linux-kernel - Re: [RFC PATCH v2 00/18] scsi: scsi_error: Introduce new error handle mechanism

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Date:   Wed, 27 Sep 2023 17:41:44 +0800
From:   Wenchao Hao <haowenchao2@...wei.com>
To:     Hannes Reinecke <hare@...e.de>,
        Mike Christie <michael.christie@...cle.com>,
        Christoph Hellwig <hch@...radead.org>
CC:     "James E . J . Bottomley" <jejb@...ux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <louhongxiang@...wei.com>, <lixiaokeng@...wei.com>
Subject: Re: [RFC PATCH v2 00/18] scsi: scsi_error: Introduce new error handle
 mechanism

On 2023/9/27 15:59, Hannes Reinecke wrote:
> On 9/26/23 14:57, Wenchao Hao wrote:
>> On 2023/9/26 1:54, Mike Christie wrote:
>>> On 9/25/23 10:07 AM, Wenchao Hao wrote:
>>>> On 2023/9/25 22:55, Christoph Hellwig wrote:
>>>>> Before we add another new error handling mechanism we need to fix the
>>>>> old one first.  Hannes' work on not passing the scsi_cmnd to the various
>>>>> reset handlers hasn't made a lot of progress in the last five years and
>>>>> we'll need to urgently fix that first before adding even more
>>>>> complexity.
>>>>>
>>>> I observed Hannes's patches posted about one year ago, it has not been
>>>> applied yet. I don't know if he is still working on it.
>>>>
>>>> My patches do not depend much on that work, I think the conflict can be
>>>> solved fast between two changes.
>>>
>>> I think we want to figure out Hannes's patches first.
>>>
>>> For a new EH design we will want to be able to do multiple TMFs in parallel
>>> on the same host/target right?
>>>
>>
>> It's not necessary to do multiple TMFs in parallel, it's ok to make sure
>> each TMFs do not affect each other.
>>
>> For example, we have two devices: 0:0:0:0 and 0:0:0:1
>>
>> Both of them request device reset, they do not happened in parallel, but
>> would in serial. If 0:0:0:0 is performing device reset in progress, 0:0:0:1
>> just wait 0:0:0:0 to finish.
>>
> Well, not quite. Any higher-order TMFs are serialized by virtue of SCSI-EH, but command aborts (which also devolve down to TMFs on certain drivers) do run in parallel, and there we will be requiring multiple TMFs.
> 

It's best that multiple  TMFs can run in parallel, again, looking forwarding
to your changes.

> Cheers,
> 
> Hannes