dcache.c 78.7 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
/*
 * fs/dcache.c
 *
 * Complete reimplementation
 * (C) 1997 Thomas Schoebel-Theuer,
 * with heavy changes by Linus Torvalds
 */

/*
 * Notes on the allocation strategy:
 *
 * The dcache is a master of the icache - whenever a dcache entry
 * exists, the inode will always exist. "iput()" is done either when
 * the dcache entry is deleted or garbage collected.
 */

#include <linux/syscalls.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/fs.h>
21
#include <linux/fsnotify.h>
L
Linus Torvalds 已提交
22 23 24 25
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/cache.h>
26
#include <linux/export.h>
L
Linus Torvalds 已提交
27 28 29 30 31 32 33
#include <linux/mount.h>
#include <linux/file.h>
#include <asm/uaccess.h>
#include <linux/security.h>
#include <linux/seqlock.h>
#include <linux/swap.h>
#include <linux/bootmem.h>
34
#include <linux/fs_struct.h>
35
#include <linux/hardirq.h>
36 37
#include <linux/bit_spinlock.h>
#include <linux/rculist_bl.h>
38
#include <linux/prefetch.h>
39
#include <linux/ratelimit.h>
40
#include "internal.h"
41
#include "mount.h"
L
Linus Torvalds 已提交
42

N
Nick Piggin 已提交
43 44
/*
 * Usage:
45 46
 * dcache->d_inode->i_lock protects:
 *   - i_dentry, d_alias, d_inode of aliases
47 48 49 50
 * dcache_hash_bucket lock protects:
 *   - the dcache hash table
 * s_anon bl list spinlock protects:
 *   - the s_anon list (see __d_drop)
N
Nick Piggin 已提交
51 52 53 54 55 56
 * dcache_lru_lock protects:
 *   - the dcache lru lists and counters
 * d_lock protects:
 *   - d_flags
 *   - d_name
 *   - d_lru
N
Nick Piggin 已提交
57
 *   - d_count
N
Nick Piggin 已提交
58
 *   - d_unhashed()
N
Nick Piggin 已提交
59 60
 *   - d_parent and d_subdirs
 *   - childrens' d_child and d_parent
N
Nick Piggin 已提交
61
 *   - d_alias, d_inode
N
Nick Piggin 已提交
62 63
 *
 * Ordering:
64
 * dentry->d_inode->i_lock
N
Nick Piggin 已提交
65 66
 *   dentry->d_lock
 *     dcache_lru_lock
67 68
 *     dcache_hash_bucket lock
 *     s_anon lock
N
Nick Piggin 已提交
69
 *
N
Nick Piggin 已提交
70 71 72 73 74 75 76
 * If there is an ancestor relationship:
 * dentry->d_parent->...->d_parent->d_lock
 *   ...
 *     dentry->d_parent->d_lock
 *       dentry->d_lock
 *
 * If no ancestor relationship:
N
Nick Piggin 已提交
77 78 79 80
 * if (dentry1 < dentry2)
 *   dentry1->d_lock
 *     dentry2->d_lock
 */
81
int sysctl_vfs_cache_pressure __read_mostly = 100;
L
Linus Torvalds 已提交
82 83
EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);

N
Nick Piggin 已提交
84
static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
A
Al Viro 已提交
85
__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
L
Linus Torvalds 已提交
86

87
EXPORT_SYMBOL(rename_lock);
L
Linus Torvalds 已提交
88

89
static struct kmem_cache *dentry_cache __read_mostly;
L
Linus Torvalds 已提交
90 91 92 93 94 95 96 97 98 99 100 101

/*
 * This is the single most critical data structure when it comes
 * to the dcache: the hashtable for lookups. Somebody should try
 * to make this good - I've just made it work.
 *
 * This hash-function tries to avoid losing too many bits of hash
 * information, yet avoid using a prime hash-size or similar.
 */
#define D_HASHBITS     d_hash_shift
#define D_HASHMASK     d_hash_mask

102 103
static unsigned int d_hash_mask __read_mostly;
static unsigned int d_hash_shift __read_mostly;
104

105
static struct hlist_bl_head *dentry_hashtable __read_mostly;
106

107
static inline struct hlist_bl_head *d_hash(const struct dentry *parent,
108
					unsigned int hash)
109
{
110 111
	hash += (unsigned long) parent / L1_CACHE_BYTES;
	hash = hash + (hash >> D_HASHBITS);
112 113 114
	return dentry_hashtable + (hash & D_HASHMASK);
}

L
Linus Torvalds 已提交
115 116 117 118 119
/* Statistics gathering. */
struct dentry_stat_t dentry_stat = {
	.age_limit = 45,
};

120
static DEFINE_PER_CPU(unsigned int, nr_dentry);
121 122

#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
123 124 125 126 127 128 129 130 131
static int get_nr_dentry(void)
{
	int i;
	int sum = 0;
	for_each_possible_cpu(i)
		sum += per_cpu(nr_dentry, i);
	return sum < 0 ? 0 : sum;
}

132 133 134
int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
		   size_t *lenp, loff_t *ppos)
{
135
	dentry_stat.nr_dentry = get_nr_dentry();
136 137 138 139
	return proc_dointvec(table, write, buffer, lenp, ppos);
}
#endif

140 141 142 143
/*
 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
 * The strings are both count bytes long, and count is non-zero.
 */
144 145 146 147 148 149 150 151 152 153 154 155
#ifdef CONFIG_DCACHE_WORD_ACCESS

#include <asm/word-at-a-time.h>
/*
 * NOTE! 'cs' and 'scount' come from a dentry, so it has a
 * aligned allocation for this particular component. We don't
 * strictly need the load_unaligned_zeropad() safety, but it
 * doesn't hurt either.
 *
 * In contrast, 'ct' and 'tcount' can be from a pathname, and do
 * need the careful unaligned handling.
 */
156
static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
157
{
158 159 160
	unsigned long a,b,mask;

	for (;;) {
161
		a = *(unsigned long *)cs;
162
		b = load_unaligned_zeropad(ct);
163 164 165 166 167 168 169 170 171 172 173 174
		if (tcount < sizeof(unsigned long))
			break;
		if (unlikely(a != b))
			return 1;
		cs += sizeof(unsigned long);
		ct += sizeof(unsigned long);
		tcount -= sizeof(unsigned long);
		if (!tcount)
			return 0;
	}
	mask = ~(~0ul << tcount*8);
	return unlikely(!!((a ^ b) & mask));
175 176
}

177
#else
178

179
static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
180
{
181 182 183 184 185 186 187 188 189 190
	do {
		if (*cs != *ct)
			return 1;
		cs++;
		ct++;
		tcount--;
	} while (tcount);
	return 0;
}

191 192
#endif

193 194
static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
{
195
	const unsigned char *cs;
196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211
	/*
	 * Be careful about RCU walk racing with rename:
	 * use ACCESS_ONCE to fetch the name pointer.
	 *
	 * NOTE! Even if a rename will mean that the length
	 * was not loaded atomically, we don't care. The
	 * RCU walk will check the sequence count eventually,
	 * and catch it. And we won't overrun the buffer,
	 * because we're reading the name pointer atomically,
	 * and a dentry name is guaranteed to be properly
	 * terminated with a NUL byte.
	 *
	 * End result: even if 'len' is wrong, we'll exit
	 * early because the data cannot match (there can
	 * be no NUL in the ct/tcount data)
	 */
212 213 214
	cs = ACCESS_ONCE(dentry->d_name.name);
	smp_read_barrier_depends();
	return dentry_string_cmp(cs, ct, tcount);
215 216
}

C
Christoph Hellwig 已提交
217
static void __d_free(struct rcu_head *head)
L
Linus Torvalds 已提交
218
{
C
Christoph Hellwig 已提交
219 220
	struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);

A
Al Viro 已提交
221
	WARN_ON(!hlist_unhashed(&dentry->d_alias));
L
Linus Torvalds 已提交
222 223 224 225 226 227
	if (dname_external(dentry))
		kfree(dentry->d_name.name);
	kmem_cache_free(dentry_cache, dentry); 
}

/*
N
Nick Piggin 已提交
228
 * no locks, please.
L
Linus Torvalds 已提交
229 230 231
 */
static void d_free(struct dentry *dentry)
{
N
Nick Piggin 已提交
232
	BUG_ON(dentry->d_count);
233
	this_cpu_dec(nr_dentry);
L
Linus Torvalds 已提交
234 235
	if (dentry->d_op && dentry->d_op->d_release)
		dentry->d_op->d_release(dentry);
236

237 238
	/* if dentry was never visible to RCU, immediate free is OK */
	if (!(dentry->d_flags & DCACHE_RCUACCESS))
C
Christoph Hellwig 已提交
239
		__d_free(&dentry->d_u.d_rcu);
240
	else
C
Christoph Hellwig 已提交
241
		call_rcu(&dentry->d_u.d_rcu, __d_free);
L
Linus Torvalds 已提交
242 243
}

N
Nick Piggin 已提交
244 245
/**
 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
246
 * @dentry: the target dentry
N
Nick Piggin 已提交
247 248 249 250 251 252 253 254 255 256 257
 * After this call, in-progress rcu-walk path lookup will fail. This
 * should be called after unhashing, and after changing d_inode (if
 * the dentry has not already been unhashed).
 */
static inline void dentry_rcuwalk_barrier(struct dentry *dentry)
{
	assert_spin_locked(&dentry->d_lock);
	/* Go through a barrier */
	write_seqcount_barrier(&dentry->d_seq);
}

L
Linus Torvalds 已提交
258 259
/*
 * Release the dentry's inode, using the filesystem
N
Nick Piggin 已提交
260 261
 * d_iput() operation if defined. Dentry has no refcount
 * and is unhashed.
L
Linus Torvalds 已提交
262
 */
263
static void dentry_iput(struct dentry * dentry)
264
	__releases(dentry->d_lock)
265
	__releases(dentry->d_inode->i_lock)
L
Linus Torvalds 已提交
266 267 268 269
{
	struct inode *inode = dentry->d_inode;
	if (inode) {
		dentry->d_inode = NULL;
A
Al Viro 已提交
270
		hlist_del_init(&dentry->d_alias);
L
Linus Torvalds 已提交
271
		spin_unlock(&dentry->d_lock);
272
		spin_unlock(&inode->i_lock);
273 274
		if (!inode->i_nlink)
			fsnotify_inoderemove(inode);
L
Linus Torvalds 已提交
275 276 277 278 279 280 281 282 283
		if (dentry->d_op && dentry->d_op->d_iput)
			dentry->d_op->d_iput(dentry, inode);
		else
			iput(inode);
	} else {
		spin_unlock(&dentry->d_lock);
	}
}

N
Nick Piggin 已提交
284 285 286 287 288 289
/*
 * Release the dentry's inode, using the filesystem
 * d_iput() operation if defined. dentry remains in-use.
 */
static void dentry_unlink_inode(struct dentry * dentry)
	__releases(dentry->d_lock)
290
	__releases(dentry->d_inode->i_lock)
N
Nick Piggin 已提交
291 292 293
{
	struct inode *inode = dentry->d_inode;
	dentry->d_inode = NULL;
A
Al Viro 已提交
294
	hlist_del_init(&dentry->d_alias);
N
Nick Piggin 已提交
295 296
	dentry_rcuwalk_barrier(dentry);
	spin_unlock(&dentry->d_lock);
297
	spin_unlock(&inode->i_lock);
N
Nick Piggin 已提交
298 299 300 301 302 303 304 305
	if (!inode->i_nlink)
		fsnotify_inoderemove(inode);
	if (dentry->d_op && dentry->d_op->d_iput)
		dentry->d_op->d_iput(dentry, inode);
	else
		iput(inode);
}

306
/*
S
Sage Weil 已提交
307
 * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
308 309 310
 */
static void dentry_lru_add(struct dentry *dentry)
{
311
	if (list_empty(&dentry->d_lru)) {
N
Nick Piggin 已提交
312
		spin_lock(&dcache_lru_lock);
313 314
		list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
		dentry->d_sb->s_nr_dentry_unused++;
315
		dentry_stat.nr_unused++;
N
Nick Piggin 已提交
316
		spin_unlock(&dcache_lru_lock);
317
	}
318 319
}

N
Nick Piggin 已提交
320 321 322
static void __dentry_lru_del(struct dentry *dentry)
{
	list_del_init(&dentry->d_lru);
323
	dentry->d_flags &= ~DCACHE_SHRINK_LIST;
N
Nick Piggin 已提交
324 325 326 327
	dentry->d_sb->s_nr_dentry_unused--;
	dentry_stat.nr_unused--;
}

S
Sage Weil 已提交
328 329 330
/*
 * Remove a dentry with references from the LRU.
 */
331 332 333
static void dentry_lru_del(struct dentry *dentry)
{
	if (!list_empty(&dentry->d_lru)) {
N
Nick Piggin 已提交
334 335 336
		spin_lock(&dcache_lru_lock);
		__dentry_lru_del(dentry);
		spin_unlock(&dcache_lru_lock);
337 338 339
	}
}

S
Sage Weil 已提交
340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356
/*
 * Remove a dentry that is unreferenced and about to be pruned
 * (unhashed and destroyed) from the LRU, and inform the file system.
 * This wrapper should be called _prior_ to unhashing a victim dentry.
 */
static void dentry_lru_prune(struct dentry *dentry)
{
	if (!list_empty(&dentry->d_lru)) {
		if (dentry->d_flags & DCACHE_OP_PRUNE)
			dentry->d_op->d_prune(dentry);

		spin_lock(&dcache_lru_lock);
		__dentry_lru_del(dentry);
		spin_unlock(&dcache_lru_lock);
	}
}

357
static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)
358
{
N
Nick Piggin 已提交
359
	spin_lock(&dcache_lru_lock);
360
	if (list_empty(&dentry->d_lru)) {
361
		list_add_tail(&dentry->d_lru, list);
362
		dentry->d_sb->s_nr_dentry_unused++;
363
		dentry_stat.nr_unused++;
364
	} else {
365
		list_move_tail(&dentry->d_lru, list);
366
	}
N
Nick Piggin 已提交
367
	spin_unlock(&dcache_lru_lock);
368 369
}

370 371 372
/**
 * d_kill - kill dentry and return parent
 * @dentry: dentry to kill
373
 * @parent: parent dentry
374
 *
375
 * The dentry must already be unhashed and removed from the LRU.
376 377
 *
 * If this is the root of the dentry tree, return NULL.
N
Nick Piggin 已提交
378
 *
N
Nick Piggin 已提交
379 380
 * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
 * d_kill.
381
 */
N
Nick Piggin 已提交
382
static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
383
	__releases(dentry->d_lock)
N
Nick Piggin 已提交
384
	__releases(parent->d_lock)
385
	__releases(dentry->d_inode->i_lock)
386 387
{
	list_del(&dentry->d_u.d_child);
388 389 390 391
	/*
	 * Inform try_to_ascend() that we are no longer attached to the
	 * dentry tree
	 */
392
	dentry->d_flags |= DCACHE_DENTRY_KILLED;
N
Nick Piggin 已提交
393 394
	if (parent)
		spin_unlock(&parent->d_lock);
395
	dentry_iput(dentry);
N
Nick Piggin 已提交
396 397 398 399
	/*
	 * dentry_iput drops the locks, at which point nobody (except
	 * transient RCU lookups) can reach this dentry.
	 */
400
	d_free(dentry);
401
	return parent;
402 403
}

