1 /* 2 * Copyright (C) 2009 Red Hat, Inc. 3 * 4 * This work is licensed under the terms of the GNU GPL, version 2. See 5 * the COPYING file in the top-level directory. 6 */ 7 8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 9 10 #include <linux/mm.h> 11 #include <linux/sched.h> 12 #include <linux/highmem.h> 13 #include <linux/hugetlb.h> 14 #include <linux/mmu_notifier.h> 15 #include <linux/rmap.h> 16 #include <linux/swap.h> 17 #include <linux/shrinker.h> 18 #include <linux/mm_inline.h> 19 #include <linux/swapops.h> 20 #include <linux/dax.h> 21 #include <linux/kthread.h> 22 #include <linux/khugepaged.h> 23 #include <linux/freezer.h> 24 #include <linux/pfn_t.h> 25 #include <linux/mman.h> 26 #include <linux/memremap.h> 27 #include <linux/pagemap.h> 28 #include <linux/debugfs.h> 29 #include <linux/migrate.h> 30 #include <linux/hashtable.h> 31 #include <linux/userfaultfd_k.h> 32 #include <linux/page_idle.h> 33 34 #include <asm/tlb.h> 35 #include <asm/pgalloc.h> 36 #include "internal.h" 37 38 enum scan_result { 39 SCAN_FAIL, 40 SCAN_SUCCEED, 41 SCAN_PMD_NULL, 42 SCAN_EXCEED_NONE_PTE, 43 SCAN_PTE_NON_PRESENT, 44 SCAN_PAGE_RO, 45 SCAN_NO_REFERENCED_PAGE, 46 SCAN_PAGE_NULL, 47 SCAN_SCAN_ABORT, 48 SCAN_PAGE_COUNT, 49 SCAN_PAGE_LRU, 50 SCAN_PAGE_LOCK, 51 SCAN_PAGE_ANON, 52 SCAN_PAGE_COMPOUND, 53 SCAN_ANY_PROCESS, 54 SCAN_VMA_NULL, 55 SCAN_VMA_CHECK, 56 SCAN_ADDRESS_RANGE, 57 SCAN_SWAP_CACHE_PAGE, 58 SCAN_DEL_PAGE_LRU, 59 SCAN_ALLOC_HUGE_PAGE_FAIL, 60 SCAN_CGROUP_CHARGE_FAIL 61 }; 62 63 #define CREATE_TRACE_POINTS 64 #include <trace/events/huge_memory.h> 65 66 /* 67 * By default transparent hugepage support is disabled in order that avoid 68 * to risk increase the memory footprint of applications without a guaranteed 69 * benefit. When transparent hugepage support is enabled, is for all mappings, 70 * and khugepaged scans all mappings. 71 * Defrag is invoked by khugepaged hugepage allocations and by page faults 72 * for all hugepage allocations. 73 */ 74 unsigned long transparent_hugepage_flags __read_mostly = 75 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS 76 (1<<TRANSPARENT_HUGEPAGE_FLAG)| 77 #endif 78 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE 79 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| 80 #endif 81 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)| 82 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)| 83 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 84 85 /* default scan 8*512 pte (or vmas) every 30 second */ 86 static unsigned int khugepaged_pages_to_scan __read_mostly; 87 static unsigned int khugepaged_pages_collapsed; 88 static unsigned int khugepaged_full_scans; 89 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 90 /* during fragmentation poll the hugepage allocator once every minute */ 91 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 92 static unsigned long khugepaged_sleep_expire; 93 static struct task_struct *khugepaged_thread __read_mostly; 94 static DEFINE_MUTEX(khugepaged_mutex); 95 static DEFINE_SPINLOCK(khugepaged_mm_lock); 96 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 97 /* 98 * default collapse hugepages if there is at least one pte mapped like 99 * it would have happened if the vma was large enough during page 100 * fault. 101 */ 102 static unsigned int khugepaged_max_ptes_none __read_mostly; 103 104 static int khugepaged(void *none); 105 static int khugepaged_slab_init(void); 106 static void khugepaged_slab_exit(void); 107 108 #define MM_SLOTS_HASH_BITS 10 109 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); 110 111 static struct kmem_cache *mm_slot_cache __read_mostly; 112 113 /** 114 * struct mm_slot - hash lookup from mm to mm_slot 115 * @hash: hash collision list 116 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 117 * @mm: the mm that this information is valid for 118 */ 119 struct mm_slot { 120 struct hlist_node hash; 121 struct list_head mm_node; 122 struct mm_struct *mm; 123 }; 124 125 /** 126 * struct khugepaged_scan - cursor for scanning 127 * @mm_head: the head of the mm list to scan 128 * @mm_slot: the current mm_slot we are scanning 129 * @address: the next address inside that to be scanned 130 * 131 * There is only the one khugepaged_scan instance of this cursor structure. 132 */ 133 struct khugepaged_scan { 134 struct list_head mm_head; 135 struct mm_slot *mm_slot; 136 unsigned long address; 137 }; 138 static struct khugepaged_scan khugepaged_scan = { 139 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 140 }; 141 142 static struct shrinker deferred_split_shrinker; 143 144 static void set_recommended_min_free_kbytes(void) 145 { 146 struct zone *zone; 147 int nr_zones = 0; 148 unsigned long recommended_min; 149 150 for_each_populated_zone(zone) 151 nr_zones++; 152 153 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */ 154 recommended_min = pageblock_nr_pages * nr_zones * 2; 155 156 /* 157 * Make sure that on average at least two pageblocks are almost free 158 * of another type, one for a migratetype to fall back to and a 159 * second to avoid subsequent fallbacks of other types There are 3 160 * MIGRATE_TYPES we care about. 161 */ 162 recommended_min += pageblock_nr_pages * nr_zones * 163 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; 164 165 /* don't ever allow to reserve more than 5% of the lowmem */ 166 recommended_min = min(recommended_min, 167 (unsigned long) nr_free_buffer_pages() / 20); 168 recommended_min <<= (PAGE_SHIFT-10); 169 170 if (recommended_min > min_free_kbytes) { 171 if (user_min_free_kbytes >= 0) 172 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", 173 min_free_kbytes, recommended_min); 174 175 min_free_kbytes = recommended_min; 176 } 177 setup_per_zone_wmarks(); 178 } 179 180 static int start_stop_khugepaged(void) 181 { 182 int err = 0; 183 if (khugepaged_enabled()) { 184 if (!khugepaged_thread) 185 khugepaged_thread = kthread_run(khugepaged, NULL, 186 "khugepaged"); 187 if (IS_ERR(khugepaged_thread)) { 188 pr_err("khugepaged: kthread_run(khugepaged) failed\n"); 189 err = PTR_ERR(khugepaged_thread); 190 khugepaged_thread = NULL; 191 goto fail; 192 } 193 194 if (!list_empty(&khugepaged_scan.mm_head)) 195 wake_up_interruptible(&khugepaged_wait); 196 197 set_recommended_min_free_kbytes(); 198 } else if (khugepaged_thread) { 199 kthread_stop(khugepaged_thread); 200 khugepaged_thread = NULL; 201 } 202 fail: 203 return err; 204 } 205 206 static atomic_t huge_zero_refcount; 207 struct page *huge_zero_page __read_mostly; 208 209 struct page *get_huge_zero_page(void) 210 { 211 struct page *zero_page; 212 retry: 213 if (likely(atomic_inc_not_zero(&huge_zero_refcount))) 214 return READ_ONCE(huge_zero_page); 215 216 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, 217 HPAGE_PMD_ORDER); 218 if (!zero_page) { 219 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); 220 return NULL; 221 } 222 count_vm_event(THP_ZERO_PAGE_ALLOC); 223 preempt_disable(); 224 if (cmpxchg(&huge_zero_page, NULL, zero_page)) { 225 preempt_enable(); 226 __free_pages(zero_page, compound_order(zero_page)); 227 goto retry; 228 } 229 230 /* We take additional reference here. It will be put back by shrinker */ 231 atomic_set(&huge_zero_refcount, 2); 232 preempt_enable(); 233 return READ_ONCE(huge_zero_page); 234 } 235 236 void put_huge_zero_page(void) 237 { 238 /* 239 * Counter should never go to zero here. Only shrinker can put 240 * last reference. 241 */ 242 BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); 243 } 244 245 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, 246 struct shrink_control *sc) 247 { 248 /* we can free zero page only if last reference remains */ 249 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; 250 } 251 252 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, 253 struct shrink_control *sc) 254 { 255 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { 256 struct page *zero_page = xchg(&huge_zero_page, NULL); 257 BUG_ON(zero_page == NULL); 258 __free_pages(zero_page, compound_order(zero_page)); 259 return HPAGE_PMD_NR; 260 } 261 262 return 0; 263 } 264 265 static struct shrinker huge_zero_page_shrinker = { 266 .count_objects = shrink_huge_zero_page_count, 267 .scan_objects = shrink_huge_zero_page_scan, 268 .seeks = DEFAULT_SEEKS, 269 }; 270 271 #ifdef CONFIG_SYSFS 272 273 static ssize_t triple_flag_store(struct kobject *kobj, 274 struct kobj_attribute *attr, 275 const char *buf, size_t count, 276 enum transparent_hugepage_flag enabled, 277 enum transparent_hugepage_flag deferred, 278 enum transparent_hugepage_flag req_madv) 279 { 280 if (!memcmp("defer", buf, 281 min(sizeof("defer")-1, count))) { 282 if (enabled == deferred) 283 return -EINVAL; 284 clear_bit(enabled, &transparent_hugepage_flags); 285 clear_bit(req_madv, &transparent_hugepage_flags); 286 set_bit(deferred, &transparent_hugepage_flags); 287 } else if (!memcmp("always", buf, 288 min(sizeof("always")-1, count))) { 289 clear_bit(deferred, &transparent_hugepage_flags); 290 clear_bit(req_madv, &transparent_hugepage_flags); 291 set_bit(enabled, &transparent_hugepage_flags); 292 } else if (!memcmp("madvise", buf, 293 min(sizeof("madvise")-1, count))) { 294 clear_bit(enabled, &transparent_hugepage_flags); 295 clear_bit(deferred, &transparent_hugepage_flags); 296 set_bit(req_madv, &transparent_hugepage_flags); 297 } else if (!memcmp("never", buf, 298 min(sizeof("never")-1, count))) { 299 clear_bit(enabled, &transparent_hugepage_flags); 300 clear_bit(req_madv, &transparent_hugepage_flags); 301 clear_bit(deferred, &transparent_hugepage_flags); 302 } else 303 return -EINVAL; 304 305 return count; 306 } 307 308 static ssize_t enabled_show(struct kobject *kobj, 309 struct kobj_attribute *attr, char *buf) 310 { 311 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags)) 312 return sprintf(buf, "[always] madvise never\n"); 313 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags)) 314 return sprintf(buf, "always [madvise] never\n"); 315 else 316 return sprintf(buf, "always madvise [never]\n"); 317 } 318 319 static ssize_t enabled_store(struct kobject *kobj, 320 struct kobj_attribute *attr, 321 const char *buf, size_t count) 322 { 323 ssize_t ret; 324 325 ret = triple_flag_store(kobj, attr, buf, count, 326 TRANSPARENT_HUGEPAGE_FLAG, 327 TRANSPARENT_HUGEPAGE_FLAG, 328 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 329 330 if (ret > 0) { 331 int err; 332 333 mutex_lock(&khugepaged_mutex); 334 err = start_stop_khugepaged(); 335 mutex_unlock(&khugepaged_mutex); 336 337 if (err) 338 ret = err; 339 } 340 341 return ret; 342 } 343 static struct kobj_attribute enabled_attr = 344 __ATTR(enabled, 0644, enabled_show, enabled_store); 345 346 static ssize_t single_flag_show(struct kobject *kobj, 347 struct kobj_attribute *attr, char *buf, 348 enum transparent_hugepage_flag flag) 349 { 350 return sprintf(buf, "%d\n", 351 !!test_bit(flag, &transparent_hugepage_flags)); 352 } 353 354 static ssize_t single_flag_store(struct kobject *kobj, 355 struct kobj_attribute *attr, 356 const char *buf, size_t count, 357 enum transparent_hugepage_flag flag) 358 { 359 unsigned long value; 360 int ret; 361 362 ret = kstrtoul(buf, 10, &value); 363 if (ret < 0) 364 return ret; 365 if (value > 1) 366 return -EINVAL; 367 368 if (value) 369 set_bit(flag, &transparent_hugepage_flags); 370 else 371 clear_bit(flag, &transparent_hugepage_flags); 372 373 return count; 374 } 375 376 /* 377 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind 378 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of 379 * memory just to allocate one more hugepage. 