1ac4c36e13bbd9a70a07ba310e01bc053614c103
[muen/linux.git] / drivers / base / node.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Basic Node interface support
4  */
5
6 #include <linux/module.h>
7 #include <linux/init.h>
8 #include <linux/mm.h>
9 #include <linux/memory.h>
10 #include <linux/vmstat.h>
11 #include <linux/notifier.h>
12 #include <linux/node.h>
13 #include <linux/hugetlb.h>
14 #include <linux/compaction.h>
15 #include <linux/cpumask.h>
16 #include <linux/topology.h>
17 #include <linux/nodemask.h>
18 #include <linux/cpu.h>
19 #include <linux/device.h>
20 #include <linux/swap.h>
21 #include <linux/slab.h>
22
23 static struct bus_type node_subsys = {
24         .name = "node",
25         .dev_name = "node",
26 };
27
28
29 static ssize_t node_read_cpumap(struct device *dev, bool list, char *buf)
30 {
31         ssize_t n;
32         cpumask_var_t mask;
33         struct node *node_dev = to_node(dev);
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         if (!alloc_cpumask_var(&mask, GFP_KERNEL))
39                 return 0;
40
41         cpumask_and(mask, cpumask_of_node(node_dev->dev.id), cpu_online_mask);
42         n = cpumap_print_to_pagebuf(list, buf, mask);
43         free_cpumask_var(mask);
44
45         return n;
46 }
47
48 static inline ssize_t node_read_cpumask(struct device *dev,
49                                 struct device_attribute *attr, char *buf)
50 {
51         return node_read_cpumap(dev, false, buf);
52 }
53 static inline ssize_t node_read_cpulist(struct device *dev,
54                                 struct device_attribute *attr, char *buf)
55 {
56         return node_read_cpumap(dev, true, buf);
57 }
58
59 static DEVICE_ATTR(cpumap,  S_IRUGO, node_read_cpumask, NULL);
60 static DEVICE_ATTR(cpulist, S_IRUGO, node_read_cpulist, NULL);
61
62 #define K(x) ((x) << (PAGE_SHIFT - 10))
63 static ssize_t node_read_meminfo(struct device *dev,
64                         struct device_attribute *attr, char *buf)
65 {
66         int n;
67         int nid = dev->id;
68         struct pglist_data *pgdat = NODE_DATA(nid);
69         struct sysinfo i;
70
71         si_meminfo_node(&i, nid);
72         n = sprintf(buf,
73                        "Node %d MemTotal:       %8lu kB\n"
74                        "Node %d MemFree:        %8lu kB\n"
75                        "Node %d MemUsed:        %8lu kB\n"
76                        "Node %d Active:         %8lu kB\n"
77                        "Node %d Inactive:       %8lu kB\n"
78                        "Node %d Active(anon):   %8lu kB\n"
79                        "Node %d Inactive(anon): %8lu kB\n"
80                        "Node %d Active(file):   %8lu kB\n"
81                        "Node %d Inactive(file): %8lu kB\n"
82                        "Node %d Unevictable:    %8lu kB\n"
83                        "Node %d Mlocked:        %8lu kB\n",
84                        nid, K(i.totalram),
85                        nid, K(i.freeram),
86                        nid, K(i.totalram - i.freeram),
87                        nid, K(node_page_state(pgdat, NR_ACTIVE_ANON) +
88                                 node_page_state(pgdat, NR_ACTIVE_FILE)),
89                        nid, K(node_page_state(pgdat, NR_INACTIVE_ANON) +
90                                 node_page_state(pgdat, NR_INACTIVE_FILE)),
91                        nid, K(node_page_state(pgdat, NR_ACTIVE_ANON)),
92                        nid, K(node_page_state(pgdat, NR_INACTIVE_ANON)),
93                        nid, K(node_page_state(pgdat, NR_ACTIVE_FILE)),
94                        nid, K(node_page_state(pgdat, NR_INACTIVE_FILE)),
95                        nid, K(node_page_state(pgdat, NR_UNEVICTABLE)),
96                        nid, K(sum_zone_node_page_state(nid, NR_MLOCK)));
97
98 #ifdef CONFIG_HIGHMEM
99         n += sprintf(buf + n,
100                        "Node %d HighTotal:      %8lu kB\n"
101                        "Node %d HighFree:       %8lu kB\n"
102                        "Node %d LowTotal:       %8lu kB\n"
103                        "Node %d LowFree:        %8lu kB\n",
104                        nid, K(i.totalhigh),
105                        nid, K(i.freehigh),
106                        nid, K(i.totalram - i.totalhigh),
