1 /* 2 * Copyright (C) 2009 Red Hat, Inc. 3 * 4 * This work is licensed under the terms of the GNU GPL, version 2. See 5 * the COPYING file in the top-level directory. 6 */ 7 8 #include <linux/mm.h> 9 #include <linux/sched.h> 10 #include <linux/highmem.h> 11 #include <linux/hugetlb.h> 12 #include <linux/mmu_notifier.h> 13 #include <linux/rmap.h> 14 #include <linux/swap.h> 15 #include <linux/mm_inline.h> 16 #include <linux/kthread.h> 17 #include <linux/khugepaged.h> 18 #include <linux/freezer.h> 19 #include <linux/mman.h> 20 #include <asm/tlb.h> 21 #include <asm/pgalloc.h> 22 #include "internal.h" 23 24 /* 25 * By default transparent hugepage support is enabled for all mappings 26 * and khugepaged scans all mappings. Defrag is only invoked by 27 * khugepaged hugepage allocations and by page faults inside 28 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived 29 * allocations. 30 */ 31 unsigned long transparent_hugepage_flags __read_mostly = 32 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS 33 (1<<TRANSPARENT_HUGEPAGE_FLAG)| 34 #endif 35 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE 36 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| 37 #endif 38 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)| 39 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 40 41 /* default scan 8*512 pte (or vmas) every 30 second */ 42 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8; 43 static unsigned int khugepaged_pages_collapsed; 44 static unsigned int khugepaged_full_scans; 45 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; 46 /* during fragmentation poll the hugepage allocator once every minute */ 47 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; 48 static struct task_struct *khugepaged_thread __read_mostly; 49 static DEFINE_MUTEX(khugepaged_mutex); 50 static DEFINE_SPINLOCK(khugepaged_mm_lock); 51 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); 52 /* 53 * default collapse hugepages if there is at least one pte mapped like 54 * it would have happened if the vma was large enough during page 55 * fault. 56 */ 57 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1; 58 59 static int khugepaged(void *none); 60 static int mm_slots_hash_init(void); 61 static int khugepaged_slab_init(void); 62 static void khugepaged_slab_free(void); 63 64 #define MM_SLOTS_HASH_HEADS 1024 65 static struct hlist_head *mm_slots_hash __read_mostly; 66 static struct kmem_cache *mm_slot_cache __read_mostly; 67 68 /** 69 * struct mm_slot - hash lookup from mm to mm_slot 70 * @hash: hash collision list 71 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head 72 * @mm: the mm that this information is valid for 73 */ 74 struct mm_slot { 75 struct hlist_node hash; 76 struct list_head mm_node; 77 struct mm_struct *mm; 78 }; 79 80 /** 81 * struct khugepaged_scan - cursor for scanning 82 * @mm_head: the head of the mm list to scan 83 * @mm_slot: the current mm_slot we are scanning 84 * @address: the next address inside that to be scanned 85 * 86 * There is only the one khugepaged_scan instance of this cursor structure. 87 */ 88 struct khugepaged_scan { 89 struct list_head mm_head; 90 struct mm_slot *mm_slot; 91 unsigned long address; 92 }; 93 static struct khugepaged_scan khugepaged_scan = { 94 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), 95 }; 96 97 98 static int set_recommended_min_free_kbytes(void) 99 { 100 struct zone *zone; 101 int nr_zones = 0; 102 unsigned long recommended_min; 103 extern int min_free_kbytes; 104 105 if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG, 106 &transparent_hugepage_flags) && 107 !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 108 &transparent_hugepage_flags)) 109 return 0; 110 111 for_each_populated_zone(zone) 112 nr_zones++; 113 114 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */ 115 recommended_min = pageblock_nr_pages * nr_zones * 2; 116 117 /* 118 * Make sure that on average at least two pageblocks are almost free 119 * of another type, one for a migratetype to fall back to and a 120 * second to avoid subsequent fallbacks of other types There are 3 121 * MIGRATE_TYPES we care about. 122 */ 123 recommended_min += pageblock_nr_pages * nr_zones * 124 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; 125 126 /* don't ever allow to reserve more than 5% of the lowmem */ 127 recommended_min = min(recommended_min, 128 (unsigned long) nr_free_buffer_pages() / 20); 129 recommended_min <<= (PAGE_SHIFT-10); 130 131 if (recommended_min > min_free_kbytes) 132 min_free_kbytes = recommended_min; 133 setup_per_zone_wmarks(); 134 return 0; 135 } 136 late_initcall(set_recommended_min_free_kbytes); 137 138 static int start_khugepaged(void) 139 { 140 int err = 0; 141 if (khugepaged_enabled()) { 142 int wakeup; 143 if (unlikely(!mm_slot_cache || !mm_slots_hash)) { 144 err = -ENOMEM; 145 goto out; 146 } 147 mutex_lock(&khugepaged_mutex); 148 if (!khugepaged_thread) 149 khugepaged_thread = kthread_run(khugepaged, NULL, 150 "khugepaged"); 151 if (unlikely(IS_ERR(khugepaged_thread))) { 152 printk(KERN_ERR 153 "khugepaged: kthread_run(khugepaged) failed\n"); 154 err = PTR_ERR(khugepaged_thread); 155 khugepaged_thread = NULL; 156 } 157 wakeup = !list_empty(&khugepaged_scan.mm_head); 158 mutex_unlock(&khugepaged_mutex); 159 if (wakeup) 160 wake_up_interruptible(&khugepaged_wait); 161 162 set_recommended_min_free_kbytes(); 163 } else 164 /* wakeup to exit */ 165 wake_up_interruptible(&khugepaged_wait); 166 out: 167 return err; 168 } 169 170 #ifdef CONFIG_SYSFS 171 172 static ssize_t double_flag_show(struct kobject *kobj, 173 struct kobj_attribute *attr, char *buf, 174 enum transparent_hugepage_flag enabled, 175 enum transparent_hugepage_flag req_madv) 176 { 177 if (test_bit(enabled, &transparent_hugepage_flags)) { 178 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); 179 return sprintf(buf, "[always] madvise never\n"); 180 } else if (test_bit(req_madv, &transparent_hugepage_flags)) 181 return sprintf(buf, "always [madvise] never\n"); 182 else 183 return sprintf(buf, "always madvise [never]\n"); 184 } 185 static ssize_t double_flag_store(struct kobject *kobj, 186 struct kobj_attribute *attr, 187 const char *buf, size_t count, 188 enum transparent_hugepage_flag enabled, 189 enum transparent_hugepage_flag req_madv) 190 { 191 if (!memcmp("always", buf, 192 min(sizeof("always")-1, count))) { 193 set_bit(enabled, &transparent_hugepage_flags); 194 clear_bit(req_madv, &transparent_hugepage_flags); 195 } else if (!memcmp("madvise", buf, 196 min(sizeof("madvise")-1, count))) { 197 clear_bit(enabled, &transparent_hugepage_flags); 198 set_bit(req_madv, &transparent_hugepage_flags); 199 } else if (!memcmp("never", buf, 200 min(sizeof("never")-1, count))) { 201 clear_bit(enabled, &transparent_hugepage_flags); 202 clear_bit(req_madv, &transparent_hugepage_flags); 203 } else 204 return -EINVAL; 205 206 return count; 207 } 208 209 static ssize_t enabled_show(struct kobject *kobj, 210 struct kobj_attribute *attr, char *buf) 211 { 212 return double_flag_show(kobj, attr, buf, 213 TRANSPARENT_HUGEPAGE_FLAG, 214 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 215 } 216 static ssize_t enabled_store(struct kobject *kobj, 217 struct kobj_attribute *attr, 218 const char *buf, size_t count) 219 { 220 ssize_t ret; 221 222 ret = double_flag_store(kobj, attr, buf, count, 223 TRANSPARENT_HUGEPAGE_FLAG, 224 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); 225 226 if (ret > 0) { 227 int err = start_khugepaged(); 228 if (err) 229 ret = err; 230 } 231 232 if (ret > 0 && 233 (test_bit(TRANSPARENT_HUGEPAGE_FLAG, 234 &transparent_hugepage_flags) || 235 test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 236 &transparent_hugepage_flags))) 237 set_recommended_min_free_kbytes(); 238 239 return ret; 240 } 241 static struct kobj_attribute enabled_attr = 242 __ATTR(enabled, 0644, enabled_show, enabled_store); 243 244 static ssize_t single_flag_show(struct kobject *kobj, 245 struct kobj_attribute *attr, char *buf, 246 enum transparent_hugepage_flag flag) 247 { 248 return sprintf(buf, "%d\n", 249 !!test_bit(flag, &transparent_hugepage_flags)); 250 } 251 252 static ssize_t single_flag_store(struct kobject *kobj, 253 struct kobj_attribute *attr, 254 const char *buf, size_t count, 255 enum transparent_hugepage_flag flag) 256 { 257 unsigned long value; 258 int ret; 259 260 ret = kstrtoul(buf, 10, &value); 261 if (ret < 0) 262 return ret; 263 if (value > 1) 264 return -EINVAL; 265 266 if (value) 267 set_bit(flag, &transparent_hugepage_flags); 268 else 269 clear_bit(flag, &transparent_hugepage_flags); 270 271 return count; 272 } 273 274 /* 275 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind 276 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of 277 * memory just to allocate one more hugepage. 