1 files changed, 94 insertions, 90 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index e7a1a99b746..a1d86c7f3e6 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -69,6 +69,7 @@ struct dentry_stat_t dentry_stat = {
 
 static void __d_free(struct dentry *dentry)
 {
+	WARN_ON(!list_empty(&dentry->d_alias));
 	if (dname_external(dentry))
 		kfree(dentry->d_name.name);
 	kmem_cache_free(dentry_cache, dentry); 
@@ -174,9 +175,12 @@ static struct dentry *d_kill(struct dentry *dentry)
 	dentry_stat.nr_dentry--;	/* For d_free, below */
 	/*drops the locks, at that point nobody can reach this dentry */
 	dentry_iput(dentry);
-	parent = dentry->d_parent;
+	if (IS_ROOT(dentry))
+		parent = NULL;
+	else
+		parent = dentry->d_parent;
 	d_free(dentry);
-	return dentry == parent ? NULL : parent;
+	return parent;
 }
 
 /* 
@@ -666,11 +670,12 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
 				BUG();
 			}
 
-			parent = dentry->d_parent;
-			if (parent == dentry)
+			if (IS_ROOT(dentry))
 				parent = NULL;
-			else
+			else {
+				parent = dentry->d_parent;
 				atomic_dec(&parent->d_count);
+			}
 
 			list_del(&dentry->d_u.d_child);
 			detached++;
@@ -977,6 +982,15 @@ struct dentry *d_alloc_name(struct dentry *parent, const char *name)
 	return d_alloc(parent, &q);
 }
 
+/* the caller must hold dcache_lock */
+static void __d_instantiate(struct dentry *dentry, struct inode *inode)
+{
+	if (inode)
+		list_add(&dentry->d_alias, &inode->i_dentry);
+	dentry->d_inode = inode;
+	fsnotify_d_instantiate(dentry, inode);
+}
+
 /**
  * d_instantiate - fill in inode information for a dentry
  * @entry: dentry to complete
@@ -996,10 +1010,7 @@ void d_instantiate(struct dentry *entry, struct inode * inode)
 {
 	BUG_ON(!list_empty(&entry->d_alias));
 	spin_lock(&dcache_lock);
-	if (inode)
-		list_add(&entry->d_alias, &inode->i_dentry);
-	entry->d_inode = inode;
-	fsnotify_d_instantiate(entry, inode);
+	__d_instantiate(entry, inode);
 	spin_unlock(&dcache_lock);
 	security_d_instantiate(entry, inode);
 }
@@ -1029,7 +1040,7 @@ static struct dentry *__d_instantiate_unique(struct dentry *entry,
 	unsigned int hash = entry->d_name.hash;
 
 	if (!inode) {
-		entry->d_inode = NULL;
+		__d_instantiate(entry, NULL);
 		return NULL;
 	}
 
@@ -1048,9 +1059,7 @@ static struct dentry *__d_instantiate_unique(struct dentry *entry,
 		return alias;
 	}
 
-	list_add(&entry->d_alias, &inode->i_dentry);
-	entry->d_inode = inode;
-	fsnotify_d_instantiate(entry, inode);
+	__d_instantiate(entry, inode);
 	return NULL;
 }
 
@@ -1111,69 +1120,71 @@ static inline struct hlist_head *d_hash(struct dentry *parent,
 }
 
 /**
- * d_alloc_anon - allocate an anonymous dentry
+ * d_obtain_alias - find or allocate a dentry for a given inode
  * @inode: inode to allocate the dentry for
  *
- * This is similar to d_alloc_root.  It is used by filesystems when
- * creating a dentry for a given inode, often in the process of 
- * mapping a filehandle to a dentry.  The returned dentry may be
- * anonymous, or may have a full name (if the inode was already
- * in the cache).  The file system may need to make further
- * efforts to connect this dentry into the dcache properly.
+ * 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.
+ * 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.  If %NULL is returned (indicating kmalloc failure),
- * the reference on the inode has not been released.
+ * 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_alloc_anon(struct inode *inode)
+struct dentry *d_obtain_alias(struct inode *inode)
 {
 	static const struct qstr anonstring = { .name = "" };
 	struct dentry *tmp;
 	struct dentry *res;
 
-	if ((res = d_find_alias(inode))) {
-		iput(inode);
-		return res;
-	}
+	if (!inode)
+		return ERR_PTR(-ESTALE);
+	if (IS_ERR(inode))
+		return ERR_CAST(inode);
 
-	tmp = d_alloc(NULL, &anonstring);
-	if (!tmp)
-		return NULL;
+	res = d_find_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(&dcache_lock);
 	res = __d_find_alias(inode, 0);
-	if (!res) {
-		/* attach a disconnected dentry */
-		res = tmp;
-		tmp = NULL;
-		spin_lock(&res->d_lock);
-		res->d_sb = inode->i_sb;
-		res->d_parent = res;
-		res->d_inode = inode;
-		res->d_flags |= DCACHE_DISCONNECTED;
-		res->d_flags &= ~DCACHE_UNHASHED;
-		list_add(&res->d_alias, &inode->i_dentry);
-		hlist_add_head(&res->d_hash, &inode->i_sb->s_anon);
-		spin_unlock(&res->d_lock);
-
-		inode = NULL; /* don't drop reference */
+	if (res) {
+		spin_unlock(&dcache_lock);
+		dput(tmp);
+		goto out_iput;
 	}
+
+	/* attach a disconnected dentry */
+	spin_lock(&tmp->d_lock);
+	tmp->d_sb = inode->i_sb;
+	tmp->d_inode = inode;
+	tmp->d_flags |= DCACHE_DISCONNECTED;
+	tmp->d_flags &= ~DCACHE_UNHASHED;
+	list_add(&tmp->d_alias, &inode->i_dentry);
+	hlist_add_head(&tmp->d_hash, &inode->i_sb->s_anon);
+	spin_unlock(&tmp->d_lock);
+
 	spin_unlock(&dcache_lock);
+	return tmp;
 
