Merge tag 'linux-watchdog-6.6-rc1' of git://www.linux-watchdog.org/linux-watchdog
[platform/kernel/linux-rpi.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         WARN(1, "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         return D_WALK_CONTINUE;
1677 }
1678
1679 static void do_one_tree(struct dentry *dentry)
1680 {
1681         shrink_dcache_parent(dentry);
1682         d_walk(dentry, dentry, umount_check);
1683         d_drop(dentry);
1684         dput(dentry);
1685 }
1686
1687 /*
1688  * destroy the dentries attached to a superblock on unmounting
1689  */
1690 void shrink_dcache_for_umount(struct super_block *sb)
1691 {
1692         struct dentry *dentry;
1693
1694         WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked");
1695
1696         dentry = sb->s_root;
1697         sb->s_root = NULL;
1698         do_one_tree(dentry);
1699
1700         while (!hlist_bl_empty(&sb->s_roots)) {
1701                 dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_roots), struct dentry, d_hash));
1702                 do_one_tree(dentry);
1703         }
1704 }
1705
1706 static enum d_walk_ret find_submount(void *_data, struct dentry *dentry)
1707 {
1708         struct dentry **victim = _data;
1709         if (d_mountpoint(dentry)) {
1710                 __dget_dlock(dentry);
1711                 *victim = dentry;
1712                 return D_WALK_QUIT;
1713         }
1714         return D_WALK_CONTINUE;
1715 }
1716
1717 /**
1718  * d_invalidate - detach submounts, prune dcache, and drop
1719  * @dentry: dentry to invalidate (aka detach, prune and drop)
1720  */
1721 void d_invalidate(struct dentry *dentry)
1722 {
1723         bool had_submounts = false;
1724         spin_lock(&dentry->d_lock);
1725         if (d_unhashed(dentry)) {
1726                 spin_unlock(&dentry->d_lock);
1727                 return;
1728         }
1729         __d_drop(dentry);
1730         spin_unlock(&dentry->d_lock);
1731
1732         /* Negative dentries can be dropped without further checks */
1733         if (!dentry->d_inode)
1734                 return;
1735
1736         shrink_dcache_parent(dentry);
1737         for (;;) {
1738                 struct dentry *victim = NULL;
1739                 d_walk(dentry, &victim, find_submount);
1740                 if (!victim) {
1741                         if (had_submounts)
1742                                 shrink_dcache_parent(dentry);
1743                         return;
1744                 }
1745                 had_submounts = true;
1746                 detach_mounts(victim);
1747                 dput(victim);
1748         }
1749 }
1750 EXPORT_SYMBOL(d_invalidate);
1751
1752 /**
1753  * __d_alloc    -       allocate a dcache entry
1754  * @sb: filesystem it will belong to
1755  * @name: qstr of the name
1756  *
1757  * Allocates a dentry. It returns %NULL if there is insufficient memory
1758  * available. On a success the dentry is returned. The name passed in is
1759  * copied and the copy passed in may be reused after this call.
1760  */
1761  
1762 static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
1763 {
1764         struct dentry *dentry;
1765         char *dname;
1766         int err;
1767
1768         dentry = kmem_cache_alloc_lru(dentry_cache, &sb->s_dentry_lru,
1769                                       GFP_KERNEL);
1770         if (!dentry)
1771                 return NULL;
1772
1773         /*
1774          * We guarantee that the inline name is always NUL-terminated.
1775          * This way the memcpy() done by the name switching in rename
1776          * will still always have a NUL at the end, even if we might
1777          * be overwriting an internal NUL character
1778          */
1779         dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
1780         if (unlikely(!name)) {
1781                 name = &slash_name;
1782                 dname = dentry->d_iname;
1783         } else if (name->len > DNAME_INLINE_LEN-1) {
1784                 size_t size = offsetof(struct external_name, name[1]);
1785                 struct external_name *p = kmalloc(size + name->len,
1786                                                   GFP_KERNEL_ACCOUNT |
1787                                                   __GFP_RECLAIMABLE);
1788                 if (!p) {
1789                         kmem_cache_free(dentry_cache, dentry); 
1790                         return NULL;
1791                 }
1792                 atomic_set(&p->u.count, 1);
1793                 dname = p->name;
1794         } else  {
1795                 dname = dentry->d_iname;
1796         }       
1797
1798         dentry->d_name.len = name->len;
1799         dentry->d_name.hash = name->hash;
1800         memcpy(dname, name->name, name->len);
1801         dname[name->len] = 0;
1802
1803         /* Make sure we always see the terminating NUL character */
1804         smp_store_release(&dentry->d_name.name, dname); /* ^^^ */
1805
1806         dentry->d_lockref.count = 1;
1807         dentry->d_flags = 0;
1808         spin_lock_init(&dentry->d_lock);
1809         seqcount_spinlock_init(&dentry->d_seq, &dentry->d_lock);
1810         dentry->d_inode = NULL;
1811         dentry->d_parent = dentry;
1812         dentry->d_sb = sb;
1813         dentry->d_op = NULL;
1814         dentry->d_fsdata = NULL;
1815         INIT_HLIST_BL_NODE(&dentry->d_hash);
1816         INIT_LIST_HEAD(&dentry->d_lru);
1817         INIT_LIST_HEAD(&dentry->d_subdirs);
1818         INIT_HLIST_NODE(&dentry->d_u.d_alias);
1819         INIT_LIST_HEAD(&dentry->d_child);
1820         d_set_d_op(dentry, dentry->d_sb->s_d_op);
1821
1822         if (dentry->d_op && dentry->d_op->d_init) {
1823                 err = dentry->d_op->d_init(dentry);
1824                 if (err) {
1825                         if (dname_external(dentry))
1826                                 kfree(external_name(dentry));
1827                         kmem_cache_free(dentry_cache, dentry);
1828                         return NULL;
1829                 }
1830         }
1831
1832         this_cpu_inc(nr_dentry);
1833
1834         return dentry;
1835 }
1836
1837 /**
1838  * d_alloc      -       allocate a dcache entry
1839  * @parent: parent of entry to allocate
1840  * @name: qstr of the name
1841  *
1842  * Allocates a dentry. It returns %NULL if there is insufficient memory
1843  * available. On a success the dentry is returned. The name passed in is
1844  * copied and the copy passed in may be reused after this call.
1845  */
1846 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
1847 {
1848         struct dentry *dentry = __d_alloc(parent->d_sb, name);
1849         if (!dentry)
1850                 return NULL;
1851         spin_lock(&parent->d_lock);
1852         /*
1853          * don't need child lock because it is not subject
1854          * to concurrency here
1855          */
1856         __dget_dlock(parent);
1857         dentry->d_parent = parent;
1858         list_add(&dentry->d_child, &parent->d_subdirs);
1859         spin_unlock(&parent->d_lock);
1860
1861         return dentry;
1862 }
1863 EXPORT_SYMBOL(d_alloc);
1864
1865 struct dentry *d_alloc_anon(struct super_block *sb)
1866 {
1867         return __d_alloc(sb, NULL);
1868 }
1869 EXPORT_SYMBOL(d_alloc_anon);
1870
1871 struct dentry *d_alloc_cursor(struct dentry * parent)
1872 {
1873         struct dentry *dentry = d_alloc_anon(parent->d_sb);
1874         if (dentry) {
1875                 dentry->d_flags |= DCACHE_DENTRY_CURSOR;
1876                 dentry->d_parent = dget(parent);
1877         }
1878         return dentry;
1879 }
1880
1881 /**
1882  * d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
1883  * @sb: the superblock
1884  * @name: qstr of the name
1885  *
1886  * For a filesystem that just pins its dentries in memory and never
1887  * performs lookups at all, return an unhashed IS_ROOT dentry.
