blob: 86d4db15473e51b3b95fa4103eedf28227cc336a [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>
Al Viro5ad4e532009-03-29 19:50:06 -040034#include <linux/fs_struct.h>
Frederic Weisbecker613afbf2009-07-16 15:44:29 +020035#include <linux/hardirq.h>
David Howells07f3f052006-09-30 20:52:18 +020036#include "internal.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -070037
Eric Dumazetfa3536c2006-03-26 01:37:24 -080038int sysctl_vfs_cache_pressure __read_mostly = 100;
Linus Torvalds1da177e2005-04-16 15:20:36 -070039EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
40
41 __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
Al Viro74c3cbe2007-07-22 08:04:18 -040042__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -070043
44EXPORT_SYMBOL(dcache_lock);
45
Christoph Lametere18b8902006-12-06 20:33:20 -080046static struct kmem_cache *dentry_cache __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -070047
48#define DNAME_INLINE_LEN (sizeof(struct dentry)-offsetof(struct dentry,d_iname))
49
50/*
51 * This is the single most critical data structure when it comes
52 * to the dcache: the hashtable for lookups. Somebody should try
53 * to make this good - I've just made it work.
54 *
55 * This hash-function tries to avoid losing too many bits of hash
56 * information, yet avoid using a prime hash-size or similar.
57 */
58#define D_HASHBITS d_hash_shift
59#define D_HASHMASK d_hash_mask
60
Eric Dumazetfa3536c2006-03-26 01:37:24 -080061static unsigned int d_hash_mask __read_mostly;
62static unsigned int d_hash_shift __read_mostly;
63static struct hlist_head *dentry_hashtable __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -070064
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{
Arjan van de Venfd217f42008-10-21 06:47:33 -070072 WARN_ON(!list_empty(&dentry->d_alias));
Linus Torvalds1da177e2005-04-16 15:20:36 -070073 if (dname_external(dentry))
74 kfree(dentry->d_name.name);
75 kmem_cache_free(dentry_cache, dentry);
76}
77
Eric Dumazetb3423412006-12-06 20:38:48 -080078static void d_callback(struct rcu_head *head)
79{
80 struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
81 __d_free(dentry);
82}
83
Linus Torvalds1da177e2005-04-16 15:20:36 -070084/*
85 * no dcache_lock, please. The caller must decrement dentry_stat.nr_dentry
86 * inside dcache_lock.
87 */
88static void d_free(struct dentry *dentry)
89{
90 if (dentry->d_op && dentry->d_op->d_release)
91 dentry->d_op->d_release(dentry);
Eric Dumazetb3423412006-12-06 20:38:48 -080092 /* if dentry was never inserted into hash, immediate free is OK */
Akinobu Mitae8462ca2008-02-06 01:37:07 -080093 if (hlist_unhashed(&dentry->d_hash))
Eric Dumazetb3423412006-12-06 20:38:48 -080094 __d_free(dentry);
95 else
96 call_rcu(&dentry->d_u.d_rcu, d_callback);
Linus Torvalds1da177e2005-04-16 15:20:36 -070097}
98
99/*
100 * Release the dentry's inode, using the filesystem
101 * d_iput() operation if defined.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 */
Arjan van de Ven858119e2006-01-14 13:20:43 -0800103static void dentry_iput(struct dentry * dentry)
Miklos Szeredi31f3e0b2008-06-23 18:11:52 +0200104 __releases(dentry->d_lock)
105 __releases(dcache_lock)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106{
107 struct inode *inode = dentry->d_inode;
108 if (inode) {
109 dentry->d_inode = NULL;
110 list_del_init(&dentry->d_alias);
111 spin_unlock(&dentry->d_lock);
112 spin_unlock(&dcache_lock);
Linus Torvaldsf805fbd2005-09-19 19:54:29 -0700113 if (!inode->i_nlink)
114 fsnotify_inoderemove(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 if (dentry->d_op && dentry->d_op->d_iput)
116 dentry->d_op->d_iput(dentry, inode);
117 else
118 iput(inode);
119 } else {
120 spin_unlock(&dentry->d_lock);
121 spin_unlock(&dcache_lock);
122 }
123}
124
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700125/*
126 * dentry_lru_(add|add_tail|del|del_init) must be called with dcache_lock held.
127 */
128static void dentry_lru_add(struct dentry *dentry)
129{
130 list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
131 dentry->d_sb->s_nr_dentry_unused++;
132 dentry_stat.nr_unused++;
133}
134
135static void dentry_lru_add_tail(struct dentry *dentry)
136{
137 list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
138 dentry->d_sb->s_nr_dentry_unused++;
139 dentry_stat.nr_unused++;
140}
141
142static void dentry_lru_del(struct dentry *dentry)
143{
144 if (!list_empty(&dentry->d_lru)) {
145 list_del(&dentry->d_lru);
146 dentry->d_sb->s_nr_dentry_unused--;
147 dentry_stat.nr_unused--;
148 }
149}
150
151static void dentry_lru_del_init(struct dentry *dentry)
152{
153 if (likely(!list_empty(&dentry->d_lru))) {
154 list_del_init(&dentry->d_lru);
155 dentry->d_sb->s_nr_dentry_unused--;
156 dentry_stat.nr_unused--;
157 }
158}
159
Miklos Szeredid52b9082007-05-08 00:23:46 -0700160/**
161 * d_kill - kill dentry and return parent
162 * @dentry: dentry to kill
163 *
Miklos Szeredi31f3e0b2008-06-23 18:11:52 +0200164 * The dentry must already be unhashed and removed from the LRU.
Miklos Szeredid52b9082007-05-08 00:23:46 -0700165 *
166 * If this is the root of the dentry tree, return NULL.
167 */
168static struct dentry *d_kill(struct dentry *dentry)
Miklos Szeredi31f3e0b2008-06-23 18:11:52 +0200169 __releases(dentry->d_lock)
170 __releases(dcache_lock)
Miklos Szeredid52b9082007-05-08 00:23:46 -0700171{
172 struct dentry *parent;
173
174 list_del(&dentry->d_u.d_child);
175 dentry_stat.nr_dentry--; /* For d_free, below */
176 /*drops the locks, at that point nobody can reach this dentry */
177 dentry_iput(dentry);
OGAWA Hirofumi871c0062008-10-16 07:50:27 +0900178 if (IS_ROOT(dentry))
179 parent = NULL;
180 else
181 parent = dentry->d_parent;
Miklos Szeredid52b9082007-05-08 00:23:46 -0700182 d_free(dentry);
OGAWA Hirofumi871c0062008-10-16 07:50:27 +0900183 return parent;
Miklos Szeredid52b9082007-05-08 00:23:46 -0700184}
185
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186/*
187 * This is dput
188 *
189 * This is complicated by the fact that we do not want to put
190 * dentries that are no longer on any hash chain on the unused
191 * list: we'd much rather just get rid of them immediately.
192 *
193 * However, that implies that we have to traverse the dentry
194 * tree upwards to the parents which might _also_ now be
195 * scheduled for deletion (it may have been only waiting for
196 * its last child to go away).
197 *
198 * This tail recursion is done by hand as we don't want to depend
199 * on the compiler to always get this right (gcc generally doesn't).
200 * Real recursion would eat up our stack space.
201 */
202
203/*
204 * dput - release a dentry
205 * @dentry: dentry to release
206 *
207 * Release a dentry. This will drop the usage count and if appropriate
208 * call the dentry unlink method as well as removing it from the queues and
209 * releasing its resources. If the parent dentries were scheduled for release
210 * they too may now get deleted.
211 *
212 * no dcache lock, please.
213 */
214
215void dput(struct dentry *dentry)
216{
217 if (!dentry)
218 return;
219
220repeat:
221 if (atomic_read(&dentry->d_count) == 1)
222 might_sleep();
223 if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
224 return;
225
226 spin_lock(&dentry->d_lock);
227 if (atomic_read(&dentry->d_count)) {
228 spin_unlock(&dentry->d_lock);
229 spin_unlock(&dcache_lock);
230 return;
231 }
232
233 /*
234 * AV: ->d_delete() is _NOT_ allowed to block now.
235 */
236 if (dentry->d_op && dentry->d_op->d_delete) {
237 if (dentry->d_op->d_delete(dentry))
238 goto unhash_it;
239 }
240 /* Unreachable? Get rid of it */
241 if (d_unhashed(dentry))
242 goto kill_it;
243 if (list_empty(&dentry->d_lru)) {
244 dentry->d_flags |= DCACHE_REFERENCED;
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700245 dentry_lru_add(dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700246 }
247 spin_unlock(&dentry->d_lock);
248 spin_unlock(&dcache_lock);
249 return;
250
251unhash_it:
252 __d_drop(dentry);
Miklos Szeredid52b9082007-05-08 00:23:46 -0700253kill_it:
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700254 /* if dentry was on the d_lru list delete it from there */
255 dentry_lru_del(dentry);
Miklos Szeredid52b9082007-05-08 00:23:46 -0700256 dentry = d_kill(dentry);
257 if (dentry)
258 goto repeat;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700259}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -0700260EXPORT_SYMBOL(dput);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700261
262/**
263 * d_invalidate - invalidate a dentry
264 * @dentry: dentry to invalidate
265 *
266 * Try to invalidate the dentry if it turns out to be
267 * possible. If there are other dentries that can be
268 * reached through this one we can't delete it and we
269 * return -EBUSY. On success we return 0.
270 *
271 * no dcache lock.
272 */
273
274int d_invalidate(struct dentry * dentry)
275{
276 /*
277 * If it's already been dropped, return OK.
278 */
279 spin_lock(&dcache_lock);
280 if (d_unhashed(dentry)) {
281 spin_unlock(&dcache_lock);
282 return 0;
283 }
284 /*
285 * Check whether to do a partial shrink_dcache
286 * to get rid of unused child entries.
287 */
288 if (!list_empty(&dentry->d_subdirs)) {
289 spin_unlock(&dcache_lock);
290 shrink_dcache_parent(dentry);
291 spin_lock(&dcache_lock);
292 }
293
294 /*
295 * Somebody else still using it?
296 *
297 * If it's a directory, we can't drop it
298 * for fear of somebody re-populating it
299 * with children (even though dropping it
300 * would make it unreachable from the root,
301 * we might still populate it if it was a
302 * working directory or similar).
303 */
304 spin_lock(&dentry->d_lock);
305 if (atomic_read(&dentry->d_count) > 1) {
306 if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
307 spin_unlock(&dentry->d_lock);
308 spin_unlock(&dcache_lock);
309 return -EBUSY;
310 }
311 }
312
313 __d_drop(dentry);
314 spin_unlock(&dentry->d_lock);
315 spin_unlock(&dcache_lock);
316 return 0;
317}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -0700318EXPORT_SYMBOL(d_invalidate);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700319
320/* This should be called _only_ with dcache_lock held */
321
322static inline struct dentry * __dget_locked(struct dentry *dentry)
323{
324 atomic_inc(&dentry->d_count);
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700325 dentry_lru_del_init(dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700326 return dentry;
327}
328
329struct dentry * dget_locked(struct dentry *dentry)
330{
331 return __dget_locked(dentry);
332}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -0700333EXPORT_SYMBOL(dget_locked);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700334
335/**
336 * d_find_alias - grab a hashed alias of inode
337 * @inode: inode in question
338 * @want_discon: flag, used by d_splice_alias, to request
339 * that only a DISCONNECTED alias be returned.
340 *
341 * If inode has a hashed alias, or is a directory and has any alias,
342 * acquire the reference to alias and return it. Otherwise return NULL.
343 * Notice that if inode is a directory there can be only one alias and
344 * it can be unhashed only if it has no children, or if it is the root
345 * of a filesystem.
