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/malloc.h>
22 #include <linux/slab.h>
23 #include <linux/init.h>
24 #include <linux/smp_lock.h>
25 #include <linux/cache.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 struct {
56 int nr_dentry;
57 int nr_unused;
58 int age_limit; /* age in seconds */
59 int want_pages; /* pages requested by system */
60 int dummy[2];
61 } dentry_stat = {0, 0, 45, 0,};
62
63 /* no dcache_lock, please */
64 static inline void d_free(struct dentry *dentry)
65 {
66 if (dentry->d_op && dentry->d_op->d_release)
67 dentry->d_op->d_release(dentry);
68 if (dname_external(dentry))
69 kfree(dentry->d_name.name);
70 kmem_cache_free(dentry_cache, dentry);
71 dentry_stat.nr_dentry--;
72 }
73
74 /*
75 * Release the dentry's inode, using the fileystem
76 * d_iput() operation if defined.
77 * Called with dcache_lock held, drops it.
78 */
79 static inline void dentry_iput(struct dentry * dentry)
80 {
81 struct inode *inode = dentry->d_inode;
82 if (inode) {
83 dentry->d_inode = NULL;
84 list_del_init(&dentry->d_alias);
85 spin_unlock(&dcache_lock);
86 if (dentry->d_op && dentry->d_op->d_iput)
87 dentry->d_op->d_iput(dentry, inode);
88 else
89 iput(inode);
90 } else
91 spin_unlock(&dcache_lock);
92 }
93
94 /*
95 * This is dput
96 *
97 * This is complicated by the fact that we do not want to put
98 * dentries that are no longer on any hash chain on the unused
99 * list: we'd much rather just get rid of them immediately.
100 *
101 * However, that implies that we have to traverse the dentry
102 * tree upwards to the parents which might _also_ now be
103 * scheduled for deletion (it may have been only waiting for
104 * its last child to go away).
105 *
106 * This tail recursion is done by hand as we don't want to depend
107 * on the compiler to always get this right (gcc generally doesn't).
108 * Real recursion would eat up our stack space.
109 */
110
111 /*
112 * dput - release a dentry
113 * @dentry: dentry to release
114 *
115 * Release a dentry. This will drop the usage count and if appropriate
116 * call the dentry unlink method as well as removing it from the queues and
117 * releasing its resources. If the parent dentries were scheduled for release
118 * they too may now get deleted.
119 *
120 * no dcache lock, please.
121 */
122
123 void dput(struct dentry *dentry)
124 {
125 if (!dentry)
126 return;
127
128 repeat:
129 if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
130 return;
131
132 /* dput on a free dentry? */
133 if (!list_empty(&dentry->d_lru))
134 BUG();
135 /*
136 * AV: ->d_delete() is _NOT_ allowed to block now.
137 */
138 if (dentry->d_op && dentry->d_op->d_delete) {
139 if (dentry->d_op->d_delete(dentry))
140 goto unhash_it;
141 }
142 /* Unreachable? Get rid of it */
143 if (list_empty(&dentry->d_hash))
144 goto kill_it;
145 list_add(&dentry->d_lru, &dentry_unused);
146 dentry_stat.nr_unused++;
147 /*
148 * Update the timestamp
149 */
150 dentry->d_reftime = jiffies;
151 spin_unlock(&dcache_lock);
152 return;
153
154 unhash_it:
155 list_del_init(&dentry->d_hash);
156
157 kill_it: {
158 struct dentry *parent;
159 list_del(&dentry->d_child);
160 /* drops the lock, at that point nobody can reach this dentry */
161 dentry_iput(dentry);
162 parent = dentry->d_parent;
163 d_free(dentry);
164 if (dentry == parent)
165 return;
166 dentry = parent;
167 goto repeat;
168 }
169 }
170
171 /**
172 * d_invalidate - invalidate a dentry
173 * @dentry: dentry to invalidate
174 *
175 * Try to invalidate the dentry if it turns out to be
176 * possible. If there are other dentries that can be
177 * reached through this one we can't delete it and we
178 * return -EBUSY. On success we return 0.
179 *
180 * no dcache lock.
181 */
182
183 int d_invalidate(struct dentry * dentry)
184 {
185 /*
186 * If it's already been dropped, return OK.
187 */
188 spin_lock(&dcache_lock);
189 if (list_empty(&dentry->d_hash)) {
190 spin_unlock(&dcache_lock);
191 return 0;
192 }
193 /*
194 * Check whether to do a partial shrink_dcache
195 * to get rid of unused child entries.
196 */
197 if (!list_empty(&dentry->d_subdirs)) {
198 spin_unlock(&dcache_lock);
199 shrink_dcache_parent(dentry);
200 spin_lock(&dcache_lock);
201 }
202
203 /*
204 * Somebody else still using it?
205 *
206 * If it's a directory, we can't drop it
207 * for fear of somebody re-populating it
208 * with children (even though dropping it
209 * would make it unreachable from the root,
210 * we might still populate it if it was a
211 * working directory or similar).
