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 static struct page *get_huge_zero_page(void)
  66 {
  67         struct page *zero_page;
  68 retry:
  69         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
  70                 return READ_ONCE(huge_zero_page);
  71
  72         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
  73                         HPAGE_PMD_ORDER);
  74         if (!zero_page) {
  75                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
  76                 return NULL;
  77         }
  78         count_vm_event(THP_ZERO_PAGE_ALLOC);
  79         preempt_disable();
  80         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
  81                 preempt_enable();
  82                 __free_pages(zero_page, compound_order(zero_page));
  83                 goto retry;
  84         }
  85
  86         /* We take additional reference here. It will be put back by shrinker */
  87         atomic_set(&huge_zero_refcount, 2);
  88         preempt_enable();
  89         return READ_ONCE(huge_zero_page);
  90 }
  91
  92 static void put_huge_zero_page(void)
  93 {
  94         /*
  95          * Counter should never go to zero here. Only shrinker can put
  96          * last reference.
  97          */
  98         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
  99 }
 100
 101 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
 102 {
 103         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 104                 return READ_ONCE(huge_zero_page);
 105
 106         if (!get_huge_zero_page())
 107                 return NULL;
 108
 109         if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 110                 put_huge_zero_page();
 111
 112         return READ_ONCE(huge_zero_page);
 113 }
 114
 115 void mm_put_huge_zero_page(struct mm_struct *mm)
 116 {
 117         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 118                 put_huge_zero_page();
 119 }
 120
 121 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
 122                                         struct shrink_control *sc)
 123 {
 124         /* we can free zero page only if last reference remains */
 125         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 126 }
 127
 128 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 129                                        struct shrink_control *sc)
 130 {
 131         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 132                 struct page *zero_page = xchg(&huge_zero_page, NULL);
 133                 BUG_ON(zero_page == NULL);
 134                 __free_pages(zero_page, compound_order(zero_page));
 135                 return HPAGE_PMD_NR;
 136         }
 137
 138         return 0;
 139 }
 140
 141 static struct shrinker huge_zero_page_shrinker = {
 142         .count_objects = shrink_huge_zero_page_count,
 143         .scan_objects = shrink_huge_zero_page_scan,
 144         .seeks = DEFAULT_SEEKS,
 145 };
 146
 147 #ifdef CONFIG_SYSFS
 148 static ssize_t enabled_show(struct kobject *kobj,
 149                             struct kobj_attribute *attr, char *buf)
 150 {
 151         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
 152                 return sprintf(buf, "[always] madvise never\n");
 153         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
 154                 return sprintf(buf, "always [madvise] never\n");
 155         else
 156                 return sprintf(buf, "always madvise [never]\n");
 157 }
 158
 159 static ssize_t enabled_store(struct kobject *kobj,
 160                              struct kobj_attribute *attr,
 161                              const char *buf, size_t count)
 162 {
 163         ssize_t ret = count;
 164
 165         if (!memcmp("always", buf,
 166                     min(sizeof("always")-1, count))) {
 167                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 168                 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 169         } else if (!memcmp("madvise", buf,
 170                            min(sizeof("madvise")-1, count))) {
 171                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 172                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 173         } else if (!memcmp("never", buf,
 174                            min(sizeof("never")-1, count))) {
 175                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 176                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 177         } else
 178                 ret = -EINVAL;
 179
 180         if (ret > 0) {
 181                 int err = start_stop_khugepaged();
 182                 if (err)
 183                         ret = err;
 184         }
 185         return ret;
 186 }
 187 static struct kobj_attribute enabled_attr =
 188         __ATTR(enabled, 0644, enabled_show, enabled_store);
 189
 190 ssize_t single_hugepage_flag_show(struct kobject *kobj,
 191                                 struct kobj_attribute *attr, char *buf,
 192                                 enum transparent_hugepage_flag flag)
 193 {
 194         return sprintf(buf, "%d\n",
 195                        !!test_bit(flag, &transparent_hugepage_flags));
 196 }
 197
 198 ssize_t single_hugepage_flag_store(struct kobject *kobj,
 199                                  struct kobj_attribute *attr,
 200                                  const char *buf, size_t count,
 201                                  enum transparent_hugepage_flag flag)
 202 {
 203         unsigned long value;
 204         int ret;
 205
 206         ret = kstrtoul(buf, 10, &value);
 207         if (ret < 0)
 208                 return ret;
 209         if (value > 1)
 210                 return -EINVAL;
 211
 212         if (value)
 213                 set_bit(flag, &transparent_hugepage_flags);
 214         else
 215                 clear_bit(flag, &transparent_hugepage_flags);
 216
 217         return count;
 218 }
 219
 220 static ssize_t defrag_show(struct kobject *kobj,
 221                            struct kobj_attribute *attr, char *buf)
 222 {
 223         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 224                 return sprintf(buf, "[always] defer defer+madvise madvise never\n");
 225         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 226                 return sprintf(buf, "always [defer] defer+madvise madvise never\n");
 227         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 228                 return sprintf(buf, "always defer [defer+madvise] madvise never\n");
 229         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 230                 return sprintf(buf, "always defer defer+madvise [madvise] never\n");
 231         return sprintf(buf, "always defer defer+madvise madvise [never]\n");
 232 }
 233
 234 static ssize_t defrag_store(struct kobject *kobj,
 235                             struct kobj_attribute *attr,
 236                             const char *buf, size_t count)
 237 {
 238         if (!memcmp("always", buf,
 239                     min(sizeof("always")-1, count))) {
 240                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 241                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 242                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 243                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 244         } else if (!memcmp("defer+madvise", buf,
 245                     min(sizeof("defer+madvise")-1, count))) {
 246                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 247                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 248                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 249                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 250         } else if (!memcmp("defer", buf,
 251                     min(sizeof("defer")-1, count))) {
 252                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 253                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 254                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 255                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 256         } else if (!memcmp("madvise", buf,
 257                            min(sizeof("madvise")-1, count))) {
 258                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 259                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 260                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 261                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 262         } else if (!memcmp("never", buf,
 263                            min(sizeof("never")-1, count))) {
 264                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 265                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 266                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 267                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 268         } else
 269                 return -EINVAL;
 270
 271         return count;
 272 }
 273 static struct kobj_attribute defrag_attr =
 274         __ATTR(defrag, 0644, defrag_show, defrag_store);
 275
 276 static ssize_t use_zero_page_show(struct kobject *kobj,
 277                 struct kobj_attribute *attr, char *buf)
 278 {
 279         return single_hugepage_flag_show(kobj, attr, buf,
 280                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 281 }
 282 static ssize_t use_zero_page_store(struct kobject *kobj,
 283                 struct kobj_attribute *attr, const char *buf, size_t count)
 284 {
 285         return single_hugepage_flag_store(kobj, attr, buf, count,
 286                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 287 }
 288 static struct kobj_attribute use_zero_page_attr =
 289         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 290
 291 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
 292                 struct kobj_attribute *attr, char *buf)
 293 {
 294         return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
 295 }
 296 static struct kobj_attribute hpage_pmd_size_attr =
 297         __ATTR_RO(hpage_pmd_size);
 298
 299 #ifdef CONFIG_DEBUG_VM
 300 static ssize_t debug_cow_show(struct kobject *kobj,
 301                                 struct kobj_attribute *attr, char *buf)
 302 {
 303         return single_hugepage_flag_show(kobj, attr, buf,
 304                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 305 }
 306 static ssize_t debug_cow_store(struct kobject *kobj,
 307                                struct kobj_attribute *attr,
 308                                const char *buf, size_t count)
 309 {
 310         return single_hugepage_flag_store(kobj, attr, buf, count,
 311                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 312 }
 313 static struct kobj_attribute debug_cow_attr =
 314         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 315 #endif /* CONFIG_DEBUG_VM */
 316
 317 static struct attribute *hugepage_attr[] = {
 318         &enabled_attr.attr,
 319         &defrag_attr.attr,
 320         &use_zero_page_attr.attr,
 321         &hpage_pmd_size_attr.attr,
 322 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
 323         &shmem_enabled_attr.attr,
 324 #endif
 325 #ifdef CONFIG_DEBUG_VM
 326         &debug_cow_attr.attr,
 327 #endif
 328         NULL,
 329 };
 330
 331 static const struct attribute_group hugepage_attr_group = {
 332         .attrs = hugepage_attr,
 333 };
 334
 335 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 336 {
 337         int err;
 338
 339         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 340         if (unlikely(!*hugepage_kobj)) {
 341                 pr_err("failed to create transparent hugepage kobject\n");
 342                 return -ENOMEM;
 343         }
 344
 345         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 346         if (err) {
 347                 pr_err("failed to register transparent hugepage group\n");
 348                 goto delete_obj;
 349         }
 350
 351         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 352         if (err) {
 353                 pr_err("failed to register transparent hugepage group\n");
 354                 goto remove_hp_group;
 355         }
 356
 357         return 0;
 358
 359 remove_hp_group:
 360         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 361 delete_obj:
 362         kobject_put(*hugepage_kobj);
 363         return err;
 364 }
 365
 366 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 367 {
 368         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 369         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 370         kobject_put(hugepage_kobj);
 371 }
 372 #else
 373 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 374 {
 375         return 0;
 376 }
 377
 378 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 379 {
 380 }
 381 #endif /* CONFIG_SYSFS */
 382
 383 static int __init hugepage_init(void)
 384 {
 385         int err;
 386         struct kobject *hugepage_kobj;
 387
 388         if (!has_transparent_hugepage()) {
 389                 transparent_hugepage_flags = 0;
 390                 return -EINVAL;
 391         }
 392
 393         /*
 394          * hugepages can't be allocated by the buddy allocator
 395          */
 396         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
 397         /*
 398          * we use page->mapping and page->index in second tail page
 399          * as list_head: assuming THP order >= 2
 400          */
 401         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
 402
 403         err = hugepage_init_sysfs(&hugepage_kobj);
 404         if (err)
 405                 goto err_sysfs;
 406
 407         err = khugepaged_init();
 408         if (err)
 409                 goto err_slab;
 410
 411         err = register_shrinker(&huge_zero_page_shrinker);
 412         if (err)
 413                 goto err_hzp_shrinker;
 414         err = register_shrinker(&deferred_split_shrinker);
 415         if (err)
 416                 goto err_split_shrinker;
 417
 418         /*
 419          * By default disable transparent hugepages on smaller systems,
 420          * where the extra memory used could hurt more than TLB overhead
 421          * is likely to save.  The admin can still enable it through /sys.
