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         /*
 487          * ->lru in the tail pages is occupied by compound_head.
 488          * Let's use ->mapping + ->index in the second tail page as list_head.
 489          */
 490         return (struct list_head *)&page[2].mapping;
 491 }
 492
 493 void prep_transhuge_page(struct page *page)
 494 {
 495         /*
 496          * we use page->mapping and page->indexlru in second tail page
 497          * as list_head: assuming THP order >= 2
 498          */
 499
 500         INIT_LIST_HEAD(page_deferred_list(page));
 501         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 502 }
 503
 504 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
 505                 loff_t off, unsigned long flags, unsigned long size)
 506 {
 507         unsigned long addr;
 508         loff_t off_end = off + len;
 509         loff_t off_align = round_up(off, size);
 510         unsigned long len_pad;
 511
 512         if (off_end <= off_align || (off_end - off_align) < size)
 513                 return 0;
 514
 515         len_pad = len + size;
 516         if (len_pad < len || (off + len_pad) < off)
 517                 return 0;
 518
 519         addr = current->mm->get_unmapped_area(filp, 0, len_pad,
 520                                               off >> PAGE_SHIFT, flags);
 521         if (IS_ERR_VALUE(addr))
 522                 return 0;
 523
 524         addr += (off - addr) & (size - 1);
 525         return addr;
 526 }
 527
 528 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 529                 unsigned long len, unsigned long pgoff, unsigned long flags)
 530 {
 531         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 532
 533         if (addr)
 534                 goto out;
 535         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
 536                 goto out;
 537
 538         addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
 539         if (addr)
 540                 return addr;
 541
 542  out:
 543         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 544 }
 545 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 546
 547 static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page,
 548                 gfp_t gfp)
 549 {
 550         struct vm_area_struct *vma = vmf->vma;
 551         struct mem_cgroup *memcg;
 552         pgtable_t pgtable;
 553         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 554         int ret = 0;
 555
 556         VM_BUG_ON_PAGE(!PageCompound(page), page);
 557
 558         if (mem_cgroup_try_charge(page, vma->vm_mm, gfp, &memcg, true)) {
 559                 put_page(page);
 560                 count_vm_event(THP_FAULT_FALLBACK);
 561                 return VM_FAULT_FALLBACK;
 562         }
 563
 564         pgtable = pte_alloc_one(vma->vm_mm, haddr);
 565         if (unlikely(!pgtable)) {
 566                 ret = VM_FAULT_OOM;
 567                 goto release;
 568         }
 569
 570         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
 571         /*
 572          * The memory barrier inside __SetPageUptodate makes sure that
 573          * clear_huge_page writes become visible before the set_pmd_at()
 574          * write.
 575          */
 576         __SetPageUptodate(page);
 577
 578         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 579         if (unlikely(!pmd_none(*vmf->pmd))) {
 580                 goto unlock_release;
 581         } else {
 582                 pmd_t entry;
 583
 584                 ret = check_stable_address_space(vma->vm_mm);
 585                 if (ret)
 586                         goto unlock_release;
 587
 588                 /* Deliver the page fault to userland */
 589                 if (userfaultfd_missing(vma)) {
 590                         int ret;
 591
 592                         spin_unlock(vmf->ptl);
 593                         mem_cgroup_cancel_charge(page, memcg, true);
 594                         put_page(page);
 595                         pte_free(vma->vm_mm, pgtable);
 596                         ret = handle_userfault(vmf, VM_UFFD_MISSING);
 597                         VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 598                         return ret;
 599                 }
 600
 601                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 602                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 603                 page_add_new_anon_rmap(page, vma, haddr, true);
 604                 mem_cgroup_commit_charge(page, memcg, false, true);
 605                 lru_cache_add_active_or_unevictable(page, vma);
 606                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 607                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 608                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 609                 mm_inc_nr_ptes(vma->vm_mm);
 610                 spin_unlock(vmf->ptl);
 611                 count_vm_event(THP_FAULT_ALLOC);
 612         }
 613
 614         return 0;
 615 unlock_release:
 616         spin_unlock(vmf->ptl);
 617 release:
 618         if (pgtable)
 619                 pte_free(vma->vm_mm, pgtable);
 620         mem_cgroup_cancel_charge(page, memcg, true);
 621         put_page(page);
 622         return ret;
 623
 624 }
 625
 626 /*
 627  * always: directly stall for all thp allocations
 628  * defer: wake kswapd and fail if not immediately available
 629  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
 630  *                fail if not immediately available
 631  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
 632  *          available
 633  * never: never stall for any thp allocation
 634  */
 635 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
 636 {
 637         const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
 638
 639         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 640                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
 641         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 642                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
 643         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 644                 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
 645                                                              __GFP_KSWAPD_RECLAIM);
 646         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 647                 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
 648                                                              0);
 649         return GFP_TRANSHUGE_LIGHT;
 650 }
 651
 652 /* Caller must hold page table lock. */
 653 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 654                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 655                 struct page *zero_page)
 656 {
 657         pmd_t entry;
 658         if (!pmd_none(*pmd))
 659                 return false;
 660         entry = mk_pmd(zero_page, vma->vm_page_prot);
 661         entry = pmd_mkhuge(entry);
 662         if (pgtable)
 663                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 664         set_pmd_at(mm, haddr, pmd, entry);
 665         mm_inc_nr_ptes(mm);
 666         return true;
 667 }
 668
 669 int do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 670 {
 671         struct vm_area_struct *vma = vmf->vma;
 672         gfp_t gfp;
 673         struct page *page;
 674         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 675
 676         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
 677                 return VM_FAULT_FALLBACK;
 678         if (unlikely(anon_vma_prepare(vma)))
 679                 return VM_FAULT_OOM;
 680         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 681                 return VM_FAULT_OOM;
 682         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
 683                         !mm_forbids_zeropage(vma->vm_mm) &&
 684                         transparent_hugepage_use_zero_page()) {
 685                 pgtable_t pgtable;
 686                 struct page *zero_page;
 687                 bool set;
 688                 int ret;
 689                 pgtable = pte_alloc_one(vma->vm_mm, haddr);
 690                 if (unlikely(!pgtable))
 691                         return VM_FAULT_OOM;
 692                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
 693                 if (unlikely(!zero_page)) {
 694                         pte_free(vma->vm_mm, pgtable);
 695                         count_vm_event(THP_FAULT_FALLBACK);
 696                         return VM_FAULT_FALLBACK;
 697                 }
 698                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 699                 ret = 0;
 700                 set = false;
 701                 if (pmd_none(*vmf->pmd)) {
 702                         ret = check_stable_address_space(vma->vm_mm);
 703                         if (ret) {
 704                                 spin_unlock(vmf->ptl);
 705                         } else if (userfaultfd_missing(vma)) {
 706                                 spin_unlock(vmf->ptl);
 707                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
 708                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 709                         } else {
 710                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
 711                                                    haddr, vmf->pmd, zero_page);
 712                                 spin_unlock(vmf->ptl);
 713                                 set = true;
 714                         }
 715                 } else
 716                         spin_unlock(vmf->ptl);
 717                 if (!set)
 718                         pte_free(vma->vm_mm, pgtable);
 719                 return ret;
 720         }
 721         gfp = alloc_hugepage_direct_gfpmask(vma);
 722         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 723         if (unlikely(!page)) {
 724                 count_vm_event(THP_FAULT_FALLBACK);
 725                 return VM_FAULT_FALLBACK;
 726         }
 727         prep_transhuge_page(page);
 728         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
 729 }
 730
 731 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 732                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
 733                 pgtable_t pgtable)
 734 {
 735         struct mm_struct *mm = vma->vm_mm;
 736         pmd_t entry;
 737         spinlock_t *ptl;
 738
 739         ptl = pmd_lock(mm, pmd);
 740         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 741         if (pfn_t_devmap(pfn))
 742                 entry = pmd_mkdevmap(entry);
 743         if (write) {
 744                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 745                 entry = maybe_pmd_mkwrite(entry, vma);
 746         }
 747
 748         if (pgtable) {
 749                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 750                 mm_inc_nr_ptes(mm);
 751         }
 752
 753         set_pmd_at(mm, addr, pmd, entry);
 754         update_mmu_cache_pmd(vma, addr, pmd);
 755         spin_unlock(ptl);
 756 }
 757
 758 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 759                         pmd_t *pmd, pfn_t pfn, bool write)
 760 {
 761         pgprot_t pgprot = vma->vm_page_prot;
 762         pgtable_t pgtable = NULL;
 763         /*
 764          * If we had pmd_special, we could avoid all these restrictions,
 765          * but we need to be consistent with PTEs and architectures that
 766          * can't support a 'special' bit.