212 */
213 if (atomic_read(&dentry->d_count) > 1) {
214 if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
215 spin_unlock(&dcache_lock);
216 return -EBUSY;
217 }
218 }
219
220 list_del_init(&dentry->d_hash);
221 spin_unlock(&dcache_lock);
222 return 0;
223 }
224
225 /* This should be called _only_ with dcache_lock held */
226
227 static inline struct dentry * __dget_locked(struct dentry *dentry)
228 {
229 atomic_inc(&dentry->d_count);
230 if (atomic_read(&dentry->d_count) == 1) {
231 dentry_stat.nr_unused--;
232 list_del(&dentry->d_lru);
233 INIT_LIST_HEAD(&dentry->d_lru); /* make "list_empty()" work */
234 }
235 return dentry;
236 }
237
238 struct dentry * dget_locked(struct dentry *dentry)
239 {
240 return __dget_locked(dentry);
241 }
242
243 /**
244 * d_find_alias - grab a hashed alias of inode
245 * @inode: inode in question
246 *
247 * If inode has a hashed alias - acquire the reference to alias and
248 * return it. Otherwise return NULL. Notice that if inode is a directory
249 * there can be only one alias and it can be unhashed only if it has
250 * no children.
251 */
252
253 struct dentry * d_find_alias(struct inode *inode)
254 {
255 struct list_head *head, *next, *tmp;
256 struct dentry *alias;
257
258 spin_lock(&dcache_lock);
259 head = &inode->i_dentry;
260 next = inode->i_dentry.next;
261 while (next != head) {
262 tmp = next;
263 next = tmp->next;
264 alias = list_entry(tmp, struct dentry, d_alias);
265 if (!list_empty(&alias->d_hash)) {
266 __dget_locked(alias);
267 spin_unlock(&dcache_lock);
268 return alias;
269 }
270 }
271 spin_unlock(&dcache_lock);
272 return NULL;
273 }
274
275 /*
276 * Try to kill dentries associated with this inode.
277 * WARNING: you must own a reference to inode.
278 */
279 void d_prune_aliases(struct inode *inode)
280 {
281 struct list_head *tmp, *head = &inode->i_dentry;
282 restart:
283 spin_lock(&dcache_lock);
284 tmp = head;
285 while ((tmp = tmp->next) != head) {
286 struct dentry *dentry = list_entry(tmp, struct dentry, d_alias);
287 if (!atomic_read(&dentry->d_count)) {
288 __dget_locked(dentry);
289 spin_unlock(&dcache_lock);
290 d_drop(dentry);
291 dput(dentry);
292 goto restart;
293 }
294 }
295 spin_unlock(&dcache_lock);
296 }
297
298 /*
299 * Throw away a dentry - free the inode, dput the parent.
300 * This requires that the LRU list has already been
301 * removed.
302 * Called with dcache_lock, drops it and then regains.
303 */
304 static inline void prune_one_dentry(struct dentry * dentry)
305 {
306 struct dentry * parent;
307
308 list_del_init(&dentry->d_hash);
309 list_del(&dentry->d_child);
310 dentry_iput(dentry);
311 parent = dentry->d_parent;
312 d_free(dentry);
313 if (parent != dentry)
314 dput(parent);
315 spin_lock(&dcache_lock);
316 }
317
318 /**
319 * prune_dcache - shrink the dcache
320 * @count: number of entries to try and free
321 *
322 * Shrink the dcache. This is done when we need
323 * more memory, or simply when we need to unmount
324 * something (at which point we need to unuse
325 * all dentries).
326 *
327 * This function may fail to free any resources if
328 * all the dentries are in use.
329 */
330
331 void prune_dcache(int count)
332 {
333 spin_lock(&dcache_lock);
334 for (;;) {
335 struct dentry *dentry;
336 struct list_head *tmp;
337
338 tmp = dentry_unused.prev;
339
340 if (tmp == &dentry_unused)
341 break;
342 list_del_init(tmp);
343 dentry = list_entry(tmp, struct dentry, d_lru);
344
345 /* If the dentry was recently referenced, don't free it. */
346 if (dentry->d_flags & DCACHE_REFERENCED) {
347 dentry->d_flags &= ~DCACHE_REFERENCED;
348 list_add(&dentry->d_lru, &dentry_unused);
349 count--;
350 continue;
351 }
352 dentry_stat.nr_unused--;
353
354 /* Unused dentry with a count? */
355 if (atomic_read(&dentry->d_count))
356 BUG();
357
358 prune_one_dentry(dentry);
359 if (!--count)
360 break;
361 }
362 spin_unlock(&dcache_lock);
363 }
364
365 /*
366 * Shrink the dcache for the specified super block.
367 * This allows us to unmount a device without disturbing
368 * the dcache for the other devices.
369 *
370 * This implementation makes just two traversals of the
371 * unused list. On the first pass we move the selected
372 * dentries to the most recent end, and on the second
373 * pass we free them. The second pass must restart after
374 * each dput(), but since the target dentries are all at
375 * the end, it's really just a single traversal.
