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1 | /* | |
2 | * fs/dcache.c | |
3 | * | |
4 | * Complete reimplementation | |
5 | * (C) 1997 Thomas Schoebel-Theuer, | |
6 | * with heavy changes by Linus Torvalds | |
7 | */ | |
8 | ||
9 | /* | |
10 | * Notes on the allocation strategy: | |
11 | * | |
12 | * The dcache is a master of the icache - whenever a dcache entry | |
13 | * exists, the inode will always exist. "iput()" is done either when | |
14 | * the dcache entry is deleted or garbage collected. | |
15 | */ | |
16 | ||
17 | #include <linux/syscalls.h> | |
18 | #include <linux/string.h> | |
19 | #include <linux/mm.h> | |
20 | #include <linux/fs.h> | |
21 | #include <linux/fsnotify.h> | |
22 | #include <linux/slab.h> | |
23 | #include <linux/init.h> | |
24 | #include <linux/hash.h> | |
25 | #include <linux/cache.h> | |
26 | #include <linux/export.h> | |
27 | #include <linux/mount.h> | |
28 | #include <linux/file.h> | |
29 | #include <asm/uaccess.h> | |
30 | #include <linux/security.h> | |
31 | #include <linux/seqlock.h> | |
32 | #include <linux/swap.h> | |
33 | #include <linux/bootmem.h> | |
34 | #include <linux/fs_struct.h> | |
35 | #include <linux/hardirq.h> | |
36 | #include <linux/bit_spinlock.h> | |
37 | #include <linux/rculist_bl.h> | |
38 | #include <linux/prefetch.h> | |
39 | #include <linux/ratelimit.h> | |
40 | #include "internal.h" | |
41 | #include "mount.h" | |
42 | ||
43 | /* | |
44 | * Usage: | |
45 | * dcache->d_inode->i_lock protects: | |
46 | * - i_dentry, d_alias, d_inode of aliases | |
47 | * dcache_hash_bucket lock protects: | |
48 | * - the dcache hash table | |
49 | * s_anon bl list spinlock protects: | |
50 | * - the s_anon list (see __d_drop) | |
51 | * dcache_lru_lock protects: | |
52 | * - the dcache lru lists and counters | |
53 | * d_lock protects: | |
54 | * - d_flags | |
55 | * - d_name | |
56 | * - d_lru | |
57 | * - d_count | |
58 | * - d_unhashed() | |
59 | * - d_parent and d_subdirs | |
60 | * - childrens' d_child and d_parent | |
61 | * - d_alias, d_inode | |
62 | * | |
63 | * Ordering: | |
64 | * dentry->d_inode->i_lock | |
65 | * dentry->d_lock | |
66 | * dcache_lru_lock | |
67 | * dcache_hash_bucket lock | |
68 | * s_anon lock | |
69 | * | |
70 | * If there is an ancestor relationship: | |
71 | * dentry->d_parent->...->d_parent->d_lock | |
72 | * ... | |
73 | * dentry->d_parent->d_lock | |
74 | * dentry->d_lock | |
75 | * | |
76 | * If no ancestor relationship: | |
77 | * if (dentry1 < dentry2) | |
78 | * dentry1->d_lock | |
79 | * dentry2->d_lock | |
80 | */ | |
81 | int sysctl_vfs_cache_pressure __read_mostly = 100; | |
82 | EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure); | |
83 | ||
84 | static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock); | |
85 | __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock); | |
86 | ||
87 | EXPORT_SYMBOL(rename_lock); | |
88 | ||
89 | static struct kmem_cache *dentry_cache __read_mostly; | |
90 | ||
91 | /** | |
92 | * read_seqbegin_or_lock - begin a sequence number check or locking block | |
93 | * @lock: sequence lock | |
94 | * @seq : sequence number to be checked | |
95 | * | |
96 | * First try it once optimistically without taking the lock. If that fails, | |
97 | * take the lock. The sequence number is also used as a marker for deciding | |
98 | * whether to be a reader (even) or writer (odd). | |
99 | * N.B. seq must be initialized to an even number to begin with. | |
100 | */ | |
101 | static inline void read_seqbegin_or_lock(seqlock_t *lock, int *seq) | |
102 | { | |
103 | if (!(*seq & 1)) /* Even */ | |
104 | *seq = read_seqbegin(lock); | |
105 | else /* Odd */ | |
106 | read_seqlock_excl(lock); | |
107 | } | |
108 | ||
109 | static inline int need_seqretry(seqlock_t *lock, int seq) | |
110 | { | |
111 | return !(seq & 1) && read_seqretry(lock, seq); | |
112 | } | |
113 | ||
114 | static inline void done_seqretry(seqlock_t *lock, int seq) | |
115 | { | |
116 | if (seq & 1) | |
117 | read_sequnlock_excl(lock); | |
118 | } | |
119 | ||
120 | /* | |
121 | * This is the single most critical data structure when it comes | |
122 | * to the dcache: the hashtable for lookups. Somebody should try | |
123 | * to make this good - I've just made it work. | |
124 | * | |
125 | * This hash-function tries to avoid losing too many bits of hash | |
126 | * information, yet avoid using a prime hash-size or similar. | |
127 | */ | |
128 | #define D_HASHBITS d_hash_shift | |
129 | #define D_HASHMASK d_hash_mask | |
130 | ||
131 | static unsigned int d_hash_mask __read_mostly; | |
132 | static unsigned int d_hash_shift __read_mostly; | |
133 | ||
134 | static struct hlist_bl_head *dentry_hashtable __read_mostly; | |
135 | ||
136 | static inline struct hlist_bl_head *d_hash(const struct dentry *parent, | |
137 | unsigned int hash) | |
138 | { | |
139 | hash += (unsigned long) parent / L1_CACHE_BYTES; | |
140 | hash = hash + (hash >> D_HASHBITS); | |
141 | return dentry_hashtable + (hash & D_HASHMASK); | |
142 | } | |
143 | ||
144 | /* Statistics gathering. */ | |
145 | struct dentry_stat_t dentry_stat = { | |
146 | .age_limit = 45, | |
147 | }; | |
148 | ||
149 | static DEFINE_PER_CPU(unsigned int, nr_dentry); | |
150 | ||
151 | #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS) | |
152 | static int get_nr_dentry(void) | |
153 | { | |
154 | int i; | |
155 | int sum = 0; | |
156 | for_each_possible_cpu(i) | |
157 | sum += per_cpu(nr_dentry, i); | |
158 | return sum < 0 ? 0 : sum; | |
159 | } | |
160 | ||
161 | int proc_nr_dentry(ctl_table *table, int write, void __user *buffer, | |
162 | size_t *lenp, loff_t *ppos) | |
163 | { | |
164 | dentry_stat.nr_dentry = get_nr_dentry(); | |
165 | return proc_dointvec(table, write, buffer, lenp, ppos); | |
166 | } | |
167 | #endif | |
168 | ||
169 | /* | |
170 | * Compare 2 name strings, return 0 if they match, otherwise non-zero. | |
171 | * The strings are both count bytes long, and count is non-zero. | |
172 | */ | |
173 | #ifdef CONFIG_DCACHE_WORD_ACCESS | |
174 | ||
175 | #include <asm/word-at-a-time.h> | |
176 | /* | |
177 | * NOTE! 'cs' and 'scount' come from a dentry, so it has a | |
178 | * aligned allocation for this particular component. We don't | |
179 | * strictly need the load_unaligned_zeropad() safety, but it | |
180 | * doesn't hurt either. | |
181 | * | |
182 | * In contrast, 'ct' and 'tcount' can be from a pathname, and do | |
183 | * need the careful unaligned handling. | |
184 | */ | |
185 | static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount) | |
186 | { | |
187 | unsigned long a,b,mask; | |
188 | ||
189 | for (;;) { | |
190 | a = *(unsigned long *)cs; | |
191 | b = load_unaligned_zeropad(ct); | |
192 | if (tcount < sizeof(unsigned long)) | |
193 | break; | |
194 | if (unlikely(a != b)) | |
195 | return 1; | |
196 | cs += sizeof(unsigned long); | |
197 | ct += sizeof(unsigned long); | |
198 | tcount -= sizeof(unsigned long); | |
199 | if (!tcount) | |
200 | return 0; | |
201 | } | |
202 | mask = ~(~0ul << tcount*8); | |
203 | return unlikely(!!((a ^ b) & mask)); | |
204 | } | |
205 | ||
206 | #else | |
207 | ||
208 | static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount) | |
209 | { | |
210 | do { | |
211 | if (*cs != *ct) | |
212 | return 1; | |
213 | cs++; | |
214 | ct++; | |
215 | tcount--; | |
216 | } while (tcount); | |
217 | return 0; | |
218 | } | |
219 | ||
220 | #endif | |
221 | ||
222 | static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount) | |
223 | { | |
224 | const unsigned char *cs; | |
225 | /* | |
226 | * Be careful about RCU walk racing with rename: | |
227 | * use ACCESS_ONCE to fetch the name pointer. | |
228 | * | |
229 | * NOTE! Even if a rename will mean that the length | |
230 | * was not loaded atomically, we don't care. The | |
231 | * RCU walk will check the sequence count eventually, | |
232 | * and catch it. And we won't overrun the buffer, | |
233 | * because we're reading the name pointer atomically, | |
234 | * and a dentry name is guaranteed to be properly | |
235 | * terminated with a NUL byte. | |
236 | * | |
237 | * End result: even if 'len' is wrong, we'll exit | |
238 | * early because the data cannot match (there can | |
239 | * be no NUL in the ct/tcount data) | |
240 | */ | |
241 | cs = ACCESS_ONCE(dentry->d_name.name); | |
242 | smp_read_barrier_depends(); | |
243 | return dentry_string_cmp(cs, ct, tcount); | |
244 | } | |
245 | ||
246 | static void __d_free(struct rcu_head *head) | |
247 | { | |
248 | struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu); | |
249 | ||
250 | WARN_ON(!hlist_unhashed(&dentry->d_alias)); | |
251 | if (dname_external(dentry)) | |
252 | kfree(dentry->d_name.name); | |
253 | kmem_cache_free(dentry_cache, dentry); | |
254 | } | |
255 | ||
256 | /* | |
257 | * no locks, please. | |
258 | */ | |
259 | static void d_free(struct dentry *dentry) | |
260 | { | |
261 | BUG_ON((int)dentry->d_lockref.count > 0); | |
262 | this_cpu_dec(nr_dentry); | |
263 | if (dentry->d_op && dentry->d_op->d_release) | |
264 | dentry->d_op->d_release(dentry); | |
265 | ||
266 | /* if dentry was never visible to RCU, immediate free is OK */ | |
267 | if (!(dentry->d_flags & DCACHE_RCUACCESS)) | |
268 | __d_free(&dentry->d_u.d_rcu); | |
269 | else | |
270 | call_rcu(&dentry->d_u.d_rcu, __d_free); | |
271 | } | |
272 | ||
273 | /** | |
274 | * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups | |
275 | * @dentry: the target dentry | |
276 | * After this call, in-progress rcu-walk path lookup will fail. This | |
277 | * should be called after unhashing, and after changing d_inode (if | |
278 | * the dentry has not already been unhashed). | |
279 | */ | |
280 | static inline void dentry_rcuwalk_barrier(struct dentry *dentry) | |
281 | { | |
282 | assert_spin_locked(&dentry->d_lock); | |
283 | /* Go through a barrier */ | |
284 | write_seqcount_barrier(&dentry->d_seq); | |
285 | } | |
286 | ||
287 | /* | |
288 | * Release the dentry's inode, using the filesystem | |
289 | * d_iput() operation if defined. Dentry has no refcount | |
290 | * and is unhashed. | |
291 | */ | |
292 | static void dentry_iput(struct dentry * dentry) | |
293 | __releases(dentry->d_lock) | |
294 | __releases(dentry->d_inode->i_lock) | |
295 | { | |
296 | struct inode *inode = dentry->d_inode; | |
297 | if (inode) { | |
298 | dentry->d_inode = NULL; | |
299 | hlist_del_init(&dentry->d_alias); | |
300 | spin_unlock(&dentry->d_lock); | |
301 | spin_unlock(&inode->i_lock); | |
302 | if (!inode->i_nlink) | |
303 | fsnotify_inoderemove(inode); | |
304 | if (dentry->d_op && dentry->d_op->d_iput) | |
305 | dentry->d_op->d_iput(dentry, inode); | |
306 | else | |
307 | iput(inode); | |
308 | } else { | |
309 | spin_unlock(&dentry->d_lock); | |
310 | } | |
311 | } | |
312 | ||
313 | /* | |
314 | * Release the dentry's inode, using the filesystem | |
315 | * d_iput() operation if defined. dentry remains in-use. | |
316 | */ | |
317 | static void dentry_unlink_inode(struct dentry * dentry) | |
318 | __releases(dentry->d_lock) | |
319 | __releases(dentry->d_inode->i_lock) | |
320 | { | |
321 | struct inode *inode = dentry->d_inode; | |
322 | dentry->d_inode = NULL; | |
323 | hlist_del_init(&dentry->d_alias); | |
324 | dentry_rcuwalk_barrier(dentry); | |
325 | spin_unlock(&dentry->d_lock); | |
326 | spin_unlock(&inode->i_lock); | |
327 | if (!inode->i_nlink) | |
328 | fsnotify_inoderemove(inode); | |
329 | if (dentry->d_op && dentry->d_op->d_iput) | |
330 | dentry->d_op->d_iput(dentry, inode); | |
331 | else | |
332 | iput(inode); | |
333 | } | |
334 | ||
335 | /* | |
336 | * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held. | |
337 | */ | |
338 | static void dentry_lru_add(struct dentry *dentry) | |
339 | { | |
340 | if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST))) { | |
341 | spin_lock(&dcache_lru_lock); | |
342 | dentry->d_flags |= DCACHE_LRU_LIST; | |
343 | list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru); | |
344 | dentry->d_sb->s_nr_dentry_unused++; | |
345 | dentry_stat.nr_unused++; | |
346 | spin_unlock(&dcache_lru_lock); | |
347 | } | |
348 | } | |
349 | ||
350 | static void __dentry_lru_del(struct dentry *dentry) | |
351 | { | |
352 | list_del_init(&dentry->d_lru); | |
353 | dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST); | |
354 | dentry->d_sb->s_nr_dentry_unused--; | |
355 | dentry_stat.nr_unused--; | |
356 | } | |
357 | ||
358 | /* | |
359 | * Remove a dentry with references from the LRU. | |
360 | */ | |
361 | static void dentry_lru_del(struct dentry *dentry) | |
362 | { | |
363 | if (!list_empty(&dentry->d_lru)) { | |
364 | spin_lock(&dcache_lru_lock); | |
365 | __dentry_lru_del(dentry); | |
366 | spin_unlock(&dcache_lru_lock); | |
367 | } | |
368 | } | |
369 | ||
370 | static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list) | |
371 | { | |
372 | spin_lock(&dcache_lru_lock); | |
373 | if (list_empty(&dentry->d_lru)) { | |
374 | dentry->d_flags |= DCACHE_LRU_LIST; | |
375 | list_add_tail(&dentry->d_lru, list); | |
376 | dentry->d_sb->s_nr_dentry_unused++; | |
377 | dentry_stat.nr_unused++; | |
378 | } else { | |
379 | list_move_tail(&dentry->d_lru, list); | |
380 | } | |
381 | spin_unlock(&dcache_lru_lock); | |
382 | } | |
383 | ||
384 | /** | |
385 | * d_kill - kill dentry and return parent | |
386 | * @dentry: dentry to kill | |
387 | * @parent: parent dentry | |
388 | * | |
389 | * The dentry must already be unhashed and removed from the LRU. | |
390 | * | |
391 | * If this is the root of the dentry tree, return NULL. | |
392 | * | |
393 | * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by | |
394 | * d_kill. | |
395 | */ | |
396 | static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent) | |
397 | __releases(dentry->d_lock) | |
398 | __releases(parent->d_lock) | |
399 | __releases(dentry->d_inode->i_lock) | |
400 | { | |
401 | list_del(&dentry->d_u.d_child); | |
402 | /* | |
403 | * Inform try_to_ascend() that we are no longer attached to the | |
404 | * dentry tree | |
405 | */ | |
406 | dentry->d_flags |= DCACHE_DENTRY_KILLED; | |
407 | if (parent) | |
408 | spin_unlock(&parent->d_lock); | |
409 | dentry_iput(dentry); | |
410 | /* | |
411 | * dentry_iput drops the locks, at which point nobody (except | |