346 *
NeilBrown21c0d8f2006-10-04 02:16:16 -0700347 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
Linus Torvalds1da177e2005-04-16 15:20:36 -0700348 * any other hashed alias over that one unless @want_discon is set,
NeilBrown21c0d8f2006-10-04 02:16:16 -0700349 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700350 */
351
352static struct dentry * __d_find_alias(struct inode *inode, int want_discon)
353{
354 struct list_head *head, *next, *tmp;
355 struct dentry *alias, *discon_alias=NULL;
356
357 head = &inode->i_dentry;
358 next = inode->i_dentry.next;
359 while (next != head) {
360 tmp = next;
361 next = tmp->next;
362 prefetch(next);
363 alias = list_entry(tmp, struct dentry, d_alias);
364 if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
NeilBrown21c0d8f2006-10-04 02:16:16 -0700365 if (IS_ROOT(alias) &&
366 (alias->d_flags & DCACHE_DISCONNECTED))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 discon_alias = alias;
368 else if (!want_discon) {
369 __dget_locked(alias);
370 return alias;
371 }
372 }
373 }
374 if (discon_alias)
375 __dget_locked(discon_alias);
376 return discon_alias;
377}
378
379struct dentry * d_find_alias(struct inode *inode)
380{
David Howells214fda12006-03-25 03:06:36 -0800381 struct dentry *de = NULL;
382
383 if (!list_empty(&inode->i_dentry)) {
384 spin_lock(&dcache_lock);
385 de = __d_find_alias(inode, 0);
386 spin_unlock(&dcache_lock);
387 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700388 return de;
389}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -0700390EXPORT_SYMBOL(d_find_alias);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700391
392/*
393 * Try to kill dentries associated with this inode.
394 * WARNING: you must own a reference to inode.
395 */
396void d_prune_aliases(struct inode *inode)
397{
Domen Puncer0cdca3f2005-09-10 00:27:07 -0700398 struct dentry *dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399restart:
400 spin_lock(&dcache_lock);
Domen Puncer0cdca3f2005-09-10 00:27:07 -0700401 list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700402 spin_lock(&dentry->d_lock);
403 if (!atomic_read(&dentry->d_count)) {
404 __dget_locked(dentry);
405 __d_drop(dentry);
406 spin_unlock(&dentry->d_lock);
407 spin_unlock(&dcache_lock);
408 dput(dentry);
409 goto restart;
410 }
411 spin_unlock(&dentry->d_lock);
412 }
413 spin_unlock(&dcache_lock);
414}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -0700415EXPORT_SYMBOL(d_prune_aliases);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700416
417/*
Andrew Mortond702ccb2006-06-22 14:47:31 -0700418 * Throw away a dentry - free the inode, dput the parent. This requires that
419 * the LRU list has already been removed.
420 *
Miklos Szeredi85864e12007-10-16 23:27:09 -0700421 * Try to prune ancestors as well. This is necessary to prevent
422 * quadratic behavior of shrink_dcache_parent(), but is also expected
423 * to be beneficial in reducing dentry cache fragmentation.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700424 */
Miklos Szeredi85864e12007-10-16 23:27:09 -0700425static void prune_one_dentry(struct dentry * dentry)
Miklos Szeredi31f3e0b2008-06-23 18:11:52 +0200426 __releases(dentry->d_lock)
427 __releases(dcache_lock)
428 __acquires(dcache_lock)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700429{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700430 __d_drop(dentry);
Miklos Szeredid52b9082007-05-08 00:23:46 -0700431 dentry = d_kill(dentry);
Miklos Szeredid52b9082007-05-08 00:23:46 -0700432
433 /*
434 * Prune ancestors. Locking is simpler than in dput(),
435 * because dcache_lock needs to be taken anyway.
436 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700437 spin_lock(&dcache_lock);
Miklos Szeredid52b9082007-05-08 00:23:46 -0700438 while (dentry) {
439 if (!atomic_dec_and_lock(&dentry->d_count, &dentry->d_lock))
440 return;
441
442 if (dentry->d_op && dentry->d_op->d_delete)
443 dentry->d_op->d_delete(dentry);
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700444 dentry_lru_del_init(dentry);
Miklos Szeredid52b9082007-05-08 00:23:46 -0700445 __d_drop(dentry);
446 dentry = d_kill(dentry);
447 spin_lock(&dcache_lock);
448 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700449}
450
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700451/*
452 * Shrink the dentry LRU on a given superblock.
453 * @sb : superblock to shrink dentry LRU.
454 * @count: If count is NULL, we prune all dentries on superblock.
455 * @flags: If flags is non-zero, we need to do special processing based on
456 * which flags are set. This means we don't need to maintain multiple
457 * similar copies of this loop.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700458 */
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700459static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700460{
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700461 LIST_HEAD(referenced);
462 LIST_HEAD(tmp);
463 struct dentry *dentry;
464 int cnt = 0;
465
466 BUG_ON(!sb);
467 BUG_ON((flags & DCACHE_REFERENCED) && count == NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700468 spin_lock(&dcache_lock);
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700469 if (count != NULL)
470 /* called from prune_dcache() and shrink_dcache_parent() */
471 cnt = *count;
472restart:
473 if (count == NULL)
474 list_splice_init(&sb->s_dentry_lru, &tmp);
475 else {
476 while (!list_empty(&sb->s_dentry_lru)) {
477 dentry = list_entry(sb->s_dentry_lru.prev,
478 struct dentry, d_lru);
479 BUG_ON(dentry->d_sb != sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700480
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700481 spin_lock(&dentry->d_lock);
482 /*
483 * If we are honouring the DCACHE_REFERENCED flag and
484 * the dentry has this flag set, don't free it. Clear
485 * the flag and put it back on the LRU.
NeilBrown0feae5c2006-06-22 14:47:28 -0700486 */
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700487 if ((flags & DCACHE_REFERENCED)
488 && (dentry->d_flags & DCACHE_REFERENCED)) {
489 dentry->d_flags &= ~DCACHE_REFERENCED;
npiggin@suse.dec490d792009-04-26 20:25:53 +1000490 list_move(&dentry->d_lru, &referenced);
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700491 spin_unlock(&dentry->d_lock);
492 } else {
493 list_move_tail(&dentry->d_lru, &tmp);
494 spin_unlock(&dentry->d_lock);
495 cnt--;
496 if (!cnt)
497 break;
NeilBrown0feae5c2006-06-22 14:47:28 -0700498 }
Kentaro Makitaf3c6ba92008-07-25 19:44:40 -0700499 cond_resched_lock(&dcache_lock);
NeilBrown0feae5c2006-06-22 14:47:28 -0700500 }
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700501 }
502 while (!list_empty(&tmp)) {
503 dentry = list_entry(tmp.prev, struct dentry, d_lru);
504 dentry_lru_del_init(dentry);
505 spin_lock(&dentry->d_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506 /*
507 * We found an inuse dentry which was not removed from
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700508 * the LRU because of laziness during lookup. Do not free
509 * it - just keep it off the LRU list.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700510 */
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700511 if (atomic_read(&dentry->d_count)) {
512 spin_unlock(&dentry->d_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513 continue;
514 }
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700515 prune_one_dentry(dentry);
516 /* dentry->d_lock was dropped in prune_one_dentry() */
517 cond_resched_lock(&dcache_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700518 }
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700519 if (count == NULL && !list_empty(&sb->s_dentry_lru))
520 goto restart;
521 if (count != NULL)
522 *count = cnt;
523 if (!list_empty(&referenced))
524 list_splice(&referenced, &sb->s_dentry_lru);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700525 spin_unlock(&dcache_lock);
526}
527
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700528/**
529 * prune_dcache - shrink the dcache
530 * @count: number of entries to try to free
Linus Torvalds1da177e2005-04-16 15:20:36 -0700531 *
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700532 * Shrink the dcache. This is done when we need more memory, or simply when we
533 * need to unmount something (at which point we need to unuse all dentries).
534 *
535 * This function may fail to free any resources if all the dentries are in use.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700536 */
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700537static void prune_dcache(int count)
538{
Al Viro79893c12010-03-22 20:27:55 -0400539 struct super_block *sb, *n;
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700540 int w_count;
541 int unused = dentry_stat.nr_unused;
542 int prune_ratio;
543 int pruned;
544
545 if (unused == 0 || count == 0)
546 return;
547 spin_lock(&dcache_lock);
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700548 if (count >= unused)
549 prune_ratio = 1;
550 else
551 prune_ratio = unused / count;
552 spin_lock(&sb_lock);
Al Viro79893c12010-03-22 20:27:55 -0400553 list_for_each_entry_safe(sb, n, &super_blocks, s_list) {
Al Viro551de6f2010-03-22 19:36:35 -0400554 if (list_empty(&sb->s_instances))
555 continue;
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700556 if (sb->s_nr_dentry_unused == 0)
557 continue;
558 sb->s_count++;
559 /* Now, we reclaim unused dentrins with fairness.
560 * We reclaim them same percentage from each superblock.
561 * We calculate number of dentries to scan on this sb
562 * as follows, but the implementation is arranged to avoid
563 * overflows:
564 * number of dentries to scan on this sb =
565 * count * (number of dentries on this sb /
566 * number of dentries in the machine)
567 */
568 spin_unlock(&sb_lock);
569 if (prune_ratio != 1)
570 w_count = (sb->s_nr_dentry_unused / prune_ratio) + 1;
571 else
572 w_count = sb->s_nr_dentry_unused;
573 pruned = w_count;
574 /*
575 * We need to be sure this filesystem isn't being unmounted,
576 * otherwise we could race with generic_shutdown_super(), and
577 * end up holding a reference to an inode while the filesystem
578 * is unmounted. So we try to get s_umount, and make sure
579 * s_root isn't NULL.
580 */
581 if (down_read_trylock(&sb->s_umount)) {
582 if ((sb->s_root != NULL) &&
583 (!list_empty(&sb->s_dentry_lru))) {
584 spin_unlock(&dcache_lock);
585 __shrink_dcache_sb(sb, &w_count,
586 DCACHE_REFERENCED);
587 pruned -= w_count;
588 spin_lock(&dcache_lock);
589 }
590 up_read(&sb->s_umount);
591 }
592 spin_lock(&sb_lock);
npiggin@suse.de57439f82010-06-24 13:02:14 +1000593 /* lock was dropped, must reset next */
594 list_safe_reset_next(sb, n, s_list);
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700595 count -= pruned;
Al Viro79893c12010-03-22 20:27:55 -0400596 __put_super(sb);
597 /* more work left to do? */
598 if (count <= 0)
599 break;
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700600 }
601 spin_unlock(&sb_lock);
602 spin_unlock(&dcache_lock);
603}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700604
605/**
606 * shrink_dcache_sb - shrink dcache for a superblock
607 * @sb: superblock
608 *
609 * Shrink the dcache for the specified super block. This
610 * is used to free the dcache before unmounting a file
611 * system
612 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700613void shrink_dcache_sb(struct super_block * sb)
614{
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700615 __shrink_dcache_sb(sb, NULL, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700616}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -0700617EXPORT_SYMBOL(shrink_dcache_sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700618
619/*
David Howellsc636ebd2006-10-11 01:22:19 -0700620 * destroy a single subtree of dentries for unmount
621 * - see the comments on shrink_dcache_for_umount() for a description of the
622 * locking
623 */
624static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
625{
626 struct dentry *parent;
David Howellsf8713572006-10-28 10:38:46 -0700627 unsigned detached = 0;
David Howellsc636ebd2006-10-11 01:22:19 -0700628
629 BUG_ON(!IS_ROOT(dentry));
630
631 /* detach this root from the system */
632 spin_lock(&dcache_lock);
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700633 dentry_lru_del_init(dentry);
David Howellsc636ebd2006-10-11 01:22:19 -0700634 __d_drop(dentry);
635 spin_unlock(&dcache_lock);
636
637 for (;;) {
638 /* descend to the first leaf in the current subtree */
639 while (!list_empty(&dentry->d_subdirs)) {
640 struct dentry *loop;
641
642 /* this is a branch with children - detach all of them
643 * from the system in one go */
644 spin_lock(&dcache_lock);
645 list_for_each_entry(loop, &dentry->d_subdirs,
646 d_u.d_child) {
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700647 dentry_lru_del_init(loop);
David Howellsc636ebd2006-10-11 01:22:19 -0700648 __d_drop(loop);
649 cond_resched_lock(&dcache_lock);
650 }
651 spin_unlock(&dcache_lock);
652
653 /* move to the first child */
654 dentry = list_entry(dentry->d_subdirs.next,
655 struct dentry, d_u.d_child);
656 }
657
658 /* consume the dentries from this leaf up through its parents
659 * until we find one with children or run out altogether */
660 do {
661 struct inode *inode;
662
663 if (atomic_read(&dentry->d_count) != 0) {
664 printk(KERN_ERR
665 "BUG: Dentry %p{i=%lx,n=%s}"
666 " still in use (%d)"
667 " [unmount of %s %s]\n",
668 dentry,
669 dentry->d_inode ?
