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 <linux/pagemap.h> 21 #include <asm/tlb.h> 22 #include <asm/pgalloc.h> 23 #include "internal.h" 24 25 /* 26 * By default transparent hugepage support is enabled for all mappings 27 * and khugepaged scans all mappings. Defrag is only invoked by 28 * khugepaged hugepage allocations and by page faults inside 29 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived 30 * allocations. 31 */ 32 unsigned long transparent_hugepage_flags __read_mostly = 33 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS 34 (1<<TRANSPARENT_HUGEPAGE_FLAG)| 35 #endif 36 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE 37 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| 38 #endif 39 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)| 40 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 41 42 /* default scan 8*512 pte (or vmas) every 30 second */ 43 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8; 44 static unsigned int khugepaged_pages_collapsed; 45 static unsigned int khugepaged_full_scans; 46 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 47 /* during fragmentation poll the hugepage allocator once every minute */ 48 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 49 static struct task_struct *khugepaged_thread __read_mostly; 50 static DEFINE_MUTEX(khugepaged_mutex); 51 static DEFINE_SPINLOCK(khugepaged_mm_lock); 52 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 53 /* 54 * default collapse hugepages if there is at least one pte mapped like 55 * it would have happened if the vma was large enough during page 56 * fault. 57 */ 58 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1; 59 60 static int khugepaged(void *none); 61 static int mm_slots_hash_init(void); 62 static int khugepaged_slab_init(void); 63 static void khugepaged_slab_free(void); 64 65 #define MM_SLOTS_HASH_HEADS 1024 66 static struct hlist_head *mm_slots_hash __read_mostly; 67 static struct kmem_cache *mm_slot_cache __read_mostly; 68 69 /** 70 * struct mm_slot - hash lookup from mm to mm_slot 71 * @hash: hash collision list 72 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 73 * @mm: the mm that this information is valid for 74 */ 75 struct mm_slot { 76 struct hlist_node hash; 77 struct list_head mm_node; 78 struct mm_struct *mm; 79 }; 80 81 /** 82 * struct khugepaged_scan - cursor for scanning 83 * @mm_head: the head of the mm list to scan 84 * @mm_slot: the current mm_slot we are scanning 85 * @address: the next address inside that to be scanned 86 * 87 * There is only the one khugepaged_scan instance of this cursor structure. 88 */ 89 struct khugepaged_scan { 90 struct list_head mm_head; 91 struct mm_slot *mm_slot; 92 unsigned long address; 93 }; 94 static struct khugepaged_scan khugepaged_scan = { 95 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 96 }; 97 98 99 static int set_recommended_min_free_kbytes(void) 100 { 101 struct zone *zone; 102 int nr_zones = 0; 103 unsigned long recommended_min; 104 extern int min_free_kbytes; 105 106 if (!khugepaged_enabled()) 107 return 0; 108 109 for_each_populated_zone(zone) 110 nr_zones++; 111 112 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */ 113 recommended_min = pageblock_nr_pages * nr_zones * 2; 114 115 /* 116 * Make sure that on average at least two pageblocks are almost free 117 * of another type, one for a migratetype to fall back to and a 118 * second to avoid subsequent fallbacks of other types There are 3 119 * MIGRATE_TYPES we care about. 120 */ 121 recommended_min += pageblock_nr_pages * nr_zones * 122 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; 123 124 /* don't ever allow to reserve more than 5% of the lowmem */ 125 recommended_min = min(recommended_min, 126 (unsigned long) nr_free_buffer_pages() / 20); 127 recommended_min <<= (PAGE_SHIFT-10); 128 129 if (recommended_min > min_free_kbytes) 130 min_free_kbytes = recommended_min; 131 setup_per_zone_wmarks(); 132 return 0; 133 } 134 late_initcall(set_recommended_min_free_kbytes); 135 136 static int start_khugepaged(void) 137 { 138 int err = 0; 139 if (khugepaged_enabled()) { 140 if (!khugepaged_thread) 141 khugepaged_thread = kthread_run(khugepaged, NULL, 142 "khugepaged"); 143 if (unlikely(IS_ERR(khugepaged_thread))) { 144 printk(KERN_ERR 145 "khugepaged: kthread_run(khugepaged) failed\n"); 146 err = PTR_ERR(khugepaged_thread); 147 khugepaged_thread = NULL; 148 } 149 150 if (!list_empty(&khugepaged_scan.mm_head)) 151 wake_up_interruptible(&khugepaged_wait); 152 153 set_recommended_min_free_kbytes(); 154 } else if (khugepaged_thread) { 155 kthread_stop(khugepaged_thread); 156 khugepaged_thread = NULL; 157 } 158 159 return err; 160 } 161 162 #ifdef CONFIG_SYSFS 163 164 static ssize_t double_flag_show(struct kobject *kobj, 165 struct kobj_attribute *attr, char *buf, 166 enum transparent_hugepage_flag enabled, 167 enum transparent_hugepage_flag req_madv) 168 { 169 if (test_bit(enabled, &transparent_hugepage_flags)) { 170 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); 171 return sprintf(buf, "[always] madvise never\n"); 172 } else if (test_bit(req_madv, &transparent_hugepage_flags)) 173 return sprintf(buf, "always [madvise] never\n"); 174 else 175 return sprintf(buf, "always madvise [never]\n"); 176 } 177 static ssize_t double_flag_store(struct kobject *kobj, 178 struct kobj_attribute *attr, 179 const char *buf, size_t count, 180 enum transparent_hugepage_flag enabled, 181 enum transparent_hugepage_flag req_madv) 182 { 183 if (!memcmp("always", buf, 184 min(sizeof("always")-1, count))) { 185 set_bit(enabled, &transparent_hugepage_flags); 186 clear_bit(req_madv, &transparent_hugepage_flags); 187 } else if (!memcmp("madvise", buf, 188 min(sizeof("madvise")-1, count))) { 189 clear_bit(enabled, &transparent_hugepage_flags); 190 set_bit(req_madv, &transparent_hugepage_flags); 191 } else if (!memcmp("never", buf, 192 min(sizeof("never")-1, count))) { 193 clear_bit(enabled, &transparent_hugepage_flags); 194 clear_bit(req_madv, &transparent_hugepage_flags); 195 } else 196 return -EINVAL; 197 198 return count; 199 } 200 201 static ssize_t enabled_show(struct kobject *kobj, 202 struct kobj_attribute *attr, char *buf) 203 { 204 return double_flag_show(kobj, attr, buf, 205 TRANSPARENT_HUGEPAGE_FLAG, 206 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 207 } 208 static ssize_t enabled_store(struct kobject *kobj, 209 struct kobj_attribute *attr, 210 const char *buf, size_t count) 211 { 212 ssize_t ret; 213 214 ret = double_flag_store(kobj, attr, buf, count, 215 TRANSPARENT_HUGEPAGE_FLAG, 216 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 217 218 if (ret > 0) { 219 int err; 220 221 mutex_lock(&khugepaged_mutex); 222 err = start_khugepaged(); 223 mutex_unlock(&khugepaged_mutex); 224 225 if (err) 226 ret = err; 227 } 228 229 return ret; 230 } 231 static struct kobj_attribute enabled_attr = 232 __ATTR(enabled, 0644, enabled_show, enabled_store); 233 234 static ssize_t single_flag_show(struct kobject *kobj, 235 struct kobj_attribute *attr, char *buf, 236 enum transparent_hugepage_flag flag) 237 { 238 return sprintf(buf, "%d\n", 239 !!test_bit(flag, &transparent_hugepage_flags)); 240 } 241 242 static ssize_t single_flag_store(struct kobject *kobj, 243 struct kobj_attribute *attr, 244 const char *buf, size_t count, 245 enum transparent_hugepage_flag flag) 246 { 247 unsigned long value; 248 int ret; 249 250 ret = kstrtoul(buf, 10, &value); 251 if (ret < 0) 252 return ret; 253 if (value > 1) 254 return -EINVAL; 255 256 if (value) 257 set_bit(flag, &transparent_hugepage_flags); 258 else 259 clear_bit(flag, &transparent_hugepage_flags); 260 261 return count; 262 } 263 264 /* 265 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind 266 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of 267 * memory just to allocate one more hugepage. 