mm/huge_memory.c

   1 /*
   2  *  Copyright (C) 2009  Red Hat, Inc.
   3  *
   4  *  This work is licensed under the terms of the GNU GPL, version 2. See
   5  *  the COPYING file in the top-level directory.
   6  */
   7
   8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9
  10 #include <linux/mm.h>
  11 #include <linux/sched.h>
  12 #include <linux/sched/coredump.h>
  13 #include <linux/sched/numa_balancing.h>
  14 #include <linux/highmem.h>
  15 #include <linux/hugetlb.h>
  16 #include <linux/mmu_notifier.h>
  17 #include <linux/rmap.h>
  18 #include <linux/swap.h>
  19 #include <linux/shrinker.h>
  20 #include <linux/mm_inline.h>
  21 #include <linux/swapops.h>
  22 #include <linux/dax.h>
  23 #include <linux/khugepaged.h>
  24 #include <linux/freezer.h>
  25 #include <linux/pfn_t.h>
  26 #include <linux/mman.h>
  27 #include <linux/memremap.h>
  28 #include <linux/pagemap.h>
  29 #include <linux/debugfs.h>
  30 #include <linux/migrate.h>
  31 #include <linux/hashtable.h>
  32 #include <linux/userfaultfd_k.h>
  33 #include <linux/page_idle.h>
  34 #include <linux/shmem_fs.h>
  35 #include <linux/oom.h>
  36
  37 #include <asm/tlb.h>
  38 #include <asm/pgalloc.h>
  39 #include "internal.h"
  40
  41 /*
  42  * By default, transparent hugepage support is disabled in order to avoid
  43  * risking an increased memory footprint for applications that are not
  44  * guaranteed to benefit from it. When transparent hugepage support is
  45  * enabled, it is for all mappings, and khugepaged scans all mappings.
  46  * Defrag is invoked by khugepaged hugepage allocations and by page faults
  47  * for all hugepage allocations.
  48  */
  49 unsigned long transparent_hugepage_flags __read_mostly =
  50 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  51         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  52 #endif
  53 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  54         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  55 #endif
  56         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
  57         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
  58         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
  59
  60 static struct shrinker deferred_split_shrinker;
  61
  62 static atomic_t huge_zero_refcount;
  63 struct page *huge_zero_page __read_mostly;
  64
  65 bool transparent_hugepage_enabled(struct vm_area_struct *vma)
  66 {
  67         if (vma_is_anonymous(vma))
  68                 return __transparent_hugepage_enabled(vma);
  69         if (vma_is_shmem(vma) && shmem_huge_enabled(vma))
  70                 return __transparent_hugepage_enabled(vma);
  71
  72         return false;
  73 }
  74
  75 static struct page *get_huge_zero_page(void)
  76 {
  77         struct page *zero_page;
  78 retry:
  79         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
  80                 return READ_ONCE(huge_zero_page);
  81
  82         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
  83                         HPAGE_PMD_ORDER);
  84         if (!zero_page) {
  85                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
  86                 return NULL;
  87         }
  88         count_vm_event(THP_ZERO_PAGE_ALLOC);
  89         preempt_disable();
  90         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
  91                 preempt_enable();
  92                 __free_pages(zero_page, compound_order(zero_page));
  93                 goto retry;
  94         }
  95
  96         /* We take additional reference here. It will be put back by shrinker */
  97         atomic_set(&huge_zero_refcount, 2);
  98         preempt_enable();
  99         return READ_ONCE(huge_zero_page);
 100 }
 101
 102 static void put_huge_zero_page(void)
 103 {
 104         /*
 105          * Counter should never go to zero here. Only shrinker can put
 106          * last reference.
 107          */
 108         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
 109 }
 110
 111 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
 112 {
 113         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 114                 return READ_ONCE(huge_zero_page);
 115
 116         if (!get_huge_zero_page())
 117                 return NULL;
 118
 119         if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 120                 put_huge_zero_page();
 121
 122         return READ_ONCE(huge_zero_page);
 123 }
 124
 125 void mm_put_huge_zero_page(struct mm_struct *mm)
 126 {
 127         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 128                 put_huge_zero_page();
 129 }
 130
 131 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
 132                                         struct shrink_control *sc)
 133 {
 134         /* we can free zero page only if last reference remains */
 135         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 136 }
 137
 138 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 139                                        struct shrink_control *sc)
 140 {
 141         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 142                 struct page *zero_page = xchg(&huge_zero_page, NULL);
 143                 BUG_ON(zero_page == NULL);
 144                 __free_pages(zero_page, compound_order(zero_page));
 145                 return HPAGE_PMD_NR;
 146         }
 147
 148         return 0;
 149 }
 150
 151 static struct shrinker huge_zero_page_shrinker = {
 152         .count_objects = shrink_huge_zero_page_count,
 153         .scan_objects = shrink_huge_zero_page_scan,
 154         .seeks = DEFAULT_SEEKS,
 155 };
 156
 157 #ifdef CONFIG_SYSFS
 158 static ssize_t enabled_show(struct kobject *kobj,
 159                             struct kobj_attribute *attr, char *buf)
 160 {
 161         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
 162                 return sprintf(buf, "[always] madvise never\n");
 163         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
 164                 return sprintf(buf, "always [madvise] never\n");
 165         else
 166                 return sprintf(buf, "always madvise [never]\n");
 167 }
 168
 169 static ssize_t enabled_store(struct kobject *kobj,
 170                              struct kobj_attribute *attr,
 171                              const char *buf, size_t count)
 172 {
 173         ssize_t ret = count;
 174
 175         if (!memcmp("always", buf,
 176                     min(sizeof("always")-1, count))) {
 177                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 178                 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 179         } else if (!memcmp("madvise", buf,
 180                            min(sizeof("madvise")-1, count))) {
 181                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 182                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 183         } else if (!memcmp("never", buf,
 184                            min(sizeof("never")-1, count))) {
 185                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 186                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 187         } else
 188                 ret = -EINVAL;
 189
 190         if (ret > 0) {
 191                 int err = start_stop_khugepaged();
 192                 if (err)
 193                         ret = err;
 194         }
 195         return ret;
 196 }
 197 static struct kobj_attribute enabled_attr =
 198         __ATTR(enabled, 0644, enabled_show, enabled_store);
 199
 200 ssize_t single_hugepage_flag_show(struct kobject *kobj,
 201                                 struct kobj_attribute *attr, char *buf,
 202                                 enum transparent_hugepage_flag flag)
 203 {
 204         return sprintf(buf, "%d\n",
 205                        !!test_bit(flag, &transparent_hugepage_flags));
 206 }
 207
 208 ssize_t single_hugepage_flag_store(struct kobject *kobj,
 209                                  struct kobj_attribute *attr,
 210                                  const char *buf, size_t count,
 211                                  enum transparent_hugepage_flag flag)
 212 {
 213         unsigned long value;
 214         int ret;
 215
 216         ret = kstrtoul(buf, 10, &value);
 217         if (ret < 0)
 218                 return ret;
 219         if (value > 1)
 220                 return -EINVAL;
 221
 222         if (value)
 223                 set_bit(flag, &transparent_hugepage_flags);
 224         else
 225                 clear_bit(flag, &transparent_hugepage_flags);
 226
 227         return count;
 228 }
 229
 230 static ssize_t defrag_show(struct kobject *kobj,
 231                            struct kobj_attribute *attr, char *buf)
 232 {
 233         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 234                 return sprintf(buf, "[always] defer defer+madvise madvise never\n");
 235         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 236                 return sprintf(buf, "always [defer] defer+madvise madvise never\n");
 237         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 238                 return sprintf(buf, "always defer [defer+madvise] madvise never\n");
 239         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 240                 return sprintf(buf, "always defer defer+madvise [madvise] never\n");
 241         return sprintf(buf, "always defer defer+madvise madvise [never]\n");
 242 }
 243
 244 static ssize_t defrag_store(struct kobject *kobj,
 245                             struct kobj_attribute *attr,
 246                             const char *buf, size_t count)
 247 {
 248         if (!memcmp("always", buf,
 249                     min(sizeof("always")-1, count))) {
 250                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 251                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 252                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 253                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 254         } else if (!memcmp("defer+madvise", buf,
 255                     min(sizeof("defer+madvise")-1, count))) {
 256                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 257                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 258                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 259                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 260         } else if (!memcmp("defer", buf,
 261                     min(sizeof("defer")-1, count))) {
 262                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 263                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 264                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 265                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 266         } else if (!memcmp("madvise", buf,
 267                            min(sizeof("madvise")-1, count))) {
 268                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 269                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 270                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 271                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 272         } else if (!memcmp("never", buf,
 273                            min(sizeof("never")-1, count))) {
 274                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 275                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 276                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 277                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 278         } else
 279                 return -EINVAL;
 280
 281         return count;
 282 }
 283 static struct kobj_attribute defrag_attr =
 284         __ATTR(defrag, 0644, defrag_show, defrag_store);
 285
 286 static ssize_t use_zero_page_show(struct kobject *kobj,
 287                 struct kobj_attribute *attr, char *buf)
 288 {
 289         return single_hugepage_flag_show(kobj, attr, buf,
 290                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 291 }
 292 static ssize_t use_zero_page_store(struct kobject *kobj,
 293                 struct kobj_attribute *attr, const char *buf, size_t count)
 294 {
 295         return single_hugepage_flag_store(kobj, attr, buf, count,
 296                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 297 }
 298 static struct kobj_attribute use_zero_page_attr =
 299         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 300
 301 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
 302                 struct kobj_attribute *attr, char *buf)
 303 {
 304         return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
 305 }
 306 static struct kobj_attribute hpage_pmd_size_attr =
 307         __ATTR_RO(hpage_pmd_size);
 308
 309 #ifdef CONFIG_DEBUG_VM
 310 static ssize_t debug_cow_show(struct kobject *kobj,
 311                                 struct kobj_attribute *attr, char *buf)
 312 {
 313         return single_hugepage_flag_show(kobj, attr, buf,
 314                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 315 }
 316 static ssize_t debug_cow_store(struct kobject *kobj,
 317                                struct kobj_attribute *attr,
 318                                const char *buf, size_t count)
 319 {
 320         return single_hugepage_flag_store(kobj, attr, buf, count,
 321                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 322 }
 323 static struct kobj_attribute debug_cow_attr =
 324         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 325 #endif /* CONFIG_DEBUG_VM */
 326
 327 static struct attribute *hugepage_attr[] = {
 328         &enabled_attr.attr,
 329         &defrag_attr.attr,
 330         &use_zero_page_attr.attr,
 331         &hpage_pmd_size_attr.attr,
 332 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
 333         &shmem_enabled_attr.attr,
 334 #endif
 335 #ifdef CONFIG_DEBUG_VM
 336         &debug_cow_attr.attr,
 337 #endif
 338         NULL,
 339 };
 340
 341 static const struct attribute_group hugepage_attr_group = {
 342         .attrs = hugepage_attr,
 343 };
 344
 345 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 346 {
 347         int err;
 348
 349         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 350         if (unlikely(!*hugepage_kobj)) {
 351                 pr_err("failed to create transparent hugepage kobject\n");
 352                 return -ENOMEM;
 353         }
 354
 355         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 356         if (err) {
 357                 pr_err("failed to register transparent hugepage group\n");
 358                 goto delete_obj;
 359         }
 360
 361         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 362         if (err) {
 363                 pr_err("failed to register transparent hugepage group\n");
 364                 goto remove_hp_group;
 365         }
 366
 367         return 0;
 368
 369 remove_hp_group:
 370         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 371 delete_obj:
 372         kobject_put(*hugepage_kobj);
 373         return err;
 374 }
 375
 376 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 377 {
 378         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 379         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 380         kobject_put(hugepage_kobj);
 381 }
 382 #else
 383 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 384 {
 385         return 0;
 386 }
 387
 388 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 389 {
 390 }
 391 #endif /* CONFIG_SYSFS */
 392
 393 static int __init hugepage_init(void)
 394 {
 395         int err;
 396         struct kobject *hugepage_kobj;
 397
 398         if (!has_transparent_hugepage()) {
 399                 transparent_hugepage_flags = 0;
 400                 return -EINVAL;
 401         }
 402
 403         /*
 404          * hugepages can't be allocated by the buddy allocator
 405          */
 406         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
 407         /*
 408          * we use page->mapping and page->index in second tail page
 409          * as list_head: assuming THP order >= 2
 410          */
 411         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
 412
 413         err = hugepage_init_sysfs(&hugepage_kobj);
 414         if (err)
 415                 goto err_sysfs;
 416
 417         err = khugepaged_init();
 418         if (err)
 419                 goto err_slab;
 420
 421         err = register_shrinker(&huge_zero_page_shrinker);
 422         if (err)
 423                 goto err_hzp_shrinker;
 424         err = register_shrinker(&deferred_split_shrinker);
 425         if (err)
 426                 goto err_split_shrinker;
 427
 428         /*
 429          * By default disable transparent hugepages on smaller systems,
 430          * where the extra memory used could hurt more than TLB overhead
 431          * is likely to save.  The admin can still enable it through /sys.
