blob: 3ee588d5f585b54d7aa50358648521b64423b3f8 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
Linus Torvalds1da177e2005-04-16 15:20:36 -070017#include <linux/syscalls.h>
18#include <linux/string.h>
19#include <linux/mm.h>
20#include <linux/fs.h>
John McCutchan7a91bf72005-08-08 13:52:16 -040021#include <linux/fsnotify.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070022#include <linux/slab.h>
23#include <linux/init.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070024#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>
David Howells07f3f052006-09-30 20:52:18 +020034#include "internal.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -070035
Linus Torvalds1da177e2005-04-16 15:20:36 -070036
Eric Dumazetfa3536c2006-03-26 01:37:24 -080037int sysctl_vfs_cache_pressure __read_mostly = 100;
Linus Torvalds1da177e2005-04-16 15:20:36 -070038EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
39
40 __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
Al Viro74c3cbe2007-07-22 08:04:18 -040041__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -070042
43EXPORT_SYMBOL(dcache_lock);
44
Christoph Lametere18b8902006-12-06 20:33:20 -080045static struct kmem_cache *dentry_cache __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -070046
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
Eric Dumazetfa3536c2006-03-26 01:37:24 -080060static unsigned int d_hash_mask __read_mostly;
61static unsigned int d_hash_shift __read_mostly;
62static struct hlist_head *dentry_hashtable __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -070063static LIST_HEAD(dentry_unused);
64
65/* Statistics gathering. */
66struct dentry_stat_t dentry_stat = {
67 .age_limit = 45,
68};
69
Eric Dumazetb3423412006-12-06 20:38:48 -080070static void __d_free(struct dentry *dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -070071{
Linus Torvalds1da177e2005-04-16 15:20:36 -070072 if (dname_external(dentry))
73 kfree(dentry->d_name.name);
74 kmem_cache_free(dentry_cache, dentry);
75}
76
Eric Dumazetb3423412006-12-06 20:38:48 -080077static 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
Linus Torvalds1da177e2005-04-16 15:20:36 -070083/*
84 * no dcache_lock, please. The caller must decrement dentry_stat.nr_dentry
85 * inside dcache_lock.
86 */
87static void d_free(struct dentry *dentry)
88{
89 if (dentry->d_op && dentry->d_op->d_release)
90 dentry->d_op->d_release(dentry);
Eric Dumazetb3423412006-12-06 20:38:48 -080091 /* if dentry was never inserted into hash, immediate free is OK */
Akinobu Mitae8462ca2008-02-06 01:37:07 -080092 if (hlist_unhashed(&dentry->d_hash))
Eric Dumazetb3423412006-12-06 20:38:48 -080093 __d_free(dentry);
94 else
95 call_rcu(&dentry->d_u.d_rcu, d_callback);
Linus Torvalds1da177e2005-04-16 15:20:36 -070096}
97
Christoph Lameter4a0962a2008-02-14 19:38:45 -080098static 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
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106/*
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 */
Arjan van de Ven858119e2006-01-14 13:20:43 -0800111static void dentry_iput(struct dentry * dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700112{
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);
Linus Torvaldsf805fbd2005-09-19 19:54:29 -0700119 if (!inode->i_nlink)
120 fsnotify_inoderemove(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121 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
Miklos Szeredid52b9082007-05-08 00:23:46 -0700131/**
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 */
140static 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
Linus Torvalds1da177e2005-04-16 15:20:36 -0700153/*
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
182void dput(struct dentry *dentry)
183{
184 if (!dentry)
185 return;
186
187repeat:
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
219unhash_it:
220 __d_drop(dentry);
Miklos Szeredid52b9082007-05-08 00:23:46 -0700221kill_it:
Christoph Lameter4a0962a2008-02-14 19:38:45 -0800222 dentry_lru_remove(dentry);
Miklos Szeredid52b9082007-05-08 00:23:46 -0700223 dentry = d_kill(dentry);
224 if (dentry)
225 goto repeat;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700226}
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
240int 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
287static inline struct dentry * __dget_locked(struct dentry *dentry)
288{
289 atomic_inc(&dentry->d_count);
Christoph Lameter4a0962a2008-02-14 19:38:45 -0800290 dentry_lru_remove(dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291 return dentry;
292}
293
294struct 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 *
NeilBrown21c0d8f2006-10-04 02:16:16 -0700311 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
Linus Torvalds1da177e2005-04-16 15:20:36 -0700312 * any other hashed alias over that one unless @want_discon is set,
NeilBrown21c0d8f2006-10-04 02:16:16 -0700313 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700314 */
315
316static 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)) {
NeilBrown21c0d8f2006-10-04 02:16:16 -0700329 if (IS_ROOT(alias) &&
330 (alias->d_flags & DCACHE_DISCONNECTED))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700331 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
343struct dentry * d_find_alias(struct inode *inode)
344{
David Howells214fda12006-03-25 03:06:36 -0800345 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 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700352 return de;
353}
354
355/*
356 * Try to kill dentries associated with this inode.
357 * WARNING: you must own a reference to inode.
358 */
359void d_prune_aliases(struct inode *inode)
360{
Domen Puncer0cdca3f2005-09-10 00:27:07 -0700361 struct dentry *dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700362restart:
363 spin_lock(&dcache_lock);
Domen Puncer0cdca3f2005-09-10 00:27:07 -0700364 list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700365 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/*
Andrew Mortond702ccb2006-06-22 14:47:31 -0700380 * Throw away a dentry - free the inode, dput the parent. This requires that
381 * the LRU list has already been removed.
