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 can write to even unwritable pmd's, but only 1519 * 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) || 1524 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd)); 1525 } 1526 1527 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, 1528 unsigned long addr, 1529 pmd_t *pmd, 1530 unsigned int flags) 1531 { 1532 struct mm_struct *mm = vma->vm_mm; 1533 struct page *page = NULL; 1534 1535 assert_spin_locked(pmd_lockptr(mm, pmd)); 1536 1537 if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags)) 1538 goto out; 1539 1540 /* Avoid dumping huge zero page */ 1541 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) 1542 return ERR_PTR(-EFAULT); 1543 1544 /* Full NUMA hinting faults to serialise migration in fault paths */ 1545 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) 1546 goto out; 1547 1548 page = pmd_page(*pmd); 1549 VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page); 1550 1551 if (!try_grab_page(page, flags)) 1552 return ERR_PTR(-ENOMEM); 1553 1554 if (flags & FOLL_TOUCH) 1555 touch_pmd(vma, addr, pmd, flags); 1556 1557 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { 1558 /* 1559 * We don't mlock() pte-mapped THPs. This way we can avoid 1560 * leaking mlocked pages into non-VM_LOCKED VMAs. 1561 * 1562 * For anon THP: 1563 * 1564 * In most cases the pmd is the only mapping of the page as we 1565 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for 1566 * writable private mappings in populate_vma_page_range(). 1567 * 1568 * The only scenario when we have the page shared here is if we 1569 * mlocking read-only mapping shared over fork(). We skip 1570 * mlocking such pages. 1571 * 1572 * For file THP: 1573 * 1574 * We can expect PageDoubleMap() to be stable under page lock: 1575 * for file pages we set it in page_add_file_rmap(), which 1576 * requires page to be locked. 1577 */ 1578 1579 if (PageAnon(page) && compound_mapcount(page) != 1) 1580 goto skip_mlock; 1581 if (PageDoubleMap(page) || !page->mapping) 1582 goto skip_mlock; 1583 if (!trylock_page(page)) 1584 goto skip_mlock; 1585 lru_add_drain(); 1586 if (page->mapping && !PageDoubleMap(page)) 1587 mlock_vma_page(page); 1588 unlock_page(page); 1589 } 1590 skip_mlock: 1591 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; 1592 VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page); 1593 1594 out: 1595 return page; 1596 } 1597 1598 /* NUMA hinting page fault entry point for trans huge pmds */ 1599 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) 1600 { 1601 struct vm_area_struct *vma = vmf->vma; 1602 struct anon_vma *anon_vma = NULL; 1603 struct page *page; 1604 unsigned long haddr = vmf->address & HPAGE_PMD_MASK; 1605 int page_nid = NUMA_NO_NODE, this_nid = numa_node_id(); 1606 int target_nid, last_cpupid = -1; 1607 bool page_locked; 1608 bool migrated = false; 1609 bool was_writable; 1610 int flags = 0; 1611 1612 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); 1613 if (unlikely(!pmd_same(pmd, *vmf->pmd))) 1614 goto out_unlock; 1615 1616 /* 1617 * If there are potential migrations, wait for completion and retry 1618 * without disrupting NUMA hinting information. Do not relock and 1619 * check_same as the page may no longer be mapped. 1620 */ 1621 if (unlikely(pmd_trans_migrating(*vmf->pmd))) { 1622 page = pmd_page(*vmf->pmd); 1623 if (!get_page_unless_zero(page)) 1624 goto out_unlock; 1625 spin_unlock(vmf->ptl); 1626 put_and_wait_on_page_locked(page); 1627 goto out; 1628 } 1629 1630 page = pmd_page(pmd); 1631 BUG_ON(is_huge_zero_page(page)); 1632 page_nid = page_to_nid(page); 1633 last_cpupid = page_cpupid_last(page); 1634 count_vm_numa_event(NUMA_HINT_FAULTS); 1635 if (page_nid == this_nid) { 1636 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); 1637 flags |= TNF_FAULT_LOCAL; 1638 } 1639 1640 /* See similar comment in do_numa_page for explanation */ 1641 if (!pmd_savedwrite(pmd)) 1642 flags |= TNF_NO_GROUP; 1643 1644 /* 1645 * Acquire the page lock to serialise THP migrations but avoid dropping 1646 * page_table_lock if at all possible 1647 */ 1648 page_locked = trylock_page(page); 1649 target_nid = mpol_misplaced(page, vma, haddr); 1650 if (target_nid == NUMA_NO_NODE) { 1651 /* If the page was locked, there are no parallel migrations */ 1652 if (page_locked) 1653 goto clear_pmdnuma; 1654 } 1655 1656 /* Migration could have started since the pmd_trans_migrating check */ 1657 if (!page_locked) { 1658 page_nid = NUMA_NO_NODE; 1659 if (!get_page_unless_zero(page)) 1660 goto out_unlock; 1661 spin_unlock(vmf->ptl); 1662 put_and_wait_on_page_locked(page); 1663 goto out; 1664 } 1665 1666 /* 1667 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma 1668 * to serialises splits 1669 */ 1670 get_page(page); 1671 spin_unlock(vmf->ptl); 1672 anon_vma = page_lock_anon_vma_read(page); 1673 1674 /* Confirm the PMD did not change while page_table_lock was released */ 1675 spin_lock(vmf->ptl); 1676 if (unlikely(!pmd_same(pmd, *vmf->pmd))) { 1677 unlock_page(page); 1678 put_page(page); 1679 page_nid = NUMA_NO_NODE; 1680 goto out_unlock; 1681 } 1682 1683 /* Bail if we fail to protect against THP splits for any reason */ 1684 if (unlikely(!anon_vma)) { 1685 put_page(page); 1686 page_nid = NUMA_NO_NODE; 1687 goto clear_pmdnuma; 1688 } 1689 1690 /* 1691 * Since we took the NUMA fault, we must have observed the !accessible 1692 * bit. Make sure all other CPUs agree with that, to avoid them 1693 * modifying the page we're about to migrate. 1694 * 1695 * Must be done under PTL such that we'll observe the relevant 1696 * inc_tlb_flush_pending(). 1697 * 1698 * We are not sure a pending tlb flush here is for a huge page 1699 * mapping or not. Hence use the tlb range variant 1700 */ 1701 if (mm_tlb_flush_pending(vma->vm_mm)) { 1702 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE); 1703 /* 1704 * change_huge_pmd() released the pmd lock before 1705 * invalidating the secondary MMUs sharing the primary 1706 * MMU pagetables (with ->invalidate_range()). The 1707 * mmu_notifier_invalidate_range_end() (which 1708 * internally calls ->invalidate_range()) in 1709 * change_pmd_range() will run after us, so we can't 1710 * rely on it here and we need an explicit invalidate. 1711 */ 1712 mmu_notifier_invalidate_range(vma->vm_mm, haddr, 1713 haddr + HPAGE_PMD_SIZE); 1714 } 1715 1716 /* 1717 * Migrate the THP to the requested node, returns with page unlocked 1718 * and access rights restored. 