 767          */
 768         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
 769         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 770                                                 (VM_PFNMAP|VM_MIXEDMAP));
 771         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 772         BUG_ON(!pfn_t_devmap(pfn));
 773
 774         if (addr < vma->vm_start || addr >= vma->vm_end)
 775                 return VM_FAULT_SIGBUS;
 776
 777         if (arch_needs_pgtable_deposit()) {
 778                 pgtable = pte_alloc_one(vma->vm_mm, addr);
 779                 if (!pgtable)
 780                         return VM_FAULT_OOM;
 781         }
 782
 783         track_pfn_insert(vma, &pgprot, pfn);
 784
 785         insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable);
 786         return VM_FAULT_NOPAGE;
 787 }
 788 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
 789
 790 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 791 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 792 {
 793         if (likely(vma->vm_flags & VM_WRITE))
 794                 pud = pud_mkwrite(pud);
 795         return pud;
 796 }
 797
 798 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 799                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 800 {
 801         struct mm_struct *mm = vma->vm_mm;
 802         pud_t entry;
 803         spinlock_t *ptl;
 804
 805         ptl = pud_lock(mm, pud);
 806         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
 807         if (pfn_t_devmap(pfn))
 808                 entry = pud_mkdevmap(entry);
 809         if (write) {
 810                 entry = pud_mkyoung(pud_mkdirty(entry));
 811                 entry = maybe_pud_mkwrite(entry, vma);
 812         }
 813         set_pud_at(mm, addr, pud, entry);
 814         update_mmu_cache_pud(vma, addr, pud);
 815         spin_unlock(ptl);
 816 }
 817
 818 int vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 819                         pud_t *pud, pfn_t pfn, bool write)
 820 {
 821         pgprot_t pgprot = vma->vm_page_prot;
 822         /*
 823          * If we had pud_special, we could avoid all these restrictions,
 824          * but we need to be consistent with PTEs and architectures that
 825          * can't support a 'special' bit.
 826          */
 827         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
 828         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 829                                                 (VM_PFNMAP|VM_MIXEDMAP));
 830         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 831         BUG_ON(!pfn_t_devmap(pfn));
 832
 833         if (addr < vma->vm_start || addr >= vma->vm_end)
 834                 return VM_FAULT_SIGBUS;
 835
 836         track_pfn_insert(vma, &pgprot, pfn);
 837
 838         insert_pfn_pud(vma, addr, pud, pfn, pgprot, write);
 839         return VM_FAULT_NOPAGE;
 840 }
 841 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
 842 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 843
 844 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
 845                 pmd_t *pmd, int flags)
 846 {
 847         pmd_t _pmd;
 848
 849         _pmd = pmd_mkyoung(*pmd);
 850         if (flags & FOLL_WRITE)
 851                 _pmd = pmd_mkdirty(_pmd);
 852         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 853                                 pmd, _pmd, flags & FOLL_WRITE))
 854                 update_mmu_cache_pmd(vma, addr, pmd);
 855 }
 856
 857 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 858                 pmd_t *pmd, int flags)
 859 {
 860         unsigned long pfn = pmd_pfn(*pmd);
 861         struct mm_struct *mm = vma->vm_mm;
 862         struct dev_pagemap *pgmap;
 863         struct page *page;
 864
 865         assert_spin_locked(pmd_lockptr(mm, pmd));
 866
 867         /*
 868          * When we COW a devmap PMD entry, we split it into PTEs, so we should
 869          * not be in this function with `flags & FOLL_COW` set.
 870          */
 871         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
 872
 873         if (flags & FOLL_WRITE && !pmd_write(*pmd))
 874                 return NULL;
 875
 876         if (pmd_present(*pmd) && pmd_devmap(*pmd))
 877                 /* pass */;
 878         else
 879                 return NULL;
 880
 881         if (flags & FOLL_TOUCH)
 882                 touch_pmd(vma, addr, pmd, flags);
 883
 884         /*
 885          * device mapped pages can only be returned if the
 886          * caller will manage the page reference count.
 887          */
 888         if (!(flags & FOLL_GET))
 889                 return ERR_PTR(-EEXIST);
 890
 891         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
 892         pgmap = get_dev_pagemap(pfn, NULL);
 893         if (!pgmap)
 894                 return ERR_PTR(-EFAULT);
 895         page = pfn_to_page(pfn);
 896         get_page(page);
 897         put_dev_pagemap(pgmap);
 898
 899         return page;
 900 }
 901
 902 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 903                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 904                   struct vm_area_struct *vma)
 905 {
 906         spinlock_t *dst_ptl, *src_ptl;
 907         struct page *src_page;
 908         pmd_t pmd;
 909         pgtable_t pgtable = NULL;
 910         int ret = -ENOMEM;
 911
 912         /* Skip if can be re-fill on fault */
 913         if (!vma_is_anonymous(vma))
 914                 return 0;
 915
 916         pgtable = pte_alloc_one(dst_mm, addr);
 917         if (unlikely(!pgtable))
 918                 goto out;
 919
 920         dst_ptl = pmd_lock(dst_mm, dst_pmd);
 921         src_ptl = pmd_lockptr(src_mm, src_pmd);
 922         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 923
 924         ret = -EAGAIN;
 925         pmd = *src_pmd;
 926
 927 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
 928         if (unlikely(is_swap_pmd(pmd))) {
 929                 swp_entry_t entry = pmd_to_swp_entry(pmd);
 930
 931                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
 932                 if (is_write_migration_entry(entry)) {
 933                         make_migration_entry_read(&entry);
 934                         pmd = swp_entry_to_pmd(entry);
 935                         if (pmd_swp_soft_dirty(*src_pmd))
 936                                 pmd = pmd_swp_mksoft_dirty(pmd);
 937                         set_pmd_at(src_mm, addr, src_pmd, pmd);
 938                 }
 939                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 940                 mm_inc_nr_ptes(dst_mm);
 941                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 942                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 943                 ret = 0;
 944                 goto out_unlock;
 945         }
 946 #endif
 947
 948         if (unlikely(!pmd_trans_huge(pmd))) {
 949                 pte_free(dst_mm, pgtable);
 950                 goto out_unlock;
 951         }
 952         /*
 953          * When page table lock is held, the huge zero pmd should not be
 954          * under splitting since we don't split the page itself, only pmd to
 955          * a page table.
 956          */
 957         if (is_huge_zero_pmd(pmd)) {
 958                 struct page *zero_page;
 959                 /*
 960                  * get_huge_zero_page() will never allocate a new page here,
 961                  * since we already have a zero page to copy. It just takes a
 962                  * reference.
 963                  */
 964                 zero_page = mm_get_huge_zero_page(dst_mm);
 965                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
 966                                 zero_page);
 967                 ret = 0;
 968                 goto out_unlock;
 969         }
 970
 971         src_page = pmd_page(pmd);
 972         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
 973         get_page(src_page);
 974         page_dup_rmap(src_page, true);
 975         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 976         mm_inc_nr_ptes(dst_mm);
 977         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 978
 979         pmdp_set_wrprotect(src_mm, addr, src_pmd);
 980         pmd = pmd_mkold(pmd_wrprotect(pmd));
 981         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 982
 983         ret = 0;
 984 out_unlock:
 985         spin_unlock(src_ptl);
 986         spin_unlock(dst_ptl);
 987 out:
 988         return ret;
 989 }
 990
 991 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 992 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
 993                 pud_t *pud, int flags)
 994 {
 995         pud_t _pud;
 996
 997         _pud = pud_mkyoung(*pud);
 998         if (flags & FOLL_WRITE)
 999                 _pud = pud_mkdirty(_pud);
1000         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1001                                 pud, _pud, flags & FOLL_WRITE))
1002                 update_mmu_cache_pud(vma, addr, pud);
1003 }
1004
1005 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1006                 pud_t *pud, int flags)
1007 {
1008         unsigned long pfn = pud_pfn(*pud);
1009         struct mm_struct *mm = vma->vm_mm;
1010         struct dev_pagemap *pgmap;
1011         struct page *page;
1012
1013         assert_spin_locked(pud_lockptr(mm, pud));
1014
1015         if (flags & FOLL_WRITE && !pud_write(*pud))
1016                 return NULL;
1017
1018         if (pud_present(*pud) && pud_devmap(*pud))
1019                 /* pass */;
1020         else
1021                 return NULL;
1022
1023         if (flags & FOLL_TOUCH)
1024                 touch_pud(vma, addr, pud, flags);
1025
1026         /*
1027          * device mapped pages can only be returned if the
1028          * caller will manage the page reference count.
