block: null_blk: batched complete poll requests

Complete poll requests via blk_mq_add_to_batch() and
blk_mq_end_request_batch(), so that we can cover batched complete
code path by running null_blk test.

Meantime this way shows ~14% IOPS boost on 't/io_uring /dev/nullb0'
in my test.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20211203081703.3506020-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index b4ff5ae..20534a2 100644 (file)
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -1574,7 +1574,9 @@ static int null_poll(struct blk_mq_hw_ctx *hctx, struct io_comp_batch *iob)
                cmd = blk_mq_rq_to_pdu(req);
                cmd->error = null_process_cmd(cmd, req_op(req), blk_rq_pos(req),
                                                blk_rq_sectors(req));
-               end_cmd(cmd);
+               if (!blk_mq_add_to_batch(req, iob, cmd->error,
+                                       blk_mq_end_request_batch))
+                       end_cmd(cmd);
                nr++;
        }