drivers/base/memory.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Memory subsystem support
   4  *
   5  * Written by Matt Tolentino <matthew.e.tolentino@intel.com>
   6  *            Dave Hansen <haveblue@us.ibm.com>
   7  *
   8  * This file provides the necessary infrastructure to represent
   9  * a SPARSEMEM-memory-model system's physical memory in /sysfs.
  10  * All arch-independent code that assumes MEMORY_HOTPLUG requires
  11  * SPARSEMEM should be contained here, or in mm/memory_hotplug.c.
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/init.h>
  16 #include <linux/topology.h>
  17 #include <linux/capability.h>
  18 #include <linux/device.h>
  19 #include <linux/memory.h>
  20 #include <linux/memory_hotplug.h>
  21 #include <linux/mm.h>
  22 #include <linux/mutex.h>
  23 #include <linux/stat.h>
  24 #include <linux/slab.h>
  25
  26 #include <linux/atomic.h>
  27 #include <linux/uaccess.h>
  28
  29 static DEFINE_MUTEX(mem_sysfs_mutex);
  30
  31 #define MEMORY_CLASS_NAME       "memory"
  32
  33 #define to_memory_block(dev) container_of(dev, struct memory_block, dev)
  34
  35 static int sections_per_block;
  36
  37 static inline int base_memory_block_id(int section_nr)
  38 {
  39         return section_nr / sections_per_block;
  40 }
  41
  42 static int memory_subsys_online(struct device *dev);
  43 static int memory_subsys_offline(struct device *dev);
  44
  45 static struct bus_type memory_subsys = {
  46         .name = MEMORY_CLASS_NAME,
  47         .dev_name = MEMORY_CLASS_NAME,
  48         .online = memory_subsys_online,
  49         .offline = memory_subsys_offline,
  50 };
  51
  52 static BLOCKING_NOTIFIER_HEAD(memory_chain);
  53
  54 int register_memory_notifier(struct notifier_block *nb)
  55 {
  56         return blocking_notifier_chain_register(&memory_chain, nb);
  57 }
  58 EXPORT_SYMBOL(register_memory_notifier);
  59
  60 void unregister_memory_notifier(struct notifier_block *nb)
  61 {
  62         blocking_notifier_chain_unregister(&memory_chain, nb);
  63 }
  64 EXPORT_SYMBOL(unregister_memory_notifier);
  65
  66 static ATOMIC_NOTIFIER_HEAD(memory_isolate_chain);
  67
  68 int register_memory_isolate_notifier(struct notifier_block *nb)
  69 {
  70         return atomic_notifier_chain_register(&memory_isolate_chain, nb);
  71 }
  72 EXPORT_SYMBOL(register_memory_isolate_notifier);
  73
  74 void unregister_memory_isolate_notifier(struct notifier_block *nb)
  75 {
  76         atomic_notifier_chain_unregister(&memory_isolate_chain, nb);
  77 }
  78 EXPORT_SYMBOL(unregister_memory_isolate_notifier);
  79
  80 static void memory_block_release(struct device *dev)
  81 {
  82         struct memory_block *mem = to_memory_block(dev);
  83
  84         kfree(mem);
  85 }
  86
  87 unsigned long __weak memory_block_size_bytes(void)
  88 {
  89         return MIN_MEMORY_BLOCK_SIZE;
  90 }
  91
  92 static unsigned long get_memory_block_size(void)
  93 {
  94         unsigned long block_sz;
  95
  96         block_sz = memory_block_size_bytes();
  97
  98         /* Validate blk_sz is a power of 2 and not less than section size */
  99         if ((block_sz & (block_sz - 1)) || (block_sz < MIN_MEMORY_BLOCK_SIZE)) {
 100                 WARN_ON(1);
 101                 block_sz = MIN_MEMORY_BLOCK_SIZE;
 102         }
 103
 104         return block_sz;
 105 }
 106
 107 /*
 108  * use this as the physical section index that this memsection
 109  * uses.