 422          */
 423         if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
 424                 transparent_hugepage_flags = 0;
 425                 return 0;
 426         }
 427
 428         err = start_stop_khugepaged();
 429         if (err)
 430                 goto err_khugepaged;
 431
 432         return 0;
 433 err_khugepaged:
 434         unregister_shrinker(&deferred_split_shrinker);
 435 err_split_shrinker:
 436         unregister_shrinker(&huge_zero_page_shrinker);
 437 err_hzp_shrinker:
 438         khugepaged_destroy();
 439 err_slab:
 440         hugepage_exit_sysfs(hugepage_kobj);
 441 err_sysfs:
 442         return err;
 443 }
 444 subsys_initcall(hugepage_init);
 445
 446 static int __init setup_transparent_hugepage(char *str)
 447 {
 448         int ret = 0;
 449         if (!str)
 450                 goto out;
 451         if (!strcmp(str, "always")) {
 452                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 453                         &transparent_hugepage_flags);
 454                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 455                           &transparent_hugepage_flags);
 456                 ret = 1;
 457         } else if (!strcmp(str, "madvise")) {
 458                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 459                           &transparent_hugepage_flags);
 460                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 461                         &transparent_hugepage_flags);
 462                 ret = 1;
 463         } else if (!strcmp(str, "never")) {
 464                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 465                           &transparent_hugepage_flags);
 466                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 467                           &transparent_hugepage_flags);
 468                 ret = 1;
 469         }
 470 out:
 471         if (!ret)
 472                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
 473         return ret;
 474 }
 475 __setup("transparent_hugepage=", setup_transparent_hugepage);
 476
 477 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 478 {
 479         if (likely(vma->vm_flags & VM_WRITE))
 480                 pmd = pmd_mkwrite(pmd);
 481         return pmd;
 482 }
 483
 484 static inline struct list_head *page_deferred_list(struct page *page)
 485 {
 486         /* ->lru in the tail pages is occupied by compound_head. */
 487         return &page[2].deferred_list;
 488 }
 489
 490 void prep_transhuge_page(struct page *page)
 491 {
 492         /*
 493          * we use page->mapping and page->indexlru in second tail page
 494          * as list_head: assuming THP order >= 2
 495          */
 496
 497         INIT_LIST_HEAD(page_deferred_list(page));
 498         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 499 }
 500
 501 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
 502                 loff_t off, unsigned long flags, unsigned long size)
 503 {
 504         unsigned long addr;
 505         loff_t off_end = off + len;
 506         loff_t off_align = round_up(off, size);
 507         unsigned long len_pad;
 508
 509         if (off_end <= off_align || (off_end - off_align) < size)
 510                 return 0;
 511
 512         len_pad = len + size;
 513         if (len_pad < len || (off + len_pad) < off)
 514                 return 0;
 515
 516         addr = current->mm->get_unmapped_area(filp, 0, len_pad,
 517                                               off >> PAGE_SHIFT, flags);
 518         if (IS_ERR_VALUE(addr))
 519                 return 0;
 520
 521         addr += (off - addr) & (size - 1);
 522         return addr;
 523 }
 524
 525 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 526                 unsigned long len, unsigned long pgoff, unsigned long flags)
 527 {
 528         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 529
 530         if (addr)
 531                 goto out;
 532         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
 533                 goto out;
 534
 535         addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
 536         if (addr)
 537                 return addr;
 538
 539  out:
 540         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 541 }
 542 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 543
 544 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
 545                         struct page *page, gfp_t gfp)
 546 {
 547         struct vm_area_struct *vma = vmf->vma;
 548         struct mem_cgroup *memcg;
 549         pgtable_t pgtable;
 550         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 551         vm_fault_t ret = 0;
 552
 553         VM_BUG_ON_PAGE(!PageCompound(page), page);
 554
 555         if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
 556                 put_page(page);
 557                 count_vm_event(THP_FAULT_FALLBACK);
 558                 return VM_FAULT_FALLBACK;
 559         }
 560
 561         pgtable = pte_alloc_one(vma->vm_mm, haddr);
 562         if (unlikely(!pgtable)) {
 563                 ret = VM_FAULT_OOM;
 564                 goto release;
 565         }
 566
 567         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
 568         /*
 569          * The memory barrier inside __SetPageUptodate makes sure that
 570          * clear_huge_page writes become visible before the set_pmd_at()
 571          * write.
 572          */
 573         __SetPageUptodate(page);
 574
 575         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 576         if (unlikely(!pmd_none(*vmf->pmd))) {
 577                 goto unlock_release;
 578         } else {
 579                 pmd_t entry;
 580
 581                 ret = check_stable_address_space(vma->vm_mm);
 582                 if (ret)
 583                         goto unlock_release;
 584
 585                 /* Deliver the page fault to userland */
 586                 if (userfaultfd_missing(vma)) {
 587                         vm_fault_t ret2;
 588
 589                         spin_unlock(vmf->ptl);
 590                         mem_cgroup_cancel_charge(page, memcg, true);
 591                         put_page(page);
 592                         pte_free(vma->vm_mm, pgtable);
 593                         ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
 594                         VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
 595                         return ret2;
 596                 }
 597
 598                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 599                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 600                 page_add_new_anon_rmap(page, vma, haddr, true);
 601                 mem_cgroup_commit_charge(page, memcg, false, true);
 602                 lru_cache_add_active_or_unevictable(page, vma);
 603                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 604                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 605                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 606                 mm_inc_nr_ptes(vma->vm_mm);
 607                 spin_unlock(vmf->ptl);
 608                 count_vm_event(THP_FAULT_ALLOC);
 609         }
 610
 611         return 0;
 612 unlock_release:
 613         spin_unlock(vmf->ptl);
 614 release:
 615         if (pgtable)
 616                 pte_free(vma->vm_mm, pgtable);
 617         mem_cgroup_cancel_charge(page, memcg, true);
 618         put_page(page);
 619         return ret;
 620
 621 }
 622
 623 /*
 624  * always: directly stall for all thp allocations
 625  * defer: wake kswapd and fail if not immediately available
 626  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
 627  *                fail if not immediately available
 628  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
 629  *          available
 630  * never: never stall for any thp allocation
 631  */
 632 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
 633 {
 634         const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
 635
 636         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 637                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
 638         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 639                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
 640         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 641                 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
 642                                                              __GFP_KSWAPD_RECLAIM);
 643         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 644                 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
 645                                                              0);
 646         return GFP_TRANSHUGE_LIGHT;
 647 }
 648
 649 /* Caller must hold page table lock. */
 650 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 651                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 652                 struct page *zero_page)
 653 {
 654         pmd_t entry;
 655         if (!pmd_none(*pmd))
 656                 return false;
 657         entry = mk_pmd(zero_page, vma->vm_page_prot);
 658         entry = pmd_mkhuge(entry);
 659         if (pgtable)
 660                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 661         set_pmd_at(mm, haddr, pmd, entry);
 662         mm_inc_nr_ptes(mm);
 663         return true;
 664 }
 665
 666 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 667 {
 668         struct vm_area_struct *vma = vmf->vma;
 669         gfp_t gfp;
 670         struct page *page;
 671         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 672
 673         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
 674                 return VM_FAULT_FALLBACK;
 675         if (unlikely(anon_vma_prepare(vma)))
 676                 return VM_FAULT_OOM;
 677         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 678                 return VM_FAULT_OOM;
 679         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
 680                         !mm_forbids_zeropage(vma->vm_mm) &&
 681                         transparent_hugepage_use_zero_page()) {
 682                 pgtable_t pgtable;
 683                 struct page *zero_page;
 684                 bool set;
 685                 vm_fault_t ret;
 686                 pgtable = pte_alloc_one(vma->vm_mm, haddr);
 687                 if (unlikely(!pgtable))
 688                         return VM_FAULT_OOM;
 689                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
 690                 if (unlikely(!zero_page)) {
 691                         pte_free(vma->vm_mm, pgtable);
 692                         count_vm_event(THP_FAULT_FALLBACK);
 693                         return VM_FAULT_FALLBACK;
 694                 }
 695                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 696                 ret = 0;
 697                 set = false;
 698                 if (pmd_none(*vmf->pmd)) {
 699                         ret = check_stable_address_space(vma->vm_mm);
 700                         if (ret) {
 701                                 spin_unlock(vmf->ptl);
 702                         } else if (userfaultfd_missing(vma)) {
 703                                 spin_unlock(vmf->ptl);
 704                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
 705                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 706                         } else {
 707                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
 708                                                    haddr, vmf->pmd, zero_page);
 709                                 spin_unlock(vmf->ptl);
 710                                 set = true;
 711                         }
 712                 } else
 713                         spin_unlock(vmf->ptl);
 714                 if (!set)
 715                         pte_free(vma->vm_mm, pgtable);
 716                 return ret;
 717         }
 718         gfp = alloc_hugepage_direct_gfpmask(vma);
 719         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 720         if (unlikely(!page)) {
 721                 count_vm_event(THP_FAULT_FALLBACK);
 722                 return VM_FAULT_FALLBACK;
 723         }
 724         prep_transhuge_page(page);
 725         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
 726 }
 727
 728 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 729                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
 730                 pgtable_t pgtable)
 731 {
 732         struct mm_struct *mm = vma->vm_mm;
 733         pmd_t entry;
 734         spinlock_t *ptl;
 735
 736         ptl = pmd_lock(mm, pmd);
 737         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 738         if (pfn_t_devmap(pfn))
 739                 entry = pmd_mkdevmap(entry);
 740         if (write) {
 741                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 742                 entry = maybe_pmd_mkwrite(entry, vma);
 743         }
 744
 745         if (pgtable) {
 746                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 747                 mm_inc_nr_ptes(mm);
 748         }
 749
 750         set_pmd_at(mm, addr, pmd, entry);
 751         update_mmu_cache_pmd(vma, addr, pmd);
 752         spin_unlock(ptl);
 753 }
 754
 755 vm_fault_t vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 756                         pmd_t *pmd, pfn_t pfn, bool write)
 757 {
 758         pgprot_t pgprot = vma->vm_page_prot;
 759         pgtable_t pgtable = NULL;
 760         /*
 761          * If we had pmd_special, we could avoid all these restrictions,
 762          * but we need to be consistent with PTEs and architectures that
 763          * can't support a 'special' bit.
 764          */
 765         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 766                         !pfn_t_devmap(pfn));
 767         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 768                                                 (VM_PFNMAP|VM_MIXEDMAP));
 769         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 770
 771         if (addr < vma->vm_start || addr >= vma->vm_end)
 772                 return VM_FAULT_SIGBUS;
 773
 774         if (arch_needs_pgtable_deposit()) {
 775                 pgtable = pte_alloc_one(vma->vm_mm, addr);
 776                 if (!pgtable)
 777                         return VM_FAULT_OOM;
 778         }
 779
 780         track_pfn_insert(vma, &pgprot, pfn);
 781
 782         insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable);
 783         return VM_FAULT_NOPAGE;
 784 }
 785 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
 786
 787 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 788 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 789 {
 790         if (likely(vma->vm_flags & VM_WRITE))
 791                 pud = pud_mkwrite(pud);
 792         return pud;
 793 }
 794
 795 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 796                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 797 {
 798         struct mm_struct *mm = vma->vm_mm;
 799         pud_t entry;
 800         spinlock_t *ptl;
 801
 802         ptl = pud_lock(mm, pud);
 803         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
 804         if (pfn_t_devmap(pfn))
 805                 entry = pud_mkdevmap(entry);
 806         if (write) {
 807                 entry = pud_mkyoung(pud_mkdirty(entry));
 808                 entry = maybe_pud_mkwrite(entry, vma);
 809         }
 810         set_pud_at(mm, addr, pud, entry);
 811         update_mmu_cache_pud(vma, addr, pud);
 812         spin_unlock(ptl);
 813 }
 814
 815 vm_fault_t vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 816                         pud_t *pud, pfn_t pfn, bool write)
 817 {
 818         pgprot_t pgprot = vma->vm_page_prot;
 819         /*
 820          * If we had pud_special, we could avoid all these restrictions,
 821          * but we need to be consistent with PTEs and architectures that
 822          * can't support a 'special' bit.
