On Fri, Apr 16 2021 at 4:52pm -0400,
Ewan D. Milne <emilne@xxxxxxxxxx> wrote:
> On Thu, 2021-04-15 at 19:15 -0400, Mike Snitzer wrote:
> > If REQ_FAILFAST_TRANSPORT is set it means the driver should not retry
> > IO that completed with transport errors. REQ_FAILFAST_TRANSPORT is
> > set by multipathing software (e.g. dm-multipath) before it issues IO.
> >
> > Update NVMe to allow failover of requests marked with either
> > REQ_NVME_MPATH or REQ_FAILFAST_TRANSPORT. This allows such requests
> > to be given a disposition of either FAILOVER or FAILUP respectively.
> > FAILUP handling ensures a retryable error is returned up from NVMe.
> >
> > Introduce nvme_failup_req() for use in nvme_complete_rq() if
> > nvme_decide_disposition() returns FAILUP. nvme_failup_req() ensures
> > the request is completed with a retryable IO error when appropriate.
> > __nvme_end_req() was factored out for use by both nvme_end_req() and
> > nvme_failup_req().
> >
> > Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
> > ---
> > drivers/nvme/host/core.c | 31 ++++++++++++++++++++++++++-----
> > 1 file changed, 26 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> > index 4134cf3c7e48..10375197dd53 100644
> > --- a/drivers/nvme/host/core.c
> > +++ b/drivers/nvme/host/core.c
> > @@ -299,6 +299,7 @@ enum nvme_disposition {
> > COMPLETE,
> > RETRY,
> > FAILOVER,
> > + FAILUP,
> > };
> >
> > static inline enum nvme_disposition nvme_decide_disposition(struct
> > request *req)
> > @@ -318,10 +319,11 @@ static inline enum nvme_disposition
> > nvme_decide_disposition(struct request *req)
> > nvme_req(req)->retries >= nvme_max_retries)
> > return COMPLETE;
> >
> > - if (req->cmd_flags & REQ_NVME_MPATH) {
> > + if (req->cmd_flags & (REQ_NVME_MPATH | REQ_FAILFAST_TRANSPORT))
> > {
> > if (nvme_is_path_error(nvme_req(req)->status) ||
> > blk_queue_dying(req->q))
> > - return FAILOVER;
> > + return (req->cmd_flags & REQ_NVME_MPATH) ?
> > + FAILOVER : FAILUP;
> > } else {
> > if (blk_queue_dying(req->q))
> > return COMPLETE;
> > @@ -330,10 +332,8 @@ static inline enum nvme_disposition
> > nvme_decide_disposition(struct request *req)
> > return RETRY;
> > }
> >
> > -static inline void nvme_end_req(struct request *req)
> > +static inline void __nvme_end_req(struct request *req, blk_status_t
> > status)
> > {
> > - blk_status_t status = nvme_error_status(nvme_req(req)->status);
> > -
> > if (IS_ENABLED(CONFIG_BLK_DEV_ZONED) &&
> > req_op(req) == REQ_OP_ZONE_APPEND)
> > req->__sector = nvme_lba_to_sect(req->q->queuedata,
> > @@ -343,6 +343,24 @@ static inline void nvme_end_req(struct request
> > *req)
> > blk_mq_end_request(req, status);
> > }
> >
> > +static inline void nvme_end_req(struct request *req)
> > +{
> > + __nvme_end_req(req, nvme_error_status(nvme_req(req)->status));
> > +}
> > +
> > +static void nvme_failup_req(struct request *req)
> > +{
> > + blk_status_t status = nvme_error_status(nvme_req(req)->status);
> > +
> > + if (WARN_ON_ONCE(!blk_path_error(status))) {
> > + pr_debug("Request meant for failover but blk_status_t
> > (errno=%d) was not retryable.\n",
> > + blk_status_to_errno(status));
> > + status = BLK_STS_IOERR;
> > + }
> > +
> > + __nvme_end_req(req, status);
>
> It seems like adding __nvme_end_req() was unnecessary, since
> nvme_end_req() just calls it and does nothing else?
The __nvme_end_req helper allowed the status to be passed in, making it
easy to override status for unlikley edge-case where the BLK_STS is
!blk_path_error() but should be given nvme_is_path_error() returned
true.
Anyway, I can avoid the need to factor out __nvme_end_req() and just:
nvme_req(req)->status = NVME_SC_HOST_PATH_ERROR;
nvme_end_req(req);
Thanks,
Mike
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