huge_memory.c revision ba76149f47d8c939efa0acc07a191237af900471
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 <asm/tlb.h> 19#include <asm/pgalloc.h> 20#include "internal.h" 21 22/* 23 * By default transparent hugepage support is enabled for all mappings 24 * and khugepaged scans all mappings. Defrag is only invoked by 25 * khugepaged hugepage allocations and by page faults inside 26 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived 27 * allocations. 28 */ 29unsigned long transparent_hugepage_flags __read_mostly = 30 (1<<TRANSPARENT_HUGEPAGE_FLAG)| 31 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 32 33/* default scan 8*512 pte (or vmas) every 30 second */ 34static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8; 35static unsigned int khugepaged_pages_collapsed; 36static unsigned int khugepaged_full_scans; 37static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 38/* during fragmentation poll the hugepage allocator once every minute */ 39static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 40static struct task_struct *khugepaged_thread __read_mostly; 41static DEFINE_MUTEX(khugepaged_mutex); 42static DEFINE_SPINLOCK(khugepaged_mm_lock); 43static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 44/* 45 * default collapse hugepages if there is at least one pte mapped like 46 * it would have happened if the vma was large enough during page 47 * fault. 48 */ 49static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1; 50 51static int khugepaged(void *none); 52static int mm_slots_hash_init(void); 53static int khugepaged_slab_init(void); 54static void khugepaged_slab_free(void); 55 56#define MM_SLOTS_HASH_HEADS 1024 57static struct hlist_head *mm_slots_hash __read_mostly; 58static struct kmem_cache *mm_slot_cache __read_mostly; 59 60/** 61 * struct mm_slot - hash lookup from mm to mm_slot 62 * @hash: hash collision list 63 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 64 * @mm: the mm that this information is valid for 65 */ 66struct mm_slot { 67 struct hlist_node hash; 68 struct list_head mm_node; 69 struct mm_struct *mm; 70}; 71 72/** 73 * struct khugepaged_scan - cursor for scanning 74 * @mm_head: the head of the mm list to scan 75 * @mm_slot: the current mm_slot we are scanning 76 * @address: the next address inside that to be scanned 77 * 78 * There is only the one khugepaged_scan instance of this cursor structure. 79 */ 80struct khugepaged_scan { 81 struct list_head mm_head; 82 struct mm_slot *mm_slot; 83 unsigned long address; 84} khugepaged_scan = { 85 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 86}; 87 88static int start_khugepaged(void) 89{ 90 int err = 0; 91 if (khugepaged_enabled()) { 92 int wakeup; 93 if (unlikely(!mm_slot_cache || !mm_slots_hash)) { 94 err = -ENOMEM; 95 goto out; 96 } 97 mutex_lock(&khugepaged_mutex); 98 if (!khugepaged_thread) 99 khugepaged_thread = kthread_run(khugepaged, NULL, 100 "khugepaged"); 101 if (unlikely(IS_ERR(khugepaged_thread))) { 102 printk(KERN_ERR 103 "khugepaged: kthread_run(khugepaged) failed\n"); 104 err = PTR_ERR(khugepaged_thread); 105 khugepaged_thread = NULL; 106 } 107 wakeup = !list_empty(&khugepaged_scan.mm_head); 108 mutex_unlock(&khugepaged_mutex); 109 if (wakeup) 110 wake_up_interruptible(&khugepaged_wait); 111 } else 112 /* wakeup to exit */ 113 wake_up_interruptible(&khugepaged_wait); 114out: 115 return err; 116} 117 118#ifdef CONFIG_SYSFS 119 120static ssize_t double_flag_show(struct kobject *kobj, 121 struct kobj_attribute *attr, char *buf, 122 enum transparent_hugepage_flag enabled, 123 enum transparent_hugepage_flag req_madv) 124{ 125 if (test_bit(enabled, &transparent_hugepage_flags)) { 126 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); 127 return sprintf(buf, "[always] madvise never\n"); 128 } else if (test_bit(req_madv, &transparent_hugepage_flags)) 129 return sprintf(buf, "always [madvise] never\n"); 130 else 131 return sprintf(buf, "always madvise [never]\n"); 132} 133static ssize_t double_flag_store(struct kobject *kobj, 134 struct kobj_attribute *attr, 135 const char *buf, size_t count, 136 enum transparent_hugepage_flag enabled, 137 enum transparent_hugepage_flag req_madv) 138{ 139 if (!memcmp("always", buf, 140 min(sizeof("always")-1, count))) { 141 set_bit(enabled, &transparent_hugepage_flags); 142 clear_bit(req_madv, &transparent_hugepage_flags); 143 } else if (!memcmp("madvise", buf, 144 min(sizeof("madvise")-1, count))) { 145 clear_bit(enabled, &transparent_hugepage_flags); 146 set_bit(req_madv, &transparent_hugepage_flags); 147 } else if (!memcmp("never", buf, 148 min(sizeof("never")-1, count))) { 149 clear_bit(enabled, &transparent_hugepage_flags); 150 clear_bit(req_madv, &transparent_hugepage_flags); 151 } else 152 return -EINVAL; 153 154 return count; 155} 156 157static ssize_t enabled_show(struct kobject *kobj, 158 struct kobj_attribute *attr, char *buf) 159{ 160 return double_flag_show(kobj, attr, buf, 161 TRANSPARENT_HUGEPAGE_FLAG, 162 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 163} 164static ssize_t enabled_store(struct kobject *kobj, 165 struct kobj_attribute *attr, 166 const char *buf, size_t count) 167{ 168 ssize_t ret; 169 170 ret = double_flag_store(kobj, attr, buf, count, 171 TRANSPARENT_HUGEPAGE_FLAG, 172 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 173 174 if (ret > 0) { 175 int err = start_khugepaged(); 176 if (err) 177 ret = err; 178 } 179 180 return ret; 181} 182static struct kobj_attribute enabled_attr = 183 __ATTR(enabled, 0644, enabled_show, enabled_store); 184 185static ssize_t single_flag_show(struct kobject *kobj, 186 struct kobj_attribute *attr, char *buf, 187 enum transparent_hugepage_flag flag) 188{ 189 if (test_bit(flag, &transparent_hugepage_flags)) 190 return sprintf(buf, "[yes] no\n"); 191 else 192 return sprintf(buf, "yes [no]\n"); 193} 194static ssize_t single_flag_store(struct kobject *kobj, 195 struct kobj_attribute *attr, 196 const char *buf, size_t count, 197 enum transparent_hugepage_flag flag) 198{ 199 if (!memcmp("yes", buf, 200 min(sizeof("yes")-1, count))) { 201 set_bit(flag, &transparent_hugepage_flags); 202 } else if (!memcmp("no", buf, 203 min(sizeof("no")-1, count))) { 204 clear_bit(flag, &transparent_hugepage_flags); 205 } else 206 return -EINVAL; 207 208 return count; 209} 210 211/* 212 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind 213 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of 214 * memory just to allocate one more hugepage. 