 432          */
 433         if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
 434                 transparent_hugepage_flags = 0;
 435                 return 0;
 436         }
 437
 438         err = start_stop_khugepaged();
 439         if (err)
 440                 goto err_khugepaged;
 441
 442         return 0;
 443 err_khugepaged:
 444         unregister_shrinker(&deferred_split_shrinker);
 445 err_split_shrinker:
 446         unregister_shrinker(&huge_zero_page_shrinker);
 447 err_hzp_shrinker:
 448         khugepaged_destroy();
 449 err_slab:
 450         hugepage_exit_sysfs(hugepage_kobj);
 451 err_sysfs:
 452         return err;
 453 }
 454 subsys_initcall(hugepage_init);
 455
 456 static int __init setup_transparent_hugepage(char *str)
 457 {
 458         int ret = 0;
 459         if (!str)
 460                 goto out;
 461         if (!strcmp(str, "always")) {
 462                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 463                         &transparent_hugepage_flags);
 464                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 465                           &transparent_hugepage_flags);
 466                 ret = 1;
 467         } else if (!strcmp(str, "madvise")) {
 468                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 469                           &transparent_hugepage_flags);
 470                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 471                         &transparent_hugepage_flags);
 472                 ret = 1;
 473         } else if (!strcmp(str, "never")) {
 474                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 475                           &transparent_hugepage_flags);
 476                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 477                           &transparent_hugepage_flags);
 478                 ret = 1;
 479         }
 480 out:
 481         if (!ret)
 482                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
 483         return ret;
 484 }
 485 __setup("transparent_hugepage=", setup_transparent_hugepage);
 486
 487 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 488 {
 489         if (likely(vma->vm_flags & VM_WRITE))
 490                 pmd = pmd_mkwrite(pmd);
 491         return pmd;
 492 }
 493
 494 static inline struct list_head *page_deferred_list(struct page *page)
 495 {
 496         /* ->lru in the tail pages is occupied by compound_head. */
 497         return &page[2].deferred_list;
 498 }
 499
 500 void prep_transhuge_page(struct page *page)
 501 {
 502         /*
 503          * we use page->mapping and page->indexlru in second tail page
 504          * as list_head: assuming THP order >= 2
 505          */
 506
 507         INIT_LIST_HEAD(page_deferred_list(page));
 508         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 509 }
 510
 511 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
 512                 loff_t off, unsigned long flags, unsigned long size)
 513 {
 514         unsigned long addr;
 515         loff_t off_end = off + len;
 516         loff_t off_align = round_up(off, size);
 517         unsigned long len_pad;
 518
 519         if (off_end <= off_align || (off_end - off_align) < size)
 520                 return 0;
 521
 522         len_pad = len + size;
 523         if (len_pad < len || (off + len_pad) < off)
 524                 return 0;
 525
 526         addr = current->mm->get_unmapped_area(filp, 0, len_pad,
 527                                               off >> PAGE_SHIFT, flags);
 528         if (IS_ERR_VALUE(addr))
 529                 return 0;
 530
 531         addr += (off - addr) & (size - 1);
 532         return addr;
 533 }
 534
 535 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 536                 unsigned long len, unsigned long pgoff, unsigned long flags)
 537 {
 538         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 539
 540         if (addr)
 541                 goto out;
 542         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
 543                 goto out;
 544
 545         addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
 546         if (addr)
 547                 return addr;
 548
 549  out:
 550         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 551 }
 552 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 553
 554 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
 555                         struct page *page, gfp_t gfp)
 556 {
 557         struct vm_area_struct *vma = vmf->vma;
 558         struct mem_cgroup *memcg;
 559         pgtable_t pgtable;
 560         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 561         vm_fault_t ret = 0;
 562
 563         VM_BUG_ON_PAGE(!PageCompound(page), page);
 564
 565         if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
 566                 put_page(page);
 567                 count_vm_event(THP_FAULT_FALLBACK);
 568                 return VM_FAULT_FALLBACK;
 569         }
 570
 571         pgtable = pte_alloc_one(vma->vm_mm);
 572         if (unlikely(!pgtable)) {
 573                 ret = VM_FAULT_OOM;
 574                 goto release;
 575         }
 576
 577         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
 578         /*
 579          * The memory barrier inside __SetPageUptodate makes sure that
 580          * clear_huge_page writes become visible before the set_pmd_at()
 581          * write.
 582          */
 583         __SetPageUptodate(page);
 584
 585         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 586         if (unlikely(!pmd_none(*vmf->pmd))) {
 587                 goto unlock_release;
 588         } else {
 589                 pmd_t entry;
 590
 591                 ret = check_stable_address_space(vma->vm_mm);
 592                 if (ret)
 593                         goto unlock_release;
 594
 595                 /* Deliver the page fault to userland */
 596                 if (userfaultfd_missing(vma)) {
 597                         vm_fault_t ret2;
 598
 599                         spin_unlock(vmf->ptl);
 600                         mem_cgroup_cancel_charge(page, memcg, true);
 601                         put_page(page);
 602                         pte_free(vma->vm_mm, pgtable);
 603                         ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
 604                         VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
 605                         return ret2;
 606                 }
 607
 608                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 609                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 610                 page_add_new_anon_rmap(page, vma, haddr, true);
 611                 mem_cgroup_commit_charge(page, memcg, false, true);
 612                 lru_cache_add_active_or_unevictable(page, vma);
 613                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 614                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 615                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 616                 mm_inc_nr_ptes(vma->vm_mm);
 617                 spin_unlock(vmf->ptl);
 618                 count_vm_event(THP_FAULT_ALLOC);
 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         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 757         if (pfn_t_devmap(pfn))
 758                 entry = pmd_mkdevmap(entry);
 759         if (write) {
 760                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 761                 entry = maybe_pmd_mkwrite(entry, vma);
 762         }
 763
 764         if (pgtable) {
 765                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 766                 mm_inc_nr_ptes(mm);
 767         }
 768
 769         set_pmd_at(mm, addr, pmd, entry);
 770         update_mmu_cache_pmd(vma, addr, pmd);
 771         spin_unlock(ptl);
 772 }
 773
 774 vm_fault_t vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 775                         pmd_t *pmd, pfn_t pfn, bool write)
 776 {
 777         pgprot_t pgprot = vma->vm_page_prot;
 778         pgtable_t pgtable = NULL;
 779         /*
 780          * If we had pmd_special, we could avoid all these restrictions,
 781          * but we need to be consistent with PTEs and architectures that
 782          * can't support a 'special' bit.
 783          */
 784         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 785                         !pfn_t_devmap(pfn));
 786         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 787                                                 (VM_PFNMAP|VM_MIXEDMAP));
 788         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 789
 790         if (addr < vma->vm_start || addr >= vma->vm_end)
 791                 return VM_FAULT_SIGBUS;
 792
 793         if (arch_needs_pgtable_deposit()) {
 794                 pgtable = pte_alloc_one(vma->vm_mm);
 795                 if (!pgtable)
 796                         return VM_FAULT_OOM;
 797         }
 798
 799         track_pfn_insert(vma, &pgprot, pfn);
 800
 801         insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable);
 802         return VM_FAULT_NOPAGE;
 803 }
 804 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
 805
 806 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 807 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 808 {
 809         if (likely(vma->vm_flags & VM_WRITE))
 810                 pud = pud_mkwrite(pud);
 811         return pud;
 812 }
 813
 814 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 815                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 816 {
 817         struct mm_struct *mm = vma->vm_mm;
 818         pud_t entry;
 819         spinlock_t *ptl;
 820
 821         ptl = pud_lock(mm, pud);
 822         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
 823         if (pfn_t_devmap(pfn))
 824                 entry = pud_mkdevmap(entry);
 825         if (write) {
 826                 entry = pud_mkyoung(pud_mkdirty(entry));
 827                 entry = maybe_pud_mkwrite(entry, vma);
 828         }
 829         set_pud_at(mm, addr, pud, entry);
 830         update_mmu_cache_pud(vma, addr, pud);
 831         spin_unlock(ptl);
 832 }
 833
 834 vm_fault_t vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 835                         pud_t *pud, pfn_t pfn, bool write)
 836 {
 837         pgprot_t pgprot = vma->vm_page_prot;
 838         /*
 839          * If we had pud_special, we could avoid all these restrictions,
 840          * but we need to be consistent with PTEs and architectures that
 841          * can't support a 'special' bit.
 842          */
 843         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 844                         !pfn_t_devmap(pfn));
 845         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 846                                                 (VM_PFNMAP|VM_MIXEDMAP));
 847         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 848
 849         if (addr < vma->vm_start || addr >= vma->vm_end)
 850                 return VM_FAULT_SIGBUS;
 851
 852         track_pfn_insert(vma, &pgprot, pfn);
 853
 854         insert_pfn_pud(vma, addr, pud, pfn, pgprot, write);
 855         return VM_FAULT_NOPAGE;
 856 }
 857 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
 858 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 859
 860 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
 861                 pmd_t *pmd, int flags)
 862 {
 863         pmd_t _pmd;
 864
 865         _pmd = pmd_mkyoung(*pmd);
 866         if (flags & FOLL_WRITE)
 867                 _pmd = pmd_mkdirty(_pmd);
 868         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 869                                 pmd, _pmd, flags & FOLL_WRITE))
 870                 update_mmu_cache_pmd(vma, addr, pmd);
 871 }
 872
 873 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 874                 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
 875 {
 876         unsigned long pfn = pmd_pfn(*pmd);
 877         struct mm_struct *mm = vma->vm_mm;
 878         struct page *page;
 879
 880         assert_spin_locked(pmd_lockptr(mm, pmd));
 881
 882         /*
 883          * When we COW a devmap PMD entry, we split it into PTEs, so we should
 884          * not be in this function with `flags & FOLL_COW` set.
