1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2009 Red Hat, Inc. 4 */ 5 6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 7 8 #include <linux/mm.h> 9 #include <linux/sched.h> 10 #include <linux/sched/coredump.h> 11 #include <linux/sched/numa_balancing.h> 12 #include <linux/highmem.h> 13 #include <linux/hugetlb.h> 14 #include <linux/mmu_notifier.h> 15 #include <linux/rmap.h> 16 #include <linux/swap.h> 17 #include <linux/shrinker.h> 18 #include <linux/mm_inline.h> 19 #include <linux/swapops.h> 20 #include <linux/dax.h> 21 #include <linux/khugepaged.h> 22 #include <linux/freezer.h> 23 #include <linux/pfn_t.h> 24 #include <linux/mman.h> 25 #include <linux/memremap.h> 26 #include <linux/pagemap.h> 27 #include <linux/debugfs.h> 28 #include <linux/migrate.h> 29 #include <linux/hashtable.h> 30 #include <linux/userfaultfd_k.h> 31 #include <linux/page_idle.h> 32 #include <linux/shmem_fs.h> 33 #include <linux/oom.h> 34 #include <linux/numa.h> 35 #include <linux/page_owner.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 to avoid 43 * risking an increased memory footprint for applications that are not 44 * guaranteed to benefit from it. When transparent hugepage support is 45 * enabled, it is for all mappings, 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 bool transparent_hugepage_enabled(struct vm_area_struct *vma) 66 { 67 /* The addr is used to check if the vma size fits */ 68 unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE; 69 70 if (!transhuge_vma_suitable(vma, addr)) 71 return false; 72 if (vma_is_anonymous(vma)) 73 return __transparent_hugepage_enabled(vma); 74 if (vma_is_shmem(vma)) 75 return shmem_huge_enabled(vma); 76 77 return false; 78 } 79 80 static struct page *get_huge_zero_page(void) 81 { 82 struct page *zero_page; 83 retry: 84 if (likely(atomic_inc_not_zero(&huge_zero_refcount))) 85 return READ_ONCE(huge_zero_page); 86 87 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, 88 HPAGE_PMD_ORDER); 89 if (!zero_page) { 90 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); 91 return NULL; 92 } 93 count_vm_event(THP_ZERO_PAGE_ALLOC); 94 preempt_disable(); 95 if (cmpxchg(&huge_zero_page, NULL, zero_page)) { 96 preempt_enable(); 97 __free_pages(zero_page, compound_order(zero_page)); 98 goto retry; 99 } 100 101 /* We take additional reference here. It will be put back by shrinker */ 102 atomic_set(&huge_zero_refcount, 2); 103 preempt_enable(); 104 return READ_ONCE(huge_zero_page); 105 } 106 107 static void put_huge_zero_page(void) 108 { 109 /* 110 * Counter should never go to zero here. Only shrinker can put 111 * last reference. 112 */ 113 BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); 114 } 115 116 struct page *mm_get_huge_zero_page(struct mm_struct *mm) 117 { 118 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) 119 return READ_ONCE(huge_zero_page); 120 121 if (!get_huge_zero_page()) 122 return NULL; 123 124 if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) 125 put_huge_zero_page(); 126 127 return READ_ONCE(huge_zero_page); 128 } 129 130 void mm_put_huge_zero_page(struct mm_struct *mm) 131 { 132 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) 133 put_huge_zero_page(); 134 } 135 136 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, 137 struct shrink_control *sc) 138 { 139 /* we can free zero page only if last reference remains */ 140 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; 141 } 142 143 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, 144 struct shrink_control *sc) 145 { 146 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { 147 struct page *zero_page = xchg(&huge_zero_page, NULL); 148 BUG_ON(zero_page == NULL); 149 __free_pages(zero_page, compound_order(zero_page)); 150 return HPAGE_PMD_NR; 151 } 152 153 return 0; 154 } 155 156 static struct shrinker huge_zero_page_shrinker = { 157 .count_objects = shrink_huge_zero_page_count, 158 .scan_objects = shrink_huge_zero_page_scan, 159 .seeks = DEFAULT_SEEKS, 160 }; 161 162 #ifdef CONFIG_SYSFS 163 static ssize_t enabled_show(struct kobject *kobj, 164 struct kobj_attribute *attr, char *buf) 165 { 166 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags)) 167 return sprintf(buf, "[always] madvise never\n"); 168 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags)) 169 return sprintf(buf, "always [madvise] never\n"); 170 else 171 return sprintf(buf, "always madvise [never]\n"); 172 } 173 174 static ssize_t enabled_store(struct kobject *kobj, 175 struct kobj_attribute *attr, 176 const char *buf, size_t count) 177 { 178 ssize_t ret = count; 179 180 if (sysfs_streq(buf, "always")) { 181 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); 182 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); 183 } else if (sysfs_streq(buf, "madvise")) { 184 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); 185 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); 186 } else if (sysfs_streq(buf, "never")) { 187 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); 188 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); 189 } else 190 ret = -EINVAL; 191 192 if (ret > 0) { 193 int err = start_stop_khugepaged(); 194 if (err) 195 ret = err; 196 } 197 return ret; 198 } 199 static struct kobj_attribute enabled_attr = 200 __ATTR(enabled, 0644, enabled_show, enabled_store); 201 202 ssize_t single_hugepage_flag_show(struct kobject *kobj, 203 struct kobj_attribute *attr, char *buf, 204 enum transparent_hugepage_flag flag) 205 { 206 return sprintf(buf, "%d\n", 207 !!test_bit(flag, &transparent_hugepage_flags)); 208 } 209 210 ssize_t single_hugepage_flag_store(struct kobject *kobj, 211 struct kobj_attribute *attr, 212 const char *buf, size_t count, 213 enum transparent_hugepage_flag flag) 214 { 215 unsigned long value; 216 int ret; 217 218 ret = kstrtoul(buf, 10, &value); 219 if (ret < 0) 220 return ret; 221 if (value > 1) 222 return -EINVAL; 223 224 if (value) 225 set_bit(flag, &transparent_hugepage_flags); 226 else 227 clear_bit(flag, &transparent_hugepage_flags); 228 229 return count; 230 } 231 232 static ssize_t defrag_show(struct kobject *kobj, 233 struct kobj_attribute *attr, char *buf) 234 { 235 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) 236 return sprintf(buf, "[always] defer defer+madvise madvise never\n"); 237 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) 238 return sprintf(buf, "always [defer] defer+madvise madvise never\n"); 239 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags)) 240 return sprintf(buf, "always defer [defer+madvise] madvise never\n"); 241 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) 242 return sprintf(buf, "always defer defer+madvise [madvise] never\n"); 243 return sprintf(buf, "always defer defer+madvise madvise [never]\n"); 244 } 245 246 static ssize_t defrag_store(struct kobject *kobj, 247 struct kobj_attribute *attr, 248 const char *buf, size_t count) 249 { 250 if (sysfs_streq(buf, "always")) { 251 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 252 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 253 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 254 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 255 } else if (sysfs_streq(buf, "defer+madvise")) { 256 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 257 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 258 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 259 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 260 } else if (sysfs_streq(buf, "defer")) { 261 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 262 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 263 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 264 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 265 } else if (sysfs_streq(buf, "madvise")) { 266 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 267 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 268 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 269 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 270 } else if (sysfs_streq(buf, "never")) { 271 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); 272 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); 273 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); 274 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); 275 } else 276 return -EINVAL; 277 278 return count; 279 } 280 static struct kobj_attribute defrag_attr = 281 __ATTR(defrag, 0644, defrag_show, defrag_store); 282 283 static ssize_t use_zero_page_show(struct kobject *kobj, 284 struct kobj_attribute *attr, char *buf) 285 { 286 return single_hugepage_flag_show(kobj, attr, buf, 287 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 288 } 289 static ssize_t use_zero_page_store(struct kobject *kobj, 290 struct kobj_attribute *attr, const char *buf, size_t count) 291 { 292 return single_hugepage_flag_store(kobj, attr, buf, count, 293 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); 294 } 295 static struct kobj_attribute use_zero_page_attr = 296 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); 297 298 static ssize_t hpage_pmd_size_show(struct kobject *kobj, 299 struct kobj_attribute *attr, char *buf) 300 { 301 return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE); 302 } 303 static struct kobj_attribute hpage_pmd_size_attr = 304 __ATTR_RO(hpage_pmd_size); 305 306 #ifdef CONFIG_DEBUG_VM 307 static ssize_t debug_cow_show(struct kobject *kobj, 308 struct kobj_attribute *attr, char *buf) 309 { 310 return single_hugepage_flag_show(kobj, attr, buf, 311 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 312 } 313 static ssize_t debug_cow_store(struct kobject *kobj, 314 struct kobj_attribute *attr, 315 const char *buf, size_t count) 316 { 317 return single_hugepage_flag_store(kobj, attr, buf, count, 318 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); 319 } 320 static struct kobj_attribute debug_cow_attr = 321 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); 322 #endif /* CONFIG_DEBUG_VM */ 323 324 static struct attribute *hugepage_attr[] = { 325 &enabled_attr.attr, 326 &defrag_attr.attr, 327 &use_zero_page_attr.attr, 328 &hpage_pmd_size_attr.attr, 329 #ifdef CONFIG_SHMEM 330 &shmem_enabled_attr.attr, 331 #endif 332 #ifdef CONFIG_DEBUG_VM 333 &debug_cow_attr.attr, 334 #endif 335 NULL, 336 }; 337 338 static const struct attribute_group hugepage_attr_group = { 339 .attrs = hugepage_attr, 340 }; 341 342 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) 343 { 344 int err; 345 346 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); 347 if (unlikely(!