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 struct task_struct *khugepaged_thread __read_mostly; 93 static DEFINE_MUTEX(khugepaged_mutex); 94 static DEFINE_SPINLOCK(khugepaged_mm_lock); 95 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 96 /* 97 * default collapse hugepages if there is at least one pte mapped like 98 * it would have happened if the vma was large enough during page 99 * fault. 100 */ 101 static unsigned int khugepaged_max_ptes_none __read_mostly; 102 103 static int khugepaged(void *none); 104 static int khugepaged_slab_init(void); 105 static void khugepaged_slab_exit(void); 106 107 #define MM_SLOTS_HASH_BITS 10 108 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); 109 110 static struct kmem_cache *mm_slot_cache __read_mostly; 111 112 /** 113 * struct mm_slot - hash lookup from mm to mm_slot 114 * @hash: hash collision list 115 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 116 * @mm: the mm that this information is valid for 117 */ 118 struct mm_slot { 119 struct hlist_node hash; 120 struct list_head mm_node; 121 struct mm_struct *mm; 122 }; 123 124 /** 125 * struct khugepaged_scan - cursor for scanning 126 * @mm_head: the head of the mm list to scan 127 * @mm_slot: the current mm_slot we are scanning 128 * @address: the next address inside that to be scanned 129 * 130 * There is only the one khugepaged_scan instance of this cursor structure. 131 */ 132 struct khugepaged_scan { 133 struct list_head mm_head; 134 struct mm_slot *mm_slot; 135 unsigned long address; 136 }; 137 static struct khugepaged_scan khugepaged_scan = { 138 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 139 }; 140 141 static struct shrinker deferred_split_shrinker; 142 143 static void set_recommended_min_free_kbytes(void) 144 { 145 struct zone *zone; 146 int nr_zones = 0; 147 unsigned long recommended_min; 148 149 for_each_populated_zone(zone) 150 nr_zones++; 151 152 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */ 153 recommended_min = pageblock_nr_pages * nr_zones * 2; 154 155 /* 156 * Make sure that on average at least two pageblocks are almost free 157 * of another type, one for a migratetype to fall back to and a 158 * second to avoid subsequent fallbacks of other types There are 3 159 * MIGRATE_TYPES we care about. 160 */ 161 recommended_min += pageblock_nr_pages * nr_zones * 162 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; 163 164 /* don't ever allow to reserve more than 5% of the lowmem */ 165 recommended_min = min(recommended_min, 166 (unsigned long) nr_free_buffer_pages() / 20); 167 recommended_min <<= (PAGE_SHIFT-10); 168 169 if (recommended_min > min_free_kbytes) { 170 if (user_min_free_kbytes >= 0) 171 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", 172 min_free_kbytes, recommended_min); 173 174 min_free_kbytes = recommended_min; 175 } 176 setup_per_zone_wmarks(); 177 } 178 179 static int start_stop_khugepaged(void) 180 { 181 int err = 0; 182 if (khugepaged_enabled()) { 183 if (!khugepaged_thread) 184 khugepaged_thread = kthread_run(khugepaged, NULL, 185 "khugepaged"); 186 if (IS_ERR(khugepaged_thread)) { 187 pr_err("khugepaged: kthread_run(khugepaged) failed\n"); 188 err = PTR_ERR(khugepaged_thread); 189 khugepaged_thread = NULL; 190 goto fail; 191 } 192 193 if (!list_empty(&khugepaged_scan.mm_head)) 194 wake_up_interruptible(&khugepaged_wait); 195 196 set_recommended_min_free_kbytes(); 197 } else if (khugepaged_thread) { 198 kthread_stop(khugepaged_thread); 199 khugepaged_thread = NULL; 200 } 201 fail: 202 return err; 203 } 204 205 static atomic_t huge_zero_refcount; 206 struct page *huge_zero_page __read_mostly; 207 208 struct page *get_huge_zero_page(void) 209 { 210 struct page *zero_page; 211 retry: 212 if (likely(atomic_inc_not_zero(&huge_zero_refcount))) 213 return READ_ONCE(huge_zero_page); 214 215 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, 216 HPAGE_PMD_ORDER); 217 if (!zero_page) { 218 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); 219 return NULL; 220 } 221 count_vm_event(THP_ZERO_PAGE_ALLOC); 222 preempt_disable(); 223 if (cmpxchg(&huge_zero_page, NULL, zero_page)) { 224 preempt_enable(); 225 __free_pages(zero_page, compound_order(zero_page)); 226 goto retry; 227 } 228 229 /* We take additional reference here. It will be put back by shrinker */ 230 atomic_set(&huge_zero_refcount, 2); 231 preempt_enable(); 232 return READ_ONCE(huge_zero_page); 233 } 234 235 void put_huge_zero_page(void) 236 { 237 /* 238 * Counter should never go to zero here. Only shrinker can put 239 * last reference. 240 */ 241 BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); 242 } 243 244 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, 245 struct shrink_control *sc) 246 { 247 /* we can free zero page only if last reference remains */ 248 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; 249 } 250 251 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, 252 struct shrink_control *sc) 253 { 254 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { 255 struct page *zero_page = xchg(&huge_zero_page, NULL); 256 BUG_ON(zero_page == NULL); 257 __free_pages(zero_page, compound_order(zero_page)); 258 return HPAGE_PMD_NR; 259 } 260 261 return 0; 262 } 263 264 static struct shrinker huge_zero_page_shrinker = { 265 .count_objects = shrink_huge_zero_page_count, 266 .scan_objects = shrink_huge_zero_page_scan, 267 .seeks = DEFAULT_SEEKS, 268 }; 269 270 #ifdef CONFIG_SYSFS 271 272 static ssize_t triple_flag_store(struct kobject *kobj, 273 struct kobj_attribute *attr, 274 const char *buf, size_t count, 275 enum transparent_hugepage_flag enabled, 276 enum transparent_hugepage_flag deferred, 277 enum transparent_hugepage_flag req_madv) 278 { 279 if (!memcmp("defer", buf, 280 min(sizeof("defer")-1, count))) { 281 if (enabled == deferred) 282 return -EINVAL; 283 clear_bit(enabled, &transparent_hugepage_flags); 284 clear_bit(req_madv, &transparent_hugepage_flags); 285 set_bit(deferred, &transparent_hugepage_flags); 286 } else if (!memcmp("always", buf, 287 min(sizeof("always")-1, count))) { 288 clear_bit(deferred, &transparent_hugepage_flags); 289 clear_bit(req_madv, &transparent_hugepage_flags); 290 set_bit(enabled, &transparent_hugepage_flags); 291 } else if (!memcmp("madvise", buf, 292 min(sizeof("madvise")-1, count))) { 293 clear_bit(enabled, &transparent_hugepage_flags); 294 clear_bit(deferred, &transparent_hugepage_flags); 295 set_bit(req_madv, &transparent_hugepage_flags); 296 } else if (!memcmp("never", buf, 297 min(sizeof("never")-1, count))) { 298 clear_bit(enabled, &transparent_hugepage_flags); 299 clear_bit(req_madv, &transparent_hugepage_flags); 300 clear_bit(deferred, &transparent_hugepage_flags); 301 } else 302 return -EINVAL; 303 304 return count; 305 } 306 307 static ssize_t enabled_show(struct kobject *kobj, 308 struct kobj_attribute *attr, char *buf) 309 { 310 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags)) 311 return sprintf(buf, "[always] madvise never\n"); 312 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags)) 313 return sprintf(buf, "always [madvise] never\n"); 314 else 315 return sprintf(buf, "always madvise [never]\n"); 316 } 317 318 static ssize_t enabled_store(struct kobject *kobj, 319 struct kobj_attribute *attr, 320 const char *buf, size_t count) 321 { 322 ssize_t ret; 323 324 ret = triple_flag_store(kobj, attr, buf, count, 325 TRANSPARENT_HUGEPAGE_FLAG, 326 TRANSPARENT_HUGEPAGE_FLAG, 327 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 328 329 if (ret > 0) { 330 int err; 331 332 mutex_lock(&khugepaged_mutex); 333 err = start_stop_khugepaged(); 334 mutex_unlock(&khugepaged_mutex); 335 336 if (err) 337 ret = err; 338 } 339 340 return ret; 341 } 342 static struct kobj_attribute enabled_attr = 343 __ATTR(enabled, 0644, enabled_show, enabled_store); 344 345 static ssize_t single_flag_show(struct kobject *kobj, 346 struct kobj_attribute *attr, char *buf, 347 enum transparent_hugepage_flag flag) 348 { 349 return sprintf(buf, "%d\n", 350 !!test_bit(flag, &transparent_hugepage_flags)); 351 } 352 353 static ssize_t single_flag_store(struct kobject *kobj, 354 struct kobj_attribute *attr, 355 const char *buf, size_t count, 356 enum transparent_hugepage_flag flag) 357 { 358 unsigned long value; 359 int ret; 360 361 ret = kstrtoul(buf, 10, &value); 362 if (ret < 0) 363 return ret; 364 if (value > 1) 365 return -EINVAL; 366 367 if (value) 368 set_bit(flag, &transparent_hugepage_flags); 369 else 370 clear_bit(flag, &transparent_hugepage_flags); 371 372 return count; 373 } 374 375 /* 376 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind 377 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of 378 * memory just to allocate one more hugepage. 