1888  * This is used for pipes, sockets et.al. - the stuff that should
1889  * never be anyone's children or parents.  Unlike all other
1890  * dentries, these will not have RCU delay between dropping the
1891  * last reference and freeing them.
1892  *
1893  * The only user is alloc_file_pseudo() and that's what should
1894  * be considered a public interface.  Don't use directly.
1895  */
1896 struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
1897 {
1898         struct dentry *dentry = __d_alloc(sb, name);
1899         if (likely(dentry))
1900                 dentry->d_flags |= DCACHE_NORCU;
1901         return dentry;
1902 }
1903
1904 struct dentry *d_alloc_name(struct dentry *parent, const char *name)
1905 {
1906         struct qstr q;
1907
1908         q.name = name;
1909         q.hash_len = hashlen_string(parent, name);
1910         return d_alloc(parent, &q);
1911 }
1912 EXPORT_SYMBOL(d_alloc_name);
1913
1914 void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
1915 {
1916         WARN_ON_ONCE(dentry->d_op);
1917         WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH  |
1918                                 DCACHE_OP_COMPARE       |
1919                                 DCACHE_OP_REVALIDATE    |
1920                                 DCACHE_OP_WEAK_REVALIDATE       |
1921                                 DCACHE_OP_DELETE        |
1922                                 DCACHE_OP_REAL));
1923         dentry->d_op = op;
1924         if (!op)
1925                 return;
1926         if (op->d_hash)
1927                 dentry->d_flags |= DCACHE_OP_HASH;
1928         if (op->d_compare)
1929                 dentry->d_flags |= DCACHE_OP_COMPARE;
1930         if (op->d_revalidate)
1931                 dentry->d_flags |= DCACHE_OP_REVALIDATE;
1932         if (op->d_weak_revalidate)
1933                 dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
1934         if (op->d_delete)
1935                 dentry->d_flags |= DCACHE_OP_DELETE;
1936         if (op->d_prune)
1937                 dentry->d_flags |= DCACHE_OP_PRUNE;
1938         if (op->d_real)
1939                 dentry->d_flags |= DCACHE_OP_REAL;
1940
1941 }
1942 EXPORT_SYMBOL(d_set_d_op);
1943
1944
1945 /*
1946  * d_set_fallthru - Mark a dentry as falling through to a lower layer
1947  * @dentry - The dentry to mark
1948  *
1949  * Mark a dentry as falling through to the lower layer (as set with
1950  * d_pin_lower()).  This flag may be recorded on the medium.
1951  */
1952 void d_set_fallthru(struct dentry *dentry)
1953 {
1954         spin_lock(&dentry->d_lock);
1955         dentry->d_flags |= DCACHE_FALLTHRU;
1956         spin_unlock(&dentry->d_lock);
1957 }
1958 EXPORT_SYMBOL(d_set_fallthru);
1959
1960 static unsigned d_flags_for_inode(struct inode *inode)
1961 {
1962         unsigned add_flags = DCACHE_REGULAR_TYPE;
1963
1964         if (!inode)
1965                 return DCACHE_MISS_TYPE;
1966
1967         if (S_ISDIR(inode->i_mode)) {
1968                 add_flags = DCACHE_DIRECTORY_TYPE;
1969                 if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) {
1970                         if (unlikely(!inode->i_op->lookup))
1971                                 add_flags = DCACHE_AUTODIR_TYPE;
1972                         else
1973                                 inode->i_opflags |= IOP_LOOKUP;
1974                 }
1975                 goto type_determined;
1976         }
1977
1978         if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1979                 if (unlikely(inode->i_op->get_link)) {
1980                         add_flags = DCACHE_SYMLINK_TYPE;
1981                         goto type_determined;
1982                 }
1983                 inode->i_opflags |= IOP_NOFOLLOW;
1984         }
1985
1986         if (unlikely(!S_ISREG(inode->i_mode)))
1987                 add_flags = DCACHE_SPECIAL_TYPE;
1988
1989 type_determined:
1990         if (unlikely(IS_AUTOMOUNT(inode)))
1991                 add_flags |= DCACHE_NEED_AUTOMOUNT;
1992         return add_flags;
1993 }
1994
1995 static void __d_instantiate(struct dentry *dentry, struct inode *inode)
1996 {
1997         unsigned add_flags = d_flags_for_inode(inode);
1998         WARN_ON(d_in_lookup(dentry));
1999
2000         spin_lock(&dentry->d_lock);
2001         /*
2002          * Decrement negative dentry count if it was in the LRU list.
2003          */
2004         if (dentry->d_flags & DCACHE_LRU_LIST)
2005                 this_cpu_dec(nr_dentry_negative);
2006         hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2007         raw_write_seqcount_begin(&dentry->d_seq);
2008         __d_set_inode_and_type(dentry, inode, add_flags);
2009         raw_write_seqcount_end(&dentry->d_seq);
2010         fsnotify_update_flags(dentry);
2011         spin_unlock(&dentry->d_lock);
2012 }
2013
2014 /**
2015  * d_instantiate - fill in inode information for a dentry
2016  * @entry: dentry to complete
2017  * @inode: inode to attach to this dentry
2018  *
2019  * Fill in inode information in the entry.
2020  *
2021  * This turns negative dentries into productive full members
2022  * of society.
2023  *
2024  * NOTE! This assumes that the inode count has been incremented
2025  * (or otherwise set) by the caller to indicate that it is now
2026  * in use by the dcache.
2027  */
2028  
2029 void d_instantiate(struct dentry *entry, struct inode * inode)
2030 {
2031         BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
2032         if (inode) {
2033                 security_d_instantiate(entry, inode);
2034                 spin_lock(&inode->i_lock);
2035                 __d_instantiate(entry, inode);
2036                 spin_unlock(&inode->i_lock);
2037         }
2038 }
2039 EXPORT_SYMBOL(d_instantiate);
2040
2041 /*
2042  * This should be equivalent to d_instantiate() + unlock_new_inode(),
2043  * with lockdep-related part of unlock_new_inode() done before
2044  * anything else.  Use that instead of open-coding d_instantiate()/
2045  * unlock_new_inode() combinations.
