Message-ID: <3FCA1DD3.70004@pobox.com>
Date: Sun, 30 Nov 2003 11:41:55 -0500
From: Jeff Garzik <jgarzik@pobox.com>
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To: Jens Axboe <axboe@suse.de>
CC: Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>,
       "Prakash K. Cheemplavam" <prakashkc@gmx.de>, marcush@onlinehome.de,
       linux-kernel@vger.kernel.org, eric_mudama@Maxtor.com
Subject: Re: Silicon Image 3112A SATA trouble
References: <3FC36057.40108@gmx.de> <200311301547.32347.bzolnier@elka.pw.edu.pl> <3FCA1220.2040508@gmx.de> <200311301721.41812.bzolnier@elka.pw.edu.pl> <20031130162523.GV10679@suse.de>
In-Reply-To: <20031130162523.GV10679@suse.de>
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Jens Axboe wrote:
> On Sun, Nov 30 2003, Bartlomiej Zolnierkiewicz wrote:
>>Hmm. actually I was under influence that we have generic ioctls in 2.6.x,
>>but I can find only BLKSECTGET, BLKSECTSET was somehow lost.  Jens?
> 
> 
> Probably because it's very dangerous to expose, echo something too big
> and watch your data disappear.


IMO, agreed.

Max KB per request really should be set by the driver, as it's a 
hardware-specific thing that (as we see :)) is often errata-dependent.

Tangent:  My non-pessimistic fix will involve submitting a single sector 
DMA r/w taskfile manually, then proceeding with the remaining sectors in 
another r/w taskfile.  This doubles the interrupts on the affected 
chipset/drive combos, but still allows large requests.  I'm not terribly 
fond of partial completions, as I feel they add complexity, particularly 
so in my case:  I can simply use the same error paths for both the 
single-sector taskfile and the "everything else" taskfile, regardless of 
which taskfile throws the error.

(thinking out loud)  Though best for simplicity, I am curious if a 
succession of "tiny/huge" transaction pairs are efficient?  I am hoping 
that the drive's cache, coupled with the fact that each pair of 
taskfiles is sequentially contiguous, will not hurt speed too much over 
a non-errata configuration...

	Jeff


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