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/memory_hotplug.h>
  20 #include <linux/mm.h>
  21 #include <linux/mutex.h>
  22 #include <linux/stat.h>
  23 #include <linux/slab.h>
  24
  25 #include <linux/atomic.h>
  26 #include <asm/uaccess.h>
  27
  28 static DEFINE_MUTEX(mem_sysfs_mutex);
  29
  30 #define MEMORY_CLASS_NAME       "memory"
  31
  32 #define to_memory_block(dev) container_of(dev, struct memory_block, dev)
  33
  34 static int sections_per_block;
  35
  36 static inline int base_memory_block_id(int section_nr)
  37 {
  38         return section_nr / sections_per_block;
  39 }
  40
  41 static int memory_subsys_online(struct device *dev);
  42 static int memory_subsys_offline(struct device *dev);
  43
  44 static struct bus_type memory_subsys = {
  45         .name = MEMORY_CLASS_NAME,
  46         .dev_name = MEMORY_CLASS_NAME,
  47         .online = memory_subsys_online,
  48         .offline = memory_subsys_offline,
  49 };
  50
  51 static BLOCKING_NOTIFIER_HEAD(memory_chain);
  52
  53 int register_memory_notifier(struct notifier_block *nb)
  54 {
  55         return blocking_notifier_chain_register(&memory_chain, nb);
  56 }
  57 EXPORT_SYMBOL(register_memory_notifier);
  58
  59 void unregister_memory_notifier(struct notifier_block *nb)
  60 {
  61         blocking_notifier_chain_unregister(&memory_chain, nb);
  62 }
  63 EXPORT_SYMBOL(unregister_memory_notifier);
  64
  65 static ATOMIC_NOTIFIER_HEAD(memory_isolate_chain);
  66
  67 int register_memory_isolate_notifier(struct notifier_block *nb)
  68 {
  69         return atomic_notifier_chain_register(&memory_isolate_chain, nb);
  70 }
  71 EXPORT_SYMBOL(register_memory_isolate_notifier);
  72
  73 void unregister_memory_isolate_notifier(struct notifier_block *nb)
  74 {
  75         atomic_notifier_chain_unregister(&memory_isolate_chain, nb);
  76 }
  77 EXPORT_SYMBOL(unregister_memory_isolate_notifier);
  78
  79 static void memory_block_release(struct device *dev)
  80 {
  81         struct memory_block *mem = to_memory_block(dev);
  82
  83         kfree(mem);
  84 }
  85
  86 unsigned long __weak memory_block_size_bytes(void)
  87 {
  88         return MIN_MEMORY_BLOCK_SIZE;
  89 }
  90
  91 static unsigned long get_memory_block_size(void)
  92 {
  93         unsigned long block_sz;
  94
  95         block_sz = memory_block_size_bytes();
  96
  97         /* Validate blk_sz is a power of 2 and not less than section size */
  98         if ((block_sz & (block_sz - 1)) || (block_sz < MIN_MEMORY_BLOCK_SIZE)) {
  99                 WARN_ON(1);
 100                 block_sz = MIN_MEMORY_BLOCK_SIZE;
 101         }
 102
 103         return block_sz;
 104 }
 105
 106 /*
 107  * use this as the physical section index that this memsection
 108  * uses.