1719 */ 1720 spin_unlock(vmf->ptl); 1721 1722 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma, 1723 vmf->pmd, pmd, vmf->address, page, target_nid); 1724 if (migrated) { 1725 flags |= TNF_MIGRATED; 1726 page_nid = target_nid; 1727 } else 1728 flags |= TNF_MIGRATE_FAIL; 1729 1730 goto out; 1731 clear_pmdnuma: 1732 BUG_ON(!PageLocked(page)); 1733 was_writable = pmd_savedwrite(pmd); 1734 pmd = pmd_modify(pmd, vma->vm_page_prot); 1735 pmd = pmd_mkyoung(pmd); 1736 if (was_writable) 1737 pmd = pmd_mkwrite(pmd); 1738 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd); 1739 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); 1740 unlock_page(page); 1741 out_unlock: 1742 spin_unlock(vmf->ptl); 1743 1744 out: 1745 if (anon_vma) 1746 page_unlock_anon_vma_read(anon_vma); 1747 1748 if (page_nid != NUMA_NO_NODE) 1749 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, 1750 flags); 1751 1752 return 0; 1753 } 1754 1755 /* 1756 * Return true if we do MADV_FREE successfully on entire pmd page. 1757 * Otherwise, return false. 1758 */ 1759 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1760 pmd_t *pmd, unsigned long addr, unsigned long next) 1761 { 1762 spinlock_t *ptl; 1763 pmd_t orig_pmd; 1764 struct page *page; 1765 struct mm_struct *mm = tlb->mm; 1766 bool ret = false; 1767 1768 tlb_change_page_size(tlb, HPAGE_PMD_SIZE); 1769 1770 ptl = pmd_trans_huge_lock(pmd, vma); 1771 if (!ptl) 1772 goto out_unlocked; 1773 1774 orig_pmd = *pmd; 1775 if (is_huge_zero_pmd(orig_pmd)) 1776 goto out; 1777 1778 if (unlikely(!pmd_present(orig_pmd))) { 1779 VM_BUG_ON(thp_migration_supported() && 1780 !is_pmd_migration_entry(orig_pmd)); 1781 goto out; 1782 } 1783 1784 page = pmd_page(orig_pmd); 1785 /* 1786 * If other processes are mapping this page, we couldn't discard 1787 * the page unless they all do MADV_FREE so let's skip the page. 1788 */ 1789 if (page_mapcount(page) != 1) 1790 goto out; 1791 1792 if (!trylock_page(page)) 1793 goto out; 1794 1795 /* 1796 * If user want to discard part-pages of THP, split it so MADV_FREE 1797 * will deactivate only them. 1798 */ 1799 if (next - addr != HPAGE_PMD_SIZE) { 1800 get_page(page); 1801 spin_unlock(ptl); 1802 split_huge_page(page); 1803 unlock_page(page); 1804 put_page(page); 1805 goto out_unlocked; 1806 } 1807 1808 if (PageDirty(page)) 1809 ClearPageDirty(page); 1810 unlock_page(page); 1811 1812 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { 1813 pmdp_invalidate(vma, addr, pmd); 1814 orig_pmd = pmd_mkold(orig_pmd); 1815 orig_pmd = pmd_mkclean(orig_pmd); 1816 1817 set_pmd_at(mm, addr, pmd, orig_pmd); 1818 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1819 } 1820 1821 mark_page_lazyfree(page); 1822 ret = true; 1823 out: 1824 spin_unlock(ptl); 1825 out_unlocked: 1826 return ret; 1827 } 1828 1829 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd) 1830 { 1831 pgtable_t pgtable; 1832 1833 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 1834 pte_free(mm, pgtable); 1835 mm_dec_nr_ptes(mm); 1836 } 1837 1838 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 1839 pmd_t *pmd, unsigned long addr) 1840 { 1841 pmd_t orig_pmd; 1842 spinlock_t *ptl; 1843 1844 tlb_change_page_size(tlb, HPAGE_PMD_SIZE); 1845 1846 ptl = __pmd_trans_huge_lock(pmd, vma); 1847 if (!ptl) 1848 return 0; 1849 /* 1850 * For architectures like ppc64 we look at deposited pgtable 1851 * when calling pmdp_huge_get_and_clear. So do the 1852 * pgtable_trans_huge_withdraw after finishing pmdp related 1853 * operations. 1854 */ 1855 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, 1856 tlb->fullmm); 1857 tlb_remove_pmd_tlb_entry(tlb, pmd, addr); 1858 if (vma_is_special_huge(vma)) { 1859 if (arch_needs_pgtable_deposit()) 1860 zap_deposited_table(tlb->mm, pmd); 1861 spin_unlock(ptl); 1862 if (is_huge_zero_pmd(orig_pmd)) 1863 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); 1864 } else if (is_huge_zero_pmd(orig_pmd)) { 1865 zap_deposited_table(tlb->mm, pmd); 1866 spin_unlock(ptl); 1867 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); 1868 } else { 1869 struct page *page = NULL; 1870 int flush_needed = 1; 1871 1872 if (pmd_present(orig_pmd)) { 1873 page = pmd_page(orig_pmd); 1874 page_remove_rmap(page, true); 1875 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); 1876 VM_BUG_ON_PAGE(!PageHead(page), page); 1877 } else if (thp_migration_supported()) { 1878 swp_entry_t entry; 1879 1880 VM_BUG_ON(!is_pmd_migration_entry(orig_pmd)); 1881 entry = pmd_to_swp_entry(orig_pmd); 1882 page = pfn_to_page(swp_offset(entry)); 1883 flush_needed = 0; 1884 } else 1885 WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!"); 1886 1887 if (PageAnon(page)) { 1888 zap_deposited_table(tlb->mm, pmd); 1889 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); 1890 } else { 1891 if (arch_needs_pgtable_deposit()) 1892 zap_deposited_table(tlb->mm, pmd); 1893 add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR); 1894 } 1895 1896 spin_unlock(ptl); 1897 if (flush_needed) 1898 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE); 1899 } 1900 return 1; 1901 } 1902 1903 #ifndef pmd_move_must_withdraw 1904 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl, 1905 spinlock_t *old_pmd_ptl, 1906 struct vm_area_struct *vma) 1907 { 1908 /* 1909 * With split pmd lock we also need to move preallocated 1910 * PTE page table if new_pmd is on different PMD page table. 1911 * 1912 * We also don't deposit and withdraw tables for file pages. 1913 */ 1914 return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma); 1915 } 1916 #endif 1917 1918 static pmd_t move_soft_dirty_pmd(pmd_t pmd) 1919 { 1920 #ifdef CONFIG_MEM_SOFT_DIRTY 1921 if (unlikely(is_pmd_migration_entry(pmd))) 1922 pmd = pmd_swp_mksoft_dirty(pmd); 1923 else if (pmd_present(pmd)) 1924 pmd = pmd_mksoft_dirty(pmd); 1925 #endif 1926 return pmd; 1927 } 1928 1929 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr, 1930 unsigned long new_addr, unsigned long old_end, 1931 pmd_t *old_pmd, pmd_t *new_pmd) 1932 { 1933 spinlock_t *old_ptl, *new_ptl; 1934 pmd_t pmd; 1935 struct mm_struct *mm = vma->vm_mm; 1936 bool force_flush = false; 1937 1938 if ((old_addr & ~HPAGE_PMD_MASK) || 1939 (new_addr & ~HPAGE_PMD_MASK) || 1940 old_end - old_addr < HPAGE_PMD_SIZE) 1941 return false; 1942 1943 /* 1944 * The destination pmd shouldn't be established, free_pgtables() 1945 * should have release it. 1946 */ 1947 if (WARN_ON(!pmd_none(*new_pmd))) { 1948 VM_BUG_ON(pmd_trans_huge(*new_pmd)); 1949 return false; 1950 } 1951 1952 /* 1953 * We don't have to worry about the ordering of src and dst 1954 * ptlocks because exclusive mmap_sem prevents deadlock. 