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
  36 #include <asm/tlb.h>
  37 #include <asm/pgalloc.h>
  38 #include "internal.h"
  39
  40 /*
  41  * By default, transparent hugepage support is disabled in order to avoid
  42  * risking an increased memory footprint for applications that are not
  43  * guaranteed to benefit from it. When transparent hugepage support is
  44  * enabled, it is for all mappings, and khugepaged scans all mappings.
  45  * Defrag is invoked by khugepaged hugepage allocations and by page faults
  46  * for all hugepage allocations.
  47  */
  48 unsigned long transparent_hugepage_flags __read_mostly =
  49 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  50         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  51 #endif
  52 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  53         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  54 #endif
  55         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
  56         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
  57         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
  58
  59 static struct shrinker deferred_split_shrinker;
  60
  61 static atomic_t huge_zero_refcount;
  62 struct page *huge_zero_page __read_mostly;
  63
  64 bool transparent_hugepage_enabled(struct vm_area_struct *vma)
  65 {
  66         if (vma_is_anonymous(vma))
  67                 return __transparent_hugepage_enabled(vma);
  68         if (vma_is_shmem(vma) && shmem_huge_enabled(vma))
  69                 return __transparent_hugepage_enabled(vma);
  70
  71         return false;
  72 }
  73
  74 static struct page *get_huge_zero_page(void)
  75 {
  76         struct page *zero_page;
  77 retry:
  78         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
  79                 return READ_ONCE(huge_zero_page);
  80
  81         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
  82                         HPAGE_PMD_ORDER);
  83         if (!zero_page) {
  84                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
  85                 return NULL;
  86         }
  87         count_vm_event(THP_ZERO_PAGE_ALLOC);
  88         preempt_disable();
  89         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
  90                 preempt_enable();
  91                 __free_pages(zero_page, compound_order(zero_page));
  92                 goto retry;
  93         }
  94
  95         /* We take additional reference here. It will be put back by shrinker */
  96         atomic_set(&huge_zero_refcount, 2);
  97         preempt_enable();
  98         return READ_ONCE(huge_zero_page);
  99 }
 100
 101 static void put_huge_zero_page(void)
 102 {
 103         /*
 104          * Counter should never go to zero here. Only shrinker can put
 105          * last reference.
 106          */
 107         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
 108 }
 109
 110 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
 111 {
 112         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 113                 return READ_ONCE(huge_zero_page);
 114
 115         if (!get_huge_zero_page())
 116                 return NULL;
 117
 118         if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 119                 put_huge_zero_page();
 120
 121         return READ_ONCE(huge_zero_page);
 122 }
 123
 124 void mm_put_huge_zero_page(struct mm_struct *mm)
 125 {
 126         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 127                 put_huge_zero_page();
 128 }
 129
 130 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
 131                                         struct shrink_control *sc)
 132 {
 133         /* we can free zero page only if last reference remains */
 134         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 135 }
 136
 137 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 138                                        struct shrink_control *sc)
 139 {
 140         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 141                 struct page *zero_page = xchg(&huge_zero_page, NULL);
 142                 BUG_ON(zero_page == NULL);
 143                 __free_pages(zero_page, compound_order(zero_page));
 144                 return HPAGE_PMD_NR;
 145         }
 146
 147         return 0;
 148 }
 149
 150 static struct shrinker huge_zero_page_shrinker = {
 151         .count_objects = shrink_huge_zero_page_count,
 152         .scan_objects = shrink_huge_zero_page_scan,
 153         .seeks = DEFAULT_SEEKS,
 154 };
 155
 156 #ifdef CONFIG_SYSFS
 157 static ssize_t enabled_show(struct kobject *kobj,
 158                             struct kobj_attribute *attr, char *buf)
 159 {
 160         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
 161                 return sprintf(buf, "[always] madvise never\n");
 162         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
 163                 return sprintf(buf, "always [madvise] never\n");
 164         else
 165                 return sprintf(buf, "always madvise [never]\n");
 166 }
 167
 168 static ssize_t enabled_store(struct kobject *kobj,
 169                              struct kobj_attribute *attr,
 170                              const char *buf, size_t count)
 171 {
 172         ssize_t ret = count;
 173
 174         if (!memcmp("always", buf,
 175                     min(sizeof("always")-1, count))) {
 176                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 177                 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 178         } else if (!memcmp("madvise", buf,
 179                            min(sizeof("madvise")-1, count))) {
 180                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 181                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 182         } else if (!memcmp("never", buf,
 183                            min(sizeof("never")-1, count))) {
 184                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 185                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 186         } else
 187                 ret = -EINVAL;
 188
 189         if (ret > 0) {
 190                 int err = start_stop_khugepaged();
 191                 if (err)
 192                         ret = err;
 193         }
 194         return ret;
 195 }
 196 static struct kobj_attribute enabled_attr =
 197         __ATTR(enabled, 0644, enabled_show, enabled_store);
 198
 199 ssize_t single_hugepage_flag_show(struct kobject *kobj,
 200                                 struct kobj_attribute *attr, char *buf,
 201                                 enum transparent_hugepage_flag flag)
 202 {
 203         return sprintf(buf, "%d\n",
 204                        !!test_bit(flag, &transparent_hugepage_flags));
 205 }
 206
 207 ssize_t single_hugepage_flag_store(struct kobject *kobj,
 208                                  struct kobj_attribute *attr,
 209                                  const char *buf, size_t count,
 210                                  enum transparent_hugepage_flag flag)
 211 {
 212         unsigned long value;
 213         int ret;
 214
 215         ret = kstrtoul(buf, 10, &value);
 216         if (ret < 0)
 217                 return ret;
 218         if (value > 1)
 219                 return -EINVAL;
 220
 221         if (value)
 222                 set_bit(flag, &transparent_hugepage_flags);
 223         else
 224                 clear_bit(flag, &transparent_hugepage_flags);
 225
 226         return count;
 227 }
 228
 229 static ssize_t defrag_show(struct kobject *kobj,
 230                            struct kobj_attribute *attr, char *buf)
 231 {
 232         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 233                 return sprintf(buf, "[always] defer defer+madvise madvise never\n");
 234         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 235                 return sprintf(buf, "always [defer] defer+madvise madvise never\n");
 236         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 237                 return sprintf(buf, "always defer [defer+madvise] madvise never\n");
 238         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 239                 return sprintf(buf, "always defer defer+madvise [madvise] never\n");
 240         return sprintf(buf, "always defer defer+madvise madvise [never]\n");
 241 }
 242
 243 static ssize_t defrag_store(struct kobject *kobj,
 244                             struct kobj_attribute *attr,
 245                             const char *buf, size_t count)
 246 {
 247         if (!memcmp("always", buf,
 248                     min(sizeof("always")-1, count))) {
 249                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 250                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 251                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 252                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 253         } else if (!memcmp("defer+madvise", buf,
 254                     min(sizeof("defer+madvise")-1, count))) {
 255                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 256                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 257                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 258                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 259         } else if (!memcmp("defer", buf,
 260                     min(sizeof("defer")-1, count))) {
 261                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 262                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 263                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 264                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 265         } else if (!memcmp("madvise", buf,
 266                            min(sizeof("madvise")-1, count))) {
 267                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 268                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 269                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 270                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 271         } else if (!memcmp("never", buf,
 272                            min(sizeof("never")-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                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 277         } else
 278                 return -EINVAL;
 279
 280         return count;
 281 }
 282 static struct kobj_attribute defrag_attr =
 283         __ATTR(defrag, 0644, defrag_show, defrag_store);
 284
 285 static ssize_t use_zero_page_show(struct kobject *kobj,
 286                 struct kobj_attribute *attr, char *buf)
 287 {
 288         return single_hugepage_flag_show(kobj, attr, buf,
 289                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 290 }
 291 static ssize_t use_zero_page_store(struct kobject *kobj,
 292                 struct kobj_attribute *attr, const char *buf, size_t count)
 293 {
 294         return single_hugepage_flag_store(kobj, attr, buf, count,
 295                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 296 }
 297 static struct kobj_attribute use_zero_page_attr =
 298         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 299
 300 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
 301                 struct kobj_attribute *attr, char *buf)
 302 {
 303         return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
 304 }
 305 static struct kobj_attribute hpage_pmd_size_attr =
 306         __ATTR_RO(hpage_pmd_size);
 307
 308 #ifdef CONFIG_DEBUG_VM
 309 static ssize_t debug_cow_show(struct kobject *kobj,
 310                                 struct kobj_attribute *attr, char *buf)
 311 {
 312         return single_hugepage_flag_show(kobj, attr, buf,
 313                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 314 }
 315 static ssize_t debug_cow_store(struct kobject *kobj,
 316                                struct kobj_attribute *attr,
 317                                const char *buf, size_t count)
 318 {
 319         return single_hugepage_flag_store(kobj, attr, buf, count,
 320                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 321 }
 322 static struct kobj_attribute debug_cow_attr =
 323         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 324 #endif /* CONFIG_DEBUG_VM */
 325
 326 static struct attribute *hugepage_attr[] = {
 327         &enabled_attr.attr,
 328         &defrag_attr.attr,
 329         &use_zero_page_attr.attr,
 330         &hpage_pmd_size_attr.attr,
 331 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
 332         &shmem_enabled_attr.attr,
 333 #endif
 334 #ifdef CONFIG_DEBUG_VM
 335         &debug_cow_attr.attr,
 336 #endif
 337         NULL,
 338 };
 339
 340 static const struct attribute_group hugepage_attr_group = {
 341         .attrs = hugepage_attr,
 342 };
 343
 344 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 345 {
 346         int err;
 347
 348         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 349         if (unlikely(!*hugepage_kobj)) {
 350                 pr_err("failed to create transparent hugepage kobject\n");
 351                 return -ENOMEM;
 352         }
 353
 354         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 355         if (err) {
 356                 pr_err("failed to register transparent hugepage group\n");
 357                 goto delete_obj;
 358         }
 359
 360         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 361         if (err) {
 362                 pr_err("failed to register transparent hugepage group\n");
 363                 goto remove_hp_group;
 364         }
 365
 366         return 0;
 367
 368 remove_hp_group:
 369         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 370 delete_obj:
 371         kobject_put(*hugepage_kobj);
 372         return err;
 373 }
 374
 375 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 376 {
 377         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 378         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 379         kobject_put(hugepage_kobj);
 380 }
 381 #else
 382 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 383 {
 384         return 0;
 385 }
 386
 387 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 388 {
 389 }
 390 #endif /* CONFIG_SYSFS */
 391
 392 static int __init hugepage_init(void)
 393 {
 394         int err;
 395         struct kobject *hugepage_kobj;
 396
 397         if (!has_transparent_hugepage()) {
 398                 transparent_hugepage_flags = 0;
 399                 return -EINVAL;
 400         }
 401
 402         /*
 403          * hugepages can't be allocated by the buddy allocator
 404          */
 405         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
 406         /*
 407          * we use page->mapping and page->index in second tail page
 408          * as list_head: assuming THP order >= 2
 409          */
 410         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
 411
 412         err = hugepage_init_sysfs(&hugepage_kobj);
 413         if (err)
 414                 goto err_sysfs;
 415
 416         err = khugepaged_init();
 417         if (err)
 418                 goto err_slab;
 419
 420         err = register_shrinker(&huge_zero_page_shrinker);
 421         if (err)
 422                 goto err_hzp_shrinker;
 423         err = register_shrinker(&deferred_split_shrinker);
 424         if (err)
 425                 goto err_split_shrinker;
 426
 427         /*
 428          * By default disable transparent hugepages on smaller systems,
 429          * where the extra memory used could hurt more than TLB overhead
 430          * is likely to save.  The admin can still enable it through /sys.
