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/cpuset.h>
  26 #include <linux/delay.h>
  27 #include <linux/migrate.h>
  28 #include <linux/page-isolation.h>
  29
  30 #include <asm/tlbflush.h>
  31
  32 /* add this memory to iomem resource */
  33 static struct resource *register_memory_resource(u64 start, u64 size)
  34 {
  35         struct resource *res;
  36         res = kzalloc(sizeof(struct resource), GFP_KERNEL);
  37         BUG_ON(!res);
  38
  39         res->name = "System RAM";
  40         res->start = start;
  41         res->end = start + size - 1;
  42         res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
  43         if (request_resource(&iomem_resource, res) < 0) {
  44                 printk("System RAM resource %llx - %llx cannot be added\n",
  45                 (unsigned long long)res->start, (unsigned long long)res->end);
  46                 kfree(res);
  47                 res = NULL;
  48         }
  49         return res;
  50 }
  51
  52 static void release_memory_resource(struct resource *res)
  53 {
  54         if (!res)
  55                 return;
  56         release_resource(res);
  57         kfree(res);
  58         return;
  59 }
  60
  61 #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
  62 #ifndef CONFIG_SPARSEMEM_VMEMMAP
  63 static void get_page_bootmem(unsigned long info,  struct page *page, int magic)
  64 {
  65         atomic_set(&page->_mapcount, magic);
  66         SetPagePrivate(page);
  67         set_page_private(page, info);
  68         atomic_inc(&page->_count);
  69 }
  70
  71 void put_page_bootmem(struct page *page)
  72 {
  73         int magic;
  74
  75         magic = atomic_read(&page->_mapcount);
  76         BUG_ON(magic >= -1);
  77
  78         if (atomic_dec_return(&page->_count) == 1) {
  79                 ClearPagePrivate(page);
  80                 set_page_private(page, 0);
  81                 reset_page_mapcount(page);
  82                 __free_pages_bootmem(page, 0);
  83         }
  84
  85 }
  86
  87 void register_page_bootmem_info_section(unsigned long start_pfn)
  88 {
  89         unsigned long *usemap, mapsize, section_nr, i;
  90         struct mem_section *ms;
  91         struct page *page, *memmap;
  92
  93         if (!pfn_valid(start_pfn))
  94                 return;
  95
  96         section_nr = pfn_to_section_nr(start_pfn);
  97         ms = __nr_to_section(section_nr);
  98
  99         /* Get section's memmap address */
 100         memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
 101
 102         /*
 103          * Get page for the memmap's phys address
 104          * XXX: need more consideration for sparse_vmemmap...
 105          */
 106         page = virt_to_page(memmap);
 107         mapsize = sizeof(struct page) * PAGES_PER_SECTION;
 108         mapsize = PAGE_ALIGN(mapsize) >> PAGE_SHIFT;
 109
 110         /* remember memmap's page */
 111         for (i = 0; i < mapsize; i++, page++)
 112                 get_page_bootmem(section_nr, page, SECTION_INFO);
 113
 114         usemap = __nr_to_section(section_nr)->pageblock_flags;
 115         page = virt_to_page(usemap);
 116
 117         mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT;
 118
 119         for (i = 0; i < mapsize; i++, page++)
 120                 get_page_bootmem(section_nr, page, MIX_INFO);
 121
 122 }
 123
 124 void register_page_bootmem_info_node(struct pglist_data *pgdat)
 125 {
 126         unsigned long i, pfn, end_pfn, nr_pages;
 127         int node = pgdat->node_id;
 128         struct page *page;
 129         struct zone *zone;
 130
 131         nr_pages = PAGE_ALIGN(sizeof(struct pglist_data)) >> PAGE_SHIFT;
 132         page = virt_to_page(pgdat);
 133
 134         for (i = 0; i < nr_pages; i++, page++)
 135                 get_page_bootmem(node, page, NODE_INFO);
 136
 137         zone = &pgdat->node_zones[0];
 138         for (; zone < pgdat->node_zones + MAX_NR_ZONES - 1; zone++) {
 139                 if (zone->wait_table) {
 140                         nr_pages = zone->wait_table_hash_nr_entries
 141                                 * sizeof(wait_queue_head_t);
 142                         nr_pages = PAGE_ALIGN(nr_pages) >> PAGE_SHIFT;
 143                         page = virt_to_page(zone->wait_table);
 144
