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 static 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. We can do it by checking page_mapcount() on each sub-page, but 1302 * it's expensive. 1303 * The cheaper way is to check page_count() to be equal 1: every 1304 * mapcount takes page reference reference, so this way we can 1305 * guarantee, that the PMD is the only mapping. 1306 * This can give false negative if somebody pinned the page, but that's 1307 * fine. 1308 */ 1309 if (page_mapcount(page) == 1 && page_count(page) == 1) { 1310 pmd_t entry; 1311 entry = pmd_mkyoung(orig_pmd); 1312 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1313 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 1314 update_mmu_cache_pmd(vma, address, pmd); 1315 ret |= VM_FAULT_WRITE; 1316 goto out_unlock; 1317 } 1318 get_page(page); 1319 spin_unlock(ptl); 1320 alloc: 1321 if (transparent_hugepage_enabled(vma) && 1322 !transparent_hugepage_debug_cow()) { 1323 huge_gfp = alloc_hugepage_direct_gfpmask(vma); 1324 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER); 1325 } else 1326 new_page = NULL; 1327 1328 if (likely(new_page)) { 1329 prep_transhuge_page(new_page); 1330 } else { 1331 if (!page) { 1332 split_huge_pmd(vma, pmd, address); 1333 ret |= VM_FAULT_FALLBACK; 1334 } else { 1335 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 1336 pmd, orig_pmd, page, haddr); 1337 if (ret & VM_FAULT_OOM) { 1338 split_huge_pmd(vma, pmd, address); 1339 ret |= VM_FAULT_FALLBACK; 1340 } 1341 put_page(page); 1342 } 1343 count_vm_event(THP_FAULT_FALLBACK); 1344 goto out; 1345 } 1346 1347 if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg, 1348 true))) { 1349 put_page(new_page); 1350 if (page) { 1351 split_huge_pmd(vma, pmd, address); 1352 put_page(page); 1353 } else 1354 split_huge_pmd(vma, pmd, address); 1355 ret |= VM_FAULT_FALLBACK; 1356 count_vm_event(THP_FAULT_FALLBACK); 1357 goto out; 1358 } 1359 1360 count_vm_event(THP_FAULT_ALLOC); 1361 1362 if (!page) 1363 clear_huge_page(new_page, haddr, HPAGE_PMD_NR); 1364 else 1365 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 1366 __SetPageUptodate(new_page); 1367 1368 mmun_start = haddr; 1369 mmun_end = haddr + HPAGE_PMD_SIZE; 1370 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1371 1372 spin_lock(ptl); 1373 if (page) 1374 put_page(page); 1375 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 1376 spin_unlock(ptl); 1377 mem_cgroup_cancel_charge(new_page, memcg, true); 1378 put_page(new_page); 1379 goto out_mn; 1380 } else { 1381 pmd_t entry; 1382 entry = mk_huge_pmd(new_page, vma->vm_page_prot); 1383 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1384 pmdp_huge_clear_flush_notify(vma, haddr, pmd); 1385 page_add_new_anon_rmap(new_page, vma, haddr, true); 1386 mem_cgroup_commit_charge(new_page, memcg, false, true); 1387 lru_cache_add_active_or_unevictable(new_page, vma); 1388 set_pmd_at(mm, haddr, pmd, entry); 1389 update_mmu_cache_pmd(vma, address, pmd); 1390 if (!page) { 1391 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 1392 put_huge_zero_page(); 1393 } else { 1394 VM_BUG_ON_PAGE(!PageHead(page), page); 1395 page_remove_rmap(page, true); 1396 put_page(page); 1397 } 1398 ret |= VM_FAULT_WRITE; 1399 } 1400 spin_unlock(ptl); 1401 out_mn: 1402 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1403 out: 1404 return ret; 1405 out_unlock: 1406 spin_unlock(ptl); 1407 return ret; 1408 } 1409 1410 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1411 unsigned long addr, 1412 pmd_t *pmd, 1413 unsigned int flags) 1414 { 1415 struct mm_struct *mm = vma->vm_mm; 1416 struct page *page = NULL; 1417 1418 assert_spin_locked(pmd_lockptr(mm, pmd)); 1419 1420 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 1421 goto out; 1422 1423 /* Avoid dumping huge zero page */ 1424 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) 1425 return ERR_PTR(-EFAULT); 1426 1427 /* Full NUMA hinting faults to serialise migration in fault paths */ 1428 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) 1429 goto out; 1430 1431 page = pmd_page(*pmd); 1432 VM_BUG_ON_PAGE(!PageHead(page), page); 1433 if (flags & FOLL_TOUCH) 1434 touch_pmd(vma, addr, pmd); 1435 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 1436 /* 1437 * We don't mlock() pte-mapped THPs. This way we can avoid 1438 * leaking mlocked pages into non-VM_LOCKED VMAs. 1439 * 1440 * In most cases the pmd is the only mapping of the page as we 1441 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for 1442 * writable private mappings in populate_vma_page_range(). 1443 * 1444 * The only scenario when we have the page shared here is if we 1445 * mlocking read-only mapping shared over fork(). We skip 1446 * mlocking such pages. 1447 */ 1448 if (compound_mapcount(page) == 1 && !PageDoubleMap(page) && 1449 page->mapping && trylock_page(page)) { 1450 lru_add_drain(); 1451 if (page->mapping) 1452 mlock_vma_page(page); 1453 unlock_page(page); 1454 } 1455 } 1456 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1457 VM_BUG_ON_PAGE(!PageCompound(page), page); 1458 if (flags & FOLL_GET) 1459 get_page(page); 1460 1461 out: 1462 return page; 1463 } 1464 1465 /* NUMA hinting page fault entry point for trans huge pmds */ 1466 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, 1467 unsigned long addr, pmd_t pmd, pmd_t *pmdp) 1468 { 1469 spinlock_t *ptl; 1470 struct anon_vma *anon_vma = NULL; 1471 struct page *page; 1472 unsigned long haddr = addr & HPAGE_PMD_MASK; 1473 int page_nid = -1, this_nid = numa_node_id(); 1474 int target_nid, last_cpupid = -1; 1475 bool page_locked; 1476 bool migrated = false; 1477 bool was_writable; 1478 int flags = 0; 1479 1480 /* A PROT_NONE fault should not end up here */ 1481 BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))); 1482 1483 ptl = pmd_lock(mm, pmdp); 1484 if (unlikely(!pmd_same(pmd, *pmdp))) 1485 goto out_unlock; 1486 1487 /* 1488 * If there are potential migrations, wait for completion and retry 1489 * without disrupting NUMA hinting information. Do not relock and 1490 * check_same as the page may no longer be mapped. 1491 */ 1492 if (unlikely(pmd_trans_migrating(*pmdp))) { 1493 page = pmd_page(*pmdp); 1494 spin_unlock(ptl); 1495 wait_on_page_locked(page); 1496 goto out; 1497 } 1498 1499 page = pmd_page(pmd); 1500 BUG_ON(is_huge_zero_page(page)); 1501 page_nid = page_to_nid(page); 1502 last_cpupid = page_cpupid_last(page); 1503 count_vm_numa_event(NUMA_HINT_FAULTS); 1504 if (page_nid == this_nid) { 1505 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); 1506 flags |= TNF_FAULT_LOCAL; 1507 } 1508 1509 /* See similar comment in do_numa_page for explanation */ 1510 if (!(vma->vm_flags & VM_WRITE)) 1511 flags |= TNF_NO_GROUP; 1512 1513 /* 1514 * Acquire the page lock to serialise THP migrations but avoid dropping 1515 * page_table_lock if at all possible 1516 */ 1517 page_locked = trylock_page(page); 1518 target_nid = mpol_misplaced(page, vma, haddr); 1519 if (target_nid == -1) { 1520 /* If the page was locked, there are no parallel migrations */ 1521 if (page_locked) 1522 goto clear_pmdnuma; 1523 } 1524 1525 /* Migration could have started since the pmd_trans_migrating check */ 1526 if (!page_locked) { 1527 spin_unlock(ptl); 1528 wait_on_page_locked(page); 1529 page_nid = -1; 1530 goto out; 1531 } 1532 1533 /* 1534 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma 1535 * to serialises splits 1536 */ 1537 get_page(page); 1538 spin_unlock(ptl); 1539 anon_vma = page_lock_anon_vma_read(page); 1540 1541 /* Confirm the PMD did not change while page_table_lock was released */ 1542 spin_lock(ptl); 1543 if (unlikely(!pmd_same(pmd, *pmdp))) { 1544 unlock_page(page); 1545 put_page(page); 1546 page_nid = -1; 1547 goto out_unlock; 1548 } 1549 1550 /* Bail if we fail to protect against THP splits for any reason */ 1551 if (unlikely(!anon_vma)) { 1552 put_page(page); 1553 page_nid = -1; 1554 goto clear_pmdnuma; 1555 } 1556 1557 /* 1558 * Migrate the THP to the requested node, returns with page unlocked 1559 * and access rights restored. 