268 */ 269 static ssize_t defrag_show(struct kobject *kobj, 270 struct kobj_attribute *attr, char *buf) 271 { 272 return double_flag_show(kobj, attr, buf, 273 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 274 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 275 } 276 static ssize_t defrag_store(struct kobject *kobj, 277 struct kobj_attribute *attr, 278 const char *buf, size_t count) 279 { 280 return double_flag_store(kobj, attr, buf, count, 281 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 282 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 283 } 284 static struct kobj_attribute defrag_attr = 285 __ATTR(defrag, 0644, defrag_show, defrag_store); 286 287 #ifdef CONFIG_DEBUG_VM 288 static ssize_t debug_cow_show(struct kobject *kobj, 289 struct kobj_attribute *attr, char *buf) 290 { 291 return single_flag_show(kobj, attr, buf, 292 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 293 } 294 static ssize_t debug_cow_store(struct kobject *kobj, 295 struct kobj_attribute *attr, 296 const char *buf, size_t count) 297 { 298 return single_flag_store(kobj, attr, buf, count, 299 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 300 } 301 static struct kobj_attribute debug_cow_attr = 302 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 303 #endif /* CONFIG_DEBUG_VM */ 304 305 static struct attribute *hugepage_attr[] = { 306 &enabled_attr.attr, 307 &defrag_attr.attr, 308 #ifdef CONFIG_DEBUG_VM 309 &debug_cow_attr.attr, 310 #endif 311 NULL, 312 }; 313 314 static struct attribute_group hugepage_attr_group = { 315 .attrs = hugepage_attr, 316 }; 317 318 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 319 struct kobj_attribute *attr, 320 char *buf) 321 { 322 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 323 } 324 325 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 326 struct kobj_attribute *attr, 327 const char *buf, size_t count) 328 { 329 unsigned long msecs; 330 int err; 331 332 err = strict_strtoul(buf, 10, &msecs); 333 if (err || msecs > UINT_MAX) 334 return -EINVAL; 335 336 khugepaged_scan_sleep_millisecs = msecs; 337 wake_up_interruptible(&khugepaged_wait); 338 339 return count; 340 } 341 static struct kobj_attribute scan_sleep_millisecs_attr = 342 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 343 scan_sleep_millisecs_store); 344 345 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 346 struct kobj_attribute *attr, 347 char *buf) 348 { 349 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 350 } 351 352 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 353 struct kobj_attribute *attr, 354 const char *buf, size_t count) 355 { 356 unsigned long msecs; 357 int err; 358 359 err = strict_strtoul(buf, 10, &msecs); 360 if (err || msecs > UINT_MAX) 361 return -EINVAL; 362 363 khugepaged_alloc_sleep_millisecs = msecs; 364 wake_up_interruptible(&khugepaged_wait); 365 366 return count; 367 } 368 static struct kobj_attribute alloc_sleep_millisecs_attr = 369 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 370 alloc_sleep_millisecs_store); 371 372 static ssize_t pages_to_scan_show(struct kobject *kobj, 373 struct kobj_attribute *attr, 374 char *buf) 375 { 376 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 377 } 378 static ssize_t pages_to_scan_store(struct kobject *kobj, 379 struct kobj_attribute *attr, 380 const char *buf, size_t count) 381 { 382 int err; 383 unsigned long pages; 384 385 err = strict_strtoul(buf, 10, &pages); 386 if (err || !pages || pages > UINT_MAX) 387 return -EINVAL; 388 389 khugepaged_pages_to_scan = pages; 390 391 return count; 392 } 393 static struct kobj_attribute pages_to_scan_attr = 394 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 395 pages_to_scan_store); 396 397 static ssize_t pages_collapsed_show(struct kobject *kobj, 398 struct kobj_attribute *attr, 399 char *buf) 400 { 401 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 402 } 403 static struct kobj_attribute pages_collapsed_attr = 404 __ATTR_RO(pages_collapsed); 405 406 static ssize_t full_scans_show(struct kobject *kobj, 407 struct kobj_attribute *attr, 408 char *buf) 409 { 410 return sprintf(buf, "%u\n", khugepaged_full_scans); 411 } 412 static struct kobj_attribute full_scans_attr = 413 __ATTR_RO(full_scans); 414 415 static ssize_t khugepaged_defrag_show(struct kobject *kobj, 416 struct kobj_attribute *attr, char *buf) 417 { 418 return single_flag_show(kobj, attr, buf, 419 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 420 } 421 static ssize_t khugepaged_defrag_store(struct kobject *kobj, 422 struct kobj_attribute *attr, 423 const char *buf, size_t count) 424 { 425 return single_flag_store(kobj, attr, buf, count, 426 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 427 } 428 static struct kobj_attribute khugepaged_defrag_attr = 429 __ATTR(defrag, 0644, khugepaged_defrag_show, 430 khugepaged_defrag_store); 431 432 /* 433 * max_ptes_none controls if khugepaged should collapse hugepages over 434 * any unmapped ptes in turn potentially increasing the memory 435 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 436 * reduce the available free memory in the system as it 437 * runs. Increasing max_ptes_none will instead potentially reduce the 438 * free memory in the system during the khugepaged scan. 439 */ 440 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 441 struct kobj_attribute *attr, 442 char *buf) 443 { 444 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 445 } 446 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 447 struct kobj_attribute *attr, 448 const char *buf, size_t count) 449 { 450 int err; 451 unsigned long max_ptes_none; 452 453 err = strict_strtoul(buf, 10, &max_ptes_none); 454 if (err || max_ptes_none > HPAGE_PMD_NR-1) 455 return -EINVAL; 456 457 khugepaged_max_ptes_none = max_ptes_none; 458 459 return count; 460 } 461 static struct kobj_attribute khugepaged_max_ptes_none_attr = 462 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 463 khugepaged_max_ptes_none_store); 464 465 static struct attribute *khugepaged_attr[] = { 466 &khugepaged_defrag_attr.attr, 467 &khugepaged_max_ptes_none_attr.attr, 468 &pages_to_scan_attr.attr, 469 &pages_collapsed_attr.attr, 470 &full_scans_attr.attr, 471 &scan_sleep_millisecs_attr.attr, 472 &alloc_sleep_millisecs_attr.attr, 473 NULL, 474 }; 475 476 static struct attribute_group khugepaged_attr_group = { 477 .attrs = khugepaged_attr, 478 .name = "khugepaged", 479 }; 480 481 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) 482 { 483 int err; 484 485 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 486 if (unlikely(!*hugepage_kobj)) { 487 printk(KERN_ERR "hugepage: failed kobject create\n"); 488 return -ENOMEM; 489 } 490 491 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); 492 if (err) { 493 printk(KERN_ERR "hugepage: failed register hugeage group\n"); 494 goto delete_obj; 495 } 496 497 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); 498 if (err) { 499 printk(KERN_ERR "hugepage: failed register hugeage group\n"); 500 goto remove_hp_group; 501 } 502 503 return 0; 504 505 remove_hp_group: 506 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); 507 delete_obj: 508 kobject_put(*hugepage_kobj); 509 return err; 510 } 511 512 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) 513 { 514 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); 515 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); 516 kobject_put(hugepage_kobj); 517 } 518 #else 519 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) 520 { 521 return 0; 522 } 523 524 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) 525 { 526 } 527 #endif /* CONFIG_SYSFS */ 528 529 static int __init hugepage_init(void) 530 { 531 int err; 532 struct kobject *hugepage_kobj; 533 534 if (!has_transparent_hugepage()) { 535 transparent_hugepage_flags = 0; 536 return -EINVAL; 537 } 538 539 err = hugepage_init_sysfs(&hugepage_kobj); 540 if (err) 541 return err; 542 543 err = khugepaged_slab_init(); 544 if (err) 545 goto out; 546 547 err = mm_slots_hash_init(); 548 if (err) { 549 khugepaged_slab_free(); 550 goto out; 551 } 552 553 /* 554 * By default disable transparent hugepages on smaller systems, 555 * where the extra memory used could hurt more than TLB overhead 556 * is likely to save. The admin can still enable it through /sys. 557 */ 558 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) 559 transparent_hugepage_flags = 0; 560 561 start_khugepaged(); 562 563 return 0; 564 out: 565 hugepage_exit_sysfs(hugepage_kobj); 566 return err; 567 } 568 module_init(hugepage_init) 569 570 static int __init setup_transparent_hugepage(char *str) 571 { 572 int ret = 0; 573 if (!str) 574 goto out; 575 if (!strcmp(str, "always")) { 576 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 577 &transparent_hugepage_flags); 578 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 579 &transparent_hugepage_flags); 580 ret = 1; 581 } else if (!strcmp(str, "madvise")) { 582 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 583 &transparent_hugepage_flags); 584 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 585 &transparent_hugepage_flags); 586 ret = 1; 587 } else if (!strcmp(str, "never")) { 588 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 589 &transparent_hugepage_flags); 590 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 591 &transparent_hugepage_flags); 592 ret = 1; 593 } 594 out: 595 if (!ret) 596 printk(KERN_WARNING 597 "transparent_hugepage= cannot parse, ignored\n"); 598 return ret; 599 } 600 __setup("transparent_hugepage=", setup_transparent_hugepage); 601 602 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 603 { 604 if (likely(vma->vm_flags & VM_WRITE)) 605 pmd = pmd_mkwrite(pmd); 606 return pmd; 607 } 608 609 static inline pmd_t mk_huge_pmd(struct page *page, struct vm_area_struct *vma) 610 { 611 pmd_t entry; 612 entry = mk_pmd(page, vma->vm_page_prot); 613 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 614 entry = pmd_mkhuge(entry); 615 return entry; 616 } 617 618 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, 619 struct vm_area_struct *vma, 620 unsigned long haddr, pmd_t *pmd, 621 struct page *page) 622 { 623 pgtable_t pgtable; 624 625 VM_BUG_ON(!PageCompound(page)); 626 pgtable = pte_alloc_one(mm, haddr); 627 if (unlikely(!pgtable)) 628 return VM_FAULT_OOM; 629 630 clear_huge_page(page, haddr, HPAGE_PMD_NR); 631 __SetPageUptodate(page); 632 633 spin_lock(&mm->page_table_lock); 634 if (unlikely(!pmd_none(*pmd))) { 635 spin_unlock(&mm->page_table_lock); 636 mem_cgroup_uncharge_page(page); 637 put_page(page); 638 pte_free(mm, pgtable); 639 } else { 640 pmd_t entry; 641 entry = mk_huge_pmd(page, vma); 642 /* 643 * The spinlocking to take the lru_lock inside 644 * page_add_new_anon_rmap() acts as a full memory 645 * barrier to be sure clear_huge_page writes become 646 * visible after the set_pmd_at() write. 