2046  */
2047 void d_instantiate_new(struct dentry *entry, struct inode *inode)
2048 {
2049         BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
2050         BUG_ON(!inode);
2051         lockdep_annotate_inode_mutex_key(inode);
2052         security_d_instantiate(entry, inode);
2053         spin_lock(&inode->i_lock);
2054         __d_instantiate(entry, inode);
2055         WARN_ON(!(inode->i_state & I_NEW));
2056         inode->i_state &= ~I_NEW & ~I_CREATING;
2057         smp_mb();
2058         wake_up_bit(&inode->i_state, __I_NEW);
2059         spin_unlock(&inode->i_lock);
2060 }
2061 EXPORT_SYMBOL(d_instantiate_new);
2062
2063 struct dentry *d_make_root(struct inode *root_inode)
2064 {
2065         struct dentry *res = NULL;
2066
2067         if (root_inode) {
2068                 res = d_alloc_anon(root_inode->i_sb);
2069                 if (res)
2070                         d_instantiate(res, root_inode);
2071                 else
2072                         iput(root_inode);
2073         }
2074         return res;
2075 }
2076 EXPORT_SYMBOL(d_make_root);
2077
2078 static struct dentry *__d_instantiate_anon(struct dentry *dentry,
2079                                            struct inode *inode,
2080                                            bool disconnected)
2081 {
2082         struct dentry *res;
2083         unsigned add_flags;
2084
2085         security_d_instantiate(dentry, inode);
2086         spin_lock(&inode->i_lock);
2087         res = __d_find_any_alias(inode);
2088         if (res) {
2089                 spin_unlock(&inode->i_lock);
2090                 dput(dentry);
2091                 goto out_iput;
2092         }
2093
2094         /* attach a disconnected dentry */
2095         add_flags = d_flags_for_inode(inode);
2096
2097         if (disconnected)
2098                 add_flags |= DCACHE_DISCONNECTED;
2099
2100         spin_lock(&dentry->d_lock);
2101         __d_set_inode_and_type(dentry, inode, add_flags);
2102         hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2103         if (!disconnected) {
2104                 hlist_bl_lock(&dentry->d_sb->s_roots);
2105                 hlist_bl_add_head(&dentry->d_hash, &dentry->d_sb->s_roots);
2106                 hlist_bl_unlock(&dentry->d_sb->s_roots);
2107         }
2108         spin_unlock(&dentry->d_lock);
2109         spin_unlock(&inode->i_lock);
2110
2111         return dentry;
2112
2113  out_iput:
2114         iput(inode);
2115         return res;
2116 }
2117
2118 struct dentry *d_instantiate_anon(struct dentry *dentry, struct inode *inode)
2119 {
2120         return __d_instantiate_anon(dentry, inode, true);
2121 }
2122 EXPORT_SYMBOL(d_instantiate_anon);
2123
2124 static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected)
2125 {
2126         struct dentry *tmp;
2127         struct dentry *res;
2128
2129         if (!inode)
2130                 return ERR_PTR(-ESTALE);
2131         if (IS_ERR(inode))
2132                 return ERR_CAST(inode);
2133
2134         res = d_find_any_alias(inode);
2135         if (res)
2136                 goto out_iput;
2137
2138         tmp = d_alloc_anon(inode->i_sb);
2139         if (!tmp) {
2140                 res = ERR_PTR(-ENOMEM);
2141                 goto out_iput;
2142         }
2143
2144         return __d_instantiate_anon(tmp, inode, disconnected);
2145
2146 out_iput:
2147         iput(inode);
2148         return res;
2149 }
2150
2151 /**
2152  * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
2153  * @inode: inode to allocate the dentry for
2154  *
2155  * Obtain a dentry for an inode resulting from NFS filehandle conversion or
2156  * similar open by handle operations.  The returned dentry may be anonymous,
2157  * or may have a full name (if the inode was already in the cache).
2158  *
2159  * When called on a directory inode, we must ensure that the inode only ever
2160  * has one dentry.  If a dentry is found, that is returned instead of
2161  * allocating a new one.
2162  *
2163  * On successful return, the reference to the inode has been transferred
2164  * to the dentry.  In case of an error the reference on the inode is released.
2165  * To make it easier to use in export operations a %NULL or IS_ERR inode may
2166  * be passed in and the error will be propagated to the return value,
2167  * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
2168  */
2169 struct dentry *d_obtain_alias(struct inode *inode)
2170 {
2171         return __d_obtain_alias(inode, true);
2172 }
2173 EXPORT_SYMBOL(d_obtain_alias);
2174
2175 /**
2176  * d_obtain_root - find or allocate a dentry for a given inode
2177  * @inode: inode to allocate the dentry for
2178  *
2179  * Obtain an IS_ROOT dentry for the root of a filesystem.
2180  *
2181  * We must ensure that directory inodes only ever have one dentry.  If a
2182  * dentry is found, that is returned instead of allocating a new one.
2183  *
2184  * On successful return, the reference to the inode has been transferred
2185  * to the dentry.  In case of an error the reference on the inode is
2186  * released.  A %NULL or IS_ERR inode may be passed in and will be the
2187  * error will be propagate to the return value, with a %NULL @inode
2188  * replaced by ERR_PTR(-ESTALE).
2189  */
2190 struct dentry *d_obtain_root(struct inode *inode)
2191 {
2192         return __d_obtain_alias(inode, false);
2193 }
2194 EXPORT_SYMBOL(d_obtain_root);
2195
2196 /**
2197  * d_add_ci - lookup or allocate new dentry with case-exact name
2198  * @inode:  the inode case-insensitive lookup has found
2199  * @dentry: the negative dentry that was passed to the parent's lookup func
2200  * @name:   the case-exact name to be associated with the returned dentry
2201  *
2202  * This is to avoid filling the dcache with case-insensitive names to the
2203  * same inode, only the actual correct case is stored in the dcache for
2204  * case-insensitive filesystems.
2205  *
2206  * For a case-insensitive lookup match and if the case-exact dentry
2207  * already exists in the dcache, use it and return it.
2208  *
2209  * If no entry exists with the exact case name, allocate new dentry with
2210  * the exact case, and return the spliced entry.
2211  */
2212 struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
2213                         struct qstr *name)
2214 {
2215         struct dentry *found, *res;
2216
2217         /*
2218          * First check if a dentry matching the name already exists,
2219          * if not go ahead and create it now.
2220          */
2221         found = d_hash_and_lookup(dentry->d_parent, name);
2222         if (found) {
2223                 iput(inode);
2224                 return found;
2225         }
2226         if (d_in_lookup(dentry)) {
2227                 found = d_alloc_parallel(dentry->d_parent, name,
2228                                         dentry->d_wait);
2229                 if (IS_ERR(found) || !d_in_lookup(found)) {
2230                         iput(inode);
2231                         return found;
2232                 }
2233         } else {
2234                 found = d_alloc(dentry->d_parent, name);
2235                 if (!found) {
2236                         iput(inode);
2237                         return ERR_PTR(-ENOMEM);
2238                 } 
2239         }
2240         res = d_splice_alias(inode, found);
2241         if (res) {
2242                 d_lookup_done(found);
2243                 dput(found);
2244                 return res;
2245         }
2246         return found;
2247 }
2248 EXPORT_SYMBOL(d_add_ci);
2249
2250 /**
2251  * d_same_name - compare dentry name with case-exact name
2252  * @parent: parent dentry
2253  * @dentry: the negative dentry that was passed to the parent's lookup func
2254  * @name:   the case-exact name to be associated with the returned dentry
2255  *
2256  * Return: true if names are same, or false
2257  */
2258 bool d_same_name(const struct dentry *dentry, const struct dentry *parent,
2259                  const struct qstr *name)
2260 {
2261         if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
2262                 if (dentry->d_name.len != name->len)
2263                         return false;
2264                 return dentry_cmp(dentry, name->name, name->len) == 0;
2265         }
2266         return parent->d_op->d_compare(dentry,
2267                                        dentry->d_name.len, dentry->d_name.name,
2268                                        name) == 0;
2269 }
2270 EXPORT_SYMBOL_GPL(d_same_name);
2271
2272 /*
2273  * This is __d_lookup_rcu() when the parent dentry has
2274  * DCACHE_OP_COMPARE, which makes things much nastier.