 110  */
 111
 112 static ssize_t show_mem_start_phys_index(struct device *dev,
 113                         struct device_attribute *attr, char *buf)
 114 {
 115         struct memory_block *mem = to_memory_block(dev);
 116         unsigned long phys_index;
 117
 118         phys_index = mem->start_section_nr / sections_per_block;
 119         return sprintf(buf, "%08lx\n", phys_index);
 120 }
 121
 122 /*
 123  * Show whether the section of memory is likely to be hot-removable
 124  */
 125 static ssize_t show_mem_removable(struct device *dev,
 126                         struct device_attribute *attr, char *buf)
 127 {
 128         unsigned long i, pfn;
 129         int ret = 1;
 130         struct memory_block *mem = to_memory_block(dev);
 131
 132         if (mem->state != MEM_ONLINE)
 133                 goto out;
 134
 135         for (i = 0; i < sections_per_block; i++) {
 136                 if (!present_section_nr(mem->start_section_nr + i))
 137                         continue;
 138                 pfn = section_nr_to_pfn(mem->start_section_nr + i);
 139                 ret &= is_mem_section_removable(pfn, PAGES_PER_SECTION);
 140         }
 141
 142 out:
 143         return sprintf(buf, "%d\n", ret);
 144 }
 145
 146 /*
 147  * online, offline, going offline, etc.
 148  */
 149 static ssize_t show_mem_state(struct device *dev,
 150                         struct device_attribute *attr, char *buf)
 151 {
 152         struct memory_block *mem = to_memory_block(dev);
 153         ssize_t len = 0;
 154
 155         /*
 156          * We can probably put these states in a nice little array
 157          * so that they're not open-coded
 158          */
 159         switch (mem->state) {
 160         case MEM_ONLINE:
 161                 len = sprintf(buf, "online\n");
 162                 break;
 163         case MEM_OFFLINE:
 164                 len = sprintf(buf, "offline\n");
 165                 break;
 166         case MEM_GOING_OFFLINE:
 167                 len = sprintf(buf, "going-offline\n");
 168                 break;
 169         default:
 170                 len = sprintf(buf, "ERROR-UNKNOWN-%ld\n",
 171                                 mem->state);
 172                 WARN_ON(1);
 173                 break;
 174         }
 175
 176         return len;
 177 }
 178
 179 int memory_notify(unsigned long val, void *v)
 180 {
 181         return blocking_notifier_call_chain(&memory_chain, val, v);
 182 }
 183
 184 int memory_isolate_notify(unsigned long val, void *v)
 185 {
 186         return atomic_notifier_call_chain(&memory_isolate_chain, val, v);
 187 }
 188
 189 /*
 190  * The probe routines leave the pages uninitialized, just as the bootmem code
 191  * does. Make sure we do not access them, but instead use only information from
 192  * within sections.
 193  */
 194 static bool pages_correctly_probed(unsigned long start_pfn)
 195 {
 196         unsigned long section_nr = pfn_to_section_nr(start_pfn);
 197         unsigned long section_nr_end = section_nr + sections_per_block;
 198         unsigned long pfn = start_pfn;
 199
 200         /*
 201          * memmap between sections is not contiguous except with
 202          * SPARSEMEM_VMEMMAP. We lookup the page once per section
 203          * and assume memmap is contiguous within each section
 204          */
 205         for (; section_nr < section_nr_end; section_nr++) {
 206                 if (WARN_ON_ONCE(!pfn_valid(pfn)))
 207                         return false;
 208
 209                 if (!present_section_nr(section_nr)) {
 210                         pr_warn("section %ld pfn[%lx, %lx) not present",
 211                                 section_nr, pfn, pfn + PAGES_PER_SECTION);
 212                         return false;
 213                 } else if (!valid_section_nr(section_nr)) {
 214                         pr_warn("section %ld pfn[%lx, %lx) no valid memmap",
 215                                 section_nr, pfn, pfn + PAGES_PER_SECTION);
 216                         return false;
 217                 } else if (online_section_nr(section_nr)) {
 218                         pr_warn("section %ld pfn[%lx, %lx) is already online",
 219                                 section_nr, pfn, pfn + PAGES_PER_SECTION);
 220                         return false;
 221                 }
 222                 pfn += PAGES_PER_SECTION;
 223         }
 224
 225         return true;
 226 }
 227
 228 /*
 229  * MEMORY_HOTPLUG depends on SPARSEMEM in mm/Kconfig, so it is
 230  * OK to have direct references to sparsemem variables in here.
 231  * Must already be protected by mem_hotplug_begin().
