mm/page_isolation.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * linux/mm/page_isolation.c
   4  */
   5
   6 #include <linux/mm.h>
   7 #include <linux/page-isolation.h>
   8 #include <linux/pageblock-flags.h>
   9 #include <linux/memory.h>
  10 #include <linux/hugetlb.h>
  11 #include <linux/page_owner.h>
  12 #include <linux/migrate.h>
  13 #include "internal.h"
  14
  15 #define CREATE_TRACE_POINTS
  16 #include <trace/events/page_isolation.h>
  17
  18 static int set_migratetype_isolate(struct page *page, int migratetype,
  19                                 bool skip_hwpoisoned_pages)
  20 {
  21         struct zone *zone;
  22         unsigned long flags, pfn;
  23         struct memory_isolate_notify arg;
  24         int notifier_ret;
  25         int ret = -EBUSY;
  26
  27         zone = page_zone(page);
  28
  29         spin_lock_irqsave(&zone->lock, flags);
  30
  31         /*
  32          * We assume the caller intended to SET migrate type to isolate.
  33          * If it is already set, then someone else must have raced and
  34          * set it before us.  Return -EBUSY
  35          */
  36         if (is_migrate_isolate_page(page))
  37                 goto out;
  38
  39         pfn = page_to_pfn(page);
  40         arg.start_pfn = pfn;
  41         arg.nr_pages = pageblock_nr_pages;
  42         arg.pages_found = 0;
  43
  44         /*
  45          * It may be possible to isolate a pageblock even if the
  46          * migratetype is not MIGRATE_MOVABLE. The memory isolation
  47          * notifier chain is used by balloon drivers to return the
  48          * number of pages in a range that are held by the balloon
  49          * driver to shrink memory. If all the pages are accounted for
  50          * by balloons, are free, or on the LRU, isolation can continue.
  51          * Later, for example, when memory hotplug notifier runs, these
  52          * pages reported as "can be isolated" should be isolated(freed)
  53          * by the balloon driver through the memory notifier chain.
  54          */
  55         notifier_ret = memory_isolate_notify(MEM_ISOLATE_COUNT, &arg);
  56         notifier_ret = notifier_to_errno(notifier_ret);
  57         if (notifier_ret)
  58                 goto out;
  59         /*
  60          * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
  61          * We just check MOVABLE pages.
  62          */
  63         if (!has_unmovable_pages(zone, page, arg.pages_found, migratetype,
  64                                  skip_hwpoisoned_pages))
  65                 ret = 0;
  66
  67         /*
  68          * immobile means "not-on-lru" pages. If immobile is larger than
  69          * removable-by-driver pages reported by notifier, we'll fail.
  70          */
  71
  72 out:
  73         if (!ret) {
  74                 unsigned long nr_pages;
  75                 int mt = get_pageblock_migratetype(page);
  76
  77                 set_pageblock_migratetype(page, MIGRATE_ISOLATE);
  78                 zone->nr_isolate_pageblock++;
  79                 nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE,
  80                                                                         NULL);
  81
  82                 __mod_zone_freepage_state(zone, -nr_pages, mt);
  83         }
  84
  85         spin_unlock_irqrestore(&zone->lock, flags);
  86         if (!ret)
  87                 drain_all_pages(zone);
  88         return ret;
  89 }
  90
  91 static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
  92 {
  93         struct zone *zone;
  94         unsigned long flags, nr_pages;
  95         bool isolated_page = false;
  96         unsigned int order;
  97         unsigned long pfn, buddy_pfn;
  98         struct page *buddy;
  99
 100         zone = page_zone(page);
 101         spin_lock_irqsave(&zone->lock, flags);
 102         if (!is_migrate_isolate_page(page))
 103                 goto out;
 104
 105         /*
 106          * Because freepage with more than pageblock_order on isolated
 107          * pageblock is restricted to merge due to freepage counting problem,
 108          * it is possible that there is free buddy page.
 109          * move_freepages_block() doesn't care of merge so we need other
 110          * approach in order to merge them. Isolation and free will make
 111          * these pages to be merged.
 112          */
 113         if (PageBuddy(page)) {
 114                 order = page_order(page);
 115                 if (order >= pageblock_order) {
 116                         pfn = page_to_pfn(page);
 117                         buddy_pfn = __find_buddy_pfn(pfn, order);
 118                         buddy = page + (buddy_pfn - pfn);
 119
 120                         if (pfn_valid_within(buddy_pfn) &&
 121                             !is_migrate_isolate_page(buddy)) {
 122                                 __isolate_free_page(page, order);
 123                                 isolated_page = true;
 124                         }
 125                 }
 126         }
 127
 128         /*
 129          * If we isolate freepage with more than pageblock_order, there
 130          * should be no freepage in the range, so we could avoid costly
 131          * pageblock scanning for freepage moving.
 132          */
 133         if (!isolated_page) {
 134                 nr_pages = move_freepages_block(zone, page, migratetype, NULL);
 135                 __mod_zone_freepage_state(zone, nr_pages, migratetype);
 136         }
 137         set_pageblock_migratetype(page, migratetype);
 138         zone->nr_isolate_pageblock--;
 139 out:
 140         spin_unlock_irqrestore(&zone->lock, flags);
 141         if (isolated_page) {
 142                 post_alloc_hook(page, order, __GFP_MOVABLE);
 143                 __free_pages(page, order);
 144         }
 145 }
 146
 147 static inline struct page *
 148 __first_valid_page(unsigned long pfn, unsigned long nr_pages)
 149 {
 150         int i;
 151
 152         for (i = 0; i < nr_pages; i++) {
 153                 struct page *page;
 154
 155                 if (!pfn_valid_within(pfn + i))
 156                         continue;
 157                 page = pfn_to_online_page(pfn + i);
 158                 if (!page)
 159                         continue;
 160                 return page;
 161         }
 162         return NULL;
 163 }
 164
 165 /*
 166  * start_isolate_page_range() -- make page-allocation-type of range of pages
 167  * to be MIGRATE_ISOLATE.
