initial_commit

1 files changed, 3124 insertions, 0 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
new file mode 100644
index 00000000..0b51cfc9
--- /dev/null
+++ b/fs/dcache.c
@@ -0,0 +1,3124 @@
+/*
+ * 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>
+#include <linux/fsnotify.h>
+#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>
+#include <linux/fs_struct.h>
+#include <linux/hardirq.h>
+#include <linux/bit_spinlock.h>
+#include <linux/rculist_bl.h>
+#include <linux/prefetch.h>
+#include "internal.h"
+
+/*
+ * Usage:
+ * dcache->d_inode->i_lock protects:
+ *   - i_dentry, d_alias, d_inode of aliases
+ * dcache_hash_bucket lock protects:
+ *   - the dcache hash table
+ * s_anon bl list spinlock protects:
+ *   - the s_anon list (see __d_drop)
+ * dcache_lru_lock protects:
+ *   - the dcache lru lists and counters
+ * d_lock protects:
+ *   - d_flags
+ *   - d_name
+ *   - d_lru
+ *   - d_count
+ *   - d_unhashed()
+ *   - d_parent and d_subdirs
+ *   - childrens' d_child and d_parent
+ *   - d_alias, d_inode
+ *
+ * Ordering:
+ * dentry->d_inode->i_lock
+ *   dentry->d_lock
+ *     dcache_lru_lock
+ *     dcache_hash_bucket lock
+ *     s_anon lock
+ *
+ * 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:
+ * if (dentry1 < dentry2)
+ *   dentry1->d_lock
+ *     dentry2->d_lock
+ */
+int sysctl_vfs_cache_pressure __read_mostly = 100;
+EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
+
+static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
+__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
+
+EXPORT_SYMBOL(rename_lock);
+
+static struct kmem_cache *dentry_cache __read_mostly;
+
+/*
+ * 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
+
+static unsigned int d_hash_mask __read_mostly;
+static unsigned int d_hash_shift __read_mostly;
+
+static struct hlist_bl_head *dentry_hashtable __read_mostly;
+
+static inline struct hlist_bl_head *d_hash(struct dentry *parent,
+					unsigned long hash)
+{
+	hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
+	hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
+	return dentry_hashtable + (hash & D_HASHMASK);
+}
+
+/* Statistics gathering. */
+struct dentry_stat_t dentry_stat = {
+	.age_limit = 45,
+};
+
+static DEFINE_PER_CPU(unsigned int, nr_dentry);
+
+#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
+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;
+}
+
+int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
+		   size_t *lenp, loff_t *ppos)
+{
+	dentry_stat.nr_dentry = get_nr_dentry();
+	return proc_dointvec(table, write, buffer, lenp, ppos);
+}
+#endif
+
+static void __d_free(struct rcu_head *head)
+{
+	struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
+
+	WARN_ON(!list_empty(&dentry->d_alias));
+	if (dname_external(dentry))
+		kfree(dentry->d_name.name);
+	kmem_cache_free(dentry_cache, dentry); 
+}
+
+/*
+ * no locks, please.
+ */
+static void d_free(struct dentry *dentry)
+{
+	BUG_ON(dentry->d_count);
+	this_cpu_dec(nr_dentry);
+	if (dentry->d_op && dentry->d_op->d_release)
+		dentry->d_op->d_release(dentry);
+
+	/* if dentry was never visible to RCU, immediate free is OK */
+	if (!(dentry->d_flags & DCACHE_RCUACCESS))
+		__d_free(&dentry->d_u.d_rcu);
+	else
+		call_rcu(&dentry->d_u.d_rcu, __d_free);
+}
+
+/**
+ * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
+ * @dentry: the target dentry
+ * 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);
+}
+
+/*
+ * Release the dentry's inode, using the filesystem
+ * d_iput() operation if defined. Dentry has no refcount
+ * and is unhashed.
+ */
+static void dentry_iput(struct dentry * dentry)
+	__releases(dentry->d_lock)
+	__releases(dentry->d_inode->i_lock)
+{
+	struct inode *inode = dentry->d_inode;
+	if (inode) {
+		dentry->d_inode = NULL;
+		list_del_init(&dentry->d_alias);
+		spin_unlock(&dentry->d_lock);
+		spin_unlock(&inode->i_lock);
+		if (!inode->i_nlink)
+			fsnotify_inoderemove(inode);
+		if (dentry->d_op && dentry->d_op->d_iput)
+			dentry->d_op->d_iput(dentry, inode);
+		else
+			iput(inode);
+	} else {
+		spin_unlock(&dentry->d_lock);
+	}
+}
+
+/*
+ * Release the dentry's inode, using the filesystem
+ * d_iput() operation if defined. dentry remains in-use.
+ */
+static void dentry_unlink_inode(struct dentry * dentry)
+	__releases(dentry->d_lock)
+	__releases(dentry->d_inode->i_lock)
+{
+	struct inode *inode = dentry->d_inode;
+	dentry->d_inode = NULL;
+	list_del_init(&dentry->d_alias);
+	dentry_rcuwalk_barrier(dentry);
+	spin_unlock(&dentry->d_lock);
+	spin_unlock(&inode->i_lock);
+	if (!inode->i_nlink)
+		fsnotify_inoderemove(inode);
+	if (dentry->d_op && dentry->d_op->d_iput)
+		dentry->d_op->d_iput(dentry, inode);
+	else
+		iput(inode);
+}
+
+/*
+ * dentry_lru_(add|del|move_tail) must be called with d_lock held.
+ */
+static void dentry_lru_add(struct dentry *dentry)
+{
+	if (list_empty(&dentry->d_lru)) {
+		spin_lock(&dcache_lru_lock);
+		list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
+		dentry->d_sb->s_nr_dentry_unused++;
+		dentry_stat.nr_unused++;
+		spin_unlock(&dcache_lru_lock);
+	}
+}
+
+static void __dentry_lru_del(struct dentry *dentry)
+{
+	list_del_init(&dentry->d_lru);
+	dentry->d_flags &= ~DCACHE_SHRINK_LIST;
+	dentry->d_sb->s_nr_dentry_unused--;
+	dentry_stat.nr_unused--;
+}
+
+static void dentry_lru_del(struct dentry *dentry)
+{
+	if (!list_empty(&dentry->d_lru)) {
+		spin_lock(&dcache_lru_lock);
+		__dentry_lru_del(dentry);
+		spin_unlock(&dcache_lru_lock);
+	}
+}
+
+static void dentry_lru_move_tail(struct dentry *dentry)
+{
+	spin_lock(&dcache_lru_lock);
+	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++;
+		dentry_stat.nr_unused++;
+	} else {
+		list_move_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
+	}
+	spin_unlock(&dcache_lru_lock);
+}
+
+/**
+ * d_kill - kill dentry and return parent
+ * @dentry: dentry to kill
+ * @parent: parent dentry
+ *
+ * The dentry must already be unhashed and removed from the LRU.
+ *
+ * If this is the root of the dentry tree, return NULL.
+ *
+ * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
+ * d_kill.
+ */
+static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
+	__releases(dentry->d_lock)
+	__releases(parent->d_lock)
+	__releases(dentry->d_inode->i_lock)
+{
+	list_del(&dentry->d_u.d_child);
+	/*
+	 * Inform try_to_ascend() that we are no longer attached to the
+	 * dentry tree
+	 */
+	dentry->d_flags |= DCACHE_DISCONNECTED;
+	if (parent)
+		spin_unlock(&parent->d_lock);
+	dentry_iput(dentry);
+	/*
+	 * dentry_iput drops the locks, at which point nobody (except
+	 * transient RCU lookups) can reach this dentry.
+	 */
+	d_free(dentry);
+	return parent;
+}
+
+/**
+ * d_drop - drop a dentry
+ * @dentry: dentry to drop
+ *
+ * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
+ * be found through a VFS lookup any more. Note that this is different from
+ * deleting the dentry - d_delete will try to mark the dentry negative if
+ * possible, giving a successful _negative_ lookup, while d_drop will
+ * just make the cache lookup fail.
+ *
+ * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
+ * reason (NFS timeouts or autofs deletes).
+ *
+ * __d_drop requires dentry->d_lock.
+ */
+void __d_drop(struct dentry *dentry)
+{
+	if (!d_unhashed(dentry)) {
+		struct hlist_bl_head *b;
+		if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
+			b = &dentry->d_sb->s_anon;
+		else
+			b = d_hash(dentry->d_parent, dentry->d_name.hash);
+
+		hlist_bl_lock(b);
+		__hlist_bl_del(&dentry->d_hash);
+		dentry->d_hash.pprev = NULL;
+		hlist_bl_unlock(b);
+
+		dentry_rcuwalk_barrier(dentry);
+	}
+}
+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);
+
+/*
+ * Finish off a dentry we've decided to kill.
+ * dentry->d_lock must be held, returns with it unlocked.
+ * If ref is non-zero, then decrement the refcount too.
+ * Returns dentry requiring refcount drop, or NULL if we're done.
