huge_memory.c revision e27e6151b154ff6e5e8162efa291bc60196d29ea
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#include <linux/mm.h> 9#include <linux/sched.h> 10#include <linux/highmem.h> 11#include <linux/hugetlb.h> 12#include <linux/mmu_notifier.h> 13#include <linux/rmap.h> 14#include <linux/swap.h> 15#include <linux/mm_inline.h> 16#include <linux/kthread.h> 17#include <linux/khugepaged.h> 18#include <linux/freezer.h> 19#include <linux/mman.h> 20#include <asm/tlb.h> 21#include <asm/pgalloc.h> 22#include "internal.h" 23 24/* 25 * By default transparent hugepage support is enabled for all mappings 26 * and khugepaged scans all mappings. Defrag is only invoked by 27 * khugepaged hugepage allocations and by page faults inside 28 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived 29 * allocations. 30 */ 31unsigned long transparent_hugepage_flags __read_mostly = 32#ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS 33 (1<<TRANSPARENT_HUGEPAGE_FLAG)| 34#endif 35#ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE 36 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| 37#endif 38 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)| 39 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 40 41/* default scan 8*512 pte (or vmas) every 30 second */ 42static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8; 43static unsigned int khugepaged_pages_collapsed; 44static unsigned int khugepaged_full_scans; 45static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 46/* during fragmentation poll the hugepage allocator once every minute */ 47static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 48static struct task_struct *khugepaged_thread __read_mostly; 49static DEFINE_MUTEX(khugepaged_mutex); 50static DEFINE_SPINLOCK(khugepaged_mm_lock); 51static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 52/* 53 * default collapse hugepages if there is at least one pte mapped like 54 * it would have happened if the vma was large enough during page 55 * fault. 56 */ 57static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1; 58 59static int khugepaged(void *none); 60static int mm_slots_hash_init(void); 61static int khugepaged_slab_init(void); 62static void khugepaged_slab_free(void); 63 64#define MM_SLOTS_HASH_HEADS 1024 65static struct hlist_head *mm_slots_hash __read_mostly; 66static struct kmem_cache *mm_slot_cache __read_mostly; 67 68/** 69 * struct mm_slot - hash lookup from mm to mm_slot 70 * @hash: hash collision list 71 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 72 * @mm: the mm that this information is valid for 73 */ 74struct mm_slot { 75 struct hlist_node hash; 76 struct list_head mm_node; 77 struct mm_struct *mm; 78}; 79 80/** 81 * struct khugepaged_scan - cursor for scanning 82 * @mm_head: the head of the mm list to scan 83 * @mm_slot: the current mm_slot we are scanning 84 * @address: the next address inside that to be scanned 85 * 86 * There is only the one khugepaged_scan instance of this cursor structure. 87 */ 88struct khugepaged_scan { 89 struct list_head mm_head; 90 struct mm_slot *mm_slot; 91 unsigned long address; 92} khugepaged_scan = { 93 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 94}; 95 96 97static int set_recommended_min_free_kbytes(void) 98{ 99 struct zone *zone; 100 int nr_zones = 0; 101 unsigned long recommended_min; 102 extern int min_free_kbytes; 103 104 if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG, 105 &transparent_hugepage_flags) && 106 !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 107 &transparent_hugepage_flags)) 108 return 0; 109 110 for_each_populated_zone(zone) 111 nr_zones++; 112 113 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */ 114 recommended_min = pageblock_nr_pages * nr_zones * 2; 115 116 /* 117 * Make sure that on average at least two pageblocks are almost free 118 * of another type, one for a migratetype to fall back to and a 119 * second to avoid subsequent fallbacks of other types There are 3 120 * MIGRATE_TYPES we care about. 121 */ 122 recommended_min += pageblock_nr_pages * nr_zones * 123 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; 124 125 /* don't ever allow to reserve more than 5% of the lowmem */ 126 recommended_min = min(recommended_min, 127 (unsigned long) nr_free_buffer_pages() / 20); 128 recommended_min <<= (PAGE_SHIFT-10); 129 130 if (recommended_min > min_free_kbytes) 131 min_free_kbytes = recommended_min; 132 setup_per_zone_wmarks(); 133 return 0; 134} 135late_initcall(set_recommended_min_free_kbytes); 136 137static int start_khugepaged(void) 138{ 139 int err = 0; 140 if (khugepaged_enabled()) { 141 int wakeup; 142 if (unlikely(!mm_slot_cache || !mm_slots_hash)) { 143 err = -ENOMEM; 144 goto out; 145 } 146 mutex_lock(&khugepaged_mutex); 147 if (!khugepaged_thread) 148 khugepaged_thread = kthread_run(khugepaged, NULL, 149 "khugepaged"); 150 if (unlikely(IS_ERR(khugepaged_thread))) { 151 printk(KERN_ERR 152 "khugepaged: kthread_run(khugepaged) failed\n"); 153 err = PTR_ERR(khugepaged_thread); 154 khugepaged_thread = NULL; 155 } 156 wakeup = !list_empty(&khugepaged_scan.mm_head); 157 mutex_unlock(&khugepaged_mutex); 158 if (wakeup) 159 wake_up_interruptible(&khugepaged_wait); 160 161 set_recommended_min_free_kbytes(); 162 } else 163 /* wakeup to exit */ 164 wake_up_interruptible(&khugepaged_wait); 165out: 166 return err; 167} 168 169#ifdef CONFIG_SYSFS 170 171static ssize_t double_flag_show(struct kobject *kobj, 172 struct kobj_attribute *attr, char *buf, 173 enum transparent_hugepage_flag enabled, 174 enum transparent_hugepage_flag req_madv) 175{ 176 if (test_bit(enabled, &transparent_hugepage_flags)) { 177 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); 178 return sprintf(buf, "[always] madvise never\n"); 179 } else if (test_bit(req_madv, &transparent_hugepage_flags)) 180 return sprintf(buf, "always [madvise] never\n"); 181 else 182 return sprintf(buf, "always madvise [never]\n"); 183} 184static ssize_t double_flag_store(struct kobject *kobj, 185 struct kobj_attribute *attr, 186 const char *buf, size_t count, 187 enum transparent_hugepage_flag enabled, 188 enum transparent_hugepage_flag req_madv) 189{ 190 if (!memcmp("always", buf, 191 min(sizeof("always")-1, count))) { 192 set_bit(enabled, &transparent_hugepage_flags); 193 clear_bit(req_madv, &transparent_hugepage_flags); 194 } else if (!memcmp("madvise", buf, 195 min(sizeof("madvise")-1, count))) { 196 clear_bit(enabled, &transparent_hugepage_flags); 197 set_bit(req_madv, &transparent_hugepage_flags); 198 } else if (!memcmp("never", buf, 199 min(sizeof("never")-1, count))) { 200 clear_bit(enabled, &transparent_hugepage_flags); 201 clear_bit(req_madv, &transparent_hugepage_flags); 202 } else 203 return -EINVAL; 204 205 return count; 206} 207 208static ssize_t enabled_show(struct kobject *kobj, 209 struct kobj_attribute *attr, char *buf) 210{ 211 return double_flag_show(kobj, attr, buf, 212 TRANSPARENT_HUGEPAGE_FLAG, 213 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 214} 215static ssize_t enabled_store(struct kobject *kobj, 216 struct kobj_attribute *attr, 217 const char *buf, size_t count) 218{ 219 ssize_t ret; 220 221 ret = double_flag_store(kobj, attr, buf, count, 222 TRANSPARENT_HUGEPAGE_FLAG, 223 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 224 225 if (ret > 0) { 226 int err = start_khugepaged(); 227 if (err) 228 ret = err; 229 } 230 231 if (ret > 0 && 232 (test_bit(TRANSPARENT_HUGEPAGE_FLAG, 233 &transparent_hugepage_flags) || 234 test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 235 &transparent_hugepage_flags))) 236 set_recommended_min_free_kbytes(); 237 238 return ret; 239} 240static struct kobj_attribute enabled_attr = 241 __ATTR(enabled, 0644, enabled_show, enabled_store); 242 243static ssize_t single_flag_show(struct kobject *kobj, 244 struct kobj_attribute *attr, char *buf, 245 enum transparent_hugepage_flag flag) 246{ 247 return sprintf(buf, "%d\n", 248 !!test_bit(flag, &transparent_hugepage_flags)); 249} 250 251static ssize_t single_flag_store(struct kobject *kobj, 252 struct kobj_attribute *attr, 253 const char *buf, size_t count, 254 enum transparent_hugepage_flag flag) 255{ 256 unsigned long value; 257 int ret; 258 259 ret = kstrtoul(buf, 10, &value); 260 if (ret < 0) 261 return ret; 262 if (value > 1) 263 return -EINVAL; 264 265 if (value) 266 set_bit(flag, &transparent_hugepage_flags); 267 else 268 clear_bit(flag, &transparent_hugepage_flags); 269 270 return count; 271} 272 273/* 274 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind 275 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of 276 * memory just to allocate one more hugepage. 