Re: [PATCH] nvme-fabrics: reject I/O to offline device

[Hannes Reinecke <hare@suse.de>]

On 12/6/19 11:18 PM, Sagi Grimberg wrote:
> 
>>> ---
>>> diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
>>> index 74b8818..b58abc1 100644
>>> --- a/drivers/nvme/host/fabrics.c
>>> +++ b/drivers/nvme/host/fabrics.c
>>> @@ -549,6 +549,8 @@ blk_status_t nvmf_fail_nonready_command(struct 
>>> nvme_ctrl *ctrl,
>>>   {
>>>          if (ctrl->state != NVME_CTRL_DELETING &&
>>>              ctrl->state != NVME_CTRL_DEAD &&
>>> +           !(ctrl->state == NVME_CTRL_CONNECTING &&
>>> +            ((ktime_get_ns() - rq->start_time_ns) > 
>>> jiffies_to_nsecs(rq->timeout))) &&
>>>              !blk_noretry_request(rq) && !(rq->cmd_flags & 
>>> REQ_NVME_MPATH))
>>>                  return BLK_STS_RESOURCE;
>>>
>>
>> Did you test this to ensure it's doing what you expect. I'm not sure 
>> that all the timers are set right at this point. Most I/O's timeout 
>> from a deadline time stamped at blk_mq_start_request(). But that 
>> routine is actually called by the transports post the 
>> nvmf_check_ready/fail_nonready calls.  E.g. the io is not yet in 
>> flight, thus queued, and the blk-mq internal queuing doesn't count 
>> against the io timeout.  I can't see anything that guarantees 
>> start_time_ns is set.
> 
> I'm not sure this behavior for failing I/O always desired? some
> consumers would actually not want the I/O to fail prematurely if we
> are not multipathing...
> 
> I think we need a fail_fast_tmo set in when establishing the controller
> to get it right.
> 
Agreed. This whole patch looks like someone is trying to reimplement 
fast_io_fail_tmo / dev_loss_tmo.
As we're moving into unreliable fabrics I guess we'll need a similar 
mechanism.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke            Teamlead Storage & Networking
hare@suse.de                               +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

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