376 */
377
378 /**
379 * shrink_dcache_sb - shrink dcache for a superblock
380 * @sb: superblock
381 *
382 * Shrink the dcache for the specified super block. This
383 * is used to free the dcache before unmounting a file
384 * system
385 */
386
387 void shrink_dcache_sb(struct super_block * sb)
388 {
389 struct list_head *tmp, *next;
390 struct dentry *dentry;
391
392 /*
393 * Pass one ... move the dentries for the specified
394 * superblock to the most recent end of the unused list.
395 */
396 spin_lock(&dcache_lock);
397 next = dentry_unused.next;
398 while (next != &dentry_unused) {
399 tmp = next;
400 next = tmp->next;
401 dentry = list_entry(tmp, struct dentry, d_lru);
402 if (dentry->d_sb != sb)
403 continue;
404 list_del(tmp);
405 list_add(tmp, &dentry_unused);
406 }
407
408 /*
409 * Pass two ... free the dentries for this superblock.
410 */
411 repeat:
412 next = dentry_unused.next;
413 while (next != &dentry_unused) {
414 tmp = next;
415 next = tmp->next;
416 dentry = list_entry(tmp, struct dentry, d_lru);
417 if (dentry->d_sb != sb)
418 continue;
419 if (atomic_read(&dentry->d_count))
420 continue;
421 dentry_stat.nr_unused--;
422 list_del(tmp);
423 INIT_LIST_HEAD(tmp);
424 prune_one_dentry(dentry);
425 goto repeat;
426 }
427 spin_unlock(&dcache_lock);
428 }
429
430 /*
431 * Search for at least 1 mount point in the dentry's subdirs.
432 * We descend to the next level whenever the d_subdirs
433 * list is non-empty and continue searching.
434 */
435
436 /**
437 * have_submounts - check for mounts over a dentry
438 * @parent: dentry to check.
439 *
440 * Return true if the parent or its subdirectories contain
441 * a mount point
442 */
443
444 int have_submounts(struct dentry *parent)
445 {
446 struct dentry *this_parent = parent;
447 struct list_head *next;
448
449 spin_lock(&dcache_lock);
450 if (d_mountpoint(parent))
451 goto positive;
452 repeat:
453 next = this_parent->d_subdirs.next;
454 resume:
455 while (next != &this_parent->d_subdirs) {
456 struct list_head *tmp = next;
457 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
458 next = tmp->next;
459 /* Have we found a mount point ? */
460 if (d_mountpoint(dentry))
461 goto positive;
462 if (!list_empty(&dentry->d_subdirs)) {
463 this_parent = dentry;
464 goto repeat;
465 }
466 }
467 /*
468 * All done at this level ... ascend and resume the search.
469 */
470 if (this_parent != parent) {
471 next = this_parent->d_child.next;
472 this_parent = this_parent->d_parent;
473 goto resume;
474 }
475 spin_unlock(&dcache_lock);
476 return 0; /* No mount points found in tree */
477 positive:
478 spin_unlock(&dcache_lock);
479 return 1;
480 }
481
482 /*
483 * Search the dentry child list for the specified parent,
484 * and move any unused dentries to the end of the unused
485 * list for prune_dcache(). We descend to the next level
486 * whenever the d_subdirs list is non-empty and continue
487 * searching.
488 */
489 static int select_parent(struct dentry * parent)
490 {
491 struct dentry *this_parent = parent;
492 struct list_head *next;
493 int found = 0;
494
495 spin_lock(&dcache_lock);
496 repeat:
497 next = this_parent->d_subdirs.next;
498 resume:
499 while (next != &this_parent->d_subdirs) {
500 struct list_head *tmp = next;
501 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
502 next = tmp->next;
503 if (!atomic_read(&dentry->d_count)) {
504 list_del(&dentry->d_lru);
505 list_add(&dentry->d_lru, dentry_unused.prev);
506 found++;
507 }
508 /*
509 * Descend a level if the d_subdirs list is non-empty.
510 */
511 if (!list_empty(&dentry->d_subdirs)) {
512 this_parent = dentry;
513 #ifdef DCACHE_DEBUG
514 printk(KERN_DEBUG "select_parent: descending to %s/%s, found=%d\n",
515 dentry->d_parent->d_name.name, dentry->d_name.name, found);
516 #endif
517 goto repeat;
518 }
519 }
520 /*
521 * All done at this level ... ascend and resume the search.
522 */
523 if (this_parent != parent) {
524 next = this_parent->d_child.next;
525 this_parent = this_parent->d_parent;
526 #ifdef DCACHE_DEBUG
527 printk(KERN_DEBUG "select_parent: ascending to %s/%s, found=%d\n",
528 this_parent->d_parent->d_name.name, this_parent->d_name.name, found);
529 #endif
530 goto resume;
531 }
532 spin_unlock(&dcache_lock);
533 return found;
534 }
535
536 /**
537 * shrink_dcache_parent - prune dcache
538 * @parent: parent of entries to prune
539 *
540 * Prune the dcache to remove unused children of the parent dentry.
