null_blk: fix passing of REQ_FUA flag in null_handle_rq

[ Upstream commit 2d62e6b038e729c3e4bfbfcfbd44800ef0883680 ]

REQ_FUA should be checked using rq->cmd_flags instead of req_op().

Fixes: deb78b419dfda ("nullb: emulate cache")
Signed-off-by: Hou Pu <houpu@bytedance.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index d2d7dc9..4fef1fb 100644
--- a/drivers/block/null_blk_main.c
+++ b/drivers/block/null_blk_main.c
@@ -1086,7 +1086,7 @@
 		len = bvec.bv_len;
 		err = null_transfer(nullb, bvec.bv_page, len, bvec.bv_offset,
 				     op_is_write(req_op(rq)), sector,
-				     req_op(rq) & REQ_FUA);
+				     rq->cmd_flags & REQ_FUA);
 		if (err) {
 			spin_unlock_irq(&nullb->lock);
 			return err;