+ */
+static inline struct dentry *dentry_kill(struct dentry *dentry, int ref)
+	__releases(dentry->d_lock)
+{
+	struct inode *inode;
+	struct dentry *parent;
+
+	inode = dentry->d_inode;
+	if (inode && !spin_trylock(&inode->i_lock)) {
+relock:
+		spin_unlock(&dentry->d_lock);
+		cpu_relax();
+		return dentry; /* try again with same dentry */
+	}
+	if (IS_ROOT(dentry))
+		parent = NULL;
+	else
+		parent = dentry->d_parent;
+	if (parent && !spin_trylock(&parent->d_lock)) {
+		if (inode)
+			spin_unlock(&inode->i_lock);
+		goto relock;
+	}
+
+	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);
+}
+
+/* 
+ * 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:
+	if (dentry->d_count == 1)
+		might_sleep();
+	spin_lock(&dentry->d_lock);
+	BUG_ON(!dentry->d_count);
+	if (dentry->d_count > 1) {
+		dentry->d_count--;
+		spin_unlock(&dentry->d_lock);
+		return;
+	}
+
+	if (dentry->d_flags & DCACHE_OP_DELETE) {
+		if (dentry->d_op->d_delete(dentry))
+			goto kill_it;
+	}
+
+	/* Unreachable? Get rid of it */
+ 	if (d_unhashed(dentry))
+		goto kill_it;
+
+	/* Otherwise leave it cached and ensure it's on the LRU */
+	dentry->d_flags |= DCACHE_REFERENCED;
+	dentry_lru_add(dentry);
+
+	dentry->d_count--;
+	spin_unlock(&dentry->d_lock);
+	return;
+
+kill_it:
+	dentry = dentry_kill(dentry, 1);
+	if (dentry)
+		goto repeat;
+}
+EXPORT_SYMBOL(dput);
+
+/**
+ * d_invalidate - invalidate a dentry
+ * @dentry: dentry to invalidate
+ *
+ * Try to invalidate the dentry if it turns out to be
+ * possible. If there are other dentries that can be
+ * reached through this one we can't delete it and we
+ * return -EBUSY. On success we return 0.
+ *
+ * no dcache lock.
+ */
+ 
+int d_invalidate(struct dentry * dentry)
+{
+	/*
+	 * If it's already been dropped, return OK.
+	 */
+	spin_lock(&dentry->d_lock);
+	if (d_unhashed(dentry)) {
+		spin_unlock(&dentry->d_lock);
+		return 0;
+	}
+	/*
+	 * Check whether to do a partial shrink_dcache
+	 * to get rid of unused child entries.
+	 */
+	if (!list_empty(&dentry->d_subdirs)) {
+		spin_unlock(&dentry->d_lock);
+		shrink_dcache_parent(dentry);
+		spin_lock(&dentry->d_lock);
+	}
+
+	/*
+	 * Somebody else still using it?
+	 *
+	 * If it's a directory, we can't drop it
+	 * for fear of somebody re-populating it
+	 * with children (even though dropping it
+	 * would make it unreachable from the root,
+	 * we might still populate it if it was a
+	 * working directory or similar).
+	 */
+	if (dentry->d_count > 1) {
+		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;
+}
+EXPORT_SYMBOL(d_invalidate);
+
+/* This must be called with d_lock held */
+static inline void __dget_dlock(struct dentry *dentry)
+{
+	dentry->d_count++;
+}
+
+static inline void __dget(struct dentry *dentry)
+{
+	spin_lock(&dentry->d_lock);
+	__dget_dlock(dentry);
+	spin_unlock(&dentry->d_lock);
+}
+
+struct dentry *dget_parent(struct dentry *dentry)
+{
+	struct dentry *ret;
+
+repeat:
+	/*
+	 * Don't need rcu_dereference because we re-check it was correct under
+	 * the lock.
+	 */
+	rcu_read_lock();
+	ret = dentry->d_parent;
+	if (!ret) {
+		rcu_read_unlock();
+		goto out;
+	}
+	spin_lock(&ret->d_lock);
+	if (unlikely(ret != dentry->d_parent)) {
+		spin_unlock(&ret->d_lock);
+		rcu_read_unlock();
+		goto repeat;
+	}
+	rcu_read_unlock();
+	BUG_ON(!ret->d_count);
+	ret->d_count++;
+	spin_unlock(&ret->d_lock);
+out:
+	return ret;
+}
+EXPORT_SYMBOL(dget_parent);
+
+/**
+ * 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.
+ *
+ * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
+ * any other hashed alias over that one unless @want_discon is set,
+ * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
+ */
+static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
+{
+	struct dentry *alias, *discon_alias;
+
+again:
+	discon_alias = NULL;
+	list_for_each_entry(alias, &inode->i_dentry, d_alias) {
+		spin_lock(&alias->d_lock);
+ 		if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
+			if (IS_ROOT(alias) &&
+			    (alias->d_flags & DCACHE_DISCONNECTED)) {
+				discon_alias = alias;
+			} else if (!want_discon) {
+				__dget_dlock(alias);
+				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)) {
+				__dget_dlock(alias);
+				spin_unlock(&alias->d_lock);
+				return alias;
+			}
+		}
+		spin_unlock(&alias->d_lock);
+		goto again;
+	}
+	return NULL;
+}
+
+struct dentry *d_find_alias(struct inode *inode)
+{
+	struct dentry *de = NULL;
+
+	if (!list_empty(&inode->i_dentry)) {
+		spin_lock(&inode->i_lock);
+		de = __d_find_alias(inode, 0);
+		spin_unlock(&inode->i_lock);
+	}
+	return de;
+}
+EXPORT_SYMBOL(d_find_alias);
+
+/*
+ *	Try to kill dentries associated with this inode.
+ * WARNING: you must own a reference to inode.
+ */
+void d_prune_aliases(struct inode *inode)
+{
+	struct dentry *dentry;
+restart:
+	spin_lock(&inode->i_lock);
+	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
+		spin_lock(&dentry->d_lock);
+		if (!dentry->d_count) {
+			__dget_dlock(dentry);
+			__d_drop(dentry);
+			spin_unlock(&dentry->d_lock);
+			spin_unlock(&inode->i_lock);
+			dput(dentry);
+			goto restart;
+		}
+		spin_unlock(&dentry->d_lock);
+	}
+	spin_unlock(&inode->i_lock);
+}
+EXPORT_SYMBOL(d_prune_aliases);
+
+/*
+ * 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.
+ *
+ * This may fail if locks cannot be acquired no problem, just try again.
+ */
+static void try_prune_one_dentry(struct dentry *dentry)
+	__releases(dentry->d_lock)
+{
+	struct dentry *parent;
+
+	parent = dentry_kill(dentry, 0);
+	/*
+	 * 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.
+	 */
+	if (!parent)
+		return;
+	if (parent == dentry)
+		return;
+
+	/* Prune ancestors. */
+	dentry = parent;
+	while (dentry) {
+		spin_lock(&dentry->d_lock);
+		if (dentry->d_count > 1) {
+			dentry->d_count--;
+			spin_unlock(&dentry->d_lock);
+			return;
+		}
+		dentry = dentry_kill(dentry, 1);
+	}
+}
+
+static void shrink_dentry_list(struct list_head *list)
+{
+	struct dentry *dentry;
+
+	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);
+			continue;
+		}
+
+		/*
+		 * We found an inuse dentry which was not removed from
+		 * the LRU because of laziness during lookup.  Do not free
+		 * it - just keep it off the LRU list.
+		 */
+		if (dentry->d_count) {
+			dentry_lru_del(dentry);
+			spin_unlock(&dentry->d_lock);
+			continue;
+		}
+
+		rcu_read_unlock();
+
+		try_prune_one_dentry(dentry);
+
+		rcu_read_lock();
+	}
+	rcu_read_unlock();
+}
+
+/**
+ * __shrink_dcache_sb - shrink the dentry LRU on a given superblock
+ * @sb:		superblock to shrink dentry LRU.
+ * @count:	number of entries to prune
+ * @flags:	flags to control the dentry processing
+ *
+ * If flags contains DCACHE_REFERENCED reference dentries will not be pruned.
+ */
+static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
+{
+	/* called from prune_dcache() and shrink_dcache_parent() */
+	struct dentry *dentry;
+	LIST_HEAD(referenced);
+	LIST_HEAD(tmp);
+	int cnt = *count;
+
+relock:
+	spin_lock(&dcache_lru_lock);
+	while (!list_empty(&sb->s_dentry_lru)) {
+		dentry = list_entry(sb->s_dentry_lru.prev,
+				struct dentry, d_lru);
+		BUG_ON(dentry->d_sb != sb);
+
+		if (!spin_trylock(&dentry->d_lock)) {
+			spin_unlock(&dcache_lru_lock);
+			cpu_relax();
+			goto relock;
+		}
+
+		/*
+		 * If we are honouring the DCACHE_REFERENCED flag and the
+		 * dentry has this flag set, don't free it.  Clear the flag
+		 * and put it back on the LRU.