379 */ 380 static ssize_t defrag_show(struct kobject *kobj, 381 struct kobj_attribute *attr, char *buf) 382 { 383 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) 384 return sprintf(buf, "[always] defer madvise never\n"); 385 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) 386 return sprintf(buf, "always [defer] madvise never\n"); 387 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) 388 return sprintf(buf, "always defer [madvise] never\n"); 389 else 390 return sprintf(buf, "always defer madvise [never]\n"); 391 392 } 393 static ssize_t defrag_store(struct kobject *kobj, 394 struct kobj_attribute *attr, 395 const char *buf, size_t count) 396 { 397 return triple_flag_store(kobj, attr, buf, count, 398 TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, 399 TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, 400 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 401 } 402 static struct kobj_attribute defrag_attr = 403 __ATTR(defrag, 0644, defrag_show, defrag_store); 404 405 static ssize_t use_zero_page_show(struct kobject *kobj, 406 struct kobj_attribute *attr, char *buf) 407 { 408 return single_flag_show(kobj, attr, buf, 409 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 410 } 411 static ssize_t use_zero_page_store(struct kobject *kobj, 412 struct kobj_attribute *attr, const char *buf, size_t count) 413 { 414 return single_flag_store(kobj, attr, buf, count, 415 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 416 } 417 static struct kobj_attribute use_zero_page_attr = 418 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); 419 #ifdef CONFIG_DEBUG_VM 420 static ssize_t debug_cow_show(struct kobject *kobj, 421 struct kobj_attribute *attr, char *buf) 422 { 423 return single_flag_show(kobj, attr, buf, 424 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 425 } 426 static ssize_t debug_cow_store(struct kobject *kobj, 427 struct kobj_attribute *attr, 428 const char *buf, size_t count) 429 { 430 return single_flag_store(kobj, attr, buf, count, 431 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 432 } 433 static struct kobj_attribute debug_cow_attr = 434 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 435 #endif /* CONFIG_DEBUG_VM */ 436 437 static struct attribute *hugepage_attr[] = { 438 &enabled_attr.attr, 439 &defrag_attr.attr, 440 &use_zero_page_attr.attr, 441 #ifdef CONFIG_DEBUG_VM 442 &debug_cow_attr.attr, 443 #endif 444 NULL, 445 }; 446 447 static struct attribute_group hugepage_attr_group = { 448 .attrs = hugepage_attr, 449 }; 450 451 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 452 struct kobj_attribute *attr, 453 char *buf) 454 { 455 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 456 } 457 458 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 459 struct kobj_attribute *attr, 460 const char *buf, size_t count) 461 { 462 unsigned long msecs; 463 int err; 464 465 err = kstrtoul(buf, 10, &msecs); 466 if (err || msecs > UINT_MAX) 467 return -EINVAL; 468 469 khugepaged_scan_sleep_millisecs = msecs; 470 wake_up_interruptible(&khugepaged_wait); 471 472 return count; 473 } 474 static struct kobj_attribute scan_sleep_millisecs_attr = 475 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 476 scan_sleep_millisecs_store); 477 478 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 479 struct kobj_attribute *attr, 480 char *buf) 481 { 482 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 483 } 484 485 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 486 struct kobj_attribute *attr, 487 const char *buf, size_t count) 488 { 489 unsigned long msecs; 490 int err; 491 492 err = kstrtoul(buf, 10, &msecs); 493 if (err || msecs > UINT_MAX) 494 return -EINVAL; 495 496 khugepaged_alloc_sleep_millisecs = msecs; 497 wake_up_interruptible(&khugepaged_wait); 498 499 return count; 500 } 501 static struct kobj_attribute alloc_sleep_millisecs_attr = 502 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 503 alloc_sleep_millisecs_store); 504 505 static ssize_t pages_to_scan_show(struct kobject *kobj, 506 struct kobj_attribute *attr, 507 char *buf) 508 { 509 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 510 } 511 static ssize_t pages_to_scan_store(struct kobject *kobj, 512 struct kobj_attribute *attr, 513 const char *buf, size_t count) 514 { 515 int err; 516 unsigned long pages; 517 518 err = kstrtoul(buf, 10, &pages); 519 if (err || !pages || pages > UINT_MAX) 520 return -EINVAL; 521 522 khugepaged_pages_to_scan = pages; 523 524 return count; 525 } 526 static struct kobj_attribute pages_to_scan_attr = 527 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 528 pages_to_scan_store); 529 530 static ssize_t pages_collapsed_show(struct kobject *kobj, 531 struct kobj_attribute *attr, 532 char *buf) 533 { 534 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 535 } 536 static struct kobj_attribute pages_collapsed_attr = 537 __ATTR_RO(pages_collapsed); 538 539 static ssize_t full_scans_show(struct kobject *kobj, 540 struct kobj_attribute *attr, 541 char *buf) 542 { 543 return sprintf(buf, "%u\n", khugepaged_full_scans); 544 } 545 static struct kobj_attribute full_scans_attr = 546 __ATTR_RO(full_scans); 547 548 static ssize_t khugepaged_defrag_show(struct kobject *kobj, 549 struct kobj_attribute *attr, char *buf) 550 { 551 return single_flag_show(kobj, attr, buf, 552 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 553 } 554 static ssize_t khugepaged_defrag_store(struct kobject *kobj, 555 struct kobj_attribute *attr, 556 const char *buf, size_t count) 557 { 558 return single_flag_store(kobj, attr, buf, count, 559 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 560 } 561 static struct kobj_attribute khugepaged_defrag_attr = 562 __ATTR(defrag, 0644, khugepaged_defrag_show, 563 khugepaged_defrag_store); 564 565 /* 566 * max_ptes_none controls if khugepaged should collapse hugepages over 567 * any unmapped ptes in turn potentially increasing the memory 568 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 569 * reduce the available free memory in the system as it 570 * runs. Increasing max_ptes_none will instead potentially reduce the 571 * free memory in the system during the khugepaged scan. 572 */ 573 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 574 struct kobj_attribute *attr, 575 char *buf) 576 { 577 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 578 } 579 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 580 struct kobj_attribute *attr, 581 const char *buf, size_t count) 582 { 583 int err; 584 unsigned long max_ptes_none; 585 586 err = kstrtoul(buf, 10, &max_ptes_none); 587 if (err || max_ptes_none > HPAGE_PMD_NR-1) 588 return -EINVAL; 589 590 khugepaged_max_ptes_none = max_ptes_none; 591 592 return count; 593 } 594 static struct kobj_attribute khugepaged_max_ptes_none_attr = 595 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 596 khugepaged_max_ptes_none_store); 597 598 static struct attribute *khugepaged_attr[] = { 599 &khugepaged_defrag_attr.attr, 600 &khugepaged_max_ptes_none_attr.attr, 601 &pages_to_scan_attr.attr, 602 &pages_collapsed_attr.attr, 603 &full_scans_attr.attr, 604 &scan_sleep_millisecs_attr.attr, 605 &alloc_sleep_millisecs_attr.attr, 606 NULL, 607 }; 608 609 static struct attribute_group khugepaged_attr_group = { 610 .attrs = khugepaged_attr, 611 .name = "khugepaged", 612 }; 613 614 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) 615 { 616 int err; 617 618 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 619 if (unlikely(!*hugepage_kobj)) { 620 pr_err("failed to create transparent hugepage kobject\n"); 621 return -ENOMEM; 622 } 623 624 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); 625 if (err) { 626 pr_err("failed to register transparent hugepage group\n"); 627 goto delete_obj; 628 } 629 630 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); 631 if (err) { 632 pr_err("failed to register transparent hugepage group\n"); 633 goto remove_hp_group; 634 } 635 636 return 0; 637 638 remove_hp_group: 639 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); 640 delete_obj: 641 kobject_put(*hugepage_kobj); 642 return err; 643 } 644 645 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) 646 { 647 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); 648 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); 649 kobject_put(hugepage_kobj); 650 } 651 #else 652 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) 653 { 654 return 0; 655 } 656 657 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) 658 { 659 } 660 #endif /* CONFIG_SYSFS */ 661 662 static int __init hugepage_init(void) 663 { 664 int err; 665 struct kobject *hugepage_kobj; 666 667 if (!has_transparent_hugepage()) { 668 transparent_hugepage_flags = 0; 669 return -EINVAL; 670 } 671 672 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; 673 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; 674 /* 675 * hugepages can't be allocated by the buddy allocator 676 */ 677 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER); 678 /* 679 * we use page->mapping and page->index in second tail page 680 * as list_head: assuming THP order >= 2 681 */ 682 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2); 683 684 err = hugepage_init_sysfs(&hugepage_kobj); 685 if (err) 686 goto err_sysfs; 687 688 err = khugepaged_slab_init(); 689 if (err) 690 goto err_slab; 691 692 err = register_shrinker(&huge_zero_page_shrinker); 693 if (err) 694 goto err_hzp_shrinker; 695 err = register_shrinker(&deferred_split_shrinker); 696 if (err) 697 goto err_split_shrinker; 698 699 /* 700 * By default disable transparent hugepages on smaller systems, 701 * where the extra memory used could hurt more than TLB overhead 702 * is likely to save. The admin can still enable it through /sys. 703 */ 704 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) { 705 