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