 431          */
 432         if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
 433                 transparent_hugepage_flags = 0;
 434                 return 0;
 435         }
 436
 437         err = start_stop_khugepaged();
 438         if (err)
 439                 goto err_khugepaged;
 440
 441         return 0;
 442 err_khugepaged:
 443         unregister_shrinker(&deferred_split_shrinker);
 444 err_split_shrinker:
 445         unregister_shrinker(&huge_zero_page_shrinker);
 446 err_hzp_shrinker:
 447         khugepaged_destroy();
 448 err_slab:
 449         hugepage_exit_sysfs(hugepage_kobj);
 450 err_sysfs:
 451         return err;
 452 }
 453 subsys_initcall(hugepage_init);
 454
 455 static int __init setup_transparent_hugepage(char *str)
 456 {
 457         int ret = 0;
 458         if (!str)
 459                 goto out;
 460         if (!strcmp(str, "always")) {
 461                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 462                         &transparent_hugepage_flags);
 463                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 464                           &transparent_hugepage_flags);
 465                 ret = 1;
 466         } else if (!strcmp(str, "madvise")) {
 467                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 468                           &transparent_hugepage_flags);
 469                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 470                         &transparent_hugepage_flags);
 471                 ret = 1;
 472         } else if (!strcmp(str, "never")) {
 473                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 474                           &transparent_hugepage_flags);
 475                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 476                           &transparent_hugepage_flags);
 477                 ret = 1;
 478         }
 479 out:
 480         if (!ret)
 481                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
 482         return ret;
 483 }
 484 __setup("transparent_hugepage=", setup_transparent_hugepage);
 485
 486 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 487 {
 488         if (likely(vma->vm_flags & VM_WRITE))
 489                 pmd = pmd_mkwrite(pmd);
 490         return pmd;
 491 }
 492
 493 static inline struct list_head *page_deferred_list(struct page *page)
 494 {
 495         /* ->lru in the tail pages is occupied by compound_head. */
 496         return &page[2].deferred_list;
 497 }
 498
 499 void prep_transhuge_page(struct page *page)
 500 {
 501         /*
 502          * we use page->mapping and page->indexlru in second tail page
 503          * as list_head: assuming THP order >= 2
 504          */
 505
 506         INIT_LIST_HEAD(page_deferred_list(page));
 507         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 508 }
 509
 510 static unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
 511                 loff_t off, unsigned long flags, unsigned long size)
 512 {
 513         unsigned long addr;
 514         loff_t off_end = off + len;
 515         loff_t off_align = round_up(off, size);
 516         unsigned long len_pad;
 517
 518         if (off_end <= off_align || (off_end - off_align) < size)
 519                 return 0;
 520
 521         len_pad = len + size;
 522         if (len_pad < len || (off + len_pad) < off)
 523                 return 0;
 524
 525         addr = current->mm->get_unmapped_area(filp, 0, len_pad,
 526                                               off >> PAGE_SHIFT, flags);
 527         if (IS_ERR_VALUE(addr))
 528                 return 0;
 529
 530         addr += (off - addr) & (size - 1);
 531         return addr;
 532 }
 533
 534 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 535                 unsigned long len, unsigned long pgoff, unsigned long flags)
 536 {
 537         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 538
 539         if (addr)
 540                 goto out;
 541         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
 542                 goto out;
 543
 544         addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
 545         if (addr)
 546                 return addr;
 547
 548  out:
 549         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 550 }
 551 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 552
 553 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
 554                         struct page *page, gfp_t gfp)
 555 {
 556         struct vm_area_struct *vma = vmf->vma;
 557         struct mem_cgroup *memcg;
 558         pgtable_t pgtable;
 559         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 560         vm_fault_t ret = 0;
 561
 562         VM_BUG_ON_PAGE(!PageCompound(page), page);
 563
 564         if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
 565                 put_page(page);
 566                 count_vm_event(THP_FAULT_FALLBACK);
 567                 return VM_FAULT_FALLBACK;
 568         }
 569
 570         pgtable = pte_alloc_one(vma->vm_mm);
 571         if (unlikely(!pgtable)) {
 572                 ret = VM_FAULT_OOM;
 573                 goto release;
 574         }
 575
 576         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
 577         /*
 578          * The memory barrier inside __SetPageUptodate makes sure that
 579          * clear_huge_page writes become visible before the set_pmd_at()
 580          * write.
 581          */
 582         __SetPageUptodate(page);
 583
 584         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 585         if (unlikely(!pmd_none(*vmf->pmd))) {
 586                 goto unlock_release;
 587         } else {
 588                 pmd_t entry;
 589
 590                 ret = check_stable_address_space(vma->vm_mm);
 591                 if (ret)
 592                         goto unlock_release;
 593
 594                 /* Deliver the page fault to userland */
 595                 if (userfaultfd_missing(vma)) {
 596                         vm_fault_t ret2;
 597
 598                         spin_unlock(vmf->ptl);
 599                         mem_cgroup_cancel_charge(page, memcg, true);
 600                         put_page(page);
 601                         pte_free(vma->vm_mm, pgtable);
 602                         ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
 603                         VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
 604                         return ret2;
 605                 }
 606
 607                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 608                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 609                 page_add_new_anon_rmap(page, vma, haddr, true);
 610                 mem_cgroup_commit_charge(page, memcg, false, true);
 611                 lru_cache_add_active_or_unevictable(page, vma);
 612                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 613                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 614                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 615                 mm_inc_nr_ptes(vma->vm_mm);
 616                 spin_unlock(vmf->ptl);
 617                 count_vm_event(THP_FAULT_ALLOC);
 618                 count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
 619         }
 620
 621         return 0;
 622 unlock_release:
 623         spin_unlock(vmf->ptl);
 624 release:
 625         if (pgtable)
 626                 pte_free(vma->vm_mm, pgtable);
 627         mem_cgroup_cancel_charge(page, memcg, true);
 628         put_page(page);
 629         return ret;
 630
 631 }
 632
 633 /*
 634  * always: directly stall for all thp allocations
 635  * defer: wake kswapd and fail if not immediately available
 636  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
 637  *                fail if not immediately available
 638  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
 639  *          available
 640  * never: never stall for any thp allocation
 641  */
 642 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
 643 {
 644         const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
 645
 646         /* Always do synchronous compaction */
 647         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 648                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
 649
 650         /* Kick kcompactd and fail quickly */
 651         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 652                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
 653
 654         /* Synchronous compaction if madvised, otherwise kick kcompactd */
 655         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 656                 return GFP_TRANSHUGE_LIGHT |
 657                         (vma_madvised ? __GFP_DIRECT_RECLAIM :
 658                                         __GFP_KSWAPD_RECLAIM);
 659
 660         /* Only do synchronous compaction if madvised */
 661         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 662                 return GFP_TRANSHUGE_LIGHT |
 663                        (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
 664
 665         return GFP_TRANSHUGE_LIGHT;
 666 }
 667
 668 /* Caller must hold page table lock. */
 669 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 670                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 671                 struct page *zero_page)
 672 {
 673         pmd_t entry;
 674         if (!pmd_none(*pmd))
 675                 return false;
 676         entry = mk_pmd(zero_page, vma->vm_page_prot);
 677         entry = pmd_mkhuge(entry);
 678         if (pgtable)
 679                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 680         set_pmd_at(mm, haddr, pmd, entry);
 681         mm_inc_nr_ptes(mm);
 682         return true;
 683 }
 684
 685 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 686 {
 687         struct vm_area_struct *vma = vmf->vma;
 688         gfp_t gfp;
 689         struct page *page;
 690         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 691
 692         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
 693                 return VM_FAULT_FALLBACK;
 694         if (unlikely(anon_vma_prepare(vma)))
 695                 return VM_FAULT_OOM;
 696         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 697                 return VM_FAULT_OOM;
 698         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
 699                         !mm_forbids_zeropage(vma->vm_mm) &&
 700                         transparent_hugepage_use_zero_page()) {
 701                 pgtable_t pgtable;
 702                 struct page *zero_page;
 703                 bool set;
 704                 vm_fault_t ret;
 705                 pgtable = pte_alloc_one(vma->vm_mm);
 706                 if (unlikely(!pgtable))
 707                         return VM_FAULT_OOM;
 708                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
 709                 if (unlikely(!zero_page)) {
 710                         pte_free(vma->vm_mm, pgtable);
 711                         count_vm_event(THP_FAULT_FALLBACK);
 712                         return VM_FAULT_FALLBACK;
 713                 }
 714                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 715                 ret = 0;
 716                 set = false;
 717                 if (pmd_none(*vmf->pmd)) {
 718                         ret = check_stable_address_space(vma->vm_mm);
 719                         if (ret) {
 720                                 spin_unlock(vmf->ptl);
 721                         } else if (userfaultfd_missing(vma)) {
 722                                 spin_unlock(vmf->ptl);
 723                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
 724                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 725                         } else {
 726                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
 727                                                    haddr, vmf->pmd, zero_page);
 728                                 spin_unlock(vmf->ptl);
 729                                 set = true;
 730                         }
 731                 } else
 732                         spin_unlock(vmf->ptl);
 733                 if (!set)
 734                         pte_free(vma->vm_mm, pgtable);
 735                 return ret;
 736         }
 737         gfp = alloc_hugepage_direct_gfpmask(vma);
 738         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 739         if (unlikely(!page)) {
 740                 count_vm_event(THP_FAULT_FALLBACK);
 741                 return VM_FAULT_FALLBACK;
 742         }
 743         prep_transhuge_page(page);
 744         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
 745 }
 746
 747 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 748                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
 749                 pgtable_t pgtable)
 750 {
 751         struct mm_struct *mm = vma->vm_mm;
 752         pmd_t entry;
 753         spinlock_t *ptl;
 754
 755         ptl = pmd_lock(mm, pmd);
 756         if (!pmd_none(*pmd)) {
 757                 if (write) {
 758                         if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
 759                                 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
 760                                 goto out_unlock;
 761                         }
 762                         entry = pmd_mkyoung(*pmd);
 763                         entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 764                         if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
 765                                 update_mmu_cache_pmd(vma, addr, pmd);
 766                 }
 767
 768                 goto out_unlock;
 769         }
 770
 771         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 772         if (pfn_t_devmap(pfn))
 773                 entry = pmd_mkdevmap(entry);
 774         if (write) {
 775                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 776                 entry = maybe_pmd_mkwrite(entry, vma);
 777         }
 778
 779         if (pgtable) {
 780                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 781                 mm_inc_nr_ptes(mm);
 782                 pgtable = NULL;
 783         }
 784
 785         set_pmd_at(mm, addr, pmd, entry);
 786         update_mmu_cache_pmd(vma, addr, pmd);
 787
 788 out_unlock:
 789         spin_unlock(ptl);
 790         if (pgtable)
 791                 pte_free(mm, pgtable);
 792 }
 793
 794 vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write)
 795 {
 796         unsigned long addr = vmf->address & PMD_MASK;
 797         struct vm_area_struct *vma = vmf->vma;
 798         pgprot_t pgprot = vma->vm_page_prot;
 799         pgtable_t pgtable = NULL;
 800
 801         /*
 802          * If we had pmd_special, we could avoid all these restrictions,
 803          * but we need to be consistent with PTEs and architectures that
 804          * can't support a 'special' bit.