 232  */
 233 static int
 234 memory_block_action(unsigned long phys_index, unsigned long action, int online_type)
 235 {
 236         unsigned long start_pfn;
 237         unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
 238         int ret;
 239
 240         start_pfn = section_nr_to_pfn(phys_index);
 241
 242         switch (action) {
 243         case MEM_ONLINE:
 244                 if (!pages_correctly_probed(start_pfn))
 245                         return -EBUSY;
 246
 247                 ret = online_pages(start_pfn, nr_pages, online_type);
 248                 break;
 249         case MEM_OFFLINE:
 250                 ret = offline_pages(start_pfn, nr_pages);
 251                 break;
 252         default:
 253                 WARN(1, KERN_WARNING "%s(%ld, %ld) unknown action: "
 254                      "%ld\n", __func__, phys_index, action, action);
 255                 ret = -EINVAL;
 256         }
 257
 258         return ret;
 259 }
 260
 261 static int memory_block_change_state(struct memory_block *mem,
 262                 unsigned long to_state, unsigned long from_state_req)
 263 {
 264         int ret = 0;
 265
 266         if (mem->state != from_state_req)
 267                 return -EINVAL;
 268
 269         if (to_state == MEM_OFFLINE)
 270                 mem->state = MEM_GOING_OFFLINE;
 271
 272         ret = memory_block_action(mem->start_section_nr, to_state,
 273                                 mem->online_type);
 274
 275         mem->state = ret ? from_state_req : to_state;
 276
 277         return ret;
 278 }
 279
 280 /* The device lock serializes operations on memory_subsys_[online|offline] */
 281 static int memory_subsys_online(struct device *dev)
 282 {
 283         struct memory_block *mem = to_memory_block(dev);
 284         int ret;
 285
 286         if (mem->state == MEM_ONLINE)
 287                 return 0;
 288
 289         /*
 290          * If we are called from store_mem_state(), online_type will be
 291          * set >= 0 Otherwise we were called from the device online
 292          * attribute and need to set the online_type.
 293          */
 294         if (mem->online_type < 0)
 295                 mem->online_type = MMOP_ONLINE_KEEP;
 296
 297         /* Already under protection of mem_hotplug_begin() */
 298         ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE);
 299
 300         /* clear online_type */
 301         mem->online_type = -1;
 302
 303         return ret;
 304 }
 305
 306 static int memory_subsys_offline(struct device *dev)
 307 {
 308         struct memory_block *mem = to_memory_block(dev);
 309
 310         if (mem->state == MEM_OFFLINE)
 311                 return 0;
 312
 313         /* Can't offline block with non-present sections */
 314         if (mem->section_count != sections_per_block)
 315                 return -EINVAL;
 316
 317         return memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);
 318 }
 319
 320 static ssize_t
 321 store_mem_state(struct device *dev,
 322                 struct device_attribute *attr, const char *buf, size_t count)
 323 {
 324         struct memory_block *mem = to_memory_block(dev);
 325         int ret, online_type;
 326
 327         ret = lock_device_hotplug_sysfs();
 328         if (ret)
 329                 return ret;
 330
 331         if (sysfs_streq(buf, "online_kernel"))
 332                 online_type = MMOP_ONLINE_KERNEL;
 333         else if (sysfs_streq(buf, "online_movable"))
 334                 online_type = MMOP_ONLINE_MOVABLE;
 335         else if (sysfs_streq(buf, "online"))
 336                 online_type = MMOP_ONLINE_KEEP;
 337         else if (sysfs_streq(buf, "offline"))
 338                 online_type = MMOP_OFFLINE;
 339         else {
 340                 ret = -EINVAL;
 341                 goto err;
 342         }
 343
 344         /*
 345          * Memory hotplug needs to hold mem_hotplug_begin() for probe to find
 346          * the correct memory block to online before doing device_online(dev),
 347          * which will take dev->mutex.  Take the lock early to prevent an
 348          * inversion, memory_subsys_online() callbacks will be implemented by
 349          * assuming it's already protected.
