dcache.c 79.1 KB
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/*
 * fs/dcache.c
 *
 * Complete reimplementation
 * (C) 1997 Thomas Schoebel-Theuer,
 * with heavy changes by Linus Torvalds
 */

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

#include <linux/syscalls.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/fs.h>
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#include <linux/fsnotify.h>
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#include <linux/slab.h>
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/cache.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/file.h>
#include <asm/uaccess.h>
#include <linux/security.h>
#include <linux/seqlock.h>
#include <linux/swap.h>
#include <linux/bootmem.h>
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#include <linux/fs_struct.h>
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#include <linux/hardirq.h>
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#include <linux/bit_spinlock.h>
#include <linux/rculist_bl.h>
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#include <linux/prefetch.h>
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#include "internal.h"
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/*
 * Usage:
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 * dcache->d_inode->i_lock protects:
 *   - i_dentry, d_alias, d_inode of aliases
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 * dcache_hash_bucket lock protects:
 *   - the dcache hash table
 * s_anon bl list spinlock protects:
 *   - the s_anon list (see __d_drop)
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 * dcache_lru_lock protects:
 *   - the dcache lru lists and counters
 * d_lock protects:
 *   - d_flags
 *   - d_name
 *   - d_lru
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 *   - d_count
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 *   - d_unhashed()
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 *   - d_parent and d_subdirs
 *   - childrens' d_child and d_parent
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 *   - d_alias, d_inode
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 *
 * Ordering:
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 * dentry->d_inode->i_lock
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 *   dentry->d_lock
 *     dcache_lru_lock
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 *     dcache_hash_bucket lock
 *     s_anon lock
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 *
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 * If there is an ancestor relationship:
 * dentry->d_parent->...->d_parent->d_lock
 *   ...
 *     dentry->d_parent->d_lock
 *       dentry->d_lock
 *
 * If no ancestor relationship:
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 * if (dentry1 < dentry2)
 *   dentry1->d_lock
 *     dentry2->d_lock
 */
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int sysctl_vfs_cache_pressure __read_mostly = 100;
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EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);

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

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static unsigned int d_hash_mask __read_mostly;
static unsigned int d_hash_shift __read_mostly;
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static struct hlist_bl_head *dentry_hashtable __read_mostly;
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static inline struct hlist_bl_head *d_hash(struct dentry *parent,
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					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);
}

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

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static DEFINE_PER_CPU(unsigned int, nr_dentry);
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#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
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static int get_nr_dentry(void)
{
	int i;
	int sum = 0;
	for_each_possible_cpu(i)
		sum += per_cpu(nr_dentry, i);
	return sum < 0 ? 0 : sum;
}

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

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

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

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

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/**
 * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
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 * @dentry: the target dentry
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 * After this call, in-progress rcu-walk path lookup will fail. This
 * should be called after unhashing, and after changing d_inode (if
 * the dentry has not already been unhashed).
 */
static inline void dentry_rcuwalk_barrier(struct dentry *dentry)
{
	assert_spin_locked(&dentry->d_lock);
	/* Go through a barrier */
	write_seqcount_barrier(&dentry->d_seq);
}

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

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/*
 * Release the dentry's inode, using the filesystem
 * d_iput() operation if defined. dentry remains in-use.
 */
static void dentry_unlink_inode(struct dentry * dentry)
	__releases(dentry->d_lock)
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	__releases(dentry->d_inode->i_lock)
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{
	struct inode *inode = dentry->d_inode;
	dentry->d_inode = NULL;
	list_del_init(&dentry->d_alias);
	dentry_rcuwalk_barrier(dentry);
	spin_unlock(&dentry->d_lock);
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	spin_unlock(&inode->i_lock);
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	if (!inode->i_nlink)
		fsnotify_inoderemove(inode);
	if (dentry->d_op && dentry->d_op->d_iput)
		dentry->d_op->d_iput(dentry, inode);
	else
		iput(inode);
}

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

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static void __dentry_lru_del(struct dentry *dentry)
{
	list_del_init(&dentry->d_lru);
	dentry->d_sb->s_nr_dentry_unused--;
	dentry_stat.nr_unused--;
}

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static void dentry_lru_del(struct dentry *dentry)
{
	if (!list_empty(&dentry->d_lru)) {
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		spin_lock(&dcache_lru_lock);
		__dentry_lru_del(dentry);
		spin_unlock(&dcache_lru_lock);
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	}
}

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static void dentry_lru_move_tail(struct dentry *dentry)
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{
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	spin_lock(&dcache_lru_lock);
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	if (list_empty(&dentry->d_lru)) {
		list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
		dentry->d_sb->s_nr_dentry_unused++;
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		dentry_stat.nr_unused++;
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	} else {
		list_move_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
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	}
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	spin_unlock(&dcache_lru_lock);
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}

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

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/**
 * d_drop - drop a dentry
 * @dentry: dentry to drop
 *
 * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
 * be found through a VFS lookup any more. Note that this is different from
 * deleting the dentry - d_delete will try to mark the dentry negative if
 * possible, giving a successful _negative_ lookup, while d_drop will
 * just make the cache lookup fail.
 *
 * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
 * reason (NFS timeouts or autofs deletes).
 *
 * __d_drop requires dentry->d_lock.
 */
void __d_drop(struct dentry *dentry)
{
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	if (!d_unhashed(dentry)) {
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		struct hlist_bl_head *b;
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		if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
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			b = &dentry->d_sb->s_anon;
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		else
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			b = d_hash(dentry->d_parent, dentry->d_name.hash);
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		hlist_bl_lock(b);
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		__hlist_bl_del(&dentry->d_hash);
		dentry->d_hash.pprev = NULL;
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		hlist_bl_unlock(b);
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		dentry_rcuwalk_barrier(dentry);
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	}
}
EXPORT_SYMBOL(__d_drop);

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

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/*
 * d_clear_need_lookup - drop a dentry from cache and clear the need lookup flag
 * @dentry: dentry to drop
 *
 * This is called when we do a lookup on a placeholder dentry that needed to be
 * looked up.  The dentry should have been hashed in order for it to be found by
 * the lookup code, but now needs to be unhashed while we do the actual lookup
 * and clear the DCACHE_NEED_LOOKUP flag.
 */
void d_clear_need_lookup(struct dentry *dentry)
{
	spin_lock(&dentry->d_lock);
	__d_drop(dentry);
	dentry->d_flags &= ~DCACHE_NEED_LOOKUP;
	spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(d_clear_need_lookup);

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

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	inode = dentry->d_inode;
	if (inode && !spin_trylock(&inode->i_lock)) {
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relock:
		spin_unlock(&dentry->d_lock);
		cpu_relax();
		return dentry; /* try again with same dentry */
	}
	if (IS_ROOT(dentry))
		parent = NULL;
	else
		parent = dentry->d_parent;
	if (parent && !spin_trylock(&parent->d_lock)) {
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		if (inode)
			spin_unlock(&inode->i_lock);
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		goto relock;
	}
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	if (ref)
		dentry->d_count--;
	/* if dentry was on the d_lru list delete it from there */
	dentry_lru_del(dentry);
	/* if it was on the hash then remove it */
	__d_drop(dentry);
	return d_kill(dentry, parent);
}

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/* 
 * This is dput
 *
 * This is complicated by the fact that we do not want to put
 * dentries that are no longer on any hash chain on the unused
 * list: we'd much rather just get rid of them immediately.
 *
 * However, that implies that we have to traverse the dentry
 * tree upwards to the parents which might _also_ now be
 * scheduled for deletion (it may have been only waiting for
 * its last child to go away).
 *
 * This tail recursion is done by hand as we don't want to depend
 * on the compiler to always get this right (gcc generally doesn't).
 * Real recursion would eat up our stack space.
 */

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

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

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	if (dentry->d_flags & DCACHE_OP_DELETE) {
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		if (dentry->d_op->d_delete(dentry))
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			goto kill_it;
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	}
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	/* Unreachable? Get rid of it */
 	if (d_unhashed(dentry))
		goto kill_it;
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	/*
	 * If this dentry needs lookup, don't set the referenced flag so that it
	 * is more likely to be cleaned up by the dcache shrinker in case of
	 * memory pressure.
	 */
	if (!d_need_lookup(dentry))
		dentry->d_flags |= DCACHE_REFERENCED;
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	dentry_lru_add(dentry);
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	dentry->d_count--;
	spin_unlock(&dentry->d_lock);
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	return;

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kill_it:
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	dentry = dentry_kill(dentry, 1);
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	if (dentry)
		goto repeat;
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}
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EXPORT_SYMBOL(dput);
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/**
 * d_invalidate - invalidate a dentry
 * @dentry: dentry to invalidate
 *
 * Try to invalidate the dentry if it turns out to be
 * possible. If there are other dentries that can be
 * reached through this one we can't delete it and we
 * return -EBUSY. On success we return 0.
 *
 * no dcache lock.
 */
 
int d_invalidate(struct dentry * dentry)
{
	/*
	 * If it's already been dropped, return OK.
	 */
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	spin_lock(&dentry->d_lock);
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	if (d_unhashed(dentry)) {
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		spin_unlock(&dentry->d_lock);
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		return 0;
	}
	/*
	 * Check whether to do a partial shrink_dcache
	 * to get rid of unused child entries.
	 */
	if (!list_empty(&dentry->d_subdirs)) {
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		spin_unlock(&dentry->d_lock);
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		shrink_dcache_parent(dentry);
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		spin_lock(&dentry->d_lock);
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	}

	/*
	 * Somebody else still using it?
	 *
	 * If it's a directory, we can't drop it
	 * for fear of somebody re-populating it
	 * with children (even though dropping it
	 * would make it unreachable from the root,
	 * we might still populate it if it was a
	 * working directory or similar).
	 */
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	if (dentry->d_count > 1) {
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		if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
			spin_unlock(&dentry->d_lock);
			return -EBUSY;
		}
	}

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

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

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

repeat:
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	/*
	 * Don't need rcu_dereference because we re-check it was correct under
	 * the lock.
	 */
	rcu_read_lock();
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	ret = dentry->d_parent;
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	if (!ret) {
		rcu_read_unlock();
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		goto out;
	}
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	spin_lock(&ret->d_lock);
	if (unlikely(ret != dentry->d_parent)) {
		spin_unlock(&ret->d_lock);
		rcu_read_unlock();
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		goto repeat;
	}
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	rcu_read_unlock();
N
Nick Piggin 已提交
563 564 565 566 567 568 569 570
	BUG_ON(!ret->d_count);
	ret->d_count++;
	spin_unlock(&ret->d_lock);
out:
	return ret;
}
EXPORT_SYMBOL(dget_parent);

