xref: /openbmc/linux/mm/memory_hotplug.c (revision 63dc02bd)
1 /*
2  *  linux/mm/memory_hotplug.c
3  *
4  *  Copyright (C)
5  */
6 
7 #include <linux/stddef.h>
8 #include <linux/mm.h>
9 #include <linux/swap.h>
10 #include <linux/interrupt.h>
11 #include <linux/pagemap.h>
12 #include <linux/bootmem.h>
13 #include <linux/compiler.h>
14 #include <linux/export.h>
15 #include <linux/pagevec.h>
16 #include <linux/writeback.h>
17 #include <linux/slab.h>
18 #include <linux/sysctl.h>
19 #include <linux/cpu.h>
20 #include <linux/memory.h>
21 #include <linux/memory_hotplug.h>
22 #include <linux/highmem.h>
23 #include <linux/vmalloc.h>
24 #include <linux/ioport.h>
25 #include <linux/delay.h>
26 #include <linux/migrate.h>
27 #include <linux/page-isolation.h>
28 #include <linux/pfn.h>
29 #include <linux/suspend.h>
30 #include <linux/mm_inline.h>
31 #include <linux/firmware-map.h>
32 
33 #include <asm/tlbflush.h>
34 
35 #include "internal.h"
36 
37 /*
38  * online_page_callback contains pointer to current page onlining function.
39  * Initially it is generic_online_page(). If it is required it could be
40  * changed by calling set_online_page_callback() for callback registration
41  * and restore_online_page_callback() for generic callback restore.
42  */
43 
44 static void generic_online_page(struct page *page);
45 
46 static online_page_callback_t online_page_callback = generic_online_page;
47 
48 DEFINE_MUTEX(mem_hotplug_mutex);
49 
50 void lock_memory_hotplug(void)
51 {
52 	mutex_lock(&mem_hotplug_mutex);
53 
54 	/* for exclusive hibernation if CONFIG_HIBERNATION=y */
55 	lock_system_sleep();
56 }
57 
58 void unlock_memory_hotplug(void)
59 {
60 	unlock_system_sleep();
61 	mutex_unlock(&mem_hotplug_mutex);
62 }
63 
64 
65 /* add this memory to iomem resource */
66 static struct resource *register_memory_resource(u64 start, u64 size)
67 {
68 	struct resource *res;
69 	res = kzalloc(sizeof(struct resource), GFP_KERNEL);
70 	BUG_ON(!res);
71 
72 	res->name = "System RAM";
73 	res->start = start;
74 	res->end = start + size - 1;
75 	res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
76 	if (request_resource(&iomem_resource, res) < 0) {
77 		printk("System RAM resource %llx - %llx cannot be added\n",
78 		(unsigned long long)res->start, (unsigned long long)res->end);
79 		kfree(res);
80 		res = NULL;
81 	}
82 	return res;
83 }
84 
85 static void release_memory_resource(struct resource *res)
86 {
87 	if (!res)
88 		return;
89 	release_resource(res);
90 	kfree(res);
91 	return;
92 }
93 
94 #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
95 #ifndef CONFIG_SPARSEMEM_VMEMMAP
96 static void get_page_bootmem(unsigned long info,  struct page *page,
97 			     unsigned long type)
98 {
99 	page->lru.next = (struct list_head *) type;
100 	SetPagePrivate(page);
101 	set_page_private(page, info);
102 	atomic_inc(&page->_count);
103 }
104 
105 /* reference to __meminit __free_pages_bootmem is valid
106  * so use __ref to tell modpost not to generate a warning */
107 void __ref put_page_bootmem(struct page *page)
108 {
109 	unsigned long type;
110 
111 	type = (unsigned long) page->lru.next;
112 	BUG_ON(type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
113 	       type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE);
114 
115 	if (atomic_dec_return(&page->_count) == 1) {
116 		ClearPagePrivate(page);
117 		set_page_private(page, 0);
118 		INIT_LIST_HEAD(&page->lru);
119 		__free_pages_bootmem(page, 0);
120 	}
121 
122 }
123 
124 static void register_page_bootmem_info_section(unsigned long start_pfn)
125 {
126 	unsigned long *usemap, mapsize, section_nr, i;
127 	struct mem_section *ms;
128 	struct page *page, *memmap;
129 
130 	if (!pfn_valid(start_pfn))
131 		return;
132 
133 	section_nr = pfn_to_section_nr(start_pfn);
134 	ms = __nr_to_section(section_nr);
135 
136 	/* Get section's memmap address */
137 	memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
138 
139 	/*
140 	 * Get page for the memmap's phys address
141 	 * XXX: need more consideration for sparse_vmemmap...