541 */
542
543 void shrink_dcache_parent(struct dentry * parent)
544 {
545 int found;
546
547 while ((found = select_parent(parent)) != 0)
548 prune_dcache(found);
549 }
550
551 /*
552 * This is called from kswapd when we think we need some
553 * more memory, but aren't really sure how much. So we
554 * carefully try to free a _bit_ of our dcache, but not
555 * too much.
556 *
557 * Priority:
558 * 0 - very urgent: shrink everything
559 * ...
560 * 6 - base-level: try to shrink a bit.
561 */
562 void shrink_dcache_memory(int priority, unsigned int gfp_mask)
563 {
564 int count = 0;
565
566 /*
567 * Nasty deadlock avoidance.
568 *
569 * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
570 * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->
571 * put_inode->ext2_discard_prealloc->ext2_free_blocks->lock_super->
572 * DEADLOCK.
573 *
574 * We should make sure we don't hold the superblock lock over
575 * block allocations, but for now:
576 */
577 if (!(gfp_mask & __GFP_IO))
578 return;
579
580 if (priority)
581 count = dentry_stat.nr_unused / priority;
582
583 prune_dcache(count);
584 kmem_cache_shrink(dentry_cache);
585 }
586
587 #define NAME_ALLOC_LEN(len) ((len+16) & ~15)
588
589 /**
590 * d_alloc - allocate a dcache entry
591 * @parent: parent of entry to allocate
592 * @name: qstr of the name
593 *
594 * Allocates a dentry. It returns %NULL if there is insufficient memory
595 * available. On a success the dentry is returned. The name passed in is
596 * copied and the copy passed in may be reused after this call.
597 */
598
599 struct dentry * d_alloc(struct dentry * parent, const struct qstr *name)
600 {
601 char * str;
602 struct dentry *dentry;
603
604 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
605 if (!dentry)
606 return NULL;
607
608 if (name->len > DNAME_INLINE_LEN-1) {
609 str = kmalloc(NAME_ALLOC_LEN(name->len), GFP_KERNEL);
610 if (!str) {
611 kmem_cache_free(dentry_cache, dentry);
612 return NULL;
613 }
614 } else
615 str = dentry->d_iname;
616
617 memcpy(str, name->name, name->len);
618 str[name->len] = 0;
619
620 atomic_set(&dentry->d_count, 1);
621 dentry->d_flags = 0;
622 dentry->d_inode = NULL;
623 dentry->d_parent = NULL;
624 dentry->d_sb = NULL;
625 dentry->d_name.name = str;
626 dentry->d_name.len = name->len;
627 dentry->d_name.hash = name->hash;
628 dentry->d_op = NULL;
629 dentry->d_fsdata = NULL;
630 INIT_LIST_HEAD(&dentry->d_vfsmnt);
631 INIT_LIST_HEAD(&dentry->d_hash);
632 INIT_LIST_HEAD(&dentry->d_lru);
633 INIT_LIST_HEAD(&dentry->d_subdirs);
634 INIT_LIST_HEAD(&dentry->d_alias);
635 if (parent) {
636 dentry->d_parent = dget(parent);
637 dentry->d_sb = parent->d_sb;
638 spin_lock(&dcache_lock);
639 list_add(&dentry->d_child, &parent->d_subdirs);
640 spin_unlock(&dcache_lock);
641 } else
642 INIT_LIST_HEAD(&dentry->d_child);
643
644 dentry_stat.nr_dentry++;
645 return dentry;
646 }
647
648 /**
649 * d_instantiate - fill in inode information for a dentry
650 * @entry: dentry to complete
651 * @inode: inode to attach to this dentry
652 *
653 * Fill in inode information in the entry.
654 *
655 * This turns negative dentries into productive full members
656 * of society.
657 *
658 * NOTE! This assumes that the inode count has been incremented
659 * (or otherwise set) by the caller to indicate that it is now
660 * in use by the dcache.
661 */
662
663 void d_instantiate(struct dentry *entry, struct inode * inode)
664 {
665 spin_lock(&dcache_lock);
666 if (inode)
667 list_add(&entry->d_alias, &inode->i_dentry);
668 entry->d_inode = inode;
669 spin_unlock(&dcache_lock);
670 }
671
672 /**
673 * d_alloc_root - allocate root dentry
674 * @root_inode: inode to allocate the root for
675 *
676 * Allocate a root ("/") dentry for the inode given. The inode is
677 * instantiated and returned. %NULL is returned if there is insufficient
678 * memory or the inode passed is %NULL.