277 */ 278static ssize_t defrag_show(struct kobject *kobj, 279 struct kobj_attribute *attr, char *buf) 280{ 281 return double_flag_show(kobj, attr, buf, 282 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 283 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 284} 285static ssize_t defrag_store(struct kobject *kobj, 286 struct kobj_attribute *attr, 287 const char *buf, size_t count) 288{ 289 return double_flag_store(kobj, attr, buf, count, 290 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 291 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 292} 293static struct kobj_attribute defrag_attr = 294 __ATTR(defrag, 0644, defrag_show, defrag_store); 295 296#ifdef CONFIG_DEBUG_VM 297static ssize_t debug_cow_show(struct kobject *kobj, 298 struct kobj_attribute *attr, char *buf) 299{ 300 return single_flag_show(kobj, attr, buf, 301 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 302} 303static ssize_t debug_cow_store(struct kobject *kobj, 304 struct kobj_attribute *attr, 305 const char *buf, size_t count) 306{ 307 return single_flag_store(kobj, attr, buf, count, 308 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 309} 310static struct kobj_attribute debug_cow_attr = 311 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 312#endif /* CONFIG_DEBUG_VM */ 313 314static struct attribute *hugepage_attr[] = { 315 &enabled_attr.attr, 316 &defrag_attr.attr, 317#ifdef CONFIG_DEBUG_VM 318 &debug_cow_attr.attr, 319#endif 320 NULL, 321}; 322 323static struct attribute_group hugepage_attr_group = { 324 .attrs = hugepage_attr, 325}; 326 327static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 328 struct kobj_attribute *attr, 329 char *buf) 330{ 331 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 332} 333 334static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 335 struct kobj_attribute *attr, 336 const char *buf, size_t count) 337{ 338 unsigned long msecs; 339 int err; 340 341 err = strict_strtoul(buf, 10, &msecs); 342 if (err || msecs > UINT_MAX) 343 return -EINVAL; 344 345 khugepaged_scan_sleep_millisecs = msecs; 346 wake_up_interruptible(&khugepaged_wait); 347 348 return count; 349} 350static struct kobj_attribute scan_sleep_millisecs_attr = 351 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 352 scan_sleep_millisecs_store); 353 354static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 355 struct kobj_attribute *attr, 356 char *buf) 357{ 358 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 359} 360 361static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 362 struct kobj_attribute *attr, 363 const char *buf, size_t count) 364{ 365 unsigned long msecs; 366 int err; 367 368 err = strict_strtoul(buf, 10, &msecs); 369 if (err || msecs > UINT_MAX) 370 return -EINVAL; 371 372 khugepaged_alloc_sleep_millisecs = msecs; 373 wake_up_interruptible(&khugepaged_wait); 374 375 return count; 376} 377static struct kobj_attribute alloc_sleep_millisecs_attr = 378 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 379 alloc_sleep_millisecs_store); 380 381static ssize_t pages_to_scan_show(struct kobject *kobj, 382 struct kobj_attribute *attr, 383 char *buf) 384{ 385 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 386} 387static ssize_t pages_to_scan_store(struct kobject *kobj, 388 struct kobj_attribute *attr, 389 const char *buf, size_t count) 390{ 391 int err; 392 unsigned long pages; 393 394 err = strict_strtoul(buf, 10, &pages); 395 if (err || !pages || pages > UINT_MAX) 396 return -EINVAL; 397 398 khugepaged_pages_to_scan = pages; 399 400 return count; 401} 402static struct kobj_attribute pages_to_scan_attr = 403 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 404 pages_to_scan_store); 405 406static ssize_t pages_collapsed_show(struct kobject *kobj, 407 struct kobj_attribute *attr, 408 char *buf) 409{ 410 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 411} 412static struct kobj_attribute pages_collapsed_attr = 413 __ATTR_RO(pages_collapsed); 414 415static ssize_t full_scans_show(struct kobject *kobj, 416 struct kobj_attribute *attr, 417 char *buf) 418{ 419 return sprintf(buf, "%u\n", khugepaged_full_scans); 420} 421static struct kobj_attribute full_scans_attr = 422 __ATTR_RO(full_scans); 423 424static ssize_t khugepaged_defrag_show(struct kobject *kobj, 425 struct kobj_attribute *attr, char *buf) 426{ 427 return single_flag_show(kobj, attr, buf, 428 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 429} 430static ssize_t khugepaged_defrag_store(struct kobject *kobj, 431 struct kobj_attribute *attr, 432 const char *buf, size_t count) 433{ 434 return single_flag_store(kobj, attr, buf, count, 435 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 436} 437static struct kobj_attribute khugepaged_defrag_attr = 438 __ATTR(defrag, 0644, khugepaged_defrag_show, 439 khugepaged_defrag_store); 440 441/* 442 * max_ptes_none controls if khugepaged should collapse hugepages over 443 * any unmapped ptes in turn potentially increasing the memory 444 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 445 * reduce the available free memory in the system as it 446 * runs. Increasing max_ptes_none will instead potentially reduce the 447 * free memory in the system during the khugepaged scan. 448 */ 449static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 450 struct kobj_attribute *attr, 451 char *buf) 452{ 453 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 454} 455static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 456 struct kobj_attribute *attr, 457 const char *buf, size_t count) 458{ 459 int err; 460 unsigned long max_ptes_none; 461 462 err = strict_strtoul(buf, 10, &max_ptes_none); 463 if (err || max_ptes_none > HPAGE_PMD_NR-1) 464 return -EINVAL; 465 466 khugepaged_max_ptes_none = max_ptes_none; 467 468 return count; 469} 470static struct kobj_attribute khugepaged_max_ptes_none_attr = 471 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 472 khugepaged_max_ptes_none_store); 473 474static struct attribute *khugepaged_attr[] = { 475 &khugepaged_defrag_attr.attr, 476 &khugepaged_max_ptes_none_attr.attr, 477 &pages_to_scan_attr.attr, 478 &pages_collapsed_attr.attr, 479 &full_scans_attr.attr, 480 &scan_sleep_millisecs_attr.attr, 481 &alloc_sleep_millisecs_attr.attr, 482 NULL, 483}; 484 485static struct attribute_group khugepaged_attr_group = { 486 .attrs = khugepaged_attr, 487 .name = "khugepaged", 488}; 489#endif /* CONFIG_SYSFS */ 490 491static int __init hugepage_init(void) 492{ 493 int err; 494#ifdef CONFIG_SYSFS 495 static struct kobject *hugepage_kobj; 496#endif 497 498 err = -EINVAL; 499 if (!has_transparent_hugepage()) { 500 transparent_hugepage_flags = 0; 501 goto out; 502 } 503 504#ifdef CONFIG_SYSFS 505 err = -ENOMEM; 506 hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 507 if (unlikely(!hugepage_kobj)) { 508 printk(KERN_ERR "hugepage: failed kobject create\n"); 509 goto out; 510 } 511 512 err = sysfs_create_group(hugepage_kobj, &hugepage_attr_group); 513 if (err) { 514 printk(KERN_ERR "hugepage: failed register hugeage group\n"); 515 goto out; 516 } 517 518 err = sysfs_create_group(hugepage_kobj, &khugepaged_attr_group); 519 if (err) { 520 printk(KERN_ERR "hugepage: failed register hugeage group\n"); 521 goto out; 522 } 523#endif 524 525 err = khugepaged_slab_init(); 526 if (err) 527 goto out; 528 529 err = mm_slots_hash_init(); 530 if (err) { 531 khugepaged_slab_free(); 532 goto out; 533 } 534 535 /* 536 * By default disable transparent hugepages on smaller systems, 537 * where the extra memory used could hurt more than TLB overhead 538 * is likely to save. The admin can still enable it through /sys. 539 */ 540 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) 541 transparent_hugepage_flags = 0; 542 543 start_khugepaged(); 544 545 set_recommended_min_free_kbytes(); 546 547out: 548 return err; 549} 550module_init(hugepage_init) 551 552static int __init setup_transparent_hugepage(char *str) 553{ 554 int ret = 0; 555 if (!str) 556 goto out; 557 if (!strcmp(str, "always")) { 558 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 559 &transparent_hugepage_flags); 560 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 561 &transparent_hugepage_flags); 562 ret = 1; 563 } else if (!strcmp(str, "madvise")) { 564 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 565 &transparent_hugepage_flags); 566 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 567 &transparent_hugepage_flags); 568 ret = 1; 569 } else if (!strcmp(str, "never")) { 570 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 571 &transparent_hugepage_flags); 572 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 573 &transparent_hugepage_flags); 