*hugepage_kobj)) { 348 pr_err("failed to create transparent hugepage kobject\n"); 349 return -ENOMEM; 350 } 351 352 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); 353 if (err) { 354 pr_err("failed to register transparent hugepage group\n"); 355 goto delete_obj; 356 } 357 358 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); 359 if (err) { 360 pr_err("failed to register transparent hugepage group\n"); 361 goto remove_hp_group; 362 } 363 364 return 0; 365 366 remove_hp_group: 367 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); 368 delete_obj: 369 kobject_put(*hugepage_kobj); 370 return err; 371 } 372 373 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) 374 { 375 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); 376 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); 377 kobject_put(hugepage_kobj); 378 } 379 #else 380 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) 381 { 382 return 0; 383 } 384 385 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) 386 { 387 } 388 #endif /* CONFIG_SYSFS */ 389 390 static int __init hugepage_init(void) 391 { 392 int err; 393 struct kobject *hugepage_kobj; 394 395 if (!has_transparent_hugepage()) { 396 transparent_hugepage_flags = 0; 397 return -EINVAL; 398 } 399 400 /* 401 * hugepages can't be allocated by the buddy allocator 402 */ 403 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER); 404 /* 405 * we use page->mapping and page->index in second tail page 406 * as list_head: assuming THP order >= 2 407 */ 408 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2); 409 410 err = hugepage_init_sysfs(&hugepage_kobj); 411 if (err) 412 goto err_sysfs; 413 414 err = khugepaged_init(); 415 if (err) 416 goto err_slab; 417 418 err = register_shrinker(&huge_zero_page_shrinker); 419 if (err) 420 goto err_hzp_shrinker; 421 err = register_shrinker(&deferred_split_shrinker); 422 if (err) 423 goto err_split_shrinker; 424 425 /* 426 * By default disable transparent hugepages on smaller systems, 427 * where the extra memory used could hurt more than TLB overhead 428 * is likely to save. The admin can still enable it through /sys. 429 */ 430 if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) { 431 transparent_hugepage_flags = 0; 432 return 0; 433 } 434 435 err = start_stop_khugepaged(); 436 if (err) 437 goto err_khugepaged; 438 439 return 0; 440 err_khugepaged: 441 unregister_shrinker(&deferred_split_shrinker); 442 err_split_shrinker: 443 unregister_shrinker(&huge_zero_page_shrinker); 444 err_hzp_shrinker: 445 khugepaged_destroy(); 446 err_slab: 447 hugepage_exit_sysfs(hugepage_kobj); 448 err_sysfs: 449 return err; 450 } 451 subsys_initcall(hugepage_init); 452 453 static int __init setup_transparent_hugepage(char *str) 454 { 455 int ret = 0; 456 if (!str) 457 goto out; 458 if (!strcmp(str, "always")) { 459 set_bit(TRANSPARENT_HUGEPAGE_FLAG, 460 &transparent_hugepage_flags); 461 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 462 &transparent_hugepage_flags); 463 ret = 1; 464 } else if (!strcmp(str, "madvise")) { 465 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 466 &transparent_hugepage_flags); 467 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 468 &transparent_hugepage_flags); 469 ret = 1; 470 } else if (!strcmp(str, "never")) { 471 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, 472 &transparent_hugepage_flags); 473 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, 474 &transparent_hugepage_flags); 475 ret = 1; 476 } 477 out: 478 if (!ret) 479 pr_warn("transparent_hugepage= cannot parse, ignored\n"); 480 return ret; 481 } 482 __setup("transparent_hugepage=", setup_transparent_hugepage); 483 484 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) 485 { 486 if (likely(vma->vm_flags & VM_WRITE)) 487 pmd = pmd_mkwrite(pmd); 488 return pmd; 489 } 490 491 #ifdef CONFIG_MEMCG 492 static inline struct deferred_split *get_deferred_split_queue(struct page *page) 493 { 494 struct mem_cgroup *memcg = compound_head(page)->mem_cgroup; 495 struct pglist_data *pgdat = NODE_DATA(page_to_nid(page)); 496 497 if (memcg) 498 return &memcg->deferred_split_queue; 499 else 500 return &pgdat->deferred_split_queue; 501 } 502 #else 503 static inline struct deferred_split *get_deferred_split_queue(struct page *page) 504 { 505 struct pglist_data *pgdat = NODE_DATA(page_to_nid(page)); 506 507 return &pgdat->deferred_split_queue; 508 } 509 #endif 510 511 void prep_transhuge_page(struct page *page) 512 { 513 /* 514 * we use page->mapping and page->indexlru in second tail page 515 * as list_head: assuming THP order >= 2 516 */ 517 518 INIT_LIST_HEAD(page_deferred_list(page)); 519 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR); 520 } 521 522 bool is_transparent_hugepage(struct page *page) 523 { 524 if (!PageCompound(page)) 525 return 0; 526 527 page = compound_head(page); 528 return is_huge_zero_page(page) || 529 page[1].compound_dtor == TRANSHUGE_PAGE_DTOR; 530 } 531 EXPORT_SYMBOL_GPL(is_transparent_hugepage); 532 533 static unsigned long __thp_get_unmapped_area(struct file *filp, 534 unsigned long addr, unsigned long len, 535 loff_t off, unsigned long flags, unsigned long size) 536 { 537 loff_t off_end = off + len; 538 loff_t off_align = round_up(off, size); 539 unsigned long len_pad, ret; 540 541 if (off_end <= off_align || (off_end - off_align) < size) 542 return 0; 543 544 len_pad = len + size; 545 if (len_pad < len || (off + len_pad) < off) 546 return 0; 547 548 ret = current->mm->get_unmapped_area(filp, addr, len_pad, 549 off >> PAGE_SHIFT, flags); 550 551 /* 552 * The failure might be due to length padding. The caller will retry 553 * without the padding. 554 */ 555 if (IS_ERR_VALUE(ret)) 556 return 0; 557 558 /* 559 * Do not try to align to THP boundary if allocation at the address 560 * hint succeeds. 561 */ 562 if (ret == addr) 563 return addr; 564 565 ret += (off - ret) & (size - 1); 566 return ret; 567 } 568 569 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr, 570 unsigned long len, unsigned long pgoff, unsigned long flags) 571 { 572 unsigned long ret; 573 loff_t off = (loff_t)pgoff << PAGE_SHIFT; 574 575 if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD)) 576 goto out; 577 578 ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE); 579 if (ret) 580 return ret; 581 out: 582 return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags); 583 } 584 EXPORT_SYMBOL_GPL(thp_get_unmapped_area); 585 586 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf, 587 struct page *page, gfp_t gfp) 588 { 589 struct vm_area_struct *vma = vmf->vma; 590 struct mem_cgroup *memcg; 591 pgtable_t pgtable; 592 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 593 vm_fault_t ret = 0; 594 595 VM_BUG_ON_PAGE(!PageCompound(page), page); 596 597 if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) { 598 put_page(page); 599 count_vm_event(THP_FAULT_FALLBACK); 600 count_vm_event(THP_FAULT_FALLBACK_CHARGE); 601 return VM_FAULT_FALLBACK; 602 } 603 604 pgtable = pte_alloc_one(vma->vm_mm); 605 if (unlikely(!pgtable)) { 606 ret = VM_FAULT_OOM; 607 goto release; 608 } 609 610 clear_huge_page(page, vmf->address, HPAGE_PMD_NR); 611 /* 612 * The memory barrier inside __SetPageUptodate makes sure that 613 * clear_huge_page writes become visible before the set_pmd_at() 614 * write. 615 */ 616 __SetPageUptodate(page); 617 618 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 619 if (unlikely(!pmd_none(*vmf->pmd))) { 620 goto unlock_release; 621 } else { 622 pmd_t entry; 623 624 ret = check_stable_address_space(vma->vm_mm); 625 if (ret) 626 goto unlock_release; 627 628 /* Deliver the page fault to userland */ 629 if (userfaultfd_missing(vma)) { 630 vm_fault_t ret2; 631 632 spin_unlock(vmf->ptl); 633 mem_cgroup_cancel_charge(page, memcg, true); 634 put_page(page); 635 pte_free(vma->vm_mm, pgtable); 636 ret2 = handle_userfault(vmf, VM_UFFD_MISSING); 637 VM_BUG_ON(ret2 & VM_FAULT_FALLBACK); 638 return ret2; 639 } 640 641 entry = mk_huge_pmd(page, vma->vm_page_prot); 642 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 643 page_add_new_anon_rmap(page, vma, haddr, true); 644 mem_cgroup_commit_charge(page, memcg, false, true); 645 lru_cache_add_active_or_unevictable(page, vma); 646 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable); 647 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); 648 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); 649 mm_inc_nr_ptes(vma->vm_mm); 650 spin_unlock(vmf->ptl); 651 count_vm_event(THP_FAULT_ALLOC); 652 count_memcg_events(memcg, THP_FAULT_ALLOC, 1); 653 } 654 655 return 0; 656 unlock_release: 657 spin_unlock(vmf->ptl); 658 release: 659 if (pgtable) 660 pte_free(vma->vm_mm, pgtable); 661 mem_cgroup_cancel_charge(page, memcg, true); 662 put_page(page); 663 return ret; 664 665 } 666 667 /* 668 * always: directly stall for all thp allocations 669 * defer: wake kswapd and fail if not immediately available 670 * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise 671 * fail if not immediately available 672 * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately 673 * available 674 * never: never stall for any thp allocation 675 */ 676 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma) 677 { 678 const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE); 679 680 /* Always do synchronous compaction */ 681 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) 682 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY); 683 684 /* Kick kcompactd and fail quickly */ 685 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) 686 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM; 687 688 /* Synchronous compaction if madvised, otherwise kick kcompactd */ 689 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags)) 690 return GFP_TRANSHUGE_LIGHT | 691 (vma_madvised ? __GFP_DIRECT_RECLAIM : 692 __GFP_KSWAPD_RECLAIM); 693 694 /* Only do synchronous compaction if madvised */ 695 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) 696 return GFP_TRANSHUGE_LIGHT | 697 (vma_madvised ? __GFP_DIRECT_RECLAIM : 0); 698 699 return GFP_TRANSHUGE_LIGHT; 700 } 701 702 /* Caller must hold page table lock. */ 703 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, 704 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, 705 struct page *zero_page) 706 { 707 pmd_t entry; 708 if (!pmd_none(*pmd)) 709 return false; 710 entry = mk_pmd(zero_page, vma->vm_page_prot); 711 entry = pmd_mkhuge(entry); 712 if (pgtable) 713 pgtable_trans_huge_deposit(mm, pmd, pgtable); 714 set_pmd_at(mm, haddr, pmd, entry); 715 mm_inc_nr_ptes(mm); 716 return true; 717 } 718 719 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf) 720 { 721 struct vm_area_struct *vma = vmf->vma; 722 gfp_t gfp; 723 struct page *page; 724 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 725 726 if (!transhuge_vma_suitable(vma, haddr)) 727 return VM_FAULT_FALLBACK; 728 if (unlikely(anon_vma_prepare(vma))) 729 return VM_FAULT_OOM; 730 if (unlikely(khugepaged_enter(vma, vma->vm_flags))) 731 return VM_FAULT_OOM; 732 if (!(vmf->flags & FAULT_FLAG_WRITE) && 733 !mm_forbids_zeropage(vma->vm_mm) && 734 transparent_hugepage_use_zero_page()) { 735 pgtable_t pgtable; 736 struct page *zero_page; 737 bool set; 738 vm_fault_t ret; 739 pgtable = pte_alloc_one(vma->vm_mm); 740 if (unlikely(!pgtable)) 741 return VM_FAULT_OOM; 742 zero_page = mm_get_huge_zero_page(vma->vm_mm); 743 if (unlikely(!zero_page)) { 744 pte_free(vma->vm_mm, pgtable); 745 count_vm_event(THP_FAULT_FALLBACK); 746 return VM_FAULT_FALLBACK; 747 } 748 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 749 ret = 0; 750 set = false; 751 if (pmd_none(*vmf->pmd)) { 752 ret = check_stable_address_space(vma->vm_mm); 753 if (ret) { 754 spin_unlock(vmf->ptl); 755 } else if (userfaultfd_missing(vma)) { 756 spin_unlock(vmf->ptl); 757 ret = handle_userfault(vmf, VM_UFFD_MISSING); 758 VM_BUG_ON(ret & VM_FAULT_FALLBACK); 759 } else { 760 set_huge_zero_page(pgtable, vma->vm_mm, vma, 761 haddr, vmf->pmd, zero_page); 762 spin_unlock(vmf->ptl); 763 set = true; 764 } 765 } else 766 spin_unlock(vmf->ptl); 767 if (!set) 768 pte_free(vma->vm_mm, pgtable); 769 return ret; 770 } 771 gfp = alloc_hugepage_direct_gfpmask(vma); 772 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER); 773 if (unlikely(!page)) { 774 count_vm_event(THP_FAULT_FALLBACK); 775 return VM_FAULT_FALLBACK; 776 } 777 prep_transhuge_page(page); 778 return __do_huge_pmd_anonymous_page(vmf, page, gfp); 779 } 780 781 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, 782 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write, 783 pgtable_t pgtable) 784 { 785 struct mm_struct *mm = vma->vm_mm; 786 pmd_t entry; 787 spinlock_t *ptl; 788 789 ptl = pmd_lock(mm, pmd); 790 if (!pmd_none(*pmd)) { 791 if (write) { 792 if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) { 793 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd)); 794 goto out_unlock; 795 } 796 entry = pmd_mkyoung(*pmd); 797 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 798 if (pmdp_set_access_flags(vma, addr, pmd, entry, 1)) 799 update_mmu_cache_pmd(vma, addr, pmd); 800 } 801 802 goto out_unlock; 803 } 804 805 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot)); 806 if (pfn_t_devmap(pfn)) 807 entry = pmd_mkdevmap(entry); 808 if (write) { 809 entry = pmd_mkyoung(pmd_mkdirty(entry)); 810 entry = maybe_pmd_mkwrite(entry, vma); 811 } 812 813 if (pgtable) { 814 pgtable_trans_huge_deposit(mm, pmd, pgtable); 815 mm_inc_nr_ptes(mm); 816 pgtable = NULL; 817 } 818 819 set_pmd_at(mm, addr, pmd, entry); 820 update_mmu_cache_pmd(vma, addr, pmd); 821 822 out_unlock: 823 spin_unlock(ptl); 824 if (pgtable) 825 pte_free(mm, pgtable); 826 } 827 828 /** 829 * vmf_insert_pfn_pmd_prot - insert a pmd size pfn 830 * @vmf: Structure describing the fault 831 * @pfn: pfn to insert 832 * @pgprot: page protection to use 833 * @write: whether it's a write fault 834 * 835 * Insert a pmd size pfn. See vmf_insert_pfn() for additional info and 836 * also consult the vmf_insert_mixed_prot() documentation when 837 * @pgprot != @vmf->vma->vm_page_prot. 838 * 839 * Return: vm_fault_t value. 