Re: [External] Re: [PATCH 1/2] nvmet: introduce transport layer keep-alive

[zhenwei pi]

On 10/28/20 3:15 PM, Sagi Grimberg wrote:
> On 10/27/20 5:15 AM, zhenwei pi wrote:
> > In the zero KATO scenario, if initiator crashes without transport
> > layer disconnection, target side would never reclaim resources.
> >
> > A target could start transport layer keep-alive to detect dead
> > connection for the admin queue.
>
> Not sure why we should worry about kato=0, it's really
> more for debug purposes. I'd rather that we block this
> option from the host altogether.

A target can't suppose that initiator always runs as expected.
I'm developing a user level NVMeOF library, in my plan, user level KATO 
timer gets a little complex, I'd like to use TCP level keep-alive
to make code simple. So the target side needs to handle zero KATO case.

> > Signed-off-by: zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
> > ---
> >   drivers/nvme/target/admin-cmd.c |  2 +-
> >   drivers/nvme/target/core.c      | 14 +++++++++++---
> >   drivers/nvme/target/nvmet.h     |  3 ++-
> >   3 files changed, 14 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/nvme/target/admin-cmd.c 
> > b/drivers/nvme/target/admin-cmd.c
> > index dca34489a1dc..53fbd5c193a1 100644
> > --- a/drivers/nvme/target/admin-cmd.c
> > +++ b/drivers/nvme/target/admin-cmd.c
> > @@ -729,7 +729,7 @@ u16 nvmet_set_feat_kato(struct nvmet_req *req)
> >       nvmet_stop_keep_alive_timer(req->sq->ctrl);
> >       req->sq->ctrl->kato = DIV_ROUND_UP(val32, 1000);
> > -    nvmet_start_keep_alive_timer(req->sq->ctrl);
> > +    nvmet_start_keep_alive_timer(req->sq->ctrl, req);
> >       nvmet_set_result(req, req->sq->ctrl->kato);
> > diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
> > index 957b39a82431..451192f7ad6a 100644
> > --- a/drivers/nvme/target/core.c
> > +++ b/drivers/nvme/target/core.c
> > @@ -395,10 +395,18 @@ static void nvmet_keep_alive_timer(struct 
> > work_struct *work)
> >       nvmet_ctrl_fatal_error(ctrl);
> >   }
> > -void nvmet_start_keep_alive_timer(struct nvmet_ctrl *ctrl)
> > +void nvmet_start_keep_alive_timer(struct nvmet_ctrl *ctrl, struct 
> > nvmet_req *req)
> >   {
> > -    if (unlikely(ctrl->kato == 0))
> > +    if (unlikely(ctrl->kato == 0)) {
> > +        if (req->ops->keep_alive)
> > +            pr_info("ctrl %d starts with transport keep-alive %s\n", 
> > ctrl->cntlid,
> > +                req->ops->keep_alive(req) ? "failed" : "succeed");
> > +        else
> > +            pr_info("ctrl %d starts without both NVMeOF and transport 
> > keep-alive",
> > +                ctrl->cntlid);
> > +
> >           return;
> > +    }
> >       pr_debug("ctrl %d start keep-alive timer for %d secs\n",
> >           ctrl->cntlid, ctrl->kato);
> > @@ -1383,7 +1391,7 @@ u16 nvmet_alloc_ctrl(const char *subsysnqn, 
> > const char *hostnqn,
> >       ctrl->err_counter = 0;
> >       spin_lock_init(&ctrl->error_lock);
> > -    nvmet_start_keep_alive_timer(ctrl);
> > +    nvmet_start_keep_alive_timer(ctrl, req);
> >       mutex_lock(&subsys->lock);
> >       list_add_tail(&ctrl->subsys_entry, &subsys->ctrls);
> > diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
> > index 559a15ccc322..de1785ce9fcd 100644
> > --- a/drivers/nvme/target/nvmet.h
> > +++ b/drivers/nvme/target/nvmet.h
> > @@ -305,6 +305,7 @@ struct nvmet_fabrics_ops {
> >       u16 (*install_queue)(struct nvmet_sq *nvme_sq);
> >       void (*discovery_chg)(struct nvmet_port *port);
> >       u8 (*get_mdts)(const struct nvmet_ctrl *ctrl);
> > +    int (*keep_alive)(struct nvmet_req *req);
> >   };
> >   #define NVMET_MAX_INLINE_BIOVEC    8
> > @@ -395,7 +396,7 @@ void nvmet_get_feat_async_event(struct nvmet_req 
> > *req);
> >   u16 nvmet_set_feat_kato(struct nvmet_req *req);
> >   u16 nvmet_set_feat_async_event(struct nvmet_req *req, u32 mask);
> >   void nvmet_execute_async_event(struct nvmet_req *req);
> > -void nvmet_start_keep_alive_timer(struct nvmet_ctrl *ctrl);
> > +void nvmet_start_keep_alive_timer(struct nvmet_ctrl *ctrl, struct 
> > nvmet_req *req);
> >   void nvmet_stop_keep_alive_timer(struct nvmet_ctrl *ctrl);
> >   u16 nvmet_parse_connect_cmd(struct nvmet_req *req);

--
zhenwei pi