404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424
/*
 * Unhash a dentry without inserting an RCU walk barrier or checking that
 * dentry->d_lock is locked.  The caller must take care of that, if
 * appropriate.
 */
static void __d_shrink(struct dentry *dentry)
{
	if (!d_unhashed(dentry)) {
		struct hlist_bl_head *b;
		if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
			b = &dentry->d_sb->s_anon;
		else
			b = d_hash(dentry->d_parent, dentry->d_name.hash);

		hlist_bl_lock(b);
		__hlist_bl_del(&dentry->d_hash);
		dentry->d_hash.pprev = NULL;
		hlist_bl_unlock(b);
	}
}

N
Nick Piggin 已提交
425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441
/**
 * d_drop - drop a dentry
 * @dentry: dentry to drop
 *
 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
 * be found through a VFS lookup any more. Note that this is different from
 * deleting the dentry - d_delete will try to mark the dentry negative if
 * possible, giving a successful _negative_ lookup, while d_drop will
 * just make the cache lookup fail.
 *
 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
 * reason (NFS timeouts or autofs deletes).
 *
 * __d_drop requires dentry->d_lock.
 */
void __d_drop(struct dentry *dentry)
{
442
	if (!d_unhashed(dentry)) {
443
		__d_shrink(dentry);
444
		dentry_rcuwalk_barrier(dentry);
N
Nick Piggin 已提交
445 446 447 448 449 450 451 452 453 454 455 456
	}
}
EXPORT_SYMBOL(__d_drop);

void d_drop(struct dentry *dentry)
{
	spin_lock(&dentry->d_lock);
	__d_drop(dentry);
	spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(d_drop);

457 458 459 460 461 462 463 464 465
/*
 * Finish off a dentry we've decided to kill.
 * dentry->d_lock must be held, returns with it unlocked.
 * If ref is non-zero, then decrement the refcount too.
 * Returns dentry requiring refcount drop, or NULL if we're done.
 */
static inline struct dentry *dentry_kill(struct dentry *dentry, int ref)
	__releases(dentry->d_lock)
{
466
	struct inode *inode;
467 468
	struct dentry *parent;

469 470
	inode = dentry->d_inode;
	if (inode && !spin_trylock(&inode->i_lock)) {
471 472 473 474 475 476 477 478 479 480
relock:
		spin_unlock(&dentry->d_lock);
		cpu_relax();
		return dentry; /* try again with same dentry */
	}
	if (IS_ROOT(dentry))
		parent = NULL;
	else
		parent = dentry->d_parent;
	if (parent && !spin_trylock(&parent->d_lock)) {
481 482
		if (inode)
			spin_unlock(&inode->i_lock);
483 484
		goto relock;
	}
N
Nick Piggin 已提交
485

486 487
	if (ref)
		dentry->d_count--;
S
Sage Weil 已提交
488 489 490 491 492 493
	/*
	 * if dentry was on the d_lru list delete it from there.
	 * inform the fs via d_prune that this dentry is about to be
	 * unhashed and destroyed.
	 */
	dentry_lru_prune(dentry);
494 495 496 497 498
	/* if it was on the hash then remove it */
	__d_drop(dentry);
	return d_kill(dentry, parent);
}

L
Linus Torvalds 已提交
499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530
/* 
 * This is dput
 *
 * This is complicated by the fact that we do not want to put
 * dentries that are no longer on any hash chain on the unused
 * list: we'd much rather just get rid of them immediately.
 *
 * However, that implies that we have to traverse the dentry
 * tree upwards to the parents which might _also_ now be
 * scheduled for deletion (it may have been only waiting for
 * its last child to go away).
 *
 * This tail recursion is done by hand as we don't want to depend
 * on the compiler to always get this right (gcc generally doesn't).
 * Real recursion would eat up our stack space.
 */

/*
 * dput - release a dentry
 * @dentry: dentry to release 
 *
 * Release a dentry. This will drop the usage count and if appropriate
 * call the dentry unlink method as well as removing it from the queues and
 * releasing its resources. If the parent dentries were scheduled for release
 * they too may now get deleted.
 */
void dput(struct dentry *dentry)
{
	if (!dentry)
		return;

repeat:
N
Nick Piggin 已提交
531
	if (dentry->d_count == 1)
L
Linus Torvalds 已提交
532 533
		might_sleep();
	spin_lock(&dentry->d_lock);
N
Nick Piggin 已提交
534 535 536
	BUG_ON(!dentry->d_count);
	if (dentry->d_count > 1) {
		dentry->d_count--;
L
Linus Torvalds 已提交
537 538 539 540
		spin_unlock(&dentry->d_lock);
		return;
	}

541
	if (dentry->d_flags & DCACHE_OP_DELETE) {
L
Linus Torvalds 已提交
542
		if (dentry->d_op->d_delete(dentry))
N
Nick Piggin 已提交
543
			goto kill_it;
L
Linus Torvalds 已提交
544
	}
N
Nick Piggin 已提交
545

L
Linus Torvalds 已提交
546 547 548
	/* Unreachable? Get rid of it */
 	if (d_unhashed(dentry))
		goto kill_it;
N
Nick Piggin 已提交
549

J
Jeff Layton 已提交
550
	dentry->d_flags |= DCACHE_REFERENCED;
551
	dentry_lru_add(dentry);
N
Nick Piggin 已提交
552

N
Nick Piggin 已提交
553 554
	dentry->d_count--;
	spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
555 556
	return;

557
kill_it:
558
	dentry = dentry_kill(dentry, 1);
559 560
	if (dentry)
		goto repeat;
L
Linus Torvalds 已提交
561
}
562
EXPORT_SYMBOL(dput);
L
Linus Torvalds 已提交
563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580

/**
 * d_invalidate - invalidate a dentry
 * @dentry: dentry to invalidate
 *
 * Try to invalidate the dentry if it turns out to be
 * possible. If there are other dentries that can be
 * reached through this one we can't delete it and we
 * return -EBUSY. On success we return 0.
 *
 * no dcache lock.
 */
 
int d_invalidate(struct dentry * dentry)
{
	/*
	 * If it's already been dropped, return OK.
	 */
N
Nick Piggin 已提交
581
	spin_lock(&dentry->d_lock);
L
Linus Torvalds 已提交
582
	if (d_unhashed(dentry)) {
N
Nick Piggin 已提交
583
		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
584 585 586 587 588 589 590
		return 0;
	}
	/*
	 * Check whether to do a partial shrink_dcache
	 * to get rid of unused child entries.
	 */
	if (!list_empty(&dentry->d_subdirs)) {
N
Nick Piggin 已提交
591
		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
592
		shrink_dcache_parent(dentry);
N
Nick Piggin 已提交
593
		spin_lock(&dentry->d_lock);
L
Linus Torvalds 已提交
594 595 596 597 598 599 600 601 602 603 604
	}

	/*
	 * Somebody else still using it?
	 *
	 * If it's a directory, we can't drop it
	 * for fear of somebody re-populating it
	 * with children (even though dropping it
	 * would make it unreachable from the root,
	 * we might still populate it if it was a
	 * working directory or similar).
605 606
	 * We also need to leave mountpoints alone,
	 * directory or not.
L
Linus Torvalds 已提交
607
	 */
608 609
	if (dentry->d_count > 1 && dentry->d_inode) {
		if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) {
L
Linus Torvalds 已提交
610 611 612 613 614 615 616 617 618
			spin_unlock(&dentry->d_lock);
			return -EBUSY;
		}
	}

	__d_drop(dentry);
	spin_unlock(&dentry->d_lock);
	return 0;
}
619
EXPORT_SYMBOL(d_invalidate);
L
Linus Torvalds 已提交
620

N
Nick Piggin 已提交
621
/* This must be called with d_lock held */
622
static inline void __dget_dlock(struct dentry *dentry)
N
Nick Piggin 已提交
623
{
N
Nick Piggin 已提交
624
	dentry->d_count++;
N
Nick Piggin 已提交
625 626
}

627
static inline void __dget(struct dentry *dentry)
L
Linus Torvalds 已提交
628
{
N
Nick Piggin 已提交
629
	spin_lock(&dentry->d_lock);
630
	__dget_dlock(dentry);
N
Nick Piggin 已提交
631
	spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
632 633
}

N
Nick Piggin 已提交
634 635 636 637 638
struct dentry *dget_parent(struct dentry *dentry)
{
	struct dentry *ret;

repeat:
N
Nick Piggin 已提交
639 640 641 642 643
	/*
	 * Don't need rcu_dereference because we re-check it was correct under
	 * the lock.
	 */
	rcu_read_lock();
N
Nick Piggin 已提交
644
	ret = dentry->d_parent;
N
Nick Piggin 已提交
645 646 647 648
	spin_lock(&ret->d_lock);
	if (unlikely(ret != dentry->d_parent)) {
		spin_unlock(&ret->d_lock);
		rcu_read_unlock();
N
Nick Piggin 已提交
649 650
		goto repeat;
	}
N
Nick Piggin 已提交
651
	rcu_read_unlock();
N
Nick Piggin 已提交
652 653 654 655 656 657 658
	BUG_ON(!ret->d_count);
	ret->d_count++;
	spin_unlock(&ret->d_lock);
	return ret;
}
EXPORT_SYMBOL(dget_parent);

L
Linus Torvalds 已提交
659 660 661
/**
 * d_find_alias - grab a hashed alias of inode
 * @inode: inode in question
662 663
 * @want_discon:  flag, used by d_splice_alias, to request
 *          that only a DISCONNECTED alias be returned.
L
Linus Torvalds 已提交
664 665 666 667 668 669 670
 *
 * If inode has a hashed alias, or is a directory and has any alias,
 * acquire the reference to alias and return it. Otherwise return NULL.
 * Notice that if inode is a directory there can be only one alias and
 * it can be unhashed only if it has no children, or if it is the root
 * of a filesystem.
 *
671
 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
672 673
 * any other hashed alias over that one unless @want_discon is set,
 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
L
Linus Torvalds 已提交
674
 */
675
static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
L
Linus Torvalds 已提交
676
{
N
Nick Piggin 已提交
677
	struct dentry *alias, *discon_alias;
A
Al Viro 已提交
678
	struct hlist_node *p;
L
Linus Torvalds 已提交
679

N
Nick Piggin 已提交
680 681
again:
	discon_alias = NULL;
A
Al Viro 已提交
682
	hlist_for_each_entry(alias, p, &inode->i_dentry, d_alias) {
N
Nick Piggin 已提交
683
		spin_lock(&alias->d_lock);
L
Linus Torvalds 已提交
684
 		if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
685
			if (IS_ROOT(alias) &&
N
Nick Piggin 已提交
686
			    (alias->d_flags & DCACHE_DISCONNECTED)) {
L
Linus Torvalds 已提交
687
				discon_alias = alias;
688
			} else if (!want_discon) {
689
				__dget_dlock(alias);
N
Nick Piggin 已提交
690 691 692 693 694 695 696 697 698 699 700 701
				spin_unlock(&alias->d_lock);
				return alias;
			}
		}
		spin_unlock(&alias->d_lock);
	}
	if (discon_alias) {
		alias = discon_alias;
		spin_lock(&alias->d_lock);
		if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
			if (IS_ROOT(alias) &&
			    (alias->d_flags & DCACHE_DISCONNECTED)) {
702
				__dget_dlock(alias);
N
Nick Piggin 已提交
703
				spin_unlock(&alias->d_lock);
L
Linus Torvalds 已提交
704 705 706
				return alias;
			}
		}
N
Nick Piggin 已提交
707 708
		spin_unlock(&alias->d_lock);
		goto again;
L
Linus Torvalds 已提交
709
	}
N
Nick Piggin 已提交
710
	return NULL;
L
Linus Torvalds 已提交
711 712
}

N
Nick Piggin 已提交
713
struct dentry *d_find_alias(struct inode *inode)
L
Linus Torvalds 已提交
714
{
D
David Howells 已提交
715 716
	struct dentry *de = NULL;

A
Al Viro 已提交
717
	if (!hlist_empty(&inode->i_dentry)) {
718
		spin_lock(&inode->i_lock);
719
		de = __d_find_alias(inode, 0);
720
		spin_unlock(&inode->i_lock);
D
David Howells 已提交
721
	}
L
Linus Torvalds 已提交
722 723
	return de;
}
724
EXPORT_SYMBOL(d_find_alias);
L
Linus Torvalds 已提交
725 726 727 728 729 730 731

/*
 *	Try to kill dentries associated with this inode.
 * WARNING: you must own a reference to inode.
 */
void d_prune_aliases(struct inode *inode)
{
732
	struct dentry *dentry;
A
Al Viro 已提交
733
	struct hlist_node *p;
L
Linus Torvalds 已提交
734
restart:
735
	spin_lock(&inode->i_lock);
A
Al Viro 已提交
736
	hlist_for_each_entry(dentry, p, &inode->i_dentry, d_alias) {
L
Linus Torvalds 已提交
737
		spin_lock(&dentry->d_lock);
N
Nick Piggin 已提交
738
		if (!dentry->d_count) {
739
			__dget_dlock(dentry);
L
Linus Torvalds 已提交
740 741
			__d_drop(dentry);
			spin_unlock(&dentry->d_lock);
742
			spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
743 744 745 746 747
			dput(dentry);
			goto restart;
		}
		spin_unlock(&dentry->d_lock);
	}
748
	spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
749
}
750
EXPORT_SYMBOL(d_prune_aliases);
L
Linus Torvalds 已提交
751 752

/*
753 754 755
 * Try to throw away a dentry - free the inode, dput the parent.
 * Requires dentry->d_lock is held, and dentry->d_count == 0.
 * Releases dentry->d_lock.
756
 *
757
 * This may fail if locks cannot be acquired no problem, just try again.
L
Linus Torvalds 已提交
758
 */
759
static void try_prune_one_dentry(struct dentry *dentry)
760
	__releases(dentry->d_lock)
L
Linus Torvalds 已提交
761
{
762
	struct dentry *parent;
763

764
	parent = dentry_kill(dentry, 0);
765
	/*
766 767 768 769 770 771 772 773
	 * If dentry_kill returns NULL, we have nothing more to do.
	 * if it returns the same dentry, trylocks failed. In either
	 * case, just loop again.
	 *
	 * Otherwise, we need to prune ancestors too. This is necessary
	 * to prevent quadratic behavior of shrink_dcache_parent(), but
	 * is also expected to be beneficial in reducing dentry cache
	 * fragmentation.
774
	 */
775 776 777 778 779 780 781
	if (!parent)
		return;
	if (parent == dentry)
		return;

