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Subject: Re: [Qemu-devel] [PATCH 3/3] block/nbd: Make the NBD block device
	use the AIO interface
From: Nicholas Thomas <nick@bytemark.co.uk>
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Date: Thu, 17 Feb 2011 19:28:37 +0000
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To: Kevin Wolf <kwolf@redhat.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org

Ho hum.

On Thu, 2011-02-17 at 16:34 +0000, Nicholas Thomas wrote:
> Signed-off-by: Nick Thomas <nick@bytemark.co.uk>
> ---
>  block/nbd.c |  549
> ++++++++++++++++++++++++++++++++++++++++++++++++++---------
>  1 files changed, 464 insertions(+), 85 deletions(-)

Additional testing has revealed that this code breaks the stock
nbd-server (the one on sourceforge) when large (well, 1.3MiB) write
requests are sent to it.

The server process receives a valid-looking NBD write request header
followed by the first ~200K of the write data (sent from
add_aio_request). It then exits (errcode 1).

add_aio_request returns the error, and subsequently, read_aio_response
picks up the aioreq and loops forever, trying to read a response from a
closed socket.

Reads and small writes seem to work fine, however.

I'll debug the server tomorrow and try to see what's breaking it - no
good having a technically compliant client if it breaks the most common
server out there ;)

/Nick