transparent_hugepage_flags = 0; 706 return 0; 707 } 708 709 err = start_stop_khugepaged(); 710 if (err) 711 goto err_khugepaged; 712 713 return 0; 714 err_khugepaged: 715 unregister_shrinker(&deferred_split_shrinker); 716 err_split_shrinker: 717 unregister_shrinker(&huge_zero_page_shrinker); 718 err_hzp_shrinker: 719 khugepaged_slab_exit(); 720 err_slab: 721 hugepage_exit_sysfs(hugepage_kobj); 722 err_sysfs: 723 return err; 724 } 725 subsys_initcall(hugepage_init); 726 727 static int __init setup_transparent_hugepage(char *str) 728 { 729 int ret = 0; 730 if (!str) 731 goto out; 732 if (!strcmp(str, "always")) { 733 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 734 &transparent_hugepage_flags); 735 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 736 &transparent_hugepage_flags); 737 ret = 1; 738 } else if (!strcmp(str, "madvise")) { 739 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 740 &transparent_hugepage_flags); 741 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 742 &transparent_hugepage_flags); 743 ret = 1; 744 } else if (!strcmp(str, "never")) { 745 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 746 &transparent_hugepage_flags); 747 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 748 &transparent_hugepage_flags); 749 ret = 1; 750 } 751 out: 752 if (!ret) 753 pr_warn("transparent_hugepage= cannot parse, ignored\n"); 754 return ret; 755 } 756 __setup("transparent_hugepage=", setup_transparent_hugepage); 757 758 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 759 { 760 if (likely(vma->vm_flags & VM_WRITE)) 761 pmd = pmd_mkwrite(pmd); 762 return pmd; 763 } 764 765 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot) 766 { 767 pmd_t entry; 768 entry = mk_pmd(page, prot); 769 entry = pmd_mkhuge(entry); 770 return entry; 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, struct vm_area_struct *new_vma, 1702 unsigned long old_addr, 1703 unsigned long new_addr, unsigned long old_end, 1704 pmd_t *old_pmd, pmd_t *new_pmd) 1705 { 1706 spinlock_t *old_ptl, *new_ptl; 1707 pmd_t pmd; 1708 1709 struct mm_struct *mm = vma->vm_mm; 1710 1711 if ((old_addr & ~HPAGE_PMD_MASK) || 1712 (new_addr & ~HPAGE_PMD_MASK) || 1713 old_end - old_addr < HPAGE_PMD_SIZE || 1714 (new_vma->vm_flags & VM_NOHUGEPAGE)) 1715 return false; 1716 1717 /* 1718 * The destination pmd shouldn't be established, free_pgtables() 1719 * should have release it. 1720 */ 1721 if (WARN_ON(!pmd_none(*new_pmd))) { 1722 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1723 return false; 1724 } 1725 1726 /* 1727 * We don't have to worry about the ordering of src and dst 1728 * ptlocks because exclusive mmap_sem prevents deadlock. 1729 */ 1730 old_ptl = __pmd_trans_huge_lock(old_pmd, vma); 1731 if (old_ptl) { 1732 new_ptl = pmd_lockptr(mm, new_pmd); 1733 if (new_ptl != old_ptl) 1734 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 1735 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd); 1736 VM_BUG_ON(!pmd_none(*new_pmd)); 1737 1738 if (pmd_move_must_withdraw(new_ptl, old_ptl) && 1739 vma_is_anonymous(vma)) { 1740 pgtable_t pgtable; 1741 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); 1742 pgtable_trans_huge_deposit(mm, new_pmd, pgtable); 1743 } 1744 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd)); 1745 if (new_ptl != old_ptl) 1746 spin_unlock(new_ptl); 1747 spin_unlock(old_ptl); 1748 return true; 1749 } 1750 return false; 1751 } 1752 1753 /* 1754 * Returns 1755 * - 0 if PMD could not be locked 1756 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary 1757 * - HPAGE_PMD_NR is protections changed and TLB flush necessary 1758 */ 1759 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1760 unsigned long addr, pgprot_t newprot, int prot_numa) 1761 { 1762 struct mm_struct *mm = vma->vm_mm; 1763 spinlock_t *ptl; 1764 int ret = 0; 1765 1766 ptl = __pmd_trans_huge_lock(pmd, vma); 1767 if (ptl) { 1768 pmd_t entry; 1769 bool preserve_write = prot_numa && pmd_write(*pmd); 1770 ret = 1; 1771 1772 /* 1773 * Avoid trapping faults against the zero page. The read-only 1774 * data is likely to be read-cached on the local CPU and 1775 * local/remote hits to the zero page are not interesting. 1776 */ 1777 if (prot_numa && is_huge_zero_pmd(*pmd)) { 1778 spin_unlock(ptl); 1779 return ret; 1780 } 1781 1782 if (!prot_numa || !pmd_protnone(*pmd)) { 1783 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd); 1784 entry = pmd_modify(entry, newprot); 1785 if (preserve_write) 1786 entry = pmd_mkwrite(entry); 1787 ret = HPAGE_PMD_NR; 1788 set_pmd_at(mm, addr, pmd, entry); 1789 BUG_ON(!preserve_write && pmd_write(entry)); 1790 } 1791 spin_unlock(ptl); 1792 } 1793 1794 return ret; 1795 } 1796 1797 /* 1798 * Returns true if a given pmd maps a thp, false otherwise. 1799 * 1800 * Note that if it returns true, this routine returns without unlocking page 1801 * table lock. So callers must unlock it. 1802 */ 1803 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) 1804 { 1805 spinlock_t *ptl; 1806 ptl = pmd_lock(vma->vm_mm, pmd); 1807 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd))) 1808 return ptl; 1809 spin_unlock(ptl); 1810 return NULL; 1811 } 1812 1813 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE) 1814 1815 int hugepage_madvise(struct vm_area_struct *vma, 1816 unsigned long *vm_flags, int advice) 1817 { 1818 switch (advice) { 1819 case MADV_HUGEPAGE: 1820 #ifdef CONFIG_S390 1821 /* 1822 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 1823 * can't handle this properly after s390_enable_sie, so we simply 1824 * ignore the madvise to prevent qemu from causing a SIGSEGV. 1825 */ 1826 if (mm_has_pgste(vma->vm_mm)) 1827 return 0; 1828 #endif 1829 /* 1830 * Be somewhat over-protective like KSM for now! 1831 */ 1832 if (*vm_flags & VM_NO_THP) 1833 return -EINVAL; 1834 *vm_flags &= ~VM_NOHUGEPAGE; 1835 *vm_flags |= VM_HUGEPAGE; 1836 /* 1837 * If the vma become good for khugepaged to scan, 1838 * register it here without waiting a page fault that 1839 * may not happen any time soon. 1840 */ 1841 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags))) 1842 return -ENOMEM; 1843 break; 1844 case MADV_NOHUGEPAGE: 1845 /* 1846 * Be somewhat over-protective like KSM for now! 1847 */ 1848 if (*vm_flags & VM_NO_THP) 1849 return -EINVAL; 1850 *vm_flags &= ~VM_HUGEPAGE; 1851 *vm_flags |= VM_NOHUGEPAGE; 1852 /* 1853 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1854 * this vma even if we leave the mm registered in khugepaged if 1855 * it got registered before VM_NOHUGEPAGE was set. 1856 */ 1857 break; 1858 } 1859 1860 return 0; 1861 } 1862 1863 static int __init khugepaged_slab_init(void) 1864 { 1865 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1866 sizeof(struct mm_slot), 1867 __alignof__(struct mm_slot), 0, NULL); 1868 if (!mm_slot_cache) 1869 return -ENOMEM; 1870 1871 return 0; 1872 } 1873 1874 static void __init khugepaged_slab_exit(void) 1875 { 1876 kmem_cache_destroy(mm_slot_cache); 1877 } 1878 1879 static inline struct mm_slot *alloc_mm_slot(void) 1880 { 1881 if (!mm_slot_cache) /* initialization failed */ 1882 return NULL; 1883 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 1884 } 1885 1886 static inline void free_mm_slot(struct mm_slot *mm_slot) 1887 { 1888 kmem_cache_free(mm_slot_cache, mm_slot); 1889 } 1890 1891 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 1892 { 1893 struct mm_slot *mm_slot; 1894 1895 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) 1896 if (mm == mm_slot->mm) 1897 return mm_slot; 1898 1899 return NULL; 1900 } 1901 1902 static void insert_to_mm_slots_hash(struct mm_struct *mm, 1903 struct mm_slot *mm_slot) 1904 { 1905 mm_slot->mm = mm; 1906 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); 1907 } 1908 1909 static inline int khugepaged_test_exit(struct mm_struct *mm) 1910 { 1911 return atomic_read(&mm->mm_users) == 0; 1912 } 1913 1914 int __khugepaged_enter(struct mm_struct *mm) 1915 { 1916 struct mm_slot *mm_slot; 1917 int wakeup; 1918 1919 mm_slot = alloc_mm_slot(); 1920 if (!mm_slot) 1921 return -ENOMEM; 1922 1923 /* __khugepaged_exit() must not run from under us */ 1924 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); 1925 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 1926 free_mm_slot(mm_slot); 1927 return 0; 1928 } 1929 1930 spin_lock(&khugepaged_mm_lock); 1931 insert_to_mm_slots_hash(mm, mm_slot); 1932 /* 1933 * Insert just behind the scanning cursor, to let the area settle 1934 * down a little. 1935 */ 1936 wakeup = list_empty(&khugepaged_scan.mm_head); 1937 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 1938 spin_unlock(&khugepaged_mm_lock); 1939 1940 atomic_inc(&mm->mm_count); 1941 if (wakeup) 1942 wake_up_interruptible(&khugepaged_wait); 1943 1944 return 0; 1945 } 1946 1947 int khugepaged_enter_vma_merge(struct vm_area_struct *vma, 1948 unsigned long vm_flags) 1949 { 1950 unsigned long hstart, hend; 1951 if (!vma->anon_vma) 1952 /* 1953 * Not yet faulted in so we will register later in the 1954 * page fault if needed. 