	/* Prune ancestors. */
	dentry = parent;
782
	while (dentry) {
N
Nick Piggin 已提交
783
		spin_lock(&dentry->d_lock);
784 785 786 787 788
		if (dentry->d_count > 1) {
			dentry->d_count--;
			spin_unlock(&dentry->d_lock);
			return;
		}
789
		dentry = dentry_kill(dentry, 1);
790
	}
L
Linus Torvalds 已提交
791 792
}

C
Christoph Hellwig 已提交
793
static void shrink_dentry_list(struct list_head *list)
L
Linus Torvalds 已提交
794
{
795 796
	struct dentry *dentry;

797 798 799 800 801 802 803 804
	rcu_read_lock();
	for (;;) {
		dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
		if (&dentry->d_lru == list)
			break; /* empty */
		spin_lock(&dentry->d_lock);
		if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
			spin_unlock(&dentry->d_lock);
N
Nick Piggin 已提交
805 806 807
			continue;
		}

L
Linus Torvalds 已提交
808 809
		/*
		 * We found an inuse dentry which was not removed from
810 811
		 * the LRU because of laziness during lookup.  Do not free
		 * it - just keep it off the LRU list.
L
Linus Torvalds 已提交
812
		 */
N
Nick Piggin 已提交
813
		if (dentry->d_count) {
814
			dentry_lru_del(dentry);
815
			spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
816 817
			continue;
		}
818 819

		rcu_read_unlock();
820 821 822

		try_prune_one_dentry(dentry);

823
		rcu_read_lock();
824
	}
825
	rcu_read_unlock();
C
Christoph Hellwig 已提交
826 827 828
}

/**
829 830 831 832 833 834 835
 * prune_dcache_sb - shrink the dcache
 * @sb: superblock
 * @count: number of entries to try to free
 *
 * Attempt to shrink the superblock dcache LRU by @count entries. This is
 * done when we need more memory an called from the superblock shrinker
 * function.
C
Christoph Hellwig 已提交
836
 *
837 838
 * This function may fail to free any resources if all the dentries are in
 * use.
C
Christoph Hellwig 已提交
839
 */
840
void prune_dcache_sb(struct super_block *sb, int count)
C
Christoph Hellwig 已提交
841 842 843 844 845
{
	struct dentry *dentry;
	LIST_HEAD(referenced);
	LIST_HEAD(tmp);

N
Nick Piggin 已提交
846 847
relock:
	spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
848 849 850 851 852
	while (!list_empty(&sb->s_dentry_lru)) {
		dentry = list_entry(sb->s_dentry_lru.prev,
				struct dentry, d_lru);
		BUG_ON(dentry->d_sb != sb);

N
Nick Piggin 已提交
853 854 855 856 857 858
		if (!spin_trylock(&dentry->d_lock)) {
			spin_unlock(&dcache_lru_lock);
			cpu_relax();
			goto relock;
		}

859
		if (dentry->d_flags & DCACHE_REFERENCED) {
N
Nick Piggin 已提交
860 861
			dentry->d_flags &= ~DCACHE_REFERENCED;
			list_move(&dentry->d_lru, &referenced);
C
Christoph Hellwig 已提交
862
			spin_unlock(&dentry->d_lock);
N
Nick Piggin 已提交
863 864
		} else {
			list_move_tail(&dentry->d_lru, &tmp);
865
			dentry->d_flags |= DCACHE_SHRINK_LIST;
N
Nick Piggin 已提交
866
			spin_unlock(&dentry->d_lock);
867
			if (!--count)
N
Nick Piggin 已提交
868
				break;
C
Christoph Hellwig 已提交
869
		}
870
		cond_resched_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
871
	}
872 873
	if (!list_empty(&referenced))
		list_splice(&referenced, &sb->s_dentry_lru);
N
Nick Piggin 已提交
874
	spin_unlock(&dcache_lru_lock);
875 876

	shrink_dentry_list(&tmp);
877 878
}

L
Linus Torvalds 已提交
879 880 881 882
/**
 * shrink_dcache_sb - shrink dcache for a superblock
 * @sb: superblock
 *
C
Christoph Hellwig 已提交
883 884
 * Shrink the dcache for the specified super block. This is used to free
 * the dcache before unmounting a file system.
L
Linus Torvalds 已提交
885
 */
C
Christoph Hellwig 已提交
886
void shrink_dcache_sb(struct super_block *sb)
L
Linus Torvalds 已提交
887
{
C
Christoph Hellwig 已提交
888 889
	LIST_HEAD(tmp);

N
Nick Piggin 已提交
890
	spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
891 892
	while (!list_empty(&sb->s_dentry_lru)) {
		list_splice_init(&sb->s_dentry_lru, &tmp);
893
		spin_unlock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
894
		shrink_dentry_list(&tmp);
895
		spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
896
	}
N
Nick Piggin 已提交
897
	spin_unlock(&dcache_lru_lock);
L
Linus Torvalds 已提交
898
}
899
EXPORT_SYMBOL(shrink_dcache_sb);
L
Linus Torvalds 已提交
900

901 902 903 904 905 906 907 908 909 910 911 912 913
/*
 * destroy a single subtree of dentries for unmount
 * - see the comments on shrink_dcache_for_umount() for a description of the
 *   locking
 */
static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
{
	struct dentry *parent;

	BUG_ON(!IS_ROOT(dentry));

	for (;;) {
		/* descend to the first leaf in the current subtree */
914
		while (!list_empty(&dentry->d_subdirs))
915 916 917 918 919 920 921 922
			dentry = list_entry(dentry->d_subdirs.next,
					    struct dentry, d_u.d_child);

		/* consume the dentries from this leaf up through its parents
		 * until we find one with children or run out altogether */
		do {
			struct inode *inode;

S
Sage Weil 已提交
923 924 925 926 927 928
			/*
			 * remove the dentry from the lru, and inform
			 * the fs that this dentry is about to be
			 * unhashed and destroyed.
			 */
			dentry_lru_prune(dentry);
929 930
			__d_shrink(dentry);

N
Nick Piggin 已提交
931
			if (dentry->d_count != 0) {
932 933 934 935 936 937 938 939
				printk(KERN_ERR
				       "BUG: Dentry %p{i=%lx,n=%s}"
				       " still in use (%d)"
				       " [unmount of %s %s]\n",
				       dentry,
				       dentry->d_inode ?
				       dentry->d_inode->i_ino : 0UL,
				       dentry->d_name.name,
N
Nick Piggin 已提交
940
				       dentry->d_count,
941 942 943 944 945
				       dentry->d_sb->s_type->name,
				       dentry->d_sb->s_id);
				BUG();
			}

N
Nick Piggin 已提交
946
			if (IS_ROOT(dentry)) {
947
				parent = NULL;
N
Nick Piggin 已提交
948 949
				list_del(&dentry->d_u.d_child);
			} else {
950
				parent = dentry->d_parent;
N
Nick Piggin 已提交
951
				parent->d_count--;
N
Nick Piggin 已提交
952
				list_del(&dentry->d_u.d_child);
953
			}
954 955 956 957

			inode = dentry->d_inode;
			if (inode) {
				dentry->d_inode = NULL;
A
Al Viro 已提交
958
				hlist_del_init(&dentry->d_alias);
959 960 961 962 963 964 965 966 967 968 969 970
				if (dentry->d_op && dentry->d_op->d_iput)
					dentry->d_op->d_iput(dentry, inode);
				else
					iput(inode);
			}

			d_free(dentry);

			/* finished when we fall off the top of the tree,
			 * otherwise we ascend to the parent and move to the
			 * next sibling if there is one */
			if (!parent)
971
				return;
972 973 974 975 976 977 978 979 980 981
			dentry = parent;
		} while (list_empty(&dentry->d_subdirs));

		dentry = list_entry(dentry->d_subdirs.next,
				    struct dentry, d_u.d_child);
	}
}

/*
 * destroy the dentries attached to a superblock on unmounting
N
Nick Piggin 已提交
982
 * - we don't need to use dentry->d_lock because:
983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998
 *   - the superblock is detached from all mountings and open files, so the
 *     dentry trees will not be rearranged by the VFS
 *   - s_umount is write-locked, so the memory pressure shrinker will ignore
 *     any dentries belonging to this superblock that it comes across
 *   - the filesystem itself is no longer permitted to rearrange the dentries
 *     in this superblock
 */
void shrink_dcache_for_umount(struct super_block *sb)
{
	struct dentry *dentry;

	if (down_read_trylock(&sb->s_umount))
		BUG();

	dentry = sb->s_root;
	sb->s_root = NULL;
N
Nick Piggin 已提交
999
	dentry->d_count--;
1000 1001
	shrink_dcache_for_umount_subtree(dentry);

1002 1003
	while (!hlist_bl_empty(&sb->s_anon)) {
		dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
1004 1005 1006 1007
		shrink_dcache_for_umount_subtree(dentry);
	}
}

1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026
/*
 * This tries to ascend one level of parenthood, but
 * we can race with renaming, so we need to re-check
 * the parenthood after dropping the lock and check
 * that the sequence number still matches.
 */
static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq)
{
	struct dentry *new = old->d_parent;

	rcu_read_lock();
	spin_unlock(&old->d_lock);
	spin_lock(&new->d_lock);

	/*
	 * might go back up the wrong parent if we have had a rename
	 * or deletion
	 */
	if (new != old->d_parent ||
1027
		 (old->d_flags & DCACHE_DENTRY_KILLED) ||
1028 1029 1030 1031 1032 1033 1034 1035 1036
		 (!locked && read_seqretry(&rename_lock, seq))) {
		spin_unlock(&new->d_lock);
		new = NULL;
	}
	rcu_read_unlock();
	return new;
}


L
Linus Torvalds 已提交
1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051
/*
 * Search for at least 1 mount point in the dentry's subdirs.
 * We descend to the next level whenever the d_subdirs
 * list is non-empty and continue searching.
 */
 
/**
 * have_submounts - check for mounts over a dentry
 * @parent: dentry to check.
 *
 * Return true if the parent or its subdirectories contain
 * a mount point
 */
int have_submounts(struct dentry *parent)
{
1052
	struct dentry *this_parent;
L
Linus Torvalds 已提交
1053
	struct list_head *next;
1054
	unsigned seq;
1055
	int locked = 0;
1056 1057

	seq = read_seqbegin(&rename_lock);
1058 1059
again:
	this_parent = parent;
L
Linus Torvalds 已提交
1060 1061 1062

	if (d_mountpoint(parent))
		goto positive;
N
Nick Piggin 已提交
1063
	spin_lock(&this_parent->d_lock);
L
Linus Torvalds 已提交
1064 1065 1066 1067 1068
repeat:
	next = this_parent->d_subdirs.next;
resume:
	while (next != &this_parent->d_subdirs) {
		struct list_head *tmp = next;
E
Eric Dumazet 已提交
1069
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
1070
		next = tmp->next;
N
Nick Piggin 已提交
1071 1072

		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
L
Linus Torvalds 已提交
1073
		/* Have we found a mount point ? */
N
Nick Piggin 已提交
1074 1075 1076
		if (d_mountpoint(dentry)) {
			spin_unlock(&dentry->d_lock);
			spin_unlock(&this_parent->d_lock);
L
Linus Torvalds 已提交
1077
			goto positive;
N
Nick Piggin 已提交
1078
		}
L
Linus Torvalds 已提交
1079
		if (!list_empty(&dentry->d_subdirs)) {
N
Nick Piggin 已提交
1080 1081
			spin_unlock(&this_parent->d_lock);
			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
L
Linus Torvalds 已提交
1082
			this_parent = dentry;
N
Nick Piggin 已提交
1083
			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
L
Linus Torvalds 已提交
1084 1085
			goto repeat;
		}
N
Nick Piggin 已提交
1086
		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
1087 1088 1089 1090 1091
	}
	/*
	 * All done at this level ... ascend and resume the search.
	 */
	if (this_parent != parent) {
1092 1093 1094
		struct dentry *child = this_parent;
		this_parent = try_to_ascend(this_parent, locked, seq);
		if (!this_parent)
1095 1096
			goto rename_retry;
		next = child->d_u.d_child.next;
L
Linus Torvalds 已提交
1097 1098
		goto resume;
	}
N
Nick Piggin 已提交
1099
	spin_unlock(&this_parent->d_lock);
1100
	if (!locked && read_seqretry(&rename_lock, seq))
1101
		goto rename_retry;
1102 1103
	if (locked)
		write_sequnlock(&rename_lock);
L
Linus Torvalds 已提交
1104 1105
	return 0; /* No mount points found in tree */
positive:
1106
	if (!locked && read_seqretry(&rename_lock, seq))
1107
		goto rename_retry;
1108 1109
	if (locked)
		write_sequnlock(&rename_lock);
L
Linus Torvalds 已提交
1110
	return 1;
1111 1112

rename_retry:
1113 1114
	if (locked)
		goto again;
1115 1116 1117
	locked = 1;
	write_seqlock(&rename_lock);
	goto again;
L
Linus Torvalds 已提交
1118
}
1119
EXPORT_SYMBOL(have_submounts);
L
Linus Torvalds 已提交
1120 1121

/*
1122
 * Search the dentry child list of the specified parent,
L
Linus Torvalds 已提交
1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134
 * and move any unused dentries to the end of the unused
 * list for prune_dcache(). We descend to the next level
 * whenever the d_subdirs list is non-empty and continue
 * searching.
 *
 * It returns zero iff there are no unused children,
 * otherwise  it returns the number of children moved to
 * the end of the unused list. This may not be the total
 * number of unused children, because select_parent can
 * drop the lock and return early due to latency
 * constraints.
 */
1135
static int select_parent(struct dentry *parent, struct list_head *dispose)
L
Linus Torvalds 已提交
1136
{
1137
	struct dentry *this_parent;
L
Linus Torvalds 已提交
1138
	struct list_head *next;
1139
	unsigned seq;
L
Linus Torvalds 已提交
1140
	int found = 0;
1141
	int locked = 0;
L
Linus Torvalds 已提交
1142

1143
	seq = read_seqbegin(&rename_lock);
1144 1145
again:
	this_parent = parent;
N
Nick Piggin 已提交
1146
	spin_lock(&this_parent->d_lock);
L
Linus Torvalds 已提交
1147 1148 1149 1150 1151
repeat:
	next = this_parent->d_subdirs.next;
resume:
	while (next != &this_parent->d_subdirs) {
		struct list_head *tmp = next;
E
Eric Dumazet 已提交
1152
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
1153 1154
		next = tmp->next;

N
Nick Piggin 已提交
1155
		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
N
Nick Piggin 已提交
1156

