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/bootmem.h>
  13 #include <linux/compiler.h>
  14 #include <linux/module.h>
  15 #include <linux/pagevec.h>
  16 #include <linux/writeback.h>
  17 #include <linux/slab.h>
  18 #include <linux/sysctl.h>
  19 #include <linux/cpu.h>
  20 #include <linux/memory.h>
  21 #include <linux/memory_hotplug.h>
  22 #include <linux/highmem.h>
  23 #include <linux/vmalloc.h>
  24 #include <linux/ioport.h>
  25 #include <linux/delay.h>
  26 #include <linux/migrate.h>
  27 #include <linux/page-isolation.h>
  28 #include <linux/pfn.h>
  29 #include <linux/suspend.h>
  30 #include <linux/mm_inline.h>
  31 #include <linux/firmware-map.h>
  32
  33 #include <asm/tlbflush.h>
  34
  35 #include "internal.h"
  36
  37 DEFINE_MUTEX(mem_hotplug_mutex);
  38
  39 void lock_memory_hotplug(void)
  40 {
  41         mutex_lock(&mem_hotplug_mutex);
  42
  43         /* for exclusive hibernation if CONFIG_HIBERNATION=y */
  44         lock_system_sleep();
  45 }
  46
  47 void unlock_memory_hotplug(void)
  48 {
  49         unlock_system_sleep();
  50         mutex_unlock(&mem_hotplug_mutex);
  51 }
  52
  53
  54 /* add this memory to iomem resource */
  55 static struct resource *register_memory_resource(u64 start, u64 size)
  56 {
  57         struct resource *res;
  58         res = kzalloc(sizeof(struct resource), GFP_KERNEL);
  59         BUG_ON(!res);
  60
  61         res->name = "System RAM";
  62         res->start = start;
  63         res->end = start + size - 1;
  64         res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
  65         if (request_resource(&iomem_resource, res) < 0) {
  66                 printk("System RAM resource %llx - %llx cannot be added\n",
  67                 (unsigned long long)res->start, (unsigned long long)res->end);
  68                 kfree(res);
  69                 res = NULL;
  70         }
  71         return res;
  72 }
  73
  74 static void release_memory_resource(struct resource *res)
  75 {
  76         if (!res)
  77                 return;
  78         release_resource(res);
  79         kfree(res);
  80         return;
  81 }
  82
  83 #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
  84 #ifndef CONFIG_SPARSEMEM_VMEMMAP
  85 static void get_page_bootmem(unsigned long info,  struct page *page,
  86                              unsigned long type)
  87 {
  88         page->lru.next = (struct list_head *) type;
  89         SetPagePrivate(page);
  90         set_page_private(page, info);
  91         atomic_inc(&page->_count);
  92 }
  93
  94 /* reference to __meminit __free_pages_bootmem is valid
  95  * so use __ref to tell modpost not to generate a warning */
  96 void __ref put_page_bootmem(struct page *page)
  97 {
  98         unsigned long type;
  99
 100         type = (unsigned long) page->lru.next;
 101         BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
 102                type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE);
 103
 104         if (atomic_dec_return(&page->_count) == 1) {
 105                 ClearPagePrivate(page);
 106                 set_page_private(page, 0);
 107                 INIT_LIST_HEAD(&page->lru);
 108                 __free_pages_bootmem(page, 0);
 109         }
 110
 111 }
 112
 113 static void register_page_bootmem_info_section(unsigned long start_pfn)
 114 {
 115         unsigned long *usemap, mapsize, section_nr, i;
 116         struct mem_section *ms;
 117         struct page *page, *memmap;
 118
 119         if (!pfn_valid(start_pfn))
 120                 return;
 121
 122         section_nr = pfn_to_section_nr(start_pfn);
 123         ms = __nr_to_section(section_nr);
 124
 125         /* Get section's memmap address */
 126         memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
 127
 128         /*
 129          * Get page for the memmap's phys address
 130          * XXX: need more consideration for sparse_vmemmap...
