dcache.c 80.3 KB
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/*
 * 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>
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#include <linux/fsnotify.h>
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#include <linux/slab.h>
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/cache.h>
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#include <linux/export.h>
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#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>
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#include <linux/fs_struct.h>
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#include <linux/hardirq.h>
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#include <linux/bit_spinlock.h>
#include <linux/rculist_bl.h>
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#include <linux/prefetch.h>
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#include <linux/ratelimit.h>
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#include "internal.h"
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#include "mount.h"
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/*
 * Usage:
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 * dcache->d_inode->i_lock protects:
 *   - i_dentry, d_alias, d_inode of aliases
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 * dcache_hash_bucket lock protects:
 *   - the dcache hash table
 * s_anon bl list spinlock protects:
 *   - the s_anon list (see __d_drop)
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 * dcache_lru_lock protects:
 *   - the dcache lru lists and counters
 * d_lock protects:
 *   - d_flags
 *   - d_name
 *   - d_lru
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 *   - d_count
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 *   - d_unhashed()
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 *   - d_parent and d_subdirs
 *   - childrens' d_child and d_parent
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 *   - d_alias, d_inode
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 *
 * Ordering:
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 * dentry->d_inode->i_lock
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 *   dentry->d_lock
 *     dcache_lru_lock
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 *     dcache_hash_bucket lock
 *     s_anon lock
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 *
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 * 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:
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 * if (dentry1 < dentry2)
 *   dentry1->d_lock
 *     dentry2->d_lock
 */
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int sysctl_vfs_cache_pressure __read_mostly = 100;
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EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);

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static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
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__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
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EXPORT_SYMBOL(rename_lock);
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static struct kmem_cache *dentry_cache __read_mostly;
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/*
 * 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

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static unsigned int d_hash_mask __read_mostly;
static unsigned int d_hash_shift __read_mostly;
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static struct hlist_bl_head *dentry_hashtable __read_mostly;
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static inline struct hlist_bl_head *d_hash(const struct dentry *parent,
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					unsigned int hash)
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{
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	hash += (unsigned long) parent / L1_CACHE_BYTES;
	hash = hash + (hash >> D_HASHBITS);
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	return dentry_hashtable + (hash & D_HASHMASK);
}

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/* Statistics gathering. */
struct dentry_stat_t dentry_stat = {
	.age_limit = 45,
};

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static DEFINE_PER_CPU(unsigned int, nr_dentry);
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#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
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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;
}

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int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
		   size_t *lenp, loff_t *ppos)
{
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	dentry_stat.nr_dentry = get_nr_dentry();
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	return proc_dointvec(table, write, buffer, lenp, ppos);
}
#endif

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/*
 * Compare 2 name strings, return 0 if they match, otherwise non-zero.
 * The strings are both count bytes long, and count is non-zero.
 */
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#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.
 */
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static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
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{
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	unsigned long a,b,mask;

	for (;;) {
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		a = *(unsigned long *)cs;
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		b = load_unaligned_zeropad(ct);
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		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));
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}

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#else
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static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
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{
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	do {
		if (*cs != *ct)
			return 1;
		cs++;
		ct++;
		tcount--;
	} while (tcount);
	return 0;
}

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#endif

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static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
{
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	const unsigned char *cs;
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	/*
	 * 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)
	 */
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	cs = ACCESS_ONCE(dentry->d_name.name);
	smp_read_barrier_depends();
	return dentry_string_cmp(cs, ct, tcount);
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}

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static void __d_free(struct rcu_head *head)
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{
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	struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);

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	WARN_ON(!hlist_unhashed(&dentry->d_alias));
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	if (dname_external(dentry))
		kfree(dentry->d_name.name);
	kmem_cache_free(dentry_cache, dentry); 
}

/*
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 * no locks, please.
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 */
static void d_free(struct dentry *dentry)
{
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	BUG_ON(dentry->d_lockref.count);
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	this_cpu_dec(nr_dentry);
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	if (dentry->d_op && dentry->d_op->d_release)
		dentry->d_op->d_release(dentry);
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	/* if dentry was never visible to RCU, immediate free is OK */
	if (!(dentry->d_flags & DCACHE_RCUACCESS))
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		__d_free(&dentry->d_u.d_rcu);
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	else
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		call_rcu(&dentry->d_u.d_rcu, __d_free);
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}

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/**
 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
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 * @dentry: the target dentry
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 * 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);
}

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/*
 * Release the dentry's inode, using the filesystem
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 * d_iput() operation if defined. Dentry has no refcount
 * and is unhashed.
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 */
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static void dentry_iput(struct dentry * dentry)
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	__releases(dentry->d_lock)
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	__releases(dentry->d_inode->i_lock)
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{
	struct inode *inode = dentry->d_inode;
	if (inode) {
		dentry->d_inode = NULL;
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		hlist_del_init(&dentry->d_alias);
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		spin_unlock(&dentry->d_lock);
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		spin_unlock(&inode->i_lock);
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		if (!inode->i_nlink)
			fsnotify_inoderemove(inode);
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		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);
	}
}

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/*
 * 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)
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	__releases(dentry->d_inode->i_lock)
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{
	struct inode *inode = dentry->d_inode;
	dentry->d_inode = NULL;
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	hlist_del_init(&dentry->d_alias);
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	dentry_rcuwalk_barrier(dentry);
	spin_unlock(&dentry->d_lock);
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	spin_unlock(&inode->i_lock);
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	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);
}

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/*
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 * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
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 */
static void dentry_lru_add(struct dentry *dentry)
{
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	if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST))) {
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		spin_lock(&dcache_lru_lock);
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		dentry->d_flags |= DCACHE_LRU_LIST;
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		list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
		dentry->d_sb->s_nr_dentry_unused++;
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		dentry_stat.nr_unused++;
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		spin_unlock(&dcache_lru_lock);
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	}
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}

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static void __dentry_lru_del(struct dentry *dentry)
{
	list_del_init(&dentry->d_lru);
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	dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
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	dentry->d_sb->s_nr_dentry_unused--;
	dentry_stat.nr_unused--;
}

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/*
 * Remove a dentry with references from the LRU.
 */
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static void dentry_lru_del(struct dentry *dentry)
{
	if (!list_empty(&dentry->d_lru)) {
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		spin_lock(&dcache_lru_lock);
		__dentry_lru_del(dentry);
		spin_unlock(&dcache_lru_lock);
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	}
}

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static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)
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{
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	spin_lock(&dcache_lru_lock);
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	if (list_empty(&dentry->d_lru)) {
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		dentry->d_flags |= DCACHE_LRU_LIST;
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		list_add_tail(&dentry->d_lru, list);
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		dentry->d_sb->s_nr_dentry_unused++;
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		dentry_stat.nr_unused++;
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	} else {
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		list_move_tail(&dentry->d_lru, list);
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	}
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	spin_unlock(&dcache_lru_lock);
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}

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/**
 * d_kill - kill dentry and return parent
 * @dentry: dentry to kill
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 * @parent: parent dentry
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 *
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 * The dentry must already be unhashed and removed from the LRU.
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 *
 * If this is the root of the dentry tree, return NULL.
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 *
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 * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
 * d_kill.
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 */
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static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
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	__releases(dentry->d_lock)
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	__releases(parent->d_lock)
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	__releases(dentry->d_inode->i_lock)
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{
	list_del(&dentry->d_u.d_child);
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	/*
	 * Inform try_to_ascend() that we are no longer attached to the
	 * dentry tree
	 */
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	dentry->d_flags |= DCACHE_DENTRY_KILLED;
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	if (parent)
		spin_unlock(&parent->d_lock);
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	dentry_iput(dentry);
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	/*
	 * dentry_iput drops the locks, at which point nobody (except
	 * transient RCU lookups) can reach this dentry.
	 */
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	d_free(dentry);
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	return parent;
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}

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/*
 * 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);
	}
}

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/**
 * 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)
{
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	if (!d_unhashed(dentry)) {
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		__d_shrink(dentry);
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		dentry_rcuwalk_barrier(dentry);
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	}
}
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);

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/*
 * 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)
{
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	struct inode *inode;
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	struct dentry *parent;

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	inode = dentry->d_inode;
	if (inode && !spin_trylock(&inode->i_lock)) {
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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)) {
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		if (inode)
			spin_unlock(&inode->i_lock);
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		goto relock;
	}
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	if (ref)
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		dentry->d_lockref.count--;
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	/*
	 * inform the fs via d_prune that this dentry is about to be
	 * unhashed and destroyed.
	 */
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	if ((dentry->d_flags & DCACHE_OP_PRUNE) && !d_unhashed(dentry))
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		dentry->d_op->d_prune(dentry);

	dentry_lru_del(dentry);
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	/* if it was on the hash then remove it */
	__d_drop(dentry);
	return d_kill(dentry, parent);
}

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/* 
 * 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)
{
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	if (unlikely(!dentry))
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		return;

repeat:
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	if (lockref_put_or_lock(&dentry->d_lockref))
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		return;

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	/* Unreachable? Get rid of it */
	if (unlikely(d_unhashed(dentry)))
		goto kill_it;

	if (unlikely(dentry->d_flags & DCACHE_OP_DELETE)) {
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		if (dentry->d_op->d_delete(dentry))
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			goto kill_it;
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	}
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	dentry->d_flags |= DCACHE_REFERENCED;
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	dentry_lru_add(dentry);
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	dentry->d_lockref.count--;
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	spin_unlock(&dentry->d_lock);
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	return;

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kill_it:
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	dentry = dentry_kill(dentry, 1);
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	if (dentry)
		goto repeat;
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}
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EXPORT_SYMBOL(dput);
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/**
 * 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.
	 */
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	spin_lock(&dentry->d_lock);
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	if (d_unhashed(dentry)) {
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		spin_unlock(&dentry->d_lock);
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		return 0;
	}
	/*
	 * Check whether to do a partial shrink_dcache
	 * to get rid of unused child entries.
	 */
	if (!list_empty(&dentry->d_subdirs)) {
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		spin_unlock(&dentry->d_lock);
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		shrink_dcache_parent(dentry);
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Nick Piggin 已提交
573
		spin_lock(&dentry->d_lock);
L
Linus Torvalds 已提交
574 575 576 577 578 579 580 581 582 583 584
	}

	/*
	 * 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).
585 586
	 * We also need to leave mountpoints alone,
	 * directory or not.
L
Linus Torvalds 已提交
587
	 */
588
	if (dentry->d_lockref.count > 1 && dentry->d_inode) {
589
		if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) {
L
Linus Torvalds 已提交
590 591 592 593 594 595 596 597 598
			spin_unlock(&dentry->d_lock);
			return -EBUSY;
		}
	}