1560 */ 1561 spin_unlock(ptl); 1562 migrated = migrate_misplaced_transhuge_page(mm, vma, 1563 pmdp, pmd, addr, page, target_nid); 1564 if (migrated) { 1565 flags |= TNF_MIGRATED; 1566 page_nid = target_nid; 1567 } else 1568 flags |= TNF_MIGRATE_FAIL; 1569 1570 goto out; 1571 clear_pmdnuma: 1572 BUG_ON(!PageLocked(page)); 1573 was_writable = pmd_write(pmd); 1574 pmd = pmd_modify(pmd, vma->vm_page_prot); 1575 pmd = pmd_mkyoung(pmd); 1576 if (was_writable) 1577 pmd = pmd_mkwrite(pmd); 1578 set_pmd_at(mm, haddr, pmdp, pmd); 1579 update_mmu_cache_pmd(vma, addr, pmdp); 1580 unlock_page(page); 1581 out_unlock: 1582 spin_unlock(ptl); 1583 1584 out: 1585 if (anon_vma) 1586 page_unlock_anon_vma_read(anon_vma); 1587 1588 if (page_nid != -1) 1589 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags); 1590 1591 return 0; 1592 } 1593 1594 int madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1595 pmd_t *pmd, unsigned long addr, unsigned long next) 1596 1597 { 1598 spinlock_t *ptl; 1599 pmd_t orig_pmd; 1600 struct page *page; 1601 struct mm_struct *mm = tlb->mm; 1602 int ret = 0; 1603 1604 ptl = pmd_trans_huge_lock(pmd, vma); 1605 if (!ptl) 1606 goto out_unlocked; 1607 1608 orig_pmd = *pmd; 1609 if (is_huge_zero_pmd(orig_pmd)) { 1610 ret = 1; 1611 goto out; 1612 } 1613 1614 page = pmd_page(orig_pmd); 1615 /* 1616 * If other processes are mapping this page, we couldn't discard 1617 * the page unless they all do MADV_FREE so let's skip the page. 1618 */ 1619 if (page_mapcount(page) != 1) 1620 goto out; 1621 1622 if (!trylock_page(page)) 1623 goto out; 1624 1625 /* 1626 * If user want to discard part-pages of THP, split it so MADV_FREE 1627 * will deactivate only them. 1628 */ 1629 if (next - addr != HPAGE_PMD_SIZE) { 1630 get_page(page); 1631 spin_unlock(ptl); 1632 if (split_huge_page(page)) { 1633 put_page(page); 1634 unlock_page(page); 1635 goto out_unlocked; 1636 } 1637 put_page(page); 1638 unlock_page(page); 1639 ret = 1; 1640 goto out_unlocked; 1641 } 1642 1643 if (PageDirty(page)) 1644 ClearPageDirty(page); 1645 unlock_page(page); 1646 1647 if (PageActive(page)) 1648 deactivate_page(page); 1649 1650 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { 1651 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, 1652 tlb->fullmm); 1653 orig_pmd = pmd_mkold(orig_pmd); 1654 orig_pmd = pmd_mkclean(orig_pmd); 1655 1656 set_pmd_at(mm, addr, pmd, orig_pmd); 1657 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1658 } 1659 ret = 1; 1660 out: 1661 spin_unlock(ptl); 1662 out_unlocked: 1663 return ret; 1664 } 1665 1666 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1667 pmd_t *pmd, unsigned long addr) 1668 { 1669 pmd_t orig_pmd; 1670 spinlock_t *ptl; 1671 1672 ptl = __pmd_trans_huge_lock(pmd, vma); 1673 if (!ptl) 1674 return 0; 1675 /* 1676 * For architectures like ppc64 we look at deposited pgtable 1677 * when calling pmdp_huge_get_and_clear. So do the 1678 * pgtable_trans_huge_withdraw after finishing pmdp related 1679 * operations. 1680 */ 1681 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, 1682 tlb->fullmm); 1683 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1684 if (vma_is_dax(vma)) { 1685 spin_unlock(ptl); 1686 if (is_huge_zero_pmd(orig_pmd)) 1687 put_huge_zero_page(); 1688 } else if (is_huge_zero_pmd(orig_pmd)) { 1689 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd)); 1690 atomic_long_dec(&tlb->mm->nr_ptes); 1691 spin_unlock(ptl); 1692 put_huge_zero_page(); 1693 } else { 1694 struct page *page = pmd_page(orig_pmd); 1695 page_remove_rmap(page, true); 1696 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); 1697 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1698 VM_BUG_ON_PAGE(!PageHead(page), page); 1699 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd)); 1700 atomic_long_dec(&tlb->mm->nr_ptes); 1701 spin_unlock(ptl); 1702 tlb_remove_page(tlb, page); 1703 } 1704 return 1; 1705 } 1706 1707 bool move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, 1708 unsigned long old_addr, 1709 unsigned long new_addr, unsigned long old_end, 1710 pmd_t *old_pmd, pmd_t *new_pmd) 1711 { 1712 spinlock_t *old_ptl, *new_ptl; 1713 pmd_t pmd; 1714 1715 struct mm_struct *mm = vma->vm_mm; 1716 1717 if ((old_addr & ~HPAGE_PMD_MASK) || 1718 (new_addr & ~HPAGE_PMD_MASK) || 1719 old_end - old_addr < HPAGE_PMD_SIZE || 1720 (new_vma->vm_flags & VM_NOHUGEPAGE)) 1721 return false; 1722 1723 /* 1724 * The destination pmd shouldn't be established, free_pgtables() 1725 * should have release it. 1726 */ 1727 if (WARN_ON(!pmd_none(*new_pmd))) { 1728 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1729 return false; 1730 } 1731 1732 /* 1733 * We don't have to worry about the ordering of src and dst 1734 * ptlocks because exclusive mmap_sem prevents deadlock. 1735 */ 1736 old_ptl = __pmd_trans_huge_lock(old_pmd, vma); 1737 if (old_ptl) { 1738 new_ptl = pmd_lockptr(mm, new_pmd); 1739 if (new_ptl != old_ptl) 1740 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 1741 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd); 1742 VM_BUG_ON(!pmd_none(*new_pmd)); 1743 1744 if (pmd_move_must_withdraw(new_ptl, old_ptl) && 1745 vma_is_anonymous(vma)) { 1746 pgtable_t pgtable; 1747 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); 1748 pgtable_trans_huge_deposit(mm, new_pmd, pgtable); 1749 } 1750 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd)); 1751 if (new_ptl != old_ptl) 1752 spin_unlock(new_ptl); 1753 spin_unlock(old_ptl); 1754 return true; 1755 } 1756 return false; 1757 } 1758 1759 /* 1760 * Returns 1761 * - 0 if PMD could not be locked 1762 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary 1763 * - HPAGE_PMD_NR is protections changed and TLB flush necessary 1764 */ 1765 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1766 unsigned long addr, pgprot_t newprot, int prot_numa) 1767 { 1768 struct mm_struct *mm = vma->vm_mm; 1769 spinlock_t *ptl; 1770 int ret = 0; 1771 1772 ptl = __pmd_trans_huge_lock(pmd, vma); 1773 if (ptl) { 1774 pmd_t entry; 1775 bool preserve_write = prot_numa && pmd_write(*pmd); 1776 ret = 1; 1777 1778 /* 1779 * Avoid trapping faults against the zero page. The read-only 1780 * data is likely to be read-cached on the local CPU and 1781 * local/remote hits to the zero page are not interesting. 1782 */ 1783 if (prot_numa && is_huge_zero_pmd(*pmd)) { 1784 spin_unlock(ptl); 1785 return ret; 1786 } 1787 1788 if (!prot_numa || !pmd_protnone(*pmd)) { 1789 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd); 1790 entry = pmd_modify(entry, newprot); 1791 if (preserve_write) 1792 entry = pmd_mkwrite(entry); 1793 ret = HPAGE_PMD_NR; 1794 set_pmd_at(mm, addr, pmd, entry); 1795 BUG_ON(!preserve_write && pmd_write(entry)); 1796 } 1797 spin_unlock(ptl); 1798 } 1799 1800 return ret; 1801 } 1802 1803 /* 1804 * Returns true if a given pmd maps a thp, false otherwise. 1805 * 1806 * Note that if it returns true, this routine returns without unlocking page 1807 * table lock. So callers must unlock it. 1808 */ 1809 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) 1810 { 1811 spinlock_t *ptl; 1812 ptl = pmd_lock(vma->vm_mm, pmd); 1813 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd))) 1814 return ptl; 1815 spin_unlock(ptl); 1816 return NULL; 1817 } 1818 1819 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE) 1820 1821 int hugepage_madvise(struct vm_area_struct *vma, 1822 unsigned long *vm_flags, int advice) 1823 { 1824 switch (advice) { 1825 case MADV_HUGEPAGE: 1826 #ifdef CONFIG_S390 1827 /* 1828 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 1829 * can't handle this properly after s390_enable_sie, so we simply 1830 * ignore the madvise to prevent qemu from causing a SIGSEGV. 