parent);
632         spin_lock(&parent->d_lock);
633         /*
634          * We can't blindly lock dentry until we are sure
635          * that we won't violate the locking order.
636          * Any changes of dentry->d_parent must have
637          * been done with parent->d_lock held, so
638          * spin_lock() above is enough of a barrier
639          * for checking if it's still our child.
640          */
641         if (unlikely(parent != dentry->d_parent)) {
642                 spin_unlock(&parent->d_lock);
643                 goto again;
644         }
645         rcu_read_unlock();
646         if (parent != dentry)
647                 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
648         else
649                 parent = NULL;
650         return parent;
651 }
652
653 static inline struct dentry *lock_parent(struct dentry *dentry)
654 {
655         struct dentry *parent = dentry->d_parent;
656         if (IS_ROOT(dentry))
657                 return NULL;
658         if (likely(spin_trylock(&parent->d_lock)))
659                 return parent;
660         return __lock_parent(dentry);
661 }
662
663 static inline bool retain_dentry(struct dentry *dentry)
664 {
665         WARN_ON(d_in_lookup(dentry));
666
667         /* Unreachable? Get rid of it */
668         if (unlikely(d_unhashed(dentry)))
669                 return false;
670
671         if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
672                 return false;
673
674         if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) {
675                 if (dentry->d_op->d_delete(dentry))
676                         return false;
677         }
678
679         if (unlikely(dentry->d_flags & DCACHE_DONTCACHE))
680                 return false;
681
682         /* retain; LRU fodder */
683         dentry->d_lockref.count--;
684         if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
685                 d_lru_add(dentry);
686         else if (unlikely(!(dentry->d_flags & DCACHE_REFERENCED)))
687                 dentry->d_flags |= DCACHE_REFERENCED;
688         return true;
689 }
690
691 void d_mark_dontcache(struct inode *inode)
692 {
693         struct dentry *de;
694
695         spin_lock(&inode->i_lock);
696         hlist_for_each_entry(de, &inode->i_dentry, d_u.d_alias) {
697                 spin_lock(&de->d_lock);
698                 de->d_flags |= DCACHE_DONTCACHE;
699                 spin_unlock(&de->d_lock);
700         }
701         inode->i_state |= I_DONTCACHE;
702         spin_unlock(&inode->i_lock);
703 }
704 EXPORT_SYMBOL(d_mark_dontcache);
705
706 /*
707  * Finish off a dentry we've decided to kill.
708  * dentry->d_lock must be held, returns with it unlocked.
709  * Returns dentry requiring refcount drop, or NULL if we're done.
710  */
711 static struct dentry *dentry_kill(struct dentry *dentry)
712         __releases(dentry->d_lock)
713 {
714         struct inode *inode = dentry->d_inode;
715         struct dentry *parent = NULL;
716
717         if (inode && unlikely(!spin_trylock(&inode->i_lock)))
718                 goto slow_positive;
719
720         if (!IS_ROOT(dentry)) {
721                 parent = dentry->d_parent;
722                 if (unlikely(!spin_trylock(&parent->d_lock))) {
723                         parent = __lock_parent(dentry);
724                         if (likely(inode || !dentry->d_inode))
725                                 goto got_locks;
726                         /* negative that became positive */
727                         if (parent)
728                                 spin_unlock(&parent->d_lock);
729                         inode = dentry->d_inode;
730                         goto slow_positive;
731                 }
732         }
733         __dentry_kill(dentry);
734         return parent;
735
736 slow_positive:
737         spin_unlock(&dentry->d_lock);
738         spin_lock(&inode->i_lock);
739         spin_lock(&dentry->d_lock);
740         parent = lock_parent(dentry);
741 got_locks:
742         if (unlikely(dentry->d_lockref.count != 1)) {
743                 dentry->d_lockref.count--;
744         } else if (likely(!retain_dentry(dentry))) {
745                 __dentry_kill(dentry);
746                 return parent;
747         }
748         /* we are keeping it, after all */
749         if (inode)
750                 spin_unlock(&inode->i_lock);
751         if (parent)
752                 spin_unlock(&parent->d_lock);
753         spin_unlock(&dentry->d_lock);
754         return NULL;
755 }
756
757 /*
758  * Try to do a lockless dput(), and return whether that was successful.
759  *
760  * If unsuccessful, we return false, having already taken the dentry lock.
761  *
762  * The caller needs to hold the RCU read lock, so that the dentry is
763  * guaranteed to stay around even if the refcount goes down to zero!
764  */
765 static inline bool fast_dput(struct dentry *dentry)
766 {
767         int ret;
768         unsigned int d_flags;
769
770         /*
771          * If we have a d_op->d_delete() operation, we sould not
772          * let the dentry count go to zero, so use "put_or_lock".
773          */
774         if (unlikely(dentry->d_flags & DCACHE_OP_DELETE))
775                 return lockref_put_or_lock(&dentry->d_lockref);
776
777         /*
778          * .. otherwise, we can try to just decrement the
779          * lockref optimistically.
780          */
781         ret = lockref_put_return(&dentry->d_lockref);
782
783         /*
784          * If the lockref_put_return() failed due to the lock being held
785          * by somebody else, the fast path has failed. We will need to
786          * get the lock, and then check the count again.
787          */
788         if (unlikely(ret < 0)) {
789                 spin_lock(&dentry->d_lock);
790                 if (dentry->d_lockref.count > 1) {
791                         dentry->d_lockref.count--;
792                         spin_unlock(&dentry->d_lock);
793                         return true;
794                 }
795                 return false;
796         }
797
798         /*
799          * If we weren't the last ref, we're done.
800          */
801         if (ret)
802                 return true;
803
804         /*
805          * Careful, careful. The reference count went down
806          * to zero, but we don't hold the dentry lock, so
807          * somebody else could get it again, and do another
808          * dput(), and we need to not race with that.
809          *
810          * However, there is a very special and common case
811          * where we don't care, because there is nothing to
812          * do: the dentry is still hashed, it does not have
813          * a 'delete' op, and it's referenced and already on
814          * the LRU list.
815          *
816          * NOTE! Since we aren't locked, these values are
817          * not "stable". However, it is sufficient that at
818          * some point after we dropped the reference the
819          * dentry was hashed and the flags had the proper
820          * value. Other dentry users may have re-gotten
821          * a reference to the dentry and change that, but
822          * our work is done - we can leave the dentry
823          * around with a zero refcount.
824          *
825          * Nevertheless, there are two cases that we should kill
826          * the dentry anyway.
827          * 1. free disconnected dentries as soon as their refcount
828          *    reached zero.
829          * 2. free dentries if they should not be cached.
830          */
831         smp_rmb();
832         d_flags = READ_ONCE(dentry->d_flags);
833         d_flags &= DCACHE_REFERENCED | DCACHE_LRU_LIST |
834                         DCACHE_DISCONNECTED | DCACHE_DONTCACHE;
835
836         /* Nothing to do? Dropping the reference was all we needed? */
837         if (d_flags == (DCACHE_REFERENCED | DCACHE_LRU_LIST) && !d_unhashed(dentry))
838                 return true;
839
840         /*
841          * Not the fast normal case? Get the lock. We've already decremented
842          * the refcount, but we'll need to re-check the situation after
843          * getting the lock.
844          */
845         spin_lock(&dentry->d_lock);
846
847         /*
848          * Did somebody else grab a reference to it in the meantime, and
849          * we're no longer the last user after all? Alternatively, somebody
850          * else could have killed it and marked it dead. Either way, we
851          * don't need to do anything else.
852          */
853         if (dentry->d_lockref.count) {
854                 spin_unlock(&dentry->d_lock);
855                 return true;
856         }
857
858         /*
859          * Re-get the reference we optimistically dropped. We hold the
860          * lock, and we just tested that it was zero, so we can just
861          * set it to 1.
862          */
863         dentry->d_lockref.count = 1;
864         return false;
865 }
866
867
868 /* 
869  * This is dput
870  *
871  * This is complicated by the fact that we do not want to put
872  * dentries that are no longer on any hash chain on the unused
873  * list: we'd much rather just get rid of them immediately.
874  *
875  * However, that implies that we have to traverse the dentry
876  * tree upwards to the parents which might _also_ now be
877  * scheduled for deletion (it may have been only waiting for
878  * its last child to go away).
879  *
880  * This tail recursion is done by hand as we don't want to depend
881  * on the compiler to always get this right (gcc generally doesn't).
882  * Real recursion would eat up our stack space.
883  */
884
885 /*
886  * dput - release a dentry
887  * @dentry: dentry to release 
888  *
889  * Release a dentry. This will drop the usage count and if appropriate
890  * call the dentry unlink method as well as removing it from the queues and
891  * releasing its resources. If the parent dentries were scheduled for release
892  * they too may now get deleted.
893  */
894 void dput(struct dentry *dentry)
895 {
896         while (dentry) {
897                 might_sleep();
898
899                 rcu_read_lock();
900                 if (likely(fast_dput(dentry))) {
901                         rcu_read_unlock();
902                         return;
903                 }
904
905                 /* Slow case: now with the dentry lock held */
906                 rcu_read_unlock();
907
908                 if (likely(retain_dentry(dentry))) {
909                         spin_unlock(&dentry->d_lock);
910                         return;
911                 }
912
913                 dentry = dentry_kill(dentry);
914         }
915 }
916 EXPORT_SYMBOL(dput);
917
918 static void __dput_to_list(struct dentry *dentry, struct list_head *list)
919 __must_hold(&dentry->d_lock)
920 {
921         if (dentry->d_flags & DCACHE_SHRINK_LIST) {
922                 /* let the owner of the list it's on deal with it */
923                 --dentry->d_lockref.count;
924         } else {
925                 if (dentry->d_flags & DCACHE_LRU_LIST)
926                         d_lru_del(dentry);
927                 if (!--dentry->d_lockref.count)
928                         d_shrink_add(dentry, list);
929         }
930 }
931
932 void dput_to_list(struct dentry *dentry, struct list_head *list)
933 {
934         rcu_read_lock();
935         if (likely(fast_dput(dentry))) {
936                 rcu_read_unlock();
937                 return;
938         }
939         rcu_read_unlock();
940         if (!retain_dentry(dentry))
941                 __dput_to_list(dentry, list);
942         spin_unlock(&dentry->d_lock);
943 }
944
945 /* This must be called with d_lock held */
946 static inline void __dget_dlock(struct dentry *dentry)
947 {
948         dentry->d_lockref.count++;
949 }
950
951 static inline void __dget(struct dentry *dentry)
952 {
953         lockref_get(&dentry->d_lockref);
954 }
955
956 struct dentry *dget_parent(struct dentry *dentry)
957 {
958         int gotref;
959         struct dentry *ret;
960         unsigned seq;
961
962         /*
963          * Do optimistic parent lookup without any
964          * locking.
965          */
966         rcu_read_lock();
967         seq = raw_seqcount_begin(&dentry->d_seq);
968         ret = READ_ONCE(dentry->d_parent);
969         gotref = lockref_get_not_zero(&ret->d_lockref);
970         rcu_read_unlock();
971         if (likely(gotref)) {
972                 if (!read_seqcount_retry(&dentry->d_seq, seq))
973                         return ret;
974                 dput(ret);
975         }
976
977 repeat:
978         /*
979          * Don't need rcu_dereference because we re-check it was correct under
980          * the lock.
