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Date: Sun, 25 Oct 2009 08:19:07 +0100
From: Christoph Hellwig <hch@lst.de>
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Subject: [Qemu-devel] Re: [PATCH] raw/linux-aio: Also initialize POSIX AIO
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To: Kevin Wolf <kwolf@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, qemu-devel@nongnu.org

On Thu, Oct 22, 2009 at 11:05:55AM +0200, Kevin Wolf wrote:
> Yes, it might look like overkill to introduce a abstraction for exactly
> two backends. I felt the same way. But then, the current implementation
> just feels totally wrong. It absolutely intransparent when we fall back
> to paio, and before debugging the bdrv_read/write emulation I didn't
> even know that we're doing it. And, like I said, why should a block
> format driver know what AIO method works which way?

Because the aio method is part of the block driver.  Despite our
code organization linux-aio.c and compat-posix-aio.c aren't generic
abstractions but sub-modules of raw-posix.  They would be better of
beeing renamed to block/raw-posix-aio-linux.c and
block/raw-posix-aio-pthreads.c, but with the latency of getting patches
into qemu that would just make developing any block code a nightmare
while those patches are in the queue.