 131          */
 132         page = virt_to_page(memmap);
 133         mapsize = sizeof(struct page) * PAGES_PER_SECTION;
 134         mapsize = PAGE_ALIGN(mapsize) >> PAGE_SHIFT;
 135
 136         /* remember memmap's page */
 137         for (i = 0; i < mapsize; i++, page++)
 138                 get_page_bootmem(section_nr, page, SECTION_INFO);
 139
 140         usemap = __nr_to_section(section_nr)->pageblock_flags;
 141         page = virt_to_page(usemap);
 142
 143         mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT;
 144
 145         for (i = 0; i < mapsize; i++, page++)
 146                 get_page_bootmem(section_nr, page, MIX_SECTION_INFO);
 147
 148 }
 149
 150 void register_page_bootmem_info_node(struct pglist_data *pgdat)
 151 {
 152         unsigned long i, pfn, end_pfn, nr_pages;
 153         int node = pgdat->node_id;
 154         struct page *page;
 155         struct zone *zone;
 156
 157         nr_pages = PAGE_ALIGN(sizeof(struct pglist_data)) >> PAGE_SHIFT;
 158         page = virt_to_page(pgdat);
 159
 160         for (i = 0; i < nr_pages; i++, page++)
 161                 get_page_bootmem(node, page, NODE_INFO);
 162
 163         zone = &pgdat->node_zones[0];
 164         for (; zone < pgdat->node_zones + MAX_NR_ZONES - 1; zone++) {
 165                 if (zone->wait_table) {
 166                         nr_pages = zone->wait_table_hash_nr_entries
 167                                 * sizeof(wait_queue_head_t);
 168                         nr_pages = PAGE_ALIGN(nr_pages) >> PAGE_SHIFT;
 169                         page = virt_to_page(zone->wait_table);
 170
 171                         for (i = 0; i < nr_pages; i++, page++)
 172                                 get_page_bootmem(node, page, NODE_INFO);
 173                 }
 174         }
 175
 176         pfn = pgdat->node_start_pfn;
 177         end_pfn = pfn + pgdat->node_spanned_pages;
 178
 179         /* register_section info */
 180         for (; pfn < end_pfn; pfn += PAGES_PER_SECTION)
 181                 register_page_bootmem_info_section(pfn);
 182
 183 }
 184 #endif /* !CONFIG_SPARSEMEM_VMEMMAP */
 185
 186 static void grow_zone_span(struct zone *zone, unsigned long start_pfn,
 187                            unsigned long end_pfn)
 188 {
 189         unsigned long old_zone_end_pfn;
 190
 191         zone_span_writelock(zone);
 192
 193         old_zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
 194         if (start_pfn < zone->zone_start_pfn)
 195                 zone->zone_start_pfn = start_pfn;
 196
 197         zone->spanned_pages = max(old_zone_end_pfn, end_pfn) -
 198                                 zone->zone_start_pfn;
 199
 200         zone_span_writeunlock(zone);
 201 }
 202
 203 static void grow_pgdat_span(struct pglist_data *pgdat, unsigned long start_pfn,
 204                             unsigned long end_pfn)
 205 {
 206         unsigned long old_pgdat_end_pfn =
 207                 pgdat->node_start_pfn + pgdat->node_spanned_pages;
 208
 209         if (start_pfn < pgdat->node_start_pfn)
 210                 pgdat->node_start_pfn = start_pfn;
 211
 212         pgdat->node_spanned_pages = max(old_pgdat_end_pfn, end_pfn) -
 213                                         pgdat->node_start_pfn;
 214 }
 215
 216 static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)
 217 {
 218         struct pglist_data *pgdat = zone->zone_pgdat;
 219         int nr_pages = PAGES_PER_SECTION;
 220         int nid = pgdat->node_id;
 221         int zone_type;
 222         unsigned long flags;
 223
 224         zone_type = zone - pgdat->node_zones;
 225         if (!zone->wait_table) {
 226                 int ret;
 227
 228                 ret = init_currently_empty_zone(zone, phys_start_pfn,
 229                                                 nr_pages, MEMMAP_HOTPLUG);
 230                 if (ret)
 231                         return ret;
 232         }
