dcache.c 62.0 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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int sysctl_vfs_cache_pressure __read_mostly = 100;
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EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);

 __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
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__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
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EXPORT_SYMBOL(dcache_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 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); 
}

/*
 * no dcache_lock, please.  The caller must decrement dentry_stat.nr_dentry
 * inside dcache_lock.
 */
static void d_free(struct dentry *dentry)
{
	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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}

/*
 * Release the dentry's inode, using the filesystem
 * d_iput() operation if defined.
 */
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static void dentry_iput(struct dentry * dentry)
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	__releases(dentry->d_lock)
	__releases(dcache_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);
		spin_unlock(&dcache_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);
		spin_unlock(&dcache_lock);
	}
}

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/*
 * dentry_lru_(add|add_tail|del|del_init) must be called with dcache_lock held.
 */
static void dentry_lru_add(struct dentry *dentry)
{
	list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
	dentry->d_sb->s_nr_dentry_unused++;
	dentry_stat.nr_unused++;
}

static void dentry_lru_add_tail(struct dentry *dentry)
{
	list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
	dentry->d_sb->s_nr_dentry_unused++;
	dentry_stat.nr_unused++;
}

static void dentry_lru_del(struct dentry *dentry)
{
	if (!list_empty(&dentry->d_lru)) {
		list_del(&dentry->d_lru);
		dentry->d_sb->s_nr_dentry_unused--;
		dentry_stat.nr_unused--;
	}
}

static void dentry_lru_del_init(struct dentry *dentry)
{
	if (likely(!list_empty(&dentry->d_lru))) {
		list_del_init(&dentry->d_lru);
		dentry->d_sb->s_nr_dentry_unused--;
		dentry_stat.nr_unused--;
	}
}

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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.
 */
static struct dentry *d_kill(struct dentry *dentry)
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	__releases(dentry->d_lock)
	__releases(dcache_lock)
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{
	struct dentry *parent;

	list_del(&dentry->d_u.d_child);
	dentry_stat.nr_dentry--;	/* For d_free, below */
	/*drops the locks, at that point nobody can reach this dentry */
	dentry_iput(dentry);
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	if (IS_ROOT(dentry))
		parent = NULL;
	else
		parent = dentry->d_parent;
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	d_free(dentry);
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	return parent;
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}

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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.
 *
 * no dcache lock, please.
 */

void dput(struct dentry *dentry)
{
	if (!dentry)
		return;

repeat:
	if (atomic_read(&dentry->d_count) == 1)
		might_sleep();
	if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
		return;

	spin_lock(&dentry->d_lock);
	if (atomic_read(&dentry->d_count)) {
		spin_unlock(&dentry->d_lock);
		spin_unlock(&dcache_lock);
		return;
	}

	/*
	 * AV: ->d_delete() is _NOT_ allowed to block now.
	 */
	if (dentry->d_op && dentry->d_op->d_delete) {
		if (dentry->d_op->d_delete(dentry))
			goto unhash_it;
	}
	/* Unreachable? Get rid of it */
 	if (d_unhashed(dentry))
		goto kill_it;
  	if (list_empty(&dentry->d_lru)) {
  		dentry->d_flags |= DCACHE_REFERENCED;
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		dentry_lru_add(dentry);
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  	}
 	spin_unlock(&dentry->d_lock);
	spin_unlock(&dcache_lock);
	return;

unhash_it:
	__d_drop(dentry);
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kill_it:
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	/* if dentry was on the d_lru list delete it from there */
	dentry_lru_del(dentry);
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	dentry = d_kill(dentry);
	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.
	 */
	spin_lock(&dcache_lock);
	if (d_unhashed(dentry)) {
		spin_unlock(&dcache_lock);
		return 0;
	}
	/*
	 * Check whether to do a partial shrink_dcache
	 * to get rid of unused child entries.
	 */
	if (!list_empty(&dentry->d_subdirs)) {
		spin_unlock(&dcache_lock);
		shrink_dcache_parent(dentry);
		spin_lock(&dcache_lock);
	}

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

	__d_drop(dentry);
	spin_unlock(&dentry->d_lock);
	spin_unlock(&dcache_lock);
	return 0;
}
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EXPORT_SYMBOL(d_invalidate);
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/* This should be called _only_ with dcache_lock held */

static inline struct dentry * __dget_locked(struct dentry *dentry)
{
	atomic_inc(&dentry->d_count);
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	dentry_lru_del_init(dentry);
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	return dentry;
}

struct dentry * dget_locked(struct dentry *dentry)
{
	return __dget_locked(dentry);
}
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EXPORT_SYMBOL(dget_locked);
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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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 */

static struct dentry * __d_find_alias(struct inode *inode, int want_discon)
{
	struct list_head *head, *next, *tmp;
	struct dentry *alias, *discon_alias=NULL;

	head = &inode->i_dentry;
	next = inode->i_dentry.next;
	while (next != head) {
		tmp = next;
		next = tmp->next;
		prefetch(next);
		alias = list_entry(tmp, struct dentry, d_alias);
 		if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
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			if (IS_ROOT(alias) &&
			    (alias->d_flags & DCACHE_DISCONNECTED))
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				discon_alias = alias;
			else if (!want_discon) {
				__dget_locked(alias);
				return alias;
			}
		}
	}
	if (discon_alias)
		__dget_locked(discon_alias);
	return discon_alias;
}

struct dentry * d_find_alias(struct inode *inode)
{
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	struct dentry *de = NULL;

	if (!list_empty(&inode->i_dentry)) {
		spin_lock(&dcache_lock);
		de = __d_find_alias(inode, 0);
		spin_unlock(&dcache_lock);
	}
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	return de;
}
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EXPORT_SYMBOL(d_find_alias);
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/*
 *	Try to kill dentries associated with this inode.
 * WARNING: you must own a reference to inode.
 */
void d_prune_aliases(struct inode *inode)
{
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	struct dentry *dentry;
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restart:
	spin_lock(&dcache_lock);
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	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
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		spin_lock(&dentry->d_lock);
		if (!atomic_read(&dentry->d_count)) {
			__dget_locked(dentry);
			__d_drop(dentry);
			spin_unlock(&dentry->d_lock);
			spin_unlock(&dcache_lock);
			dput(dentry);
			goto restart;
		}
		spin_unlock(&dentry->d_lock);
	}
	spin_unlock(&dcache_lock);
}
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EXPORT_SYMBOL(d_prune_aliases);
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/*
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 * Throw away a dentry - free the inode, dput the parent.  This requires that
 * the LRU list has already been removed.
 *
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 * Try to prune ancestors as well.  This is necessary to prevent
 * quadratic behavior of shrink_dcache_parent(), but is also expected
 * to be beneficial in reducing dentry cache fragmentation.
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 */
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static void prune_one_dentry(struct dentry * dentry)
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	__releases(dentry->d_lock)
	__releases(dcache_lock)
	__acquires(dcache_lock)
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{
	__d_drop(dentry);
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	dentry = d_kill(dentry);