 885          */
 886         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
 887
 888         if (flags & FOLL_WRITE && !pmd_write(*pmd))
 889                 return NULL;
 890
 891         if (pmd_present(*pmd) && pmd_devmap(*pmd))
 892                 /* pass */;
 893         else
 894                 return NULL;
 895
 896         if (flags & FOLL_TOUCH)
 897                 touch_pmd(vma, addr, pmd, flags);
 898
 899         /*
 900          * device mapped pages can only be returned if the
 901          * caller will manage the page reference count.
 902          */
 903         if (!(flags & FOLL_GET))
 904                 return ERR_PTR(-EEXIST);
 905
 906         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
 907         *pgmap = get_dev_pagemap(pfn, *pgmap);
 908         if (!*pgmap)
 909                 return ERR_PTR(-EFAULT);
 910         page = pfn_to_page(pfn);
 911         get_page(page);
 912
 913         return page;
 914 }
 915
 916 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 917                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 918                   struct vm_area_struct *vma)
 919 {
 920         spinlock_t *dst_ptl, *src_ptl;
 921         struct page *src_page;
 922         pmd_t pmd;
 923         pgtable_t pgtable = NULL;
 924         int ret = -ENOMEM;
 925
 926         /* Skip if can be re-fill on fault */
 927         if (!vma_is_anonymous(vma))
 928                 return 0;
 929
 930         pgtable = pte_alloc_one(dst_mm);
 931         if (unlikely(!pgtable))
 932                 goto out;
 933
 934         dst_ptl = pmd_lock(dst_mm, dst_pmd);
 935         src_ptl = pmd_lockptr(src_mm, src_pmd);
 936         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 937
 938         ret = -EAGAIN;
 939         pmd = *src_pmd;
 940
 941 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
 942         if (unlikely(is_swap_pmd(pmd))) {
 943                 swp_entry_t entry = pmd_to_swp_entry(pmd);
 944
 945                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
 946                 if (is_write_migration_entry(entry)) {
 947                         make_migration_entry_read(&entry);
 948                         pmd = swp_entry_to_pmd(entry);
 949                         if (pmd_swp_soft_dirty(*src_pmd))
 950                                 pmd = pmd_swp_mksoft_dirty(pmd);
 951                         set_pmd_at(src_mm, addr, src_pmd, pmd);
 952                 }
 953                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 954                 mm_inc_nr_ptes(dst_mm);
 955                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 956                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 957                 ret = 0;
 958                 goto out_unlock;
 959         }
 960 #endif
 961
 962         if (unlikely(!pmd_trans_huge(pmd))) {
 963                 pte_free(dst_mm, pgtable);
 964                 goto out_unlock;
 965         }
 966         /*
 967          * When page table lock is held, the huge zero pmd should not be
 968          * under splitting since we don't split the page itself, only pmd to
 969          * a page table.
 970          */
 971         if (is_huge_zero_pmd(pmd)) {
 972                 struct page *zero_page;
 973                 /*
 974                  * get_huge_zero_page() will never allocate a new page here,
 975                  * since we already have a zero page to copy. It just takes a
 976                  * reference.
 977                  */
 978                 zero_page = mm_get_huge_zero_page(dst_mm);
 979                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
 980                                 zero_page);
 981                 ret = 0;
 982                 goto out_unlock;
 983         }
 984
 985         src_page = pmd_page(pmd);
 986         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
 987         get_page(src_page);
 988         page_dup_rmap(src_page, true);
 989         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 990         mm_inc_nr_ptes(dst_mm);
 991         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 992
 993         pmdp_set_wrprotect(src_mm, addr, src_pmd);
 994         pmd = pmd_mkold(pmd_wrprotect(pmd));
 995         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 996
 997         ret = 0;
 998 out_unlock:
 999         spin_unlock(src_ptl);
1000         spin_unlock(dst_ptl);
1001 out:
1002         return ret;
1003 }
1004
1005 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1006 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1007                 pud_t *pud, int flags)
1008 {
1009         pud_t _pud;
1010
1011         _pud = pud_mkyoung(*pud);
1012         if (flags & FOLL_WRITE)
1013                 _pud = pud_mkdirty(_pud);
1014         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1015                                 pud, _pud, flags & FOLL_WRITE))
1016                 update_mmu_cache_pud(vma, addr, pud);
1017 }
1018
1019 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1020                 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1021 {
1022         unsigned long pfn = pud_pfn(*pud);
1023         struct mm_struct *mm = vma->vm_mm;
1024         struct page *page;
1025
1026         assert_spin_locked(pud_lockptr(mm, pud));
1027
1028         if (flags & FOLL_WRITE && !pud_write(*pud))
1029                 return NULL;
1030
1031         if (pud_present(*pud) && pud_devmap(*pud))
1032                 /* pass */;
1033         else
1034                 return NULL;
1035
1036         if (flags & FOLL_TOUCH)
1037                 touch_pud(vma, addr, pud, flags);
1038
1039         /*
1040          * device mapped pages can only be returned if the
1041          * caller will manage the page reference count.
1042          */
1043         if (!(flags & FOLL_GET))
1044                 return ERR_PTR(-EEXIST);
1045
1046         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1047         *pgmap = get_dev_pagemap(pfn, *pgmap);
1048         if (!*pgmap)
1049                 return ERR_PTR(-EFAULT);
1050         page = pfn_to_page(pfn);
1051         get_page(page);
1052
1053         return page;
1054 }
1055
1056 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1057                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1058                   struct vm_area_struct *vma)
1059 {
1060         spinlock_t *dst_ptl, *src_ptl;
1061         pud_t pud;
1062         int ret;
1063
1064         dst_ptl = pud_lock(dst_mm, dst_pud);
1065         src_ptl = pud_lockptr(src_mm, src_pud);
1066         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1067
1068         ret = -EAGAIN;
1069         pud = *src_pud;
1070         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1071                 goto out_unlock;
1072
1073         /*
1074          * When page table lock is held, the huge zero pud should not be
1075          * under splitting since we don't split the page itself, only pud to
1076          * a page table.
1077          */
1078         if (is_huge_zero_pud(pud)) {
1079                 /* No huge zero pud yet */
1080         }
1081
1082         pudp_set_wrprotect(src_mm, addr, src_pud);
1083         pud = pud_mkold(pud_wrprotect(pud));
1084         set_pud_at(dst_mm, addr, dst_pud, pud);
1085
1086         ret = 0;
1087 out_unlock:
1088         spin_unlock(src_ptl);
1089         spin_unlock(dst_ptl);
1090         return ret;
1091 }
1092
1093 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1094 {
1095         pud_t entry;
1096         unsigned long haddr;
1097         bool write = vmf->flags & FAULT_FLAG_WRITE;
1098
1099         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1100         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1101                 goto unlock;
1102
1103         entry = pud_mkyoung(orig_pud);
1104         if (write)
1105                 entry = pud_mkdirty(entry);
1106         haddr = vmf->address & HPAGE_PUD_MASK;
1107         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1108                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1109
1110 unlock:
1111         spin_unlock(vmf->ptl);
1112 }
1113 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1114
1115 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1116 {
1117         pmd_t entry;
1118         unsigned long haddr;
1119         bool write = vmf->flags & FAULT_FLAG_WRITE;
1120
1121         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1122         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1123                 goto unlock;
1124
1125         entry = pmd_mkyoung(orig_pmd);
1126         if (write)
1127                 entry = pmd_mkdirty(entry);
1128         haddr = vmf->address & HPAGE_PMD_MASK;
1129         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1130                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1131
1132 unlock:
1133         spin_unlock(vmf->ptl);
1134 }
1135
1136 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1137                         pmd_t orig_pmd, struct page *page)
1138 {
1139         struct vm_area_struct *vma = vmf->vma;
1140         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1141         struct mem_cgroup *memcg;
1142         pgtable_t pgtable;
1143         pmd_t _pmd;
1144         int i;
1145         vm_fault_t ret = 0;
1146         struct page **pages;
1147         struct mmu_notifier_range range;
1148
1149         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1150                               GFP_KERNEL);
1151         if (unlikely(!pages)) {
1152                 ret |= VM_FAULT_OOM;
1153                 goto out;
1154         }
1155
1156         for (i = 0; i < HPAGE_PMD_NR; i++) {
1157                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1158                                                vmf->address, page_to_nid(page));
1159                 if (unlikely(!pages[i] ||
1160                              mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1161                                      GFP_KERNEL, &memcg, false))) {
1162                         if (pages[i])
1163                                 put_page(pages[i]);
1164                         while (--i >= 0) {
1165                                 memcg = (void *)page_private(pages[i]);
1166                                 set_page_private(pages[i], 0);
1167                                 mem_cgroup_cancel_charge(pages[i], memcg,
1168                                                 false);
1169                                 put_page(pages[i]);
1170                         }
1171                         kfree(pages);
1172                         ret |= VM_FAULT_OOM;
1173                         goto out;
1174                 }
1175                 set_page_private(pages[i], (unsigned long)memcg);
1176         }
1177
1178         for (i = 0; i < HPAGE_PMD_NR; i++) {
1179                 copy_user_highpage(pages[i], page + i,
1180                                    haddr + PAGE_SIZE * i, vma);
1181                 __SetPageUptodate(pages[i]);
1182                 cond_resched();
1183         }
1184
1185         mmu_notifier_range_init(&range, vma->vm_mm, haddr,
1186                                 haddr + HPAGE_PMD_SIZE);
1187         mmu_notifier_invalidate_range_start(&range);
1188
1189         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1190         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1191                 goto out_free_pages;
1192         VM_BUG_ON_PAGE(!PageHead(page), page);
1193
1194         /*
1195          * Leave pmd empty until pte is filled note we must notify here as
1196          * concurrent CPU thread might write to new page before the call to
1197          * mmu_notifier_invalidate_range_end() happens which can lead to a
1198          * device seeing memory write in different order than CPU.
1199          *
1200          * See Documentation/vm/mmu_notifier.rst
1201          */
1202         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1203
1204         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1205         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1206
1207         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1208                 pte_t entry;
1209                 entry = mk_pte(pages[i], vma->vm_page_prot);
1210                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1211                 memcg = (void *)page_private(pages[i]);
1212                 set_page_private(pages[i], 0);
1213                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1214                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1215                 lru_cache_add_active_or_unevictable(pages[i], vma);
1216                 vmf->pte = pte_offset_map(&_pmd, haddr);
1217                 VM_BUG_ON(!pte_none(*vmf->pte));
1218                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1219                 pte_unmap(vmf->pte);
1220         }
1221         kfree(pages);
1222
1223         smp_wmb(); /* make pte visible before pmd */
1224         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1225         page_remove_rmap(page, true);
1226         spin_unlock(vmf->ptl);
1227
1228         /*
1229          * No need to double call mmu_notifier->invalidate_range() callback as
1230          * the above pmdp_huge_clear_flush_notify() did already call it.