	__d_drop(dentry);
	spin_unlock(&dentry->d_lock);
	return 0;
}
599
EXPORT_SYMBOL(d_invalidate);
L
Linus Torvalds 已提交
600

N
Nick Piggin 已提交
601
/* This must be called with d_lock held */
602
static inline void __dget_dlock(struct dentry *dentry)
N
Nick Piggin 已提交
603
{
604
	dentry->d_lockref.count++;
N
Nick Piggin 已提交
605 606
}

607
static inline void __dget(struct dentry *dentry)
L
Linus Torvalds 已提交
608
{
609
	lockref_get(&dentry->d_lockref);
L
Linus Torvalds 已提交
610 611
}

N
Nick Piggin 已提交
612 613
struct dentry *dget_parent(struct dentry *dentry)
{
614
	int gotref;
N
Nick Piggin 已提交
615 616
	struct dentry *ret;

617 618 619 620 621 622 623 624 625 626 627 628 629 630
	/*
	 * Do optimistic parent lookup without any
	 * locking.
	 */
	rcu_read_lock();
	ret = ACCESS_ONCE(dentry->d_parent);
	gotref = lockref_get_not_zero(&ret->d_lockref);
	rcu_read_unlock();
	if (likely(gotref)) {
		if (likely(ret == ACCESS_ONCE(dentry->d_parent)))
			return ret;
		dput(ret);
	}

N
Nick Piggin 已提交
631
repeat:
N
Nick Piggin 已提交
632 633 634 635 636
	/*
	 * Don't need rcu_dereference because we re-check it was correct under
	 * the lock.
	 */
	rcu_read_lock();
N
Nick Piggin 已提交
637
	ret = dentry->d_parent;
N
Nick Piggin 已提交
638 639 640 641
	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
642 643
		goto repeat;
	}
N
Nick Piggin 已提交
644
	rcu_read_unlock();
645 646
	BUG_ON(!ret->d_lockref.count);
	ret->d_lockref.count++;
N
Nick Piggin 已提交
647 648 649 650 651
	spin_unlock(&ret->d_lock);
	return ret;
}
EXPORT_SYMBOL(dget_parent);

L
Linus Torvalds 已提交
652 653 654
/**
 * d_find_alias - grab a hashed alias of inode
 * @inode: inode in question
655 656
 * @want_discon:  flag, used by d_splice_alias, to request
 *          that only a DISCONNECTED alias be returned.
L
Linus Torvalds 已提交
657 658 659 660 661 662 663
 *
 * 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.
 *
664
 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
665 666
 * 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
667
 */
668
static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
L
Linus Torvalds 已提交
669
{
N
Nick Piggin 已提交
670
	struct dentry *alias, *discon_alias;
L
Linus Torvalds 已提交
671

N
Nick Piggin 已提交
672 673
again:
	discon_alias = NULL;
674
	hlist_for_each_entry(alias, &inode->i_dentry, d_alias) {
N
Nick Piggin 已提交
675
		spin_lock(&alias->d_lock);
L
Linus Torvalds 已提交
676
 		if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
677
			if (IS_ROOT(alias) &&
N
Nick Piggin 已提交
678
			    (alias->d_flags & DCACHE_DISCONNECTED)) {
L
Linus Torvalds 已提交
679
				discon_alias = alias;
680
			} else if (!want_discon) {
681
				__dget_dlock(alias);
N
Nick Piggin 已提交
682 683 684 685 686 687 688 689 690 691 692 693
				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)) {
694
				__dget_dlock(alias);
N
Nick Piggin 已提交
695
				spin_unlock(&alias->d_lock);
L
Linus Torvalds 已提交
696 697 698
				return alias;
			}
		}
N
Nick Piggin 已提交
699 700
		spin_unlock(&alias->d_lock);
		goto again;
L
Linus Torvalds 已提交
701
	}
N
Nick Piggin 已提交
702
	return NULL;
L
Linus Torvalds 已提交
703 704
}

N
Nick Piggin 已提交
705
struct dentry *d_find_alias(struct inode *inode)
L
Linus Torvalds 已提交
706
{
D
David Howells 已提交
707 708
	struct dentry *de = NULL;

A
Al Viro 已提交
709
	if (!hlist_empty(&inode->i_dentry)) {
710
		spin_lock(&inode->i_lock);
711
		de = __d_find_alias(inode, 0);
712
		spin_unlock(&inode->i_lock);
D
David Howells 已提交
713
	}
L
Linus Torvalds 已提交
714 715
	return de;
}
716
EXPORT_SYMBOL(d_find_alias);
L
Linus Torvalds 已提交
717 718 719 720 721 722 723

/*
 *	Try to kill dentries associated with this inode.
 * WARNING: you must own a reference to inode.
 */
void d_prune_aliases(struct inode *inode)
{
724
	struct dentry *dentry;
L
Linus Torvalds 已提交
725
restart:
726
	spin_lock(&inode->i_lock);
727
	hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
L
Linus Torvalds 已提交
728
		spin_lock(&dentry->d_lock);
729
		if (!dentry->d_lockref.count) {
730 731 732 733 734 735 736 737
			/*
			 * inform the fs via d_prune that this dentry
			 * is about to be unhashed and destroyed.
			 */
			if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
			    !d_unhashed(dentry))
				dentry->d_op->d_prune(dentry);

738
			__dget_dlock(dentry);
L
Linus Torvalds 已提交
739 740
			__d_drop(dentry);
			spin_unlock(&dentry->d_lock);
741
			spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
742 743 744 745 746
			dput(dentry);
			goto restart;
		}
		spin_unlock(&dentry->d_lock);
	}
747
	spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
748
}
749
EXPORT_SYMBOL(d_prune_aliases);
L
Linus Torvalds 已提交
750 751

/*
752 753 754
 * 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.
755
 *
756
 * This may fail if locks cannot be acquired no problem, just try again.
L
Linus Torvalds 已提交
757
 */
758
static void try_prune_one_dentry(struct dentry *dentry)
759
	__releases(dentry->d_lock)
L
Linus Torvalds 已提交
760
{
761
	struct dentry *parent;
762

763
	parent = dentry_kill(dentry, 0);
764
	/*
765 766 767 768 769 770 771 772
	 * 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.
773
	 */
774 775 776 777 778 779 780
	if (!parent)
		return;
	if (parent == dentry)
		return;

	/* Prune ancestors. */
	dentry = parent;
781
	while (dentry) {
782
		if (lockref_put_or_lock(&dentry->d_lockref))
783
			return;
784
		dentry = dentry_kill(dentry, 1);
785
	}
L
Linus Torvalds 已提交
786 787
}

C
Christoph Hellwig 已提交
788
static void shrink_dentry_list(struct list_head *list)
L
Linus Torvalds 已提交
789
{
790 791
	struct dentry *dentry;

792 793 794 795 796 797 798 799
	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
800 801 802
			continue;
		}

L
Linus Torvalds 已提交
803 804
		/*
		 * We found an inuse dentry which was not removed from
805 806
		 * the LRU because of laziness during lookup.  Do not free
		 * it - just keep it off the LRU list.
L
Linus Torvalds 已提交
807
		 */
808
		if (dentry->d_lockref.count) {
809
			dentry_lru_del(dentry);
810
			spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
811 812
			continue;
		}
813 814

		rcu_read_unlock();
815 816 817

		try_prune_one_dentry(dentry);

818
		rcu_read_lock();
819
	}
820
	rcu_read_unlock();
C
Christoph Hellwig 已提交
821 822 823
}

/**
824 825 826 827 828 829 830
 * 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
831
 *
832 833
 * This function may fail to free any resources if all the dentries are in
 * use.
C
Christoph Hellwig 已提交
834
 */
835
void prune_dcache_sb(struct super_block *sb, int count)
C
Christoph Hellwig 已提交
836 837 838 839 840
{
	struct dentry *dentry;
	LIST_HEAD(referenced);
	LIST_HEAD(tmp);

N
Nick Piggin 已提交
841 842
relock:
	spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
843 844 845 846 847
	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
848 849 850 851 852 853
		if (!spin_trylock(&dentry->d_lock)) {
			spin_unlock(&dcache_lru_lock);
			cpu_relax();
			goto relock;
		}

854
		if (dentry->d_flags & DCACHE_REFERENCED) {
N
Nick Piggin 已提交
855 856
			dentry->d_flags &= ~DCACHE_REFERENCED;
			list_move(&dentry->d_lru, &referenced);
C
Christoph Hellwig 已提交
857
			spin_unlock(&dentry->d_lock);
N
Nick Piggin 已提交
858 859
		} else {
			list_move_tail(&dentry->d_lru, &tmp);
860
			dentry->d_flags |= DCACHE_SHRINK_LIST;
N
Nick Piggin 已提交
861
			spin_unlock(&dentry->d_lock);
862
			if (!--count)
N
Nick Piggin 已提交
863
				break;
C
Christoph Hellwig 已提交
864
		}
865
		cond_resched_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
866
	}
867 868
	if (!list_empty(&referenced))
		list_splice(&referenced, &sb->s_dentry_lru);
N
Nick Piggin 已提交
869
	spin_unlock(&dcache_lru_lock);
870 871

	shrink_dentry_list(&tmp);
872 873
}

L
Linus Torvalds 已提交
874 875 876 877
/**
 * shrink_dcache_sb - shrink dcache for a superblock
 * @sb: superblock
 *
C
Christoph Hellwig 已提交
878 879
 * 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
880
 */
C
Christoph Hellwig 已提交
881
void shrink_dcache_sb(struct super_block *sb)
L
Linus Torvalds 已提交
882
{
C
Christoph Hellwig 已提交
883 884
	LIST_HEAD(tmp);

N
Nick Piggin 已提交
885
	spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
886 887
	while (!list_empty(&sb->s_dentry_lru)) {
		list_splice_init(&sb->s_dentry_lru, &tmp);
888
		spin_unlock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
889
		shrink_dentry_list(&tmp);
890
		spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
891
	}
N
Nick Piggin 已提交
892
	spin_unlock(&dcache_lru_lock);
L
Linus Torvalds 已提交
893
}
894
EXPORT_SYMBOL(shrink_dcache_sb);
L
Linus Torvalds 已提交
895