380 */ 381 static ssize_t defrag_show(struct kobject *kobj, 382 struct kobj_attribute *attr, char *buf) 383 { 384 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) 385 return sprintf(buf, "[always] defer madvise never\n"); 386 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) 387 return sprintf(buf, "always [defer] madvise never\n"); 388 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) 389 return sprintf(buf, "always defer [madvise] never\n"); 390 else 391 return sprintf(buf, "always defer madvise [never]\n"); 392 393 } 394 static ssize_t defrag_store(struct kobject *kobj, 395 struct kobj_attribute *attr, 396 const char *buf, size_t count) 397 { 398 return triple_flag_store(kobj, attr, buf, count, 399 TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, 400 TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, 401 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 402 } 403 static struct kobj_attribute defrag_attr = 404 __ATTR(defrag, 0644, defrag_show, defrag_store); 405 406 static ssize_t use_zero_page_show(struct kobject *kobj, 407 struct kobj_attribute *attr, char *buf) 408 { 409 return single_flag_show(kobj, attr, buf, 410 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 411 } 412 static ssize_t use_zero_page_store(struct kobject *kobj, 413 struct kobj_attribute *attr, const char *buf, size_t count) 414 { 415 return single_flag_store(kobj, attr, buf, count, 416 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 417 } 418 static struct kobj_attribute use_zero_page_attr = 419 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); 420 #ifdef CONFIG_DEBUG_VM 421 static ssize_t debug_cow_show(struct kobject *kobj, 422 struct kobj_attribute *attr, char *buf) 423 { 424 return single_flag_show(kobj, attr, buf, 425 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 426 } 427 static ssize_t debug_cow_store(struct kobject *kobj, 428 struct kobj_attribute *attr, 429 const char *buf, size_t count) 430 { 431 return single_flag_store(kobj, attr, buf, count, 432 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 433 } 434 static struct kobj_attribute debug_cow_attr = 435 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 436 #endif /* CONFIG_DEBUG_VM */ 437 438 static struct attribute *hugepage_attr[] = { 439 &enabled_attr.attr, 440 &defrag_attr.attr, 441 &use_zero_page_attr.attr, 442 #ifdef CONFIG_DEBUG_VM 443 &debug_cow_attr.attr, 444 #endif 445 NULL, 446 }; 447 448 static struct attribute_group hugepage_attr_group = { 449 .attrs = hugepage_attr, 450 }; 451 452 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 453 struct kobj_attribute *attr, 454 char *buf) 455 { 456 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 457 } 458 459 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 460 struct kobj_attribute *attr, 461 const char *buf, size_t count) 462 { 463 unsigned long msecs; 464 int err; 465 466 err = kstrtoul(buf, 10, &msecs); 467 if (err || msecs > UINT_MAX) 468 return -EINVAL; 469 470 khugepaged_scan_sleep_millisecs = msecs; 471 khugepaged_sleep_expire = 0; 472 wake_up_interruptible(&khugepaged_wait); 473 474 return count; 475 } 476 static struct kobj_attribute scan_sleep_millisecs_attr = 477 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 478 scan_sleep_millisecs_store); 479 480 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 481 struct kobj_attribute *attr, 482 char *buf) 483 { 484 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 485 } 486 487 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 488 struct kobj_attribute *attr, 489 const char *buf, size_t count) 490 { 491 unsigned long msecs; 492 int err; 493 494 err = kstrtoul(buf, 10, &msecs); 495 if (err || msecs > UINT_MAX) 496 return -EINVAL; 497 498 khugepaged_alloc_sleep_millisecs = msecs; 499 khugepaged_sleep_expire = 0; 500 wake_up_interruptible(&khugepaged_wait); 501 502 return count; 503 } 504 static struct kobj_attribute alloc_sleep_millisecs_attr = 505 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 506 alloc_sleep_millisecs_store); 507 508 static ssize_t pages_to_scan_show(struct kobject *kobj, 509 struct kobj_attribute *attr, 510 char *buf) 511 { 512 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 513 } 514 static ssize_t pages_to_scan_store(struct kobject *kobj, 515 struct kobj_attribute *attr, 516 const char *buf, size_t count) 517 { 518 int err; 519 unsigned long pages; 520 521 err = kstrtoul(buf, 10, &pages); 522 if (err || !pages || pages > UINT_MAX) 523 return -EINVAL; 524 525 khugepaged_pages_to_scan = pages; 526 527 return count; 528 } 529 static struct kobj_attribute pages_to_scan_attr = 530 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 531 pages_to_scan_store); 532 533 static ssize_t pages_collapsed_show(struct kobject *kobj, 534 struct kobj_attribute *attr, 535 char *buf) 536 { 537 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 538 } 539 static struct kobj_attribute pages_collapsed_attr = 540 __ATTR_RO(pages_collapsed); 541 542 static ssize_t full_scans_show(struct kobject *kobj, 543 struct kobj_attribute *attr, 544 char *buf) 545 { 546 return sprintf(buf, "%u\n", khugepaged_full_scans); 547 } 548 static struct kobj_attribute full_scans_attr = 549 __ATTR_RO(full_scans); 550 551 static ssize_t khugepaged_defrag_show(struct kobject *kobj, 552 struct kobj_attribute *attr, char *buf) 553 { 554 return single_flag_show(kobj, attr, buf, 555 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 556 } 557 static ssize_t khugepaged_defrag_store(struct kobject *kobj, 558 struct kobj_attribute *attr, 559 const char *buf, size_t count) 560 { 561 return single_flag_store(kobj, attr, buf, count, 562 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 563 } 564 static struct kobj_attribute khugepaged_defrag_attr = 565 __ATTR(defrag, 0644, khugepaged_defrag_show, 566 khugepaged_defrag_store); 567 568 /* 569 * max_ptes_none controls if khugepaged should collapse hugepages over 570 * any unmapped ptes in turn potentially increasing the memory 571 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 572 * reduce the available free memory in the system as it 573 * runs. Increasing max_ptes_none will instead potentially reduce the 574 * free memory in the system during the khugepaged scan. 575 */ 576 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 577 struct kobj_attribute *attr, 578 char *buf) 579 { 580 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 581 } 582 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 583 struct kobj_attribute *attr, 584 const char *buf, size_t count) 585 { 586 int err; 587 unsigned long max_ptes_none; 588 589 err = kstrtoul(buf, 10, &max_ptes_none); 590 if (err || max_ptes_none > HPAGE_PMD_NR-1) 591 return -EINVAL; 592 593 khugepaged_max_ptes_none = max_ptes_none; 594 595 return count; 596 } 597 static struct kobj_attribute khugepaged_max_ptes_none_attr = 598 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 599 khugepaged_max_ptes_none_store); 600 601 static struct attribute *khugepaged_attr[] = { 602 &khugepaged_defrag_attr.attr, 603 &khugepaged_max_ptes_none_attr.attr, 604 &pages_to_scan_attr.attr, 605 &pages_collapsed_attr.attr, 606 &full_scans_attr.attr, 607 &scan_sleep_millisecs_attr.attr, 608 &alloc_sleep_millisecs_attr.attr, 609 NULL, 610 }; 611 612 static struct attribute_group khugepaged_attr_group = { 613 .attrs = khugepaged_attr, 614 .name = "khugepaged", 615 }; 616 617 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) 618 { 619 int err; 620 621 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 622 if (unlikely(!*hugepage_kobj)) { 623 pr_err("failed to create transparent hugepage kobject\n"); 624 return -ENOMEM; 625 } 626 627 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); 628 if (err) { 629 pr_err("failed to register transparent hugepage group\n"); 630 goto delete_obj; 631 } 632 633 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); 634 if (err) { 635 pr_err("failed to register transparent hugepage group\n"); 636 goto remove_hp_group; 637 } 638 639 return 0; 640 641 remove_hp_group: 642 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); 643 delete_obj: 644 kobject_put(*hugepage_kobj); 645 return err; 646 } 647 648 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) 649 { 650 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); 651 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); 652 kobject_put(hugepage_kobj); 653 } 654 #else 655 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) 656 { 657 return 0; 658 } 659 660 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) 661 { 662 } 663 #endif /* CONFIG_SYSFS */ 664 665 static int __init hugepage_init(void) 666 { 667 int err; 668 struct kobject *hugepage_kobj; 669 670 if (!has_transparent_hugepage()) { 671 transparent_hugepage_flags = 0; 672 return -EINVAL; 673 } 674 675 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; 676 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; 677 /* 678 * hugepages can't be allocated by the buddy allocator 679 */ 680 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER); 681 /* 682 * we use page->mapping and page->index in second tail page 683 * as list_head: assuming THP order >= 2 684 */ 685 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2); 686 687 err = hugepage_init_sysfs(&hugepage_kobj); 688 if (err) 689 goto err_sysfs; 690 691 err = khugepaged_slab_init(); 692 if (err) 693 goto err_slab; 694 695 err = register_shrinker(&huge_zero_page_shrinker); 696 if (err) 697 goto err_hzp_shrinker; 698 err = register_shrinker(&deferred_split_shrinker); 699 if (err) 700 goto err_split_shrinker; 701 702 /* 703 * By default disable transparent hugepages on smaller systems, 704 * where the extra memory used could hurt more than TLB overhead 705 * is likely to save. The admin can still enable it through /sys. 706 */ 707 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) { 708 transparent_hugepage_flags = 0; 709 return 0; 710 } 711 712 err = start_stop_khugepaged(); 713 if (err) 714 goto err_khugepaged; 715 716 return 0; 717 err_khugepaged: 718 unregister_shrinker(&deferred_split_shrinker); 719 err_split_shrinker: 720 unregister_shrinker(&huge_zero_page_shrinker); 721 err_hzp_shrinker: 722 khugepaged_slab_exit(); 723 err_slab: 724 hugepage_exit_sysfs(hugepage_kobj); 725 err_sysfs: 726 return err; 727 } 728 subsys_initcall(hugepage_init); 729 730 static int __init setup_transparent_hugepage(char *str) 731 { 732 int ret = 0; 733 if (!str) 734 goto out; 735 if (!strcmp(str, "always")) { 736 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 737 &transparent_hugepage_flags); 738 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 739 &transparent_hugepage_flags); 740 ret = 1; 741 } else if (!strcmp(str, "madvise")) { 742 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 743 &transparent_hugepage_flags); 744 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 745 &transparent_hugepage_flags); 746 ret = 1; 747 } else if (!strcmp(str, "never")) { 748 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 749 &transparent_hugepage_flags); 750 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 751 &transparent_hugepage_flags); 752 ret = 1; 753 } 754 out: 755 if (!ret) 756 pr_warn("transparent_hugepage= cannot parse, ignored\n"); 757 return ret; 758 } 759 __setup("transparent_hugepage=", setup_transparent_hugepage); 760 761 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 762 { 763 if (likely(vma->vm_flags & VM_WRITE)) 764 pmd = pmd_mkwrite(pmd); 765 return pmd; 766 } 767 768 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot) 769 { 770 return pmd_mkhuge(mk_pmd(page, prot)); 771 } 772 773 static inline struct list_head *page_deferred_list(struct page *page) 774 { 775 /* 776 * ->lru in the tail pages is occupied by compound_head. 777 * Let's use ->mapping + ->index in the second tail page as list_head. 778 */ 779 return (struct list_head *)&page[2].mapping; 780 } 781 782 void prep_transhuge_page(struct page *page) 783 { 784 /* 785 * we use page->mapping and page->indexlru in second tail page 786 * as list_head: assuming THP order >= 2 787 */ 788 789 INIT_LIST_HEAD(page_deferred_list(page)); 790 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR); 791 } 792 793 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, 794 struct vm_area_struct *vma, 795 unsigned long address, pmd_t *pmd, 796 struct page *page, gfp_t gfp, 797 unsigned int flags) 798 { 799 struct mem_cgroup *memcg; 800 pgtable_t pgtable; 801 spinlock_t *ptl; 802 unsigned long haddr = address & HPAGE_PMD_MASK; 803 804 VM_BUG_ON_PAGE(!PageCompound(page), page); 805 806 if (mem_cgroup_try_charge(page, mm, gfp, &memcg, true)) { 807 put_page(page); 808 count_vm_event(THP_FAULT_FALLBACK); 809 return VM_FAULT_FALLBACK; 810 } 811 812 pgtable = pte_alloc_one(mm, haddr); 813 if (unlikely(!pgtable)) { 814 mem_cgroup_cancel_charge(page, memcg, true); 815 put_page(page); 816 return VM_FAULT_OOM; 817 } 818 819 clear_huge_page(page, haddr, HPAGE_PMD_NR); 820 /* 821 * The memory barrier inside __SetPageUptodate makes sure that 822 * clear_huge_page writes become visible before the set_pmd_at() 823 * write. 