+		 */
+		if (flags & DCACHE_REFERENCED &&
+				dentry->d_flags & DCACHE_REFERENCED) {
+			dentry->d_flags &= ~DCACHE_REFERENCED;
+			list_move(&dentry->d_lru, &referenced);
+			spin_unlock(&dentry->d_lock);
+		} else {
+			list_move_tail(&dentry->d_lru, &tmp);
+			dentry->d_flags |= DCACHE_SHRINK_LIST;
+			spin_unlock(&dentry->d_lock);
+			if (!--cnt)
+				break;
+		}
+		cond_resched_lock(&dcache_lru_lock);
+	}
+	if (!list_empty(&referenced))
+		list_splice(&referenced, &sb->s_dentry_lru);
+	spin_unlock(&dcache_lru_lock);
+
+	shrink_dentry_list(&tmp);
+
+	*count = cnt;
+}
+
+/**
+ * prune_dcache - shrink the dcache
+ * @count: number of entries to try to free
+ *
+ * Shrink the dcache. This is done when we need more memory, or simply when we
+ * need to unmount something (at which point we need to unuse all dentries).
+ *
+ * This function may fail to free any resources if all the dentries are in use.
+ */
+static void prune_dcache(int count)
+{
+	struct super_block *sb, *p = NULL;
+	int w_count;
+	int unused = dentry_stat.nr_unused;
+	int prune_ratio;
+	int pruned;
+
+	if (unused == 0 || count == 0)
+		return;
+	if (count >= unused)
+		prune_ratio = 1;
+	else
+		prune_ratio = unused / count;
+	spin_lock(&sb_lock);
+	list_for_each_entry(sb, &super_blocks, s_list) {
+		if (list_empty(&sb->s_instances))
+			continue;
+		if (sb->s_nr_dentry_unused == 0)
+			continue;
+		sb->s_count++;
+		/* Now, we reclaim unused dentrins with fairness.
+		 * We reclaim them same percentage from each superblock.
+		 * We calculate number of dentries to scan on this sb
+		 * as follows, but the implementation is arranged to avoid
+		 * overflows:
+		 * number of dentries to scan on this sb =
+		 * count * (number of dentries on this sb /
+		 * number of dentries in the machine)
+		 */
+		spin_unlock(&sb_lock);
+		if (prune_ratio != 1)
+			w_count = (sb->s_nr_dentry_unused / prune_ratio) + 1;
+		else
+			w_count = sb->s_nr_dentry_unused;
+		pruned = w_count;
+		/*
+		 * We need to be sure this filesystem isn't being unmounted,
+		 * otherwise we could race with generic_shutdown_super(), and
+		 * end up holding a reference to an inode while the filesystem
+		 * is unmounted.  So we try to get s_umount, and make sure
+		 * s_root isn't NULL.
+		 */
+		if (down_read_trylock(&sb->s_umount)) {
+			if ((sb->s_root != NULL) &&
+			    (!list_empty(&sb->s_dentry_lru))) {
+				__shrink_dcache_sb(sb, &w_count,
+						DCACHE_REFERENCED);
+				pruned -= w_count;
+			}
+			up_read(&sb->s_umount);
+		}
+		spin_lock(&sb_lock);
+		if (p)
+			__put_super(p);
+		count -= pruned;
+		p = sb;
+		/* more work left to do? */
+		if (count <= 0)
+			break;
+	}
+	if (p)
+		__put_super(p);
+	spin_unlock(&sb_lock);
+}
+
+/**
+ * shrink_dcache_sb - shrink dcache for a superblock
+ * @sb: superblock
+ *
+ * Shrink the dcache for the specified super block. This is used to free
+ * the dcache before unmounting a file system.
+ */
+void shrink_dcache_sb(struct super_block *sb)
+{
+	LIST_HEAD(tmp);
+
+	spin_lock(&dcache_lru_lock);
+	while (!list_empty(&sb->s_dentry_lru)) {
+		list_splice_init(&sb->s_dentry_lru, &tmp);
+		spin_unlock(&dcache_lru_lock);
+		shrink_dentry_list(&tmp);
+		spin_lock(&dcache_lru_lock);
+	}
+	spin_unlock(&dcache_lru_lock);
+}
+EXPORT_SYMBOL(shrink_dcache_sb);
+
+/*
+ * 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;
+	unsigned detached = 0;
+
+	BUG_ON(!IS_ROOT(dentry));
+
+	/* detach this root from the system */
+	spin_lock(&dentry->d_lock);
+	dentry_lru_del(dentry);
+	__d_drop(dentry);
+	spin_unlock(&dentry->d_lock);
+
+	for (;;) {
+		/* descend to the first leaf in the current subtree */
+		while (!list_empty(&dentry->d_subdirs)) {
+			struct dentry *loop;
+
+			/* this is a branch with children - detach all of them
+			 * from the system in one go */
+			spin_lock(&dentry->d_lock);
+			list_for_each_entry(loop, &dentry->d_subdirs,
+					    d_u.d_child) {
+				spin_lock_nested(&loop->d_lock,
+						DENTRY_D_LOCK_NESTED);
+				dentry_lru_del(loop);
+				__d_drop(loop);
+				spin_unlock(&loop->d_lock);
+			}
+			spin_unlock(&dentry->d_lock);
+
+			/* move to the first child */
+			dentry = list_entry(dentry->d_subdirs.next,
+					    struct dentry, d_u.d_child);
+		}
+
+		/* consume the dentries from this leaf up through its parents
+		 * until we find one with children or run out altogether */
+		do {
+			struct inode *inode;
+
+			if (dentry->d_count != 0) {
+				printk(KERN_ERR
+				       "BUG: Dentry %p{i=%lx,n=%s}"
+				       " still in use (%d)"
+				       " [unmount of %s %s]\n",
+				       dentry,
+				       dentry->d_inode ?
+				       dentry->d_inode->i_ino : 0UL,
+				       dentry->d_name.name,
+				       dentry->d_count,
+				       dentry->d_sb->s_type->name,
+				       dentry->d_sb->s_id);
+				BUG();
+			}
+
+			if (IS_ROOT(dentry)) {
+				parent = NULL;
+				list_del(&dentry->d_u.d_child);
+			} else {
+				parent = dentry->d_parent;
+				spin_lock(&parent->d_lock);
+				parent->d_count--;
+				list_del(&dentry->d_u.d_child);
+				spin_unlock(&parent->d_lock);
+			}
+
+			detached++;
+
+			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)
+				return;
+			dentry = parent;
+		} while (list_empty(&dentry->d_subdirs));
+
+		dentry = list_entry(dentry->d_subdirs.next,
+				    struct dentry, d_u.d_child);
+	}
+}
+
+/*
+ * destroy the dentries attached to a superblock on unmounting
+ * - we don't need to use dentry->d_lock because:
+ *   - the superblock is detached from all mountings and open files, so the
+ *     dentry trees will not be rearranged by the VFS
+ *   - s_umount is write-locked, so the memory pressure shrinker will ignore
+ *     any dentries belonging to this superblock that it comes across
+ *   - the filesystem itself is no longer permitted to rearrange the dentries
+ *     in this superblock
+ */
+void shrink_dcache_for_umount(struct super_block *sb)
+{
+	struct dentry *dentry;
+
+	if (down_read_trylock(&sb->s_umount))
+		BUG();
+
+	dentry = sb->s_root;
+	sb->s_root = NULL;
+	spin_lock(&dentry->d_lock);
+	dentry->d_count--;
+	spin_unlock(&dentry->d_lock);
+	shrink_dcache_for_umount_subtree(dentry);
+
+	while (!hlist_bl_empty(&sb->s_anon)) {
+		dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
+		shrink_dcache_for_umount_subtree(dentry);
+	}
+}
+
+/*
+ * 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 ||
+		 (old->d_flags & DCACHE_DISCONNECTED) ||
+		 (!locked && read_seqretry(&rename_lock, seq))) {
+		spin_unlock(&new->d_lock);
+		new = NULL;
+	}
+	rcu_read_unlock();
+	return new;
+}
+
+
+/*
+ * Search for at least 1 mount point in the dentry's subdirs.
+ * We descend to the next level whenever the d_subdirs
+ * list is non-empty and continue searching.
+ */
+ 
+/**
+ * have_submounts - check for mounts over a dentry
+ * @parent: dentry to check.
+ *
+ * Return true if the parent or its subdirectories contain
+ * a mount point
+ */
+int have_submounts(struct dentry *parent)
+{
+	struct dentry *this_parent;
+	struct list_head *next;
+	unsigned seq;
+	int locked = 0;
+
+	seq = read_seqbegin(&rename_lock);
+again:
+	this_parent = parent;
+
+	if (d_mountpoint(parent))
+		goto positive;
+	spin_lock(&this_parent->d_lock);
+repeat:
+	next = this_parent->d_subdirs.next;
+resume:
+	while (next != &this_parent->d_subdirs) {
+		struct list_head *tmp = next;
+		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
+		next = tmp->next;
+
+		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+		/* Have we found a mount point ? */
+		if (d_mountpoint(dentry)) {
+			spin_unlock(&dentry->d_lock);
+			spin_unlock(&this_parent->d_lock);
+			goto positive;
+		}
+		if (!list_empty(&dentry->d_subdirs)) {
+			spin_unlock(&this_parent->d_lock);
+			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
+			this_parent = dentry;
+			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
+			goto repeat;
+		}
+		spin_unlock(&dentry->d_lock);
+	}
+	/*
+	 * All done at this level ... ascend and resume the search.
