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
set_migratetype_isolate(struct page * page,int migratetype,int isol_flags)18 static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags)
19 {
20 struct zone *zone = page_zone(page);
21 struct page *unmovable;
22 unsigned long flags;
23
24 spin_lock_irqsave(&zone->lock, flags);
25
26 /*
27 * We assume the caller intended to SET migrate type to isolate.
28 * If it is already set, then someone else must have raced and
29 * set it before us.
30 */
31 if (is_migrate_isolate_page(page)) {
32 spin_unlock_irqrestore(&zone->lock, flags);
33 return -EBUSY;
34 }
35
36 /*
37 * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
38 * We just check MOVABLE pages.
39 */
40 unmovable = has_unmovable_pages(zone, page, migratetype, isol_flags);
41 if (!unmovable) {
42 unsigned long nr_pages;
43 int mt = get_pageblock_migratetype(page);
44
45 set_pageblock_migratetype(page, MIGRATE_ISOLATE);
46 zone->nr_isolate_pageblock++;
47 nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE,
48 NULL);
49
50 __mod_zone_freepage_state(zone, -nr_pages, mt);
51 spin_unlock_irqrestore(&zone->lock, flags);
52 drain_all_pages(zone);
53 return 0;
54 }
55
56 spin_unlock_irqrestore(&zone->lock, flags);
57 if (isol_flags & REPORT_FAILURE) {
58 /*
59 * printk() with zone->lock held will likely trigger a
60 * lockdep splat, so defer it here.
61 */
62 dump_page(unmovable, "unmovable page");
63 }
64
65 return -EBUSY;
66 }
67
unset_migratetype_isolate(struct page * page,unsigned migratetype)68 static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
69 {
70 struct zone *zone;
71 unsigned long flags, nr_pages;
72 bool isolated_page = false;
73 unsigned int order;
74 unsigned long pfn, buddy_pfn;
75 struct page *buddy;
76
77 zone = page_zone(page);
78 spin_lock_irqsave(&zone->lock, flags);
79 if (!is_migrate_isolate_page(page))
80 goto out;
81
82 /*
83 * Because freepage with more than pageblock_order on isolated
84 * pageblock is restricted to merge due to freepage counting problem,
85 * it is possible that there is free buddy page.
86 * move_freepages_block() doesn't care of merge so we need other
87 * approach in order to merge them. Isolation and free will make
88 * these pages to be merged.
89 */
90 if (PageBuddy(page)) {
91 order = buddy_order(page);
92 if (order >= pageblock_order) {
93 pfn = page_to_pfn(page);
94 buddy_pfn = __find_buddy_pfn(pfn, order);
95 buddy = page + (buddy_pfn - pfn);
96
97 if (pfn_valid_within(buddy_pfn) &&
98 !is_migrate_isolate_page(buddy)) {
99 __isolate_free_page(page, order);
100 isolated_page = true;
101 }
102 }
103 }
104
105 /*
106 * If we isolate freepage with more than pageblock_order, there
107 * should be no freepage in the range, so we could avoid costly
108 * pageblock scanning for freepage moving.
109 *
110 * We didn't actually touch any of the isolated pages, so place them
111 * to the tail of the freelist. This is an optimization for memory
112 * onlining - just onlined memory won't immediately be considered for
113 * allocation.
114 */
115 if (!isolated_page) {
116 nr_pages = move_freepages_block(zone, page, migratetype, NULL);
117 __mod_zone_freepage_state(zone, nr_pages, migratetype);
118 }
119 set_pageblock_migratetype(page, migratetype);
120 if (isolated_page)
121 __putback_isolated_page(page, order, migratetype);
122 zone->nr_isolate_pageblock--;
123 out:
124 spin_unlock_irqrestore(&zone->lock, flags);
125 }
126
127 static inline struct page *
__first_valid_page(unsigned long pfn,unsigned long nr_pages)128 __first_valid_page(unsigned long pfn, unsigned long nr_pages)
129 {
130 int i;
131
132 for (i = 0; i < nr_pages; i++) {
133 struct page *page;
134
135 page = pfn_to_online_page(pfn + i);
136 if (!page)
137 continue;
138 return page;
139 }
140 return NULL;
141 }
142
143 /**
144 * start_isolate_page_range() - make page-allocation-type of range of pages to
145 * 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 * start_pfn/end_pfn must be aligned to pageblock_order.
149 * @migratetype: Migrate type to set in error recovery.
150 * @flags: The following flags are allowed (they can be combined in
151 * a bit mask)
152 * MEMORY_OFFLINE - isolate to offline (!allocate) memory
153 * e.g., skip over PageHWPoison() pages
154 * and PageOffline() pages.
155 * REPORT_FAILURE - report details about the failure to
156 * isolate the range
157 *
158 * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
159 * the range will never be allocated. Any free pages and pages freed in the
160 * future will not be allocated again. If specified range includes migrate types
161 * other than MOVABLE or CMA, this will fail with -EBUSY. For isolating all
162 * pages in the range finally, the caller have to free all pages in the range.
163 * test_page_isolated() can be used for test it.