824 */ 825 __SetPageUptodate(page); 826 827 ptl = pmd_lock(mm, pmd); 828 if (unlikely(!pmd_none(*pmd))) { 829 spin_unlock(ptl); 830 mem_cgroup_cancel_charge(page, memcg, true); 831 put_page(page); 832 pte_free(mm, pgtable); 833 } else { 834 pmd_t entry; 835 836 /* Deliver the page fault to userland */ 837 if (userfaultfd_missing(vma)) { 838 int ret; 839 840 spin_unlock(ptl); 841 mem_cgroup_cancel_charge(page, memcg, true); 842 put_page(page); 843 pte_free(mm, pgtable); 844 ret = handle_userfault(vma, address, flags, 845 VM_UFFD_MISSING); 846 VM_BUG_ON(ret & VM_FAULT_FALLBACK); 847 return ret; 848 } 849 850 entry = mk_huge_pmd(page, vma->vm_page_prot); 851 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 852 page_add_new_anon_rmap(page, vma, haddr, true); 853 mem_cgroup_commit_charge(page, memcg, false, true); 854 lru_cache_add_active_or_unevictable(page, vma); 855 pgtable_trans_huge_deposit(mm, pmd, pgtable); 856 set_pmd_at(mm, haddr, pmd, entry); 857 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 858 atomic_long_inc(&mm->nr_ptes); 859 spin_unlock(ptl); 860 count_vm_event(THP_FAULT_ALLOC); 861 } 862 863 return 0; 864 } 865 866 /* 867 * If THP is set to always then directly reclaim/compact as necessary 868 * If set to defer then do no reclaim and defer to khugepaged 869 * If set to madvise and the VMA is flagged then directly reclaim/compact 870 */ 871 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma) 872 { 873 gfp_t reclaim_flags = 0; 874 875 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags) && 876 (vma->vm_flags & VM_HUGEPAGE)) 877 reclaim_flags = __GFP_DIRECT_RECLAIM; 878 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) 879 reclaim_flags = __GFP_KSWAPD_RECLAIM; 880 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) 881 reclaim_flags = __GFP_DIRECT_RECLAIM; 882 883 return GFP_TRANSHUGE | reclaim_flags; 884 } 885 886 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ 887 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) 888 { 889 return GFP_TRANSHUGE | (khugepaged_defrag() ? __GFP_DIRECT_RECLAIM : 0); 890 } 891 892 /* Caller must hold page table lock. */ 893 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, 894 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, 895 struct page *zero_page) 896 { 897 pmd_t entry; 898 if (!pmd_none(*pmd)) 899 return false; 900 entry = mk_pmd(zero_page, vma->vm_page_prot); 901 entry = pmd_mkhuge(entry); 902 if (pgtable) 903 pgtable_trans_huge_deposit(mm, pmd, pgtable); 904 set_pmd_at(mm, haddr, pmd, entry); 905 atomic_long_inc(&mm->nr_ptes); 906 return true; 907 } 908 909 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 910 unsigned long address, pmd_t *pmd, 911 unsigned int flags) 912 { 913 gfp_t gfp; 914 struct page *page; 915 unsigned long haddr = address & HPAGE_PMD_MASK; 916 917 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end) 918 return VM_FAULT_FALLBACK; 919 if (unlikely(anon_vma_prepare(vma))) 920 return VM_FAULT_OOM; 921 if (unlikely(khugepaged_enter(vma, vma->vm_flags))) 922 return VM_FAULT_OOM; 923 if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) && 924 transparent_hugepage_use_zero_page()) { 925 spinlock_t *ptl; 926 pgtable_t pgtable; 927 struct page *zero_page; 928 bool set; 929 int ret; 930 pgtable = pte_alloc_one(mm, haddr); 931 if (unlikely(!pgtable)) 932 return VM_FAULT_OOM; 933 zero_page = get_huge_zero_page(); 934 if (unlikely(!zero_page)) { 935 pte_free(mm, pgtable); 936 count_vm_event(THP_FAULT_FALLBACK); 937 return VM_FAULT_FALLBACK; 938 } 939 ptl = pmd_lock(mm, pmd); 940 ret = 0; 941 set = false; 942 if (pmd_none(*pmd)) { 943 if (userfaultfd_missing(vma)) { 944 spin_unlock(ptl); 945 ret = handle_userfault(vma, address, flags, 946 VM_UFFD_MISSING); 947 VM_BUG_ON(ret & VM_FAULT_FALLBACK); 948 } else { 949 set_huge_zero_page(pgtable, mm, vma, 950 haddr, pmd, 951 zero_page); 952 spin_unlock(ptl); 953 set = true; 954 } 955 } else 956 spin_unlock(ptl); 957 if (!set) { 958 pte_free(mm, pgtable); 959 put_huge_zero_page(); 960 } 961 return ret; 962 } 963 gfp = alloc_hugepage_direct_gfpmask(vma); 964 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER); 965 if (unlikely(!page)) { 966 count_vm_event(THP_FAULT_FALLBACK); 967 return VM_FAULT_FALLBACK; 968 } 969 prep_transhuge_page(page); 970 return __do_huge_pmd_anonymous_page(mm, vma, address, pmd, page, gfp, 971 flags); 972 } 973 974 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, 975 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write) 976 { 977 struct mm_struct *mm = vma->vm_mm; 978 pmd_t entry; 979 spinlock_t *ptl; 980 981 ptl = pmd_lock(mm, pmd); 982 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot)); 983 if (pfn_t_devmap(pfn)) 984 entry = pmd_mkdevmap(entry); 985 if (write) { 986 entry = pmd_mkyoung(pmd_mkdirty(entry)); 987 entry = maybe_pmd_mkwrite(entry, vma); 988 } 989 set_pmd_at(mm, addr, pmd, entry); 990 update_mmu_cache_pmd(vma, addr, pmd); 991 spin_unlock(ptl); 992 } 993 994 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, 995 pmd_t *pmd, pfn_t pfn, bool write) 996 { 997 pgprot_t pgprot = vma->vm_page_prot; 998 /* 999 * If we had pmd_special, we could avoid all these restrictions, 1000 * but we need to be consistent with PTEs and architectures that 1001 * can't support a 'special' bit. 1002 */ 1003 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))); 1004 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == 1005 (VM_PFNMAP|VM_MIXEDMAP)); 1006 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); 1007 BUG_ON(!pfn_t_devmap(pfn)); 1008 1009 if (addr < vma->vm_start || addr >= vma->vm_end) 1010 return VM_FAULT_SIGBUS; 1011 if (track_pfn_insert(vma, &pgprot, pfn)) 1012 return VM_FAULT_SIGBUS; 1013 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write); 1014 return VM_FAULT_NOPAGE; 1015 } 1016 1017 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr, 1018 pmd_t *pmd) 1019 { 1020 pmd_t _pmd; 1021 1022 /* 1023 * We should set the dirty bit only for FOLL_WRITE but for now 1024 * the dirty bit in the pmd is meaningless. And if the dirty 1025 * bit will become meaningful and we'll only set it with 1026 * FOLL_WRITE, an atomic set_bit will be required on the pmd to 1027 * set the young bit, instead of the current set_pmd_at. 1028 */ 1029 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 1030 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, 1031 pmd, _pmd, 1)) 1032 update_mmu_cache_pmd(vma, addr, pmd); 1033 } 1034 1035 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, 1036 pmd_t *pmd, int flags) 1037 { 1038 unsigned long pfn = pmd_pfn(*pmd); 1039 struct mm_struct *mm = vma->vm_mm; 1040 struct dev_pagemap *pgmap; 1041 struct page *page; 1042 1043 assert_spin_locked(pmd_lockptr(mm, pmd)); 1044 1045 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 1046 return NULL; 1047 1048 if (pmd_present(*pmd) && pmd_devmap(*pmd)) 1049 /* pass */; 1050 else 1051 return NULL; 1052 1053 if (flags & FOLL_TOUCH) 1054 touch_pmd(vma, addr, pmd); 1055 1056 /* 1057 * device mapped pages can only be returned if the 1058 * caller will manage the page reference count. 1059 */ 1060 if (!(flags & FOLL_GET)) 1061 return ERR_PTR(-EEXIST); 1062 1063 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT; 1064 pgmap = get_dev_pagemap(pfn, NULL); 1065 if (!pgmap) 1066 return ERR_PTR(-EFAULT); 1067 page = pfn_to_page(pfn); 1068 get_page(page); 1069 put_dev_pagemap(pgmap); 1070 1071 return page; 1072 } 1073 1074 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 1075 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 1076 struct vm_area_struct *vma) 1077 { 1078 spinlock_t *dst_ptl, *src_ptl; 1079 struct page *src_page; 1080 pmd_t pmd; 1081 pgtable_t pgtable = NULL; 1082 int ret; 1083 1084 if (!vma_is_dax(vma)) { 1085 ret = -ENOMEM; 1086 pgtable = pte_alloc_one(dst_mm, addr); 1087 if (unlikely(!pgtable)) 1088 goto out; 1089 } 1090 1091 dst_ptl = pmd_lock(dst_mm, dst_pmd); 1092 src_ptl = pmd_lockptr(src_mm, src_pmd); 1093 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); 1094 1095 ret = -EAGAIN; 1096 pmd = *src_pmd; 1097 if (unlikely(!pmd_trans_huge(pmd) && !pmd_devmap(pmd))) { 1098 pte_free(dst_mm, pgtable); 1099 goto out_unlock; 1100 } 1101 /* 1102 * When page table lock is held, the huge zero pmd should not be 1103 * under splitting since we don't split the page itself, only pmd to 1104 * a page table. 1105 */ 1106 if (is_huge_zero_pmd(pmd)) { 1107 struct page *zero_page; 1108 /* 1109 * get_huge_zero_page() will never allocate a new page here, 1110 * since we already have a zero page to copy. It just takes a 1111 * reference. 1112 */ 1113 zero_page = get_huge_zero_page(); 1114 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, 1115 zero_page); 1116 ret = 0; 1117 goto out_unlock; 1118 } 1119 1120 if (!vma_is_dax(vma)) { 1121 /* thp accounting separate from pmd_devmap accounting */ 1122 src_page = pmd_page(pmd); 1123 VM_BUG_ON_PAGE(!PageHead(src_page), src_page); 1124 get_page(src_page); 1125 page_dup_rmap(src_page, true); 1126 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 1127 atomic_long_inc(&dst_mm->nr_ptes); 1128 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); 1129 } 1130 1131 pmdp_set_wrprotect(src_mm, addr, src_pmd); 1132 pmd = pmd_mkold(pmd_wrprotect(pmd)); 1133 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 1134 1135 ret = 0; 1136 out_unlock: 1137 spin_unlock(src_ptl); 1138 spin_unlock(dst_ptl); 1139 out: 1140 return ret; 1141 } 1142 1143 void huge_pmd_set_accessed(struct mm_struct *mm, 1144 struct vm_area_struct *vma, 1145 unsigned long address, 1146 pmd_t *pmd, pmd_t orig_pmd, 1147 int dirty) 1148 { 1149 spinlock_t *ptl; 1150 pmd_t entry; 1151 unsigned long haddr; 1152 1153 ptl = pmd_lock(mm, pmd); 1154 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1155 goto unlock; 1156 1157 entry = pmd_mkyoung(orig_pmd); 1158 haddr = address & HPAGE_PMD_MASK; 1159 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty)) 1160 update_mmu_cache_pmd(vma, address, pmd); 1161 1162 unlock: 1163 spin_unlock(ptl); 1164 } 1165 1166 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, 1167 struct vm_area_struct *vma, 1168 unsigned long address, 1169 pmd_t *pmd, pmd_t orig_pmd, 1170 struct page *page, 1171 unsigned long haddr) 1172 { 1173 struct mem_cgroup *memcg; 1174 spinlock_t *ptl; 1175 pgtable_t pgtable; 1176 pmd_t _pmd; 1177 int ret = 0, i; 1178 struct page **pages; 1179 unsigned long mmun_start; /* For mmu_notifiers */ 1180 unsigned long mmun_end; /* For mmu_notifiers */ 1181 1182 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 1183 GFP_KERNEL); 1184 if (unlikely(!pages)) { 1185 ret |= VM_FAULT_OOM; 1186 goto out; 1187 } 1188 1189 for (i = 0; i < HPAGE_PMD_NR; i++) { 1190 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | 1191 __GFP_OTHER_NODE, 1192 vma, address, page_to_nid(page)); 1193 if (unlikely(!pages[i] || 1194 mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL, 1195 &memcg, false))) { 1196 if (pages[i]) 1197 put_page(pages[i]); 1198 while (--i >= 0) { 1199 memcg = (void *)page_private(pages[i]); 1200 set_page_private(pages[i], 0); 1201 mem_cgroup_cancel_charge(pages[i], memcg, 1202 false); 1203 put_page(pages[i]); 1204 } 1205 kfree(pages); 1206 ret |= VM_FAULT_OOM; 1207 goto out; 1208 } 1209 set_page_private(pages[i], (unsigned long)memcg); 1210 } 1211 1212 for (i = 0; i < HPAGE_PMD_NR; i++) { 1213 copy_user_highpage(pages[i], page + i, 1214 haddr + PAGE_SIZE * i, vma); 1215 __SetPageUptodate(pages[i]); 1216 cond_resched(); 1217 } 1218 1219 mmun_start = haddr; 1220 mmun_end = haddr + HPAGE_PMD_SIZE; 1221 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1222 1223 ptl = pmd_lock(mm, pmd); 1224 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1225 goto out_free_pages; 1226 VM_BUG_ON_PAGE(!PageHead(page), page); 1227 1228 pmdp_huge_clear_flush_notify(vma, haddr, pmd); 1229 /* leave pmd empty until pte is filled */ 1230 1231 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1232 pmd_populate(mm, &_pmd, pgtable); 1233 1234 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1235 pte_t *pte, entry; 1236 entry = mk_pte(pages[i], vma->vm_page_prot); 1237 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1238 memcg = (void *)page_private(pages[i]); 1239 set_page_private(pages[i], 0); 1240 page_add_new_anon_rmap(pages[i], vma, haddr, false); 1241 mem_cgroup_commit_charge(pages[i], memcg, false, false); 1242 lru_cache_add_active_or_unevictable(pages[i], vma); 1243 pte = pte_offset_map(&_pmd, haddr); 1244 VM_BUG_ON(!pte_none(*pte)); 1245 set_pte_at(mm, haddr, pte, entry); 1246 pte_unmap(pte); 1247 } 1248 kfree(pages); 1249 1250 smp_wmb(); /* make pte visible before pmd */ 1251 pmd_populate(mm, pmd, pgtable); 1252 page_remove_rmap(page, true); 1253 spin_unlock(ptl); 1254 1255 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1256 1257 ret |= VM_FAULT_WRITE; 1258 put_page(page); 1259 1260 out: 1261 return ret; 1262 1263 out_free_pages: 1264 spin_unlock(ptl); 1265 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1266 for (i = 0; i < HPAGE_PMD_NR; i++) { 1267 memcg = (void *)page_private(pages[i]); 1268 set_page_private(pages[i], 0); 1269 mem_cgroup_cancel_charge(pages[i], memcg, false); 1270 put_page(pages[i]); 1271 } 1272 kfree(pages); 1273 goto out; 1274 } 1275 1276 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 1277 unsigned long address, pmd_t *pmd, pmd_t orig_pmd) 1278 { 1279 spinlock_t *ptl; 1280 int ret = 0; 1281 struct page *page = NULL, *new_page; 1282 struct mem_cgroup *memcg; 1283 unsigned long haddr; 1284 unsigned long mmun_start; /* For mmu_notifiers */ 1285 unsigned long mmun_end; /* For mmu_notifiers */ 1286 gfp_t huge_gfp; /* for allocation and charge */ 1287 1288 ptl = pmd_lockptr(mm, pmd); 1289 VM_BUG_ON_VMA(!vma->anon_vma, vma); 1290 haddr = address & HPAGE_PMD_MASK; 1291 if (is_huge_zero_pmd(orig_pmd)) 1292 goto alloc; 1293 spin_lock(ptl); 1294 if (unlikely(!pmd_same(*pmd, orig_pmd))) 1295 goto out_unlock; 1296 1297 page = pmd_page(orig_pmd); 1298 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); 1299 /* 1300 * We can only reuse the page if nobody else maps the huge page or it's 1301 * part. 1302 */ 1303 if (page_trans_huge_mapcount(page, NULL) == 1) { 1304 pmd_t entry; 1305 entry = pmd_mkyoung(orig_pmd); 1306 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1307 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 1308 update_mmu_cache_pmd(vma, address, pmd); 1309 ret |= VM_FAULT_WRITE; 1310 goto