L
Linus Torvalds 已提交
571 572 573 574 575 576 577 578 579 580 581 582
/**
 * 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.
 *
583
 * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
L
Linus Torvalds 已提交
584
 * any other hashed alias over that one unless @want_discon is set,
585
 * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
L
Linus Torvalds 已提交
586
 */
N
Nick Piggin 已提交
587
static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
L
Linus Torvalds 已提交
588
{
N
Nick Piggin 已提交
589
	struct dentry *alias, *discon_alias;
L
Linus Torvalds 已提交
590

N
Nick Piggin 已提交
591 592 593 594
again:
	discon_alias = NULL;
	list_for_each_entry(alias, &inode->i_dentry, d_alias) {
		spin_lock(&alias->d_lock);
L
Linus Torvalds 已提交
595
 		if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
596
			if (IS_ROOT(alias) &&
N
Nick Piggin 已提交
597
			    (alias->d_flags & DCACHE_DISCONNECTED)) {
L
Linus Torvalds 已提交
598
				discon_alias = alias;
N
Nick Piggin 已提交
599
			} else if (!want_discon) {
600
				__dget_dlock(alias);
N
Nick Piggin 已提交
601 602 603 604 605 606 607 608 609 610 611 612
				spin_unlock(&alias->d_lock);
				return alias;
			}
		}
		spin_unlock(&alias->d_lock);
	}
	if (discon_alias) {
		alias = discon_alias;
		spin_lock(&alias->d_lock);
		if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
			if (IS_ROOT(alias) &&
			    (alias->d_flags & DCACHE_DISCONNECTED)) {
613
				__dget_dlock(alias);
N
Nick Piggin 已提交
614
				spin_unlock(&alias->d_lock);
L
Linus Torvalds 已提交
615 616 617
				return alias;
			}
		}
N
Nick Piggin 已提交
618 619
		spin_unlock(&alias->d_lock);
		goto again;
L
Linus Torvalds 已提交
620
	}
N
Nick Piggin 已提交
621
	return NULL;
L
Linus Torvalds 已提交
622 623
}

N
Nick Piggin 已提交
624
struct dentry *d_find_alias(struct inode *inode)
L
Linus Torvalds 已提交
625
{
D
David Howells 已提交
626 627 628
	struct dentry *de = NULL;

	if (!list_empty(&inode->i_dentry)) {
629
		spin_lock(&inode->i_lock);
D
David Howells 已提交
630
		de = __d_find_alias(inode, 0);
631
		spin_unlock(&inode->i_lock);
D
David Howells 已提交
632
	}
L
Linus Torvalds 已提交
633 634
	return de;
}
635
EXPORT_SYMBOL(d_find_alias);
L
Linus Torvalds 已提交
636 637 638 639 640 641 642

/*
 *	Try to kill dentries associated with this inode.
 * WARNING: you must own a reference to inode.
 */
void d_prune_aliases(struct inode *inode)
{
643
	struct dentry *dentry;
L
Linus Torvalds 已提交
644
restart:
645
	spin_lock(&inode->i_lock);
646
	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
L
Linus Torvalds 已提交
647
		spin_lock(&dentry->d_lock);
N
Nick Piggin 已提交
648
		if (!dentry->d_count) {
649
			__dget_dlock(dentry);
L
Linus Torvalds 已提交
650 651
			__d_drop(dentry);
			spin_unlock(&dentry->d_lock);
652
			spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
653 654 655 656 657
			dput(dentry);
			goto restart;
		}
		spin_unlock(&dentry->d_lock);
	}
658
	spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
659
}
660
EXPORT_SYMBOL(d_prune_aliases);
L
Linus Torvalds 已提交
661 662

/*
663 664 665
 * Try to throw away a dentry - free the inode, dput the parent.
 * Requires dentry->d_lock is held, and dentry->d_count == 0.
 * Releases dentry->d_lock.
666
 *
667
 * This may fail if locks cannot be acquired no problem, just try again.
L
Linus Torvalds 已提交
668
 */
669
static void try_prune_one_dentry(struct dentry *dentry)
670
	__releases(dentry->d_lock)
L
Linus Torvalds 已提交
671
{
672
	struct dentry *parent;
673

674
	parent = dentry_kill(dentry, 0);
675
	/*
676 677 678 679 680 681 682 683
	 * If dentry_kill returns NULL, we have nothing more to do.
	 * if it returns the same dentry, trylocks failed. In either
	 * case, just loop again.
	 *
	 * Otherwise, we need to prune ancestors too. This is necessary
	 * to prevent quadratic behavior of shrink_dcache_parent(), but
	 * is also expected to be beneficial in reducing dentry cache
	 * fragmentation.
684
	 */
685 686 687 688 689 690 691
	if (!parent)
		return;
	if (parent == dentry)
		return;

	/* Prune ancestors. */
	dentry = parent;
692
	while (dentry) {
N
Nick Piggin 已提交
693
		spin_lock(&dentry->d_lock);
694 695 696 697 698
		if (dentry->d_count > 1) {
			dentry->d_count--;
			spin_unlock(&dentry->d_lock);
			return;
		}
699
		dentry = dentry_kill(dentry, 1);
700
	}
L
Linus Torvalds 已提交
701 702
}

C
Christoph Hellwig 已提交
703
static void shrink_dentry_list(struct list_head *list)
L
Linus Torvalds 已提交
704
{
705 706
	struct dentry *dentry;

707 708 709 710 711 712 713 714
	rcu_read_lock();
	for (;;) {
		dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
		if (&dentry->d_lru == list)
			break; /* empty */
		spin_lock(&dentry->d_lock);
		if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
			spin_unlock(&dentry->d_lock);
N
Nick Piggin 已提交
715 716 717
			continue;
		}

L
Linus Torvalds 已提交
718 719
		/*
		 * We found an inuse dentry which was not removed from
720 721
		 * the LRU because of laziness during lookup.  Do not free
		 * it - just keep it off the LRU list.
L
Linus Torvalds 已提交
722
		 */
N
Nick Piggin 已提交
723
		if (dentry->d_count) {
724
			dentry_lru_del(dentry);
725
			spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
726 727
			continue;
		}
728 729

		rcu_read_unlock();
730 731 732

		try_prune_one_dentry(dentry);

733
		rcu_read_lock();
734
	}
735
	rcu_read_unlock();
C
Christoph Hellwig 已提交
736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753
}

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

N
Nick Piggin 已提交
754 755
relock:
	spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
756 757 758 759 760
	while (!list_empty(&sb->s_dentry_lru)) {
		dentry = list_entry(sb->s_dentry_lru.prev,
				struct dentry, d_lru);
		BUG_ON(dentry->d_sb != sb);

N
Nick Piggin 已提交
761 762 763 764 765 766
		if (!spin_trylock(&dentry->d_lock)) {
			spin_unlock(&dcache_lru_lock);
			cpu_relax();
			goto relock;
		}

C
Christoph Hellwig 已提交
767 768 769 770 771
		/*
		 * If we are honouring the DCACHE_REFERENCED flag and the
		 * dentry has this flag set, don't free it.  Clear the flag
		 * and put it back on the LRU.
		 */
N
Nick Piggin 已提交
772 773 774 775
		if (flags & DCACHE_REFERENCED &&
				dentry->d_flags & DCACHE_REFERENCED) {
			dentry->d_flags &= ~DCACHE_REFERENCED;
			list_move(&dentry->d_lru, &referenced);
C
Christoph Hellwig 已提交
776
			spin_unlock(&dentry->d_lock);
N
Nick Piggin 已提交
777 778 779 780 781
		} else {
			list_move_tail(&dentry->d_lru, &tmp);
			spin_unlock(&dentry->d_lock);
			if (!--cnt)
				break;
C
Christoph Hellwig 已提交
782
		}
783
		cond_resched_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
784
	}
785 786
	if (!list_empty(&referenced))
		list_splice(&referenced, &sb->s_dentry_lru);
N
Nick Piggin 已提交
787
	spin_unlock(&dcache_lru_lock);
788 789 790 791

	shrink_dentry_list(&tmp);

	*count = cnt;
792 793 794 795 796 797 798 799 800 801 802 803 804
}

/**
 * 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)
{
805
	struct super_block *sb, *p = NULL;
806
	int w_count;
807
	int unused = dentry_stat.nr_unused;
808 809 810 811 812 813 814 815 816 817
	int prune_ratio;
	int pruned;

	if (unused == 0 || count == 0)
		return;
	if (count >= unused)
		prune_ratio = 1;
	else
		prune_ratio = unused / count;
	spin_lock(&sb_lock);
818
	list_for_each_entry(sb, &super_blocks, s_list) {
819 820
		if (list_empty(&sb->s_instances))
			continue;
821
		if (sb->s_nr_dentry_unused == 0)
L
Linus Torvalds 已提交
822
			continue;
823 824 825 826 827 828 829 830 831
		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)
832
		 */
833 834 835 836 837 838
		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;
839
		/*
840 841 842 843 844
		 * 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.
845
		 */
846 847 848 849 850 851
		if (down_read_trylock(&sb->s_umount)) {
			if ((sb->s_root != NULL) &&
			    (!list_empty(&sb->s_dentry_lru))) {
				__shrink_dcache_sb(sb, &w_count,
						DCACHE_REFERENCED);
				pruned -= w_count;
852
			}
853
			up_read(&sb->s_umount);
854
		}
855
		spin_lock(&sb_lock);
856 857
		if (p)
			__put_super(p);
858
		count -= pruned;
859
		p = sb;
A
Al Viro 已提交
860 861 862
		/* more work left to do? */
		if (count <= 0)
			break;
L
Linus Torvalds 已提交
863
	}
864 865
	if (p)
		__put_super(p);
866
	spin_unlock(&sb_lock);
L
Linus Torvalds 已提交
867 868 869 870 871 872
}

/**
 * shrink_dcache_sb - shrink dcache for a superblock
 * @sb: superblock
 *
C
Christoph Hellwig 已提交
873 874
 * 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
875
 */
C
Christoph Hellwig 已提交
876
void shrink_dcache_sb(struct super_block *sb)
L
Linus Torvalds 已提交
877
{
C
Christoph Hellwig 已提交
878 879
	LIST_HEAD(tmp);

