mm/memory_hotplug.c

   1 /*
   2  *  linux/mm/memory_hotplug.c
   3  *
   4  *  Copyright (C)
   5  */
   6
   7 #include <linux/stddef.h>
   8 #include <linux/mm.h>
   9 #include <linux/swap.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/pagemap.h>
  12 #include <linux/compiler.h>
  13 #include <linux/export.h>
  14 #include <linux/pagevec.h>
  15 #include <linux/writeback.h>
  16 #include <linux/slab.h>
  17 #include <linux/sysctl.h>
  18 #include <linux/cpu.h>
  19 #include <linux/memory.h>
  20 #include <linux/memory_hotplug.h>
  21 #include <linux/highmem.h>
  22 #include <linux/vmalloc.h>
  23 #include <linux/ioport.h>
  24 #include <linux/delay.h>
  25 #include <linux/migrate.h>
  26 #include <linux/page-isolation.h>
  27 #include <linux/pfn.h>
  28 #include <linux/suspend.h>
  29 #include <linux/mm_inline.h>
  30 #include <linux/firmware-map.h>
  31 #include <linux/stop_machine.h>
  32 #include <linux/hugetlb.h>
  33 #include <linux/memblock.h>
  34 #include <linux/bootmem.h>
  35
  36 #include <asm/tlbflush.h>
  37
  38 #include "internal.h"
  39
  40 /*
  41  * online_page_callback contains pointer to current page onlining function.
  42  * Initially it is generic_online_page(). If it is required it could be
  43  * changed by calling set_online_page_callback() for callback registration
  44  * and restore_online_page_callback() for generic callback restore.
  45  */
  46
  47 static void generic_online_page(struct page *page);
  48
  49 static online_page_callback_t online_page_callback = generic_online_page;
  50 static DEFINE_MUTEX(online_page_callback_lock);
  51
  52 /* The same as the cpu_hotplug lock, but for memory hotplug. */
  53 static struct {
  54         struct task_struct *active_writer;
  55         struct mutex lock; /* Synchronizes accesses to refcount, */
  56         /*
  57          * Also blocks the new readers during
  58          * an ongoing mem hotplug operation.
  59          */
  60         int refcount;
  61
  62 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  63         struct lockdep_map dep_map;
  64 #endif
  65 } mem_hotplug = {
  66         .active_writer = NULL,
  67         .lock = __MUTEX_INITIALIZER(mem_hotplug.lock),
  68         .refcount = 0,
  69 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  70         .dep_map = {.name = "mem_hotplug.lock" },
  71 #endif
  72 };
  73
  74 /* Lockdep annotations for get/put_online_mems() and mem_hotplug_begin/end() */
  75 #define memhp_lock_acquire_read() lock_map_acquire_read(&mem_hotplug.dep_map)
  76 #define memhp_lock_acquire()      lock_map_acquire(&mem_hotplug.dep_map)
  77 #define memhp_lock_release()      lock_map_release(&mem_hotplug.dep_map)
  78
  79 void get_online_mems(void)
  80 {
  81         might_sleep();
  82         if (mem_hotplug.active_writer == current)
  83                 return;
  84         memhp_lock_acquire_read();
  85         mutex_lock(&mem_hotplug.lock);
  86         mem_hotplug.refcount++;
  87         mutex_unlock(&mem_hotplug.lock);
  88
  89 }
  90
  91 void put_online_mems(void)
  92 {
  93         if (mem_hotplug.active_writer == current)
  94                 return;
  95         mutex_lock(&mem_hotplug.lock);
  96
  97         if (WARN_ON(!mem_hotplug.refcount))
  98                 mem_hotplug.refcount++; /* try to fix things up */
  99
 100         if (!--mem_hotplug.refcount && unlikely(mem_hotplug.active_writer))
 101                 wake_up_process(mem_hotplug.active_writer);
 102         mutex_unlock(&mem_hotplug.lock);
 103         memhp_lock_release();
 104
 105 }
 106
 107 static void mem_hotplug_begin(void)
 108 {
 109         mem_hotplug.active_writer = current;
 110
 111         memhp_lock_acquire();
 112         for (;;) {
 113                 mutex_lock(&mem_hotplug.lock);
 114                 if (likely(!mem_hotplug.refcount))
 115                         break;
 116                 __set_current_state(TASK_UNINTERRUPTIBLE);
 117                 mutex_unlock(&mem_hotplug.lock);
 118                 schedule();
 119         }
 120 }
 121
 122 static void mem_hotplug_done(void)
 123 {
 124         mem_hotplug.active_writer = NULL;
 125         mutex_unlock(&mem_hotplug.lock);
 126         memhp_lock_release();
 127 }
 128
 129 /* add this memory to iomem resource */
 130 static struct resource *register_memory_resource(u64 start, u64 size)
 131 {
 132         struct resource *res;
 133         res = kzalloc(sizeof(struct resource), GFP_KERNEL);
 134         BUG_ON(!res);
 135
 136         res->name = "System RAM";
 137         res->start = start;
 138         res->end = start + size - 1;
 139         res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
 140         if (request_resource(&iomem_resource, res) < 0) {
 141                 pr_debug("System RAM resource %pR cannot be added\n", res);
 142                 kfree(res);
 143                 res = NULL;
 144         }
 145         return res;
 146 }
 147
 148 static void release_memory_resource(struct resource *res)
 149 {
 150         if (!res)
 151                 return;
 152         release_resource(res);
 153         kfree(res);
 154         return;
 155 }
 156
 157 #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
 158 void get_page_bootmem(unsigned long info,  struct page *page,
 159                       unsigned long type)
 160 {
 161         page->lru.next = (struct list_head *) type;
 162         SetPagePrivate(page);
 163         set_page_private(page, info);
 164         atomic_inc(&page->_count);
 165 }
 166
 167 void put_page_bootmem(struct page *page)
 168 {
 169         unsigned long type;
 170
 171         type = (unsigned long) page->lru.next;
 172         BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
 173                type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE);
 174
 175         if (atomic_dec_return(&page->_count) == 1) {
 176                 ClearPagePrivate(page);
 177                 set_page_private(page, 0);
 178                 INIT_LIST_HEAD(&page->lru);
 179                 free_reserved_page(page);
 180         }
 181 }
 182
 183 #ifdef CONFIG_HAVE_BOOTMEM_INFO_NODE
 184 #ifndef CONFIG_SPARSEMEM_VMEMMAP
 185 static void register_page_bootmem_info_section(unsigned long start_pfn)
 186 {
 187         unsigned long *usemap, mapsize, section_nr, i;
 188         struct mem_section *ms;
 189         struct page *page, *memmap;
 190
 191         section_nr = pfn_to_section_nr(start_pfn);
 192         ms = __nr_to_section(section_nr);
 193
 194         /* Get section's memmap address */
 195         memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
 196
 197         /*
 198          * Get page for the memmap's phys address
 199          * XXX: need more consideration for sparse_vmemmap...
 200          */
 201         page = virt_to_page(memmap);
 202         mapsize = sizeof(struct page) * PAGES_PER_SECTION;
 203         mapsize = PAGE_ALIGN(mapsize) >> PAGE_SHIFT;
 204
 205         /* remember memmap's page */
 206         for (i = 0; i < mapsize; i++, page++)
 207                 get_page_bootmem(section_nr, page, SECTION_INFO);
 208
 209         usemap = __nr_to_section(section_nr)->pageblock_flags;
 210         page = virt_to_page(usemap);
 211
 212         mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT;
 213
 214         for (i = 0; i < mapsize; i++, page++)
 215                 get_page_bootmem(section_nr, page, MIX_SECTION_INFO);
 216
 217 }
 218 #else /* CONFIG_SPARSEMEM_VMEMMAP */
 219 static void register_page_bootmem_info_section(unsigned long start_pfn)
 220 {
 221         unsigned long *usemap, mapsize, section_nr, i;
 222         struct mem_section *ms;
 223         struct page *page, *memmap;
 224
 225         if (!pfn_valid(start_pfn))
 226                 return;
 227
 228         section_nr = pfn_to_section_nr(start_pfn);
 229         ms = __nr_to_section(section_nr);
 230
 231         memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
 232
 233         register_page_bootmem_memmap(section_nr, memmap, PAGES_PER_SECTION);
 234
 235         usemap = __nr_to_section(section_nr)->pageblock_flags;
 236         page = virt_to_page(usemap);
 237
 238         mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT;
 239
 240         for (i = 0; i < mapsize; i++, page++)
 241                 get_page_bootmem(section_nr, page, MIX_SECTION_INFO);
 242 }
 243 #endif /* !CONFIG_SPARSEMEM_VMEMMAP */
 244
 245 void register_page_bootmem_info_node(struct pglist_data *pgdat)
 246 {
 247         unsigned long i, pfn, end_pfn, nr_pages;
 248         int node = pgdat->node_id;
 249         struct page *page;
 250         struct zone *zone;
 251
 252         nr_pages = PAGE_ALIGN(sizeof(struct pglist_data)) >> PAGE_SHIFT;
 253         page = virt_to_page(pgdat);
 254
 255         for (i = 0; i < nr_pages; i++, page++)
 256                 get_page_bootmem(node, page, NODE_INFO);
 257
 258         zone = &pgdat->node_zones[0];
 259         for (; zone < pgdat->node_zones + MAX_NR_ZONES - 1; zone++) {
 260                 if (zone_is_initialized(zone)) {
 261                         nr_pages = zone->wait_table_hash_nr_entries
 262                                 * sizeof(wait_queue_head_t);
 263                         nr_pages = PAGE_ALIGN(nr_pages) >> PAGE_SHIFT;
 264                         page = virt_to_page(zone->wait_table);
 265
 266                         for (i = 0; i < nr_pages; i++, page++)
 267                                 get_page_bootmem(node, page, NODE_INFO);
 268                 }
 269         }
 270
 271         pfn = pgdat->node_start_pfn;
 272         end_pfn = pgdat_end_pfn(pgdat);
 273
 274         /* register section info */
 275         for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
 276                 /*
 277                  * Some platforms can assign the same pfn to multiple nodes - on
 278                  * node0 as well as nodeN.  To avoid registering a pfn against
 279                  * multiple nodes we check that this pfn does not already
 280                  * reside in some other nodes.