574 ret = 1; 575 } 576out: 577 if (!ret) 578 printk(KERN_WARNING 579 "transparent_hugepage= cannot parse, ignored\n"); 580 return ret; 581} 582__setup("transparent_hugepage=", setup_transparent_hugepage); 583 584static void prepare_pmd_huge_pte(pgtable_t pgtable, 585 struct mm_struct *mm) 586{ 587 assert_spin_locked(&mm->page_table_lock); 588 589 /* FIFO */ 590 if (!mm->pmd_huge_pte) 591 INIT_LIST_HEAD(&pgtable->lru); 592 else 593 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru); 594 mm->pmd_huge_pte = pgtable; 595} 596 597static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 598{ 599 if (likely(vma->vm_flags & VM_WRITE)) 600 pmd = pmd_mkwrite(pmd); 601 return pmd; 602} 603 604static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, 605 struct vm_area_struct *vma, 606 unsigned long haddr, pmd_t *pmd, 607 struct page *page) 608{ 609 int ret = 0; 610 pgtable_t pgtable; 611 612 VM_BUG_ON(!PageCompound(page)); 613 pgtable = pte_alloc_one(mm, haddr); 614 if (unlikely(!pgtable)) { 615 mem_cgroup_uncharge_page(page); 616 put_page(page); 617 return VM_FAULT_OOM; 618 } 619 620 clear_huge_page(page, haddr, HPAGE_PMD_NR); 621 __SetPageUptodate(page); 622 623 spin_lock(&mm->page_table_lock); 624 if (unlikely(!pmd_none(*pmd))) { 625 spin_unlock(&mm->page_table_lock); 626 mem_cgroup_uncharge_page(page); 627 put_page(page); 628 pte_free(mm, pgtable); 629 } else { 630 pmd_t entry; 631 entry = mk_pmd(page, vma->vm_page_prot); 632 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 633 entry = pmd_mkhuge(entry); 634 /* 635 * The spinlocking to take the lru_lock inside 636 * page_add_new_anon_rmap() acts as a full memory 637 * barrier to be sure clear_huge_page writes become 638 * visible after the set_pmd_at() write. 639 */ 640 page_add_new_anon_rmap(page, vma, haddr); 641 set_pmd_at(mm, haddr, pmd, entry); 642 prepare_pmd_huge_pte(pgtable, mm); 643 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 644 spin_unlock(&mm->page_table_lock); 645 } 646 647 return ret; 648} 649 650static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) 651{ 652 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; 653} 654 655static inline struct page *alloc_hugepage_vma(int defrag, 656 struct vm_area_struct *vma, 657 unsigned long haddr, int nd, 658 gfp_t extra_gfp) 659{ 660 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp), 661 HPAGE_PMD_ORDER, vma, haddr, nd); 662} 663 664#ifndef CONFIG_NUMA 665static inline struct page *alloc_hugepage(int defrag) 666{ 667 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), 668 HPAGE_PMD_ORDER); 669} 670#endif 671 672int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 673 unsigned long address, pmd_t *pmd, 674 unsigned int flags) 675{ 676 struct page *page; 677 unsigned long haddr = address & HPAGE_PMD_MASK; 678 pte_t *pte; 679 680 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) { 681 if (unlikely(anon_vma_prepare(vma))) 682 return VM_FAULT_OOM; 683 if (unlikely(khugepaged_enter(vma))) 684 return VM_FAULT_OOM; 685 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 686 vma, haddr, numa_node_id(), 0); 687 if (unlikely(!page)) { 688 count_vm_event(THP_FAULT_FALLBACK); 689 goto out; 690 } 691 count_vm_event(THP_FAULT_ALLOC); 692 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) { 693 put_page(page); 694 goto out; 695 } 696 697 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page); 698 } 699out: 700 /* 701 * Use __pte_alloc instead of pte_alloc_map, because we can't 702 * run pte_offset_map on the pmd, if an huge pmd could 703 * materialize from under us from a different thread. 704 */ 705 if (unlikely(__pte_alloc(mm, vma, pmd, address))) 706 return VM_FAULT_OOM; 707 /* if an huge pmd materialized from under us just retry later */ 708 if (unlikely(pmd_trans_huge(*pmd))) 709 return 0; 710 /* 711 * A regular pmd is established and it can't morph into a huge pmd 712 * from under us anymore at this point because we hold the mmap_sem 713 * read mode and khugepaged takes it in write mode. So now it's 714 * safe to run pte_offset_map(). 715 */ 716 pte = pte_offset_map(pmd, address); 717 return handle_pte_fault(mm, vma, address, pte, pmd, flags); 718} 719 720int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 721 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 722 struct vm_area_struct *vma) 723{ 724 struct page *src_page; 725 pmd_t pmd; 726 pgtable_t pgtable; 727 int ret; 728 729 ret = -ENOMEM; 730 pgtable = pte_alloc_one(dst_mm, addr); 731 if (unlikely(!pgtable)) 732 goto out; 733 734 spin_lock(&dst_mm->page_table_lock); 735 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING); 736 737 ret = -EAGAIN; 738 pmd = *src_pmd; 739 if (unlikely(!pmd_trans_huge(pmd))) { 740 pte_free(dst_mm, pgtable); 741 goto out_unlock; 742 } 743 if (unlikely(pmd_trans_splitting(pmd))) { 744 /* split huge page running from under us */ 745 spin_unlock(&src_mm->page_table_lock); 746 spin_unlock(&dst_mm->page_table_lock); 747 pte_free(dst_mm, pgtable); 748 749 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ 750 goto out; 751 } 752 src_page = pmd_page(pmd); 753 VM_BUG_ON(!PageHead(src_page)); 754 get_page(src_page); 755 page_dup_rmap(src_page); 756 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 757 758 pmdp_set_wrprotect(src_mm, addr, src_pmd); 759 pmd = pmd_mkold(pmd_wrprotect(pmd)); 760 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 761 prepare_pmd_huge_pte(pgtable, dst_mm); 762 763 ret = 0; 764out_unlock: 765 spin_unlock(&src_mm->page_table_lock); 766 spin_unlock(&dst_mm->page_table_lock); 767out: 768 return ret; 769} 770 771/* no "address" argument so destroys page coloring of some arch */ 772pgtable_t get_pmd_huge_pte(struct mm_struct *mm) 773{ 774 pgtable_t pgtable; 775 776 assert_spin_locked(&mm->page_table_lock); 777 778 /* FIFO */ 779 pgtable = mm->pmd_huge_pte; 780 if (list_empty(&pgtable->lru)) 781 mm->pmd_huge_pte = NULL; 782 else { 783 mm->pmd_huge_pte = list_entry(pgtable->lru.next, 784 struct page, lru); 785 list_del(&pgtable->lru); 786 } 787 return pgtable; 788} 789 790static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, 791 struct vm_area_struct *vma, 792 unsigned long address, 793 pmd_t *pmd, pmd_t orig_pmd, 794 struct page *page, 795 unsigned long haddr) 796{ 797 pgtable_t pgtable; 798 pmd_t _pmd; 799 int ret = 0, i; 800 struct page **pages; 801 802 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 803 GFP_KERNEL); 804 if (unlikely(!pages)) { 805 ret |= VM_FAULT_OOM; 806 goto out; 807 } 808 809 for (i = 0; i < HPAGE_PMD_NR; i++) { 810 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | 811 __GFP_OTHER_NODE, 812 vma, address, page_to_nid(page)); 813 if (unlikely(!pages[i] || 814 mem_cgroup_newpage_charge(pages[i], mm, 815 GFP_KERNEL))) { 816 if (pages[i]) 817 put_page(pages[i]); 818 mem_cgroup_uncharge_start(); 819 while (--i >= 0) { 820 mem_cgroup_uncharge_page(pages[i]); 821 put_page(pages[i]); 822 } 823 mem_cgroup_uncharge_end(); 824 kfree(pages); 825 ret |= VM_FAULT_OOM; 826 goto out; 827 } 828 } 829 830 for (i = 0; i < HPAGE_PMD_NR; i++) { 831 copy_user_highpage(pages[i], page + i, 832 haddr + PAGE_SHIFT*i, vma); 833 __SetPageUptodate(pages[i]); 834 cond_resched(); 835 } 836 837 spin_lock(&mm->page_table_lock); 838 if (unlikely(!pmd_same(*pmd, orig_pmd))) 839 goto out_free_pages; 840 VM_BUG_ON(!PageHead(page)); 841 842 pmdp_clear_flush_notify(vma, haddr, pmd); 843 /* leave pmd empty until pte is filled */ 844 845 pgtable = get_pmd_huge_pte(mm); 846 pmd_populate(mm, &_pmd, pgtable); 847 848 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 849 pte_t *pte, entry; 850 entry = mk_pte(pages[i], vma->vm_page_prot); 851 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 852 page_add_new_anon_rmap(pages[i], vma, haddr); 853 pte = pte_offset_map(&_pmd, haddr); 854 VM_BUG_ON(!pte_none(*pte)); 855 set_pte_at(mm, haddr, pte, entry); 856 pte_unmap(pte); 857 } 858 kfree(pages); 859 860 mm->nr_ptes++; 861 smp_wmb(); /* make pte visible before pmd */ 862 pmd_populate(mm, pmd, pgtable); 863 page_remove_rmap(page); 864 spin_unlock(&mm->page_table_lock); 865 866 ret |= VM_FAULT_WRITE; 867 put_page(page); 868 869out: 870 return ret; 871 872out_free_pages: 873 spin_unlock(&mm->page_table_lock); 874 mem_cgroup_uncharge_start(); 875 for (i = 0; i < HPAGE_PMD_NR; i++) { 876 mem_cgroup_uncharge_page(pages[i]); 877 put_page(pages[i]); 878 } 879 mem_cgroup_uncharge_end(); 880 kfree(pages); 881 goto out; 882} 883 884int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 885 unsigned long address, pmd_t *pmd, pmd_t orig_pmd) 886{ 887 int ret = 0; 888 struct page *page, *new_page; 889 unsigned long haddr; 890 891 