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Date: Wed, 12 Mar 2003 09:47:10 +0100
From: Andries Brouwer <aebr@win.tue.nl>
To: Andre Hedrick <andre@linux-ide.org>
Cc: scott thomason <scott-kernel@thomasons.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: bio too big device
Message-ID: <20030312084710.GA4816@win.tue.nl>
References: <200303112055.31854.scott-kernel@thomasons.org> <Pine.LNX.4.10.10303112100270.391-100000@master.linux-ide.org>
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> 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

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