 281                  */
 282                 if (pfn_valid(pfn) && (pfn_to_nid(pfn) == node))
 283                         register_page_bootmem_info_section(pfn);
 284         }
 285 }
 286 #endif /* CONFIG_HAVE_BOOTMEM_INFO_NODE */
 287
 288 static void grow_zone_span(struct zone *zone, unsigned long start_pfn,
 289                            unsigned long end_pfn)
 290 {
 291         unsigned long old_zone_end_pfn;
 292
 293         zone_span_writelock(zone);
 294
 295         old_zone_end_pfn = zone_end_pfn(zone);
 296         if (zone_is_empty(zone) || start_pfn < zone->zone_start_pfn)
 297                 zone->zone_start_pfn = start_pfn;
 298
 299         zone->spanned_pages = max(old_zone_end_pfn, end_pfn) -
 300                                 zone->zone_start_pfn;
 301
 302         zone_span_writeunlock(zone);
 303 }
 304
 305 static void resize_zone(struct zone *zone, unsigned long start_pfn,
 306                 unsigned long end_pfn)
 307 {
 308         zone_span_writelock(zone);
 309
 310         if (end_pfn - start_pfn) {
 311                 zone->zone_start_pfn = start_pfn;
 312                 zone->spanned_pages = end_pfn - start_pfn;
 313         } else {
 314                 /*
 315                  * make it consist as free_area_init_core(),
 316                  * if spanned_pages = 0, then keep start_pfn = 0
 317                  */
 318                 zone->zone_start_pfn = 0;
 319                 zone->spanned_pages = 0;
 320         }
 321
 322         zone_span_writeunlock(zone);
 323 }
 324
 325 static void fix_zone_id(struct zone *zone, unsigned long start_pfn,
 326                 unsigned long end_pfn)
 327 {
 328         enum zone_type zid = zone_idx(zone);
 329         int nid = zone->zone_pgdat->node_id;
 330         unsigned long pfn;
 331
 332         for (pfn = start_pfn; pfn < end_pfn; pfn++)
 333                 set_page_links(pfn_to_page(pfn), zid, nid, pfn);
 334 }
 335
 336 /* Can fail with -ENOMEM from allocating a wait table with vmalloc() or
 337  * alloc_bootmem_node_nopanic()/memblock_virt_alloc_node_nopanic() */
 338 static int __ref ensure_zone_is_initialized(struct zone *zone,
 339                         unsigned long start_pfn, unsigned long num_pages)
 340 {
 341         if (!zone_is_initialized(zone))
 342                 return init_currently_empty_zone(zone, start_pfn, num_pages,
 343                                                  MEMMAP_HOTPLUG);
 344         return 0;
 345 }
 346
 347 static int __meminit move_pfn_range_left(struct zone *z1, struct zone *z2,
 348                 unsigned long start_pfn, unsigned long end_pfn)
 349 {
 350         int ret;
 351         unsigned long flags;
 352         unsigned long z1_start_pfn;
 353
 354         ret = ensure_zone_is_initialized(z1, start_pfn, end_pfn - start_pfn);
 355         if (ret)
 356                 return ret;
 357
 358         pgdat_resize_lock(z1->zone_pgdat, &flags);
 359
 360         /* can't move pfns which are higher than @z2 */
 361         if (end_pfn > zone_end_pfn(z2))
 362                 goto out_fail;
 363         /* the move out part must be at the left most of @z2 */
 364         if (start_pfn > z2->zone_start_pfn)
 365                 goto out_fail;
 366         /* must included/overlap */
 367         if (end_pfn <= z2->zone_start_pfn)
 368                 goto out_fail;
 369
 370         /* use start_pfn for z1's start_pfn if z1 is empty */
 371         if (!zone_is_empty(z1))
 372                 z1_start_pfn = z1->zone_start_pfn;
 373         else
 374                 z1_start_pfn = start_pfn;
 375
 376         resize_zone(z1, z1_start_pfn, end_pfn);
 377         resize_zone(z2, end_pfn, zone_end_pfn(z2));
 378
 379         pgdat_resize_unlock(z1->zone_pgdat, &flags);
 380
 381         fix_zone_id(z1, start_pfn, end_pfn);
 382
 383         return 0;
 384 out_fail:
 385         pgdat_resize_unlock(z1->zone_pgdat, &flags);
 386         return -1;
 387 }
 388
 389 static int __meminit move_pfn_range_right(struct zone *z1, struct zone *z2,
 390                 unsigned long start_pfn, unsigned long end_pfn)
 391 {
 392         int ret;
 393         unsigned long flags;
 394         unsigned long z2_end_pfn;
 395
 396         ret = ensure_zone_is_initialized(z2, start_pfn, end_pfn - start_pfn);
 397         if (ret)
 398                 return ret;
 399
 400         pgdat_resize_lock(z1->zone_pgdat, &flags);
 401
 402         /* can't move pfns which are lower than @z1 */
 403         if (z1->zone_start_pfn > start_pfn)
 404                 goto out_fail;
 405         /* the move out part mast at the right most of @z1 */
 406         if (zone_end_pfn(z1) >  end_pfn)
 407                 goto out_fail;
 408         /* must included/overlap */
 409         if (start_pfn >= zone_end_pfn(z1))
 410                 goto out_fail;
 411
 412         /* use end_pfn for z2's end_pfn if z2 is empty */
 413         if (!zone_is_empty(z2))
 414                 z2_end_pfn = zone_end_pfn(z2);
 415         else
 416                 z2_end_pfn = end_pfn;
 417
 418         resize_zone(z1, z1->zone_start_pfn, start_pfn);
 419         resize_zone(z2, start_pfn, z2_end_pfn);
 420
 421         pgdat_resize_unlock(z1->zone_pgdat, &flags);
 422
 423         fix_zone_id(z2, start_pfn, end_pfn);
 424
 425         return 0;
 426 out_fail:
 427         pgdat_resize_unlock(z1->zone_pgdat, &flags);
 428         return -1;
 429 }
 430
 431 static void grow_pgdat_span(struct pglist_data *pgdat, unsigned long start_pfn,
 432                             unsigned long end_pfn)
 433 {
 434         unsigned long old_pgdat_end_pfn = pgdat_end_pfn(pgdat);
 435
 436         if (!pgdat->node_spanned_pages || start_pfn < pgdat->node_start_pfn)
 437                 pgdat->node_start_pfn = start_pfn;
 438
 439         pgdat->node_spanned_pages = max(old_pgdat_end_pfn, end_pfn) -
 440                                         pgdat->node_start_pfn;
 441 }
 442
 443 static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)
 444 {
 445         struct pglist_data *pgdat = zone->zone_pgdat;
 446         int nr_pages = PAGES_PER_SECTION;
 447         int nid = pgdat->node_id;
 448         int zone_type;
 449         unsigned long flags;
 450         int ret;
 451
 452         zone_type = zone - pgdat->node_zones;
 453         ret = ensure_zone_is_initialized(zone, phys_start_pfn, nr_pages);
 454         if (ret)
 455                 return ret;
 456
 457         pgdat_resize_lock(zone->zone_pgdat, &flags);
 458         grow_zone_span(zone, phys_start_pfn, phys_start_pfn + nr_pages);
 459         grow_pgdat_span(zone->zone_pgdat, phys_start_pfn,
 460                         phys_start_pfn + nr_pages);
 461         pgdat_resize_unlock(zone->zone_pgdat, &flags);
 462         memmap_init_zone(nr_pages, nid, zone_type,
 463                          phys_start_pfn, MEMMAP_HOTPLUG);
 464         return 0;
 465 }
 466
 467 static int __meminit __add_section(int nid, struct zone *zone,
 468                                         unsigned long phys_start_pfn)
 469 {
 470         int ret;
 471
 472         if (pfn_valid(phys_start_pfn))
 473                 return -EEXIST;
 474
 475         ret = sparse_add_one_section(zone, phys_start_pfn);
 476
 477         if (ret < 0)
 478                 return ret;
 479
 480         ret = __add_zone(zone, phys_start_pfn);
 481
 482         if (ret < 0)
 483                 return ret;
 484
 485         return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
 486 }
 487
 488 /*
 489  * Reasonably generic function for adding memory.  It is
 490  * expected that archs that support memory hotplug will
 491  * call this function after deciding the zone to which to
 492  * add the new pages.
