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