1029          */
1030         if (!(flags & FOLL_GET))
1031                 return ERR_PTR(-EEXIST);
1032
1033         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1034         pgmap = get_dev_pagemap(pfn, NULL);
1035         if (!pgmap)
1036                 return ERR_PTR(-EFAULT);
1037         page = pfn_to_page(pfn);
1038         get_page(page);
1039         put_dev_pagemap(pgmap);
1040
1041         return page;
1042 }
1043
1044 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1045                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1046                   struct vm_area_struct *vma)
1047 {
1048         spinlock_t *dst_ptl, *src_ptl;
1049         pud_t pud;
1050         int ret;
1051
1052         dst_ptl = pud_lock(dst_mm, dst_pud);
1053         src_ptl = pud_lockptr(src_mm, src_pud);
1054         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1055
1056         ret = -EAGAIN;
1057         pud = *src_pud;
1058         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1059                 goto out_unlock;
1060
1061         /*
1062          * When page table lock is held, the huge zero pud should not be
1063          * under splitting since we don't split the page itself, only pud to
1064          * a page table.
1065          */
1066         if (is_huge_zero_pud(pud)) {
1067                 /* No huge zero pud yet */
1068         }
1069
1070         pudp_set_wrprotect(src_mm, addr, src_pud);
1071         pud = pud_mkold(pud_wrprotect(pud));
1072         set_pud_at(dst_mm, addr, dst_pud, pud);
1073
1074         ret = 0;
1075 out_unlock:
1076         spin_unlock(src_ptl);
1077         spin_unlock(dst_ptl);
1078         return ret;
1079 }
1080
1081 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1082 {
1083         pud_t entry;
1084         unsigned long haddr;
1085         bool write = vmf->flags & FAULT_FLAG_WRITE;
1086
1087         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1088         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1089                 goto unlock;
1090
1091         entry = pud_mkyoung(orig_pud);
1092         if (write)
1093                 entry = pud_mkdirty(entry);
1094         haddr = vmf->address & HPAGE_PUD_MASK;
1095         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1096                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1097
1098 unlock:
1099         spin_unlock(vmf->ptl);
1100 }
1101 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1102
1103 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1104 {
1105         pmd_t entry;
1106         unsigned long haddr;
1107         bool write = vmf->flags & FAULT_FLAG_WRITE;
1108
1109         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1110         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1111                 goto unlock;
1112
1113         entry = pmd_mkyoung(orig_pmd);
1114         if (write)
1115                 entry = pmd_mkdirty(entry);
1116         haddr = vmf->address & HPAGE_PMD_MASK;
1117         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1118                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1119
1120 unlock:
1121         spin_unlock(vmf->ptl);
1122 }
1123
1124 static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd,
1125                 struct page *page)
1126 {
1127         struct vm_area_struct *vma = vmf->vma;
1128         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1129         struct mem_cgroup *memcg;
1130         pgtable_t pgtable;
1131         pmd_t _pmd;
1132         int ret = 0, i;
1133         struct page **pages;
1134         unsigned long mmun_start;       /* For mmu_notifiers */
1135         unsigned long mmun_end;         /* For mmu_notifiers */
1136
1137         pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1138                         GFP_KERNEL);
1139         if (unlikely(!pages)) {
1140                 ret |= VM_FAULT_OOM;
1141                 goto out;
1142         }
1143
1144         for (i = 0; i < HPAGE_PMD_NR; i++) {
1145                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1146                                                vmf->address, page_to_nid(page));
1147                 if (unlikely(!pages[i] ||
1148                              mem_cgroup_try_charge(pages[i], vma->vm_mm,
1149                                      GFP_KERNEL, &memcg, false))) {
1150                         if (pages[i])
1151                                 put_page(pages[i]);
1152                         while (--i >= 0) {
1153                                 memcg = (void *)page_private(pages[i]);
1154                                 set_page_private(pages[i], 0);
1155                                 mem_cgroup_cancel_charge(pages[i], memcg,
1156                                                 false);
1157                                 put_page(pages[i]);
1158                         }
1159                         kfree(pages);
1160                         ret |= VM_FAULT_OOM;
1161                         goto out;
1162                 }
1163                 set_page_private(pages[i], (unsigned long)memcg);
1164         }
1165
1166         for (i = 0; i < HPAGE_PMD_NR; i++) {
1167                 copy_user_highpage(pages[i], page + i,
1168                                    haddr + PAGE_SIZE * i, vma);
1169                 __SetPageUptodate(pages[i]);
1170                 cond_resched();
1171         }
1172
1173         mmun_start = haddr;
1174         mmun_end   = haddr + HPAGE_PMD_SIZE;
1175         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1176
1177         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1178         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1179                 goto out_free_pages;
1180         VM_BUG_ON_PAGE(!PageHead(page), page);
1181
1182         /*
1183          * Leave pmd empty until pte is filled note we must notify here as
1184          * concurrent CPU thread might write to new page before the call to
1185          * mmu_notifier_invalidate_range_end() happens which can lead to a
1186          * device seeing memory write in different order than CPU.
1187          *
1188          * See Documentation/vm/mmu_notifier.txt
1189          */
1190         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1191
1192         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1193         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1194
1195         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1196                 pte_t entry;
1197                 entry = mk_pte(pages[i], vma->vm_page_prot);
1198                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1199                 memcg = (void *)page_private(pages[i]);
1200                 set_page_private(pages[i], 0);
1201                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1202                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1203                 lru_cache_add_active_or_unevictable(pages[i], vma);
1204                 vmf->pte = pte_offset_map(&_pmd, haddr);
1205                 VM_BUG_ON(!pte_none(*vmf->pte));
1206                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1207                 pte_unmap(vmf->pte);
1208         }
1209         kfree(pages);
1210
1211         smp_wmb(); /* make pte visible before pmd */
1212         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1213         page_remove_rmap(page, true);
1214         spin_unlock(vmf->ptl);
1215
1216         /*
1217          * No need to double call mmu_notifier->invalidate_range() callback as
1218          * the above pmdp_huge_clear_flush_notify() did already call it.
1219          */
1220         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1221                                                 mmun_end);
1222
1223         ret |= VM_FAULT_WRITE;
1224         put_page(page);
1225
1226 out:
1227         return ret;
1228
1229 out_free_pages:
1230         spin_unlock(vmf->ptl);
1231         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1232         for (i = 0; i < HPAGE_PMD_NR; i++) {
1233                 memcg = (void *)page_private(pages[i]);
1234                 set_page_private(pages[i], 0);
1235                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1236                 put_page(pages[i]);
1237         }
1238         kfree(pages);
1239         goto out;
1240 }
1241
1242 int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1243 {
1244         struct vm_area_struct *vma = vmf->vma;
1245         struct page *page = NULL, *new_page;
1246         struct mem_cgroup *memcg;
1247         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1248         unsigned long mmun_start;       /* For mmu_notifiers */
1249         unsigned long mmun_end;         /* For mmu_notifiers */
1250         gfp_t huge_gfp;                 /* for allocation and charge */
1251         int ret = 0;
1252
1253         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1254         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1255         if (is_huge_zero_pmd(orig_pmd))
1256                 goto alloc;
1257         spin_lock(vmf->ptl);
1258         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1259                 goto out_unlock;
1260
1261         page = pmd_page(orig_pmd);
1262         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1263         /*
1264          * We can only reuse the page if nobody else maps the huge page or it's
1265          * part.
1266          */
1267         if (!trylock_page(page)) {
1268                 get_page(page);
1269                 spin_unlock(vmf->ptl);
1270                 lock_page(page);
1271                 spin_lock(vmf->ptl);
1272                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1273                         unlock_page(page);
1274                         put_page(page);
1275                         goto out_unlock;
1276                 }
1277                 put_page(page);
1278         }
1279         if (reuse_swap_page(page, NULL)) {
1280                 pmd_t entry;
1281                 entry = pmd_mkyoung(orig_pmd);
1282                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1283                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1284                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1285                 ret |= VM_FAULT_WRITE;
1286                 unlock_page(page);
1287                 goto out_unlock;
1288         }
1289         unlock_page(page);
1290         get_page(page);
1291         spin_unlock(vmf->ptl);
1292 alloc:
1293         if (transparent_hugepage_enabled(vma) &&
1294             !transparent_hugepage_debug_cow()) {
1295                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1296                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1297         } else
1298                 new_page = NULL;
1299
1300         if (likely(new_page)) {
1301                 prep_transhuge_page(new_page);
1302         } else {
1303                 if (!page) {
1304                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1305                         ret |= VM_FAULT_FALLBACK;
1306                 } else {
1307                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1308                         if (ret & VM_FAULT_OOM) {
1309                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1310                                 ret |= VM_FAULT_FALLBACK;
1311                         }
1312                         put_page(page);
1313                 }
1314                 count_vm_event(THP_FAULT_FALLBACK);
1315                 goto out;
1316         }
1317
1318         if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm,
1319                                         huge_gfp, &memcg, true))) {
1320                 put_page(new_page);
1321                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1322                 if (page)
1323                         put_page(page);
1324                 ret |= VM_FAULT_FALLBACK;
1325                 count_vm_event(THP_FAULT_FALLBACK);
1326                 goto out;
1327         }
1328
1329         count_vm_event(THP_FAULT_ALLOC);
1330
1331         if (!page)
1332                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1333         else
1334                 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1335         __SetPageUptodate(new_page);
1336
1337         mmun_start = haddr;
1338         mmun_end   = haddr + HPAGE_PMD_SIZE;
1339         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1340
1341         spin_lock(vmf->ptl);
1342         if (page)
1343                 put_page(page);
1344         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1345                 spin_unlock(vmf->ptl);
1346                 mem_cgroup_cancel_charge(new_page, memcg, true);
1347                 put_page(new_page);
1348                 goto out_mn;
1349         } else {
1350                 pmd_t entry;
1351                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1352                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1353                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1354                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1355                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1356                 lru_cache_add_active_or_unevictable(new_page, vma);
1357                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1358                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1359                 if (!page) {
1360                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1361                 } else {
1362                         VM_BUG_ON_PAGE(!PageHead(page), page);
1363                         page_remove_rmap(page, true);
1364                         put_page(page);
1365                 }
1366                 ret |= VM_FAULT_WRITE;
1367         }
1368         spin_unlock(vmf->ptl);
1369 out_mn:
1370         /*
1371          * No need to double call mmu_notifier->invalidate_range() callback as
1372          * the above pmdp_huge_clear_flush_notify() did already call it.
