btrfs: add assertions for releasing trans handle reservations

These are useful for debugging problems where we mess with
trans->block_rsv to make sure we're not screwing something up.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent-tree.c

@@ -5823,12 +5823,15 @@ static void release_global_block_rsv(struct btrfs_fs_info *fs_info)
 void btrfs_trans_release_metadata(struct btrfs_trans_handle *trans,
 				  struct btrfs_fs_info *fs_info)
 {
-	if (!trans->block_rsv)
+	if (!trans->block_rsv) {
+		ASSERT(!trans->bytes_reserved);
 		return;
+	}
 
 	if (!trans->bytes_reserved)
 		return;
 
+	ASSERT(trans->block_rsv == &fs_info->trans_block_rsv);
 	trace_btrfs_space_reservation(fs_info, "transaction",
 				      trans->transid, trans->bytes_reserved, 0);
 	btrfs_block_rsv_release(fs_info, trans->block_rsv,