412 | * transient RCU lookups) can reach this dentry. | |
413 | */ | |
414 | d_free(dentry); | |
415 | return parent; | |
416 | } | |
417 | ||
418 | /* | |
419 | * Unhash a dentry without inserting an RCU walk barrier or checking that | |
420 | * dentry->d_lock is locked. The caller must take care of that, if | |
421 | * appropriate. | |
422 | */ | |
423 | static void __d_shrink(struct dentry *dentry) | |
424 | { | |
425 | if (!d_unhashed(dentry)) { | |
426 | struct hlist_bl_head *b; | |
427 | if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED)) | |
428 | b = &dentry->d_sb->s_anon; | |
429 | else | |
430 | b = d_hash(dentry->d_parent, dentry->d_name.hash); | |
431 | ||
432 | hlist_bl_lock(b); | |
433 | __hlist_bl_del(&dentry->d_hash); | |
434 | dentry->d_hash.pprev = NULL; | |
435 | hlist_bl_unlock(b); | |
436 | } | |
437 | } | |
438 | ||
439 | /** | |
440 | * d_drop - drop a dentry | |
441 | * @dentry: dentry to drop | |
442 | * | |
443 | * d_drop() unhashes the entry from the parent dentry hashes, so that it won't | |
444 | * be found through a VFS lookup any more. Note that this is different from | |
445 | * deleting the dentry - d_delete will try to mark the dentry negative if | |
446 | * possible, giving a successful _negative_ lookup, while d_drop will | |
447 | * just make the cache lookup fail. | |
448 | * | |
449 | * d_drop() is used mainly for stuff that wants to invalidate a dentry for some | |
450 | * reason (NFS timeouts or autofs deletes). | |
451 | * | |
452 | * __d_drop requires dentry->d_lock. | |
453 | */ | |
454 | void __d_drop(struct dentry *dentry) | |
455 | { | |
456 | if (!d_unhashed(dentry)) { | |
457 | __d_shrink(dentry); | |
458 | dentry_rcuwalk_barrier(dentry); | |
459 | } | |
460 | } | |
461 | EXPORT_SYMBOL(__d_drop); | |
462 | ||
463 | void d_drop(struct dentry *dentry) | |
464 | { | |
465 | spin_lock(&dentry->d_lock); | |
466 | __d_drop(dentry); | |
467 | spin_unlock(&dentry->d_lock); | |
468 | } | |
469 | EXPORT_SYMBOL(d_drop); | |
470 | ||
471 | /* | |
472 | * Finish off a dentry we've decided to kill. | |
473 | * dentry->d_lock must be held, returns with it unlocked. | |
474 | * If ref is non-zero, then decrement the refcount too. | |
475 | * Returns dentry requiring refcount drop, or NULL if we're done. | |
476 | */ | |
477 | static inline struct dentry *dentry_kill(struct dentry *dentry) | |
478 | __releases(dentry->d_lock) | |
479 | { | |
480 | struct inode *inode; | |
481 | struct dentry *parent; | |
482 | ||
483 | inode = dentry->d_inode; | |
484 | if (inode && !spin_trylock(&inode->i_lock)) { | |
485 | relock: | |
486 | spin_unlock(&dentry->d_lock); | |
487 | cpu_relax(); | |
488 | return dentry; /* try again with same dentry */ | |
489 | } | |
490 | if (IS_ROOT(dentry)) | |
491 | parent = NULL; | |
492 | else | |
493 | parent = dentry->d_parent; | |
494 | if (parent && !spin_trylock(&parent->d_lock)) { | |
495 | if (inode) | |
496 | spin_unlock(&inode->i_lock); | |
497 | goto relock; | |
498 | } | |
499 | ||
500 | /* | |
501 | * The dentry is now unrecoverably dead to the world. | |
502 | */ | |
503 | lockref_mark_dead(&dentry->d_lockref); | |
504 | ||
505 | /* | |
506 | * inform the fs via d_prune that this dentry is about to be | |
507 | * unhashed and destroyed. | |
508 | */ | |
509 | if ((dentry->d_flags & DCACHE_OP_PRUNE) && !d_unhashed(dentry)) | |
510 | dentry->d_op->d_prune(dentry); | |
511 | ||
512 | dentry_lru_del(dentry); | |
513 | /* if it was on the hash then remove it */ | |
514 | __d_drop(dentry); | |
515 | return d_kill(dentry, parent); | |
516 | } | |
517 | ||
518 | /* | |
519 | * This is dput | |
520 | * | |
521 | * This is complicated by the fact that we do not want to put | |
522 | * dentries that are no longer on any hash chain on the unused | |
523 | * list: we'd much rather just get rid of them immediately. | |
524 | * | |
525 | * However, that implies that we have to traverse the dentry | |
526 | * tree upwards to the parents which might _also_ now be | |
527 | * scheduled for deletion (it may have been only waiting for | |
528 | * its last child to go away). | |
529 | * | |
530 | * This tail recursion is done by hand as we don't want to depend | |
531 | * on the compiler to always get this right (gcc generally doesn't). | |
532 | * Real recursion would eat up our stack space. | |
533 | */ | |
534 | ||
535 | /* | |
536 | * dput - release a dentry | |
537 | * @dentry: dentry to release | |
538 | * | |
539 | * Release a dentry. This will drop the usage count and if appropriate | |
540 | * call the dentry unlink method as well as removing it from the queues and | |
541 | * releasing its resources. If the parent dentries were scheduled for release | |
542 | * they too may now get deleted. | |
543 | */ | |
544 | void dput(struct dentry *dentry) | |
545 | { | |
546 | if (unlikely(!dentry)) | |
547 | return; | |
548 | ||
549 | repeat: | |
550 | if (lockref_put_or_lock(&dentry->d_lockref)) | |
551 | return; | |
552 | ||
553 | /* Unreachable? Get rid of it */ | |
554 | if (unlikely(d_unhashed(dentry))) | |
555 | goto kill_it; | |
556 | ||
557 | if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) { | |
558 | if (dentry->d_op->d_delete(dentry)) | |
559 | goto kill_it; | |
560 | } | |
561 | ||
562 | dentry->d_flags |= DCACHE_REFERENCED; | |
563 | dentry_lru_add(dentry); | |
564 | ||
565 | dentry->d_lockref.count--; | |
566 | spin_unlock(&dentry->d_lock); | |
567 | return; | |
568 | ||
569 | kill_it: | |
570 | dentry = dentry_kill(dentry); | |
571 | if (dentry) | |
572 | goto repeat; | |
573 | } | |
574 | EXPORT_SYMBOL(dput); | |
575 | ||
576 | /** | |
577 | * d_invalidate - invalidate a dentry | |
578 | * @dentry: dentry to invalidate | |
579 | * | |
580 | * Try to invalidate the dentry if it turns out to be | |
581 | * possible. If there are other dentries that can be | |
582 | * reached through this one we can't delete it and we | |
583 | * return -EBUSY. On success we return 0. | |
584 | * | |
585 | * no dcache lock. | |
586 | */ | |
587 | ||
588 | int d_invalidate(struct dentry * dentry) | |
589 | { | |
590 | /* | |
591 | * If it's already been dropped, return OK. | |
592 | */ | |
593 | spin_lock(&dentry->d_lock); | |
594 | if (d_unhashed(dentry)) { | |
595 | spin_unlock(&dentry->d_lock); | |
596 | return 0; | |
597 | } | |
598 | /* | |
599 | * Check whether to do a partial shrink_dcache | |
600 | * to get rid of unused child entries. | |
601 | */ | |
602 | if (!list_empty(&dentry->d_subdirs)) { | |
603 | spin_unlock(&dentry->d_lock); | |
604 | shrink_dcache_parent(dentry); | |
605 | spin_lock(&dentry->d_lock); | |
606 | } | |
607 | ||
608 | /* | |
609 | * Somebody else still using it? | |
610 | * | |
611 | * If it's a directory, we can't drop it | |
612 | * for fear of somebody re-populating it | |
613 | * with children (even though dropping it | |
614 | * would make it unreachable from the root, | |
615 | * we might still populate it if it was a | |
616 | * working directory or similar). | |
617 | * We also need to leave mountpoints alone, | |
618 | * directory or not. | |
619 | */ | |
620 | if (dentry->d_lockref.count > 1 && dentry->d_inode) { | |
621 | if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) { | |
622 | spin_unlock(&dentry->d_lock); | |
623 | return -EBUSY; | |
624 | } | |
625 | } | |
626 | ||
627 | __d_drop(dentry); | |
628 | spin_unlock(&dentry->d_lock); | |
629 | return 0; | |
630 | } | |
631 | EXPORT_SYMBOL(d_invalidate); | |
632 | ||
633 | /* This must be called with d_lock held */ | |
634 | static inline void __dget_dlock(struct dentry *dentry) | |
635 | { | |
636 | dentry->d_lockref.count++; | |
637 | } | |
638 | ||
639 | static inline void __dget(struct dentry *dentry) | |
640 | { | |
641 | lockref_get(&dentry->d_lockref); | |
642 | } | |
643 | ||
644 | struct dentry *dget_parent(struct dentry *dentry) | |
645 | { | |
646 | int gotref; | |
647 | struct dentry *ret; | |
648 | ||
649 | /* | |
650 | * Do optimistic parent lookup without any | |
651 | * locking. | |
652 | */ | |
653 | rcu_read_lock(); | |
654 | ret = ACCESS_ONCE(dentry->d_parent); | |
655 | gotref = lockref_get_not_zero(&ret->d_lockref); | |
656 | rcu_read_unlock(); | |
657 | if (likely(gotref)) { | |
658 | if (likely(ret == ACCESS_ONCE(dentry->d_parent))) | |
659 | return ret; | |
660 | dput(ret); | |
661 | } | |
662 | ||
663 | repeat: | |
664 | /* | |
665 | * Don't need rcu_dereference because we re-check it was correct under | |
666 | * the lock. | |
667 | */ | |
668 | rcu_read_lock(); | |
669 | ret = dentry->d_parent; | |
670 | spin_lock(&ret->d_lock); | |
671 | if (unlikely(ret != dentry->d_parent)) { | |
672 | spin_unlock(&ret->d_lock); | |
673 | rcu_read_unlock(); | |
674 | goto repeat; | |
675 | } | |
676 | rcu_read_unlock(); | |
677 | BUG_ON(!ret->d_lockref.count); | |
678 | ret->d_lockref.count++; | |
679 | spin_unlock(&ret->d_lock); | |
680 | return ret; | |
681 | } | |
682 | EXPORT_SYMBOL(dget_parent); | |
683 | ||
684 | /** | |
685 | * d_find_alias - grab a hashed alias of inode | |
686 | * @inode: inode in question | |
687 | * @want_discon: flag, used by d_splice_alias, to request | |
688 | * that only a DISCONNECTED alias be returned. | |
689 | * | |
690 | * If inode has a hashed alias, or is a directory and has any alias, | |
691 | * acquire the reference to alias and return it. Otherwise return NULL. | |
692 | * Notice that if inode is a directory there can be only one alias and | |
693 | * it can be unhashed only if it has no children, or if it is the root | |
694 | * of a filesystem. | |
695 | * | |
696 | * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer | |
697 | * any other hashed alias over that one unless @want_discon is set, | |
698 | * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias. | |
699 | */ | |
700 | static struct dentry *__d_find_alias(struct inode *inode, int want_discon) | |
701 | { | |
702 | struct dentry *alias, *discon_alias; | |
703 | ||
704 | again: | |
705 | discon_alias = NULL; | |
706 | hlist_for_each_entry(alias, &inode->i_dentry, d_alias) { | |
707 | spin_lock(&alias->d_lock); | |
708 | if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) { | |
709 | if (IS_ROOT(alias) && | |
710 | (alias->d_flags & DCACHE_DISCONNECTED)) { | |
711 | discon_alias = alias; | |
712 | } else if (!want_discon) { | |
713 | __dget_dlock(alias); | |
714 | spin_unlock(&alias->d_lock); | |
715 | return alias; | |
716 | } | |
717 | } | |
718 | spin_unlock(&alias->d_lock); | |
719 | } | |
720 | if (discon_alias) { | |
721 | alias = discon_alias; | |
722 | spin_lock(&alias->d_lock); | |
723 | if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) { | |
724 | if (IS_ROOT(alias) && | |
725 | (alias->d_flags & DCACHE_DISCONNECTED)) { | |
726 | __dget_dlock(alias); | |
727 | spin_unlock(&alias->d_lock); | |
728 | return alias; | |
729 | } | |
730 | } | |
731 | spin_unlock(&alias->d_lock); | |
732 | goto again; | |
733 | } | |
734 | return NULL; | |
735 | } | |
736 | ||
737 | struct dentry *d_find_alias(struct inode *inode) | |
738 | { | |
739 | struct dentry *de = NULL; | |
740 | ||
741 | if (!hlist_empty(&inode->i_dentry)) { | |
742 | spin_lock(&inode->i_lock); | |
743 | de = __d_find_alias(inode, 0); | |
744 | spin_unlock(&inode->i_lock); | |
745 | } | |
746 | return de; | |
747 | } | |
748 | EXPORT_SYMBOL(d_find_alias); | |
749 | ||
750 | /* | |
751 | * Try to kill dentries associated with this inode. | |
752 | * WARNING: you must own a reference to inode. | |
753 | */ | |
754 | void d_prune_aliases(struct inode *inode) | |
755 | { | |
756 | struct dentry *dentry; | |
757 | restart: | |
758 | spin_lock(&inode->i_lock); | |
759 | hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) { | |
760 | spin_lock(&dentry->d_lock); | |
761 | if (!dentry->d_lockref.count) { | |
762 | /* | |
763 | * inform the fs via d_prune that this dentry | |
764 | * is about to be unhashed and destroyed. | |
765 | */ | |
766 | if ((dentry->d_flags & DCACHE_OP_PRUNE) && | |
767 | !d_unhashed(dentry)) | |
768 | dentry->d_op->d_prune(dentry); | |
769 | ||
770 | __dget_dlock(dentry); | |
771 | __d_drop(dentry); | |
772 | spin_unlock(&dentry->d_lock); | |
773 | spin_unlock(&inode->i_lock); | |
774 | dput(dentry); | |
775 | goto restart; | |
776 | } | |
777 | spin_unlock(&dentry->d_lock); | |
778 | } | |
779 | spin_unlock(&inode->i_lock); | |
780 | } | |
781 | EXPORT_SYMBOL(d_prune_aliases); | |
782 | ||
783 | /* | |
784 | * Try to throw away a dentry - free the inode, dput the parent. | |
785 | * Requires dentry->d_lock is held, and dentry->d_count == 0. | |
786 | * Releases dentry->d_lock. | |
787 | * | |
788 | * This may fail if locks cannot be acquired no problem, just try again. | |
789 | */ | |
790 | static void try_prune_one_dentry(struct dentry *dentry) | |
791 | __releases(dentry->d_lock) | |
792 | { | |
793 | struct dentry *parent; | |
794 | ||
795 | parent = dentry_kill(dentry); | |
796 | /* | |
797 | * If dentry_kill returns NULL, we have nothing more to do. | |
798 | * if it returns the same dentry, trylocks failed. In either | |
799 | * case, just loop again. | |
800 | * | |
801 | * Otherwise, we need to prune ancestors too. This is necessary | |
802 | * to prevent quadratic behavior of shrink_dcache_parent(), but | |
803 | * is also expected to be beneficial in reducing dentry cache | |
804 | * fragmentation. | |
805 | */ | |
806 | if (!parent) | |
807 | return; | |
808 | if (parent == dentry) | |
809 | return; | |
810 | ||
811 | /* Prune ancestors. */ | |
812 | dentry = parent; | |
813 | while (dentry) { | |
814 | if (lockref_put_or_lock(&dentry->d_lockref)) | |
815 | return; | |
816 | dentry = dentry_kill(dentry); | |
817 | } | |
818 | } | |
819 | ||
820 | static void shrink_dentry_list(struct list_head *list) | |
821 | { | |
822 | struct dentry *dentry; | |
823 | ||
824 | rcu_read_lock(); | |
825 | for (;;) { | |
826 | dentry = list_entry_rcu(list->prev, struct dentry, d_lru); | |
827 | if (&dentry->d_lru == list) | |
828 | break; /* empty */ | |
829 | spin_lock(&dentry->d_lock); | |
830 | if (dentry != list_entry(list->prev, struct dentry, d_lru)) { | |
831 | spin_unlock(&dentry->d_lock); | |
832 | continue; | |
833 | } | |
834 | ||
835 | /* | |
836 | * We found an inuse dentry which was not removed from | |
837 | * the LRU because of laziness during lookup. Do not free | |