1373          */
1374         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1375                                                mmun_end);
1376 out:
1377         return ret;
1378 out_unlock:
1379         spin_unlock(vmf->ptl);
1380         return ret;
1381 }
1382
1383 /*
1384  * FOLL_FORCE can write to even unwritable pmd's, but only
1385  * after we've gone through a COW cycle and they are dirty.
1386  */
1387 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1388 {
1389         return pmd_write(pmd) ||
1390                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1391 }
1392
1393 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1394                                    unsigned long addr,
1395                                    pmd_t *pmd,
1396                                    unsigned int flags)
1397 {
1398         struct mm_struct *mm = vma->vm_mm;
1399         struct page *page = NULL;
1400
1401         assert_spin_locked(pmd_lockptr(mm, pmd));
1402
1403         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1404                 goto out;
1405
1406         /* Avoid dumping huge zero page */
1407         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1408                 return ERR_PTR(-EFAULT);
1409
1410         /* Full NUMA hinting faults to serialise migration in fault paths */
1411         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1412                 goto out;
1413
1414         page = pmd_page(*pmd);
1415         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1416         if (flags & FOLL_TOUCH)
1417                 touch_pmd(vma, addr, pmd, flags);
1418         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1419                 /*
1420                  * We don't mlock() pte-mapped THPs. This way we can avoid
1421                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1422                  *
1423                  * For anon THP:
1424                  *
1425                  * In most cases the pmd is the only mapping of the page as we
1426                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1427                  * writable private mappings in populate_vma_page_range().
1428                  *
1429                  * The only scenario when we have the page shared here is if we
1430                  * mlocking read-only mapping shared over fork(). We skip
1431                  * mlocking such pages.
1432                  *
1433                  * For file THP:
1434                  *
1435                  * We can expect PageDoubleMap() to be stable under page lock:
1436                  * for file pages we set it in page_add_file_rmap(), which
1437                  * requires page to be locked.
1438                  */
1439
1440                 if (PageAnon(page) && compound_mapcount(page) != 1)
1441                         goto skip_mlock;
1442                 if (PageDoubleMap(page) || !page->mapping)
1443                         goto skip_mlock;
1444                 if (!trylock_page(page))
1445                         goto skip_mlock;
1446                 lru_add_drain();
1447                 if (page->mapping && !PageDoubleMap(page))
1448                         mlock_vma_page(page);
1449                 unlock_page(page);
1450         }
1451 skip_mlock:
1452         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1453         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1454         if (flags & FOLL_GET)
1455                 get_page(page);
1456
1457 out:
1458         return page;
1459 }
1460
1461 /* NUMA hinting page fault entry point for trans huge pmds */
1462 int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1463 {
1464         struct vm_area_struct *vma = vmf->vma;
1465         struct anon_vma *anon_vma = NULL;
1466         struct page *page;
1467         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1468         int page_nid = -1, this_nid = numa_node_id();
1469         int target_nid, last_cpupid = -1;
1470         bool page_locked;
1471         bool migrated = false;
1472         bool was_writable;
1473         int flags = 0;
1474
1475         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1476         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1477                 goto out_unlock;
1478
1479         /*
1480          * If there are potential migrations, wait for completion and retry
1481          * without disrupting NUMA hinting information. Do not relock and
1482          * check_same as the page may no longer be mapped.
1483          */
1484         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1485                 page = pmd_page(*vmf->pmd);
1486                 if (!get_page_unless_zero(page))
1487                         goto out_unlock;
1488                 spin_unlock(vmf->ptl);
1489                 wait_on_page_locked(page);
1490                 put_page(page);
1491                 goto out;
1492         }
1493
1494         page = pmd_page(pmd);
1495         BUG_ON(is_huge_zero_page(page));
1496         page_nid = page_to_nid(page);
1497         last_cpupid = page_cpupid_last(page);
1498         count_vm_numa_event(NUMA_HINT_FAULTS);
1499         if (page_nid == this_nid) {
1500                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1501                 flags |= TNF_FAULT_LOCAL;
1502         }
1503
1504         /* See similar comment in do_numa_page for explanation */
1505         if (!pmd_savedwrite(pmd))
1506                 flags |= TNF_NO_GROUP;
1507
1508         /*
1509          * Acquire the page lock to serialise THP migrations but avoid dropping
1510          * page_table_lock if at all possible
1511          */
1512         page_locked = trylock_page(page);
1513         target_nid = mpol_misplaced(page, vma, haddr);
1514         if (target_nid == -1) {
1515                 /* If the page was locked, there are no parallel migrations */
1516                 if (page_locked)
1517                         goto clear_pmdnuma;
1518         }
1519
1520         /* Migration could have started since the pmd_trans_migrating check */
1521         if (!page_locked) {
1522                 page_nid = -1;
1523                 if (!get_page_unless_zero(page))
1524                         goto out_unlock;
1525                 spin_unlock(vmf->ptl);
1526                 wait_on_page_locked(page);
1527                 put_page(page);
1528                 goto out;
1529         }
1530
1531         /*
1532          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1533          * to serialises splits
1534          */
1535         get_page(page);
1536         spin_unlock(vmf->ptl);
1537         anon_vma = page_lock_anon_vma_read(page);
1538
1539         /* Confirm the PMD did not change while page_table_lock was released */
1540         spin_lock(vmf->ptl);
1541         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1542                 unlock_page(page);
1543                 put_page(page);
1544                 page_nid = -1;
1545                 goto out_unlock;
1546         }
1547
1548         /* Bail if we fail to protect against THP splits for any reason */
1549         if (unlikely(!anon_vma)) {
1550                 put_page(page);
1551                 page_nid = -1;
1552                 goto clear_pmdnuma;
1553         }
1554
1555         /*
1556          * Since we took the NUMA fault, we must have observed the !accessible
1557          * bit. Make sure all other CPUs agree with that, to avoid them
1558          * modifying the page we're about to migrate.
1559          *
1560          * Must be done under PTL such that we'll observe the relevant
1561          * inc_tlb_flush_pending().
1562          *
1563          * We are not sure a pending tlb flush here is for a huge page
1564          * mapping or not. Hence use the tlb range variant
1565          */
1566         if (mm_tlb_flush_pending(vma->vm_mm))
1567                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1568
1569         /*
1570          * Migrate the THP to the requested node, returns with page unlocked
1571          * and access rights restored.
1572          */
1573         spin_unlock(vmf->ptl);
1574
1575         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1576                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1577         if (migrated) {
1578                 flags |= TNF_MIGRATED;
1579                 page_nid = target_nid;
1580         } else
1581                 flags |= TNF_MIGRATE_FAIL;
1582
1583         goto out;
1584 clear_pmdnuma:
1585         BUG_ON(!PageLocked(page));
1586         was_writable = pmd_savedwrite(pmd);
1587         pmd = pmd_modify(pmd, vma->vm_page_prot);
1588         pmd = pmd_mkyoung(pmd);
1589         if (was_writable)
1590                 pmd = pmd_mkwrite(pmd);
1591         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1592         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1593         unlock_page(page);
1594 out_unlock:
1595         spin_unlock(vmf->ptl);
1596
1597 out:
1598         if (anon_vma)
1599                 page_unlock_anon_vma_read(anon_vma);
1600
1601         if (page_nid != -1)
1602                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1603                                 flags);
1604
1605         return 0;
1606 }
1607
1608 /*
1609  * Return true if we do MADV_FREE successfully on entire pmd page.
1610  * Otherwise, return false.
