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)
 846 {
 847         pmd_t _pmd;
 848
 849         /*
 850          * We should set the dirty bit only for FOLL_WRITE but for now
 851          * the dirty bit in the pmd is meaningless.  And if the dirty
 852          * bit will become meaningful and we'll only set it with
 853          * FOLL_WRITE, an atomic set_bit will be required on the pmd to
 854          * set the young bit, instead of the current set_pmd_at.
 855          */
 856         _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
 857         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 858                                 pmd, _pmd,  1))
 859                 update_mmu_cache_pmd(vma, addr, pmd);
 860 }
 861
 862 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 863                 pmd_t *pmd, int flags)
 864 {
 865         unsigned long pfn = pmd_pfn(*pmd);
 866         struct mm_struct *mm = vma->vm_mm;
 867         struct dev_pagemap *pgmap;
 868         struct page *page;
 869
 870         assert_spin_locked(pmd_lockptr(mm, pmd));
 871
 872         /*
 873          * When we COW a devmap PMD entry, we split it into PTEs, so we should
 874          * not be in this function with `flags & FOLL_COW` set.
 875          */
 876         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
 877
 878         if (flags & FOLL_WRITE && !pmd_write(*pmd))
 879                 return NULL;
 880
 881         if (pmd_present(*pmd) && pmd_devmap(*pmd))
 882                 /* pass */;
 883         else
 884                 return NULL;
 885
 886         if (flags & FOLL_TOUCH)
 887                 touch_pmd(vma, addr, pmd);
 888
 889         /*
 890          * device mapped pages can only be returned if the
 891          * caller will manage the page reference count.
 892          */
 893         if (!(flags & FOLL_GET))
 894                 return ERR_PTR(-EEXIST);
 895
 896         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
 897         pgmap = get_dev_pagemap(pfn, NULL);
 898         if (!pgmap)
 899                 return ERR_PTR(-EFAULT);
 900         page = pfn_to_page(pfn);
 901         get_page(page);
 902         put_dev_pagemap(pgmap);
 903
 904         return page;
 905 }
 906
 907 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 908                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 909                   struct vm_area_struct *vma)
 910 {
 911         spinlock_t *dst_ptl, *src_ptl;
 912         struct page *src_page;
 913         pmd_t pmd;
 914         pgtable_t pgtable = NULL;
 915         int ret = -ENOMEM;
 916
 917         /* Skip if can be re-fill on fault */
 918         if (!vma_is_anonymous(vma))
 919                 return 0;
 920
 921         pgtable = pte_alloc_one(dst_mm, addr);
 922         if (unlikely(!pgtable))
 923                 goto out;
 924
 925         dst_ptl = pmd_lock(dst_mm, dst_pmd);
 926         src_ptl = pmd_lockptr(src_mm, src_pmd);
 927         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 928
 929         ret = -EAGAIN;
 930         pmd = *src_pmd;
 931
 932 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
 933         if (unlikely(is_swap_pmd(pmd))) {
 934                 swp_entry_t entry = pmd_to_swp_entry(pmd);
 935
 936                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
 937                 if (is_write_migration_entry(entry)) {
 938                         make_migration_entry_read(&entry);
 939                         pmd = swp_entry_to_pmd(entry);
 940                         if (pmd_swp_soft_dirty(*src_pmd))
 941                                 pmd = pmd_swp_mksoft_dirty(pmd);
 942                         set_pmd_at(src_mm, addr, src_pmd, pmd);
 943                 }
 944                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 945                 mm_inc_nr_ptes(dst_mm);
 946                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 947                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 948                 ret = 0;
 949                 goto out_unlock;
 950         }
 951 #endif
 952
 953         if (unlikely(!pmd_trans_huge(pmd))) {
 954                 pte_free(dst_mm, pgtable);
 955                 goto out_unlock;
 956         }
 957         /*
 958          * When page table lock is held, the huge zero pmd should not be
 959          * under splitting since we don't split the page itself, only pmd to
 960          * a page table.
 961          */
 962         if (is_huge_zero_pmd(pmd)) {
 963                 struct page *zero_page;
 964                 /*
 965                  * get_huge_zero_page() will never allocate a new page here,
 966                  * since we already have a zero page to copy. It just takes a
 967                  * reference.
 968                  */
 969                 zero_page = mm_get_huge_zero_page(dst_mm);
 970                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
 971                                 zero_page);
 972                 ret = 0;
 973                 goto out_unlock;
 974         }
 975
 976         src_page = pmd_page(pmd);
 977         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
 978         get_page(src_page);
 979         page_dup_rmap(src_page, true);
 980         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 981         mm_inc_nr_ptes(dst_mm);
 982         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 983
 984         pmdp_set_wrprotect(src_mm, addr, src_pmd);
 985         pmd = pmd_mkold(pmd_wrprotect(pmd));
 986         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 987
 988         ret = 0;
 989 out_unlock:
 990         spin_unlock(src_ptl);
 991         spin_unlock(dst_ptl);
 992 out:
 993         return ret;
 994 }
 995
 996 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 997 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
 998                 pud_t *pud)
 999 {
1000         pud_t _pud;
1001
1002         /*
1003          * We should set the dirty bit only for FOLL_WRITE but for now
1004          * the dirty bit in the pud is meaningless.  And if the dirty
1005          * bit will become meaningful and we'll only set it with
1006          * FOLL_WRITE, an atomic set_bit will be required on the pud to
1007          * set the young bit, instead of the current set_pud_at.
1008          */
1009         _pud = pud_mkyoung(pud_mkdirty(*pud));
1010         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1011                                 pud, _pud,  1))
1012                 update_mmu_cache_pud(vma, addr, pud);
1013 }
1014
1015 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1016                 pud_t *pud, int flags)
1017 {
1018         unsigned long pfn = pud_pfn(*pud);
1019         struct mm_struct *mm = vma->vm_mm;
1020         struct dev_pagemap *pgmap;
1021         struct page *page;
1022
1023         assert_spin_locked(pud_lockptr(mm, pud));
1024
1025         if (flags & FOLL_WRITE && !pud_write(*pud))
1026                 return NULL;
1027
1028         if (pud_present(*pud) && pud_devmap(*pud))
1029                 /* pass */;
1030         else
1031                 return NULL;
1032
1033         if (flags & FOLL_TOUCH)
1034                 touch_pud(vma, addr, pud);
1035
1036         /*
1037          * device mapped pages can only be returned if the
1038          * caller will manage the page reference count.
1039          */
1040         if (!(flags & FOLL_GET))
1041                 return ERR_PTR(-EEXIST);
1042
1043         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1044         pgmap = get_dev_pagemap(pfn, NULL);
1045         if (!pgmap)
1046                 return ERR_PTR(-EFAULT);
1047         page = pfn_to_page(pfn);
1048         get_page(page);
1049         put_dev_pagemap(pgmap);
1050
1051         return page;
1052 }
1053
1054 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1055                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1056                   struct vm_area_struct *vma)
1057 {
1058         spinlock_t *dst_ptl, *src_ptl;
1059         pud_t pud;
1060         int ret;
1061
1062         dst_ptl = pud_lock(dst_mm, dst_pud);
1063         src_ptl = pud_lockptr(src_mm, src_pud);
1064         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1065
1066         ret = -EAGAIN;
1067         pud = *src_pud;
1068         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1069                 goto out_unlock;
1070
1071         /*
1072          * When page table lock is held, the huge zero pud should not be
1073          * under splitting since we don't split the page itself, only pud to
1074          * a page table.