N
Nick Piggin 已提交
880
	spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
881 882
	while (!list_empty(&sb->s_dentry_lru)) {
		list_splice_init(&sb->s_dentry_lru, &tmp);
883
		spin_unlock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
884
		shrink_dentry_list(&tmp);
885
		spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
886
	}
N
Nick Piggin 已提交
887
	spin_unlock(&dcache_lru_lock);
L
Linus Torvalds 已提交
888
}
889
EXPORT_SYMBOL(shrink_dcache_sb);
L
Linus Torvalds 已提交
890

891 892 893 894 895 896 897 898
/*
 * 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;
899
	unsigned detached = 0;
900 901 902 903

	BUG_ON(!IS_ROOT(dentry));

	/* detach this root from the system */
N
Nick Piggin 已提交
904
	spin_lock(&dentry->d_lock);
905
	dentry_lru_del(dentry);
906
	__d_drop(dentry);
N
Nick Piggin 已提交
907
	spin_unlock(&dentry->d_lock);
908 909 910 911 912 913 914 915

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

			/* this is a branch with children - detach all of them
			 * from the system in one go */
N
Nick Piggin 已提交
916
			spin_lock(&dentry->d_lock);
917 918
			list_for_each_entry(loop, &dentry->d_subdirs,
					    d_u.d_child) {
N
Nick Piggin 已提交
919 920
				spin_lock_nested(&loop->d_lock,
						DENTRY_D_LOCK_NESTED);
921
				dentry_lru_del(loop);
922
				__d_drop(loop);
N
Nick Piggin 已提交
923
				spin_unlock(&loop->d_lock);
924
			}
N
Nick Piggin 已提交
925
			spin_unlock(&dentry->d_lock);
926 927 928 929 930 931 932 933 934 935 936

			/* move to the first child */
			dentry = list_entry(dentry->d_subdirs.next,
					    struct dentry, d_u.d_child);
		}

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

N
Nick Piggin 已提交
937
			if (dentry->d_count != 0) {
938 939 940 941 942 943 944 945
				printk(KERN_ERR
				       "BUG: Dentry %p{i=%lx,n=%s}"
				       " still in use (%d)"
				       " [unmount of %s %s]\n",
				       dentry,
				       dentry->d_inode ?
				       dentry->d_inode->i_ino : 0UL,
				       dentry->d_name.name,
N
Nick Piggin 已提交
946
				       dentry->d_count,
947 948 949 950 951
				       dentry->d_sb->s_type->name,
				       dentry->d_sb->s_id);
				BUG();
			}

N
Nick Piggin 已提交
952
			if (IS_ROOT(dentry)) {
953
				parent = NULL;
N
Nick Piggin 已提交
954 955
				list_del(&dentry->d_u.d_child);
			} else {
956
				parent = dentry->d_parent;
N
Nick Piggin 已提交
957 958
				spin_lock(&parent->d_lock);
				parent->d_count--;
N
Nick Piggin 已提交
959
				list_del(&dentry->d_u.d_child);
N
Nick Piggin 已提交
960
				spin_unlock(&parent->d_lock);
961
			}
962

963
			detached++;
964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980

			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)
981
				return;
982 983 984 985 986 987 988 989 990 991
			dentry = parent;
		} while (list_empty(&dentry->d_subdirs));

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

/*
 * destroy the dentries attached to a superblock on unmounting
N
Nick Piggin 已提交
992
 * - we don't need to use dentry->d_lock because:
993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008
 *   - the superblock is detached from all mountings and open files, so the
 *     dentry trees will not be rearranged by the VFS
 *   - s_umount is write-locked, so the memory pressure shrinker will ignore
 *     any dentries belonging to this superblock that it comes across
 *   - the filesystem itself is no longer permitted to rearrange the dentries
 *     in this superblock
 */
void shrink_dcache_for_umount(struct super_block *sb)
{
	struct dentry *dentry;

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

	dentry = sb->s_root;
	sb->s_root = NULL;
N
Nick Piggin 已提交
1009 1010 1011
	spin_lock(&dentry->d_lock);
	dentry->d_count--;
	spin_unlock(&dentry->d_lock);
1012 1013
	shrink_dcache_for_umount_subtree(dentry);

1014 1015
	while (!hlist_bl_empty(&sb->s_anon)) {
		dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
1016 1017 1018 1019
		shrink_dcache_for_umount_subtree(dentry);
	}
}

1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038
/*
 * This tries to ascend one level of parenthood, but
 * we can race with renaming, so we need to re-check
 * the parenthood after dropping the lock and check
 * that the sequence number still matches.
 */
static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq)
{
	struct dentry *new = old->d_parent;

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

	/*
	 * might go back up the wrong parent if we have had a rename
	 * or deletion
	 */
	if (new != old->d_parent ||
1039
		 (old->d_flags & DCACHE_DISCONNECTED) ||
1040 1041 1042 1043 1044 1045 1046 1047 1048
		 (!locked && read_seqretry(&rename_lock, seq))) {
		spin_unlock(&new->d_lock);
		new = NULL;
	}
	rcu_read_unlock();
	return new;
}


L
Linus Torvalds 已提交
1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063
/*
 * 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)
{
1064
	struct dentry *this_parent;
L
Linus Torvalds 已提交
1065
	struct list_head *next;
1066
	unsigned seq;
1067
	int locked = 0;
1068 1069

	seq = read_seqbegin(&rename_lock);
1070 1071
again:
	this_parent = parent;
L
Linus Torvalds 已提交
1072 1073 1074

	if (d_mountpoint(parent))
		goto positive;
N
Nick Piggin 已提交
1075
	spin_lock(&this_parent->d_lock);
L
Linus Torvalds 已提交
1076 1077 1078 1079 1080
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
1081
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
1082
		next = tmp->next;
N
Nick Piggin 已提交
1083 1084

		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
L
Linus Torvalds 已提交
1085
		/* Have we found a mount point ? */
N
Nick Piggin 已提交
1086 1087 1088
		if (d_mountpoint(dentry)) {
			spin_unlock(&dentry->d_lock);
			spin_unlock(&this_parent->d_lock);
L
Linus Torvalds 已提交
1089
			goto positive;
N
Nick Piggin 已提交
1090
		}
L
Linus Torvalds 已提交
1091
		if (!list_empty(&dentry->d_subdirs)) {
N
Nick Piggin 已提交
1092 1093
			spin_unlock(&this_parent->d_lock);
			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
L
Linus Torvalds 已提交
1094
			this_parent = dentry;
N
Nick Piggin 已提交
1095
			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
L
Linus Torvalds 已提交
1096 1097
			goto repeat;
		}
N
Nick Piggin 已提交
1098
		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
1099 1100 1101 1102 1103
	}
	/*
	 * All done at this level ... ascend and resume the search.
	 */
	if (this_parent != parent) {
1104 1105 1106
		struct dentry *child = this_parent;
		this_parent = try_to_ascend(this_parent, locked, seq);
		if (!this_parent)
1107 1108
			goto rename_retry;
		next = child->d_u.d_child.next;
L
Linus Torvalds 已提交
1109 1110
		goto resume;
	}
N
Nick Piggin 已提交
1111
	spin_unlock(&this_parent->d_lock);
1112
	if (!locked && read_seqretry(&rename_lock, seq))
1113
		goto rename_retry;
1114 1115
	if (locked)
		write_sequnlock(&rename_lock);
L
Linus Torvalds 已提交
1116 1117
	return 0; /* No mount points found in tree */
positive:
1118
	if (!locked && read_seqretry(&rename_lock, seq))
1119
		goto rename_retry;
1120 1121
	if (locked)
		write_sequnlock(&rename_lock);
L
Linus Torvalds 已提交
1122
	return 1;
1123 1124 1125 1126 1127

rename_retry:
	locked = 1;
	write_seqlock(&rename_lock);
	goto again;
L
Linus Torvalds 已提交
1128
}
1129
EXPORT_SYMBOL(have_submounts);
L
Linus Torvalds 已提交
1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146

/*
 * 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)
{
1147
	struct dentry *this_parent;
L
Linus Torvalds 已提交
1148
	struct list_head *next;
1149
	unsigned seq;
L
Linus Torvalds 已提交
1150
	int found = 0;
1151
	int locked = 0;
L
Linus Torvalds 已提交
1152

1153
	seq = read_seqbegin(&rename_lock);
1154 1155
again:
	this_parent = parent;
N
Nick Piggin 已提交
1156
	spin_lock(&this_parent->d_lock);
L
Linus Torvalds 已提交
1157 1158 1159 1160 1161
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
1162
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
1163 1164
		next = tmp->next;

N
Nick Piggin 已提交
1165
		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
N
Nick Piggin 已提交
1166

L
Linus Torvalds 已提交
1167 1168 1169 1170
		/* 
		 * move only zero ref count dentries to the end 
		 * of the unused list for prune_dcache
		 */
N
Nick Piggin 已提交
1171
		if (!dentry->d_count) {
1172
			dentry_lru_move_tail(dentry);
L
Linus Torvalds 已提交
1173
			found++;
1174 1175
		} else {
			dentry_lru_del(dentry);
L
Linus Torvalds 已提交
1176 1177 1178 1179 1180 1181 1182
		}

		/*
		 * We can return to the caller if we have found some (this
		 * ensures forward progress). We'll be coming back to find
		 * the rest.
		 */
N
Nick Piggin 已提交
1183 1184
		if (found && need_resched()) {
			spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
1185
			goto out;
N
Nick Piggin 已提交
1186
		}
L
Linus Torvalds 已提交
1187 1188 1189 1190 1191

		/*
		 * Descend a level if the d_subdirs list is non-empty.
		 */
		if (!list_empty(&dentry->d_subdirs)) {
N
Nick Piggin 已提交
1192 1193
			spin_unlock(&this_parent->d_lock);
			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
L
Linus Torvalds 已提交
1194
			this_parent = dentry;
N
Nick Piggin 已提交
1195
			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
L
Linus Torvalds 已提交
1196 1197
			goto repeat;
		}
N
Nick Piggin 已提交
1198 1199

		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
1200 1201 1202 1203 1204
	}
	/*
	 * All done at this level ... ascend and resume the search.
	 */
	if (this_parent != parent) {
1205 1206 1207
		struct dentry *child = this_parent;
		this_parent = try_to_ascend(this_parent, locked, seq);
		if (!this_parent)
1208 1209
			goto rename_retry;
		next = child->d_u.d_child.next;
L
Linus Torvalds 已提交
1210 1211 1212
		goto resume;
	}
out:
N
Nick Piggin 已提交
1213
	spin_unlock(&this_parent->d_lock);
1214
	if (!locked && read_seqretry(&rename_lock, seq))
1215
		goto rename_retry;
1216 1217
	if (locked)
		write_sequnlock(&rename_lock);
L
Linus Torvalds 已提交
1218
	return found;
1219 1220 1221 1222 1223 1224 1225

rename_retry:
	if (found)
		return found;
	locked = 1;
	write_seqlock(&rename_lock);
	goto again;
L
Linus Torvalds 已提交
1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236
}

