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Date: Wed, 8 Aug 2018 16:22:28 +0800 From: Jianchao Wang <jianchao.w.wang@...cle.com> To: axboe@...nel.dk Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org Subject: [PATCH] blk-mq: count the hctx as active before allocate tag Currently, we count the hctx as active after allocate tag successfully. The other shared-tags users could exhaust the tags and starve a non-active and waiting-tag hctx. Count the hctx as active before try to allocate tag to fix this. Signed-off-by: Jianchao Wang <jianchao.w.wang@...cle.com> --- block/blk-mq.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index ae44e85..acd40eb 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -369,6 +369,8 @@ static struct request *blk_mq_get_request(struct request_queue *q, e->type->ops.mq.limit_depth(op, data); } + blk_mq_tag_busy(data.hctx); + tag = blk_mq_get_tag(data); if (tag == BLK_MQ_TAG_FAIL) { if (put_ctx_on_error) { @@ -972,6 +974,7 @@ bool blk_mq_get_driver_tag(struct request *rq, struct blk_mq_hw_ctx **hctx, .hctx = blk_mq_map_queue(rq->q, rq->mq_ctx->cpu), .flags = wait ? 0 : BLK_MQ_REQ_NOWAIT, }; + bool shared; might_sleep_if(wait); @@ -981,9 +984,10 @@ bool blk_mq_get_driver_tag(struct request *rq, struct blk_mq_hw_ctx **hctx, if (blk_mq_tag_is_reserved(data.hctx->sched_tags, rq->internal_tag)) data.flags |= BLK_MQ_REQ_RESERVED; + shared = blk_mq_tag_busy(data.hctx); rq->tag = blk_mq_get_tag(&data); if (rq->tag >= 0) { - if (blk_mq_tag_busy(data.hctx)) { + if (shared) { rq->rq_flags |= RQF_MQ_INFLIGHT; atomic_inc(&data.hctx->nr_active); } -- 2.7.4
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