dcache.c 76.1 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>
#include <linux/module.h>
#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 "internal.h"
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/*
 * Usage:
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 * dcache_inode_lock protects:
 *   - i_dentry, d_alias, d_inode
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 * dcache_hash_lock protects:
 *   - the dcache hash table, s_anon lists
 * 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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 * dcache_inode_lock
 *   dentry->d_lock
 *     dcache_lru_lock
 *     dcache_hash_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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__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_inode_lock);
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static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_hash_lock);
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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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EXPORT_SYMBOL(dcache_inode_lock);
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static struct kmem_cache *dentry_cache __read_mostly;
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#define DNAME_INLINE_LEN (sizeof(struct dentry)-offsetof(struct dentry,d_iname))

/*
 * 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;
static struct hlist_head *dentry_hashtable __read_mostly;
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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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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(!list_empty(&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_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 inserted into hash, immediate free is OK */
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	if (hlist_unhashed(&dentry->d_hash))
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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
 * 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(dcache_inode_lock)
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{
	struct inode *inode = dentry->d_inode;
	if (inode) {
		dentry->d_inode = NULL;
		list_del_init(&dentry->d_alias);
		spin_unlock(&dentry->d_lock);
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		spin_unlock(&dcache_inode_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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		spin_unlock(&dcache_inode_lock);
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	}
}

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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)
	__releases(dcache_inode_lock)
{
	struct inode *inode = dentry->d_inode;
	dentry->d_inode = NULL;
	list_del_init(&dentry->d_alias);
	dentry_rcuwalk_barrier(dentry);
	spin_unlock(&dentry->d_lock);
	spin_unlock(&dcache_inode_lock);
	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|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 (list_empty(&dentry->d_lru)) {
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		spin_lock(&dcache_lru_lock);
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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);
	dentry->d_sb->s_nr_dentry_unused--;
	dentry_stat.nr_unused--;
}

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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_tail(struct dentry *dentry)
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{
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	spin_lock(&dcache_lru_lock);
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	if (list_empty(&dentry->d_lru)) {
		list_add_tail(&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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	} else {
		list_move_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
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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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 * 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(dcache_inode_lock)
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{
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	dentry->d_parent = NULL;
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	list_del(&dentry->d_u.d_child);
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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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/**
 * 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)
{
	if (!(dentry->d_flags & DCACHE_UNHASHED)) {
		dentry->d_flags |= DCACHE_UNHASHED;
		spin_lock(&dcache_hash_lock);
		hlist_del_rcu(&dentry->d_hash);
		spin_unlock(&dcache_hash_lock);
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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)
{
	struct dentry *parent;

	if (!spin_trylock(&dcache_inode_lock)) {
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)) {
		spin_unlock(&dcache_inode_lock);
		goto relock;
	}
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	if (ref)
		dentry->d_count--;
	/* if dentry was on the d_lru list delete it from there */
	dentry_lru_del(dentry);
	/* 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)
{
	if (!dentry)
		return;

repeat:
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	if (dentry->d_count == 1)
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		might_sleep();
	spin_lock(&dentry->d_lock);
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	BUG_ON(!dentry->d_count);
	if (dentry->d_count > 1) {
		dentry->d_count--;
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		spin_unlock(&dentry->d_lock);
		return;
	}

	if (dentry->d_op && dentry->d_op->d_delete) {
		if (dentry->d_op->d_delete(dentry))
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			goto kill_it;
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	}
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	/* Unreachable? Get rid of it */
 	if (d_unhashed(dentry))
		goto kill_it;
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	/* Otherwise leave it cached and ensure it's on the LRU */
	dentry->d_flags |= DCACHE_REFERENCED;
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	dentry_lru_add(dentry);
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	dentry->d_count--;
	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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		spin_lock(&dentry->d_lock);
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	}

	/*
	 * 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).
	 */
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	if (dentry->d_count > 1) {
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		if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
			spin_unlock(&dentry->d_lock);
			return -EBUSY;
		}
	}

	__d_drop(dentry);
	spin_unlock(&dentry->d_lock);
	return 0;
}
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EXPORT_SYMBOL(d_invalidate);
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/* This must be called with d_lock held */
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static inline void __dget_dlock(struct dentry *dentry)
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{
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	dentry->d_count++;
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}

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static inline void __dget(struct dentry *dentry)
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{
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	spin_lock(&dentry->d_lock);
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	__dget_dlock(dentry);
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	spin_unlock(&dentry->d_lock);
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}

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struct dentry *dget_parent(struct dentry *dentry)
{
	struct dentry *ret;

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	/*
	 * Don't need rcu_dereference because we re-check it was correct under
	 * the lock.
	 */
	rcu_read_lock();
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	ret = dentry->d_parent;
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	if (!ret) {
		rcu_read_unlock();
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		goto out;
	}
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	spin_lock(&ret->d_lock);
	if (unlikely(ret != dentry->d_parent)) {
		spin_unlock(&ret->d_lock);
		rcu_read_unlock();
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		goto repeat;
	}
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	rcu_read_unlock();
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	BUG_ON(!ret->d_count);
	ret->d_count++;
	spin_unlock(&ret->d_lock);
out:
	return ret;
}
EXPORT_SYMBOL(dget_parent);

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/**
 * d_find_alias - grab a hashed alias of inode
 * @inode: inode in question
 * @want_discon:  flag, used by d_splice_alias, to request
 *          that only a DISCONNECTED alias be returned.
 *
 * 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.
 *
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 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
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 * any other hashed alias over that one unless @want_discon is set,
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 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
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 */
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static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
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{
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	struct dentry *alias, *discon_alias;
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again:
	discon_alias = NULL;
	list_for_each_entry(alias, &inode->i_dentry, d_alias) {
		spin_lock(&alias->d_lock);
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 		if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
548
			if (IS_ROOT(alias) &&
N
Nick Piggin 已提交
549
			    (alias->d_flags & DCACHE_DISCONNECTED)) {
L
Linus Torvalds 已提交
550
				discon_alias = alias;
N
Nick Piggin 已提交
551
			} else if (!want_discon) {
552
				__dget_dlock(alias);
N
Nick Piggin 已提交
553 554 555 556 557 558 559 560 561 562 563 564
				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)) {
565
				__dget_dlock(alias);
N
Nick Piggin 已提交
566
				spin_unlock(&alias->d_lock);
L
Linus Torvalds 已提交
567 568 569
				return alias;
			}
		}
N
Nick Piggin 已提交
570 571
		spin_unlock(&alias->d_lock);
		goto again;
L
Linus Torvalds 已提交
572
	}
N
Nick Piggin 已提交
573
	return NULL;
L
Linus Torvalds 已提交
574 575
}

N
Nick Piggin 已提交
576
struct dentry *d_find_alias(struct inode *inode)
L
Linus Torvalds 已提交
577
{
D
David Howells 已提交
578 579 580
	struct dentry *de = NULL;

	if (!list_empty(&inode->i_dentry)) {
N
Nick Piggin 已提交
581
		spin_lock(&dcache_inode_lock);
D
David Howells 已提交
582
		de = __d_find_alias(inode, 0);
N
Nick Piggin 已提交
583
		spin_unlock(&dcache_inode_lock);
D
David Howells 已提交
584
	}
L
Linus Torvalds 已提交
585 586
	return de;
}
587
EXPORT_SYMBOL(d_find_alias);
L
Linus Torvalds 已提交
588 589 590 591 592 593 594

/*
 *	Try to kill dentries associated with this inode.
 * WARNING: you must own a reference to inode.
 */
void d_prune_aliases(struct inode *inode)
{
595
	struct dentry *dentry;
L
Linus Torvalds 已提交
596
restart:
N
Nick Piggin 已提交
597
	spin_lock(&dcache_inode_lock);
598
	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
L
Linus Torvalds 已提交
599
		spin_lock(&dentry->d_lock);
N
Nick Piggin 已提交
600
		if (!dentry->d_count) {
601
			__dget_dlock(dentry);
L
Linus Torvalds 已提交
602 603
			__d_drop(dentry);
			spin_unlock(&dentry->d_lock);
N
Nick Piggin 已提交
604
			spin_unlock(&dcache_inode_lock);
L
Linus Torvalds 已提交
605 606 607 608 609
			dput(dentry);
			goto restart;
		}
		spin_unlock(&dentry->d_lock);
	}
N
Nick Piggin 已提交
610
	spin_unlock(&dcache_inode_lock);
L
Linus Torvalds 已提交
611
}
612
EXPORT_SYMBOL(d_prune_aliases);
L
Linus Torvalds 已提交
613 614

/*
615 616 617
 * 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.
618
 *
619
 * This may fail if locks cannot be acquired no problem, just try again.
L
Linus Torvalds 已提交
620
 */
621
static void try_prune_one_dentry(struct dentry *dentry)
622
	__releases(dentry->d_lock)
L
Linus Torvalds 已提交
623
{
624
	struct dentry *parent;
625

626
	parent = dentry_kill(dentry, 0);
627
	/*
628 629 630 631 632 633 634 635
	 * 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.
636
	 */
637 638 639 640 641 642 643
	if (!parent)
		return;
	if (parent == dentry)
		return;

	/* Prune ancestors. */
	dentry = parent;
644
	while (dentry) {
N
Nick Piggin 已提交
645
		spin_lock(&dentry->d_lock);
646 647 648 649 650
		if (dentry->d_count > 1) {
			dentry->d_count--;
			spin_unlock(&dentry->d_lock);
			return;
		}
651
		dentry = dentry_kill(dentry, 1);
652
	}
L
Linus Torvalds 已提交
653 654
}

C
Christoph Hellwig 已提交
655
static void shrink_dentry_list(struct list_head *list)
L
Linus Torvalds 已提交
656
{
657 658
	struct dentry *dentry;

659 660 661 662 663 664 665 666
	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
667 668 669
			continue;
		}

L
Linus Torvalds 已提交
670 671
		/*
		 * We found an inuse dentry which was not removed from
672 673
		 * the LRU because of laziness during lookup.  Do not free
		 * it - just keep it off the LRU list.
L
Linus Torvalds 已提交
674
		 */
N
Nick Piggin 已提交
675
		if (dentry->d_count) {
676
			dentry_lru_del(dentry);
677
			spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
678 679
			continue;
		}
680 681

		rcu_read_unlock();
682 683 684

		try_prune_one_dentry(dentry);

