File: /usr/src/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/config.h>
18 #include <linux/string.h>
19 #include <linux/mm.h>
20 #include <linux/fs.h>
21 #include <linux/slab.h>
22 #include <linux/init.h>
23 #include <linux/smp_lock.h>
24 #include <linux/cache.h>
25 #include <linux/module.h>
26
27 #include <asm/uaccess.h>
28
29 #define DCACHE_PARANOIA 1
30 /* #define DCACHE_DEBUG 1 */
31
32 spinlock_t dcache_lock = SPIN_LOCK_UNLOCKED;
33
34 /* Right now the dcache depends on the kernel lock */
35 #define check_lock() if (!kernel_locked()) BUG()
36
37 static kmem_cache_t *dentry_cache;
38
39 /*
40 * This is the single most critical data structure when it comes
41 * to the dcache: the hashtable for lookups. Somebody should try
42 * to make this good - I've just made it work.
43 *
44 * This hash-function tries to avoid losing too many bits of hash
45 * information, yet avoid using a prime hash-size or similar.
46 */
47 #define D_HASHBITS d_hash_shift
48 #define D_HASHMASK d_hash_mask
49
50 static unsigned int d_hash_mask;
51 static unsigned int d_hash_shift;
52 static struct list_head *dentry_hashtable;
53 static LIST_HEAD(dentry_unused);
54
55 /* Statistics gathering. */
56 struct dentry_stat_t dentry_stat = {0, 0, 45, 0,};
57
58 /* no dcache_lock, please */
59 static inline void d_free(struct dentry *dentry)
60 {
61 if (dentry->d_op && dentry->d_op->d_release)
62 dentry->d_op->d_release(dentry);
63 if (dname_external(dentry))
64 kfree(dentry->d_name.name);
65 kmem_cache_free(dentry_cache, dentry);
66 dentry_stat.nr_dentry--;
67 }
68
69 /*
70 * Release the dentry's inode, using the fileystem
71 * d_iput() operation if defined.
72 * Called with dcache_lock held, drops it.
73 */
74 static inline void dentry_iput(struct dentry * dentry)
75 {
76 struct inode *inode = dentry->d_inode;
77 if (inode) {
78 dentry->d_inode = NULL;
79 list_del_init(&dentry->d_alias);
80 spin_unlock(&dcache_lock);
81 if (dentry->d_op && dentry->d_op->d_iput)
82 dentry->d_op->d_iput(dentry, inode);
83 else
84 iput(inode);
85 } else
86 spin_unlock(&dcache_lock);
87 }
88
89 /*
90 * This is dput
91 *
92 * This is complicated by the fact that we do not want to put
93 * dentries that are no longer on any hash chain on the unused
94 * list: we'd much rather just get rid of them immediately.
95 *
96 * However, that implies that we have to traverse the dentry
97 * tree upwards to the parents which might _also_ now be
98 * scheduled for deletion (it may have been only waiting for
99 * its last child to go away).
100 *
101 * This tail recursion is done by hand as we don't want to depend
102 * on the compiler to always get this right (gcc generally doesn't).
103 * Real recursion would eat up our stack space.
104 */
105
106 /*
107 * dput - release a dentry
108 * @dentry: dentry to release
109 *
110 * Release a dentry. This will drop the usage count and if appropriate
111 * call the dentry unlink method as well as removing it from the queues and
112 * releasing its resources. If the parent dentries were scheduled for release
113 * they too may now get deleted.
114 *
115 * no dcache lock, please.
116 */
117
118 void dput(struct dentry *dentry)
119 {
120 if (!dentry)
121 return;
122
123 repeat:
124 if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
125 return;
126
127 /* dput on a free dentry? */
128 if (!list_empty(&dentry->d_lru))
129 BUG();
130 /*
131 * AV: ->d_delete() is _NOT_ allowed to block now.
132 */
133 if (dentry->d_op && dentry->d_op->d_delete) {
134 if (dentry->d_op->d_delete(dentry))
135 goto unhash_it;
136 }
137 /* Unreachable? Get rid of it */
138 if (list_empty(&dentry->d_hash))
139 goto kill_it;
140 list_add(&dentry->d_lru, &dentry_unused);
141 dentry_stat.nr_unused++;
142 spin_unlock(&dcache_lock);
143 return;
144
145 unhash_it:
146 list_del_init(&dentry->d_hash);
147
148 kill_it: {
149 struct dentry *parent;
150 list_del(&dentry->d_child);
151 /* drops the lock, at that point nobody can reach this dentry */
152 dentry_iput(dentry);
153 parent = dentry->d_parent;
154 d_free(dentry);
155 if (dentry == parent)
156 return;
157 dentry = parent;
158 goto repeat;
159 }
160 }
161
162 /**
163 * d_invalidate - invalidate a dentry
164 * @dentry: dentry to invalidate
165 *
166 * Try to invalidate the dentry if it turns out to be
167 * possible. If there are other dentries that can be
168 * reached through this one we can't delete it and we
169 * return -EBUSY. On success we return 0.
170 *
171 * no dcache lock.
172 */
173
174 int d_invalidate(struct dentry * dentry)
175 {
176 /*
177 * If it's already been dropped, return OK.
