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Linux/fs/dcache.c

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

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