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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 9 10 #include <linux/mm.h> 11 #include <linux/sched.h> 12 #include <linux/sched/coredump.h> 13 #include <linux/sched/numa_balancing.h> 14 #include <linux/highmem.h> 15 #include <linux/hugetlb.h> 16 #include <linux/mmu_notifier.h> 17 #include <linux/rmap.h> 18 #include <linux/swap.h> 19 #include <linux/shrinker.h> 20 #include <linux/mm_inline.h> 21 #include <linux/swapops.h> 22 #include <linux/dax.h> 23 #include <linux/khugepaged.h> 24 #include <linux/freezer.h> 25 #include <linux/pfn_t.h> 26 #include <linux/mman.h> 27 #include <linux/memremap.h> 28 #include <linux/pagemap.h> 29 #include <linux/debugfs.h> 30 #include <linux/migrate.h> 31 #include <linux/hashtable.h> 32 #include <linux/userfaultfd_k.h> 33 #include <linux/page_idle.h> 34 #include <linux/shmem_fs.h> 35 #include <linux/oom.h> 36 37 #include <asm/tlb.h> 38 #include <asm/pgalloc.h> 39 #include "internal.h" 40 41 /* 42 * By default transparent hugepage support is disabled in order that avoid 43 * to risk increase the memory footprint of applications without a guaranteed 44 * benefit. When transparent hugepage support is enabled, is for all mappings, 45 * and khugepaged scans all mappings. 46 * Defrag is invoked by khugepaged hugepage allocations and by page faults 47 * for all hugepage allocations. 48 */ 49 unsigned long transparent_hugepage_flags __read_mostly = 50 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS 51 (1<<TRANSPARENT_HUGEPAGE_FLAG)| 52 #endif 53 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE 54 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| 55 #endif 56 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)| 57 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)| 58 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 59 60 static struct shrinker deferred_split_shrinker; 61 62 static atomic_t huge_zero_refcount; 63 struct page *huge_zero_page __read_mostly; 64 65 static struct page *get_huge_zero_page(void) 66 { 67 struct page *zero_page; 68 retry: 69 if (likely(atomic_inc_not_zero(&huge_zero_refcount))) 70 return READ_ONCE(huge_zero_page); 71 72 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, 73 HPAGE_PMD_ORDER); 74 if (!zero_page) { 75 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); 76 return NULL; 77 } 78 count_vm_event(THP_ZERO_PAGE_ALLOC); 79 preempt_disable(); 80 if (cmpxchg(&huge_zero_page, NULL, zero_page)) { 81 preempt_enable(); 82 __free_pages(zero_page, compound_order(zero_page)); 83 goto retry; 84 } 85 86 /* We take additional reference here. It will be put back by shrinker */ 87 atomic_set(&huge_zero_refcount, 2); 88 preempt_enable(); 89 return READ_ONCE(huge_zero_page); 90 } 91 92 static void put_huge_zero_page(void) 93 { 94 /* 95 * Counter should never go to zero here. Only shrinker can put 96 * last reference. 97 */ 98 BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); 99 } 100 101 struct page *mm_get_huge_zero_page(struct mm_struct *mm) 102 { 103 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) 104 return READ_ONCE(huge_zero_page); 105 106 if (!get_huge_zero_page()) 107 return NULL; 108 109 if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) 110 put_huge_zero_page(); 111 112 return READ_ONCE(huge_zero_page); 113 } 114 115 void mm_put_huge_zero_page(struct mm_struct *mm) 116 { 117 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) 118 put_huge_zero_page(); 119 } 120 121 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, 122 struct shrink_control *sc) 123 { 124 /* we can free zero page only if last reference remains */ 125 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; 126 } 127 128 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, 129 struct shrink_control *sc) 130 { 131 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { 132 struct page *zero_page = xchg(&huge_zero_page, NULL); 133 BUG_ON(zero_page == NULL); 134 __free_pages(zero_page, compound_order(zero_page)); 135 return HPAGE_PMD_NR; 136 } 137 138 return 0; 139 } 140 141 static struct shrinker huge_zero_page_shrinker = { 142 .count_objects = shrink_huge_zero_page_count, 143 .scan_objects = shrink_huge_zero_page_scan, 144 .seeks = DEFAULT_SEEKS, 145 }; 146 147 #ifdef CONFIG_SYSFS 148 static ssize_t enabled_show(struct kobject *kobj, 149 struct kobj_attribute *attr, char *buf) 150 { 151 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags)) 152 return sprintf(buf, "[always] madvise never\n"); 153 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags)) 154 return sprintf(buf, "always [madvise] never\n"); 155 else 156 return sprintf(buf, "always madvise [never]\n"); 157 } 158 159 static ssize_t enabled_store(struct kobject *kobj, 160 struct kobj_attribute *attr, 161 const char *buf, size_t count) 162 { 163 ssize_t ret = count; 164 165 if (!memcmp("always", buf, 166 min(sizeof("always")-1, count))) { 167 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); 168 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); 169 } else if (!memcmp("madvise", buf, 170 min(sizeof("madvise")-1, count))) { 171 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); 172 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); 173 } else if (!memcmp("never", buf, 174 min(sizeof("never")-1, count))) { 175 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); 176 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); 177 } else 178 ret = -EINVAL; 179 180 if (ret > 0) { 181 int err = start_stop_khugepaged(); 182 if (err) 183 ret = err; 184 } 185 return ret; 186 } 187 static struct kobj_attribute enabled_attr = 188 __ATTR(enabled, 0644, enabled_show, enabled_store); 189 190 ssize_t single_hugepage_flag_show(struct kobject *kobj, 191 struct kobj_attribute *attr, char *buf, 192 enum transparent_hugepage_flag flag) 193 { 194 return sprintf(buf, "%d\n", 195 !!test_bit(flag, &transparent_hugepage_flags)); 196 } 197 198 ssize_t single_hugepage_flag_store(struct kobject *kobj, 199 struct kobj_attribute *attr, 200 const char *buf, size_t count, 201 enum transparent_hugepage_flag flag) 202 { 203 unsigned long value; 204 int ret; 205 206 ret = kstrtoul(buf, 10, &value); 207 if (ret < 0) 208 return ret; 209 if (value > 1) 210 return -EINVAL; 211 212 if (value) 213 set_bit(flag, &transparent_hugepage_flags); 214 else 215 clear_bit(flag, &transparent_hugepage_flags); 216 217 return count; 218 } 219 220 static ssize_t defrag_show(struct kobject *kobj, 221 struct kobj_attribute *attr, char *buf) 222 { 223 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) 224 return sprintf(buf, "[always] defer defer+madvise madvise never\n"); 225 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) 226 return sprintf(buf, "always [defer] defer+madvise madvise never\n"); 227 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags)) 228 return sprintf(buf, "always defer [defer+madvise] madvise never\n"); 229 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) 230 return sprintf(buf, "always defer defer+madvise [madvise] never\n"); 231 return sprintf(buf, "always defer defer+madvise madvise [never]\n"); 232 } 233 234 static ssize_t defrag_store(struct kobject *kobj, 235 struct kobj_attribute *attr, 236 const char *buf, size_t count) 237 { 238 if (!memcmp("always", buf, 239 min(sizeof("always")-1, count))) { 240 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 241 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 242 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 243 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 244 } else if (!memcmp("defer+madvise", buf, 245 min(sizeof("defer+madvise")-1, count))) { 246 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 247 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 248 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 249 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 250 } else if (!memcmp("defer", buf, 251 min(sizeof("defer")-1, count))) { 252 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 253 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 254 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 255 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 256 } else if (!memcmp("madvise", buf, 257 min(sizeof("madvise")-1, count))) { 258 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 259 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 260 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 261 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 262 } else if (!memcmp("never", buf, 263 min(sizeof("never")-1, count))) { 264 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 265 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 266 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 267 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 268 } else 269 return -EINVAL; 270 271 return count; 272 } 273 static struct kobj_attribute defrag_attr = 274 __ATTR(defrag, 0644, defrag_show, defrag_store); 275 276 static ssize_t use_zero_page_show(struct kobject *kobj, 277 struct kobj_attribute *attr, char *buf) 278 { 279 return single_hugepage_flag_show(kobj, attr, buf, 280 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 281 } 282 static ssize_t use_zero_page_store(struct kobject *kobj, 283 struct kobj_attribute *attr, const char *buf, size_t count) 284 { 285 return single_hugepage_flag_store(kobj, attr, buf, count, 286 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 287 } 288 static struct kobj_attribute use_zero_page_attr = 289 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); 290 291 static ssize_t hpage_pmd_size_show(struct kobject *kobj, 292 struct kobj_attribute *attr, char *buf) 293 { 294 return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE); 295 } 296 static struct kobj_attribute hpage_pmd_size_attr = 297 __ATTR_RO(hpage_pmd_size); 298 299 #ifdef CONFIG_DEBUG_VM 300 static ssize_t debug_cow_show(struct kobject *kobj, 301 struct kobj_attribute *attr, char *buf) 302 { 303 return single_hugepage_flag_show(kobj, attr, buf, 304 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 305 } 306 static ssize_t debug_cow_store(struct kobject *kobj, 307 struct kobj_attribute *attr, 308 const char *buf, size_t count) 309 { 310 return single_hugepage_flag_store(kobj, attr, buf, count, 311 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 312 } 313 static struct kobj_attribute debug_cow_attr = 314 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 315 #endif /* CONFIG_DEBUG_VM */ 316 317 static struct attribute *hugepage_attr[] = { 318 &enabled_attr.attr, 319 &defrag_attr.attr, 320 &use_zero_page_attr.attr, 321 &hpage_pmd_size_attr.attr, 322 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) 323 &shmem_enabled_attr.attr, 324 #endif 325 #ifdef CONFIG_DEBUG_VM 326 &debug_cow_attr.attr, 327 #endif 328 NULL, 329 }; 330 331 static const struct attribute_group hugepage_attr_group = { 332 .attrs = hugepage_attr, 333 }; 334 335 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) 336 { 337 int err; 338 339 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 340 if (unlikely(!