 145                         for (i = 0; i < nr_pages; i++, page++)
 146                                 get_page_bootmem(node, page, NODE_INFO);
 147                 }
 148         }
 149
 150         pfn = pgdat->node_start_pfn;
 151         end_pfn = pfn + pgdat->node_spanned_pages;
 152
 153         /* register_section info */
 154         for (; pfn < end_pfn; pfn += PAGES_PER_SECTION)
 155                 register_page_bootmem_info_section(pfn);
 156
 157 }
 158 #endif /* !CONFIG_SPARSEMEM_VMEMMAP */
 159
 160 static int __add_zone(struct zone *zone, unsigned long phys_start_pfn)
 161 {
 162         struct pglist_data *pgdat = zone->zone_pgdat;
 163         int nr_pages = PAGES_PER_SECTION;
 164         int nid = pgdat->node_id;
 165         int zone_type;
 166
 167         zone_type = zone - pgdat->node_zones;
 168         if (!zone->wait_table) {
 169                 int ret = 0;
 170                 ret = init_currently_empty_zone(zone, phys_start_pfn,
 171                                                 nr_pages, MEMMAP_HOTPLUG);
 172                 if (ret < 0)
 173                         return ret;
 174         }
 175         memmap_init_zone(nr_pages, nid, zone_type,
 176                          phys_start_pfn, MEMMAP_HOTPLUG);
 177         return 0;
 178 }
 179
 180 static int __add_section(struct zone *zone, unsigned long phys_start_pfn)
 181 {
 182         int nr_pages = PAGES_PER_SECTION;
 183         int ret;
 184
 185         if (pfn_valid(phys_start_pfn))
 186                 return -EEXIST;
 187
 188         ret = sparse_add_one_section(zone, phys_start_pfn, nr_pages);
 189
 190         if (ret < 0)
 191                 return ret;
 192
 193         ret = __add_zone(zone, phys_start_pfn);
 194
 195         if (ret < 0)
 196                 return ret;
 197
 198         return register_new_memory(__pfn_to_section(phys_start_pfn));
 199 }
 200
 201 static int __remove_section(struct zone *zone, struct mem_section *ms)
 202 {
 203         unsigned long flags;
 204         struct pglist_data *pgdat = zone->zone_pgdat;
 205         int ret = -EINVAL;
 206
 207         if (!valid_section(ms))
 208                 return ret;
 209
 210         ret = unregister_memory_section(ms);
 211         if (ret)
 212                 return ret;
 213
 214         pgdat_resize_lock(pgdat, &flags);
 215         sparse_remove_one_section(zone, ms);
 216         pgdat_resize_unlock(pgdat, &flags);
 217         return 0;
 218 }
 219
 220 /*
 221  * Reasonably generic function for adding memory.  It is
 222  * expected that archs that support memory hotplug will
 223  * call this function after deciding the zone to which to
 224  * add the new pages.
 225  */
 226 int __add_pages(struct zone *zone, unsigned long phys_start_pfn,
 227                  unsigned long nr_pages)
 228 {
 229         unsigned long i;
 230         int err = 0;
 231         int start_sec, end_sec;
 232         /* during initialize mem_map, align hot-added range to section */
 233         start_sec = pfn_to_section_nr(phys_start_pfn);
 234         end_sec = pfn_to_section_nr(phys_start_pfn + nr_pages - 1);
 235
 236         for (i = start_sec; i <= end_sec; i++) {
 237                 err = __add_section(zone, i << PFN_SECTION_SHIFT);
 238
 239                 /*
 240                  * EEXIST is finally dealt with by ioresource collision
 241                  * check. see add_memory() => register_memory_resource()
 242                  * Warning will be printed if there is collision.
 243                  */
 244                 if (err && (err != -EEXIST))
 245                         break;
 246                 err = 0;
 247         }
 248
 249         return err;
 250 }
 251 EXPORT_SYMBOL_GPL(__add_pages);
 252
 253 /**
 254  * __remove_pages() - remove sections of pages from a zone
 255  * @zone: zone from which pages need to be removed
 256  * @phys_start_pfn: starting pageframe (must be aligned to start of a section)
 257  * @nr_pages: number of pages to remove (must be multiple of section size)
 258  *
 259  * Generic helper function to remove section mappings and sysfs entries
 260  * for the section of the memory we are removing. Caller needs to make
 261  * sure that pages are marked reserved and zones are adjust properly by
 262  * calling offline_pages().
