mm/mmzone.c

/*
 * linux/mm/mmzone.c
 *
 * management codes for pgdats and zones.
 */


#include <linux/stddef.h>
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/module.h>

struct pglist_data *first_online_pgdat(void)
{
	return NODE_DATA(first_online_node);
}

struct pglist_data *next_online_pgdat(struct pglist_data *pgdat)
{
	int nid = next_online_node(pgdat->node_id);

	if (nid == MAX_NUMNODES)
		return NULL;
	return NODE_DATA(nid);
}

/*
 * next_zone - helper magic for for_each_zone()
 */
struct zone *next_zone(struct zone *zone)
{
	pg_data_t *pgdat = zone->zone_pgdat;

	if (zone < pgdat->node_zones + MAX_NR_ZONES - 1)
		zone++;
	else {
		pgdat = next_online_pgdat(pgdat);
		if (pgdat)
			zone = pgdat->node_zones;
		else
			zone = NULL;
	}
	return zone;
}

static inline int zref_in_nodemask(struct zoneref *zref, nodemask_t *nodes)
{
#ifdef CONFIG_NUMA
	return node_isset(zonelist_node_idx(zref), *nodes);
#else
	return 1;
#endif /* CONFIG_NUMA */
}

/* Returns the next zone at or below highest_zoneidx in a zonelist */
struct zoneref *next_zones_zonelist(struct zoneref *z,
					enum zone_type highest_zoneidx,
					nodemask_t *nodes,
					struct zone **zone)
{
	/*
	 * Find the next suitable zone to use for the allocation.
	 * Only filter based on nodemask if it's set
	 */
	if (likely(nodes == NULL))
		while (zonelist_zone_idx(z) > highest_zoneidx)
			z++;
	else
		while (zonelist_zone_idx(z) > highest_zoneidx ||
				(z->zone && !zref_in_nodemask(z, nodes)))
			z++;

	*zone = zonelist_zone(z);
	return z;
}

#ifdef CONFIG_ARCH_HAS_HOLES_MEMORYMODEL
int memmap_valid_within(unsigned long pfn,
					struct page *page, struct zone *zone)
{
	if (page_to_pfn(page) != pfn)
		return 0;

	if (page_zone(page) != zone)
		return 0;

	return 1;
}
#endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */

#ifdef CONFIG_SMP
/* Called when a more accurate view of NR_FREE_PAGES is needed */
unsigned long zone_nr_free_pages(struct zone *zone)
{
	unsigned long nr_free_pages = zone_page_state(zone, NR_FREE_PAGES);

	/*
	 * While kswapd is awake, it is considered the zone is under some
	 * memory pressure. Under pressure, there is a risk that
	 * per-cpu-counter-drift will allow the min watermark to be breached
	 * potentially causing a live-lock. While kswapd is awake and
	 * free pages are low, get a better estimate for free pages
	 */
	if (nr_free_pages < zone->percpu_drift_mark &&
			!waitqueue_active(&zone->zone_pgdat->kswapd_wait))
		return zone_page_state_snapshot(zone, NR_FREE_PAGES);

	return nr_free_pages;
}
#endif /* CONFIG_SMP */