xref: /linux/drivers/base/node.c (revision dc6876a288cc6a446a6617ccfcb96082f67fa0c4)
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 		       nid, K(node_page_state(nid, NR_ANON_PAGES)
128 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
129 			+ node_page_state(nid, NR_ANON_TRANSPARENT_HUGEPAGES) *
130 			HPAGE_PMD_NR
131 #endif
132 		       ),
133 		       nid, K(node_page_state(nid, NR_SHMEM)),
134 		       nid, node_page_state(nid, NR_KERNEL_STACK) *
135 				THREAD_SIZE / 1024,
136 		       nid, K(node_page_state(nid, NR_PAGETABLE)),
137 		       nid, K(node_page_state(nid, NR_UNSTABLE_NFS)),
138 		       nid, K(node_page_state(nid, NR_BOUNCE)),
139 		       nid, K(node_page_state(nid, NR_WRITEBACK_TEMP)),
140 		       nid, K(node_page_state(nid, NR_SLAB_RECLAIMABLE) +
141 				node_page_state(nid, NR_SLAB_UNRECLAIMABLE)),
142 		       nid, K(node_page_state(nid, NR_SLAB_RECLAIMABLE)),
143 		       nid, K(node_page_state(nid, NR_SLAB_UNRECLAIMABLE))
144 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
145 			, nid,
146 			K(node_page_state(nid, NR_ANON_TRANSPARENT_HUGEPAGES) *
147 			HPAGE_PMD_NR)
148 #endif
149 		       );
150 	n += hugetlb_report_node_meminfo(nid, buf + n);
151 	return n;
152 }
153 
154 #undef K
155 static DEVICE_ATTR(meminfo, S_IRUGO, node_read_meminfo, NULL);
156 
157 static ssize_t node_read_numastat(struct device *dev,
158 				struct device_attribute *attr, char *buf)
159 {
160 	return sprintf(buf,
161 		       "numa_hit %lu\n"
162 		       "numa_miss %lu\n"
163 		       "numa_foreign %lu\n"
164 		       "interleave_hit %lu\n"
165 		       "local_node %lu\n"
166 		       "other_node %lu\n",
167 		       node_page_state(dev->id, NUMA_HIT),
168 		       node_page_state(dev->id, NUMA_MISS),
169 		       node_page_state(dev->id, NUMA_FOREIGN),
170 		       node_page_state(dev->id, NUMA_INTERLEAVE_HIT),
171 		       node_page_state(dev->id, NUMA_LOCAL),
172 		       node_page_state(dev->id, NUMA_OTHER));
173 }
174 static DEVICE_ATTR(numastat, S_IRUGO, node_read_numastat, NULL);
175 
176 static ssize_t node_read_vmstat(struct device *dev,
177 				struct device_attribute *attr, char *buf)
178 {
179 	int nid = dev->id;
180 	int i;
181 	int n = 0;
182 
183 	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
184 		n += sprintf(buf+n, "%s %lu\n", vmstat_text[i],
185 			     node_page_state(nid, i));
186 
187 	return n;
188 }
189 static DEVICE_ATTR(vmstat, S_IRUGO, node_read_vmstat, NULL);
190 
191 static ssize_t node_read_distance(struct device *dev,
192 			struct device_attribute *attr, char * buf)
193 {
194 	int nid = dev->id;
195 	int len = 0;
196 	int i;
197 
198 	/*
199 	 * buf is currently PAGE_SIZE in length and each node needs 4 chars
200 	 * at the most (distance + space or newline).
201 	 */
202 	BUILD_BUG_ON(MAX_NUMNODES * 4 > PAGE_SIZE);
203 
204 	for_each_online_node(i)
205 		len += sprintf(buf + len, "%s%d", i ? " " : "", node_distance(nid, i));
206 
207 	len += sprintf(buf + len, "\n");
208 	return len;
209 }
210 static DEVICE_ATTR(distance, S_IRUGO, node_read_distance, NULL);
211 
212 #ifdef CONFIG_HUGETLBFS
213 /*
214  * hugetlbfs per node attributes registration interface:
215  * When/if hugetlb[fs] subsystem initializes [sometime after this module],
216  * it will register its per node attributes for all online nodes with
217  * memory.  It will also call register_hugetlbfs_with_node(), below, to
218  * register its attribute registration functions with this node driver.
219  * Once these hooks have been initialized, the node driver will call into
220  * the hugetlb module to [un]register attributes for hot-plugged nodes.
