Re: [PATCH 0/3] Separate zone requests from medium access requests

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Martin,

On 3/1/17 11:52, Martin K. Petersen wrote:
>>>>>> "Christoph" == Christoph Hellwig <hch@xxxxxx> writes:
> 
> Christoph> I don't really like this too much - this is too many SCSI
> Christoph> specifics for the block layer to care.  Maybe using bios for
> Christoph> the zone ops was a mistake after all, and we should just have
> Christoph> operations in struct block_device instead..
> 
> Yeah, I'm afraid I don't like this either.
> 
> Short term I still think we should adjust in sd. And then maybe longer
> term revisit whether these hybrid commands should be something other
> than bios.

OK. I will think about it.

The problem remains that the mpt3sas driver needs fixing. As you
suggest, we can do that in sd, or directly in mpt3sas.
I tried to do a clean fix in sd, but always end up consuming a lot of
aspirin because of all the potential corner cases to deal with. So I
would prefer really just a fix in mpt3sas for now and think of the sd
changes (if any) together with a redesign of the zone commands execution
(not as BIOs).

The file sd.h has the inline function scsi_medium_access_command()
defined. We could move that to include/scsi/scsi.h (or scsi_proto.h) and
use it in place of blk_rq_accesses_medium() in the mpt3sas driver to not
force unaligned resid corrections for zone commands. Would that be
acceptable ?

Best regards.

-- 
Damien Le Moal, Ph.D.
Sr. Manager, System Software Research Group,
Western Digital Corporation
Damien.LeMoal@xxxxxxx
(+81) 0466-98-3593 (ext. 513593)
1 kirihara-cho, Fujisawa,
Kanagawa, 252-0888 Japan
www.wdc.com, www.hgst.com



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