*hugepage_kobj)) { 341 pr_err("failed to create transparent hugepage kobject\n"); 342 return -ENOMEM; 343 } 344 345 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); 346 if (err) { 347 pr_err("failed to register transparent hugepage group\n"); 348 goto delete_obj; 349 } 350 351 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); 352 if (err) { 353 pr_err("failed to register transparent hugepage group\n"); 354 goto remove_hp_group; 355 } 356 357 return 0; 358 359 remove_hp_group: 360 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); 361 delete_obj: 362 kobject_put(*hugepage_kobj); 363 return err; 364 } 365 366 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) 367 { 368 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); 369 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); 370 kobject_put(hugepage_kobj); 371 } 372 #else 373 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) 374 { 375 return 0; 376 } 377 378 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) 379 { 380 } 381 #endif /* CONFIG_SYSFS */ 382 383 static int __init hugepage_init(void) 384 { 385 int err; 386 struct kobject *hugepage_kobj; 387 388 if (!has_transparent_hugepage()) { 389 transparent_hugepage_flags = 0; 390 return -EINVAL; 391 } 392 393 /* 394 * hugepages can't be allocated by the buddy allocator 395 */ 396 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER); 397 /* 398 * we use page->mapping and page->index in second tail page 399 * as list_head: assuming THP order >= 2 400 */ 401 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2); 402 403 err = hugepage_init_sysfs(&hugepage_kobj); 404 if (err) 405 goto err_sysfs; 406 407 err = khugepaged_init(); 408 if (err) 409 goto err_slab; 410 411 err = register_shrinker(&huge_zero_page_shrinker); 412 if (err) 413 goto err_hzp_shrinker; 414 err = register_shrinker(&deferred_split_shrinker); 415 if (err) 416 goto err_split_shrinker; 417 418 /* 419 * By default disable transparent hugepages on smaller systems, 420 * where the extra memory used could hurt more than TLB overhead 421 * is likely to save. The admin can still enable it through /sys. 422 */ 423 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) { 424 transparent_hugepage_flags = 0; 425 return 0; 426 } 427 428 err = start_stop_khugepaged(); 429 if (err) 430 goto err_khugepaged; 431 432 return 0; 433 err_khugepaged: 434 unregister_shrinker(&deferred_split_shrinker); 435 err_split_shrinker: 436 unregister_shrinker(&huge_zero_page_shrinker); 437 err_hzp_shrinker: 438 khugepaged_destroy(); 439 err_slab: 440 hugepage_exit_sysfs(hugepage_kobj); 441 err_sysfs: 442 return err; 443 } 444 subsys_initcall(hugepage_init); 445 446 static int __init setup_transparent_hugepage(char *str) 447 { 448 int ret = 0; 449 if (!str) 450 goto out; 451 if (!strcmp(str, "always")) { 452 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 453 &transparent_hugepage_flags); 454 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 455 &transparent_hugepage_flags); 456 ret = 1; 457 } else if (!strcmp(str, "madvise")) { 458 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 459 &transparent_hugepage_flags); 460 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 461 &transparent_hugepage_flags); 462 ret = 1; 463 } else if (!strcmp(str, "never")) { 464 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 465 &transparent_hugepage_flags); 466 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 467 &transparent_hugepage_flags); 468 ret = 1; 469 } 470 out: 471 if (!ret) 472 pr_warn("transparent_hugepage= cannot parse, ignored\n"); 473 return ret; 474 } 475 __setup("transparent_hugepage=", setup_transparent_hugepage); 476 477 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 478 { 479 if (likely(vma->vm_flags & VM_WRITE)) 480 pmd = pmd_mkwrite(pmd); 481 return pmd; 482 } 483 484 static inline struct list_head *page_deferred_list(struct page *page) 485 { 486 /* 487 * ->lru in the tail pages is occupied by compound_head. 488 * Let's use ->mapping + ->index in the second tail page as list_head. 489 */ 490 return (struct list_head *)&page[2].mapping; 491 } 492 493 void prep_transhuge_page(struct page *page) 494 { 495 /* 496 * we use page->mapping and page->indexlru in second tail page 497 * as list_head: assuming THP order >= 2 498 */ 499 500 INIT_LIST_HEAD(page_deferred_list(page)); 501 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR); 502 } 503 504 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len, 505 loff_t off, unsigned long flags, unsigned long size) 506 { 507 unsigned long addr; 508 loff_t off_end = off + len; 509 loff_t off_align = round_up(off, size); 510 unsigned long len_pad; 511 512 if (off_end <= off_align || (off_end - off_align) < size) 513 return 0; 514 515 len_pad = len + size; 516 if (len_pad < len || (off + len_pad) < off) 517 return 0; 518 519 addr = current->mm->get_unmapped_area(filp, 0, len_pad, 520 off >> PAGE_SHIFT, flags); 521 if (IS_ERR_VALUE(addr)) 522 return 0; 523 524 addr += (off - addr) & (size - 1); 525 return addr; 526 } 527 528 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr, 529 unsigned long len, unsigned long pgoff, unsigned long flags) 530 { 531 loff_t off = (loff_t)pgoff << PAGE_SHIFT; 532 533 if (addr) 534 goto out; 535 if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD)) 536 goto out; 537 538 addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE); 539 if (addr) 540 return addr; 541 542 out: 543 return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags); 544 } 545 EXPORT_SYMBOL_GPL(thp_get_unmapped_area); 546 547 static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page, 548 gfp_t gfp) 549 { 550 struct vm_area_struct *vma = vmf->vma; 551 struct mem_cgroup *memcg; 552 pgtable_t pgtable; 553 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 554 int ret = 0; 555 556 VM_BUG_ON_PAGE(!PageCompound(page), page); 557 558 if (mem_cgroup_try_charge(page, vma->vm_mm, gfp, &memcg, true)) { 559 put_page(page); 560 count_vm_event(THP_FAULT_FALLBACK); 561 return VM_FAULT_FALLBACK; 562 } 563 564 pgtable = pte_alloc_one(vma->vm_mm, haddr); 565 if (unlikely(!pgtable)) { 566 ret = VM_FAULT_OOM; 567 goto release; 568 } 569 570 clear_huge_page(page, vmf->address, HPAGE_PMD_NR); 571 /* 572 * The memory barrier inside __SetPageUptodate makes sure that 573 * clear_huge_page writes become visible before the set_pmd_at() 574 * write. 575 */ 576 __SetPageUptodate(page); 577 578 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 579 if (unlikely(!pmd_none(*vmf->pmd))) { 580 goto unlock_release; 581 } else { 582 pmd_t entry; 583 584 ret = check_stable_address_space(vma->vm_mm); 585 if (ret) 586 goto unlock_release; 587 588 /* Deliver the page fault to userland */ 589 if (userfaultfd_missing(vma)) { 590 int ret; 591 592 spin_unlock(vmf->ptl); 593 mem_cgroup_cancel_charge(page, memcg, true); 594 put_page(page); 595 pte_free(vma->vm_mm, pgtable); 596 ret = handle_userfault(vmf, VM_UFFD_MISSING); 597 VM_BUG_ON(ret & VM_FAULT_FALLBACK); 598 return ret; 599 } 600 601 entry = mk_huge_pmd(page, vma->vm_page_prot); 602 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 603 page_add_new_anon_rmap(page, vma, haddr, true); 604 mem_cgroup_commit_charge(page, memcg, false, true); 605 lru_cache_add_active_or_unevictable(page, vma); 606 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable); 607 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); 608 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); 609 atomic_long_inc(&vma->vm_mm->nr_ptes); 610 spin_unlock(vmf->ptl); 611 count_vm_event(THP_FAULT_ALLOC); 612 } 613 614 return 0; 615 unlock_release: 616 spin_unlock(vmf->ptl); 617 release: 618 if (pgtable) 619 pte_free(vma->vm_mm, pgtable); 620 mem_cgroup_cancel_charge(page, memcg, true); 621 put_page(page); 622 return ret; 623 624 } 625 626 /* 627 * always: directly stall for all thp allocations 628 * defer: wake kswapd and fail if not immediately available 629 * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise 630 * fail if not immediately available 631 * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately 632 * available 633 * never: never stall for any thp allocation 634 */ 635 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma) 636 { 637 const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE); 638 639 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) 640 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY); 641 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) 642 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM; 643 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags)) 644 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM : 645 __GFP_KSWAPD_RECLAIM); 646 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) 647 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM : 648 0); 649 return GFP_TRANSHUGE_LIGHT; 650 } 651 652 /* Caller must hold page table lock. */ 653 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, 654 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, 655 struct page *zero_page) 656 { 657 pmd_t entry; 658 if (!pmd_none(*pmd)) 659 return false; 660 entry = mk_pmd(zero_page, vma->vm_page_prot); 661 entry = pmd_mkhuge(entry); 662 if (pgtable) 663 pgtable_trans_huge_deposit(mm, pmd, pgtable); 664 set_pmd_at(mm, haddr, pmd, entry); 665 atomic_long_inc(&mm->nr_ptes); 666 return true; 667 } 668 669 int do_huge_pmd_anonymous_page(struct vm_fault *vmf) 670 { 671 struct vm_area_struct *vma = vmf->vma; 672 gfp_t gfp; 673 struct page *page; 674 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 675 676 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end) 677 return VM_FAULT_FALLBACK; 678 if (unlikely(anon_vma_prepare(vma))) 679 return VM_FAULT_OOM; 680 if (unlikely(khugepaged_enter(vma, vma->vm_flags))) 681 return VM_FAULT_OOM; 682 if (!