drivers/base/node.c

   1 /*
   2  * drivers/base/node.c - basic Node class support
   3  */
   4
   5 #include <linux/sysdev.h>
   6 #include <linux/module.h>
   7 #include <linux/init.h>
   8 #include <linux/mm.h>
   9 #include <linux/memory.h>
  10 #include <linux/node.h>
  11 #include <linux/hugetlb.h>
  12 #include <linux/compaction.h>
  13 #include <linux/cpumask.h>
  14 #include <linux/topology.h>
  15 #include <linux/nodemask.h>
  16 #include <linux/cpu.h>
  17 #include <linux/device.h>
  18 #include <linux/swap.h>
  19 #include <linux/slab.h>
  20
  21 static struct sysdev_class_attribute *node_state_attrs[];
  22
  23 static struct sysdev_class node_class = {
  24         .name = "node",
  25         .attrs = node_state_attrs,
  26 };
  27
  28
  29 static ssize_t node_read_cpumap(struct sys_device *dev, int type, char *buf)
  30 {
  31         struct node *node_dev = to_node(dev);
  32         const struct cpumask *mask = cpumask_of_node(node_dev->sysdev.id);
  33         int len;
  34
  35         /* 2008/04/07: buf currently PAGE_SIZE, need 9 chars per 32 bits. */
  36         BUILD_BUG_ON((NR_CPUS/32 * 9) > (PAGE_SIZE-1));
  37
  38         len = type?
  39                 cpulist_scnprintf(buf, PAGE_SIZE-2, mask) :
  40                 cpumask_scnprintf(buf, PAGE_SIZE-2, mask);
  41         buf[len++] = '\n';
  42         buf[len] = '\0';
  43         return len;
  44 }
  45
  46 static inline ssize_t node_read_cpumask(struct sys_device *dev,
  47                                 struct sysdev_attribute *attr, char *buf)
  48 {
  49         return node_read_cpumap(dev, 0, buf);
  50 }
  51 static inline ssize_t node_read_cpulist(struct sys_device *dev,
  52                                 struct sysdev_attribute *attr, char *buf)
  53 {
  54         return node_read_cpumap(dev, 1, buf);
  55 }
  56
  57 static SYSDEV_ATTR(cpumap,  S_IRUGO, node_read_cpumask, NULL);
  58 static SYSDEV_ATTR(cpulist, S_IRUGO, node_read_cpulist, NULL);
  59
  60 #define K(x) ((x) << (PAGE_SHIFT - 10))
  61 static ssize_t node_read_meminfo(struct sys_device * dev,
  62                         struct sysdev_attribute *attr, char * buf)
  63 {
  64         int n;
  65         int nid = dev->id;
  66         struct sysinfo i;
  67
  68         si_meminfo_node(&i, nid);
  69         n = sprintf(buf,
  70                        "Node %d MemTotal:       %8lu kB\n"
  71                        "Node %d MemFree:        %8lu kB\n"
  72                        "Node %d MemUsed:        %8lu kB\n"
  73                        "Node %d Active:         %8lu kB\n"
  74                        "Node %d Inactive:       %8lu kB\n"
  75                        "Node %d Active(anon):   %8lu kB\n"
  76                        "Node %d Inactive(anon): %8lu kB\n"
  77                        "Node %d Active(file):   %8lu kB\n"
  78                        "Node %d Inactive(file): %8lu kB\n"
  79                        "Node %d Unevictable:    %8lu kB\n"
  80                        "Node %d Mlocked:        %8lu kB\n",
  81                        nid, K(i.totalram),
  82                        nid, K(i.freeram),
  83                        nid, K(i.totalram - i.freeram),
  84                        nid, K(node_page_state(nid, NR_ACTIVE_ANON) +
  85                                 node_page_state(nid, NR_ACTIVE_FILE)),
  86                        nid, K(node_page_state(nid, NR_INACTIVE_ANON) +
  87                                 node_page_state(nid, NR_INACTIVE_FILE)),
  88                        nid, K(node_page_state(nid, NR_ACTIVE_ANON)),
  89                        nid, K(node_page_state(nid, NR_INACTIVE_ANON)),
  90                        nid, K(node_page_state(nid, NR_ACTIVE_FILE)),
  91                        nid, K(node_page_state(nid, NR_INACTIVE_FILE)),
  92                        nid, K(node_page_state(nid, NR_UNEVICTABLE)),
  93                        nid, K(node_page_state(nid, NR_MLOCK)));
  94
  95 #ifdef CONFIG_HIGHMEM
  96         n += sprintf(buf + n,
  97                        "Node %d HighTotal:      %8lu kB\n"
  98                        "Node %d HighFree:       %8lu kB\n"
  99                        "Node %d LowTotal:       %8lu kB\n"
 100                        "Node %d LowFree:        %8lu kB\n",
 101                        nid, K(i.totalhigh),