1075          */
1076         if (is_huge_zero_pud(pud)) {
1077                 /* No huge zero pud yet */
1078         }
1079
1080         pudp_set_wrprotect(src_mm, addr, src_pud);
1081         pud = pud_mkold(pud_wrprotect(pud));
1082         set_pud_at(dst_mm, addr, dst_pud, pud);
1083
1084         ret = 0;
1085 out_unlock:
1086         spin_unlock(src_ptl);
1087         spin_unlock(dst_ptl);
1088         return ret;
1089 }
1090
1091 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1092 {
1093         pud_t entry;
1094         unsigned long haddr;
1095         bool write = vmf->flags & FAULT_FLAG_WRITE;
1096
1097         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1098         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1099                 goto unlock;
1100
1101         entry = pud_mkyoung(orig_pud);
1102         if (write)
1103                 entry = pud_mkdirty(entry);
1104         haddr = vmf->address & HPAGE_PUD_MASK;
1105         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1106                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1107
1108 unlock:
1109         spin_unlock(vmf->ptl);
1110 }
1111 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1112
1113 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1114 {
1115         pmd_t entry;
1116         unsigned long haddr;
1117         bool write = vmf->flags & FAULT_FLAG_WRITE;
1118
1119         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1120         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1121                 goto unlock;
1122
1123         entry = pmd_mkyoung(orig_pmd);
1124         if (write)
1125                 entry = pmd_mkdirty(entry);
1126         haddr = vmf->address & HPAGE_PMD_MASK;
1127         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1128                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1129
1130 unlock:
1131         spin_unlock(vmf->ptl);
1132 }
1133
1134 static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd,
1135                 struct page *page)
1136 {
1137         struct vm_area_struct *vma = vmf->vma;
1138         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1139         struct mem_cgroup *memcg;
1140         pgtable_t pgtable;
1141         pmd_t _pmd;
1142         int ret = 0, i;
1143         struct page **pages;
1144         unsigned long mmun_start;       /* For mmu_notifiers */
1145         unsigned long mmun_end;         /* For mmu_notifiers */
1146
1147         pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1148                         GFP_KERNEL);
1149         if (unlikely(!pages)) {
1150                 ret |= VM_FAULT_OOM;
1151                 goto out;
1152         }
1153
1154         for (i = 0; i < HPAGE_PMD_NR; i++) {
1155                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1156                                                vmf->address, page_to_nid(page));
1157                 if (unlikely(!pages[i] ||
1158                              mem_cgroup_try_charge(pages[i], vma->vm_mm,
1159                                      GFP_KERNEL, &memcg, false))) {
1160                         if (pages[i])
1161                                 put_page(pages[i]);
1162                         while (--i >= 0) {
1163                                 memcg = (void *)page_private(pages[i]);
1164                                 set_page_private(pages[i], 0);
1165                                 mem_cgroup_cancel_charge(pages[i], memcg,
1166                                                 false);
1167                                 put_page(pages[i]);
1168                         }
1169                         kfree(pages);
1170                         ret |= VM_FAULT_OOM;
1171                         goto out;
1172                 }
1173                 set_page_private(pages[i], (unsigned long)memcg);
1174         }
1175
1176         for (i = 0; i < HPAGE_PMD_NR; i++) {
1177                 copy_user_highpage(pages[i], page + i,
1178                                    haddr + PAGE_SIZE * i, vma);
1179                 __SetPageUptodate(pages[i]);
1180                 cond_resched();
1181         }
1182
1183         mmun_start = haddr;
1184         mmun_end   = haddr + HPAGE_PMD_SIZE;
1185         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1186
1187         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1188         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1189                 goto out_free_pages;
1190         VM_BUG_ON_PAGE(!PageHead(page), page);
1191
1192         /*
1193          * Leave pmd empty until pte is filled note we must notify here as
1194          * concurrent CPU thread might write to new page before the call to
1195          * mmu_notifier_invalidate_range_end() happens which can lead to a
1196          * device seeing memory write in different order than CPU.
1197          *
1198          * See Documentation/vm/mmu_notifier.txt
1199          */
1200         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1201
1202         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1203         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1204
1205         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1206                 pte_t entry;
1207                 entry = mk_pte(pages[i], vma->vm_page_prot);
1208                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1209                 memcg = (void *)page_private(pages[i]);
1210                 set_page_private(pages[i], 0);
1211                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1212                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1213                 lru_cache_add_active_or_unevictable(pages[i], vma);
1214                 vmf->pte = pte_offset_map(&_pmd, haddr);
1215                 VM_BUG_ON(!pte_none(*vmf->pte));
1216                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1217                 pte_unmap(vmf->pte);
1218         }
1219         kfree(pages);
1220
1221         smp_wmb(); /* make pte visible before pmd */
1222         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1223         page_remove_rmap(page, true);
1224         spin_unlock(vmf->ptl);
1225
1226         /*
1227          * No need to double call mmu_notifier->invalidate_range() callback as
1228          * the above pmdp_huge_clear_flush_notify() did already call it.
1229          */
1230         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1231                                                 mmun_end);
1232
1233         ret |= VM_FAULT_WRITE;
1234         put_page(page);
1235
1236 out:
1237         return ret;
1238
1239 out_free_pages:
1240         spin_unlock(vmf->ptl);
1241         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1242         for (i = 0; i < HPAGE_PMD_NR; i++) {
1243                 memcg = (void *)page_private(pages[i]);
1244                 set_page_private(pages[i], 0);
1245                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1246                 put_page(pages[i]);
1247         }
1248         kfree(pages);
1249         goto out;
1250 }
1251
1252 int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1253 {
1254         struct vm_area_struct *vma = vmf->vma;
1255         struct page *page = NULL, *new_page;
1256         struct mem_cgroup *memcg;
1257         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1258         unsigned long mmun_start;       /* For mmu_notifiers */
1259         unsigned long mmun_end;         /* For mmu_notifiers */
1260         gfp_t huge_gfp;                 /* for allocation and charge */
1261         int ret = 0;
1262
1263         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1264         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1265         if (is_huge_zero_pmd(orig_pmd))
1266                 goto alloc;
1267         spin_lock(vmf->ptl);
1268         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1269                 goto out_unlock;
1270
1271         page = pmd_page(orig_pmd);
1272         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1273         /*
1274          * We can only reuse the page if nobody else maps the huge page or it's
1275          * part.