 109  */
 110
 111 static ssize_t show_mem_start_phys_index(struct device *dev,
 112                         struct device_attribute *attr, char *buf)
 113 {
 114         struct memory_block *mem = to_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 = to_memory_block(dev);
 125         unsigned long phys_index;
 126
 127         phys_index = mem->end_section_nr / sections_per_block;
 128         return sprintf(buf, "%08lx\n", phys_index);
 129 }
 130
 131 /*
 132  * Show whether the section of memory is likely to be hot-removable
 133  */
 134 static ssize_t show_mem_removable(struct device *dev,
 135                         struct device_attribute *attr, char *buf)
 136 {
 137         unsigned long i, pfn;
 138         int ret = 1;
 139         struct memory_block *mem = to_memory_block(dev);
 140
 141         for (i = 0; i < sections_per_block; i++) {
 142                 if (!present_section_nr(mem->start_section_nr + i))
 143                         continue;
 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 = to_memory_block(dev);
 158         ssize_t len = 0;
 159
 160         /*
 161          * We can probably put these states in a nice little array
 162          * so that they're not open-coded
 163          */
 164         switch (mem->state) {
 165                 case MEM_ONLINE:
 166                         len = sprintf(buf, "online\n");
 167                         break;
 168                 case MEM_OFFLINE:
 169                         len = sprintf(buf, "offline\n");
 170                         break;
 171                 case MEM_GOING_OFFLINE:
 172                         len = sprintf(buf, "going-offline\n");
 173                         break;
 174                 default:
 175                         len = sprintf(buf, "ERROR-UNKNOWN-%ld\n",
 176                                         mem->state);
 177                         WARN_ON(1);
 178                         break;
 179         }
 180
 181         return len;
 182 }
 183
 184 int memory_notify(unsigned long val, void *v)
 185 {
 186         return blocking_notifier_call_chain(&memory_chain, val, v);
 187 }
 188
 189 int memory_isolate_notify(unsigned long val, void *v)
 190 {
 191         return atomic_notifier_call_chain(&memory_isolate_chain, val, v);
 192 }
 193
 194 /*
 195  * The probe routines leave the pages reserved, just as the bootmem code does.
 196  * Make sure they're still that way.
 197  */
 198 static bool pages_correctly_reserved(unsigned long start_pfn)
 199 {
 200         int i, j;
 201         struct page *page;
 202         unsigned long pfn = start_pfn;
 203
 204         /*
 205          * memmap between sections is not contiguous except with
 206          * SPARSEMEM_VMEMMAP. We lookup the page once per section
 207          * and assume memmap is contiguous within each section
 208          */
 209         for (i = 0; i < sections_per_block; i++, pfn += PAGES_PER_SECTION) {
 210                 if (WARN_ON_ONCE(!pfn_valid(pfn)))
 211                         return false;
 212                 page = pfn_to_page(pfn);
 213
 214                 for (j = 0; j < PAGES_PER_SECTION; j++) {
 215                         if (PageReserved(page + j))
 216                                 continue;
 217
 218                         printk(KERN_WARNING "section number %ld page number %d "
 219                                 "not reserved, was it already online?\n",
 220                                 pfn_to_section_nr(pfn), j);
 221
 222                         return false;
 223                 }
 224         }
 225
 226         return true;
 227 }
 228
 229 /*
 230  * MEMORY_HOTPLUG depends on SPARSEMEM in mm/Kconfig, so it is
 231  * OK to have direct references to sparsemem variables in here.
 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         struct page *first_page;
 239         int ret;
 240
 241         first_page = pfn_to_page(phys_index << PFN_SECTION_SHIFT);
 242         start_pfn = page_to_pfn(first_page);
 243
 244         switch (action) {
 245                 case MEM_ONLINE:
 246                         if (!pages_correctly_reserved(start_pfn))
 247                                 return -EBUSY;
 248
 249                         ret = online_pages(start_pfn, nr_pages, online_type);
 250                         break;
 251                 case MEM_OFFLINE:
 252                         ret = offline_pages(start_pfn, nr_pages);
 253                         break;
 254                 default:
 255                         WARN(1, KERN_WARNING "%s(%ld, %ld) unknown action: "
 256                              "%ld\n", __func__, phys_index, action, action);
 257                         ret = -EINVAL;
 258         }
 259
 260         return ret;
 261 }
 262
 263 static int memory_block_change_state(struct memory_block *mem,
 264                 unsigned long to_state, unsigned long from_state_req)
 265 {
 266         int ret = 0;
 267
 268         if (mem->state != from_state_req)
 269                 return -EINVAL;
 270
 271         if (to_state == MEM_OFFLINE)
 272                 mem->state = MEM_GOING_OFFLINE;
 273
 274         ret = memory_block_action(mem->start_section_nr, to_state,
 275                                 mem->online_type);
 276
 277         mem->state = ret ? from_state_req : to_state;
 278
 279         return ret;
 280 }
 281
 282 /* The device lock serializes operations on memory_subsys_[online|offline] */
 283 static int memory_subsys_online(struct device *dev)
 284 {
 285         struct memory_block *mem = to_memory_block(dev);
 286         int ret;
 287
 288         if (mem->state == MEM_ONLINE)
 289                 return 0;
 290
 291         /*
 292          * If we are called from store_mem_state(), online_type will be
 293          * set >= 0 Otherwise we were called from the device online
 294          * attribute and need to set the online_type.