215 */ 216static ssize_t defrag_show(struct kobject *kobj, 217 struct kobj_attribute *attr, char *buf) 218{ 219 return double_flag_show(kobj, attr, buf, 220 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 221 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 222} 223static ssize_t defrag_store(struct kobject *kobj, 224 struct kobj_attribute *attr, 225 const char *buf, size_t count) 226{ 227 return double_flag_store(kobj, attr, buf, count, 228 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 229 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 230} 231static struct kobj_attribute defrag_attr = 232 __ATTR(defrag, 0644, defrag_show, defrag_store); 233 234#ifdef CONFIG_DEBUG_VM 235static ssize_t debug_cow_show(struct kobject *kobj, 236 struct kobj_attribute *attr, char *buf) 237{ 238 return single_flag_show(kobj, attr, buf, 239 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 240} 241static ssize_t debug_cow_store(struct kobject *kobj, 242 struct kobj_attribute *attr, 243 const char *buf, size_t count) 244{ 245 return single_flag_store(kobj, attr, buf, count, 246 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 247} 248static struct kobj_attribute debug_cow_attr = 249 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 250#endif /* CONFIG_DEBUG_VM */ 251 252static struct attribute *hugepage_attr[] = { 253 &enabled_attr.attr, 254 &defrag_attr.attr, 255#ifdef CONFIG_DEBUG_VM 256 &debug_cow_attr.attr, 257#endif 258 NULL, 259}; 260 261static struct attribute_group hugepage_attr_group = { 262 .attrs = hugepage_attr, 263}; 264 265static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 266 struct kobj_attribute *attr, 267 char *buf) 268{ 269 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 270} 271 272static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 273 struct kobj_attribute *attr, 274 const char *buf, size_t count) 275{ 276 unsigned long msecs; 277 int err; 278 279 err = strict_strtoul(buf, 10, &msecs); 280 if (err || msecs > UINT_MAX) 281 return -EINVAL; 282 283 khugepaged_scan_sleep_millisecs = msecs; 284 wake_up_interruptible(&khugepaged_wait); 285 286 return count; 287} 288static struct kobj_attribute scan_sleep_millisecs_attr = 289 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 290 scan_sleep_millisecs_store); 291 292static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 293 struct kobj_attribute *attr, 294 char *buf) 295{ 296 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 297} 298 299static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 300 struct kobj_attribute *attr, 301 const char *buf, size_t count) 302{ 303 unsigned long msecs; 304 int err; 305 306 err = strict_strtoul(buf, 10, &msecs); 307 if (err || msecs > UINT_MAX) 308 return -EINVAL; 309 310 khugepaged_alloc_sleep_millisecs = msecs; 311 wake_up_interruptible(&khugepaged_wait); 312 313 return count; 314} 315static struct kobj_attribute alloc_sleep_millisecs_attr = 316 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 317 alloc_sleep_millisecs_store); 318 319static ssize_t pages_to_scan_show(struct kobject *kobj, 320 struct kobj_attribute *attr, 321 char *buf) 322{ 323 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 324} 325static ssize_t pages_to_scan_store(struct kobject *kobj, 326 struct kobj_attribute *attr, 327 const char *buf, size_t count) 328{ 329 int err; 330 unsigned long pages; 331 332 err = strict_strtoul(buf, 10, &pages); 333 if (err || !pages || pages > UINT_MAX) 334 return -EINVAL; 335 336 khugepaged_pages_to_scan = pages; 337 338 return count; 339} 340static struct kobj_attribute pages_to_scan_attr = 341 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 342 pages_to_scan_store); 343 344static ssize_t pages_collapsed_show(struct kobject *kobj, 345 struct kobj_attribute *attr, 346 char *buf) 347{ 348 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 349} 350static struct kobj_attribute pages_collapsed_attr = 351 __ATTR_RO(pages_collapsed); 352 353static ssize_t full_scans_show(struct kobject *kobj, 354 struct kobj_attribute *attr, 355 char *buf) 356{ 357 return sprintf(buf, "%u\n", khugepaged_full_scans); 358} 359static struct kobj_attribute full_scans_attr = 360 __ATTR_RO(full_scans); 361 362static ssize_t khugepaged_defrag_show(struct kobject *kobj, 363 struct kobj_attribute *attr, char *buf) 364{ 365 return single_flag_show(kobj, attr, buf, 366 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 367} 368static ssize_t khugepaged_defrag_store(struct kobject *kobj, 369 struct kobj_attribute *attr, 370 const char *buf, size_t count) 371{ 372 return single_flag_store(kobj, attr, buf, count, 373 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 374} 375static struct kobj_attribute khugepaged_defrag_attr = 376 __ATTR(defrag, 0644, khugepaged_defrag_show, 377 khugepaged_defrag_store); 378 379/* 380 * max_ptes_none controls if khugepaged should collapse hugepages over 381 * any unmapped ptes in turn potentially increasing the memory 382 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 383 * reduce the available free memory in the system as it 384 * runs. Increasing max_ptes_none will instead potentially reduce the 385 * free memory in the system during the khugepaged scan. 386 */ 387static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 388 struct kobj_attribute *attr, 389 char *buf) 390{ 391 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 392} 393static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 394 struct kobj_attribute *attr, 395 const char *buf, size_t count) 396{ 397 int err; 398 unsigned long max_ptes_none; 399 400 err = strict_strtoul(buf, 10, &max_ptes_none); 401 if (err || max_ptes_none > HPAGE_PMD_NR-1) 402 return -EINVAL; 403 404 khugepaged_max_ptes_none = max_ptes_none; 405 406 return count; 407} 408static struct kobj_attribute khugepaged_max_ptes_none_attr = 409 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 410 khugepaged_max_ptes_none_store); 411 412static struct attribute *khugepaged_attr[] = { 413 &khugepaged_defrag_attr.attr, 414 &khugepaged_max_ptes_none_attr.attr, 415 &pages_to_scan_attr.attr, 416 &pages_collapsed_attr.attr, 417 &full_scans_attr.attr, 418 &scan_sleep_millisecs_attr.attr, 419 &alloc_sleep_millisecs_attr.attr, 420 NULL, 421}; 422 423static struct attribute_group khugepaged_attr_group = { 424 .attrs = khugepaged_attr, 425 .name = "khugepaged", 426}; 427#endif /* CONFIG_SYSFS */ 428 429static int __init hugepage_init(void) 430{ 431 int err; 432#ifdef CONFIG_SYSFS 433 static struct kobject *hugepage_kobj; 434 435 err = -ENOMEM; 436 hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 437 if (unlikely(!hugepage_kobj)) { 438 printk(KERN_ERR "hugepage: failed kobject create\n"); 439 goto out; 440 } 441 442 err = sysfs_create_group(hugepage_kobj, &hugepage_attr_group); 443 if (err) { 444 printk(KERN_ERR "hugepage: failed register hugeage group\n"); 445 goto out; 446 } 447 448 err = sysfs_create_group(hugepage_kobj, &khugepaged_attr_group); 449 if (err) { 450 printk(KERN_ERR "hugepage: failed register hugeage group\n"); 451 goto out; 452 } 453#endif 454 455 err = khugepaged_slab_init(); 456 if (err) 457 goto out; 458 459 err = mm_slots_hash_init(); 460 if (err) { 461 khugepaged_slab_free(); 462 goto out; 463 } 464 465 start_khugepaged(); 466 467out: 468 return err; 469} 470module_init(hugepage_init) 471 472static int __init setup_transparent_hugepage(char *str) 473{ 474 int ret = 0; 475 if (!str) 476 goto out; 477 if (!strcmp(str, "always")) { 478 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 479 &transparent_hugepage_flags); 480 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 481 &transparent_hugepage_flags); 482 ret = 1; 483 } else if (!strcmp(str, "madvise")) { 484 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 485 &transparent_hugepage_flags); 486 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 487 &transparent_hugepage_flags); 488 ret = 1; 489 } else if (!strcmp(str, "never")) { 490 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 491 &transparent_hugepage_flags); 492 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 493 &transparent_hugepage_flags); 494 ret = 1; 495 } 496out: 497 if (!ret) 498 printk(KERN_WARNING 499 "transparent_hugepage= cannot parse, ignored\n"); 500 return ret; 501} 502__setup("transparent_hugepage=", setup_transparent_hugepage); 503 504static void prepare_pmd_huge_pte(pgtable_t pgtable, 505 struct mm_struct *mm) 506{ 507 assert_spin_locked(&mm->page_table_lock); 508 509 /* FIFO */ 510 if (!mm->pmd_huge_pte) 511 INIT_LIST_HEAD(&pgtable->lru); 512 else 513 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru); 514 mm->pmd_huge_pte = pgtable; 515} 516 517static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 518{ 519 if (likely(vma->vm_flags & VM_WRITE)) 520 pmd = pmd_mkwrite(pmd); 521 return pmd; 522} 523 524static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, 525 struct vm_area_struct *vma, 526 unsigned long haddr, pmd_t *pmd, 527 struct page *page) 528{ 529 int ret = 0; 530 pgtable_t pgtable; 531 532 VM_BUG_ON(!PageCompound(page)); 533 pgtable = pte_alloc_one(mm, haddr); 534 if (unlikely(!pgtable)) { 535 mem_cgroup_uncharge_page(page); 536 put_page(page); 537 return VM_FAULT_OOM; 538 } 539 540 clear_huge_page(page, haddr, HPAGE_PMD_NR); 541 __SetPageUptodate(page); 542 543 spin_lock(&mm->page_table_lock); 544 if (unlikely(!pmd_none(*pmd))) { 545 spin_unlock(&mm->page_table_lock); 546 mem_cgroup_uncharge_page(page); 547 put_page(page); 548 pte_free(mm, pgtable); 549 } else { 550 pmd_t entry; 551 entry = mk_pmd(page, vma->vm_page_prot); 552 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 553 entry = pmd_mkhuge(entry); 554 /* 555 * The spinlocking to take the lru_lock inside 556 * page_add_new_anon_rmap() acts as a full memory 557 * barrier to be sure clear_huge_page writes become 558 * visible after the set_pmd_at() write. 559 */ 560 page_add_new_anon_rmap(page, vma, haddr); 561 set_pmd_at(mm, haddr, pmd, entry); 562 prepare_pmd_huge_pte(pgtable, mm); 563 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 564 spin_unlock(&mm->page_table_lock); 565 } 566 567 return ret; 568} 569 570static inline struct page *alloc_hugepage(int defrag) 571{ 572 return alloc_pages(GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT), 573 HPAGE_PMD_ORDER); 574} 575 576int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 577 unsigned long address, pmd_t *pmd, 578 unsigned int flags) 579{ 580 struct page *page; 581 unsigned long haddr = address & HPAGE_PMD_MASK; 582 pte_t *pte; 583 584 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) { 585 if (unlikely(anon_vma_prepare(vma))) 586 return VM_FAULT_OOM; 587 if (unlikely(khugepaged_enter(vma))) 588 return VM_FAULT_OOM; 589 page = alloc_hugepage(transparent_hugepage_defrag(vma)); 590 if (unlikely(!page)) 591 goto out; 592 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) { 593 put_page(page); 594 goto out; 595 } 596 597 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page); 598 } 599out: 600 /* 601 * Use __pte_alloc instead of pte_alloc_map, because we can't 602 * run pte_offset_map on the pmd, if an huge pmd could 603 * materialize from under us from a different thread. 604 */ 605 if (unlikely(__pte_alloc(mm, vma, pmd, address))) 606 return VM_FAULT_OOM; 607 /* if an huge pmd materialized from under us just retry later */ 608 if (unlikely(pmd_trans_huge(*pmd))) 609 return 0; 610 /* 611 * A regular pmd is established and it can't morph into a huge pmd 612 * from under us anymore at this point because we hold the mmap_sem 613 * read mode and khugepaged takes it in write mode. So now it's 614 * safe to run pte_offset_map(). 615 */ 616 pte = pte_offset_map(pmd, address); 617 return handle_pte_fault(mm, vma, address, pte, pmd, flags); 618} 619 620int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 621 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 622 struct vm_area_struct *vma) 623{ 624 struct page *src_page; 625 pmd_t pmd; 626 pgtable_t pgtable; 627 int ret; 628 629 ret = -ENOMEM; 630 pgtable = pte_alloc_one(dst_mm, addr); 631 if (unlikely(!pgtable)) 632 goto out; 633 634 spin_lock(&dst_mm->page_table_lock); 635 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING); 636 637 ret = -EAGAIN; 638 pmd = *src_pmd; 639 if (unlikely(!pmd_trans_huge(pmd))) { 640 pte_free(dst_mm, pgtable); 641 goto out_unlock; 642 } 643 if (unlikely(pmd_trans_splitting(pmd))) { 644 /* split huge page running from under us */ 645 spin_unlock(&src_mm->page_table_lock); 646 spin_unlock(&dst_mm->page_table_lock); 647 pte_free(dst_mm, pgtable); 648 649 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ 650 goto out; 651 } 652 src_page = pmd_page(pmd); 653 VM_BUG_ON(!PageHead(src_page)); 654 get_page(src_page); 655 page_dup_rmap(src_page); 656 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 657 658 pmdp_set_wrprotect(src_mm, addr, src_pmd); 659 pmd = pmd_mkold(pmd_wrprotect(pmd)); 660 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 661 prepare_pmd_huge_pte(pgtable, dst_mm); 662 663 ret = 0; 664out_unlock: 665 spin_unlock(&src_mm->page_table_lock); 666 spin_unlock(&dst_mm->page_table_lock); 667out: 668 return ret; 669} 670 671/* no "address" argument so destroys page coloring of some arch */ 672pgtable_t get_pmd_huge_pte(struct mm_struct *mm) 673{ 674 pgtable_t pgtable; 675 676 assert_spin_locked(&mm->page_table_lock); 677 678 /* FIFO */ 679 pgtable = mm->pmd_huge_pte; 680 if (list_empty(&pgtable->lru)) 681 mm->pmd_huge_pte = NULL; 682 else { 683 mm->pmd_huge_pte = list_entry(pgtable->lru.next, 684 struct page, lru); 685 list_del(&pgtable->lru); 686 } 687 return pgtable; 688} 689 690static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, 691 struct vm_area_struct *vma, 692 unsigned long address, 693 pmd_t *pmd, pmd_t orig_pmd, 694 struct page *page, 695 unsigned long haddr) 696{ 697 pgtable_t pgtable; 698 pmd_t _pmd; 699 int ret = 0, i; 700 struct page **pages; 701 702 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 703 GFP_KERNEL); 704 if (unlikely(!pages)) { 705 ret |= VM_FAULT_OOM; 706 goto out; 707 } 708 709 for (i = 0; i < HPAGE_PMD_NR; i++) { 710 pages[i] = alloc_page_vma(GFP_HIGHUSER_MOVABLE, 711 vma, address); 712 if (unlikely(!pages[i] || 713 mem_cgroup_newpage_charge(pages[i], mm, 714 GFP_KERNEL))) { 715 if (pages[i]) 716 put_page(pages[i]); 717 mem_cgroup_uncharge_start(); 718 while (--i >= 0) { 719 mem_cgroup_uncharge_page(pages[i]); 720 put_page(pages[i]); 721 } 722 mem_cgroup_uncharge_end(); 723 kfree(pages); 724 ret |= VM_FAULT_OOM; 725 goto out; 726 } 727 } 728 729 for (i = 0; i < HPAGE_PMD_NR; i++) { 730 copy_user_highpage(pages[i], page + i, 731 haddr + PAGE_SHIFT*i, vma); 732 __SetPageUptodate(pages[i]); 733 cond_resched(); 734 } 735 736 spin_lock(&mm->page_table_lock); 737 if (unlikely(!pmd_same(*pmd, orig_pmd))) 738 goto out_free_pages; 739 VM_BUG_ON(!PageHead(page)); 740 741 pmdp_clear_flush_notify(vma, haddr, pmd); 742 /* leave pmd empty until pte is filled */ 743 744 pgtable = get_pmd_huge_pte(mm); 745 pmd_populate(mm, &_pmd, pgtable); 746 747 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 