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mm: cleanup register_node()
[~shefty/rdma-dev.git] / drivers / base / node.c
1 /*
2  * Basic Node interface support
3  */
4
5 #include <linux/module.h>
6 #include <linux/init.h>
7 #include <linux/mm.h>
8 #include <linux/memory.h>
9 #include <linux/vmstat.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 bus_type node_subsys = {
22         .name = "node",
23         .dev_name = "node",
24 };
25
26
27 static ssize_t node_read_cpumap(struct device *dev, int type, char *buf)
28 {
29         struct node *node_dev = to_node(dev);
30         const struct cpumask *mask = cpumask_of_node(node_dev->dev.id);
31         int len;
32
33         /* 2008/04/07: buf currently PAGE_SIZE, need 9 chars per 32 bits. */
34         BUILD_BUG_ON((NR_CPUS/32 * 9) > (PAGE_SIZE-1));
35
36         len = type?
37                 cpulist_scnprintf(buf, PAGE_SIZE-2, mask) :
38                 cpumask_scnprintf(buf, PAGE_SIZE-2, mask);
39         buf[len++] = '\n';
40         buf[len] = '\0';
41         return len;
42 }
43
44 static inline ssize_t node_read_cpumask(struct device *dev,
45                                 struct device_attribute *attr, char *buf)
46 {
47         return node_read_cpumap(dev, 0, buf);
48 }
49 static inline ssize_t node_read_cpulist(struct device *dev,
50                                 struct device_attribute *attr, char *buf)
51 {
52         return node_read_cpumap(dev, 1, buf);
53 }
54
55 static DEVICE_ATTR(cpumap,  S_IRUGO, node_read_cpumask, NULL);
56 static DEVICE_ATTR(cpulist, S_IRUGO, node_read_cpulist, NULL);
57
58 #define K(x) ((x) << (PAGE_SHIFT - 10))
59 static ssize_t node_read_meminfo(struct device *dev,
60                         struct device_attribute *attr, char *buf)
61 {
62         int n;
63         int nid = dev->id;
64         struct sysinfo i;
65
66         si_meminfo_node(&i, nid);
67         n = sprintf(buf,
68                        "Node %d MemTotal:       %8lu kB\n"
69                        "Node %d MemFree:        %8lu kB\n"
70                        "Node %d MemUsed:        %8lu kB\n"
71                        "Node %d Active:         %8lu kB\n"
72                        "Node %d Inactive:       %8lu kB\n"
73                        "Node %d Active(anon):   %8lu kB\n"
74                        "Node %d Inactive(anon): %8lu kB\n"
75                        "Node %d Active(file):   %8lu kB\n"
76                        "Node %d Inactive(file): %8lu kB\n"
77                        "Node %d Unevictable:    %8lu kB\n"
78                        "Node %d Mlocked:        %8lu kB\n",
79                        nid, K(i.totalram),
80                        nid, K(i.freeram),
81                        nid, K(i.totalram - i.freeram),
82                        nid, K(node_page_state(nid, NR_ACTIVE_ANON) +
83                                 node_page_state(nid, NR_ACTIVE_FILE)),
84                        nid, K(node_page_state(nid, NR_INACTIVE_ANON) +
85                                 node_page_state(nid, NR_INACTIVE_FILE)),
86                        nid, K(node_page_state(nid, NR_ACTIVE_ANON)),
87                        nid, K(node_page_state(nid, NR_INACTIVE_ANON)),
88                        nid, K(node_page_state(nid, NR_ACTIVE_FILE)),
89                        nid, K(node_page_state(nid, NR_INACTIVE_FILE)),
90                        nid, K(node_page_state(nid, NR_UNEVICTABLE)),
91                        nid, K(node_page_state(nid, NR_MLOCK)));
92
93 #ifdef CONFIG_HIGHMEM
94         n += sprintf(buf + n,
95                        "Node %d HighTotal:      %8lu kB\n"
96                        "Node %d HighFree:       %8lu kB\n"
97                        "Node %d LowTotal:       %8lu kB\n"
98                        "Node %d LowFree:        %8lu kB\n",
99                        nid, K(i.totalhigh),
100                        nid, K(i.freehigh),
101                        nid, K(i.totalram - i.totalhigh),
102                        nid, K(i.freeram - i.freehigh));
103 #endif
104         n += sprintf(buf + n,
105                        "Node %d Dirty:          %8lu kB\n"
106                        "Node %d Writeback:      %8lu kB\n"
107                        "Node %d FilePages:      %8lu kB\n"
108                        "Node %d Mapped:         %8lu kB\n"
109                        "Node %d AnonPages:      %8lu kB\n"
110                        "Node %d Shmem:          %8lu kB\n"
