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, 63 isol_flags)) 64 ret = 0; 65 66 /* 67 * immobile means "not-on-lru" pages. If immobile is larger than 68 * removable-by-driver pages reported by notifier, we'll fail. 69 */ 70 71 out: 72 if (!ret) { 73 unsigned long nr_pages; 74 int mt = get_pageblock_migratetype(page); 75 76 set_pageblock_migratetype(page, MIGRATE_ISOLATE); 77 zone->nr_isolate_pageblock++; 78 nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE, 79 NULL); 80 81 __mod_zone_freepage_state(zone, -nr_pages, mt); 82 } 83 84 spin_unlock_irqrestore(&zone->lock, flags); 85 if (!ret) 86 drain_all_pages(zone); 87 return ret; 88 } 89 90 static void unset_migratetype_isolate(struct page *page, unsigned migratetype) 91 { 92 struct zone *zone; 93 unsigned long flags, nr_pages; 94 bool isolated_page = false; 95 unsigned int order; 96 unsigned long pfn, buddy_pfn; 97 struct page *buddy; 98 99 zone = page_zone(page); 100 spin_lock_irqsave(&zone->lock, flags); 101 if (!is_migrate_isolate_page(page)) 102 goto out; 103 104 /* 105 * Because freepage with more than pageblock_order on isolated 106 * pageblock is restricted to merge due to freepage counting problem, 107 * it is possible that there is free buddy page. 108 * move_freepages_block() doesn't care of merge so we need other 109 * approach in order to merge them. Isolation and free will make 110 * these pages to be merged. 111 */ 112 if (PageBuddy(page)) { 113 order = page_order(page); 114 if (order >= pageblock_order) { 115 pfn = page_to_pfn(page); 116 buddy_pfn = __find_buddy_pfn(pfn, order); 117 buddy = page + (buddy_pfn - pfn); 118 119 if (pfn_valid_within(buddy_pfn) && 120 !is_migrate_isolate_page(buddy)) { 121 __isolate_free_page(page, order); 122 isolated_page = true; 123 } 124 } 125 } 126 127 /* 128 * If we isolate freepage with more than pageblock_order, there 129 * should be no freepage in the range, so we could avoid costly 130 * pageblock scanning for freepage moving. 131 */ 132 if (!isolated_page) { 133 nr_pages = move_freepages_block(zone, page, migratetype, NULL); 134 __mod_zone_freepage_state(zone, nr_pages, migratetype); 135 } 136 set_pageblock_migratetype(page, migratetype); 137 zone->nr_isolate_pageblock--; 138 out: 139 spin_unlock_irqrestore(&zone->lock, flags); 140 if (isolated_page) { 141 post_alloc_hook(page, order, __GFP_MOVABLE); 142 __free_pages(page, order); 143 } 144 } 145 146 static inline struct page * 147 __first_valid_page(unsigned long pfn, unsigned long nr_pages) 148 { 149 int i; 150 151 for (i = 0; i < nr_pages; i++) { 152 struct page *page; 153 154 if (!pfn_valid_within(pfn + i)) 155 continue; 156 page = pfn_to_online_page(pfn + i); 157 if (!page) 158 continue; 159 return page; 160 } 161 return NULL; 162 } 163 164 /** 165 * start_isolate_page_range() - make page-allocation-type of range of pages to 166 * be MIGRATE_ISOLATE. 167 * @start_pfn: The lower PFN of the range to be isolated. 168 * @end_pfn: The upper PFN of the range to be isolated. 169 * start_pfn/end_pfn must be aligned to pageblock_order. 170 * @migratetype: Migrate type to set in error recovery. 171 * @flags: The following flags are allowed (they can be combined in 172 * a bit mask) 173 * SKIP_HWPOISON - ignore hwpoison pages 174 * REPORT_FAILURE - report details about the failure to 175 * isolate the range 176 * 177 * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in 178 * the range will never be allocated. Any free pages and pages freed in the 179 * future will not be allocated again. If specified range includes migrate types 180 * other than MOVABLE or CMA, this will fail with -EBUSY. For isolating all 181 * pages in the range finally, the caller have to free all pages in the range. 182 * test_page_isolated() can be used for test it. 183 * 184 * There is no high level synchronization mechanism that prevents two threads 185 * from trying to isolate overlapping ranges. If this happens, one thread 186 * will notice pageblocks in the overlapping range already set to isolate. 