 233         pgdat_resize_lock(zone->zone_pgdat, &flags);
 234         grow_zone_span(zone, phys_start_pfn, phys_start_pfn + nr_pages);
 235         grow_pgdat_span(zone->zone_pgdat, phys_start_pfn,
 236                         phys_start_pfn + nr_pages);
 237         pgdat_resize_unlock(zone->zone_pgdat, &flags);
 238         memmap_init_zone(nr_pages, nid, zone_type,
 239                          phys_start_pfn, MEMMAP_HOTPLUG);
 240         return 0;
 241 }
 242
 243 static int __meminit __add_section(int nid, struct zone *zone,
 244                                         unsigned long phys_start_pfn)
 245 {
 246         int nr_pages = PAGES_PER_SECTION;
 247         int ret;
 248
 249         if (pfn_valid(phys_start_pfn))
 250                 return -EEXIST;
 251
 252         ret = sparse_add_one_section(zone, phys_start_pfn, nr_pages);
 253
 254         if (ret < 0)
 255                 return ret;
 256
 257         ret = __add_zone(zone, phys_start_pfn);
 258
 259         if (ret < 0)
 260                 return ret;
 261
 262         return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
 263 }
 264
 265 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 266 static int __remove_section(struct zone *zone, struct mem_section *ms)
 267 {
 268         /*
 269          * XXX: Freeing memmap with vmemmap is not implement yet.
 270          *      This should be removed later.
 271          */
 272         return -EBUSY;
 273 }
 274 #else
 275 static int __remove_section(struct zone *zone, struct mem_section *ms)
 276 {
 277         unsigned long flags;
 278         struct pglist_data *pgdat = zone->zone_pgdat;
 279         int ret = -EINVAL;
 280
 281         if (!valid_section(ms))
 282                 return ret;
 283
 284         ret = unregister_memory_section(ms);
 285         if (ret)
 286                 return ret;
 287
 288         pgdat_resize_lock(pgdat, &flags);
 289         sparse_remove_one_section(zone, ms);
 290         pgdat_resize_unlock(pgdat, &flags);
 291         return 0;
 292 }
 293 #endif
 294
 295 /*
 296  * Reasonably generic function for adding memory.  It is
 297  * expected that archs that support memory hotplug will
 298  * call this function after deciding the zone to which to
 299  * add the new pages.
 300  */
 301 int __ref __add_pages(int nid, struct zone *zone, unsigned long phys_start_pfn,
 302                         unsigned long nr_pages)
 303 {
 304         unsigned long i;
 305         int err = 0;
 306         int start_sec, end_sec;
 307         /* during initialize mem_map, align hot-added range to section */
 308         start_sec = pfn_to_section_nr(phys_start_pfn);
 309         end_sec = pfn_to_section_nr(phys_start_pfn + nr_pages - 1);
 310
 311         for (i = start_sec; i <= end_sec; i++) {
 312                 err = __add_section(nid, zone, i << PFN_SECTION_SHIFT);
 313
 314                 /*
 315                  * EEXIST is finally dealt with by ioresource collision
 316                  * check. see add_memory() => register_memory_resource()
 317                  * Warning will be printed if there is collision.
 318                  */
 319                 if (err && (err != -EEXIST))
 320                         break;
 321                 err = 0;
 322         }
 323
 324         return err;
 325 }
 326 EXPORT_SYMBOL_GPL(__add_pages);
 327
 328 /**
 329  * __remove_pages() - remove sections of pages from a zone
 330  * @zone: zone from which pages need to be removed
 331  * @phys_start_pfn: starting pageframe (must be aligned to start of a section)
 332  * @nr_pages: number of pages to remove (must be multiple of section size)
 333  *
 334  * Generic helper function to remove section mappings and sysfs entries
 335  * for the section of the memory we are removing. Caller needs to make
 336  * sure that pages are marked reserved and zones are adjust properly by
 337  * calling offline_pages().