 350          */
 351         mem_hotplug_begin();
 352
 353         switch (online_type) {
 354         case MMOP_ONLINE_KERNEL:
 355         case MMOP_ONLINE_MOVABLE:
 356         case MMOP_ONLINE_KEEP:
 357                 mem->online_type = online_type;
 358                 ret = device_online(&mem->dev);
 359                 break;
 360         case MMOP_OFFLINE:
 361                 ret = device_offline(&mem->dev);
 362                 break;
 363         default:
 364                 ret = -EINVAL; /* should never happen */
 365         }
 366
 367         mem_hotplug_done();
 368 err:
 369         unlock_device_hotplug();
 370
 371         if (ret < 0)
 372                 return ret;
 373         if (ret)
 374                 return -EINVAL;
 375
 376         return count;
 377 }
 378
 379 /*
 380  * phys_device is a bad name for this.  What I really want
 381  * is a way to differentiate between memory ranges that
 382  * are part of physical devices that constitute
 383  * a complete removable unit or fru.
 384  * i.e. do these ranges belong to the same physical device,
 385  * s.t. if I offline all of these sections I can then
 386  * remove the physical device?
 387  */
 388 static ssize_t show_phys_device(struct device *dev,
 389                                 struct device_attribute *attr, char *buf)
 390 {
 391         struct memory_block *mem = to_memory_block(dev);
 392         return sprintf(buf, "%d\n", mem->phys_device);
 393 }
 394
 395 #ifdef CONFIG_MEMORY_HOTREMOVE
 396 static void print_allowed_zone(char *buf, int nid, unsigned long start_pfn,
 397                 unsigned long nr_pages, int online_type,
 398                 struct zone *default_zone)
 399 {
 400         struct zone *zone;
 401
 402         zone = zone_for_pfn_range(online_type, nid, start_pfn, nr_pages);
 403         if (zone != default_zone) {
 404                 strcat(buf, " ");
 405                 strcat(buf, zone->name);
 406         }
 407 }
 408
 409 static ssize_t show_valid_zones(struct device *dev,
 410                                 struct device_attribute *attr, char *buf)
 411 {
 412         struct memory_block *mem = to_memory_block(dev);
 413         unsigned long start_pfn = section_nr_to_pfn(mem->start_section_nr);
 414         unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
 415         unsigned long valid_start_pfn, valid_end_pfn;
 416         struct zone *default_zone;
 417         int nid;
 418
 419         /*
 420          * Check the existing zone. Make sure that we do that only on the
 421          * online nodes otherwise the page_zone is not reliable
 422          */
 423         if (mem->state == MEM_ONLINE) {
 424                 /*
 425                  * The block contains more than one zone can not be offlined.
 426                  * This can happen e.g. for ZONE_DMA and ZONE_DMA32
 427                  */
 428                 if (!test_pages_in_a_zone(start_pfn, start_pfn + nr_pages,
 429                                           &valid_start_pfn, &valid_end_pfn))
 430                         return sprintf(buf, "none\n");
 431                 start_pfn = valid_start_pfn;
 432                 strcat(buf, page_zone(pfn_to_page(start_pfn))->name);
 433                 goto out;
 434         }
 435
 436         nid = mem->nid;
 437         default_zone = zone_for_pfn_range(MMOP_ONLINE_KEEP, nid, start_pfn, nr_pages);
 438         strcat(buf, default_zone->name);
 439
 440         print_allowed_zone(buf, nid, start_pfn, nr_pages, MMOP_ONLINE_KERNEL,
 441                         default_zone);
 442         print_allowed_zone(buf, nid, start_pfn, nr_pages, MMOP_ONLINE_MOVABLE,
 443                         default_zone);
 444 out:
 445         strcat(buf, "\n");
 446
 447         return strlen(buf);
 448 }
 449 static DEVICE_ATTR(valid_zones, 0444, show_valid_zones, NULL);
 450 #endif
 451
 452 static DEVICE_ATTR(phys_index, 0444, show_mem_start_phys_index, NULL);
 453 static DEVICE_ATTR(state, 0644, show_mem_state, store_mem_state);
 454 static DEVICE_ATTR(phys_device, 0444, show_phys_device, NULL);
 455 static DEVICE_ATTR(removable, 0444, show_mem_removable, NULL);
 456
 457 /*
 458  * Block size attribute stuff
 459  */
 460 static ssize_t
 461 print_block_size(struct device *dev, struct device_attribute *attr,
 462                  char *buf)
 463 {
 464         return sprintf(buf, "%lx\n", get_memory_block_size());
 465 }
 466
 467 static DEVICE_ATTR(block_size_bytes, 0444, print_block_size, NULL);
 468
 469 /*
 470  * Memory auto online policy.
