dcache.c 62.8 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 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 dcache_lock, please.
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 */
static void d_free(struct dentry *dentry)
{
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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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}

/*
 * 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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/*
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 * dentry_lru_(add|del|move_tail) must be called with dcache_lock held.
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 */
static void dentry_lru_add(struct dentry *dentry)
{
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	if (list_empty(&dentry->d_lru)) {
		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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	}
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}

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

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		dentry_lru_del(dentry);
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		__d_drop(dentry);
		dentry = d_kill(dentry);
		spin_lock(&dcache_lock);
	}
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}

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static void shrink_dentry_list(struct list_head *list)
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{
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	struct dentry *dentry;

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	while (!list_empty(list)) {
		dentry = list_entry(list->prev, struct dentry, d_lru);
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		dentry_lru_del(dentry);
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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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		spin_lock(&dentry->d_lock);
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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);
	}
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}

/**
 * __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;

	spin_lock(&dcache_lock);
	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);

		/*
		 * 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.
		 */
		if (flags & DCACHE_REFERENCED) {
			spin_lock(&dentry->d_lock);
			if (dentry->d_flags & DCACHE_REFERENCED) {
				dentry->d_flags &= ~DCACHE_REFERENCED;
				list_move(&dentry->d_lru, &referenced);
				spin_unlock(&dentry->d_lock);
				cond_resched_lock(&dcache_lock);
				continue;
			}
			spin_unlock(&dentry->d_lock);
		}

		list_move_tail(&dentry->d_lru, &tmp);
		if (!--cnt)
			break;
		cond_resched_lock(&dcache_lock);
	}

	*count = cnt;
	shrink_dentry_list(&tmp);

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	if (!list_empty(&referenced))
		list_splice(&referenced, &sb->s_dentry_lru);
	spin_unlock(&dcache_lock);
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}

/**
 * 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;
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	int unused = dentry_stat.nr_unused;
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	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;
609
		p = sb;
A
Al Viro 已提交
610 611 612
		/* more work left to do? */
		if (count <= 0)
			break;
L
Linus Torvalds 已提交
613
	}
614 615
	if (p)
		__put_super(p);
616
	spin_unlock(&sb_lock);
L
Linus Torvalds 已提交
617 618 619 620 621 622 623
	spin_unlock(&dcache_lock);
}

/**
 * shrink_dcache_sb - shrink dcache for a superblock
 * @sb: superblock
 *
C
Christoph Hellwig 已提交
624 625
 * 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
626
 */
C
Christoph Hellwig 已提交
627
void shrink_dcache_sb(struct super_block *sb)
L
Linus Torvalds 已提交
628
{
C
Christoph Hellwig 已提交
629 630 631 632 633 634 635 636
	LIST_HEAD(tmp);

	spin_lock(&dcache_lock);
	while (!list_empty(&sb->s_dentry_lru)) {
		list_splice_init(&sb->s_dentry_lru, &tmp);
		shrink_dentry_list(&tmp);
	}
	spin_unlock(&dcache_lock);
L
Linus Torvalds 已提交
637
}
638
EXPORT_SYMBOL(shrink_dcache_sb);
L
Linus Torvalds 已提交
639

640 641 642 643 644 645 646 647
/*
 * 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;
648
	unsigned detached = 0;
649 650 651 652 653

	BUG_ON(!IS_ROOT(dentry));

	/* detach this root from the system */
	spin_lock(&dcache_lock);
654
	dentry_lru_del(dentry);
655 656 657 658 659 660 661 662 663 664 665 666 667
	__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) {
668
				dentry_lru_del(loop);
669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698
				__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();
			}

699
			if (IS_ROOT(dentry))
700
				parent = NULL;
701 702
			else {
				parent = dentry->d_parent;
703
				atomic_dec(&parent->d_count);
704
			}
705 706

			list_del(&dentry->d_u.d_child);
707
			detached++;
708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724