1231          */
1232         mmu_notifier_invalidate_range_only_end(&range);
1233
1234         ret |= VM_FAULT_WRITE;
1235         put_page(page);
1236
1237 out:
1238         return ret;
1239
1240 out_free_pages:
1241         spin_unlock(vmf->ptl);
1242         mmu_notifier_invalidate_range_end(&range);
1243         for (i = 0; i < HPAGE_PMD_NR; i++) {
1244                 memcg = (void *)page_private(pages[i]);
1245                 set_page_private(pages[i], 0);
1246                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1247                 put_page(pages[i]);
1248         }
1249         kfree(pages);
1250         goto out;
1251 }
1252
1253 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1254 {
1255         struct vm_area_struct *vma = vmf->vma;
1256         struct page *page = NULL, *new_page;
1257         struct mem_cgroup *memcg;
1258         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1259         struct mmu_notifier_range range;
1260         gfp_t huge_gfp;                 /* for allocation and charge */
1261         vm_fault_t ret = 0;
1262
1263         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1264         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1265         if (is_huge_zero_pmd(orig_pmd))
1266                 goto alloc;
1267         spin_lock(vmf->ptl);
1268         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1269                 goto out_unlock;
1270
1271         page = pmd_page(orig_pmd);
1272         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1273         /*
1274          * We can only reuse the page if nobody else maps the huge page or it's
1275          * part.
1276          */
1277         if (!trylock_page(page)) {
1278                 get_page(page);
1279                 spin_unlock(vmf->ptl);
1280                 lock_page(page);
1281                 spin_lock(vmf->ptl);
1282                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1283                         unlock_page(page);
1284                         put_page(page);
1285                         goto out_unlock;
1286                 }
1287                 put_page(page);
1288         }
1289         if (reuse_swap_page(page, NULL)) {
1290                 pmd_t entry;
1291                 entry = pmd_mkyoung(orig_pmd);
1292                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1293                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1294                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1295                 ret |= VM_FAULT_WRITE;
1296                 unlock_page(page);
1297                 goto out_unlock;
1298         }
1299         unlock_page(page);
1300         get_page(page);
1301         spin_unlock(vmf->ptl);
1302 alloc:
1303         if (__transparent_hugepage_enabled(vma) &&
1304             !transparent_hugepage_debug_cow()) {
1305                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1306                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1307         } else
1308                 new_page = NULL;
1309
1310         if (likely(new_page)) {
1311                 prep_transhuge_page(new_page);
1312         } else {
1313                 if (!page) {
1314                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1315                         ret |= VM_FAULT_FALLBACK;
1316                 } else {
1317                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1318                         if (ret & VM_FAULT_OOM) {
1319                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1320                                 ret |= VM_FAULT_FALLBACK;
1321                         }
1322                         put_page(page);
1323                 }
1324                 count_vm_event(THP_FAULT_FALLBACK);
1325                 goto out;
1326         }
1327
1328         if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1329                                         huge_gfp, &memcg, true))) {
1330                 put_page(new_page);
1331                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1332                 if (page)
1333                         put_page(page);
1334                 ret |= VM_FAULT_FALLBACK;
1335                 count_vm_event(THP_FAULT_FALLBACK);
1336                 goto out;
1337         }
1338
1339         count_vm_event(THP_FAULT_ALLOC);
1340
1341         if (!page)
1342                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1343         else
1344                 copy_user_huge_page(new_page, page, vmf->address,
1345                                     vma, HPAGE_PMD_NR);
1346         __SetPageUptodate(new_page);
1347
1348         mmu_notifier_range_init(&range, vma->vm_mm, haddr,
1349                                 haddr + HPAGE_PMD_SIZE);
1350         mmu_notifier_invalidate_range_start(&range);
1351
1352         spin_lock(vmf->ptl);
1353         if (page)
1354                 put_page(page);
1355         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1356                 spin_unlock(vmf->ptl);
1357                 mem_cgroup_cancel_charge(new_page, memcg, true);
1358                 put_page(new_page);
1359                 goto out_mn;
1360         } else {
1361                 pmd_t entry;
1362                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1363                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1364                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1365                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1366                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1367                 lru_cache_add_active_or_unevictable(new_page, vma);
1368                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1369                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1370                 if (!page) {
1371                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1372                 } else {
1373                         VM_BUG_ON_PAGE(!PageHead(page), page);
1374                         page_remove_rmap(page, true);
1375                         put_page(page);
1376                 }
1377                 ret |= VM_FAULT_WRITE;
1378         }
1379         spin_unlock(vmf->ptl);
1380 out_mn:
1381         /*
1382          * No need to double call mmu_notifier->invalidate_range() callback as
1383          * the above pmdp_huge_clear_flush_notify() did already call it.
1384          */
1385         mmu_notifier_invalidate_range_only_end(&range);
1386 out:
1387         return ret;
1388 out_unlock:
1389         spin_unlock(vmf->ptl);
1390         return ret;
1391 }
1392
1393 /*
1394  * FOLL_FORCE can write to even unwritable pmd's, but only
1395  * after we've gone through a COW cycle and they are dirty.
1396  */
1397 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1398 {
1399         return pmd_write(pmd) ||
1400                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1401 }
1402
1403 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1404                                    unsigned long addr,
1405                                    pmd_t *pmd,
1406                                    unsigned int flags)
1407 {
1408         struct mm_struct *mm = vma->vm_mm;
1409         struct page *page = NULL;
1410
1411         assert_spin_locked(pmd_lockptr(mm, pmd));
1412
1413         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1414                 goto out;
1415
1416         /* Avoid dumping huge zero page */
1417         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1418                 return ERR_PTR(-EFAULT);
1419
1420         /* Full NUMA hinting faults to serialise migration in fault paths */
1421         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1422                 goto out;
1423
1424         page = pmd_page(*pmd);
1425         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1426         if (flags & FOLL_TOUCH)
1427                 touch_pmd(vma, addr, pmd, flags);
1428         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1429                 /*
1430                  * We don't mlock() pte-mapped THPs. This way we can avoid
1431                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1432                  *
1433                  * For anon THP:
1434                  *
1435                  * In most cases the pmd is the only mapping of the page as we
1436                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1437                  * writable private mappings in populate_vma_page_range().
1438                  *
1439                  * The only scenario when we have the page shared here is if we
1440                  * mlocking read-only mapping shared over fork(). We skip
1441                  * mlocking such pages.
1442                  *
1443                  * For file THP:
1444                  *
1445                  * We can expect PageDoubleMap() to be stable under page lock:
1446                  * for file pages we set it in page_add_file_rmap(), which
1447                  * requires page to be locked.
1448                  */
1449
1450                 if (PageAnon(page) && compound_mapcount(page) != 1)
1451                         goto skip_mlock;
1452                 if (PageDoubleMap(page) || !page->mapping)
1453                         goto skip_mlock;
1454                 if (!trylock_page(page))
1455                         goto skip_mlock;
1456                 lru_add_drain();
1457                 if (page->mapping && !PageDoubleMap(page))
1458                         mlock_vma_page(page);
1459                 unlock_page(page);
1460         }
1461 skip_mlock:
1462         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1463         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1464         if (flags & FOLL_GET)
1465                 get_page(page);
1466
1467 out:
1468         return page;
1469 }
1470
1471 /* NUMA hinting page fault entry point for trans huge pmds */
1472 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1473 {
1474         struct vm_area_struct *vma = vmf->vma;
1475         struct anon_vma *anon_vma = NULL;
1476         struct page *page;
1477         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1478         int page_nid = -1, this_nid = numa_node_id();
1479         int target_nid, last_cpupid = -1;
1480         bool page_locked;
1481         bool migrated = false;
1482         bool was_writable;
1483         int flags = 0;
1484
1485         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1486         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1487                 goto out_unlock;
1488
1489         /*
1490          * If there are potential migrations, wait for completion and retry
1491          * without disrupting NUMA hinting information. Do not relock and
1492          * check_same as the page may no longer be mapped.
1493          */
1494         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1495                 page = pmd_page(*vmf->pmd);
1496                 if (!get_page_unless_zero(page))
1497                         goto out_unlock;
1498                 spin_unlock(vmf->ptl);
1499                 put_and_wait_on_page_locked(page);
1500                 goto out;
1501         }
1502
1503         page = pmd_page(pmd);
1504         BUG_ON(is_huge_zero_page(page));
1505         page_nid = page_to_nid(page);
1506         last_cpupid = page_cpupid_last(page);
1507         count_vm_numa_event(NUMA_HINT_FAULTS);
1508         if (page_nid == this_nid) {
1509                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1510                 flags |= TNF_FAULT_LOCAL;
1511         }
1512
1513         /* See similar comment in do_numa_page for explanation */
1514         if (!pmd_savedwrite(pmd))
1515                 flags |= TNF_NO_GROUP;
1516
1517         /*
1518          * Acquire the page lock to serialise THP migrations but avoid dropping
1519          * page_table_lock if at all possible
1520          */
1521         page_locked = trylock_page(page);
1522         target_nid = mpol_misplaced(page, vma, haddr);
1523         if (target_nid == -1) {
1524                 /* If the page was locked, there are no parallel migrations */
1525                 if (page_locked)
1526                         goto clear_pmdnuma;
1527         }
1528
1529         /* Migration could have started since the pmd_trans_migrating check */
1530         if (!page_locked) {
1531                 page_nid = -1;
1532                 if (!get_page_unless_zero(page))
1533                         goto out_unlock;
1534                 spin_unlock(vmf->ptl);
1535                 put_and_wait_on_page_locked(page);
1536                 goto out;
1537         }
1538
1539         /*
1540          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1541          * to serialises splits
1542          */
1543         get_page(page);
1544         spin_unlock(vmf->ptl);
1545         anon_vma = page_lock_anon_vma_read(page);
1546
1547         /* Confirm the PMD did not change while page_table_lock was released */
1548         spin_lock(vmf->ptl);
1549         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1550                 unlock_page(page);
1551                 put_page(page);
1552                 page_nid = -1;
1553                 goto out_unlock;
1554         }
1555
1556         /* Bail if we fail to protect against THP splits for any reason */
1557         if (unlikely(!anon_vma)) {
1558                 put_page(page);
1559                 page_nid = -1;
1560                 goto clear_pmdnuma;
1561         }
1562
1563         /*
1564          * Since we took the NUMA fault, we must have observed the !accessible
1565          * bit. Make sure all other CPUs agree with that, to avoid them
1566          * modifying the page we're about to migrate.
1567          *
1568          * Must be done under PTL such that we'll observe the relevant
1569          * inc_tlb_flush_pending().
1570          *
1571          * We are not sure a pending tlb flush here is for a huge page
1572          * mapping or not. Hence use the tlb range variant
1573          */
1574         if (mm_tlb_flush_pending(vma->vm_mm)) {
1575                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1576                 /*
1577                  * change_huge_pmd() released the pmd lock before
1578                  * invalidating the secondary MMUs sharing the primary
1579                  * MMU pagetables (with ->invalidate_range()). The
1580                  * mmu_notifier_invalidate_range_end() (which
1581                  * internally calls ->invalidate_range()) in
1582                  * change_pmd_range() will run after us, so we can't
1583                  * rely on it here and we need an explicit invalidate.