896 897 898 899 900 901 902 903 904 905 906 907 908
/*
 * 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 */
909
		while (!list_empty(&dentry->d_subdirs))
910 911 912 913 914 915 916 917
			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
918
			/*
Y
Yan, Zheng 已提交
919
			 * inform the fs that this dentry is about to be
S
Sage Weil 已提交
920 921
			 * unhashed and destroyed.
			 */
922 923
			if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
			    !d_unhashed(dentry))
Y
Yan, Zheng 已提交
924 925 926
				dentry->d_op->d_prune(dentry);

			dentry_lru_del(dentry);
927 928
			__d_shrink(dentry);

929
			if (dentry->d_lockref.count != 0) {
930 931 932 933 934 935 936 937
				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,
938
				       dentry->d_lockref.count,
939 940 941 942 943
				       dentry->d_sb->s_type->name,
				       dentry->d_sb->s_id);
				BUG();
			}

N
Nick Piggin 已提交
944
			if (IS_ROOT(dentry)) {
945
				parent = NULL;
N
Nick Piggin 已提交
946 947
				list_del(&dentry->d_u.d_child);
			} else {
948
				parent = dentry->d_parent;
949
				parent->d_lockref.count--;
N
Nick Piggin 已提交
950
				list_del(&dentry->d_u.d_child);
951
			}
952 953 954 955

			inode = dentry->d_inode;
			if (inode) {
				dentry->d_inode = NULL;
A
Al Viro 已提交
956
				hlist_del_init(&dentry->d_alias);
957 958 959 960 961 962 963 964 965 966 967 968
				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)
969
				return;
970 971 972 973 974 975 976 977 978 979
			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
980
 * - we don't need to use dentry->d_lock because:
981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996
 *   - 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;
997
	dentry->d_lockref.count--;
998 999
	shrink_dcache_for_umount_subtree(dentry);

1000 1001
	while (!hlist_bl_empty(&sb->s_anon)) {
		dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
1002 1003 1004 1005
		shrink_dcache_for_umount_subtree(dentry);
	}
}

1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024
/*
 * 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 ||
1025
		 (old->d_flags & DCACHE_DENTRY_KILLED) ||
1026 1027 1028 1029 1030 1031 1032 1033
		 (!locked && read_seqretry(&rename_lock, seq))) {
		spin_unlock(&new->d_lock);
		new = NULL;
	}
	rcu_read_unlock();
	return new;
}

M
Miklos Szeredi 已提交
1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046
/**
 * enum d_walk_ret - action to talke during tree walk
 * @D_WALK_CONTINUE:	contrinue walk
 * @D_WALK_QUIT:	quit walk
 * @D_WALK_NORETRY:	quit when retry is needed
 * @D_WALK_SKIP:	skip this dentry and its children
 */
enum d_walk_ret {
	D_WALK_CONTINUE,
	D_WALK_QUIT,
	D_WALK_NORETRY,
	D_WALK_SKIP,
};
1047

L
Linus Torvalds 已提交
1048
/**
M
Miklos Szeredi 已提交
1049 1050 1051 1052 1053
 * d_walk - walk the dentry tree
 * @parent:	start of walk
 * @data:	data passed to @enter() and @finish()
 * @enter:	callback when first entering the dentry
 * @finish:	callback when successfully finished the walk
L
Linus Torvalds 已提交
1054
 *
M
Miklos Szeredi 已提交
1055
 * The @enter() and @finish() callbacks are called with d_lock held.
L
Linus Torvalds 已提交
1056
 */
M
Miklos Szeredi 已提交
1057 1058 1059
static void d_walk(struct dentry *parent, void *data,
		   enum d_walk_ret (*enter)(void *, struct dentry *),
		   void (*finish)(void *))
L
Linus Torvalds 已提交
1060
{
1061
	struct dentry *this_parent;
L
Linus Torvalds 已提交
1062
	struct list_head *next;
1063
	unsigned seq;
1064
	int locked = 0;
M
Miklos Szeredi 已提交
1065 1066
	enum d_walk_ret ret;
	bool retry = true;
1067 1068

	seq = read_seqbegin(&rename_lock);
1069 1070
again:
	this_parent = parent;
N
Nick Piggin 已提交
1071
	spin_lock(&this_parent->d_lock);
M
Miklos Szeredi 已提交
1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083

	ret = enter(data, this_parent);
	switch (ret) {
	case D_WALK_CONTINUE:
		break;
	case D_WALK_QUIT:
	case D_WALK_SKIP:
		goto out_unlock;
	case D_WALK_NORETRY:
		retry = false;
		break;
	}
L
Linus Torvalds 已提交
1084 1085 1086 1087 1088
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
1089
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
1090
		next = tmp->next;
N
Nick Piggin 已提交
1091 1092

		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
M
Miklos Szeredi 已提交
1093 1094 1095 1096 1097 1098

		ret = enter(data, dentry);
		switch (ret) {
		case D_WALK_CONTINUE:
			break;
		case D_WALK_QUIT:
N
Nick Piggin 已提交
1099
			spin_unlock(&dentry->d_lock);
M
Miklos Szeredi 已提交
1100 1101 1102 1103 1104 1105 1106
			goto out_unlock;
		case D_WALK_NORETRY:
			retry = false;
			break;
		case D_WALK_SKIP:
			spin_unlock(&dentry->d_lock);
			continue;
N
Nick Piggin 已提交
1107
		}
M
Miklos Szeredi 已提交
1108

L
Linus Torvalds 已提交
1109
		if (!list_empty(&dentry->d_subdirs)) {
N
Nick Piggin 已提交
1110 1111
			spin_unlock(&this_parent->d_lock);
			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
L
Linus Torvalds 已提交
1112
			this_parent = dentry;
N
Nick Piggin 已提交
1113
			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
L
Linus Torvalds 已提交
1114 1115
			goto repeat;
		}
N
Nick Piggin 已提交
1116
		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
1117 1118 1119 1120 1121
	}
	/*
	 * All done at this level ... ascend and resume the search.
	 */
	if (this_parent != parent) {
1122 1123 1124
		struct dentry *child = this_parent;
		this_parent = try_to_ascend(this_parent, locked, seq);
		if (!this_parent)
1125 1126
			goto rename_retry;
		next = child->d_u.d_child.next;
L
Linus Torvalds 已提交
1127 1128
		goto resume;
	}
M
Miklos Szeredi 已提交
1129 1130
	if (!locked && read_seqretry(&rename_lock, seq)) {
		spin_unlock(&this_parent->d_lock);
1131
		goto rename_retry;
M
Miklos Szeredi 已提交
1132 1133 1134 1135 1136 1137
	}
	if (finish)
		finish(data);

out_unlock:
	spin_unlock(&this_parent->d_lock);
1138 1139
	if (locked)
		write_sequnlock(&rename_lock);
M
Miklos Szeredi 已提交
1140
	return;
1141 1142

rename_retry:
M
Miklos Szeredi 已提交
1143 1144
	if (!retry)
		return;
1145 1146
	if (locked)
		goto again;
1147 1148 1149
	locked = 1;
	write_seqlock(&rename_lock);
	goto again;
L
Linus Torvalds 已提交
1150
}
M
Miklos Szeredi 已提交
1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183

/*
 * 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
 */

static enum d_walk_ret check_mount(void *data, struct dentry *dentry)
{
	int *ret = data;
	if (d_mountpoint(dentry)) {
		*ret = 1;
		return D_WALK_QUIT;
	}
	return D_WALK_CONTINUE;
}

int have_submounts(struct dentry *parent)
{
	int ret = 0;

	d_walk(parent, &ret, check_mount, NULL);

	return ret;
}
1184
EXPORT_SYMBOL(have_submounts);
L
Linus Torvalds 已提交
1185

1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218
/*
 * Called by mount code to set a mountpoint and check if the mountpoint is
 * reachable (e.g. NFS can unhash a directory dentry and then the complete
 * subtree can become unreachable).
 *
 * Only one of check_submounts_and_drop() and d_set_mounted() must succeed.  For
 * this reason take rename_lock and d_lock on dentry and ancestors.
 */
int d_set_mounted(struct dentry *dentry)
{
	struct dentry *p;
	int ret = -ENOENT;
	write_seqlock(&rename_lock);
	for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
		/* Need exclusion wrt. check_submounts_and_drop() */
		spin_lock(&p->d_lock);
		if (unlikely(d_unhashed(p))) {
			spin_unlock(&p->d_lock);
			goto out;
		}
		spin_unlock(&p->d_lock);
	}
	spin_lock(&dentry->d_lock);
	if (!d_unlinked(dentry)) {
		dentry->d_flags |= DCACHE_MOUNTED;
		ret = 0;
	}
 	spin_unlock(&dentry->d_lock);
out:
	write_sequnlock(&rename_lock);
	return ret;
}

L
Linus Torvalds 已提交
1219
/*
1220
 * Search the dentry child list of the specified parent,
L
Linus Torvalds 已提交
1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233
 * 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.
 */

M
Miklos Szeredi 已提交
1234 1235 1236 1237 1238
struct select_data {
	struct dentry *start;
	struct list_head dispose;
	int found;
};
N
Nick Piggin 已提交
1239

M
Miklos Szeredi 已提交
1240 1241 1242 1243
static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
{
	struct select_data *data = _data;
	enum d_walk_ret ret = D_WALK_CONTINUE;
L
Linus Torvalds 已提交
1244

M
Miklos Szeredi 已提交
1245 1246
	if (data->start == dentry)
		goto out;
N
Nick Piggin 已提交
1247

L
Linus Torvalds 已提交
1248
	/*
M
Miklos Szeredi 已提交
1249 1250 1251 1252 1253 1254
	 * move only zero ref count dentries to the dispose list.
	 *
	 * 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
1255
	 */
M
Miklos Szeredi 已提交
1256 1257 1258 1259 1260 1261 1262
	if (dentry->d_lockref.count) {
		dentry_lru_del(dentry);
	} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
		dentry_lru_move_list(dentry, &data->dispose);
		dentry->d_flags |= DCACHE_SHRINK_LIST;
		data->found++;
		ret = D_WALK_NORETRY;
L
Linus Torvalds 已提交
1263
	}
M
Miklos Szeredi 已提交
1264 1265 1266 1267 1268 1269 1270
	/*
	 * We can return to the caller if we have found some (this
	 * ensures forward progress). We'll be coming back to find
	 * the rest.
	 */
	if (data->found && need_resched())
		ret = D_WALK_QUIT;
L
Linus Torvalds 已提交
1271
out:
M
Miklos Szeredi 已提交
1272
	return ret;
L
Linus Torvalds 已提交
1273 1274 1275 1276 1277 1278 1279 1280
}

