dcache.c 76.5 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
}

/**
 * __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.
 */
746
static void __shrink_dcache_sb(struct super_block *sb, int count, int flags)
C
Christoph Hellwig 已提交
747 748 749 750 751
{
	struct dentry *dentry;
	LIST_HEAD(referenced);
	LIST_HEAD(tmp);

N
Nick Piggin 已提交
752 753
relock:
	spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
754 755 756 757 758
	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
759 760 761 762 763 764
		if (!spin_trylock(&dentry->d_lock)) {
			spin_unlock(&dcache_lru_lock);
			cpu_relax();
			goto relock;
		}

C
Christoph Hellwig 已提交
765 766 767 768 769
		/*
		 * 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
770 771 772 773
		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
774
			spin_unlock(&dentry->d_lock);
N
Nick Piggin 已提交
775 776 777
		} else {
			list_move_tail(&dentry->d_lru, &tmp);
			spin_unlock(&dentry->d_lock);
778
			if (!--count)
N
Nick Piggin 已提交
779
				break;
C
Christoph Hellwig 已提交
780
		}
781
		cond_resched_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
782
	}
783 784
	if (!list_empty(&referenced))
		list_splice(&referenced, &sb->s_dentry_lru);
N
Nick Piggin 已提交
785
	spin_unlock(&dcache_lru_lock);
786 787

	shrink_dentry_list(&tmp);
788 789 790
}

/**
791 792
 * prune_dcache_sb - shrink the dcache
 * @nr_to_scan: number of entries to try to free
793
 *
794 795 796
 * Attempt to shrink the superblock dcache LRU by @nr_to_scan entries. This is
 * done when we need more memory an called from the superblock shrinker
 * function.
797
 *
798 799
 * This function may fail to free any resources if all the dentries are in
 * use.
800
 */
801
void prune_dcache_sb(struct super_block *sb, int nr_to_scan)
802
{
803
	__shrink_dcache_sb(sb, nr_to_scan, DCACHE_REFERENCED);
L
Linus Torvalds 已提交
804 805 806 807 808 809
}

/**
 * shrink_dcache_sb - shrink dcache for a superblock
 * @sb: superblock
 *
C
Christoph Hellwig 已提交
810 811
 * 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
812
 */
C
Christoph Hellwig 已提交
813
void shrink_dcache_sb(struct super_block *sb)
L
Linus Torvalds 已提交
814
{
C
Christoph Hellwig 已提交
815 816
	LIST_HEAD(tmp);

N
Nick Piggin 已提交
817
	spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
818 819
	while (!list_empty(&sb->s_dentry_lru)) {
		list_splice_init(&sb->s_dentry_lru, &tmp);
820
		spin_unlock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
821
		shrink_dentry_list(&tmp);
822
		spin_lock(&dcache_lru_lock);
C
Christoph Hellwig 已提交
823
	}
N
Nick Piggin 已提交
824
	spin_unlock(&dcache_lru_lock);
L
Linus Torvalds 已提交
825
}
826
EXPORT_SYMBOL(shrink_dcache_sb);
L
Linus Torvalds 已提交
827

828 829 830 831 832 833 834 835
/*
 * 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;
836
	unsigned detached = 0;
837 838 839 840

	BUG_ON(!IS_ROOT(dentry));

	/* detach this root from the system */
N
Nick Piggin 已提交
841
	spin_lock(&dentry->d_lock);
842
	dentry_lru_del(dentry);
843
	__d_drop(dentry);
N
Nick Piggin 已提交
844
	spin_unlock(&dentry->d_lock);
845 846 847 848 849 850 851 852

	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
853
			spin_lock(&dentry->d_lock);
854 855
			list_for_each_entry(loop, &dentry->d_subdirs,
					    d_u.d_child) {
N
Nick Piggin 已提交
856 857
				spin_lock_nested(&loop->d_lock,
						DENTRY_D_LOCK_NESTED);
858
				dentry_lru_del(loop);
859
				__d_drop(loop);
N
Nick Piggin 已提交
860
				spin_unlock(&loop->d_lock);
861
			}
N
Nick Piggin 已提交
862
			spin_unlock(&dentry->d_lock);
863 864 865 866 867 868 869 870 871 872 873

			/* 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
874
			if (dentry->d_count != 0) {
875 876 877 878 879 880 881 882
				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
883
				       dentry->d_count,
884 885 886 887 888
				       dentry->d_sb->s_type->name,
				       dentry->d_sb->s_id);
				BUG();
			}

N
Nick Piggin 已提交
889
			if (IS_ROOT(dentry)) {
890
				parent = NULL;
N
Nick Piggin 已提交
891 892
				list_del(&dentry->d_u.d_child);
			} else {
893
				parent = dentry->d_parent;
N
Nick Piggin 已提交
894 895
				spin_lock(&parent->d_lock);
				parent->d_count--;
N
Nick Piggin 已提交
896
				list_del(&dentry->d_u.d_child);
N
Nick Piggin 已提交
897
				spin_unlock(&parent->d_lock);
898
			}
899

900
			detached++;
901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917

			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)
918
				return;
919 920 921 922 923 924 925 926 927 928
			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
929
 * - we don't need to use dentry->d_lock because:
930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945
 *   - 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
946 947 948
	spin_lock(&dentry->d_lock);
	dentry->d_count--;
	spin_unlock(&dentry->d_lock);
949 950
	shrink_dcache_for_umount_subtree(dentry);

951 952
	while (!hlist_bl_empty(&sb->s_anon)) {
		dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
953 954 955 956
		shrink_dcache_for_umount_subtree(dentry);
	}
}

957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975
/*
 * 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 ||
976
		 (old->d_flags & DCACHE_DISCONNECTED) ||
977 978 979 980 981 982 983 984 985
		 (!locked && read_seqretry(&rename_lock, seq))) {
		spin_unlock(&new->d_lock);
		new = NULL;
	}
	rcu_read_unlock();
	return new;
}


L
Linus Torvalds 已提交
986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000
/*
 * 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)
{
1001
	struct dentry *this_parent;
L
Linus Torvalds 已提交
1002
	struct list_head *next;
1003
	unsigned seq;
1004
	int locked = 0;
1005 1006

	seq = read_seqbegin(&rename_lock);
1007 1008
again:
	this_parent = parent;
L
Linus Torvalds 已提交
1009 1010 1011

	if (d_mountpoint(parent))
		goto positive;
N
Nick Piggin 已提交
1012
	spin_lock(&this_parent->d_lock);
L
Linus Torvalds 已提交
1013 1014 1015 1016 1017
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
1018
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
1019
		next = tmp->next;
N
Nick Piggin 已提交
1020 1021