	/*
	 * Prune ancestors.  Locking is simpler than in dput(),
	 * because dcache_lock needs to be taken anyway.
	 */
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	spin_lock(&dcache_lock);
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	while (dentry) {
		if (!atomic_dec_and_lock(&dentry->d_count, &dentry->d_lock))
			return;

		if (dentry->d_op && dentry->d_op->d_delete)
			dentry->d_op->d_delete(dentry);
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		dentry_lru_del_init(dentry);
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		__d_drop(dentry);
		dentry = d_kill(dentry);
		spin_lock(&dcache_lock);
	}
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}

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/*
 * Shrink the dentry LRU on a given superblock.
 * @sb   : superblock to shrink dentry LRU.
 * @count: If count is NULL, we prune all dentries on superblock.
 * @flags: If flags is non-zero, we need to do special processing based on
 * which flags are set. This means we don't need to maintain multiple
 * similar copies of this loop.
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 */
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static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
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{
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	LIST_HEAD(referenced);
	LIST_HEAD(tmp);
	struct dentry *dentry;
	int cnt = 0;
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	BUG_ON(!sb);
	BUG_ON((flags & DCACHE_REFERENCED) && count == NULL);
	spin_lock(&dcache_lock);
	if (count != NULL)
		/* called from prune_dcache() and shrink_dcache_parent() */
		cnt = *count;
restart:
	if (count == NULL)
		list_splice_init(&sb->s_dentry_lru, &tmp);
	else {
		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);

			spin_lock(&dentry->d_lock);
			/*
			 * 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.
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			 */
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			if ((flags & DCACHE_REFERENCED)
				&& (dentry->d_flags & DCACHE_REFERENCED)) {
				dentry->d_flags &= ~DCACHE_REFERENCED;
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				list_move(&dentry->d_lru, &referenced);
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				spin_unlock(&dentry->d_lock);
			} else {
				list_move_tail(&dentry->d_lru, &tmp);
				spin_unlock(&dentry->d_lock);
				cnt--;
				if (!cnt)
					break;
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			}
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			cond_resched_lock(&dcache_lock);
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		}
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	}
	while (!list_empty(&tmp)) {
		dentry = list_entry(tmp.prev, struct dentry, d_lru);
		dentry_lru_del_init(dentry);
		spin_lock(&dentry->d_lock);
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		/*
		 * We found an inuse dentry which was not removed from
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		 * the LRU because of laziness during lookup.  Do not free
		 * it - just keep it off the LRU list.
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		 */
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		if (atomic_read(&dentry->d_count)) {
			spin_unlock(&dentry->d_lock);
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			continue;
		}
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		prune_one_dentry(dentry);
		/* dentry->d_lock was dropped in prune_one_dentry() */
		cond_resched_lock(&dcache_lock);
	}
	if (count == NULL && !list_empty(&sb->s_dentry_lru))
		goto restart;
	if (count != NULL)
		*count = cnt;
	if (!list_empty(&referenced))
		list_splice(&referenced, &sb->s_dentry_lru);
	spin_unlock(&dcache_lock);
}

/**
 * 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)
{
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	struct super_block *sb, *p = NULL;
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	int w_count;
	int unused = dentry_stat.nr_unused;
	int prune_ratio;
	int pruned;

	if (unused == 0 || count == 0)
		return;
	spin_lock(&dcache_lock);
	if (count >= unused)
		prune_ratio = 1;
	else
		prune_ratio = unused / count;
	spin_lock(&sb_lock);
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	list_for_each_entry(sb, &super_blocks, s_list) {
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		if (list_empty(&sb->s_instances))
			continue;
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		if (sb->s_nr_dentry_unused == 0)
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			continue;
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		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)
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		 */
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		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;
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		/*
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		 * 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.
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		 */
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		if (down_read_trylock(&sb->s_umount)) {
			if ((sb->s_root != NULL) &&
			    (!list_empty(&sb->s_dentry_lru))) {
				spin_unlock(&dcache_lock);
				__shrink_dcache_sb(sb, &w_count,
						DCACHE_REFERENCED);
				pruned -= w_count;
				spin_lock(&dcache_lock);
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			}
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			up_read(&sb->s_umount);
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		}
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		spin_lock(&sb_lock);
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		if (p)
			__put_super(p);
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		count -= pruned;
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		p = sb;
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		/* more work left to do? */
		if (count <= 0)
			break;
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	}
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	if (p)
		__put_super(p);
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	spin_unlock(&sb_lock);
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	spin_unlock(&dcache_lock);
}

/**
 * shrink_dcache_sb - shrink dcache for a superblock
 * @sb: superblock
 *
 * Shrink the dcache for the specified super block. This
 * is used to free the dcache before unmounting a file
 * system
 */
void shrink_dcache_sb(struct super_block * sb)
{
613
	__shrink_dcache_sb(sb, NULL, 0);
L
Linus Torvalds 已提交
614
}
615
EXPORT_SYMBOL(shrink_dcache_sb);
L
Linus Torvalds 已提交
616

617 618 619 620 621 622 623 624
/*
 * 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;
625
	unsigned detached = 0;
626 627 628 629 630

	BUG_ON(!IS_ROOT(dentry));

	/* detach this root from the system */
	spin_lock(&dcache_lock);
631
	dentry_lru_del_init(dentry);
632 633 634 635 636 637 638 639 640 641 642 643 644
	__d_drop(dentry);
	spin_unlock(&dcache_lock);

	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 */
			spin_lock(&dcache_lock);
			list_for_each_entry(loop, &dentry->d_subdirs,
					    d_u.d_child) {
645
				dentry_lru_del_init(loop);
646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675
				__d_drop(loop);
				cond_resched_lock(&dcache_lock);
			}
			spin_unlock(&dcache_lock);

			/* 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;

			if (atomic_read(&dentry->d_count) != 0) {
				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,
				       atomic_read(&dentry->d_count),
				       dentry->d_sb->s_type->name,
				       dentry->d_sb->s_id);
				BUG();
			}

