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, flags)) 63 ret = 0; 64 65 /* 66 * immobile means "not-on-lru" pages. If immobile is larger than 67 * removable-by-driver pages reported by notifier, we'll fail. 68 */ 69 70 out: 71 if (!ret) { 72 unsigned long nr_pages; 73 int mt = get_pageblock_migratetype(page); 74 75 set_pageblock_migratetype(page, MIGRATE_ISOLATE); 76 zone->nr_isolate_pageblock++; 77 nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE, 78 NULL); 79 80 __mod_zone_freepage_state(zone, -nr_pages, mt); 81 } 82 83 spin_unlock_irqrestore(&zone->lock, flags); 84 if (!ret) 85 drain_all_pages(zone); 86 return ret; 87 } 88 89 static void unset_migratetype_isolate(struct page *page, unsigned migratetype) 90 { 91 struct zone *zone; 92 unsigned long flags, nr_pages; 93 bool isolated_page = false; 94 unsigned int order; 95 unsigned long pfn, buddy_pfn; 96 struct page *buddy; 97 98 zone = page_zone(page); 99 spin_lock_irqsave(&zone->lock, flags); 100 if (!is_migrate_isolate_page(page)) 101 goto out; 102 103 /* 104 * Because freepage with more than pageblock_order on isolated 105 * pageblock is restricted to merge due to freepage counting problem, 106 * it is possible that there is free buddy page. 107 * move_freepages_block() doesn't care of merge so we need other 108 * approach in order to merge them. Isolation and free will make 109 * these pages to be merged. 110 */ 111 if (PageBuddy(page)) { 112 order = page_order(page); 113 if (order >= pageblock_order) { 114 pfn = page_to_pfn(page); 115 buddy_pfn = __find_buddy_pfn(pfn, order); 116 buddy = page + (buddy_pfn - pfn); 117 118 if (pfn_valid_within(buddy_pfn) && 119 !is_migrate_isolate_page(buddy)) { 120 __isolate_free_page(page, order); 121 isolated_page = true; 122 } 123 } 124 } 125 126 /* 127 * If we isolate freepage with more than pageblock_order, there 128 * should be no freepage in the range, so we could avoid costly 129 * pageblock scanning for freepage moving. 130 */ 131 if (!isolated_page) { 132 nr_pages = move_freepages_block(zone, page, migratetype, NULL); 133 __mod_zone_freepage_state(zone, nr_pages, migratetype); 134 } 135 set_pageblock_migratetype(page, migratetype); 136 zone->nr_isolate_pageblock--; 137 out: 138 spin_unlock_irqrestore(&zone->lock, flags); 139 if (isolated_page) { 140 post_alloc_hook(page, order, __GFP_MOVABLE); 141 __free_pages(page, order); 142 } 143 } 144 145 static inline struct page * 146 __first_valid_page(unsigned long pfn, unsigned long nr_pages) 147 { 148 int i; 149 150 for (i = 0; i < nr_pages; i++) { 151 struct page *page; 152 153 if (!pfn_valid_within(pfn + i)) 154 continue; 155 page = pfn_to_online_page(pfn + i); 156 if (!page) 157 continue; 158 return page; 159 } 160 return NULL; 161 } 162 163 /* 164 * start_isolate_page_range() -- make page-allocation-type of range of pages 165 * to be MIGRATE_ISOLATE. 166 * @start_pfn: The lower PFN of the range to be isolated. 167 * @end_pfn: The upper PFN of the range to be isolated. 168 * @migratetype: migrate type to set in error recovery. 169 * 170 * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in 171 * the range will never be allocated. Any free pages and pages freed in the 172 * future will not be allocated again. 173 * 174 * start_pfn/end_pfn must be aligned to pageblock_order. 175 * Return 0 on success and -EBUSY if any part of range cannot be isolated. 176 * 177 * There is no high level synchronization mechanism that prevents two threads 178 * from trying to isolate overlapping ranges. If this happens, one thread 179 * will notice pageblocks in the overlapping range already set to isolate. 180 * This happens in set_migratetype_isolate, and set_migratetype_isolate 181 * returns an error. We then clean up by restoring the migration type on 182 * pageblocks we may have modified and return -EBUSY to caller. This 183 * prevents two threads from simultaneously working on overlapping ranges. 