Linux kernel & device driver programming

Cross-Referenced Linux and Device Driver Code

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Version: [ 2.6.11.8 ] [ 2.6.25 ] [ 2.6.25.8 ] [ 2.6.31.13 ] Architecture: [ i386 ]
  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/module.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 "internal.h"
 35 
 36 
 37 int sysctl_vfs_cache_pressure __read_mostly = 100;
 38 EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
 39 
 40  __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
 41 __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
 42 
 43 EXPORT_SYMBOL(dcache_lock);
 44 
 45 static struct kmem_cache *dentry_cache __read_mostly;
 46 
 47 #define DNAME_INLINE_LEN (sizeof(struct dentry)-offsetof(struct dentry,d_iname))
 48 
 49 /*
 50  * This is the single most critical data structure when it comes
 51  * to the dcache: the hashtable for lookups. Somebody should try
 52  * to make this good - I've just made it work.
 53  *
 54  * This hash-function tries to avoid losing too many bits of hash
 55  * information, yet avoid using a prime hash-size or similar.
 56  */
 57 #define D_HASHBITS     d_hash_shift
 58 #define D_HASHMASK     d_hash_mask
 59 
 60 static unsigned int d_hash_mask __read_mostly;
 61 static unsigned int d_hash_shift __read_mostly;
 62 static struct hlist_head *dentry_hashtable __read_mostly;
 63 static LIST_HEAD(dentry_unused);
 64 
 65 /* Statistics gathering. */
 66 struct dentry_stat_t dentry_stat = {
 67         .age_limit = 45,
 68 };
 69 
 70 static void __d_free(struct dentry *dentry)
 71 {
 72         if (dname_external(dentry))
 73                 kfree(dentry->d_name.name);
 74         kmem_cache_free(dentry_cache, dentry); 
 75 }
 76 
 77 static void d_callback(struct rcu_head *head)
 78 {
 79         struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
 80         __d_free(dentry);
 81 }
 82 
 83 /*
 84  * no dcache_lock, please.  The caller must decrement dentry_stat.nr_dentry
 85  * inside dcache_lock.
 86  */
 87 static void d_free(struct dentry *dentry)
 88 {
 89         if (dentry->d_op && dentry->d_op->d_release)
 90                 dentry->d_op->d_release(dentry);
 91         /* if dentry was never inserted into hash, immediate free is OK */
 92         if (hlist_unhashed(&dentry->d_hash))
 93                 __d_free(dentry);
 94         else
 95                 call_rcu(&dentry->d_u.d_rcu, d_callback);
 96 }
 97 
 98 static void dentry_lru_remove(struct dentry *dentry)
 99 {
100         if (!list_empty(&dentry->d_lru)) {
101                 list_del_init(&dentry->d_lru);
102                 dentry_stat.nr_unused--;
103         }
104 }
105 
106 /*
107  * Release the dentry's inode, using the filesystem
108  * d_iput() operation if defined.
109  * Called with dcache_lock and per dentry lock held, drops both.
110  */
111 static void dentry_iput(struct dentry * dentry)
112 {
113         struct inode *inode = dentry->d_inode;
114         if (inode) {
115                 dentry->d_inode = NULL;
116                 list_del_init(&dentry->d_alias);
117                 spin_unlock(&dentry->d_lock);
118                 spin_unlock(&dcache_lock);
119                 if (!inode->i_nlink)
120                         fsnotify_inoderemove(inode);
121                 if (dentry->d_op && dentry->d_op->d_iput)
122                         dentry->d_op->d_iput(dentry, inode);
123                 else
124                         iput(inode);
125         } else {
126                 spin_unlock(&dentry->d_lock);
127                 spin_unlock(&dcache_lock);
128         }
129 }
130 
131 /**
132  * d_kill - kill dentry and return parent
133  * @dentry: dentry to kill
134  *
135  * Called with dcache_lock and d_lock, releases both.  The dentry must
136  * already be unhashed and removed from the LRU.
137  *
138  * If this is the root of the dentry tree, return NULL.
139  */
140 static struct dentry *d_kill(struct dentry *dentry)
141 {
142         struct dentry *parent;
143 
144         list_del(&dentry->d_u.d_child);
145         dentry_stat.nr_dentry--;        /* For d_free, below */
146         /*drops the locks, at that point nobody can reach this dentry */
147         dentry_iput(dentry);
148         parent = dentry->d_parent;
149         d_free(dentry);
150         return dentry == parent ? NULL : parent;
151 }
152 
153 /* 
154  * This is dput
155  *
156  * This is complicated by the fact that we do not want to put
157  * dentries that are no longer on any hash chain on the unused
158  * list: we'd much rather just get rid of them immediately.
159  *
160  * However, that implies that we have to traverse the dentry
161  * tree upwards to the parents which might _also_ now be
162  * scheduled for deletion (it may have been only waiting for
163  * its last child to go away).
164  *
165  * This tail recursion is done by hand as we don't want to depend
166  * on the compiler to always get this right (gcc generally doesn't).
167  * Real recursion would eat up our stack space.
168  */
169 
170 /*
171  * dput - release a dentry
172  * @dentry: dentry to release 
173  *
174  * Release a dentry. This will drop the usage count and if appropriate
175  * call the dentry unlink method as well as removing it from the queues and
176  * releasing its resources. If the parent dentries were scheduled for release
177  * they too may now get deleted.
178  *
179  * no dcache lock, please.
180  */
181 
182 void dput(struct dentry *dentry)
183 {
184         if (!dentry)
185                 return;
186 
187 repeat:
188         if (atomic_read(&dentry->d_count) == 1)
189                 might_sleep();
190         if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
191                 return;
192 
193         spin_lock(&dentry->d_lock);
194         if (atomic_read(&dentry->d_count)) {
195                 spin_unlock(&dentry->d_lock);
196                 spin_unlock(&dcache_lock);
197                 return;
198         }
199 
200         /*
201          * AV: ->d_delete() is _NOT_ allowed to block now.
202          */
203         if (dentry->d_op && dentry->d_op->d_delete) {
204                 if (dentry->d_op->d_delete(dentry))
205                         goto unhash_it;
206         }
207         /* Unreachable? Get rid of it */
208         if (d_unhashed(dentry))
209                 goto kill_it;
210         if (list_empty(&dentry->d_lru)) {
211                 dentry->d_flags |= DCACHE_REFERENCED;
212                 list_add(&dentry->d_lru, &dentry_unused);
213                 dentry_stat.nr_unused++;
214         }
215         spin_unlock(&dentry->d_lock);
216         spin_unlock(&dcache_lock);
217         return;
218 
219 unhash_it:
220         __d_drop(dentry);
221 kill_it:
222         dentry_lru_remove(dentry);
223         dentry = d_kill(dentry);
224         if (dentry)
225                 goto repeat;
226 }
227 
228 /**
229  * d_invalidate - invalidate a dentry
230  * @dentry: dentry to invalidate
231  *
232  * Try to invalidate the dentry if it turns out to be
233  * possible. If there are other dentries that can be
234  * reached through this one we can't delete it and we
235  * return -EBUSY. On success we return 0.
236  *
237  * no dcache lock.
238  */
239  
240 int d_invalidate(struct dentry * dentry)
241 {
242         /*
243          * If it's already been dropped, return OK.
244          */
245         spin_lock(&dcache_lock);
246         if (d_unhashed(dentry)) {
247                 spin_unlock(&dcache_lock);
248                 return 0;
249         }
250         /*
251          * Check whether to do a partial shrink_dcache
252          * to get rid of unused child entries.
253          */
254         if (!list_empty(&dentry->d_subdirs)) {
255                 spin_unlock(&dcache_lock);
256                 shrink_dcache_parent(dentry);
257                 spin_lock(&dcache_lock);
258         }
259 
260         /*
261          * Somebody else still using it?
262          *
263          * If it's a directory, we can't drop it
264          * for fear of somebody re-populating it
265          * with children (even though dropping it
266          * would make it unreachable from the root,
267          * we might still populate it if it was a
268          * working directory or similar).
269          */
270         spin_lock(&dentry->d_lock);
271         if (atomic_read(&dentry->d_count) > 1) {
272                 if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
273                         spin_unlock(&dentry->d_lock);
274                         spin_unlock(&dcache_lock);
275                         return -EBUSY;
276                 }
277         }
278 
279         __d_drop(dentry);
280         spin_unlock(&dentry->d_lock);
281         spin_unlock(&dcache_lock);
282         return 0;
283 }
284 
285 /* This should be called _only_ with dcache_lock held */
286 
287 static inline struct dentry * __dget_locked(struct dentry *dentry)
288 {
289         atomic_inc(&dentry->d_count);
290         dentry_lru_remove(dentry);
291         return dentry;
292 }
293 
294 struct dentry * dget_locked(struct dentry *dentry)
295 {
296         return __dget_locked(dentry);
297 }
298 
299 /**
300  * d_find_alias - grab a hashed alias of inode
301  * @inode: inode in question
302  * @want_discon:  flag, used by d_splice_alias, to request
303  *          that only a DISCONNECTED alias be returned.