142 	 */
143 	page = virt_to_page(memmap);
144 	mapsize = sizeof(struct page) * PAGES_PER_SECTION;
145 	mapsize = PAGE_ALIGN(mapsize) >> PAGE_SHIFT;
146 
147 	/* remember memmap's page */
148 	for (i = 0; i < mapsize; i++, page++)
149 		get_page_bootmem(section_nr, page, SECTION_INFO);
150 
151 	usemap = __nr_to_section(section_nr)->pageblock_flags;
152 	page = virt_to_page(usemap);
153 
154 	mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT;
155 
156 	for (i = 0; i < mapsize; i++, page++)
157 		get_page_bootmem(section_nr, page, MIX_SECTION_INFO);
158 
159 }
160 
161 void register_page_bootmem_info_node(struct pglist_data *pgdat)
162 {
163 	unsigned long i, pfn, end_pfn, nr_pages;
164 	int node = pgdat->node_id;
165 	struct page *page;
166 	struct zone *zone;
167 
168 	nr_pages = PAGE_ALIGN(sizeof(struct pglist_data)) >> PAGE_SHIFT;
169 	page = virt_to_page(pgdat);
170 
171 	for (i = 0; i < nr_pages; i++, page++)
172 		get_page_bootmem(node, page, NODE_INFO);
173 
174 	zone = &pgdat->node_zones[0];
175 	for (; zone < pgdat->node_zones + MAX_NR_ZONES - 1; zone++) {
176 		if (zone->wait_table) {
177 			nr_pages = zone->wait_table_hash_nr_entries
178 				* sizeof(wait_queue_head_t);
179 			nr_pages = PAGE_ALIGN(nr_pages) >> PAGE_SHIFT;
180 			page = virt_to_page(zone->wait_table);
181 
182 			for (i = 0; i < nr_pages; i++, page++)
183 				get_page_bootmem(node, page, NODE_INFO);
184 		}
185 	}
186 
187 	pfn = pgdat->node_start_pfn;
188 	end_pfn = pfn + pgdat->node_spanned_pages;
189 
190 	/* register_section info */
191 	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION)
192 		register_page_bootmem_info_section(pfn);
193 
194 }
195 #endif /* !CONFIG_SPARSEMEM_VMEMMAP */
196 
197 static void grow_zone_span(struct zone *zone, unsigned long start_pfn,
198 			   unsigned long end_pfn)
199 {
200 	unsigned long old_zone_end_pfn;
201 
202 	zone_span_writelock(zone);
203 
204 	old_zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
205 	if (start_pfn < zone->zone_start_pfn)
206 		zone->zone_start_pfn = start_pfn;
207 
208 	zone->spanned_pages = max(old_zone_end_pfn, end_pfn) -
209 				zone->zone_start_pfn;
210 
211 	zone_span_writeunlock(zone);
212 }
213 
214 static void grow_pgdat_span(struct pglist_data *pgdat, unsigned long start_pfn,
215 			    unsigned long end_pfn)
216 {
217 	unsigned long old_pgdat_end_pfn =
218 		pgdat->node_start_pfn + pgdat->node_spanned_pages;
219 
220 	if (start_pfn < pgdat->node_start_pfn)
221 		pgdat->node_start_pfn = start_pfn;
222 
223 	pgdat->node_spanned_pages = max(old_pgdat_end_pfn, end_pfn) -
224 					pgdat->node_start_pfn;
225 }
226 
227 static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)
228 {
229 	struct pglist_data *pgdat = zone->zone_pgdat;
230 	int nr_pages = PAGES_PER_SECTION;
231 	int nid = pgdat->node_id;
232 	int zone_type;
233 	unsigned long flags;
234 
235 	zone_type = zone - pgdat->node_zones;
236 	if (!zone->wait_table) {
237 		int ret;
238 
239 		ret = init_currently_empty_zone(zone, phys_start_pfn,
240 						nr_pages, MEMMAP_HOTPLUG);
241 		if (ret)
242 			return ret;
243 	}
244 	pgdat_resize_lock(zone->zone_pgdat, &flags);