+	 */
+	if (this_parent != parent) {
+		struct dentry *child = this_parent;
+		this_parent = try_to_ascend(this_parent, locked, seq);
+		if (!this_parent)
+			goto rename_retry;
+		next = child->d_u.d_child.next;
+		goto resume;
+	}
+	spin_unlock(&this_parent->d_lock);
+	if (!locked && read_seqretry(&rename_lock, seq))
+		goto rename_retry;
+	if (locked)
+		write_sequnlock(&rename_lock);
+	return 0; /* No mount points found in tree */
+positive:
+	if (!locked && read_seqretry(&rename_lock, seq))
+		goto rename_retry;
+	if (locked)
+		write_sequnlock(&rename_lock);
+	return 1;
+
+rename_retry:
+	locked = 1;
+	write_seqlock(&rename_lock);
+	goto again;
+}
+EXPORT_SYMBOL(have_submounts);
+
+/*
+ * Search the dentry child list for the specified parent,
+ * and move any unused dentries to the end of the unused
+ * list for prune_dcache(). We descend to the next level
+ * whenever the d_subdirs list is non-empty and continue
+ * searching.
+ *
+ * It returns zero iff there are no unused children,
+ * otherwise  it returns the number of children moved to
+ * the end of the unused list. This may not be the total
+ * number of unused children, because select_parent can
+ * drop the lock and return early due to latency
+ * constraints.
+ */
+static int select_parent(struct dentry * parent)
+{
+	struct dentry *this_parent;
+	struct list_head *next;
+	unsigned seq;
+	int found = 0;
+	int locked = 0;
+
+	seq = read_seqbegin(&rename_lock);
+again:
+	this_parent = parent;
+	spin_lock(&this_parent->d_lock);
+repeat:
+	next = this_parent->d_subdirs.next;
+resume:
+	while (next != &this_parent->d_subdirs) {
+		struct list_head *tmp = next;
+		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
+		next = tmp->next;
+
+		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+
+		/* 
+		 * move only zero ref count dentries to the end 
+		 * of the unused list for prune_dcache
+		 *
+		 * Those which are presently on the shrink list, being processed
+		 * by shrink_dentry_list(), shouldn't be moved.  Otherwise the
+		 * loop in shrink_dcache_parent() might not make any progress
+		 * and loop forever.
+		 */
+		if (dentry->d_count) {
+			dentry_lru_del(dentry);
+		} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
+			dentry_lru_move_tail(dentry);
+			found++;
+		}
+		/*
+		 * We can return to the caller if we have found some (this
+		 * ensures forward progress). We'll be coming back to find
+		 * the rest.
+		 */
+		if (found && need_resched()) {
+			spin_unlock(&dentry->d_lock);
+			goto out;
+		}
+
+		/*
+		 * Descend a level if the d_subdirs list is non-empty.
+		 */
+		if (!list_empty(&dentry->d_subdirs)) {
+			spin_unlock(&this_parent->d_lock);
+			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
+			this_parent = dentry;
+			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
+			goto repeat;
+		}
+
+		spin_unlock(&dentry->d_lock);
+	}
+	/*
+	 * All done at this level ... ascend and resume the search.
+	 */
+	if (this_parent != parent) {
+		struct dentry *child = this_parent;
+		this_parent = try_to_ascend(this_parent, locked, seq);
+		if (!this_parent)
+			goto rename_retry;
+		next = child->d_u.d_child.next;
+		goto resume;
+	}
+out:
+	spin_unlock(&this_parent->d_lock);
+	if (!locked && read_seqretry(&rename_lock, seq))
+		goto rename_retry;
+	if (locked)
+		write_sequnlock(&rename_lock);
+	return found;
+
+rename_retry:
+	if (found)
+		return found;
+	locked = 1;
+	write_seqlock(&rename_lock);
+	goto again;
+}
+
+/**
+ * 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)
+{
+	struct super_block *sb = parent->d_sb;
+	int found;
+
+	while ((found = select_parent(parent)) != 0)
+		__shrink_dcache_sb(sb, &found, 0);
+}
+EXPORT_SYMBOL(shrink_dcache_parent);
+
+/*
+ * Scan `sc->nr_slab_to_reclaim' dentries and return the number which remain.
+ *
+ * We need to avoid reentering the filesystem if the caller is performing a
+ * GFP_NOFS allocation attempt.  One example deadlock is:
+ *
+ * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
+ * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
+ * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
+ *
+ * In this case we return -1 to tell the caller that we baled.
+ */
+static int shrink_dcache_memory(struct shrinker *shrink,
+				struct shrink_control *sc)
+{
+	int nr = sc->nr_to_scan;
+	gfp_t gfp_mask = sc->gfp_mask;
+
+	if (nr) {
+		if (!(gfp_mask & __GFP_FS))
+			return -1;
+		prune_dcache(nr);
+	}
+
+	return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
+}
+
+static struct shrinker dcache_shrinker = {
+	.shrink = shrink_dcache_memory,
+	.seeks = DEFAULT_SEEKS,
+};
+
+/**
+ * d_alloc	-	allocate a dcache entry
+ * @parent: parent of entry to allocate
+ * @name: qstr of the name
+ *
+ * Allocates a dentry. It returns %NULL if there is insufficient memory
+ * available. On a success the dentry is returned. The name passed in is
+ * copied and the copy passed in may be reused after this call.
+ */
+ 
+struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
+{
+	struct dentry *dentry;
+	char *dname;
+
+	dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
+	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;
+
+	dentry->d_count = 1;
+	dentry->d_flags = 0;
+	spin_lock_init(&dentry->d_lock);
+	seqcount_init(&dentry->d_seq);
+	dentry->d_inode = NULL;
+	dentry->d_parent = NULL;
+	dentry->d_sb = NULL;
+	dentry->d_op = NULL;
+	dentry->d_fsdata = NULL;
+	INIT_HLIST_BL_NODE(&dentry->d_hash);
+	INIT_LIST_HEAD(&dentry->d_lru);
+	INIT_LIST_HEAD(&dentry->d_subdirs);
+	INIT_LIST_HEAD(&dentry->d_alias);
+	INIT_LIST_HEAD(&dentry->d_u.d_child);
+
+	if (parent) {
+		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;
+		dentry->d_sb = parent->d_sb;
+		d_set_d_op(dentry, dentry->d_sb->s_d_op);
+		list_add(&dentry->d_u.d_child, &parent->d_subdirs);
+		spin_unlock(&parent->d_lock);
+	}
+
+	this_cpu_inc(nr_dentry);
+
+	return dentry;
+}
+EXPORT_SYMBOL(d_alloc);
+
+struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
+{
+	struct dentry *dentry = d_alloc(NULL, name);
+	if (dentry) {
+		dentry->d_sb = sb;
+		d_set_d_op(dentry, dentry->d_sb->s_d_op);
+		dentry->d_parent = dentry;
+		dentry->d_flags |= DCACHE_DISCONNECTED;
+	}
+	return dentry;
+}
+EXPORT_SYMBOL(d_alloc_pseudo);
+
+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);
+}
+EXPORT_SYMBOL(d_alloc_name);
+
+void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
+{
+	WARN_ON_ONCE(dentry->d_op);
+	WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH	|
+				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);
+
+static void __d_instantiate(struct dentry *dentry, struct inode *inode)
+{
+	spin_lock(&dentry->d_lock);
+	if (inode) {
+		if (unlikely(IS_AUTOMOUNT(inode)))
+			dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
+		list_add(&dentry->d_alias, &inode->i_dentry);
+	}
+	dentry->d_inode = inode;
+	dentry_rcuwalk_barrier(dentry);
+	spin_unlock(&dentry->d_lock);
+	fsnotify_d_instantiate(dentry, inode);
+}
+
+/**
+ * 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)
+{
+	BUG_ON(!list_empty(&entry->d_alias));
+	if (inode)
+		spin_lock(&inode->i_lock);
+	__d_instantiate(entry, inode);
+	if (inode)
+		spin_unlock(&inode->i_lock);
+	security_d_instantiate(entry, inode);
+}
+EXPORT_SYMBOL(d_instantiate);
+
+/**
+ * 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
+ * aliased dentry instead and drop one reference to inode.
+ *
+ * Note that in order to avoid conflicts with rename() etc, the caller
+ * had better be holding the parent directory semaphore.
+ *
+ * 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.