107                        nid, K(i.freeram - i.freehigh));
108 #endif
109         n += sprintf(buf + n,
110                        "Node %d Dirty:          %8lu kB\n"
111                        "Node %d Writeback:      %8lu kB\n"
112                        "Node %d FilePages:      %8lu kB\n"
113                        "Node %d Mapped:         %8lu kB\n"
114                        "Node %d AnonPages:      %8lu kB\n"
115                        "Node %d Shmem:          %8lu kB\n"
116                        "Node %d KernelStack:    %8lu kB\n"
117                        "Node %d PageTables:     %8lu kB\n"
118                        "Node %d NFS_Unstable:   %8lu kB\n"
119                        "Node %d Bounce:         %8lu kB\n"
120                        "Node %d WritebackTmp:   %8lu kB\n"
121                        "Node %d Slab:           %8lu kB\n"
122                        "Node %d SReclaimable:   %8lu kB\n"
123                        "Node %d SUnreclaim:     %8lu kB\n"
124 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
125                        "Node %d AnonHugePages:  %8lu kB\n"
126                        "Node %d ShmemHugePages: %8lu kB\n"
127                        "Node %d ShmemPmdMapped: %8lu kB\n"
128 #endif
129                         ,
130                        nid, K(node_page_state(pgdat, NR_FILE_DIRTY)),
131                        nid, K(node_page_state(pgdat, NR_WRITEBACK)),
132                        nid, K(node_page_state(pgdat, NR_FILE_PAGES)),
133                        nid, K(node_page_state(pgdat, NR_FILE_MAPPED)),
134                        nid, K(node_page_state(pgdat, NR_ANON_MAPPED)),
135                        nid, K(i.sharedram),
136                        nid, sum_zone_node_page_state(nid, NR_KERNEL_STACK_KB),
137                        nid, K(sum_zone_node_page_state(nid, NR_PAGETABLE)),
138                        nid, K(node_page_state(pgdat, NR_UNSTABLE_NFS)),
139                        nid, K(sum_zone_node_page_state(nid, NR_BOUNCE)),
140                        nid, K(node_page_state(pgdat, NR_WRITEBACK_TEMP)),
141                        nid, K(node_page_state(pgdat, NR_SLAB_RECLAIMABLE) +
142                               node_page_state(pgdat, NR_SLAB_UNRECLAIMABLE)),
143                        nid, K(node_page_state(pgdat, NR_SLAB_RECLAIMABLE)),
144 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
145                        nid, K(node_page_state(pgdat, NR_SLAB_UNRECLAIMABLE)),
146                        nid, K(node_page_state(pgdat, NR_ANON_THPS) *
147                                        HPAGE_PMD_NR),
148                        nid, K(node_page_state(pgdat, NR_SHMEM_THPS) *
149                                        HPAGE_PMD_NR),
150                        nid, K(node_page_state(pgdat, NR_SHMEM_PMDMAPPED) *
151                                        HPAGE_PMD_NR));
152 #else
153                        nid, K(node_page_state(pgdat, NR_SLAB_UNRECLAIMABLE)));
154 #endif
155         n += hugetlb_report_node_meminfo(nid, buf + n);
156         return n;
157 }
158
159 #undef K
160 static DEVICE_ATTR(meminfo, S_IRUGO, node_read_meminfo, NULL);
161
162 static ssize_t node_read_numastat(struct device *dev,
163                                 struct device_attribute *attr, char *buf)
164 {
165         return sprintf(buf,
166                        "numa_hit %lu\n"
167                        "numa_miss %lu\n"
168                        "numa_foreign %lu\n"
169                        "interleave_hit %lu\n"
170                        "local_node %lu\n"
171                        "other_node %lu\n",
172                        sum_zone_numa_state(dev->id, NUMA_HIT),
173                        sum_zone_numa_state(dev->id, NUMA_MISS),
174                        sum_zone_numa_state(dev->id, NUMA_FOREIGN),
175                        sum_zone_numa_state(dev->id, NUMA_INTERLEAVE_HIT),
176                        sum_zone_numa_state(dev->id, NUMA_LOCAL),
177                        sum_zone_numa_state(dev->id, NUMA_OTHER));
178 }
179 static DEVICE_ATTR(numastat, S_IRUGO, node_read_numastat, NULL);
180
181 static ssize_t node_read_vmstat(struct device *dev,