245 	grow_zone_span(zone, phys_start_pfn, phys_start_pfn + nr_pages);
246 	grow_pgdat_span(zone->zone_pgdat, phys_start_pfn,
247 			phys_start_pfn + nr_pages);
248 	pgdat_resize_unlock(zone->zone_pgdat, &flags);
249 	memmap_init_zone(nr_pages, nid, zone_type,
250 			 phys_start_pfn, MEMMAP_HOTPLUG);
251 	return 0;
252 }
253 
254 static int __meminit __add_section(int nid, struct zone *zone,
255 					unsigned long phys_start_pfn)
256 {
257 	int nr_pages = PAGES_PER_SECTION;
258 	int ret;
259 
260 	if (pfn_valid(phys_start_pfn))
261 		return -EEXIST;
262 
263 	ret = sparse_add_one_section(zone, phys_start_pfn, nr_pages);
264 
265 	if (ret < 0)
266 		return ret;
267 
268 	ret = __add_zone(zone, phys_start_pfn);
269 
270 	if (ret < 0)
271 		return ret;
272 
273 	return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
274 }
275 
276 #ifdef CONFIG_SPARSEMEM_VMEMMAP
277 static int __remove_section(struct zone *zone, struct mem_section *ms)
278 {
279 	/*
280 	 * XXX: Freeing memmap with vmemmap is not implement yet.
281 	 *      This should be removed later.
282 	 */
283 	return -EBUSY;
284 }
285 #else
286 static int __remove_section(struct zone *zone, struct mem_section *ms)
287 {
288 	unsigned long flags;
289 	struct pglist_data *pgdat = zone->zone_pgdat;
290 	int ret = -EINVAL;
291 
292 	if (!valid_section(ms))
293 		return ret;
294 
295 	ret = unregister_memory_section(ms);
296 	if (ret)
297 		return ret;
298 
299 	pgdat_resize_lock(pgdat, &flags);
300 	sparse_remove_one_section(zone, ms);
301 	pgdat_resize_unlock(pgdat, &flags);
302 	return 0;
303 }
304 #endif
305 
306 /*
307  * Reasonably generic function for adding memory.  It is
308  * expected that archs that support memory hotplug will
309  * call this function after deciding the zone to which to
310  * add the new pages.
311  */
312 int __ref __add_pages(int nid, struct zone *zone, unsigned long phys_start_pfn,
313 			unsigned long nr_pages)
314 {
315 	unsigned long i;
316 	int err = 0;
317 	int start_sec, end_sec;
318 	/* during initialize mem_map, align hot-added range to section */
319 	start_sec = pfn_to_section_nr(phys_start_pfn);
320 	end_sec = pfn_to_section_nr(phys_start_pfn + nr_pages - 1);
321 
322 	for (i = start_sec; i <= end_sec; i++) {
323 		err = __add_section(nid, zone, i << PFN_SECTION_SHIFT);
324 
325 		/*
326 		 * EEXIST is finally dealt with by ioresource collision
327 		 * check. see add_memory() => register_memory_resource()
328 		 * Warning will be printed if there is collision.
329 		 */
330 		if (err && (err != -EEXIST))
331 			break;
332 		err = 0;
333 	}
334 
335 	return err;
336 }
337 EXPORT_SYMBOL_GPL(__add_pages);
338 
339 /**
340  * __remove_pages() - remove sections of pages from a zone
341  * @zone: zone from which pages need to be removed
342  * @phys_start_pfn: starting pageframe (must be aligned to start of a section)
343  * @nr_pages: number of pages to remove (must be multiple of section size)
344  *
345  * Generic helper function to remove section mappings and sysfs entries
346  * for the section of the memory we are removing. Caller needs to make
347  * sure that pages are marked reserved and zones are adjust properly by
348  * calling offline_pages().