838 | * it - just keep it off the LRU list. | |
839 | */ | |
840 | if (dentry->d_lockref.count) { | |
841 | dentry_lru_del(dentry); | |
842 | spin_unlock(&dentry->d_lock); | |
843 | continue; | |
844 | } | |
845 | ||
846 | rcu_read_unlock(); | |
847 | ||
848 | try_prune_one_dentry(dentry); | |
849 | ||
850 | rcu_read_lock(); | |
851 | } | |
852 | rcu_read_unlock(); | |
853 | } | |
854 | ||
855 | /** | |
856 | * prune_dcache_sb - shrink the dcache | |
857 | * @sb: superblock | |
858 | * @count: number of entries to try to free | |
859 | * | |
860 | * Attempt to shrink the superblock dcache LRU by @count entries. This is | |
861 | * done when we need more memory an called from the superblock shrinker | |
862 | * function. | |
863 | * | |
864 | * This function may fail to free any resources if all the dentries are in | |
865 | * use. | |
866 | */ | |
867 | void prune_dcache_sb(struct super_block *sb, int count) | |
868 | { | |
869 | struct dentry *dentry; | |
870 | LIST_HEAD(referenced); | |
871 | LIST_HEAD(tmp); | |
872 | ||
873 | relock: | |
874 | spin_lock(&dcache_lru_lock); | |
875 | while (!list_empty(&sb->s_dentry_lru)) { | |
876 | dentry = list_entry(sb->s_dentry_lru.prev, | |
877 | struct dentry, d_lru); | |
878 | BUG_ON(dentry->d_sb != sb); | |
879 | ||
880 | if (!spin_trylock(&dentry->d_lock)) { | |
881 | spin_unlock(&dcache_lru_lock); | |
882 | cpu_relax(); | |
883 | goto relock; | |
884 | } | |
885 | ||
886 | if (dentry->d_flags & DCACHE_REFERENCED) { | |
887 | dentry->d_flags &= ~DCACHE_REFERENCED; | |
888 | list_move(&dentry->d_lru, &referenced); | |
889 | spin_unlock(&dentry->d_lock); | |
890 | } else { | |
891 | list_move_tail(&dentry->d_lru, &tmp); | |
892 | dentry->d_flags |= DCACHE_SHRINK_LIST; | |
893 | spin_unlock(&dentry->d_lock); | |
894 | if (!--count) | |
895 | break; | |
896 | } | |
897 | cond_resched_lock(&dcache_lru_lock); | |
898 | } | |
899 | if (!list_empty(&referenced)) | |
900 | list_splice(&referenced, &sb->s_dentry_lru); | |
901 | spin_unlock(&dcache_lru_lock); | |
902 | ||
903 | shrink_dentry_list(&tmp); | |
904 | } | |
905 | ||
906 | /** | |
907 | * shrink_dcache_sb - shrink dcache for a superblock | |
908 | * @sb: superblock | |
909 | * | |
910 | * Shrink the dcache for the specified super block. This is used to free | |
911 | * the dcache before unmounting a file system. | |
912 | */ | |
913 | void shrink_dcache_sb(struct super_block *sb) | |
914 | { | |
915 | LIST_HEAD(tmp); | |
916 | ||
917 | spin_lock(&dcache_lru_lock); | |
918 | while (!list_empty(&sb->s_dentry_lru)) { | |
919 | list_splice_init(&sb->s_dentry_lru, &tmp); | |
920 | spin_unlock(&dcache_lru_lock); | |
921 | shrink_dentry_list(&tmp); | |
922 | spin_lock(&dcache_lru_lock); | |
923 | } | |
924 | spin_unlock(&dcache_lru_lock); | |
925 | } | |
926 | EXPORT_SYMBOL(shrink_dcache_sb); | |
927 | ||
928 | /* | |
929 | * destroy a single subtree of dentries for unmount | |
930 | * - see the comments on shrink_dcache_for_umount() for a description of the | |
931 | * locking | |
932 | */ | |
933 | static void shrink_dcache_for_umount_subtree(struct dentry *dentry) | |
934 | { | |
935 | struct dentry *parent; | |
936 | ||
937 | BUG_ON(!IS_ROOT(dentry)); | |
938 | ||
939 | for (;;) { | |
940 | /* descend to the first leaf in the current subtree */ | |
941 | while (!list_empty(&dentry->d_subdirs)) | |
942 | dentry = list_entry(dentry->d_subdirs.next, | |
943 | struct dentry, d_u.d_child); | |
944 | ||
945 | /* consume the dentries from this leaf up through its parents | |
946 | * until we find one with children or run out altogether */ | |
947 | do { | |
948 | struct inode *inode; | |
949 | ||
950 | /* | |
951 | * inform the fs that this dentry is about to be | |
952 | * unhashed and destroyed. | |
953 | */ | |
954 | if ((dentry->d_flags & DCACHE_OP_PRUNE) && | |
955 | !d_unhashed(dentry)) | |
956 | dentry->d_op->d_prune(dentry); | |
957 | ||
958 | dentry_lru_del(dentry); | |
959 | __d_shrink(dentry); | |
960 | ||
961 | if (dentry->d_lockref.count != 0) { | |
962 | printk(KERN_ERR | |
963 | "BUG: Dentry %p{i=%lx,n=%s}" | |
964 | " still in use (%d)" | |
965 | " [unmount of %s %s]\n", | |
966 | dentry, | |
967 | dentry->d_inode ? | |
968 | dentry->d_inode->i_ino : 0UL, | |
969 | dentry->d_name.name, | |
970 | dentry->d_lockref.count, | |
971 | dentry->d_sb->s_type->name, | |
972 | dentry->d_sb->s_id); | |
973 | BUG(); | |
974 | } | |
975 | ||
976 | if (IS_ROOT(dentry)) { | |
977 | parent = NULL; | |
978 | list_del(&dentry->d_u.d_child); | |
979 | } else { | |
980 | parent = dentry->d_parent; | |
981 | parent->d_lockref.count--; | |
982 | list_del(&dentry->d_u.d_child); | |
983 | } | |
984 | ||
985 | inode = dentry->d_inode; | |
986 | if (inode) { | |
987 | dentry->d_inode = NULL; | |
988 | hlist_del_init(&dentry->d_alias); | |
989 | if (dentry->d_op && dentry->d_op->d_iput) | |
990 | dentry->d_op->d_iput(dentry, inode); | |
991 | else | |
992 | iput(inode); | |
993 | } | |
994 | ||
995 | d_free(dentry); | |
996 | ||
997 | /* finished when we fall off the top of the tree, | |
998 | * otherwise we ascend to the parent and move to the | |
999 | * next sibling if there is one */ | |
1000 | if (!parent) | |
1001 | return; | |
1002 | dentry = parent; | |
1003 | } while (list_empty(&dentry->d_subdirs)); | |
1004 | ||
1005 | dentry = list_entry(dentry->d_subdirs.next, | |
1006 | struct dentry, d_u.d_child); | |
1007 | } | |
1008 | } | |
1009 | ||
1010 | /* | |
1011 | * destroy the dentries attached to a superblock on unmounting | |
1012 | * - we don't need to use dentry->d_lock because: | |
1013 | * - the superblock is detached from all mountings and open files, so the | |
1014 | * dentry trees will not be rearranged by the VFS | |
1015 | * - s_umount is write-locked, so the memory pressure shrinker will ignore | |
1016 | * any dentries belonging to this superblock that it comes across | |
1017 | * - the filesystem itself is no longer permitted to rearrange the dentries | |
1018 | * in this superblock | |
1019 | */ | |
1020 | void shrink_dcache_for_umount(struct super_block *sb) | |
1021 | { | |
1022 | struct dentry *dentry; | |
1023 | ||
1024 | if (down_read_trylock(&sb->s_umount)) | |
1025 | BUG(); | |
1026 | ||
1027 | dentry = sb->s_root; | |
1028 | sb->s_root = NULL; | |
1029 | dentry->d_lockref.count--; | |
1030 | shrink_dcache_for_umount_subtree(dentry); | |
1031 | ||
1032 | while (!hlist_bl_empty(&sb->s_anon)) { | |
1033 | dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash); | |
1034 | shrink_dcache_for_umount_subtree(dentry); | |
1035 | } | |
1036 | } | |
1037 | ||
1038 | /* | |
1039 | * This tries to ascend one level of parenthood, but | |
1040 | * we can race with renaming, so we need to re-check | |
1041 | * the parenthood after dropping the lock and check | |
1042 | * that the sequence number still matches. | |
1043 | */ | |
1044 | static struct dentry *try_to_ascend(struct dentry *old, unsigned seq) | |
1045 | { | |
1046 | struct dentry *new = old->d_parent; | |
1047 | ||
1048 | rcu_read_lock(); | |
1049 | spin_unlock(&old->d_lock); | |
1050 | spin_lock(&new->d_lock); | |
1051 | ||
1052 | /* | |
1053 | * might go back up the wrong parent if we have had a rename | |
1054 | * or deletion | |
1055 | */ | |
1056 | if (new != old->d_parent || | |
1057 | (old->d_flags & DCACHE_DENTRY_KILLED) || | |
1058 | need_seqretry(&rename_lock, seq)) { | |
1059 | spin_unlock(&new->d_lock); | |
1060 | new = NULL; | |
1061 | } | |
1062 | rcu_read_unlock(); | |
1063 | return new; | |
1064 | } | |
1065 | ||
1066 | /** | |
1067 | * enum d_walk_ret - action to talke during tree walk | |
1068 | * @D_WALK_CONTINUE: contrinue walk | |
1069 | * @D_WALK_QUIT: quit walk | |
1070 | * @D_WALK_NORETRY: quit when retry is needed | |
1071 | * @D_WALK_SKIP: skip this dentry and its children | |
1072 | */ | |
1073 | enum d_walk_ret { | |
1074 | D_WALK_CONTINUE, | |
1075 | D_WALK_QUIT, | |
1076 | D_WALK_NORETRY, | |
1077 | D_WALK_SKIP, | |
1078 | }; | |
1079 | ||
1080 | /** | |
1081 | * d_walk - walk the dentry tree | |
1082 | * @parent: start of walk | |
1083 | * @data: data passed to @enter() and @finish() | |
1084 | * @enter: callback when first entering the dentry | |
1085 | * @finish: callback when successfully finished the walk | |
1086 | * | |
1087 | * The @enter() and @finish() callbacks are called with d_lock held. | |
1088 | */ | |
1089 | static void d_walk(struct dentry *parent, void *data, | |
1090 | enum d_walk_ret (*enter)(void *, struct dentry *), | |
1091 | void (*finish)(void *)) | |
1092 | { | |
1093 | struct dentry *this_parent; | |
1094 | struct list_head *next; | |
1095 | unsigned seq = 0; | |
1096 | enum d_walk_ret ret; | |
1097 | bool retry = true; | |
1098 | ||
1099 | again: | |
1100 | read_seqbegin_or_lock(&rename_lock, &seq); | |
1101 | this_parent = parent; | |
1102 | spin_lock(&this_parent->d_lock); | |
1103 | ||
1104 | ret = enter(data, this_parent); | |
1105 | switch (ret) { | |
1106 | case D_WALK_CONTINUE: | |
1107 | break; | |
1108 | case D_WALK_QUIT: | |
1109 | case D_WALK_SKIP: | |
1110 | goto out_unlock; | |
1111 | case D_WALK_NORETRY: | |
1112 | retry = false; | |
1113 | break; | |
1114 | } | |
1115 | repeat: | |
1116 | next = this_parent->d_subdirs.next; | |
1117 | resume: | |
1118 | while (next != &this_parent->d_subdirs) { | |
1119 | struct list_head *tmp = next; | |
1120 | struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child); | |
1121 | next = tmp->next; | |
1122 | ||
1123 | spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); | |
1124 | ||
1125 | ret = enter(data, dentry); | |
1126 | switch (ret) { | |
1127 | case D_WALK_CONTINUE: | |
1128 | break; | |
1129 | case D_WALK_QUIT: | |
1130 | spin_unlock(&dentry->d_lock); | |
1131 | goto out_unlock; | |
1132 | case D_WALK_NORETRY: | |
1133 | retry = false; | |
1134 | break; | |
1135 | case D_WALK_SKIP: | |
1136 | spin_unlock(&dentry->d_lock); | |
1137 | continue; | |
1138 | } | |
1139 | ||
1140 | if (!list_empty(&dentry->d_subdirs)) { | |
1141 | spin_unlock(&this_parent->d_lock); | |
1142 | spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_); | |
1143 | this_parent = dentry; | |
1144 | spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); | |
1145 | goto repeat; | |
1146 | } | |
1147 | spin_unlock(&dentry->d_lock); | |
1148 | } | |
1149 | /* | |
1150 | * All done at this level ... ascend and resume the search. | |
1151 | */ | |
1152 | if (this_parent != parent) { | |
1153 | struct dentry *child = this_parent; | |
1154 | this_parent = try_to_ascend(this_parent, seq); | |
1155 | if (!this_parent) | |
1156 | goto rename_retry; | |
1157 | next = child->d_u.d_child.next; | |
1158 | goto resume; | |
1159 | } | |
1160 | if (need_seqretry(&rename_lock, seq)) { | |
1161 | spin_unlock(&this_parent->d_lock); | |
1162 | goto rename_retry; | |
1163 | } | |
1164 | if (finish) | |
1165 | finish(data); | |
1166 | ||
1167 | out_unlock: | |
1168 | spin_unlock(&this_parent->d_lock); | |
1169 | done_seqretry(&rename_lock, seq); | |
1170 | return; | |
1171 | ||
1172 | rename_retry: | |
1173 | if (!retry) | |
1174 | return; | |
1175 | seq = 1; | |
1176 | goto again; | |
1177 | } | |
1178 | ||
1179 | /* | |
1180 | * Search for at least 1 mount point in the dentry's subdirs. | |
1181 | * We descend to the next level whenever the d_subdirs | |
1182 | * list is non-empty and continue searching. | |
1183 | */ | |
1184 | ||
1185 | /** | |
1186 | * have_submounts - check for mounts over a dentry | |
1187 | * @parent: dentry to check. | |
1188 | * | |
1189 | * Return true if the parent or its subdirectories contain | |
1190 | * a mount point | |
1191 | */ | |
1192 | ||
1193 | static enum d_walk_ret check_mount(void *data, struct dentry *dentry) | |
1194 | { | |
1195 | int *ret = data; | |
1196 | if (d_mountpoint(dentry)) { | |
1197 | *ret = 1; | |
1198 | return D_WALK_QUIT; | |
1199 | } | |
1200 | return D_WALK_CONTINUE; | |
1201 | } | |
1202 | ||
1203 | int have_submounts(struct dentry *parent) | |
1204 | { | |
1205 | int ret = 0; | |
1206 | ||
1207 | d_walk(parent, &ret, check_mount, NULL); | |
1208 | ||
1209 | return ret; | |
1210 | } | |
1211 | EXPORT_SYMBOL(have_submounts); | |
1212 | ||
1213 | /* | |
1214 | * Called by mount code to set a mountpoint and check if the mountpoint is | |
1215 | * reachable (e.g. NFS can unhash a directory dentry and then the complete | |
1216 | * subtree can become unreachable). | |
1217 | * | |
1218 | * Only one of check_submounts_and_drop() and d_set_mounted() must succeed. For | |
1219 | * this reason take rename_lock and d_lock on dentry and ancestors. | |
1220 | */ | |
1221 | int d_set_mounted(struct dentry *dentry) | |
1222 | { | |
1223 | struct dentry *p; | |
1224 | int ret = -ENOENT; | |
1225 | write_seqlock(&rename_lock); | |
1226 | for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) { | |
1227 | /* Need exclusion wrt. check_submounts_and_drop() */ | |
1228 | spin_lock(&p->d_lock); | |
1229 | if (unlikely(d_unhashed(p))) { | |
1230 | spin_unlock(&p->d_lock); | |
1231 | goto out; | |
1232 | } | |
1233 | spin_unlock(&p->d_lock); | |
1234 | } | |
1235 | spin_lock(&dentry->d_lock); | |
1236 | if (!d_unlinked(dentry)) { | |
1237 | dentry->d_flags |= DCACHE_MOUNTED; | |
1238 | ret = 0; | |
1239 | } | |
1240 | spin_unlock(&dentry->d_lock); | |
1241 | out: | |
1242 | write_sequnlock(&rename_lock); | |
1243 | return ret; | |
1244 | } | |
1245 | ||
1246 | /* | |
1247 | * Search the dentry child list of the specified parent, | |
1248 | * and move any unused dentries to the end of the unused | |
1249 | * list for prune_dcache(). We descend to the next level | |
1250 | * whenever the d_subdirs list is non-empty and continue | |
1251 | * searching. | |
1252 | * | |
1253 | * It returns zero iff there are no unused children, | |
1254 | * otherwise it returns the number of children moved to | |
1255 | * the end of the unused list. This may not be the total | |
1256 | * number of unused children, because select_parent can | |
1257 | * drop the lock and return early due to latency | |
1258 | * constraints. | |
1259 | */ | |
1260 | ||
1261 | struct select_data { | |
1262 | struct dentry *start; | |
1263 | struct list_head dispose; | |
1264 | int found; | |
1265 | }; | |
1266 | ||
1267 | static enum d_walk_ret select_collect(void *_data, struct dentry *dentry) | |