647 */ 648 page_add_new_anon_rmap(page, vma, haddr); 649 set_pmd_at(mm, haddr, pmd, entry); 650 pgtable_trans_huge_deposit(mm, pgtable); 651 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 652 mm->nr_ptes++; 653 spin_unlock(&mm->page_table_lock); 654 } 655 656 return 0; 657 } 658 659 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) 660 { 661 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; 662 } 663 664 static inline struct page *alloc_hugepage_vma(int defrag, 665 struct vm_area_struct *vma, 666 unsigned long haddr, int nd, 667 gfp_t extra_gfp) 668 { 669 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp), 670 HPAGE_PMD_ORDER, vma, haddr, nd); 671 } 672 673 #ifndef CONFIG_NUMA 674 static inline struct page *alloc_hugepage(int defrag) 675 { 676 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), 677 HPAGE_PMD_ORDER); 678 } 679 #endif 680 681 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 682 unsigned long address, pmd_t *pmd, 683 unsigned int flags) 684 { 685 struct page *page; 686 unsigned long haddr = address & HPAGE_PMD_MASK; 687 pte_t *pte; 688 689 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) { 690 if (unlikely(anon_vma_prepare(vma))) 691 return VM_FAULT_OOM; 692 if (unlikely(khugepaged_enter(vma))) 693 return VM_FAULT_OOM; 694 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 695 vma, haddr, numa_node_id(), 0); 696 if (unlikely(!page)) { 697 count_vm_event(THP_FAULT_FALLBACK); 698 goto out; 699 } 700 count_vm_event(THP_FAULT_ALLOC); 701 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) { 702 put_page(page); 703 goto out; 704 } 705 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, 706 page))) { 707 mem_cgroup_uncharge_page(page); 708 put_page(page); 709 goto out; 710 } 711 712 return 0; 713 } 714 out: 715 /* 716 * Use __pte_alloc instead of pte_alloc_map, because we can't 717 * run pte_offset_map on the pmd, if an huge pmd could 718 * materialize from under us from a different thread. 719 */ 720 if (unlikely(__pte_alloc(mm, vma, pmd, address))) 721 return VM_FAULT_OOM; 722 /* if an huge pmd materialized from under us just retry later */ 723 if (unlikely(pmd_trans_huge(*pmd))) 724 return 0; 725 /* 726 * A regular pmd is established and it can't morph into a huge pmd 727 * from under us anymore at this point because we hold the mmap_sem 728 * read mode and khugepaged takes it in write mode. So now it's 729 * safe to run pte_offset_map(). 730 */ 731 pte = pte_offset_map(pmd, address); 732 return handle_pte_fault(mm, vma, address, pte, pmd, flags); 733 } 734 735 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 736 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 737 struct vm_area_struct *vma) 738 { 739 struct page *src_page; 740 pmd_t pmd; 741 pgtable_t pgtable; 742 int ret; 743 744 ret = -ENOMEM; 745 pgtable = pte_alloc_one(dst_mm, addr); 746 if (unlikely(!pgtable)) 747 goto out; 748 749 spin_lock(&dst_mm->page_table_lock); 750 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING); 751 752 ret = -EAGAIN; 753 pmd = *src_pmd; 754 if (unlikely(!pmd_trans_huge(pmd))) { 755 pte_free(dst_mm, pgtable); 756 goto out_unlock; 757 } 758 if (unlikely(pmd_trans_splitting(pmd))) { 759 /* split huge page running from under us */ 760 spin_unlock(&src_mm->page_table_lock); 761 spin_unlock(&dst_mm->page_table_lock); 762 pte_free(dst_mm, pgtable); 763 764 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ 765 goto out; 766 } 767 src_page = pmd_page(pmd); 768 VM_BUG_ON(!PageHead(src_page)); 769 get_page(src_page); 770 page_dup_rmap(src_page); 771 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 772 773 pmdp_set_wrprotect(src_mm, addr, src_pmd); 774 pmd = pmd_mkold(pmd_wrprotect(pmd)); 775 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 776 pgtable_trans_huge_deposit(dst_mm, pgtable); 777 dst_mm->nr_ptes++; 778 779 ret = 0; 780 out_unlock: 781 spin_unlock(&src_mm->page_table_lock); 782 spin_unlock(&dst_mm->page_table_lock); 783 out: 784 return ret; 785 } 786 787 void huge_pmd_set_accessed(struct mm_struct *mm, 788 struct vm_area_struct *vma, 789 unsigned long address, 790 pmd_t *pmd, pmd_t orig_pmd, 791 int dirty) 792 { 793 pmd_t entry; 794 unsigned long haddr; 795 796 spin_lock(&mm->page_table_lock); 797 if (unlikely(!pmd_same(*pmd, orig_pmd))) 798 goto unlock; 799 800 entry = pmd_mkyoung(orig_pmd); 801 haddr = address & HPAGE_PMD_MASK; 802 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty)) 803 update_mmu_cache_pmd(vma, address, pmd); 804 805 unlock: 806 spin_unlock(&mm->page_table_lock); 807 } 808 809 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, 810 struct vm_area_struct *vma, 811 unsigned long address, 812 pmd_t *pmd, pmd_t orig_pmd, 813 struct page *page, 814 unsigned long haddr) 815 { 816 pgtable_t pgtable; 817 pmd_t _pmd; 818 int ret = 0, i; 819 struct page **pages; 820 unsigned long mmun_start; /* For mmu_notifiers */ 821 unsigned long mmun_end; /* For mmu_notifiers */ 822 823 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 824 GFP_KERNEL); 825 if (unlikely(!pages)) { 826 ret |= VM_FAULT_OOM; 827 goto out; 828 } 829 830 for (i = 0; i < HPAGE_PMD_NR; i++) { 831 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | 832 __GFP_OTHER_NODE, 833 vma, address, page_to_nid(page)); 834 if (unlikely(!pages[i] || 835 mem_cgroup_newpage_charge(pages[i], mm, 836 GFP_KERNEL))) { 837 if (pages[i]) 838 put_page(pages[i]); 839 mem_cgroup_uncharge_start(); 840 while (--i >= 0) { 841 mem_cgroup_uncharge_page(pages[i]); 842 put_page(pages[i]); 843 } 844 mem_cgroup_uncharge_end(); 845 kfree(pages); 846 ret |= VM_FAULT_OOM; 847 goto out; 848 } 849 } 850 851 for (i = 0; i < HPAGE_PMD_NR; i++) { 852 copy_user_highpage(pages[i], page + i, 853 haddr + PAGE_SIZE * i, vma); 854 __SetPageUptodate(pages[i]); 855 cond_resched(); 856 } 857 858 mmun_start = haddr; 859 mmun_end = haddr + HPAGE_PMD_SIZE; 860 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 861 862 spin_lock(&mm->page_table_lock); 863 if (unlikely(!pmd_same(*pmd, orig_pmd))) 864 goto out_free_pages; 865 VM_BUG_ON(!PageHead(page)); 866 867 pmdp_clear_flush(vma, haddr, pmd); 868 /* leave pmd empty until pte is filled */ 869 870 pgtable = pgtable_trans_huge_withdraw(mm); 871 pmd_populate(mm, &_pmd, pgtable); 872 873 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 874 pte_t *pte, entry; 875 entry = mk_pte(pages[i], vma->vm_page_prot); 876 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 877 page_add_new_anon_rmap(pages[i], vma, haddr); 878 pte = pte_offset_map(&_pmd, haddr); 879 VM_BUG_ON(!pte_none(*pte)); 880 set_pte_at(mm, haddr, pte, entry); 881 pte_unmap(pte); 882 } 883 kfree(pages); 884 885 smp_wmb(); /* make pte visible before pmd */ 886 pmd_populate(mm, pmd, pgtable); 887 page_remove_rmap(page); 888 spin_unlock(&mm->page_table_lock); 889 890 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 891 892 ret |= VM_FAULT_WRITE; 893 put_page(page); 894 895 out: 896 return ret; 897 898 out_free_pages: 899 spin_unlock(&mm->page_table_lock); 900 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 901 mem_cgroup_uncharge_start(); 902 for (i = 0; i < HPAGE_PMD_NR; i++) { 903 mem_cgroup_uncharge_page(pages[i]); 904 put_page(pages[i]); 905 } 906 mem_cgroup_uncharge_end(); 907 kfree(pages); 908 goto out; 909 } 910 911 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 912 unsigned long address, pmd_t *pmd, pmd_t orig_pmd) 913 { 914 int ret = 0; 915 struct page *page, *new_page; 916 unsigned long haddr; 917 unsigned long mmun_start; /* For mmu_notifiers */ 918 unsigned long