221  */
222 static node_registration_func_t __hugetlb_register_node;
223 static node_registration_func_t __hugetlb_unregister_node;
224 
225 static inline bool hugetlb_register_node(struct node *node)
226 {
227 	if (__hugetlb_register_node &&
228 			node_state(node->dev.id, N_HIGH_MEMORY)) {
229 		__hugetlb_register_node(node);
230 		return true;
231 	}
232 	return false;
233 }
234 
235 static inline void hugetlb_unregister_node(struct node *node)
236 {
237 	if (__hugetlb_unregister_node)
238 		__hugetlb_unregister_node(node);
239 }
240 
241 void register_hugetlbfs_with_node(node_registration_func_t doregister,
242 				  node_registration_func_t unregister)
243 {
244 	__hugetlb_register_node   = doregister;
245 	__hugetlb_unregister_node = unregister;
246 }
247 #else
248 static inline void hugetlb_register_node(struct node *node) {}
249 
250 static inline void hugetlb_unregister_node(struct node *node) {}
251 #endif
252 
253 
254 /*
255  * register_node - Setup a sysfs device for a node.
256  * @num - Node number to use when creating the device.
257  *
258  * Initialize and register the node device.
259  */
260 int register_node(struct node *node, int num, struct node *parent)
261 {
262 	int error;
263 
264 	node->dev.id = num;
265 	node->dev.bus = &node_subsys;
266 	error = device_register(&node->dev);
267 
268 	if (!error){
269 		device_create_file(&node->dev, &dev_attr_cpumap);
270 		device_create_file(&node->dev, &dev_attr_cpulist);
271 		device_create_file(&node->dev, &dev_attr_meminfo);
272 		device_create_file(&node->dev, &dev_attr_numastat);
273 		device_create_file(&node->dev, &dev_attr_distance);
274 		device_create_file(&node->dev, &dev_attr_vmstat);
275 
276 		scan_unevictable_register_node(node);
277 
278 		hugetlb_register_node(node);
279 
280 		compaction_register_node(node);
281 	}
282 	return error;
283 }
284 
285 /**
286  * unregister_node - unregister a node device
287  * @node: node going away
288  *
289  * Unregisters a node device @node.  All the devices on the node must be
290  * unregistered before calling this function.
291  */
292 void unregister_node(struct node *node)
293 {
294 	device_remove_file(&node->dev, &dev_attr_cpumap);
295 	device_remove_file(&node->dev, &dev_attr_cpulist);
296 	device_remove_file(&node->dev, &dev_attr_meminfo);
297 	device_remove_file(&node->dev, &dev_attr_numastat);
298 	device_remove_file(&node->dev, &dev_attr_distance);
299 	device_remove_file(&node->dev, &dev_attr_vmstat);
300 
301 	scan_unevictable_unregister_node(node);
302 	hugetlb_unregister_node(node);		/* no-op, if memoryless node */
303 
304 	device_unregister(&node->dev);
305 }
306 
307 struct node node_devices[MAX_NUMNODES];
308 
309 /*
310  * register cpu under node
311  */
312 int register_cpu_under_node(unsigned int cpu, unsigned int nid)
313 {
314 	int ret;
315 	struct device *obj;
316 
317 	if (!node_online(nid))
318 		return 0;
319 
320 	obj = get_cpu_device(cpu);
321 	if (!obj)
322 		return 0;
323 
324 	ret = sysfs_create_link(&node_devices[nid].dev.kobj,
325 				&obj->kobj,
326 				kobject_name(&obj->kobj));
327 	if (ret)
328 		return ret;
329 
330 	return sysfs_create_link(&obj->kobj,
331 				 &node_devices[nid].dev.kobj,
332 				 kobject_name(&node_devices[nid].dev.kobj));
333 }
334 
335 int unregister_cpu_under_node(unsigned int cpu, unsigned int nid)
336 {
337 	struct device *obj;
338 
339 	if (!node_online(nid))
340 		return 0;
341 
342 	obj = get_cpu_device(cpu);
343 	if (!obj)
344 		return 0;
345 
346 	sysfs_remove_link(&node_devices[nid].dev.kobj,
347 			  kobject_name(&obj->kobj));
348 	sysfs_remove_link(&obj->kobj,
349 			  kobject_name(&node_devices[nid].dev.kobj));
350 
351 	return 0;
352 }
353 
354 #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
355 #define page_initialized(page)  (page->lru.next)
356 
357 static int get_nid_for_pfn(unsigned long pfn)
358 {
359 	struct page *page;
360 
361 	if (!pfn_valid_within(pfn))
362 		return -1;
363 	page = pfn_to_page(pfn);
364 	if (!page_initialized(page))
365 		return -1;
366 	return pfn_to_nid(pfn);
367 }
368 
369 /* register memory section under specified node if it spans that node */
370 int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