		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
L
Linus Torvalds 已提交
1022
		/* Have we found a mount point ? */
N
Nick Piggin 已提交
1023 1024 1025
		if (d_mountpoint(dentry)) {
			spin_unlock(&dentry->d_lock);
			spin_unlock(&this_parent->d_lock);
L
Linus Torvalds 已提交
1026
			goto positive;
N
Nick Piggin 已提交
1027
		}
L
Linus Torvalds 已提交
1028
		if (!list_empty(&dentry->d_subdirs)) {
N
Nick Piggin 已提交
1029 1030
			spin_unlock(&this_parent->d_lock);
			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
L
Linus Torvalds 已提交
1031
			this_parent = dentry;
N
Nick Piggin 已提交
1032
			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
L
Linus Torvalds 已提交
1033 1034
			goto repeat;
		}
N
Nick Piggin 已提交
1035
		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
1036 1037 1038 1039 1040
	}
	/*
	 * All done at this level ... ascend and resume the search.
	 */
	if (this_parent != parent) {
1041 1042 1043
		struct dentry *child = this_parent;
		this_parent = try_to_ascend(this_parent, locked, seq);
		if (!this_parent)
1044 1045
			goto rename_retry;
		next = child->d_u.d_child.next;
L
Linus Torvalds 已提交
1046 1047
		goto resume;
	}
N
Nick Piggin 已提交
1048
	spin_unlock(&this_parent->d_lock);
1049
	if (!locked && read_seqretry(&rename_lock, seq))
1050
		goto rename_retry;
1051 1052
	if (locked)
		write_sequnlock(&rename_lock);
L
Linus Torvalds 已提交
1053 1054
	return 0; /* No mount points found in tree */
positive:
1055
	if (!locked && read_seqretry(&rename_lock, seq))
1056
		goto rename_retry;
1057 1058
	if (locked)
		write_sequnlock(&rename_lock);
L
Linus Torvalds 已提交
1059
	return 1;
1060 1061 1062 1063 1064

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

/*
 * Search the dentry child list for the specified parent,
 * and move any unused dentries to the end of the unused
 * list for prune_dcache(). We descend to the next level
 * whenever the d_subdirs list is non-empty and continue
 * searching.
 *
 * It returns zero iff there are no unused children,
 * otherwise  it returns the number of children moved to
 * the end of the unused list. This may not be the total
 * number of unused children, because select_parent can
 * drop the lock and return early due to latency
 * constraints.
 */
static int select_parent(struct dentry * parent)
{
1084
	struct dentry *this_parent;
L
Linus Torvalds 已提交
1085
	struct list_head *next;
1086
	unsigned seq;
L
Linus Torvalds 已提交
1087
	int found = 0;
1088
	int locked = 0;
L
Linus Torvalds 已提交
1089

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

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

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

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

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

		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
1137 1138 1139 1140 1141
	}
	/*
	 * All done at this level ... ascend and resume the search.
	 */
	if (this_parent != parent) {
1142 1143 1144
		struct dentry *child = this_parent;
		this_parent = try_to_ascend(this_parent, locked, seq);
		if (!this_parent)
1145 1146
			goto rename_retry;
		next = child->d_u.d_child.next;
L
Linus Torvalds 已提交
1147 1148 1149
		goto resume;
	}
out:
N
Nick Piggin 已提交
1150
	spin_unlock(&this_parent->d_lock);
1151
	if (!locked && read_seqretry(&rename_lock, seq))
1152
		goto rename_retry;
1153 1154
	if (locked)
		write_sequnlock(&rename_lock);
L
Linus Torvalds 已提交
1155
	return found;
1156 1157 1158 1159 1160 1161 1162

rename_retry:
	if (found)
		return found;
	locked = 1;
	write_seqlock(&rename_lock);
	goto again;
L
Linus Torvalds 已提交
1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173
}

/**
 * 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)
{
1174
	struct super_block *sb = parent->d_sb;
L
Linus Torvalds 已提交
1175 1176 1177
	int found;

	while ((found = select_parent(parent)) != 0)
1178
		__shrink_dcache_sb(sb, found, 0);
L
Linus Torvalds 已提交
1179
}
1180
EXPORT_SYMBOL(shrink_dcache_parent);
L
Linus Torvalds 已提交
1181 1182

/**
1183 1184
 * __d_alloc	-	allocate a dcache entry
 * @sb: filesystem it will belong to
L
Linus Torvalds 已提交
1185 1186 1187 1188 1189 1190 1191
 * @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.
 */
 
1192
struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
L
Linus Torvalds 已提交
1193 1194 1195 1196
{
	struct dentry *dentry;
	char *dname;

1197
	dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
L
Linus Torvalds 已提交
1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216
	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
1217
	dentry->d_count = 1;
1218
	dentry->d_flags = 0;
L
Linus Torvalds 已提交
1219
	spin_lock_init(&dentry->d_lock);
N
Nick Piggin 已提交
1220
	seqcount_init(&dentry->d_seq);
L
Linus Torvalds 已提交
1221
	dentry->d_inode = NULL;
1222 1223
	dentry->d_parent = dentry;
	dentry->d_sb = sb;
L
Linus Torvalds 已提交
1224 1225
	dentry->d_op = NULL;
	dentry->d_fsdata = NULL;
1226
	INIT_HLIST_BL_NODE(&dentry->d_hash);
L
Linus Torvalds 已提交
1227 1228 1229
	INIT_LIST_HEAD(&dentry->d_lru);
	INIT_LIST_HEAD(&dentry->d_subdirs);
	INIT_LIST_HEAD(&dentry->d_alias);
N
Nick Piggin 已提交
1230
	INIT_LIST_HEAD(&dentry->d_u.d_child);
1231
	d_set_d_op(dentry, dentry->d_sb->s_d_op);
L
Linus Torvalds 已提交
1232

1233
	this_cpu_inc(nr_dentry);
1234

L
Linus Torvalds 已提交
1235 1236
	return dentry;
}
1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264

/**
 * 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;
}
1265
EXPORT_SYMBOL(d_alloc);
L
Linus Torvalds 已提交
1266

1267 1268
struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
{
1269 1270
	struct dentry *dentry = __d_alloc(sb, name);
	if (dentry)
1271 1272 1273 1274 1275
		dentry->d_flags |= DCACHE_DISCONNECTED;
	return dentry;
}
EXPORT_SYMBOL(d_alloc_pseudo);

L
Linus Torvalds 已提交
1276 1277 1278 1279 1280 1281 1282 1283 1284
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);
}
1285
EXPORT_SYMBOL(d_alloc_name);
L
Linus Torvalds 已提交
1286

1287 1288
void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
{
1289 1290
	WARN_ON_ONCE(dentry->d_op);
	WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH	|
1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308
				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);

1309 1310
static void __d_instantiate(struct dentry *dentry, struct inode *inode)
{
N
Nick Piggin 已提交
1311
	spin_lock(&dentry->d_lock);
1312 1313 1314
	if (inode) {
		if (unlikely(IS_AUTOMOUNT(inode)))
			dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
1315
		list_add(&dentry->d_alias, &inode->i_dentry);
1316
	}
1317
	dentry->d_inode = inode;
N
Nick Piggin 已提交
1318
	dentry_rcuwalk_barrier(dentry);
N
Nick Piggin 已提交
1319
	spin_unlock(&dentry->d_lock);
1320 1321 1322
	fsnotify_d_instantiate(dentry, inode);
}