670 dentry->d_inode->i_ino : 0UL,
671 dentry->d_name.name,
672 atomic_read(&dentry->d_count),
673 dentry->d_sb->s_type->name,
674 dentry->d_sb->s_id);
675 BUG();
676 }
677
OGAWA Hirofumi871c0062008-10-16 07:50:27 +0900678 if (IS_ROOT(dentry))
David Howellsc636ebd2006-10-11 01:22:19 -0700679 parent = NULL;
OGAWA Hirofumi871c0062008-10-16 07:50:27 +0900680 else {
681 parent = dentry->d_parent;
David Howellsc636ebd2006-10-11 01:22:19 -0700682 atomic_dec(&parent->d_count);
OGAWA Hirofumi871c0062008-10-16 07:50:27 +0900683 }
David Howellsc636ebd2006-10-11 01:22:19 -0700684
685 list_del(&dentry->d_u.d_child);
David Howellsf8713572006-10-28 10:38:46 -0700686 detached++;
David Howellsc636ebd2006-10-11 01:22:19 -0700687
688 inode = dentry->d_inode;
689 if (inode) {
690 dentry->d_inode = NULL;
691 list_del_init(&dentry->d_alias);
692 if (dentry->d_op && dentry->d_op->d_iput)
693 dentry->d_op->d_iput(dentry, inode);
694 else
695 iput(inode);
696 }
697
698 d_free(dentry);
699
700 /* finished when we fall off the top of the tree,
701 * otherwise we ascend to the parent and move to the
702 * next sibling if there is one */
703 if (!parent)
David Howellsf8713572006-10-28 10:38:46 -0700704 goto out;
David Howellsc636ebd2006-10-11 01:22:19 -0700705
706 dentry = parent;
707
708 } while (list_empty(&dentry->d_subdirs));
709
710 dentry = list_entry(dentry->d_subdirs.next,
711 struct dentry, d_u.d_child);
712 }
David Howellsf8713572006-10-28 10:38:46 -0700713out:
714 /* several dentries were freed, need to correct nr_dentry */
715 spin_lock(&dcache_lock);
716 dentry_stat.nr_dentry -= detached;
717 spin_unlock(&dcache_lock);
David Howellsc636ebd2006-10-11 01:22:19 -0700718}
719
720/*
721 * destroy the dentries attached to a superblock on unmounting
722 * - we don't need to use dentry->d_lock, and only need dcache_lock when
723 * removing the dentry from the system lists and hashes because:
724 * - the superblock is detached from all mountings and open files, so the
725 * dentry trees will not be rearranged by the VFS
726 * - s_umount is write-locked, so the memory pressure shrinker will ignore
727 * any dentries belonging to this superblock that it comes across
728 * - the filesystem itself is no longer permitted to rearrange the dentries
729 * in this superblock
730 */
731void shrink_dcache_for_umount(struct super_block *sb)
732{
733 struct dentry *dentry;
734
735 if (down_read_trylock(&sb->s_umount))
736 BUG();
737
738 dentry = sb->s_root;
739 sb->s_root = NULL;
740 atomic_dec(&dentry->d_count);
741 shrink_dcache_for_umount_subtree(dentry);
742
743 while (!hlist_empty(&sb->s_anon)) {
744 dentry = hlist_entry(sb->s_anon.first, struct dentry, d_hash);
745 shrink_dcache_for_umount_subtree(dentry);
746 }
747}
748
749/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700750 * Search for at least 1 mount point in the dentry's subdirs.
751 * We descend to the next level whenever the d_subdirs
752 * list is non-empty and continue searching.
753 */
754
755/**
756 * have_submounts - check for mounts over a dentry
757 * @parent: dentry to check.
758 *
759 * Return true if the parent or its subdirectories contain
760 * a mount point
761 */
762
763int have_submounts(struct dentry *parent)
764{
765 struct dentry *this_parent = parent;
766 struct list_head *next;
767
768 spin_lock(&dcache_lock);
769 if (d_mountpoint(parent))
770 goto positive;
771repeat:
772 next = this_parent->d_subdirs.next;
773resume:
774 while (next != &this_parent->d_subdirs) {
775 struct list_head *tmp = next;
Eric Dumazet5160ee62006-01-08 01:03:32 -0800776 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700777 next = tmp->next;
778 /* Have we found a mount point ? */
779 if (d_mountpoint(dentry))
780 goto positive;
781 if (!list_empty(&dentry->d_subdirs)) {
782 this_parent = dentry;
783 goto repeat;
784 }
785 }
786 /*
787 * All done at this level ... ascend and resume the search.
788 */
789 if (this_parent != parent) {
Eric Dumazet5160ee62006-01-08 01:03:32 -0800790 next = this_parent->d_u.d_child.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700791 this_parent = this_parent->d_parent;
792 goto resume;
793 }
794 spin_unlock(&dcache_lock);
795 return 0; /* No mount points found in tree */
796positive:
797 spin_unlock(&dcache_lock);
798 return 1;
799}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -0700800EXPORT_SYMBOL(have_submounts);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700801
802/*
803 * Search the dentry child list for the specified parent,
804 * and move any unused dentries to the end of the unused
805 * list for prune_dcache(). We descend to the next level
806 * whenever the d_subdirs list is non-empty and continue
807 * searching.
808 *
809 * It returns zero iff there are no unused children,
810 * otherwise it returns the number of children moved to
811 * the end of the unused list. This may not be the total
812 * number of unused children, because select_parent can
813 * drop the lock and return early due to latency
814 * constraints.
815 */
816static int select_parent(struct dentry * parent)
817{
818 struct dentry *this_parent = parent;
819 struct list_head *next;
820 int found = 0;
821
822 spin_lock(&dcache_lock);
823repeat:
824 next = this_parent->d_subdirs.next;
825resume:
826 while (next != &this_parent->d_subdirs) {
827 struct list_head *tmp = next;
Eric Dumazet5160ee62006-01-08 01:03:32 -0800828 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700829 next = tmp->next;
830
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700831 dentry_lru_del_init(dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700832 /*
833 * move only zero ref count dentries to the end
834 * of the unused list for prune_dcache
835 */
836 if (!atomic_read(&dentry->d_count)) {
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700837 dentry_lru_add_tail(dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700838 found++;
839 }
840
841 /*
842 * We can return to the caller if we have found some (this
843 * ensures forward progress). We'll be coming back to find
844 * the rest.
845 */
846 if (found && need_resched())
847 goto out;
848
849 /*
850 * Descend a level if the d_subdirs list is non-empty.
851 */
852 if (!list_empty(&dentry->d_subdirs)) {
853 this_parent = dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700854 goto repeat;
855 }
856 }
857 /*
858 * All done at this level ... ascend and resume the search.
859 */
860 if (this_parent != parent) {
Eric Dumazet5160ee62006-01-08 01:03:32 -0800861 next = this_parent->d_u.d_child.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700862 this_parent = this_parent->d_parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700863 goto resume;
864 }
865out:
866 spin_unlock(&dcache_lock);
867 return found;
868}
869
870/**
871 * shrink_dcache_parent - prune dcache
872 * @parent: parent of entries to prune
873 *
874 * Prune the dcache to remove unused children of the parent dentry.
875 */
876
877void shrink_dcache_parent(struct dentry * parent)
878{
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700879 struct super_block *sb = parent->d_sb;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700880 int found;
881
882 while ((found = select_parent(parent)) != 0)
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700883 __shrink_dcache_sb(sb, &found, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700884}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -0700885EXPORT_SYMBOL(shrink_dcache_parent);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700886
Linus Torvalds1da177e2005-04-16 15:20:36 -0700887/*
888 * Scan `nr' dentries and return the number which remain.
889 *
890 * We need to avoid reentering the filesystem if the caller is performing a
891 * GFP_NOFS allocation attempt. One example deadlock is:
892 *
893 * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
894 * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
895 * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
896 *
897 * In this case we return -1 to tell the caller that we baled.
898 */
Dave Chinner7f8275d2010-07-19 14:56:17 +1000899static int shrink_dcache_memory(struct shrinker *shrink, int nr, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700900{
901 if (nr) {
902 if (!(gfp_mask & __GFP_FS))
903 return -1;
Kentaro Makitada3bbdd2008-07-23 21:27:13 -0700904 prune_dcache(nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700905 }
906 return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
907}
908
Rusty Russell8e1f9362007-07-17 04:03:17 -0700909static struct shrinker dcache_shrinker = {
910 .shrink = shrink_dcache_memory,
911 .seeks = DEFAULT_SEEKS,
912};
913
Linus Torvalds1da177e2005-04-16 15:20:36 -0700914/**
915 * d_alloc - allocate a dcache entry
916 * @parent: parent of entry to allocate
917 * @name: qstr of the name
918 *
919 * Allocates a dentry. It returns %NULL if there is insufficient memory
920 * available. On a success the dentry is returned. The name passed in is
921 * copied and the copy passed in may be reused after this call.
922 */
923
924struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
925{
926 struct dentry *dentry;
927 char *dname;
928
Mel Gormane12ba742007-10-16 01:25:52 -0700929 dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700930 if (!dentry)
931 return NULL;
932
933 if (name->len > DNAME_INLINE_LEN-1) {
934 dname = kmalloc(name->len + 1, GFP_KERNEL);
935 if (!dname) {
936 kmem_cache_free(dentry_cache, dentry);
937 return NULL;
938 }
939 } else {
940 dname = dentry->d_iname;
941 }
942 dentry->d_name.name = dname;
943
944 dentry->d_name.len = name->len;
945 dentry->d_name.hash = name->hash;
946 memcpy(dname, name->name, name->len);
947 dname[name->len] = 0;
948
949 atomic_set(&dentry->d_count, 1);
950 dentry->d_flags = DCACHE_UNHASHED;
951 spin_lock_init(&dentry->d_lock);
952 dentry->d_inode = NULL;
953 dentry->d_parent = NULL;
954 dentry->d_sb = NULL;
955 dentry->d_op = NULL;
956 dentry->d_fsdata = NULL;
957 dentry->d_mounted = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700958 INIT_HLIST_NODE(&dentry->d_hash);
959 INIT_LIST_HEAD(&dentry->d_lru);
960 INIT_LIST_HEAD(&dentry->d_subdirs);
961 INIT_LIST_HEAD(&dentry->d_alias);
962
963 if (parent) {
964 dentry->d_parent = dget(parent);
965 dentry->d_sb = parent->d_sb;
966 } else {
Eric Dumazet5160ee62006-01-08 01:03:32 -0800967 INIT_LIST_HEAD(&dentry->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700968 }
969
970 spin_lock(&dcache_lock);
971 if (parent)
Eric Dumazet5160ee62006-01-08 01:03:32 -0800972 list_add(&dentry->d_u.d_child, &parent->d_subdirs);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700973 dentry_stat.nr_dentry++;
974 spin_unlock(&dcache_lock);
975
976 return dentry;
977}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -0700978EXPORT_SYMBOL(d_alloc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700979
980struct dentry *d_alloc_name(struct dentry *parent, const char *name)
981{
982 struct qstr q;
983
984 q.name = name;
985 q.len = strlen(name);
986 q.hash = full_name_hash(q.name, q.len);
987 return d_alloc(parent, &q);
988}
H Hartley Sweetenef26ca92009-09-29 20:09:42 -0400989EXPORT_SYMBOL(d_alloc_name);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700990
OGAWA Hirofumi360da902008-10-16 07:50:28 +0900991/* the caller must hold dcache_lock */
992static void __d_instantiate(struct dentry *dentry, struct inode *inode)
993{
994 if (inode)
995 list_add(&dentry->d_alias, &inode->i_dentry);
996 dentry->d_inode = inode;
997 fsnotify_d_instantiate(dentry, inode);
998}
999
Linus Torvalds1da177e2005-04-16 15:20:36 -07001000/**
1001 * d_instantiate - fill in inode information for a dentry
1002 * @entry: dentry to complete
1003 * @inode: inode to attach to this dentry
1004 *
1005 * Fill in inode information in the entry.
