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 <linux/memory.h>
   9 #include <linux/hugetlb.h>
  10 #include "internal.h"
  11
  12 static int set_migratetype_isolate(struct page *page,
  13                                 bool skip_hwpoisoned_pages)
  14 {
  15         struct zone *zone;
  16         unsigned long flags, pfn;
  17         struct memory_isolate_notify arg;
  18         int notifier_ret;
  19         int ret = -EBUSY;
  20
  21         zone = page_zone(page);
  22
  23         spin_lock_irqsave(&zone->lock, flags);
  24
  25         pfn = page_to_pfn(page);
  26         arg.start_pfn = pfn;
  27         arg.nr_pages = pageblock_nr_pages;
  28         arg.pages_found = 0;
  29
  30         /*
  31          * It may be possible to isolate a pageblock even if the
  32          * migratetype is not MIGRATE_MOVABLE. The memory isolation
  33          * notifier chain is used by balloon drivers to return the
  34          * number of pages in a range that are held by the balloon
  35          * driver to shrink memory. If all the pages are accounted for
  36          * by balloons, are free, or on the LRU, isolation can continue.
  37          * Later, for example, when memory hotplug notifier runs, these
  38          * pages reported as "can be isolated" should be isolated(freed)
  39          * by the balloon driver through the memory notifier chain.
  40          */
  41         notifier_ret = memory_isolate_notify(MEM_ISOLATE_COUNT, &arg);
  42         notifier_ret = notifier_to_errno(notifier_ret);
  43         if (notifier_ret)
  44                 goto out;
  45         /*
  46          * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
  47          * We just check MOVABLE pages.
  48          */
  49         if (!has_unmovable_pages(zone, page, arg.pages_found,
  50                                  skip_hwpoisoned_pages))
  51                 ret = 0;
  52
  53         /*
  54          * immobile means "not-on-lru" paes. If immobile is larger than
  55          * removable-by-driver pages reported by notifier, we'll fail.
  56          */
  57
  58 out:
  59         if (!ret) {
  60                 unsigned long nr_pages;
  61                 int migratetype = get_pageblock_migratetype(page);
  62
  63                 set_pageblock_migratetype(page, MIGRATE_ISOLATE);
  64                 zone->nr_isolate_pageblock++;
  65                 nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);
  66
  67                 __mod_zone_freepage_state(zone, -nr_pages, migratetype);
  68         }
  69
  70         spin_unlock_irqrestore(&zone->lock, flags);
  71         if (!ret)
  72                 drain_all_pages(zone);
  73         return ret;
  74 }
  75
  76 static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
  77 {
  78         struct zone *zone;
  79         unsigned long flags, nr_pages;
  80         struct page *isolated_page = NULL;
  81         unsigned int order;
  82         unsigned long page_idx, buddy_idx;
  83         struct page *buddy;
  84
  85         zone = page_zone(page);
  86         spin_lock_irqsave(&zone->lock, flags);
  87         if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
  88                 goto out;
  89
  90         /*
  91          * Because freepage with more than pageblock_order on isolated
  92          * pageblock is restricted to merge due to freepage counting problem,
  93          * it is possible that there is free buddy page.
  94          * move_freepages_block() doesn't care of merge so we need other
  95          * approach in order to merge them. Isolation and free will make
  96          * these pages to be merged.
  97          */
  98         if (PageBuddy(page)) {
  99                 order = page_order(page);
 100                 if (order >= pageblock_order) {
 101                         page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
 102                         buddy_idx = __find_buddy_index(page_idx, order);
 103                         buddy = page + (buddy_idx - page_idx);
 104
 105                         if (pfn_valid_within(page_to_pfn(buddy)) &&
 106                             !is_migrate_isolate_page(buddy)) {
 107                                 __isolate_free_page(page, order);
 108                                 kernel_map_pages(page, (1 << order), 1);
 109                                 set_page_refcounted(page);
 110                                 isolated_page = page;
 111                         }
 112                 }
 113         }
 114
 115         /*
 116          * If we isolate freepage with more than pageblock_order, there
 117          * should be no freepage in the range, so we could avoid costly
 118          * pageblock scanning for freepage moving.
 119          */
 120         if (!isolated_page) {
 121                 nr_pages = move_freepages_block(zone, page, migratetype);
 122                 __mod_zone_freepage_state(zone, nr_pages, migratetype);
 123         }
 124         set_pageblock_migratetype(page, migratetype);
 125         zone->nr_isolate_pageblock--;
 126 out:
 127         spin_unlock_irqrestore(&zone->lock, flags);
 128         if (isolated_page)
 129                 __free_pages(isolated_page, order);
 130 }
 131
 132 static inline struct page *
 133 __first_valid_page(unsigned long pfn, unsigned long nr_pages)
 134 {
 135         int i;
 136         for (i = 0; i < nr_pages; i++)
 137                 if (pfn_valid_within(pfn + i))
 138                         break;
 139         if (unlikely(i == nr_pages))
 140                 return NULL;
 141         return pfn_to_page(pfn + i);
 142 }
 143
 144 /*
 145  * start_isolate_page_range() -- make page-allocation-type of range of pages
 146  * to be MIGRATE_ISOLATE.