184 */ 185 int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, 186 unsigned migratetype, int flags) 187 { 188 unsigned long pfn; 189 unsigned long undo_pfn; 190 struct page *page; 191 192 BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages)); 193 BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages)); 194 195 for (pfn = start_pfn; 196 pfn < end_pfn; 197 pfn += pageblock_nr_pages) { 198 page = __first_valid_page(pfn, pageblock_nr_pages); 199 if (page && 200 set_migratetype_isolate(page, migratetype, flags)) { 201 undo_pfn = pfn; 202 goto undo; 203 } 204 } 205 return 0; 206 undo: 207 for (pfn = start_pfn; 208 pfn < undo_pfn; 209 pfn += pageblock_nr_pages) { 210 struct page *page = pfn_to_online_page(pfn); 211 if (!page) 212 continue; 213 unset_migratetype_isolate(page, migratetype); 214 } 215 216 return -EBUSY; 217 } 218 219 /* 220 * Make isolated pages available again. 221 */ 222 int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, 223 unsigned migratetype) 224 { 225 unsigned long pfn; 226 struct page *page; 227 228 BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages)); 229 BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages)); 230 231 for (pfn = start_pfn; 232 pfn < end_pfn; 233 pfn += pageblock_nr_pages) { 234 page = __first_valid_page(pfn, pageblock_nr_pages); 235 if (!page || !is_migrate_isolate_page(page)) 236 continue; 237 unset_migratetype_isolate(page, migratetype); 238 } 239 return 0; 240 } 241 /* 242 * Test all pages in the range is free(means isolated) or not. 243 * all pages in [start_pfn...end_pfn) must be in the same zone. 244 * zone->lock must be held before call this. 245 * 246 * Returns the last tested pfn. 247 */ 248 static unsigned long 249 __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn, 250 bool skip_hwpoisoned_pages) 251 { 252 struct page *page; 253 254 while (pfn < end_pfn) { 255 if (!pfn_valid_within(pfn)) { 256 pfn++; 257 continue; 258 } 259 page = pfn_to_page(pfn); 260 if (PageBuddy(page)) 261 /* 262 * If the page is on a free list, it has to be on 263 * the correct MIGRATE_ISOLATE freelist. There is no 264 * simple way to verify that as VM_BUG_ON(), though. 265 */ 266 pfn += 1 << page_order(page); 267 else if (skip_hwpoisoned_pages && PageHWPoison(page)) 268 /* A HWPoisoned page cannot be also PageBuddy */ 269 pfn++; 270 else 271 break; 272 } 273 274 return pfn; 275 } 276 277 /* Caller should ensure that requested range is in a single zone */ 278 int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn, 279 bool skip_hwpoisoned_pages) 280 { 281 unsigned long pfn, flags; 282 struct page *page; 283 struct zone *zone; 284 285 /* 286 * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages 287 * are not aligned to pageblock_nr_pages. 288 * Then we just check migratetype first. 289 */ 290 for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) { 291 page = __first_valid_page(pfn, pageblock_nr_pages); 292 if (page && !is_migrate_isolate_page(page)) 293 break; 294 } 295 page = __first_valid_page(start_pfn, end_pfn - start_pfn); 296 if ((pfn < end_pfn) || !page) 297 return -EBUSY; 298 /* Check all pages are free or marked as ISOLATED */ 299 zone = page_zone(page); 300 spin_lock_irqsave(&zone->lock, flags); 301 pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn, 302 skip_hwpoisoned_pages); 303 spin_unlock_irqrestore(&zone->lock, flags); 304 305 trace_test_pages_isolated(start_pfn, end_pfn, pfn); 306 307 return pfn < end_pfn ? -EBUSY : 0; 308 } 309 310 struct page *alloc_migrate_target(struct page *page, unsigned long private) 311 { 312 return new_page_nodemask(page, numa_node_id(), &node_states[N_MEMORY]); 313 } 314