840 */ 841 vm_fault_t vmf_insert_pfn_pmd_prot(struct vm_fault *vmf, pfn_t pfn, 842 pgprot_t pgprot, bool write) 843 { 844 unsigned long addr = vmf->address & PMD_MASK; 845 struct vm_area_struct *vma = vmf->vma; 846 pgtable_t pgtable = NULL; 847 848 /* 849 * If we had pmd_special, we could avoid all these restrictions, 850 * but we need to be consistent with PTEs and architectures that 851 * can't support a 'special' bit. 852 */ 853 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) && 854 !pfn_t_devmap(pfn)); 855 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == 856 (VM_PFNMAP|VM_MIXEDMAP)); 857 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); 858 859 if (addr < vma->vm_start || addr >= vma->vm_end) 860 return VM_FAULT_SIGBUS; 861 862 if (arch_needs_pgtable_deposit()) { 863 pgtable = pte_alloc_one(vma->vm_mm); 864 if (!pgtable) 865 return VM_FAULT_OOM; 866 } 867 868 track_pfn_insert(vma, &pgprot, pfn); 869 870 insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable); 871 return VM_FAULT_NOPAGE; 872 } 873 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd_prot); 874 875 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 876 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma) 877 { 878 if (likely(vma->vm_flags & VM_WRITE)) 879 pud = pud_mkwrite(pud); 880 return pud; 881 } 882 883 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr, 884 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write) 885 { 886 struct mm_struct *mm = vma->vm_mm; 887 pud_t entry; 888 spinlock_t *ptl; 889 890 ptl = pud_lock(mm, pud); 891 if (!pud_none(*pud)) { 892 if (write) { 893 if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) { 894 WARN_ON_ONCE(!is_huge_zero_pud(*pud)); 895 goto out_unlock; 896 } 897 entry = pud_mkyoung(*pud); 898 entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma); 899 if (pudp_set_access_flags(vma, addr, pud, entry, 1)) 900 update_mmu_cache_pud(vma, addr, pud); 901 } 902 goto out_unlock; 903 } 904 905 entry = pud_mkhuge(pfn_t_pud(pfn, prot)); 906 if (pfn_t_devmap(pfn)) 907 entry = pud_mkdevmap(entry); 908 if (write) { 909 entry = pud_mkyoung(pud_mkdirty(entry)); 910 entry = maybe_pud_mkwrite(entry, vma); 911 } 912 set_pud_at(mm, addr, pud, entry); 913 update_mmu_cache_pud(vma, addr, pud); 914 915 out_unlock: 916 spin_unlock(ptl); 917 } 918 919 /** 920 * vmf_insert_pfn_pud_prot - insert a pud size pfn 921 * @vmf: Structure describing the fault 922 * @pfn: pfn to insert 923 * @pgprot: page protection to use 924 * @write: whether it's a write fault 925 * 926 * Insert a pud size pfn. See vmf_insert_pfn() for additional info and 927 * also consult the vmf_insert_mixed_prot() documentation when 928 * @pgprot != @vmf->vma->vm_page_prot. 929 * 930 * Return: vm_fault_t value. 931 */ 932 vm_fault_t vmf_insert_pfn_pud_prot(struct vm_fault *vmf, pfn_t pfn, 933 pgprot_t pgprot, bool write) 934 { 935 unsigned long addr = vmf->address & PUD_MASK; 936 struct vm_area_struct *vma = vmf->vma; 937 938 /* 939 * If we had pud_special, we could avoid all these restrictions, 940 * but we need to be consistent with PTEs and architectures that 941 * can't support a 'special' bit. 942 */ 943 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) && 944 !pfn_t_devmap(pfn)); 945 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == 946 (VM_PFNMAP|VM_MIXEDMAP)); 947 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); 948 949 if (addr < vma->vm_start || addr >= vma->vm_end) 950 return VM_FAULT_SIGBUS; 951 952 track_pfn_insert(vma, &pgprot, pfn); 953 954 insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write); 955 return VM_FAULT_NOPAGE; 956 } 957 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud_prot); 958 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ 959 960 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr, 961 pmd_t *pmd, int flags) 962 { 963 pmd_t _pmd; 964 965 _pmd = pmd_mkyoung(*pmd); 966 if (flags & FOLL_WRITE) 967 _pmd = pmd_mkdirty(_pmd); 968 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, 969 pmd, _pmd, flags & FOLL_WRITE)) 970 update_mmu_cache_pmd(vma, addr, pmd); 971 } 972 973 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, 974 pmd_t *pmd, int flags, struct dev_pagemap **pgmap) 975 { 976 unsigned long pfn = pmd_pfn(*pmd); 977 struct mm_struct *mm = vma->vm_mm; 978 struct page *page; 979 980 assert_spin_locked(pmd_lockptr(mm, pmd)); 981 982 /* 983 * When we COW a devmap PMD entry, we split it into PTEs, so we should 984 * not be in this function with `flags & FOLL_COW` set. 985 */ 986 WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set"); 987 988 /* FOLL_GET and FOLL_PIN are mutually exclusive. */ 989 if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == 990 (FOLL_PIN | FOLL_GET))) 991 return NULL; 992 993 if (flags & FOLL_WRITE && !pmd_write(*pmd)) 994 return NULL; 995 996 if (pmd_present(*pmd) && pmd_devmap(*pmd)) 997 /* pass */; 998 else 999 return NULL; 1000 1001 if (flags & FOLL_TOUCH) 1002 touch_pmd(vma, addr, pmd, flags); 1003 1004 /* 1005 * device mapped pages can only be returned if the 1006 * caller will manage the page reference count. 1007 */ 1008 if (!(flags & (FOLL_GET | FOLL_PIN))) 1009 return ERR_PTR(-EEXIST); 1010 1011 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT; 1012 *pgmap = get_dev_pagemap(pfn, *pgmap); 1013 if (!*pgmap) 1014 return ERR_PTR(-EFAULT); 1015 page = pfn_to_page(pfn); 1016 if (!try_grab_page(page, flags)) 1017 page = ERR_PTR(-ENOMEM); 1018 1019 return page; 1020 } 1021 1022 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 1023 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, 1024 struct vm_area_struct *vma) 1025 { 1026 spinlock_t *dst_ptl, *src_ptl; 1027 struct page *src_page; 1028 pmd_t pmd; 1029 pgtable_t pgtable = NULL; 1030 int ret = -ENOMEM; 1031 1032 /* Skip if can be re-fill on fault */ 1033 if (!vma_is_anonymous(vma)) 1034 return 0; 1035 1036 pgtable = pte_alloc_one(dst_mm); 1037 if (unlikely(!pgtable)) 1038 goto out; 1039 1040 dst_ptl = pmd_lock(dst_mm, dst_pmd); 1041 src_ptl = pmd_lockptr(src_mm, src_pmd); 1042 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); 1043 1044 ret = -EAGAIN; 1045 pmd = *src_pmd; 1046 1047 /* 1048 * Make sure the _PAGE_UFFD_WP bit is cleared if the new VMA 1049 * does not have the VM_UFFD_WP, which means that the uffd 1050 * fork event is not enabled. 1051 */ 1052 if (!(vma->vm_flags & VM_UFFD_WP)) 1053 pmd = pmd_clear_uffd_wp(pmd); 1054 1055 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 1056 if (unlikely(is_swap_pmd(pmd))) { 1057 swp_entry_t entry = pmd_to_swp_entry(pmd); 1058 1059 VM_BUG_ON(!is_pmd_migration_entry(pmd)); 1060 if (is_write_migration_entry(entry)) { 1061 make_migration_entry_read(&entry); 1062 pmd = swp_entry_to_pmd(entry); 1063 if (pmd_swp_soft_dirty(*src_pmd)) 1064 pmd = pmd_swp_mksoft_dirty(pmd); 1065 set_pmd_at(src_mm, addr, src_pmd, pmd); 1066 } 1067 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 1068 mm_inc_nr_ptes(dst_mm); 1069 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); 1070 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 1071 ret = 0; 1072 goto out_unlock; 1073 } 1074 #endif 1075 1076 if (unlikely(!pmd_trans_huge(pmd))) { 1077 pte_free(dst_mm, pgtable); 1078 goto out_unlock; 1079 } 1080 /* 1081 * When page table lock is held, the huge zero pmd should not be 1082 * under splitting since we don't split the page itself, only pmd to 1083 * a page table. 1084 */ 1085 if (is_huge_zero_pmd(pmd)) { 1086 struct page *zero_page; 1087 /* 1088 * get_huge_zero_page() will never allocate a new page here, 1089 * since we already have a zero page to copy. It just takes a 1090 * reference. 1091 */ 1092 zero_page = mm_get_huge_zero_page(dst_mm); 1093 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, 1094 zero_page); 1095 ret = 0; 1096 goto out_unlock; 1097 } 1098 1099 src_page = pmd_page(pmd); 1100 VM_BUG_ON_PAGE(!PageHead(src_page), src_page); 1101 get_page(src_page); 1102 page_dup_rmap(src_page, true); 1103 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); 1104 mm_inc_nr_ptes(dst_mm); 1105 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); 1106 1107 pmdp_set_wrprotect(src_mm, addr, src_pmd); 1108 pmd = pmd_mkold(pmd_wrprotect(pmd)); 1109 set_pmd_at(dst_mm, addr, dst_pmd, pmd); 1110 1111 ret = 0; 1112 out_unlock: 1113 spin_unlock(src_ptl); 1114 spin_unlock(dst_ptl); 1115 out: 1116 return ret; 1117 } 1118 1119 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 1120 static void touch_pud(struct vm_area_struct *vma, unsigned long addr, 1121 pud_t *pud, int flags) 1122 { 1123 pud_t _pud; 1124 1125 _pud = pud_mkyoung(*pud); 1126 if (flags & FOLL_WRITE) 1127 _pud = pud_mkdirty(_pud); 1128 if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK, 1129 pud, _pud, flags & FOLL_WRITE)) 1130 update_mmu_cache_pud(vma, addr, pud); 1131 } 1132 1133 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr, 1134 pud_t *pud, int flags, struct dev_pagemap **pgmap) 1135 { 1136 unsigned long pfn = pud_pfn(*pud); 1137 struct mm_struct *mm = vma->vm_mm; 1138 struct page *page; 1139 1140 assert_spin_locked(pud_lockptr(mm, pud)); 1141 1142 if (flags & FOLL_WRITE && !pud_write(*pud)) 1143 return NULL; 1144 1145 /* FOLL_GET and FOLL_PIN are mutually exclusive. */ 1146 if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == 1147 (FOLL_PIN | FOLL_GET))) 1148 return NULL; 1149 1150 if (pud_present(*pud) && pud_devmap(*pud)) 1151 /* pass */; 1152 else 1153 return NULL; 1154 1155 if (flags & FOLL_TOUCH) 1156 touch_pud(vma, addr, pud, flags); 1157 1158 /* 1159 * device mapped pages can only be returned if the 1160 * caller will manage the page reference count. 1161 * 1162 * At least one of FOLL_GET | FOLL_PIN must be set, so assert that here: 1163 */ 1164 if (!(flags & (FOLL_GET | FOLL_PIN))) 1165 return ERR_PTR(-EEXIST); 1166 1167 pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT; 1168 *pgmap = get_dev_pagemap(pfn, *pgmap); 1169 if (!*pgmap) 1170 return ERR_PTR(-EFAULT); 1171 page = pfn_to_page(pfn); 1172 if (!try_grab_page(page, flags)) 1173 page = ERR_PTR(-ENOMEM); 1174 1175 return page; 1176 } 1177 1178 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm, 1179 pud_t *dst_pud, pud_t *src_pud, unsigned long addr, 1180 struct vm_area_struct *vma) 1181 { 1182 spinlock_t *dst_ptl, *src_ptl; 1183 pud_t pud; 1184 int ret; 1185 1186 dst_ptl = pud_lock(dst_mm, dst_pud); 1187 src_ptl = pud_lockptr(src_mm, src_pud); 1188 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); 1189 1190 ret = -EAGAIN; 1191 pud = *src_pud; 1192 if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud))) 1193 goto out_unlock; 1194 1195 /* 1196 * When page table lock is held, the huge zero pud should not be 1197 * under splitting since we don't split the page itself, only pud to 1198 * a page table. 