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From: "Peter T. Breuer" <ptb@it.uc3m.es>
Message-Id: <200208291214.g7TCEtZ10901@oboe.it.uc3m.es>
Subject: Re: O_DIRECT
In-Reply-To: <200208291113.g7TBDut26852@tench.street-vision.com> from "kernel@street-vision.com"
 at "Aug 29, 2002 11:13:56 am"
To: kernel@street-vision.com
Date: Thu, 29 Aug 2002 14:14:55 +0200 (MET DST)
Cc: linux kernel <linux-kernel@vger.kernel.org>
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"A month of sundays ago kernel@street-vision.com wrote:"
> > 
> > What functions does a block driver have to implement in order to
> > support read/write when it has been opened with O_DIRECT from user
> > space.

> Remeber that the memory you read/write from must be page aligned (ie
> mmap /dev/zero not malloc) and reads and writes must be multiples of the
> page size. I think block devices work on 2.4 too, but I forget (otherwise
> you can use raw devices).

I do believe you are right. Multiples of 4096 seem to work fine. No
support needed in the block device driver.

Peter
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