685
		rcu_read_lock();
686
	}
687
	rcu_read_unlock();
C
Christoph Hellwig 已提交
688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705
}

/**
 * __shrink_dcache_sb - shrink the dentry LRU on a given superblock
 * @sb:		superblock to shrink dentry LRU.
 * @count:	number of entries to prune
 * @flags:	flags to control the dentry processing
 *
 * If flags contains DCACHE_REFERENCED reference dentries will not be pruned.
 */
static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
{
	/* called from prune_dcache() and shrink_dcache_parent() */
	struct dentry *dentry;
	LIST_HEAD(referenced);
	LIST_HEAD(tmp);
	int cnt = *count;

N
Nick Piggin 已提交
706 707
relock:
	spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
708 709 710 711 712
	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
713 714 715 716 717 718
		if (!spin_trylock(&dentry->d_lock)) {
			spin_unlock(&dcache_lru_lock);
			cpu_relax();
			goto relock;
		}

C
Christoph Hellwig 已提交
719 720 721 722 723
		/*
		 * If we are honouring the DCACHE_REFERENCED flag and the
		 * dentry has this flag set, don't free it.  Clear the flag
		 * and put it back on the LRU.
		 */
N
Nick Piggin 已提交
724 725 726 727
		if (flags & DCACHE_REFERENCED &&
				dentry->d_flags & DCACHE_REFERENCED) {
			dentry->d_flags &= ~DCACHE_REFERENCED;
			list_move(&dentry->d_lru, &referenced);
C
Christoph Hellwig 已提交
728
			spin_unlock(&dentry->d_lock);
N
Nick Piggin 已提交
729 730 731 732 733
		} else {
			list_move_tail(&dentry->d_lru, &tmp);
			spin_unlock(&dentry->d_lock);
			if (!--cnt)
				break;
C
Christoph Hellwig 已提交
734
		}
735
		cond_resched_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
736
	}
737 738
	if (!list_empty(&referenced))
		list_splice(&referenced, &sb->s_dentry_lru);
N
Nick Piggin 已提交
739
	spin_unlock(&dcache_lru_lock);
740 741 742 743

	shrink_dentry_list(&tmp);

	*count = cnt;
744 745 746 747 748 749 750 751 752 753 754 755 756
}

/**
 * prune_dcache - shrink the dcache
 * @count: number of entries to try to free
 *
 * Shrink the dcache. This is done when we need more memory, or simply when we
 * need to unmount something (at which point we need to unuse all dentries).
 *
 * This function may fail to free any resources if all the dentries are in use.
 */
static void prune_dcache(int count)
{
757
	struct super_block *sb, *p = NULL;
758
	int w_count;
759
	int unused = dentry_stat.nr_unused;
760 761 762 763 764 765 766 767 768 769
	int prune_ratio;
	int pruned;

	if (unused == 0 || count == 0)
		return;
	if (count >= unused)
		prune_ratio = 1;
	else
		prune_ratio = unused / count;
	spin_lock(&sb_lock);
770
	list_for_each_entry(sb, &super_blocks, s_list) {
771 772
		if (list_empty(&sb->s_instances))
			continue;
773
		if (sb->s_nr_dentry_unused == 0)
L
Linus Torvalds 已提交
774
			continue;
775 776 777 778 779 780 781 782 783
		sb->s_count++;
		/* Now, we reclaim unused dentrins with fairness.
		 * We reclaim them same percentage from each superblock.
		 * We calculate number of dentries to scan on this sb
		 * as follows, but the implementation is arranged to avoid
		 * overflows:
		 * number of dentries to scan on this sb =
		 * count * (number of dentries on this sb /
		 * number of dentries in the machine)
784
		 */
785 786 787 788 789 790
		spin_unlock(&sb_lock);
		if (prune_ratio != 1)
			w_count = (sb->s_nr_dentry_unused / prune_ratio) + 1;
		else
			w_count = sb->s_nr_dentry_unused;
		pruned = w_count;
791
		/*
792 793 794 795 796
		 * We need to be sure this filesystem isn't being unmounted,
		 * otherwise we could race with generic_shutdown_super(), and
		 * end up holding a reference to an inode while the filesystem
		 * is unmounted.  So we try to get s_umount, and make sure
		 * s_root isn't NULL.
797
		 */
798 799 800 801 802 803
		if (down_read_trylock(&sb->s_umount)) {
			if ((sb->s_root != NULL) &&
			    (!list_empty(&sb->s_dentry_lru))) {
				__shrink_dcache_sb(sb, &w_count,
						DCACHE_REFERENCED);
				pruned -= w_count;
804
			}
805
			up_read(&sb->s_umount);
806
		}
807
		spin_lock(&sb_lock);
808 809
		if (p)
			__put_super(p);
810
		count -= pruned;
811
		p = sb;
A
Al Viro 已提交
812 813 814
		/* more work left to do? */
		if (count <= 0)
			break;
L
Linus Torvalds 已提交
815
	}
816 817
	if (p)
		__put_super(p);
818
	spin_unlock(&sb_lock);
L
Linus Torvalds 已提交
819 820 821 822 823 824
}

/**
 * shrink_dcache_sb - shrink dcache for a superblock
 * @sb: superblock
 *
C
Christoph Hellwig 已提交
825 826
 * 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
827
 */
C
Christoph Hellwig 已提交
828
void shrink_dcache_sb(struct super_block *sb)
L
Linus Torvalds 已提交
829
{
C
Christoph Hellwig 已提交
830 831
	LIST_HEAD(tmp);

N
Nick Piggin 已提交
832
	spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
833 834
	while (!list_empty(&sb->s_dentry_lru)) {
		list_splice_init(&sb->s_dentry_lru, &tmp);
835
		spin_unlock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
836
		shrink_dentry_list(&tmp);
837
		spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
838
	}
N
Nick Piggin 已提交
839
	spin_unlock(&dcache_lru_lock);
L
Linus Torvalds 已提交
840
}
841
EXPORT_SYMBOL(shrink_dcache_sb);
L
Linus Torvalds 已提交
842

843 844 845 846 847 848 849 850
/*
 * 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;
851
	unsigned detached = 0;
852 853 854 855

	BUG_ON(!IS_ROOT(dentry));

	/* detach this root from the system */
N
Nick Piggin 已提交
856
	spin_lock(&dentry->d_lock);
857
	dentry_lru_del(dentry);
858
	__d_drop(dentry);
N
Nick Piggin 已提交
859
	spin_unlock(&dentry->d_lock);
860 861 862 863 864 865 866 867

	for (;;) {
		/* descend to the first leaf in the current subtree */
		while (!list_empty(&dentry->d_subdirs)) {
			struct dentry *loop;

			/* this is a branch with children - detach all of them
			 * from the system in one go */
N
Nick Piggin 已提交
868
			spin_lock(&dentry->d_lock);
869 870
			list_for_each_entry(loop, &dentry->d_subdirs,
					    d_u.d_child) {
N
Nick Piggin 已提交
871 872
				spin_lock_nested(&loop->d_lock,
						DENTRY_D_LOCK_NESTED);
873
				dentry_lru_del(loop);
874
				__d_drop(loop);
N
Nick Piggin 已提交
875
				spin_unlock(&loop->d_lock);
876
			}
N
Nick Piggin 已提交
877
			spin_unlock(&dentry->d_lock);
878 879 880 881 882 883 884 885 886 887 888

			/* move to the first child */
			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;

N
Nick Piggin 已提交
889
			if (dentry->d_count != 0) {
890 891 892 893 894 895 896 897
				printk(KERN_ERR
				       "BUG: Dentry %p{i=%lx,n=%s}"
				       " still in use (%d)"
				       " [unmount of %s %s]\n",
				       dentry,
				       dentry->d_inode ?
				       dentry->d_inode->i_ino : 0UL,
				       dentry->d_name.name,
N
Nick Piggin 已提交
898
				       dentry->d_count,
899 900 901 902 903
				       dentry->d_sb->s_type->name,
				       dentry->d_sb->s_id);
				BUG();
			}

N
Nick Piggin 已提交
904
			if (IS_ROOT(dentry)) {
905
				parent = NULL;
N
Nick Piggin 已提交
906 907
				list_del(&dentry->d_u.d_child);
			} else {
908
				parent = dentry->d_parent;
N
Nick Piggin 已提交
909 910
				spin_lock(&parent->d_lock);
				parent->d_count--;
N
Nick Piggin 已提交
911
				list_del(&dentry->d_u.d_child);
N
Nick Piggin 已提交
912
				spin_unlock(&parent->d_lock);
913
			}
914

915
			detached++;
916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932

			inode = dentry->d_inode;
			if (inode) {
				dentry->d_inode = NULL;
				list_del_init(&dentry->d_alias);
				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)
933
				return;
934 935 936 937 938 939 940 941 942 943
			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
944
 * - we don't need to use dentry->d_lock because:
945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960
 *   - the superblock is detached from all mountings and open files, so the
 *     dentry trees will not be rearranged by the VFS
 *   - s_umount is write-locked, so the memory pressure shrinker will ignore
 *     any dentries belonging to this superblock that it comes across
 *   - the filesystem itself is no longer permitted to rearrange the dentries
 *     in this superblock
 */
void shrink_dcache_for_umount(struct super_block *sb)
{
	struct dentry *dentry;

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

	dentry = sb->s_root;
	sb->s_root = NULL;
N
Nick Piggin 已提交
961 962 963
	spin_lock(&dentry->d_lock);
	dentry->d_count--;
	spin_unlock(&dentry->d_lock);
964 965 966 967 968 969 970 971
	shrink_dcache_for_umount_subtree(dentry);

	while (!hlist_empty(&sb->s_anon)) {
		dentry = hlist_entry(sb->s_anon.first, struct dentry, d_hash);
		shrink_dcache_for_umount_subtree(dentry);
	}
}

L
Linus Torvalds 已提交
972 973 974 975 976 977 978 979 980 981 982 983 984 985 986
/*
 * Search for at least 1 mount point in the dentry's subdirs.
 * We descend to the next level whenever the d_subdirs
 * list is non-empty and continue searching.
 */
 