1955 */ 1956 old_ptl = __pmd_trans_huge_lock(old_pmd, vma); 1957 if (old_ptl) { 1958 new_ptl = pmd_lockptr(mm, new_pmd); 1959 if (new_ptl != old_ptl) 1960 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 1961 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd); 1962 if (pmd_present(pmd)) 1963 force_flush = true; 1964 VM_BUG_ON(!pmd_none(*new_pmd)); 1965 1966 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) { 1967 pgtable_t pgtable; 1968 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); 1969 pgtable_trans_huge_deposit(mm, new_pmd, pgtable); 1970 } 1971 pmd = move_soft_dirty_pmd(pmd); 1972 set_pmd_at(mm, new_addr, new_pmd, pmd); 1973 if (force_flush) 1974 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE); 1975 if (new_ptl != old_ptl) 1976 spin_unlock(new_ptl); 1977 spin_unlock(old_ptl); 1978 return true; 1979 } 1980 return false; 1981 } 1982 1983 /* 1984 * Returns 1985 * - 0 if PMD could not be locked 1986 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary 1987 * - HPAGE_PMD_NR is protections changed and TLB flush necessary 1988 */ 1989 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 1990 unsigned long addr, pgprot_t newprot, unsigned long cp_flags) 1991 { 1992 struct mm_struct *mm = vma->vm_mm; 1993 spinlock_t *ptl; 1994 pmd_t entry; 1995 bool preserve_write; 1996 int ret; 1997 bool prot_numa = cp_flags & MM_CP_PROT_NUMA; 1998 bool uffd_wp = cp_flags & MM_CP_UFFD_WP; 1999 bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; 2000 2001 ptl = __pmd_trans_huge_lock(pmd, vma); 2002 if (!ptl) 2003 return 0; 2004 2005 preserve_write = prot_numa && pmd_write(*pmd); 2006 ret = 1; 2007 2008 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 2009 if (is_swap_pmd(*pmd)) { 2010 swp_entry_t entry = pmd_to_swp_entry(*pmd); 2011 2012 VM_BUG_ON(!is_pmd_migration_entry(*pmd)); 2013 if (is_write_migration_entry(entry)) { 2014 pmd_t newpmd; 2015 /* 2016 * A protection check is difficult so 2017 * just be safe and disable write 2018 */ 2019 make_migration_entry_read(&entry); 2020 newpmd = swp_entry_to_pmd(entry); 2021 if (pmd_swp_soft_dirty(*pmd)) 2022 newpmd = pmd_swp_mksoft_dirty(newpmd); 2023 set_pmd_at(mm, addr, pmd, newpmd); 2024 } 2025 goto unlock; 2026 } 2027 #endif 2028 2029 /* 2030 * Avoid trapping faults against the zero page. The read-only 2031 * data is likely to be read-cached on the local CPU and 2032 * local/remote hits to the zero page are not interesting. 2033 */ 2034 if (prot_numa && is_huge_zero_pmd(*pmd)) 2035 goto unlock; 2036 2037 if (prot_numa && pmd_protnone(*pmd)) 2038 goto unlock; 2039 2040 /* 2041 * In case prot_numa, we are under down_read(mmap_sem). It's critical 2042 * to not clear pmd intermittently to avoid race with MADV_DONTNEED 2043 * which is also under down_read(mmap_sem): 2044 * 2045 * CPU0: CPU1: 2046 * change_huge_pmd(prot_numa=1) 2047 * pmdp_huge_get_and_clear_notify() 2048 * madvise_dontneed() 2049 * zap_pmd_range() 2050 * pmd_trans_huge(*pmd) == 0 (without ptl) 2051 * // skip the pmd 2052 * set_pmd_at(); 2053 * // pmd is re-established 2054 * 2055 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it 2056 * which may break userspace. 2057 * 2058 * pmdp_invalidate() is required to make sure we don't miss 2059 * dirty/young flags set by hardware. 2060 */ 2061 entry = pmdp_invalidate(vma, addr, pmd); 2062 2063 entry = pmd_modify(entry, newprot); 2064 if (preserve_write) 2065 entry = pmd_mk_savedwrite(entry); 2066 if (uffd_wp) { 2067 entry = pmd_wrprotect(entry); 2068 entry = pmd_mkuffd_wp(entry); 2069 } else if (uffd_wp_resolve) { 2070 /* 2071 * Leave the write bit to be handled by PF interrupt 2072 * handler, then things like COW could be properly 2073 * handled. 2074 */ 2075 entry = pmd_clear_uffd_wp(entry); 2076 } 2077 ret = HPAGE_PMD_NR; 2078 set_pmd_at(mm, addr, pmd, entry); 2079 BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry)); 2080 unlock: 2081 spin_unlock(ptl); 2082 return ret; 2083 } 2084 2085 /* 2086 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise. 2087 * 2088 * Note that if it returns page table lock pointer, this routine returns without 2089 * unlocking page table lock. So callers must unlock it. 2090 */ 2091 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) 2092 { 2093 spinlock_t *ptl; 2094 ptl = pmd_lock(vma->vm_mm, pmd); 2095 if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || 2096 pmd_devmap(*pmd))) 2097 return ptl; 2098 spin_unlock(ptl); 2099 return NULL; 2100 } 2101 2102 /* 2103 * Returns true if a given pud maps a thp, false otherwise. 2104 * 2105 * Note that if it returns true, this routine returns without unlocking page 2106 * table lock. So callers must unlock it. 2107 */ 2108 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma) 2109 { 2110 spinlock_t *ptl; 2111 2112 ptl = pud_lock(vma->vm_mm, pud); 2113 if (likely(pud_trans_huge(*pud) || pud_devmap(*pud))) 2114 return ptl; 2115 spin_unlock(ptl); 2116 return NULL; 2117 } 2118 2119 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 2120 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma, 2121 pud_t *pud, unsigned long addr) 2122 { 2123 spinlock_t *ptl; 2124 2125 ptl = __pud_trans_huge_lock(pud, vma); 2126 if (!ptl) 2127 return 0; 2128 /* 2129 * For architectures like ppc64 we look at deposited pgtable 2130 * when calling pudp_huge_get_and_clear. So do the 2131 * pgtable_trans_huge_withdraw after finishing pudp related 2132 * operations. 