Btrfs: kfree correct pointer during mount option parsing

We kstrdup the options string, but then strsep screws with the pointer,
so when we kfree() it, we're not giving it the right pointer.
Tested-by: Andy Lutomirski <luto@mit.edu>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/super.c

@@ -128,7 +128,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 {
 	struct btrfs_fs_info *info = root->fs_info;
 	substring_t args[MAX_OPT_ARGS];
-	char *p, *num;
+	char *p, *num, *orig;
 	int intarg;
 	int ret = 0;
 
@@ -143,6 +143,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 	if (!options)
 		return -ENOMEM;
 
+	orig = options;
 
 	while ((p = strsep(&options, ",")) != NULL) {
 		int token;
@@ -280,7 +281,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 		}
 	}
 out:
-	kfree(options);
+	kfree(orig);
 	return ret;
 }