VM_BUG_ON(!vma->anon_vma); 892 spin_lock(&mm->page_table_lock); 893 if (unlikely(!pmd_same(*pmd, orig_pmd))) 894 goto out_unlock; 895 896 page = pmd_page(orig_pmd); 897 VM_BUG_ON(!PageCompound(page) || !PageHead(page)); 898 haddr = address & HPAGE_PMD_MASK; 899 if (page_mapcount(page) == 1) { 900 pmd_t entry; 901 entry = pmd_mkyoung(orig_pmd); 902 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 903 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 904 update_mmu_cache(vma, address, entry); 905 ret |= VM_FAULT_WRITE; 906 goto out_unlock; 907 } 908 get_page(page); 909 spin_unlock(&mm->page_table_lock); 910 911 if (transparent_hugepage_enabled(vma) && 912 !transparent_hugepage_debug_cow()) 913 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 914 vma, haddr, numa_node_id(), 0); 915 else 916 new_page = NULL; 917 918 if (unlikely(!new_page)) { 919 count_vm_event(THP_FAULT_FALLBACK); 920 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 921 pmd, orig_pmd, page, haddr); 922 put_page(page); 923 goto out; 924 } 925 count_vm_event(THP_FAULT_ALLOC); 926 927 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 928 put_page(new_page); 929 put_page(page); 930 ret |= VM_FAULT_OOM; 931 goto out; 932 } 933 934 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 935 __SetPageUptodate(new_page); 936 937 spin_lock(&mm->page_table_lock); 938 put_page(page); 939 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 940 mem_cgroup_uncharge_page(new_page); 941 put_page(new_page); 942 } else { 943 pmd_t entry; 944 VM_BUG_ON(!PageHead(page)); 945 entry = mk_pmd(new_page, vma->vm_page_prot); 946 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 947 entry = pmd_mkhuge(entry); 948 pmdp_clear_flush_notify(vma, haddr, pmd); 949 page_add_new_anon_rmap(new_page, vma, haddr); 950 set_pmd_at(mm, haddr, pmd, entry); 951 update_mmu_cache(vma, address, entry); 952 page_remove_rmap(page); 953 put_page(page); 954 ret |= VM_FAULT_WRITE; 955 } 956out_unlock: 957 spin_unlock(&mm->page_table_lock); 958out: 959 return ret; 960} 961 962struct page *follow_trans_huge_pmd(struct mm_struct *mm, 963 unsigned long addr, 964 pmd_t *pmd, 965 unsigned int flags) 966{ 967 struct page *page = NULL; 968 969 assert_spin_locked(&mm->page_table_lock); 970 971 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 972 goto out; 973 974 page = pmd_page(*pmd); 975 VM_BUG_ON(!PageHead(page)); 976 if (flags & FOLL_TOUCH) { 977 pmd_t _pmd; 978 /* 979 * We should set the dirty bit only for FOLL_WRITE but 980 * for now the dirty bit in the pmd is meaningless. 981 * And if the dirty bit will become meaningful and 982 * we'll only set it with FOLL_WRITE, an atomic 983 * set_bit will be required on the pmd to set the 984 * young bit, instead of the current set_pmd_at. 985 */ 986 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 987 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd); 988 } 989 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 990 VM_BUG_ON(!PageCompound(page)); 991 if (flags & FOLL_GET) 992 get_page(page); 993 994out: 995 return page; 996} 997 998int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 999 pmd_t *pmd) 1000{ 1001 int ret = 0; 1002 1003 spin_lock(&tlb->mm->page_table_lock); 1004 if (likely(pmd_trans_huge(*pmd))) { 1005 if (unlikely(pmd_trans_splitting(*pmd))) { 1006 spin_unlock(&tlb->mm->page_table_lock); 1007 wait_split_huge_page(vma->anon_vma, 1008 pmd); 1009 } else { 1010 struct page *page; 1011 pgtable_t pgtable; 1012 pgtable = get_pmd_huge_pte(tlb->mm); 1013 page = pmd_page(*pmd); 1014 pmd_clear(pmd); 1015 page_remove_rmap(page); 1016 VM_BUG_ON(page_mapcount(page) < 0); 1017 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1018 VM_BUG_ON(!PageHead(page)); 1019 spin_unlock(&tlb->mm->page_table_lock); 1020 tlb_remove_page(tlb, page); 1021 pte_free(tlb->mm, pgtable); 1022 ret = 1; 1023 } 1024 } else 1025 spin_unlock(&tlb->mm->page_table_lock); 1026 1027 return ret; 1028} 1029 1030int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1031 unsigned long addr, unsigned long end, 1032 unsigned char *vec) 1033{ 1034 int ret = 0; 1035 1036 spin_lock(&vma->vm_mm->page_table_lock); 1037 if (likely(pmd_trans_huge(*pmd))) { 1038 ret = !pmd_trans_splitting(*pmd); 1039 spin_unlock(&vma->vm_mm->page_table_lock); 1040 if (unlikely(!ret)) 1041 wait_split_huge_page(vma->anon_vma, pmd); 1042 else { 1043 /* 1044 * All logical pages in the range are present 1045 * if backed by a huge page. 1046 */ 1047 memset(vec, 1, (end - addr) >> PAGE_SHIFT); 1048 } 1049 } else 1050 spin_unlock(&vma->vm_mm->page_table_lock); 1051 1052 return ret; 1053} 1054 1055int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1056 unsigned long addr, pgprot_t newprot) 1057{ 1058 struct mm_struct *mm = vma->vm_mm; 1059 int ret = 0; 1060 1061 spin_lock(&mm->page_table_lock); 1062 if (likely(pmd_trans_huge(*pmd))) { 1063 if (unlikely(pmd_trans_splitting(*pmd))) { 1064 spin_unlock(&mm->page_table_lock); 1065 wait_split_huge_page(vma->anon_vma, pmd); 1066 } else { 1067 pmd_t entry; 1068 1069 entry = pmdp_get_and_clear(mm, addr, pmd); 1070 entry = pmd_modify(entry, newprot); 1071 set_pmd_at(mm, addr, pmd, entry); 1072 spin_unlock(&vma->vm_mm->page_table_lock); 1073 flush_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE); 1074 ret = 1; 1075 } 1076 } else 1077 spin_unlock(&vma->vm_mm->page_table_lock); 1078 1079 return ret; 1080} 1081 1082pmd_t *page_check_address_pmd(struct page *page, 1083 struct mm_struct *mm, 1084 unsigned long address, 1085 enum page_check_address_pmd_flag flag) 1086{ 1087 pgd_t *pgd; 1088 pud_t *pud; 1089 pmd_t *pmd, *ret = NULL; 1090 1091 if (address & ~HPAGE_PMD_MASK) 1092 goto out; 1093 1094 pgd = pgd_offset(mm, address); 1095 if (!pgd_present(*pgd)) 1096 goto out; 1097 1098 pud = pud_offset(pgd, address); 1099 if (!pud_present(*pud)) 1100 goto out; 1101 1102 pmd = pmd_offset(pud, address); 1103 if (pmd_none(*pmd)) 1104 goto out; 1105 if (pmd_page(*pmd) != page) 1106 goto out; 1107 /* 1108 * split_vma() may create temporary aliased mappings. There is 1109 * no risk as long as all huge pmd are found and have their 1110 * splitting bit set before __split_huge_page_refcount 1111 * runs. Finding the same huge pmd more than once during the 1112 * same rmap walk is not a problem. 1113 */ 1114 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && 1115 pmd_trans_splitting(*pmd)) 1116 goto out; 1117 if (pmd_trans_huge(*pmd)) { 1118 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && 1119 !pmd_trans_splitting(*pmd)); 1120 ret = pmd; 1121 } 1122out: 1123 return ret; 1124} 1125 1126static int __split_huge_page_splitting(struct page *page, 1127 struct vm_area_struct *vma, 1128 unsigned long address) 1129{ 1130 struct mm_struct *mm = vma->vm_mm; 1131 pmd_t *pmd; 1132 int ret = 0; 1133 1134 spin_lock(&mm->page_table_lock); 1135 pmd = page_check_address_pmd(page, mm, address, 1136 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG); 1137 if (pmd) { 1138 /* 1139 * We can't temporarily set the pmd to null in order 1140 * to split it, the pmd must remain marked huge at all 1141 * times or the VM won't take the pmd_trans_huge paths 1142 * and it won't wait on the anon_vma->root->lock to 1143 * serialize against split_huge_page*. 1144 */ 1145 pmdp_splitting_flush_notify(vma, address, pmd); 1146 ret = 1; 1147 } 1148 spin_unlock(&mm->page_table_lock); 1149 1150 return ret; 1151} 1152 1153static void __split_huge_page_refcount(struct page *page) 1154{ 1155 int i; 1156 unsigned long head_index = page->index; 1157 struct zone *zone = page_zone(page); 1158 int zonestat; 1159 1160 /* prevent PageLRU to go away from under us, and freeze lru stats */ 1161 spin_lock_irq(&zone->lru_lock); 1162 compound_lock(page); 1163 1164 for (i = 1; i < HPAGE_PMD_NR; i++) { 1165 struct page *page_tail = page + i; 1166 1167 /* tail_page->_count cannot change */ 1168 atomic_sub(atomic_read(&page_tail->_count), &page->_count); 1169 BUG_ON(page_count(page) <= 0); 1170 atomic_add(page_mapcount(page) + 1, &page_tail->_count); 1171 BUG_ON(atomic_read(&page_tail->_count) <= 0); 1172 1173 /* after clearing PageTail the gup refcount can be released */ 1174 smp_mb(); 1175 1176 /* 1177 * retain hwpoison flag of the poisoned tail page: 1178 * fix for the unsuitable process killed on Guest Machine(KVM) 1179 * by the memory-failure. 