out_unlock; 1311 } 1312 get_page(page); 1313 spin_unlock(ptl); 1314 alloc: 1315 if (transparent_hugepage_enabled(vma) && 1316 !transparent_hugepage_debug_cow()) { 1317 huge_gfp = alloc_hugepage_direct_gfpmask(vma); 1318 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER); 1319 } else 1320 new_page = NULL; 1321 1322 if (likely(new_page)) { 1323 prep_transhuge_page(new_page); 1324 } else { 1325 if (!page) { 1326 split_huge_pmd(vma, pmd, address); 1327 ret |= VM_FAULT_FALLBACK; 1328 } else { 1329 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 1330 pmd, orig_pmd, page, haddr); 1331 if (ret & VM_FAULT_OOM) { 1332 split_huge_pmd(vma, pmd, address); 1333 ret |= VM_FAULT_FALLBACK; 1334 } 1335 put_page(page); 1336 } 1337 count_vm_event(THP_FAULT_FALLBACK); 1338 goto out; 1339 } 1340 1341 if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg, 1342 true))) { 1343 put_page(new_page); 1344 if (page) { 1345 split_huge_pmd(vma, pmd, address); 1346 put_page(page); 1347 } else 1348 split_huge_pmd(vma, pmd, address); 1349 ret |= VM_FAULT_FALLBACK; 1350 count_vm_event(THP_FAULT_FALLBACK); 1351 goto out; 1352 } 1353 1354 count_vm_event(THP_FAULT_ALLOC); 1355 1356 if (!page) 1357 clear_huge_page(new_page, haddr, HPAGE_PMD_NR); 1358 else 1359 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 1360 __SetPageUptodate(new_page); 1361 1362 mmun_start = haddr; 1363 mmun_end = haddr + HPAGE_PMD_SIZE; 1364 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1365 1366 spin_lock(ptl); 1367 if (page) 1368 put_page(page); 1369 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 1370 spin_unlock(ptl); 1371 mem_cgroup_cancel_charge(new_page, memcg, true); 1372 put_page(new_page); 1373 goto out_mn; 1374 } else { 1375 pmd_t entry; 1376 entry = mk_huge_pmd(new_page, vma->vm_page_prot); 1377 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1378 pmdp_huge_clear_flush_notify(vma, haddr, pmd); 1379 page_add_new_anon_rmap(new_page, vma, haddr, true); 1380 mem_cgroup_commit_charge(new_page, memcg, false, true); 1381 lru_cache_add_active_or_unevictable(new_page, vma); 1382 set_pmd_at(mm, haddr, pmd, entry); 1383 update_mmu_cache_pmd(vma, address, pmd); 1384 if (!page) { 1385 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 1386 put_huge_zero_page(); 1387 } else { 1388 VM_BUG_ON_PAGE(!PageHead(page), page); 1389 page_remove_rmap(page, true); 1390 put_page(page); 1391 } 1392 ret |= VM_FAULT_WRITE; 1393 } 1394 spin_unlock(ptl); 1395 out_mn: 1396 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1397 out: 1398 return ret; 1399 out_unlock: 1400 spin_unlock(ptl); 1401 return ret; 1402 } 1403 1404 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1405 unsigned long addr, 1406 pmd_t *pmd, 1407 unsigned int flags) 1408 { 1409 struct mm_struct *mm = vma->vm_mm; 1410 struct page *page = NULL; 1411 1412 assert_spin_locked(pmd_lockptr(mm, pmd)); 1413 1414 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 1415 goto out; 1416 1417 /* Avoid dumping huge zero page */ 1418 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) 1419 return ERR_PTR(-EFAULT); 1420 1421 /* Full NUMA hinting faults to serialise migration in fault paths */ 1422 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) 1423 goto out; 1424 1425 page = pmd_page(*pmd); 1426 VM_BUG_ON_PAGE(!PageHead(page), page); 1427 if (flags & FOLL_TOUCH) 1428 touch_pmd(vma, addr, pmd); 1429 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 1430 /* 1431 * We don't mlock() pte-mapped THPs. This way we can avoid 1432 * leaking mlocked pages into non-VM_LOCKED VMAs. 1433 * 1434 * In most cases the pmd is the only mapping of the page as we 1435 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for 1436 * writable private mappings in populate_vma_page_range(). 1437 * 1438 * The only scenario when we have the page shared here is if we 1439 * mlocking read-only mapping shared over fork(). We skip 1440 * mlocking such pages. 1441 */ 1442 if (compound_mapcount(page) == 1 && !PageDoubleMap(page) && 1443 page->mapping && trylock_page(page)) { 1444 lru_add_drain(); 1445 if (page->mapping) 1446 mlock_vma_page(page); 1447 unlock_page(page); 1448 } 1449 } 1450 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1451 VM_BUG_ON_PAGE(!PageCompound(page), page); 1452 if (flags & FOLL_GET) 1453 get_page(page); 1454 1455 out: 1456 return page; 1457 } 1458 1459 /* NUMA hinting page fault entry point for trans huge pmds */ 1460 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, 1461 unsigned long addr, pmd_t pmd, pmd_t *pmdp) 1462 { 1463 spinlock_t *ptl; 1464 struct anon_vma *anon_vma = NULL; 1465 struct page *page; 1466 unsigned long haddr = addr & HPAGE_PMD_MASK; 1467 int page_nid = -1, this_nid = numa_node_id(); 1468 int target_nid, last_cpupid = -1; 1469 bool page_locked; 1470 bool migrated = false; 1471 bool was_writable; 1472 int flags = 0; 1473 1474 /* A PROT_NONE fault should not end up here */ 1475 BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))); 1476 1477 ptl = pmd_lock(mm, pmdp); 1478 if (unlikely(!pmd_same(pmd, *pmdp))) 1479 goto out_unlock; 1480 1481 /* 1482 * If there are potential migrations, wait for completion and retry 1483 * without disrupting NUMA hinting information. Do not relock and 1484 * check_same as the page may no longer be mapped. 1485 */ 1486 if (unlikely(pmd_trans_migrating(*pmdp))) { 1487 page = pmd_page(*pmdp); 1488 spin_unlock(ptl); 1489 wait_on_page_locked(page); 1490 goto out; 1491 } 1492 1493 page = pmd_page(pmd); 1494 BUG_ON(is_huge_zero_page(page)); 1495 page_nid = page_to_nid(page); 1496 last_cpupid = page_cpupid_last(page); 1497 count_vm_numa_event(NUMA_HINT_FAULTS); 1498 if (page_nid == this_nid) { 1499 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); 1500 flags |= TNF_FAULT_LOCAL; 1501 } 1502 1503 /* See similar comment in do_numa_page for explanation */ 1504 if (!(vma->vm_flags & VM_WRITE)) 1505 flags |= TNF_NO_GROUP; 1506 1507 /* 1508 * Acquire the page lock to serialise THP migrations but avoid dropping 1509 * page_table_lock if at all possible 1510 */ 1511 page_locked = trylock_page(page); 1512 target_nid = mpol_misplaced(page, vma, haddr); 1513 if (target_nid == -1) { 1514 /* If the page was locked, there are no parallel migrations */ 1515 if (page_locked) 1516 goto clear_pmdnuma; 1517 } 1518 1519 /* Migration could have started since the pmd_trans_migrating check */ 1520 if (!page_locked) { 1521 spin_unlock(ptl); 1522 wait_on_page_locked(page); 1523 page_nid = -1; 1524 goto out; 1525 } 1526 1527 /* 1528 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma 1529 * to serialises splits 1530 */ 1531 get_page(page); 1532 spin_unlock(ptl); 1533 anon_vma = page_lock_anon_vma_read(page); 1534 1535 /* Confirm the PMD did not change while page_table_lock was released */ 1536 spin_lock(ptl); 1537 if (unlikely(!pmd_same(pmd, *pmdp))) { 1538 unlock_page(page); 1539 put_page(page); 1540 page_nid = -1; 1541 goto out_unlock; 1542 } 1543 1544 /* Bail if we fail to protect against THP splits for any reason */ 1545 if (unlikely(!anon_vma)) { 1546 put_page(page); 1547 page_nid = -1; 1548 goto clear_pmdnuma; 1549 } 1550 1551 /* 1552 * Migrate the THP to the requested node, returns with page unlocked 1553 * and access rights restored. 1554 */ 1555 spin_unlock(ptl); 1556 migrated = migrate_misplaced_transhuge_page(mm, vma, 1557 pmdp, pmd, addr, page, target_nid); 1558 if (migrated) { 1559 flags |= TNF_MIGRATED; 1560 page_nid = target_nid; 1561 } else 1562 flags |= TNF_MIGRATE_FAIL; 1563 1564 goto out; 1565 clear_pmdnuma: 1566 BUG_ON(!PageLocked(page)); 1567 was_writable = pmd_write(pmd); 1568 pmd = pmd_modify(pmd, vma->vm_page_prot); 1569 pmd = pmd_mkyoung(pmd); 1570 if (was_writable) 1571 pmd = pmd_mkwrite(pmd); 1572 set_pmd_at(mm, haddr, pmdp, pmd); 1573 update_mmu_cache_pmd(vma, addr, pmdp); 1574 unlock_page(page); 1575 out_unlock: 1576 spin_unlock(ptl); 1577 1578 out: 1579 if (anon_vma) 1580 page_unlock_anon_vma_read(anon_vma); 1581 1582 if (page_nid != -1) 1583 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags); 1584 1585 return 0; 1586 } 1587 1588 int madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1589 pmd_t *pmd, unsigned long addr, unsigned long next) 1590 1591 { 1592 spinlock_t *ptl; 1593 pmd_t orig_pmd; 1594 struct page *page; 1595 struct mm_struct *mm = tlb->mm; 1596 int ret = 0; 1597 1598 ptl = pmd_trans_huge_lock(pmd, vma); 1599 if (!ptl) 1600 goto out_unlocked; 1601 1602 orig_pmd = *pmd; 1603 if (is_huge_zero_pmd(orig_pmd)) { 1604 ret = 1; 1605 goto out; 1606 } 1607 1608 page = pmd_page(orig_pmd); 1609 /* 1610 * If other processes are mapping this page, we couldn't discard 1611 * the page unless they all do MADV_FREE so let's skip the page. 1612 */ 1613 if (page_mapcount(page) != 1) 1614 goto out; 1615 1616 if (!trylock_page(page)) 1617 goto out; 1618 1619 /* 1620 * If user want to discard part-pages of THP, split it so MADV_FREE 1621 * will deactivate only them. 1622 */ 1623 if (next - addr != HPAGE_PMD_SIZE) { 1624 get_page(page); 1625 spin_unlock(ptl); 1626 if (split_huge_page(page)) { 1627 put_page(page); 1628 unlock_page(page); 1629 goto out_unlocked; 1630 } 1631 put_page(page); 1632 unlock_page(page); 1633 ret = 1; 1634 goto out_unlocked; 1635 } 1636 1637 if (PageDirty(page)) 1638 ClearPageDirty(page); 1639 unlock_page(page); 1640 1641 if (PageActive(page)) 1642 deactivate_page(page); 1643 1644 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { 1645 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, 1646 tlb->fullmm); 1647 orig_pmd = pmd_mkold(orig_pmd); 1648 orig_pmd = pmd_mkclean(orig_pmd); 1649 1650 set_pmd_at(mm, addr, pmd, orig_pmd); 1651 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1652 } 1653 ret = 1; 1654 out: 1655 spin_unlock(ptl); 1656 out_unlocked: 1657 return ret; 1658 } 1659 1660 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1661 pmd_t *pmd, unsigned long addr) 1662 { 1663 pmd_t orig_pmd; 1664 spinlock_t *ptl; 1665 1666 ptl = __pmd_trans_huge_lock(pmd, vma); 1667 if (!ptl) 1668 return 0; 1669 /* 1670 * For architectures like ppc64 we look at deposited pgtable 1671 * when calling pmdp_huge_get_and_clear. So do the 1672 * pgtable_trans_huge_withdraw after finishing pmdp related 1673 * operations. 1674 */ 1675 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, 1676 tlb->fullmm); 1677 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1678 if (vma_is_dax(vma)) { 1679 spin_unlock(ptl); 1680 if (is_huge_zero_pmd(orig_pmd)) 1681 tlb_remove_page(tlb, pmd_page(orig_pmd)); 1682 } else if (is_huge_zero_pmd(orig_pmd)) { 1683 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd)); 1684 atomic_long_dec(&tlb->mm->nr_ptes); 1685 spin_unlock(ptl); 1686 tlb_remove_page(tlb, pmd_page(orig_pmd)); 1687 } else { 1688 struct page *page = pmd_page(orig_pmd); 1689 page_remove_rmap(page, true); 1690 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); 1691 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1692 VM_BUG_ON_PAGE(!PageHead(page), page); 1693 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd)); 1694 atomic_long_dec(&tlb->mm->nr_ptes); 1695 spin_unlock(ptl); 1696 tlb_remove_page(tlb, page); 1697 } 1698 return 1; 1699 } 1700 1701 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr, 1702 unsigned long new_addr, unsigned long old_end, 1703 pmd_t *old_pmd, pmd_t *new_pmd) 1704 { 1705 spinlock_t *old_ptl, *new_ptl; 1706 pmd_t pmd; 1707 struct mm_struct *mm = vma->vm_mm; 1708 1709 if ((old_addr & ~HPAGE_PMD_MASK) || 1710 (new_addr & ~HPAGE_PMD_MASK) || 1711 old_end - old_addr < HPAGE_PMD_SIZE) 1712 return false; 1713 1714 /* 1715 * The destination pmd shouldn't be established, free_pgtables() 1716 * should have release it. 1717 */ 1718 if (WARN_ON(!pmd_none(*new_pmd))) { 1719 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1720 return false; 1721 } 1722 1723 /* 1724 * We don't have to worry about the ordering of src and dst 1725 * ptlocks because exclusive mmap_sem prevents deadlock. 1726 */ 1727 old_ptl = __pmd_trans_huge_lock(old_pmd, vma); 1728 if (old_ptl) { 1729 new_ptl = pmd_lockptr(mm, new_pmd); 1730 if (new_ptl != old_ptl) 1731 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 1732 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd); 1733 VM_BUG_ON(!pmd_none(*new_pmd)); 1734 1735 if (pmd_move_must_withdraw(new_ptl, old_ptl) && 1736 vma_is_anonymous(vma)) { 1737 pgtable_t pgtable; 1738 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); 1739 pgtable_trans_huge_deposit(mm, new_pmd, pgtable); 1740 } 1741 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd)); 1742 if (new_ptl != old_ptl) 1743 spin_unlock(new_ptl); 1744 spin_unlock(old_ptl); 1745 return true; 1746 } 1747 return false; 1748 } 1749 1750 /* 1751 * Returns 1752 * - 0 if PMD could not be locked 1753 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary 1754 * - HPAGE_PMD_NR is protections changed and TLB flush necessary 1755 */ 1756 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1757 unsigned long addr, pgprot_t newprot, int prot_numa) 1758 { 1759 struct mm_struct *mm = vma->vm_mm; 1760 spinlock_t *ptl; 1761 int ret = 0; 1762 1763 ptl = __pmd_trans_huge_lock(pmd, vma); 1764 if (ptl) { 1765 pmd_t entry; 1766 bool preserve_write = prot_numa && pmd_write(*pmd); 1767 ret = 1; 1768 1769 /* 1770 * Avoid trapping faults against the zero page. The read-only 1771 * data is likely to be read-cached on the local CPU and 1772 * local/remote hits to the zero page are not interesting. 