/**
 * 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)
{
1237
	struct super_block *sb = parent->d_sb;
L
Linus Torvalds 已提交
1238 1239 1240
	int found;

	while ((found = select_parent(parent)) != 0)
1241
		__shrink_dcache_sb(sb, &found, 0);
L
Linus Torvalds 已提交
1242
}
1243
EXPORT_SYMBOL(shrink_dcache_parent);
L
Linus Torvalds 已提交
1244 1245

/*
1246
 * Scan `sc->nr_slab_to_reclaim' dentries and return the number which remain.
L
Linus Torvalds 已提交
1247 1248 1249 1250 1251 1252 1253 1254 1255 1256
 *
 * 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.
 */
1257 1258
static int shrink_dcache_memory(struct shrinker *shrink,
				struct shrink_control *sc)
L
Linus Torvalds 已提交
1259
{
1260 1261 1262
	int nr = sc->nr_to_scan;
	gfp_t gfp_mask = sc->gfp_mask;

L
Linus Torvalds 已提交
1263 1264 1265
	if (nr) {
		if (!(gfp_mask & __GFP_FS))
			return -1;
1266
		prune_dcache(nr);
L
Linus Torvalds 已提交
1267
	}
1268

1269
	return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
L
Linus Torvalds 已提交
1270 1271
}

1272 1273 1274 1275 1276
static struct shrinker dcache_shrinker = {
	.shrink = shrink_dcache_memory,
	.seeks = DEFAULT_SEEKS,
};

L
Linus Torvalds 已提交
1277
/**
1278 1279
 * __d_alloc	-	allocate a dcache entry
 * @sb: filesystem it will belong to
L
Linus Torvalds 已提交
1280 1281 1282 1283 1284 1285 1286
 * @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.
 */
 
1287
struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
L
Linus Torvalds 已提交
1288 1289 1290 1291
{
	struct dentry *dentry;
	char *dname;

1292
	dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
L
Linus Torvalds 已提交
1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311
	if (!dentry)
		return NULL;

	if (name->len > DNAME_INLINE_LEN-1) {
		dname = kmalloc(name->len + 1, GFP_KERNEL);
		if (!dname) {
			kmem_cache_free(dentry_cache, dentry); 
			return NULL;
		}
	} else  {
		dname = dentry->d_iname;
	}	
	dentry->d_name.name = dname;

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

N
Nick Piggin 已提交
1312
	dentry->d_count = 1;
1313
	dentry->d_flags = 0;
L
Linus Torvalds 已提交
1314
	spin_lock_init(&dentry->d_lock);
N
Nick Piggin 已提交
1315
	seqcount_init(&dentry->d_seq);
L
Linus Torvalds 已提交
1316
	dentry->d_inode = NULL;
1317 1318
	dentry->d_parent = dentry;
	dentry->d_sb = sb;
L
Linus Torvalds 已提交
1319 1320
	dentry->d_op = NULL;
	dentry->d_fsdata = NULL;
1321
	INIT_HLIST_BL_NODE(&dentry->d_hash);
L
Linus Torvalds 已提交
1322 1323 1324
	INIT_LIST_HEAD(&dentry->d_lru);
	INIT_LIST_HEAD(&dentry->d_subdirs);
	INIT_LIST_HEAD(&dentry->d_alias);
N
Nick Piggin 已提交
1325
	INIT_LIST_HEAD(&dentry->d_u.d_child);
1326
	d_set_d_op(dentry, dentry->d_sb->s_d_op);
L
Linus Torvalds 已提交
1327

1328
	this_cpu_inc(nr_dentry);
1329

L
Linus Torvalds 已提交
1330 1331
	return dentry;
}
1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359

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

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

	return dentry;
}
1360
EXPORT_SYMBOL(d_alloc);
L
Linus Torvalds 已提交
1361

1362 1363
struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
{
1364 1365
	struct dentry *dentry = __d_alloc(sb, name);
	if (dentry)
1366 1367 1368 1369 1370
		dentry->d_flags |= DCACHE_DISCONNECTED;
	return dentry;
}
EXPORT_SYMBOL(d_alloc_pseudo);

L
Linus Torvalds 已提交
1371 1372 1373 1374 1375 1376 1377 1378 1379
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);
}
1380
EXPORT_SYMBOL(d_alloc_name);
L
Linus Torvalds 已提交
1381

1382 1383
void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
{
1384 1385
	WARN_ON_ONCE(dentry->d_op);
	WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH	|
1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403
				DCACHE_OP_COMPARE	|
				DCACHE_OP_REVALIDATE	|
				DCACHE_OP_DELETE ));
	dentry->d_op = op;
	if (!op)
		return;
	if (op->d_hash)
		dentry->d_flags |= DCACHE_OP_HASH;
	if (op->d_compare)
		dentry->d_flags |= DCACHE_OP_COMPARE;
	if (op->d_revalidate)
		dentry->d_flags |= DCACHE_OP_REVALIDATE;
	if (op->d_delete)
		dentry->d_flags |= DCACHE_OP_DELETE;

}
EXPORT_SYMBOL(d_set_d_op);

1404 1405
static void __d_instantiate(struct dentry *dentry, struct inode *inode)
{
N
Nick Piggin 已提交
1406
	spin_lock(&dentry->d_lock);
1407 1408 1409
	if (inode) {
		if (unlikely(IS_AUTOMOUNT(inode)))
			dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
1410
		list_add(&dentry->d_alias, &inode->i_dentry);
1411
	}
1412
	dentry->d_inode = inode;
N
Nick Piggin 已提交
1413
	dentry_rcuwalk_barrier(dentry);
N
Nick Piggin 已提交
1414
	spin_unlock(&dentry->d_lock);
1415 1416 1417
	fsnotify_d_instantiate(dentry, inode);
}

L
Linus Torvalds 已提交
1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434
/**
 * 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)
{
1435
	BUG_ON(!list_empty(&entry->d_alias));
1436 1437
	if (inode)
		spin_lock(&inode->i_lock);
1438
	__d_instantiate(entry, inode);
1439 1440
	if (inode)
		spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
1441 1442
	security_d_instantiate(entry, inode);
}
1443
EXPORT_SYMBOL(d_instantiate);
L
Linus Torvalds 已提交
1444 1445 1446 1447 1448 1449 1450 1451

/**
 * 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
1452
 * aliased dentry instead and drop one reference to inode.
L
Linus Torvalds 已提交
1453 1454 1455
 *
 * Note that in order to avoid conflicts with rename() etc, the caller
 * had better be holding the parent directory semaphore.
1456 1457 1458 1459
 *
 * 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
1460
 */
1461 1462
static struct dentry *__d_instantiate_unique(struct dentry *entry,
					     struct inode *inode)
L
Linus Torvalds 已提交
1463 1464 1465 1466 1467 1468
{
	struct dentry *alias;
	int len = entry->d_name.len;
	const char *name = entry->d_name.name;
	unsigned int hash = entry->d_name.hash;

1469
	if (!inode) {
1470
		__d_instantiate(entry, NULL);
1471 1472 1473
		return NULL;
	}

L
Linus Torvalds 已提交
1474 1475 1476
	list_for_each_entry(alias, &inode->i_dentry, d_alias) {
		struct qstr *qstr = &alias->d_name;

N
Nick Piggin 已提交
1477 1478 1479 1480 1481
		/*
		 * Don't need alias->d_lock here, because aliases with
		 * d_parent == entry->d_parent are not subject to name or
		 * parent changes, because the parent inode i_mutex is held.
		 */
L
Linus Torvalds 已提交
1482 1483 1484 1485
		if (qstr->hash != hash)
			continue;
		if (alias->d_parent != entry->d_parent)
			continue;
N
Nick Piggin 已提交
1486
		if (dentry_cmp(qstr->name, qstr->len, name, len))
L
Linus Torvalds 已提交
1487
			continue;
1488
		__dget(alias);
L
Linus Torvalds 已提交
1489 1490
		return alias;
	}
1491

1492
	__d_instantiate(entry, inode);
L
Linus Torvalds 已提交
1493 1494
	return NULL;
}
1495 1496 1497 1498 1499 1500 1501

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

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

1502 1503
	if (inode)
		spin_lock(&inode->i_lock);
1504
	result = __d_instantiate_unique(entry, inode);
1505 1506
	if (inode)
		spin_unlock(&inode->i_lock);
1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517

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

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

L
Linus Torvalds 已提交
1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535
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 };

1536 1537
		res = __d_alloc(root_inode->i_sb, &name);
		if (res)
L
Linus Torvalds 已提交
1538 1539 1540 1541
			d_instantiate(res, root_inode);
	}
	return res;
}
1542
EXPORT_SYMBOL(d_alloc_root);
L
Linus Torvalds 已提交
1543

1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565
static struct dentry * __d_find_any_alias(struct inode *inode)
{
	struct dentry *alias;

	if (list_empty(&inode->i_dentry))
		return NULL;
	alias = list_first_entry(&inode->i_dentry, struct dentry, d_alias);
	__dget(alias);
	return alias;
}

static struct dentry * d_find_any_alias(struct inode *inode)
{
	struct dentry *de;

	spin_lock(&inode->i_lock);
	de = __d_find_any_alias(inode);
	spin_unlock(&inode->i_lock);
	return de;
}


1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578
/**
 * 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
1579 1580 1581 1582
 * 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).
1583 1584 1585
 */
struct dentry *d_obtain_alias(struct inode *inode)
{
C
Christoph Hellwig 已提交
1586 1587 1588
	static const struct qstr anonstring = { .name = "" };
	struct dentry *tmp;
	struct dentry *res;
1589 1590

	if (!inode)
1591
		return ERR_PTR(-ESTALE);
1592 1593 1594
	if (IS_ERR(inode))
		return ERR_CAST(inode);

1595
	res = d_find_any_alias(inode);
C
Christoph Hellwig 已提交
1596 1597 1598
	if (res)
		goto out_iput;