 338  */
 339 int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
 340                  unsigned long nr_pages)
 341 {
 342         unsigned long i, ret = 0;
 343         int sections_to_remove;
 344
 345         /*
 346          * We can only remove entire sections
 347          */
 348         BUG_ON(phys_start_pfn & ~PAGE_SECTION_MASK);
 349         BUG_ON(nr_pages % PAGES_PER_SECTION);
 350
 351         sections_to_remove = nr_pages / PAGES_PER_SECTION;
 352         for (i = 0; i < sections_to_remove; i++) {
 353                 unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;
 354                 release_mem_region(pfn << PAGE_SHIFT,
 355                                    PAGES_PER_SECTION << PAGE_SHIFT);
 356                 ret = __remove_section(zone, __pfn_to_section(pfn));
 357                 if (ret)
 358                         break;
 359         }
 360         return ret;
 361 }
 362 EXPORT_SYMBOL_GPL(__remove_pages);
 363
 364 void online_page(struct page *page)
 365 {
 366         unsigned long pfn = page_to_pfn(page);
 367
 368         totalram_pages++;
 369         if (pfn >= num_physpages)
 370                 num_physpages = pfn + 1;
 371
 372 #ifdef CONFIG_HIGHMEM
 373         if (PageHighMem(page))
 374                 totalhigh_pages++;
 375 #endif
 376
 377         ClearPageReserved(page);
 378         init_page_count(page);
 379         __free_page(page);
 380 }
 381
 382 static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
 383                         void *arg)
 384 {
 385         unsigned long i;
 386         unsigned long onlined_pages = *(unsigned long *)arg;
 387         struct page *page;
 388         if (PageReserved(pfn_to_page(start_pfn)))
 389                 for (i = 0; i < nr_pages; i++) {
 390                         page = pfn_to_page(start_pfn + i);
 391                         online_page(page);
 392                         onlined_pages++;
 393                 }
 394         *(unsigned long *)arg = onlined_pages;
 395         return 0;
 396 }
 397
 398
 399 int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
 400 {
 401         unsigned long onlined_pages = 0;
 402         struct zone *zone;
 403         int need_zonelists_rebuild = 0;
 404         int nid;
 405         int ret;
 406         struct memory_notify arg;
 407
 408         lock_memory_hotplug();
 409         arg.start_pfn = pfn;
 410         arg.nr_pages = nr_pages;
 411         arg.status_change_nid = -1;
 412
 413         nid = page_to_nid(pfn_to_page(pfn));
 414         if (node_present_pages(nid) == 0)
 415                 arg.status_change_nid = nid;
 416
 417         ret = memory_notify(MEM_GOING_ONLINE, &arg);
 418         ret = notifier_to_errno(ret);
 419         if (ret) {
 420                 memory_notify(MEM_CANCEL_ONLINE, &arg);
 421                 unlock_memory_hotplug();
 422                 return ret;
 423         }
 424         /*
 425          * This doesn't need a lock to do pfn_to_page().
 426          * The section can't be removed here because of the
 427          * memory_block->state_mutex.
 428          */
 429         zone = page_zone(pfn_to_page(pfn));
 430         /*
 431          * If this zone is not populated, then it is not in zonelist.
 432          * This means the page allocator ignores this zone.
 433          * So, zonelist must be updated after online.