(vmf->flags & FAULT_FLAG_WRITE) && 683 !mm_forbids_zeropage(vma->vm_mm) && 684 transparent_hugepage_use_zero_page()) { 685 pgtable_t pgtable; 686 struct page *zero_page; 687 bool set; 688 int ret; 689 pgtable = pte_alloc_one(vma->vm_mm, haddr); 690 if (unlikely(!pgtable)) 691 return VM_FAULT_OOM; 692 zero_page = mm_get_huge_zero_page(vma->vm_mm); 693 if (unlikely(!zero_page)) { 694 pte_free(vma->vm_mm, pgtable); 695 count_vm_event(THP_FAULT_FALLBACK); 696 return VM_FAULT_FALLBACK; 697 } 698 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 699 ret = 0; 700 set = false; 701 if (pmd_none(*vmf->pmd)) { 702 ret = check_stable_address_space(vma->vm_mm); 703 if (ret) { 704 spin_unlock(vmf->ptl); 705 } else if (userfaultfd_missing(vma)) { 706 spin_unlock(vmf->ptl); 707 ret = handle_userfault(vmf, VM_UFFD_MISSING); 708 VM_BUG_ON(ret & VM_FAULT_FALLBACK); 709 } else { 710 set_huge_zero_page(pgtable, vma->vm_mm, vma, 711 haddr, vmf->pmd, zero_page); 712 spin_unlock(vmf->ptl); 713 set = true; 714 } 715 } else 716 spin_unlock(vmf->ptl); 717 if (!set) 718 pte_free(vma->vm_mm, pgtable); 719 return ret; 720 } 721 gfp = alloc_hugepage_direct_gfpmask(vma); 722 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER); 723 if (unlikely(!page)) { 724 count_vm_event(THP_FAULT_FALLBACK); 725 return VM_FAULT_FALLBACK; 726 } 727 prep_transhuge_page(page); 728 return __do_huge_pmd_anonymous_page(vmf, page, gfp); 729 } 730 731 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, 732 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write, 733 pgtable_t pgtable) 734 { 735 struct mm_struct *mm = vma->vm_mm; 736 pmd_t entry; 737 spinlock_t *ptl; 738 739 ptl = pmd_lock(mm, pmd); 740 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot)); 741 if (pfn_t_devmap(pfn)) 742 entry = pmd_mkdevmap(entry); 743 if (write) { 744 entry = pmd_mkyoung(pmd_mkdirty(entry)); 745 entry = maybe_pmd_mkwrite(entry, vma); 746 } 747 748 if (pgtable) { 749 pgtable_trans_huge_deposit(mm, pmd, pgtable); 750 atomic_long_inc(&mm->nr_ptes); 751 } 752 753 set_pmd_at(mm, addr, pmd, entry); 754 update_mmu_cache_pmd(vma, addr, pmd); 755 spin_unlock(ptl); 756 } 757 758 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, 759 pmd_t *pmd, pfn_t pfn, bool write) 760 { 761 pgprot_t pgprot = vma->vm_page_prot; 762 pgtable_t pgtable = NULL; 763 /* 764 * If we had pmd_special, we could avoid all these restrictions, 765 * but we need to be consistent with PTEs and architectures that 766 * can't support a 'special' bit. 767 */ 768 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))); 769 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == 770 (VM_PFNMAP|VM_MIXEDMAP)); 771 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); 772 BUG_ON(!pfn_t_devmap(pfn)); 773 774 if (addr < vma->vm_start || addr >= vma->vm_end) 775 return VM_FAULT_SIGBUS; 776 777 if (arch_needs_pgtable_deposit()) { 778 pgtable = pte_alloc_one(vma->vm_mm, addr); 779 if (!pgtable) 780 return VM_FAULT_OOM; 781 } 782 783 track_pfn_insert(vma, &pgprot, pfn); 784 785 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable); 786 return VM_FAULT_NOPAGE; 787 } 788 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd); 789 790 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 791 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma) 792 { 793 if (likely(vma->vm_flags & VM_WRITE)) 794 pud = pud_mkwrite(pud); 795 return pud; 796 } 797 798 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr, 799 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write) 800 { 801 struct mm_struct *mm = vma->vm_mm; 802 pud_t entry; 803 spinlock_t *ptl; 804 805 ptl = pud_lock(mm, pud); 806 entry = pud_mkhuge(pfn_t_pud(pfn, prot)); 807 if (pfn_t_devmap(pfn)) 808 entry = pud_mkdevmap(entry); 809 if (write) { 810 entry = pud_mkyoung(pud_mkdirty(entry)); 811 entry = maybe_pud_mkwrite(entry, vma); 812 } 813 set_pud_at(mm, addr, pud, entry); 814 update_mmu_cache_pud(vma, addr, pud); 815 spin_unlock(ptl); 816 } 817 818 int vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr, 819 pud_t *pud, pfn_t pfn, bool write) 820 { 821 pgprot_t pgprot = vma->vm_page_prot; 822 /* 823 * If we had pud_special, we could avoid all these restrictions, 824 * but we need to be consistent with PTEs and architectures that 825 * can't support a 'special' bit. 826 */ 827 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))); 828 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == 829 (VM_PFNMAP|VM_MIXEDMAP)); 830 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); 831 BUG_ON(!pfn_t_devmap(pfn)); 832 833 if (addr < vma->vm_start || addr >= vma->vm_end) 834 return VM_FAULT_SIGBUS; 835 836 track_pfn_insert(vma, &pgprot, pfn); 837 838 insert_pfn_pud(vma, addr, pud, pfn, pgprot, write); 839 return VM_FAULT_NOPAGE; 840 } 841 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud); 842 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ 843 844 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr, 845 pmd_t *pmd) 846 { 847 pmd_t _pmd; 848 849 /* 850 * We should set the dirty bit only for FOLL_WRITE but for now 851 * the dirty bit in the pmd is meaningless. And if the dirty 852 * bit will become meaningful and we'll only set it with 853 * FOLL_WRITE, an atomic set_bit will be required on the pmd to 854 * set the young bit, instead of the current set_pmd_at. 855 */ 856 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); 857 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, 858 pmd, _pmd, 1)) 859 update_mmu_cache_pmd(vma, addr, pmd); 860 } 861 862 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, 863 pmd_t *pmd, int flags) 864 { 865 unsigned long pfn = pmd_pfn(*pmd); 866 struct mm_struct *mm = vma->vm_mm; 867 struct dev_pagemap *pgmap; 868 struct page *page; 869 870 assert_spin_locked(pmd_lockptr(mm, pmd)); 871 872 /* 873 * When we COW a devmap PMD entry, we split it into PTEs, so we should 874 * not be in this function with `flags & FOLL_COW` set. 875 */ 876 WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set"); 877 878 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 879 return NULL; 880 881 if (pmd_present(*pmd) && pmd_devmap(*pmd)) 882 /* pass */; 883 else 884 return NULL; 885 886 if (flags & FOLL_TOUCH) 887 touch_pmd(vma, addr, pmd); 888 889 /* 890 * device mapped pages can only be returned if the 891 * caller will manage the page reference count. 892 */ 893 if (!(flags & FOLL_GET)) 894 return ERR_PTR(-EEXIST); 895 896 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT; 897 pgmap = get_dev_pagemap(pfn, NULL); 898 if (!pgmap) 899 return ERR_PTR(-EFAULT); 900 page = pfn_to_page(pfn); 901 get_page(page); 902 put_dev_pagemap(pgmap); 903 904 return page; 905 } 906 907 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 908 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 909 struct vm_area_struct *vma) 910 { 911 spinlock_t *dst_ptl, *src_ptl; 912 struct page *src_page; 913 pmd_t pmd; 914 pgtable_t pgtable = NULL; 915 int ret = -ENOMEM; 916 917 /* Skip if can be re-fill on fault */ 918 if (!vma_is_anonymous(vma)) 919 return 0; 920 921 pgtable = pte_alloc_one(dst_mm, addr); 922 if (unlikely(!pgtable)) 923 goto out; 924 925 dst_ptl = pmd_lock(dst_mm, dst_pmd); 926 src_ptl = pmd_lockptr(src_mm, src_pmd); 927 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); 928 929 ret = -EAGAIN; 930 pmd = *src_pmd; 931 932 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 933 if (unlikely(is_swap_pmd(pmd))) { 934 swp_entry_t entry = pmd_to_swp_entry(pmd); 935 936 VM_BUG_ON(!is_pmd_migration_entry(pmd)); 937 if (is_write_migration_entry(entry)) { 938 make_migration_entry_read(&entry); 939 pmd = swp_entry_to_pmd(entry); 940 if (pmd_swp_soft_dirty(*src_pmd)) 941 pmd = pmd_swp_mksoft_dirty(pmd); 942 set_pmd_at(src_mm, addr, src_pmd, pmd); 943 } 944 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 945 ret = 0; 946 goto out_unlock; 947 } 948 #endif 949 950 if (unlikely(!pmd_trans_huge(pmd))) { 951 pte_free(dst_mm, pgtable); 952 goto out_unlock; 953 } 954 /* 955 * When page table lock is held, the huge zero pmd should not be 956 * under splitting since we don't split the page itself, only pmd to 957 * a page table. 958 */ 959 if (is_huge_zero_pmd(pmd)) { 960 struct page *zero_page; 961 /* 962 * get_huge_zero_page() will never allocate a new page here, 963 * since we already have a zero page to copy. It just takes a 964 * reference. 965 */ 966 zero_page = mm_get_huge_zero_page(dst_mm); 967 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, 968 zero_page); 969 ret = 0; 970 goto out_unlock; 971 } 972 973 src_page = pmd_page(pmd); 974 VM_BUG_ON_PAGE(!PageHead(src_page), src_page); 975 get_page(src_page); 976 page_dup_rmap(src_page, true); 977 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 978 atomic_long_inc(&dst_mm->nr_ptes); 979 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); 980 981 pmdp_set_wrprotect(src_mm, addr, src_pmd); 982 pmd = pmd_mkold(pmd_wrprotect(pmd)); 983 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 984 985 ret = 0; 986 out_unlock: 987 spin_unlock(src_ptl); 988 spin_unlock(dst_ptl); 989 out: 990 return ret; 991 } 992 993 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 994 static void touch_pud(struct vm_area_struct *vma, unsigned long addr, 995 pud_t *pud) 996 { 997 pud_t _pud; 998 999 /* 1000 * We should set the dirty bit only for FOLL_WRITE but for now 1001 * the dirty bit in the pud is meaningless. And if the dirty 1002 * bit will become meaningful and we'll only set it with 1003 * FOLL_WRITE, an atomic set_bit will be required on the pud to 1004 * set the young bit, instead of the current set_pud_at. 1005 */ 1006 _pud = pud_mkyoung(pud_mkdirty(*pud)); 1007 if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK, 1008 pud, _pud, 1)) 1009 update_mmu_cache_pud(vma, addr, pud); 1010 } 1011 1012 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr, 1013 pud_t *pud, int flags) 1014 { 1015 unsigned long pfn = pud_pfn(*pud); 1016 struct mm_struct *mm = vma->vm_mm; 1017 struct dev_pagemap *pgmap; 1018 struct page *page; 1019 1020 assert_spin_locked(pud_lockptr(mm, pud)); 1021 1022 if (flags & FOLL_WRITE && !pud_write(*pud)) 1023 return NULL; 1024 1025 if (pud_present(*pud) && pud_devmap(*pud)) 1026 /* pass */; 1027 else 1028 return NULL; 1029 1030 if (flags & FOLL_TOUCH) 1031 touch_pud(vma, addr, pud); 1032 1033 /* 1034 * device mapped pages can only be returned if the 1035 * caller will manage the page reference count. 1036 */ 1037 if (!(flags & FOLL_GET)) 1038 return ERR_PTR(-EEXIST); 1039 1040 pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT; 1041 pgmap = get_dev_pagemap(pfn, NULL); 1042 if (!pgmap) 1043 return ERR_PTR(-EFAULT); 1044 page = pfn_to_page(pfn); 1045 get_page(page); 1046 put_dev_pagemap(pgmap); 1047 1048 return page; 1049 } 1050 1051 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm, 1052 pud_t *dst_pud, pud_t *src_pud, unsigned long addr, 1053 struct vm_area_struct *vma) 1054 { 1055 spinlock_t *dst_ptl, *src_ptl; 1056 pud_t pud; 1057 int ret; 1058 1059 dst_ptl = pud_lock(dst_mm, dst_pud); 1060 src_ptl = pud_lockptr(src_mm, src_pud); 1061 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); 1062 1063 ret = -EAGAIN; 1064 pud = *src_pud; 1065 if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud))) 1066 goto out_unlock; 1067 1068 /* 1069 * When page table lock is held, the huge zero pud should not be 1070 * under splitting since we don't split the page itself, only pud to 1071 * a page table. 