111                        "Node %d KernelStack:    %8lu kB\n"
112                        "Node %d PageTables:     %8lu kB\n"
113                        "Node %d NFS_Unstable:   %8lu kB\n"
114                        "Node %d Bounce:         %8lu kB\n"
115                        "Node %d WritebackTmp:   %8lu kB\n"
116                        "Node %d Slab:           %8lu kB\n"
117                        "Node %d SReclaimable:   %8lu kB\n"
118                        "Node %d SUnreclaim:     %8lu kB\n"
119 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
120                        "Node %d AnonHugePages:  %8lu kB\n"
121 #endif
122                         ,
123                        nid, K(node_page_state(nid, NR_FILE_DIRTY)),
124                        nid, K(node_page_state(nid, NR_WRITEBACK)),
125                        nid, K(node_page_state(nid, NR_FILE_PAGES)),
126                        nid, K(node_page_state(nid, NR_FILE_MAPPED)),
127 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
128                        nid, K(node_page_state(nid, NR_ANON_PAGES)
129                         + node_page_state(nid, NR_ANON_TRANSPARENT_HUGEPAGES) *
130                         HPAGE_PMD_NR),
131 #else
132                        nid, K(node_page_state(nid, NR_ANON_PAGES)),
133 #endif
134                        nid, K(node_page_state(nid, NR_SHMEM)),
135                        nid, node_page_state(nid, NR_KERNEL_STACK) *
136                                 THREAD_SIZE / 1024,
137                        nid, K(node_page_state(nid, NR_PAGETABLE)),
138                        nid, K(node_page_state(nid, NR_UNSTABLE_NFS)),
139                        nid, K(node_page_state(nid, NR_BOUNCE)),
140                        nid, K(node_page_state(nid, NR_WRITEBACK_TEMP)),
141                        nid, K(node_page_state(nid, NR_SLAB_RECLAIMABLE) +
142                                 node_page_state(nid, NR_SLAB_UNRECLAIMABLE)),
143                        nid, K(node_page_state(nid, NR_SLAB_RECLAIMABLE)),
144 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
145                        nid, K(node_page_state(nid, NR_SLAB_UNRECLAIMABLE))
146                         , nid,
147                         K(node_page_state(nid, NR_ANON_TRANSPARENT_HUGEPAGES) *
148                         HPAGE_PMD_NR));
149 #else
150                        nid, K(node_page_state(nid, NR_SLAB_UNRECLAIMABLE)));
151 #endif
152         n += hugetlb_report_node_meminfo(nid, buf + n);
153         return n;
154 }
155
156 #undef K
157 static DEVICE_ATTR(meminfo, S_IRUGO, node_read_meminfo, NULL);
158
159 static ssize_t node_read_numastat(struct device *dev,
160                                 struct device_attribute *attr, char *buf)
161 {
162         return sprintf(buf,
163                        "numa_hit %lu\n"
164                        "numa_miss %lu\n"
165                        "numa_foreign %lu\n"
166                        "interleave_hit %lu\n"
167                        "local_node %lu\n"
168                        "other_node %lu\n",
169                        node_page_state(dev->id, NUMA_HIT),
170                        node_page_state(dev->id, NUMA_MISS),
171                        node_page_state(dev->id, NUMA_FOREIGN),
172                        node_page_state(dev->id, NUMA_INTERLEAVE_HIT),
173                        node_page_state(dev->id, NUMA_LOCAL),
174                        node_page_state(dev->id, NUMA_OTHER));
175 }
176 static DEVICE_ATTR(numastat, S_IRUGO, node_read_numastat, NULL);
177
178 static ssize_t node_read_vmstat(struct device *dev,
179                                 struct device_attribute *attr, char *buf)
180 {
181         int nid = dev->id;
182         int i;
183         int n = 0;
184
185         for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
186                 n += sprintf(buf+n, "%s %lu\n", vmstat_text[i],
187                              node_page_state(nid, i));
188
189         return n;
190 }
191 static DEVICE_ATTR(vmstat, S_IRUGO, node_read_vmstat, NULL);
192
193 static ssize_t node_read_distance(struct device *dev,
194                         struct device_attribute *attr, char * buf)
195 {
196         int nid = dev->id;
197         int len = 0;
198         int i;
199
200         /*
201          * buf is currently PAGE_SIZE in length and each node needs 4 chars
202          * at the most (distance + space or newline).