1584                  */
1585                 mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1586                                               haddr + HPAGE_PMD_SIZE);
1587         }
1588
1589         /*
1590          * Migrate the THP to the requested node, returns with page unlocked
1591          * and access rights restored.
1592          */
1593         spin_unlock(vmf->ptl);
1594
1595         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1596                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1597         if (migrated) {
1598                 flags |= TNF_MIGRATED;
1599                 page_nid = target_nid;
1600         } else
1601                 flags |= TNF_MIGRATE_FAIL;
1602
1603         goto out;
1604 clear_pmdnuma:
1605         BUG_ON(!PageLocked(page));
1606         was_writable = pmd_savedwrite(pmd);
1607         pmd = pmd_modify(pmd, vma->vm_page_prot);
1608         pmd = pmd_mkyoung(pmd);
1609         if (was_writable)
1610                 pmd = pmd_mkwrite(pmd);
1611         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1612         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1613         unlock_page(page);
1614 out_unlock:
1615         spin_unlock(vmf->ptl);
1616
1617 out:
1618         if (anon_vma)
1619                 page_unlock_anon_vma_read(anon_vma);
1620
1621         if (page_nid != -1)
1622                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1623                                 flags);
1624
1625         return 0;
1626 }
1627
1628 /*
1629  * Return true if we do MADV_FREE successfully on entire pmd page.
1630  * Otherwise, return false.
1631  */
1632 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1633                 pmd_t *pmd, unsigned long addr, unsigned long next)
1634 {
1635         spinlock_t *ptl;
1636         pmd_t orig_pmd;
1637         struct page *page;
1638         struct mm_struct *mm = tlb->mm;
1639         bool ret = false;
1640
1641         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1642
1643         ptl = pmd_trans_huge_lock(pmd, vma);
1644         if (!ptl)
1645                 goto out_unlocked;
1646
1647         orig_pmd = *pmd;
1648         if (is_huge_zero_pmd(orig_pmd))
1649                 goto out;
1650
1651         if (unlikely(!pmd_present(orig_pmd))) {
1652                 VM_BUG_ON(thp_migration_supported() &&
1653                                   !is_pmd_migration_entry(orig_pmd));
1654                 goto out;
1655         }
1656
1657         page = pmd_page(orig_pmd);
1658         /*
1659          * If other processes are mapping this page, we couldn't discard
1660          * the page unless they all do MADV_FREE so let's skip the page.
1661          */
1662         if (page_mapcount(page) != 1)
1663                 goto out;
1664
1665         if (!trylock_page(page))
1666                 goto out;
1667
1668         /*
1669          * If user want to discard part-pages of THP, split it so MADV_FREE
1670          * will deactivate only them.
1671          */
1672         if (next - addr != HPAGE_PMD_SIZE) {
1673                 get_page(page);
1674                 spin_unlock(ptl);
1675                 split_huge_page(page);
1676                 unlock_page(page);
1677                 put_page(page);
1678                 goto out_unlocked;
1679         }
1680
1681         if (PageDirty(page))
1682                 ClearPageDirty(page);
1683         unlock_page(page);
1684
1685         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1686                 pmdp_invalidate(vma, addr, pmd);
1687                 orig_pmd = pmd_mkold(orig_pmd);
1688                 orig_pmd = pmd_mkclean(orig_pmd);
1689
1690                 set_pmd_at(mm, addr, pmd, orig_pmd);
1691                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1692         }
1693
1694         mark_page_lazyfree(page);
1695         ret = true;
1696 out:
1697         spin_unlock(ptl);
1698 out_unlocked:
1699         return ret;
1700 }
1701
1702 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1703 {
1704         pgtable_t pgtable;
1705
1706         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1707         pte_free(mm, pgtable);
1708         mm_dec_nr_ptes(mm);
1709 }
1710
1711 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1712                  pmd_t *pmd, unsigned long addr)
1713 {
1714         pmd_t orig_pmd;
1715         spinlock_t *ptl;
1716
1717         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1718
1719         ptl = __pmd_trans_huge_lock(pmd, vma);
1720         if (!ptl)
1721                 return 0;
1722         /*
1723          * For architectures like ppc64 we look at deposited pgtable
1724          * when calling pmdp_huge_get_and_clear. So do the
1725          * pgtable_trans_huge_withdraw after finishing pmdp related
1726          * operations.
1727          */
1728         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1729                         tlb->fullmm);
1730         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1731         if (vma_is_dax(vma)) {
1732                 if (arch_needs_pgtable_deposit())
1733                         zap_deposited_table(tlb->mm, pmd);
1734                 spin_unlock(ptl);
1735                 if (is_huge_zero_pmd(orig_pmd))
1736                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1737         } else if (is_huge_zero_pmd(orig_pmd)) {
1738                 zap_deposited_table(tlb->mm, pmd);
1739                 spin_unlock(ptl);
1740                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1741         } else {
1742                 struct page *page = NULL;
1743                 int flush_needed = 1;
1744
1745                 if (pmd_present(orig_pmd)) {
1746                         page = pmd_page(orig_pmd);
1747                         page_remove_rmap(page, true);
1748                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1749                         VM_BUG_ON_PAGE(!PageHead(page), page);
1750                 } else if (thp_migration_supported()) {
1751                         swp_entry_t entry;
1752
1753                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1754                         entry = pmd_to_swp_entry(orig_pmd);
1755                         page = pfn_to_page(swp_offset(entry));
1756                         flush_needed = 0;
1757                 } else
1758                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1759
1760                 if (PageAnon(page)) {
1761                         zap_deposited_table(tlb->mm, pmd);
1762                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1763                 } else {
1764                         if (arch_needs_pgtable_deposit())
1765                                 zap_deposited_table(tlb->mm, pmd);
1766                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1767                 }
1768
1769                 spin_unlock(ptl);
1770                 if (flush_needed)
1771                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1772         }
1773         return 1;
1774 }
1775
1776 #ifndef pmd_move_must_withdraw
1777 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1778                                          spinlock_t *old_pmd_ptl,
1779                                          struct vm_area_struct *vma)
1780 {
1781         /*
1782          * With split pmd lock we also need to move preallocated
1783          * PTE page table if new_pmd is on different PMD page table.
1784          *
1785          * We also don't deposit and withdraw tables for file pages.
1786          */
1787         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1788 }
1789 #endif
1790
1791 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1792 {
1793 #ifdef CONFIG_MEM_SOFT_DIRTY
1794         if (unlikely(is_pmd_migration_entry(pmd)))
1795                 pmd = pmd_swp_mksoft_dirty(pmd);
1796         else if (pmd_present(pmd))
1797                 pmd = pmd_mksoft_dirty(pmd);
1798 #endif
1799         return pmd;
1800 }
1801
1802 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1803                   unsigned long new_addr, unsigned long old_end,
1804                   pmd_t *old_pmd, pmd_t *new_pmd)
1805 {
1806         spinlock_t *old_ptl, *new_ptl;
1807         pmd_t pmd;
1808         struct mm_struct *mm = vma->vm_mm;
1809         bool force_flush = false;
1810
1811         if ((old_addr & ~HPAGE_PMD_MASK) ||
1812             (new_addr & ~HPAGE_PMD_MASK) ||
1813             old_end - old_addr < HPAGE_PMD_SIZE)
1814                 return false;
1815
1816         /*
1817          * The destination pmd shouldn't be established, free_pgtables()
1818          * should have release it.
1819          */
1820         if (WARN_ON(!pmd_none(*new_pmd))) {
1821                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1822                 return false;
1823         }
1824
1825         /*
1826          * We don't have to worry about the ordering of src and dst
1827          * ptlocks because exclusive mmap_sem prevents deadlock.
1828          */
1829         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1830         if (old_ptl) {
1831                 new_ptl = pmd_lockptr(mm, new_pmd);
1832                 if (new_ptl != old_ptl)
1833                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1834                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1835                 if (pmd_present(pmd))
1836                         force_flush = true;
1837                 VM_BUG_ON(!pmd_none(*new_pmd));
1838
1839                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1840                         pgtable_t pgtable;
1841                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1842                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1843                 }
1844                 pmd = move_soft_dirty_pmd(pmd);
1845                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1846                 if (force_flush)
1847                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1848                 if (new_ptl != old_ptl)
1849                         spin_unlock(new_ptl);
1850                 spin_unlock(old_ptl);
1851                 return true;
1852         }
1853         return false;
1854 }
1855
1856 /*
1857  * Returns
1858  *  - 0 if PMD could not be locked
1859  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1860  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1861  */
1862 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1863                 unsigned long addr, pgprot_t newprot, int prot_numa)
1864 {
1865         struct mm_struct *mm = vma->vm_mm;
1866         spinlock_t *ptl;
1867         pmd_t entry;
1868         bool preserve_write;
1869         int ret;
1870
1871         ptl = __pmd_trans_huge_lock(pmd, vma);
1872         if (!ptl)
1873                 return 0;
1874
1875         preserve_write = prot_numa && pmd_write(*pmd);
1876         ret = 1;
1877
1878 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1879         if (is_swap_pmd(*pmd)) {
1880                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1881
1882                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1883                 if (is_write_migration_entry(entry)) {
1884                         pmd_t newpmd;
1885                         /*
1886                          * A protection check is difficult so
1887                          * just be safe and disable write
1888                          */
1889                         make_migration_entry_read(&entry);
1890                         newpmd = swp_entry_to_pmd(entry);
1891                         if (pmd_swp_soft_dirty(*pmd))
1892                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1893                         set_pmd_at(mm, addr, pmd, newpmd);
1894                 }
1895                 goto unlock;
1896         }
1897 #endif
1898
1899         /*
1900          * Avoid trapping faults against the zero page. The read-only
1901          * data is likely to be read-cached on the local CPU and
1902          * local/remote hits to the zero page are not interesting.
1903          */
1904         if (prot_numa && is_huge_zero_pmd(*pmd))
1905                 goto unlock;
1906
1907         if (prot_numa && pmd_protnone(*pmd))
1908                 goto unlock;
1909
1910         /*
1911          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1912          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1913          * which is also under down_read(mmap_sem):
1914          *
1915          *      CPU0:                           CPU1:
1916          *                              change_huge_pmd(prot_numa=1)
1917          *                               pmdp_huge_get_and_clear_notify()
1918          * madvise_dontneed()
1919          *  zap_pmd_range()
1920          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1921          *   // skip the pmd
1922          *                               set_pmd_at();
1923          *                               // pmd is re-established
1924          *
1925          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1926          * which may break userspace.
1927          *
1928          * pmdp_invalidate() is required to make sure we don't miss
1929          * dirty/young flags set by hardware.
1930          */
1931         entry = pmdp_invalidate(vma, addr, pmd);
1932
1933         entry = pmd_modify(entry, newprot);
1934         if (preserve_write)
1935                 entry = pmd_mk_savedwrite(entry);
1936         ret = HPAGE_PMD_NR;
1937         set_pmd_at(mm, addr, pmd, entry);
1938         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1939 unlock:
1940         spin_unlock(ptl);
1941         return ret;
1942 }
1943
1944 /*
1945  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1946  *
1947  * Note that if it returns page table lock pointer, this routine returns without
1948  * unlocking page table lock. So callers must unlock it.