1268 | { | |
1269 | struct select_data *data = _data; | |
1270 | enum d_walk_ret ret = D_WALK_CONTINUE; | |
1271 | ||
1272 | if (data->start == dentry) | |
1273 | goto out; | |
1274 | ||
1275 | /* | |
1276 | * move only zero ref count dentries to the dispose list. | |
1277 | * | |
1278 | * Those which are presently on the shrink list, being processed | |
1279 | * by shrink_dentry_list(), shouldn't be moved. Otherwise the | |
1280 | * loop in shrink_dcache_parent() might not make any progress | |
1281 | * and loop forever. | |
1282 | */ | |
1283 | if (dentry->d_lockref.count) { | |
1284 | dentry_lru_del(dentry); | |
1285 | } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) { | |
1286 | dentry_lru_move_list(dentry, &data->dispose); | |
1287 | dentry->d_flags |= DCACHE_SHRINK_LIST; | |
1288 | data->found++; | |
1289 | ret = D_WALK_NORETRY; | |
1290 | } | |
1291 | /* | |
1292 | * We can return to the caller if we have found some (this | |
1293 | * ensures forward progress). We'll be coming back to find | |
1294 | * the rest. | |
1295 | */ | |
1296 | if (data->found && need_resched()) | |
1297 | ret = D_WALK_QUIT; | |
1298 | out: | |
1299 | return ret; | |
1300 | } | |
1301 | ||
1302 | /** | |
1303 | * shrink_dcache_parent - prune dcache | |
1304 | * @parent: parent of entries to prune | |
1305 | * | |
1306 | * Prune the dcache to remove unused children of the parent dentry. | |
1307 | */ | |
1308 | void shrink_dcache_parent(struct dentry *parent) | |
1309 | { | |
1310 | for (;;) { | |
1311 | struct select_data data; | |
1312 | ||
1313 | INIT_LIST_HEAD(&data.dispose); | |
1314 | data.start = parent; | |
1315 | data.found = 0; | |
1316 | ||
1317 | d_walk(parent, &data, select_collect, NULL); | |
1318 | if (!data.found) | |
1319 | break; | |
1320 | ||
1321 | shrink_dentry_list(&data.dispose); | |
1322 | cond_resched(); | |
1323 | } | |
1324 | } | |
1325 | EXPORT_SYMBOL(shrink_dcache_parent); | |
1326 | ||
1327 | static enum d_walk_ret check_and_collect(void *_data, struct dentry *dentry) | |
1328 | { | |
1329 | struct select_data *data = _data; | |
1330 | ||
1331 | if (d_mountpoint(dentry)) { | |
1332 | data->found = -EBUSY; | |
1333 | return D_WALK_QUIT; | |
1334 | } | |
1335 | ||
1336 | return select_collect(_data, dentry); | |
1337 | } | |
1338 | ||
1339 | static void check_and_drop(void *_data) | |
1340 | { | |
1341 | struct select_data *data = _data; | |
1342 | ||
1343 | if (d_mountpoint(data->start)) | |
1344 | data->found = -EBUSY; | |
1345 | if (!data->found) | |
1346 | __d_drop(data->start); | |
1347 | } | |
1348 | ||
1349 | /** | |
1350 | * check_submounts_and_drop - prune dcache, check for submounts and drop | |
1351 | * | |
1352 | * All done as a single atomic operation relative to has_unlinked_ancestor(). | |
1353 | * Returns 0 if successfully unhashed @parent. If there were submounts then | |
1354 | * return -EBUSY. | |
1355 | * | |
1356 | * @dentry: dentry to prune and drop | |
1357 | */ | |
1358 | int check_submounts_and_drop(struct dentry *dentry) | |
1359 | { | |
1360 | int ret = 0; | |
1361 | ||
1362 | /* Negative dentries can be dropped without further checks */ | |
1363 | if (!dentry->d_inode) { | |
1364 | d_drop(dentry); | |
1365 | goto out; | |
1366 | } | |
1367 | ||
1368 | for (;;) { | |
1369 | struct select_data data; | |
1370 | ||
1371 | INIT_LIST_HEAD(&data.dispose); | |
1372 | data.start = dentry; | |
1373 | data.found = 0; | |
1374 | ||
1375 | d_walk(dentry, &data, check_and_collect, check_and_drop); | |
1376 | ret = data.found; | |
1377 | ||
1378 | if (!list_empty(&data.dispose)) | |
1379 | shrink_dentry_list(&data.dispose); | |
1380 | ||
1381 | if (ret <= 0) | |
1382 | break; | |
1383 | ||
1384 | cond_resched(); | |
1385 | } | |
1386 | ||
1387 | out: | |
1388 | return ret; | |
1389 | } | |
1390 | EXPORT_SYMBOL(check_submounts_and_drop); | |
1391 | ||
1392 | /** | |
1393 | * __d_alloc - allocate a dcache entry | |
1394 | * @sb: filesystem it will belong to | |
1395 | * @name: qstr of the name | |
1396 | * | |
1397 | * Allocates a dentry. It returns %NULL if there is insufficient memory | |
1398 | * available. On a success the dentry is returned. The name passed in is | |
1399 | * copied and the copy passed in may be reused after this call. | |
1400 | */ | |
1401 | ||
1402 | struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name) | |
1403 | { | |
1404 | struct dentry *dentry; | |
1405 | char *dname; | |
1406 | ||
1407 | dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL); | |
1408 | if (!dentry) | |
1409 | return NULL; | |
1410 | ||
1411 | /* | |
1412 | * We guarantee that the inline name is always NUL-terminated. | |
1413 | * This way the memcpy() done by the name switching in rename | |
1414 | * will still always have a NUL at the end, even if we might | |
1415 | * be overwriting an internal NUL character | |
1416 | */ | |
1417 | dentry->d_iname[DNAME_INLINE_LEN-1] = 0; | |
1418 | if (name->len > DNAME_INLINE_LEN-1) { | |
1419 | dname = kmalloc(name->len + 1, GFP_KERNEL); | |
1420 | if (!dname) { | |
1421 | kmem_cache_free(dentry_cache, dentry); | |
1422 | return NULL; | |
1423 | } | |
1424 | } else { | |
1425 | dname = dentry->d_iname; | |
1426 | } | |
1427 | ||
1428 | dentry->d_name.len = name->len; | |
1429 | dentry->d_name.hash = name->hash; | |
1430 | memcpy(dname, name->name, name->len); | |
1431 | dname[name->len] = 0; | |
1432 | ||
1433 | /* Make sure we always see the terminating NUL character */ | |
1434 | smp_wmb(); | |
1435 | dentry->d_name.name = dname; | |
1436 | ||
1437 | dentry->d_lockref.count = 1; | |
1438 | dentry->d_flags = 0; | |
1439 | spin_lock_init(&dentry->d_lock); | |
1440 | seqcount_init(&dentry->d_seq); | |
1441 | dentry->d_inode = NULL; | |
1442 | dentry->d_parent = dentry; | |
1443 | dentry->d_sb = sb; | |
1444 | dentry->d_op = NULL; | |
1445 | dentry->d_fsdata = NULL; | |
1446 | INIT_HLIST_BL_NODE(&dentry->d_hash); | |
1447 | INIT_LIST_HEAD(&dentry->d_lru); | |
1448 | INIT_LIST_HEAD(&dentry->d_subdirs); | |
1449 | INIT_HLIST_NODE(&dentry->d_alias); | |
1450 | INIT_LIST_HEAD(&dentry->d_u.d_child); | |
1451 | d_set_d_op(dentry, dentry->d_sb->s_d_op); | |
1452 | ||
1453 | this_cpu_inc(nr_dentry); | |
1454 | ||
1455 | return dentry; | |
1456 | } | |
1457 | ||
1458 | /** | |
1459 | * d_alloc - allocate a dcache entry | |
1460 | * @parent: parent of entry to allocate | |
1461 | * @name: qstr of the name | |
1462 | * | |
1463 | * Allocates a dentry. It returns %NULL if there is insufficient memory | |
1464 | * available. On a success the dentry is returned. The name passed in is | |
1465 | * copied and the copy passed in may be reused after this call. | |
1466 | */ | |
1467 | struct dentry *d_alloc(struct dentry * parent, const struct qstr *name) | |
1468 | { | |
1469 | struct dentry *dentry = __d_alloc(parent->d_sb, name); | |
1470 | if (!dentry) | |
1471 | return NULL; | |
1472 | ||
1473 | spin_lock(&parent->d_lock); | |
1474 | /* | |
1475 | * don't need child lock because it is not subject | |
1476 | * to concurrency here | |
1477 | */ | |
1478 | __dget_dlock(parent); | |
1479 | dentry->d_parent = parent; | |
1480 | list_add(&dentry->d_u.d_child, &parent->d_subdirs); | |
1481 | spin_unlock(&parent->d_lock); | |
1482 | ||
1483 | return dentry; | |
1484 | } | |
1485 | EXPORT_SYMBOL(d_alloc); | |
1486 | ||
1487 | struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name) | |
1488 | { | |
1489 | struct dentry *dentry = __d_alloc(sb, name); | |
1490 | if (dentry) | |
1491 | dentry->d_flags |= DCACHE_DISCONNECTED; | |
1492 | return dentry; | |
1493 | } | |
1494 | EXPORT_SYMBOL(d_alloc_pseudo); | |
1495 | ||
1496 | struct dentry *d_alloc_name(struct dentry *parent, const char *name) | |
1497 | { | |
1498 | struct qstr q; | |
1499 | ||
1500 | q.name = name; | |
1501 | q.len = strlen(name); | |
1502 | q.hash = full_name_hash(q.name, q.len); | |
1503 | return d_alloc(parent, &q); | |
1504 | } | |
1505 | EXPORT_SYMBOL(d_alloc_name); | |
1506 | ||
1507 | void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op) | |
1508 | { | |
1509 | WARN_ON_ONCE(dentry->d_op); | |
1510 | WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH | | |
1511 | DCACHE_OP_COMPARE | | |
1512 | DCACHE_OP_REVALIDATE | | |
1513 | DCACHE_OP_WEAK_REVALIDATE | | |
1514 | DCACHE_OP_DELETE )); | |
1515 | dentry->d_op = op; | |
1516 | if (!op) | |
1517 | return; | |
1518 | if (op->d_hash) | |
1519 | dentry->d_flags |= DCACHE_OP_HASH; | |
1520 | if (op->d_compare) | |
1521 | dentry->d_flags |= DCACHE_OP_COMPARE; | |
1522 | if (op->d_revalidate) | |
1523 | dentry->d_flags |= DCACHE_OP_REVALIDATE; | |
1524 | if (op->d_weak_revalidate) | |
1525 | dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE; | |
1526 | if (op->d_delete) | |
1527 | dentry->d_flags |= DCACHE_OP_DELETE; | |
1528 | if (op->d_prune) | |
1529 | dentry->d_flags |= DCACHE_OP_PRUNE; | |
1530 | ||
1531 | } | |
1532 | EXPORT_SYMBOL(d_set_d_op); | |
1533 | ||
1534 | static void __d_instantiate(struct dentry *dentry, struct inode *inode) | |
1535 | { | |
1536 | spin_lock(&dentry->d_lock); | |
1537 | if (inode) { | |
1538 | if (unlikely(IS_AUTOMOUNT(inode))) | |
1539 | dentry->d_flags |= DCACHE_NEED_AUTOMOUNT; | |
1540 | hlist_add_head(&dentry->d_alias, &inode->i_dentry); | |
1541 | } | |
1542 | dentry->d_inode = inode; | |
1543 | dentry_rcuwalk_barrier(dentry); | |
1544 | spin_unlock(&dentry->d_lock); | |
1545 | fsnotify_d_instantiate(dentry, inode); | |
1546 | } | |
1547 | ||
1548 | /** | |
1549 | * d_instantiate - fill in inode information for a dentry | |
1550 | * @entry: dentry to complete | |
1551 | * @inode: inode to attach to this dentry | |
1552 | * | |
1553 | * Fill in inode information in the entry. | |
1554 | * | |
1555 | * This turns negative dentries into productive full members | |
1556 | * of society. | |
1557 | * | |
1558 | * NOTE! This assumes that the inode count has been incremented | |
1559 | * (or otherwise set) by the caller to indicate that it is now | |
1560 | * in use by the dcache. | |
1561 | */ | |
1562 | ||
1563 | void d_instantiate(struct dentry *entry, struct inode * inode) | |
1564 | { | |
1565 | BUG_ON(!hlist_unhashed(&entry->d_alias)); | |
1566 | if (inode) | |
1567 | spin_lock(&inode->i_lock); | |
1568 | __d_instantiate(entry, inode); | |
1569 | if (inode) | |
1570 | spin_unlock(&inode->i_lock); | |
1571 | security_d_instantiate(entry, inode); | |
1572 | } | |
1573 | EXPORT_SYMBOL(d_instantiate); | |
1574 | ||
1575 | /** | |
1576 | * d_instantiate_unique - instantiate a non-aliased dentry | |
1577 | * @entry: dentry to instantiate | |
1578 | * @inode: inode to attach to this dentry | |
1579 | * | |
1580 | * Fill in inode information in the entry. On success, it returns NULL. | |
1581 | * If an unhashed alias of "entry" already exists, then we return the | |
1582 | * aliased dentry instead and drop one reference to inode. | |
1583 | * | |
1584 | * Note that in order to avoid conflicts with rename() etc, the caller | |
1585 | * had better be holding the parent directory semaphore. | |
1586 | * | |
1587 | * This also assumes that the inode count has been incremented | |
1588 | * (or otherwise set) by the caller to indicate that it is now | |
1589 | * in use by the dcache. | |
1590 | */ | |
1591 | static struct dentry *__d_instantiate_unique(struct dentry *entry, | |
1592 | struct inode *inode) | |
1593 | { | |
1594 | struct dentry *alias; | |
1595 | int len = entry->d_name.len; | |
1596 | const char *name = entry->d_name.name; | |
1597 | unsigned int hash = entry->d_name.hash; | |
1598 | ||
1599 | if (!inode) { | |
1600 | __d_instantiate(entry, NULL); | |
1601 | return NULL; | |
1602 | } | |
1603 | ||
1604 | hlist_for_each_entry(alias, &inode->i_dentry, d_alias) { | |
1605 | /* | |
1606 | * Don't need alias->d_lock here, because aliases with | |
1607 | * d_parent == entry->d_parent are not subject to name or | |
1608 | * parent changes, because the parent inode i_mutex is held. | |
1609 | */ | |
1610 | if (alias->d_name.hash != hash) | |
1611 | continue; | |
1612 | if (alias->d_parent != entry->d_parent) | |
1613 | continue; | |
1614 | if (alias->d_name.len != len) | |
1615 | continue; | |
1616 | if (dentry_cmp(alias, name, len)) | |
1617 | continue; | |
1618 | __dget(alias); | |
1619 | return alias; | |
1620 | } | |
1621 | ||
1622 | __d_instantiate(entry, inode); | |
1623 | return NULL; | |
1624 | } | |
1625 | ||
1626 | struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode) | |
1627 | { | |
1628 | struct dentry *result; | |
1629 | ||
1630 | BUG_ON(!hlist_unhashed(&entry->d_alias)); | |
1631 | ||
1632 | if (inode) | |
1633 | spin_lock(&inode->i_lock); | |
1634 | result = __d_instantiate_unique(entry, inode); | |
1635 | if (inode) | |
1636 | spin_unlock(&inode->i_lock); | |
1637 | ||
1638 | if (!result) { | |
1639 | security_d_instantiate(entry, inode); | |
1640 | return NULL; | |
1641 | } | |
1642 | ||
1643 | BUG_ON(!d_unhashed(result)); | |
1644 | iput(inode); | |
1645 | return result; | |
1646 | } | |
1647 | ||
1648 | EXPORT_SYMBOL(d_instantiate_unique); | |
1649 | ||
1650 | struct dentry *d_make_root(struct inode *root_inode) | |
1651 | { | |
1652 | struct dentry *res = NULL; | |
1653 | ||
1654 | if (root_inode) { | |
1655 | static const struct qstr name = QSTR_INIT("/", 1); | |
1656 | ||
1657 | res = __d_alloc(root_inode->i_sb, &name); | |
1658 | if (res) | |
1659 | d_instantiate(res, root_inode); | |
1660 | else | |
1661 | iput(root_inode); | |
1662 | } | |
1663 | return res; | |
1664 | } | |
1665 | EXPORT_SYMBOL(d_make_root); | |
1666 | ||
1667 | static struct dentry * __d_find_any_alias(struct inode *inode) | |
1668 | { | |
1669 | struct dentry *alias; | |
1670 | ||
1671 | if (hlist_empty(&inode->i_dentry)) | |
1672 | return NULL; | |
1673 | alias = hlist_entry(inode->i_dentry.first, struct dentry, d_alias); | |
1674 | __dget(alias); | |
1675 | return alias; | |
1676 | } | |
1677 | ||
1678 | /** | |
1679 | * d_find_any_alias - find any alias for a given inode | |
1680 | * @inode: inode to find an alias for | |
1681 | * | |
1682 | * If any aliases exist for the given inode, take and return a | |
1683 | * reference for one of them. If no aliases exist, return %NULL. | |
1684 | */ | |
1685 | struct dentry *d_find_any_alias(struct inode *inode) | |
