Re: [PATCH v9] nvme-fabrics: reject I/O to offline device

[Hannes Reinecke <hare@suse.de>]

On 11/15/20 4:45 PM, Victor Gladkov wrote:
>> -----Original Message-----
>> From: Hannes Reinecke [mailto:hare@suse.de]
>> Sent: Thursday, 01 October, 2020 11:55
> 
>>> ---
>>>    drivers/nvme/host/core.c      | 49
>>> ++++++++++++++++++++++++++++++++++++++++++-
>>>    drivers/nvme/host/fabrics.c   | 25 +++++++++++++++++++---
>>>    drivers/nvme/host/fabrics.h   |  5 +++++
>>>    drivers/nvme/host/multipath.c |  5 ++++-
>>>    drivers/nvme/host/nvme.h      |  3 +++
>>>    5 files changed, 82 insertions(+), 5 deletions(-)
>>>
>> I did some more experiments with this, and found that there are some issues
>> with ANA handling.
>> If reconnect works, but the ANA state indicates that we still can't sent I/O (eg
>> by still being in transitioning), we hit the 'requeueing I/O'
>> state despite fast_io_fail_tmo being set. Not sure if that's the expected
>> outcome.
>> For that it might be better to move the FAILFAST_EXPIRED bit into the
>> namespace, as then we could selectively clear the bit in
>> nvme_failfast_work():
>>
>> @@ -151,12 +151,16 @@ EXPORT_SYMBOL_GPL(nvme_try_sched_reset);
>>    static void nvme_failfast_work(struct work_struct *work) {
>>           struct nvme_ctrl *ctrl = container_of(to_delayed_work(work),
>>                           struct nvme_ctrl, failfast_work);
>> +       struct nvme_ns *ns;
>>
>> -       if (ctrl->state != NVME_CTRL_CONNECTING)
>> -               return;
>> -
>> -
>> -       set_bit(NVME_CTRL_FAILFAST_EXPIRED, &ctrl->flags);
>> +       down_read(&ctrl->namespaces_rwsem);
>> +       list_for_each_entry(ns, &ctrl->namespaces, list) {
>> +               if (ctrl->state != NVME_CTRL_LIVE ||
>> +                   (ns->ana_state != NVME_ANA_OPTIMIZED &&
>> +                    ns->ana_state != NVME_ANA_NONOPTIMIZED))
>> +                       set_bit(NVME_NS_FAILFAST_EXPIRED, &ns->flags);
>> +       }
>> +       up_read(&ctrl->namespaces_rwsem);
>>           dev_info(ctrl->device, "failfast expired\n");
>>
>> ...and we could leave the failfast worker running even after the controller
>> transitioned to LIVE.
>> Cf the attached patch for details.
>>
>> Cheers,
>>
>> Hannes
>> --
> 
> I'm not sure what makes sense to move the FAILFAST_EXPIRED bit into the namespace,
> Because the failfast mechanism characterizes the controller as a whole.
> 
Oh, yes, I'm aware of that. But the problem here is with multipath; how 
do we handle the situation where all controllers have the 
'failfast_expired' bit set?
Should I/O be terminated (which I think it should, given that failfast 
is supposed to terminate the I/O)?
Or should I/O continue to run (as it does with your original patch)?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
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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