			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)
725
				return;
726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762
			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
 * - 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
763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789
/*
 * 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
790
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
791 792 793 794 795 796 797 798 799 800 801 802 803
		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
804
		next = this_parent->d_u.d_child.next;
L
Linus Torvalds 已提交
805 806 807 808 809 810 811 812 813
		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;
}
814
EXPORT_SYMBOL(have_submounts);
L
Linus Torvalds 已提交
815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841

/*
 * 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
842
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
843 844 845 846 847 848 849
		next = tmp->next;

		/* 
		 * move only zero ref count dentries to the end 
		 * of the unused list for prune_dcache
		 */
		if (!atomic_read(&dentry->d_count)) {
850
			dentry_lru_move_tail(dentry);
L
Linus Torvalds 已提交
851
			found++;
852 853
		} else {
			dentry_lru_del(dentry);
L
Linus Torvalds 已提交
854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875
		}

		/*
		 * 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
876
		next = this_parent->d_u.d_child.next;
L
Linus Torvalds 已提交
877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893
		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)
{
894
	struct super_block *sb = parent->d_sb;
L
Linus Torvalds 已提交
895 896 897
	int found;

	while ((found = select_parent(parent)) != 0)
898
		__shrink_dcache_sb(sb, &found, 0);
L
Linus Torvalds 已提交
899
}
900
EXPORT_SYMBOL(shrink_dcache_parent);
L
Linus Torvalds 已提交
901 902 903 904 905 906 907 908 909 910 911 912 913

/*
 * 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.
 */
914
static int shrink_dcache_memory(struct shrinker *shrink, int nr, gfp_t gfp_mask)
L
Linus Torvalds 已提交
915 916 917 918
{
	if (nr) {
		if (!(gfp_mask & __GFP_FS))
			return -1;
919
		prune_dcache(nr);
L
Linus Torvalds 已提交
920
	}
921

922
	return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
L
Linus Torvalds 已提交
923 924
}

925 926 927 928 929
static struct shrinker dcache_shrinker = {
	.shrink = shrink_dcache_memory,
	.seeks = DEFAULT_SEEKS,
};

L
Linus Torvalds 已提交
930 931 932 933 934 935 936 937 938 939 940 941 942 943 944
/**
 * 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;

945
	dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
L
Linus Torvalds 已提交
946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982
	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
983
		INIT_LIST_HEAD(&dentry->d_u.d_child);
L
Linus Torvalds 已提交
984 985 986 987
	}

	spin_lock(&dcache_lock);
	if (parent)
E
Eric Dumazet 已提交
988
		list_add(&dentry->d_u.d_child, &parent->d_subdirs);
L
Linus Torvalds 已提交
989 990
	spin_unlock(&dcache_lock);

991
	this_cpu_inc(nr_dentry);
992

L
Linus Torvalds 已提交
993 994
	return dentry;
}
995
EXPORT_SYMBOL(d_alloc);
L
Linus Torvalds 已提交
996 997 998 999 1000 1001 1002 1003 1004 1005

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);
}
1006
EXPORT_SYMBOL(d_alloc_name);
L
Linus Torvalds 已提交
1007

1008 1009 1010 1011 1012 1013 1014 1015 1016
/* 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
1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033
/**
 * 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)
{
1034
	BUG_ON(!list_empty(&entry->d_alias));
L
Linus Torvalds 已提交
1035
	spin_lock(&dcache_lock);
1036
	__d_instantiate(entry, inode);
L
Linus Torvalds 已提交
1037 1038 1039
	spin_unlock(&dcache_lock);
	security_d_instantiate(entry, inode);
}
1040
EXPORT_SYMBOL(d_instantiate);
L
Linus Torvalds 已提交
1041 1042 1043 1044 1045 1046 1047 1048

/**
 * 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
1049
 * aliased dentry instead and drop one reference to inode.
L
Linus Torvalds 已提交
1050 1051 1052
 *
 * Note that in order to avoid conflicts with rename() etc, the caller
 * had better be holding the parent directory semaphore.
1053 1054 1055 1056
 *
 * 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
1057
 */
1058 1059
static struct dentry *__d_instantiate_unique(struct dentry *entry,
					     struct inode *inode)
L
Linus Torvalds 已提交
1060 1061 1062 1063 1064 1065
{
	struct dentry *alias;
	int len = entry->d_name.len;
	const char *name = entry->d_name.name;
	unsigned int hash = entry->d_name.hash;

