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