ext2: check xattr name_len before acquiring xattr_sem in ext2_xattr_get

In ext2_xattr_get(), the code will acquire xattr_sem first, later checks
the length of xattr name_len > 255. It's unnecessarily time consuming and
also ext2_xattr_set() checks the length before other checks. So move the
check before acquiring xattr_sem to make these two functions consistent.

Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/ext2/xattr.c

@@ -161,6 +161,10 @@ ext2_xattr_get(struct inode *inode, int name_index, const char *name,
 
 	if (name == NULL)
 		return -EINVAL;
+	name_len = strlen(name);
+	if (name_len > 255)
+		return -ERANGE;
+
 	down_read(&EXT2_I(inode)->xattr_sem);
 	error = -ENODATA;
 	if (!EXT2_I(inode)->i_file_acl)
@@ -181,12 +185,8 @@ bad_block:	ext2_error(inode->i_sb, "ext2_xattr_get",
 		error = -EIO;
 		goto cleanup;
 	}
-	/* find named attribute */
-	name_len = strlen(name);
 
-	error = -ERANGE;
-	if (name_len > 255)
-		goto cleanup;
+	/* find named attribute */
 	entry = FIRST_ENTRY(bh);
 	while (!IS_LAST_ENTRY(entry)) {
 		struct ext2_xattr_entry *next =