 263  */
 264 int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
 265                  unsigned long nr_pages)
 266 {
 267         unsigned long i, ret = 0;
 268         int sections_to_remove;
 269
 270         /*
 271          * We can only remove entire sections
 272          */
 273         BUG_ON(phys_start_pfn & ~PAGE_SECTION_MASK);
 274         BUG_ON(nr_pages % PAGES_PER_SECTION);
 275
 276         release_mem_region(phys_start_pfn << PAGE_SHIFT, nr_pages * PAGE_SIZE);
 277
 278         sections_to_remove = nr_pages / PAGES_PER_SECTION;
 279         for (i = 0; i < sections_to_remove; i++) {
 280                 unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;
 281                 ret = __remove_section(zone, __pfn_to_section(pfn));
 282                 if (ret)
 283                         break;
 284         }
 285         return ret;
 286 }
 287 EXPORT_SYMBOL_GPL(__remove_pages);
 288
 289 static void grow_zone_span(struct zone *zone,
 290                 unsigned long start_pfn, unsigned long end_pfn)
 291 {
 292         unsigned long old_zone_end_pfn;
 293
 294         zone_span_writelock(zone);
 295
 296         old_zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
 297         if (start_pfn < zone->zone_start_pfn)
 298                 zone->zone_start_pfn = start_pfn;
 299
 300         zone->spanned_pages = max(old_zone_end_pfn, end_pfn) -
 301                                 zone->zone_start_pfn;
 302
 303         zone_span_writeunlock(zone);
 304 }
 305
 306 static void grow_pgdat_span(struct pglist_data *pgdat,
 307                 unsigned long start_pfn, unsigned long end_pfn)
 308 {
 309         unsigned long old_pgdat_end_pfn =
 310                 pgdat->node_start_pfn + pgdat->node_spanned_pages;
 311
 312         if (start_pfn < pgdat->node_start_pfn)
 313                 pgdat->node_start_pfn = start_pfn;
 314
 315         pgdat->node_spanned_pages = max(old_pgdat_end_pfn, end_pfn) -
 316                                         pgdat->node_start_pfn;
 317 }
 318
 319 void online_page(struct page *page)
 320 {
 321         totalram_pages++;
 322         num_physpages++;
 323
 324 #ifdef CONFIG_HIGHMEM
 325         if (PageHighMem(page))
 326                 totalhigh_pages++;
 327 #endif
 328
 329 #ifdef CONFIG_FLATMEM
 330         max_mapnr = max(page_to_pfn(page), max_mapnr);
 331 #endif
 332
 333         ClearPageReserved(page);
 334         init_page_count(page);
 335         __free_page(page);
 336 }
 337
 338 static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
 339                         void *arg)
 340 {
 341         unsigned long i;
 342         unsigned long onlined_pages = *(unsigned long *)arg;
 343         struct page *page;
 344         if (PageReserved(pfn_to_page(start_pfn)))
 345                 for (i = 0; i < nr_pages; i++) {
 346                         page = pfn_to_page(start_pfn + i);
 347                         online_page(page);
 348                         onlined_pages++;
 349                 }
 350         *(unsigned long *)arg = onlined_pages;
 351         return 0;
 352 }
 353
 354
 355 int online_pages(unsigned long pfn, unsigned long nr_pages)
 356 {
 357         unsigned long flags;
 358         unsigned long onlined_pages = 0;
 359         struct zone *zone;
 360         int need_zonelists_rebuild = 0;
 361         int nid;
 362         int ret;
 363         struct memory_notify arg;
 364
 365         arg.start_pfn = pfn;
 366         arg.nr_pages = nr_pages;
 367         arg.status_change_nid = -1;
 368
 369         nid = page_to_nid(pfn_to_page(pfn));
 370         if (node_present_pages(nid) == 0)
 371                 arg.status_change_nid = nid;
 372
 373         ret = memory_notify(MEM_GOING_ONLINE, &arg);
 374         ret = notifier_to_errno(ret);
 375         if (ret) {
 376                 memory_notify(MEM_CANCEL_ONLINE, &arg);
 377                 return ret;
 378         }
 379         /*
 380          * This doesn't need a lock to do pfn_to_page().
 381          * The section can't be removed here because of the
 382          * memory_block->state_mutex.
 383          */
 384         zone = page_zone(pfn_to_page(pfn));
 385         pgdat_resize_lock(zone->zone_pgdat, &flags);
 386         grow_zone_span(zone, pfn, pfn + nr_pages);
 387         grow_pgdat_span(zone->zone_pgdat, pfn, pfn + nr_pages);
 388         pgdat_resize_unlock(zone->zone_pgdat, &flags);
 389
 390         /*
 391          * If this zone is not populated, then it is not in zonelist.