1066
	if (!inode) {
1067
		__d_instantiate(entry, NULL);
1068 1069 1070
		return NULL;
	}

L
Linus Torvalds 已提交
1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084
	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;
	}
1085

1086
	__d_instantiate(entry, inode);
L
Linus Torvalds 已提交
1087 1088
	return NULL;
}
1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109

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
1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136
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;
}
1137
EXPORT_SYMBOL(d_alloc_root);
L
Linus Torvalds 已提交
1138 1139 1140 1141 1142 1143 1144 1145 1146

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);
}

1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159
/**
 * 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
1160 1161 1162 1163
 * 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).
1164 1165 1166
 */
struct dentry *d_obtain_alias(struct inode *inode)
{
C
Christoph Hellwig 已提交
1167 1168 1169
	static const struct qstr anonstring = { .name = "" };
	struct dentry *tmp;
	struct dentry *res;
1170 1171

	if (!inode)
1172
		return ERR_PTR(-ESTALE);
1173 1174 1175
	if (IS_ERR(inode))
		return ERR_CAST(inode);

C
Christoph Hellwig 已提交
1176 1177 1178 1179 1180 1181 1182 1183
	res = d_find_alias(inode);
	if (res)
		goto out_iput;

	tmp = d_alloc(NULL, &anonstring);
	if (!tmp) {
		res = ERR_PTR(-ENOMEM);
		goto out_iput;
1184
	}
C
Christoph Hellwig 已提交
1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210
	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;
1211
}
1212
EXPORT_SYMBOL(d_obtain_alias);
L
Linus Torvalds 已提交
1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233

/**
 * 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;

1234
	if (inode && S_ISDIR(inode->i_mode)) {
L
Linus Torvalds 已提交
1235 1236 1237 1238 1239 1240 1241 1242 1243
		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 {
1244 1245
			/* already taking dcache_lock, so d_add() by hand */
			__d_instantiate(dentry, inode);
L
Linus Torvalds 已提交
1246 1247 1248 1249 1250 1251 1252 1253
			spin_unlock(&dcache_lock);
			security_d_instantiate(dentry, inode);
			d_rehash(dentry);
		}
	} else
		d_add(dentry, inode);
	return new;
}
1254
EXPORT_SYMBOL(d_splice_alias);
L
Linus Torvalds 已提交
1255

1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271
/**
 * 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.
 */
1272
struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
1273 1274 1275 1276 1277 1278
			struct qstr *name)
{
	int error;
	struct dentry *found;
	struct dentry *new;

C
Christoph Hellwig 已提交
1279 1280 1281 1282
	/*
	 * First check if a dentry matching the name already exists,
	 * if not go ahead and create it now.
	 */
1283 1284 1285 1286 1287 1288 1289
	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
1290

1291 1292 1293 1294 1295 1296 1297
		found = d_splice_alias(inode, new);
		if (found) {
			dput(new);
			return found;
		}
		return new;
	}
C
Christoph Hellwig 已提交
1298 1299 1300 1301 1302 1303 1304

	/*
	 * If a matching dentry exists, and it's not negative use it.
	 *
	 * Decrement the reference count to balance the iget() done
	 * earlier on.
	 */
1305 1306 1307 1308 1309 1310 1311 1312 1313
	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
1314

1315 1316
	/*
	 * Negative dentry: instantiate it unless the inode is a directory and
C
Christoph Hellwig 已提交
1317
	 * already has a dentry.
1318 1319
	 */
	spin_lock(&dcache_lock);
C
Christoph Hellwig 已提交
1320
	if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) {
1321
		__d_instantiate(found, inode);
1322 1323 1324 1325
		spin_unlock(&dcache_lock);
		security_d_instantiate(found, inode);
		return found;
	}
C
Christoph Hellwig 已提交
1326

