diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 6a4fd1738b08..904d8285c226 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1005,6 +1005,7 @@ xfs_reflink_remap_extent(
 	xfs_filblks_t		rlen;
 	xfs_filblks_t		unmap_len;
 	xfs_off_t		newlen;
+	int64_t			qres;
 	int			error;
 
 	unmap_len = irec->br_startoff + irec->br_blockcount - destoff;
@@ -1027,13 +1028,19 @@ xfs_reflink_remap_extent(
 	xfs_ilock(ip, XFS_ILOCK_EXCL);
 	xfs_trans_ijoin(tp, ip, 0);
 
-	/* If we're not just clearing space, then do we have enough quota? */
-	if (real_extent) {
-		error = xfs_trans_reserve_quota_nblks(tp, ip,
-				irec->br_blockcount, 0, XFS_QMOPT_RES_REGBLKS);
-		if (error)
-			goto out_cancel;
-	}
+	/*
+	 * Reserve quota for this operation.  We don't know if the first unmap
+	 * in the dest file will cause a bmap btree split, so we always reserve
+	 * at least enough blocks for that split.  If the extent being mapped
+	 * in is written, we need to reserve quota for that too.
+	 */
+	qres = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
+	if (real_extent)
+		qres += irec->br_blockcount;
+	error = xfs_trans_reserve_quota_nblks(tp, ip, qres, 0,
+			XFS_QMOPT_RES_REGBLKS);
+	if (error)
+		goto out_cancel;
 
 	trace_xfs_reflink_remap(ip, irec->br_startoff,
 				irec->br_blockcount, irec->br_startblock);