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Date: Tue, 23 Sep 2008 16:53:31 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] Re: [PATCH 2/3] Move aio implementation out of raw
	block driver
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To: Ryan Harper <ryanh@us.ibm.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>, Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel@nongnu.org, kvm@vger.kernel.org

Ryan Harper wrote:
>> So what happens if !defined(CONFIG_AIO)?  By my reading of the code, 
>> aio_drv will be NULL and this will SEGV.
> 
> raw_aio_read/write/cancel aren't included in the bdrv structure unless
> CONFIG_AIO is defined.  Rather in bdrv_register, the aio emulation
> functions are used instead.

How about providing a aio interface implementation which simply uses
read/write syscalls (thereby not being really async obviously)?  Then
use that as fallback instead of aio emulation?  And also drop CONFIG_AIO
then?

cheers,
  Gerd