Re: [Qemu-devel] [Qemu-block] [PATCH] iotests: test clearing unknown autoclear_features by qcow2

[John Snow <jsnow@redhat.com>]

On 11/10/2017 03:02 PM, Kevin Wolf wrote:
> Am 10.11.2017 um 18:54 hat Vladimir Sementsov-Ogievskiy geschrieben:
>> Test clearing unknown autoclear_features by qcow2 on incoming
>> migration.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
>>
>> Hi all!
>>
>> This patch shows degradation, added in 2.10 in commit
>>
>> commit 9c5e6594f15b7364624a3ad40306c396c93a2145
>> Author: Kevin Wolf <kwolf@redhat.com>
>> Date:   Thu May 4 18:52:40 2017 +0200
>>
>>     block: Fix write/resize permissions for inactive images
>>
>> The problem:
>> When on incoming migration with shared storage we reopen image to RW mode
>> we call bdrv_invalidate_cache it firstly call drv->bdrv_invalidate_cache and
>> only after it, through "parent->role->activate(parent, &local_err);" we set
>> appropriate RW permission.
>>
>> Because of this, if drv->bdrv_invalidate_cache wants to write something
>> (image is RW and BDRV_O_INACTIVE is not set) it goes into
>> "bdrv_aligned_pwritev: Assertion `child->perm & BLK_PERM_WRITE' failed"
>>
>> One case, when qcow2_invalidate_cache wants to write
>> something - when it wants to clear some unknown autoclear features. So,
>> here is a test for it.
>>
>> Another case is when we try to migrate persistent dirty bitmaps through
>> shared storage, on invalidate_cache qcow2 will try to set DIRTY bit in
>> all loaded bitmaps.
>>
>> Kevin, what do you think? I understand that operation order should be changed
>> somehow in bdrv_invalidate_cache, but I'm not sure about how "parent->role->.."
>> things works and can we safely move this part from function end to the middle.
> 
> I don't think you need to move the parent->role->activate() callback,
> but just the bdrv_set_perm() so that we request the correct permissions
> for operation without the BDRV_O_INACTIVE flag.
> 
> The following seems to work for me (including a fix for the test case,
> we don't seem to get a RESUME event). I'm not sure about the error paths
> yet. We should probably try do undo the permission changes there. I can
> have a closer look into this next week.
> 
> Kevin
> 

What's the status here, something we need to be paying attention to for
2.11?