+ */
+static struct dentry *__d_instantiate_unique(struct dentry *entry,
+					     struct inode *inode)
+{
+	struct dentry *alias;
+	int len = entry->d_name.len;
+	const char *name = entry->d_name.name;
+	unsigned int hash = entry->d_name.hash;
+
+	if (!inode) {
+		__d_instantiate(entry, NULL);
+		return NULL;
+	}
+
+	list_for_each_entry(alias, &inode->i_dentry, d_alias) {
+		struct qstr *qstr = &alias->d_name;
+
+		/*
+		 * 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.
+		 */
+		if (qstr->hash != hash)
+			continue;
+		if (alias->d_parent != entry->d_parent)
+			continue;
+		if (dentry_cmp(qstr->name, qstr->len, name, len))
+			continue;
+		__dget(alias);
+		return alias;
+	}
+
+	__d_instantiate(entry, inode);
+	return NULL;
+}
+
+struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
+{
+	struct dentry *result;
+
+	BUG_ON(!list_empty(&entry->d_alias));
+
+	if (inode)
+		spin_lock(&inode->i_lock);
+	result = __d_instantiate_unique(entry, inode);
+	if (inode)
+		spin_unlock(&inode->i_lock);
+
+	if (!result) {
+		security_d_instantiate(entry, inode);
+		return NULL;
+	}
+
+	BUG_ON(!d_unhashed(result));
+	iput(inode);
+	return result;
+}
+
+EXPORT_SYMBOL(d_instantiate_unique);
+
+/**
+ * d_alloc_root - allocate root dentry
+ * @root_inode: inode to allocate the root for
+ *
+ * Allocate a root ("/") dentry for the inode given. The inode is
+ * instantiated and returned. %NULL is returned if there is insufficient
+ * memory or the inode passed is %NULL.
+ */
+ 
+struct dentry * d_alloc_root(struct inode * root_inode)
+{
+	struct dentry *res = NULL;
+
+	if (root_inode) {
+		static const struct qstr name = { .name = "/", .len = 1 };
+
+		res = d_alloc(NULL, &name);
+		if (res) {
+			res->d_sb = root_inode->i_sb;
+			d_set_d_op(res, res->d_sb->s_d_op);
+			res->d_parent = res;
+			d_instantiate(res, root_inode);
+		}
+	}
+	return res;
+}
+EXPORT_SYMBOL(d_alloc_root);
+
+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;
+}
+
+
+/**
+ * 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
+ * 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).
+ */
+struct dentry *d_obtain_alias(struct inode *inode)
+{
+	static const struct qstr anonstring = { .name = "" };
+	struct dentry *tmp;
+	struct dentry *res;
+
+	if (!inode)
+		return ERR_PTR(-ESTALE);
+	if (IS_ERR(inode))
+		return ERR_CAST(inode);
+
+	res = d_find_any_alias(inode);
+	if (res)
+		goto out_iput;
+
+	tmp = d_alloc(NULL, &anonstring);
+	if (!tmp) {
+		res = ERR_PTR(-ENOMEM);
+		goto out_iput;
+	}
+	tmp->d_parent = tmp; /* make sure dput doesn't croak */
+
+
+	spin_lock(&inode->i_lock);
+	res = __d_find_any_alias(inode);
+	if (res) {
+		spin_unlock(&inode->i_lock);
+		dput(tmp);
+		goto out_iput;
+	}
+
+	/* attach a disconnected dentry */
+	spin_lock(&tmp->d_lock);
+	tmp->d_sb = inode->i_sb;
+	d_set_d_op(tmp, tmp->d_sb->s_d_op);
+	tmp->d_inode = inode;
+	tmp->d_flags |= DCACHE_DISCONNECTED;
+	list_add(&tmp->d_alias, &inode->i_dentry);
+	hlist_bl_lock(&tmp->d_sb->s_anon);
+	hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
+	hlist_bl_unlock(&tmp->d_sb->s_anon);
+	spin_unlock(&tmp->d_lock);
+	spin_unlock(&inode->i_lock);
+	security_d_instantiate(tmp, inode);
+
+	return tmp;
+
+ out_iput:
+	if (res && !IS_ERR(res))
+		security_d_instantiate(res, inode);
+	iput(inode);
+	return res;
+}
+EXPORT_SYMBOL(d_obtain_alias);
+
+/**
+ * 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;
+
+	if (inode && S_ISDIR(inode->i_mode)) {
+		spin_lock(&inode->i_lock);
+		new = __d_find_alias(inode, 1);
+		if (new) {
+			BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
+			spin_unlock(&inode->i_lock);
+			security_d_instantiate(new, inode);
+			d_move(new, dentry);
+			iput(inode);
+		} else {
+			/* already taking inode->i_lock, so d_add() by hand */
+			__d_instantiate(dentry, inode);
+			spin_unlock(&inode->i_lock);
+			security_d_instantiate(dentry, inode);
+			d_rehash(dentry);
+		}
+	} else
+		d_add(dentry, inode);
+	return new;
+}
+EXPORT_SYMBOL(d_splice_alias);
+
+/**
+ * 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.
+ */
+struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
+			struct qstr *name)
+{
+	int error;
+	struct dentry *found;
+	struct dentry *new;
+
+	/*
+	 * First check if a dentry matching the name already exists,
+	 * if not go ahead and create it now.
+	 */
+	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;
+		}
+
+		found = d_splice_alias(inode, new);
+		if (found) {
+			dput(new);
+			return found;
+		}
+		return new;
+	}
+
+	/*
+	 * If a matching dentry exists, and it's not negative use it.
+	 *
+	 * Decrement the reference count to balance the iget() done
+	 * earlier on.
+	 */
+	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;
+	}
+
+	/*
+	 * Negative dentry: instantiate it unless the inode is a directory and
+	 * already has a dentry.
+	 */
+	spin_lock(&inode->i_lock);
+	if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) {
+		__d_instantiate(found, inode);
+		spin_unlock(&inode->i_lock);
+		security_d_instantiate(found, inode);
+		return found;
+	}
+
+	/*
+	 * In case a directory already has a (disconnected) entry grab a
+	 * reference to it, move it in place and use it.
+	 */
+	new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
+	__dget(new);
+	spin_unlock(&inode->i_lock);
+	security_d_instantiate(found, inode);
+	d_move(new, found);
+	iput(inode);
+	dput(found);
+	return new;
+
+err_out:
+	iput(inode);
+	return ERR_PTR(error);
+}
+EXPORT_SYMBOL(d_add_ci);
+
+/**
+ * __d_lookup_rcu - search for a dentry (racy, store-free)
+ * @parent: parent dentry
+ * @name: qstr of name we wish to find
+ * @seq: returns d_seq value at the point where the dentry was found
+ * @inode: returns dentry->d_inode when the inode was found valid.
+ * Returns: dentry, or NULL
+ *
+ * __d_lookup_rcu is the dcache lookup function for rcu-walk name
+ * resolution (store-free path walking) design described in
+ * Documentation/filesystems/path-lookup.txt.
+ *
+ * This is not to be used outside core vfs.
+ *
+ * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
+ * held, and rcu_read_lock held. The returned dentry must not be stored into
+ * without taking d_lock and checking d_seq sequence count against @seq
+ * returned here.
+ *
+ * A refcount may be taken on the found dentry with the __d_rcu_to_refcount
+ * function.
+ *
+ * Alternatively, __d_lookup_rcu may be called again to look up the child of
+ * the returned dentry, so long as its parent's seqlock is checked after the
+ * child is looked up. Thus, an interlocking stepping of sequence lock checks
+ * is formed, giving integrity down the path walk.
+ */
+struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
+				unsigned *seq, struct inode **inode)
+{
+	unsigned int len = name->len;
+	unsigned int hash = name->hash;
+	const unsigned char *str = name->name;
+	struct hlist_bl_head *b = d_hash(parent, hash);
+	struct hlist_bl_node *node;
+	struct dentry *dentry;
+
+	/*
+	 * Note: There is significant duplication with __d_lookup_rcu which is
+	 * required to prevent single threaded performance regressions
+	 * especially on architectures where smp_rmb (in seqcounts) are costly.
+	 * Keep the two functions in sync.
+	 */
+
+	/*
+	 * The hash list is protected using RCU.
+	 *
+	 * Carefully use d_seq when comparing a candidate dentry, to avoid
+	 * races with d_move().
+	 *
+	 * It is possible that concurrent renames can mess up our list
+	 * walk here and result in missing our dentry, resulting in the
+	 * false-negative result. d_lookup() protects against concurrent
+	 * renames using rename_lock seqlock.
+	 *
+	 * See Documentation/filesystems/path-lookup.txt for more details.
+	 */
+	hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
+		struct inode *i;
+		const char *tname;
+		int tlen;
+
+		if (dentry->d_name.hash != hash)
+			continue;
+
+seqretry:
+		*seq = read_seqcount_begin(&dentry->d_seq);
+		if (dentry->d_parent != parent)
+			continue;
+		if (d_unhashed(dentry))
+			continue;
+		tlen = dentry->d_name.len;
+		tname = dentry->d_name.name;
+		i = dentry->d_inode;
+		prefetch(tname);
+		/*
+		 * This seqcount check is required to ensure name and
+		 * len are loaded atomically, so as not to walk off the
+		 * edge of memory when walking. If we could load this
+		 * atomically some other way, we could drop this check.