mmun_end; /* For mmu_notifiers */ 919 920 VM_BUG_ON(!vma->anon_vma); 921 spin_lock(&mm->page_table_lock); 922 if (unlikely(!pmd_same(*pmd, orig_pmd))) 923 goto out_unlock; 924 925 page = pmd_page(orig_pmd); 926 VM_BUG_ON(!PageCompound(page) || !PageHead(page)); 927 haddr = address & HPAGE_PMD_MASK; 928 if (page_mapcount(page) == 1) { 929 pmd_t entry; 930 entry = pmd_mkyoung(orig_pmd); 931 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 932 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 933 update_mmu_cache_pmd(vma, address, pmd); 934 ret |= VM_FAULT_WRITE; 935 goto out_unlock; 936 } 937 get_page(page); 938 spin_unlock(&mm->page_table_lock); 939 940 if (transparent_hugepage_enabled(vma) && 941 !transparent_hugepage_debug_cow()) 942 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 943 vma, haddr, numa_node_id(), 0); 944 else 945 new_page = NULL; 946 947 if (unlikely(!new_page)) { 948 count_vm_event(THP_FAULT_FALLBACK); 949 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 950 pmd, orig_pmd, page, haddr); 951 if (ret & VM_FAULT_OOM) 952 split_huge_page(page); 953 put_page(page); 954 goto out; 955 } 956 count_vm_event(THP_FAULT_ALLOC); 957 958 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 959 put_page(new_page); 960 split_huge_page(page); 961 put_page(page); 962 ret |= VM_FAULT_OOM; 963 goto out; 964 } 965 966 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 967 __SetPageUptodate(new_page); 968 969 mmun_start = haddr; 970 mmun_end = haddr + HPAGE_PMD_SIZE; 971 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 972 973 spin_lock(&mm->page_table_lock); 974 put_page(page); 975 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 976 spin_unlock(&mm->page_table_lock); 977 mem_cgroup_uncharge_page(new_page); 978 put_page(new_page); 979 goto out_mn; 980 } else { 981 pmd_t entry; 982 VM_BUG_ON(!PageHead(page)); 983 entry = mk_huge_pmd(new_page, vma); 984 pmdp_clear_flush(vma, haddr, pmd); 985 page_add_new_anon_rmap(new_page, vma, haddr); 986 set_pmd_at(mm, haddr, pmd, entry); 987 update_mmu_cache_pmd(vma, address, pmd); 988 page_remove_rmap(page); 989 put_page(page); 990 ret |= VM_FAULT_WRITE; 991 } 992 spin_unlock(&mm->page_table_lock); 993 out_mn: 994 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 995 out: 996 return ret; 997 out_unlock: 998 spin_unlock(&mm->page_table_lock); 999 return ret; 1000 } 1001 1002 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1003 unsigned long addr, 1004 pmd_t *pmd, 1005 unsigned int flags) 1006 { 1007 struct mm_struct *mm = vma->vm_mm; 1008 struct page *page = NULL; 1009 1010 assert_spin_locked(&mm->page_table_lock); 1011 1012 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 1013 goto out; 1014 1015 page = pmd_page(*pmd); 1016 VM_BUG_ON(!PageHead(page)); 1017 if (flags & FOLL_TOUCH) { 1018 pmd_t _pmd; 1019 /* 1020 * We should set the dirty bit only for FOLL_WRITE but 1021 * for now the dirty bit in the pmd is meaningless. 1022 * And if the dirty bit will become meaningful and 1023 * we'll only set it with FOLL_WRITE, an atomic 1024 * set_bit will be required on the pmd to set the 1025 * young bit, instead of the current set_pmd_at. 1026 */ 1027 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 1028 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd); 1029 } 1030 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 1031 if (page->mapping && trylock_page(page)) { 1032 lru_add_drain(); 1033 if (page->mapping) 1034 mlock_vma_page(page); 1035 unlock_page(page); 1036 } 1037 } 1038 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1039 VM_BUG_ON(!PageCompound(page)); 1040 if (flags & FOLL_GET) 1041 get_page_foll(page); 1042 1043 out: 1044 return page; 1045 } 1046 1047 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1048 pmd_t *pmd, unsigned long addr) 1049 { 1050 int ret = 0; 1051 1052 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1053 struct page *page; 1054 pgtable_t pgtable; 1055 pmd_t orig_pmd; 1056 pgtable = pgtable_trans_huge_withdraw(tlb->mm); 1057 orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd); 1058 page = pmd_page(orig_pmd); 1059 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1060 page_remove_rmap(page); 1061 VM_BUG_ON(page_mapcount(page) < 0); 1062 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1063 VM_BUG_ON(!PageHead(page)); 1064 tlb->mm->nr_ptes--; 1065 spin_unlock(&tlb->mm->page_table_lock); 1066 tlb_remove_page(tlb, page); 1067 pte_free(tlb->mm, pgtable); 1068 ret = 1; 1069 } 1070 return ret; 1071 } 1072 1073 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1074 unsigned long addr, unsigned long end, 1075 unsigned char *vec) 1076 { 1077 int ret = 0; 1078 1079 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1080 /* 1081 * All logical pages in the range are present 1082 * if backed by a huge page. 1083 */ 1084 spin_unlock(&vma->vm_mm->page_table_lock); 1085 memset(vec, 1, (end - addr) >> PAGE_SHIFT); 1086 ret = 1; 1087 } 1088 1089 return ret; 1090 } 1091 1092 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, 1093 unsigned long old_addr, 1094 unsigned long new_addr, unsigned long old_end, 1095 pmd_t *old_pmd, pmd_t *new_pmd) 1096 { 1097 int ret = 0; 1098 pmd_t pmd; 1099 1100 struct mm_struct *mm = vma->vm_mm; 1101 1102 if ((old_addr & ~HPAGE_PMD_MASK) || 1103 (new_addr & ~HPAGE_PMD_MASK) || 1104 old_end - old_addr < HPAGE_PMD_SIZE || 1105 (new_vma->vm_flags & VM_NOHUGEPAGE)) 1106 goto out; 1107 1108 /* 1109 * The destination pmd shouldn't be established, free_pgtables() 1110 * should have release it. 1111 */ 1112 if (WARN_ON(!pmd_none(*new_pmd))) { 1113 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1114 goto out; 1115 } 1116 1117 ret = __pmd_trans_huge_lock(old_pmd, vma); 1118 if (ret == 1) { 1119 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); 1120 VM_BUG_ON(!pmd_none(*new_pmd)); 1121 set_pmd_at(mm, new_addr, new_pmd, pmd); 1122 spin_unlock(&mm->page_table_lock); 1123 } 1124 out: 1125 return ret; 1126 } 1127 1128 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1129 unsigned long addr, pgprot_t newprot) 1130 { 1131 struct mm_struct *mm = vma->vm_mm; 1132 int ret = 0; 1133 1134 if (__pmd_trans_huge_lock(pmd, vma) == 1) { 1135 pmd_t entry; 1136 entry = pmdp_get_and_clear(mm, addr, pmd); 1137 entry = pmd_modify(entry, newprot); 1138 set_pmd_at(mm, addr, pmd, entry); 1139 spin_unlock(&vma->vm_mm->page_table_lock); 1140 ret = 1; 1141 } 1142 1143 return ret; 1144 } 1145 1146 /* 1147 * Returns 1 if a given pmd maps a stable (not under splitting) thp. 1148 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise. 1149 * 1150 * Note that if it returns 1, this routine returns without unlocking page 1151 * table locks. So callers must unlock them. 1152 */ 1153 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) 1154 { 1155 spin_lock(&vma->vm_mm->page_table_lock); 1156 if (likely(pmd_trans_huge(*pmd))) { 1157 if (unlikely(pmd_trans_splitting(*pmd))) { 1158 spin_unlock(&vma->vm_mm->page_table_lock); 1159 wait_split_huge_page(vma->anon_vma, pmd); 1160 return -1; 1161 } else { 1162 /* Thp mapped by 'pmd' is stable, so we can 1163 * handle it as it is. */ 1164 return 1; 1165 } 1166 } 1167 spin_unlock(&vma->vm_mm->page_table_lock); 1168 return 0; 1169 } 1170 1171 pmd_t *page_check_address_pmd(struct page *page, 1172 struct mm_struct *mm, 1173 unsigned long address, 1174 enum page_check_address_pmd_flag flag) 1175 { 1176 pmd_t *pmd, *ret = NULL; 1177 1178 if (address & ~HPAGE_PMD_MASK) 1179 goto out; 1180 1181 pmd = mm_find_pmd(mm, address); 1182 if (!pmd) 1183 goto out; 1184 if (pmd_none(*pmd)) 1185 goto out; 1186 if (pmd_page(*pmd) != page) 1187 goto out; 1188 /* 1189 * split_vma() may create temporary aliased mappings. There is 1190 * no risk as long as all huge pmd are found and have their 1191 * splitting bit set before __split_huge_page_refcount 1192 * runs. Finding the same huge pmd more than once during the 1193 * same rmap walk is not a problem. 1194 */ 1195 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && 1196 pmd_trans_splitting(*pmd)) 1197 goto out; 1198 if (pmd_trans_huge(*pmd)) { 1199 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && 1200 !pmd_trans_splitting(*pmd)); 1201 ret = pmd; 1202 } 1203 out: 1204 return ret; 1205 } 1206 1207 static int __split_huge_page_splitting(struct page *page, 1208 struct vm_area_struct *vma, 1209 unsigned long address) 1210 { 1211 struct mm_struct *mm = vma->vm_mm; 1212 pmd_t *pmd; 1213 int ret = 0; 1214 /* For mmu_notifiers */ 1215 const unsigned long mmun_start = address; 1216 const unsigned long mmun_end = address + HPAGE_PMD_SIZE; 1217 1218 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1219 spin_lock(&mm->page_table_lock); 1220 pmd = page_check_address_pmd(page, mm, address, 1221 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG); 1222 if (pmd) { 1223 /* 1224 * We can't temporarily set the pmd to null in order 1225 * to split it, the pmd must remain marked huge at all 1226 * times or the VM won't take the pmd_trans_huge paths 1227 * and it won't wait on the anon_vma->root->mutex to 1228 * serialize against split_huge_page*. 