 434          */
 435         mutex_lock(&zonelists_mutex);
 436         if (!populated_zone(zone))
 437                 need_zonelists_rebuild = 1;
 438
 439         ret = walk_system_ram_range(pfn, nr_pages, &onlined_pages,
 440                 online_pages_range);
 441         if (ret) {
 442                 mutex_unlock(&zonelists_mutex);
 443                 printk(KERN_DEBUG "online_pages %lx at %lx failed\n",
 444                         nr_pages, pfn);
 445                 memory_notify(MEM_CANCEL_ONLINE, &arg);
 446                 unlock_memory_hotplug();
 447                 return ret;
 448         }
 449
 450         zone->present_pages += onlined_pages;
 451         zone->zone_pgdat->node_present_pages += onlined_pages;
 452         if (need_zonelists_rebuild)
 453                 build_all_zonelists(zone);
 454         else
 455                 zone_pcp_update(zone);
 456
 457         mutex_unlock(&zonelists_mutex);
 458
 459         init_per_zone_wmark_min();
 460
 461         if (onlined_pages) {
 462                 kswapd_run(zone_to_nid(zone));
 463                 node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
 464         }
 465
 466         vm_total_pages = nr_free_pagecache_pages();
 467
 468         writeback_set_ratelimit();
 469
 470         if (onlined_pages)
 471                 memory_notify(MEM_ONLINE, &arg);
 472         unlock_memory_hotplug();
 473
 474         return 0;
 475 }
 476 #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
 477
 478 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
 479 static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
 480 {
 481         struct pglist_data *pgdat;
 482         unsigned long zones_size[MAX_NR_ZONES] = {0};
 483         unsigned long zholes_size[MAX_NR_ZONES] = {0};
 484         unsigned long start_pfn = start >> PAGE_SHIFT;
 485
 486         pgdat = arch_alloc_nodedata(nid);
 487         if (!pgdat)
 488                 return NULL;
 489
 490         arch_refresh_nodedata(nid, pgdat);
 491
 492         /* we can use NODE_DATA(nid) from here */
 493
 494         /* init node's zones as empty zones, we don't have any present pages.*/
 495         free_area_init_node(nid, zones_size, start_pfn, zholes_size);
 496
 497         /*
 498          * The node we allocated has no zone fallback lists. For avoiding
 499          * to access not-initialized zonelist, build here.
 500          */
 501         mutex_lock(&zonelists_mutex);
 502         build_all_zonelists(NULL);
 503         mutex_unlock(&zonelists_mutex);
 504
 505         return pgdat;
 506 }
 507
 508 static void rollback_node_hotadd(int nid, pg_data_t *pgdat)
 509 {
 510         arch_refresh_nodedata(nid, NULL);
 511         arch_free_nodedata(pgdat);
 512         return;
 513 }
 514
 515
 516 /*
 517  * called by cpu_up() to online a node without onlined memory.
 518  */
 519 int mem_online_node(int nid)
 520 {
 521         pg_data_t       *pgdat;
 522         int     ret;
 523
 524         lock_memory_hotplug();
 525         pgdat = hotadd_new_pgdat(nid, 0);
 526         if (!pgdat) {
 527                 ret = -ENOMEM;
 528                 goto out;
 529         }
 530         node_set_online(nid);
 531         ret = register_one_node(nid);
 532         BUG_ON(ret);
 533
 534 out:
 535         unlock_memory_hotplug();
 536         return ret;
 537 }
 538
 539 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
 540 int __ref add_memory(int nid, u64 start, u64 size)
 541 {
 542         pg_data_t *pgdat = NULL;
 543         int new_pgdat = 0;
 544         struct resource *res;
 545         int ret;
 546
 547         lock_memory_hotplug();
 548
 549         res = register_memory_resource(start, size);
 550         ret = -EEXIST;
 551         if (!res)
 552                 goto out;
 553
 554         if (!node_online(nid)) {
 555                 pgdat = hotadd_new_pgdat(nid, start);
 556                 ret = -ENOMEM;
 557                 if (!pgdat)
 558                         goto out;
 559                 new_pgdat = 1;
 560         }
 561
 562         /* call arch's memory hotadd */
 563         ret = arch_add_memory(nid, start, size);
 564
 565         if (ret < 0)
 566                 goto error;
 567
 568         /* we online node here. we can't roll back from here. */
 569         node_set_online(nid);
 570
 571         if (new_pgdat) {
 572                 ret = register_one_node(nid);
 573                 /*
 574                  * If sysfs file of new node can't create, cpu on the node
 575                  * can't be hot-added. There is no rollback way now.
 576                  * So, check by BUG_ON() to catch it reluctantly..