+		 */
+		if (read_seqcount_retry(&dentry->d_seq, *seq))
+			goto seqretry;
+		if (parent->d_flags & DCACHE_OP_COMPARE) {
+			if (parent->d_op->d_compare(parent, *inode,
+						dentry, i,
+						tlen, tname, name))
+				continue;
+		} else {
+			if (dentry_cmp(tname, tlen, str, len))
+				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;
+}
+
+/**
+ * d_lookup - search for a dentry
+ * @parent: parent dentry
+ * @name: qstr of name we wish to find
+ * Returns: dentry, or NULL
+ *
+ * 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.
+ */
+struct dentry *d_lookup(struct dentry *parent, struct qstr *name)
+{
+	struct dentry *dentry;
+	unsigned seq;
+
+        do {
+                seq = read_seqbegin(&rename_lock);
+                dentry = __d_lookup(parent, name);
+                if (dentry)
+			break;
+	} while (read_seqretry(&rename_lock, seq));
+	return dentry;
+}
+EXPORT_SYMBOL(d_lookup);
+
+/**
+ * __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.
+ */
+struct dentry *__d_lookup(struct dentry *parent, struct qstr *name)
+{
+	unsigned int len = name->len;
+	unsigned int hash = name->hash;
+	const unsigned char *str = name->name;
+	struct hlist_bl_head *b = d_hash(parent, hash);
+	struct hlist_bl_node *node;
+	struct dentry *found = NULL;
+	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.
+	 *
+	 * Take d_lock when comparing a candidate dentry, to avoid races
+	 * with d_move().
+	 *
+	 * It is possible that concurrent renames can mess up our list
+	 * walk here and result in missing our dentry, resulting in the
+	 * false-negative result. d_lookup() protects against concurrent
+	 * renames using rename_lock seqlock.
+	 *
+	 * See Documentation/filesystems/path-lookup.txt for more details.
+	 */
+	rcu_read_lock();
+	
+	hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
+		const char *tname;
+		int tlen;
+
+		if (dentry->d_name.hash != hash)
+			continue;
+
+		spin_lock(&dentry->d_lock);
+		if (dentry->d_parent != parent)
+			goto next;
+		if (d_unhashed(dentry))
+			goto next;
+
+		/*
+		 * It is safe to compare names since d_move() cannot
+		 * change the qstr (protected by d_lock).
+		 */
+		tlen = dentry->d_name.len;
+		tname = dentry->d_name.name;
+		if (parent->d_flags & DCACHE_OP_COMPARE) {
+			if (parent->d_op->d_compare(parent, parent->d_inode,
+						dentry, dentry->d_inode,
+						tlen, tname, name))
+				goto next;
+		} else {
+			if (dentry_cmp(tname, tlen, str, len))
+				goto next;
+		}
+
+		dentry->d_count++;
+		found = dentry;
+		spin_unlock(&dentry->d_lock);
+		break;
+next:
+		spin_unlock(&dentry->d_lock);
+ 	}
+ 	rcu_read_unlock();
+
+ 	return found;
+}
+
+/**
+ * d_hash_and_lookup - hash the qstr then search for a dentry
+ * @dir: Directory to search in
+ * @name: qstr of name we wish to find
+ *
+ * On hash failure or on lookup failure NULL is returned.
+ */
+struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
+{
+	struct dentry *dentry = NULL;
+
+	/*
+	 * Check for a fs-specific hash function. Note that we must
+	 * calculate the standard hash first, as the d_op->d_hash()
+	 * routine may choose to leave the hash value unchanged.
+	 */
+	name->hash = full_name_hash(name->name, name->len);
+	if (dir->d_flags & DCACHE_OP_HASH) {
+		if (dir->d_op->d_hash(dir, dir->d_inode, name) < 0)
+			goto out;
+	}
+	dentry = d_lookup(dir, name);
+out:
+	return dentry;
+}
+
+/**
+ * d_validate - verify dentry provided from insecure source (deprecated)
+ * @dentry: The dentry alleged to be valid child of @dparent
+ * @dparent: The parent dentry (known to be valid)
+ *
+ * An insecure source has sent us a dentry, here we verify it and dget() it.
+ * This is used by ncpfs in its readdir implementation.
+ * Zero is returned in the dentry is invalid.
+ *
+ * This function is slow for big directories, and deprecated, do not use it.
+ */
+int d_validate(struct dentry *dentry, struct dentry *dparent)
+{
+	struct dentry *child;
+
+	spin_lock(&dparent->d_lock);
+	list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
+		if (dentry == child) {
+			spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+			__dget_dlock(dentry);
+			spin_unlock(&dentry->d_lock);
+			spin_unlock(&dparent->d_lock);
+			return 1;
+		}
+	}
+	spin_unlock(&dparent->d_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL(d_validate);
+
+/*
+ * 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)
+{
+	struct inode *inode;
+	int isdir = 0;
+	/*
+	 * Are we the only user?
+	 */
+again:
+	spin_lock(&dentry->d_lock);
+	inode = dentry->d_inode;
+	isdir = S_ISDIR(inode->i_mode);
+	if (dentry->d_count == 1) {
+		if (inode && !spin_trylock(&inode->i_lock)) {
+			spin_unlock(&dentry->d_lock);
+			cpu_relax();
+			goto again;
+		}
+		dentry->d_flags &= ~DCACHE_CANT_MOUNT;
+		dentry_unlink_inode(dentry);
+		fsnotify_nameremove(dentry, isdir);
+		return;
+	}
+
+	if (!d_unhashed(dentry))
+		__d_drop(dentry);
+
+	spin_unlock(&dentry->d_lock);
+
+	fsnotify_nameremove(dentry, isdir);
+}
+EXPORT_SYMBOL(d_delete);
+
+static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
+{
+	BUG_ON(!d_unhashed(entry));
+	hlist_bl_lock(b);
+	entry->d_flags |= DCACHE_RCUACCESS;
+	hlist_bl_add_head_rcu(&entry->d_hash, b);
+	hlist_bl_unlock(b);
+}
+
+static void _d_rehash(struct dentry * entry)
+{
+	__d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
+}
+
+/**
+ * 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);
+	_d_rehash(entry);
+	spin_unlock(&entry->d_lock);
+}
+EXPORT_SYMBOL(d_rehash);
+
+/**
+ * dentry_update_name_case - update case insensitive dentry with a new name
+ * @dentry: dentry to be updated
+ * @name: new name
+ *
+ * Update a case insensitive dentry with new case of name.
+ *
+ * dentry must have been returned by d_lookup with name @name. Old and new
+ * name lengths must match (ie. no d_compare which allows mismatched name
+ * lengths).
+ *
+ * Parent inode i_mutex must be held over d_lookup and into this call (to
+ * keep renames and concurrent inserts, and readdir(2) away).
+ */
+void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
+{
+	BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));
+	BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
+
+	spin_lock(&dentry->d_lock);
+	write_seqcount_begin(&dentry->d_seq);
+	memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
+	write_seqcount_end(&dentry->d_seq);
+	spin_unlock(&dentry->d_lock);
+}
+EXPORT_SYMBOL(dentry_update_name_case);
+
+static void switch_names(struct dentry *dentry, struct dentry *target)
+{
+	if (dname_external(target)) {
+		if (dname_external(dentry)) {
+			/*
+			 * Both external: swap the pointers
+			 */
+			swap(target->d_name.name, dentry->d_name.name);
+		} else {
+			/*
+			 * dentry:internal, target:external.  Steal target's
+			 * storage and make target internal.
+			 */
+			memcpy(target->d_iname, dentry->d_name.name,
+					dentry->d_name.len + 1);
+			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);
+			dentry->d_name.len = target->d_name.len;
+			return;
+		}
+	}
+	swap(dentry->d_name.len, target->d_name.len);
+}
+
+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);
+}
+
+/*
+ * 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..
+ */
+/*
+ * __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.  Caller hold
+ * rename_lock.
+ */
+static void __d_move(struct dentry * dentry, struct dentry * target)
+{
+	if (!dentry->d_inode)
+		printk(KERN_WARNING "VFS: moving negative dcache entry\n");
+
+	BUG_ON(d_ancestor(dentry, target));
+	BUG_ON(d_ancestor(target, dentry));
+
+	dentry_lock_for_move(dentry, target);
+
+	write_seqcount_begin(&dentry->d_seq);
+	write_seqcount_begin(&target->d_seq);
+
+	/* __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);
+	__d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
+
+	/* Unhash the target: dput() will then get rid of it */
+	__d_drop(target);
+
+	list_del(&dentry->d_u.d_child);
+	list_del(&target->d_u.d_child);
+
+	/* Switch the names.. */
+	switch_names(dentry, target);
+	swap(dentry->d_name.hash, target->d_name.hash);
+
+	/* ... and switch the parents */
+	if (IS_ROOT(dentry)) {
+		dentry->d_parent = target->d_parent;
+		target->d_parent = target;
+		INIT_LIST_HEAD(&target->d_u.d_child);
+	} else {
+		swap(dentry->d_parent, target->d_parent);
+
+		/* And add them back to the (new) parent lists */
+		list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
+	}
+
+	list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
+
+	write_seqcount_end(&target->d_seq);
+	write_seqcount_end(&dentry->d_seq);
+
+	dentry_unlock_parents_for_move(dentry, target);
+	spin_unlock(&target->d_lock);
+	fsnotify_d_move(dentry);
+	spin_unlock(&dentry->d_lock);
+}
+
+/*
+ * 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);
+	write_sequnlock(&rename_lock);
+}
+EXPORT_SYMBOL(d_move);
+
+/**
+ * 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.