349  */
350 int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
351 		 unsigned long nr_pages)
352 {
353 	unsigned long i, ret = 0;
354 	int sections_to_remove;
355 
356 	/*
357 	 * We can only remove entire sections
358 	 */
359 	BUG_ON(phys_start_pfn & ~PAGE_SECTION_MASK);
360 	BUG_ON(nr_pages % PAGES_PER_SECTION);
361 
362 	sections_to_remove = nr_pages / PAGES_PER_SECTION;
363 	for (i = 0; i < sections_to_remove; i++) {
364 		unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;
365 		release_mem_region(pfn << PAGE_SHIFT,
366 				   PAGES_PER_SECTION << PAGE_SHIFT);
367 		ret = __remove_section(zone, __pfn_to_section(pfn));
368 		if (ret)
369 			break;
370 	}
371 	return ret;
372 }
373 EXPORT_SYMBOL_GPL(__remove_pages);
374 
375 int set_online_page_callback(online_page_callback_t callback)
376 {
377 	int rc = -EINVAL;
378 
379 	lock_memory_hotplug();
380 
381 	if (online_page_callback == generic_online_page) {
382 		online_page_callback = callback;
383 		rc = 0;
384 	}
385 
386 	unlock_memory_hotplug();
387 
388 	return rc;
389 }
390 EXPORT_SYMBOL_GPL(set_online_page_callback);
391 
392 int restore_online_page_callback(online_page_callback_t callback)
393 {
394 	int rc = -EINVAL;
395 
396 	lock_memory_hotplug();
397 
398 	if (online_page_callback == callback) {
399 		online_page_callback = generic_online_page;
400 		rc = 0;
401 	}
402 
403 	unlock_memory_hotplug();
404 
405 	return rc;
406 }
407 EXPORT_SYMBOL_GPL(restore_online_page_callback);
408 
409 void __online_page_set_limits(struct page *page)
410 {
411 	unsigned long pfn = page_to_pfn(page);
412 
413 	if (pfn >= num_physpages)
414 		num_physpages = pfn + 1;
415 }
416 EXPORT_SYMBOL_GPL(__online_page_set_limits);
417 
418 void __online_page_increment_counters(struct page *page)
419 {
420 	totalram_pages++;
421 
422 #ifdef CONFIG_HIGHMEM
423 	if (PageHighMem(page))
424 		totalhigh_pages++;
425 #endif
426 }
427 EXPORT_SYMBOL_GPL(__online_page_increment_counters);
428 
429 void __online_page_free(struct page *page)
430 {
431 	ClearPageReserved(page);
432 	init_page_count(page);
433 	__free_page(page);
434 }
435 EXPORT_SYMBOL_GPL(__online_page_free);
436 
437 static void generic_online_page(struct page *page)
438 {
439 	__online_page_set_limits(page);
440 	__online_page_increment_counters(page);
441 	__online_page_free(page);
442 }
443 
444 static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
445 			void *arg)
446 {
447 	unsigned long i;
448 	unsigned long onlined_pages = *(unsigned long *)arg;
449 	struct page *page;
450 	if (PageReserved(pfn_to_page(start_pfn)))
451 		for (i = 0; i < nr_pages; i++) {
452 			page = pfn_to_page(start_pfn + i);
453 			(*online_page_callback)(page);
454 			onlined_pages++;
455 		}
456 	*(unsigned long *)arg = onlined_pages;
457 	return 0;
458 }
459 
460 
461 int __ref online_pages(unsigned long pfn, unsigned long nr_pages)
462 {
463 	unsigned long onlined_pages = 0;
464 	struct zone *zone;
465 	int need_zonelists_rebuild = 0;
466 	int nid;
467 	int ret;
468 	struct memory_notify arg;
469 
470 	lock_memory_hotplug();
471 	arg.start_pfn = pfn;
472 	arg.nr_pages = nr_pages;
473 	arg.status_change_nid = -1;
474 
475 	nid = page_to_nid(pfn_to_page(pfn));
476 	if (node_present_pages(nid) == 0)
477 		arg.status_change_nid = nid;
478 
479 	ret = memory_notify(MEM_GOING_ONLINE, &arg);
480 	ret = notifier_to_errno(ret);
481 	if (ret) {
482 		memory_notify(MEM_CANCEL_ONLINE, &arg);
483 		unlock_memory_hotplug();
484 		return ret;
485 	}
486 	/*
487 	 * This doesn't need a lock to do pfn_to_page().
488 	 * The section can't be removed here because of the
489 	 * memory_block->state_mutex.