1955 */ 1956 return 0; 1957 if (vma->vm_ops || (vm_flags & VM_NO_THP)) 1958 /* khugepaged not yet working on file or special mappings */ 1959 return 0; 1960 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1961 hend = vma->vm_end & HPAGE_PMD_MASK; 1962 if (hstart < hend) 1963 return khugepaged_enter(vma, vm_flags); 1964 return 0; 1965 } 1966 1967 void __khugepaged_exit(struct mm_struct *mm) 1968 { 1969 struct mm_slot *mm_slot; 1970 int free = 0; 1971 1972 spin_lock(&khugepaged_mm_lock); 1973 mm_slot = get_mm_slot(mm); 1974 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 1975 hash_del(&mm_slot->hash); 1976 list_del(&mm_slot->mm_node); 1977 free = 1; 1978 } 1979 spin_unlock(&khugepaged_mm_lock); 1980 1981 if (free) { 1982 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1983 free_mm_slot(mm_slot); 1984 mmdrop(mm); 1985 } else if (mm_slot) { 1986 /* 1987 * This is required to serialize against 1988 * khugepaged_test_exit() (which is guaranteed to run 1989 * under mmap sem read mode). Stop here (after we 1990 * return all pagetables will be destroyed) until 1991 * khugepaged has finished working on the pagetables 1992 * under the mmap_sem. 1993 */ 1994 down_write(&mm->mmap_sem); 1995 up_write(&mm->mmap_sem); 1996 } 1997 } 1998 1999 static void release_pte_page(struct page *page) 2000 { 2001 /* 0 stands for page_is_file_cache(page) == false */ 2002 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 2003 unlock_page(page); 2004 putback_lru_page(page); 2005 } 2006 2007 static void release_pte_pages(pte_t *pte, pte_t *_pte) 2008 { 2009 while (--_pte >= pte) { 2010 pte_t pteval = *_pte; 2011 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) 2012 release_pte_page(pte_page(pteval)); 2013 } 2014 } 2015 2016 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 2017 unsigned long address, 2018 pte_t *pte) 2019 { 2020 struct page *page = NULL; 2021 pte_t *_pte; 2022 int none_or_zero = 0, result = 0; 2023 bool referenced = false, writable = false; 2024 2025 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 2026 _pte++, address += PAGE_SIZE) { 2027 pte_t pteval = *_pte; 2028 if (pte_none(pteval) || (pte_present(pteval) && 2029 is_zero_pfn(pte_pfn(pteval)))) { 2030 if (!userfaultfd_armed(vma) && 2031 ++none_or_zero <= khugepaged_max_ptes_none) { 2032 continue; 2033 } else { 2034 result = SCAN_EXCEED_NONE_PTE; 2035 goto out; 2036 } 2037 } 2038 if (!pte_present(pteval)) { 2039 result = SCAN_PTE_NON_PRESENT; 2040 goto out; 2041 } 2042 page = vm_normal_page(vma, address, pteval); 2043 if (unlikely(!page)) { 2044 result = SCAN_PAGE_NULL; 2045 goto out; 2046 } 2047 2048 VM_BUG_ON_PAGE(PageCompound(page), page); 2049 VM_BUG_ON_PAGE(!PageAnon(page), page); 2050 VM_BUG_ON_PAGE(!PageSwapBacked(page), page); 2051 2052 /* 2053 * We can do it before isolate_lru_page because the 2054 * page can't be freed from under us. NOTE: PG_lock 2055 * is needed to serialize against split_huge_page 2056 * when invoked from the VM. 2057 */ 2058 if (!trylock_page(page)) { 2059 result = SCAN_PAGE_LOCK; 2060 goto out; 2061 } 2062 2063 /* 2064 * cannot use mapcount: can't collapse if there's a gup pin. 2065 * The page must only be referenced by the scanned process 2066 * and page swap cache. 2067 */ 2068 if (page_count(page) != 1 + !!PageSwapCache(page)) { 2069 unlock_page(page); 2070 result = SCAN_PAGE_COUNT; 2071 goto out; 2072 } 2073 if (pte_write(pteval)) { 2074 writable = true; 2075 } else { 2076 if (PageSwapCache(page) && 2077 !reuse_swap_page(page, NULL)) { 2078 unlock_page(page); 2079 result = SCAN_SWAP_CACHE_PAGE; 2080 goto out; 2081 } 2082 /* 2083 * Page is not in the swap cache. It can be collapsed 2084 * into a THP. 2085 */ 2086 } 2087 2088 /* 2089 * Isolate the page to avoid collapsing an hugepage 2090 * currently in use by the VM. 2091 */ 2092 if (isolate_lru_page(page)) { 2093 unlock_page(page); 2094 result = SCAN_DEL_PAGE_LRU; 2095 goto out; 2096 } 2097 /* 0 stands for page_is_file_cache(page) == false */ 2098 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 2099 VM_BUG_ON_PAGE(!PageLocked(page), page); 2100 VM_BUG_ON_PAGE(PageLRU(page), page); 2101 2102 /* If there is no mapped pte young don't collapse the page */ 2103 if (pte_young(pteval) || 2104 page_is_young(page) || PageReferenced(page) || 2105 mmu_notifier_test_young(vma->vm_mm, address)) 2106 referenced = true; 2107 } 2108 if (likely(writable)) { 2109 if (likely(referenced)) { 2110 result = SCAN_SUCCEED; 2111 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 2112 referenced, writable, result); 2113 return 1; 2114 } 2115 } else { 2116 result = SCAN_PAGE_RO; 2117 } 2118 2119 out: 2120 release_pte_pages(pte, _pte); 2121 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 2122 referenced, writable, result); 2123 return 0; 2124 } 2125 2126 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 2127 struct vm_area_struct *vma, 2128 unsigned long address, 2129 spinlock_t *ptl) 2130 { 2131 pte_t *_pte; 2132 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 2133 pte_t pteval = *_pte; 2134 struct page *src_page; 2135 2136 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 2137 clear_user_highpage(page, address); 2138 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 2139 if (is_zero_pfn(pte_pfn(pteval))) { 2140 /* 2141 * ptl mostly unnecessary. 2142 */ 2143 spin_lock(ptl); 2144 /* 2145 * paravirt calls inside pte_clear here are 2146 * superfluous. 2147 */ 2148 pte_clear(vma->vm_mm, address, _pte); 2149 spin_unlock(ptl); 2150 } 2151 } else { 2152 src_page = pte_page(pteval); 2153 copy_user_highpage(page, src_page, address, vma); 2154 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); 2155 release_pte_page(src_page); 2156 /* 2157 * ptl mostly unnecessary, but preempt has to 2158 * be disabled to update the per-cpu stats 2159 * inside page_remove_rmap(). 2160 */ 2161 spin_lock(ptl); 2162 /* 2163 * paravirt calls inside pte_clear here are 2164 * superfluous. 2165 */ 2166 pte_clear(vma->vm_mm, address, _pte); 2167 page_remove_rmap(src_page, false); 2168 spin_unlock(ptl); 2169 free_page_and_swap_cache(src_page); 2170 } 2171 2172 address += PAGE_SIZE; 2173 page++; 2174 } 2175 } 2176 2177 static void khugepaged_alloc_sleep(void) 2178 { 2179 DEFINE_WAIT(wait); 2180 2181 add_wait_queue(&khugepaged_wait, &wait); 2182 freezable_schedule_timeout_interruptible( 2183 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 2184 remove_wait_queue(&khugepaged_wait, &wait); 2185 } 2186 2187 static int khugepaged_node_load[MAX_NUMNODES]; 2188 2189 static bool khugepaged_scan_abort(int nid) 2190 { 2191 int i; 2192 2193 /* 2194 * If zone_reclaim_mode is disabled, then no extra effort is made to 2195 * allocate memory locally. 2196 */ 2197 if (!zone_reclaim_mode) 2198 return false; 2199 2200 /* If there is a count for this node already, it must be acceptable */ 2201 if (khugepaged_node_load[nid]) 2202 return false; 2203 2204 for (i = 0; i < MAX_NUMNODES; i++) { 2205 if (!khugepaged_node_load[i]) 2206 continue; 2207 if (node_distance(nid, i) > RECLAIM_DISTANCE) 2208 return true; 2209 } 2210 return false; 2211 } 2212 2213 #ifdef CONFIG_NUMA 2214 static int khugepaged_find_target_node(void) 2215 { 2216 static int last_khugepaged_target_node = NUMA_NO_NODE; 2217 int nid, target_node = 0, max_value = 0; 2218 2219 /* find first node with max normal pages hit */ 2220 for (nid = 0; nid < MAX_NUMNODES; nid++) 2221 if (khugepaged_node_load[nid] > max_value) { 2222 max_value = khugepaged_node_load[nid]; 2223 target_node = nid; 2224 } 2225 2226 /* do some balance if several nodes have the same hit record */ 2227 if (target_node <= last_khugepaged_target_node) 2228 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; 2229 nid++) 2230 if (max_value == khugepaged_node_load[nid]) { 2231 target_node = nid; 2232 break; 2233 } 2234 2235 last_khugepaged_target_node = target_node; 2236 return target_node; 2237 } 2238 2239 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2240 { 2241 if (IS_ERR(*hpage)) { 2242 if (!*wait) 2243 return false; 2244 2245 *wait = false; 2246 *hpage = NULL; 2247 khugepaged_alloc_sleep(); 2248 } else if (*hpage) { 2249 put_page(*hpage); 2250 *hpage = NULL; 2251 } 2252 2253 return true; 2254 } 2255 2256 static struct page * 2257 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm, 2258 unsigned long address, int node) 2259 { 2260 VM_BUG_ON_PAGE(*hpage, *hpage); 2261 2262 /* 2263 * Before allocating the hugepage, release the mmap_sem read lock. 2264 * The allocation can take potentially a long time if it involves 2265 * sync compaction, and we do not need to hold the mmap_sem during 2266 * that. We will recheck the vma after taking it again in write mode. 2267 */ 2268 up_read(&mm->mmap_sem); 2269 2270 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); 2271 if (unlikely(!*hpage)) { 2272 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2273 *hpage = ERR_PTR(-ENOMEM); 2274 return NULL; 2275 } 2276 2277 prep_transhuge_page(*hpage); 2278 count_vm_event(THP_COLLAPSE_ALLOC); 2279 return *hpage; 2280 } 2281 #else 2282 static int khugepaged_find_target_node(void) 2283 { 2284 return 0; 2285 } 2286 2287 static inline struct page *alloc_khugepaged_hugepage(void) 2288 { 2289 struct page *page; 2290 2291 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), 2292 HPAGE_PMD_ORDER); 2293 if (page) 2294 prep_transhuge_page(page); 2295 return page; 2296 } 2297 2298 static struct page *khugepaged_alloc_hugepage(bool *wait) 2299 { 2300 struct page *hpage; 2301 2302 do { 2303 hpage = alloc_khugepaged_hugepage(); 2304 if (!hpage) { 2305 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2306 if (!