278 */ 279 static ssize_t defrag_show(struct kobject *kobj, 280 struct kobj_attribute *attr, char *buf) 281 { 282 return double_flag_show(kobj, attr, buf, 283 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 284 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 285 } 286 static ssize_t defrag_store(struct kobject *kobj, 287 struct kobj_attribute *attr, 288 const char *buf, size_t count) 289 { 290 return double_flag_store(kobj, attr, buf, count, 291 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, 292 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); 293 } 294 static struct kobj_attribute defrag_attr = 295 __ATTR(defrag, 0644, defrag_show, defrag_store); 296 297 #ifdef CONFIG_DEBUG_VM 298 static ssize_t debug_cow_show(struct kobject *kobj, 299 struct kobj_attribute *attr, char *buf) 300 { 301 return single_flag_show(kobj, attr, buf, 302 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 303 } 304 static ssize_t debug_cow_store(struct kobject *kobj, 305 struct kobj_attribute *attr, 306 const char *buf, size_t count) 307 { 308 return single_flag_store(kobj, attr, buf, count, 309 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 310 } 311 static struct kobj_attribute debug_cow_attr = 312 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 313 #endif /* CONFIG_DEBUG_VM */ 314 315 static struct attribute *hugepage_attr[] = { 316 &enabled_attr.attr, 317 &defrag_attr.attr, 318 #ifdef CONFIG_DEBUG_VM 319 &debug_cow_attr.attr, 320 #endif 321 NULL, 322 }; 323 324 static struct attribute_group hugepage_attr_group = { 325 .attrs = hugepage_attr, 326 }; 327 328 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, 329 struct kobj_attribute *attr, 330 char *buf) 331 { 332 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); 333 } 334 335 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, 336 struct kobj_attribute *attr, 337 const char *buf, size_t count) 338 { 339 unsigned long msecs; 340 int err; 341 342 err = strict_strtoul(buf, 10, &msecs); 343 if (err || msecs > UINT_MAX) 344 return -EINVAL; 345 346 khugepaged_scan_sleep_millisecs = msecs; 347 wake_up_interruptible(&khugepaged_wait); 348 349 return count; 350 } 351 static struct kobj_attribute scan_sleep_millisecs_attr = 352 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, 353 scan_sleep_millisecs_store); 354 355 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, 356 struct kobj_attribute *attr, 357 char *buf) 358 { 359 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); 360 } 361 362 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, 363 struct kobj_attribute *attr, 364 const char *buf, size_t count) 365 { 366 unsigned long msecs; 367 int err; 368 369 err = strict_strtoul(buf, 10, &msecs); 370 if (err || msecs > UINT_MAX) 371 return -EINVAL; 372 373 khugepaged_alloc_sleep_millisecs = msecs; 374 wake_up_interruptible(&khugepaged_wait); 375 376 return count; 377 } 378 static struct kobj_attribute alloc_sleep_millisecs_attr = 379 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, 380 alloc_sleep_millisecs_store); 381 382 static ssize_t pages_to_scan_show(struct kobject *kobj, 383 struct kobj_attribute *attr, 384 char *buf) 385 { 386 return sprintf(buf, "%u\n", khugepaged_pages_to_scan); 387 } 388 static ssize_t pages_to_scan_store(struct kobject *kobj, 389 struct kobj_attribute *attr, 390 const char *buf, size_t count) 391 { 392 int err; 393 unsigned long pages; 394 395 err = strict_strtoul(buf, 10, &pages); 396 if (err || !pages || pages > UINT_MAX) 397 return -EINVAL; 398 399 khugepaged_pages_to_scan = pages; 400 401 return count; 402 } 403 static struct kobj_attribute pages_to_scan_attr = 404 __ATTR(pages_to_scan, 0644, pages_to_scan_show, 405 pages_to_scan_store); 406 407 static ssize_t pages_collapsed_show(struct kobject *kobj, 408 struct kobj_attribute *attr, 409 char *buf) 410 { 411 return sprintf(buf, "%u\n", khugepaged_pages_collapsed); 412 } 413 static struct kobj_attribute pages_collapsed_attr = 414 __ATTR_RO(pages_collapsed); 415 416 static ssize_t full_scans_show(struct kobject *kobj, 417 struct kobj_attribute *attr, 418 char *buf) 419 { 420 return sprintf(buf, "%u\n", khugepaged_full_scans); 421 } 422 static struct kobj_attribute full_scans_attr = 423 __ATTR_RO(full_scans); 424 425 static ssize_t khugepaged_defrag_show(struct kobject *kobj, 426 struct kobj_attribute *attr, char *buf) 427 { 428 return single_flag_show(kobj, attr, buf, 429 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 430 } 431 static ssize_t khugepaged_defrag_store(struct kobject *kobj, 432 struct kobj_attribute *attr, 433 const char *buf, size_t count) 434 { 435 return single_flag_store(kobj, attr, buf, count, 436 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); 437 } 438 static struct kobj_attribute khugepaged_defrag_attr = 439 __ATTR(defrag, 0644, khugepaged_defrag_show, 440 khugepaged_defrag_store); 441 442 /* 443 * max_ptes_none controls if khugepaged should collapse hugepages over 444 * any unmapped ptes in turn potentially increasing the memory 445 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not 446 * reduce the available free memory in the system as it 447 * runs. Increasing max_ptes_none will instead potentially reduce the 448 * free memory in the system during the khugepaged scan. 449 */ 450 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, 451 struct kobj_attribute *attr, 452 char *buf) 453 { 454 return sprintf(buf, "%u\n", khugepaged_max_ptes_none); 455 } 456 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, 457 struct kobj_attribute *attr, 458 const char *buf, size_t count) 459 { 460 int err; 461 unsigned long max_ptes_none; 462 463 err = strict_strtoul(buf, 10, &max_ptes_none); 464 if (err || max_ptes_none > HPAGE_PMD_NR-1) 465 return -EINVAL; 466 467 khugepaged_max_ptes_none = max_ptes_none; 468 469 return count; 470 } 471 static struct kobj_attribute khugepaged_max_ptes_none_attr = 472 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, 473 khugepaged_max_ptes_none_store); 474 475 static struct attribute *khugepaged_attr[] = { 476 &khugepaged_defrag_attr.attr, 477 &khugepaged_max_ptes_none_attr.attr, 478 &pages_to_scan_attr.attr, 479 &pages_collapsed_attr.attr, 480 &full_scans_attr.attr, 481 &scan_sleep_millisecs_attr.attr, 482 &alloc_sleep_millisecs_attr.attr, 483 NULL, 484 }; 485 486 static struct attribute_group khugepaged_attr_group = { 487 .attrs = khugepaged_attr, 488 .name = "khugepaged", 489 }; 490 #endif /* CONFIG_SYSFS */ 491 492 static int __init hugepage_init(void) 493 { 494 int err; 495 #ifdef CONFIG_SYSFS 496 static struct kobject *hugepage_kobj; 497 #endif 498 499 err = -EINVAL; 500 if (!has_transparent_hugepage()) { 501 transparent_hugepage_flags = 0; 502 goto out; 503 } 504 505 #ifdef CONFIG_SYSFS 506 err = -ENOMEM; 507 hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 508 if (unlikely(!hugepage_kobj)) { 509 printk(KERN_ERR "hugepage: failed kobject create\n"); 510 goto out; 511 } 512 513 err = sysfs_create_group(hugepage_kobj, &hugepage_attr_group); 514 if (err) { 515 printk(KERN_ERR "hugepage: failed register hugeage group\n"); 516 goto out; 517 } 518 519 err = sysfs_create_group(hugepage_kobj, &khugepaged_attr_group); 520 if (err) { 521 printk(KERN_ERR "hugepage: failed register hugeage group\n"); 522 goto out; 523 } 524 #endif 525 526 err = khugepaged_slab_init(); 527 if (err) 528 goto out; 529 530 err = mm_slots_hash_init(); 531 if (err) { 532 khugepaged_slab_free(); 533 goto out; 534 } 535 536 /* 537 * By default disable transparent hugepages on smaller systems, 538 * where the extra memory used could hurt more than TLB overhead 539 * is likely to save. The admin can still enable it through /sys. 540 */ 541 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) 542 transparent_hugepage_flags = 0; 543 544 start_khugepaged(); 545 546 set_recommended_min_free_kbytes(); 547 548 out: 549 return err; 550 } 551 module_init(hugepage_init) 552 553 static int __init setup_transparent_hugepage(char *str) 554 { 555 int ret = 0; 556 if (!str) 557 goto out; 558 if (!strcmp(str, "always")) { 559 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 560 &transparent_hugepage_flags); 561 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 562 &transparent_hugepage_flags); 563 ret = 1; 564 } else if (!strcmp(str, "madvise")) { 565 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 566 &transparent_hugepage_flags); 567 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 568 &transparent_hugepage_flags); 569 ret = 1; 570 } else if (!strcmp(str, "never")) { 571 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 572 &transparent_hugepage_flags); 573 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 574 &transparent_hugepage_flags); 575 ret = 1; 576 } 577 out: 578 if (!ret) 579 printk(KERN_WARNING 580 "transparent_hugepage= cannot parse, ignored\n"); 581 return ret; 582 } 583 __setup("transparent_hugepage=", setup_transparent_hugepage); 584 585 static void prepare_pmd_huge_pte(pgtable_t pgtable, 586 struct mm_struct *mm) 587 { 588 