1599
	tmp = __d_alloc(inode->i_sb, &anonstring);
C
Christoph Hellwig 已提交
1600 1601 1602
	if (!tmp) {
		res = ERR_PTR(-ENOMEM);
		goto out_iput;
1603
	}
N
Nick Piggin 已提交
1604

1605
	spin_lock(&inode->i_lock);
1606
	res = __d_find_any_alias(inode);
C
Christoph Hellwig 已提交
1607
	if (res) {
1608
		spin_unlock(&inode->i_lock);
C
Christoph Hellwig 已提交
1609 1610 1611 1612 1613 1614 1615 1616 1617
		dput(tmp);
		goto out_iput;
	}

	/* attach a disconnected dentry */
	spin_lock(&tmp->d_lock);
	tmp->d_inode = inode;
	tmp->d_flags |= DCACHE_DISCONNECTED;
	list_add(&tmp->d_alias, &inode->i_dentry);
1618
	hlist_bl_lock(&tmp->d_sb->s_anon);
1619
	hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
1620
	hlist_bl_unlock(&tmp->d_sb->s_anon);
C
Christoph Hellwig 已提交
1621
	spin_unlock(&tmp->d_lock);
1622
	spin_unlock(&inode->i_lock);
1623
	security_d_instantiate(tmp, inode);
C
Christoph Hellwig 已提交
1624 1625 1626 1627

	return tmp;

 out_iput:
1628 1629
	if (res && !IS_ERR(res))
		security_d_instantiate(res, inode);
C
Christoph Hellwig 已提交
1630 1631
	iput(inode);
	return res;
1632
}
1633
EXPORT_SYMBOL(d_obtain_alias);
L
Linus Torvalds 已提交
1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654

/**
 * 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;

1655 1656 1657
	if (IS_ERR(inode))
		return ERR_CAST(inode);

1658
	if (inode && S_ISDIR(inode->i_mode)) {
1659
		spin_lock(&inode->i_lock);
L
Linus Torvalds 已提交
1660 1661 1662
		new = __d_find_alias(inode, 1);
		if (new) {
			BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
1663
			spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
1664 1665 1666 1667
			security_d_instantiate(new, inode);
			d_move(new, dentry);
			iput(inode);
		} else {
1668
			/* already taking inode->i_lock, so d_add() by hand */
1669
			__d_instantiate(dentry, inode);
1670
			spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
1671 1672 1673 1674 1675 1676 1677
			security_d_instantiate(dentry, inode);
			d_rehash(dentry);
		}
	} else
		d_add(dentry, inode);
	return new;
}
1678
EXPORT_SYMBOL(d_splice_alias);
L
Linus Torvalds 已提交
1679

1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695
/**
 * 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.
 */
1696
struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
1697 1698 1699 1700 1701 1702
			struct qstr *name)
{
	int error;
	struct dentry *found;
	struct dentry *new;

C
Christoph Hellwig 已提交
1703 1704 1705 1706
	/*
	 * First check if a dentry matching the name already exists,
	 * if not go ahead and create it now.
	 */
1707 1708 1709 1710 1711 1712 1713
	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
1714

1715 1716 1717 1718 1719 1720 1721
		found = d_splice_alias(inode, new);
		if (found) {
			dput(new);
			return found;
		}
		return new;
	}
C
Christoph Hellwig 已提交
1722 1723 1724 1725 1726 1727 1728

	/*
	 * If a matching dentry exists, and it's not negative use it.
	 *
	 * Decrement the reference count to balance the iget() done
	 * earlier on.
	 */
1729 1730 1731 1732 1733 1734 1735 1736 1737
	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
1738

1739 1740 1741 1742 1743 1744 1745
	/*
	 * We are going to instantiate this dentry, unhash it and clear the
	 * lookup flag so we can do that.
	 */
	if (unlikely(d_need_lookup(found)))
		d_clear_need_lookup(found);

1746 1747
	/*
	 * Negative dentry: instantiate it unless the inode is a directory and
C
Christoph Hellwig 已提交
1748
	 * already has a dentry.
1749
	 */
1750
	spin_lock(&inode->i_lock);
C
Christoph Hellwig 已提交
1751
	if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) {
1752
		__d_instantiate(found, inode);
1753
		spin_unlock(&inode->i_lock);
1754 1755 1756
		security_d_instantiate(found, inode);
		return found;
	}
C
Christoph Hellwig 已提交
1757

1758
	/*
C
Christoph Hellwig 已提交
1759 1760
	 * In case a directory already has a (disconnected) entry grab a
	 * reference to it, move it in place and use it.
1761 1762
	 */
	new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
1763
	__dget(new);
1764
	spin_unlock(&inode->i_lock);
1765 1766 1767 1768 1769 1770 1771 1772 1773 1774
	security_d_instantiate(found, inode);
	d_move(new, found);
	iput(inode);
	dput(found);
	return new;

err_out:
	iput(inode);
	return ERR_PTR(error);
}
1775
EXPORT_SYMBOL(d_add_ci);
L
Linus Torvalds 已提交
1776

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

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

	/*
	 * The hash list is protected using RCU.
	 *
	 * Carefully use d_seq when comparing a candidate dentry, to avoid
	 * races with d_move().
	 *
	 * It is possible that concurrent renames can mess up our list
	 * walk here and result in missing our dentry, resulting in the
	 * false-negative result. d_lookup() protects against concurrent
	 * renames using rename_lock seqlock.
	 *
1832
	 * See Documentation/filesystems/path-lookup.txt for more details.
N
Nick Piggin 已提交
1833
	 */
1834
	hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
N
Nick Piggin 已提交
1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850
		struct inode *i;
		const char *tname;
		int tlen;

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

seqretry:
		*seq = read_seqcount_begin(&dentry->d_seq);
		if (dentry->d_parent != parent)
			continue;
		if (d_unhashed(dentry))
			continue;
		tlen = dentry->d_name.len;
		tname = dentry->d_name.name;
		i = dentry->d_inode;
1851 1852 1853
		prefetch(tname);
		if (i)
			prefetch(i);
N
Nick Piggin 已提交
1854 1855 1856 1857 1858 1859 1860 1861
		/*
		 * This seqcount check is required to ensure name and
		 * len are loaded atomically, so as not to walk off the
		 * edge of memory when walking. If we could load this
		 * atomically some other way, we could drop this check.
		 */
		if (read_seqcount_retry(&dentry->d_seq, *seq))
			goto seqretry;
1862
		if (parent->d_flags & DCACHE_OP_COMPARE) {
N
Nick Piggin 已提交
1863 1864 1865 1866 1867
			if (parent->d_op->d_compare(parent, *inode,
						dentry, i,
						tlen, tname, name))
				continue;
		} else {
N
Nick Piggin 已提交
1868
			if (dentry_cmp(tname, tlen, str, len))
N
Nick Piggin 已提交
1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882
				continue;
		}
		/*
		 * No extra seqcount check is required after the name
		 * compare. The caller must perform a seqcount check in
		 * order to do anything useful with the returned dentry
		 * anyway.
		 */
		*inode = i;
		return dentry;
	}
	return NULL;
}

L
Linus Torvalds 已提交
1883 1884 1885 1886
/**
 * d_lookup - search for a dentry
 * @parent: parent dentry
 * @name: qstr of name we wish to find
1887
 * Returns: dentry, or NULL
L
Linus Torvalds 已提交
1888
 *
1889 1890 1891 1892
 * 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
1893
 */
N
Nick Piggin 已提交
1894
struct dentry *d_lookup(struct dentry *parent, struct qstr *name)
L
Linus Torvalds 已提交
1895
{
N
Nick Piggin 已提交
1896
	struct dentry *dentry;
1897
	unsigned seq;
L
Linus Torvalds 已提交
1898 1899 1900 1901 1902 1903 1904 1905 1906

        do {
                seq = read_seqbegin(&rename_lock);
                dentry = __d_lookup(parent, name);
                if (dentry)
			break;
	} while (read_seqretry(&rename_lock, seq));
	return dentry;
}
1907
EXPORT_SYMBOL(d_lookup);
L
Linus Torvalds 已提交
1908

N
Nick Piggin 已提交
1909
/**
1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923
 * __d_lookup - search for a dentry (racy)
 * @parent: parent dentry
 * @name: qstr of name we wish to find
 * Returns: dentry, or NULL
 *
 * __d_lookup is like d_lookup, however it may (rarely) return a
 * false-negative result due to unrelated rename activity.
 *
 * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
 * however it must be used carefully, eg. with a following d_lookup in
 * the case of failure.
 *
 * __d_lookup callers must be commented.
 */
N
Nick Piggin 已提交
1924
struct dentry *__d_lookup(struct dentry *parent, struct qstr *name)
L
Linus Torvalds 已提交
1925 1926 1927 1928
{
	unsigned int len = name->len;
	unsigned int hash = name->hash;
	const unsigned char *str = name->name;
1929
	struct hlist_bl_head *b = d_hash(parent, hash);
1930
	struct hlist_bl_node *node;
N
Nick Piggin 已提交
1931
	struct dentry *found = NULL;
1932
	struct dentry *dentry;
L
Linus Torvalds 已提交
1933

N
Nick Piggin 已提交
1934 1935 1936 1937 1938 1939 1940
	/*
	 * Note: There is significant duplication with __d_lookup_rcu which is
	 * required to prevent single threaded performance regressions
	 * especially on architectures where smp_rmb (in seqcounts) are costly.
	 * Keep the two functions in sync.
	 */

1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951
	/*
	 * 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.
	 *
1952
	 * See Documentation/filesystems/path-lookup.txt for more details.
1953
	 */
L
Linus Torvalds 已提交
1954 1955
	rcu_read_lock();
	
1956
	hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
N
Nick Piggin 已提交
1957 1958
		const char *tname;
		int tlen;
L
Linus Torvalds 已提交
1959 1960 1961 1962 1963 1964 1965

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

		spin_lock(&dentry->d_lock);
		if (dentry->d_parent != parent)
			goto next;
1966 1967 1968
		if (d_unhashed(dentry))
			goto next;

L
Linus Torvalds 已提交
1969 1970 1971 1972
		/*
		 * It is safe to compare names since d_move() cannot
		 * change the qstr (protected by d_lock).
		 */
N
Nick Piggin 已提交
1973 1974
		tlen = dentry->d_name.len;
		tname = dentry->d_name.name;
1975
		if (parent->d_flags & DCACHE_OP_COMPARE) {
N
Nick Piggin 已提交
1976 1977
			if (parent->d_op->d_compare(parent, parent->d_inode,
						dentry, dentry->d_inode,
N
Nick Piggin 已提交
1978
						tlen, tname, name))
L
Linus Torvalds 已提交
1979 1980
				goto next;
		} else {
N
Nick Piggin 已提交
1981
			if (dentry_cmp(tname, tlen, str, len))
L
Linus Torvalds 已提交
1982 1983 1984
				goto next;
		}