 471  */
 472
 473 static ssize_t
 474 show_auto_online_blocks(struct device *dev, struct device_attribute *attr,
 475                         char *buf)
 476 {
 477         if (memhp_auto_online)
 478                 return sprintf(buf, "online\n");
 479         else
 480                 return sprintf(buf, "offline\n");
 481 }
 482
 483 static ssize_t
 484 store_auto_online_blocks(struct device *dev, struct device_attribute *attr,
 485                          const char *buf, size_t count)
 486 {
 487         if (sysfs_streq(buf, "online"))
 488                 memhp_auto_online = true;
 489         else if (sysfs_streq(buf, "offline"))
 490                 memhp_auto_online = false;
 491         else
 492                 return -EINVAL;
 493
 494         return count;
 495 }
 496
 497 static DEVICE_ATTR(auto_online_blocks, 0644, show_auto_online_blocks,
 498                    store_auto_online_blocks);
 499
 500 /*
 501  * Some architectures will have custom drivers to do this, and
 502  * will not need to do it from userspace.  The fake hot-add code
 503  * as well as ppc64 will do all of their discovery in userspace
 504  * and will require this interface.
 505  */
 506 #ifdef CONFIG_ARCH_MEMORY_PROBE
 507 static ssize_t
 508 memory_probe_store(struct device *dev, struct device_attribute *attr,
 509                    const char *buf, size_t count)
 510 {
 511         u64 phys_addr;
 512         int nid, ret;
 513         unsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block;
 514
 515         ret = kstrtoull(buf, 0, &phys_addr);
 516         if (ret)
 517                 return ret;
 518
 519         if (phys_addr & ((pages_per_block << PAGE_SHIFT) - 1))
 520                 return -EINVAL;
 521
 522         nid = memory_add_physaddr_to_nid(phys_addr);
 523         ret = add_memory(nid, phys_addr,
 524                          MIN_MEMORY_BLOCK_SIZE * sections_per_block);
 525
 526         if (ret)
 527                 goto out;
 528
 529         ret = count;
 530 out:
 531         return ret;
 532 }
 533
 534 static DEVICE_ATTR(probe, S_IWUSR, NULL, memory_probe_store);
 535 #endif
 536
 537 #ifdef CONFIG_MEMORY_FAILURE
 538 /*
 539  * Support for offlining pages of memory
 540  */
 541
 542 /* Soft offline a page */
 543 static ssize_t
 544 store_soft_offline_page(struct device *dev,
 545                         struct device_attribute *attr,
 546                         const char *buf, size_t count)
 547 {
 548         int ret;
 549         u64 pfn;
 550         if (!capable(CAP_SYS_ADMIN))
 551                 return -EPERM;
 552         if (kstrtoull(buf, 0, &pfn) < 0)
 553                 return -EINVAL;
 554         pfn >>= PAGE_SHIFT;
 555         if (!pfn_valid(pfn))
 556                 return -ENXIO;
 557         ret = soft_offline_page(pfn_to_page(pfn), 0);
 558         return ret == 0 ? count : ret;
 559 }
 560
 561 /* Forcibly offline a page, including killing processes. */
 562 static ssize_t
 563 store_hard_offline_page(struct device *dev,
 564                         struct device_attribute *attr,
 565                         const char *buf, size_t count)
 566 {
 567         int ret;
 568         u64 pfn;
 569         if (!capable(CAP_SYS_ADMIN))
 570                 return -EPERM;
 571         if (kstrtoull(buf, 0, &pfn) < 0)
 572                 return -EINVAL;
 573         pfn >>= PAGE_SHIFT;
 574         ret = memory_failure(pfn, 0);
 575         return ret ? ret : count;
 576 }
 577
 578 static DEVICE_ATTR(soft_offline_page, S_IWUSR, NULL, store_soft_offline_page);
 579 static DEVICE_ATTR(hard_offline_page, S_IWUSR, NULL, store_hard_offline_page);
 580 #endif
 581
 582 /*
 583  * Note that phys_device is optional.  It is here to allow for
 584  * differentiation between which *physical* devices each
 585  * section belongs to...
 586  */
 587 int __weak arch_get_memory_phys_device(unsigned long start_pfn)
 588 {
 589         return 0;
 590 }
 591
 592 /*
 593  * A reference for the returned object is held and the reference for the
 594  * hinted object is released.