1327
	/*
C
Christoph Hellwig 已提交
1328 1329
	 * In case a directory already has a (disconnected) entry grab a
	 * reference to it, move it in place and use it.
1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343
	 */
	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);
}
1344
EXPORT_SYMBOL(d_add_ci);
L
Linus Torvalds 已提交
1345 1346 1347 1348 1349

/**
 * d_lookup - search for a dentry
 * @parent: parent dentry
 * @name: qstr of name we wish to find
1350
 * Returns: dentry, or NULL
L
Linus Torvalds 已提交
1351
 *
1352 1353 1354 1355
 * 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
1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369
 */
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;
}
1370
EXPORT_SYMBOL(d_lookup);
L
Linus Torvalds 已提交
1371

1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386
/*
 * __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
1387 1388 1389 1390 1391 1392 1393 1394
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;
1395
	struct dentry *dentry;
L
Linus Torvalds 已提交
1396

1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409
	/*
	 * 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
1410 1411
	rcu_read_lock();
	
1412
	hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
L
Linus Torvalds 已提交
1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423
		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
1424 1425
		 * changed things. Don't bother checking the hash because
		 * we're about to compare the whole name anyway.
L
Linus Torvalds 已提交
1426 1427 1428 1429
		 */
		if (dentry->d_parent != parent)
			goto next;

1430 1431 1432 1433
		/* non-existing due to RCU? */
		if (d_unhashed(dentry))
			goto next;

L
Linus Torvalds 已提交
1434 1435 1436 1437 1438 1439
		/*
		 * 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) {
N
Nick Piggin 已提交
1440 1441 1442
			if (parent->d_op->d_compare(parent, parent->d_inode,
						dentry, dentry->d_inode,
						qstr->len, qstr->name, name))
L
Linus Torvalds 已提交
1443 1444 1445 1446 1447 1448 1449 1450
				goto next;
		} else {
			if (qstr->len != len)
				goto next;
			if (memcmp(qstr->name, str, len))
				goto next;
		}

1451 1452
		atomic_inc(&dentry->d_count);
		found = dentry;
L
Linus Torvalds 已提交
1453 1454 1455 1456 1457 1458 1459 1460 1461 1462
		spin_unlock(&dentry->d_lock);
		break;
next:
		spin_unlock(&dentry->d_lock);
 	}
 	rcu_read_unlock();

 	return found;
}

1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488
/**
 * 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
1489
/**
N
Nick Piggin 已提交
1490
 * d_validate - verify dentry provided from insecure source (deprecated)
L
Linus Torvalds 已提交
1491 1492 1493 1494 1495 1496
 * @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
1497 1498
 *
 * This function is slow for big directories, and deprecated, do not use it.
L
Linus Torvalds 已提交
1499
 */
1500
int d_validate(struct dentry *dentry, struct dentry *dparent)
L
Linus Torvalds 已提交
1501
{
N
Nick Piggin 已提交
1502
	struct dentry *child;
1503 1504

	spin_lock(&dcache_lock);
N
Nick Piggin 已提交
1505 1506
	list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
		if (dentry == child) {
1507 1508
			__dget_locked(dentry);
			spin_unlock(&dcache_lock);
L
Linus Torvalds 已提交
1509 1510 1511
			return 1;
		}
	}
1512
	spin_unlock(&dcache_lock);
N
Nick Piggin 已提交
1513

L
Linus Torvalds 已提交
1514 1515
	return 0;
}
1516
EXPORT_SYMBOL(d_validate);
L
Linus Torvalds 已提交
1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540

/*
 * 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)
{
1541
	int isdir = 0;
L
Linus Torvalds 已提交
1542 1543 1544 1545 1546
	/*
	 * Are we the only user?
	 */
	spin_lock(&dcache_lock);
	spin_lock(&dentry->d_lock);
1547
	isdir = S_ISDIR(dentry->d_inode->i_mode);
L
Linus Torvalds 已提交
1548
	if (atomic_read(&dentry->d_count) == 1) {
A
Al Viro 已提交
1549
		dentry->d_flags &= ~DCACHE_CANT_MOUNT;
L
Linus Torvalds 已提交
1550
		dentry_iput(dentry);
1551
		fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
1552 1553 1554 1555 1556 1557 1558 1559
		return;
	}