178 */
179 spin_lock(&dcache_lock);
180 if (list_empty(&dentry->d_hash)) {
181 spin_unlock(&dcache_lock);
182 return 0;
183 }
184 /*
185 * Check whether to do a partial shrink_dcache
186 * to get rid of unused child entries.
187 */
188 if (!list_empty(&dentry->d_subdirs)) {
189 spin_unlock(&dcache_lock);
190 shrink_dcache_parent(dentry);
191 spin_lock(&dcache_lock);
192 }
193
194 /*
195 * Somebody else still using it?
196 *
197 * If it's a directory, we can't drop it
198 * for fear of somebody re-populating it
199 * with children (even though dropping it
200 * would make it unreachable from the root,
201 * we might still populate it if it was a
202 * working directory or similar).
203 */
204 if (atomic_read(&dentry->d_count) > 1) {
205 if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
206 spin_unlock(&dcache_lock);
207 return -EBUSY;
208 }
209 }
210
211 list_del_init(&dentry->d_hash);
212 spin_unlock(&dcache_lock);
213 return 0;
214 }
215
216 /* This should be called _only_ with dcache_lock held */
217
218 static inline struct dentry * __dget_locked(struct dentry *dentry)
219 {
220 atomic_inc(&dentry->d_count);
221 if (atomic_read(&dentry->d_count) == 1) {
222 dentry_stat.nr_unused--;
223 list_del_init(&dentry->d_lru);
224 }
225 return dentry;
226 }
227
228 struct dentry * dget_locked(struct dentry *dentry)
229 {
230 return __dget_locked(dentry);
231 }
232
233 /**
234 * d_find_alias - grab a hashed alias of inode
235 * @inode: inode in question
236 *
237 * If inode has a hashed alias - acquire the reference to alias and
238 * return it. Otherwise return NULL. Notice that if inode is a directory
239 * there can be only one alias and it can be unhashed only if it has
240 * no children.
241 */
242
243 struct dentry * d_find_alias(struct inode *inode)
244 {
245 struct list_head *head, *next, *tmp;
246 struct dentry *alias;
247
248 spin_lock(&dcache_lock);
249 head = &inode->i_dentry;
250 next = inode->i_dentry.next;
251 while (next != head) {
252 tmp = next;
253 next = tmp->next;
254 alias = list_entry(tmp, struct dentry, d_alias);
255 if (!list_empty(&alias->d_hash)) {
256 __dget_locked(alias);
257 spin_unlock(&dcache_lock);
258 return alias;
259 }
260 }
261 spin_unlock(&dcache_lock);
262 return NULL;
263 }
264
265 /*
266 * Try to kill dentries associated with this inode.
267 * WARNING: you must own a reference to inode.
268 */
269 void d_prune_aliases(struct inode *inode)
270 {
271 struct list_head *tmp, *head = &inode->i_dentry;
272 restart:
273 spin_lock(&dcache_lock);
274 tmp = head;
275 while ((tmp = tmp->next) != head) {
276 struct dentry *dentry = list_entry(tmp, struct dentry, d_alias);
277 if (!atomic_read(&dentry->d_count)) {
278 __dget_locked(dentry);
279 spin_unlock(&dcache_lock);
280 d_drop(dentry);
281 dput(dentry);
282 goto restart;
283 }
284 }
285 spin_unlock(&dcache_lock);
286 }
287
288 /*
289 * Throw away a dentry - free the inode, dput the parent.
290 * This requires that the LRU list has already been
291 * removed.
292 * Called with dcache_lock, drops it and then regains.
293 */
294 static inline void prune_one_dentry(struct dentry * dentry)
295 {
296 struct dentry * parent;
297
298 list_del_init(&dentry->d_hash);
299 list_del(&dentry->d_child);
300 dentry_iput(dentry);
301 parent = dentry->d_parent;
302 d_free(dentry);
303 if (parent != dentry)
304 dput(parent);
305 spin_lock(&dcache_lock);
306 }
307
308 /**
309 * prune_dcache - shrink the dcache
310 * @count: number of entries to try and free
311 *
312 * Shrink the dcache. This is done when we need
313 * more memory, or simply when we need to unmount
314 * something (at which point we need to unuse
315 * all dentries).
316 *
317 * This function may fail to free any resources if
318 * all the dentries are in use.
319 */
320
321 void prune_dcache(int count)
322 {
323 spin_lock(&dcache_lock);
324 for (;;) {
325 struct dentry *dentry;
326 struct list_head *tmp;
327
328 tmp = dentry_unused.prev;
329
330 if (tmp == &dentry_unused)
331 break;
332 list_del_init(tmp);
333 dentry = list_entry(tmp, struct dentry, d_lru);
334
335 /* If the dentry was recently referenced, don't free it. */
336 if (dentry->d_vfs_flags & DCACHE_REFERENCED) {
337 dentry->d_vfs_flags &= ~DCACHE_REFERENCED;
338 list_add(&dentry->d_lru, &dentry_unused);
339 continue;
340 }
341 dentry_stat.nr_unused--;
342
343 /* Unused dentry with a count? */
344 if (atomic_read(&dentry->d_count))
345 BUG();
346
347 prune_one_dentry(dentry);
348 if (!--count)
349 break;
350 }
351 spin_unlock(&dcache_lock);
352 }
353
354 /*
355 * Shrink the dcache for the specified super block.