 595  */
 596 struct memory_block *find_memory_block_hinted(struct mem_section *section,
 597                                               struct memory_block *hint)
 598 {
 599         int block_id = base_memory_block_id(__section_nr(section));
 600         struct device *hintdev = hint ? &hint->dev : NULL;
 601         struct device *dev;
 602
 603         dev = subsys_find_device_by_id(&memory_subsys, block_id, hintdev);
 604         if (hint)
 605                 put_device(&hint->dev);
 606         if (!dev)
 607                 return NULL;
 608         return to_memory_block(dev);
 609 }
 610
 611 /*
 612  * For now, we have a linear search to go find the appropriate
 613  * memory_block corresponding to a particular phys_index. If
 614  * this gets to be a real problem, we can always use a radix
 615  * tree or something here.
 616  *
 617  * This could be made generic for all device subsystems.
 618  */
 619 struct memory_block *find_memory_block(struct mem_section *section)
 620 {
 621         return find_memory_block_hinted(section, NULL);
 622 }
 623
 624 static struct attribute *memory_memblk_attrs[] = {
 625         &dev_attr_phys_index.attr,
 626         &dev_attr_state.attr,
 627         &dev_attr_phys_device.attr,
 628         &dev_attr_removable.attr,
 629 #ifdef CONFIG_MEMORY_HOTREMOVE
 630         &dev_attr_valid_zones.attr,
 631 #endif
 632         NULL
 633 };
 634
 635 static struct attribute_group memory_memblk_attr_group = {
 636         .attrs = memory_memblk_attrs,
 637 };
 638
 639 static const struct attribute_group *memory_memblk_attr_groups[] = {
 640         &memory_memblk_attr_group,
 641         NULL,
 642 };
 643
 644 /*
 645  * register_memory - Setup a sysfs device for a memory block
 646  */
 647 static
 648 int register_memory(struct memory_block *memory)
 649 {
 650         int ret;
 651
 652         memory->dev.bus = &memory_subsys;
 653         memory->dev.id = memory->start_section_nr / sections_per_block;
 654         memory->dev.release = memory_block_release;
 655         memory->dev.groups = memory_memblk_attr_groups;
 656         memory->dev.offline = memory->state == MEM_OFFLINE;
 657
 658         ret = device_register(&memory->dev);
 659         if (ret)
 660                 put_device(&memory->dev);
 661
 662         return ret;
 663 }
 664
 665 static int init_memory_block(struct memory_block **memory,
 666                              struct mem_section *section, unsigned long state)
 667 {
 668         struct memory_block *mem;
 669         unsigned long start_pfn;
 670         int scn_nr;
 671         int ret = 0;
 672
 673         mem = kzalloc(sizeof(*mem), GFP_KERNEL);
 674         if (!mem)
 675                 return -ENOMEM;
 676
 677         scn_nr = __section_nr(section);
 678         mem->start_section_nr =
 679                         base_memory_block_id(scn_nr) * sections_per_block;
 680         mem->end_section_nr = mem->start_section_nr + sections_per_block - 1;
 681         mem->state = state;
 682         start_pfn = section_nr_to_pfn(mem->start_section_nr);
 683         mem->phys_device = arch_get_memory_phys_device(start_pfn);
 684
 685         ret = register_memory(mem);
 686
 687         *memory = mem;
 688         return ret;
 689 }
 690
 691 static int add_memory_block(int base_section_nr)
 692 {
 693         struct memory_block *mem;
 694         int i, ret, section_count = 0, section_nr;
 695
 696         for (i = base_section_nr;
 697              (i < base_section_nr + sections_per_block) && i < NR_MEM_SECTIONS;
 698              i++) {
 699                 if (!present_section_nr(i))
 700                         continue;
 701                 if (section_count == 0)
 702                         section_nr = i;
 703                 section_count++;
 704         }
 705
 706         if (section_count == 0)
 707                 return 0;
 708         ret = init_memory_block(&mem, __nr_to_section(section_nr), MEM_ONLINE);
 709         if (ret)
 710                 return ret;
 711         mem->section_count = section_count;
 712         return 0;
 713 }
 714
 715 /*
 716  * need an interface for the VM to add new memory regions,
 717  * but without onlining it.