 805          */
 806         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 807                         !pfn_t_devmap(pfn));
 808         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 809                                                 (VM_PFNMAP|VM_MIXEDMAP));
 810         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 811
 812         if (addr < vma->vm_start || addr >= vma->vm_end)
 813                 return VM_FAULT_SIGBUS;
 814
 815         if (arch_needs_pgtable_deposit()) {
 816                 pgtable = pte_alloc_one(vma->vm_mm);
 817                 if (!pgtable)
 818                         return VM_FAULT_OOM;
 819         }
 820
 821         track_pfn_insert(vma, &pgprot, pfn);
 822
 823         insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
 824         return VM_FAULT_NOPAGE;
 825 }
 826 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
 827
 828 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 829 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 830 {
 831         if (likely(vma->vm_flags & VM_WRITE))
 832                 pud = pud_mkwrite(pud);
 833         return pud;
 834 }
 835
 836 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 837                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 838 {
 839         struct mm_struct *mm = vma->vm_mm;
 840         pud_t entry;
 841         spinlock_t *ptl;
 842
 843         ptl = pud_lock(mm, pud);
 844         if (!pud_none(*pud)) {
 845                 if (write) {
 846                         if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
 847                                 WARN_ON_ONCE(!is_huge_zero_pud(*pud));
 848                                 goto out_unlock;
 849                         }
 850                         entry = pud_mkyoung(*pud);
 851                         entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
 852                         if (pudp_set_access_flags(vma, addr, pud, entry, 1))
 853                                 update_mmu_cache_pud(vma, addr, pud);
 854                 }
 855                 goto out_unlock;
 856         }
 857
 858         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
 859         if (pfn_t_devmap(pfn))
 860                 entry = pud_mkdevmap(entry);
 861         if (write) {
 862                 entry = pud_mkyoung(pud_mkdirty(entry));
 863                 entry = maybe_pud_mkwrite(entry, vma);
 864         }
 865         set_pud_at(mm, addr, pud, entry);
 866         update_mmu_cache_pud(vma, addr, pud);
 867
 868 out_unlock:
 869         spin_unlock(ptl);
 870 }
 871
 872 vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
 873 {
 874         unsigned long addr = vmf->address & PUD_MASK;
 875         struct vm_area_struct *vma = vmf->vma;
 876         pgprot_t pgprot = vma->vm_page_prot;
 877
 878         /*
 879          * If we had pud_special, we could avoid all these restrictions,
 880          * but we need to be consistent with PTEs and architectures that
 881          * can't support a 'special' bit.
 882          */
 883         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 884                         !pfn_t_devmap(pfn));
 885         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 886                                                 (VM_PFNMAP|VM_MIXEDMAP));
 887         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 888
 889         if (addr < vma->vm_start || addr >= vma->vm_end)
 890                 return VM_FAULT_SIGBUS;
 891
 892         track_pfn_insert(vma, &pgprot, pfn);
 893
 894         insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
 895         return VM_FAULT_NOPAGE;
 896 }
 897 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
 898 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 899
 900 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
 901                 pmd_t *pmd, int flags)
 902 {
 903         pmd_t _pmd;
 904
 905         _pmd = pmd_mkyoung(*pmd);
 906         if (flags & FOLL_WRITE)
 907                 _pmd = pmd_mkdirty(_pmd);
 908         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 909                                 pmd, _pmd, flags & FOLL_WRITE))
 910                 update_mmu_cache_pmd(vma, addr, pmd);
 911 }
 912
 913 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 914                 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
 915 {
 916         unsigned long pfn = pmd_pfn(*pmd);
 917         struct mm_struct *mm = vma->vm_mm;
 918         struct page *page;
 919
 920         assert_spin_locked(pmd_lockptr(mm, pmd));
 921
 922         /*
 923          * When we COW a devmap PMD entry, we split it into PTEs, so we should
 924          * not be in this function with `flags & FOLL_COW` set.
 925          */
 926         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
 927
 928         if (flags & FOLL_WRITE && !pmd_write(*pmd))
 929                 return NULL;
 930
 931         if (pmd_present(*pmd) && pmd_devmap(*pmd))
 932                 /* pass */;
 933         else
 934                 return NULL;
 935
 936         if (flags & FOLL_TOUCH)
 937                 touch_pmd(vma, addr, pmd, flags);
 938
 939         /*
 940          * device mapped pages can only be returned if the
 941          * caller will manage the page reference count.
 942          */
 943         if (!(flags & FOLL_GET))
 944                 return ERR_PTR(-EEXIST);
 945
 946         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
 947         *pgmap = get_dev_pagemap(pfn, *pgmap);
 948         if (!*pgmap)
 949                 return ERR_PTR(-EFAULT);
 950         page = pfn_to_page(pfn);
 951         get_page(page);
 952
 953         return page;
 954 }
 955
 956 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 957                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 958                   struct vm_area_struct *vma)
 959 {
 960         spinlock_t *dst_ptl, *src_ptl;
 961         struct page *src_page;
 962         pmd_t pmd;
 963         pgtable_t pgtable = NULL;
 964         int ret = -ENOMEM;
 965
 966         /* Skip if can be re-fill on fault */
 967         if (!vma_is_anonymous(vma))
 968                 return 0;
 969
 970         pgtable = pte_alloc_one(dst_mm);
 971         if (unlikely(!pgtable))
 972                 goto out;
 973
 974         dst_ptl = pmd_lock(dst_mm, dst_pmd);
 975         src_ptl = pmd_lockptr(src_mm, src_pmd);
 976         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 977
 978         ret = -EAGAIN;
 979         pmd = *src_pmd;
 980
 981 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
 982         if (unlikely(is_swap_pmd(pmd))) {
 983                 swp_entry_t entry = pmd_to_swp_entry(pmd);
 984
 985                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
 986                 if (is_write_migration_entry(entry)) {
 987                         make_migration_entry_read(&entry);
 988                         pmd = swp_entry_to_pmd(entry);
 989                         if (pmd_swp_soft_dirty(*src_pmd))
 990                                 pmd = pmd_swp_mksoft_dirty(pmd);
 991                         set_pmd_at(src_mm, addr, src_pmd, pmd);
 992                 }
 993                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 994                 mm_inc_nr_ptes(dst_mm);
 995                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 996                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 997                 ret = 0;
 998                 goto out_unlock;
 999         }
1000 #endif
1001
1002         if (unlikely(!pmd_trans_huge(pmd))) {
1003                 pte_free(dst_mm, pgtable);
1004                 goto out_unlock;
1005         }
1006         /*
1007          * When page table lock is held, the huge zero pmd should not be
1008          * under splitting since we don't split the page itself, only pmd to
1009          * a page table.
1010          */
1011         if (is_huge_zero_pmd(pmd)) {
1012                 struct page *zero_page;
1013                 /*
1014                  * get_huge_zero_page() will never allocate a new page here,
1015                  * since we already have a zero page to copy. It just takes a
1016                  * reference.
1017                  */
1018                 zero_page = mm_get_huge_zero_page(dst_mm);
1019                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1020                                 zero_page);
1021                 ret = 0;
1022                 goto out_unlock;
1023         }
1024
1025         src_page = pmd_page(pmd);
1026         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1027         get_page(src_page);
1028         page_dup_rmap(src_page, true);
1029         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1030         mm_inc_nr_ptes(dst_mm);
1031         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1032
1033         pmdp_set_wrprotect(src_mm, addr, src_pmd);
1034         pmd = pmd_mkold(pmd_wrprotect(pmd));
1035         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1036
1037         ret = 0;
1038 out_unlock:
1039         spin_unlock(src_ptl);
1040         spin_unlock(dst_ptl);
1041 out:
1042         return ret;
1043 }
1044
1045 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1046 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1047                 pud_t *pud, int flags)
1048 {
1049         pud_t _pud;
1050
1051         _pud = pud_mkyoung(*pud);
1052         if (flags & FOLL_WRITE)
1053                 _pud = pud_mkdirty(_pud);
1054         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1055                                 pud, _pud, flags & FOLL_WRITE))
1056                 update_mmu_cache_pud(vma, addr, pud);
1057 }
1058
1059 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1060                 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1061 {
1062         unsigned long pfn = pud_pfn(*pud);
1063         struct mm_struct *mm = vma->vm_mm;
1064         struct page *page;
1065
1066         assert_spin_locked(pud_lockptr(mm, pud));
1067
1068         if (flags & FOLL_WRITE && !pud_write(*pud))
1069                 return NULL;
1070
1071         if (pud_present(*pud) && pud_devmap(*pud))
1072                 /* pass */;
1073         else
1074                 return NULL;
1075
1076         if (flags & FOLL_TOUCH)
1077                 touch_pud(vma, addr, pud, flags);
1078
1079         /*
1080          * device mapped pages can only be returned if the
1081          * caller will manage the page reference count.
1082          */
1083         if (!(flags & FOLL_GET))
1084                 return ERR_PTR(-EEXIST);
1085
1086         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1087         *pgmap = get_dev_pagemap(pfn, *pgmap);
1088         if (!*pgmap)
1089                 return ERR_PTR(-EFAULT);
1090         page = pfn_to_page(pfn);
1091         get_page(page);
1092
1093         return page;
1094 }
1095
1096 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1097                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1098                   struct vm_area_struct *vma)
1099 {
1100         spinlock_t *dst_ptl, *src_ptl;
1101         pud_t pud;
1102         int ret;
1103
1104         dst_ptl = pud_lock(dst_mm, dst_pud);
1105         src_ptl = pud_lockptr(src_mm, src_pud);
1106         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1107
1108         ret = -EAGAIN;
1109         pud = *src_pud;
1110         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1111                 goto out_unlock;
1112
1113         /*
1114          * When page table lock is held, the huge zero pud should not be
1115          * under splitting since we don't split the page itself, only pud to
1116          * a page table.
1117          */
1118         if (is_huge_zero_pud(pud)) {
1119                 /* No huge zero pud yet */
1120         }
1121
1122         pudp_set_wrprotect(src_mm, addr, src_pud);
1123         pud = pud_mkold(pud_wrprotect(pud));
1124         set_pud_at(dst_mm, addr, dst_pud, pud);
1125
1126         ret = 0;
1127 out_unlock:
1128         spin_unlock(src_ptl);
1129         spin_unlock(dst_ptl);
1130         return ret;
1131 }
1132
1133 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1134 {
1135         pud_t entry;
1136         unsigned long haddr;
1137         bool write = vmf->flags & FAULT_FLAG_WRITE;
1138
1139         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1140         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1141                 goto unlock;
1142
1143         entry = pud_mkyoung(orig_pud);
1144         if (write)
1145                 entry = pud_mkdirty(entry);
1146         haddr = vmf->address & HPAGE_PUD_MASK;
1147         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1148                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1149
1150 unlock:
1151         spin_unlock(vmf->ptl);
1152 }
1153 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1154
1155 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1156 {
1157         pmd_t entry;
1158         unsigned long haddr;
1159         bool write = vmf->flags & FAULT_FLAG_WRITE;
1160
1161         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1162         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1163                 goto unlock;
1164
1165         entry = pmd_mkyoung(orig_pmd);
1166         if (write)
1167                 entry = pmd_mkdirty(entry);
1168         haddr = vmf->address & HPAGE_PMD_MASK;
1169         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1170                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1171
1172 unlock:
1173         spin_unlock(vmf->ptl);
1174 }
1175
1176 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1177                         pmd_t orig_pmd, struct page *page)
1178 {
1179         struct vm_area_struct *vma = vmf->vma;
1180         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1181         struct mem_cgroup *memcg;
1182         pgtable_t pgtable;
1183         pmd_t _pmd;
1184         int i;
1185         vm_fault_t ret = 0;
1186         struct page **pages;
1187         struct mmu_notifier_range range;
1188
1189         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1190                               GFP_KERNEL);
1191         if (unlikely(!pages)) {
1192                 ret |= VM_FAULT_OOM;
1193                 goto out;
1194         }
1195
1196         for (i = 0; i < HPAGE_PMD_NR; i++) {
1197                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1198                                                vmf->address, page_to_nid(page));
1199                 if (unlikely(!pages[i] ||
1200                              mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1201                                      GFP_KERNEL, &memcg, false))) {
1202                         if (pages[i])
1203                                 put_page(pages[i]);
1204                         while (--i >= 0) {
1205                                 memcg = (void *)page_private(pages[i]);
1206                                 set_page_private(pages[i], 0);
1207                                 mem_cgroup_cancel_charge(pages[i], memcg,
1208                                                 false);
1209                                 put_page(pages[i]);
1210                         }
1211                         kfree(pages);
1212                         ret |= VM_FAULT_OOM;
1213                         goto out;
1214                 }
1215                 set_page_private(pages[i], (unsigned long)memcg);
1216         }
1217
1218         for (i = 0; i < HPAGE_PMD_NR; i++) {
1219                 copy_user_highpage(pages[i], page + i,
1220                                    haddr + PAGE_SIZE * i, vma);
1221                 __SetPageUptodate(pages[i]);
1222                 cond_resched();
1223         }
1224
1225         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1226                                 haddr, haddr + HPAGE_PMD_SIZE);
1227         mmu_notifier_invalidate_range_start(&range);
1228
1229         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1230         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1231                 goto out_free_pages;
1232         VM_BUG_ON_PAGE(!PageHead(page), page);
1233
1234         /*
1235          * Leave pmd empty until pte is filled note we must notify here as
1236          * concurrent CPU thread might write to new page before the call to
1237          * mmu_notifier_invalidate_range_end() happens which can lead to a
1238          * device seeing memory write in different order than CPU.