1229 */ 1230 pmdp_splitting_flush(vma, address, pmd); 1231 ret = 1; 1232 } 1233 spin_unlock(&mm->page_table_lock); 1234 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 1235 1236 return ret; 1237 } 1238 1239 static void __split_huge_page_refcount(struct page *page) 1240 { 1241 int i; 1242 struct zone *zone = page_zone(page); 1243 struct lruvec *lruvec; 1244 int tail_count = 0; 1245 1246 /* prevent PageLRU to go away from under us, and freeze lru stats */ 1247 spin_lock_irq(&zone->lru_lock); 1248 lruvec = mem_cgroup_page_lruvec(page, zone); 1249 1250 compound_lock(page); 1251 /* complete memcg works before add pages to LRU */ 1252 mem_cgroup_split_huge_fixup(page); 1253 1254 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 1255 struct page *page_tail = page + i; 1256 1257 /* tail_page->_mapcount cannot change */ 1258 BUG_ON(page_mapcount(page_tail) < 0); 1259 tail_count += page_mapcount(page_tail); 1260 /* check for overflow */ 1261 BUG_ON(tail_count < 0); 1262 BUG_ON(atomic_read(&page_tail->_count) != 0); 1263 /* 1264 * tail_page->_count is zero and not changing from 1265 * under us. But get_page_unless_zero() may be running 1266 * from under us on the tail_page. If we used 1267 * atomic_set() below instead of atomic_add(), we 1268 * would then run atomic_set() concurrently with 1269 * get_page_unless_zero(), and atomic_set() is 1270 * implemented in C not using locked ops. spin_unlock 1271 * on x86 sometime uses locked ops because of PPro 1272 * errata 66, 92, so unless somebody can guarantee 1273 * atomic_set() here would be safe on all archs (and 1274 * not only on x86), it's safer to use atomic_add(). 1275 */ 1276 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, 1277 &page_tail->_count); 1278 1279 /* after clearing PageTail the gup refcount can be released */ 1280 smp_mb(); 1281 1282 /* 1283 * retain hwpoison flag of the poisoned tail page: 1284 * fix for the unsuitable process killed on Guest Machine(KVM) 1285 * by the memory-failure. 1286 */ 1287 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON; 1288 page_tail->flags |= (page->flags & 1289 ((1L << PG_referenced) | 1290 (1L << PG_swapbacked) | 1291 (1L << PG_mlocked) | 1292 (1L << PG_uptodate))); 1293 page_tail->flags |= (1L << PG_dirty); 1294 1295 /* clear PageTail before overwriting first_page */ 1296 smp_wmb(); 1297 1298 /* 1299 * __split_huge_page_splitting() already set the 1300 * splitting bit in all pmd that could map this 1301 * hugepage, that will ensure no CPU can alter the 1302 * mapcount on the head page. The mapcount is only 1303 * accounted in the head page and it has to be 1304 * transferred to all tail pages in the below code. So 1305 * for this code to be safe, the split the mapcount 1306 * can't change. But that doesn't mean userland can't 1307 * keep changing and reading the page contents while 1308 * we transfer the mapcount, so the pmd splitting 1309 * status is achieved setting a reserved bit in the 1310 * pmd, not by clearing the present bit. 1311 */ 1312 page_tail->_mapcount = page->_mapcount; 1313 1314 BUG_ON(page_tail->mapping); 1315 page_tail->mapping = page->mapping; 1316 1317 page_tail->index = page->index + i; 1318 1319 BUG_ON(!PageAnon(page_tail)); 1320 BUG_ON(!PageUptodate(page_tail)); 1321 BUG_ON(!PageDirty(page_tail)); 1322 BUG_ON(!PageSwapBacked(page_tail)); 1323 1324 lru_add_page_tail(page, page_tail, lruvec); 1325 } 1326 atomic_sub(tail_count, &page->_count); 1327 BUG_ON(atomic_read(&page->_count) <= 0); 1328 1329 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1); 1330 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR); 1331 1332 ClearPageCompound(page); 1333 compound_unlock(page); 1334 spin_unlock_irq(&zone->lru_lock); 1335 1336 for (i = 1; i < HPAGE_PMD_NR; i++) { 1337 struct page *page_tail = page + i; 1338 BUG_ON(page_count(page_tail) <= 0); 1339 /* 1340 * Tail pages may be freed if there wasn't any mapping 1341 * like if add_to_swap() is running on a lru page that 1342 * had its mapping zapped. And freeing these pages 1343 * requires taking the lru_lock so we do the put_page 1344 * of the tail pages after the split is complete. 1345 */ 1346 put_page(page_tail); 1347 } 1348 1349 /* 1350 * Only the head page (now become a regular page) is required 1351 * to be pinned by the caller. 1352 */ 1353 BUG_ON(page_count(page) <= 0); 1354 } 1355 1356 static int __split_huge_page_map(struct page *page, 1357 struct vm_area_struct *vma, 1358 unsigned long address) 1359 { 1360 struct mm_struct *mm = vma->vm_mm; 1361 pmd_t *pmd, _pmd; 1362 int ret = 0, i; 1363 pgtable_t pgtable; 1364 unsigned long haddr; 1365 1366 spin_lock(&mm->page_table_lock); 1367 pmd = page_check_address_pmd(page, mm, address, 1368 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG); 1369 if (pmd) { 1370 pgtable = pgtable_trans_huge_withdraw(mm); 1371 pmd_populate(mm, &_pmd, pgtable); 1372 1373 haddr = address; 1374 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1375 pte_t *pte, entry; 1376 BUG_ON(PageCompound(page+i)); 1377 entry = mk_pte(page + i, vma->vm_page_prot); 1378 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1379 if (!pmd_write(*pmd)) 1380 entry = pte_wrprotect(entry); 1381 else 1382 BUG_ON(page_mapcount(page) != 1); 1383 if (!pmd_young(*pmd)) 1384 entry = pte_mkold(entry); 1385 pte = pte_offset_map(&_pmd, haddr); 1386 BUG_ON(!pte_none(*pte)); 1387 set_pte_at(mm, haddr, pte, entry); 1388 pte_unmap(pte); 1389 } 1390 1391 smp_wmb(); /* make pte visible before pmd */ 1392 /* 1393 * Up to this point the pmd is present and huge and 1394 * userland has the whole access to the hugepage 1395 * during the split (which happens in place). If we 1396 * overwrite the pmd with the not-huge version 1397 * pointing to the pte here (which of course we could 1398 * if all CPUs were bug free), userland could trigger 1399 * a small page size TLB miss on the small sized TLB 1400 * while the hugepage TLB entry is still established 1401 * in the huge TLB. Some CPU doesn't like that. See 1402 * http://support.amd.com/us/Processor_TechDocs/41322.pdf, 1403 * Erratum 383 on page 93. Intel should be safe but is 1404 * also warns that it's only safe if the permission 1405 * and cache attributes of the two entries loaded in 1406 * the two TLB is identical (which should be the case 1407 * here). But it is generally safer to never allow 1408 * small and huge TLB entries for the same virtual 1409 * address to be loaded simultaneously. So instead of 1410 * doing "pmd_populate(); flush_tlb_range();" we first 1411 * mark the current pmd notpresent (atomically because 1412 * here the pmd_trans_huge and pmd_trans_splitting 1413 * must remain set at all times on the pmd until the 1414 * split is complete for this pmd), then we flush the 1415 * SMP TLB and finally we write the non-huge version 1416 * of the pmd entry with pmd_populate. 1417 */ 1418 pmdp_invalidate(vma, address, pmd); 1419 pmd_populate(mm, pmd, pgtable); 1420 ret = 1; 1421 } 1422 spin_unlock(&mm->page_table_lock); 1423 1424 return ret; 1425 } 1426 1427 /* must be called with anon_vma->root->mutex hold */ 1428 static void __split_huge_page(struct page *page, 1429 struct anon_vma *anon_vma) 1430 { 1431 int mapcount, mapcount2; 1432 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); 1433 struct anon_vma_chain *avc; 1434 1435 BUG_ON(!PageHead(page)); 1436 BUG_ON(PageTail(page)); 1437 1438 mapcount = 0; 1439 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1440 struct vm_area_struct *vma = avc->vma; 1441 unsigned long addr = vma_address(page, vma); 1442 BUG_ON(is_vma_temporary_stack(vma)); 1443 mapcount += __split_huge_page_splitting(page, vma, addr); 1444 } 1445 /* 1446 * It is critical that new vmas are added to the tail of the 1447 * anon_vma list. This guarantes that if copy_huge_pmd() runs 1448 * and establishes a child pmd before 1449 * __split_huge_page_splitting() freezes the parent pmd (so if 1450 * we fail to prevent copy_huge_pmd() from running until the 1451 * whole __split_huge_page() is complete), we will still see 1452 * the newly established pmd of the child later during the 1453 * walk, to be able to set it as pmd_trans_splitting too. 1454 */ 1455 if (mapcount != page_mapcount(page)) 1456 printk(KERN_ERR "mapcount %d page_mapcount %d\n", 1457 mapcount, page_mapcount(page)); 1458 BUG_ON(mapcount != page_mapcount(page)); 1459 1460 __split_huge_page_refcount(page); 1461 1462 mapcount2 = 0; 