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