N
Nick Piggin 已提交
1985
		dentry->d_count++;
1986
		found = dentry;
L
Linus Torvalds 已提交
1987 1988 1989 1990 1991 1992 1993 1994 1995 1996
		spin_unlock(&dentry->d_lock);
		break;
next:
		spin_unlock(&dentry->d_lock);
 	}
 	rcu_read_unlock();

 	return found;
}

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
/**
 * 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);
2014
	if (dir->d_flags & DCACHE_OP_HASH) {
N
Nick Piggin 已提交
2015
		if (dir->d_op->d_hash(dir, dir->d_inode, name) < 0)
2016 2017 2018 2019 2020 2021 2022
			goto out;
	}
	dentry = d_lookup(dir, name);
out:
	return dentry;
}

L
Linus Torvalds 已提交
2023
/**
N
Nick Piggin 已提交
2024
 * d_validate - verify dentry provided from insecure source (deprecated)
L
Linus Torvalds 已提交
2025
 * @dentry: The dentry alleged to be valid child of @dparent
2026
 * @dparent: The parent dentry (known to be valid)
L
Linus Torvalds 已提交
2027 2028 2029 2030
 *
 * 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
2031 2032
 *
 * This function is slow for big directories, and deprecated, do not use it.
L
Linus Torvalds 已提交
2033
 */
2034
int d_validate(struct dentry *dentry, struct dentry *dparent)
L
Linus Torvalds 已提交
2035
{
N
Nick Piggin 已提交
2036
	struct dentry *child;
2037

N
Nick Piggin 已提交
2038
	spin_lock(&dparent->d_lock);
N
Nick Piggin 已提交
2039 2040
	list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
		if (dentry == child) {
N
Nick Piggin 已提交
2041
			spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
2042
			__dget_dlock(dentry);
N
Nick Piggin 已提交
2043 2044
			spin_unlock(&dentry->d_lock);
			spin_unlock(&dparent->d_lock);
L
Linus Torvalds 已提交
2045 2046 2047
			return 1;
		}
	}
N
Nick Piggin 已提交
2048
	spin_unlock(&dparent->d_lock);
N
Nick Piggin 已提交
2049

L
Linus Torvalds 已提交
2050 2051
	return 0;
}
2052
EXPORT_SYMBOL(d_validate);
L
Linus Torvalds 已提交
2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076

/*
 * 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)
{
2077
	struct inode *inode;
2078
	int isdir = 0;
L
Linus Torvalds 已提交
2079 2080 2081
	/*
	 * Are we the only user?
	 */
2082
again:
L
Linus Torvalds 已提交
2083
	spin_lock(&dentry->d_lock);
2084 2085
	inode = dentry->d_inode;
	isdir = S_ISDIR(inode->i_mode);
N
Nick Piggin 已提交
2086
	if (dentry->d_count == 1) {
2087
		if (inode && !spin_trylock(&inode->i_lock)) {
2088 2089 2090 2091
			spin_unlock(&dentry->d_lock);
			cpu_relax();
			goto again;
		}
A
Al Viro 已提交
2092
		dentry->d_flags &= ~DCACHE_CANT_MOUNT;
N
Nick Piggin 已提交
2093
		dentry_unlink_inode(dentry);
2094
		fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
2095 2096 2097 2098 2099 2100 2101
		return;
	}

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

	spin_unlock(&dentry->d_lock);
2102 2103

	fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
2104
}
2105
EXPORT_SYMBOL(d_delete);
L
Linus Torvalds 已提交
2106

2107
static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
L
Linus Torvalds 已提交
2108
{
2109
	BUG_ON(!d_unhashed(entry));
2110
	hlist_bl_lock(b);
2111
	entry->d_flags |= DCACHE_RCUACCESS;
2112
	hlist_bl_add_head_rcu(&entry->d_hash, b);
2113
	hlist_bl_unlock(b);
L
Linus Torvalds 已提交
2114 2115
}

2116 2117 2118 2119 2120
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
2121 2122 2123 2124 2125 2126 2127 2128 2129 2130
/**
 * d_rehash	- add an entry back to the hash
 * @entry: dentry to add to the hash
 *
 * Adds a dentry to the hash according to its name.
 */
 
void d_rehash(struct dentry * entry)
{
	spin_lock(&entry->d_lock);
2131
	_d_rehash(entry);
L
Linus Torvalds 已提交
2132 2133
	spin_unlock(&entry->d_lock);
}
2134
EXPORT_SYMBOL(d_rehash);
L
Linus Torvalds 已提交
2135

N
Nick Piggin 已提交
2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151
/**
 * 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)
{
2152
	BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));
N
Nick Piggin 已提交
2153 2154 2155
	BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */

	spin_lock(&dentry->d_lock);
N
Nick Piggin 已提交
2156
	write_seqcount_begin(&dentry->d_seq);
N
Nick Piggin 已提交
2157
	memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
N
Nick Piggin 已提交
2158
	write_seqcount_end(&dentry->d_seq);
N
Nick Piggin 已提交
2159 2160 2161 2162
	spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(dentry_update_name_case);

L
Linus Torvalds 已提交
2163 2164 2165 2166 2167 2168 2169
static void switch_names(struct dentry *dentry, struct dentry *target)
{
	if (dname_external(target)) {
		if (dname_external(dentry)) {
			/*
			 * Both external: swap the pointers
			 */
2170
			swap(target->d_name.name, dentry->d_name.name);
L
Linus Torvalds 已提交
2171 2172 2173 2174 2175
		} else {
			/*
			 * dentry:internal, target:external.  Steal target's
			 * storage and make target internal.
			 */
2176 2177
			memcpy(target->d_iname, dentry->d_name.name,
					dentry->d_name.len + 1);
L
Linus Torvalds 已提交
2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196
			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);
2197 2198
			dentry->d_name.len = target->d_name.len;
			return;
L
Linus Torvalds 已提交
2199 2200
		}
	}
2201
	swap(dentry->d_name.len, target->d_name.len);
L
Linus Torvalds 已提交
2202 2203
}

N
Nick Piggin 已提交
2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239
static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
{
	/*
	 * XXXX: do we really need to take target->d_lock?
	 */
	if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent)
		spin_lock(&target->d_parent->d_lock);
	else {
		if (d_ancestor(dentry->d_parent, target->d_parent)) {
			spin_lock(&dentry->d_parent->d_lock);
			spin_lock_nested(&target->d_parent->d_lock,
						DENTRY_D_LOCK_NESTED);
		} else {
			spin_lock(&target->d_parent->d_lock);
			spin_lock_nested(&dentry->d_parent->d_lock,
						DENTRY_D_LOCK_NESTED);
		}
	}
	if (target < dentry) {
		spin_lock_nested(&target->d_lock, 2);
		spin_lock_nested(&dentry->d_lock, 3);
	} else {
		spin_lock_nested(&dentry->d_lock, 2);
		spin_lock_nested(&target->d_lock, 3);
	}
}

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

L
Linus Torvalds 已提交
2240
/*
N
Nick Piggin 已提交
2241 2242 2243 2244 2245 2246 2247 2248 2249
 * When switching names, the actual string doesn't strictly have to
 * be preserved in the target - because we're dropping the target
 * anyway. As such, we can just do a simple memcpy() to copy over
 * the new name before we switch.
 *
 * Note that we have to be a lot more careful about getting the hash
 * switched - we have to switch the hash value properly even if it
 * then no longer matches the actual (corrupted) string of the target.
 * The hash value has to match the hash queue that the dentry is on..
L
Linus Torvalds 已提交
2250
 */
2251
/*
2252
 * __d_move - move a dentry
L
Linus Torvalds 已提交
2253 2254 2255 2256
 * @dentry: entry to move
 * @target: new dentry
 *
 * Update the dcache to reflect the move of a file name. Negative
2257 2258
 * dcache entries should not be moved in this way.  Caller hold
 * rename_lock.
L
Linus Torvalds 已提交
2259
 */
2260
static void __d_move(struct dentry * dentry, struct dentry * target)
L
Linus Torvalds 已提交
2261 2262 2263 2264
{
	if (!dentry->d_inode)
		printk(KERN_WARNING "VFS: moving negative dcache entry\n");

N
Nick Piggin 已提交
2265 2266 2267 2268
	BUG_ON(d_ancestor(dentry, target));
	BUG_ON(d_ancestor(target, dentry));

	dentry_lock_for_move(dentry, target);
L
Linus Torvalds 已提交
2269

N
Nick Piggin 已提交
2270 2271 2272
	write_seqcount_begin(&dentry->d_seq);
	write_seqcount_begin(&target->d_seq);

2273 2274 2275 2276 2277 2278 2279
	/* __d_drop does write_seqcount_barrier, but they're OK to nest. */

	/*
	 * Move the dentry to the target hash queue. Don't bother checking
	 * for the same hash queue because of how unlikely it is.
	 */
	__d_drop(dentry);
N
Nick Piggin 已提交
2280
	__d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
L
Linus Torvalds 已提交
2281 2282 2283 2284

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

E
Eric Dumazet 已提交
2285 2286
	list_del(&dentry->d_u.d_child);
	list_del(&target->d_u.d_child);
L
Linus Torvalds 已提交
2287 2288 2289

	/* Switch the names.. */
	switch_names(dentry, target);
2290
	swap(dentry->d_name.hash, target->d_name.hash);
L
Linus Torvalds 已提交
2291 2292 2293 2294 2295

	/* ... and switch the parents */
	if (IS_ROOT(dentry)) {
		dentry->d_parent = target->d_parent;
		target->d_parent = target;
E
Eric Dumazet 已提交
2296
		INIT_LIST_HEAD(&target->d_u.d_child);
L
Linus Torvalds 已提交
2297
	} else {
2298
		swap(dentry->d_parent, target->d_parent);
L
Linus Torvalds 已提交
2299 2300

		/* And add them back to the (new) parent lists */
E
Eric Dumazet 已提交
2301
		list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
L
Linus Torvalds 已提交
2302 2303
	}

E
Eric Dumazet 已提交
2304
	list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
N
Nick Piggin 已提交
2305

N
Nick Piggin 已提交
2306 2307 2308
	write_seqcount_end(&target->d_seq);
	write_seqcount_end(&dentry->d_seq);