304  *
305  * If inode has a hashed alias, or is a directory and has any alias,
306  * acquire the reference to alias and return it. Otherwise return NULL.
307  * Notice that if inode is a directory there can be only one alias and
308  * it can be unhashed only if it has no children, or if it is the root
309  * of a filesystem.
310  *
311  * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
312  * any other hashed alias over that one unless @want_discon is set,
313  * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
314  */
315 
316 static struct dentry * __d_find_alias(struct inode *inode, int want_discon)
317 {
318         struct list_head *head, *next, *tmp;
319         struct dentry *alias, *discon_alias=NULL;
320 
321         head = &inode->i_dentry;
322         next = inode->i_dentry.next;
323         while (next != head) {
324                 tmp = next;
325                 next = tmp->next;
326                 prefetch(next);
327                 alias = list_entry(tmp, struct dentry, d_alias);
328                 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
329                         if (IS_ROOT(alias) &&
330                             (alias->d_flags & DCACHE_DISCONNECTED))
331                                 discon_alias = alias;
332                         else if (!want_discon) {
333                                 __dget_locked(alias);
334                                 return alias;
335                         }
336                 }
337         }
338         if (discon_alias)
339                 __dget_locked(discon_alias);
340         return discon_alias;
341 }
342 
343 struct dentry * d_find_alias(struct inode *inode)
344 {
345         struct dentry *de = NULL;
346 
347         if (!list_empty(&inode->i_dentry)) {
348                 spin_lock(&dcache_lock);
349                 de = __d_find_alias(inode, 0);
350                 spin_unlock(&dcache_lock);
351         }
352         return de;
353 }
354 
355 /*
356  *      Try to kill dentries associated with this inode.
357  * WARNING: you must own a reference to inode.
358  */
359 void d_prune_aliases(struct inode *inode)
360 {
361         struct dentry *dentry;
362 restart:
363         spin_lock(&dcache_lock);
364         list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
365                 spin_lock(&dentry->d_lock);
366                 if (!atomic_read(&dentry->d_count)) {
367                         __dget_locked(dentry);
368                         __d_drop(dentry);
369                         spin_unlock(&dentry->d_lock);
370                         spin_unlock(&dcache_lock);
371                         dput(dentry);
372                         goto restart;
373                 }
374                 spin_unlock(&dentry->d_lock);
375         }
376         spin_unlock(&dcache_lock);
377 }
378 
379 /*
380  * Throw away a dentry - free the inode, dput the parent.  This requires that
381  * the LRU list has already been removed.
382  *
383  * Try to prune ancestors as well.  This is necessary to prevent
384  * quadratic behavior of shrink_dcache_parent(), but is also expected
385  * to be beneficial in reducing dentry cache fragmentation.
386  *
387  * Called with dcache_lock, drops it and then regains.
388  * Called with dentry->d_lock held, drops it.
389  */
390 static void prune_one_dentry(struct dentry * dentry)
391 {
392         __d_drop(dentry);
393         dentry = d_kill(dentry);
394 
395         /*
396          * Prune ancestors.  Locking is simpler than in dput(),
397          * because dcache_lock needs to be taken anyway.
398          */
399         spin_lock(&dcache_lock);
400         while (dentry) {
401                 if (!atomic_dec_and_lock(&dentry->d_count, &dentry->d_lock))
402                         return;
403 
404                 if (dentry->d_op && dentry->d_op->d_delete)
405                         dentry->d_op->d_delete(dentry);
406                 dentry_lru_remove(dentry);
407                 __d_drop(dentry);
408                 dentry = d_kill(dentry);
409                 spin_lock(&dcache_lock);
410         }
411 }
412 
413 /**
414  * prune_dcache - shrink the dcache
415  * @count: number of entries to try and free
416  * @sb: if given, ignore dentries for other superblocks
417  *         which are being unmounted.
418  *
419  * Shrink the dcache. This is done when we need
420  * more memory, or simply when we need to unmount
421  * something (at which point we need to unuse
422  * all dentries).
423  *
424  * This function may fail to free any resources if
425  * all the dentries are in use.
426  */
427  
428 static void prune_dcache(int count, struct super_block *sb)
429 {
430         spin_lock(&dcache_lock);
431         for (; count ; count--) {
432                 struct dentry *dentry;
433                 struct list_head *tmp;
434                 struct rw_semaphore *s_umount;
435 
436                 cond_resched_lock(&dcache_lock);
437 
438                 tmp = dentry_unused.prev;
439                 if (sb) {
440                         /* Try to find a dentry for this sb, but don't try
441                          * too hard, if they aren't near the tail they will
442                          * be moved down again soon
443                          */
444                         int skip = count;
445                         while (skip && tmp != &dentry_unused &&
446                             list_entry(tmp, struct dentry, d_lru)->d_sb != sb) {
447                                 skip--;
448                                 tmp = tmp->prev;
449                         }
450                 }
451                 if (tmp == &dentry_unused)
452                         break;
453                 list_del_init(tmp);
454                 prefetch(dentry_unused.prev);
455                 dentry_stat.nr_unused--;
456                 dentry = list_entry(tmp, struct dentry, d_lru);
457 
458                 spin_lock(&dentry->d_lock);
459                 /*
460                  * We found an inuse dentry which was not removed from
461                  * dentry_unused because of laziness during lookup.  Do not free
462                  * it - just keep it off the dentry_unused list.
463                  */
464                 if (atomic_read(&dentry->d_count)) {
465                         spin_unlock(&dentry->d_lock);
466                         continue;
467                 }
468                 /* If the dentry was recently referenced, don't free it. */
469                 if (dentry->d_flags & DCACHE_REFERENCED) {
470                         dentry->d_flags &= ~DCACHE_REFERENCED;
471                         list_add(&dentry->d_lru, &dentry_unused);
472                         dentry_stat.nr_unused++;
473                         spin_unlock(&dentry->d_lock);
474                         continue;
475                 }
476                 /*
477                  * If the dentry is not DCACHED_REFERENCED, it is time
478                  * to remove it from the dcache, provided the super block is
479                  * NULL (which means we are trying to reclaim memory)
480                  * or this dentry belongs to the same super block that
481                  * we want to shrink.
482                  */
483                 /*
484                  * If this dentry is for "my" filesystem, then I can prune it
485                  * without taking the s_umount lock (I already hold it).
486                  */
487                 if (sb && dentry->d_sb == sb) {
488                         prune_one_dentry(dentry);
489                         continue;
490                 }
491                 /*
492                  * ...otherwise we need to be sure this filesystem isn't being
493                  * unmounted, otherwise we could race with
494                  * generic_shutdown_super(), and end up holding a reference to
495                  * an inode while the filesystem is unmounted.
496                  * So we try to get s_umount, and make sure s_root isn't NULL.
497                  * (Take a local copy of s_umount to avoid a use-after-free of
498                  * `dentry').
499                  */
500                 s_umount = &dentry->d_sb->s_umount;
501                 if (down_read_trylock(s_umount)) {
502                         if (dentry->d_sb->s_root != NULL) {
503                                 prune_one_dentry(dentry);
504                                 up_read(s_umount);
505                                 continue;
506                         }
507                         up_read(s_umount);
508                 }
509                 spin_unlock(&dentry->d_lock);
510                 /*
511                  * Insert dentry at the head of the list as inserting at the
512                  * tail leads to a cycle.
513                  */
514                 list_add(&dentry->d_lru, &dentry_unused);
515                 dentry_stat.nr_unused++;
516         }
517         spin_unlock(&dcache_lock);
518 }
519 
520 /*
521  * Shrink the dcache for the specified super block.
522  * This allows us to unmount a device without disturbing
523  * the dcache for the other devices.
524  *
525  * This implementation makes just two traversals of the
526  * unused list.  On the first pass we move the selected
527  * dentries to the most recent end, and on the second
528  * pass we free them.  The second pass must restart after
529  * each dput(), but since the target dentries are all at
530  * the end, it's really just a single traversal.
531  */
532 
533 /**
534  * shrink_dcache_sb - shrink dcache for a superblock
535  * @sb: superblock
536  *
537  * Shrink the dcache for the specified super block. This
538  * is used to free the dcache before unmounting a file
539  * system
540  */
541 
542 void shrink_dcache_sb(struct super_block * sb)
543 {
544         struct list_head *tmp, *next;
545         struct dentry *dentry;
546 
547         /*
548          * Pass one ... move the dentries for the specified
549          * superblock to the most recent end of the unused list.
550          */
551         spin_lock(&dcache_lock);
552         list_for_each_prev_safe(tmp, next, &dentry_unused) {
553                 dentry = list_entry(tmp, struct dentry, d_lru);
554                 if (dentry->d_sb != sb)
555                         continue;
556                 list_move_tail(tmp, &dentry_unused);
557         }
558 
559         /*
560          * Pass two ... free the dentries for this superblock.