1276          */
1277         if (!trylock_page(page)) {
1278                 get_page(page);
1279                 spin_unlock(vmf->ptl);
1280                 lock_page(page);
1281                 spin_lock(vmf->ptl);
1282                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1283                         unlock_page(page);
1284                         put_page(page);
1285                         goto out_unlock;
1286                 }
1287                 put_page(page);
1288         }
1289         if (reuse_swap_page(page, NULL)) {
1290                 pmd_t entry;
1291                 entry = pmd_mkyoung(orig_pmd);
1292                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1293                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1294                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1295                 ret |= VM_FAULT_WRITE;
1296                 unlock_page(page);
1297                 goto out_unlock;
1298         }
1299         unlock_page(page);
1300         get_page(page);
1301         spin_unlock(vmf->ptl);
1302 alloc:
1303         if (transparent_hugepage_enabled(vma) &&
1304             !transparent_hugepage_debug_cow()) {
1305                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1306                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1307         } else
1308                 new_page = NULL;
1309
1310         if (likely(new_page)) {
1311                 prep_transhuge_page(new_page);
1312         } else {
1313                 if (!page) {
1314                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1315                         ret |= VM_FAULT_FALLBACK;
1316                 } else {
1317                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1318                         if (ret & VM_FAULT_OOM) {
1319                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1320                                 ret |= VM_FAULT_FALLBACK;
1321                         }
1322                         put_page(page);
1323                 }
1324                 count_vm_event(THP_FAULT_FALLBACK);
1325                 goto out;
1326         }
1327
1328         if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm,
1329                                         huge_gfp, &memcg, true))) {
1330                 put_page(new_page);
1331                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1332                 if (page)
1333                         put_page(page);
1334                 ret |= VM_FAULT_FALLBACK;
1335                 count_vm_event(THP_FAULT_FALLBACK);
1336                 goto out;
1337         }
1338
1339         count_vm_event(THP_FAULT_ALLOC);
1340
1341         if (!page)
1342                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1343         else
1344                 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1345         __SetPageUptodate(new_page);
1346
1347         mmun_start = haddr;
1348         mmun_end   = haddr + HPAGE_PMD_SIZE;
1349         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1350
1351         spin_lock(vmf->ptl);
1352         if (page)
1353                 put_page(page);
1354         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1355                 spin_unlock(vmf->ptl);
1356                 mem_cgroup_cancel_charge(new_page, memcg, true);
1357                 put_page(new_page);
1358                 goto out_mn;
1359         } else {
1360                 pmd_t entry;
1361                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1362                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1363                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1364                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1365                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1366                 lru_cache_add_active_or_unevictable(new_page, vma);
1367                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1368                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1369                 if (!page) {
1370                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1371                 } else {
1372                         VM_BUG_ON_PAGE(!PageHead(page), page);
1373                         page_remove_rmap(page, true);
1374                         put_page(page);
1375                 }
1376                 ret |= VM_FAULT_WRITE;
1377         }
1378         spin_unlock(vmf->ptl);
1379 out_mn:
1380         /*
1381          * No need to double call mmu_notifier->invalidate_range() callback as
1382          * the above pmdp_huge_clear_flush_notify() did already call it.
1383          */
1384         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1385                                                mmun_end);
1386 out:
1387         return ret;
1388 out_unlock:
1389         spin_unlock(vmf->ptl);
1390         return ret;
1391 }
1392
1393 /*
1394  * FOLL_FORCE can write to even unwritable pmd's, but only
1395  * after we've gone through a COW cycle and they are dirty.
1396  */
1397 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1398 {
1399         return pmd_write(pmd) ||
1400                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1401 }
1402
1403 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1404                                    unsigned long addr,
1405                                    pmd_t *pmd,
1406                                    unsigned int flags)
1407 {
1408         struct mm_struct *mm = vma->vm_mm;
1409         struct page *page = NULL;
1410
1411         assert_spin_locked(pmd_lockptr(mm, pmd));
1412
1413         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1414                 goto out;
1415
1416         /* Avoid dumping huge zero page */
1417         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1418                 return ERR_PTR(-EFAULT);
1419
1420         /* Full NUMA hinting faults to serialise migration in fault paths */
1421         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1422                 goto out;
1423
1424         page = pmd_page(*pmd);
1425         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1426         if (flags & FOLL_TOUCH)
1427                 touch_pmd(vma, addr, pmd);
1428         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1429                 /*
1430                  * We don't mlock() pte-mapped THPs. This way we can avoid
1431                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1432                  *
1433                  * For anon THP:
1434                  *
1435                  * In most cases the pmd is the only mapping of the page as we
1436                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1437                  * writable private mappings in populate_vma_page_range().
1438                  *
1439                  * The only scenario when we have the page shared here is if we
1440                  * mlocking read-only mapping shared over fork(). We skip
1441                  * mlocking such pages.
1442                  *
1443                  * For file THP:
1444                  *
1445                  * We can expect PageDoubleMap() to be stable under page lock:
1446                  * for file pages we set it in page_add_file_rmap(), which
1447                  * requires page to be locked.
1448                  */
1449
1450                 if (PageAnon(page) && compound_mapcount(page) != 1)
1451                         goto skip_mlock;
1452                 if (PageDoubleMap(page) || !page->mapping)
1453                         goto skip_mlock;
1454                 if (!trylock_page(page))
1455                         goto skip_mlock;
1456                 lru_add_drain();
1457                 if (page->mapping && !PageDoubleMap(page))
1458                         mlock_vma_page(page);
1459                 unlock_page(page);
1460         }
1461 skip_mlock:
1462         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1463         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1464         if (flags & FOLL_GET)
1465                 get_page(page);
1466
1467 out:
1468         return page;
1469 }
1470
1471 /* NUMA hinting page fault entry point for trans huge pmds */
1472 int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1473 {
1474         struct vm_area_struct *vma = vmf->vma;
1475         struct anon_vma *anon_vma = NULL;
1476         struct page *page;
1477         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1478         int page_nid = -1, this_nid = numa_node_id();
1479         int target_nid, last_cpupid = -1;
1480         bool page_locked;
1481         bool migrated = false;
1482         bool was_writable;
1483         int flags = 0;
1484
1485         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1486         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1487                 goto out_unlock;
1488
1489         /*
1490          * If there are potential migrations, wait for completion and retry
1491          * without disrupting NUMA hinting information. Do not relock and
1492          * check_same as the page may no longer be mapped.
1493          */
1494         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1495                 page = pmd_page(*vmf->pmd);
1496                 if (!get_page_unless_zero(page))
1497                         goto out_unlock;
1498                 spin_unlock(vmf->ptl);
1499                 wait_on_page_locked(page);
1500                 put_page(page);
1501                 goto out;
1502         }
1503
1504         page = pmd_page(pmd);
1505         BUG_ON(is_huge_zero_page(page));
1506         page_nid = page_to_nid(page);
1507         last_cpupid = page_cpupid_last(page);
1508         count_vm_numa_event(NUMA_HINT_FAULTS);
1509         if (page_nid == this_nid) {
1510                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1511                 flags |= TNF_FAULT_LOCAL;
1512         }
1513
1514         /* See similar comment in do_numa_page for explanation */
1515         if (!pmd_savedwrite(pmd))
1516                 flags |= TNF_NO_GROUP;
1517
1518         /*
1519          * Acquire the page lock to serialise THP migrations but avoid dropping
1520          * page_table_lock if at all possible
1521          */
1522         page_locked = trylock_page(page);
1523         target_nid = mpol_misplaced(page, vma, haddr);
1524         if (target_nid == -1) {
1525                 /* If the page was locked, there are no parallel migrations */
1526                 if (page_locked)
1527                         goto clear_pmdnuma;
1528         }
1529
1530         /* Migration could have started since the pmd_trans_migrating check */
1531         if (!page_locked) {
1532                 page_nid = -1;
1533                 if (!get_page_unless_zero(page))
1534                         goto out_unlock;
1535                 spin_unlock(vmf->ptl);
1536                 wait_on_page_locked(page);
1537                 put_page(page);
1538                 goto out;
1539         }
1540
1541         /*
1542          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1543          * to serialises splits
1544          */
1545         get_page(page);
1546         spin_unlock(vmf->ptl);
1547         anon_vma = page_lock_anon_vma_read(page);
1548
1549         /* Confirm the PMD did not change while page_table_lock was released */
1550         spin_lock(vmf->ptl);
1551         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1552                 unlock_page(page);
1553                 put_page(page);
1554                 page_nid = -1;
1555                 goto out_unlock;
1556         }
1557
1558         /* Bail if we fail to protect against THP splits for any reason */
1559         if (unlikely(!anon_vma)) {
1560                 put_page(page);
1561                 page_nid = -1;
1562                 goto clear_pmdnuma;
1563         }
1564
1565         /*
1566          * Since we took the NUMA fault, we must have observed the !accessible
1567          * bit. Make sure all other CPUs agree with that, to avoid them
1568          * modifying the page we're about to migrate.