1072 */ 1073 if (is_huge_zero_pud(pud)) { 1074 /* No huge zero pud yet */ 1075 } 1076 1077 pudp_set_wrprotect(src_mm, addr, src_pud); 1078 pud = pud_mkold(pud_wrprotect(pud)); 1079 set_pud_at(dst_mm, addr, dst_pud, pud); 1080 1081 ret = 0; 1082 out_unlock: 1083 spin_unlock(src_ptl); 1084 spin_unlock(dst_ptl); 1085 return ret; 1086 } 1087 1088 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud) 1089 { 1090 pud_t entry; 1091 unsigned long haddr; 1092 bool write = vmf->flags & FAULT_FLAG_WRITE; 1093 1094 vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud); 1095 if (unlikely(!pud_same(*vmf->pud, orig_pud))) 1096 goto unlock; 1097 1098 entry = pud_mkyoung(orig_pud); 1099 if (write) 1100 entry = pud_mkdirty(entry); 1101 haddr = vmf->address & HPAGE_PUD_MASK; 1102 if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write)) 1103 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud); 1104 1105 unlock: 1106 spin_unlock(vmf->ptl); 1107 } 1108 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ 1109 1110 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd) 1111 { 1112 pmd_t entry; 1113 unsigned long haddr; 1114 bool write = vmf->flags & FAULT_FLAG_WRITE; 1115 1116 vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); 1117 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) 1118 goto unlock; 1119 1120 entry = pmd_mkyoung(orig_pmd); 1121 if (write) 1122 entry = pmd_mkdirty(entry); 1123 haddr = vmf->address & HPAGE_PMD_MASK; 1124 if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write)) 1125 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd); 1126 1127 unlock: 1128 spin_unlock(vmf->ptl); 1129 } 1130 1131 static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd, 1132 struct page *page) 1133 { 1134 struct vm_area_struct *vma = vmf->vma; 1135 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 1136 struct mem_cgroup *memcg; 1137 pgtable_t pgtable; 1138 pmd_t _pmd; 1139 int ret = 0, i; 1140 struct page **pages; 1141 unsigned long mmun_start; /* For mmu_notifiers */ 1142 unsigned long mmun_end; /* For mmu_notifiers */ 1143 1144 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, 1145 GFP_KERNEL); 1146 if (unlikely(!pages)) { 1147 ret |= VM_FAULT_OOM; 1148 goto out; 1149 } 1150 1151 for (i = 0; i < HPAGE_PMD_NR; i++) { 1152 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma, 1153 vmf->address, page_to_nid(page)); 1154 if (unlikely(!pages[i] || 1155 mem_cgroup_try_charge(pages[i], vma->vm_mm, 1156 GFP_KERNEL, &memcg, false))) { 1157 if (pages[i]) 1158 put_page(pages[i]); 1159 while (--i >= 0) { 1160 memcg = (void *)page_private(pages[i]); 1161 set_page_private(pages[i], 0); 1162 mem_cgroup_cancel_charge(pages[i], memcg, 1163 false); 1164 put_page(pages[i]); 1165 } 1166 kfree(pages); 1167 ret |= VM_FAULT_OOM; 1168 goto out; 1169 } 1170 set_page_private(pages[i], (unsigned long)memcg); 1171 } 1172 1173 for (i = 0; i < HPAGE_PMD_NR; i++) { 1174 copy_user_highpage(pages[i], page + i, 1175 haddr + PAGE_SIZE * i, vma); 1176 __SetPageUptodate(pages[i]); 1177 cond_resched(); 1178 } 1179 1180 mmun_start = haddr; 1181 mmun_end = haddr + HPAGE_PMD_SIZE; 1182 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end); 1183 1184 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 1185 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) 1186 goto out_free_pages; 1187 VM_BUG_ON_PAGE(!PageHead(page), page); 1188 1189 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd); 1190 /* leave pmd empty until pte is filled */ 1191 1192 pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd); 1193 pmd_populate(vma->vm_mm, &_pmd, pgtable); 1194 1195 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1196 pte_t entry; 1197 entry = mk_pte(pages[i], vma->vm_page_prot); 1198 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1199 memcg = (void *)page_private(pages[i]); 1200 set_page_private(pages[i], 0); 1201 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false); 1202 mem_cgroup_commit_charge(pages[i], memcg, false, false); 1203 lru_cache_add_active_or_unevictable(pages[i], vma); 1204 vmf->pte = pte_offset_map(&_pmd, haddr); 1205 VM_BUG_ON(!pte_none(*vmf->pte)); 1206 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry); 1207 pte_unmap(vmf->pte); 1208 } 1209 kfree(pages); 1210 1211 smp_wmb(); /* make pte visible before pmd */ 1212 pmd_populate(vma->vm_mm, vmf->pmd, pgtable); 1213 page_remove_rmap(page, true); 1214 spin_unlock(vmf->ptl); 1215 1216 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end); 1217 1218 ret |= VM_FAULT_WRITE; 1219 put_page(page); 1220 1221 out: 1222 return ret; 1223 1224 out_free_pages: 1225 spin_unlock(vmf->ptl); 1226 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end); 1227 for (i = 0; i < HPAGE_PMD_NR; i++) { 1228 memcg = (void *)page_private(pages[i]); 1229 set_page_private(pages[i], 0); 1230 mem_cgroup_cancel_charge(pages[i], memcg, false); 1231 put_page(pages[i]); 1232 } 1233 kfree(pages); 1234 goto out; 1235 } 1236 1237 int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd) 1238 { 1239 struct vm_area_struct *vma = vmf->vma; 1240 struct page *page = NULL, *new_page; 1241 struct mem_cgroup *memcg; 1242 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 1243 unsigned long mmun_start; /* For mmu_notifiers */ 1244 unsigned long mmun_end; /* For mmu_notifiers */ 1245 gfp_t huge_gfp; /* for allocation and charge */ 1246 int ret = 0; 1247 1248 vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd); 1249 VM_BUG_ON_VMA(!vma->anon_vma, vma); 1250 if (is_huge_zero_pmd(orig_pmd)) 1251 goto alloc; 1252 spin_lock(vmf->ptl); 1253 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) 1254 goto out_unlock; 1255 1256 page = pmd_page(orig_pmd); 1257 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); 1258 /* 1259 * We can only reuse the page if nobody else maps the huge page or it's 1260 * part. 1261 */ 1262 if (!trylock_page(page)) { 1263 get_page(page); 1264 spin_unlock(vmf->ptl); 1265 lock_page(page); 1266 spin_lock(vmf->ptl); 1267 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { 1268 unlock_page(page); 1269 put_page(page); 1270 goto out_unlock; 1271 } 1272 put_page(page); 1273 } 1274 if (reuse_swap_page(page, NULL)) { 1275 pmd_t entry; 1276 entry = pmd_mkyoung(orig_pmd); 1277 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1278 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1)) 1279 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 1280 ret |= VM_FAULT_WRITE; 1281 unlock_page(page); 1282 goto out_unlock; 1283 } 1284 unlock_page(page); 1285 get_page(page); 1286 spin_unlock(vmf->ptl); 1287 alloc: 1288 if (transparent_hugepage_enabled(vma) && 1289 !transparent_hugepage_debug_cow()) { 1290 huge_gfp = alloc_hugepage_direct_gfpmask(vma); 1291 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER); 1292 } else 1293 new_page = NULL; 1294 1295 if (likely(new_page)) { 1296 prep_transhuge_page(new_page); 1297 } else { 1298 if (!page) { 1299 split_huge_pmd(vma, vmf->pmd, vmf->address); 1300 ret |= VM_FAULT_FALLBACK; 1301 } else { 1302 ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page); 1303 if (ret & VM_FAULT_OOM) { 1304 split_huge_pmd(vma, vmf->pmd, vmf->address); 1305 ret |= VM_FAULT_FALLBACK; 1306 } 1307 put_page(page); 1308 } 1309 count_vm_event(THP_FAULT_FALLBACK); 1310 goto out; 1311 } 1312 1313 if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm, 1314 huge_gfp, &memcg, true))) { 1315 put_page(new_page); 1316 split_huge_pmd(vma, vmf->pmd, vmf->address); 1317 if (page) 1318 put_page(page); 1319 ret |= VM_FAULT_FALLBACK; 1320 count_vm_event(THP_FAULT_FALLBACK); 1321 goto out; 1322 } 1323 1324 count_vm_event(THP_FAULT_ALLOC); 1325 1326 if (!page) 1327 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR); 1328 else 1329 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); 1330 __SetPageUptodate(new_page); 1331 1332 mmun_start = haddr; 1333 mmun_end = haddr + HPAGE_PMD_SIZE; 1334 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end); 1335 1336 spin_lock(vmf->ptl); 1337 if (page) 1338 put_page(page); 1339 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { 1340 spin_unlock(vmf->ptl); 1341 mem_cgroup_cancel_charge(new_page, memcg, true); 1342 put_page(new_page); 1343 goto out_mn; 1344 } else { 1345 pmd_t entry; 1346 entry = mk_huge_pmd(new_page, vma->vm_page_prot); 1347 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1348 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd); 1349 page_add_new_anon_rmap(new_page, vma, haddr, true); 1350 mem_cgroup_commit_charge(new_page, memcg, false, true); 1351 lru_cache_add_active_or_unevictable(new_page, vma); 1352 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); 1353 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 1354 if (!page) { 1355 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); 1356 } else { 1357 VM_BUG_ON_PAGE(!PageHead(page), page); 1358 page_remove_rmap(page, true); 1359 put_page(page); 1360 } 1361 ret |= VM_FAULT_WRITE; 1362 } 1363 spin_unlock(vmf->ptl); 1364 out_mn: 1365 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end); 1366 out: 1367 return ret; 1368 out_unlock: 1369 spin_unlock(vmf->ptl); 1370 return ret; 1371 } 1372 1373 /* 1374 * FOLL_FORCE can write to even unwritable pmd's, but only 1375 * after we've gone through a COW cycle and they are dirty. 1376 */ 1377 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags) 1378 { 1379 return pmd_write(pmd) || 1380 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd)); 1381 } 1382 1383 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1384 unsigned long addr, 1385 pmd_t *pmd, 1386 unsigned int flags) 1387 { 1388 struct mm_struct *mm = vma->vm_mm; 1389 struct page *page = NULL; 1390 1391 assert_spin_locked(pmd_lockptr(mm, pmd)); 1392 1393 if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags)) 1394 goto out; 1395 1396 /* Avoid dumping huge zero page */ 1397 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) 1398 return ERR_PTR(-EFAULT); 1399 1400 /* Full NUMA hinting faults to serialise migration in fault paths */ 1401 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) 1402 goto out; 1403 1404 page = pmd_page(*pmd); 1405 VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page); 1406 if (flags & FOLL_TOUCH) 1407 touch_pmd(vma, addr, pmd); 1408 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 1409 /* 1410 * We don't mlock() pte-mapped THPs. This way we can avoid 1411 * leaking mlocked pages into non-VM_LOCKED VMAs. 1412 * 1413 * For anon THP: 1414 * 1415 * In most cases the pmd is the only mapping of the page as we 1416 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for 1417 * writable private mappings in populate_vma_page_range(). 1418 * 1419 * The only scenario when we have the page shared here is if we 1420 * mlocking read-only mapping shared over fork(). We skip 1421 * mlocking such pages. 1422 * 1423 * For file THP: 1424 * 1425 * We can expect PageDoubleMap() to be stable under page lock: 1426 * for file pages we set it in page_add_file_rmap(), which 1427 * requires page to be locked. 1428 */ 1429 1430 if (PageAnon(page) && compound_mapcount(page) != 1) 1431 goto skip_mlock; 1432 if (PageDoubleMap(page) || !page->mapping) 1433 goto skip_mlock; 1434 if (!trylock_page(page)) 1435 goto skip_mlock; 1436 lru_add_drain(); 1437 if (page->mapping && !PageDoubleMap(page)) 1438 mlock_vma_page(page); 1439 unlock_page(page); 1440 } 1441 skip_mlock: 1442 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1443 VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page); 1444 if (flags & FOLL_GET) 1445 get_page(page); 1446 1447 out: 1448 return page; 1449 } 1450 1451 /* NUMA hinting page fault entry point for trans huge pmds */ 1452 int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) 1453 { 1454 struct vm_area_struct *vma = vmf->vma; 1455 struct anon_vma *anon_vma = NULL; 1456 struct page *page; 1457 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 1458 int page_nid = -1, this_nid = numa_node_id(); 1459 int target_nid, last_cpupid = -1; 1460 bool page_locked; 1461 bool migrated = false; 1462 bool was_writable; 1463 int flags = 0; 1464 1465 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 1466 if (unlikely(!pmd_same(pmd, *vmf->pmd))) 1467 goto out_unlock; 1468 1469 /* 1470 * If there are potential migrations, wait for completion and retry 1471 * without disrupting NUMA hinting information. Do not relock and 1472 * check_same as the page may no longer be mapped. 