1157 1158
		/*
		 * move only zero ref count dentries to the dispose list.
1159 1160 1161 1162 1163
		 *
		 * Those which are presently on the shrink list, being processed
		 * by shrink_dentry_list(), shouldn't be moved.  Otherwise the
		 * loop in shrink_dcache_parent() might not make any progress
		 * and loop forever.
L
Linus Torvalds 已提交
1164
		 */
1165 1166 1167
		if (dentry->d_count) {
			dentry_lru_del(dentry);
		} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
1168
			dentry_lru_move_list(dentry, dispose);
1169
			dentry->d_flags |= DCACHE_SHRINK_LIST;
L
Linus Torvalds 已提交
1170 1171 1172 1173 1174 1175 1176
			found++;
		}
		/*
		 * We can return to the caller if we have found some (this
		 * ensures forward progress). We'll be coming back to find
		 * the rest.
		 */
N
Nick Piggin 已提交
1177 1178
		if (found && need_resched()) {
			spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
1179
			goto out;
N
Nick Piggin 已提交
1180
		}
L
Linus Torvalds 已提交
1181 1182 1183 1184 1185

		/*
		 * Descend a level if the d_subdirs list is non-empty.
		 */
		if (!list_empty(&dentry->d_subdirs)) {
N
Nick Piggin 已提交
1186 1187
			spin_unlock(&this_parent->d_lock);
			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
L
Linus Torvalds 已提交
1188
			this_parent = dentry;
N
Nick Piggin 已提交
1189
			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
L
Linus Torvalds 已提交
1190 1191
			goto repeat;
		}
N
Nick Piggin 已提交
1192 1193

		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
1194 1195 1196 1197 1198
	}
	/*
	 * All done at this level ... ascend and resume the search.
	 */
	if (this_parent != parent) {
1199 1200 1201
		struct dentry *child = this_parent;
		this_parent = try_to_ascend(this_parent, locked, seq);
		if (!this_parent)
1202 1203
			goto rename_retry;
		next = child->d_u.d_child.next;
L
Linus Torvalds 已提交
1204 1205 1206
		goto resume;
	}
out:
N
Nick Piggin 已提交
1207
	spin_unlock(&this_parent->d_lock);
1208
	if (!locked && read_seqretry(&rename_lock, seq))
1209
		goto rename_retry;
1210 1211
	if (locked)
		write_sequnlock(&rename_lock);
L
Linus Torvalds 已提交
1212
	return found;
1213 1214 1215 1216

rename_retry:
	if (found)
		return found;
1217 1218
	if (locked)
		goto again;
1219 1220 1221
	locked = 1;
	write_seqlock(&rename_lock);
	goto again;
L
Linus Torvalds 已提交
1222 1223 1224 1225 1226 1227 1228 1229 1230 1231
}

/**
 * shrink_dcache_parent - prune dcache
 * @parent: parent of entries to prune
 *
 * Prune the dcache to remove unused children of the parent dentry.
 */
void shrink_dcache_parent(struct dentry * parent)
{
1232
	LIST_HEAD(dispose);
L
Linus Torvalds 已提交
1233 1234
	int found;

1235 1236
	while ((found = select_parent(parent, &dispose)) != 0)
		shrink_dentry_list(&dispose);
L
Linus Torvalds 已提交
1237
}
1238
EXPORT_SYMBOL(shrink_dcache_parent);
L
Linus Torvalds 已提交
1239 1240

/**
1241 1242
 * __d_alloc	-	allocate a dcache entry
 * @sb: filesystem it will belong to
L
Linus Torvalds 已提交
1243 1244 1245 1246 1247 1248 1249
 * @name: qstr of the name
 *
 * Allocates a dentry. It returns %NULL if there is insufficient memory
 * available. On a success the dentry is returned. The name passed in is
 * copied and the copy passed in may be reused after this call.
 */
 
1250
struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
L
Linus Torvalds 已提交
1251 1252 1253 1254
{
	struct dentry *dentry;
	char *dname;

1255
	dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
L
Linus Torvalds 已提交
1256 1257 1258
	if (!dentry)
		return NULL;

1259 1260 1261 1262 1263 1264 1265
	/*
	 * We guarantee that the inline name is always NUL-terminated.
	 * This way the memcpy() done by the name switching in rename
	 * will still always have a NUL at the end, even if we might
	 * be overwriting an internal NUL character
	 */
	dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
L
Linus Torvalds 已提交
1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280
	if (name->len > DNAME_INLINE_LEN-1) {
		dname = kmalloc(name->len + 1, GFP_KERNEL);
		if (!dname) {
			kmem_cache_free(dentry_cache, dentry); 
			return NULL;
		}
	} else  {
		dname = dentry->d_iname;
	}	

	dentry->d_name.len = name->len;
	dentry->d_name.hash = name->hash;
	memcpy(dname, name->name, name->len);
	dname[name->len] = 0;

1281 1282 1283 1284
	/* Make sure we always see the terminating NUL character */
	smp_wmb();
	dentry->d_name.name = dname;

N
Nick Piggin 已提交
1285
	dentry->d_count = 1;
1286
	dentry->d_flags = 0;
L
Linus Torvalds 已提交
1287
	spin_lock_init(&dentry->d_lock);
N
Nick Piggin 已提交
1288
	seqcount_init(&dentry->d_seq);
L
Linus Torvalds 已提交
1289
	dentry->d_inode = NULL;
1290 1291
	dentry->d_parent = dentry;
	dentry->d_sb = sb;
L
Linus Torvalds 已提交
1292 1293
	dentry->d_op = NULL;
	dentry->d_fsdata = NULL;
1294
	INIT_HLIST_BL_NODE(&dentry->d_hash);
L
Linus Torvalds 已提交
1295 1296
	INIT_LIST_HEAD(&dentry->d_lru);
	INIT_LIST_HEAD(&dentry->d_subdirs);
A
Al Viro 已提交
1297
	INIT_HLIST_NODE(&dentry->d_alias);
N
Nick Piggin 已提交
1298
	INIT_LIST_HEAD(&dentry->d_u.d_child);
1299
	d_set_d_op(dentry, dentry->d_sb->s_d_op);
L
Linus Torvalds 已提交
1300

1301
	this_cpu_inc(nr_dentry);
1302

L
Linus Torvalds 已提交
1303 1304
	return dentry;
}
1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332

/**
 * d_alloc	-	allocate a dcache entry
 * @parent: parent of entry to allocate
 * @name: qstr of the name
 *
 * Allocates a dentry. It returns %NULL if there is insufficient memory
 * available. On a success the dentry is returned. The name passed in is
 * copied and the copy passed in may be reused after this call.
 */
struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
{
	struct dentry *dentry = __d_alloc(parent->d_sb, name);
	if (!dentry)
		return NULL;

	spin_lock(&parent->d_lock);
	/*
	 * don't need child lock because it is not subject
	 * to concurrency here
	 */
	__dget_dlock(parent);
	dentry->d_parent = parent;
	list_add(&dentry->d_u.d_child, &parent->d_subdirs);
	spin_unlock(&parent->d_lock);

	return dentry;
}
1333
EXPORT_SYMBOL(d_alloc);
L
Linus Torvalds 已提交
1334

1335 1336
struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
{
1337 1338
	struct dentry *dentry = __d_alloc(sb, name);
	if (dentry)
1339 1340 1341 1342 1343
		dentry->d_flags |= DCACHE_DISCONNECTED;
	return dentry;
}
EXPORT_SYMBOL(d_alloc_pseudo);

L
Linus Torvalds 已提交
1344 1345 1346 1347 1348 1349 1350 1351 1352
struct dentry *d_alloc_name(struct dentry *parent, const char *name)
{
	struct qstr q;

	q.name = name;
	q.len = strlen(name);
	q.hash = full_name_hash(q.name, q.len);
	return d_alloc(parent, &q);
}
1353
EXPORT_SYMBOL(d_alloc_name);
L
Linus Torvalds 已提交
1354

1355 1356
void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
{
1357 1358
	WARN_ON_ONCE(dentry->d_op);
	WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH	|
1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372
				DCACHE_OP_COMPARE	|
				DCACHE_OP_REVALIDATE	|
				DCACHE_OP_DELETE ));
	dentry->d_op = op;
	if (!op)
		return;
	if (op->d_hash)
		dentry->d_flags |= DCACHE_OP_HASH;
	if (op->d_compare)
		dentry->d_flags |= DCACHE_OP_COMPARE;
	if (op->d_revalidate)
		dentry->d_flags |= DCACHE_OP_REVALIDATE;
	if (op->d_delete)
		dentry->d_flags |= DCACHE_OP_DELETE;
S
Sage Weil 已提交
1373 1374
	if (op->d_prune)
		dentry->d_flags |= DCACHE_OP_PRUNE;
1375 1376 1377 1378

}
EXPORT_SYMBOL(d_set_d_op);

1379 1380
static void __d_instantiate(struct dentry *dentry, struct inode *inode)
{
N
Nick Piggin 已提交
1381
	spin_lock(&dentry->d_lock);
1382 1383 1384
	if (inode) {
		if (unlikely(IS_AUTOMOUNT(inode)))
			dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
A
Al Viro 已提交
1385
		hlist_add_head(&dentry->d_alias, &inode->i_dentry);
1386
	}
1387
	dentry->d_inode = inode;
N
Nick Piggin 已提交
1388
	dentry_rcuwalk_barrier(dentry);
N
Nick Piggin 已提交
1389
	spin_unlock(&dentry->d_lock);
1390 1391 1392
	fsnotify_d_instantiate(dentry, inode);
}

L
Linus Torvalds 已提交
1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409
/**
 * d_instantiate - fill in inode information for a dentry
 * @entry: dentry to complete
 * @inode: inode to attach to this dentry
 *
 * Fill in inode information in the entry.
 *
 * This turns negative dentries into productive full members
 * of society.
 *
 * NOTE! This assumes that the inode count has been incremented
 * (or otherwise set) by the caller to indicate that it is now
 * in use by the dcache.
 */
 
void d_instantiate(struct dentry *entry, struct inode * inode)
{
A
Al Viro 已提交
1410
	BUG_ON(!hlist_unhashed(&entry->d_alias));
1411 1412
	if (inode)
		spin_lock(&inode->i_lock);
1413
	__d_instantiate(entry, inode);
1414 1415
	if (inode)
		spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
1416 1417
	security_d_instantiate(entry, inode);
}
1418
EXPORT_SYMBOL(d_instantiate);
L
Linus Torvalds 已提交
1419 1420 1421 1422 1423 1424 1425 1426

/**
 * d_instantiate_unique - instantiate a non-aliased dentry
 * @entry: dentry to instantiate
 * @inode: inode to attach to this dentry
 *
 * Fill in inode information in the entry. On success, it returns NULL.
 * If an unhashed alias of "entry" already exists, then we return the
1427
 * aliased dentry instead and drop one reference to inode.
L
Linus Torvalds 已提交
1428 1429 1430
 *
 * Note that in order to avoid conflicts with rename() etc, the caller
 * had better be holding the parent directory semaphore.
1431 1432 1433 1434
 *
 * This also assumes that the inode count has been incremented
 * (or otherwise set) by the caller to indicate that it is now
 * in use by the dcache.
L
Linus Torvalds 已提交
1435
 */
1436 1437
static struct dentry *__d_instantiate_unique(struct dentry *entry,
					     struct inode *inode)
L
Linus Torvalds 已提交
1438 1439 1440 1441 1442
{
	struct dentry *alias;
	int len = entry->d_name.len;
	const char *name = entry->d_name.name;
	unsigned int hash = entry->d_name.hash;
A
Al Viro 已提交
1443
	struct hlist_node *p;
L
Linus Torvalds 已提交
1444

1445
	if (!inode) {
1446
		__d_instantiate(entry, NULL);
1447 1448 1449
		return NULL;
	}

A
Al Viro 已提交
1450
	hlist_for_each_entry(alias, p, &inode->i_dentry, d_alias) {
N
Nick Piggin 已提交
1451 1452 1453 1454 1455
		/*
		 * Don't need alias->d_lock here, because aliases with
		 * d_parent == entry->d_parent are not subject to name or
		 * parent changes, because the parent inode i_mutex is held.
		 */
1456
		if (alias->d_name.hash != hash)
L
Linus Torvalds 已提交
1457 1458 1459
			continue;
		if (alias->d_parent != entry->d_parent)
			continue;
1460 1461
		if (alias->d_name.len != len)
			continue;
1462
		if (dentry_cmp(alias, name, len))
L
Linus Torvalds 已提交
1463
			continue;
1464
		__dget(alias);
L
Linus Torvalds 已提交
1465 1466
		return alias;
	}
1467

1468
	__d_instantiate(entry, inode);
L
Linus Torvalds 已提交
1469 1470
	return NULL;
}
1471 1472 1473 1474 1475

struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
{
	struct dentry *result;

A
Al Viro 已提交
1476
	BUG_ON(!hlist_unhashed(&entry->d_alias));
1477

1478 1479
	if (inode)
		spin_lock(&inode->i_lock);
1480
	result = __d_instantiate_unique(entry, inode);
1481 1482
	if (inode)
		spin_unlock(&inode->i_lock);
1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493

	if (!result) {
		security_d_instantiate(entry, inode);
		return NULL;
	}

	BUG_ON(!d_unhashed(result));
	iput(inode);
	return result;
}

L
Linus Torvalds 已提交
1494 1495
EXPORT_SYMBOL(d_instantiate_unique);

A
Al Viro 已提交
1496 1497 1498 1499 1500
struct dentry *d_make_root(struct inode *root_inode)
{
	struct dentry *res = NULL;

	if (root_inode) {
1501
		static const struct qstr name = QSTR_INIT("/", 1);
A
Al Viro 已提交
1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512

		res = __d_alloc(root_inode->i_sb, &name);
		if (res)
			d_instantiate(res, root_inode);
		else
			iput(root_inode);
	}
	return res;
}
EXPORT_SYMBOL(d_make_root);

1513 1514 1515 1516
static struct dentry * __d_find_any_alias(struct inode *inode)
{
	struct dentry *alias;

A
Al Viro 已提交
1517
	if (hlist_empty(&inode->i_dentry))
1518
		return NULL;
A
Al Viro 已提交
1519
	alias = hlist_entry(inode->i_dentry.first, struct dentry, d_alias);
1520 1521 1522 1523
	__dget(alias);
	return alias;
}

1524 1525 1526 1527 1528 1529 1530 1531
/**
 * d_find_any_alias - find any alias for a given inode
 * @inode: inode to find an alias for
 *
 * If any aliases exist for the given inode, take and return a
 * reference for one of them.  If no aliases exist, return %NULL.
 */
struct dentry *d_find_any_alias(struct inode *inode)
1532 1533 1534 1535 1536 1537 1538 1539
{
	struct dentry *de;

	spin_lock(&inode->i_lock);
	de = __d_find_any_alias(inode);
	spin_unlock(&inode->i_lock);
	return de;
}
1540
EXPORT_SYMBOL(d_find_any_alias);
1541