561          */
562 repeat:
563         list_for_each_prev_safe(tmp, next, &dentry_unused) {
564                 dentry = list_entry(tmp, struct dentry, d_lru);
565                 if (dentry->d_sb != sb)
566                         continue;
567                 dentry_stat.nr_unused--;
568                 list_del_init(tmp);
569                 spin_lock(&dentry->d_lock);
570                 if (atomic_read(&dentry->d_count)) {
571                         spin_unlock(&dentry->d_lock);
572                         continue;
573                 }
574                 prune_one_dentry(dentry);
575                 cond_resched_lock(&dcache_lock);
576                 goto repeat;
577         }
578         spin_unlock(&dcache_lock);
579 }
580 
581 /*
582  * destroy a single subtree of dentries for unmount
583  * - see the comments on shrink_dcache_for_umount() for a description of the
584  *   locking
585  */
586 static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
587 {
588         struct dentry *parent;
589         unsigned detached = 0;
590 
591         BUG_ON(!IS_ROOT(dentry));
592 
593         /* detach this root from the system */
594         spin_lock(&dcache_lock);
595         dentry_lru_remove(dentry);
596         __d_drop(dentry);
597         spin_unlock(&dcache_lock);
598 
599         for (;;) {
600                 /* descend to the first leaf in the current subtree */
601                 while (!list_empty(&dentry->d_subdirs)) {
602                         struct dentry *loop;
603 
604                         /* this is a branch with children - detach all of them
605                          * from the system in one go */
606                         spin_lock(&dcache_lock);
607                         list_for_each_entry(loop, &dentry->d_subdirs,
608                                             d_u.d_child) {
609                                 dentry_lru_remove(loop);
610                                 __d_drop(loop);
611                                 cond_resched_lock(&dcache_lock);
612                         }
613                         spin_unlock(&dcache_lock);
614 
615                         /* move to the first child */
616                         dentry = list_entry(dentry->d_subdirs.next,
617                                             struct dentry, d_u.d_child);
618                 }
619 
620                 /* consume the dentries from this leaf up through its parents
621                  * until we find one with children or run out altogether */
622                 do {
623                         struct inode *inode;
624 
625                         if (atomic_read(&dentry->d_count) != 0) {
626                                 printk(KERN_ERR
627                                        "BUG: Dentry %p{i=%lx,n=%s}"
628                                        " still in use (%d)"
629                                        " [unmount of %s %s]\n",
630                                        dentry,
631                                        dentry->d_inode ?
632                                        dentry->d_inode->i_ino : 0UL,
633                                        dentry->d_name.name,
634                                        atomic_read(&dentry->d_count),
635                                        dentry->d_sb->s_type->name,
636                                        dentry->d_sb->s_id);
637                                 BUG();
638                         }
639 
640                         parent = dentry->d_parent;
641                         if (parent == dentry)
642                                 parent = NULL;
643                         else
644                                 atomic_dec(&parent->d_count);
645 
646                         list_del(&dentry->d_u.d_child);
647                         detached++;
648 
649                         inode = dentry->d_inode;
650                         if (inode) {
651                                 dentry->d_inode = NULL;
652                                 list_del_init(&dentry->d_alias);
653                                 if (dentry->d_op && dentry->d_op->d_iput)
654                                         dentry->d_op->d_iput(dentry, inode);
655                                 else
656                                         iput(inode);
657                         }
658 
659                         d_free(dentry);
660 
661                         /* finished when we fall off the top of the tree,
662                          * otherwise we ascend to the parent and move to the
663                          * next sibling if there is one */
664                         if (!parent)
665                                 goto out;
666 
667                         dentry = parent;
668 
669                 } while (list_empty(&dentry->d_subdirs));
670 
671                 dentry = list_entry(dentry->d_subdirs.next,
672                                     struct dentry, d_u.d_child);
673         }
674 out:
675         /* several dentries were freed, need to correct nr_dentry */
676         spin_lock(&dcache_lock);
677         dentry_stat.nr_dentry -= detached;
678         spin_unlock(&dcache_lock);
679 }
680 
681 /*
682  * destroy the dentries attached to a superblock on unmounting
683  * - we don't need to use dentry->d_lock, and only need dcache_lock when
684  *   removing the dentry from the system lists and hashes because:
685  *   - the superblock is detached from all mountings and open files, so the
686  *     dentry trees will not be rearranged by the VFS
687  *   - s_umount is write-locked, so the memory pressure shrinker will ignore
688  *     any dentries belonging to this superblock that it comes across
689  *   - the filesystem itself is no longer permitted to rearrange the dentries
690  *     in this superblock
691  */
692 void shrink_dcache_for_umount(struct super_block *sb)
693 {
694         struct dentry *dentry;
695 
696         if (down_read_trylock(&sb->s_umount))
697                 BUG();
698 
699         dentry = sb->s_root;
700         sb->s_root = NULL;
701         atomic_dec(&dentry->d_count);
702         shrink_dcache_for_umount_subtree(dentry);
703 
704         while (!hlist_empty(&sb->s_anon)) {
705                 dentry = hlist_entry(sb->s_anon.first, struct dentry, d_hash);
706                 shrink_dcache_for_umount_subtree(dentry);
707         }
708 }
709 
710 /*
711  * Search for at least 1 mount point in the dentry's subdirs.
712  * We descend to the next level whenever the d_subdirs
713  * list is non-empty and continue searching.
714  */
715  
716 /**
717  * have_submounts - check for mounts over a dentry
718  * @parent: dentry to check.
719  *
720  * Return true if the parent or its subdirectories contain
721  * a mount point
722  */
723  
724 int have_submounts(struct dentry *parent)
725 {
726         struct dentry *this_parent = parent;
727         struct list_head *next;
728 
729         spin_lock(&dcache_lock);
730         if (d_mountpoint(parent))
731                 goto positive;
732 repeat:
733         next = this_parent->d_subdirs.next;
734 resume:
735         while (next != &this_parent->d_subdirs) {
736                 struct list_head *tmp = next;
737                 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
738                 next = tmp->next;
739                 /* Have we found a mount point ? */
740                 if (d_mountpoint(dentry))
741                         goto positive;
742                 if (!list_empty(&dentry->d_subdirs)) {
743                         this_parent = dentry;
744                         goto repeat;
745                 }
746         }
747         /*
748          * All done at this level ... ascend and resume the search.
749          */
750         if (this_parent != parent) {
751                 next = this_parent->d_u.d_child.next;
752                 this_parent = this_parent->d_parent;
753                 goto resume;
754         }
755         spin_unlock(&dcache_lock);
756         return 0; /* No mount points found in tree */
757 positive:
758         spin_unlock(&dcache_lock);
759         return 1;
760 }
761 
762 /*
763  * Search the dentry child list for the specified parent,
764  * and move any unused dentries to the end of the unused
765  * list for prune_dcache(). We descend to the next level
766  * whenever the d_subdirs list is non-empty and continue
767  * searching.
768  *
769  * It returns zero iff there are no unused children,
770  * otherwise  it returns the number of children moved to
771  * the end of the unused list. This may not be the total
772  * number of unused children, because select_parent can
773  * drop the lock and return early due to latency
774  * constraints.
775  */
776 static int select_parent(struct dentry * parent)
777 {
778         struct dentry *this_parent = parent;
779         struct list_head *next;
780         int found = 0;
781 
782         spin_lock(&dcache_lock);
783 repeat:
784         next = this_parent->d_subdirs.next;
785 resume:
786         while (next != &this_parent->d_subdirs) {
787                 struct list_head *tmp = next;
788                 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
789                 next = tmp->next;
790 
791                 dentry_lru_remove(dentry);
792                 /* 
793                  * move only zero ref count dentries to the end 
794                  * of the unused list for prune_dcache
795                  */
796                 if (!atomic_read(&dentry->d_count)) {
797                         list_add_tail(&dentry->d_lru, &dentry_unused);
798                         dentry_stat.nr_unused++;
799                         found++;
800                 }
801 
802                 /*
803                  * We can return to the caller if we have found some (this
804                  * ensures forward progress). We'll be coming back to find
805                  * the rest.
806                  */
807                 if (found && need_resched())
808                         goto out;
809 
810                 /*
811                  * Descend a level if the d_subdirs list is non-empty.
812                  */
813                 if (!list_empty(&dentry->d_subdirs)) {
814                         this_parent = dentry;
815                         goto repeat;
816                 }
817         }
818         /*
819          * All done at this level ... ascend and resume the search.
820          */
821         if (this_parent != parent) {
822                 next = this_parent->d_u.d_child.next;
823                 this_parent = this_parent->d_parent;
824                 goto resume;
825         }
826 out:
827         spin_unlock(&dcache_lock);
828         return found;
829 }
830 
831 /**
832  * shrink_dcache_parent - prune dcache
833  * @parent: parent of entries to prune
834  *
835  * Prune the dcache to remove unused children of the parent dentry.
836  */
837  
838 void shrink_dcache_parent(struct dentry * parent)
839 {
840         int found;
841 
842         while ((found = select_parent(parent)) != 0)
843                 prune_dcache(found, parent->d_sb);
844 }
845 
846 /*
847  * Scan `nr' dentries and return the number which remain.
