eCryptfs: Revert "dont call lookup_one_len to avoid NULL nameidata"

This reverts commit 21edad32205e97dc7ccb81a85234c77e760364c8 and commit
93c3fe40c279f002906ad14584c30671097d4394, which fixed a regression by
the former.

Al Viro pointed out bypassed dcache lookups in
ecryptfs_new_lower_dentry(), misuse of vfs_path_lookup() in
ecryptfs_lookup_one_lower() and a dislike of passing nameidata to the
lower filesystem.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

fs/ecryptfs/inode.c

@@ -348,75 +348,6 @@ out:
 	return rc;
 }
 
-/**
- * ecryptfs_new_lower_dentry
- * @name: The name of the new dentry.
- * @lower_dir_dentry: Parent directory of the new dentry.
- * @nd: nameidata from last lookup.
- *
- * Create a new dentry or get it from lower parent dir.
- */
-static struct dentry *
-ecryptfs_new_lower_dentry(struct qstr *name, struct dentry *lower_dir_dentry,
-			  struct nameidata *nd)
-{
-	struct dentry *new_dentry;
-	struct dentry *tmp;
-	struct inode *lower_dir_inode;
-
-	lower_dir_inode = lower_dir_dentry->d_inode;
-
-	tmp = d_alloc(lower_dir_dentry, name);
-	if (!tmp)
-		return ERR_PTR(-ENOMEM);
-
-	mutex_lock(&lower_dir_inode->i_mutex);
-	new_dentry = lower_dir_inode->i_op->lookup(lower_dir_inode, tmp, nd);
-	mutex_unlock(&lower_dir_inode->i_mutex);
-
-	if (!new_dentry)
-		new_dentry = tmp;
-	else
-		dput(tmp);
-
-	return new_dentry;
-}
-
-
-/**
- * ecryptfs_lookup_one_lower
- * @ecryptfs_dentry: The eCryptfs dentry that we are looking up
- * @lower_dir_dentry: lower parent directory
- * @name: lower file name
- *
- * Get the lower dentry from vfs. If lower dentry does not exist yet,
- * create it.
- */
-static struct dentry *
-ecryptfs_lookup_one_lower(struct dentry *ecryptfs_dentry,
-			  struct dentry *lower_dir_dentry, struct qstr *name)
-{
-	struct nameidata nd;
-	struct vfsmount *lower_mnt;
-	int err;
-
-	lower_mnt = mntget(ecryptfs_dentry_to_lower_mnt(
-				    ecryptfs_dentry->d_parent));
-	err = vfs_path_lookup(lower_dir_dentry, lower_mnt, name->name , 0, &nd);
-	mntput(lower_mnt);
-
-	if (!err) {
-		/* we dont need the mount */
-		mntput(nd.path.mnt);
-		return nd.path.dentry;
-	}
-	if (err != -ENOENT)
-		return ERR_PTR(err);
-
-	/* create a new lower dentry */
-	return ecryptfs_new_lower_dentry(name, lower_dir_dentry, &nd);
-}
-
 /**
  * ecryptfs_lookup
  * @ecryptfs_dir_inode: The eCryptfs directory inode
@@ -434,7 +365,6 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
 	size_t encrypted_and_encoded_name_size;
 	struct ecryptfs_mount_crypt_stat *mount_crypt_stat = NULL;
 	struct dentry *lower_dir_dentry, *lower_dentry;
-	struct qstr lower_name;
 	int rc = 0;
 
 	if ((ecryptfs_dentry->d_name.len == 1
@@ -444,20 +374,14 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
 		goto out_d_drop;
 	}
 	lower_dir_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry->d_parent);
-	lower_name.name = ecryptfs_dentry->d_name.name;
-	lower_name.len = ecryptfs_dentry->d_name.len;
-	lower_name.hash = ecryptfs_dentry->d_name.hash;
-	if (lower_dir_dentry->d_op && lower_dir_dentry->d_op->d_hash) {
-		rc = lower_dir_dentry->d_op->d_hash(lower_dir_dentry,
-				lower_dir_dentry->d_inode, &lower_name);
-		if (rc < 0)
-			goto out_d_drop;
-	}
-	lower_dentry = ecryptfs_lookup_one_lower(ecryptfs_dentry,
-						 lower_dir_dentry, &lower_name);
+	mutex_lock(&lower_dir_dentry->d_inode->i_mutex);
+	lower_dentry = lookup_one_len(ecryptfs_dentry->d_name.name,
+				      lower_dir_dentry,
+				      ecryptfs_dentry->d_name.len);
+	mutex_unlock(&lower_dir_dentry->d_inode->i_mutex);
 	if (IS_ERR(lower_dentry)) {
 		rc = PTR_ERR(lower_dentry);
-		ecryptfs_printk(KERN_DEBUG, "%s: lookup_one_lower() returned "
+		ecryptfs_printk(KERN_DEBUG, "%s: lookup_one_len() returned "
 				"[%d] on lower_dentry = [%s]\n", __func__, rc,
 				encrypted_and_encoded_name);
 		goto out_d_drop;
@@ -479,20 +403,14 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
 		       "filename; rc = [%d]\n", __func__, rc);
 		goto out_d_drop;
 	}
-	lower_name.name = encrypted_and_encoded_name;
-	lower_name.len = encrypted_and_encoded_name_size;
-	lower_name.hash = full_name_hash(lower_name.name, lower_name.len);
-	if (lower_dir_dentry->d_op && lower_dir_dentry->d_op->d_hash) {
-		rc = lower_dir_dentry->d_op->d_hash(lower_dir_dentry,
-				lower_dir_dentry->d_inode, &lower_name);
-		if (rc < 0)
-			goto out_d_drop;
-	}
-	lower_dentry = ecryptfs_lookup_one_lower(ecryptfs_dentry,
-						 lower_dir_dentry, &lower_name);
+	mutex_lock(&lower_dir_dentry->d_inode->i_mutex);
+	lower_dentry = lookup_one_len(encrypted_and_encoded_name,
+				      lower_dir_dentry,
+				      encrypted_and_encoded_name_size);
+	mutex_unlock(&lower_dir_dentry->d_inode->i_mutex);
 	if (IS_ERR(lower_dentry)) {
 		rc = PTR_ERR(lower_dentry);
-		ecryptfs_printk(KERN_DEBUG, "%s: lookup_one_lower() returned "
+		ecryptfs_printk(KERN_DEBUG, "%s: lookup_one_len() returned "
 				"[%d] on lower_dentry = [%s]\n", __func__, rc,
 				encrypted_and_encoded_name);
 		goto out_d_drop;