1831 */ 1832 if (mm_has_pgste(vma->vm_mm)) 1833 return 0; 1834 #endif 1835 /* 1836 * Be somewhat over-protective like KSM for now! 1837 */ 1838 if (*vm_flags & VM_NO_THP) 1839 return -EINVAL; 1840 *vm_flags &= ~VM_NOHUGEPAGE; 1841 *vm_flags |= VM_HUGEPAGE; 1842 /* 1843 * If the vma become good for khugepaged to scan, 1844 * register it here without waiting a page fault that 1845 * may not happen any time soon. 1846 */ 1847 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags))) 1848 return -ENOMEM; 1849 break; 1850 case MADV_NOHUGEPAGE: 1851 /* 1852 * Be somewhat over-protective like KSM for now! 1853 */ 1854 if (*vm_flags & VM_NO_THP) 1855 return -EINVAL; 1856 *vm_flags &= ~VM_HUGEPAGE; 1857 *vm_flags |= VM_NOHUGEPAGE; 1858 /* 1859 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1860 * this vma even if we leave the mm registered in khugepaged if 1861 * it got registered before VM_NOHUGEPAGE was set. 1862 */ 1863 break; 1864 } 1865 1866 return 0; 1867 } 1868 1869 static int __init khugepaged_slab_init(void) 1870 { 1871 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1872 sizeof(struct mm_slot), 1873 __alignof__(struct mm_slot), 0, NULL); 1874 if (!mm_slot_cache) 1875 return -ENOMEM; 1876 1877 return 0; 1878 } 1879 1880 static void __init khugepaged_slab_exit(void) 1881 { 1882 kmem_cache_destroy(mm_slot_cache); 1883 } 1884 1885 static inline struct mm_slot *alloc_mm_slot(void) 1886 { 1887 if (!mm_slot_cache) /* initialization failed */ 1888 return NULL; 1889 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 1890 } 1891 1892 static inline void free_mm_slot(struct mm_slot *mm_slot) 1893 { 1894 kmem_cache_free(mm_slot_cache, mm_slot); 1895 } 1896 1897 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 1898 { 1899 struct mm_slot *mm_slot; 1900 1901 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) 1902 if (mm == mm_slot->mm) 1903 return mm_slot; 1904 1905 return NULL; 1906 } 1907 1908 static void insert_to_mm_slots_hash(struct mm_struct *mm, 1909 struct mm_slot *mm_slot) 1910 { 1911 mm_slot->mm = mm; 1912 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); 1913 } 1914 1915 static inline int khugepaged_test_exit(struct mm_struct *mm) 1916 { 1917 return atomic_read(&mm->mm_users) == 0; 1918 } 1919 1920 int __khugepaged_enter(struct mm_struct *mm) 1921 { 1922 struct mm_slot *mm_slot; 1923 int wakeup; 1924 1925 mm_slot = alloc_mm_slot(); 1926 if (!mm_slot) 1927 return -ENOMEM; 1928 1929 /* __khugepaged_exit() must not run from under us */ 1930 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); 1931 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 1932 free_mm_slot(mm_slot); 1933 return 0; 1934 } 1935 1936 spin_lock(&khugepaged_mm_lock); 1937 insert_to_mm_slots_hash(mm, mm_slot); 1938 /* 1939 * Insert just behind the scanning cursor, to let the area settle 1940 * down a little. 1941 */ 1942 wakeup = list_empty(&khugepaged_scan.mm_head); 1943 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 1944 spin_unlock(&khugepaged_mm_lock); 1945 1946 atomic_inc(&mm->mm_count); 1947 if (wakeup) 1948 wake_up_interruptible(&khugepaged_wait); 1949 1950 return 0; 1951 } 1952 1953 int khugepaged_enter_vma_merge(struct vm_area_struct *vma, 1954 unsigned long vm_flags) 1955 { 1956 unsigned long hstart, hend; 1957 if (!vma->anon_vma) 1958 /* 1959 * Not yet faulted in so we will register later in the 1960 * page fault if needed. 1961 */ 1962 return 0; 1963 if (vma->vm_ops) 1964 /* khugepaged not yet working on file or special mappings */ 1965 return 0; 1966 VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma); 1967 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1968 hend = vma->vm_end & HPAGE_PMD_MASK; 1969 if (hstart < hend) 1970 return khugepaged_enter(vma, vm_flags); 1971 return 0; 1972 } 1973 1974 void __khugepaged_exit(struct mm_struct *mm) 1975 { 1976 struct mm_slot *mm_slot; 1977 int free = 0; 1978 1979 spin_lock(&khugepaged_mm_lock); 1980 mm_slot = get_mm_slot(mm); 1981 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 1982 hash_del(&mm_slot->hash); 1983 list_del(&mm_slot->mm_node); 1984 free = 1; 1985 } 1986 spin_unlock(&khugepaged_mm_lock); 1987 1988 if (free) { 1989 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1990 free_mm_slot(mm_slot); 1991 mmdrop(mm); 1992 } else if (mm_slot) { 1993 /* 1994 * This is required to serialize against 1995 * khugepaged_test_exit() (which is guaranteed to run 1996 * under mmap sem read mode). Stop here (after we 1997 * return all pagetables will be destroyed) until 1998 * khugepaged has finished working on the pagetables 1999 * under the mmap_sem. 2000 */ 2001 down_write(&mm->mmap_sem); 2002 up_write(&mm->mmap_sem); 2003 } 2004 } 2005 2006 static void release_pte_page(struct page *page) 2007 { 2008 /* 0 stands for page_is_file_cache(page) == false */ 2009 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 2010 unlock_page(page); 2011 putback_lru_page(page); 2012 } 2013 2014 static void release_pte_pages(pte_t *pte, pte_t *_pte) 2015 { 2016 while (--_pte >= pte) { 2017 pte_t pteval = *_pte; 2018 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) 2019 release_pte_page(pte_page(pteval)); 2020 } 2021 } 2022 2023 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 2024 unsigned long address, 2025 pte_t *pte) 2026 { 2027 struct page *page = NULL; 2028 pte_t *_pte; 2029 int none_or_zero = 0, result = 0; 2030 bool referenced = false, writable = false; 2031 2032 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 2033 _pte++, address += PAGE_SIZE) { 2034 pte_t pteval = *_pte; 2035 if (pte_none(pteval) || (pte_present(pteval) && 2036 is_zero_pfn(pte_pfn(pteval)))) { 2037 if (!userfaultfd_armed(vma) && 2038 ++none_or_zero <= khugepaged_max_ptes_none) { 2039 continue; 2040 } else { 2041 result = SCAN_EXCEED_NONE_PTE; 2042 goto out; 2043 } 2044 } 2045 if (!pte_present(pteval)) { 2046 result = SCAN_PTE_NON_PRESENT; 2047 goto out; 2048 } 2049 page = vm_normal_page(vma, address, pteval); 2050 if (unlikely(!page)) { 2051 result = SCAN_PAGE_NULL; 2052 goto out; 2053 } 2054 2055 VM_BUG_ON_PAGE(PageCompound(page), page); 2056 VM_BUG_ON_PAGE(!PageAnon(page), page); 2057 VM_BUG_ON_PAGE(!PageSwapBacked(page), page); 2058 2059 /* 2060 * We can do it before isolate_lru_page because the 2061 * page can't be freed from under us. NOTE: PG_lock 2062 * is needed to serialize against split_huge_page 2063 * when invoked from the VM. 2064 */ 2065 if (!trylock_page(page)) { 2066 result = SCAN_PAGE_LOCK; 2067 goto out; 2068 } 2069 2070 /* 2071 * cannot use mapcount: can't collapse if there's a gup pin. 2072 * The page must only be referenced by the scanned process 2073 * and page swap cache. 2074 */ 2075 if (page_count(page) != 1 + !!PageSwapCache(page)) { 2076 unlock_page(page); 2077 result = SCAN_PAGE_COUNT; 2078 goto out; 2079 } 2080 if (pte_write(pteval)) { 2081 writable = true; 2082 } else { 2083 if (PageSwapCache(page) && !reuse_swap_page(page)) { 2084 unlock_page(page); 2085 result = SCAN_SWAP_CACHE_PAGE; 2086 goto out; 2087 } 2088 /* 2089 * Page is not in the swap cache. It can be collapsed 2090 * into a THP. 2091 */ 2092 } 2093 2094 /* 2095 * Isolate the page to avoid collapsing an hugepage 2096 * currently in use by the VM. 2097 */ 2098 if (isolate_lru_page(page)) { 2099 unlock_page(page); 2100 result = SCAN_DEL_PAGE_LRU; 2101 goto out; 2102 } 2103 /* 0 stands for page_is_file_cache(page) == false */ 2104 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 2105 VM_BUG_ON_PAGE(!PageLocked(page), page); 2106 VM_BUG_ON_PAGE(PageLRU(page), page); 2107 2108 /* If there is no mapped pte young don't collapse the page */ 2109 if (pte_young(pteval) || 2110 page_is_young(page) || PageReferenced(page) || 2111 mmu_notifier_test_young(vma->vm_mm, address)) 2112 referenced = true; 2113 } 2114 if (likely(writable)) { 2115 if (likely(referenced)) { 2116 result = SCAN_SUCCEED; 2117 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 2118 referenced, writable, result); 2119 return 1; 2120 } 2121 } else { 2122 result = SCAN_PAGE_RO; 2123 } 2124 2125 out: 2126 release_pte_pages(pte, _pte); 2127 trace_mm_collapse_huge_page_isolate(page, none_or_zero, 2128 referenced, writable, result); 2129 return 0; 2130 } 2131 2132 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 2133 struct vm_area_struct *vma, 2134 unsigned long address, 2135 spinlock_t *ptl) 2136 { 2137 pte_t *_pte; 2138 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 2139 pte_t pteval = *_pte; 2140 struct page *src_page; 2141 2142 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 2143 clear_user_highpage(page, address); 2144 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 2145 if (is_zero_pfn(pte_pfn(pteval))) { 2146 /* 2147 * ptl mostly unnecessary. 