182                                 struct device_attribute *attr, char *buf)
183 {
184         int nid = dev->id;
185         struct pglist_data *pgdat = NODE_DATA(nid);
186         int i;
187         int n = 0;
188
189         for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
190                 n += sprintf(buf+n, "%s %lu\n", vmstat_text[i],
191                              sum_zone_node_page_state(nid, i));
192
193 #ifdef CONFIG_NUMA
194         for (i = 0; i < NR_VM_NUMA_STAT_ITEMS; i++)
195                 n += sprintf(buf+n, "%s %lu\n",
196                              vmstat_text[i + NR_VM_ZONE_STAT_ITEMS],
197                              sum_zone_numa_state(nid, i));
198 #endif
199
200         for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
201                 n += sprintf(buf+n, "%s %lu\n",
202                              vmstat_text[i + NR_VM_ZONE_STAT_ITEMS +
203                              NR_VM_NUMA_STAT_ITEMS],
204                              node_page_state(pgdat, i));
205
206         return n;
207 }
208 static DEVICE_ATTR(vmstat, S_IRUGO, node_read_vmstat, NULL);
209
210 static ssize_t node_read_distance(struct device *dev,
211                         struct device_attribute *attr, char *buf)
212 {
213         int nid = dev->id;
214         int len = 0;
215         int i;
216
217         /*
218          * buf is currently PAGE_SIZE in length and each node needs 4 chars
219          * at the most (distance + space or newline).
220          */
221         BUILD_BUG_ON(MAX_NUMNODES * 4 > PAGE_SIZE);
222
223         for_each_online_node(i)
224                 len += sprintf(buf + len, "%s%d", i ? " " : "", node_distance(nid, i));
225
226         len += sprintf(buf + len, "\n");
227         return len;
228 }
229 static DEVICE_ATTR(distance, S_IRUGO, node_read_distance, NULL);
230
231 static struct attribute *node_dev_attrs[] = {
232         &dev_attr_cpumap.attr,
233         &dev_attr_cpulist.attr,
234         &dev_attr_meminfo.attr,
235         &dev_attr_numastat.attr,
236         &dev_attr_distance.attr,
237         &dev_attr_vmstat.attr,
238         NULL
239 };
240 ATTRIBUTE_GROUPS(node_dev);
241
242 #ifdef CONFIG_HUGETLBFS
243 /*
244  * hugetlbfs per node attributes registration interface:
245  * When/if hugetlb[fs] subsystem initializes [sometime after this module],
246  * it will register its per node attributes for all online nodes with
247  * memory.  It will also call register_hugetlbfs_with_node(), below, to
248  * register its attribute registration functions with this node driver.
249  * Once these hooks have been initialized, the node driver will call into
250  * the hugetlb module to [un]register attributes for hot-plugged nodes.
251  */
252 static node_registration_func_t __hugetlb_register_node;
253 static node_registration_func_t __hugetlb_unregister_node;
254
255 static inline bool hugetlb_register_node(struct node *node)
256 {
257         if (__hugetlb_register_node &&
258                         node_state(node->dev.id, N_MEMORY)) {
259                 __hugetlb_register_node(node);
260                 return true;
261         }
262         return false;
263 }
264
265 static inline void hugetlb_unregister_node(struct node *node)
266 {
267         if (__hugetlb_unregister_node)
268                 __hugetlb_unregister_node(node);
269 }
270
271 void register_hugetlbfs_with_node(node_registration_func_t doregister,
272                                   node_registration_func_t unregister)
273 {
274         __hugetlb_register_node   = doregister;
275         __hugetlb_unregister_node = unregister;
276 }
277 #else
278 static inline void hugetlb_register_node(struct node *node) {}
279
280 static inline void hugetlb_unregister_node(struct node *node) {}
281 #endif
282
283 static void node_device_release(struct device *dev)
284 {
285         struct node *node = to_node(dev);
286
287 #if defined(CONFIG_MEMORY_HOTPLUG_SPARSE) && defined(CONFIG_HUGETLBFS)
288         /*
289          * We schedule the work only when a memory section is
290          * onlined/offlined on this node. When we come here,
291          * all the memory on this node has been offlined,
292          * so we won't enqueue new work to this work.