 718  */
 719 int hotplug_memory_register(int nid, struct mem_section *section)
 720 {
 721         int ret = 0;
 722         struct memory_block *mem;
 723
 724         mutex_lock(&mem_sysfs_mutex);
 725
 726         mem = find_memory_block(section);
 727         if (mem) {
 728                 mem->section_count++;
 729                 put_device(&mem->dev);
 730         } else {
 731                 ret = init_memory_block(&mem, section, MEM_OFFLINE);
 732                 if (ret)
 733                         goto out;
 734                 mem->section_count++;
 735         }
 736
 737 out:
 738         mutex_unlock(&mem_sysfs_mutex);
 739         return ret;
 740 }
 741
 742 #ifdef CONFIG_MEMORY_HOTREMOVE
 743 static void
 744 unregister_memory(struct memory_block *memory)
 745 {
 746         BUG_ON(memory->dev.bus != &memory_subsys);
 747
 748         /* drop the ref. we got in remove_memory_block() */
 749         put_device(&memory->dev);
 750         device_unregister(&memory->dev);
 751 }
 752
 753 static int remove_memory_section(unsigned long node_id,
 754                                struct mem_section *section, int phys_device)
 755 {
 756         struct memory_block *mem;
 757
 758         mutex_lock(&mem_sysfs_mutex);
 759
 760         /*
 761          * Some users of the memory hotplug do not want/need memblock to
 762          * track all sections. Skip over those.
 763          */
 764         mem = find_memory_block(section);
 765         if (!mem)
 766                 goto out_unlock;
 767
 768         unregister_mem_sect_under_nodes(mem, __section_nr(section));
 769
 770         mem->section_count--;
 771         if (mem->section_count == 0)
 772                 unregister_memory(mem);
 773         else
 774                 put_device(&mem->dev);
 775
 776 out_unlock:
 777         mutex_unlock(&mem_sysfs_mutex);
 778         return 0;
 779 }
 780
 781 int unregister_memory_section(struct mem_section *section)
 782 {
 783         if (!present_section(section))
 784                 return -EINVAL;
 785
 786         return remove_memory_section(0, section, 0);
 787 }
 788 #endif /* CONFIG_MEMORY_HOTREMOVE */
 789
 790 /* return true if the memory block is offlined, otherwise, return false */
 791 bool is_memblock_offlined(struct memory_block *mem)
 792 {
 793         return mem->state == MEM_OFFLINE;
 794 }
 795
 796 static struct attribute *memory_root_attrs[] = {
 797 #ifdef CONFIG_ARCH_MEMORY_PROBE
 798         &dev_attr_probe.attr,
 799 #endif
 800
 801 #ifdef CONFIG_MEMORY_FAILURE
 802         &dev_attr_soft_offline_page.attr,
 803         &dev_attr_hard_offline_page.attr,
 804 #endif
 805
 806         &dev_attr_block_size_bytes.attr,
 807         &dev_attr_auto_online_blocks.attr,
 808         NULL
 809 };
 810
 811 static struct attribute_group memory_root_attr_group = {
 812         .attrs = memory_root_attrs,
 813 };
 814
 815 static const struct attribute_group *memory_root_attr_groups[] = {
 816         &memory_root_attr_group,
 817         NULL,
 818 };
 819
 820 /*
 821  * Initialize the sysfs support for memory devices...
 822  */
 823 int __init memory_dev_init(void)
 824 {
 825         unsigned int i;
 826         int ret;
 827         int err;
 828         unsigned long block_sz;
 829
 830         ret = subsys_system_register(&memory_subsys, memory_root_attr_groups);
 831         if (ret)
 832                 goto out;
 833
 834         block_sz = get_memory_block_size();
 835         sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;
 836
 837         /*
 838          * Create entries for memory sections that were found
 839          * during boot and have been initialized
 840          */
 841         mutex_lock(&mem_sysfs_mutex);
 842         for (i = 0; i <= __highest_present_section_nr;
 843                 i += sections_per_block) {
 844                 err = add_memory_block(i);
 845                 if (!ret)
 846                         ret = err;
 847         }
 848         mutex_unlock(&mem_sysfs_mutex);
 849
 850 out:
 851         if (ret)
 852                 printk(KERN_ERR "%s() failed: %d\n", __func__, ret);
 853         return ret;
 854 }