748 pte_t *pte, entry; 749 entry = mk_pte(pages[i], vma->vm_page_prot); 750 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 751 page_add_new_anon_rmap(pages[i], vma, haddr); 752 pte = pte_offset_map(&_pmd, haddr); 753 VM_BUG_ON(!pte_none(*pte)); 754 set_pte_at(mm, haddr, pte, entry); 755 pte_unmap(pte); 756 } 757 kfree(pages); 758 759 mm->nr_ptes++; 760 smp_wmb(); /* make pte visible before pmd */ 761 pmd_populate(mm, pmd, pgtable); 762 page_remove_rmap(page); 763 spin_unlock(&mm->page_table_lock); 764 765 ret |= VM_FAULT_WRITE; 766 put_page(page); 767 768out: 769 return ret; 770 771out_free_pages: 772 spin_unlock(&mm->page_table_lock); 773 mem_cgroup_uncharge_start(); 774 for (i = 0; i < HPAGE_PMD_NR; i++) { 775 mem_cgroup_uncharge_page(pages[i]); 776 put_page(pages[i]); 777 } 778 mem_cgroup_uncharge_end(); 779 kfree(pages); 780 goto out; 781} 782 783int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 784 unsigned long address, pmd_t *pmd, pmd_t orig_pmd) 785{ 786 int ret = 0; 787 struct page *page, *new_page; 788 unsigned long haddr; 789 790 VM_BUG_ON(!vma->anon_vma); 791 spin_lock(&mm->page_table_lock); 792 if (unlikely(!pmd_same(*pmd, orig_pmd))) 793 goto out_unlock; 794 795 page = pmd_page(orig_pmd); 796 VM_BUG_ON(!PageCompound(page) || !PageHead(page)); 797 haddr = address & HPAGE_PMD_MASK; 798 if (page_mapcount(page) == 1) { 799 pmd_t entry; 800 entry = pmd_mkyoung(orig_pmd); 801 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 802 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 803 update_mmu_cache(vma, address, entry); 804 ret |= VM_FAULT_WRITE; 805 goto out_unlock; 806 } 807 get_page(page); 808 spin_unlock(&mm->page_table_lock); 809 810 if (transparent_hugepage_enabled(vma) && 811 !transparent_hugepage_debug_cow()) 812 new_page = alloc_hugepage(transparent_hugepage_defrag(vma)); 813 else 814 new_page = NULL; 815 816 if (unlikely(!new_page)) { 817 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 818 pmd, orig_pmd, page, haddr); 819 put_page(page); 820 goto out; 821 } 822 823 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 824 put_page(new_page); 825 put_page(page); 826 ret |= VM_FAULT_OOM; 827 goto out; 828 } 829 830 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 831 __SetPageUptodate(new_page); 832 833 spin_lock(&mm->page_table_lock); 834 put_page(page); 835 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 836 mem_cgroup_uncharge_page(new_page); 837 put_page(new_page); 838 } else { 839 pmd_t entry; 840 VM_BUG_ON(!PageHead(page)); 841 entry = mk_pmd(new_page, vma->vm_page_prot); 842 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 843 entry = pmd_mkhuge(entry); 844 pmdp_clear_flush_notify(vma, haddr, pmd); 845 page_add_new_anon_rmap(new_page, vma, haddr); 846 set_pmd_at(mm, haddr, pmd, entry); 847 update_mmu_cache(vma, address, entry); 848 page_remove_rmap(page); 849 put_page(page); 850 ret |= VM_FAULT_WRITE; 851 } 852out_unlock: 853 spin_unlock(&mm->page_table_lock); 854out: 855 return ret; 856} 857 858struct page *follow_trans_huge_pmd(struct mm_struct *mm, 859 unsigned long addr, 860 pmd_t *pmd, 861 unsigned int flags) 862{ 863 struct page *page = NULL; 864 865 assert_spin_locked(&mm->page_table_lock); 866 867 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 868 goto out; 869 870 page = pmd_page(*pmd); 871 VM_BUG_ON(!PageHead(page)); 872 if (flags & FOLL_TOUCH) { 873 pmd_t _pmd; 874 /* 875 * We should set the dirty bit only for FOLL_WRITE but 876 * for now the dirty bit in the pmd is meaningless. 877 * And if the dirty bit will become meaningful and 878 * we'll only set it with FOLL_WRITE, an atomic 879 * set_bit will be required on the pmd to set the 880 * young bit, instead of the current set_pmd_at. 881 */ 882 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 883 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd); 884 } 885 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 886 VM_BUG_ON(!PageCompound(page)); 887 if (flags & FOLL_GET) 888 get_page(page); 889 890out: 891 return page; 892} 893 894int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 895 pmd_t *pmd) 896{ 897 int ret = 0; 898 899 spin_lock(&tlb->mm->page_table_lock); 900 if (likely(pmd_trans_huge(*pmd))) { 901 if (unlikely(pmd_trans_splitting(*pmd))) { 902 spin_unlock(&tlb->mm->page_table_lock); 903 wait_split_huge_page(vma->anon_vma, 904 pmd); 905 } else { 906 struct page *page; 907 pgtable_t pgtable; 908 pgtable = get_pmd_huge_pte(tlb->mm); 909 page = pmd_page(*pmd); 910 pmd_clear(pmd); 911 page_remove_rmap(page); 912 VM_BUG_ON(page_mapcount(page) < 0); 913 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 914 VM_BUG_ON(!PageHead(page)); 915 spin_unlock(&tlb->mm->page_table_lock); 916 tlb_remove_page(tlb, page); 917 pte_free(tlb->mm, pgtable); 918 ret = 1; 919 } 920 } else 921 spin_unlock(&tlb->mm->page_table_lock); 922 923 return ret; 924} 925 926pmd_t *page_check_address_pmd(struct page *page, 927 struct mm_struct *mm, 928 unsigned long address, 929 enum page_check_address_pmd_flag flag) 930{ 931 pgd_t *pgd; 932 pud_t *pud; 933 pmd_t *pmd, *ret = NULL; 934 935 if (address & ~HPAGE_PMD_MASK) 936 goto out; 937 938 pgd = pgd_offset(mm, address); 939 if (!pgd_present(*pgd)) 940 goto out; 941 942 pud = pud_offset(pgd, address); 943 if (!pud_present(*pud)) 944 goto out; 945 946 pmd = pmd_offset(pud, address); 947 if (pmd_none(*pmd)) 948 goto out; 949 if (pmd_page(*pmd) != page) 950 goto out; 951 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && 952 pmd_trans_splitting(*pmd)); 953 if (pmd_trans_huge(*pmd)) { 954 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && 955 !pmd_trans_splitting(*pmd)); 956 ret = pmd; 957 } 958out: 959 return ret; 960} 961 962static int __split_huge_page_splitting(struct page *page, 963 struct vm_area_struct *vma, 964 unsigned long address) 965{ 966 struct mm_struct *mm = vma->vm_mm; 967 pmd_t *pmd; 968 int ret = 0; 969 970 spin_lock(&mm->page_table_lock); 971 pmd = page_check_address_pmd(page, mm, address, 972 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG); 973 if (pmd) { 974 /* 975 * We can't temporarily set the pmd to null in order 976 * to split it, the pmd must remain marked huge at all 977 * times or the VM won't take the pmd_trans_huge paths 978 * and it won't wait on the anon_vma->root->lock to 979 * serialize against split_huge_page*. 