linux-kernel - Re: [PATCH v2 4/5] nvme-fc: Make initial connect attempt synchronous

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Message-ID: <17321e5d-3744-dd7c-5ed9-cecf055ada39@suse.de>
Date:   Tue, 27 Jun 2023 08:39:12 +0200
From:   Hannes Reinecke <hare@...e.de>
To:     Daniel Wagner <dwagner@...e.de>,
        Dan Carpenter <dan.carpenter@...aro.org>
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, Chaitanya Kulkarni <kch@...dia.com>,
        Shin'ichiro Kawasaki <shinichiro@...tmail.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        James Smart <jsmart2021@...il.com>
Subject: Re: [PATCH v2 4/5] nvme-fc: Make initial connect attempt synchronous

On 6/27/23 08:18, Daniel Wagner wrote:
> On Mon, Jun 26, 2023 at 02:33:18PM +0300, Dan Carpenter wrote:
>>> @@ -2943,6 +2943,8 @@ nvme_fc_create_io_queues(struct nvme_fc_ctrl *ctrl)
>>>   	/* force put free routine to ignore io queues */
>>>   	ctrl->ctrl.tagset = NULL;
>>>   
>>> +	if (ret > 0)
>>> +		ret = -EIO;
>>
>> All these checks for ret > 0 make me unhappy.  I don't understand how
>> they are a part of the commit.
> 
> We have two types of error message types in the nvme subsystem. The negative
> values are the usual ones and positive ones are nvme protocol errors.
> 
> For example if the authentication fails because of invalid credentials when
> doing the authentication nvmf_connect_admin_queue() will return a value of
> NVME_SC_AUTH_REQUIRED. This is also the value which gets propagated to this
> point here. The problem is any positive error code is interpreted as a valid
> pointer later in the code, which results in a crash.
> 
>> I have tried to look at the context and I think maybe you are working
>> around the fact that qla_nvme_ls_req() returns QLA_FUNCTION_FAILED on
>> error.
> 
> The auth blktests are exercising the error path here and that's why I added
> this check. BTW, we already use in other places, this is not completely new in
> this subsystem.
> 
>> Also the qla_nvme_ls_req() function EINVAL on error.  I just wrote a
>> commit message saying that none of the callers cared but I missed that
>> apparently gets returned to nvme_fc_init_ctrl().  :/
>> https://lore.kernel.org/all/49866d28-4cfe-47b0-842b-78f110e61aab@moroto.mountain/
> 
> Thank!
> 
>> Let's just fix qla_nvme_ls_req() instead of working around it here.
>>
>> And let's add a WARN_ON_ONCE() somewhere to prevent future bugs.
> 
> This makes sense for the driver APIs. Though for the core nvme subsystem this
> needs to be discusses/redesigned how to handle the protocol errors first.
> 
I would stick with the 'normal' nvme syntax of having negative errors as 
internal errors (ie errnos), '0' for no error, and positive numbers as 
NVMe protocol errors.
As such I would also advocate to not map NVMe protocol errors onto error 
numbers but rather fix the callers to not do a pointer conversion.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@...e.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
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