848  *
849  * We need to avoid reentering the filesystem if the caller is performing a
850  * GFP_NOFS allocation attempt.  One example deadlock is:
851  *
852  * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
853  * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
854  * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
855  *
856  * In this case we return -1 to tell the caller that we baled.
857  */
858 static int shrink_dcache_memory(int nr, gfp_t gfp_mask)
859 {
860         if (nr) {
861                 if (!(gfp_mask & __GFP_FS))
862                         return -1;
863                 prune_dcache(nr, NULL);
864         }
865         return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
866 }
867 
868 static struct shrinker dcache_shrinker = {
869         .shrink = shrink_dcache_memory,
870         .seeks = DEFAULT_SEEKS,
871 };
872 
873 /**
874  * d_alloc      -       allocate a dcache entry
875  * @parent: parent of entry to allocate
876  * @name: qstr of the name
877  *
878  * Allocates a dentry. It returns %NULL if there is insufficient memory
879  * available. On a success the dentry is returned. The name passed in is
880  * copied and the copy passed in may be reused after this call.
881  */
882  
883 struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
884 {
885         struct dentry *dentry;
886         char *dname;
887 
888         dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
889         if (!dentry)
890                 return NULL;
891 
892         if (name->len > DNAME_INLINE_LEN-1) {
893                 dname = kmalloc(name->len + 1, GFP_KERNEL);
894                 if (!dname) {
895                         kmem_cache_free(dentry_cache, dentry); 
896                         return NULL;
897                 }
898         } else  {
899                 dname = dentry->d_iname;
900         }       
901         dentry->d_name.name = dname;
902 
903         dentry->d_name.len = name->len;
904         dentry->d_name.hash = name->hash;
905         memcpy(dname, name->name, name->len);
906         dname[name->len] = 0;
907 
908         atomic_set(&dentry->d_count, 1);
909         dentry->d_flags = DCACHE_UNHASHED;
910         spin_lock_init(&dentry->d_lock);
911         dentry->d_inode = NULL;
912         dentry->d_parent = NULL;
913         dentry->d_sb = NULL;
914         dentry->d_op = NULL;
915         dentry->d_fsdata = NULL;
916         dentry->d_mounted = 0;
917 #ifdef CONFIG_PROFILING
918         dentry->d_cookie = NULL;
919 #endif
920         INIT_HLIST_NODE(&dentry->d_hash);
921         INIT_LIST_HEAD(&dentry->d_lru);
922         INIT_LIST_HEAD(&dentry->d_subdirs);
923         INIT_LIST_HEAD(&dentry->d_alias);
924 
925         if (parent) {
926                 dentry->d_parent = dget(parent);
927                 dentry->d_sb = parent->d_sb;
928         } else {
929                 INIT_LIST_HEAD(&dentry->d_u.d_child);
930         }
931 
932         spin_lock(&dcache_lock);
933         if (parent)
934                 list_add(&dentry->d_u.d_child, &parent->d_subdirs);
935         dentry_stat.nr_dentry++;
936         spin_unlock(&dcache_lock);
937 
938         return dentry;
939 }
940 
941 struct dentry *d_alloc_name(struct dentry *parent, const char *name)
942 {
943         struct qstr q;
944 
945         q.name = name;
946         q.len = strlen(name);
947         q.hash = full_name_hash(q.name, q.len);
948         return d_alloc(parent, &q);
949 }
950 
951 /**
952  * d_instantiate - fill in inode information for a dentry
953  * @entry: dentry to complete
954  * @inode: inode to attach to this dentry
955  *
956  * Fill in inode information in the entry.
957  *
958  * This turns negative dentries into productive full members
959  * of society.
960  *
961  * NOTE! This assumes that the inode count has been incremented
962  * (or otherwise set) by the caller to indicate that it is now
963  * in use by the dcache.
964  */
965  
966 void d_instantiate(struct dentry *entry, struct inode * inode)
967 {
968         BUG_ON(!list_empty(&entry->d_alias));
969         spin_lock(&dcache_lock);
970         if (inode)
971                 list_add(&entry->d_alias, &inode->i_dentry);
972         entry->d_inode = inode;
973         fsnotify_d_instantiate(entry, inode);
974         spin_unlock(&dcache_lock);
975         security_d_instantiate(entry, inode);
976 }
977 
978 /**
979  * d_instantiate_unique - instantiate a non-aliased dentry
980  * @entry: dentry to instantiate
981  * @inode: inode to attach to this dentry
982  *
983  * Fill in inode information in the entry. On success, it returns NULL.
984  * If an unhashed alias of "entry" already exists, then we return the
985  * aliased dentry instead and drop one reference to inode.
986  *
987  * Note that in order to avoid conflicts with rename() etc, the caller
988  * had better be holding the parent directory semaphore.
989  *
990  * This also assumes that the inode count has been incremented
991  * (or otherwise set) by the caller to indicate that it is now
992  * in use by the dcache.
993  */
994 static struct dentry *__d_instantiate_unique(struct dentry *entry,
995                                              struct inode *inode)
996 {
997         struct dentry *alias;
998         int len = entry->d_name.len;
999         const char *name = entry->d_name.name;
1000         unsigned int hash = entry->d_name.hash;
1001 
1002         if (!inode) {
1003                 entry->d_inode = NULL;
1004                 return NULL;
1005         }
1006 
1007         list_for_each_entry(alias, &inode->i_dentry, d_alias) {
1008                 struct qstr *qstr = &alias->d_name;
1009 
1010                 if (qstr->hash != hash)
1011                         continue;
1012                 if (alias->d_parent != entry->d_parent)
1013                         continue;
1014                 if (qstr->len != len)
1015                         continue;
1016                 if (memcmp(qstr->name, name, len))
1017                         continue;
1018                 dget_locked(alias);
1019                 return alias;
1020         }
1021 
1022         list_add(&entry->d_alias, &inode->i_dentry);
1023         entry->d_inode = inode;
1024         fsnotify_d_instantiate(entry, inode);
1025         return NULL;
1026 }
1027 
1028 struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
1029 {
1030         struct dentry *result;
1031 
1032         BUG_ON(!list_empty(&entry->d_alias));
1033 
1034         spin_lock(&dcache_lock);
1035         result = __d_instantiate_unique(entry, inode);
1036         spin_unlock(&dcache_lock);
1037 
1038         if (!result) {
1039                 security_d_instantiate(entry, inode);
1040                 return NULL;
1041         }
1042 
1043         BUG_ON(!d_unhashed(result));
1044         iput(inode);
1045         return result;
1046 }
1047 
1048 EXPORT_SYMBOL(d_instantiate_unique);
1049 
1050 /**
1051  * d_alloc_root - allocate root dentry
1052  * @root_inode: inode to allocate the root for
1053  *
1054  * Allocate a root ("/") dentry for the inode given. The inode is
1055  * instantiated and returned. %NULL is returned if there is insufficient
1056  * memory or the inode passed is %NULL.
1057  */
1058  
1059 struct dentry * d_alloc_root(struct inode * root_inode)
1060 {
1061         struct dentry *res = NULL;
1062 
1063         if (root_inode) {
1064                 static const struct qstr name = { .name = "/", .len = 1 };
1065 
1066                 res = d_alloc(NULL, &name);
1067                 if (res) {
1068                         res->d_sb = root_inode->i_sb;
1069                         res->d_parent = res;
1070                         d_instantiate(res, root_inode);
1071                 }
1072         }
1073         return res;
1074 }
1075 
1076 static inline struct hlist_head *d_hash(struct dentry *parent,
1077                                         unsigned long hash)
1078 {
1079         hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
1080         hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
1081         return dentry_hashtable + (hash & D_HASHMASK);
1082 }
1083 
1084 /**
1085  * d_alloc_anon - allocate an anonymous dentry
1086  * @inode: inode to allocate the dentry for
1087  *
1088  * This is similar to d_alloc_root.  It is used by filesystems when
1089  * creating a dentry for a given inode, often in the process of 
1090  * mapping a filehandle to a dentry.  The returned dentry may be
1091  * anonymous, or may have a full name (if the inode was already
1092  * in the cache).  The file system may need to make further
1093  * efforts to connect this dentry into the dcache properly.
1094  *
1095  * When called on a directory inode, we must ensure that
1096  * the inode only ever has one dentry.  If a dentry is
1097  * found, that is returned instead of allocating a new one.
1098  *
1099  * On successful return, the reference to the inode has been transferred
1100  * to the dentry.  If %NULL is returned (indicating kmalloc failure),
1101  * the reference on the inode has not been released.