 493  */
 494 int __ref __add_pages(int nid, struct zone *zone, unsigned long phys_start_pfn,
 495                         unsigned long nr_pages)
 496 {
 497         unsigned long i;
 498         int err = 0;
 499         int start_sec, end_sec;
 500         /* during initialize mem_map, align hot-added range to section */
 501         start_sec = pfn_to_section_nr(phys_start_pfn);
 502         end_sec = pfn_to_section_nr(phys_start_pfn + nr_pages - 1);
 503
 504         for (i = start_sec; i <= end_sec; i++) {
 505                 err = __add_section(nid, zone, i << PFN_SECTION_SHIFT);
 506
 507                 /*
 508                  * EEXIST is finally dealt with by ioresource collision
 509                  * check. see add_memory() => register_memory_resource()
 510                  * Warning will be printed if there is collision.
 511                  */
 512                 if (err && (err != -EEXIST))
 513                         break;
 514                 err = 0;
 515         }
 516
 517         return err;
 518 }
 519 EXPORT_SYMBOL_GPL(__add_pages);
 520
 521 #ifdef CONFIG_MEMORY_HOTREMOVE
 522 /* find the smallest valid pfn in the range [start_pfn, end_pfn) */
 523 static int find_smallest_section_pfn(int nid, struct zone *zone,
 524                                      unsigned long start_pfn,
 525                                      unsigned long end_pfn)
 526 {
 527         struct mem_section *ms;
 528
 529         for (; start_pfn < end_pfn; start_pfn += PAGES_PER_SECTION) {
 530                 ms = __pfn_to_section(start_pfn);
 531
 532                 if (unlikely(!valid_section(ms)))
 533                         continue;
 534
 535                 if (unlikely(pfn_to_nid(start_pfn) != nid))
 536                         continue;
 537
 538                 if (zone && zone != page_zone(pfn_to_page(start_pfn)))
 539                         continue;
 540
 541                 return start_pfn;
 542         }
 543
 544         return 0;
 545 }
 546
 547 /* find the biggest valid pfn in the range [start_pfn, end_pfn). */
 548 static int find_biggest_section_pfn(int nid, struct zone *zone,
 549                                     unsigned long start_pfn,
 550                                     unsigned long end_pfn)
 551 {
 552         struct mem_section *ms;
 553         unsigned long pfn;
 554
 555         /* pfn is the end pfn of a memory section. */
 556         pfn = end_pfn - 1;
 557         for (; pfn >= start_pfn; pfn -= PAGES_PER_SECTION) {
 558                 ms = __pfn_to_section(pfn);
 559
 560                 if (unlikely(!valid_section(ms)))
 561                         continue;
 562
 563                 if (unlikely(pfn_to_nid(pfn) != nid))
 564                         continue;
 565
 566                 if (zone && zone != page_zone(pfn_to_page(pfn)))
 567                         continue;
 568
 569                 return pfn;
 570         }
 571
 572         return 0;
 573 }
 574
 575 static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
 576                              unsigned long end_pfn)
 577 {
 578         unsigned long zone_start_pfn = zone->zone_start_pfn;
 579         unsigned long z = zone_end_pfn(zone); /* zone_end_pfn namespace clash */
 580         unsigned long zone_end_pfn = z;
 581         unsigned long pfn;
 582         struct mem_section *ms;
 583         int nid = zone_to_nid(zone);
 584
 585         zone_span_writelock(zone);
 586         if (zone_start_pfn == start_pfn) {
 587                 /*
 588                  * If the section is smallest section in the zone, it need
 589                  * shrink zone->zone_start_pfn and zone->zone_spanned_pages.
 590                  * In this case, we find second smallest valid mem_section
 591                  * for shrinking zone.
 592                  */
 593                 pfn = find_smallest_section_pfn(nid, zone, end_pfn,
 594                                                 zone_end_pfn);
 595                 if (pfn) {
 596                         zone->zone_start_pfn = pfn;
 597                         zone->spanned_pages = zone_end_pfn - pfn;
 598                 }
 599         } else if (zone_end_pfn == end_pfn) {
 600                 /*
 601                  * If the section is biggest section in the zone, it need
 602                  * shrink zone->spanned_pages.
 603                  * In this case, we find second biggest valid mem_section for
 604                  * shrinking zone.
 605                  */
 606                 pfn = find_biggest_section_pfn(nid, zone, zone_start_pfn,
 607                                                start_pfn);
 608                 if (pfn)
 609                         zone->spanned_pages = pfn - zone_start_pfn + 1;
 610         }
 611
 612         /*
 613          * The section is not biggest or smallest mem_section in the zone, it
 614          * only creates a hole in the zone. So in this case, we need not
 615          * change the zone. But perhaps, the zone has only hole data. Thus
 616          * it check the zone has only hole or not.
 617          */
 618         pfn = zone_start_pfn;
 619         for (; pfn < zone_end_pfn; pfn += PAGES_PER_SECTION) {
 620                 ms = __pfn_to_section(pfn);
 621
 622                 if (unlikely(!valid_section(ms)))
 623                         continue;
 624
 625                 if (page_zone(pfn_to_page(pfn)) != zone)
 626                         continue;
 627
 628                  /* If the section is current section, it continues the loop */
 629                 if (start_pfn == pfn)
 630                         continue;
 631
 632                 /* If we find valid section, we have nothing to do */
 633                 zone_span_writeunlock(zone);
 634                 return;
 635         }
 636
 637         /* The zone has no valid section */
 638         zone->zone_start_pfn = 0;
 639         zone->spanned_pages = 0;
 640         zone_span_writeunlock(zone);
 641 }
 642
 643 static void shrink_pgdat_span(struct pglist_data *pgdat,
 644                               unsigned long start_pfn, unsigned long end_pfn)
 645 {
 646         unsigned long pgdat_start_pfn = pgdat->node_start_pfn;
 647         unsigned long p = pgdat_end_pfn(pgdat); /* pgdat_end_pfn namespace clash */
 648         unsigned long pgdat_end_pfn = p;
 649         unsigned long pfn;
 650         struct mem_section *ms;
 651         int nid = pgdat->node_id;
 652
 653         if (pgdat_start_pfn == start_pfn) {
 654                 /*
 655                  * If the section is smallest section in the pgdat, it need
 656                  * shrink pgdat->node_start_pfn and pgdat->node_spanned_pages.
 657                  * In this case, we find second smallest valid mem_section
 658                  * for shrinking zone.
 659                  */
 660                 pfn = find_smallest_section_pfn(nid, NULL, end_pfn,
 661                                                 pgdat_end_pfn);
 662                 if (pfn) {
 663                         pgdat->node_start_pfn = pfn;
 664                         pgdat->node_spanned_pages = pgdat_end_pfn - pfn;
 665                 }
 666         } else if (pgdat_end_pfn == end_pfn) {
 667                 /*
 668                  * If the section is biggest section in the pgdat, it need
 669                  * shrink pgdat->node_spanned_pages.
 670                  * In this case, we find second biggest valid mem_section for
 671                  * shrinking zone.
 672                  */
 673                 pfn = find_biggest_section_pfn(nid, NULL, pgdat_start_pfn,
 674                                                start_pfn);
 675                 if (pfn)
 676                         pgdat->node_spanned_pages = pfn - pgdat_start_pfn + 1;
 677         }
 678
 679         /*
 680          * If the section is not biggest or smallest mem_section in the pgdat,
 681          * it only creates a hole in the pgdat. So in this case, we need not
 682          * change the pgdat.
 683          * But perhaps, the pgdat has only hole data. Thus it check the pgdat
 684          * has only hole or not.
 685          */
 686         pfn = pgdat_start_pfn;
 687         for (; pfn < pgdat_end_pfn; pfn += PAGES_PER_SECTION) {
 688                 ms = __pfn_to_section(pfn);
 689
 690                 if (unlikely(!valid_section(ms)))
 691                         continue;
 692
 693                 if (pfn_to_nid(pfn) != nid)
 694                         continue;
 695
 696                  /* If the section is current section, it continues the loop */
 697                 if (start_pfn == pfn)
 698                         continue;
 699
 700                 /* If we find valid section, we have nothing to do */
 701                 return;
 702         }
 703
 704         /* The pgdat has no valid section */
 705         pgdat->node_start_pfn = 0;
 706         pgdat->node_spanned_pages = 0;
 707 }
 708
 709 static void __remove_zone(struct zone *zone, unsigned long start_pfn)
 710 {
 711         struct pglist_data *pgdat = zone->zone_pgdat;
 712         int nr_pages = PAGES_PER_SECTION;
 713         int zone_type;
 714         unsigned long flags;
 715
 716         zone_type = zone - pgdat->node_zones;
 717
 718         pgdat_resize_lock(zone->zone_pgdat, &flags);
 719         shrink_zone_span(zone, start_pfn, start_pfn + nr_pages);
 720         shrink_pgdat_span(pgdat, start_pfn, start_pfn + nr_pages);
 721         pgdat_resize_unlock(zone->zone_pgdat, &flags);
 722 }
 723
 724 static int __remove_section(struct zone *zone, struct mem_section *ms)
 725 {
 726         unsigned long start_pfn;
 727         int scn_nr;
 728         int ret = -EINVAL;
 729
 730         if (!valid_section(ms))
 731                 return ret;
 732
 733         ret = unregister_memory_section(ms);
 734         if (ret)
 735                 return ret;
 736
 737         scn_nr = __section_nr(ms);
 738         start_pfn = section_nr_to_pfn(scn_nr);
 739         __remove_zone(zone, start_pfn);
 740
 741         sparse_remove_one_section(zone, ms);
 742         return 0;
 743 }
 744
 745 /**
 746  * __remove_pages() - remove sections of pages from a zone
 747  * @zone: zone from which pages need to be removed
 748  * @phys_start_pfn: starting pageframe (must be aligned to start of a section)
 749  * @nr_pages: number of pages to remove (must be multiple of section size)
 750  *
 751  * Generic helper function to remove section mappings and sysfs entries
 752  * for the section of the memory we are removing. Caller needs to make
 753  * sure that pages are marked reserved and zones are adjust properly by
 754  * calling offline_pages().