1199 */ 1200 if (is_huge_zero_pud(pud)) { 1201 /* No huge zero pud yet */ 1202 } 1203 1204 pudp_set_wrprotect(src_mm, addr, src_pud); 1205 pud = pud_mkold(pud_wrprotect(pud)); 1206 set_pud_at(dst_mm, addr, dst_pud, pud); 1207 1208 ret = 0; 1209 out_unlock: 1210 spin_unlock(src_ptl); 1211 spin_unlock(dst_ptl); 1212 return ret; 1213 } 1214 1215 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud) 1216 { 1217 pud_t entry; 1218 unsigned long haddr; 1219 bool write = vmf->flags & FAULT_FLAG_WRITE; 1220 1221 vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud); 1222 if (unlikely(!pud_same(*vmf->pud, orig_pud))) 1223 goto unlock; 1224 1225 entry = pud_mkyoung(orig_pud); 1226 if (write) 1227 entry = pud_mkdirty(entry); 1228 haddr = vmf->address & HPAGE_PUD_MASK; 1229 if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write)) 1230 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud); 1231 1232 unlock: 1233 spin_unlock(vmf->ptl); 1234 } 1235 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ 1236 1237 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd) 1238 { 1239 pmd_t entry; 1240 unsigned long haddr; 1241 bool write = vmf->flags & FAULT_FLAG_WRITE; 1242 1243 vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); 1244 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) 1245 goto unlock; 1246 1247 entry = pmd_mkyoung(orig_pmd); 1248 if (write) 1249 entry = pmd_mkdirty(entry); 1250 haddr = vmf->address & HPAGE_PMD_MASK; 1251 if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write)) 1252 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd); 1253 1254 unlock: 1255 spin_unlock(vmf->ptl); 1256 } 1257 1258 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, 1259 pmd_t orig_pmd, struct page *page) 1260 { 1261 struct vm_area_struct *vma = vmf->vma; 1262 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 1263 struct mem_cgroup *memcg; 1264 pgtable_t pgtable; 1265 pmd_t _pmd; 1266 int i; 1267 vm_fault_t ret = 0; 1268 struct page **pages; 1269 struct mmu_notifier_range range; 1270 1271 pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *), 1272 GFP_KERNEL); 1273 if (unlikely(!pages)) { 1274 ret |= VM_FAULT_OOM; 1275 goto out; 1276 } 1277 1278 for (i = 0; i < HPAGE_PMD_NR; i++) { 1279 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma, 1280 vmf->address, page_to_nid(page)); 1281 if (unlikely(!pages[i] || 1282 mem_cgroup_try_charge_delay(pages[i], vma->vm_mm, 1283 GFP_KERNEL, &memcg, false))) { 1284 if (pages[i]) 1285 put_page(pages[i]); 1286 while (--i >= 0) { 1287 memcg = (void *)page_private(pages[i]); 1288 set_page_private(pages[i], 0); 1289 mem_cgroup_cancel_charge(pages[i], memcg, 1290 false); 1291 put_page(pages[i]); 1292 } 1293 kfree(pages); 1294 ret |= VM_FAULT_OOM; 1295 goto out; 1296 } 1297 set_page_private(pages[i], (unsigned long)memcg); 1298 } 1299 1300 for (i = 0; i < HPAGE_PMD_NR; i++) { 1301 copy_user_highpage(pages[i], page + i, 1302 haddr + PAGE_SIZE * i, vma); 1303 __SetPageUptodate(pages[i]); 1304 cond_resched(); 1305 } 1306 1307 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, 1308 haddr, haddr + HPAGE_PMD_SIZE); 1309 mmu_notifier_invalidate_range_start(&range); 1310 1311 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 1312 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) 1313 goto out_free_pages; 1314 VM_BUG_ON_PAGE(!PageHead(page), page); 1315 1316 /* 1317 * Leave pmd empty until pte is filled note we must notify here as 1318 * concurrent CPU thread might write to new page before the call to 1319 * mmu_notifier_invalidate_range_end() happens which can lead to a 1320 * device seeing memory write in different order than CPU. 1321 * 1322 * See Documentation/vm/mmu_notifier.rst 1323 */ 1324 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd); 1325 1326 pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd); 1327 pmd_populate(vma->vm_mm, &_pmd, pgtable); 1328 1329 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 1330 pte_t entry; 1331 entry = mk_pte(pages[i], vma->vm_page_prot); 1332 entry = maybe_mkwrite(pte_mkdirty(entry), vma); 1333 memcg = (void *)page_private(pages[i]); 1334 set_page_private(pages[i], 0); 1335 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false); 1336 mem_cgroup_commit_charge(pages[i], memcg, false, false); 1337 lru_cache_add_active_or_unevictable(pages[i], vma); 1338 vmf->pte = pte_offset_map(&_pmd, haddr); 1339 VM_BUG_ON(!pte_none(*vmf->pte)); 1340 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry); 1341 pte_unmap(vmf->pte); 1342 } 1343 kfree(pages); 1344 1345 smp_wmb(); /* make pte visible before pmd */ 1346 pmd_populate(vma->vm_mm, vmf->pmd, pgtable); 1347 page_remove_rmap(page, true); 1348 spin_unlock(vmf->ptl); 1349 1350 /* 1351 * No need to double call mmu_notifier->invalidate_range() callback as 1352 * the above pmdp_huge_clear_flush_notify() did already call it. 1353 */ 1354 mmu_notifier_invalidate_range_only_end(&range); 1355 1356 ret |= VM_FAULT_WRITE; 1357 put_page(page); 1358 1359 out: 1360 return ret; 1361 1362 out_free_pages: 1363 spin_unlock(vmf->ptl); 1364 mmu_notifier_invalidate_range_end(&range); 1365 for (i = 0; i < HPAGE_PMD_NR; i++) { 1366 memcg = (void *)page_private(pages[i]); 1367 set_page_private(pages[i], 0); 1368 mem_cgroup_cancel_charge(pages[i], memcg, false); 1369 put_page(pages[i]); 1370 } 1371 kfree(pages); 1372 goto out; 1373 } 1374 1375 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd) 1376 { 1377 struct vm_area_struct *vma = vmf->vma; 1378 struct page *page = NULL, *new_page; 1379 struct mem_cgroup *memcg; 1380 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 1381 struct mmu_notifier_range range; 1382 gfp_t huge_gfp; /* for allocation and charge */ 1383 vm_fault_t ret = 0; 1384 1385 vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd); 1386 VM_BUG_ON_VMA(!vma->anon_vma, vma); 1387 if (is_huge_zero_pmd(orig_pmd)) 1388 goto alloc; 1389 spin_lock(vmf->ptl); 1390 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) 1391 goto out_unlock; 1392 1393 page = pmd_page(orig_pmd); 1394 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); 1395 /* 1396 * We can only reuse the page if nobody else maps the huge page or it's 1397 * part. 1398 */ 1399 if (!trylock_page(page)) { 1400 get_page(page); 1401 spin_unlock(vmf->ptl); 1402 lock_page(page); 1403 spin_lock(vmf->ptl); 1404 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { 1405 unlock_page(page); 1406 put_page(page); 1407 goto out_unlock; 1408 } 1409 put_page(page); 1410 } 1411 if (reuse_swap_page(page, NULL)) { 1412 pmd_t entry; 1413 entry = pmd_mkyoung(orig_pmd); 1414 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1415 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1)) 1416 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 1417 ret |= VM_FAULT_WRITE; 1418 unlock_page(page); 1419 goto out_unlock; 1420 } 1421 unlock_page(page); 1422 get_page(page); 1423 spin_unlock(vmf->ptl); 1424 alloc: 1425 if (__transparent_hugepage_enabled(vma) && 1426 !transparent_hugepage_debug_cow()) { 1427 huge_gfp = alloc_hugepage_direct_gfpmask(vma); 1428 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER); 1429 } else 1430 new_page = NULL; 1431 1432 if (likely(new_page)) { 1433 prep_transhuge_page(new_page); 1434 } else { 1435 if (!page) { 1436 split_huge_pmd(vma, vmf->pmd, vmf->address); 1437 ret |= VM_FAULT_FALLBACK; 1438 } else { 1439 ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page); 1440 if (ret & VM_FAULT_OOM) { 1441 split_huge_pmd(vma, vmf->pmd, vmf->address); 1442 ret |= VM_FAULT_FALLBACK; 1443 } 1444 put_page(page); 1445 } 1446 count_vm_event(THP_FAULT_FALLBACK); 1447 goto out; 1448 } 1449 1450 if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm, 1451 huge_gfp, &memcg, true))) { 1452 put_page(new_page); 1453 split_huge_pmd(vma, vmf->pmd, vmf->address); 1454 if (page) 1455 put_page(page); 1456 ret |= VM_FAULT_FALLBACK; 1457 count_vm_event(THP_FAULT_FALLBACK); 1458 count_vm_event(THP_FAULT_FALLBACK_CHARGE); 1459 goto out; 1460 } 1461 1462 count_vm_event(THP_FAULT_ALLOC); 1463 count_memcg_events(memcg, THP_FAULT_ALLOC, 1); 1464 1465 if (!page) 1466 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR); 1467 else 1468 copy_user_huge_page(new_page, page, vmf->address, 1469 vma, HPAGE_PMD_NR); 1470 __SetPageUptodate(new_page); 1471 1472 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, 1473 haddr, haddr + HPAGE_PMD_SIZE); 1474 mmu_notifier_invalidate_range_start(&range); 1475 1476 spin_lock(vmf->ptl); 1477 if (page) 1478 put_page(page); 1479 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { 1480 spin_unlock(vmf->ptl); 1481 mem_cgroup_cancel_charge(new_page, memcg, true); 1482 put_page(new_page); 1483 goto out_mn; 1484 } else { 1485 pmd_t entry; 1486 entry = mk_huge_pmd(new_page, vma->vm_page_prot); 1487 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 1488 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd); 1489 page_add_new_anon_rmap(new_page, vma, haddr, true); 1490 mem_cgroup_commit_charge(new_page, memcg, false, true); 1491 lru_cache_add_active_or_unevictable(new_page, vma); 1492 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); 1493 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 1494 if (!page) { 1495 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); 1496 } else { 1497 VM_BUG_ON_PAGE(!PageHead(page), page); 1498 page_remove_rmap(page, true); 1499 put_page(page); 1500 } 1501 ret |= VM_FAULT_WRITE; 1502 } 1503 spin_unlock(vmf->ptl); 1504 out_mn: 1505 /* 1506 * No need to double call mmu_notifier->invalidate_range() callback as 1507 * the above pmdp_huge_clear_flush_notify() did already call it. 1508 */ 1509 mmu_notifier_invalidate_range_only_end(&range); 1510 out: 1511 return ret; 1512 out_unlock: 1513 spin_unlock(vmf->ptl); 1514 return ret; 1515 } 1516 1517 /* 1518 * FOLL_FORCE or a forced COW break can write even to unwritable pmd's, 1519 * but only after we've gone through a COW cycle and they are dirty. 1520 */ 1521 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags) 1522 { 1523 return pmd_write(pmd) || ((flags & FOLL_COW) && pmd_dirty(pmd)); 1524 } 1525 1526 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1527 unsigned long addr, 1528 pmd_t *pmd, 1529 unsigned int flags) 1530 { 1531 struct mm_struct *mm = vma->vm_mm; 1532 struct page *page = NULL; 1533 1534 assert_spin_locked(pmd_lockptr(mm, pmd)); 1535 1536 if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags)) 1537 goto out; 1538 1539 /* Avoid dumping huge zero page */ 1540 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) 1541 return ERR_PTR(-EFAULT); 1542 1543 /* Full NUMA hinting faults to serialise migration in fault paths */ 1544 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) 1545 goto out; 1546 1547 page = pmd_page(*pmd); 1548 VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page); 1549 1550 if (!try_grab_page(page, flags)) 1551 return ERR_PTR(-ENOMEM); 1552 1553 if (flags & FOLL_TOUCH) 1554 touch_pmd(vma, addr, pmd, flags); 1555 1556 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 1557 /* 1558 * We don't mlock() pte-mapped THPs. This way we can avoid 1559 * leaking mlocked pages into non-VM_LOCKED VMAs. 1560 * 1561 * For anon THP: 1562 * 1563 * In most cases the pmd is the only mapping of the page as we 1564 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for 1565 * writable private mappings in populate_vma_page_range(). 1566 * 1567 * The only scenario when we have the page shared here is if we 1568 * mlocking read-only mapping shared over fork(). We skip 1569 * mlocking such pages. 1570 * 1571 * For file THP: 1572 * 1573 * We can expect PageDoubleMap() to be stable under page lock: 1574 * for file pages we set it in page_add_file_rmap(), which 1575 * requires page to be locked. 1576 */ 1577 1578 if (PageAnon(page) && compound_mapcount(page) != 1) 1579 goto skip_mlock; 1580 if (PageDoubleMap(page) || !page->mapping) 1581 goto skip_mlock; 1582 if (!trylock_page(page)) 1583 goto skip_mlock; 1584 lru_add_drain(); 1585 if (page->mapping && !PageDoubleMap(page)) 1586 mlock_vma_page(page); 1587 unlock_page(page); 1588 } 1589 skip_mlock: 1590 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1591 VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page); 1592 1593 out: 1594 return page; 1595 } 1596 1597 /* NUMA hinting page fault entry point for trans huge pmds */ 1598 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) 1599 { 1600 struct vm_area_struct *vma = vmf->vma; 1601 struct anon_vma *anon_vma = NULL; 1602 struct page *page; 1603 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 1604 int page_nid = NUMA_NO_NODE, this_nid = numa_node_id(); 1605 int target_nid, last_cpupid = -1; 1606 bool page_locked; 1607 bool migrated = false; 1608 bool was_writable; 1609 int flags = 0; 1610 1611 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 1612 if (unlikely(!pmd_same(pmd, *vmf->pmd))) 1613 goto out_unlock; 1614 1615 /* 1616 * If there are potential migrations, wait for completion and retry 1617 * without disrupting NUMA hinting information. Do not relock and 1618 * check_same as the page may no longer be mapped. 