1611  */
1612 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1613                 pmd_t *pmd, unsigned long addr, unsigned long next)
1614 {
1615         spinlock_t *ptl;
1616         pmd_t orig_pmd;
1617         struct page *page;
1618         struct mm_struct *mm = tlb->mm;
1619         bool ret = false;
1620
1621         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1622
1623         ptl = pmd_trans_huge_lock(pmd, vma);
1624         if (!ptl)
1625                 goto out_unlocked;
1626
1627         orig_pmd = *pmd;
1628         if (is_huge_zero_pmd(orig_pmd))
1629                 goto out;
1630
1631         if (unlikely(!pmd_present(orig_pmd))) {
1632                 VM_BUG_ON(thp_migration_supported() &&
1633                                   !is_pmd_migration_entry(orig_pmd));
1634                 goto out;
1635         }
1636
1637         page = pmd_page(orig_pmd);
1638         /*
1639          * If other processes are mapping this page, we couldn't discard
1640          * the page unless they all do MADV_FREE so let's skip the page.
1641          */
1642         if (page_mapcount(page) != 1)
1643                 goto out;
1644
1645         if (!trylock_page(page))
1646                 goto out;
1647
1648         /*
1649          * If user want to discard part-pages of THP, split it so MADV_FREE
1650          * will deactivate only them.
1651          */
1652         if (next - addr != HPAGE_PMD_SIZE) {
1653                 get_page(page);
1654                 spin_unlock(ptl);
1655                 split_huge_page(page);
1656                 unlock_page(page);
1657                 put_page(page);
1658                 goto out_unlocked;
1659         }
1660
1661         if (PageDirty(page))
1662                 ClearPageDirty(page);
1663         unlock_page(page);
1664
1665         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1666                 pmdp_invalidate(vma, addr, pmd);
1667                 orig_pmd = pmd_mkold(orig_pmd);
1668                 orig_pmd = pmd_mkclean(orig_pmd);
1669
1670                 set_pmd_at(mm, addr, pmd, orig_pmd);
1671                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1672         }
1673
1674         mark_page_lazyfree(page);
1675         ret = true;
1676 out:
1677         spin_unlock(ptl);
1678 out_unlocked:
1679         return ret;
1680 }
1681
1682 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1683 {
1684         pgtable_t pgtable;
1685
1686         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1687         pte_free(mm, pgtable);
1688         mm_dec_nr_ptes(mm);
1689 }
1690
1691 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1692                  pmd_t *pmd, unsigned long addr)
1693 {
1694         pmd_t orig_pmd;
1695         spinlock_t *ptl;
1696
1697         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1698
1699         ptl = __pmd_trans_huge_lock(pmd, vma);
1700         if (!ptl)
1701                 return 0;
1702         /*
1703          * For architectures like ppc64 we look at deposited pgtable
1704          * when calling pmdp_huge_get_and_clear. So do the
1705          * pgtable_trans_huge_withdraw after finishing pmdp related
1706          * operations.
1707          */
1708         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1709                         tlb->fullmm);
1710         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1711         if (vma_is_dax(vma)) {
1712                 if (arch_needs_pgtable_deposit())
1713                         zap_deposited_table(tlb->mm, pmd);
1714                 spin_unlock(ptl);
1715                 if (is_huge_zero_pmd(orig_pmd))
1716                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1717         } else if (is_huge_zero_pmd(orig_pmd)) {
1718                 zap_deposited_table(tlb->mm, pmd);
1719                 spin_unlock(ptl);
1720                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1721         } else {
1722                 struct page *page = NULL;
1723                 int flush_needed = 1;
1724
1725                 if (pmd_present(orig_pmd)) {
1726                         page = pmd_page(orig_pmd);
1727                         page_remove_rmap(page, true);
1728                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1729                         VM_BUG_ON_PAGE(!PageHead(page), page);
1730                 } else if (thp_migration_supported()) {
1731                         swp_entry_t entry;
1732
1733                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1734                         entry = pmd_to_swp_entry(orig_pmd);
1735                         page = pfn_to_page(swp_offset(entry));
1736                         flush_needed = 0;
1737                 } else
1738                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1739
1740                 if (PageAnon(page)) {
1741                         zap_deposited_table(tlb->mm, pmd);
1742                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1743                 } else {
1744                         if (arch_needs_pgtable_deposit())
1745                                 zap_deposited_table(tlb->mm, pmd);
1746                         add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1747                 }
1748
1749                 spin_unlock(ptl);
1750                 if (flush_needed)
1751                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1752         }
1753         return 1;
1754 }
1755
1756 #ifndef pmd_move_must_withdraw
1757 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1758                                          spinlock_t *old_pmd_ptl,
1759                                          struct vm_area_struct *vma)
1760 {
1761         /*
1762          * With split pmd lock we also need to move preallocated
1763          * PTE page table if new_pmd is on different PMD page table.
1764          *
1765          * We also don't deposit and withdraw tables for file pages.
1766          */
1767         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1768 }
1769 #endif
1770
1771 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1772 {
1773 #ifdef CONFIG_MEM_SOFT_DIRTY
1774         if (unlikely(is_pmd_migration_entry(pmd)))
1775                 pmd = pmd_swp_mksoft_dirty(pmd);
1776         else if (pmd_present(pmd))
1777                 pmd = pmd_mksoft_dirty(pmd);
1778 #endif
1779         return pmd;
1780 }
1781
1782 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1783                   unsigned long new_addr, unsigned long old_end,
1784                   pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush)
1785 {
1786         spinlock_t *old_ptl, *new_ptl;
1787         pmd_t pmd;
1788         struct mm_struct *mm = vma->vm_mm;
1789         bool force_flush = false;
1790
1791         if ((old_addr & ~HPAGE_PMD_MASK) ||
1792             (new_addr & ~HPAGE_PMD_MASK) ||
1793             old_end - old_addr < HPAGE_PMD_SIZE)
1794                 return false;
1795
1796         /*
1797          * The destination pmd shouldn't be established, free_pgtables()
1798          * should have release it.
1799          */
1800         if (WARN_ON(!pmd_none(*new_pmd))) {
1801                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1802                 return false;
1803         }
1804
1805         /*
1806          * We don't have to worry about the ordering of src and dst
1807          * ptlocks because exclusive mmap_sem prevents deadlock.
1808          */
1809         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1810         if (old_ptl) {
1811                 new_ptl = pmd_lockptr(mm, new_pmd);
1812                 if (new_ptl != old_ptl)
1813                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1814                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1815                 if (pmd_present(pmd) && pmd_dirty(pmd))
1816                         force_flush = true;
1817                 VM_BUG_ON(!pmd_none(*new_pmd));
1818
1819                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1820                         pgtable_t pgtable;
1821                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1822                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1823                 }
1824                 pmd = move_soft_dirty_pmd(pmd);
1825                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1826                 if (new_ptl != old_ptl)
1827                         spin_unlock(new_ptl);
1828                 if (force_flush)
1829                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1830                 else
1831                         *need_flush = true;
1832                 spin_unlock(old_ptl);
1833                 return true;
1834         }
1835         return false;
1836 }
1837
1838 /*
1839  * Returns
1840  *  - 0 if PMD could not be locked
1841  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1842  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1843  */
1844 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1845                 unsigned long addr, pgprot_t newprot, int prot_numa)
1846 {
1847         struct mm_struct *mm = vma->vm_mm;
1848         spinlock_t *ptl;
1849         pmd_t entry;
1850         bool preserve_write;
1851         int ret;
1852
1853         ptl = __pmd_trans_huge_lock(pmd, vma);
1854         if (!ptl)
1855                 return 0;
1856
1857         preserve_write = prot_numa && pmd_write(*pmd);
1858         ret = 1;
1859
1860 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1861         if (is_swap_pmd(*pmd)) {
1862                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1863
1864                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1865                 if (is_write_migration_entry(entry)) {
1866                         pmd_t newpmd;
1867                         /*
1868                          * A protection check is difficult so
1869                          * just be safe and disable write
1870                          */
1871                         make_migration_entry_read(&entry);
1872                         newpmd = swp_entry_to_pmd(entry);
1873                         if (pmd_swp_soft_dirty(*pmd))
1874                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1875                         set_pmd_at(mm, addr, pmd, newpmd);
1876                 }
1877                 goto unlock;
1878         }
1879 #endif
1880
1881         /*
1882          * Avoid trapping faults against the zero page. The read-only
1883          * data is likely to be read-cached on the local CPU and
1884          * local/remote hits to the zero page are not interesting.
1885          */
1886         if (prot_numa && is_huge_zero_pmd(*pmd))
1887                 goto unlock;
1888
1889         if (prot_numa && pmd_protnone(*pmd))
1890                 goto unlock;
1891
1892         /*
1893          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1894          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1895          * which is also under down_read(mmap_sem):
1896          *
1897          *      CPU0:                           CPU1:
1898          *                              change_huge_pmd(prot_numa=1)
1899          *                               pmdp_huge_get_and_clear_notify()
1900          * madvise_dontneed()
1901          *  zap_pmd_range()
1902          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1903          *   // skip the pmd
1904          *                               set_pmd_at();
1905          *                               // pmd is re-established
1906          *
1907          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1908          * which may break userspace.