981          */
982         rcu_read_lock();
983         ret = dentry->d_parent;
984         spin_lock(&ret->d_lock);
985         if (unlikely(ret != dentry->d_parent)) {
986                 spin_unlock(&ret->d_lock);
987                 rcu_read_unlock();
988                 goto repeat;
989         }
990         rcu_read_unlock();
991         BUG_ON(!ret->d_lockref.count);
992         ret->d_lockref.count++;
993         spin_unlock(&ret->d_lock);
994         return ret;
995 }
996 EXPORT_SYMBOL(dget_parent);
997
998 static struct dentry * __d_find_any_alias(struct inode *inode)
999 {
1000         struct dentry *alias;
1001
1002         if (hlist_empty(&inode->i_dentry))
1003                 return NULL;
1004         alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
1005         __dget(alias);
1006         return alias;
1007 }
1008
1009 /**
1010  * d_find_any_alias - find any alias for a given inode
1011  * @inode: inode to find an alias for
1012  *
1013  * If any aliases exist for the given inode, take and return a
1014  * reference for one of them.  If no aliases exist, return %NULL.
1015  */
1016 struct dentry *d_find_any_alias(struct inode *inode)
1017 {
1018         struct dentry *de;
1019
1020         spin_lock(&inode->i_lock);
1021         de = __d_find_any_alias(inode);
1022         spin_unlock(&inode->i_lock);
1023         return de;
1024 }
1025 EXPORT_SYMBOL(d_find_any_alias);
1026
1027 static struct dentry *__d_find_alias(struct inode *inode)
1028 {
1029         struct dentry *alias;
1030
1031         if (S_ISDIR(inode->i_mode))
1032                 return __d_find_any_alias(inode);
1033
1034         hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
1035                 spin_lock(&alias->d_lock);
1036                 if (!d_unhashed(alias)) {
1037                         __dget_dlock(alias);
1038                         spin_unlock(&alias->d_lock);
1039                         return alias;
1040                 }
1041                 spin_unlock(&alias->d_lock);
1042         }
1043         return NULL;
1044 }
1045
1046 /**
1047  * d_find_alias - grab a hashed alias of inode
1048  * @inode: inode in question
1049  *
1050  * If inode has a hashed alias, or is a directory and has any alias,
1051  * acquire the reference to alias and return it. Otherwise return NULL.
1052  * Notice that if inode is a directory there can be only one alias and
1053  * it can be unhashed only if it has no children, or if it is the root
1054  * of a filesystem, or if the directory was renamed and d_revalidate
1055  * was the first vfs operation to notice.
1056  *
1057  * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
1058  * any other hashed alias over that one.
1059  */
1060 struct dentry *d_find_alias(struct inode *inode)
1061 {
1062         struct dentry *de = NULL;
1063
1064         if (!hlist_empty(&inode->i_dentry)) {
1065                 spin_lock(&inode->i_lock);
1066                 de = __d_find_alias(inode);
1067                 spin_unlock(&inode->i_lock);
1068         }
1069         return de;
1070 }
1071 EXPORT_SYMBOL(d_find_alias);
1072
1073 /*
1074  *  Caller MUST be holding rcu_read_lock() and be guaranteed
1075  *  that inode won't get freed until rcu_read_unlock().
1076  */
1077 struct dentry *d_find_alias_rcu(struct inode *inode)
1078 {
1079         struct hlist_head *l = &inode->i_dentry;
1080         struct dentry *de = NULL;
1081
1082         spin_lock(&inode->i_lock);
1083         // ->i_dentry and ->i_rcu are colocated, but the latter won't be
1084         // used without having I_FREEING set, which means no aliases left
1085         if (likely(!(inode->i_state & I_FREEING) && !hlist_empty(l))) {
1086                 if (S_ISDIR(inode->i_mode)) {
1087                         de = hlist_entry(l->first, struct dentry, d_u.d_alias);
1088                 } else {
1089                         hlist_for_each_entry(de, l, d_u.d_alias)
1090                                 if (!d_unhashed(de))
1091                                         break;
1092                 }
1093         }
1094         spin_unlock(&inode->i_lock);
1095         return de;
1096 }
1097
1098 /*
1099  *      Try to kill dentries associated with this inode.
1100  * WARNING: you must own a reference to inode.
1101  */
1102 void d_prune_aliases(struct inode *inode)
1103 {
1104         struct dentry *dentry;
1105 restart:
1106         spin_lock(&inode->i_lock);
1107         hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
1108                 spin_lock(&dentry->d_lock);
1109                 if (!dentry->d_lockref.count) {
1110                         struct dentry *parent = lock_parent(dentry);
1111                         if (likely(!dentry->d_lockref.count)) {
1112                                 __dentry_kill(dentry);
1113                                 dput(parent);
1114                                 goto restart;
1115                         }
1116                         if (parent)
1117                                 spin_unlock(&parent->d_lock);
1118                 }
1119                 spin_unlock(&dentry->d_lock);
1120         }
1121         spin_unlock(&inode->i_lock);
1122 }
1123 EXPORT_SYMBOL(d_prune_aliases);
1124
1125 /*
1126  * Lock a dentry from shrink list.
1127  * Called under rcu_read_lock() and dentry->d_lock; the former
1128  * guarantees that nothing we access will be freed under us.
1129  * Note that dentry is *not* protected from concurrent dentry_kill(),
1130  * d_delete(), etc.
1131  *
1132  * Return false if dentry has been disrupted or grabbed, leaving
1133  * the caller to kick it off-list.  Otherwise, return true and have
1134  * that dentry's inode and parent both locked.
1135  */
1136 static bool shrink_lock_dentry(struct dentry *dentry)
1137 {
1138         struct inode *inode;
1139         struct dentry *parent;
1140
1141         if (dentry->d_lockref.count)
1142                 return false;
1143
1144         inode = dentry->d_inode;
1145         if (inode && unlikely(!spin_trylock(&inode->i_lock))) {
1146                 spin_unlock(&dentry->d_lock);
1147                 spin_lock(&inode->i_lock);
1148                 spin_lock(&dentry->d_lock);
1149                 if (unlikely(dentry->d_lockref.count))
1150                         goto out;
1151                 /* changed inode means that somebody had grabbed it */
1152                 if (unlikely(inode != dentry->d_inode))
1153                         goto out;
1154         }
1155
1156         parent = dentry->d_parent;
1157         if (IS_ROOT(dentry) || likely(spin_trylock(&parent->d_lock)))
1158                 return true;
1159
1160         spin_unlock(&dentry->d_lock);
1161         spin_lock(&parent->d_lock);
1162         if (unlikely(parent != dentry->d_parent)) {
1163                 spin_unlock(&parent->d_lock);
1164                 spin_lock(&dentry->d_lock);
1165                 goto out;
1166         }
1167         spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1168         if (likely(!dentry->d_lockref.count))
1169                 return true;
1170         spin_unlock(&parent->d_lock);
1171 out:
1172         if (inode)
1173                 spin_unlock(&inode->i_lock);
1174         return false;
1175 }
1176
1177 void shrink_dentry_list(struct list_head *list)
1178 {
1179         while (!list_empty(list)) {
1180                 struct dentry *dentry, *parent;
1181
1182                 dentry = list_entry(list->prev, struct dentry, d_lru);
1183                 spin_lock(&dentry->d_lock);
1184                 rcu_read_lock();
1185                 if (!shrink_lock_dentry(dentry)) {
1186                         bool can_free = false;
1187                         rcu_read_unlock();
1188                         d_shrink_del(dentry);
1189                         if (dentry->d_lockref.count < 0)
1190                                 can_free = dentry->d_flags & DCACHE_MAY_FREE;
1191                         spin_unlock(&dentry->d_lock);
1192                         if (can_free)
1193                                 dentry_free(dentry);
1194                         continue;
1195                 }
1196                 rcu_read_unlock();
1197                 d_shrink_del(dentry);
1198                 parent = dentry->d_parent;
1199                 if (parent != dentry)
1200                         __dput_to_list(parent, list);
1201                 __dentry_kill(dentry);
1202         }
1203 }
1204
1205 static enum lru_status dentry_lru_isolate(struct list_head *item,
1206                 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1207 {
1208         struct list_head *freeable = arg;
1209         struct dentry   *dentry = container_of(item, struct dentry, d_lru);
1210
1211
1212         /*
1213          * we are inverting the lru lock/dentry->d_lock here,
1214          * so use a trylock. If we fail to get the lock, just skip
1215          * it
1216          */
1217         if (!spin_trylock(&dentry->d_lock))
1218                 return LRU_SKIP;
1219
1220         /*
1221          * Referenced dentries are still in use. If they have active
1222          * counts, just remove them from the LRU. Otherwise give them
1223          * another pass through the LRU.
1224          */
1225         if (dentry->d_lockref.count) {
1226                 d_lru_isolate(lru, dentry);
1227                 spin_unlock(&dentry->d_lock);
1228                 return LRU_REMOVED;
1229         }
1230
1231         if (dentry->d_flags & DCACHE_REFERENCED) {
1232                 dentry->d_flags &= ~DCACHE_REFERENCED;
1233                 spin_unlock(&dentry->d_lock);
1234
1235                 /*
1236                  * The list move itself will be made by the common LRU code. At
1237                  * this point, we've dropped the dentry->d_lock but keep the
1238                  * lru lock. This is safe to do, since every list movement is
1239                  * protected by the lru lock even if both locks are held.
1240                  *
1241                  * This is guaranteed by the fact that all LRU management
1242                  * functions are intermediated by the LRU API calls like
1243                  * list_lru_add and list_lru_del. List movement in this file
1244                  * only ever occur through this functions or through callbacks
1245                  * like this one, that are called from the LRU API.
1246                  *
1247                  * The only exceptions to this are functions like
1248                  * shrink_dentry_list, and code that first checks for the
1249                  * DCACHE_SHRINK_LIST flag.  Those are guaranteed to be
1250                  * operating only with stack provided lists after they are
1251                  * properly isolated from the main list.  It is thus, always a
1252                  * local access.
1253                  */
1254                 return LRU_ROTATE;
1255         }
1256
1257         d_lru_shrink_move(lru, dentry, freeable);
1258         spin_unlock(&dentry->d_lock);
1259
1260         return LRU_REMOVED;
1261 }
1262
1263 /**
1264  * prune_dcache_sb - shrink the dcache
1265  * @sb: superblock
1266  * @sc: shrink control, passed to list_lru_shrink_walk()
1267  *
1268  * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
1269  * is done when we need more memory and called from the superblock shrinker
1270  * function.
1271  *
1272  * This function may fail to free any resources if all the dentries are in
1273  * use.
1274  */
1275 long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc)
1276 {
1277         LIST_HEAD(dispose);
1278         long freed;
1279
1280         freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc,
1281                                      dentry_lru_isolate, &dispose);
1282         shrink_dentry_list(&dispose);
1283         return freed;
1284 }
1285
1286 static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
1287                 struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
1288 {
1289         struct list_head *freeable = arg;
1290         struct dentry   *dentry = container_of(item, struct dentry, d_lru);
1291
1292         /*
1293          * we are inverting the lru lock/dentry->d_lock here,
1294          * so use a trylock. If we fail to get the lock, just skip
1295          * it
1296          */
1297         if (!spin_trylock(&dentry->d_lock))
1298                 return LRU_SKIP;
1299
1300         d_lru_shrink_move(lru, dentry, freeable);
1301         spin_unlock(&dentry->d_lock);
1302
1303         return LRU_REMOVED;
1304 }
1305
1306
1307 /**
1308  * shrink_dcache_sb - shrink dcache for a superblock
1309  * @sb: superblock
1310  *
1311  * Shrink the dcache for the specified super block. This is used to free
1312  * the dcache before unmounting a file system.