1619 */ 1620 if (unlikely(pmd_trans_migrating(*vmf->pmd))) { 1621 page = pmd_page(*vmf->pmd); 1622 if (!get_page_unless_zero(page)) 1623 goto out_unlock; 1624 spin_unlock(vmf->ptl); 1625 put_and_wait_on_page_locked(page); 1626 goto out; 1627 } 1628 1629 page = pmd_page(pmd); 1630 BUG_ON(is_huge_zero_page(page)); 1631 page_nid = page_to_nid(page); 1632 last_cpupid = page_cpupid_last(page); 1633 count_vm_numa_event(NUMA_HINT_FAULTS); 1634 if (page_nid == this_nid) { 1635 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); 1636 flags |= TNF_FAULT_LOCAL; 1637 } 1638 1639 /* See similar comment in do_numa_page for explanation */ 1640 if (!pmd_savedwrite(pmd)) 1641 flags |= TNF_NO_GROUP; 1642 1643 /* 1644 * Acquire the page lock to serialise THP migrations but avoid dropping 1645 * page_table_lock if at all possible 1646 */ 1647 page_locked = trylock_page(page); 1648 target_nid = mpol_misplaced(page, vma, haddr); 1649 if (target_nid == NUMA_NO_NODE) { 1650 /* If the page was locked, there are no parallel migrations */ 1651 if (page_locked) 1652 goto clear_pmdnuma; 1653 } 1654 1655 /* Migration could have started since the pmd_trans_migrating check */ 1656 if (!page_locked) { 1657 page_nid = NUMA_NO_NODE; 1658 if (!get_page_unless_zero(page)) 1659 goto out_unlock; 1660 spin_unlock(vmf->ptl); 1661 put_and_wait_on_page_locked(page); 1662 goto out; 1663 } 1664 1665 /* 1666 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma 1667 * to serialises splits 1668 */ 1669 get_page(page); 1670 spin_unlock(vmf->ptl); 1671 anon_vma = page_lock_anon_vma_read(page); 1672 1673 /* Confirm the PMD did not change while page_table_lock was released */ 1674 spin_lock(vmf->ptl); 1675 if (unlikely(!pmd_same(pmd, *vmf->pmd))) { 1676 unlock_page(page); 1677 put_page(page); 1678 page_nid = NUMA_NO_NODE; 1679 goto out_unlock; 1680 } 1681 1682 /* Bail if we fail to protect against THP splits for any reason */ 1683 if (unlikely(!anon_vma)) { 1684 put_page(page); 1685 page_nid = NUMA_NO_NODE; 1686 goto clear_pmdnuma; 1687 } 1688 1689 /* 1690 * Since we took the NUMA fault, we must have observed the !accessible 1691 * bit. Make sure all other CPUs agree with that, to avoid them 1692 * modifying the page we're about to migrate. 1693 * 1694 * Must be done under PTL such that we'll observe the relevant 1695 * inc_tlb_flush_pending(). 1696 * 1697 * We are not sure a pending tlb flush here is for a huge page 1698 * mapping or not. Hence use the tlb range variant 1699 */ 1700 if (mm_tlb_flush_pending(vma->vm_mm)) { 1701 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE); 1702 /* 1703 * change_huge_pmd() released the pmd lock before 1704 * invalidating the secondary MMUs sharing the primary 1705 * MMU pagetables (with ->invalidate_range()). The 1706 * mmu_notifier_invalidate_range_end() (which 1707 * internally calls ->invalidate_range()) in 1708 * change_pmd_range() will run after us, so we can't 1709 * rely on it here and we need an explicit invalidate. 1710 */ 1711 mmu_notifier_invalidate_range(vma->vm_mm, haddr, 1712 haddr + HPAGE_PMD_SIZE); 1713 } 1714 1715 /* 1716 * Migrate the THP to the requested node, returns with page unlocked 1717 * and access rights restored. 1718 */ 1719 spin_unlock(vmf->ptl); 1720 1721 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma, 1722 vmf->pmd, pmd, vmf->address, page, target_nid); 1723 if (migrated) { 1724 flags |= TNF_MIGRATED; 1725 page_nid = target_nid; 1726 } else 1727 flags |= TNF_MIGRATE_FAIL; 1728 1729 goto out; 1730 clear_pmdnuma: 1731 BUG_ON(!PageLocked(page)); 1732 was_writable = pmd_savedwrite(pmd); 1733 pmd = pmd_modify(pmd, vma->vm_page_prot); 1734 pmd = pmd_mkyoung(pmd); 1735 if (was_writable) 1736 pmd = pmd_mkwrite(pmd); 1737 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd); 1738 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 1739 unlock_page(page); 1740 out_unlock: 1741 spin_unlock(vmf->ptl); 1742 1743 out: 1744 if (anon_vma) 1745 page_unlock_anon_vma_read(anon_vma); 1746 1747 if (page_nid != NUMA_NO_NODE) 1748 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, 1749 flags); 1750 1751 return 0; 1752 } 1753 1754 /* 1755 * Return true if we do MADV_FREE successfully on entire pmd page. 1756 * Otherwise, return false. 1757 */ 1758 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1759 pmd_t *pmd, unsigned long addr, unsigned long next) 1760 { 1761 spinlock_t *ptl; 1762 pmd_t orig_pmd; 1763 struct page *page; 1764 struct mm_struct *mm = tlb->mm; 1765 bool ret = false; 1766 1767 tlb_change_page_size(tlb, HPAGE_PMD_SIZE); 1768 1769 ptl = pmd_trans_huge_lock(pmd, vma); 1770 if (!ptl) 1771 goto out_unlocked; 1772 1773 orig_pmd = *pmd; 1774 if (is_huge_zero_pmd(orig_pmd)) 1775 goto out; 1776 1777 if (unlikely(!pmd_present(orig_pmd))) { 1778 VM_BUG_ON(thp_migration_supported() && 1779 !is_pmd_migration_entry(orig_pmd)); 1780 goto out; 1781 } 1782 1783 page = pmd_page(orig_pmd); 1784 /* 1785 * If other processes are mapping this page, we couldn't discard 1786 * the page unless they all do MADV_FREE so let's skip the page. 1787 */ 1788 if (page_mapcount(page) != 1) 1789 goto out; 1790 1791 if (!trylock_page(page)) 1792 goto out; 1793 1794 /* 1795 * If user want to discard part-pages of THP, split it so MADV_FREE 1796 * will deactivate only them. 1797 */ 1798 if (next - addr != HPAGE_PMD_SIZE) { 1799 get_page(page); 1800 spin_unlock(ptl); 1801 split_huge_page(page); 1802 unlock_page(page); 1803 put_page(page); 1804 goto out_unlocked; 1805 } 1806 1807 if (PageDirty(page)) 1808 ClearPageDirty(page); 1809 unlock_page(page); 1810 1811 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { 1812 pmdp_invalidate(vma, addr, pmd); 1813 orig_pmd = pmd_mkold(orig_pmd); 1814 orig_pmd = pmd_mkclean(orig_pmd); 1815 1816 set_pmd_at(mm, addr, pmd, orig_pmd); 1817 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1818 } 1819 1820 mark_page_lazyfree(page); 1821 ret = true; 1822 out: 1823 spin_unlock(ptl); 1824 out_unlocked: 1825 return ret; 1826 } 1827 1828 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd) 1829 { 1830 pgtable_t pgtable; 1831 1832 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1833 pte_free(mm, pgtable); 1834 mm_dec_nr_ptes(mm); 1835 } 1836 1837 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1838 pmd_t *pmd, unsigned long addr) 1839 { 1840 pmd_t orig_pmd; 1841 spinlock_t *ptl; 1842 1843 tlb_change_page_size(tlb, HPAGE_PMD_SIZE); 1844 1845 ptl = __pmd_trans_huge_lock(pmd, vma); 1846 if (!ptl) 1847 return 0; 1848 /* 1849 * For architectures like ppc64 we look at deposited pgtable 1850 * when calling pmdp_huge_get_and_clear. So do the 1851 * pgtable_trans_huge_withdraw after finishing pmdp related 1852 * operations. 1853 */ 1854 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, 1855 tlb->fullmm); 1856 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1857 if (vma_is_special_huge(vma)) { 1858 if (arch_needs_pgtable_deposit()) 1859 zap_deposited_table(tlb->mm, pmd); 1860 spin_unlock(ptl); 1861 if (is_huge_zero_pmd(orig_pmd)) 1862 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); 1863 } else if (is_huge_zero_pmd(orig_pmd)) { 1864 zap_deposited_table(tlb->mm, pmd); 1865 spin_unlock(ptl); 1866 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); 1867 } else { 1868 struct page *page = NULL; 1869 int flush_needed = 1; 1870 1871 if (pmd_present(orig_pmd)) { 1872 page = pmd_page(orig_pmd); 1873 page_remove_rmap(page, true); 1874 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); 1875 VM_BUG_ON_PAGE(!PageHead(page), page); 1876 } else if (thp_migration_supported()) { 1877 swp_entry_t entry; 1878 1879 VM_BUG_ON(!is_pmd_migration_entry(orig_pmd)); 1880 entry = pmd_to_swp_entry(orig_pmd); 1881 page = pfn_to_page(swp_offset(entry)); 1882 flush_needed = 0; 1883 } else 1884 WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!"); 1885 1886 if (PageAnon(page)) { 1887 zap_deposited_table(tlb->mm, pmd); 1888 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1889 } else { 1890 if (arch_needs_pgtable_deposit()) 1891 zap_deposited_table(tlb->mm, pmd); 1892 add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR); 1893 } 1894 1895 spin_unlock(ptl); 1896 if (flush_needed) 1897 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE); 1898 } 1899 return 1; 1900 } 1901 1902 #ifndef pmd_move_must_withdraw 1903 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl, 1904 spinlock_t *old_pmd_ptl, 1905 struct vm_area_struct *vma) 1906 { 1907 /* 1908 * With split pmd lock we also need to move preallocated 1909 * PTE page table if new_pmd is on different PMD page table. 1910 * 1911 * We also don't deposit and withdraw tables for file pages. 1912 */ 1913 return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma); 1914 } 1915 #endif 1916 1917 static pmd_t move_soft_dirty_pmd(pmd_t pmd) 1918 { 1919 #ifdef CONFIG_MEM_SOFT_DIRTY 1920 if (unlikely(is_pmd_migration_entry(pmd))) 1921 pmd = pmd_swp_mksoft_dirty(pmd); 1922 else if (pmd_present(pmd)) 1923 pmd = pmd_mksoft_dirty(pmd); 1924 #endif 1925 return pmd; 1926 } 1927 1928 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr, 1929 unsigned long new_addr, unsigned long old_end, 1930 pmd_t *old_pmd, pmd_t *new_pmd) 1931 { 1932 spinlock_t *old_ptl, *new_ptl; 1933 pmd_t pmd; 1934 struct mm_struct *mm = vma->vm_mm; 1935 bool force_flush = false; 1936 1937 if ((old_addr & ~HPAGE_PMD_MASK) || 1938 (new_addr & ~HPAGE_PMD_MASK) || 1939 old_end - old_addr < HPAGE_PMD_SIZE) 1940 return false; 1941 1942 /* 1943 * The destination pmd shouldn't be established, free_pgtables() 1944 * should have release it. 1945 */ 1946 if (WARN_ON(!pmd_none(*new_pmd))) { 1947 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1948 return false; 1949 } 1950 1951 /* 1952 * We don't have to worry about the ordering of src and dst 1953 * ptlocks because exclusive mmap_sem prevents deadlock. 1954 */ 1955 old_ptl = __pmd_trans_huge_lock(old_pmd, vma); 1956 if (old_ptl) { 1957 new_ptl = pmd_lockptr(mm, new_pmd); 1958 if (new_ptl != old_ptl) 1959 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 1960 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd); 1961 if (pmd_present(pmd)) 1962 force_flush = true; 1963 VM_BUG_ON(!pmd_none(*new_pmd)); 1964 1965 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) { 1966 pgtable_t pgtable; 1967 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); 1968 pgtable_trans_huge_deposit(mm, new_pmd, pgtable); 1969 } 1970 pmd = move_soft_dirty_pmd(pmd); 1971 set_pmd_at(mm, new_addr, new_pmd, pmd); 1972 if (force_flush) 1973 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE); 1974 if (new_ptl != old_ptl) 1975 spin_unlock(new_ptl); 1976 spin_unlock(old_ptl); 1977 return true; 1978 } 1979 return false; 1980 } 1981 1982 /* 1983 * Returns 1984 * - 0 if PMD could not be locked 1985 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary 1986 * - HPAGE_PMD_NR is protections changed and TLB flush necessary 1987 */ 1988 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1989 unsigned long addr, pgprot_t newprot, unsigned long cp_flags) 1990 { 1991 struct mm_struct *mm = vma->vm_mm; 1992 spinlock_t *ptl; 1993 pmd_t entry; 1994 bool preserve_write; 1995 int ret; 1996 bool prot_numa = cp_flags & MM_CP_PROT_NUMA; 1997 bool uffd_wp = cp_flags & MM_CP_UFFD_WP; 1998 bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; 1999 2000 ptl = __pmd_trans_huge_lock(pmd, vma); 2001 if (!ptl) 2002 return 0; 2003 2004 preserve_write = prot_numa && pmd_write(*pmd); 2005 ret = 1; 2006 2007 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 2008 if (is_swap_pmd(*pmd)) { 2009 swp_entry_t entry = pmd_to_swp_entry(*pmd); 2010 2011 VM_BUG_ON(!is_pmd_migration_entry(*pmd)); 2012 if (is_write_migration_entry(entry)) { 2013 pmd_t newpmd; 2014 /* 2015 * A protection check is difficult so 2016 * just be safe and disable write 2017 */ 2018 make_migration_entry_read(&entry); 2019 newpmd = swp_entry_to_pmd(entry); 2020 if (pmd_swp_soft_dirty(*pmd)) 2021 newpmd = pmd_swp_mksoft_dirty(newpmd); 2022 set_pmd_at(mm, addr, pmd, newpmd); 2023 } 2024 goto unlock; 2025 } 2026 #endif 2027 2028 /* 2029 * Avoid trapping faults against the zero page. The read-only 2030 * data is likely to be read-cached on the local CPU and 2031 * local/remote hits to the zero page are not interesting. 