L
Linus Torvalds 已提交
1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339
/**
 * 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)
{
1340
	BUG_ON(!list_empty(&entry->d_alias));
1341 1342
	if (inode)
		spin_lock(&inode->i_lock);
1343
	__d_instantiate(entry, inode);
1344 1345
	if (inode)
		spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
1346 1347
	security_d_instantiate(entry, inode);
}
1348
EXPORT_SYMBOL(d_instantiate);
L
Linus Torvalds 已提交
1349 1350 1351 1352 1353 1354 1355 1356

/**
 * 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
1357
 * aliased dentry instead and drop one reference to inode.
L
Linus Torvalds 已提交
1358 1359 1360
 *
 * Note that in order to avoid conflicts with rename() etc, the caller
 * had better be holding the parent directory semaphore.
1361 1362 1363 1364
 *
 * 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
1365
 */
1366 1367
static struct dentry *__d_instantiate_unique(struct dentry *entry,
					     struct inode *inode)
L
Linus Torvalds 已提交
1368 1369 1370 1371 1372 1373
{
	struct dentry *alias;
	int len = entry->d_name.len;
	const char *name = entry->d_name.name;
	unsigned int hash = entry->d_name.hash;

1374
	if (!inode) {
1375
		__d_instantiate(entry, NULL);
1376 1377 1378
		return NULL;
	}

L
Linus Torvalds 已提交
1379 1380 1381
	list_for_each_entry(alias, &inode->i_dentry, d_alias) {
		struct qstr *qstr = &alias->d_name;

N
Nick Piggin 已提交
1382 1383 1384 1385 1386
		/*
		 * 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
1387 1388 1389 1390
		if (qstr->hash != hash)
			continue;
		if (alias->d_parent != entry->d_parent)
			continue;
N
Nick Piggin 已提交
1391
		if (dentry_cmp(qstr->name, qstr->len, name, len))
L
Linus Torvalds 已提交
1392
			continue;
1393
		__dget(alias);
L
Linus Torvalds 已提交
1394 1395
		return alias;
	}
1396

1397
	__d_instantiate(entry, inode);
L
Linus Torvalds 已提交
1398 1399
	return NULL;
}
1400 1401 1402 1403 1404 1405 1406

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

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

1407 1408
	if (inode)
		spin_lock(&inode->i_lock);
1409
	result = __d_instantiate_unique(entry, inode);
1410 1411
	if (inode)
		spin_unlock(&inode->i_lock);
1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422

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

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

L
Linus Torvalds 已提交
1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440
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 };

1441 1442
		res = __d_alloc(root_inode->i_sb, &name);
		if (res)
L
Linus Torvalds 已提交
1443 1444 1445 1446
			d_instantiate(res, root_inode);
	}
	return res;
}
1447
EXPORT_SYMBOL(d_alloc_root);
L
Linus Torvalds 已提交
1448

1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470
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;
}


1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483
/**
 * 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
1484 1485 1486 1487
 * 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).
1488 1489 1490
 */
struct dentry *d_obtain_alias(struct inode *inode)
{
C
Christoph Hellwig 已提交
1491 1492 1493
	static const struct qstr anonstring = { .name = "" };
	struct dentry *tmp;
	struct dentry *res;
1494 1495

	if (!inode)
1496
		return ERR_PTR(-ESTALE);
1497 1498 1499
	if (IS_ERR(inode))
		return ERR_CAST(inode);

1500
	res = d_find_any_alias(inode);
C
Christoph Hellwig 已提交
1501 1502 1503
	if (res)
		goto out_iput;

1504
	tmp = __d_alloc(inode->i_sb, &anonstring);
C
Christoph Hellwig 已提交
1505 1506 1507
	if (!tmp) {
		res = ERR_PTR(-ENOMEM);
		goto out_iput;
1508
	}
N
Nick Piggin 已提交
1509

1510
	spin_lock(&inode->i_lock);
1511
	res = __d_find_any_alias(inode);
C
Christoph Hellwig 已提交
1512
	if (res) {
1513
		spin_unlock(&inode->i_lock);
C
Christoph Hellwig 已提交
1514 1515 1516 1517 1518 1519 1520 1521 1522
		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);
1523
	hlist_bl_lock(&tmp->d_sb->s_anon);
1524
	hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
1525
	hlist_bl_unlock(&tmp->d_sb->s_anon);
C
Christoph Hellwig 已提交
1526
	spin_unlock(&tmp->d_lock);
1527
	spin_unlock(&inode->i_lock);
1528
	security_d_instantiate(tmp, inode);
C
Christoph Hellwig 已提交
1529 1530 1531 1532

	return tmp;

 out_iput:
1533 1534
	if (res && !IS_ERR(res))
		security_d_instantiate(res, inode);
C
Christoph Hellwig 已提交
1535 1536
	iput(inode);
	return res;
1537
}
1538
EXPORT_SYMBOL(d_obtain_alias);
L
Linus Torvalds 已提交
1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559

/**
 * 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;

1560 1561 1562
	if (IS_ERR(inode))
		return ERR_CAST(inode);

1563
	if (inode && S_ISDIR(inode->i_mode)) {
1564
		spin_lock(&inode->i_lock);
L
Linus Torvalds 已提交
1565 1566 1567
		new = __d_find_alias(inode, 1);
		if (new) {
			BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
1568
			spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
1569 1570 1571 1572
			security_d_instantiate(new, inode);
			d_move(new, dentry);
			iput(inode);
		} else {
1573
			/* already taking inode->i_lock, so d_add() by hand */
1574
			__d_instantiate(dentry, inode);
1575
			spin_unlock(&inode->i_lock);
L
Linus Torvalds 已提交
1576 1577 1578 1579 1580 1581 1582
			security_d_instantiate(dentry, inode);
			d_rehash(dentry);
		}
	} else
		d_add(dentry, inode);
	return new;
}
1583
EXPORT_SYMBOL(d_splice_alias);
L
Linus Torvalds 已提交
1584

1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600
/**
 * 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.
 */
1601
struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
1602 1603 1604 1605 1606 1607
			struct qstr *name)
{
	int error;
	struct dentry *found;
	struct dentry *new;

C
Christoph Hellwig 已提交
1608 1609 1610 1611
	/*
	 * First check if a dentry matching the name already exists,
	 * if not go ahead and create it now.
	 */
1612 1613 1614 1615 1616 1617 1618
	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
1619

1620 1621 1622 1623 1624 1625 1626
		found = d_splice_alias(inode, new);
		if (found) {
			dput(new);
			return found;
		}
		return new;
	}
C
Christoph Hellwig 已提交
1627 1628 1629 1630 1631 1632 1633

	/*
	 * If a matching dentry exists, and it's not negative use it.
	 *
	 * Decrement the reference count to balance the iget() done
	 * earlier on.
	 */
1634 1635 1636 1637 1638 1639 1640 1641 1642
	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
1643