1239          *
1240          * See Documentation/vm/mmu_notifier.rst
1241          */
1242         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1243
1244         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1245         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1246
1247         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1248                 pte_t entry;
1249                 entry = mk_pte(pages[i], vma->vm_page_prot);
1250                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1251                 memcg = (void *)page_private(pages[i]);
1252                 set_page_private(pages[i], 0);
1253                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1254                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1255                 lru_cache_add_active_or_unevictable(pages[i], vma);
1256                 vmf->pte = pte_offset_map(&_pmd, haddr);
1257                 VM_BUG_ON(!pte_none(*vmf->pte));
1258                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1259                 pte_unmap(vmf->pte);
1260         }
1261         kfree(pages);
1262
1263         smp_wmb(); /* make pte visible before pmd */
1264         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1265         page_remove_rmap(page, true);
1266         spin_unlock(vmf->ptl);
1267
1268         /*
1269          * No need to double call mmu_notifier->invalidate_range() callback as
1270          * the above pmdp_huge_clear_flush_notify() did already call it.
1271          */
1272         mmu_notifier_invalidate_range_only_end(&range);
1273
1274         ret |= VM_FAULT_WRITE;
1275         put_page(page);
1276
1277 out:
1278         return ret;
1279
1280 out_free_pages:
1281         spin_unlock(vmf->ptl);
1282         mmu_notifier_invalidate_range_end(&range);
1283         for (i = 0; i < HPAGE_PMD_NR; i++) {
1284                 memcg = (void *)page_private(pages[i]);
1285                 set_page_private(pages[i], 0);
1286                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1287                 put_page(pages[i]);
1288         }
1289         kfree(pages);
1290         goto out;
1291 }
1292
1293 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1294 {
1295         struct vm_area_struct *vma = vmf->vma;
1296         struct page *page = NULL, *new_page;
1297         struct mem_cgroup *memcg;
1298         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1299         struct mmu_notifier_range range;
1300         gfp_t huge_gfp;                 /* for allocation and charge */
1301         vm_fault_t ret = 0;
1302
1303         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1304         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1305         if (is_huge_zero_pmd(orig_pmd))
1306                 goto alloc;
1307         spin_lock(vmf->ptl);
1308         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1309                 goto out_unlock;
1310
1311         page = pmd_page(orig_pmd);
1312         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1313         /*
1314          * We can only reuse the page if nobody else maps the huge page or it's
1315          * part.
1316          */
1317         if (!trylock_page(page)) {
1318                 get_page(page);
1319                 spin_unlock(vmf->ptl);
1320                 lock_page(page);
1321                 spin_lock(vmf->ptl);
1322                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1323                         unlock_page(page);
1324                         put_page(page);
1325                         goto out_unlock;
1326                 }
1327                 put_page(page);
1328         }
1329         if (reuse_swap_page(page, NULL)) {
1330                 pmd_t entry;
1331                 entry = pmd_mkyoung(orig_pmd);
1332                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1333                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1334                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1335                 ret |= VM_FAULT_WRITE;
1336                 unlock_page(page);
1337                 goto out_unlock;
1338         }
1339         unlock_page(page);
1340         get_page(page);
1341         spin_unlock(vmf->ptl);
1342 alloc:
1343         if (__transparent_hugepage_enabled(vma) &&
1344             !transparent_hugepage_debug_cow()) {
1345                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1346                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1347         } else
1348                 new_page = NULL;
1349
1350         if (likely(new_page)) {
1351                 prep_transhuge_page(new_page);
1352         } else {
1353                 if (!page) {
1354                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1355                         ret |= VM_FAULT_FALLBACK;
1356                 } else {
1357                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1358                         if (ret & VM_FAULT_OOM) {
1359                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1360                                 ret |= VM_FAULT_FALLBACK;
1361                         }
1362                         put_page(page);
1363                 }
1364                 count_vm_event(THP_FAULT_FALLBACK);
1365                 goto out;
1366         }
1367
1368         if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1369                                         huge_gfp, &memcg, true))) {
1370                 put_page(new_page);
1371                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1372                 if (page)
1373                         put_page(page);
1374                 ret |= VM_FAULT_FALLBACK;
1375                 count_vm_event(THP_FAULT_FALLBACK);
1376                 goto out;
1377         }
1378
1379         count_vm_event(THP_FAULT_ALLOC);
1380         count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
1381
1382         if (!page)
1383                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1384         else
1385                 copy_user_huge_page(new_page, page, vmf->address,
1386                                     vma, HPAGE_PMD_NR);
1387         __SetPageUptodate(new_page);
1388
1389         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1390                                 haddr, haddr + HPAGE_PMD_SIZE);
1391         mmu_notifier_invalidate_range_start(&range);
1392
1393         spin_lock(vmf->ptl);
1394         if (page)
1395                 put_page(page);
1396         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1397                 spin_unlock(vmf->ptl);
1398                 mem_cgroup_cancel_charge(new_page, memcg, true);
1399                 put_page(new_page);
1400                 goto out_mn;
1401         } else {
1402                 pmd_t entry;
1403                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1404                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1405                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1406                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1407                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1408                 lru_cache_add_active_or_unevictable(new_page, vma);
1409                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1410                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1411                 if (!page) {
1412                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1413                 } else {
1414                         VM_BUG_ON_PAGE(!PageHead(page), page);
1415                         page_remove_rmap(page, true);
1416                         put_page(page);
1417                 }
1418                 ret |= VM_FAULT_WRITE;
1419         }
1420         spin_unlock(vmf->ptl);
1421 out_mn:
1422         /*
1423          * No need to double call mmu_notifier->invalidate_range() callback as
1424          * the above pmdp_huge_clear_flush_notify() did already call it.
1425          */
1426         mmu_notifier_invalidate_range_only_end(&range);
1427 out:
1428         return ret;
1429 out_unlock:
1430         spin_unlock(vmf->ptl);
1431         return ret;
1432 }
1433
1434 /*
1435  * FOLL_FORCE can write to even unwritable pmd's, but only
1436  * after we've gone through a COW cycle and they are dirty.
1437  */
1438 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1439 {
1440         return pmd_write(pmd) ||
1441                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1442 }
1443
1444 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1445                                    unsigned long addr,
1446                                    pmd_t *pmd,
1447                                    unsigned int flags)
1448 {
1449         struct mm_struct *mm = vma->vm_mm;
1450         struct page *page = NULL;
1451
1452         assert_spin_locked(pmd_lockptr(mm, pmd));
1453
1454         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1455                 goto out;
1456
1457         /* Avoid dumping huge zero page */
1458         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1459                 return ERR_PTR(-EFAULT);
1460
1461         /* Full NUMA hinting faults to serialise migration in fault paths */
1462         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1463                 goto out;
1464
1465         page = pmd_page(*pmd);
1466         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1467         if (flags & FOLL_TOUCH)
1468                 touch_pmd(vma, addr, pmd, flags);
1469         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1470                 /*
1471                  * We don't mlock() pte-mapped THPs. This way we can avoid
1472                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1473                  *
1474                  * For anon THP:
1475                  *
1476                  * In most cases the pmd is the only mapping of the page as we
1477                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1478                  * writable private mappings in populate_vma_page_range().
1479                  *
1480                  * The only scenario when we have the page shared here is if we
1481                  * mlocking read-only mapping shared over fork(). We skip
1482                  * mlocking such pages.
1483                  *
1484                  * For file THP:
1485                  *
1486                  * We can expect PageDoubleMap() to be stable under page lock:
1487                  * for file pages we set it in page_add_file_rmap(), which
1488                  * requires page to be locked.
1489                  */
1490
1491                 if (PageAnon(page) && compound_mapcount(page) != 1)
1492                         goto skip_mlock;
1493                 if (PageDoubleMap(page) || !page->mapping)
1494                         goto skip_mlock;
1495                 if (!trylock_page(page))
1496                         goto skip_mlock;
1497                 lru_add_drain();
1498                 if (page->mapping && !PageDoubleMap(page))
1499                         mlock_vma_page(page);
1500                 unlock_page(page);
1501         }
1502 skip_mlock:
1503         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1504         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1505         if (flags & FOLL_GET)
1506                 get_page(page);
1507
1508 out:
1509         return page;
1510 }
1511
1512 /* NUMA hinting page fault entry point for trans huge pmds */
1513 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1514 {
1515         struct vm_area_struct *vma = vmf->vma;
1516         struct anon_vma *anon_vma = NULL;
1517         struct page *page;
1518         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1519         int page_nid = NUMA_NO_NODE, this_nid = numa_node_id();
1520         int target_nid, last_cpupid = -1;
1521         bool page_locked;
1522         bool migrated = false;
1523         bool was_writable;
1524         int flags = 0;
1525
1526         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1527         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1528                 goto out_unlock;
1529
1530         /*
1531          * If there are potential migrations, wait for completion and retry
1532          * without disrupting NUMA hinting information. Do not relock and
1533          * check_same as the page may no longer be mapped.
1534          */
1535         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1536                 page = pmd_page(*vmf->pmd);
1537                 if (!get_page_unless_zero(page))
1538                         goto out_unlock;
1539                 spin_unlock(vmf->ptl);
1540                 put_and_wait_on_page_locked(page);
1541                 goto out;
1542         }
1543
1544         page = pmd_page(pmd);
1545         BUG_ON(is_huge_zero_page(page));
1546         page_nid = page_to_nid(page);
1547         last_cpupid = page_cpupid_last(page);
1548         count_vm_numa_event(NUMA_HINT_FAULTS);
1549         if (page_nid == this_nid) {
1550                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1551                 flags |= TNF_FAULT_LOCAL;
1552         }
1553
1554         /* See similar comment in do_numa_page for explanation */
1555         if (!pmd_savedwrite(pmd))
1556                 flags |= TNF_NO_GROUP;
1557
1558         /*
1559          * Acquire the page lock to serialise THP migrations but avoid dropping
1560          * page_table_lock if at all possible
1561          */
1562         page_locked = trylock_page(page);
1563         target_nid = mpol_misplaced(page, vma, haddr);
1564         if (target_nid == NUMA_NO_NODE) {
1565                 /* If the page was locked, there are no parallel migrations */
1566                 if (page_locked)
1567                         goto clear_pmdnuma;
1568         }
1569
1570         /* Migration could have started since the pmd_trans_migrating check */
1571         if (!page_locked) {
1572                 page_nid = NUMA_NO_NODE;
1573                 if (!get_page_unless_zero(page))
1574                         goto out_unlock;
1575                 spin_unlock(vmf->ptl);
1576                 put_and_wait_on_page_locked(page);
1577                 goto out;
1578         }
1579
1580         /*
1581          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1582          * to serialises splits
1583          */
1584         get_page(page);
1585         spin_unlock(vmf->ptl);
1586         anon_vma = page_lock_anon_vma_read(page);
1587
1588         /* Confirm the PMD did not change while page_table_lock was released */
1589         spin_lock(vmf->ptl);
1590         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1591                 unlock_page(page);
1592                 put_page(page);
1593                 page_nid = NUMA_NO_NODE;
1594                 goto out_unlock;
1595         }
1596
1597         /* Bail if we fail to protect against THP splits for any reason */
1598         if (unlikely(!anon_vma)) {
1599                 put_page(page);
1600                 page_nid = NUMA_NO_NODE;
1601                 goto clear_pmdnuma;
1602         }
1603
1604         /*
1605          * Since we took the NUMA fault, we must have observed the !accessible
1606          * bit. Make sure all other CPUs agree with that, to avoid them
1607          * modifying the page we're about to migrate.