676
			if (IS_ROOT(dentry))
677
				parent = NULL;
678 679
			else {
				parent = dentry->d_parent;
680
				atomic_dec(&parent->d_count);
681
			}
682 683

			list_del(&dentry->d_u.d_child);
684
			detached++;
685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701

			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)
702
				goto out;
703 704 705 706 707 708 709 710

			dentry = parent;

		} while (list_empty(&dentry->d_subdirs));

		dentry = list_entry(dentry->d_subdirs.next,
				    struct dentry, d_u.d_child);
	}
711 712 713 714 715
out:
	/* several dentries were freed, need to correct nr_dentry */
	spin_lock(&dcache_lock);
	dentry_stat.nr_dentry -= detached;
	spin_unlock(&dcache_lock);
716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746
}

/*
 * destroy the dentries attached to a superblock on unmounting
 * - we don't need to use dentry->d_lock, and only need dcache_lock when
 *   removing the dentry from the system lists and hashes because:
 *   - 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;
	atomic_dec(&dentry->d_count);
	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
747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773
/*
 * 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)
{
	struct dentry *this_parent = parent;
	struct list_head *next;

	spin_lock(&dcache_lock);
	if (d_mountpoint(parent))
		goto positive;
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
774
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
775 776 777 778 779 780 781 782 783 784 785 786 787
		next = tmp->next;
		/* Have we found a mount point ? */
		if (d_mountpoint(dentry))
			goto positive;
		if (!list_empty(&dentry->d_subdirs)) {
			this_parent = dentry;
			goto repeat;
		}
	}
	/*
	 * All done at this level ... ascend and resume the search.
	 */
	if (this_parent != parent) {
E
Eric Dumazet 已提交
788
		next = this_parent->d_u.d_child.next;
L
Linus Torvalds 已提交
789 790 791 792 793 794 795 796 797
		this_parent = this_parent->d_parent;
		goto resume;
	}
	spin_unlock(&dcache_lock);
	return 0; /* No mount points found in tree */
positive:
	spin_unlock(&dcache_lock);
	return 1;
}
798
EXPORT_SYMBOL(have_submounts);
L
Linus Torvalds 已提交
799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825

/*
 * 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)
{
	struct dentry *this_parent = parent;
	struct list_head *next;
	int found = 0;

	spin_lock(&dcache_lock);
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
826
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
827 828
		next = tmp->next;

829
		dentry_lru_del_init(dentry);
L
Linus Torvalds 已提交
830 831 832 833 834
		/* 
		 * move only zero ref count dentries to the end 
		 * of the unused list for prune_dcache
		 */
		if (!atomic_read(&dentry->d_count)) {
835
			dentry_lru_add_tail(dentry);
L
Linus Torvalds 已提交
836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858
			found++;
		}

		/*
		 * We can return to the caller if we have found some (this
		 * ensures forward progress). We'll be coming back to find
		 * the rest.
		 */
		if (found && need_resched())
			goto out;

		/*
		 * Descend a level if the d_subdirs list is non-empty.
		 */
		if (!list_empty(&dentry->d_subdirs)) {
			this_parent = dentry;
			goto repeat;
		}
	}
	/*
	 * All done at this level ... ascend and resume the search.
	 */
	if (this_parent != parent) {
E
Eric Dumazet 已提交
859
		next = this_parent->d_u.d_child.next;
L
Linus Torvalds 已提交
860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876
		this_parent = this_parent->d_parent;
		goto resume;
	}
out:
	spin_unlock(&dcache_lock);
	return found;
}

/**
 * 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)
{
877
	struct super_block *sb = parent->d_sb;
L
Linus Torvalds 已提交
878 879 880
	int found;

	while ((found = select_parent(parent)) != 0)
881
		__shrink_dcache_sb(sb, &found, 0);
L
Linus Torvalds 已提交
882
}
883
EXPORT_SYMBOL(shrink_dcache_parent);
L
Linus Torvalds 已提交
884 885 886 887 888 889 890 891 892 893 894 895 896

/*
 * 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.
 */
897
static int shrink_dcache_memory(struct shrinker *shrink, int nr, gfp_t gfp_mask)
L
Linus Torvalds 已提交
898 899 900 901
{
	if (nr) {
		if (!(gfp_mask & __GFP_FS))
			return -1;
902
		prune_dcache(nr);
L
Linus Torvalds 已提交
903 904 905 906
	}
	return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
}

907 908 909 910 911
static struct shrinker dcache_shrinker = {
	.shrink = shrink_dcache_memory,
	.seeks = DEFAULT_SEEKS,
};

L
Linus Torvalds 已提交
912 913 914 915 916 917 918 919 920 921 922 923 924 925 926
/**
 * 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;

927
	dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
L
Linus Torvalds 已提交
928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964
	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;

	atomic_set(&dentry->d_count, 1);
	dentry->d_flags = DCACHE_UNHASHED;
	spin_lock_init(&dentry->d_lock);
	dentry->d_inode = NULL;
	dentry->d_parent = NULL;
	dentry->d_sb = NULL;
	dentry->d_op = NULL;
	dentry->d_fsdata = NULL;
	dentry->d_mounted = 0;
	INIT_HLIST_NODE(&dentry->d_hash);
	INIT_LIST_HEAD(&dentry->d_lru);
	INIT_LIST_HEAD(&dentry->d_subdirs);
	INIT_LIST_HEAD(&dentry->d_alias);

	if (parent) {
		dentry->d_parent = dget(parent);
		dentry->d_sb = parent->d_sb;
	} else {
E
Eric Dumazet 已提交
965
		INIT_LIST_HEAD(&dentry->d_u.d_child);
L
Linus Torvalds 已提交
966 967 968 969
	}

	spin_lock(&dcache_lock);
	if (parent)
E
Eric Dumazet 已提交
970
		list_add(&dentry->d_u.d_child, &parent->d_subdirs);
L
Linus Torvalds 已提交
971 972 973 974 975
	dentry_stat.nr_dentry++;
	spin_unlock(&dcache_lock);

	return dentry;
}
976
EXPORT_SYMBOL(d_alloc);
L
Linus Torvalds 已提交
977 978 979 980 981 982 983 984 985 986

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);
}
987
EXPORT_SYMBOL(d_alloc_name);
L
Linus Torvalds 已提交
988