203          */
204         BUILD_BUG_ON(MAX_NUMNODES * 4 > PAGE_SIZE);
205
206         for_each_online_node(i)
207                 len += sprintf(buf + len, "%s%d", i ? " " : "", node_distance(nid, i));
208
209         len += sprintf(buf + len, "\n");
210         return len;
211 }
212 static DEVICE_ATTR(distance, S_IRUGO, node_read_distance, NULL);
213
214 #ifdef CONFIG_HUGETLBFS
215 /*
216  * hugetlbfs per node attributes registration interface:
217  * When/if hugetlb[fs] subsystem initializes [sometime after this module],
218  * it will register its per node attributes for all online nodes with
219  * memory.  It will also call register_hugetlbfs_with_node(), below, to
220  * register its attribute registration functions with this node driver.
221  * Once these hooks have been initialized, the node driver will call into
222  * the hugetlb module to [un]register attributes for hot-plugged nodes.
223  */
224 static node_registration_func_t __hugetlb_register_node;
225 static node_registration_func_t __hugetlb_unregister_node;
226
227 static inline bool hugetlb_register_node(struct node *node)
228 {
229         if (__hugetlb_register_node &&
230                         node_state(node->dev.id, N_HIGH_MEMORY)) {
231                 __hugetlb_register_node(node);
232                 return true;
233         }
234         return false;
235 }
236
237 static inline void hugetlb_unregister_node(struct node *node)
238 {
239         if (__hugetlb_unregister_node)
240                 __hugetlb_unregister_node(node);
241 }
242
243 void register_hugetlbfs_with_node(node_registration_func_t doregister,
244                                   node_registration_func_t unregister)
245 {
246         __hugetlb_register_node   = doregister;
247         __hugetlb_unregister_node = unregister;
248 }
249 #else
250 static inline void hugetlb_register_node(struct node *node) {}
251
252 static inline void hugetlb_unregister_node(struct node *node) {}
253 #endif
254
255 static void node_device_release(struct device *dev)
256 {
257         struct node *node = to_node(dev);
258
259 #if defined(CONFIG_MEMORY_HOTPLUG_SPARSE) && defined(CONFIG_HUGETLBFS)
260         /*
261          * We schedule the work only when a memory section is
262          * onlined/offlined on this node. When we come here,
263          * all the memory on this node has been offlined,
264          * so we won't enqueue new work to this work.
265          *
266          * The work is using node->node_work, so we should
267          * flush work before freeing the memory.
268          */
269         flush_work(&node->node_work);
270 #endif
271         kfree(node);
272 }
273
274 /*
275  * register_node - Setup a sysfs device for a node.
276  * @num - Node number to use when creating the device.
277  *
278  * Initialize and register the node device.
279  */
280 static int register_node(struct node *node, int num, struct node *parent)
281 {
282         int error;
283
284         node->dev.id = num;
285         node->dev.bus = &node_subsys;
286         node->dev.release = node_device_release;
287         error = device_register(&node->dev);
288
289         if (!error){
290                 device_create_file(&node->dev, &dev_attr_cpumap);
291                 device_create_file(&node->dev, &dev_attr_cpulist);
292                 device_create_file(&node->dev, &dev_attr_meminfo);
293                 device_create_file(&node->dev, &dev_attr_numastat);
294                 device_create_file(&node->dev, &dev_attr_distance);
295                 device_create_file(&node->dev, &dev_attr_vmstat);
296
297                 scan_unevictable_register_node(node);
298
299                 hugetlb_register_node(node);
300
301                 compaction_register_node(node);
302         }
303         return error;
304 }
305
306 /**
307  * unregister_node - unregister a node device
308  * @node: node going away
309  *
310  * Unregisters a node device @node.  All the devices on the node must be
311  * unregistered before calling this function.
