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 int 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
  57 out:
  58         if (!ret) {
  59                 unsigned long nr_pages;
  60                 int migratetype = get_pageblock_migratetype(page);
  61
  62                 set_pageblock_migratetype(page, MIGRATE_ISOLATE);
  63                 zone->nr_isolate_pageblock++;
  64                 nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);
  65
  66                 __mod_zone_freepage_state(zone, -nr_pages, migratetype);
  67         }
  68
  69         spin_unlock_irqrestore(&zone->lock, flags);
  70         if (!ret)
  71                 drain_all_pages(zone);
  72         return ret;
  73 }
  74
  75 void unset_migratetype_isolate(struct page *page, unsigned migratetype)
  76 {
  77         struct zone *zone;
  78         unsigned long flags, nr_pages;
  79         struct page *isolated_page = NULL;
  80         unsigned int order;
  81         unsigned long page_idx, buddy_idx;
  82         struct page *buddy;
  83
  84         zone = page_zone(page);
  85         spin_lock_irqsave(&zone->lock, flags);
  86         if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
  87                 goto out;
  88
  89         /*
  90          * Because freepage with more than pageblock_order on isolated
  91          * pageblock is restricted to merge due to freepage counting problem,
  92          * it is possible that there is free buddy page.
  93          * move_freepages_block() doesn't care of merge so we need other
  94          * approach in order to merge them. Isolation and free will make
  95          * these pages to be merged.
  96          */
  97         if (PageBuddy(page)) {
  98                 order = page_order(page);
  99                 if (order >= pageblock_order) {
 100                         page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
 101                         buddy_idx = __find_buddy_index(page_idx, order);
 102                         buddy = page + (buddy_idx - page_idx);
 103
 104                         if (!is_migrate_isolate_page(buddy)) {
 105                                 __isolate_free_page(page, order);
 106                                 kernel_map_pages(page, (1 << order), 1);
 107                                 set_page_refcounted(page);
 108                                 isolated_page = page;
 109                         }
 110                 }
 111         }
 112
 113         /*
 114          * If we isolate freepage with more than pageblock_order, there
 115          * should be no freepage in the range, so we could avoid costly
 116          * pageblock scanning for freepage moving.
 117          */
 118         if (!isolated_page) {
 119                 nr_pages = move_freepages_block(zone, page, migratetype);
 120                 __mod_zone_freepage_state(zone, nr_pages, migratetype);
 121         }
 122         set_pageblock_migratetype(page, migratetype);
 123         zone->nr_isolate_pageblock--;
 124 out:
 125         spin_unlock_irqrestore(&zone->lock, flags);
 126         if (isolated_page)
 127                 __free_pages(isolated_page, order);
 128 }
 129
 130 static inline struct page *
 131 __first_valid_page(unsigned long pfn, unsigned long nr_pages)
 132 {
 133         int i;
 134         for (i = 0; i < nr_pages; i++)
 135                 if (pfn_valid_within(pfn + i))
 136                         break;
 137         if (unlikely(i == nr_pages))
 138                 return NULL;
 139         return pfn_to_page(pfn + i);
 140 }
 141
 142 /*
 143  * start_isolate_page_range() -- make page-allocation-type of range of pages
 144  * to be MIGRATE_ISOLATE.
 145  * @start_pfn: The lower PFN of the range to be isolated.
 146  * @end_pfn: The upper PFN of the range to be isolated.
 147  * @migratetype: migrate type to set in error recovery.
 148  *
 149  * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
 150  * the range will never be allocated. Any free pages and pages freed in the
 151  * future will not be allocated again.
 152  *
 153  * start_pfn/end_pfn must be aligned to pageblock_order.
 154  * Returns 0 on success and -EBUSY if any part of range cannot be isolated.
 155  */
 156 int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 157                              unsigned migratetype, bool skip_hwpoisoned_pages)
 158 {
 159         unsigned long pfn;
 160         unsigned long undo_pfn;
 161         struct page *page;
 162
 163         BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
 164         BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
 165
 166         for (pfn = start_pfn;
 167              pfn < end_pfn;
 168              pfn += pageblock_nr_pages) {
 169                 page = __first_valid_page(pfn, pageblock_nr_pages);
 170                 if (page &&
 171                     set_migratetype_isolate(page, skip_hwpoisoned_pages)) {
 172                         undo_pfn = pfn;
 173                         goto undo;
 174                 }
 175         }
 176         return 0;
 177 undo:
 178         for (pfn = start_pfn;
 179              pfn < undo_pfn;
 180              pfn += pageblock_nr_pages)
 181                 unset_migratetype_isolate(pfn_to_page(pfn), migratetype);
 182
 183         return -EBUSY;
 184 }
 185
 186 /*
 187  * Make isolated pages available again.