1313  */
1314 void shrink_dcache_sb(struct super_block *sb)
1315 {
1316         do {
1317                 LIST_HEAD(dispose);
1318
1319                 list_lru_walk(&sb->s_dentry_lru,
1320                         dentry_lru_isolate_shrink, &dispose, 1024);
1321                 shrink_dentry_list(&dispose);
1322         } while (list_lru_count(&sb->s_dentry_lru) > 0);
1323 }
1324 EXPORT_SYMBOL(shrink_dcache_sb);
1325
1326 /**
1327  * enum d_walk_ret - action to talke during tree walk
1328  * @D_WALK_CONTINUE:    contrinue walk
1329  * @D_WALK_QUIT:        quit walk
1330  * @D_WALK_NORETRY:     quit when retry is needed
1331  * @D_WALK_SKIP:        skip this dentry and its children
1332  */
1333 enum d_walk_ret {
1334         D_WALK_CONTINUE,
1335         D_WALK_QUIT,
1336         D_WALK_NORETRY,
1337         D_WALK_SKIP,
1338 };
1339
1340 /**
1341  * d_walk - walk the dentry tree
1342  * @parent:     start of walk
1343  * @data:       data passed to @enter() and @finish()
1344  * @enter:      callback when first entering the dentry
1345  *
1346  * The @enter() callbacks are called with d_lock held.
1347  */
1348 static void d_walk(struct dentry *parent, void *data,
1349                    enum d_walk_ret (*enter)(void *, struct dentry *))
1350 {
1351         struct dentry *this_parent;
1352         struct list_head *next;
1353         unsigned seq = 0;
1354         enum d_walk_ret ret;
1355         bool retry = true;
1356
1357 again:
1358         read_seqbegin_or_lock(&rename_lock, &seq);
1359         this_parent = parent;
1360         spin_lock(&this_parent->d_lock);
1361
1362         ret = enter(data, this_parent);
1363         switch (ret) {
1364         case D_WALK_CONTINUE:
1365                 break;
1366         case D_WALK_QUIT:
1367         case D_WALK_SKIP:
1368                 goto out_unlock;
1369         case D_WALK_NORETRY:
1370                 retry = false;
1371                 break;
1372         }
1373 repeat:
1374         next = this_parent->d_subdirs.next;
1375 resume:
1376         while (next != &this_parent->d_subdirs) {
1377                 struct list_head *tmp = next;
1378                 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
1379                 next = tmp->next;
1380
1381                 if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR))
1382                         continue;
1383
1384                 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1385
1386                 ret = enter(data, dentry);
1387                 switch (ret) {
1388                 case D_WALK_CONTINUE:
1389                         break;
1390                 case D_WALK_QUIT:
1391                         spin_unlock(&dentry->d_lock);
1392                         goto out_unlock;
1393                 case D_WALK_NORETRY:
1394                         retry = false;
1395                         break;
1396                 case D_WALK_SKIP:
1397                         spin_unlock(&dentry->d_lock);
1398                         continue;
1399                 }
1400
1401                 if (!list_empty(&dentry->d_subdirs)) {
1402                         spin_unlock(&this_parent->d_lock);
1403                         spin_release(&dentry->d_lock.dep_map, _RET_IP_);
1404                         this_parent = dentry;
1405                         spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
1406                         goto repeat;
1407                 }
1408                 spin_unlock(&dentry->d_lock);
1409         }
1410         /*
1411          * All done at this level ... ascend and resume the search.
1412          */
1413         rcu_read_lock();
1414 ascend:
1415         if (this_parent != parent) {
1416                 struct dentry *child = this_parent;
1417                 this_parent = child->d_parent;
1418
1419                 spin_unlock(&child->d_lock);
1420                 spin_lock(&this_parent->d_lock);
1421
1422                 /* might go back up the wrong parent if we have had a rename. */
1423                 if (need_seqretry(&rename_lock, seq))
1424                         goto rename_retry;
1425                 /* go into the first sibling still alive */
1426                 do {
1427                         next = child->d_child.next;
1428                         if (next == &this_parent->d_subdirs)
1429                                 goto ascend;
1430                         child = list_entry(next, struct dentry, d_child);
1431                 } while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
1432                 rcu_read_unlock();
1433                 goto resume;
1434         }
1435         if (need_seqretry(&rename_lock, seq))
1436                 goto rename_retry;
1437         rcu_read_unlock();
1438
1439 out_unlock:
1440         spin_unlock(&this_parent->d_lock);
1441         done_seqretry(&rename_lock, seq);
1442         return;
1443
1444 rename_retry:
1445         spin_unlock(&this_parent->d_lock);
1446         rcu_read_unlock();
1447         BUG_ON(seq & 1);
1448         if (!retry)
1449                 return;
1450         seq = 1;
1451         goto again;
1452 }
1453
1454 struct check_mount {
1455         struct vfsmount *mnt;
1456         unsigned int mounted;
1457 };
1458
1459 static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry)
1460 {
1461         struct check_mount *info = data;
1462         struct path path = { .mnt = info->mnt, .dentry = dentry };
1463
1464         if (likely(!d_mountpoint(dentry)))
1465                 return D_WALK_CONTINUE;
1466         if (__path_is_mountpoint(&path)) {
1467                 info->mounted = 1;
1468                 return D_WALK_QUIT;
1469         }
1470         return D_WALK_CONTINUE;
1471 }
1472
1473 /**
1474  * path_has_submounts - check for mounts over a dentry in the
1475  *                      current namespace.
1476  * @parent: path to check.
1477  *
1478  * Return true if the parent or its subdirectories contain
1479  * a mount point in the current namespace.
1480  */
1481 int path_has_submounts(const struct path *parent)
1482 {
1483         struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
1484
1485         read_seqlock_excl(&mount_lock);
1486         d_walk(parent->dentry, &data, path_check_mount);
1487         read_sequnlock_excl(&mount_lock);
1488
1489         return data.mounted;
1490 }
1491 EXPORT_SYMBOL(path_has_submounts);
1492
1493 /*
1494  * Called by mount code to set a mountpoint and check if the mountpoint is
1495  * reachable (e.g. NFS can unhash a directory dentry and then the complete
1496  * subtree can become unreachable).
1497  *
1498  * Only one of d_invalidate() and d_set_mounted() must succeed.  For
1499  * this reason take rename_lock and d_lock on dentry and ancestors.
1500  */
1501 int d_set_mounted(struct dentry *dentry)
1502 {
1503         struct dentry *p;
1504         int ret = -ENOENT;
1505         write_seqlock(&rename_lock);
1506         for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
1507                 /* Need exclusion wrt. d_invalidate() */
1508                 spin_lock(&p->d_lock);
1509                 if (unlikely(d_unhashed(p))) {
1510                         spin_unlock(&p->d_lock);
1511                         goto out;
1512                 }
1513                 spin_unlock(&p->d_lock);
1514         }
1515         spin_lock(&dentry->d_lock);
1516         if (!d_unlinked(dentry)) {
1517                 ret = -EBUSY;
1518                 if (!d_mountpoint(dentry)) {
1519                         dentry->d_flags |= DCACHE_MOUNTED;
1520                         ret = 0;
1521                 }
1522         }
1523         spin_unlock(&dentry->d_lock);
1524 out:
1525         write_sequnlock(&rename_lock);
1526         return ret;
1527 }
1528
1529 /*
1530  * Search the dentry child list of the specified parent,
1531  * and move any unused dentries to the end of the unused
1532  * list for prune_dcache(). We descend to the next level
1533  * whenever the d_subdirs list is non-empty and continue
1534  * searching.
1535  *
1536  * It returns zero iff there are no unused children,
1537  * otherwise  it returns the number of children moved to
1538  * the end of the unused list. This may not be the total
1539  * number of unused children, because select_parent can
1540  * drop the lock and return early due to latency
1541  * constraints.
1542  */
1543
1544 struct select_data {
1545         struct dentry *start;
1546         union {
1547                 long found;
1548                 struct dentry *victim;
1549         };
1550         struct list_head dispose;
1551 };
1552
1553 static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
1554 {
1555         struct select_data *data = _data;
1556         enum d_walk_ret ret = D_WALK_CONTINUE;
1557
1558         if (data->start == dentry)
1559                 goto out;
1560
1561         if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1562                 data->found++;
1563         } else {
1564                 if (dentry->d_flags & DCACHE_LRU_LIST)
1565                         d_lru_del(dentry);
1566                 if (!dentry->d_lockref.count) {
1567                         d_shrink_add(dentry, &data->dispose);
1568                         data->found++;
1569                 }
1570         }
1571         /*
1572          * We can return to the caller if we have found some (this
1573          * ensures forward progress). We'll be coming back to find
1574          * the rest.
1575          */
1576         if (!list_empty(&data->dispose))
1577                 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1578 out:
1579         return ret;
1580 }
1581
1582 static enum d_walk_ret select_collect2(void *_data, struct dentry *dentry)
1583 {
1584         struct select_data *data = _data;
1585         enum d_walk_ret ret = D_WALK_CONTINUE;
1586
1587         if (data->start == dentry)
1588                 goto out;
1589
1590         if (dentry->d_flags & DCACHE_SHRINK_LIST) {
1591                 if (!dentry->d_lockref.count) {
1592                         rcu_read_lock();
1593                         data->victim = dentry;
1594                         return D_WALK_QUIT;
1595                 }
1596         } else {
1597                 if (dentry->d_flags & DCACHE_LRU_LIST)
1598                         d_lru_del(dentry);
1599                 if (!dentry->d_lockref.count)
1600                         d_shrink_add(dentry, &data->dispose);
1601         }
1602         /*
1603          * We can return to the caller if we have found some (this
1604          * ensures forward progress). We'll be coming back to find
1605          * the rest.
1606          */
1607         if (!list_empty(&data->dispose))
1608                 ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
1609 out:
1610         return ret;
1611 }
1612
1613 /**
1614  * shrink_dcache_parent - prune dcache
1615  * @parent: parent of entries to prune
1616  *
1617  * Prune the dcache to remove unused children of the parent dentry.
1618  */
1619 void shrink_dcache_parent(struct dentry *parent)
1620 {
1621         for (;;) {
1622                 struct select_data data = {.start = parent};
1623
1624                 INIT_LIST_HEAD(&data.dispose);
1625                 d_walk(parent, &data, select_collect);
1626
1627                 if (!list_empty(&data.dispose)) {
1628                         shrink_dentry_list(&data.dispose);
1629                         continue;
1630                 }
1631
1632                 cond_resched();
1633                 if (!data.found)
1634                         break;
1635                 data.victim = NULL;
1636                 d_walk(parent, &data, select_collect2);
1637                 if (data.victim) {
1638                         struct dentry *parent;
1639                         spin_lock(&data.victim->d_lock);
1640                         if (!shrink_lock_dentry(data.victim)) {
1641                                 spin_unlock(&data.victim->d_lock);
1642                                 rcu_read_unlock();
1643                         } else {
1644                                 rcu_read_unlock();
1645                                 parent = data.victim->d_parent;
1646                                 if (parent != data.victim)
1647                                         __dput_to_list(parent, &data.dispose);
1648                                 __dentry_kill(data.victim);
1649                         }
1650                 }
1651                 if (!list_empty(&data.dispose))
1652                         shrink_dentry_list(&data.dispose);
1653         }
1654 }
1655 EXPORT_SYMBOL(shrink_dcache_parent);
1656
1657 static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
1658 {
1659         /* it has busy descendents; complain about those instead */
1660         if (!list_empty(&dentry->d_subdirs))
1661                 return D_WALK_CONTINUE;
1662
1663         /* root with refcount 1 is fine */
1664         if (dentry == _data && dentry->d_lockref.count == 1)
1665                 return D_WALK_CONTINUE;
1666
1667         printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%pd} "
1668                         " still in use (%d) [unmount of %s %s]\n",
1669                        dentry,
1670                        dentry->d_inode ?