 295          */
 296         if (mem->online_type < 0)
 297                 mem->online_type = ONLINE_KEEP;
 298
 299         ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE);
 300
 301         /* clear online_type */
 302         mem->online_type = -1;
 303
 304         return ret;
 305 }
 306
 307 static int memory_subsys_offline(struct device *dev)
 308 {
 309         struct memory_block *mem = to_memory_block(dev);
 310
 311         if (mem->state == MEM_OFFLINE)
 312                 return 0;
 313
 314         return memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);
 315 }
 316
 317 static ssize_t
 318 store_mem_state(struct device *dev,
 319                 struct device_attribute *attr, const char *buf, size_t count)
 320 {
 321         struct memory_block *mem = to_memory_block(dev);
 322         int ret, online_type;
 323
 324         ret = lock_device_hotplug_sysfs();
 325         if (ret)
 326                 return ret;
 327
 328         if (!strncmp(buf, "online_kernel", min_t(int, count, 13)))
 329                 online_type = ONLINE_KERNEL;
 330         else if (!strncmp(buf, "online_movable", min_t(int, count, 14)))
 331                 online_type = ONLINE_MOVABLE;
 332         else if (!strncmp(buf, "online", min_t(int, count, 6)))
 333                 online_type = ONLINE_KEEP;
 334         else if (!strncmp(buf, "offline", min_t(int, count, 7)))
 335                 online_type = -1;
 336         else {
 337                 ret = -EINVAL;
 338                 goto err;
 339         }
 340
 341         switch (online_type) {
 342         case ONLINE_KERNEL:
 343         case ONLINE_MOVABLE:
 344         case ONLINE_KEEP:
 345                 /*
 346                  * mem->online_type is not protected so there can be a
 347                  * race here.  However, when racing online, the first
 348                  * will succeed and the second will just return as the
 349                  * block will already be online.  The online type
 350                  * could be either one, but that is expected.
 351                  */
 352                 mem->online_type = online_type;
 353                 ret = device_online(&mem->dev);
 354                 break;
 355         case -1:
 356                 ret = device_offline(&mem->dev);
 357                 break;
 358         default:
 359                 ret = -EINVAL; /* should never happen */
 360         }
 361
 362 err:
 363         unlock_device_hotplug();
 364
 365         if (ret)
 366                 return ret;
 367         return count;
 368 }
 369
 370 /*
 371  * phys_device is a bad name for this.  What I really want
 372  * is a way to differentiate between memory ranges that
 373  * are part of physical devices that constitute
 374  * a complete removable unit or fru.
 375  * i.e. do these ranges belong to the same physical device,
 376  * s.t. if I offline all of these sections I can then
 377  * remove the physical device?
 378  */
 379 static ssize_t show_phys_device(struct device *dev,
 380                                 struct device_attribute *attr, char *buf)
 381 {
 382         struct memory_block *mem = to_memory_block(dev);
 383         return sprintf(buf, "%d\n", mem->phys_device);
 384 }
 385
 386 static DEVICE_ATTR(phys_index, 0444, show_mem_start_phys_index, NULL);
 387 static DEVICE_ATTR(end_phys_index, 0444, show_mem_end_phys_index, NULL);
 388 static DEVICE_ATTR(state, 0644, show_mem_state, store_mem_state);
 389 static DEVICE_ATTR(phys_device, 0444, show_phys_device, NULL);
 390 static DEVICE_ATTR(removable, 0444, show_mem_removable, NULL);
 391
 392 /*
 393  * Block size attribute stuff
 394  */
 395 static ssize_t
 396 print_block_size(struct device *dev, struct device_attribute *attr,
 397                  char *buf)
 398 {
 399         return sprintf(buf, "%lx\n", get_memory_block_size());
 400 }
 401
 402 static DEVICE_ATTR(block_size_bytes, 0444, print_block_size, NULL);
 403
 404 /*
 405  * Some architectures will have custom drivers to do this, and
 406  * will not need to do it from userspace.  The fake hot-add code
 407  * as well as ppc64 will do all of their discovery in userspace
 408  * and will require this interface.