187 * This happens in set_migratetype_isolate, and set_migratetype_isolate 188 * returns an error. We then clean up by restoring the migration type on 189 * pageblocks we may have modified and return -EBUSY to caller. This 190 * prevents two threads from simultaneously working on overlapping ranges. 191 * 192 * Return: the number of isolated pageblocks on success and -EBUSY if any part 193 * of range cannot be isolated. 194 */ 195 int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, 196 unsigned migratetype, int flags) 197 { 198 unsigned long pfn; 199 unsigned long undo_pfn; 200 struct page *page; 201 int nr_isolate_pageblock = 0; 202 203 BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages)); 204 BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages)); 205 206 for (pfn = start_pfn; 207 pfn < end_pfn; 208 pfn += pageblock_nr_pages) { 209 page = __first_valid_page(pfn, pageblock_nr_pages); 210 if (page) { 211 if (set_migratetype_isolate(page, migratetype, flags)) { 212 undo_pfn = pfn; 213 goto undo; 214 } 215 nr_isolate_pageblock++; 216 } 217 } 218 return nr_isolate_pageblock; 219 undo: 220 for (pfn = start_pfn; 221 pfn < undo_pfn; 222 pfn += pageblock_nr_pages) { 223 struct page *page = pfn_to_online_page(pfn); 224 if (!page) 225 continue; 226 unset_migratetype_isolate(page, migratetype); 227 } 228 229 return -EBUSY; 230 } 231 232 /* 233 * Make isolated pages available again. 234 */ 235 int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, 236 unsigned migratetype) 237 { 238 unsigned long pfn; 239 struct page *page; 240 241 BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages)); 242 BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages)); 243 244 for (pfn = start_pfn; 245 pfn < end_pfn; 246 pfn += pageblock_nr_pages) { 247 page = __first_valid_page(pfn, pageblock_nr_pages); 248 if (!page || !is_migrate_isolate_page(page)) 249 continue; 250 unset_migratetype_isolate(page, migratetype); 251 } 252 return 0; 253 } 254 /* 255 * Test all pages in the range is free(means isolated) or not. 256 * all pages in [start_pfn...end_pfn) must be in the same zone. 257 * zone->lock must be held before call this. 258 * 259 * Returns the last tested pfn. 260 */ 261 static unsigned long 262 __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn, 263 bool skip_hwpoisoned_pages) 264 { 265 struct page *page; 266 267 while (pfn < end_pfn) { 268 if (!pfn_valid_within(pfn)) { 269 pfn++; 270 continue; 271 } 272 page = pfn_to_page(pfn); 273 if (PageBuddy(page)) 274 /* 275 * If the page is on a free list, it has to be on 276 * the correct MIGRATE_ISOLATE freelist. There is no 277 * simple way to verify that as VM_BUG_ON(), though. 278 */ 279 pfn += 1 << page_order(page); 280 else if (skip_hwpoisoned_pages && PageHWPoison(page)) 281 /* A HWPoisoned page cannot be also PageBuddy */ 282 pfn++; 283 else 284 break; 285 } 286 287 return pfn; 288 } 289 290 /* Caller should ensure that requested range is in a single zone */ 291 int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn, 292 bool skip_hwpoisoned_pages) 293 { 294 unsigned long pfn, flags; 295 struct page *page; 296 struct zone *zone; 297 298 /* 299 * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages 300 * are not aligned to pageblock_nr_pages. 301 * Then we just check migratetype first. 302 */ 303 for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) { 304 page = __first_valid_page(pfn, pageblock_nr_pages); 305 if (page && !is_migrate_isolate_page(page)) 306 break; 307 } 308 page = __first_valid_page(start_pfn, end_pfn - start_pfn); 309 if ((pfn < end_pfn) || !page) 310 return -EBUSY; 311 /* Check all pages are free or marked as ISOLATED */ 312 zone = page_zone(page); 313 spin_lock_irqsave(&zone->lock, flags); 314 pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn, 315 skip_hwpoisoned_pages); 316 spin_unlock_irqrestore(&zone->lock, flags); 317 318 trace_test_pages_isolated(start_pfn, end_pfn, pfn); 319 320 return pfn < end_pfn ? -EBUSY : 0; 321 } 322 323 struct page *alloc_migrate_target(struct page *page, unsigned long private) 324 { 325 return new_page_nodemask(page, numa_node_id(), &node_states[N_MEMORY]); 326 } 327