1006 *
1007 * This turns negative dentries into productive full members
1008 * of society.
1009 *
1010 * NOTE! This assumes that the inode count has been incremented
1011 * (or otherwise set) by the caller to indicate that it is now
1012 * in use by the dcache.
1013 */
1014
1015void d_instantiate(struct dentry *entry, struct inode * inode)
1016{
Eric Sesterhenn28133c72006-03-26 18:25:39 +02001017 BUG_ON(!list_empty(&entry->d_alias));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001018 spin_lock(&dcache_lock);
OGAWA Hirofumi360da902008-10-16 07:50:28 +09001019 __d_instantiate(entry, inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001020 spin_unlock(&dcache_lock);
1021 security_d_instantiate(entry, inode);
1022}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -07001023EXPORT_SYMBOL(d_instantiate);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001024
1025/**
1026 * d_instantiate_unique - instantiate a non-aliased dentry
1027 * @entry: dentry to instantiate
1028 * @inode: inode to attach to this dentry
1029 *
1030 * Fill in inode information in the entry. On success, it returns NULL.
1031 * If an unhashed alias of "entry" already exists, then we return the
Oleg Drokine866cfa2006-01-09 20:52:51 -08001032 * aliased dentry instead and drop one reference to inode.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033 *
1034 * Note that in order to avoid conflicts with rename() etc, the caller
1035 * had better be holding the parent directory semaphore.
Oleg Drokine866cfa2006-01-09 20:52:51 -08001036 *
1037 * This also assumes that the inode count has been incremented
1038 * (or otherwise set) by the caller to indicate that it is now
1039 * in use by the dcache.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001040 */
David Howells770bfad2006-08-22 20:06:07 -04001041static struct dentry *__d_instantiate_unique(struct dentry *entry,
1042 struct inode *inode)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001043{
1044 struct dentry *alias;
1045 int len = entry->d_name.len;
1046 const char *name = entry->d_name.name;
1047 unsigned int hash = entry->d_name.hash;
1048
David Howells770bfad2006-08-22 20:06:07 -04001049 if (!inode) {
OGAWA Hirofumi360da902008-10-16 07:50:28 +09001050 __d_instantiate(entry, NULL);
David Howells770bfad2006-08-22 20:06:07 -04001051 return NULL;
1052 }
1053
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054 list_for_each_entry(alias, &inode->i_dentry, d_alias) {
1055 struct qstr *qstr = &alias->d_name;
1056
1057 if (qstr->hash != hash)
1058 continue;
1059 if (alias->d_parent != entry->d_parent)
1060 continue;
1061 if (qstr->len != len)
1062 continue;
1063 if (memcmp(qstr->name, name, len))
1064 continue;
1065 dget_locked(alias);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066 return alias;
1067 }
David Howells770bfad2006-08-22 20:06:07 -04001068
OGAWA Hirofumi360da902008-10-16 07:50:28 +09001069 __d_instantiate(entry, inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001070 return NULL;
1071}
David Howells770bfad2006-08-22 20:06:07 -04001072
1073struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
1074{
1075 struct dentry *result;
1076
1077 BUG_ON(!list_empty(&entry->d_alias));
1078
1079 spin_lock(&dcache_lock);
1080 result = __d_instantiate_unique(entry, inode);
1081 spin_unlock(&dcache_lock);
1082
1083 if (!result) {
1084 security_d_instantiate(entry, inode);
1085 return NULL;
1086 }
1087
1088 BUG_ON(!d_unhashed(result));
1089 iput(inode);
1090 return result;
1091}
1092
Linus Torvalds1da177e2005-04-16 15:20:36 -07001093EXPORT_SYMBOL(d_instantiate_unique);
1094
1095/**
1096 * d_alloc_root - allocate root dentry
1097 * @root_inode: inode to allocate the root for
1098 *
1099 * Allocate a root ("/") dentry for the inode given. The inode is
1100 * instantiated and returned. %NULL is returned if there is insufficient
1101 * memory or the inode passed is %NULL.
1102 */
1103
1104struct dentry * d_alloc_root(struct inode * root_inode)
1105{
1106 struct dentry *res = NULL;
1107
1108 if (root_inode) {
1109 static const struct qstr name = { .name = "/", .len = 1 };
1110
1111 res = d_alloc(NULL, &name);
1112 if (res) {
1113 res->d_sb = root_inode->i_sb;
1114 res->d_parent = res;
1115 d_instantiate(res, root_inode);
1116 }
1117 }
1118 return res;
1119}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -07001120EXPORT_SYMBOL(d_alloc_root);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001121
1122static inline struct hlist_head *d_hash(struct dentry *parent,
1123 unsigned long hash)
1124{
1125 hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
1126 hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
1127 return dentry_hashtable + (hash & D_HASHMASK);
1128}
1129
1130/**
Christoph Hellwig4ea3ada2008-08-11 15:48:57 +02001131 * d_obtain_alias - find or allocate a dentry for a given inode
1132 * @inode: inode to allocate the dentry for
1133 *
1134 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
1135 * similar open by handle operations. The returned dentry may be anonymous,
1136 * or may have a full name (if the inode was already in the cache).
1137 *
1138 * When called on a directory inode, we must ensure that the inode only ever
1139 * has one dentry. If a dentry is found, that is returned instead of
1140 * allocating a new one.
1141 *
1142 * On successful return, the reference to the inode has been transferred
Christoph Hellwig44003722008-08-11 15:49:04 +02001143 * to the dentry. In case of an error the reference on the inode is released.
1144 * To make it easier to use in export operations a %NULL or IS_ERR inode may
1145 * be passed in and will be the error will be propagate to the return value,
1146 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
Christoph Hellwig4ea3ada2008-08-11 15:48:57 +02001147 */
1148struct dentry *d_obtain_alias(struct inode *inode)
1149{
Christoph Hellwig9308a612008-08-11 15:49:12 +02001150 static const struct qstr anonstring = { .name = "" };
1151 struct dentry *tmp;
1152 struct dentry *res;
Christoph Hellwig4ea3ada2008-08-11 15:48:57 +02001153
1154 if (!inode)
Christoph Hellwig44003722008-08-11 15:49:04 +02001155 return ERR_PTR(-ESTALE);
Christoph Hellwig4ea3ada2008-08-11 15:48:57 +02001156 if (IS_ERR(inode))
1157 return ERR_CAST(inode);
1158
Christoph Hellwig9308a612008-08-11 15:49:12 +02001159 res = d_find_alias(inode);
1160 if (res)
1161 goto out_iput;
1162
1163 tmp = d_alloc(NULL, &anonstring);
1164 if (!tmp) {
1165 res = ERR_PTR(-ENOMEM);
1166 goto out_iput;
Christoph Hellwig4ea3ada2008-08-11 15:48:57 +02001167 }
Christoph Hellwig9308a612008-08-11 15:49:12 +02001168 tmp->d_parent = tmp; /* make sure dput doesn't croak */
1169
1170 spin_lock(&dcache_lock);
1171 res = __d_find_alias(inode, 0);
1172 if (res) {
1173 spin_unlock(&dcache_lock);
1174 dput(tmp);
1175 goto out_iput;
1176 }
1177
1178 /* attach a disconnected dentry */
1179 spin_lock(&tmp->d_lock);
1180 tmp->d_sb = inode->i_sb;
1181 tmp->d_inode = inode;
1182 tmp->d_flags |= DCACHE_DISCONNECTED;
1183 tmp->d_flags &= ~DCACHE_UNHASHED;
1184 list_add(&tmp->d_alias, &inode->i_dentry);
1185 hlist_add_head(&tmp->d_hash, &inode->i_sb->s_anon);
1186 spin_unlock(&tmp->d_lock);
1187
1188 spin_unlock(&dcache_lock);
1189 return tmp;
1190
1191 out_iput:
1192 iput(inode);
1193 return res;
Christoph Hellwig4ea3ada2008-08-11 15:48:57 +02001194}
Benny Halevyadc48722009-02-27 14:02:59 -08001195EXPORT_SYMBOL(d_obtain_alias);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001196
1197/**
1198 * d_splice_alias - splice a disconnected dentry into the tree if one exists
1199 * @inode: the inode which may have a disconnected dentry
1200 * @dentry: a negative dentry which we want to point to the inode.
1201 *
1202 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
1203 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
1204 * and return it, else simply d_add the inode to the dentry and return NULL.
1205 *
1206 * This is needed in the lookup routine of any filesystem that is exportable
1207 * (via knfsd) so that we can build dcache paths to directories effectively.
1208 *
1209 * If a dentry was found and moved, then it is returned. Otherwise NULL
1210 * is returned. This matches the expected return value of ->lookup.
1211 *
1212 */
1213struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
1214{
1215 struct dentry *new = NULL;
1216
NeilBrown21c0d8f2006-10-04 02:16:16 -07001217 if (inode && S_ISDIR(inode->i_mode)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001218 spin_lock(&dcache_lock);
1219 new = __d_find_alias(inode, 1);
1220 if (new) {
1221 BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
1222 spin_unlock(&dcache_lock);
1223 security_d_instantiate(new, inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001224 d_move(new, dentry);
1225 iput(inode);
1226 } else {
OGAWA Hirofumi360da902008-10-16 07:50:28 +09001227 /* already taking dcache_lock, so d_add() by hand */
1228 __d_instantiate(dentry, inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001229 spin_unlock(&dcache_lock);
1230 security_d_instantiate(dentry, inode);
1231 d_rehash(dentry);
1232 }
1233 } else
1234 d_add(dentry, inode);
1235 return new;
1236}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -07001237EXPORT_SYMBOL(d_splice_alias);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001238
Barry Naujok94035402008-05-21 16:50:46 +10001239/**
1240 * d_add_ci - lookup or allocate new dentry with case-exact name
1241 * @inode: the inode case-insensitive lookup has found
1242 * @dentry: the negative dentry that was passed to the parent's lookup func
1243 * @name: the case-exact name to be associated with the returned dentry
1244 *
1245 * This is to avoid filling the dcache with case-insensitive names to the
1246 * same inode, only the actual correct case is stored in the dcache for
1247 * case-insensitive filesystems.
1248 *
1249 * For a case-insensitive lookup match and if the the case-exact dentry
1250 * already exists in in the dcache, use it and return it.
1251 *
1252 * If no entry exists with the exact case name, allocate new dentry with
1253 * the exact case, and return the spliced entry.
1254 */
Christoph Hellwige45b5902008-08-07 23:49:07 +02001255struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
Barry Naujok94035402008-05-21 16:50:46 +10001256 struct qstr *name)
1257{
1258 int error;
1259 struct dentry *found;
1260 struct dentry *new;
1261
Christoph Hellwigb6520c82009-01-05 19:10:37 +01001262 /*
1263 * First check if a dentry matching the name already exists,
1264 * if not go ahead and create it now.
