Re: [Qemu-block] [PATCH v2 15/17] block: Switch discard length bounds to byte-based

[Fam Zheng]

On Thu, 06/16 08:21, Eric Blake wrote:
> On 06/15/2016 11:46 PM, Fam Zheng wrote:
> > On Tue, 06/14 15:30, 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.  In iscsi.c, sector_limits_lun2qemu()
> >> is no longer needed; and the BlockLimits type is now completely
> >> byte-based.
> >>
> >> Signed-off-by: Eric Blake <address@hidden>
> >>
> 
> >>
> >>  typedef struct BlockLimits {
> >> -    /* maximum number of sectors that can be discarded at once */
> >> -    int max_discard;
> >> +    /* maximum number of bytes that can be discarded at once (since it
> >> +     * is signed, it must be < 2G, if set), should be multiple of
> >> +     * pdiscard_alignment, but need not be power of 2. May be 0 if no
> >> +     * inherent 32-bit limit */
> >> +    int32_t max_pdiscard;
> > 
> > Why not use uint32_t?
> > 
> >>
> >> -    /* 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
> >> +     * bs->request_alignment. May be 0 if bs->request_alignment is
> >> +     * good enough */
> >> +    uint32_t pdiscard_alignment;
> >>
> >>      /* maximum number of bytes that can zeroized at once (since it is
> >> -     * signed, it must be < 2G, if set) */
> >> +     * signed, it must be < 2G, if set), should be multiple of
> >> +     * pwrite_zeroes_alignment. May be 0 if no inherent 32-bit limit */
> >>      int32_t max_pwrite_zeroes;
> 
> Because max_pwrite_zeroes didn't.
> 
> And because we're still limited by INT_MAX (or it's alternative spelling
> BDRV_REQUEST_MAX_SECTORS).
> 
> Maybe we should switch both to uint32_t, but that can be a followup.
> 

OK, thanks!

Reviewed-by: Fam Zheng <address@hidden>