1569          *
1570          * Must be done under PTL such that we'll observe the relevant
1571          * inc_tlb_flush_pending().
1572          *
1573          * We are not sure a pending tlb flush here is for a huge page
1574          * mapping or not. Hence use the tlb range variant
1575          */
1576         if (mm_tlb_flush_pending(vma->vm_mm))
1577                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1578
1579         /*
1580          * Migrate the THP to the requested node, returns with page unlocked
1581          * and access rights restored.
1582          */
1583         spin_unlock(vmf->ptl);
1584
1585         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1586                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1587         if (migrated) {
1588                 flags |= TNF_MIGRATED;
1589                 page_nid = target_nid;
1590         } else
1591                 flags |= TNF_MIGRATE_FAIL;
1592
1593         goto out;
1594 clear_pmdnuma:
1595         BUG_ON(!PageLocked(page));
1596         was_writable = pmd_savedwrite(pmd);
1597         pmd = pmd_modify(pmd, vma->vm_page_prot);
1598         pmd = pmd_mkyoung(pmd);
1599         if (was_writable)
1600                 pmd = pmd_mkwrite(pmd);
1601         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1602         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1603         unlock_page(page);
1604 out_unlock:
1605         spin_unlock(vmf->ptl);
1606
1607 out:
1608         if (anon_vma)
1609                 page_unlock_anon_vma_read(anon_vma);
1610
1611         if (page_nid != -1)
1612                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1613                                 flags);
1614
1615         return 0;
1616 }
1617
1618 /*
1619  * Return true if we do MADV_FREE successfully on entire pmd page.
1620  * Otherwise, return false.
1621  */
1622 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1623                 pmd_t *pmd, unsigned long addr, unsigned long next)
1624 {
1625         spinlock_t *ptl;
1626         pmd_t orig_pmd;
1627         struct page *page;
1628         struct mm_struct *mm = tlb->mm;
1629         bool ret = false;
1630
1631         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1632
1633         ptl = pmd_trans_huge_lock(pmd, vma);
1634         if (!ptl)
1635                 goto out_unlocked;
1636
1637         orig_pmd = *pmd;
1638         if (is_huge_zero_pmd(orig_pmd))
1639                 goto out;
1640
1641         if (unlikely(!pmd_present(orig_pmd))) {
1642                 VM_BUG_ON(thp_migration_supported() &&
1643                                   !is_pmd_migration_entry(orig_pmd));
1644                 goto out;
1645         }
1646
1647         page = pmd_page(orig_pmd);
1648         /*
1649          * If other processes are mapping this page, we couldn't discard
1650          * the page unless they all do MADV_FREE so let's skip the page.
1651          */
1652         if (page_mapcount(page) != 1)
1653                 goto out;
1654
1655         if (!trylock_page(page))
1656                 goto out;
1657
1658         /*
1659          * If user want to discard part-pages of THP, split it so MADV_FREE
1660          * will deactivate only them.
1661          */
1662         if (next - addr != HPAGE_PMD_SIZE) {
1663                 get_page(page);
1664                 spin_unlock(ptl);
1665                 split_huge_page(page);
1666                 unlock_page(page);
1667                 put_page(page);
1668                 goto out_unlocked;
1669         }
1670
1671         if (PageDirty(page))
1672                 ClearPageDirty(page);
1673         unlock_page(page);
1674
1675         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1676                 pmdp_invalidate(vma, addr, pmd);
1677                 orig_pmd = pmd_mkold(orig_pmd);
1678                 orig_pmd = pmd_mkclean(orig_pmd);
1679
1680                 set_pmd_at(mm, addr, pmd, orig_pmd);
1681                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1682         }
1683
1684         mark_page_lazyfree(page);
1685         ret = true;
1686 out:
1687         spin_unlock(ptl);
1688 out_unlocked:
1689         return ret;
1690 }
1691
1692 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1693 {
1694         pgtable_t pgtable;
1695
1696         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1697         pte_free(mm, pgtable);
1698         mm_dec_nr_ptes(mm);
1699 }
1700
1701 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1702                  pmd_t *pmd, unsigned long addr)
1703 {
1704         pmd_t orig_pmd;
1705         spinlock_t *ptl;
1706
1707         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1708
1709         ptl = __pmd_trans_huge_lock(pmd, vma);
1710         if (!ptl)
1711                 return 0;
1712         /*
1713          * For architectures like ppc64 we look at deposited pgtable
1714          * when calling pmdp_huge_get_and_clear. So do the
1715          * pgtable_trans_huge_withdraw after finishing pmdp related
1716          * operations.
1717          */
1718         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1719                         tlb->fullmm);
1720         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1721         if (vma_is_dax(vma)) {
1722                 if (arch_needs_pgtable_deposit())
1723                         zap_deposited_table(tlb->mm, pmd);
1724                 spin_unlock(ptl);
1725                 if (is_huge_zero_pmd(orig_pmd))
1726                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1727         } else if (is_huge_zero_pmd(orig_pmd)) {
1728                 zap_deposited_table(tlb->mm, pmd);
1729                 spin_unlock(ptl);
1730                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1731         } else {
1732                 struct page *page = NULL;
1733                 int flush_needed = 1;
1734
1735                 if (pmd_present(orig_pmd)) {
1736                         page = pmd_page(orig_pmd);
1737                         page_remove_rmap(page, true);
1738                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1739                         VM_BUG_ON_PAGE(!PageHead(page), page);
1740                 } else if (thp_migration_supported()) {
1741                         swp_entry_t entry;
1742
1743                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1744                         entry = pmd_to_swp_entry(orig_pmd);
1745                         page = pfn_to_page(swp_offset(entry));
1746                         flush_needed = 0;
1747                 } else
1748                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1749
1750                 if (PageAnon(page)) {
1751                         zap_deposited_table(tlb->mm, pmd);
1752                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1753                 } else {
1754                         if (arch_needs_pgtable_deposit())
1755                                 zap_deposited_table(tlb->mm, pmd);
1756                         add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1757                 }
1758
1759                 spin_unlock(ptl);
1760                 if (flush_needed)
1761                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1762         }
1763         return 1;
1764 }
1765
1766 #ifndef pmd_move_must_withdraw
1767 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1768                                          spinlock_t *old_pmd_ptl,
1769                                          struct vm_area_struct *vma)
1770 {
1771         /*
1772          * With split pmd lock we also need to move preallocated
1773          * PTE page table if new_pmd is on different PMD page table.
1774          *
1775          * We also don't deposit and withdraw tables for file pages.
