xfs: preserve DIFLAG2_NREXT64 when setting other inode attributes

It is vitally important that we preserve the state of the NREXT64 inode
flag when we're changing the other flags2 fields.

Fixes: 9b7d16e3 ("xfs: Introduce XFS_DIFLAG2_NREXT64 and associated helpers")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>

fs/xfs/xfs_ioctl.c

@@ -1096,7 +1096,8 @@ xfs_flags2diflags2(
 {
 	uint64_t		di_flags2 =
 		(ip->i_diflags2 & (XFS_DIFLAG2_REFLINK |
-				   XFS_DIFLAG2_BIGTIME));
+				   XFS_DIFLAG2_BIGTIME |
+				   XFS_DIFLAG2_NREXT64));
 
 	if (xflags & FS_XFLAG_DAX)
 		di_flags2 |= XFS_DIFLAG2_DAX;