1473 */ 1474 if (unlikely(pmd_trans_migrating(*vmf->pmd))) { 1475 page = pmd_page(*vmf->pmd); 1476 if (!get_page_unless_zero(page)) 1477 goto out_unlock; 1478 spin_unlock(vmf->ptl); 1479 wait_on_page_locked(page); 1480 put_page(page); 1481 goto out; 1482 } 1483 1484 page = pmd_page(pmd); 1485 BUG_ON(is_huge_zero_page(page)); 1486 page_nid = page_to_nid(page); 1487 last_cpupid = page_cpupid_last(page); 1488 count_vm_numa_event(NUMA_HINT_FAULTS); 1489 if (page_nid == this_nid) { 1490 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); 1491 flags |= TNF_FAULT_LOCAL; 1492 } 1493 1494 /* See similar comment in do_numa_page for explanation */ 1495 if (!pmd_savedwrite(pmd)) 1496 flags |= TNF_NO_GROUP; 1497 1498 /* 1499 * Acquire the page lock to serialise THP migrations but avoid dropping 1500 * page_table_lock if at all possible 1501 */ 1502 page_locked = trylock_page(page); 1503 target_nid = mpol_misplaced(page, vma, haddr); 1504 if (target_nid == -1) { 1505 /* If the page was locked, there are no parallel migrations */ 1506 if (page_locked) 1507 goto clear_pmdnuma; 1508 } 1509 1510 /* Migration could have started since the pmd_trans_migrating check */ 1511 if (!page_locked) { 1512 page_nid = -1; 1513 if (!get_page_unless_zero(page)) 1514 goto out_unlock; 1515 spin_unlock(vmf->ptl); 1516 wait_on_page_locked(page); 1517 put_page(page); 1518 goto out; 1519 } 1520 1521 /* 1522 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma 1523 * to serialises splits 1524 */ 1525 get_page(page); 1526 spin_unlock(vmf->ptl); 1527 anon_vma = page_lock_anon_vma_read(page); 1528 1529 /* Confirm the PMD did not change while page_table_lock was released */ 1530 spin_lock(vmf->ptl); 1531 if (unlikely(!pmd_same(pmd, *vmf->pmd))) { 1532 unlock_page(page); 1533 put_page(page); 1534 page_nid = -1; 1535 goto out_unlock; 1536 } 1537 1538 /* Bail if we fail to protect against THP splits for any reason */ 1539 if (unlikely(!anon_vma)) { 1540 put_page(page); 1541 page_nid = -1; 1542 goto clear_pmdnuma; 1543 } 1544 1545 /* 1546 * Since we took the NUMA fault, we must have observed the !accessible 1547 * bit. Make sure all other CPUs agree with that, to avoid them 1548 * modifying the page we're about to migrate. 1549 * 1550 * Must be done under PTL such that we'll observe the relevant 1551 * inc_tlb_flush_pending(). 1552 * 1553 * We are not sure a pending tlb flush here is for a huge page 1554 * mapping or not. Hence use the tlb range variant 1555 */ 1556 if (mm_tlb_flush_pending(vma->vm_mm)) 1557 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE); 1558 1559 /* 1560 * Migrate the THP to the requested node, returns with page unlocked 1561 * and access rights restored. 1562 */ 1563 spin_unlock(vmf->ptl); 1564 1565 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma, 1566 vmf->pmd, pmd, vmf->address, page, target_nid); 1567 if (migrated) { 1568 flags |= TNF_MIGRATED; 1569 page_nid = target_nid; 1570 } else 1571 flags |= TNF_MIGRATE_FAIL; 1572 1573 goto out; 1574 clear_pmdnuma: 1575 BUG_ON(!PageLocked(page)); 1576 was_writable = pmd_savedwrite(pmd); 1577 pmd = pmd_modify(pmd, vma->vm_page_prot); 1578 pmd = pmd_mkyoung(pmd); 1579 if (was_writable) 1580 pmd = pmd_mkwrite(pmd); 1581 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd); 1582 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 1583 unlock_page(page); 1584 out_unlock: 1585 spin_unlock(vmf->ptl); 1586 1587 out: 1588 if (anon_vma) 1589 page_unlock_anon_vma_read(anon_vma); 1590 1591 if (page_nid != -1) 1592 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, 1593 flags); 1594 1595 return 0; 1596 } 1597 1598 /* 1599 * Return true if we do MADV_FREE successfully on entire pmd page. 1600 * Otherwise, return false. 1601 */ 1602 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1603 pmd_t *pmd, unsigned long addr, unsigned long next) 1604 { 1605 spinlock_t *ptl; 1606 pmd_t orig_pmd; 1607 struct page *page; 1608 struct mm_struct *mm = tlb->mm; 1609 bool ret = false; 1610 1611 tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE); 1612 1613 ptl = pmd_trans_huge_lock(pmd, vma); 1614 if (!ptl) 1615 goto out_unlocked; 1616 1617 orig_pmd = *pmd; 1618 if (is_huge_zero_pmd(orig_pmd)) 1619 goto out; 1620 1621 if (unlikely(!pmd_present(orig_pmd))) { 1622 VM_BUG_ON(thp_migration_supported() && 1623 !is_pmd_migration_entry(orig_pmd)); 1624 goto out; 1625 } 1626 1627 page = pmd_page(orig_pmd); 1628 /* 1629 * If other processes are mapping this page, we couldn't discard 1630 * the page unless they all do MADV_FREE so let's skip the page. 1631 */ 1632 if (page_mapcount(page) != 1) 1633 goto out; 1634 1635 if (!trylock_page(page)) 1636 goto out; 1637 1638 /* 1639 * If user want to discard part-pages of THP, split it so MADV_FREE 1640 * will deactivate only them. 1641 */ 1642 if (next - addr != HPAGE_PMD_SIZE) { 1643 get_page(page); 1644 spin_unlock(ptl); 1645 split_huge_page(page); 1646 unlock_page(page); 1647 put_page(page); 1648 goto out_unlocked; 1649 } 1650 1651 if (PageDirty(page)) 1652 ClearPageDirty(page); 1653 unlock_page(page); 1654 1655 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { 1656 pmdp_invalidate(vma, addr, pmd); 1657 orig_pmd = pmd_mkold(orig_pmd); 1658 orig_pmd = pmd_mkclean(orig_pmd); 1659 1660 set_pmd_at(mm, addr, pmd, orig_pmd); 1661 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1662 } 1663 1664 mark_page_lazyfree(page); 1665 ret = true; 1666 out: 1667 spin_unlock(ptl); 1668 out_unlocked: 1669 return ret; 1670 } 1671 1672 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd) 1673 { 1674 pgtable_t pgtable; 1675 1676 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1677 pte_free(mm, pgtable); 1678 atomic_long_dec(&mm->nr_ptes); 1679 } 1680 1681 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1682 pmd_t *pmd, unsigned long addr) 1683 { 1684 pmd_t orig_pmd; 1685 spinlock_t *ptl; 1686 1687 tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE); 1688 1689 ptl = __pmd_trans_huge_lock(pmd, vma); 1690 if (!ptl) 1691 return 0; 1692 /* 1693 * For architectures like ppc64 we look at deposited pgtable 1694 * when calling pmdp_huge_get_and_clear. So do the 1695 * pgtable_trans_huge_withdraw after finishing pmdp related 1696 * operations. 1697 */ 1698 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, 1699 tlb->fullmm); 1700 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1701 if (vma_is_dax(vma)) { 1702 if (arch_needs_pgtable_deposit()) 1703 zap_deposited_table(tlb->mm, pmd); 1704 spin_unlock(ptl); 1705 if (is_huge_zero_pmd(orig_pmd)) 1706 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); 1707 } else if (is_huge_zero_pmd(orig_pmd)) { 1708 zap_deposited_table(tlb->mm, pmd); 1709 spin_unlock(ptl); 1710 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); 1711 } else { 1712 struct page *page = NULL; 1713 int flush_needed = 1; 1714 1715 if (pmd_present(orig_pmd)) { 1716 page = pmd_page(orig_pmd); 1717 page_remove_rmap(page, true); 1718 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); 1719 VM_BUG_ON_PAGE(!PageHead(page), page); 1720 } else if (thp_migration_supported()) { 1721 swp_entry_t entry; 1722 1723 VM_BUG_ON(!is_pmd_migration_entry(orig_pmd)); 1724 entry = pmd_to_swp_entry(orig_pmd); 1725 page = pfn_to_page(swp_offset(entry)); 1726 flush_needed = 0; 1727 } else 1728 WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!"); 1729 1730 if (PageAnon(page)) { 1731 zap_deposited_table(tlb->mm, pmd); 1732 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1733 } else { 1734 if (arch_needs_pgtable_deposit()) 1735 zap_deposited_table(tlb->mm, pmd); 1736 add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR); 1737 } 1738 1739 spin_unlock(ptl); 1740 if (flush_needed) 1741 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE); 1742 } 1743 return 1; 1744 } 1745 1746 #ifndef pmd_move_must_withdraw 1747 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl, 1748 spinlock_t *old_pmd_ptl, 1749 struct vm_area_struct *vma) 1750 { 1751 /* 1752 * With split pmd lock we also need to move preallocated 1753 * PTE page table if new_pmd is on different PMD page table. 1754 * 1755 * We also don't deposit and withdraw tables for file pages. 1756 */ 1757 return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma); 1758 } 1759 #endif 1760 1761 static pmd_t move_soft_dirty_pmd(pmd_t pmd) 1762 { 1763 #ifdef CONFIG_MEM_SOFT_DIRTY 1764 if (unlikely(is_pmd_migration_entry(pmd))) 1765 pmd = pmd_swp_mksoft_dirty(pmd); 1766 else if (pmd_present(pmd)) 1767 pmd = pmd_mksoft_dirty(pmd); 1768 #endif 1769 return pmd; 1770 } 1771 1772 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr, 1773 unsigned long new_addr, unsigned long old_end, 1774 pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush) 1775 { 1776 spinlock_t *old_ptl, *new_ptl; 1777 pmd_t pmd; 1778 struct mm_struct *mm = vma->vm_mm; 1779 bool force_flush = false; 1780 1781 if ((old_addr & ~HPAGE_PMD_MASK) || 1782 (new_addr & ~HPAGE_PMD_MASK) || 1783 old_end - old_addr < HPAGE_PMD_SIZE) 1784 return false; 1785 1786 /* 1787 * The destination pmd shouldn't be established, free_pgtables() 1788 * should have release it. 1789 */ 1790 if (WARN_ON(!pmd_none(*new_pmd))) { 1791 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1792 return false; 1793 } 1794 1795 /* 1796 * We don't have to worry about the ordering of src and dst 1797 * ptlocks because exclusive mmap_sem prevents deadlock. 1798 */ 1799 old_ptl = __pmd_trans_huge_lock(old_pmd, vma); 1800 if (old_ptl) { 1801 new_ptl = pmd_lockptr(mm, new_pmd); 1802 if (new_ptl != old_ptl) 1803 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 1804 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd); 1805 if (pmd_present(pmd) && pmd_dirty(pmd)) 1806 force_flush = true; 1807 VM_BUG_ON(!pmd_none(*new_pmd)); 1808 1809 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) { 1810 pgtable_t pgtable; 1811 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); 1812 pgtable_trans_huge_deposit(mm, new_pmd, pgtable); 1813 } 1814 pmd = move_soft_dirty_pmd(pmd); 1815 set_pmd_at(mm, new_addr, new_pmd, pmd); 1816 if (new_ptl != old_ptl) 1817 spin_unlock(new_ptl); 1818 if (force_flush) 1819 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE); 1820 else 1821 *need_flush = true; 1822 spin_unlock(old_ptl); 1823 return true; 1824 } 1825 return false; 1826 } 1827 1828 /* 1829 * Returns 1830 * - 0 if PMD could not be locked 1831 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary 1832 * - HPAGE_PMD_NR is protections changed and TLB flush necessary 1833 */ 1834 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1835 unsigned long addr, pgprot_t newprot, int prot_numa) 1836 { 1837 struct mm_struct *mm = vma->vm_mm; 1838 spinlock_t *ptl; 1839 pmd_t entry; 1840 bool preserve_write; 1841 int ret; 1842 1843 ptl = __pmd_trans_huge_lock(pmd, vma); 1844 if (!ptl) 1845 return 0; 1846 1847 preserve_write = prot_numa && pmd_write(*pmd); 1848 ret = 1; 1849 1850 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 1851 if (is_swap_pmd(*pmd)) { 1852 swp_entry_t entry = pmd_to_swp_entry(*pmd); 1853 1854 VM_BUG_ON(!is_pmd_migration_entry(*pmd)); 1855 if (is_write_migration_entry(entry)) { 1856 pmd_t newpmd; 1857 /* 1858 * A protection check is difficult so 1859 * just be safe and disable write 1860 */ 1861 make_migration_entry_read(&entry); 1862 newpmd = swp_entry_to_pmd(entry); 1863 if (pmd_swp_soft_dirty(*pmd)) 1864 newpmd = pmd_swp_mksoft_dirty(newpmd); 1865 set_pmd_at(mm, addr, pmd, newpmd); 1866 } 1867 goto unlock; 1868 } 1869 #endif 1870 1871 /* 1872 * Avoid trapping faults against the zero page. The read-only 1873 * data is likely to be read-cached on the local CPU and 1874 * local/remote hits to the zero page are not interesting. 