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Re: [Qemu-block] [PATCH v3] block/vdi: Add locking for parallel requests
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-block] [PATCH v3] block/vdi: Add locking for parallel requests |
Date: |
Mon, 2 Mar 2015 11:31:14 -0600 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Fri, Feb 27, 2015 at 02:54:39PM -0500, Max Reitz wrote:
> When allocating a new cluster, the first write to it must be the one
> doing the allocation, because that one pads its write request to the
> cluster size; if another write to that cluster is executed before it,
> that write will be overwritten due to the padding.
>
> See https://bugs.launchpad.net/qemu/+bug/1422307 for what can go wrong
> without this patch.
>
> Cc: qemu-stable <address@hidden>
> Signed-off-by: Max Reitz <address@hidden>
> ---
> v3: Hopefully finally found the real issue which causes the problems
> described in the bug report; at least it sounds very reasonable and
> I can no longer reproduce any of the issues described there.
> Thank you, Paolo and Stefan!
> ---
> block/vdi.c | 25 +++++++++++++++++++++++++
> 1 file changed, 25 insertions(+)
I think this is overkill but let's merge it since the patch has been
written. A simple s->lock for I/O operations would have been fine since
this block driver was never designed for parallel I/O.
Reviewed-by: Stefan Hajnoczi <address@hidden>
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