+ */
+struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
+{
+	struct dentry *p;
+
+	for (p = p2; !IS_ROOT(p); p = p->d_parent) {
+		if (p->d_parent == p1)
+			return p;
+	}
+	return NULL;
+}
+
+/*
+ * This helper attempts to cope with remotely renamed directories
+ *
+ * It assumes that the caller is already holding
+ * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
+ *
+ * Note: If ever the locking in lock_rename() changes, then please
+ * remember to update this too...
+ */
+static struct dentry *__d_unalias(struct inode *inode,
+		struct dentry *dentry, struct dentry *alias)
+{
+	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:
+	__d_move(alias, dentry);
+	ret = alias;
+out_err:
+	spin_unlock(&inode->i_lock);
+	if (m2)
+		mutex_unlock(m2);
+	if (m1)
+		mutex_unlock(m1);
+	return ret;
+}
+
+/*
+ * Prepare an anonymous dentry for life in the superblock's dentry tree as a
+ * named dentry in place of the dentry to be replaced.
+ * returns with anon->d_lock held!
+ */
+static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
+{
+	struct dentry *dparent, *aparent;
+
+	dentry_lock_for_move(anon, dentry);
+
+	write_seqcount_begin(&dentry->d_seq);
+	write_seqcount_begin(&anon->d_seq);
+
+	dparent = dentry->d_parent;
+	aparent = anon->d_parent;
+
+	switch_names(dentry, anon);
+	swap(dentry->d_name.hash, anon->d_name.hash);
+
+	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);
+
+	write_seqcount_end(&dentry->d_seq);
+	write_seqcount_end(&anon->d_seq);
+
+	dentry_unlock_parents_for_move(anon, dentry);
+	spin_unlock(&dentry->d_lock);
+
+	/* anon->d_lock still locked, returns locked */
+	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)
+{
+	struct dentry *actual;
+
+	BUG_ON(!d_unhashed(dentry));
+
+	if (!inode) {
+		actual = dentry;
+		__d_instantiate(dentry, NULL);
+		d_rehash(actual);
+		goto out_nolock;
+	}
+
+	spin_lock(&inode->i_lock);
+
+	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;
+			write_seqlock(&rename_lock);
+
+			if (d_ancestor(alias, dentry)) {
+				/* Check for loops */
+				actual = ERR_PTR(-ELOOP);
+				spin_unlock(&inode->i_lock);
+			} else if (IS_ROOT(alias)) {
+				/* Is this an anonymous mountpoint that we
+				 * could splice into our tree? */
+				__d_materialise_dentry(dentry, alias);
+				write_sequnlock(&rename_lock);
+				__d_drop(alias);
+				goto found;
+			} else {
+				/* Nope, but we must(!) avoid directory
+				 * aliasing. This drops inode->i_lock */
+				actual = __d_unalias(inode, dentry, alias);
+			}
+			write_sequnlock(&rename_lock);
+			if (IS_ERR(actual))
+				dput(alias);
+			goto out_nolock;
+		}
+	}
+
+	/* Add a unique reference */
+	actual = __d_instantiate_unique(dentry, inode);
+	if (!actual)
+		actual = dentry;
+	else
+		BUG_ON(!d_unhashed(actual));
+
+	spin_lock(&actual->d_lock);
+found:
+	_d_rehash(actual);
+	spin_unlock(&actual->d_lock);
+	spin_unlock(&inode->i_lock);
+out_nolock:
+	if (actual == dentry) {
+		security_d_instantiate(dentry, inode);
+		return NULL;
+	}
+
+	iput(inode);
+	return actual;
+}
+EXPORT_SYMBOL_GPL(d_materialise_unique);
+
+static int prepend(char **buffer, int *buflen, const char *str, int namelen)
+{
+	*buflen -= namelen;
+	if (*buflen < 0)
+		return -ENAMETOOLONG;
+	*buffer -= namelen;
+	memcpy(*buffer, str, namelen);
+	return 0;
+}
+
+static int prepend_name(char **buffer, int *buflen, struct qstr *name)
+{
+	return prepend(buffer, buflen, name->name, name->len);
+}
+
+/**
+ * prepend_path - Prepend path string to a buffer
+ * @path: the dentry/vfsmount to report
+ * @root: root vfsmnt/dentry
+ * @buffer: pointer to the end of the buffer
+ * @buflen: pointer to buffer length
+ *
+ * Caller holds the rename_lock.
+ */
+static int prepend_path(const struct path *path,
+			const struct path *root,
+			char **buffer, int *buflen)
+{
+	struct dentry *dentry = path->dentry;
+	struct vfsmount *vfsmnt = path->mnt;
+	bool slash = false;
+	int error = 0;
+
+	br_read_lock(vfsmount_lock);
+	while (dentry != root->dentry || vfsmnt != root->mnt) {
+		struct dentry * parent;
+
+		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
+			/* Global root? */
+			if (vfsmnt->mnt_parent == vfsmnt) {
+				goto global_root;
+			}
+			dentry = vfsmnt->mnt_mountpoint;
+			vfsmnt = vfsmnt->mnt_parent;
+			continue;
+		}
+		parent = dentry->d_parent;
+		prefetch(parent);
+		spin_lock(&dentry->d_lock);
+		error = prepend_name(buffer, buflen, &dentry->d_name);
+		spin_unlock(&dentry->d_lock);
+		if (!error)
+			error = prepend(buffer, buflen, "/", 1);
+		if (error)
+			break;
+
+		slash = true;
+		dentry = parent;
+	}
+
+	if (!error && !slash)
+		error = prepend(buffer, buflen, "/", 1);
+
+out:
+	br_read_unlock(vfsmount_lock);
+	return error;
+
+global_root:
+	/*
+	 * 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);
+	}
+	if (!slash)
+		error = prepend(buffer, buflen, "/", 1);
+	if (!error)
+		error = vfsmnt->mnt_ns ? 1 : 2;
+	goto out;
+}
+
+/**
+ * __d_path - return the path of a dentry
+ * @path: the dentry/vfsmount to report
+ * @root: root vfsmnt/dentry
+ * @buf: buffer to return value in
+ * @buflen: buffer length
+ *
+ * Convert a dentry into an ASCII path name.
+ *
+ * Returns a pointer into the buffer or an error code if the
+ * path was too long.
+ *
+ * "buflen" should be positive.
+ *
+ * If the path is not reachable from the supplied root, return %NULL.
+ */
+char *__d_path(const struct path *path,
+	       const struct path *root,
+	       char *buf, int buflen)
+{
+	char *res = buf + buflen;
+	int error;
+
+	prepend(&res, &buflen, "\0", 1);
+	write_seqlock(&rename_lock);
+	error = prepend_path(path, root, &res, &buflen);
+	write_sequnlock(&rename_lock);
+
+	if (error < 0)
+		return ERR_PTR(error);
+	if (error > 0)
+		return NULL;
+	return res;
+}
+
+char *d_absolute_path(const struct path *path,
+	       char *buf, int buflen)
+{
+	struct path root = {};
+	char *res = buf + buflen;
+	int error;
+
+	prepend(&res, &buflen, "\0", 1);
+	write_seqlock(&rename_lock);
+	error = prepend_path(path, &root, &res, &buflen);
+	write_sequnlock(&rename_lock);
+
+	if (error > 1)
+		error = -EINVAL;
+	if (error < 0)
+		return ERR_PTR(error);
+	return res;
+}
+
+/*
+ * same as __d_path but appends "(deleted)" for unlinked files.
+ */
+static int path_with_deleted(const struct path *path,
+			     const 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);
+}
+
+static int prepend_unreachable(char **buffer, int *buflen)
+{
+	return prepend(buffer, buflen, "(unreachable)", 13);
+}
+
+/**
+ * d_path - return the path of a dentry
+ * @path: path to report
+ * @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.
+ *
+ * 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.
+ *
+ * "buflen" should be positive.