2148 */ 2149 spin_lock(ptl); 2150 /* 2151 * paravirt calls inside pte_clear here are 2152 * superfluous. 2153 */ 2154 pte_clear(vma->vm_mm, address, _pte); 2155 spin_unlock(ptl); 2156 } 2157 } else { 2158 src_page = pte_page(pteval); 2159 copy_user_highpage(page, src_page, address, vma); 2160 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); 2161 release_pte_page(src_page); 2162 /* 2163 * ptl mostly unnecessary, but preempt has to 2164 * be disabled to update the per-cpu stats 2165 * inside page_remove_rmap(). 2166 */ 2167 spin_lock(ptl); 2168 /* 2169 * paravirt calls inside pte_clear here are 2170 * superfluous. 2171 */ 2172 pte_clear(vma->vm_mm, address, _pte); 2173 page_remove_rmap(src_page, false); 2174 spin_unlock(ptl); 2175 free_page_and_swap_cache(src_page); 2176 } 2177 2178 address += PAGE_SIZE; 2179 page++; 2180 } 2181 } 2182 2183 static void khugepaged_alloc_sleep(void) 2184 { 2185 DEFINE_WAIT(wait); 2186 2187 add_wait_queue(&khugepaged_wait, &wait); 2188 freezable_schedule_timeout_interruptible( 2189 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 2190 remove_wait_queue(&khugepaged_wait, &wait); 2191 } 2192 2193 static int khugepaged_node_load[MAX_NUMNODES]; 2194 2195 static bool khugepaged_scan_abort(int nid) 2196 { 2197 int i; 2198 2199 /* 2200 * If zone_reclaim_mode is disabled, then no extra effort is made to 2201 * allocate memory locally. 2202 */ 2203 if (!zone_reclaim_mode) 2204 return false; 2205 2206 /* If there is a count for this node already, it must be acceptable */ 2207 if (khugepaged_node_load[nid]) 2208 return false; 2209 2210 for (i = 0; i < MAX_NUMNODES; i++) { 2211 if (!khugepaged_node_load[i]) 2212 continue; 2213 if (node_distance(nid, i) > RECLAIM_DISTANCE) 2214 return true; 2215 } 2216 return false; 2217 } 2218 2219 #ifdef CONFIG_NUMA 2220 static int khugepaged_find_target_node(void) 2221 { 2222 static int last_khugepaged_target_node = NUMA_NO_NODE; 2223 int nid, target_node = 0, max_value = 0; 2224 2225 /* find first node with max normal pages hit */ 2226 for (nid = 0; nid < MAX_NUMNODES; nid++) 2227 if (khugepaged_node_load[nid] > max_value) { 2228 max_value = khugepaged_node_load[nid]; 2229 target_node = nid; 2230 } 2231 2232 /* do some balance if several nodes have the same hit record */ 2233 if (target_node <= last_khugepaged_target_node) 2234 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; 2235 nid++) 2236 if (max_value == khugepaged_node_load[nid]) { 2237 target_node = nid; 2238 break; 2239 } 2240 2241 last_khugepaged_target_node = target_node; 2242 return target_node; 2243 } 2244 2245 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2246 { 2247 if (IS_ERR(*hpage)) { 2248 if (!*wait) 2249 return false; 2250 2251 *wait = false; 2252 *hpage = NULL; 2253 khugepaged_alloc_sleep(); 2254 } else if (*hpage) { 2255 put_page(*hpage); 2256 *hpage = NULL; 2257 } 2258 2259 return true; 2260 } 2261 2262 static struct page * 2263 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm, 2264 unsigned long address, int node) 2265 { 2266 VM_BUG_ON_PAGE(*hpage, *hpage); 2267 2268 /* 2269 * Before allocating the hugepage, release the mmap_sem read lock. 2270 * The allocation can take potentially a long time if it involves 2271 * sync compaction, and we do not need to hold the mmap_sem during 2272 * that. We will recheck the vma after taking it again in write mode. 2273 */ 2274 up_read(&mm->mmap_sem); 2275 2276 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); 2277 if (unlikely(!*hpage)) { 2278 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2279 *hpage = ERR_PTR(-ENOMEM); 2280 return NULL; 2281 } 2282 2283 prep_transhuge_page(*hpage); 2284 count_vm_event(THP_COLLAPSE_ALLOC); 2285 return *hpage; 2286 } 2287 #else 2288 static int khugepaged_find_target_node(void) 2289 { 2290 return 0; 2291 } 2292 2293 static inline struct page *alloc_khugepaged_hugepage(void) 2294 { 2295 struct page *page; 2296 2297 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), 2298 HPAGE_PMD_ORDER); 2299 if (page) 2300 prep_transhuge_page(page); 2301 return page; 2302 } 2303 2304 static struct page *khugepaged_alloc_hugepage(bool *wait) 2305 { 2306 struct page *hpage; 2307 2308 do { 2309 hpage = alloc_khugepaged_hugepage(); 2310 if (!hpage) { 2311 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2312 if (!*wait) 2313 return NULL; 2314 2315 *wait = false; 2316 khugepaged_alloc_sleep(); 2317 } else 2318 count_vm_event(THP_COLLAPSE_ALLOC); 2319 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 2320 2321 return hpage; 2322 } 2323 2324 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 2325 { 2326 if (!*hpage) 2327 *hpage = khugepaged_alloc_hugepage(wait); 2328 2329 if (unlikely(!*hpage)) 2330 return false; 2331 2332 return true; 2333 } 2334 2335 static struct page * 2336 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm, 2337 unsigned long address, int node) 2338 { 2339 up_read(&mm->mmap_sem); 2340 VM_BUG_ON(!*hpage); 2341 2342 return *hpage; 2343 } 2344 #endif 2345 2346 static bool hugepage_vma_check(struct vm_area_struct *vma) 2347 { 2348 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 2349 (vma->vm_flags & VM_NOHUGEPAGE)) 2350 return false; 2351 if (!vma->anon_vma || vma->vm_ops) 2352 return false; 2353 if (is_vma_temporary_stack(vma)) 2354 return false; 2355 VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma); 2356 return true; 2357 } 2358 2359 static void collapse_huge_page(struct mm_struct *mm, 2360 unsigned long address, 2361 struct page **hpage, 2362 struct vm_area_struct *vma, 2363 int node) 2364 { 2365 pmd_t *pmd, _pmd; 2366 pte_t *pte; 2367 pgtable_t pgtable; 2368 struct page *new_page; 2369 spinlock_t *pmd_ptl, *pte_ptl; 2370 int isolated = 0, result = 0; 2371 unsigned long hstart, hend; 2372 struct mem_cgroup *memcg; 2373 unsigned long mmun_start; /* For mmu_notifiers */ 2374 unsigned long mmun_end; /* For mmu_notifiers */ 2375 gfp_t gfp; 2376 2377 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2378 2379 /* Only allocate from the target node */ 2380 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE; 2381 2382 /* release the mmap_sem read lock. */ 2383 new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node); 2384 if (!new_page) { 2385 result = SCAN_ALLOC_HUGE_PAGE_FAIL; 2386 goto out_nolock; 2387 } 2388 2389 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { 2390 result = SCAN_CGROUP_CHARGE_FAIL; 2391 goto out_nolock; 2392 } 2393 2394 /* 2395 * Prevent all access to pagetables with the exception of 2396 * gup_fast later hanlded by the ptep_clear_flush and the VM 2397 * handled by the anon_vma lock + PG_lock. 2398 */ 2399 down_write(&mm->mmap_sem); 2400 if (unlikely(khugepaged_test_exit(mm))) { 2401 result = SCAN_ANY_PROCESS; 2402 goto out; 2403 } 2404 2405 vma = find_vma(mm, address); 2406 if (!vma) { 2407 result = SCAN_VMA_NULL; 2408 goto out; 2409 } 2410 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2411 hend = vma->vm_end & HPAGE_PMD_MASK; 2412 if (address < hstart || address + HPAGE_PMD_SIZE > hend) { 2413 result = SCAN_ADDRESS_RANGE; 2414 goto out; 2415 } 2416 if (!hugepage_vma_check(vma)) { 2417 result = SCAN_VMA_CHECK; 2418 goto out; 2419 } 2420 pmd = mm_find_pmd(mm, address); 2421 if (!pmd) { 2422 result = SCAN_PMD_NULL; 2423 goto out; 2424 } 2425 2426 anon_vma_lock_write(vma->anon_vma); 