If we have that hook, we know the driver handles bd->last == true in
a smart fashion. If it does, even for multiple hardware queues, it's
a good idea to flush batches of requests to the device, if we have
batches of requests from the submitter.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
block/blk-mq.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9e1045152e45..091557a43d53 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1945,7 +1945,12 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
/* bypass scheduler for flush rq */
blk_insert_flush(rq);
blk_mq_run_hw_queue(data.hctx, true);
- } else if (plug && q->nr_hw_queues == 1) {
+ } else if (plug && (q->nr_hw_queues == 1 || q->mq_ops->commit_rqs)) {
+ /*
+ * Use plugging if we have a ->commit_rqs() hook as well,
+ * as we know the driver uses bd->last in a smart
+ * fashion.
+ */
unsigned int request_count = plug->rq_count;
struct request *last = NULL;
--
2.17.1