980 */ 981 pmdp_splitting_flush_notify(vma, address, pmd); 982 ret = 1; 983 } 984 spin_unlock(&mm->page_table_lock); 985 986 return ret; 987} 988 989static void __split_huge_page_refcount(struct page *page) 990{ 991 int i; 992 unsigned long head_index = page->index; 993 struct zone *zone = page_zone(page); 994 995 /* prevent PageLRU to go away from under us, and freeze lru stats */ 996 spin_lock_irq(&zone->lru_lock); 997 compound_lock(page); 998 999 for (i = 1; i < HPAGE_PMD_NR; i++) { 1000 struct page *page_tail = page + i; 1001 1002 /* tail_page->_count cannot change */ 1003 atomic_sub(atomic_read(&page_tail->_count), &page->_count); 1004 BUG_ON(page_count(page) <= 0); 1005 atomic_add(page_mapcount(page) + 1, &page_tail->_count); 1006 BUG_ON(atomic_read(&page_tail->_count) <= 0); 1007 1008 /* after clearing PageTail the gup refcount can be released */ 1009 smp_mb(); 1010 1011 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; 1012 page_tail->flags |= (page->flags & 1013 ((1L << PG_referenced) | 1014 (1L << PG_swapbacked) | 1015 (1L << PG_mlocked) | 1016 (1L << PG_uptodate))); 1017 page_tail->flags |= (1L << PG_dirty); 1018 1019 /* 1020 * 1) clear PageTail before overwriting first_page 1021 * 2) clear PageTail before clearing PageHead for VM_BUG_ON 1022 */ 1023 smp_wmb(); 1024 1025 /* 1026 * __split_huge_page_splitting() already set the 1027 * splitting bit in all pmd that could map this 1028 * hugepage, that will ensure no CPU can alter the 1029 * mapcount on the head page. The mapcount is only 1030 * accounted in the head page and it has to be 1031 * transferred to all tail pages in the below code. So 1032 * for this code to be safe, the split the mapcount 1033 * can't change. But that doesn't mean userland can't 1034 * keep changing and reading the page contents while 1035 * we transfer the mapcount, so the pmd splitting 1036 * status is achieved setting a reserved bit in the 1037 * pmd, not by clearing the present bit. 1038 */ 1039 BUG_ON(page_mapcount(page_tail)); 1040 page_tail->_mapcount = page->_mapcount; 1041 1042 BUG_ON(page_tail->mapping); 1043 page_tail->mapping = page->mapping; 1044 1045 page_tail->index = ++head_index; 1046 1047 BUG_ON(!PageAnon(page_tail)); 1048 BUG_ON(!PageUptodate(page_tail)); 1049 BUG_ON(!PageDirty(page_tail)); 1050 BUG_ON(!PageSwapBacked(page_tail)); 1051 1052 lru_add_page_tail(zone, page, page_tail); 1053 } 1054 1055 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); 1056 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR); 1057 1058 ClearPageCompound(page); 1059 compound_unlock(page); 1060 spin_unlock_irq(&zone->lru_lock); 1061 1062 for (i = 1; i < HPAGE_PMD_NR; i++) { 1063 struct page *page_tail = page + i; 1064 BUG_ON(page_count(page_tail) <= 0); 1065 /* 1066 * Tail pages may be freed if there wasn't any mapping 1067 * like if add_to_swap() is running on a lru page that 1068 * had its mapping zapped. And freeing these pages 1069 * requires taking the lru_lock so we do the put_page 1070 * of the tail pages after the split is complete. 1071 */ 1072 put_page(page_tail); 1073 } 1074 1075 /* 1076 * Only the head page (now become a regular page) is required 1077 * to be pinned by the caller. 1078 */ 1079 BUG_ON(page_count(page) <= 0); 1080} 1081 1082static int __split_huge_page_map(struct page *page, 1083 struct vm_area_struct *vma, 1084 unsigned long address) 1085{ 1086 struct mm_struct *mm = vma->vm_mm; 1087 pmd_t *pmd, _pmd; 1088 int ret = 0, i; 1089 pgtable_t pgtable; 1090 unsigned long haddr; 1091 1092 spin_lock(&mm->page_table_lock); 1093 pmd = page_check_address_pmd(page, mm, address, 1094 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG); 1095 if (pmd) { 1096 pgtable = get_pmd_huge_pte(mm); 1097 pmd_populate(mm, &_pmd, pgtable); 1098 1099 for (i = 0, haddr = address; i < HPAGE_PMD_NR; 1100 i++, haddr += PAGE_SIZE) { 1101 pte_t *pte, entry; 1102 BUG_ON(PageCompound(page+i)); 1103 entry = mk_pte(page + i, vma->vm_page_prot); 1104 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1105 if (!pmd_write(*pmd)) 1106 entry = pte_wrprotect(entry); 1107 else 1108 BUG_ON(page_mapcount(page) != 1); 1109 if (!pmd_young(*pmd)) 1110 entry = pte_mkold(entry); 1111 pte = pte_offset_map(&_pmd, haddr); 1112 BUG_ON(!pte_none(*pte)); 1113 set_pte_at(mm, haddr, pte, entry); 1114 pte_unmap(pte); 1115 } 1116 1117 mm->nr_ptes++; 1118 smp_wmb(); /* make pte visible before pmd */ 1119 /* 1120 * Up to this point the pmd is present and huge and 1121 * userland has the whole access to the hugepage 1122 * during the split (which happens in place). If we 1123 * overwrite the pmd with the not-huge version 1124 * pointing to the pte here (which of course we could 1125 * if all CPUs were bug free), userland could trigger 1126 * a small page size TLB miss on the small sized TLB 1127 * while the hugepage TLB entry is still established 1128 * in the huge TLB. Some CPU doesn't like that. See 1129 * http://support.amd.com/us/Processor_TechDocs/41322.pdf, 1130 * Erratum 383 on page 93. Intel should be safe but is 1131 * also warns that it's only safe if the permission 1132 * and cache attributes of the two entries loaded in 1133 * the two TLB is identical (which should be the case 1134 * here). But it is generally safer to never allow 1135 * small and huge TLB entries for the same virtual 1136 * address to be loaded simultaneously. So instead of 1137 * doing "pmd_populate(); flush_tlb_range();" we first 1138 * mark the current pmd notpresent (atomically because 1139 * here the pmd_trans_huge and pmd_trans_splitting 1140 * must remain set at all times on the pmd until the 1141 * split is complete for this pmd), then we flush the 1142 * SMP TLB and finally we write the non-huge version 1143 * of the pmd entry with pmd_populate. 1144 */ 1145 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd)); 1146 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE); 1147 pmd_populate(mm, pmd, pgtable); 1148 ret = 1; 1149 } 1150 spin_unlock(&mm->page_table_lock); 1151 1152 return ret; 1153} 1154 1155/* must be called with anon_vma->root->lock hold */ 1156static void __split_huge_page(struct page *page, 1157 struct anon_vma *anon_vma) 1158{ 1159 int mapcount, mapcount2; 1160 struct anon_vma_chain *avc; 1161 1162 BUG_ON(!PageHead(page)); 1163 BUG_ON(PageTail(page)); 1164 1165 mapcount = 0; 1166 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { 1167 struct vm_area_struct *vma = avc->vma; 1168 unsigned long addr = vma_address(page, vma); 1169 BUG_ON(is_vma_temporary_stack(vma)); 1170 if (addr == -EFAULT) 1171 continue; 1172 mapcount += __split_huge_page_splitting(page, vma, addr); 1173 } 1174 /* 1175 * It is critical that new vmas are added to the tail of the 1176 * anon_vma list. This guarantes that if copy_huge_pmd() runs 1177 * and establishes a child pmd before 1178 * __split_huge_page_splitting() freezes the parent pmd (so if 1179 * we fail to prevent copy_huge_pmd() from running until the 1180 * whole __split_huge_page() is complete), we will still see 1181 * the newly established pmd of the child later during the 1182 * walk, to be able to set it as pmd_trans_splitting too. 1183 */ 1184 if (mapcount != page_mapcount(page)) 1185 printk(KERN_ERR "mapcount %d page_mapcount %d\n", 1186 mapcount, page_mapcount(page)); 1187 BUG_ON(mapcount != page_mapcount(page)); 1188 1189 __split_huge_page_refcount(page); 1190 1191 mapcount2 = 0; 1192 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { 1193 struct vm_area_struct *vma = avc->vma; 1194 unsigned long addr = vma_address(page, vma); 1195 BUG_ON(is_vma_temporary_stack(vma)); 1196 if (addr == -EFAULT) 1197 continue; 1198 mapcount2 += __split_huge_page_map(page, vma, addr); 1199 } 1200 if (mapcount != mapcount2) 1201 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n", 1202 mapcount, mapcount2, page_mapcount(page)); 1203 BUG_ON(mapcount != mapcount2); 1204} 1205 1206int split_huge_page(struct page *page) 1207{ 1208 struct anon_vma *anon_vma; 1209 int ret = 1; 1210 1211 BUG_ON(!PageAnon(page)); 1212 anon_vma = page_lock_anon_vma(page); 