/**
 * shrink_dcache_parent - prune dcache
 * @parent: parent of entries to prune
 *
 * Prune the dcache to remove unused children of the parent dentry.
 */
M
Miklos Szeredi 已提交
1281
void shrink_dcache_parent(struct dentry *parent)
L
Linus Torvalds 已提交
1282
{
M
Miklos Szeredi 已提交
1283 1284
	for (;;) {
		struct select_data data;
L
Linus Torvalds 已提交
1285

M
Miklos Szeredi 已提交
1286 1287 1288 1289 1290 1291 1292 1293 1294
		INIT_LIST_HEAD(&data.dispose);
		data.start = parent;
		data.found = 0;

		d_walk(parent, &data, select_collect, NULL);
		if (!data.found)
			break;

		shrink_dentry_list(&data.dispose);
1295 1296
		cond_resched();
	}
L
Linus Torvalds 已提交
1297
}
1298
EXPORT_SYMBOL(shrink_dcache_parent);
L
Linus Torvalds 已提交
1299

1300 1301 1302 1303 1304 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 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364
static enum d_walk_ret check_and_collect(void *_data, struct dentry *dentry)
{
	struct select_data *data = _data;

	if (d_mountpoint(dentry)) {
		data->found = -EBUSY;
		return D_WALK_QUIT;
	}

	return select_collect(_data, dentry);
}

static void check_and_drop(void *_data)
{
	struct select_data *data = _data;

	if (d_mountpoint(data->start))
		data->found = -EBUSY;
	if (!data->found)
		__d_drop(data->start);
}

/**
 * check_submounts_and_drop - prune dcache, check for submounts and drop
 *
 * All done as a single atomic operation relative to has_unlinked_ancestor().
 * Returns 0 if successfully unhashed @parent.  If there were submounts then
 * return -EBUSY.
 *
 * @dentry: dentry to prune and drop
 */
int check_submounts_and_drop(struct dentry *dentry)
{
	int ret = 0;

	/* Negative dentries can be dropped without further checks */
	if (!dentry->d_inode) {
		d_drop(dentry);
		goto out;
	}

	for (;;) {
		struct select_data data;

		INIT_LIST_HEAD(&data.dispose);
		data.start = dentry;
		data.found = 0;

		d_walk(dentry, &data, check_and_collect, check_and_drop);
		ret = data.found;

		if (!list_empty(&data.dispose))
			shrink_dentry_list(&data.dispose);

		if (ret <= 0)
			break;

		cond_resched();
	}

out:
	return ret;
}
EXPORT_SYMBOL(check_submounts_and_drop);

L
Linus Torvalds 已提交
1365
/**
1366 1367
 * __d_alloc	-	allocate a dcache entry
 * @sb: filesystem it will belong to
L
Linus Torvalds 已提交
1368 1369 1370 1371 1372 1373 1374
 * @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.
 */
 
1375
struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
L
Linus Torvalds 已提交
1376 1377 1378 1379
{
	struct dentry *dentry;
	char *dname;

1380
	dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
L
Linus Torvalds 已提交
1381 1382 1383
	if (!dentry)
		return NULL;

1384 1385 1386 1387 1388 1389 1390
	/*
	 * 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
1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405
	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;

1406 1407 1408 1409
	/* Make sure we always see the terminating NUL character */
	smp_wmb();
	dentry->d_name.name = dname;

1410
	dentry->d_lockref.count = 1;
1411
	dentry->d_flags = 0;
L
Linus Torvalds 已提交
1412
	spin_lock_init(&dentry->d_lock);
N
Nick Piggin 已提交
1413
	seqcount_init(&dentry->d_seq);
L
Linus Torvalds 已提交
1414
	dentry->d_inode = NULL;
1415 1416
	dentry->d_parent = dentry;
	dentry->d_sb = sb;
L
Linus Torvalds 已提交
1417 1418
	dentry->d_op = NULL;
	dentry->d_fsdata = NULL;
1419
	INIT_HLIST_BL_NODE(&dentry->d_hash);
L
Linus Torvalds 已提交
1420 1421
	INIT_LIST_HEAD(&dentry->d_lru);
	INIT_LIST_HEAD(&dentry->d_subdirs);
A
Al Viro 已提交
1422
	INIT_HLIST_NODE(&dentry->d_alias);
N
Nick Piggin 已提交
1423
	INIT_LIST_HEAD(&dentry->d_u.d_child);
1424
	d_set_d_op(dentry, dentry->d_sb->s_d_op);
L
Linus Torvalds 已提交
1425

1426
	this_cpu_inc(nr_dentry);
1427

L
Linus Torvalds 已提交
1428 1429
	return dentry;
}
1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457

/**
 * 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;
}
1458
EXPORT_SYMBOL(d_alloc);
L
Linus Torvalds 已提交
1459

1460 1461
struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
{
1462 1463
	struct dentry *dentry = __d_alloc(sb, name);
	if (dentry)
1464 1465 1466 1467 1468
		dentry->d_flags |= DCACHE_DISCONNECTED;
	return dentry;
}
EXPORT_SYMBOL(d_alloc_pseudo);

L
Linus Torvalds 已提交
1469 1470 1471 1472 1473 1474 1475 1476 1477
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);
}
1478
EXPORT_SYMBOL(d_alloc_name);
L
Linus Torvalds 已提交
1479

1480 1481
void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
{
1482 1483
	WARN_ON_ONCE(dentry->d_op);
	WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH	|
1484 1485
				DCACHE_OP_COMPARE	|
				DCACHE_OP_REVALIDATE	|
1486
				DCACHE_OP_WEAK_REVALIDATE	|
1487 1488 1489 1490 1491 1492 1493 1494 1495 1496
				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;
1497 1498
	if (op->d_weak_revalidate)
		dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
1499 1500
	if (op->d_delete)
		dentry->d_flags |= DCACHE_OP_DELETE;
S
Sage Weil 已提交
1501 1502
	if (op->d_prune)
		dentry->d_flags |= DCACHE_OP_PRUNE;
1503 1504 1505 1506

}
EXPORT_SYMBOL(d_set_d_op);

1507 1508
static void __d_instantiate(struct dentry *dentry, struct inode *inode)
{
N
Nick Piggin 已提交
1509
	spin_lock(&dentry->d_lock);
1510 1511 1512
	if (inode) {
		if (unlikely(IS_AUTOMOUNT(inode)))
			dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
A
Al Viro 已提交
1513
		hlist_add_head(&dentry->d_alias, &inode->i_dentry);
1514
	}
1515
	dentry->d_inode = inode;
N
Nick Piggin 已提交
1516
	dentry_rcuwalk_barrier(dentry);
N
Nick Piggin 已提交
1517
	spin_unlock(&dentry->d_lock);
1518 1519 1520
	fsnotify_d_instantiate(dentry, inode);
}

L
Linus Torvalds 已提交
1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537
/**
 * 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
1538
	BUG_ON(!hlist_unhashed(&entry->d_alias));
1539 1540
	if (inode)
		spin_lock(&inode->i_lock);
1541
	__d_instantiate(entry, inode);
1542 1543
	if (inode)
		spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
1544 1545
	security_d_instantiate(entry, inode);
}
1546
EXPORT_SYMBOL(d_instantiate);
L
Linus Torvalds 已提交
1547 1548 1549 1550 1551 1552 1553 1554

/**
 * 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
1555
 * aliased dentry instead and drop one reference to inode.
L
Linus Torvalds 已提交
1556 1557 1558
 *
 * Note that in order to avoid conflicts with rename() etc, the caller
 * had better be holding the parent directory semaphore.
1559 1560 1561 1562
 *
 * 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
1563
 */
1564 1565
static struct dentry *__d_instantiate_unique(struct dentry *entry,
					     struct inode *inode)
L
Linus Torvalds 已提交
1566 1567 1568 1569 1570 1571
{
	struct dentry *alias;
	int len = entry->d_name.len;
	const char *name = entry->d_name.name;
	unsigned int hash = entry->d_name.hash;

1572
	if (!inode) {
1573
		__d_instantiate(entry, NULL);
1574 1575 1576
		return NULL;
	}

1577
	hlist_for_each_entry(alias, &inode->i_dentry, d_alias) {
N
Nick Piggin 已提交
1578 1579 1580 1581 1582
		/*
		 * 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.
		 */
1583
		if (alias->d_name.hash != hash)
L
Linus Torvalds 已提交
1584 1585 1586
			continue;
		if (alias->d_parent != entry->d_parent)
			continue;
1587 1588
		if (alias->d_name.len != len)
			continue;
1589
		if (dentry_cmp(alias, name, len))
L
Linus Torvalds 已提交
1590
			continue;
1591
		__dget(alias);
L
Linus Torvalds 已提交
1592 1593
		return alias;
	}
1594

1595
	__d_instantiate(entry, inode);
L
Linus Torvalds 已提交
1596 1597
	return NULL;
}
1598 1599 1600 1601 1602

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

A
Al Viro 已提交
1603
	BUG_ON(!hlist_unhashed(&entry->d_alias));
1604

1605 1606
	if (inode)
		spin_lock(&inode->i_lock);
1607
	result = __d_instantiate_unique(entry, inode);
1608 1609
	if (inode)
		spin_unlock(&inode->i_lock);
1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620

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

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

L
Linus Torvalds 已提交
1621 1622
EXPORT_SYMBOL(d_instantiate_unique);

A
Al Viro 已提交
1623 1624 1625 1626 1627
struct dentry *d_make_root(struct inode *root_inode)
{
	struct dentry *res = NULL;

	if (root_inode) {
1628
		static const struct qstr name = QSTR_INIT("/", 1);
A
Al Viro 已提交
1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639

		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);

1640 1641 1642 1643
static struct dentry * __d_find_any_alias(struct inode *inode)
{
	struct dentry *alias;

A
Al Viro 已提交
1644
	if (hlist_empty(&inode->i_dentry))
1645
		return NULL;
A
Al Viro 已提交
1646
	alias = hlist_entry(inode->i_dentry.first, struct dentry, d_alias);
1647 1648 1649 1650
	__dget(alias);
	return alias;
}

1651 1652 1653 1654 1655 1656 1657 1658
/**
 * 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)
1659 1660 1661 1662 1663 1664 1665 1666
{
	struct dentry *de;

	spin_lock(&inode->i_lock);
	de = __d_find_any_alias(inode);
	spin_unlock(&inode->i_lock);
	return de;
}
1667
EXPORT_SYMBOL(d_find_any_alias);
1668

