On Fri, Jul 06, 2018 at 03:25:15PM -0700, Dan Williams wrote:
> This is going in the right direction... but still needs to account for
> the blk_overlap.
>
> So, on a given DIMM BLK capacity is allocated from the top of DPA
> space going down and PMEM capacity is allocated from the bottom of the
> DPA space going up.
>
> Since BLK capacity is single DIMM, and PMEM capacity is striped you
> could get into the situation where one DIMM is fully allocated for BLK
> usage and that would shade / remove the possibility to use the PMEM
> capacity on the other DIMMs in the PMEM set. PMEM needs all the same
> DPAs in all the DIMMs to be free.
>
> >
> > ---
> > diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c
> > index 8d348b22ba45..f30e0c3b0282 100644
> > --- a/drivers/nvdimm/dimm_devs.c
> > +++ b/drivers/nvdimm/dimm_devs.c
> > @@ -536,6 +536,31 @@ resource_size_t nd_blk_available_dpa(struct nd_region *nd_region)
> > return info.available;
> > }
> >
> > +/**
> > + * nd_pmem_max_contiguous_dpa - For the given dimm+region, return the max
> > + * contiguous unallocated dpa range.
> > + * @nd_region: constrain available space check to this reference region
> > + * @nd_mapping: container of dpa-resource-root + labels
> > + */
> > +resource_size_t nd_pmem_max_contiguous_dpa(struct nd_region *nd_region,
> > + struct nd_mapping *nd_mapping)
> > +{
> > + struct nvdimm_drvdata *ndd = to_ndd(nd_mapping);
> > + resource_size_t max = 0;
> > + struct resource *res;
> > +
> > + if (!ndd)
> > + return 0;
> > +
> > + for_each_dpa_resource(ndd, res) {
> > + if (strcmp(res->name, "pmem-reserve") != 0)
> > + continue;
> > + if (resource_size(res) > max)
>
> ...so instead straight resource_size() here you need trim the end of
> this "pmem-reserve" resource to the start of the first BLK allocation
> in any of the DIMMs in the set.
>
> See blk_start calculation in nd_pmem_available_dpa().
Hmm, the resources defining this are a bit inconvenient given these
constraints. If an unallocated portion of a DIMM may only be used for
BLK because an overlapping range in another DIMM is allocated that way,
would it make since to insert something like a "blk-reserve" resource
in all the other DIMMs so we don't need multiple iterations to calculate
which DPAs can be used for PMEM?