679 */
680
681 struct dentry * d_alloc_root(struct inode * root_inode)
682 {
683 struct dentry *res = NULL;
684
685 if (root_inode) {
686 res = d_alloc(NULL, &(const struct qstr) { "/", 1, 0 });
687 if (res) {
688 res->d_sb = root_inode->i_sb;
689 res->d_parent = res;
690 d_instantiate(res, root_inode);
691 }
692 }
693 return res;
694 }
695
696 static inline struct list_head * d_hash(struct dentry * parent, unsigned long hash)
697 {
698 hash += (unsigned long) parent / L1_CACHE_BYTES;
699 hash = hash ^ (hash >> D_HASHBITS) ^ (hash >> D_HASHBITS*2);
700 return dentry_hashtable + (hash & D_HASHMASK);
701 }
702
703 /**
704 * d_lookup - search for a dentry
705 * @parent: parent dentry
706 * @name: qstr of name we wish to find
707 *
708 * Searches the children of the parent dentry for the name in question. If
709 * the dentry is found its reference count is incremented and the dentry
710 * is returned. The caller must use d_put to free the entry when it has
711 * finished using it. %NULL is returned on failure.
712 */
713
714 struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
715 {
716 unsigned int len = name->len;
717 unsigned int hash = name->hash;
718 const unsigned char *str = name->name;
719 struct list_head *head = d_hash(parent,hash);
720 struct list_head *tmp;
721
722 spin_lock(&dcache_lock);
723 tmp = head->next;
724 for (;;) {
725 struct dentry * dentry = list_entry(tmp, struct dentry, d_hash);
726 if (tmp == head)
727 break;
728 tmp = tmp->next;
729 if (dentry->d_name.hash != hash)
730 continue;
731 if (dentry->d_parent != parent)
732 continue;
733 if (parent->d_op && parent->d_op->d_compare) {
734 if (parent->d_op->d_compare(parent, &dentry->d_name, name))
735 continue;
736 } else {
737 if (dentry->d_name.len != len)
738 continue;
739 if (memcmp(dentry->d_name.name, str, len))
740 continue;
741 }
742 __dget_locked(dentry);
743 dentry->d_flags |= DCACHE_REFERENCED;
744 spin_unlock(&dcache_lock);
745 return dentry;
746 }
747 spin_unlock(&dcache_lock);
748 return NULL;
749 }
750
751 /**
752 * d_validate - verify dentry provided from insecure source
753 * @dentry: The dentry alleged to be valid
754 * @dparent: The parent dentry
755 * @hash: Hash of the dentry
756 * @len: Length of the name
757 *
758 * An insecure source has sent us a dentry, here we verify it and dget() it.
759 * This is used by ncpfs in its readdir implementation.
760 * Zero is returned in the dentry is invalid.
761 *
762 * NOTE: This function does _not_ dereference the pointers before we have
763 * validated them. We can test the pointer values, but we
764 * must not actually use them until we have found a valid
765 * copy of the pointer in kernel space..
766 */
767
768 int d_validate(struct dentry *dentry, struct dentry *dparent,
769 unsigned int hash, unsigned int len)
770 {
771 struct list_head *base, *lhp;
772 int valid = 1;
773
774 spin_lock(&dcache_lock);
775 if (dentry != dparent) {
776 base = d_hash(dparent, hash);
777 lhp = base;
778 while ((lhp = lhp->next) != base) {
779 if (dentry == list_entry(lhp, struct dentry, d_hash)) {
780 __dget_locked(dentry);
781 goto out;
782 }
783 }
784 } else {
785 /*
786 * Special case: local mount points don't live in
787 * the hashes, so we search the super blocks.
788 */
789 struct super_block *sb = sb_entry(super_blocks.next);
790
791 for (; sb != sb_entry(&super_blocks);
792 sb = sb_entry(sb->s_list.next)) {
793 if (!sb->s_dev)
794 continue;
795 if (sb->s_root == dentry) {
796 __dget_locked(dentry);
797 goto out;
798 }
799 }
800 }
801 valid = 0;
802 out:
803 spin_unlock(&dcache_lock);
804 return valid;
805 }
806
807 /*
808 * When a file is deleted, we have two options:
809 * - turn this dentry into a negative dentry
810 * - unhash this dentry and free it.
811 *
812 * Usually, we want to just turn this into
813 * a negative dentry, but if anybody else is
814 * currently using the dentry or the inode
815 * we can't do that and we fall back on removing
816 * it from the hash queues and waiting for
817 * it to be deleted later when it has no users
818 */
819
820 /**
821 * d_delete - delete a dentry
822 * @dentry: The dentry to delete
823 *
824 * Turn the dentry into a negative dentry if possible, otherwise
825 * remove it from the hash queues so it can be deleted later
826 */
827
828 void d_delete(struct dentry * dentry)
829 {
830 /*
831 * Are we the only user?
832 */
833 spin_lock(&dcache_lock);
834 if (atomic_read(&dentry->d_count) == 1) {
835 dentry_iput(dentry);
836 return;
837 }
838 spin_unlock(&dcache_lock);
839
840 /*
841 * If not, just drop the dentry and let dput
842 * pick up the tab..
843 */
844 d_drop(dentry);
845 }
846
847 /**
848 * d_rehash - add an entry back to the hash
849 * @entry: dentry to add to the hash
850 *
851 * Adds a dentry to the hash according to its name.