1686 | { | |
1687 | struct dentry *de; | |
1688 | ||
1689 | spin_lock(&inode->i_lock); | |
1690 | de = __d_find_any_alias(inode); | |
1691 | spin_unlock(&inode->i_lock); | |
1692 | return de; | |
1693 | } | |
1694 | EXPORT_SYMBOL(d_find_any_alias); | |
1695 | ||
1696 | /** | |
1697 | * d_obtain_alias - find or allocate a dentry for a given inode | |
1698 | * @inode: inode to allocate the dentry for | |
1699 | * | |
1700 | * Obtain a dentry for an inode resulting from NFS filehandle conversion or | |
1701 | * similar open by handle operations. The returned dentry may be anonymous, | |
1702 | * or may have a full name (if the inode was already in the cache). | |
1703 | * | |
1704 | * When called on a directory inode, we must ensure that the inode only ever | |
1705 | * has one dentry. If a dentry is found, that is returned instead of | |
1706 | * allocating a new one. | |
1707 | * | |
1708 | * On successful return, the reference to the inode has been transferred | |
1709 | * to the dentry. In case of an error the reference on the inode is released. | |
1710 | * To make it easier to use in export operations a %NULL or IS_ERR inode may | |
1711 | * be passed in and will be the error will be propagate to the return value, | |
1712 | * with a %NULL @inode replaced by ERR_PTR(-ESTALE). | |
1713 | */ | |
1714 | struct dentry *d_obtain_alias(struct inode *inode) | |
1715 | { | |
1716 | static const struct qstr anonstring = QSTR_INIT("/", 1); | |
1717 | struct dentry *tmp; | |
1718 | struct dentry *res; | |
1719 | ||
1720 | if (!inode) | |
1721 | return ERR_PTR(-ESTALE); | |
1722 | if (IS_ERR(inode)) | |
1723 | return ERR_CAST(inode); | |
1724 | ||
1725 | res = d_find_any_alias(inode); | |
1726 | if (res) | |
1727 | goto out_iput; | |
1728 | ||
1729 | tmp = __d_alloc(inode->i_sb, &anonstring); | |
1730 | if (!tmp) { | |
1731 | res = ERR_PTR(-ENOMEM); | |
1732 | goto out_iput; | |
1733 | } | |
1734 | ||
1735 | spin_lock(&inode->i_lock); | |
1736 | res = __d_find_any_alias(inode); | |
1737 | if (res) { | |
1738 | spin_unlock(&inode->i_lock); | |
1739 | dput(tmp); | |
1740 | goto out_iput; | |
1741 | } | |
1742 | ||
1743 | /* attach a disconnected dentry */ | |
1744 | spin_lock(&tmp->d_lock); | |
1745 | tmp->d_inode = inode; | |
1746 | tmp->d_flags |= DCACHE_DISCONNECTED; | |
1747 | hlist_add_head(&tmp->d_alias, &inode->i_dentry); | |
1748 | hlist_bl_lock(&tmp->d_sb->s_anon); | |
1749 | hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon); | |
1750 | hlist_bl_unlock(&tmp->d_sb->s_anon); | |
1751 | spin_unlock(&tmp->d_lock); | |
1752 | spin_unlock(&inode->i_lock); | |
1753 | security_d_instantiate(tmp, inode); | |
1754 | ||
1755 | return tmp; | |
1756 | ||
1757 | out_iput: | |
1758 | if (res && !IS_ERR(res)) | |
1759 | security_d_instantiate(res, inode); | |
1760 | iput(inode); | |
1761 | return res; | |
1762 | } | |
1763 | EXPORT_SYMBOL(d_obtain_alias); | |
1764 | ||
1765 | /** | |
1766 | * d_splice_alias - splice a disconnected dentry into the tree if one exists | |
1767 | * @inode: the inode which may have a disconnected dentry | |
1768 | * @dentry: a negative dentry which we want to point to the inode. | |
1769 | * | |
1770 | * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and | |
1771 | * DCACHE_DISCONNECTED), then d_move that in place of the given dentry | |
1772 | * and return it, else simply d_add the inode to the dentry and return NULL. | |
1773 | * | |
1774 | * This is needed in the lookup routine of any filesystem that is exportable | |
1775 | * (via knfsd) so that we can build dcache paths to directories effectively. | |
1776 | * | |
1777 | * If a dentry was found and moved, then it is returned. Otherwise NULL | |
1778 | * is returned. This matches the expected return value of ->lookup. | |
1779 | * | |
1780 | * Cluster filesystems may call this function with a negative, hashed dentry. | |
1781 | * In that case, we know that the inode will be a regular file, and also this | |
1782 | * will only occur during atomic_open. So we need to check for the dentry | |
1783 | * being already hashed only in the final case. | |
1784 | */ | |
1785 | struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry) | |
1786 | { | |
1787 | struct dentry *new = NULL; | |
1788 | ||
1789 | if (IS_ERR(inode)) | |
1790 | return ERR_CAST(inode); | |
1791 | ||
1792 | if (inode && S_ISDIR(inode->i_mode)) { | |
1793 | spin_lock(&inode->i_lock); | |
1794 | new = __d_find_alias(inode, 1); | |
1795 | if (new) { | |
1796 | BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED)); | |
1797 | spin_unlock(&inode->i_lock); | |
1798 | security_d_instantiate(new, inode); | |
1799 | d_move(new, dentry); | |
1800 | iput(inode); | |
1801 | } else { | |
1802 | /* already taking inode->i_lock, so d_add() by hand */ | |
1803 | __d_instantiate(dentry, inode); | |
1804 | spin_unlock(&inode->i_lock); | |
1805 | security_d_instantiate(dentry, inode); | |
1806 | d_rehash(dentry); | |
1807 | } | |
1808 | } else { | |
1809 | d_instantiate(dentry, inode); | |
1810 | if (d_unhashed(dentry)) | |
1811 | d_rehash(dentry); | |
1812 | } | |
1813 | return new; | |
1814 | } | |
1815 | EXPORT_SYMBOL(d_splice_alias); | |
1816 | ||
1817 | /** | |
1818 | * d_add_ci - lookup or allocate new dentry with case-exact name | |
1819 | * @inode: the inode case-insensitive lookup has found | |
1820 | * @dentry: the negative dentry that was passed to the parent's lookup func | |
1821 | * @name: the case-exact name to be associated with the returned dentry | |
1822 | * | |
1823 | * This is to avoid filling the dcache with case-insensitive names to the | |
1824 | * same inode, only the actual correct case is stored in the dcache for | |
1825 | * case-insensitive filesystems. | |
1826 | * | |
1827 | * For a case-insensitive lookup match and if the the case-exact dentry | |
1828 | * already exists in in the dcache, use it and return it. | |
1829 | * | |
1830 | * If no entry exists with the exact case name, allocate new dentry with | |
1831 | * the exact case, and return the spliced entry. | |
1832 | */ | |
1833 | struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode, | |
1834 | struct qstr *name) | |
1835 | { | |
1836 | struct dentry *found; | |
1837 | struct dentry *new; | |
1838 | ||
1839 | /* | |
1840 | * First check if a dentry matching the name already exists, | |
1841 | * if not go ahead and create it now. | |
1842 | */ | |
1843 | found = d_hash_and_lookup(dentry->d_parent, name); | |
1844 | if (unlikely(IS_ERR(found))) | |
1845 | goto err_out; | |
1846 | if (!found) { | |
1847 | new = d_alloc(dentry->d_parent, name); | |
1848 | if (!new) { | |
1849 | found = ERR_PTR(-ENOMEM); | |
1850 | goto err_out; | |
1851 | } | |
1852 | ||
1853 | found = d_splice_alias(inode, new); | |
1854 | if (found) { | |
1855 | dput(new); | |
1856 | return found; | |
1857 | } | |
1858 | return new; | |
1859 | } | |
1860 | ||
1861 | /* | |
1862 | * If a matching dentry exists, and it's not negative use it. | |
1863 | * | |
1864 | * Decrement the reference count to balance the iget() done | |
1865 | * earlier on. | |
1866 | */ | |
1867 | if (found->d_inode) { | |
1868 | if (unlikely(found->d_inode != inode)) { | |
1869 | /* This can't happen because bad inodes are unhashed. */ | |
1870 | BUG_ON(!is_bad_inode(inode)); | |
1871 | BUG_ON(!is_bad_inode(found->d_inode)); | |
1872 | } | |
1873 | iput(inode); | |
1874 | return found; | |
1875 | } | |
1876 | ||
1877 | /* | |
1878 | * Negative dentry: instantiate it unless the inode is a directory and | |
1879 | * already has a dentry. | |
1880 | */ | |
1881 | new = d_splice_alias(inode, found); | |
1882 | if (new) { | |
1883 | dput(found); | |
1884 | found = new; | |
1885 | } | |
1886 | return found; | |
1887 | ||
1888 | err_out: | |
1889 | iput(inode); | |
1890 | return found; | |
1891 | } | |
1892 | EXPORT_SYMBOL(d_add_ci); | |
1893 | ||
1894 | /* | |
1895 | * Do the slow-case of the dentry name compare. | |
1896 | * | |
1897 | * Unlike the dentry_cmp() function, we need to atomically | |
1898 | * load the name and length information, so that the | |
1899 | * filesystem can rely on them, and can use the 'name' and | |
1900 | * 'len' information without worrying about walking off the | |
1901 | * end of memory etc. | |
1902 | * | |
1903 | * Thus the read_seqcount_retry() and the "duplicate" info | |
1904 | * in arguments (the low-level filesystem should not look | |
1905 | * at the dentry inode or name contents directly, since | |
1906 | * rename can change them while we're in RCU mode). | |
1907 | */ | |
1908 | enum slow_d_compare { | |
1909 | D_COMP_OK, | |
1910 | D_COMP_NOMATCH, | |
1911 | D_COMP_SEQRETRY, | |
1912 | }; | |
1913 | ||
1914 | static noinline enum slow_d_compare slow_dentry_cmp( | |
1915 | const struct dentry *parent, | |
1916 | struct dentry *dentry, | |
1917 | unsigned int seq, | |
1918 | const struct qstr *name) | |
1919 | { | |
1920 | int tlen = dentry->d_name.len; | |
1921 | const char *tname = dentry->d_name.name; | |
1922 | ||
1923 | if (read_seqcount_retry(&dentry->d_seq, seq)) { | |
1924 | cpu_relax(); | |
1925 | return D_COMP_SEQRETRY; | |
1926 | } | |
1927 | if (parent->d_op->d_compare(parent, dentry, tlen, tname, name)) | |
1928 | return D_COMP_NOMATCH; | |
1929 | return D_COMP_OK; | |
1930 | } | |
1931 | ||
1932 | /** | |
1933 | * __d_lookup_rcu - search for a dentry (racy, store-free) | |
1934 | * @parent: parent dentry | |
1935 | * @name: qstr of name we wish to find | |
1936 | * @seqp: returns d_seq value at the point where the dentry was found | |
1937 | * Returns: dentry, or NULL | |
1938 | * | |
1939 | * __d_lookup_rcu is the dcache lookup function for rcu-walk name | |
1940 | * resolution (store-free path walking) design described in | |
1941 | * Documentation/filesystems/path-lookup.txt. | |
1942 | * | |
1943 | * This is not to be used outside core vfs. | |
1944 | * | |
1945 | * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock | |
1946 | * held, and rcu_read_lock held. The returned dentry must not be stored into | |
1947 | * without taking d_lock and checking d_seq sequence count against @seq | |
1948 | * returned here. | |
1949 | * | |
1950 | * A refcount may be taken on the found dentry with the d_rcu_to_refcount | |
1951 | * function. | |
1952 | * | |
1953 | * Alternatively, __d_lookup_rcu may be called again to look up the child of | |
1954 | * the returned dentry, so long as its parent's seqlock is checked after the | |
1955 | * child is looked up. Thus, an interlocking stepping of sequence lock checks | |
1956 | * is formed, giving integrity down the path walk. | |
1957 | * | |
1958 | * NOTE! The caller *has* to check the resulting dentry against the sequence | |
1959 | * number we've returned before using any of the resulting dentry state! | |
1960 | */ | |
1961 | struct dentry *__d_lookup_rcu(const struct dentry *parent, | |
1962 | const struct qstr *name, | |
1963 | unsigned *seqp) | |
1964 | { | |
1965 | u64 hashlen = name->hash_len; | |
1966 | const unsigned char *str = name->name; | |
1967 | struct hlist_bl_head *b = d_hash(parent, hashlen_hash(hashlen)); | |
1968 | struct hlist_bl_node *node; | |
1969 | struct dentry *dentry; | |
1970 | ||
1971 | /* | |
1972 | * Note: There is significant duplication with __d_lookup_rcu which is | |
1973 | * required to prevent single threaded performance regressions | |
1974 | * especially on architectures where smp_rmb (in seqcounts) are costly. | |
1975 | * Keep the two functions in sync. | |
1976 | */ | |
1977 | ||
1978 | /* | |
1979 | * The hash list is protected using RCU. | |
1980 | * | |
1981 | * Carefully use d_seq when comparing a candidate dentry, to avoid | |
1982 | * races with d_move(). | |
1983 | * | |
1984 | * It is possible that concurrent renames can mess up our list | |
1985 | * walk here and result in missing our dentry, resulting in the | |
1986 | * false-negative result. d_lookup() protects against concurrent | |
1987 | * renames using rename_lock seqlock. | |
1988 | * | |
1989 | * See Documentation/filesystems/path-lookup.txt for more details. | |
1990 | */ | |
1991 | hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { | |
1992 | unsigned seq; | |
1993 | ||
1994 | seqretry: | |
1995 | /* | |
1996 | * The dentry sequence count protects us from concurrent | |
1997 | * renames, and thus protects parent and name fields. | |
1998 | * | |
1999 | * The caller must perform a seqcount check in order | |
2000 | * to do anything useful with the returned dentry. | |
2001 | * | |
2002 | * NOTE! We do a "raw" seqcount_begin here. That means that | |
2003 | * we don't wait for the sequence count to stabilize if it | |
2004 | * is in the middle of a sequence change. If we do the slow | |
2005 | * dentry compare, we will do seqretries until it is stable, | |
2006 | * and if we end up with a successful lookup, we actually | |
2007 | * want to exit RCU lookup anyway. | |
2008 | */ | |
2009 | seq = raw_seqcount_begin(&dentry->d_seq); | |
2010 | if (dentry->d_parent != parent) | |
2011 | continue; | |
2012 | if (d_unhashed(dentry)) | |
2013 | continue; | |
2014 | ||
2015 | if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) { | |
2016 | if (dentry->d_name.hash != hashlen_hash(hashlen)) | |
2017 | continue; | |
2018 | *seqp = seq; | |
2019 | switch (slow_dentry_cmp(parent, dentry, seq, name)) { | |
2020 | case D_COMP_OK: | |
2021 | return dentry; | |
2022 | case D_COMP_NOMATCH: | |
2023 | continue; | |
2024 | default: | |
2025 | goto seqretry; | |
2026 | } | |
2027 | } | |
2028 | ||
2029 | if (dentry->d_name.hash_len != hashlen) | |
2030 | continue; | |
2031 | *seqp = seq; | |
2032 | if (!dentry_cmp(dentry, str, hashlen_len(hashlen))) | |
2033 | return dentry; | |
2034 | } | |
2035 | return NULL; | |
2036 | } | |
2037 | ||
2038 | /** | |
2039 | * d_lookup - search for a dentry | |
2040 | * @parent: parent dentry | |
2041 | * @name: qstr of name we wish to find | |
2042 | * Returns: dentry, or NULL | |
2043 | * | |
2044 | * d_lookup searches the children of the parent dentry for the name in | |
2045 | * question. If the dentry is found its reference count is incremented and the | |
2046 | * dentry is returned. The caller must use dput to free the entry when it has | |
2047 | * finished using it. %NULL is returned if the dentry does not exist. | |