356 * This allows us to unmount a device without disturbing
357 * the dcache for the other devices.
358 *
359 * This implementation makes just two traversals of the
360 * unused list. On the first pass we move the selected
361 * dentries to the most recent end, and on the second
362 * pass we free them. The second pass must restart after
363 * each dput(), but since the target dentries are all at
364 * the end, it's really just a single traversal.
365 */
366
367 /**
368 * shrink_dcache_sb - shrink dcache for a superblock
369 * @sb: superblock
370 *
371 * Shrink the dcache for the specified super block. This
372 * is used to free the dcache before unmounting a file
373 * system
374 */
375
376 void shrink_dcache_sb(struct super_block * sb)
377 {
378 struct list_head *tmp, *next;
379 struct dentry *dentry;
380
381 /*
382 * Pass one ... move the dentries for the specified
383 * superblock to the most recent end of the unused list.
384 */
385 spin_lock(&dcache_lock);
386 next = dentry_unused.next;
387 while (next != &dentry_unused) {
388 tmp = next;
389 next = tmp->next;
390 dentry = list_entry(tmp, struct dentry, d_lru);
391 if (dentry->d_sb != sb)
392 continue;
393 list_del(tmp);
394 list_add(tmp, &dentry_unused);
395 }
396
397 /*
398 * Pass two ... free the dentries for this superblock.
399 */
400 repeat:
401 next = dentry_unused.next;
402 while (next != &dentry_unused) {
403 tmp = next;
404 next = tmp->next;
405 dentry = list_entry(tmp, struct dentry, d_lru);
406 if (dentry->d_sb != sb)
407 continue;
408 if (atomic_read(&dentry->d_count))
409 continue;
410 dentry_stat.nr_unused--;
411 list_del_init(tmp);
412 prune_one_dentry(dentry);
413 goto repeat;
414 }
415 spin_unlock(&dcache_lock);
416 }
417
418 /*
419 * Search for at least 1 mount point in the dentry's subdirs.
420 * We descend to the next level whenever the d_subdirs
421 * list is non-empty and continue searching.
422 */
423
424 /**
425 * have_submounts - check for mounts over a dentry
426 * @parent: dentry to check.
427 *
428 * Return true if the parent or its subdirectories contain
429 * a mount point
430 */
431
432 int have_submounts(struct dentry *parent)
433 {
434 struct dentry *this_parent = parent;
435 struct list_head *next;
436
437 spin_lock(&dcache_lock);
438 if (d_mountpoint(parent))
439 goto positive;
440 repeat:
441 next = this_parent->d_subdirs.next;
442 resume:
443 while (next != &this_parent->d_subdirs) {
444 struct list_head *tmp = next;
445 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
446 next = tmp->next;
447 /* Have we found a mount point ? */
448 if (d_mountpoint(dentry))
449 goto positive;
450 if (!list_empty(&dentry->d_subdirs)) {
451 this_parent = dentry;
452 goto repeat;
453 }
454 }
455 /*
456 * All done at this level ... ascend and resume the search.
457 */
458 if (this_parent != parent) {
459 next = this_parent->d_child.next;
460 this_parent = this_parent->d_parent;
461 goto resume;
462 }
463 spin_unlock(&dcache_lock);
464 return 0; /* No mount points found in tree */
465 positive:
466 spin_unlock(&dcache_lock);
467 return 1;
468 }
469
470 /*
471 * Search the dentry child list for the specified parent,
472 * and move any unused dentries to the end of the unused
473 * list for prune_dcache(). We descend to the next level
474 * whenever the d_subdirs list is non-empty and continue
475 * searching.
476 */
477 static int select_parent(struct dentry * parent)
478 {
479 struct dentry *this_parent = parent;
480 struct list_head *next;
481 int found = 0;
482
483 spin_lock(&dcache_lock);
484 repeat:
485 next = this_parent->d_subdirs.next;
486 resume:
487 while (next != &this_parent->d_subdirs) {
488 struct list_head *tmp = next;
489 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
490 next = tmp->next;
491 if (!atomic_read(&dentry->d_count)) {
492 list_del(&dentry->d_lru);
493 list_add(&dentry->d_lru, dentry_unused.prev);
494 found++;
495 }
496 /*
497 * Descend a level if the d_subdirs list is non-empty.
498 */
499 if (!list_empty(&dentry->d_subdirs)) {
500 this_parent = dentry;
501 #ifdef DCACHE_DEBUG
502 printk(KERN_DEBUG "select_parent: descending to %s/%s, found=%d\n",
503 dentry->d_parent->d_name.name, dentry->d_name.name, found);
504 #endif
505 goto repeat;
506 }
507 }
508 /*
509 * All done at this level ... ascend and resume the search.
