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 <linux/page_owner.h>
  11 #include "internal.h"
  12
  13 #define CREATE_TRACE_POINTS
  14 #include <trace/events/page_isolation.h>
  15
  16 static int set_migratetype_isolate(struct page *page,
  17                                 bool skip_hwpoisoned_pages)
  18 {
  19         struct zone *zone;
  20         unsigned long flags, pfn;
  21         struct memory_isolate_notify arg;
  22         int notifier_ret;
  23         int ret = -EBUSY;
  24
  25         zone = page_zone(page);
  26
  27         spin_lock_irqsave(&zone->lock, flags);
  28
  29         pfn = page_to_pfn(page);
  30         arg.start_pfn = pfn;
  31         arg.nr_pages = pageblock_nr_pages;
  32         arg.pages_found = 0;
  33
  34         /*
  35          * It may be possible to isolate a pageblock even if the
  36          * migratetype is not MIGRATE_MOVABLE. The memory isolation
  37          * notifier chain is used by balloon drivers to return the
  38          * number of pages in a range that are held by the balloon
  39          * driver to shrink memory. If all the pages are accounted for
  40          * by balloons, are free, or on the LRU, isolation can continue.
  41          * Later, for example, when memory hotplug notifier runs, these
  42          * pages reported as "can be isolated" should be isolated(freed)
  43          * by the balloon driver through the memory notifier chain.
  44          */
  45         notifier_ret = memory_isolate_notify(MEM_ISOLATE_COUNT, &arg);
  46         notifier_ret = notifier_to_errno(notifier_ret);
  47         if (notifier_ret)
  48                 goto out;
  49         /*
  50          * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
  51          * We just check MOVABLE pages.
  52          */
  53         if (!has_unmovable_pages(zone, page, arg.pages_found,
  54                                  skip_hwpoisoned_pages))
  55                 ret = 0;
  56
  57         /*
  58          * immobile means "not-on-lru" pages. If immobile is larger than
  59          * removable-by-driver pages reported by notifier, we'll fail.
  60          */
  61
  62 out:
  63         if (!ret) {
  64                 unsigned long nr_pages;
  65                 int migratetype = get_pageblock_migratetype(page);
  66
  67                 set_pageblock_migratetype(page, MIGRATE_ISOLATE);
  68                 zone->nr_isolate_pageblock++;
  69                 nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE,
  70                                                                         NULL);
  71
  72                 __mod_zone_freepage_state(zone, -nr_pages, migratetype);
  73         }
  74
  75         spin_unlock_irqrestore(&zone->lock, flags);
  76         if (!ret)
  77                 drain_all_pages(zone);
  78         return ret;
  79 }
  80
  81 static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
  82 {
  83         struct zone *zone;
  84         unsigned long flags, nr_pages;
  85         bool isolated_page = false;
  86         unsigned int order;
  87         unsigned long pfn, buddy_pfn;
  88         struct page *buddy;
  89
  90         zone = page_zone(page);
  91         spin_lock_irqsave(&zone->lock, flags);
  92         if (!is_migrate_isolate_page(page))
  93                 goto out;
  94
  95         /*
  96          * Because freepage with more than pageblock_order on isolated
  97          * pageblock is restricted to merge due to freepage counting problem,
  98          * it is possible that there is free buddy page.
  99          * move_freepages_block() doesn't care of merge so we need other
 100          * approach in order to merge them. Isolation and free will make
 101          * these pages to be merged.
 102          */
 103         if (PageBuddy(page)) {
 104                 order = page_order(page);
 105                 if (order >= pageblock_order) {
 106                         pfn = page_to_pfn(page);
 107                         buddy_pfn = __find_buddy_pfn(pfn, order);
 108                         buddy = page + (buddy_pfn - pfn);
 109
 110                         if (pfn_valid_within(buddy_pfn) &&
 111                             !is_migrate_isolate_page(buddy)) {
 112                                 __isolate_free_page(page, order);
 113                                 isolated_page = true;
 114                         }
 115                 }
 116         }
 117
 118         /*
 119          * If we isolate freepage with more than pageblock_order, there
 120          * should be no freepage in the range, so we could avoid costly
 121          * pageblock scanning for freepage moving.
 122          */
 123         if (!isolated_page) {
 124                 nr_pages = move_freepages_block(zone, page, migratetype, NULL);
 125                 __mod_zone_freepage_state(zone, nr_pages, migratetype);
 126         }
 127         set_pageblock_migratetype(page, migratetype);
 128         zone->nr_isolate_pageblock--;
 129 out:
 130         spin_unlock_irqrestore(&zone->lock, flags);
 131         if (isolated_page) {
 132                 post_alloc_hook(page, order, __GFP_MOVABLE);
 133                 __free_pages(page, order);
 134         }
 135 }
 136
 137 static inline struct page *
 138 __first_valid_page(unsigned long pfn, unsigned long nr_pages)
 139 {
 140         int i;
 141         for (i = 0; i < nr_pages; i++)
 142                 if (pfn_valid_within(pfn + i))
 143                         break;
 144         if (unlikely(i == nr_pages))
 145                 return NULL;
 146         return pfn_to_page(pfn + i);
 147 }
 148
 149 /*
 150  * start_isolate_page_range() -- make page-allocation-type of range of pages
 151  * to be MIGRATE_ISOLATE.