 755  */
 756 int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
 757                  unsigned long nr_pages)
 758 {
 759         unsigned long i;
 760         int sections_to_remove;
 761         resource_size_t start, size;
 762         int ret = 0;
 763
 764         /*
 765          * We can only remove entire sections
 766          */
 767         BUG_ON(phys_start_pfn & ~PAGE_SECTION_MASK);
 768         BUG_ON(nr_pages % PAGES_PER_SECTION);
 769
 770         start = phys_start_pfn << PAGE_SHIFT;
 771         size = nr_pages * PAGE_SIZE;
 772         ret = release_mem_region_adjustable(&iomem_resource, start, size);
 773         if (ret) {
 774                 resource_size_t endres = start + size - 1;
 775
 776                 pr_warn("Unable to release resource <%pa-%pa> (%d)\n",
 777                                 &start, &endres, ret);
 778         }
 779
 780         sections_to_remove = nr_pages / PAGES_PER_SECTION;
 781         for (i = 0; i < sections_to_remove; i++) {
 782                 unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;
 783                 ret = __remove_section(zone, __pfn_to_section(pfn));
 784                 if (ret)
 785                         break;
 786         }
 787         return ret;
 788 }
 789 EXPORT_SYMBOL_GPL(__remove_pages);
 790 #endif /* CONFIG_MEMORY_HOTREMOVE */
 791
 792 int set_online_page_callback(online_page_callback_t callback)
 793 {
 794         int rc = -EINVAL;
 795
 796         get_online_mems();
 797         mutex_lock(&online_page_callback_lock);
 798
 799         if (online_page_callback == generic_online_page) {
 800                 online_page_callback = callback;
 801                 rc = 0;
 802         }
 803
 804         mutex_unlock(&online_page_callback_lock);
 805         put_online_mems();
 806
 807         return rc;
 808 }
 809 EXPORT_SYMBOL_GPL(set_online_page_callback);
 810
 811 int restore_online_page_callback(online_page_callback_t callback)
 812 {
 813         int rc = -EINVAL;
 814
 815         get_online_mems();
 816         mutex_lock(&online_page_callback_lock);
 817
 818         if (online_page_callback == callback) {
 819                 online_page_callback = generic_online_page;
 820                 rc = 0;
 821         }
 822
 823         mutex_unlock(&online_page_callback_lock);
 824         put_online_mems();
 825
 826         return rc;
 827 }
 828 EXPORT_SYMBOL_GPL(restore_online_page_callback);
 829
 830 void __online_page_set_limits(struct page *page)
 831 {
 832 }
 833 EXPORT_SYMBOL_GPL(__online_page_set_limits);
 834
 835 void __online_page_increment_counters(struct page *page)
 836 {
 837         adjust_managed_page_count(page, 1);
 838 }
 839 EXPORT_SYMBOL_GPL(__online_page_increment_counters);
 840
 841 void __online_page_free(struct page *page)
 842 {
 843         __free_reserved_page(page);
 844 }
 845 EXPORT_SYMBOL_GPL(__online_page_free);
 846
 847 static void generic_online_page(struct page *page)
 848 {
 849         __online_page_set_limits(page);
 850         __online_page_increment_counters(page);
 851         __online_page_free(page);
 852 }
 853
 854 static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
 855                         void *arg)
 856 {
 857         unsigned long i;
 858         unsigned long onlined_pages = *(unsigned long *)arg;
 859         struct page *page;
 860         if (PageReserved(pfn_to_page(start_pfn)))
 861                 for (i = 0; i < nr_pages; i++) {
 862                         page = pfn_to_page(start_pfn + i);
 863                         (*online_page_callback)(page);
 864                         onlined_pages++;
 865                 }
 866         *(unsigned long *)arg = onlined_pages;
 867         return 0;
 868 }
 869
 870 #ifdef CONFIG_MOVABLE_NODE
 871 /*
 872  * When CONFIG_MOVABLE_NODE, we permit onlining of a node which doesn't have
 873  * normal memory.
 874  */
 875 static bool can_online_high_movable(struct zone *zone)
 876 {
 877         return true;
 878 }
 879 #else /* CONFIG_MOVABLE_NODE */
 880 /* ensure every online node has NORMAL memory */
 881 static bool can_online_high_movable(struct zone *zone)
 882 {
 883         return node_state(zone_to_nid(zone), N_NORMAL_MEMORY);
 884 }
 885 #endif /* CONFIG_MOVABLE_NODE */
 886
 887 /* check which state of node_states will be changed when online memory */
 888 static void node_states_check_changes_online(unsigned long nr_pages,
 889         struct zone *zone, struct memory_notify *arg)
 890 {
 891         int nid = zone_to_nid(zone);
 892         enum zone_type zone_last = ZONE_NORMAL;
 893
 894         /*
 895          * If we have HIGHMEM or movable node, node_states[N_NORMAL_MEMORY]
 896          * contains nodes which have zones of 0...ZONE_NORMAL,
 897          * set zone_last to ZONE_NORMAL.
 898          *
 899          * If we don't have HIGHMEM nor movable node,
 900          * node_states[N_NORMAL_MEMORY] contains nodes which have zones of
 901          * 0...ZONE_MOVABLE, set zone_last to ZONE_MOVABLE.
 902          */
 903         if (N_MEMORY == N_NORMAL_MEMORY)
 904                 zone_last = ZONE_MOVABLE;
 905
 906         /*
 907          * if the memory to be online is in a zone of 0...zone_last, and
 908          * the zones of 0...zone_last don't have memory before online, we will
 909          * need to set the node to node_states[N_NORMAL_MEMORY] after
 910          * the memory is online.
 911          */
 912         if (zone_idx(zone) <= zone_last && !node_state(nid, N_NORMAL_MEMORY))
 913                 arg->status_change_nid_normal = nid;
 914         else
 915                 arg->status_change_nid_normal = -1;
 916
 917 #ifdef CONFIG_HIGHMEM
 918         /*
 919          * If we have movable node, node_states[N_HIGH_MEMORY]
 920          * contains nodes which have zones of 0...ZONE_HIGHMEM,
 921          * set zone_last to ZONE_HIGHMEM.
 922          *
 923          * If we don't have movable node, node_states[N_NORMAL_MEMORY]
 924          * contains nodes which have zones of 0...ZONE_MOVABLE,
 925          * set zone_last to ZONE_MOVABLE.
 926          */
 927         zone_last = ZONE_HIGHMEM;
 928         if (N_MEMORY == N_HIGH_MEMORY)
 929                 zone_last = ZONE_MOVABLE;
 930
 931         if (zone_idx(zone) <= zone_last && !node_state(nid, N_HIGH_MEMORY))
 932                 arg->status_change_nid_high = nid;
 933         else
 934                 arg->status_change_nid_high = -1;
 935 #else
 936         arg->status_change_nid_high = arg->status_change_nid_normal;
 937 #endif
 938
 939         /*
 940          * if the node don't have memory befor online, we will need to
 941          * set the node to node_states[N_MEMORY] after the memory
 942          * is online.
 943          */
 944         if (!node_state(nid, N_MEMORY))
 945                 arg->status_change_nid = nid;
 946         else
 947                 arg->status_change_nid = -1;
 948 }
 949
 950 static void node_states_set_node(int node, struct memory_notify *arg)
 951 {
 952         if (arg->status_change_nid_normal >= 0)
 953                 node_set_state(node, N_NORMAL_MEMORY);
 954
 955         if (arg->status_change_nid_high >= 0)
 956                 node_set_state(node, N_HIGH_MEMORY);
 957
 958         node_set_state(node, N_MEMORY);
 959 }
 960
 961
 962 int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_type)
 963 {
 964         unsigned long flags;
 965         unsigned long onlined_pages = 0;
 966         struct zone *zone;
 967         int need_zonelists_rebuild = 0;
 968         int nid;
 969         int ret;
 970         struct memory_notify arg;
 971
 972         mem_hotplug_begin();
 973         /*
 974          * This doesn't need a lock to do pfn_to_page().