 823          */
 824         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 825                         !pfn_t_devmap(pfn));
 826         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 827                                                 (VM_PFNMAP|VM_MIXEDMAP));
 828         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 829
 830         if (addr < vma->vm_start || addr >= vma->vm_end)
 831                 return VM_FAULT_SIGBUS;
 832
 833         track_pfn_insert(vma, &pgprot, pfn);
 834
 835         insert_pfn_pud(vma, addr, pud, pfn, pgprot, write);
 836         return VM_FAULT_NOPAGE;
 837 }
 838 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
 839 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 840
 841 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
 842                 pmd_t *pmd, int flags)
 843 {
 844         pmd_t _pmd;
 845
 846         _pmd = pmd_mkyoung(*pmd);
 847         if (flags & FOLL_WRITE)
 848                 _pmd = pmd_mkdirty(_pmd);
 849         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 850                                 pmd, _pmd, flags & FOLL_WRITE))
 851                 update_mmu_cache_pmd(vma, addr, pmd);
 852 }
 853
 854 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 855                 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
 856 {
 857         unsigned long pfn = pmd_pfn(*pmd);
 858         struct mm_struct *mm = vma->vm_mm;
 859         struct page *page;
 860
 861         assert_spin_locked(pmd_lockptr(mm, pmd));
 862
 863         /*
 864          * When we COW a devmap PMD entry, we split it into PTEs, so we should
 865          * not be in this function with `flags & FOLL_COW` set.
 866          */
 867         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
 868
 869         if (flags & FOLL_WRITE && !pmd_write(*pmd))
 870                 return NULL;
 871
 872         if (pmd_present(*pmd) && pmd_devmap(*pmd))
 873                 /* pass */;
 874         else
 875                 return NULL;
 876
 877         if (flags & FOLL_TOUCH)
 878                 touch_pmd(vma, addr, pmd, flags);
 879
 880         /*
 881          * device mapped pages can only be returned if the
 882          * caller will manage the page reference count.
 883          */
 884         if (!(flags & FOLL_GET))
 885                 return ERR_PTR(-EEXIST);
 886
 887         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
 888         *pgmap = get_dev_pagemap(pfn, *pgmap);
 889         if (!*pgmap)
 890                 return ERR_PTR(-EFAULT);
 891         page = pfn_to_page(pfn);
 892         get_page(page);
 893
 894         return page;
 895 }
 896
 897 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 898                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 899                   struct vm_area_struct *vma)
 900 {
 901         spinlock_t *dst_ptl, *src_ptl;
 902         struct page *src_page;
 903         pmd_t pmd;
 904         pgtable_t pgtable = NULL;
 905         int ret = -ENOMEM;
 906
 907         /* Skip if can be re-fill on fault */
 908         if (!vma_is_anonymous(vma))
 909                 return 0;
 910
 911         pgtable = pte_alloc_one(dst_mm, addr);
 912         if (unlikely(!pgtable))
 913                 goto out;
 914
 915         dst_ptl = pmd_lock(dst_mm, dst_pmd);
 916         src_ptl = pmd_lockptr(src_mm, src_pmd);
 917         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 918
 919         ret = -EAGAIN;
 920         pmd = *src_pmd;
 921
 922 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
 923         if (unlikely(is_swap_pmd(pmd))) {
 924                 swp_entry_t entry = pmd_to_swp_entry(pmd);
 925
 926                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
 927                 if (is_write_migration_entry(entry)) {
 928                         make_migration_entry_read(&entry);
 929                         pmd = swp_entry_to_pmd(entry);
 930                         if (pmd_swp_soft_dirty(*src_pmd))
 931                                 pmd = pmd_swp_mksoft_dirty(pmd);
 932                         set_pmd_at(src_mm, addr, src_pmd, pmd);
 933                 }
 934                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 935                 mm_inc_nr_ptes(dst_mm);
 936                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 937                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 938                 ret = 0;
 939                 goto out_unlock;
 940         }
 941 #endif
 942
 943         if (unlikely(!pmd_trans_huge(pmd))) {
 944                 pte_free(dst_mm, pgtable);
 945                 goto out_unlock;
 946         }
 947         /*
 948          * When page table lock is held, the huge zero pmd should not be
 949          * under splitting since we don't split the page itself, only pmd to
 950          * a page table.
 951          */
 952         if (is_huge_zero_pmd(pmd)) {
 953                 struct page *zero_page;
 954                 /*
 955                  * get_huge_zero_page() will never allocate a new page here,
 956                  * since we already have a zero page to copy. It just takes a
 957                  * reference.
 958                  */
 959                 zero_page = mm_get_huge_zero_page(dst_mm);
 960                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
 961                                 zero_page);
 962                 ret = 0;
 963                 goto out_unlock;
 964         }
 965
 966         src_page = pmd_page(pmd);
 967         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
 968         get_page(src_page);
 969         page_dup_rmap(src_page, true);
 970         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 971         mm_inc_nr_ptes(dst_mm);
 972         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 973
 974         pmdp_set_wrprotect(src_mm, addr, src_pmd);
 975         pmd = pmd_mkold(pmd_wrprotect(pmd));
 976         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 977
 978         ret = 0;
 979 out_unlock:
 980         spin_unlock(src_ptl);
 981         spin_unlock(dst_ptl);
 982 out:
 983         return ret;
 984 }
 985
 986 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 987 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
 988                 pud_t *pud, int flags)
 989 {
 990         pud_t _pud;
 991
 992         _pud = pud_mkyoung(*pud);
 993         if (flags & FOLL_WRITE)
 994                 _pud = pud_mkdirty(_pud);
 995         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
 996                                 pud, _pud, flags & FOLL_WRITE))
 997                 update_mmu_cache_pud(vma, addr, pud);
 998 }
 999
1000 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1001                 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1002 {
1003         unsigned long pfn = pud_pfn(*pud);
1004         struct mm_struct *mm = vma->vm_mm;
1005         struct page *page;
1006
1007         assert_spin_locked(pud_lockptr(mm, pud));
1008
1009         if (flags & FOLL_WRITE && !pud_write(*pud))
1010                 return NULL;
1011
1012         if (pud_present(*pud) && pud_devmap(*pud))
1013                 /* pass */;
1014         else
1015                 return NULL;
1016
1017         if (flags & FOLL_TOUCH)
1018                 touch_pud(vma, addr, pud, flags);
1019
1020         /*
1021          * device mapped pages can only be returned if the
1022          * caller will manage the page reference count.
1023          */
1024         if (!(flags & FOLL_GET))
1025                 return ERR_PTR(-EEXIST);
1026
1027         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1028         *pgmap = get_dev_pagemap(pfn, *pgmap);
1029         if (!*pgmap)
1030                 return ERR_PTR(-EFAULT);
1031         page = pfn_to_page(pfn);
1032         get_page(page);
1033
1034         return page;
1035 }
1036
1037 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1038                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1039                   struct vm_area_struct *vma)
1040 {
1041         spinlock_t *dst_ptl, *src_ptl;
1042         pud_t pud;
1043         int ret;
1044
1045         dst_ptl = pud_lock(dst_mm, dst_pud);
1046         src_ptl = pud_lockptr(src_mm, src_pud);
1047         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1048
1049         ret = -EAGAIN;
1050         pud = *src_pud;
1051         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1052                 goto out_unlock;
1053
1054         /*
1055          * When page table lock is held, the huge zero pud should not be
1056          * under splitting since we don't split the page itself, only pud to
1057          * a page table.
1058          */
1059         if (is_huge_zero_pud(pud)) {
1060                 /* No huge zero pud yet */
1061         }
1062
1063         pudp_set_wrprotect(src_mm, addr, src_pud);
1064         pud = pud_mkold(pud_wrprotect(pud));
1065         set_pud_at(dst_mm, addr, dst_pud, pud);
1066
1067         ret = 0;
1068 out_unlock:
1069         spin_unlock(src_ptl);
1070         spin_unlock(dst_ptl);
1071         return ret;
1072 }
1073
1074 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1075 {
1076         pud_t entry;
1077         unsigned long haddr;
1078         bool write = vmf->flags & FAULT_FLAG_WRITE;
1079
1080         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1081         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1082                 goto unlock;
1083
1084         entry = pud_mkyoung(orig_pud);
1085         if (write)
1086                 entry = pud_mkdirty(entry);
1087         haddr = vmf->address & HPAGE_PUD_MASK;
1088         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1089                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1090
1091 unlock:
1092         spin_unlock(vmf->ptl);
1093 }
1094 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1095
1096 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1097 {
1098         pmd_t entry;
1099         unsigned long haddr;
1100         bool write = vmf->flags & FAULT_FLAG_WRITE;
1101
1102         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1103         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1104                 goto unlock;
1105
1106         entry = pmd_mkyoung(orig_pmd);
1107         if (write)
1108                 entry = pmd_mkdirty(entry);
1109         haddr = vmf->address & HPAGE_PMD_MASK;
1110         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1111                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1112
1113 unlock:
1114         spin_unlock(vmf->ptl);
1115 }
1116
1117 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1118                         pmd_t orig_pmd, struct page *page)
1119 {
1120         struct vm_area_struct *vma = vmf->vma;
1121         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1122         struct mem_cgroup *memcg;
1123         pgtable_t pgtable;
1124         pmd_t _pmd;
1125         int i;
1126         vm_fault_t ret = 0;
1127         struct page **pages;
1128         unsigned long mmun_start;       /* For mmu_notifiers */
1129         unsigned long mmun_end;         /* For mmu_notifiers */
1130
1131         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1132                               GFP_KERNEL);
1133         if (unlikely(!pages)) {
1134                 ret |= VM_FAULT_OOM;
1135                 goto out;
1136         }
1137
1138         for (i = 0; i < HPAGE_PMD_NR; i++) {
1139                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1140                                                vmf->address, page_to_nid(page));
1141                 if (unlikely(!pages[i] ||
1142                              mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1143                                      GFP_KERNEL, &memcg, false))) {
1144                         if (pages[i])
1145                                 put_page(pages[i]);
1146                         while (--i >= 0) {
1147                                 memcg = (void *)page_private(pages[i]);
1148                                 set_page_private(pages[i], 0);
1149                                 mem_cgroup_cancel_charge(pages[i], memcg,
1150                                                 false);
1151                                 put_page(pages[i]);
1152                         }
1153                         kfree(pages);
1154                         ret |= VM_FAULT_OOM;
1155                         goto out;
1156                 }
1157                 set_page_private(pages[i], (unsigned long)memcg);
1158         }
1159
1160         for (i = 0; i < HPAGE_PMD_NR; i++) {
1161                 copy_user_highpage(pages[i], page + i,
1162                                    haddr + PAGE_SIZE * i, vma);
1163                 __SetPageUptodate(pages[i]);
1164                 cond_resched();
1165         }
1166
1167         mmun_start = haddr;
1168         mmun_end   = haddr + HPAGE_PMD_SIZE;
1169         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1170
1171         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1172         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1173                 goto out_free_pages;
1174         VM_BUG_ON_PAGE(!PageHead(page), page);
1175
1176         /*
1177          * Leave pmd empty until pte is filled note we must notify here as
1178          * concurrent CPU thread might write to new page before the call to
1179          * mmu_notifier_invalidate_range_end() happens which can lead to a
1180          * device seeing memory write in different order than CPU.
