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Message-ID: <d837ebda-2dbd-46d9-b04a-3d086ab5ba92@suse.de>
Date:   Wed, 27 Sep 2023 08:26:05 +0200
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Subject: Re: [RFC PATCH v2 00/18] scsi: scsi_error: Introduce new error handle
 mechanism
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To:     Christoph Hellwig <hch@infradead.org>,
        Mike Christie <michael.christie@oracle.com>
Cc:     Wenchao Hao <haowenchao2@huawei.com>,
        "James E . J . Bottomley" <jejb@linux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@oracle.com>,
        linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
        louhongxiang@huawei.com, lixiaokeng@huawei.com
References: <20230901094127.2010873-1-haowenchao2@huawei.com>
 <ZRGfc73BSW0yyUtI@infradead.org>
 <47bed3cb-f307-ec55-5c28-051687dab1ea@huawei.com>
 <a92f5e0c-1976-4fc6-ba48-7ff49546318a@oracle.com>
 <ZRKHokGtOE/AgAFY@infradead.org>
From:   Hannes Reinecke <hare@suse.de>
In-Reply-To: <ZRKHokGtOE/AgAFY@infradead.org>
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On 9/26/23 09:26, Christoph Hellwig wrote:
> On Mon, Sep 25, 2023 at 12:54:48PM -0500, Mike Christie wrote:
>> I think we want to figure out Hannes's patches first.
> 
> Yes.
> 
>> For a new EH design we will want to be able to do multiple TMFs in parallel
>> on the same host/target right?
>>
>> The problem is that we need to be able to make forward progress in the EH
>> path and not fail just because we can't allocate memory for a TMF related
>> struct. To accomplish this now, drivers will use mempools, preallocate TMF
>> related structs/mem/tags with their scsi_cmnd related structs, preallocate
>> per host/target/device related structs or ignore what I wrote above and just
>> fail.
>>
>> Hannes's patches fix up the eh callouts so they don't pass in a scsi_cmnd
>> when it's not needed. That seems nice because after that, then for your new
>> EH we can begin to standardize on how to handle preallocation of drivers
>> resources needed to perform TMFs for your new EH. It could be a per
>> device/target/host callout to allow drivers to preallocate, then scsi-ml calls
>> into the drivers with that data. It doesn't have to be exactly like that or
>> anything close. It would be nice for drivers to not have to think about this
>> type of thing and scsi-ml just to handle the resource management for us when
>> there are multiple TMFs in progress.
> 
> Exactly!

Yeah, thanks for the vote of support.
Last time I tried the attempt got shot down, as it had been using the 
'wrong' interface. But seeing that there's renewed interest I'll be 
reposting them.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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