510 */
511 if (this_parent != parent) {
512 next = this_parent->d_child.next;
513 this_parent = this_parent->d_parent;
514 #ifdef DCACHE_DEBUG
515 printk(KERN_DEBUG "select_parent: ascending to %s/%s, found=%d\n",
516 this_parent->d_parent->d_name.name, this_parent->d_name.name, found);
517 #endif
518 goto resume;
519 }
520 spin_unlock(&dcache_lock);
521 return found;
522 }
523
524 /**
525 * shrink_dcache_parent - prune dcache
526 * @parent: parent of entries to prune
527 *
528 * Prune the dcache to remove unused children of the parent dentry.
529 */
530
531 void shrink_dcache_parent(struct dentry * parent)
532 {
533 int found;
534
535 while ((found = select_parent(parent)) != 0)
536 prune_dcache(found);
537 }
538
539 /*
540 * This is called from kswapd when we think we need some
541 * more memory, but aren't really sure how much. So we
542 * carefully try to free a _bit_ of our dcache, but not
543 * too much.
544 *
545 * Priority:
546 * 0 - very urgent: shrink everything
547 * ...
548 * 6 - base-level: try to shrink a bit.
549 */
550 int shrink_dcache_memory(int priority, unsigned int gfp_mask)
551 {
552 int count = 0;
553
554 /*
555 * Nasty deadlock avoidance.
556 *
557 * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
558 * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->
559 * put_inode->ext2_discard_prealloc->ext2_free_blocks->lock_super->
560 * DEADLOCK.
561 *
562 * We should make sure we don't hold the superblock lock over
563 * block allocations, but for now:
564 */
565 if (!(gfp_mask & __GFP_FS))
566 return 0;
567
568 count = dentry_stat.nr_unused / priority;
569
570 prune_dcache(count);
571 kmem_cache_shrink(dentry_cache);
572 return 0;
573 }
574
575 #define NAME_ALLOC_LEN(len) ((len+16) & ~15)
576
577 /**
578 * d_alloc - allocate a dcache entry
579 * @parent: parent of entry to allocate
580 * @name: qstr of the name
581 *
582 * Allocates a dentry. It returns %NULL if there is insufficient memory
583 * available. On a success the dentry is returned. The name passed in is
584 * copied and the copy passed in may be reused after this call.
585 */
586
587 struct dentry * d_alloc(struct dentry * parent, const struct qstr *name)
588 {
589 char * str;
590 struct dentry *dentry;
591
592 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
593 if (!dentry)
594 return NULL;
595
596 if (name->len > DNAME_INLINE_LEN-1) {
597 str = kmalloc(NAME_ALLOC_LEN(name->len), GFP_KERNEL);
598 if (!str) {
599 kmem_cache_free(dentry_cache, dentry);
600 return NULL;
601 }
602 } else
603 str = dentry->d_iname;
604
605 memcpy(str, name->name, name->len);
606 str[name->len] = 0;
607
608 atomic_set(&dentry->d_count, 1);
609 dentry->d_vfs_flags = 0;
610 dentry->d_flags = 0;
611 dentry->d_inode = NULL;
612 dentry->d_parent = NULL;
613 dentry->d_sb = NULL;
614 dentry->d_name.name = str;
615 dentry->d_name.len = name->len;
616 dentry->d_name.hash = name->hash;
617 dentry->d_op = NULL;
618 dentry->d_fsdata = NULL;
619 dentry->d_mounted = 0;
620 INIT_LIST_HEAD(&dentry->d_hash);
621 INIT_LIST_HEAD(&dentry->d_lru);
622 INIT_LIST_HEAD(&dentry->d_subdirs);
623 INIT_LIST_HEAD(&dentry->d_alias);
624 if (parent) {
625 dentry->d_parent = dget(parent);
626 dentry->d_sb = parent->d_sb;
627 spin_lock(&dcache_lock);
628 list_add(&dentry->d_child, &parent->d_subdirs);
629 spin_unlock(&dcache_lock);
630 } else
631 INIT_LIST_HEAD(&dentry->d_child);
632
633 dentry_stat.nr_dentry++;
634 return dentry;
635 }
636
637 /**
638 * d_instantiate - fill in inode information for a dentry
639 * @entry: dentry to complete
640 * @inode: inode to attach to this dentry
641 *
642 * Fill in inode information in the entry.
643 *
644 * This turns negative dentries into productive full members
645 * of society.
646 *
647 * NOTE! This assumes that the inode count has been incremented
648 * (or otherwise set) by the caller to indicate that it is now
649 * in use by the dcache.
650 */
651
652 void d_instantiate(struct dentry *entry, struct inode * inode)
653 {
654 if (!list_empty(&entry->d_alias)) BUG();
655 spin_lock(&dcache_lock);
656 if (inode)
657 list_add(&entry->d_alias, &inode->i_dentry);
658 entry->d_inode = inode;
659 spin_unlock(&dcache_lock);
660 }
661
662 /**
663 * d_alloc_root - allocate root dentry
664 * @root_inode: inode to allocate the root for
665 *
666 * Allocate a root ("/") dentry for the inode given. The inode is
667 * instantiated and returned. %NULL is returned if there is insufficient
668 * memory or the inode passed is %NULL.