assert_spin_locked(&mm->page_table_lock); 589 590 /* FIFO */ 591 if (!mm->pmd_huge_pte) 592 INIT_LIST_HEAD(&pgtable->lru); 593 else 594 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru); 595 mm->pmd_huge_pte = pgtable; 596 } 597 598 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 599 { 600 if (likely(vma->vm_flags & VM_WRITE)) 601 pmd = pmd_mkwrite(pmd); 602 return pmd; 603 } 604 605 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, 606 struct vm_area_struct *vma, 607 unsigned long haddr, pmd_t *pmd, 608 struct page *page) 609 { 610 int ret = 0; 611 pgtable_t pgtable; 612 613 VM_BUG_ON(!PageCompound(page)); 614 pgtable = pte_alloc_one(mm, haddr); 615 if (unlikely(!pgtable)) { 616 mem_cgroup_uncharge_page(page); 617 put_page(page); 618 return VM_FAULT_OOM; 619 } 620 621 clear_huge_page(page, haddr, HPAGE_PMD_NR); 622 __SetPageUptodate(page); 623 624 spin_lock(&mm->page_table_lock); 625 if (unlikely(!pmd_none(*pmd))) { 626 spin_unlock(&mm->page_table_lock); 627 mem_cgroup_uncharge_page(page); 628 put_page(page); 629 pte_free(mm, pgtable); 630 } else { 631 pmd_t entry; 632 entry = mk_pmd(page, vma->vm_page_prot); 633 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 634 entry = pmd_mkhuge(entry); 635 /* 636 * The spinlocking to take the lru_lock inside 637 * page_add_new_anon_rmap() acts as a full memory 638 * barrier to be sure clear_huge_page writes become 639 * visible after the set_pmd_at() write. 640 */ 641 page_add_new_anon_rmap(page, vma, haddr); 642 set_pmd_at(mm, haddr, pmd, entry); 643 prepare_pmd_huge_pte(pgtable, mm); 644 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); 645 spin_unlock(&mm->page_table_lock); 646 } 647 648 return ret; 649 } 650 651 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) 652 { 653 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; 654 } 655 656 static inline struct page *alloc_hugepage_vma(int defrag, 657 struct vm_area_struct *vma, 658 unsigned long haddr, int nd, 659 gfp_t extra_gfp) 660 { 661 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp), 662 HPAGE_PMD_ORDER, vma, haddr, nd); 663 } 664 665 #ifndef CONFIG_NUMA 666 static inline struct page *alloc_hugepage(int defrag) 667 { 668 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), 669 HPAGE_PMD_ORDER); 670 } 671 #endif 672 673 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 674 unsigned long address, pmd_t *pmd, 675 unsigned int flags) 676 { 677 struct page *page; 678 unsigned long haddr = address & HPAGE_PMD_MASK; 679 pte_t *pte; 680 681 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) { 682 if (unlikely(anon_vma_prepare(vma))) 683 return VM_FAULT_OOM; 684 if (unlikely(khugepaged_enter(vma))) 685 return VM_FAULT_OOM; 686 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 687 vma, haddr, numa_node_id(), 0); 688 if (unlikely(!page)) { 689 count_vm_event(THP_FAULT_FALLBACK); 690 goto out; 691 } 692 count_vm_event(THP_FAULT_ALLOC); 693 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) { 694 put_page(page); 695 goto out; 696 } 697 698 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page); 699 } 700 out: 701 /* 702 * Use __pte_alloc instead of pte_alloc_map, because we can't 703 * run pte_offset_map on the pmd, if an huge pmd could 704 * materialize from under us from a different thread. 705 */ 706 if (unlikely(__pte_alloc(mm, vma, pmd, address))) 707 return VM_FAULT_OOM; 708 /* if an huge pmd materialized from under us just retry later */ 709 if (unlikely(pmd_trans_huge(*pmd))) 710 return 0; 711 /* 712 * A regular pmd is established and it can't morph into a huge pmd 713 * from under us anymore at this point because we hold the mmap_sem 714 * read mode and khugepaged takes it in write mode. So now it's 715 * safe to run pte_offset_map(). 716 */ 717 pte = pte_offset_map(pmd, address); 718 return handle_pte_fault(mm, vma, address, pte, pmd, flags); 719 } 720 721 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 722 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 723 struct vm_area_struct *vma) 724 { 725 struct page *src_page; 726 pmd_t pmd; 727 pgtable_t pgtable; 728 int ret; 729 730 ret = -ENOMEM; 731 pgtable = pte_alloc_one(dst_mm, addr); 732 if (unlikely(!pgtable)) 733 goto out; 734 735 spin_lock(&dst_mm->page_table_lock); 736 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING); 737 738 ret = -EAGAIN; 739 pmd = *src_pmd; 740 if (unlikely(!pmd_trans_huge(pmd))) { 741 pte_free(dst_mm, pgtable); 742 goto out_unlock; 743 } 744 if (unlikely(pmd_trans_splitting(pmd))) { 745 /* split huge page running from under us */ 746 spin_unlock(&src_mm->page_table_lock); 747 spin_unlock(&dst_mm->page_table_lock); 748 pte_free(dst_mm, pgtable); 749 750 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ 751 goto out; 752 } 753 src_page = pmd_page(pmd); 754 VM_BUG_ON(!PageHead(src_page)); 755 get_page(src_page); 756 page_dup_rmap(src_page); 757 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 758 759 pmdp_set_wrprotect(src_mm, addr, src_pmd); 760 pmd = pmd_mkold(pmd_wrprotect(pmd)); 761 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 762 prepare_pmd_huge_pte(pgtable, dst_mm); 763 764 ret = 0; 765 out_unlock: 766 spin_unlock(&src_mm->page_table_lock); 767 spin_unlock(&dst_mm->page_table_lock); 768 out: 769 return ret; 770 } 771 772 /* no "address" argument so destroys page coloring of some arch */ 773 pgtable_t get_pmd_huge_pte(struct mm_struct *mm) 774 { 775 pgtable_t pgtable; 776 777 assert_spin_locked(&mm->page_table_lock); 778 779 /* FIFO */ 780 pgtable = mm->pmd_huge_pte; 781 if (list_empty(&pgtable->lru)) 782 mm->pmd_huge_pte = NULL; 783 else { 784 mm->pmd_huge_pte = list_entry(pgtable->lru.next, 785 struct page, lru); 786 list_del(&pgtable->lru); 787 } 788 return pgtable; 789 } 790 791 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, 792 struct vm_area_struct *vma, 793 unsigned long address, 794 pmd_t *pmd, pmd_t orig_pmd, 795 struct page *page, 796 unsigned long haddr) 797 { 798 pgtable_t pgtable; 799 pmd_t _pmd; 800 int ret = 0, i; 801 struct page **pages; 802 803 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 804 GFP_KERNEL); 805 if (unlikely(!pages)) { 806 ret |= VM_FAULT_OOM; 807 goto out; 808 } 809 810 for (i = 0; i < HPAGE_PMD_NR; i++) { 811 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | 812 __GFP_OTHER_NODE, 813 vma, address, page_to_nid(page)); 814 if (unlikely(!pages[i] || 815 mem_cgroup_newpage_charge(pages[i], mm, 816 GFP_KERNEL))) { 817 if (pages[i]) 818 put_page(pages[i]); 819 mem_cgroup_uncharge_start(); 820 while (--i >= 0) { 821 mem_cgroup_uncharge_page(pages[i]); 822 put_page(pages[i]); 823 } 824 mem_cgroup_uncharge_end(); 825 kfree(pages); 826 ret |= VM_FAULT_OOM; 827 goto out; 828 } 829 } 830 831 for (i = 0; i < HPAGE_PMD_NR; i++) { 832 copy_user_highpage(pages[i], page + i, 833 haddr + PAGE_SIZE * i, vma); 834 __SetPageUptodate(pages[i]); 835 cond_resched(); 836 } 837 838 spin_lock(&mm->page_table_lock); 839 if (unlikely(!pmd_same(*pmd, orig_pmd))) 840 goto out_free_pages; 841 VM_BUG_ON(!PageHead(page)); 842 843 pmdp_clear_flush_notify(vma, haddr, pmd); 844 /* leave pmd empty until pte is filled */ 845 846 pgtable = get_pmd_huge_pte(mm); 847 pmd_populate(mm, &_pmd, pgtable); 848 849 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 850 pte_t *pte, entry; 851 entry = mk_pte(pages[i], vma->vm_page_prot); 852 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 853 page_add_new_anon_rmap(pages[i], vma, haddr); 854 pte = pte_offset_map(&_pmd, haddr); 855 VM_BUG_ON(!pte_none(*pte)); 856 set_pte_at(mm, haddr, pte, entry); 857 pte_unmap(pte); 858 } 859 kfree(pages); 860 861 mm->nr_ptes++; 862 smp_wmb(); /* make pte visible before pmd */ 863 pmd_populate(mm, pmd, pgtable); 864 page_remove_rmap(page); 865 spin_unlock(&mm->page_table_lock); 866 867 ret |= VM_FAULT_WRITE; 868 put_page(page); 869 870 out: 871 return ret; 872 873 out_free_pages: 874 spin_unlock(&mm->page_table_lock); 875 mem_cgroup_uncharge_start(); 876 for (i = 0; i < HPAGE_PMD_NR; i++) { 877 mem_cgroup_uncharge_page(pages[i]); 878 put_page(pages[i]); 879 } 880 mem_cgroup_uncharge_end(); 881 kfree(pages); 882 goto out; 883 } 884 885 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, 886 unsigned long address, pmd_t *pmd, pmd_t orig_pmd) 887 { 888 int ret = 0; 889 struct page *page, *new_page; 890 unsigned long haddr; 891 892 VM_BUG_ON(!vma->anon_vma); 893 spin_lock(&mm->page_table_lock); 894 if (unlikely(!pmd_same(*pmd, orig_pmd))) 895 goto out_unlock; 896 897 page = pmd_page(orig_pmd); 898 VM_BUG_ON(!PageCompound(page) || !PageHead(page)); 899 haddr = address & HPAGE_PMD_MASK; 900 if (page_mapcount(page) == 1) { 901 pmd_t entry; 902 entry = pmd_mkyoung(orig_pmd); 903 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 904 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) 905 update_mmu_cache(vma, address, entry); 906 ret |= VM_FAULT_WRITE; 907 goto out_unlock; 908 } 909 get_page(page); 910 