1180 */ 1181 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON; 1182 page_tail->flags |= (page->flags & 1183 ((1L << PG_referenced) | 1184 (1L << PG_swapbacked) | 1185 (1L << PG_mlocked) | 1186 (1L << PG_uptodate))); 1187 page_tail->flags |= (1L << PG_dirty); 1188 1189 /* 1190 * 1) clear PageTail before overwriting first_page 1191 * 2) clear PageTail before clearing PageHead for VM_BUG_ON 1192 */ 1193 smp_wmb(); 1194 1195 /* 1196 * __split_huge_page_splitting() already set the 1197 * splitting bit in all pmd that could map this 1198 * hugepage, that will ensure no CPU can alter the 1199 * mapcount on the head page. The mapcount is only 1200 * accounted in the head page and it has to be 1201 * transferred to all tail pages in the below code. So 1202 * for this code to be safe, the split the mapcount 1203 * can't change. But that doesn't mean userland can't 1204 * keep changing and reading the page contents while 1205 * we transfer the mapcount, so the pmd splitting 1206 * status is achieved setting a reserved bit in the 1207 * pmd, not by clearing the present bit. 1208 */ 1209 BUG_ON(page_mapcount(page_tail)); 1210 page_tail->_mapcount = page->_mapcount; 1211 1212 BUG_ON(page_tail->mapping); 1213 page_tail->mapping = page->mapping; 1214 1215 page_tail->index = ++head_index; 1216 1217 BUG_ON(!PageAnon(page_tail)); 1218 BUG_ON(!PageUptodate(page_tail)); 1219 BUG_ON(!PageDirty(page_tail)); 1220 BUG_ON(!PageSwapBacked(page_tail)); 1221 1222 mem_cgroup_split_huge_fixup(page, page_tail); 1223 1224 lru_add_page_tail(zone, page, page_tail); 1225 } 1226 1227 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); 1228 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR); 1229 1230 /* 1231 * A hugepage counts for HPAGE_PMD_NR pages on the LRU statistics, 1232 * so adjust those appropriately if this page is on the LRU. 1233 */ 1234 if (PageLRU(page)) { 1235 zonestat = NR_LRU_BASE + page_lru(page); 1236 __mod_zone_page_state(zone, zonestat, -(HPAGE_PMD_NR-1)); 1237 } 1238 1239 ClearPageCompound(page); 1240 compound_unlock(page); 1241 spin_unlock_irq(&zone->lru_lock); 1242 1243 for (i = 1; i < HPAGE_PMD_NR; i++) { 1244 struct page *page_tail = page + i; 1245 BUG_ON(page_count(page_tail) <= 0); 1246 /* 1247 * Tail pages may be freed if there wasn't any mapping 1248 * like if add_to_swap() is running on a lru page that 1249 * had its mapping zapped. And freeing these pages 1250 * requires taking the lru_lock so we do the put_page 1251 * of the tail pages after the split is complete. 1252 */ 1253 put_page(page_tail); 1254 } 1255 1256 /* 1257 * Only the head page (now become a regular page) is required 1258 * to be pinned by the caller. 1259 */ 1260 BUG_ON(page_count(page) <= 0); 1261} 1262 1263static int __split_huge_page_map(struct page *page, 1264 struct vm_area_struct *vma, 1265 unsigned long address) 1266{ 1267 struct mm_struct *mm = vma->vm_mm; 1268 pmd_t *pmd, _pmd; 1269 int ret = 0, i; 1270 pgtable_t pgtable; 1271 unsigned long haddr; 1272 1273 spin_lock(&mm->page_table_lock); 1274 pmd = page_check_address_pmd(page, mm, address, 1275 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG); 1276 if (pmd) { 1277 pgtable = get_pmd_huge_pte(mm); 1278 pmd_populate(mm, &_pmd, pgtable); 1279 1280 for (i = 0, haddr = address; i < HPAGE_PMD_NR; 1281 i++, haddr += PAGE_SIZE) { 1282 pte_t *pte, entry; 1283 BUG_ON(PageCompound(page+i)); 1284 entry = mk_pte(page + i, vma->vm_page_prot); 1285 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1286 if (!pmd_write(*pmd)) 1287 entry = pte_wrprotect(entry); 1288 else 1289 BUG_ON(page_mapcount(page) != 1); 1290 if (!pmd_young(*pmd)) 1291 entry = pte_mkold(entry); 1292 pte = pte_offset_map(&_pmd, haddr); 1293 BUG_ON(!pte_none(*pte)); 1294 set_pte_at(mm, haddr, pte, entry); 1295 pte_unmap(pte); 1296 } 1297 1298 mm->nr_ptes++; 1299 smp_wmb(); /* make pte visible before pmd */ 1300 /* 1301 * Up to this point the pmd is present and huge and 1302 * userland has the whole access to the hugepage 1303 * during the split (which happens in place). If we 1304 * overwrite the pmd with the not-huge version 1305 * pointing to the pte here (which of course we could 1306 * if all CPUs were bug free), userland could trigger 1307 * a small page size TLB miss on the small sized TLB 1308 * while the hugepage TLB entry is still established 1309 * in the huge TLB. Some CPU doesn't like that. See 1310 * http://support.amd.com/us/Processor_TechDocs/41322.pdf, 1311 * Erratum 383 on page 93. Intel should be safe but is 1312 * also warns that it's only safe if the permission 1313 * and cache attributes of the two entries loaded in 1314 * the two TLB is identical (which should be the case 1315 * here). But it is generally safer to never allow 1316 * small and huge TLB entries for the same virtual 1317 * address to be loaded simultaneously. So instead of 1318 * doing "pmd_populate(); flush_tlb_range();" we first 1319 * mark the current pmd notpresent (atomically because 1320 * here the pmd_trans_huge and pmd_trans_splitting 1321 * must remain set at all times on the pmd until the 1322 * split is complete for this pmd), then we flush the 1323 * SMP TLB and finally we write the non-huge version 1324 * of the pmd entry with pmd_populate. 1325 */ 1326 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd)); 1327 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE); 1328 pmd_populate(mm, pmd, pgtable); 1329 ret = 1; 1330 } 1331 spin_unlock(&mm->page_table_lock); 1332 1333 return ret; 1334} 1335 1336/* must be called with anon_vma->root->lock hold */ 1337static void __split_huge_page(struct page *page, 1338 struct anon_vma *anon_vma) 1339{ 1340 int mapcount, mapcount2; 1341 struct anon_vma_chain *avc; 1342 1343 BUG_ON(!PageHead(page)); 1344 BUG_ON(PageTail(page)); 1345 1346 mapcount = 0; 1347 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { 1348 struct vm_area_struct *vma = avc->vma; 1349 unsigned long addr = vma_address(page, vma); 1350 BUG_ON(is_vma_temporary_stack(vma)); 1351 if (addr == -EFAULT) 1352 continue; 1353 mapcount += __split_huge_page_splitting(page, vma, addr); 1354 } 1355 /* 1356 * It is critical that new vmas are added to the tail of the 1357 * anon_vma list. This guarantes that if copy_huge_pmd() runs 1358 * and establishes a child pmd before 1359 * __split_huge_page_splitting() freezes the parent pmd (so if 1360 * we fail to prevent copy_huge_pmd() from running until the 1361 * whole __split_huge_page() is complete), we will still see 1362 * the newly established pmd of the child later during the 1363 * walk, to be able to set it as pmd_trans_splitting too. 1364 */ 1365 if (mapcount != page_mapcount(page)) 1366 printk(KERN_ERR "mapcount %d page_mapcount %d\n", 1367 mapcount, page_mapcount(page)); 1368 BUG_ON(mapcount != page_mapcount(page)); 1369 1370 __split_huge_page_refcount(page); 1371 1372 mapcount2 = 0; 1373 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { 1374 struct vm_area_struct *vma = avc->vma; 1375 unsigned long addr = vma_address(page, vma); 1376 BUG_ON(is_vma_temporary_stack(vma)); 1377 if (addr == -EFAULT) 1378 continue; 1379 mapcount2 += __split_huge_page_map(page, vma, addr); 1380 } 1381 if (mapcount != mapcount2) 1382 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n", 1383 mapcount, mapcount2, page_mapcount(page)); 1384 BUG_ON(mapcount != mapcount2); 1385} 1386 1387int split_huge_page(struct page *page) 1388{ 1389 struct anon_vma *anon_vma; 1390 int ret = 1; 1391 1392 BUG_ON(!PageAnon(page)); 1393 anon_vma = page_lock_anon_vma(page); 1394 if (!anon_vma) 1395 goto out; 1396 ret = 0; 1397 if (!PageCompound(page)) 1398 goto out_unlock; 1399 1400 BUG_ON(!PageSwapBacked(page)); 1401 __split_huge_page(page, anon_vma); 1402 count_vm_event(THP_SPLIT); 1403 1404 BUG_ON(PageCompound(page)); 1405out_unlock: 1406 page_unlock_anon_vma(anon_vma); 1407out: 1408 return ret; 1409} 1410 1411int hugepage_madvise(struct vm_area_struct *vma, 1412 unsigned long *vm_flags, int advice) 1413{ 1414 switch (advice) { 1415 case MADV_HUGEPAGE: 1416 /* 1417 * Be somewhat over-protective like KSM for now! 1418 */ 1419 if (*vm_flags & (VM_HUGEPAGE | 1420 VM_SHARED | VM_MAYSHARE | 1421 VM_PFNMAP | VM_IO | VM_DONTEXPAND | 1422 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | 1423 VM_MIXEDMAP | VM_SAO)) 1424 return -EINVAL; 1425 *vm_flags &= ~VM_NOHUGEPAGE; 1426 *vm_flags |= VM_HUGEPAGE; 1427 /* 1428 * If the vma become good for khugepaged to scan, 1429 * register it here without waiting a page fault that 1430 * may not happen any time soon. 1431 */ 1432 if (unlikely(khugepaged_enter_vma_merge(vma))) 1433 return -ENOMEM; 1434 break; 1435 case MADV_NOHUGEPAGE: 1436 /* 1437 * Be somewhat over-protective like KSM for now! 1438 */ 1439 if (*vm_flags & (VM_NOHUGEPAGE | 1440 VM_SHARED | VM_MAYSHARE | 1441 VM_PFNMAP | VM_IO | VM_DONTEXPAND | 1442 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | 1443 VM_MIXEDMAP | VM_SAO)) 1444 return -EINVAL; 1445 *vm_flags &= ~VM_HUGEPAGE; 1446 *vm_flags |= VM_NOHUGEPAGE; 