drivers/base/memory.c

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