1102  */
1103 
1104 struct dentry * d_alloc_anon(struct inode *inode)
1105 {
1106         static const struct qstr anonstring = { .name = "" };
1107         struct dentry *tmp;
1108         struct dentry *res;
1109 
1110         if ((res = d_find_alias(inode))) {
1111                 iput(inode);
1112                 return res;
1113         }
1114 
1115         tmp = d_alloc(NULL, &anonstring);
1116         if (!tmp)
1117                 return NULL;
1118 
1119         tmp->d_parent = tmp; /* make sure dput doesn't croak */
1120         
1121         spin_lock(&dcache_lock);
1122         res = __d_find_alias(inode, 0);
1123         if (!res) {
1124                 /* attach a disconnected dentry */
1125                 res = tmp;
1126                 tmp = NULL;
1127                 spin_lock(&res->d_lock);
1128                 res->d_sb = inode->i_sb;
1129                 res->d_parent = res;
1130                 res->d_inode = inode;
1131                 res->d_flags |= DCACHE_DISCONNECTED;
1132                 res->d_flags &= ~DCACHE_UNHASHED;
1133                 list_add(&res->d_alias, &inode->i_dentry);
1134                 hlist_add_head(&res->d_hash, &inode->i_sb->s_anon);
1135                 spin_unlock(&res->d_lock);
1136 
1137                 inode = NULL; /* don't drop reference */
1138         }
1139         spin_unlock(&dcache_lock);
1140 
1141         if (inode)
1142                 iput(inode);
1143         if (tmp)
1144                 dput(tmp);
1145         return res;
1146 }
1147 
1148 
1149 /**
1150  * d_splice_alias - splice a disconnected dentry into the tree if one exists
1151  * @inode:  the inode which may have a disconnected dentry
1152  * @dentry: a negative dentry which we want to point to the inode.
1153  *
1154  * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1155  * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1156  * and return it, else simply d_add the inode to the dentry and return NULL.
1157  *
1158  * This is needed in the lookup routine of any filesystem that is exportable
1159  * (via knfsd) so that we can build dcache paths to directories effectively.
1160  *
1161  * If a dentry was found and moved, then it is returned.  Otherwise NULL
1162  * is returned.  This matches the expected return value of ->lookup.
1163  *
1164  */
1165 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
1166 {
1167         struct dentry *new = NULL;
1168 
1169         if (inode && S_ISDIR(inode->i_mode)) {
1170                 spin_lock(&dcache_lock);
1171                 new = __d_find_alias(inode, 1);
1172                 if (new) {
1173                         BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
1174                         fsnotify_d_instantiate(new, inode);
1175                         spin_unlock(&dcache_lock);
1176                         security_d_instantiate(new, inode);
1177                         d_rehash(dentry);
1178                         d_move(new, dentry);
1179                         iput(inode);
1180                 } else {
1181                         /* d_instantiate takes dcache_lock, so we do it by hand */
1182                         list_add(&dentry->d_alias, &inode->i_dentry);
1183                         dentry->d_inode = inode;
1184                         fsnotify_d_instantiate(dentry, inode);
1185                         spin_unlock(&dcache_lock);
1186                         security_d_instantiate(dentry, inode);
1187                         d_rehash(dentry);
1188                 }
1189         } else
1190                 d_add(dentry, inode);
1191         return new;
1192 }
1193 
1194 
1195 /**
1196  * d_lookup - search for a dentry
1197  * @parent: parent dentry
1198  * @name: qstr of name we wish to find
1199  *
1200  * Searches the children of the parent dentry for the name in question. If
1201  * the dentry is found its reference count is incremented and the dentry
1202  * is returned. The caller must use d_put to free the entry when it has
1203  * finished using it. %NULL is returned on failure.
1204  *
1205  * __d_lookup is dcache_lock free. The hash list is protected using RCU.
1206  * Memory barriers are used while updating and doing lockless traversal. 
1207  * To avoid races with d_move while rename is happening, d_lock is used.
1208  *
1209  * Overflows in memcmp(), while d_move, are avoided by keeping the length
1210  * and name pointer in one structure pointed by d_qstr.
1211  *
1212  * rcu_read_lock() and rcu_read_unlock() are used to disable preemption while
1213  * lookup is going on.
1214  *
1215  * dentry_unused list is not updated even if lookup finds the required dentry
1216  * in there. It is updated in places such as prune_dcache, shrink_dcache_sb,
1217  * select_parent and __dget_locked. This laziness saves lookup from dcache_lock
1218  * acquisition.
1219  *
1220  * d_lookup() is protected against the concurrent renames in some unrelated
1221  * directory using the seqlockt_t rename_lock.
1222  */
1223 
1224 struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
1225 {
1226         struct dentry * dentry = NULL;
1227         unsigned long seq;
1228 
1229         do {
1230                 seq = read_seqbegin(&rename_lock);
1231                 dentry = __d_lookup(parent, name);
1232                 if (dentry)
1233                         break;
1234         } while (read_seqretry(&rename_lock, seq));
1235         return dentry;
1236 }
1237 
1238 struct dentry * __d_lookup(struct dentry * parent, struct qstr * name)
1239 {
1240         unsigned int len = name->len;
1241         unsigned int hash = name->hash;
1242         const unsigned char *str = name->name;
1243         struct hlist_head *head = d_hash(parent,hash);
1244         struct dentry *found = NULL;
1245         struct hlist_node *node;
1246         struct dentry *dentry;
1247 
1248         rcu_read_lock();
1249         
1250         hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
1251                 struct qstr *qstr;
1252 
1253                 if (dentry->d_name.hash != hash)
1254                         continue;
1255                 if (dentry->d_parent != parent)
1256                         continue;
1257 
1258                 spin_lock(&dentry->d_lock);
1259 
1260                 /*
1261                  * Recheck the dentry after taking the lock - d_move may have
1262                  * changed things.  Don't bother checking the hash because we're
1263                  * about to compare the whole name anyway.
1264                  */
1265                 if (dentry->d_parent != parent)
1266                         goto next;
1267 
1268                 /*
1269                  * It is safe to compare names since d_move() cannot
1270                  * change the qstr (protected by d_lock).
1271                  */
1272                 qstr = &dentry->d_name;
1273                 if (parent->d_op && parent->d_op->d_compare) {
1274                         if (parent->d_op->d_compare(parent, qstr, name))
1275                                 goto next;
1276                 } else {
1277                         if (qstr->len != len)
1278                                 goto next;
1279                         if (memcmp(qstr->name, str, len))
1280                                 goto next;
1281                 }
1282 
1283                 if (!d_unhashed(dentry)) {
1284                         atomic_inc(&dentry->d_count);
1285                         found = dentry;
1286                 }
1287                 spin_unlock(&dentry->d_lock);
1288                 break;
1289 next:
1290                 spin_unlock(&dentry->d_lock);
1291         }
1292         rcu_read_unlock();
1293 
1294         return found;
1295 }
1296 
1297 /**
1298  * d_hash_and_lookup - hash the qstr then search for a dentry
1299  * @dir: Directory to search in
1300  * @name: qstr of name we wish to find
1301  *
1302  * On hash failure or on lookup failure NULL is returned.
1303  */
1304 struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
1305 {
1306         struct dentry *dentry = NULL;
1307 
1308         /*
1309          * Check for a fs-specific hash function. Note that we must
1310          * calculate the standard hash first, as the d_op->d_hash()
1311          * routine may choose to leave the hash value unchanged.
1312          */
1313         name->hash = full_name_hash(name->name, name->len);
1314         if (dir->d_op && dir->d_op->d_hash) {
1315                 if (dir->d_op->d_hash(dir, name) < 0)
1316                         goto out;
1317         }
1318         dentry = d_lookup(dir, name);
1319 out:
1320         return dentry;
1321 }
1322 
1323 /**
1324  * d_validate - verify dentry provided from insecure source
1325  * @dentry: The dentry alleged to be valid child of @dparent
1326  * @dparent: The parent dentry (known to be valid)
1327  * @hash: Hash of the dentry
1328  * @len: Length of the name
1329  *
1330  * An insecure source has sent us a dentry, here we verify it and dget() it.
1331  * This is used by ncpfs in its readdir implementation.
1332  * Zero is returned in the dentry is invalid.
1333  */
1334  
1335 int d_validate(struct dentry *dentry, struct dentry *dparent)
1336 {
1337         struct hlist_head *base;
1338         struct hlist_node *lhp;
1339 
1340         /* Check whether the ptr might be valid at all.. */
1341         if (!kmem_ptr_validate(dentry_cache, dentry))
1342                 goto out;
1343 
1344         if (dentry->d_parent != dparent)
1345                 goto out;
1346 
1347         spin_lock(&dcache_lock);
1348         base = d_hash(dparent, dentry->d_name.hash);
1349         hlist_for_each(lhp,base) { 
1350                 /* hlist_for_each_entry_rcu() not required for d_hash list
1351                  * as it is parsed under dcache_lock
1352                  */
1353                 if (dentry == hlist_entry(lhp, struct dentry, d_hash)) {
1354                         __dget_locked(dentry);
1355                         spin_unlock(&dcache_lock);
1356                         return 1;
1357                 }
1358         }
1359         spin_unlock(&dcache_lock);
1360 out:
1361         return 0;
1362 }
1363 
1364 /*
1365  * When a file is deleted, we have two options:
1366  * - turn this dentry into a negative dentry
1367  * - unhash this dentry and free it.
