nvme: don't hard code size of struct t10_pi_tuple

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/core.c

@@ -356,7 +356,8 @@ static inline blk_status_t nvme_setup_rw(struct nvme_ns *ns,
 	 * unless this namespace is formated such that the metadata can be
 	 * stripped/generated by the controller with PRACT=1.
 	 */
-	if (ns && ns->ms && (!ns->pi_type || ns->ms != 8) &&
+	if (ns && ns->ms &&
+	    (!ns->pi_type || ns->ms != sizeof(struct t10_pi_tuple)) &&
 	    !blk_integrity_rq(req) && !blk_rq_is_passthrough(req))
 		return BLK_STS_NOTSUPP;