1213 if (!anon_vma) 1214 goto out; 1215 ret = 0; 1216 if (!PageCompound(page)) 1217 goto out_unlock; 1218 1219 BUG_ON(!PageSwapBacked(page)); 1220 __split_huge_page(page, anon_vma); 1221 1222 BUG_ON(PageCompound(page)); 1223out_unlock: 1224 page_unlock_anon_vma(anon_vma); 1225out: 1226 return ret; 1227} 1228 1229int hugepage_madvise(unsigned long *vm_flags) 1230{ 1231 /* 1232 * Be somewhat over-protective like KSM for now! 1233 */ 1234 if (*vm_flags & (VM_HUGEPAGE | VM_SHARED | VM_MAYSHARE | 1235 VM_PFNMAP | VM_IO | VM_DONTEXPAND | 1236 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | 1237 VM_MIXEDMAP | VM_SAO)) 1238 return -EINVAL; 1239 1240 *vm_flags |= VM_HUGEPAGE; 1241 1242 return 0; 1243} 1244 1245static int __init khugepaged_slab_init(void) 1246{ 1247 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1248 sizeof(struct mm_slot), 1249 __alignof__(struct mm_slot), 0, NULL); 1250 if (!mm_slot_cache) 1251 return -ENOMEM; 1252 1253 return 0; 1254} 1255 1256static void __init khugepaged_slab_free(void) 1257{ 1258 kmem_cache_destroy(mm_slot_cache); 1259 mm_slot_cache = NULL; 1260} 1261 1262static inline struct mm_slot *alloc_mm_slot(void) 1263{ 1264 if (!mm_slot_cache) /* initialization failed */ 1265 return NULL; 1266 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 1267} 1268 1269static inline void free_mm_slot(struct mm_slot *mm_slot) 1270{ 1271 kmem_cache_free(mm_slot_cache, mm_slot); 1272} 1273 1274static int __init mm_slots_hash_init(void) 1275{ 1276 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), 1277 GFP_KERNEL); 1278 if (!mm_slots_hash) 1279 return -ENOMEM; 1280 return 0; 1281} 1282 1283#if 0 1284static void __init mm_slots_hash_free(void) 1285{ 1286 kfree(mm_slots_hash); 1287 mm_slots_hash = NULL; 1288} 1289#endif 1290 1291static struct mm_slot *get_mm_slot(struct mm_struct *mm) 1292{ 1293 struct mm_slot *mm_slot; 1294 struct hlist_head *bucket; 1295 struct hlist_node *node; 1296 1297 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1298 % MM_SLOTS_HASH_HEADS]; 1299 hlist_for_each_entry(mm_slot, node, bucket, hash) { 1300 if (mm == mm_slot->mm) 1301 return mm_slot; 1302 } 1303 return NULL; 1304} 1305 1306static void insert_to_mm_slots_hash(struct mm_struct *mm, 1307 struct mm_slot *mm_slot) 1308{ 1309 struct hlist_head *bucket; 1310 1311 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1312 % MM_SLOTS_HASH_HEADS]; 1313 mm_slot->mm = mm; 1314 hlist_add_head(&mm_slot->hash, bucket); 1315} 1316 1317static inline int khugepaged_test_exit(struct mm_struct *mm) 1318{ 1319 return atomic_read(&mm->mm_users) == 0; 1320} 1321 1322int __khugepaged_enter(struct mm_struct *mm) 1323{ 1324 struct mm_slot *mm_slot; 1325 int wakeup; 1326 1327 mm_slot = alloc_mm_slot(); 1328 if (!mm_slot) 1329 return -ENOMEM; 1330 1331 /* __khugepaged_exit() must not run from under us */ 1332 VM_BUG_ON(khugepaged_test_exit(mm)); 1333 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 1334 free_mm_slot(mm_slot); 1335 return 0; 1336 } 1337 1338 spin_lock(&khugepaged_mm_lock); 1339 insert_to_mm_slots_hash(mm, mm_slot); 1340 /* 1341 * Insert just behind the scanning cursor, to let the area settle 1342 * down a little. 1343 */ 1344 wakeup = list_empty(&khugepaged_scan.mm_head); 1345 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 1346 spin_unlock(&khugepaged_mm_lock); 1347 1348 atomic_inc(&mm->mm_count); 1349 if (wakeup) 1350 wake_up_interruptible(&khugepaged_wait); 1351 1352 return 0; 1353} 1354 1355int khugepaged_enter_vma_merge(struct vm_area_struct *vma) 1356{ 1357 unsigned long hstart, hend; 1358 if (!vma->anon_vma) 1359 /* 1360 * Not yet faulted in so we will register later in the 1361 * page fault if needed. 1362 */ 1363 return 0; 1364 if (vma->vm_file || vma->vm_ops) 1365 /* khugepaged not yet working on file or special mappings */ 1366 return 0; 1367 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma)); 1368 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1369 hend = vma->vm_end & HPAGE_PMD_MASK; 1370 if (hstart < hend) 1371 return khugepaged_enter(vma); 1372 return 0; 1373} 1374 1375void __khugepaged_exit(struct mm_struct *mm) 1376{ 1377 struct mm_slot *mm_slot; 1378 int free = 0; 1379 1380 spin_lock(&khugepaged_mm_lock); 1381 mm_slot = get_mm_slot(mm); 1382 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 1383 hlist_del(&mm_slot->hash); 1384 list_del(&mm_slot->mm_node); 1385 free = 1; 1386 } 1387 1388 if (free) { 1389 spin_unlock(&khugepaged_mm_lock); 1390 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1391 free_mm_slot(mm_slot); 1392 mmdrop(mm); 1393 } else if (mm_slot) { 1394 spin_unlock(&khugepaged_mm_lock); 1395 /* 1396 * This is required to serialize against 1397 * khugepaged_test_exit() (which is guaranteed to run 1398 * under mmap sem read mode). Stop here (after we 1399 * return all pagetables will be destroyed) until 1400 * khugepaged has finished working on the pagetables 1401 * under the mmap_sem. 1402 */ 1403 down_write(&mm->mmap_sem); 1404 up_write(&mm->mmap_sem); 1405 } else 1406 spin_unlock(&khugepaged_mm_lock); 1407} 1408 1409static void release_pte_page(struct page *page) 1410{ 1411 /* 0 stands for page_is_file_cache(page) == false */ 1412 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 1413 unlock_page(page); 1414 putback_lru_page(page); 1415} 1416 1417static void release_pte_pages(pte_t *pte, pte_t *_pte) 1418{ 1419 while (--_pte >= pte) { 1420 pte_t pteval = *_pte; 1421 if (!pte_none(pteval)) 1422 release_pte_page(pte_page(pteval)); 1423 } 1424} 1425 1426static void release_all_pte_pages(pte_t *pte) 1427{ 1428 release_pte_pages(pte, pte + HPAGE_PMD_NR); 1429} 1430 1431static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 1432 unsigned long address, 1433 pte_t *pte) 1434{ 1435 struct page *page; 1436 pte_t *_pte; 1437 int referenced = 0, isolated = 0, none = 0; 1438 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 1439 _pte++, address += PAGE_SIZE) { 1440 pte_t pteval = *_pte; 1441 if (pte_none(pteval)) { 1442 if (++none <= khugepaged_max_ptes_none) 1443 continue; 1444 else { 1445 release_pte_pages(pte, _pte); 1446 goto out; 1447 } 1448 } 1449 if (!pte_present(pteval) || !pte_write(pteval)) { 1450 release_pte_pages(pte, _pte); 1451 goto out; 1452 } 1453 page = vm_normal_page(vma, address, pteval); 1454 if (unlikely(!page)) { 1455 release_pte_pages(pte, _pte); 1456 goto out; 1457 } 1458 VM_BUG_ON(PageCompound(page)); 1459 BUG_ON(!PageAnon(page)); 1460 VM_BUG_ON(!PageSwapBacked(page)); 1461 1462 /* cannot use mapcount: can't collapse if there's a gup pin */ 1463 if (page_count(page) != 1) { 1464 release_pte_pages(pte, _pte); 1465 goto out; 1466 } 1467 /* 1468 * We can do it before isolate_lru_page because the 1469 * page can't be freed from under us. NOTE: PG_lock 1470 * is needed to serialize against split_huge_page 1471 * when invoked from the VM. 1472 */ 1473 if (!trylock_page(page)) { 1474 release_pte_pages(pte, _pte); 1475 goto out; 1476 } 1477 /* 1478 * Isolate the page to avoid collapsing an hugepage 1479 * currently in use by the VM. 1480 */ 1481 if (isolate_lru_page(page)) { 1482 unlock_page(page); 1483 release_pte_pages(pte, _pte); 1484 goto out; 1485 } 1486 /* 0 stands for