2133 */ 2134 pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm); 2135 tlb_remove_pud_tlb_entry(tlb, pud, addr); 2136 if (vma_is_special_huge(vma)) { 2137 spin_unlock(ptl); 2138 /* No zero page support yet */ 2139 } else { 2140 /* No support for anonymous PUD pages yet */ 2141 BUG(); 2142 } 2143 return 1; 2144 } 2145 2146 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud, 2147 unsigned long haddr) 2148 { 2149 VM_BUG_ON(haddr & ~HPAGE_PUD_MASK); 2150 VM_BUG_ON_VMA(vma->vm_start > haddr, vma); 2151 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma); 2152 VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud)); 2153 2154 count_vm_event(THP_SPLIT_PUD); 2155 2156 pudp_huge_clear_flush_notify(vma, haddr, pud); 2157 } 2158 2159 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud, 2160 unsigned long address) 2161 { 2162 spinlock_t *ptl; 2163 struct mmu_notifier_range range; 2164 2165 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, 2166 address & HPAGE_PUD_MASK, 2167 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE); 2168 mmu_notifier_invalidate_range_start(&range); 2169 ptl = pud_lock(vma->vm_mm, pud); 2170 if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud))) 2171 goto out; 2172 __split_huge_pud_locked(vma, pud, range.start); 2173 2174 out: 2175 spin_unlock(ptl); 2176 /* 2177 * No need to double call mmu_notifier->invalidate_range() callback as 2178 * the above pudp_huge_clear_flush_notify() did already call it. 2179 */ 2180 mmu_notifier_invalidate_range_only_end(&range); 2181 } 2182 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ 2183 2184 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, 2185 unsigned long haddr, pmd_t *pmd) 2186 { 2187 struct mm_struct *mm = vma->vm_mm; 2188 pgtable_t pgtable; 2189 pmd_t _pmd; 2190 int i; 2191 2192 /* 2193 * Leave pmd empty until pte is filled note that it is fine to delay 2194 * notification until mmu_notifier_invalidate_range_end() as we are 2195 * replacing a zero pmd write protected page with a zero pte write 2196 * protected page. 2197 * 2198 * See Documentation/vm/mmu_notifier.rst 2199 */ 2200 pmdp_huge_clear_flush(vma, haddr, pmd); 2201 2202 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2203 pmd_populate(mm, &_pmd, pgtable); 2204 2205 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { 2206 pte_t *pte, entry; 2207 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); 2208 entry = pte_mkspecial(entry); 2209 pte = pte_offset_map(&_pmd, haddr); 2210 VM_BUG_ON(!pte_none(*pte)); 2211 set_pte_at(mm, haddr, pte, entry); 2212 pte_unmap(pte); 2213 } 2214 smp_wmb(); /* make pte visible before pmd */ 2215 pmd_populate(mm, pmd, pgtable); 2216 } 2217 2218 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 2219 unsigned long haddr, bool freeze) 2220 { 2221 struct mm_struct *mm = vma->vm_mm; 2222 struct page *page; 2223 pgtable_t pgtable; 2224 pmd_t old_pmd, _pmd; 2225 bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false; 2226 unsigned long addr; 2227 int i; 2228 2229 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK); 2230 VM_BUG_ON_VMA(vma->vm_start > haddr, vma); 2231 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma); 2232 VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd) 2233 && !pmd_devmap(*pmd)); 2234 2235 count_vm_event(THP_SPLIT_PMD); 2236 2237 if (!vma_is_anonymous(vma)) { 2238 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd); 2239 /* 2240 * We are going to unmap this huge page. So 2241 * just go ahead and zap it 2242 */ 2243 if (arch_needs_pgtable_deposit()) 2244 zap_deposited_table(mm, pmd); 2245 if (vma_is_special_huge(vma)) 2246 return; 2247 page = pmd_page(_pmd); 2248 if (!PageDirty(page) && pmd_dirty(_pmd)) 2249 set_page_dirty(page); 2250 if (!PageReferenced(page) && pmd_young(_pmd)) 2251 SetPageReferenced(page); 2252 page_remove_rmap(page, true); 2253 put_page(page); 2254 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR); 2255 return; 2256 } else if (is_huge_zero_pmd(*pmd)) { 2257 /* 2258 * FIXME: Do we want to invalidate secondary mmu by calling 2259 * mmu_notifier_invalidate_range() see comments below inside 2260 * __split_huge_pmd() ? 2261 * 2262 * We are going from a zero huge page write protected to zero 2263 * small page also write protected so it does not seems useful 2264 * to invalidate secondary mmu at this time. 2265 */ 2266 return __split_huge_zero_page_pmd(vma, haddr, pmd); 2267 } 2268 2269 /* 2270 * Up to this point the pmd is present and huge and userland has the 2271 * whole access to the hugepage during the split (which happens in 2272 * place). If we overwrite the pmd with the not-huge version pointing 2273 * to the pte here (which of course we could if all CPUs were bug 2274 * free), userland could trigger a small page size TLB miss on the 2275 * small sized TLB while the hugepage TLB entry is still established in 2276 * the huge TLB. Some CPU doesn't like that. 2277 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum 2278 * 383 on page 93. Intel should be safe but is also warns that it's 2279 * only safe if the permission and cache attributes of the two entries 2280 * loaded in the two TLB is identical (which should be the case here). 2281 * But it is generally safer to never allow small and huge TLB entries 2282 * for the same virtual address to be loaded simultaneously. So instead 2283 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the 2284 * current pmd notpresent (atomically because here the pmd_trans_huge 2285 * must remain set at all times on the pmd until the split is complete 2286 * for this pmd), then we flush the SMP TLB and finally we write the 2287 * non-huge version of the pmd entry with pmd_populate. 2288 */ 2289 old_pmd = pmdp_invalidate(vma, haddr, pmd); 2290 2291 pmd_migration = is_pmd_migration_entry(old_pmd); 2292 if (unlikely(pmd_migration)) { 2293 swp_entry_t entry; 2294 2295 entry = pmd_to_swp_entry(old_pmd); 2296 page = pfn_to_page(swp_offset(entry)); 2297 write = is_write_migration_entry(entry); 2298 young = false; 2299 soft_dirty = pmd_swp_soft_dirty(old_pmd); 2300 uffd_wp = pmd_swp_uffd_wp(old_pmd); 2301 } else { 2302 page = pmd_page(old_pmd); 2303 if (pmd_dirty(old_pmd)) 2304 SetPageDirty(page); 2305 write = pmd_write(old_pmd); 2306 young = pmd_young(old_pmd); 2307 soft_dirty = pmd_soft_dirty(old_pmd); 2308 uffd_wp = pmd_uffd_wp(old_pmd); 2309 } 2310 VM_BUG_ON_PAGE(!page_count(page), page); 2311 page_ref_add(page, HPAGE_PMD_NR - 1); 2312 2313 /* 2314 * Withdraw the table only after we mark the pmd entry invalid. 2315 * This's critical for some architectures (Power). 2316 */ 2317 pgtable = pgtable_trans_huge_withdraw(mm, pmd); 2318 pmd_populate(mm, &_pmd, pgtable); 2319 2320 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { 2321 pte_t entry, *pte; 2322 /* 2323 * Note that NUMA hinting access restrictions are not 2324 * transferred to avoid any possibility of altering 2325 * permissions across VMAs. 2326 */ 2327 if (freeze || pmd_migration) { 2328 swp_entry_t swp_entry; 2329 swp_entry = make_migration_entry(page + i, write); 2330 entry = swp_entry_to_pte(swp_entry); 2331 if (soft_dirty) 2332 entry = pte_swp_mksoft_dirty(entry); 2333 if (uffd_wp) 2334 entry = pte_swp_mkuffd_wp(entry); 2335 } else { 2336 entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot)); 2337 entry = maybe_mkwrite(entry, vma); 2338 if (!write) 2339 entry = pte_wrprotect(entry); 2340 if (!young) 2341 entry = pte_mkold(entry); 2342 if (soft_dirty) 2343 entry = pte_mksoft_dirty(entry); 2344 if (uffd_wp) 2345 entry = pte_mkuffd_wp(entry); 2346 } 2347 pte = pte_offset_map(&_pmd, addr); 2348 BUG_ON(!pte_none(*pte)); 2349 set_pte_at(mm, addr, pte, entry); 2350 atomic_inc(&page[i]._mapcount); 2351 pte_unmap(pte); 2352 } 2353 2354 /* 2355 * Set PG_double_map before dropping compound_mapcount to avoid 2356 * false-negative page_mapped(). 