 168  * @start_pfn: The lower PFN of the range to be isolated.
 169  * @end_pfn: The upper PFN of the range to be isolated.
 170  * @migratetype: migrate type to set in error recovery.
 171  *
 172  * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
 173  * the range will never be allocated. Any free pages and pages freed in the
 174  * future will not be allocated again.
 175  *
 176  * start_pfn/end_pfn must be aligned to pageblock_order.
 177  * Return 0 on success and -EBUSY if any part of range cannot be isolated.
 178  *
 179  * There is no high level synchronization mechanism that prevents two threads
 180  * from trying to isolate overlapping ranges.  If this happens, one thread
 181  * will notice pageblocks in the overlapping range already set to isolate.
 182  * This happens in set_migratetype_isolate, and set_migratetype_isolate
 183  * returns an error.  We then clean up by restoring the migration type on
 184  * pageblocks we may have modified and return -EBUSY to caller.  This
 185  * prevents two threads from simultaneously working on overlapping ranges.
 186  */
 187 int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 188                              unsigned migratetype, bool skip_hwpoisoned_pages)
 189 {
 190         unsigned long pfn;
 191         unsigned long undo_pfn;
 192         struct page *page;
 193
 194         BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
 195         BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
 196
 197         for (pfn = start_pfn;
 198              pfn < end_pfn;
 199              pfn += pageblock_nr_pages) {
 200                 page = __first_valid_page(pfn, pageblock_nr_pages);
 201                 if (page &&
 202                     set_migratetype_isolate(page, migratetype, skip_hwpoisoned_pages)) {
 203                         undo_pfn = pfn;
 204                         goto undo;
 205                 }
 206         }
 207         return 0;
 208 undo:
 209         for (pfn = start_pfn;
 210              pfn < undo_pfn;
 211              pfn += pageblock_nr_pages) {
 212                 struct page *page = pfn_to_online_page(pfn);
 213                 if (!page)
 214                         continue;
 215                 unset_migratetype_isolate(page, migratetype);
 216         }
 217
 218         return -EBUSY;
 219 }
 220
 221 /*
 222  * Make isolated pages available again.
 223  */
 224 int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 225                             unsigned migratetype)
 226 {
 227         unsigned long pfn;
 228         struct page *page;
 229
 230         BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
 231         BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
 232
 233         for (pfn = start_pfn;
 234              pfn < end_pfn;
 235              pfn += pageblock_nr_pages) {
 236                 page = __first_valid_page(pfn, pageblock_nr_pages);
 237                 if (!page || !is_migrate_isolate_page(page))
 238                         continue;
 239                 unset_migratetype_isolate(page, migratetype);
 240         }
 241         return 0;
 242 }
 243 /*
 244  * Test all pages in the range is free(means isolated) or not.
 245  * all pages in [start_pfn...end_pfn) must be in the same zone.
 246  * zone->lock must be held before call this.
 247  *
 248  * Returns the last tested pfn.
 249  */
 250 static unsigned long
 251 __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
 252                                   bool skip_hwpoisoned_pages)
 253 {
 254         struct page *page;
 255
 256         while (pfn < end_pfn) {
 257                 if (!pfn_valid_within(pfn)) {
 258                         pfn++;
 259                         continue;
 260                 }
 261                 page = pfn_to_page(pfn);
 262                 if (PageBuddy(page))
 263                         /*
 264                          * If the page is on a free list, it has to be on
 265                          * the correct MIGRATE_ISOLATE freelist. There is no
 266                          * simple way to verify that as VM_BUG_ON(), though.
 267                          */
 268                         pfn += 1 << page_order(page);
 269                 else if (skip_hwpoisoned_pages && PageHWPoison(page))
 270                         /* A HWPoisoned page cannot be also PageBuddy */
 271                         pfn++;
 272                 else
 273                         break;
 274         }
 275
 276         return pfn;
 277 }
 278
 279 /* Caller should ensure that requested range is in a single zone */
 280 int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
 281                         bool skip_hwpoisoned_pages)
 282 {
 283         unsigned long pfn, flags;
 284         struct page *page;
 285         struct zone *zone;
 286
 287         /*
 288          * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
 289          * are not aligned to pageblock_nr_pages.
 290          * Then we just check migratetype first.
 291          */
 292         for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
 293                 page = __first_valid_page(pfn, pageblock_nr_pages);
 294                 if (page && !is_migrate_isolate_page(page))
 295                         break;
 296         }
 297         page = __first_valid_page(start_pfn, end_pfn - start_pfn);
 298         if ((pfn < end_pfn) || !page)
 299                 return -EBUSY;
 300         /* Check all pages are free or marked as ISOLATED */
 301         zone = page_zone(page);
 302         spin_lock_irqsave(&zone->lock, flags);
 303         pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn,
 304                                                 skip_hwpoisoned_pages);
 305         spin_unlock_irqrestore(&zone->lock, flags);
 306
 307         trace_test_pages_isolated(start_pfn, end_pfn, pfn);
 308
 309         return pfn < end_pfn ? -EBUSY : 0;
 310 }
 311
 312 struct page *alloc_migrate_target(struct page *page, unsigned long private)
 313 {
 314         return new_page_nodemask(page, numa_node_id(), &node_states[N_MEMORY]);
 315 }