490 	 */
491 	zone = page_zone(pfn_to_page(pfn));
492 	/*
493 	 * If this zone is not populated, then it is not in zonelist.
494 	 * This means the page allocator ignores this zone.
495 	 * So, zonelist must be updated after online.
496 	 */
497 	mutex_lock(&zonelists_mutex);
498 	if (!populated_zone(zone))
499 		need_zonelists_rebuild = 1;
500 
501 	ret = walk_system_ram_range(pfn, nr_pages, &onlined_pages,
502 		online_pages_range);
503 	if (ret) {
504 		mutex_unlock(&zonelists_mutex);
505 		printk(KERN_DEBUG "online_pages %lx at %lx failed\n",
506 			nr_pages, pfn);
507 		memory_notify(MEM_CANCEL_ONLINE, &arg);
508 		unlock_memory_hotplug();
509 		return ret;
510 	}
511 
512 	zone->present_pages += onlined_pages;
513 	zone->zone_pgdat->node_present_pages += onlined_pages;
514 	if (need_zonelists_rebuild)
515 		build_all_zonelists(zone);
516 	else
517 		zone_pcp_update(zone);
518 
519 	mutex_unlock(&zonelists_mutex);
520 
521 	init_per_zone_wmark_min();
522 
523 	if (onlined_pages) {
524 		kswapd_run(zone_to_nid(zone));
525 		node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
526 	}
527 
528 	vm_total_pages = nr_free_pagecache_pages();
529 
530 	writeback_set_ratelimit();
531 
532 	if (onlined_pages)
533 		memory_notify(MEM_ONLINE, &arg);
534 	unlock_memory_hotplug();
535 
536 	return 0;
537 }
538 #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
539 
540 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
541 static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
542 {
543 	struct pglist_data *pgdat;
544 	unsigned long zones_size[MAX_NR_ZONES] = {0};
545 	unsigned long zholes_size[MAX_NR_ZONES] = {0};
546 	unsigned long start_pfn = start >> PAGE_SHIFT;
547 
548 	pgdat = arch_alloc_nodedata(nid);
549 	if (!pgdat)
550 		return NULL;
551 
552 	arch_refresh_nodedata(nid, pgdat);
553 
554 	/* we can use NODE_DATA(nid) from here */
555 
556 	/* init node's zones as empty zones, we don't have any present pages.*/
557 	free_area_init_node(nid, zones_size, start_pfn, zholes_size);
558 
559 	/*
560 	 * The node we allocated has no zone fallback lists. For avoiding
561 	 * to access not-initialized zonelist, build here.
562 	 */
563 	mutex_lock(&zonelists_mutex);
564 	build_all_zonelists(NULL);
565 	mutex_unlock(&zonelists_mutex);
566 
567 	return pgdat;
568 }
569 
570 static void rollback_node_hotadd(int nid, pg_data_t *pgdat)
571 {
572 	arch_refresh_nodedata(nid, NULL);
573 	arch_free_nodedata(pgdat);
574 	return;
575 }
576 
577 
578 /*
579  * called by cpu_up() to online a node without onlined memory.
580  */
581 int mem_online_node(int nid)
582 {
583 	pg_data_t	*pgdat;
584 	int	ret;
585 
586 	lock_memory_hotplug();
587 	pgdat = hotadd_new_pgdat(nid, 0);
588 	if (!pgdat) {
589 		ret = -ENOMEM;
590 		goto out;
591 	}
592 	node_set_online(nid);
593 	ret = register_one_node(nid);
594 	BUG_ON(ret);
595 
596 out:
597 	unlock_memory_hotplug();
598 	return ret;
599 }
600 
601 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
602 int __ref add_memory(int nid, u64 start, u64 size)
603 {
604 	pg_data_t *pgdat = NULL;
605 	int new_pgdat = 0;
606 	struct resource *res;
607 	int ret;
608 
609 	lock_memory_hotplug();
610 
611 	res = register_memory_resource(start, size);
612 	ret = -EEXIST;
613 	if (!res)
614 		goto out;
615 
616 	if (!node_online(nid)) {
617 		pgdat = hotadd_new_pgdat(nid, start);
618 		ret = -ENOMEM;
619 		if (!pgdat)
620 			goto out;
621 		new_pgdat = 1;
622 	}
623 
624 	/* call arch's memory hotadd */
625 	ret = arch_add_memory(nid, start, size);
626 
627 	if (ret < 0)
628 		goto error;
629 
630 	/* we online node here. we can't roll back from here. */
631 	node_set_online(nid);
632 
633 	if (new_pgdat) {
634 		ret = register_one_node(nid);
635 		/*
636 		 * If sysfs file of new node can't create, cpu on the node
637 		 * can't be hot-added. There is no rollback way now.
