From e167dfb53cb85fde7b15f644e9dbef7ba31896b6 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Wed, 29 Oct 2014 11:18:26 -0600 Subject: blk-mq: add BLK_MQ_F_DEFER_ISSUE support flag Drivers can now tell blk-mq if they take advantage of the deferred issue through 'last' or not. If they do, don't do queue-direct for sync IO. This is a preparation patch for the nvme conversion. Signed-off-by: Jens Axboe --- block/blk-mq.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'block') diff --git a/block/blk-mq.c b/block/blk-mq.c index 7e5303820452..b355b5957cd7 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1172,7 +1172,12 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio) goto run_queue; } - if (is_sync) { + /* + * If the driver supports defer issued based on 'last', then + * queue it up like normal since we can potentially save some + * CPU this way. + */ + if (is_sync && !(data.hctx->flags & BLK_MQ_F_DEFER_ISSUE)) { struct blk_mq_queue_data bd = { .rq = rq, .list = NULL, -- cgit v1.2.1