 975          * The section can't be removed here because of the
 976          * memory_block->state_mutex.
 977          */
 978         zone = page_zone(pfn_to_page(pfn));
 979
 980         ret = -EINVAL;
 981         if ((zone_idx(zone) > ZONE_NORMAL || online_type == ONLINE_MOVABLE) &&
 982             !can_online_high_movable(zone))
 983                 goto out;
 984
 985         if (online_type == ONLINE_KERNEL && zone_idx(zone) == ZONE_MOVABLE) {
 986                 if (move_pfn_range_left(zone - 1, zone, pfn, pfn + nr_pages))
 987                         goto out;
 988         }
 989         if (online_type == ONLINE_MOVABLE && zone_idx(zone) == ZONE_MOVABLE - 1) {
 990                 if (move_pfn_range_right(zone, zone + 1, pfn, pfn + nr_pages))
 991                         goto out;
 992         }
 993
 994         /* Previous code may changed the zone of the pfn range */
 995         zone = page_zone(pfn_to_page(pfn));
 996
 997         arg.start_pfn = pfn;
 998         arg.nr_pages = nr_pages;
 999         node_states_check_changes_online(nr_pages, zone, &arg);
1000
1001         nid = pfn_to_nid(pfn);
1002
1003         ret = memory_notify(MEM_GOING_ONLINE, &arg);
1004         ret = notifier_to_errno(ret);
1005         if (ret) {
1006                 memory_notify(MEM_CANCEL_ONLINE, &arg);
1007                 goto out;
1008         }
1009         /*
1010          * If this zone is not populated, then it is not in zonelist.
1011          * This means the page allocator ignores this zone.
1012          * So, zonelist must be updated after online.
1013          */
1014         mutex_lock(&zonelists_mutex);
1015         if (!populated_zone(zone)) {
1016                 need_zonelists_rebuild = 1;
1017                 build_all_zonelists(NULL, zone);
1018         }
1019
1020         ret = walk_system_ram_range(pfn, nr_pages, &onlined_pages,
1021                 online_pages_range);
1022         if (ret) {
1023                 if (need_zonelists_rebuild)
1024                         zone_pcp_reset(zone);
1025                 mutex_unlock(&zonelists_mutex);
1026                 printk(KERN_DEBUG "online_pages [mem %#010llx-%#010llx] failed\n",
1027                        (unsigned long long) pfn << PAGE_SHIFT,
1028                        (((unsigned long long) pfn + nr_pages)
1029                             << PAGE_SHIFT) - 1);
1030                 memory_notify(MEM_CANCEL_ONLINE, &arg);
1031                 goto out;
1032         }
1033
1034         zone->present_pages += onlined_pages;
1035
1036         pgdat_resize_lock(zone->zone_pgdat, &flags);
1037         zone->zone_pgdat->node_present_pages += onlined_pages;
1038         pgdat_resize_unlock(zone->zone_pgdat, &flags);
1039
1040         if (onlined_pages) {
1041                 node_states_set_node(zone_to_nid(zone), &arg);
1042                 if (need_zonelists_rebuild)
1043                         build_all_zonelists(NULL, NULL);
1044                 else
1045                         zone_pcp_update(zone);
1046         }
1047
1048         mutex_unlock(&zonelists_mutex);
1049
1050         init_per_zone_wmark_min();
1051
1052         if (onlined_pages)
1053                 kswapd_run(zone_to_nid(zone));
1054
1055         vm_total_pages = nr_free_pagecache_pages();
1056
1057         writeback_set_ratelimit();
1058
1059         if (onlined_pages)
1060                 memory_notify(MEM_ONLINE, &arg);
1061 out:
1062         mem_hotplug_done();
1063         return ret;
1064 }
1065 #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
1066
1067 static void reset_node_present_pages(pg_data_t *pgdat)
1068 {
1069         struct zone *z;
1070
1071         for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
1072                 z->present_pages = 0;
1073
1074         pgdat->node_present_pages = 0;
1075 }
1076
1077 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
1078 static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
1079 {
1080         struct pglist_data *pgdat;
1081         unsigned long zones_size[MAX_NR_ZONES] = {0};
1082         unsigned long zholes_size[MAX_NR_ZONES] = {0};
1083         unsigned long start_pfn = PFN_DOWN(start);
1084
1085         pgdat = NODE_DATA(nid);
1086         if (!pgdat) {
1087                 pgdat = arch_alloc_nodedata(nid);
1088                 if (!pgdat)
1089                         return NULL;
1090
1091                 arch_refresh_nodedata(nid, pgdat);
1092         } else {
1093                 /* Reset the nr_zones and classzone_idx to 0 before reuse */
1094                 pgdat->nr_zones = 0;
1095                 pgdat->classzone_idx = 0;
1096         }
1097
1098         /* we can use NODE_DATA(nid) from here */
1099
1100         /* init node's zones as empty zones, we don't have any present pages.*/
1101         free_area_init_node(nid, zones_size, start_pfn, zholes_size);
1102
1103         /*
1104          * The node we allocated has no zone fallback lists. For avoiding
1105          * to access not-initialized zonelist, build here.
1106          */
1107         mutex_lock(&zonelists_mutex);
1108         build_all_zonelists(pgdat, NULL);
1109         mutex_unlock(&zonelists_mutex);
1110
1111         /*
1112          * zone->managed_pages is set to an approximate value in
1113          * free_area_init_core(), which will cause
1114          * /sys/device/system/node/nodeX/meminfo has wrong data.
1115          * So reset it to 0 before any memory is onlined.
1116          */
1117         reset_node_managed_pages(pgdat);
1118
1119         /*
1120          * When memory is hot-added, all the memory is in offline state. So
1121          * clear all zones' present_pages because they will be updated in
1122          * online_pages() and offline_pages().
1123          */
1124         reset_node_present_pages(pgdat);
1125
1126         return pgdat;
1127 }
1128
1129 static void rollback_node_hotadd(int nid, pg_data_t *pgdat)
1130 {
1131         arch_refresh_nodedata(nid, NULL);
1132         arch_free_nodedata(pgdat);
1133         return;
1134 }
1135
1136
1137 /**
1138  * try_online_node - online a node if offlined
1139  *
1140  * called by cpu_up() to online a node without onlined memory.
1141  */
1142 int try_online_node(int nid)
1143 {
1144         pg_data_t       *pgdat;
1145         int     ret;
1146
1147         if (node_online(nid))
1148                 return 0;
1149
1150         mem_hotplug_begin();
1151         pgdat = hotadd_new_pgdat(nid, 0);
1152         if (!pgdat) {
1153                 pr_err("Cannot online node %d due to NULL pgdat\n", nid);
1154                 ret = -ENOMEM;
1155                 goto out;
1156         }
1157         node_set_online(nid);
1158         ret = register_one_node(nid);
1159         BUG_ON(ret);
1160
1161         if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
1162                 mutex_lock(&zonelists_mutex);
1163                 build_all_zonelists(NULL, NULL);
1164                 mutex_unlock(&zonelists_mutex);
1165         }
1166
1167 out:
1168         mem_hotplug_done();
1169         return ret;
1170 }
1171
1172 static int check_hotplug_memory_range(u64 start, u64 size)
1173 {
1174         u64 start_pfn = PFN_DOWN(start);
1175         u64 nr_pages = size >> PAGE_SHIFT;
1176
1177         /* Memory range must be aligned with section */
1178         if ((start_pfn & ~PAGE_SECTION_MASK) ||
1179             (nr_pages % PAGES_PER_SECTION) || (!nr_pages)) {
1180                 pr_err("Section-unaligned hotplug range: start 0x%llx, size 0x%llx\n",
1181                                 (unsigned long long)start,
1182                                 (unsigned long long)size);
1183                 return -EINVAL;
1184         }
1185
1186         return 0;
1187 }
1188
1189 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
1190 int __ref add_memory(int nid, u64 start, u64 size)
1191 {
1192         pg_data_t *pgdat = NULL;
1193         bool new_pgdat;
1194         bool new_node;
1195         struct resource *res;
1196         int ret;
1197
1198         ret = check_hotplug_memory_range(start, size);
1199         if (ret)
1200                 return ret;
1201
1202         res = register_memory_resource(start, size);
1203         ret = -EEXIST;
1204         if (!res)
1205                 return ret;
1206
1207         {       /* Stupid hack to suppress address-never-null warning */
1208                 void *p = NODE_DATA(nid);
1209                 new_pgdat = !p;
1210         }
1211
1212         mem_hotplug_begin();
1213
1214         new_node = !node_online(nid);
1215         if (new_node) {
1216                 pgdat = hotadd_new_pgdat(nid, start);
1217                 ret = -ENOMEM;
1218                 if (!pgdat)
1219                         goto error;
1220         }
1221
1222         /* call arch's memory hotadd */
1223         ret = arch_add_memory(nid, start, size);
1224
1225         if (ret < 0)
1226                 goto error;
1227
1228         /* we online node here. we can't roll back from here. */
1229         node_set_online(nid);
1230
1231         if (new_node) {
1232                 ret = register_one_node(nid);
1233                 /*
1234                  * If sysfs file of new node can't create, cpu on the node
1235                  * can't be hot-added. There is no rollback way now.
