1/*
2 * linux/mm/page_isolation.c
3 */
4
5#include <linux/mm.h>
6#include <linux/page-isolation.h>
7#include <linux/pageblock-flags.h>
8#include <linux/memory.h>
9#include <linux/hugetlb.h>
10#include "internal.h"
11
12int set_migratetype_isolate(struct page *page, bool skip_hwpoisoned_pages)
13{
14	struct zone *zone;
15	unsigned long flags, pfn;
16	struct memory_isolate_notify arg;
17	int notifier_ret;
18	int ret = -EBUSY;
19
20	zone = page_zone(page);
21
22	spin_lock_irqsave(&zone->lock, flags);
23
24	pfn = page_to_pfn(page);
25	arg.start_pfn = pfn;
26	arg.nr_pages = pageblock_nr_pages;
27	arg.pages_found = 0;
28
29	/*
30	 * It may be possible to isolate a pageblock even if the
31	 * migratetype is not MIGRATE_MOVABLE. The memory isolation
32	 * notifier chain is used by balloon drivers to return the
33	 * number of pages in a range that are held by the balloon
34	 * driver to shrink memory. If all the pages are accounted for
35	 * by balloons, are free, or on the LRU, isolation can continue.
36	 * Later, for example, when memory hotplug notifier runs, these
37	 * pages reported as "can be isolated" should be isolated(freed)
38	 * by the balloon driver through the memory notifier chain.
39	 */
40	notifier_ret = memory_isolate_notify(MEM_ISOLATE_COUNT, &arg);
41	notifier_ret = notifier_to_errno(notifier_ret);
42	if (notifier_ret)
43		goto out;
44	/*
45	 * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
46	 * We just check MOVABLE pages.
47	 */
48	if (!has_unmovable_pages(zone, page, arg.pages_found,
49				 skip_hwpoisoned_pages))
50		ret = 0;
51
52	/*
53	 * immobile means "not-on-lru" paes. If immobile is larger than
54	 * removable-by-driver pages reported by notifier, we'll fail.
55	 */
56
57out:
58	if (!ret) {
59		unsigned long nr_pages;
60		int migratetype = get_pageblock_migratetype(page);
61
62		set_pageblock_migratetype(page, MIGRATE_ISOLATE);
63		zone->nr_isolate_pageblock++;
64		nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);
65
66		__mod_zone_freepage_state(zone, -nr_pages, migratetype);
67	}
68
69	spin_unlock_irqrestore(&zone->lock, flags);
70	if (!ret)
71		drain_all_pages(zone);
72	return ret;
73}
74
75void unset_migratetype_isolate(struct page *page, unsigned migratetype)
76{
77	struct zone *zone;
78	unsigned long flags, nr_pages;
79	struct page *isolated_page = NULL;
80	unsigned int order;
81	unsigned long page_idx, buddy_idx;
82	struct page *buddy;
83
84	zone = page_zone(page);
85	spin_lock_irqsave(&zone->lock, flags);
86	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
87		goto out;
88
89	/*
90	 * Because freepage with more than pageblock_order on isolated
91	 * pageblock is restricted to merge due to freepage counting problem,
92	 * it is possible that there is free buddy page.
93	 * move_freepages_block() doesn't care of merge so we need other
94	 * approach in order to merge them. Isolation and free will make
95	 * these pages to be merged.
96	 */
97	if (PageBuddy(page)) {
98		order = page_order(page);
99		if (order >= pageblock_order) {
100			page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
101			buddy_idx = __find_buddy_index(page_idx, order);
102			buddy = page + (buddy_idx - page_idx);
103
104			if (pfn_valid_within(page_to_pfn(buddy)) &&
105			    !is_migrate_isolate_page(buddy)) {
106				__isolate_free_page(page, order);
107				kernel_map_pages(page, (1 << order), 1);
108				set_page_refcounted(page);
109				isolated_page = page;
110			}
111		}
112	}
113
114	/*
115	 * If we isolate freepage with more than pageblock_order, there
116	 * should be no freepage in the range, so we could avoid costly
117	 * pageblock scanning for freepage moving.
118	 */
119	if (!isolated_page) {
120		nr_pages = move_freepages_block(zone, page, migratetype);
121		__mod_zone_freepage_state(zone, nr_pages, migratetype);
122	}
123	set_pageblock_migratetype(page, migratetype);
124	zone->nr_isolate_pageblock--;
125out:
126	spin_unlock_irqrestore(&zone->lock, flags);
127	if (isolated_page)
128		__free_pages(isolated_page, order);
129}
130
131static inline struct page *
132__first_valid_page(unsigned long pfn, unsigned long nr_pages)
133{
134	int i;
135	for (i = 0; i < nr_pages; i++)
136		if (pfn_valid_within(pfn + i))
137			break;
138	if (unlikely(i == nr_pages))
139		return NULL;
140	return pfn_to_page(pfn + i);
141}
142
143/*
144 * start_isolate_page_range() -- make page-allocation-type of range of pages
145 * to be MIGRATE_ISOLATE.
146 * @start_pfn: The lower PFN of the range to be isolated.
147 * @end_pfn: The upper PFN of the range to be isolated.
