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

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Date:   Wed, 28 Oct 2020 17:29:00 +0800
From:   zhenwei pi <pizhenwei@...edance.com>
To:     Sagi Grimberg <sagi@...mberg.me>, hch@....de,
        chaitanya.kulkarni@....com
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [PATCH 1/2] nvmet: introduce transport layer
 keep-alive

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@...edance.com>
>> ---
>>   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