1236                  * So, check by BUG_ON() to catch it reluctantly..
1237                  */
1238                 BUG_ON(ret);
1239         }
1240
1241         /* create new memmap entry */
1242         firmware_map_add_hotplug(start, start + size, "System RAM");
1243
1244         goto out;
1245
1246 error:
1247         /* rollback pgdat allocation and others */
1248         if (new_pgdat)
1249                 rollback_node_hotadd(nid, pgdat);
1250         release_memory_resource(res);
1251
1252 out:
1253         mem_hotplug_done();
1254         return ret;
1255 }
1256 EXPORT_SYMBOL_GPL(add_memory);
1257
1258 #ifdef CONFIG_MEMORY_HOTREMOVE
1259 /*
1260  * A free page on the buddy free lists (not the per-cpu lists) has PageBuddy
1261  * set and the size of the free page is given by page_order(). Using this,
1262  * the function determines if the pageblock contains only free pages.
1263  * Due to buddy contraints, a free page at least the size of a pageblock will
1264  * be located at the start of the pageblock
1265  */
1266 static inline int pageblock_free(struct page *page)
1267 {
1268         return PageBuddy(page) && page_order(page) >= pageblock_order;
1269 }
1270
1271 /* Return the start of the next active pageblock after a given page */
1272 static struct page *next_active_pageblock(struct page *page)
1273 {
1274         /* Ensure the starting page is pageblock-aligned */
1275         BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1));
1276
1277         /* If the entire pageblock is free, move to the end of free page */
1278         if (pageblock_free(page)) {
1279                 int order;
1280                 /* be careful. we don't have locks, page_order can be changed.*/
1281                 order = page_order(page);
1282                 if ((order < MAX_ORDER) && (order >= pageblock_order))
1283                         return page + (1 << order);
1284         }
1285
1286         return page + pageblock_nr_pages;
1287 }
1288
1289 /* Checks if this range of memory is likely to be hot-removable. */
1290 int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
1291 {
1292         struct page *page = pfn_to_page(start_pfn);
1293         struct page *end_page = page + nr_pages;
1294
1295         /* Check the starting page of each pageblock within the range */
1296         for (; page < end_page; page = next_active_pageblock(page)) {
1297                 if (!is_pageblock_removable_nolock(page))
1298                         return 0;
1299                 cond_resched();
1300         }
1301
1302         /* All pageblocks in the memory block are likely to be hot-removable */
1303         return 1;
1304 }
1305
1306 /*
1307  * Confirm all pages in a range [start, end) is belongs to the same zone.
1308  */
1309 static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
1310 {
1311         unsigned long pfn, sec_end_pfn;
1312         struct zone *zone = NULL;
1313         struct page *page;
1314         int i;
1315         for (pfn = start_pfn, sec_end_pfn = SECTION_ALIGN_UP(start_pfn);
1316              pfn < end_pfn;
1317              pfn = sec_end_pfn + 1, sec_end_pfn += PAGES_PER_SECTION) {
1318                 /* Make sure the memory section is present first */
1319                 if (!present_section_nr(pfn_to_section_nr(pfn)))
1320                         continue;
1321                 for (; pfn < sec_end_pfn && pfn < end_pfn;
1322                      pfn += MAX_ORDER_NR_PAGES) {
1323                         i = 0;
1324                         /* This is just a CONFIG_HOLES_IN_ZONE check.*/
1325                         while ((i < MAX_ORDER_NR_PAGES) &&
1326                                 !pfn_valid_within(pfn + i))
1327                                 i++;
1328                         if (i == MAX_ORDER_NR_PAGES)
1329                                 continue;
1330                         page = pfn_to_page(pfn + i);
1331                         if (zone && page_zone(page) != zone)
1332                                 return 0;
1333                         zone = page_zone(page);
1334                 }
1335         }
1336         return 1;
1337 }
1338
1339 /*
1340  * Scan pfn range [start,end) to find movable/migratable pages (LRU pages
1341  * and hugepages). We scan pfn because it's much easier than scanning over
1342  * linked list. This function returns the pfn of the first found movable
1343  * page if it's found, otherwise 0.
1344  */
1345 static unsigned long scan_movable_pages(unsigned long start, unsigned long end)
1346 {
1347         unsigned long pfn;
1348         struct page *page;
1349         for (pfn = start; pfn < end; pfn++) {
1350                 if (pfn_valid(pfn)) {
1351                         page = pfn_to_page(pfn);
1352                         if (PageLRU(page))
1353                                 return pfn;
1354                         if (PageHuge(page)) {
1355                                 if (is_hugepage_active(page))
1356                                         return pfn;
1357                                 else
1358                                         pfn = round_up(pfn + 1,
1359                                                 1 << compound_order(page)) - 1;
1360                         }
1361                 }
1362         }
1363         return 0;
1364 }
1365
1366 #define NR_OFFLINE_AT_ONCE_PAGES        (256)
1367 static int
1368 do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
1369 {
1370         unsigned long pfn;
1371         struct page *page;
1372         int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
1373         int not_managed = 0;
1374         int ret = 0;
1375         LIST_HEAD(source);
1376
1377         for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) {
1378                 if (!pfn_valid(pfn))
1379                         continue;
1380                 page = pfn_to_page(pfn);
1381
1382                 if (PageHuge(page)) {
1383                         struct page *head = compound_head(page);
1384                         pfn = page_to_pfn(head) + (1<<compound_order(head)) - 1;
1385                         if (compound_order(head) > PFN_SECTION_SHIFT) {
1386                                 ret = -EBUSY;
1387                                 break;
1388                         }
1389                         if (isolate_huge_page(page, &source))
1390                                 move_pages -= 1 << compound_order(head);
1391                         continue;
1392                 }
1393
1394                 if (!get_page_unless_zero(page))
1395                         continue;
1396                 /*
1397                  * We can skip free pages. And we can only deal with pages on
1398                  * LRU.
1399                  */
1400                 ret = isolate_lru_page(page);
1401                 if (!ret) { /* Success */
1402                         put_page(page);
1403                         list_add_tail(&page->lru, &source);
1404                         move_pages--;
1405                         inc_zone_page_state(page, NR_ISOLATED_ANON +
1406                                             page_is_file_cache(page));
1407
1408                 } else {
1409 #ifdef CONFIG_DEBUG_VM
1410                         printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
1411                                pfn);
1412                         dump_page(page, "failed to remove from LRU");
1413 #endif
1414                         put_page(page);
1415                         /* Because we don't have big zone->lock. we should
1416                            check this again here. */
1417                         if (page_count(page)) {
1418                                 not_managed++;
1419                                 ret = -EBUSY;
1420                                 break;
1421                         }
1422                 }
1423         }
1424         if (!list_empty(&source)) {
1425                 if (not_managed) {
1426                         putback_movable_pages(&source);
1427                         goto out;
1428                 }
1429
1430                 /*
1431                  * alloc_migrate_target should be improooooved!!
1432                  * migrate_pages returns # of failed pages.
1433                  */
1434                 ret = migrate_pages(&source, alloc_migrate_target, NULL, 0,
1435                                         MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
1436                 if (ret)
1437                         putback_movable_pages(&source);
1438         }
1439 out:
1440         return ret;
1441 }
1442
1443 /*
1444  * remove from free_area[] and mark all as Reserved.
1445  */
1446 static int
1447 offline_isolated_pages_cb(unsigned long start, unsigned long nr_pages,
1448                         void *data)
1449 {
1450         __offline_isolated_pages(start, start + nr_pages);
1451         return 0;
1452 }
1453
1454 static void
1455 offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
1456 {
1457         walk_system_ram_range(start_pfn, end_pfn - start_pfn, NULL,
1458                                 offline_isolated_pages_cb);
1459 }
1460
1461 /*
1462  * Check all pages in range, recoreded as memory resource, are isolated.
1463  */
1464 static int
1465 check_pages_isolated_cb(unsigned long start_pfn, unsigned long nr_pages,
1466                         void *data)
1467 {
1468         int ret;
1469         long offlined = *(long *)data;
1470         ret = test_pages_isolated(start_pfn, start_pfn + nr_pages, true);
1471         offlined = nr_pages;
1472         if (!ret)
1473                 *(long *)data += offlined;
1474         return ret;
1475 }
1476
1477 static long
1478 check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
1479 {
1480         long offlined = 0;
1481         int ret;
1482
1483         ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn, &offlined,
1484                         check_pages_isolated_cb);
1485         if (ret < 0)
1486                 offlined = (long)ret;
1487         return offlined;
1488 }
1489
1490 #ifdef CONFIG_MOVABLE_NODE
1491 /*
1492  * When CONFIG_MOVABLE_NODE, we permit offlining of a node which doesn't have
1493  * normal memory.
1494  */
1495 static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
1496 {
1497         return true;
1498 }
1499 #else /* CONFIG_MOVABLE_NODE */
1500 /* ensure the node has NORMAL memory if it is still online */
1501 static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
1502 {
1503         struct pglist_data *pgdat = zone->zone_pgdat;
1504         unsigned long present_pages = 0;
1505         enum zone_type zt;
1506
1507         for (zt = 0; zt <= ZONE_NORMAL; zt++)
1508                 present_pages += pgdat->node_zones[zt].present_pages;
1509
1510         if (present_pages > nr_pages)
1511                 return true;
1512
1513         present_pages = 0;
1514         for (; zt <= ZONE_MOVABLE; zt++)
1515                 present_pages += pgdat->node_zones[zt].present_pages;
1516
1517         /*
1518          * we can't offline the last normal memory until all
1519          * higher memory is offlined.
