btrfs: streamline fsid checks in alloc_fs_devices

We currently have redundant checks for the non-null value of fsid
simplify it.

And, no one is using alloc_fs_devices() with a NULL metadata_uuid
while fsid is not NULL, add an assert() to verify this condition.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -370,6 +370,8 @@ static struct btrfs_fs_devices *alloc_fs_devices(const u8 *fsid,
 {
 	struct btrfs_fs_devices *fs_devs;
 
+	ASSERT(fsid || !metadata_fsid);
+
 	fs_devs = kzalloc(sizeof(*fs_devs), GFP_KERNEL);
 	if (!fs_devs)
 		return ERR_PTR(-ENOMEM);
@@ -380,13 +382,12 @@ static struct btrfs_fs_devices *alloc_fs_devices(const u8 *fsid,
 	INIT_LIST_HEAD(&fs_devs->alloc_list);
 	INIT_LIST_HEAD(&fs_devs->fs_list);
 	INIT_LIST_HEAD(&fs_devs->seed_list);
-	if (fsid)
-		memcpy(fs_devs->fsid, fsid, BTRFS_FSID_SIZE);
 
-	if (metadata_fsid)
-		memcpy(fs_devs->metadata_uuid, metadata_fsid, BTRFS_FSID_SIZE);
-	else if (fsid)
-		memcpy(fs_devs->metadata_uuid, fsid, BTRFS_FSID_SIZE);
+	if (fsid) {
+		memcpy(fs_devs->fsid, fsid, BTRFS_FSID_SIZE);
+		memcpy(fs_devs->metadata_uuid,
+		       metadata_fsid ?: fsid, BTRFS_FSID_SIZE);
+	}
 
 	return fs_devs;
 }