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Message-ID: <48D91403.8090007@us.ibm.com>
Date: Tue, 23 Sep 2008 11:06:27 -0500
From: Anthony Liguori <aliguori@us.ibm.com>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] Re: [PATCH 2/3] Move aio implementation out of raw
	block driver
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To: Gerd Hoffmann <kraxel@redhat.com>
Cc: Ryan Harper <ryanh@us.ibm.com>, qemu-devel@nongnu.org, kvm@vger.kernel.org, Marcelo Tosatti <mtosatti@redhat.com>

Gerd Hoffmann wrote:
> 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?
>   

Yeah, this is basically what block-raw-posix does today.  I was thinking 
the same thing.  I was also thinking that you could do an aio 
implementation for win32 and possibly reunify block-raw-posix and 
block-raw-linux.

But before going down this route, I want to see if linux-aio is really 
the right tool for the job.

Regards,

Anthony Liguori

> cheers,
>   Gerd
>