1773 */ 1774 if (prot_numa && is_huge_zero_pmd(*pmd)) { 1775 spin_unlock(ptl); 1776 return ret; 1777 } 1778 1779 if (!prot_numa || !pmd_protnone(*pmd)) { 1780 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd); 1781 entry = pmd_modify(entry, newprot); 1782 if (preserve_write) 1783 entry = pmd_mkwrite(entry); 1784 ret = HPAGE_PMD_NR; 1785 set_pmd_at(mm, addr, pmd, entry); 1786 BUG_ON(!preserve_write && pmd_write(entry)); 1787 } 1788 spin_unlock(ptl); 1789 } 1790 1791 return ret; 1792 } 1793 1794 /* 1795 * Returns true if a given pmd maps a thp, false otherwise. 1796 * 1797 * Note that if it returns true, this routine returns without unlocking page 1798 * table lock. So callers must unlock it. 1799 */ 1800 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) 1801 { 1802 spinlock_t *ptl; 1803 ptl = pmd_lock(vma->vm_mm, pmd); 1804 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd))) 1805 return ptl; 1806 spin_unlock(ptl); 1807 return NULL; 1808 } 1809 1810 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE) 1811 1812 int hugepage_madvise(struct vm_area_struct *vma, 1813 unsigned long *vm_flags, int advice) 1814 { 1815 switch (advice) { 1816 case MADV_HUGEPAGE: 1817 #ifdef CONFIG_S390 1818 /* 1819 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 1820 * can't handle this properly after s390_enable_sie, so we simply 1821 * ignore the madvise to prevent qemu from causing a SIGSEGV. 1822 */ 1823 if (mm_has_pgste(vma->vm_mm)) 1824 return 0; 1825 #endif 1826 /* 1827 * Be somewhat over-protective like KSM for now! 1828 */ 1829 if (*vm_flags & VM_NO_THP) 1830 return -EINVAL; 1831 *vm_flags &= ~VM_NOHUGEPAGE; 1832 *vm_flags |= VM_HUGEPAGE; 1833 /* 1834 * If the vma become good for khugepaged to scan, 1835 * register it here without waiting a page fault that 1836 * may not happen any time soon. 1837 */ 1838 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags))) 1839 return -ENOMEM; 1840 break; 1841 case MADV_NOHUGEPAGE: 1842 /* 1843 * Be somewhat over-protective like KSM for now! 1844 */ 1845 if (*vm_flags & VM_NO_THP) 1846 return -EINVAL; 1847 *vm_flags &= ~VM_HUGEPAGE; 1848 *vm_flags |= VM_NOHUGEPAGE; 1849 /* 1850 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1851 * this vma even if we leave the mm registered in khugepaged if 1852 * it got registered before VM_NOHUGEPAGE was set. 1853 */ 1854 break; 1855 } 1856 1857 return 0; 1858 } 1859 1860 static int __init khugepaged_slab_init(void) 1861 { 1862 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1863 sizeof(struct mm_slot), 1864 __alignof__(struct mm_slot), 0, NULL); 1865 if (!mm_slot_cache) 1866 return -ENOMEM; 1867 1868 return 0; 1869 } 1870 1871 static void __init khugepaged_slab_exit(void) 1872 { 1873 kmem_cache_destroy(mm_slot_cache); 1874 } 1875 1876 static inline struct mm_slot *alloc_mm_slot(void) 1877 { 1878 if (!mm_slot_cache) /* initialization failed */ 1879 return NULL; 1880 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 1881 } 1882 1883 static inline void free_mm_slot(struct mm_slot *mm_slot) 1884 { 1885 kmem_cache_free(mm_slot_cache, mm_slot); 1886 } 1887 1888 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 1889 { 1890 struct mm_slot *mm_slot; 1891 1892 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) 1893 if (mm == mm_slot->mm) 1894 return mm_slot; 1895 1896 return NULL; 1897 } 1898 1899 static void insert_to_mm_slots_hash(struct mm_struct *mm, 1900 struct mm_slot *mm_slot) 1901 { 1902 mm_slot->mm = mm; 1903 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); 1904 } 1905 1906 static inline int khugepaged_test_exit(struct mm_struct *mm) 1907 { 1908 return atomic_read(&mm->mm_users) == 0; 1909 } 1910 1911 int __khugepaged_enter(struct mm_struct *mm) 1912 { 1913 struct mm_slot *mm_slot; 1914 int wakeup; 1915 1916 mm_slot = alloc_mm_slot(); 1917 if (!mm_slot) 1918 return -ENOMEM; 1919 1920 /* __khugepaged_exit() must not run from under us */ 1921 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); 1922 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 1923 free_mm_slot(mm_slot); 1924 return 0; 1925 } 1926 1927 spin_lock(&khugepaged_mm_lock); 1928 insert_to_mm_slots_hash(mm, mm_slot); 1929 /* 1930 * Insert just behind the scanning cursor, to let the area settle 1931 * down a little. 1932 */ 1933 wakeup = list_empty(&khugepaged_scan.mm_head); 1934 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 1935 spin_unlock(&khugepaged_mm_lock); 1936 1937 atomic_inc(&mm->mm_count); 1938 if (wakeup) 1939 wake_up_interruptible(&khugepaged_wait); 1940 1941 return 0; 1942 } 1943 1944 int khugepaged_enter_vma_merge(struct vm_area_struct *vma, 1945 unsigned long vm_flags) 1946 { 1947 unsigned long hstart, hend; 1948 if (!vma->anon_vma) 1949 /* 1950 * Not yet faulted in so we will register later in the 1951 * page fault if needed. 1952 */ 1953 return 0; 1954 if (vma->vm_ops || (vm_flags & VM_NO_THP)) 1955 /* khugepaged not yet working on file or special mappings */ 1956 return 0; 1957 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1958 hend = vma->vm_end & HPAGE_PMD_MASK; 1959 if (hstart < hend) 1960 return khugepaged_enter(vma, vm_flags); 1961 return 0; 1962 } 1963 1964 void __khugepaged_exit(struct mm_struct *mm) 1965 { 1966 struct mm_slot *mm_slot; 1967 int free = 0; 1968 1969 spin_lock(&khugepaged_mm_lock); 1970 mm_slot = get_mm_slot(mm); 1971 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 1972 hash_del(&mm_slot->hash); 1973 list_del(&mm_slot->mm_node); 1974 free = 1; 1975 } 1976 spin_unlock(&khugepaged_mm_lock); 1977 1978 if (free) { 1979 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1980 free_mm_slot(mm_slot); 1981 mmdrop(mm); 1982 } else if (mm_slot) { 1983 /* 1984 * This is required to serialize against 1985 * khugepaged_test_exit() (which is guaranteed to run 1986 * under mmap sem read mode). Stop here (after we 1987 * return all pagetables will be destroyed) until 1988 * khugepaged has finished working on the pagetables 1989 * under the mmap_sem. 1990 */ 1991 down_write(&mm->mmap_sem); 1992 up_write(&mm->mmap_sem); 1993 } 1994 } 1995 1996 static void release_pte_page(struct page *page) 1997 { 1998 /* 0 stands for page_is_file_cache(page) == false */ 1999 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 2000 unlock_page(page); 2001 putback_lru_page(page); 2002 } 2003 2004 static void release_pte_pages(pte_t *pte, pte_t *_pte) 2005 { 2006 while (--_pte >= pte) { 2007 pte_t pteval = *_pte; 2008 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) 2009 release_pte_page(pte_page(pteval)); 2010 } 2011 } 2012 2013 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 2014 unsigned long address, 2015 pte_t *pte) 2016 { 2017 struct page *page = NULL; 2018 pte_t *_pte; 2019 int none_or_zero = 0, result = 0; 2020 bool referenced = false, writable = false; 2021 2022 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 2023 _pte++, address += PAGE_SIZE) { 2024 pte_t pteval = *_pte; 2025 if (pte_none(pteval) || (pte_present(pteval) && 2026 is_zero_pfn(pte_pfn(pteval)))) { 2027 if (!userfaultfd_armed(vma) && 2028 ++none_or_zero <= khugepaged_max_ptes_none) { 2029 continue; 2030 } else { 2031 result = SCAN_EXCEED_NONE_PTE; 2032 goto out; 2033 } 2034 } 2035 if (!pte_present(pteval)) { 2036 result = SCAN_PTE_NON_PRESENT; 2037 goto out; 2038 } 2039 page = vm_normal_page(vma, address, pteval); 2040 if (unlikely(!page)) { 2041 result = SCAN_PAGE_NULL; 2042 goto out; 2043 } 2044 2045 VM_BUG_ON_PAGE(PageCompound(page), page); 2046 VM_BUG_ON_PAGE(!PageAnon(page), page); 2047 VM_BUG_ON_PAGE(!PageSwapBacked(page), page); 2048 2049 /* 2050 * We can do it before isolate_lru_page because the 2051 * page can't be freed from under us. NOTE: PG_lock 2052 * is needed to serialize against split_huge_page 2053 * when invoked from the VM. 2054 */ 2055 if (!trylock_page(page)) { 2056 result = SCAN_PAGE_LOCK; 2057 goto out; 2058 } 2059 2060 /* 2061 * cannot use mapcount: can't collapse if there's a gup pin. 2062 * The page must only be referenced by the scanned process 2063 * and page swap cache. 2064 */ 2065 if (page_count(page) != 1 + !!PageSwapCache(page)) { 2066 unlock_page(page); 2067 result = SCAN_PAGE_COUNT; 2068 goto out; 2069 } 2070 if (pte_write(pteval)) { 2071 writable = true; 2072 } else { 2073 if (PageSwapCache(page) && 2074 !reuse_swap_page(page, NULL)) { 2075 unlock_page(page); 2076 result = SCAN_SWAP_CACHE_PAGE; 2077 goto out; 2078 } 2079 /* 2080 * Page is not in the swap cache. It can be collapsed 2081 * into a THP. 2082 */ 2083 } 2084 2085 /* 2086 * Isolate the page to avoid collapsing an hugepage 2087 * currently in use by the VM. 2088 */ 2089 if (isolate_lru_page(page)) { 2090 unlock_page(page); 2091 result = SCAN_DEL_PAGE_LRU; 2092 goto out; 2093 } 2094 /* 0 stands for page_is_file_cache(page) == false */ 2095 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 2096 VM_BUG_ON_PAGE(!PageLocked(page), page); 2097 VM_BUG_ON_PAGE(PageLRU(page), page); 2098 2099 /* If there is no mapped pte young don't collapse the page */ 2100 if (pte_young(pteval) || 2101 page_is_young(page) || PageReferenced(page) || 2102 mmu_notifier_test_young(vma->vm_mm, address)) 2103 referenced = true; 2104 } 2105 if (likely(writable)) { 2106 if (likely(referenced)) { 2107 result = SCAN_SUCCEED; 2108 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 2109 referenced, writable, result); 2110 return 1; 2111 } 2112 } else { 2113 result = SCAN_PAGE_RO; 2114 } 2115 2116 out: 2117 release_pte_pages(pte, _pte); 2118 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 2119 referenced, writable, result); 2120 return 0; 2121 } 2122 2123 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 2124 struct vm_area_struct *vma, 2125 unsigned long address, 2126 spinlock_t *ptl) 2127 { 2128 pte_t *_pte; 2129 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 2130 pte_t pteval = *_pte; 2131 struct page *src_page; 2132 2133 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 2134 clear_user_highpage(page, address); 2135 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 2136 if (is_zero_pfn(pte_pfn(pteval))) { 2137 /* 2138 * ptl mostly unnecessary. 2139 */ 2140 spin_lock(ptl); 2141 /* 2142 * paravirt calls inside pte_clear here are 2143 * superfluous. 2144 */ 2145 pte_clear(vma->vm_mm, address, _pte); 2146 spin_unlock(ptl); 2147 } 2148 } else { 2149 src_page = pte_page(pteval); 2150 copy_user_highpage(page, src_page, address, vma); 2151 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); 2152 release_pte_page(src_page); 2153 /* 2154 * ptl mostly unnecessary, but preempt has to 2155 * be disabled to update the per-cpu stats 2156 * inside page_remove_rmap(). 2157 */ 2158 spin_lock(ptl); 2159 /* 2160 * paravirt calls inside pte_clear here are 2161 * superfluous. 2162 */ 2163 pte_clear(vma->vm_mm, address, _pte); 2164 page_remove_rmap(src_page, false); 2165 spin_unlock(ptl); 2166 free_page_and_swap_cache(src_page); 2167 } 2168 2169 address += PAGE_SIZE; 2170 page++; 2171 } 2172 } 2173 2174 static void khugepaged_alloc_sleep(void) 2175 { 2176 DEFINE_WAIT(wait); 2177 2178 add_wait_queue(&khugepaged_wait, &wait); 2179 freezable_schedule_timeout_interruptible( 2180 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 2181 remove_wait_queue(&khugepaged_wait, &wait); 2182 } 2183 2184 static int khugepaged_node_load[MAX_NUMNODES]; 2185 2186 static bool khugepaged_scan_abort(int nid) 2187 { 2188 int i; 2189 2190 /* 2191 * If zone_reclaim_mode is disabled, then no extra effort is made to 2192 * allocate memory locally. 2193 */ 2194 if (!zone_reclaim_mode) 2195 return false; 2196 2197 /* If there is a count for this node already, it must be acceptable */ 2198 if (khugepaged_node_load[nid]) 2199 return false; 2200 2201 for (i = 0; i < MAX_NUMNODES; i++) { 2202 if (!khugepaged_node_load[i]) 2203 continue; 2204 if (node_distance(nid, i) > RECLAIM_DISTANCE) 2205 return true; 2206 } 2207 return false; 2208 } 2209 2210 #ifdef CONFIG_NUMA 2211 static int khugepaged_find_target_node(void) 2212 { 2213 static int last_khugepaged_target_node = NUMA_NO_NODE; 2214 int nid, target_node = 0, max_value = 0; 2215 2216 /* find first node with max normal pages hit */ 2217 for (nid = 0; nid < MAX_NUMNODES; nid++) 2218 if (khugepaged_node_load[nid] > max_value) { 2219 max_value = khugepaged_node_load[nid]; 2220 target_node = nid; 2221 } 2222 2223 /* do some balance if several nodes have the same hit record */ 2224 if (target_node <= last_khugepaged_target_node) 2225 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; 2226 nid++) 2227 if (max_value == khugepaged_node_load[nid]) { 2228 target_node = nid; 2229 break; 2230 } 2231 2232 last_khugepaged_target_node = target_node; 2233 return target_node; 2234 } 2235 2236 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2237 { 2238 if (IS_ERR(*hpage)) { 2239 if (!