linux/mm/page_isolation.c
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   1/*
   2 * linux/mm/page_isolation.c
   3 */
   4
   5#include <linux/mm.h>
   6#include <linux/page-isolation.h>
   7#include <linux/pageblock-flags.h>
   8#include "internal.h"
   9
  10static inline struct page *
  11__first_valid_page(unsigned long pfn, unsigned long nr_pages)
  12{
  13        int i;
  14        for (i = 0; i < nr_pages; i++)
  15                if (pfn_valid_within(pfn + i))
  16                        break;
  17        if (unlikely(i == nr_pages))
  18                return NULL;
  19        return pfn_to_page(pfn + i);
  20}
  21
  22/*
  23 * start_isolate_page_range() -- make page-allocation-type of range of pages
  24 * to be MIGRATE_ISOLATE.
  25 * @start_pfn: The lower PFN of the range to be isolated.
  26 * @end_pfn: The upper PFN of the range to be isolated.
  27 *
  28 * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
  29 * the range will never be allocated. Any free pages and pages freed in the
  30 * future will not be allocated again.
  31 *
  32 * start_pfn/end_pfn must be aligned to pageblock_order.
  33 * Returns 0 on success and -EBUSY if any part of range cannot be isolated.
  34 */
  35int
  36start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn)
  37{
  38        unsigned long pfn;
  39        unsigned long undo_pfn;
  40        struct page *page;
  41
  42        BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
  43        BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
  44
  45        for (pfn = start_pfn;
  46             pfn < end_pfn;
  47             pfn += pageblock_nr_pages) {
  48                page = __first_valid_page(pfn, pageblock_nr_pages);
  49                if (page && set_migratetype_isolate(page)) {
  50                        undo_pfn = pfn;
  51                        goto undo;
  52                }
  53        }
  54        return 0;
  55undo:
  56        for (pfn = start_pfn;
  57             pfn < undo_pfn;
  58             pfn += pageblock_nr_pages)
  59                unset_migratetype_isolate(pfn_to_page(pfn));
  60
  61        return -EBUSY;
  62}
  63
  64/*
  65 * Make isolated pages available again.
  66 */
  67int
  68undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn)
  69{
  70        unsigned long pfn;
  71        struct page *page;
  72        BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
  73        BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
  74        for (pfn = start_pfn;
  75             pfn < end_pfn;
  76             pfn += pageblock_nr_pages) {
  77                page = __first_valid_page(pfn, pageblock_nr_pages);
  78                if (!page || get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
  79                        continue;
  80                unset_migratetype_isolate(page);
  81        }
  82        return 0;
  83}
  84/*
  85 * Test all pages in the range is free(means isolated) or not.
  86 * all pages in [start_pfn...end_pfn) must be in the same zone.
  87 * zone->lock must be held before call this.
  88 *
  89 * Returns 0 if all pages in the range is isolated.
  90 */
  91static int
  92__test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn)
  93{
  94        struct page *page;
  95
  96        while (pfn < end_pfn) {
  97                if (!pfn_valid_within(pfn)) {
  98                        pfn++;
  99                        continue;
 100                }
 101                page = pfn_to_page(pfn);
 102                if (PageBuddy(page))
 103                        pfn += 1 << page_order(page);
 104                else if (page_count(page) == 0 &&
 105                                page_private(page) == MIGRATE_ISOLATE)
 106                        pfn += 1;
 107                else
 108                        break;
 109        }
 110        if (pfn < end_pfn)
 111                return 0;
 112        return 1;
 113}
 114
 115int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
 116{
 117        unsigned long pfn, flags;
 118        struct page *page;
 119        struct zone *zone;
 120        int ret;
 121
 122        pfn = start_pfn;
 123        /*
 124         * Note: pageblock_nr_page != MAX_ORDER. Then, chunks of free page
 125         * is not aligned to pageblock_nr_pages.
 126         * Then we just check pagetype fist.
 127         */
 128        for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
 129                page = __first_valid_page(pfn, pageblock_nr_pages);
 130                if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
 131                        break;
 132        }
 133        page = __first_valid_page(start_pfn, end_pfn - start_pfn);
 134        if ((pfn < end_pfn) || !page)
 135                return -EBUSY;
 136        /* Check all pages are free or Marked as ISOLATED */
 137        zone = page_zone(page);
 138        spin_lock_irqsave(&zone->lock, flags);
 139        ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn);
 140        spin_unlock_irqrestore(&zone->lock, flags);
 141        return ret ? 0 : -EBUSY;
 142}
 143
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