1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681
/**
 * 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
1682 1683 1684 1685
 * 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).
1686 1687 1688
 */
struct dentry *d_obtain_alias(struct inode *inode)
{
1689
	static const struct qstr anonstring = QSTR_INIT("/", 1);
C
Christoph Hellwig 已提交
1690 1691
	struct dentry *tmp;
	struct dentry *res;
1692 1693

	if (!inode)
1694
		return ERR_PTR(-ESTALE);
1695 1696 1697
	if (IS_ERR(inode))
		return ERR_CAST(inode);

1698
	res = d_find_any_alias(inode);
C
Christoph Hellwig 已提交
1699 1700 1701
	if (res)
		goto out_iput;

1702
	tmp = __d_alloc(inode->i_sb, &anonstring);
C
Christoph Hellwig 已提交
1703 1704 1705
	if (!tmp) {
		res = ERR_PTR(-ENOMEM);
		goto out_iput;
1706
	}
N
Nick Piggin 已提交
1707

1708
	spin_lock(&inode->i_lock);
1709
	res = __d_find_any_alias(inode);
C
Christoph Hellwig 已提交
1710
	if (res) {
1711
		spin_unlock(&inode->i_lock);
C
Christoph Hellwig 已提交
1712 1713 1714 1715 1716 1717 1718 1719
		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
1720
	hlist_add_head(&tmp->d_alias, &inode->i_dentry);
1721
	hlist_bl_lock(&tmp->d_sb->s_anon);
1722
	hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
1723
	hlist_bl_unlock(&tmp->d_sb->s_anon);
C
Christoph Hellwig 已提交
1724
	spin_unlock(&tmp->d_lock);
1725
	spin_unlock(&inode->i_lock);
1726
	security_d_instantiate(tmp, inode);
C
Christoph Hellwig 已提交
1727 1728 1729 1730

	return tmp;

 out_iput:
1731 1732
	if (res && !IS_ERR(res))
		security_d_instantiate(res, inode);
C
Christoph Hellwig 已提交
1733 1734
	iput(inode);
	return res;
1735
}
1736
EXPORT_SYMBOL(d_obtain_alias);
L
Linus Torvalds 已提交
1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752

/**
 * 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.
 *
1753 1754 1755 1756
 * Cluster filesystems may call this function with a negative, hashed dentry.
 * In that case, we know that the inode will be a regular file, and also this
 * will only occur during atomic_open. So we need to check for the dentry
 * being already hashed only in the final case.
L
Linus Torvalds 已提交
1757 1758 1759 1760 1761
 */
struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
{
	struct dentry *new = NULL;

1762 1763 1764
	if (IS_ERR(inode))
		return ERR_CAST(inode);

1765
	if (inode && S_ISDIR(inode->i_mode)) {
1766
		spin_lock(&inode->i_lock);
1767
		new = __d_find_alias(inode, 1);
L
Linus Torvalds 已提交
1768
		if (new) {
1769
			BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
1770
			spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
1771 1772 1773 1774
			security_d_instantiate(new, inode);
			d_move(new, dentry);
			iput(inode);
		} else {
1775
			/* already taking inode->i_lock, so d_add() by hand */
1776
			__d_instantiate(dentry, inode);
1777
			spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
1778 1779 1780
			security_d_instantiate(dentry, inode);
			d_rehash(dentry);
		}
1781 1782 1783 1784 1785
	} else {
		d_instantiate(dentry, inode);
		if (d_unhashed(dentry))
			d_rehash(dentry);
	}
L
Linus Torvalds 已提交
1786 1787
	return new;
}
1788
EXPORT_SYMBOL(d_splice_alias);
L
Linus Torvalds 已提交
1789

1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805
/**
 * 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.
 */
1806
struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
1807 1808 1809 1810 1811
			struct qstr *name)
{
	struct dentry *found;
	struct dentry *new;

C
Christoph Hellwig 已提交
1812 1813 1814 1815
	/*
	 * First check if a dentry matching the name already exists,
	 * if not go ahead and create it now.
	 */
1816
	found = d_hash_and_lookup(dentry->d_parent, name);
1817 1818
	if (unlikely(IS_ERR(found)))
		goto err_out;
1819 1820 1821
	if (!found) {
		new = d_alloc(dentry->d_parent, name);
		if (!new) {
1822
			found = ERR_PTR(-ENOMEM);
1823 1824
			goto err_out;
		}
C
Christoph Hellwig 已提交
1825

1826 1827 1828 1829 1830 1831 1832
		found = d_splice_alias(inode, new);
		if (found) {
			dput(new);
			return found;
		}
		return new;
	}
C
Christoph Hellwig 已提交
1833 1834 1835 1836 1837 1838 1839

	/*
	 * If a matching dentry exists, and it's not negative use it.
	 *
	 * Decrement the reference count to balance the iget() done
	 * earlier on.
	 */
1840 1841 1842 1843 1844 1845 1846 1847 1848
	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
1849

1850 1851
	/*
	 * Negative dentry: instantiate it unless the inode is a directory and
C
Christoph Hellwig 已提交
1852
	 * already has a dentry.
1853
	 */
1854 1855 1856 1857
	new = d_splice_alias(inode, found);
	if (new) {
		dput(found);
		found = new;
1858
	}
1859
	return found;
1860 1861 1862

err_out:
	iput(inode);
1863
	return found;
1864
}
1865
EXPORT_SYMBOL(d_add_ci);
L
Linus Torvalds 已提交
1866

1867 1868 1869 1870
/*
 * Do the slow-case of the dentry name compare.
 *
 * Unlike the dentry_cmp() function, we need to atomically
1871
 * load the name and length information, so that the
1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899
 * 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 dentry *dentry,
		unsigned int seq,
		const struct qstr *name)
{
	int tlen = dentry->d_name.len;
	const char *tname = dentry->d_name.name;

	if (read_seqcount_retry(&dentry->d_seq, seq)) {
		cpu_relax();
		return D_COMP_SEQRETRY;
	}
1900
	if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
1901 1902 1903 1904
		return D_COMP_NOMATCH;
	return D_COMP_OK;
}

N
Nick Piggin 已提交
1905 1906 1907 1908
/**
 * __d_lookup_rcu - search for a dentry (racy, store-free)
 * @parent: parent dentry
 * @name: qstr of name we wish to find
1909
 * @seqp: returns d_seq value at the point where the dentry was found
N
Nick Piggin 已提交
1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922
 * 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.
 *
1923
 * A refcount may be taken on the found dentry with the d_rcu_to_refcount
N
Nick Piggin 已提交
1924 1925 1926 1927 1928 1929
 * 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.
1930 1931 1932
 *
 * 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
1933
 */
1934 1935
struct dentry *__d_lookup_rcu(const struct dentry *parent,
				const struct qstr *name,
1936
				unsigned *seqp)
N
Nick Piggin 已提交
1937
{
1938
	u64 hashlen = name->hash_len;
N
Nick Piggin 已提交
1939
	const unsigned char *str = name->name;
1940
	struct hlist_bl_head *b = d_hash(parent, hashlen_hash(hashlen));
1941
	struct hlist_bl_node *node;
N
Nick Piggin 已提交
1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961
	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.
	 *
1962
	 * See Documentation/filesystems/path-lookup.txt for more details.
N
Nick Piggin 已提交
1963
	 */
1964
	hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
1965
		unsigned seq;
N
Nick Piggin 已提交
1966 1967

seqretry:
1968 1969
		/*
		 * The dentry sequence count protects us from concurrent
1970
		 * renames, and thus protects parent and name fields.
1971 1972
		 *
		 * The caller must perform a seqcount check in order
1973
		 * to do anything useful with the returned dentry.
1974 1975 1976 1977 1978 1979 1980 1981 1982
		 *
		 * 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
1983 1984
		if (dentry->d_parent != parent)
			continue;
1985 1986
		if (d_unhashed(dentry))
			continue;
1987

1988
		if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
1989 1990
			if (dentry->d_name.hash != hashlen_hash(hashlen))
				continue;
1991 1992
			*seqp = seq;
			switch (slow_dentry_cmp(parent, dentry, seq, name)) {
1993 1994 1995
			case D_COMP_OK:
				return dentry;
			case D_COMP_NOMATCH:
N
Nick Piggin 已提交
1996
				continue;
1997 1998 1999
			default:
				goto seqretry;
			}
N
Nick Piggin 已提交
2000
		}
2001

2002
		if (dentry->d_name.hash_len != hashlen)
2003
			continue;
2004
		*seqp = seq;
2005
		if (!dentry_cmp(dentry, str, hashlen_len(hashlen)))
2006
			return dentry;
N
Nick Piggin 已提交
2007 2008 2009 2010
	}
	return NULL;
}

L
Linus Torvalds 已提交
2011 2012 2013 2014
/**
 * d_lookup - search for a dentry
 * @parent: parent dentry
 * @name: qstr of name we wish to find
2015
 * Returns: dentry, or NULL
L
Linus Torvalds 已提交
2016
 *
2017 2018 2019 2020
 * 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
2021
 */
A
Al Viro 已提交
2022
struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
L
Linus Torvalds 已提交
2023
{
N
Nick Piggin 已提交
2024
	struct dentry *dentry;
2025
	unsigned seq;
L
Linus Torvalds 已提交
2026 2027 2028 2029 2030 2031 2032 2033 2034

        do {
                seq = read_seqbegin(&rename_lock);
                dentry = __d_lookup(parent, name);
                if (dentry)
			break;
	} while (read_seqretry(&rename_lock, seq));
	return dentry;
}
2035
EXPORT_SYMBOL(d_lookup);
L
Linus Torvalds 已提交
2036

N
Nick Piggin 已提交
2037
/**
2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051
 * __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
2052
struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
L
Linus Torvalds 已提交
2053 2054 2055 2056
{
	unsigned int len = name->len;
	unsigned int hash = name->hash;
	const unsigned char *str = name->name;
2057
	struct hlist_bl_head *b = d_hash(parent, hash);
2058
	struct hlist_bl_node *node;
N
Nick Piggin 已提交
2059
	struct dentry *found = NULL;
2060
	struct dentry *dentry;
L
Linus Torvalds 已提交
2061

N
Nick Piggin 已提交
2062 2063 2064 2065 2066 2067 2068
	/*
	 * 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.
	 */

2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079
	/*
	 * 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.
	 *
2080
	 * See Documentation/filesystems/path-lookup.txt for more details.
2081
	 */
L
Linus Torvalds 已提交
2082 2083
	rcu_read_lock();
	
2084
	hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
L
Linus Torvalds 已提交
2085 2086 2087 2088 2089 2090 2091

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

		spin_lock(&dentry->d_lock);
		if (dentry->d_parent != parent)
			goto next;
2092 2093 2094
		if (d_unhashed(dentry))
			goto next;