1875 */ 1876 if (prot_numa && is_huge_zero_pmd(*pmd)) 1877 goto unlock; 1878 1879 if (prot_numa && pmd_protnone(*pmd)) 1880 goto unlock; 1881 1882 /* 1883 * In case prot_numa, we are under down_read(mmap_sem). It's critical 1884 * to not clear pmd intermittently to avoid race with MADV_DONTNEED 1885 * which is also under down_read(mmap_sem): 1886 * 1887 * CPU0: CPU1: 1888 * change_huge_pmd(prot_numa=1) 1889 * pmdp_huge_get_and_clear_notify() 1890 * madvise_dontneed() 1891 * zap_pmd_range() 1892 * pmd_trans_huge(*pmd) == 0 (without ptl) 1893 * // skip the pmd 1894 * set_pmd_at(); 1895 * // pmd is re-established 1896 * 1897 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it 1898 * which may break userspace. 1899 * 1900 * pmdp_invalidate() is required to make sure we don't miss 1901 * dirty/young flags set by hardware. 1902 */ 1903 entry = *pmd; 1904 pmdp_invalidate(vma, addr, pmd); 1905 1906 /* 1907 * Recover dirty/young flags. It relies on pmdp_invalidate to not 1908 * corrupt them. 1909 */ 1910 if (pmd_dirty(*pmd)) 1911 entry = pmd_mkdirty(entry); 1912 if (pmd_young(*pmd)) 1913 entry = pmd_mkyoung(entry); 1914 1915 entry = pmd_modify(entry, newprot); 1916 if (preserve_write) 1917 entry = pmd_mk_savedwrite(entry); 1918 ret = HPAGE_PMD_NR; 1919 set_pmd_at(mm, addr, pmd, entry); 1920 BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry)); 1921 unlock: 1922 spin_unlock(ptl); 1923 return ret; 1924 } 1925 1926 /* 1927 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise. 1928 * 1929 * Note that if it returns page table lock pointer, this routine returns without 1930 * unlocking page table lock. So callers must unlock it. 1931 */ 1932 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) 1933 { 1934 spinlock_t *ptl; 1935 ptl = pmd_lock(vma->vm_mm, pmd); 1936 if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || 1937 pmd_devmap(*pmd))) 1938 return ptl; 1939 spin_unlock(ptl); 1940 return NULL; 1941 } 1942 1943 /* 1944 * Returns true if a given pud maps a thp, false otherwise. 1945 * 1946 * Note that if it returns true, this routine returns without unlocking page 1947 * table lock. So callers must unlock it. 1948 */ 1949 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma) 1950 { 1951 spinlock_t *ptl; 1952 1953 ptl = pud_lock(vma->vm_mm, pud); 1954 if (likely(pud_trans_huge(*pud) || pud_devmap(*pud))) 1955 return ptl; 1956 spin_unlock(ptl); 1957 return NULL; 1958 } 1959 1960 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 1961 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma, 1962 pud_t *pud, unsigned long addr) 1963 { 1964 pud_t orig_pud; 1965 spinlock_t *ptl; 1966 1967 ptl = __pud_trans_huge_lock(pud, vma); 1968 if (!ptl) 1969 return 0; 1970 /* 1971 * For architectures like ppc64 we look at deposited pgtable 1972 * when calling pudp_huge_get_and_clear. So do the 1973 * pgtable_trans_huge_withdraw after finishing pudp related 1974 * operations. 1975 */ 1976 orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud, 1977 tlb->fullmm); 1978 tlb_remove_pud_tlb_entry(tlb, pud, addr); 1979 if (vma_is_dax(vma)) { 1980 spin_unlock(ptl); 1981 /* No zero page support yet */ 1982 } else { 1983 /* No support for anonymous PUD pages yet */ 1984 BUG(); 1985 } 1986 return 1; 1987 } 1988 1989 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud, 1990 unsigned long haddr) 1991 { 1992 VM_BUG_ON(haddr & ~HPAGE_PUD_MASK); 1993 VM_BUG_ON_VMA(vma->vm_start > haddr, vma); 1994 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma); 1995 VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud)); 1996 1997 count_vm_event(THP_SPLIT_PUD); 1998 1999 pudp_huge_clear_flush_notify(vma, haddr, pud); 2000 } 2001 2002 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud, 2003 unsigned long address) 2004 { 2005 spinlock_t *ptl; 2006 struct mm_struct *mm = vma->vm_mm; 2007 unsigned long haddr = address & HPAGE_PUD_MASK; 2008 2009 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE); 2010 ptl = pud_lock(mm, pud); 2011 if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud))) 2012 goto out; 2013 __split_huge_pud_locked(vma, pud, haddr); 2014 2015 out: 2016 spin_unlock(ptl); 2017 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PUD_SIZE); 2018 } 2019 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ 2020 2021 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2022 unsigned long haddr, pmd_t *pmd) 2023 { 2024 struct mm_struct *mm = vma->vm_mm; 2025 pgtable_t pgtable; 2026 pmd_t _pmd; 2027 int i; 2028 2029 /* leave pmd empty until pte is filled */ 2030 pmdp_huge_clear_flush_notify(vma, haddr, pmd); 2031 2032 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2033 pmd_populate(mm, &_pmd, pgtable); 2034 2035 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2036 pte_t *pte, entry; 2037 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2038 entry = pte_mkspecial(entry); 2039 pte = pte_offset_map(&_pmd, haddr); 2040 VM_BUG_ON(!pte_none(*pte)); 2041 set_pte_at(mm, haddr, pte, entry); 2042 pte_unmap(pte); 2043 } 2044 smp_wmb(); /* make pte visible before pmd */ 2045 pmd_populate(mm, pmd, pgtable); 2046 } 2047 2048 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 2049 unsigned long haddr, bool freeze) 2050 { 2051 struct mm_struct *mm = vma->vm_mm; 2052 struct page *page; 2053 pgtable_t pgtable; 2054 pmd_t _pmd; 2055 bool young, write, dirty, soft_dirty, pmd_migration = false; 2056 unsigned long addr; 2057 int i; 2058 2059 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK); 2060 VM_BUG_ON_VMA(vma->vm_start > haddr, vma); 2061 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma); 2062 VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd) 2063 && !pmd_devmap(*pmd)); 2064 2065 count_vm_event(THP_SPLIT_PMD); 2066 2067 if (!vma_is_anonymous(vma)) { 2068 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd); 2069 /* 2070 * We are going to unmap this huge page. So 2071 * just go ahead and zap it 2072 */ 2073 if (arch_needs_pgtable_deposit()) 2074 zap_deposited_table(mm, pmd); 2075 if (vma_is_dax(vma)) 2076 return; 2077 page = pmd_page(_pmd); 2078 if (!PageReferenced(page) && pmd_young(_pmd)) 2079 SetPageReferenced(page); 2080 page_remove_rmap(page, true); 2081 put_page(page); 2082 add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR); 2083 return; 2084 } else if (is_huge_zero_pmd(*pmd)) { 2085 return __split_huge_zero_page_pmd(vma, haddr, pmd); 2086 } 2087 2088 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 2089 pmd_migration = is_pmd_migration_entry(*pmd); 2090 if (pmd_migration) { 2091 swp_entry_t entry; 2092 2093 entry = pmd_to_swp_entry(*pmd); 2094 page = pfn_to_page(swp_offset(entry)); 2095 } else 2096 #endif 2097 page = pmd_page(*pmd); 2098 VM_BUG_ON_PAGE(!page_count(page), page); 2099 page_ref_add(page, HPAGE_PMD_NR - 1); 2100 write = pmd_write(*pmd); 2101 young = pmd_young(*pmd); 2102 dirty = pmd_dirty(*pmd); 2103 soft_dirty = pmd_soft_dirty(*pmd); 2104 2105 pmdp_huge_split_prepare(vma, haddr, pmd); 2106 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2107 pmd_populate(mm, &_pmd, pgtable); 2108 2109 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { 2110 pte_t entry, *pte; 2111 /* 2112 * Note that NUMA hinting access restrictions are not 2113 * transferred to avoid any possibility of altering 2114 * permissions across VMAs. 2115 */ 2116 if (freeze || pmd_migration) { 2117 swp_entry_t swp_entry; 2118 swp_entry = make_migration_entry(page + i, write); 2119 entry = swp_entry_to_pte(swp_entry); 2120 if (soft_dirty) 2121 entry = pte_swp_mksoft_dirty(entry); 2122 } else { 2123 entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot)); 2124 entry = maybe_mkwrite(entry, vma); 2125 if (!write) 2126 entry = pte_wrprotect(entry); 2127 if (!young) 2128 entry = pte_mkold(entry); 2129 if (soft_dirty) 2130 entry = pte_mksoft_dirty(entry); 2131 } 2132 if (dirty) 2133 SetPageDirty(page + i); 2134 pte = pte_offset_map(&_pmd, addr); 2135 BUG_ON(!pte_none(*pte)); 2136 set_pte_at(mm, addr, pte, entry); 2137 atomic_inc(&page[i]._mapcount); 2138 pte_unmap(pte); 2139 } 2140 2141 /* 2142 * Set PG_double_map before dropping compound_mapcount to avoid 2143 * false-negative page_mapped(). 2144 */ 2145 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) { 2146 for (i = 0; i < HPAGE_PMD_NR; i++) 2147 atomic_inc(&page[i]._mapcount); 2148 } 2149 2150 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { 2151 /* Last compound_mapcount is gone. */ 2152 __dec_node_page_state(page, NR_ANON_THPS); 2153 if (TestClearPageDoubleMap(page)) { 2154 /* No need in mapcount reference anymore */ 2155 for (i = 0; i < HPAGE_PMD_NR; i++) 2156 atomic_dec(&page[i]._mapcount); 2157 } 2158 } 2159 2160 smp_wmb(); /* make pte visible before pmd */ 2161 /* 2162 * Up to this point the pmd is present and huge and userland has the 2163 * whole access to the hugepage during the split (which happens in 2164 * place). If we overwrite the pmd with the not-huge version pointing 2165 * to the pte here (which of course we could if all CPUs were bug 2166 * free), userland could trigger a small page size TLB miss on the 2167 * small sized TLB while the hugepage TLB entry is still established in 2168 * the huge TLB. Some CPU doesn't like that. 2169 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum 2170 * 383 on page 93. Intel should be safe but is also warns that it's 2171 * only safe if the permission and cache attributes of the two entries 2172 * loaded in the two TLB is identical (which should be the case here). 2173 * But it is generally safer to never allow small and huge TLB entries 2174 * for the same virtual address to be loaded simultaneously. So instead 2175 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the 2176 * current pmd notpresent (atomically because here the pmd_trans_huge 2177 * and pmd_trans_splitting must remain set at all times on the pmd 2178 * until the split is complete for this pmd), then we flush the SMP TLB 2179 * and finally we write the non-huge version of the pmd entry with 2180 * pmd_populate. 