-	if (inode)
-		iput(inode);
-	if (tmp)
-		dput(tmp);
+ out_iput:
+	iput(inode);
 	return res;
 }
-
+EXPORT_SYMBOL_GPL(d_obtain_alias);
 
 /**
  * d_splice_alias - splice a disconnected dentry into the tree if one exists
@@ -1200,17 +1211,14 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
 		new = __d_find_alias(inode, 1);
 		if (new) {
 			BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
-			fsnotify_d_instantiate(new, inode);
 			spin_unlock(&dcache_lock);
 			security_d_instantiate(new, inode);
 			d_rehash(dentry);
 			d_move(new, dentry);
 			iput(inode);
 		} else {
-			/* d_instantiate takes dcache_lock, so we do it by hand */
-			list_add(&dentry->d_alias, &inode->i_dentry);
-			dentry->d_inode = inode;
-			fsnotify_d_instantiate(dentry, inode);
+			/* already taking dcache_lock, so d_add() by hand */
+			__d_instantiate(dentry, inode);
 			spin_unlock(&dcache_lock);
 			security_d_instantiate(dentry, inode);
 			d_rehash(dentry);
@@ -1293,8 +1301,7 @@ struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
 		 * d_instantiate() by hand because it takes dcache_lock which
 		 * we already hold.
 		 */
-		list_add(&found->d_alias, &inode->i_dentry);
-		found->d_inode = inode;
+		__d_instantiate(found, inode);
 		spin_unlock(&dcache_lock);
 		security_d_instantiate(found, inode);
 		return found;
@@ -1456,8 +1463,6 @@ out:
  * d_validate - verify dentry provided from insecure source
  * @dentry: The dentry alleged to be valid child of @dparent
  * @dparent: The parent dentry (known to be valid)
- * @hash: Hash of the dentry
- * @len: Length of the name
  *
  * An insecure source has sent us a dentry, here we verify it and dget() it.
  * This is used by ncpfs in its readdir implementation.
@@ -1714,18 +1719,23 @@ void d_move(struct dentry * dentry, struct dentry * target)
 	spin_unlock(&dcache_lock);
 }
 
-/*
- * Helper that returns 1 if p1 is a parent of p2, else 0
+/**
+ * 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.
  */
-static int d_isparent(struct dentry *p1, struct dentry *p2)
+struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
 {
 	struct dentry *p;
 
-	for (p = p2; p->d_parent != p; p = p->d_parent) {
+	for (p = p2; !IS_ROOT(p); p = p->d_parent) {
 		if (p->d_parent == p1)
-			return 1;
+			return p;
 	}
-	return 0;
+	return NULL;
 }
 
 /*
@@ -1749,7 +1759,7 @@ static struct dentry *__d_unalias(struct dentry *dentry, struct dentry *alias)
 
 	/* Check for loops */
 	ret = ERR_PTR(-ELOOP);
-	if (d_isparent(alias, dentry))
+	if (d_ancestor(alias, dentry))
 		goto out_err;
 
 	/* See lock_rename() */
@@ -1822,7 +1832,7 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
 
 	if (!inode) {
 		actual = dentry;
-		dentry->d_inode = NULL;
+		__d_instantiate(dentry, NULL);
 		goto found_lock;
 	}
 
@@ -2149,32 +2159,27 @@ out:
  * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
  */
   
-int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
+int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
 {
 	int result;
-	struct dentry * saved = new_dentry;
 	unsigned long seq;
 
-	/* need rcu_readlock to protect against the d_parent trashing due to
-	 * d_move
+	/* FIXME: This is old behavior, needed? Please check callers. */
+	if (new_dentry == old_dentry)
+		return 1;
+
+	/*
+	 * Need rcu_readlock to protect against the d_parent trashing
+	 * due to d_move
 	 */
 	rcu_read_lock();
-        do {
+	do {
 		/* for restarting inner loop in case of seq retry */
-		new_dentry = saved;
-		result = 0;
 		seq = read_seqbegin(&rename_lock);
-		for (;;) {
-			if (new_dentry != old_dentry) {
-				struct dentry * parent = new_dentry->d_parent;
-				if (parent == new_dentry)
-					break;
-				new_dentry = parent;
-				continue;
-			}
+		if (d_ancestor(old_dentry, new_dentry))
 			result = 1;
-			break;
-		}
+		else
+			result = 0;
 	} while (read_seqretry(&rename_lock, seq));
 	rcu_read_unlock();
 
@@ -2344,7 +2349,6 @@ void __init vfs_caches_init(unsigned long mempages)
 }
 
 EXPORT_SYMBOL(d_alloc);
-EXPORT_SYMBOL(d_alloc_anon);
 EXPORT_SYMBOL(d_alloc_root);
 EXPORT_SYMBOL(d_delete);
 EXPORT_SYMBOL(d_find_alias);