1909          *
1910          * pmdp_invalidate() is required to make sure we don't miss
1911          * dirty/young flags set by hardware.
1912          */
1913         entry = *pmd;
1914         pmdp_invalidate(vma, addr, pmd);
1915
1916         /*
1917          * Recover dirty/young flags.  It relies on pmdp_invalidate to not
1918          * corrupt them.
1919          */
1920         if (pmd_dirty(*pmd))
1921                 entry = pmd_mkdirty(entry);
1922         if (pmd_young(*pmd))
1923                 entry = pmd_mkyoung(entry);
1924
1925         entry = pmd_modify(entry, newprot);
1926         if (preserve_write)
1927                 entry = pmd_mk_savedwrite(entry);
1928         ret = HPAGE_PMD_NR;
1929         set_pmd_at(mm, addr, pmd, entry);
1930         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1931 unlock:
1932         spin_unlock(ptl);
1933         return ret;
1934 }
1935
1936 /*
1937  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1938  *
1939  * Note that if it returns page table lock pointer, this routine returns without
1940  * unlocking page table lock. So callers must unlock it.
1941  */
1942 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1943 {
1944         spinlock_t *ptl;
1945         ptl = pmd_lock(vma->vm_mm, pmd);
1946         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1947                         pmd_devmap(*pmd)))
1948                 return ptl;
1949         spin_unlock(ptl);
1950         return NULL;
1951 }
1952
1953 /*
1954  * Returns true if a given pud maps a thp, false otherwise.
1955  *
1956  * Note that if it returns true, this routine returns without unlocking page
1957  * table lock. So callers must unlock it.
1958  */
1959 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1960 {
1961         spinlock_t *ptl;
1962
1963         ptl = pud_lock(vma->vm_mm, pud);
1964         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1965                 return ptl;
1966         spin_unlock(ptl);
1967         return NULL;
1968 }
1969
1970 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1971 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1972                  pud_t *pud, unsigned long addr)
1973 {
1974         pud_t orig_pud;
1975         spinlock_t *ptl;
1976
1977         ptl = __pud_trans_huge_lock(pud, vma);
1978         if (!ptl)
1979                 return 0;
1980         /*
1981          * For architectures like ppc64 we look at deposited pgtable
1982          * when calling pudp_huge_get_and_clear. So do the
1983          * pgtable_trans_huge_withdraw after finishing pudp related
1984          * operations.
1985          */
1986         orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1987                         tlb->fullmm);
1988         tlb_remove_pud_tlb_entry(tlb, pud, addr);
1989         if (vma_is_dax(vma)) {
1990                 spin_unlock(ptl);
1991                 /* No zero page support yet */
1992         } else {
1993                 /* No support for anonymous PUD pages yet */
1994                 BUG();
1995         }
1996         return 1;
1997 }
1998
1999 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2000                 unsigned long haddr)
2001 {
2002         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2003         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2004         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2005         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2006
2007         count_vm_event(THP_SPLIT_PUD);
2008
2009         pudp_huge_clear_flush_notify(vma, haddr, pud);
2010 }
2011
2012 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2013                 unsigned long address)
2014 {
2015         spinlock_t *ptl;
2016         struct mm_struct *mm = vma->vm_mm;
2017         unsigned long haddr = address & HPAGE_PUD_MASK;
2018
2019         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
2020         ptl = pud_lock(mm, pud);
2021         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2022                 goto out;
2023         __split_huge_pud_locked(vma, pud, haddr);
2024
2025 out:
2026         spin_unlock(ptl);
2027         /*
2028          * No need to double call mmu_notifier->invalidate_range() callback as
2029          * the above pudp_huge_clear_flush_notify() did already call it.
2030          */
2031         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2032                                                HPAGE_PUD_SIZE);
2033 }
2034 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2035
2036 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2037                 unsigned long haddr, pmd_t *pmd)
2038 {
2039         struct mm_struct *mm = vma->vm_mm;
2040         pgtable_t pgtable;
2041         pmd_t _pmd;
2042         int i;
2043
2044         /*
2045          * Leave pmd empty until pte is filled note that it is fine to delay
2046          * notification until mmu_notifier_invalidate_range_end() as we are
2047          * replacing a zero pmd write protected page with a zero pte write
2048          * protected page.
2049          *
2050          * See Documentation/vm/mmu_notifier.txt
2051          */
2052         pmdp_huge_clear_flush(vma, haddr, pmd);
2053
2054         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2055         pmd_populate(mm, &_pmd, pgtable);
2056
2057         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2058                 pte_t *pte, entry;
2059                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2060                 entry = pte_mkspecial(entry);
2061                 pte = pte_offset_map(&_pmd, haddr);
2062                 VM_BUG_ON(!pte_none(*pte));
2063                 set_pte_at(mm, haddr, pte, entry);
2064                 pte_unmap(pte);
2065         }
2066         smp_wmb(); /* make pte visible before pmd */
2067         pmd_populate(mm, pmd, pgtable);
2068 }
2069
2070 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2071                 unsigned long haddr, bool freeze)
2072 {
2073         struct mm_struct *mm = vma->vm_mm;
2074         struct page *page;
2075         pgtable_t pgtable;
2076         pmd_t _pmd;
2077         bool young, write, dirty, soft_dirty, pmd_migration = false;
2078         unsigned long addr;
2079         int i;
2080
2081         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2082         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2083         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2084         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2085                                 && !pmd_devmap(*pmd));
2086
2087         count_vm_event(THP_SPLIT_PMD);
2088
2089         if (!vma_is_anonymous(vma)) {
2090                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2091                 /*
2092                  * We are going to unmap this huge page. So
2093                  * just go ahead and zap it
2094                  */
2095                 if (arch_needs_pgtable_deposit())
2096                         zap_deposited_table(mm, pmd);
2097                 if (vma_is_dax(vma))
2098                         return;
2099                 page = pmd_page(_pmd);
2100                 if (!PageReferenced(page) && pmd_young(_pmd))
2101                         SetPageReferenced(page);
2102                 page_remove_rmap(page, true);
2103                 put_page(page);
2104                 add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
2105                 return;
2106         } else if (is_huge_zero_pmd(*pmd)) {
2107                 /*
2108                  * FIXME: Do we want to invalidate secondary mmu by calling
2109                  * mmu_notifier_invalidate_range() see comments below inside
2110                  * __split_huge_pmd() ?
2111                  *
2112                  * We are going from a zero huge page write protected to zero
2113                  * small page also write protected so it does not seems useful
2114                  * to invalidate secondary mmu at this time.
2115                  */
2116                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2117         }
2118
2119 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2120         pmd_migration = is_pmd_migration_entry(*pmd);
2121         if (pmd_migration) {
2122                 swp_entry_t entry;
2123
2124                 entry = pmd_to_swp_entry(*pmd);
2125                 page = pfn_to_page(swp_offset(entry));
2126         } else
2127 #endif
2128                 page = pmd_page(*pmd);
2129         VM_BUG_ON_PAGE(!page_count(page), page);
2130         page_ref_add(page, HPAGE_PMD_NR - 1);
2131         write = pmd_write(*pmd);
2132         young = pmd_young(*pmd);
2133         dirty = pmd_dirty(*pmd);
2134         soft_dirty = pmd_soft_dirty(*pmd);
2135
2136         pmdp_huge_split_prepare(vma, haddr, pmd);
2137         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2138         pmd_populate(mm, &_pmd, pgtable);
2139
2140         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2141                 pte_t entry, *pte;
2142                 /*
2143                  * Note that NUMA hinting access restrictions are not
2144                  * transferred to avoid any possibility of altering
2145                  * permissions across VMAs.
2146                  */
2147                 if (freeze || pmd_migration) {
2148                         swp_entry_t swp_entry;
2149                         swp_entry = make_migration_entry(page + i, write);
2150                         entry = swp_entry_to_pte(swp_entry);
2151                         if (soft_dirty)
2152                                 entry = pte_swp_mksoft_dirty(entry);
2153                 } else {
2154                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2155                         entry = maybe_mkwrite(entry, vma);
2156                         if (!write)
2157                                 entry = pte_wrprotect(entry);
2158                         if (!young)
2159                                 entry = pte_mkold(entry);
2160                         if (soft_dirty)
2161                                 entry = pte_mksoft_dirty(entry);
2162                 }
2163                 if (dirty)
2164                         SetPageDirty(page + i);
2165                 pte = pte_offset_map(&_pmd, addr);
2166                 BUG_ON(!pte_none(*pte));
2167                 set_pte_at(mm, addr, pte, entry);
2168                 atomic_inc(&page[i]._mapcount);
2169                 pte_unmap(pte);
2170         }
2171
2172         /*
2173          * Set PG_double_map before dropping compound_mapcount to avoid
2174          * false-negative page_mapped().