2181 */ 2182 pmdp_invalidate(vma, haddr, pmd); 2183 pmd_populate(mm, pmd, pgtable); 2184 2185 if (freeze) { 2186 for (i = 0; i < HPAGE_PMD_NR; i++) { 2187 page_remove_rmap(page + i, false); 2188 put_page(page + i); 2189 } 2190 } 2191 } 2192 2193 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 2194 unsigned long address, bool freeze, struct page *page) 2195 { 2196 spinlock_t *ptl; 2197 struct mm_struct *mm = vma->vm_mm; 2198 unsigned long haddr = address & HPAGE_PMD_MASK; 2199 2200 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE); 2201 ptl = pmd_lock(mm, pmd); 2202 2203 /* 2204 * If caller asks to setup a migration entries, we need a page to check 2205 * pmd against. Otherwise we can end up replacing wrong page. 2206 */ 2207 VM_BUG_ON(freeze && !page); 2208 if (page && page != pmd_page(*pmd)) 2209 goto out; 2210 2211 if (pmd_trans_huge(*pmd)) { 2212 page = pmd_page(*pmd); 2213 if (PageMlocked(page)) 2214 clear_page_mlock(page); 2215 } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd))) 2216 goto out; 2217 __split_huge_pmd_locked(vma, pmd, haddr, freeze); 2218 out: 2219 spin_unlock(ptl); 2220 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE); 2221 } 2222 2223 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, 2224 bool freeze, struct page *page) 2225 { 2226 pgd_t *pgd; 2227 p4d_t *p4d; 2228 pud_t *pud; 2229 pmd_t *pmd; 2230 2231 pgd = pgd_offset(vma->vm_mm, address); 2232 if (!pgd_present(*pgd)) 2233 return; 2234 2235 p4d = p4d_offset(pgd, address); 2236 if (!p4d_present(*p4d)) 2237 return; 2238 2239 pud = pud_offset(p4d, address); 2240 if (!pud_present(*pud)) 2241 return; 2242 2243 pmd = pmd_offset(pud, address); 2244 2245 __split_huge_pmd(vma, pmd, address, freeze, page); 2246 } 2247 2248 void vma_adjust_trans_huge(struct vm_area_struct *vma, 2249 unsigned long start, 2250 unsigned long end, 2251 long adjust_next) 2252 { 2253 /* 2254 * If the new start address isn't hpage aligned and it could 2255 * previously contain an hugepage: check if we need to split 2256 * an huge pmd. 2257 */ 2258 if (start & ~HPAGE_PMD_MASK && 2259 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2260 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2261 split_huge_pmd_address(vma, start, false, NULL); 2262 2263 /* 2264 * If the new end address isn't hpage aligned and it could 2265 * previously contain an hugepage: check if we need to split 2266 * an huge pmd. 2267 */ 2268 if (end & ~HPAGE_PMD_MASK && 2269 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2270 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2271 split_huge_pmd_address(vma, end, false, NULL); 2272 2273 /* 2274 * If we're also updating the vma->vm_next->vm_start, if the new 2275 * vm_next->vm_start isn't page aligned and it could previously 2276 * contain an hugepage: check if we need to split an huge pmd. 2277 */ 2278 if (adjust_next > 0) { 2279 struct vm_area_struct *next = vma->vm_next; 2280 unsigned long nstart = next->vm_start; 2281 nstart += adjust_next << PAGE_SHIFT; 2282 if (nstart & ~HPAGE_PMD_MASK && 2283 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2284 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2285 split_huge_pmd_address(next, nstart, false, NULL); 2286 } 2287 } 2288 2289 static void freeze_page(struct page *page) 2290 { 2291 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS | 2292 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD; 2293 bool unmap_success; 2294 2295 VM_BUG_ON_PAGE(!PageHead(page), page); 2296 2297 if (PageAnon(page)) 2298 ttu_flags |= TTU_SPLIT_FREEZE; 2299 2300 unmap_success = try_to_unmap(page, ttu_flags); 2301 VM_BUG_ON_PAGE(!unmap_success, page); 2302 } 2303 2304 static void unfreeze_page(struct page *page) 2305 { 2306 int i; 2307 if (PageTransHuge(page)) { 2308 remove_migration_ptes(page, page, true); 2309 } else { 2310 for (i = 0; i < HPAGE_PMD_NR; i++) 2311 remove_migration_ptes(page + i, page + i, true); 2312 } 2313 } 2314 2315 static void __split_huge_page_tail(struct page *head, int tail, 2316 struct lruvec *lruvec, struct list_head *list) 2317 { 2318 struct page *page_tail = head + tail; 2319 2320 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); 2321 VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail); 2322 2323 /* 2324 * tail_page->_refcount is zero and not changing from under us. But 2325 * get_page_unless_zero() may be running from under us on the 2326 * tail_page. If we used atomic_set() below instead of atomic_inc() or 2327 * atomic_add(), we would then run atomic_set() concurrently with 2328 * get_page_unless_zero(), and atomic_set() is implemented in C not 2329 * using locked ops. spin_unlock on x86 sometime uses locked ops 2330 * because of PPro errata 66, 92, so unless somebody can guarantee 2331 * atomic_set() here would be safe on all archs (and not only on x86), 2332 * it's safer to use atomic_inc()/atomic_add(). 2333 */ 2334 if (PageAnon(head) && !PageSwapCache(head)) { 2335 page_ref_inc(page_tail); 2336 } else { 2337 /* Additional pin to radix tree */ 2338 page_ref_add(page_tail, 2); 2339 } 2340 2341 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; 2342 page_tail->flags |= (head->flags & 2343 ((1L << PG_referenced) | 2344 (1L << PG_swapbacked) | 2345 (1L << PG_swapcache) | 2346 (1L << PG_mlocked) | 2347 (1L << PG_uptodate) | 2348 (1L << PG_active) | 2349 (1L << PG_locked) | 2350 (1L << PG_unevictable) | 2351 (1L << PG_dirty))); 2352 2353 /* 2354 * After clearing PageTail the gup refcount can be released. 2355 * Page flags also must be visible before we make the page non-compound. 2356 */ 2357 smp_wmb(); 2358 2359 clear_compound_head(page_tail); 2360 2361 if (page_is_young(head)) 2362 set_page_young(page_tail); 2363 if (page_is_idle(head)) 2364 set_page_idle(page_tail); 2365 2366 /* ->mapping in first tail page is compound_mapcount */ 2367 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING, 2368 page_tail); 2369 page_tail->mapping = head->mapping; 2370 2371 page_tail->index = head->index + tail; 2372 page_cpupid_xchg_last(page_tail, page_cpupid_last(head)); 2373 lru_add_page_tail(head, page_tail, lruvec, list); 2374 } 2375 2376 static void __split_huge_page(struct page *page, struct list_head *list, 2377 unsigned long flags) 2378 { 2379 struct page *head = compound_head(page); 2380 struct zone *zone = page_zone(head); 2381 struct lruvec *lruvec; 2382 pgoff_t end = -1; 2383 int i; 2384 2385 lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat); 2386 2387 /* complete memcg works before add pages to LRU */ 2388 mem_cgroup_split_huge_fixup(head); 2389 2390 if (!PageAnon(page)) 2391 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE); 2392 2393 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 2394 __split_huge_page_tail(head, i, lruvec, list); 2395 /* Some pages can be beyond i_size: drop them from page cache */ 2396 if (head[i].index >= end) { 2397 __ClearPageDirty(head + i); 2398 __delete_from_page_cache(head + i, NULL); 2399 if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head)) 2400 shmem_uncharge(head->mapping->host, 1); 2401 put_page(head + i); 2402 } 2403 } 2404 2405 ClearPageCompound(head); 2406 /* See comment in __split_huge_page_tail() */ 2407 if (PageAnon(head)) { 2408 /* Additional pin to radix tree of swap cache */ 2409 if (PageSwapCache(head)) 2410 page_ref_add(head, 2); 2411 else 2412 page_ref_inc(head); 2413 } else { 2414 /* Additional pin to radix tree */ 2415 page_ref_add(head, 2); 2416 spin_unlock(&head->mapping->tree_lock); 2417 } 2418 2419 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags); 2420 2421 unfreeze_page(head); 2422 2423 for (i = 0; i < HPAGE_PMD_NR; i++) { 2424 struct page *subpage = head + i; 2425 if (subpage == page) 2426 continue; 2427 unlock_page(subpage); 2428 2429 /* 2430 * Subpages may be freed if there wasn't any mapping 2431 * like if add_to_swap() is running on a lru page that 2432 * had its mapping zapped. And freeing these pages 2433 * requires taking the lru_lock so we do the put_page 2434 * of the tail pages after the split is complete. 2435 */ 2436 put_page(subpage); 2437 } 2438 } 2439 2440 int total_mapcount(struct page *page) 2441 { 2442 int i, compound, ret; 2443 2444 VM_BUG_ON_PAGE(PageTail(page), page); 2445 2446 if (likely(!PageCompound(page))) 2447 return atomic_read(&page->_mapcount) + 1; 2448 2449 compound = compound_mapcount(page); 2450 if (PageHuge(page)) 2451 return compound; 2452 ret = compound; 2453 for (i = 0; i < HPAGE_PMD_NR; i++) 2454 ret += atomic_read(&page[i]._mapcount) + 1; 2455 /* File pages has compound_mapcount included in _mapcount */ 2456 if (!PageAnon(page)) 2457 return ret - compound * HPAGE_PMD_NR; 2458 if (PageDoubleMap(page)) 2459 ret -= HPAGE_PMD_NR; 2460 return ret; 2461 } 2462 2463 /* 2464 * This calculates accurately how many mappings a transparent hugepage 2465 * has (unlike page_mapcount() which isn't fully accurate). This full 2466 * accuracy is primarily needed to know if copy-on-write faults can 2467 * reuse the page and change the mapping to read-write instead of 2468 * copying them. At the same time this returns the total_mapcount too. 2469 * 2470 * The function returns the highest mapcount any one of the subpages 2471 * has. If the return value is one, even if different processes are 2472 * mapping different subpages of the transparent hugepage, they can 2473 * all reuse it, because each process is reusing a different subpage. 2474 * 2475 * The total_mapcount is instead counting all virtual mappings of the 2476 * subpages. If the total_mapcount is equal to "one", it tells the 2477 * caller all mappings belong to the same "mm" and in turn the 2478 * anon_vma of the transparent hugepage can become the vma->anon_vma 2479 * local one as no other process may be mapping any of the subpages. 2480 * 2481 * It would be more accurate to replace page_mapcount() with 2482 * page_trans_huge_mapcount(), however we only use 2483 * page_trans_huge_mapcount() in the copy-on-write faults where we 2484 * need full accuracy to avoid breaking page pinning, because 2485 * page_trans_huge_mapcount() is slower than page_mapcount(). 2486 */ 2487 int page_trans_huge_mapcount(struct page *page, int *total_mapcount) 2488 { 2489 int i, ret, _total_mapcount, mapcount; 2490 2491 /* hugetlbfs shouldn't call it */ 2492 VM_BUG_ON_PAGE(PageHuge(page), page); 2493 2494 if (likely(!PageTransCompound(page))) { 2495 mapcount = atomic_read(&page->_mapcount) + 1; 2496 if (total_mapcount) 2497 *total_mapcount = mapcount; 2498 return mapcount; 2499 } 2500 2501 page = compound_head(page); 2502 2503 _total_mapcount = ret = 0; 2504 for (i = 0; i < HPAGE_PMD_NR; i++) { 2505 mapcount = atomic_read(&page[i]._mapcount) + 1; 2506 ret = max(ret, mapcount); 2507 _total_mapcount += mapcount; 2508 } 2509 if (PageDoubleMap(page)) { 2510 ret -= 1; 2511 _total_mapcount -= HPAGE_PMD_NR; 2512 } 2513 mapcount = compound_mapcount(page); 2514 ret += mapcount; 2515 _total_mapcount += mapcount; 2516 if (total_mapcount) 2517 *total_mapcount = _total_mapcount; 2518 return ret; 2519 } 2520 2521 /* Racy check whether the huge page can be split */ 2522 bool can_split_huge_page(struct page *page, int *pextra_pins) 2523 { 2524 int extra_pins; 2525 2526 /* Additional pins from radix tree */ 2527 if (PageAnon(page)) 2528 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0; 2529 else 2530 extra_pins = HPAGE_PMD_NR; 2531 if (pextra_pins) 2532 *pextra_pins = extra_pins; 2533 return total_mapcount(page) == page_count(page) - extra_pins - 1; 2534 } 2535 2536 /* 2537 * This function splits huge page into normal pages. @page can point to any 2538 * subpage of huge page to split. Split doesn't change the position of @page. 2539 * 2540 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY. 2541 * The huge page must be locked. 