mm/page_isolation.c

   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
  10 static 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  */
  35 int
  36 start_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;
  55 undo:
  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  */
  67 int
  68 undo_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  */
  91 static 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
 115 int 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 }