Re: [PATCH v2 3/6] block: Clarify that @bytes is no limit on *pnum

[Max Reitz <mreitz@redhat.com>]

On 28.06.21 21:10, Eric Blake wrote:
>>>> +++ b/include/block/block_int.h
>>>> @@ -347,6 +347,11 @@ struct BlockDriver {
>>>>         * clamped to bdrv_getlength() and aligned to request_alignment,
>>>>         * as well as non-NULL pnum, map, and file; in turn, the driver
>>>>         * must return an error or set pnum to an aligned non-zero value.
>>>> +     *
>>>> +     * Note that @bytes is just a hint on how big of a region the
>>>> +     * caller wants to inspect.  It is not a limit on *pnum.
>>>> +     * Implementations are free to return larger values of *pnum if
>>>> +     * doing so does not incur a performance penalty.
>>> Worth mention that the cache will benefit of it?
>> Oh, right, absolutely.  Like so:
>>
>> "block/io.c's bdrv_co_block_status() will clamp *pnum before returning it to
>> its caller, but it itself can still make use of the unclamped *pnum value.
>> Specifically, the block-status cache for protocol nodes will benefit from
>> storing as large a region as possible."
> How about this tweak to the wording to make it flow a little better:
>
> block/io.c's bdrv_co_block_status() will utilize an unclamped *pnum
> value for the block-status cache on protocol nodes, prior to clamping
> *pnum for return to its caller.

Sure, thanks!

Max