1265 */
Barry Naujok94035402008-05-21 16:50:46 +10001266 found = d_hash_and_lookup(dentry->d_parent, name);
Barry Naujok94035402008-05-21 16:50:46 +10001267 if (!found) {
1268 new = d_alloc(dentry->d_parent, name);
1269 if (!new) {
1270 error = -ENOMEM;
1271 goto err_out;
1272 }
Christoph Hellwigb6520c82009-01-05 19:10:37 +01001273
Barry Naujok94035402008-05-21 16:50:46 +10001274 found = d_splice_alias(inode, new);
1275 if (found) {
1276 dput(new);
1277 return found;
1278 }
1279 return new;
1280 }
Christoph Hellwigb6520c82009-01-05 19:10:37 +01001281
1282 /*
1283 * If a matching dentry exists, and it's not negative use it.
1284 *
1285 * Decrement the reference count to balance the iget() done
1286 * earlier on.
1287 */
Barry Naujok94035402008-05-21 16:50:46 +10001288 if (found->d_inode) {
1289 if (unlikely(found->d_inode != inode)) {
1290 /* This can't happen because bad inodes are unhashed. */
1291 BUG_ON(!is_bad_inode(inode));
1292 BUG_ON(!is_bad_inode(found->d_inode));
1293 }
Barry Naujok94035402008-05-21 16:50:46 +10001294 iput(inode);
1295 return found;
1296 }
Christoph Hellwigb6520c82009-01-05 19:10:37 +01001297
Barry Naujok94035402008-05-21 16:50:46 +10001298 /*
1299 * Negative dentry: instantiate it unless the inode is a directory and
Christoph Hellwigb6520c82009-01-05 19:10:37 +01001300 * already has a dentry.
Barry Naujok94035402008-05-21 16:50:46 +10001301 */
Barry Naujok94035402008-05-21 16:50:46 +10001302 spin_lock(&dcache_lock);
Christoph Hellwigb6520c82009-01-05 19:10:37 +01001303 if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) {
OGAWA Hirofumi360da902008-10-16 07:50:28 +09001304 __d_instantiate(found, inode);
Barry Naujok94035402008-05-21 16:50:46 +10001305 spin_unlock(&dcache_lock);
1306 security_d_instantiate(found, inode);
1307 return found;
1308 }
Christoph Hellwigb6520c82009-01-05 19:10:37 +01001309
Barry Naujok94035402008-05-21 16:50:46 +10001310 /*
Christoph Hellwigb6520c82009-01-05 19:10:37 +01001311 * In case a directory already has a (disconnected) entry grab a
1312 * reference to it, move it in place and use it.
Barry Naujok94035402008-05-21 16:50:46 +10001313 */
1314 new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
1315 dget_locked(new);
1316 spin_unlock(&dcache_lock);
Barry Naujok94035402008-05-21 16:50:46 +10001317 security_d_instantiate(found, inode);
Barry Naujok94035402008-05-21 16:50:46 +10001318 d_move(new, found);
Barry Naujok94035402008-05-21 16:50:46 +10001319 iput(inode);
Barry Naujok94035402008-05-21 16:50:46 +10001320 dput(found);
Barry Naujok94035402008-05-21 16:50:46 +10001321 return new;
1322
1323err_out:
1324 iput(inode);
1325 return ERR_PTR(error);
1326}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -07001327EXPORT_SYMBOL(d_add_ci);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001328
1329/**
1330 * d_lookup - search for a dentry
1331 * @parent: parent dentry
1332 * @name: qstr of name we wish to find
1333 *
1334 * Searches the children of the parent dentry for the name in question. If
1335 * the dentry is found its reference count is incremented and the dentry
Zhaoleibe42c4c2008-12-01 14:34:58 -08001336 * is returned. The caller must use dput to free the entry when it has
Linus Torvalds1da177e2005-04-16 15:20:36 -07001337 * finished using it. %NULL is returned on failure.
1338 *
1339 * __d_lookup is dcache_lock free. The hash list is protected using RCU.
1340 * Memory barriers are used while updating and doing lockless traversal.
1341 * To avoid races with d_move while rename is happening, d_lock is used.
1342 *
1343 * Overflows in memcmp(), while d_move, are avoided by keeping the length
1344 * and name pointer in one structure pointed by d_qstr.
1345 *
1346 * rcu_read_lock() and rcu_read_unlock() are used to disable preemption while
1347 * lookup is going on.
1348 *
Kentaro Makitada3bbdd2008-07-23 21:27:13 -07001349 * The dentry unused LRU is not updated even if lookup finds the required dentry
Linus Torvalds1da177e2005-04-16 15:20:36 -07001350 * in there. It is updated in places such as prune_dcache, shrink_dcache_sb,
1351 * select_parent and __dget_locked. This laziness saves lookup from dcache_lock
1352 * acquisition.
1353 *
1354 * d_lookup() is protected against the concurrent renames in some unrelated
1355 * directory using the seqlockt_t rename_lock.
1356 */
1357
1358struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
1359{
1360 struct dentry * dentry = NULL;
1361 unsigned long seq;
1362
1363 do {
1364 seq = read_seqbegin(&rename_lock);
1365 dentry = __d_lookup(parent, name);
1366 if (dentry)
1367 break;
1368 } while (read_seqretry(&rename_lock, seq));
1369 return dentry;
1370}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -07001371EXPORT_SYMBOL(d_lookup);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001372
1373struct dentry * __d_lookup(struct dentry * parent, struct qstr * name)
1374{
1375 unsigned int len = name->len;
1376 unsigned int hash = name->hash;
1377 const unsigned char *str = name->name;
1378 struct hlist_head *head = d_hash(parent,hash);
1379 struct dentry *found = NULL;
1380 struct hlist_node *node;
Paul E. McKenney665a7582005-11-07 00:59:17 -08001381 struct dentry *dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001382
1383 rcu_read_lock();
1384
Paul E. McKenney665a7582005-11-07 00:59:17 -08001385 hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001386 struct qstr *qstr;
1387
Linus Torvalds1da177e2005-04-16 15:20:36 -07001388 if (dentry->d_name.hash != hash)
1389 continue;
1390 if (dentry->d_parent != parent)
1391 continue;
1392
1393 spin_lock(&dentry->d_lock);
1394
1395 /*
1396 * Recheck the dentry after taking the lock - d_move may have
1397 * changed things. Don't bother checking the hash because we're
1398 * about to compare the whole name anyway.
1399 */
1400 if (dentry->d_parent != parent)
1401 goto next;
1402
Linus Torvaldsd0185c02008-09-29 07:42:57 -07001403 /* non-existing due to RCU? */
1404 if (d_unhashed(dentry))
1405 goto next;
1406
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407 /*
1408 * It is safe to compare names since d_move() cannot
1409 * change the qstr (protected by d_lock).
1410 */
1411 qstr = &dentry->d_name;
1412 if (parent->d_op && parent->d_op->d_compare) {
1413 if (parent->d_op->d_compare(parent, qstr, name))
1414 goto next;
1415 } else {
1416 if (qstr->len != len)
1417 goto next;
1418 if (memcmp(qstr->name, str, len))
1419 goto next;
1420 }
1421
Linus Torvaldsd0185c02008-09-29 07:42:57 -07001422 atomic_inc(&dentry->d_count);
1423 found = dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001424 spin_unlock(&dentry->d_lock);
1425 break;
1426next:
1427 spin_unlock(&dentry->d_lock);
1428 }
1429 rcu_read_unlock();
1430
1431 return found;
1432}
1433
1434/**
Eric W. Biederman3e7e2412006-03-31 02:31:43 -08001435 * d_hash_and_lookup - hash the qstr then search for a dentry
1436 * @dir: Directory to search in
1437 * @name: qstr of name we wish to find
1438 *
1439 * On hash failure or on lookup failure NULL is returned.
1440 */
1441struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
1442{
1443 struct dentry *dentry = NULL;
1444
1445 /*
1446 * Check for a fs-specific hash function. Note that we must
1447 * calculate the standard hash first, as the d_op->d_hash()
1448 * routine may choose to leave the hash value unchanged.
1449 */
1450 name->hash = full_name_hash(name->name, name->len);
1451 if (dir->d_op && dir->d_op->d_hash) {
1452 if (dir->d_op->d_hash(dir, name) < 0)
1453 goto out;
1454 }
1455 dentry = d_lookup(dir, name);
1456out:
1457 return dentry;
1458}
1459
1460/**
Linus Torvalds1da177e2005-04-16 15:20:36 -07001461 * d_validate - verify dentry provided from insecure source
1462 * @dentry: The dentry alleged to be valid child of @dparent
1463 * @dparent: The parent dentry (known to be valid)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464 *
1465 * An insecure source has sent us a dentry, here we verify it and dget() it.
1466 * This is used by ncpfs in its readdir implementation.
1467 * Zero is returned in the dentry is invalid.
1468 */
1469
1470int d_validate(struct dentry *dentry, struct dentry *dparent)
1471{
1472 struct hlist_head *base;
1473 struct hlist_node *lhp;
1474
1475 /* Check whether the ptr might be valid at all.. */
1476 if (!kmem_ptr_validate(dentry_cache, dentry))
1477 goto out;
1478
1479 if (dentry->d_parent != dparent)
1480 goto out;
1481
1482 spin_lock(&dcache_lock);
1483 base = d_hash(dparent, dentry->d_name.hash);
1484 hlist_for_each(lhp,base) {
Paul E. McKenney665a7582005-11-07 00:59:17 -08001485 /* hlist_for_each_entry_rcu() not required for d_hash list
Linus Torvalds1da177e2005-04-16 15:20:36 -07001486 * as it is parsed under dcache_lock
1487 */
1488 if (dentry == hlist_entry(lhp, struct dentry, d_hash)) {
1489 __dget_locked(dentry);
1490 spin_unlock(&dcache_lock);
1491 return 1;
1492 }
1493 }
1494 spin_unlock(&dcache_lock);
1495out:
1496 return 0;
1497}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -07001498EXPORT_SYMBOL(d_validate);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001499
1500/*
1501 * When a file is deleted, we have two options:
1502 * - turn this dentry into a negative dentry
1503 * - unhash this dentry and free it.
1504 *
1505 * Usually, we want to just turn this into
1506 * a negative dentry, but if anybody else is
1507 * currently using the dentry or the inode
1508 * we can't do that and we fall back on removing
1509 * it from the hash queues and waiting for
1510 * it to be deleted later when it has no users
1511 */
1512
1513/**
1514 * d_delete - delete a dentry
1515 * @dentry: The dentry to delete
1516 *
1517 * Turn the dentry into a negative dentry if possible, otherwise
1518 * remove it from the hash queues so it can be deleted later
1519 */
1520
1521void d_delete(struct dentry * dentry)
1522{
John McCutchan7a91bf72005-08-08 13:52:16 -04001523 int isdir = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001524 /*
1525 * Are we the only user?
1526 */
1527 spin_lock(&dcache_lock);
1528 spin_lock(&dentry->d_lock);
John McCutchan7a91bf72005-08-08 13:52:16 -04001529 isdir = S_ISDIR(dentry->d_inode->i_mode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001530 if (atomic_read(&dentry->d_count) == 1) {
Al Viro13e3c5e2010-05-21 16:11:04 -04001531 dentry->d_flags &= ~DCACHE_CANT_MOUNT;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001532 dentry_iput(dentry);
John McCutchan7a91bf72005-08-08 13:52:16 -04001533 fsnotify_nameremove(dentry, isdir);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001534 return;
1535 }
1536
1537 if (!d_unhashed(dentry))
1538 __d_drop(dentry);
1539
1540 spin_unlock(&dentry->d_lock);
1541 spin_unlock(&dcache_lock);
John McCutchan7a91bf72005-08-08 13:52:16 -04001542
1543 fsnotify_nameremove(dentry, isdir);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001544}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -07001545EXPORT_SYMBOL(d_delete);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001546
1547static void __d_rehash(struct dentry * entry, struct hlist_head *list)
1548{
1549
1550 entry->d_flags &= ~DCACHE_UNHASHED;
1551 hlist_add_head_rcu(&entry->d_hash, list);
1552}
1553
David Howells770bfad2006-08-22 20:06:07 -04001554static void _d_rehash(struct dentry * entry)
1555{
1556 __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
1557}
1558
Linus Torvalds1da177e2005-04-16 15:20:36 -07001559/**
1560 * d_rehash - add an entry back to the hash
1561 * @entry: dentry to add to the hash
1562 *
1563 * Adds a dentry to the hash according to its name.