638 		 * So, check by BUG_ON() to catch it reluctantly..
639 		 */
640 		BUG_ON(ret);
641 	}
642 
643 	/* create new memmap entry */
644 	firmware_map_add_hotplug(start, start + size, "System RAM");
645 
646 	goto out;
647 
648 error:
649 	/* rollback pgdat allocation and others */
650 	if (new_pgdat)
651 		rollback_node_hotadd(nid, pgdat);
652 	if (res)
653 		release_memory_resource(res);
654 
655 out:
656 	unlock_memory_hotplug();
657 	return ret;
658 }
659 EXPORT_SYMBOL_GPL(add_memory);
660 
661 #ifdef CONFIG_MEMORY_HOTREMOVE
662 /*
663  * A free page on the buddy free lists (not the per-cpu lists) has PageBuddy
664  * set and the size of the free page is given by page_order(). Using this,
665  * the function determines if the pageblock contains only free pages.
666  * Due to buddy contraints, a free page at least the size of a pageblock will
667  * be located at the start of the pageblock
668  */
669 static inline int pageblock_free(struct page *page)
670 {
671 	return PageBuddy(page) && page_order(page) >= pageblock_order;
672 }
673 
674 /* Return the start of the next active pageblock after a given page */
675 static struct page *next_active_pageblock(struct page *page)
676 {
677 	/* Ensure the starting page is pageblock-aligned */
678 	BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1));
679 
680 	/* If the entire pageblock is free, move to the end of free page */
681 	if (pageblock_free(page)) {
682 		int order;
683 		/* be careful. we don't have locks, page_order can be changed.*/
684 		order = page_order(page);
685 		if ((order < MAX_ORDER) && (order >= pageblock_order))
686 			return page + (1 << order);
687 	}
688 
689 	return page + pageblock_nr_pages;
690 }
691 
692 /* Checks if this range of memory is likely to be hot-removable. */
693 int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
694 {
695 	struct page *page = pfn_to_page(start_pfn);
696 	struct page *end_page = page + nr_pages;
697 
698 	/* Check the starting page of each pageblock within the range */
699 	for (; page < end_page; page = next_active_pageblock(page)) {
700 		if (!is_pageblock_removable_nolock(page))
701 			return 0;
702 		cond_resched();
703 	}
704 
705 	/* All pageblocks in the memory block are likely to be hot-removable */
706 	return 1;
707 }
708 
709 /*
710  * Confirm all pages in a range [start, end) is belongs to the same zone.
711  */
712 static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
713 {
714 	unsigned long pfn;
715 	struct zone *zone = NULL;
716 	struct page *page;
717 	int i;
718 	for (pfn = start_pfn;
719 	     pfn < end_pfn;
720 	     pfn += MAX_ORDER_NR_PAGES) {
721 		i = 0;
722 		/* This is just a CONFIG_HOLES_IN_ZONE check.*/
723 		while ((i < MAX_ORDER_NR_PAGES) && !pfn_valid_within(pfn + i))
724 			i++;
725 		if (i == MAX_ORDER_NR_PAGES)
726 			continue;
727 		page = pfn_to_page(pfn + i);
728 		if (zone && page_zone(page) != zone)
729 			return 0;
730 		zone = page_zone(page);
731 	}
732 	return 1;
733 }
734 
735 /*
736  * Scanning pfn is much easier than scanning lru list.
737  * Scan pfn from start to end and Find LRU page.