1463 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { 1464 struct vm_area_struct *vma = avc->vma; 1465 unsigned long addr = vma_address(page, vma); 1466 BUG_ON(is_vma_temporary_stack(vma)); 1467 mapcount2 += __split_huge_page_map(page, vma, addr); 1468 } 1469 if (mapcount != mapcount2) 1470 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n", 1471 mapcount, mapcount2, page_mapcount(page)); 1472 BUG_ON(mapcount != mapcount2); 1473 } 1474 1475 int split_huge_page(struct page *page) 1476 { 1477 struct anon_vma *anon_vma; 1478 int ret = 1; 1479 1480 BUG_ON(!PageAnon(page)); 1481 anon_vma = page_lock_anon_vma(page); 1482 if (!anon_vma) 1483 goto out; 1484 ret = 0; 1485 if (!PageCompound(page)) 1486 goto out_unlock; 1487 1488 BUG_ON(!PageSwapBacked(page)); 1489 __split_huge_page(page, anon_vma); 1490 count_vm_event(THP_SPLIT); 1491 1492 BUG_ON(PageCompound(page)); 1493 out_unlock: 1494 page_unlock_anon_vma(anon_vma); 1495 out: 1496 return ret; 1497 } 1498 1499 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE) 1500 1501 int hugepage_madvise(struct vm_area_struct *vma, 1502 unsigned long *vm_flags, int advice) 1503 { 1504 struct mm_struct *mm = vma->vm_mm; 1505 1506 switch (advice) { 1507 case MADV_HUGEPAGE: 1508 /* 1509 * Be somewhat over-protective like KSM for now! 1510 */ 1511 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) 1512 return -EINVAL; 1513 if (mm->def_flags & VM_NOHUGEPAGE) 1514 return -EINVAL; 1515 *vm_flags &= ~VM_NOHUGEPAGE; 1516 *vm_flags |= VM_HUGEPAGE; 1517 /* 1518 * If the vma become good for khugepaged to scan, 1519 * register it here without waiting a page fault that 1520 * may not happen any time soon. 1521 */ 1522 if (unlikely(khugepaged_enter_vma_merge(vma))) 1523 return -ENOMEM; 1524 break; 1525 case MADV_NOHUGEPAGE: 1526 /* 1527 * Be somewhat over-protective like KSM for now! 1528 */ 1529 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) 1530 return -EINVAL; 1531 *vm_flags &= ~VM_HUGEPAGE; 1532 *vm_flags |= VM_NOHUGEPAGE; 1533 /* 1534 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1535 * this vma even if we leave the mm registered in khugepaged if 1536 * it got registered before VM_NOHUGEPAGE was set. 1537 */ 1538 break; 1539 } 1540 1541 return 0; 1542 } 1543 1544 static int __init khugepaged_slab_init(void) 1545 { 1546 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1547 sizeof(struct mm_slot), 1548 __alignof__(struct mm_slot), 0, NULL); 1549 if (!mm_slot_cache) 1550 return -ENOMEM; 1551 1552 return 0; 1553 } 1554 1555 static void __init khugepaged_slab_free(void) 1556 { 1557 kmem_cache_destroy(mm_slot_cache); 1558 mm_slot_cache = NULL; 1559 } 1560 1561 static inline struct mm_slot *alloc_mm_slot(void) 1562 { 1563 if (!mm_slot_cache) /* initialization failed */ 1564 return NULL; 1565 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 1566 } 1567 1568 static inline void free_mm_slot(struct mm_slot *mm_slot) 1569 { 1570 kmem_cache_free(mm_slot_cache, mm_slot); 1571 } 1572 1573 static int __init mm_slots_hash_init(void) 1574 { 1575 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), 1576 GFP_KERNEL); 1577 if (!mm_slots_hash) 1578 return -ENOMEM; 1579 return 0; 1580 } 1581 1582 #if 0 1583 static void __init mm_slots_hash_free(void) 1584 { 1585 kfree(mm_slots_hash); 1586 mm_slots_hash = NULL; 1587 } 1588 #endif 1589 1590 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 1591 { 1592 struct mm_slot *mm_slot; 1593 struct hlist_head *bucket; 1594 struct hlist_node *node; 1595 1596 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1597 % MM_SLOTS_HASH_HEADS]; 1598 hlist_for_each_entry(mm_slot, node, bucket, hash) { 1599 if (mm == mm_slot->mm) 1600 return mm_slot; 1601 } 1602 return NULL; 1603 } 1604 1605 static void insert_to_mm_slots_hash(struct mm_struct *mm, 1606 struct mm_slot *mm_slot) 1607 { 1608 struct hlist_head *bucket; 1609 1610 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1611 % MM_SLOTS_HASH_HEADS]; 1612 mm_slot->mm = mm; 1613 hlist_add_head(&mm_slot->hash, bucket); 1614 } 1615 1616 static inline int khugepaged_test_exit(struct mm_struct *mm) 1617 { 1618 return atomic_read(&mm->mm_users) == 0; 1619 } 1620 1621 int __khugepaged_enter(struct mm_struct *mm) 1622 { 1623 struct mm_slot *mm_slot; 1624 int wakeup; 1625 1626 mm_slot = alloc_mm_slot(); 1627 if (!mm_slot) 1628 return -ENOMEM; 1629 1630 /* __khugepaged_exit() must not run from under us */ 1631 VM_BUG_ON(khugepaged_test_exit(mm)); 1632 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 1633 free_mm_slot(mm_slot); 1634 return 0; 1635 } 1636 1637 spin_lock(&khugepaged_mm_lock); 1638 insert_to_mm_slots_hash(mm, mm_slot); 1639 /* 1640 * Insert just behind the scanning cursor, to let the area settle 1641 * down a little. 1642 */ 1643 wakeup = list_empty(&khugepaged_scan.mm_head); 1644 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 1645 spin_unlock(&khugepaged_mm_lock); 1646 1647 atomic_inc(&mm->mm_count); 1648 if (wakeup) 1649 wake_up_interruptible(&khugepaged_wait); 1650 1651 return 0; 1652 } 1653 1654 int khugepaged_enter_vma_merge(struct vm_area_struct *vma) 1655 { 1656 unsigned long hstart, hend; 1657 if (!vma->anon_vma) 1658 /* 1659 * Not yet faulted in so we will register later in the 1660 * page fault if needed. 1661 */ 1662 return 0; 1663 if (vma->vm_ops) 1664 /* khugepaged not yet working on file or special mappings */ 1665 return 0; 1666 VM_BUG_ON(vma->vm_flags & VM_NO_THP); 1667 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1668 hend = vma->vm_end & HPAGE_PMD_MASK; 1669 if (hstart < hend) 1670 return khugepaged_enter(vma); 1671 return 0; 1672 } 1673 1674 void __khugepaged_exit(struct mm_struct *mm) 1675 { 1676 struct mm_slot *mm_slot; 1677 int free = 0; 1678 1679 spin_lock(&khugepaged_mm_lock); 1680 mm_slot = get_mm_slot(mm); 1681 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 1682 hlist_del(&mm_slot->hash); 1683 list_del(&mm_slot->mm_node); 1684 free = 1; 1685 } 1686 spin_unlock(&khugepaged_mm_lock); 1687 1688 if (free) { 1689 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1690 free_mm_slot(mm_slot); 1691 mmdrop(mm); 1692 } else if (mm_slot) { 1693 /* 1694 * This is required to serialize against 1695 * khugepaged_test_exit() (which is guaranteed to run 1696 * under mmap sem read mode). Stop here (after we 1697 * return all pagetables will be destroyed) until 1698 * khugepaged has finished working on the pagetables 1699 * under the mmap_sem. 1700 */ 1701 down_write(&mm->mmap_sem); 1702 up_write(&mm->mmap_sem); 1703 } 1704 } 1705 1706 static void release_pte_page(struct page *page) 1707 { 1708 /* 0 stands for page_is_file_cache(page) == false */ 1709 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 1710 unlock_page(page); 1711 putback_lru_page(page); 1712 } 1713 1714 static void release_pte_pages(pte_t *pte, pte_t *_pte) 1715 { 1716 while (--_pte >= pte) { 1717 pte_t pteval = *_pte; 1718 if (!pte_none(pteval)) 1719 release_pte_page(pte_page(pteval)); 1720 } 1721 } 1722 1723 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 1724 unsigned long address, 1725 pte_t *pte) 1726 { 1727 struct page *page; 1728 pte_t *_pte; 1729 int referenced = 0, none = 0; 1730 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 1731 _pte++, address += PAGE_SIZE) { 1732 pte_t pteval = *_pte; 1733 if (pte_none(pteval)) { 1734 if (++none <= khugepaged_max_ptes_none) 1735 continue; 1736 else 1737 goto out; 1738 } 1739 if (!pte_present(pteval) || !pte_write(pteval)) 1740 goto out; 1741 page = vm_normal_page(vma, address, pteval); 1742 if (unlikely(!page)) 1743 goto out; 1744 1745 VM_BUG_ON(PageCompound(page)); 1746 BUG_ON(!PageAnon(page)); 1747 VM_BUG_ON(!PageSwapBacked(page)); 1748 1749 /* cannot use mapcount: can't collapse if there's a gup pin */ 1750 if (page_count(page) != 1) 1751 goto out; 1752 /* 1753 * We can do it before isolate_lru_page because the 1754 * page can't be freed from under us. NOTE: PG_lock 1755 * is needed to serialize against split_huge_page 1756 * when invoked from the VM. 1757 */ 1758 if (!trylock_page(page)) 1759 goto out; 1760 /* 1761 * Isolate the page to avoid collapsing an hugepage 1762 * currently in use by the VM. 1763 */ 1764 if (isolate_lru_page(page)) { 1765 unlock_page(page); 1766 goto out; 1767 } 1768 /* 0 stands for page_is_file_cache(page) == false */ 1769 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 1770 VM_BUG_ON(!PageLocked(page)); 1771 VM_BUG_ON(PageLRU(page)); 1772 1773 /* If there is no mapped pte young don't collapse the page */ 1774 if (pte_young(pteval) || PageReferenced(page) || 1775 mmu_notifier_test_young(vma->vm_mm, address)) 1776 referenced = 1; 1777 } 1778 if (likely(referenced)) 1779 return 1; 1780 out: 1781 release_pte_pages(pte, _pte); 1782 return 0; 1783 } 1784 1785 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 1786 struct vm_area_struct *vma, 1787 unsigned long address, 1788 spinlock_t *ptl) 1789 { 1790 pte_t *_pte; 1791 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 1792 pte_t pteval = *_pte; 1793 struct page *src_page; 1794 1795 if (pte_none(pteval)) { 1796 clear_user_highpage(page, address); 1797 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 1798 } else { 1799 src_page = pte_page(pteval); 1800 copy_user_highpage(page, src_page, address, vma); 1801 VM_BUG_ON(page_mapcount(src_page) != 1); 1802 release_pte_page(src_page); 1803 /* 1804 * ptl mostly unnecessary, but preempt has to 1805 * be disabled to update the per-cpu stats 1806 * inside page_remove_rmap(). 