371 {
372 	int ret;
373 	unsigned long pfn, sect_start_pfn, sect_end_pfn;
374 
375 	if (!mem_blk)
376 		return -EFAULT;
377 	if (!node_online(nid))
378 		return 0;
379 
380 	sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
381 	sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
382 	sect_end_pfn += PAGES_PER_SECTION - 1;
383 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
384 		int page_nid;
385 
386 		page_nid = get_nid_for_pfn(pfn);
387 		if (page_nid < 0)
388 			continue;
389 		if (page_nid != nid)
390 			continue;
391 		ret = sysfs_create_link_nowarn(&node_devices[nid].dev.kobj,
392 					&mem_blk->dev.kobj,
393 					kobject_name(&mem_blk->dev.kobj));
394 		if (ret)
395 			return ret;
396 
397 		return sysfs_create_link_nowarn(&mem_blk->dev.kobj,
398 				&node_devices[nid].dev.kobj,
399 				kobject_name(&node_devices[nid].dev.kobj));
400 	}
401 	/* mem section does not span the specified node */
402 	return 0;
403 }
404 
405 /* unregister memory section under all nodes that it spans */
406 int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
407 				    unsigned long phys_index)
408 {
409 	NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
410 	unsigned long pfn, sect_start_pfn, sect_end_pfn;
411 
412 	if (!mem_blk) {
413 		NODEMASK_FREE(unlinked_nodes);
414 		return -EFAULT;
415 	}
416 	if (!unlinked_nodes)
417 		return -ENOMEM;
418 	nodes_clear(*unlinked_nodes);
419 
420 	sect_start_pfn = section_nr_to_pfn(phys_index);
421 	sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
422 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
423 		int nid;
424 
425 		nid = get_nid_for_pfn(pfn);
426 		if (nid < 0)
427 			continue;
428 		if (!node_online(nid))
429 			continue;
430 		if (node_test_and_set(nid, *unlinked_nodes))
431 			continue;
432 		sysfs_remove_link(&node_devices[nid].dev.kobj,
433 			 kobject_name(&mem_blk->dev.kobj));
434 		sysfs_remove_link(&mem_blk->dev.kobj,
435 			 kobject_name(&node_devices[nid].dev.kobj));
436 	}
437 	NODEMASK_FREE(unlinked_nodes);
438 	return 0;
439 }
440 
441 static int link_mem_sections(int nid)
442 {
443 	unsigned long start_pfn = NODE_DATA(nid)->node_start_pfn;
444 	unsigned long end_pfn = start_pfn + NODE_DATA(nid)->node_spanned_pages;
445 	unsigned long pfn;
446 	struct memory_block *mem_blk = NULL;
447 	int err = 0;
448 
449 	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
450 		unsigned long section_nr = pfn_to_section_nr(pfn);
451 		struct mem_section *mem_sect;
452 		int ret;
453 
454 		if (!present_section_nr(section_nr))
455 			continue;
456 		mem_sect = __nr_to_section(section_nr);
457 		mem_blk = find_memory_block_hinted(mem_sect, mem_blk);
458 		ret = register_mem_sect_under_node(mem_blk, nid);
459 		if (!err)
460 			err = ret;
461 
462 		/* discard ref obtained in find_memory_block() */
463 	}
464 
465 	if (mem_blk)
466 		kobject_put(&mem_blk->dev.kobj);
467 	return err;
468 }
469 
470 #ifdef CONFIG_HUGETLBFS
471 /*
472  * Handle per node hstate attribute [un]registration on transistions
473  * to/from memoryless state.
474  */
475 static void node_hugetlb_work(struct work_struct *work)
476 {
477 	struct node *node = container_of(work, struct node, node_work);
478 
479 	/*
480 	 * We only get here when a node transitions to/from memoryless state.
481 	 * We can detect which transition occurred by examining whether the
482 	 * node has memory now.  hugetlb_register_node() already check this
483 	 * so we try to register the attributes.  If that fails, then the
484 	 * node has transitioned to memoryless, try to unregister the
485 	 * attributes.
486 	 */
487 	if (!hugetlb_register_node(node))
488 		hugetlb_unregister_node(node);
489 }
490 
491 static void init_node_hugetlb_work(int nid)
492 {
493 	INIT_WORK(&node_devices[nid].node_work, node_hugetlb_work);
494 }
495 
496 static int node_memory_callback(struct notifier_block *self,
497 				unsigned long action, void *arg)
498 {
499 	struct memory_notify *mnb = arg;
500 	int nid = mnb->status_change_nid;
501 
502 	switch (action) {
503 	case MEM_ONLINE:
504 	case MEM_OFFLINE:
505 		/*
506 		 * offload per node hstate [un]registration to a work thread
507 		 * when transitioning to/from memoryless state.