989 990 991 992 993 994 995 996 997
/* the caller must hold dcache_lock */
static void __d_instantiate(struct dentry *dentry, struct inode *inode)
{
	if (inode)
		list_add(&dentry->d_alias, &inode->i_dentry);
	dentry->d_inode = inode;
	fsnotify_d_instantiate(dentry, inode);
}

L
Linus Torvalds 已提交
998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014
/**
 * 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)
{
1015
	BUG_ON(!list_empty(&entry->d_alias));
L
Linus Torvalds 已提交
1016
	spin_lock(&dcache_lock);
1017
	__d_instantiate(entry, inode);
L
Linus Torvalds 已提交
1018 1019 1020
	spin_unlock(&dcache_lock);
	security_d_instantiate(entry, inode);
}
1021
EXPORT_SYMBOL(d_instantiate);
L
Linus Torvalds 已提交
1022 1023 1024 1025 1026 1027 1028 1029

/**
 * 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
1030
 * aliased dentry instead and drop one reference to inode.
L
Linus Torvalds 已提交
1031 1032 1033
 *
 * Note that in order to avoid conflicts with rename() etc, the caller
 * had better be holding the parent directory semaphore.
1034 1035 1036 1037
 *
 * 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
1038
 */
1039 1040
static struct dentry *__d_instantiate_unique(struct dentry *entry,
					     struct inode *inode)
L
Linus Torvalds 已提交
1041 1042 1043 1044 1045 1046
{
	struct dentry *alias;
	int len = entry->d_name.len;
	const char *name = entry->d_name.name;
	unsigned int hash = entry->d_name.hash;

1047
	if (!inode) {
1048
		__d_instantiate(entry, NULL);
1049 1050 1051
		return NULL;
	}

L
Linus Torvalds 已提交
1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065
	list_for_each_entry(alias, &inode->i_dentry, d_alias) {
		struct qstr *qstr = &alias->d_name;

		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;
		dget_locked(alias);
		return alias;
	}
1066

1067
	__d_instantiate(entry, inode);
L
Linus Torvalds 已提交
1068 1069
	return NULL;
}
1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090

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

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

	spin_lock(&dcache_lock);
	result = __d_instantiate_unique(entry, inode);
	spin_unlock(&dcache_lock);

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

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

L
Linus Torvalds 已提交
1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117
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;
}
1118
EXPORT_SYMBOL(d_alloc_root);
L
Linus Torvalds 已提交
1119 1120 1121 1122 1123 1124 1125 1126 1127

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);
}

1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140
/**
 * 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
1141 1142 1143 1144
 * 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).
1145 1146 1147
 */
struct dentry *d_obtain_alias(struct inode *inode)
{
C
Christoph Hellwig 已提交
1148 1149 1150
	static const struct qstr anonstring = { .name = "" };
	struct dentry *tmp;
	struct dentry *res;
1151 1152

	if (!inode)
1153
		return ERR_PTR(-ESTALE);
1154 1155 1156
	if (IS_ERR(inode))
		return ERR_CAST(inode);

C
Christoph Hellwig 已提交
1157 1158 1159 1160 1161 1162 1163 1164
	res = d_find_alias(inode);
	if (res)
		goto out_iput;

	tmp = d_alloc(NULL, &anonstring);
	if (!tmp) {
		res = ERR_PTR(-ENOMEM);
		goto out_iput;
1165
	}
C
Christoph Hellwig 已提交
1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191
	tmp->d_parent = tmp; /* make sure dput doesn't croak */

	spin_lock(&dcache_lock);
	res = __d_find_alias(inode, 0);
	if (res) {
		spin_unlock(&dcache_lock);
		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);
	hlist_add_head(&tmp->d_hash, &inode->i_sb->s_anon);
	spin_unlock(&tmp->d_lock);

	spin_unlock(&dcache_lock);
	return tmp;

 out_iput:
	iput(inode);
	return res;
1192
}
1193
EXPORT_SYMBOL(d_obtain_alias);
L
Linus Torvalds 已提交
1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214

/**
 * 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;

1215
	if (inode && S_ISDIR(inode->i_mode)) {
L
Linus Torvalds 已提交
1216 1217 1218 1219 1220 1221 1222 1223 1224
		spin_lock(&dcache_lock);
		new = __d_find_alias(inode, 1);
		if (new) {
			BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
			spin_unlock(&dcache_lock);
			security_d_instantiate(new, inode);
			d_move(new, dentry);
			iput(inode);
		} else {
1225 1226
			/* already taking dcache_lock, so d_add() by hand */
			__d_instantiate(dentry, inode);
L
Linus Torvalds 已提交
1227 1228 1229 1230 1231 1232 1233 1234
			spin_unlock(&dcache_lock);
			security_d_instantiate(dentry, inode);
			d_rehash(dentry);
		}
	} else
		d_add(dentry, inode);
	return new;
}
1235
EXPORT_SYMBOL(d_splice_alias);
L
Linus Torvalds 已提交
1236

1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252
/**
 * 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.
 */
1253
struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
1254 1255 1256 1257 1258 1259
			struct qstr *name)
{
	int error;
	struct dentry *found;
	struct dentry *new;

C
Christoph Hellwig 已提交
1260 1261 1262 1263
	/*
	 * First check if a dentry matching the name already exists,
	 * if not go ahead and create it now.
	 */
1264 1265 1266 1267 1268 1269 1270
	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
1271

1272 1273 1274 1275 1276 1277 1278
		found = d_splice_alias(inode, new);
		if (found) {
			dput(new);
			return found;
		}
		return new;
	}
C
Christoph Hellwig 已提交
1279 1280 1281 1282 1283 1284 1285

	/*
	 * If a matching dentry exists, and it's not negative use it.
	 *
	 * Decrement the reference count to balance the iget() done
	 * earlier on.
	 */
1286 1287 1288 1289 1290 1291 1292 1293 1294
	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
1295

1296 1297
	/*
	 * Negative dentry: instantiate it unless the inode is a directory and
C
Christoph Hellwig 已提交
1298
	 * already has a dentry.
1299 1300
	 */
	spin_lock(&dcache_lock);
C
Christoph Hellwig 已提交
1301
	if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) {
1302
		__d_instantiate(found, inode);
1303 1304 1305 1306
		spin_unlock(&dcache_lock);
		security_d_instantiate(found, inode);
		return found;
	}
C
Christoph Hellwig 已提交
1307

