/*
   * 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 */