2427 2428 pte = pte_offset_map(pmd, address); 2429 pte_ptl = pte_lockptr(mm, pmd); 2430 2431 mmun_start = address; 2432 mmun_end = address + HPAGE_PMD_SIZE; 2433 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 2434 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ 2435 /* 2436 * After this gup_fast can't run anymore. This also removes 2437 * any huge TLB entry from the CPU so we won't allow 2438 * huge and small TLB entries for the same virtual address 2439 * to avoid the risk of CPU bugs in that area. 2440 */ 2441 _pmd = pmdp_collapse_flush(vma, address, pmd); 2442 spin_unlock(pmd_ptl); 2443 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2444 2445 spin_lock(pte_ptl); 2446 isolated = __collapse_huge_page_isolate(vma, address, pte); 2447 spin_unlock(pte_ptl); 2448 2449 if (unlikely(!isolated)) { 2450 pte_unmap(pte); 2451 spin_lock(pmd_ptl); 2452 BUG_ON(!pmd_none(*pmd)); 2453 /* 2454 * We can only use set_pmd_at when establishing 2455 * hugepmds and never for establishing regular pmds that 2456 * points to regular pagetables. Use pmd_populate for that 2457 */ 2458 pmd_populate(mm, pmd, pmd_pgtable(_pmd)); 2459 spin_unlock(pmd_ptl); 2460 anon_vma_unlock_write(vma->anon_vma); 2461 result = SCAN_FAIL; 2462 goto out; 2463 } 2464 2465 /* 2466 * All pages are isolated and locked so anon_vma rmap 2467 * can't run anymore. 2468 */ 2469 anon_vma_unlock_write(vma->anon_vma); 2470 2471 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); 2472 pte_unmap(pte); 2473 __SetPageUptodate(new_page); 2474 pgtable = pmd_pgtable(_pmd); 2475 2476 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); 2477 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 2478 2479 /* 2480 * spin_lock() below is not the equivalent of smp_wmb(), so 2481 * this is needed to avoid the copy_huge_page writes to become 2482 * visible after the set_pmd_at() write. 2483 */ 2484 smp_wmb(); 2485 2486 spin_lock(pmd_ptl); 2487 BUG_ON(!pmd_none(*pmd)); 2488 page_add_new_anon_rmap(new_page, vma, address, true); 2489 mem_cgroup_commit_charge(new_page, memcg, false, true); 2490 lru_cache_add_active_or_unevictable(new_page, vma); 2491 pgtable_trans_huge_deposit(mm, pmd, pgtable); 2492 set_pmd_at(mm, address, pmd, _pmd); 2493 update_mmu_cache_pmd(vma, address, pmd); 2494 spin_unlock(pmd_ptl); 2495 2496 *hpage = NULL; 2497 2498 khugepaged_pages_collapsed++; 2499 result = SCAN_SUCCEED; 2500 out_up_write: 2501 up_write(&mm->mmap_sem); 2502 trace_mm_collapse_huge_page(mm, isolated, result); 2503 return; 2504 2505 out_nolock: 2506 trace_mm_collapse_huge_page(mm, isolated, result); 2507 return; 2508 out: 2509 mem_cgroup_cancel_charge(new_page, memcg, true); 2510 goto out_up_write; 2511 } 2512 2513 static int khugepaged_scan_pmd(struct mm_struct *mm, 2514 struct vm_area_struct *vma, 2515 unsigned long address, 2516 struct page **hpage) 2517 { 2518 pmd_t *pmd; 2519 pte_t *pte, *_pte; 2520 int ret = 0, none_or_zero = 0, result = 0; 2521 struct page *page = NULL; 2522 unsigned long _address; 2523 spinlock_t *ptl; 2524 int node = NUMA_NO_NODE; 2525 bool writable = false, referenced = false; 2526 2527 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2528 2529 pmd = mm_find_pmd(mm, address); 2530 if (!pmd) { 2531 result = SCAN_PMD_NULL; 2532 goto out; 2533 } 2534 2535 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); 2536 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2537 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2538 _pte++, _address += PAGE_SIZE) { 2539 pte_t pteval = *_pte; 2540 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { 2541 if (!userfaultfd_armed(vma) && 2542 ++none_or_zero <= khugepaged_max_ptes_none) { 2543 continue; 2544 } else { 2545 result = SCAN_EXCEED_NONE_PTE; 2546 goto out_unmap; 2547 } 2548 } 2549 if (!pte_present(pteval)) { 2550 result = SCAN_PTE_NON_PRESENT; 2551 goto out_unmap; 2552 } 2553 if (pte_write(pteval)) 2554 writable = true; 2555 2556 page = vm_normal_page(vma, _address, pteval); 2557 if (unlikely(!page)) { 2558 result = SCAN_PAGE_NULL; 2559 goto out_unmap; 2560 } 2561 2562 /* TODO: teach khugepaged to collapse THP mapped with pte */ 2563 if (PageCompound(page)) { 2564 result = SCAN_PAGE_COMPOUND; 2565 goto out_unmap; 2566 } 2567 2568 /* 2569 * Record which node the original page is from and save this 2570 * information to khugepaged_node_load[]. 2571 * Khupaged will allocate hugepage from the node has the max 2572 * hit record. 2573 */ 2574 node = page_to_nid(page); 2575 if (khugepaged_scan_abort(node)) { 2576 result = SCAN_SCAN_ABORT; 2577 goto out_unmap; 2578 } 2579 khugepaged_node_load[node]++; 2580 if (!PageLRU(page)) { 2581 result = SCAN_PAGE_LRU; 2582 goto out_unmap; 2583 } 2584 if (PageLocked(page)) { 2585 result = SCAN_PAGE_LOCK; 2586 goto out_unmap; 2587 } 2588 if (!PageAnon(page)) { 2589 result = SCAN_PAGE_ANON; 2590 goto out_unmap; 2591 } 2592 2593 /* 2594 * cannot use mapcount: can't collapse if there's a gup pin. 2595 * The page must only be referenced by the scanned process 2596 * and page swap cache. 2597 */ 2598 if (page_count(page) != 1 + !!PageSwapCache(page)) { 2599 result = SCAN_PAGE_COUNT; 2600 goto out_unmap; 2601 } 2602 if (pte_young(pteval) || 2603 page_is_young(page) || PageReferenced(page) || 2604 mmu_notifier_test_young(vma->vm_mm, address)) 2605 referenced = true; 2606 } 2607 if (writable) { 2608 if (referenced) { 2609 result = SCAN_SUCCEED; 2610 ret = 1; 2611 } else { 2612 result = SCAN_NO_REFERENCED_PAGE; 2613 } 2614 } else { 2615 result = SCAN_PAGE_RO; 2616 } 2617 out_unmap: 2618 pte_unmap_unlock(pte, ptl); 2619 if (ret) { 2620 node = khugepaged_find_target_node(); 2621 /* collapse_huge_page will return with the mmap_sem released */ 2622 collapse_huge_page(mm, address, hpage, vma, node); 2623 } 2624 out: 2625 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, 2626 none_or_zero, result); 2627 return ret; 2628 } 2629 2630 static void collect_mm_slot(struct mm_slot *mm_slot) 2631 { 2632 struct mm_struct *mm = mm_slot->mm; 2633 2634 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2635 2636 if (khugepaged_test_exit(mm)) { 2637 /* free mm_slot */ 2638 hash_del(&mm_slot->hash); 2639 list_del(&mm_slot->mm_node); 2640 2641 /* 2642 * Not strictly needed because the mm exited already. 2643 * 2644 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2645 */ 2646 2647 /* khugepaged_mm_lock actually not necessary for the below */ 2648 free_mm_slot(mm_slot); 2649 mmdrop(mm); 2650 } 2651 } 2652 2653 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2654 struct page **hpage) 2655 __releases(&khugepaged_mm_lock) 2656 __acquires(&khugepaged_mm_lock) 2657 { 2658 struct mm_slot *mm_slot; 2659 struct mm_struct *mm; 2660 struct vm_area_struct *vma; 2661 int progress = 0; 2662 2663 VM_BUG_ON(!pages); 2664 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2665 2666 if (khugepaged_scan.mm_slot) 2667 mm_slot = khugepaged_scan.mm_slot; 2668 else { 2669 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2670 struct mm_slot, mm_node); 2671 khugepaged_scan.address = 0; 2672 khugepaged_scan.mm_slot = mm_slot; 2673 } 2674 spin_unlock(&khugepaged_mm_lock); 2675 2676 mm = mm_slot->mm; 2677 down_read(&mm->mmap_sem); 2678 if (unlikely(khugepaged_test_exit(mm))) 2679 vma = NULL; 2680 else 2681 vma = find_vma(mm, khugepaged_scan.address); 2682 2683 progress++; 2684 for (; vma; vma = vma->vm_next) { 2685 unsigned long hstart, hend; 2686 2687 cond_resched(); 2688 if (unlikely(khugepaged_test_exit(mm))) { 2689 progress++; 2690 break; 2691 } 2692 if (!hugepage_vma_check(vma)) { 2693 skip: 2694 progress++; 2695 continue; 2696 } 2697 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2698 hend = vma->vm_end & HPAGE_PMD_MASK; 2699 if (hstart >= hend) 2700 goto skip; 2701 if (khugepaged_scan.address > hend) 2702 goto skip; 2703 if (khugepaged_scan.address < hstart) 2704 khugepaged_scan.address = hstart; 2705 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2706 