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

	spin_unlock(&dentry->d_lock);
	spin_unlock(&dcache_lock);
1560 1561

	fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
1562
}
1563
EXPORT_SYMBOL(d_delete);
L
Linus Torvalds 已提交
1564 1565 1566 1567 1568 1569 1570 1571

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

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

1572 1573 1574 1575 1576
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
1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587
/**
 * 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);
1588
	_d_rehash(entry);
L
Linus Torvalds 已提交
1589 1590 1591
	spin_unlock(&entry->d_lock);
	spin_unlock(&dcache_lock);
}
1592
EXPORT_SYMBOL(d_rehash);
L
Linus Torvalds 已提交
1593

N
Nick Piggin 已提交
1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620
/**
 * 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(&dcache_lock);
	spin_lock(&dentry->d_lock);
	memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
	spin_unlock(&dentry->d_lock);
	spin_unlock(&dcache_lock);
}
EXPORT_SYMBOL(dentry_update_name_case);

L
Linus Torvalds 已提交
1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638
/*
 * 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
			 */
1639
			swap(target->d_name.name, dentry->d_name.name);
L
Linus Torvalds 已提交
1640 1641 1642 1643 1644
		} else {
			/*
			 * dentry:internal, target:external.  Steal target's
			 * storage and make target internal.
			 */
1645 1646
			memcpy(target->d_iname, dentry->d_name.name,
					dentry->d_name.len + 1);
L
Linus Torvalds 已提交
1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665
			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);
1666 1667
			dentry->d_name.len = target->d_name.len;
			return;
L
Linus Torvalds 已提交
1668 1669
		}
	}
1670
	swap(dentry->d_name.len, target->d_name.len);
L
Linus Torvalds 已提交
1671 1672 1673 1674 1675 1676 1677 1678 1679 1680
}

/*
 * 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
1681 1682
 * 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
1683 1684
 */
 
1685 1686
/*
 * d_move_locked - move a dentry
L
Linus Torvalds 已提交
1687 1688 1689 1690 1691 1692
 * @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.
 */
1693
static void d_move_locked(struct dentry * dentry, struct dentry * target)
L
Linus Torvalds 已提交
1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705
{
	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
1706
		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
L
Linus Torvalds 已提交
1707 1708
	} else {
		spin_lock(&dentry->d_lock);
I
Ingo Molnar 已提交
1709
		spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
L
Linus Torvalds 已提交
1710 1711 1712
	}

	/* Move the dentry to the target hash queue, if on different bucket */
1713
	if (d_unhashed(dentry))
L
Linus Torvalds 已提交
1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724
		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
1725 1726
	list_del(&dentry->d_u.d_child);
	list_del(&target->d_u.d_child);
L
Linus Torvalds 已提交
1727 1728 1729

	/* Switch the names.. */
	switch_names(dentry, target);
1730
	swap(dentry->d_name.hash, target->d_name.hash);
L
Linus Torvalds 已提交
1731 1732 1733 1734 1735

	/* ... and switch the parents */
	if (IS_ROOT(dentry)) {
		dentry->d_parent = target->d_parent;
		target->d_parent = target;
E
Eric Dumazet 已提交
1736
		INIT_LIST_HEAD(&target->d_u.d_child);
L
Linus Torvalds 已提交
1737
	} else {
1738
		swap(dentry->d_parent, target->d_parent);
L
Linus Torvalds 已提交
1739 1740

		/* And add them back to the (new) parent lists */
E
Eric Dumazet 已提交
1741
		list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
L
Linus Torvalds 已提交
1742 1743
	}

E
Eric Dumazet 已提交
1744
	list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
L
Linus Torvalds 已提交
1745
	spin_unlock(&target->d_lock);
1746
	fsnotify_d_move(dentry);
L
Linus Torvalds 已提交
1747 1748
	spin_unlock(&dentry->d_lock);
	write_sequnlock(&rename_lock);
1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763
}