164 *
165 * There is no high level synchronization mechanism that prevents two threads
166 * from trying to isolate overlapping ranges. If this happens, one thread
167 * will notice pageblocks in the overlapping range already set to isolate.
168 * This happens in set_migratetype_isolate, and set_migratetype_isolate
169 * returns an error. We then clean up by restoring the migration type on
170 * pageblocks we may have modified and return -EBUSY to caller. This
171 * prevents two threads from simultaneously working on overlapping ranges.
172 *
173 * Please note that there is no strong synchronization with the page allocator
174 * either. Pages might be freed while their page blocks are marked ISOLATED.
175 * In some cases pages might still end up on pcp lists and that would allow
176 * for their allocation even when they are in fact isolated already. Depending
177 * on how strong of a guarantee the caller needs drain_all_pages might be needed
178 * (e.g. __offline_pages will need to call it after check for isolated range for
179 * a next retry).
180 *
181 * Return: 0 on success and -EBUSY if any part of range cannot be isolated.
182 */
start_isolate_page_range(unsigned long start_pfn,unsigned long end_pfn,unsigned migratetype,int flags)183 int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
184 unsigned migratetype, int flags)
185 {
186 unsigned long pfn;
187 unsigned long undo_pfn;
188 struct page *page;
189
190 BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
191 BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
192
193 for (pfn = start_pfn;
194 pfn < end_pfn;
195 pfn += pageblock_nr_pages) {
196 page = __first_valid_page(pfn, pageblock_nr_pages);
197 if (page) {
198 if (set_migratetype_isolate(page, migratetype, flags)) {
199 undo_pfn = pfn;
200 goto undo;
201 }
202 }
203 }
204 return 0;
205 undo:
206 for (pfn = start_pfn;
207 pfn < undo_pfn;
208 pfn += pageblock_nr_pages) {
209 struct page *page = pfn_to_online_page(pfn);
210 if (!page)
211 continue;
212 unset_migratetype_isolate(page, migratetype);
213 }
214
215 return -EBUSY;
216 }
217
218 /*
219 * Make isolated pages available again.
220 */
undo_isolate_page_range(unsigned long start_pfn,unsigned long end_pfn,unsigned migratetype)221 void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
222 unsigned migratetype)
223 {
224 unsigned long pfn;
225 struct page *page;
226
227 BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
228 BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
229
230 for (pfn = start_pfn;
231 pfn < end_pfn;
232 pfn += pageblock_nr_pages) {
233 page = __first_valid_page(pfn, pageblock_nr_pages);
234 if (!page || !is_migrate_isolate_page(page))
235 continue;
236 unset_migratetype_isolate(page, migratetype);
237 }
238 }
239 /*
240 * Test all pages in the range is free(means isolated) or not.
241 * all pages in [start_pfn...end_pfn) must be in the same zone.
242 * zone->lock must be held before call this.
243 *
244 * Returns the last tested pfn.
245 */
246 static unsigned long
__test_page_isolated_in_pageblock(unsigned long pfn,unsigned long end_pfn,int flags)247 __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
248 int flags)
249 {
250 struct page *page;
251
252 while (pfn < end_pfn) {
253 if (!pfn_valid_within(pfn)) {
254 pfn++;
255 continue;
256 }
257 page = pfn_to_page(pfn);
258 if (PageBuddy(page))
259 /*
260 * If the page is on a free list, it has to be on
261 * the correct MIGRATE_ISOLATE freelist. There is no
262 * simple way to verify that as VM_BUG_ON(), though.
263 */
264 pfn += 1 << buddy_order(page);
265 else if ((flags & MEMORY_OFFLINE) && PageHWPoison(page))
266 /* A HWPoisoned page cannot be also PageBuddy */
267 pfn++;
268 else if ((flags & MEMORY_OFFLINE) && PageOffline(page) &&
269 !page_count(page))
270 /*
271 * The responsible driver agreed to skip PageOffline()
272 * pages when offlining memory by dropping its
273 * reference in MEM_GOING_OFFLINE.
274 */
275 pfn++;
276 else
277 break;
278 }
279
280 return pfn;
281 }
282
283 /* Caller should ensure that requested range is in a single zone */
test_pages_isolated(unsigned long start_pfn,unsigned long end_pfn,int isol_flags)284 int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
285 int isol_flags)
286 {
287 unsigned long pfn, flags;
288 struct page *page;
289 struct zone *zone;
290
291 /*
292 * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
293 * are not aligned to pageblock_nr_pages.
294 * Then we just check migratetype first.
295 */
296 for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
297 page = __first_valid_page(pfn, pageblock_nr_pages);
298 if (page && !is_migrate_isolate_page(page))
299 break;
300 }
301 page = __first_valid_page(start_pfn, end_pfn - start_pfn);
302 if ((pfn < end_pfn) || !page)
303 return -EBUSY;
304 /* Check all pages are free or marked as ISOLATED */
305 zone = page_zone(page);
306 spin_lock_irqsave(&zone->lock, flags);
307 pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn, isol_flags);
308 spin_unlock_irqrestore(&zone->lock, flags);
309
310 trace_test_pages_isolated(start_pfn, end_pfn, pfn);
311
312 return pfn < end_pfn ? -EBUSY : 0;
313 }
314