382 *
Miklos Szeredi85864e12007-10-16 23:27:09 -0700383 * 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.
Miklos Szeredid52b9082007-05-08 00:23:46 -0700386 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387 * Called with dcache_lock, drops it and then regains.
Andrew Mortond702ccb2006-06-22 14:47:31 -0700388 * Called with dentry->d_lock held, drops it.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700389 */
Miklos Szeredi85864e12007-10-16 23:27:09 -0700390static void prune_one_dentry(struct dentry * dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700391{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700392 __d_drop(dentry);
Miklos Szeredid52b9082007-05-08 00:23:46 -0700393 dentry = d_kill(dentry);
Miklos Szeredid52b9082007-05-08 00:23:46 -0700394
395 /*
396 * Prune ancestors. Locking is simpler than in dput(),
397 * because dcache_lock needs to be taken anyway.
398 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399 spin_lock(&dcache_lock);
Miklos Szeredid52b9082007-05-08 00:23:46 -0700400 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);
Christoph Lameter4a0962a2008-02-14 19:38:45 -0800406 dentry_lru_remove(dentry);
Miklos Szeredid52b9082007-05-08 00:23:46 -0700407 __d_drop(dentry);
408 dentry = d_kill(dentry);
409 spin_lock(&dcache_lock);
410 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700411}
412
413/**
414 * prune_dcache - shrink the dcache
415 * @count: number of entries to try and free
NeilBrown0feae5c2006-06-22 14:47:28 -0700416 * @sb: if given, ignore dentries for other superblocks
417 * which are being unmounted.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700418 *
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
Miklos Szeredi85864e12007-10-16 23:27:09 -0700428static void prune_dcache(int count, struct super_block *sb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700429{
430 spin_lock(&dcache_lock);
431 for (; count ; count--) {
432 struct dentry *dentry;
433 struct list_head *tmp;
NeilBrown0feae5c2006-06-22 14:47:28 -0700434 struct rw_semaphore *s_umount;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700435
436 cond_resched_lock(&dcache_lock);
437
438 tmp = dentry_unused.prev;
Hua Zhongf58a1eb2006-06-25 05:49:32 -0700439 if (sb) {
NeilBrown0feae5c2006-06-22 14:47:28 -0700440 /* 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 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700451 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 }
NeilBrown0feae5c2006-06-22 14:47:28 -0700476 /*
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) {
Miklos Szeredi85864e12007-10-16 23:27:09 -0700488 prune_one_dentry(dentry);
NeilBrown0feae5c2006-06-22 14:47:28 -0700489 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) {
Miklos Szeredi85864e12007-10-16 23:27:09 -0700503 prune_one_dentry(dentry);
NeilBrown0feae5c2006-06-22 14:47:28 -0700504 up_read(s_umount);
505 continue;
506 }
507 up_read(s_umount);
508 }
509 spin_unlock(&dentry->d_lock);
Vasily Averin6eac3f92006-10-28 10:38:44 -0700510 /*
511 * Insert dentry at the head of the list as inserting at the
512 * tail leads to a cycle.
NeilBrown0feae5c2006-06-22 14:47:28 -0700513 */
Vasily Averin6eac3f92006-10-28 10:38:44 -0700514 list_add(&dentry->d_lru, &dentry_unused);
515 dentry_stat.nr_unused++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516 }
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
542void 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);
Denis V. Lunev37c42522007-10-16 23:29:53 -0700552 list_for_each_prev_safe(tmp, next, &dentry_unused) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553 dentry = list_entry(tmp, struct dentry, d_lru);
554 if (dentry->d_sb != sb)
555 continue;
Denis V. Lunev37c42522007-10-16 23:29:53 -0700556 list_move_tail(tmp, &dentry_unused);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700557 }
558
559 /*
560 * Pass two ... free the dentries for this superblock.
561 */
562repeat:
Denis V. Lunev37c42522007-10-16 23:29:53 -0700563 list_for_each_prev_safe(tmp, next, &dentry_unused) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700564 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 }
Miklos Szeredi85864e12007-10-16 23:27:09 -0700574 prune_one_dentry(dentry);
Kirill Korotaev2ab13462006-03-25 03:07:45 -0800575 cond_resched_lock(&dcache_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700576 goto repeat;
577 }
578 spin_unlock(&dcache_lock);
579}
580
581/*
David Howellsc636ebd2006-10-11 01:22:19 -0700582 * 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 */
586static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
587{
588 struct dentry *parent;
David Howellsf8713572006-10-28 10:38:46 -0700589 unsigned detached = 0;
David Howellsc636ebd2006-10-11 01:22:19 -0700590
591 BUG_ON(!IS_ROOT(dentry));
592
593 /* detach this root from the system */
594 spin_lock(&dcache_lock);
Christoph Lameter4a0962a2008-02-14 19:38:45 -0800595 dentry_lru_remove(dentry);
David Howellsc636ebd2006-10-11 01:22:19 -0700596 __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) {
Christoph Lameter4a0962a2008-02-14 19:38:45 -0800609 dentry_lru_remove(loop);
David Howellsc636ebd2006-10-11 01:22:19 -0700610 __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);
David Howellsf8713572006-10-28 10:38:46 -0700647 detached++;
David Howellsc636ebd2006-10-11 01:22:19 -0700648
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)
David Howellsf8713572006-10-28 10:38:46 -0700665 goto out;
David Howellsc636ebd2006-10-11 01:22:19 -0700666
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 }
David Howellsf8713572006-10-28 10:38:46 -0700674out:
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);
David Howellsc636ebd2006-10-11 01:22:19 -0700679}
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 */
692void 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/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700711 * 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
724int 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;
732repeat:
733 next = this_parent->d_subdirs.next;
734resume:
735 while (next != &this_parent->d_subdirs) {
736 struct list_head *tmp = next;
Eric Dumazet5160ee62006-01-08 01:03:32 -0800737 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700738 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) {
Eric Dumazet5160ee62006-01-08 01:03:32 -0800751 next = this_parent->d_u.d_child.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700752 this_parent = this_parent->d_parent;
753 goto resume;
754 }
755 spin_unlock(&dcache_lock);
756 return 0; /* No mount points found in tree */
757positive:
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 */
776static 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);
783repeat:
784 next = this_parent->d_subdirs.next;
785resume:
786 while (next != &this_parent->d_subdirs) {
787 struct list_head *tmp = next;
Eric Dumazet5160ee62006-01-08 01:03:32 -0800788 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700789 next = tmp->next;
790
Christoph Lameter4a0962a2008-02-14 19:38:45 -0800791 dentry_lru_remove(dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700792 /*
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)) {
Akinobu Mita8e130592006-06-26 00:24:37 -0700797 list_add_tail(&dentry->d_lru, &dentry_unused);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700798 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;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700815 goto repeat;
816 }
817 }
818 /*
819 * All done at this level ... ascend and resume the search.