669 */
670
671 struct dentry * d_alloc_root(struct inode * root_inode)
672 {
673 struct dentry *res = NULL;
674
675 if (root_inode) {
676 res = d_alloc(NULL, &(const struct qstr) { "/", 1, 0 });
677 if (res) {
678 res->d_sb = root_inode->i_sb;
679 res->d_parent = res;
680 d_instantiate(res, root_inode);
681 }
682 }
683 return res;
684 }
685
686 static inline struct list_head * d_hash(struct dentry * parent, unsigned long hash)
687 {
688 hash += (unsigned long) parent / L1_CACHE_BYTES;
689 hash = hash ^ (hash >> D_HASHBITS);
690 return dentry_hashtable + (hash & D_HASHMASK);
691 }
692
693 /**
694 * d_lookup - search for a dentry
695 * @parent: parent dentry
696 * @name: qstr of name we wish to find
697 *
698 * Searches the children of the parent dentry for the name in question. If
699 * the dentry is found its reference count is incremented and the dentry
700 * is returned. The caller must use d_put to free the entry when it has
701 * finished using it. %NULL is returned on failure.
702 */
703
704 struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
705 {
706 unsigned int len = name->len;
707 unsigned int hash = name->hash;
708 const unsigned char *str = name->name;
709 struct list_head *head = d_hash(parent,hash);
710 struct list_head *tmp;
711
712 spin_lock(&dcache_lock);
713 tmp = head->next;
714 for (;;) {
715 struct dentry * dentry = list_entry(tmp, struct dentry, d_hash);
716 if (tmp == head)
717 break;
718 tmp = tmp->next;
719 if (dentry->d_name.hash != hash)
720 continue;
721 if (dentry->d_parent != parent)
722 continue;
723 if (parent->d_op && parent->d_op->d_compare) {
724 if (parent->d_op->d_compare(parent, &dentry->d_name, name))
725 continue;
726 } else {
727 if (dentry->d_name.len != len)
728 continue;
729 if (memcmp(dentry->d_name.name, str, len))
730 continue;
731 }
732 __dget_locked(dentry);
733 dentry->d_vfs_flags |= DCACHE_REFERENCED;
734 spin_unlock(&dcache_lock);
735 return dentry;
736 }
737 spin_unlock(&dcache_lock);
738 return NULL;
739 }
740
741 /**
742 * d_validate - verify dentry provided from insecure source
743 * @dentry: The dentry alleged to be valid child of @dparent
744 * @dparent: The parent dentry (known to be valid)
745 * @hash: Hash of the dentry
746 * @len: Length of the name
747 *
748 * An insecure source has sent us a dentry, here we verify it and dget() it.
749 * This is used by ncpfs in its readdir implementation.
750 * Zero is returned in the dentry is invalid.
751 */
752
753 int d_validate(struct dentry *dentry, struct dentry *dparent)
754 {
755 unsigned long dent_addr = (unsigned long) dentry;
756 unsigned long min_addr = PAGE_OFFSET;
757 unsigned long align_mask = 0x0F;
758 struct list_head *base, *lhp;
759
760 if (dent_addr < min_addr)
761 goto out;
762 if (dent_addr > (unsigned long)high_memory - sizeof(struct dentry))
763 goto out;
764 if (dent_addr & align_mask)
765 goto out;
766 if ((!kern_addr_valid(dent_addr)) || (!kern_addr_valid(dent_addr -1 +
767 sizeof(struct dentry))))
768 goto out;
769
770 if (dentry->d_parent != dparent)
771 goto out;
772
773 spin_lock(&dcache_lock);
774 lhp = base = d_hash(dparent, dentry->d_name.hash);
775 while ((lhp = lhp->next) != base) {
776 if (dentry == list_entry(lhp, struct dentry, d_hash)) {
777 __dget_locked(dentry);
778 spin_unlock(&dcache_lock);
779 return 1;
780 }
781 }
782 spin_unlock(&dcache_lock);
783 out:
784 return 0;
785 }
786
787 /*
788 * When a file is deleted, we have two options:
789 * - turn this dentry into a negative dentry
790 * - unhash this dentry and free it.
791 *
792 * Usually, we want to just turn this into
793 * a negative dentry, but if anybody else is
794 * currently using the dentry or the inode
795 * we can't do that and we fall back on removing
796 * it from the hash queues and waiting for
797 * it to be deleted later when it has no users
798 */
799
800 /**
801 * d_delete - delete a dentry
802 * @dentry: The dentry to delete
803 *
804 * Turn the dentry into a negative dentry if possible, otherwise
805 * remove it from the hash queues so it can be deleted later
806 */
807
808 void d_delete(struct dentry * dentry)
809 {
810 /*
811 * Are we the only user?
812 */
813 spin_lock(&dcache_lock);
814 if (atomic_read(&dentry->d_count) == 1) {
815 dentry_iput(dentry);
816 return;
817 }
818 spin_unlock(&dcache_lock);
819
820 /*
821 * If not, just drop the dentry and let dput
822 * pick up the tab..
823 */
824 d_drop(dentry);
825 }
826
827 /**
828 * d_rehash - add an entry back to the hash
829 * @entry: dentry to add to the hash
830 *
831 * Adds a dentry to the hash according to its name.
