diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index c497886d30e6..8b6a99b8d7f6 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -601,15 +601,16 @@ start_transaction(struct btrfs_root *root, unsigned int num_items,
 		/*
 		 * We want to reserve all the bytes we may need all at once, so
 		 * we only do 1 enospc flushing cycle per transaction start.  We
-		 * accomplish this by simply assuming we'll do 2 x num_items
-		 * worth of delayed refs updates in this trans handle, and
-		 * refill that amount for whatever is missing in the reserve.
+		 * accomplish this by simply assuming we'll do num_items worth
+		 * of delayed refs updates in this trans handle, and refill that
+		 * amount for whatever is missing in the reserve.
 		 */
 		num_bytes = btrfs_calc_insert_metadata_size(fs_info, num_items);
 		if (flush == BTRFS_RESERVE_FLUSH_ALL &&
 		    !btrfs_block_rsv_full(delayed_refs_rsv)) {
-			delayed_refs_bytes = num_bytes;
-			num_bytes <<= 1;
+			delayed_refs_bytes = btrfs_calc_delayed_ref_bytes(fs_info,
+									  num_items);
+			num_bytes += delayed_refs_bytes;
 		}
 
 		/*