1308
	/*
C
Christoph Hellwig 已提交
1309 1310
	 * In case a directory already has a (disconnected) entry grab a
	 * reference to it, move it in place and use it.
1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324
	 */
	new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
	dget_locked(new);
	spin_unlock(&dcache_lock);
	security_d_instantiate(found, inode);
	d_move(new, found);
	iput(inode);
	dput(found);
	return new;

err_out:
	iput(inode);
	return ERR_PTR(error);
}
1325
EXPORT_SYMBOL(d_add_ci);
L
Linus Torvalds 已提交
1326 1327 1328 1329 1330

/**
 * d_lookup - search for a dentry
 * @parent: parent dentry
 * @name: qstr of name we wish to find
1331
 * Returns: dentry, or NULL
L
Linus Torvalds 已提交
1332
 *
1333 1334 1335 1336
 * 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
1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350
 */
struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
{
	struct dentry * dentry = NULL;
	unsigned long seq;

        do {
                seq = read_seqbegin(&rename_lock);
                dentry = __d_lookup(parent, name);
                if (dentry)
			break;
	} while (read_seqretry(&rename_lock, seq));
	return dentry;
}
1351
EXPORT_SYMBOL(d_lookup);
L
Linus Torvalds 已提交
1352

1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367
/*
 * __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.
 */
L
Linus Torvalds 已提交
1368 1369 1370 1371 1372 1373 1374 1375
struct dentry * __d_lookup(struct dentry * parent, struct qstr * name)
{
	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 dentry *found = NULL;
	struct hlist_node *node;
1376
	struct dentry *dentry;
L
Linus Torvalds 已提交
1377

1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390
	/*
	 * 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
1391 1392
	rcu_read_lock();
	
1393
	hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
L
Linus Torvalds 已提交
1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404
		struct qstr *qstr;

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

		spin_lock(&dentry->d_lock);

		/*
		 * Recheck the dentry after taking the lock - d_move may have
1405 1406
		 * changed things. Don't bother checking the hash because
		 * we're about to compare the whole name anyway.
L
Linus Torvalds 已提交
1407 1408 1409 1410
		 */
		if (dentry->d_parent != parent)
			goto next;

1411 1412 1413 1414
		/* non-existing due to RCU? */
		if (d_unhashed(dentry))
			goto next;

L
Linus Torvalds 已提交
1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429
		/*
		 * It is safe to compare names since d_move() cannot
		 * change the qstr (protected by d_lock).
		 */
		qstr = &dentry->d_name;
		if (parent->d_op && parent->d_op->d_compare) {
			if (parent->d_op->d_compare(parent, qstr, name))
				goto next;
		} else {
			if (qstr->len != len)
				goto next;
			if (memcmp(qstr->name, str, len))
				goto next;
		}

1430 1431
		atomic_inc(&dentry->d_count);
		found = dentry;
L
Linus Torvalds 已提交
1432 1433 1434 1435 1436 1437 1438 1439 1440 1441
		spin_unlock(&dentry->d_lock);
		break;
next:
		spin_unlock(&dentry->d_lock);
 	}
 	rcu_read_unlock();

 	return found;
}

1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467
/**
 * 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) {
		if (dir->d_op->d_hash(dir, name) < 0)
			goto out;
	}
	dentry = d_lookup(dir, name);
out:
	return dentry;
}

L
Linus Torvalds 已提交
1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492
/**
 * d_validate - verify dentry provided from insecure source
 * @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.
 */
 
int d_validate(struct dentry *dentry, struct dentry *dparent)
{
	struct hlist_head *base;
	struct hlist_node *lhp;

	/* Check whether the ptr might be valid at all.. */
	if (!kmem_ptr_validate(dentry_cache, dentry))
		goto out;

	if (dentry->d_parent != dparent)
		goto out;

	spin_lock(&dcache_lock);
	base = d_hash(dparent, dentry->d_name.hash);
	hlist_for_each(lhp,base) { 
1493
		/* hlist_for_each_entry_rcu() not required for d_hash list
L
Linus Torvalds 已提交
1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505
		 * as it is parsed under dcache_lock
		 */
		if (dentry == hlist_entry(lhp, struct dentry, d_hash)) {
			__dget_locked(dentry);
			spin_unlock(&dcache_lock);
			return 1;
		}
	}
	spin_unlock(&dcache_lock);
out:
	return 0;
}
1506
EXPORT_SYMBOL(d_validate);
L
Linus Torvalds 已提交
1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530

/*
 * 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)
{
1531
	int isdir = 0;
L
Linus Torvalds 已提交
1532 1533 1534 1535 1536
	/*
	 * Are we the only user?
	 */
	spin_lock(&dcache_lock);
	spin_lock(&dentry->d_lock);
1537
	isdir = S_ISDIR(dentry->d_inode->i_mode);
L
Linus Torvalds 已提交
1538
	if (atomic_read(&dentry->d_count) == 1) {
A
Al Viro 已提交
1539
		dentry->d_flags &= ~DCACHE_CANT_MOUNT;
L
Linus Torvalds 已提交
1540
		dentry_iput(dentry);
1541
		fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
1542 1543 1544 1545 1546 1547 1548 1549
		return;
	}

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

	spin_unlock(&dentry->d_lock);
	spin_unlock(&dcache_lock);
1550 1551

	fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
1552
}
1553
EXPORT_SYMBOL(d_delete);
L
Linus Torvalds 已提交
1554 1555 1556 1557 1558 1559 1560 1561

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

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

1562 1563 1564 1565 1566
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
1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577
/**
 * 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(&dcache_lock);
	spin_lock(&entry->d_lock);
1578
	_d_rehash(entry);
L
Linus Torvalds 已提交
1579 1580 1581
	spin_unlock(&entry->d_lock);
	spin_unlock(&dcache_lock);
}
1582
EXPORT_SYMBOL(d_rehash);
L
Linus Torvalds 已提交
1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601

/*
 * 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..
 */
static void switch_names(struct dentry *dentry, struct dentry *target)
{
	if (dname_external(target)) {
		if (dname_external(dentry)) {
			/*
			 * Both external: swap the pointers
			 */
1602
			swap(target->d_name.name, dentry->d_name.name);
L
Linus Torvalds 已提交
1603 1604 1605 1606 1607
		} else {
			/*
			 * dentry:internal, target:external.  Steal target's
			 * storage and make target internal.
			 */
1608 1609
			memcpy(target->d_iname, dentry->d_name.name,
					dentry->d_name.len + 1);
L
Linus Torvalds 已提交
1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628
			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);
1629 1630
			dentry->d_name.len = target->d_name.len;
			return;
L
Linus Torvalds 已提交
1631 1632
		}
	}
1633
	swap(dentry->d_name.len, target->d_name.len);
L
Linus Torvalds 已提交
1634 1635 1636 1637 1638 1639 1640 1641 1642 1643
}