1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554
/**
 * d_obtain_alias - find or allocate a dentry for a given inode
 * @inode: inode to allocate the dentry for
 *
 * Obtain a dentry for an inode resulting from NFS filehandle conversion or
 * similar open by handle operations.  The returned dentry may be anonymous,
 * or may have a full name (if the inode was already in the cache).
 *
 * When called on a directory inode, we must ensure that the inode only ever
 * has one dentry.  If a dentry is found, that is returned instead of
 * allocating a new one.
 *
 * On successful return, the reference to the inode has been transferred
1555 1556 1557 1558
 * to the dentry.  In case of an error the reference on the inode is released.
 * To make it easier to use in export operations a %NULL or IS_ERR inode may
 * be passed in and will be the error will be propagate to the return value,
 * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
1559 1560 1561
 */
struct dentry *d_obtain_alias(struct inode *inode)
{
1562
	static const struct qstr anonstring = QSTR_INIT("/", 1);
C
Christoph Hellwig 已提交
1563 1564
	struct dentry *tmp;
	struct dentry *res;
1565 1566

	if (!inode)
1567
		return ERR_PTR(-ESTALE);
1568 1569 1570
	if (IS_ERR(inode))
		return ERR_CAST(inode);

1571
	res = d_find_any_alias(inode);
C
Christoph Hellwig 已提交
1572 1573 1574
	if (res)
		goto out_iput;

1575
	tmp = __d_alloc(inode->i_sb, &anonstring);
C
Christoph Hellwig 已提交
1576 1577 1578
	if (!tmp) {
		res = ERR_PTR(-ENOMEM);
		goto out_iput;
1579
	}
N
Nick Piggin 已提交
1580

1581
	spin_lock(&inode->i_lock);
1582
	res = __d_find_any_alias(inode);
C
Christoph Hellwig 已提交
1583
	if (res) {
1584
		spin_unlock(&inode->i_lock);
C
Christoph Hellwig 已提交
1585 1586 1587 1588 1589 1590 1591 1592
		dput(tmp);
		goto out_iput;
	}

	/* attach a disconnected dentry */
	spin_lock(&tmp->d_lock);
	tmp->d_inode = inode;
	tmp->d_flags |= DCACHE_DISCONNECTED;
A
Al Viro 已提交
1593
	hlist_add_head(&tmp->d_alias, &inode->i_dentry);
1594
	hlist_bl_lock(&tmp->d_sb->s_anon);
1595
	hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
1596
	hlist_bl_unlock(&tmp->d_sb->s_anon);
C
Christoph Hellwig 已提交
1597
	spin_unlock(&tmp->d_lock);
1598
	spin_unlock(&inode->i_lock);
1599
	security_d_instantiate(tmp, inode);
C
Christoph Hellwig 已提交
1600 1601 1602 1603

	return tmp;

 out_iput:
1604 1605
	if (res && !IS_ERR(res))
		security_d_instantiate(res, inode);
C
Christoph Hellwig 已提交
1606 1607
	iput(inode);
	return res;
1608
}
1609
EXPORT_SYMBOL(d_obtain_alias);
L
Linus Torvalds 已提交
1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630

/**
 * d_splice_alias - splice a disconnected dentry into the tree if one exists
 * @inode:  the inode which may have a disconnected dentry
 * @dentry: a negative dentry which we want to point to the inode.
 *
 * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
 * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
 * and return it, else simply d_add the inode to the dentry and return NULL.
 *
 * This is needed in the lookup routine of any filesystem that is exportable
 * (via knfsd) so that we can build dcache paths to directories effectively.
 *
 * If a dentry was found and moved, then it is returned.  Otherwise NULL
 * is returned.  This matches the expected return value of ->lookup.
 *
 */
struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
{
	struct dentry *new = NULL;

1631 1632 1633
	if (IS_ERR(inode))
		return ERR_CAST(inode);

1634
	if (inode && S_ISDIR(inode->i_mode)) {
1635
		spin_lock(&inode->i_lock);
1636
		new = __d_find_alias(inode, 1);
L
Linus Torvalds 已提交
1637
		if (new) {
1638
			BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
1639
			spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
1640 1641 1642 1643
			security_d_instantiate(new, inode);
			d_move(new, dentry);
			iput(inode);
		} else {
1644
			/* already taking inode->i_lock, so d_add() by hand */
1645
			__d_instantiate(dentry, inode);
1646
			spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
1647 1648 1649 1650 1651 1652 1653
			security_d_instantiate(dentry, inode);
			d_rehash(dentry);
		}
	} else
		d_add(dentry, inode);
	return new;
}
1654
EXPORT_SYMBOL(d_splice_alias);
L
Linus Torvalds 已提交
1655

1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671
/**
 * d_add_ci - lookup or allocate new dentry with case-exact name
 * @inode:  the inode case-insensitive lookup has found
 * @dentry: the negative dentry that was passed to the parent's lookup func
 * @name:   the case-exact name to be associated with the returned dentry
 *
 * This is to avoid filling the dcache with case-insensitive names to the
 * same inode, only the actual correct case is stored in the dcache for
 * case-insensitive filesystems.
 *
 * For a case-insensitive lookup match and if the the case-exact dentry
 * already exists in in the dcache, use it and return it.
 *
 * If no entry exists with the exact case name, allocate new dentry with
 * the exact case, and return the spliced entry.
 */
1672
struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
1673 1674 1675 1676 1677 1678
			struct qstr *name)
{
	int error;
	struct dentry *found;
	struct dentry *new;

C
Christoph Hellwig 已提交
1679 1680 1681 1682
	/*
	 * First check if a dentry matching the name already exists,
	 * if not go ahead and create it now.
	 */
1683 1684 1685 1686 1687 1688 1689
	found = d_hash_and_lookup(dentry->d_parent, name);
	if (!found) {
		new = d_alloc(dentry->d_parent, name);
		if (!new) {
			error = -ENOMEM;
			goto err_out;
		}
C
Christoph Hellwig 已提交
1690

1691 1692 1693 1694 1695 1696 1697
		found = d_splice_alias(inode, new);
		if (found) {
			dput(new);
			return found;
		}
		return new;
	}
C
Christoph Hellwig 已提交
1698 1699 1700 1701 1702 1703 1704

	/*
	 * If a matching dentry exists, and it's not negative use it.
	 *
	 * Decrement the reference count to balance the iget() done
	 * earlier on.
	 */
1705 1706 1707 1708 1709 1710 1711 1712 1713
	if (found->d_inode) {
		if (unlikely(found->d_inode != inode)) {
			/* This can't happen because bad inodes are unhashed. */
			BUG_ON(!is_bad_inode(inode));
			BUG_ON(!is_bad_inode(found->d_inode));
		}
		iput(inode);
		return found;
	}
C
Christoph Hellwig 已提交
1714

1715 1716
	/*
	 * Negative dentry: instantiate it unless the inode is a directory and
C
Christoph Hellwig 已提交
1717
	 * already has a dentry.
1718
	 */
1719 1720 1721 1722
	new = d_splice_alias(inode, found);
	if (new) {
		dput(found);
		found = new;
1723
	}
1724
	return found;
1725 1726 1727 1728 1729

err_out:
	iput(inode);
	return ERR_PTR(error);
}
1730
EXPORT_SYMBOL(d_add_ci);
L
Linus Torvalds 已提交
1731

1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773
/*
 * Do the slow-case of the dentry name compare.
 *
 * Unlike the dentry_cmp() function, we need to atomically
 * load the name, length and inode information, so that the
 * filesystem can rely on them, and can use the 'name' and
 * 'len' information without worrying about walking off the
 * end of memory etc.
 *
 * Thus the read_seqcount_retry() and the "duplicate" info
 * in arguments (the low-level filesystem should not look
 * at the dentry inode or name contents directly, since
 * rename can change them while we're in RCU mode).
 */
enum slow_d_compare {
	D_COMP_OK,
	D_COMP_NOMATCH,
	D_COMP_SEQRETRY,
};

static noinline enum slow_d_compare slow_dentry_cmp(
		const struct dentry *parent,
		struct inode *inode,
		struct dentry *dentry,
		unsigned int seq,
		const struct qstr *name)
{
	int tlen = dentry->d_name.len;
	const char *tname = dentry->d_name.name;
	struct inode *i = dentry->d_inode;

	if (read_seqcount_retry(&dentry->d_seq, seq)) {
		cpu_relax();
		return D_COMP_SEQRETRY;
	}
	if (parent->d_op->d_compare(parent, inode,
				dentry, i,
				tlen, tname, name))
		return D_COMP_NOMATCH;
	return D_COMP_OK;
}

N
Nick Piggin 已提交
1774 1775 1776 1777
/**
 * __d_lookup_rcu - search for a dentry (racy, store-free)
 * @parent: parent dentry
 * @name: qstr of name we wish to find
1778
 * @seqp: returns d_seq value at the point where the dentry was found
N
Nick Piggin 已提交
1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799
 * @inode: returns dentry->d_inode when the inode was found valid.
 * Returns: dentry, or NULL
 *
 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
 * resolution (store-free path walking) design described in
 * Documentation/filesystems/path-lookup.txt.
 *
 * This is not to be used outside core vfs.
 *
 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
 * held, and rcu_read_lock held. The returned dentry must not be stored into
 * without taking d_lock and checking d_seq sequence count against @seq
 * returned here.
 *
 * A refcount may be taken on the found dentry with the __d_rcu_to_refcount
 * function.
 *
 * Alternatively, __d_lookup_rcu may be called again to look up the child of
 * the returned dentry, so long as its parent's seqlock is checked after the
 * child is looked up. Thus, an interlocking stepping of sequence lock checks
 * is formed, giving integrity down the path walk.
1800 1801 1802
 *
 * NOTE! The caller *has* to check the resulting dentry against the sequence
 * number we've returned before using any of the resulting dentry state!
N
Nick Piggin 已提交
1803
 */
1804 1805
struct dentry *__d_lookup_rcu(const struct dentry *parent,
				const struct qstr *name,
1806
				unsigned *seqp, struct inode *inode)
N
Nick Piggin 已提交
1807
{
1808
	u64 hashlen = name->hash_len;
N
Nick Piggin 已提交
1809
	const unsigned char *str = name->name;
1810
	struct hlist_bl_head *b = d_hash(parent, hashlen_hash(hashlen));
1811
	struct hlist_bl_node *node;
N
Nick Piggin 已提交
1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831
	struct dentry *dentry;

	/*
	 * Note: There is significant duplication with __d_lookup_rcu which is
	 * required to prevent single threaded performance regressions
	 * especially on architectures where smp_rmb (in seqcounts) are costly.
	 * Keep the two functions in sync.
	 */

	/*
	 * The hash list is protected using RCU.
	 *
	 * Carefully use d_seq when comparing a candidate dentry, to avoid
	 * races with d_move().
	 *
	 * It is possible that concurrent renames can mess up our list
	 * walk here and result in missing our dentry, resulting in the
	 * false-negative result. d_lookup() protects against concurrent
	 * renames using rename_lock seqlock.
	 *
1832
	 * See Documentation/filesystems/path-lookup.txt for more details.
N
Nick Piggin 已提交
1833
	 */
1834
	hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
1835
		unsigned seq;
N
Nick Piggin 已提交
1836 1837

seqretry:
1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853
		/*
		 * The dentry sequence count protects us from concurrent
		 * renames, and thus protects inode, parent and name fields.
		 *
		 * The caller must perform a seqcount check in order
		 * to do anything useful with the returned dentry,
		 * including using the 'd_inode' pointer.
		 *
		 * NOTE! We do a "raw" seqcount_begin here. That means that
		 * we don't wait for the sequence count to stabilize if it
		 * is in the middle of a sequence change. If we do the slow
		 * dentry compare, we will do seqretries until it is stable,
		 * and if we end up with a successful lookup, we actually
		 * want to exit RCU lookup anyway.
		 */
		seq = raw_seqcount_begin(&dentry->d_seq);
N
Nick Piggin 已提交
1854 1855
		if (dentry->d_parent != parent)
			continue;
1856 1857
		if (d_unhashed(dentry))
			continue;
1858 1859
		*seqp = seq;

1860
		if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
1861 1862
			if (dentry->d_name.hash != hashlen_hash(hashlen))
				continue;
1863 1864 1865 1866
			switch (slow_dentry_cmp(parent, inode, dentry, seq, name)) {
			case D_COMP_OK:
				return dentry;
			case D_COMP_NOMATCH:
N
Nick Piggin 已提交
1867
				continue;
1868 1869 1870
			default:
				goto seqretry;
			}
N
Nick Piggin 已提交
1871
		}
1872

1873
		if (dentry->d_name.hash_len != hashlen)
1874
			continue;
1875
		if (!dentry_cmp(dentry, str, hashlen_len(hashlen)))
1876
			return dentry;
N
Nick Piggin 已提交
1877 1878 1879 1880
	}
	return NULL;
}

L
Linus Torvalds 已提交
1881 1882 1883 1884
/**
 * d_lookup - search for a dentry
 * @parent: parent dentry
 * @name: qstr of name we wish to find
1885
 * Returns: dentry, or NULL
L
Linus Torvalds 已提交
1886
 *
1887 1888 1889 1890
 * d_lookup searches the children of the parent dentry for the name in
 * question. If the dentry is found its reference count is incremented and the
 * dentry is returned. The caller must use dput to free the entry when it has
 * finished using it. %NULL is returned if the dentry does not exist.
L
Linus Torvalds 已提交
1891
 */
A
Al Viro 已提交
1892
struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
L
Linus Torvalds 已提交
1893
{
N
Nick Piggin 已提交
1894
	struct dentry *dentry;
1895
	unsigned seq;
L
Linus Torvalds 已提交
1896 1897 1898 1899 1900 1901 1902 1903 1904

        do {
                seq = read_seqbegin(&rename_lock);
                dentry = __d_lookup(parent, name);
                if (dentry)
			break;
	} while (read_seqretry(&rename_lock, seq));
	return dentry;
}
1905
EXPORT_SYMBOL(d_lookup);
L
Linus Torvalds 已提交
1906

N
Nick Piggin 已提交
1907
/**
1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921
 * __d_lookup - search for a dentry (racy)
 * @parent: parent dentry
 * @name: qstr of name we wish to find
 * Returns: dentry, or NULL
 *
 * __d_lookup is like d_lookup, however it may (rarely) return a
 * false-negative result due to unrelated rename activity.
 *
 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
 * however it must be used carefully, eg. with a following d_lookup in
 * the case of failure.
 *
 * __d_lookup callers must be commented.
 */
A
Al Viro 已提交
1922
struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
L
Linus Torvalds 已提交
1923 1924 1925 1926
{
	unsigned int len = name->len;
	unsigned int hash = name->hash;
	const unsigned char *str = name->name;
1927
	struct hlist_bl_head *b = d_hash(parent, hash);
1928
	struct hlist_bl_node *node;
N
Nick Piggin 已提交
1929
	struct dentry *found = NULL;
1930
	struct dentry *dentry;
L
Linus Torvalds 已提交
1931