*wait) 2307 return NULL; 2308 2309 *wait = false; 2310 khugepaged_alloc_sleep(); 2311 } else 2312 count_vm_event(THP_COLLAPSE_ALLOC); 2313 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 2314 2315 return hpage; 2316 } 2317 2318 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2319 { 2320 if (!*hpage) 2321 *hpage = khugepaged_alloc_hugepage(wait); 2322 2323 if (unlikely(!*hpage)) 2324 return false; 2325 2326 return true; 2327 } 2328 2329 static struct page * 2330 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm, 2331 unsigned long address, int node) 2332 { 2333 up_read(&mm->mmap_sem); 2334 VM_BUG_ON(!*hpage); 2335 2336 return *hpage; 2337 } 2338 #endif 2339 2340 static bool hugepage_vma_check(struct vm_area_struct *vma) 2341 { 2342 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 2343 (vma->vm_flags & VM_NOHUGEPAGE)) 2344 return false; 2345 if (!vma->anon_vma || vma->vm_ops) 2346 return false; 2347 if (is_vma_temporary_stack(vma)) 2348 return false; 2349 return !(vma->vm_flags & VM_NO_THP); 2350 } 2351 2352 static void collapse_huge_page(struct mm_struct *mm, 2353 unsigned long address, 2354 struct page **hpage, 2355 struct vm_area_struct *vma, 2356 int node) 2357 { 2358 pmd_t *pmd, _pmd; 2359 pte_t *pte; 2360 pgtable_t pgtable; 2361 struct page *new_page; 2362 spinlock_t *pmd_ptl, *pte_ptl; 2363 int isolated = 0, result = 0; 2364 unsigned long hstart, hend; 2365 struct mem_cgroup *memcg; 2366 unsigned long mmun_start; /* For mmu_notifiers */ 2367 unsigned long mmun_end; /* For mmu_notifiers */ 2368 gfp_t gfp; 2369 2370 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2371 2372 /* Only allocate from the target node */ 2373 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE; 2374 2375 /* release the mmap_sem read lock. */ 2376 new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node); 2377 if (!new_page) { 2378 result = SCAN_ALLOC_HUGE_PAGE_FAIL; 2379 goto out_nolock; 2380 } 2381 2382 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { 2383 result = SCAN_CGROUP_CHARGE_FAIL; 2384 goto out_nolock; 2385 } 2386 2387 /* 2388 * Prevent all access to pagetables with the exception of 2389 * gup_fast later hanlded by the ptep_clear_flush and the VM 2390 * handled by the anon_vma lock + PG_lock. 2391 */ 2392 down_write(&mm->mmap_sem); 2393 if (unlikely(khugepaged_test_exit(mm))) { 2394 result = SCAN_ANY_PROCESS; 2395 goto out; 2396 } 2397 2398 vma = find_vma(mm, address); 2399 if (!vma) { 2400 result = SCAN_VMA_NULL; 2401 goto out; 2402 } 2403 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2404 hend = vma->vm_end & HPAGE_PMD_MASK; 2405 if (address < hstart || address + HPAGE_PMD_SIZE > hend) { 2406 result = SCAN_ADDRESS_RANGE; 2407 goto out; 2408 } 2409 if (!hugepage_vma_check(vma)) { 2410 result = SCAN_VMA_CHECK; 2411 goto out; 2412 } 2413 pmd = mm_find_pmd(mm, address); 2414 if (!pmd) { 2415 result = SCAN_PMD_NULL; 2416 goto out; 2417 } 2418 2419 anon_vma_lock_write(vma->anon_vma); 2420 2421 pte = pte_offset_map(pmd, address); 2422 pte_ptl = pte_lockptr(mm, pmd); 2423 2424 mmun_start = address; 2425 mmun_end = address + HPAGE_PMD_SIZE; 2426 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2427 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ 2428 /* 2429 * After this gup_fast can't run anymore. This also removes 2430 * any huge TLB entry from the CPU so we won't allow 2431 * huge and small TLB entries for the same virtual address 2432 * to avoid the risk of CPU bugs in that area. 2433 */ 2434 _pmd = pmdp_collapse_flush(vma, address, pmd); 2435 spin_unlock(pmd_ptl); 2436 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2437 2438 spin_lock(pte_ptl); 2439 isolated = __collapse_huge_page_isolate(vma, address, pte); 2440 spin_unlock(pte_ptl); 2441 2442 if (unlikely(!isolated)) { 2443 pte_unmap(pte); 2444 spin_lock(pmd_ptl); 2445 BUG_ON(!pmd_none(*pmd)); 2446 /* 2447 * We can only use set_pmd_at when establishing 2448 * hugepmds and never for establishing regular pmds that 2449 * points to regular pagetables. Use pmd_populate for that 2450 */ 2451 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 2452 spin_unlock(pmd_ptl); 2453 anon_vma_unlock_write(vma->anon_vma); 2454 result = SCAN_FAIL; 2455 goto out; 2456 } 2457 2458 /* 2459 * All pages are isolated and locked so anon_vma rmap 2460 * can't run anymore. 2461 */ 2462 anon_vma_unlock_write(vma->anon_vma); 2463 2464 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); 2465 pte_unmap(pte); 2466 __SetPageUptodate(new_page); 2467 pgtable = pmd_pgtable(_pmd); 2468 2469 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); 2470 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 2471 2472 /* 2473 * spin_lock() below is not the equivalent of smp_wmb(), so 2474 * this is needed to avoid the copy_huge_page writes to become 2475 * visible after the set_pmd_at() write. 2476 */ 2477 smp_wmb(); 2478 2479 spin_lock(pmd_ptl); 2480 BUG_ON(!pmd_none(*pmd)); 2481 page_add_new_anon_rmap(new_page, vma, address, true); 2482 mem_cgroup_commit_charge(new_page, memcg, false, true); 2483 lru_cache_add_active_or_unevictable(new_page, vma); 2484 pgtable_trans_huge_deposit(mm, pmd, pgtable); 2485 set_pmd_at(mm, address, pmd, _pmd); 2486 update_mmu_cache_pmd(vma, address, pmd); 2487 spin_unlock(pmd_ptl); 2488 2489 *hpage = NULL; 2490 2491 khugepaged_pages_collapsed++; 2492 result = SCAN_SUCCEED; 2493 out_up_write: 2494 up_write(&mm->mmap_sem); 2495 trace_mm_collapse_huge_page(mm, isolated, result); 2496 return; 2497 2498 out_nolock: 2499 trace_mm_collapse_huge_page(mm, isolated, result); 2500 return; 2501 out: 2502 mem_cgroup_cancel_charge(new_page, memcg, true); 2503 goto out_up_write; 2504 } 2505 2506 static int khugepaged_scan_pmd(struct mm_struct *mm, 2507 struct vm_area_struct *vma, 2508 unsigned long address, 2509 struct page **hpage) 2510 { 2511 pmd_t *pmd; 2512 pte_t *pte, *_pte; 2513 int ret = 0, none_or_zero = 0, result = 0; 2514 struct page *page = NULL; 2515 unsigned long _address; 2516 spinlock_t *ptl; 2517 int node = NUMA_NO_NODE; 2518 bool writable = false, referenced = false; 2519 2520 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2521 2522 pmd = mm_find_pmd(mm, address); 2523 if (!pmd) { 2524 result = SCAN_PMD_NULL; 2525 goto out; 2526 } 2527 2528 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 2529 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2530 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2531 _pte++, _address += PAGE_SIZE) { 2532 pte_t pteval = *_pte; 2533 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 2534 if (!userfaultfd_armed(vma) && 2535 ++none_or_zero <= khugepaged_max_ptes_none) { 2536 continue; 2537 } else { 2538 result = SCAN_EXCEED_NONE_PTE; 2539 goto out_unmap; 2540 } 2541 } 2542 if (!pte_present(pteval)) { 2543 result = SCAN_PTE_NON_PRESENT; 2544 goto out_unmap; 2545 } 2546 if (pte_write(pteval)) 2547 writable = true; 2548 2549 page = vm_normal_page(vma, _address, pteval); 2550 if (unlikely(!page)) { 2551 result = SCAN_PAGE_NULL; 2552 goto out_unmap; 2553 } 2554 2555 /* TODO: teach khugepaged to collapse THP mapped with pte */ 2556 if (PageCompound(page)) { 2557 result = SCAN_PAGE_COMPOUND; 2558 goto out_unmap; 2559 } 2560 2561 /* 2562 * Record which node the original page is from and save this 2563 * information to khugepaged_node_load[]. 2564 * Khupaged will allocate hugepage from the node has the max 2565 * hit record. 2566 */ 2567 node = page_to_nid(page); 2568 if (khugepaged_scan_abort(node)) { 2569 result = SCAN_SCAN_ABORT; 2570 goto out_unmap; 2571 } 2572 khugepaged_node_load[node]++; 2573 if (!PageLRU(page)) { 2574 result = SCAN_PAGE_LRU; 2575 goto out_unmap; 2576 } 2577 if (PageLocked(page)) { 2578 result = SCAN_PAGE_LOCK; 2579 goto out_unmap; 2580 } 2581 if (!PageAnon(page)) { 2582 result = SCAN_PAGE_ANON; 2583 goto out_unmap; 2584 } 2585 2586 /* 2587 * cannot use mapcount: can't collapse if there's a gup pin. 2588 * The page must only be referenced by the scanned process 2589 * and page swap cache. 2590 */ 2591 if (page_count(page) != 1 + !!PageSwapCache(page)) { 2592 result = SCAN_PAGE_COUNT; 2593 goto out_unmap; 2594 } 2595 if (pte_young(pteval) || 2596 page_is_young(page) || PageReferenced(page) || 2597 mmu_notifier_test_young(vma->vm_mm, address)) 2598 referenced = true; 2599 } 2600 if (writable) { 2601 if (referenced) { 2602 result = SCAN_SUCCEED; 2603 ret = 1; 2604 } else { 2605 result = SCAN_NO_REFERENCED_PAGE; 2606 } 2607 } else { 2608 result = SCAN_PAGE_RO; 2609 } 2610 out_unmap: 2611 pte_unmap_unlock(pte, ptl); 2612 if (ret) { 2613 node = khugepaged_find_target_node(); 2614 /* collapse_huge_page will return with the mmap_sem released */ 2615 collapse_huge_page(mm, address, hpage, vma, node); 2616 } 2617 out: 2618 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, 2619 none_or_zero, result); 2620 return ret; 2621 } 2622 2623 static void collect_mm_slot(struct mm_slot *mm_slot) 2624 { 2625 struct mm_struct *mm = mm_slot->mm; 2626 2627 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2628 2629 if (khugepaged_test_exit(mm)) { 2630 /* free mm_slot */ 2631 hash_del(&mm_slot->hash); 2632 list_del(&mm_slot->mm_node); 2633 2634 /* 2635 * Not strictly needed because the mm exited already. 