1671                        dentry->d_inode->i_ino : 0UL,
1672                        dentry,
1673                        dentry->d_lockref.count,
1674                        dentry->d_sb->s_type->name,
1675                        dentry->d_sb->s_id);
1676         WARN_ON(1);
1677         return D_WALK_CONTINUE;
1678 }
1679
1680 static void do_one_tree(struct dentry *dentry)
1681 {
1682         shrink_dcache_parent(dentry);
1683         d_walk(dentry, dentry, umount_check);
1684         d_drop(dentry);
1685         dput(dentry);
1686 }
1687
1688 /*
1689  * destroy the dentries attached to a superblock on unmounting
1690  */
1691 void shrink_dcache_for_umount(struct super_block *sb)
1692 {
1693         struct dentry *dentry;
1694
1695         WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked");
1696
1697         dentry = sb->s_root;
1698         sb->s_root = NULL;
1699         do_one_tree(dentry);
1700
1701         while (!hlist_bl_empty(&sb->s_roots)) {
1702                 dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_roots), struct dentry, d_hash));
1703                 do_one_tree(dentry);
1704         }
1705 }
1706
1707 static enum d_walk_ret find_submount(void *_data, struct dentry *dentry)
1708 {
1709         struct dentry **victim = _data;
1710         if (d_mountpoint(dentry)) {
1711                 __dget_dlock(dentry);
1712                 *victim = dentry;
1713                 return D_WALK_QUIT;
1714         }
1715         return D_WALK_CONTINUE;
1716 }
1717
1718 /**
1719  * d_invalidate - detach submounts, prune dcache, and drop
1720  * @dentry: dentry to invalidate (aka detach, prune and drop)
1721  */
1722 void d_invalidate(struct dentry *dentry)
1723 {
1724         bool had_submounts = false;
1725         spin_lock(&dentry->d_lock);
1726         if (d_unhashed(dentry)) {
1727                 spin_unlock(&dentry->d_lock);
1728                 return;
1729         }
1730         __d_drop(dentry);
1731         spin_unlock(&dentry->d_lock);
1732
1733         /* Negative dentries can be dropped without further checks */
1734         if (!dentry->d_inode)
1735                 return;
1736
1737         shrink_dcache_parent(dentry);
1738         for (;;) {
1739                 struct dentry *victim = NULL;
1740                 d_walk(dentry, &victim, find_submount);
1741                 if (!victim) {
1742                         if (had_submounts)
1743                                 shrink_dcache_parent(dentry);
1744                         return;
1745                 }
1746                 had_submounts = true;
1747                 detach_mounts(victim);
1748                 dput(victim);
1749         }
1750 }
1751 EXPORT_SYMBOL(d_invalidate);
1752
1753 /**
1754  * __d_alloc    -       allocate a dcache entry
1755  * @sb: filesystem it will belong to
1756  * @name: qstr of the name
1757  *
1758  * Allocates a dentry. It returns %NULL if there is insufficient memory
1759  * available. On a success the dentry is returned. The name passed in is
1760  * copied and the copy passed in may be reused after this call.
1761  */
1762  
1763 static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1764 {
1765         struct dentry *dentry;
1766         char *dname;
1767         int err;
1768
1769         dentry = kmem_cache_alloc_lru(dentry_cache, &sb->s_dentry_lru,
1770                                       GFP_KERNEL);
1771         if (!dentry)
1772                 return NULL;
1773
1774         /*
1775          * We guarantee that the inline name is always NUL-terminated.
1776          * This way the memcpy() done by the name switching in rename
1777          * will still always have a NUL at the end, even if we might
1778          * be overwriting an internal NUL character
1779          */
1780         dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
1781         if (unlikely(!name)) {
1782                 name = &slash_name;
1783                 dname = dentry->d_iname;
1784         } else if (name->len > DNAME_INLINE_LEN-1) {
1785                 size_t size = offsetof(struct external_name, name[1]);
1786                 struct external_name *p = kmalloc(size + name->len,
1787                                                   GFP_KERNEL_ACCOUNT |
1788                                                   __GFP_RECLAIMABLE);
1789                 if (!p) {
1790                         kmem_cache_free(dentry_cache, dentry); 
1791                         return NULL;
1792                 }
1793                 atomic_set(&p->u.count, 1);
1794                 dname = p->name;
1795         } else  {
1796                 dname = dentry->d_iname;
1797         }       
1798
1799         dentry->d_name.len = name->len;
1800         dentry->d_name.hash = name->hash;
1801         memcpy(dname, name->name, name->len);
1802         dname[name->len] = 0;
1803
1804         /* Make sure we always see the terminating NUL character */
1805         smp_store_release(&dentry->d_name.name, dname); /* ^^^ */
1806
1807         dentry->d_lockref.count = 1;
1808         dentry->d_flags = 0;
1809         spin_lock_init(&dentry->d_lock);
1810         seqcount_spinlock_init(&dentry->d_seq, &dentry->d_lock);
1811         dentry->d_inode = NULL;
1812         dentry->d_parent = dentry;
1813         dentry->d_sb = sb;
1814         dentry->d_op = NULL;
1815         dentry->d_fsdata = NULL;
1816         INIT_HLIST_BL_NODE(&dentry->d_hash);
1817         INIT_LIST_HEAD(&dentry->d_lru);
1818         INIT_LIST_HEAD(&dentry->d_subdirs);
1819         INIT_HLIST_NODE(&dentry->d_u.d_alias);
1820         INIT_LIST_HEAD(&dentry->d_child);
1821         d_set_d_op(dentry, dentry->d_sb->s_d_op);
1822
1823         if (dentry->d_op && dentry->d_op->d_init) {
1824                 err = dentry->d_op->d_init(dentry);
1825                 if (err) {
1826                         if (dname_external(dentry))
1827                                 kfree(external_name(dentry));
1828                         kmem_cache_free(dentry_cache, dentry);
1829                         return NULL;
1830                 }
1831         }
1832
1833         this_cpu_inc(nr_dentry);
1834
1835         return dentry;
1836 }
1837
1838 /**
1839  * d_alloc      -       allocate a dcache entry
1840  * @parent: parent of entry to allocate
1841  * @name: qstr of the name
1842  *
1843  * Allocates a dentry. It returns %NULL if there is insufficient memory
1844  * available. On a success the dentry is returned. The name passed in is
1845  * copied and the copy passed in may be reused after this call.
1846  */
1847 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1848 {
1849         struct dentry *dentry = __d_alloc(parent->d_sb, name);
1850         if (!dentry)
1851                 return NULL;
1852         spin_lock(&parent->d_lock);
1853         /*
1854          * don't need child lock because it is not subject
1855          * to concurrency here
1856          */
1857         __dget_dlock(parent);
1858         dentry->d_parent = parent;
1859         list_add(&dentry->d_child, &parent->d_subdirs);
1860         spin_unlock(&parent->d_lock);
1861
1862         return dentry;
1863 }
1864 EXPORT_SYMBOL(d_alloc);
1865
1866 struct dentry *d_alloc_anon(struct super_block *sb)
1867 {
1868         return __d_alloc(sb, NULL);
1869 }
1870 EXPORT_SYMBOL(d_alloc_anon);
1871
1872 struct dentry *d_alloc_cursor(struct dentry * parent)
1873 {
1874         struct dentry *dentry = d_alloc_anon(parent->d_sb);
1875         if (dentry) {
1876                 dentry->d_flags |= DCACHE_DENTRY_CURSOR;
1877                 dentry->d_parent = dget(parent);
1878         }
1879         return dentry;
1880 }
1881
1882 /**
1883  * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1884  * @sb: the superblock
1885  * @name: qstr of the name
1886  *
1887  * For a filesystem that just pins its dentries in memory and never
1888  * performs lookups at all, return an unhashed IS_ROOT dentry.
1889  * This is used for pipes, sockets et.al. - the stuff that should
1890  * never be anyone's children or parents.  Unlike all other
1891  * dentries, these will not have RCU delay between dropping the
1892  * last reference and freeing them.
1893  *
1894  * The only user is alloc_file_pseudo() and that's what should
1895  * be considered a public interface.  Don't use directly.
1896  */
1897 struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1898 {
1899         struct dentry *dentry = __d_alloc(sb, name);
1900         if (likely(dentry))
1901                 dentry->d_flags |= DCACHE_NORCU;
1902         return dentry;
1903 }
1904
1905 struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1906 {
1907         struct qstr q;
1908
1909         q.name = name;
1910         q.hash_len = hashlen_string(parent, name);
1911         return d_alloc(parent, &q);
1912 }
1913 EXPORT_SYMBOL(d_alloc_name);
1914
1915 void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1916 {
1917         WARN_ON_ONCE(dentry->d_op);
1918         WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH  |
1919                                 DCACHE_OP_COMPARE       |
1920                                 DCACHE_OP_REVALIDATE    |
1921                                 DCACHE_OP_WEAK_REVALIDATE       |
1922                                 DCACHE_OP_DELETE        |
1923                                 DCACHE_OP_REAL));
1924         dentry->d_op = op;
1925         if (!op)
1926                 return;
1927         if (op->d_hash)
1928                 dentry->d_flags |= DCACHE_OP_HASH;
1929         if (op->d_compare)
1930                 dentry->d_flags |= DCACHE_OP_COMPARE;
1931         if (op->d_revalidate)
1932                 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1933         if (op->d_weak_revalidate)
1934                 dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
1935         if (op->d_delete)
1936                 dentry->d_flags |= DCACHE_OP_DELETE;
1937         if (op->d_prune)
1938                 dentry->d_flags |= DCACHE_OP_PRUNE;
1939         if (op->d_real)
1940                 dentry->d_flags |= DCACHE_OP_REAL;
1941
1942 }
1943 EXPORT_SYMBOL(d_set_d_op);
1944
1945
1946 /*
1947  * d_set_fallthru - Mark a dentry as falling through to a lower layer
1948  * @dentry - The dentry to mark
1949  *
1950  * Mark a dentry as falling through to the lower layer (as set with
1951  * d_pin_lower()).  This flag may be recorded on the medium.
1952  */
1953 void d_set_fallthru(struct dentry *dentry)
1954 {
1955         spin_lock(&dentry->d_lock);
1956         dentry->d_flags |= DCACHE_FALLTHRU;
1957         spin_unlock(&dentry->d_lock);
1958 }
1959 EXPORT_SYMBOL(d_set_fallthru);
1960
1961 static unsigned d_flags_for_inode(struct inode *inode)
1962 {
1963         unsigned add_flags = DCACHE_REGULAR_TYPE;
1964
1965         if (!inode)
1966                 return DCACHE_MISS_TYPE;
1967
1968         if (S_ISDIR(inode->i_mode)) {
1969                 add_flags = DCACHE_DIRECTORY_TYPE;
1970                 if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) {
1971                         if (unlikely(!inode->i_op->lookup))
1972                                 add_flags = DCACHE_AUTODIR_TYPE;
1973                         else
1974                                 inode->i_opflags |= IOP_LOOKUP;
1975                 }
1976                 goto type_determined;
1977         }
1978
1979         if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1980                 if (unlikely(inode->i_op->get_link)) {
1981                         add_flags = DCACHE_SYMLINK_TYPE;
1982                         goto type_determined;
1983                 }
1984                 inode->i_opflags |= IOP_NOFOLLOW;
1985         }
1986
1987         if (unlikely(!S_ISREG(inode->i_mode)))
1988                 add_flags = DCACHE_SPECIAL_TYPE;
1989
1990 type_determined:
1991         if (unlikely(IS_AUTOMOUNT(inode)))
1992                 add_flags |= DCACHE_NEED_AUTOMOUNT;
1993         return add_flags;
1994 }
1995
1996 static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1997 {
1998         unsigned add_flags = d_flags_for_inode(inode);
1999         WARN_ON(d_in_lookup(dentry));
2000
2001         spin_lock(&dentry->d_lock);
2002         /*
2003          * Decrement negative dentry count if it was in the LRU list.
