Root/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
13struct pglist_data *first_online_pgdat(void)
14{
15    return NODE_DATA(first_online_node);
16}
17
18struct 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 */
30struct 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
46static 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 */
56struct 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
78int 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 */
93unsigned 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 */
111

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