btrfs: enhance btrfs_find_device_by_user_input() to check device path

The operation of device replace and device delete follows same steps upto
some depth with in btrfs kernel, however they don't share codes. This
enhancement will help replace and delete to share codes.
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/dev-replace.c

@@ -320,10 +320,6 @@ int btrfs_dev_replace_start(struct btrfs_root *root,
 		return -EINVAL;
 	}
 
-	if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
-	    args->start.tgtdev_name[0] == '\0')
-		return -EINVAL;
-
 	/* the disk copy procedure reuses the scrub code */
 	mutex_lock(&fs_info->volume_mutex);
 	ret = btrfs_find_device_by_user_input(root, args->start.srcdevid,

fs/btrfs/volumes.c

@@ -2113,6 +2113,9 @@ int btrfs_find_device_by_user_input(struct btrfs_root *root, u64 srcdevid,
 		if (!*device)
 			ret = -ENOENT;
 	} else {
+		if (!srcdev_name || !srcdev_name[0])
+			return -EINVAL;
+
 		ret = btrfs_find_device_missing_or_by_path(root, srcdev_name,
 							   device);
 	}