From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Martin Steigerwald To: Jianchao Wang Cc: axboe@kernel.dk, bart.vanassche@wdc.com, tj@kernel.org, ming.lei@redhat.com, stable@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] blk-mq: start request gstate with gen 1 Date: Tue, 17 Apr 2018 14:10:08 +0200 Message-ID: <2612135.Ur0PZolWSD@merkaba> In-Reply-To: <1523936780-1589-1-git-send-email-jianchao.w.wang@oracle.com> References: <1523936780-1589-1-git-send-email-jianchao.w.wang@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" List-ID: Hi Jianchao, Jianchao Wang - 17.04.18, 05:46: > rq->gstate and rq->aborted_gstate both are zero before rqs are > allocated. If we have a small timeout, when the timer fires, > there could be rqs that are never allocated, and also there could > be rq that has been allocated but not initialized and started. At > the moment, the rq->gstate and rq->aborted_gstate both are 0, thus > the blk_mq_terminate_expired will identify the rq is timed out and > invoke .timeout early. For testing it I add it to 4.16.2 with the patches I have already? - '[PATCH] blk-mq_Directly schedule q->timeout_work when aborting a request.mbox' - '[PATCH v2] block: Change a rcu_read_{lock,unlock}_sched() pair into rcu_read_{lock,unlock}().mbox' - '[PATCH V4 1_2] blk-mq_set RQF_MQ_TIMEOUT_EXPIRED when the rq'\''s timeout isn'\''t handled.mbox' - '[PATCH V4 2_2] blk-mq_fix race between complete and BLK_EH_RESET_TIMER.mbox' > For scsi, this will cause scsi_times_out to be invoked before the > scsi_cmnd is not initialized, scsi_cmnd->device is still NULL at > the moment, then we will get crash. > > Cc: Bart Van Assche > Cc: Tejun Heo > Cc: Ming Lei > Cc: Martin Steigerwald > Cc: stable@vger.kernel.org > Signed-off-by: Jianchao Wang > --- > block/blk-core.c | 4 ++++ > block/blk-mq.c | 7 +++++++ > 2 files changed, 11 insertions(+) > > diff --git a/block/blk-core.c b/block/blk-core.c > index abcb868..ce62681 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -201,6 +201,10 @@ void blk_rq_init(struct request_queue *q, struct > request *rq) rq->part = NULL; > seqcount_init(&rq->gstate_seq); > u64_stats_init(&rq->aborted_gstate_sync); > + /* > + * See comment of blk_mq_init_request > + */ > + WRITE_ONCE(rq->gstate, MQ_RQ_GEN_INC); > } > EXPORT_SYMBOL(blk_rq_init); > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index f5c7dbc..d62030a 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -2069,6 +2069,13 @@ static int blk_mq_init_request(struct > blk_mq_tag_set *set, struct request *rq, > > seqcount_init(&rq->gstate_seq); > u64_stats_init(&rq->aborted_gstate_sync); > + /* > + * start gstate with gen 1 instead of 0, otherwise it will be equal > + * to aborted_gstate, and be identified timed out by > + * blk_mq_terminate_expired. > + */ > + WRITE_ONCE(rq->gstate, MQ_RQ_GEN_INC); > + > return 0; > } -- Martin