 409  */
 410 #ifdef CONFIG_ARCH_MEMORY_PROBE
 411 static ssize_t
 412 memory_probe_store(struct device *dev, struct device_attribute *attr,
 413                    const char *buf, size_t count)
 414 {
 415         u64 phys_addr;
 416         int nid;
 417         int i, ret;
 418         unsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block;
 419
 420         phys_addr = simple_strtoull(buf, NULL, 0);
 421
 422         if (phys_addr & ((pages_per_block << PAGE_SHIFT) - 1))
 423                 return -EINVAL;
 424
 425         for (i = 0; i < sections_per_block; i++) {
 426                 nid = memory_add_physaddr_to_nid(phys_addr);
 427                 ret = add_memory(nid, phys_addr,
 428                                  PAGES_PER_SECTION << PAGE_SHIFT);
 429                 if (ret)
 430                         goto out;
 431
 432                 phys_addr += MIN_MEMORY_BLOCK_SIZE;
 433         }
 434
 435         ret = count;
 436 out:
 437         return ret;
 438 }
 439
 440 static DEVICE_ATTR(probe, S_IWUSR, NULL, memory_probe_store);
 441 #endif
 442
 443 #ifdef CONFIG_MEMORY_FAILURE
 444 /*
 445  * Support for offlining pages of memory
 446  */
 447
 448 /* Soft offline a page */
 449 static ssize_t
 450 store_soft_offline_page(struct device *dev,
 451                         struct device_attribute *attr,
 452                         const char *buf, size_t count)
 453 {
 454         int ret;
 455         u64 pfn;
 456         if (!capable(CAP_SYS_ADMIN))
 457                 return -EPERM;
 458         if (kstrtoull(buf, 0, &pfn) < 0)
 459                 return -EINVAL;
 460         pfn >>= PAGE_SHIFT;
 461         if (!pfn_valid(pfn))
 462                 return -ENXIO;
 463         ret = soft_offline_page(pfn_to_page(pfn), 0);
 464         return ret == 0 ? count : ret;
 465 }
 466
 467 /* Forcibly offline a page, including killing processes. */
 468 static ssize_t
 469 store_hard_offline_page(struct device *dev,
 470                         struct device_attribute *attr,
 471                         const char *buf, size_t count)
 472 {
 473         int ret;
 474         u64 pfn;
 475         if (!capable(CAP_SYS_ADMIN))
 476                 return -EPERM;
 477         if (kstrtoull(buf, 0, &pfn) < 0)
 478                 return -EINVAL;
 479         pfn >>= PAGE_SHIFT;
 480         ret = memory_failure(pfn, 0, 0);
 481         return ret ? ret : count;
 482 }
 483
 484 static DEVICE_ATTR(soft_offline_page, S_IWUSR, NULL, store_soft_offline_page);
 485 static DEVICE_ATTR(hard_offline_page, S_IWUSR, NULL, store_hard_offline_page);
 486 #endif
 487
 488 /*
 489  * Note that phys_device is optional.  It is here to allow for
 490  * differentiation between which *physical* devices each
 491  * section belongs to...
 492  */
 493 int __weak arch_get_memory_phys_device(unsigned long start_pfn)
 494 {
 495         return 0;
 496 }
 497
 498 /*
 499  * A reference for the returned object is held and the reference for the
 500  * hinted object is released.
