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SubjectRe: [PATCH v6 3/6] mm/cma: populate ZONE_CMA
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On 10/14/2016 05:03 AM, js1304@gmail.com 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
zone_start_pfn is UINT_MAX and zone->spanned_pages is 1? So at least the
max/min should be swapped?
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.

> + }

I'm guessing the initial values come from this part in patch 2/6:

> @@ -5723,6 +5738,8 @@ static void __meminit calculate_node_totalpages(struct pglist_data *pgdat,
> unsigned long *zholes_size)
> {
> unsigned long realtotalpages = 0, totalpages = 0;
> + unsigned long zone_cma_start_pfn = UINT_MAX;
> + unsigned long zone_cma_end_pfn = 0;
> enum zone_type i;
>
> for (i = 0; i < MAX_NR_ZONES; i++) {
> @@ -5730,6 +5747,13 @@ static void __meminit calculate_node_totalpages(struct pglist_data *pgdat,
> unsigned long zone_start_pfn, zone_end_pfn;
> unsigned long size, real_size;
>
> + if (is_zone_cma_idx(i)) {
> + zone->zone_start_pfn = zone_cma_start_pfn;
> + size = zone_cma_end_pfn - zone_cma_start_pfn;
> + real_size = 0;
> + goto init_zone;
> + }

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