/*
 * We cannibalize "target" when moving dentry on top of it,
 * because it's going to be thrown away anyway. We could be more
 * polite about it, though.
 *
 * This forceful removal will result in ugly /proc output if
 * somebody holds a file open that got deleted due to a rename.
 * We could be nicer about the deleted file, and let it show
J
J. Bruce Fields 已提交
1644 1645
 * up under the name it had before it was deleted rather than
 * under the original name of the file that was moved on top of it.
L
Linus Torvalds 已提交
1646 1647
 */
 
1648 1649
/*
 * d_move_locked - move a dentry
L
Linus Torvalds 已提交
1650 1651 1652 1653 1654 1655
 * @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.
 */
1656
static void d_move_locked(struct dentry * dentry, struct dentry * target)
L
Linus Torvalds 已提交
1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668
{
	struct hlist_head *list;

	if (!dentry->d_inode)
		printk(KERN_WARNING "VFS: moving negative dcache entry\n");

	write_seqlock(&rename_lock);
	/*
	 * XXXX: do we really need to take target->d_lock?
	 */
	if (target < dentry) {
		spin_lock(&target->d_lock);
I
Ingo Molnar 已提交
1669
		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
L
Linus Torvalds 已提交
1670 1671
	} else {
		spin_lock(&dentry->d_lock);
I
Ingo Molnar 已提交
1672
		spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
L
Linus Torvalds 已提交
1673 1674 1675
	}

	/* Move the dentry to the target hash queue, if on different bucket */
1676
	if (d_unhashed(dentry))
L
Linus Torvalds 已提交
1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687
		goto already_unhashed;

	hlist_del_rcu(&dentry->d_hash);

already_unhashed:
	list = d_hash(target->d_parent, target->d_name.hash);
	__d_rehash(dentry, list);

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

E
Eric Dumazet 已提交
1688 1689
	list_del(&dentry->d_u.d_child);
	list_del(&target->d_u.d_child);
L
Linus Torvalds 已提交
1690 1691 1692

	/* Switch the names.. */
	switch_names(dentry, target);
1693
	swap(dentry->d_name.hash, target->d_name.hash);
L
Linus Torvalds 已提交
1694 1695 1696 1697 1698

	/* ... and switch the parents */
	if (IS_ROOT(dentry)) {
		dentry->d_parent = target->d_parent;
		target->d_parent = target;
E
Eric Dumazet 已提交
1699
		INIT_LIST_HEAD(&target->d_u.d_child);
L
Linus Torvalds 已提交
1700
	} else {
1701
		swap(dentry->d_parent, target->d_parent);
L
Linus Torvalds 已提交
1702 1703

		/* And add them back to the (new) parent lists */
E
Eric Dumazet 已提交
1704
		list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
L
Linus Torvalds 已提交
1705 1706
	}

E
Eric Dumazet 已提交
1707
	list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
L
Linus Torvalds 已提交
1708
	spin_unlock(&target->d_lock);
1709
	fsnotify_d_move(dentry);
L
Linus Torvalds 已提交
1710 1711
	spin_unlock(&dentry->d_lock);
	write_sequnlock(&rename_lock);
1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726
}

/**
 * d_move - move a dentry
 * @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.
 */

void d_move(struct dentry * dentry, struct dentry * target)
{
	spin_lock(&dcache_lock);
	d_move_locked(dentry, target);
L
Linus Torvalds 已提交
1727 1728
	spin_unlock(&dcache_lock);
}
1729
EXPORT_SYMBOL(d_move);
L
Linus Torvalds 已提交
1730

1731 1732 1733 1734 1735 1736 1737
/**
 * 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.
1738
 */
1739
struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
1740 1741 1742
{
	struct dentry *p;

1743
	for (p = p2; !IS_ROOT(p); p = p->d_parent) {
1744
		if (p->d_parent == p1)
1745
			return p;
1746
	}
1747
	return NULL;
1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759
}

/*
 * This helper attempts to cope with remotely renamed directories
 *
 * It assumes that the caller is already holding
 * dentry->d_parent->d_inode->i_mutex and the dcache_lock
 *
 * 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)
1760
	__releases(dcache_lock)
1761 1762 1763 1764 1765 1766 1767 1768 1769 1770
{
	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);
1771
	if (d_ancestor(alias, dentry))
1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793
		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:
	d_move_locked(alias, dentry);
	ret = alias;
out_err:
	spin_unlock(&dcache_lock);
	if (m2)
		mutex_unlock(m2);
	if (m1)
		mutex_unlock(m1);
	return ret;
}

1794 1795 1796 1797 1798 1799 1800 1801 1802
/*
 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
 * named dentry in place of the dentry to be replaced.
 */
static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
{
	struct dentry *dparent, *aparent;

	switch_names(dentry, anon);
1803
	swap(dentry->d_name.hash, anon->d_name.hash);
1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834

	dparent = dentry->d_parent;
	aparent = anon->d_parent;

	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);

	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)
{
1835
	struct dentry *actual;
1836 1837 1838 1839 1840 1841 1842

	BUG_ON(!d_unhashed(dentry));

	spin_lock(&dcache_lock);

	if (!inode) {
		actual = dentry;
1843
		__d_instantiate(dentry, NULL);
1844 1845 1846
		goto found_lock;
	}

1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867
	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)) {
				spin_lock(&alias->d_lock);
				__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;
		}
1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882
	}

	/* Add a unique reference */
	actual = __d_instantiate_unique(dentry, inode);
	if (!actual)
		actual = dentry;
	else if (unlikely(!d_unhashed(actual)))
		goto shouldnt_be_hashed;

found_lock:
	spin_lock(&actual->d_lock);
found:
	_d_rehash(actual);
	spin_unlock(&actual->d_lock);
	spin_unlock(&dcache_lock);
1883
out_nolock:
1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895
	if (actual == dentry) {
		security_d_instantiate(dentry, inode);
		return NULL;
	}

	iput(inode);
	return actual;

shouldnt_be_hashed:
	spin_unlock(&dcache_lock);
	BUG();
}
1896
EXPORT_SYMBOL_GPL(d_materialise_unique);
1897