2048 | */ | |
2049 | struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name) | |
2050 | { | |
2051 | struct dentry *dentry; | |
2052 | unsigned seq; | |
2053 | ||
2054 | do { | |
2055 | seq = read_seqbegin(&rename_lock); | |
2056 | dentry = __d_lookup(parent, name); | |
2057 | if (dentry) | |
2058 | break; | |
2059 | } while (read_seqretry(&rename_lock, seq)); | |
2060 | return dentry; | |
2061 | } | |
2062 | EXPORT_SYMBOL(d_lookup); | |
2063 | ||
2064 | /** | |
2065 | * __d_lookup - search for a dentry (racy) | |
2066 | * @parent: parent dentry | |
2067 | * @name: qstr of name we wish to find | |
2068 | * Returns: dentry, or NULL | |
2069 | * | |
2070 | * __d_lookup is like d_lookup, however it may (rarely) return a | |
2071 | * false-negative result due to unrelated rename activity. | |
2072 | * | |
2073 | * __d_lookup is slightly faster by avoiding rename_lock read seqlock, | |
2074 | * however it must be used carefully, eg. with a following d_lookup in | |
2075 | * the case of failure. | |
2076 | * | |
2077 | * __d_lookup callers must be commented. | |
2078 | */ | |
2079 | struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name) | |
2080 | { | |
2081 | unsigned int len = name->len; | |
2082 | unsigned int hash = name->hash; | |
2083 | const unsigned char *str = name->name; | |
2084 | struct hlist_bl_head *b = d_hash(parent, hash); | |
2085 | struct hlist_bl_node *node; | |
2086 | struct dentry *found = NULL; | |
2087 | struct dentry *dentry; | |
2088 | ||
2089 | /* | |
2090 | * Note: There is significant duplication with __d_lookup_rcu which is | |
2091 | * required to prevent single threaded performance regressions | |
2092 | * especially on architectures where smp_rmb (in seqcounts) are costly. | |
2093 | * Keep the two functions in sync. | |
2094 | */ | |
2095 | ||
2096 | /* | |
2097 | * The hash list is protected using RCU. | |
2098 | * | |
2099 | * Take d_lock when comparing a candidate dentry, to avoid races | |
2100 | * with d_move(). | |
2101 | * | |
2102 | * It is possible that concurrent renames can mess up our list | |
2103 | * walk here and result in missing our dentry, resulting in the | |
2104 | * false-negative result. d_lookup() protects against concurrent | |
2105 | * renames using rename_lock seqlock. | |
2106 | * | |
2107 | * See Documentation/filesystems/path-lookup.txt for more details. | |
2108 | */ | |
2109 | rcu_read_lock(); | |
2110 | ||
2111 | hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) { | |
2112 | ||
2113 | if (dentry->d_name.hash != hash) | |
2114 | continue; | |
2115 | ||
2116 | spin_lock(&dentry->d_lock); | |
2117 | if (dentry->d_parent != parent) | |
2118 | goto next; | |
2119 | if (d_unhashed(dentry)) | |
2120 | goto next; | |
2121 | ||
2122 | /* | |
2123 | * It is safe to compare names since d_move() cannot | |
2124 | * change the qstr (protected by d_lock). | |
2125 | */ | |
2126 | if (parent->d_flags & DCACHE_OP_COMPARE) { | |
2127 | int tlen = dentry->d_name.len; | |
2128 | const char *tname = dentry->d_name.name; | |
2129 | if (parent->d_op->d_compare(parent, dentry, tlen, tname, name)) | |
2130 | goto next; | |
2131 | } else { | |
2132 | if (dentry->d_name.len != len) | |
2133 | goto next; | |
2134 | if (dentry_cmp(dentry, str, len)) | |
2135 | goto next; | |
2136 | } | |
2137 | ||
2138 | dentry->d_lockref.count++; | |
2139 | found = dentry; | |
2140 | spin_unlock(&dentry->d_lock); | |
2141 | break; | |
2142 | next: | |
2143 | spin_unlock(&dentry->d_lock); | |
2144 | } | |
2145 | rcu_read_unlock(); | |
2146 | ||
2147 | return found; | |
2148 | } | |
2149 | ||
2150 | /** | |
2151 | * d_hash_and_lookup - hash the qstr then search for a dentry | |
2152 | * @dir: Directory to search in | |
2153 | * @name: qstr of name we wish to find | |
2154 | * | |
2155 | * On lookup failure NULL is returned; on bad name - ERR_PTR(-error) | |
2156 | */ | |
2157 | struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name) | |
2158 | { | |
2159 | /* | |
2160 | * Check for a fs-specific hash function. Note that we must | |
2161 | * calculate the standard hash first, as the d_op->d_hash() | |
2162 | * routine may choose to leave the hash value unchanged. | |
2163 | */ | |
2164 | name->hash = full_name_hash(name->name, name->len); | |
2165 | if (dir->d_flags & DCACHE_OP_HASH) { | |
2166 | int err = dir->d_op->d_hash(dir, name); | |
2167 | if (unlikely(err < 0)) | |
2168 | return ERR_PTR(err); | |
2169 | } | |
2170 | return d_lookup(dir, name); | |
2171 | } | |
2172 | EXPORT_SYMBOL(d_hash_and_lookup); | |
2173 | ||
2174 | /** | |
2175 | * d_validate - verify dentry provided from insecure source (deprecated) | |
2176 | * @dentry: The dentry alleged to be valid child of @dparent | |
2177 | * @dparent: The parent dentry (known to be valid) | |
2178 | * | |
2179 | * An insecure source has sent us a dentry, here we verify it and dget() it. | |
2180 | * This is used by ncpfs in its readdir implementation. | |
2181 | * Zero is returned in the dentry is invalid. | |
2182 | * | |
2183 | * This function is slow for big directories, and deprecated, do not use it. | |
2184 | */ | |
2185 | int d_validate(struct dentry *dentry, struct dentry *dparent) | |
2186 | { | |
2187 | struct dentry *child; | |
2188 | ||
2189 | spin_lock(&dparent->d_lock); | |
2190 | list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) { | |
2191 | if (dentry == child) { | |
2192 | spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); | |
2193 | __dget_dlock(dentry); | |
2194 | spin_unlock(&dentry->d_lock); | |
2195 | spin_unlock(&dparent->d_lock); | |
2196 | return 1; | |
2197 | } | |
2198 | } | |
2199 | spin_unlock(&dparent->d_lock); | |
2200 | ||
2201 | return 0; | |
2202 | } | |
2203 | EXPORT_SYMBOL(d_validate); | |
2204 | ||
2205 | /* | |
2206 | * When a file is deleted, we have two options: | |
2207 | * - turn this dentry into a negative dentry | |
2208 | * - unhash this dentry and free it. | |
2209 | * | |
2210 | * Usually, we want to just turn this into | |
2211 | * a negative dentry, but if anybody else is | |
2212 | * currently using the dentry or the inode | |
2213 | * we can't do that and we fall back on removing | |
2214 | * it from the hash queues and waiting for | |
2215 | * it to be deleted later when it has no users | |
2216 | */ | |
2217 | ||
2218 | /** | |
2219 | * d_delete - delete a dentry | |
2220 | * @dentry: The dentry to delete | |
2221 | * | |
2222 | * Turn the dentry into a negative dentry if possible, otherwise | |
2223 | * remove it from the hash queues so it can be deleted later | |
2224 | */ | |
2225 | ||
2226 | void d_delete(struct dentry * dentry) | |
2227 | { | |
2228 | struct inode *inode; | |
2229 | int isdir = 0; | |
2230 | /* | |
2231 | * Are we the only user? | |
2232 | */ | |
2233 | again: | |
2234 | spin_lock(&dentry->d_lock); | |
2235 | inode = dentry->d_inode; | |
2236 | isdir = S_ISDIR(inode->i_mode); | |
2237 | if (dentry->d_lockref.count == 1) { | |
2238 | if (!spin_trylock(&inode->i_lock)) { | |
2239 | spin_unlock(&dentry->d_lock); | |
2240 | cpu_relax(); | |
2241 | goto again; | |
2242 | } | |
2243 | dentry->d_flags &= ~DCACHE_CANT_MOUNT; | |
2244 | dentry_unlink_inode(dentry); | |
2245 | fsnotify_nameremove(dentry, isdir); | |
2246 | return; | |
2247 | } | |
2248 | ||
2249 | if (!d_unhashed(dentry)) | |
2250 | __d_drop(dentry); | |
2251 | ||
2252 | spin_unlock(&dentry->d_lock); | |
2253 | ||
2254 | fsnotify_nameremove(dentry, isdir); | |
2255 | } | |
2256 | EXPORT_SYMBOL(d_delete); | |
2257 | ||
2258 | static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b) | |
2259 | { | |
2260 | BUG_ON(!d_unhashed(entry)); | |
2261 | hlist_bl_lock(b); | |
2262 | entry->d_flags |= DCACHE_RCUACCESS; | |
2263 | hlist_bl_add_head_rcu(&entry->d_hash, b); | |
2264 | hlist_bl_unlock(b); | |
2265 | } | |
2266 | ||
2267 | static void _d_rehash(struct dentry * entry) | |
2268 | { | |
2269 | __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash)); | |
2270 | } | |
2271 | ||
2272 | /** | |
2273 | * d_rehash - add an entry back to the hash | |
2274 | * @entry: dentry to add to the hash | |
2275 | * | |
2276 | * Adds a dentry to the hash according to its name. | |
2277 | */ | |
2278 | ||
2279 | void d_rehash(struct dentry * entry) | |
2280 | { | |
2281 | spin_lock(&entry->d_lock); | |
2282 | _d_rehash(entry); | |
2283 | spin_unlock(&entry->d_lock); | |
2284 | } | |
2285 | EXPORT_SYMBOL(d_rehash); | |
2286 | ||
2287 | /** | |
2288 | * dentry_update_name_case - update case insensitive dentry with a new name | |
2289 | * @dentry: dentry to be updated | |
2290 | * @name: new name | |
2291 | * | |
2292 | * Update a case insensitive dentry with new case of name. | |
2293 | * | |
2294 | * dentry must have been returned by d_lookup with name @name. Old and new | |
2295 | * name lengths must match (ie. no d_compare which allows mismatched name | |
2296 | * lengths). | |
2297 | * | |
2298 | * Parent inode i_mutex must be held over d_lookup and into this call (to | |
2299 | * keep renames and concurrent inserts, and readdir(2) away). | |
2300 | */ | |
2301 | void dentry_update_name_case(struct dentry *dentry, struct qstr *name) | |
2302 | { | |
2303 | BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex)); | |
2304 | BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */ | |
2305 | ||
2306 | spin_lock(&dentry->d_lock); | |
2307 | write_seqcount_begin(&dentry->d_seq); | |
2308 | memcpy((unsigned char *)dentry->d_name.name, name->name, name->len); | |
2309 | write_seqcount_end(&dentry->d_seq); | |
2310 | spin_unlock(&dentry->d_lock); | |
2311 | } | |
2312 | EXPORT_SYMBOL(dentry_update_name_case); | |
2313 | ||
2314 | static void switch_names(struct dentry *dentry, struct dentry *target) | |
2315 | { | |
2316 | if (dname_external(target)) { | |
2317 | if (dname_external(dentry)) { | |
2318 | /* | |
2319 | * Both external: swap the pointers | |
2320 | */ | |
2321 | swap(target->d_name.name, dentry->d_name.name); | |
2322 | } else { | |
2323 | /* | |
2324 | * dentry:internal, target:external. Steal target's | |
2325 | * storage and make target internal. | |
2326 | */ | |
2327 | memcpy(target->d_iname, dentry->d_name.name, | |
2328 | dentry->d_name.len + 1); | |
2329 | dentry->d_name.name = target->d_name.name; | |
2330 | target->d_name.name = target->d_iname; | |
2331 | } | |
2332 | } else { | |
2333 | if (dname_external(dentry)) { | |
2334 | /* | |
2335 | * dentry:external, target:internal. Give dentry's | |
2336 | * storage to target and make dentry internal | |
2337 | */ | |
2338 | memcpy(dentry->d_iname, target->d_name.name, | |
2339 | target->d_name.len + 1); | |
2340 | target->d_name.name = dentry->d_name.name; | |
2341 | dentry->d_name.name = dentry->d_iname; | |
2342 | } else { | |
2343 | /* | |
2344 | * Both are internal. Just copy target to dentry | |
2345 | */ | |
2346 | memcpy(dentry->d_iname, target->d_name.name, | |
2347 | target->d_name.len + 1); | |
2348 | dentry->d_name.len = target->d_name.len; | |
2349 | return; | |
2350 | } | |
2351 | } | |
2352 | swap(dentry->d_name.len, target->d_name.len); | |
2353 | } | |
2354 | ||
2355 | static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target) | |
2356 | { | |
2357 | /* | |
2358 | * XXXX: do we really need to take target->d_lock? | |
2359 | */ | |
2360 | if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent) | |
2361 | spin_lock(&target->d_parent->d_lock); | |
2362 | else { | |
2363 | if (d_ancestor(dentry->d_parent, target->d_parent)) { | |
2364 | spin_lock(&dentry->d_parent->d_lock); | |
2365 | spin_lock_nested(&target->d_parent->d_lock, | |
2366 | DENTRY_D_LOCK_NESTED); | |
2367 | } else { | |
2368 | spin_lock(&target->d_parent->d_lock); | |
2369 | spin_lock_nested(&dentry->d_parent->d_lock, | |
2370 | DENTRY_D_LOCK_NESTED); | |
2371 | } | |
2372 | } | |
2373 | if (target < dentry) { | |
2374 | spin_lock_nested(&target->d_lock, 2); | |
2375 | spin_lock_nested(&dentry->d_lock, 3); | |
2376 | } else { | |
2377 | spin_lock_nested(&dentry->d_lock, 2); | |
2378 | spin_lock_nested(&target->d_lock, 3); | |
2379 | } | |
2380 | } | |
2381 | ||
2382 | static void dentry_unlock_parents_for_move(struct dentry *dentry, | |
2383 | struct dentry *target) | |
2384 | { | |
2385 | if (target->d_parent != dentry->d_parent) | |
2386 | spin_unlock(&dentry->d_parent->d_lock); | |
2387 | if (target->d_parent != target) | |
2388 | spin_unlock(&target->d_parent->d_lock); | |
2389 | } | |
2390 | ||
2391 | /* | |
2392 | * When switching names, the actual string doesn't strictly have to | |
2393 | * be preserved in the target - because we're dropping the target | |
2394 | * anyway. As such, we can just do a simple memcpy() to copy over | |
2395 | * the new name before we switch. | |
2396 | * | |
2397 | * Note that we have to be a lot more careful about getting the hash | |
2398 | * switched - we have to switch the hash value properly even if it | |
2399 | * then no longer matches the actual (corrupted) string of the target. | |
2400 | * The hash value has to match the hash queue that the dentry is on.. | |
2401 | */ | |
2402 | /* | |
2403 | * __d_move - move a dentry | |
2404 | * @dentry: entry to move | |
2405 | * @target: new dentry | |
2406 | * | |
2407 | * Update the dcache to reflect the move of a file name. Negative | |
2408 | * dcache entries should not be moved in this way. Caller must hold | |
2409 | * rename_lock, the i_mutex of the source and target directories, | |
2410 | * and the sb->s_vfs_rename_mutex if they differ. See lock_rename(). | |
2411 | */ | |
2412 | static void __d_move(struct dentry * dentry, struct dentry * target) | |
2413 | { | |
2414 | if (!dentry->d_inode) | |
2415 | printk(KERN_WARNING "VFS: moving negative dcache entry\n"); | |
2416 | ||
2417 | BUG_ON(d_ancestor(dentry, target)); | |
2418 | BUG_ON(d_ancestor(target, dentry)); | |
2419 | ||
2420 | dentry_lock_for_move(dentry, target); | |
2421 | ||
2422 | write_seqcount_begin(&dentry->d_seq); | |
2423 | write_seqcount_begin(&target->d_seq); | |
2424 | ||
2425 | /* __d_drop does write_seqcount_barrier, but they're OK to nest. */ | |
2426 | ||
2427 | /* | |
2428 | * Move the dentry to the target hash queue. Don't bother checking | |
2429 | * for the same hash queue because of how unlikely it is. | |
2430 | */ | |
2431 | __d_drop(dentry); | |