1564 */
1565
1566void d_rehash(struct dentry * entry)
1567{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001568 spin_lock(&dcache_lock);
1569 spin_lock(&entry->d_lock);
David Howells770bfad2006-08-22 20:06:07 -04001570 _d_rehash(entry);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001571 spin_unlock(&entry->d_lock);
1572 spin_unlock(&dcache_lock);
1573}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -07001574EXPORT_SYMBOL(d_rehash);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001575
Linus Torvalds1da177e2005-04-16 15:20:36 -07001576/*
1577 * When switching names, the actual string doesn't strictly have to
1578 * be preserved in the target - because we're dropping the target
1579 * anyway. As such, we can just do a simple memcpy() to copy over
1580 * the new name before we switch.
1581 *
1582 * Note that we have to be a lot more careful about getting the hash
1583 * switched - we have to switch the hash value properly even if it
1584 * then no longer matches the actual (corrupted) string of the target.
1585 * The hash value has to match the hash queue that the dentry is on..
1586 */
1587static void switch_names(struct dentry *dentry, struct dentry *target)
1588{
1589 if (dname_external(target)) {
1590 if (dname_external(dentry)) {
1591 /*
1592 * Both external: swap the pointers
1593 */
Wu Fengguang9a8d5bb2009-01-07 18:09:14 -08001594 swap(target->d_name.name, dentry->d_name.name);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001595 } else {
1596 /*
1597 * dentry:internal, target:external. Steal target's
1598 * storage and make target internal.
1599 */
J. Bruce Fields321bcf92007-10-21 16:41:38 -07001600 memcpy(target->d_iname, dentry->d_name.name,
1601 dentry->d_name.len + 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001602 dentry->d_name.name = target->d_name.name;
1603 target->d_name.name = target->d_iname;
1604 }
1605 } else {
1606 if (dname_external(dentry)) {
1607 /*
1608 * dentry:external, target:internal. Give dentry's
1609 * storage to target and make dentry internal
1610 */
1611 memcpy(dentry->d_iname, target->d_name.name,
1612 target->d_name.len + 1);
1613 target->d_name.name = dentry->d_name.name;
1614 dentry->d_name.name = dentry->d_iname;
1615 } else {
1616 /*
1617 * Both are internal. Just copy target to dentry
1618 */
1619 memcpy(dentry->d_iname, target->d_name.name,
1620 target->d_name.len + 1);
Al Virodc711ca2008-11-03 15:03:50 -05001621 dentry->d_name.len = target->d_name.len;
1622 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001623 }
1624 }
Wu Fengguang9a8d5bb2009-01-07 18:09:14 -08001625 swap(dentry->d_name.len, target->d_name.len);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001626}
1627
1628/*
1629 * We cannibalize "target" when moving dentry on top of it,
1630 * because it's going to be thrown away anyway. We could be more
1631 * polite about it, though.
1632 *
1633 * This forceful removal will result in ugly /proc output if
1634 * somebody holds a file open that got deleted due to a rename.
1635 * We could be nicer about the deleted file, and let it show
J. Bruce Fieldsbc154b12007-10-16 23:29:42 -07001636 * up under the name it had before it was deleted rather than
1637 * under the original name of the file that was moved on top of it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001638 */
1639
Trond Myklebust9eaef272006-10-21 10:24:20 -07001640/*
1641 * d_move_locked - move a dentry
Linus Torvalds1da177e2005-04-16 15:20:36 -07001642 * @dentry: entry to move
1643 * @target: new dentry
1644 *
1645 * Update the dcache to reflect the move of a file name. Negative
1646 * dcache entries should not be moved in this way.
1647 */
Trond Myklebust9eaef272006-10-21 10:24:20 -07001648static void d_move_locked(struct dentry * dentry, struct dentry * target)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001649{
1650 struct hlist_head *list;
1651
1652 if (!dentry->d_inode)
1653 printk(KERN_WARNING "VFS: moving negative dcache entry\n");
1654
Linus Torvalds1da177e2005-04-16 15:20:36 -07001655 write_seqlock(&rename_lock);
1656 /*
1657 * XXXX: do we really need to take target->d_lock?
1658 */
1659 if (target < dentry) {
1660 spin_lock(&target->d_lock);
Ingo Molnara90b9c02006-07-03 00:25:04 -07001661 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001662 } else {
1663 spin_lock(&dentry->d_lock);
Ingo Molnara90b9c02006-07-03 00:25:04 -07001664 spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001665 }
1666
1667 /* Move the dentry to the target hash queue, if on different bucket */
Denis Chengf77e3492007-10-16 23:30:11 -07001668 if (d_unhashed(dentry))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001669 goto already_unhashed;
1670
1671 hlist_del_rcu(&dentry->d_hash);
1672
1673already_unhashed:
1674 list = d_hash(target->d_parent, target->d_name.hash);
1675 __d_rehash(dentry, list);
1676
1677 /* Unhash the target: dput() will then get rid of it */
1678 __d_drop(target);
1679
Eric Dumazet5160ee62006-01-08 01:03:32 -08001680 list_del(&dentry->d_u.d_child);
1681 list_del(&target->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001682
1683 /* Switch the names.. */
1684 switch_names(dentry, target);
Wu Fengguang9a8d5bb2009-01-07 18:09:14 -08001685 swap(dentry->d_name.hash, target->d_name.hash);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001686
1687 /* ... and switch the parents */
1688 if (IS_ROOT(dentry)) {
1689 dentry->d_parent = target->d_parent;
1690 target->d_parent = target;
Eric Dumazet5160ee62006-01-08 01:03:32 -08001691 INIT_LIST_HEAD(&target->d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001692 } else {
Wu Fengguang9a8d5bb2009-01-07 18:09:14 -08001693 swap(dentry->d_parent, target->d_parent);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001694
1695 /* And add them back to the (new) parent lists */
Eric Dumazet5160ee62006-01-08 01:03:32 -08001696 list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001697 }
1698
Eric Dumazet5160ee62006-01-08 01:03:32 -08001699 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001700 spin_unlock(&target->d_lock);
Nick Pigginc32ccd82006-03-25 03:07:09 -08001701 fsnotify_d_move(dentry);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001702 spin_unlock(&dentry->d_lock);
1703 write_sequnlock(&rename_lock);
Trond Myklebust9eaef272006-10-21 10:24:20 -07001704}
1705
1706/**
1707 * d_move - move a dentry
1708 * @dentry: entry to move
1709 * @target: new dentry
1710 *
1711 * Update the dcache to reflect the move of a file name. Negative
1712 * dcache entries should not be moved in this way.
1713 */
1714
1715void d_move(struct dentry * dentry, struct dentry * target)
1716{
1717 spin_lock(&dcache_lock);
1718 d_move_locked(dentry, target);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001719 spin_unlock(&dcache_lock);
1720}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -07001721EXPORT_SYMBOL(d_move);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001722
OGAWA Hirofumie2761a12008-10-16 07:50:28 +09001723/**
1724 * d_ancestor - search for an ancestor
1725 * @p1: ancestor dentry
1726 * @p2: child dentry
1727 *
1728 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
1729 * an ancestor of p2, else NULL.
Trond Myklebust9eaef272006-10-21 10:24:20 -07001730 */
OGAWA Hirofumie2761a12008-10-16 07:50:28 +09001731struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
Trond Myklebust9eaef272006-10-21 10:24:20 -07001732{
1733 struct dentry *p;
1734
OGAWA Hirofumi871c0062008-10-16 07:50:27 +09001735 for (p = p2; !IS_ROOT(p); p = p->d_parent) {
Trond Myklebust9eaef272006-10-21 10:24:20 -07001736 if (p->d_parent == p1)
OGAWA Hirofumie2761a12008-10-16 07:50:28 +09001737 return p;
Trond Myklebust9eaef272006-10-21 10:24:20 -07001738 }
OGAWA Hirofumie2761a12008-10-16 07:50:28 +09001739 return NULL;
Trond Myklebust9eaef272006-10-21 10:24:20 -07001740}
1741
1742/*
1743 * This helper attempts to cope with remotely renamed directories
1744 *
1745 * It assumes that the caller is already holding
1746 * dentry->d_parent->d_inode->i_mutex and the dcache_lock
1747 *
1748 * Note: If ever the locking in lock_rename() changes, then please
1749 * remember to update this too...
Trond Myklebust9eaef272006-10-21 10:24:20 -07001750 */
1751static struct dentry *__d_unalias(struct dentry *dentry, struct dentry *alias)
Miklos Szeredi31f3e0b2008-06-23 18:11:52 +02001752 __releases(dcache_lock)
Trond Myklebust9eaef272006-10-21 10:24:20 -07001753{
1754 struct mutex *m1 = NULL, *m2 = NULL;
1755 struct dentry *ret;
1756
1757 /* If alias and dentry share a parent, then no extra locks required */
1758 if (alias->d_parent == dentry->d_parent)
1759 goto out_unalias;
1760
1761 /* Check for loops */
1762 ret = ERR_PTR(-ELOOP);
OGAWA Hirofumie2761a12008-10-16 07:50:28 +09001763 if (d_ancestor(alias, dentry))
Trond Myklebust9eaef272006-10-21 10:24:20 -07001764 goto out_err;
1765
1766 /* See lock_rename() */
1767 ret = ERR_PTR(-EBUSY);
1768 if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
1769 goto out_err;
1770 m1 = &dentry->d_sb->s_vfs_rename_mutex;
1771 if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
1772 goto out_err;
1773 m2 = &alias->d_parent->d_inode->i_mutex;
1774out_unalias:
1775 d_move_locked(alias, dentry);
1776 ret = alias;
1777out_err:
1778 spin_unlock(&dcache_lock);
1779 if (m2)
1780 mutex_unlock(m2);
1781 if (m1)
1782 mutex_unlock(m1);
1783 return ret;
1784}
1785
1786/*
David Howells770bfad2006-08-22 20:06:07 -04001787 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
1788 * named dentry in place of the dentry to be replaced.