1520          */
1521         return present_pages == 0;
1522 }
1523 #endif /* CONFIG_MOVABLE_NODE */
1524
1525 static int __init cmdline_parse_movable_node(char *p)
1526 {
1527 #ifdef CONFIG_MOVABLE_NODE
1528         /*
1529          * Memory used by the kernel cannot be hot-removed because Linux
1530          * cannot migrate the kernel pages. When memory hotplug is
1531          * enabled, we should prevent memblock from allocating memory
1532          * for the kernel.
1533          *
1534          * ACPI SRAT records all hotpluggable memory ranges. But before
1535          * SRAT is parsed, we don't know about it.
1536          *
1537          * The kernel image is loaded into memory at very early time. We
1538          * cannot prevent this anyway. So on NUMA system, we set any
1539          * node the kernel resides in as un-hotpluggable.
1540          *
1541          * Since on modern servers, one node could have double-digit
1542          * gigabytes memory, we can assume the memory around the kernel
1543          * image is also un-hotpluggable. So before SRAT is parsed, just
1544          * allocate memory near the kernel image to try the best to keep
1545          * the kernel away from hotpluggable memory.
1546          */
1547         memblock_set_bottom_up(true);
1548         movable_node_enabled = true;
1549 #else
1550         pr_warn("movable_node option not supported\n");
1551 #endif
1552         return 0;
1553 }
1554 early_param("movable_node", cmdline_parse_movable_node);
1555
1556 /* check which state of node_states will be changed when offline memory */
1557 static void node_states_check_changes_offline(unsigned long nr_pages,
1558                 struct zone *zone, struct memory_notify *arg)
1559 {
1560         struct pglist_data *pgdat = zone->zone_pgdat;
1561         unsigned long present_pages = 0;
1562         enum zone_type zt, zone_last = ZONE_NORMAL;
1563
1564         /*
1565          * If we have HIGHMEM or movable node, node_states[N_NORMAL_MEMORY]
1566          * contains nodes which have zones of 0...ZONE_NORMAL,
1567          * set zone_last to ZONE_NORMAL.
1568          *
1569          * If we don't have HIGHMEM nor movable node,
1570          * node_states[N_NORMAL_MEMORY] contains nodes which have zones of
1571          * 0...ZONE_MOVABLE, set zone_last to ZONE_MOVABLE.
1572          */
1573         if (N_MEMORY == N_NORMAL_MEMORY)
1574                 zone_last = ZONE_MOVABLE;
1575
1576         /*
1577          * check whether node_states[N_NORMAL_MEMORY] will be changed.
1578          * If the memory to be offline is in a zone of 0...zone_last,
1579          * and it is the last present memory, 0...zone_last will
1580          * become empty after offline , thus we can determind we will
1581          * need to clear the node from node_states[N_NORMAL_MEMORY].
1582          */
1583         for (zt = 0; zt <= zone_last; zt++)
1584                 present_pages += pgdat->node_zones[zt].present_pages;
1585         if (zone_idx(zone) <= zone_last && nr_pages >= present_pages)
1586                 arg->status_change_nid_normal = zone_to_nid(zone);
1587         else
1588                 arg->status_change_nid_normal = -1;
1589
1590 #ifdef CONFIG_HIGHMEM
1591         /*
1592          * If we have movable node, node_states[N_HIGH_MEMORY]
1593          * contains nodes which have zones of 0...ZONE_HIGHMEM,
1594          * set zone_last to ZONE_HIGHMEM.
1595          *
1596          * If we don't have movable node, node_states[N_NORMAL_MEMORY]
1597          * contains nodes which have zones of 0...ZONE_MOVABLE,
1598          * set zone_last to ZONE_MOVABLE.
1599          */
1600         zone_last = ZONE_HIGHMEM;
1601         if (N_MEMORY == N_HIGH_MEMORY)
1602                 zone_last = ZONE_MOVABLE;
1603
1604         for (; zt <= zone_last; zt++)
1605                 present_pages += pgdat->node_zones[zt].present_pages;
1606         if (zone_idx(zone) <= zone_last && nr_pages >= present_pages)
1607                 arg->status_change_nid_high = zone_to_nid(zone);
1608         else
1609                 arg->status_change_nid_high = -1;
1610 #else
1611         arg->status_change_nid_high = arg->status_change_nid_normal;
1612 #endif
1613
1614         /*
1615          * node_states[N_HIGH_MEMORY] contains nodes which have 0...ZONE_MOVABLE
1616          */
1617         zone_last = ZONE_MOVABLE;
1618
1619         /*
1620          * check whether node_states[N_HIGH_MEMORY] will be changed
1621          * If we try to offline the last present @nr_pages from the node,
1622          * we can determind we will need to clear the node from
1623          * node_states[N_HIGH_MEMORY].
1624          */
1625         for (; zt <= zone_last; zt++)
1626                 present_pages += pgdat->node_zones[zt].present_pages;
1627         if (nr_pages >= present_pages)
1628                 arg->status_change_nid = zone_to_nid(zone);
1629         else
1630                 arg->status_change_nid = -1;
1631 }
1632
1633 static void node_states_clear_node(int node, struct memory_notify *arg)
1634 {
1635         if (arg->status_change_nid_normal >= 0)
1636                 node_clear_state(node, N_NORMAL_MEMORY);
1637
1638         if ((N_MEMORY != N_NORMAL_MEMORY) &&
1639             (arg->status_change_nid_high >= 0))
1640                 node_clear_state(node, N_HIGH_MEMORY);
1641
1642         if ((N_MEMORY != N_HIGH_MEMORY) &&
1643             (arg->status_change_nid >= 0))
1644                 node_clear_state(node, N_MEMORY);
1645 }
1646
1647 static int __ref __offline_pages(unsigned long start_pfn,
1648                   unsigned long end_pfn, unsigned long timeout)
1649 {
1650         unsigned long pfn, nr_pages, expire;
1651         long offlined_pages;
1652         int ret, drain, retry_max, node;
1653         unsigned long flags;
1654         struct zone *zone;
1655         struct memory_notify arg;
1656
1657         /* at least, alignment against pageblock is necessary */
1658         if (!IS_ALIGNED(start_pfn, pageblock_nr_pages))
1659                 return -EINVAL;
1660         if (!IS_ALIGNED(end_pfn, pageblock_nr_pages))
1661                 return -EINVAL;
1662         /* This makes hotplug much easier...and readable.
1663            we assume this for now. .*/
1664         if (!test_pages_in_a_zone(start_pfn, end_pfn))
1665                 return -EINVAL;
1666
1667         mem_hotplug_begin();
1668
1669         zone = page_zone(pfn_to_page(start_pfn));
1670         node = zone_to_nid(zone);
1671         nr_pages = end_pfn - start_pfn;
1672
1673         ret = -EINVAL;
1674         if (zone_idx(zone) <= ZONE_NORMAL && !can_offline_normal(zone, nr_pages))
1675                 goto out;
1676
1677         /* set above range as isolated */
1678         ret = start_isolate_page_range(start_pfn, end_pfn,
1679                                        MIGRATE_MOVABLE, true);
1680         if (ret)
1681                 goto out;
1682
1683         arg.start_pfn = start_pfn;
1684         arg.nr_pages = nr_pages;
1685         node_states_check_changes_offline(nr_pages, zone, &arg);
1686
1687         ret = memory_notify(MEM_GOING_OFFLINE, &arg);
1688         ret = notifier_to_errno(ret);
1689         if (ret)
1690                 goto failed_removal;
1691
1692         pfn = start_pfn;
1693         expire = jiffies + timeout;
1694         drain = 0;
1695         retry_max = 5;
1696 repeat:
1697         /* start memory hot removal */
1698         ret = -EAGAIN;
1699         if (time_after(jiffies, expire))
1700                 goto failed_removal;
1701         ret = -EINTR;
1702         if (signal_pending(current))
1703                 goto failed_removal;
1704         ret = 0;
1705         if (drain) {
1706                 lru_add_drain_all();
1707                 cond_resched();
1708                 drain_all_pages();
1709         }
1710
1711         pfn = scan_movable_pages(start_pfn, end_pfn);
1712         if (pfn) { /* We have movable pages */
1713                 ret = do_migrate_range(pfn, end_pfn);
1714                 if (!ret) {
1715                         drain = 1;
1716                         goto repeat;
1717                 } else {
1718                         if (ret < 0)
1719                                 if (--retry_max == 0)
1720                                         goto failed_removal;
1721                         yield();
1722                         drain = 1;
1723                         goto repeat;
1724                 }
1725         }
1726         /* drain all zone's lru pagevec, this is asynchronous... */
1727         lru_add_drain_all();
1728         yield();
1729         /* drain pcp pages, this is synchronous. */
1730         drain_all_pages();
1731         /*
1732          * dissolve free hugepages in the memory block before doing offlining
1733          * actually in order to make hugetlbfs's object counting consistent.