820 */
821 if (this_parent != parent) {
Eric Dumazet5160ee62006-01-08 01:03:32 -0800822 next = this_parent->d_u.d_child.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700823 this_parent = this_parent->d_parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700824 goto resume;
825 }
826out:
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
838void shrink_dcache_parent(struct dentry * parent)
839{
840 int found;
841
842 while ((found = select_parent(parent)) != 0)
Miklos Szeredi85864e12007-10-16 23:27:09 -0700843 prune_dcache(found, parent->d_sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700844}
845
Linus Torvalds1da177e2005-04-16 15:20:36 -0700846/*
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 */
Al Viro27496a82005-10-21 03:20:48 -0400858static int shrink_dcache_memory(int nr, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700859{
860 if (nr) {
861 if (!(gfp_mask & __GFP_FS))
862 return -1;
Miklos Szeredi85864e12007-10-16 23:27:09 -0700863 prune_dcache(nr, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700864 }
865 return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
866}
867
Rusty Russell8e1f9362007-07-17 04:03:17 -0700868static struct shrinker dcache_shrinker = {
869 .shrink = shrink_dcache_memory,
870 .seeks = DEFAULT_SEEKS,
871};
872
Linus Torvalds1da177e2005-04-16 15:20:36 -0700873/**
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
883struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
884{
885 struct dentry *dentry;
886 char *dname;
887
Mel Gormane12ba742007-10-16 01:25:52 -0700888 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700889 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;
Marcelo Tosatti47ba87e2006-02-03 03:04:06 -0800917#ifdef CONFIG_PROFILING
Linus Torvalds1da177e2005-04-16 15:20:36 -0700918 dentry->d_cookie = NULL;
Marcelo Tosatti47ba87e2006-02-03 03:04:06 -0800919#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700920 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 {
Eric Dumazet5160ee62006-01-08 01:03:32 -0800929 INIT_LIST_HEAD(&dentry->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700930 }
931
932 spin_lock(&dcache_lock);
933 if (parent)
Eric Dumazet5160ee62006-01-08 01:03:32 -0800934 list_add(&dentry->d_u.d_child, &parent->d_subdirs);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700935 dentry_stat.nr_dentry++;
936 spin_unlock(&dcache_lock);
937
938 return dentry;
939}
940
941struct 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
966void d_instantiate(struct dentry *entry, struct inode * inode)
967{
Eric Sesterhenn28133c72006-03-26 18:25:39 +0200968 BUG_ON(!list_empty(&entry->d_alias));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700969 spin_lock(&dcache_lock);
970 if (inode)
971 list_add(&entry->d_alias, &inode->i_dentry);
972 entry->d_inode = inode;
Nick Pigginc32ccd82006-03-25 03:07:09 -0800973 fsnotify_d_instantiate(entry, inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700974 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
Oleg Drokine866cfa2006-01-09 20:52:51 -0800985 * aliased dentry instead and drop one reference to inode.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700986 *
987 * Note that in order to avoid conflicts with rename() etc, the caller
988 * had better be holding the parent directory semaphore.