 102                        nid, K(i.freehigh),
 103                        nid, K(i.totalram - i.totalhigh),
 104                        nid, K(i.freeram - i.freehigh));
 105 #endif
 106         n += sprintf(buf + n,
 107                        "Node %d Dirty:          %8lu kB\n"
 108                        "Node %d Writeback:      %8lu kB\n"
 109                        "Node %d FilePages:      %8lu kB\n"
 110                        "Node %d Mapped:         %8lu kB\n"
 111                        "Node %d AnonPages:      %8lu kB\n"
 112                        "Node %d Shmem:          %8lu kB\n"
 113                        "Node %d KernelStack:    %8lu kB\n"
 114                        "Node %d PageTables:     %8lu kB\n"
 115                        "Node %d NFS_Unstable:   %8lu kB\n"
 116                        "Node %d Bounce:         %8lu kB\n"
 117                        "Node %d WritebackTmp:   %8lu kB\n"
 118                        "Node %d Slab:           %8lu kB\n"
 119                        "Node %d SReclaimable:   %8lu kB\n"
 120                        "Node %d SUnreclaim:     %8lu kB\n",
 121                        nid, K(node_page_state(nid, NR_FILE_DIRTY)),
 122                        nid, K(node_page_state(nid, NR_WRITEBACK)),
 123                        nid, K(node_page_state(nid, NR_FILE_PAGES)),
 124                        nid, K(node_page_state(nid, NR_FILE_MAPPED)),
 125                        nid, K(node_page_state(nid, NR_ANON_PAGES)),
 126                        nid, K(node_page_state(nid, NR_SHMEM)),
 127                        nid, node_page_state(nid, NR_KERNEL_STACK) *
 128                                 THREAD_SIZE / 1024,
 129                        nid, K(node_page_state(nid, NR_PAGETABLE)),
 130                        nid, K(node_page_state(nid, NR_UNSTABLE_NFS)),
 131                        nid, K(node_page_state(nid, NR_BOUNCE)),
 132                        nid, K(node_page_state(nid, NR_WRITEBACK_TEMP)),
 133                        nid, K(node_page_state(nid, NR_SLAB_RECLAIMABLE) +
 134                                 node_page_state(nid, NR_SLAB_UNRECLAIMABLE)),
 135                        nid, K(node_page_state(nid, NR_SLAB_RECLAIMABLE)),
 136                        nid, K(node_page_state(nid, NR_SLAB_UNRECLAIMABLE)));
 137         n += hugetlb_report_node_meminfo(nid, buf + n);
 138         return n;
 139 }
 140
 141 #undef K
 142 static SYSDEV_ATTR(meminfo, S_IRUGO, node_read_meminfo, NULL);
 143
 144 static ssize_t node_read_numastat(struct sys_device * dev,
 145                                 struct sysdev_attribute *attr, char * buf)
 146 {
 147         return sprintf(buf,
 148                        "numa_hit %lu\n"
 149                        "numa_miss %lu\n"
 150                        "numa_foreign %lu\n"
 151                        "interleave_hit %lu\n"
 152                        "local_node %lu\n"
 153                        "other_node %lu\n",
 154                        node_page_state(dev->id, NUMA_HIT),
 155                        node_page_state(dev->id, NUMA_MISS),
 156                        node_page_state(dev->id, NUMA_FOREIGN),
 157                        node_page_state(dev->id, NUMA_INTERLEAVE_HIT),
 158                        node_page_state(dev->id, NUMA_LOCAL),
 159                        node_page_state(dev->id, NUMA_OTHER));
 160 }
 161 static SYSDEV_ATTR(numastat, S_IRUGO, node_read_numastat, NULL);
 162
 163 static ssize_t node_read_vmstat(struct sys_device *dev,
 164                                 struct sysdev_attribute *attr, char *buf)
 165 {
 166         int nid = dev->id;
 167         return sprintf(buf,
 168                 "nr_written %lu\n"
 169                 "nr_dirtied %lu\n",
 170                 node_page_state(nid, NR_WRITTEN),
 171                 node_page_state(nid, NR_DIRTIED));
 172 }
 173 static SYSDEV_ATTR(vmstat, S_IRUGO, node_read_vmstat, NULL);
 174
 175 static ssize_t node_read_distance(struct sys_device * dev,
 176                         struct sysdev_attribute *attr, char * buf)
 177 {
 178         int nid = dev->id;
 179         int len = 0;
 180         int i;
 181
 182         /*
 183          * buf is currently PAGE_SIZE in length and each node needs 4 chars
 184          * at the most (distance + space or newline).