508 		 */
509 		if (nid != NUMA_NO_NODE)
510 			schedule_work(&node_devices[nid].node_work);
511 		break;
512 
513 	case MEM_GOING_ONLINE:
514 	case MEM_GOING_OFFLINE:
515 	case MEM_CANCEL_ONLINE:
516 	case MEM_CANCEL_OFFLINE:
517 	default:
518 		break;
519 	}
520 
521 	return NOTIFY_OK;
522 }
523 #endif	/* CONFIG_HUGETLBFS */
524 #else	/* !CONFIG_MEMORY_HOTPLUG_SPARSE */
525 
526 static int link_mem_sections(int nid) { return 0; }
527 #endif	/* CONFIG_MEMORY_HOTPLUG_SPARSE */
528 
529 #if !defined(CONFIG_MEMORY_HOTPLUG_SPARSE) || \
530     !defined(CONFIG_HUGETLBFS)
531 static inline int node_memory_callback(struct notifier_block *self,
532 				unsigned long action, void *arg)
533 {
534 	return NOTIFY_OK;
535 }
536 
537 static void init_node_hugetlb_work(int nid) { }
538 
539 #endif
540 
541 int register_one_node(int nid)
542 {
543 	int error = 0;
544 	int cpu;
545 
546 	if (node_online(nid)) {
547 		int p_node = parent_node(nid);
548 		struct node *parent = NULL;
549 
550 		if (p_node != nid)
551 			parent = &node_devices[p_node];
552 
553 		error = register_node(&node_devices[nid], nid, parent);
554 
555 		/* link cpu under this node */
556 		for_each_present_cpu(cpu) {
557 			if (cpu_to_node(cpu) == nid)
558 				register_cpu_under_node(cpu, nid);
559 		}
560 
561 		/* link memory sections under this node */
562 		error = link_mem_sections(nid);
563 
564 		/* initialize work queue for memory hot plug */
565 		init_node_hugetlb_work(nid);
566 	}
567 
568 	return error;
569 
570 }
571 
572 void unregister_one_node(int nid)
573 {
574 	unregister_node(&node_devices[nid]);
575 }
576 
577 /*
578  * node states attributes
579  */
580 
581 static ssize_t print_nodes_state(enum node_states state, char *buf)
582 {
583 	int n;
584 
585 	n = nodelist_scnprintf(buf, PAGE_SIZE, node_states[state]);
586 	if (n > 0 && PAGE_SIZE > n + 1) {
587 		*(buf + n++) = '\n';
588 		*(buf + n++) = '\0';
589 	}
590 	return n;
591 }
592 
593 struct node_attr {
594 	struct device_attribute attr;
595 	enum node_states state;
596 };
597 
598 static ssize_t show_node_state(struct device *dev,
599 			       struct device_attribute *attr, char *buf)
600 {
601 	struct node_attr *na = container_of(attr, struct node_attr, attr);
602 	return print_nodes_state(na->state, buf);
603 }
604 
605 #define _NODE_ATTR(name, state) \
606 	{ __ATTR(name, 0444, show_node_state, NULL), state }
607 
608 static struct node_attr node_state_attr[] = {
609 	_NODE_ATTR(possible, N_POSSIBLE),
610 	_NODE_ATTR(online, N_ONLINE),
611 	_NODE_ATTR(has_normal_memory, N_NORMAL_MEMORY),
612 	_NODE_ATTR(has_cpu, N_CPU),
613 #ifdef CONFIG_HIGHMEM
614 	_NODE_ATTR(has_high_memory, N_HIGH_MEMORY),
615 #endif
616 };
617 
618 static struct attribute *node_state_attrs[] = {
619 	&node_state_attr[0].attr.attr,
620 	&node_state_attr[1].attr.attr,
621 	&node_state_attr[2].attr.attr,
622 	&node_state_attr[3].attr.attr,
623 #ifdef CONFIG_HIGHMEM
624 	&node_state_attr[4].attr.attr,
625 #endif
626 	NULL
627 };
628 
629 static struct attribute_group memory_root_attr_group = {
630 	.attrs = node_state_attrs,
631 };
632 
633 static const struct attribute_group *cpu_root_attr_groups[] = {
634 	&memory_root_attr_group,
635 	NULL,
636 };
637 
638 #define NODE_CALLBACK_PRI	2	/* lower than SLAB */
639 static int __init register_node_type(void)
640 {
641 	int ret;
642 
643  	BUILD_BUG_ON(ARRAY_SIZE(node_state_attr) != NR_NODE_STATES);
644  	BUILD_BUG_ON(ARRAY_SIZE(node_state_attrs)-1 != NR_NODE_STATES);
645 
646 	ret = subsys_system_register(&node_subsys, cpu_root_attr_groups);
647 	if (!ret) {
648 		hotplug_memory_notifier(node_memory_callback,
649 					NODE_CALLBACK_PRI);
650 	}
651 
652 	/*
653 	 * Note:  we're not going to unregister the node class if we fail
654 	 * to register the node state class attribute files.
655 	 */
656 	return ret;
657 }
658 postcore_initcall(register_node_type);
659