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Re: [Qemu-block] [Qemu-devel] [PATCH v2] util/hbitmap: strict hbitmap_re
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
Re: [Qemu-block] [Qemu-devel] [PATCH v2] util/hbitmap: strict hbitmap_reset |
Date: |
Wed, 11 Sep 2019 15:13:15 +0000 |
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
- Re: [Qemu-block] [Qemu-devel] [PATCH v2] util/hbitmap: strict hbitmap_reset,
Vladimir Sementsov-Ogievskiy <=