1181          *
1182          * See Documentation/vm/mmu_notifier.rst
1183          */
1184         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1185
1186         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1187         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1188
1189         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1190                 pte_t entry;
1191                 entry = mk_pte(pages[i], vma->vm_page_prot);
1192                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1193                 memcg = (void *)page_private(pages[i]);
1194                 set_page_private(pages[i], 0);
1195                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1196                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1197                 lru_cache_add_active_or_unevictable(pages[i], vma);
1198                 vmf->pte = pte_offset_map(&_pmd, haddr);
1199                 VM_BUG_ON(!pte_none(*vmf->pte));
1200                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1201                 pte_unmap(vmf->pte);
1202         }
1203         kfree(pages);
1204
1205         smp_wmb(); /* make pte visible before pmd */
1206         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1207         page_remove_rmap(page, true);
1208         spin_unlock(vmf->ptl);
1209
1210         /*
1211          * No need to double call mmu_notifier->invalidate_range() callback as
1212          * the above pmdp_huge_clear_flush_notify() did already call it.
1213          */
1214         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1215                                                 mmun_end);
1216
1217         ret |= VM_FAULT_WRITE;
1218         put_page(page);
1219
1220 out:
1221         return ret;
1222
1223 out_free_pages:
1224         spin_unlock(vmf->ptl);
1225         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1226         for (i = 0; i < HPAGE_PMD_NR; i++) {
1227                 memcg = (void *)page_private(pages[i]);
1228                 set_page_private(pages[i], 0);
1229                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1230                 put_page(pages[i]);
1231         }
1232         kfree(pages);
1233         goto out;
1234 }
1235
1236 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1237 {
1238         struct vm_area_struct *vma = vmf->vma;
1239         struct page *page = NULL, *new_page;
1240         struct mem_cgroup *memcg;
1241         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1242         unsigned long mmun_start;       /* For mmu_notifiers */
1243         unsigned long mmun_end;         /* For mmu_notifiers */
1244         gfp_t huge_gfp;                 /* for allocation and charge */
1245         vm_fault_t ret = 0;
1246
1247         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1248         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1249         if (is_huge_zero_pmd(orig_pmd))
1250                 goto alloc;
1251         spin_lock(vmf->ptl);
1252         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1253                 goto out_unlock;
1254
1255         page = pmd_page(orig_pmd);
1256         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1257         /*
1258          * We can only reuse the page if nobody else maps the huge page or it's
1259          * part.
1260          */
1261         if (!trylock_page(page)) {
1262                 get_page(page);
1263                 spin_unlock(vmf->ptl);
1264                 lock_page(page);
1265                 spin_lock(vmf->ptl);
1266                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1267                         unlock_page(page);
1268                         put_page(page);
1269                         goto out_unlock;
1270                 }
1271                 put_page(page);
1272         }
1273         if (reuse_swap_page(page, NULL)) {
1274                 pmd_t entry;
1275                 entry = pmd_mkyoung(orig_pmd);
1276                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1277                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1278                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1279                 ret |= VM_FAULT_WRITE;
1280                 unlock_page(page);
1281                 goto out_unlock;
1282         }
1283         unlock_page(page);
1284         get_page(page);
1285         spin_unlock(vmf->ptl);
1286 alloc:
1287         if (transparent_hugepage_enabled(vma) &&
1288             !transparent_hugepage_debug_cow()) {
1289                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1290                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1291         } else
1292                 new_page = NULL;
1293
1294         if (likely(new_page)) {
1295                 prep_transhuge_page(new_page);
1296         } else {
1297                 if (!page) {
1298                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1299                         ret |= VM_FAULT_FALLBACK;
1300                 } else {
1301                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1302                         if (ret & VM_FAULT_OOM) {
1303                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1304                                 ret |= VM_FAULT_FALLBACK;
1305                         }
1306                         put_page(page);
1307                 }
1308                 count_vm_event(THP_FAULT_FALLBACK);
1309                 goto out;
1310         }
1311
1312         if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1313                                         huge_gfp, &memcg, true))) {
1314                 put_page(new_page);
1315                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1316                 if (page)
1317                         put_page(page);
1318                 ret |= VM_FAULT_FALLBACK;
1319                 count_vm_event(THP_FAULT_FALLBACK);
1320                 goto out;
1321         }
1322
1323         count_vm_event(THP_FAULT_ALLOC);
1324
1325         if (!page)
1326                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1327         else
1328                 copy_user_huge_page(new_page, page, vmf->address,
1329                                     vma, HPAGE_PMD_NR);
1330         __SetPageUptodate(new_page);
1331
1332         mmun_start = haddr;
1333         mmun_end   = haddr + HPAGE_PMD_SIZE;
1334         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1335
1336         spin_lock(vmf->ptl);
1337         if (page)
1338                 put_page(page);
1339         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1340                 spin_unlock(vmf->ptl);
1341                 mem_cgroup_cancel_charge(new_page, memcg, true);
1342                 put_page(new_page);
1343                 goto out_mn;
1344         } else {
1345                 pmd_t entry;
1346                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1347                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1348                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1349                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1350                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1351                 lru_cache_add_active_or_unevictable(new_page, vma);
1352                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1353                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1354                 if (!page) {
1355                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1356                 } else {
1357                         VM_BUG_ON_PAGE(!PageHead(page), page);
1358                         page_remove_rmap(page, true);
1359                         put_page(page);
1360                 }
1361                 ret |= VM_FAULT_WRITE;
1362         }
1363         spin_unlock(vmf->ptl);
1364 out_mn:
1365         /*
1366          * No need to double call mmu_notifier->invalidate_range() callback as
1367          * the above pmdp_huge_clear_flush_notify() did already call it.
1368          */
1369         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1370                                                mmun_end);
1371 out:
1372         return ret;
1373 out_unlock:
1374         spin_unlock(vmf->ptl);
1375         return ret;
1376 }
1377
1378 /*
1379  * FOLL_FORCE can write to even unwritable pmd's, but only
1380  * after we've gone through a COW cycle and they are dirty.
1381  */
1382 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1383 {
1384         return pmd_write(pmd) ||
1385                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1386 }
1387
1388 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1389                                    unsigned long addr,
1390                                    pmd_t *pmd,
1391                                    unsigned int flags)
1392 {
1393         struct mm_struct *mm = vma->vm_mm;
1394         struct page *page = NULL;
1395
1396         assert_spin_locked(pmd_lockptr(mm, pmd));
1397
1398         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1399                 goto out;
1400
1401         /* Avoid dumping huge zero page */
1402         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1403                 return ERR_PTR(-EFAULT);
1404
1405         /* Full NUMA hinting faults to serialise migration in fault paths */
1406         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1407                 goto out;
1408
1409         page = pmd_page(*pmd);
1410         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1411         if (flags & FOLL_TOUCH)
1412                 touch_pmd(vma, addr, pmd, flags);
1413         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1414                 /*
1415                  * We don't mlock() pte-mapped THPs. This way we can avoid
1416                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1417                  *
1418                  * For anon THP:
1419                  *
1420                  * In most cases the pmd is the only mapping of the page as we
1421                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1422                  * writable private mappings in populate_vma_page_range().
1423                  *
1424                  * The only scenario when we have the page shared here is if we
1425                  * mlocking read-only mapping shared over fork(). We skip
1426                  * mlocking such pages.
1427                  *
1428                  * For file THP:
1429                  *
1430                  * We can expect PageDoubleMap() to be stable under page lock:
1431                  * for file pages we set it in page_add_file_rmap(), which
1432                  * requires page to be locked.
1433                  */
1434
1435                 if (PageAnon(page) && compound_mapcount(page) != 1)
1436                         goto skip_mlock;
1437                 if (PageDoubleMap(page) || !page->mapping)
1438                         goto skip_mlock;
1439                 if (!trylock_page(page))
1440                         goto skip_mlock;
1441                 lru_add_drain();
1442                 if (page->mapping && !PageDoubleMap(page))
1443                         mlock_vma_page(page);
1444                 unlock_page(page);
1445         }
1446 skip_mlock:
1447         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1448         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1449         if (flags & FOLL_GET)
1450                 get_page(page);
1451
1452 out:
1453         return page;
1454 }
1455
1456 /* NUMA hinting page fault entry point for trans huge pmds */
1457 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1458 {
1459         struct vm_area_struct *vma = vmf->vma;
1460         struct anon_vma *anon_vma = NULL;
1461         struct page *page;
1462         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1463         int page_nid = -1, this_nid = numa_node_id();
1464         int target_nid, last_cpupid = -1;
1465         bool page_locked;
1466         bool migrated = false;
1467         bool was_writable;
1468         int flags = 0;
1469
1470         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1471         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1472                 goto out_unlock;
1473
1474         /*
1475          * If there are potential migrations, wait for completion and retry
1476          * without disrupting NUMA hinting information. Do not relock and
1477          * check_same as the page may no longer be mapped.
1478          */
1479         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1480                 page = pmd_page(*vmf->pmd);
1481                 if (!get_page_unless_zero(page))
1482                         goto out_unlock;
1483                 spin_unlock(vmf->ptl);
1484                 wait_on_page_locked(page);
1485                 put_page(page);
1486                 goto out;
1487         }
1488
1489         page = pmd_page(pmd);
1490         BUG_ON(is_huge_zero_page(page));
1491         page_nid = page_to_nid(page);
1492         last_cpupid = page_cpupid_last(page);
1493         count_vm_numa_event(NUMA_HINT_FAULTS);
1494         if (page_nid == this_nid) {
1495                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1496                 flags |= TNF_FAULT_LOCAL;
1497         }
1498
1499         /* See similar comment in do_numa_page for explanation */
1500         if (!pmd_savedwrite(pmd))
1501                 flags |= TNF_NO_GROUP;
1502
1503         /*
1504          * Acquire the page lock to serialise THP migrations but avoid dropping
1505          * page_table_lock if at all possible
1506          */
1507         page_locked = trylock_page(page);
1508         target_nid = mpol_misplaced(page, vma, haddr);
1509         if (target_nid == -1) {
1510                 /* If the page was locked, there are no parallel migrations */
1511                 if (page_locked)
1512                         goto clear_pmdnuma;
1513         }
1514
1515         /* Migration could have started since the pmd_trans_migrating check */
1516         if (!page_locked) {
1517                 page_nid = -1;
1518                 if (!get_page_unless_zero(page))
1519                         goto out_unlock;
1520                 spin_unlock(vmf->ptl);
1521                 wait_on_page_locked(page);
1522                 put_page(page);
1523                 goto out;
1524         }
1525
1526         /*
1527          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1528          * to serialises splits
1529          */
1530         get_page(page);
1531         spin_unlock(vmf->ptl);
1532         anon_vma = page_lock_anon_vma_read(page);
1533
1534         /* Confirm the PMD did not change while page_table_lock was released */
1535         spin_lock(vmf->ptl);
1536         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1537                 unlock_page(page);
1538                 put_page(page);
1539                 page_nid = -1;
1540                 goto out_unlock;
1541         }
1542
1543         /* Bail if we fail to protect against THP splits for any reason */
1544         if (unlikely(!anon_vma)) {
1545                 put_page(page);
1546                 page_nid = -1;
1547                 goto clear_pmdnuma;
1548         }
1549
1550         /*
1551          * Since we took the NUMA fault, we must have observed the !accessible
1552          * bit. Make sure all other CPUs agree with that, to avoid them
1553          * modifying the page we're about to migrate.
