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