2275  */
2276 static noinline struct dentry *__d_lookup_rcu_op_compare(
2277         const struct dentry *parent,
2278         const struct qstr *name,
2279         unsigned *seqp)
2280 {
2281         u64 hashlen = name->hash_len;
2282         struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
2283         struct hlist_bl_node *node;
2284         struct dentry *dentry;
2285
2286         hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2287                 int tlen;
2288                 const char *tname;
2289                 unsigned seq;
2290
2291 seqretry:
2292                 seq = raw_seqcount_begin(&dentry->d_seq);
2293                 if (dentry->d_parent != parent)
2294                         continue;
2295                 if (d_unhashed(dentry))
2296                         continue;
2297                 if (dentry->d_name.hash != hashlen_hash(hashlen))
2298                         continue;
2299                 tlen = dentry->d_name.len;
2300                 tname = dentry->d_name.name;
2301                 /* we want a consistent (name,len) pair */
2302                 if (read_seqcount_retry(&dentry->d_seq, seq)) {
2303                         cpu_relax();
2304                         goto seqretry;
2305                 }
2306                 if (parent->d_op->d_compare(dentry, tlen, tname, name) != 0)
2307                         continue;
2308                 *seqp = seq;
2309                 return dentry;
2310         }
2311         return NULL;
2312 }
2313
2314 /**
2315  * __d_lookup_rcu - search for a dentry (racy, store-free)
2316  * @parent: parent dentry
2317  * @name: qstr of name we wish to find
2318  * @seqp: returns d_seq value at the point where the dentry was found
2319  * Returns: dentry, or NULL
2320  *
2321  * __d_lookup_rcu is the dcache lookup function for rcu-walk name
2322  * resolution (store-free path walking) design described in
2323  * Documentation/filesystems/path-lookup.txt.
2324  *
2325  * This is not to be used outside core vfs.
2326  *
2327  * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
2328  * held, and rcu_read_lock held. The returned dentry must not be stored into
2329  * without taking d_lock and checking d_seq sequence count against @seq
2330  * returned here.
2331  *
2332  * A refcount may be taken on the found dentry with the d_rcu_to_refcount
2333  * function.
2334  *
2335  * Alternatively, __d_lookup_rcu may be called again to look up the child of
2336  * the returned dentry, so long as its parent's seqlock is checked after the
2337  * child is looked up. Thus, an interlocking stepping of sequence lock checks
2338  * is formed, giving integrity down the path walk.
2339  *
2340  * NOTE! The caller *has* to check the resulting dentry against the sequence
2341  * number we've returned before using any of the resulting dentry state!
2342  */
2343 struct dentry *__d_lookup_rcu(const struct dentry *parent,
2344                                 const struct qstr *name,
2345                                 unsigned *seqp)
2346 {
2347         u64 hashlen = name->hash_len;
2348         const unsigned char *str = name->name;
2349         struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
2350         struct hlist_bl_node *node;
2351         struct dentry *dentry;
2352
2353         /*
2354          * Note: There is significant duplication with __d_lookup_rcu which is
2355          * required to prevent single threaded performance regressions
2356          * especially on architectures where smp_rmb (in seqcounts) are costly.
2357          * Keep the two functions in sync.
2358          */
2359
2360         if (unlikely(parent->d_flags & DCACHE_OP_COMPARE))
2361                 return __d_lookup_rcu_op_compare(parent, name, seqp);
2362
2363         /*
2364          * The hash list is protected using RCU.
2365          *
2366          * Carefully use d_seq when comparing a candidate dentry, to avoid
2367          * races with d_move().
2368          *
2369          * It is possible that concurrent renames can mess up our list
2370          * walk here and result in missing our dentry, resulting in the
2371          * false-negative result. d_lookup() protects against concurrent
2372          * renames using rename_lock seqlock.
2373          *
2374          * See Documentation/filesystems/path-lookup.txt for more details.
2375          */
2376         hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2377                 unsigned seq;
2378
2379                 /*
2380                  * The dentry sequence count protects us from concurrent
2381                  * renames, and thus protects parent and name fields.
2382                  *
2383                  * The caller must perform a seqcount check in order
2384                  * to do anything useful with the returned dentry.
2385                  *
2386                  * NOTE! We do a "raw" seqcount_begin here. That means that
2387                  * we don't wait for the sequence count to stabilize if it
2388                  * is in the middle of a sequence change. If we do the slow
2389                  * dentry compare, we will do seqretries until it is stable,
2390                  * and if we end up with a successful lookup, we actually
2391                  * want to exit RCU lookup anyway.
2392                  *
2393                  * Note that raw_seqcount_begin still *does* smp_rmb(), so
2394                  * we are still guaranteed NUL-termination of ->d_name.name.
2395                  */
2396                 seq = raw_seqcount_begin(&dentry->d_seq);
2397                 if (dentry->d_parent != parent)
2398                         continue;
2399                 if (d_unhashed(dentry))
2400                         continue;
2401                 if (dentry->d_name.hash_len != hashlen)
2402                         continue;
2403                 if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
2404                         continue;
2405                 *seqp = seq;
2406                 return dentry;
2407         }
2408         return NULL;
2409 }
2410
2411 /**
2412  * d_lookup - search for a dentry
2413  * @parent: parent dentry
2414  * @name: qstr of name we wish to find
2415  * Returns: dentry, or NULL
2416  *
2417  * d_lookup searches the children of the parent dentry for the name in
2418  * question. If the dentry is found its reference count is incremented and the
2419  * dentry is returned. The caller must use dput to free the entry when it has
2420  * finished using it. %NULL is returned if the dentry does not exist.
2421  */
2422 struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
2423 {
2424         struct dentry *dentry;
2425         unsigned seq;
2426
2427         do {
2428                 seq = read_seqbegin(&rename_lock);
2429                 dentry = __d_lookup(parent, name);
2430                 if (dentry)
2431                         break;
2432         } while (read_seqretry(&rename_lock, seq));
2433         return dentry;
2434 }
2435 EXPORT_SYMBOL(d_lookup);
2436
2437 /**
2438  * __d_lookup - search for a dentry (racy)
2439  * @parent: parent dentry
2440  * @name: qstr of name we wish to find
2441  * Returns: dentry, or NULL
2442  *
2443  * __d_lookup is like d_lookup, however it may (rarely) return a
2444  * false-negative result due to unrelated rename activity.
2445  *
2446  * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
2447  * however it must be used carefully, eg. with a following d_lookup in
2448  * the case of failure.
2449  *
2450  * __d_lookup callers must be commented.
2451  */
2452 struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
2453 {
2454         unsigned int hash = name->hash;
2455         struct hlist_bl_head *b = d_hash(hash);
2456         struct hlist_bl_node *node;
2457         struct dentry *found = NULL;
2458         struct dentry *dentry;
2459
2460         /*
2461          * Note: There is significant duplication with __d_lookup_rcu which is
2462          * required to prevent single threaded performance regressions
2463          * especially on architectures where smp_rmb (in seqcounts) are costly.
2464          * Keep the two functions in sync.
2465          */
2466
2467         /*
2468          * The hash list is protected using RCU.
2469          *
2470          * Take d_lock when comparing a candidate dentry, to avoid races
2471          * with d_move().
2472          *
2473          * It is possible that concurrent renames can mess up our list
2474          * walk here and result in missing our dentry, resulting in the
2475          * false-negative result. d_lookup() protects against concurrent
2476          * renames using rename_lock seqlock.
2477          *
2478          * See Documentation/filesystems/path-lookup.txt for more details.