 501  */
 502 struct memory_block *find_memory_block_hinted(struct mem_section *section,
 503                                               struct memory_block *hint)
 504 {
 505         int block_id = base_memory_block_id(__section_nr(section));
 506         struct device *hintdev = hint ? &hint->dev : NULL;
 507         struct device *dev;
 508
 509         dev = subsys_find_device_by_id(&memory_subsys, block_id, hintdev);
 510         if (hint)
 511                 put_device(&hint->dev);
 512         if (!dev)
 513                 return NULL;
 514         return to_memory_block(dev);
 515 }
 516
 517 /*
 518  * For now, we have a linear search to go find the appropriate
 519  * memory_block corresponding to a particular phys_index. If
 520  * this gets to be a real problem, we can always use a radix
 521  * tree or something here.
 522  *
 523  * This could be made generic for all device subsystems.
 524  */
 525 struct memory_block *find_memory_block(struct mem_section *section)
 526 {
 527         return find_memory_block_hinted(section, NULL);
 528 }
 529
 530 static struct attribute *memory_memblk_attrs[] = {
 531         &dev_attr_phys_index.attr,
 532         &dev_attr_end_phys_index.attr,
 533         &dev_attr_state.attr,
 534         &dev_attr_phys_device.attr,
 535         &dev_attr_removable.attr,
 536         NULL
 537 };
 538
 539 static struct attribute_group memory_memblk_attr_group = {
 540         .attrs = memory_memblk_attrs,
 541 };
 542
 543 static const struct attribute_group *memory_memblk_attr_groups[] = {
 544         &memory_memblk_attr_group,
 545         NULL,
 546 };
 547
 548 /*
 549  * register_memory - Setup a sysfs device for a memory block
 550  */
 551 static
 552 int register_memory(struct memory_block *memory)
 553 {
 554         memory->dev.bus = &memory_subsys;
 555         memory->dev.id = memory->start_section_nr / sections_per_block;
 556         memory->dev.release = memory_block_release;
 557         memory->dev.groups = memory_memblk_attr_groups;
 558         memory->dev.offline = memory->state == MEM_OFFLINE;
 559
 560         return device_register(&memory->dev);
 561 }
 562
 563 static int init_memory_block(struct memory_block **memory,
 564                              struct mem_section *section, unsigned long state)
 565 {
 566         struct memory_block *mem;
 567         unsigned long start_pfn;
 568         int scn_nr;
 569         int ret = 0;
 570
 571         mem = kzalloc(sizeof(*mem), GFP_KERNEL);
 572         if (!mem)
 573                 return -ENOMEM;
 574
 575         scn_nr = __section_nr(section);
 576         mem->start_section_nr =
 577                         base_memory_block_id(scn_nr) * sections_per_block;
 578         mem->end_section_nr = mem->start_section_nr + sections_per_block - 1;
 579         mem->state = state;
 580         mem->section_count++;
 581         start_pfn = section_nr_to_pfn(mem->start_section_nr);
 582         mem->phys_device = arch_get_memory_phys_device(start_pfn);
 583
 584         ret = register_memory(mem);
 585
 586         *memory = mem;
 587         return ret;
 588 }
 589
 590 static int add_memory_block(int base_section_nr)
 591 {
 592         struct memory_block *mem;
 593         int i, ret, section_count = 0, section_nr;
 594
 595         for (i = base_section_nr;
 596              (i < base_section_nr + sections_per_block) && i < NR_MEM_SECTIONS;
 597              i++) {
 598                 if (!present_section_nr(i))
 599                         continue;
 600                 if (section_count == 0)
 601                         section_nr = i;
 602                 section_count++;
 603         }
 604
 605         if (section_count == 0)
 606                 return 0;
 607         ret = init_memory_block(&mem, __nr_to_section(section_nr), MEM_ONLINE);
 608         if (ret)
 609                 return ret;
 610         mem->section_count = section_count;
 611         return 0;
 612 }
 613
 614
 615 /*
 616  * need an interface for the VM to add new memory regions,
 617  * but without onlining it.