2032 */ 2033 if (prot_numa && is_huge_zero_pmd(*pmd)) 2034 goto unlock; 2035 2036 if (prot_numa && pmd_protnone(*pmd)) 2037 goto unlock; 2038 2039 /* 2040 * In case prot_numa, we are under down_read(mmap_sem). It's critical 2041 * to not clear pmd intermittently to avoid race with MADV_DONTNEED 2042 * which is also under down_read(mmap_sem): 2043 * 2044 * CPU0: CPU1: 2045 * change_huge_pmd(prot_numa=1) 2046 * pmdp_huge_get_and_clear_notify() 2047 * madvise_dontneed() 2048 * zap_pmd_range() 2049 * pmd_trans_huge(*pmd) == 0 (without ptl) 2050 * // skip the pmd 2051 * set_pmd_at(); 2052 * // pmd is re-established 2053 * 2054 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it 2055 * which may break userspace. 2056 * 2057 * pmdp_invalidate() is required to make sure we don't miss 2058 * dirty/young flags set by hardware. 2059 */ 2060 entry = pmdp_invalidate(vma, addr, pmd); 2061 2062 entry = pmd_modify(entry, newprot); 2063 if (preserve_write) 2064 entry = pmd_mk_savedwrite(entry); 2065 if (uffd_wp) { 2066 entry = pmd_wrprotect(entry); 2067 entry = pmd_mkuffd_wp(entry); 2068 } else if (uffd_wp_resolve) { 2069 /* 2070 * Leave the write bit to be handled by PF interrupt 2071 * handler, then things like COW could be properly 2072 * handled. 2073 */ 2074 entry = pmd_clear_uffd_wp(entry); 2075 } 2076 ret = HPAGE_PMD_NR; 2077 set_pmd_at(mm, addr, pmd, entry); 2078 BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry)); 2079 unlock: 2080 spin_unlock(ptl); 2081 return ret; 2082 } 2083 2084 /* 2085 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise. 2086 * 2087 * Note that if it returns page table lock pointer, this routine returns without 2088 * unlocking page table lock. So callers must unlock it. 2089 */ 2090 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) 2091 { 2092 spinlock_t *ptl; 2093 ptl = pmd_lock(vma->vm_mm, pmd); 2094 if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || 2095 pmd_devmap(*pmd))) 2096 return ptl; 2097 spin_unlock(ptl); 2098 return NULL; 2099 } 2100 2101 /* 2102 * Returns true if a given pud maps a thp, false otherwise. 2103 * 2104 * Note that if it returns true, this routine returns without unlocking page 2105 * table lock. So callers must unlock it. 2106 */ 2107 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma) 2108 { 2109 spinlock_t *ptl; 2110 2111 ptl = pud_lock(vma->vm_mm, pud); 2112 if (likely(pud_trans_huge(*pud) || pud_devmap(*pud))) 2113 return ptl; 2114 spin_unlock(ptl); 2115 return NULL; 2116 } 2117 2118 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 2119 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma, 2120 pud_t *pud, unsigned long addr) 2121 { 2122 spinlock_t *ptl; 2123 2124 ptl = __pud_trans_huge_lock(pud, vma); 2125 if (!ptl) 2126 return 0; 2127 /* 2128 * For architectures like ppc64 we look at deposited pgtable 2129 * when calling pudp_huge_get_and_clear. So do the 2130 * pgtable_trans_huge_withdraw after finishing pudp related 2131 * operations. 2132 */ 2133 pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm); 2134 tlb_remove_pud_tlb_entry(tlb, pud, addr); 2135 if (vma_is_special_huge(vma)) { 2136 spin_unlock(ptl); 2137 /* No zero page support yet */ 2138 } else { 2139 /* No support for anonymous PUD pages yet */ 2140 BUG(); 2141 } 2142 return 1; 2143 } 2144 2145 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud, 2146 unsigned long haddr) 2147 { 2148 VM_BUG_ON(haddr & ~HPAGE_PUD_MASK); 2149 VM_BUG_ON_VMA(vma->vm_start > haddr, vma); 2150 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma); 2151 VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud)); 2152 2153 count_vm_event(THP_SPLIT_PUD); 2154 2155 pudp_huge_clear_flush_notify(vma, haddr, pud); 2156 } 2157 2158 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud, 2159 unsigned long address) 2160 { 2161 spinlock_t *ptl; 2162 struct mmu_notifier_range range; 2163 2164 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, 2165 address & HPAGE_PUD_MASK, 2166 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE); 2167 mmu_notifier_invalidate_range_start(&range); 2168 ptl = pud_lock(vma->vm_mm, pud); 2169 if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud))) 2170 goto out; 2171 __split_huge_pud_locked(vma, pud, range.start); 2172 2173 out: 2174 spin_unlock(ptl); 2175 /* 2176 * No need to double call mmu_notifier->invalidate_range() callback as 2177 * the above pudp_huge_clear_flush_notify() did already call it. 2178 */ 2179 mmu_notifier_invalidate_range_only_end(&range); 2180 } 2181 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ 2182 2183 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2184 unsigned long haddr, pmd_t *pmd) 2185 { 2186 struct mm_struct *mm = vma->vm_mm; 2187 pgtable_t pgtable; 2188 pmd_t _pmd; 2189 int i; 2190 2191 /* 2192 * Leave pmd empty until pte is filled note that it is fine to delay 2193 * notification until mmu_notifier_invalidate_range_end() as we are 2194 * replacing a zero pmd write protected page with a zero pte write 2195 * protected page. 2196 * 2197 * See Documentation/vm/mmu_notifier.rst 2198 */ 2199 pmdp_huge_clear_flush(vma, haddr, pmd); 2200 2201 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2202 pmd_populate(mm, &_pmd, pgtable); 2203 2204 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2205 pte_t *pte, entry; 2206 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2207 entry = pte_mkspecial(entry); 2208 pte = pte_offset_map(&_pmd, haddr); 2209 VM_BUG_ON(!pte_none(*pte)); 2210 set_pte_at(mm, haddr, pte, entry); 2211 pte_unmap(pte); 2212 } 2213 smp_wmb(); /* make pte visible before pmd */ 2214 pmd_populate(mm, pmd, pgtable); 2215 } 2216 2217 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 2218 unsigned long haddr, bool freeze) 2219 { 2220 struct mm_struct *mm = vma->vm_mm; 2221 struct page *page; 2222 pgtable_t pgtable; 2223 pmd_t old_pmd, _pmd; 2224 bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false; 2225 unsigned long addr; 2226 int i; 2227 2228 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK); 2229 VM_BUG_ON_VMA(vma->vm_start > haddr, vma); 2230 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma); 2231 VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd) 2232 && !pmd_devmap(*pmd)); 2233 2234 count_vm_event(THP_SPLIT_PMD); 2235 2236 if (!vma_is_anonymous(vma)) { 2237 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd); 2238 /* 2239 * We are going to unmap this huge page. So 2240 * just go ahead and zap it 2241 */ 2242 if (arch_needs_pgtable_deposit()) 2243 zap_deposited_table(mm, pmd); 2244 if (vma_is_special_huge(vma)) 2245 return; 2246 page = pmd_page(_pmd); 2247 if (!PageDirty(page) && pmd_dirty(_pmd)) 2248 set_page_dirty(page); 2249 if (!PageReferenced(page) && pmd_young(_pmd)) 2250 SetPageReferenced(page); 2251 page_remove_rmap(page, true); 2252 put_page(page); 2253 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR); 2254 return; 2255 } else if (is_huge_zero_pmd(*pmd)) { 2256 /* 2257 * FIXME: Do we want to invalidate secondary mmu by calling 2258 * mmu_notifier_invalidate_range() see comments below inside 2259 * __split_huge_pmd() ? 2260 * 2261 * We are going from a zero huge page write protected to zero 2262 * small page also write protected so it does not seems useful 2263 * to invalidate secondary mmu at this time. 2264 */ 2265 return __split_huge_zero_page_pmd(vma, haddr, pmd); 2266 } 2267 2268 /* 2269 * Up to this point the pmd is present and huge and userland has the 2270 * whole access to the hugepage during the split (which happens in 2271 * place). If we overwrite the pmd with the not-huge version pointing 2272 * to the pte here (which of course we could if all CPUs were bug 2273 * free), userland could trigger a small page size TLB miss on the 2274 * small sized TLB while the hugepage TLB entry is still established in 2275 * the huge TLB. Some CPU doesn't like that. 2276 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum 2277 * 383 on page 93. Intel should be safe but is also warns that it's 2278 * only safe if the permission and cache attributes of the two entries 2279 * loaded in the two TLB is identical (which should be the case here). 2280 * But it is generally safer to never allow small and huge TLB entries 2281 * for the same virtual address to be loaded simultaneously. So instead 2282 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the 2283 * current pmd notpresent (atomically because here the pmd_trans_huge 2284 * must remain set at all times on the pmd until the split is complete 2285 * for this pmd), then we flush the SMP TLB and finally we write the 2286 * non-huge version of the pmd entry with pmd_populate. 2287 */ 2288 old_pmd = pmdp_invalidate(vma, haddr, pmd); 2289 2290 pmd_migration = is_pmd_migration_entry(old_pmd); 2291 if (unlikely(pmd_migration)) { 2292 swp_entry_t entry; 2293 2294 entry = pmd_to_swp_entry(old_pmd); 2295 page = pfn_to_page(swp_offset(entry)); 2296 write = is_write_migration_entry(entry); 2297 young = false; 2298 soft_dirty = pmd_swp_soft_dirty(old_pmd); 2299 uffd_wp = pmd_swp_uffd_wp(old_pmd); 2300 } else { 2301 page = pmd_page(old_pmd); 2302 if (pmd_dirty(old_pmd)) 2303 SetPageDirty(page); 2304 write = pmd_write(old_pmd); 2305 young = pmd_young(old_pmd); 2306 soft_dirty = pmd_soft_dirty(old_pmd); 2307 uffd_wp = pmd_uffd_wp(old_pmd); 2308 } 2309 VM_BUG_ON_PAGE(!page_count(page), page); 2310 page_ref_add(page, HPAGE_PMD_NR - 1); 2311 2312 /* 2313 * Withdraw the table only after we mark the pmd entry invalid. 2314 * This's critical for some architectures (Power). 2315 */ 2316 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2317 pmd_populate(mm, &_pmd, pgtable); 2318 2319 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { 2320 pte_t entry, *pte; 2321 /* 2322 * Note that NUMA hinting access restrictions are not 2323 * transferred to avoid any possibility of altering 2324 * permissions across VMAs. 2325 */ 2326 if (freeze || pmd_migration) { 2327 swp_entry_t swp_entry; 2328 swp_entry = make_migration_entry(page + i, write); 2329 entry = swp_entry_to_pte(swp_entry); 2330 if (soft_dirty) 2331 entry = pte_swp_mksoft_dirty(entry); 2332 if (uffd_wp) 2333 entry = pte_swp_mkuffd_wp(entry); 2334 } else { 2335 entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot)); 2336 entry = maybe_mkwrite(entry, vma); 2337 if (!write) 2338 entry = pte_wrprotect(entry); 2339 if (!young) 2340 entry = pte_mkold(entry); 2341 if (soft_dirty) 2342 entry = pte_mksoft_dirty(entry); 2343 if (uffd_wp) 2344 entry = pte_mkuffd_wp(entry); 2345 } 2346 pte = pte_offset_map(&_pmd, addr); 2347 BUG_ON(!pte_none(*pte)); 2348 set_pte_at(mm, addr, pte, entry); 2349 atomic_inc(&page[i]._mapcount); 2350 pte_unmap(pte); 2351 } 2352 2353 /* 2354 * Set PG_double_map before dropping compound_mapcount to avoid 2355 * false-negative page_mapped(). 2356 */ 2357 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) { 2358 for (i = 0; i < HPAGE_PMD_NR; i++) 2359 atomic_inc(&page[i]._mapcount); 2360 } 2361 2362 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { 2363 /* Last compound_mapcount is gone. */ 2364 __dec_node_page_state(page, NR_ANON_THPS); 2365 if (TestClearPageDoubleMap(page)) { 2366 /* No need in mapcount reference anymore */ 2367 for (i = 0; i < HPAGE_PMD_NR; i++) 2368 atomic_dec(&page[i]._mapcount); 2369 } 2370 } 2371 2372 smp_wmb(); /* make pte visible before pmd */ 2373 pmd_populate(mm, pmd, pgtable); 2374 2375 if (freeze) { 2376 for (i = 0; i < HPAGE_PMD_NR; i++) { 2377 page_remove_rmap(page + i, false); 2378 put_page(page + i); 2379 } 2380 } 2381 } 2382 2383 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 2384 unsigned long address, bool freeze, struct page *page) 2385 { 2386 spinlock_t *ptl; 2387 struct mmu_notifier_range range; 2388 2389 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, 2390 address & HPAGE_PMD_MASK, 2391 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE); 2392 mmu_notifier_invalidate_range_start(&range); 2393 ptl = pmd_lock(vma->vm_mm, pmd); 2394 2395 /* 2396 * If caller asks to setup a migration entries, we need a page to check 2397 * pmd against. Otherwise we can end up replacing wrong page. 2398 */ 2399 VM_BUG_ON(freeze && !page); 2400 if (page && page != pmd_page(*pmd)) 2401 goto out; 2402 2403 if (pmd_trans_huge(*pmd)) { 2404 page = pmd_page(*pmd); 2405 if (PageMlocked(page)) 2406 clear_page_mlock(page); 2407 } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd))) 2408 goto out; 2409 __split_huge_pmd_locked(vma, pmd, range.start, freeze); 2410 out: 2411 spin_unlock(ptl); 2412 /* 2413 * No need to double call mmu_notifier->invalidate_range() callback. 