1644 1645 1646 1647 1648 1649 1650
	/*
	 * 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);

1651 1652
	/*
	 * Negative dentry: instantiate it unless the inode is a directory and
C
Christoph Hellwig 已提交
1653
	 * already has a dentry.
1654
	 */
1655
	spin_lock(&inode->i_lock);
C
Christoph Hellwig 已提交
1656
	if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) {
1657
		__d_instantiate(found, inode);
1658
		spin_unlock(&inode->i_lock);
1659 1660 1661
		security_d_instantiate(found, inode);
		return found;
	}
C
Christoph Hellwig 已提交
1662

1663
	/*
C
Christoph Hellwig 已提交
1664 1665
	 * In case a directory already has a (disconnected) entry grab a
	 * reference to it, move it in place and use it.
1666 1667
	 */
	new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
1668
	__dget(new);
1669
	spin_unlock(&inode->i_lock);
1670 1671 1672 1673 1674 1675 1676 1677 1678 1679
	security_d_instantiate(found, inode);
	d_move(new, found);
	iput(inode);
	dput(found);
	return new;

err_out:
	iput(inode);
	return ERR_PTR(error);
}
1680
EXPORT_SYMBOL(d_add_ci);
L
Linus Torvalds 已提交
1681

N
Nick Piggin 已提交
1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714
/**
 * __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;
1715
	struct hlist_bl_head *b = d_hash(parent, hash);
1716
	struct hlist_bl_node *node;
N
Nick Piggin 已提交
1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736
	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.
	 *
1737
	 * See Documentation/filesystems/path-lookup.txt for more details.
N
Nick Piggin 已提交
1738
	 */
1739
	hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
N
Nick Piggin 已提交
1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755
		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;
1756 1757 1758
		prefetch(tname);
		if (i)
			prefetch(i);
N
Nick Piggin 已提交
1759 1760 1761 1762 1763 1764 1765 1766
		/*
		 * 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;
1767
		if (parent->d_flags & DCACHE_OP_COMPARE) {
N
Nick Piggin 已提交
1768 1769 1770 1771 1772
			if (parent->d_op->d_compare(parent, *inode,
						dentry, i,
						tlen, tname, name))
				continue;
		} else {
N
Nick Piggin 已提交
1773
			if (dentry_cmp(tname, tlen, str, len))
N
Nick Piggin 已提交
1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787
				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
1788 1789 1790 1791
/**
 * d_lookup - search for a dentry
 * @parent: parent dentry
 * @name: qstr of name we wish to find
1792
 * Returns: dentry, or NULL
L
Linus Torvalds 已提交
1793
 *
1794 1795 1796 1797
 * 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
1798
 */
N
Nick Piggin 已提交
1799
struct dentry *d_lookup(struct dentry *parent, struct qstr *name)
L
Linus Torvalds 已提交
1800
{
N
Nick Piggin 已提交
1801
	struct dentry *dentry;
1802
	unsigned seq;
L
Linus Torvalds 已提交
1803 1804 1805 1806 1807 1808 1809 1810 1811

        do {
                seq = read_seqbegin(&rename_lock);
                dentry = __d_lookup(parent, name);
                if (dentry)
			break;
	} while (read_seqretry(&rename_lock, seq));
	return dentry;
}
1812
EXPORT_SYMBOL(d_lookup);
L
Linus Torvalds 已提交
1813

N
Nick Piggin 已提交
1814
/**
1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828
 * __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
1829
struct dentry *__d_lookup(struct dentry *parent, struct qstr *name)
L
Linus Torvalds 已提交
1830 1831 1832 1833
{
	unsigned int len = name->len;
	unsigned int hash = name->hash;
	const unsigned char *str = name->name;
1834
	struct hlist_bl_head *b = d_hash(parent, hash);
1835
	struct hlist_bl_node *node;
N
Nick Piggin 已提交
1836
	struct dentry *found = NULL;
1837
	struct dentry *dentry;
L
Linus Torvalds 已提交
1838

N
Nick Piggin 已提交
1839 1840 1841 1842 1843 1844 1845
	/*
	 * 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.
	 */

1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856
	/*
	 * 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.
	 *
1857
	 * See Documentation/filesystems/path-lookup.txt for more details.
1858
	 */
L
Linus Torvalds 已提交
1859 1860
	rcu_read_lock();
	
1861
	hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
N
Nick Piggin 已提交
1862 1863
		const char *tname;
		int tlen;
L
Linus Torvalds 已提交
1864 1865 1866 1867 1868 1869 1870

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

		spin_lock(&dentry->d_lock);
		if (dentry->d_parent != parent)
			goto next;
1871 1872 1873
		if (d_unhashed(dentry))
			goto next;

L
Linus Torvalds 已提交
1874 1875 1876 1877
		/*
		 * It is safe to compare names since d_move() cannot
		 * change the qstr (protected by d_lock).
		 */
N
Nick Piggin 已提交
1878 1879
		tlen = dentry->d_name.len;
		tname = dentry->d_name.name;
1880
		if (parent->d_flags & DCACHE_OP_COMPARE) {
N
Nick Piggin 已提交
1881 1882
			if (parent->d_op->d_compare(parent, parent->d_inode,
						dentry, dentry->d_inode,
N
Nick Piggin 已提交
1883
						tlen, tname, name))
L
Linus Torvalds 已提交
1884 1885
				goto next;
		} else {
N
Nick Piggin 已提交
1886
			if (dentry_cmp(tname, tlen, str, len))
L
Linus Torvalds 已提交
1887 1888 1889
				goto next;
		}

N
Nick Piggin 已提交
1890
		dentry->d_count++;
1891
		found = dentry;
L
Linus Torvalds 已提交
1892 1893 1894 1895 1896 1897 1898 1899 1900 1901
		spin_unlock(&dentry->d_lock);
		break;
next:
		spin_unlock(&dentry->d_lock);
 	}
 	rcu_read_unlock();

 	return found;
}

1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918
/**
 * 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);
1919
	if (dir->d_flags & DCACHE_OP_HASH) {
N
Nick Piggin 已提交
1920
		if (dir->d_op->d_hash(dir, dir->d_inode, name) < 0)
1921 1922 1923 1924 1925 1926 1927
			goto out;
	}
	dentry = d_lookup(dir, name);
out:
	return dentry;
}

L
Linus Torvalds 已提交
1928
/**
N
Nick Piggin 已提交
1929
 * d_validate - verify dentry provided from insecure source (deprecated)
L
Linus Torvalds 已提交
1930
 * @dentry: The dentry alleged to be valid child of @dparent
1931
 * @dparent: The parent dentry (known to be valid)
L
Linus Torvalds 已提交
1932 1933 1934 1935
 *
 * 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
1936 1937
 *
 * This function is slow for big directories, and deprecated, do not use it.
L
Linus Torvalds 已提交
1938
 */
1939
int d_validate(struct dentry *dentry, struct dentry *dparent)
L
Linus Torvalds 已提交
1940
{
N
Nick Piggin 已提交
1941
	struct dentry *child;
1942