2479          */
2480         rcu_read_lock();
2481         
2482         hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
2483
2484                 if (dentry->d_name.hash != hash)
2485                         continue;
2486
2487                 spin_lock(&dentry->d_lock);
2488                 if (dentry->d_parent != parent)
2489                         goto next;
2490                 if (d_unhashed(dentry))
2491                         goto next;
2492
2493                 if (!d_same_name(dentry, parent, name))
2494                         goto next;
2495
2496                 dentry->d_lockref.count++;
2497                 found = dentry;
2498                 spin_unlock(&dentry->d_lock);
2499                 break;
2500 next:
2501                 spin_unlock(&dentry->d_lock);
2502         }
2503         rcu_read_unlock();
2504
2505         return found;
2506 }
2507
2508 /**
2509  * d_hash_and_lookup - hash the qstr then search for a dentry
2510  * @dir: Directory to search in
2511  * @name: qstr of name we wish to find
2512  *
2513  * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2514  */
2515 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
2516 {
2517         /*
2518          * Check for a fs-specific hash function. Note that we must
2519          * calculate the standard hash first, as the d_op->d_hash()
2520          * routine may choose to leave the hash value unchanged.
2521          */
2522         name->hash = full_name_hash(dir, name->name, name->len);
2523         if (dir->d_flags & DCACHE_OP_HASH) {
2524                 int err = dir->d_op->d_hash(dir, name);
2525                 if (unlikely(err < 0))
2526                         return ERR_PTR(err);
2527         }
2528         return d_lookup(dir, name);
2529 }
2530 EXPORT_SYMBOL(d_hash_and_lookup);
2531
2532 /*
2533  * When a file is deleted, we have two options:
2534  * - turn this dentry into a negative dentry
2535  * - unhash this dentry and free it.
2536  *
2537  * Usually, we want to just turn this into
2538  * a negative dentry, but if anybody else is
2539  * currently using the dentry or the inode
2540  * we can't do that and we fall back on removing
2541  * it from the hash queues and waiting for
2542  * it to be deleted later when it has no users
2543  */
2544  
2545 /**
2546  * d_delete - delete a dentry
2547  * @dentry: The dentry to delete
2548  *
2549  * Turn the dentry into a negative dentry if possible, otherwise
2550  * remove it from the hash queues so it can be deleted later
2551  */
2552  
2553 void d_delete(struct dentry * dentry)
2554 {
2555         struct inode *inode = dentry->d_inode;
2556
2557         spin_lock(&inode->i_lock);
2558         spin_lock(&dentry->d_lock);
2559         /*
2560          * Are we the only user?
2561          */
2562         if (dentry->d_lockref.count == 1) {
2563                 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
2564                 dentry_unlink_inode(dentry);
2565         } else {
2566                 __d_drop(dentry);
2567                 spin_unlock(&dentry->d_lock);
2568                 spin_unlock(&inode->i_lock);
2569         }
2570 }
2571 EXPORT_SYMBOL(d_delete);
2572
2573 static void __d_rehash(struct dentry *entry)
2574 {
2575         struct hlist_bl_head *b = d_hash(entry->d_name.hash);
2576
2577         hlist_bl_lock(b);
2578         hlist_bl_add_head_rcu(&entry->d_hash, b);
2579         hlist_bl_unlock(b);
2580 }
2581
2582 /**
2583  * d_rehash     - add an entry back to the hash
2584  * @entry: dentry to add to the hash
2585  *
2586  * Adds a dentry to the hash according to its name.
2587  */
2588  
2589 void d_rehash(struct dentry * entry)
2590 {
2591         spin_lock(&entry->d_lock);
2592         __d_rehash(entry);
2593         spin_unlock(&entry->d_lock);
2594 }
2595 EXPORT_SYMBOL(d_rehash);
2596
2597 static inline unsigned start_dir_add(struct inode *dir)
2598 {
2599         preempt_disable_nested();
2600         for (;;) {
2601                 unsigned n = dir->i_dir_seq;
2602                 if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
2603                         return n;
2604                 cpu_relax();
2605         }
2606 }
2607
2608 static inline void end_dir_add(struct inode *dir, unsigned int n,
2609                                wait_queue_head_t *d_wait)
2610 {
2611         smp_store_release(&dir->i_dir_seq, n + 2);
2612         preempt_enable_nested();
2613         wake_up_all(d_wait);
2614 }
2615
2616 static void d_wait_lookup(struct dentry *dentry)
2617 {
2618         if (d_in_lookup(dentry)) {
2619                 DECLARE_WAITQUEUE(wait, current);
2620                 add_wait_queue(dentry->d_wait, &wait);
2621                 do {
2622                         set_current_state(TASK_UNINTERRUPTIBLE);
2623                         spin_unlock(&dentry->d_lock);
2624                         schedule();
2625                         spin_lock(&dentry->d_lock);
2626                 } while (d_in_lookup(dentry));
2627         }
2628 }
2629
2630 struct dentry *d_alloc_parallel(struct dentry *parent,
2631                                 const struct qstr *name,
2632                                 wait_queue_head_t *wq)
2633 {
2634         unsigned int hash = name->hash;
2635         struct hlist_bl_head *b = in_lookup_hash(parent, hash);
2636         struct hlist_bl_node *node;
2637         struct dentry *new = d_alloc(parent, name);
2638         struct dentry *dentry;
2639         unsigned seq, r_seq, d_seq;
2640
2641         if (unlikely(!new))
2642                 return ERR_PTR(-ENOMEM);
2643
2644 retry:
2645         rcu_read_lock();
2646         seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
2647         r_seq = read_seqbegin(&rename_lock);
2648         dentry = __d_lookup_rcu(parent, name, &d_seq);
2649         if (unlikely(dentry)) {
2650                 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2651                         rcu_read_unlock();
2652                         goto retry;
2653                 }
2654                 if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
2655                         rcu_read_unlock();
2656                         dput(dentry);
2657                         goto retry;
2658                 }
2659                 rcu_read_unlock();
2660                 dput(new);
2661                 return dentry;
2662         }
2663         if (unlikely(read_seqretry(&rename_lock, r_seq))) {
2664                 rcu_read_unlock();
2665                 goto retry;
2666         }
2667
2668         if (unlikely(seq & 1)) {
2669                 rcu_read_unlock();
2670                 goto retry;
2671         }
2672
2673         hlist_bl_lock(b);
2674         if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
2675                 hlist_bl_unlock(b);
2676                 rcu_read_unlock();
2677                 goto retry;
2678         }
2679         /*
2680          * No changes for the parent since the beginning of d_lookup().
2681          * Since all removals from the chain happen with hlist_bl_lock(),
2682          * any potential in-lookup matches are going to stay here until
2683          * we unlock the chain.  All fields are stable in everything
2684          * we encounter.
2685          */
2686         hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
2687                 if (dentry->d_name.hash != hash)
2688                         continue;
2689                 if (dentry->d_parent != parent)
2690                         continue;
2691                 if (!d_same_name(dentry, parent, name))
2692                         continue;
2693                 hlist_bl_unlock(b);
2694                 /* now we can try to grab a reference */
2695                 if (!lockref_get_not_dead(&dentry->d_lockref)) {
2696                         rcu_read_unlock();
2697                         goto retry;
2698                 }
2699
2700                 rcu_read_unlock();
2701                 /*
2702                  * somebody is likely to be still doing lookup for it;
2703                  * wait for them to finish
2704                  */
2705                 spin_lock(&dentry->d_lock);
2706                 d_wait_lookup(dentry);
2707                 /*
2708                  * it's not in-lookup anymore; in principle we should repeat
2709                  * everything from dcache lookup, but it's likely to be what
2710                  * d_lookup() would've found anyway.  If it is, just return it;
2711                  * otherwise we really have to repeat the whole thing.