2636 * 2637 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2638 */ 2639 2640 /* khugepaged_mm_lock actually not necessary for the below */ 2641 free_mm_slot(mm_slot); 2642 mmdrop(mm); 2643 } 2644 } 2645 2646 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2647 struct page **hpage) 2648 __releases(&khugepaged_mm_lock) 2649 __acquires(&khugepaged_mm_lock) 2650 { 2651 struct mm_slot *mm_slot; 2652 struct mm_struct *mm; 2653 struct vm_area_struct *vma; 2654 int progress = 0; 2655 2656 VM_BUG_ON(!pages); 2657 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2658 2659 if (khugepaged_scan.mm_slot) 2660 mm_slot = khugepaged_scan.mm_slot; 2661 else { 2662 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2663 struct mm_slot, mm_node); 2664 khugepaged_scan.address = 0; 2665 khugepaged_scan.mm_slot = mm_slot; 2666 } 2667 spin_unlock(&khugepaged_mm_lock); 2668 2669 mm = mm_slot->mm; 2670 down_read(&mm->mmap_sem); 2671 if (unlikely(khugepaged_test_exit(mm))) 2672 vma = NULL; 2673 else 2674 vma = find_vma(mm, khugepaged_scan.address); 2675 2676 progress++; 2677 for (; vma; vma = vma->vm_next) { 2678 unsigned long hstart, hend; 2679 2680 cond_resched(); 2681 if (unlikely(khugepaged_test_exit(mm))) { 2682 progress++; 2683 break; 2684 } 2685 if (!hugepage_vma_check(vma)) { 2686 skip: 2687 progress++; 2688 continue; 2689 } 2690 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2691 hend = vma->vm_end & HPAGE_PMD_MASK; 2692 if (hstart >= hend) 2693 goto skip; 2694 if (khugepaged_scan.address > hend) 2695 goto skip; 2696 if (khugepaged_scan.address < hstart) 2697 khugepaged_scan.address = hstart; 2698 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2699 2700 while (khugepaged_scan.address < hend) { 2701 int ret; 2702 cond_resched(); 2703 if (unlikely(khugepaged_test_exit(mm))) 2704 goto breakouterloop; 2705 2706 VM_BUG_ON(khugepaged_scan.address < hstart || 2707 khugepaged_scan.address + HPAGE_PMD_SIZE > 2708 hend); 2709 ret = khugepaged_scan_pmd(mm, vma, 2710 khugepaged_scan.address, 2711 hpage); 2712 /* move to next address */ 2713 khugepaged_scan.address += HPAGE_PMD_SIZE; 2714 progress += HPAGE_PMD_NR; 2715 if (ret) 2716 /* we released mmap_sem so break loop */ 2717 goto breakouterloop_mmap_sem; 2718 if (progress >= pages) 2719 goto breakouterloop; 2720 } 2721 } 2722 breakouterloop: 2723 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2724 breakouterloop_mmap_sem: 2725 2726 spin_lock(&khugepaged_mm_lock); 2727 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2728 /* 2729 * Release the current mm_slot if this mm is about to die, or 2730 * if we scanned all vmas of this mm. 2731 */ 2732 if (khugepaged_test_exit(mm) || !vma) { 2733 /* 2734 * Make sure that if mm_users is reaching zero while 2735 * khugepaged runs here, khugepaged_exit will find 2736 * mm_slot not pointing to the exiting mm. 2737 */ 2738 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2739 khugepaged_scan.mm_slot = list_entry( 2740 mm_slot->mm_node.next, 2741 struct mm_slot, mm_node); 2742 khugepaged_scan.address = 0; 2743 } else { 2744 khugepaged_scan.mm_slot = NULL; 2745 khugepaged_full_scans++; 2746 } 2747 2748 collect_mm_slot(mm_slot); 2749 } 2750 2751 return progress; 2752 } 2753 2754 static int khugepaged_has_work(void) 2755 { 2756 return !list_empty(&khugepaged_scan.mm_head) && 2757 khugepaged_enabled(); 2758 } 2759 2760 static int khugepaged_wait_event(void) 2761 { 2762 return !list_empty(&khugepaged_scan.mm_head) || 2763 kthread_should_stop(); 2764 } 2765 2766 static void khugepaged_do_scan(void) 2767 { 2768 struct page *hpage = NULL; 2769 unsigned int progress = 0, pass_through_head = 0; 2770 unsigned int pages = khugepaged_pages_to_scan; 2771 bool wait = true; 2772 2773 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2774 2775 while (progress < pages) { 2776 if (!khugepaged_prealloc_page(&hpage, &wait)) 2777 break; 2778 2779 cond_resched(); 2780 2781 if (unlikely(kthread_should_stop() || try_to_freeze())) 2782 break; 2783 2784 spin_lock(&khugepaged_mm_lock); 2785 if (!khugepaged_scan.mm_slot) 2786 pass_through_head++; 2787 if (khugepaged_has_work() && 2788 pass_through_head < 2) 2789 progress += khugepaged_scan_mm_slot(pages - progress, 2790 &hpage); 2791 else 2792 progress = pages; 2793 spin_unlock(&khugepaged_mm_lock); 2794 } 2795 2796 if (!IS_ERR_OR_NULL(hpage)) 2797 put_page(hpage); 2798 } 2799 2800 static void khugepaged_wait_work(void) 2801 { 2802 if (khugepaged_has_work()) { 2803 if (!khugepaged_scan_sleep_millisecs) 2804 return; 2805 2806 wait_event_freezable_timeout(khugepaged_wait, 2807 kthread_should_stop(), 2808 msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); 2809 return; 2810 } 2811 2812 if (khugepaged_enabled()) 2813 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 2814 } 2815 2816 static int khugepaged(void *none) 2817 { 2818 struct mm_slot *mm_slot; 2819 2820 set_freezable(); 2821 set_user_nice(current, MAX_NICE); 2822 2823 while (!kthread_should_stop()) { 2824 khugepaged_do_scan(); 2825 khugepaged_wait_work(); 2826 } 2827 2828 spin_lock(&khugepaged_mm_lock); 2829 mm_slot = khugepaged_scan.mm_slot; 2830 khugepaged_scan.mm_slot = NULL; 2831 if (mm_slot) 2832 collect_mm_slot(mm_slot); 2833 spin_unlock(&khugepaged_mm_lock); 2834 return 0; 2835 } 2836 2837 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2838 unsigned long haddr, pmd_t *pmd) 2839 { 2840 struct mm_struct *mm = vma->vm_mm; 2841 pgtable_t pgtable; 2842 pmd_t _pmd; 2843 int i; 2844 2845 /* leave pmd empty until pte is filled */ 2846 pmdp_huge_clear_flush_notify(vma, haddr, pmd); 2847 2848 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2849 pmd_populate(mm, &_pmd, pgtable); 2850 2851 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2852 pte_t *pte, entry; 2853 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2854 entry = pte_mkspecial(entry); 2855 pte = pte_offset_map(&_pmd, haddr); 2856 VM_BUG_ON(!pte_none(*pte)); 2857 set_pte_at(mm, haddr, pte, entry); 2858 pte_unmap(pte); 2859 } 2860 smp_wmb(); /* make pte visible before pmd */ 2861 pmd_populate(mm, pmd, pgtable); 2862 put_huge_zero_page(); 2863 } 2864 2865 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 2866 unsigned long haddr, bool freeze) 2867 { 2868 struct mm_struct *mm = vma->vm_mm; 2869 struct page *page; 2870 pgtable_t pgtable; 2871 pmd_t _pmd; 2872 bool young, write, dirty; 2873 unsigned long addr; 2874 int i; 2875 2876 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK); 2877 VM_BUG_ON_VMA(vma->vm_start > haddr, vma); 2878 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma); 2879 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)); 2880 2881 count_vm_event(THP_SPLIT_PMD); 2882 2883 if (vma_is_dax(vma)) { 2884 pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd); 2885 if (is_huge_zero_pmd(_pmd)) 2886 put_huge_zero_page(); 2887 return; 2888 } else if (is_huge_zero_pmd(*pmd)) { 2889 return __split_huge_zero_page_pmd(vma, haddr, pmd); 2890 } 2891 2892 page = pmd_page(*pmd); 2893 VM_BUG_ON_PAGE(!page_count(page), page); 2894 page_ref_add(page, HPAGE_PMD_NR - 1); 2895 write = pmd_write(*pmd); 2896 young = pmd_young(*pmd); 2897 dirty = pmd_dirty(*pmd); 2898 2899 pmdp_huge_split_prepare(vma, haddr, pmd); 2900 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2901 pmd_populate(mm, &_pmd, pgtable); 2902 2903 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { 2904 pte_t entry, *pte; 2905 /* 2906 * Note that NUMA hinting access restrictions are not 2907 * transferred to avoid any possibility of altering 2908 * permissions across VMAs. 2909 */ 2910 if (freeze) { 2911 swp_entry_t swp_entry; 2912 swp_entry = make_migration_entry(page + i, write); 2913 entry = swp_entry_to_pte(swp_entry); 2914 } else { 2915 entry = mk_pte(page + i, vma->vm_page_prot); 2916 entry = maybe_mkwrite(entry, vma); 2917 if (!write) 2918 entry = pte_wrprotect(entry); 2919 if (!young) 2920 entry = pte_mkold(entry); 2921 } 2922 if (dirty) 2923 SetPageDirty(page + i); 2924 pte = pte_offset_map(&_pmd, addr); 2925 BUG_ON(!pte_none(*pte)); 2926 set_pte_at(mm, addr, pte, entry); 2927 atomic_inc(&page[i]._mapcount); 2928 pte_unmap(pte); 2929 } 2930 2931 /* 2932 * Set PG_double_map before dropping compound_mapcount to avoid 2933 * false-negative page_mapped(). 2934 */ 2935 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) { 2936 for (i = 0; i < HPAGE_PMD_NR; i++) 2937 atomic_inc(&page[i]._mapcount); 2938 } 2939 2940 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { 2941 /* Last compound_mapcount is gone. */ 2942 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); 2943 if (TestClearPageDoubleMap(page)) { 2944 /* No need in mapcount reference anymore */ 2945 for (i = 0; i < HPAGE_PMD_NR; i++) 2946 atomic_dec(&page[i]._mapcount); 2947 } 2948 } 2949 2950 smp_wmb(); /* make pte visible before pmd */ 2951 /* 2952 * Up to this point the pmd is present and huge and userland has the 2953 * whole access to the hugepage during the split (which happens in 2954 * place). If we overwrite the pmd with the not-huge version pointing 2955 * to the pte here (which of course we could if all CPUs were bug 2956 * free), userland could trigger a small page size TLB miss on the 2957 * small sized TLB while the hugepage TLB entry is still established in 2958 * the huge TLB. Some CPU doesn't like that. 2959 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum 2960 * 383 on page 93. Intel should be safe but is also warns that it's 2961 * only safe if the permission and cache attributes of the two entries 2962 * loaded in the two TLB is identical (which should be the case here). 