N
Nick Piggin 已提交
1943
	spin_lock(&dparent->d_lock);
N
Nick Piggin 已提交
1944 1945
	list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
		if (dentry == child) {
N
Nick Piggin 已提交
1946
			spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1947
			__dget_dlock(dentry);
N
Nick Piggin 已提交
1948 1949
			spin_unlock(&dentry->d_lock);
			spin_unlock(&dparent->d_lock);
L
Linus Torvalds 已提交
1950 1951 1952
			return 1;
		}
	}
N
Nick Piggin 已提交
1953
	spin_unlock(&dparent->d_lock);
N
Nick Piggin 已提交
1954

L
Linus Torvalds 已提交
1955 1956
	return 0;
}
1957
EXPORT_SYMBOL(d_validate);
L
Linus Torvalds 已提交
1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981

/*
 * 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)
{
1982
	struct inode *inode;
1983
	int isdir = 0;
L
Linus Torvalds 已提交
1984 1985 1986
	/*
	 * Are we the only user?
	 */
1987
again:
L
Linus Torvalds 已提交
1988
	spin_lock(&dentry->d_lock);
1989 1990
	inode = dentry->d_inode;
	isdir = S_ISDIR(inode->i_mode);
N
Nick Piggin 已提交
1991
	if (dentry->d_count == 1) {
1992
		if (inode && !spin_trylock(&inode->i_lock)) {
1993 1994 1995 1996
			spin_unlock(&dentry->d_lock);
			cpu_relax();
			goto again;
		}
A
Al Viro 已提交
1997
		dentry->d_flags &= ~DCACHE_CANT_MOUNT;
N
Nick Piggin 已提交
1998
		dentry_unlink_inode(dentry);
1999
		fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
2000 2001 2002 2003 2004 2005 2006
		return;
	}

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

	spin_unlock(&dentry->d_lock);
2007 2008

	fsnotify_nameremove(dentry, isdir);
L
Linus Torvalds 已提交
2009
}
2010
EXPORT_SYMBOL(d_delete);
L
Linus Torvalds 已提交
2011

2012
static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
L
Linus Torvalds 已提交
2013
{
2014
	BUG_ON(!d_unhashed(entry));
2015
	hlist_bl_lock(b);
2016
	entry->d_flags |= DCACHE_RCUACCESS;
2017
	hlist_bl_add_head_rcu(&entry->d_hash, b);
2018
	hlist_bl_unlock(b);
L
Linus Torvalds 已提交
2019 2020
}

2021 2022 2023 2024 2025
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
2026 2027 2028 2029 2030 2031 2032 2033 2034 2035
/**
 * 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);
2036
	_d_rehash(entry);
L
Linus Torvalds 已提交
2037 2038
	spin_unlock(&entry->d_lock);
}
2039
EXPORT_SYMBOL(d_rehash);
L
Linus Torvalds 已提交
2040

N
Nick Piggin 已提交
2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056
/**
 * 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)
{
2057
	BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));
N
Nick Piggin 已提交
2058 2059 2060
	BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */

	spin_lock(&dentry->d_lock);
N
Nick Piggin 已提交
2061
	write_seqcount_begin(&dentry->d_seq);
N
Nick Piggin 已提交
2062
	memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
N
Nick Piggin 已提交
2063
	write_seqcount_end(&dentry->d_seq);
N
Nick Piggin 已提交
2064 2065 2066 2067
	spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(dentry_update_name_case);

L
Linus Torvalds 已提交
2068 2069 2070 2071 2072 2073 2074
static void switch_names(struct dentry *dentry, struct dentry *target)
{
	if (dname_external(target)) {
		if (dname_external(dentry)) {
			/*
			 * Both external: swap the pointers
			 */
2075
			swap(target->d_name.name, dentry->d_name.name);
L
Linus Torvalds 已提交
2076 2077 2078 2079 2080
		} else {
			/*
			 * dentry:internal, target:external.  Steal target's
			 * storage and make target internal.
			 */
2081 2082
			memcpy(target->d_iname, dentry->d_name.name,
					dentry->d_name.len + 1);
L
Linus Torvalds 已提交
2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101
			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);
2102 2103
			dentry->d_name.len = target->d_name.len;
			return;
L
Linus Torvalds 已提交
2104 2105
		}
	}
2106
	swap(dentry->d_name.len, target->d_name.len);
L
Linus Torvalds 已提交
2107 2108
}

N
Nick Piggin 已提交
2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144
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
2145
/*
N
Nick Piggin 已提交
2146 2147 2148 2149 2150 2151 2152 2153 2154
 * 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
2155
 */
2156
/*
2157
 * __d_move - move a dentry
L
Linus Torvalds 已提交
2158 2159 2160 2161
 * @dentry: entry to move
 * @target: new dentry
 *
 * Update the dcache to reflect the move of a file name. Negative
2162 2163
 * dcache entries should not be moved in this way.  Caller hold
 * rename_lock.
L
Linus Torvalds 已提交
2164
 */
2165
static void __d_move(struct dentry * dentry, struct dentry * target)
L
Linus Torvalds 已提交
2166 2167 2168 2169
{
	if (!dentry->d_inode)
		printk(KERN_WARNING "VFS: moving negative dcache entry\n");

N
Nick Piggin 已提交
2170 2171 2172 2173
	BUG_ON(d_ancestor(dentry, target));
	BUG_ON(d_ancestor(target, dentry));

	dentry_lock_for_move(dentry, target);
L
Linus Torvalds 已提交
2174

N
Nick Piggin 已提交
2175 2176 2177
	write_seqcount_begin(&dentry->d_seq);
	write_seqcount_begin(&target->d_seq);

2178 2179 2180 2181 2182 2183 2184
	/* __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
2185
	__d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
L
Linus Torvalds 已提交
2186 2187 2188 2189

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

E
Eric Dumazet 已提交
2190 2191
	list_del(&dentry->d_u.d_child);
	list_del(&target->d_u.d_child);
L
Linus Torvalds 已提交
2192 2193 2194

	/* Switch the names.. */
	switch_names(dentry, target);
2195
	swap(dentry->d_name.hash, target->d_name.hash);
L
Linus Torvalds 已提交
2196 2197 2198 2199 2200

	/* ... and switch the parents */
	if (IS_ROOT(dentry)) {
		dentry->d_parent = target->d_parent;
		target->d_parent = target;
E
Eric Dumazet 已提交
2201
		INIT_LIST_HEAD(&target->d_u.d_child);
L
Linus Torvalds 已提交
2202
	} else {
2203
		swap(dentry->d_parent, target->d_parent);
L
Linus Torvalds 已提交
2204 2205

		/* And add them back to the (new) parent lists */
E
Eric Dumazet 已提交
2206
		list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
L
Linus Torvalds 已提交
2207 2208
	}