2707 while (khugepaged_scan.address < hend) { 2708 int ret; 2709 cond_resched(); 2710 if (unlikely(khugepaged_test_exit(mm))) 2711 goto breakouterloop; 2712 2713 VM_BUG_ON(khugepaged_scan.address < hstart || 2714 khugepaged_scan.address + HPAGE_PMD_SIZE > 2715 hend); 2716 ret = khugepaged_scan_pmd(mm, vma, 2717 khugepaged_scan.address, 2718 hpage); 2719 /* move to next address */ 2720 khugepaged_scan.address += HPAGE_PMD_SIZE; 2721 progress += HPAGE_PMD_NR; 2722 if (ret) 2723 /* we released mmap_sem so break loop */ 2724 goto breakouterloop_mmap_sem; 2725 if (progress >= pages) 2726 goto breakouterloop; 2727 } 2728 } 2729 breakouterloop: 2730 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2731 breakouterloop_mmap_sem: 2732 2733 spin_lock(&khugepaged_mm_lock); 2734 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2735 /* 2736 * Release the current mm_slot if this mm is about to die, or 2737 * if we scanned all vmas of this mm. 2738 */ 2739 if (khugepaged_test_exit(mm) || !vma) { 2740 /* 2741 * Make sure that if mm_users is reaching zero while 2742 * khugepaged runs here, khugepaged_exit will find 2743 * mm_slot not pointing to the exiting mm. 2744 */ 2745 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2746 khugepaged_scan.mm_slot = list_entry( 2747 mm_slot->mm_node.next, 2748 struct mm_slot, mm_node); 2749 khugepaged_scan.address = 0; 2750 } else { 2751 khugepaged_scan.mm_slot = NULL; 2752 khugepaged_full_scans++; 2753 } 2754 2755 collect_mm_slot(mm_slot); 2756 } 2757 2758 return progress; 2759 } 2760 2761 static int khugepaged_has_work(void) 2762 { 2763 return !list_empty(&khugepaged_scan.mm_head) && 2764 khugepaged_enabled(); 2765 } 2766 2767 static int khugepaged_wait_event(void) 2768 { 2769 return !list_empty(&khugepaged_scan.mm_head) || 2770 kthread_should_stop(); 2771 } 2772 2773 static void khugepaged_do_scan(void) 2774 { 2775 struct page *hpage = NULL; 2776 unsigned int progress = 0, pass_through_head = 0; 2777 unsigned int pages = khugepaged_pages_to_scan; 2778 bool wait = true; 2779 2780 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2781 2782 while (progress < pages) { 2783 if (!khugepaged_prealloc_page(&hpage, &wait)) 2784 break; 2785 2786 cond_resched(); 2787 2788 if (unlikely(kthread_should_stop() || try_to_freeze())) 2789 break; 2790 2791 spin_lock(&khugepaged_mm_lock); 2792 if (!khugepaged_scan.mm_slot) 2793 pass_through_head++; 2794 if (khugepaged_has_work() && 2795 pass_through_head < 2) 2796 progress += khugepaged_scan_mm_slot(pages - progress, 2797 &hpage); 2798 else 2799 progress = pages; 2800 spin_unlock(&khugepaged_mm_lock); 2801 } 2802 2803 if (!IS_ERR_OR_NULL(hpage)) 2804 put_page(hpage); 2805 } 2806 2807 static void khugepaged_wait_work(void) 2808 { 2809 if (khugepaged_has_work()) { 2810 if (!khugepaged_scan_sleep_millisecs) 2811 return; 2812 2813 wait_event_freezable_timeout(khugepaged_wait, 2814 kthread_should_stop(), 2815 msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); 2816 return; 2817 } 2818 2819 if (khugepaged_enabled()) 2820 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 2821 } 2822 2823 static int khugepaged(void *none) 2824 { 2825 struct mm_slot *mm_slot; 2826 2827 set_freezable(); 2828 set_user_nice(current, MAX_NICE); 2829 2830 while (!kthread_should_stop()) { 2831 khugepaged_do_scan(); 2832 khugepaged_wait_work(); 2833 } 2834 2835 spin_lock(&khugepaged_mm_lock); 2836 mm_slot = khugepaged_scan.mm_slot; 2837 khugepaged_scan.mm_slot = NULL; 2838 if (mm_slot) 2839 collect_mm_slot(mm_slot); 2840 spin_unlock(&khugepaged_mm_lock); 2841 return 0; 2842 } 2843 2844 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2845 unsigned long haddr, pmd_t *pmd) 2846 { 2847 struct mm_struct *mm = vma->vm_mm; 2848 pgtable_t pgtable; 2849 pmd_t _pmd; 2850 int i; 2851 2852 /* leave pmd empty until pte is filled */ 2853 pmdp_huge_clear_flush_notify(vma, haddr, pmd); 2854 2855 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2856 pmd_populate(mm, &_pmd, pgtable); 2857 2858 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2859 pte_t *pte, entry; 2860 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2861 entry = pte_mkspecial(entry); 2862 pte = pte_offset_map(&_pmd, haddr); 2863 VM_BUG_ON(!pte_none(*pte)); 2864 set_pte_at(mm, haddr, pte, entry); 2865 pte_unmap(pte); 2866 } 2867 smp_wmb(); /* make pte visible before pmd */ 2868 pmd_populate(mm, pmd, pgtable); 2869 put_huge_zero_page(); 2870 } 2871 2872 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 2873 unsigned long haddr, bool freeze) 2874 { 2875 struct mm_struct *mm = vma->vm_mm; 2876 struct page *page; 2877 pgtable_t pgtable; 2878 pmd_t _pmd; 2879 bool young, write, dirty; 2880 unsigned long addr; 2881 int i; 2882 2883 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK); 2884 VM_BUG_ON_VMA(vma->vm_start > haddr, vma); 2885 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma); 2886 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)); 2887 2888 count_vm_event(THP_SPLIT_PMD); 2889 2890 if (vma_is_dax(vma)) { 2891 pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd); 2892 if (is_huge_zero_pmd(_pmd)) 2893 put_huge_zero_page(); 2894 return; 2895 } else if (is_huge_zero_pmd(*pmd)) { 2896 return __split_huge_zero_page_pmd(vma, haddr, pmd); 2897 } 2898 2899 page = pmd_page(*pmd); 2900 VM_BUG_ON_PAGE(!page_count(page), page); 2901 page_ref_add(page, HPAGE_PMD_NR - 1); 2902 write = pmd_write(*pmd); 2903 young = pmd_young(*pmd); 2904 dirty = pmd_dirty(*pmd); 2905 2906 pmdp_huge_split_prepare(vma, haddr, pmd); 2907 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2908 pmd_populate(mm, &_pmd, pgtable); 2909 2910 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { 2911 pte_t entry, *pte; 2912 /* 2913 * Note that NUMA hinting access restrictions are not 2914 * transferred to avoid any possibility of altering 2915 * permissions across VMAs. 2916 */ 2917 if (freeze) { 2918 swp_entry_t swp_entry; 2919 swp_entry = make_migration_entry(page + i, write); 2920 entry = swp_entry_to_pte(swp_entry); 2921 } else { 2922 entry = mk_pte(page + i, vma->vm_page_prot); 2923 entry = maybe_mkwrite(entry, vma); 2924 if (!write) 2925 entry = pte_wrprotect(entry); 2926 if (!young) 2927 entry = pte_mkold(entry); 2928 } 2929 if (dirty) 2930 SetPageDirty(page + i); 2931 pte = pte_offset_map(&_pmd, addr); 2932 BUG_ON(!pte_none(*pte)); 2933 set_pte_at(mm, addr, pte, entry); 2934 atomic_inc(&page[i]._mapcount); 2935 pte_unmap(pte); 2936 } 2937 2938 /* 2939 * Set PG_double_map before dropping compound_mapcount to avoid 2940 * false-negative page_mapped(). 2941 */ 2942 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) { 2943 for (i = 0; i < HPAGE_PMD_NR; i++) 2944 atomic_inc(&page[i]._mapcount); 2945 } 2946 2947 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { 2948 /* Last compound_mapcount is gone. */ 2949 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); 2950 if (TestClearPageDoubleMap(page)) { 2951 /* No need in mapcount reference anymore */ 2952 for (i = 0; i < HPAGE_PMD_NR; i++) 2953 atomic_dec(&page[i]._mapcount); 2954 } 2955 } 2956 2957 smp_wmb(); /* make pte visible before pmd */ 2958 /* 2959 * Up to this point the pmd is present and huge and userland has the 2960 * whole access to the hugepage during the split (which happens in 2961 * place). If we overwrite the pmd with the not-huge version pointing 2962 * to the pte here (which of course we could if all CPUs were bug 2963 * free), userland could trigger a small page size TLB miss on the 2964 * small sized TLB while the hugepage TLB entry is still established in 2965 * the huge TLB. Some CPU doesn't like that. 2966 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum 2967 * 383 on page 93. Intel should be safe but is also warns that it's 2968 * only safe if the permission and cache attributes of the two entries 2969 * loaded in the two TLB is identical (which should be the case here). 