N
Nick Piggin 已提交
1932 1933 1934 1935 1936 1937 1938
	/*
	 * Note: There is significant duplication with __d_lookup_rcu which is
	 * required to prevent single threaded performance regressions
	 * especially on architectures where smp_rmb (in seqcounts) are costly.
	 * Keep the two functions in sync.
	 */

1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949
	/*
	 * The hash list is protected using RCU.
	 *
	 * Take d_lock when comparing a candidate dentry, to avoid races
	 * with d_move().
	 *
	 * It is possible that concurrent renames can mess up our list
	 * walk here and result in missing our dentry, resulting in the
	 * false-negative result. d_lookup() protects against concurrent
	 * renames using rename_lock seqlock.
	 *
1950
	 * See Documentation/filesystems/path-lookup.txt for more details.
1951
	 */
L
Linus Torvalds 已提交
1952 1953
	rcu_read_lock();
	
1954
	hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
L
Linus Torvalds 已提交
1955 1956 1957 1958 1959 1960 1961

		if (dentry->d_name.hash != hash)
			continue;

		spin_lock(&dentry->d_lock);
		if (dentry->d_parent != parent)
			goto next;
1962 1963 1964
		if (d_unhashed(dentry))
			goto next;

L
Linus Torvalds 已提交
1965 1966 1967 1968
		/*
		 * It is safe to compare names since d_move() cannot
		 * change the qstr (protected by d_lock).
		 */
1969
		if (parent->d_flags & DCACHE_OP_COMPARE) {
1970 1971
			int tlen = dentry->d_name.len;
			const char *tname = dentry->d_name.name;
N
Nick Piggin 已提交
1972 1973
			if (parent->d_op->d_compare(parent, parent->d_inode,
						dentry, dentry->d_inode,
N
Nick Piggin 已提交
1974
						tlen, tname, name))
L
Linus Torvalds 已提交
1975 1976
				goto next;
		} else {
1977 1978
			if (dentry->d_name.len != len)
				goto next;
1979
			if (dentry_cmp(dentry, str, len))
L
Linus Torvalds 已提交
1980 1981 1982
				goto next;
		}

N
Nick Piggin 已提交
1983
		dentry->d_count++;
1984
		found = dentry;
L
Linus Torvalds 已提交
1985 1986 1987 1988 1989 1990 1991 1992 1993 1994
		spin_unlock(&dentry->d_lock);
		break;
next:
		spin_unlock(&dentry->d_lock);
 	}
 	rcu_read_unlock();

 	return found;
}

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
/**
 * d_hash_and_lookup - hash the qstr then search for a dentry
 * @dir: Directory to search in
 * @name: qstr of name we wish to find
 *
 * On hash failure or on lookup failure NULL is returned.
 */
struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
{
	struct dentry *dentry = NULL;

	/*
	 * Check for a fs-specific hash function. Note that we must
	 * calculate the standard hash first, as the d_op->d_hash()
	 * routine may choose to leave the hash value unchanged.
	 */
	name->hash = full_name_hash(name->name, name->len);
2012
	if (dir->d_flags & DCACHE_OP_HASH) {
N
Nick Piggin 已提交
2013
		if (dir->d_op->d_hash(dir, dir->d_inode, name) < 0)
2014 2015 2016 2017 2018 2019 2020
			goto out;
	}
	dentry = d_lookup(dir, name);
out:
	return dentry;
}

L
Linus Torvalds 已提交
2021
/**
N
Nick Piggin 已提交
2022
 * d_validate - verify dentry provided from insecure source (deprecated)
L
Linus Torvalds 已提交
2023
 * @dentry: The dentry alleged to be valid child of @dparent
2024
 * @dparent: The parent dentry (known to be valid)
L
Linus Torvalds 已提交
2025 2026 2027 2028
 *
 * An insecure source has sent us a dentry, here we verify it and dget() it.
 * This is used by ncpfs in its readdir implementation.
 * Zero is returned in the dentry is invalid.
N
Nick Piggin 已提交
2029 2030
 *
 * This function is slow for big directories, and deprecated, do not use it.
L
Linus Torvalds 已提交
2031
 */
2032
int d_validate(struct dentry *dentry, struct dentry *dparent)
L
Linus Torvalds 已提交
2033
{
N
Nick Piggin 已提交
2034
	struct dentry *child;
2035

N
Nick Piggin 已提交
2036
	spin_lock(&dparent->d_lock);
N
Nick Piggin 已提交
2037 2038
	list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
		if (dentry == child) {
N
Nick Piggin 已提交
2039
			spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
2040
			__dget_dlock(dentry);
N
Nick Piggin 已提交
2041 2042
			spin_unlock(&dentry->d_lock);
			spin_unlock(&dparent->d_lock);
L
Linus Torvalds 已提交
2043 2044 2045
			return 1;
		}
	}
N
Nick Piggin 已提交
2046
	spin_unlock(&dparent->d_lock);
N
Nick Piggin 已提交
2047

L
Linus Torvalds 已提交
2048 2049
	return 0;
}
2050
EXPORT_SYMBOL(d_validate);
L
Linus Torvalds 已提交
2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074

/*
 * When a file is deleted, we have two options:
 * - turn this dentry into a negative dentry
 * - unhash this dentry and free it.
 *
 * Usually, we want to just turn this into
 * a negative dentry, but if anybody else is
 * currently using the dentry or the inode
 * we can't do that and we fall back on removing
 * it from the hash queues and waiting for
 * it to be deleted later when it has no users
 */
 
/**
 * d_delete - delete a dentry
 * @dentry: The dentry to delete
 *
 * Turn the dentry into a negative dentry if possible, otherwise
 * remove it from the hash queues so it can be deleted later
 */
 
void d_delete(struct dentry * dentry)
{
2075
	struct inode *inode;
2076
	int isdir = 0;
L
Linus Torvalds 已提交
2077 2078 2079
	/*
	 * Are we the only user?
	 */
2080
again:
L
Linus Torvalds 已提交
2081
	spin_lock(&dentry->d_lock);
2082 2083
	inode = dentry->d_inode;
	isdir = S_ISDIR(inode->i_mode);
N
Nick Piggin 已提交
2084
	if (dentry->d_count == 1) {
A
Alan Cox 已提交
2085
		if (!spin_trylock(&inode->i_lock)) {
2086 2087 2088 2089
			spin_unlock(&dentry->d_lock);
			cpu_relax();
			goto again;
		}
A
Al Viro 已提交
2090
		dentry->d_flags &= ~DCACHE_CANT_MOUNT;
N
Nick Piggin 已提交
2091
		dentry_unlink_inode(dentry);
2092
		fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
2093 2094 2095 2096 2097 2098 2099
		return;
	}

	if (!d_unhashed(dentry))
		__d_drop(dentry);

	spin_unlock(&dentry->d_lock);
2100 2101

	fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
2102
}
2103
EXPORT_SYMBOL(d_delete);
L
Linus Torvalds 已提交
2104

2105
static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
L
Linus Torvalds 已提交
2106
{
2107
	BUG_ON(!d_unhashed(entry));
2108
	hlist_bl_lock(b);
2109
	entry->d_flags |= DCACHE_RCUACCESS;
2110
	hlist_bl_add_head_rcu(&entry->d_hash, b);
2111
	hlist_bl_unlock(b);
L
Linus Torvalds 已提交
2112 2113
}

2114 2115 2116 2117 2118
static void _d_rehash(struct dentry * entry)
{
	__d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
}

L
Linus Torvalds 已提交
2119 2120 2121 2122 2123 2124 2125 2126 2127 2128
/**
 * d_rehash	- add an entry back to the hash
 * @entry: dentry to add to the hash
 *
 * Adds a dentry to the hash according to its name.
 */
 
void d_rehash(struct dentry * entry)
{
	spin_lock(&entry->d_lock);
2129
	_d_rehash(entry);
L
Linus Torvalds 已提交
2130 2131
	spin_unlock(&entry->d_lock);
}
2132
EXPORT_SYMBOL(d_rehash);
L
Linus Torvalds 已提交
2133

N
Nick Piggin 已提交
2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149
/**
 * dentry_update_name_case - update case insensitive dentry with a new name
 * @dentry: dentry to be updated
 * @name: new name
 *
 * Update a case insensitive dentry with new case of name.
 *
 * dentry must have been returned by d_lookup with name @name. Old and new
 * name lengths must match (ie. no d_compare which allows mismatched name
 * lengths).
 *
 * Parent inode i_mutex must be held over d_lookup and into this call (to
 * keep renames and concurrent inserts, and readdir(2) away).
 */
void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
{
2150
	BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));
N
Nick Piggin 已提交
2151 2152 2153
	BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */

	spin_lock(&dentry->d_lock);
N
Nick Piggin 已提交
2154
	write_seqcount_begin(&dentry->d_seq);
N
Nick Piggin 已提交
2155
	memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
N
Nick Piggin 已提交
2156
	write_seqcount_end(&dentry->d_seq);
N
Nick Piggin 已提交
2157 2158 2159 2160
	spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(dentry_update_name_case);

L
Linus Torvalds 已提交
2161 2162 2163 2164 2165 2166 2167
static void switch_names(struct dentry *dentry, struct dentry *target)
{
	if (dname_external(target)) {
		if (dname_external(dentry)) {
			/*
			 * Both external: swap the pointers
			 */
2168
			swap(target->d_name.name, dentry->d_name.name);
L
Linus Torvalds 已提交
2169 2170 2171 2172 2173
		} else {
			/*
			 * dentry:internal, target:external.  Steal target's
			 * storage and make target internal.
			 */
2174 2175
			memcpy(target->d_iname, dentry->d_name.name,
					dentry->d_name.len + 1);
L
Linus Torvalds 已提交
2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194
			dentry->d_name.name = target->d_name.name;
			target->d_name.name = target->d_iname;
		}
	} else {
		if (dname_external(dentry)) {
			/*
			 * dentry:external, target:internal.  Give dentry's
			 * storage to target and make dentry internal
			 */
			memcpy(dentry->d_iname, target->d_name.name,
					target->d_name.len + 1);
			target->d_name.name = dentry->d_name.name;
			dentry->d_name.name = dentry->d_iname;
		} else {
			/*
			 * Both are internal.  Just copy target to dentry
			 */
			memcpy(dentry->d_iname, target->d_name.name,
					target->d_name.len + 1);
2195 2196
			dentry->d_name.len = target->d_name.len;
			return;
L
Linus Torvalds 已提交
2197 2198
		}
	}
2199
	swap(dentry->d_name.len, target->d_name.len);
L
Linus Torvalds 已提交
2200 2201
}

N
Nick Piggin 已提交
2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237
static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
{
	/*
	 * XXXX: do we really need to take target->d_lock?
	 */
	if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent)
		spin_lock(&target->d_parent->d_lock);
	else {
		if (d_ancestor(dentry->d_parent, target->d_parent)) {
			spin_lock(&dentry->d_parent->d_lock);
			spin_lock_nested(&target->d_parent->d_lock,
						DENTRY_D_LOCK_NESTED);
		} else {
			spin_lock(&target->d_parent->d_lock);
			spin_lock_nested(&dentry->d_parent->d_lock,
						DENTRY_D_LOCK_NESTED);
		}
	}
	if (target < dentry) {
		spin_lock_nested(&target->d_lock, 2);
		spin_lock_nested(&dentry->d_lock, 3);
	} else {
		spin_lock_nested(&dentry->d_lock, 2);
		spin_lock_nested(&target->d_lock, 3);
	}
}

static void dentry_unlock_parents_for_move(struct dentry *dentry,
					struct dentry *target)
{
	if (target->d_parent != dentry->d_parent)
		spin_unlock(&dentry->d_parent->d_lock);
	if (target->d_parent != target)
		spin_unlock(&target->d_parent->d_lock);
}

L
Linus Torvalds 已提交
2238
/*
N
Nick Piggin 已提交
2239 2240 2241 2242 2243 2244 2245 2246 2247
 * When switching names, the actual string doesn't strictly have to
 * be preserved in the target - because we're dropping the target
 * anyway. As such, we can just do a simple memcpy() to copy over
 * the new name before we switch.
 *
 * Note that we have to be a lot more careful about getting the hash
 * switched - we have to switch the hash value properly even if it
 * then no longer matches the actual (corrupted) string of the target.
 * The hash value has to match the hash queue that the dentry is on..
L
Linus Torvalds 已提交
2248
 */
2249
/*
2250
 * __d_move - move a dentry
L
Linus Torvalds 已提交
2251 2252 2253 2254
 * @dentry: entry to move
 * @target: new dentry
 *
 * Update the dcache to reflect the move of a file name. Negative
2255 2256 2257
 * dcache entries should not be moved in this way. Caller must hold
 * rename_lock, the i_mutex of the source and target directories,
 * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
L
Linus Torvalds 已提交
2258
 */
2259
static void __d_move(struct dentry * dentry, struct dentry * target)
L
Linus Torvalds 已提交
2260 2261 2262 2263
{
	if (!dentry->d_inode)
		printk(KERN_WARNING "VFS: moving negative dcache entry\n");

N
Nick Piggin 已提交
2264 2265 2266 2267
	BUG_ON(d_ancestor(dentry, target));
	BUG_ON(d_ancestor(target, dentry));

	dentry_lock_for_move(dentry, target);
L
Linus Torvalds 已提交
2268

N
Nick Piggin 已提交
2269 2270 2271
	write_seqcount_begin(&dentry->d_seq);
	write_seqcount_begin(&target->d_seq);

2272 2273 2274 2275 2276 2277 2278
	/* __d_drop does write_seqcount_barrier, but they're OK to nest. */

	/*
	 * Move the dentry to the target hash queue. Don't bother checking
	 * for the same hash queue because of how unlikely it is.
	 */
	__d_drop(dentry);
N
Nick Piggin 已提交
2279
	__d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
L
Linus Torvalds 已提交
2280 2281 2282 2283

	/* Unhash the target: dput() will then get rid of it */
	__d_drop(target);

E
Eric Dumazet 已提交
2284 2285
	list_del(&dentry->d_u.d_child);
	list_del(&target->d_u.d_child);
L
Linus Torvalds 已提交
2286 2287 2288

	/* Switch the names.. */
	switch_names(dentry, target);
2289
	swap(dentry->d_name.hash, target->d_name.hash);
L
Linus Torvalds 已提交
2290 2291 2292 2293 2294

	/* ... and switch the parents */
	if (IS_ROOT(dentry)) {
		dentry->d_parent = target->d_parent;
		target->d_parent = target;
E
Eric Dumazet 已提交
2295
		INIT_LIST_HEAD(&target->d_u.d_child);
L
Linus Torvalds 已提交
2296
	} else {
2297
		swap(dentry->d_parent, target->d_parent);
L
Linus Torvalds 已提交
2298 2299