1789 */
1790static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
1791{
1792 struct dentry *dparent, *aparent;
1793
1794 switch_names(dentry, anon);
Wu Fengguang9a8d5bb2009-01-07 18:09:14 -08001795 swap(dentry->d_name.hash, anon->d_name.hash);
David Howells770bfad2006-08-22 20:06:07 -04001796
1797 dparent = dentry->d_parent;
1798 aparent = anon->d_parent;
1799
1800 dentry->d_parent = (aparent == anon) ? dentry : aparent;
1801 list_del(&dentry->d_u.d_child);
1802 if (!IS_ROOT(dentry))
1803 list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
1804 else
1805 INIT_LIST_HEAD(&dentry->d_u.d_child);
1806
1807 anon->d_parent = (dparent == dentry) ? anon : dparent;
1808 list_del(&anon->d_u.d_child);
1809 if (!IS_ROOT(anon))
1810 list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
1811 else
1812 INIT_LIST_HEAD(&anon->d_u.d_child);
1813
1814 anon->d_flags &= ~DCACHE_DISCONNECTED;
1815}
1816
1817/**
1818 * d_materialise_unique - introduce an inode into the tree
1819 * @dentry: candidate dentry
1820 * @inode: inode to bind to the dentry, to which aliases may be attached
1821 *
1822 * Introduces an dentry into the tree, substituting an extant disconnected
1823 * root directory alias in its place if there is one
1824 */
1825struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
1826{
Trond Myklebust9eaef272006-10-21 10:24:20 -07001827 struct dentry *actual;
David Howells770bfad2006-08-22 20:06:07 -04001828
1829 BUG_ON(!d_unhashed(dentry));
1830
1831 spin_lock(&dcache_lock);
1832
1833 if (!inode) {
1834 actual = dentry;
OGAWA Hirofumi360da902008-10-16 07:50:28 +09001835 __d_instantiate(dentry, NULL);
David Howells770bfad2006-08-22 20:06:07 -04001836 goto found_lock;
1837 }
1838
Trond Myklebust9eaef272006-10-21 10:24:20 -07001839 if (S_ISDIR(inode->i_mode)) {
1840 struct dentry *alias;
David Howells770bfad2006-08-22 20:06:07 -04001841
Trond Myklebust9eaef272006-10-21 10:24:20 -07001842 /* Does an aliased dentry already exist? */
1843 alias = __d_find_alias(inode, 0);
1844 if (alias) {
1845 actual = alias;
1846 /* Is this an anonymous mountpoint that we could splice
1847 * into our tree? */
1848 if (IS_ROOT(alias)) {
1849 spin_lock(&alias->d_lock);
1850 __d_materialise_dentry(dentry, alias);
1851 __d_drop(alias);
1852 goto found;
1853 }
1854 /* Nope, but we must(!) avoid directory aliasing */
1855 actual = __d_unalias(dentry, alias);
1856 if (IS_ERR(actual))
1857 dput(alias);
1858 goto out_nolock;
1859 }
David Howells770bfad2006-08-22 20:06:07 -04001860 }
1861
1862 /* Add a unique reference */
1863 actual = __d_instantiate_unique(dentry, inode);
1864 if (!actual)
1865 actual = dentry;
1866 else if (unlikely(!d_unhashed(actual)))
1867 goto shouldnt_be_hashed;
1868
1869found_lock:
1870 spin_lock(&actual->d_lock);
1871found:
1872 _d_rehash(actual);
1873 spin_unlock(&actual->d_lock);
1874 spin_unlock(&dcache_lock);
Trond Myklebust9eaef272006-10-21 10:24:20 -07001875out_nolock:
David Howells770bfad2006-08-22 20:06:07 -04001876 if (actual == dentry) {
1877 security_d_instantiate(dentry, inode);
1878 return NULL;
1879 }
1880
1881 iput(inode);
1882 return actual;
1883
David Howells770bfad2006-08-22 20:06:07 -04001884shouldnt_be_hashed:
1885 spin_unlock(&dcache_lock);
1886 BUG();
David Howells770bfad2006-08-22 20:06:07 -04001887}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -07001888EXPORT_SYMBOL_GPL(d_materialise_unique);
David Howells770bfad2006-08-22 20:06:07 -04001889
Miklos Szeredicdd16d02008-06-23 18:11:53 +02001890static int prepend(char **buffer, int *buflen, const char *str, int namelen)
Ram Pai6092d042008-03-27 13:06:20 +01001891{
1892 *buflen -= namelen;
1893 if (*buflen < 0)
1894 return -ENAMETOOLONG;
1895 *buffer -= namelen;
1896 memcpy(*buffer, str, namelen);
1897 return 0;
1898}
1899
Miklos Szeredicdd16d02008-06-23 18:11:53 +02001900static int prepend_name(char **buffer, int *buflen, struct qstr *name)
1901{
1902 return prepend(buffer, buflen, name->name, name->len);
1903}
1904
Linus Torvalds1da177e2005-04-16 15:20:36 -07001905/**
Miklos Szeredi31f3e0b2008-06-23 18:11:52 +02001906 * __d_path - return the path of a dentry
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001907 * @path: the dentry/vfsmount to report
1908 * @root: root vfsmnt/dentry (may be modified by this function)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001909 * @buffer: buffer to return value in
1910 * @buflen: buffer length
1911 *
Linus Torvalds552ce542007-02-13 12:08:18 -08001912 * Convert a dentry into an ASCII path name. If the entry has been deleted
1913 * the string " (deleted)" is appended. Note that this is ambiguous.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001914 *
Arjan van de Ven52afeef2008-12-01 14:35:00 -08001915 * Returns a pointer into the buffer or an error code if the
1916 * path was too long.
Linus Torvalds552ce542007-02-13 12:08:18 -08001917 *
1918 * "buflen" should be positive. Caller holds the dcache_lock.
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001919 *
1920 * If path is not reachable from the supplied root, then the value of
1921 * root is changed (without modifying refcounts).
Linus Torvalds1da177e2005-04-16 15:20:36 -07001922 */
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001923char *__d_path(const struct path *path, struct path *root,
1924 char *buffer, int buflen)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001925{
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001926 struct dentry *dentry = path->dentry;
1927 struct vfsmount *vfsmnt = path->mnt;
Miklos Szeredicdd16d02008-06-23 18:11:53 +02001928 char *end = buffer + buflen;
1929 char *retval;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001930
Andreas Gruenbacherbe285c72008-06-16 13:28:07 +02001931 spin_lock(&vfsmount_lock);
Ram Pai6092d042008-03-27 13:06:20 +01001932 prepend(&end, &buflen, "\0", 1);
Alexey Dobriyanf3da3922009-05-04 03:32:03 +04001933 if (d_unlinked(dentry) &&
Ram Pai6092d042008-03-27 13:06:20 +01001934 (prepend(&end, &buflen, " (deleted)", 10) != 0))
Linus Torvalds552ce542007-02-13 12:08:18 -08001935 goto Elong;
Linus Torvalds552ce542007-02-13 12:08:18 -08001936
1937 if (buflen < 1)
1938 goto Elong;
1939 /* Get '/' right */
1940 retval = end-1;
1941 *retval = '/';
1942
1943 for (;;) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001944 struct dentry * parent;
1945
Jan Blunck329c97f2008-02-14 19:38:31 -08001946 if (dentry == root->dentry && vfsmnt == root->mnt)
Linus Torvalds552ce542007-02-13 12:08:18 -08001947 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001948 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
Linus Torvalds552ce542007-02-13 12:08:18 -08001949 /* Global root? */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001950 if (vfsmnt->mnt_parent == vfsmnt) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001951 goto global_root;
1952 }
1953 dentry = vfsmnt->mnt_mountpoint;
1954 vfsmnt = vfsmnt->mnt_parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001955 continue;
1956 }
1957 parent = dentry->d_parent;
1958 prefetch(parent);
Miklos Szeredicdd16d02008-06-23 18:11:53 +02001959 if ((prepend_name(&end, &buflen, &dentry->d_name) != 0) ||
Ram Pai6092d042008-03-27 13:06:20 +01001960 (prepend(&end, &buflen, "/", 1) != 0))
Linus Torvalds552ce542007-02-13 12:08:18 -08001961 goto Elong;
Linus Torvalds552ce542007-02-13 12:08:18 -08001962 retval = end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001963 dentry = parent;
1964 }
1965
Andreas Gruenbacherbe285c72008-06-16 13:28:07 +02001966out:
1967 spin_unlock(&vfsmount_lock);
Linus Torvalds552ce542007-02-13 12:08:18 -08001968 return retval;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001969
1970global_root:
Ram Pai6092d042008-03-27 13:06:20 +01001971 retval += 1; /* hit the slash */
Miklos Szeredicdd16d02008-06-23 18:11:53 +02001972 if (prepend_name(&retval, &buflen, &dentry->d_name) != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001973 goto Elong;
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01001974 root->mnt = vfsmnt;
1975 root->dentry = dentry;
Andreas Gruenbacherbe285c72008-06-16 13:28:07 +02001976 goto out;
1977
Linus Torvalds1da177e2005-04-16 15:20:36 -07001978Elong:
Andreas Gruenbacherbe285c72008-06-16 13:28:07 +02001979 retval = ERR_PTR(-ENAMETOOLONG);
1980 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001981}
1982
Jan Bluncka03a8a702008-02-14 19:38:32 -08001983/**
1984 * d_path - return the path of a dentry
Jan Blunckcf28b482008-02-14 19:38:44 -08001985 * @path: path to report
Jan Bluncka03a8a702008-02-14 19:38:32 -08001986 * @buf: buffer to return value in
1987 * @buflen: buffer length
1988 *
1989 * Convert a dentry into an ASCII path name. If the entry has been deleted
1990 * the string " (deleted)" is appended. Note that this is ambiguous.
1991 *
Arjan van de Ven52afeef2008-12-01 14:35:00 -08001992 * Returns a pointer into the buffer or an error code if the path was
1993 * too long. Note: Callers should use the returned pointer, not the passed
1994 * in buffer, to use the name! The implementation often starts at an offset
1995 * into the buffer, and may leave 0 bytes at the start.
Jan Bluncka03a8a702008-02-14 19:38:32 -08001996 *
Miklos Szeredi31f3e0b2008-06-23 18:11:52 +02001997 * "buflen" should be positive.
Jan Bluncka03a8a702008-02-14 19:38:32 -08001998 */
Jan Engelhardt20d4fdc2008-06-09 16:40:36 -07001999char *d_path(const struct path *path, char *buf, int buflen)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002000{
2001 char *res;
Jan Blunck6ac08c32008-02-14 19:34:38 -08002002 struct path root;
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01002003 struct path tmp;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002004
Eric Dumazetc23fbb62007-05-08 00:26:18 -07002005 /*
2006 * We have various synthetic filesystems that never get mounted. On
2007 * these filesystems dentries are never used for lookup purposes, and
2008 * thus don't need to be hashed. They also don't need a name until a
2009 * user wants to identify the object in /proc/pid/fd/. The little hack
2010 * below allows us to generate a name for these objects on demand:
2011 */
Jan Blunckcf28b482008-02-14 19:38:44 -08002012 if (path->dentry->d_op && path->dentry->d_op->d_dname)
2013 return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
Eric Dumazetc23fbb62007-05-08 00:26:18 -07002014
Linus Torvalds1da177e2005-04-16 15:20:36 -07002015 read_lock(&current->fs->lock);
Jan Blunck6ac08c32008-02-14 19:34:38 -08002016 root = current->fs->root;
Ram Pai6092d042008-03-27 13:06:20 +01002017 path_get(&root);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002018 read_unlock(&current->fs->lock);
Linus Torvalds552ce542007-02-13 12:08:18 -08002019 spin_lock(&dcache_lock);
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01002020 tmp = root;
2021 res = __d_path(path, &tmp, buf, buflen);
Linus Torvalds552ce542007-02-13 12:08:18 -08002022 spin_unlock(&dcache_lock);
Jan Blunck6ac08c32008-02-14 19:34:38 -08002023 path_put(&root);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002024 return res;
2025}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -07002026EXPORT_SYMBOL(d_path);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002027
2028/*
Eric Dumazetc23fbb62007-05-08 00:26:18 -07002029 * Helper function for dentry_operations.d_dname() members
2030 */
2031char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
2032 const char *fmt, ...)
2033{
2034 va_list args;
2035 char temp[64];
2036 int sz;
2037
2038 va_start(args, fmt);
2039 sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
2040 va_end(args);
2041
2042 if (sz > sizeof(temp) || sz > buflen)
2043 return ERR_PTR(-ENAMETOOLONG);
2044
2045 buffer += buflen - sz;
2046 return memcpy(buffer, temp, sz);
2047}
2048
2049/*
Ram Pai6092d042008-03-27 13:06:20 +01002050 * Write full pathname from the root of the filesystem into the buffer.
