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Message-ID: <402aea05-8d04-99e2-5e31-803d2423283d@oracle.com> Date: Wed, 13 Dec 2017 11:30:48 +0800 From: "jianchao.wang" <jianchao.w.wang@...cle.com> To: Tejun Heo <tj@...nel.org>, axboe@...nel.dk Cc: linux-kernel@...r.kernel.org, oleg@...hat.com, peterz@...radead.org, kernel-team@...com, osandov@...com, linux-block@...r.kernel.org, hch@....de Subject: Re: [PATCH 1/6] blk-mq: protect completion path with RCU Hello tejun Sorry for missing the V2, same comment again. On 12/13/2017 03:01 AM, Tejun Heo wrote: > Currently, blk-mq protects only the issue path with RCU. This patch > puts the completion path under the same RCU protection. This will be > used to synchronize issue/completion against timeout by later patches, > which will also add the comments. > > Signed-off-by: Tejun Heo <tj@...nel.org> > --- > block/blk-mq.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 1109747..acf4fbb 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -568,11 +568,23 @@ static void __blk_mq_complete_request(struct request *rq) > void blk_mq_complete_request(struct request *rq) > { > struct request_queue *q = rq->q; > + struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu); > + int srcu_idx; > > if (unlikely(blk_should_fake_timeout(q))) > return; > - if (!blk_mark_rq_complete(rq)) > - __blk_mq_complete_request(rq); > + > + if (!(hctx->flags & BLK_MQ_F_BLOCKING)) { > + rcu_read_lock(); > + if (!blk_mark_rq_complete(rq)) > + __blk_mq_complete_request(rq); > + rcu_read_unlock(); > + } else { > + srcu_idx = srcu_read_lock(hctx->queue_rq_srcu); > + if (!blk_mark_rq_complete(rq)) > + __blk_mq_complete_request(rq); > + srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx); The __blk_mq_complete_request() could be executed in irq context. There should not be any sleeping operations in it. If just synchronize with the timeout path to ensure the aborted_gstate to be seen, only rcu is needed here ,as well as the blk_mq_timeout_work. > + } > } > EXPORT_SYMBOL(blk_mq_complete_request); > >
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