1554          *
1555          * Must be done under PTL such that we'll observe the relevant
1556          * inc_tlb_flush_pending().
1557          *
1558          * We are not sure a pending tlb flush here is for a huge page
1559          * mapping or not. Hence use the tlb range variant
1560          */
1561         if (mm_tlb_flush_pending(vma->vm_mm)) {
1562                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1563                 /*
1564                  * change_huge_pmd() released the pmd lock before
1565                  * invalidating the secondary MMUs sharing the primary
1566                  * MMU pagetables (with ->invalidate_range()). The
1567                  * mmu_notifier_invalidate_range_end() (which
1568                  * internally calls ->invalidate_range()) in
1569                  * change_pmd_range() will run after us, so we can't
1570                  * rely on it here and we need an explicit invalidate.
1571                  */
1572                 mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1573                                               haddr + HPAGE_PMD_SIZE);
1574         }
1575
1576         /*
1577          * Migrate the THP to the requested node, returns with page unlocked
1578          * and access rights restored.
1579          */
1580         spin_unlock(vmf->ptl);
1581
1582         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1583                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1584         if (migrated) {
1585                 flags |= TNF_MIGRATED;
1586                 page_nid = target_nid;
1587         } else
1588                 flags |= TNF_MIGRATE_FAIL;
1589
1590         goto out;
1591 clear_pmdnuma:
1592         BUG_ON(!PageLocked(page));
1593         was_writable = pmd_savedwrite(pmd);
1594         pmd = pmd_modify(pmd, vma->vm_page_prot);
1595         pmd = pmd_mkyoung(pmd);
1596         if (was_writable)
1597                 pmd = pmd_mkwrite(pmd);
1598         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1599         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1600         unlock_page(page);
1601 out_unlock:
1602         spin_unlock(vmf->ptl);
1603
1604 out:
1605         if (anon_vma)
1606                 page_unlock_anon_vma_read(anon_vma);
1607
1608         if (page_nid != -1)
1609                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1610                                 flags);
1611
1612         return 0;
1613 }
1614
1615 /*
1616  * Return true if we do MADV_FREE successfully on entire pmd page.
1617  * Otherwise, return false.
1618  */
1619 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1620                 pmd_t *pmd, unsigned long addr, unsigned long next)
1621 {
1622         spinlock_t *ptl;
1623         pmd_t orig_pmd;
1624         struct page *page;
1625         struct mm_struct *mm = tlb->mm;
1626         bool ret = false;
1627
1628         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1629
1630         ptl = pmd_trans_huge_lock(pmd, vma);
1631         if (!ptl)
1632                 goto out_unlocked;
1633
1634         orig_pmd = *pmd;
1635         if (is_huge_zero_pmd(orig_pmd))
1636                 goto out;
1637
1638         if (unlikely(!pmd_present(orig_pmd))) {
1639                 VM_BUG_ON(thp_migration_supported() &&
1640                                   !is_pmd_migration_entry(orig_pmd));
1641                 goto out;
1642         }
1643
1644         page = pmd_page(orig_pmd);
1645         /*
1646          * If other processes are mapping this page, we couldn't discard
1647          * the page unless they all do MADV_FREE so let's skip the page.
1648          */
1649         if (page_mapcount(page) != 1)
1650                 goto out;
1651
1652         if (!trylock_page(page))
1653                 goto out;
1654
1655         /*
1656          * If user want to discard part-pages of THP, split it so MADV_FREE
1657          * will deactivate only them.
1658          */
1659         if (next - addr != HPAGE_PMD_SIZE) {
1660                 get_page(page);
1661                 spin_unlock(ptl);
1662                 split_huge_page(page);
1663                 unlock_page(page);
1664                 put_page(page);
1665                 goto out_unlocked;
1666         }
1667
1668         if (PageDirty(page))
1669                 ClearPageDirty(page);
1670         unlock_page(page);
1671
1672         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1673                 pmdp_invalidate(vma, addr, pmd);
1674                 orig_pmd = pmd_mkold(orig_pmd);
1675                 orig_pmd = pmd_mkclean(orig_pmd);
1676
1677                 set_pmd_at(mm, addr, pmd, orig_pmd);
1678                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1679         }
1680
1681         mark_page_lazyfree(page);
1682         ret = true;
1683 out:
1684         spin_unlock(ptl);
1685 out_unlocked:
1686         return ret;
1687 }
1688
1689 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1690 {
1691         pgtable_t pgtable;
1692
1693         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1694         pte_free(mm, pgtable);
1695         mm_dec_nr_ptes(mm);
1696 }
1697
1698 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1699                  pmd_t *pmd, unsigned long addr)
1700 {
1701         pmd_t orig_pmd;
1702         spinlock_t *ptl;
1703
1704         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1705
1706         ptl = __pmd_trans_huge_lock(pmd, vma);
1707         if (!ptl)
1708                 return 0;
1709         /*
1710          * For architectures like ppc64 we look at deposited pgtable
1711          * when calling pmdp_huge_get_and_clear. So do the
1712          * pgtable_trans_huge_withdraw after finishing pmdp related
1713          * operations.
1714          */
1715         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1716                         tlb->fullmm);
1717         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1718         if (vma_is_dax(vma)) {
1719                 if (arch_needs_pgtable_deposit())
1720                         zap_deposited_table(tlb->mm, pmd);
1721                 spin_unlock(ptl);
1722                 if (is_huge_zero_pmd(orig_pmd))
1723                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1724         } else if (is_huge_zero_pmd(orig_pmd)) {
1725                 zap_deposited_table(tlb->mm, pmd);
1726                 spin_unlock(ptl);
1727                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1728         } else {
1729                 struct page *page = NULL;
1730                 int flush_needed = 1;
1731
1732                 if (pmd_present(orig_pmd)) {
1733                         page = pmd_page(orig_pmd);
1734                         page_remove_rmap(page, true);
1735                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1736                         VM_BUG_ON_PAGE(!PageHead(page), page);
1737                 } else if (thp_migration_supported()) {
1738                         swp_entry_t entry;
1739
1740                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1741                         entry = pmd_to_swp_entry(orig_pmd);
1742                         page = pfn_to_page(swp_offset(entry));
1743                         flush_needed = 0;
1744                 } else
1745                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1746
1747                 if (PageAnon(page)) {
1748                         zap_deposited_table(tlb->mm, pmd);
1749                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1750                 } else {
1751                         if (arch_needs_pgtable_deposit())
1752                                 zap_deposited_table(tlb->mm, pmd);
1753                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1754                 }
1755
1756                 spin_unlock(ptl);
1757                 if (flush_needed)
1758                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1759         }
1760         return 1;
1761 }
1762
1763 #ifndef pmd_move_must_withdraw
1764 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1765                                          spinlock_t *old_pmd_ptl,
1766                                          struct vm_area_struct *vma)
1767 {
1768         /*
1769          * With split pmd lock we also need to move preallocated
1770          * PTE page table if new_pmd is on different PMD page table.
1771          *
1772          * We also don't deposit and withdraw tables for file pages.
1773          */
1774         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1775 }
1776 #endif
1777
1778 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1779 {
1780 #ifdef CONFIG_MEM_SOFT_DIRTY
1781         if (unlikely(is_pmd_migration_entry(pmd)))
1782                 pmd = pmd_swp_mksoft_dirty(pmd);
1783         else if (pmd_present(pmd))
1784                 pmd = pmd_mksoft_dirty(pmd);
1785 #endif
1786         return pmd;
1787 }
1788
1789 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1790                   unsigned long new_addr, unsigned long old_end,
1791                   pmd_t *old_pmd, pmd_t *new_pmd)
1792 {
1793         spinlock_t *old_ptl, *new_ptl;
1794         pmd_t pmd;
1795         struct mm_struct *mm = vma->vm_mm;
1796         bool force_flush = false;
1797
1798         if ((old_addr & ~HPAGE_PMD_MASK) ||
1799             (new_addr & ~HPAGE_PMD_MASK) ||
1800             old_end - old_addr < HPAGE_PMD_SIZE)
1801                 return false;
1802
1803         /*
1804          * The destination pmd shouldn't be established, free_pgtables()
1805          * should have release it.
1806          */
1807         if (WARN_ON(!pmd_none(*new_pmd))) {
1808                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1809                 return false;
1810         }
1811
1812         /*
1813          * We don't have to worry about the ordering of src and dst
1814          * ptlocks because exclusive mmap_sem prevents deadlock.
1815          */
1816         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1817         if (old_ptl) {
1818                 new_ptl = pmd_lockptr(mm, new_pmd);
1819                 if (new_ptl != old_ptl)
1820                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1821                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1822                 if (pmd_present(pmd))
1823                         force_flush = true;
1824                 VM_BUG_ON(!pmd_none(*new_pmd));
1825
1826                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1827                         pgtable_t pgtable;
1828                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1829                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1830                 }
1831                 pmd = move_soft_dirty_pmd(pmd);
1832                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1833                 if (force_flush)
1834                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1835                 if (new_ptl != old_ptl)
1836                         spin_unlock(new_ptl);
1837                 spin_unlock(old_ptl);
1838                 return true;
1839         }
1840         return false;
1841 }
1842
1843 /*
1844  * Returns
1845  *  - 0 if PMD could not be locked
1846  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1847  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1848  */
1849 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1850                 unsigned long addr, pgprot_t newprot, int prot_numa)
1851 {
1852         struct mm_struct *mm = vma->vm_mm;
1853         spinlock_t *ptl;
1854         pmd_t entry;
1855         bool preserve_write;
1856         int ret;
1857
1858         ptl = __pmd_trans_huge_lock(pmd, vma);
1859         if (!ptl)
1860                 return 0;
1861
1862         preserve_write = prot_numa && pmd_write(*pmd);
1863         ret = 1;
1864
1865 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1866         if (is_swap_pmd(*pmd)) {
1867                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1868
1869                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1870                 if (is_write_migration_entry(entry)) {
1871                         pmd_t newpmd;
1872                         /*
1873                          * A protection check is difficult so
1874                          * just be safe and disable write
1875                          */
1876                         make_migration_entry_read(&entry);
1877                         newpmd = swp_entry_to_pmd(entry);
1878                         if (pmd_swp_soft_dirty(*pmd))
1879                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1880                         set_pmd_at(mm, addr, pmd, newpmd);
1881                 }
1882                 goto unlock;
1883         }
1884 #endif
1885
1886         /*
1887          * Avoid trapping faults against the zero page. The read-only
1888          * data is likely to be read-cached on the local CPU and
1889          * local/remote hits to the zero page are not interesting.
1890          */
1891         if (prot_numa && is_huge_zero_pmd(*pmd))
1892                 goto unlock;
1893
1894         if (prot_numa && pmd_protnone(*pmd))
1895                 goto unlock;
1896
1897         /*
1898          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1899          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1900          * which is also under down_read(mmap_sem):
1901          *
1902          *      CPU0:                           CPU1:
1903          *                              change_huge_pmd(prot_numa=1)
1904          *                               pmdp_huge_get_and_clear_notify()
1905          * madvise_dontneed()
1906          *  zap_pmd_range()
1907          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1908          *   // skip the pmd
1909          *                               set_pmd_at();
1910          *                               // pmd is re-established
1911          *
1912          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1913          * which may break userspace.