1447 /* 1448 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1449 * this vma even if we leave the mm registered in khugepaged if 1450 * it got registered before VM_NOHUGEPAGE was set. 1451 */ 1452 break; 1453 } 1454 1455 return 0; 1456} 1457 1458static int __init khugepaged_slab_init(void) 1459{ 1460 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1461 sizeof(struct mm_slot), 1462 __alignof__(struct mm_slot), 0, NULL); 1463 if (!mm_slot_cache) 1464 return -ENOMEM; 1465 1466 return 0; 1467} 1468 1469static void __init khugepaged_slab_free(void) 1470{ 1471 kmem_cache_destroy(mm_slot_cache); 1472 mm_slot_cache = NULL; 1473} 1474 1475static inline struct mm_slot *alloc_mm_slot(void) 1476{ 1477 if (!mm_slot_cache) /* initialization failed */ 1478 return NULL; 1479 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 1480} 1481 1482static inline void free_mm_slot(struct mm_slot *mm_slot) 1483{ 1484 kmem_cache_free(mm_slot_cache, mm_slot); 1485} 1486 1487static int __init mm_slots_hash_init(void) 1488{ 1489 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), 1490 GFP_KERNEL); 1491 if (!mm_slots_hash) 1492 return -ENOMEM; 1493 return 0; 1494} 1495 1496#if 0 1497static void __init mm_slots_hash_free(void) 1498{ 1499 kfree(mm_slots_hash); 1500 mm_slots_hash = NULL; 1501} 1502#endif 1503 1504static struct mm_slot *get_mm_slot(struct mm_struct *mm) 1505{ 1506 struct mm_slot *mm_slot; 1507 struct hlist_head *bucket; 1508 struct hlist_node *node; 1509 1510 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1511 % MM_SLOTS_HASH_HEADS]; 1512 hlist_for_each_entry(mm_slot, node, bucket, hash) { 1513 if (mm == mm_slot->mm) 1514 return mm_slot; 1515 } 1516 return NULL; 1517} 1518 1519static void insert_to_mm_slots_hash(struct mm_struct *mm, 1520 struct mm_slot *mm_slot) 1521{ 1522 struct hlist_head *bucket; 1523 1524 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1525 % MM_SLOTS_HASH_HEADS]; 1526 mm_slot->mm = mm; 1527 hlist_add_head(&mm_slot->hash, bucket); 1528} 1529 1530static inline int khugepaged_test_exit(struct mm_struct *mm) 1531{ 1532 return atomic_read(&mm->mm_users) == 0; 1533} 1534 1535int __khugepaged_enter(struct mm_struct *mm) 1536{ 1537 struct mm_slot *mm_slot; 1538 int wakeup; 1539 1540 mm_slot = alloc_mm_slot(); 1541 if (!mm_slot) 1542 return -ENOMEM; 1543 1544 /* __khugepaged_exit() must not run from under us */ 1545 VM_BUG_ON(khugepaged_test_exit(mm)); 1546 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 1547 free_mm_slot(mm_slot); 1548 return 0; 1549 } 1550 1551 spin_lock(&khugepaged_mm_lock); 1552 insert_to_mm_slots_hash(mm, mm_slot); 1553 /* 1554 * Insert just behind the scanning cursor, to let the area settle 1555 * down a little. 1556 */ 1557 wakeup = list_empty(&khugepaged_scan.mm_head); 1558 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 1559 spin_unlock(&khugepaged_mm_lock); 1560 1561 atomic_inc(&mm->mm_count); 1562 if (wakeup) 1563 wake_up_interruptible(&khugepaged_wait); 1564 1565 return 0; 1566} 1567 1568int khugepaged_enter_vma_merge(struct vm_area_struct *vma) 1569{ 1570 unsigned long hstart, hend; 1571 if (!vma->anon_vma) 1572 /* 1573 * Not yet faulted in so we will register later in the 1574 * page fault if needed. 1575 */ 1576 return 0; 1577 if (vma->vm_file || vma->vm_ops) 1578 /* khugepaged not yet working on file or special mappings */ 1579 return 0; 1580 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma)); 1581 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1582 hend = vma->vm_end & HPAGE_PMD_MASK; 1583 if (hstart < hend) 1584 return khugepaged_enter(vma); 1585 return 0; 1586} 1587 1588void __khugepaged_exit(struct mm_struct *mm) 1589{ 1590 struct mm_slot *mm_slot; 1591 int free = 0; 1592 1593 spin_lock(&khugepaged_mm_lock); 1594 mm_slot = get_mm_slot(mm); 1595 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 1596 hlist_del(&mm_slot->hash); 1597 list_del(&mm_slot->mm_node); 1598 free = 1; 1599 } 1600 1601 if (free) { 1602 spin_unlock(&khugepaged_mm_lock); 1603 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1604 free_mm_slot(mm_slot); 1605 mmdrop(mm); 1606 } else if (mm_slot) { 1607 spin_unlock(&khugepaged_mm_lock); 1608 /* 1609 * This is required to serialize against 1610 * khugepaged_test_exit() (which is guaranteed to run 1611 * under mmap sem read mode). Stop here (after we 1612 * return all pagetables will be destroyed) until 1613 * khugepaged has finished working on the pagetables 1614 * under the mmap_sem. 1615 */ 1616 down_write(&mm->mmap_sem); 1617 up_write(&mm->mmap_sem); 1618 } else 1619 spin_unlock(&khugepaged_mm_lock); 1620} 1621 1622static void release_pte_page(struct page *page) 1623{ 1624 /* 0 stands for page_is_file_cache(page) == false */ 1625 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 1626 unlock_page(page); 1627 putback_lru_page(page); 1628} 1629 1630static void release_pte_pages(pte_t *pte, pte_t *_pte) 1631{ 1632 while (--_pte >= pte) { 1633 pte_t pteval = *_pte; 1634 if (!pte_none(pteval)) 1635 release_pte_page(pte_page(pteval)); 1636 } 1637} 1638 1639static void release_all_pte_pages(pte_t *pte) 1640{ 1641 release_pte_pages(pte, pte + HPAGE_PMD_NR); 1642} 1643 1644static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 1645 unsigned long address, 1646 pte_t *pte) 1647{ 1648 struct page *page; 1649 pte_t *_pte; 1650 int referenced = 0, isolated = 0, none = 0; 1651 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 1652 _pte++, address += PAGE_SIZE) { 1653 pte_t pteval = *_pte; 1654 if (pte_none(pteval)) { 1655 if (++none <= khugepaged_max_ptes_none) 1656 continue; 1657 else { 1658 release_pte_pages(pte, _pte); 1659 goto out; 1660 } 1661 } 1662 if (!pte_present(pteval) || !pte_write(pteval)) { 1663 release_pte_pages(pte, _pte); 1664 goto out; 1665 } 1666 page = vm_normal_page(vma, address, pteval); 1667 if (unlikely(!page)) { 1668 release_pte_pages(pte, _pte); 1669 goto out; 1670 } 1671 VM_BUG_ON(PageCompound(page)); 1672 BUG_ON(!PageAnon(page)); 1673 VM_BUG_ON(!PageSwapBacked(page)); 1674 1675 /* cannot use mapcount: can't collapse if there's a gup pin */ 1676 if (page_count(page) != 1) { 1677 release_pte_pages(pte, _pte); 1678 goto out; 1679 } 1680 /* 1681 * We can do it before isolate_lru_page because the 1682 * page can't be freed from under us. NOTE: PG_lock 1683 * is needed to serialize against split_huge_page 1684 * when invoked from the VM. 1685 */ 1686 if (!trylock_page(page)) { 1687 release_pte_pages(pte, _pte); 1688 goto out; 1689 } 1690 /* 1691 * Isolate the page to avoid collapsing an hugepage 1692 * currently in use by the VM. 1693 */ 1694 if (isolate_lru_page(page)) { 1695 unlock_page(page); 1696 release_pte_pages(pte, _pte); 1697 goto out; 1698 } 1699 /* 0 stands for page_is_file_cache(page) == false */ 1700 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 1701 VM_BUG_ON(!PageLocked(page)); 1702 VM_BUG_ON(PageLRU(page)); 1703 1704 /* If there is no mapped pte young don't collapse the page */ 1705 if (pte_young(pteval) || PageReferenced(page) || 1706 mmu_notifier_test_young(vma->vm_mm, address)) 1707 referenced = 1; 1708 } 1709 if (unlikely(!referenced)) 1710 release_all_pte_pages(pte); 1711 else 1712 isolated = 1; 1713out: 1714 return isolated; 1715} 1716 1717static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 1718 struct vm_area_struct *vma, 1719 unsigned long address, 1720 spinlock_t *ptl) 1721{ 1722 pte_t *_pte; 1723 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 1724 pte_t pteval = *_pte; 1725 struct page *src_page; 1726 1727 if (pte_none(pteval)) { 1728 clear_user_highpage(page, address); 1729 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 1730 } else { 1731 src_page = pte_page(pteval); 1732 copy_user_highpage(page, src_page, address, vma); 1733 VM_BUG_ON(page_mapcount(src_page) != 1); 1734 VM_BUG_ON(page_count(src_page) != 2); 1735 release_pte_page(src_page); 1736 /* 1737 * ptl mostly unnecessary, but preempt has to 1738 * be disabled to update the per-cpu stats 1739 * inside page_remove_rmap(). 1740 */ 1741 spin_lock(ptl); 1742 /* 1743 * paravirt calls inside pte_clear here are 1744 * superfluous. 1745 */ 1746 pte_clear(vma->vm_mm, address, _pte); 1747 page_remove_rmap(src_page); 1748 spin_unlock(ptl); 1749 free_page_and_swap_cache(src_page); 1750 } 1751 1752 address += PAGE_SIZE; 1753 page++; 1754 } 1755} 1756 1757static void collapse_huge_page(struct mm_struct *mm, 1758 unsigned long address, 1759 struct page **hpage, 1760 struct vm_area_struct *vma, 1761 int node) 1762{ 1763 pgd_t *pgd; 1764 pud_t *pud; 1765 pmd_t *pmd, _pmd; 1766 pte_t *pte; 1767 pgtable_t pgtable; 1768 struct page *new_page; 1769 spinlock_t *ptl; 1770 int isolated; 1771 unsigned long hstart, hend; 1772 1773 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1774#ifndef CONFIG_NUMA 1775 VM_BUG_ON(!