L
Linus Torvalds 已提交
2095 2096 2097 2098
		/*
		 * It is safe to compare names since d_move() cannot
		 * change the qstr (protected by d_lock).
		 */
2099
		if (parent->d_flags & DCACHE_OP_COMPARE) {
2100 2101
			int tlen = dentry->d_name.len;
			const char *tname = dentry->d_name.name;
2102
			if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
L
Linus Torvalds 已提交
2103 2104
				goto next;
		} else {
2105 2106
			if (dentry->d_name.len != len)
				goto next;
2107
			if (dentry_cmp(dentry, str, len))
L
Linus Torvalds 已提交
2108 2109 2110
				goto next;
		}

2111
		dentry->d_lockref.count++;
2112
		found = dentry;
L
Linus Torvalds 已提交
2113 2114 2115 2116 2117 2118 2119 2120 2121 2122
		spin_unlock(&dentry->d_lock);
		break;
next:
		spin_unlock(&dentry->d_lock);
 	}
 	rcu_read_unlock();

 	return found;
}

2123 2124 2125 2126 2127
/**
 * 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
 *
2128
 * On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
2129 2130 2131 2132 2133 2134 2135 2136 2137
 */
struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
{
	/*
	 * 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);
2138
	if (dir->d_flags & DCACHE_OP_HASH) {
2139
		int err = dir->d_op->d_hash(dir, name);
2140 2141
		if (unlikely(err < 0))
			return ERR_PTR(err);
2142
	}
2143
	return d_lookup(dir, name);
2144
}
2145
EXPORT_SYMBOL(d_hash_and_lookup);
2146

L
Linus Torvalds 已提交
2147
/**
N
Nick Piggin 已提交
2148
 * d_validate - verify dentry provided from insecure source (deprecated)
L
Linus Torvalds 已提交
2149
 * @dentry: The dentry alleged to be valid child of @dparent
2150
 * @dparent: The parent dentry (known to be valid)
L
Linus Torvalds 已提交
2151 2152 2153 2154
 *
 * 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
2155 2156
 *
 * This function is slow for big directories, and deprecated, do not use it.
L
Linus Torvalds 已提交
2157
 */
2158
int d_validate(struct dentry *dentry, struct dentry *dparent)
L
Linus Torvalds 已提交
2159
{
N
Nick Piggin 已提交
2160
	struct dentry *child;
2161

N
Nick Piggin 已提交
2162
	spin_lock(&dparent->d_lock);
N
Nick Piggin 已提交
2163 2164
	list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
		if (dentry == child) {
N
Nick Piggin 已提交
2165
			spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
2166
			__dget_dlock(dentry);
N
Nick Piggin 已提交
2167 2168
			spin_unlock(&dentry->d_lock);
			spin_unlock(&dparent->d_lock);
L
Linus Torvalds 已提交
2169 2170 2171
			return 1;
		}
	}
N
Nick Piggin 已提交
2172
	spin_unlock(&dparent->d_lock);
N
Nick Piggin 已提交
2173

L
Linus Torvalds 已提交
2174 2175
	return 0;
}
2176
EXPORT_SYMBOL(d_validate);
L
Linus Torvalds 已提交
2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200

/*
 * 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)
{
2201
	struct inode *inode;
2202
	int isdir = 0;
L
Linus Torvalds 已提交
2203 2204 2205
	/*
	 * Are we the only user?
	 */
2206
again:
L
Linus Torvalds 已提交
2207
	spin_lock(&dentry->d_lock);
2208 2209
	inode = dentry->d_inode;
	isdir = S_ISDIR(inode->i_mode);
2210
	if (dentry->d_lockref.count == 1) {
A
Alan Cox 已提交
2211
		if (!spin_trylock(&inode->i_lock)) {
2212 2213 2214 2215
			spin_unlock(&dentry->d_lock);
			cpu_relax();
			goto again;
		}
A
Al Viro 已提交
2216
		dentry->d_flags &= ~DCACHE_CANT_MOUNT;
N
Nick Piggin 已提交
2217
		dentry_unlink_inode(dentry);
2218
		fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
2219 2220 2221 2222 2223 2224 2225
		return;
	}

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

	spin_unlock(&dentry->d_lock);
2226 2227

	fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
2228
}
2229
EXPORT_SYMBOL(d_delete);
L
Linus Torvalds 已提交
2230

2231
static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
L
Linus Torvalds 已提交
2232
{
2233
	BUG_ON(!d_unhashed(entry));
2234
	hlist_bl_lock(b);
2235
	entry->d_flags |= DCACHE_RCUACCESS;
2236
	hlist_bl_add_head_rcu(&entry->d_hash, b);
2237
	hlist_bl_unlock(b);
L
Linus Torvalds 已提交
2238 2239
}

2240 2241 2242 2243 2244
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
2245 2246 2247 2248 2249 2250 2251 2252 2253 2254
/**
 * 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);
2255
	_d_rehash(entry);
L
Linus Torvalds 已提交
2256 2257
	spin_unlock(&entry->d_lock);
}
2258
EXPORT_SYMBOL(d_rehash);
L
Linus Torvalds 已提交
2259

N
Nick Piggin 已提交
2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275
/**
 * 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)
{
2276
	BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));
N
Nick Piggin 已提交
2277 2278 2279
	BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */

	spin_lock(&dentry->d_lock);
N
Nick Piggin 已提交
2280
	write_seqcount_begin(&dentry->d_seq);
N
Nick Piggin 已提交
2281
	memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
N
Nick Piggin 已提交
2282
	write_seqcount_end(&dentry->d_seq);
N
Nick Piggin 已提交
2283 2284 2285 2286
	spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(dentry_update_name_case);

L
Linus Torvalds 已提交
2287 2288 2289 2290 2291 2292 2293
static void switch_names(struct dentry *dentry, struct dentry *target)
{
	if (dname_external(target)) {
		if (dname_external(dentry)) {
			/*
			 * Both external: swap the pointers
			 */
2294
			swap(target->d_name.name, dentry->d_name.name);
L
Linus Torvalds 已提交
2295 2296 2297 2298 2299
		} else {
			/*
			 * dentry:internal, target:external.  Steal target's
			 * storage and make target internal.
			 */
2300 2301
			memcpy(target->d_iname, dentry->d_name.name,
					dentry->d_name.len + 1);
L
Linus Torvalds 已提交
2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320
			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);
2321 2322
			dentry->d_name.len = target->d_name.len;
			return;
L
Linus Torvalds 已提交
2323 2324
		}
	}
2325
	swap(dentry->d_name.len, target->d_name.len);
L
Linus Torvalds 已提交
2326 2327
}

N
Nick Piggin 已提交
2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363
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
2364
/*
N
Nick Piggin 已提交
2365 2366 2367 2368 2369 2370 2371 2372 2373
 * 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
2374
 */
2375
/*
2376
 * __d_move - move a dentry
L
Linus Torvalds 已提交
2377 2378 2379 2380
 * @dentry: entry to move
 * @target: new dentry
 *
 * Update the dcache to reflect the move of a file name. Negative
2381 2382 2383
 * 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
2384
 */
2385
static void __d_move(struct dentry * dentry, struct dentry * target)
L
Linus Torvalds 已提交
2386 2387 2388 2389
{
	if (!dentry->d_inode)
		printk(KERN_WARNING "VFS: moving negative dcache entry\n");

N
Nick Piggin 已提交
2390 2391 2392 2393
	BUG_ON(d_ancestor(dentry, target));
	BUG_ON(d_ancestor(target, dentry));

	dentry_lock_for_move(dentry, target);
L
Linus Torvalds 已提交
2394

N
Nick Piggin 已提交
2395 2396 2397
	write_seqcount_begin(&dentry->d_seq);
	write_seqcount_begin(&target->d_seq);

2398 2399 2400 2401 2402 2403 2404
	/* __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
2405
	__d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
L
Linus Torvalds 已提交
2406 2407 2408 2409

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

E
Eric Dumazet 已提交
2410 2411
	list_del(&dentry->d_u.d_child);
	list_del(&target->d_u.d_child);
L
Linus Torvalds 已提交
2412 2413 2414

	/* Switch the names.. */
	switch_names(dentry, target);
2415
	swap(dentry->d_name.hash, target->d_name.hash);
L
Linus Torvalds 已提交
2416 2417 2418 2419 2420

	/* ... and switch the parents */
	if (IS_ROOT(dentry)) {
		dentry->d_parent = target->d_parent;
		target->d_parent = target;
E
Eric Dumazet 已提交
2421
		INIT_LIST_HEAD(&target->d_u.d_child);
L
Linus Torvalds 已提交
2422
	} else {
2423
		swap(dentry->d_parent, target->d_parent);
L
Linus Torvalds 已提交
2424 2425

		/* And add them back to the (new) parent lists */
E
Eric Dumazet 已提交
2426
		list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
L
Linus Torvalds 已提交
2427 2428
	}

E
Eric Dumazet 已提交
2429
	list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
N
Nick Piggin 已提交
2430

N
Nick Piggin 已提交
2431 2432 2433
	write_seqcount_end(&target->d_seq);
	write_seqcount_end(&dentry->d_seq);

N
Nick Piggin 已提交
2434
	dentry_unlock_parents_for_move(dentry, target);
L
Linus Torvalds 已提交
2435
	spin_unlock(&target->d_lock);
2436
	fsnotify_d_move(dentry);
L
Linus Torvalds 已提交
2437
	spin_unlock(&dentry->d_lock);
2438 2439 2440 2441 2442 2443 2444 2445
}

/*
 * d_move - move a dentry
 * @dentry: entry to move
 * @target: new dentry
 *
 * Update the dcache to reflect the move of a file name. Negative
2446 2447
 * dcache entries should not be moved in this way. See the locking
 * requirements for __d_move.
2448 2449 2450 2451 2452
 */
void d_move(struct dentry *dentry, struct dentry *target)
{
	write_seqlock(&rename_lock);
	__d_move(dentry, target);
L
Linus Torvalds 已提交
2453
	write_sequnlock(&rename_lock);
2454
}
2455
EXPORT_SYMBOL(d_move);
L
Linus Torvalds 已提交
2456

2457 2458 2459 2460 2461 2462 2463
/**
 * 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.
2464
 */
2465
struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2466 2467 2468
{
	struct dentry *p;

2469
	for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2470
		if (p->d_parent == p1)
2471
			return p;
2472
	}
2473
	return NULL;
2474 2475 2476 2477 2478 2479
}