 618  */
 619 int register_new_memory(int nid, struct mem_section *section)
 620 {
 621         int ret = 0;
 622         struct memory_block *mem;
 623
 624         mutex_lock(&mem_sysfs_mutex);
 625
 626         mem = find_memory_block(section);
 627         if (mem) {
 628                 mem->section_count++;
 629                 put_device(&mem->dev);
 630         } else {
 631                 ret = init_memory_block(&mem, section, MEM_OFFLINE);
 632                 if (ret)
 633                         goto out;
 634         }
 635
 636         if (mem->section_count == sections_per_block)
 637                 ret = register_mem_sect_under_node(mem, nid);
 638 out:
 639         mutex_unlock(&mem_sysfs_mutex);
 640         return ret;
 641 }
 642
 643 #ifdef CONFIG_MEMORY_HOTREMOVE
 644 static void
 645 unregister_memory(struct memory_block *memory)
 646 {
 647         BUG_ON(memory->dev.bus != &memory_subsys);
 648
 649         /* drop the ref. we got in remove_memory_block() */
 650         put_device(&memory->dev);
 651         device_unregister(&memory->dev);
 652 }
 653
 654 static int remove_memory_block(unsigned long node_id,
 655                                struct mem_section *section, int phys_device)
 656 {
 657         struct memory_block *mem;
 658
 659         mutex_lock(&mem_sysfs_mutex);
 660         mem = find_memory_block(section);
 661         unregister_mem_sect_under_nodes(mem, __section_nr(section));
 662
 663         mem->section_count--;
 664         if (mem->section_count == 0)
 665                 unregister_memory(mem);
 666         else
 667                 put_device(&mem->dev);
 668
 669         mutex_unlock(&mem_sysfs_mutex);
 670         return 0;
 671 }
 672
 673 int unregister_memory_section(struct mem_section *section)
 674 {
 675         if (!present_section(section))
 676                 return -EINVAL;
 677
 678         return remove_memory_block(0, section, 0);
 679 }
 680 #endif /* CONFIG_MEMORY_HOTREMOVE */
 681
 682 /* return true if the memory block is offlined, otherwise, return false */
 683 bool is_memblock_offlined(struct memory_block *mem)
 684 {
 685         return mem->state == MEM_OFFLINE;
 686 }
 687
 688 static struct attribute *memory_root_attrs[] = {
 689 #ifdef CONFIG_ARCH_MEMORY_PROBE
 690         &dev_attr_probe.attr,
 691 #endif
 692
 693 #ifdef CONFIG_MEMORY_FAILURE
 694         &dev_attr_soft_offline_page.attr,
 695         &dev_attr_hard_offline_page.attr,
 696 #endif
 697
 698         &dev_attr_block_size_bytes.attr,
 699         NULL
 700 };
 701
 702 static struct attribute_group memory_root_attr_group = {
 703         .attrs = memory_root_attrs,
 704 };
 705
 706 static const struct attribute_group *memory_root_attr_groups[] = {
 707         &memory_root_attr_group,
 708         NULL,
 709 };
 710
 711 /*
 712  * Initialize the sysfs support for memory devices...
 713  */
 714 int __init memory_dev_init(void)
 715 {
 716         unsigned int i;
 717         int ret;
 718         int err;
 719         unsigned long block_sz;
 720
 721         ret = subsys_system_register(&memory_subsys, memory_root_attr_groups);
 722         if (ret)
 723                 goto out;
 724
 725         block_sz = get_memory_block_size();
 726         sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;
 727
 728         /*
 729          * Create entries for memory sections that were found
 730          * during boot and have been initialized
 731          */
 732         mutex_lock(&mem_sysfs_mutex);
 733         for (i = 0; i < NR_MEM_SECTIONS; i += sections_per_block) {
 734                 err = add_memory_block(i);
 735                 if (!ret)
 736                         ret = err;
 737         }
 738         mutex_unlock(&mem_sysfs_mutex);
 739
 740 out:
 741         if (ret)
 742                 printk(KERN_ERR "%s() failed: %d\n", __func__, ret);
 743         return ret;
 744 }