1776          */
1777         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1778 }
1779 #endif
1780
1781 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1782 {
1783 #ifdef CONFIG_MEM_SOFT_DIRTY
1784         if (unlikely(is_pmd_migration_entry(pmd)))
1785                 pmd = pmd_swp_mksoft_dirty(pmd);
1786         else if (pmd_present(pmd))
1787                 pmd = pmd_mksoft_dirty(pmd);
1788 #endif
1789         return pmd;
1790 }
1791
1792 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1793                   unsigned long new_addr, unsigned long old_end,
1794                   pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush)
1795 {
1796         spinlock_t *old_ptl, *new_ptl;
1797         pmd_t pmd;
1798         struct mm_struct *mm = vma->vm_mm;
1799         bool force_flush = false;
1800
1801         if ((old_addr & ~HPAGE_PMD_MASK) ||
1802             (new_addr & ~HPAGE_PMD_MASK) ||
1803             old_end - old_addr < HPAGE_PMD_SIZE)
1804                 return false;
1805
1806         /*
1807          * The destination pmd shouldn't be established, free_pgtables()
1808          * should have release it.
1809          */
1810         if (WARN_ON(!pmd_none(*new_pmd))) {
1811                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1812                 return false;
1813         }
1814
1815         /*
1816          * We don't have to worry about the ordering of src and dst
1817          * ptlocks because exclusive mmap_sem prevents deadlock.
1818          */
1819         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1820         if (old_ptl) {
1821                 new_ptl = pmd_lockptr(mm, new_pmd);
1822                 if (new_ptl != old_ptl)
1823                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1824                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1825                 if (pmd_present(pmd) && pmd_dirty(pmd))
1826                         force_flush = true;
1827                 VM_BUG_ON(!pmd_none(*new_pmd));
1828
1829                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1830                         pgtable_t pgtable;
1831                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1832                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1833                 }
1834                 pmd = move_soft_dirty_pmd(pmd);
1835                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1836                 if (new_ptl != old_ptl)
1837                         spin_unlock(new_ptl);
1838                 if (force_flush)
1839                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1840                 else
1841                         *need_flush = true;
1842                 spin_unlock(old_ptl);
1843                 return true;
1844         }
1845         return false;
1846 }
1847
1848 /*
1849  * Returns
1850  *  - 0 if PMD could not be locked
1851  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1852  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1853  */
1854 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1855                 unsigned long addr, pgprot_t newprot, int prot_numa)
1856 {
1857         struct mm_struct *mm = vma->vm_mm;
1858         spinlock_t *ptl;
1859         pmd_t entry;
1860         bool preserve_write;
1861         int ret;
1862
1863         ptl = __pmd_trans_huge_lock(pmd, vma);
1864         if (!ptl)
1865                 return 0;
1866
1867         preserve_write = prot_numa && pmd_write(*pmd);
1868         ret = 1;
1869
1870 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1871         if (is_swap_pmd(*pmd)) {
1872                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1873
1874                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1875                 if (is_write_migration_entry(entry)) {
1876                         pmd_t newpmd;
1877                         /*
1878                          * A protection check is difficult so
1879                          * just be safe and disable write
1880                          */
1881                         make_migration_entry_read(&entry);
1882                         newpmd = swp_entry_to_pmd(entry);
1883                         if (pmd_swp_soft_dirty(*pmd))
1884                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1885                         set_pmd_at(mm, addr, pmd, newpmd);
1886                 }
1887                 goto unlock;
1888         }
1889 #endif
1890
1891         /*
1892          * Avoid trapping faults against the zero page. The read-only
1893          * data is likely to be read-cached on the local CPU and
1894          * local/remote hits to the zero page are not interesting.
1895          */
1896         if (prot_numa && is_huge_zero_pmd(*pmd))
1897                 goto unlock;
1898
1899         if (prot_numa && pmd_protnone(*pmd))
1900                 goto unlock;
1901
1902         /*
1903          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1904          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1905          * which is also under down_read(mmap_sem):
1906          *
1907          *      CPU0:                           CPU1:
1908          *                              change_huge_pmd(prot_numa=1)
1909          *                               pmdp_huge_get_and_clear_notify()
1910          * madvise_dontneed()
1911          *  zap_pmd_range()
1912          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1913          *   // skip the pmd
1914          *                               set_pmd_at();
1915          *                               // pmd is re-established
1916          *
1917          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1918          * which may break userspace.
1919          *
1920          * pmdp_invalidate() is required to make sure we don't miss
1921          * dirty/young flags set by hardware.
1922          */
1923         entry = *pmd;
1924         pmdp_invalidate(vma, addr, pmd);
1925
1926         /*
1927          * Recover dirty/young flags.  It relies on pmdp_invalidate to not
1928          * corrupt them.
1929          */
1930         if (pmd_dirty(*pmd))
1931                 entry = pmd_mkdirty(entry);
1932         if (pmd_young(*pmd))
1933                 entry = pmd_mkyoung(entry);
1934
1935         entry = pmd_modify(entry, newprot);
1936         if (preserve_write)
1937                 entry = pmd_mk_savedwrite(entry);
1938         ret = HPAGE_PMD_NR;
1939         set_pmd_at(mm, addr, pmd, entry);
1940         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1941 unlock:
1942         spin_unlock(ptl);
1943         return ret;
1944 }
1945
1946 /*
1947  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1948  *
1949  * Note that if it returns page table lock pointer, this routine returns without
1950  * unlocking page table lock. So callers must unlock it.
1951  */
1952 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1953 {
1954         spinlock_t *ptl;
1955         ptl = pmd_lock(vma->vm_mm, pmd);
1956         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1957                         pmd_devmap(*pmd)))
1958                 return ptl;
1959         spin_unlock(ptl);
1960         return NULL;
1961 }
1962
1963 /*
1964  * Returns true if a given pud maps a thp, false otherwise.
1965  *
1966  * Note that if it returns true, this routine returns without unlocking page
1967  * table lock. So callers must unlock it.
1968  */
1969 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1970 {
1971         spinlock_t *ptl;
1972
1973         ptl = pud_lock(vma->vm_mm, pud);
1974         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1975                 return ptl;
1976         spin_unlock(ptl);
1977         return NULL;
1978 }
1979
1980 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1981 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1982                  pud_t *pud, unsigned long addr)
1983 {
1984         pud_t orig_pud;
1985         spinlock_t *ptl;
1986
1987         ptl = __pud_trans_huge_lock(pud, vma);
1988         if (!ptl)
1989                 return 0;
1990         /*
1991          * For architectures like ppc64 we look at deposited pgtable
1992          * when calling pudp_huge_get_and_clear. So do the
1993          * pgtable_trans_huge_withdraw after finishing pudp related
1994          * operations.
1995          */
1996         orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1997                         tlb->fullmm);
1998         tlb_remove_pud_tlb_entry(tlb, pud, addr);
1999         if (vma_is_dax(vma)) {
2000                 spin_unlock(ptl);
2001                 /* No zero page support yet */
2002         } else {
2003                 /* No support for anonymous PUD pages yet */
2004                 BUG();
2005         }
2006         return 1;
2007 }
2008
2009 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2010                 unsigned long haddr)
2011 {
2012         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2013         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2014         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2015         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2016
2017         count_vm_event(THP_SPLIT_PUD);
2018
2019         pudp_huge_clear_flush_notify(vma, haddr, pud);
2020 }
2021
2022 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2023                 unsigned long address)
2024 {
2025         spinlock_t *ptl;
2026         struct mm_struct *mm = vma->vm_mm;
2027         unsigned long haddr = address & HPAGE_PUD_MASK;
2028
2029         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
2030         ptl = pud_lock(mm, pud);
2031         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2032                 goto out;
2033         __split_huge_pud_locked(vma, pud, haddr);
2034
2035 out:
2036         spin_unlock(ptl);
2037         /*
2038          * No need to double call mmu_notifier->invalidate_range() callback as
2039          * the above pudp_huge_clear_flush_notify() did already call it.