2712                  */
2713                 if (unlikely(dentry->d_name.hash != hash))
2714                         goto mismatch;
2715                 if (unlikely(dentry->d_parent != parent))
2716                         goto mismatch;
2717                 if (unlikely(d_unhashed(dentry)))
2718                         goto mismatch;
2719                 if (unlikely(!d_same_name(dentry, parent, name)))
2720                         goto mismatch;
2721                 /* OK, it *is* a hashed match; return it */
2722                 spin_unlock(&dentry->d_lock);
2723                 dput(new);
2724                 return dentry;
2725         }
2726         rcu_read_unlock();
2727         /* we can't take ->d_lock here; it's OK, though. */
2728         new->d_flags |= DCACHE_PAR_LOOKUP;
2729         new->d_wait = wq;
2730         hlist_bl_add_head_rcu(&new->d_u.d_in_lookup_hash, b);
2731         hlist_bl_unlock(b);
2732         return new;
2733 mismatch:
2734         spin_unlock(&dentry->d_lock);
2735         dput(dentry);
2736         goto retry;
2737 }
2738 EXPORT_SYMBOL(d_alloc_parallel);
2739
2740 /*
2741  * - Unhash the dentry
2742  * - Retrieve and clear the waitqueue head in dentry
2743  * - Return the waitqueue head
2744  */
2745 static wait_queue_head_t *__d_lookup_unhash(struct dentry *dentry)
2746 {
2747         wait_queue_head_t *d_wait;
2748         struct hlist_bl_head *b;
2749
2750         lockdep_assert_held(&dentry->d_lock);
2751
2752         b = in_lookup_hash(dentry->d_parent, dentry->d_name.hash);
2753         hlist_bl_lock(b);
2754         dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
2755         __hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
2756         d_wait = dentry->d_wait;
2757         dentry->d_wait = NULL;
2758         hlist_bl_unlock(b);
2759         INIT_HLIST_NODE(&dentry->d_u.d_alias);
2760         INIT_LIST_HEAD(&dentry->d_lru);
2761         return d_wait;
2762 }
2763
2764 void __d_lookup_unhash_wake(struct dentry *dentry)
2765 {
2766         spin_lock(&dentry->d_lock);
2767         wake_up_all(__d_lookup_unhash(dentry));
2768         spin_unlock(&dentry->d_lock);
2769 }
2770 EXPORT_SYMBOL(__d_lookup_unhash_wake);
2771
2772 /* inode->i_lock held if inode is non-NULL */
2773
2774 static inline void __d_add(struct dentry *dentry, struct inode *inode)
2775 {
2776         wait_queue_head_t *d_wait;
2777         struct inode *dir = NULL;
2778         unsigned n;
2779         spin_lock(&dentry->d_lock);
2780         if (unlikely(d_in_lookup(dentry))) {
2781                 dir = dentry->d_parent->d_inode;
2782                 n = start_dir_add(dir);
2783                 d_wait = __d_lookup_unhash(dentry);
2784         }
2785         if (inode) {
2786                 unsigned add_flags = d_flags_for_inode(inode);
2787                 hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
2788                 raw_write_seqcount_begin(&dentry->d_seq);
2789                 __d_set_inode_and_type(dentry, inode, add_flags);
2790                 raw_write_seqcount_end(&dentry->d_seq);
2791                 fsnotify_update_flags(dentry);
2792         }
2793         __d_rehash(dentry);
2794         if (dir)
2795                 end_dir_add(dir, n, d_wait);
2796         spin_unlock(&dentry->d_lock);
2797         if (inode)
2798                 spin_unlock(&inode->i_lock);
2799 }
2800
2801 /**
2802  * d_add - add dentry to hash queues
2803  * @entry: dentry to add
2804  * @inode: The inode to attach to this dentry
2805  *
2806  * This adds the entry to the hash queues and initializes @inode.
2807  * The entry was actually filled in earlier during d_alloc().
2808  */
2809
2810 void d_add(struct dentry *entry, struct inode *inode)
2811 {
2812         if (inode) {
2813                 security_d_instantiate(entry, inode);
2814                 spin_lock(&inode->i_lock);
2815         }
2816         __d_add(entry, inode);
2817 }
2818 EXPORT_SYMBOL(d_add);
2819
2820 /**
2821  * d_exact_alias - find and hash an exact unhashed alias
2822  * @entry: dentry to add
2823  * @inode: The inode to go with this dentry
2824  *
2825  * If an unhashed dentry with the same name/parent and desired
2826  * inode already exists, hash and return it.  Otherwise, return
2827  * NULL.
2828  *
2829  * Parent directory should be locked.
2830  */
2831 struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
2832 {
2833         struct dentry *alias;
2834         unsigned int hash = entry->d_name.hash;
2835
2836         spin_lock(&inode->i_lock);
2837         hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
2838                 /*
2839                  * Don't need alias->d_lock here, because aliases with
2840                  * d_parent == entry->d_parent are not subject to name or
2841                  * parent changes, because the parent inode i_mutex is held.
2842                  */
2843                 if (alias->d_name.hash != hash)
2844                         continue;
2845                 if (alias->d_parent != entry->d_parent)
2846                         continue;
2847                 if (!d_same_name(alias, entry->d_parent, &entry->d_name))
2848                         continue;
2849                 spin_lock(&alias->d_lock);
2850                 if (!d_unhashed(alias)) {
2851                         spin_unlock(&alias->d_lock);
2852                         alias = NULL;
2853                 } else {
2854                         __dget_dlock(alias);
2855                         __d_rehash(alias);
2856                         spin_unlock(&alias->d_lock);
2857                 }
2858                 spin_unlock(&inode->i_lock);
2859                 return alias;
2860         }
2861         spin_unlock(&inode->i_lock);
2862         return NULL;
2863 }
2864 EXPORT_SYMBOL(d_exact_alias);
2865
2866 static void swap_names(struct dentry *dentry, struct dentry *target)
2867 {
2868         if (unlikely(dname_external(target))) {
2869                 if (unlikely(dname_external(dentry))) {
2870                         /*
2871                          * Both external: swap the pointers
2872                          */
2873                         swap(target->d_name.name, dentry->d_name.name);
2874                 } else {
2875                         /*
2876                          * dentry:internal, target:external.  Steal target's
2877                          * storage and make target internal.
2878                          */
2879                         memcpy(target->d_iname, dentry->d_name.name,
2880                                         dentry->d_name.len + 1);
2881                         dentry->d_name.name = target->d_name.name;
2882                         target->d_name.name = target->d_iname;
2883                 }
2884         } else {
2885                 if (unlikely(dname_external(dentry))) {
2886                         /*
2887                          * dentry:external, target:internal.  Give dentry's
2888                          * storage to target and make dentry internal
2889                          */
2890                         memcpy(dentry->d_iname, target->d_name.name,
2891                                         target->d_name.len + 1);
2892                         target->d_name.name = dentry->d_name.name;
2893                         dentry->d_name.name = dentry->d_iname;
2894                 } else {
2895                         /*
2896                          * Both are internal.
