block/null_blk: add queue_rqs() support

Add batched mq_ops.queue_rqs() support in null_blk for testing. The
implementation is much easy since null_blk doesn't have commit_rqs().

We simply handle each request one by one, if errors are encountered,
leave them in the passed in list and return back.

There is about 3.6% improvement in IOPS of fio/t/io_uring on null_blk
with hw_queue_depth=256 on my test VM, from 1.09M to 1.13M.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230913151616.3164338-6-chengming.zhou@linux.dev
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 968090935eb23f9418c742e89688ec0277f84e02..79d6cd3c3d4148967ddd9a76dd1c77bfc239f82f 100644 (file)
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -1750,6 +1750,25 @@ static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx,
        return null_handle_cmd(cmd, sector, nr_sectors, req_op(rq));
 }
 
+static void null_queue_rqs(struct request **rqlist)
+{
+       struct request *requeue_list = NULL;
+       struct request **requeue_lastp = &requeue_list;
+       struct blk_mq_queue_data bd = { };
+       blk_status_t ret;
+
+       do {
+               struct request *rq = rq_list_pop(rqlist);
+
+               bd.rq = rq;
+               ret = null_queue_rq(rq->mq_hctx, &bd);
+               if (ret != BLK_STS_OK)
+                       rq_list_add_tail(&requeue_lastp, rq);
+       } while (!rq_list_empty(*rqlist));
+
+       *rqlist = requeue_list;
+}
+
 static void cleanup_queue(struct nullb_queue *nq)
 {
        bitmap_free(nq->tag_map);
@@ -1802,6 +1821,7 @@ static int null_init_hctx(struct blk_mq_hw_ctx *hctx, void *driver_data,
 
 static const struct blk_mq_ops null_mq_ops = {
        .queue_rq       = null_queue_rq,
+       .queue_rqs      = null_queue_rqs,
        .complete       = null_complete_rq,
        .timeout        = null_timeout_rq,
        .poll           = null_poll,