/**
 * have_submounts - check for mounts over a dentry
 * @parent: dentry to check.
 *
 * Return true if the parent or its subdirectories contain
 * a mount point
 */
int have_submounts(struct dentry *parent)
{
987
	struct dentry *this_parent;
L
Linus Torvalds 已提交
988
	struct list_head *next;
989
	unsigned seq;
990
	int locked = 0;
991 992

	seq = read_seqbegin(&rename_lock);
993 994
again:
	this_parent = parent;
L
Linus Torvalds 已提交
995 996 997

	if (d_mountpoint(parent))
		goto positive;
N
Nick Piggin 已提交
998
	spin_lock(&this_parent->d_lock);
L
Linus Torvalds 已提交
999 1000 1001 1002 1003
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
1004
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
1005
		next = tmp->next;
N
Nick Piggin 已提交
1006 1007

		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
L
Linus Torvalds 已提交
1008
		/* Have we found a mount point ? */
N
Nick Piggin 已提交
1009 1010 1011
		if (d_mountpoint(dentry)) {
			spin_unlock(&dentry->d_lock);
			spin_unlock(&this_parent->d_lock);
L
Linus Torvalds 已提交
1012
			goto positive;
N
Nick Piggin 已提交
1013
		}
L
Linus Torvalds 已提交
1014
		if (!list_empty(&dentry->d_subdirs)) {
N
Nick Piggin 已提交
1015 1016
			spin_unlock(&this_parent->d_lock);
			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
L
Linus Torvalds 已提交
1017
			this_parent = dentry;
N
Nick Piggin 已提交
1018
			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
L
Linus Torvalds 已提交
1019 1020
			goto repeat;
		}
N
Nick Piggin 已提交
1021
		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
1022 1023 1024 1025 1026
	}
	/*
	 * All done at this level ... ascend and resume the search.
	 */
	if (this_parent != parent) {
1027 1028 1029 1030 1031
		struct dentry *tmp;
		struct dentry *child;

		tmp = this_parent->d_parent;
		rcu_read_lock();
N
Nick Piggin 已提交
1032
		spin_unlock(&this_parent->d_lock);
1033 1034
		child = this_parent;
		this_parent = tmp;
N
Nick Piggin 已提交
1035
		spin_lock(&this_parent->d_lock);
1036 1037 1038
		/* might go back up the wrong parent if we have had a rename
		 * or deletion */
		if (this_parent != child->d_parent ||
1039
			 (!locked && read_seqretry(&rename_lock, seq))) {
1040 1041 1042 1043 1044 1045
			spin_unlock(&this_parent->d_lock);
			rcu_read_unlock();
			goto rename_retry;
		}
		rcu_read_unlock();
		next = child->d_u.d_child.next;
L
Linus Torvalds 已提交
1046 1047
		goto resume;
	}
N
Nick Piggin 已提交
1048
	spin_unlock(&this_parent->d_lock);
1049
	if (!locked && read_seqretry(&rename_lock, seq))
1050
		goto rename_retry;
1051 1052
	if (locked)
		write_sequnlock(&rename_lock);
L
Linus Torvalds 已提交
1053 1054
	return 0; /* No mount points found in tree */
positive:
1055
	if (!locked && read_seqretry(&rename_lock, seq))
1056
		goto rename_retry;
1057 1058
	if (locked)
		write_sequnlock(&rename_lock);
L
Linus Torvalds 已提交
1059
	return 1;
1060 1061 1062 1063 1064

rename_retry:
	locked = 1;
	write_seqlock(&rename_lock);
	goto again;
L
Linus Torvalds 已提交
1065
}
1066
EXPORT_SYMBOL(have_submounts);
L
Linus Torvalds 已提交
1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083

/*
 * Search the dentry child list for the specified parent,
 * 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.
 */
static int select_parent(struct dentry * parent)
{
1084
	struct dentry *this_parent;
L
Linus Torvalds 已提交
1085
	struct list_head *next;
1086
	unsigned seq;
L
Linus Torvalds 已提交
1087
	int found = 0;
1088
	int locked = 0;
L
Linus Torvalds 已提交
1089

1090
	seq = read_seqbegin(&rename_lock);
1091 1092
again:
	this_parent = parent;
N
Nick Piggin 已提交
1093
	spin_lock(&this_parent->d_lock);
L
Linus Torvalds 已提交
1094 1095 1096 1097 1098
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
1099
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
1100 1101
		next = tmp->next;

N
Nick Piggin 已提交
1102
		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
N
Nick Piggin 已提交
1103

L
Linus Torvalds 已提交
1104 1105 1106 1107
		/* 
		 * move only zero ref count dentries to the end 
		 * of the unused list for prune_dcache
		 */
N
Nick Piggin 已提交
1108
		if (!dentry->d_count) {
1109
			dentry_lru_move_tail(dentry);
L
Linus Torvalds 已提交
1110
			found++;
1111 1112
		} else {
			dentry_lru_del(dentry);
L
Linus Torvalds 已提交
1113 1114 1115 1116 1117 1118 1119
		}

		/*
		 * We can return to the caller if we have found some (this
		 * ensures forward progress). We'll be coming back to find
		 * the rest.
		 */
N
Nick Piggin 已提交
1120 1121
		if (found && need_resched()) {
			spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
1122
			goto out;
N
Nick Piggin 已提交
1123
		}
L
Linus Torvalds 已提交
1124 1125 1126 1127 1128

		/*
		 * Descend a level if the d_subdirs list is non-empty.
		 */
		if (!list_empty(&dentry->d_subdirs)) {
N
Nick Piggin 已提交
1129 1130
			spin_unlock(&this_parent->d_lock);
			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
L
Linus Torvalds 已提交
1131
			this_parent = dentry;
N
Nick Piggin 已提交
1132
			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
L
Linus Torvalds 已提交
1133 1134
			goto repeat;
		}
N
Nick Piggin 已提交
1135 1136

		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
1137 1138 1139 1140 1141
	}
	/*
	 * All done at this level ... ascend and resume the search.
	 */
	if (this_parent != parent) {
N
Nick Piggin 已提交
1142
		struct dentry *tmp;
1143 1144
		struct dentry *child;

N
Nick Piggin 已提交
1145
		tmp = this_parent->d_parent;
1146
		rcu_read_lock();
N
Nick Piggin 已提交
1147
		spin_unlock(&this_parent->d_lock);
1148
		child = this_parent;
N
Nick Piggin 已提交
1149 1150
		this_parent = tmp;
		spin_lock(&this_parent->d_lock);
1151 1152 1153
		/* might go back up the wrong parent if we have had a rename
		 * or deletion */
		if (this_parent != child->d_parent ||
1154
			(!locked && read_seqretry(&rename_lock, seq))) {
1155 1156 1157 1158 1159 1160
			spin_unlock(&this_parent->d_lock);
			rcu_read_unlock();
			goto rename_retry;
		}
		rcu_read_unlock();
		next = child->d_u.d_child.next;
L
Linus Torvalds 已提交
1161 1162 1163
		goto resume;
	}
out:
N
Nick Piggin 已提交
1164
	spin_unlock(&this_parent->d_lock);
1165
	if (!locked && read_seqretry(&rename_lock, seq))
1166
		goto rename_retry;
1167 1168
	if (locked)
		write_sequnlock(&rename_lock);
L
Linus Torvalds 已提交
1169
	return found;
1170 1171 1172 1173 1174 1175 1176

rename_retry:
	if (found)
		return found;
	locked = 1;
	write_seqlock(&rename_lock);
	goto again;
L
Linus Torvalds 已提交
1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187
}

/**
 * shrink_dcache_parent - prune dcache
 * @parent: parent of entries to prune
 *
 * Prune the dcache to remove unused children of the parent dentry.
 */
 
void shrink_dcache_parent(struct dentry * parent)
{
1188
	struct super_block *sb = parent->d_sb;
L
Linus Torvalds 已提交
1189 1190 1191
	int found;

	while ((found = select_parent(parent)) != 0)
1192
		__shrink_dcache_sb(sb, &found, 0);
L
Linus Torvalds 已提交
1193
}
1194
EXPORT_SYMBOL(shrink_dcache_parent);
L
Linus Torvalds 已提交
1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207

/*
 * Scan `nr' dentries and return the number which remain.
 *
 * We need to avoid reentering the filesystem if the caller is performing a
 * GFP_NOFS allocation attempt.  One example deadlock is:
 *
 * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
 * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
 * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
 *
 * In this case we return -1 to tell the caller that we baled.
 */
1208
static int shrink_dcache_memory(struct shrinker *shrink, int nr, gfp_t gfp_mask)
L
Linus Torvalds 已提交
1209 1210 1211 1212
{
	if (nr) {
		if (!(gfp_mask & __GFP_FS))
			return -1;
1213
		prune_dcache(nr);
L
Linus Torvalds 已提交
1214
	}
1215

1216
	return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
L
Linus Torvalds 已提交
1217 1218
}

1219 1220 1221 1222 1223
static struct shrinker dcache_shrinker = {
	.shrink = shrink_dcache_memory,
	.seeks = DEFAULT_SEEKS,
};

L
Linus Torvalds 已提交
1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238
/**
 * 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;
	char *dname;

1239
	dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
L
Linus Torvalds 已提交
1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258
	if (!dentry)
		return NULL;

	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.name = dname;

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

N
Nick Piggin 已提交
1259
	dentry->d_count = 1;
L
Linus Torvalds 已提交
1260 1261
	dentry->d_flags = DCACHE_UNHASHED;
	spin_lock_init(&dentry->d_lock);
N
Nick Piggin 已提交
1262
	seqcount_init(&dentry->d_seq);
L
Linus Torvalds 已提交
1263 1264 1265 1266 1267 1268 1269 1270 1271
	dentry->d_inode = NULL;
	dentry->d_parent = NULL;
	dentry->d_sb = NULL;
	dentry->d_op = NULL;
	dentry->d_fsdata = NULL;
	INIT_HLIST_NODE(&dentry->d_hash);
	INIT_LIST_HEAD(&dentry->d_lru);
	INIT_LIST_HEAD(&dentry->d_subdirs);
	INIT_LIST_HEAD(&dentry->d_alias);
N
Nick Piggin 已提交
1272
	INIT_LIST_HEAD(&dentry->d_u.d_child);
L
Linus Torvalds 已提交
1273 1274

	if (parent) {
N
Nick Piggin 已提交
1275
		spin_lock(&parent->d_lock);
1276 1277 1278 1279
		/*
		 * don't need child lock because it is not subject
		 * to concurrency here
		 */
1280 1281
		__dget_dlock(parent);
		dentry->d_parent = parent;
L
Linus Torvalds 已提交
1282
		dentry->d_sb = parent->d_sb;
E
Eric Dumazet 已提交
1283
		list_add(&dentry->d_u.d_child, &parent->d_subdirs);
N
Nick Piggin 已提交
1284 1285
		spin_unlock(&parent->d_lock);
	}
L
Linus Torvalds 已提交
1286