2970 * But it is generally safer to never allow small and huge TLB entries 2971 * for the same virtual address to be loaded simultaneously. So instead 2972 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the 2973 * current pmd notpresent (atomically because here the pmd_trans_huge 2974 * and pmd_trans_splitting must remain set at all times on the pmd 2975 * until the split is complete for this pmd), then we flush the SMP TLB 2976 * and finally we write the non-huge version of the pmd entry with 2977 * pmd_populate. 2978 */ 2979 pmdp_invalidate(vma, haddr, pmd); 2980 pmd_populate(mm, pmd, pgtable); 2981 2982 if (freeze) { 2983 for (i = 0; i < HPAGE_PMD_NR; i++) { 2984 page_remove_rmap(page + i, false); 2985 put_page(page + i); 2986 } 2987 } 2988 } 2989 2990 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 2991 unsigned long address, bool freeze) 2992 { 2993 spinlock_t *ptl; 2994 struct mm_struct *mm = vma->vm_mm; 2995 unsigned long haddr = address & HPAGE_PMD_MASK; 2996 2997 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE); 2998 ptl = pmd_lock(mm, pmd); 2999 if (pmd_trans_huge(*pmd)) { 3000 struct page *page = pmd_page(*pmd); 3001 if (PageMlocked(page)) 3002 clear_page_mlock(page); 3003 } else if (!pmd_devmap(*pmd)) 3004 goto out; 3005 __split_huge_pmd_locked(vma, pmd, haddr, freeze); 3006 out: 3007 spin_unlock(ptl); 3008 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE); 3009 } 3010 3011 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, 3012 bool freeze, struct page *page) 3013 { 3014 pgd_t *pgd; 3015 pud_t *pud; 3016 pmd_t *pmd; 3017 3018 pgd = pgd_offset(vma->vm_mm, address); 3019 if (!pgd_present(*pgd)) 3020 return; 3021 3022 pud = pud_offset(pgd, address); 3023 if (!pud_present(*pud)) 3024 return; 3025 3026 pmd = pmd_offset(pud, address); 3027 if (!pmd_present(*pmd) || (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd))) 3028 return; 3029 3030 /* 3031 * If caller asks to setup a migration entries, we need a page to check 3032 * pmd against. Otherwise we can end up replacing wrong page. 3033 */ 3034 VM_BUG_ON(freeze && !page); 3035 if (page && page != pmd_page(*pmd)) 3036 return; 3037 3038 /* 3039 * Caller holds the mmap_sem write mode, so a huge pmd cannot 3040 * materialize from under us. 3041 */ 3042 __split_huge_pmd(vma, pmd, address, freeze); 3043 } 3044 3045 void vma_adjust_trans_huge(struct vm_area_struct *vma, 3046 unsigned long start, 3047 unsigned long end, 3048 long adjust_next) 3049 { 3050 /* 3051 * If the new start address isn't hpage aligned and it could 3052 * previously contain an hugepage: check if we need to split 3053 * an huge pmd. 3054 */ 3055 if (start & ~HPAGE_PMD_MASK && 3056 (start & HPAGE_PMD_MASK) >= vma->vm_start && 3057 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 3058 split_huge_pmd_address(vma, start, false, NULL); 3059 3060 /* 3061 * If the new end address isn't hpage aligned and it could 3062 * previously contain an hugepage: check if we need to split 3063 * an huge pmd. 3064 */ 3065 if (end & ~HPAGE_PMD_MASK && 3066 (end & HPAGE_PMD_MASK) >= vma->vm_start && 3067 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 3068 split_huge_pmd_address(vma, end, false, NULL); 3069 3070 /* 3071 * If we're also updating the vma->vm_next->vm_start, if the new 3072 * vm_next->vm_start isn't page aligned and it could previously 3073 * contain an hugepage: check if we need to split an huge pmd. 3074 */ 3075 if (adjust_next > 0) { 3076 struct vm_area_struct *next = vma->vm_next; 3077 unsigned long nstart = next->vm_start; 3078 nstart += adjust_next << PAGE_SHIFT; 3079 if (nstart & ~HPAGE_PMD_MASK && 3080 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 3081 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 3082 split_huge_pmd_address(next, nstart, false, NULL); 3083 } 3084 } 3085 3086 static void freeze_page(struct page *page) 3087 { 3088 enum ttu_flags ttu_flags = TTU_MIGRATION | TTU_IGNORE_MLOCK | 3089 TTU_IGNORE_ACCESS | TTU_RMAP_LOCKED; 3090 int i, ret; 3091 3092 VM_BUG_ON_PAGE(!PageHead(page), page); 3093 3094 /* We only need TTU_SPLIT_HUGE_PMD once */ 3095 ret = try_to_unmap(page, ttu_flags | TTU_SPLIT_HUGE_PMD); 3096 for (i = 1; !ret && i < HPAGE_PMD_NR; i++) { 3097 /* Cut short if the page is unmapped */ 3098 if (page_count(page) == 1) 3099 return; 3100 3101 ret = try_to_unmap(page + i, ttu_flags); 3102 } 3103 VM_BUG_ON(ret); 3104 } 3105 3106 static void unfreeze_page(struct page *page) 3107 { 3108 int i; 3109 3110 for (i = 0; i < HPAGE_PMD_NR; i++) 3111 remove_migration_ptes(page + i, page + i, true); 3112 } 3113 3114 static void __split_huge_page_tail(struct page *head, int tail, 3115 struct lruvec *lruvec, struct list_head *list) 3116 { 3117 struct page *page_tail = head + tail; 3118 3119 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); 3120 VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail); 3121 3122 /* 3123 * tail_page->_count is zero and not changing from under us. But 3124 * get_page_unless_zero() may be running from under us on the 3125 * tail_page. If we used atomic_set() below instead of atomic_inc(), we 3126 * would then run atomic_set() concurrently with 3127 * get_page_unless_zero(), and atomic_set() is implemented in C not 3128 * using locked ops. spin_unlock on x86 sometime uses locked ops 3129 * because of PPro errata 66, 92, so unless somebody can guarantee 3130 * atomic_set() here would be safe on all archs (and not only on x86), 3131 * it's safer to use atomic_inc(). 3132 */ 3133 page_ref_inc(page_tail); 3134 3135 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; 3136 page_tail->flags |= (head->flags & 3137 ((1L << PG_referenced) | 3138 (1L << PG_swapbacked) | 3139 (1L << PG_mlocked) | 3140 (1L << PG_uptodate) | 3141 (1L << PG_active) | 3142 (1L << PG_locked) | 3143 (1L << PG_unevictable) | 3144 (1L << PG_dirty))); 3145 3146 /* 3147 * After clearing PageTail the gup refcount can be released. 3148 * Page flags also must be visible before we make the page non-compound. 3149 */ 3150 smp_wmb(); 3151 3152 clear_compound_head(page_tail); 3153 3154 if (page_is_young(head)) 3155 set_page_young(page_tail); 3156 if (page_is_idle(head)) 3157 set_page_idle(page_tail); 3158 3159 /* ->mapping in first tail page is compound_mapcount */ 3160 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING, 3161 page_tail); 3162 page_tail->mapping = head->mapping; 3163 3164 page_tail->index = head->index + tail; 3165 page_cpupid_xchg_last(page_tail, page_cpupid_last(head)); 3166 lru_add_page_tail(head, page_tail, lruvec, list); 3167 } 3168 3169 static void __split_huge_page(struct page *page, struct list_head *list) 3170 { 3171 struct page *head = compound_head(page); 3172 struct zone *zone = page_zone(head); 3173 struct lruvec *lruvec; 3174 int i; 3175 3176 /* prevent PageLRU to go away from under us, and freeze lru stats */ 3177 spin_lock_irq(&zone->lru_lock); 3178 lruvec = mem_cgroup_page_lruvec(head, zone); 3179 3180 /* complete memcg works before add pages to LRU */ 3181 mem_cgroup_split_huge_fixup(head); 3182 3183 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) 3184 __split_huge_page_tail(head, i, lruvec, list); 3185 3186 ClearPageCompound(head); 3187 spin_unlock_irq(&zone->lru_lock); 3188 3189 unfreeze_page(head); 3190 3191 for (i = 0; i < HPAGE_PMD_NR; i++) { 3192 struct page *subpage = head + i; 3193 if (subpage == page) 3194 continue; 3195 unlock_page(subpage); 3196 3197 /* 3198 * Subpages may be freed if there wasn't any mapping 3199 * like if add_to_swap() is running on a lru page that 3200 * had its mapping zapped. And freeing these pages 3201 * requires taking the lru_lock so we do the put_page 3202 * of the tail pages after the split is complete. 