 185          */
 186         BUILD_BUG_ON(MAX_NUMNODES * 4 > PAGE_SIZE);
 187
 188         for_each_online_node(i)
 189                 len += sprintf(buf + len, "%s%d", i ? " " : "", node_distance(nid, i));
 190
 191         len += sprintf(buf + len, "\n");
 192         return len;
 193 }
 194 static SYSDEV_ATTR(distance, S_IRUGO, node_read_distance, NULL);
 195
 196 #ifdef CONFIG_HUGETLBFS
 197 /*
 198  * hugetlbfs per node attributes registration interface:
 199  * When/if hugetlb[fs] subsystem initializes [sometime after this module],
 200  * it will register its per node attributes for all online nodes with
 201  * memory.  It will also call register_hugetlbfs_with_node(), below, to
 202  * register its attribute registration functions with this node driver.
 203  * Once these hooks have been initialized, the node driver will call into
 204  * the hugetlb module to [un]register attributes for hot-plugged nodes.
 205  */
 206 static node_registration_func_t __hugetlb_register_node;
 207 static node_registration_func_t __hugetlb_unregister_node;
 208
 209 static inline bool hugetlb_register_node(struct node *node)
 210 {
 211         if (__hugetlb_register_node &&
 212                         node_state(node->sysdev.id, N_HIGH_MEMORY)) {
 213                 __hugetlb_register_node(node);
 214                 return true;
 215         }
 216         return false;
 217 }
 218
 219 static inline void hugetlb_unregister_node(struct node *node)
 220 {
 221         if (__hugetlb_unregister_node)
 222                 __hugetlb_unregister_node(node);
 223 }
 224
 225 void register_hugetlbfs_with_node(node_registration_func_t doregister,
 226                                   node_registration_func_t unregister)
 227 {
 228         __hugetlb_register_node   = doregister;
 229         __hugetlb_unregister_node = unregister;
 230 }
 231 #else
 232 static inline void hugetlb_register_node(struct node *node) {}
 233
 234 static inline void hugetlb_unregister_node(struct node *node) {}
 235 #endif
 236
 237
 238 /*
 239  * register_node - Setup a sysfs device for a node.
 240  * @num - Node number to use when creating the device.
 241  *
 242  * Initialize and register the node device.
 243  */
 244 int register_node(struct node *node, int num, struct node *parent)
 245 {
 246         int error;
 247
 248         node->sysdev.id = num;
 249         node->sysdev.cls = &node_class;
 250         error = sysdev_register(&node->sysdev);
 251
 252         if (!error){
 253                 sysdev_create_file(&node->sysdev, &attr_cpumap);
 254                 sysdev_create_file(&node->sysdev, &attr_cpulist);
 255                 sysdev_create_file(&node->sysdev, &attr_meminfo);
 256                 sysdev_create_file(&node->sysdev, &attr_numastat);
 257                 sysdev_create_file(&node->sysdev, &attr_distance);
 258                 sysdev_create_file(&node->sysdev, &attr_vmstat);
 259
 260                 scan_unevictable_register_node(node);
 261
 262                 hugetlb_register_node(node);
 263
 264                 compaction_register_node(node);
 265         }
 266         return error;
 267 }
 268
 269 /**
 270  * unregister_node - unregister a node device
 271  * @node: node going away
 272  *
 273  * Unregisters a node device @node.  All the devices on the node must be
 274  * unregistered before calling this function.