738  */
739 static unsigned long scan_lru_pages(unsigned long start, unsigned long end)
740 {
741 	unsigned long pfn;
742 	struct page *page;
743 	for (pfn = start; pfn < end; pfn++) {
744 		if (pfn_valid(pfn)) {
745 			page = pfn_to_page(pfn);
746 			if (PageLRU(page))
747 				return pfn;
748 		}
749 	}
750 	return 0;
751 }
752 
753 static struct page *
754 hotremove_migrate_alloc(struct page *page, unsigned long private, int **x)
755 {
756 	/* This should be improooooved!! */
757 	return alloc_page(GFP_HIGHUSER_MOVABLE);
758 }
759 
760 #define NR_OFFLINE_AT_ONCE_PAGES	(256)
761 static int
762 do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
763 {
764 	unsigned long pfn;
765 	struct page *page;
766 	int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
767 	int not_managed = 0;
768 	int ret = 0;
769 	LIST_HEAD(source);
770 
771 	for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) {
772 		if (!pfn_valid(pfn))
773 			continue;
774 		page = pfn_to_page(pfn);
775 		if (!get_page_unless_zero(page))
776 			continue;
777 		/*
778 		 * We can skip free pages. And we can only deal with pages on
779 		 * LRU.
780 		 */
781 		ret = isolate_lru_page(page);
782 		if (!ret) { /* Success */
783 			put_page(page);
784 			list_add_tail(&page->lru, &source);
785 			move_pages--;
786 			inc_zone_page_state(page, NR_ISOLATED_ANON +
787 					    page_is_file_cache(page));
788 
789 		} else {
790 #ifdef CONFIG_DEBUG_VM
791 			printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
792 			       pfn);
793 			dump_page(page);
794 #endif
795 			put_page(page);
796 			/* Because we don't have big zone->lock. we should
797 			   check this again here. */
798 			if (page_count(page)) {
799 				not_managed++;
800 				ret = -EBUSY;
801 				break;
802 			}
803 		}
804 	}
805 	if (!list_empty(&source)) {
806 		if (not_managed) {
807 			putback_lru_pages(&source);
808 			goto out;
809 		}
810 		/* this function returns # of failed pages */
811 		ret = migrate_pages(&source, hotremove_migrate_alloc, 0,
812 							true, MIGRATE_SYNC);
813 		if (ret)
814 			putback_lru_pages(&source);
815 	}
816 out:
817 	return ret;
818 }
819 
820 /*
821  * remove from free_area[] and mark all as Reserved.
822  */
823 static int
824 offline_isolated_pages_cb(unsigned long start, unsigned long nr_pages,
825 			void *data)
826 {
827 	__offline_isolated_pages(start, start + nr_pages);
828 	return 0;
829 }
830 
831 static void
832 offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
833 {
834 	walk_system_ram_range(start_pfn, end_pfn - start_pfn, NULL,
835 				offline_isolated_pages_cb);
836 }
837 
838 /*
839  * Check all pages in range, recoreded as memory resource, are isolated.
840  */
841 static int
842 check_pages_isolated_cb(unsigned long start_pfn, unsigned long nr_pages,
843 			void *data)
844 {
845 	int ret;
846 	long offlined = *(long *)data;
847 	ret = test_pages_isolated(start_pfn, start_pfn + nr_pages);
848 	offlined = nr_pages;
849 	if (!ret)
850 		*(long *)data += offlined;
851 	return ret;
852 }
853 
854 static long
855 check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
856 {
857 	long offlined = 0;
858 	int ret;
859 
860 	ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn, &offlined,
861 			check_pages_isolated_cb);
862 	if (ret < 0)
863 		offlined = (long)ret;
864 	return offlined;
865 }
866 
867 static int __ref offline_pages(unsigned long start_pfn,
868 		  unsigned long end_pfn, unsigned long timeout)
869 {
870 	unsigned long pfn, nr_pages, expire;
871 	long offlined_pages;
872 	int ret, drain, retry_max, node;
873 	struct zone *zone;
874 	struct memory_notify arg;
875 
876 	BUG_ON(start_pfn >= end_pfn);
877 	/* at least, alignment against pageblock is necessary */
878 	if (!IS_ALIGNED(start_pfn, pageblock_nr_pages))
879 		return -EINVAL;
880 	if (!IS_ALIGNED(end_pfn, pageblock_nr_pages))
881 		return -EINVAL;
882 	/* This makes hotplug much easier...and readable.