N
Nick Piggin 已提交
2309
	dentry_unlock_parents_for_move(dentry, target);
L
Linus Torvalds 已提交
2310
	spin_unlock(&target->d_lock);
2311
	fsnotify_d_move(dentry);
L
Linus Torvalds 已提交
2312
	spin_unlock(&dentry->d_lock);
2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326
}

/*
 * 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)
{
	write_seqlock(&rename_lock);
	__d_move(dentry, target);
L
Linus Torvalds 已提交
2327
	write_sequnlock(&rename_lock);
2328
}
2329
EXPORT_SYMBOL(d_move);
L
Linus Torvalds 已提交
2330

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

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

/*
 * This helper attempts to cope with remotely renamed directories
 *
 * It assumes that the caller is already holding
2354
 * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
2355 2356 2357 2358
 *
 * Note: If ever the locking in lock_rename() changes, then please
 * remember to update this too...
 */
2359 2360
static struct dentry *__d_unalias(struct inode *inode,
		struct dentry *dentry, struct dentry *alias)
2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377
{
	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;

	/* 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:
2378
	__d_move(alias, dentry);
2379 2380
	ret = alias;
out_err:
2381
	spin_unlock(&inode->i_lock);
2382 2383 2384 2385 2386 2387 2388
	if (m2)
		mutex_unlock(m2);
	if (m1)
		mutex_unlock(m1);
	return ret;
}

2389 2390 2391
/*
 * Prepare an anonymous dentry for life in the superblock's dentry tree as a
 * named dentry in place of the dentry to be replaced.
N
Nick Piggin 已提交
2392
 * returns with anon->d_lock held!
2393 2394 2395 2396 2397
 */
static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
{
	struct dentry *dparent, *aparent;

N
Nick Piggin 已提交
2398
	dentry_lock_for_move(anon, dentry);
2399

N
Nick Piggin 已提交
2400 2401 2402
	write_seqcount_begin(&dentry->d_seq);
	write_seqcount_begin(&anon->d_seq);

2403 2404 2405
	dparent = dentry->d_parent;
	aparent = anon->d_parent;

N
Nick Piggin 已提交
2406 2407 2408
	switch_names(dentry, anon);
	swap(dentry->d_name.hash, anon->d_name.hash);

2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422
	dentry->d_parent = (aparent == anon) ? dentry : aparent;
	list_del(&dentry->d_u.d_child);
	if (!IS_ROOT(dentry))
		list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
	else
		INIT_LIST_HEAD(&dentry->d_u.d_child);

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

N
Nick Piggin 已提交
2423 2424 2425
	write_seqcount_end(&dentry->d_seq);
	write_seqcount_end(&anon->d_seq);

N
Nick Piggin 已提交
2426 2427 2428 2429
	dentry_unlock_parents_for_move(anon, dentry);
	spin_unlock(&dentry->d_lock);

	/* anon->d_lock still locked, returns locked */
2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442
	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)
{
2443
	struct dentry *actual;
2444 2445 2446 2447 2448

	BUG_ON(!d_unhashed(dentry));

	if (!inode) {
		actual = dentry;
2449
		__d_instantiate(dentry, NULL);
2450 2451
		d_rehash(actual);
		goto out_nolock;
2452 2453
	}

2454
	spin_lock(&inode->i_lock);
2455

2456 2457 2458 2459 2460 2461 2462
	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;
2463 2464 2465 2466 2467 2468 2469 2470
			write_seqlock(&rename_lock);

			if (d_ancestor(alias, dentry)) {
				/* Check for loops */
				actual = ERR_PTR(-ELOOP);
			} else if (IS_ROOT(alias)) {
				/* Is this an anonymous mountpoint that we
				 * could splice into our tree? */
2471
				__d_materialise_dentry(dentry, alias);
2472
				write_sequnlock(&rename_lock);
2473 2474
				__d_drop(alias);
				goto found;
2475 2476 2477 2478
			} else {
				/* Nope, but we must(!) avoid directory
				 * aliasing */
				actual = __d_unalias(inode, dentry, alias);
2479
			}
2480
			write_sequnlock(&rename_lock);
2481 2482 2483 2484
			if (IS_ERR(actual))
				dput(alias);
			goto out_nolock;
		}
2485 2486 2487 2488 2489 2490
	}

	/* Add a unique reference */
	actual = __d_instantiate_unique(dentry, inode);
	if (!actual)
		actual = dentry;
2491 2492
	else
		BUG_ON(!d_unhashed(actual));
2493 2494 2495 2496 2497

	spin_lock(&actual->d_lock);
found:
	_d_rehash(actual);
	spin_unlock(&actual->d_lock);
2498
	spin_unlock(&inode->i_lock);
2499
out_nolock:
2500 2501 2502 2503 2504 2505 2506 2507
	if (actual == dentry) {
		security_d_instantiate(dentry, inode);
		return NULL;
	}

	iput(inode);
	return actual;
}
2508
EXPORT_SYMBOL_GPL(d_materialise_unique);
2509

2510
static int prepend(char **buffer, int *buflen, const char *str, int namelen)
2511 2512 2513 2514 2515 2516 2517 2518 2519
{
	*buflen -= namelen;
	if (*buflen < 0)
		return -ENAMETOOLONG;
	*buffer -= namelen;
	memcpy(*buffer, str, namelen);
	return 0;
}

2520 2521 2522 2523 2524
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
2525
/**
2526
 * prepend_path - Prepend path string to a buffer
2527 2528
 * @path: the dentry/vfsmount to report
 * @root: root vfsmnt/dentry (may be modified by this function)
M
Miklos Szeredi 已提交
2529 2530
 * @buffer: pointer to the end of the buffer
 * @buflen: pointer to buffer length
2531
 *
2532
 * Caller holds the rename_lock.
2533 2534 2535
 *
 * 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
2536
 */
M
Miklos Szeredi 已提交
2537 2538
static int prepend_path(const struct path *path, struct path *root,
			char **buffer, int *buflen)
L
Linus Torvalds 已提交
2539
{
2540 2541
	struct dentry *dentry = path->dentry;
	struct vfsmount *vfsmnt = path->mnt;
M
Miklos Szeredi 已提交
2542 2543
	bool slash = false;
	int error = 0;
2544

N
Nick Piggin 已提交
2545
	br_read_lock(vfsmount_lock);
M
Miklos Szeredi 已提交
2546
	while (dentry != root->dentry || vfsmnt != root->mnt) {
L
Linus Torvalds 已提交
2547 2548 2549
		struct dentry * parent;

		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
2550
			/* Global root? */
L
Linus Torvalds 已提交
2551 2552 2553 2554 2555 2556 2557 2558 2559
			if (vfsmnt->mnt_parent == vfsmnt) {
				goto global_root;
			}
			dentry = vfsmnt->mnt_mountpoint;
			vfsmnt = vfsmnt->mnt_parent;
			continue;
		}
		parent = dentry->d_parent;
		prefetch(parent);
N
Nick Piggin 已提交
2560
		spin_lock(&dentry->d_lock);
M
Miklos Szeredi 已提交
2561
		error = prepend_name(buffer, buflen, &dentry->d_name);
N
Nick Piggin 已提交
2562
		spin_unlock(&dentry->d_lock);
M
Miklos Szeredi 已提交
2563 2564 2565 2566 2567 2568
		if (!error)
			error = prepend(buffer, buflen, "/", 1);
		if (error)
			break;

		slash = true;
L
Linus Torvalds 已提交
2569 2570 2571
		dentry = parent;
	}

2572
out:
M
Miklos Szeredi 已提交
2573 2574 2575
	if (!error && !slash)
		error = prepend(buffer, buflen, "/", 1);

N
Nick Piggin 已提交
2576
	br_read_unlock(vfsmount_lock);
M
Miklos Szeredi 已提交
2577
	return error;
L
Linus Torvalds 已提交
2578 2579

global_root:
2580 2581 2582 2583 2584 2585 2586 2587 2588
	/*
	 * 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);
	}
2589 2590
	root->mnt = vfsmnt;
	root->dentry = dentry;
2591
	goto out;
M
Miklos Szeredi 已提交
2592
}
2593

M
Miklos Szeredi 已提交
2594 2595 2596 2597
/**
 * __d_path - return the path of a dentry
 * @path: the dentry/vfsmount to report
 * @root: root vfsmnt/dentry (may be modified by this function)
2598
 * @buf: buffer to return value in
M
Miklos Szeredi 已提交
2599 2600
 * @buflen: buffer length
 *
2601
 * Convert a dentry into an ASCII path name.
M
Miklos Szeredi 已提交
2602 2603 2604 2605
 *
 * Returns a pointer into the buffer or an error code if the
 * path was too long.
 *
2606
 * "buflen" should be positive.
M
Miklos Szeredi 已提交
2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617
 *
 * 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);
2618
	write_seqlock(&rename_lock);
M
Miklos Szeredi 已提交
2619
	error = prepend_path(path, root, &res, &buflen);
2620
	write_sequnlock(&rename_lock);
2621

M
Miklos Szeredi 已提交
2622 2623 2624
	if (error)
		return ERR_PTR(error);
	return res;
L
Linus Torvalds 已提交
2625 2626
}

2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642
/*
 * 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);
}

2643 2644 2645 2646 2647
static int prepend_unreachable(char **buffer, int *buflen)
{
	return prepend(buffer, buflen, "(unreachable)", 13);
}

J
Jan Blunck 已提交
2648 2649
/**
 * d_path - return the path of a dentry
2650
 * @path: path to report
J
Jan Blunck 已提交
2651 2652 2653 2654 2655 2656
 * @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.
 *
2657 2658 2659 2660
 * 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
2661
 *
2662
 * "buflen" should be positive.
J
Jan Blunck 已提交
2663
 */
2664
char *d_path(const struct path *path, char *buf, int buflen)
L
Linus Torvalds 已提交
2665
{
2666
	char *res = buf + buflen;
J
Jan Blunck 已提交
2667
	struct path root;
2668
	struct path tmp;
2669
	int error;
L
Linus Torvalds 已提交
2670

2671 2672 2673 2674 2675 2676 2677
	/*
	 * 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:
	 */
2678 2679
	if (path->dentry->d_op && path->dentry->d_op->d_dname)
		return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2680