312  */
313 void unregister_node(struct node *node)
314 {
315         device_remove_file(&node->dev, &dev_attr_cpumap);
316         device_remove_file(&node->dev, &dev_attr_cpulist);
317         device_remove_file(&node->dev, &dev_attr_meminfo);
318         device_remove_file(&node->dev, &dev_attr_numastat);
319         device_remove_file(&node->dev, &dev_attr_distance);
320         device_remove_file(&node->dev, &dev_attr_vmstat);
321
322         scan_unevictable_unregister_node(node);
323         hugetlb_unregister_node(node);          /* no-op, if memoryless node */
324
325         device_unregister(&node->dev);
326 }
327
328 struct node *node_devices[MAX_NUMNODES];
329
330 /*
331  * register cpu under node
332  */
333 int register_cpu_under_node(unsigned int cpu, unsigned int nid)
334 {
335         int ret;
336         struct device *obj;
337
338         if (!node_online(nid))
339                 return 0;
340
341         obj = get_cpu_device(cpu);
342         if (!obj)
343                 return 0;
344
345         ret = sysfs_create_link(&node_devices[nid]->dev.kobj,
346                                 &obj->kobj,
347                                 kobject_name(&obj->kobj));
348         if (ret)
349                 return ret;
350
351         return sysfs_create_link(&obj->kobj,
352                                  &node_devices[nid]->dev.kobj,
353                                  kobject_name(&node_devices[nid]->dev.kobj));
354 }
355
356 int unregister_cpu_under_node(unsigned int cpu, unsigned int nid)
357 {
358         struct device *obj;
359
360         if (!node_online(nid))
361                 return 0;
362
363         obj = get_cpu_device(cpu);
364         if (!obj)
365                 return 0;
366
367         sysfs_remove_link(&node_devices[nid]->dev.kobj,
368                           kobject_name(&obj->kobj));
369         sysfs_remove_link(&obj->kobj,
370                           kobject_name(&node_devices[nid]->dev.kobj));
371
372         return 0;
373 }
374
375 #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
376 #define page_initialized(page)  (page->lru.next)
377
378 static int get_nid_for_pfn(unsigned long pfn)
379 {
380         struct page *page;
381
382         if (!pfn_valid_within(pfn))
383                 return -1;
384         page = pfn_to_page(pfn);
385         if (!page_initialized(page))
386                 return -1;
387         return pfn_to_nid(pfn);
388 }
389
390 /* register memory section under specified node if it spans that node */
391 int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
392 {
393         int ret;
394         unsigned long pfn, sect_start_pfn, sect_end_pfn;
395
396         if (!mem_blk)
397                 return -EFAULT;
398         if (!node_online(nid))
399                 return 0;
400
401         sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
402         sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
403         sect_end_pfn += PAGES_PER_SECTION - 1;
404         for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
405                 int page_nid;
406
407                 page_nid = get_nid_for_pfn(pfn);
408                 if (page_nid < 0)
409                         continue;
410                 if (page_nid != nid)
411                         continue;
412                 ret = sysfs_create_link_nowarn(&node_devices[nid]->dev.kobj,
413                                         &mem_blk->dev.kobj,
414                                         kobject_name(&mem_blk->dev.kobj));
415                 if (ret)
416                         return ret;
417
418                 return sysfs_create_link_nowarn(&mem_blk->dev.kobj,
419                                 &node_devices[nid]->dev.kobj,
420                                 kobject_name(&node_devices[nid]->dev.kobj));
421         }
422         /* mem section does not span the specified node */
423         return 0;
424 }
425
426 /* unregister memory section under all nodes that it spans */
427 int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
428                                     unsigned long phys_index)
429 {