2357 */ 2358 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) { 2359 for (i = 0; i < HPAGE_PMD_NR; i++) 2360 atomic_inc(&page[i]._mapcount); 2361 } 2362 2363 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { 2364 /* Last compound_mapcount is gone. */ 2365 __dec_node_page_state(page, NR_ANON_THPS); 2366 if (TestClearPageDoubleMap(page)) { 2367 /* No need in mapcount reference anymore */ 2368 for (i = 0; i < HPAGE_PMD_NR; i++) 2369 atomic_dec(&page[i]._mapcount); 2370 } 2371 } 2372 2373 smp_wmb(); /* make pte visible before pmd */ 2374 pmd_populate(mm, pmd, pgtable); 2375 2376 if (freeze) { 2377 for (i = 0; i < HPAGE_PMD_NR; i++) { 2378 page_remove_rmap(page + i, false); 2379 put_page(page + i); 2380 } 2381 } 2382 } 2383 2384 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 2385 unsigned long address, bool freeze, struct page *page) 2386 { 2387 spinlock_t *ptl; 2388 struct mmu_notifier_range range; 2389 2390 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, 2391 address & HPAGE_PMD_MASK, 2392 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE); 2393 mmu_notifier_invalidate_range_start(&range); 2394 ptl = pmd_lock(vma->vm_mm, pmd); 2395 2396 /* 2397 * If caller asks to setup a migration entries, we need a page to check 2398 * pmd against. Otherwise we can end up replacing wrong page. 2399 */ 2400 VM_BUG_ON(freeze && !page); 2401 if (page && page != pmd_page(*pmd)) 2402 goto out; 2403 2404 if (pmd_trans_huge(*pmd)) { 2405 page = pmd_page(*pmd); 2406 if (PageMlocked(page)) 2407 clear_page_mlock(page); 2408 } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd))) 2409 goto out; 2410 __split_huge_pmd_locked(vma, pmd, range.start, freeze); 2411 out: 2412 spin_unlock(ptl); 2413 /* 2414 * No need to double call mmu_notifier->invalidate_range() callback. 2415 * They are 3 cases to consider inside __split_huge_pmd_locked(): 2416 * 1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious 2417 * 2) __split_huge_zero_page_pmd() read only zero page and any write 2418 * fault will trigger a flush_notify before pointing to a new page 2419 * (it is fine if the secondary mmu keeps pointing to the old zero 2420 * page in the meantime) 2421 * 3) Split a huge pmd into pte pointing to the same page. No need 2422 * to invalidate secondary tlb entry they are all still valid. 2423 * any further changes to individual pte will notify. So no need 2424 * to call mmu_notifier->invalidate_range() 2425 */ 2426 mmu_notifier_invalidate_range_only_end(&range); 2427 } 2428 2429 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, 2430 bool freeze, struct page *page) 2431 { 2432 pgd_t *pgd; 2433 p4d_t *p4d; 2434 pud_t *pud; 2435 pmd_t *pmd; 2436 2437 pgd = pgd_offset(vma->vm_mm, address); 2438 if (!pgd_present(*pgd)) 2439 return; 2440 2441 p4d = p4d_offset(pgd, address); 2442 if (!p4d_present(*p4d)) 2443 return; 2444 2445 pud = pud_offset(p4d, address); 2446 if (!pud_present(*pud)) 2447 return; 2448 2449 pmd = pmd_offset(pud, address); 2450 2451 __split_huge_pmd(vma, pmd, address, freeze, page); 2452 } 2453 2454 void vma_adjust_trans_huge(struct vm_area_struct *vma, 2455 unsigned long start, 2456 unsigned long end, 2457 long adjust_next) 2458 { 2459 /* 2460 * If the new start address isn't hpage aligned and it could 2461 * previously contain an hugepage: check if we need to split 2462 * an huge pmd. 2463 */ 2464 if (start & ~HPAGE_PMD_MASK && 2465 (start & HPAGE_PMD_MASK) >= vma->vm_start && 2466 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2467 split_huge_pmd_address(vma, start, false, NULL); 2468 2469 /* 2470 * If the new end address isn't hpage aligned and it could 2471 * previously contain an hugepage: check if we need to split 2472 * an huge pmd. 2473 */ 2474 if (end & ~HPAGE_PMD_MASK && 2475 (end & HPAGE_PMD_MASK) >= vma->vm_start && 2476 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) 2477 split_huge_pmd_address(vma, end, false, NULL); 2478 2479 /* 2480 * If we're also updating the vma->vm_next->vm_start, if the new 2481 * vm_next->vm_start isn't page aligned and it could previously 2482 * contain an hugepage: check if we need to split an huge pmd. 2483 */ 2484 if (adjust_next > 0) { 2485 struct vm_area_struct *next = vma->vm_next; 2486 unsigned long nstart = next->vm_start; 2487 nstart += adjust_next << PAGE_SHIFT; 2488 if (nstart & ~HPAGE_PMD_MASK && 2489 (nstart & HPAGE_PMD_MASK) >= next->vm_start && 2490 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) 2491 split_huge_pmd_address(next, nstart, false, NULL); 2492 } 2493 } 2494 2495 static void unmap_page(struct page *page) 2496 { 2497 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS | 2498 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD; 2499 bool unmap_success; 2500 2501 VM_BUG_ON_PAGE(!PageHead(page), page); 2502 2503 if (PageAnon(page)) 2504 ttu_flags |= TTU_SPLIT_FREEZE; 2505 2506 unmap_success = try_to_unmap(page, ttu_flags); 2507 VM_BUG_ON_PAGE(!unmap_success, page); 2508 } 2509 2510 static void remap_page(struct page *page) 2511 { 2512 int i; 2513 if (PageTransHuge(page)) { 2514 remove_migration_ptes(page, page, true); 2515 } else { 2516 for (i = 0; i < HPAGE_PMD_NR; i++) 2517 remove_migration_ptes(page + i, page + i, true); 2518 } 2519 } 2520 2521 static void __split_huge_page_tail(struct page *head, int tail, 2522 struct lruvec *lruvec, struct list_head *list) 2523 { 2524 struct page *page_tail = head + tail; 2525 2526 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); 2527 2528 /* 2529 * Clone page flags before unfreezing refcount. 2530 * 2531 * After successful get_page_unless_zero() might follow flags change, 2532 * for exmaple lock_page() which set PG_waiters. 2533 */ 2534 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; 2535 page_tail->flags |= (head->flags & 2536 ((1L << PG_referenced) | 2537 (1L << PG_swapbacked) | 2538 (1L << PG_swapcache) | 2539 (1L << PG_mlocked) | 2540 (1L << PG_uptodate) | 2541 (1L << PG_active) | 2542 (1L << PG_workingset) | 2543 (1L << PG_locked) | 2544 (1L << PG_unevictable) | 2545 (1L << PG_dirty))); 2546 2547 /* ->mapping in first tail page is compound_mapcount */ 2548 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING, 2549 page_tail); 2550 page_tail->mapping = head->mapping; 2551 page_tail->index = head->index + tail; 2552 2553 /* Page flags must be visible before we make the page non-compound. */ 2554 smp_wmb(); 2555 2556 /* 2557 * Clear PageTail before unfreezing page refcount. 