148 * @migratetype: migrate type to set in error recovery.
149 *
150 * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
151 * the range will never be allocated. Any free pages and pages freed in the
152 * future will not be allocated again.
153 *
154 * start_pfn/end_pfn must be aligned to pageblock_order.
155 * Returns 0 on success and -EBUSY if any part of range cannot be isolated.
156 */
157int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
158			     unsigned migratetype, bool skip_hwpoisoned_pages)
159{
160	unsigned long pfn;
161	unsigned long undo_pfn;
162	struct page *page;
163
164	BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
165	BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
166
167	for (pfn = start_pfn;
168	     pfn < end_pfn;
169	     pfn += pageblock_nr_pages) {
170		page = __first_valid_page(pfn, pageblock_nr_pages);
171		if (page &&
172		    set_migratetype_isolate(page, skip_hwpoisoned_pages)) {
173			undo_pfn = pfn;
174			goto undo;
175		}
176	}
177	return 0;
178undo:
179	for (pfn = start_pfn;
180	     pfn < undo_pfn;
181	     pfn += pageblock_nr_pages)
182		unset_migratetype_isolate(pfn_to_page(pfn), migratetype);
183
184	return -EBUSY;
185}
186
187/*
188 * Make isolated pages available again.
189 */
190int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
191			    unsigned migratetype)
192{
193	unsigned long pfn;
194	struct page *page;
195	BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
196	BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
197	for (pfn = start_pfn;
198	     pfn < end_pfn;
199	     pfn += pageblock_nr_pages) {
200		page = __first_valid_page(pfn, pageblock_nr_pages);
201		if (!page || get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
202			continue;
203		unset_migratetype_isolate(page, migratetype);
204	}
205	return 0;
206}
207/*
208 * Test all pages in the range is free(means isolated) or not.
209 * all pages in [start_pfn...end_pfn) must be in the same zone.
210 * zone->lock must be held before call this.
211 *
212 * Returns 1 if all pages in the range are isolated.
213 */
214static int
215__test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
216				  bool skip_hwpoisoned_pages)
217{
218	struct page *page;
219
220	while (pfn < end_pfn) {
221		if (!pfn_valid_within(pfn)) {
222			pfn++;
223			continue;
224		}
225		page = pfn_to_page(pfn);
226		if (PageBuddy(page)) {
227			/*
228			 * If race between isolatation and allocation happens,
229			 * some free pages could be in MIGRATE_MOVABLE list
230			 * although pageblock's migratation type of the page
231			 * is MIGRATE_ISOLATE. Catch it and move the page into
232			 * MIGRATE_ISOLATE list.
233			 */
234			if (get_freepage_migratetype(page) != MIGRATE_ISOLATE) {
235				struct page *end_page;
236
237				end_page = page + (1 << page_order(page)) - 1;
238				move_freepages(page_zone(page), page, end_page,
239						MIGRATE_ISOLATE);
240			}
241			pfn += 1 << page_order(page);
242		}
243		else if (page_count(page) == 0 &&
244			get_freepage_migratetype(page) == MIGRATE_ISOLATE)
245			pfn += 1;
246		else if (skip_hwpoisoned_pages && PageHWPoison(page)) {
247			/*
248			 * The HWPoisoned page may be not in buddy
249			 * system, and page_count() is not 0.
250			 */
251			pfn++;
252			continue;
253		}
254		else
255			break;
256	}
257	if (pfn < end_pfn)
258		return 0;
259	return 1;
260}
261
262int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
263			bool skip_hwpoisoned_pages)
264{
265	unsigned long pfn, flags;
266	struct page *page;
267	struct zone *zone;
268	int ret;
269
270	/*
271	 * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
272	 * are not aligned to pageblock_nr_pages.
273	 * Then we just check migratetype first.
274	 */
275	for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
276		page = __first_valid_page(pfn, pageblock_nr_pages);
277		if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
278			break;
279	}
280	page = __first_valid_page(start_pfn, end_pfn - start_pfn);
281	if ((pfn < end_pfn) || !page)
282		return -EBUSY;
283	/* Check all pages are free or marked as ISOLATED */
284	zone = page_zone(page);
285	spin_lock_irqsave(&zone->lock, flags);
286	ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn,
287						skip_hwpoisoned_pages);
288	spin_unlock_irqrestore(&zone->lock, flags);
289	return ret ? 0 : -EBUSY;
290}
291
292struct page *alloc_migrate_target(struct page *page, unsigned long private,
293				  int **resultp)
294{
295	gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
296
297	/*
298	 * TODO: allocate a destination hugepage from a nearest neighbor node,
299	 * accordance with memory policy of the user process if possible. For
300	 * now as a simple work-around, we use the next node for destination.
301	 */
302	if (PageHuge(page)) {
303		nodemask_t src = nodemask_of_node(page_to_nid(page));
304		nodemask_t dst;
305		nodes_complement(dst, src);
306		return alloc_huge_page_node(page_hstate(compound_head(page)),
307					    next_node(page_to_nid(page), dst));
308	}
309
310	if (PageHighMem(page))
311		gfp_mask |= __GFP_HIGHMEM;
312
313	return alloc_page(gfp_mask);
314}
315