1898
static int prepend(char **buffer, int *buflen, const char *str, int namelen)
1899 1900 1901 1902 1903 1904 1905 1906 1907
{
	*buflen -= namelen;
	if (*buflen < 0)
		return -ENAMETOOLONG;
	*buffer -= namelen;
	memcpy(*buffer, str, namelen);
	return 0;
}

1908 1909 1910 1911 1912
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
1913
/**
M
Miklos Szeredi 已提交
1914 1915
 * Prepend path string to a buffer
 *
1916 1917
 * @path: the dentry/vfsmount to report
 * @root: root vfsmnt/dentry (may be modified by this function)
M
Miklos Szeredi 已提交
1918 1919
 * @buffer: pointer to the end of the buffer
 * @buflen: pointer to buffer length
1920
 *
M
Miklos Szeredi 已提交
1921
 * Caller holds the dcache_lock.
1922 1923 1924
 *
 * 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
1925
 */
M
Miklos Szeredi 已提交
1926 1927
static int prepend_path(const struct path *path, struct path *root,
			char **buffer, int *buflen)
L
Linus Torvalds 已提交
1928
{
1929 1930
	struct dentry *dentry = path->dentry;
	struct vfsmount *vfsmnt = path->mnt;
M
Miklos Szeredi 已提交
1931 1932
	bool slash = false;
	int error = 0;
1933

N
Nick Piggin 已提交
1934
	br_read_lock(vfsmount_lock);
M
Miklos Szeredi 已提交
1935
	while (dentry != root->dentry || vfsmnt != root->mnt) {
L
Linus Torvalds 已提交
1936 1937 1938
		struct dentry * parent;

		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
1939
			/* Global root? */
L
Linus Torvalds 已提交
1940 1941 1942 1943 1944 1945 1946 1947 1948
			if (vfsmnt->mnt_parent == vfsmnt) {
				goto global_root;
			}
			dentry = vfsmnt->mnt_mountpoint;
			vfsmnt = vfsmnt->mnt_parent;
			continue;
		}
		parent = dentry->d_parent;
		prefetch(parent);
M
Miklos Szeredi 已提交
1949 1950 1951 1952 1953 1954 1955
		error = prepend_name(buffer, buflen, &dentry->d_name);
		if (!error)
			error = prepend(buffer, buflen, "/", 1);
		if (error)
			break;

		slash = true;
L
Linus Torvalds 已提交
1956 1957 1958
		dentry = parent;
	}

1959
out:
M
Miklos Szeredi 已提交
1960 1961 1962
	if (!error && !slash)
		error = prepend(buffer, buflen, "/", 1);

N
Nick Piggin 已提交
1963
	br_read_unlock(vfsmount_lock);
M
Miklos Szeredi 已提交
1964
	return error;
L
Linus Torvalds 已提交
1965 1966

global_root:
1967 1968 1969 1970 1971 1972 1973 1974 1975
	/*
	 * 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);
	}
1976 1977
	root->mnt = vfsmnt;
	root->dentry = dentry;
1978
	goto out;
M
Miklos Szeredi 已提交
1979
}
1980

M
Miklos Szeredi 已提交
1981 1982 1983 1984
/**
 * __d_path - return the path of a dentry
 * @path: the dentry/vfsmount to report
 * @root: root vfsmnt/dentry (may be modified by this function)
1985
 * @buf: buffer to return value in
M
Miklos Szeredi 已提交
1986 1987
 * @buflen: buffer length
 *
1988
 * Convert a dentry into an ASCII path name.
M
Miklos Szeredi 已提交
1989 1990 1991 1992
 *
 * Returns a pointer into the buffer or an error code if the
 * path was too long.
 *
1993
 * "buflen" should be positive.
M
Miklos Szeredi 已提交
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
 *
 * 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);
2005
	spin_lock(&dcache_lock);
M
Miklos Szeredi 已提交
2006
	error = prepend_path(path, root, &res, &buflen);
2007 2008
	spin_unlock(&dcache_lock);

M
Miklos Szeredi 已提交
2009 2010 2011
	if (error)
		return ERR_PTR(error);
	return res;
L
Linus Torvalds 已提交
2012 2013
}

2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029
/*
 * 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);
}

2030 2031 2032 2033 2034
static int prepend_unreachable(char **buffer, int *buflen)
{
	return prepend(buffer, buflen, "(unreachable)", 13);
}

J
Jan Blunck 已提交
2035 2036
/**
 * d_path - return the path of a dentry
2037
 * @path: path to report
J
Jan Blunck 已提交
2038 2039 2040 2041 2042 2043
 * @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.
 *
2044 2045 2046 2047
 * 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
2048
 *
2049
 * "buflen" should be positive.
J
Jan Blunck 已提交
2050
 */
2051
char *d_path(const struct path *path, char *buf, int buflen)
L
Linus Torvalds 已提交
2052
{
2053
	char *res = buf + buflen;
J
Jan Blunck 已提交
2054
	struct path root;
2055
	struct path tmp;
2056
	int error;
L
Linus Torvalds 已提交
2057

2058 2059 2060 2061 2062 2063 2064
	/*
	 * 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:
	 */
2065 2066
	if (path->dentry->d_op && path->dentry->d_op->d_dname)
		return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2067

2068
	get_fs_root(current->fs, &root);
2069
	spin_lock(&dcache_lock);
2070
	tmp = root;
2071 2072 2073
	error = path_with_deleted(path, &tmp, &res, &buflen);
	if (error)
		res = ERR_PTR(error);
2074
	spin_unlock(&dcache_lock);
J
Jan Blunck 已提交
2075
	path_put(&root);
L
Linus Torvalds 已提交
2076 2077
	return res;
}
2078
EXPORT_SYMBOL(d_path);
L
Linus Torvalds 已提交
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
/**
 * 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);
	spin_lock(&dcache_lock);
	tmp = root;
	error = path_with_deleted(path, &tmp, &res, &buflen);
	if (!error && !path_equal(&tmp, &root))
		error = prepend_unreachable(&res, &buflen);
	spin_unlock(&dcache_lock);
	path_put(&root);
	if (error)
		res =  ERR_PTR(error);

	return res;
}

2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133
/*
 * 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);
}

2134 2135 2136
/*
 * Write full pathname from the root of the filesystem into the buffer.
 */
A
Al Viro 已提交
2137
char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148
{
	char *end = buf + buflen;
	char *retval;

