From d666ba98f849ad44c4405ecc2180390ebe80f4f9 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 27 Nov 2018 17:02:25 -0700 Subject: blk-mq: add mq_ops->commit_rqs() blk-mq passes information to the hardware about any given request being the last that we will issue in this sequence. The point is that hardware can defer costly doorbell type writes to the last request. But if we run into errors issuing a sequence of requests, we may never send the request with bd->last == true set. For that case, we need a hook that tells the hardware that nothing else is coming right now. For failures returned by the drivers ->queue_rq() hook, the driver is responsible for flushing pending requests, if it uses bd->last to optimize that part. This works like before, no changes there. Reviewed-by: Omar Sandoval Reviewed-by: Ming Lei Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe --- block/blk-mq.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'block/blk-mq.c') diff --git a/block/blk-mq.c b/block/blk-mq.c index 2a1a653a8054..d8534107bb6f 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1259,6 +1259,14 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list, if (!list_empty(list)) { bool needs_restart; + /* + * If we didn't flush the entire list, we could have told + * the driver there was more coming, but that turned out to + * be a lie. + */ + if (q->mq_ops->commit_rqs) + q->mq_ops->commit_rqs(hctx); + spin_lock(&hctx->lock); list_splice_init(list, &hctx->dispatch); spin_unlock(&hctx->lock); @@ -1865,6 +1873,14 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx, blk_mq_end_request(rq, ret); } } + + /* + * If we didn't flush the entire list, we could have told + * the driver there was more coming, but that turned out to + * be a lie. + */ + if (!list_empty(list) && hctx->queue->mq_ops->commit_rqs) + hctx->queue->mq_ops->commit_rqs(hctx); } static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq) -- cgit