Re: [Qemu-devel] [PATCH v2] util/hbitmap: strict hbitmap_reset

[Vladimir Sementsov-Ogievskiy]

07.08.2019 19:27, John Snow wrote:
> 
> 
> On 8/6/19 12:19 PM, Vladimir Sementsov-Ogievskiy wrote:
>> 06.08.2019 19:09, Max Reitz wrote:
>>> On 06.08.19 17:26, Vladimir Sementsov-Ogievskiy wrote:
>>>> hbitmap_reset has an unobvious property: it rounds requested region up.
>>>> It may provoke bugs, like in recently fixed write-blocking mode of
>>>> mirror: user calls reset on unaligned region, not keeping in mind that
>>>> there are possible unrelated dirty bytes, covered by rounded-up region
>>>> and information of this unrelated "dirtiness" will be lost.
>>>>
>>>> Make hbitmap_reset strict: assert that arguments are aligned, allowing
>>>> only one exception when @start + @count == hb->orig_size. It's needed
>>>> to comfort users of hbitmap_next_dirty_area, which cares about
>>>> hb->orig_size.
>>>>
>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
>>>> ---
>>>>
>>>> v2 based on Max's https://github.com/XanClic/qemu.git block
>>>> which will be merged soon to 4.1, and this patch goes to 4.2
>>>> Based-on: https://github.com/XanClic/qemu.git block
>>>>
>>>> v1 was "[PATCH] util/hbitmap: fix unaligned reset", and as I understand
>>>> we all agreed to just assert alignment instead of aligning down
>>>> automatically.
>>>>
>>>>    include/qemu/hbitmap.h | 5 +++++
>>>>    tests/test-hbitmap.c   | 2 +-
>>>>    util/hbitmap.c         | 4 ++++
>>>>    3 files changed, 10 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/include/qemu/hbitmap.h b/include/qemu/hbitmap.h
>>>> index 4afbe6292e..7865e819ca 100644
>>>> --- a/include/qemu/hbitmap.h
>>>> +++ b/include/qemu/hbitmap.h
>>>> @@ -132,6 +132,11 @@ void hbitmap_set(HBitmap *hb, uint64_t start, 
>>>> uint64_t count);
>>>>     * @count: Number of bits to reset.
>>>>     *
>>>>     * Reset a consecutive range of bits in an HBitmap.
>>>> + * @start and @count must be aligned to bitmap granularity. The only 
>>>> exception
>>>> + * is resetting the tail of the bitmap: @count may be equal to @start +
>>>> + * hb->orig_size,
>>>
>>> s/@start + hb->orig_size/hb->orig_size - @start/, I think.
>>
>> Ha, I wanted to say start + count equal to orig_size. Yours is OK too of 
>> course.
>>
>>>
>>>>       in this case @count may be not aligned. @start + @count
>>>
>>> +are
>>>
>>> With those fixed:
>>>
>>> Reviewed-by: Max Reitz <address@hidden>
>>
>> Thanks!
>>
> 
> I'll add this to the pile for 4.2, after I fix the rebase conflicts that
> arose from 4.1-rc4.
> 

Hi!

Didn't you forget, or should I resend?


-- 
Best regards,
Vladimir