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

2149 2150
	while (!IS_ROOT(dentry)) {
		struct dentry *parent = dentry->d_parent;
2151 2152

		prefetch(parent);
2153
		if ((prepend_name(&end, &buflen, &dentry->d_name) != 0) ||
2154 2155 2156 2157 2158 2159
		    (prepend(&end, &buflen, "/", 1) != 0))
			goto Elong;

		retval = end;
		dentry = parent;
	}
A
Al Viro 已提交
2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178
	return retval;
Elong:
	return ERR_PTR(-ENAMETOOLONG);
}
EXPORT_SYMBOL(__dentry_path);

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

	spin_lock(&dcache_lock);
	if (d_unlinked(dentry)) {
		p = buf + buflen;
		if (prepend(&p, &buflen, "//deleted", 10) != 0)
			goto Elong;
		buflen++;
	}
	retval = __dentry_path(dentry, buf, buflen);
2179
	spin_unlock(&dcache_lock);
A
Al Viro 已提交
2180 2181
	if (!IS_ERR(retval) && p)
		*p = '/';	/* restore '/' overriden with '\0' */
2182 2183 2184 2185 2186 2187
	return retval;
Elong:
	spin_unlock(&dcache_lock);
	return ERR_PTR(-ENAMETOOLONG);
}

L
Linus Torvalds 已提交
2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205
/*
 * 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;
 *	}
 */
2206
SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
L
Linus Torvalds 已提交
2207
{
2208
	int error;
J
Jan Blunck 已提交
2209
	struct path pwd, root;
2210
	char *page = (char *) __get_free_page(GFP_USER);
L
Linus Torvalds 已提交
2211 2212 2213 2214

	if (!page)
		return -ENOMEM;

2215
	get_fs_root_and_pwd(current->fs, &root, &pwd);
L
Linus Torvalds 已提交
2216

2217 2218
	error = -ENOENT;
	spin_lock(&dcache_lock);
2219
	if (!d_unlinked(pwd.dentry)) {
2220
		unsigned long len;
2221
		struct path tmp = root;
2222 2223
		char *cwd = page + PAGE_SIZE;
		int buflen = PAGE_SIZE;
L
Linus Torvalds 已提交
2224

2225 2226
		prepend(&cwd, &buflen, "\0", 1);
		error = prepend_path(&pwd, &tmp, &cwd, &buflen);
2227 2228
		spin_unlock(&dcache_lock);

2229
		if (error)
2230 2231
			goto out;

2232 2233 2234 2235 2236 2237 2238
		/* Unreachable from current root */
		if (!path_equal(&tmp, &root)) {
			error = prepend_unreachable(&cwd, &buflen);
			if (error)
				goto out;
		}

2239 2240 2241 2242 2243 2244 2245 2246 2247
		error = -ERANGE;
		len = PAGE_SIZE + page - cwd;
		if (len <= size) {
			error = len;
			if (copy_to_user(buf, cwd, len))
				error = -EFAULT;
		}
	} else
		spin_unlock(&dcache_lock);
L
Linus Torvalds 已提交
2248 2249

out:
J
Jan Blunck 已提交
2250 2251
	path_put(&pwd);
	path_put(&root);
L
Linus Torvalds 已提交
2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271
	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()
 */
  
2272
int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
L
Linus Torvalds 已提交
2273 2274 2275 2276
{
	int result;
	unsigned long seq;

2277 2278 2279 2280 2281 2282
	if (new_dentry == old_dentry)
		return 1;

	/*
	 * Need rcu_readlock to protect against the d_parent trashing
	 * due to d_move
L
Linus Torvalds 已提交
2283 2284
	 */
	rcu_read_lock();
2285
	do {
L
Linus Torvalds 已提交
2286 2287
		/* for restarting inner loop in case of seq retry */
		seq = read_seqbegin(&rename_lock);
2288
		if (d_ancestor(old_dentry, new_dentry))
L
Linus Torvalds 已提交
2289
			result = 1;
2290 2291
		else
			result = 0;
L
Linus Torvalds 已提交
2292 2293 2294 2295 2296 2297
	} while (read_seqretry(&rename_lock, seq));
	rcu_read_unlock();

	return result;
}

2298 2299 2300 2301 2302
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
2303 2304

	br_read_lock(vfsmount_lock);
2305 2306 2307
	if (mnt != path2->mnt) {
		for (;;) {
			if (mnt->mnt_parent == mnt) {
N
Nick Piggin 已提交
2308
				br_read_unlock(vfsmount_lock);
2309 2310 2311 2312 2313 2314 2315 2316 2317
				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
2318
	br_read_unlock(vfsmount_lock);
2319 2320 2321 2322
	return res;
}
EXPORT_SYMBOL(path_is_under);

L
Linus Torvalds 已提交
2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333
void d_genocide(struct dentry *root)
{
	struct dentry *this_parent = root;
	struct list_head *next;

	spin_lock(&dcache_lock);
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
2334
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
2335 2336 2337 2338 2339 2340 2341 2342 2343 2344
		next = tmp->next;
		if (d_unhashed(dentry)||!dentry->d_inode)
			continue;
		if (!list_empty(&dentry->d_subdirs)) {
			this_parent = dentry;
			goto repeat;
		}
		atomic_dec(&dentry->d_count);
	}
	if (this_parent != root) {
E
Eric Dumazet 已提交
2345
		next = this_parent->d_u.d_child.next;
L
Linus Torvalds 已提交
2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371
		atomic_dec(&this_parent->d_count);
		this_parent = this_parent->d_parent;
		goto resume;
	}
	spin_unlock(&dcache_lock);
}

/**
 * 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;

2372 2373
	dentry = d_hash_and_lookup(dir, name);
	if (dentry) {
L
Linus Torvalds 已提交
2374 2375 2376 2377 2378 2379
		if (dentry->d_inode)
			ino = dentry->d_inode->i_ino;
		dput(dentry);
	}
	return ino;
}
2380
EXPORT_SYMBOL(find_inode_number);
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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]);
}

2416
static void __init dcache_init(void)
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{
	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. 
	 */
2425 2426
	dentry_cache = KMEM_CACHE(dentry,
		SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
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2428
	register_shrinker(&dcache_shrinker);
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	/* 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 */
2449
struct kmem_cache *names_cachep __read_mostly;
2450
EXPORT_SYMBOL(names_cachep);
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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,
2471
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
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2473 2474
	dcache_init();
	inode_init();
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	files_init(mempages);
2476
	mnt_init();
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	bdev_cache_init();
	chrdev_init();
}