On Tue, Apr 17, 2018 at 11:46:20AM +0800, Jianchao Wang wrote: > 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 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 <bart.vanass...@wdc.com> > Cc: Tejun Heo <t...@kernel.org> > Cc: Ming Lei <ming....@redhat.com> > Cc: Martin Steigerwald <mar...@lichtvoll.de> > Cc: sta...@vger.kernel.org > Signed-off-by: Jianchao Wang <jianchao.w.w...@oracle.com> > --- > 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; > }
Good catch, blk_mq_check_expired() is bypassed, but it is still hit by blk_mq_terminate_expired(). Reviewed-by: Ming Lei <ming....@redhat.com> -- Ming
