mm/huge_memory.c

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