2040          */
2041         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2042                                                HPAGE_PUD_SIZE);
2043 }
2044 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2045
2046 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2047                 unsigned long haddr, pmd_t *pmd)
2048 {
2049         struct mm_struct *mm = vma->vm_mm;
2050         pgtable_t pgtable;
2051         pmd_t _pmd;
2052         int i;
2053
2054         /*
2055          * Leave pmd empty until pte is filled note that it is fine to delay
2056          * notification until mmu_notifier_invalidate_range_end() as we are
2057          * replacing a zero pmd write protected page with a zero pte write
2058          * protected page.
2059          *
2060          * See Documentation/vm/mmu_notifier.txt
2061          */
2062         pmdp_huge_clear_flush(vma, haddr, pmd);
2063
2064         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2065         pmd_populate(mm, &_pmd, pgtable);
2066
2067         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2068                 pte_t *pte, entry;
2069                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2070                 entry = pte_mkspecial(entry);
2071                 pte = pte_offset_map(&_pmd, haddr);
2072                 VM_BUG_ON(!pte_none(*pte));
2073                 set_pte_at(mm, haddr, pte, entry);
2074                 pte_unmap(pte);
2075         }
2076         smp_wmb(); /* make pte visible before pmd */
2077         pmd_populate(mm, pmd, pgtable);
2078 }
2079
2080 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2081                 unsigned long haddr, bool freeze)
2082 {
2083         struct mm_struct *mm = vma->vm_mm;
2084         struct page *page;
2085         pgtable_t pgtable;
2086         pmd_t _pmd;
2087         bool young, write, dirty, soft_dirty, pmd_migration = false;
2088         unsigned long addr;
2089         int i;
2090
2091         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2092         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2093         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2094         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2095                                 && !pmd_devmap(*pmd));
2096
2097         count_vm_event(THP_SPLIT_PMD);
2098
2099         if (!vma_is_anonymous(vma)) {
2100                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2101                 /*
2102                  * We are going to unmap this huge page. So
2103                  * just go ahead and zap it
2104                  */
2105                 if (arch_needs_pgtable_deposit())
2106                         zap_deposited_table(mm, pmd);
2107                 if (vma_is_dax(vma))
2108                         return;
2109                 page = pmd_page(_pmd);
2110                 if (!PageReferenced(page) && pmd_young(_pmd))
2111                         SetPageReferenced(page);
2112                 page_remove_rmap(page, true);
2113                 put_page(page);
2114                 add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
2115                 return;
2116         } else if (is_huge_zero_pmd(*pmd)) {
2117                 /*
2118                  * FIXME: Do we want to invalidate secondary mmu by calling
2119                  * mmu_notifier_invalidate_range() see comments below inside
2120                  * __split_huge_pmd() ?
2121                  *
2122                  * We are going from a zero huge page write protected to zero
2123                  * small page also write protected so it does not seems useful
2124                  * to invalidate secondary mmu at this time.
2125                  */
2126                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2127         }
2128
2129 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2130         pmd_migration = is_pmd_migration_entry(*pmd);
2131         if (pmd_migration) {
2132                 swp_entry_t entry;
2133
2134                 entry = pmd_to_swp_entry(*pmd);
2135                 page = pfn_to_page(swp_offset(entry));
2136         } else
2137 #endif
2138                 page = pmd_page(*pmd);
2139         VM_BUG_ON_PAGE(!page_count(page), page);
2140         page_ref_add(page, HPAGE_PMD_NR - 1);
2141         write = pmd_write(*pmd);
2142         young = pmd_young(*pmd);
2143         dirty = pmd_dirty(*pmd);
2144         soft_dirty = pmd_soft_dirty(*pmd);
2145
2146         pmdp_huge_split_prepare(vma, haddr, pmd);
2147         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2148         pmd_populate(mm, &_pmd, pgtable);
2149
2150         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2151                 pte_t entry, *pte;
2152                 /*
2153                  * Note that NUMA hinting access restrictions are not
2154                  * transferred to avoid any possibility of altering
2155                  * permissions across VMAs.
2156                  */
2157                 if (freeze || pmd_migration) {
2158                         swp_entry_t swp_entry;
2159                         swp_entry = make_migration_entry(page + i, write);
2160                         entry = swp_entry_to_pte(swp_entry);
2161                         if (soft_dirty)
2162                                 entry = pte_swp_mksoft_dirty(entry);
2163                 } else {
2164                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2165                         entry = maybe_mkwrite(entry, vma);
2166                         if (!write)
2167                                 entry = pte_wrprotect(entry);
2168                         if (!young)
2169                                 entry = pte_mkold(entry);
2170                         if (soft_dirty)
2171                                 entry = pte_mksoft_dirty(entry);
2172                 }
2173                 if (dirty)
2174                         SetPageDirty(page + i);
2175                 pte = pte_offset_map(&_pmd, addr);
2176                 BUG_ON(!pte_none(*pte));
2177                 set_pte_at(mm, addr, pte, entry);
2178                 atomic_inc(&page[i]._mapcount);
2179                 pte_unmap(pte);
2180         }
2181
2182         /*
2183          * Set PG_double_map before dropping compound_mapcount to avoid
2184          * false-negative page_mapped().
2185          */
2186         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2187                 for (i = 0; i < HPAGE_PMD_NR; i++)
2188                         atomic_inc(&page[i]._mapcount);
2189         }
2190
2191         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2192                 /* Last compound_mapcount is gone. */
2193                 __dec_node_page_state(page, NR_ANON_THPS);
2194                 if (TestClearPageDoubleMap(page)) {
2195                         /* No need in mapcount reference anymore */
2196                         for (i = 0; i < HPAGE_PMD_NR; i++)
2197                                 atomic_dec(&page[i]._mapcount);
2198                 }
2199         }
2200
2201         smp_wmb(); /* make pte visible before pmd */
2202         /*
2203          * Up to this point the pmd is present and huge and userland has the
2204          * whole access to the hugepage during the split (which happens in
2205          * place). If we overwrite the pmd with the not-huge version pointing
2206          * to the pte here (which of course we could if all CPUs were bug
2207          * free), userland could trigger a small page size TLB miss on the
2208          * small sized TLB while the hugepage TLB entry is still established in
2209          * the huge TLB. Some CPU doesn't like that.
2210          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2211          * 383 on page 93. Intel should be safe but is also warns that it's
2212          * only safe if the permission and cache attributes of the two entries
2213          * loaded in the two TLB is identical (which should be the case here).
2214          * But it is generally safer to never allow small and huge TLB entries
2215          * for the same virtual address to be loaded simultaneously. So instead
2216          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2217          * current pmd notpresent (atomically because here the pmd_trans_huge
2218          * and pmd_trans_splitting must remain set at all times on the pmd
2219          * until the split is complete for this pmd), then we flush the SMP TLB
2220          * and finally we write the non-huge version of the pmd entry with
2221          * pmd_populate.