1608          *
1609          * Must be done under PTL such that we'll observe the relevant
1610          * inc_tlb_flush_pending().
1611          *
1612          * We are not sure a pending tlb flush here is for a huge page
1613          * mapping or not. Hence use the tlb range variant
1614          */
1615         if (mm_tlb_flush_pending(vma->vm_mm)) {
1616                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1617                 /*
1618                  * change_huge_pmd() released the pmd lock before
1619                  * invalidating the secondary MMUs sharing the primary
1620                  * MMU pagetables (with ->invalidate_range()). The
1621                  * mmu_notifier_invalidate_range_end() (which
1622                  * internally calls ->invalidate_range()) in
1623                  * change_pmd_range() will run after us, so we can't
1624                  * rely on it here and we need an explicit invalidate.
1625                  */
1626                 mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1627                                               haddr + HPAGE_PMD_SIZE);
1628         }
1629
1630         /*
1631          * Migrate the THP to the requested node, returns with page unlocked
1632          * and access rights restored.
1633          */
1634         spin_unlock(vmf->ptl);
1635
1636         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1637                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1638         if (migrated) {
1639                 flags |= TNF_MIGRATED;
1640                 page_nid = target_nid;
1641         } else
1642                 flags |= TNF_MIGRATE_FAIL;
1643
1644         goto out;
1645 clear_pmdnuma:
1646         BUG_ON(!PageLocked(page));
1647         was_writable = pmd_savedwrite(pmd);
1648         pmd = pmd_modify(pmd, vma->vm_page_prot);
1649         pmd = pmd_mkyoung(pmd);
1650         if (was_writable)
1651                 pmd = pmd_mkwrite(pmd);
1652         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1653         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1654         unlock_page(page);
1655 out_unlock:
1656         spin_unlock(vmf->ptl);
1657
1658 out:
1659         if (anon_vma)
1660                 page_unlock_anon_vma_read(anon_vma);
1661
1662         if (page_nid != NUMA_NO_NODE)
1663                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1664                                 flags);
1665
1666         return 0;
1667 }
1668
1669 /*
1670  * Return true if we do MADV_FREE successfully on entire pmd page.
1671  * Otherwise, return false.
1672  */
1673 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1674                 pmd_t *pmd, unsigned long addr, unsigned long next)
1675 {
1676         spinlock_t *ptl;
1677         pmd_t orig_pmd;
1678         struct page *page;
1679         struct mm_struct *mm = tlb->mm;
1680         bool ret = false;
1681
1682         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1683
1684         ptl = pmd_trans_huge_lock(pmd, vma);
1685         if (!ptl)
1686                 goto out_unlocked;
1687
1688         orig_pmd = *pmd;
1689         if (is_huge_zero_pmd(orig_pmd))
1690                 goto out;
1691
1692         if (unlikely(!pmd_present(orig_pmd))) {
1693                 VM_BUG_ON(thp_migration_supported() &&
1694                                   !is_pmd_migration_entry(orig_pmd));
1695                 goto out;
1696         }
1697
1698         page = pmd_page(orig_pmd);
1699         /*
1700          * If other processes are mapping this page, we couldn't discard
1701          * the page unless they all do MADV_FREE so let's skip the page.
1702          */
1703         if (page_mapcount(page) != 1)
1704                 goto out;
1705
1706         if (!trylock_page(page))
1707                 goto out;
1708
1709         /*
1710          * If user want to discard part-pages of THP, split it so MADV_FREE
1711          * will deactivate only them.
1712          */
1713         if (next - addr != HPAGE_PMD_SIZE) {
1714                 get_page(page);
1715                 spin_unlock(ptl);
1716                 split_huge_page(page);
1717                 unlock_page(page);
1718                 put_page(page);
1719                 goto out_unlocked;
1720         }
1721
1722         if (PageDirty(page))
1723                 ClearPageDirty(page);
1724         unlock_page(page);
1725
1726         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1727                 pmdp_invalidate(vma, addr, pmd);
1728                 orig_pmd = pmd_mkold(orig_pmd);
1729                 orig_pmd = pmd_mkclean(orig_pmd);
1730
1731                 set_pmd_at(mm, addr, pmd, orig_pmd);
1732                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1733         }
1734
1735         mark_page_lazyfree(page);
1736         ret = true;
1737 out:
1738         spin_unlock(ptl);
1739 out_unlocked:
1740         return ret;
1741 }
1742
1743 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1744 {
1745         pgtable_t pgtable;
1746
1747         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1748         pte_free(mm, pgtable);
1749         mm_dec_nr_ptes(mm);
1750 }
1751
1752 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1753                  pmd_t *pmd, unsigned long addr)
1754 {
1755         pmd_t orig_pmd;
1756         spinlock_t *ptl;
1757
1758         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1759
1760         ptl = __pmd_trans_huge_lock(pmd, vma);
1761         if (!ptl)
1762                 return 0;
1763         /*
1764          * For architectures like ppc64 we look at deposited pgtable
1765          * when calling pmdp_huge_get_and_clear. So do the
1766          * pgtable_trans_huge_withdraw after finishing pmdp related
1767          * operations.
1768          */
1769         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1770                         tlb->fullmm);
1771         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1772         if (vma_is_dax(vma)) {
1773                 if (arch_needs_pgtable_deposit())
1774                         zap_deposited_table(tlb->mm, pmd);
1775                 spin_unlock(ptl);
1776                 if (is_huge_zero_pmd(orig_pmd))
1777                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1778         } else if (is_huge_zero_pmd(orig_pmd)) {
1779                 zap_deposited_table(tlb->mm, pmd);
1780                 spin_unlock(ptl);
1781                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1782         } else {
1783                 struct page *page = NULL;
1784                 int flush_needed = 1;
1785
1786                 if (pmd_present(orig_pmd)) {
1787                         page = pmd_page(orig_pmd);
1788                         page_remove_rmap(page, true);
1789                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1790                         VM_BUG_ON_PAGE(!PageHead(page), page);
1791                 } else if (thp_migration_supported()) {
1792                         swp_entry_t entry;
1793
1794                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1795                         entry = pmd_to_swp_entry(orig_pmd);
1796                         page = pfn_to_page(swp_offset(entry));
1797                         flush_needed = 0;
1798                 } else
1799                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1800
1801                 if (PageAnon(page)) {
1802                         zap_deposited_table(tlb->mm, pmd);
1803                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1804                 } else {
1805                         if (arch_needs_pgtable_deposit())
1806                                 zap_deposited_table(tlb->mm, pmd);
1807                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1808                 }
1809
1810                 spin_unlock(ptl);
1811                 if (flush_needed)
1812                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1813         }
1814         return 1;
1815 }
1816
1817 #ifndef pmd_move_must_withdraw
1818 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1819                                          spinlock_t *old_pmd_ptl,
1820                                          struct vm_area_struct *vma)
1821 {
1822         /*
1823          * With split pmd lock we also need to move preallocated
1824          * PTE page table if new_pmd is on different PMD page table.
1825          *
1826          * We also don't deposit and withdraw tables for file pages.
1827          */
1828         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1829 }
1830 #endif
1831
1832 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1833 {
1834 #ifdef CONFIG_MEM_SOFT_DIRTY
1835         if (unlikely(is_pmd_migration_entry(pmd)))
1836                 pmd = pmd_swp_mksoft_dirty(pmd);
1837         else if (pmd_present(pmd))
1838                 pmd = pmd_mksoft_dirty(pmd);
1839 #endif
1840         return pmd;
1841 }
1842
1843 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1844                   unsigned long new_addr, unsigned long old_end,
1845                   pmd_t *old_pmd, pmd_t *new_pmd)
1846 {
1847         spinlock_t *old_ptl, *new_ptl;
1848         pmd_t pmd;
1849         struct mm_struct *mm = vma->vm_mm;
1850         bool force_flush = false;
1851
1852         if ((old_addr & ~HPAGE_PMD_MASK) ||
1853             (new_addr & ~HPAGE_PMD_MASK) ||
1854             old_end - old_addr < HPAGE_PMD_SIZE)
1855                 return false;
1856
1857         /*
1858          * The destination pmd shouldn't be established, free_pgtables()
1859          * should have release it.
1860          */
1861         if (WARN_ON(!pmd_none(*new_pmd))) {
1862                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1863                 return false;
1864         }
1865
1866         /*
1867          * We don't have to worry about the ordering of src and dst
1868          * ptlocks because exclusive mmap_sem prevents deadlock.
1869          */
1870         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1871         if (old_ptl) {
1872                 new_ptl = pmd_lockptr(mm, new_pmd);
1873                 if (new_ptl != old_ptl)
1874                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1875                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1876                 if (pmd_present(pmd))
1877                         force_flush = true;
1878                 VM_BUG_ON(!pmd_none(*new_pmd));
1879
1880                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1881                         pgtable_t pgtable;
1882                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1883                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1884                 }
1885                 pmd = move_soft_dirty_pmd(pmd);
1886                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1887                 if (force_flush)
1888                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1889                 if (new_ptl != old_ptl)
1890                         spin_unlock(new_ptl);
1891                 spin_unlock(old_ptl);
1892                 return true;
1893         }
1894         return false;
1895 }
1896
1897 /*
1898  * Returns
1899  *  - 0 if PMD could not be locked
1900  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1901  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1902  */
1903 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1904                 unsigned long addr, pgprot_t newprot, int prot_numa)
1905 {
1906         struct mm_struct *mm = vma->vm_mm;
1907         spinlock_t *ptl;
1908         pmd_t entry;
1909         bool preserve_write;
1910         int ret;
1911
1912         ptl = __pmd_trans_huge_lock(pmd, vma);
1913         if (!ptl)
1914                 return 0;
1915
1916         preserve_write = prot_numa && pmd_write(*pmd);
1917         ret = 1;
1918
1919 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1920         if (is_swap_pmd(*pmd)) {
1921                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1922
1923                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1924                 if (is_write_migration_entry(entry)) {
1925                         pmd_t newpmd;
1926                         /*
1927                          * A protection check is difficult so
1928                          * just be safe and disable write
1929                          */
1930                         make_migration_entry_read(&entry);
1931                         newpmd = swp_entry_to_pmd(entry);
1932                         if (pmd_swp_soft_dirty(*pmd))
1933                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1934                         set_pmd_at(mm, addr, pmd, newpmd);
1935                 }
1936                 goto unlock;
1937         }
1938 #endif
1939
1940         /*
1941          * Avoid trapping faults against the zero page. The read-only
1942          * data is likely to be read-cached on the local CPU and
1943          * local/remote hits to the zero page are not interesting.