/**
 * 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
1764 1765
	spin_unlock(&dcache_lock);
}
1766
EXPORT_SYMBOL(d_move);
L
Linus Torvalds 已提交
1767

1768 1769 1770 1771 1772 1773 1774
/**
 * 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.
1775
 */
1776
struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
1777 1778 1779
{
	struct dentry *p;

1780
	for (p = p2; !IS_ROOT(p); p = p->d_parent) {
1781
		if (p->d_parent == p1)
1782
			return p;
1783
	}
1784
	return NULL;
1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796
}

/*
 * 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)
1797
	__releases(dcache_lock)
1798 1799 1800 1801 1802 1803 1804 1805 1806 1807
{
	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);
1808
	if (d_ancestor(alias, dentry))
1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830
		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;
}

1831 1832 1833 1834 1835 1836 1837 1838 1839
/*
 * 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);
1840
	swap(dentry->d_name.hash, anon->d_name.hash);
1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871

	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)
{
1872
	struct dentry *actual;
1873 1874 1875 1876 1877 1878 1879

	BUG_ON(!d_unhashed(dentry));

	spin_lock(&dcache_lock);

	if (!inode) {
		actual = dentry;
1880
		__d_instantiate(dentry, NULL);
1881 1882 1883
		goto found_lock;
	}

1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904
	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;
		}
1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919
	}

	/* 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);
1920
out_nolock:
1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932
	if (actual == dentry) {
		security_d_instantiate(dentry, inode);
		return NULL;
	}

	iput(inode);
	return actual;

shouldnt_be_hashed:
	spin_unlock(&dcache_lock);
	BUG();
}
1933
EXPORT_SYMBOL_GPL(d_materialise_unique);
1934

1935
static int prepend(char **buffer, int *buflen, const char *str, int namelen)
1936 1937 1938 1939 1940 1941 1942 1943 1944
{
	*buflen -= namelen;
	if (*buflen < 0)
		return -ENAMETOOLONG;
	*buffer -= namelen;
	memcpy(*buffer, str, namelen);
	return 0;
}

1945 1946 1947 1948 1949
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
1950
/**
M
Miklos Szeredi 已提交
1951 1952
 * Prepend path string to a buffer
 *
1953 1954
 * @path: the dentry/vfsmount to report
 * @root: root vfsmnt/dentry (may be modified by this function)
M
Miklos Szeredi 已提交
1955 1956
 * @buffer: pointer to the end of the buffer
 * @buflen: pointer to buffer length
1957
 *
M
Miklos Szeredi 已提交
1958
 * Caller holds the dcache_lock.
1959 1960 1961
 *
 * 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
1962
 */
M
Miklos Szeredi 已提交
1963 1964
static int prepend_path(const struct path *path, struct path *root,
			char **buffer, int *buflen)
L
Linus Torvalds 已提交
1965
{
1966 1967
	struct dentry *dentry = path->dentry;
	struct vfsmount *vfsmnt = path->mnt;
M
Miklos Szeredi 已提交
1968 1969
	bool slash = false;
	int error = 0;
1970

N
Nick Piggin 已提交
1971
	br_read_lock(vfsmount_lock);
M
Miklos Szeredi 已提交
1972
	while (dentry != root->dentry || vfsmnt != root->mnt) {
L
Linus Torvalds 已提交
1973 1974 1975
		struct dentry * parent;

		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
1976
			/* Global root? */
L
Linus Torvalds 已提交
1977 1978 1979 1980 1981 1982 1983 1984 1985
			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
1986 1987 1988 1989 1990 1991 1992
		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
1993 1994 1995
		dentry = parent;
	}

1996
out:
M
Miklos Szeredi 已提交
1997 1998 1999
	if (!error && !slash)
		error = prepend(buffer, buflen, "/", 1);