2963 * But it is generally safer to never allow small and huge TLB entries 2964 * for the same virtual address to be loaded simultaneously. So instead 2965 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the 2966 * current pmd notpresent (atomically because here the pmd_trans_huge 2967 * and pmd_trans_splitting must remain set at all times on the pmd 2968 * until the split is complete for this pmd), then we flush the SMP TLB 2969 * and finally we write the non-huge version of the pmd entry with 2970 * pmd_populate. 2971 */ 2972 pmdp_invalidate(vma, haddr, pmd); 2973 pmd_populate(mm, pmd, pgtable); 2974 2975 if (freeze) { 2976 for (i = 0; i < HPAGE_PMD_NR; i++) { 2977 page_remove_rmap(page + i, false); 2978 put_page(page + i); 2979 } 2980 } 2981 } 2982 2983 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 2984 unsigned long address, bool freeze) 2985 { 2986 spinlock_t *ptl; 2987 struct mm_struct *mm = vma->vm_mm; 2988 unsigned long haddr = address & HPAGE_PMD_MASK; 2989 2990 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE); 2991 ptl = pmd_lock(mm, pmd); 2992 if (pmd_trans_huge(*pmd)) { 2993 struct page *page = pmd_page(*pmd); 2994 if (PageMlocked(page)) 2995 clear_page_mlock(page); 2996 } else if (!pmd_devmap(*pmd)) 2997 goto out; 2998 __split_huge_pmd_locked(vma, pmd, haddr, freeze); 2999 out: 3000 spin_unlock(ptl); 3001 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE); 3002 } 3003 3004 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, 3005 bool freeze, struct page *page) 3006 { 3007 pgd_t *pgd; 3008 pud_t *pud; 3009 pmd_t *pmd; 3010 3011 pgd = pgd_offset(vma->vm_mm, address); 3012 if (!pgd_present(*pgd)) 3013 return; 3014 3015 pud = pud_offset(pgd, address); 3016 if (!pud_present(*pud)) 3017 return; 3018 3019 pmd = pmd_offset(pud, address); 3020 if (!pmd_present(*pmd) || (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd))) 3021 return; 3022 3023 /* 3024 * If caller asks to setup a migration entries, we need a page to check 3025 * pmd against. Otherwise we can end up replacing wrong page. 3026 */ 3027 VM_BUG_ON(freeze && !page); 3028 if (page && page != pmd_page(*pmd)) 3029 return; 3030 3031 /* 3032 * Caller holds the mmap_sem write mode, so a huge pmd cannot 3033 * materialize from under us. 3034 */ 3035 __split_huge_pmd(vma, pmd, address, freeze); 3036 } 3037 3038 void vma_adjust_trans_huge(struct vm_area_struct *vma, 3039 unsigned long start, 3040 unsigned long end, 3041 long adjust_next) 3042 { 3043 /* 3044 * If the new start address isn't hpage aligned and it could 3045 * previously contain an hugepage: check if we need to split 3046 * an huge pmd. 3047 */ 3048 if (start & ~HPAGE_PMD_MASK && 3049 (start & HPAGE_PMD_MASK) >= vma->vm_start && 3050 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 3051 split_huge_pmd_address(vma, start, false, NULL); 3052 3053 /* 3054 * If the new end address isn't hpage aligned and it could 3055 * previously contain an hugepage: check if we need to split 3056 * an huge pmd. 3057 */ 3058 if (end & ~HPAGE_PMD_MASK && 3059 (end & HPAGE_PMD_MASK) >= vma->vm_start && 3060 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 3061 split_huge_pmd_address(vma, end, false, NULL); 3062 3063 /* 3064 * If we're also updating the vma->vm_next->vm_start, if the new 3065 * vm_next->vm_start isn't page aligned and it could previously 3066 * contain an hugepage: check if we need to split an huge pmd. 3067 */ 3068 if (adjust_next > 0) { 3069 struct vm_area_struct *next = vma->vm_next; 3070 unsigned long nstart = next->vm_start; 3071 nstart += adjust_next << PAGE_SHIFT; 3072 if (nstart & ~HPAGE_PMD_MASK && 3073 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 3074 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 3075 split_huge_pmd_address(next, nstart, false, NULL); 3076 } 3077 } 3078 3079 static void freeze_page(struct page *page) 3080 { 3081 enum ttu_flags ttu_flags = TTU_MIGRATION | TTU_IGNORE_MLOCK | 3082 TTU_IGNORE_ACCESS | TTU_RMAP_LOCKED; 3083 int i, ret; 3084 3085 VM_BUG_ON_PAGE(!PageHead(page), page); 3086 3087 /* We only need TTU_SPLIT_HUGE_PMD once */ 3088 ret = try_to_unmap(page, ttu_flags | TTU_SPLIT_HUGE_PMD); 3089 for (i = 1; !ret && i < HPAGE_PMD_NR; i++) { 3090 /* Cut short if the page is unmapped */ 3091 if (page_count(page) == 1) 3092 return; 3093 3094 ret = try_to_unmap(page + i, ttu_flags); 3095 } 3096 VM_BUG_ON(ret); 3097 } 3098 3099 static void unfreeze_page(struct page *page) 3100 { 3101 int i; 3102 3103 for (i = 0; i < HPAGE_PMD_NR; i++) 3104 remove_migration_ptes(page + i, page + i, true); 3105 } 3106 3107 static void __split_huge_page_tail(struct page *head, int tail, 3108 struct lruvec *lruvec, struct list_head *list) 3109 { 3110 struct page *page_tail = head + tail; 3111 3112 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); 3113 VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail); 3114 3115 /* 3116 * tail_page->_count is zero and not changing from under us. But 3117 * get_page_unless_zero() may be running from under us on the 3118 * tail_page. If we used atomic_set() below instead of atomic_inc(), we 3119 * would then run atomic_set() concurrently with 3120 * get_page_unless_zero(), and atomic_set() is implemented in C not 3121 * using locked ops. spin_unlock on x86 sometime uses locked ops 3122 * because of PPro errata 66, 92, so unless somebody can guarantee 3123 * atomic_set() here would be safe on all archs (and not only on x86), 3124 * it's safer to use atomic_inc(). 3125 */ 3126 page_ref_inc(page_tail); 3127 3128 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; 3129 page_tail->flags |= (head->flags & 3130 ((1L << PG_referenced) | 3131 (1L << PG_swapbacked) | 3132 (1L << PG_mlocked) | 3133 (1L << PG_uptodate) | 3134 (1L << PG_active) | 3135 (1L << PG_locked) | 3136 (1L << PG_unevictable) | 3137 (1L << PG_dirty))); 3138 3139 /* 3140 * After clearing PageTail the gup refcount can be released. 3141 * Page flags also must be visible before we make the page non-compound. 3142 */ 3143 smp_wmb(); 3144 3145 clear_compound_head(page_tail); 3146 3147 if (page_is_young(head)) 3148 set_page_young(page_tail); 3149 if (page_is_idle(head)) 3150 set_page_idle(page_tail); 3151 3152 /* ->mapping in first tail page is compound_mapcount */ 3153 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING, 3154 page_tail); 3155 page_tail->mapping = head->mapping; 3156 3157 page_tail->index = head->index + tail; 3158 page_cpupid_xchg_last(page_tail, page_cpupid_last(head)); 3159 lru_add_page_tail(head, page_tail, lruvec, list); 3160 } 3161 3162 static void __split_huge_page(struct page *page, struct list_head *list) 3163 { 3164 struct page *head = compound_head(page); 3165 struct zone *zone = page_zone(head); 3166 struct lruvec *lruvec; 3167 int i; 3168 3169 /* prevent PageLRU to go away from under us, and freeze lru stats */ 3170 spin_lock_irq(&zone->lru_lock); 3171 lruvec = mem_cgroup_page_lruvec(head, zone); 3172 3173 /* complete memcg works before add pages to LRU */ 3174 mem_cgroup_split_huge_fixup(head); 3175 3176 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) 3177 __split_huge_page_tail(head, i, lruvec, list); 3178 3179 ClearPageCompound(head); 3180 spin_unlock_irq(&zone->lru_lock); 3181 3182 unfreeze_page(head); 3183 3184 for (i = 0; i < HPAGE_PMD_NR; i++) { 3185 struct page *subpage = head + i; 3186 if (subpage == page) 3187 continue; 3188 unlock_page(subpage); 3189 3190 /* 3191 * Subpages may be freed if there wasn't any mapping 3192 * like if add_to_swap() is running on a lru page that 3193 * had its mapping zapped. And freeing these pages 3194 * requires taking the lru_lock so we do the put_page 3195 * of the tail pages after the split is complete. 3196 */ 3197 put_page(subpage); 3198 } 3199 } 3200 3201 int total_mapcount(struct page *page) 3202 { 3203 int i, ret; 3204 3205 VM_BUG_ON_PAGE(PageTail(page), page); 3206 3207 if (likely(!PageCompound(page))) 3208 return atomic_read(&page->_mapcount) + 1; 3209 3210 ret = compound_mapcount(page); 3211 if (PageHuge(page)) 3212 return ret; 3213 for (i = 0; i < HPAGE_PMD_NR; i++) 3214 ret += atomic_read(&page[i]._mapcount) + 1; 3215 if (PageDoubleMap(page)) 3216 ret -= HPAGE_PMD_NR; 3217 return ret; 3218 } 3219 3220 /* 3221 * This calculates accurately how many mappings a transparent hugepage 3222 * has (unlike page_mapcount() which isn't fully accurate). This full 3223 * accuracy is primarily needed to know if copy-on-write faults can 3224 * reuse the page and change the mapping to read-write instead of 3225 * copying them. At the same time this returns the total_mapcount too. 3226 * 3227 * The function returns the highest mapcount any one of the subpages 3228 * has. If the return value is one, even if different processes are 3229 * mapping different subpages of the transparent hugepage, they can 3230 * all reuse it, because each process is reusing a different subpage. 