Oleg Drokine866cfa2006-01-09 20:52:51 -0800989 *
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.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700993 */
David Howells770bfad2006-08-22 20:06:07 -0400994static struct dentry *__d_instantiate_unique(struct dentry *entry,
995 struct inode *inode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700996{
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
David Howells770bfad2006-08-22 20:06:07 -04001002 if (!inode) {
1003 entry->d_inode = NULL;
1004 return NULL;
1005 }
1006
Linus Torvalds1da177e2005-04-16 15:20:36 -07001007 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);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001019 return alias;
1020 }
David Howells770bfad2006-08-22 20:06:07 -04001021
Linus Torvalds1da177e2005-04-16 15:20:36 -07001022 list_add(&entry->d_alias, &inode->i_dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001023 entry->d_inode = inode;
Nick Pigginc32ccd82006-03-25 03:07:09 -08001024 fsnotify_d_instantiate(entry, inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001025 return NULL;
1026}
David Howells770bfad2006-08-22 20:06:07 -04001027
1028struct 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
Linus Torvalds1da177e2005-04-16 15:20:36 -07001048EXPORT_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
1059struct 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
1076static 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
1104struct 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 */
1165struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
1166{
1167 struct dentry *new = NULL;
1168
NeilBrown21c0d8f2006-10-04 02:16:16 -07001169 if (inode && S_ISDIR(inode->i_mode)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001170 spin_lock(&dcache_lock);
1171 new = __d_find_alias(inode, 1);
1172 if (new) {
1173 BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
Nick Pigginc32ccd82006-03-25 03:07:09 -08001174 fsnotify_d_instantiate(new, inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001175 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;
Nick Pigginc32ccd82006-03-25 03:07:09 -08001184 fsnotify_d_instantiate(dentry, inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001185 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
1224struct 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
1238struct 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;
Paul E. McKenney665a7582005-11-07 00:59:17 -08001246 struct dentry *dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001247
1248 rcu_read_lock();
1249
Paul E. McKenney665a7582005-11-07 00:59:17 -08001250 hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001251 struct qstr *qstr;
1252
Linus Torvalds1da177e2005-04-16 15:20:36 -07001253 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;
1289next:
1290 spin_unlock(&dentry->d_lock);
1291 }
1292 rcu_read_unlock();
1293
1294 return found;
1295}
1296
1297/**
Eric W. Biederman3e7e2412006-03-31 02:31:43 -08001298 * 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 */
1304struct 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);
1319out:
1320 return dentry;
1321}
1322
1323/**
Linus Torvalds1da177e2005-04-16 15:20:36 -07001324 * 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
1335int 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) {
Paul E. McKenney665a7582005-11-07 00:59:17 -08001350 /* hlist_for_each_entry_rcu() not required for d_hash list
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351 * 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);
1360out:
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
1385void d_delete(struct dentry * dentry)
1386{
John McCutchan7a91bf72005-08-08 13:52:16 -04001387 int isdir = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001388 /*
1389 * Are we the only user?
1390 */
1391 spin_lock(&dcache_lock);
1392 spin_lock(&dentry->d_lock);
John McCutchan7a91bf72005-08-08 13:52:16 -04001393 isdir = S_ISDIR(dentry->d_inode->i_mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001394 if (atomic_read(&dentry->d_count) == 1) {
1395 dentry_iput(dentry);
John McCutchan7a91bf72005-08-08 13:52:16 -04001396 fsnotify_nameremove(dentry, isdir);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001397 return;
1398 }
1399
1400 if (!d_unhashed(dentry))
1401 __d_drop(dentry);
1402
1403 spin_unlock(&dentry->d_lock);
1404 spin_unlock(&dcache_lock);
John McCutchan7a91bf72005-08-08 13:52:16 -04001405
1406 fsnotify_nameremove(dentry, isdir);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407}
1408
1409static 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
David Howells770bfad2006-08-22 20:06:07 -04001416static void _d_rehash(struct dentry * entry)
1417{
1418 __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
1419}
1420
Linus Torvalds1da177e2005-04-16 15:20:36 -07001421/**
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
1428void d_rehash(struct dentry * entry)
1429{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001430 spin_lock(&dcache_lock);
1431 spin_lock(&entry->d_lock);
David Howells770bfad2006-08-22 20:06:07 -04001432 _d_rehash(entry);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001433 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 */
1452static 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 */
J. Bruce Fields321bcf92007-10-21 16:41:38 -07001465 memcpy(target->d_iname, dentry->d_name.name,
1466 dentry->d_name.len + 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001467 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
J. Bruce Fieldsbc154b12007-10-16 23:29:42 -07001498 * 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.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001500 */
1501
Trond Myklebust9eaef272006-10-21 10:24:20 -07001502/*
1503 * d_move_locked - move a dentry
Linus Torvalds1da177e2005-04-16 15:20:36 -07001504 * @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 */
Trond Myklebust9eaef272006-10-21 10:24:20 -07001510static void d_move_locked(struct dentry * dentry, struct dentry * target)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001511{
1512 struct hlist_head *list;
1513
1514 if (!dentry->d_inode)
1515 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
1516
Linus Torvalds1da177e2005-04-16 15:20:36 -07001517 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);
Ingo Molnara90b9c02006-07-03 00:25:04 -07001523 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001524 } else {
1525 spin_lock(&dentry->d_lock);
Ingo Molnara90b9c02006-07-03 00:25:04 -07001526 spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001527 }
1528
1529 /* Move the dentry to the target hash queue, if on different bucket */
Denis Chengf77e3492007-10-16 23:30:11 -07001530 if (d_unhashed(dentry))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001531 goto already_unhashed;
1532
1533 hlist_del_rcu(&dentry->d_hash);
1534
1535already_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
Eric Dumazet5160ee62006-01-08 01:03:32 -08001542 list_del(&dentry->d_u.d_child);
1543 list_del(&target->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001544
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;
Eric Dumazet5160ee62006-01-08 01:03:32 -08001554 INIT_LIST_HEAD(&target->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001555 } else {