2222          */
2223         pmdp_invalidate(vma, haddr, pmd);
2224         pmd_populate(mm, pmd, pgtable);
2225
2226         if (freeze) {
2227                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2228                         page_remove_rmap(page + i, false);
2229                         put_page(page + i);
2230                 }
2231         }
2232 }
2233
2234 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2235                 unsigned long address, bool freeze, struct page *page)
2236 {
2237         spinlock_t *ptl;
2238         struct mm_struct *mm = vma->vm_mm;
2239         unsigned long haddr = address & HPAGE_PMD_MASK;
2240
2241         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2242         ptl = pmd_lock(mm, pmd);
2243
2244         /*
2245          * If caller asks to setup a migration entries, we need a page to check
2246          * pmd against. Otherwise we can end up replacing wrong page.
2247          */
2248         VM_BUG_ON(freeze && !page);
2249         if (page && page != pmd_page(*pmd))
2250                 goto out;
2251
2252         if (pmd_trans_huge(*pmd)) {
2253                 page = pmd_page(*pmd);
2254                 if (PageMlocked(page))
2255                         clear_page_mlock(page);
2256         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2257                 goto out;
2258         __split_huge_pmd_locked(vma, pmd, haddr, freeze);
2259 out:
2260         spin_unlock(ptl);
2261         /*
2262          * No need to double call mmu_notifier->invalidate_range() callback.
2263          * They are 3 cases to consider inside __split_huge_pmd_locked():
2264          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2265          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2266          *    fault will trigger a flush_notify before pointing to a new page
2267          *    (it is fine if the secondary mmu keeps pointing to the old zero
2268          *    page in the meantime)
2269          *  3) Split a huge pmd into pte pointing to the same page. No need
2270          *     to invalidate secondary tlb entry they are all still valid.
2271          *     any further changes to individual pte will notify. So no need
2272          *     to call mmu_notifier->invalidate_range()
2273          */
2274         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2275                                                HPAGE_PMD_SIZE);
2276 }
2277
2278 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2279                 bool freeze, struct page *page)
2280 {
2281         pgd_t *pgd;
2282         p4d_t *p4d;
2283         pud_t *pud;
2284         pmd_t *pmd;
2285
2286         pgd = pgd_offset(vma->vm_mm, address);
2287         if (!pgd_present(*pgd))
2288                 return;
2289
2290         p4d = p4d_offset(pgd, address);
2291         if (!p4d_present(*p4d))
2292                 return;
2293
2294         pud = pud_offset(p4d, address);
2295         if (!pud_present(*pud))
2296                 return;
2297
2298         pmd = pmd_offset(pud, address);
2299
2300         __split_huge_pmd(vma, pmd, address, freeze, page);
2301 }
2302
2303 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2304                              unsigned long start,
2305                              unsigned long end,
2306                              long adjust_next)
2307 {
2308         /*
2309          * If the new start 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 (start & ~HPAGE_PMD_MASK &&
2314             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2315             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2316                 split_huge_pmd_address(vma, start, false, NULL);
2317
2318         /*
2319          * If the new end address isn't hpage aligned and it could
2320          * previously contain an hugepage: check if we need to split
2321          * an huge pmd.
2322          */
2323         if (end & ~HPAGE_PMD_MASK &&
2324             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2325             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2326                 split_huge_pmd_address(vma, end, false, NULL);
2327
2328         /*
2329          * If we're also updating the vma->vm_next->vm_start, if the new
2330          * vm_next->vm_start isn't page aligned and it could previously
2331          * contain an hugepage: check if we need to split an huge pmd.
2332          */
2333         if (adjust_next > 0) {
2334                 struct vm_area_struct *next = vma->vm_next;
2335                 unsigned long nstart = next->vm_start;
2336                 nstart += adjust_next << PAGE_SHIFT;
2337                 if (nstart & ~HPAGE_PMD_MASK &&
2338                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2339                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2340                         split_huge_pmd_address(next, nstart, false, NULL);
2341         }
2342 }
2343
2344 static void freeze_page(struct page *page)
2345 {
2346         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2347                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2348         bool unmap_success;
2349
2350         VM_BUG_ON_PAGE(!PageHead(page), page);
2351
2352         if (PageAnon(page))
2353                 ttu_flags |= TTU_SPLIT_FREEZE;
2354
2355         unmap_success = try_to_unmap(page, ttu_flags);
2356         VM_BUG_ON_PAGE(!unmap_success, page);
2357 }
2358
2359 static void unfreeze_page(struct page *page)
2360 {
2361         int i;
2362         if (PageTransHuge(page)) {
2363                 remove_migration_ptes(page, page, true);
2364         } else {
2365                 for (i = 0; i < HPAGE_PMD_NR; i++)
2366                         remove_migration_ptes(page + i, page + i, true);
2367         }
2368 }
2369
2370 static void __split_huge_page_tail(struct page *head, int tail,
2371                 struct lruvec *lruvec, struct list_head *list)
2372 {
2373         struct page *page_tail = head + tail;
2374
2375         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2376         VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
2377
2378         /*
2379          * tail_page->_refcount is zero and not changing from under us. But
2380          * get_page_unless_zero() may be running from under us on the
2381          * tail_page. If we used atomic_set() below instead of atomic_inc() or
2382          * atomic_add(), we would then run atomic_set() concurrently with
2383          * get_page_unless_zero(), and atomic_set() is implemented in C not
2384          * using locked ops. spin_unlock on x86 sometime uses locked ops
2385          * because of PPro errata 66, 92, so unless somebody can guarantee
2386          * atomic_set() here would be safe on all archs (and not only on x86),
2387          * it's safer to use atomic_inc()/atomic_add().
2388          */
2389         if (PageAnon(head) && !PageSwapCache(head)) {
2390                 page_ref_inc(page_tail);
2391         } else {
2392                 /* Additional pin to radix tree */
2393                 page_ref_add(page_tail, 2);
2394         }
2395
2396         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2397         page_tail->flags |= (head->flags &
2398                         ((1L << PG_referenced) |
2399                          (1L << PG_swapbacked) |
2400                          (1L << PG_swapcache) |
2401                          (1L << PG_mlocked) |
2402                          (1L << PG_uptodate) |
2403                          (1L << PG_active) |
2404                          (1L << PG_locked) |
2405                          (1L << PG_unevictable) |
2406                          (1L << PG_dirty)));
2407
2408         /*
2409          * After clearing PageTail the gup refcount can be released.
2410          * Page flags also must be visible before we make the page non-compound.
