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 = page_zone(page);
  21         struct page *unmovable;
  22         unsigned long flags;
  23
  24         spin_lock_irqsave(&zone->lock, flags);
  25
  26         /*
  27          * We assume the caller intended to SET migrate type to isolate.
  28          * If it is already set, then someone else must have raced and
  29          * set it before us.
  30          */
  31         if (is_migrate_isolate_page(page)) {
  32                 spin_unlock_irqrestore(&zone->lock, flags);
  33                 return -EBUSY;
  34         }
  35
  36         /*
  37          * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
  38          * We just check MOVABLE pages.
  39          */
  40         unmovable = has_unmovable_pages(zone, page, migratetype, isol_flags);
  41         if (!unmovable) {
  42                 unsigned long nr_pages;
  43                 int mt = get_pageblock_migratetype(page);
  44
  45                 set_pageblock_migratetype(page, MIGRATE_ISOLATE);
  46                 zone->nr_isolate_pageblock++;
  47                 nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE,
  48                                                                         NULL);
  49
  50                 __mod_zone_freepage_state(zone, -nr_pages, mt);
  51                 spin_unlock_irqrestore(&zone->lock, flags);
  52                 return 0;
  53         }
  54
  55         spin_unlock_irqrestore(&zone->lock, flags);
  56         if (isol_flags & REPORT_FAILURE) {
  57                 /*
  58                  * printk() with zone->lock held will likely trigger a
  59                  * lockdep splat, so defer it here.
  60                  */
  61                 dump_page(unmovable, "unmovable page");
  62         }
  63
  64         return -EBUSY;
  65 }
  66
  67 static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
  68 {
  69         struct zone *zone;
  70         unsigned long flags, nr_pages;
  71         bool isolated_page = false;
  72         unsigned int order;
  73         unsigned long pfn, buddy_pfn;
  74         struct page *buddy;
  75
  76         zone = page_zone(page);
  77         spin_lock_irqsave(&zone->lock, flags);
  78         if (!is_migrate_isolate_page(page))
  79                 goto out;
  80
  81         /*
  82          * Because freepage with more than pageblock_order on isolated
  83          * pageblock is restricted to merge due to freepage counting problem,
  84          * it is possible that there is free buddy page.
  85          * move_freepages_block() doesn't care of merge so we need other
  86          * approach in order to merge them. Isolation and free will make
  87          * these pages to be merged.
  88          */
  89         if (PageBuddy(page)) {
  90                 order = buddy_order(page);
  91                 if (order >= pageblock_order && order < MAX_ORDER - 1) {
  92                         pfn = page_to_pfn(page);
  93                         buddy_pfn = __find_buddy_pfn(pfn, order);
  94                         buddy = page + (buddy_pfn - pfn);
  95
  96                         if (!is_migrate_isolate_page(buddy)) {
  97                                 __isolate_free_page(page, order);
  98                                 isolated_page = true;
  99                         }
 100                 }
 101         }
 102
 103         /*
 104          * If we isolate freepage with more than pageblock_order, there
 105          * should be no freepage in the range, so we could avoid costly
 106          * pageblock scanning for freepage moving.
 107          *
 108          * We didn't actually touch any of the isolated pages, so place them
 109          * to the tail of the freelist. This is an optimization for memory
 110          * onlining - just onlined memory won't immediately be considered for
 111          * allocation.
 112          */
 113         if (!isolated_page) {
 114                 nr_pages = move_freepages_block(zone, page, migratetype, NULL);
 115                 __mod_zone_freepage_state(zone, nr_pages, migratetype);
 116         }
 117         set_pageblock_migratetype(page, migratetype);
 118         if (isolated_page)
 119                 __putback_isolated_page(page, order, migratetype);
 120         zone->nr_isolate_pageblock--;
 121 out:
 122         spin_unlock_irqrestore(&zone->lock, flags);
 123 }
 124
 125 static inline struct page *
 126 __first_valid_page(unsigned long pfn, unsigned long nr_pages)
 127 {
 128         int i;
 129
 130         for (i = 0; i < nr_pages; i++) {
 131                 struct page *page;
 132
 133                 page = pfn_to_online_page(pfn + i);
 134                 if (!page)
 135                         continue;
 136                 return page;
 137         }
 138         return NULL;
 139 }
 140
 141 /**
 142  * start_isolate_page_range() - make page-allocation-type of range of pages to
 143  * be MIGRATE_ISOLATE.
 144  * @start_pfn:          The lower PFN of the range to be isolated.
 145  * @end_pfn:            The upper PFN of the range to be isolated.
 146  *                      start_pfn/end_pfn must be aligned to pageblock_order.
 147  * @migratetype:        Migrate type to set in error recovery.
 148  * @flags:              The following flags are allowed (they can be combined in
 149  *                      a bit mask)
 150  *                      MEMORY_OFFLINE - isolate to offline (!allocate) memory
 151  *                                       e.g., skip over PageHWPoison() pages
 152  *                                       and PageOffline() pages.
 153  *                      REPORT_FAILURE - report details about the failure to
 154  *                      isolate the range
 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. If specified range includes migrate types
 159  * other than MOVABLE or CMA, this will fail with -EBUSY. For isolating all
 160  * pages in the range finally, the caller have to free all pages in the range.
