1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/mm/page_isolation.c
4 */
5
6 #include <linux/mm.h>
7 #include <linux/page-isolation.h>
8 #include <linux/pageblock-flags.h>
9 #include <linux/memory.h>
10 #include <linux/hugetlb.h>
11 #include <linux/page_owner.h>
12 #include <linux/migrate.h>
13 #include "internal.h"
14
15 #define CREATE_TRACE_POINTS
16 #include <trace/events/page_isolation.h>
17
18 static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags)
19 {
20 struct zone *zone;
21 unsigned long flags, pfn;
22 struct memory_isolate_notify arg;
23 int notifier_ret;
24 int ret = -EBUSY;
25
26 zone = page_zone(page);
27
28 spin_lock_irqsave(&zone->lock, flags);
29
30 /*
31 * We assume the caller intended to SET migrate type to isolate.
32 * If it is already set, then someone else must have raced and
33 * set it before us. Return -EBUSY
34 */
35 if (is_migrate_isolate_page(page))
36 goto out;
37
38 pfn = page_to_pfn(page);
39 arg.start_pfn = pfn;
40 arg.nr_pages = pageblock_nr_pages;
41 arg.pages_found = 0;
42
43 /*
44 * It may be possible to isolate a pageblock even if the
45 * migratetype is not MIGRATE_MOVABLE. The memory isolation
46 * notifier chain is used by balloon drivers to return the
47 * number of pages in a range that are held by the balloon
48 * driver to shrink memory. If all the pages are accounted for
49 * by balloons, are free, or on the LRU, isolation can continue.
50 * Later, for example, when memory hotplug notifier runs, these
51 * pages reported as "can be isolated" should be isolated(freed)
52 * by the balloon driver through the memory notifier chain.
53 */
54 notifier_ret = memory_isolate_notify(MEM_ISOLATE_COUNT, &arg);
55 notifier_ret = notifier_to_errno(notifier_ret);
56 if (notifier_ret)
57 goto out;
58 /*
59 * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
60 * We just check MOVABLE pages.
61 */
62 if (!has_unmovable_pages(zone, page, arg.pages_found, migratetype,
63 isol_flags))
64 ret = 0;
65
66 /*
67 * immobile means "not-on-lru" pages. If immobile is larger than
68 * removable-by-driver pages reported by notifier, we'll fail.
69 */
70
71 out:
72 if (!ret) {
73 unsigned long nr_pages;
74 int mt = get_pageblock_migratetype(page);
75
76 set_pageblock_migratetype(page, MIGRATE_ISOLATE);
77 zone->nr_isolate_pageblock++;
78 nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE,
79 NULL);
80
81 __mod_zone_freepage_state(zone, -nr_pages, mt);
82 }
83
84 spin_unlock_irqrestore(&zone->lock, flags);
85 if (!ret)
86 drain_all_pages(zone);
87 return ret;
88 }
89
90 static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
91 {
92 struct zone *zone;
93 unsigned long flags, nr_pages;
94 bool isolated_page = false;
95 unsigned int order;
96 unsigned long pfn, buddy_pfn;
97 struct page *buddy;
98
99 zone = page_zone(page);
100 spin_lock_irqsave(&zone->lock, flags);
101 if (!is_migrate_isolate_page(page))
102 goto out;
103
104 /*
105 * Because freepage with more than pageblock_order on isolated
106 * pageblock is restricted to merge due to freepage counting problem,
107 * it is possible that there is free buddy page.
108 * move_freepages_block() doesn't care of merge so we need other
109 * approach in order to merge them. Isolation and free will make
110 * these pages to be merged.
111 */
112 if (PageBuddy(page)) {
113 order = page_order(page);
114 if (order >= pageblock_order) {
115 pfn = page_to_pfn(page);
116 buddy_pfn = __find_buddy_pfn(pfn, order);
117 buddy = page + (buddy_pfn - pfn);
118
119 if (pfn_valid_within(buddy_pfn) &&
120 !is_migrate_isolate_page(buddy)) {
121 __isolate_free_page(page, order);
122 isolated_page = true;
123 }
124 }
125 }
126
127 /*
128 * If we isolate freepage with more than pageblock_order, there
129 * should be no freepage in the range, so we could avoid costly
130 * pageblock scanning for freepage moving.
131 */
132 if (!isolated_page) {
133 nr_pages = move_freepages_block(zone, page, migratetype, NULL);
134 __mod_zone_freepage_state(zone, nr_pages, migratetype);
135 }
136 set_pageblock_migratetype(page, migratetype);
137 zone->nr_isolate_pageblock--;
138 out:
139 spin_unlock_irqrestore(&zone->lock, flags);
140 if (isolated_page) {
141 post_alloc_hook(page, order, __GFP_MOVABLE);
142 __free_pages(page, order);
143 }
144 }
145
146 static inline struct page *
147 __first_valid_page(unsigned long pfn, unsigned long nr_pages)
148 {
149 int i;
150
151 for (i = 0; i < nr_pages; i++) {
152 struct page *page;
153
154 page = pfn_to_online_page(pfn + i);
155 if (!page)
156 continue;
157 return page;
158 }
159 return NULL;
160 }
161
162 /**
163 * start_isolate_page_range() - make page-allocation-type of range of pages to
164 * be MIGRATE_ISOLATE.