293          *
294          * The work is using node->node_work, so we should
295          * flush work before freeing the memory.
296          */
297         flush_work(&node->node_work);
298 #endif
299         kfree(node);
300 }
301
302 /*
303  * register_node - Setup a sysfs device for a node.
304  * @num - Node number to use when creating the device.
305  *
306  * Initialize and register the node device.
307  */
308 static int register_node(struct node *node, int num)
309 {
310         int error;
311
312         node->dev.id = num;
313         node->dev.bus = &node_subsys;
314         node->dev.release = node_device_release;
315         node->dev.groups = node_dev_groups;
316         error = device_register(&node->dev);
317
318         if (error)
319                 put_device(&node->dev);
320         else {
321                 hugetlb_register_node(node);
322
323                 compaction_register_node(node);
324         }
325         return error;
326 }
327
328 /**
329  * unregister_node - unregister a node device
330  * @node: node going away
331  *
332  * Unregisters a node device @node.  All the devices on the node must be
333  * unregistered before calling this function.
334  */
335 void unregister_node(struct node *node)
336 {
337         hugetlb_unregister_node(node);          /* no-op, if memoryless node */
338
339         device_unregister(&node->dev);
340 }
341
342 struct node *node_devices[MAX_NUMNODES];
343
344 /*
345  * register cpu under node
346  */
347 int register_cpu_under_node(unsigned int cpu, unsigned int nid)
348 {
349         int ret;
350         struct device *obj;
351
352         if (!node_online(nid))
353                 return 0;
354
355         obj = get_cpu_device(cpu);
356         if (!obj)
357                 return 0;
358
359         ret = sysfs_create_link(&node_devices[nid]->dev.kobj,
360                                 &obj->kobj,
361                                 kobject_name(&obj->kobj));
362         if (ret)
363                 return ret;
364
365         return sysfs_create_link(&obj->kobj,
366                                  &node_devices[nid]->dev.kobj,
367                                  kobject_name(&node_devices[nid]->dev.kobj));
368 }
369
370 int unregister_cpu_under_node(unsigned int cpu, unsigned int nid)
371 {
372         struct device *obj;
373
374         if (!node_online(nid))
375                 return 0;
376
377         obj = get_cpu_device(cpu);
378         if (!obj)
379                 return 0;
380
381         sysfs_remove_link(&node_devices[nid]->dev.kobj,
382                           kobject_name(&obj->kobj));
383         sysfs_remove_link(&obj->kobj,
384                           kobject_name(&node_devices[nid]->dev.kobj));
385
386         return 0;
387 }
388
389 #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
390 static int __ref get_nid_for_pfn(unsigned long pfn)
391 {
392         if (!pfn_valid_within(pfn))
393                 return -1;
394 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
395         if (system_state < SYSTEM_RUNNING)
396                 return early_pfn_to_nid(pfn);
397 #endif
398         return pfn_to_nid(pfn);
399 }
400
401 /* register memory section under specified node if it spans that node */
402 int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg)
403 {
404         int ret, nid = *(int *)arg;
405         unsigned long pfn, sect_start_pfn, sect_end_pfn;
406
407         mem_blk->nid = nid;
408
409         sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
410         sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
411         sect_end_pfn += PAGES_PER_SECTION - 1;
412         for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
413                 int page_nid;
414
415                 /*
416                  * memory block could have several absent sections from start.
417                  * skip pfn range from absent section
418                  */
419                 if (!pfn_present(pfn)) {
420                         pfn = round_down(pfn + PAGES_PER_SECTION,
421                                          PAGES_PER_SECTION) - 1;
422                         continue;
423                 }
424
425                 /*
426                  * We need to check if page belongs to nid only for the boot
427                  * case, during hotplug we know that all pages in the memory
428                  * block belong to the same node.
