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Date: Wed, 12 Mar 2003 00:59:48 -0800 (PST)
From: Andre Hedrick <andre@linux-ide.org>
To: Andries Brouwer <aebr@win.tue.nl>
cc: scott thomason <scott-kernel@thomasons.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: bio too big device
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Well that is the first complete explaination of the 255 limit.
That belongs in a simple dirty drive list in ide-probe.c (or whatever the
latest filename is) and then dump this issue for good.

Cheer,

On Wed, 12 Mar 2003, Andries Brouwer wrote:

> > On Tue, 11 Mar 2003, scott thomason wrote:
> > 
> > > I frequently receive this message in my syslog, apparently 
> > > whenever there are periods of significant write activity:
> > > 
> > >     bio too big device ide0(3,7) (256 > 255)
> > >     bio too big device ide1(22,6) (256 > 255)
> 
> On Tue, Mar 11, 2003 at 09:01:25PM -0800, Andre Hedrick wrote:
> 
> > That has to be a BIO bug or IDE setup bug.
> > 
> > 256 sectors is legal and correct for 28-bit addressing.
> 
> Yes, it is. However, Paul Gortmaker reported on his old 700MB
> Maxtor 7850 AV that would give errors with 256-sector requests
> and work well with 255-sector requests. In a later post he
> added that one has to work hard to evoke this error - usually
> 256-sector requests are fine, but after torturing the disk with
> an hour of simultaneous untar and make, an error occurred.
> 
> Maybe that is the only disk that gives problems.
> 
> Jens replied:
> 
> = The 256 is _not_ a bug in the driver, it's more likely a bug in your
> = drive. 256 is a perfectly legal transfer size. That said, maybe it is
> = a good idea to leave it at 255 just for safety
> 
> So that is how this length was limited.
> 
> In short: 256 is legal, has always been legal, nothing wrong with it.
> But at least one old disk has been discovered that was happier with 255.
> 
> Andries
> 

Andre Hedrick
LAD Storage Consulting Group

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