1556 do_switch(dentry->d_parent, target->d_parent);
1557
1558 /* And add them back to the (new) parent lists */
Eric Dumazet5160ee62006-01-08 01:03:32 -08001559 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001560 }
1561
Eric Dumazet5160ee62006-01-08 01:03:32 -08001562 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001563 spin_unlock(&target->d_lock);
Nick Pigginc32ccd82006-03-25 03:07:09 -08001564 fsnotify_d_move(dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001565 spin_unlock(&dentry->d_lock);
1566 write_sequnlock(&rename_lock);
Trond Myklebust9eaef272006-10-21 10:24:20 -07001567}
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
1578void d_move(struct dentry * dentry, struct dentry * target)
1579{
1580 spin_lock(&dcache_lock);
1581 d_move_locked(dentry, target);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001582 spin_unlock(&dcache_lock);
1583}
1584
David Howells770bfad2006-08-22 20:06:07 -04001585/*
Trond Myklebust9eaef272006-10-21 10:24:20 -07001586 * Helper that returns 1 if p1 is a parent of p2, else 0
1587 */
1588static 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 */
1610static 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;
1632out_unalias:
1633 d_move_locked(alias, dentry);
1634 ret = alias;
1635out_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/*
David Howells770bfad2006-08-22 20:06:07 -04001645 * 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 */
1648static 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 */
1684struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
1685{
Trond Myklebust9eaef272006-10-21 10:24:20 -07001686 struct dentry *actual;
David Howells770bfad2006-08-22 20:06:07 -04001687
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
Trond Myklebust9eaef272006-10-21 10:24:20 -07001698 if (S_ISDIR(inode->i_mode)) {
1699 struct dentry *alias;
David Howells770bfad2006-08-22 20:06:07 -04001700
Trond Myklebust9eaef272006-10-21 10:24:20 -07001701 /* 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 }
David Howells770bfad2006-08-22 20:06:07 -04001719 }
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
1728found_lock:
1729 spin_lock(&actual->d_lock);
1730found:
1731 _d_rehash(actual);
1732 spin_unlock(&actual->d_lock);
1733 spin_unlock(&dcache_lock);
Trond Myklebust9eaef272006-10-21 10:24:20 -07001734out_nolock:
David Howells770bfad2006-08-22 20:06:07 -04001735 if (actual == dentry) {
1736 security_d_instantiate(dentry, inode);
1737 return NULL;
1738 }
1739
1740 iput(inode);
1741 return actual;
1742
David Howells770bfad2006-08-22 20:06:07 -04001743shouldnt_be_hashed:
1744 spin_unlock(&dcache_lock);
1745 BUG();
1746 goto shouldnt_be_hashed;
1747}
1748
Ram Pai6092d042008-03-27 13:06:20 +01001749static int prepend(char **buffer, int *buflen, const char *str,
1750 int namelen)
1751{
1752 *buflen -= namelen;
1753 if (*buflen < 0)
1754 return -ENAMETOOLONG;
1755 *buffer -= namelen;
1756 memcpy(*buffer, str, namelen);
1757 return 0;
1758}
1759
Linus Torvalds1da177e2005-04-16 15:20:36 -07001760/**
1761 * d_path - return the path of a dentry
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001762 * @path: the dentry/vfsmount to report
1763 * @root: root vfsmnt/dentry (may be modified by this function)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001764 * @buffer: buffer to return value in
1765 * @buflen: buffer length
1766 *
Linus Torvalds552ce542007-02-13 12:08:18 -08001767 * Convert a dentry into an ASCII path name. If the entry has been deleted
1768 * the string " (deleted)" is appended. Note that this is ambiguous.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001769 *
Linus Torvalds552ce542007-02-13 12:08:18 -08001770 * Returns the buffer or an error code if the path was too long.
1771 *
1772 * "buflen" should be positive. Caller holds the dcache_lock.
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001773 *
1774 * If path is not reachable from the supplied root, then the value of
1775 * root is changed (without modifying refcounts).
Linus Torvalds1da177e2005-04-16 15:20:36 -07001776 */
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001777char *__d_path(const struct path *path, struct path *root,
1778 char *buffer, int buflen)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001779{
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001780 struct dentry *dentry = path->dentry;
1781 struct vfsmount *vfsmnt = path->mnt;
Linus Torvalds552ce542007-02-13 12:08:18 -08001782 char * end = buffer+buflen;
1783 char * retval;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001784
Ram Pai6092d042008-03-27 13:06:20 +01001785 prepend(&end, &buflen, "\0", 1);
1786 if (!IS_ROOT(dentry) && d_unhashed(dentry) &&
1787 (prepend(&end, &buflen, " (deleted)", 10) != 0))
Linus Torvalds552ce542007-02-13 12:08:18 -08001788 goto Elong;
Linus Torvalds552ce542007-02-13 12:08:18 -08001789
1790 if (buflen < 1)
1791 goto Elong;
1792 /* Get '/' right */
1793 retval = end-1;
1794 *retval = '/';
1795
1796 for (;;) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001797 struct dentry * parent;
1798
Jan Blunck329c97f2008-02-14 19:38:31 -08001799 if (dentry == root->dentry && vfsmnt == root->mnt)
Linus Torvalds552ce542007-02-13 12:08:18 -08001800 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001801 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
Linus Torvalds552ce542007-02-13 12:08:18 -08001802 /* Global root? */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001803 spin_lock(&vfsmount_lock);
1804 if (vfsmnt->mnt_parent == vfsmnt) {
1805 spin_unlock(&vfsmount_lock);
1806 goto global_root;
1807 }
1808 dentry = vfsmnt->mnt_mountpoint;
1809 vfsmnt = vfsmnt->mnt_parent;
1810 spin_unlock(&vfsmount_lock);
1811 continue;
1812 }
1813 parent = dentry->d_parent;
1814 prefetch(parent);
Ram Pai6092d042008-03-27 13:06:20 +01001815 if ((prepend(&end, &buflen, dentry->d_name.name,
1816 dentry->d_name.len) != 0) ||
1817 (prepend(&end, &buflen, "/", 1) != 0))
Linus Torvalds552ce542007-02-13 12:08:18 -08001818 goto Elong;
Linus Torvalds552ce542007-02-13 12:08:18 -08001819 retval = end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001820 dentry = parent;
1821 }
1822
Linus Torvalds552ce542007-02-13 12:08:18 -08001823 return retval;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001824
1825global_root:
Ram Pai6092d042008-03-27 13:06:20 +01001826 retval += 1; /* hit the slash */
1827 if (prepend(&retval, &buflen, dentry->d_name.name,
1828 dentry->d_name.len) != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001829 goto Elong;
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001830 root->mnt = vfsmnt;
1831 root->dentry = dentry;
Linus Torvalds552ce542007-02-13 12:08:18 -08001832 return retval;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001833Elong:
Linus Torvalds552ce542007-02-13 12:08:18 -08001834 return ERR_PTR(-ENAMETOOLONG);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001835}
1836
Jan Bluncka03a8a702008-02-14 19:38:32 -08001837/**
1838 * d_path - return the path of a dentry
Jan Blunckcf28b482008-02-14 19:38:44 -08001839 * @path: path to report
Jan Bluncka03a8a702008-02-14 19:38:32 -08001840 * @buf: buffer to return value in
1841 * @buflen: buffer length
1842 *
1843 * Convert a dentry into an ASCII path name. If the entry has been deleted
1844 * the string " (deleted)" is appended. Note that this is ambiguous.