*hpage); 1776 new_page = *hpage; 1777 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 1778 up_read(&mm->mmap_sem); 1779 return; 1780 } 1781#else 1782 VM_BUG_ON(*hpage); 1783 /* 1784 * Allocate the page while the vma is still valid and under 1785 * the mmap_sem read mode so there is no memory allocation 1786 * later when we take the mmap_sem in write mode. This is more 1787 * friendly behavior (OTOH it may actually hide bugs) to 1788 * filesystems in userland with daemons allocating memory in 1789 * the userland I/O paths. Allocating memory with the 1790 * mmap_sem in read mode is good idea also to allow greater 1791 * scalability. 1792 */ 1793 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address, 1794 node, __GFP_OTHER_NODE); 1795 if (unlikely(!new_page)) { 1796 up_read(&mm->mmap_sem); 1797 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 1798 *hpage = ERR_PTR(-ENOMEM); 1799 return; 1800 } 1801 count_vm_event(THP_COLLAPSE_ALLOC); 1802 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 1803 up_read(&mm->mmap_sem); 1804 put_page(new_page); 1805 return; 1806 } 1807#endif 1808 1809 /* after allocating the hugepage upgrade to mmap_sem write mode */ 1810 up_read(&mm->mmap_sem); 1811 1812 /* 1813 * Prevent all access to pagetables with the exception of 1814 * gup_fast later hanlded by the ptep_clear_flush and the VM 1815 * handled by the anon_vma lock + PG_lock. 1816 */ 1817 down_write(&mm->mmap_sem); 1818 if (unlikely(khugepaged_test_exit(mm))) 1819 goto out; 1820 1821 vma = find_vma(mm, address); 1822 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1823 hend = vma->vm_end & HPAGE_PMD_MASK; 1824 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 1825 goto out; 1826 1827 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 1828 (vma->vm_flags & VM_NOHUGEPAGE)) 1829 goto out; 1830 1831 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */ 1832 if (!vma->anon_vma || vma->vm_ops || vma->vm_file) 1833 goto out; 1834 if (is_vma_temporary_stack(vma)) 1835 goto out; 1836 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma)); 1837 1838 pgd = pgd_offset(mm, address); 1839 if (!pgd_present(*pgd)) 1840 goto out; 1841 1842 pud = pud_offset(pgd, address); 1843 if (!pud_present(*pud)) 1844 goto out; 1845 1846 pmd = pmd_offset(pud, address); 1847 /* pmd can't go away or become huge under us */ 1848 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd)) 1849 goto out; 1850 1851 anon_vma_lock(vma->anon_vma); 1852 1853 pte = pte_offset_map(pmd, address); 1854 ptl = pte_lockptr(mm, pmd); 1855 1856 spin_lock(&mm->page_table_lock); /* probably unnecessary */ 1857 /* 1858 * After this gup_fast can't run anymore. This also removes 1859 * any huge TLB entry from the CPU so we won't allow 1860 * huge and small TLB entries for the same virtual address 1861 * to avoid the risk of CPU bugs in that area. 1862 */ 1863 _pmd = pmdp_clear_flush_notify(vma, address, pmd); 1864 spin_unlock(&mm->page_table_lock); 1865 1866 spin_lock(ptl); 1867 isolated = __collapse_huge_page_isolate(vma, address, pte); 1868 spin_unlock(ptl); 1869 1870 if (unlikely(!isolated)) { 1871 pte_unmap(pte); 1872 spin_lock(&mm->page_table_lock); 1873 BUG_ON(!pmd_none(*pmd)); 1874 set_pmd_at(mm, address, pmd, _pmd); 1875 spin_unlock(&mm->page_table_lock); 1876 anon_vma_unlock(vma->anon_vma); 1877 goto out; 1878 } 1879 1880 /* 1881 * All pages are isolated and locked so anon_vma rmap 1882 * can't run anymore. 1883 */ 1884 anon_vma_unlock(vma->anon_vma); 1885 1886 __collapse_huge_page_copy(pte, new_page, vma, address, ptl); 1887 pte_unmap(pte); 1888 __SetPageUptodate(new_page); 1889 pgtable = pmd_pgtable(_pmd); 1890 VM_BUG_ON(page_count(pgtable) != 1); 1891 VM_BUG_ON(page_mapcount(pgtable) != 0); 1892 1893 _pmd = mk_pmd(new_page, vma->vm_page_prot); 1894 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 1895 _pmd = pmd_mkhuge(_pmd); 1896 1897 /* 1898 * spin_lock() below is not the equivalent of smp_wmb(), so 1899 * this is needed to avoid the copy_huge_page writes to become 1900 * visible after the set_pmd_at() write. 1901 */ 1902 smp_wmb(); 1903 1904 spin_lock(&mm->page_table_lock); 1905 BUG_ON(!pmd_none(*pmd)); 1906 page_add_new_anon_rmap(new_page, vma, address); 1907 set_pmd_at(mm, address, pmd, _pmd); 1908 update_mmu_cache(vma, address, entry); 1909 prepare_pmd_huge_pte(pgtable, mm); 1910 mm->nr_ptes--; 1911 spin_unlock(&mm->page_table_lock); 1912 1913#ifndef CONFIG_NUMA 1914 *hpage = NULL; 1915#endif 1916 khugepaged_pages_collapsed++; 1917out_up_write: 1918 up_write(&mm->mmap_sem); 1919 return; 1920 1921out: 1922 mem_cgroup_uncharge_page(new_page); 1923#ifdef CONFIG_NUMA 1924 put_page(new_page); 1925#endif 1926 goto out_up_write; 1927} 1928 1929static int khugepaged_scan_pmd(struct mm_struct *mm, 1930 struct vm_area_struct *vma, 1931 unsigned long address, 1932 struct page **hpage) 1933{ 1934 pgd_t *pgd; 1935 pud_t *pud; 1936 pmd_t *pmd; 1937 pte_t *pte, *_pte; 1938 int ret = 0, referenced = 0, none = 0; 1939 struct page *page; 1940 unsigned long _address; 1941 spinlock_t *ptl; 1942 int node = -1; 1943 1944 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1945 1946 pgd = pgd_offset(mm, address); 1947 if (!pgd_present(*pgd)) 1948 goto out; 1949 1950 pud = pud_offset(pgd, address); 1951 if (!pud_present(*pud)) 1952 goto out; 1953 1954 pmd = pmd_offset(pud, address); 1955 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd)) 1956 goto out; 1957 1958 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 1959 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 1960 _pte++, _address += PAGE_SIZE) { 1961 pte_t pteval = *_pte; 1962 if (pte_none(pteval)) { 1963 if (++none <= khugepaged_max_ptes_none) 1964 continue; 1965 else 1966 goto out_unmap; 1967 } 1968 if (!pte_present(pteval) || !pte_write(pteval)) 1969 goto out_unmap; 1970 page = vm_normal_page(vma, _address, pteval); 1971 if (unlikely(!page)) 1972 goto out_unmap; 1973 /* 1974 * Chose the node of the first page. This could 1975 * be more sophisticated and look at more pages, 1976 * but isn't for now. 1977 */ 1978 if (node == -1) 1979 node = page_to_nid(page); 1980 VM_BUG_ON(PageCompound(page)); 1981 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) 1982 goto out_unmap; 1983 /* cannot use mapcount: can't collapse if there's a gup pin */ 1984 if (page_count(page) != 1) 1985 goto out_unmap; 1986 if (pte_young(pteval) || PageReferenced(page) || 1987 mmu_notifier_test_young(vma->vm_mm, address)) 1988 referenced = 1; 1989 } 1990 if (referenced) 1991 ret = 1; 1992out_unmap: 1993 pte_unmap_unlock(pte, ptl); 1994 if (ret) 1995 /* collapse_huge_page will return with the mmap_sem released */ 1996 collapse_huge_page(mm, address, hpage, vma, node); 1997out: 1998 return ret; 1999} 2000 2001static void collect_mm_slot(struct mm_slot *mm_slot) 2002{ 2003 struct mm_struct *mm = mm_slot->mm; 2004 2005 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock)); 2006 2007 if (khugepaged_test_exit(mm)) { 2008 /* free mm_slot */ 2009 hlist_del(&mm_slot->hash); 2010 list_del(&mm_slot->mm_node); 2011 2012 /* 2013 * Not strictly needed because the mm exited already. 2014 * 2015 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2016 */ 2017 2018 /* khugepaged_mm_lock actually not necessary for the below */ 2019 free_mm_slot(mm_slot); 2020 mmdrop(mm); 2021 } 2022} 2023 2024static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2025 struct page **hpage) 2026{ 2027 struct mm_slot *mm_slot; 2028 struct mm_struct *mm; 2029 struct vm_area_struct *vma; 2030 int progress = 0; 2031 2032 VM_BUG_ON(!pages); 2033 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock)); 2034 2035 if (khugepaged_scan.mm_slot) 2036 mm_slot = khugepaged_scan.mm_slot; 2037 else { 2038 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2039 struct mm_slot, mm_node); 2040 khugepaged_scan.address = 0; 2041 khugepaged_scan.mm_slot = mm_slot; 2042 } 2043 spin_unlock(&khugepaged_mm_lock); 2044 2045 mm = mm_slot->mm; 2046 down_read(&mm->mmap_sem); 2047 if (unlikely(khugepaged_test_exit(mm))) 2048 vma = NULL; 2049 else 2050 vma = find_vma(mm, khugepaged_scan.address); 2051 2052 progress++; 2053 for (; vma; vma = vma->vm_next) { 2054 unsigned long hstart, hend; 2055 2056 cond_resched(); 2057 if (unlikely(khugepaged_test_exit(mm))) { 2058 progress++; 2059 break; 2060 } 2061 2062 if ((!