430         NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
431         unsigned long pfn, sect_start_pfn, sect_end_pfn;
432
433         if (!mem_blk) {
434                 NODEMASK_FREE(unlinked_nodes);
435                 return -EFAULT;
436         }
437         if (!unlinked_nodes)
438                 return -ENOMEM;
439         nodes_clear(*unlinked_nodes);
440
441         sect_start_pfn = section_nr_to_pfn(phys_index);
442         sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
443         for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
444                 int nid;
445
446                 nid = get_nid_for_pfn(pfn);
447                 if (nid < 0)
448                         continue;
449                 if (!node_online(nid))
450                         continue;
451                 if (node_test_and_set(nid, *unlinked_nodes))
452                         continue;
453                 sysfs_remove_link(&node_devices[nid]->dev.kobj,
454                          kobject_name(&mem_blk->dev.kobj));
455                 sysfs_remove_link(&mem_blk->dev.kobj,
456                          kobject_name(&node_devices[nid]->dev.kobj));
457         }
458         NODEMASK_FREE(unlinked_nodes);
459         return 0;
460 }
461
462 static int link_mem_sections(int nid)
463 {
464         unsigned long start_pfn = NODE_DATA(nid)->node_start_pfn;
465         unsigned long end_pfn = start_pfn + NODE_DATA(nid)->node_spanned_pages;
466         unsigned long pfn;
467         struct memory_block *mem_blk = NULL;
468         int err = 0;
469
470         for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
471                 unsigned long section_nr = pfn_to_section_nr(pfn);
472                 struct mem_section *mem_sect;
473                 int ret;
474
475                 if (!present_section_nr(section_nr))
476                         continue;
477                 mem_sect = __nr_to_section(section_nr);
478
479                 /* same memblock ? */
480                 if (mem_blk)
481                         if ((section_nr >= mem_blk->start_section_nr) &&
482                             (section_nr <= mem_blk->end_section_nr))
483                                 continue;
484
485                 mem_blk = find_memory_block_hinted(mem_sect, mem_blk);
486
487                 ret = register_mem_sect_under_node(mem_blk, nid);
488                 if (!err)
489                         err = ret;
490
491                 /* discard ref obtained in find_memory_block() */
492         }
493
494         if (mem_blk)
495                 kobject_put(&mem_blk->dev.kobj);
496         return err;
497 }
498
499 #ifdef CONFIG_HUGETLBFS
500 /*
501  * Handle per node hstate attribute [un]registration on transistions
502  * to/from memoryless state.
503  */
504 static void node_hugetlb_work(struct work_struct *work)
505 {
506         struct node *node = container_of(work, struct node, node_work);
507
508         /*
509          * We only get here when a node transitions to/from memoryless state.
510          * We can detect which transition occurred by examining whether the
511          * node has memory now.  hugetlb_register_node() already check this
512          * so we try to register the attributes.  If that fails, then the
513          * node has transitioned to memoryless, try to unregister the
514          * attributes.
515          */
516         if (!hugetlb_register_node(node))
517                 hugetlb_unregister_node(node);
518 }
519
520 static void init_node_hugetlb_work(int nid)
521 {
522         INIT_WORK(&node_devices[nid]->node_work, node_hugetlb_work);
523 }
524
525 static int node_memory_callback(struct notifier_block *self,
526                                 unsigned long action, void *arg)
527 {
528         struct memory_notify *mnb = arg;
529         int nid = mnb->status_change_nid;
530
531         switch (action) {
532         case MEM_ONLINE:
533         case MEM_OFFLINE:
534                 /*
535                  * offload per node hstate [un]registration to a work thread
536                  * when transitioning to/from memoryless state.