 275  */
 276 void unregister_node(struct node *node)
 277 {
 278         sysdev_remove_file(&node->sysdev, &attr_cpumap);
 279         sysdev_remove_file(&node->sysdev, &attr_cpulist);
 280         sysdev_remove_file(&node->sysdev, &attr_meminfo);
 281         sysdev_remove_file(&node->sysdev, &attr_numastat);
 282         sysdev_remove_file(&node->sysdev, &attr_distance);
 283         sysdev_remove_file(&node->sysdev, &attr_vmstat);
 284
 285         scan_unevictable_unregister_node(node);
 286         hugetlb_unregister_node(node);          /* no-op, if memoryless node */
 287
 288         sysdev_unregister(&node->sysdev);
 289 }
 290
 291 struct node node_devices[MAX_NUMNODES];
 292
 293 /*
 294  * register cpu under node
 295  */
 296 int register_cpu_under_node(unsigned int cpu, unsigned int nid)
 297 {
 298         int ret;
 299         struct sys_device *obj;
 300
 301         if (!node_online(nid))
 302                 return 0;
 303
 304         obj = get_cpu_sysdev(cpu);
 305         if (!obj)
 306                 return 0;
 307
 308         ret = sysfs_create_link(&node_devices[nid].sysdev.kobj,
 309                                 &obj->kobj,
 310                                 kobject_name(&obj->kobj));
 311         if (ret)
 312                 return ret;
 313
 314         return sysfs_create_link(&obj->kobj,
 315                                  &node_devices[nid].sysdev.kobj,
 316                                  kobject_name(&node_devices[nid].sysdev.kobj));
 317 }
 318
 319 int unregister_cpu_under_node(unsigned int cpu, unsigned int nid)
 320 {
 321         struct sys_device *obj;
 322
 323         if (!node_online(nid))
 324                 return 0;
 325
 326         obj = get_cpu_sysdev(cpu);
 327         if (!obj)
 328                 return 0;
 329
 330         sysfs_remove_link(&node_devices[nid].sysdev.kobj,
 331                           kobject_name(&obj->kobj));
 332         sysfs_remove_link(&obj->kobj,
 333                           kobject_name(&node_devices[nid].sysdev.kobj));
 334
 335         return 0;
 336 }
 337
 338 #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
 339 #define page_initialized(page)  (page->lru.next)
 340
 341 static int get_nid_for_pfn(unsigned long pfn)
 342 {
 343         struct page *page;
 344
 345         if (!pfn_valid_within(pfn))
 346                 return -1;
 347         page = pfn_to_page(pfn);
 348         if (!page_initialized(page))
 349                 return -1;
 350         return pfn_to_nid(pfn);
 351 }
 352
 353 /* register memory section under specified node if it spans that node */
 354 int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
 355 {
 356         int ret;
 357         unsigned long pfn, sect_start_pfn, sect_end_pfn;
 358
 359         if (!mem_blk)
 360                 return -EFAULT;
 361         if (!node_online(nid))
 362                 return 0;
 363         sect_start_pfn = section_nr_to_pfn(mem_blk->phys_index);
 364         sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
 365         for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
 366                 int page_nid;
 367
 368                 page_nid = get_nid_for_pfn(pfn);
 369                 if (page_nid < 0)
 370                         continue;
 371                 if (page_nid != nid)
 372                         continue;
 373                 ret = sysfs_create_link_nowarn(&node_devices[nid].sysdev.kobj,
 374                                         &mem_blk->sysdev.kobj,
 375                                         kobject_name(&mem_blk->sysdev.kobj));
 376                 if (ret)
 377                         return ret;
 378
 379                 return sysfs_create_link_nowarn(&mem_blk->sysdev.kobj,
 380                                 &node_devices[nid].sysdev.kobj,
 381                                 kobject_name(&node_devices[nid].sysdev.kobj));
 382         }
 383         /* mem section does not span the specified node */
 384         return 0;
 385 }
 386
 387 /* unregister memory section under all nodes that it spans */