429                  */
430                 if (system_state == SYSTEM_BOOTING) {
431                         page_nid = get_nid_for_pfn(pfn);
432                         if (page_nid < 0)
433                                 continue;
434                         if (page_nid != nid)
435                                 continue;
436                 }
437                 ret = sysfs_create_link_nowarn(&node_devices[nid]->dev.kobj,
438                                         &mem_blk->dev.kobj,
439                                         kobject_name(&mem_blk->dev.kobj));
440                 if (ret)
441                         return ret;
442
443                 return sysfs_create_link_nowarn(&mem_blk->dev.kobj,
444                                 &node_devices[nid]->dev.kobj,
445                                 kobject_name(&node_devices[nid]->dev.kobj));
446         }
447         /* mem section does not span the specified node */
448         return 0;
449 }
450
451 /* unregister memory section under all nodes that it spans */
452 int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
453                                     unsigned long phys_index)
454 {
455         NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
456         unsigned long pfn, sect_start_pfn, sect_end_pfn;
457
458         if (!mem_blk) {
459                 NODEMASK_FREE(unlinked_nodes);
460                 return -EFAULT;
461         }
462         if (!unlinked_nodes)
463                 return -ENOMEM;
464         nodes_clear(*unlinked_nodes);
465
466         sect_start_pfn = section_nr_to_pfn(phys_index);
467         sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
468         for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
469                 int nid;
470
471                 nid = get_nid_for_pfn(pfn);
472                 if (nid < 0)
473                         continue;
474                 if (!node_online(nid))
475                         continue;
476                 if (node_test_and_set(nid, *unlinked_nodes))
477                         continue;
478                 sysfs_remove_link(&node_devices[nid]->dev.kobj,
479                          kobject_name(&mem_blk->dev.kobj));
480                 sysfs_remove_link(&mem_blk->dev.kobj,
481                          kobject_name(&node_devices[nid]->dev.kobj));
482         }
483         NODEMASK_FREE(unlinked_nodes);
484         return 0;
485 }
486
487 int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn)
488 {
489         return walk_memory_range(start_pfn, end_pfn, (void *)&nid,
490                                         register_mem_sect_under_node);
491 }
492
493 #ifdef CONFIG_HUGETLBFS
494 /*
495  * Handle per node hstate attribute [un]registration on transistions
496  * to/from memoryless state.
497  */
498 static void node_hugetlb_work(struct work_struct *work)
499 {
500         struct node *node = container_of(work, struct node, node_work);
501
502         /*
503          * We only get here when a node transitions to/from memoryless state.
504          * We can detect which transition occurred by examining whether the
505          * node has memory now.  hugetlb_register_node() already check this
506          * so we try to register the attributes.  If that fails, then the
507          * node has transitioned to memoryless, try to unregister the
508          * attributes.
509          */
510         if (!hugetlb_register_node(node))
511                 hugetlb_unregister_node(node);
512 }
513
514 static void init_node_hugetlb_work(int nid)
515 {
516         INIT_WORK(&node_devices[nid]->node_work, node_hugetlb_work);
517 }
518
519 static int node_memory_callback(struct notifier_block *self,
520                                 unsigned long action, void *arg)
521 {
522         struct memory_notify *mnb = arg;
523         int nid = mnb->status_change_nid;
524
525         switch (action) {
526         case MEM_ONLINE:
527         case MEM_OFFLINE:
528                 /*
529                  * offload per node hstate [un]registration to a work thread
530                  * when transitioning to/from memoryless state.