2051 */
2052char *dentry_path(struct dentry *dentry, char *buf, int buflen)
2053{
2054 char *end = buf + buflen;
2055 char *retval;
2056
2057 spin_lock(&dcache_lock);
2058 prepend(&end, &buflen, "\0", 1);
Alexey Dobriyanf3da3922009-05-04 03:32:03 +04002059 if (d_unlinked(dentry) &&
Ram Pai6092d042008-03-27 13:06:20 +01002060 (prepend(&end, &buflen, "//deleted", 9) != 0))
2061 goto Elong;
2062 if (buflen < 1)
2063 goto Elong;
2064 /* Get '/' right */
2065 retval = end-1;
2066 *retval = '/';
2067
Miklos Szeredicdd16d02008-06-23 18:11:53 +02002068 while (!IS_ROOT(dentry)) {
2069 struct dentry *parent = dentry->d_parent;
Ram Pai6092d042008-03-27 13:06:20 +01002070
Ram Pai6092d042008-03-27 13:06:20 +01002071 prefetch(parent);
Miklos Szeredicdd16d02008-06-23 18:11:53 +02002072 if ((prepend_name(&end, &buflen, &dentry->d_name) != 0) ||
Ram Pai6092d042008-03-27 13:06:20 +01002073 (prepend(&end, &buflen, "/", 1) != 0))
2074 goto Elong;
2075
2076 retval = end;
2077 dentry = parent;
2078 }
2079 spin_unlock(&dcache_lock);
2080 return retval;
2081Elong:
2082 spin_unlock(&dcache_lock);
2083 return ERR_PTR(-ENAMETOOLONG);
2084}
2085
2086/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002087 * NOTE! The user-level library version returns a
2088 * character pointer. The kernel system call just
2089 * returns the length of the buffer filled (which
2090 * includes the ending '\0' character), or a negative
2091 * error value. So libc would do something like
2092 *
2093 * char *getcwd(char * buf, size_t size)
2094 * {
2095 * int retval;
2096 *
2097 * retval = sys_getcwd(buf, size);
2098 * if (retval >= 0)
2099 * return buf;
2100 * errno = -retval;
2101 * return NULL;
2102 * }
2103 */
Heiko Carstens3cdad422009-01-14 14:14:22 +01002104SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002105{
Linus Torvalds552ce542007-02-13 12:08:18 -08002106 int error;
Jan Blunck6ac08c32008-02-14 19:34:38 -08002107 struct path pwd, root;
Linus Torvalds552ce542007-02-13 12:08:18 -08002108 char *page = (char *) __get_free_page(GFP_USER);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002109
2110 if (!page)
2111 return -ENOMEM;
2112
2113 read_lock(&current->fs->lock);
Jan Blunck6ac08c32008-02-14 19:34:38 -08002114 pwd = current->fs->pwd;
Ram Pai6092d042008-03-27 13:06:20 +01002115 path_get(&pwd);
Jan Blunck6ac08c32008-02-14 19:34:38 -08002116 root = current->fs->root;
Ram Pai6092d042008-03-27 13:06:20 +01002117 path_get(&root);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002118 read_unlock(&current->fs->lock);
2119
Linus Torvalds552ce542007-02-13 12:08:18 -08002120 error = -ENOENT;
Linus Torvalds552ce542007-02-13 12:08:18 -08002121 spin_lock(&dcache_lock);
Alexey Dobriyanf3da3922009-05-04 03:32:03 +04002122 if (!d_unlinked(pwd.dentry)) {
Linus Torvalds552ce542007-02-13 12:08:18 -08002123 unsigned long len;
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01002124 struct path tmp = root;
Linus Torvalds552ce542007-02-13 12:08:18 -08002125 char * cwd;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002126
Miklos Szeredi9d1bc6012008-03-27 13:06:21 +01002127 cwd = __d_path(&pwd, &tmp, page, PAGE_SIZE);
Linus Torvalds552ce542007-02-13 12:08:18 -08002128 spin_unlock(&dcache_lock);
2129
2130 error = PTR_ERR(cwd);
2131 if (IS_ERR(cwd))
2132 goto out;
2133
2134 error = -ERANGE;
2135 len = PAGE_SIZE + page - cwd;
2136 if (len <= size) {
2137 error = len;
2138 if (copy_to_user(buf, cwd, len))
2139 error = -EFAULT;
2140 }
2141 } else
2142 spin_unlock(&dcache_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002143
2144out:
Jan Blunck6ac08c32008-02-14 19:34:38 -08002145 path_put(&pwd);
2146 path_put(&root);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002147 free_page((unsigned long) page);
2148 return error;
2149}
2150
2151/*
2152 * Test whether new_dentry is a subdirectory of old_dentry.
2153 *
2154 * Trivially implemented using the dcache structure
2155 */
2156
2157/**
2158 * is_subdir - is new dentry a subdirectory of old_dentry
2159 * @new_dentry: new dentry
2160 * @old_dentry: old dentry
2161 *
2162 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
2163 * Returns 0 otherwise.
2164 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
2165 */
2166
OGAWA Hirofumie2761a12008-10-16 07:50:28 +09002167int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002168{
2169 int result;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002170 unsigned long seq;
2171
OGAWA Hirofumie2761a12008-10-16 07:50:28 +09002172 if (new_dentry == old_dentry)
2173 return 1;
2174
2175 /*
2176 * Need rcu_readlock to protect against the d_parent trashing
2177 * due to d_move
Linus Torvalds1da177e2005-04-16 15:20:36 -07002178 */
2179 rcu_read_lock();
OGAWA Hirofumie2761a12008-10-16 07:50:28 +09002180 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002181 /* for restarting inner loop in case of seq retry */
Linus Torvalds1da177e2005-04-16 15:20:36 -07002182 seq = read_seqbegin(&rename_lock);
OGAWA Hirofumie2761a12008-10-16 07:50:28 +09002183 if (d_ancestor(old_dentry, new_dentry))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002184 result = 1;
OGAWA Hirofumie2761a12008-10-16 07:50:28 +09002185 else
2186 result = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002187 } while (read_seqretry(&rename_lock, seq));
2188 rcu_read_unlock();
2189
2190 return result;
2191}
2192
Al Viro2096f752010-01-30 13:16:21 -05002193int path_is_under(struct path *path1, struct path *path2)
2194{
2195 struct vfsmount *mnt = path1->mnt;
2196 struct dentry *dentry = path1->dentry;
2197 int res;
2198 spin_lock(&vfsmount_lock);
2199 if (mnt != path2->mnt) {
2200 for (;;) {
2201 if (mnt->mnt_parent == mnt) {
2202 spin_unlock(&vfsmount_lock);
2203 return 0;
2204 }
2205 if (mnt->mnt_parent == path2->mnt)
2206 break;
2207 mnt = mnt->mnt_parent;
2208 }
2209 dentry = mnt->mnt_mountpoint;
2210 }
2211 res = is_subdir(dentry, path2->dentry);
2212 spin_unlock(&vfsmount_lock);
2213 return res;
2214}
2215EXPORT_SYMBOL(path_is_under);
2216
Linus Torvalds1da177e2005-04-16 15:20:36 -07002217void d_genocide(struct dentry *root)
2218{
2219 struct dentry *this_parent = root;
2220 struct list_head *next;
2221
2222 spin_lock(&dcache_lock);
2223repeat:
2224 next = this_parent->d_subdirs.next;
2225resume:
2226 while (next != &this_parent->d_subdirs) {
2227 struct list_head *tmp = next;
Eric Dumazet5160ee62006-01-08 01:03:32 -08002228 struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002229 next = tmp->next;
2230 if (d_unhashed(dentry)||!dentry->d_inode)
2231 continue;
2232 if (!list_empty(&dentry->d_subdirs)) {
2233 this_parent = dentry;
2234 goto repeat;
2235 }
2236 atomic_dec(&dentry->d_count);
2237 }
2238 if (this_parent != root) {
Eric Dumazet5160ee62006-01-08 01:03:32 -08002239 next = this_parent->d_u.d_child.next;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002240 atomic_dec(&this_parent->d_count);
2241 this_parent = this_parent->d_parent;
2242 goto resume;
2243 }
2244 spin_unlock(&dcache_lock);
2245}
2246
2247/**
2248 * find_inode_number - check for dentry with name
2249 * @dir: directory to check
2250 * @name: Name to find.
2251 *
2252 * Check whether a dentry already exists for the given name,
2253 * and return the inode number if it has an inode. Otherwise
2254 * 0 is returned.
2255 *
2256 * This routine is used to post-process directory listings for
2257 * filesystems using synthetic inode numbers, and is necessary
2258 * to keep getcwd() working.
2259 */
2260
2261ino_t find_inode_number(struct dentry *dir, struct qstr *name)
2262{
2263 struct dentry * dentry;
2264 ino_t ino = 0;
2265
Eric W. Biederman3e7e2412006-03-31 02:31:43 -08002266 dentry = d_hash_and_lookup(dir, name);
2267 if (dentry) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002268 if (dentry->d_inode)
2269 ino = dentry->d_inode->i_ino;
2270 dput(dentry);
2271 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002272 return ino;
2273}
H Hartley Sweetenec4f8602010-01-05 13:45:18 -07002274EXPORT_SYMBOL(find_inode_number);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002275
2276static __initdata unsigned long dhash_entries;
2277static int __init set_dhash_entries(char *str)
2278{
2279 if (!str)
2280 return 0;
2281 dhash_entries = simple_strtoul(str, &str, 0);
2282 return 1;
2283}
2284__setup("dhash_entries=", set_dhash_entries);
2285
2286static void __init dcache_init_early(void)
2287{
2288 int loop;
2289
2290 /* If hashes are distributed across NUMA nodes, defer
2291 * hash allocation until vmalloc space is available.
2292 */
2293 if (hashdist)
2294 return;
2295
2296 dentry_hashtable =
2297 alloc_large_system_hash("Dentry cache",
2298 sizeof(struct hlist_head),
2299 dhash_entries,
2300 13,
2301 HASH_EARLY,
2302 &d_hash_shift,
2303 &d_hash_mask,
2304 0);
2305
2306 for (loop = 0; loop < (1 << d_hash_shift); loop++)
2307 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
2308}
2309
Denis Cheng74bf17c2007-10-16 23:26:30 -07002310static void __init dcache_init(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002311{
2312 int loop;
2313
2314 /*
2315 * A constructor could be added for stable state like the lists,
2316 * but it is probably not worth it because of the cache nature
2317 * of the dcache.
2318 */
Christoph Lameter0a31bd52007-05-06 14:49:57 -07002319 dentry_cache = KMEM_CACHE(dentry,
2320 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002321
Rusty Russell8e1f9362007-07-17 04:03:17 -07002322 register_shrinker(&dcache_shrinker);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002323
2324 /* Hash may have been set up in dcache_init_early */
2325 if (!hashdist)
2326 return;
2327
2328 dentry_hashtable =
2329 alloc_large_system_hash("Dentry cache",
2330 sizeof(struct hlist_head),
2331 dhash_entries,
2332 13,
2333 0,
2334 &d_hash_shift,
2335 &d_hash_mask,
2336 0);
2337
2338 for (loop = 0; loop < (1 << d_hash_shift); loop++)
2339 INIT_HLIST_HEAD(&dentry_hashtable[loop]);
2340}
2341
2342/* SLAB cache for __getname() consumers */
Christoph Lametere18b8902006-12-06 20:33:20 -08002343struct kmem_cache *names_cachep __read_mostly;
H Hartley Sweetenec4f8602010-01-05 13:45:18 -07002344EXPORT_SYMBOL(names_cachep);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002345
Linus Torvalds1da177e2005-04-16 15:20:36 -07002346EXPORT_SYMBOL(d_genocide);
2347
Linus Torvalds1da177e2005-04-16 15:20:36 -07002348void __init vfs_caches_init_early(void)
2349{
2350 dcache_init_early();
2351 inode_init_early();
2352}
2353
2354void __init vfs_caches_init(unsigned long mempages)
2355{
2356 unsigned long reserve;
2357
2358 /* Base hash sizes on available memory, with a reserve equal to
2359 150% of current kernel size */
2360
2361 reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
2362 mempages -= reserve;
2363
2364 names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
Paul Mundt20c2df82007-07-20 10:11:58 +09002365 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002366
Denis Cheng74bf17c2007-10-16 23:26:30 -07002367 dcache_init();
2368 inode_init();
Linus Torvalds1da177e2005-04-16 15:20:36 -07002369 files_init(mempages);
Denis Cheng74bf17c2007-10-16 23:26:30 -07002370 mnt_init();
Linus Torvalds1da177e2005-04-16 15:20:36 -07002371 bdev_cache_init();
2372 chrdev_init();
2373}