Re: [Qemu-devel] [PATCH v22 06/30] block/dirty-bitmap: add deserialize_ones func

[John Snow]

On 06/29/2017 10:01 PM, Eric Blake wrote:
> On 06/29/2017 08:55 PM, Eric Blake wrote:
>> On 06/28/2017 07:05 AM, Vladimir Sementsov-Ogievskiy wrote:
>>> Add bdrv_dirty_bitmap_deserialize_ones() function, which is needed for
>>> qcow2 bitmap loading, to handle unallocated bitmap parts, marked as
>>> all-ones.
>>>
> 
>>> + * hbitmap_deserialize_ones
>>> + * @hb: HBitmap to operate on.
>>> + * @start: First bit to restore.
>>> + * @count: Number of bits to restore.
>>
>> This part is accurate (the dirty-bitmap is using an underlying bitmap
>> with "one bit per sector" before my series, afterwards it will be "one
>> bit per byte", remembering that hbitmap really stores only one bit per
>> granularity multiple of the underlying unit), if incomplete (the code
>> asserts that things are aligned, but doesn't document that the caller
>> must pass in aligned values); but again, that's matching the
>> pre-existing deserialize_zeroes code.
> 
> Okay, I looked again; the documentation for
> hbitmap_serialization_granularity() has a blanket statement that all
> other hbitmap_serialization_* functions taking a start and count must be
> aligned. Indirect, but at least documented, so I retract my statement
> about the docs being incomplete.
> 

If the docs are confusing, please send patches to amend them; the bitmap
code is definitely very confusing at times and I appreciate any and all
insight to make the names, variable and documentation read better to be
more intuitive.

Thanks!