E
Eric Dumazet 已提交
2209
	list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
N
Nick Piggin 已提交
2210

N
Nick Piggin 已提交
2211 2212 2213
	write_seqcount_end(&target->d_seq);
	write_seqcount_end(&dentry->d_seq);

N
Nick Piggin 已提交
2214
	dentry_unlock_parents_for_move(dentry, target);
L
Linus Torvalds 已提交
2215
	spin_unlock(&target->d_lock);
2216
	fsnotify_d_move(dentry);
L
Linus Torvalds 已提交
2217
	spin_unlock(&dentry->d_lock);
2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231
}

/*
 * 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
2232
	write_sequnlock(&rename_lock);
2233
}
2234
EXPORT_SYMBOL(d_move);
L
Linus Torvalds 已提交
2235

2236 2237 2238 2239 2240 2241 2242
/**
 * 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.
2243
 */
2244
struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
2245 2246 2247
{
	struct dentry *p;

2248
	for (p = p2; !IS_ROOT(p); p = p->d_parent) {
2249
		if (p->d_parent == p1)
2250
			return p;
2251
	}
2252
	return NULL;
2253 2254 2255 2256 2257 2258
}

/*
 * This helper attempts to cope with remotely renamed directories
 *
 * It assumes that the caller is already holding
2259
 * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
2260 2261 2262 2263
 *
 * Note: If ever the locking in lock_rename() changes, then please
 * remember to update this too...
 */
2264 2265
static struct dentry *__d_unalias(struct inode *inode,
		struct dentry *dentry, struct dentry *alias)
2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282
{
	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:
2283
	__d_move(alias, dentry);
2284 2285
	ret = alias;
out_err:
2286
	spin_unlock(&inode->i_lock);
2287 2288 2289 2290 2291 2292 2293
	if (m2)
		mutex_unlock(m2);
	if (m1)
		mutex_unlock(m1);
	return ret;
}

2294 2295 2296
/*
 * 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
2297
 * returns with anon->d_lock held!
2298 2299 2300 2301 2302
 */
static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
{
	struct dentry *dparent, *aparent;

N
Nick Piggin 已提交
2303
	dentry_lock_for_move(anon, dentry);
2304

N
Nick Piggin 已提交
2305 2306 2307
	write_seqcount_begin(&dentry->d_seq);
	write_seqcount_begin(&anon->d_seq);

2308 2309 2310
	dparent = dentry->d_parent;
	aparent = anon->d_parent;

N
Nick Piggin 已提交
2311 2312 2313
	switch_names(dentry, anon);
	swap(dentry->d_name.hash, anon->d_name.hash);

2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327
	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
2328 2329 2330
	write_seqcount_end(&dentry->d_seq);
	write_seqcount_end(&anon->d_seq);

N
Nick Piggin 已提交
2331 2332 2333 2334
	dentry_unlock_parents_for_move(anon, dentry);
	spin_unlock(&dentry->d_lock);

	/* anon->d_lock still locked, returns locked */
2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347
	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)
{
2348
	struct dentry *actual;
2349 2350 2351 2352 2353

	BUG_ON(!d_unhashed(dentry));

	if (!inode) {
		actual = dentry;
2354
		__d_instantiate(dentry, NULL);
2355 2356
		d_rehash(actual);
		goto out_nolock;
2357 2358
	}

2359
	spin_lock(&inode->i_lock);
2360

2361 2362 2363 2364 2365 2366 2367
	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;
2368 2369 2370 2371 2372 2373 2374 2375
			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? */
2376
				__d_materialise_dentry(dentry, alias);
2377
				write_sequnlock(&rename_lock);
2378 2379
				__d_drop(alias);
				goto found;
2380 2381 2382 2383
			} else {
				/* Nope, but we must(!) avoid directory
				 * aliasing */
				actual = __d_unalias(inode, dentry, alias);
2384
			}
2385
			write_sequnlock(&rename_lock);
2386 2387 2388 2389
			if (IS_ERR(actual))
				dput(alias);
			goto out_nolock;
		}
2390 2391 2392 2393 2394 2395
	}

	/* Add a unique reference */
	actual = __d_instantiate_unique(dentry, inode);
	if (!actual)
		actual = dentry;
2396 2397
	else
		BUG_ON(!d_unhashed(actual));
2398 2399 2400 2401 2402

	spin_lock(&actual->d_lock);
found:
	_d_rehash(actual);
	spin_unlock(&actual->d_lock);
2403
	spin_unlock(&inode->i_lock);
2404
out_nolock:
2405 2406 2407 2408 2409 2410 2411 2412
	if (actual == dentry) {
		security_d_instantiate(dentry, inode);
		return NULL;
	}

	iput(inode);
	return actual;
}
2413
EXPORT_SYMBOL_GPL(d_materialise_unique);
2414

2415
static int prepend(char **buffer, int *buflen, const char *str, int namelen)
2416 2417 2418 2419 2420 2421 2422 2423 2424
{
	*buflen -= namelen;
	if (*buflen < 0)
		return -ENAMETOOLONG;
	*buffer -= namelen;
	memcpy(*buffer, str, namelen);
	return 0;
}

2425 2426 2427 2428 2429
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
2430
/**
2431
 * prepend_path - Prepend path string to a buffer
2432 2433
 * @path: the dentry/vfsmount to report
 * @root: root vfsmnt/dentry (may be modified by this function)
M
Miklos Szeredi 已提交
2434 2435
 * @buffer: pointer to the end of the buffer
 * @buflen: pointer to buffer length
2436
 *
2437
 * Caller holds the rename_lock.
2438 2439 2440
 *
 * 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
2441
 */
M
Miklos Szeredi 已提交
2442 2443
static int prepend_path(const struct path *path, struct path *root,
			char **buffer, int *buflen)
L
Linus Torvalds 已提交
2444
{
2445 2446
	struct dentry *dentry = path->dentry;
	struct vfsmount *vfsmnt = path->mnt;
M
Miklos Szeredi 已提交
2447 2448
	bool slash = false;
	int error = 0;
2449

N
Nick Piggin 已提交
2450
	br_read_lock(vfsmount_lock);
M
Miklos Szeredi 已提交
2451
	while (dentry != root->dentry || vfsmnt != root->mnt) {
L
Linus Torvalds 已提交
2452 2453 2454
		struct dentry * parent;

		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
2455
			/* Global root? */
L
Linus Torvalds 已提交
2456 2457 2458 2459 2460 2461 2462 2463 2464
			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
2465
		spin_lock(&dentry->d_lock);
M
Miklos Szeredi 已提交
2466
		error = prepend_name(buffer, buflen, &dentry->d_name);
N
Nick Piggin 已提交
2467
		spin_unlock(&dentry->d_lock);
M
Miklos Szeredi 已提交
2468 2469 2470 2471 2472 2473
		if (!error)
			error = prepend(buffer, buflen, "/", 1);
		if (error)
			break;

		slash = true;
L
Linus Torvalds 已提交
2474 2475 2476
		dentry = parent;
	}

2477
out:
M
Miklos Szeredi 已提交
2478 2479 2480
	if (!error && !slash)
		error = prepend(buffer, buflen, "/", 1);