531                  */
532                 if (nid != NUMA_NO_NODE)
533                         schedule_work(&node_devices[nid]->node_work);
534                 break;
535
536         case MEM_GOING_ONLINE:
537         case MEM_GOING_OFFLINE:
538         case MEM_CANCEL_ONLINE:
539         case MEM_CANCEL_OFFLINE:
540         default:
541                 break;
542         }
543
544         return NOTIFY_OK;
545 }
546 #endif  /* CONFIG_HUGETLBFS */
547 #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
548
549 #if !defined(CONFIG_MEMORY_HOTPLUG_SPARSE) || \
550     !defined(CONFIG_HUGETLBFS)
551 static inline int node_memory_callback(struct notifier_block *self,
552                                 unsigned long action, void *arg)
553 {
554         return NOTIFY_OK;
555 }
556
557 static void init_node_hugetlb_work(int nid) { }
558
559 #endif
560
561 int __register_one_node(int nid)
562 {
563         int error;
564         int cpu;
565
566         node_devices[nid] = kzalloc(sizeof(struct node), GFP_KERNEL);
567         if (!node_devices[nid])
568                 return -ENOMEM;
569
570         error = register_node(node_devices[nid], nid);
571
572         /* link cpu under this node */
573         for_each_present_cpu(cpu) {
574                 if (cpu_to_node(cpu) == nid)
575                         register_cpu_under_node(cpu, nid);
576         }
577
578         /* initialize work queue for memory hot plug */
579         init_node_hugetlb_work(nid);
580
581         return error;
582 }
583
584 void unregister_one_node(int nid)
585 {
586         if (!node_devices[nid])
587                 return;
588
589         unregister_node(node_devices[nid]);
590         node_devices[nid] = NULL;
591 }
592
593 /*
594  * node states attributes
595  */
596
597 static ssize_t print_nodes_state(enum node_states state, char *buf)
598 {
599         int n;
600
601         n = scnprintf(buf, PAGE_SIZE - 1, "%*pbl",
602                       nodemask_pr_args(&node_states[state]));
603         buf[n++] = '\n';
604         buf[n] = '\0';
605         return n;
606 }
607
608 struct node_attr {
609         struct device_attribute attr;
610         enum node_states state;
611 };
612
613 static ssize_t show_node_state(struct device *dev,
614                                struct device_attribute *attr, char *buf)
615 {
616         struct node_attr *na = container_of(attr, struct node_attr, attr);
617         return print_nodes_state(na->state, buf);
618 }
619
620 #define _NODE_ATTR(name, state) \
621         { __ATTR(name, 0444, show_node_state, NULL), state }
622
623 static struct node_attr node_state_attr[] = {
624         [N_POSSIBLE] = _NODE_ATTR(possible, N_POSSIBLE),
625         [N_ONLINE] = _NODE_ATTR(online, N_ONLINE),
626         [N_NORMAL_MEMORY] = _NODE_ATTR(has_normal_memory, N_NORMAL_MEMORY),
627 #ifdef CONFIG_HIGHMEM
628         [N_HIGH_MEMORY] = _NODE_ATTR(has_high_memory, N_HIGH_MEMORY),
629 #endif
630         [N_MEMORY] = _NODE_ATTR(has_memory, N_MEMORY),
631         [N_CPU] = _NODE_ATTR(has_cpu, N_CPU),
632 };
633
634 static struct attribute *node_state_attrs[] = {
635         &node_state_attr[N_POSSIBLE].attr.attr,
636         &node_state_attr[N_ONLINE].attr.attr,
637         &node_state_attr[N_NORMAL_MEMORY].attr.attr,
638 #ifdef CONFIG_HIGHMEM
639         &node_state_attr[N_HIGH_MEMORY].attr.attr,
640 #endif
641         &node_state_attr[N_MEMORY].attr.attr,
642         &node_state_attr[N_CPU].attr.attr,
643         NULL
644 };
645
646 static struct attribute_group memory_root_attr_group = {
647         .attrs = node_state_attrs,
648 };
649
650 static const struct attribute_group *cpu_root_attr_groups[] = {
651         &memory_root_attr_group,
652         NULL,
653 };
654
655 #define NODE_CALLBACK_PRI       2       /* lower than SLAB */
656 static int __init register_node_type(void)
657 {
658         int ret;
659
660         BUILD_BUG_ON(ARRAY_SIZE(node_state_attr) != NR_NODE_STATES);
661         BUILD_BUG_ON(ARRAY_SIZE(node_state_attrs)-1 != NR_NODE_STATES);
662
663         ret = subsys_system_register(&node_subsys, cpu_root_attr_groups);
664         if (!ret) {
665                 static struct notifier_block node_memory_callback_nb = {
666                         .notifier_call = node_memory_callback,
667                         .priority = NODE_CALLBACK_PRI,
668                 };
669                 register_hotmemory_notifier(&node_memory_callback_nb);
670         }
671
672         /*
673          * Note:  we're not going to unregister the node class if we fail
674          * to register the node state class attribute files.
675          */
676         return ret;
677 }
678 postcore_initcall(register_node_type);