Re: [Qemu-devel] [PATCH] block/mirror: limit qiov to IOV_MAX elements

[Jeff Cody]

On Wed, Jul 01, 2015 at 03:45:50PM +0100, Stefan Hajnoczi wrote:
> If mirror has more free buffers than IOV_MAX, preadv(2)/pwritev(2)
> EINVAL failures may be encountered.
> 
> It is possible to trigger this by setting granularity to a low value
> like 8192.
> 
> This patch stops appending chunks once IOV_MAX is reached.
> 
> The spurious EINVAL failure can be reproduced with a qcow2 image file
> and the following QMP invocation:
> 
>   qmp.command('drive-mirror', device='virtio0', target='/tmp/r7.s1',
>               granularity=8192, sync='full', mode='absolute-paths',
>               format='raw')
> 
> While the guest is running dd if=/dev/zero of=/var/tmp/foo oflag=direct
> bs=4k.
> 

Thanks,

Applied to my 'block-next' branch:

https://github.com/codyprime/qemu-kvm-jtc/tree/block-next

-Jeff