2432 | __d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash)); | |
2433 | ||
2434 | /* Unhash the target: dput() will then get rid of it */ | |
2435 | __d_drop(target); | |
2436 | ||
2437 | list_del(&dentry->d_u.d_child); | |
2438 | list_del(&target->d_u.d_child); | |
2439 | ||
2440 | /* Switch the names.. */ | |
2441 | switch_names(dentry, target); | |
2442 | swap(dentry->d_name.hash, target->d_name.hash); | |
2443 | ||
2444 | /* ... and switch the parents */ | |
2445 | if (IS_ROOT(dentry)) { | |
2446 | dentry->d_parent = target->d_parent; | |
2447 | target->d_parent = target; | |
2448 | INIT_LIST_HEAD(&target->d_u.d_child); | |
2449 | } else { | |
2450 | swap(dentry->d_parent, target->d_parent); | |
2451 | ||
2452 | /* And add them back to the (new) parent lists */ | |
2453 | list_add(&target->d_u.d_child, &target->d_parent->d_subdirs); | |
2454 | } | |
2455 | ||
2456 | list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs); | |
2457 | ||
2458 | write_seqcount_end(&target->d_seq); | |
2459 | write_seqcount_end(&dentry->d_seq); | |
2460 | ||
2461 | dentry_unlock_parents_for_move(dentry, target); | |
2462 | spin_unlock(&target->d_lock); | |
2463 | fsnotify_d_move(dentry); | |
2464 | spin_unlock(&dentry->d_lock); | |
2465 | } | |
2466 | ||
2467 | /* | |
2468 | * d_move - move a dentry | |
2469 | * @dentry: entry to move | |
2470 | * @target: new dentry | |
2471 | * | |
2472 | * Update the dcache to reflect the move of a file name. Negative | |
2473 | * dcache entries should not be moved in this way. See the locking | |
2474 | * requirements for __d_move. | |
2475 | */ | |
2476 | void d_move(struct dentry *dentry, struct dentry *target) | |
2477 | { | |
2478 | write_seqlock(&rename_lock); | |
2479 | __d_move(dentry, target); | |
2480 | write_sequnlock(&rename_lock); | |
2481 | } | |
2482 | EXPORT_SYMBOL(d_move); | |
2483 | ||
2484 | /** | |
2485 | * d_ancestor - search for an ancestor | |
2486 | * @p1: ancestor dentry | |
2487 | * @p2: child dentry | |
2488 | * | |
2489 | * Returns the ancestor dentry of p2 which is a child of p1, if p1 is | |
2490 | * an ancestor of p2, else NULL. | |
2491 | */ | |
2492 | struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2) | |
2493 | { | |
2494 | struct dentry *p; | |
2495 | ||
2496 | for (p = p2; !IS_ROOT(p); p = p->d_parent) { | |
2497 | if (p->d_parent == p1) | |
2498 | return p; | |
2499 | } | |
2500 | return NULL; | |
2501 | } | |
2502 | ||
2503 | /* | |
2504 | * This helper attempts to cope with remotely renamed directories | |
2505 | * | |
2506 | * It assumes that the caller is already holding | |
2507 | * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock | |
2508 | * | |
2509 | * Note: If ever the locking in lock_rename() changes, then please | |
2510 | * remember to update this too... | |
2511 | */ | |
2512 | static struct dentry *__d_unalias(struct inode *inode, | |
2513 | struct dentry *dentry, struct dentry *alias) | |
2514 | { | |
2515 | struct mutex *m1 = NULL, *m2 = NULL; | |
2516 | struct dentry *ret = ERR_PTR(-EBUSY); | |
2517 | ||
2518 | /* If alias and dentry share a parent, then no extra locks required */ | |
2519 | if (alias->d_parent == dentry->d_parent) | |
2520 | goto out_unalias; | |
2521 | ||
2522 | /* See lock_rename() */ | |
2523 | if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex)) | |
2524 | goto out_err; | |
2525 | m1 = &dentry->d_sb->s_vfs_rename_mutex; | |
2526 | if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex)) | |
2527 | goto out_err; | |
2528 | m2 = &alias->d_parent->d_inode->i_mutex; | |
2529 | out_unalias: | |
2530 | if (likely(!d_mountpoint(alias))) { | |
2531 | __d_move(alias, dentry); | |
2532 | ret = alias; | |
2533 | } | |
2534 | out_err: | |
2535 | spin_unlock(&inode->i_lock); | |
2536 | if (m2) | |
2537 | mutex_unlock(m2); | |
2538 | if (m1) | |
2539 | mutex_unlock(m1); | |
2540 | return ret; | |
2541 | } | |
2542 | ||
2543 | /* | |
2544 | * Prepare an anonymous dentry for life in the superblock's dentry tree as a | |
2545 | * named dentry in place of the dentry to be replaced. | |
2546 | * returns with anon->d_lock held! | |
2547 | */ | |
2548 | static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon) | |
2549 | { | |
2550 | struct dentry *dparent; | |
2551 | ||
2552 | dentry_lock_for_move(anon, dentry); | |
2553 | ||
2554 | write_seqcount_begin(&dentry->d_seq); | |
2555 | write_seqcount_begin(&anon->d_seq); | |
2556 | ||
2557 | dparent = dentry->d_parent; | |
2558 | ||
2559 | switch_names(dentry, anon); | |
2560 | swap(dentry->d_name.hash, anon->d_name.hash); | |
2561 | ||
2562 | dentry->d_parent = dentry; | |
2563 | list_del_init(&dentry->d_u.d_child); | |
2564 | anon->d_parent = dparent; | |
2565 | list_move(&anon->d_u.d_child, &dparent->d_subdirs); | |
2566 | ||
2567 | write_seqcount_end(&dentry->d_seq); | |
2568 | write_seqcount_end(&anon->d_seq); | |
2569 | ||
2570 | dentry_unlock_parents_for_move(anon, dentry); | |
2571 | spin_unlock(&dentry->d_lock); | |
2572 | ||
2573 | /* anon->d_lock still locked, returns locked */ | |
2574 | anon->d_flags &= ~DCACHE_DISCONNECTED; | |
2575 | } | |
2576 | ||
2577 | /** | |
2578 | * d_materialise_unique - introduce an inode into the tree | |
2579 | * @dentry: candidate dentry | |
2580 | * @inode: inode to bind to the dentry, to which aliases may be attached | |
2581 | * | |
2582 | * Introduces an dentry into the tree, substituting an extant disconnected | |
2583 | * root directory alias in its place if there is one. Caller must hold the | |
2584 | * i_mutex of the parent directory. | |
2585 | */ | |
2586 | struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode) | |
2587 | { | |
2588 | struct dentry *actual; | |
2589 | ||
2590 | BUG_ON(!d_unhashed(dentry)); | |
2591 | ||
2592 | if (!inode) { | |
2593 | actual = dentry; | |
2594 | __d_instantiate(dentry, NULL); | |
2595 | d_rehash(actual); | |
2596 | goto out_nolock; | |
2597 | } | |
2598 | ||
2599 | spin_lock(&inode->i_lock); | |
2600 | ||
2601 | if (S_ISDIR(inode->i_mode)) { | |
2602 | struct dentry *alias; | |
2603 | ||
2604 | /* Does an aliased dentry already exist? */ | |
2605 | alias = __d_find_alias(inode, 0); | |
2606 | if (alias) { | |
2607 | actual = alias; | |
2608 | write_seqlock(&rename_lock); | |
2609 | ||
2610 | if (d_ancestor(alias, dentry)) { | |
2611 | /* Check for loops */ | |
2612 | actual = ERR_PTR(-ELOOP); | |
2613 | spin_unlock(&inode->i_lock); | |
2614 | } else if (IS_ROOT(alias)) { | |
2615 | /* Is this an anonymous mountpoint that we | |
2616 | * could splice into our tree? */ | |
2617 | __d_materialise_dentry(dentry, alias); | |
2618 | write_sequnlock(&rename_lock); | |
2619 | __d_drop(alias); | |
2620 | goto found; | |
2621 | } else { | |
2622 | /* Nope, but we must(!) avoid directory | |
2623 | * aliasing. This drops inode->i_lock */ | |
2624 | actual = __d_unalias(inode, dentry, alias); | |
2625 | } | |
2626 | write_sequnlock(&rename_lock); | |
2627 | if (IS_ERR(actual)) { | |
2628 | if (PTR_ERR(actual) == -ELOOP) | |
2629 | pr_warn_ratelimited( | |
2630 | "VFS: Lookup of '%s' in %s %s" | |
2631 | " would have caused loop\n", | |
2632 | dentry->d_name.name, | |
2633 | inode->i_sb->s_type->name, | |
2634 | inode->i_sb->s_id); | |
2635 | dput(alias); | |
2636 | } | |
2637 | goto out_nolock; | |
2638 | } | |
2639 | } | |
2640 | ||
2641 | /* Add a unique reference */ | |
2642 | actual = __d_instantiate_unique(dentry, inode); | |
2643 | if (!actual) | |
2644 | actual = dentry; | |
2645 | else | |
2646 | BUG_ON(!d_unhashed(actual)); | |
2647 | ||
2648 | spin_lock(&actual->d_lock); | |
2649 | found: | |
2650 | _d_rehash(actual); | |
2651 | spin_unlock(&actual->d_lock); | |
2652 | spin_unlock(&inode->i_lock); | |
2653 | out_nolock: | |
2654 | if (actual == dentry) { | |
2655 | security_d_instantiate(dentry, inode); | |
2656 | return NULL; | |
2657 | } | |
2658 | ||
2659 | iput(inode); | |
2660 | return actual; | |
2661 | } | |
2662 | EXPORT_SYMBOL_GPL(d_materialise_unique); | |
2663 | ||
2664 | static int prepend(char **buffer, int *buflen, const char *str, int namelen) | |
2665 | { | |
2666 | *buflen -= namelen; | |
2667 | if (*buflen < 0) | |
2668 | return -ENAMETOOLONG; | |
2669 | *buffer -= namelen; | |
2670 | memcpy(*buffer, str, namelen); | |
2671 | return 0; | |
2672 | } | |
2673 | ||
2674 | /** | |
2675 | * prepend_name - prepend a pathname in front of current buffer pointer | |
2676 | * @buffer: buffer pointer | |
2677 | * @buflen: allocated length of the buffer | |
2678 | * @name: name string and length qstr structure | |
2679 | * | |
2680 | * With RCU path tracing, it may race with d_move(). Use ACCESS_ONCE() to | |
2681 | * make sure that either the old or the new name pointer and length are | |
2682 | * fetched. However, there may be mismatch between length and pointer. | |
2683 | * The length cannot be trusted, we need to copy it byte-by-byte until | |
2684 | * the length is reached or a null byte is found. It also prepends "/" at | |
2685 | * the beginning of the name. The sequence number check at the caller will | |
2686 | * retry it again when a d_move() does happen. So any garbage in the buffer | |
2687 | * due to mismatched pointer and length will be discarded. | |
2688 | */ | |
2689 | static int prepend_name(char **buffer, int *buflen, struct qstr *name) | |
2690 | { | |
2691 | const char *dname = ACCESS_ONCE(name->name); | |
2692 | u32 dlen = ACCESS_ONCE(name->len); | |
2693 | char *p; | |
2694 | ||
2695 | if (*buflen < dlen + 1) | |
2696 | return -ENAMETOOLONG; | |
2697 | *buflen -= dlen + 1; | |
2698 | p = *buffer -= dlen + 1; | |
2699 | *p++ = '/'; | |
2700 | while (dlen--) { | |
2701 | char c = *dname++; | |
2702 | if (!c) | |
2703 | break; | |
2704 | *p++ = c; | |
2705 | } | |
2706 | return 0; | |
2707 | } | |
2708 | ||
2709 | /** | |
2710 | * prepend_path - Prepend path string to a buffer | |
2711 | * @path: the dentry/vfsmount to report | |
2712 | * @root: root vfsmnt/dentry | |
2713 | * @buffer: pointer to the end of the buffer | |
2714 | * @buflen: pointer to buffer length | |
2715 | * | |
2716 | * The function will first try to write out the pathname without taking any | |
2717 | * lock other than the RCU read lock to make sure that dentries won't go away. | |
2718 | * It only checks the sequence number of the global rename_lock as any change | |
2719 | * in the dentry's d_seq will be preceded by changes in the rename_lock | |
2720 | * sequence number. If the sequence number had been changed, it will restart | |
2721 | * the whole pathname back-tracing sequence again by taking the rename_lock. | |
2722 | * In this case, there is no need to take the RCU read lock as the recursive | |
2723 | * parent pointer references will keep the dentry chain alive as long as no | |
2724 | * rename operation is performed. | |
2725 | */ | |
2726 | static int prepend_path(const struct path *path, | |
2727 | const struct path *root, | |
2728 | char **buffer, int *buflen) | |
2729 | { | |
2730 | struct dentry *dentry = path->dentry; | |
2731 | struct vfsmount *vfsmnt = path->mnt; | |
2732 | struct mount *mnt = real_mount(vfsmnt); | |
2733 | int error = 0; | |
2734 | unsigned seq = 0; | |
2735 | char *bptr; | |
2736 | int blen; | |
2737 | ||
2738 | rcu_read_lock(); | |
2739 | restart: | |
2740 | bptr = *buffer; | |
2741 | blen = *buflen; | |
2742 | read_seqbegin_or_lock(&rename_lock, &seq); | |
2743 | while (dentry != root->dentry || vfsmnt != root->mnt) { | |
2744 | struct dentry * parent; | |
2745 | ||
2746 | if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) { | |
2747 | /* Global root? */ | |
2748 | if (mnt_has_parent(mnt)) { | |
2749 | dentry = mnt->mnt_mountpoint; | |
2750 | mnt = mnt->mnt_parent; | |
2751 | vfsmnt = &mnt->mnt; | |
2752 | continue; | |
2753 | } | |
2754 | /* | |
2755 | * Filesystems needing to implement special "root names" | |
2756 | * should do so with ->d_dname() | |
2757 | */ | |
2758 | if (IS_ROOT(dentry) && | |
2759 | (dentry->d_name.len != 1 || | |
2760 | dentry->d_name.name[0] != '/')) { | |
2761 | WARN(1, "Root dentry has weird name <%.*s>\n", | |
2762 | (int) dentry->d_name.len, | |
2763 | dentry->d_name.name); | |
2764 | } | |
2765 | if (!error) | |
2766 | error = is_mounted(vfsmnt) ? 1 : 2; | |
2767 | break; | |
2768 | } | |
2769 | parent = dentry->d_parent; | |
2770 | prefetch(parent); | |
2771 | error = prepend_name(&bptr, &blen, &dentry->d_name); | |
2772 | if (error) | |
2773 | break; | |
2774 | ||
2775 | dentry = parent; | |
2776 | } | |
2777 | if (!(seq & 1)) | |
2778 | rcu_read_unlock(); | |
2779 | if (need_seqretry(&rename_lock, seq)) { | |
2780 | seq = 1; | |
2781 | goto restart; | |
2782 | } | |
2783 | done_seqretry(&rename_lock, seq); | |
2784 | ||
2785 | if (error >= 0 && bptr == *buffer) { | |
2786 | if (--blen < 0) | |
2787 | error = -ENAMETOOLONG; | |
2788 | else | |
2789 | *--bptr = '/'; | |
2790 | } | |
2791 | *buffer = bptr; | |
2792 | *buflen = blen; | |
2793 | return error; | |
2794 | } | |
2795 | ||
2796 | /** | |
2797 | * __d_path - return the path of a dentry | |
2798 | * @path: the dentry/vfsmount to report | |
2799 | * @root: root vfsmnt/dentry | |
2800 | * @buf: buffer to return value in | |
2801 | * @buflen: buffer length | |
2802 | * | |
2803 | * Convert a dentry into an ASCII path name. | |
2804 | * | |
2805 | * Returns a pointer into the buffer or an error code if the | |
2806 | * path was too long. | |
2807 | * | |
2808 | * "buflen" should be positive. | |
2809 | * | |
2810 | * If the path is not reachable from the supplied root, return %NULL. | |
2811 | */ | |
2812 | char *__d_path(const struct path *path, | |
2813 | const struct path *root, | |
2814 | char *buf, int buflen) | |
2815 | { | |
2816 | char *res = buf + buflen; | |
2817 | int error; | |
2818 | ||
2819 | prepend(&res, &buflen, "\0", 1); | |
2820 | br_read_lock(&vfsmount_lock); | |
2821 | error = prepend_path(path, root, &res, &buflen); | |
2822 | br_read_unlock(&vfsmount_lock); | |
2823 | ||
2824 | if (error < 0) | |
2825 | return ERR_PTR(error); | |
2826 | if (error > 0) | |
2827 | return NULL; | |
2828 | return res; | |
2829 | } | |
2830 | ||
2831 | char *d_absolute_path(const struct path *path, | |
2832 | char *buf, int buflen) | |
2833 | { | |
2834 | struct path root = {}; | |
2835 | char *res = buf + buflen; | |
2836 | int error; | |