 147  * @start_pfn: The lower PFN of the range to be isolated.
 148  * @end_pfn: The upper PFN of the range to be isolated.
 149  * @migratetype: migrate type to set in error recovery.
 150  *
 151  * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
 152  * the range will never be allocated. Any free pages and pages freed in the
 153  * future will not be allocated again.
 154  *
 155  * start_pfn/end_pfn must be aligned to pageblock_order.
 156  * Returns 0 on success and -EBUSY if any part of range cannot be isolated.
 157  */
 158 int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 159                              unsigned migratetype, bool skip_hwpoisoned_pages)
 160 {
 161         unsigned long pfn;
 162         unsigned long undo_pfn;
 163         struct page *page;
 164
 165         BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
 166         BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
 167
 168         for (pfn = start_pfn;
 169              pfn < end_pfn;
 170              pfn += pageblock_nr_pages) {
 171                 page = __first_valid_page(pfn, pageblock_nr_pages);
 172                 if (page &&
 173                     set_migratetype_isolate(page, skip_hwpoisoned_pages)) {
 174                         undo_pfn = pfn;
 175                         goto undo;
 176                 }
 177         }
 178         return 0;
 179 undo:
 180         for (pfn = start_pfn;
 181              pfn < undo_pfn;
 182              pfn += pageblock_nr_pages)
 183                 unset_migratetype_isolate(pfn_to_page(pfn), migratetype);
 184
 185         return -EBUSY;
 186 }
 187
 188 /*
 189  * Make isolated pages available again.
 190  */
 191 int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 192                             unsigned migratetype)
 193 {
 194         unsigned long pfn;
 195         struct page *page;
 196         BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
 197         BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
 198         for (pfn = start_pfn;
 199              pfn < end_pfn;
 200              pfn += pageblock_nr_pages) {
 201                 page = __first_valid_page(pfn, pageblock_nr_pages);
 202                 if (!page || get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
 203                         continue;
 204                 unset_migratetype_isolate(page, migratetype);
 205         }
 206         return 0;
 207 }
 208 /*
 209  * Test all pages in the range is free(means isolated) or not.
 210  * all pages in [start_pfn...end_pfn) must be in the same zone.
 211  * zone->lock must be held before call this.
 212  *
 213  * Returns 1 if all pages in the range are isolated.
 214  */
 215 static int
 216 __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
 217                                   bool skip_hwpoisoned_pages)
 218 {
 219         struct page *page;
 220
 221         while (pfn < end_pfn) {
 222                 if (!pfn_valid_within(pfn)) {
 223                         pfn++;
 224                         continue;
 225                 }
 226                 page = pfn_to_page(pfn);
 227                 if (PageBuddy(page))
 228                         /*
 229                          * If the page is on a free list, it has to be on
 230                          * the correct MIGRATE_ISOLATE freelist. There is no
 231                          * simple way to verify that as VM_BUG_ON(), though.
 232                          */
 233                         pfn += 1 << page_order(page);
 234                 else if (skip_hwpoisoned_pages && PageHWPoison(page))
 235                         /* A HWPoisoned page cannot be also PageBuddy */
 236                         pfn++;
 237                 else
 238                         break;
 239         }
 240         if (pfn < end_pfn)
 241                 return 0;
 242         return 1;
 243 }
 244
 245 int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
 246                         bool skip_hwpoisoned_pages)
 247 {
 248         unsigned long pfn, flags;
 249         struct page *page;
 250         struct zone *zone;
 251         int ret;
 252
 253         /*
 254          * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
 255          * are not aligned to pageblock_nr_pages.
 256          * Then we just check migratetype first.
 257          */
 258         for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
 259                 page = __first_valid_page(pfn, pageblock_nr_pages);
 260                 if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
 261                         break;
 262         }
 263         page = __first_valid_page(start_pfn, end_pfn - start_pfn);
 264         if ((pfn < end_pfn) || !page)
 265                 return -EBUSY;
 266         /* Check all pages are free or marked as ISOLATED */
 267         zone = page_zone(page);
 268         spin_lock_irqsave(&zone->lock, flags);
 269         ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn,
 270                                                 skip_hwpoisoned_pages);
 271         spin_unlock_irqrestore(&zone->lock, flags);
 272         return ret ? 0 : -EBUSY;
 273 }
 274
 275 struct page *alloc_migrate_target(struct page *page, unsigned long private,
 276                                   int **resultp)
 277 {
 278         gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
 279
 280         /*
 281          * TODO: allocate a destination hugepage from a nearest neighbor node,
 282          * accordance with memory policy of the user process if possible. For
 283          * now as a simple work-around, we use the next node for destination.
 284          */
 285         if (PageHuge(page)) {
 286                 int node = next_online_node(page_to_nid(page));
 287                 if (node == MAX_NUMNODES)
 288                         node = first_online_node;
 289                 return alloc_huge_page_node(page_hstate(compound_head(page)),
 290                                             node);
 291         }
 292
 293         if (PageHighMem(page))
 294                 gfp_mask |= __GFP_HIGHMEM;
 295
 296         return alloc_page(gfp_mask);
 297 }