spin_unlock(&mm->page_table_lock); 911 912 if (transparent_hugepage_enabled(vma) && 913 !transparent_hugepage_debug_cow()) 914 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), 915 vma, haddr, numa_node_id(), 0); 916 else 917 new_page = NULL; 918 919 if (unlikely(!new_page)) { 920 count_vm_event(THP_FAULT_FALLBACK); 921 ret = do_huge_pmd_wp_page_fallback(mm, vma, address, 922 pmd, orig_pmd, page, haddr); 923 put_page(page); 924 goto out; 925 } 926 count_vm_event(THP_FAULT_ALLOC); 927 928 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 929 put_page(new_page); 930 put_page(page); 931 ret |= VM_FAULT_OOM; 932 goto out; 933 } 934 935 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 936 __SetPageUptodate(new_page); 937 938 spin_lock(&mm->page_table_lock); 939 put_page(page); 940 if (unlikely(!pmd_same(*pmd, orig_pmd))) { 941 mem_cgroup_uncharge_page(new_page); 942 put_page(new_page); 943 } else { 944 pmd_t entry; 945 VM_BUG_ON(!PageHead(page)); 946 entry = mk_pmd(new_page, vma->vm_page_prot); 947 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 948 entry = pmd_mkhuge(entry); 949 pmdp_clear_flush_notify(vma, haddr, pmd); 950 page_add_new_anon_rmap(new_page, vma, haddr); 951 set_pmd_at(mm, haddr, pmd, entry); 952 update_mmu_cache(vma, address, entry); 953 page_remove_rmap(page); 954 put_page(page); 955 ret |= VM_FAULT_WRITE; 956 } 957 out_unlock: 958 spin_unlock(&mm->page_table_lock); 959 out: 960 return ret; 961 } 962 963 struct page *follow_trans_huge_pmd(struct mm_struct *mm, 964 unsigned long addr, 965 pmd_t *pmd, 966 unsigned int flags) 967 { 968 struct page *page = NULL; 969 970 assert_spin_locked(&mm->page_table_lock); 971 972 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 973 goto out; 974 975 page = pmd_page(*pmd); 976 VM_BUG_ON(!PageHead(page)); 977 if (flags & FOLL_TOUCH) { 978 pmd_t _pmd; 979 /* 980 * We should set the dirty bit only for FOLL_WRITE but 981 * for now the dirty bit in the pmd is meaningless. 982 * And if the dirty bit will become meaningful and 983 * we'll only set it with FOLL_WRITE, an atomic 984 * set_bit will be required on the pmd to set the 985 * young bit, instead of the current set_pmd_at. 986 */ 987 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 988 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd); 989 } 990 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 991 VM_BUG_ON(!PageCompound(page)); 992 if (flags & FOLL_GET) 993 get_page_foll(page); 994 995 out: 996 return page; 997 } 998 999 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1000 pmd_t *pmd) 1001 { 1002 int ret = 0; 1003 1004 spin_lock(&tlb->mm->page_table_lock); 1005 if (likely(pmd_trans_huge(*pmd))) { 1006 if (unlikely(pmd_trans_splitting(*pmd))) { 1007 spin_unlock(&tlb->mm->page_table_lock); 1008 wait_split_huge_page(vma->anon_vma, 1009 pmd); 1010 } else { 1011 struct page *page; 1012 pgtable_t pgtable; 1013 pgtable = get_pmd_huge_pte(tlb->mm); 1014 page = pmd_page(*pmd); 1015 pmd_clear(pmd); 1016 page_remove_rmap(page); 1017 VM_BUG_ON(page_mapcount(page) < 0); 1018 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1019 VM_BUG_ON(!PageHead(page)); 1020 spin_unlock(&tlb->mm->page_table_lock); 1021 tlb_remove_page(tlb, page); 1022 pte_free(tlb->mm, pgtable); 1023 ret = 1; 1024 } 1025 } else 1026 spin_unlock(&tlb->mm->page_table_lock); 1027 1028 return ret; 1029 } 1030 1031 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1032 unsigned long addr, unsigned long end, 1033 unsigned char *vec) 1034 { 1035 int ret = 0; 1036 1037 spin_lock(&vma->vm_mm->page_table_lock); 1038 if (likely(pmd_trans_huge(*pmd))) { 1039 ret = !pmd_trans_splitting(*pmd); 1040 spin_unlock(&vma->vm_mm->page_table_lock); 1041 if (unlikely(!ret)) 1042 wait_split_huge_page(vma->anon_vma, pmd); 1043 else { 1044 /* 1045 * All logical pages in the range are present 1046 * if backed by a huge page. 1047 */ 1048 memset(vec, 1, (end - addr) >> PAGE_SHIFT); 1049 } 1050 } else 1051 spin_unlock(&vma->vm_mm->page_table_lock); 1052 1053 return ret; 1054 } 1055 1056 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, 1057 unsigned long old_addr, 1058 unsigned long new_addr, unsigned long old_end, 1059 pmd_t *old_pmd, pmd_t *new_pmd) 1060 { 1061 int ret = 0; 1062 pmd_t pmd; 1063 1064 struct mm_struct *mm = vma->vm_mm; 1065 1066 if ((old_addr & ~HPAGE_PMD_MASK) || 1067 (new_addr & ~HPAGE_PMD_MASK) || 1068 old_end - old_addr < HPAGE_PMD_SIZE || 1069 (new_vma->vm_flags & VM_NOHUGEPAGE)) 1070 goto out; 1071 1072 /* 1073 * The destination pmd shouldn't be established, free_pgtables() 1074 * should have release it. 1075 */ 1076 if (WARN_ON(!pmd_none(*new_pmd))) { 1077 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1078 goto out; 1079 } 1080 1081 spin_lock(&mm->page_table_lock); 1082 if (likely(pmd_trans_huge(*old_pmd))) { 1083 if (pmd_trans_splitting(*old_pmd)) { 1084 spin_unlock(&mm->page_table_lock); 1085 wait_split_huge_page(vma->anon_vma, old_pmd); 1086 ret = -1; 1087 } else { 1088 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); 1089 VM_BUG_ON(!pmd_none(*new_pmd)); 1090 set_pmd_at(mm, new_addr, new_pmd, pmd); 1091 spin_unlock(&mm->page_table_lock); 1092 ret = 1; 1093 } 1094 } else { 1095 spin_unlock(&mm->page_table_lock); 1096 } 1097 out: 1098 return ret; 1099 } 1100 1101 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1102 unsigned long addr, pgprot_t newprot) 1103 { 1104 struct mm_struct *mm = vma->vm_mm; 1105 int ret = 0; 1106 1107 spin_lock(&mm->page_table_lock); 1108 if (likely(pmd_trans_huge(*pmd))) { 1109 if (unlikely(pmd_trans_splitting(*pmd))) { 1110 spin_unlock(&mm->page_table_lock); 1111 wait_split_huge_page(vma->anon_vma, pmd); 1112 } else { 1113 pmd_t entry; 1114 1115 entry = pmdp_get_and_clear(mm, addr, pmd); 1116 entry = pmd_modify(entry, newprot); 1117 set_pmd_at(mm, addr, pmd, entry); 1118 spin_unlock(&vma->vm_mm->page_table_lock); 1119 flush_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE); 1120 ret = 1; 1121 } 1122 } else 1123 spin_unlock(&vma->vm_mm->page_table_lock); 1124 1125 return ret; 1126 } 1127 1128 pmd_t *page_check_address_pmd(struct page *page, 1129 struct mm_struct *mm, 1130 unsigned long address, 1131 enum page_check_address_pmd_flag flag) 1132 { 1133 pgd_t *pgd; 1134 pud_t *pud; 1135 pmd_t *pmd, *ret = NULL; 1136 1137 if (address & ~HPAGE_PMD_MASK) 1138 goto out; 1139 1140 pgd = pgd_offset(mm, address); 1141 if (!pgd_present(*pgd)) 1142 goto out; 1143 1144 pud = pud_offset(pgd, address); 1145 if (!pud_present(*pud)) 1146 goto out; 1147 1148 pmd = pmd_offset(pud, address); 1149 if (pmd_none(*pmd)) 1150 goto out; 1151 if (pmd_page(*pmd) != page) 1152 goto out; 1153 /* 1154 * split_vma() may create temporary aliased mappings. There is 1155 * no risk as long as all huge pmd are found and have their 1156 * splitting bit set before __split_huge_page_refcount 1157 * runs. Finding the same huge pmd more than once during the 1158 * same rmap walk is not a problem. 1159 */ 1160 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && 1161 pmd_trans_splitting(*pmd)) 1162 goto out; 1163 if (pmd_trans_huge(*pmd)) { 1164 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && 1165 !pmd_trans_splitting(*pmd)); 1166 ret = pmd; 1167 } 1168 out: 1169 return ret; 1170 } 1171 1172 static int __split_huge_page_splitting(struct page *page, 1173 struct vm_area_struct *vma, 1174 unsigned long address) 1175 { 1176 struct mm_struct *mm = vma->vm_mm; 1177 pmd_t *pmd; 1178 int ret = 0; 1179 1180 spin_lock(&mm->page_table_lock); 1181 pmd = page_check_address_pmd(page, mm, address, 1182 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG); 1183 if (pmd) { 1184 /* 1185 * We can't temporarily set the pmd to null in order 1186 * to split it, the pmd must remain marked huge at all 1187 * times or the VM won't take the pmd_trans_huge paths 1188 * and it won't wait on the anon_vma->root->mutex to 1189 * serialize against split_huge_page*. 1190 */ 1191 pmdp_splitting_flush_notify(vma, address, pmd); 1192 ret = 1; 1193 } 1194 spin_unlock(&mm->page_table_lock); 1195 1196 return ret; 1197 } 1198 1199 static void __split_huge_page_refcount(struct page *page) 1200 { 1201 int i; 1202 unsigned long head_index = page->index; 1203 struct zone *zone = page_zone(page); 1204 int zonestat; 1205 int tail_count = 0; 1206 1207 /* prevent PageLRU to go away from under us, and freeze lru stats */ 1208 spin_lock_irq(&zone->lru_lock); 1209 compound_lock(page); 1210 1211 for (i = 1; i < HPAGE_PMD_NR; i++) { 1212 struct page *page_tail = page + i; 1213 1214 /* tail_page->_mapcount cannot change */ 1215 BUG_ON(page_mapcount(page_tail) < 0); 1216 tail_count += page_mapcount(page_tail); 1217 /* check for overflow */ 1218 BUG_ON(tail_count < 0); 1219 BUG_ON(atomic_read(&page_tail->_count) != 0); 1220 /* 1221 * tail_page->_count is zero and not changing from 1222 * under us. But get_page_unless_zero() may be running 1223 * from under us on the tail_page. If we used 1224 * atomic_set() below instead of atomic_add(), we 1225 * would then run atomic_set() concurrently with 1226 * get_page_unless_zero(), and atomic_set() is 1227 * implemented in C not using locked ops. spin_unlock 1228 * on x86 sometime uses locked ops because of PPro 1229 * errata 66, 92, so unless somebody can guarantee 1230 * atomic_set() here would be safe on all archs (and 1231 * not only on x86), it's safer to use atomic_add(). 