		/* And add them back to the (new) parent lists */
E
Eric Dumazet 已提交
2300
		list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
L
Linus Torvalds 已提交
2301 2302
	}

E
Eric Dumazet 已提交
2303
	list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
N
Nick Piggin 已提交
2304

N
Nick Piggin 已提交
2305 2306 2307
	write_seqcount_end(&target->d_seq);
	write_seqcount_end(&dentry->d_seq);

N
Nick Piggin 已提交
2308
	dentry_unlock_parents_for_move(dentry, target);
L
Linus Torvalds 已提交
2309
	spin_unlock(&target->d_lock);
2310
	fsnotify_d_move(dentry);
L
Linus Torvalds 已提交
2311
	spin_unlock(&dentry->d_lock);
2312 2313 2314 2315 2316 2317 2318 2319
}

/*
 * d_move - move a dentry
 * @dentry: entry to move
 * @target: new dentry
 *
 * Update the dcache to reflect the move of a file name. Negative
2320 2321
 * dcache entries should not be moved in this way. See the locking
 * requirements for __d_move.
2322 2323 2324 2325 2326
 */
void d_move(struct dentry *dentry, struct dentry *target)
{
	write_seqlock(&rename_lock);
	__d_move(dentry, target);
L
Linus Torvalds 已提交
2327
	write_sequnlock(&rename_lock);
2328
}
2329
EXPORT_SYMBOL(d_move);
L
Linus Torvalds 已提交
2330

2331 2332 2333 2334 2335 2336 2337
/**
 * d_ancestor - search for an ancestor
 * @p1: ancestor dentry
 * @p2: child dentry
 *
 * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
 * an ancestor of p2, else NULL.
2338
 */
2339
struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2340 2341 2342
{
	struct dentry *p;

2343
	for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2344
		if (p->d_parent == p1)
2345
			return p;
2346
	}
2347
	return NULL;
2348 2349 2350 2351 2352 2353
}

/*
 * This helper attempts to cope with remotely renamed directories
 *
 * It assumes that the caller is already holding
2354
 * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
2355 2356 2357 2358
 *
 * Note: If ever the locking in lock_rename() changes, then please
 * remember to update this too...
 */
2359 2360
static struct dentry *__d_unalias(struct inode *inode,
		struct dentry *dentry, struct dentry *alias)
2361 2362
{
	struct mutex *m1 = NULL, *m2 = NULL;
2363
	struct dentry *ret = ERR_PTR(-EBUSY);
2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376

	/* If alias and dentry share a parent, then no extra locks required */
	if (alias->d_parent == dentry->d_parent)
		goto out_unalias;

	/* See lock_rename() */
	if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
		goto out_err;
	m1 = &dentry->d_sb->s_vfs_rename_mutex;
	if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
		goto out_err;
	m2 = &alias->d_parent->d_inode->i_mutex;
out_unalias:
2377 2378 2379 2380
	if (likely(!d_mountpoint(alias))) {
		__d_move(alias, dentry);
		ret = alias;
	}
2381
out_err:
2382
	spin_unlock(&inode->i_lock);
2383 2384 2385 2386 2387 2388 2389
	if (m2)
		mutex_unlock(m2);
	if (m1)
		mutex_unlock(m1);
	return ret;
}

2390 2391 2392
/*
 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
 * named dentry in place of the dentry to be replaced.
N
Nick Piggin 已提交
2393
 * returns with anon->d_lock held!
2394 2395 2396 2397 2398
 */
static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
{
	struct dentry *dparent, *aparent;

N
Nick Piggin 已提交
2399
	dentry_lock_for_move(anon, dentry);
2400

N
Nick Piggin 已提交
2401 2402 2403
	write_seqcount_begin(&dentry->d_seq);
	write_seqcount_begin(&anon->d_seq);

2404 2405 2406
	dparent = dentry->d_parent;
	aparent = anon->d_parent;

N
Nick Piggin 已提交
2407 2408 2409
	switch_names(dentry, anon);
	swap(dentry->d_name.hash, anon->d_name.hash);

2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423
	dentry->d_parent = (aparent == anon) ? dentry : aparent;
	list_del(&dentry->d_u.d_child);
	if (!IS_ROOT(dentry))
		list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
	else
		INIT_LIST_HEAD(&dentry->d_u.d_child);

	anon->d_parent = (dparent == dentry) ? anon : dparent;
	list_del(&anon->d_u.d_child);
	if (!IS_ROOT(anon))
		list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
	else
		INIT_LIST_HEAD(&anon->d_u.d_child);

N
Nick Piggin 已提交
2424 2425 2426
	write_seqcount_end(&dentry->d_seq);
	write_seqcount_end(&anon->d_seq);

N
Nick Piggin 已提交
2427 2428 2429 2430
	dentry_unlock_parents_for_move(anon, dentry);
	spin_unlock(&dentry->d_lock);

	/* anon->d_lock still locked, returns locked */
2431 2432 2433 2434 2435 2436 2437 2438 2439
	anon->d_flags &= ~DCACHE_DISCONNECTED;
}

/**
 * d_materialise_unique - introduce an inode into the tree
 * @dentry: candidate dentry
 * @inode: inode to bind to the dentry, to which aliases may be attached
 *
 * Introduces an dentry into the tree, substituting an extant disconnected
2440 2441
 * root directory alias in its place if there is one. Caller must hold the
 * i_mutex of the parent directory.
2442 2443 2444
 */
struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
{
2445
	struct dentry *actual;
2446 2447 2448 2449 2450

	BUG_ON(!d_unhashed(dentry));

	if (!inode) {
		actual = dentry;
2451
		__d_instantiate(dentry, NULL);
2452 2453
		d_rehash(actual);
		goto out_nolock;
2454 2455
	}

2456
	spin_lock(&inode->i_lock);
2457

2458 2459 2460 2461
	if (S_ISDIR(inode->i_mode)) {
		struct dentry *alias;

		/* Does an aliased dentry already exist? */
2462
		alias = __d_find_alias(inode, 0);
2463 2464
		if (alias) {
			actual = alias;
2465 2466 2467 2468 2469
			write_seqlock(&rename_lock);

			if (d_ancestor(alias, dentry)) {
				/* Check for loops */
				actual = ERR_PTR(-ELOOP);
2470
				spin_unlock(&inode->i_lock);
2471 2472 2473
			} else if (IS_ROOT(alias)) {
				/* Is this an anonymous mountpoint that we
				 * could splice into our tree? */
2474
				__d_materialise_dentry(dentry, alias);
2475
				write_sequnlock(&rename_lock);
2476 2477
				__d_drop(alias);
				goto found;
2478 2479
			} else {
				/* Nope, but we must(!) avoid directory
2480
				 * aliasing. This drops inode->i_lock */
2481
				actual = __d_unalias(inode, dentry, alias);
2482
			}
2483
			write_sequnlock(&rename_lock);
2484 2485 2486 2487 2488 2489 2490 2491
			if (IS_ERR(actual)) {
				if (PTR_ERR(actual) == -ELOOP)
					pr_warn_ratelimited(
						"VFS: Lookup of '%s' in %s %s"
						" would have caused loop\n",
						dentry->d_name.name,
						inode->i_sb->s_type->name,
						inode->i_sb->s_id);
2492
				dput(alias);
2493
			}
2494 2495
			goto out_nolock;
		}
2496 2497 2498 2499 2500 2501
	}

	/* Add a unique reference */
	actual = __d_instantiate_unique(dentry, inode);
	if (!actual)
		actual = dentry;
2502 2503
	else
		BUG_ON(!d_unhashed(actual));
2504 2505 2506 2507 2508

	spin_lock(&actual->d_lock);
found:
	_d_rehash(actual);
	spin_unlock(&actual->d_lock);
2509
	spin_unlock(&inode->i_lock);
2510
out_nolock:
2511 2512 2513 2514 2515 2516 2517 2518
	if (actual == dentry) {
		security_d_instantiate(dentry, inode);
		return NULL;
	}

	iput(inode);
	return actual;
}
2519
EXPORT_SYMBOL_GPL(d_materialise_unique);
2520

2521
static int prepend(char **buffer, int *buflen, const char *str, int namelen)
2522 2523 2524 2525 2526 2527 2528 2529 2530
{
	*buflen -= namelen;
	if (*buflen < 0)
		return -ENAMETOOLONG;
	*buffer -= namelen;
	memcpy(*buffer, str, namelen);
	return 0;
}

2531 2532 2533 2534 2535
static int prepend_name(char **buffer, int *buflen, struct qstr *name)
{
	return prepend(buffer, buflen, name->name, name->len);
}

L
Linus Torvalds 已提交
2536
/**
2537
 * prepend_path - Prepend path string to a buffer
2538
 * @path: the dentry/vfsmount to report
2539
 * @root: root vfsmnt/dentry
M
Miklos Szeredi 已提交
2540 2541
 * @buffer: pointer to the end of the buffer
 * @buflen: pointer to buffer length
2542
 *
2543
 * Caller holds the rename_lock.
L
Linus Torvalds 已提交
2544
 */
2545 2546
static int prepend_path(const struct path *path,
			const struct path *root,
M
Miklos Szeredi 已提交
2547
			char **buffer, int *buflen)
L
Linus Torvalds 已提交
2548
{
2549 2550
	struct dentry *dentry = path->dentry;
	struct vfsmount *vfsmnt = path->mnt;
2551
	struct mount *mnt = real_mount(vfsmnt);
M
Miklos Szeredi 已提交
2552 2553
	bool slash = false;
	int error = 0;
2554

A
Andi Kleen 已提交
2555
	br_read_lock(&vfsmount_lock);
M
Miklos Szeredi 已提交
2556
	while (dentry != root->dentry || vfsmnt != root->mnt) {
L
Linus Torvalds 已提交
2557 2558 2559
		struct dentry * parent;

		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
2560
			/* Global root? */
2561
			if (!mnt_has_parent(mnt))
L
Linus Torvalds 已提交
2562
				goto global_root;
2563
			dentry = mnt->mnt_mountpoint;
2564 2565
			mnt = mnt->mnt_parent;
			vfsmnt = &mnt->mnt;
L
Linus Torvalds 已提交
2566 2567 2568 2569
			continue;
		}
		parent = dentry->d_parent;
		prefetch(parent);
N
Nick Piggin 已提交
2570
		spin_lock(&dentry->d_lock);
M
Miklos Szeredi 已提交
2571
		error = prepend_name(buffer, buflen, &dentry->d_name);
N
Nick Piggin 已提交
2572
		spin_unlock(&dentry->d_lock);
M
Miklos Szeredi 已提交
2573 2574 2575 2576 2577 2578
		if (!error)
			error = prepend(buffer, buflen, "/", 1);
		if (error)
			break;

		slash = true;
L
Linus Torvalds 已提交
2579 2580 2581
		dentry = parent;
	}

M
Miklos Szeredi 已提交
2582 2583 2584
	if (!error && !slash)
		error = prepend(buffer, buflen, "/", 1);

2585
out:
A
Andi Kleen 已提交
2586
	br_read_unlock(&vfsmount_lock);
M
Miklos Szeredi 已提交
2587
	return error;
L
Linus Torvalds 已提交
2588 2589

global_root:
2590 2591 2592 2593 2594 2595 2596 2597 2598
	/*
	 * Filesystems needing to implement special "root names"
	 * should do so with ->d_dname()
	 */
	if (IS_ROOT(dentry) &&
	    (dentry->d_name.len != 1 || dentry->d_name.name[0] != '/')) {
		WARN(1, "Root dentry has weird name <%.*s>\n",
		     (int) dentry->d_name.len, dentry->d_name.name);
	}
2599 2600 2601
	if (!slash)
		error = prepend(buffer, buflen, "/", 1);
	if (!error)
A
Al Viro 已提交
2602
		error = is_mounted(vfsmnt) ? 1 : 2;
2603
	goto out;
M
Miklos Szeredi 已提交
2604
}
2605

M
Miklos Szeredi 已提交
2606 2607 2608
/**
 * __d_path - return the path of a dentry
 * @path: the dentry/vfsmount to report
2609
 * @root: root vfsmnt/dentry
2610
 * @buf: buffer to return value in
M
Miklos Szeredi 已提交
2611 2612
 * @buflen: buffer length
 *
2613
 * Convert a dentry into an ASCII path name.
M
Miklos Szeredi 已提交
2614 2615 2616 2617
 *
 * Returns a pointer into the buffer or an error code if the
 * path was too long.
 *
2618
 * "buflen" should be positive.
M
Miklos Szeredi 已提交
2619
 *
2620
 * If the path is not reachable from the supplied root, return %NULL.
M
Miklos Szeredi 已提交
2621
 */
2622 2623
char *__d_path(const struct path *path,
	       const struct path *root,
M
Miklos Szeredi 已提交
2624 2625 2626 2627 2628 2629
	       char *buf, int buflen)
{
	char *res = buf + buflen;
	int error;

	prepend(&res, &buflen, "\0", 1);
2630
	write_seqlock(&rename_lock);
M
Miklos Szeredi 已提交
2631
	error = prepend_path(path, root, &res, &buflen);
2632
	write_sequnlock(&rename_lock);
2633

2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655
	if (error < 0)
		return ERR_PTR(error);
	if (error > 0)
		return NULL;
	return res;
}

char *d_absolute_path(const struct path *path,
	       char *buf, int buflen)
{
	struct path root = {};
	char *res = buf + buflen;
	int error;

	prepend(&res, &buflen, "\0", 1);
	write_seqlock(&rename_lock);
	error = prepend_path(path, &root, &res, &buflen);
	write_sequnlock(&rename_lock);

	if (error > 1)
		error = -EINVAL;
	if (error < 0)
M
Miklos Szeredi 已提交
2656 2657
		return ERR_PTR(error);
	return res;
L
Linus Torvalds 已提交
2658 2659
}

2660 2661 2662
/*
 * same as __d_path but appends "(deleted)" for unlinked files.
 */
2663 2664 2665
static int path_with_deleted(const struct path *path,
			     const struct path *root,
			     char **buf, int *buflen)
2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676
{
	prepend(buf, buflen, "\0", 1);
	if (d_unlinked(path->dentry)) {
		int error = prepend(buf, buflen, " (deleted)", 10);
		if (error)
			return error;
	}

	return prepend_path(path, root, buf, buflen);
}

2677 2678 2679 2680 2681
static int prepend_unreachable(char **buffer, int *buflen)
{
	return prepend(buffer, buflen, "(unreachable)", 13);
}