+ */
+char *d_path(const struct path *path, char *buf, int buflen)
+{
+	char *res = buf + buflen;
+	struct path root;
+	int error;
+
+	/*
+	 * 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:
+	 */
+	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);
+	write_seqlock(&rename_lock);
+	error = path_with_deleted(path, &root, &res, &buflen);
+	if (error < 0)
+		res = ERR_PTR(error);
+	write_sequnlock(&rename_lock);
+	path_put(&root);
+	return res;
+}
+EXPORT_SYMBOL(d_path);
+
+/**
+ * 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;
+	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);
+	write_seqlock(&rename_lock);
+	error = path_with_deleted(path, &root, &res, &buflen);
+	if (error > 0)
+		error = prepend_unreachable(&res, &buflen);
+	write_sequnlock(&rename_lock);
+	path_put(&root);
+	if (error)
+		res =  ERR_PTR(error);
+
+	return res;
+}
+
+/*
+ * 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);
+}
+
+/*
+ * Write full pathname from the root of the filesystem into the buffer.
+ */
+static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
+{
+	char *end = buf + buflen;
+	char *retval;
+
+	prepend(&end, &buflen, "\0", 1);
+	if (buflen < 1)
+		goto Elong;
+	/* Get '/' right */
+	retval = end-1;
+	*retval = '/';
+
+	while (!IS_ROOT(dentry)) {
+		struct dentry *parent = dentry->d_parent;
+		int error;
+
+		prefetch(parent);
+		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)
+			goto Elong;
+
+		retval = end;
+		dentry = parent;
+	}
+	return retval;
+Elong:
+	return ERR_PTR(-ENAMETOOLONG);
+}
+
+char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
+{
+	char *retval;
+
+	write_seqlock(&rename_lock);
+	retval = __dentry_path(dentry, buf, buflen);
+	write_sequnlock(&rename_lock);
+
+	return retval;
+}
+EXPORT_SYMBOL(dentry_path_raw);
+
+char *dentry_path(struct dentry *dentry, char *buf, int buflen)
+{
+	char *p = NULL;
+	char *retval;
+
+	write_seqlock(&rename_lock);
+	if (d_unlinked(dentry)) {
+		p = buf + buflen;
+		if (prepend(&p, &buflen, "//deleted", 10) != 0)
+			goto Elong;
+		buflen++;
+	}
+	retval = __dentry_path(dentry, buf, buflen);
+	write_sequnlock(&rename_lock);
+	if (!IS_ERR(retval) && p)
+		*p = '/';	/* restore '/' overriden with '\0' */
+	return retval;
+Elong:
+	return ERR_PTR(-ENAMETOOLONG);
+}
+
+/*
+ * 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;
+ *	}
+ */
+SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
+{
+	int error;
+	struct path pwd, root;
+	char *page = (char *) __get_free_page(GFP_USER);
+
+	if (!page)
+		return -ENOMEM;
+
+	get_fs_root_and_pwd(current->fs, &root, &pwd);
+
+	error = -ENOENT;
+	write_seqlock(&rename_lock);
+	if (!d_unlinked(pwd.dentry)) {
+		unsigned long len;
+		char *cwd = page + PAGE_SIZE;
+		int buflen = PAGE_SIZE;
+
+		prepend(&cwd, &buflen, "\0", 1);
+		error = prepend_path(&pwd, &root, &cwd, &buflen);
+		write_sequnlock(&rename_lock);
+
+		if (error < 0)
+			goto out;
+
+		/* Unreachable from current root */
+		if (error > 0) {
+			error = prepend_unreachable(&cwd, &buflen);
+			if (error)
+				goto out;
+		}
+
+		error = -ERANGE;
+		len = PAGE_SIZE + page - cwd;
+		if (len <= size) {
+			error = len;
+			if (copy_to_user(buf, cwd, len))
+				error = -EFAULT;
+		}
+	} else {
+		write_sequnlock(&rename_lock);
+	}
+
+out:
+	path_put(&pwd);
+	path_put(&root);
+	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()
+ */
+  
+int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
+{
+	int result;
+	unsigned seq;
+
+	if (new_dentry == old_dentry)
+		return 1;
+
+	do {
+		/* for restarting inner loop in case of seq retry */
+		seq = read_seqbegin(&rename_lock);
+		/*
+		 * Need rcu_readlock to protect against the d_parent trashing
+		 * due to d_move
+		 */
+		rcu_read_lock();
+		if (d_ancestor(old_dentry, new_dentry))
+			result = 1;
+		else
+			result = 0;
+		rcu_read_unlock();
+	} while (read_seqretry(&rename_lock, seq));
+
+	return result;
+}
+
+int path_is_under(struct path *path1, struct path *path2)
+{
+	struct vfsmount *mnt = path1->mnt;
+	struct dentry *dentry = path1->dentry;
+	int res;
+
+	br_read_lock(vfsmount_lock);
+	if (mnt != path2->mnt) {
+		for (;;) {
+			if (mnt->mnt_parent == mnt) {
+				br_read_unlock(vfsmount_lock);
+				return 0;
+			}
+			if (mnt->mnt_parent == path2->mnt)
+				break;
+			mnt = mnt->mnt_parent;
+		}
+		dentry = mnt->mnt_mountpoint;
+	}
+	res = is_subdir(dentry, path2->dentry);
+	br_read_unlock(vfsmount_lock);
+	return res;
+}
+EXPORT_SYMBOL(path_is_under);
+
+void d_genocide(struct dentry *root)
+{
+	struct dentry *this_parent;
+	struct list_head *next;
+	unsigned seq;
+	int locked = 0;
+
+	seq = read_seqbegin(&rename_lock);
+again:
+	this_parent = root;
+	spin_lock(&this_parent->d_lock);
+repeat:
+	next = this_parent->d_subdirs.next;
+resume:
+	while (next != &this_parent->d_subdirs) {
+		struct list_head *tmp = next;
+		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
+		next = tmp->next;
+
+		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+		if (d_unhashed(dentry) || !dentry->d_inode) {
+			spin_unlock(&dentry->d_lock);
+			continue;
+		}
+		if (!list_empty(&dentry->d_subdirs)) {
+			spin_unlock(&this_parent->d_lock);
+			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
+			this_parent = dentry;
+			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
+			goto repeat;
+		}
+		if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
+			dentry->d_flags |= DCACHE_GENOCIDE;
+			dentry->d_count--;
+		}
+		spin_unlock(&dentry->d_lock);
+	}
+	if (this_parent != root) {
+		struct dentry *child = this_parent;
+		if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
+			this_parent->d_flags |= DCACHE_GENOCIDE;
+			this_parent->d_count--;
+		}
+		this_parent = try_to_ascend(this_parent, locked, seq);
+		if (!this_parent)
+			goto rename_retry;
+		next = child->d_u.d_child.next;
+		goto resume;
+	}
+	spin_unlock(&this_parent->d_lock);
+	if (!locked && read_seqretry(&rename_lock, seq))
+		goto rename_retry;
+	if (locked)
+		write_sequnlock(&rename_lock);
+	return;
+
+rename_retry:
+	locked = 1;
+	write_seqlock(&rename_lock);
+	goto again;
+}
+
+/**
+ * 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;
+
+	dentry = d_hash_and_lookup(dir, name);
+	if (dentry) {
+		if (dentry->d_inode)
+			ino = dentry->d_inode->i_ino;
+		dput(dentry);
+	}
+	return ino;
+}
+EXPORT_SYMBOL(find_inode_number);
+
+static __initdata unsigned long dhash_entries;
+static int __init set_dhash_entries(char *str)
+{
+	if (!str)
+		return 0;
+	dhash_entries = simple_strtoul(str, &str, 0);
+	return 1;
+}
+__setup("dhash_entries=", set_dhash_entries);
+
+static void __init dcache_init_early(void)
+{
+	int loop;
+
+	/* If hashes are distributed across NUMA nodes, defer
+	 * hash allocation until vmalloc space is available.
+	 */
+	if (hashdist)
+		return;
+
+	dentry_hashtable =
+		alloc_large_system_hash("Dentry cache",
+					sizeof(struct hlist_bl_head),
+					dhash_entries,
+					13,
+					HASH_EARLY,
+					&d_hash_shift,
+					&d_hash_mask,
+					0);
+
+	for (loop = 0; loop < (1 << d_hash_shift); loop++)
+		INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
+}
+
+static void __init dcache_init(void)
+{
+	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. 
+	 */
+	dentry_cache = KMEM_CACHE(dentry,
+		SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
+	
+	register_shrinker(&dcache_shrinker);
+
+	/* Hash may have been set up in dcache_init_early */
+	if (!hashdist)
+		return;
+
+	dentry_hashtable =
+		alloc_large_system_hash("Dentry cache",
+					sizeof(struct hlist_bl_head),
+					dhash_entries,
+					13,
+					0,
+					&d_hash_shift,
+					&d_hash_mask,
+					0);
+
+	for (loop = 0; loop < (1 << d_hash_shift); loop++)
+		INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
+}
+
+/* SLAB cache for __getname() consumers */
+struct kmem_cache *names_cachep __read_mostly;
+EXPORT_SYMBOL(names_cachep);
+
+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,
+			SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
+
+	dcache_init();
+	inode_init();
+	files_init(mempages);
+	mnt_init();
+	bdev_cache_init();
+	chrdev_init();
+}