1914          *
1915          * pmdp_invalidate() is required to make sure we don't miss
1916          * dirty/young flags set by hardware.
1917          */
1918         entry = pmdp_invalidate(vma, addr, pmd);
1919
1920         entry = pmd_modify(entry, newprot);
1921         if (preserve_write)
1922                 entry = pmd_mk_savedwrite(entry);
1923         ret = HPAGE_PMD_NR;
1924         set_pmd_at(mm, addr, pmd, entry);
1925         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1926 unlock:
1927         spin_unlock(ptl);
1928         return ret;
1929 }
1930
1931 /*
1932  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1933  *
1934  * Note that if it returns page table lock pointer, this routine returns without
1935  * unlocking page table lock. So callers must unlock it.
1936  */
1937 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1938 {
1939         spinlock_t *ptl;
1940         ptl = pmd_lock(vma->vm_mm, pmd);
1941         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1942                         pmd_devmap(*pmd)))
1943                 return ptl;
1944         spin_unlock(ptl);
1945         return NULL;
1946 }
1947
1948 /*
1949  * Returns true if a given pud maps a thp, false otherwise.
1950  *
1951  * Note that if it returns true, this routine returns without unlocking page
1952  * table lock. So callers must unlock it.
1953  */
1954 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1955 {
1956         spinlock_t *ptl;
1957
1958         ptl = pud_lock(vma->vm_mm, pud);
1959         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1960                 return ptl;
1961         spin_unlock(ptl);
1962         return NULL;
1963 }
1964
1965 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1966 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1967                  pud_t *pud, unsigned long addr)
1968 {
1969         pud_t orig_pud;
1970         spinlock_t *ptl;
1971
1972         ptl = __pud_trans_huge_lock(pud, vma);
1973         if (!ptl)
1974                 return 0;
1975         /*
1976          * For architectures like ppc64 we look at deposited pgtable
1977          * when calling pudp_huge_get_and_clear. So do the
1978          * pgtable_trans_huge_withdraw after finishing pudp related
1979          * operations.
1980          */
1981         orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1982                         tlb->fullmm);
1983         tlb_remove_pud_tlb_entry(tlb, pud, addr);
1984         if (vma_is_dax(vma)) {
1985                 spin_unlock(ptl);
1986                 /* No zero page support yet */
1987         } else {
1988                 /* No support for anonymous PUD pages yet */
1989                 BUG();
1990         }
1991         return 1;
1992 }
1993
1994 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
1995                 unsigned long haddr)
1996 {
1997         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
1998         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1999         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2000         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2001
2002         count_vm_event(THP_SPLIT_PUD);
2003
2004         pudp_huge_clear_flush_notify(vma, haddr, pud);
2005 }
2006
2007 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2008                 unsigned long address)
2009 {
2010         spinlock_t *ptl;
2011         struct mm_struct *mm = vma->vm_mm;
2012         unsigned long haddr = address & HPAGE_PUD_MASK;
2013
2014         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
2015         ptl = pud_lock(mm, pud);
2016         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2017                 goto out;
2018         __split_huge_pud_locked(vma, pud, haddr);
2019
2020 out:
2021         spin_unlock(ptl);
2022         /*
2023          * No need to double call mmu_notifier->invalidate_range() callback as
2024          * the above pudp_huge_clear_flush_notify() did already call it.
2025          */
2026         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2027                                                HPAGE_PUD_SIZE);
2028 }
2029 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2030
2031 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2032                 unsigned long haddr, pmd_t *pmd)
2033 {
2034         struct mm_struct *mm = vma->vm_mm;
2035         pgtable_t pgtable;
2036         pmd_t _pmd;
2037         int i;
2038
2039         /*
2040          * Leave pmd empty until pte is filled note that it is fine to delay
2041          * notification until mmu_notifier_invalidate_range_end() as we are
2042          * replacing a zero pmd write protected page with a zero pte write
2043          * protected page.
2044          *
2045          * See Documentation/vm/mmu_notifier.rst
2046          */
2047         pmdp_huge_clear_flush(vma, haddr, pmd);
2048
2049         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2050         pmd_populate(mm, &_pmd, pgtable);
2051
2052         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2053                 pte_t *pte, entry;
2054                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2055                 entry = pte_mkspecial(entry);
2056                 pte = pte_offset_map(&_pmd, haddr);
2057                 VM_BUG_ON(!pte_none(*pte));
2058                 set_pte_at(mm, haddr, pte, entry);
2059                 pte_unmap(pte);
2060         }
2061         smp_wmb(); /* make pte visible before pmd */
2062         pmd_populate(mm, pmd, pgtable);
2063 }
2064
2065 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2066                 unsigned long haddr, bool freeze)
2067 {
2068         struct mm_struct *mm = vma->vm_mm;
2069         struct page *page;
2070         pgtable_t pgtable;
2071         pmd_t old_pmd, _pmd;
2072         bool young, write, soft_dirty, pmd_migration = false;
2073         unsigned long addr;
2074         int i;
2075
2076         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2077         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2078         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2079         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2080                                 && !pmd_devmap(*pmd));
2081
2082         count_vm_event(THP_SPLIT_PMD);
2083
2084         if (!vma_is_anonymous(vma)) {
2085                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2086                 /*
2087                  * We are going to unmap this huge page. So
2088                  * just go ahead and zap it
2089                  */
2090                 if (arch_needs_pgtable_deposit())
2091                         zap_deposited_table(mm, pmd);
2092                 if (vma_is_dax(vma))
2093                         return;
2094                 page = pmd_page(_pmd);
2095                 if (!PageDirty(page) && pmd_dirty(_pmd))
2096                         set_page_dirty(page);
2097                 if (!PageReferenced(page) && pmd_young(_pmd))
2098                         SetPageReferenced(page);
2099                 page_remove_rmap(page, true);
2100                 put_page(page);
2101                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2102                 return;
2103         } else if (is_huge_zero_pmd(*pmd)) {
2104                 /*
2105                  * FIXME: Do we want to invalidate secondary mmu by calling
2106                  * mmu_notifier_invalidate_range() see comments below inside
2107                  * __split_huge_pmd() ?
2108                  *
2109                  * We are going from a zero huge page write protected to zero
2110                  * small page also write protected so it does not seems useful
2111                  * to invalidate secondary mmu at this time.
2112                  */
2113                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2114         }
2115
2116         /*
2117          * Up to this point the pmd is present and huge and userland has the
2118          * whole access to the hugepage during the split (which happens in
2119          * place). If we overwrite the pmd with the not-huge version pointing
2120          * to the pte here (which of course we could if all CPUs were bug
2121          * free), userland could trigger a small page size TLB miss on the
2122          * small sized TLB while the hugepage TLB entry is still established in
2123          * the huge TLB. Some CPU doesn't like that.
2124          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2125          * 383 on page 93. Intel should be safe but is also warns that it's
2126          * only safe if the permission and cache attributes of the two entries
2127          * loaded in the two TLB is identical (which should be the case here).
2128          * But it is generally safer to never allow small and huge TLB entries
2129          * for the same virtual address to be loaded simultaneously. So instead
2130          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2131          * current pmd notpresent (atomically because here the pmd_trans_huge
2132          * must remain set at all times on the pmd until the split is complete
2133          * for this pmd), then we flush the SMP TLB and finally we write the
2134          * non-huge version of the pmd entry with pmd_populate.
2135          */
2136         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2137
2138 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2139         pmd_migration = is_pmd_migration_entry(old_pmd);
2140         if (pmd_migration) {
2141                 swp_entry_t entry;
2142
2143                 entry = pmd_to_swp_entry(old_pmd);
2144                 page = pfn_to_page(swp_offset(entry));
2145         } else
2146 #endif
2147                 page = pmd_page(old_pmd);
2148         VM_BUG_ON_PAGE(!page_count(page), page);
2149         page_ref_add(page, HPAGE_PMD_NR - 1);
2150         if (pmd_dirty(old_pmd))
2151                 SetPageDirty(page);
2152         write = pmd_write(old_pmd);
2153         young = pmd_young(old_pmd);
2154         soft_dirty = pmd_soft_dirty(old_pmd);
2155
2156         /*
2157          * Withdraw the table only after we mark the pmd entry invalid.
2158          * This's critical for some architectures (Power).
2159          */
2160         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2161         pmd_populate(mm, &_pmd, pgtable);
2162
2163         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2164                 pte_t entry, *pte;
2165                 /*
2166                  * Note that NUMA hinting access restrictions are not
2167                  * transferred to avoid any possibility of altering
2168                  * permissions across VMAs.
2169                  */
2170                 if (freeze || pmd_migration) {
2171                         swp_entry_t swp_entry;
2172                         swp_entry = make_migration_entry(page + i, write);
2173                         entry = swp_entry_to_pte(swp_entry);
2174                         if (soft_dirty)
2175                                 entry = pte_swp_mksoft_dirty(entry);
2176                 } else {
2177                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2178                         entry = maybe_mkwrite(entry, vma);
2179                         if (!write)
2180                                 entry = pte_wrprotect(entry);
2181                         if (!young)
2182                                 entry = pte_mkold(entry);
2183                         if (soft_dirty)
2184                                 entry = pte_mksoft_dirty(entry);
2185                 }
2186                 pte = pte_offset_map(&_pmd, addr);
2187                 BUG_ON(!pte_none(*pte));
2188                 set_pte_at(mm, addr, pte, entry);
2189                 atomic_inc(&page[i]._mapcount);
2190                 pte_unmap(pte);
2191         }
2192
2193         /*
2194          * Set PG_double_map before dropping compound_mapcount to avoid
2195          * false-negative page_mapped().
2196          */
2197         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2198                 for (i = 0; i < HPAGE_PMD_NR; i++)
2199                         atomic_inc(&page[i]._mapcount);
2200         }
2201
2202         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2203                 /* Last compound_mapcount is gone. */
2204                 __dec_node_page_state(page, NR_ANON_THPS);
2205                 if (TestClearPageDoubleMap(page)) {
2206                         /* No need in mapcount reference anymore */
2207                         for (i = 0; i < HPAGE_PMD_NR; i++)
2208                                 atomic_dec(&page[i]._mapcount);
2209                 }
2210         }
2211
2212         smp_wmb(); /* make pte visible before pmd */
2213         pmd_populate(mm, pmd, pgtable);
2214
2215         if (freeze) {
2216                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2217                         page_remove_rmap(page + i, false);
2218                         put_page(page + i);
2219                 }
2220         }
2221 }
2222
2223 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2224                 unsigned long address, bool freeze, struct page *page)
2225 {
2226         spinlock_t *ptl;
2227         struct mm_struct *mm = vma->vm_mm;
2228         unsigned long haddr = address & HPAGE_PMD_MASK;
2229
2230         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2231         ptl = pmd_lock(mm, pmd);
2232
2233         /*
2234          * If caller asks to setup a migration entries, we need a page to check
2235          * pmd against. Otherwise we can end up replacing wrong page.