832 */
833
834 void d_rehash(struct dentry * entry)
835 {
836 struct list_head *list = d_hash(entry->d_parent, entry->d_name.hash);
837 if (!list_empty(&entry->d_hash)) BUG();
838 spin_lock(&dcache_lock);
839 list_add(&entry->d_hash, list);
840 spin_unlock(&dcache_lock);
841 }
842
843 #define do_switch(x,y) do { \
844 __typeof__ (x) __tmp = x; \
845 x = y; y = __tmp; } while (0)
846
847 /*
848 * When switching names, the actual string doesn't strictly have to
849 * be preserved in the target - because we're dropping the target
850 * anyway. As such, we can just do a simple memcpy() to copy over
851 * the new name before we switch.
852 *
853 * Note that we have to be a lot more careful about getting the hash
854 * switched - we have to switch the hash value properly even if it
855 * then no longer matches the actual (corrupted) string of the target.
856 * The hash value has to match the hash queue that the dentry is on..
857 */
858 static inline void switch_names(struct dentry * dentry, struct dentry * target)
859 {
860 const unsigned char *old_name, *new_name;
861
862 check_lock();
863 memcpy(dentry->d_iname, target->d_iname, DNAME_INLINE_LEN);
864 old_name = target->d_name.name;
865 new_name = dentry->d_name.name;
866 if (old_name == target->d_iname)
867 old_name = dentry->d_iname;
868 if (new_name == dentry->d_iname)
869 new_name = target->d_iname;
870 target->d_name.name = new_name;
871 dentry->d_name.name = old_name;
872 }
873
874 /*
875 * We cannibalize "target" when moving dentry on top of it,
876 * because it's going to be thrown away anyway. We could be more
877 * polite about it, though.
878 *
879 * This forceful removal will result in ugly /proc output if
880 * somebody holds a file open that got deleted due to a rename.
881 * We could be nicer about the deleted file, and let it show
882 * up under the name it got deleted rather than the name that
883 * deleted it.
884 *
885 * Careful with the hash switch. The hash switch depends on
886 * the fact that any list-entry can be a head of the list.
887 * Think about it.
888 */
889
890 /**
891 * d_move - move a dentry
892 * @dentry: entry to move
893 * @target: new dentry
894 *
895 * Update the dcache to reflect the move of a file name. Negative
896 * dcache entries should not be moved in this way.
897 */
898
899 void d_move(struct dentry * dentry, struct dentry * target)
900 {
901 check_lock();
902
903 if (!dentry->d_inode)
904 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
905
906 spin_lock(&dcache_lock);
907 /* Move the dentry to the target hash queue */
908 list_del(&dentry->d_hash);
909 list_add(&dentry->d_hash, &target->d_hash);
910
911 /* Unhash the target: dput() will then get rid of it */
912 list_del_init(&target->d_hash);
913
914 list_del(&dentry->d_child);
915 list_del(&target->d_child);
916
917 /* Switch the parents and the names.. */
918 switch_names(dentry, target);
919 do_switch(dentry->d_parent, target->d_parent);
920 do_switch(dentry->d_name.len, target->d_name.len);
921 do_switch(dentry->d_name.hash, target->d_name.hash);
922
923 /* And add them back to the (new) parent lists */
924 list_add(&target->d_child, &target->d_parent->d_subdirs);
925 list_add(&dentry->d_child, &dentry->d_parent->d_subdirs);
926 spin_unlock(&dcache_lock);
927 }
928
929 /**
930 * d_path - return the path of a dentry
931 * @dentry: dentry to report
932 * @vfsmnt: vfsmnt to which the dentry belongs
933 * @root: root dentry
934 * @rootmnt: vfsmnt to which the root dentry belongs
935 * @buffer: buffer to return value in
936 * @buflen: buffer length
937 *
938 * Convert a dentry into an ASCII path name. If the entry has been deleted
939 * the string " (deleted)" is appended. Note that this is ambiguous. Returns
940 * the buffer.
941 *
942 * "buflen" should be %PAGE_SIZE or more. Caller holds the dcache_lock.