(vma->vm_flags & VM_HUGEPAGE) && 2063 !khugepaged_always()) || 2064 (vma->vm_flags & VM_NOHUGEPAGE)) { 2065 skip: 2066 progress++; 2067 continue; 2068 } 2069 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */ 2070 if (!vma->anon_vma || vma->vm_ops || vma->vm_file) 2071 goto skip; 2072 if (is_vma_temporary_stack(vma)) 2073 goto skip; 2074 2075 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma)); 2076 2077 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2078 hend = vma->vm_end & HPAGE_PMD_MASK; 2079 if (hstart >= hend) 2080 goto skip; 2081 if (khugepaged_scan.address > hend) 2082 goto skip; 2083 if (khugepaged_scan.address < hstart) 2084 khugepaged_scan.address = hstart; 2085 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2086 2087 while (khugepaged_scan.address < hend) { 2088 int ret; 2089 cond_resched(); 2090 if (unlikely(khugepaged_test_exit(mm))) 2091 goto breakouterloop; 2092 2093 VM_BUG_ON(khugepaged_scan.address < hstart || 2094 khugepaged_scan.address + HPAGE_PMD_SIZE > 2095 hend); 2096 ret = khugepaged_scan_pmd(mm, vma, 2097 khugepaged_scan.address, 2098 hpage); 2099 /* move to next address */ 2100 khugepaged_scan.address += HPAGE_PMD_SIZE; 2101 progress += HPAGE_PMD_NR; 2102 if (ret) 2103 /* we released mmap_sem so break loop */ 2104 goto breakouterloop_mmap_sem; 2105 if (progress >= pages) 2106 goto breakouterloop; 2107 } 2108 } 2109breakouterloop: 2110 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2111breakouterloop_mmap_sem: 2112 2113 spin_lock(&khugepaged_mm_lock); 2114 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2115 /* 2116 * Release the current mm_slot if this mm is about to die, or 2117 * if we scanned all vmas of this mm. 2118 */ 2119 if (khugepaged_test_exit(mm) || !vma) { 2120 /* 2121 * Make sure that if mm_users is reaching zero while 2122 * khugepaged runs here, khugepaged_exit will find 2123 * mm_slot not pointing to the exiting mm. 2124 */ 2125 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2126 khugepaged_scan.mm_slot = list_entry( 2127 mm_slot->mm_node.next, 2128 struct mm_slot, mm_node); 2129 khugepaged_scan.address = 0; 2130 } else { 2131 khugepaged_scan.mm_slot = NULL; 2132 khugepaged_full_scans++; 2133 } 2134 2135 collect_mm_slot(mm_slot); 2136 } 2137 2138 return progress; 2139} 2140 2141static int khugepaged_has_work(void) 2142{ 2143 return !list_empty(&khugepaged_scan.mm_head) && 2144 khugepaged_enabled(); 2145} 2146 2147static int khugepaged_wait_event(void) 2148{ 2149 return !list_empty(&khugepaged_scan.mm_head) || 2150 !khugepaged_enabled(); 2151} 2152 2153static void khugepaged_do_scan(struct page **hpage) 2154{ 2155 unsigned int progress = 0, pass_through_head = 0; 2156 unsigned int pages = khugepaged_pages_to_scan; 2157 2158 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2159 2160 while (progress < pages) { 2161 cond_resched(); 2162 2163#ifndef CONFIG_NUMA 2164 if (!*hpage) { 2165 *hpage = alloc_hugepage(khugepaged_defrag()); 2166 if (unlikely(!*hpage)) { 2167 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2168 break; 2169 } 2170 count_vm_event(THP_COLLAPSE_ALLOC); 2171 } 2172#else 2173 if (IS_ERR(*hpage)) 2174 break; 2175#endif 2176 2177 if (unlikely(kthread_should_stop() || freezing(current))) 2178 break; 2179 2180 spin_lock(&khugepaged_mm_lock); 2181 if (!khugepaged_scan.mm_slot) 2182 pass_through_head++; 2183 if (khugepaged_has_work() && 2184 pass_through_head < 2) 2185 progress += khugepaged_scan_mm_slot(pages - progress, 2186 hpage); 2187 else 2188 progress = pages; 2189 spin_unlock(&khugepaged_mm_lock); 2190 } 2191} 2192 2193static void khugepaged_alloc_sleep(void) 2194{ 2195 DEFINE_WAIT(wait); 2196 add_wait_queue(&khugepaged_wait, &wait); 2197 schedule_timeout_interruptible( 2198 msecs_to_jiffies( 2199 khugepaged_alloc_sleep_millisecs)); 2200 remove_wait_queue(&khugepaged_wait, &wait); 2201} 2202 2203#ifndef CONFIG_NUMA 2204static struct page *khugepaged_alloc_hugepage(void) 2205{ 2206 struct page *hpage; 2207 2208 do { 2209 hpage = alloc_hugepage(khugepaged_defrag()); 2210 if (!hpage) { 2211 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2212 khugepaged_alloc_sleep(); 2213 } else 2214 count_vm_event(THP_COLLAPSE_ALLOC); 2215 } while (unlikely(!hpage) && 2216 likely(khugepaged_enabled())); 2217 return hpage; 2218} 2219#endif 2220 2221static void khugepaged_loop(void) 2222{ 2223 struct page *hpage; 2224 2225#ifdef CONFIG_NUMA 2226 hpage = NULL; 2227#endif 2228 while (likely(khugepaged_enabled())) { 2229#ifndef CONFIG_NUMA 2230 hpage = khugepaged_alloc_hugepage(); 2231 if (unlikely(!hpage)) { 2232 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2233 break; 2234 } 2235 count_vm_event(THP_COLLAPSE_ALLOC); 2236#else 2237 if (IS_ERR(hpage)) { 2238 khugepaged_alloc_sleep(); 2239 hpage = NULL; 2240 } 2241#endif 2242 2243 khugepaged_do_scan(&hpage); 2244#ifndef CONFIG_NUMA 2245 if (hpage) 2246 put_page(hpage); 2247#endif 2248 try_to_freeze(); 2249 if (unlikely(kthread_should_stop())) 2250 break; 2251 if (khugepaged_has_work()) { 2252 DEFINE_WAIT(wait); 2253 if (!khugepaged_scan_sleep_millisecs) 2254 continue; 2255 add_wait_queue(&khugepaged_wait, &wait); 2256 schedule_timeout_interruptible( 2257 msecs_to_jiffies( 2258 khugepaged_scan_sleep_millisecs)); 2259 remove_wait_queue(&khugepaged_wait, &wait); 2260 } else if (khugepaged_enabled()) 2261 wait_event_freezable(khugepaged_wait, 2262 khugepaged_wait_event()); 2263 } 2264} 2265 2266static int khugepaged(void *none) 2267{ 2268 struct mm_slot *mm_slot; 2269 2270 set_freezable(); 2271 set_user_nice(current, 19); 2272 2273 /* serialize with start_khugepaged() */ 2274 mutex_lock(&khugepaged_mutex); 2275 2276 for (;;) { 2277 mutex_unlock(&khugepaged_mutex); 2278 VM_BUG_ON(khugepaged_thread != current); 2279 khugepaged_loop(); 2280 VM_BUG_ON(khugepaged_thread != current); 2281 2282 mutex_lock(&khugepaged_mutex); 2283 if (!khugepaged_enabled()) 2284 break; 2285 if (unlikely(kthread_should_stop())) 2286 break; 2287 } 2288 2289 spin_lock(&khugepaged_mm_lock); 2290 mm_slot = khugepaged_scan.mm_slot; 2291 khugepaged_scan.mm_slot = NULL; 2292 if (mm_slot) 2293 collect_mm_slot(mm_slot); 2294 spin_unlock(&khugepaged_mm_lock); 2295 2296 khugepaged_thread = NULL; 2297 mutex_unlock(&khugepaged_mutex); 2298 2299 return 0; 2300} 2301 2302void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd) 2303{ 2304 struct page *page; 2305 2306 spin_lock(&mm->page_table_lock); 2307 if (unlikely(!pmd_trans_huge(*pmd))) { 2308 spin_unlock(&mm->page_table_lock); 2309 return; 2310 } 2311 page = pmd_page(*pmd); 2312 VM_BUG_ON(!page_count(page)); 2313 get_page(page); 2314 spin_unlock(&mm->page_table_lock); 2315 2316 split_huge_page(page); 2317 2318 put_page(page); 2319 BUG_ON(pmd_trans_huge(*pmd)); 2320} 2321 2322static void split_huge_page_address(struct mm_struct *mm, 2323 unsigned long address) 2324{ 2325 pgd_t *pgd; 2326 pud_t *pud; 2327 pmd_t *pmd; 2328 2329 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); 2330 2331 pgd = pgd_offset(mm, address); 2332 if (!pgd_present(*pgd)) 2333 return; 2334 2335 pud = pud_offset(pgd, address); 2336 if (!pud_present(*pud)) 2337 return; 2338 2339 pmd = pmd_offset(pud, address); 2340 if (!pmd_present(*pmd)) 2341 return; 2342 /* 2343 * Caller holds the mmap_sem write mode, so a huge pmd cannot 2344 * materialize from under us. 2345 */ 2346 split_huge_page_pmd(mm, pmd); 2347} 2348 2349void __vma_adjust_trans_huge(struct vm_area_struct *vma, 2350 unsigned long start, 2351 unsigned long end, 2352 long adjust_next) 2353{ 2354 /* 2355 * If the new start address isn't hpage aligned and it could 2356 * previously contain an hugepage: check if we need to split 2357 * an huge pmd. 2358 */ 2359 if (start & ~HPAGE_PMD_MASK && 2360 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2361 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2362 split_huge_page_address(vma->vm_mm, start); 2363 2364 /* 2365 * If the new end address isn't hpage aligned and it could 2366 * previously contain an hugepage: check if we need to split 2367 * an huge pmd. 2368 */ 2369 if (end & ~HPAGE_PMD_MASK && 2370 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2371 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2372 split_huge_page_address(vma->vm_mm, end); 2373 2374 /* 2375 * If we're also updating the vma->vm_next->vm_start, if the new 2376 * vm_next->vm_start isn't page aligned and it could previously 2377 * contain an hugepage: check if we need to split an huge pmd. 2378 */ 2379 if (adjust_next > 0) { 2380 struct vm_area_struct *next = vma->vm_next; 2381 unsigned long nstart = next->vm_start; 2382 nstart += adjust_next << PAGE_SHIFT; 2383 if (nstart & ~HPAGE_PMD_MASK && 2384 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2385 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2386 split_huge_page_address(next->vm_mm, nstart); 2387 } 2388} 2389