2175          */
2176         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2177                 for (i = 0; i < HPAGE_PMD_NR; i++)
2178                         atomic_inc(&page[i]._mapcount);
2179         }
2180
2181         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2182                 /* Last compound_mapcount is gone. */
2183                 __dec_node_page_state(page, NR_ANON_THPS);
2184                 if (TestClearPageDoubleMap(page)) {
2185                         /* No need in mapcount reference anymore */
2186                         for (i = 0; i < HPAGE_PMD_NR; i++)
2187                                 atomic_dec(&page[i]._mapcount);
2188                 }
2189         }
2190
2191         smp_wmb(); /* make pte visible before pmd */
2192         /*
2193          * Up to this point the pmd is present and huge and userland has the
2194          * whole access to the hugepage during the split (which happens in
2195          * place). If we overwrite the pmd with the not-huge version pointing
2196          * to the pte here (which of course we could if all CPUs were bug
2197          * free), userland could trigger a small page size TLB miss on the
2198          * small sized TLB while the hugepage TLB entry is still established in
2199          * the huge TLB. Some CPU doesn't like that.
2200          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2201          * 383 on page 93. Intel should be safe but is also warns that it's
2202          * only safe if the permission and cache attributes of the two entries
2203          * loaded in the two TLB is identical (which should be the case here).
2204          * But it is generally safer to never allow small and huge TLB entries
2205          * for the same virtual address to be loaded simultaneously. So instead
2206          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2207          * current pmd notpresent (atomically because here the pmd_trans_huge
2208          * and pmd_trans_splitting must remain set at all times on the pmd
2209          * until the split is complete for this pmd), then we flush the SMP TLB
2210          * and finally we write the non-huge version of the pmd entry with
2211          * pmd_populate.
2212          */
2213         pmdp_invalidate(vma, haddr, pmd);
2214         pmd_populate(mm, pmd, pgtable);
2215
2216         if (freeze) {
2217                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2218                         page_remove_rmap(page + i, false);
2219                         put_page(page + i);
2220                 }
2221         }
2222 }
2223
2224 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2225                 unsigned long address, bool freeze, struct page *page)
2226 {
2227         spinlock_t *ptl;
2228         struct mm_struct *mm = vma->vm_mm;
2229         unsigned long haddr = address & HPAGE_PMD_MASK;
2230
2231         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2232         ptl = pmd_lock(mm, pmd);
2233
2234         /*
2235          * If caller asks to setup a migration entries, we need a page to check
2236          * pmd against. Otherwise we can end up replacing wrong page.
2237          */
2238         VM_BUG_ON(freeze && !page);
2239         if (page && page != pmd_page(*pmd))
2240                 goto out;
2241
2242         if (pmd_trans_huge(*pmd)) {
2243                 page = pmd_page(*pmd);
2244                 if (PageMlocked(page))
2245                         clear_page_mlock(page);
2246         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2247                 goto out;
2248         __split_huge_pmd_locked(vma, pmd, haddr, freeze);
2249 out:
2250         spin_unlock(ptl);
2251         /*
2252          * No need to double call mmu_notifier->invalidate_range() callback.
2253          * They are 3 cases to consider inside __split_huge_pmd_locked():
2254          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2255          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2256          *    fault will trigger a flush_notify before pointing to a new page
2257          *    (it is fine if the secondary mmu keeps pointing to the old zero
2258          *    page in the meantime)
2259          *  3) Split a huge pmd into pte pointing to the same page. No need
2260          *     to invalidate secondary tlb entry they are all still valid.
2261          *     any further changes to individual pte will notify. So no need
2262          *     to call mmu_notifier->invalidate_range()
2263          */
2264         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2265                                                HPAGE_PMD_SIZE);
2266 }
2267
2268 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2269                 bool freeze, struct page *page)
2270 {
2271         pgd_t *pgd;
2272         p4d_t *p4d;
2273         pud_t *pud;
2274         pmd_t *pmd;
2275
2276         pgd = pgd_offset(vma->vm_mm, address);
2277         if (!pgd_present(*pgd))
2278                 return;
2279
2280         p4d = p4d_offset(pgd, address);
2281         if (!p4d_present(*p4d))
2282                 return;
2283
2284         pud = pud_offset(p4d, address);
2285         if (!pud_present(*pud))
2286                 return;
2287
2288         pmd = pmd_offset(pud, address);
2289
2290         __split_huge_pmd(vma, pmd, address, freeze, page);
2291 }
2292
2293 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2294                              unsigned long start,
2295                              unsigned long end,
2296                              long adjust_next)
2297 {
2298         /*
2299          * If the new start address isn't hpage aligned and it could
2300          * previously contain an hugepage: check if we need to split
2301          * an huge pmd.
2302          */
2303         if (start & ~HPAGE_PMD_MASK &&
2304             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2305             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2306                 split_huge_pmd_address(vma, start, false, NULL);
2307
2308         /*
2309          * If the new end address isn't hpage aligned and it could
2310          * previously contain an hugepage: check if we need to split
2311          * an huge pmd.
2312          */
2313         if (end & ~HPAGE_PMD_MASK &&
2314             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2315             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2316                 split_huge_pmd_address(vma, end, false, NULL);
2317
2318         /*
2319          * If we're also updating the vma->vm_next->vm_start, if the new
2320          * vm_next->vm_start isn't page aligned and it could previously
2321          * contain an hugepage: check if we need to split an huge pmd.
2322          */
2323         if (adjust_next > 0) {
2324                 struct vm_area_struct *next = vma->vm_next;
2325                 unsigned long nstart = next->vm_start;
2326                 nstart += adjust_next << PAGE_SHIFT;
2327                 if (nstart & ~HPAGE_PMD_MASK &&
2328                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2329                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2330                         split_huge_pmd_address(next, nstart, false, NULL);
2331         }
2332 }
2333
2334 static void freeze_page(struct page *page)
2335 {
2336         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2337                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2338         bool unmap_success;
2339
2340         VM_BUG_ON_PAGE(!PageHead(page), page);
2341
2342         if (PageAnon(page))
2343                 ttu_flags |= TTU_SPLIT_FREEZE;
2344
2345         unmap_success = try_to_unmap(page, ttu_flags);
2346         VM_BUG_ON_PAGE(!unmap_success, page);
2347 }
2348
2349 static void unfreeze_page(struct page *page)
2350 {
2351         int i;
2352         if (PageTransHuge(page)) {
2353                 remove_migration_ptes(page, page, true);
2354         } else {
2355                 for (i = 0; i < HPAGE_PMD_NR; i++)
2356                         remove_migration_ptes(page + i, page + i, true);
2357         }
2358 }
2359
2360 static void __split_huge_page_tail(struct page *head, int tail,
2361                 struct lruvec *lruvec, struct list_head *list)
2362 {
2363         struct page *page_tail = head + tail;
2364
2365         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2366         VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
2367
2368         /*
2369          * tail_page->_refcount is zero and not changing from under us. But
2370          * get_page_unless_zero() may be running from under us on the
2371          * tail_page. If we used atomic_set() below instead of atomic_inc() or
2372          * atomic_add(), we would then run atomic_set() concurrently with
2373          * get_page_unless_zero(), and atomic_set() is implemented in C not
2374          * using locked ops. spin_unlock on x86 sometime uses locked ops
2375          * because of PPro errata 66, 92, so unless somebody can guarantee
2376          * atomic_set() here would be safe on all archs (and not only on x86),
2377          * it's safer to use atomic_inc()/atomic_add().
2378          */
2379         if (PageAnon(head) && !PageSwapCache(head)) {
2380                 page_ref_inc(page_tail);
2381         } else {
2382                 /* Additional pin to radix tree */
2383                 page_ref_add(page_tail, 2);
2384         }
2385
2386         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2387         page_tail->flags |= (head->flags &
2388                         ((1L << PG_referenced) |
2389                          (1L << PG_swapbacked) |
2390                          (1L << PG_swapcache) |
2391                          (1L << PG_mlocked) |
2392                          (1L << PG_uptodate) |
2393                          (1L << PG_active) |
2394                          (1L << PG_locked) |
2395                          (1L << PG_unevictable) |
2396                          (1L << PG_dirty)));
2397
2398         /*
2399          * After clearing PageTail the gup refcount can be released.
2400          * Page flags also must be visible before we make the page non-compound.