1807 */ 1808 spin_lock(ptl); 1809 /* 1810 * paravirt calls inside pte_clear here are 1811 * superfluous. 1812 */ 1813 pte_clear(vma->vm_mm, address, _pte); 1814 page_remove_rmap(src_page); 1815 spin_unlock(ptl); 1816 free_page_and_swap_cache(src_page); 1817 } 1818 1819 address += PAGE_SIZE; 1820 page++; 1821 } 1822 } 1823 1824 static void khugepaged_alloc_sleep(void) 1825 { 1826 wait_event_freezable_timeout(khugepaged_wait, false, 1827 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); 1828 } 1829 1830 #ifdef CONFIG_NUMA 1831 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 1832 { 1833 if (IS_ERR(*hpage)) { 1834 if (!*wait) 1835 return false; 1836 1837 *wait = false; 1838 *hpage = NULL; 1839 khugepaged_alloc_sleep(); 1840 } else if (*hpage) { 1841 put_page(*hpage); 1842 *hpage = NULL; 1843 } 1844 1845 return true; 1846 } 1847 1848 static struct page 1849 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 1850 struct vm_area_struct *vma, unsigned long address, 1851 int node) 1852 { 1853 VM_BUG_ON(*hpage); 1854 /* 1855 * Allocate the page while the vma is still valid and under 1856 * the mmap_sem read mode so there is no memory allocation 1857 * later when we take the mmap_sem in write mode. This is more 1858 * friendly behavior (OTOH it may actually hide bugs) to 1859 * filesystems in userland with daemons allocating memory in 1860 * the userland I/O paths. Allocating memory with the 1861 * mmap_sem in read mode is good idea also to allow greater 1862 * scalability. 1863 */ 1864 *hpage = alloc_hugepage_vma(khugepaged_defrag(), vma, address, 1865 node, __GFP_OTHER_NODE); 1866 1867 /* 1868 * After allocating the hugepage, release the mmap_sem read lock in 1869 * preparation for taking it in write mode. 1870 */ 1871 up_read(&mm->mmap_sem); 1872 if (unlikely(!*hpage)) { 1873 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 1874 *hpage = ERR_PTR(-ENOMEM); 1875 return NULL; 1876 } 1877 1878 count_vm_event(THP_COLLAPSE_ALLOC); 1879 return *hpage; 1880 } 1881 #else 1882 static struct page *khugepaged_alloc_hugepage(bool *wait) 1883 { 1884 struct page *hpage; 1885 1886 do { 1887 hpage = alloc_hugepage(khugepaged_defrag()); 1888 if (!hpage) { 1889 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 1890 if (!*wait) 1891 return NULL; 1892 1893 *wait = false; 1894 khugepaged_alloc_sleep(); 1895 } else 1896 count_vm_event(THP_COLLAPSE_ALLOC); 1897 } while (unlikely(!hpage) && likely(khugepaged_enabled())); 1898 1899 return hpage; 1900 } 1901 1902 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) 1903 { 1904 if (!*hpage) 1905 *hpage = khugepaged_alloc_hugepage(wait); 1906 1907 if (unlikely(!*hpage)) 1908 return false; 1909 1910 return true; 1911 } 1912 1913 static struct page 1914 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm, 1915 struct vm_area_struct *vma, unsigned long address, 1916 int node) 1917 { 1918 up_read(&mm->mmap_sem); 1919 VM_BUG_ON(!*hpage); 1920 return *hpage; 1921 } 1922 #endif 1923 1924 static bool hugepage_vma_check(struct vm_area_struct *vma) 1925 { 1926 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 1927 (vma->vm_flags & VM_NOHUGEPAGE)) 1928 return false; 1929 1930 if (!vma->anon_vma || vma->vm_ops) 1931 return false; 1932 if (is_vma_temporary_stack(vma)) 1933 return false; 1934 VM_BUG_ON(vma->vm_flags & VM_NO_THP); 1935 return true; 1936 } 1937 1938 static void collapse_huge_page(struct mm_struct *mm, 1939 unsigned long address, 1940 struct page **hpage, 1941 struct vm_area_struct *vma, 1942 int node) 1943 { 1944 pmd_t *pmd, _pmd; 1945 pte_t *pte; 1946 pgtable_t pgtable; 1947 struct page *new_page; 1948 spinlock_t *ptl; 1949 int isolated; 1950 unsigned long hstart, hend; 1951 unsigned long mmun_start; /* For mmu_notifiers */ 1952 unsigned long mmun_end; /* For mmu_notifiers */ 1953 1954 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1955 1956 /* release the mmap_sem read lock. */ 1957 new_page = khugepaged_alloc_page(hpage, mm, vma, address, node); 1958 if (!new_page) 1959 return; 1960 1961 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) 1962 return; 1963 1964 /* 1965 * Prevent all access to pagetables with the exception of 1966 * gup_fast later hanlded by the ptep_clear_flush and the VM 1967 * handled by the anon_vma lock + PG_lock. 1968 */ 1969 down_write(&mm->mmap_sem); 1970 if (unlikely(khugepaged_test_exit(mm))) 1971 goto out; 1972 1973 vma = find_vma(mm, address); 1974 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1975 hend = vma->vm_end & HPAGE_PMD_MASK; 1976 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 1977 goto out; 1978 if (!hugepage_vma_check(vma)) 1979 goto out; 1980 pmd = mm_find_pmd(mm, address); 1981 if (!pmd) 1982 goto out; 1983 if (pmd_trans_huge(*pmd)) 1984 goto out; 1985 1986 anon_vma_lock(vma->anon_vma); 1987 1988 pte = pte_offset_map(pmd, address); 1989 ptl = pte_lockptr(mm, pmd); 1990 1991 mmun_start = address; 1992 mmun_end = address + HPAGE_PMD_SIZE; 1993 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); 1994 spin_lock(&mm->page_table_lock); /* probably unnecessary */ 1995 /* 1996 * After this gup_fast can't run anymore. This also removes 1997 * any huge TLB entry from the CPU so we won't allow 1998 * huge and small TLB entries for the same virtual address 1999 * to avoid the risk of CPU bugs in that area. 2000 */ 2001 _pmd = pmdp_clear_flush(vma, address, pmd); 2002 spin_unlock(&mm->page_table_lock); 2003 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); 2004 2005 spin_lock(ptl); 2006 isolated = __collapse_huge_page_isolate(vma, address, pte); 2007 spin_unlock(ptl); 2008 2009 if (unlikely(!isolated)) { 2010 pte_unmap(pte); 2011 spin_lock(&mm->page_table_lock); 2012 BUG_ON(!pmd_none(*pmd)); 2013 set_pmd_at(mm, address, pmd, _pmd); 2014 spin_unlock(&mm->page_table_lock); 2015 anon_vma_unlock(vma->anon_vma); 2016 goto out; 2017 } 2018 2019 /* 2020 * All pages are isolated and locked so anon_vma rmap 2021 * can't run anymore. 2022 */ 2023 anon_vma_unlock(vma->anon_vma); 2024 2025 __collapse_huge_page_copy(pte, new_page, vma, address, ptl); 2026 pte_unmap(pte); 2027 __SetPageUptodate(new_page); 2028 pgtable = pmd_pgtable(_pmd); 2029 2030 _pmd = mk_huge_pmd(new_page, vma); 2031 2032 /* 2033 * spin_lock() below is not the equivalent of smp_wmb(), so 2034 * this is needed to avoid the copy_huge_page writes to become 2035 * visible after the set_pmd_at() write. 2036 */ 2037 smp_wmb(); 2038 2039 spin_lock(&mm->page_table_lock); 2040 BUG_ON(!pmd_none(*pmd)); 2041 page_add_new_anon_rmap(new_page, vma, address); 2042 set_pmd_at(mm, address, pmd, _pmd); 2043 update_mmu_cache_pmd(vma, address, pmd); 2044 pgtable_trans_huge_deposit(mm, pgtable); 2045 spin_unlock(&mm->page_table_lock); 2046 2047 *hpage = NULL; 2048 2049 khugepaged_pages_collapsed++; 2050 out_up_write: 2051 up_write(&mm->mmap_sem); 2052 return; 2053 2054 out: 2055 mem_cgroup_uncharge_page(new_page); 2056 goto out_up_write; 2057 } 2058 2059 static int khugepaged_scan_pmd(struct mm_struct *mm, 2060 struct vm_area_struct *vma, 2061 unsigned long address, 2062 struct page **hpage) 2063 { 2064 pmd_t *pmd; 2065 pte_t *pte, *_pte; 2066 int ret = 0, referenced = 0, none = 0; 2067 struct page *page; 2068 unsigned long _address; 2069 spinlock_t *ptl; 2070 int node = -1; 2071 2072 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2073 2074 pmd = mm_find_pmd(mm, address); 2075 if (!pmd) 2076 goto out; 2077 if (pmd_trans_huge(*pmd)) 2078 goto out; 2079 2080 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2081 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2082 _pte++, _address += PAGE_SIZE) { 2083 pte_t pteval = *_pte; 2084 if (pte_none(pteval)) { 2085 if (++none <= khugepaged_max_ptes_none) 2086 continue; 2087 else 2088 goto out_unmap; 2089 } 2090 if (!pte_present(pteval) || !pte_write(pteval)) 2091 goto out_unmap; 2092 page = vm_normal_page(vma, _address, pteval); 2093 if (unlikely(!page)) 2094 goto out_unmap; 2095 /* 2096 * Chose the node of the first page. This could 2097 * be more sophisticated and look at more pages, 2098 * but isn't for now. 2099 */ 2100 if (node == -1) 2101 node = page_to_nid(page); 2102 VM_BUG_ON(PageCompound(page)); 2103 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) 2104 goto out_unmap; 2105 /* cannot use mapcount: can't collapse if there's a gup pin */ 2106 if (page_count(page) != 1) 2107 goto out_unmap; 2108 if (pte_young(pteval) || PageReferenced(page) || 2109 mmu_notifier_test_young(vma->vm_mm, address)) 2110 referenced = 1; 2111 } 2112 if (referenced) 2113 ret = 1; 2114 out_unmap: 2115 pte_unmap_unlock(pte, ptl); 2116 if (ret) 2117 /* collapse_huge_page will return with the mmap_sem released */ 2118 collapse_huge_page(mm, address, hpage, vma, node); 2119 out: 2120 return ret; 2121 } 2122 2123 static void collect_mm_slot(struct mm_slot *mm_slot) 2124 { 2125 struct mm_struct *mm = mm_slot->mm; 2126 2127 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2128 2129 if (khugepaged_test_exit(mm)) { 2130 /* free mm_slot */ 2131 hlist_del(&mm_slot->hash); 2132 list_del(&mm_slot->mm_node); 2133 2134 /* 2135 * Not strictly needed because the mm exited already. 