2837 | ||
2838 | prepend(&res, &buflen, "\0", 1); | |
2839 | br_read_lock(&vfsmount_lock); | |
2840 | error = prepend_path(path, &root, &res, &buflen); | |
2841 | br_read_unlock(&vfsmount_lock); | |
2842 | ||
2843 | if (error > 1) | |
2844 | error = -EINVAL; | |
2845 | if (error < 0) | |
2846 | return ERR_PTR(error); | |
2847 | return res; | |
2848 | } | |
2849 | ||
2850 | /* | |
2851 | * same as __d_path but appends "(deleted)" for unlinked files. | |
2852 | */ | |
2853 | static int path_with_deleted(const struct path *path, | |
2854 | const struct path *root, | |
2855 | char **buf, int *buflen) | |
2856 | { | |
2857 | prepend(buf, buflen, "\0", 1); | |
2858 | if (d_unlinked(path->dentry)) { | |
2859 | int error = prepend(buf, buflen, " (deleted)", 10); | |
2860 | if (error) | |
2861 | return error; | |
2862 | } | |
2863 | ||
2864 | return prepend_path(path, root, buf, buflen); | |
2865 | } | |
2866 | ||
2867 | static int prepend_unreachable(char **buffer, int *buflen) | |
2868 | { | |
2869 | return prepend(buffer, buflen, "(unreachable)", 13); | |
2870 | } | |
2871 | ||
2872 | /** | |
2873 | * d_path - return the path of a dentry | |
2874 | * @path: path to report | |
2875 | * @buf: buffer to return value in | |
2876 | * @buflen: buffer length | |
2877 | * | |
2878 | * Convert a dentry into an ASCII path name. If the entry has been deleted | |
2879 | * the string " (deleted)" is appended. Note that this is ambiguous. | |
2880 | * | |
2881 | * Returns a pointer into the buffer or an error code if the path was | |
2882 | * too long. Note: Callers should use the returned pointer, not the passed | |
2883 | * in buffer, to use the name! The implementation often starts at an offset | |
2884 | * into the buffer, and may leave 0 bytes at the start. | |
2885 | * | |
2886 | * "buflen" should be positive. | |
2887 | */ | |
2888 | char *d_path(const struct path *path, char *buf, int buflen) | |
2889 | { | |
2890 | char *res = buf + buflen; | |
2891 | struct path root; | |
2892 | int error; | |
2893 | ||
2894 | /* | |
2895 | * We have various synthetic filesystems that never get mounted. On | |
2896 | * these filesystems dentries are never used for lookup purposes, and | |
2897 | * thus don't need to be hashed. They also don't need a name until a | |
2898 | * user wants to identify the object in /proc/pid/fd/. The little hack | |
2899 | * below allows us to generate a name for these objects on demand: | |
2900 | */ | |
2901 | if (path->dentry->d_op && path->dentry->d_op->d_dname) | |
2902 | return path->dentry->d_op->d_dname(path->dentry, buf, buflen); | |
2903 | ||
2904 | get_fs_root(current->fs, &root); | |
2905 | br_read_lock(&vfsmount_lock); | |
2906 | error = path_with_deleted(path, &root, &res, &buflen); | |
2907 | br_read_unlock(&vfsmount_lock); | |
2908 | if (error < 0) | |
2909 | res = ERR_PTR(error); | |
2910 | path_put(&root); | |
2911 | return res; | |
2912 | } | |
2913 | EXPORT_SYMBOL(d_path); | |
2914 | ||
2915 | /* | |
2916 | * Helper function for dentry_operations.d_dname() members | |
2917 | */ | |
2918 | char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen, | |
2919 | const char *fmt, ...) | |
2920 | { | |
2921 | va_list args; | |
2922 | char temp[64]; | |
2923 | int sz; | |
2924 | ||
2925 | va_start(args, fmt); | |
2926 | sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1; | |
2927 | va_end(args); | |
2928 | ||
2929 | if (sz > sizeof(temp) || sz > buflen) | |
2930 | return ERR_PTR(-ENAMETOOLONG); | |
2931 | ||
2932 | buffer += buflen - sz; | |
2933 | return memcpy(buffer, temp, sz); | |
2934 | } | |
2935 | ||
2936 | char *simple_dname(struct dentry *dentry, char *buffer, int buflen) | |
2937 | { | |
2938 | char *end = buffer + buflen; | |
2939 | /* these dentries are never renamed, so d_lock is not needed */ | |
2940 | if (prepend(&end, &buflen, " (deleted)", 11) || | |
2941 | prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len) || | |
2942 | prepend(&end, &buflen, "/", 1)) | |
2943 | end = ERR_PTR(-ENAMETOOLONG); | |
2944 | return end; | |
2945 | } | |
2946 | ||
2947 | /* | |
2948 | * Write full pathname from the root of the filesystem into the buffer. | |
2949 | */ | |
2950 | static char *__dentry_path(struct dentry *dentry, char *buf, int buflen) | |
2951 | { | |
2952 | char *end, *retval; | |
2953 | int len, seq = 0; | |
2954 | int error = 0; | |
2955 | ||
2956 | rcu_read_lock(); | |
2957 | restart: | |
2958 | end = buf + buflen; | |
2959 | len = buflen; | |
2960 | prepend(&end, &len, "\0", 1); | |
2961 | if (buflen < 1) | |
2962 | goto Elong; | |
2963 | /* Get '/' right */ | |
2964 | retval = end-1; | |
2965 | *retval = '/'; | |
2966 | read_seqbegin_or_lock(&rename_lock, &seq); | |
2967 | while (!IS_ROOT(dentry)) { | |
2968 | struct dentry *parent = dentry->d_parent; | |
2969 | int error; | |
2970 | ||
2971 | prefetch(parent); | |
2972 | error = prepend_name(&end, &len, &dentry->d_name); | |
2973 | if (error) | |
2974 | break; | |
2975 | ||
2976 | retval = end; | |
2977 | dentry = parent; | |
2978 | } | |
2979 | if (!(seq & 1)) | |
2980 | rcu_read_unlock(); | |
2981 | if (need_seqretry(&rename_lock, seq)) { | |
2982 | seq = 1; | |
2983 | goto restart; | |
2984 | } | |
2985 | done_seqretry(&rename_lock, seq); | |
2986 | if (error) | |
2987 | goto Elong; | |
2988 | return retval; | |
2989 | Elong: | |
2990 | return ERR_PTR(-ENAMETOOLONG); | |
2991 | } | |
2992 | ||
2993 | char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen) | |
2994 | { | |
2995 | return __dentry_path(dentry, buf, buflen); | |
2996 | } | |
2997 | EXPORT_SYMBOL(dentry_path_raw); | |
2998 | ||
2999 | char *dentry_path(struct dentry *dentry, char *buf, int buflen) | |
3000 | { | |
3001 | char *p = NULL; | |
3002 | char *retval; | |
3003 | ||
3004 | if (d_unlinked(dentry)) { | |
3005 | p = buf + buflen; | |
3006 | if (prepend(&p, &buflen, "//deleted", 10) != 0) | |
3007 | goto Elong; | |
3008 | buflen++; | |
3009 | } | |
3010 | retval = __dentry_path(dentry, buf, buflen); | |
3011 | if (!IS_ERR(retval) && p) | |
3012 | *p = '/'; /* restore '/' overriden with '\0' */ | |
3013 | return retval; | |
3014 | Elong: | |
3015 | return ERR_PTR(-ENAMETOOLONG); | |
3016 | } | |
3017 | ||
3018 | static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root, | |
3019 | struct path *pwd) | |
3020 | { | |
3021 | unsigned seq; | |
3022 | ||
3023 | do { | |
3024 | seq = read_seqcount_begin(&fs->seq); | |
3025 | *root = fs->root; | |
3026 | *pwd = fs->pwd; | |
3027 | } while (read_seqcount_retry(&fs->seq, seq)); | |
3028 | } | |
3029 | ||
3030 | /* | |
3031 | * NOTE! The user-level library version returns a | |
3032 | * character pointer. The kernel system call just | |
3033 | * returns the length of the buffer filled (which | |
3034 | * includes the ending '\0' character), or a negative | |
3035 | * error value. So libc would do something like | |
3036 | * | |
3037 | * char *getcwd(char * buf, size_t size) | |
3038 | * { | |
3039 | * int retval; | |
3040 | * | |
3041 | * retval = sys_getcwd(buf, size); | |
3042 | * if (retval >= 0) | |
3043 | * return buf; | |
3044 | * errno = -retval; | |
3045 | * return NULL; | |
3046 | * } | |
3047 | */ | |
3048 | SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) | |
3049 | { | |
3050 | int error; | |
3051 | struct path pwd, root; | |
3052 | char *page = (char *) __get_free_page(GFP_USER); | |
3053 | ||
3054 | if (!page) | |
3055 | return -ENOMEM; | |
3056 | ||
3057 | rcu_read_lock(); | |
3058 | get_fs_root_and_pwd_rcu(current->fs, &root, &pwd); | |
3059 | ||
3060 | error = -ENOENT; | |
3061 | br_read_lock(&vfsmount_lock); | |
3062 | if (!d_unlinked(pwd.dentry)) { | |
3063 | unsigned long len; | |
3064 | char *cwd = page + PAGE_SIZE; | |
3065 | int buflen = PAGE_SIZE; | |
3066 | ||
3067 | prepend(&cwd, &buflen, "\0", 1); | |
3068 | error = prepend_path(&pwd, &root, &cwd, &buflen); | |
3069 | br_read_unlock(&vfsmount_lock); | |
3070 | ||
3071 | if (error < 0) | |
3072 | goto out; | |
3073 | ||
3074 | /* Unreachable from current root */ | |
3075 | if (error > 0) { | |
3076 | error = prepend_unreachable(&cwd, &buflen); | |
3077 | if (error) | |
3078 | goto out; | |
3079 | } | |
3080 | ||
3081 | error = -ERANGE; | |
3082 | len = PAGE_SIZE + page - cwd; | |
3083 | if (len <= size) { | |
3084 | error = len; | |
3085 | if (copy_to_user(buf, cwd, len)) | |
3086 | error = -EFAULT; | |
3087 | } | |
3088 | } else { | |
3089 | br_read_unlock(&vfsmount_lock); | |
3090 | } | |
3091 | ||
3092 | out: | |
3093 | rcu_read_unlock(); | |
3094 | free_page((unsigned long) page); | |
3095 | return error; | |
3096 | } | |
3097 | ||
3098 | /* | |
3099 | * Test whether new_dentry is a subdirectory of old_dentry. | |
3100 | * | |
3101 | * Trivially implemented using the dcache structure | |
3102 | */ | |
3103 | ||
3104 | /** | |
3105 | * is_subdir - is new dentry a subdirectory of old_dentry | |
3106 | * @new_dentry: new dentry | |
3107 | * @old_dentry: old dentry | |
3108 | * | |
3109 | * Returns 1 if new_dentry is a subdirectory of the parent (at any depth). | |
3110 | * Returns 0 otherwise. | |
3111 | * Caller must ensure that "new_dentry" is pinned before calling is_subdir() | |
3112 | */ | |
3113 | ||
3114 | int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry) | |
3115 | { | |
3116 | int result; | |
3117 | unsigned seq; | |
3118 | ||
3119 | if (new_dentry == old_dentry) | |
3120 | return 1; | |
3121 | ||
3122 | do { | |
3123 | /* for restarting inner loop in case of seq retry */ | |
3124 | seq = read_seqbegin(&rename_lock); | |
3125 | /* | |
3126 | * Need rcu_readlock to protect against the d_parent trashing | |
3127 | * due to d_move | |
3128 | */ | |
3129 | rcu_read_lock(); | |
3130 | if (d_ancestor(old_dentry, new_dentry)) | |
3131 | result = 1; | |
3132 | else | |
3133 | result = 0; | |
3134 | rcu_read_unlock(); | |
3135 | } while (read_seqretry(&rename_lock, seq)); | |
3136 | ||
3137 | return result; | |
3138 | } | |
3139 | ||
3140 | static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry) | |
3141 | { | |
3142 | struct dentry *root = data; | |
3143 | if (dentry != root) { | |
3144 | if (d_unhashed(dentry) || !dentry->d_inode) | |
3145 | return D_WALK_SKIP; | |
3146 | ||
3147 | if (!(dentry->d_flags & DCACHE_GENOCIDE)) { | |
3148 | dentry->d_flags |= DCACHE_GENOCIDE; | |
3149 | dentry->d_lockref.count--; | |
3150 | } | |
3151 | } | |
3152 | return D_WALK_CONTINUE; | |
3153 | } | |
3154 | ||
3155 | void d_genocide(struct dentry *parent) | |
3156 | { | |
3157 | d_walk(parent, parent, d_genocide_kill, NULL); | |
3158 | } | |
3159 | ||
3160 | void d_tmpfile(struct dentry *dentry, struct inode *inode) | |
3161 | { | |
3162 | inode_dec_link_count(inode); | |
3163 | BUG_ON(dentry->d_name.name != dentry->d_iname || | |
3164 | !hlist_unhashed(&dentry->d_alias) || | |
3165 | !d_unlinked(dentry)); | |
3166 | spin_lock(&dentry->d_parent->d_lock); | |
3167 | spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); | |
3168 | dentry->d_name.len = sprintf(dentry->d_iname, "#%llu", | |
3169 | (unsigned long long)inode->i_ino); | |
3170 | spin_unlock(&dentry->d_lock); | |
3171 | spin_unlock(&dentry->d_parent->d_lock); | |
3172 | d_instantiate(dentry, inode); | |
3173 | } | |
3174 | EXPORT_SYMBOL(d_tmpfile); | |
3175 | ||
3176 | static __initdata unsigned long dhash_entries; | |
3177 | static int __init set_dhash_entries(char *str) | |
3178 | { | |
3179 | if (!str) | |
3180 | return 0; | |
3181 | dhash_entries = simple_strtoul(str, &str, 0); | |
3182 | return 1; | |
3183 | } | |
3184 | __setup("dhash_entries=", set_dhash_entries); | |
3185 | ||
3186 | static void __init dcache_init_early(void) | |
3187 | { | |
3188 | unsigned int loop; | |
3189 | ||
3190 | /* If hashes are distributed across NUMA nodes, defer | |
3191 | * hash allocation until vmalloc space is available. | |
3192 | */ | |
3193 | if (hashdist) | |
3194 | return; | |
3195 | ||
3196 | dentry_hashtable = | |
3197 | alloc_large_system_hash("Dentry cache", | |
3198 | sizeof(struct hlist_bl_head), | |
3199 | dhash_entries, | |
3200 | 13, | |
3201 | HASH_EARLY, | |
3202 | &d_hash_shift, | |
3203 | &d_hash_mask, | |
3204 | 0, | |
3205 | 0); | |
3206 | ||
3207 | for (loop = 0; loop < (1U << d_hash_shift); loop++) | |
3208 | INIT_HLIST_BL_HEAD(dentry_hashtable + loop); | |
3209 | } | |
3210 | ||
3211 | static void __init dcache_init(void) | |
3212 | { | |
3213 | unsigned int loop; | |
3214 | ||
3215 | /* | |
3216 | * A constructor could be added for stable state like the lists, | |
3217 | * but it is probably not worth it because of the cache nature | |
3218 | * of the dcache. | |
3219 | */ | |
3220 | dentry_cache = KMEM_CACHE(dentry, | |
3221 | SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD); | |
3222 | ||
3223 | /* Hash may have been set up in dcache_init_early */ | |
3224 | if (!hashdist) | |
3225 | return; | |
3226 | ||
3227 | dentry_hashtable = | |
3228 | alloc_large_system_hash("Dentry cache", | |
3229 | sizeof(struct hlist_bl_head), | |
3230 | dhash_entries, | |
3231 | 13, | |
3232 | 0, | |
3233 | &d_hash_shift, | |
3234 | &d_hash_mask, | |
3235 | 0, | |
3236 | 0); | |
3237 | ||
3238 | for (loop = 0; loop < (1U << d_hash_shift); loop++) | |
3239 | INIT_HLIST_BL_HEAD(dentry_hashtable + loop); | |
3240 | } | |
3241 | ||
3242 | /* SLAB cache for __getname() consumers */ | |
3243 | struct kmem_cache *names_cachep __read_mostly; | |
3244 | EXPORT_SYMBOL(names_cachep); | |
3245 | ||
3246 | EXPORT_SYMBOL(d_genocide); | |
3247 | ||
3248 | void __init vfs_caches_init_early(void) | |
3249 | { | |
3250 | dcache_init_early(); | |
3251 | inode_init_early(); | |
3252 | } | |
3253 | ||
3254 | void __init vfs_caches_init(unsigned long mempages) | |
3255 | { | |
3256 | unsigned long reserve; | |
3257 | ||
3258 | /* Base hash sizes on available memory, with a reserve equal to | |
3259 | 150% of current kernel size */ | |
3260 | ||
3261 | reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1); | |
3262 | mempages -= reserve; | |
3263 | ||
3264 | names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0, | |
3265 | SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); | |
3266 | ||
3267 | dcache_init(); | |
3268 | inode_init(); | |
3269 | files_init(mempages); | |
3270 | mnt_init(); | |
3271 | bdev_cache_init(); | |
3272 | chrdev_init(); | |
3273 | } |