1232 */ 1233 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, 1234 &page_tail->_count); 1235 1236 /* after clearing PageTail the gup refcount can be released */ 1237 smp_mb(); 1238 1239 /* 1240 * retain hwpoison flag of the poisoned tail page: 1241 * fix for the unsuitable process killed on Guest Machine(KVM) 1242 * by the memory-failure. 1243 */ 1244 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON; 1245 page_tail->flags |= (page->flags & 1246 ((1L << PG_referenced) | 1247 (1L << PG_swapbacked) | 1248 (1L << PG_mlocked) | 1249 (1L << PG_uptodate))); 1250 page_tail->flags |= (1L << PG_dirty); 1251 1252 /* clear PageTail before overwriting first_page */ 1253 smp_wmb(); 1254 1255 /* 1256 * __split_huge_page_splitting() already set the 1257 * splitting bit in all pmd that could map this 1258 * hugepage, that will ensure no CPU can alter the 1259 * mapcount on the head page. The mapcount is only 1260 * accounted in the head page and it has to be 1261 * transferred to all tail pages in the below code. So 1262 * for this code to be safe, the split the mapcount 1263 * can't change. But that doesn't mean userland can't 1264 * keep changing and reading the page contents while 1265 * we transfer the mapcount, so the pmd splitting 1266 * status is achieved setting a reserved bit in the 1267 * pmd, not by clearing the present bit. 1268 */ 1269 page_tail->_mapcount = page->_mapcount; 1270 1271 BUG_ON(page_tail->mapping); 1272 page_tail->mapping = page->mapping; 1273 1274 page_tail->index = ++head_index; 1275 1276 BUG_ON(!PageAnon(page_tail)); 1277 BUG_ON(!PageUptodate(page_tail)); 1278 BUG_ON(!PageDirty(page_tail)); 1279 BUG_ON(!PageSwapBacked(page_tail)); 1280 1281 mem_cgroup_split_huge_fixup(page, page_tail); 1282 1283 lru_add_page_tail(zone, page, page_tail); 1284 } 1285 atomic_sub(tail_count, &page->_count); 1286 BUG_ON(atomic_read(&page->_count) <= 0); 1287 1288 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); 1289 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR); 1290 1291 /* 1292 * A hugepage counts for HPAGE_PMD_NR pages on the LRU statistics, 1293 * so adjust those appropriately if this page is on the LRU. 1294 */ 1295 if (PageLRU(page)) { 1296 zonestat = NR_LRU_BASE + page_lru(page); 1297 __mod_zone_page_state(zone, zonestat, -(HPAGE_PMD_NR-1)); 1298 } 1299 1300 ClearPageCompound(page); 1301 compound_unlock(page); 1302 spin_unlock_irq(&zone->lru_lock); 1303 1304 for (i = 1; i < HPAGE_PMD_NR; i++) { 1305 struct page *page_tail = page + i; 1306 BUG_ON(page_count(page_tail) <= 0); 1307 /* 1308 * Tail pages may be freed if there wasn't any mapping 1309 * like if add_to_swap() is running on a lru page that 1310 * had its mapping zapped. And freeing these pages 1311 * requires taking the lru_lock so we do the put_page 1312 * of the tail pages after the split is complete. 1313 */ 1314 put_page(page_tail); 1315 } 1316 1317 /* 1318 * Only the head page (now become a regular page) is required 1319 * to be pinned by the caller. 1320 */ 1321 BUG_ON(page_count(page) <= 0); 1322 } 1323 1324 static int __split_huge_page_map(struct page *page, 1325 struct vm_area_struct *vma, 1326 unsigned long address) 1327 { 1328 struct mm_struct *mm = vma->vm_mm; 1329 pmd_t *pmd, _pmd; 1330 int ret = 0, i; 1331 pgtable_t pgtable; 1332 unsigned long haddr; 1333 1334 spin_lock(&mm->page_table_lock); 1335 pmd = page_check_address_pmd(page, mm, address, 1336 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG); 1337 if (pmd) { 1338 pgtable = get_pmd_huge_pte(mm); 1339 pmd_populate(mm, &_pmd, pgtable); 1340 1341 for (i = 0, haddr = address; i < HPAGE_PMD_NR; 1342 i++, haddr += PAGE_SIZE) { 1343 pte_t *pte, entry; 1344 BUG_ON(PageCompound(page+i)); 1345 entry = mk_pte(page + i, vma->vm_page_prot); 1346 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1347 if (!pmd_write(*pmd)) 1348 entry = pte_wrprotect(entry); 1349 else 1350 BUG_ON(page_mapcount(page) != 1); 1351 if (!pmd_young(*pmd)) 1352 entry = pte_mkold(entry); 1353 pte = pte_offset_map(&_pmd, haddr); 1354 BUG_ON(!pte_none(*pte)); 1355 set_pte_at(mm, haddr, pte, entry); 1356 pte_unmap(pte); 1357 } 1358 1359 mm->nr_ptes++; 1360 smp_wmb(); /* make pte visible before pmd */ 1361 /* 1362 * Up to this point the pmd is present and huge and 1363 * userland has the whole access to the hugepage 1364 * during the split (which happens in place). If we 1365 * overwrite the pmd with the not-huge version 1366 * pointing to the pte here (which of course we could 1367 * if all CPUs were bug free), userland could trigger 1368 * a small page size TLB miss on the small sized TLB 1369 * while the hugepage TLB entry is still established 1370 * in the huge TLB. Some CPU doesn't like that. See 1371 * http://support.amd.com/us/Processor_TechDocs/41322.pdf, 1372 * Erratum 383 on page 93. Intel should be safe but is 1373 * also warns that it's only safe if the permission 1374 * and cache attributes of the two entries loaded in 1375 * the two TLB is identical (which should be the case 1376 * here). But it is generally safer to never allow 1377 * small and huge TLB entries for the same virtual 1378 * address to be loaded simultaneously. So instead of 1379 * doing "pmd_populate(); flush_tlb_range();" we first 1380 * mark the current pmd notpresent (atomically because 1381 * here the pmd_trans_huge and pmd_trans_splitting 1382 * must remain set at all times on the pmd until the 1383 * split is complete for this pmd), then we flush the 1384 * SMP TLB and finally we write the non-huge version 1385 * of the pmd entry with pmd_populate. 1386 */ 1387 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd)); 1388 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE); 1389 pmd_populate(mm, pmd, pgtable); 1390 ret = 1; 1391 } 1392 spin_unlock(&mm->page_table_lock); 1393 1394 return ret; 1395 } 1396 1397 /* must be called with anon_vma->root->mutex hold */ 1398 static void __split_huge_page(struct page *page, 1399 struct anon_vma *anon_vma) 1400 { 1401 int mapcount, mapcount2; 1402 struct anon_vma_chain *avc; 1403 1404 BUG_ON(!PageHead(page)); 1405 BUG_ON(PageTail(page)); 1406 1407 mapcount = 0; 1408 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { 1409 struct vm_area_struct *vma = avc->vma; 1410 unsigned long addr = vma_address(page, vma); 1411 BUG_ON(is_vma_temporary_stack(vma)); 1412 if (addr == -EFAULT) 1413 continue; 1414 mapcount += __split_huge_page_splitting(page, vma, addr); 1415 } 1416 /* 1417 * It is critical that new vmas are added to the tail of the 1418 * anon_vma list. This guarantes that if copy_huge_pmd() runs 1419 * and establishes a child pmd before 1420 * __split_huge_page_splitting() freezes the parent pmd (so if 1421 * we fail to prevent copy_huge_pmd() from running until the 1422 * whole __split_huge_page() is complete), we will still see 1423 * the newly established pmd of the child later during the 1424 * walk, to be able to set it as pmd_trans_splitting too. 1425 */ 1426 if (mapcount != page_mapcount(page)) 1427 printk(KERN_ERR "mapcount %d page_mapcount %d\n", 1428 mapcount, page_mapcount(page)); 1429 BUG_ON(mapcount != page_mapcount(page)); 1430 1431 __split_huge_page_refcount(page); 1432 1433 mapcount2 = 0; 1434 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { 1435 struct vm_area_struct *vma = avc->vma; 1436 unsigned long addr = vma_address(page, vma); 1437 BUG_ON(is_vma_temporary_stack(vma)); 1438 if (addr == -EFAULT) 1439 continue; 1440 mapcount2 += __split_huge_page_map(page, vma, addr); 1441 } 1442 if (mapcount != mapcount2) 1443 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n", 1444 mapcount, mapcount2, page_mapcount(page)); 1445 BUG_ON(mapcount != mapcount2); 1446 } 1447 1448 int split_huge_page(struct page *page) 1449 { 1450 struct anon_vma *anon_vma; 1451 int ret = 1; 1452 1453 BUG_ON(!PageAnon(page)); 1454 anon_vma = page_lock_anon_vma(page); 1455 if (!anon_vma) 1456 goto out; 1457 ret = 0; 1458 if (!PageCompound(page)) 1459 goto out_unlock; 1460 1461 BUG_ON(!PageSwapBacked(page)); 1462 __split_huge_page(page, anon_vma); 1463 count_vm_event(THP_SPLIT); 1464 1465 BUG_ON(PageCompound(page)); 1466 out_unlock: 1467 page_unlock_anon_vma(anon_vma); 1468 out: 1469 return ret; 1470 } 1471 1472 #define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \ 1473 VM_HUGETLB|VM_SHARED|VM_MAYSHARE) 1474 1475 int hugepage_madvise(struct vm_area_struct *vma, 1476 unsigned long *vm_flags, int advice) 1477 { 1478 switch (advice) { 1479 case MADV_HUGEPAGE: 1480 /* 1481 * Be somewhat over-protective like KSM for