1368  *
1369  * Usually, we want to just turn this into
1370  * a negative dentry, but if anybody else is
1371  * currently using the dentry or the inode
1372  * we can't do that and we fall back on removing
1373  * it from the hash queues and waiting for
1374  * it to be deleted later when it has no users
1375  */
1376  
1377 /**
1378  * d_delete - delete a dentry
1379  * @dentry: The dentry to delete
1380  *
1381  * Turn the dentry into a negative dentry if possible, otherwise
1382  * remove it from the hash queues so it can be deleted later
1383  */
1384  
1385 void d_delete(struct dentry * dentry)
1386 {
1387         int isdir = 0;
1388         /*
1389          * Are we the only user?
1390          */
1391         spin_lock(&dcache_lock);
1392         spin_lock(&dentry->d_lock);
1393         isdir = S_ISDIR(dentry->d_inode->i_mode);
1394         if (atomic_read(&dentry->d_count) == 1) {
1395                 dentry_iput(dentry);
1396                 fsnotify_nameremove(dentry, isdir);
1397                 return;
1398         }
1399 
1400         if (!d_unhashed(dentry))
1401                 __d_drop(dentry);
1402 
1403         spin_unlock(&dentry->d_lock);
1404         spin_unlock(&dcache_lock);
1405 
1406         fsnotify_nameremove(dentry, isdir);
1407 }
1408 
1409 static void __d_rehash(struct dentry * entry, struct hlist_head *list)
1410 {
1411 
1412         entry->d_flags &= ~DCACHE_UNHASHED;
1413         hlist_add_head_rcu(&entry->d_hash, list);
1414 }
1415 
1416 static void _d_rehash(struct dentry * entry)
1417 {
1418         __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
1419 }
1420 
1421 /**
1422  * d_rehash     - add an entry back to the hash
1423  * @entry: dentry to add to the hash
1424  *
1425  * Adds a dentry to the hash according to its name.
1426  */
1427  
1428 void d_rehash(struct dentry * entry)
1429 {
1430         spin_lock(&dcache_lock);
1431         spin_lock(&entry->d_lock);
1432         _d_rehash(entry);
1433         spin_unlock(&entry->d_lock);
1434         spin_unlock(&dcache_lock);
1435 }
1436 
1437 #define do_switch(x,y) do { \
1438         __typeof__ (x) __tmp = x; \
1439         x = y; y = __tmp; } while (0)
1440 
1441 /*
1442  * When switching names, the actual string doesn't strictly have to
1443  * be preserved in the target - because we're dropping the target
1444  * anyway. As such, we can just do a simple memcpy() to copy over
1445  * the new name before we switch.
1446  *
1447  * Note that we have to be a lot more careful about getting the hash
1448  * switched - we have to switch the hash value properly even if it
1449  * then no longer matches the actual (corrupted) string of the target.
1450  * The hash value has to match the hash queue that the dentry is on..
1451  */
1452 static void switch_names(struct dentry *dentry, struct dentry *target)
1453 {
1454         if (dname_external(target)) {
1455                 if (dname_external(dentry)) {
1456                         /*
1457                          * Both external: swap the pointers
1458                          */
1459                         do_switch(target->d_name.name, dentry->d_name.name);
1460                 } else {
1461                         /*
1462                          * dentry:internal, target:external.  Steal target's
1463                          * storage and make target internal.
1464                          */
1465                         memcpy(target->d_iname, dentry->d_name.name,
1466                                         dentry->d_name.len + 1);
1467                         dentry->d_name.name = target->d_name.name;
1468                         target->d_name.name = target->d_iname;
1469                 }
1470         } else {
1471                 if (dname_external(dentry)) {
1472                         /*
1473                          * dentry:external, target:internal.  Give dentry's
1474                          * storage to target and make dentry internal
1475                          */
1476                         memcpy(dentry->d_iname, target->d_name.name,
1477                                         target->d_name.len + 1);
1478                         target->d_name.name = dentry->d_name.name;
1479                         dentry->d_name.name = dentry->d_iname;
1480                 } else {
1481                         /*
1482                          * Both are internal.  Just copy target to dentry
1483                          */
1484                         memcpy(dentry->d_iname, target->d_name.name,
1485                                         target->d_name.len + 1);
1486                 }
1487         }
1488 }
1489 
1490 /*
1491  * We cannibalize "target" when moving dentry on top of it,
1492  * because it's going to be thrown away anyway. We could be more
1493  * polite about it, though.
1494  *
1495  * This forceful removal will result in ugly /proc output if
1496  * somebody holds a file open that got deleted due to a rename.
1497  * We could be nicer about the deleted file, and let it show
1498  * up under the name it had before it was deleted rather than
1499  * under the original name of the file that was moved on top of it.
1500  */
1501  
1502 /*
1503  * d_move_locked - move a dentry
1504  * @dentry: entry to move
1505  * @target: new dentry
1506  *
1507  * Update the dcache to reflect the move of a file name. Negative
1508  * dcache entries should not be moved in this way.
1509  */
1510 static void d_move_locked(struct dentry * dentry, struct dentry * target)
1511 {
1512         struct hlist_head *list;
1513 
1514         if (!dentry->d_inode)
1515                 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
1516 
1517         write_seqlock(&rename_lock);
1518         /*
1519          * XXXX: do we really need to take target->d_lock?
1520          */
1521         if (target < dentry) {
1522                 spin_lock(&target->d_lock);
1523                 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1524         } else {
1525                 spin_lock(&dentry->d_lock);
1526                 spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
1527         }
1528 
1529         /* Move the dentry to the target hash queue, if on different bucket */
1530         if (d_unhashed(dentry))
1531                 goto already_unhashed;
1532 
1533         hlist_del_rcu(&dentry->d_hash);
1534 
1535 already_unhashed:
1536         list = d_hash(target->d_parent, target->d_name.hash);
1537         __d_rehash(dentry, list);
1538 
1539         /* Unhash the target: dput() will then get rid of it */
1540         __d_drop(target);
1541 
1542         list_del(&dentry->d_u.d_child);
1543         list_del(&target->d_u.d_child);
1544 
1545         /* Switch the names.. */
1546         switch_names(dentry, target);
1547         do_switch(dentry->d_name.len, target->d_name.len);
1548         do_switch(dentry->d_name.hash, target->d_name.hash);
1549 
1550         /* ... and switch the parents */
1551         if (IS_ROOT(dentry)) {
1552                 dentry->d_parent = target->d_parent;
1553                 target->d_parent = target;
1554                 INIT_LIST_HEAD(&target->d_u.d_child);
1555         } else {
1556                 do_switch(dentry->d_parent, target->d_parent);
1557 
1558                 /* And add them back to the (new) parent lists */
1559                 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
1560         }
1561 
1562         list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
1563         spin_unlock(&target->d_lock);
1564         fsnotify_d_move(dentry);
1565         spin_unlock(&dentry->d_lock);
1566         write_sequnlock(&rename_lock);
1567 }
1568 
1569 /**
1570  * d_move - move a dentry
1571  * @dentry: entry to move
1572  * @target: new dentry
1573  *
1574  * Update the dcache to reflect the move of a file name. Negative
1575  * dcache entries should not be moved in this way.
1576  */
1577 
1578 void d_move(struct dentry * dentry, struct dentry * target)
1579 {
1580         spin_lock(&dcache_lock);
1581         d_move_locked(dentry, target);
1582         spin_unlock(&dcache_lock);
1583 }
1584 
1585 /*
1586  * Helper that returns 1 if p1 is a parent of p2, else 0
1587  */
1588 static int d_isparent(struct dentry *p1, struct dentry *p2)
1589 {
1590         struct dentry *p;
1591 
1592         for (p = p2; p->d_parent != p; p = p->d_parent) {
1593                 if (p->d_parent == p1)
1594                         return 1;
1595         }
1596         return 0;
1597 }
1598 
1599 /*
1600  * This helper attempts to cope with remotely renamed directories
1601  *
1602  * It assumes that the caller is already holding
1603  * dentry->d_parent->d_inode->i_mutex and the dcache_lock
1604  *
1605  * Note: If ever the locking in lock_rename() changes, then please
1606  * remember to update this too...
1607  *
1608  * On return, dcache_lock will have been unlocked.
1609  */
1610 static struct dentry *__d_unalias(struct dentry *dentry, struct dentry *alias)
1611 {
1612         struct mutex *m1 = NULL, *m2 = NULL;
1613         struct dentry *ret;
1614 
1615         /* If alias and dentry share a parent, then no extra locks required */
1616         if (alias->d_parent == dentry->d_parent)
1617                 goto out_unalias;
1618 
1619         /* Check for loops */
1620         ret = ERR_PTR(-ELOOP);
1621         if (d_isparent(alias, dentry))
1622                 goto out_err;
1623 
1624         /* See lock_rename() */
1625         ret = ERR_PTR(-EBUSY);
1626         if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
1627                 goto out_err;
1628         m1 = &dentry->d_sb->s_vfs_rename_mutex;
1629         if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
1630                 goto out_err;
1631         m2 = &alias->d_parent->d_inode->i_mutex;
1632 out_unalias:
1633         d_move_locked(alias, dentry);
1634         ret = alias;
1635 out_err:
1636         spin_unlock(&dcache_lock);
1637         if (m2)
1638                 mutex_unlock(m2);
1639         if (m1)
1640                 mutex_unlock(m1);
1641         return ret;
1642 }
1643 
1644 /*
1645  * Prepare an anonymous dentry for life in the superblock's dentry tree as a
1646  * named dentry in place of the dentry to be replaced.