2681
	get_fs_root(current->fs, &root);
2682
	write_seqlock(&rename_lock);
2683
	tmp = root;
2684 2685 2686
	error = path_with_deleted(path, &tmp, &res, &buflen);
	if (error)
		res = ERR_PTR(error);
2687
	write_sequnlock(&rename_lock);
J
Jan Blunck 已提交
2688
	path_put(&root);
L
Linus Torvalds 已提交
2689 2690
	return res;
}
2691
EXPORT_SYMBOL(d_path);
L
Linus Torvalds 已提交
2692

2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712
/**
 * 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);
2713
	write_seqlock(&rename_lock);
2714 2715 2716 2717
	tmp = root;
	error = path_with_deleted(path, &tmp, &res, &buflen);
	if (!error && !path_equal(&tmp, &root))
		error = prepend_unreachable(&res, &buflen);
2718
	write_sequnlock(&rename_lock);
2719 2720 2721 2722 2723 2724 2725
	path_put(&root);
	if (error)
		res =  ERR_PTR(error);

	return res;
}

2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746
/*
 * 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);
}

2747 2748 2749
/*
 * Write full pathname from the root of the filesystem into the buffer.
 */
N
Nick Piggin 已提交
2750
static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761
{
	char *end = buf + buflen;
	char *retval;

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

2762 2763
	while (!IS_ROOT(dentry)) {
		struct dentry *parent = dentry->d_parent;
N
Nick Piggin 已提交
2764
		int error;
2765 2766

		prefetch(parent);
N
Nick Piggin 已提交
2767 2768 2769 2770
		spin_lock(&dentry->d_lock);
		error = prepend_name(&end, &buflen, &dentry->d_name);
		spin_unlock(&dentry->d_lock);
		if (error != 0 || prepend(&end, &buflen, "/", 1) != 0)
2771 2772 2773 2774 2775
			goto Elong;

		retval = end;
		dentry = parent;
	}
A
Al Viro 已提交
2776 2777 2778 2779
	return retval;
Elong:
	return ERR_PTR(-ENAMETOOLONG);
}
N
Nick Piggin 已提交
2780 2781 2782 2783 2784

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

2785
	write_seqlock(&rename_lock);
N
Nick Piggin 已提交
2786
	retval = __dentry_path(dentry, buf, buflen);
2787
	write_sequnlock(&rename_lock);
N
Nick Piggin 已提交
2788 2789 2790 2791

	return retval;
}
EXPORT_SYMBOL(dentry_path_raw);
A
Al Viro 已提交
2792 2793 2794 2795 2796 2797

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

2798
	write_seqlock(&rename_lock);
A
Al Viro 已提交
2799 2800 2801 2802 2803 2804 2805
	if (d_unlinked(dentry)) {
		p = buf + buflen;
		if (prepend(&p, &buflen, "//deleted", 10) != 0)
			goto Elong;
		buflen++;
	}
	retval = __dentry_path(dentry, buf, buflen);
2806
	write_sequnlock(&rename_lock);
A
Al Viro 已提交
2807 2808
	if (!IS_ERR(retval) && p)
		*p = '/';	/* restore '/' overriden with '\0' */
2809 2810 2811 2812 2813
	return retval;
Elong:
	return ERR_PTR(-ENAMETOOLONG);
}

L
Linus Torvalds 已提交
2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831
/*
 * 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;
 *	}
 */
2832
SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
L
Linus Torvalds 已提交
2833
{
2834
	int error;
J
Jan Blunck 已提交
2835
	struct path pwd, root;
2836
	char *page = (char *) __get_free_page(GFP_USER);
L
Linus Torvalds 已提交
2837 2838 2839 2840

	if (!page)
		return -ENOMEM;

2841
	get_fs_root_and_pwd(current->fs, &root, &pwd);
L
Linus Torvalds 已提交
2842

2843
	error = -ENOENT;
2844
	write_seqlock(&rename_lock);
2845
	if (!d_unlinked(pwd.dentry)) {
2846
		unsigned long len;
2847
		struct path tmp = root;
2848 2849
		char *cwd = page + PAGE_SIZE;
		int buflen = PAGE_SIZE;
L
Linus Torvalds 已提交
2850

2851 2852
		prepend(&cwd, &buflen, "\0", 1);
		error = prepend_path(&pwd, &tmp, &cwd, &buflen);
2853
		write_sequnlock(&rename_lock);
2854

2855
		if (error)
2856 2857
			goto out;

2858 2859 2860 2861 2862 2863 2864
		/* Unreachable from current root */
		if (!path_equal(&tmp, &root)) {
			error = prepend_unreachable(&cwd, &buflen);
			if (error)
				goto out;
		}

2865 2866 2867 2868 2869 2870 2871
		error = -ERANGE;
		len = PAGE_SIZE + page - cwd;
		if (len <= size) {
			error = len;
			if (copy_to_user(buf, cwd, len))
				error = -EFAULT;
		}
2872 2873 2874
	} else {
		write_sequnlock(&rename_lock);
	}
L
Linus Torvalds 已提交
2875 2876

out:
J
Jan Blunck 已提交
2877 2878
	path_put(&pwd);
	path_put(&root);
L
Linus Torvalds 已提交
2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898
	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()
 */
  
2899
int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
L
Linus Torvalds 已提交
2900 2901
{
	int result;
2902
	unsigned seq;
L
Linus Torvalds 已提交
2903

2904 2905 2906 2907
	if (new_dentry == old_dentry)
		return 1;

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

	return result;
}

2925 2926 2927 2928 2929
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
2930 2931

	br_read_lock(vfsmount_lock);
2932 2933 2934
	if (mnt != path2->mnt) {
		for (;;) {
			if (mnt->mnt_parent == mnt) {
N
Nick Piggin 已提交
2935
				br_read_unlock(vfsmount_lock);
2936 2937 2938 2939 2940 2941 2942 2943 2944
				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
2945
	br_read_unlock(vfsmount_lock);
2946 2947 2948 2949
	return res;
}
EXPORT_SYMBOL(path_is_under);

L
Linus Torvalds 已提交
2950 2951
void d_genocide(struct dentry *root)
{
2952
	struct dentry *this_parent;
L
Linus Torvalds 已提交
2953
	struct list_head *next;
2954
	unsigned seq;
2955
	int locked = 0;
L
Linus Torvalds 已提交
2956

2957
	seq = read_seqbegin(&rename_lock);
2958 2959
again:
	this_parent = root;
N
Nick Piggin 已提交
2960
	spin_lock(&this_parent->d_lock);
L
Linus Torvalds 已提交
2961 2962 2963 2964 2965
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
2966
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
2967
		next = tmp->next;
2968

N
Nick Piggin 已提交
2969 2970 2971
		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
		if (d_unhashed(dentry) || !dentry->d_inode) {
			spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
2972
			continue;
N
Nick Piggin 已提交
2973
		}
L
Linus Torvalds 已提交
2974
		if (!list_empty(&dentry->d_subdirs)) {
N
Nick Piggin 已提交
2975 2976
			spin_unlock(&this_parent->d_lock);
			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
L
Linus Torvalds 已提交
2977
			this_parent = dentry;
N
Nick Piggin 已提交
2978
			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
L
Linus Torvalds 已提交
2979 2980
			goto repeat;
		}
2981 2982 2983 2984
		if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
			dentry->d_flags |= DCACHE_GENOCIDE;
			dentry->d_count--;
		}
N
Nick Piggin 已提交
2985
		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
2986 2987
	}
	if (this_parent != root) {
2988
		struct dentry *child = this_parent;
2989 2990 2991 2992
		if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
			this_parent->d_flags |= DCACHE_GENOCIDE;
			this_parent->d_count--;
		}
2993 2994
		this_parent = try_to_ascend(this_parent, locked, seq);
		if (!this_parent)
2995 2996
			goto rename_retry;
		next = child->d_u.d_child.next;
L
Linus Torvalds 已提交
2997 2998
		goto resume;
	}
N
Nick Piggin 已提交
2999
	spin_unlock(&this_parent->d_lock);
3000
	if (!locked && read_seqretry(&rename_lock, seq))
3001
		goto rename_retry;
3002 3003 3004 3005 3006 3007 3008 3009
	if (locked)
		write_sequnlock(&rename_lock);
	return;

rename_retry:
	locked = 1;
	write_seqlock(&rename_lock);
	goto again;
L
Linus Torvalds 已提交
3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030
}

/**
 * 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;

3031 3032
	dentry = d_hash_and_lookup(dir, name);
	if (dentry) {
L
Linus Torvalds 已提交
3033 3034 3035 3036 3037 3038
		if (dentry->d_inode)
			ino = dentry->d_inode->i_ino;
		dput(dentry);
	}
	return ino;
}
3039
EXPORT_SYMBOL(find_inode_number);
L
Linus Torvalds 已提交
3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062

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",
3063
					sizeof(struct hlist_bl_head),
L
Linus Torvalds 已提交
3064 3065 3066 3067 3068 3069 3070 3071
					dhash_entries,
					13,
					HASH_EARLY,
					&d_hash_shift,
					&d_hash_mask,
					0);

	for (loop = 0; loop < (1 << d_hash_shift); loop++)
3072
		INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
L
Linus Torvalds 已提交
3073 3074
}

3075
static void __init dcache_init(void)
L
Linus Torvalds 已提交
3076 3077 3078 3079 3080 3081 3082 3083
{
	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. 
	 */
3084 3085
	dentry_cache = KMEM_CACHE(dentry,
		SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
L
Linus Torvalds 已提交
3086
	
3087
	register_shrinker(&dcache_shrinker);
L
Linus Torvalds 已提交
3088 3089 3090 3091 3092 3093 3094

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

	dentry_hashtable =
		alloc_large_system_hash("Dentry cache",
3095
					sizeof(struct hlist_bl_head),
L
Linus Torvalds 已提交
3096 3097 3098 3099 3100 3101 3102 3103
					dhash_entries,
					13,
					0,
					&d_hash_shift,
					&d_hash_mask,
					0);

	for (loop = 0; loop < (1 << d_hash_shift); loop++)
3104
		INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
L
Linus Torvalds 已提交
3105 3106 3107
}

/* SLAB cache for __getname() consumers */
3108
struct kmem_cache *names_cachep __read_mostly;
3109
EXPORT_SYMBOL(names_cachep);
L
Linus Torvalds 已提交
3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129

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,
3130
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
L
Linus Torvalds 已提交
3131

3132 3133
	dcache_init();
	inode_init();
L
Linus Torvalds 已提交
3134
	files_init(mempages);
3135
	mnt_init();
L
Linus Torvalds 已提交
3136 3137 3138
	bdev_cache_init();
	chrdev_init();
}