now! 1482 */ 1483 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) 1484 return -EINVAL; 1485 *vm_flags &= ~VM_NOHUGEPAGE; 1486 *vm_flags |= VM_HUGEPAGE; 1487 /* 1488 * If the vma become good for khugepaged to scan, 1489 * register it here without waiting a page fault that 1490 * may not happen any time soon. 1491 */ 1492 if (unlikely(khugepaged_enter_vma_merge(vma))) 1493 return -ENOMEM; 1494 break; 1495 case MADV_NOHUGEPAGE: 1496 /* 1497 * Be somewhat over-protective like KSM for now! 1498 */ 1499 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) 1500 return -EINVAL; 1501 *vm_flags &= ~VM_HUGEPAGE; 1502 *vm_flags |= VM_NOHUGEPAGE; 1503 /* 1504 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning 1505 * this vma even if we leave the mm registered in khugepaged if 1506 * it got registered before VM_NOHUGEPAGE was set. 1507 */ 1508 break; 1509 } 1510 1511 return 0; 1512 } 1513 1514 static int __init khugepaged_slab_init(void) 1515 { 1516 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", 1517 sizeof(struct mm_slot), 1518 __alignof__(struct mm_slot), 0, NULL); 1519 if (!mm_slot_cache) 1520 return -ENOMEM; 1521 1522 return 0; 1523 } 1524 1525 static void __init khugepaged_slab_free(void) 1526 { 1527 kmem_cache_destroy(mm_slot_cache); 1528 mm_slot_cache = NULL; 1529 } 1530 1531 static inline struct mm_slot *alloc_mm_slot(void) 1532 { 1533 if (!mm_slot_cache) /* initialization failed */ 1534 return NULL; 1535 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); 1536 } 1537 1538 static inline void free_mm_slot(struct mm_slot *mm_slot) 1539 { 1540 kmem_cache_free(mm_slot_cache, mm_slot); 1541 } 1542 1543 static int __init mm_slots_hash_init(void) 1544 { 1545 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), 1546 GFP_KERNEL); 1547 if (!mm_slots_hash) 1548 return -ENOMEM; 1549 return 0; 1550 } 1551 1552 #if 0 1553 static void __init mm_slots_hash_free(void) 1554 { 1555 kfree(mm_slots_hash); 1556 mm_slots_hash = NULL; 1557 } 1558 #endif 1559 1560 static struct mm_slot *get_mm_slot(struct mm_struct *mm) 1561 { 1562 struct mm_slot *mm_slot; 1563 struct hlist_head *bucket; 1564 struct hlist_node *node; 1565 1566 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1567 % MM_SLOTS_HASH_HEADS]; 1568 hlist_for_each_entry(mm_slot, node, bucket, hash) { 1569 if (mm == mm_slot->mm) 1570 return mm_slot; 1571 } 1572 return NULL; 1573 } 1574 1575 static void insert_to_mm_slots_hash(struct mm_struct *mm, 1576 struct mm_slot *mm_slot) 1577 { 1578 struct hlist_head *bucket; 1579 1580 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) 1581 % MM_SLOTS_HASH_HEADS]; 1582 mm_slot->mm = mm; 1583 hlist_add_head(&mm_slot->hash, bucket); 1584 } 1585 1586 static inline int khugepaged_test_exit(struct mm_struct *mm) 1587 { 1588 return atomic_read(&mm->mm_users) == 0; 1589 } 1590 1591 int __khugepaged_enter(struct mm_struct *mm) 1592 { 1593 struct mm_slot *mm_slot; 1594 int wakeup; 1595 1596 mm_slot = alloc_mm_slot(); 1597 if (!mm_slot) 1598 return -ENOMEM; 1599 1600 /* __khugepaged_exit() must not run from under us */ 1601 VM_BUG_ON(khugepaged_test_exit(mm)); 1602 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { 1603 free_mm_slot(mm_slot); 1604 return 0; 1605 } 1606 1607 spin_lock(&khugepaged_mm_lock); 1608 insert_to_mm_slots_hash(mm, mm_slot); 1609 /* 1610 * Insert just behind the scanning cursor, to let the area settle 1611 * down a little. 1612 */ 1613 wakeup = list_empty(&khugepaged_scan.mm_head); 1614 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); 1615 spin_unlock(&khugepaged_mm_lock); 1616 1617 atomic_inc(&mm->mm_count); 1618 if (wakeup) 1619 wake_up_interruptible(&khugepaged_wait); 1620 1621 return 0; 1622 } 1623 1624 int khugepaged_enter_vma_merge(struct vm_area_struct *vma) 1625 { 1626 unsigned long hstart, hend; 1627 if (!vma->anon_vma) 1628 /* 1629 * Not yet faulted in so we will register later in the 1630 * page fault if needed. 1631 */ 1632 return 0; 1633 if (vma->vm_ops) 1634 /* khugepaged not yet working on file or special mappings */ 1635 return 0; 1636 /* 1637 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be 1638 * true too, verify it here. 1639 */ 1640 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP); 1641 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1642 hend = vma->vm_end & HPAGE_PMD_MASK; 1643 if (hstart < hend) 1644 return khugepaged_enter(vma); 1645 return 0; 1646 } 1647 1648 void __khugepaged_exit(struct mm_struct *mm) 1649 { 1650 struct mm_slot *mm_slot; 1651 int free = 0; 1652 1653 spin_lock(&khugepaged_mm_lock); 1654 mm_slot = get_mm_slot(mm); 1655 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { 1656 hlist_del(&mm_slot->hash); 1657 list_del(&mm_slot->mm_node); 1658 free = 1; 1659 } 1660 spin_unlock(&khugepaged_mm_lock); 1661 1662 if (free) { 1663 clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 1664 free_mm_slot(mm_slot); 1665 mmdrop(mm); 1666 } else if (mm_slot) { 1667 /* 1668 * This is required to serialize against 1669 * khugepaged_test_exit() (which is guaranteed to run 1670 * under mmap sem read mode). Stop here (after we 1671 * return all pagetables will be destroyed) until 1672 * khugepaged has finished working on the pagetables 1673 * under the mmap_sem. 1674 */ 1675 down_write(&mm->mmap_sem); 1676 up_write(&mm->mmap_sem); 1677 } 1678 } 1679 1680 static void release_pte_page(struct page *page) 1681 { 1682 /* 0 stands for page_is_file_cache(page) == false */ 1683 dec_zone_page_state(page, NR_ISOLATED_ANON + 0); 1684 unlock_page(page); 1685 putback_lru_page(page); 1686 } 1687 1688 static void release_pte_pages(pte_t *pte, pte_t *_pte) 1689 { 1690 while (--_pte >= pte) { 1691 pte_t pteval = *_pte; 1692 if (!pte_none(pteval)) 1693 release_pte_page(pte_page(pteval)); 1694 } 1695 } 1696 1697 static void release_all_pte_pages(pte_t *pte) 1698 { 1699 release_pte_pages(pte, pte + HPAGE_PMD_NR); 1700 } 1701 1702 static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 1703 unsigned long address, 1704 pte_t *pte) 1705 { 1706 struct page *page; 1707 pte_t *_pte; 1708 int referenced = 0, isolated = 0, none = 0; 1709 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; 1710 _pte++, address += PAGE_SIZE) { 1711 pte_t pteval = *_pte; 1712 if (pte_none(pteval)) { 1713 if (++none <= khugepaged_max_ptes_none) 1714 continue; 1715 else { 1716 release_pte_pages(pte, _pte); 1717 goto out; 1718 } 1719 } 1720 if (!pte_present(pteval) || !pte_write(pteval)) { 1721 release_pte_pages(pte, _pte); 1722 goto out; 1723 } 1724 page = vm_normal_page(vma, address, pteval); 1725 if (unlikely(!page)) { 1726 release_pte_pages(pte, _pte); 1727 goto out; 1728 } 1729 VM_BUG_ON(PageCompound(page)); 1730 BUG_ON(!PageAnon(page)); 1731 VM_BUG_ON(!PageSwapBacked(page)); 1732 1733 /* cannot use mapcount: can't collapse if there's a gup pin */ 1734 if (page_count(page) != 1) { 1735 release_pte_pages(pte, _pte); 1736 goto out; 1737 } 1738 /* 1739 * We can do it before isolate_lru_page because the 1740 * page can't be freed from under us. NOTE: PG_lock 1741 * is needed to serialize against split_huge_page 1742 * when invoked from the VM. 1743 */ 1744 if (!trylock_page(page)) { 1745 release_pte_pages(pte, _pte); 1746 goto out; 1747 } 1748 /* 1749 * Isolate the page to avoid collapsing an hugepage 1750 * currently in use by the VM. 1751 */ 1752 if (isolate_lru_page(page)) { 1753 unlock_page(page); 1754 release_pte_pages(pte, _pte); 1755 goto out; 1756 } 1757 /* 0 stands for page_is_file_cache(page) == false */ 1758 inc_zone_page_state(page, NR_ISOLATED_ANON + 0); 1759 VM_BUG_ON(!PageLocked(page)); 1760 VM_BUG_ON(PageLRU(page)); 1761 1762 /* If there is no mapped pte young don't collapse the page */ 1763 if (pte_young(pteval) || PageReferenced(page) || 1764 mmu_notifier_test_young(vma->vm_mm, address)) 1765 referenced = 1; 1766 } 1767 if (unlikely(!referenced)) 1768 release_all_pte_pages(pte); 1769 else 1770 isolated = 1; 1771 out: 1772 return isolated; 1773 } 1774 1775 static void __collapse_huge_page_copy(pte_t *pte, struct page *page, 1776 struct vm_area_struct *vma, 1777 unsigned long address, 1778 spinlock_t *ptl) 1779 { 1780 pte_t *_pte; 1781 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { 1782 pte_t pteval = *_pte; 1783 struct page *src_page; 1784 1785 if (pte_none(pteval)) { 1786 clear_user_highpage(page, address); 1787 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); 1788 } else { 1789 src_page = pte_page(pteval); 1790 copy_user_highpage(page, src_page, address, vma); 1791 VM_BUG_ON(page_mapcount(src_page) != 1); 1792 VM_BUG_ON(page_count(src_page) != 2); 1793 release_pte_page(src_page); 1794 /* 1795 * ptl mostly unnecessary, but preempt has to 1796 * be disabled to update the per-cpu stats 1797 * inside page_remove_rmap(). 1798 */ 1799 spin_lock(ptl); 1800 /* 1801 * paravirt calls inside pte_clear here are 1802 * superfluous. 