1647  */
1648 static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
1649 {
1650         struct dentry *dparent, *aparent;
1651 
1652         switch_names(dentry, anon);
1653         do_switch(dentry->d_name.len, anon->d_name.len);
1654         do_switch(dentry->d_name.hash, anon->d_name.hash);
1655 
1656         dparent = dentry->d_parent;
1657         aparent = anon->d_parent;
1658 
1659         dentry->d_parent = (aparent == anon) ? dentry : aparent;
1660         list_del(&dentry->d_u.d_child);
1661         if (!IS_ROOT(dentry))
1662                 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
1663         else
1664                 INIT_LIST_HEAD(&dentry->d_u.d_child);
1665 
1666         anon->d_parent = (dparent == dentry) ? anon : dparent;
1667         list_del(&anon->d_u.d_child);
1668         if (!IS_ROOT(anon))
1669                 list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
1670         else
1671                 INIT_LIST_HEAD(&anon->d_u.d_child);
1672 
1673         anon->d_flags &= ~DCACHE_DISCONNECTED;
1674 }
1675 
1676 /**
1677  * d_materialise_unique - introduce an inode into the tree
1678  * @dentry: candidate dentry
1679  * @inode: inode to bind to the dentry, to which aliases may be attached
1680  *
1681  * Introduces an dentry into the tree, substituting an extant disconnected
1682  * root directory alias in its place if there is one
1683  */
1684 struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
1685 {
1686         struct dentry *actual;
1687 
1688         BUG_ON(!d_unhashed(dentry));
1689 
1690         spin_lock(&dcache_lock);
1691 
1692         if (!inode) {
1693                 actual = dentry;
1694                 dentry->d_inode = NULL;
1695                 goto found_lock;
1696         }
1697 
1698         if (S_ISDIR(inode->i_mode)) {
1699                 struct dentry *alias;
1700 
1701                 /* Does an aliased dentry already exist? */
1702                 alias = __d_find_alias(inode, 0);
1703                 if (alias) {
1704                         actual = alias;
1705                         /* Is this an anonymous mountpoint that we could splice
1706                          * into our tree? */
1707                         if (IS_ROOT(alias)) {
1708                                 spin_lock(&alias->d_lock);
1709                                 __d_materialise_dentry(dentry, alias);
1710                                 __d_drop(alias);
1711                                 goto found;
1712                         }
1713                         /* Nope, but we must(!) avoid directory aliasing */
1714                         actual = __d_unalias(dentry, alias);
1715                         if (IS_ERR(actual))
1716                                 dput(alias);
1717                         goto out_nolock;
1718                 }
1719         }
1720 
1721         /* Add a unique reference */
1722         actual = __d_instantiate_unique(dentry, inode);
1723         if (!actual)
1724                 actual = dentry;
1725         else if (unlikely(!d_unhashed(actual)))
1726                 goto shouldnt_be_hashed;
1727 
1728 found_lock:
1729         spin_lock(&actual->d_lock);
1730 found:
1731         _d_rehash(actual);
1732         spin_unlock(&actual->d_lock);
1733         spin_unlock(&dcache_lock);
1734 out_nolock:
1735         if (actual == dentry) {
1736                 security_d_instantiate(dentry, inode);
1737                 return NULL;
1738         }
1739 
1740         iput(inode);
1741         return actual;
1742 
1743 shouldnt_be_hashed:
1744         spin_unlock(&dcache_lock);
1745         BUG();
1746         goto shouldnt_be_hashed;
1747 }
1748 
1749 /**
1750  * d_path - return the path of a dentry
1751  * @dentry: dentry to report
1752  * @vfsmnt: vfsmnt to which the dentry belongs
1753  * @root: root dentry
1754  * @rootmnt: vfsmnt to which the root dentry belongs
1755  * @buffer: buffer to return value in
1756  * @buflen: buffer length
1757  *
1758  * Convert a dentry into an ASCII path name. If the entry has been deleted
1759  * the string " (deleted)" is appended. Note that this is ambiguous.
1760  *
1761  * Returns the buffer or an error code if the path was too long.
1762  *
1763  * "buflen" should be positive. Caller holds the dcache_lock.
1764  */
1765 static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
1766                        struct path *root, char *buffer, int buflen)
1767 {
1768         char * end = buffer+buflen;
1769         char * retval;
1770         int namelen;
1771 
1772         *--end = '\0';
1773         buflen--;
1774         if (!IS_ROOT(dentry) && d_unhashed(dentry)) {
1775                 buflen -= 10;
1776                 end -= 10;
1777                 if (buflen < 0)
1778                         goto Elong;
1779                 memcpy(end, " (deleted)", 10);
1780         }
1781 
1782         if (buflen < 1)
1783                 goto Elong;
1784         /* Get '/' right */
1785         retval = end-1;
1786         *retval = '/';
1787 
1788         for (;;) {
1789                 struct dentry * parent;
1790 
1791                 if (dentry == root->dentry && vfsmnt == root->mnt)
1792                         break;
1793                 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
1794                         /* Global root? */
1795                         spin_lock(&vfsmount_lock);
1796                         if (vfsmnt->mnt_parent == vfsmnt) {
1797                                 spin_unlock(&vfsmount_lock);
1798                                 goto global_root;
1799                         }
1800                         dentry = vfsmnt->mnt_mountpoint;
1801                         vfsmnt = vfsmnt->mnt_parent;
1802                         spin_unlock(&vfsmount_lock);
1803                         continue;
1804                 }
1805                 parent = dentry->d_parent;
1806                 prefetch(parent);
1807                 namelen = dentry->d_name.len;
1808                 buflen -= namelen + 1;
1809                 if (buflen < 0)
1810                         goto Elong;
1811                 end -= namelen;
1812                 memcpy(end, dentry->d_name.name, namelen);
1813                 *--end = '/';
1814                 retval = end;
1815                 dentry = parent;
1816         }
1817 
1818         return retval;
1819 
1820 global_root:
1821         namelen = dentry->d_name.len;
1822         buflen -= namelen;
1823         if (buflen < 0)
1824                 goto Elong;
1825         retval -= namelen-1;    /* hit the slash */
1826         memcpy(retval, dentry->d_name.name, namelen);
1827         return retval;
1828 Elong:
1829         return ERR_PTR(-ENAMETOOLONG);
1830 }
1831 
1832 /**
1833  * d_path - return the path of a dentry
1834  * @path: path to report
1835  * @buf: buffer to return value in
1836  * @buflen: buffer length
1837  *
1838  * Convert a dentry into an ASCII path name. If the entry has been deleted
1839  * the string " (deleted)" is appended. Note that this is ambiguous.
1840  *
1841  * Returns the buffer or an error code if the path was too long.
1842  *
1843  * "buflen" should be positive. Caller holds the dcache_lock.
1844  */
1845 char *d_path(struct path *path, char *buf, int buflen)
1846 {
1847         char *res;
1848         struct path root;
1849 
1850         /*
1851          * We have various synthetic filesystems that never get mounted.  On
1852          * these filesystems dentries are never used for lookup purposes, and
1853          * thus don't need to be hashed.  They also don't need a name until a
1854          * user wants to identify the object in /proc/pid/fd/.  The little hack
1855          * below allows us to generate a name for these objects on demand:
1856          */
1857         if (path->dentry->d_op && path->dentry->d_op->d_dname)
1858                 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
1859 
1860         read_lock(&current->fs->lock);
1861         root = current->fs->root;
1862         path_get(&current->fs->root);
1863         read_unlock(&current->fs->lock);
1864         spin_lock(&dcache_lock);
1865         res = __d_path(path->dentry, path->mnt, &root, buf, buflen);
1866         spin_unlock(&dcache_lock);
1867         path_put(&root);
1868         return res;
1869 }
1870 
1871 /*
1872  * Helper function for dentry_operations.d_dname() members
1873  */
1874 char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
1875                         const char *fmt, ...)
