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