852 */
853
854 void d_rehash(struct dentry * entry)
855 {
856 struct list_head *list = d_hash(entry->d_parent, entry->d_name.hash);
857 spin_lock(&dcache_lock);
858 list_add(&entry->d_hash, list);
859 spin_unlock(&dcache_lock);
860 }
861
862 #define do_switch(x,y) do { \
863 __typeof__ (x) __tmp = x; \
864 x = y; y = __tmp; } while (0)
865
866 /*
867 * When switching names, the actual string doesn't strictly have to
868 * be preserved in the target - because we're dropping the target
869 * anyway. As such, we can just do a simple memcpy() to copy over
870 * the new name before we switch.
871 *
872 * Note that we have to be a lot more careful about getting the hash
873 * switched - we have to switch the hash value properly even if it
874 * then no longer matches the actual (corrupted) string of the target.
875 * The hash value has to match the hash queue that the dentry is on..
876 */
877 static inline void switch_names(struct dentry * dentry, struct dentry * target)
878 {
879 const unsigned char *old_name, *new_name;
880
881 check_lock();
882 memcpy(dentry->d_iname, target->d_iname, DNAME_INLINE_LEN);
883 old_name = target->d_name.name;
884 new_name = dentry->d_name.name;
885 if (old_name == target->d_iname)
886 old_name = dentry->d_iname;
887 if (new_name == dentry->d_iname)
888 new_name = target->d_iname;
889 target->d_name.name = new_name;
890 dentry->d_name.name = old_name;
891 }
892
893 /*
894 * We cannibalize "target" when moving dentry on top of it,
895 * because it's going to be thrown away anyway. We could be more
896 * polite about it, though.
897 *
898 * This forceful removal will result in ugly /proc output if
899 * somebody holds a file open that got deleted due to a rename.
900 * We could be nicer about the deleted file, and let it show
901 * up under the name it got deleted rather than the name that
902 * deleted it.
903 *
904 * Careful with the hash switch. The hash switch depends on
905 * the fact that any list-entry can be a head of the list.
906 * Think about it.
907 */
908
909 /**
910 * d_move - move a dentry
911 * @dentry: entry to move
912 * @target: new dentry
913 *
914 * Update the dcache to reflect the move of a file name. Negative
915 * dcache entries should not be moved in this way.
916 */
917
918 void d_move(struct dentry * dentry, struct dentry * target)
919 {
920 check_lock();
921
922 if (!dentry->d_inode)
923 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
924
925 spin_lock(&dcache_lock);
926 /* Move the dentry to the target hash queue */
927 list_del(&dentry->d_hash);
928 list_add(&dentry->d_hash, &target->d_hash);
929
930 /* Unhash the target: dput() will then get rid of it */
931 list_del(&target->d_hash);
932 INIT_LIST_HEAD(&target->d_hash);
933
934 list_del(&dentry->d_child);
935 list_del(&target->d_child);
936
937 /* Switch the parents and the names.. */
938 switch_names(dentry, target);
939 do_switch(dentry->d_parent, target->d_parent);
940 do_switch(dentry->d_name.len, target->d_name.len);
941 do_switch(dentry->d_name.hash, target->d_name.hash);
942
943 /* And add them back to the (new) parent lists */
944 list_add(&target->d_child, &target->d_parent->d_subdirs);
945 list_add(&dentry->d_child, &dentry->d_parent->d_subdirs);
946 spin_unlock(&dcache_lock);
947 }
948
949 /**
950 * d_path - return the path of a dentry
951 * @dentry: dentry to report
952 * @vfsmnt: vfsmnt to which the dentry belongs
953 * @root: root dentry
954 * @rootmnt: vfsmnt to which the root dentry belongs
955 * @buffer: buffer to return value in
956 * @buflen: buffer length
957 *
958 * Convert a dentry into an ASCII path name. If the entry has been deleted
959 * the string " (deleted)" is appended. Note that this is ambiguous. Returns
960 * the buffer.
961 *
962 * "buflen" should be %PAGE_SIZE or more. Caller holds the dcache_lock.