1949  */
1950 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1951 {
1952         spinlock_t *ptl;
1953         ptl = pmd_lock(vma->vm_mm, pmd);
1954         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1955                         pmd_devmap(*pmd)))
1956                 return ptl;
1957         spin_unlock(ptl);
1958         return NULL;
1959 }
1960
1961 /*
1962  * Returns true if a given pud maps a thp, false otherwise.
1963  *
1964  * Note that if it returns true, this routine returns without unlocking page
1965  * table lock. So callers must unlock it.
1966  */
1967 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1968 {
1969         spinlock_t *ptl;
1970
1971         ptl = pud_lock(vma->vm_mm, pud);
1972         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1973                 return ptl;
1974         spin_unlock(ptl);
1975         return NULL;
1976 }
1977
1978 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1979 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1980                  pud_t *pud, unsigned long addr)
1981 {
1982         pud_t orig_pud;
1983         spinlock_t *ptl;
1984
1985         ptl = __pud_trans_huge_lock(pud, vma);
1986         if (!ptl)
1987                 return 0;
1988         /*
1989          * For architectures like ppc64 we look at deposited pgtable
1990          * when calling pudp_huge_get_and_clear. So do the
1991          * pgtable_trans_huge_withdraw after finishing pudp related
1992          * operations.
1993          */
1994         orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1995                         tlb->fullmm);
1996         tlb_remove_pud_tlb_entry(tlb, pud, addr);
1997         if (vma_is_dax(vma)) {
1998                 spin_unlock(ptl);
1999                 /* No zero page support yet */
2000         } else {
2001                 /* No support for anonymous PUD pages yet */
2002                 BUG();
2003         }
2004         return 1;
2005 }
2006
2007 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2008                 unsigned long haddr)
2009 {
2010         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2011         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2012         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2013         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2014
2015         count_vm_event(THP_SPLIT_PUD);
2016
2017         pudp_huge_clear_flush_notify(vma, haddr, pud);
2018 }
2019
2020 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2021                 unsigned long address)
2022 {
2023         spinlock_t *ptl;
2024         struct mmu_notifier_range range;
2025
2026         mmu_notifier_range_init(&range, vma->vm_mm, address & HPAGE_PUD_MASK,
2027                                 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
2028         mmu_notifier_invalidate_range_start(&range);
2029         ptl = pud_lock(vma->vm_mm, pud);
2030         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2031                 goto out;
2032         __split_huge_pud_locked(vma, pud, range.start);
2033
2034 out:
2035         spin_unlock(ptl);
2036         /*
2037          * No need to double call mmu_notifier->invalidate_range() callback as
2038          * the above pudp_huge_clear_flush_notify() did already call it.
2039          */
2040         mmu_notifier_invalidate_range_only_end(&range);
2041 }
2042 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2043
2044 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2045                 unsigned long haddr, pmd_t *pmd)
2046 {
2047         struct mm_struct *mm = vma->vm_mm;
2048         pgtable_t pgtable;
2049         pmd_t _pmd;
2050         int i;
2051
2052         /*
2053          * Leave pmd empty until pte is filled note that it is fine to delay
2054          * notification until mmu_notifier_invalidate_range_end() as we are
2055          * replacing a zero pmd write protected page with a zero pte write
2056          * protected page.
2057          *
2058          * See Documentation/vm/mmu_notifier.rst
2059          */
2060         pmdp_huge_clear_flush(vma, haddr, pmd);
2061
2062         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2063         pmd_populate(mm, &_pmd, pgtable);
2064
2065         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2066                 pte_t *pte, entry;
2067                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2068                 entry = pte_mkspecial(entry);
2069                 pte = pte_offset_map(&_pmd, haddr);
2070                 VM_BUG_ON(!pte_none(*pte));
2071                 set_pte_at(mm, haddr, pte, entry);
2072                 pte_unmap(pte);
2073         }
2074         smp_wmb(); /* make pte visible before pmd */
2075         pmd_populate(mm, pmd, pgtable);
2076 }
2077
2078 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2079                 unsigned long haddr, bool freeze)
2080 {
2081         struct mm_struct *mm = vma->vm_mm;
2082         struct page *page;
2083         pgtable_t pgtable;
2084         pmd_t old_pmd, _pmd;
2085         bool young, write, soft_dirty, pmd_migration = false;
2086         unsigned long addr;
2087         int i;
2088
2089         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2090         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2091         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2092         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2093                                 && !pmd_devmap(*pmd));
2094
2095         count_vm_event(THP_SPLIT_PMD);
2096
2097         if (!vma_is_anonymous(vma)) {
2098                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2099                 /*
2100                  * We are going to unmap this huge page. So
2101                  * just go ahead and zap it
2102                  */
2103                 if (arch_needs_pgtable_deposit())
2104                         zap_deposited_table(mm, pmd);
2105                 if (vma_is_dax(vma))
2106                         return;
2107                 page = pmd_page(_pmd);
2108                 if (!PageDirty(page) && pmd_dirty(_pmd))
2109                         set_page_dirty(page);
2110                 if (!PageReferenced(page) && pmd_young(_pmd))
2111                         SetPageReferenced(page);
2112                 page_remove_rmap(page, true);
2113                 put_page(page);
2114                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2115                 return;
2116         } else if (is_huge_zero_pmd(*pmd)) {
2117                 /*
2118                  * FIXME: Do we want to invalidate secondary mmu by calling
2119                  * mmu_notifier_invalidate_range() see comments below inside
2120                  * __split_huge_pmd() ?
2121                  *
2122                  * We are going from a zero huge page write protected to zero
2123                  * small page also write protected so it does not seems useful
2124                  * to invalidate secondary mmu at this time.
2125                  */
2126                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2127         }
2128
2129         /*
2130          * Up to this point the pmd is present and huge and userland has the
2131          * whole access to the hugepage during the split (which happens in
2132          * place). If we overwrite the pmd with the not-huge version pointing
2133          * to the pte here (which of course we could if all CPUs were bug
2134          * free), userland could trigger a small page size TLB miss on the
2135          * small sized TLB while the hugepage TLB entry is still established in
2136          * the huge TLB. Some CPU doesn't like that.
2137          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2138          * 383 on page 93. Intel should be safe but is also warns that it's
2139          * only safe if the permission and cache attributes of the two entries
2140          * loaded in the two TLB is identical (which should be the case here).
2141          * But it is generally safer to never allow small and huge TLB entries
2142          * for the same virtual address to be loaded simultaneously. So instead
2143          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2144          * current pmd notpresent (atomically because here the pmd_trans_huge
2145          * must remain set at all times on the pmd until the split is complete
2146          * for this pmd), then we flush the SMP TLB and finally we write the
2147          * non-huge version of the pmd entry with pmd_populate.
2148          */
2149         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2150
2151         pmd_migration = is_pmd_migration_entry(old_pmd);
2152         if (unlikely(pmd_migration)) {
2153                 swp_entry_t entry;
2154
2155                 entry = pmd_to_swp_entry(old_pmd);
2156                 page = pfn_to_page(swp_offset(entry));
2157                 write = is_write_migration_entry(entry);
2158                 young = false;
2159                 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2160         } else {
2161                 page = pmd_page(old_pmd);
2162                 if (pmd_dirty(old_pmd))
2163                         SetPageDirty(page);
2164                 write = pmd_write(old_pmd);
2165                 young = pmd_young(old_pmd);
2166                 soft_dirty = pmd_soft_dirty(old_pmd);
2167         }
2168         VM_BUG_ON_PAGE(!page_count(page), page);
2169         page_ref_add(page, HPAGE_PMD_NR - 1);
2170
2171         /*
2172          * Withdraw the table only after we mark the pmd entry invalid.
2173          * This's critical for some architectures (Power).
2174          */
2175         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2176         pmd_populate(mm, &_pmd, pgtable);
2177
2178         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2179                 pte_t entry, *pte;
2180                 /*
2181                  * Note that NUMA hinting access restrictions are not
2182                  * transferred to avoid any possibility of altering
2183                  * permissions across VMAs.
2184                  */
2185                 if (freeze || pmd_migration) {
2186                         swp_entry_t swp_entry;
2187                         swp_entry = make_migration_entry(page + i, write);
2188                         entry = swp_entry_to_pte(swp_entry);
2189                         if (soft_dirty)
2190                                 entry = pte_swp_mksoft_dirty(entry);
2191                 } else {
2192                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2193                         entry = maybe_mkwrite(entry, vma);
2194                         if (!write)
2195                                 entry = pte_wrprotect(entry);
2196                         if (!young)
2197                                 entry = pte_mkold(entry);
2198                         if (soft_dirty)
2199                                 entry = pte_mksoft_dirty(entry);
2200                 }
2201                 pte = pte_offset_map(&_pmd, addr);
2202                 BUG_ON(!pte_none(*pte));
2203                 set_pte_at(mm, addr, pte, entry);
2204                 atomic_inc(&page[i]._mapcount);
2205                 pte_unmap(pte);
2206         }
2207
2208         /*
2209          * Set PG_double_map before dropping compound_mapcount to avoid
2210          * false-negative page_mapped().
2211          */
2212         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2213                 for (i = 0; i < HPAGE_PMD_NR; i++)
2214                         atomic_inc(&page[i]._mapcount);
2215         }
2216
2217         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2218                 /* Last compound_mapcount is gone. */
2219                 __dec_node_page_state(page, NR_ANON_THPS);
2220                 if (TestClearPageDoubleMap(page)) {
2221                         /* No need in mapcount reference anymore */
2222                         for (i = 0; i < HPAGE_PMD_NR; i++)
2223                                 atomic_dec(&page[i]._mapcount);
2224                 }
2225         }
2226
2227         smp_wmb(); /* make pte visible before pmd */
2228         pmd_populate(mm, pmd, pgtable);
2229
2230         if (freeze) {
2231                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2232                         page_remove_rmap(page + i, false);
2233                         put_page(page + i);
2234                 }
2235         }
2236 }
2237
2238 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2239                 unsigned long address, bool freeze, struct page *page)
2240 {
2241         spinlock_t *ptl;
2242         struct mmu_notifier_range range;
2243
2244         mmu_notifier_range_init(&range, vma->vm_mm, address & HPAGE_PMD_MASK,
2245                                 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2246         mmu_notifier_invalidate_range_start(&range);
2247         ptl = pmd_lock(vma->vm_mm, pmd);
2248
2249         /*
2250          * If caller asks to setup a migration entries, we need a page to check
2251          * pmd against. Otherwise we can end up replacing wrong page.
2252          */
2253         VM_BUG_ON(freeze && !page);
2254         if (page && page != pmd_page(*pmd))
2255                 goto out;
2256
2257         if (pmd_trans_huge(*pmd)) {
2258                 page = pmd_page(*pmd);
2259                 if (PageMlocked(page))
2260                         clear_page_mlock(page);
2261         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2262                 goto out;
2263         __split_huge_pmd_locked(vma, pmd, range.start, freeze);
2264 out:
2265         spin_unlock(ptl);
2266         /*
2267          * No need to double call mmu_notifier->invalidate_range() callback.