2414 * They are 3 cases to consider inside __split_huge_pmd_locked(): 2415 * 1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious 2416 * 2) __split_huge_zero_page_pmd() read only zero page and any write 2417 * fault will trigger a flush_notify before pointing to a new page 2418 * (it is fine if the secondary mmu keeps pointing to the old zero 2419 * page in the meantime) 2420 * 3) Split a huge pmd into pte pointing to the same page. No need 2421 * to invalidate secondary tlb entry they are all still valid. 2422 * any further changes to individual pte will notify. So no need 2423 * to call mmu_notifier->invalidate_range() 2424 */ 2425 mmu_notifier_invalidate_range_only_end(&range); 2426 } 2427 2428 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, 2429 bool freeze, struct page *page) 2430 { 2431 pgd_t *pgd; 2432 p4d_t *p4d; 2433 pud_t *pud; 2434 pmd_t *pmd; 2435 2436 pgd = pgd_offset(vma->vm_mm, address); 2437 if (!pgd_present(*pgd)) 2438 return; 2439 2440 p4d = p4d_offset(pgd, address); 2441 if (!p4d_present(*p4d)) 2442 return; 2443 2444 pud = pud_offset(p4d, address); 2445 if (!pud_present(*pud)) 2446 return; 2447 2448 pmd = pmd_offset(pud, address); 2449 2450 __split_huge_pmd(vma, pmd, address, freeze, page); 2451 } 2452 2453 void vma_adjust_trans_huge(struct vm_area_struct *vma, 2454 unsigned long start, 2455 unsigned long end, 2456 long adjust_next) 2457 { 2458 /* 2459 * If the new start address isn't hpage aligned and it could 2460 * previously contain an hugepage: check if we need to split 2461 * an huge pmd. 2462 */ 2463 if (start & ~HPAGE_PMD_MASK && 2464 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2465 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2466 split_huge_pmd_address(vma, start, false, NULL); 2467 2468 /* 2469 * If the new end address isn't hpage aligned and it could 2470 * previously contain an hugepage: check if we need to split 2471 * an huge pmd. 2472 */ 2473 if (end & ~HPAGE_PMD_MASK && 2474 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2475 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2476 split_huge_pmd_address(vma, end, false, NULL); 2477 2478 /* 2479 * If we're also updating the vma->vm_next->vm_start, if the new 2480 * vm_next->vm_start isn't page aligned and it could previously 2481 * contain an hugepage: check if we need to split an huge pmd. 2482 */ 2483 if (adjust_next > 0) { 2484 struct vm_area_struct *next = vma->vm_next; 2485 unsigned long nstart = next->vm_start; 2486 nstart += adjust_next << PAGE_SHIFT; 2487 if (nstart & ~HPAGE_PMD_MASK && 2488 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2489 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2490 split_huge_pmd_address(next, nstart, false, NULL); 2491 } 2492 } 2493 2494 static void unmap_page(struct page *page) 2495 { 2496 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS | 2497 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD; 2498 bool unmap_success; 2499 2500 VM_BUG_ON_PAGE(!PageHead(page), page); 2501 2502 if (PageAnon(page)) 2503 ttu_flags |= TTU_SPLIT_FREEZE; 2504 2505 unmap_success = try_to_unmap(page, ttu_flags); 2506 VM_BUG_ON_PAGE(!unmap_success, page); 2507 } 2508 2509 static void remap_page(struct page *page) 2510 { 2511 int i; 2512 if (PageTransHuge(page)) { 2513 remove_migration_ptes(page, page, true); 2514 } else { 2515 for (i = 0; i < HPAGE_PMD_NR; i++) 2516 remove_migration_ptes(page + i, page + i, true); 2517 } 2518 } 2519 2520 static void __split_huge_page_tail(struct page *head, int tail, 2521 struct lruvec *lruvec, struct list_head *list) 2522 { 2523 struct page *page_tail = head + tail; 2524 2525 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); 2526 2527 /* 2528 * Clone page flags before unfreezing refcount. 2529 * 2530 * After successful get_page_unless_zero() might follow flags change, 2531 * for exmaple lock_page() which set PG_waiters. 2532 */ 2533 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; 2534 page_tail->flags |= (head->flags & 2535 ((1L << PG_referenced) | 2536 (1L << PG_swapbacked) | 2537 (1L << PG_swapcache) | 2538 (1L << PG_mlocked) | 2539 (1L << PG_uptodate) | 2540 (1L << PG_active) | 2541 (1L << PG_workingset) | 2542 (1L << PG_locked) | 2543 (1L << PG_unevictable) | 2544 (1L << PG_dirty))); 2545 2546 /* ->mapping in first tail page is compound_mapcount */ 2547 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING, 2548 page_tail); 2549 page_tail->mapping = head->mapping; 2550 page_tail->index = head->index + tail; 2551 2552 /* Page flags must be visible before we make the page non-compound. */ 2553 smp_wmb(); 2554 2555 /* 2556 * Clear PageTail before unfreezing page refcount. 2557 * 2558 * After successful get_page_unless_zero() might follow put_page() 2559 * which needs correct compound_head(). 2560 */ 2561 clear_compound_head(page_tail); 2562 2563 /* Finally unfreeze refcount. Additional reference from page cache. */ 2564 page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) || 2565 PageSwapCache(head))); 2566 2567 if (page_is_young(head)) 2568 set_page_young(page_tail); 2569 if (page_is_idle(head)) 2570 set_page_idle(page_tail); 2571 2572 page_cpupid_xchg_last(page_tail, page_cpupid_last(head)); 2573 2574 /* 2575 * always add to the tail because some iterators expect new 2576 * pages to show after the currently processed elements - e.g. 2577 * migrate_pages 2578 */ 2579 lru_add_page_tail(head, page_tail, lruvec, list); 2580 } 2581 2582 static void __split_huge_page(struct page *page, struct list_head *list, 2583 pgoff_t end, unsigned long flags) 2584 { 2585 struct page *head = compound_head(page); 2586 pg_data_t *pgdat = page_pgdat(head); 2587 struct lruvec *lruvec; 2588 struct address_space *swap_cache = NULL; 2589 unsigned long offset = 0; 2590 int i; 2591 2592 lruvec = mem_cgroup_page_lruvec(head, pgdat); 2593 2594 /* complete memcg works before add pages to LRU */ 2595 mem_cgroup_split_huge_fixup(head); 2596 2597 if (PageAnon(head) && PageSwapCache(head)) { 2598 swp_entry_t entry = { .val = page_private(head) }; 2599 2600 offset = swp_offset(entry); 2601 swap_cache = swap_address_space(entry); 2602 xa_lock(&swap_cache->i_pages); 2603 } 2604 2605 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 2606 __split_huge_page_tail(head, i, lruvec, list); 2607 /* Some pages can be beyond i_size: drop them from page cache */ 2608 if (head[i].index >= end) { 2609 ClearPageDirty(head + i); 2610 __delete_from_page_cache(head + i, NULL); 2611 if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head)) 2612 shmem_uncharge(head->mapping->host, 1); 2613 put_page(head + i); 2614 } else if (!PageAnon(page)) { 2615 __xa_store(&head->mapping->i_pages, head[i].index, 2616 head + i, 0); 2617 } else if (swap_cache) { 2618 __xa_store(&swap_cache->i_pages, offset + i, 2619 head + i, 0); 2620 } 2621 } 2622 2623 ClearPageCompound(head); 2624 2625 split_page_owner(head, HPAGE_PMD_ORDER); 2626 2627 /* See comment in __split_huge_page_tail() */ 2628 if (PageAnon(head)) { 2629 /* Additional pin to swap cache */ 2630 if (PageSwapCache(head)) { 2631 page_ref_add(head, 2); 2632 xa_unlock(&swap_cache->i_pages); 2633 } else { 2634 page_ref_inc(head); 2635 } 2636 } else { 2637 /* Additional pin to page cache */ 2638 page_ref_add(head, 2); 2639 xa_unlock(&head->mapping->i_pages); 2640 } 2641 2642 spin_unlock_irqrestore(&pgdat->lru_lock, flags); 2643 2644 remap_page(head); 2645 2646 for (i = 0; i < HPAGE_PMD_NR; i++) { 2647 struct page *subpage = head + i; 2648 if (subpage == page) 2649 continue; 2650 unlock_page(subpage); 2651 2652 /* 2653 * Subpages may be freed if there wasn't any mapping 2654 * like if add_to_swap() is running on a lru page that 2655 * had its mapping zapped. And freeing these pages 2656 * requires taking the lru_lock so we do the put_page 2657 * of the tail pages after the split is complete. 2658 */ 2659 put_page(subpage); 2660 } 2661 } 2662 2663 int total_mapcount(struct page *page) 2664 { 2665 int i, compound, ret; 2666 2667 VM_BUG_ON_PAGE(PageTail(page), page); 2668 2669 if (likely(!PageCompound(page))) 2670 return atomic_read(&page->_mapcount) + 1; 2671 2672 compound = compound_mapcount(page); 2673 if (PageHuge(page)) 2674 return compound; 2675 ret = compound; 2676 for (i = 0; i < HPAGE_PMD_NR; i++) 2677 ret += atomic_read(&page[i]._mapcount) + 1; 2678 /* File pages has compound_mapcount included in _mapcount */ 2679 if (!PageAnon(page)) 2680 return ret - compound * HPAGE_PMD_NR; 2681 if (PageDoubleMap(page)) 2682 ret -= HPAGE_PMD_NR; 2683 return ret; 2684 } 2685 2686 /* 2687 * This calculates accurately how many mappings a transparent hugepage 2688 * has (unlike page_mapcount() which isn't fully accurate). This full 2689 * accuracy is primarily needed to know if copy-on-write faults can 2690 * reuse the page and change the mapping to read-write instead of 2691 * copying them. At the same time this returns the total_mapcount too. 2692 * 2693 * The function returns the highest mapcount any one of the subpages 2694 * has. If the return value is one, even if different processes are 2695 * mapping different subpages of the transparent hugepage, they can 2696 * all reuse it, because each process is reusing a different subpage. 2697 * 2698 * The total_mapcount is instead counting all virtual mappings of the 2699 * subpages. If the total_mapcount is equal to "one", it tells the 2700 * caller all mappings belong to the same "mm" and in turn the 2701 * anon_vma of the transparent hugepage can become the vma->anon_vma 2702 * local one as no other process may be mapping any of the subpages. 2703 * 2704 * It would be more accurate to replace page_mapcount() with 2705 * page_trans_huge_mapcount(), however we only use 2706 * page_trans_huge_mapcount() in the copy-on-write faults where we 2707 * need full accuracy to avoid breaking page pinning, because 2708 * page_trans_huge_mapcount() is slower than page_mapcount(). 2709 */ 2710 int page_trans_huge_mapcount(struct page *page, int *total_mapcount) 2711 { 2712 int i, ret, _total_mapcount, mapcount; 2713 2714 /* hugetlbfs shouldn't call it */ 2715 VM_BUG_ON_PAGE(PageHuge(page), page); 2716 2717 if (likely(!PageTransCompound(page))) { 2718 mapcount = atomic_read(&page->_mapcount) + 1; 2719 if (total_mapcount) 2720 *total_mapcount = mapcount; 2721 return mapcount; 2722 } 2723 2724 page = compound_head(page); 2725 2726 _total_mapcount = ret = 0; 2727 for (i = 0; i < HPAGE_PMD_NR; i++) { 2728 mapcount = atomic_read(&page[i]._mapcount) + 1; 2729 ret = max(ret, mapcount); 2730 _total_mapcount += mapcount; 2731 } 2732 if (PageDoubleMap(page)) { 2733 ret -= 1; 2734 _total_mapcount -= HPAGE_PMD_NR; 2735 } 2736 mapcount = compound_mapcount(page); 2737 ret += mapcount; 2738 _total_mapcount += mapcount; 2739 if (total_mapcount) 2740 *total_mapcount = _total_mapcount; 2741 return ret; 2742 } 2743 2744 /* Racy check whether the huge page can be split */ 2745 bool can_split_huge_page(struct page *page, int *pextra_pins) 2746 { 2747 int extra_pins; 2748 2749 /* Additional pins from page cache */ 2750 if (PageAnon(page)) 2751 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0; 2752 else 2753 extra_pins = HPAGE_PMD_NR; 2754 if (pextra_pins) 2755 *pextra_pins = extra_pins; 2756 return total_mapcount(page) == page_count(page) - extra_pins - 1; 2757 } 2758 2759 /* 2760 * This function splits huge page into normal pages. @page can point to any 2761 * subpage of huge page to split. Split doesn't change the position of @page. 2762 * 2763 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY. 2764 * The huge page must be locked. 