2401          */
2402         smp_wmb();
2403
2404         clear_compound_head(page_tail);
2405
2406         if (page_is_young(head))
2407                 set_page_young(page_tail);
2408         if (page_is_idle(head))
2409                 set_page_idle(page_tail);
2410
2411         /* ->mapping in first tail page is compound_mapcount */
2412         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2413                         page_tail);
2414         page_tail->mapping = head->mapping;
2415
2416         page_tail->index = head->index + tail;
2417         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
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 radix tree of 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 radix tree */
2460                 page_ref_add(head, 2);
2461                 spin_unlock(&head->mapping->tree_lock);
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 radix tree */
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                 void **pslot;
2668
2669                 spin_lock(&mapping->tree_lock);
2670                 pslot = radix_tree_lookup_slot(&mapping->page_tree,
2671                                 page_index(head));
2672                 /*
2673                  * Check if the head page is present in radix tree.
2674                  * We assume all tail are present too, if head is there.
2675                  */
2676                 if (radix_tree_deref_slot_protected(pslot,
2677                                         &mapping->tree_lock) != head)
2678                         goto fail;
2679         }
2680
2681         /* Prevent deferred_split_scan() touching ->_refcount */
2682         spin_lock(&pgdata->split_queue_lock);
2683         count = page_count(head);
2684         mapcount = total_mapcount(head);
2685         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2686                 if (!list_empty(page_deferred_list(head))) {
2687                         pgdata->split_queue_len--;
2688                         list_del(page_deferred_list(head));
2689                 }
2690                 if (mapping)
2691                         __dec_node_page_state(page, NR_SHMEM_THPS);
2692                 spin_unlock(&pgdata->split_queue_lock);
2693                 __split_huge_page(page, list, flags);
2694                 if (PageSwapCache(head)) {
2695                         swp_entry_t entry = { .val = page_private(head) };
2696
2697                         ret = split_swap_cluster(entry);
2698                 } else
2699                         ret = 0;
2700         } else {
2701                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2702                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2703                                         mapcount, count);
2704                         if (PageTail(page))
2705                                 dump_page(head, NULL);
2706                         dump_page(page, "total_mapcount(head) > 0");
2707                         BUG();
2708                 }
2709                 spin_unlock(&pgdata->split_queue_lock);
2710 fail:           if (mapping)
2711                         spin_unlock(&mapping->tree_lock);
2712                 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2713                 unfreeze_page(head);
2714                 ret = -EBUSY;
2715         }
2716
2717 out_unlock:
2718         if (anon_vma) {
2719                 anon_vma_unlock_write(anon_vma);
2720                 put_anon_vma(anon_vma);
2721         }
2722         if (mapping)
2723                 i_mmap_unlock_read(mapping);
2724 out:
2725         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2726         return ret;
2727 }
2728
2729 void free_transhuge_page(struct page *page)
2730 {
2731         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2732         unsigned long flags;
2733
2734         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2735         if (!list_empty(page_deferred_list(page))) {
2736                 pgdata->split_queue_len--;
2737                 list_del(page_deferred_list(page));
2738         }
2739         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2740         free_compound_page(page);
2741 }
2742
2743 void deferred_split_huge_page(struct page *page)
2744 {
2745         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2746         unsigned long flags;
2747
2748         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2749
2750         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2751         if (list_empty(page_deferred_list(page))) {
2752                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2753                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2754                 pgdata->split_queue_len++;
2755         }
2756         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2757 }
2758
2759 static unsigned long deferred_split_count(struct shrinker *shrink,
2760                 struct shrink_control *sc)
2761 {
2762         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2763         return READ_ONCE(pgdata->split_queue_len);
2764 }
2765
2766 static unsigned long deferred_split_scan(struct shrinker *shrink,
2767                 struct shrink_control *sc)
2768 {
2769         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2770         unsigned long flags;
2771         LIST_HEAD(list), *pos, *next;
2772         struct page *page;
2773         int split = 0;
2774
2775         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2776         /* Take pin on all head pages to avoid freeing them under us */
2777         list_for_each_safe(pos, next, &pgdata->split_queue) {
2778                 page = list_entry((void *)pos, struct page, mapping);
2779                 page = compound_head(page);
2780                 if (get_page_unless_zero(page)) {
2781                         list_move(page_deferred_list(page), &list);
2782                 } else {
2783                         /* We lost race with put_compound_page() */
2784                         list_del_init(page_deferred_list(page));
2785                         pgdata->split_queue_len--;
2786                 }
2787                 if (!--sc->nr_to_scan)
2788                         break;
2789         }
2790         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2791
2792         list_for_each_safe(pos, next, &list) {
2793                 page = list_entry((void *)pos, struct page, mapping);
2794                 lock_page(page);
2795                 /* split_huge_page() removes page from list on success */
2796                 if (!split_huge_page(page))
2797                         split++;
2798                 unlock_page(page);
2799                 put_page(page);
2800         }
2801
2802         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2803         list_splice_tail(&list, &pgdata->split_queue);
2804         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2805
2806         /*
2807          * Stop shrinker if we didn't split any page, but the queue is empty.
2808          * This can happen if pages were freed under us.
2809          */
2810         if (!split && list_empty(&pgdata->split_queue))
2811                 return SHRINK_STOP;
2812         return split;
2813 }
2814
2815 static struct shrinker deferred_split_shrinker = {
2816         .count_objects = deferred_split_count,
2817         .scan_objects = deferred_split_scan,
2818         .seeks = DEFAULT_SEEKS,
2819         .flags = SHRINKER_NUMA_AWARE,
2820 };
2821
2822 #ifdef CONFIG_DEBUG_FS
2823 static int split_huge_pages_set(void *data, u64 val)
2824 {
2825         struct zone *zone;
2826         struct page *page;
2827         unsigned long pfn, max_zone_pfn;
2828         unsigned long total = 0, split = 0;
2829
2830         if (val != 1)
2831                 return -EINVAL;
2832
2833         for_each_populated_zone(zone) {
2834                 max_zone_pfn = zone_end_pfn(zone);
2835                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2836                         if (!pfn_valid(pfn))
2837                                 continue;
2838
2839                         page = pfn_to_page(pfn);
2840                         if (!get_page_unless_zero(page))
2841                                 continue;
2842
2843                         if (zone != page_zone(page))
2844                                 goto next;
2845
2846                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2847                                 goto next;
2848
2849                         total++;
2850                         lock_page(page);
2851                         if (!split_huge_page(page))
2852                                 split++;
2853                         unlock_page(page);
2854 next:
2855                         put_page(page);
2856                 }
2857         }
2858
2859         pr_info("%lu of %lu THP split\n", split, total);
2860
2861         return 0;
2862 }
2863 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2864                 "%llu\n");
2865
2866 static int __init split_huge_pages_debugfs(void)
2867 {
2868         void *ret;
2869
2870         ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2871                         &split_huge_pages_fops);
2872         if (!ret)
2873                 pr_warn("Failed to create split_huge_pages in debugfs");
2874         return 0;
2875 }
2876 late_initcall(split_huge_pages_debugfs);
2877 #endif
2878
2879 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2880 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2881                 struct page *page)
2882 {
2883         struct vm_area_struct *vma = pvmw->vma;
2884         struct mm_struct *mm = vma->vm_mm;
2885         unsigned long address = pvmw->address;
2886         pmd_t pmdval;
2887         swp_entry_t entry;
2888         pmd_t pmdswp;
2889
2890         if (!(pvmw->pmd && !pvmw->pte))
2891                 return;
2892
2893         mmu_notifier_invalidate_range_start(mm, address,
2894                         address + HPAGE_PMD_SIZE);
2895
2896         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2897         pmdval = *pvmw->pmd;
2898         pmdp_invalidate(vma, address, pvmw->pmd);
2899         if (pmd_dirty(pmdval))
2900                 set_page_dirty(page);
2901         entry = make_migration_entry(page, pmd_write(pmdval));
2902         pmdswp = swp_entry_to_pmd(entry);
2903         if (pmd_soft_dirty(pmdval))
2904                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2905         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2906         page_remove_rmap(page, true);
2907         put_page(page);
2908
2909         mmu_notifier_invalidate_range_end(mm, address,
2910                         address + HPAGE_PMD_SIZE);
2911 }
2912
2913 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2914 {
2915         struct vm_area_struct *vma = pvmw->vma;
2916         struct mm_struct *mm = vma->vm_mm;
2917         unsigned long address = pvmw->address;
2918         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2919         pmd_t pmde;
2920         swp_entry_t entry;
2921
2922         if (!(pvmw->pmd && !pvmw->pte))
2923                 return;
2924
2925         entry = pmd_to_swp_entry(*pvmw->pmd);
2926         get_page(new);
2927         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2928         if (pmd_swp_soft_dirty(*pvmw->pmd))
2929                 pmde = pmd_mksoft_dirty(pmde);
2930         if (is_write_migration_entry(entry))
2931                 pmde = maybe_pmd_mkwrite(pmde, vma);
2932
2933         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2934         page_add_anon_rmap(new, vma, mmun_start, true);
2935         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
2936         if (vma->vm_flags & VM_LOCKED)
2937                 mlock_vma_page(new);
2938         update_mmu_cache_pmd(vma, address, pvmw->pmd);
2939 }
2940 #endif