1845 *
1846 * Returns the buffer or an error code if the path was too long.
1847 *
1848 * "buflen" should be positive. Caller holds the dcache_lock.
1849 */
Jan Blunckcf28b482008-02-14 19:38:44 -08001850char *d_path(struct path *path, char *buf, int buflen)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001851{
1852 char *res;
Jan Blunck6ac08c32008-02-14 19:34:38 -08001853 struct path root;
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001854 struct path tmp;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001855
Eric Dumazetc23fbb62007-05-08 00:26:18 -07001856 /*
1857 * We have various synthetic filesystems that never get mounted. On
1858 * these filesystems dentries are never used for lookup purposes, and
1859 * thus don't need to be hashed. They also don't need a name until a
1860 * user wants to identify the object in /proc/pid/fd/. The little hack
1861 * below allows us to generate a name for these objects on demand:
1862 */
Jan Blunckcf28b482008-02-14 19:38:44 -08001863 if (path->dentry->d_op && path->dentry->d_op->d_dname)
1864 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
Eric Dumazetc23fbb62007-05-08 00:26:18 -07001865
Linus Torvalds1da177e2005-04-16 15:20:36 -07001866 read_lock(&current->fs->lock);
Jan Blunck6ac08c32008-02-14 19:34:38 -08001867 root = current->fs->root;
Ram Pai6092d042008-03-27 13:06:20 +01001868 path_get(&root);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001869 read_unlock(&current->fs->lock);
Linus Torvalds552ce542007-02-13 12:08:18 -08001870 spin_lock(&dcache_lock);
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001871 tmp = root;
1872 res = __d_path(path, &tmp, buf, buflen);
Linus Torvalds552ce542007-02-13 12:08:18 -08001873 spin_unlock(&dcache_lock);
Jan Blunck6ac08c32008-02-14 19:34:38 -08001874 path_put(&root);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001875 return res;
1876}
1877
1878/*
Eric Dumazetc23fbb62007-05-08 00:26:18 -07001879 * Helper function for dentry_operations.d_dname() members
1880 */
1881char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
1882 const char *fmt, ...)
1883{
1884 va_list args;
1885 char temp[64];
1886 int sz;
1887
1888 va_start(args, fmt);
1889 sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
1890 va_end(args);
1891
1892 if (sz > sizeof(temp) || sz > buflen)
1893 return ERR_PTR(-ENAMETOOLONG);
1894
1895 buffer += buflen - sz;
1896 return memcpy(buffer, temp, sz);
1897}
1898
1899/*
Ram Pai6092d042008-03-27 13:06:20 +01001900 * Write full pathname from the root of the filesystem into the buffer.