1803 */ 1804 pte_clear(vma->vm_mm, address, _pte); 1805 page_remove_rmap(src_page); 1806 spin_unlock(ptl); 1807 free_page_and_swap_cache(src_page); 1808 } 1809 1810 address += PAGE_SIZE; 1811 page++; 1812 } 1813 } 1814 1815 static void collapse_huge_page(struct mm_struct *mm, 1816 unsigned long address, 1817 struct page **hpage, 1818 struct vm_area_struct *vma, 1819 int node) 1820 { 1821 pgd_t *pgd; 1822 pud_t *pud; 1823 pmd_t *pmd, _pmd; 1824 pte_t *pte; 1825 pgtable_t pgtable; 1826 struct page *new_page; 1827 spinlock_t *ptl; 1828 int isolated; 1829 unsigned long hstart, hend; 1830 1831 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 1832 #ifndef CONFIG_NUMA 1833 up_read(&mm->mmap_sem); 1834 VM_BUG_ON(!*hpage); 1835 new_page = *hpage; 1836 #else 1837 VM_BUG_ON(*hpage); 1838 /* 1839 * Allocate the page while the vma is still valid and under 1840 * the mmap_sem read mode so there is no memory allocation 1841 * later when we take the mmap_sem in write mode. This is more 1842 * friendly behavior (OTOH it may actually hide bugs) to 1843 * filesystems in userland with daemons allocating memory in 1844 * the userland I/O paths. Allocating memory with the 1845 * mmap_sem in read mode is good idea also to allow greater 1846 * scalability. 1847 */ 1848 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address, 1849 node, __GFP_OTHER_NODE); 1850 1851 /* 1852 * After allocating the hugepage, release the mmap_sem read lock in 1853 * preparation for taking it in write mode. 1854 */ 1855 up_read(&mm->mmap_sem); 1856 if (unlikely(!new_page)) { 1857 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 1858 *hpage = ERR_PTR(-ENOMEM); 1859 return; 1860 } 1861 #endif 1862 1863 count_vm_event(THP_COLLAPSE_ALLOC); 1864 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { 1865 #ifdef CONFIG_NUMA 1866 put_page(new_page); 1867 #endif 1868 return; 1869 } 1870 1871 /* 1872 * Prevent all access to pagetables with the exception of 1873 * gup_fast later hanlded by the ptep_clear_flush and the VM 1874 * handled by the anon_vma lock + PG_lock. 1875 */ 1876 down_write(&mm->mmap_sem); 1877 if (unlikely(khugepaged_test_exit(mm))) 1878 goto out; 1879 1880 vma = find_vma(mm, address); 1881 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 1882 hend = vma->vm_end & HPAGE_PMD_MASK; 1883 if (address < hstart || address + HPAGE_PMD_SIZE > hend) 1884 goto out; 1885 1886 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || 1887 (vma->vm_flags & VM_NOHUGEPAGE)) 1888 goto out; 1889 1890 if (!vma->anon_vma || vma->vm_ops) 1891 goto out; 1892 if (is_vma_temporary_stack(vma)) 1893 goto out; 1894 /* 1895 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be 1896 * true too, verify it here. 1897 */ 1898 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP); 1899 1900 pgd = pgd_offset(mm, address); 1901 if (!pgd_present(*pgd)) 1902 goto out; 1903 1904 pud = pud_offset(pgd, address); 1905 if (!pud_present(*pud)) 1906 goto out; 1907 1908 pmd = pmd_offset(pud, address); 1909 /* pmd can't go away or become huge under us */ 1910 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd)) 1911 goto out; 1912 1913 anon_vma_lock(vma->anon_vma); 1914 1915 pte = pte_offset_map(pmd, address); 1916 ptl = pte_lockptr(mm, pmd); 1917 1918 spin_lock(&mm->page_table_lock); /* probably unnecessary */ 1919 /* 1920 * After this gup_fast can't run anymore. This also removes 1921 * any huge TLB entry from the CPU so we won't allow 1922 * huge and small TLB entries for the same virtual address 1923 * to avoid the risk of CPU bugs in that area. 1924 */ 1925 _pmd = pmdp_clear_flush_notify(vma, address, pmd); 1926 spin_unlock(&mm->page_table_lock); 1927 1928 spin_lock(ptl); 1929 isolated = __collapse_huge_page_isolate(vma, address, pte); 1930 spin_unlock(ptl); 1931 1932 if (unlikely(!isolated)) { 1933 pte_unmap(pte); 1934 spin_lock(&mm->page_table_lock); 1935 BUG_ON(!pmd_none(*pmd)); 1936 set_pmd_at(mm, address, pmd, _pmd); 1937 spin_unlock(&mm->page_table_lock); 1938 anon_vma_unlock(vma->anon_vma); 1939 goto out; 1940 } 1941 1942 /* 1943 * All pages are isolated and locked so anon_vma rmap 1944 * can't run anymore. 1945 */ 1946 anon_vma_unlock(vma->anon_vma); 1947 1948 __collapse_huge_page_copy(pte, new_page, vma, address, ptl); 1949 pte_unmap(pte); 1950 __SetPageUptodate(new_page); 1951 pgtable = pmd_pgtable(_pmd); 1952 VM_BUG_ON(page_count(pgtable) != 1); 1953 VM_BUG_ON(page_mapcount(pgtable) != 0); 1954 1955 _pmd = mk_pmd(new_page, vma->vm_page_prot); 1956 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); 1957 _pmd = pmd_mkhuge(_pmd); 1958 1959 /* 1960 * spin_lock() below is not the equivalent of smp_wmb(), so 1961 * this is needed to avoid the copy_huge_page writes to become 1962 * visible after the set_pmd_at() write. 1963 */ 1964 smp_wmb(); 1965 1966 spin_lock(&mm->page_table_lock); 1967 BUG_ON(!pmd_none(*pmd)); 1968 page_add_new_anon_rmap(new_page, vma, address); 1969 set_pmd_at(mm, address, pmd, _pmd); 1970 update_mmu_cache(vma, address, _pmd); 1971 prepare_pmd_huge_pte(pgtable, mm); 1972 mm->nr_ptes--; 1973 spin_unlock(&mm->page_table_lock); 1974 1975 #ifndef CONFIG_NUMA 1976 *hpage = NULL; 1977 #endif 1978 khugepaged_pages_collapsed++; 1979 out_up_write: 1980 up_write(&mm->mmap_sem); 1981 return; 1982 1983 out: 1984 mem_cgroup_uncharge_page(new_page); 1985 #ifdef CONFIG_NUMA 1986 put_page(new_page); 1987 #endif 1988 goto out_up_write; 1989 } 1990 1991 static int khugepaged_scan_pmd(struct mm_struct *mm, 1992 struct vm_area_struct *vma, 1993 unsigned long address, 1994 struct page **hpage) 1995 { 1996 pgd_t *pgd; 1997 pud_t *pud; 1998 pmd_t *pmd; 1999 pte_t *pte, *_pte; 2000 int ret = 0, referenced = 0, none = 0; 2001 struct page *page; 2002 unsigned long _address; 2003 spinlock_t *ptl; 2004 int node = -1; 2005 2006 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 2007 2008 pgd = pgd_offset(mm, address); 2009 if (!pgd_present(*pgd)) 2010 goto out; 2011 2012 pud = pud_offset(pgd, address); 2013 if (!pud_present(*pud)) 2014 goto out; 2015 2016 pmd = pmd_offset(pud, address); 2017 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd)) 2018 goto out; 2019 2020 pte = pte_offset_map_lock(mm, pmd, address, &ptl); 2021 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; 2022 _pte++, _address += PAGE_SIZE) { 2023 pte_t pteval = *_pte; 2024 if (pte_none(pteval)) { 2025 if (++none <= khugepaged_max_ptes_none) 2026 continue; 2027 else 2028 goto out_unmap; 2029 } 2030 if (!pte_present(pteval) || !pte_write(pteval)) 2031 goto out_unmap; 2032 page = vm_normal_page(vma, _address, pteval); 2033 if (unlikely(!page)) 2034 goto out_unmap; 2035 /* 2036 * Chose the node of the first page. This could 2037 * be more sophisticated and look at more pages, 2038 * but isn't for now. 2039 */ 2040 if (node == -1) 2041 node = page_to_nid(page); 2042 VM_BUG_ON(PageCompound(page)); 2043 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) 2044 goto out_unmap; 2045 /* cannot use mapcount: can't collapse if there's a gup pin */ 2046 if (page_count(page) != 1) 2047 goto out_unmap; 2048 if (pte_young(pteval) || PageReferenced(page) || 2049 mmu_notifier_test_young(vma->vm_mm, address)) 2050 referenced = 1; 2051 } 2052 if (referenced) 2053 ret = 1; 2054 out_unmap: 2055 pte_unmap_unlock(pte, ptl); 2056 if (ret) 2057 /* collapse_huge_page will return with the mmap_sem released */ 2058 collapse_huge_page(mm, address, hpage, vma, node); 2059 out: 2060 return ret; 2061 } 2062 2063 static void collect_mm_slot(struct mm_slot *mm_slot) 2064 { 2065 struct mm_struct *mm = mm_slot->mm; 2066 2067 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock)); 2068 2069 if (khugepaged_test_exit(mm)) { 2070 /* free mm_slot */ 2071 hlist_del(&mm_slot->hash); 2072 list_del(&mm_slot->mm_node); 2073 2074 /* 2075 * Not strictly needed because the mm exited already. 2076 * 2077 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); 2078 */ 2079 2080 /* khugepaged_mm_lock actually not necessary for the below */ 2081 free_mm_slot(mm_slot); 2082 mmdrop(mm); 2083 } 2084 } 2085 2086 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, 2087 struct page **hpage) 2088 __releases(&khugepaged_mm_lock) 2089 __acquires(&khugepaged_mm_lock) 2090 { 2091 struct mm_slot *mm_slot; 2092 struct mm_struct *mm; 2093 struct vm_area_struct *vma; 2094 int progress = 0; 2095 2096 VM_BUG_ON(!pages); 2097 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock)); 2098 2099 if (khugepaged_scan.mm_slot) 2100 mm_slot = khugepaged_scan.mm_slot; 2101 else { 2102 mm_slot = list_entry(khugepaged_scan.mm_head.next, 2103 struct mm_slot, mm_node); 2104 khugepaged_scan.address = 0; 2105 khugepaged_scan.mm_slot = mm_slot; 2106 } 2107 spin_unlock(&khugepaged_mm_lock); 2108 2109 mm = mm_slot->mm; 2110 down_read(&mm->mmap_sem); 2111 if (unlikely(khugepaged_test_exit(mm))) 2112 vma = NULL; 2113 else 2114 vma = find_vma(mm, khugepaged_scan.address); 2115 2116 progress++; 2117 for (; vma; vma = vma->vm_next) { 2118 unsigned long hstart, hend; 2119 2120 cond_resched(); 2121 if (unlikely(khugepaged_test_exit(mm))) { 2122 progress++; 2123 break; 2124 } 2125 2126 if ((!