*wait) 2240 return false; 2241 2242 *wait = false; 2243 *hpage = NULL; 2244 khugepaged_alloc_sleep(); 2245 } else if (*hpage) { 2246 put_page(*hpage); 2247 *hpage = NULL; 2248 } 2249 2250 return true; 2251 } 2252 2253 static struct page * 2254 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm, 2255 unsigned long address, int node) 2256 { 2257 VM_BUG_ON_PAGE(*hpage, *hpage); 2258 2259 /* 2260 * Before allocating the hugepage, release the mmap_sem read lock. 2261 * The allocation can take potentially a long time if it involves 2262 * sync compaction, and we do not need to hold the mmap_sem during 2263 * that. We will recheck the vma after taking it again in write mode. 2264 */ 2265 up_read(&mm->mmap_sem); 2266 2267 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); 2268 if (unlikely(!*hpage)) { 2269 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2270 *hpage = ERR_PTR(-ENOMEM); 2271 return NULL; 2272 } 2273 2274 prep_transhuge_page(*hpage); 2275 count_vm_event(THP_COLLAPSE_ALLOC); 2276 return *hpage; 2277 } 2278 #else 2279 static int khugepaged_find_target_node(void) 2280 { 2281 return 0; 2282 } 2283 2284 static inline struct page *alloc_khugepaged_hugepage(void) 2285 { 2286 struct page *page; 2287 2288 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), 2289 HPAGE_PMD_ORDER); 2290 if (page) 2291 prep_transhuge_page(page); 2292 return page; 2293 } 2294 2295 static struct page *khugepaged_alloc_hugepage(bool *wait) 2296 { 2297 struct page *hpage; 2298 2299 do { 2300 hpage = alloc_khugepaged_hugepage(); 2301 if (!hpage) { 2302 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2303 if (!*wait) 2304 return NULL; 2305 2306 *wait = false; 2307 khugepaged_alloc_sleep(); 2308 } else 2309 count_vm_event(THP_COLLAPSE_ALLOC); 2310 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 2311 2312 return hpage; 2313 } 2314 2315 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2316 { 2317 if (!*hpage) 2318 *hpage = khugepaged_alloc_hugepage(wait); 2319 2320 if (unlikely(!*hpage)) 2321 return false; 2322 2323 return true; 2324 } 2325 2326 static struct page * 2327 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm, 2328 unsigned long address, int node) 2329 { 2330 up_read(&mm->mmap_sem); 2331 VM_BUG_ON(!*hpage); 2332 2333 return *hpage; 2334 } 2335 #endif 2336 2337 static bool hugepage_vma_check(struct vm_area_struct *vma) 2338 { 2339 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 2340 (vma->vm_flags & VM_NOHUGEPAGE)) 2341 return false; 2342 if (!vma->anon_vma || vma->vm_ops) 2343 return false; 2344 if (is_vma_temporary_stack(vma)) 2345 return false; 2346 return !(vma->vm_flags & VM_NO_THP); 2347 } 2348 2349 static void collapse_huge_page(struct mm_struct *mm, 2350 unsigned long address, 2351 struct page **hpage, 2352 struct vm_area_struct *vma, 2353 int node) 2354 { 2355 pmd_t *pmd, _pmd; 2356 pte_t *pte; 2357 pgtable_t pgtable; 2358 struct page *new_page; 2359 spinlock_t *pmd_ptl, *pte_ptl; 2360 int isolated = 0, result = 0; 2361 unsigned long hstart, hend; 2362 struct mem_cgroup *memcg; 2363 unsigned long mmun_start; /* For mmu_notifiers */ 2364 unsigned long mmun_end; /* For mmu_notifiers */ 2365 gfp_t gfp; 2366 2367 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2368 2369 /* Only allocate from the target node */ 2370 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE; 2371 2372 /* release the mmap_sem read lock. */ 2373 new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node); 2374 if (!new_page) { 2375 result = SCAN_ALLOC_HUGE_PAGE_FAIL; 2376 goto out_nolock; 2377 } 2378 2379 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { 2380 result = SCAN_CGROUP_CHARGE_FAIL; 2381 goto out_nolock; 2382 } 2383 2384 /* 2385 * Prevent all access to pagetables with the exception of 2386 * gup_fast later hanlded by the ptep_clear_flush and the VM 2387 * handled by the anon_vma lock + PG_lock. 2388 */ 2389 down_write(&mm->mmap_sem); 2390 if (unlikely(khugepaged_test_exit(mm))) { 2391 result = SCAN_ANY_PROCESS; 2392 goto out; 2393 } 2394 2395 vma = find_vma(mm, address); 2396 if (!vma) { 2397 result = SCAN_VMA_NULL; 2398 goto out; 2399 } 2400 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2401 hend = vma->vm_end & HPAGE_PMD_MASK; 2402 if (address < hstart || address + HPAGE_PMD_SIZE > hend) { 2403 result = SCAN_ADDRESS_RANGE; 2404 goto out; 2405 } 2406 if (!hugepage_vma_check(vma)) { 2407 result = SCAN_VMA_CHECK; 2408 goto out; 2409 } 2410 pmd = mm_find_pmd(mm, address); 2411 if (!pmd) { 2412 result = SCAN_PMD_NULL; 2413 goto out; 2414 } 2415 2416 anon_vma_lock_write(vma->anon_vma); 2417 2418 pte = pte_offset_map(pmd, address); 2419 pte_ptl = pte_lockptr(mm, pmd); 2420 2421 mmun_start = address; 2422 mmun_end = address + HPAGE_PMD_SIZE; 2423 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2424 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ 2425 /* 2426 * After this gup_fast can't run anymore. This also removes 2427 * any huge TLB entry from the CPU so we won't allow 2428 * huge and small TLB entries for the same virtual address 2429 * to avoid the risk of CPU bugs in that area. 2430 */ 2431 _pmd = pmdp_collapse_flush(vma, address, pmd); 2432 spin_unlock(pmd_ptl); 2433 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2434 2435 spin_lock(pte_ptl); 2436 isolated = __collapse_huge_page_isolate(vma, address, pte); 2437 spin_unlock(pte_ptl); 2438 2439 if (unlikely(!isolated)) { 2440 pte_unmap(pte); 2441 spin_lock(pmd_ptl); 2442 BUG_ON(!pmd_none(*pmd)); 2443 /* 2444 * We can only use set_pmd_at when establishing 2445 * hugepmds and never for establishing regular pmds that 2446 * points to regular pagetables. Use pmd_populate for that 2447 */ 2448 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 2449 spin_unlock(pmd_ptl); 2450 anon_vma_unlock_write(vma->anon_vma); 2451 result = SCAN_FAIL; 2452 goto out; 2453 } 2454 2455 /* 2456 * All pages are isolated and locked so anon_vma rmap 2457 * can't run anymore. 2458 */ 2459 anon_vma_unlock_write(vma->anon_vma); 2460 2461 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); 2462 pte_unmap(pte); 2463 __SetPageUptodate(new_page); 2464 pgtable = pmd_pgtable(_pmd); 2465 2466 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); 2467 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 2468 2469 /* 2470 * spin_lock() below is not the equivalent of smp_wmb(), so 2471 * this is needed to avoid the copy_huge_page writes to become 2472 * visible after the set_pmd_at() write. 2473 */ 2474 smp_wmb(); 2475 2476 spin_lock(pmd_ptl); 2477 BUG_ON(!pmd_none(*pmd)); 2478 page_add_new_anon_rmap(new_page, vma, address, true); 2479 mem_cgroup_commit_charge(new_page, memcg, false, true); 2480 lru_cache_add_active_or_unevictable(new_page, vma); 2481 pgtable_trans_huge_deposit(mm, pmd, pgtable); 2482 set_pmd_at(mm, address, pmd, _pmd); 2483 update_mmu_cache_pmd(vma, address, pmd); 2484 spin_unlock(pmd_ptl); 2485 2486 *hpage = NULL; 2487 2488 khugepaged_pages_collapsed++; 2489 result = SCAN_SUCCEED; 2490 out_up_write: 2491 up_write(&mm->mmap_sem); 2492 trace_mm_collapse_huge_page(mm, isolated, result); 2493 return; 2494 2495 out_nolock: 2496 trace_mm_collapse_huge_page(mm, isolated, result); 2497 return; 2498 out: 2499 mem_cgroup_cancel_charge(new_page, memcg, true); 2500 goto out_up_write; 2501 } 2502 2503 static int khugepaged_scan_pmd(struct mm_struct *mm, 2504 struct vm_area_struct *vma, 2505 unsigned long address, 2506 struct page **hpage) 2507 { 2508 pmd_t *pmd; 2509 pte_t *pte, *_pte; 2510 int ret = 0, none_or_zero = 0, result = 0; 2511 struct page *page = NULL; 2512 unsigned long _address; 2513 spinlock_t *ptl; 2514 int node = NUMA_NO_NODE; 2515 bool writable = false, referenced = false; 2516 2517 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2518 2519 pmd = mm_find_pmd(mm, address); 2520 if (!pmd) { 2521 result = SCAN_PMD_NULL; 2522 goto out; 2523 } 2524 2525 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 2526 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2527 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2528 _pte++, _address += PAGE_SIZE) { 2529 pte_t pteval = *_pte; 2530 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 2531 if (!userfaultfd_armed(vma) && 2532 ++none_or_zero <= khugepaged_max_ptes_none) { 2533 continue; 2534 } else { 2535 result = SCAN_EXCEED_NONE_PTE; 2536 goto out_unmap; 2537 } 2538 } 2539 if (!pte_present(pteval)) { 2540 result = SCAN_PTE_NON_PRESENT; 2541 goto out_unmap; 2542 } 2543 if (pte_write(pteval)) 2544 writable = true; 2545 2546 page = vm_normal_page(vma, _address, pteval); 2547 if (unlikely(!page)) { 2548 result = SCAN_PAGE_NULL; 2549 goto out_unmap; 2550 } 2551 2552 /* TODO: teach khugepaged to collapse THP mapped with pte */ 2553 if (PageCompound(page)) { 2554 result = SCAN_PAGE_COMPOUND; 2555 goto out_unmap; 2556 } 2557 2558 /* 2559 * Record which node the original page is from and save this 2560 * information to khugepaged_node_load[]. 2561 * Khupaged will allocate hugepage from the node has the max 2562 * hit record. 2563 */ 2564 node = page_to_nid(page); 2565 if (khugepaged_scan_abort(node)) { 2566 result = SCAN_SCAN_ABORT; 2567 goto out_unmap; 2568 } 2569 khugepaged_node_load[node]++; 2570 if (!PageLRU(page)) { 2571 result = SCAN_PAGE_LRU; 2572 goto out_unmap; 2573 } 2574 if (PageLocked(page)) { 2575 result = SCAN_PAGE_LOCK; 2576 goto out_unmap; 2577 } 2578 if (!PageAnon(page)) { 2579 result = SCAN_PAGE_ANON; 2580 goto out_unmap; 2581 } 2582 2583 /* 2584 * cannot use mapcount: can't collapse if there's a gup pin. 2585 * The page must only be referenced by the scanned process 2586 * and page swap cache. 2587 */ 2588 if (page_count(page) != 1 + !!PageSwapCache(page)) { 2589 result = SCAN_PAGE_COUNT; 2590 goto out_unmap; 2591 } 2592 if (pte_young(pteval) || 2593 page_is_young(page) || PageReferenced(page) || 2594 mmu_notifier_test_young(vma->vm_mm, address)) 2595 referenced = true; 2596 } 2597 if (writable) { 2598 if (referenced) { 2599 result = SCAN_SUCCEED; 2600 ret = 1; 2601 } else { 2602 result = SCAN_NO_REFERENCED_PAGE; 2603 } 2604 } else { 2605 result = SCAN_PAGE_RO; 2606 } 2607 out_unmap: 2608 pte_unmap_unlock(pte, ptl); 2609 if (ret) { 2610 node = khugepaged_find_target_node(); 2611 /* collapse_huge_page will return with the mmap_sem released */ 2612 collapse_huge_page(mm, address, hpage, vma, node); 2613 } 2614 out: 2615 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, 2616 none_or_zero, result); 2617 return ret; 2618 } 2619 2620 static void collect_mm_slot(struct mm_slot *mm_slot) 2621 { 2622 struct mm_struct *mm = mm_slot->mm; 2623 2624 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2625 2626 if (khugepaged_test_exit(mm)) { 2627 /* free mm_slot */ 2628 hash_del(&mm_slot->hash); 2629 list_del(&mm_slot->mm_node); 2630 2631 /* 2632 * Not strictly needed because the mm exited already. 2633 * 2634 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2635 */ 2636 2637 /* khugepaged_mm_lock actually not necessary for the below */ 2638 free_mm_slot(mm_slot); 2639 mmdrop(mm); 2640 } 2641 } 2642 2643 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2644 struct page **hpage) 2645 __releases(&khugepaged_mm_lock) 2646 __acquires(&khugepaged_mm_lock) 2647 { 2648 struct mm_slot *mm_slot; 2649 struct mm_struct *mm; 2650 struct vm_area_struct *vma; 2651 int progress = 0; 2652 2653 VM_BUG_ON(!pages); 2654 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2655 2656 if (khugepaged_scan.mm_slot) 2657 mm_slot = khugepaged_scan.mm_slot; 2658 else { 2659 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2660 struct mm_slot, mm_node); 2661 khugepaged_scan.address = 0; 2662 khugepaged_scan.mm_slot = mm_slot; 2663 } 2664 spin_unlock(&khugepaged_mm_lock); 2665 2666 mm = mm_slot->mm; 2667 down_read(&mm->mmap_sem); 2668 if (unlikely(khugepaged_test_exit(mm))) 2669 vma = NULL; 2670 else 2671 vma = find_vma(mm, khugepaged_scan.address); 2672 2673 progress++; 2674 for (; vma; vma = vma->vm_next) { 2675 unsigned long hstart, hend; 2676 2677 cond_resched(); 2678 if (unlikely(khugepaged_test_exit(mm))) { 2679 progress++; 2680 break; 2681 } 2682 if (!hugepage_vma_check(vma)) { 2683 skip: 2684 progress++; 2685 continue; 2686 } 2687 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2688 hend = vma->vm_end & HPAGE_PMD_MASK; 2689 if (hstart >= hend) 2690 goto skip; 2691 if (khugepaged_scan.address > hend) 2692 goto skip; 2693 if (khugepaged_scan.address < hstart) 2694 khugepaged_scan.address = hstart; 2695 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2696 2697 while (khugepaged_scan.address < hend) { 2698 int ret; 2699 cond_resched(); 2700 if (unlikely(khugepaged_test_exit(mm))) 2701 goto breakouterloop; 2702 2703 VM_BUG_ON(khugepaged_scan.address < hstart || 2704 khugepaged_scan.address + HPAGE_PMD_SIZE > 2705 hend); 2706 ret = khugepaged_scan_pmd(mm, vma, 2707 khugepaged_scan.address, 2708 hpage); 2709 /* move to next address */ 2710 