1901 */
1902char *dentry_path(struct dentry *dentry, char *buf, int buflen)
1903{
1904 char *end = buf + buflen;
1905 char *retval;
1906
1907 spin_lock(&dcache_lock);
1908 prepend(&end, &buflen, "\0", 1);
1909 if (!IS_ROOT(dentry) && d_unhashed(dentry) &&
1910 (prepend(&end, &buflen, "//deleted", 9) != 0))
1911 goto Elong;
1912 if (buflen < 1)
1913 goto Elong;
1914 /* Get '/' right */
1915 retval = end-1;
1916 *retval = '/';
1917
1918 for (;;) {
1919 struct dentry *parent;
1920 if (IS_ROOT(dentry))
1921 break;
1922
1923 parent = dentry->d_parent;
1924 prefetch(parent);
1925
1926 if ((prepend(&end, &buflen, dentry->d_name.name,
1927 dentry->d_name.len) != 0) ||
1928 (prepend(&end, &buflen, "/", 1) != 0))
1929 goto Elong;
1930
1931 retval = end;
1932 dentry = parent;
1933 }
1934 spin_unlock(&dcache_lock);
1935 return retval;
1936Elong:
1937 spin_unlock(&dcache_lock);
1938 return ERR_PTR(-ENAMETOOLONG);
1939}
1940
1941/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001942 * NOTE! The user-level library version returns a
1943 * character pointer. The kernel system call just
1944 * returns the length of the buffer filled (which
1945 * includes the ending '\0' character), or a negative
1946 * error value. So libc would do something like
1947 *
1948 * char *getcwd(char * buf, size_t size)
1949 * {
1950 * int retval;
1951 *
1952 * retval = sys_getcwd(buf, size);
1953 * if (retval >= 0)
1954 * return buf;
1955 * errno = -retval;
1956 * return NULL;
1957 * }
1958 */
1959asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
1960{
Linus Torvalds552ce542007-02-13 12:08:18 -08001961 int error;
Jan Blunck6ac08c32008-02-14 19:34:38 -08001962 struct path pwd, root;
Linus Torvalds552ce542007-02-13 12:08:18 -08001963 char *page = (char *) __get_free_page(GFP_USER);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001964
1965 if (!page)
1966 return -ENOMEM;
1967
1968 read_lock(&current->fs->lock);
Jan Blunck6ac08c32008-02-14 19:34:38 -08001969 pwd = current->fs->pwd;
Ram Pai6092d042008-03-27 13:06:20 +01001970 path_get(&pwd);
Jan Blunck6ac08c32008-02-14 19:34:38 -08001971 root = current->fs->root;
Ram Pai6092d042008-03-27 13:06:20 +01001972 path_get(&root);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001973 read_unlock(&current->fs->lock);
1974
Linus Torvalds552ce542007-02-13 12:08:18 -08001975 error = -ENOENT;
1976 /* Has the current directory has been unlinked? */
1977 spin_lock(&dcache_lock);
Jan Blunck6ac08c32008-02-14 19:34:38 -08001978 if (pwd.dentry->d_parent == pwd.dentry || !d_unhashed(pwd.dentry)) {
Linus Torvalds552ce542007-02-13 12:08:18 -08001979 unsigned long len;
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001980 struct path tmp = root;
Linus Torvalds552ce542007-02-13 12:08:18 -08001981 char * cwd;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001982
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001983 cwd = __d_path(&pwd, &tmp, page, PAGE_SIZE);
Linus Torvalds552ce542007-02-13 12:08:18 -08001984 spin_unlock(&dcache_lock);
1985
1986 error = PTR_ERR(cwd);
1987 if (IS_ERR(cwd))
1988 goto out;
1989
1990 error = -ERANGE;
1991 len = PAGE_SIZE + page - cwd;
1992 if (len <= size) {
1993 error = len;
1994 if (copy_to_user(buf, cwd, len))
1995 error = -EFAULT;
1996 }
1997 } else
1998 spin_unlock(&dcache_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001999
2000out:
Jan Blunck6ac08c32008-02-14 19:34:38 -08002001 path_put(&pwd);
2002 path_put(&root);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002003 free_page((unsigned long) page);
2004 return error;
2005}
2006
2007/*
2008 * Test whether new_dentry is a subdirectory of old_dentry.
2009 *
2010 * Trivially implemented using the dcache structure
2011 */
2012
2013/**
2014 * is_subdir - is new dentry a subdirectory of old_dentry
2015 * @new_dentry: new dentry
2016 * @old_dentry: old dentry
2017 *
2018 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
2019 * Returns 0 otherwise.
2020 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
2021 */
2022
2023int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
2024{
2025 int result;
2026 struct dentry * saved = new_dentry;
2027 unsigned long seq;
2028
2029 /* need rcu_readlock to protect against the d_parent trashing due to
2030 * d_move
2031 */
2032 rcu_read_lock();
2033 do {
2034 /* for restarting inner loop in case of seq retry */
2035 new_dentry = saved;
2036 result = 0;
2037 seq = read_seqbegin(&rename_lock);
2038 for (;;) {
2039 if (new_dentry != old_dentry) {
2040 struct dentry * parent = new_dentry->d_parent;
2041 if (parent == new_dentry)
2042 break;
2043 new_dentry = parent;
2044 continue;
2045 }
2046 result = 1;
2047 break;
2048 }
2049 } while (read_seqretry(&rename_lock, seq));
2050 rcu_read_unlock();
2051
2052 return result;
2053}
2054
2055void d_genocide(struct dentry *root)
2056{
2057 struct dentry *this_parent = root;
2058 struct list_head *next;
2059
2060 spin_lock(&dcache_lock);
2061repeat:
2062 next = this_parent->d_subdirs.next;
2063resume:
2064 while (next != &this_parent->d_subdirs) {
2065 struct list_head *tmp = next;
Eric Dumazet5160ee62006-01-08 01:03:32 -08002066 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002067 next = tmp->next;
2068 if (d_unhashed(dentry)||!dentry->d_inode)
2069 continue;
2070 if (!list_empty(&dentry->d_subdirs)) {
2071 this_parent = dentry;
2072 goto repeat;
2073 }
2074 atomic_dec(&dentry->d_count);
2075 }
2076 if (this_parent != root) {
Eric Dumazet5160ee62006-01-08 01:03:32 -08002077 next = this_parent->d_u.d_child.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002078 atomic_dec(&this_parent->d_count);
2079 this_parent = this_parent->d_parent;
2080 goto resume;
2081 }
2082 spin_unlock(&dcache_lock);
2083}
2084
2085/**
2086 * find_inode_number - check for dentry with name
2087 * @dir: directory to check
2088 * @name: Name to find.
2089 *
2090 * Check whether a dentry already exists for the given name,
2091 * and return the inode number if it has an inode. Otherwise
2092 * 0 is returned.