943 */
944 char * __d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
945 struct dentry *root, struct vfsmount *rootmnt,
946 char *buffer, int buflen)
947 {
948 char * end = buffer+buflen;
949 char * retval;
950 int namelen;
951
952 *--end = '\0';
953 buflen--;
954 if (!IS_ROOT(dentry) && list_empty(&dentry->d_hash)) {
955 buflen -= 10;
956 end -= 10;
957 memcpy(end, " (deleted)", 10);
958 }
959
960 /* Get '/' right */
961 retval = end-1;
962 *retval = '/';
963
964 for (;;) {
965 struct dentry * parent;
966
967 if (dentry == root && vfsmnt == rootmnt)
968 break;
969 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
970 /* Global root? */
971 if (vfsmnt->mnt_parent == vfsmnt)
972 goto global_root;
973 dentry = vfsmnt->mnt_mountpoint;
974 vfsmnt = vfsmnt->mnt_parent;
975 continue;
976 }
977 parent = dentry->d_parent;
978 namelen = dentry->d_name.len;
979 buflen -= namelen + 1;
980 if (buflen < 0)
981 break;
982 end -= namelen;
983 memcpy(end, dentry->d_name.name, namelen);
984 *--end = '/';
985 retval = end;
986 dentry = parent;
987 }
988 return retval;
989 global_root:
990 namelen = dentry->d_name.len;
991 buflen -= namelen;
992 if (buflen >= 0) {
993 retval -= namelen-1; /* hit the slash */
994 memcpy(retval, dentry->d_name.name, namelen);
995 }
996 return retval;
997 }
998
999 /*
1000 * NOTE! The user-level library version returns a
1001 * character pointer. The kernel system call just
1002 * returns the length of the buffer filled (which
1003 * includes the ending '\0' character), or a negative
1004 * error value. So libc would do something like
1005 *
1006 * char *getcwd(char * buf, size_t size)
1007 * {
1008 * int retval;
1009 *
1010 * retval = sys_getcwd(buf, size);
1011 * if (retval >= 0)
1012 * return buf;
1013 * errno = -retval;
1014 * return NULL;
1015 * }
1016 */
1017 asmlinkage long sys_getcwd(char *buf, unsigned long size)
1018 {
1019 int error;
1020 struct vfsmount *pwdmnt, *rootmnt;
1021 struct dentry *pwd, *root;
1022 char *page = (char *) __get_free_page(GFP_USER);
1023
1024 if (!page)
1025 return -ENOMEM;
1026
1027 read_lock(¤t->fs->lock);
1028 pwdmnt = mntget(current->fs->pwdmnt);
1029 pwd = dget(current->fs->pwd);
1030 rootmnt = mntget(current->fs->rootmnt);
1031 root = dget(current->fs->root);
1032 read_unlock(¤t->fs->lock);
1033
1034 error = -ENOENT;
1035 /* Has the current directory has been unlinked? */
1036 spin_lock(&dcache_lock);
1037 if (pwd->d_parent == pwd || !list_empty(&pwd->d_hash)) {
1038 unsigned long len;
1039 char * cwd;
1040
1041 cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE);
1042 spin_unlock(&dcache_lock);
1043
1044 error = -ERANGE;
1045 len = PAGE_SIZE + page - cwd;
1046 if (len <= size) {
1047 error = len;
1048 if (copy_to_user(buf, cwd, len))
1049 error = -EFAULT;
1050 }
1051 } else
1052 spin_unlock(&dcache_lock);
1053 dput(pwd);
1054 mntput(pwdmnt);
1055 dput(root);
1056 mntput(rootmnt);
1057 free_page((unsigned long) page);
1058 return error;
1059 }
1060
1061 /*
1062 * Test whether new_dentry is a subdirectory of old_dentry.
1063 *
1064 * Trivially implemented using the dcache structure
1065 */
1066
1067 /**
1068 * is_subdir - is new dentry a subdirectory of old_dentry
1069 * @new_dentry: new dentry
1070 * @old_dentry: old dentry
1071 *
1072 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
1073 * Returns 0 otherwise.
1074 */
1075
1076 int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
1077 {
1078 int result;
1079
1080 result = 0;
1081 for (;;) {
1082 if (new_dentry != old_dentry) {
1083 struct dentry * parent = new_dentry->d_parent;
1084 if (parent == new_dentry)
1085 break;
1086 new_dentry = parent;
1087 continue;
1088 }
1089 result = 1;
1090 break;
1091 }
1092 return result;
1093 }
1094
1095 void d_genocide(struct dentry *root)
1096 {
1097 struct dentry *this_parent = root;
1098 struct list_head *next;
1099
1100 spin_lock(&dcache_lock);
1101 repeat:
1102 next = this_parent->d_subdirs.next;
1103 resume:
1104 while (next != &this_parent->d_subdirs) {
1105 struct list_head *tmp = next;
1106 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
1107 next = tmp->next;
1108 if (d_unhashed(dentry)||!dentry->d_inode)
1109 continue;
1110 if (!list_empty(&dentry->d_subdirs)) {
1111 this_parent = dentry;
1112 goto repeat;
1113 }
1114 atomic_dec(&dentry->d_count);
1115 }
1116 if (this_parent != root) {
1117 next = this_parent->d_child.next;
1118 atomic_dec(&this_parent->d_count);
1119 this_parent = this_parent->d_parent;
1120 goto resume;
1121 }
1122 spin_unlock(&dcache_lock);
1123 }
1124
1125 /**
1126 * find_inode_number - check for dentry with name
1127 * @dir: directory to check
1128 * @name: Name to find.
1129 *
1130 * Check whether a dentry already exists for the given name,
1131 * and return the inode number if it has an inode. Otherwise
1132 * 0 is returned.
1133 *
1134 * This routine is used to post-process directory listings for
1135 * filesystems using synthetic inode numbers, and is necessary
1136 * to keep getcwd() working.
1137 */
1138
1139 ino_t find_inode_number(struct dentry *dir, struct qstr *name)
1140 {
1141 struct dentry * dentry;
1142 ino_t ino = 0;
1143
1144 /*
1145 * Check for a fs-specific hash function. Note that we must
1146 * calculate the standard hash first, as the d_op->d_hash()
1147 * routine may choose to leave the hash value unchanged.