2558 * 2559 * After successful get_page_unless_zero() might follow put_page() 2560 * which needs correct compound_head(). 2561 */ 2562 clear_compound_head(page_tail); 2563 2564 /* Finally unfreeze refcount. Additional reference from page cache. */ 2565 page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) || 2566 PageSwapCache(head))); 2567 2568 if (page_is_young(head)) 2569 set_page_young(page_tail); 2570 if (page_is_idle(head)) 2571 set_page_idle(page_tail); 2572 2573 page_cpupid_xchg_last(page_tail, page_cpupid_last(head)); 2574 2575 /* 2576 * always add to the tail because some iterators expect new 2577 * pages to show after the currently processed elements - e.g. 2578 * migrate_pages 2579 */ 2580 lru_add_page_tail(head, page_tail, lruvec, list); 2581 } 2582 2583 static void __split_huge_page(struct page *page, struct list_head *list, 2584 pgoff_t end, unsigned long flags) 2585 { 2586 struct page *head = compound_head(page); 2587 pg_data_t *pgdat = page_pgdat(head); 2588 struct lruvec *lruvec; 2589 struct address_space *swap_cache = NULL; 2590 unsigned long offset = 0; 2591 int i; 2592 2593 lruvec = mem_cgroup_page_lruvec(head, pgdat); 2594 2595 /* complete memcg works before add pages to LRU */ 2596 mem_cgroup_split_huge_fixup(head); 2597 2598 if (PageAnon(head) && PageSwapCache(head)) { 2599 swp_entry_t entry = { .val = page_private(head) }; 2600 2601 offset = swp_offset(entry); 2602 swap_cache = swap_address_space(entry); 2603 xa_lock(&swap_cache->i_pages); 2604 } 2605 2606 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { 2607 __split_huge_page_tail(head, i, lruvec, list); 2608 /* Some pages can be beyond i_size: drop them from page cache */ 2609 if (head[i].index >= end) { 2610 ClearPageDirty(head + i); 2611 __delete_from_page_cache(head + i, NULL); 2612 if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head)) 2613 shmem_uncharge(head->mapping->host, 1); 2614 put_page(head + i); 2615 } else if (!PageAnon(page)) { 2616 __xa_store(&head->mapping->i_pages, head[i].index, 2617 head + i, 0); 2618 } else if (swap_cache) { 2619 __xa_store(&swap_cache->i_pages, offset + i, 2620 head + i, 0); 2621 } 2622 } 2623 2624 ClearPageCompound(head); 2625 2626 split_page_owner(head, HPAGE_PMD_ORDER); 2627 2628 /* See comment in __split_huge_page_tail() */ 2629 if (PageAnon(head)) { 2630 /* Additional pin to swap cache */ 2631 if (PageSwapCache(head)) { 2632 page_ref_add(head, 2); 2633 xa_unlock(&swap_cache->i_pages); 2634 } else { 2635 page_ref_inc(head); 2636 } 2637 } else { 2638 /* Additional pin to page cache */ 2639 page_ref_add(head, 2); 2640 xa_unlock(&head->mapping->i_pages); 2641 } 2642 2643 spin_unlock_irqrestore(&pgdat->lru_lock, flags); 2644 2645 remap_page(head); 2646 2647 for (i = 0; i < HPAGE_PMD_NR; i++) { 2648 struct page *subpage = head + i; 2649 if (subpage == page) 2650 continue; 2651 unlock_page(subpage); 2652 2653 /* 2654 * Subpages may be freed if there wasn't any mapping 2655 * like if add_to_swap() is running on a lru page that 2656 * had its mapping zapped. And freeing these pages 2657 * requires taking the lru_lock so we do the put_page 2658 * of the tail pages after the split is complete. 2659 */ 2660 put_page(subpage); 2661 } 2662 } 2663 2664 int total_mapcount(struct page *page) 2665 { 2666 int i, compound, ret; 2667 2668 VM_BUG_ON_PAGE(PageTail(page), page); 2669 2670 if (likely(!PageCompound(page))) 2671 return atomic_read(&page->_mapcount) + 1; 2672 2673 compound = compound_mapcount(page); 2674 if (PageHuge(page)) 2675 return compound; 2676 ret = compound; 2677 for (i = 0; i < HPAGE_PMD_NR; i++) 2678 ret += atomic_read(&page[i]._mapcount) + 1; 2679 /* File pages has compound_mapcount included in _mapcount */ 2680 if (!PageAnon(page)) 2681 return ret - compound * HPAGE_PMD_NR; 2682 if (PageDoubleMap(page)) 2683 ret -= HPAGE_PMD_NR; 2684 return ret; 2685 } 2686 2687 /* 2688 * This calculates accurately how many mappings a transparent hugepage 2689 * has (unlike page_mapcount() which isn't fully accurate). This full 2690 * accuracy is primarily needed to know if copy-on-write faults can 2691 * reuse the page and change the mapping to read-write instead of 2692 * copying them. At the same time this returns the total_mapcount too. 2693 * 2694 * The function returns the highest mapcount any one of the subpages 2695 * has. If the return value is one, even if different processes are 2696 * mapping different subpages of the transparent hugepage, they can 2697 * all reuse it, because each process is reusing a different subpage. 2698 * 2699 * The total_mapcount is instead counting all virtual mappings of the 2700 * subpages. If the total_mapcount is equal to "one", it tells the 2701 * caller all mappings belong to the same "mm" and in turn the 2702 * anon_vma of the transparent hugepage can become the vma->anon_vma 2703 * local one as no other process may be mapping any of the subpages. 2704 * 2705 * It would be more accurate to replace page_mapcount() with 2706 * page_trans_huge_mapcount(), however we only use 2707 * page_trans_huge_mapcount() in the copy-on-write faults where we 2708 * need full accuracy to avoid breaking page pinning, because 2709 * page_trans_huge_mapcount() is slower than page_mapcount(). 2710 */ 2711 int page_trans_huge_mapcount(struct page *page, int *total_mapcount) 2712 { 2713 int i, ret, _total_mapcount, mapcount; 2714 2715 /* hugetlbfs shouldn't call it */ 2716 VM_BUG_ON_PAGE(PageHuge(page), page); 2717 2718 if (likely(!PageTransCompound(page))) { 2719 mapcount = atomic_read(&page->_mapcount) + 1; 2720 if (total_mapcount) 2721 *total_mapcount = mapcount; 2722 return mapcount; 2723 } 2724 2725 page = compound_head(page); 2726 2727 _total_mapcount = ret = 0; 2728 for (i = 0; i < HPAGE_PMD_NR; i++) { 2729 mapcount = atomic_read(&page[i]._mapcount) + 1; 2730 ret = max(ret, mapcount); 2731 _total_mapcount += mapcount; 2732 } 2733 if (PageDoubleMap(page)) { 2734 ret -= 1; 2735 _total_mapcount -= HPAGE_PMD_NR; 2736 } 2737 mapcount = compound_mapcount(page); 2738 ret += mapcount; 2739 _total_mapcount += mapcount; 2740 if (total_mapcount) 2741 *total_mapcount = _total_mapcount; 2742 return ret; 2743 } 2744 2745 /* Racy check whether the huge page can be split */ 2746 bool can_split_huge_page(struct page *page, int *pextra_pins) 2747 { 2748 int extra_pins; 2749 2750 /* Additional pins from page cache */ 2751 if (PageAnon(page)) 2752 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0; 2753 else 2754 extra_pins = HPAGE_PMD_NR; 2755 if (pextra_pins) 2756 *pextra_pins = extra_pins; 2757 return total_mapcount(page) == page_count(page) - extra_pins - 1; 2758 } 2759 2760 /* 2761 * This function splits huge page into normal pages. @page can point to any 2762 * subpage of huge page to split. Split doesn't change the position of @page. 2763 * 2764 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY. 2765 * The huge page must be locked. 