 392          * This means the page allocator ignores this zone.
 393          * So, zonelist must be updated after online.
 394          */
 395         if (!populated_zone(zone))
 396                 need_zonelists_rebuild = 1;
 397
 398         walk_memory_resource(pfn, nr_pages, &onlined_pages,
 399                 online_pages_range);
 400         zone->present_pages += onlined_pages;
 401         zone->zone_pgdat->node_present_pages += onlined_pages;
 402
 403         setup_per_zone_pages_min();
 404         if (onlined_pages) {
 405                 kswapd_run(zone_to_nid(zone));
 406                 node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
 407         }
 408
 409         if (need_zonelists_rebuild)
 410                 build_all_zonelists();
 411         vm_total_pages = nr_free_pagecache_pages();
 412         writeback_set_ratelimit();
 413
 414         if (onlined_pages)
 415                 memory_notify(MEM_ONLINE, &arg);
 416
 417         return 0;
 418 }
 419 #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
 420
 421 static pg_data_t *hotadd_new_pgdat(int nid, u64 start)
 422 {
 423         struct pglist_data *pgdat;
 424         unsigned long zones_size[MAX_NR_ZONES] = {0};
 425         unsigned long zholes_size[MAX_NR_ZONES] = {0};
 426         unsigned long start_pfn = start >> PAGE_SHIFT;
 427
 428         pgdat = arch_alloc_nodedata(nid);
 429         if (!pgdat)
 430                 return NULL;
 431
 432         arch_refresh_nodedata(nid, pgdat);
 433
 434         /* we can use NODE_DATA(nid) from here */
 435
 436         /* init node's zones as empty zones, we don't have any present pages.*/
 437         free_area_init_node(nid, pgdat, zones_size, start_pfn, zholes_size);
 438
 439         return pgdat;
 440 }
 441
 442 static void rollback_node_hotadd(int nid, pg_data_t *pgdat)
 443 {
 444         arch_refresh_nodedata(nid, NULL);
 445         arch_free_nodedata(pgdat);
 446         return;
 447 }
 448
 449
 450 int add_memory(int nid, u64 start, u64 size)
 451 {
 452         pg_data_t *pgdat = NULL;
 453         int new_pgdat = 0;
 454         struct resource *res;
 455         int ret;
 456
 457         res = register_memory_resource(start, size);
 458         if (!res)
 459                 return -EEXIST;
 460
 461         if (!node_online(nid)) {
 462                 pgdat = hotadd_new_pgdat(nid, start);
 463                 if (!pgdat)
 464                         return -ENOMEM;
 465                 new_pgdat = 1;
 466         }
 467
 468         /* call arch's memory hotadd */
 469         ret = arch_add_memory(nid, start, size);
 470
 471         if (ret < 0)
 472                 goto error;
 473
 474         /* we online node here. we can't roll back from here. */
 475         node_set_online(nid);
 476
 477         cpuset_track_online_nodes();
 478
 479         if (new_pgdat) {
 480                 ret = register_one_node(nid);
 481                 /*
 482                  * If sysfs file of new node can't create, cpu on the node
 483                  * can't be hot-added. There is no rollback way now.
 484                  * So, check by BUG_ON() to catch it reluctantly..
 485                  */
 486                 BUG_ON(ret);
 487         }
 488
 489         return ret;
 490 error:
 491         /* rollback pgdat allocation and others */
 492         if (new_pgdat)
 493                 rollback_node_hotadd(nid, pgdat);
 494         if (res)
 495                 release_memory_resource(res);
 496
 497         return ret;
 498 }
 499 EXPORT_SYMBOL_GPL(add_memory);
 500
 501 #ifdef CONFIG_MEMORY_HOTREMOVE
 502 /*
 503  * Confirm all pages in a range [start, end) is belongs to the same zone.
 504  */
 505 static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
 506 {
 507         unsigned long pfn;
 508         struct zone *zone = NULL;
 509         struct page *page;
 510         int i;
 511         for (pfn = start_pfn;
 512              pfn < end_pfn;
 513              pfn += MAX_ORDER_NR_PAGES) {
 514                 i = 0;
 515                 /* This is just a CONFIG_HOLES_IN_ZONE check.*/
 516                 while ((i < MAX_ORDER_NR_PAGES) && !pfn_valid_within(pfn + i))
 517                         i++;
 518                 if (i == MAX_ORDER_NR_PAGES)
 519                         continue;
 520                 page = pfn_to_page(pfn + i);
 521                 if (zone && page_zone(page) != zone)
 522                         return 0;
 523                 zone = page_zone(page);
 524         }
 525         return 1;
 526 }
 527
 528 /*
 529  * Scanning pfn is much easier than scanning lru list.