N
Nick Piggin 已提交
2000
	br_read_unlock(vfsmount_lock);
M
Miklos Szeredi 已提交
2001
	return error;
L
Linus Torvalds 已提交
2002 2003

global_root:
2004 2005 2006 2007 2008 2009 2010 2011 2012
	/*
	 * 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);
	}
2013 2014
	root->mnt = vfsmnt;
	root->dentry = dentry;
2015
	goto out;
M
Miklos Szeredi 已提交
2016
}
2017

M
Miklos Szeredi 已提交
2018 2019 2020 2021
/**
 * __d_path - return the path of a dentry
 * @path: the dentry/vfsmount to report
 * @root: root vfsmnt/dentry (may be modified by this function)
2022
 * @buf: buffer to return value in
M
Miklos Szeredi 已提交
2023 2024
 * @buflen: buffer length
 *
2025
 * Convert a dentry into an ASCII path name.
M
Miklos Szeredi 已提交
2026 2027 2028 2029
 *
 * Returns a pointer into the buffer or an error code if the
 * path was too long.
 *
2030
 * "buflen" should be positive.
M
Miklos Szeredi 已提交
2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041
 *
 * 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);
2042
	spin_lock(&dcache_lock);
M
Miklos Szeredi 已提交
2043
	error = prepend_path(path, root, &res, &buflen);
2044 2045
	spin_unlock(&dcache_lock);

M
Miklos Szeredi 已提交
2046 2047 2048
	if (error)
		return ERR_PTR(error);
	return res;
L
Linus Torvalds 已提交
2049 2050
}

2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066
/*
 * 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);
}

2067 2068 2069 2070 2071
static int prepend_unreachable(char **buffer, int *buflen)
{
	return prepend(buffer, buflen, "(unreachable)", 13);
}

J
Jan Blunck 已提交
2072 2073
/**
 * d_path - return the path of a dentry
2074
 * @path: path to report
J
Jan Blunck 已提交
2075 2076 2077 2078 2079 2080
 * @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.
 *
2081 2082 2083 2084
 * 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
2085
 *
2086
 * "buflen" should be positive.
J
Jan Blunck 已提交
2087
 */
2088
char *d_path(const struct path *path, char *buf, int buflen)
L
Linus Torvalds 已提交
2089
{
2090
	char *res = buf + buflen;
J
Jan Blunck 已提交
2091
	struct path root;
2092
	struct path tmp;
2093
	int error;
L
Linus Torvalds 已提交
2094

2095 2096 2097 2098 2099 2100 2101
	/*
	 * 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:
	 */
2102 2103
	if (path->dentry->d_op && path->dentry->d_op->d_dname)
		return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2104

2105
	get_fs_root(current->fs, &root);
2106
	spin_lock(&dcache_lock);
2107
	tmp = root;
2108 2109 2110
	error = path_with_deleted(path, &tmp, &res, &buflen);
	if (error)
		res = ERR_PTR(error);
2111
	spin_unlock(&dcache_lock);
J
Jan Blunck 已提交
2112
	path_put(&root);
L
Linus Torvalds 已提交
2113 2114
	return res;
}
2115
EXPORT_SYMBOL(d_path);
L
Linus Torvalds 已提交
2116

2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149
/**
 * 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;
}

2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170
/*
 * 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);
}

2171 2172 2173
/*
 * Write full pathname from the root of the filesystem into the buffer.
 */
A
Al Viro 已提交
2174
char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185
{
	char *end = buf + buflen;
	char *retval;

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

2186 2187
	while (!IS_ROOT(dentry)) {
		struct dentry *parent = dentry->d_parent;
2188 2189

		prefetch(parent);
2190
		if ((prepend_name(&end, &buflen, &dentry->d_name) != 0) ||
2191 2192 2193 2194 2195 2196
		    (prepend(&end, &buflen, "/", 1) != 0))
			goto Elong;

		retval = end;
		dentry = parent;
	}
A
Al Viro 已提交
2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215
	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);
2216
	spin_unlock(&dcache_lock);
A
Al Viro 已提交
2217 2218
	if (!IS_ERR(retval) && p)
		*p = '/';	/* restore '/' overriden with '\0' */
2219 2220 2221 2222 2223 2224
	return retval;
Elong:
	spin_unlock(&dcache_lock);
	return ERR_PTR(-ENAMETOOLONG);
}

