diff --git a/fs/xfs/libxfs/xfs_exchmaps.c b/fs/xfs/libxfs/xfs_exchmaps.c
index dcd0bd0b13b4..3efed37cb98a 100644
--- a/fs/xfs/libxfs/xfs_exchmaps.c
+++ b/fs/xfs/libxfs/xfs_exchmaps.c
@@ -959,6 +959,16 @@ xmi_can_exchange_reflink_flags(
 {
 	struct xfs_mount		*mp = req->ip1->i_mount;
 
+	/*
+	 * The INO1_WRITTEN optimization can skip exchanging hole and
+	 * unwritten mappings, which means we cannot guarantee that all
+	 * shared extents actually moved to the other file.  Clearing the
+	 * reflink flag of an inode that still holds shared extents breaks
+	 * the CoW write path, so refuse to exchange the flags in that case.
+	 */
+	if (req->flags & XFS_EXCHMAPS_INO1_WRITTEN)
+		return false;
+
 	if (hweight32(reflink_state) != 1)
 		return false;
 	if (req->startoff1 != 0 || req->startoff2 != 0)