1734          */
1735         dissolve_free_huge_pages(start_pfn, end_pfn);
1736         /* check again */
1737         offlined_pages = check_pages_isolated(start_pfn, end_pfn);
1738         if (offlined_pages < 0) {
1739                 ret = -EBUSY;
1740                 goto failed_removal;
1741         }
1742         printk(KERN_INFO "Offlined Pages %ld\n", offlined_pages);
1743         /* Ok, all of our target is isolated.
1744            We cannot do rollback at this point. */
1745         offline_isolated_pages(start_pfn, end_pfn);
1746         /* reset pagetype flags and makes migrate type to be MOVABLE */
1747         undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE);
1748         /* removal success */
1749         adjust_managed_page_count(pfn_to_page(start_pfn), -offlined_pages);
1750         zone->present_pages -= offlined_pages;
1751
1752         pgdat_resize_lock(zone->zone_pgdat, &flags);
1753         zone->zone_pgdat->node_present_pages -= offlined_pages;
1754         pgdat_resize_unlock(zone->zone_pgdat, &flags);
1755
1756         init_per_zone_wmark_min();
1757
1758         if (!populated_zone(zone)) {
1759                 zone_pcp_reset(zone);
1760                 mutex_lock(&zonelists_mutex);
1761                 build_all_zonelists(NULL, NULL);
1762                 mutex_unlock(&zonelists_mutex);
1763         } else
1764                 zone_pcp_update(zone);
1765
1766         node_states_clear_node(node, &arg);
1767         if (arg.status_change_nid >= 0)
1768                 kswapd_stop(node);
1769
1770         vm_total_pages = nr_free_pagecache_pages();
1771         writeback_set_ratelimit();
1772
1773         memory_notify(MEM_OFFLINE, &arg);
1774         mem_hotplug_done();
1775         return 0;
1776
1777 failed_removal:
1778         printk(KERN_INFO "memory offlining [mem %#010llx-%#010llx] failed\n",
1779                (unsigned long long) start_pfn << PAGE_SHIFT,
1780                ((unsigned long long) end_pfn << PAGE_SHIFT) - 1);
1781         memory_notify(MEM_CANCEL_OFFLINE, &arg);
1782         /* pushback to free area */
1783         undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE);
1784
1785 out:
1786         mem_hotplug_done();
1787         return ret;
1788 }
1789
1790 int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
1791 {
1792         return __offline_pages(start_pfn, start_pfn + nr_pages, 120 * HZ);
1793 }
1794 #endif /* CONFIG_MEMORY_HOTREMOVE */
1795
1796 /**
1797  * walk_memory_range - walks through all mem sections in [start_pfn, end_pfn)
1798  * @start_pfn: start pfn of the memory range
1799  * @end_pfn: end pfn of the memory range
1800  * @arg: argument passed to func
1801  * @func: callback for each memory section walked
1802  *
1803  * This function walks through all present mem sections in range
1804  * [start_pfn, end_pfn) and call func on each mem section.
1805  *
1806  * Returns the return value of func.
1807  */
1808 int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,
1809                 void *arg, int (*func)(struct memory_block *, void *))
1810 {
1811         struct memory_block *mem = NULL;
1812         struct mem_section *section;
1813         unsigned long pfn, section_nr;
1814         int ret;
1815
1816         for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
1817                 section_nr = pfn_to_section_nr(pfn);
1818                 if (!present_section_nr(section_nr))
1819                         continue;
1820
1821                 section = __nr_to_section(section_nr);
1822                 /* same memblock? */
1823                 if (mem)
1824                         if ((section_nr >= mem->start_section_nr) &&
1825                             (section_nr <= mem->end_section_nr))
1826                                 continue;
1827
1828                 mem = find_memory_block_hinted(section, mem);
1829                 if (!mem)
1830                         continue;
1831
1832                 ret = func(mem, arg);
1833                 if (ret) {
1834                         kobject_put(&mem->dev.kobj);
1835                         return ret;
1836                 }
1837         }
1838
1839         if (mem)
1840                 kobject_put(&mem->dev.kobj);
1841
1842         return 0;
1843 }
1844
1845 #ifdef CONFIG_MEMORY_HOTREMOVE
1846 static int check_memblock_offlined_cb(struct memory_block *mem, void *arg)
1847 {
1848         int ret = !is_memblock_offlined(mem);
1849
1850         if (unlikely(ret)) {
1851                 phys_addr_t beginpa, endpa;
1852
1853                 beginpa = PFN_PHYS(section_nr_to_pfn(mem->start_section_nr));
1854                 endpa = PFN_PHYS(section_nr_to_pfn(mem->end_section_nr + 1))-1;
1855                 pr_warn("removing memory fails, because memory "
1856                         "[%pa-%pa] is onlined\n",
1857                         &beginpa, &endpa);
1858         }
1859
1860         return ret;
1861 }
1862
1863 static int check_cpu_on_node(pg_data_t *pgdat)
1864 {
1865         int cpu;
1866
1867         for_each_present_cpu(cpu) {
1868                 if (cpu_to_node(cpu) == pgdat->node_id)
1869                         /*
1870                          * the cpu on this node isn't removed, and we can't
1871                          * offline this node.
1872                          */
1873                         return -EBUSY;
1874         }
1875
1876         return 0;
1877 }
1878
1879 static void unmap_cpu_on_node(pg_data_t *pgdat)
1880 {
1881 #ifdef CONFIG_ACPI_NUMA
1882         int cpu;
1883
1884         for_each_possible_cpu(cpu)
1885                 if (cpu_to_node(cpu) == pgdat->node_id)
1886                         numa_clear_node(cpu);
1887 #endif
1888 }
1889
1890 static int check_and_unmap_cpu_on_node(pg_data_t *pgdat)
1891 {
1892         int ret;
1893
1894         ret = check_cpu_on_node(pgdat);
1895         if (ret)
1896                 return ret;
1897
1898         /*
1899          * the node will be offlined when we come here, so we can clear
1900          * the cpu_to_node() now.
1901          */
1902
1903         unmap_cpu_on_node(pgdat);
1904         return 0;
1905 }
1906
1907 /**
1908  * try_offline_node
1909  *
1910  * Offline a node if all memory sections and cpus of the node are removed.
1911  *
1912  * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
1913  * and online/offline operations before this call.
1914  */
1915 void try_offline_node(int nid)
1916 {
1917         pg_data_t *pgdat = NODE_DATA(nid);
1918         unsigned long start_pfn = pgdat->node_start_pfn;
1919         unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;
1920         unsigned long pfn;
1921         struct page *pgdat_page = virt_to_page(pgdat);
1922         int i;
1923
1924         for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
1925                 unsigned long section_nr = pfn_to_section_nr(pfn);
1926
1927                 if (!present_section_nr(section_nr))
1928                         continue;
1929
1930                 if (pfn_to_nid(pfn) != nid)
1931                         continue;
1932
1933                 /*
1934                  * some memory sections of this node are not removed, and we
1935                  * can't offline node now.
1936                  */
1937                 return;
1938         }
1939
1940         if (check_and_unmap_cpu_on_node(pgdat))
1941                 return;
1942
1943         /*
1944          * all memory/cpu of this node are removed, we can offline this
1945          * node now.
1946          */
1947         node_set_offline(nid);
1948         unregister_one_node(nid);
1949
1950         if (!PageSlab(pgdat_page) && !PageCompound(pgdat_page))
1951                 /* node data is allocated from boot memory */
1952                 return;
1953
1954         /* free waittable in each zone */
1955         for (i = 0; i < MAX_NR_ZONES; i++) {
1956                 struct zone *zone = pgdat->node_zones + i;
1957
1958                 /*
1959                  * wait_table may be allocated from boot memory,
1960                  * here only free if it's allocated by vmalloc.
1961                  */
1962                 if (is_vmalloc_addr(zone->wait_table)) {
1963                         vfree(zone->wait_table);
1964                         zone->wait_table = NULL;
1965                 }
1966         }
1967 }
1968 EXPORT_SYMBOL(try_offline_node);
1969
1970 /**
1971  * remove_memory
1972  *
1973  * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
1974  * and online/offline operations before this call, as required by
1975  * try_offline_node().
1976  */
1977 void __ref remove_memory(int nid, u64 start, u64 size)
1978 {
1979         int ret;
1980
1981         BUG_ON(check_hotplug_memory_range(start, size));
1982
1983         mem_hotplug_begin();
1984
1985         /*
1986          * All memory blocks must be offlined before removing memory.  Check
1987          * whether all memory blocks in question are offline and trigger a BUG()
1988          * if this is not the case.
1989          */
1990         ret = walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1), NULL,
1991                                 check_memblock_offlined_cb);
1992         if (ret)
1993                 BUG();
1994
1995         /* remove memmap entry */
1996         firmware_map_remove(start, start + size, "System RAM");
1997
1998         arch_remove_memory(start, size);
1999
2000         try_offline_node(nid);
2001
2002         mem_hotplug_done();
2003 }
2004 EXPORT_SYMBOL_GPL(remove_memory);
2005 #endif /* CONFIG_MEMORY_HOTREMOVE */