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Re: [Qemu-devel] [PATCH v5 4/6] qemu-io: Allow unaligned access by defau

From: Eric Blake
Subject: Re: [Qemu-devel] [PATCH v5 4/6] qemu-io: Allow unaligned access by default
Date: Thu, 12 May 2016 09:50:30 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0

On 05/12/2016 08:38 AM, Kevin Wolf wrote:
> Am 08.05.2016 um 05:16 hat Eric Blake geschrieben:
>> There's no reason to require the user to specify a flag just so
>> they can pass in unaligned numbers.  Keep 'read -p' and 'write -p'
>> as no-ops so that I don't have to hunt down and update all users
>> of qemu-io, but otherwise make their behavior default as 'read' and
>> 'write'.  Also fix 'write -z', 'readv', 'writev', 'writev',
>> 'aio_read', 'aio_write', and 'aio_write -z'.  For now, 'read -b',
>> 'write -b', and 'write -c' still require alignment (and 'multiwrite',
>> but that's slated to die soon).
>> qemu-iotest 23 is updated to match, as the only test that was
>> previously explicitly expecting an error on an unaligned request.

I found that one by 'git grep "sector aligned"', and tested with ./check

>> Signed-off-by: Eric Blake <address@hidden>
> This breaks qemu-iotests 136 for raw. It's pretty obvious that this is a
> test case problem (uses unaligned requests to test error accounting), so
> I'm not dropping the patch, but please do send a follow-up.

...which explains why I missed this failure with ./check -raw.  Will
fix, and maybe I should have grepped a bit harder, since it is fairly

tests/qemu-iotests/136:        # Two types of invalid operations:
unaligned length and unaligned offset

I will also check if this needs updating:

tests/qemu-iotests/109:    # qemu-img compare can't handle unaligned
file sizes

as both of those tests run under -raw but not -qcow2

> Maybe negative length and offset work as a replacement.

Indeed, since unaligned length and unaligned offset are now explicitly
handled by the block layer.

Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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