 388 int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
 389 {
 390         NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
 391         unsigned long pfn, sect_start_pfn, sect_end_pfn;
 392
 393         if (!mem_blk) {
 394                 NODEMASK_FREE(unlinked_nodes);
 395                 return -EFAULT;
 396         }
 397         if (!unlinked_nodes)
 398                 return -ENOMEM;
 399         nodes_clear(*unlinked_nodes);
 400         sect_start_pfn = section_nr_to_pfn(mem_blk->phys_index);
 401         sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
 402         for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
 403                 int nid;
 404
 405                 nid = get_nid_for_pfn(pfn);
 406                 if (nid < 0)
 407                         continue;
 408                 if (!node_online(nid))
 409                         continue;
 410                 if (node_test_and_set(nid, *unlinked_nodes))
 411                         continue;
 412                 sysfs_remove_link(&node_devices[nid].sysdev.kobj,
 413                          kobject_name(&mem_blk->sysdev.kobj));
 414                 sysfs_remove_link(&mem_blk->sysdev.kobj,
 415                          kobject_name(&node_devices[nid].sysdev.kobj));
 416         }
 417         NODEMASK_FREE(unlinked_nodes);
 418         return 0;
 419 }
 420
 421 static int link_mem_sections(int nid)
 422 {
 423         unsigned long start_pfn = NODE_DATA(nid)->node_start_pfn;
 424         unsigned long end_pfn = start_pfn + NODE_DATA(nid)->node_spanned_pages;
 425         unsigned long pfn;
 426         struct memory_block *mem_blk = NULL;
 427         int err = 0;
 428
 429         for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
 430                 unsigned long section_nr = pfn_to_section_nr(pfn);
 431                 struct mem_section *mem_sect;
 432                 int ret;
 433
 434                 if (!present_section_nr(section_nr))
 435                         continue;
 436                 mem_sect = __nr_to_section(section_nr);
 437                 mem_blk = find_memory_block_hinted(mem_sect, mem_blk);
 438                 ret = register_mem_sect_under_node(mem_blk, nid);
 439                 if (!err)
 440                         err = ret;
 441
 442                 /* discard ref obtained in find_memory_block() */
 443         }
 444
 445         if (mem_blk)
 446                 kobject_put(&mem_blk->sysdev.kobj);
 447         return err;
 448 }
 449
 450 #ifdef CONFIG_HUGETLBFS
 451 /*
 452  * Handle per node hstate attribute [un]registration on transistions
 453  * to/from memoryless state.
 454  */
 455 static void node_hugetlb_work(struct work_struct *work)
 456 {
 457         struct node *node = container_of(work, struct node, node_work);
 458
 459         /*
 460          * We only get here when a node transitions to/from memoryless state.
 461          * We can detect which transition occurred by examining whether the
 462          * node has memory now.  hugetlb_register_node() already check this
 463          * so we try to register the attributes.  If that fails, then the
 464          * node has transitioned to memoryless, try to unregister the
 465          * attributes.
 466          */
 467         if (!hugetlb_register_node(node))
 468                 hugetlb_unregister_node(node);
 469 }
 470
 471 static void init_node_hugetlb_work(int nid)
 472 {
 473         INIT_WORK(&node_devices[nid].node_work, node_hugetlb_work);
 474 }
 475
 476 static int node_memory_callback(struct notifier_block *self,
 477                                 unsigned long action, void *arg)
 478 {
 479         struct memory_notify *mnb = arg;
 480         int nid = mnb->status_change_nid;
 481
 482         switch (action) {
 483         case MEM_ONLINE:
 484         case MEM_OFFLINE:
 485                 /*
 486                  * offload per node hstate [un]registration to a work thread
 487                  * when transitioning to/from memoryless state.