/*
 * This helper attempts to cope with remotely renamed directories
 *
 * It assumes that the caller is already holding
2480
 * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
2481 2482 2483 2484
 *
 * Note: If ever the locking in lock_rename() changes, then please
 * remember to update this too...
 */
2485 2486
static struct dentry *__d_unalias(struct inode *inode,
		struct dentry *dentry, struct dentry *alias)
2487 2488
{
	struct mutex *m1 = NULL, *m2 = NULL;
2489
	struct dentry *ret = ERR_PTR(-EBUSY);
2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502

	/* 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:
2503 2504 2505 2506
	if (likely(!d_mountpoint(alias))) {
		__d_move(alias, dentry);
		ret = alias;
	}
2507
out_err:
2508
	spin_unlock(&inode->i_lock);
2509 2510 2511 2512 2513 2514 2515
	if (m2)
		mutex_unlock(m2);
	if (m1)
		mutex_unlock(m1);
	return ret;
}

2516 2517 2518
/*
 * 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
2519
 * returns with anon->d_lock held!
2520 2521 2522
 */
static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
{
2523
	struct dentry *dparent;
2524

N
Nick Piggin 已提交
2525
	dentry_lock_for_move(anon, dentry);
2526

N
Nick Piggin 已提交
2527 2528 2529
	write_seqcount_begin(&dentry->d_seq);
	write_seqcount_begin(&anon->d_seq);

2530 2531
	dparent = dentry->d_parent;

N
Nick Piggin 已提交
2532 2533 2534
	switch_names(dentry, anon);
	swap(dentry->d_name.hash, anon->d_name.hash);

2535 2536 2537
	dentry->d_parent = dentry;
	list_del_init(&dentry->d_u.d_child);
	anon->d_parent = dparent;
2538
	list_move(&anon->d_u.d_child, &dparent->d_subdirs);
2539

N
Nick Piggin 已提交
2540 2541 2542
	write_seqcount_end(&dentry->d_seq);
	write_seqcount_end(&anon->d_seq);

N
Nick Piggin 已提交
2543 2544 2545 2546
	dentry_unlock_parents_for_move(anon, dentry);
	spin_unlock(&dentry->d_lock);

	/* anon->d_lock still locked, returns locked */
2547 2548 2549 2550 2551 2552 2553 2554 2555
	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
2556 2557
 * root directory alias in its place if there is one. Caller must hold the
 * i_mutex of the parent directory.
2558 2559 2560
 */
struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
{
2561
	struct dentry *actual;
2562 2563 2564 2565 2566

	BUG_ON(!d_unhashed(dentry));

	if (!inode) {
		actual = dentry;
2567
		__d_instantiate(dentry, NULL);
2568 2569
		d_rehash(actual);
		goto out_nolock;
2570 2571
	}

2572
	spin_lock(&inode->i_lock);
2573

2574 2575 2576 2577
	if (S_ISDIR(inode->i_mode)) {
		struct dentry *alias;

		/* Does an aliased dentry already exist? */
2578
		alias = __d_find_alias(inode, 0);
2579 2580
		if (alias) {
			actual = alias;
2581 2582 2583 2584 2585
			write_seqlock(&rename_lock);

			if (d_ancestor(alias, dentry)) {
				/* Check for loops */
				actual = ERR_PTR(-ELOOP);
2586
				spin_unlock(&inode->i_lock);
2587 2588 2589
			} else if (IS_ROOT(alias)) {
				/* Is this an anonymous mountpoint that we
				 * could splice into our tree? */
2590
				__d_materialise_dentry(dentry, alias);
2591
				write_sequnlock(&rename_lock);
2592 2593
				__d_drop(alias);
				goto found;
2594 2595
			} else {
				/* Nope, but we must(!) avoid directory
2596
				 * aliasing. This drops inode->i_lock */
2597
				actual = __d_unalias(inode, dentry, alias);
2598
			}
2599
			write_sequnlock(&rename_lock);
2600 2601 2602 2603 2604 2605 2606 2607
			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);
2608
				dput(alias);
2609
			}
2610 2611
			goto out_nolock;
		}
2612 2613 2614 2615 2616 2617
	}

	/* Add a unique reference */
	actual = __d_instantiate_unique(dentry, inode);
	if (!actual)
		actual = dentry;
2618 2619
	else
		BUG_ON(!d_unhashed(actual));
2620 2621 2622 2623 2624

	spin_lock(&actual->d_lock);
found:
	_d_rehash(actual);
	spin_unlock(&actual->d_lock);
2625
	spin_unlock(&inode->i_lock);
2626
out_nolock:
2627 2628 2629 2630 2631 2632 2633 2634
	if (actual == dentry) {
		security_d_instantiate(dentry, inode);
		return NULL;
	}

	iput(inode);
	return actual;
}
2635
EXPORT_SYMBOL_GPL(d_materialise_unique);
2636

2637
static int prepend(char **buffer, int *buflen, const char *str, int namelen)
2638 2639 2640 2641 2642 2643 2644 2645 2646
{
	*buflen -= namelen;
	if (*buflen < 0)
		return -ENAMETOOLONG;
	*buffer -= namelen;
	memcpy(*buffer, str, namelen);
	return 0;
}

2647 2648 2649 2650 2651
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
2652
/**
2653
 * prepend_path - Prepend path string to a buffer
2654
 * @path: the dentry/vfsmount to report
2655
 * @root: root vfsmnt/dentry
M
Miklos Szeredi 已提交
2656 2657
 * @buffer: pointer to the end of the buffer
 * @buflen: pointer to buffer length
2658
 *
2659
 * Caller holds the rename_lock.
L
Linus Torvalds 已提交
2660
 */
2661 2662
static int prepend_path(const struct path *path,
			const struct path *root,
M
Miklos Szeredi 已提交
2663
			char **buffer, int *buflen)
L
Linus Torvalds 已提交
2664
{
2665 2666
	struct dentry *dentry = path->dentry;
	struct vfsmount *vfsmnt = path->mnt;
2667
	struct mount *mnt = real_mount(vfsmnt);
M
Miklos Szeredi 已提交
2668 2669
	bool slash = false;
	int error = 0;
2670

M
Miklos Szeredi 已提交
2671
	while (dentry != root->dentry || vfsmnt != root->mnt) {
L
Linus Torvalds 已提交
2672 2673 2674
		struct dentry * parent;

		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
2675
			/* Global root? */
2676
			if (!mnt_has_parent(mnt))
L
Linus Torvalds 已提交
2677
				goto global_root;
2678
			dentry = mnt->mnt_mountpoint;
2679 2680
			mnt = mnt->mnt_parent;
			vfsmnt = &mnt->mnt;
L
Linus Torvalds 已提交
2681 2682 2683 2684
			continue;
		}
		parent = dentry->d_parent;
		prefetch(parent);
N
Nick Piggin 已提交
2685
		spin_lock(&dentry->d_lock);
M
Miklos Szeredi 已提交
2686
		error = prepend_name(buffer, buflen, &dentry->d_name);
N
Nick Piggin 已提交
2687
		spin_unlock(&dentry->d_lock);
M
Miklos Szeredi 已提交
2688 2689 2690 2691 2692 2693
		if (!error)
			error = prepend(buffer, buflen, "/", 1);
		if (error)
			break;

		slash = true;
L
Linus Torvalds 已提交
2694 2695 2696
		dentry = parent;
	}

M
Miklos Szeredi 已提交
2697 2698 2699 2700
	if (!error && !slash)
		error = prepend(buffer, buflen, "/", 1);

	return error;
L
Linus Torvalds 已提交
2701 2702

global_root:
2703 2704 2705 2706 2707 2708 2709 2710 2711
	/*
	 * 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);
	}
2712 2713 2714
	if (!slash)
		error = prepend(buffer, buflen, "/", 1);
	if (!error)
A
Al Viro 已提交
2715
		error = is_mounted(vfsmnt) ? 1 : 2;
A
Al Viro 已提交
2716
	return error;
M
Miklos Szeredi 已提交
2717
}
2718

M
Miklos Szeredi 已提交
2719 2720 2721
/**
 * __d_path - return the path of a dentry
 * @path: the dentry/vfsmount to report
2722
 * @root: root vfsmnt/dentry
2723
 * @buf: buffer to return value in
M
Miklos Szeredi 已提交
2724 2725
 * @buflen: buffer length
 *
2726
 * Convert a dentry into an ASCII path name.
M
Miklos Szeredi 已提交
2727 2728 2729 2730
 *
 * Returns a pointer into the buffer or an error code if the
 * path was too long.
 *
2731
 * "buflen" should be positive.
M
Miklos Szeredi 已提交
2732
 *
2733
 * If the path is not reachable from the supplied root, return %NULL.
M
Miklos Szeredi 已提交
2734
 */
2735 2736
char *__d_path(const struct path *path,
	       const struct path *root,
M
Miklos Szeredi 已提交
2737 2738 2739 2740 2741 2742
	       char *buf, int buflen)
{
	char *res = buf + buflen;
	int error;

	prepend(&res, &buflen, "\0", 1);
A
Al Viro 已提交
2743
	br_read_lock(&vfsmount_lock);
2744
	write_seqlock(&rename_lock);
M
Miklos Szeredi 已提交
2745
	error = prepend_path(path, root, &res, &buflen);
2746
	write_sequnlock(&rename_lock);
A
Al Viro 已提交
2747
	br_read_unlock(&vfsmount_lock);
2748

2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763
	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);
A
Al Viro 已提交
2764
	br_read_lock(&vfsmount_lock);
2765 2766 2767
	write_seqlock(&rename_lock);
	error = prepend_path(path, &root, &res, &buflen);
	write_sequnlock(&rename_lock);
A
Al Viro 已提交
2768
	br_read_unlock(&vfsmount_lock);
2769 2770 2771 2772

	if (error > 1)
		error = -EINVAL;
	if (error < 0)
M
Miklos Szeredi 已提交
2773 2774
		return ERR_PTR(error);
	return res;
L
Linus Torvalds 已提交
2775 2776
}

2777 2778 2779
/*
 * same as __d_path but appends "(deleted)" for unlinked files.
 */
2780 2781 2782
static int path_with_deleted(const struct path *path,
			     const struct path *root,
			     char **buf, int *buflen)
2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793
{
	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);
}

2794 2795 2796 2797 2798
static int prepend_unreachable(char **buffer, int *buflen)
{
	return prepend(buffer, buflen, "(unreachable)", 13);
}