 530  * Scan pfn from start to end and Find LRU page.
 531  */
 532 int scan_lru_pages(unsigned long start, unsigned long end)
 533 {
 534         unsigned long pfn;
 535         struct page *page;
 536         for (pfn = start; pfn < end; pfn++) {
 537                 if (pfn_valid(pfn)) {
 538                         page = pfn_to_page(pfn);
 539                         if (PageLRU(page))
 540                                 return pfn;
 541                 }
 542         }
 543         return 0;
 544 }
 545
 546 static struct page *
 547 hotremove_migrate_alloc(struct page *page,
 548                         unsigned long private,
 549                         int **x)
 550 {
 551         /* This should be improoooooved!! */
 552         return alloc_page(GFP_HIGHUSER_PAGECACHE);
 553 }
 554
 555
 556 #define NR_OFFLINE_AT_ONCE_PAGES        (256)
 557 static int
 558 do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 559 {
 560         unsigned long pfn;
 561         struct page *page;
 562         int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
 563         int not_managed = 0;
 564         int ret = 0;
 565         LIST_HEAD(source);
 566
 567         for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) {
 568                 if (!pfn_valid(pfn))
 569                         continue;
 570                 page = pfn_to_page(pfn);
 571                 if (!page_count(page))
 572                         continue;
 573                 /*
 574                  * We can skip free pages. And we can only deal with pages on
 575                  * LRU.
 576                  */
 577                 ret = isolate_lru_page(page, &source);
 578                 if (!ret) { /* Success */
 579                         move_pages--;
 580                 } else {
 581                         /* Becasue we don't have big zone->lock. we should
 582                            check this again here. */
 583                         if (page_count(page))
 584                                 not_managed++;
 585 #ifdef CONFIG_DEBUG_VM
 586                         printk(KERN_INFO "removing from LRU failed"
 587                                          " %lx/%d/%lx\n",
 588                                 pfn, page_count(page), page->flags);
 589 #endif
 590                 }
 591         }
 592         ret = -EBUSY;
 593         if (not_managed) {
 594                 if (!list_empty(&source))
 595                         putback_lru_pages(&source);
 596                 goto out;
 597         }
 598         ret = 0;
 599         if (list_empty(&source))
 600                 goto out;
 601         /* this function returns # of failed pages */
 602         ret = migrate_pages(&source, hotremove_migrate_alloc, 0);
 603
 604 out:
 605         return ret;
 606 }
 607
 608 /*
 609  * remove from free_area[] and mark all as Reserved.
 610  */
 611 static int
 612 offline_isolated_pages_cb(unsigned long start, unsigned long nr_pages,
 613                         void *data)
 614 {
 615         __offline_isolated_pages(start, start + nr_pages);
 616         return 0;
 617 }
 618
 619 static void
 620 offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
 621 {
 622         walk_memory_resource(start_pfn, end_pfn - start_pfn, NULL,
 623                                 offline_isolated_pages_cb);
 624 }
 625
 626 /*
 627  * Check all pages in range, recoreded as memory resource, are isolated.
 628  */
 629 static int
 630 check_pages_isolated_cb(unsigned long start_pfn, unsigned long nr_pages,
 631                         void *data)
 632 {
 633         int ret;
 634         long offlined = *(long *)data;
 635         ret = test_pages_isolated(start_pfn, start_pfn + nr_pages);
 636         offlined = nr_pages;
 637         if (!ret)
 638                 *(long *)data += offlined;
 639         return ret;
 640 }
 641
 642 static long
 643 check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
 644 {
 645         long offlined = 0;
 646         int ret;
 647
 648         ret = walk_memory_resource(start_pfn, end_pfn - start_pfn, &offlined,
 649                         check_pages_isolated_cb);
 650         if (ret < 0)
 651                 offlined = (long)ret;
 652         return offlined;
 653 }
 654
 655 int offline_pages(unsigned long start_pfn,
 656                   unsigned long end_pfn, unsigned long timeout)
 657 {
 658         unsigned long pfn, nr_pages, expire;
 659         long offlined_pages;
 660         int ret, drain, retry_max, node;
 661         struct zone *zone;
 662         struct memory_notify arg;
 663
 664         BUG_ON(start_pfn >= end_pfn);
 665         /* at least, alignment against pageblock is necessary */
 666         if (!IS_ALIGNED(start_pfn, pageblock_nr_pages))
 667                 return -EINVAL;
 668         if (!IS_ALIGNED(end_pfn, pageblock_nr_pages))
 669                 return -EINVAL;
 670         /* This makes hotplug much easier...and readable.