2004          */
2005         if (dentry->d_flags & DCACHE_LRU_LIST)
2006                 this_cpu_dec(nr_dentry_negative);
2007         hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2008         raw_write_seqcount_begin(&dentry->d_seq);
2009         __d_set_inode_and_type(dentry, inode, add_flags);
2010         raw_write_seqcount_end(&dentry->d_seq);
2011         fsnotify_update_flags(dentry);
2012         spin_unlock(&dentry->d_lock);
2013 }
2014
2015 /**
2016  * d_instantiate - fill in inode information for a dentry
2017  * @entry: dentry to complete
2018  * @inode: inode to attach to this dentry
2019  *
2020  * Fill in inode information in the entry.
2021  *
2022  * This turns negative dentries into productive full members
2023  * of society.
2024  *
2025  * NOTE! This assumes that the inode count has been incremented
2026  * (or otherwise set) by the caller to indicate that it is now
2027  * in use by the dcache.
2028  */
2029  
2030 void d_instantiate(struct dentry *entry, struct inode * inode)
2031 {
2032         BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
2033         if (inode) {
2034                 security_d_instantiate(entry, inode);
2035                 spin_lock(&inode->i_lock);
2036                 __d_instantiate(entry, inode);
2037                 spin_unlock(&inode->i_lock);
2038         }
2039 }
2040 EXPORT_SYMBOL(d_instantiate);
2041
2042 /*
2043  * This should be equivalent to d_instantiate() + unlock_new_inode(),
2044  * with lockdep-related part of unlock_new_inode() done before
2045  * anything else.  Use that instead of open-coding d_instantiate()/
2046  * unlock_new_inode() combinations.
2047  */
2048 void d_instantiate_new(struct dentry *entry, struct inode *inode)
2049 {
2050         BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
2051         BUG_ON(!inode);
2052         lockdep_annotate_inode_mutex_key(inode);
2053         security_d_instantiate(entry, inode);
2054         spin_lock(&inode->i_lock);
2055         __d_instantiate(entry, inode);
2056         WARN_ON(!(inode->i_state & I_NEW));
2057         inode->i_state &= ~I_NEW & ~I_CREATING;
2058         smp_mb();
2059         wake_up_bit(&inode->i_state, __I_NEW);
2060         spin_unlock(&inode->i_lock);
2061 }
2062 EXPORT_SYMBOL(d_instantiate_new);
2063
2064 struct dentry *d_make_root(struct inode *root_inode)
2065 {
2066         struct dentry *res = NULL;
2067
2068         if (root_inode) {
2069                 res = d_alloc_anon(root_inode->i_sb);
2070                 if (res)
2071                         d_instantiate(res, root_inode);
2072                 else
2073                         iput(root_inode);
2074         }
2075         return res;
2076 }
2077 EXPORT_SYMBOL(d_make_root);
2078
2079 static struct dentry *__d_instantiate_anon(struct dentry *dentry,
2080                                            struct inode *inode,
2081                                            bool disconnected)
2082 {
2083         struct dentry *res;
2084         unsigned add_flags;
2085
2086         security_d_instantiate(dentry, inode);
2087         spin_lock(&inode->i_lock);
2088         res = __d_find_any_alias(inode);
2089         if (res) {
2090                 spin_unlock(&inode->i_lock);
2091                 dput(dentry);
2092                 goto out_iput;
2093         }
2094
2095         /* attach a disconnected dentry */
2096         add_flags = d_flags_for_inode(inode);
2097
2098         if (disconnected)
2099                 add_flags |= DCACHE_DISCONNECTED;
2100
2101         spin_lock(&dentry->d_lock);
2102         __d_set_inode_and_type(dentry, inode, add_flags);
2103         hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2104         if (!disconnected) {
2105                 hlist_bl_lock(&dentry->d_sb->s_roots);
2106                 hlist_bl_add_head(&dentry->d_hash, &dentry->d_sb->s_roots);
2107                 hlist_bl_unlock(&dentry->d_sb->s_roots);
2108         }
2109         spin_unlock(&dentry->d_lock);
2110         spin_unlock(&inode->i_lock);
2111
2112         return dentry;
2113
2114  out_iput:
2115         iput(inode);
2116         return res;
2117 }
2118
2119 struct dentry *d_instantiate_anon(struct dentry *dentry, struct inode *inode)
2120 {
2121         return __d_instantiate_anon(dentry, inode, true);
2122 }
2123 EXPORT_SYMBOL(d_instantiate_anon);
2124
2125 static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected)
2126 {
2127         struct dentry *tmp;
2128         struct dentry *res;
2129
2130         if (!inode)
2131                 return ERR_PTR(-ESTALE);
2132         if (IS_ERR(inode))
2133                 return ERR_CAST(inode);
2134
2135         res = d_find_any_alias(inode);
2136         if (res)
2137                 goto out_iput;
2138
2139         tmp = d_alloc_anon(inode->i_sb);
2140         if (!tmp) {
2141                 res = ERR_PTR(-ENOMEM);
2142                 goto out_iput;
2143         }
2144
2145         return __d_instantiate_anon(tmp, inode, disconnected);
2146
2147 out_iput:
2148         iput(inode);
2149         return res;
2150 }
2151
2152 /**
2153  * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
2154  * @inode: inode to allocate the dentry for
2155  *
2156  * Obtain a dentry for an inode resulting from NFS filehandle conversion or
2157  * similar open by handle operations.  The returned dentry may be anonymous,
2158  * or may have a full name (if the inode was already in the cache).
2159  *
2160  * When called on a directory inode, we must ensure that the inode only ever
2161  * has one dentry.  If a dentry is found, that is returned instead of
2162  * allocating a new one.
2163  *
2164  * On successful return, the reference to the inode has been transferred
2165  * to the dentry.  In case of an error the reference on the inode is released.
2166  * To make it easier to use in export operations a %NULL or IS_ERR inode may
2167  * be passed in and the error will be propagated to the return value,
2168  * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
2169  */
2170 struct dentry *d_obtain_alias(struct inode *inode)
2171 {
2172         return __d_obtain_alias(inode, true);
2173 }
2174 EXPORT_SYMBOL(d_obtain_alias);
2175
2176 /**
2177  * d_obtain_root - find or allocate a dentry for a given inode
2178  * @inode: inode to allocate the dentry for
2179  *
2180  * Obtain an IS_ROOT dentry for the root of a filesystem.
2181  *
2182  * We must ensure that directory inodes only ever have one dentry.  If a
2183  * dentry is found, that is returned instead of allocating a new one.
2184  *
2185  * On successful return, the reference to the inode has been transferred
2186  * to the dentry.  In case of an error the reference on the inode is
2187  * released.  A %NULL or IS_ERR inode may be passed in and will be the
2188  * error will be propagate to the return value, with a %NULL @inode
2189  * replaced by ERR_PTR(-ESTALE).
2190  */
2191 struct dentry *d_obtain_root(struct inode *inode)
2192 {
2193         return __d_obtain_alias(inode, false);
2194 }
2195 EXPORT_SYMBOL(d_obtain_root);
2196
2197 /**
2198  * d_add_ci - lookup or allocate new dentry with case-exact name
2199  * @inode:  the inode case-insensitive lookup has found
2200  * @dentry: the negative dentry that was passed to the parent's lookup func
2201  * @name:   the case-exact name to be associated with the returned dentry
2202  *
2203  * This is to avoid filling the dcache with case-insensitive names to the
2204  * same inode, only the actual correct case is stored in the dcache for
2205  * case-insensitive filesystems.
2206  *
2207  * For a case-insensitive lookup match and if the case-exact dentry
2208  * already exists in the dcache, use it and return it.
2209  *
2210  * If no entry exists with the exact case name, allocate new dentry with
2211  * the exact case, and return the spliced entry.
2212  */
2213 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
2214                         struct qstr *name)
2215 {
2216         struct dentry *found, *res;
2217
2218         /*
2219          * First check if a dentry matching the name already exists,
2220          * if not go ahead and create it now.
2221          */
2222         found = d_hash_and_lookup(dentry->d_parent, name);
2223         if (found) {
2224                 iput(inode);
2225                 return found;
2226         }
2227         if (d_in_lookup(dentry)) {
2228                 found = d_alloc_parallel(dentry->d_parent, name,
2229                                         dentry->d_wait);
2230                 if (IS_ERR(found) || !d_in_lookup(found)) {
2231                         iput(inode);
2232                         return found;
2233                 }
2234         } else {
2235                 found = d_alloc(dentry->d_parent, name);
2236                 if (!found) {
2237                         iput(inode);
2238                         return ERR_PTR(-ENOMEM);
2239                 } 
2240         }
2241         res = d_splice_alias(inode, found);
2242         if (res) {
2243                 d_lookup_done(found);
2244                 dput(found);
2245                 return res;
2246         }
2247         return found;
2248 }
2249 EXPORT_SYMBOL(d_add_ci);
2250
2251 /**
2252  * d_same_name - compare dentry name with case-exact name
2253  * @parent: parent dentry
2254  * @dentry: the negative dentry that was passed to the parent's lookup func
2255  * @name:   the case-exact name to be associated with the returned dentry
2256  *
2257  * Return: true if names are same, or false
2258  */
2259 bool d_same_name(const struct dentry *dentry, const struct dentry *parent,
2260                  const struct qstr *name)
2261 {
2262         if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
2263                 if (dentry->d_name.len != name->len)
2264                         return false;
2265                 return dentry_cmp(dentry, name->name, name->len) == 0;
2266         }
2267         return parent->d_op->d_compare(dentry,
2268                                        dentry->d_name.len, dentry->d_name.name,
2269                                        name) == 0;
2270 }
2271 EXPORT_SYMBOL_GPL(d_same_name);
2272
2273 /*
2274  * This is __d_lookup_rcu() when the parent dentry has
2275  * DCACHE_OP_COMPARE, which makes things much nastier.
2276  */
2277 static noinline struct dentry *__d_lookup_rcu_op_compare(
2278         const struct dentry *parent,
2279         const struct qstr *name,
2280         unsigned *seqp)
2281 {
2282         u64 hashlen = name->hash_len;
2283         struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
2284         struct hlist_bl_node *node;
2285         struct dentry *dentry;
2286
2287         hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2288                 int tlen;
2289                 const char *tname;
2290                 unsigned seq;
2291
2292 seqretry:
2293                 seq = raw_seqcount_begin(&dentry->d_seq);
2294                 if (dentry->d_parent != parent)
2295                         continue;
2296                 if (d_unhashed(dentry))
2297                         continue;
2298                 if (dentry->d_name.hash != hashlen_hash(hashlen))
2299                         continue;
2300                 tlen = dentry->d_name.len;
2301                 tname = dentry->d_name.name;
2302                 /* we want a consistent (name,len) pair */
2303                 if (read_seqcount_retry(&dentry->d_seq, seq)) {
2304                         cpu_relax();
2305                         goto seqretry;
2306                 }
2307                 if (parent->d_op->d_compare(dentry, tlen, tname, name) != 0)
2308                         continue;
2309                 *seqp = seq;
2310                 return dentry;
2311         }
2312         return NULL;
2313 }
2314
2315 /**
2316  * __d_lookup_rcu - search for a dentry (racy, store-free)
2317  * @parent: parent dentry
2318  * @name: qstr of name we wish to find
2319  * @seqp: returns d_seq value at the point where the dentry was found
2320  * Returns: dentry, or NULL
2321  *
2322  * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2323  * resolution (store-free path walking) design described in
2324  * Documentation/filesystems/path-lookup.txt.
2325  *
2326  * This is not to be used outside core vfs.
2327  *
2328  * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2329  * held, and rcu_read_lock held. The returned dentry must not be stored into
2330  * without taking d_lock and checking d_seq sequence count against @seq
2331  * returned here.
2332  *
2333  * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2334  * function.
2335  *
2336  * Alternatively, __d_lookup_rcu may be called again to look up the child of
2337  * the returned dentry, so long as its parent's seqlock is checked after the
2338  * child is looked up. Thus, an interlocking stepping of sequence lock checks
2339  * is formed, giving integrity down the path walk.