N
Nick Piggin 已提交
2481
	br_read_unlock(vfsmount_lock);
M
Miklos Szeredi 已提交
2482
	return error;
L
Linus Torvalds 已提交
2483 2484

global_root:
2485 2486 2487 2488 2489 2490 2491 2492 2493
	/*
	 * 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);
	}
2494 2495
	root->mnt = vfsmnt;
	root->dentry = dentry;
2496
	goto out;
M
Miklos Szeredi 已提交
2497
}
2498

M
Miklos Szeredi 已提交
2499 2500 2501 2502
/**
 * __d_path - return the path of a dentry
 * @path: the dentry/vfsmount to report
 * @root: root vfsmnt/dentry (may be modified by this function)
2503
 * @buf: buffer to return value in
M
Miklos Szeredi 已提交
2504 2505
 * @buflen: buffer length
 *
2506
 * Convert a dentry into an ASCII path name.
M
Miklos Szeredi 已提交
2507 2508 2509 2510
 *
 * Returns a pointer into the buffer or an error code if the
 * path was too long.
 *
2511
 * "buflen" should be positive.
M
Miklos Szeredi 已提交
2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522
 *
 * 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);
2523
	write_seqlock(&rename_lock);
M
Miklos Szeredi 已提交
2524
	error = prepend_path(path, root, &res, &buflen);
2525
	write_sequnlock(&rename_lock);
2526

M
Miklos Szeredi 已提交
2527 2528 2529
	if (error)
		return ERR_PTR(error);
	return res;
L
Linus Torvalds 已提交
2530 2531
}

2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547
/*
 * 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);
}

2548 2549 2550 2551 2552
static int prepend_unreachable(char **buffer, int *buflen)
{
	return prepend(buffer, buflen, "(unreachable)", 13);
}

J
Jan Blunck 已提交
2553 2554
/**
 * d_path - return the path of a dentry
2555
 * @path: path to report
J
Jan Blunck 已提交
2556 2557 2558 2559 2560 2561
 * @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.
 *
2562 2563 2564 2565
 * 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
2566
 *
2567
 * "buflen" should be positive.
J
Jan Blunck 已提交
2568
 */
2569
char *d_path(const struct path *path, char *buf, int buflen)
L
Linus Torvalds 已提交
2570
{
2571
	char *res = buf + buflen;
J
Jan Blunck 已提交
2572
	struct path root;
2573
	struct path tmp;
2574
	int error;
L
Linus Torvalds 已提交
2575

2576 2577 2578 2579 2580 2581 2582
	/*
	 * 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:
	 */
2583 2584
	if (path->dentry->d_op && path->dentry->d_op->d_dname)
		return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
2585

2586
	get_fs_root(current->fs, &root);
2587
	write_seqlock(&rename_lock);
2588
	tmp = root;
2589 2590 2591
	error = path_with_deleted(path, &tmp, &res, &buflen);
	if (error)
		res = ERR_PTR(error);
2592
	write_sequnlock(&rename_lock);
J
Jan Blunck 已提交
2593
	path_put(&root);
L
Linus Torvalds 已提交
2594 2595
	return res;
}
2596
EXPORT_SYMBOL(d_path);
L
Linus Torvalds 已提交
2597

2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617
/**
 * 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);
2618
	write_seqlock(&rename_lock);
2619 2620 2621 2622
	tmp = root;
	error = path_with_deleted(path, &tmp, &res, &buflen);
	if (!error && !path_equal(&tmp, &root))
		error = prepend_unreachable(&res, &buflen);
2623
	write_sequnlock(&rename_lock);
2624 2625 2626 2627 2628 2629 2630
	path_put(&root);
	if (error)
		res =  ERR_PTR(error);

	return res;
}

2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651
/*
 * 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);
}

2652 2653 2654
/*
 * Write full pathname from the root of the filesystem into the buffer.
 */
N
Nick Piggin 已提交
2655
static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666
{
	char *end = buf + buflen;
	char *retval;

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

2667 2668
	while (!IS_ROOT(dentry)) {
		struct dentry *parent = dentry->d_parent;
N
Nick Piggin 已提交
2669
		int error;
2670 2671

		prefetch(parent);
N
Nick Piggin 已提交
2672 2673 2674 2675
		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)
2676 2677 2678 2679 2680
			goto Elong;

		retval = end;
		dentry = parent;
	}
A
Al Viro 已提交
2681 2682 2683 2684
	return retval;
Elong:
	return ERR_PTR(-ENAMETOOLONG);
}
N
Nick Piggin 已提交
2685 2686 2687 2688 2689

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

2690
	write_seqlock(&rename_lock);
N
Nick Piggin 已提交
2691
	retval = __dentry_path(dentry, buf, buflen);
2692
	write_sequnlock(&rename_lock);
N
Nick Piggin 已提交
2693 2694 2695 2696

	return retval;
}
EXPORT_SYMBOL(dentry_path_raw);
A
Al Viro 已提交
2697 2698 2699 2700 2701 2702

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

2703
	write_seqlock(&rename_lock);
A
Al Viro 已提交
2704 2705 2706 2707 2708 2709 2710
	if (d_unlinked(dentry)) {
		p = buf + buflen;
		if (prepend(&p, &buflen, "//deleted", 10) != 0)
			goto Elong;
		buflen++;
	}
	retval = __dentry_path(dentry, buf, buflen);
2711
	write_sequnlock(&rename_lock);
A
Al Viro 已提交
2712 2713
	if (!IS_ERR(retval) && p)
		*p = '/';	/* restore '/' overriden with '\0' */
2714 2715 2716 2717 2718
	return retval;
Elong:
	return ERR_PTR(-ENAMETOOLONG);
}

L
Linus Torvalds 已提交
2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736
/*
 * 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;
 *	}
 */
2737
SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
L
Linus Torvalds 已提交
2738
{
2739
	int error;
J
Jan Blunck 已提交
2740
	struct path pwd, root;
2741
	char *page = (char *) __get_free_page(GFP_USER);
L
Linus Torvalds 已提交
2742 2743 2744 2745

	if (!page)
		return -ENOMEM;

2746
	get_fs_root_and_pwd(current->fs, &root, &pwd);
L
Linus Torvalds 已提交
2747

2748
	error = -ENOENT;
2749
	write_seqlock(&rename_lock);
2750
	if (!d_unlinked(pwd.dentry)) {
2751
		unsigned long len;
2752
		struct path tmp = root;
2753 2754
		char *cwd = page + PAGE_SIZE;
		int buflen = PAGE_SIZE;
L
Linus Torvalds 已提交
2755

2756 2757
		prepend(&cwd, &buflen, "\0", 1);
		error = prepend_path(&pwd, &tmp, &cwd, &buflen);
2758
		write_sequnlock(&rename_lock);
2759

2760
		if (error)
2761 2762
			goto out;

