On Tue, Oct 18, 2016 at 09:42:57AM +0200, Vlastimil Babka wrote:
> On 10/14/2016 05:03 AM, js1304@xxxxxxxxx wrote:
> >@@ -145,6 +145,35 @@ static int __init cma_activate_area(struct cma *cma)
> > static int __init cma_init_reserved_areas(void)
> > {
> > int i;
> >+ struct zone *zone;
> >+ pg_data_t *pgdat;
> >+
> >+ if (!cma_area_count)
> >+ return 0;
> >+
> >+ for_each_online_pgdat(pgdat) {
> >+ unsigned long start_pfn = UINT_MAX, end_pfn = 0;
> >+
> >+ for (i = 0; i < cma_area_count; i++) {
> >+ if (pfn_to_nid(cma_areas[i].base_pfn) !=
> >+ pgdat->node_id)
> >+ continue;
> >+
> >+ start_pfn = min(start_pfn, cma_areas[i].base_pfn);
> >+ end_pfn = max(end_pfn, cma_areas[i].base_pfn +
> >+ cma_areas[i].count);
> >+ }
> >+
> >+ if (!end_pfn)
> >+ continue;
> >+
> >+ zone = &pgdat->node_zones[ZONE_CMA];
> >+
> >+ /* ZONE_CMA doesn't need to exceed CMA region */
> >+ zone->zone_start_pfn = max(zone->zone_start_pfn, start_pfn);
> >+ zone->spanned_pages = min(zone_end_pfn(zone), end_pfn) -
> >+ zone->zone_start_pfn;
>
> Hmm, do the max/min here work as intended? IIUC the initial
Yeap.
> zone_start_pfn is UINT_MAX and zone->spanned_pages is 1? So at least
> the max/min should be swapped?
No. CMA zone's start/end pfn are updated as node's start/end pfn.
> Also the zone_end_pfn(zone) on the second line already sees the
> changes to zone->zone_start_pfn in the first line, so it's kind of a
> mess. You should probably cache zone_end_pfn() to a temporary
> variable before changing zone_start_pfn.
You're right although it doesn't cause any problem. I look at the code
again and find that max/min isn't needed. Calculated start/end pfn
should be inbetween node's start/end pfn so max(zone->zone_start_pfn,
start_pfn) will return start_pfn and messed up min(zone_end_pfn(zone),
end_pfn) will return end_pfn in all the cases.
Anyway, I will fix it as following.
zone->zone_start_pfn = start_pfn
zone->spanned_pages = end_pfn - start_pfn
Thanks.
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