1944          */
1945         if (prot_numa && is_huge_zero_pmd(*pmd))
1946                 goto unlock;
1947
1948         if (prot_numa && pmd_protnone(*pmd))
1949                 goto unlock;
1950
1951         /*
1952          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1953          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1954          * which is also under down_read(mmap_sem):
1955          *
1956          *      CPU0:                           CPU1:
1957          *                              change_huge_pmd(prot_numa=1)
1958          *                               pmdp_huge_get_and_clear_notify()
1959          * madvise_dontneed()
1960          *  zap_pmd_range()
1961          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1962          *   // skip the pmd
1963          *                               set_pmd_at();
1964          *                               // pmd is re-established
1965          *
1966          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1967          * which may break userspace.
1968          *
1969          * pmdp_invalidate() is required to make sure we don't miss
1970          * dirty/young flags set by hardware.
1971          */
1972         entry = pmdp_invalidate(vma, addr, pmd);
1973
1974         entry = pmd_modify(entry, newprot);
1975         if (preserve_write)
1976                 entry = pmd_mk_savedwrite(entry);
1977         ret = HPAGE_PMD_NR;
1978         set_pmd_at(mm, addr, pmd, entry);
1979         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1980 unlock:
1981         spin_unlock(ptl);
1982         return ret;
1983 }
1984
1985 /*
1986  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1987  *
1988  * Note that if it returns page table lock pointer, this routine returns without
1989  * unlocking page table lock. So callers must unlock it.
1990  */
1991 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1992 {
1993         spinlock_t *ptl;
1994         ptl = pmd_lock(vma->vm_mm, pmd);
1995         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1996                         pmd_devmap(*pmd)))
1997                 return ptl;
1998         spin_unlock(ptl);
1999         return NULL;
2000 }
2001
2002 /*
2003  * Returns true if a given pud maps a thp, false otherwise.
2004  *
2005  * Note that if it returns true, this routine returns without unlocking page
2006  * table lock. So callers must unlock it.
2007  */
2008 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
2009 {
2010         spinlock_t *ptl;
2011
2012         ptl = pud_lock(vma->vm_mm, pud);
2013         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
2014                 return ptl;
2015         spin_unlock(ptl);
2016         return NULL;
2017 }
2018
2019 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
2020 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
2021                  pud_t *pud, unsigned long addr)
2022 {
2023         spinlock_t *ptl;
2024
2025         ptl = __pud_trans_huge_lock(pud, vma);
2026         if (!ptl)
2027                 return 0;
2028         /*
2029          * For architectures like ppc64 we look at deposited pgtable
2030          * when calling pudp_huge_get_and_clear. So do the
2031          * pgtable_trans_huge_withdraw after finishing pudp related
2032          * operations.
2033          */
2034         pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
2035         tlb_remove_pud_tlb_entry(tlb, pud, addr);
2036         if (vma_is_dax(vma)) {
2037                 spin_unlock(ptl);
2038                 /* No zero page support yet */
2039         } else {
2040                 /* No support for anonymous PUD pages yet */
2041                 BUG();
2042         }
2043         return 1;
2044 }
2045
2046 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2047                 unsigned long haddr)
2048 {
2049         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2050         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2051         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2052         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2053
2054         count_vm_event(THP_SPLIT_PUD);
2055
2056         pudp_huge_clear_flush_notify(vma, haddr, pud);
2057 }
2058
2059 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2060                 unsigned long address)
2061 {
2062         spinlock_t *ptl;
2063         struct mmu_notifier_range range;
2064
2065         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2066                                 address & HPAGE_PUD_MASK,
2067                                 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
2068         mmu_notifier_invalidate_range_start(&range);
2069         ptl = pud_lock(vma->vm_mm, pud);
2070         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2071                 goto out;
2072         __split_huge_pud_locked(vma, pud, range.start);
2073
2074 out:
2075         spin_unlock(ptl);
2076         /*
2077          * No need to double call mmu_notifier->invalidate_range() callback as
2078          * the above pudp_huge_clear_flush_notify() did already call it.
2079          */
2080         mmu_notifier_invalidate_range_only_end(&range);
2081 }
2082 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2083
2084 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2085                 unsigned long haddr, pmd_t *pmd)
2086 {
2087         struct mm_struct *mm = vma->vm_mm;
2088         pgtable_t pgtable;
2089         pmd_t _pmd;
2090         int i;
2091
2092         /*
2093          * Leave pmd empty until pte is filled note that it is fine to delay
2094          * notification until mmu_notifier_invalidate_range_end() as we are
2095          * replacing a zero pmd write protected page with a zero pte write
2096          * protected page.
2097          *
2098          * See Documentation/vm/mmu_notifier.rst
2099          */
2100         pmdp_huge_clear_flush(vma, haddr, pmd);
2101
2102         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2103         pmd_populate(mm, &_pmd, pgtable);
2104
2105         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2106                 pte_t *pte, entry;
2107                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2108                 entry = pte_mkspecial(entry);
2109                 pte = pte_offset_map(&_pmd, haddr);
2110                 VM_BUG_ON(!pte_none(*pte));
2111                 set_pte_at(mm, haddr, pte, entry);
2112                 pte_unmap(pte);
2113         }
2114         smp_wmb(); /* make pte visible before pmd */
2115         pmd_populate(mm, pmd, pgtable);
2116 }
2117
2118 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2119                 unsigned long haddr, bool freeze)
2120 {
2121         struct mm_struct *mm = vma->vm_mm;
2122         struct page *page;
2123         pgtable_t pgtable;
2124         pmd_t old_pmd, _pmd;
2125         bool young, write, soft_dirty, pmd_migration = false;
2126         unsigned long addr;
2127         int i;
2128
2129         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2130         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2131         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2132         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2133                                 && !pmd_devmap(*pmd));
2134
2135         count_vm_event(THP_SPLIT_PMD);
2136
2137         if (!vma_is_anonymous(vma)) {
2138                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2139                 /*
2140                  * We are going to unmap this huge page. So
2141                  * just go ahead and zap it
2142                  */
2143                 if (arch_needs_pgtable_deposit())
2144                         zap_deposited_table(mm, pmd);
2145                 if (vma_is_dax(vma))
2146                         return;
2147                 page = pmd_page(_pmd);
2148                 if (!PageDirty(page) && pmd_dirty(_pmd))
2149                         set_page_dirty(page);
2150                 if (!PageReferenced(page) && pmd_young(_pmd))
2151                         SetPageReferenced(page);
2152                 page_remove_rmap(page, true);
2153                 put_page(page);
2154                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2155                 return;
2156         } else if (is_huge_zero_pmd(*pmd)) {
2157                 /*
2158                  * FIXME: Do we want to invalidate secondary mmu by calling
2159                  * mmu_notifier_invalidate_range() see comments below inside
2160                  * __split_huge_pmd() ?
2161                  *
2162                  * We are going from a zero huge page write protected to zero
2163                  * small page also write protected so it does not seems useful
2164                  * to invalidate secondary mmu at this time.
2165                  */
2166                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2167         }
2168
2169         /*
2170          * Up to this point the pmd is present and huge and userland has the
2171          * whole access to the hugepage during the split (which happens in
2172          * place). If we overwrite the pmd with the not-huge version pointing
2173          * to the pte here (which of course we could if all CPUs were bug
2174          * free), userland could trigger a small page size TLB miss on the
2175          * small sized TLB while the hugepage TLB entry is still established in
2176          * the huge TLB. Some CPU doesn't like that.
2177          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2178          * 383 on page 93. Intel should be safe but is also warns that it's
2179          * only safe if the permission and cache attributes of the two entries
2180          * loaded in the two TLB is identical (which should be the case here).
2181          * But it is generally safer to never allow small and huge TLB entries
2182          * for the same virtual address to be loaded simultaneously. So instead
2183          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2184          * current pmd notpresent (atomically because here the pmd_trans_huge
2185          * must remain set at all times on the pmd until the split is complete
2186          * for this pmd), then we flush the SMP TLB and finally we write the
2187          * non-huge version of the pmd entry with pmd_populate.
2188          */
2189         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2190
2191         pmd_migration = is_pmd_migration_entry(old_pmd);
2192         if (unlikely(pmd_migration)) {
2193                 swp_entry_t entry;
2194
2195                 entry = pmd_to_swp_entry(old_pmd);
2196                 page = pfn_to_page(swp_offset(entry));
2197                 write = is_write_migration_entry(entry);
2198                 young = false;
2199                 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2200         } else {
2201                 page = pmd_page(old_pmd);
2202                 if (pmd_dirty(old_pmd))
2203                         SetPageDirty(page);
2204                 write = pmd_write(old_pmd);
2205                 young = pmd_young(old_pmd);
2206                 soft_dirty = pmd_soft_dirty(old_pmd);
2207         }
2208         VM_BUG_ON_PAGE(!page_count(page), page);
2209         page_ref_add(page, HPAGE_PMD_NR - 1);
2210
2211         /*
2212          * Withdraw the table only after we mark the pmd entry invalid.
2213          * This's critical for some architectures (Power).
2214          */
2215         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2216         pmd_populate(mm, &_pmd, pgtable);
2217
2218         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2219                 pte_t entry, *pte;
2220                 /*
2221                  * Note that NUMA hinting access restrictions are not
2222                  * transferred to avoid any possibility of altering
2223                  * permissions across VMAs.
2224                  */
2225                 if (freeze || pmd_migration) {
2226                         swp_entry_t swp_entry;
2227                         swp_entry = make_migration_entry(page + i, write);
2228                         entry = swp_entry_to_pte(swp_entry);
2229                         if (soft_dirty)
2230                                 entry = pte_swp_mksoft_dirty(entry);
2231                 } else {
2232                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2233                         entry = maybe_mkwrite(entry, vma);
2234                         if (!write)
2235                                 entry = pte_wrprotect(entry);
2236                         if (!young)
2237                                 entry = pte_mkold(entry);
2238                         if (soft_dirty)
2239                                 entry = pte_mksoft_dirty(entry);
2240                 }
2241                 pte = pte_offset_map(&_pmd, addr);
2242                 BUG_ON(!pte_none(*pte));
2243                 set_pte_at(mm, addr, pte, entry);
2244                 atomic_inc(&page[i]._mapcount);
2245                 pte_unmap(pte);
2246         }
2247
2248         /*
2249          * Set PG_double_map before dropping compound_mapcount to avoid
2250          * false-negative page_mapped().
2251          */
2252         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2253                 for (i = 0; i < HPAGE_PMD_NR; i++)
2254                         atomic_inc(&page[i]._mapcount);
2255         }
2256
2257         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2258                 /* Last compound_mapcount is gone. */
2259                 __dec_node_page_state(page, NR_ANON_THPS);
2260                 if (TestClearPageDoubleMap(page)) {
2261                         /* No need in mapcount reference anymore */
2262                         for (i = 0; i < HPAGE_PMD_NR; i++)
2263                                 atomic_dec(&page[i]._mapcount);
2264                 }
2265         }
2266
2267         smp_wmb(); /* make pte visible before pmd */
2268         pmd_populate(mm, pmd, pgtable);
2269
2270         if (freeze) {
2271                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2272                         page_remove_rmap(page + i, false);
2273                         put_page(page + i);
2274                 }
2275         }
2276 }
2277
2278 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2279                 unsigned long address, bool freeze, struct page *page)
2280 {
2281         spinlock_t *ptl;
2282         struct mmu_notifier_range range;
2283
2284         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2285                                 address & HPAGE_PMD_MASK,
2286                                 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2287         mmu_notifier_invalidate_range_start(&range);
2288         ptl = pmd_lock(vma->vm_mm, pmd);
2289
2290         /*
2291          * If caller asks to setup a migration entries, we need a page to check
2292          * pmd against. Otherwise we can end up replacing wrong page.
