linux-kernel - Re: [PATCH v3 3/3] nvme: handle connectivity loss in nvme_set_queue

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Message-ID: <9ab35631-4df6-495a-8dca-5cb414f17625@suse.de>
Date: Fri, 20 Dec 2024 09:32:37 +0100
From: Hannes Reinecke <hare@...e.de>
To: Daniel Wagner <dwagner@...e.de>
Cc: Daniel Wagner <wagi@...nel.org>, James Smart <james.smart@...adcom.com>,
 Keith Busch <kbusch@...nel.org>, Christoph Hellwig <hch@....de>,
 Sagi Grimberg <sagi@...mberg.me>, Paul Ely <paul.ely@...adcom.com>,
 linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] nvme: handle connectivity loss in
 nvme_set_queue_count

On 12/17/24 15:01, Daniel Wagner wrote:
> On Tue, Dec 17, 2024 at 10:45:45AM +0100, Hannes Reinecke wrote:
>> On 12/17/24 09:35, Daniel Wagner wrote:
>>> On Fri, Nov 29, 2024 at 12:10:33PM +0100, Hannes Reinecke wrote:
>>>>> +	/*
>>>>> +	 * It's either a kernel error or the host observed a connection
>>>>> +	 * lost. In either case it's not possible communicate with the
>>>>> +	 * controller and thus enter the error code path.
>>>>> +	 */
>>>>> +	if (status < 0 || status == NVME_SC_HOST_PATH_ERROR)
>>>>>     		return status;
>>>>>     	/*
>>>>>
>>>> Hmm. Maybe checking for NVME_SC_DNR, too?
>>>
>>> if no one complains I'll update the check to:
>>>
>>> 	if (status < 0 || (status > 0 && (status & NVME_STATUS_DNR)) ||
>>> 	    status == NVME_SC_HOST_PATH_ERROR)
>>> 		return status;
>>>
>>> okay?
>>
>> Which really cries out for a helper. But otherwise okay.
> 
> As far I remember, Christoph is not a big fan of single users of tiny
> helper functions. Anyway, what about this:
> 
> +static bool nvme_num_queue_updated(status)
> +{
> +       /*
> +        * It's either a kernel error or the host observed a connection
> +        * lost. In either case it's not possible communicate with the
> +        * controller and thus enter the error code path.
> +        */
> +
> +       if (status < 0 || status & NVME_STATUS_DNR ||
> +           status == NVME_SC_HOST_PATH_ERROR)
> +               return false;
> +
> +       return true;
> +}
> +
>   int nvme_set_queue_count(struct nvme_ctrl *ctrl, int *count)
>   {
>          u32 q_count = (*count - 1) | ((*count - 1) << 16);
> @@ -1701,13 +1716,8 @@ int nvme_set_queue_count(struct nvme_ctrl *ctrl, int *count)
> 
>          status = nvme_set_features(ctrl, NVME_FEAT_NUM_QUEUES, q_count, NULL, 0,
>                          &result);
> -       /*
> -        * It's either a kernel error or the host observed a connection
> -        * lost. In either case it's not possible communicate with the
> -        * controller and thus enter the error code path.
> -        */
> -       if (status < 0 || (status > 0 && (status & NVME_STATUS_DNR)) ||
> -           status == NVME_SC_HOST_PATH_ERROR)
> +
> +       if (!nvme_num_queue_updated(status))
>                  return status;
> 
>          /*

Naming is terrible. The helper does not check whether the number of 
queues updated, so why the name?

Better keep it inline, then.

Reviewed-by: Hannes Reinecke <hare@...e.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@...e.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich