linux-kernel - Re: [PATCH 06/13] async_tx: add support for asynchronous GF multiplication

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Date:	Sat, 21 Mar 2009 02:00:42 +0300
From:	Ilya Yanok <yanok@...raft.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Dan Williams <dan.j.williams@...el.com>,
	"H. Peter Anvin" <h.peter.anvin@...el.com>,
	linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
	neilb@...e.de, maciej.sosnowski@...el.com,
	Yuri Tikhonov <yur@...raft.com>
Subject: Re: [PATCH 06/13] async_tx: add support for asynchronous GF 	multiplication

Hi H. Peter,

H. Peter Anvin wrote:
>> Something is broken if we take this path.  This routine could stand to
>> have a WARN_ONCE(), because if it is ever called there is something is
>> wrong with the raid6 offload driver.  The intent is that the
>> asynchronous recovery routines will perform an early check to see if
>> the recovery can be offloaded (with a series of calls to
>> async_xor/async_pq).  If not we fall back to the optimized synchronous
>> recovery routines (raid6_2data_recov, raid6_datap_recov).  The only
>> time this path will be taken is if we have decided to perform
>> asynchronous recovery but at a later call to async_pq the offload
>> driver reports it has run out of descriptors.
>>
>
> That doesn't explain what you expect the code to do.  It still doesn't
> make sense to me.

We defined async_pq() function as hardware can do GF multiplication of
arbitrary elements and we want to take advantage of this fact. But by
the design of ASYNC_TX API we have to provide synchronous version of
that function too.

Regards, Ilya.

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