1287
	this_cpu_inc(nr_dentry);
1288

L
Linus Torvalds 已提交
1289 1290
	return dentry;
}
1291
EXPORT_SYMBOL(d_alloc);
L
Linus Torvalds 已提交
1292 1293 1294 1295 1296 1297 1298 1299 1300 1301

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);
}
1302
EXPORT_SYMBOL(d_alloc_name);
L
Linus Torvalds 已提交
1303

1304 1305
static void __d_instantiate(struct dentry *dentry, struct inode *inode)
{
N
Nick Piggin 已提交
1306
	spin_lock(&dentry->d_lock);
1307 1308 1309
	if (inode)
		list_add(&dentry->d_alias, &inode->i_dentry);
	dentry->d_inode = inode;
N
Nick Piggin 已提交
1310
	dentry_rcuwalk_barrier(dentry);
N
Nick Piggin 已提交
1311
	spin_unlock(&dentry->d_lock);
1312 1313 1314
	fsnotify_d_instantiate(dentry, inode);
}

L
Linus Torvalds 已提交
1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331
/**
 * 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)
{
1332
	BUG_ON(!list_empty(&entry->d_alias));
N
Nick Piggin 已提交
1333
	spin_lock(&dcache_inode_lock);
1334
	__d_instantiate(entry, inode);
N
Nick Piggin 已提交
1335
	spin_unlock(&dcache_inode_lock);
L
Linus Torvalds 已提交
1336 1337
	security_d_instantiate(entry, inode);
}
1338
EXPORT_SYMBOL(d_instantiate);
L
Linus Torvalds 已提交
1339 1340 1341 1342 1343 1344 1345 1346

/**
 * 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
1347
 * aliased dentry instead and drop one reference to inode.
L
Linus Torvalds 已提交
1348 1349 1350
 *
 * Note that in order to avoid conflicts with rename() etc, the caller
 * had better be holding the parent directory semaphore.
1351 1352 1353 1354
 *
 * 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
1355
 */
1356 1357
static struct dentry *__d_instantiate_unique(struct dentry *entry,
					     struct inode *inode)
L
Linus Torvalds 已提交
1358 1359 1360 1361 1362 1363
{
	struct dentry *alias;
	int len = entry->d_name.len;
	const char *name = entry->d_name.name;
	unsigned int hash = entry->d_name.hash;

1364
	if (!inode) {
1365
		__d_instantiate(entry, NULL);
1366 1367 1368
		return NULL;
	}

L
Linus Torvalds 已提交
1369 1370 1371
	list_for_each_entry(alias, &inode->i_dentry, d_alias) {
		struct qstr *qstr = &alias->d_name;

N
Nick Piggin 已提交
1372 1373 1374 1375 1376
		/*
		 * 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.
		 */
L
Linus Torvalds 已提交
1377 1378 1379 1380 1381 1382 1383 1384
		if (qstr->hash != hash)
			continue;
		if (alias->d_parent != entry->d_parent)
			continue;
		if (qstr->len != len)
			continue;
		if (memcmp(qstr->name, name, len))
			continue;
1385
		__dget(alias);
L
Linus Torvalds 已提交
1386 1387
		return alias;
	}
1388

1389
	__d_instantiate(entry, inode);
L
Linus Torvalds 已提交
1390 1391
	return NULL;
}
1392 1393 1394 1395 1396 1397 1398

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

	BUG_ON(!list_empty(&entry->d_alias));

N
Nick Piggin 已提交
1399
	spin_lock(&dcache_inode_lock);
1400
	result = __d_instantiate_unique(entry, inode);
N
Nick Piggin 已提交
1401
	spin_unlock(&dcache_inode_lock);
1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412

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

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

L
Linus Torvalds 已提交
1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439
EXPORT_SYMBOL(d_instantiate_unique);

/**
 * d_alloc_root - allocate root dentry
 * @root_inode: inode to allocate the root for
 *
 * Allocate a root ("/") dentry for the inode given. The inode is
 * instantiated and returned. %NULL is returned if there is insufficient
 * memory or the inode passed is %NULL.
 */
 
struct dentry * d_alloc_root(struct inode * root_inode)
{
	struct dentry *res = NULL;

	if (root_inode) {
		static const struct qstr name = { .name = "/", .len = 1 };

		res = d_alloc(NULL, &name);
		if (res) {
			res->d_sb = root_inode->i_sb;
			res->d_parent = res;
			d_instantiate(res, root_inode);
		}
	}
	return res;
}
1440
EXPORT_SYMBOL(d_alloc_root);
L
Linus Torvalds 已提交
1441 1442 1443 1444 1445 1446 1447 1448 1449

static inline struct hlist_head *d_hash(struct dentry *parent,
					unsigned long hash)
{
	hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
	hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
	return dentry_hashtable + (hash & D_HASHMASK);
}

1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462
/**
 * 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
1463 1464 1465 1466
 * 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).
1467 1468 1469
 */
struct dentry *d_obtain_alias(struct inode *inode)
{
C
Christoph Hellwig 已提交
1470 1471 1472
	static const struct qstr anonstring = { .name = "" };
	struct dentry *tmp;
	struct dentry *res;
1473 1474

	if (!inode)
1475
		return ERR_PTR(-ESTALE);
1476 1477 1478
	if (IS_ERR(inode))
		return ERR_CAST(inode);

C
Christoph Hellwig 已提交
1479 1480 1481 1482 1483 1484 1485 1486
	res = d_find_alias(inode);
	if (res)
		goto out_iput;

	tmp = d_alloc(NULL, &anonstring);
	if (!tmp) {
		res = ERR_PTR(-ENOMEM);
		goto out_iput;
1487
	}
C
Christoph Hellwig 已提交
1488 1489
	tmp->d_parent = tmp; /* make sure dput doesn't croak */

N
Nick Piggin 已提交
1490

N
Nick Piggin 已提交
1491
	spin_lock(&dcache_inode_lock);
C
Christoph Hellwig 已提交
1492 1493
	res = __d_find_alias(inode, 0);
	if (res) {
N
Nick Piggin 已提交
1494
		spin_unlock(&dcache_inode_lock);
C
Christoph Hellwig 已提交
1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505
		dput(tmp);
		goto out_iput;
	}

	/* attach a disconnected dentry */
	spin_lock(&tmp->d_lock);
	tmp->d_sb = inode->i_sb;
	tmp->d_inode = inode;
	tmp->d_flags |= DCACHE_DISCONNECTED;
	tmp->d_flags &= ~DCACHE_UNHASHED;
	list_add(&tmp->d_alias, &inode->i_dentry);
N
Nick Piggin 已提交
1506
	spin_lock(&dcache_hash_lock);
C
Christoph Hellwig 已提交
1507
	hlist_add_head(&tmp->d_hash, &inode->i_sb->s_anon);
N
Nick Piggin 已提交
1508
	spin_unlock(&dcache_hash_lock);
C
Christoph Hellwig 已提交
1509
	spin_unlock(&tmp->d_lock);
N
Nick Piggin 已提交
1510
	spin_unlock(&dcache_inode_lock);
C
Christoph Hellwig 已提交
1511 1512 1513 1514 1515 1516

	return tmp;

 out_iput:
	iput(inode);
	return res;
1517
}
1518
EXPORT_SYMBOL(d_obtain_alias);
L
Linus Torvalds 已提交
1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539

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

1540
	if (inode && S_ISDIR(inode->i_mode)) {
N
Nick Piggin 已提交
1541
		spin_lock(&dcache_inode_lock);
L
Linus Torvalds 已提交
1542 1543 1544
		new = __d_find_alias(inode, 1);
		if (new) {
			BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
N
Nick Piggin 已提交
1545
			spin_unlock(&dcache_inode_lock);
L
Linus Torvalds 已提交
1546 1547 1548 1549
			security_d_instantiate(new, inode);
			d_move(new, dentry);
			iput(inode);
		} else {
N
Nick Piggin 已提交
1550
			/* already taking dcache_inode_lock, so d_add() by hand */
1551
			__d_instantiate(dentry, inode);
N
Nick Piggin 已提交
1552
			spin_unlock(&dcache_inode_lock);
L
Linus Torvalds 已提交
1553 1554 1555 1556 1557 1558 1559
			security_d_instantiate(dentry, inode);
			d_rehash(dentry);
		}
	} else
		d_add(dentry, inode);
	return new;
}
1560
EXPORT_SYMBOL(d_splice_alias);
L
Linus Torvalds 已提交
1561

1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577
/**
 * 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.
 */
1578
struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
1579 1580 1581 1582 1583 1584
			struct qstr *name)
{
	int error;
	struct dentry *found;
	struct dentry *new;

C
Christoph Hellwig 已提交
1585 1586 1587 1588
	/*
	 * First check if a dentry matching the name already exists,
	 * if not go ahead and create it now.
	 */
1589 1590 1591 1592 1593 1594 1595
	found = d_hash_and_lookup(dentry->d_parent, name);
	if (!found) {
		new = d_alloc(dentry->d_parent, name);
		if (!new) {
			error = -ENOMEM;
			goto err_out;
		}
C
Christoph Hellwig 已提交
1596

1597 1598 1599 1600 1601 1602 1603
		found = d_splice_alias(inode, new);
		if (found) {
			dput(new);
			return found;
		}
		return new;
	}
C
Christoph Hellwig 已提交
1604 1605 1606 1607 1608 1609 1610