2765 * 2766 * If @list is null, tail pages will be added to LRU list, otherwise, to @list. 2767 * 2768 * Both head page and tail pages will inherit mapping, flags, and so on from 2769 * the hugepage. 2770 * 2771 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if 2772 * they are not mapped. 2773 * 2774 * Returns 0 if the hugepage is split successfully. 2775 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under 2776 * us. 2777 */ 2778 int split_huge_page_to_list(struct page *page, struct list_head *list) 2779 { 2780 struct page *head = compound_head(page); 2781 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head)); 2782 struct deferred_split *ds_queue = get_deferred_split_queue(head); 2783 struct anon_vma *anon_vma = NULL; 2784 struct address_space *mapping = NULL; 2785 int count, mapcount, extra_pins, ret; 2786 bool mlocked; 2787 unsigned long flags; 2788 pgoff_t end; 2789 2790 VM_BUG_ON_PAGE(is_huge_zero_page(head), head); 2791 VM_BUG_ON_PAGE(!PageLocked(head), head); 2792 VM_BUG_ON_PAGE(!PageCompound(head), head); 2793 2794 if (PageWriteback(head)) 2795 return -EBUSY; 2796 2797 if (PageAnon(head)) { 2798 /* 2799 * The caller does not necessarily hold an mmap_sem that would 2800 * prevent the anon_vma disappearing so we first we take a 2801 * reference to it and then lock the anon_vma for write. This 2802 * is similar to page_lock_anon_vma_read except the write lock 2803 * is taken to serialise against parallel split or collapse 2804 * operations. 2805 */ 2806 anon_vma = page_get_anon_vma(head); 2807 if (!anon_vma) { 2808 ret = -EBUSY; 2809 goto out; 2810 } 2811 end = -1; 2812 mapping = NULL; 2813 anon_vma_lock_write(anon_vma); 2814 } else { 2815 mapping = head->mapping; 2816 2817 /* Truncated ? */ 2818 if (!mapping) { 2819 ret = -EBUSY; 2820 goto out; 2821 } 2822 2823 anon_vma = NULL; 2824 i_mmap_lock_read(mapping); 2825 2826 /* 2827 *__split_huge_page() may need to trim off pages beyond EOF: 2828 * but on 32-bit, i_size_read() takes an irq-unsafe seqlock, 2829 * which cannot be nested inside the page tree lock. So note 2830 * end now: i_size itself may be changed at any moment, but 2831 * head page lock is good enough to serialize the trimming. 2832 */ 2833 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); 2834 } 2835 2836 /* 2837 * Racy check if we can split the page, before unmap_page() will 2838 * split PMDs 2839 */ 2840 if (!can_split_huge_page(head, &extra_pins)) { 2841 ret = -EBUSY; 2842 goto out_unlock; 2843 } 2844 2845 mlocked = PageMlocked(head); 2846 unmap_page(head); 2847 VM_BUG_ON_PAGE(compound_mapcount(head), head); 2848 2849 /* Make sure the page is not on per-CPU pagevec as it takes pin */ 2850 if (mlocked) 2851 lru_add_drain(); 2852 2853 /* prevent PageLRU to go away from under us, and freeze lru stats */ 2854 spin_lock_irqsave(&pgdata->lru_lock, flags); 2855 2856 if (mapping) { 2857 XA_STATE(xas, &mapping->i_pages, page_index(head)); 2858 2859 /* 2860 * Check if the head page is present in page cache. 2861 * We assume all tail are present too, if head is there. 2862 */ 2863 xa_lock(&mapping->i_pages); 2864 if (xas_load(&xas) != head) 2865 goto fail; 2866 } 2867 2868 /* Prevent deferred_split_scan() touching ->_refcount */ 2869 spin_lock(&ds_queue->split_queue_lock); 2870 count = page_count(head); 2871 mapcount = total_mapcount(head); 2872 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) { 2873 if (!list_empty(page_deferred_list(head))) { 2874 ds_queue->split_queue_len--; 2875 list_del(page_deferred_list(head)); 2876 } 2877 spin_unlock(&ds_queue->split_queue_lock); 2878 if (mapping) { 2879 if (PageSwapBacked(head)) 2880 __dec_node_page_state(head, NR_SHMEM_THPS); 2881 else 2882 __dec_node_page_state(head, NR_FILE_THPS); 2883 } 2884 2885 __split_huge_page(page, list, end, flags); 2886 if (PageSwapCache(head)) { 2887 swp_entry_t entry = { .val = page_private(head) }; 2888 2889 ret = split_swap_cluster(entry); 2890 } else 2891 ret = 0; 2892 } else { 2893 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { 2894 pr_alert("total_mapcount: %u, page_count(): %u\n", 2895 mapcount, count); 2896 if (PageTail(page)) 2897 dump_page(head, NULL); 2898 dump_page(page, "total_mapcount(head) > 0"); 2899 BUG(); 2900 } 2901 spin_unlock(&ds_queue->split_queue_lock); 2902 fail: if (mapping) 2903 xa_unlock(&mapping->i_pages); 2904 spin_unlock_irqrestore(&pgdata->lru_lock, flags); 2905 remap_page(head); 2906 ret = -EBUSY; 2907 } 2908 2909 out_unlock: 2910 if (anon_vma) { 2911 anon_vma_unlock_write(anon_vma); 2912 put_anon_vma(anon_vma); 2913 } 2914 if (mapping) 2915 i_mmap_unlock_read(mapping); 2916 out: 2917 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); 2918 return ret; 2919 } 2920 2921 void free_transhuge_page(struct page *page) 2922 { 2923 struct deferred_split *ds_queue = get_deferred_split_queue(page); 2924 unsigned long flags; 2925 2926 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 2927 if (!list_empty(page_deferred_list(page))) { 2928 ds_queue->split_queue_len--; 2929 list_del(page_deferred_list(page)); 2930 } 2931 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 2932 free_compound_page(page); 2933 } 2934 2935 void deferred_split_huge_page(struct page *page) 2936 { 2937 struct deferred_split *ds_queue = get_deferred_split_queue(page); 2938 #ifdef CONFIG_MEMCG 2939 struct mem_cgroup *memcg = compound_head(page)->mem_cgroup; 2940 #endif 2941 unsigned long flags; 2942 2943 VM_BUG_ON_PAGE(!PageTransHuge(page), page); 2944 2945 /* 2946 * The try_to_unmap() in page reclaim path might reach here too, 2947 * this may cause a race condition to corrupt deferred split queue. 2948 * And, if page reclaim is already handling the same page, it is 2949 * unnecessary to handle it again in shrinker. 2950 * 2951 * Check PageSwapCache to determine if the page is being 2952 * handled by page reclaim since THP swap would add the page into 2953 * swap cache before calling try_to_unmap(). 2954 */ 2955 if (PageSwapCache(page)) 2956 return; 2957 2958 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 2959 if (list_empty(page_deferred_list(page))) { 2960 count_vm_event(THP_DEFERRED_SPLIT_PAGE); 2961 list_add_tail(page_deferred_list(page), &ds_queue->split_queue); 2962 ds_queue->split_queue_len++; 2963 #ifdef CONFIG_MEMCG 2964 if (memcg) 2965 memcg_set_shrinker_bit(memcg, page_to_nid(page), 2966 deferred_split_shrinker.id); 2967 #endif 2968 } 2969 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 2970 } 2971 2972 static unsigned long deferred_split_count(struct shrinker *shrink, 2973 struct shrink_control *sc) 2974 { 2975 struct pglist_data *pgdata = NODE_DATA(sc->nid); 2976 struct deferred_split *ds_queue = &pgdata->deferred_split_queue; 2977 2978 #ifdef CONFIG_MEMCG 2979 if (sc->memcg) 2980 ds_queue = &sc->memcg->deferred_split_queue; 2981 #endif 2982 return READ_ONCE(ds_queue->split_queue_len); 2983 } 2984 2985 static unsigned long deferred_split_scan(struct shrinker *shrink, 2986 struct shrink_control *sc) 2987 { 2988 struct pglist_data *pgdata = NODE_DATA(sc->nid); 2989 struct deferred_split *ds_queue = &pgdata->deferred_split_queue; 2990 unsigned long flags; 2991 LIST_HEAD(list), *pos, *next; 2992 struct page *page; 2993 int split = 0; 2994 2995 #ifdef CONFIG_MEMCG 2996 if (sc->memcg) 2997 ds_queue = &sc->memcg->deferred_split_queue; 2998 #endif 2999 3000 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 3001 /* Take pin on all head pages to avoid freeing them under us */ 3002 list_for_each_safe(pos, next, &ds_queue->split_queue) { 3003 page = list_entry((void *)pos, struct page, mapping); 3004 page = compound_head(page); 3005 if (get_page_unless_zero(page)) { 3006 list_move(page_deferred_list(page), &list); 3007 } else { 3008 /* We lost race with put_compound_page() */ 3009 list_del_init(page_deferred_list(page)); 3010 ds_queue->split_queue_len--; 3011 } 3012 if (!--sc->nr_to_scan) 3013 break; 3014 } 3015 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 3016 3017 list_for_each_safe(pos, next, &list) { 3018 page = list_entry((void *)pos, struct page, mapping); 3019 if (!trylock_page(page)) 3020 goto next; 3021 /* split_huge_page() removes page from list on success */ 3022 if (!split_huge_page(page)) 3023 split++; 3024 unlock_page(page); 3025 next: 3026 put_page(page); 3027 } 3028 3029 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 3030 list_splice_tail(&list, &ds_queue->split_queue); 3031 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 3032 3033 /* 3034 * Stop shrinker if we didn't split any page, but the queue is empty. 3035 * This can happen if pages were freed under us. 3036 */ 3037 if (!split && list_empty(&ds_queue->split_queue)) 3038 return SHRINK_STOP; 3039 return split; 3040 } 3041 3042 static struct shrinker deferred_split_shrinker = { 3043 .count_objects = deferred_split_count, 3044 .scan_objects = deferred_split_scan, 3045 .seeks = DEFAULT_SEEKS, 3046 .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE | 3047 SHRINKER_NONSLAB, 3048 }; 3049 3050 #ifdef CONFIG_DEBUG_FS 3051 static int split_huge_pages_set(void *data, u64 val) 3052 { 3053 struct zone *zone; 3054 struct page *page; 3055 unsigned long pfn, max_zone_pfn; 3056 unsigned long total = 0, split = 0; 3057 3058 if (val != 1) 3059 return -EINVAL; 3060 3061 for_each_populated_zone(zone) { 3062 max_zone_pfn = zone_end_pfn(zone); 3063 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) { 3064 if (!pfn_valid(pfn)) 3065 continue; 3066 3067 page = pfn_to_page(pfn); 3068 if (!get_page_unless_zero(page)) 3069 continue; 3070 3071 if (zone != page_zone(page)) 3072 goto next; 3073 3074 if (!PageHead(page) || PageHuge(page) || !PageLRU(page)) 3075 goto next; 3076 3077 total++; 3078 lock_page(page); 3079 if (!split_huge_page(page)) 3080 split++; 3081 unlock_page(page); 3082 next: 3083 put_page(page); 3084 } 3085 } 3086 3087 pr_info("%lu of %lu THP split\n", split, total); 3088 3089 return 0; 3090 } 3091 DEFINE_DEBUGFS_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set, 3092 "%llu\n"); 3093 3094 static int __init split_huge_pages_debugfs(void) 3095 { 3096 debugfs_create_file("split_huge_pages", 0200, NULL, NULL, 3097 &split_huge_pages_fops); 3098 return 0; 3099 } 3100 late_initcall(split_huge_pages_debugfs); 3101 #endif 3102 3103 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 3104 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw, 3105 struct page *page) 3106 { 3107 struct vm_area_struct *vma = pvmw->vma; 3108 struct mm_struct *mm = vma->vm_mm; 3109 unsigned long address = pvmw->address; 3110 pmd_t pmdval; 3111 swp_entry_t entry; 3112 pmd_t pmdswp; 3113 3114 if (!(pvmw->pmd && !pvmw->pte)) 3115 return; 3116 3117 flush_cache_range(vma, address, address + HPAGE_PMD_SIZE); 3118 pmdval = pmdp_invalidate(vma, address, pvmw->pmd); 3119 if (pmd_dirty(pmdval)) 3120 set_page_dirty(page); 3121 entry = make_migration_entry(page, pmd_write(pmdval)); 3122 pmdswp = swp_entry_to_pmd(entry); 3123 if (pmd_soft_dirty(pmdval)) 3124 pmdswp = pmd_swp_mksoft_dirty(pmdswp); 3125 set_pmd_at(mm, address, pvmw->pmd, pmdswp); 3126 page_remove_rmap(page, true); 3127 put_page(page); 3128 } 3129 3130 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new) 3131 { 3132 struct vm_area_struct *vma = pvmw->vma; 3133 struct mm_struct *mm = vma->vm_mm; 3134 unsigned long address = pvmw->address; 3135 unsigned long mmun_start = address & HPAGE_PMD_MASK; 3136 pmd_t pmde; 3137 swp_entry_t entry; 3138 3139 if (!(pvmw->pmd && !pvmw->pte)) 3140 return; 3141 3142 entry = pmd_to_swp_entry(*pvmw->pmd); 3143 get_page(new); 3144 pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot)); 3145 if (pmd_swp_soft_dirty(*pvmw->pmd)) 3146 pmde = pmd_mksoft_dirty(pmde); 3147 if (is_write_migration_entry(entry)) 3148 pmde = maybe_pmd_mkwrite(pmde, vma); 3149 3150 flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE); 3151 if (PageAnon(new)) 3152 page_add_anon_rmap(new, vma, mmun_start, true); 3153 else 3154 page_add_file_rmap(new, true); 3155 set_pmd_at(mm, mmun_start, pvmw->pmd, pmde); 3156 if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new)) 3157 mlock_vma_page(new); 3158 update_mmu_cache_pmd(vma, address, pvmw->pmd); 3159 } 3160 #endif 3161