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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 = 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 | return 0; | |
53 | } | |
54 | ||
55 | spin_unlock_irqrestore(&zone->lock, flags); | |
56 | if (isol_flags & REPORT_FAILURE) { | |
57 | /* | |
58 | * printk() with zone->lock held will likely trigger a | |
59 | * lockdep splat, so defer it here. | |
60 | */ | |
61 | dump_page(unmovable, "unmovable page"); | |
62 | } | |
63 | ||
64 | return -EBUSY; | |
65 | } | |
66 | ||
67 | static void unset_migratetype_isolate(struct page *page, unsigned migratetype) | |
68 | { | |
69 | struct zone *zone; | |
70 | unsigned long flags, nr_pages; | |
71 | bool isolated_page = false; | |
72 | unsigned int order; | |
73 | unsigned long pfn, buddy_pfn; | |
74 | struct page *buddy; | |
75 | ||
76 | zone = page_zone(page); | |
77 | spin_lock_irqsave(&zone->lock, flags); | |
78 | if (!is_migrate_isolate_page(page)) | |
79 | goto out; | |
80 | ||
81 | /* | |
82 | * Because freepage with more than pageblock_order on isolated | |
83 | * pageblock is restricted to merge due to freepage counting problem, | |
84 | * it is possible that there is free buddy page. | |
85 | * move_freepages_block() doesn't care of merge so we need other | |
86 | * approach in order to merge them. Isolation and free will make | |
87 | * these pages to be merged. | |
88 | */ | |
89 | if (PageBuddy(page)) { | |
90 | order = buddy_order(page); | |
91 | if (order >= pageblock_order && order < MAX_ORDER - 1) { | |
92 | pfn = page_to_pfn(page); | |
93 | buddy_pfn = __find_buddy_pfn(pfn, order); | |
94 | buddy = page + (buddy_pfn - pfn); | |
95 | ||
96 | if (!is_migrate_isolate_page(buddy)) { | |
97 | __isolate_free_page(page, order); | |
98 | isolated_page = true; | |
99 | } | |
100 | } | |
101 | } | |
102 | ||
103 | /* | |
104 | * If we isolate freepage with more than pageblock_order, there | |
105 | * should be no freepage in the range, so we could avoid costly | |
106 | * pageblock scanning for freepage moving. | |
107 | * | |
108 | * We didn't actually touch any of the isolated pages, so place them | |
109 | * to the tail of the freelist. This is an optimization for memory | |
110 | * onlining - just onlined memory won't immediately be considered for | |
111 | * allocation. | |
112 | */ | |
113 | if (!isolated_page) { | |
114 | nr_pages = move_freepages_block(zone, page, migratetype, NULL); | |
115 | __mod_zone_freepage_state(zone, nr_pages, migratetype); | |
116 | } | |
117 | set_pageblock_migratetype(page, migratetype); | |
118 | if (isolated_page) | |
119 | __putback_isolated_page(page, order, migratetype); | |
120 | zone->nr_isolate_pageblock--; | |
121 | out: | |
122 | spin_unlock_irqrestore(&zone->lock, flags); | |
123 | } | |
124 | ||
125 | static inline struct page * | |
126 | __first_valid_page(unsigned long pfn, unsigned long nr_pages) | |
127 | { | |
128 | int i; | |
129 | ||
130 | for (i = 0; i < nr_pages; i++) { | |
131 | struct page *page; | |
132 | ||
133 | page = pfn_to_online_page(pfn + i); | |
134 | if (!page) | |
135 | continue; | |
136 | return page; | |
137 | } | |
138 | return NULL; | |
139 | } | |
140 | ||
141 | /** | |
142 | * start_isolate_page_range() - make page-allocation-type of range of pages to | |
143 | * be MIGRATE_ISOLATE. | |
144 | * @start_pfn: The lower PFN of the range to be isolated. | |
145 | * @end_pfn: The upper PFN of the range to be isolated. | |
146 | * start_pfn/end_pfn must be aligned to pageblock_order. | |
147 | * @migratetype: Migrate type to set in error recovery. | |
148 | * @flags: The following flags are allowed (they can be combined in | |
149 | * a bit mask) | |
150 | * MEMORY_OFFLINE - isolate to offline (!allocate) memory | |
151 | * e.g., skip over PageHWPoison() pages | |
152 | * and PageOffline() pages. | |
153 | * REPORT_FAILURE - report details about the failure to | |
154 | * isolate the range | |
155 | * | |
156 | * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in | |
157 | * the range will never be allocated. Any free pages and pages freed in the | |
158 | * future will not be allocated again. If specified range includes migrate types | |
159 | * other than MOVABLE or CMA, this will fail with -EBUSY. For isolating all | |
160 | * pages in the range finally, the caller have to free all pages in the range. | |
161 | * test_page_isolated() can be used for test it. | |
162 | * | |
163 | * There is no high level synchronization mechanism that prevents two threads | |
164 | * from trying to isolate overlapping ranges. If this happens, one thread | |
165 | * will notice pageblocks in the overlapping range already set to isolate. | |
166 | * This happens in set_migratetype_isolate, and set_migratetype_isolate | |
167 | * returns an error. We then clean up by restoring the migration type on | |
168 | * pageblocks we may have modified and return -EBUSY to caller. This | |
169 | * prevents two threads from simultaneously working on overlapping ranges. | |
170 | * | |
171 | * Please note that there is no strong synchronization with the page allocator | |