 188  */
 189 int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 190                             unsigned migratetype)
 191 {
 192         unsigned long pfn;
 193         struct page *page;
 194         BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
 195         BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
 196         for (pfn = start_pfn;
 197              pfn < end_pfn;
 198              pfn += pageblock_nr_pages) {
 199                 page = __first_valid_page(pfn, pageblock_nr_pages);
 200                 if (!page || get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
 201                         continue;
 202                 unset_migratetype_isolate(page, migratetype);
 203         }
 204         return 0;
 205 }
 206 /*
 207  * Test all pages in the range is free(means isolated) or not.
 208  * all pages in [start_pfn...end_pfn) must be in the same zone.
 209  * zone->lock must be held before call this.
 210  *
 211  * Returns 1 if all pages in the range are isolated.
 212  */
 213 static int
 214 __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
 215                                   bool skip_hwpoisoned_pages)
 216 {
 217         struct page *page;
 218
 219         while (pfn < end_pfn) {
 220                 if (!pfn_valid_within(pfn)) {
 221                         pfn++;
 222                         continue;
 223                 }
 224                 page = pfn_to_page(pfn);
 225                 if (PageBuddy(page)) {
 226                         /*
 227                          * If race between isolatation and allocation happens,
 228                          * some free pages could be in MIGRATE_MOVABLE list
 229                          * although pageblock's migratation type of the page
 230                          * is MIGRATE_ISOLATE. Catch it and move the page into
 231                          * MIGRATE_ISOLATE list.
 232                          */
 233                         if (get_freepage_migratetype(page) != MIGRATE_ISOLATE) {
 234                                 struct page *end_page;
 235
 236                                 end_page = page + (1 << page_order(page)) - 1;
 237                                 move_freepages(page_zone(page), page, end_page,
 238                                                 MIGRATE_ISOLATE);
 239                         }
 240                         pfn += 1 << page_order(page);
 241                 }
 242                 else if (page_count(page) == 0 &&
 243                         get_freepage_migratetype(page) == MIGRATE_ISOLATE)
 244                         pfn += 1;
 245                 else if (skip_hwpoisoned_pages && PageHWPoison(page)) {
 246                         /*
 247                          * The HWPoisoned page may be not in buddy
 248                          * system, and page_count() is not 0.
 249                          */
 250                         pfn++;
 251                         continue;
 252                 }
 253                 else
 254                         break;
 255         }
 256         if (pfn < end_pfn)
 257                 return 0;
 258         return 1;
 259 }
 260
 261 int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
 262                         bool skip_hwpoisoned_pages)
 263 {
 264         unsigned long pfn, flags;
 265         struct page *page;
 266         struct zone *zone;
 267         int ret;
 268
 269         /*
 270          * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
 271          * are not aligned to pageblock_nr_pages.
 272          * Then we just check migratetype first.
 273          */
 274         for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
 275                 page = __first_valid_page(pfn, pageblock_nr_pages);
 276                 if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
 277                         break;
 278         }
 279         page = __first_valid_page(start_pfn, end_pfn - start_pfn);
 280         if ((pfn < end_pfn) || !page)
 281                 return -EBUSY;
 282         /* Check all pages are free or marked as ISOLATED */
 283         zone = page_zone(page);
 284         spin_lock_irqsave(&zone->lock, flags);
 285         ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn,
 286                                                 skip_hwpoisoned_pages);
 287         spin_unlock_irqrestore(&zone->lock, flags);
 288         return ret ? 0 : -EBUSY;
 289 }
 290
 291 struct page *alloc_migrate_target(struct page *page, unsigned long private,
 292                                   int **resultp)
 293 {
 294         gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
 295
 296         /*
 297          * TODO: allocate a destination hugepage from a nearest neighbor node,
 298          * accordance with memory policy of the user process if possible. For
 299          * now as a simple work-around, we use the next node for destination.
 300          */
 301         if (PageHuge(page)) {
 302                 nodemask_t src = nodemask_of_node(page_to_nid(page));
 303                 nodemask_t dst;
 304                 nodes_complement(dst, src);
 305                 return alloc_huge_page_node(page_hstate(compound_head(page)),
 306                                             next_node(page_to_nid(page), dst));
 307         }
 308
 309         if (PageHighMem(page))
 310                 gfp_mask |= __GFP_HIGHMEM;
 311
 312         return alloc_page(gfp_mask);
 313 }