2897                          */
2898                         unsigned int i;
2899                         BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
2900                         for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
2901                                 swap(((long *) &dentry->d_iname)[i],
2902                                      ((long *) &target->d_iname)[i]);
2903                         }
2904                 }
2905         }
2906         swap(dentry->d_name.hash_len, target->d_name.hash_len);
2907 }
2908
2909 static void copy_name(struct dentry *dentry, struct dentry *target)
2910 {
2911         struct external_name *old_name = NULL;
2912         if (unlikely(dname_external(dentry)))
2913                 old_name = external_name(dentry);
2914         if (unlikely(dname_external(target))) {
2915                 atomic_inc(&external_name(target)->u.count);
2916                 dentry->d_name = target->d_name;
2917         } else {
2918                 memcpy(dentry->d_iname, target->d_name.name,
2919                                 target->d_name.len + 1);
2920                 dentry->d_name.name = dentry->d_iname;
2921                 dentry->d_name.hash_len = target->d_name.hash_len;
2922         }
2923         if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
2924                 kfree_rcu(old_name, u.head);
2925 }
2926
2927 /*
2928  * __d_move - move a dentry
2929  * @dentry: entry to move
2930  * @target: new dentry
2931  * @exchange: exchange the two dentries
2932  *
2933  * Update the dcache to reflect the move of a file name. Negative
2934  * dcache entries should not be moved in this way. Caller must hold
2935  * rename_lock, the i_mutex of the source and target directories,
2936  * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
2937  */
2938 static void __d_move(struct dentry *dentry, struct dentry *target,
2939                      bool exchange)
2940 {
2941         struct dentry *old_parent, *p;
2942         wait_queue_head_t *d_wait;
2943         struct inode *dir = NULL;
2944         unsigned n;
2945
2946         WARN_ON(!dentry->d_inode);
2947         if (WARN_ON(dentry == target))
2948                 return;
2949
2950         BUG_ON(d_ancestor(target, dentry));
2951         old_parent = dentry->d_parent;
2952         p = d_ancestor(old_parent, target);
2953         if (IS_ROOT(dentry)) {
2954                 BUG_ON(p);
2955                 spin_lock(&target->d_parent->d_lock);
2956         } else if (!p) {
2957                 /* target is not a descendent of dentry->d_parent */
2958                 spin_lock(&target->d_parent->d_lock);
2959                 spin_lock_nested(&old_parent->d_lock, DENTRY_D_LOCK_NESTED);
2960         } else {
2961                 BUG_ON(p == dentry);
2962                 spin_lock(&old_parent->d_lock);
2963                 if (p != target)
2964                         spin_lock_nested(&target->d_parent->d_lock,
2965                                         DENTRY_D_LOCK_NESTED);
2966         }
2967         spin_lock_nested(&dentry->d_lock, 2);
2968         spin_lock_nested(&target->d_lock, 3);
2969
2970         if (unlikely(d_in_lookup(target))) {
2971                 dir = target->d_parent->d_inode;
2972                 n = start_dir_add(dir);
2973                 d_wait = __d_lookup_unhash(target);
2974         }
2975
2976         write_seqcount_begin(&dentry->d_seq);
2977         write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
2978
2979         /* unhash both */
2980         if (!d_unhashed(dentry))
2981                 ___d_drop(dentry);
2982         if (!d_unhashed(target))
2983                 ___d_drop(target);
2984
2985         /* ... and switch them in the tree */
2986         dentry->d_parent = target->d_parent;
2987         if (!exchange) {
2988                 copy_name(dentry, target);
2989                 target->d_hash.pprev = NULL;
2990                 dentry->d_parent->d_lockref.count++;
2991                 if (dentry != old_parent) /* wasn't IS_ROOT */
2992                         WARN_ON(!--old_parent->d_lockref.count);
2993         } else {
2994                 target->d_parent = old_parent;
2995                 swap_names(dentry, target);
2996                 list_move(&target->d_child, &target->d_parent->d_subdirs);
2997                 __d_rehash(target);
2998                 fsnotify_update_flags(target);
2999         }
3000         list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
3001         __d_rehash(dentry);
3002         fsnotify_update_flags(dentry);
3003         fscrypt_handle_d_move(dentry);
3004
3005         write_seqcount_end(&target->d_seq);
3006         write_seqcount_end(&dentry->d_seq);
3007
3008         if (dir)
3009                 end_dir_add(dir, n, d_wait);
3010
3011         if (dentry->d_parent != old_parent)
3012                 spin_unlock(&dentry->d_parent->d_lock);
3013         if (dentry != old_parent)
3014                 spin_unlock(&old_parent->d_lock);
3015         spin_unlock(&target->d_lock);
3016         spin_unlock(&dentry->d_lock);
3017 }
3018
3019 /*
3020  * d_move - move a dentry
3021  * @dentry: entry to move
3022  * @target: new dentry
3023  *
3024  * Update the dcache to reflect the move of a file name. Negative
3025  * dcache entries should not be moved in this way. See the locking
3026  * requirements for __d_move.
3027  */
3028 void d_move(struct dentry *dentry, struct dentry *target)
3029 {
3030         write_seqlock(&rename_lock);
3031         __d_move(dentry, target, false);
3032         write_sequnlock(&rename_lock);
3033 }
3034 EXPORT_SYMBOL(d_move);
3035
3036 /*
3037  * d_exchange - exchange two dentries
3038  * @dentry1: first dentry
3039  * @dentry2: second dentry
3040  */
3041 void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
3042 {
3043         write_seqlock(&rename_lock);
3044
3045         WARN_ON(!dentry1->d_inode);
3046         WARN_ON(!dentry2->d_inode);
3047         WARN_ON(IS_ROOT(dentry1));
3048         WARN_ON(IS_ROOT(dentry2));
3049
3050         __d_move(dentry1, dentry2, true);
3051
3052         write_sequnlock(&rename_lock);
3053 }
3054
3055 /**
3056  * d_ancestor - search for an ancestor
3057  * @p1: ancestor dentry
3058  * @p2: child dentry
3059  *
3060  * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
3061  * an ancestor of p2, else NULL.
3062  */
3063 struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
3064 {
3065         struct dentry *p;
3066
3067         for (p = p2; !IS_ROOT(p); p = p->d_parent) {
3068                 if (p->d_parent == p1)
3069                         return p;
3070         }
3071         return NULL;
3072 }
3073
3074 /*
3075  * This helper attempts to cope with remotely renamed directories
3076  *
3077  * It assumes that the caller is already holding
3078  * dentry->d_parent->d_inode->i_mutex, and rename_lock
3079  *
3080  * Note: If ever the locking in lock_rename() changes, then please
3081  * remember to update this too...
3082  */
3083 static int __d_unalias(struct inode *inode,
3084                 struct dentry *dentry, struct dentry *alias)
3085 {
3086         struct mutex *m1 = NULL;
3087         struct rw_semaphore *m2 = NULL;
3088         int ret = -ESTALE;
3089
3090         /* If alias and dentry share a parent, then no extra locks required */
3091         if (alias->d_parent == dentry->d_parent)
3092                 goto out_unalias;
3093
3094         /* See lock_rename() */
3095         if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
3096                 goto out_err;
3097         m1 = &dentry->d_sb->s_vfs_rename_mutex;
3098         if (!inode_trylock_shared(alias->d_parent->d_inode))
3099                 goto out_err;
3100         m2 = &alias->d_parent->d_inode->i_rwsem;
3101 out_unalias:
3102         __d_move(alias, dentry, false);
3103         ret = 0;
3104 out_err:
3105         if (m2)
3106                 up_read(m2);
3107         if (m1)
3108                 mutex_unlock(m1);
3109         return ret;
3110 }
3111
3112 /**
3113  * d_splice_alias - splice a disconnected dentry into the tree if one exists
3114  * @inode:  the inode which may have a disconnected dentry
3115  * @dentry: a negative dentry which we want to point to the inode.
3116  *
3117  * If inode is a directory and has an IS_ROOT alias, then d_move that in
3118  * place of the given dentry and return it, else simply d_add the inode
3119  * to the dentry and return NULL.
3120  *
3121  * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
3122  * we should error out: directories can't have multiple aliases.
3123  *
3124  * This is needed in the lookup routine of any filesystem that is exportable
3125  * (via knfsd) so that we can build dcache paths to directories effectively.