	/*
	 * If a matching dentry exists, and it's not negative use it.
	 *
	 * Decrement the reference count to balance the iget() done
	 * earlier on.
	 */
1611 1612 1613 1614 1615 1616 1617 1618 1619
	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
1620

1621 1622
	/*
	 * Negative dentry: instantiate it unless the inode is a directory and
C
Christoph Hellwig 已提交
1623
	 * already has a dentry.
1624
	 */
N
Nick Piggin 已提交
1625
	spin_lock(&dcache_inode_lock);
C
Christoph Hellwig 已提交
1626
	if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) {
1627
		__d_instantiate(found, inode);
N
Nick Piggin 已提交
1628
		spin_unlock(&dcache_inode_lock);
1629 1630 1631
		security_d_instantiate(found, inode);
		return found;
	}
C
Christoph Hellwig 已提交
1632

1633
	/*
C
Christoph Hellwig 已提交
1634 1635
	 * In case a directory already has a (disconnected) entry grab a
	 * reference to it, move it in place and use it.
1636 1637
	 */
	new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
1638
	__dget(new);
N
Nick Piggin 已提交
1639
	spin_unlock(&dcache_inode_lock);
1640 1641 1642 1643 1644 1645 1646 1647 1648 1649
	security_d_instantiate(found, inode);
	d_move(new, found);
	iput(inode);
	dput(found);
	return new;

err_out:
	iput(inode);
	return ERR_PTR(error);
}
1650
EXPORT_SYMBOL(d_add_ci);
L
Linus Torvalds 已提交
1651

N
Nick Piggin 已提交
1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756
/**
 * __d_lookup_rcu - search for a dentry (racy, store-free)
 * @parent: parent dentry
 * @name: qstr of name we wish to find
 * @seq: returns d_seq value at the point where the dentry was found
 * @inode: returns dentry->d_inode when the inode was found valid.
 * Returns: dentry, or NULL
 *
 * __d_lookup_rcu is the dcache lookup function for rcu-walk name
 * resolution (store-free path walking) design described in
 * Documentation/filesystems/path-lookup.txt.
 *
 * This is not to be used outside core vfs.
 *
 * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
 * held, and rcu_read_lock held. The returned dentry must not be stored into
 * without taking d_lock and checking d_seq sequence count against @seq
 * returned here.
 *
 * A refcount may be taken on the found dentry with the __d_rcu_to_refcount
 * function.
 *
 * Alternatively, __d_lookup_rcu may be called again to look up the child of
 * the returned dentry, so long as its parent's seqlock is checked after the
 * child is looked up. Thus, an interlocking stepping of sequence lock checks
 * is formed, giving integrity down the path walk.
 */
struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
				unsigned *seq, struct inode **inode)
{
	unsigned int len = name->len;
	unsigned int hash = name->hash;
	const unsigned char *str = name->name;
	struct hlist_head *head = d_hash(parent, hash);
	struct hlist_node *node;
	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.
	 *
	 * See Documentation/vfs/dcache-locking.txt for more details.
	 */
	hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
		struct inode *i;
		const char *tname;
		int tlen;

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

seqretry:
		*seq = read_seqcount_begin(&dentry->d_seq);
		if (dentry->d_parent != parent)
			continue;
		if (d_unhashed(dentry))
			continue;
		tlen = dentry->d_name.len;
		tname = dentry->d_name.name;
		i = dentry->d_inode;
		/*
		 * This seqcount check is required to ensure name and
		 * len are loaded atomically, so as not to walk off the
		 * edge of memory when walking. If we could load this
		 * atomically some other way, we could drop this check.
		 */
		if (read_seqcount_retry(&dentry->d_seq, *seq))
			goto seqretry;
		if (parent->d_op && parent->d_op->d_compare) {
			if (parent->d_op->d_compare(parent, *inode,
						dentry, i,
						tlen, tname, name))
				continue;
		} else {
			if (tlen != len)
				continue;
			if (memcmp(tname, str, tlen))
				continue;
		}
		/*
		 * No extra seqcount check is required after the name
		 * compare. The caller must perform a seqcount check in
		 * order to do anything useful with the returned dentry
		 * anyway.
		 */
		*inode = i;
		return dentry;
	}
	return NULL;
}

L
Linus Torvalds 已提交
1757 1758 1759 1760
/**
 * d_lookup - search for a dentry
 * @parent: parent dentry
 * @name: qstr of name we wish to find
1761
 * Returns: dentry, or NULL
L
Linus Torvalds 已提交
1762
 *
1763 1764 1765 1766
 * 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
1767
 */
N
Nick Piggin 已提交
1768
struct dentry *d_lookup(struct dentry *parent, struct qstr *name)
L
Linus Torvalds 已提交
1769
{
N
Nick Piggin 已提交
1770
	struct dentry *dentry;
1771
	unsigned seq;
L
Linus Torvalds 已提交
1772 1773 1774 1775 1776 1777 1778 1779 1780

        do {
                seq = read_seqbegin(&rename_lock);
                dentry = __d_lookup(parent, name);
                if (dentry)
			break;
	} while (read_seqretry(&rename_lock, seq));
	return dentry;
}
1781
EXPORT_SYMBOL(d_lookup);
L
Linus Torvalds 已提交
1782

N
Nick Piggin 已提交
1783
/**
1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797
 * __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.
 */
N
Nick Piggin 已提交
1798
struct dentry *__d_lookup(struct dentry *parent, struct qstr *name)
L
Linus Torvalds 已提交
1799 1800 1801 1802 1803 1804
{
	unsigned int len = name->len;
	unsigned int hash = name->hash;
	const unsigned char *str = name->name;
	struct hlist_head *head = d_hash(parent,hash);
	struct hlist_node *node;
N
Nick Piggin 已提交
1805
	struct dentry *found = NULL;
1806
	struct dentry *dentry;
L
Linus Torvalds 已提交
1807

N
Nick Piggin 已提交
1808 1809 1810 1811 1812 1813 1814
	/*
	 * 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.
	 */

1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827
	/*
	 * 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.
	 *
	 * See Documentation/vfs/dcache-locking.txt for more details.
	 */
L
Linus Torvalds 已提交
1828 1829
	rcu_read_lock();
	
1830
	hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
N
Nick Piggin 已提交
1831 1832
		const char *tname;
		int tlen;
L
Linus Torvalds 已提交
1833 1834 1835 1836 1837 1838 1839

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

		spin_lock(&dentry->d_lock);
		if (dentry->d_parent != parent)
			goto next;
1840 1841 1842
		if (d_unhashed(dentry))
			goto next;

L
Linus Torvalds 已提交
1843 1844 1845 1846
		/*
		 * It is safe to compare names since d_move() cannot
		 * change the qstr (protected by d_lock).
		 */
N
Nick Piggin 已提交
1847 1848
		tlen = dentry->d_name.len;
		tname = dentry->d_name.name;
L
Linus Torvalds 已提交
1849
		if (parent->d_op && parent->d_op->d_compare) {
N
Nick Piggin 已提交
1850 1851
			if (parent->d_op->d_compare(parent, parent->d_inode,
						dentry, dentry->d_inode,
N
Nick Piggin 已提交
1852
						tlen, tname, name))
L
Linus Torvalds 已提交
1853 1854
				goto next;
		} else {
N
Nick Piggin 已提交
1855
			if (tlen != len)
L
Linus Torvalds 已提交
1856
				goto next;
N
Nick Piggin 已提交
1857
			if (memcmp(tname, str, tlen))
L
Linus Torvalds 已提交
1858 1859 1860
				goto next;
		}

N
Nick Piggin 已提交
1861
		dentry->d_count++;
1862
		found = dentry;
L
Linus Torvalds 已提交
1863 1864 1865 1866 1867 1868 1869 1870 1871 1872
		spin_unlock(&dentry->d_lock);
		break;
next:
		spin_unlock(&dentry->d_lock);
 	}
 	rcu_read_unlock();

 	return found;
}

1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890
/**
 * d_hash_and_lookup - hash the qstr then search for a dentry
 * @dir: Directory to search in
 * @name: qstr of name we wish to find
 *
 * On hash failure or on lookup failure NULL is returned.
 */
struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
{
	struct dentry *dentry = NULL;

	/*
	 * Check for a fs-specific hash function. Note that we must
	 * calculate the standard hash first, as the d_op->d_hash()
	 * routine may choose to leave the hash value unchanged.
	 */
	name->hash = full_name_hash(name->name, name->len);
	if (dir->d_op && dir->d_op->d_hash) {
N
Nick Piggin 已提交
1891
		if (dir->d_op->d_hash(dir, dir->d_inode, name) < 0)
1892 1893 1894 1895 1896 1897 1898
			goto out;
	}
	dentry = d_lookup(dir, name);
out:
	return dentry;
}

L
Linus Torvalds 已提交
1899
/**
N
Nick Piggin 已提交
1900
 * d_validate - verify dentry provided from insecure source (deprecated)
L
Linus Torvalds 已提交
1901 1902 1903 1904 1905 1906
 * @dentry: The dentry alleged to be valid child of @dparent
 * @dparent: The parent dentry (known to be valid)
 *
 * 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
1907 1908
 *
 * This function is slow for big directories, and deprecated, do not use it.
L
Linus Torvalds 已提交
1909
 */
1910
int d_validate(struct dentry *dentry, struct dentry *dparent)
L
Linus Torvalds 已提交
1911
{
N
Nick Piggin 已提交
1912
	struct dentry *child;
1913

N
Nick Piggin 已提交
1914
	spin_lock(&dparent->d_lock);
N
Nick Piggin 已提交
1915 1916
	list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
		if (dentry == child) {
N
Nick Piggin 已提交
1917
			spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1918
			__dget_dlock(dentry);
N
Nick Piggin 已提交
1919 1920
			spin_unlock(&dentry->d_lock);
			spin_unlock(&dparent->d_lock);
L
Linus Torvalds 已提交
1921 1922 1923
			return 1;
		}
	}
N
Nick Piggin 已提交
1924
	spin_unlock(&dparent->d_lock);
N
Nick Piggin 已提交
1925

L
Linus Torvalds 已提交
1926 1927
	return 0;
}
1928
EXPORT_SYMBOL(d_validate);
L
Linus Torvalds 已提交
1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952