2268          * They are 3 cases to consider inside __split_huge_pmd_locked():
2269          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2270          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2271          *    fault will trigger a flush_notify before pointing to a new page
2272          *    (it is fine if the secondary mmu keeps pointing to the old zero
2273          *    page in the meantime)
2274          *  3) Split a huge pmd into pte pointing to the same page. No need
2275          *     to invalidate secondary tlb entry they are all still valid.
2276          *     any further changes to individual pte will notify. So no need
2277          *     to call mmu_notifier->invalidate_range()
2278          */
2279         mmu_notifier_invalidate_range_only_end(&range);
2280 }
2281
2282 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2283                 bool freeze, struct page *page)
2284 {
2285         pgd_t *pgd;
2286         p4d_t *p4d;
2287         pud_t *pud;
2288         pmd_t *pmd;
2289
2290         pgd = pgd_offset(vma->vm_mm, address);
2291         if (!pgd_present(*pgd))
2292                 return;
2293
2294         p4d = p4d_offset(pgd, address);
2295         if (!p4d_present(*p4d))
2296                 return;
2297
2298         pud = pud_offset(p4d, address);
2299         if (!pud_present(*pud))
2300                 return;
2301
2302         pmd = pmd_offset(pud, address);
2303
2304         __split_huge_pmd(vma, pmd, address, freeze, page);
2305 }
2306
2307 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2308                              unsigned long start,
2309                              unsigned long end,
2310                              long adjust_next)
2311 {
2312         /*
2313          * If the new start address isn't hpage aligned and it could
2314          * previously contain an hugepage: check if we need to split
2315          * an huge pmd.
2316          */
2317         if (start & ~HPAGE_PMD_MASK &&
2318             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2319             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2320                 split_huge_pmd_address(vma, start, false, NULL);
2321
2322         /*
2323          * If the new end address isn't hpage aligned and it could
2324          * previously contain an hugepage: check if we need to split
2325          * an huge pmd.
2326          */
2327         if (end & ~HPAGE_PMD_MASK &&
2328             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2329             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2330                 split_huge_pmd_address(vma, end, false, NULL);
2331
2332         /*
2333          * If we're also updating the vma->vm_next->vm_start, if the new
2334          * vm_next->vm_start isn't page aligned and it could previously
2335          * contain an hugepage: check if we need to split an huge pmd.
2336          */
2337         if (adjust_next > 0) {
2338                 struct vm_area_struct *next = vma->vm_next;
2339                 unsigned long nstart = next->vm_start;
2340                 nstart += adjust_next << PAGE_SHIFT;
2341                 if (nstart & ~HPAGE_PMD_MASK &&
2342                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2343                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2344                         split_huge_pmd_address(next, nstart, false, NULL);
2345         }
2346 }
2347
2348 static void unmap_page(struct page *page)
2349 {
2350         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2351                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2352         bool unmap_success;
2353
2354         VM_BUG_ON_PAGE(!PageHead(page), page);
2355
2356         if (PageAnon(page))
2357                 ttu_flags |= TTU_SPLIT_FREEZE;
2358
2359         unmap_success = try_to_unmap(page, ttu_flags);
2360         VM_BUG_ON_PAGE(!unmap_success, page);
2361 }
2362
2363 static void remap_page(struct page *page)
2364 {
2365         int i;
2366         if (PageTransHuge(page)) {
2367                 remove_migration_ptes(page, page, true);
2368         } else {
2369                 for (i = 0; i < HPAGE_PMD_NR; i++)
2370                         remove_migration_ptes(page + i, page + i, true);
2371         }
2372 }
2373
2374 static void __split_huge_page_tail(struct page *head, int tail,
2375                 struct lruvec *lruvec, struct list_head *list)
2376 {
2377         struct page *page_tail = head + tail;
2378
2379         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2380
2381         /*
2382          * Clone page flags before unfreezing refcount.
2383          *
2384          * After successful get_page_unless_zero() might follow flags change,
2385          * for exmaple lock_page() which set PG_waiters.
2386          */
2387         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2388         page_tail->flags |= (head->flags &
2389                         ((1L << PG_referenced) |
2390                          (1L << PG_swapbacked) |
2391                          (1L << PG_swapcache) |
2392                          (1L << PG_mlocked) |
2393                          (1L << PG_uptodate) |
2394                          (1L << PG_active) |
2395                          (1L << PG_workingset) |
2396                          (1L << PG_locked) |
2397                          (1L << PG_unevictable) |
2398                          (1L << PG_dirty)));
2399
2400         /* ->mapping in first tail page is compound_mapcount */
2401         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2402                         page_tail);
2403         page_tail->mapping = head->mapping;
2404         page_tail->index = head->index + tail;
2405
2406         /* Page flags must be visible before we make the page non-compound. */
2407         smp_wmb();
2408
2409         /*
2410          * Clear PageTail before unfreezing page refcount.
2411          *
2412          * After successful get_page_unless_zero() might follow put_page()
2413          * which needs correct compound_head().
2414          */
2415         clear_compound_head(page_tail);
2416
2417         /* Finally unfreeze refcount. Additional reference from page cache. */
2418         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2419                                           PageSwapCache(head)));
2420
2421         if (page_is_young(head))
2422                 set_page_young(page_tail);
2423         if (page_is_idle(head))
2424                 set_page_idle(page_tail);
2425
2426         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2427
2428         /*
2429          * always add to the tail because some iterators expect new
2430          * pages to show after the currently processed elements - e.g.
2431          * migrate_pages
2432          */
2433         lru_add_page_tail(head, page_tail, lruvec, list);
2434 }
2435
2436 static void __split_huge_page(struct page *page, struct list_head *list,
2437                 pgoff_t end, unsigned long flags)
2438 {
2439         struct page *head = compound_head(page);
2440         struct zone *zone = page_zone(head);
2441         struct lruvec *lruvec;
2442         int i;
2443
2444         lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
2445
2446         /* complete memcg works before add pages to LRU */
2447         mem_cgroup_split_huge_fixup(head);
2448
2449         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2450                 __split_huge_page_tail(head, i, lruvec, list);
2451                 /* Some pages can be beyond i_size: drop them from page cache */
2452                 if (head[i].index >= end) {
2453                         ClearPageDirty(head + i);
2454                         __delete_from_page_cache(head + i, NULL);
2455                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2456                                 shmem_uncharge(head->mapping->host, 1);
2457                         put_page(head + i);
2458                 }
2459         }
2460
2461         ClearPageCompound(head);
2462         /* See comment in __split_huge_page_tail() */
2463         if (PageAnon(head)) {
2464                 /* Additional pin to swap cache */
2465                 if (PageSwapCache(head))
2466                         page_ref_add(head, 2);
2467                 else
2468                         page_ref_inc(head);
2469         } else {
2470                 /* Additional pin to page cache */
2471                 page_ref_add(head, 2);
2472                 xa_unlock(&head->mapping->i_pages);
2473         }
2474
2475         spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2476
2477         remap_page(head);
2478
2479         for (i = 0; i < HPAGE_PMD_NR; i++) {
2480                 struct page *subpage = head + i;
2481                 if (subpage == page)
2482                         continue;
2483                 unlock_page(subpage);
2484
2485                 /*
2486                  * Subpages may be freed if there wasn't any mapping
2487                  * like if add_to_swap() is running on a lru page that
2488                  * had its mapping zapped. And freeing these pages
2489                  * requires taking the lru_lock so we do the put_page
2490                  * of the tail pages after the split is complete.
2491                  */
2492                 put_page(subpage);
2493         }
2494 }
2495
2496 int total_mapcount(struct page *page)
2497 {
2498         int i, compound, ret;
2499
2500         VM_BUG_ON_PAGE(PageTail(page), page);
2501
2502         if (likely(!PageCompound(page)))
2503                 return atomic_read(&page->_mapcount) + 1;
2504
2505         compound = compound_mapcount(page);
2506         if (PageHuge(page))
2507                 return compound;
2508         ret = compound;
2509         for (i = 0; i < HPAGE_PMD_NR; i++)
2510                 ret += atomic_read(&page[i]._mapcount) + 1;
2511         /* File pages has compound_mapcount included in _mapcount */
2512         if (!PageAnon(page))
2513                 return ret - compound * HPAGE_PMD_NR;
2514         if (PageDoubleMap(page))
2515                 ret -= HPAGE_PMD_NR;
2516         return ret;
2517 }
2518
2519 /*
2520  * This calculates accurately how many mappings a transparent hugepage
2521  * has (unlike page_mapcount() which isn't fully accurate). This full
2522  * accuracy is primarily needed to know if copy-on-write faults can
2523  * reuse the page and change the mapping to read-write instead of
2524  * copying them. At the same time this returns the total_mapcount too.
2525  *
2526  * The function returns the highest mapcount any one of the subpages
2527  * has. If the return value is one, even if different processes are
2528  * mapping different subpages of the transparent hugepage, they can
2529  * all reuse it, because each process is reusing a different subpage.
2530  *
2531  * The total_mapcount is instead counting all virtual mappings of the
2532  * subpages. If the total_mapcount is equal to "one", it tells the
2533  * caller all mappings belong to the same "mm" and in turn the
2534  * anon_vma of the transparent hugepage can become the vma->anon_vma
2535  * local one as no other process may be mapping any of the subpages.
2536  *
2537  * It would be more accurate to replace page_mapcount() with
2538  * page_trans_huge_mapcount(), however we only use
2539  * page_trans_huge_mapcount() in the copy-on-write faults where we
2540  * need full accuracy to avoid breaking page pinning, because
2541  * page_trans_huge_mapcount() is slower than page_mapcount().
2542  */
2543 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2544 {
2545         int i, ret, _total_mapcount, mapcount;
2546
2547         /* hugetlbfs shouldn't call it */
2548         VM_BUG_ON_PAGE(PageHuge(page), page);
2549
2550         if (likely(!PageTransCompound(page))) {
2551                 mapcount = atomic_read(&page->_mapcount) + 1;
2552                 if (total_mapcount)
2553                         *total_mapcount = mapcount;
2554                 return mapcount;
2555         }
2556
2557         page = compound_head(page);
2558
2559         _total_mapcount = ret = 0;
2560         for (i = 0; i < HPAGE_PMD_NR; i++) {
2561                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2562                 ret = max(ret, mapcount);
2563                 _total_mapcount += mapcount;
2564         }
2565         if (PageDoubleMap(page)) {
2566                 ret -= 1;
2567                 _total_mapcount -= HPAGE_PMD_NR;
2568         }
2569         mapcount = compound_mapcount(page);
2570         ret += mapcount;
2571         _total_mapcount += mapcount;
2572         if (total_mapcount)
2573                 *total_mapcount = _total_mapcount;
2574         return ret;
2575 }
2576
2577 /* Racy check whether the huge page can be split */
2578 bool can_split_huge_page(struct page *page, int *pextra_pins)
2579 {
2580         int extra_pins;
2581
2582         /* Additional pins from page cache */
2583         if (PageAnon(page))
2584                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2585         else
2586                 extra_pins = HPAGE_PMD_NR;
2587         if (pextra_pins)
2588                 *pextra_pins = extra_pins;
2589         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2590 }
2591
2592 /*
2593  * This function splits huge page into normal pages. @page can point to any
2594  * subpage of huge page to split. Split doesn't change the position of @page.