172 | * either. Pages might be freed while their page blocks are marked ISOLATED. | |
173 | * A call to drain_all_pages() after isolation can flush most of them. However | |
174 | * in some cases pages might still end up on pcp lists and that would allow | |
175 | * for their allocation even when they are in fact isolated already. Depending | |
176 | * on how strong of a guarantee the caller needs, zone_pcp_disable/enable() | |
177 | * might be used to flush and disable pcplist before isolation and enable after | |
178 | * unisolation. | |
179 | * | |
180 | * Return: 0 on success and -EBUSY if any part of range cannot be isolated. | |
181 | */ | |
182 | int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, | |
183 | unsigned migratetype, int flags) | |
184 | { | |
185 | unsigned long pfn; | |
186 | unsigned long undo_pfn; | |
187 | struct page *page; | |
188 | ||
189 | BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages)); | |
190 | BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages)); | |
191 | ||
192 | for (pfn = start_pfn; | |
193 | pfn < end_pfn; | |
194 | pfn += pageblock_nr_pages) { | |
195 | page = __first_valid_page(pfn, pageblock_nr_pages); | |
196 | if (page) { | |
197 | if (set_migratetype_isolate(page, migratetype, flags)) { | |
198 | undo_pfn = pfn; | |
199 | goto undo; | |
200 | } | |
201 | } | |
202 | } | |
203 | return 0; | |
204 | undo: | |
205 | for (pfn = start_pfn; | |
206 | pfn < undo_pfn; | |
207 | pfn += pageblock_nr_pages) { | |
208 | struct page *page = pfn_to_online_page(pfn); | |
209 | if (!page) | |
210 | continue; | |
211 | unset_migratetype_isolate(page, migratetype); | |
212 | } | |
213 | ||
214 | return -EBUSY; | |
215 | } | |
216 | ||
217 | /* | |
218 | * Make isolated pages available again. | |
219 | */ | |
220 | void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, | |
221 | unsigned migratetype) | |
222 | { | |
223 | unsigned long pfn; | |
224 | struct page *page; | |
225 | ||
226 | BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages)); | |
227 | BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages)); | |
228 | ||
229 | for (pfn = start_pfn; | |
230 | pfn < end_pfn; | |
231 | pfn += pageblock_nr_pages) { | |
232 | page = __first_valid_page(pfn, pageblock_nr_pages); | |
233 | if (!page || !is_migrate_isolate_page(page)) | |
234 | continue; | |
235 | unset_migratetype_isolate(page, migratetype); | |
236 | } | |
237 | } | |
238 | /* | |
239 | * Test all pages in the range is free(means isolated) or not. | |
240 | * all pages in [start_pfn...end_pfn) must be in the same zone. | |
241 | * zone->lock must be held before call this. | |
242 | * | |
243 | * Returns the last tested pfn. | |
244 | */ | |
245 | static unsigned long | |
246 | __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn, | |
247 | int flags) | |
248 | { | |
249 | struct page *page; | |
250 | ||
251 | while (pfn < end_pfn) { | |
252 | page = pfn_to_page(pfn); | |
253 | if (PageBuddy(page)) | |
254 | /* | |
255 | * If the page is on a free list, it has to be on | |
256 | * the correct MIGRATE_ISOLATE freelist. There is no | |
257 | * simple way to verify that as VM_BUG_ON(), though. | |
258 | */ | |
259 | pfn += 1 << buddy_order(page); | |
260 | else if ((flags & MEMORY_OFFLINE) && PageHWPoison(page)) | |
261 | /* A HWPoisoned page cannot be also PageBuddy */ | |
262 | pfn++; | |
263 | else if ((flags & MEMORY_OFFLINE) && PageOffline(page) && | |
264 | !page_count(page)) | |
265 | /* | |
266 | * The responsible driver agreed to skip PageOffline() | |
267 | * pages when offlining memory by dropping its | |
268 | * reference in MEM_GOING_OFFLINE. | |
269 | */ | |
270 | pfn++; | |
271 | else | |
272 | break; | |
273 | } | |
274 | ||
275 | return pfn; | |
276 | } | |
277 | ||
278 | /* Caller should ensure that requested range is in a single zone */ | |
279 | int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn, | |
280 | int isol_flags) | |
281 | { | |
282 | unsigned long pfn, flags; | |
283 | struct page *page; | |
284 | struct zone *zone; | |
285 | int ret; | |
286 | ||
287 | /* | |
288 | * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages | |
289 | * are not aligned to pageblock_nr_pages. | |
290 | * Then we just check migratetype first. | |
291 | */ | |
292 | for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) { | |
293 | page = __first_valid_page(pfn, pageblock_nr_pages); | |
294 | if (page && !is_migrate_isolate_page(page)) | |
295 | break; | |
296 | } | |
297 | page = __first_valid_page(start_pfn, end_pfn - start_pfn); | |
298 | if ((pfn < end_pfn) || !page) { | |
299 | ret = -EBUSY; | |
300 | goto out; | |
301 | } | |
302 | ||
303 | /* Check all pages are free or marked as ISOLATED */ | |
304 | zone = page_zone(page); | |
305 | spin_lock_irqsave(&zone->lock, flags); | |
306 | pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn, isol_flags); | |
307 | spin_unlock_irqrestore(&zone->lock, flags); | |
308 | ||
309 | ret = pfn < end_pfn ? -EBUSY : 0; | |
310 | ||
311 | out: | |
312 | trace_test_pages_isolated(start_pfn, end_pfn, pfn); | |
313 | ||
314 | return ret; | |
315 | } |