 577                  */
 578                 BUG_ON(ret);
 579         }
 580
 581         /* create new memmap entry */
 582         firmware_map_add_hotplug(start, start + size, "System RAM");
 583
 584         goto out;
 585
 586 error:
 587         /* rollback pgdat allocation and others */
 588         if (new_pgdat)
 589                 rollback_node_hotadd(nid, pgdat);
 590         if (res)
 591                 release_memory_resource(res);
 592
 593 out:
 594         unlock_memory_hotplug();
 595         return ret;
 596 }
 597 EXPORT_SYMBOL_GPL(add_memory);
 598
 599 #ifdef CONFIG_MEMORY_HOTREMOVE
 600 /*
 601  * A free page on the buddy free lists (not the per-cpu lists) has PageBuddy
 602  * set and the size of the free page is given by page_order(). Using this,
 603  * the function determines if the pageblock contains only free pages.
 604  * Due to buddy contraints, a free page at least the size of a pageblock will
 605  * be located at the start of the pageblock
 606  */
 607 static inline int pageblock_free(struct page *page)
 608 {
 609         return PageBuddy(page) && page_order(page) >= pageblock_order;
 610 }
 611
 612 /* Return the start of the next active pageblock after a given page */
 613 static struct page *next_active_pageblock(struct page *page)
 614 {
 615         /* Ensure the starting page is pageblock-aligned */
 616         BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1));
 617
 618         /* If the entire pageblock is free, move to the end of free page */
 619         if (pageblock_free(page)) {
 620                 int order;
 621                 /* be careful. we don't have locks, page_order can be changed.*/
 622                 order = page_order(page);
 623                 if ((order < MAX_ORDER) && (order >= pageblock_order))
 624                         return page + (1 << order);
 625         }
 626
 627         return page + pageblock_nr_pages;
 628 }
 629
 630 /* Checks if this range of memory is likely to be hot-removable. */
 631 int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
 632 {
 633         struct page *page = pfn_to_page(start_pfn);
 634         struct page *end_page = page + nr_pages;
 635
 636         /* Check the starting page of each pageblock within the range */
 637         for (; page < end_page; page = next_active_pageblock(page)) {
 638                 if (!is_pageblock_removable_nolock(page))
 639                         return 0;
 640                 cond_resched();
 641         }
 642
 643         /* All pageblocks in the memory block are likely to be hot-removable */
 644         return 1;
 645 }
 646
 647 /*
 648  * Confirm all pages in a range [start, end) is belongs to the same zone.
 649  */
 650 static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
 651 {
 652         unsigned long pfn;
 653         struct zone *zone = NULL;
 654         struct page *page;
 655         int i;
 656         for (pfn = start_pfn;
 657              pfn < end_pfn;
 658              pfn += MAX_ORDER_NR_PAGES) {
 659                 i = 0;
 660                 /* This is just a CONFIG_HOLES_IN_ZONE check.*/
 661                 while ((i < MAX_ORDER_NR_PAGES) && !pfn_valid_within(pfn + i))
 662                         i++;
 663                 if (i == MAX_ORDER_NR_PAGES)
 664                         continue;
 665                 page = pfn_to_page(pfn + i);
 666                 if (zone && page_zone(page) != zone)
 667                         return 0;
 668                 zone = page_zone(page);
 669         }
 670         return 1;
 671 }
 672
 673 /*
 674  * Scanning pfn is much easier than scanning lru list.
 675  * Scan pfn from start to end and Find LRU page.
 676  */
 677 static unsigned long scan_lru_pages(unsigned long start, unsigned long end)
 678 {
 679         unsigned long pfn;
 680         struct page *page;
 681         for (pfn = start; pfn < end; pfn++) {
 682                 if (pfn_valid(pfn)) {
 683                         page = pfn_to_page(pfn);
 684                         if (PageLRU(page))
 685                                 return pfn;
 686                 }
 687         }
 688         return 0;
 689 }
 690
 691 static struct page *
 692 hotremove_migrate_alloc(struct page *page, unsigned long private, int **x)
 693 {
 694         /* This should be improooooved!! */
 695         return alloc_page(GFP_HIGHUSER_MOVABLE);
 696 }
 697
 698 #define NR_OFFLINE_AT_ONCE_PAGES        (256)
 699 static int
 700 do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 701 {
 702         unsigned long pfn;
 703         struct page *page;
 704         int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
 705         int not_managed = 0;
 706         int ret = 0;
 707         LIST_HEAD(source);
 708
 709         for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) {
 710                 if (!pfn_valid(pfn))
 711                         continue;
 712                 page = pfn_to_page(pfn);
 713                 if (!get_page_unless_zero(page))
 714                         continue;
 715                 /*
 716                  * We can skip free pages. And we can only deal with pages on
 717                  * LRU.