2595  *
2596  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2597  * The huge page must be locked.
2598  *
2599  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2600  *
2601  * Both head page and tail pages will inherit mapping, flags, and so on from
2602  * the hugepage.
2603  *
2604  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2605  * they are not mapped.
2606  *
2607  * Returns 0 if the hugepage is split successfully.
2608  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2609  * us.
2610  */
2611 int split_huge_page_to_list(struct page *page, struct list_head *list)
2612 {
2613         struct page *head = compound_head(page);
2614         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2615         struct anon_vma *anon_vma = NULL;
2616         struct address_space *mapping = NULL;
2617         int count, mapcount, extra_pins, ret;
2618         bool mlocked;
2619         unsigned long flags;
2620         pgoff_t end;
2621
2622         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2623         VM_BUG_ON_PAGE(!PageLocked(page), page);
2624         VM_BUG_ON_PAGE(!PageCompound(page), page);
2625
2626         if (PageWriteback(page))
2627                 return -EBUSY;
2628
2629         if (PageAnon(head)) {
2630                 /*
2631                  * The caller does not necessarily hold an mmap_sem that would
2632                  * prevent the anon_vma disappearing so we first we take a
2633                  * reference to it and then lock the anon_vma for write. This
2634                  * is similar to page_lock_anon_vma_read except the write lock
2635                  * is taken to serialise against parallel split or collapse
2636                  * operations.
2637                  */
2638                 anon_vma = page_get_anon_vma(head);
2639                 if (!anon_vma) {
2640                         ret = -EBUSY;
2641                         goto out;
2642                 }
2643                 end = -1;
2644                 mapping = NULL;
2645                 anon_vma_lock_write(anon_vma);
2646         } else {
2647                 mapping = head->mapping;
2648
2649                 /* Truncated ? */
2650                 if (!mapping) {
2651                         ret = -EBUSY;
2652                         goto out;
2653                 }
2654
2655                 anon_vma = NULL;
2656                 i_mmap_lock_read(mapping);
2657
2658                 /*
2659                  *__split_huge_page() may need to trim off pages beyond EOF:
2660                  * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2661                  * which cannot be nested inside the page tree lock. So note
2662                  * end now: i_size itself may be changed at any moment, but
2663                  * head page lock is good enough to serialize the trimming.
2664                  */
2665                 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2666         }
2667
2668         /*
2669          * Racy check if we can split the page, before unmap_page() will
2670          * split PMDs
2671          */
2672         if (!can_split_huge_page(head, &extra_pins)) {
2673                 ret = -EBUSY;
2674                 goto out_unlock;
2675         }
2676
2677         mlocked = PageMlocked(page);
2678         unmap_page(head);
2679         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2680
2681         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2682         if (mlocked)
2683                 lru_add_drain();
2684
2685         /* prevent PageLRU to go away from under us, and freeze lru stats */
2686         spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2687
2688         if (mapping) {
2689                 XA_STATE(xas, &mapping->i_pages, page_index(head));
2690
2691                 /*
2692                  * Check if the head page is present in page cache.
2693                  * We assume all tail are present too, if head is there.
2694                  */
2695                 xa_lock(&mapping->i_pages);
2696                 if (xas_load(&xas) != head)
2697                         goto fail;
2698         }
2699
2700         /* Prevent deferred_split_scan() touching ->_refcount */
2701         spin_lock(&pgdata->split_queue_lock);
2702         count = page_count(head);
2703         mapcount = total_mapcount(head);
2704         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2705                 if (!list_empty(page_deferred_list(head))) {
2706                         pgdata->split_queue_len--;
2707                         list_del(page_deferred_list(head));
2708                 }
2709                 if (mapping)
2710                         __dec_node_page_state(page, NR_SHMEM_THPS);
2711                 spin_unlock(&pgdata->split_queue_lock);
2712                 __split_huge_page(page, list, end, flags);
2713                 if (PageSwapCache(head)) {
2714                         swp_entry_t entry = { .val = page_private(head) };
2715
2716                         ret = split_swap_cluster(entry);
2717                 } else
2718                         ret = 0;
2719         } else {
2720                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2721                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2722                                         mapcount, count);
2723                         if (PageTail(page))
2724                                 dump_page(head, NULL);
2725                         dump_page(page, "total_mapcount(head) > 0");
2726                         BUG();
2727                 }
2728                 spin_unlock(&pgdata->split_queue_lock);
2729 fail:           if (mapping)
2730                         xa_unlock(&mapping->i_pages);
2731                 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2732                 remap_page(head);
2733                 ret = -EBUSY;
2734         }
2735
2736 out_unlock:
2737         if (anon_vma) {
2738                 anon_vma_unlock_write(anon_vma);
2739                 put_anon_vma(anon_vma);
2740         }
2741         if (mapping)
2742                 i_mmap_unlock_read(mapping);
2743 out:
2744         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2745         return ret;
2746 }
2747
2748 void free_transhuge_page(struct page *page)
2749 {
2750         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2751         unsigned long flags;
2752
2753         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2754         if (!list_empty(page_deferred_list(page))) {
2755                 pgdata->split_queue_len--;
2756                 list_del(page_deferred_list(page));
2757         }
2758         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2759         free_compound_page(page);
2760 }
2761
2762 void deferred_split_huge_page(struct page *page)
2763 {
2764         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2765         unsigned long flags;
2766
2767         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2768
2769         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2770         if (list_empty(page_deferred_list(page))) {
2771                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2772                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2773                 pgdata->split_queue_len++;
2774         }
2775         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2776 }
2777
2778 static unsigned long deferred_split_count(struct shrinker *shrink,
2779                 struct shrink_control *sc)
2780 {
2781         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2782         return READ_ONCE(pgdata->split_queue_len);
2783 }
2784
2785 static unsigned long deferred_split_scan(struct shrinker *shrink,
2786                 struct shrink_control *sc)
2787 {
2788         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2789         unsigned long flags;
2790         LIST_HEAD(list), *pos, *next;
2791         struct page *page;
2792         int split = 0;
2793
2794         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2795         /* Take pin on all head pages to avoid freeing them under us */
2796         list_for_each_safe(pos, next, &pgdata->split_queue) {
2797                 page = list_entry((void *)pos, struct page, mapping);
2798                 page = compound_head(page);
2799                 if (get_page_unless_zero(page)) {
2800                         list_move(page_deferred_list(page), &list);
2801                 } else {
2802                         /* We lost race with put_compound_page() */
2803                         list_del_init(page_deferred_list(page));
2804                         pgdata->split_queue_len--;
2805                 }
2806                 if (!--sc->nr_to_scan)
2807                         break;
2808         }
2809         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2810
2811         list_for_each_safe(pos, next, &list) {
2812                 page = list_entry((void *)pos, struct page, mapping);
2813                 if (!trylock_page(page))
2814                         goto next;
2815                 /* split_huge_page() removes page from list on success */
2816                 if (!split_huge_page(page))
2817                         split++;
2818                 unlock_page(page);
2819 next:
2820                 put_page(page);
2821         }
2822
2823         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2824         list_splice_tail(&list, &pgdata->split_queue);
2825         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2826
2827         /*
2828          * Stop shrinker if we didn't split any page, but the queue is empty.
2829          * This can happen if pages were freed under us.
2830          */
2831         if (!split && list_empty(&pgdata->split_queue))
2832                 return SHRINK_STOP;
2833         return split;
2834 }
2835
2836 static struct shrinker deferred_split_shrinker = {
2837         .count_objects = deferred_split_count,
2838         .scan_objects = deferred_split_scan,
2839         .seeks = DEFAULT_SEEKS,
2840         .flags = SHRINKER_NUMA_AWARE,
2841 };
2842
2843 #ifdef CONFIG_DEBUG_FS
2844 static int split_huge_pages_set(void *data, u64 val)
2845 {
2846         struct zone *zone;
2847         struct page *page;
2848         unsigned long pfn, max_zone_pfn;
2849         unsigned long total = 0, split = 0;
2850
2851         if (val != 1)
2852                 return -EINVAL;
2853
2854         for_each_populated_zone(zone) {
2855                 max_zone_pfn = zone_end_pfn(zone);
2856                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2857                         if (!pfn_valid(pfn))
2858                                 continue;
2859
2860                         page = pfn_to_page(pfn);
2861                         if (!get_page_unless_zero(page))
2862                                 continue;
2863
2864                         if (zone != page_zone(page))
2865                                 goto next;
2866
2867                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2868                                 goto next;
2869
2870                         total++;
2871                         lock_page(page);
2872                         if (!split_huge_page(page))
2873                                 split++;
2874                         unlock_page(page);
2875 next:
2876                         put_page(page);
2877                 }
2878         }
2879
2880         pr_info("%lu of %lu THP split\n", split, total);
2881
2882         return 0;
2883 }
2884 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2885                 "%llu\n");
2886
2887 static int __init split_huge_pages_debugfs(void)
2888 {
2889         void *ret;
2890
2891         ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2892                         &split_huge_pages_fops);
2893         if (!ret)
2894                 pr_warn("Failed to create split_huge_pages in debugfs");
2895         return 0;
2896 }
2897 late_initcall(split_huge_pages_debugfs);
2898 #endif
2899
2900 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2901 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2902                 struct page *page)
2903 {
2904         struct vm_area_struct *vma = pvmw->vma;
2905         struct mm_struct *mm = vma->vm_mm;
2906         unsigned long address = pvmw->address;
2907         pmd_t pmdval;
2908         swp_entry_t entry;
2909         pmd_t pmdswp;
2910
2911         if (!(pvmw->pmd && !pvmw->pte))
2912                 return;
2913
2914         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2915         pmdval = *pvmw->pmd;
2916         pmdp_invalidate(vma, address, pvmw->pmd);
2917         if (pmd_dirty(pmdval))
2918                 set_page_dirty(page);
2919         entry = make_migration_entry(page, pmd_write(pmdval));
2920         pmdswp = swp_entry_to_pmd(entry);
2921         if (pmd_soft_dirty(pmdval))
2922                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2923         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2924         page_remove_rmap(page, true);
2925         put_page(page);
2926 }
2927
2928 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2929 {
2930         struct vm_area_struct *vma = pvmw->vma;
2931         struct mm_struct *mm = vma->vm_mm;
2932         unsigned long address = pvmw->address;
2933         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2934         pmd_t pmde;
2935         swp_entry_t entry;
2936
2937         if (!(pvmw->pmd && !pvmw->pte))
2938                 return;
2939
2940         entry = pmd_to_swp_entry(*pvmw->pmd);
2941         get_page(new);
2942         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2943         if (pmd_swp_soft_dirty(*pvmw->pmd))
2944                 pmde = pmd_mksoft_dirty(pmde);
2945         if (is_write_migration_entry(entry))
2946                 pmde = maybe_pmd_mkwrite(pmde, vma);
2947
2948         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2949         if (PageAnon(new))
2950                 page_add_anon_rmap(new, vma, mmun_start, true);
2951         else
2952                 page_add_file_rmap(new, true);
2953         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
2954         if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
2955                 mlock_vma_page(new);
2956         update_mmu_cache_pmd(vma, address, pvmw->pmd);
2957 }
2958 #endif