/*
 * 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)
{
1953
	int isdir = 0;
L
Linus Torvalds 已提交
1954 1955 1956
	/*
	 * Are we the only user?
	 */
1957
again:
L
Linus Torvalds 已提交
1958
	spin_lock(&dentry->d_lock);
1959
	isdir = S_ISDIR(dentry->d_inode->i_mode);
N
Nick Piggin 已提交
1960
	if (dentry->d_count == 1) {
1961 1962 1963 1964 1965
		if (!spin_trylock(&dcache_inode_lock)) {
			spin_unlock(&dentry->d_lock);
			cpu_relax();
			goto again;
		}
A
Al Viro 已提交
1966
		dentry->d_flags &= ~DCACHE_CANT_MOUNT;
N
Nick Piggin 已提交
1967
		dentry_unlink_inode(dentry);
1968
		fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
1969 1970 1971 1972 1973 1974 1975
		return;
	}

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

	spin_unlock(&dentry->d_lock);
1976 1977

	fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
1978
}
1979
EXPORT_SYMBOL(d_delete);
L
Linus Torvalds 已提交
1980 1981 1982 1983 1984 1985 1986 1987

static void __d_rehash(struct dentry * entry, struct hlist_head *list)
{

 	entry->d_flags &= ~DCACHE_UNHASHED;
 	hlist_add_head_rcu(&entry->d_hash, list);
}

1988 1989 1990 1991 1992
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
1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
/**
 * 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);
N
Nick Piggin 已提交
2003
	spin_lock(&dcache_hash_lock);
2004
	_d_rehash(entry);
N
Nick Piggin 已提交
2005
	spin_unlock(&dcache_hash_lock);
L
Linus Torvalds 已提交
2006 2007
	spin_unlock(&entry->d_lock);
}
2008
EXPORT_SYMBOL(d_rehash);
L
Linus Torvalds 已提交
2009

N
Nick Piggin 已提交
2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029
/**
 * 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)
{
	BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
	BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */

	spin_lock(&dentry->d_lock);
N
Nick Piggin 已提交
2030
	write_seqcount_begin(&dentry->d_seq);
N
Nick Piggin 已提交
2031
	memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
N
Nick Piggin 已提交
2032
	write_seqcount_end(&dentry->d_seq);
N
Nick Piggin 已提交
2033 2034 2035 2036
	spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(dentry_update_name_case);

L
Linus Torvalds 已提交
2037 2038 2039 2040 2041 2042 2043
static void switch_names(struct dentry *dentry, struct dentry *target)
{
	if (dname_external(target)) {
		if (dname_external(dentry)) {
			/*
			 * Both external: swap the pointers
			 */
2044
			swap(target->d_name.name, dentry->d_name.name);
L
Linus Torvalds 已提交
2045 2046 2047 2048 2049
		} else {
			/*
			 * dentry:internal, target:external.  Steal target's
			 * storage and make target internal.
			 */
2050 2051
			memcpy(target->d_iname, dentry->d_name.name,
					dentry->d_name.len + 1);
L
Linus Torvalds 已提交
2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070
			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);
2071 2072
			dentry->d_name.len = target->d_name.len;
			return;
L
Linus Torvalds 已提交
2073 2074
		}
	}
2075
	swap(dentry->d_name.len, target->d_name.len);
L
Linus Torvalds 已提交
2076 2077
}

N
Nick Piggin 已提交
2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113
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
2114
/*
N
Nick Piggin 已提交
2115 2116 2117 2118 2119 2120 2121 2122 2123
 * 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
2124
 */
2125
/*
N
Nick Piggin 已提交
2126
 * d_move - move a dentry
L
Linus Torvalds 已提交
2127 2128 2129 2130 2131 2132
 * @dentry: entry to move
 * @target: new dentry
 *
 * Update the dcache to reflect the move of a file name. Negative
 * dcache entries should not be moved in this way.
 */
N
Nick Piggin 已提交
2133
void d_move(struct dentry * dentry, struct dentry * target)
L
Linus Torvalds 已提交
2134 2135 2136 2137
{
	if (!dentry->d_inode)
		printk(KERN_WARNING "VFS: moving negative dcache entry\n");

N
Nick Piggin 已提交
2138 2139 2140
	BUG_ON(d_ancestor(dentry, target));
	BUG_ON(d_ancestor(target, dentry));

L
Linus Torvalds 已提交
2141
	write_seqlock(&rename_lock);
N
Nick Piggin 已提交
2142 2143

	dentry_lock_for_move(dentry, target);
L
Linus Torvalds 已提交
2144

N
Nick Piggin 已提交
2145 2146 2147
	write_seqcount_begin(&dentry->d_seq);
	write_seqcount_begin(&target->d_seq);

L
Linus Torvalds 已提交
2148
	/* Move the dentry to the target hash queue, if on different bucket */
N
Nick Piggin 已提交
2149 2150 2151 2152 2153
	spin_lock(&dcache_hash_lock);
	if (!d_unhashed(dentry))
		hlist_del_rcu(&dentry->d_hash);
	__d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
	spin_unlock(&dcache_hash_lock);
L
Linus Torvalds 已提交
2154 2155

	/* Unhash the target: dput() will then get rid of it */
N
Nick Piggin 已提交
2156
	/* __d_drop does write_seqcount_barrier, but they're OK to nest. */
L
Linus Torvalds 已提交
2157 2158
	__d_drop(target);

E
Eric Dumazet 已提交
2159 2160
	list_del(&dentry->d_u.d_child);
	list_del(&target->d_u.d_child);
L
Linus Torvalds 已提交
2161 2162 2163

	/* Switch the names.. */
	switch_names(dentry, target);
2164
	swap(dentry->d_name.hash, target->d_name.hash);
L
Linus Torvalds 已提交
2165 2166 2167 2168 2169

	/* ... and switch the parents */
	if (IS_ROOT(dentry)) {
		dentry->d_parent = target->d_parent;
		target->d_parent = target;
E
Eric Dumazet 已提交
2170
		INIT_LIST_HEAD(&target->d_u.d_child);
L
Linus Torvalds 已提交
2171
	} else {
2172
		swap(dentry->d_parent, target->d_parent);
L
Linus Torvalds 已提交
2173 2174

		/* And add them back to the (new) parent lists */
E
Eric Dumazet 已提交
2175
		list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
L
Linus Torvalds 已提交
2176 2177
	}

E
Eric Dumazet 已提交
2178
	list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
N
Nick Piggin 已提交
2179

N
Nick Piggin 已提交
2180 2181 2182
	write_seqcount_end(&target->d_seq);
	write_seqcount_end(&dentry->d_seq);

N
Nick Piggin 已提交
2183
	dentry_unlock_parents_for_move(dentry, target);
L
Linus Torvalds 已提交
2184
	spin_unlock(&target->d_lock);
2185
	fsnotify_d_move(dentry);
L
Linus Torvalds 已提交
2186 2187
	spin_unlock(&dentry->d_lock);
	write_sequnlock(&rename_lock);
2188
}
2189
EXPORT_SYMBOL(d_move);
L
Linus Torvalds 已提交
2190

2191 2192 2193 2194 2195 2196 2197
/**
 * 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.
2198
 */
2199
struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2200 2201 2202
{
	struct dentry *p;

2203
	for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2204
		if (p->d_parent == p1)
2205
			return p;
2206
	}
2207
	return NULL;
2208 2209 2210 2211 2212 2213
}

/*
 * This helper attempts to cope with remotely renamed directories
 *
 * It assumes that the caller is already holding
N
Nick Piggin 已提交
2214
 * dentry->d_parent->d_inode->i_mutex and the dcache_inode_lock
2215 2216 2217 2218 2219
 *
 * Note: If ever the locking in lock_rename() changes, then please
 * remember to update this too...
 */
static struct dentry *__d_unalias(struct dentry *dentry, struct dentry *alias)
N
Nick Piggin 已提交
2220
	__releases(dcache_inode_lock)
2221 2222 2223 2224 2225 2226 2227 2228 2229 2230
{
	struct mutex *m1 = NULL, *m2 = NULL;
	struct dentry *ret;

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

	/* Check for loops */
	ret = ERR_PTR(-ELOOP);
2231
	if (d_ancestor(alias, dentry))
2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242
		goto out_err;

	/* See lock_rename() */
	ret = ERR_PTR(-EBUSY);
	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:
N
Nick Piggin 已提交
2243
	d_move(alias, dentry);
2244 2245
	ret = alias;
out_err:
N
Nick Piggin 已提交
2246
	spin_unlock(&dcache_inode_lock);
2247 2248 2249 2250 2251 2252 2253
	if (m2)
		mutex_unlock(m2);
	if (m1)
		mutex_unlock(m1);
	return ret;
}

2254 2255 2256
/*
 * 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
2257
 * returns with anon->d_lock held!
2258 2259 2260 2261 2262
 */
static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
{
	struct dentry *dparent, *aparent;

N
Nick Piggin 已提交
2263
	dentry_lock_for_move(anon, dentry);
2264

N
Nick Piggin 已提交
2265 2266 2267
	write_seqcount_begin(&dentry->d_seq);
	write_seqcount_begin(&anon->d_seq);

2268 2269 2270
	dparent = dentry->d_parent;
	aparent = anon->d_parent;

N
Nick Piggin 已提交
2271 2272 2273
	switch_names(dentry, anon);
	swap(dentry->d_name.hash, anon->d_name.hash);

2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287
	dentry->d_parent = (aparent == anon) ? dentry : aparent;
	list_del(&dentry->d_u.d_child);
	if (!IS_ROOT(dentry))
		list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
	else
		INIT_LIST_HEAD(&dentry->d_u.d_child);

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

N
Nick Piggin 已提交
2288 2289 2290
	write_seqcount_end(&dentry->d_seq);
	write_seqcount_end(&anon->d_seq);

N
Nick Piggin 已提交
2291 2292 2293 2294
	dentry_unlock_parents_for_move(anon, dentry);
	spin_unlock(&dentry->d_lock);

	/* anon->d_lock still locked, returns locked */
2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307
	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
 * root directory alias in its place if there is one
 */
struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
{
2308
	struct dentry *actual;
2309 2310 2311 2312 2313

