Re: [Qemu-devel] iotest 194 fails on vhdx

[Alexey Kardashevskiy]

On 27/10/17 18:12, Jeff Cody wrote:
> On Wed, Oct 25, 2017 at 05:06:37PM +1100, Alexey Kardashevskiy wrote:
>> On 25/10/17 15:29, Alexey Kardashevskiy wrote:
>>> Hi!
>>>
>>> The latest QEMU fails on:
>>> tests/qemu-iotests/check -vhdx 194
>>
>>
>> Bit more details:
>>
>> 1. the assert started appearing from
>> https://git.qemu.org/?p=qemu.git;a=commit;h=09e0c771e47 - this one just
>> added the assert;
>>
>> 2. if removed, then another assert alerts:
>> qemu-system-ppc64: /home/aik/p/qemu/block/io.c:1423: bdrv_aligned_pwritev:
>> Assertion `child->perm & BLK_PERM_WRITE' failed.
>>
>> child->perm == 1 when this happens.
>>
>> Any clues?
>>
> 
> Yes - what is happening is that if the VHDX image file is open RDWR, we
> update the VHDX header.  However, since we are INMIGRATE, the
> underlying file bs is marked as INACTIVE, and we are caught by the assert.
> 
> 
> However, per the spec the header file and data guids only need to be updated
> before the first modification is made.  We already have a latching call to
> update the headers on the first write to the VHDX image (in vhdx_co_writev),
> so the call to vhdx_update_headers() in vhdx_open() is a bug, and can be
> removed.
> 
> Once that is fixed, 194 still fails for VHDX, but it doesn't crash.  The
> failure is expected, because VHDX does not support migration (VMDK fails the
> same way). 

Probably a very ignorant question but how can an image format not support
migration at all? Is not it simple writing blocks, one-by-one? Thanks.


> So test 194 should also be updated to exclude image formats that
> set migration blockers.
> 
> (Patches sent)
-- 
Alexey