2340  *
2341  * NOTE! The caller *has* to check the resulting dentry against the sequence
2342  * number we've returned before using any of the resulting dentry state!
2343  */
2344 struct dentry *__d_lookup_rcu(const struct dentry *parent,
2345                                 const struct qstr *name,
2346                                 unsigned *seqp)
2347 {
2348         u64 hashlen = name->hash_len;
2349         const unsigned char *str = name->name;
2350         struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
2351         struct hlist_bl_node *node;
2352         struct dentry *dentry;
2353
2354         /*
2355          * Note: There is significant duplication with __d_lookup_rcu which is
2356          * required to prevent single threaded performance regressions
2357          * especially on architectures where smp_rmb (in seqcounts) are costly.
2358          * Keep the two functions in sync.
2359          */
2360
2361         if (unlikely(parent->d_flags & DCACHE_OP_COMPARE))
2362                 return __d_lookup_rcu_op_compare(parent, name, seqp);
2363
2364         /*
2365          * The hash list is protected using RCU.
2366          *
2367          * Carefully use d_seq when comparing a candidate dentry, to avoid
2368          * races with d_move().
2369          *
2370          * It is possible that concurrent renames can mess up our list
2371          * walk here and result in missing our dentry, resulting in the
2372          * false-negative result. d_lookup() protects against concurrent
2373          * renames using rename_lock seqlock.
2374          *
2375          * See Documentation/filesystems/path-lookup.txt for more details.
2376          */
2377         hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2378                 unsigned seq;
2379
2380                 /*
2381                  * The dentry sequence count protects us from concurrent
2382                  * renames, and thus protects parent and name fields.
2383                  *
2384                  * The caller must perform a seqcount check in order
2385                  * to do anything useful with the returned dentry.
2386                  *
2387                  * NOTE! We do a "raw" seqcount_begin here. That means that
2388                  * we don't wait for the sequence count to stabilize if it
2389                  * is in the middle of a sequence change. If we do the slow
2390                  * dentry compare, we will do seqretries until it is stable,
2391                  * and if we end up with a successful lookup, we actually
2392                  * want to exit RCU lookup anyway.
2393                  *
2394                  * Note that raw_seqcount_begin still *does* smp_rmb(), so
2395                  * we are still guaranteed NUL-termination of ->d_name.name.
2396                  */
2397                 seq = raw_seqcount_begin(&dentry->d_seq);
2398                 if (dentry->d_parent != parent)
2399                         continue;
2400                 if (d_unhashed(dentry))
2401                         continue;
2402                 if (dentry->d_name.hash_len != hashlen)
2403                         continue;
2404                 if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
2405                         continue;
2406                 *seqp = seq;
2407                 return dentry;
2408         }
2409         return NULL;
2410 }
2411
2412 /**
2413  * d_lookup - search for a dentry
2414  * @parent: parent dentry
2415  * @name: qstr of name we wish to find
2416  * Returns: dentry, or NULL
2417  *
2418  * d_lookup searches the children of the parent dentry for the name in
2419  * question. If the dentry is found its reference count is incremented and the
2420  * dentry is returned. The caller must use dput to free the entry when it has
2421  * finished using it. %NULL is returned if the dentry does not exist.
2422  */
2423 struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
2424 {
2425         struct dentry *dentry;
2426         unsigned seq;
2427
2428         do {
2429                 seq = read_seqbegin(&rename_lock);
2430                 dentry = __d_lookup(parent, name);
2431                 if (dentry)
2432                         break;
2433         } while (read_seqretry(&rename_lock, seq));
2434         return dentry;
2435 }
2436 EXPORT_SYMBOL(d_lookup);
2437
2438 /**
2439  * __d_lookup - search for a dentry (racy)
2440  * @parent: parent dentry
2441  * @name: qstr of name we wish to find
2442  * Returns: dentry, or NULL
2443  *
2444  * __d_lookup is like d_lookup, however it may (rarely) return a
2445  * false-negative result due to unrelated rename activity.
2446  *
2447  * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2448  * however it must be used carefully, eg. with a following d_lookup in
2449  * the case of failure.
2450  *
2451  * __d_lookup callers must be commented.
2452  */
2453 struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
2454 {
2455         unsigned int hash = name->hash;
2456         struct hlist_bl_head *b = d_hash(hash);
2457         struct hlist_bl_node *node;
2458         struct dentry *found = NULL;
2459         struct dentry *dentry;
2460
2461         /*
2462          * Note: There is significant duplication with __d_lookup_rcu which is
2463          * required to prevent single threaded performance regressions
2464          * especially on architectures where smp_rmb (in seqcounts) are costly.
2465          * Keep the two functions in sync.
2466          */
2467
2468         /*
2469          * The hash list is protected using RCU.
2470          *
2471          * Take d_lock when comparing a candidate dentry, to avoid races
2472          * with d_move().
2473          *
2474          * It is possible that concurrent renames can mess up our list
2475          * walk here and result in missing our dentry, resulting in the
2476          * false-negative result. d_lookup() protects against concurrent
2477          * renames using rename_lock seqlock.
2478          *
2479          * See Documentation/filesystems/path-lookup.txt for more details.
2480          */
2481         rcu_read_lock();
2482         
2483         hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2484
2485                 if (dentry->d_name.hash != hash)
2486                         continue;
2487
2488                 spin_lock(&dentry->d_lock);
2489                 if (dentry->d_parent != parent)
2490                         goto next;
2491                 if (d_unhashed(dentry))
2492                         goto next;
2493
2494                 if (!d_same_name(dentry, parent, name))
2495                         goto next;
2496
2497                 dentry->d_lockref.count++;
2498                 found = dentry;
2499                 spin_unlock(&dentry->d_lock);
2500                 break;
2501 next:
2502                 spin_unlock(&dentry->d_lock);
2503         }
2504         rcu_read_unlock();
2505
2506         return found;
2507 }
2508
2509 /**
2510  * d_hash_and_lookup - hash the qstr then search for a dentry
2511  * @dir: Directory to search in
2512  * @name: qstr of name we wish to find
2513  *
2514  * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2515  */
2516 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2517 {
2518         /*
2519          * Check for a fs-specific hash function. Note that we must
2520          * calculate the standard hash first, as the d_op->d_hash()
2521          * routine may choose to leave the hash value unchanged.
2522          */
2523         name->hash = full_name_hash(dir, name->name, name->len);
2524         if (dir->d_flags & DCACHE_OP_HASH) {
2525                 int err = dir->d_op->d_hash(dir, name);
2526                 if (unlikely(err < 0))
2527                         return ERR_PTR(err);
2528         }
2529         return d_lookup(dir, name);
2530 }
2531 EXPORT_SYMBOL(d_hash_and_lookup);
2532
2533 /*
2534  * When a file is deleted, we have two options:
2535  * - turn this dentry into a negative dentry
2536  * - unhash this dentry and free it.
2537  *
2538  * Usually, we want to just turn this into
2539  * a negative dentry, but if anybody else is
2540  * currently using the dentry or the inode
2541  * we can't do that and we fall back on removing
2542  * it from the hash queues and waiting for
2543  * it to be deleted later when it has no users
2544  */
2545  
2546 /**
2547  * d_delete - delete a dentry
2548  * @dentry: The dentry to delete
2549  *
2550  * Turn the dentry into a negative dentry if possible, otherwise
2551  * remove it from the hash queues so it can be deleted later
2552  */
2553  
2554 void d_delete(struct dentry * dentry)
2555 {
2556         struct inode *inode = dentry->d_inode;
2557
2558         spin_lock(&inode->i_lock);
2559         spin_lock(&dentry->d_lock);
2560         /*
2561          * Are we the only user?
2562          */
2563         if (dentry->d_lockref.count == 1) {
2564                 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2565                 dentry_unlink_inode(dentry);
2566         } else {
2567                 __d_drop(dentry);
2568                 spin_unlock(&dentry->d_lock);
2569                 spin_unlock(&inode->i_lock);
2570         }
2571 }
2572 EXPORT_SYMBOL(d_delete);
2573
2574 static void __d_rehash(struct dentry *entry)
2575 {
2576         struct hlist_bl_head *b = d_hash(entry->d_name.hash);
2577
2578         hlist_bl_lock(b);
2579         hlist_bl_add_head_rcu(&entry->d_hash, b);
2580         hlist_bl_unlock(b);
2581 }
2582
2583 /**
2584  * d_rehash     - add an entry back to the hash
2585  * @entry: dentry to add to the hash
2586  *
2587  * Adds a dentry to the hash according to its name.
2588  */
2589  
2590 void d_rehash(struct dentry * entry)
2591 {
2592         spin_lock(&entry->d_lock);
2593         __d_rehash(entry);
2594         spin_unlock(&entry->d_lock);
2595 }
2596 EXPORT_SYMBOL(d_rehash);
2597
2598 static inline unsigned start_dir_add(struct inode *dir)
2599 {
2600         preempt_disable_nested();
2601         for (;;) {
2602                 unsigned n = dir->i_dir_seq;
2603                 if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
2604                         return n;
2605                 cpu_relax();
2606         }
2607 }
2608
2609 static inline void end_dir_add(struct inode *dir, unsigned int n,
2610                                wait_queue_head_t *d_wait)
2611 {
2612         smp_store_release(&dir->i_dir_seq, n + 2);
2613         preempt_enable_nested();
2614         wake_up_all(d_wait);
2615 }
2616
2617 static void d_wait_lookup(struct dentry *dentry)
2618 {
2619         if (d_in_lookup(dentry)) {
2620                 DECLARE_WAITQUEUE(wait, current);
2621                 add_wait_queue(dentry->d_wait, &wait);
2622                 do {
2623                         set_current_state(TASK_UNINTERRUPTIBLE);
2624                         spin_unlock(&dentry->d_lock);
2625                         schedule();
2626                         spin_lock(&dentry->d_lock);
2627                 } while (d_in_lookup(dentry));
2628         }
2629 }
2630
2631 struct dentry *d_alloc_parallel(struct dentry *parent,
2632                                 const struct qstr *name,
2633                                 wait_queue_head_t *wq)
2634 {
2635         unsigned int hash = name->hash;
2636         struct hlist_bl_head *b = in_lookup_hash(parent, hash);
2637         struct hlist_bl_node *node;
2638         struct dentry *new = d_alloc(parent, name);
2639         struct dentry *dentry;
2640         unsigned seq, r_seq, d_seq;
2641
2642         if (unlikely(!new))
2643                 return ERR_PTR(-ENOMEM);
2644
2645 retry:
2646         rcu_read_lock();
2647         seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
2648         r_seq = read_seqbegin(&rename_lock);
2649         dentry = __d_lookup_rcu(parent, name, &d_seq);
2650         if (unlikely(dentry)) {
2651                 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2652                         rcu_read_unlock();
2653                         goto retry;
2654                 }
2655                 if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
2656                         rcu_read_unlock();
2657                         dput(dentry);
2658                         goto retry;
2659                 }
2660                 rcu_read_unlock();
2661                 dput(new);
2662                 return dentry;
2663         }
2664         if (unlikely(read_seqretry(&rename_lock, r_seq))) {
2665                 rcu_read_unlock();
2666                 goto retry;
2667         }
2668
2669         if (unlikely(seq & 1)) {
2670                 rcu_read_unlock();
2671                 goto retry;
2672         }
2673
2674         hlist_bl_lock(b);
2675         if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
2676                 hlist_bl_unlock(b);
2677                 rcu_read_unlock();
2678                 goto retry;
2679         }
2680         /*
2681          * No changes for the parent since the beginning of d_lookup().
2682          * Since all removals from the chain happen with hlist_bl_lock(),
2683          * any potential in-lookup matches are going to stay here until
2684          * we unlock the chain.  All fields are stable in everything
2685          * we encounter.