	BUG_ON(!d_unhashed(dentry));

	if (!inode) {
		actual = dentry;
2314
		__d_instantiate(dentry, NULL);
2315 2316
		d_rehash(actual);
		goto out_nolock;
2317 2318
	}

2319 2320
	spin_lock(&dcache_inode_lock);

2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340
	if (S_ISDIR(inode->i_mode)) {
		struct dentry *alias;

		/* Does an aliased dentry already exist? */
		alias = __d_find_alias(inode, 0);
		if (alias) {
			actual = alias;
			/* Is this an anonymous mountpoint that we could splice
			 * into our tree? */
			if (IS_ROOT(alias)) {
				__d_materialise_dentry(dentry, alias);
				__d_drop(alias);
				goto found;
			}
			/* Nope, but we must(!) avoid directory aliasing */
			actual = __d_unalias(dentry, alias);
			if (IS_ERR(actual))
				dput(alias);
			goto out_nolock;
		}
2341 2342 2343 2344 2345 2346
	}

	/* Add a unique reference */
	actual = __d_instantiate_unique(dentry, inode);
	if (!actual)
		actual = dentry;
2347 2348
	else
		BUG_ON(!d_unhashed(actual));
2349 2350 2351

	spin_lock(&actual->d_lock);
found:
N
Nick Piggin 已提交
2352
	spin_lock(&dcache_hash_lock);
2353
	_d_rehash(actual);
N
Nick Piggin 已提交
2354
	spin_unlock(&dcache_hash_lock);
2355
	spin_unlock(&actual->d_lock);
N
Nick Piggin 已提交
2356
	spin_unlock(&dcache_inode_lock);
2357
out_nolock:
2358 2359 2360 2361 2362 2363 2364 2365
	if (actual == dentry) {
		security_d_instantiate(dentry, inode);
		return NULL;
	}

	iput(inode);
	return actual;
}
2366
EXPORT_SYMBOL_GPL(d_materialise_unique);
2367

2368
static int prepend(char **buffer, int *buflen, const char *str, int namelen)
2369 2370 2371 2372 2373 2374 2375 2376 2377
{
	*buflen -= namelen;
	if (*buflen < 0)
		return -ENAMETOOLONG;
	*buffer -= namelen;
	memcpy(*buffer, str, namelen);
	return 0;
}

2378 2379 2380 2381 2382
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
2383
/**
M
Miklos Szeredi 已提交
2384 2385
 * Prepend path string to a buffer
 *
2386 2387
 * @path: the dentry/vfsmount to report
 * @root: root vfsmnt/dentry (may be modified by this function)
M
Miklos Szeredi 已提交
2388 2389
 * @buffer: pointer to the end of the buffer
 * @buflen: pointer to buffer length
2390
 *
2391
 * Caller holds the rename_lock.
2392 2393 2394
 *
 * If path is not reachable from the supplied root, then the value of
 * root is changed (without modifying refcounts).
L
Linus Torvalds 已提交
2395
 */
M
Miklos Szeredi 已提交
2396 2397
static int prepend_path(const struct path *path, struct path *root,
			char **buffer, int *buflen)
L
Linus Torvalds 已提交
2398
{
2399 2400
	struct dentry *dentry = path->dentry;
	struct vfsmount *vfsmnt = path->mnt;
M
Miklos Szeredi 已提交
2401 2402
	bool slash = false;
	int error = 0;
2403

N
Nick Piggin 已提交
2404
	br_read_lock(vfsmount_lock);
M
Miklos Szeredi 已提交
2405
	while (dentry != root->dentry || vfsmnt != root->mnt) {
L
Linus Torvalds 已提交
2406 2407 2408
		struct dentry * parent;

		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
2409
			/* Global root? */
L
Linus Torvalds 已提交
2410 2411 2412 2413 2414 2415 2416 2417 2418
			if (vfsmnt->mnt_parent == vfsmnt) {
				goto global_root;
			}
			dentry = vfsmnt->mnt_mountpoint;
			vfsmnt = vfsmnt->mnt_parent;
			continue;
		}
		parent = dentry->d_parent;
		prefetch(parent);
N
Nick Piggin 已提交
2419
		spin_lock(&dentry->d_lock);
M
Miklos Szeredi 已提交
2420
		error = prepend_name(buffer, buflen, &dentry->d_name);
N
Nick Piggin 已提交
2421
		spin_unlock(&dentry->d_lock);
M
Miklos Szeredi 已提交
2422 2423 2424 2425 2426 2427
		if (!error)
			error = prepend(buffer, buflen, "/", 1);
		if (error)
			break;

		slash = true;
L
Linus Torvalds 已提交
2428 2429 2430
		dentry = parent;
	}

2431
out:
M
Miklos Szeredi 已提交
2432 2433 2434
	if (!error && !slash)
		error = prepend(buffer, buflen, "/", 1);

N
Nick Piggin 已提交
2435
	br_read_unlock(vfsmount_lock);
M
Miklos Szeredi 已提交
2436
	return error;
L
Linus Torvalds 已提交
2437 2438

global_root:
2439 2440 2441 2442 2443 2444 2445 2446 2447
	/*
	 * 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);
	}
2448 2449
	root->mnt = vfsmnt;
	root->dentry = dentry;
2450
	goto out;
M
Miklos Szeredi 已提交
2451
}
2452

M
Miklos Szeredi 已提交
2453 2454 2455 2456
/**
 * __d_path - return the path of a dentry
 * @path: the dentry/vfsmount to report
 * @root: root vfsmnt/dentry (may be modified by this function)
2457
 * @buf: buffer to return value in
M
Miklos Szeredi 已提交
2458 2459
 * @buflen: buffer length
 *
2460
 * Convert a dentry into an ASCII path name.
M
Miklos Szeredi 已提交
2461 2462 2463 2464
 *
 * Returns a pointer into the buffer or an error code if the
 * path was too long.
 *
2465
 * "buflen" should be positive.
M
Miklos Szeredi 已提交
2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476
 *
 * If path is not reachable from the supplied root, then the value of
 * root is changed (without modifying refcounts).
 */
char *__d_path(const struct path *path, struct path *root,
	       char *buf, int buflen)
{
	char *res = buf + buflen;
	int error;

	prepend(&res, &buflen, "\0", 1);
2477
	write_seqlock(&rename_lock);
M
Miklos Szeredi 已提交
2478
	error = prepend_path(path, root, &res, &buflen);
2479
	write_sequnlock(&rename_lock);
2480

M
Miklos Szeredi 已提交
2481 2482 2483
	if (error)
		return ERR_PTR(error);
	return res;
L
Linus Torvalds 已提交
2484 2485
}

2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501
/*
 * same as __d_path but appends "(deleted)" for unlinked files.
 */
static int path_with_deleted(const struct path *path, struct path *root,
				 char **buf, int *buflen)
{
	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);
}

2502 2503 2504 2505 2506
static int prepend_unreachable(char **buffer, int *buflen)
{
	return prepend(buffer, buflen, "(unreachable)", 13);
}

J
Jan Blunck 已提交
2507 2508
/**
 * d_path - return the path of a dentry
2509
 * @path: path to report
J
Jan Blunck 已提交
2510 2511 2512 2513 2514 2515
 * @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.
 *
2516 2517 2518 2519
 * 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
2520
 *
2521
 * "buflen" should be positive.
J
Jan Blunck 已提交
2522
 */
2523
char *d_path(const struct path *path, char *buf, int buflen)
L
Linus Torvalds 已提交
2524
{
2525
	char *res = buf + buflen;
J
Jan Blunck 已提交
2526
	struct path root;
2527
	struct path tmp;
2528
	int error;
L
Linus Torvalds 已提交
2529

2530 2531 2532 2533 2534 2535 2536
	/*
	 * 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:
	 */
2537 2538
	if (path->dentry->d_op && path->dentry->d_op->d_dname)
		return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2539

2540
	get_fs_root(current->fs, &root);
2541
	write_seqlock(&rename_lock);
2542
	tmp = root;
2543 2544 2545
	error = path_with_deleted(path, &tmp, &res, &buflen);
	if (error)
		res = ERR_PTR(error);
2546
	write_sequnlock(&rename_lock);
J
Jan Blunck 已提交
2547
	path_put(&root);
L
Linus Torvalds 已提交
2548 2549
	return res;
}
2550
EXPORT_SYMBOL(d_path);
L
Linus Torvalds 已提交
2551

2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571
/**
 * d_path_with_unreachable - return the path of a dentry
 * @path: path to report
 * @buf: buffer to return value in
 * @buflen: buffer length
 *
 * The difference from d_path() is that this prepends "(unreachable)"
 * to paths which are unreachable from the current process' root.
 */
char *d_path_with_unreachable(const struct path *path, char *buf, int buflen)
{
	char *res = buf + buflen;
	struct path root;
	struct path tmp;
	int error;

	if (path->dentry->d_op && path->dentry->d_op->d_dname)
		return path->dentry->d_op->d_dname(path->dentry, buf, buflen);

	get_fs_root(current->fs, &root);
2572
	write_seqlock(&rename_lock);
2573 2574 2575 2576
	tmp = root;
	error = path_with_deleted(path, &tmp, &res, &buflen);
	if (!error && !path_equal(&tmp, &root))
		error = prepend_unreachable(&res, &buflen);
2577
	write_sequnlock(&rename_lock);
2578 2579 2580 2581 2582 2583 2584
	path_put(&root);
	if (error)
		res =  ERR_PTR(error);

	return res;
}

2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605
/*
 * 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);
}

2606 2607 2608
/*
 * Write full pathname from the root of the filesystem into the buffer.
 */
N
Nick Piggin 已提交
2609
static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620
{
	char *end = buf + buflen;
	char *retval;

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

2621 2622
	while (!IS_ROOT(dentry)) {
		struct dentry *parent = dentry->d_parent;
N
Nick Piggin 已提交
2623
		int error;
2624 2625

		prefetch(parent);
N
Nick Piggin 已提交
2626 2627 2628 2629
		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)
2630 2631 2632 2633 2634
			goto Elong;

		retval = end;
		dentry = parent;
	}
A
Al Viro 已提交
2635 2636 2637 2638
	return retval;
Elong:
	return ERR_PTR(-ENAMETOOLONG);
}
N
Nick Piggin 已提交
2639 2640 2641 2642 2643