J
Jan Blunck 已提交
2682 2683
/**
 * d_path - return the path of a dentry
2684
 * @path: path to report
J
Jan Blunck 已提交
2685 2686 2687 2688 2689 2690
 * @buf: buffer to return value in
 * @buflen: buffer length
 *
 * Convert a dentry into an ASCII path name. If the entry has been deleted
 * the string " (deleted)" is appended. Note that this is ambiguous.
 *
2691 2692 2693 2694
 * Returns a pointer into the buffer or an error code if the path was
 * too long. Note: Callers should use the returned pointer, not the passed
 * in buffer, to use the name! The implementation often starts at an offset
 * into the buffer, and may leave 0 bytes at the start.
J
Jan Blunck 已提交
2695
 *
2696
 * "buflen" should be positive.
J
Jan Blunck 已提交
2697
 */
2698
char *d_path(const struct path *path, char *buf, int buflen)
L
Linus Torvalds 已提交
2699
{
2700
	char *res = buf + buflen;
J
Jan Blunck 已提交
2701
	struct path root;
2702
	int error;
L
Linus Torvalds 已提交
2703

2704 2705 2706 2707 2708 2709 2710
	/*
	 * We have various synthetic filesystems that never get mounted.  On
	 * these filesystems dentries are never used for lookup purposes, and
	 * thus don't need to be hashed.  They also don't need a name until a
	 * user wants to identify the object in /proc/pid/fd/.  The little hack
	 * below allows us to generate a name for these objects on demand:
	 */
2711 2712
	if (path->dentry->d_op && path->dentry->d_op->d_dname)
		return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2713

2714
	get_fs_root(current->fs, &root);
2715
	write_seqlock(&rename_lock);
2716 2717
	error = path_with_deleted(path, &root, &res, &buflen);
	if (error < 0)
2718
		res = ERR_PTR(error);
2719
	write_sequnlock(&rename_lock);
J
Jan Blunck 已提交
2720
	path_put(&root);
L
Linus Torvalds 已提交
2721 2722
	return res;
}
2723
EXPORT_SYMBOL(d_path);
L
Linus Torvalds 已提交
2724

2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745
/*
 * Helper function for dentry_operations.d_dname() members
 */
char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
			const char *fmt, ...)
{
	va_list args;
	char temp[64];
	int sz;

	va_start(args, fmt);
	sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
	va_end(args);

	if (sz > sizeof(temp) || sz > buflen)
		return ERR_PTR(-ENAMETOOLONG);

	buffer += buflen - sz;
	return memcpy(buffer, temp, sz);
}

2746 2747 2748
/*
 * Write full pathname from the root of the filesystem into the buffer.
 */
N
Nick Piggin 已提交
2749
static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760
{
	char *end = buf + buflen;
	char *retval;

	prepend(&end, &buflen, "\0", 1);
	if (buflen < 1)
		goto Elong;
	/* Get '/' right */
	retval = end-1;
	*retval = '/';

2761 2762
	while (!IS_ROOT(dentry)) {
		struct dentry *parent = dentry->d_parent;
N
Nick Piggin 已提交
2763
		int error;
2764 2765

		prefetch(parent);
N
Nick Piggin 已提交
2766 2767 2768 2769
		spin_lock(&dentry->d_lock);
		error = prepend_name(&end, &buflen, &dentry->d_name);
		spin_unlock(&dentry->d_lock);
		if (error != 0 || prepend(&end, &buflen, "/", 1) != 0)
2770 2771 2772 2773 2774
			goto Elong;

		retval = end;
		dentry = parent;
	}
A
Al Viro 已提交
2775 2776 2777 2778
	return retval;
Elong:
	return ERR_PTR(-ENAMETOOLONG);
}
N
Nick Piggin 已提交
2779 2780 2781 2782 2783

char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
{
	char *retval;

2784
	write_seqlock(&rename_lock);
N
Nick Piggin 已提交
2785
	retval = __dentry_path(dentry, buf, buflen);
2786
	write_sequnlock(&rename_lock);
N
Nick Piggin 已提交
2787 2788 2789 2790

	return retval;
}
EXPORT_SYMBOL(dentry_path_raw);
A
Al Viro 已提交
2791 2792 2793 2794 2795 2796

char *dentry_path(struct dentry *dentry, char *buf, int buflen)
{
	char *p = NULL;
	char *retval;

2797
	write_seqlock(&rename_lock);
A
Al Viro 已提交
2798 2799 2800 2801 2802 2803 2804
	if (d_unlinked(dentry)) {
		p = buf + buflen;
		if (prepend(&p, &buflen, "//deleted", 10) != 0)
			goto Elong;
		buflen++;
	}
	retval = __dentry_path(dentry, buf, buflen);
2805
	write_sequnlock(&rename_lock);
A
Al Viro 已提交
2806 2807
	if (!IS_ERR(retval) && p)
		*p = '/';	/* restore '/' overriden with '\0' */
2808 2809 2810 2811 2812
	return retval;
Elong:
	return ERR_PTR(-ENAMETOOLONG);
}

L
Linus Torvalds 已提交
2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830
/*
 * NOTE! The user-level library version returns a
 * character pointer. The kernel system call just
 * returns the length of the buffer filled (which
 * includes the ending '\0' character), or a negative
 * error value. So libc would do something like
 *
 *	char *getcwd(char * buf, size_t size)
 *	{
 *		int retval;
 *
 *		retval = sys_getcwd(buf, size);
 *		if (retval >= 0)
 *			return buf;
 *		errno = -retval;
 *		return NULL;
 *	}
 */
2831
SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
L
Linus Torvalds 已提交
2832
{
2833
	int error;
J
Jan Blunck 已提交
2834
	struct path pwd, root;
2835
	char *page = (char *) __get_free_page(GFP_USER);
L
Linus Torvalds 已提交
2836 2837 2838 2839

	if (!page)
		return -ENOMEM;

2840
	get_fs_root_and_pwd(current->fs, &root, &pwd);
L
Linus Torvalds 已提交
2841

2842
	error = -ENOENT;
2843
	write_seqlock(&rename_lock);
2844
	if (!d_unlinked(pwd.dentry)) {
2845
		unsigned long len;
2846 2847
		char *cwd = page + PAGE_SIZE;
		int buflen = PAGE_SIZE;
L
Linus Torvalds 已提交
2848

2849
		prepend(&cwd, &buflen, "\0", 1);
2850
		error = prepend_path(&pwd, &root, &cwd, &buflen);
2851
		write_sequnlock(&rename_lock);
2852

2853
		if (error < 0)
2854 2855
			goto out;

2856
		/* Unreachable from current root */
2857
		if (error > 0) {
2858 2859 2860 2861 2862
			error = prepend_unreachable(&cwd, &buflen);
			if (error)
				goto out;
		}

2863 2864 2865 2866 2867 2868 2869
		error = -ERANGE;
		len = PAGE_SIZE + page - cwd;
		if (len <= size) {
			error = len;
			if (copy_to_user(buf, cwd, len))
				error = -EFAULT;
		}
2870 2871 2872
	} else {
		write_sequnlock(&rename_lock);
	}
L
Linus Torvalds 已提交
2873 2874

out:
J
Jan Blunck 已提交
2875 2876
	path_put(&pwd);
	path_put(&root);
L
Linus Torvalds 已提交
2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896
	free_page((unsigned long) page);
	return error;
}

/*
 * Test whether new_dentry is a subdirectory of old_dentry.
 *
 * Trivially implemented using the dcache structure
 */

/**
 * is_subdir - is new dentry a subdirectory of old_dentry
 * @new_dentry: new dentry
 * @old_dentry: old dentry
 *
 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
 * Returns 0 otherwise.
 * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
 */
  
2897
int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
L
Linus Torvalds 已提交
2898 2899
{
	int result;
2900
	unsigned seq;
L
Linus Torvalds 已提交
2901

2902 2903 2904 2905
	if (new_dentry == old_dentry)
		return 1;

	do {
L
Linus Torvalds 已提交
2906 2907
		/* for restarting inner loop in case of seq retry */
		seq = read_seqbegin(&rename_lock);
2908 2909 2910 2911 2912
		/*
		 * Need rcu_readlock to protect against the d_parent trashing
		 * due to d_move
		 */
		rcu_read_lock();
2913
		if (d_ancestor(old_dentry, new_dentry))
L
Linus Torvalds 已提交
2914
			result = 1;
2915 2916
		else
			result = 0;
2917
		rcu_read_unlock();
L
Linus Torvalds 已提交
2918 2919 2920 2921 2922 2923 2924
	} while (read_seqretry(&rename_lock, seq));

	return result;
}

void d_genocide(struct dentry *root)
{
2925
	struct dentry *this_parent;
L
Linus Torvalds 已提交
2926
	struct list_head *next;
2927
	unsigned seq;
2928
	int locked = 0;
L
Linus Torvalds 已提交
2929

2930
	seq = read_seqbegin(&rename_lock);
2931 2932
again:
	this_parent = root;
N
Nick Piggin 已提交
2933
	spin_lock(&this_parent->d_lock);
L
Linus Torvalds 已提交
2934 2935 2936 2937 2938
repeat:
	next = this_parent->d_subdirs.next;
resume:
	while (next != &this_parent->d_subdirs) {
		struct list_head *tmp = next;
E
Eric Dumazet 已提交
2939
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
2940
		next = tmp->next;
2941

N
Nick Piggin 已提交
2942 2943 2944
		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
		if (d_unhashed(dentry) || !dentry->d_inode) {
			spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
2945
			continue;
N
Nick Piggin 已提交
2946
		}
L
Linus Torvalds 已提交
2947
		if (!list_empty(&dentry->d_subdirs)) {
N
Nick Piggin 已提交
2948 2949
			spin_unlock(&this_parent->d_lock);
			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
L
Linus Torvalds 已提交
2950
			this_parent = dentry;
N
Nick Piggin 已提交
2951
			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
L
Linus Torvalds 已提交
2952 2953
			goto repeat;
		}
2954 2955 2956 2957
		if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
			dentry->d_flags |= DCACHE_GENOCIDE;
			dentry->d_count--;
		}
N
Nick Piggin 已提交
2958
		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
2959 2960
	}
	if (this_parent != root) {
2961
		struct dentry *child = this_parent;
2962 2963 2964 2965
		if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
			this_parent->d_flags |= DCACHE_GENOCIDE;
			this_parent->d_count--;
		}
2966 2967
		this_parent = try_to_ascend(this_parent, locked, seq);
		if (!this_parent)
2968 2969
			goto rename_retry;
		next = child->d_u.d_child.next;
L
Linus Torvalds 已提交
2970 2971
		goto resume;
	}
N
Nick Piggin 已提交
2972
	spin_unlock(&this_parent->d_lock);
2973
	if (!locked && read_seqretry(&rename_lock, seq))
2974
		goto rename_retry;
2975 2976 2977 2978 2979
	if (locked)
		write_sequnlock(&rename_lock);
	return;

rename_retry:
2980 2981
	if (locked)
		goto again;
2982 2983 2984
	locked = 1;
	write_seqlock(&rename_lock);
	goto again;
L
Linus Torvalds 已提交
2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005
}

/**
 * find_inode_number - check for dentry with name
 * @dir: directory to check
 * @name: Name to find.
 *
 * Check whether a dentry already exists for the given name,
 * and return the inode number if it has an inode. Otherwise
 * 0 is returned.
 *
 * This routine is used to post-process directory listings for
 * filesystems using synthetic inode numbers, and is necessary
 * to keep getcwd() working.
 */
 
ino_t find_inode_number(struct dentry *dir, struct qstr *name)
{
	struct dentry * dentry;
	ino_t ino = 0;

3006 3007
	dentry = d_hash_and_lookup(dir, name);
	if (dentry) {
L
Linus Torvalds 已提交
3008 3009 3010 3011 3012 3013
		if (dentry->d_inode)
			ino = dentry->d_inode->i_ino;
		dput(dentry);
	}
	return ino;
}
3014
EXPORT_SYMBOL(find_inode_number);
L
Linus Torvalds 已提交
3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027

static __initdata unsigned long dhash_entries;
static int __init set_dhash_entries(char *str)
{
	if (!str)
		return 0;
	dhash_entries = simple_strtoul(str, &str, 0);
	return 1;
}
__setup("dhash_entries=", set_dhash_entries);

static void __init dcache_init_early(void)
{
3028
	unsigned int loop;
L
Linus Torvalds 已提交
3029 3030 3031 3032 3033 3034 3035 3036 3037

	/* If hashes are distributed across NUMA nodes, defer
	 * hash allocation until vmalloc space is available.
	 */
	if (hashdist)
		return;

	dentry_hashtable =
		alloc_large_system_hash("Dentry cache",
3038
					sizeof(struct hlist_bl_head),
L
Linus Torvalds 已提交
3039 3040 3041 3042 3043
					dhash_entries,
					13,
					HASH_EARLY,
					&d_hash_shift,
					&d_hash_mask,
3044
					0,
L
Linus Torvalds 已提交
3045 3046
					0);

3047
	for (loop = 0; loop < (1U << d_hash_shift); loop++)
3048
		INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
L
Linus Torvalds 已提交
3049 3050
}

3051
static void __init dcache_init(void)
L
Linus Torvalds 已提交
3052
{
3053
	unsigned int loop;
L
Linus Torvalds 已提交
3054 3055 3056 3057 3058 3059

	/* 
	 * A constructor could be added for stable state like the lists,
	 * but it is probably not worth it because of the cache nature
	 * of the dcache. 
	 */
3060 3061
	dentry_cache = KMEM_CACHE(dentry,
		SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
L
Linus Torvalds 已提交
3062 3063 3064 3065 3066 3067 3068

	/* Hash may have been set up in dcache_init_early */
	if (!hashdist)
		return;

	dentry_hashtable =
		alloc_large_system_hash("Dentry cache",
3069
					sizeof(struct hlist_bl_head),
L
Linus Torvalds 已提交
3070 3071 3072 3073 3074
					dhash_entries,
					13,
					0,
					&d_hash_shift,
					&d_hash_mask,
3075
					0,
L
Linus Torvalds 已提交
3076 3077
					0);

3078
	for (loop = 0; loop < (1U << d_hash_shift); loop++)
3079
		INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
L
Linus Torvalds 已提交
3080 3081 3082
}

/* SLAB cache for __getname() consumers */
3083
struct kmem_cache *names_cachep __read_mostly;
3084
EXPORT_SYMBOL(names_cachep);
L
Linus Torvalds 已提交
3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104

EXPORT_SYMBOL(d_genocide);

void __init vfs_caches_init_early(void)
{
	dcache_init_early();
	inode_init_early();
}

void __init vfs_caches_init(unsigned long mempages)
{
	unsigned long reserve;

	/* Base hash sizes on available memory, with a reserve equal to
           150% of current kernel size */

	reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
	mempages -= reserve;

	names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
3105
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
L
Linus Torvalds 已提交
3106

3107 3108
	dcache_init();
	inode_init();
L
Linus Torvalds 已提交
3109
	files_init(mempages);
3110
	mnt_init();
L
Linus Torvalds 已提交
3111 3112 3113
	bdev_cache_init();
	chrdev_init();
}