 161  * test_page_isolated() can be used for test it.
 162  *
 163  * There is no high level synchronization mechanism that prevents two threads
 164  * from trying to isolate overlapping ranges. If this happens, one thread
 165  * will notice pageblocks in the overlapping range already set to isolate.
 166  * This happens in set_migratetype_isolate, and set_migratetype_isolate
 167  * returns an error. We then clean up by restoring the migration type on
 168  * pageblocks we may have modified and return -EBUSY to caller. This
 169  * prevents two threads from simultaneously working on overlapping ranges.
 170  *
 171  * Please note that there is no strong synchronization with the page allocator
 172  * either. Pages might be freed while their page blocks are marked ISOLATED.
 173  * A call to drain_all_pages() after isolation can flush most of them. However
 174  * in some cases pages might still end up on pcp lists and that would allow
 175  * for their allocation even when they are in fact isolated already. Depending
 176  * on how strong of a guarantee the caller needs, zone_pcp_disable/enable()
 177  * might be used to flush and disable pcplist before isolation and enable after
 178  * unisolation.
 179  *
 180  * Return: 0 on success and -EBUSY if any part of range cannot be isolated.
 181  */
 182 int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 183                              unsigned migratetype, int flags)
 184 {
 185         unsigned long pfn;
 186         unsigned long undo_pfn;
 187         struct page *page;
 188
 189         BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
 190         BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
 191
 192         for (pfn = start_pfn;
 193              pfn < end_pfn;
 194              pfn += pageblock_nr_pages) {
 195                 page = __first_valid_page(pfn, pageblock_nr_pages);
 196                 if (page) {
 197                         if (set_migratetype_isolate(page, migratetype, flags)) {
 198                                 undo_pfn = pfn;
 199                                 goto undo;
 200                         }
 201                 }
 202         }
 203         return 0;
 204 undo:
 205         for (pfn = start_pfn;
 206              pfn < undo_pfn;
 207              pfn += pageblock_nr_pages) {
 208                 struct page *page = pfn_to_online_page(pfn);
 209                 if (!page)
 210                         continue;
 211                 unset_migratetype_isolate(page, migratetype);
 212         }
 213
 214         return -EBUSY;
 215 }
 216
 217 /*
 218  * Make isolated pages available again.
 219  */
 220 void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 221                             unsigned migratetype)
 222 {
 223         unsigned long pfn;
 224         struct page *page;
 225
 226         BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
 227         BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
 228
 229         for (pfn = start_pfn;
 230              pfn < end_pfn;
 231              pfn += pageblock_nr_pages) {
 232                 page = __first_valid_page(pfn, pageblock_nr_pages);
 233                 if (!page || !is_migrate_isolate_page(page))
 234                         continue;
 235                 unset_migratetype_isolate(page, migratetype);
 236         }
 237 }
 238 /*
 239  * Test all pages in the range is free(means isolated) or not.
 240  * all pages in [start_pfn...end_pfn) must be in the same zone.
 241  * zone->lock must be held before call this.
 242  *
 243  * Returns the last tested pfn.
 244  */
 245 static unsigned long
 246 __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
 247                                   int flags)
 248 {
 249         struct page *page;
 250
 251         while (pfn < end_pfn) {
 252                 page = pfn_to_page(pfn);
 253                 if (PageBuddy(page))
 254                         /*
 255                          * If the page is on a free list, it has to be on
 256                          * the correct MIGRATE_ISOLATE freelist. There is no
 257                          * simple way to verify that as VM_BUG_ON(), though.
 258                          */
 259                         pfn += 1 << buddy_order(page);
 260                 else if ((flags & MEMORY_OFFLINE) && PageHWPoison(page))
 261                         /* A HWPoisoned page cannot be also PageBuddy */
 262                         pfn++;
 263                 else if ((flags & MEMORY_OFFLINE) && PageOffline(page) &&
 264                          !page_count(page))
 265                         /*
 266                          * The responsible driver agreed to skip PageOffline()
 267                          * pages when offlining memory by dropping its
 268                          * reference in MEM_GOING_OFFLINE.
 269                          */
 270                         pfn++;
 271                 else
 272                         break;
 273         }
 274
 275         return pfn;
 276 }
 277
 278 /* Caller should ensure that requested range is in a single zone */
 279 int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
 280                         int isol_flags)
 281 {
 282         unsigned long pfn, flags;
 283         struct page *page;
 284         struct zone *zone;
 285         int ret;
 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                 ret = -EBUSY;
 300                 goto out;
 301         }
 302
 303         /* Check all pages are free or marked as ISOLATED */
 304         zone = page_zone(page);
 305         spin_lock_irqsave(&zone->lock, flags);
 306         pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn, isol_flags);
 307         spin_unlock_irqrestore(&zone->lock, flags);
 308
 309         ret = pfn < end_pfn ? -EBUSY : 0;
 310
 311 out:
 312         trace_test_pages_isolated(start_pfn, end_pfn, pfn);
 313
 314         return ret;
 315 }