1876 {
1877         va_list args;
1878         char temp[64];
1879         int sz;
1880 
1881         va_start(args, fmt);
1882         sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
1883         va_end(args);
1884 
1885         if (sz > sizeof(temp) || sz > buflen)
1886                 return ERR_PTR(-ENAMETOOLONG);
1887 
1888         buffer += buflen - sz;
1889         return memcpy(buffer, temp, sz);
1890 }
1891 
1892 /*
1893  * NOTE! The user-level library version returns a
1894  * character pointer. The kernel system call just
1895  * returns the length of the buffer filled (which
1896  * includes the ending '\0' character), or a negative
1897  * error value. So libc would do something like
1898  *
1899  *      char *getcwd(char * buf, size_t size)
1900  *      {
1901  *              int retval;
1902  *
1903  *              retval = sys_getcwd(buf, size);
1904  *              if (retval >= 0)
1905  *                      return buf;
1906  *              errno = -retval;
1907  *              return NULL;
1908  *      }
1909  */
1910 asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
1911 {
1912         int error;
1913         struct path pwd, root;
1914         char *page = (char *) __get_free_page(GFP_USER);
1915 
1916         if (!page)
1917                 return -ENOMEM;
1918 
1919         read_lock(&current->fs->lock);
1920         pwd = current->fs->pwd;
1921         path_get(&current->fs->pwd);
1922         root = current->fs->root;
1923         path_get(&current->fs->root);
1924         read_unlock(&current->fs->lock);
1925 
1926         error = -ENOENT;
1927         /* Has the current directory has been unlinked? */
1928         spin_lock(&dcache_lock);
1929         if (pwd.dentry->d_parent == pwd.dentry || !d_unhashed(pwd.dentry)) {
1930                 unsigned long len;
1931                 char * cwd;
1932 
1933                 cwd = __d_path(pwd.dentry, pwd.mnt, &root, page, PAGE_SIZE);
1934                 spin_unlock(&dcache_lock);
1935 
1936                 error = PTR_ERR(cwd);
1937                 if (IS_ERR(cwd))
1938                         goto out;
1939 
1940                 error = -ERANGE;
1941                 len = PAGE_SIZE + page - cwd;
1942                 if (len <= size) {
1943                         error = len;
1944                         if (copy_to_user(buf, cwd, len))
1945                                 error = -EFAULT;
1946                 }
1947         } else
1948                 spin_unlock(&dcache_lock);
1949 
1950 out:
1951         path_put(&pwd);
1952         path_put(&root);
1953         free_page((unsigned long) page);
1954         return error;
1955 }
1956 
1957 /*
1958  * Test whether new_dentry is a subdirectory of old_dentry.
1959  *
1960  * Trivially implemented using the dcache structure
1961  */
1962 
1963 /**
1964  * is_subdir - is new dentry a subdirectory of old_dentry
1965  * @new_dentry: new dentry
1966  * @old_dentry: old dentry
1967  *
1968  * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
1969  * Returns 0 otherwise.
1970  * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
1971  */
1972   
1973 int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
1974 {
1975         int result;
1976         struct dentry * saved = new_dentry;
1977         unsigned long seq;
1978 
1979         /* need rcu_readlock to protect against the d_parent trashing due to
1980          * d_move
1981          */
1982         rcu_read_lock();
1983         do {
1984                 /* for restarting inner loop in case of seq retry */
1985                 new_dentry = saved;
1986                 result = 0;
1987                 seq = read_seqbegin(&rename_lock);
1988                 for (;;) {
1989                         if (new_dentry != old_dentry) {
1990                                 struct dentry * parent = new_dentry->d_parent;
1991                                 if (parent == new_dentry)
1992                                         break;
1993                                 new_dentry = parent;
1994                                 continue;
1995                         }
1996                         result = 1;
1997                         break;
1998                 }
1999         } while (read_seqretry(&rename_lock, seq));
2000         rcu_read_unlock();
2001 
2002         return result;
2003 }
2004 
2005 void d_genocide(struct dentry *root)
2006 {
2007         struct dentry *this_parent = root;
2008         struct list_head *next;
2009 
2010         spin_lock(&dcache_lock);
2011 repeat:
2012         next = this_parent->d_subdirs.next;
2013 resume:
2014         while (next != &this_parent->d_subdirs) {
2015                 struct list_head *tmp = next;
2016                 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
2017                 next = tmp->next;
2018                 if (d_unhashed(dentry)||!dentry->d_inode)
2019                         continue;
2020                 if (!list_empty(&dentry->d_subdirs)) {
2021                         this_parent = dentry;
2022                         goto repeat;
2023                 }
2024                 atomic_dec(&dentry->d_count);
2025         }
2026         if (this_parent != root) {
2027                 next = this_parent->d_u.d_child.next;
2028                 atomic_dec(&this_parent->d_count);
2029                 this_parent = this_parent->d_parent;
2030                 goto resume;
2031         }
2032         spin_unlock(&dcache_lock);
2033 }
2034 
2035 /**
2036  * find_inode_number - check for dentry with name
2037  * @dir: directory to check
2038  * @name: Name to find.
2039  *
2040  * Check whether a dentry already exists for the given name,
2041  * and return the inode number if it has an inode. Otherwise
2042  * 0 is returned.
2043  *
2044  * This routine is used to post-process directory listings for
2045  * filesystems using synthetic inode numbers, and is necessary
2046  * to keep getcwd() working.
2047  */
2048  
2049 ino_t find_inode_number(struct dentry *dir, struct qstr *name)
2050 {
2051         struct dentry * dentry;
2052         ino_t ino = 0;
2053 
2054         dentry = d_hash_and_lookup(dir, name);
2055         if (dentry) {
2056                 if (dentry->d_inode)
2057                         ino = dentry->d_inode->i_ino;
2058                 dput(dentry);
2059         }
2060         return ino;
2061 }
2062 
2063 static __initdata unsigned long dhash_entries;
2064 static int __init set_dhash_entries(char *str)
2065 {
2066         if (!str)
2067                 return 0;
2068         dhash_entries = simple_strtoul(str, &str, 0);
2069         return 1;
2070 }
2071 __setup("dhash_entries=", set_dhash_entries);
2072 
2073 static void __init dcache_init_early(void)
2074 {
2075         int loop;
2076 
2077         /* If hashes are distributed across NUMA nodes, defer
2078          * hash allocation until vmalloc space is available.
2079          */
2080         if (hashdist)
2081                 return;
2082 
2083         dentry_hashtable =
2084                 alloc_large_system_hash("Dentry cache",
2085                                         sizeof(struct hlist_head),
2086                                         dhash_entries,
2087                                         13,
2088                                         HASH_EARLY,
2089                                         &d_hash_shift,
2090                                         &d_hash_mask,
2091                                         0);
2092 
2093         for (loop = 0; loop < (1 << d_hash_shift); loop++)
2094                 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
2095 }
2096 
2097 static void __init dcache_init(void)
2098 {
2099         int loop;
2100 
2101         /* 
2102          * A constructor could be added for stable state like the lists,
2103          * but it is probably not worth it because of the cache nature
2104          * of the dcache. 
2105          */
2106         dentry_cache = KMEM_CACHE(dentry,
2107                 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
2108         
2109         register_shrinker(&dcache_shrinker);
2110 
2111         /* Hash may have been set up in dcache_init_early */
2112         if (!hashdist)
2113                 return;
2114 
2115         dentry_hashtable =
2116                 alloc_large_system_hash("Dentry cache",
2117                                         sizeof(struct hlist_head),
2118                                         dhash_entries,
2119                                         13,
2120                                         0,
2121                                         &d_hash_shift,
2122                                         &d_hash_mask,
2123                                         0);
2124 
2125         for (loop = 0; loop < (1 << d_hash_shift); loop++)
2126                 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
2127 }
2128 
2129 /* SLAB cache for __getname() consumers */
2130 struct kmem_cache *names_cachep __read_mostly;
2131 
2132 /* SLAB cache for file structures */
2133 struct kmem_cache *filp_cachep __read_mostly;
2134 
2135 EXPORT_SYMBOL(d_genocide);
2136 
2137 void __init vfs_caches_init_early(void)
2138 {
2139         dcache_init_early();
2140         inode_init_early();
2141 }
2142 
2143 void __init vfs_caches_init(unsigned long mempages)
2144 {
2145         unsigned long reserve;
2146 
2147         /* Base hash sizes on available memory, with a reserve equal to
2148            150% of current kernel size */
2149 
2150         reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
2151         mempages -= reserve;
2152 
2153         names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
2154                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
2155 
2156         filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
2157                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
2158 
2159         dcache_init();
2160         inode_init();
2161         files_init(mempages);
2162         mnt_init();
2163         bdev_cache_init();
2164         chrdev_init();
2165 }
2166 
2167 EXPORT_SYMBOL(d_alloc);
2168 EXPORT_SYMBOL(d_alloc_anon);
2169 EXPORT_SYMBOL(d_alloc_root);
2170 EXPORT_SYMBOL(d_delete);
2171 EXPORT_SYMBOL(d_find_alias);
2172 EXPORT_SYMBOL(d_instantiate);
2173 EXPORT_SYMBOL(d_invalidate);
2174 EXPORT_SYMBOL(d_lookup);
2175 EXPORT_SYMBOL(d_move);
2176 EXPORT_SYMBOL_GPL(d_materialise_unique);
2177 EXPORT_SYMBOL(d_path);
2178 EXPORT_SYMBOL(d_prune_aliases);
2179 EXPORT_SYMBOL(d_rehash);
2180 EXPORT_SYMBOL(d_splice_alias);
2181 EXPORT_SYMBOL(d_validate);
2182 EXPORT_SYMBOL(dget_locked);
2183 EXPORT_SYMBOL(dput);
2184 EXPORT_SYMBOL(find_inode_number);
2185 EXPORT_SYMBOL(have_submounts);
2186 EXPORT_SYMBOL(names_cachep);
2187 EXPORT_SYMBOL(shrink_dcache_parent);
2188 EXPORT_SYMBOL(shrink_dcache_sb);
2189 
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