963 */
964 char * __d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
965 struct dentry *root, struct vfsmount *rootmnt,
966 char *buffer, int buflen)
967 {
968 char * end = buffer+buflen;
969 char * retval;
970 int namelen;
971
972 *--end = '\0';
973 buflen--;
974 if (!IS_ROOT(dentry) && list_empty(&dentry->d_hash)) {
975 buflen -= 10;
976 end -= 10;
977 memcpy(end, " (deleted)", 10);
978 }
979
980 /* Get '/' right */
981 retval = end-1;
982 *retval = '/';
983
984 for (;;) {
985 struct dentry * parent;
986
987 if (dentry == root && vfsmnt == rootmnt)
988 break;
989 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
990 /* Global root? */
991 if (vfsmnt->mnt_parent == vfsmnt)
992 goto global_root;
993 dentry = vfsmnt->mnt_mountpoint;
994 vfsmnt = vfsmnt->mnt_parent;
995 continue;
996 }
997 parent = dentry->d_parent;
998 namelen = dentry->d_name.len;
999 buflen -= namelen + 1;
1000 if (buflen < 0)
1001 break;
1002 end -= namelen;
1003 memcpy(end, dentry->d_name.name, namelen);
1004 *--end = '/';
1005 retval = end;
1006 dentry = parent;
1007 }
1008 return retval;
1009 global_root:
1010 namelen = dentry->d_name.len;
1011 buflen -= namelen;
1012 if (buflen >= 0) {
1013 retval -= namelen-1; /* hit the slash */
1014 memcpy(retval, dentry->d_name.name, namelen);
1015 }
1016 return retval;
1017 }
1018
1019 /*
1020 * NOTE! The user-level library version returns a
1021 * character pointer. The kernel system call just
1022 * returns the length of the buffer filled (which
1023 * includes the ending '\0' character), or a negative
1024 * error value. So libc would do something like
1025 *
1026 * char *getcwd(char * buf, size_t size)
1027 * {
1028 * int retval;
1029 *
1030 * retval = sys_getcwd(buf, size);
1031 * if (retval >= 0)
1032 * return buf;
1033 * errno = -retval;
1034 * return NULL;
1035 * }
1036 */
1037 asmlinkage long sys_getcwd(char *buf, unsigned long size)
1038 {
1039 int error;
1040 struct vfsmount *pwdmnt, *rootmnt;
1041 struct dentry *pwd, *root;
1042 char *page = (char *) __get_free_page(GFP_USER);
1043
1044 if (!page)
1045 return -ENOMEM;
1046
1047 read_lock(¤t->fs->lock);
1048 pwdmnt = mntget(current->fs->pwdmnt);
1049 pwd = dget(current->fs->pwd);
1050 rootmnt = mntget(current->fs->rootmnt);
1051 root = dget(current->fs->root);
1052 read_unlock(¤t->fs->lock);
1053
1054 error = -ENOENT;
1055 /* Has the current directory has been unlinked? */
1056 spin_lock(&dcache_lock);
1057 if (pwd->d_parent == pwd || !list_empty(&pwd->d_hash)) {
1058 unsigned long len;
1059 char * cwd;
1060
1061 cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE);
1062 spin_unlock(&dcache_lock);
1063
1064 error = -ERANGE;
1065 len = PAGE_SIZE + page - cwd;
1066 if (len <= size) {
1067 error = len;
1068 if (copy_to_user(buf, cwd, len))
1069 error = -EFAULT;
1070 }
1071 } else
1072 spin_unlock(&dcache_lock);
1073 dput(pwd);
1074 mntput(pwdmnt);
1075 dput(root);
1076 mntput(rootmnt);
1077 free_page((unsigned long) page);
1078 return error;
1079 }
1080
1081 /*
1082 * Test whether new_dentry is a subdirectory of old_dentry.
1083 *
1084 * Trivially implemented using the dcache structure
1085 */
1086
1087 /**
1088 * is_subdir - is new dentry a subdirectory of old_dentry
1089 * @new_dentry: new dentry
1090 * @old_dentry: old dentry
1091 *
1092 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
1093 * Returns 0 otherwise.
1094 */
1095
1096 int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
1097 {
1098 int result;
1099
1100 result = 0;
1101 for (;;) {
1102 if (new_dentry != old_dentry) {
1103 struct dentry * parent = new_dentry->d_parent;
1104 if (parent == new_dentry)
1105 break;
1106 new_dentry = parent;
1107 continue;
1108 }
1109 result = 1;
1110 break;
1111 }
1112 return result;
1113 }
1114
1115 void d_genocide(struct dentry *root)
1116 {
1117 struct dentry *this_parent = root;
1118 struct list_head *next;
1119
1120 spin_lock(&dcache_lock);
1121 repeat:
1122 next = this_parent->d_subdirs.next;
1123 resume:
1124 while (next != &this_parent->d_subdirs) {
1125 struct list_head *tmp = next;
1126 struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
1127 next = tmp->next;
1128 if (d_unhashed(dentry)||!dentry->d_inode)
1129 continue;
1130 if (!list_empty(&dentry->d_subdirs)) {
1131 this_parent = dentry;
1132 goto repeat;
1133 }
1134 atomic_dec(&dentry->d_count);
1135 }
1136 if (this_parent != root) {
1137 next = this_parent->d_child.next;
1138 atomic_dec(&this_parent->d_count);
1139 this_parent = this_parent->d_parent;
1140 goto resume;
1141 }
1142 spin_unlock(&dcache_lock);
1143 }
1144
1145 /**
1146 * find_inode_number - check for dentry with name
1147 * @dir: directory to check
1148 * @name: Name to find.
1149 *
1150 * Check whether a dentry already exists for the given name,
1151 * and return the inode number if it has an inode. Otherwise
1152 * 0 is returned.
