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Re: [Qemu-devel] [PATCH] sheepdog: fix dynamic grow for running qcow2 fo
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH] sheepdog: fix dynamic grow for running qcow2 format |
Date: |
Mon, 16 Dec 2013 17:04:28 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Sat, Dec 14, 2013 at 01:29:28AM +0800, Liu Yuan wrote:
> When running qcow2 over sheepdog, we might meet following problem
>
> qemu-system-x86_64: shrinking is not supported
>
> And cause IO errors to Guest. This is because we abuse bs->total_sectors,
> which
> is manipulated by generic block layer and race with sheepdog code.
>
> We should directly check if offset > vdi_size to dynamically enlarge the
> volume
> instead of 'offset > bs->total_sectors', which will cause problem when
> following
> case happens:
>
> vdi_size > offset > bs->total_sectors
>
> # then trigger sd_truncate() to shrink the volume wrongly.
>
> Cc: address@hidden
> Cc: Kevin Wolf <address@hidden>
> Cc: Stefan Hajnoczi <address@hidden>
> Reported-by: Hadrien KOHL <address@hidden>
> Signed-off-by: Liu Yuan <address@hidden>
> ---
> block/sheepdog.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
block.c already updates bs->total_sectors if bs->growable so this patch
is safe.
Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block
Stefan