page_is_file_cache(page) == false */ 1487 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 1488 VM_BUG_ON(!PageLocked(page)); 1489 VM_BUG_ON(PageLRU(page)); 1490 1491 /* If there is no mapped pte young don't collapse the page */ 1492 if (pte_young(pteval)) 1493 referenced = 1; 1494 } 1495 if (unlikely(!referenced)) 1496 release_all_pte_pages(pte); 1497 else 1498 isolated = 1; 1499out: 1500 return isolated; 1501} 1502 1503static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 1504 struct vm_area_struct *vma, 1505 unsigned long address, 1506 spinlock_t *ptl) 1507{ 1508 pte_t *_pte; 1509 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 1510 pte_t pteval = *_pte; 1511 struct page *src_page; 1512 1513 if (pte_none(pteval)) { 1514 clear_user_highpage(page, address); 1515 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 1516 } else { 1517 src_page = pte_page(pteval); 1518 copy_user_highpage(page, src_page, address, vma); 1519 VM_BUG_ON(page_mapcount(src_page) != 1); 1520 VM_BUG_ON(page_count(src_page) != 2); 1521 release_pte_page(src_page); 1522 /* 1523 * ptl mostly unnecessary, but preempt has to 1524 * be disabled to update the per-cpu stats 1525 * inside page_remove_rmap(). 1526 */ 1527 spin_lock(ptl); 1528 /* 1529 * paravirt calls inside pte_clear here are 1530 * superfluous. 1531 */ 1532 pte_clear(vma->vm_mm, address, _pte); 1533 page_remove_rmap(src_page); 1534 spin_unlock(ptl); 1535 free_page_and_swap_cache(src_page); 1536 } 1537 1538 address += PAGE_SIZE; 1539 page++; 1540 } 1541} 1542 1543static void collapse_huge_page(struct mm_struct *mm, 1544 unsigned long address, 1545 struct page **hpage) 1546{ 1547 struct vm_area_struct *vma; 1548 pgd_t *pgd; 1549 pud_t *pud; 1550 pmd_t *pmd, _pmd; 1551 pte_t *pte; 1552 pgtable_t pgtable; 1553 struct page *new_page; 1554 spinlock_t *ptl; 1555 int isolated; 1556 unsigned long hstart, hend; 1557 1558 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1559 VM_BUG_ON(!*hpage); 1560 1561 /* 1562 * Prevent all access to pagetables with the exception of 1563 * gup_fast later hanlded by the ptep_clear_flush and the VM 1564 * handled by the anon_vma lock + PG_lock. 1565 */ 1566 down_write(&mm->mmap_sem); 1567 if (unlikely(khugepaged_test_exit(mm))) 1568 goto out; 1569 1570 vma = find_vma(mm, address); 1571 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1572 hend = vma->vm_end & HPAGE_PMD_MASK; 1573 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 1574 goto out; 1575 1576 if (!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) 1577 goto out; 1578 1579 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */ 1580 if (!vma->anon_vma || vma->vm_ops || vma->vm_file) 1581 goto out; 1582 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma)); 1583 1584 pgd = pgd_offset(mm, address); 1585 if (!pgd_present(*pgd)) 1586 goto out; 1587 1588 pud = pud_offset(pgd, address); 1589 if (!pud_present(*pud)) 1590 goto out; 1591 1592 pmd = pmd_offset(pud, address); 1593 /* pmd can't go away or become huge under us */ 1594 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd)) 1595 goto out; 1596 1597 new_page = *hpage; 1598 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) 1599 goto out; 1600 1601 anon_vma_lock(vma->anon_vma); 1602 1603 pte = pte_offset_map(pmd, address); 1604 ptl = pte_lockptr(mm, pmd); 1605 1606 spin_lock(&mm->page_table_lock); /* probably unnecessary */ 1607 /* 1608 * After this gup_fast can't run anymore. This also removes 1609 * any huge TLB entry from the CPU so we won't allow 1610 * huge and small TLB entries for the same virtual address 1611 * to avoid the risk of CPU bugs in that area. 1612 */ 1613 _pmd = pmdp_clear_flush_notify(vma, address, pmd); 1614 spin_unlock(&mm->page_table_lock); 1615 1616 spin_lock(ptl); 1617 isolated = __collapse_huge_page_isolate(vma, address, pte); 1618 spin_unlock(ptl); 1619 pte_unmap(pte); 1620 1621 if (unlikely(!isolated)) { 1622 spin_lock(&mm->page_table_lock); 1623 BUG_ON(!pmd_none(*pmd)); 1624 set_pmd_at(mm, address, pmd, _pmd); 1625 spin_unlock(&mm->page_table_lock); 1626 anon_vma_unlock(vma->anon_vma); 1627 mem_cgroup_uncharge_page(new_page); 1628 goto out; 1629 } 1630 1631 /* 1632 * All pages are isolated and locked so anon_vma rmap 1633 * can't run anymore. 1634 */ 1635 anon_vma_unlock(vma->anon_vma); 1636 1637 __collapse_huge_page_copy(pte, new_page, vma, address, ptl); 1638 __SetPageUptodate(new_page); 1639 pgtable = pmd_pgtable(_pmd); 1640 VM_BUG_ON(page_count(pgtable) != 1); 1641 VM_BUG_ON(page_mapcount(pgtable) != 0); 1642 1643 _pmd = mk_pmd(new_page, vma->vm_page_prot); 1644 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 1645 _pmd = pmd_mkhuge(_pmd); 1646 1647 /* 1648 * spin_lock() below is not the equivalent of smp_wmb(), so 1649 * this is needed to avoid the copy_huge_page writes to become 1650 * visible after the set_pmd_at() write. 1651 */ 1652 smp_wmb(); 1653 1654 spin_lock(&mm->page_table_lock); 1655 BUG_ON(!pmd_none(*pmd)); 1656 page_add_new_anon_rmap(new_page, vma, address); 1657 set_pmd_at(mm, address, pmd, _pmd); 1658 update_mmu_cache(vma, address, entry); 1659 prepare_pmd_huge_pte(pgtable, mm); 1660 mm->nr_ptes--; 1661 spin_unlock(&mm->page_table_lock); 1662 1663 *hpage = NULL; 1664 khugepaged_pages_collapsed++; 1665out: 1666 up_write(&mm->mmap_sem); 1667} 1668 1669static int khugepaged_scan_pmd(struct mm_struct *mm, 1670 struct vm_area_struct *vma, 1671 unsigned long address, 1672 struct page **hpage) 1673{ 1674 pgd_t *pgd; 1675 pud_t *pud; 1676 pmd_t *pmd; 1677 pte_t *pte, *_pte; 1678 int ret = 0, referenced = 0, none = 0; 1679 struct page *page; 1680 unsigned long _address; 1681 spinlock_t *ptl; 1682 1683 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1684 1685 pgd = pgd_offset(mm, address); 1686 if (!pgd_present(*pgd)) 1687 goto out; 1688 1689 pud = pud_offset(pgd, address); 1690 if (!pud_present(*pud)) 1691 goto out; 1692 1693 pmd = pmd_offset(pud, address); 1694 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd)) 1695 goto out; 1696 1697 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 1698 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 1699 _pte++, _address += PAGE_SIZE) { 1700 pte_t pteval = *_pte; 1701 if (pte_none(pteval)) { 1702 if (++none <= khugepaged_max_ptes_none) 1703 continue; 1704 else 1705 goto out_unmap; 1706 } 1707 if (!pte_present(pteval) || !pte_write(pteval)) 1708 goto out_unmap; 1709 page = vm_normal_page(vma, _address, pteval); 1710 if (unlikely(!page)) 1711 goto out_unmap; 1712 VM_BUG_ON(PageCompound(page)); 1713 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) 1714 goto out_unmap; 1715 /* cannot use mapcount: can't collapse if there's a gup pin */ 1716 if (page_count(page) != 1) 1717 goto out_unmap; 1718 if (pte_young(pteval)) 1719 referenced = 1; 1720 } 1721 if (referenced) 1722 ret = 1; 1723out_unmap: 1724 pte_unmap_unlock(pte, ptl); 1725 if (ret) { 1726 up_read(&mm->mmap_sem); 1727 collapse_huge_page(mm, address, hpage); 1728 } 1729out: 1730 return ret; 1731} 1732 1733static void collect_mm_slot(struct mm_slot *mm_slot) 1734{ 1735 struct mm_struct *mm = mm_slot->mm; 1736 1737 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock)); 1738 1739 if (khugepaged_test_exit(mm)) { 1740 /* free mm_slot */ 1741 hlist_del(&mm_slot->hash); 1742 list_del(&mm_slot->mm_node); 1743 1744 /* 1745 * Not strictly needed because the mm exited already. 