2093 *
2094 * This routine is used to post-process directory listings for
2095 * filesystems using synthetic inode numbers, and is necessary
2096 * to keep getcwd() working.
2097 */
2098
2099ino_t find_inode_number(struct dentry *dir, struct qstr *name)
2100{
2101 struct dentry * dentry;
2102 ino_t ino = 0;
2103
Eric W. Biederman3e7e2412006-03-31 02:31:43 -08002104 dentry = d_hash_and_lookup(dir, name);
2105 if (dentry) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002106 if (dentry->d_inode)
2107 ino = dentry->d_inode->i_ino;
2108 dput(dentry);
2109 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002110 return ino;
2111}
2112
2113static __initdata unsigned long dhash_entries;
2114static int __init set_dhash_entries(char *str)
2115{
2116 if (!str)
2117 return 0;
2118 dhash_entries = simple_strtoul(str, &str, 0);
2119 return 1;
2120}
2121__setup("dhash_entries=", set_dhash_entries);
2122
2123static void __init dcache_init_early(void)
2124{
2125 int loop;
2126
2127 /* If hashes are distributed across NUMA nodes, defer
2128 * hash allocation until vmalloc space is available.
2129 */
2130 if (hashdist)
2131 return;
2132
2133 dentry_hashtable =
2134 alloc_large_system_hash("Dentry cache",
2135 sizeof(struct hlist_head),
2136 dhash_entries,
2137 13,
2138 HASH_EARLY,
2139 &d_hash_shift,
2140 &d_hash_mask,
2141 0);
2142
2143 for (loop = 0; loop < (1 << d_hash_shift); loop++)
2144 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
2145}
2146
Denis Cheng74bf17c2007-10-16 23:26:30 -07002147static void __init dcache_init(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002148{
2149 int loop;
2150
2151 /*
2152 * A constructor could be added for stable state like the lists,
2153 * but it is probably not worth it because of the cache nature
2154 * of the dcache.
2155 */
Christoph Lameter0a31bd52007-05-06 14:49:57 -07002156 dentry_cache = KMEM_CACHE(dentry,
2157 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002158
Rusty Russell8e1f9362007-07-17 04:03:17 -07002159 register_shrinker(&dcache_shrinker);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002160
2161 /* Hash may have been set up in dcache_init_early */
2162 if (!hashdist)
2163 return;
2164
2165 dentry_hashtable =
2166 alloc_large_system_hash("Dentry cache",
2167 sizeof(struct hlist_head),
2168 dhash_entries,
2169 13,
2170 0,
2171 &d_hash_shift,
2172 &d_hash_mask,
2173 0);
2174
2175 for (loop = 0; loop < (1 << d_hash_shift); loop++)
2176 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
2177}
2178
2179/* SLAB cache for __getname() consumers */
Christoph Lametere18b8902006-12-06 20:33:20 -08002180struct kmem_cache *names_cachep __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002181
2182/* SLAB cache for file structures */
Christoph Lametere18b8902006-12-06 20:33:20 -08002183struct kmem_cache *filp_cachep __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002184
2185EXPORT_SYMBOL(d_genocide);
2186
Linus Torvalds1da177e2005-04-16 15:20:36 -07002187void __init vfs_caches_init_early(void)
2188{
2189 dcache_init_early();
2190 inode_init_early();
2191}
2192
2193void __init vfs_caches_init(unsigned long mempages)
2194{
2195 unsigned long reserve;
2196
2197 /* Base hash sizes on available memory, with a reserve equal to
2198 150% of current kernel size */
2199
2200 reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
2201 mempages -= reserve;
2202
2203 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
Paul Mundt20c2df82007-07-20 10:11:58 +09002204 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002205
2206 filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
Paul Mundt20c2df82007-07-20 10:11:58 +09002207 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002208
Denis Cheng74bf17c2007-10-16 23:26:30 -07002209 dcache_init();
2210 inode_init();
Linus Torvalds1da177e2005-04-16 15:20:36 -07002211 files_init(mempages);
Denis Cheng74bf17c2007-10-16 23:26:30 -07002212 mnt_init();
Linus Torvalds1da177e2005-04-16 15:20:36 -07002213 bdev_cache_init();
2214 chrdev_init();
2215}
2216
2217EXPORT_SYMBOL(d_alloc);
2218EXPORT_SYMBOL(d_alloc_anon);
2219EXPORT_SYMBOL(d_alloc_root);
2220EXPORT_SYMBOL(d_delete);
2221EXPORT_SYMBOL(d_find_alias);
2222EXPORT_SYMBOL(d_instantiate);
2223EXPORT_SYMBOL(d_invalidate);
2224EXPORT_SYMBOL(d_lookup);
2225EXPORT_SYMBOL(d_move);
David Howells770bfad2006-08-22 20:06:07 -04002226EXPORT_SYMBOL_GPL(d_materialise_unique);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002227EXPORT_SYMBOL(d_path);
2228EXPORT_SYMBOL(d_prune_aliases);
2229EXPORT_SYMBOL(d_rehash);
2230EXPORT_SYMBOL(d_splice_alias);
2231EXPORT_SYMBOL(d_validate);
2232EXPORT_SYMBOL(dget_locked);
2233EXPORT_SYMBOL(dput);
2234EXPORT_SYMBOL(find_inode_number);
2235EXPORT_SYMBOL(have_submounts);
2236EXPORT_SYMBOL(names_cachep);
2237EXPORT_SYMBOL(shrink_dcache_parent);
2238EXPORT_SYMBOL(shrink_dcache_sb);