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 <linux/memory.h>
   9#include <linux/hugetlb.h>
  10#include "internal.h"
  11
  12int set_migratetype_isolate(struct page *page, bool skip_hwpoisoned_pages)
  13{
  14        struct zone *zone;
  15        unsigned long flags, pfn;
  16        struct memory_isolate_notify arg;
  17        int notifier_ret;
  18        int ret = -EBUSY;
  19
  20        zone = page_zone(page);
  21
  22        spin_lock_irqsave(&zone->lock, flags);
  23
  24        pfn = page_to_pfn(page);
  25        arg.start_pfn = pfn;
  26        arg.nr_pages = pageblock_nr_pages;
  27        arg.pages_found = 0;
  28
  29        /*
  30         * It may be possible to isolate a pageblock even if the
  31         * migratetype is not MIGRATE_MOVABLE. The memory isolation
  32         * notifier chain is used by balloon drivers to return the
  33         * number of pages in a range that are held by the balloon
  34         * driver to shrink memory. If all the pages are accounted for
  35         * by balloons, are free, or on the LRU, isolation can continue.
  36         * Later, for example, when memory hotplug notifier runs, these
  37         * pages reported as "can be isolated" should be isolated(freed)
  38         * by the balloon driver through the memory notifier chain.
  39         */
  40        notifier_ret = memory_isolate_notify(MEM_ISOLATE_COUNT, &arg);
  41        notifier_ret = notifier_to_errno(notifier_ret);
  42        if (notifier_ret)
  43                goto out;
  44        /*
  45         * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
  46         * We just check MOVABLE pages.
  47         */
  48        if (!has_unmovable_pages(zone, page, arg.pages_found,
  49                                 skip_hwpoisoned_pages))
  50                ret = 0;
  51
  52        /*
  53         * immobile means "not-on-lru" paes. If immobile is larger than
  54         * removable-by-driver pages reported by notifier, we'll fail.
  55         */
  56
  57out:
  58        if (!ret) {
  59                unsigned long nr_pages;
  60                int migratetype = get_pageblock_migratetype(page);
  61
  62                set_pageblock_migratetype(page, MIGRATE_ISOLATE);
  63                nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);
  64
  65                __mod_zone_freepage_state(zone, -nr_pages, migratetype);
  66        }
  67
  68        spin_unlock_irqrestore(&zone->lock, flags);
  69        if (!ret)
  70                drain_all_pages();
  71        return ret;
  72}
  73
  74void unset_migratetype_isolate(struct page *page, unsigned migratetype)
  75{
  76        struct zone *zone;
  77        unsigned long flags, nr_pages;
  78
  79        zone = page_zone(page);
  80        spin_lock_irqsave(&zone->lock, flags);
  81        if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
  82                goto out;
  83        nr_pages = move_freepages_block(zone, page, migratetype);
  84        __mod_zone_freepage_state(zone, nr_pages, migratetype);
  85        set_pageblock_migratetype(page, migratetype);
  86out:
  87        spin_unlock_irqrestore(&zone->lock, flags);
  88}
  89
  90static inline struct page *
  91__first_valid_page(unsigned long pfn, unsigned long nr_pages)
  92{
  93        int i;
  94        for (i = 0; i < nr_pages; i++)
  95                if (pfn_valid_within(pfn + i))
  96                        break;
  97        if (unlikely(i == nr_pages))
  98                return NULL;
  99        return pfn_to_page(pfn + i);
 100}
 101
 102/*
 103 * start_isolate_page_range() -- make page-allocation-type of range of pages
 104 * to be MIGRATE_ISOLATE.
 105 * @start_pfn: The lower PFN of the range to be isolated.
 106 * @end_pfn: The upper PFN of the range to be isolated.
 107 * @migratetype: migrate type to set in error recovery.
 108 *
 109 * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
 110 * the range will never be allocated. Any free pages and pages freed in the
 111 * future will not be allocated again.
 112 *
 113 * start_pfn/end_pfn must be aligned to pageblock_order.
 114 * Returns 0 on success and -EBUSY if any part of range cannot be isolated.
 115 */
 116int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 117                             unsigned migratetype, bool skip_hwpoisoned_pages)
 118{
 119        unsigned long pfn;
 120        unsigned long undo_pfn;
 121        struct page *page;
 122
 123        BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
 124        BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
 125
 126        for (pfn = start_pfn;
 127             pfn < end_pfn;
 128             pfn += pageblock_nr_pages) {
 129                page = __first_valid_page(pfn, pageblock_nr_pages);
 130                if (page &&
 131                    set_migratetype_isolate(page, skip_hwpoisoned_pages)) {
 132                        undo_pfn = pfn;
 133                        goto undo;
 134                }
 135        }
 136        return 0;
 137undo:
 138        for (pfn = start_pfn;
 139             pfn < undo_pfn;
 140             pfn += pageblock_nr_pages)
 141                unset_migratetype_isolate(pfn_to_page(pfn), migratetype);
 142
 143        return -EBUSY;
 144}
 145
 146/*
 147 * Make isolated pages available again.