 152  * @start_pfn: The lower PFN of the range to be isolated.
 153  * @end_pfn: The upper PFN of the range to be isolated.
 154  * @migratetype: migrate type to set in error recovery.
 155  *
 156  * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
 157  * the range will never be allocated. Any free pages and pages freed in the
 158  * future will not be allocated again.
 159  *
 160  * start_pfn/end_pfn must be aligned to pageblock_order.
 161  * Returns 0 on success and -EBUSY if any part of range cannot be isolated.
 162  */
 163 int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 164                              unsigned migratetype, bool skip_hwpoisoned_pages)
 165 {
 166         unsigned long pfn;
 167         unsigned long undo_pfn;
 168         struct page *page;
 169
 170         BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
 171         BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
 172
 173         for (pfn = start_pfn;
 174              pfn < end_pfn;
 175              pfn += pageblock_nr_pages) {
 176                 page = __first_valid_page(pfn, pageblock_nr_pages);
 177                 if (page &&
 178                     set_migratetype_isolate(page, skip_hwpoisoned_pages)) {
 179                         undo_pfn = pfn;
 180                         goto undo;
 181                 }
 182         }
 183         return 0;
 184 undo:
 185         for (pfn = start_pfn;
 186              pfn < undo_pfn;
 187              pfn += pageblock_nr_pages)
 188                 unset_migratetype_isolate(pfn_to_page(pfn), migratetype);
 189
 190         return -EBUSY;
 191 }
 192
 193 /*
 194  * Make isolated pages available again.
 195  */
 196 int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 197                             unsigned migratetype)
 198 {
 199         unsigned long pfn;
 200         struct page *page;
 201
 202         BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
 203         BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
 204
 205         for (pfn = start_pfn;
 206              pfn < end_pfn;
 207              pfn += pageblock_nr_pages) {
 208                 page = __first_valid_page(pfn, pageblock_nr_pages);
 209                 if (!page || !is_migrate_isolate_page(page))
 210                         continue;
 211                 unset_migratetype_isolate(page, migratetype);
 212         }
 213         return 0;
 214 }
 215 /*
 216  * Test all pages in the range is free(means isolated) or not.
 217  * all pages in [start_pfn...end_pfn) must be in the same zone.
 218  * zone->lock must be held before call this.
 219  *
 220  * Returns the last tested pfn.
 221  */
 222 static unsigned long
 223 __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
 224                                   bool skip_hwpoisoned_pages)
 225 {
 226         struct page *page;
 227
 228         while (pfn < end_pfn) {
 229                 if (!pfn_valid_within(pfn)) {
 230                         pfn++;
 231                         continue;
 232                 }
 233                 page = pfn_to_page(pfn);
 234                 if (PageBuddy(page))
 235                         /*
 236                          * If the page is on a free list, it has to be on
 237                          * the correct MIGRATE_ISOLATE freelist. There is no
 238                          * simple way to verify that as VM_BUG_ON(), though.
 239                          */
 240                         pfn += 1 << page_order(page);
 241                 else if (skip_hwpoisoned_pages && PageHWPoison(page))
 242                         /* A HWPoisoned page cannot be also PageBuddy */
 243                         pfn++;
 244                 else
 245                         break;
 246         }
 247
 248         return pfn;
 249 }
 250
 251 /* Caller should ensure that requested range is in a single zone */
 252 int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
 253                         bool skip_hwpoisoned_pages)
 254 {
 255         unsigned long pfn, flags;
 256         struct page *page;
 257         struct zone *zone;
 258
 259         /*
 260          * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
 261          * are not aligned to pageblock_nr_pages.
 262          * Then we just check migratetype first.
 263          */
 264         for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
 265                 page = __first_valid_page(pfn, pageblock_nr_pages);
 266                 if (page && !is_migrate_isolate_page(page))
 267                         break;
 268         }
 269         page = __first_valid_page(start_pfn, end_pfn - start_pfn);
 270         if ((pfn < end_pfn) || !page)
 271                 return -EBUSY;
 272         /* Check all pages are free or marked as ISOLATED */
 273         zone = page_zone(page);
 274         spin_lock_irqsave(&zone->lock, flags);
 275         pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn,
 276                                                 skip_hwpoisoned_pages);
 277         spin_unlock_irqrestore(&zone->lock, flags);
 278
 279         trace_test_pages_isolated(start_pfn, end_pfn, pfn);
 280
 281         return pfn < end_pfn ? -EBUSY : 0;
 282 }
 283
 284 struct page *alloc_migrate_target(struct page *page, unsigned long private,
 285                                   int **resultp)
 286 {
 287         gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
 288
 289         /*
 290          * TODO: allocate a destination hugepage from a nearest neighbor node,
 291          * accordance with memory policy of the user process if possible. For
 292          * now as a simple work-around, we use the next node for destination.
 293          */
 294         if (PageHuge(page))
 295                 return alloc_huge_page_node(page_hstate(compound_head(page)),
 296                                             next_node_in(page_to_nid(page),
 297                                                          node_online_map));
 298
 299         if (PageHighMem(page))
 300                 gfp_mask |= __GFP_HIGHMEM;
 301
 302         return alloc_page(gfp_mask);
 303 }