1153 *
1154 * This routine is used to post-process directory listings for
1155 * filesystems using synthetic inode numbers, and is necessary
1156 * to keep getcwd() working.
1157 */
1158
1159 ino_t find_inode_number(struct dentry *dir, struct qstr *name)
1160 {
1161 struct dentry * dentry;
1162 ino_t ino = 0;
1163
1164 /*
1165 * Check for a fs-specific hash function. Note that we must
1166 * calculate the standard hash first, as the d_op->d_hash()
1167 * routine may choose to leave the hash value unchanged.
1168 */
1169 name->hash = full_name_hash(name->name, name->len);
1170 if (dir->d_op && dir->d_op->d_hash)
1171 {
1172 if (dir->d_op->d_hash(dir, name) != 0)
1173 goto out;
1174 }
1175
1176 dentry = d_lookup(dir, name);
1177 if (dentry)
1178 {
1179 if (dentry->d_inode)
1180 ino = dentry->d_inode->i_ino;
1181 dput(dentry);
1182 }
1183 out:
1184 return ino;
1185 }
1186
1187 static void __init dcache_init(unsigned long mempages)
1188 {
1189 struct list_head *d;
1190 unsigned long order;
1191 unsigned int nr_hash;
1192 int i;
1193
1194 /*
1195 * A constructor could be added for stable state like the lists,
1196 * but it is probably not worth it because of the cache nature
1197 * of the dcache.
1198 * If fragmentation is too bad then the SLAB_HWCACHE_ALIGN
1199 * flag could be removed here, to hint to the allocator that
1200 * it should not try to get multiple page regions.
1201 */
1202 dentry_cache = kmem_cache_create("dentry_cache",
1203 sizeof(struct dentry),
1204 0,
1205 SLAB_HWCACHE_ALIGN,
1206 NULL, NULL);
1207 if (!dentry_cache)
1208 panic("Cannot create dentry cache");
1209
1210 #if PAGE_SHIFT < 13
1211 mempages >>= (13 - PAGE_SHIFT);
1212 #endif
1213 mempages *= sizeof(struct list_head);
1214 for (order = 0; ((1UL << order) << PAGE_SHIFT) < mempages; order++)
1215 ;
1216
1217 do {
1218 unsigned long tmp;
1219
1220 nr_hash = (1UL << order) * PAGE_SIZE /
1221 sizeof(struct list_head);
1222 d_hash_mask = (nr_hash - 1);
1223
1224 tmp = nr_hash;
1225 d_hash_shift = 0;
1226 while ((tmp >>= 1UL) != 0UL)
1227 d_hash_shift++;
1228
1229 dentry_hashtable = (struct list_head *)
1230 __get_free_pages(GFP_ATOMIC, order);
1231 } while (dentry_hashtable == NULL && --order >= 0);
1232
1233 printk("Dentry-cache hash table entries: %d (order: %ld, %ld bytes)\n",
1234 nr_hash, order, (PAGE_SIZE << order));
1235
1236 if (!dentry_hashtable)
1237 panic("Failed to allocate dcache hash table\n");
1238
1239 d = dentry_hashtable;
1240 i = nr_hash;
1241 do {
1242 INIT_LIST_HEAD(d);
1243 d++;
1244 i--;
1245 } while (i);
1246 }
1247
1248 /* SLAB cache for __getname() consumers */
1249 kmem_cache_t *names_cachep;
1250
1251 /* SLAB cache for file structures */
1252 kmem_cache_t *filp_cachep;
1253
1254 /* SLAB cache for dquot structures */
1255 kmem_cache_t *dquot_cachep;
1256
1257 /* SLAB cache for buffer_head structures */
1258 kmem_cache_t *bh_cachep;
1259
1260 void __init vfs_caches_init(unsigned long mempages)
1261 {
1262 bh_cachep = kmem_cache_create("buffer_head",
1263 sizeof(struct buffer_head), 0,
1264 SLAB_HWCACHE_ALIGN, NULL, NULL);
1265 if(!bh_cachep)
1266 panic("Cannot create buffer head SLAB cache");
1267
1268 names_cachep = kmem_cache_create("names_cache",
1269 PATH_MAX + 1, 0,
1270 SLAB_HWCACHE_ALIGN, NULL, NULL);
1271 if (!names_cachep)
1272 panic("Cannot create names SLAB cache");
1273
1274 filp_cachep = kmem_cache_create("filp",
1275 sizeof(struct file), 0,
1276 SLAB_HWCACHE_ALIGN, NULL, NULL);
1277 if(!filp_cachep)
1278 panic("Cannot create filp SLAB cache");
1279
1280 #if defined (CONFIG_QUOTA)
1281 dquot_cachep = kmem_cache_create("dquot",
1282 sizeof(struct dquot), sizeof(unsigned long) * 4,
1283 SLAB_HWCACHE_ALIGN, NULL, NULL);
1284 if (!dquot_cachep)
1285 panic("Cannot create dquot SLAB cache");
1286 #endif
1287
1288 dcache_init(mempages);
1289 }
1290
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