2236          */
2237         VM_BUG_ON(freeze && !page);
2238         if (page && page != pmd_page(*pmd))
2239                 goto out;
2240
2241         if (pmd_trans_huge(*pmd)) {
2242                 page = pmd_page(*pmd);
2243                 if (PageMlocked(page))
2244                         clear_page_mlock(page);
2245         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2246                 goto out;
2247         __split_huge_pmd_locked(vma, pmd, haddr, freeze);
2248 out:
2249         spin_unlock(ptl);
2250         /*
2251          * No need to double call mmu_notifier->invalidate_range() callback.
2252          * They are 3 cases to consider inside __split_huge_pmd_locked():
2253          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2254          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2255          *    fault will trigger a flush_notify before pointing to a new page
2256          *    (it is fine if the secondary mmu keeps pointing to the old zero
2257          *    page in the meantime)
2258          *  3) Split a huge pmd into pte pointing to the same page. No need
2259          *     to invalidate secondary tlb entry they are all still valid.
2260          *     any further changes to individual pte will notify. So no need
2261          *     to call mmu_notifier->invalidate_range()
2262          */
2263         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2264                                                HPAGE_PMD_SIZE);
2265 }
2266
2267 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2268                 bool freeze, struct page *page)
2269 {
2270         pgd_t *pgd;
2271         p4d_t *p4d;
2272         pud_t *pud;
2273         pmd_t *pmd;
2274
2275         pgd = pgd_offset(vma->vm_mm, address);
2276         if (!pgd_present(*pgd))
2277                 return;
2278
2279         p4d = p4d_offset(pgd, address);
2280         if (!p4d_present(*p4d))
2281                 return;
2282
2283         pud = pud_offset(p4d, address);
2284         if (!pud_present(*pud))
2285                 return;
2286
2287         pmd = pmd_offset(pud, address);
2288
2289         __split_huge_pmd(vma, pmd, address, freeze, page);
2290 }
2291
2292 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2293                              unsigned long start,
2294                              unsigned long end,
2295                              long adjust_next)
2296 {
2297         /*
2298          * If the new start address isn't hpage aligned and it could
2299          * previously contain an hugepage: check if we need to split
2300          * an huge pmd.
2301          */
2302         if (start & ~HPAGE_PMD_MASK &&
2303             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2304             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2305                 split_huge_pmd_address(vma, start, false, NULL);
2306
2307         /*
2308          * If the new end address isn't hpage aligned and it could
2309          * previously contain an hugepage: check if we need to split
2310          * an huge pmd.
2311          */
2312         if (end & ~HPAGE_PMD_MASK &&
2313             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2314             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2315                 split_huge_pmd_address(vma, end, false, NULL);
2316
2317         /*
2318          * If we're also updating the vma->vm_next->vm_start, if the new
2319          * vm_next->vm_start isn't page aligned and it could previously
2320          * contain an hugepage: check if we need to split an huge pmd.
2321          */
2322         if (adjust_next > 0) {
2323                 struct vm_area_struct *next = vma->vm_next;
2324                 unsigned long nstart = next->vm_start;
2325                 nstart += adjust_next << PAGE_SHIFT;
2326                 if (nstart & ~HPAGE_PMD_MASK &&
2327                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2328                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2329                         split_huge_pmd_address(next, nstart, false, NULL);
2330         }
2331 }
2332
2333 static void freeze_page(struct page *page)
2334 {
2335         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2336                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2337         bool unmap_success;
2338
2339         VM_BUG_ON_PAGE(!PageHead(page), page);
2340
2341         if (PageAnon(page))
2342                 ttu_flags |= TTU_SPLIT_FREEZE;
2343
2344         unmap_success = try_to_unmap(page, ttu_flags);
2345         VM_BUG_ON_PAGE(!unmap_success, page);
2346 }
2347
2348 static void unfreeze_page(struct page *page)
2349 {
2350         int i;
2351         if (PageTransHuge(page)) {
2352                 remove_migration_ptes(page, page, true);
2353         } else {
2354                 for (i = 0; i < HPAGE_PMD_NR; i++)
2355                         remove_migration_ptes(page + i, page + i, true);
2356         }
2357 }
2358
2359 static void __split_huge_page_tail(struct page *head, int tail,
2360                 struct lruvec *lruvec, struct list_head *list)
2361 {
2362         struct page *page_tail = head + tail;
2363
2364         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2365
2366         /*
2367          * Clone page flags before unfreezing refcount.
2368          *
2369          * After successful get_page_unless_zero() might follow flags change,
2370          * for exmaple lock_page() which set PG_waiters.
2371          */
2372         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2373         page_tail->flags |= (head->flags &
2374                         ((1L << PG_referenced) |
2375                          (1L << PG_swapbacked) |
2376                          (1L << PG_swapcache) |
2377                          (1L << PG_mlocked) |
2378                          (1L << PG_uptodate) |
2379                          (1L << PG_active) |
2380                          (1L << PG_workingset) |
2381                          (1L << PG_locked) |
2382                          (1L << PG_unevictable) |
2383                          (1L << PG_dirty)));
2384
2385         /* Page flags must be visible before we make the page non-compound. */
2386         smp_wmb();
2387
2388         /*
2389          * Clear PageTail before unfreezing page refcount.
2390          *
2391          * After successful get_page_unless_zero() might follow put_page()
2392          * which needs correct compound_head().
2393          */
2394         clear_compound_head(page_tail);
2395
2396         /* Finally unfreeze refcount. Additional reference from page cache. */
2397         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2398                                           PageSwapCache(head)));
2399
2400         if (page_is_young(head))
2401                 set_page_young(page_tail);
2402         if (page_is_idle(head))
2403                 set_page_idle(page_tail);
2404
2405         /* ->mapping in first tail page is compound_mapcount */
2406         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2407                         page_tail);
2408         page_tail->mapping = head->mapping;
2409
2410         page_tail->index = head->index + tail;
2411         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2412
2413         /*
2414          * always add to the tail because some iterators expect new
2415          * pages to show after the currently processed elements - e.g.
2416          * migrate_pages
2417          */
2418         lru_add_page_tail(head, page_tail, lruvec, list);
2419 }
2420
2421 static void __split_huge_page(struct page *page, struct list_head *list,
2422                 unsigned long flags)
2423 {
2424         struct page *head = compound_head(page);
2425         struct zone *zone = page_zone(head);
2426         struct lruvec *lruvec;
2427         pgoff_t end = -1;
2428         int i;
2429
2430         lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
2431
2432         /* complete memcg works before add pages to LRU */
2433         mem_cgroup_split_huge_fixup(head);
2434
2435         if (!PageAnon(page))
2436                 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE);
2437
2438         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2439                 __split_huge_page_tail(head, i, lruvec, list);
2440                 /* Some pages can be beyond i_size: drop them from page cache */
2441                 if (head[i].index >= end) {
2442                         ClearPageDirty(head + i);
2443                         __delete_from_page_cache(head + i, NULL);
2444                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2445                                 shmem_uncharge(head->mapping->host, 1);
2446                         put_page(head + i);
2447                 }
2448         }
2449
2450         ClearPageCompound(head);
2451         /* See comment in __split_huge_page_tail() */
2452         if (PageAnon(head)) {
2453                 /* Additional pin to swap cache */
2454                 if (PageSwapCache(head))
2455                         page_ref_add(head, 2);
2456                 else
2457                         page_ref_inc(head);
2458         } else {
2459                 /* Additional pin to page cache */
2460                 page_ref_add(head, 2);
2461                 xa_unlock(&head->mapping->i_pages);
2462         }
2463
2464         spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2465
2466         unfreeze_page(head);
2467
2468         for (i = 0; i < HPAGE_PMD_NR; i++) {
2469                 struct page *subpage = head + i;
2470                 if (subpage == page)
2471                         continue;
2472                 unlock_page(subpage);
2473
2474                 /*
2475                  * Subpages may be freed if there wasn't any mapping
2476                  * like if add_to_swap() is running on a lru page that
2477                  * had its mapping zapped. And freeing these pages
2478                  * requires taking the lru_lock so we do the put_page
2479                  * of the tail pages after the split is complete.
2480                  */
2481                 put_page(subpage);
2482         }
2483 }
2484
2485 int total_mapcount(struct page *page)
2486 {
2487         int i, compound, ret;
2488
2489         VM_BUG_ON_PAGE(PageTail(page), page);
2490
2491         if (likely(!PageCompound(page)))
2492                 return atomic_read(&page->_mapcount) + 1;
2493
2494         compound = compound_mapcount(page);
2495         if (PageHuge(page))
2496                 return compound;
2497         ret = compound;
2498         for (i = 0; i < HPAGE_PMD_NR; i++)
2499                 ret += atomic_read(&page[i]._mapcount) + 1;
2500         /* File pages has compound_mapcount included in _mapcount */
2501         if (!PageAnon(page))
2502                 return ret - compound * HPAGE_PMD_NR;
2503         if (PageDoubleMap(page))
2504                 ret -= HPAGE_PMD_NR;
2505         return ret;
2506 }
2507
2508 /*
2509  * This calculates accurately how many mappings a transparent hugepage
2510  * has (unlike page_mapcount() which isn't fully accurate). This full
2511  * accuracy is primarily needed to know if copy-on-write faults can
2512  * reuse the page and change the mapping to read-write instead of
2513  * copying them. At the same time this returns the total_mapcount too.
2514  *
2515  * The function returns the highest mapcount any one of the subpages
2516  * has. If the return value is one, even if different processes are
2517  * mapping different subpages of the transparent hugepage, they can
2518  * all reuse it, because each process is reusing a different subpage.
2519  *
2520  * The total_mapcount is instead counting all virtual mappings of the
2521  * subpages. If the total_mapcount is equal to "one", it tells the
2522  * caller all mappings belong to the same "mm" and in turn the
2523  * anon_vma of the transparent hugepage can become the vma->anon_vma
2524  * local one as no other process may be mapping any of the subpages.
2525  *
2526  * It would be more accurate to replace page_mapcount() with
2527  * page_trans_huge_mapcount(), however we only use
2528  * page_trans_huge_mapcount() in the copy-on-write faults where we
2529  * need full accuracy to avoid breaking page pinning, because
2530  * page_trans_huge_mapcount() is slower than page_mapcount().
2531  */
2532 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2533 {
2534         int i, ret, _total_mapcount, mapcount;
2535
2536         /* hugetlbfs shouldn't call it */
2537         VM_BUG_ON_PAGE(PageHuge(page), page);
2538
2539         if (likely(!PageTransCompound(page))) {
2540                 mapcount = atomic_read(&page->_mapcount) + 1;
2541                 if (total_mapcount)
2542                         *total_mapcount = mapcount;
2543                 return mapcount;
2544         }
2545
2546         page = compound_head(page);
2547
2548         _total_mapcount = ret = 0;
2549         for (i = 0; i < HPAGE_PMD_NR; i++) {
2550                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2551                 ret = max(ret, mapcount);
2552                 _total_mapcount += mapcount;
2553         }
2554         if (PageDoubleMap(page)) {
2555                 ret -= 1;
2556                 _total_mapcount -= HPAGE_PMD_NR;
2557         }
2558         mapcount = compound_mapcount(page);
2559         ret += mapcount;
2560         _total_mapcount += mapcount;
2561         if (total_mapcount)
2562                 *total_mapcount = _total_mapcount;
2563         return ret;
2564 }
2565
2566 /* Racy check whether the huge page can be split */
2567 bool can_split_huge_page(struct page *page, int *pextra_pins)
2568 {
2569         int extra_pins;
2570
2571         /* Additional pins from page cache */
2572         if (PageAnon(page))
2573                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2574         else
2575                 extra_pins = HPAGE_PMD_NR;
2576         if (pextra_pins)
2577                 *pextra_pins = extra_pins;
2578         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2579 }
2580
2581 /*
2582  * This function splits huge page into normal pages. @page can point to any
2583  * subpage of huge page to split. Split doesn't change the position of @page.