1746 * 1747 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1748 */ 1749 1750 /* khugepaged_mm_lock actually not necessary for the below */ 1751 free_mm_slot(mm_slot); 1752 mmdrop(mm); 1753 } 1754} 1755 1756static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 1757 struct page **hpage) 1758{ 1759 struct mm_slot *mm_slot; 1760 struct mm_struct *mm; 1761 struct vm_area_struct *vma; 1762 int progress = 0; 1763 1764 VM_BUG_ON(!pages); 1765 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock)); 1766 1767 if (khugepaged_scan.mm_slot) 1768 mm_slot = khugepaged_scan.mm_slot; 1769 else { 1770 mm_slot = list_entry(khugepaged_scan.mm_head.next, 1771 struct mm_slot, mm_node); 1772 khugepaged_scan.address = 0; 1773 khugepaged_scan.mm_slot = mm_slot; 1774 } 1775 spin_unlock(&khugepaged_mm_lock); 1776 1777 mm = mm_slot->mm; 1778 down_read(&mm->mmap_sem); 1779 if (unlikely(khugepaged_test_exit(mm))) 1780 vma = NULL; 1781 else 1782 vma = find_vma(mm, khugepaged_scan.address); 1783 1784 progress++; 1785 for (; vma; vma = vma->vm_next) { 1786 unsigned long hstart, hend; 1787 1788 cond_resched(); 1789 if (unlikely(khugepaged_test_exit(mm))) { 1790 progress++; 1791 break; 1792 } 1793 1794 if (!(vma->vm_flags & VM_HUGEPAGE) && 1795 !khugepaged_always()) { 1796 progress++; 1797 continue; 1798 } 1799 1800 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */ 1801 if (!vma->anon_vma || vma->vm_ops || vma->vm_file) { 1802 khugepaged_scan.address = vma->vm_end; 1803 progress++; 1804 continue; 1805 } 1806 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma)); 1807 1808 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1809 hend = vma->vm_end & HPAGE_PMD_MASK; 1810 if (hstart >= hend) { 1811 progress++; 1812 continue; 1813 } 1814 if (khugepaged_scan.address < hstart) 1815 khugepaged_scan.address = hstart; 1816 if (khugepaged_scan.address > hend) { 1817 khugepaged_scan.address = hend + HPAGE_PMD_SIZE; 1818 progress++; 1819 continue; 1820 } 1821 BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 1822 1823 while (khugepaged_scan.address < hend) { 1824 int ret; 1825 cond_resched(); 1826 if (unlikely(khugepaged_test_exit(mm))) 1827 goto breakouterloop; 1828 1829 VM_BUG_ON(khugepaged_scan.address < hstart || 1830 khugepaged_scan.address + HPAGE_PMD_SIZE > 1831 hend); 1832 ret = khugepaged_scan_pmd(mm, vma, 1833 khugepaged_scan.address, 1834 hpage); 1835 /* move to next address */ 1836 khugepaged_scan.address += HPAGE_PMD_SIZE; 1837 progress += HPAGE_PMD_NR; 1838 if (ret) 1839 /* we released mmap_sem so break loop */ 1840 goto breakouterloop_mmap_sem; 1841 if (progress >= pages) 1842 goto breakouterloop; 1843 } 1844 } 1845breakouterloop: 1846 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 1847breakouterloop_mmap_sem: 1848 1849 spin_lock(&khugepaged_mm_lock); 1850 BUG_ON(khugepaged_scan.mm_slot != mm_slot); 1851 /* 1852 * Release the current mm_slot if this mm is about to die, or 1853 * if we scanned all vmas of this mm. 1854 */ 1855 if (khugepaged_test_exit(mm) || !vma) { 1856 /* 1857 * Make sure that if mm_users is reaching zero while 1858 * khugepaged runs here, khugepaged_exit will find 1859 * mm_slot not pointing to the exiting mm. 1860 */ 1861 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 1862 khugepaged_scan.mm_slot = list_entry( 1863 mm_slot->mm_node.next, 1864 struct mm_slot, mm_node); 1865 khugepaged_scan.address = 0; 1866 } else { 1867 khugepaged_scan.mm_slot = NULL; 1868 khugepaged_full_scans++; 1869 } 1870 1871 collect_mm_slot(mm_slot); 1872 } 1873 1874 return progress; 1875} 1876 1877static int khugepaged_has_work(void) 1878{ 1879 return !list_empty(&khugepaged_scan.mm_head) && 1880 khugepaged_enabled(); 1881} 1882 1883static int khugepaged_wait_event(void) 1884{ 1885 return !list_empty(&khugepaged_scan.mm_head) || 1886 !khugepaged_enabled(); 1887} 1888 1889static void khugepaged_do_scan(struct page **hpage) 1890{ 1891 unsigned int progress = 0, pass_through_head = 0; 1892 unsigned int pages = khugepaged_pages_to_scan; 1893 1894 barrier(); /* write khugepaged_pages_to_scan to local stack */ 1895 1896 while (progress < pages) { 1897 cond_resched(); 1898 1899 if (!*hpage) { 1900 *hpage = alloc_hugepage(khugepaged_defrag()); 1901 if (unlikely(!*hpage)) 1902 break; 1903 } 1904 1905 spin_lock(&khugepaged_mm_lock); 1906 if (!khugepaged_scan.mm_slot) 1907 pass_through_head++; 1908 if (khugepaged_has_work() && 1909 pass_through_head < 2) 1910 progress += khugepaged_scan_mm_slot(pages - progress, 1911 hpage); 1912 else 1913 progress = pages; 1914 spin_unlock(&khugepaged_mm_lock); 1915 } 1916} 1917 1918static struct page *khugepaged_alloc_hugepage(void) 1919{ 1920 struct page *hpage; 1921 1922 do { 1923 hpage = alloc_hugepage(khugepaged_defrag()); 1924 if (!hpage) { 1925 DEFINE_WAIT(wait); 1926 add_wait_queue(&khugepaged_wait, &wait); 1927 schedule_timeout_interruptible( 1928 msecs_to_jiffies( 1929 khugepaged_alloc_sleep_millisecs)); 1930 remove_wait_queue(&khugepaged_wait, &wait); 1931 } 1932 } while (unlikely(!hpage) && 1933 likely(khugepaged_enabled())); 1934 return hpage; 1935} 1936 1937static void khugepaged_loop(void) 1938{ 1939 struct page *hpage; 1940 1941 while (likely(khugepaged_enabled())) { 1942 hpage = khugepaged_alloc_hugepage(); 1943 if (unlikely(!hpage)) 1944 break; 1945 1946 khugepaged_do_scan(&hpage); 1947 if (hpage) 1948 put_page(hpage); 1949 if (khugepaged_has_work()) { 1950 DEFINE_WAIT(wait); 1951 if (!khugepaged_scan_sleep_millisecs) 1952 continue; 1953 add_wait_queue(&khugepaged_wait, &wait); 1954 schedule_timeout_interruptible( 1955 msecs_to_jiffies( 1956 khugepaged_scan_sleep_millisecs)); 1957 remove_wait_queue(&khugepaged_wait, &wait); 1958 } else if (khugepaged_enabled()) 1959 wait_event_interruptible(khugepaged_wait, 1960 khugepaged_wait_event()); 1961 } 1962} 1963 1964static int khugepaged(void *none) 1965{ 1966 struct mm_slot *mm_slot; 1967 1968 set_user_nice(current, 19); 1969 1970 /* serialize with start_khugepaged() */ 1971 mutex_lock(&khugepaged_mutex); 1972 1973 for (;;) { 1974 mutex_unlock(&khugepaged_mutex); 1975 BUG_ON(khugepaged_thread != current); 1976 khugepaged_loop(); 1977 BUG_ON(khugepaged_thread != current); 1978 1979 mutex_lock(&khugepaged_mutex); 1980 if (!khugepaged_enabled()) 1981 break; 1982 } 1983 1984 spin_lock(&khugepaged_mm_lock); 1985 mm_slot = khugepaged_scan.mm_slot; 1986 khugepaged_scan.mm_slot = NULL; 1987 if (mm_slot) 1988 collect_mm_slot(mm_slot); 1989 spin_unlock(&khugepaged_mm_lock); 1990 1991 khugepaged_thread = NULL; 1992 mutex_unlock(&khugepaged_mutex); 1993 1994 return 0; 1995} 1996 1997void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd) 1998{ 1999 struct page *page; 2000 2001 spin_lock(&mm->page_table_lock); 2002 if (unlikely(!pmd_trans_huge(*pmd))) { 2003 spin_unlock(&mm->page_table_lock); 2004 return; 2005 } 2006 page = pmd_page(*pmd); 2007 VM_BUG_ON(!page_count(page)); 2008 get_page(page); 2009 spin_unlock(&mm->page_table_lock); 2010 2011 split_huge_page(page); 2012 2013 put_page(page); 2014 BUG_ON(pmd_trans_huge(*pmd)); 2015} 2016