883 	   we assume this for now. .*/
884 	if (!test_pages_in_a_zone(start_pfn, end_pfn))
885 		return -EINVAL;
886 
887 	lock_memory_hotplug();
888 
889 	zone = page_zone(pfn_to_page(start_pfn));
890 	node = zone_to_nid(zone);
891 	nr_pages = end_pfn - start_pfn;
892 
893 	/* set above range as isolated */
894 	ret = start_isolate_page_range(start_pfn, end_pfn);
895 	if (ret)
896 		goto out;
897 
898 	arg.start_pfn = start_pfn;
899 	arg.nr_pages = nr_pages;
900 	arg.status_change_nid = -1;
901 	if (nr_pages >= node_present_pages(node))
902 		arg.status_change_nid = node;
903 
904 	ret = memory_notify(MEM_GOING_OFFLINE, &arg);
905 	ret = notifier_to_errno(ret);
906 	if (ret)
907 		goto failed_removal;
908 
909 	pfn = start_pfn;
910 	expire = jiffies + timeout;
911 	drain = 0;
912 	retry_max = 5;
913 repeat:
914 	/* start memory hot removal */
915 	ret = -EAGAIN;
916 	if (time_after(jiffies, expire))
917 		goto failed_removal;
918 	ret = -EINTR;
919 	if (signal_pending(current))
920 		goto failed_removal;
921 	ret = 0;
922 	if (drain) {
923 		lru_add_drain_all();
924 		cond_resched();
925 		drain_all_pages();
926 	}
927 
928 	pfn = scan_lru_pages(start_pfn, end_pfn);
929 	if (pfn) { /* We have page on LRU */
930 		ret = do_migrate_range(pfn, end_pfn);
931 		if (!ret) {
932 			drain = 1;
933 			goto repeat;
934 		} else {
935 			if (ret < 0)
936 				if (--retry_max == 0)
937 					goto failed_removal;
938 			yield();
939 			drain = 1;
940 			goto repeat;
941 		}
942 	}
943 	/* drain all zone's lru pagevec, this is asyncronous... */
944 	lru_add_drain_all();
945 	yield();
946 	/* drain pcp pages , this is synchrouns. */
947 	drain_all_pages();
948 	/* check again */
949 	offlined_pages = check_pages_isolated(start_pfn, end_pfn);
950 	if (offlined_pages < 0) {
951 		ret = -EBUSY;
952 		goto failed_removal;
953 	}
954 	printk(KERN_INFO "Offlined Pages %ld\n", offlined_pages);
955 	/* Ok, all of our target is islaoted.
956 	   We cannot do rollback at this point. */
957 	offline_isolated_pages(start_pfn, end_pfn);
958 	/* reset pagetype flags and makes migrate type to be MOVABLE */
959 	undo_isolate_page_range(start_pfn, end_pfn);
960 	/* removal success */
961 	zone->present_pages -= offlined_pages;
962 	zone->zone_pgdat->node_present_pages -= offlined_pages;
963 	totalram_pages -= offlined_pages;
964 
965 	init_per_zone_wmark_min();
966 
967 	if (!node_present_pages(node)) {
968 		node_clear_state(node, N_HIGH_MEMORY);
969 		kswapd_stop(node);
970 	}
971 
972 	vm_total_pages = nr_free_pagecache_pages();
973 	writeback_set_ratelimit();
974 
975 	memory_notify(MEM_OFFLINE, &arg);
976 	unlock_memory_hotplug();
977 	return 0;
978 
979 failed_removal:
980 	printk(KERN_INFO "memory offlining %lx to %lx failed\n",
981 		start_pfn, end_pfn);
982 	memory_notify(MEM_CANCEL_OFFLINE, &arg);
983 	/* pushback to free area */
984 	undo_isolate_page_range(start_pfn, end_pfn);
985 
986 out:
987 	unlock_memory_hotplug();
988 	return ret;
989 }
990 
991 int remove_memory(u64 start, u64 size)
992 {
993 	unsigned long start_pfn, end_pfn;
994 
995 	start_pfn = PFN_DOWN(start);
996 	end_pfn = start_pfn + PFN_DOWN(size);
997 	return offline_pages(start_pfn, end_pfn, 120 * HZ);
998 }
999 #else
1000 int remove_memory(u64 start, u64 size)
1001 {
1002 	return -EINVAL;
1003 }
1004 #endif /* CONFIG_MEMORY_HOTREMOVE */
1005 EXPORT_SYMBOL_GPL(remove_memory);
1006