165 * @start_pfn: The lower PFN of the range to be isolated.
166 * @end_pfn: The upper PFN of the range to be isolated.
167 * start_pfn/end_pfn must be aligned to pageblock_order.
168 * @migratetype: Migrate type to set in error recovery.
169 * @flags: The following flags are allowed (they can be combined in
170 * a bit mask)
171 * SKIP_HWPOISON - ignore hwpoison pages
172 * REPORT_FAILURE - report details about the failure to
173 * isolate the range
174 *
175 * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
176 * the range will never be allocated. Any free pages and pages freed in the
177 * future will not be allocated again. If specified range includes migrate types
178 * other than MOVABLE or CMA, this will fail with -EBUSY. For isolating all
179 * pages in the range finally, the caller have to free all pages in the range.
180 * test_page_isolated() can be used for test it.
181 *
182 * There is no high level synchronization mechanism that prevents two threads
183 * from trying to isolate overlapping ranges. If this happens, one thread
184 * will notice pageblocks in the overlapping range already set to isolate.
185 * This happens in set_migratetype_isolate, and set_migratetype_isolate
186 * returns an error. We then clean up by restoring the migration type on
187 * pageblocks we may have modified and return -EBUSY to caller. This
188 * prevents two threads from simultaneously working on overlapping ranges.
189 *
190 * Return: the number of isolated pageblocks on success and -EBUSY if any part
191 * of range cannot be isolated.
192 */
193 int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
194 unsigned migratetype, int flags)
195 {
196 unsigned long pfn;
197 unsigned long undo_pfn;
198 struct page *page;
199 int nr_isolate_pageblock = 0;
200
201 BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
202 BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
203
204 for (pfn = start_pfn;
205 pfn < end_pfn;
206 pfn += pageblock_nr_pages) {
207 page = __first_valid_page(pfn, pageblock_nr_pages);
208 if (page) {
209 if (set_migratetype_isolate(page, migratetype, flags)) {
210 undo_pfn = pfn;
211 goto undo;
212 }
213 nr_isolate_pageblock++;
214 }
215 }
216 return nr_isolate_pageblock;
217 undo:
218 for (pfn = start_pfn;
219 pfn < undo_pfn;
220 pfn += pageblock_nr_pages) {
221 struct page *page = pfn_to_online_page(pfn);
222 if (!page)
223 continue;
224 unset_migratetype_isolate(page, migratetype);
225 }
226
227 return -EBUSY;
228 }
229
230 /*
231 * Make isolated pages available again.
232 */
233 void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
234 unsigned migratetype)
235 {
236 unsigned long pfn;
237 struct page *page;
238
239 BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
240 BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
241
242 for (pfn = start_pfn;
243 pfn < end_pfn;
244 pfn += pageblock_nr_pages) {
245 page = __first_valid_page(pfn, pageblock_nr_pages);
246 if (!page || !is_migrate_isolate_page(page))
247 continue;
248 unset_migratetype_isolate(page, migratetype);
249 }
250 }
251 /*
252 * Test all pages in the range is free(means isolated) or not.
253 * all pages in [start_pfn...end_pfn) must be in the same zone.
254 * zone->lock must be held before call this.
255 *
256 * Returns the last tested pfn.
257 */
258 static unsigned long
259 __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
260 bool skip_hwpoisoned_pages)
261 {
262 struct page *page;
263
264 while (pfn < end_pfn) {
265 if (!pfn_valid_within(pfn)) {
266 pfn++;
267 continue;
268 }
269 page = pfn_to_page(pfn);
270 if (PageBuddy(page))
271 /*
272 * If the page is on a free list, it has to be on
273 * the correct MIGRATE_ISOLATE freelist. There is no
274 * simple way to verify that as VM_BUG_ON(), though.
275 */
276 pfn += 1 << page_order(page);
277 else if (skip_hwpoisoned_pages && PageHWPoison(page))
278 /* A HWPoisoned page cannot be also PageBuddy */
279 pfn++;
280 else
281 break;
282 }
283
284 return pfn;
285 }
286
287 /* Caller should ensure that requested range is in a single zone */
288 int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
289 bool skip_hwpoisoned_pages)
290 {
291 unsigned long pfn, flags;
292 struct page *page;
293 struct zone *zone;
294
295 /*
296 * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
297 * are not aligned to pageblock_nr_pages.
298 * Then we just check migratetype first.
299 */
300 for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
301 page = __first_valid_page(pfn, pageblock_nr_pages);
302 if (page && !is_migrate_isolate_page(page))
303 break;
304 }
305 page = __first_valid_page(start_pfn, end_pfn - start_pfn);
306 if ((pfn < end_pfn) || !page)
307 return -EBUSY;
308 /* Check all pages are free or marked as ISOLATED */
309 zone = page_zone(page);
310 spin_lock_irqsave(&zone->lock, flags);
311 pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn,
312 skip_hwpoisoned_pages);
313 spin_unlock_irqrestore(&zone->lock, flags);
314
315 trace_test_pages_isolated(start_pfn, end_pfn, pfn);
316
317 return pfn < end_pfn ? -EBUSY : 0;
318 }
319
320 struct page *alloc_migrate_target(struct page *page, unsigned long private)
321 {
322 return new_page_nodemask(page, numa_node_id(), &node_states[N_MEMORY]);
323 }