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

2644
	write_seqlock(&rename_lock);
N
Nick Piggin 已提交
2645
	retval = __dentry_path(dentry, buf, buflen);
2646
	write_sequnlock(&rename_lock);
N
Nick Piggin 已提交
2647 2648 2649 2650

	return retval;
}
EXPORT_SYMBOL(dentry_path_raw);
A
Al Viro 已提交
2651 2652 2653 2654 2655 2656

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

2657
	write_seqlock(&rename_lock);
A
Al Viro 已提交
2658 2659 2660 2661 2662 2663 2664
	if (d_unlinked(dentry)) {
		p = buf + buflen;
		if (prepend(&p, &buflen, "//deleted", 10) != 0)
			goto Elong;
		buflen++;
	}
	retval = __dentry_path(dentry, buf, buflen);
2665
	write_sequnlock(&rename_lock);
A
Al Viro 已提交
2666 2667
	if (!IS_ERR(retval) && p)
		*p = '/';	/* restore '/' overriden with '\0' */
2668 2669 2670 2671 2672
	return retval;
Elong:
	return ERR_PTR(-ENAMETOOLONG);
}

L
Linus Torvalds 已提交
2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690
/*
 * 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;
 *	}
 */
2691
SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
L
Linus Torvalds 已提交
2692
{
2693
	int error;
J
Jan Blunck 已提交
2694
	struct path pwd, root;
2695
	char *page = (char *) __get_free_page(GFP_USER);
L
Linus Torvalds 已提交
2696 2697 2698 2699

	if (!page)
		return -ENOMEM;

2700
	get_fs_root_and_pwd(current->fs, &root, &pwd);
L
Linus Torvalds 已提交
2701

2702
	error = -ENOENT;
2703
	write_seqlock(&rename_lock);
2704
	if (!d_unlinked(pwd.dentry)) {
2705
		unsigned long len;
2706
		struct path tmp = root;
2707 2708
		char *cwd = page + PAGE_SIZE;
		int buflen = PAGE_SIZE;
L
Linus Torvalds 已提交
2709

2710 2711
		prepend(&cwd, &buflen, "\0", 1);
		error = prepend_path(&pwd, &tmp, &cwd, &buflen);
2712
		write_sequnlock(&rename_lock);
2713

2714
		if (error)
2715 2716
			goto out;

2717 2718 2719 2720 2721 2722 2723
		/* Unreachable from current root */
		if (!path_equal(&tmp, &root)) {
			error = prepend_unreachable(&cwd, &buflen);
			if (error)
				goto out;
		}

2724 2725 2726 2727 2728 2729 2730
		error = -ERANGE;
		len = PAGE_SIZE + page - cwd;
		if (len <= size) {
			error = len;
			if (copy_to_user(buf, cwd, len))
				error = -EFAULT;
		}
2731 2732 2733
	} else {
		write_sequnlock(&rename_lock);
	}
L
Linus Torvalds 已提交
2734 2735

out:
J
Jan Blunck 已提交
2736 2737
	path_put(&pwd);
	path_put(&root);
L
Linus Torvalds 已提交
2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757
	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()
 */
  
2758
int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
L
Linus Torvalds 已提交
2759 2760
{
	int result;
2761
	unsigned seq;
L
Linus Torvalds 已提交
2762

2763 2764 2765 2766
	if (new_dentry == old_dentry)
		return 1;

	do {
L
Linus Torvalds 已提交
2767 2768
		/* for restarting inner loop in case of seq retry */
		seq = read_seqbegin(&rename_lock);
2769 2770 2771 2772 2773
		/*
		 * Need rcu_readlock to protect against the d_parent trashing
		 * due to d_move
		 */
		rcu_read_lock();
2774
		if (d_ancestor(old_dentry, new_dentry))
L
Linus Torvalds 已提交
2775
			result = 1;
2776 2777
		else
			result = 0;
2778
		rcu_read_unlock();
L
Linus Torvalds 已提交
2779 2780 2781 2782 2783
	} while (read_seqretry(&rename_lock, seq));

	return result;
}

2784 2785 2786 2787 2788
int path_is_under(struct path *path1, struct path *path2)
{
	struct vfsmount *mnt = path1->mnt;
	struct dentry *dentry = path1->dentry;
	int res;
N
Nick Piggin 已提交
2789 2790

	br_read_lock(vfsmount_lock);
2791 2792 2793
	if (mnt != path2->mnt) {
		for (;;) {
			if (mnt->mnt_parent == mnt) {
N
Nick Piggin 已提交
2794
				br_read_unlock(vfsmount_lock);
2795 2796 2797 2798 2799 2800 2801 2802 2803
				return 0;
			}
			if (mnt->mnt_parent == path2->mnt)
				break;
			mnt = mnt->mnt_parent;
		}
		dentry = mnt->mnt_mountpoint;
	}
	res = is_subdir(dentry, path2->dentry);
N
Nick Piggin 已提交
2804
	br_read_unlock(vfsmount_lock);
2805 2806 2807 2808
	return res;
}
EXPORT_SYMBOL(path_is_under);

L
Linus Torvalds 已提交
2809 2810
void d_genocide(struct dentry *root)
{
2811
	struct dentry *this_parent;
L
Linus Torvalds 已提交
2812
	struct list_head *next;
2813
	unsigned seq;
2814
	int locked = 0;
L
Linus Torvalds 已提交
2815

2816
	seq = read_seqbegin(&rename_lock);
2817 2818
again:
	this_parent = root;
N
Nick Piggin 已提交
2819
	spin_lock(&this_parent->d_lock);
L
Linus Torvalds 已提交
2820 2821 2822 2823 2824
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
2825
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
2826
		next = tmp->next;
2827

N
Nick Piggin 已提交
2828 2829 2830
		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
		if (d_unhashed(dentry) || !dentry->d_inode) {
			spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
2831
			continue;
N
Nick Piggin 已提交
2832
		}
L
Linus Torvalds 已提交
2833
		if (!list_empty(&dentry->d_subdirs)) {
N
Nick Piggin 已提交
2834 2835
			spin_unlock(&this_parent->d_lock);
			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
L
Linus Torvalds 已提交
2836
			this_parent = dentry;
N
Nick Piggin 已提交
2837
			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
L
Linus Torvalds 已提交
2838 2839
			goto repeat;
		}
2840 2841 2842 2843
		if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
			dentry->d_flags |= DCACHE_GENOCIDE;
			dentry->d_count--;
		}
N
Nick Piggin 已提交
2844
		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
2845 2846
	}
	if (this_parent != root) {
2847 2848 2849 2850 2851 2852 2853 2854 2855
		struct dentry *tmp;
		struct dentry *child;

		tmp = this_parent->d_parent;
		if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
			this_parent->d_flags |= DCACHE_GENOCIDE;
			this_parent->d_count--;
		}
		rcu_read_lock();
N
Nick Piggin 已提交
2856
		spin_unlock(&this_parent->d_lock);
2857 2858
		child = this_parent;
		this_parent = tmp;
N
Nick Piggin 已提交
2859
		spin_lock(&this_parent->d_lock);
2860 2861 2862
		/* might go back up the wrong parent if we have had a rename
		 * or deletion */
		if (this_parent != child->d_parent ||
2863
			 (!locked && read_seqretry(&rename_lock, seq))) {
2864 2865 2866 2867 2868 2869
			spin_unlock(&this_parent->d_lock);
			rcu_read_unlock();
			goto rename_retry;
		}
		rcu_read_unlock();
		next = child->d_u.d_child.next;
L
Linus Torvalds 已提交
2870 2871
		goto resume;
	}
N
Nick Piggin 已提交
2872
	spin_unlock(&this_parent->d_lock);
2873
	if (!locked && read_seqretry(&rename_lock, seq))
2874
		goto rename_retry;
2875 2876 2877 2878 2879 2880 2881 2882
	if (locked)
		write_sequnlock(&rename_lock);
	return;

rename_retry:
	locked = 1;
	write_seqlock(&rename_lock);
	goto again;
L
Linus Torvalds 已提交
2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903
}

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

2904 2905
	dentry = d_hash_and_lookup(dir, name);
	if (dentry) {
L
Linus Torvalds 已提交
2906 2907 2908 2909 2910 2911
		if (dentry->d_inode)
			ino = dentry->d_inode->i_ino;
		dput(dentry);
	}
	return ino;
}
2912
EXPORT_SYMBOL(find_inode_number);
L
Linus Torvalds 已提交
2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947

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)
{
	int loop;

	/* 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",
					sizeof(struct hlist_head),
					dhash_entries,
					13,
					HASH_EARLY,
					&d_hash_shift,
					&d_hash_mask,
					0);

	for (loop = 0; loop < (1 << d_hash_shift); loop++)
		INIT_HLIST_HEAD(&dentry_hashtable[loop]);
}

2948
static void __init dcache_init(void)
L
Linus Torvalds 已提交
2949 2950 2951 2952 2953 2954 2955 2956
{
	int loop;

	/* 
	 * 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. 
	 */
2957 2958
	dentry_cache = KMEM_CACHE(dentry,
		SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
L
Linus Torvalds 已提交
2959
	
2960
	register_shrinker(&dcache_shrinker);
L
Linus Torvalds 已提交
2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980

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

	dentry_hashtable =
		alloc_large_system_hash("Dentry cache",
					sizeof(struct hlist_head),
					dhash_entries,
					13,
					0,
					&d_hash_shift,
					&d_hash_mask,
					0);

	for (loop = 0; loop < (1 << d_hash_shift); loop++)
		INIT_HLIST_HEAD(&dentry_hashtable[loop]);
}

/* SLAB cache for __getname() consumers */
2981
struct kmem_cache *names_cachep __read_mostly;
2982
EXPORT_SYMBOL(names_cachep);
L
Linus Torvalds 已提交
2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002

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,
3003
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
L
Linus Torvalds 已提交
3004

3005 3006
	dcache_init();
	inode_init();
L
Linus Torvalds 已提交
3007
	files_init(mempages);
3008
	mnt_init();
L
Linus Torvalds 已提交
3009 3010 3011
	bdev_cache_init();
	chrdev_init();
}