2686          */
2687         hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
2688                 if (dentry->d_name.hash != hash)
2689                         continue;
2690                 if (dentry->d_parent != parent)
2691                         continue;
2692                 if (!d_same_name(dentry, parent, name))
2693                         continue;
2694                 hlist_bl_unlock(b);
2695                 /* now we can try to grab a reference */
2696                 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2697                         rcu_read_unlock();
2698                         goto retry;
2699                 }
2700
2701                 rcu_read_unlock();
2702                 /*
2703                  * somebody is likely to be still doing lookup for it;
2704                  * wait for them to finish
2705                  */
2706                 spin_lock(&dentry->d_lock);
2707                 d_wait_lookup(dentry);
2708                 /*
2709                  * it's not in-lookup anymore; in principle we should repeat
2710                  * everything from dcache lookup, but it's likely to be what
2711                  * d_lookup() would've found anyway.  If it is, just return it;
2712                  * otherwise we really have to repeat the whole thing.
2713                  */
2714                 if (unlikely(dentry->d_name.hash != hash))
2715                         goto mismatch;
2716                 if (unlikely(dentry->d_parent != parent))
2717                         goto mismatch;
2718                 if (unlikely(d_unhashed(dentry)))
2719                         goto mismatch;
2720                 if (unlikely(!d_same_name(dentry, parent, name)))
2721                         goto mismatch;
2722                 /* OK, it *is* a hashed match; return it */
2723                 spin_unlock(&dentry->d_lock);
2724                 dput(new);
2725                 return dentry;
2726         }
2727         rcu_read_unlock();
2728         /* we can't take ->d_lock here; it's OK, though. */
2729         new->d_flags |= DCACHE_PAR_LOOKUP;
2730         new->d_wait = wq;
2731         hlist_bl_add_head_rcu(&new->d_u.d_in_lookup_hash, b);
2732         hlist_bl_unlock(b);
2733         return new;
2734 mismatch:
2735         spin_unlock(&dentry->d_lock);
2736         dput(dentry);
2737         goto retry;
2738 }
2739 EXPORT_SYMBOL(d_alloc_parallel);
2740
2741 /*
2742  * - Unhash the dentry
2743  * - Retrieve and clear the waitqueue head in dentry
2744  * - Return the waitqueue head
2745  */
2746 static wait_queue_head_t *__d_lookup_unhash(struct dentry *dentry)
2747 {
2748         wait_queue_head_t *d_wait;
2749         struct hlist_bl_head *b;
2750
2751         lockdep_assert_held(&dentry->d_lock);
2752
2753         b = in_lookup_hash(dentry->d_parent, dentry->d_name.hash);
2754         hlist_bl_lock(b);
2755         dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
2756         __hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
2757         d_wait = dentry->d_wait;
2758         dentry->d_wait = NULL;
2759         hlist_bl_unlock(b);
2760         INIT_HLIST_NODE(&dentry->d_u.d_alias);
2761         INIT_LIST_HEAD(&dentry->d_lru);
2762         return d_wait;
2763 }
2764
2765 void __d_lookup_unhash_wake(struct dentry *dentry)
2766 {
2767         spin_lock(&dentry->d_lock);
2768         wake_up_all(__d_lookup_unhash(dentry));
2769         spin_unlock(&dentry->d_lock);
2770 }
2771 EXPORT_SYMBOL(__d_lookup_unhash_wake);
2772
2773 /* inode->i_lock held if inode is non-NULL */
2774
2775 static inline void __d_add(struct dentry *dentry, struct inode *inode)
2776 {
2777         wait_queue_head_t *d_wait;
2778         struct inode *dir = NULL;
2779         unsigned n;
2780         spin_lock(&dentry->d_lock);
2781         if (unlikely(d_in_lookup(dentry))) {
2782                 dir = dentry->d_parent->d_inode;
2783                 n = start_dir_add(dir);
2784                 d_wait = __d_lookup_unhash(dentry);
2785         }
2786         if (inode) {
2787                 unsigned add_flags = d_flags_for_inode(inode);
2788                 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2789                 raw_write_seqcount_begin(&dentry->d_seq);
2790                 __d_set_inode_and_type(dentry, inode, add_flags);
2791                 raw_write_seqcount_end(&dentry->d_seq);
2792                 fsnotify_update_flags(dentry);
2793         }
2794         __d_rehash(dentry);
2795         if (dir)
2796                 end_dir_add(dir, n, d_wait);
2797         spin_unlock(&dentry->d_lock);
2798         if (inode)
2799                 spin_unlock(&inode->i_lock);
2800 }
2801
2802 /**
2803  * d_add - add dentry to hash queues
2804  * @entry: dentry to add
2805  * @inode: The inode to attach to this dentry
2806  *
2807  * This adds the entry to the hash queues and initializes @inode.
2808  * The entry was actually filled in earlier during d_alloc().
2809  */
2810
2811 void d_add(struct dentry *entry, struct inode *inode)
2812 {
2813         if (inode) {
2814                 security_d_instantiate(entry, inode);
2815                 spin_lock(&inode->i_lock);
2816         }
2817         __d_add(entry, inode);
2818 }
2819 EXPORT_SYMBOL(d_add);
2820
2821 /**
2822  * d_exact_alias - find and hash an exact unhashed alias
2823  * @entry: dentry to add
2824  * @inode: The inode to go with this dentry
2825  *
2826  * If an unhashed dentry with the same name/parent and desired
2827  * inode already exists, hash and return it.  Otherwise, return
2828  * NULL.
2829  *
2830  * Parent directory should be locked.
2831  */
2832 struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
2833 {
2834         struct dentry *alias;
2835         unsigned int hash = entry->d_name.hash;
2836
2837         spin_lock(&inode->i_lock);
2838         hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
2839                 /*
2840                  * Don't need alias->d_lock here, because aliases with
2841                  * d_parent == entry->d_parent are not subject to name or
2842                  * parent changes, because the parent inode i_mutex is held.
2843                  */
2844                 if (alias->d_name.hash != hash)
2845                         continue;
2846                 if (alias->d_parent != entry->d_parent)
2847                         continue;
2848                 if (!d_same_name(alias, entry->d_parent, &entry->d_name))
2849                         continue;
2850                 spin_lock(&alias->d_lock);
2851                 if (!d_unhashed(alias)) {
2852                         spin_unlock(&alias->d_lock);
2853                         alias = NULL;
2854                 } else {
2855                         __dget_dlock(alias);
2856                         __d_rehash(alias);
2857                         spin_unlock(&alias->d_lock);
2858                 }
2859                 spin_unlock(&inode->i_lock);
2860                 return alias;
2861         }
2862         spin_unlock(&inode->i_lock);
2863         return NULL;
2864 }
2865 EXPORT_SYMBOL(d_exact_alias);
2866
2867 static void swap_names(struct dentry *dentry, struct dentry *target)
2868 {
2869         if (unlikely(dname_external(target))) {
2870                 if (unlikely(dname_external(dentry))) {
2871                         /*
2872                          * Both external: swap the pointers
2873                          */
2874                         swap(target->d_name.name, dentry->d_name.name);
2875                 } else {
2876                         /*
2877                          * dentry:internal, target:external.  Steal target's
2878                          * storage and make target internal.
2879                          */
2880                         memcpy(target->d_iname, dentry->d_name.name,
2881                                         dentry->d_name.len + 1);
2882                         dentry->d_name.name = target->d_name.name;
2883                         target->d_name.name = target->d_iname;
2884                 }
2885         } else {
2886                 if (unlikely(dname_external(dentry))) {
2887                         /*
2888                          * dentry:external, target:internal.  Give dentry's
2889                          * storage to target and make dentry internal
2890                          */
2891                         memcpy(dentry->d_iname, target->d_name.name,
2892                                         target->d_name.len + 1);
2893                         target->d_name.name = dentry->d_name.name;
2894                         dentry->d_name.name = dentry->d_iname;
2895                 } else {
2896                         /*
2897                          * Both are internal.
2898                          */
2899                         unsigned int i;
2900                         BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
2901                         for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
2902                                 swap(((long *) &dentry->d_iname)[i],
2903                                      ((long *) &target->d_iname)[i]);
2904                         }
2905                 }
2906         }
2907         swap(dentry->d_name.hash_len, target->d_name.hash_len);
2908 }
2909
2910 static void copy_name(struct dentry *dentry, struct dentry *target)
2911 {
2912         struct external_name *old_name = NULL;
2913         if (unlikely(dname_external(dentry)))
2914                 old_name = external_name(dentry);
2915         if (unlikely(dname_external(target))) {
2916                 atomic_inc(&external_name(target)->u.count);
2917                 dentry->d_name = target->d_name;
2918         } else {
2919                 memcpy(dentry->d_iname, target->d_name.name,
2920                                 target->d_name.len + 1);
2921                 dentry->d_name.name = dentry->d_iname;
2922                 dentry->d_name.hash_len = target->d_name.hash_len;
2923         }
2924         if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
2925                 kfree_rcu(old_name, u.head);
2926 }
2927
2928 /*
2929  * __d_move - move a dentry
2930  * @dentry: entry to move
2931  * @target: new dentry
2932  * @exchange: exchange the two dentries
2933  *
2934  * Update the dcache to reflect the move of a file name. Negative
2935  * dcache entries should not be moved in this way. Caller must hold
2936  * rename_lock, the i_mutex of the source and target directories,
2937  * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2938  */
2939 static void __d_move(struct dentry *dentry, struct dentry *target,
2940                      bool exchange)
2941 {
2942         struct dentry *old_parent, *p;
2943         wait_queue_head_t *d_wait;
2944         struct inode *dir = NULL;
2945         unsigned n;
2946
2947         WARN_ON(!dentry->d_inode);
2948         if (WARN_ON(dentry == target))
2949                 return;
2950
2951         BUG_ON(d_ancestor(target, dentry));
2952         old_parent = dentry->d_parent;
2953         p = d_ancestor(old_parent, target);
2954         if (IS_ROOT(dentry)) {
2955                 BUG_ON(p);
2956                 spin_lock(&target->d_parent->d_lock);
2957         } else if (!p) {
2958                 /* target is not a descendent of dentry->d_parent */
2959                 spin_lock(&target->d_parent->d_lock);
2960                 spin_lock_nested(&old_parent->d_lock, DENTRY_D_LOCK_NESTED);
2961         } else {
2962                 BUG_ON(p == dentry);
2963                 spin_lock(&old_parent->d_lock);
2964                 if (p != target)
2965                         spin_lock_nested(&target->d_parent->d_lock,
2966                                         DENTRY_D_LOCK_NESTED);
2967         }
2968         spin_lock_nested(&dentry->d_lock, 2);
2969         spin_lock_nested(&target->d_lock, 3);
2970
2971         if (unlikely(d_in_lookup(target))) {
2972                 dir = target->d_parent->d_inode;
2973                 n = start_dir_add(dir);
2974                 d_wait = __d_lookup_unhash(target);
2975         }
2976
2977         write_seqcount_begin(&dentry->d_seq);
2978         write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
2979
2980         /* unhash both */
2981         if (!d_unhashed(dentry))
2982                 ___d_drop(dentry);
2983         if (!d_unhashed(target))
2984                 ___d_drop(target);
2985
2986         /* ... and switch them in the tree */
2987         dentry->d_parent = target->d_parent;
2988         if (!exchange) {
2989                 copy_name(dentry, target);
2990                 target->d_hash.pprev = NULL;
2991                 dentry->d_parent->d_lockref.count++;
2992                 if (dentry != old_parent) /* wasn't IS_ROOT */
2993                         WARN_ON(!--old_parent->d_lockref.count);
2994         } else {
2995                 target->d_parent = old_parent;
2996                 swap_names(dentry, target);
2997                 list_move(&target->d_child, &target->d_parent->d_subdirs);
2998                 __d_rehash(target);
2999                 fsnotify_update_flags(target);
3000         }
3001         list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
3002         __d_rehash(dentry);
3003         fsnotify_update_flags(dentry);
3004         fscrypt_handle_d_move(dentry);
3005
3006         write_seqcount_end(&target->d_seq);
3007         write_seqcount_end(&dentry->d_seq);
3008
3009         if (dir)
3010                 end_dir_add(dir, n, d_wait);
3011
3012         if (dentry->d_parent != old_parent)
3013                 spin_unlock(&dentry->d_parent->d_lock);
3014         if (dentry != old_parent)
3015                 spin_unlock(&old_parent->d_lock);
3016         spin_unlock(&target->d_lock);
3017         spin_unlock(&dentry->d_lock);
3018 }
3019
3020 /*
3021  * d_move - move a dentry
3022  * @dentry: entry to move
3023  * @target: new dentry
3024  *
3025  * Update the dcache to reflect the move of a file name. Negative
3026  * dcache entries should not be moved in this way. See the locking
3027  * requirements for __d_move.
