nvmet: Change return code of discard command if not supported

Execute discard command on block device that doesn't support it
should return success.
Returning internal error while using multi-path fails the path.

Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Israel Rukshin <israelr@mellanox.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>

drivers/nvme/target/io-cmd.c

@@ -105,10 +105,13 @@ static void nvmet_execute_flush(struct nvmet_req *req)
 static u16 nvmet_discard_range(struct nvmet_ns *ns,
 		struct nvme_dsm_range *range, struct bio **bio)
 {
-	if (__blkdev_issue_discard(ns->bdev,
+	int ret;
+
+	ret = __blkdev_issue_discard(ns->bdev,
 			le64_to_cpu(range->slba) << (ns->blksize_shift - 9),
 			le32_to_cpu(range->nlb) << (ns->blksize_shift - 9),
-			GFP_KERNEL, 0, bio))
+			GFP_KERNEL, 0, bio);
+	if (ret && ret != -EOPNOTSUPP)
 		return NVME_SC_INTERNAL | NVME_SC_DNR;
 	return 0;
 }