2584  *
2585  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2586  * The huge page must be locked.
2587  *
2588  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2589  *
2590  * Both head page and tail pages will inherit mapping, flags, and so on from
2591  * the hugepage.
2592  *
2593  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2594  * they are not mapped.
2595  *
2596  * Returns 0 if the hugepage is split successfully.
2597  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2598  * us.
2599  */
2600 int split_huge_page_to_list(struct page *page, struct list_head *list)
2601 {
2602         struct page *head = compound_head(page);
2603         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2604         struct anon_vma *anon_vma = NULL;
2605         struct address_space *mapping = NULL;
2606         int count, mapcount, extra_pins, ret;
2607         bool mlocked;
2608         unsigned long flags;
2609
2610         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2611         VM_BUG_ON_PAGE(!PageLocked(page), page);
2612         VM_BUG_ON_PAGE(!PageCompound(page), page);
2613
2614         if (PageWriteback(page))
2615                 return -EBUSY;
2616
2617         if (PageAnon(head)) {
2618                 /*
2619                  * The caller does not necessarily hold an mmap_sem that would
2620                  * prevent the anon_vma disappearing so we first we take a
2621                  * reference to it and then lock the anon_vma for write. This
2622                  * is similar to page_lock_anon_vma_read except the write lock
2623                  * is taken to serialise against parallel split or collapse
2624                  * operations.
2625                  */
2626                 anon_vma = page_get_anon_vma(head);
2627                 if (!anon_vma) {
2628                         ret = -EBUSY;
2629                         goto out;
2630                 }
2631                 mapping = NULL;
2632                 anon_vma_lock_write(anon_vma);
2633         } else {
2634                 mapping = head->mapping;
2635
2636                 /* Truncated ? */
2637                 if (!mapping) {
2638                         ret = -EBUSY;
2639                         goto out;
2640                 }
2641
2642                 anon_vma = NULL;
2643                 i_mmap_lock_read(mapping);
2644         }
2645
2646         /*
2647          * Racy check if we can split the page, before freeze_page() will
2648          * split PMDs
2649          */
2650         if (!can_split_huge_page(head, &extra_pins)) {
2651                 ret = -EBUSY;
2652                 goto out_unlock;
2653         }
2654
2655         mlocked = PageMlocked(page);
2656         freeze_page(head);
2657         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2658
2659         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2660         if (mlocked)
2661                 lru_add_drain();
2662
2663         /* prevent PageLRU to go away from under us, and freeze lru stats */
2664         spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2665
2666         if (mapping) {
2667                 XA_STATE(xas, &mapping->i_pages, page_index(head));
2668
2669                 /*
2670                  * Check if the head page is present in page cache.
2671                  * We assume all tail are present too, if head is there.
2672                  */
2673                 xa_lock(&mapping->i_pages);
2674                 if (xas_load(&xas) != head)
2675                         goto fail;
2676         }
2677
2678         /* Prevent deferred_split_scan() touching ->_refcount */
2679         spin_lock(&pgdata->split_queue_lock);
2680         count = page_count(head);
2681         mapcount = total_mapcount(head);
2682         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2683                 if (!list_empty(page_deferred_list(head))) {
2684                         pgdata->split_queue_len--;
2685                         list_del(page_deferred_list(head));
2686                 }
2687                 if (mapping)
2688                         __dec_node_page_state(page, NR_SHMEM_THPS);
2689                 spin_unlock(&pgdata->split_queue_lock);
2690                 __split_huge_page(page, list, flags);
2691                 if (PageSwapCache(head)) {
2692                         swp_entry_t entry = { .val = page_private(head) };
2693
2694                         ret = split_swap_cluster(entry);
2695                 } else
2696                         ret = 0;
2697         } else {
2698                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2699                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2700                                         mapcount, count);
2701                         if (PageTail(page))
2702                                 dump_page(head, NULL);
2703                         dump_page(page, "total_mapcount(head) > 0");
2704                         BUG();
2705                 }
2706                 spin_unlock(&pgdata->split_queue_lock);
2707 fail:           if (mapping)
2708                         xa_unlock(&mapping->i_pages);
2709                 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2710                 unfreeze_page(head);
2711                 ret = -EBUSY;
2712         }
2713
2714 out_unlock:
2715         if (anon_vma) {
2716                 anon_vma_unlock_write(anon_vma);
2717                 put_anon_vma(anon_vma);
2718         }
2719         if (mapping)
2720                 i_mmap_unlock_read(mapping);
2721 out:
2722         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2723         return ret;
2724 }
2725
2726 void free_transhuge_page(struct page *page)
2727 {
2728         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2729         unsigned long flags;
2730
2731         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2732         if (!list_empty(page_deferred_list(page))) {
2733                 pgdata->split_queue_len--;
2734                 list_del(page_deferred_list(page));
2735         }
2736         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2737         free_compound_page(page);
2738 }
2739
2740 void deferred_split_huge_page(struct page *page)
2741 {
2742         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2743         unsigned long flags;
2744
2745         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2746
2747         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2748         if (list_empty(page_deferred_list(page))) {
2749                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2750                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2751                 pgdata->split_queue_len++;
2752         }
2753         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2754 }
2755
2756 static unsigned long deferred_split_count(struct shrinker *shrink,
2757                 struct shrink_control *sc)
2758 {
2759         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2760         return READ_ONCE(pgdata->split_queue_len);
2761 }
2762
2763 static unsigned long deferred_split_scan(struct shrinker *shrink,
2764                 struct shrink_control *sc)
2765 {
2766         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2767         unsigned long flags;
2768         LIST_HEAD(list), *pos, *next;
2769         struct page *page;
2770         int split = 0;
2771
2772         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2773         /* Take pin on all head pages to avoid freeing them under us */
2774         list_for_each_safe(pos, next, &pgdata->split_queue) {
2775                 page = list_entry((void *)pos, struct page, mapping);
2776                 page = compound_head(page);
2777                 if (get_page_unless_zero(page)) {
2778                         list_move(page_deferred_list(page), &list);
2779                 } else {
2780                         /* We lost race with put_compound_page() */
2781                         list_del_init(page_deferred_list(page));
2782                         pgdata->split_queue_len--;
2783                 }
2784                 if (!--sc->nr_to_scan)
2785                         break;
2786         }
2787         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2788
2789         list_for_each_safe(pos, next, &list) {
2790                 page = list_entry((void *)pos, struct page, mapping);
2791                 if (!trylock_page(page))
2792                         goto next;
2793                 /* split_huge_page() removes page from list on success */
2794                 if (!split_huge_page(page))
2795                         split++;
2796                 unlock_page(page);
2797 next:
2798                 put_page(page);
2799         }
2800
2801         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2802         list_splice_tail(&list, &pgdata->split_queue);
2803         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2804
2805         /*
2806          * Stop shrinker if we didn't split any page, but the queue is empty.
2807          * This can happen if pages were freed under us.
2808          */
2809         if (!split && list_empty(&pgdata->split_queue))
2810                 return SHRINK_STOP;
2811         return split;
2812 }
2813
2814 static struct shrinker deferred_split_shrinker = {
2815         .count_objects = deferred_split_count,
2816         .scan_objects = deferred_split_scan,
2817         .seeks = DEFAULT_SEEKS,
2818         .flags = SHRINKER_NUMA_AWARE,
2819 };
2820
2821 #ifdef CONFIG_DEBUG_FS
2822 static int split_huge_pages_set(void *data, u64 val)
2823 {
2824         struct zone *zone;
2825         struct page *page;
2826         unsigned long pfn, max_zone_pfn;
2827         unsigned long total = 0, split = 0;
2828
2829         if (val != 1)
2830                 return -EINVAL;
2831
2832         for_each_populated_zone(zone) {
2833                 max_zone_pfn = zone_end_pfn(zone);
2834                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2835                         if (!pfn_valid(pfn))
2836                                 continue;
2837
2838                         page = pfn_to_page(pfn);
2839                         if (!get_page_unless_zero(page))
2840                                 continue;
2841
2842                         if (zone != page_zone(page))
2843                                 goto next;
2844
2845                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2846                                 goto next;
2847
2848                         total++;
2849                         lock_page(page);
2850                         if (!split_huge_page(page))
2851                                 split++;
2852                         unlock_page(page);
2853 next:
2854                         put_page(page);
2855                 }
2856         }
2857
2858         pr_info("%lu of %lu THP split\n", split, total);
2859
2860         return 0;
2861 }
2862 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2863                 "%llu\n");
2864
2865 static int __init split_huge_pages_debugfs(void)
2866 {
2867         void *ret;
2868
2869         ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2870                         &split_huge_pages_fops);
2871         if (!ret)
2872                 pr_warn("Failed to create split_huge_pages in debugfs");
2873         return 0;
2874 }
2875 late_initcall(split_huge_pages_debugfs);
2876 #endif
2877
2878 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2879 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2880                 struct page *page)
2881 {
2882         struct vm_area_struct *vma = pvmw->vma;
2883         struct mm_struct *mm = vma->vm_mm;
2884         unsigned long address = pvmw->address;
2885         pmd_t pmdval;
2886         swp_entry_t entry;
2887         pmd_t pmdswp;
2888
2889         if (!(pvmw->pmd && !pvmw->pte))
2890                 return;
2891
2892         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2893         pmdval = *pvmw->pmd;
2894         pmdp_invalidate(vma, address, pvmw->pmd);
2895         if (pmd_dirty(pmdval))
2896                 set_page_dirty(page);
2897         entry = make_migration_entry(page, pmd_write(pmdval));
2898         pmdswp = swp_entry_to_pmd(entry);
2899         if (pmd_soft_dirty(pmdval))
2900                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2901         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2902         page_remove_rmap(page, true);
2903         put_page(page);
2904 }
2905
2906 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2907 {
2908         struct vm_area_struct *vma = pvmw->vma;
2909         struct mm_struct *mm = vma->vm_mm;
2910         unsigned long address = pvmw->address;
2911         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2912         pmd_t pmde;
2913         swp_entry_t entry;
2914
2915         if (!(pvmw->pmd && !pvmw->pte))
2916                 return;
2917
2918         entry = pmd_to_swp_entry(*pvmw->pmd);
2919         get_page(new);
2920         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2921         if (pmd_swp_soft_dirty(*pvmw->pmd))
2922                 pmde = pmd_mksoft_dirty(pmde);
2923         if (is_write_migration_entry(entry))
2924                 pmde = maybe_pmd_mkwrite(pmde, vma);
2925
2926         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2927         if (PageAnon(new))
2928                 page_add_anon_rmap(new, vma, mmun_start, true);
2929         else
2930                 page_add_file_rmap(new, true);
2931         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
2932         if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
2933                 mlock_vma_page(new);
2934         update_mmu_cache_pmd(vma, address, pvmw->pmd);
2935 }
2936 #endif