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 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 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 = page_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 if (!isolated_page) { 111 nr_pages = move_freepages_block(zone, page, migratetype, NULL); 112 __mod_zone_freepage_state(zone, nr_pages, migratetype); 113 } 114 set_pageblock_migratetype(page, migratetype); 115 if (isolated_page) 116 __putback_isolated_page(page, order, migratetype); 117 zone->nr_isolate_pageblock--; 118 out: 119 spin_unlock_irqrestore(&zone->lock, flags); 120 } 121 122 static inline struct page * 123 __first_valid_page(unsigned long pfn, unsigned long nr_pages) 124 { 125 int i; 126 127 for (i = 0; i < nr_pages; i++) { 128 struct page *page; 129 130 page = pfn_to_online_page(pfn + i); 131 if (!page) 132 continue; 133 return page; 134 } 135 return NULL; 136 } 137 138 /** 139 * start_isolate_page_range() - make page-allocation-type of range of pages to 140 * be MIGRATE_ISOLATE. 141 * @start_pfn: The lower PFN of the range to be isolated. 142 * @end_pfn: The upper PFN of the range to be isolated. 143 * start_pfn/end_pfn must be aligned to pageblock_order. 144 * @migratetype: Migrate type to set in error recovery. 145 * @flags: The following flags are allowed (they can be combined in 146 * a bit mask) 147 * MEMORY_OFFLINE - isolate to offline (!allocate) memory 148 * e.g., skip over PageHWPoison() pages 149 * and PageOffline() pages. 150 * REPORT_FAILURE - report details about the failure to 151 * isolate the range 152 * 153 * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in 154 * the range will never be allocated. Any free pages and pages freed in the 155 * future will not be allocated again. If specified range includes migrate types 156 * other than MOVABLE or CMA, this will fail with -EBUSY. For isolating all 157 * pages in the range finally, the caller have to free all pages in the range. 158 * test_page_isolated() can be used for test it. 159 * 160 * There is no high level synchronization mechanism that prevents two threads 161 * from trying to isolate overlapping ranges. If this happens, one thread 162 * will notice pageblocks in the overlapping range already set to isolate. 163 * This happens in set_migratetype_isolate, and set_migratetype_isolate 164 * returns an error. We then clean up by restoring the migration type on 165 * pageblocks we may have modified and return -EBUSY to caller. This 166 * prevents two threads from simultaneously working on overlapping ranges. 167 * 168 * Please note that there is no strong synchronization with the page allocator 169 * either. Pages might be freed while their page blocks are marked ISOLATED. 170 * In some cases pages might still end up on pcp lists and that would allow 171 * for their allocation even when they are in fact isolated already. Depending 172 * on how strong of a guarantee the caller needs drain_all_pages might be needed 173 * (e.g. __offline_pages will need to call it after check for isolated range for 174 * a next retry). 175 * 176 * Return: the number of isolated pageblocks on success and -EBUSY if any part 177 * of range cannot be isolated. 178 */ 179 int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, 180 unsigned migratetype, int flags) 181 { 182 unsigned long pfn; 183 unsigned long undo_pfn; 184 struct page *page; 185 int nr_isolate_pageblock = 0; 186 187 BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages)); 188 BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages)); 189 190 for (pfn = start_pfn; 191 pfn < end_pfn; 192 pfn += pageblock_nr_pages) { 193 page = __first_valid_page(pfn, pageblock_nr_pages); 194 if (page) { 195 if (set_migratetype_isolate(page, migratetype, flags)) { 196 undo_pfn = pfn; 197 goto undo; 198 } 199 nr_isolate_pageblock++; 200 } 201 } 202 return nr_isolate_pageblock; 203 undo: 204 for (pfn = start_pfn; 205 pfn < undo_pfn; 206 pfn += pageblock_nr_pages) { 207 struct page *page = pfn_to_online_page(pfn); 208 if (!page) 209 continue; 210 unset_migratetype_isolate(page, migratetype); 211 } 212 213 return -EBUSY; 214 } 215 216 /* 217 * Make isolated pages available again. 218 */ 219 void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, 220 unsigned migratetype) 221 { 222 unsigned long pfn; 223 struct page *page; 224 225 BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages)); 226 BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages)); 227 228 for (pfn = start_pfn; 229 pfn < end_pfn; 230 pfn += pageblock_nr_pages) { 231 page = __first_valid_page(pfn, pageblock_nr_pages); 232 if (!page || !is_migrate_isolate_page(page)) 233 continue; 234 unset_migratetype_isolate(page, migratetype); 235 } 236 } 237 /* 238 * Test all pages in the range is free(means isolated) or not. 239 * all pages in [start_pfn...end_pfn) must be in the same zone. 240 * zone->lock must be held before call this. 241 * 242 * Returns the last tested pfn. 243 */ 244 static unsigned long 245 __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn, 246 int flags) 247 { 248 struct page *page; 249 250 while (pfn < end_pfn) { 251 if (!pfn_valid_within(pfn)) { 252 pfn++; 253 continue; 254 } 255 page = pfn_to_page(pfn); 256 if (PageBuddy(page)) 257 /* 258 * If the page is on a free list, it has to be on 259 * the correct MIGRATE_ISOLATE freelist. There is no 260 * simple way to verify that as VM_BUG_ON(), though. 261 */ 262 pfn += 1 << page_order(page); 263 else if ((flags & MEMORY_OFFLINE) && PageHWPoison(page)) 264 /* A HWPoisoned page cannot be also PageBuddy */ 265 pfn++; 266 else if ((flags & MEMORY_OFFLINE) && PageOffline(page) && 267 !page_count(page)) 268 /* 269 * The responsible driver agreed to skip PageOffline() 270 * pages when offlining memory by dropping its 271 * reference in MEM_GOING_OFFLINE. 272 */ 273 pfn++; 274 else 275 break; 276 } 277 278 return pfn; 279 } 280 281 /* Caller should ensure that requested range is in a single zone */ 282 int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn, 283 int isol_flags) 284 { 285 unsigned long pfn, flags; 286 struct page *page; 287 struct zone *zone; 288 289 /* 290 * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages 291 * are not aligned to pageblock_nr_pages. 292 * Then we just check migratetype first. 293 */ 294 for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) { 295 page = __first_valid_page(pfn, pageblock_nr_pages); 296 if (page && !is_migrate_isolate_page(page)) 297 break; 298 } 299 page = __first_valid_page(start_pfn, end_pfn - start_pfn); 300 if ((pfn < end_pfn) || !page) 301 return -EBUSY; 302 /* Check all pages are free or marked as ISOLATED */ 303 zone = page_zone(page); 304 spin_lock_irqsave(&zone->lock, flags); 305 pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn, isol_flags); 306 spin_unlock_irqrestore(&zone->lock, flags); 307 308 trace_test_pages_isolated(start_pfn, end_pfn, pfn); 309 310 return pfn < end_pfn ? -EBUSY : 0; 311 } 312