 488                  */
 489                 if (nid != NUMA_NO_NODE)
 490                         schedule_work(&node_devices[nid].node_work);
 491                 break;
 492
 493         case MEM_GOING_ONLINE:
 494         case MEM_GOING_OFFLINE:
 495         case MEM_CANCEL_ONLINE:
 496         case MEM_CANCEL_OFFLINE:
 497         default:
 498                 break;
 499         }
 500
 501         return NOTIFY_OK;
 502 }
 503 #endif  /* CONFIG_HUGETLBFS */
 504 #else   /* !CONFIG_MEMORY_HOTPLUG_SPARSE */
 505
 506 static int link_mem_sections(int nid) { return 0; }
 507 #endif  /* CONFIG_MEMORY_HOTPLUG_SPARSE */
 508
 509 #if !defined(CONFIG_MEMORY_HOTPLUG_SPARSE) || \
 510     !defined(CONFIG_HUGETLBFS)
 511 static inline int node_memory_callback(struct notifier_block *self,
 512                                 unsigned long action, void *arg)
 513 {
 514         return NOTIFY_OK;
 515 }
 516
 517 static void init_node_hugetlb_work(int nid) { }
 518
 519 #endif
 520
 521 int register_one_node(int nid)
 522 {
 523         int error = 0;
 524         int cpu;
 525
 526         if (node_online(nid)) {
 527                 int p_node = parent_node(nid);
 528                 struct node *parent = NULL;
 529
 530                 if (p_node != nid)
 531                         parent = &node_devices[p_node];
 532
 533                 error = register_node(&node_devices[nid], nid, parent);
 534
 535                 /* link cpu under this node */
 536                 for_each_present_cpu(cpu) {
 537                         if (cpu_to_node(cpu) == nid)
 538                                 register_cpu_under_node(cpu, nid);
 539                 }
 540
 541                 /* link memory sections under this node */
 542                 error = link_mem_sections(nid);
 543
 544                 /* initialize work queue for memory hot plug */
 545                 init_node_hugetlb_work(nid);
 546         }
 547
 548         return error;
 549
 550 }
 551
 552 void unregister_one_node(int nid)
 553 {
 554         unregister_node(&node_devices[nid]);
 555 }
 556
 557 /*
 558  * node states attributes
 559  */
 560
 561 static ssize_t print_nodes_state(enum node_states state, char *buf)
 562 {
 563         int n;
 564
 565         n = nodelist_scnprintf(buf, PAGE_SIZE, node_states[state]);
 566         if (n > 0 && PAGE_SIZE > n + 1) {
 567                 *(buf + n++) = '\n';
 568                 *(buf + n++) = '\0';
 569         }
 570         return n;
 571 }
 572
 573 struct node_attr {
 574         struct sysdev_class_attribute attr;
 575         enum node_states state;
 576 };
 577
 578 static ssize_t show_node_state(struct sysdev_class *class,
 579                                struct sysdev_class_attribute *attr, char *buf)
 580 {
 581         struct node_attr *na = container_of(attr, struct node_attr, attr);
 582         return print_nodes_state(na->state, buf);
 583 }
 584
 585 #define _NODE_ATTR(name, state) \
 586         { _SYSDEV_CLASS_ATTR(name, 0444, show_node_state, NULL), state }
 587
 588 static struct node_attr node_state_attr[] = {
 589         _NODE_ATTR(possible, N_POSSIBLE),
 590         _NODE_ATTR(online, N_ONLINE),
 591         _NODE_ATTR(has_normal_memory, N_NORMAL_MEMORY),
 592         _NODE_ATTR(has_cpu, N_CPU),
 593 #ifdef CONFIG_HIGHMEM
 594         _NODE_ATTR(has_high_memory, N_HIGH_MEMORY),
 595 #endif
 596 };
 597
 598 static struct sysdev_class_attribute *node_state_attrs[] = {
 599         &node_state_attr[0].attr,
 600         &node_state_attr[1].attr,
 601         &node_state_attr[2].attr,
 602         &node_state_attr[3].attr,
 603 #ifdef CONFIG_HIGHMEM
 604         &node_state_attr[4].attr,
 605 #endif
 606         NULL
 607 };
 608
 609 #define NODE_CALLBACK_PRI       2       /* lower than SLAB */
 610 static int __init register_node_type(void)
 611 {
 612         int ret;
 613
 614         BUILD_BUG_ON(ARRAY_SIZE(node_state_attr) != NR_NODE_STATES);
 615         BUILD_BUG_ON(ARRAY_SIZE(node_state_attrs)-1 != NR_NODE_STATES);
 616
 617         ret = sysdev_class_register(&node_class);
 618         if (!ret) {
 619                 hotplug_memory_notifier(node_memory_callback,
 620                                         NODE_CALLBACK_PRI);
 621         }
 622
 623         /*
 624          * Note:  we're not going to unregister the node class if we fail
 625          * to register the node state class attribute files.
 626          */
 627         return ret;
 628 }
 629 postcore_initcall(register_node_type);