2763 2764 2765 2766 2767 2768 2769
		/* Unreachable from current root */
		if (!path_equal(&tmp, &root)) {
			error = prepend_unreachable(&cwd, &buflen);
			if (error)
				goto out;
		}

2770 2771 2772 2773 2774 2775 2776
		error = -ERANGE;
		len = PAGE_SIZE + page - cwd;
		if (len <= size) {
			error = len;
			if (copy_to_user(buf, cwd, len))
				error = -EFAULT;
		}
2777 2778 2779
	} else {
		write_sequnlock(&rename_lock);
	}
L
Linus Torvalds 已提交
2780 2781

out:
J
Jan Blunck 已提交
2782 2783
	path_put(&pwd);
	path_put(&root);
L
Linus Torvalds 已提交
2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803
	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()
 */
  
2804
int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
L
Linus Torvalds 已提交
2805 2806
{
	int result;
2807
	unsigned seq;
L
Linus Torvalds 已提交
2808

2809 2810 2811 2812
	if (new_dentry == old_dentry)
		return 1;

	do {
L
Linus Torvalds 已提交
2813 2814
		/* for restarting inner loop in case of seq retry */
		seq = read_seqbegin(&rename_lock);
2815 2816 2817 2818 2819
		/*
		 * Need rcu_readlock to protect against the d_parent trashing
		 * due to d_move
		 */
		rcu_read_lock();
2820
		if (d_ancestor(old_dentry, new_dentry))
L
Linus Torvalds 已提交
2821
			result = 1;
2822 2823
		else
			result = 0;
2824
		rcu_read_unlock();
L
Linus Torvalds 已提交
2825 2826 2827 2828 2829
	} while (read_seqretry(&rename_lock, seq));

	return result;
}

2830 2831 2832 2833 2834
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
2835 2836

	br_read_lock(vfsmount_lock);
2837 2838 2839
	if (mnt != path2->mnt) {
		for (;;) {
			if (mnt->mnt_parent == mnt) {
N
Nick Piggin 已提交
2840
				br_read_unlock(vfsmount_lock);
2841 2842 2843 2844 2845 2846 2847 2848 2849
				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
2850
	br_read_unlock(vfsmount_lock);
2851 2852 2853 2854
	return res;
}
EXPORT_SYMBOL(path_is_under);

L
Linus Torvalds 已提交
2855 2856
void d_genocide(struct dentry *root)
{
2857
	struct dentry *this_parent;
L
Linus Torvalds 已提交
2858
	struct list_head *next;
2859
	unsigned seq;
2860
	int locked = 0;
L
Linus Torvalds 已提交
2861

2862
	seq = read_seqbegin(&rename_lock);
2863 2864
again:
	this_parent = root;
N
Nick Piggin 已提交
2865
	spin_lock(&this_parent->d_lock);
L
Linus Torvalds 已提交
2866 2867 2868 2869 2870
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
2871
		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
L
Linus Torvalds 已提交
2872
		next = tmp->next;
2873

N
Nick Piggin 已提交
2874 2875 2876
		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
2877
			continue;
N
Nick Piggin 已提交
2878
		}
L
Linus Torvalds 已提交
2879
		if (!list_empty(&dentry->d_subdirs)) {
N
Nick Piggin 已提交
2880 2881
			spin_unlock(&this_parent->d_lock);
			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
L
Linus Torvalds 已提交
2882
			this_parent = dentry;
N
Nick Piggin 已提交
2883
			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
L
Linus Torvalds 已提交
2884 2885
			goto repeat;
		}
2886 2887 2888 2889
		if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
			dentry->d_flags |= DCACHE_GENOCIDE;
			dentry->d_count--;
		}
N
Nick Piggin 已提交
2890
		spin_unlock(&dentry->d_lock);
L
Linus Torvalds 已提交
2891 2892
	}
	if (this_parent != root) {
2893
		struct dentry *child = this_parent;
2894 2895 2896 2897
		if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
			this_parent->d_flags |= DCACHE_GENOCIDE;
			this_parent->d_count--;
		}
2898 2899
		this_parent = try_to_ascend(this_parent, locked, seq);
		if (!this_parent)
2900 2901
			goto rename_retry;
		next = child->d_u.d_child.next;
L
Linus Torvalds 已提交
2902 2903
		goto resume;
	}
N
Nick Piggin 已提交
2904
	spin_unlock(&this_parent->d_lock);
2905
	if (!locked && read_seqretry(&rename_lock, seq))
2906
		goto rename_retry;
2907 2908 2909 2910 2911 2912 2913 2914
	if (locked)
		write_sequnlock(&rename_lock);
	return;

rename_retry:
	locked = 1;
	write_seqlock(&rename_lock);
	goto again;
L
Linus Torvalds 已提交
2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935
}

/**
 * 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;

2936 2937
	dentry = d_hash_and_lookup(dir, name);
	if (dentry) {
L
Linus Torvalds 已提交
2938 2939 2940 2941 2942 2943
		if (dentry->d_inode)
			ino = dentry->d_inode->i_ino;
		dput(dentry);
	}
	return ino;
}
2944
EXPORT_SYMBOL(find_inode_number);
L
Linus Torvalds 已提交
2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967

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",
2968
					sizeof(struct hlist_bl_head),
L
Linus Torvalds 已提交
2969 2970 2971 2972 2973 2974 2975 2976
					dhash_entries,
					13,
					HASH_EARLY,
					&d_hash_shift,
					&d_hash_mask,
					0);

	for (loop = 0; loop < (1 << d_hash_shift); loop++)
2977
		INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
L
Linus Torvalds 已提交
2978 2979
}

2980
static void __init dcache_init(void)
L
Linus Torvalds 已提交
2981 2982 2983 2984 2985 2986 2987 2988
{
	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. 
	 */
2989 2990
	dentry_cache = KMEM_CACHE(dentry,
		SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
L
Linus Torvalds 已提交
2991 2992 2993 2994 2995 2996 2997

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

	dentry_hashtable =
		alloc_large_system_hash("Dentry cache",
2998
					sizeof(struct hlist_bl_head),
L
Linus Torvalds 已提交
2999 3000 3001 3002 3003 3004 3005 3006
					dhash_entries,
					13,
					0,
					&d_hash_shift,
					&d_hash_mask,
					0);

	for (loop = 0; loop < (1 << d_hash_shift); loop++)
3007
		INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
L
Linus Torvalds 已提交
3008 3009 3010
}

/* SLAB cache for __getname() consumers */
3011
struct kmem_cache *names_cachep __read_mostly;
3012
EXPORT_SYMBOL(names_cachep);
L
Linus Torvalds 已提交
3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032

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,
3033
			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
L
Linus Torvalds 已提交
3034

3035 3036
	dcache_init();
	inode_init();
L
Linus Torvalds 已提交
3037
	files_init(mempages);
3038
	mnt_init();
L
Linus Torvalds 已提交
3039 3040 3041
	bdev_cache_init();
	chrdev_init();
}