(vma->vm_flags & VM_HUGEPAGE) && 2127 !khugepaged_always()) || 2128 (vma->vm_flags & VM_NOHUGEPAGE)) { 2129 skip: 2130 progress++; 2131 continue; 2132 } 2133 if (!vma->anon_vma || vma->vm_ops) 2134 goto skip; 2135 if (is_vma_temporary_stack(vma)) 2136 goto skip; 2137 /* 2138 * If is_pfn_mapping() is true is_learn_pfn_mapping() 2139 * must be true too, verify it here. 2140 */ 2141 VM_BUG_ON(is_linear_pfn_mapping(vma) || 2142 vma->vm_flags & VM_NO_THP); 2143 2144 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; 2145 hend = vma->vm_end & HPAGE_PMD_MASK; 2146 if (hstart >= hend) 2147 goto skip; 2148 if (khugepaged_scan.address > hend) 2149 goto skip; 2150 if (khugepaged_scan.address < hstart) 2151 khugepaged_scan.address = hstart; 2152 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); 2153 2154 while (khugepaged_scan.address < hend) { 2155 int ret; 2156 cond_resched(); 2157 if (unlikely(khugepaged_test_exit(mm))) 2158 goto breakouterloop; 2159 2160 VM_BUG_ON(khugepaged_scan.address < hstart || 2161 khugepaged_scan.address + HPAGE_PMD_SIZE > 2162 hend); 2163 ret = khugepaged_scan_pmd(mm, vma, 2164 khugepaged_scan.address, 2165 hpage); 2166 /* move to next address */ 2167 khugepaged_scan.address += HPAGE_PMD_SIZE; 2168 progress += HPAGE_PMD_NR; 2169 if (ret) 2170 /* we released mmap_sem so break loop */ 2171 goto breakouterloop_mmap_sem; 2172 if (progress >= pages) 2173 goto breakouterloop; 2174 } 2175 } 2176 breakouterloop: 2177 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ 2178 breakouterloop_mmap_sem: 2179 2180 spin_lock(&khugepaged_mm_lock); 2181 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); 2182 /* 2183 * Release the current mm_slot if this mm is about to die, or 2184 * if we scanned all vmas of this mm. 2185 */ 2186 if (khugepaged_test_exit(mm) || !vma) { 2187 /* 2188 * Make sure that if mm_users is reaching zero while 2189 * khugepaged runs here, khugepaged_exit will find 2190 * mm_slot not pointing to the exiting mm. 2191 */ 2192 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { 2193 khugepaged_scan.mm_slot = list_entry( 2194 mm_slot->mm_node.next, 2195 struct mm_slot, mm_node); 2196 khugepaged_scan.address = 0; 2197 } else { 2198 khugepaged_scan.mm_slot = NULL; 2199 khugepaged_full_scans++; 2200 } 2201 2202 collect_mm_slot(mm_slot); 2203 } 2204 2205 return progress; 2206 } 2207 2208 static int khugepaged_has_work(void) 2209 { 2210 return !list_empty(&khugepaged_scan.mm_head) && 2211 khugepaged_enabled(); 2212 } 2213 2214 static int khugepaged_wait_event(void) 2215 { 2216 return !list_empty(&khugepaged_scan.mm_head) || 2217 !khugepaged_enabled(); 2218 } 2219 2220 static void khugepaged_do_scan(struct page **hpage) 2221 { 2222 unsigned int progress = 0, pass_through_head = 0; 2223 unsigned int pages = khugepaged_pages_to_scan; 2224 2225 barrier(); /* write khugepaged_pages_to_scan to local stack */ 2226 2227 while (progress < pages) { 2228 cond_resched(); 2229 2230 #ifndef CONFIG_NUMA 2231 if (!*hpage) { 2232 *hpage = alloc_hugepage(khugepaged_defrag()); 2233 if (unlikely(!*hpage)) { 2234 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2235 break; 2236 } 2237 count_vm_event(THP_COLLAPSE_ALLOC); 2238 } 2239 #else 2240 if (IS_ERR(*hpage)) 2241 break; 2242 #endif 2243 2244 if (unlikely(kthread_should_stop() || freezing(current))) 2245 break; 2246 2247 spin_lock(&khugepaged_mm_lock); 2248 if (!khugepaged_scan.mm_slot) 2249 pass_through_head++; 2250 if (khugepaged_has_work() && 2251 pass_through_head < 2) 2252 progress += khugepaged_scan_mm_slot(pages - progress, 2253 hpage); 2254 else 2255 progress = pages; 2256 spin_unlock(&khugepaged_mm_lock); 2257 } 2258 } 2259 2260 static void khugepaged_alloc_sleep(void) 2261 { 2262 DEFINE_WAIT(wait); 2263 add_wait_queue(&khugepaged_wait, &wait); 2264 schedule_timeout_interruptible( 2265 msecs_to_jiffies( 2266 khugepaged_alloc_sleep_millisecs)); 2267 remove_wait_queue(&khugepaged_wait, &wait); 2268 } 2269 2270 #ifndef CONFIG_NUMA 2271 static struct page *khugepaged_alloc_hugepage(void) 2272 { 2273 struct page *hpage; 2274 2275 do { 2276 hpage = alloc_hugepage(khugepaged_defrag()); 2277 if (!hpage) { 2278 count_vm_event(THP_COLLAPSE_ALLOC_FAILED); 2279 khugepaged_alloc_sleep(); 2280 } else 2281 count_vm_event(THP_COLLAPSE_ALLOC); 2282 } while (unlikely(!hpage) && 2283 likely(khugepaged_enabled())); 2284 return hpage; 2285 } 2286 #endif 2287 2288 static void khugepaged_loop(void) 2289 { 2290 struct page *hpage; 2291 2292 #ifdef CONFIG_NUMA 2293 hpage = NULL; 2294 #endif 2295 while (likely(khugepaged_enabled())) { 2296 #ifndef CONFIG_NUMA 2297 hpage = khugepaged_alloc_hugepage(); 2298 if (unlikely(!hpage)) 2299 break; 2300 #else 2301 if (IS_ERR(hpage)) { 2302 khugepaged_alloc_sleep(); 2303 hpage = NULL; 2304 } 2305 #endif 2306 2307 khugepaged_do_scan(&hpage); 2308 #ifndef CONFIG_NUMA 2309 if (hpage) 2310 put_page(hpage); 2311 #endif 2312 try_to_freeze(); 2313 if (unlikely(kthread_should_stop())) 2314 break; 2315 if (khugepaged_has_work()) { 2316 DEFINE_WAIT(wait); 2317 if (!khugepaged_scan_sleep_millisecs) 2318 continue; 2319 add_wait_queue(&khugepaged_wait, &wait); 2320 schedule_timeout_interruptible( 2321 msecs_to_jiffies( 2322 khugepaged_scan_sleep_millisecs)); 2323 remove_wait_queue(&khugepaged_wait, &wait); 2324 } else if (khugepaged_enabled()) 2325 wait_event_freezable(khugepaged_wait, 2326 khugepaged_wait_event()); 2327 } 2328 } 2329 2330 static int khugepaged(void *none) 2331 { 2332 struct mm_slot *mm_slot; 2333 2334 set_freezable(); 2335 set_user_nice(current, 19); 2336 2337 /* serialize with start_khugepaged() */ 2338 mutex_lock(&khugepaged_mutex); 2339 2340 for (;;) { 2341 mutex_unlock(&khugepaged_mutex); 2342 VM_BUG_ON(khugepaged_thread != current); 2343 khugepaged_loop(); 2344 VM_BUG_ON(khugepaged_thread != current); 2345 2346 mutex_lock(&khugepaged_mutex); 2347 if (!khugepaged_enabled()) 2348 break; 2349 if (unlikely(kthread_should_stop())) 2350 break; 2351 } 2352 2353 spin_lock(&khugepaged_mm_lock); 2354 mm_slot = khugepaged_scan.mm_slot; 2355 khugepaged_scan.mm_slot = NULL; 2356 if (mm_slot) 2357 collect_mm_slot(mm_slot); 2358 spin_unlock(&khugepaged_mm_lock); 2359 2360 khugepaged_thread = NULL; 2361 mutex_unlock(&khugepaged_mutex); 2362 2363 return 0; 2364 } 2365 2366 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd) 2367 { 2368 struct page *page; 2369 2370 spin_lock(&mm->page_table_lock); 2371 if (unlikely(!pmd_trans_huge(*pmd))) { 2372 spin_unlock(&mm->page_table_lock); 2373 return; 2374 } 2375 page = pmd_page(*pmd); 2376 VM_BUG_ON(!page_count(page)); 2377 get_page(page); 2378 spin_unlock(&mm->page_table_lock); 2379 2380 split_huge_page(page); 2381 2382 put_page(page); 2383 BUG_ON(pmd_trans_huge(*pmd)); 2384 } 2385 2386 static void split_huge_page_address(struct mm_struct *mm, 2387 unsigned long address) 2388 { 2389 pgd_t *pgd; 2390 pud_t *pud; 2391 pmd_t *pmd; 2392 2393 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); 2394 2395 pgd = pgd_offset(mm, address); 2396 if (!pgd_present(*pgd)) 2397 return; 2398 2399 pud = pud_offset(pgd, address); 2400 if (!pud_present(*pud)) 2401 return; 2402 2403 pmd = pmd_offset(pud, address); 2404 if (!pmd_present(*pmd)) 2405 return; 2406 /* 2407 * Caller holds the mmap_sem write mode, so a huge pmd cannot 2408 * materialize from under us. 2409 */ 2410 split_huge_page_pmd(mm, pmd); 2411 } 2412 2413 void __vma_adjust_trans_huge(struct vm_area_struct *vma, 2414 unsigned long start, 2415 unsigned long end, 2416 long adjust_next) 2417 { 2418 /* 2419 * If the new start address isn't hpage aligned and it could 2420 * previously contain an hugepage: check if we need to split 2421 * an huge pmd. 2422 */ 2423 if (start & ~HPAGE_PMD_MASK && 2424 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2425 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2426 split_huge_page_address(vma->vm_mm, start); 2427 2428 /* 2429 * If the new end address isn't hpage aligned and it could 2430 * previously contain an hugepage: check if we need to split 2431 * an huge pmd. 2432 */ 2433 if (end & ~HPAGE_PMD_MASK && 2434 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2435 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2436 split_huge_page_address(vma->vm_mm, end); 2437 2438 /* 2439 * If we're also updating the vma->vm_next->vm_start, if the new 2440 * vm_next->vm_start isn't page aligned and it could previously 2441 * contain an hugepage: check if we need to split an huge pmd. 2442 */ 2443 if (adjust_next > 0) { 2444 struct vm_area_struct *next = vma->vm_next; 2445 unsigned long nstart = next->vm_start; 2446 nstart += adjust_next << PAGE_SHIFT; 2447 if (nstart & ~HPAGE_PMD_MASK && 2448 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2449 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2450 split_huge_page_address(next->vm_mm, nstart); 2451 } 2452 } 2453