1148 */
1149 name->hash = full_name_hash(name->name, name->len);
1150 if (dir->d_op && dir->d_op->d_hash)
1151 {
1152 if (dir->d_op->d_hash(dir, name) != 0)
1153 goto out;
1154 }
1155
1156 dentry = d_lookup(dir, name);
1157 if (dentry)
1158 {
1159 if (dentry->d_inode)
1160 ino = dentry->d_inode->i_ino;
1161 dput(dentry);
1162 }
1163 out:
1164 return ino;
1165 }
1166
1167 static void __init dcache_init(unsigned long mempages)
1168 {
1169 struct list_head *d;
1170 unsigned long order;
1171 unsigned int nr_hash;
1172 int i;
1173
1174 /*
1175 * A constructor could be added for stable state like the lists,
1176 * but it is probably not worth it because of the cache nature
1177 * of the dcache.
1178 * If fragmentation is too bad then the SLAB_HWCACHE_ALIGN
1179 * flag could be removed here, to hint to the allocator that
1180 * it should not try to get multiple page regions.
1181 */
1182 dentry_cache = kmem_cache_create("dentry_cache",
1183 sizeof(struct dentry),
1184 0,
1185 SLAB_HWCACHE_ALIGN,
1186 NULL, NULL);
1187 if (!dentry_cache)
1188 panic("Cannot create dentry cache");
1189
1190 #if PAGE_SHIFT < 13
1191 mempages >>= (13 - PAGE_SHIFT);
1192 #endif
1193 mempages *= sizeof(struct list_head);
1194 for (order = 0; ((1UL << order) << PAGE_SHIFT) < mempages; order++)
1195 ;
1196
1197 do {
1198 unsigned long tmp;
1199
1200 nr_hash = (1UL << order) * PAGE_SIZE /
1201 sizeof(struct list_head);
1202 d_hash_mask = (nr_hash - 1);
1203
1204 tmp = nr_hash;
1205 d_hash_shift = 0;
1206 while ((tmp >>= 1UL) != 0UL)
1207 d_hash_shift++;
1208
1209 dentry_hashtable = (struct list_head *)
1210 __get_free_pages(GFP_ATOMIC, order);
1211 } while (dentry_hashtable == NULL && --order >= 0);
1212
1213 printk("Dentry-cache hash table entries: %d (order: %ld, %ld bytes)\n",
1214 nr_hash, order, (PAGE_SIZE << order));
1215
1216 if (!dentry_hashtable)
1217 panic("Failed to allocate dcache hash table\n");
1218
1219 d = dentry_hashtable;
1220 i = nr_hash;
1221 do {
1222 INIT_LIST_HEAD(d);
1223 d++;
1224 i--;
1225 } while (i);
1226 }
1227
1228 static void init_buffer_head(void * foo, kmem_cache_t * cachep, unsigned long flags)
1229 {
1230 if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
1231 SLAB_CTOR_CONSTRUCTOR)
1232 {
1233 struct buffer_head * bh = (struct buffer_head *) foo;
1234
1235 memset(bh, 0, sizeof(*bh));
1236 init_waitqueue_head(&bh->b_wait);
1237 }
1238 }
1239
1240 /* SLAB cache for __getname() consumers */
1241 kmem_cache_t *names_cachep;
1242
1243 /* SLAB cache for file structures */
1244 kmem_cache_t *filp_cachep;
1245
1246 /* SLAB cache for dquot structures */
1247 kmem_cache_t *dquot_cachep;
1248
1249 /* SLAB cache for buffer_head structures */
1250 kmem_cache_t *bh_cachep;
1251 EXPORT_SYMBOL(bh_cachep);
1252
1253 extern void bdev_cache_init(void);
1254 extern void cdev_cache_init(void);
1255
1256 void __init vfs_caches_init(unsigned long mempages)
1257 {
1258 bh_cachep = kmem_cache_create("buffer_head",
1259 sizeof(struct buffer_head), 0,
1260 SLAB_HWCACHE_ALIGN, init_buffer_head, NULL);
1261 if(!bh_cachep)
1262 panic("Cannot create buffer head SLAB cache");
1263
1264 names_cachep = kmem_cache_create("names_cache",
1265 PATH_MAX + 1, 0,
1266 SLAB_HWCACHE_ALIGN, NULL, NULL);
1267 if (!names_cachep)
1268 panic("Cannot create names SLAB cache");
1269
1270 filp_cachep = kmem_cache_create("filp",
1271 sizeof(struct file), 0,
1272 SLAB_HWCACHE_ALIGN, NULL, NULL);
1273 if(!filp_cachep)
1274 panic("Cannot create filp SLAB cache");
1275
1276 #if defined (CONFIG_QUOTA)
1277 dquot_cachep = kmem_cache_create("dquot",
1278 sizeof(struct dquot), sizeof(unsigned long) * 4,
1279 SLAB_HWCACHE_ALIGN, NULL, NULL);
1280 if (!dquot_cachep)
1281 panic("Cannot create dquot SLAB cache");
1282 #endif
1283
1284 dcache_init(mempages);
1285 inode_init(mempages);
1286 mnt_init(mempages);
1287 bdev_cache_init();
1288 cdev_cache_init();
1289 }
1290