3231 * 3232 * The total_mapcount is instead counting all virtual mappings of the 3233 * subpages. If the total_mapcount is equal to "one", it tells the 3234 * caller all mappings belong to the same "mm" and in turn the 3235 * anon_vma of the transparent hugepage can become the vma->anon_vma 3236 * local one as no other process may be mapping any of the subpages. 3237 * 3238 * It would be more accurate to replace page_mapcount() with 3239 * page_trans_huge_mapcount(), however we only use 3240 * page_trans_huge_mapcount() in the copy-on-write faults where we 3241 * need full accuracy to avoid breaking page pinning, because 3242 * page_trans_huge_mapcount() is slower than page_mapcount(). 3243 */ 3244 int page_trans_huge_mapcount(struct page *page, int *total_mapcount) 3245 { 3246 int i, ret, _total_mapcount, mapcount; 3247 3248 /* hugetlbfs shouldn't call it */ 3249 VM_BUG_ON_PAGE(PageHuge(page), page); 3250 3251 if (likely(!PageTransCompound(page))) { 3252 mapcount = atomic_read(&page->_mapcount) + 1; 3253 if (total_mapcount) 3254 *total_mapcount = mapcount; 3255 return mapcount; 3256 } 3257 3258 page = compound_head(page); 3259 3260 _total_mapcount = ret = 0; 3261 for (i = 0; i < HPAGE_PMD_NR; i++) { 3262 mapcount = atomic_read(&page[i]._mapcount) + 1; 3263 ret = max(ret, mapcount); 3264 _total_mapcount += mapcount; 3265 } 3266 if (PageDoubleMap(page)) { 3267 ret -= 1; 3268 _total_mapcount -= HPAGE_PMD_NR; 3269 } 3270 mapcount = compound_mapcount(page); 3271 ret += mapcount; 3272 _total_mapcount += mapcount; 3273 if (total_mapcount) 3274 *total_mapcount = _total_mapcount; 3275 return ret; 3276 } 3277 3278 /* 3279 * This function splits huge page into normal pages. @page can point to any 3280 * subpage of huge page to split. Split doesn't change the position of @page. 3281 * 3282 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY. 3283 * The huge page must be locked. 3284 * 3285 * If @list is null, tail pages will be added to LRU list, otherwise, to @list. 3286 * 3287 * Both head page and tail pages will inherit mapping, flags, and so on from 3288 * the hugepage. 3289 * 3290 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if 3291 * they are not mapped. 3292 * 3293 * Returns 0 if the hugepage is split successfully. 3294 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under 3295 * us. 3296 */ 3297 int split_huge_page_to_list(struct page *page, struct list_head *list) 3298 { 3299 struct page *head = compound_head(page); 3300 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head)); 3301 struct anon_vma *anon_vma; 3302 int count, mapcount, ret; 3303 bool mlocked; 3304 unsigned long flags; 3305 3306 VM_BUG_ON_PAGE(is_huge_zero_page(page), page); 3307 VM_BUG_ON_PAGE(!PageAnon(page), page); 3308 VM_BUG_ON_PAGE(!PageLocked(page), page); 3309 VM_BUG_ON_PAGE(!PageSwapBacked(page), page); 3310 VM_BUG_ON_PAGE(!PageCompound(page), page); 3311 3312 /* 3313 * The caller does not necessarily hold an mmap_sem that would prevent 3314 * the anon_vma disappearing so we first we take a reference to it 3315 * and then lock the anon_vma for write. This is similar to 3316 * page_lock_anon_vma_read except the write lock is taken to serialise 3317 * against parallel split or collapse operations. 3318 */ 3319 anon_vma = page_get_anon_vma(head); 3320 if (!anon_vma) { 3321 ret = -EBUSY; 3322 goto out; 3323 } 3324 anon_vma_lock_write(anon_vma); 3325 3326 /* 3327 * Racy check if we can split the page, before freeze_page() will 3328 * split PMDs 3329 */ 3330 if (total_mapcount(head) != page_count(head) - 1) { 3331 ret = -EBUSY; 3332 goto out_unlock; 3333 } 3334 3335 mlocked = PageMlocked(page); 3336 freeze_page(head); 3337 VM_BUG_ON_PAGE(compound_mapcount(head), head); 3338 3339 /* Make sure the page is not on per-CPU pagevec as it takes pin */ 3340 if (mlocked) 3341 lru_add_drain(); 3342 3343 /* Prevent deferred_split_scan() touching ->_count */ 3344 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3345 count = page_count(head); 3346 mapcount = total_mapcount(head); 3347 if (!mapcount && count == 1) { 3348 if (!list_empty(page_deferred_list(head))) { 3349 pgdata->split_queue_len--; 3350 list_del(page_deferred_list(head)); 3351 } 3352 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3353 __split_huge_page(page, list); 3354 ret = 0; 3355 } else if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { 3356 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3357 pr_alert("total_mapcount: %u, page_count(): %u\n", 3358 mapcount, count); 3359 if (PageTail(page)) 3360 dump_page(head, NULL); 3361 dump_page(page, "total_mapcount(head) > 0"); 3362 BUG(); 3363 } else { 3364 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3365 unfreeze_page(head); 3366 ret = -EBUSY; 3367 } 3368 3369 out_unlock: 3370 anon_vma_unlock_write(anon_vma); 3371 put_anon_vma(anon_vma); 3372 out: 3373 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); 3374 return ret; 3375 } 3376 3377 void free_transhuge_page(struct page *page) 3378 { 3379 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page)); 3380 unsigned long flags; 3381 3382 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3383 if (!list_empty(page_deferred_list(page))) { 3384 pgdata->split_queue_len--; 3385 list_del(page_deferred_list(page)); 3386 } 3387 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3388 free_compound_page(page); 3389 } 3390 3391 void deferred_split_huge_page(struct page *page) 3392 { 3393 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page)); 3394 unsigned long flags; 3395 3396 VM_BUG_ON_PAGE(!PageTransHuge(page), page); 3397 3398 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3399 if (list_empty(page_deferred_list(page))) { 3400 count_vm_event(THP_DEFERRED_SPLIT_PAGE); 3401 list_add_tail(page_deferred_list(page), &pgdata->split_queue); 3402 pgdata->split_queue_len++; 3403 } 3404 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3405 } 3406 3407 static unsigned long deferred_split_count(struct shrinker *shrink, 3408 struct shrink_control *sc) 3409 { 3410 struct pglist_data *pgdata = NODE_DATA(sc->nid); 3411 return ACCESS_ONCE(pgdata->split_queue_len); 3412 } 3413 3414 static unsigned long deferred_split_scan(struct shrinker *shrink, 3415 struct shrink_control *sc) 3416 { 3417 struct pglist_data *pgdata = NODE_DATA(sc->nid); 3418 unsigned long flags; 3419 LIST_HEAD(list), *pos, *next; 3420 struct page *page; 3421 int split = 0; 3422 3423 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3424 /* Take pin on all head pages to avoid freeing them under us */ 3425 list_for_each_safe(pos, next, &pgdata->split_queue) { 3426 page = list_entry((void *)pos, struct page, mapping); 3427 page = compound_head(page); 3428 if (get_page_unless_zero(page)) { 3429 list_move(page_deferred_list(page), &list); 3430 } else { 3431 /* We lost race with put_compound_page() */ 3432 list_del_init(page_deferred_list(page)); 3433 pgdata->split_queue_len--; 3434 } 3435 if (!--sc->nr_to_scan) 3436 break; 3437 } 3438 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3439 3440 list_for_each_safe(pos, next, &list) { 3441 page = list_entry((void *)pos, struct page, mapping); 3442 lock_page(page); 3443 /* split_huge_page() removes page from list on success */ 3444 if (!split_huge_page(page)) 3445 split++; 3446 unlock_page(page); 3447 put_page(page); 3448 } 3449 3450 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3451 list_splice_tail(&list, &pgdata->split_queue); 3452 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3453 3454 /* 3455 * Stop shrinker if we didn't split any page, but the queue is empty. 3456 * This can happen if pages were freed under us. 3457 */ 3458 if (!split && list_empty(&pgdata->split_queue)) 3459 return SHRINK_STOP; 3460 return split; 3461 } 3462 3463 static struct shrinker deferred_split_shrinker = { 3464 .count_objects = deferred_split_count, 3465 .scan_objects = deferred_split_scan, 3466 .seeks = DEFAULT_SEEKS, 3467 .flags = SHRINKER_NUMA_AWARE, 3468 }; 3469 3470 #ifdef CONFIG_DEBUG_FS 3471 static int split_huge_pages_set(void *data, u64 val) 3472 { 3473 struct zone *zone; 3474 struct page *page; 3475 unsigned long pfn, max_zone_pfn; 3476 unsigned long total = 0, split = 0; 3477 3478 if (val != 1) 3479 return -EINVAL; 3480 3481 for_each_populated_zone(zone) { 3482 max_zone_pfn = zone_end_pfn(zone); 3483 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) { 3484 if (!pfn_valid(pfn)) 3485 continue; 3486 3487 page = pfn_to_page(pfn); 3488 if (!get_page_unless_zero(page)) 3489 continue; 3490 3491 if (zone != page_zone(page)) 3492 goto next; 3493 3494 if (!PageHead(page) || !PageAnon(page) || 3495 PageHuge(page)) 3496 goto next; 3497 3498 total++; 3499 lock_page(page); 3500 if (!split_huge_page(page)) 3501 split++; 3502 unlock_page(page); 3503 next: 3504 put_page(page); 3505 } 3506 } 3507 3508 pr_info("%lu of %lu THP split\n", split, total); 3509 3510 return 0; 3511 } 3512 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set, 3513 "%llu\n"); 3514 3515 static int __init split_huge_pages_debugfs(void) 3516 { 3517 void *ret; 3518 3519 ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL, 3520 &split_huge_pages_fops); 3521 if (!ret) 3522 pr_warn("Failed to create split_huge_pages in debugfs"); 3523 return 0; 3524 } 3525 late_initcall(split_huge_pages_debugfs); 3526 #endif 3527