 718                  */
 719                 ret = isolate_lru_page(page);
 720                 if (!ret) { /* Success */
 721                         put_page(page);
 722                         list_add_tail(&page->lru, &source);
 723                         move_pages--;
 724                         inc_zone_page_state(page, NR_ISOLATED_ANON +
 725                                             page_is_file_cache(page));
 726
 727                 } else {
 728 #ifdef CONFIG_DEBUG_VM
 729                         printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
 730                                pfn);
 731                         dump_page(page);
 732 #endif
 733                         put_page(page);
 734                         /* Because we don't have big zone->lock. we should
 735                            check this again here. */
 736                         if (page_count(page)) {
 737                                 not_managed++;
 738                                 ret = -EBUSY;
 739                                 break;
 740                         }
 741                 }
 742         }
 743         if (!list_empty(&source)) {
 744                 if (not_managed) {
 745                         putback_lru_pages(&source);
 746                         goto out;
 747                 }
 748                 /* this function returns # of failed pages */
 749                 ret = migrate_pages(&source, hotremove_migrate_alloc, 0,
 750                                                                 true, true);
 751                 if (ret)
 752                         putback_lru_pages(&source);
 753         }
 754 out:
 755         return ret;
 756 }
 757
 758 /*
 759  * remove from free_area[] and mark all as Reserved.
 760  */
 761 static int
 762 offline_isolated_pages_cb(unsigned long start, unsigned long nr_pages,
 763                         void *data)
 764 {
 765         __offline_isolated_pages(start, start + nr_pages);
 766         return 0;
 767 }
 768
 769 static void
 770 offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
 771 {
 772         walk_system_ram_range(start_pfn, end_pfn - start_pfn, NULL,
 773                                 offline_isolated_pages_cb);
 774 }
 775
 776 /*
 777  * Check all pages in range, recoreded as memory resource, are isolated.
 778  */
 779 static int
 780 check_pages_isolated_cb(unsigned long start_pfn, unsigned long nr_pages,
 781                         void *data)
 782 {
 783         int ret;
 784         long offlined = *(long *)data;
 785         ret = test_pages_isolated(start_pfn, start_pfn + nr_pages);
 786         offlined = nr_pages;
 787         if (!ret)
 788                 *(long *)data += offlined;
 789         return ret;
 790 }
 791
 792 static long
 793 check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
 794 {
 795         long offlined = 0;
 796         int ret;
 797
 798         ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn, &offlined,
 799                         check_pages_isolated_cb);
 800         if (ret < 0)
 801                 offlined = (long)ret;
 802         return offlined;
 803 }
 804
 805 static int __ref offline_pages(unsigned long start_pfn,
 806                   unsigned long end_pfn, unsigned long timeout)
 807 {
 808         unsigned long pfn, nr_pages, expire;
 809         long offlined_pages;
 810         int ret, drain, retry_max, node;
 811         struct zone *zone;
 812         struct memory_notify arg;
 813
 814         BUG_ON(start_pfn >= end_pfn);
 815         /* at least, alignment against pageblock is necessary */
 816         if (!IS_ALIGNED(start_pfn, pageblock_nr_pages))
 817                 return -EINVAL;
 818         if (!IS_ALIGNED(end_pfn, pageblock_nr_pages))
 819                 return -EINVAL;
 820         /* This makes hotplug much easier...and readable.