J
Jan Blunck 已提交
2799 2800
/**
 * d_path - return the path of a dentry
2801
 * @path: path to report
J
Jan Blunck 已提交
2802 2803 2804 2805 2806 2807
 * @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.
 *
2808 2809 2810 2811
 * 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
2812
 *
2813
 * "buflen" should be positive.
J
Jan Blunck 已提交
2814
 */
2815
char *d_path(const struct path *path, char *buf, int buflen)
L
Linus Torvalds 已提交
2816
{
2817
	char *res = buf + buflen;
J
Jan Blunck 已提交
2818
	struct path root;
2819
	int error;
L
Linus Torvalds 已提交
2820

2821 2822 2823 2824 2825 2826 2827
	/*
	 * 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:
	 */
2828 2829
	if (path->dentry->d_op && path->dentry->d_op->d_dname)
		return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2830

2831
	get_fs_root(current->fs, &root);
A
Al Viro 已提交
2832
	br_read_lock(&vfsmount_lock);
2833
	write_seqlock(&rename_lock);
2834
	error = path_with_deleted(path, &root, &res, &buflen);
A
Al Viro 已提交
2835 2836
	write_sequnlock(&rename_lock);
	br_read_unlock(&vfsmount_lock);
2837
	if (error < 0)
2838
		res = ERR_PTR(error);
J
Jan Blunck 已提交
2839
	path_put(&root);
L
Linus Torvalds 已提交
2840 2841
	return res;
}
2842
EXPORT_SYMBOL(d_path);
L
Linus Torvalds 已提交
2843

2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864
/*
 * 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);
}

2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875
char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
{
	char *end = buffer + buflen;
	/* these dentries are never renamed, so d_lock is not needed */
	if (prepend(&end, &buflen, " (deleted)", 11) ||
	    prepend_name(&end, &buflen, &dentry->d_name) ||
	    prepend(&end, &buflen, "/", 1))  
		end = ERR_PTR(-ENAMETOOLONG);
	return end;  
}

2876 2877 2878
/*
 * Write full pathname from the root of the filesystem into the buffer.
 */
N
Nick Piggin 已提交
2879
static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890
{
	char *end = buf + buflen;
	char *retval;

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

2891 2892
	while (!IS_ROOT(dentry)) {
		struct dentry *parent = dentry->d_parent;
N
Nick Piggin 已提交
2893
		int error;
2894 2895

		prefetch(parent);
N
Nick Piggin 已提交
2896 2897 2898 2899
		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)
2900 2901 2902 2903 2904
			goto Elong;

		retval = end;
		dentry = parent;
	}
A
Al Viro 已提交
2905 2906 2907 2908
	return retval;
Elong:
	return ERR_PTR(-ENAMETOOLONG);
}
N
Nick Piggin 已提交
2909 2910 2911 2912 2913

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

2914
	write_seqlock(&rename_lock);
N
Nick Piggin 已提交
2915
	retval = __dentry_path(dentry, buf, buflen);
2916
	write_sequnlock(&rename_lock);
N
Nick Piggin 已提交
2917 2918 2919 2920

	return retval;
}
EXPORT_SYMBOL(dentry_path_raw);
A
Al Viro 已提交
2921 2922 2923 2924 2925 2926

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

2927
	write_seqlock(&rename_lock);
A
Al Viro 已提交
2928 2929 2930 2931 2932 2933 2934
	if (d_unlinked(dentry)) {
		p = buf + buflen;
		if (prepend(&p, &buflen, "//deleted", 10) != 0)
			goto Elong;
		buflen++;
	}
	retval = __dentry_path(dentry, buf, buflen);
2935
	write_sequnlock(&rename_lock);
A
Al Viro 已提交
2936 2937
	if (!IS_ERR(retval) && p)
		*p = '/';	/* restore '/' overriden with '\0' */
2938 2939 2940 2941 2942
	return retval;
Elong:
	return ERR_PTR(-ENAMETOOLONG);
}

L
Linus Torvalds 已提交
2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960
/*
 * 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;
 *	}
 */
2961
SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
L
Linus Torvalds 已提交
2962
{
2963
	int error;
J
Jan Blunck 已提交
2964
	struct path pwd, root;
2965
	char *page = (char *) __get_free_page(GFP_USER);
L
Linus Torvalds 已提交
2966 2967 2968 2969

	if (!page)
		return -ENOMEM;

2970
	get_fs_root_and_pwd(current->fs, &root, &pwd);
L
Linus Torvalds 已提交
2971

2972
	error = -ENOENT;
A
Al Viro 已提交
2973
	br_read_lock(&vfsmount_lock);
2974
	write_seqlock(&rename_lock);
2975
	if (!d_unlinked(pwd.dentry)) {
2976
		unsigned long len;
2977 2978
		char *cwd = page + PAGE_SIZE;
		int buflen = PAGE_SIZE;
L
Linus Torvalds 已提交
2979

2980
		prepend(&cwd, &buflen, "\0", 1);
2981
		error = prepend_path(&pwd, &root, &cwd, &buflen);
2982
		write_sequnlock(&rename_lock);
A
Al Viro 已提交
2983
		br_read_unlock(&vfsmount_lock);
2984

2985
		if (error < 0)
2986 2987
			goto out;

2988
		/* Unreachable from current root */
2989
		if (error > 0) {
2990 2991 2992 2993 2994
			error = prepend_unreachable(&cwd, &buflen);
			if (error)
				goto out;
		}

2995 2996 2997 2998 2999 3000 3001
		error = -ERANGE;
		len = PAGE_SIZE + page - cwd;
		if (len <= size) {
			error = len;
			if (copy_to_user(buf, cwd, len))
				error = -EFAULT;
		}
3002 3003
	} else {
		write_sequnlock(&rename_lock);
A
Al Viro 已提交
3004
		br_read_unlock(&vfsmount_lock);
3005
	}
L
Linus Torvalds 已提交
3006 3007

out:
J
Jan Blunck 已提交
3008 3009
	path_put(&pwd);
	path_put(&root);
L
Linus Torvalds 已提交
3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029
	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()
 */
  
3030
int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
L
Linus Torvalds 已提交
3031 3032
{
	int result;
3033
	unsigned seq;
L
Linus Torvalds 已提交
3034

3035 3036 3037 3038
	if (new_dentry == old_dentry)
		return 1;

	do {
L
Linus Torvalds 已提交
3039 3040
		/* for restarting inner loop in case of seq retry */
		seq = read_seqbegin(&rename_lock);
3041 3042 3043 3044 3045
		/*
		 * Need rcu_readlock to protect against the d_parent trashing
		 * due to d_move
		 */
		rcu_read_lock();
3046
		if (d_ancestor(old_dentry, new_dentry))
L
Linus Torvalds 已提交
3047
			result = 1;
3048 3049
		else
			result = 0;
3050
		rcu_read_unlock();
L
Linus Torvalds 已提交
3051 3052 3053 3054 3055
	} while (read_seqretry(&rename_lock, seq));

	return result;
}

M
Miklos Szeredi 已提交
3056
static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
L
Linus Torvalds 已提交
3057
{
M
Miklos Szeredi 已提交
3058 3059 3060 3061
	struct dentry *root = data;
	if (dentry != root) {
		if (d_unhashed(dentry) || !dentry->d_inode)
			return D_WALK_SKIP;
L
Linus Torvalds 已提交
3062

M
Miklos Szeredi 已提交
3063 3064 3065 3066
		if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
			dentry->d_flags |= DCACHE_GENOCIDE;
			dentry->d_lockref.count--;
		}
L
Linus Torvalds 已提交
3067
	}
M
Miklos Szeredi 已提交
3068 3069
	return D_WALK_CONTINUE;
}
3070

M
Miklos Szeredi 已提交
3071 3072 3073
void d_genocide(struct dentry *parent)
{
	d_walk(parent, parent, d_genocide_kill, NULL);
L
Linus Torvalds 已提交
3074 3075
}

3076
void d_tmpfile(struct dentry *dentry, struct inode *inode)
L
Linus Torvalds 已提交
3077
{
3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088
	inode_dec_link_count(inode);
	BUG_ON(dentry->d_name.name != dentry->d_iname ||
		!hlist_unhashed(&dentry->d_alias) ||
		!d_unlinked(dentry));
	spin_lock(&dentry->d_parent->d_lock);
	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
	dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
				(unsigned long long)inode->i_ino);
	spin_unlock(&dentry->d_lock);
	spin_unlock(&dentry->d_parent->d_lock);
	d_instantiate(dentry, inode);
L
Linus Torvalds 已提交
3089
}
3090
EXPORT_SYMBOL(d_tmpfile);
L
Linus Torvalds 已提交
3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103

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)
{
3104
	unsigned int loop;
L
Linus Torvalds 已提交
3105 3106 3107 3108 3109 3110 3111 3112 3113

	/* 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",
3114
					sizeof(struct hlist_bl_head),
L
Linus Torvalds 已提交
3115 3116 3117 3118 3119
					dhash_entries,
					13,
					HASH_EARLY,
					&d_hash_shift,
					&d_hash_mask,
3120
					0,
L
Linus Torvalds 已提交
3121 3122
					0);

3123
	for (loop = 0; loop < (1U << d_hash_shift); loop++)
3124
		INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
L
Linus Torvalds 已提交
3125 3126
}

3127
static void __init dcache_init(void)
L
Linus Torvalds 已提交
3128
{
3129
	unsigned int loop;
L
Linus Torvalds 已提交
3130 3131 3132 3133 3134 3135

	/* 
	 * 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. 
	 */
3136 3137
	dentry_cache = KMEM_CACHE(dentry,
		SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
L
Linus Torvalds 已提交
3138 3139 3140 3141 3142 3143 3144

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

	dentry_hashtable =
		alloc_large_system_hash("Dentry cache",
3145
					sizeof(struct hlist_bl_head),
L
Linus Torvalds 已提交
3146 3147 3148 3149 3150
					dhash_entries,
					13,
					0,
					&d_hash_shift,
					&d_hash_mask,
3151
					0,
L
Linus Torvalds 已提交
3152 3153
					0);

3154
	for (loop = 0; loop < (1U << d_hash_shift); loop++)
3155
		INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
L
Linus Torvalds 已提交
3156 3157 3158
}

/* SLAB cache for __getname() consumers */
3159
struct kmem_cache *names_cachep __read_mostly;
3160
EXPORT_SYMBOL(names_cachep);
L
Linus Torvalds 已提交
3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180

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,
3181
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
L
Linus Torvalds 已提交
3182

3183 3184
	dcache_init();
	inode_init();
L
Linus Torvalds 已提交
3185
	files_init(mempages);
3186
	mnt_init();
L
Linus Torvalds 已提交
3187 3188 3189
	bdev_cache_init();
	chrdev_init();
}