2542 * 2543 * If @list is null, tail pages will be added to LRU list, otherwise, to @list. 2544 * 2545 * Both head page and tail pages will inherit mapping, flags, and so on from 2546 * the hugepage. 2547 * 2548 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if 2549 * they are not mapped. 2550 * 2551 * Returns 0 if the hugepage is split successfully. 2552 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under 2553 * us. 2554 */ 2555 int split_huge_page_to_list(struct page *page, struct list_head *list) 2556 { 2557 struct page *head = compound_head(page); 2558 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head)); 2559 struct anon_vma *anon_vma = NULL; 2560 struct address_space *mapping = NULL; 2561 int count, mapcount, extra_pins, ret; 2562 bool mlocked; 2563 unsigned long flags; 2564 2565 VM_BUG_ON_PAGE(is_huge_zero_page(page), page); 2566 VM_BUG_ON_PAGE(!PageLocked(page), page); 2567 VM_BUG_ON_PAGE(!PageCompound(page), page); 2568 2569 if (PageWriteback(page)) 2570 return -EBUSY; 2571 2572 if (PageAnon(head)) { 2573 /* 2574 * The caller does not necessarily hold an mmap_sem that would 2575 * prevent the anon_vma disappearing so we first we take a 2576 * reference to it and then lock the anon_vma for write. This 2577 * is similar to page_lock_anon_vma_read except the write lock 2578 * is taken to serialise against parallel split or collapse 2579 * operations. 2580 */ 2581 anon_vma = page_get_anon_vma(head); 2582 if (!anon_vma) { 2583 ret = -EBUSY; 2584 goto out; 2585 } 2586 mapping = NULL; 2587 anon_vma_lock_write(anon_vma); 2588 } else { 2589 mapping = head->mapping; 2590 2591 /* Truncated ? */ 2592 if (!mapping) { 2593 ret = -EBUSY; 2594 goto out; 2595 } 2596 2597 anon_vma = NULL; 2598 i_mmap_lock_read(mapping); 2599 } 2600 2601 /* 2602 * Racy check if we can split the page, before freeze_page() will 2603 * split PMDs 2604 */ 2605 if (!can_split_huge_page(head, &extra_pins)) { 2606 ret = -EBUSY; 2607 goto out_unlock; 2608 } 2609 2610 mlocked = PageMlocked(page); 2611 freeze_page(head); 2612 VM_BUG_ON_PAGE(compound_mapcount(head), head); 2613 2614 /* Make sure the page is not on per-CPU pagevec as it takes pin */ 2615 if (mlocked) 2616 lru_add_drain(); 2617 2618 /* prevent PageLRU to go away from under us, and freeze lru stats */ 2619 spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags); 2620 2621 if (mapping) { 2622 void **pslot; 2623 2624 spin_lock(&mapping->tree_lock); 2625 pslot = radix_tree_lookup_slot(&mapping->page_tree, 2626 page_index(head)); 2627 /* 2628 * Check if the head page is present in radix tree. 2629 * We assume all tail are present too, if head is there. 2630 */ 2631 if (radix_tree_deref_slot_protected(pslot, 2632 &mapping->tree_lock) != head) 2633 goto fail; 2634 } 2635 2636 /* Prevent deferred_split_scan() touching ->_refcount */ 2637 spin_lock(&pgdata->split_queue_lock); 2638 count = page_count(head); 2639 mapcount = total_mapcount(head); 2640 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) { 2641 if (!list_empty(page_deferred_list(head))) { 2642 pgdata->split_queue_len--; 2643 list_del(page_deferred_list(head)); 2644 } 2645 if (mapping) 2646 __dec_node_page_state(page, NR_SHMEM_THPS); 2647 spin_unlock(&pgdata->split_queue_lock); 2648 __split_huge_page(page, list, flags); 2649 if (PageSwapCache(head)) { 2650 swp_entry_t entry = { .val = page_private(head) }; 2651 2652 ret = split_swap_cluster(entry); 2653 } else 2654 ret = 0; 2655 } else { 2656 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { 2657 pr_alert("total_mapcount: %u, page_count(): %u\n", 2658 mapcount, count); 2659 if (PageTail(page)) 2660 dump_page(head, NULL); 2661 dump_page(page, "total_mapcount(head) > 0"); 2662 BUG(); 2663 } 2664 spin_unlock(&pgdata->split_queue_lock); 2665 fail: if (mapping) 2666 spin_unlock(&mapping->tree_lock); 2667 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags); 2668 unfreeze_page(head); 2669 ret = -EBUSY; 2670 } 2671 2672 out_unlock: 2673 if (anon_vma) { 2674 anon_vma_unlock_write(anon_vma); 2675 put_anon_vma(anon_vma); 2676 } 2677 if (mapping) 2678 i_mmap_unlock_read(mapping); 2679 out: 2680 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); 2681 return ret; 2682 } 2683 2684 void free_transhuge_page(struct page *page) 2685 { 2686 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page)); 2687 unsigned long flags; 2688 2689 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 2690 if (!list_empty(page_deferred_list(page))) { 2691 pgdata->split_queue_len--; 2692 list_del(page_deferred_list(page)); 2693 } 2694 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 2695 free_compound_page(page); 2696 } 2697 2698 void deferred_split_huge_page(struct page *page) 2699 { 2700 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page)); 2701 unsigned long flags; 2702 2703 VM_BUG_ON_PAGE(!PageTransHuge(page), page); 2704 2705 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 2706 if (list_empty(page_deferred_list(page))) { 2707 count_vm_event(THP_DEFERRED_SPLIT_PAGE); 2708 list_add_tail(page_deferred_list(page), &pgdata->split_queue); 2709 pgdata->split_queue_len++; 2710 } 2711 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 2712 } 2713 2714 static unsigned long deferred_split_count(struct shrinker *shrink, 2715 struct shrink_control *sc) 2716 { 2717 struct pglist_data *pgdata = NODE_DATA(sc->nid); 2718 return ACCESS_ONCE(pgdata->split_queue_len); 2719 } 2720 2721 static unsigned long deferred_split_scan(struct shrinker *shrink, 2722 struct shrink_control *sc) 2723 { 2724 struct pglist_data *pgdata = NODE_DATA(sc->nid); 2725 unsigned long flags; 2726 LIST_HEAD(list), *pos, *next; 2727 struct page *page; 2728 int split = 0; 2729 2730 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 2731 /* Take pin on all head pages to avoid freeing them under us */ 2732 list_for_each_safe(pos, next, &pgdata->split_queue) { 2733 page = list_entry((void *)pos, struct page, mapping); 2734 page = compound_head(page); 2735 if (get_page_unless_zero(page)) { 2736 list_move(page_deferred_list(page), &list); 2737 } else { 2738 /* We lost race with put_compound_page() */ 2739 list_del_init(page_deferred_list(page)); 2740 pgdata->split_queue_len--; 2741 } 2742 if (!--sc->nr_to_scan) 2743 break; 2744 } 2745 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 2746 2747 list_for_each_safe(pos, next, &list) { 2748 page = list_entry((void *)pos, struct page, mapping); 2749 lock_page(page); 2750 /* split_huge_page() removes page from list on success */ 2751 if (!split_huge_page(page)) 2752 split++; 2753 unlock_page(page); 2754 put_page(page); 2755 } 2756 2757 spin_lock_irqsave(&pgdata->split_queue_lock, flags); 2758 list_splice_tail(&list, &pgdata->split_queue); 2759 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); 2760 2761 /* 2762 * Stop shrinker if we didn't split any page, but the queue is empty. 2763 * This can happen if pages were freed under us. 2764 */ 2765 if (!split && list_empty(&pgdata->split_queue)) 2766 return SHRINK_STOP; 2767 return split; 2768 } 2769 2770 static struct shrinker deferred_split_shrinker = { 2771 .count_objects = deferred_split_count, 2772 .scan_objects = deferred_split_scan, 2773 .seeks = DEFAULT_SEEKS, 2774 .flags = SHRINKER_NUMA_AWARE, 2775 }; 2776 2777 #ifdef CONFIG_DEBUG_FS 2778 static int split_huge_pages_set(void *data, u64 val) 2779 { 2780 struct zone *zone; 2781 struct page *page; 2782 unsigned long pfn, max_zone_pfn; 2783 unsigned long total = 0, split = 0; 2784 2785 if (val != 1) 2786 return -EINVAL; 2787 2788 for_each_populated_zone(zone) { 2789 max_zone_pfn = zone_end_pfn(zone); 2790 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) { 2791 if (!pfn_valid(pfn)) 2792 continue; 2793 2794 page = pfn_to_page(pfn); 2795 if (!get_page_unless_zero(page)) 2796 continue; 2797 2798 if (zone != page_zone(page)) 2799 goto next; 2800 2801 if (!PageHead(page) || PageHuge(page) || !PageLRU(page)) 2802 goto next; 2803 2804 total++; 2805 lock_page(page); 2806 if (!split_huge_page(page)) 2807 split++; 2808 unlock_page(page); 2809 next: 2810 put_page(page); 2811 } 2812 } 2813 2814 pr_info("%lu of %lu THP split\n", split, total); 2815 2816 return 0; 2817 } 2818 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set, 2819 "%llu\n"); 2820 2821 static int __init split_huge_pages_debugfs(void) 2822 { 2823 void *ret; 2824 2825 ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL, 2826 &split_huge_pages_fops); 2827 if (!ret) 2828 pr_warn("Failed to create split_huge_pages in debugfs"); 2829 return 0; 2830 } 2831 late_initcall(split_huge_pages_debugfs); 2832 #endif 2833 2834 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 2835 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw, 2836 struct page *page) 2837 { 2838 struct vm_area_struct *vma = pvmw->vma; 2839 struct mm_struct *mm = vma->vm_mm; 2840 unsigned long address = pvmw->address; 2841 pmd_t pmdval; 2842 swp_entry_t entry; 2843 pmd_t pmdswp; 2844 2845 if (!(pvmw->pmd && !pvmw->pte)) 2846 return; 2847 2848 mmu_notifier_invalidate_range_start(mm, address, 2849 address + HPAGE_PMD_SIZE); 2850 2851 flush_cache_range(vma, address, address + HPAGE_PMD_SIZE); 2852 pmdval = *pvmw->pmd; 2853 pmdp_invalidate(vma, address, pvmw->pmd); 2854 if (pmd_dirty(pmdval)) 2855 set_page_dirty(page); 2856 entry = make_migration_entry(page, pmd_write(pmdval)); 2857 pmdswp = swp_entry_to_pmd(entry); 2858 if (pmd_soft_dirty(pmdval)) 2859 pmdswp = pmd_swp_mksoft_dirty(pmdswp); 2860 set_pmd_at(mm, address, pvmw->pmd, pmdswp); 2861 page_remove_rmap(page, true); 2862 put_page(page); 2863 2864 mmu_notifier_invalidate_range_end(mm, address, 2865 address + HPAGE_PMD_SIZE); 2866 } 2867 2868 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new) 2869 { 2870 struct vm_area_struct *vma = pvmw->vma; 2871 struct mm_struct *mm = vma->vm_mm; 2872 unsigned long address = pvmw->address; 2873 unsigned long mmun_start = address & HPAGE_PMD_MASK; 2874 pmd_t pmde; 2875 swp_entry_t entry; 2876 2877 if (!(pvmw->pmd && !pvmw->pte)) 2878 return; 2879 2880 entry = pmd_to_swp_entry(*pvmw->pmd); 2881 get_page(new); 2882 pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot)); 2883 if (pmd_swp_soft_dirty(*pvmw->pmd)) 2884 pmde = pmd_mksoft_dirty(pmde); 2885 if (is_write_migration_entry(entry)) 2886 pmde = maybe_pmd_mkwrite(pmde, vma); 2887 2888 flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE); 2889 page_add_anon_rmap(new, vma, mmun_start, true); 2890 set_pmd_at(mm, mmun_start, pvmw->pmd, pmde); 2891 if (vma->vm_flags & VM_LOCKED) 2892 mlock_vma_page(new); 2893 update_mmu_cache_pmd(vma, address, pvmw->pmd); 2894 } 2895 #endif 2896