On 06/24/2016 12:43 AM, Fam Zheng wrote: > On Thu, 06/23 16:37, Eric Blake wrote: >> Sector-based limits are awkward to think about; in our on-going >> quest to move to byte-based interfaces, convert max_discard and >> discard_alignment. Rename them, using 'pdiscard' as an aid to >> track which remaining discard interfaces need conversion, and so >> that the compiler will help us catch the change in semantics >> across any rebased code. The BlockLimits type is now completely >> byte-based; and in iscsi.c, sector_limits_lun2qemu() is no >> longer needed. >> >> pdiscard_alignment is made unsigned (we use power-of-2 alignments >> as bitmasks, where unsigned is easier to think about) while >> leaving max_pdiscard signed (since we still have an 'int' >> interface); this is comparable to what commit cf081fc did for >> write zeroes limits. We may later want to make everything an >> unsigned 64-bit limit - but that requires a bigger code audit. >>
>> - /* optimal alignment for discard requests in sectors */
>> - int64_t discard_alignment;
>> + /* optimal alignment for discard requests in bytes, must be power
>> + * of 2, less than max_discard if that is set, and multiple of
>
> s/max_discard/max_pdiscard/
Maintainer could touch it up on pull request.
>> /* align request */
>> - if (bs->bl.discard_alignment &&
>> - num >= bs->bl.discard_alignment &&
>> - sector_num % bs->bl.discard_alignment) {
>> - if (num > bs->bl.discard_alignment) {
>> - num = bs->bl.discard_alignment;
>> + if (discard_alignment &&
>> + num >= discard_alignment &&
>> + sector_num % discard_alignment) {
>> + if (num > discard_alignment) {
>> + num = discard_alignment;
>> }
>> - num -= sector_num % bs->bl.discard_alignment;
>> + num -= sector_num % discard_alignment;
>
> Or just
>
> num = discard_alignment - sector_num % discard_alignment;
>
> without the if.
>
Sure. It all gets simplified later when I switch to bdrv_co_pdiscard().
Up to the maintainer.
> Otherwise looks good,
>
> Reviewed-by: Fam Zheng <f...@redhat.com>
>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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