xfs: fail dax mount if reflink is enabled on a partition

Failure notification is not supported on partitions.  So, when we mount a
reflink enabled xfs on a partition with dax option, let it fail with
-EINVAL code.

Link: https://lkml.kernel.org/r/20220609143435.393724-1-ruansy.fnst@fujitsu.com
Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/xfs/xfs_super.c

@@ -350,8 +350,10 @@ xfs_setup_dax_always(
 		goto disable_dax;
 	}
 
-	if (xfs_has_reflink(mp)) {
-		xfs_alert(mp, "DAX and reflink cannot be used together!");
+	if (xfs_has_reflink(mp) &&
+	    bdev_is_partition(mp->m_ddev_targp->bt_bdev)) {
+		xfs_alert(mp,
+			"DAX and reflink cannot work with multi-partitions!");
 		return -EINVAL;
 	}