 671            we assume this for now. .*/
 672         if (!test_pages_in_a_zone(start_pfn, end_pfn))
 673                 return -EINVAL;
 674
 675         zone = page_zone(pfn_to_page(start_pfn));
 676         node = zone_to_nid(zone);
 677         nr_pages = end_pfn - start_pfn;
 678
 679         /* set above range as isolated */
 680         ret = start_isolate_page_range(start_pfn, end_pfn);
 681         if (ret)
 682                 return ret;
 683
 684         arg.start_pfn = start_pfn;
 685         arg.nr_pages = nr_pages;
 686         arg.status_change_nid = -1;
 687         if (nr_pages >= node_present_pages(node))
 688                 arg.status_change_nid = node;
 689
 690         ret = memory_notify(MEM_GOING_OFFLINE, &arg);
 691         ret = notifier_to_errno(ret);
 692         if (ret)
 693                 goto failed_removal;
 694
 695         pfn = start_pfn;
 696         expire = jiffies + timeout;
 697         drain = 0;
 698         retry_max = 5;
 699 repeat:
 700         /* start memory hot removal */
 701         ret = -EAGAIN;
 702         if (time_after(jiffies, expire))
 703                 goto failed_removal;
 704         ret = -EINTR;
 705         if (signal_pending(current))
 706                 goto failed_removal;
 707         ret = 0;
 708         if (drain) {
 709                 lru_add_drain_all();
 710                 flush_scheduled_work();
 711                 cond_resched();
 712                 drain_all_pages();
 713         }
 714
 715         pfn = scan_lru_pages(start_pfn, end_pfn);
 716         if (pfn) { /* We have page on LRU */
 717                 ret = do_migrate_range(pfn, end_pfn);
 718                 if (!ret) {
 719                         drain = 1;
 720                         goto repeat;
 721                 } else {
 722                         if (ret < 0)
 723                                 if (--retry_max == 0)
 724                                         goto failed_removal;
 725                         yield();
 726                         drain = 1;
 727                         goto repeat;
 728                 }
 729         }
 730         /* drain all zone's lru pagevec, this is asyncronous... */
 731         lru_add_drain_all();
 732         flush_scheduled_work();
 733         yield();
 734         /* drain pcp pages , this is synchrouns. */
 735         drain_all_pages();
 736         /* check again */
 737         offlined_pages = check_pages_isolated(start_pfn, end_pfn);
 738         if (offlined_pages < 0) {
 739                 ret = -EBUSY;
 740                 goto failed_removal;
 741         }
 742         printk(KERN_INFO "Offlined Pages %ld\n", offlined_pages);
 743         /* Ok, all of our target is islaoted.
 744            We cannot do rollback at this point. */
 745         offline_isolated_pages(start_pfn, end_pfn);
 746         /* reset pagetype flags and makes migrate type to be MOVABLE */
 747         undo_isolate_page_range(start_pfn, end_pfn);
 748         /* removal success */
 749         zone->present_pages -= offlined_pages;
 750         zone->zone_pgdat->node_present_pages -= offlined_pages;
 751         totalram_pages -= offlined_pages;
 752         num_physpages -= offlined_pages;
 753
 754         vm_total_pages = nr_free_pagecache_pages();
 755         writeback_set_ratelimit();
 756
 757         memory_notify(MEM_OFFLINE, &arg);
 758         return 0;
 759
 760 failed_removal:
 761         printk(KERN_INFO "memory offlining %lx to %lx failed\n",
 762                 start_pfn, end_pfn);
 763         memory_notify(MEM_CANCEL_OFFLINE, &arg);
 764         /* pushback to free area */
 765         undo_isolate_page_range(start_pfn, end_pfn);
 766
 767         return ret;
 768 }
 769 #else
 770 int remove_memory(u64 start, u64 size)
 771 {
 772         return -EINVAL;
 773 }
 774 EXPORT_SYMBOL_GPL(remove_memory);
 775 #endif /* CONFIG_MEMORY_HOTREMOVE */