 148 */
 149int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 150                            unsigned migratetype)
 151{
 152        unsigned long pfn;
 153        struct page *page;
 154        BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
 155        BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
 156        for (pfn = start_pfn;
 157             pfn < end_pfn;
 158             pfn += pageblock_nr_pages) {
 159                page = __first_valid_page(pfn, pageblock_nr_pages);
 160                if (!page || get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
 161                        continue;
 162                unset_migratetype_isolate(page, migratetype);
 163        }
 164        return 0;
 165}
 166/*
 167 * Test all pages in the range is free(means isolated) or not.
 168 * all pages in [start_pfn...end_pfn) must be in the same zone.
 169 * zone->lock must be held before call this.
 170 *
 171 * Returns 1 if all pages in the range are isolated.
 172 */
 173static int
 174__test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
 175                                  bool skip_hwpoisoned_pages)
 176{
 177        struct page *page;
 178
 179        while (pfn < end_pfn) {
 180                if (!pfn_valid_within(pfn)) {
 181                        pfn++;
 182                        continue;
 183                }
 184                page = pfn_to_page(pfn);
 185                if (PageBuddy(page)) {
 186                        /*
 187                         * If race between isolatation and allocation happens,
 188                         * some free pages could be in MIGRATE_MOVABLE list
 189                         * although pageblock's migratation type of the page
 190                         * is MIGRATE_ISOLATE. Catch it and move the page into
 191                         * MIGRATE_ISOLATE list.
 192                         */
 193                        if (get_freepage_migratetype(page) != MIGRATE_ISOLATE) {
 194                                struct page *end_page;
 195
 196                                end_page = page + (1 << page_order(page)) - 1;
 197                                move_freepages(page_zone(page), page, end_page,
 198                                                MIGRATE_ISOLATE);
 199                        }
 200                        pfn += 1 << page_order(page);
 201                }
 202                else if (page_count(page) == 0 &&
 203                        get_freepage_migratetype(page) == MIGRATE_ISOLATE)
 204                        pfn += 1;
 205                else if (skip_hwpoisoned_pages && PageHWPoison(page)) {
 206                        /*
 207                         * The HWPoisoned page may be not in buddy
 208                         * system, and page_count() is not 0.
 209                         */
 210                        pfn++;
 211                        continue;
 212                }
 213                else
 214                        break;
 215        }
 216        if (pfn < end_pfn)
 217                return 0;
 218        return 1;
 219}
 220
 221int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
 222                        bool skip_hwpoisoned_pages)
 223{
 224        unsigned long pfn, flags;
 225        struct page *page;
 226        struct zone *zone;
 227        int ret;
 228
 229        /*
 230         * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
 231         * are not aligned to pageblock_nr_pages.
 232         * Then we just check migratetype first.
 233         */
 234        for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
 235                page = __first_valid_page(pfn, pageblock_nr_pages);
 236                if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
 237                        break;
 238        }
 239        page = __first_valid_page(start_pfn, end_pfn - start_pfn);
 240        if ((pfn < end_pfn) || !page)
 241                return -EBUSY;
 242        /* Check all pages are free or marked as ISOLATED */
 243        zone = page_zone(page);
 244        spin_lock_irqsave(&zone->lock, flags);
 245        ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn,
 246                                                skip_hwpoisoned_pages);
 247        spin_unlock_irqrestore(&zone->lock, flags);
 248        return ret ? 0 : -EBUSY;
 249}
 250
 251struct page *alloc_migrate_target(struct page *page, unsigned long private,
 252                                  int **resultp)
 253{
 254        gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
 255
 256        /*
 257         * TODO: allocate a destination hugepage from a nearest neighbor node,
 258         * accordance with memory policy of the user process if possible. For
 259         * now as a simple work-around, we use the next node for destination.
 260         */
 261        if (PageHuge(page)) {
 262                nodemask_t src = nodemask_of_node(page_to_nid(page));
 263                nodemask_t dst;
 264                nodes_complement(dst, src);
 265                return alloc_huge_page_node(page_hstate(compound_head(page)),
 266                                            next_node(page_to_nid(page), dst));
 267        }
 268
 269        if (PageHighMem(page))
 270                gfp_mask |= __GFP_HIGHMEM;
 271
 272        return alloc_page(gfp_mask);
 273}
 274
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