mm/mmzone.c

   1 /*
   2  * linux/mm/mmzone.c
   3  *
   4  * management codes for pgdats and zones.
   5  */
   6
   7
   8 #include <linux/stddef.h>
   9 #include <linux/mm.h>
  10 #include <linux/mmzone.h>
  11 #include <linux/module.h>
  12
  13 struct pglist_data *first_online_pgdat(void)
  14 {
  15         return NODE_DATA(first_online_node);
  16 }
  17
  18 struct pglist_data *next_online_pgdat(struct pglist_data *pgdat)
  19 {
  20         int nid = next_online_node(pgdat->node_id);
  21
  22         if (nid == MAX_NUMNODES)
  23                 return NULL;
  24         return NODE_DATA(nid);
  25 }
  26
  27 /*
  28  * next_zone - helper magic for for_each_zone()
  29  */
  30 struct zone *next_zone(struct zone *zone)
  31 {
  32         pg_data_t *pgdat = zone->zone_pgdat;
  33
  34         if (zone < pgdat->node_zones + MAX_NR_ZONES - 1)
  35                 zone++;
  36         else {
  37                 pgdat = next_online_pgdat(pgdat);
  38                 if (pgdat)
  39                         zone = pgdat->node_zones;
  40                 else
  41                         zone = NULL;
  42         }
  43         return zone;
  44 }
  45
  46 static inline int zref_in_nodemask(struct zoneref *zref, nodemask_t *nodes)
  47 {
  48 #ifdef CONFIG_NUMA
  49         return node_isset(zonelist_node_idx(zref), *nodes);
  50 #else
  51         return 1;
  52 #endif /* CONFIG_NUMA */
  53 }
  54
  55 /* Returns the next zone at or below highest_zoneidx in a zonelist */
  56 struct zoneref *next_zones_zonelist(struct zoneref *z,
  57                                         enum zone_type highest_zoneidx,
  58                                         nodemask_t *nodes,
  59                                         struct zone **zone)
  60 {
  61         /*
  62          * Find the next suitable zone to use for the allocation.
  63          * Only filter based on nodemask if it's set
  64          */
  65         if (likely(nodes == NULL))
  66                 while (zonelist_zone_idx(z) > highest_zoneidx)
  67                         z++;
  68         else
  69                 while (zonelist_zone_idx(z) > highest_zoneidx ||
  70                                 (z->zone && !zref_in_nodemask(z, nodes)))
  71                         z++;
  72
  73         *zone = zonelist_zone(z);
  74         return z;
  75 }
  76
  77 #ifdef CONFIG_ARCH_HAS_HOLES_MEMORYMODEL
  78 int memmap_valid_within(unsigned long pfn,
  79                                         struct page *page, struct zone *zone)
  80 {
  81         if (page_to_pfn(page) != pfn)
  82                 return 0;
  83
  84         if (page_zone(page) != zone)
  85                 return 0;
  86
  87         return 1;
  88 }
  89 #endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */
  90
  91 #ifdef CONFIG_SMP
  92 /* Called when a more accurate view of NR_FREE_PAGES is needed */
  93 unsigned long zone_nr_free_pages(struct zone *zone)
  94 {
  95         unsigned long nr_free_pages = zone_page_state(zone, NR_FREE_PAGES);
  96
  97         /*
  98          * While kswapd is awake, it is considered the zone is under some
  99          * memory pressure. Under pressure, there is a risk that
 100          * per-cpu-counter-drift will allow the min watermark to be breached
 101          * potentially causing a live-lock. While kswapd is awake and
 102          * free pages are low, get a better estimate for free pages
 103          */
 104         if (nr_free_pages < zone->percpu_drift_mark &&
 105                         !waitqueue_active(&zone->zone_pgdat->kswapd_wait))
 106                 return zone_page_state_snapshot(zone, NR_FREE_PAGES);
 107
 108         return nr_free_pages;
 109 }
 110 #endif /* CONFIG_SMP */