2136 * 2137 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2138 */ 2139 2140 /* khugepaged_mm_lock actually not necessary for the below */ 2141 free_mm_slot(mm_slot); 2142 mmdrop(mm); 2143 } 2144 } 2145 2146 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2147 struct page **hpage) 2148 __releases(&khugepaged_mm_lock) 2149 __acquires(&khugepaged_mm_lock) 2150 { 2151 struct mm_slot *mm_slot; 2152 struct mm_struct *mm; 2153 struct vm_area_struct *vma; 2154 int progress = 0; 2155 2156 VM_BUG_ON(!pages); 2157 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); 2158 2159 if (khugepaged_scan.mm_slot) 2160 mm_slot = khugepaged_scan.mm_slot; 2161 else { 2162 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2163 struct mm_slot, mm_node); 2164 khugepaged_scan.address = 0; 2165 khugepaged_scan.mm_slot = mm_slot; 2166 } 2167 spin_unlock(&khugepaged_mm_lock); 2168 2169 mm = mm_slot->mm; 2170 down_read(&mm->mmap_sem); 2171 if (unlikely(khugepaged_test_exit(mm))) 2172 vma = NULL; 2173 else 2174 vma = find_vma(mm, khugepaged_scan.address); 2175 2176 progress++; 2177 for (; vma; vma = vma->vm_next) { 2178 unsigned long hstart, hend; 2179 2180 cond_resched(); 2181 if (unlikely(khugepaged_test_exit(mm))) { 2182 progress++; 2183 break; 2184 } 2185 if (!hugepage_vma_check(vma)) { 2186 skip: 2187 progress++; 2188 continue; 2189 } 2190 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2191 hend = vma->vm_end & HPAGE_PMD_MASK; 2192 if (hstart >= hend) 2193 goto skip; 2194 if (khugepaged_scan.address > hend) 2195 goto skip; 2196 if (khugepaged_scan.address < hstart) 2197 khugepaged_scan.address = hstart; 2198 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2199 2200 while (khugepaged_scan.address < hend) { 2201 int ret; 2202 cond_resched(); 2203 if (unlikely(khugepaged_test_exit(mm))) 2204 goto breakouterloop; 2205 2206 VM_BUG_ON(khugepaged_scan.address < hstart || 2207 khugepaged_scan.address + HPAGE_PMD_SIZE > 2208 hend); 2209 ret = khugepaged_scan_pmd(mm, vma, 2210 khugepaged_scan.address, 2211 hpage); 2212 /* move to next address */ 2213 khugepaged_scan.address += HPAGE_PMD_SIZE; 2214 progress += HPAGE_PMD_NR; 2215 if (ret) 2216 /* we released mmap_sem so break loop */ 2217 goto breakouterloop_mmap_sem; 2218 if (progress >= pages) 2219 goto breakouterloop; 2220 } 2221 } 2222 breakouterloop: 2223 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2224 breakouterloop_mmap_sem: 2225 2226 spin_lock(&khugepaged_mm_lock); 2227 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2228 /* 2229 * Release the current mm_slot if this mm is about to die, or 2230 * if we scanned all vmas of this mm. 2231 */ 2232 if (khugepaged_test_exit(mm) || !vma) { 2233 /* 2234 * Make sure that if mm_users is reaching zero while 2235 * khugepaged runs here, khugepaged_exit will find 2236 * mm_slot not pointing to the exiting mm. 2237 */ 2238 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2239 khugepaged_scan.mm_slot = list_entry( 2240 mm_slot->mm_node.next, 2241 struct mm_slot, mm_node); 2242 khugepaged_scan.address = 0; 2243 } else { 2244 khugepaged_scan.mm_slot = NULL; 2245 khugepaged_full_scans++; 2246 } 2247 2248 collect_mm_slot(mm_slot); 2249 } 2250 2251 return progress; 2252 } 2253 2254 static int khugepaged_has_work(void) 2255 { 2256 return !list_empty(&khugepaged_scan.mm_head) && 2257 khugepaged_enabled(); 2258 } 2259 2260 static int khugepaged_wait_event(void) 2261 { 2262 return !list_empty(&khugepaged_scan.mm_head) || 2263 kthread_should_stop(); 2264 } 2265 2266 static void khugepaged_do_scan(void) 2267 { 2268 struct page *hpage = NULL; 2269 unsigned int progress = 0, pass_through_head = 0; 2270 unsigned int pages = khugepaged_pages_to_scan; 2271 bool wait = true; 2272 2273 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2274 2275 while (progress < pages) { 2276 if (!khugepaged_prealloc_page(&hpage, &wait)) 2277 break; 2278 2279 cond_resched(); 2280 2281 if (unlikely(kthread_should_stop() || freezing(current))) 2282 break; 2283 2284 spin_lock(&khugepaged_mm_lock); 2285 if (!khugepaged_scan.mm_slot) 2286 pass_through_head++; 2287 if (khugepaged_has_work() && 2288 pass_through_head < 2) 2289 progress += khugepaged_scan_mm_slot(pages - progress, 2290 &hpage); 2291 else 2292 progress = pages; 2293 spin_unlock(&khugepaged_mm_lock); 2294 } 2295 2296 if (!IS_ERR_OR_NULL(hpage)) 2297 put_page(hpage); 2298 } 2299 2300 static void khugepaged_wait_work(void) 2301 { 2302 try_to_freeze(); 2303 2304 if (khugepaged_has_work()) { 2305 if (!khugepaged_scan_sleep_millisecs) 2306 return; 2307 2308 wait_event_freezable_timeout(khugepaged_wait, 2309 kthread_should_stop(), 2310 msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); 2311 return; 2312 } 2313 2314 if (khugepaged_enabled()) 2315 wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); 2316 } 2317 2318 static int khugepaged(void *none) 2319 { 2320 struct mm_slot *mm_slot; 2321 2322 set_freezable(); 2323 set_user_nice(current, 19); 2324 2325 while (!kthread_should_stop()) { 2326 khugepaged_do_scan(); 2327 khugepaged_wait_work(); 2328 } 2329 2330 spin_lock(&khugepaged_mm_lock); 2331 mm_slot = khugepaged_scan.mm_slot; 2332 khugepaged_scan.mm_slot = NULL; 2333 if (mm_slot) 2334 collect_mm_slot(mm_slot); 2335 spin_unlock(&khugepaged_mm_lock); 2336 return 0; 2337 } 2338 2339 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd) 2340 { 2341 struct page *page; 2342 2343 spin_lock(&mm->page_table_lock); 2344 if (unlikely(!pmd_trans_huge(*pmd))) { 2345 spin_unlock(&mm->page_table_lock); 2346 return; 2347 } 2348 page = pmd_page(*pmd); 2349 VM_BUG_ON(!page_count(page)); 2350 get_page(page); 2351 spin_unlock(&mm->page_table_lock); 2352 2353 split_huge_page(page); 2354 2355 put_page(page); 2356 BUG_ON(pmd_trans_huge(*pmd)); 2357 } 2358 2359 static void split_huge_page_address(struct mm_struct *mm, 2360 unsigned long address) 2361 { 2362 pmd_t *pmd; 2363 2364 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); 2365 2366 pmd = mm_find_pmd(mm, address); 2367 if (!pmd) 2368 return; 2369 /* 2370 * Caller holds the mmap_sem write mode, so a huge pmd cannot 2371 * materialize from under us. 2372 */ 2373 split_huge_page_pmd(mm, pmd); 2374 } 2375 2376 void __vma_adjust_trans_huge(struct vm_area_struct *vma, 2377 unsigned long start, 2378 unsigned long end, 2379 long adjust_next) 2380 { 2381 /* 2382 * If the new start address isn't hpage aligned and it could 2383 * previously contain an hugepage: check if we need to split 2384 * an huge pmd. 2385 */ 2386 if (start & ~HPAGE_PMD_MASK && 2387 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2388 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2389 split_huge_page_address(vma->vm_mm, start); 2390 2391 /* 2392 * If the new end address isn't hpage aligned and it could 2393 * previously contain an hugepage: check if we need to split 2394 * an huge pmd. 2395 */ 2396 if (end & ~HPAGE_PMD_MASK && 2397 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2398 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2399 split_huge_page_address(vma->vm_mm, end); 2400 2401 /* 2402 * If we're also updating the vma->vm_next->vm_start, if the new 2403 * vm_next->vm_start isn't page aligned and it could previously 2404 * contain an hugepage: check if we need to split an huge pmd. 2405 */ 2406 if (adjust_next > 0) { 2407 struct vm_area_struct *next = vma->vm_next; 2408 unsigned long nstart = next->vm_start; 2409 nstart += adjust_next << PAGE_SHIFT; 2410 if (nstart & ~HPAGE_PMD_MASK && 2411 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2412 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2413 split_huge_page_address(next->vm_mm, nstart); 2414 } 2415 } 2416