3203 */ 3204 put_page(subpage); 3205 } 3206 } 3207 3208 int total_mapcount(struct page *page) 3209 { 3210 int i, ret; 3211 3212 VM_BUG_ON_PAGE(PageTail(page), page); 3213 3214 if (likely(!PageCompound(page))) 3215 return atomic_read(&page->_mapcount) + 1; 3216 3217 ret = compound_mapcount(page); 3218 if (PageHuge(page)) 3219 return ret; 3220 for (i = 0; i < HPAGE_PMD_NR; i++) 3221 ret += atomic_read(&page[i]._mapcount) + 1; 3222 if (PageDoubleMap(page)) 3223 ret -= HPAGE_PMD_NR; 3224 return ret; 3225 } 3226 3227 /* 3228 * This function splits huge page into normal pages. @page can point to any 3229 * subpage of huge page to split. Split doesn't change the position of @page. 3230 * 3231 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY. 3232 * The huge page must be locked. 3233 * 3234 * If @list is null, tail pages will be added to LRU list, otherwise, to @list. 3235 * 3236 * Both head page and tail pages will inherit mapping, flags, and so on from 3237 * the hugepage. 3238 * 3239 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if 3240 * they are not mapped. 3241 * 3242 * Returns 0 if the hugepage is split successfully. 3243 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under 3244 * us. 3245 */ 3246 int split_huge_page_to_list(struct page *page, struct list_head *list) 3247 { 3248 struct page *head = compound_head(page); 3249 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head)); 3250 struct anon_vma *anon_vma; 3251 int count, mapcount, ret; 3252 bool mlocked; 3253 unsigned long flags; 3254 3255 VM_BUG_ON_PAGE(is_huge_zero_page(page), page); 3256 VM_BUG_ON_PAGE(!PageAnon(page), page); 3257 VM_BUG_ON_PAGE(!PageLocked(page), page); 3258 VM_BUG_ON_PAGE(!PageSwapBacked(page), page); 3259 VM_BUG_ON_PAGE(!PageCompound(page), page); 3260 3261 /* 3262 * The caller does not necessarily hold an mmap_sem that would prevent 3263 * the anon_vma disappearing so we first we take a reference to it 3264 * and then lock the anon_vma for write. This is similar to 3265 * page_lock_anon_vma_read except the write lock is taken to serialise 3266 * against parallel split or collapse operations. 3267 */ 3268 anon_vma = page_get_anon_vma(head); 3269 if (!anon_vma) { 3270 ret = -EBUSY; 3271 goto out; 3272 } 3273 anon_vma_lock_write(anon_vma); 3274 3275 /* 3276 * Racy check if we can split the page, before freeze_page() will 3277 * split PMDs 3278 */ 3279 if (total_mapcount(head) != page_count(head) - 1) { 3280 ret = -EBUSY; 3281 goto out_unlock; 3282 } 3283 3284 mlocked = PageMlocked(page); 3285 freeze_page(head); 3286 VM_BUG_ON_PAGE(compound_mapcount(head), head); 3287 3288 /* Make sure the page is not on per-CPU pagevec as it takes pin */ 3289 if (mlocked) 3290 lru_add_drain(); 3291 3292 /* Prevent deferred_split_scan() touching ->_count */ 3293 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3294 count = page_count(head); 3295 mapcount = total_mapcount(head); 3296 if (!mapcount && count == 1) { 3297 if (!list_empty(page_deferred_list(head))) { 3298 pgdata->split_queue_len--; 3299 list_del(page_deferred_list(head)); 3300 } 3301 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3302 __split_huge_page(page, list); 3303 ret = 0; 3304 } else if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { 3305 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3306 pr_alert("total_mapcount: %u, page_count(): %u\n", 3307 mapcount, count); 3308 if (PageTail(page)) 3309 dump_page(head, NULL); 3310 dump_page(page, "total_mapcount(head) > 0"); 3311 BUG(); 3312 } else { 3313 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3314 unfreeze_page(head); 3315 ret = -EBUSY; 3316 } 3317 3318 out_unlock: 3319 anon_vma_unlock_write(anon_vma); 3320 put_anon_vma(anon_vma); 3321 out: 3322 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); 3323 return ret; 3324 } 3325 3326 void free_transhuge_page(struct page *page) 3327 { 3328 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page)); 3329 unsigned long flags; 3330 3331 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3332 if (!list_empty(page_deferred_list(page))) { 3333 pgdata->split_queue_len--; 3334 list_del(page_deferred_list(page)); 3335 } 3336 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3337 free_compound_page(page); 3338 } 3339 3340 void deferred_split_huge_page(struct page *page) 3341 { 3342 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page)); 3343 unsigned long flags; 3344 3345 VM_BUG_ON_PAGE(!PageTransHuge(page), page); 3346 3347 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3348 if (list_empty(page_deferred_list(page))) { 3349 count_vm_event(THP_DEFERRED_SPLIT_PAGE); 3350 list_add_tail(page_deferred_list(page), &pgdata->split_queue); 3351 pgdata->split_queue_len++; 3352 } 3353 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3354 } 3355 3356 static unsigned long deferred_split_count(struct shrinker *shrink, 3357 struct shrink_control *sc) 3358 { 3359 struct pglist_data *pgdata = NODE_DATA(sc->nid); 3360 return ACCESS_ONCE(pgdata->split_queue_len); 3361 } 3362 3363 static unsigned long deferred_split_scan(struct shrinker *shrink, 3364 struct shrink_control *sc) 3365 { 3366 struct pglist_data *pgdata = NODE_DATA(sc->nid); 3367 unsigned long flags; 3368 LIST_HEAD(list), *pos, *next; 3369 struct page *page; 3370 int split = 0; 3371 3372 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3373 /* Take pin on all head pages to avoid freeing them under us */ 3374 list_for_each_safe(pos, next, &pgdata->split_queue) { 3375 page = list_entry((void *)pos, struct page, mapping); 3376 page = compound_head(page); 3377 if (get_page_unless_zero(page)) { 3378 list_move(page_deferred_list(page), &list); 3379 } else { 3380 /* We lost race with put_compound_page() */ 3381 list_del_init(page_deferred_list(page)); 3382 pgdata->split_queue_len--; 3383 } 3384 if (!--sc->nr_to_scan) 3385 break; 3386 } 3387 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3388 3389 list_for_each_safe(pos, next, &list) { 3390 page = list_entry((void *)pos, struct page, mapping); 3391 lock_page(page); 3392 /* split_huge_page() removes page from list on success */ 3393 if (!split_huge_page(page)) 3394 split++; 3395 unlock_page(page); 3396 put_page(page); 3397 } 3398 3399 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 3400 list_splice_tail(&list, &pgdata->split_queue); 3401 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 3402 3403 /* 3404 * Stop shrinker if we didn't split any page, but the queue is empty. 3405 * This can happen if pages were freed under us. 3406 */ 3407 if (!split && list_empty(&pgdata->split_queue)) 3408 return SHRINK_STOP; 3409 return split; 3410 } 3411 3412 static struct shrinker deferred_split_shrinker = { 3413 .count_objects = deferred_split_count, 3414 .scan_objects = deferred_split_scan, 3415 .seeks = DEFAULT_SEEKS, 3416 .flags = SHRINKER_NUMA_AWARE, 3417 }; 3418 3419 #ifdef CONFIG_DEBUG_FS 3420 static int split_huge_pages_set(void *data, u64 val) 3421 { 3422 struct zone *zone; 3423 struct page *page; 3424 unsigned long pfn, max_zone_pfn; 3425 unsigned long total = 0, split = 0; 3426 3427 if (val != 1) 3428 return -EINVAL; 3429 3430 for_each_populated_zone(zone) { 3431 max_zone_pfn = zone_end_pfn(zone); 3432 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) { 3433 if (!pfn_valid(pfn)) 3434 continue; 3435 3436 page = pfn_to_page(pfn); 3437 if (!get_page_unless_zero(page)) 3438 continue; 3439 3440 if (zone != page_zone(page)) 3441 goto next; 3442 3443 if (!PageHead(page) || !PageAnon(page) || 3444 PageHuge(page)) 3445 goto next; 3446 3447 total++; 3448 lock_page(page); 3449 if (!split_huge_page(page)) 3450 split++; 3451 unlock_page(page); 3452 next: 3453 put_page(page); 3454 } 3455 } 3456 3457 pr_info("%lu of %lu THP split", split, total); 3458 3459 return 0; 3460 } 3461 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set, 3462 "%llu\n"); 3463 3464 static int __init split_huge_pages_debugfs(void) 3465 { 3466 void *ret; 3467 3468 ret = debugfs_create_file("split_huge_pages", 0644, NULL, NULL, 3469 &split_huge_pages_fops); 3470 if (!ret) 3471 pr_warn("Failed to create split_huge_pages in debugfs"); 3472 return 0; 3473 } 3474 late_initcall(split_huge_pages_debugfs); 3475 #endif 3476