khugepaged_scan.address += HPAGE_PMD_SIZE; 2711 progress += HPAGE_PMD_NR; 2712 if (ret) 2713 /* we released mmap_sem so break loop */ 2714 goto breakouterloop_mmap_sem; 2715 if (progress >= pages) 2716 goto breakouterloop; 2717 } 2718 } 2719 breakouterloop: 2720 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2721 breakouterloop_mmap_sem: 2722 2723 spin_lock(&khugepaged_mm_lock); 2724 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2725 /* 2726 * Release the current mm_slot if this mm is about to die, or 2727 * if we scanned all vmas of this mm. 2728 */ 2729 if (khugepaged_test_exit(mm) || !vma) { 2730 /* 2731 * Make sure that if mm_users is reaching zero while 2732 * khugepaged runs here, khugepaged_exit will find 2733 * mm_slot not pointing to the exiting mm. 2734 */ 2735 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2736 khugepaged_scan.mm_slot = list_entry( 2737 mm_slot->mm_node.next, 2738 struct mm_slot, mm_node); 2739 khugepaged_scan.address = 0; 2740 } else { 2741 khugepaged_scan.mm_slot = NULL; 2742 khugepaged_full_scans++; 2743 } 2744 2745 collect_mm_slot(mm_slot); 2746 } 2747 2748 return progress; 2749 } 2750 2751 static int khugepaged_has_work(void) 2752 { 2753 return !list_empty(&khugepaged_scan.mm_head) && 2754 khugepaged_enabled(); 2755 } 2756 2757 static int khugepaged_wait_event(void) 2758 { 2759 return !list_empty(&khugepaged_scan.mm_head) || 2760 kthread_should_stop(); 2761 } 2762 2763 static void khugepaged_do_scan(void) 2764 { 2765 struct page *hpage = NULL; 2766 unsigned int progress = 0, pass_through_head = 0; 2767 unsigned int pages = khugepaged_pages_to_scan; 2768 bool wait = true; 2769 2770 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2771 2772 while (progress < pages) { 2773 if (!khugepaged_prealloc_page(&hpage, &wait)) 2774 break; 2775 2776 cond_resched(); 2777 2778 if (unlikely(kthread_should_stop() || try_to_freeze())) 2779 break; 2780 2781 spin_lock(&khugepaged_mm_lock); 2782 if (!khugepaged_scan.mm_slot) 2783 pass_through_head++; 2784 if (khugepaged_has_work() && 2785 pass_through_head < 2) 2786 progress += khugepaged_scan_mm_slot(pages - progress, 2787 &hpage); 2788 else 2789 progress = pages; 2790 spin_unlock(&khugepaged_mm_lock); 2791 } 2792 2793 if (!IS_ERR_OR_NULL(hpage)) 2794 put_page(hpage); 2795 } 2796 2797 static bool khugepaged_should_wakeup(void) 2798 { 2799 return kthread_should_stop() || 2800 time_after_eq(jiffies, khugepaged_sleep_expire); 2801 } 2802 2803 static void khugepaged_wait_work(void) 2804 { 2805 if (khugepaged_has_work()) { 2806 const unsigned long scan_sleep_jiffies = 2807 msecs_to_jiffies(khugepaged_scan_sleep_millisecs); 2808 2809 if (!scan_sleep_jiffies) 2810 return; 2811 2812 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies; 2813 wait_event_freezable_timeout(khugepaged_wait, 2814 khugepaged_should_wakeup(), 2815 scan_sleep_jiffies); 2816 return; 2817 } 2818 2819 if (khugepaged_enabled()) 2820 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 2821 } 2822 2823 static int khugepaged(void *none) 2824 { 2825 struct mm_slot *mm_slot; 2826 2827 set_freezable(); 2828 set_user_nice(current, MAX_NICE); 2829 2830 while (!kthread_should_stop()) { 2831 khugepaged_do_scan(); 2832 khugepaged_wait_work(); 2833 } 2834 2835 spin_lock(&khugepaged_mm_lock); 2836 mm_slot = khugepaged_scan.mm_slot; 2837 khugepaged_scan.mm_slot = NULL; 2838 if (mm_slot) 2839 collect_mm_slot(mm_slot); 2840 spin_unlock(&khugepaged_mm_lock); 2841 return 0; 2842 } 2843 2844 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2845 unsigned long haddr, pmd_t *pmd) 2846 { 2847 struct mm_struct *mm = vma->vm_mm; 2848 pgtable_t pgtable; 2849 pmd_t _pmd; 2850 int i; 2851 2852 /* leave pmd empty until pte is filled */ 2853 pmdp_huge_clear_flush_notify(vma, haddr, pmd); 2854 2855 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2856 pmd_populate(mm, &_pmd, pgtable); 2857 2858 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2859 pte_t *pte, entry; 2860 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2861 entry = pte_mkspecial(entry); 2862 pte = pte_offset_map(&_pmd, haddr); 2863 VM_BUG_ON(!pte_none(*pte)); 2864 set_pte_at(mm, haddr, pte, entry); 2865 pte_unmap(pte); 2866 } 2867 smp_wmb(); /* make pte visible before pmd */ 2868 pmd_populate(mm, pmd, pgtable); 2869 put_huge_zero_page(); 2870 } 2871 2872 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 2873 unsigned long haddr, bool freeze) 2874 { 2875 struct mm_struct *mm = vma->vm_mm; 2876 struct page *page; 2877 pgtable_t pgtable; 2878 pmd_t _pmd; 2879 bool young, write, dirty; 2880 unsigned long addr; 2881 int i; 2882 2883 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK); 2884 VM_BUG_ON_VMA(vma->vm_start > haddr, vma); 2885 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma); 2886 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)); 2887 2888 count_vm_event(THP_SPLIT_PMD); 2889 2890 if (vma_is_dax(vma)) { 2891 pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd); 2892 if (is_huge_zero_pmd(_pmd)) 2893 put_huge_zero_page(); 2894 return; 2895 } else if (is_huge_zero_pmd(*pmd)) { 2896 return __split_huge_zero_page_pmd(vma, haddr, pmd); 2897 } 2898 2899 page = pmd_page(*pmd); 2900 VM_BUG_ON_PAGE(!page_count(page), page); 2901 page_ref_add(page, HPAGE_PMD_NR - 1); 2902 write = pmd_write(*pmd); 2903 young = pmd_young(*pmd); 2904 dirty = pmd_dirty(*pmd); 2905 2906 pmdp_huge_split_prepare(vma, haddr, pmd); 2907 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2908 pmd_populate(mm, &_pmd, pgtable); 2909 2910 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { 2911 pte_t entry, *pte; 2912 /* 2913 * Note that NUMA hinting access restrictions are not 2914 * transferred to avoid any possibility of altering 2915 * permissions across VMAs. 2916 */ 2917 if (freeze) { 2918 swp_entry_t swp_entry; 2919 swp_entry = make_migration_entry(page + i, write); 2920 entry = swp_entry_to_pte(swp_entry); 2921 } else { 2922 entry = mk_pte(page + i, vma->vm_page_prot); 2923 entry = maybe_mkwrite(entry, vma); 2924 if (!write) 2925 entry = pte_wrprotect(entry); 2926 if (!young) 2927 entry = pte_mkold(entry); 2928 } 2929 if (dirty) 2930 SetPageDirty(page + i); 2931 pte = pte_offset_map(&_pmd, addr); 2932 BUG_ON(!pte_none(*pte)); 2933 set_pte_at(mm, addr, pte, entry); 2934 atomic_inc(&page[i]._mapcount); 2935 pte_unmap(pte); 2936 } 2937 2938 /* 2939 * Set PG_double_map before dropping compound_mapcount to avoid 2940 * false-negative page_mapped(). 2941 */ 2942 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) { 2943 for (i = 0; i < HPAGE_PMD_NR; i++) 2944 atomic_inc(&page[i]._mapcount); 2945 } 2946 2947 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { 2948 /* Last compound_mapcount is gone. */ 2949 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); 2950 if (TestClearPageDoubleMap(page)) { 2951 /* No need in mapcount reference anymore */ 2952 for (i = 0; i < HPAGE_PMD_NR; i++) 2953 atomic_dec(&page[i]._mapcount); 2954 } 2955 } 2956 2957 smp_wmb(); /* make pte visible before pmd */ 2958 /* 2959 * Up to this point the pmd is present and huge and userland has the 2960 * whole access to the hugepage during the split (which happens in 2961 * place). If we overwrite the pmd with the not-huge version pointing 2962 * to the pte here (which of course we could if all CPUs were bug 2963 * free), userland could trigger a small page size TLB miss on the 2964 * small sized TLB while the hugepage TLB entry is still established in 2965 * the huge TLB. Some CPU doesn't like that. 2966 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum 2967 * 383 on page 93. Intel should be safe but is also warns that it's 2968 * only safe if the permission and cache attributes of the two entries 2969 * loaded in the two TLB is identical (which should be the case here). 2970 * But it is generally safer to never allow small and huge TLB entries 2971 * for the same virtual address to be loaded simultaneously. So instead 2972 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the 2973 * current pmd notpresent (atomically because here the pmd_trans_huge 2974 * and pmd_trans_splitting must remain set at all times on the pmd 2975 * until the split is complete for this pmd), then we flush the SMP TLB 2976 * and finally we write the non-huge version of the pmd entry with 2977 * pmd_populate. 2978 */ 2979 pmdp_invalidate(vma, haddr, pmd); 2980 pmd_populate(mm, pmd, pgtable); 2981 2982 if (freeze) { 2983 for (i = 0; i < HPAGE_PMD_NR; i++) { 2984 page_remove_rmap(page + i, false); 2985 put_page(page + i); 2986 } 2987 } 2988 } 2989 2990 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 2991 unsigned long address, bool freeze) 2992 { 2993 spinlock_t *ptl; 2994 struct mm_struct *mm = vma->vm_mm; 2995 unsigned long haddr = address & HPAGE_PMD_MASK; 2996 2997 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE); 2998 ptl = pmd_lock(mm, pmd); 2999 if (pmd_trans_huge(*pmd)) { 3000 struct page *page = pmd_page(*pmd); 3001 if (PageMlocked(page)) 3002 clear_page_mlock(page); 3003 } else if (!pmd_devmap(*pmd)) 3004 goto out; 3005 __split_huge_pmd_locked(vma, pmd, haddr, freeze); 3006 out: 3007 spin_unlock(ptl); 3008 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE); 3009 } 3010 3011 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, 3012 bool freeze, struct page *page) 3013 { 3014 pgd_t *pgd; 3015 pud_t *pud; 3016 pmd_t *pmd; 3017 3018 pgd = pgd_offset(vma->vm_mm, address); 3019 if (!pgd_present(*pgd)) 3020 return; 3021 3022 pud = pud_offset(pgd, address); 3023 if (!pud_present(*pud)) 3024 return; 3025 3026 pmd = pmd_offset(pud, address); 3027 if (!pmd_present(*pmd) || (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd))) 3028 return; 3029 3030 /* 3031 * If caller asks to setup a migration entries, we need a page to check 3032 * pmd against. Otherwise we can end up replacing wrong page. 3033 */ 3034 VM_BUG_ON(freeze && !page); 3035 if (page && page != pmd_page(*pmd)) 3036 return; 3037 3038 /* 3039 * Caller holds the mmap_sem write mode or the anon_vma lock, 3040 * so a huge pmd cannot materialize from under us (khugepaged 3041 * holds both the mmap_sem write mode and the anon_vma lock 3042 * write mode). 3043 */ 3044 __split_huge_pmd(vma, pmd, address, freeze); 3045 } 3046 3047 void vma_adjust_trans_huge(struct vm_area_struct *vma, 3048 unsigned long start, 3049 unsigned long end, 3050 long adjust_next) 3051 { 3052 /* 3053 * If the new start address isn't hpage aligned and it could 3054 * previously contain an hugepage: check if we need to split 3055 * an huge pmd. 3056 */ 3057 if (start & ~HPAGE_PMD_MASK && 3058 (start & HPAGE_PMD_MASK) >= vma->vm_start && 3059 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 3060 split_huge_pmd_address(vma, start, false, NULL); 3061 3062 /* 3063 * If the new end address isn't hpage aligned and it could 3064 * previously contain an hugepage: check if we need to split 3065 * an huge pmd. 3066 */ 3067 if (end & ~HPAGE_PMD_MASK && 3068 (end & HPAGE_PMD_MASK) >= vma->vm_start && 3069 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 3070 split_huge_pmd_address(vma, end, false, NULL); 3071 3072 /* 3073 * If we're also updating the vma->vm_next->vm_start, if the new 3074 * vm_next->vm_start isn't page aligned and it could previously 3075 * contain an hugepage: check if we need to split an huge pmd. 3076 */ 3077 if (adjust_next > 0) { 3078 struct vm_area_struct *next = vma->vm_next; 3079 unsigned long nstart = next->vm_start; 3080 nstart += adjust_next << PAGE_SHIFT; 3081 if (nstart & ~HPAGE_PMD_MASK && 3082 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 3083 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 3084 split_huge_pmd_address(next, nstart, false, NULL); 3085 } 3086 } 3087 3088 static void freeze_page(struct page *page) 3089 { 3090 enum ttu_flags ttu_flags = TTU_MIGRATION | TTU_IGNORE_MLOCK | 3091 TTU_IGNORE_ACCESS | TTU_RMAP_LOCKED; 3092 int i, ret; 3093 3094 VM_BUG_ON_PAGE(!PageHead(page), page); 3095 3096 /* We only need TTU_SPLIT_HUGE_PMD once */ 3097 ret = try_to_unmap(page, ttu_flags | TTU_SPLIT_HUGE_PMD); 3098 for (i = 1; !ret && i < HPAGE_PMD_NR; i++) { 3099 /* Cut short if the page is unmapped */ 3100 if (page_count(page) == 1) 3101 return; 3102 3103 ret = try_to_unmap(page + i, ttu_flags); 3104 } 3105 VM_BUG_ON(ret); 3106 } 3107 3108 static void unfreeze_page(struct page *page) 3109 { 3110 int i; 3111 3112 for (i = 0; i < HPAGE_PMD_NR; i++) 3113 remove_migration_ptes(page + i, page + i, true); 3114 } 3115 3116 static void __split_huge_page_tail(struct page *head, int tail, 3117 struct lruvec *lruvec, struct list_head *list) 3118 { 3119 struct page *page_tail = head + tail; 3120 3121 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); 3122 VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail); 3123 3124 /* 3125 * tail_page->_refcount is zero and not changing from under us. But 3126 * get_page_unless_zero() may be running from under us on the 3127 * tail_page. If we used atomic_set() below instead of atomic_inc(), we 3128 * would then run atomic_set() concurrently with 3129 * get_page_unless_zero(), and atomic_set() is implemented in C not 3130 * using locked ops. spin_unlock on x86 sometime uses locked ops 3131 * because of PPro errata 66, 92, so unless somebody can guarantee 3132 * atomic_set() here would be safe on all archs (and not only on x86), 3133 * it's safer to use atomic_inc(). 