2293          */
2294         VM_BUG_ON(freeze && !page);
2295         if (page && page != pmd_page(*pmd))
2296                 goto out;
2297
2298         if (pmd_trans_huge(*pmd)) {
2299                 page = pmd_page(*pmd);
2300                 if (PageMlocked(page))
2301                         clear_page_mlock(page);
2302         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2303                 goto out;
2304         __split_huge_pmd_locked(vma, pmd, range.start, freeze);
2305 out:
2306         spin_unlock(ptl);
2307         /*
2308          * No need to double call mmu_notifier->invalidate_range() callback.
2309          * They are 3 cases to consider inside __split_huge_pmd_locked():
2310          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2311          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2312          *    fault will trigger a flush_notify before pointing to a new page
2313          *    (it is fine if the secondary mmu keeps pointing to the old zero
2314          *    page in the meantime)
2315          *  3) Split a huge pmd into pte pointing to the same page. No need
2316          *     to invalidate secondary tlb entry they are all still valid.
2317          *     any further changes to individual pte will notify. So no need
2318          *     to call mmu_notifier->invalidate_range()
2319          */
2320         mmu_notifier_invalidate_range_only_end(&range);
2321 }
2322
2323 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2324                 bool freeze, struct page *page)
2325 {
2326         pgd_t *pgd;
2327         p4d_t *p4d;
2328         pud_t *pud;
2329         pmd_t *pmd;
2330
2331         pgd = pgd_offset(vma->vm_mm, address);
2332         if (!pgd_present(*pgd))
2333                 return;
2334
2335         p4d = p4d_offset(pgd, address);
2336         if (!p4d_present(*p4d))
2337                 return;
2338
2339         pud = pud_offset(p4d, address);
2340         if (!pud_present(*pud))
2341                 return;
2342
2343         pmd = pmd_offset(pud, address);
2344
2345         __split_huge_pmd(vma, pmd, address, freeze, page);
2346 }
2347
2348 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2349                              unsigned long start,
2350                              unsigned long end,
2351                              long adjust_next)
2352 {
2353         /*
2354          * If the new start address isn't hpage aligned and it could
2355          * previously contain an hugepage: check if we need to split
2356          * an huge pmd.
2357          */
2358         if (start & ~HPAGE_PMD_MASK &&
2359             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2360             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2361                 split_huge_pmd_address(vma, start, false, NULL);
2362
2363         /*
2364          * If the new end address isn't hpage aligned and it could
2365          * previously contain an hugepage: check if we need to split
2366          * an huge pmd.
2367          */
2368         if (end & ~HPAGE_PMD_MASK &&
2369             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2370             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2371                 split_huge_pmd_address(vma, end, false, NULL);
2372
2373         /*
2374          * If we're also updating the vma->vm_next->vm_start, if the new
2375          * vm_next->vm_start isn't page aligned and it could previously
2376          * contain an hugepage: check if we need to split an huge pmd.
2377          */
2378         if (adjust_next > 0) {
2379                 struct vm_area_struct *next = vma->vm_next;
2380                 unsigned long nstart = next->vm_start;
2381                 nstart += adjust_next << PAGE_SHIFT;
2382                 if (nstart & ~HPAGE_PMD_MASK &&
2383                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2384                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2385                         split_huge_pmd_address(next, nstart, false, NULL);
2386         }
2387 }
2388
2389 static void unmap_page(struct page *page)
2390 {
2391         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2392                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2393         bool unmap_success;
2394
2395         VM_BUG_ON_PAGE(!PageHead(page), page);
2396
2397         if (PageAnon(page))
2398                 ttu_flags |= TTU_SPLIT_FREEZE;
2399
2400         unmap_success = try_to_unmap(page, ttu_flags);
2401         VM_BUG_ON_PAGE(!unmap_success, page);
2402 }
2403
2404 static void remap_page(struct page *page)
2405 {
2406         int i;
2407         if (PageTransHuge(page)) {
2408                 remove_migration_ptes(page, page, true);
2409         } else {
2410                 for (i = 0; i < HPAGE_PMD_NR; i++)
2411                         remove_migration_ptes(page + i, page + i, true);
2412         }
2413 }
2414
2415 static void __split_huge_page_tail(struct page *head, int tail,
2416                 struct lruvec *lruvec, struct list_head *list)
2417 {
2418         struct page *page_tail = head + tail;
2419
2420         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2421
2422         /*
2423          * Clone page flags before unfreezing refcount.
2424          *
2425          * After successful get_page_unless_zero() might follow flags change,
2426          * for exmaple lock_page() which set PG_waiters.
2427          */
2428         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2429         page_tail->flags |= (head->flags &
2430                         ((1L << PG_referenced) |
2431                          (1L << PG_swapbacked) |
2432                          (1L << PG_swapcache) |
2433                          (1L << PG_mlocked) |
2434                          (1L << PG_uptodate) |
2435                          (1L << PG_active) |
2436                          (1L << PG_workingset) |
2437                          (1L << PG_locked) |
2438                          (1L << PG_unevictable) |
2439                          (1L << PG_dirty)));
2440
2441         /* ->mapping in first tail page is compound_mapcount */
2442         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2443                         page_tail);
2444         page_tail->mapping = head->mapping;
2445         page_tail->index = head->index + tail;
2446
2447         /* Page flags must be visible before we make the page non-compound. */
2448         smp_wmb();
2449
2450         /*
2451          * Clear PageTail before unfreezing page refcount.
2452          *
2453          * After successful get_page_unless_zero() might follow put_page()
2454          * which needs correct compound_head().
2455          */
2456         clear_compound_head(page_tail);
2457
2458         /* Finally unfreeze refcount. Additional reference from page cache. */
2459         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2460                                           PageSwapCache(head)));
2461
2462         if (page_is_young(head))
2463                 set_page_young(page_tail);
2464         if (page_is_idle(head))
2465                 set_page_idle(page_tail);
2466
2467         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2468
2469         /*
2470          * always add to the tail because some iterators expect new
2471          * pages to show after the currently processed elements - e.g.
2472          * migrate_pages
2473          */
2474         lru_add_page_tail(head, page_tail, lruvec, list);
2475 }
2476
2477 static void __split_huge_page(struct page *page, struct list_head *list,
2478                 pgoff_t end, unsigned long flags)
2479 {
2480         struct page *head = compound_head(page);
2481         pg_data_t *pgdat = page_pgdat(head);
2482         struct lruvec *lruvec;
2483         int i;
2484
2485         lruvec = mem_cgroup_page_lruvec(head, pgdat);
2486
2487         /* complete memcg works before add pages to LRU */
2488         mem_cgroup_split_huge_fixup(head);
2489
2490         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2491                 __split_huge_page_tail(head, i, lruvec, list);
2492                 /* Some pages can be beyond i_size: drop them from page cache */
2493                 if (head[i].index >= end) {
2494                         ClearPageDirty(head + i);
2495                         __delete_from_page_cache(head + i, NULL);
2496                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2497                                 shmem_uncharge(head->mapping->host, 1);
2498                         put_page(head + i);
2499                 } else if (!PageAnon(page)) {
2500                         __xa_store(&head->mapping->i_pages, head[i].index,
2501                                         head + i, 0);
2502                 }
2503         }
2504
2505         ClearPageCompound(head);
2506         /* See comment in __split_huge_page_tail() */
2507         if (PageAnon(head)) {
2508                 /* Additional pin to swap cache */
2509                 if (PageSwapCache(head))
2510                         page_ref_add(head, 2);
2511                 else
2512                         page_ref_inc(head);
2513         } else {
2514                 /* Additional pin to page cache */
2515                 page_ref_add(head, 2);
2516                 xa_unlock(&head->mapping->i_pages);
2517         }
2518
2519         spin_unlock_irqrestore(&pgdat->lru_lock, flags);
2520
2521         remap_page(head);
2522
2523         for (i = 0; i < HPAGE_PMD_NR; i++) {
2524                 struct page *subpage = head + i;
2525                 if (subpage == page)
2526                         continue;
2527                 unlock_page(subpage);
2528
2529                 /*
2530                  * Subpages may be freed if there wasn't any mapping
2531                  * like if add_to_swap() is running on a lru page that
2532                  * had its mapping zapped. And freeing these pages
2533                  * requires taking the lru_lock so we do the put_page
2534                  * of the tail pages after the split is complete.
2535                  */
2536                 put_page(subpage);
2537         }
2538 }
2539
2540 int total_mapcount(struct page *page)
2541 {
2542         int i, compound, ret;
2543
2544         VM_BUG_ON_PAGE(PageTail(page), page);
2545
2546         if (likely(!PageCompound(page)))
2547                 return atomic_read(&page->_mapcount) + 1;
2548
2549         compound = compound_mapcount(page);
2550         if (PageHuge(page))
2551                 return compound;
2552         ret = compound;
2553         for (i = 0; i < HPAGE_PMD_NR; i++)
2554                 ret += atomic_read(&page[i]._mapcount) + 1;
2555         /* File pages has compound_mapcount included in _mapcount */
2556         if (!PageAnon(page))
2557                 return ret - compound * HPAGE_PMD_NR;
2558         if (PageDoubleMap(page))
2559                 ret -= HPAGE_PMD_NR;
2560         return ret;
2561 }
2562
2563 /*
2564  * This calculates accurately how many mappings a transparent hugepage
2565  * has (unlike page_mapcount() which isn't fully accurate). This full
2566  * accuracy is primarily needed to know if copy-on-write faults can
2567  * reuse the page and change the mapping to read-write instead of
2568  * copying them. At the same time this returns the total_mapcount too.
2569  *
2570  * The function returns the highest mapcount any one of the subpages
2571  * has. If the return value is one, even if different processes are
2572  * mapping different subpages of the transparent hugepage, they can
2573  * all reuse it, because each process is reusing a different subpage.
2574  *
2575  * The total_mapcount is instead counting all virtual mappings of the
2576  * subpages. If the total_mapcount is equal to "one", it tells the
2577  * caller all mappings belong to the same "mm" and in turn the
2578  * anon_vma of the transparent hugepage can become the vma->anon_vma
2579  * local one as no other process may be mapping any of the subpages.
2580  *
2581  * It would be more accurate to replace page_mapcount() with
2582  * page_trans_huge_mapcount(), however we only use
2583  * page_trans_huge_mapcount() in the copy-on-write faults where we
2584  * need full accuracy to avoid breaking page pinning, because
2585  * page_trans_huge_mapcount() is slower than page_mapcount().
2586  */
2587 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2588 {
2589         int i, ret, _total_mapcount, mapcount;
2590
2591         /* hugetlbfs shouldn't call it */
2592         VM_BUG_ON_PAGE(PageHuge(page), page);
2593
2594         if (likely(!PageTransCompound(page))) {
2595                 mapcount = atomic_read(&page->_mapcount) + 1;
2596                 if (total_mapcount)
2597                         *total_mapcount = mapcount;
2598                 return mapcount;
2599         }
2600
2601         page = compound_head(page);
2602
2603         _total_mapcount = ret = 0;
2604         for (i = 0; i < HPAGE_PMD_NR; i++) {
2605                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2606                 ret = max(ret, mapcount);
2607                 _total_mapcount += mapcount;
2608         }
2609         if (PageDoubleMap(page)) {
2610                 ret -= 1;
2611                 _total_mapcount -= HPAGE_PMD_NR;
2612         }
2613         mapcount = compound_mapcount(page);
2614         ret += mapcount;
2615         _total_mapcount += mapcount;
2616         if (total_mapcount)
2617                 *total_mapcount = _total_mapcount;
2618         return ret;
2619 }
2620
2621 /* Racy check whether the huge page can be split */
2622 bool can_split_huge_page(struct page *page, int *pextra_pins)
2623 {
2624         int extra_pins;
2625
2626         /* Additional pins from page cache */
2627         if (PageAnon(page))
2628                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2629         else
2630                 extra_pins = HPAGE_PMD_NR;
2631         if (pextra_pins)
2632                 *pextra_pins = extra_pins;
2633         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2634 }
2635
2636 /*
2637  * This function splits huge page into normal pages. @page can point to any
2638  * subpage of huge page to split. Split doesn't change the position of @page.