3028  */
3029 void d_move(struct dentry *dentry, struct dentry *target)
3030 {
3031         write_seqlock(&rename_lock);
3032         __d_move(dentry, target, false);
3033         write_sequnlock(&rename_lock);
3034 }
3035 EXPORT_SYMBOL(d_move);
3036
3037 /*
3038  * d_exchange - exchange two dentries
3039  * @dentry1: first dentry
3040  * @dentry2: second dentry
3041  */
3042 void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
3043 {
3044         write_seqlock(&rename_lock);
3045
3046         WARN_ON(!dentry1->d_inode);
3047         WARN_ON(!dentry2->d_inode);
3048         WARN_ON(IS_ROOT(dentry1));
3049         WARN_ON(IS_ROOT(dentry2));
3050
3051         __d_move(dentry1, dentry2, true);
3052
3053         write_sequnlock(&rename_lock);
3054 }
3055
3056 /**
3057  * d_ancestor - search for an ancestor
3058  * @p1: ancestor dentry
3059  * @p2: child dentry
3060  *
3061  * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
3062  * an ancestor of p2, else NULL.
3063  */
3064 struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
3065 {
3066         struct dentry *p;
3067
3068         for (p = p2; !IS_ROOT(p); p = p->d_parent) {
3069                 if (p->d_parent == p1)
3070                         return p;
3071         }
3072         return NULL;
3073 }
3074
3075 /*
3076  * This helper attempts to cope with remotely renamed directories
3077  *
3078  * It assumes that the caller is already holding
3079  * dentry->d_parent->d_inode->i_mutex, and rename_lock
3080  *
3081  * Note: If ever the locking in lock_rename() changes, then please
3082  * remember to update this too...
3083  */
3084 static int __d_unalias(struct inode *inode,
3085                 struct dentry *dentry, struct dentry *alias)
3086 {
3087         struct mutex *m1 = NULL;
3088         struct rw_semaphore *m2 = NULL;
3089         int ret = -ESTALE;
3090
3091         /* If alias and dentry share a parent, then no extra locks required */
3092         if (alias->d_parent == dentry->d_parent)
3093                 goto out_unalias;
3094
3095         /* See lock_rename() */
3096         if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
3097                 goto out_err;
3098         m1 = &dentry->d_sb->s_vfs_rename_mutex;
3099         if (!inode_trylock_shared(alias->d_parent->d_inode))
3100                 goto out_err;
3101         m2 = &alias->d_parent->d_inode->i_rwsem;
3102 out_unalias:
3103         __d_move(alias, dentry, false);
3104         ret = 0;
3105 out_err:
3106         if (m2)
3107                 up_read(m2);
3108         if (m1)
3109                 mutex_unlock(m1);
3110         return ret;
3111 }
3112
3113 /**
3114  * d_splice_alias - splice a disconnected dentry into the tree if one exists
3115  * @inode:  the inode which may have a disconnected dentry
3116  * @dentry: a negative dentry which we want to point to the inode.
3117  *
3118  * If inode is a directory and has an IS_ROOT alias, then d_move that in
3119  * place of the given dentry and return it, else simply d_add the inode
3120  * to the dentry and return NULL.
3121  *
3122  * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
3123  * we should error out: directories can't have multiple aliases.
3124  *
3125  * This is needed in the lookup routine of any filesystem that is exportable
3126  * (via knfsd) so that we can build dcache paths to directories effectively.
3127  *
3128  * If a dentry was found and moved, then it is returned.  Otherwise NULL
3129  * is returned.  This matches the expected return value of ->lookup.
3130  *
3131  * Cluster filesystems may call this function with a negative, hashed dentry.
3132  * In that case, we know that the inode will be a regular file, and also this
3133  * will only occur during atomic_open. So we need to check for the dentry
3134  * being already hashed only in the final case.
3135  */
3136 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
3137 {
3138         if (IS_ERR(inode))
3139                 return ERR_CAST(inode);
3140
3141         BUG_ON(!d_unhashed(dentry));
3142
3143         if (!inode)
3144                 goto out;
3145
3146         security_d_instantiate(dentry, inode);
3147         spin_lock(&inode->i_lock);
3148         if (S_ISDIR(inode->i_mode)) {
3149                 struct dentry *new = __d_find_any_alias(inode);
3150                 if (unlikely(new)) {
3151                         /* The reference to new ensures it remains an alias */
3152                         spin_unlock(&inode->i_lock);
3153                         write_seqlock(&rename_lock);
3154                         if (unlikely(d_ancestor(new, dentry))) {
3155                                 write_sequnlock(&rename_lock);
3156                                 dput(new);
3157                                 new = ERR_PTR(-ELOOP);
3158                                 pr_warn_ratelimited(
3159                                         "VFS: Lookup of '%s' in %s %s"
3160                                         " would have caused loop\n",
3161                                         dentry->d_name.name,
3162                                         inode->i_sb->s_type->name,
3163                                         inode->i_sb->s_id);
3164                         } else if (!IS_ROOT(new)) {
3165                                 struct dentry *old_parent = dget(new->d_parent);
3166                                 int err = __d_unalias(inode, dentry, new);
3167                                 write_sequnlock(&rename_lock);
3168                                 if (err) {
3169                                         dput(new);
3170                                         new = ERR_PTR(err);
3171                                 }
3172                                 dput(old_parent);
3173                         } else {
3174                                 __d_move(new, dentry, false);
3175                                 write_sequnlock(&rename_lock);
3176                         }
3177                         iput(inode);
3178                         return new;
3179                 }
3180         }
3181 out:
3182         __d_add(dentry, inode);
3183         return NULL;
3184 }
3185 EXPORT_SYMBOL(d_splice_alias);
3186
3187 /*
3188  * Test whether new_dentry is a subdirectory of old_dentry.
3189  *
3190  * Trivially implemented using the dcache structure
3191  */
3192
3193 /**
3194  * is_subdir - is new dentry a subdirectory of old_dentry
3195  * @new_dentry: new dentry
3196  * @old_dentry: old dentry
3197  *
3198  * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3199  * Returns false otherwise.
3200  * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3201  */
3202   
3203 bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
3204 {
3205         bool result;
3206         unsigned seq;
3207
3208         if (new_dentry == old_dentry)
3209                 return true;
3210
3211         do {
3212                 /* for restarting inner loop in case of seq retry */
3213                 seq = read_seqbegin(&rename_lock);
3214                 /*
3215                  * Need rcu_readlock to protect against the d_parent trashing
3216                  * due to d_move
3217                  */
3218                 rcu_read_lock();
3219                 if (d_ancestor(old_dentry, new_dentry))
3220                         result = true;
3221                 else
3222                         result = false;
3223                 rcu_read_unlock();
3224         } while (read_seqretry(&rename_lock, seq));
3225
3226         return result;
3227 }
3228 EXPORT_SYMBOL(is_subdir);
3229
3230 static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
3231 {
3232         struct dentry *root = data;
3233         if (dentry != root) {
3234                 if (d_unhashed(dentry) || !dentry->d_inode)
3235                         return D_WALK_SKIP;
3236
3237                 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
3238                         dentry->d_flags |= DCACHE_GENOCIDE;
3239                         dentry->d_lockref.count--;
3240                 }
3241         }
3242         return D_WALK_CONTINUE;
3243 }
3244
3245 void d_genocide(struct dentry *parent)
3246 {
3247         d_walk(parent, parent, d_genocide_kill);
3248 }
3249
3250 EXPORT_SYMBOL(d_genocide);
3251
3252 void d_tmpfile(struct file *file, struct inode *inode)
3253 {
3254         struct dentry *dentry = file->f_path.dentry;
3255
3256         inode_dec_link_count(inode);
3257         BUG_ON(dentry->d_name.name != dentry->d_iname ||
3258                 !hlist_unhashed(&dentry->d_u.d_alias) ||
3259                 !d_unlinked(dentry));
3260         spin_lock(&dentry->d_parent->d_lock);
3261         spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
3262         dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
3263                                 (unsigned long long)inode->i_ino);
3264         spin_unlock(&dentry->d_lock);
3265         spin_unlock(&dentry->d_parent->d_lock);
3266         d_instantiate(dentry, inode);
3267 }
3268 EXPORT_SYMBOL(d_tmpfile);
3269
3270 static __initdata unsigned long dhash_entries;
3271 static int __init set_dhash_entries(char *str)
3272 {
3273         if (!str)
3274                 return 0;
3275         dhash_entries = simple_strtoul(str, &str, 0);
3276         return 1;
3277 }
3278 __setup("dhash_entries=", set_dhash_entries);
3279
3280 static void __init dcache_init_early(void)
3281 {
3282         /* If hashes are distributed across NUMA nodes, defer
3283          * hash allocation until vmalloc space is available.
3284          */
3285         if (hashdist)
3286                 return;
3287
3288         dentry_hashtable =
3289                 alloc_large_system_hash("Dentry cache",
3290                                         sizeof(struct hlist_bl_head),
3291                                         dhash_entries,
3292                                         13,
3293                                         HASH_EARLY | HASH_ZERO,
3294                                         &d_hash_shift,
3295                                         NULL,
3296                                         0,
3297                                         0);
3298         d_hash_shift = 32 - d_hash_shift;
3299 }
3300
3301 static void __init dcache_init(void)
3302 {
3303         /*
3304          * A constructor could be added for stable state like the lists,
3305          * but it is probably not worth it because of the cache nature
3306          * of the dcache.
3307          */
3308         dentry_cache = KMEM_CACHE_USERCOPY(dentry,
3309                 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT,
3310                 d_iname);
3311
3312         /* Hash may have been set up in dcache_init_early */
3313         if (!hashdist)
3314                 return;
3315
3316         dentry_hashtable =
3317                 alloc_large_system_hash("Dentry cache",
3318                                         sizeof(struct hlist_bl_head),
3319                                         dhash_entries,
3320                                         13,
3321                                         HASH_ZERO,
3322                                         &d_hash_shift,
3323                                         NULL,
3324                                         0,
3325                                         0);
3326         d_hash_shift = 32 - d_hash_shift;
3327 }
3328
3329 /* SLAB cache for __getname() consumers */
3330 struct kmem_cache *names_cachep __read_mostly;
3331 EXPORT_SYMBOL(names_cachep);
3332
3333 void __init vfs_caches_init_early(void)
3334 {
3335         int i;
3336
3337         for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++)
3338                 INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]);
3339
3340         dcache_init_early();
3341         inode_init_early();
3342 }
3343
3344 void __init vfs_caches_init(void)
3345 {
3346         names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0,
3347                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL);
3348
3349         dcache_init();
3350         inode_init();
3351         files_init();
3352         files_maxfiles_init();
3353         mnt_init();
3354         bdev_cache_init();
3355         chrdev_init();
3356 }