L
Linus Torvalds 已提交
2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242
/*
 * 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;
 *	}
 */
2243
SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
L
Linus Torvalds 已提交
2244
{
2245
	int error;
J
Jan Blunck 已提交
2246
	struct path pwd, root;
2247
	char *page = (char *) __get_free_page(GFP_USER);
L
Linus Torvalds 已提交
2248 2249 2250 2251

	if (!page)
		return -ENOMEM;

2252
	get_fs_root_and_pwd(current->fs, &root, &pwd);
L
Linus Torvalds 已提交
2253

2254 2255
	error = -ENOENT;
	spin_lock(&dcache_lock);
2256
	if (!d_unlinked(pwd.dentry)) {
2257
		unsigned long len;
2258
		struct path tmp = root;
2259 2260
		char *cwd = page + PAGE_SIZE;
		int buflen = PAGE_SIZE;
L
Linus Torvalds 已提交
2261

2262 2263
		prepend(&cwd, &buflen, "\0", 1);
		error = prepend_path(&pwd, &tmp, &cwd, &buflen);
2264 2265
		spin_unlock(&dcache_lock);

2266
		if (error)
2267 2268
			goto out;

2269 2270 2271 2272 2273 2274 2275
		/* Unreachable from current root */
		if (!path_equal(&tmp, &root)) {
			error = prepend_unreachable(&cwd, &buflen);
			if (error)
				goto out;
		}

2276 2277 2278 2279 2280 2281 2282 2283 2284
		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
2285 2286

out:
J
Jan Blunck 已提交
2287 2288
	path_put(&pwd);
	path_put(&root);
L
Linus Torvalds 已提交
2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308
	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()
 */
  
2309
int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
L
Linus Torvalds 已提交
2310 2311 2312 2313
{
	int result;
	unsigned long seq;

2314 2315 2316 2317 2318 2319
	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
2320 2321
	 */
	rcu_read_lock();
2322
	do {
L
Linus Torvalds 已提交
2323 2324
		/* for restarting inner loop in case of seq retry */
		seq = read_seqbegin(&rename_lock);
2325
		if (d_ancestor(old_dentry, new_dentry))
L
Linus Torvalds 已提交
2326
			result = 1;
2327 2328
		else
			result = 0;
L
Linus Torvalds 已提交
2329 2330 2331 2332 2333 2334
	} while (read_seqretry(&rename_lock, seq));
	rcu_read_unlock();

	return result;
}

2335 2336 2337 2338 2339
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
2340 2341

	br_read_lock(vfsmount_lock);
2342 2343 2344
	if (mnt != path2->mnt) {
		for (;;) {
			if (mnt->mnt_parent == mnt) {
N
Nick Piggin 已提交
2345
				br_read_unlock(vfsmount_lock);
2346 2347 2348 2349 2350 2351 2352 2353 2354
				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
2355
	br_read_unlock(vfsmount_lock);
2356 2357 2358 2359
	return res;
}
EXPORT_SYMBOL(path_is_under);

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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;
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		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
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		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) {
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		next = this_parent->d_u.d_child.next;
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		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;

2409 2410
	dentry = d_hash_and_lookup(dir, name);
	if (dentry) {
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		if (dentry->d_inode)
			ino = dentry->d_inode->i_ino;
		dput(dentry);
	}
	return ino;
}
2417
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]);
}

2453
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. 
	 */
2462 2463
	dentry_cache = KMEM_CACHE(dentry,
		SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
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2465
	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 */
2486
struct kmem_cache *names_cachep __read_mostly;
2487
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,
2508
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
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Linus Torvalds 已提交
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2510 2511
	dcache_init();
	inode_init();
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2512
	files_init(mempages);
2513
	mnt_init();
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	bdev_cache_init();
	chrdev_init();
}