2639  *
2640  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2641  * The huge page must be locked.
2642  *
2643  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2644  *
2645  * Both head page and tail pages will inherit mapping, flags, and so on from
2646  * the hugepage.
2647  *
2648  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2649  * they are not mapped.
2650  *
2651  * Returns 0 if the hugepage is split successfully.
2652  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2653  * us.
2654  */
2655 int split_huge_page_to_list(struct page *page, struct list_head *list)
2656 {
2657         struct page *head = compound_head(page);
2658         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2659         struct anon_vma *anon_vma = NULL;
2660         struct address_space *mapping = NULL;
2661         int count, mapcount, extra_pins, ret;
2662         bool mlocked;
2663         unsigned long flags;
2664         pgoff_t end;
2665
2666         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2667         VM_BUG_ON_PAGE(!PageLocked(page), page);
2668         VM_BUG_ON_PAGE(!PageCompound(page), page);
2669
2670         if (PageWriteback(page))
2671                 return -EBUSY;
2672
2673         if (PageAnon(head)) {
2674                 /*
2675                  * The caller does not necessarily hold an mmap_sem that would
2676                  * prevent the anon_vma disappearing so we first we take a
2677                  * reference to it and then lock the anon_vma for write. This
2678                  * is similar to page_lock_anon_vma_read except the write lock
2679                  * is taken to serialise against parallel split or collapse
2680                  * operations.
2681                  */
2682                 anon_vma = page_get_anon_vma(head);
2683                 if (!anon_vma) {
2684                         ret = -EBUSY;
2685                         goto out;
2686                 }
2687                 end = -1;
2688                 mapping = NULL;
2689                 anon_vma_lock_write(anon_vma);
2690         } else {
2691                 mapping = head->mapping;
2692
2693                 /* Truncated ? */
2694                 if (!mapping) {
2695                         ret = -EBUSY;
2696                         goto out;
2697                 }
2698
2699                 anon_vma = NULL;
2700                 i_mmap_lock_read(mapping);
2701
2702                 /*
2703                  *__split_huge_page() may need to trim off pages beyond EOF:
2704                  * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2705                  * which cannot be nested inside the page tree lock. So note
2706                  * end now: i_size itself may be changed at any moment, but
2707                  * head page lock is good enough to serialize the trimming.
2708                  */
2709                 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2710         }
2711
2712         /*
2713          * Racy check if we can split the page, before unmap_page() will
2714          * split PMDs
2715          */
2716         if (!can_split_huge_page(head, &extra_pins)) {
2717                 ret = -EBUSY;
2718                 goto out_unlock;
2719         }
2720
2721         mlocked = PageMlocked(page);
2722         unmap_page(head);
2723         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2724
2725         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2726         if (mlocked)
2727                 lru_add_drain();
2728
2729         /* prevent PageLRU to go away from under us, and freeze lru stats */
2730         spin_lock_irqsave(&pgdata->lru_lock, flags);
2731
2732         if (mapping) {
2733                 XA_STATE(xas, &mapping->i_pages, page_index(head));
2734
2735                 /*
2736                  * Check if the head page is present in page cache.
2737                  * We assume all tail are present too, if head is there.
2738                  */
2739                 xa_lock(&mapping->i_pages);
2740                 if (xas_load(&xas) != head)
2741                         goto fail;
2742         }
2743
2744         /* Prevent deferred_split_scan() touching ->_refcount */
2745         spin_lock(&pgdata->split_queue_lock);
2746         count = page_count(head);
2747         mapcount = total_mapcount(head);
2748         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2749                 if (!list_empty(page_deferred_list(head))) {
2750                         pgdata->split_queue_len--;
2751                         list_del(page_deferred_list(head));
2752                 }
2753                 if (mapping)
2754                         __dec_node_page_state(page, NR_SHMEM_THPS);
2755                 spin_unlock(&pgdata->split_queue_lock);
2756                 __split_huge_page(page, list, end, flags);
2757                 if (PageSwapCache(head)) {
2758                         swp_entry_t entry = { .val = page_private(head) };
2759
2760                         ret = split_swap_cluster(entry);
2761                 } else
2762                         ret = 0;
2763         } else {
2764                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2765                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2766                                         mapcount, count);
2767                         if (PageTail(page))
2768                                 dump_page(head, NULL);
2769                         dump_page(page, "total_mapcount(head) > 0");
2770                         BUG();
2771                 }
2772                 spin_unlock(&pgdata->split_queue_lock);
2773 fail:           if (mapping)
2774                         xa_unlock(&mapping->i_pages);
2775                 spin_unlock_irqrestore(&pgdata->lru_lock, flags);
2776                 remap_page(head);
2777                 ret = -EBUSY;
2778         }
2779
2780 out_unlock:
2781         if (anon_vma) {
2782                 anon_vma_unlock_write(anon_vma);
2783                 put_anon_vma(anon_vma);
2784         }
2785         if (mapping)
2786                 i_mmap_unlock_read(mapping);
2787 out:
2788         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2789         return ret;
2790 }
2791
2792 void free_transhuge_page(struct page *page)
2793 {
2794         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2795         unsigned long flags;
2796
2797         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2798         if (!list_empty(page_deferred_list(page))) {
2799                 pgdata->split_queue_len--;
2800                 list_del(page_deferred_list(page));
2801         }
2802         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2803         free_compound_page(page);
2804 }
2805
2806 void deferred_split_huge_page(struct page *page)
2807 {
2808         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2809         unsigned long flags;
2810
2811         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2812
2813         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2814         if (list_empty(page_deferred_list(page))) {
2815                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2816                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2817                 pgdata->split_queue_len++;
2818         }
2819         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2820 }
2821
2822 static unsigned long deferred_split_count(struct shrinker *shrink,
2823                 struct shrink_control *sc)
2824 {
2825         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2826         return READ_ONCE(pgdata->split_queue_len);
2827 }
2828
2829 static unsigned long deferred_split_scan(struct shrinker *shrink,
2830                 struct shrink_control *sc)
2831 {
2832         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2833         unsigned long flags;
2834         LIST_HEAD(list), *pos, *next;
2835         struct page *page;
2836         int split = 0;
2837
2838         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2839         /* Take pin on all head pages to avoid freeing them under us */
2840         list_for_each_safe(pos, next, &pgdata->split_queue) {
2841                 page = list_entry((void *)pos, struct page, mapping);
2842                 page = compound_head(page);
2843                 if (get_page_unless_zero(page)) {
2844                         list_move(page_deferred_list(page), &list);
2845                 } else {
2846                         /* We lost race with put_compound_page() */
2847                         list_del_init(page_deferred_list(page));
2848                         pgdata->split_queue_len--;
2849                 }
2850                 if (!--sc->nr_to_scan)
2851                         break;
2852         }
2853         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2854
2855         list_for_each_safe(pos, next, &list) {
2856                 page = list_entry((void *)pos, struct page, mapping);
2857                 if (!trylock_page(page))
2858                         goto next;
2859                 /* split_huge_page() removes page from list on success */
2860                 if (!split_huge_page(page))
2861                         split++;
2862                 unlock_page(page);
2863 next:
2864                 put_page(page);
2865         }
2866
2867         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2868         list_splice_tail(&list, &pgdata->split_queue);
2869         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2870
2871         /*
2872          * Stop shrinker if we didn't split any page, but the queue is empty.
2873          * This can happen if pages were freed under us.
2874          */
2875         if (!split && list_empty(&pgdata->split_queue))
2876                 return SHRINK_STOP;
2877         return split;
2878 }
2879
2880 static struct shrinker deferred_split_shrinker = {
2881         .count_objects = deferred_split_count,
2882         .scan_objects = deferred_split_scan,
2883         .seeks = DEFAULT_SEEKS,
2884         .flags = SHRINKER_NUMA_AWARE,
2885 };
2886
2887 #ifdef CONFIG_DEBUG_FS
2888 static int split_huge_pages_set(void *data, u64 val)
2889 {
2890         struct zone *zone;
2891         struct page *page;
2892         unsigned long pfn, max_zone_pfn;
2893         unsigned long total = 0, split = 0;
2894
2895         if (val != 1)
2896                 return -EINVAL;
2897
2898         for_each_populated_zone(zone) {
2899                 max_zone_pfn = zone_end_pfn(zone);
2900                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2901                         if (!pfn_valid(pfn))
2902                                 continue;
2903
2904                         page = pfn_to_page(pfn);
2905                         if (!get_page_unless_zero(page))
2906                                 continue;
2907
2908                         if (zone != page_zone(page))
2909                                 goto next;
2910
2911                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2912                                 goto next;
2913
2914                         total++;
2915                         lock_page(page);
2916                         if (!split_huge_page(page))
2917                                 split++;
2918                         unlock_page(page);
2919 next:
2920                         put_page(page);
2921                 }
2922         }
2923
2924         pr_info("%lu of %lu THP split\n", split, total);
2925
2926         return 0;
2927 }
2928 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2929                 "%llu\n");
2930
2931 static int __init split_huge_pages_debugfs(void)
2932 {
2933         debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2934                             &split_huge_pages_fops);
2935         return 0;
2936 }
2937 late_initcall(split_huge_pages_debugfs);
2938 #endif
2939
2940 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2941 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2942                 struct page *page)
2943 {
2944         struct vm_area_struct *vma = pvmw->vma;
2945         struct mm_struct *mm = vma->vm_mm;
2946         unsigned long address = pvmw->address;
2947         pmd_t pmdval;
2948         swp_entry_t entry;
2949         pmd_t pmdswp;
2950
2951         if (!(pvmw->pmd && !pvmw->pte))
2952                 return;
2953
2954         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2955         pmdval = *pvmw->pmd;
2956         pmdp_invalidate(vma, address, pvmw->pmd);
2957         if (pmd_dirty(pmdval))
2958                 set_page_dirty(page);
2959         entry = make_migration_entry(page, pmd_write(pmdval));
2960         pmdswp = swp_entry_to_pmd(entry);
2961         if (pmd_soft_dirty(pmdval))
2962                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2963         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2964         page_remove_rmap(page, true);
2965         put_page(page);
2966 }
2967
2968 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2969 {
2970         struct vm_area_struct *vma = pvmw->vma;
2971         struct mm_struct *mm = vma->vm_mm;
2972         unsigned long address = pvmw->address;
2973         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2974         pmd_t pmde;
2975         swp_entry_t entry;
2976
2977         if (!(pvmw->pmd && !pvmw->pte))
2978                 return;
2979
2980         entry = pmd_to_swp_entry(*pvmw->pmd);
2981         get_page(new);
2982         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2983         if (pmd_swp_soft_dirty(*pvmw->pmd))
2984                 pmde = pmd_mksoft_dirty(pmde);
2985         if (is_write_migration_entry(entry))
2986                 pmde = maybe_pmd_mkwrite(pmde, vma);
2987
2988         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2989         if (PageAnon(new))
2990                 page_add_anon_rmap(new, vma, mmun_start, true);
2991         else
2992                 page_add_file_rmap(new, true);
2993         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
2994         if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
2995                 mlock_vma_page(new);
2996         update_mmu_cache_pmd(vma, address, pvmw->pmd);
2997 }
2998 #endif