537                  */
538                 if (nid != NUMA_NO_NODE)
539                         schedule_work(&node_devices[nid]->node_work);
540                 break;
541
542         case MEM_GOING_ONLINE:
543         case MEM_GOING_OFFLINE:
544         case MEM_CANCEL_ONLINE:
545         case MEM_CANCEL_OFFLINE:
546         default:
547                 break;
548         }
549
550         return NOTIFY_OK;
551 }
552 #endif  /* CONFIG_HUGETLBFS */
553 #else   /* !CONFIG_MEMORY_HOTPLUG_SPARSE */
554
555 static int link_mem_sections(int nid) { return 0; }
556 #endif  /* CONFIG_MEMORY_HOTPLUG_SPARSE */
557
558 #if !defined(CONFIG_MEMORY_HOTPLUG_SPARSE) || \
559     !defined(CONFIG_HUGETLBFS)
560 static inline int node_memory_callback(struct notifier_block *self,
561                                 unsigned long action, void *arg)
562 {
563         return NOTIFY_OK;
564 }
565
566 static void init_node_hugetlb_work(int nid) { }
567
568 #endif
569
570 int register_one_node(int nid)
571 {
572         int error = 0;
573         int cpu;
574
575         if (node_online(nid)) {
576                 int p_node = parent_node(nid);
577                 struct node *parent = NULL;
578
579                 if (p_node != nid)
580                         parent = node_devices[p_node];
581
582                 node_devices[nid] = kzalloc(sizeof(struct node), GFP_KERNEL);
583                 if (!node_devices[nid])
584                         return -ENOMEM;
585
586                 error = register_node(node_devices[nid], nid, parent);
587
588                 /* link cpu under this node */
589                 for_each_present_cpu(cpu) {
590                         if (cpu_to_node(cpu) == nid)
591                                 register_cpu_under_node(cpu, nid);
592                 }
593
594                 /* link memory sections under this node */
595                 error = link_mem_sections(nid);
596
597                 /* initialize work queue for memory hot plug */
598                 init_node_hugetlb_work(nid);
599         }
600
601         return error;
602
603 }
604
605 void unregister_one_node(int nid)
606 {
607         unregister_node(node_devices[nid]);
608         node_devices[nid] = NULL;
609 }
610
611 /*
612  * node states attributes
613  */
614
615 static ssize_t print_nodes_state(enum node_states state, char *buf)
616 {
617         int n;
618
619         n = nodelist_scnprintf(buf, PAGE_SIZE-2, node_states[state]);
620         buf[n++] = '\n';
621         buf[n] = '\0';
622         return n;
623 }
624
625 struct node_attr {
626         struct device_attribute attr;
627         enum node_states state;
628 };
629
630 static ssize_t show_node_state(struct device *dev,
631                                struct device_attribute *attr, char *buf)
632 {
633         struct node_attr *na = container_of(attr, struct node_attr, attr);
634         return print_nodes_state(na->state, buf);
635 }
636
637 #define _NODE_ATTR(name, state) \
638         { __ATTR(name, 0444, show_node_state, NULL), state }
639
640 static struct node_attr node_state_attr[] = {
641         _NODE_ATTR(possible, N_POSSIBLE),
642         _NODE_ATTR(online, N_ONLINE),
643         _NODE_ATTR(has_normal_memory, N_NORMAL_MEMORY),
644         _NODE_ATTR(has_cpu, N_CPU),
645 #ifdef CONFIG_HIGHMEM
646         _NODE_ATTR(has_high_memory, N_HIGH_MEMORY),
647 #endif
648 };
649
650 static struct attribute *node_state_attrs[] = {
651         &node_state_attr[0].attr.attr,
652         &node_state_attr[1].attr.attr,
653         &node_state_attr[2].attr.attr,
654         &node_state_attr[3].attr.attr,
655 #ifdef CONFIG_HIGHMEM
656         &node_state_attr[4].attr.attr,
657 #endif
658         NULL
659 };
660
661 static struct attribute_group memory_root_attr_group = {
662         .attrs = node_state_attrs,
663 };
664
665 static const struct attribute_group *cpu_root_attr_groups[] = {
666         &memory_root_attr_group,
667         NULL,
668 };
669
670 #define NODE_CALLBACK_PRI       2       /* lower than SLAB */
671 static int __init register_node_type(void)
672 {
673         int ret;
674
675         BUILD_BUG_ON(ARRAY_SIZE(node_state_attr) != NR_NODE_STATES);
676         BUILD_BUG_ON(ARRAY_SIZE(node_state_attrs)-1 != NR_NODE_STATES);
677
678         ret = subsys_system_register(&node_subsys, cpu_root_attr_groups);
679         if (!ret) {
680                 hotplug_memory_notifier(node_memory_callback,
681                                         NODE_CALLBACK_PRI);
682         }
683
684         /*
685          * Note:  we're not going to unregister the node class if we fail
686          * to register the node state class attribute files.
687          */
688         return ret;
689 }
690 postcore_initcall(register_node_type);