3134 */ 3135 page_ref_inc(page_tail); 3136 3137 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; 3138 page_tail->flags |= (head->flags & 3139 ((1L << PG_referenced) | 3140 (1L << PG_swapbacked) | 3141 (1L << PG_mlocked) | 3142 (1L << PG_uptodate) | 3143 (1L << PG_active) | 3144 (1L << PG_locked) | 3145 (1L << PG_unevictable) | 3146 (1L << PG_dirty))); 3147 3148 /* 3149 * After clearing PageTail the gup refcount can be released. 3150 * Page flags also must be visible before we make the page non-compound. 3151 */ 3152 smp_wmb(); 3153 3154 clear_compound_head(page_tail); 3155 3156 if (page_is_young(head)) 3157 set_page_young(page_tail); 3158 if (page_is_idle(head)) 3159 set_page_idle(page_tail); 3160 3161 /* ->mapping in first tail page is compound_mapcount */ 3162 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING, 3163 page_tail); 3164 page_tail->mapping = head->mapping; 3165 3166 page_tail->index = head->index + tail; 3167 page_cpupid_xchg_last(page_tail, page_cpupid_last(head)); 3168 lru_add_page_tail(head, page_tail, lruvec, list); 3169 } 3170 3171 static void __split_huge_page(struct page *page, struct list_head *list) 3172 { 3173 struct page *head = compound_head(page); 3174 struct zone *zone = page_zone(head); 3175 struct lruvec *lruvec; 3176 int i; 3177 3178 /* prevent PageLRU to go away from under us, and freeze lru stats */ 3179 spin_lock_irq(&zone->lru_lock); 3180 lruvec = mem_cgroup_page_lruvec(head, zone); 3181 3182 /* complete memcg works before add pages to LRU */ 3183 mem_cgroup_split_huge_fixup(head); 3184 3185 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) 3186 __split_huge_page_tail(head, i, lruvec, list); 3187 3188 ClearPageCompound(head); 3189 spin_unlock_irq(&zone->lru_lock); 3190 3191 unfreeze_page(head); 3192 3193 for (i = 0; i < HPAGE_PMD_NR; i++) { 3194 struct page *subpage = head + i; 3195 if (subpage == page) 3196 continue; 3197 unlock_page(subpage); 3198 3199 /* 3200 * Subpages may be freed if there wasn't any mapping 3201 * like if add_to_swap() is running on a lru page that 3202 * had its mapping zapped. And freeing these pages 3203 * requires taking the lru_lock so we do the put_page 3204 * of the tail pages after the split is complete. 3205 */ 3206 put_page(subpage); 3207 } 3208 } 3209 3210 int total_mapcount(struct page *page) 3211 { 3212 int i, ret; 3213 3214 VM_BUG_ON_PAGE(PageTail(page), page); 3215 3216 if (likely(!PageCompound(page))) 3217 return atomic_read(&page->_mapcount) + 1; 3218 3219 ret = compound_mapcount(page); 3220 if (PageHuge(page)) 3221 return ret; 3222 for (i = 0; i < HPAGE_PMD_NR; i++) 3223 ret += atomic_read(&page[i]._mapcount) + 1; 3224 if (PageDoubleMap(page)) 3225 ret -= HPAGE_PMD_NR; 3226 return ret; 3227 } 3228 3229 /* 3230 * This calculates accurately how many mappings a transparent hugepage 3231 * has (unlike page_mapcount() which isn't fully accurate). This full 3232 * accuracy is primarily needed to know if copy-on-write faults can 3233 * reuse the page and change the mapping to read-write instead of 3234 * copying them. At the same time this returns the total_mapcount too. 3235 * 3236 * The function returns the highest mapcount any one of the subpages 3237 * has. If the return value is one, even if different processes are 3238 * mapping different subpages of the transparent hugepage, they can 3239 * all reuse it, because each process is reusing a different subpage. 3240 * 3241 * The total_mapcount is instead counting all virtual mappings of the 3242 * subpages. If the total_mapcount is equal to "one", it tells the 3243 * caller all mappings belong to the same "mm" and in turn the 3244 * anon_vma of the transparent hugepage can become the vma->anon_vma 3245 * local one as no other process may be mapping any of the subpages. 3246 * 3247 * It would be more accurate to replace page_mapcount() with 3248 * page_trans_huge_mapcount(), however we only use 3249 * page_trans_huge_mapcount() in the copy-on-write faults where we 3250 * need full accuracy to avoid breaking page pinning, because 3251 * page_trans_huge_mapcount() is slower than page_mapcount(). 3252 */ 3253 int page_trans_huge_mapcount(struct page *page, int *total_mapcount) 3254 { 3255 int i, ret, _total_mapcount, mapcount; 3256 3257 /* hugetlbfs shouldn't call it */ 3258 VM_BUG_ON_PAGE(PageHuge(page), page); 3259 3260 if (likely(!PageTransCompound(page))) { 3261 mapcount = atomic_read(&page->_mapcount) + 1; 3262 if (total_mapcount) 3263 *total_mapcount = mapcount; 3264 return mapcount; 3265 } 3266 3267 page = compound_head(page); 3268 3269 _total_mapcount = ret = 0; 3270 for (i = 0; i < HPAGE_PMD_NR; i++) { 3271 mapcount = atomic_read(&page[i]._mapcount) + 1; 3272 ret = max(ret, mapcount); 3273 _total_mapcount += mapcount; 3274 } 3275 if (PageDoubleMap(page)) { 3276 ret -= 1; 3277 _total_mapcount -= HPAGE_PMD_NR; 3278 } 3279 mapcount = compound_mapcount(page); 3280 ret += mapcount; 3281 _total_mapcount += mapcount; 3282 if (total_mapcount) 3283 *total_mapcount = _total_mapcount; 3284 return ret; 3285 } 3286 3287 /* 3288 * This function splits huge page into normal pages. @page can point to any 3289 * subpage of huge page to split. Split doesn't change the position of @page. 3290 * 3291 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY. 3292 * The huge page must be locked. 3293 * 3294 * If @list is null, tail pages will be added to LRU list, otherwise, to @list. 3295 * 3296 * Both head page and tail pages will inherit mapping, flags, and so on from 3297 * the hugepage. 3298 * 3299 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if 3300 * they are not mapped. 3301 * 3302 * Returns 0 if the hugepage is split successfully. 3303 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under 3304 * us. 3305 */ 3306 int split_huge_page_to_list(struct page *page, struct list_head *list) 3307 { 3308 struct page *head = compound_head(page); 3309 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head)); 3310 struct anon_vma *anon_vma; 3311 int count, mapcount, ret; 3312 bool mlocked; 3313 unsigned long flags; 3314 3315 VM_BUG_ON_PAGE(is_huge_zero_page(page), page); 3316 VM_BUG_ON_PAGE(!PageAnon(page), page); 3317 VM_BUG_ON_PAGE(!PageLocked(page), page); 3318 VM_BUG_ON_PAGE(!PageSwapBacked(page), page); 3319 VM_BUG_ON_PAGE(!PageCompound(page), page); 3320 3321 /* 3322 * The caller does not necessarily hold an mmap_sem that would prevent 3323 * the anon_vma disappearing so we first we take a reference to it 3324 * and then lock the anon_vma for write. This is similar to 3325 * page_lock_anon_vma_read except the write lock is taken to serialise 3326 * against parallel split or collapse operations. 3327 */ 3328 anon_vma = page_get_anon_vma(head); 3329 if (!anon_vma) { 3330 ret = -EBUSY; 3331 goto out; 3332 } 3333 anon_vma_lock_write(anon_vma); 3334 3335 /* 3336 * Racy check if we can split the page, before freeze_page() will 3337 * split PMDs 3338 */ 3339 if (total_mapcount(head) != page_count(head) - 1) { 3340 ret = -EBUSY; 3341 goto out_unlock; 3342 } 3343 3344 mlocked = PageMlocked(page); 3345 freeze_page(head); 3346 VM_BUG_ON_PAGE(compound_mapcount(head), head); 3347 3348 /* Make sure the page is not on per-CPU pagevec as it takes pin */ 3349 if (mlocked) 3350 lru_add_drain(); 3351 3352 /* Prevent deferred_split_scan() touching ->_refcount */ 3353 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3354 count = page_count(head); 3355 mapcount = total_mapcount(head); 3356 if (!mapcount && count == 1) { 3357 if (!list_empty(page_deferred_list(head))) { 3358 pgdata->split_queue_len--; 3359 list_del(page_deferred_list(head)); 3360 } 3361 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3362 __split_huge_page(page, list); 3363 ret = 0; 3364 } else if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { 3365 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3366 pr_alert("total_mapcount: %u, page_count(): %u\n", 3367 mapcount, count); 3368 if (PageTail(page)) 3369 dump_page(head, NULL); 3370 dump_page(page, "total_mapcount(head) > 0"); 3371 BUG(); 3372 } else { 3373 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3374 unfreeze_page(head); 3375 ret = -EBUSY; 3376 } 3377 3378 out_unlock: 3379 anon_vma_unlock_write(anon_vma); 3380 put_anon_vma(anon_vma); 3381 out: 3382 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); 3383 return ret; 3384 } 3385 3386 void free_transhuge_page(struct page *page) 3387 { 3388 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page)); 3389 unsigned long flags; 3390 3391 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3392 if (!list_empty(page_deferred_list(page))) { 3393 pgdata->split_queue_len--; 3394 list_del(page_deferred_list(page)); 3395 } 3396 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3397 free_compound_page(page); 3398 } 3399 3400 void deferred_split_huge_page(struct page *page) 3401 { 3402 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page)); 3403 unsigned long flags; 3404 3405 VM_BUG_ON_PAGE(!PageTransHuge(page), page); 3406 3407 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3408 if (list_empty(page_deferred_list(page))) { 3409 count_vm_event(THP_DEFERRED_SPLIT_PAGE); 3410 list_add_tail(page_deferred_list(page), &pgdata->split_queue); 3411 pgdata->split_queue_len++; 3412 } 3413 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3414 } 3415 3416 static unsigned long deferred_split_count(struct shrinker *shrink, 3417 struct shrink_control *sc) 3418 { 3419 struct pglist_data *pgdata = NODE_DATA(sc->nid); 3420 return ACCESS_ONCE(pgdata->split_queue_len); 3421 } 3422 3423 static unsigned long deferred_split_scan(struct shrinker *shrink, 3424 struct shrink_control *sc) 3425 { 3426 struct pglist_data *pgdata = NODE_DATA(sc->nid); 3427 unsigned long flags; 3428 LIST_HEAD(list), *pos, *next; 3429 struct page *page; 3430 int split = 0; 3431 3432 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3433 /* Take pin on all head pages to avoid freeing them under us */ 3434 list_for_each_safe(pos, next, &pgdata->split_queue) { 3435 page = list_entry((void *)pos, struct page, mapping); 3436 page = compound_head(page); 3437 if (get_page_unless_zero(page)) { 3438 list_move(page_deferred_list(page), &list); 3439 } else { 3440 /* We lost race with put_compound_page() */ 3441 list_del_init(page_deferred_list(page)); 3442 pgdata->split_queue_len--; 3443 } 3444 if (!--sc->nr_to_scan) 3445 break; 3446 } 3447 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3448 3449 list_for_each_safe(pos, next, &list) { 3450 page = list_entry((void *)pos, struct page, mapping); 3451 lock_page(page); 3452 /* split_huge_page() removes page from list on success */ 3453 if (!split_huge_page(page)) 3454 split++; 3455 unlock_page(page); 3456 put_page(page); 3457 } 3458 3459 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3460 list_splice_tail(&list, &pgdata->split_queue); 3461 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3462 3463 /* 3464 * Stop shrinker if we didn't split any page, but the queue is empty. 3465 * This can happen if pages were freed under us. 3466 */ 3467 if (!split && list_empty(&pgdata->split_queue)) 3468 return SHRINK_STOP; 3469 return split; 3470 } 3471 3472 static struct shrinker deferred_split_shrinker = { 3473 .count_objects = deferred_split_count, 3474 .scan_objects = deferred_split_scan, 3475 .seeks = DEFAULT_SEEKS, 3476 .flags = SHRINKER_NUMA_AWARE, 3477 }; 3478 3479 #ifdef CONFIG_DEBUG_FS 3480 static int split_huge_pages_set(void *data, u64 val) 3481 { 3482 struct zone *zone; 3483 struct page *page; 3484 unsigned long pfn, max_zone_pfn; 3485 unsigned long total = 0, split = 0; 3486 3487 if (val != 1) 3488 return -EINVAL; 3489 3490 for_each_populated_zone(zone) { 3491 max_zone_pfn = zone_end_pfn(zone); 3492 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) { 3493 if (!pfn_valid(pfn)) 3494 continue; 3495 3496 page = pfn_to_page(pfn); 3497 if (!get_page_unless_zero(page)) 3498 continue; 3499 3500 if (zone != page_zone(page)) 3501 goto next; 3502 3503 if (!PageHead(page) || !PageAnon(page) || 3504 PageHuge(page)) 3505 goto next; 3506 3507 total++; 3508 lock_page(page); 3509 if (!split_huge_page(page)) 3510 split++; 3511 unlock_page(page); 3512 next: 3513 put_page(page); 3514 } 3515 } 3516 3517 pr_info("%lu of %lu THP split\n", split, total); 3518 3519 return 0; 3520 } 3521 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set, 3522 "%llu\n"); 3523 3524 static int __init split_huge_pages_debugfs(void) 3525 { 3526 void *ret; 3527 3528 ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL, 3529 &split_huge_pages_fops); 3530 if (!ret) 3531 pr_warn("Failed to create split_huge_pages in debugfs"); 3532 return 0; 3533 } 3534 late_initcall(split_huge_pages_debugfs); 3535 #endif 3536