2766 * 2767 * If @list is null, tail pages will be added to LRU list, otherwise, to @list. 2768 * 2769 * Both head page and tail pages will inherit mapping, flags, and so on from 2770 * the hugepage. 2771 * 2772 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if 2773 * they are not mapped. 2774 * 2775 * Returns 0 if the hugepage is split successfully. 2776 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under 2777 * us. 2778 */ 2779 int split_huge_page_to_list(struct page *page, struct list_head *list) 2780 { 2781 struct page *head = compound_head(page); 2782 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head)); 2783 struct deferred_split *ds_queue = get_deferred_split_queue(head); 2784 struct anon_vma *anon_vma = NULL; 2785 struct address_space *mapping = NULL; 2786 int count, mapcount, extra_pins, ret; 2787 bool mlocked; 2788 unsigned long flags; 2789 pgoff_t end; 2790 2791 VM_BUG_ON_PAGE(is_huge_zero_page(head), head); 2792 VM_BUG_ON_PAGE(!PageLocked(head), head); 2793 VM_BUG_ON_PAGE(!PageCompound(head), head); 2794 2795 if (PageWriteback(head)) 2796 return -EBUSY; 2797 2798 if (PageAnon(head)) { 2799 /* 2800 * The caller does not necessarily hold an mmap_sem that would 2801 * prevent the anon_vma disappearing so we first we take a 2802 * reference to it and then lock the anon_vma for write. This 2803 * is similar to page_lock_anon_vma_read except the write lock 2804 * is taken to serialise against parallel split or collapse 2805 * operations. 2806 */ 2807 anon_vma = page_get_anon_vma(head); 2808 if (!anon_vma) { 2809 ret = -EBUSY; 2810 goto out; 2811 } 2812 end = -1; 2813 mapping = NULL; 2814 anon_vma_lock_write(anon_vma); 2815 } else { 2816 mapping = head->mapping; 2817 2818 /* Truncated ? */ 2819 if (!mapping) { 2820 ret = -EBUSY; 2821 goto out; 2822 } 2823 2824 anon_vma = NULL; 2825 i_mmap_lock_read(mapping); 2826 2827 /* 2828 *__split_huge_page() may need to trim off pages beyond EOF: 2829 * but on 32-bit, i_size_read() takes an irq-unsafe seqlock, 2830 * which cannot be nested inside the page tree lock. So note 2831 * end now: i_size itself may be changed at any moment, but 2832 * head page lock is good enough to serialize the trimming. 2833 */ 2834 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); 2835 } 2836 2837 /* 2838 * Racy check if we can split the page, before unmap_page() will 2839 * split PMDs 2840 */ 2841 if (!can_split_huge_page(head, &extra_pins)) { 2842 ret = -EBUSY; 2843 goto out_unlock; 2844 } 2845 2846 mlocked = PageMlocked(head); 2847 unmap_page(head); 2848 VM_BUG_ON_PAGE(compound_mapcount(head), head); 2849 2850 /* Make sure the page is not on per-CPU pagevec as it takes pin */ 2851 if (mlocked) 2852 lru_add_drain(); 2853 2854 /* prevent PageLRU to go away from under us, and freeze lru stats */ 2855 spin_lock_irqsave(&pgdata->lru_lock, flags); 2856 2857 if (mapping) { 2858 XA_STATE(xas, &mapping->i_pages, page_index(head)); 2859 2860 /* 2861 * Check if the head page is present in page cache. 2862 * We assume all tail are present too, if head is there. 2863 */ 2864 xa_lock(&mapping->i_pages); 2865 if (xas_load(&xas) != head) 2866 goto fail; 2867 } 2868 2869 /* Prevent deferred_split_scan() touching ->_refcount */ 2870 spin_lock(&ds_queue->split_queue_lock); 2871 count = page_count(head); 2872 mapcount = total_mapcount(head); 2873 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) { 2874 if (!list_empty(page_deferred_list(head))) { 2875 ds_queue->split_queue_len--; 2876 list_del(page_deferred_list(head)); 2877 } 2878 spin_unlock(&ds_queue->split_queue_lock); 2879 if (mapping) { 2880 if (PageSwapBacked(head)) 2881 __dec_node_page_state(head, NR_SHMEM_THPS); 2882 else 2883 __dec_node_page_state(head, NR_FILE_THPS); 2884 } 2885 2886 __split_huge_page(page, list, end, flags); 2887 if (PageSwapCache(head)) { 2888 swp_entry_t entry = { .val = page_private(head) }; 2889 2890 ret = split_swap_cluster(entry); 2891 } else 2892 ret = 0; 2893 } else { 2894 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { 2895 pr_alert("total_mapcount: %u, page_count(): %u\n", 2896 mapcount, count); 2897 if (PageTail(page)) 2898 dump_page(head, NULL); 2899 dump_page(page, "total_mapcount(head) > 0"); 2900 BUG(); 2901 } 2902 spin_unlock(&ds_queue->split_queue_lock); 2903 fail: if (mapping) 2904 xa_unlock(&mapping->i_pages); 2905 spin_unlock_irqrestore(&pgdata->lru_lock, flags); 2906 remap_page(head); 2907 ret = -EBUSY; 2908 } 2909 2910 out_unlock: 2911 if (anon_vma) { 2912 anon_vma_unlock_write(anon_vma); 2913 put_anon_vma(anon_vma); 2914 } 2915 if (mapping) 2916 i_mmap_unlock_read(mapping); 2917 out: 2918 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); 2919 return ret; 2920 } 2921 2922 void free_transhuge_page(struct page *page) 2923 { 2924 struct deferred_split *ds_queue = get_deferred_split_queue(page); 2925 unsigned long flags; 2926 2927 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 2928 if (!list_empty(page_deferred_list(page))) { 2929 ds_queue->split_queue_len--; 2930 list_del(page_deferred_list(page)); 2931 } 2932 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 2933 free_compound_page(page); 2934 } 2935 2936 void deferred_split_huge_page(struct page *page) 2937 { 2938 struct deferred_split *ds_queue = get_deferred_split_queue(page); 2939 #ifdef CONFIG_MEMCG 2940 struct mem_cgroup *memcg = compound_head(page)->mem_cgroup; 2941 #endif 2942 unsigned long flags; 2943 2944 VM_BUG_ON_PAGE(!PageTransHuge(page), page); 2945 2946 /* 2947 * The try_to_unmap() in page reclaim path might reach here too, 2948 * this may cause a race condition to corrupt deferred split queue. 2949 * And, if page reclaim is already handling the same page, it is 2950 * unnecessary to handle it again in shrinker. 