 821            we assume this for now. .*/
 822         if (!test_pages_in_a_zone(start_pfn, end_pfn))
 823                 return -EINVAL;
 824
 825         lock_memory_hotplug();
 826
 827         zone = page_zone(pfn_to_page(start_pfn));
 828         node = zone_to_nid(zone);
 829         nr_pages = end_pfn - start_pfn;
 830
 831         /* set above range as isolated */
 832         ret = start_isolate_page_range(start_pfn, end_pfn);
 833         if (ret)
 834                 goto out;
 835
 836         arg.start_pfn = start_pfn;
 837         arg.nr_pages = nr_pages;
 838         arg.status_change_nid = -1;
 839         if (nr_pages >= node_present_pages(node))
 840                 arg.status_change_nid = node;
 841
 842         ret = memory_notify(MEM_GOING_OFFLINE, &arg);
 843         ret = notifier_to_errno(ret);
 844         if (ret)
 845                 goto failed_removal;
 846
 847         pfn = start_pfn;
 848         expire = jiffies + timeout;
 849         drain = 0;
 850         retry_max = 5;
 851 repeat:
 852         /* start memory hot removal */
 853         ret = -EAGAIN;
 854         if (time_after(jiffies, expire))
 855                 goto failed_removal;
 856         ret = -EINTR;
 857         if (signal_pending(current))
 858                 goto failed_removal;
 859         ret = 0;
 860         if (drain) {
 861                 lru_add_drain_all();
 862                 cond_resched();
 863                 drain_all_pages();
 864         }
 865
 866         pfn = scan_lru_pages(start_pfn, end_pfn);
 867         if (pfn) { /* We have page on LRU */
 868                 ret = do_migrate_range(pfn, end_pfn);
 869                 if (!ret) {
 870                         drain = 1;
 871                         goto repeat;
 872                 } else {
 873                         if (ret < 0)
 874                                 if (--retry_max == 0)
 875                                         goto failed_removal;
 876                         yield();
 877                         drain = 1;
 878                         goto repeat;
 879                 }
 880         }
 881         /* drain all zone's lru pagevec, this is asyncronous... */
 882         lru_add_drain_all();
 883         yield();
 884         /* drain pcp pages , this is synchrouns. */
 885         drain_all_pages();
 886         /* check again */
 887         offlined_pages = check_pages_isolated(start_pfn, end_pfn);
 888         if (offlined_pages < 0) {
 889                 ret = -EBUSY;
 890                 goto failed_removal;
 891         }
 892         printk(KERN_INFO "Offlined Pages %ld\n", offlined_pages);
 893         /* Ok, all of our target is islaoted.
 894            We cannot do rollback at this point. */
 895         offline_isolated_pages(start_pfn, end_pfn);
 896         /* reset pagetype flags and makes migrate type to be MOVABLE */
 897         undo_isolate_page_range(start_pfn, end_pfn);
 898         /* removal success */
 899         zone->present_pages -= offlined_pages;
 900         zone->zone_pgdat->node_present_pages -= offlined_pages;
 901         totalram_pages -= offlined_pages;
 902
 903         init_per_zone_wmark_min();
 904
 905         if (!node_present_pages(node)) {
 906                 node_clear_state(node, N_HIGH_MEMORY);
 907                 kswapd_stop(node);
 908         }
 909
 910         vm_total_pages = nr_free_pagecache_pages();
 911         writeback_set_ratelimit();
 912
 913         memory_notify(MEM_OFFLINE, &arg);
 914         unlock_memory_hotplug();
 915         return 0;
 916
 917 failed_removal:
 918         printk(KERN_INFO "memory offlining %lx to %lx failed\n",
 919                 start_pfn, end_pfn);
 920         memory_notify(MEM_CANCEL_OFFLINE, &arg);
 921         /* pushback to free area */
 922         undo_isolate_page_range(start_pfn, end_pfn);
 923
 924 out:
 925         unlock_memory_hotplug();
 926         return ret;
 927 }
 928
 929 int remove_memory(u64 start, u64 size)
 930 {
 931         unsigned long start_pfn, end_pfn;
 932
 933         start_pfn = PFN_DOWN(start);
 934         end_pfn = start_pfn + PFN_DOWN(size);
 935         return offline_pages(start_pfn, end_pfn, 120 * HZ);
 936 }
 937 #else
 938 int remove_memory(u64 start, u64 size)
 939 {
 940         return -EINVAL;
 941 }
 942 #endif /* CONFIG_MEMORY_HOTREMOVE */
 943 EXPORT_SYMBOL_GPL(remove_memory);