3126  *
3127  * If a dentry was found and moved, then it is returned.  Otherwise NULL
3128  * is returned.  This matches the expected return value of ->lookup.
3129  *
3130  * Cluster filesystems may call this function with a negative, hashed dentry.
3131  * In that case, we know that the inode will be a regular file, and also this
3132  * will only occur during atomic_open. So we need to check for the dentry
3133  * being already hashed only in the final case.
3134  */
3135 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
3136 {
3137         if (IS_ERR(inode))
3138                 return ERR_CAST(inode);
3139
3140         BUG_ON(!d_unhashed(dentry));
3141
3142         if (!inode)
3143                 goto out;
3144
3145         security_d_instantiate(dentry, inode);
3146         spin_lock(&inode->i_lock);
3147         if (S_ISDIR(inode->i_mode)) {
3148                 struct dentry *new = __d_find_any_alias(inode);
3149                 if (unlikely(new)) {
3150                         /* The reference to new ensures it remains an alias */
3151                         spin_unlock(&inode->i_lock);
3152                         write_seqlock(&rename_lock);
3153                         if (unlikely(d_ancestor(new, dentry))) {
3154                                 write_sequnlock(&rename_lock);
3155                                 dput(new);
3156                                 new = ERR_PTR(-ELOOP);
3157                                 pr_warn_ratelimited(
3158                                         "VFS: Lookup of '%s' in %s %s"
3159                                         " would have caused loop\n",
3160                                         dentry->d_name.name,
3161                                         inode->i_sb->s_type->name,
3162                                         inode->i_sb->s_id);
3163                         } else if (!IS_ROOT(new)) {
3164                                 struct dentry *old_parent = dget(new->d_parent);
3165                                 int err = __d_unalias(inode, dentry, new);
3166                                 write_sequnlock(&rename_lock);
3167                                 if (err) {
3168                                         dput(new);
3169                                         new = ERR_PTR(err);
3170                                 }
3171                                 dput(old_parent);
3172                         } else {
3173                                 __d_move(new, dentry, false);
3174                                 write_sequnlock(&rename_lock);
3175                         }
3176                         iput(inode);
3177                         return new;
3178                 }
3179         }
3180 out:
3181         __d_add(dentry, inode);
3182         return NULL;
3183 }
3184 EXPORT_SYMBOL(d_splice_alias);
3185
3186 /*
3187  * Test whether new_dentry is a subdirectory of old_dentry.
3188  *
3189  * Trivially implemented using the dcache structure
3190  */
3191
3192 /**
3193  * is_subdir - is new dentry a subdirectory of old_dentry
3194  * @new_dentry: new dentry
3195  * @old_dentry: old dentry
3196  *
3197  * Returns true if new_dentry is a subdirectory of the parent (at any depth).
3198  * Returns false otherwise.
3199  * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
3200  */
3201   
3202 bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
3203 {
3204         bool result;
3205         unsigned seq;
3206
3207         if (new_dentry == old_dentry)
3208                 return true;
3209
3210         do {
3211                 /* for restarting inner loop in case of seq retry */
3212                 seq = read_seqbegin(&rename_lock);
3213                 /*
3214                  * Need rcu_readlock to protect against the d_parent trashing
3215                  * due to d_move
3216                  */
3217                 rcu_read_lock();
3218                 if (d_ancestor(old_dentry, new_dentry))
3219                         result = true;
3220                 else
3221                         result = false;
3222                 rcu_read_unlock();
3223         } while (read_seqretry(&rename_lock, seq));
3224
3225         return result;
3226 }
3227 EXPORT_SYMBOL(is_subdir);
3228
3229 static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
3230 {
3231         struct dentry *root = data;
3232         if (dentry != root) {
3233                 if (d_unhashed(dentry) || !dentry->d_inode)
3234                         return D_WALK_SKIP;
3235
3236                 if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
3237                         dentry->d_flags |= DCACHE_GENOCIDE;
3238                         dentry->d_lockref.count--;
3239                 }
3240         }
3241         return D_WALK_CONTINUE;
3242 }
3243
3244 void d_genocide(struct dentry *parent)
3245 {
3246         d_walk(parent, parent, d_genocide_kill);
3247 }
3248
3249 void d_tmpfile(struct file *file, struct inode *inode)
3250 {
3251         struct dentry *dentry = file->f_path.dentry;
3252
3253         inode_dec_link_count(inode);
3254         BUG_ON(dentry->d_name.name != dentry->d_iname ||
3255                 !hlist_unhashed(&dentry->d_u.d_alias) ||
3256                 !d_unlinked(dentry));
3257         spin_lock(&dentry->d_parent->d_lock);
3258         spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
3259         dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
3260                                 (unsigned long long)inode->i_ino);
3261         spin_unlock(&dentry->d_lock);
3262         spin_unlock(&dentry->d_parent->d_lock);
3263         d_instantiate(dentry, inode);
3264 }
3265 EXPORT_SYMBOL(d_tmpfile);
3266
3267 static __initdata unsigned long dhash_entries;
3268 static int __init set_dhash_entries(char *str)
3269 {
3270         if (!str)
3271                 return 0;
3272         dhash_entries = simple_strtoul(str, &str, 0);
3273         return 1;
3274 }
3275 __setup("dhash_entries=", set_dhash_entries);
3276
3277 static void __init dcache_init_early(void)
3278 {
3279         /* If hashes are distributed across NUMA nodes, defer
3280          * hash allocation until vmalloc space is available.
3281          */
3282         if (hashdist)
3283                 return;
3284
3285         dentry_hashtable =
3286                 alloc_large_system_hash("Dentry cache",
3287                                         sizeof(struct hlist_bl_head),
3288                                         dhash_entries,
3289                                         13,
3290                                         HASH_EARLY | HASH_ZERO,
3291                                         &d_hash_shift,
3292                                         NULL,
3293                                         0,
3294                                         0);
3295         d_hash_shift = 32 - d_hash_shift;
3296 }
3297
3298 static void __init dcache_init(void)
3299 {
3300         /*
3301          * A constructor could be added for stable state like the lists,
3302          * but it is probably not worth it because of the cache nature
3303          * of the dcache.
3304          */
3305         dentry_cache = KMEM_CACHE_USERCOPY(dentry,
3306                 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT,
3307                 d_iname);
3308
3309         /* Hash may have been set up in dcache_init_early */
3310         if (!hashdist)
3311                 return;
3312
3313         dentry_hashtable =
3314                 alloc_large_system_hash("Dentry cache",
3315                                         sizeof(struct hlist_bl_head),
3316                                         dhash_entries,
3317                                         13,
3318                                         HASH_ZERO,
3319                                         &d_hash_shift,
3320                                         NULL,
3321                                         0,
3322                                         0);
3323         d_hash_shift = 32 - d_hash_shift;
3324 }
3325
3326 /* SLAB cache for __getname() consumers */
3327 struct kmem_cache *names_cachep __read_mostly;
3328 EXPORT_SYMBOL(names_cachep);
3329
3330 void __init vfs_caches_init_early(void)
3331 {
3332         int i;
3333
3334         for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++)
3335                 INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]);
3336
3337         dcache_init_early();
3338         inode_init_early();
3339 }
3340
3341 void __init vfs_caches_init(void)
3342 {
3343         names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0,
3344                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL);
3345
3346         dcache_init();
3347         inode_init();
3348         files_init();
3349         files_maxfiles_init();
3350         mnt_init();
3351         bdev_cache_init();
3352         chrdev_init();
3353 }