2951 * 2952 * Check PageSwapCache to determine if the page is being 2953 * handled by page reclaim since THP swap would add the page into 2954 * swap cache before calling try_to_unmap(). 2955 */ 2956 if (PageSwapCache(page)) 2957 return; 2958 2959 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 2960 if (list_empty(page_deferred_list(page))) { 2961 count_vm_event(THP_DEFERRED_SPLIT_PAGE); 2962 list_add_tail(page_deferred_list(page), &ds_queue->split_queue); 2963 ds_queue->split_queue_len++; 2964 #ifdef CONFIG_MEMCG 2965 if (memcg) 2966 memcg_set_shrinker_bit(memcg, page_to_nid(page), 2967 deferred_split_shrinker.id); 2968 #endif 2969 } 2970 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 2971 } 2972 2973 static unsigned long deferred_split_count(struct shrinker *shrink, 2974 struct shrink_control *sc) 2975 { 2976 struct pglist_data *pgdata = NODE_DATA(sc->nid); 2977 struct deferred_split *ds_queue = &pgdata->deferred_split_queue; 2978 2979 #ifdef CONFIG_MEMCG 2980 if (sc->memcg) 2981 ds_queue = &sc->memcg->deferred_split_queue; 2982 #endif 2983 return READ_ONCE(ds_queue->split_queue_len); 2984 } 2985 2986 static unsigned long deferred_split_scan(struct shrinker *shrink, 2987 struct shrink_control *sc) 2988 { 2989 struct pglist_data *pgdata = NODE_DATA(sc->nid); 2990 struct deferred_split *ds_queue = &pgdata->deferred_split_queue; 2991 unsigned long flags; 2992 LIST_HEAD(list), *pos, *next; 2993 struct page *page; 2994 int split = 0; 2995 2996 #ifdef CONFIG_MEMCG 2997 if (sc->memcg) 2998 ds_queue = &sc->memcg->deferred_split_queue; 2999 #endif 3000 3001 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 3002 /* Take pin on all head pages to avoid freeing them under us */ 3003 list_for_each_safe(pos, next, &ds_queue->split_queue) { 3004 page = list_entry((void *)pos, struct page, mapping); 3005 page = compound_head(page); 3006 if (get_page_unless_zero(page)) { 3007 list_move(page_deferred_list(page), &list); 3008 } else { 3009 /* We lost race with put_compound_page() */ 3010 list_del_init(page_deferred_list(page)); 3011 ds_queue->split_queue_len--; 3012 } 3013 if (!--sc->nr_to_scan) 3014 break; 3015 } 3016 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 3017 3018 list_for_each_safe(pos, next, &list) { 3019 page = list_entry((void *)pos, struct page, mapping); 3020 if (!trylock_page(page)) 3021 goto next; 3022 /* split_huge_page() removes page from list on success */ 3023 if (!split_huge_page(page)) 3024 split++; 3025 unlock_page(page); 3026 next: 3027 put_page(page); 3028 } 3029 3030 spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 3031 list_splice_tail(&list, &ds_queue->split_queue); 3032 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); 3033 3034 /* 3035 * Stop shrinker if we didn't split any page, but the queue is empty. 3036 * This can happen if pages were freed under us. 3037 */ 3038 if (!split && list_empty(&ds_queue->split_queue)) 3039 return SHRINK_STOP; 3040 return split; 3041 } 3042 3043 static struct shrinker deferred_split_shrinker = { 3044 .count_objects = deferred_split_count, 3045 .scan_objects = deferred_split_scan, 3046 .seeks = DEFAULT_SEEKS, 3047 .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE | 3048 SHRINKER_NONSLAB, 3049 }; 3050 3051 #ifdef CONFIG_DEBUG_FS 3052 static int split_huge_pages_set(void *data, u64 val) 3053 { 3054 struct zone *zone; 3055 struct page *page; 3056 unsigned long pfn, max_zone_pfn; 3057 unsigned long total = 0, split = 0; 3058 3059 if (val != 1) 3060 return -EINVAL; 3061 3062 for_each_populated_zone(zone) { 3063 max_zone_pfn = zone_end_pfn(zone); 3064 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) { 3065 if (!pfn_valid(pfn)) 3066 continue; 3067 3068 page = pfn_to_page(pfn); 3069 if (!get_page_unless_zero(page)) 3070 continue; 3071 3072 if (zone != page_zone(page)) 3073 goto next; 3074 3075 if (!PageHead(page) || PageHuge(page) || !PageLRU(page)) 3076 goto next; 3077 3078 total++; 3079 lock_page(page); 3080 if (!split_huge_page(page)) 3081 split++; 3082 unlock_page(page); 3083 next: 3084 put_page(page); 3085 } 3086 } 3087 3088 pr_info("%lu of %lu THP split\n", split, total); 3089 3090 return 0; 3091 } 3092 DEFINE_DEBUGFS_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set, 3093 "%llu\n"); 3094 3095 static int __init split_huge_pages_debugfs(void) 3096 { 3097 debugfs_create_file("split_huge_pages", 0200, NULL, NULL, 3098 &split_huge_pages_fops); 3099 return 0; 3100 } 3101 late_initcall(split_huge_pages_debugfs); 3102 #endif 3103 3104 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION 3105 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw, 3106 struct page *page) 3107 { 3108 struct vm_area_struct *vma = pvmw->vma; 3109 struct mm_struct *mm = vma->vm_mm; 3110 unsigned long address = pvmw->address; 3111 pmd_t pmdval; 3112 swp_entry_t entry; 3113 pmd_t pmdswp; 3114 3115 if (!(pvmw->pmd && !pvmw->pte)) 3116 return; 3117 3118 flush_cache_range(vma, address, address + HPAGE_PMD_SIZE); 3119 pmdval = pmdp_invalidate(vma, address, pvmw->pmd); 3120 if (pmd_dirty(pmdval)) 3121 set_page_dirty(page); 3122 entry = make_migration_entry(page, pmd_write(pmdval)); 3123 pmdswp = swp_entry_to_pmd(entry); 3124 if (pmd_soft_dirty(pmdval)) 3125 pmdswp = pmd_swp_mksoft_dirty(pmdswp); 3126 set_pmd_at(mm, address, pvmw->pmd, pmdswp); 3127 page_remove_rmap(page, true); 3128 put_page(page); 3129 } 3130 3131 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new) 3132 { 3133 struct vm_area_struct *vma = pvmw->vma; 3134 struct mm_struct *mm = vma->vm_mm; 3135 unsigned long address = pvmw->address; 3136 unsigned long mmun_start = address & HPAGE_PMD_MASK; 3137 pmd_t pmde; 3138 swp_entry_t entry; 3139 3140 if (!(pvmw->pmd && !pvmw->pte)) 3141 return; 3142 3143 entry = pmd_to_swp_entry(*pvmw->pmd); 3144 get_page(new); 3145 pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot)); 3146 if (pmd_swp_soft_dirty(*pvmw->pmd)) 3147 pmde = pmd_mksoft_dirty(pmde); 3148 if (is_write_migration_entry(entry)) 3149 pmde = maybe_pmd_mkwrite(pmde, vma); 3150 3151 flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE); 3152 if (PageAnon(new)) 3153 page_add_anon_rmap(new, vma, mmun_start, true); 3154 else 3155 page_add_file_rmap(new, true); 3156 set_pmd_at(mm, mmun_start, pvmw->pmd, pmde); 3157 if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new)) 3158 mlock_vma_page(new); 3159 update_mmu_cache_pmd(vma, address, pvmw->pmd); 3160 } 3161 #endif 3162