2411          */
2412         smp_wmb();
2413
2414         clear_compound_head(page_tail);
2415
2416         if (page_is_young(head))
2417                 set_page_young(page_tail);
2418         if (page_is_idle(head))
2419                 set_page_idle(page_tail);
2420
2421         /* ->mapping in first tail page is compound_mapcount */
2422         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2423                         page_tail);
2424         page_tail->mapping = head->mapping;
2425
2426         page_tail->index = head->index + tail;
2427         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2428         lru_add_page_tail(head, page_tail, lruvec, list);
2429 }
2430
2431 static void __split_huge_page(struct page *page, struct list_head *list,
2432                 unsigned long flags)
2433 {
2434         struct page *head = compound_head(page);
2435         struct zone *zone = page_zone(head);
2436         struct lruvec *lruvec;
2437         pgoff_t end = -1;
2438         int i;
2439
2440         lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
2441
2442         /* complete memcg works before add pages to LRU */
2443         mem_cgroup_split_huge_fixup(head);
2444
2445         if (!PageAnon(page))
2446                 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE);
2447
2448         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2449                 __split_huge_page_tail(head, i, lruvec, list);
2450                 /* Some pages can be beyond i_size: drop them from page cache */
2451                 if (head[i].index >= end) {
2452                         __ClearPageDirty(head + i);
2453                         __delete_from_page_cache(head + i, NULL);
2454                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2455                                 shmem_uncharge(head->mapping->host, 1);
2456                         put_page(head + i);
2457                 }
2458         }
2459
2460         ClearPageCompound(head);
2461         /* See comment in __split_huge_page_tail() */
2462         if (PageAnon(head)) {
2463                 /* Additional pin to radix tree of swap cache */
2464                 if (PageSwapCache(head))
2465                         page_ref_add(head, 2);
2466                 else
2467                         page_ref_inc(head);
2468         } else {
2469                 /* Additional pin to radix tree */
2470                 page_ref_add(head, 2);
2471                 spin_unlock(&head->mapping->tree_lock);
2472         }
2473
2474         spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2475
2476         unfreeze_page(head);
2477
2478         for (i = 0; i < HPAGE_PMD_NR; i++) {
2479                 struct page *subpage = head + i;
2480                 if (subpage == page)
2481                         continue;
2482                 unlock_page(subpage);
2483
2484                 /*
2485                  * Subpages may be freed if there wasn't any mapping
2486                  * like if add_to_swap() is running on a lru page that
2487                  * had its mapping zapped. And freeing these pages
2488                  * requires taking the lru_lock so we do the put_page
2489                  * of the tail pages after the split is complete.
2490                  */
2491                 put_page(subpage);
2492         }
2493 }
2494
2495 int total_mapcount(struct page *page)
2496 {
2497         int i, compound, ret;
2498
2499         VM_BUG_ON_PAGE(PageTail(page), page);
2500
2501         if (likely(!PageCompound(page)))
2502                 return atomic_read(&page->_mapcount) + 1;
2503
2504         compound = compound_mapcount(page);
2505         if (PageHuge(page))
2506                 return compound;
2507         ret = compound;
2508         for (i = 0; i < HPAGE_PMD_NR; i++)
2509                 ret += atomic_read(&page[i]._mapcount) + 1;
2510         /* File pages has compound_mapcount included in _mapcount */
2511         if (!PageAnon(page))
2512                 return ret - compound * HPAGE_PMD_NR;
2513         if (PageDoubleMap(page))
2514                 ret -= HPAGE_PMD_NR;
2515         return ret;
2516 }
2517
2518 /*
2519  * This calculates accurately how many mappings a transparent hugepage
2520  * has (unlike page_mapcount() which isn't fully accurate). This full
2521  * accuracy is primarily needed to know if copy-on-write faults can
2522  * reuse the page and change the mapping to read-write instead of
2523  * copying them. At the same time this returns the total_mapcount too.
2524  *
2525  * The function returns the highest mapcount any one of the subpages
2526  * has. If the return value is one, even if different processes are
2527  * mapping different subpages of the transparent hugepage, they can
2528  * all reuse it, because each process is reusing a different subpage.
2529  *
2530  * The total_mapcount is instead counting all virtual mappings of the
2531  * subpages. If the total_mapcount is equal to "one", it tells the
2532  * caller all mappings belong to the same "mm" and in turn the
2533  * anon_vma of the transparent hugepage can become the vma->anon_vma
2534  * local one as no other process may be mapping any of the subpages.
2535  *
2536  * It would be more accurate to replace page_mapcount() with
2537  * page_trans_huge_mapcount(), however we only use
2538  * page_trans_huge_mapcount() in the copy-on-write faults where we
2539  * need full accuracy to avoid breaking page pinning, because
2540  * page_trans_huge_mapcount() is slower than page_mapcount().
2541  */
2542 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2543 {
2544         int i, ret, _total_mapcount, mapcount;
2545
2546         /* hugetlbfs shouldn't call it */
2547         VM_BUG_ON_PAGE(PageHuge(page), page);
2548
2549         if (likely(!PageTransCompound(page))) {
2550                 mapcount = atomic_read(&page->_mapcount) + 1;
2551                 if (total_mapcount)
2552                         *total_mapcount = mapcount;
2553                 return mapcount;
2554         }
2555
2556         page = compound_head(page);
2557
2558         _total_mapcount = ret = 0;
2559         for (i = 0; i < HPAGE_PMD_NR; i++) {
2560                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2561                 ret = max(ret, mapcount);
2562                 _total_mapcount += mapcount;
2563         }
2564         if (PageDoubleMap(page)) {
2565                 ret -= 1;
2566                 _total_mapcount -= HPAGE_PMD_NR;
2567         }
2568         mapcount = compound_mapcount(page);
2569         ret += mapcount;
2570         _total_mapcount += mapcount;
2571         if (total_mapcount)
2572                 *total_mapcount = _total_mapcount;
2573         return ret;
2574 }
2575
2576 /* Racy check whether the huge page can be split */
2577 bool can_split_huge_page(struct page *page, int *pextra_pins)
2578 {
2579         int extra_pins;
2580
2581         /* Additional pins from radix tree */
2582         if (PageAnon(page))
2583                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2584         else
2585                 extra_pins = HPAGE_PMD_NR;
2586         if (pextra_pins)
2587                 *pextra_pins = extra_pins;
2588         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2589 }
2590
2591 /*
2592  * This function splits huge page into normal pages. @page can point to any
2593  * subpage of huge page to split. Split doesn't change the position of @page.
2594  *
2595  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2596  * The huge page must be locked.
2597  *
2598  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2599  *
2600  * Both head page and tail pages will inherit mapping, flags, and so on from
2601  * the hugepage.
2602  *
2603  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2604  * they are not mapped.
2605  *
2606  * Returns 0 if the hugepage is split successfully.
2607  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2608  * us.
2609  */
2610 int split_huge_page_to_list(struct page *page, struct list_head *list)
2611 {
2612         struct page *head = compound_head(page);
2613         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2614         struct anon_vma *anon_vma = NULL;
2615         struct address_space *mapping = NULL;
2616         int count, mapcount, extra_pins, ret;
2617         bool mlocked;
2618         unsigned long flags;
2619
2620         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2621         VM_BUG_ON_PAGE(!PageLocked(page), page);
2622         VM_BUG_ON_PAGE(!PageCompound(page), page);
2623
2624         if (PageWriteback(page))
2625                 return -EBUSY;
2626
2627         if (PageAnon(head)) {
2628                 /*
2629                  * The caller does not necessarily hold an mmap_sem that would
2630                  * prevent the anon_vma disappearing so we first we take a
2631                  * reference to it and then lock the anon_vma for write. This
2632                  * is similar to page_lock_anon_vma_read except the write lock
2633                  * is taken to serialise against parallel split or collapse
2634                  * operations.
2635                  */
2636                 anon_vma = page_get_anon_vma(head);
2637                 if (!anon_vma) {
2638                         ret = -EBUSY;
2639                         goto out;
2640                 }
2641                 mapping = NULL;
2642                 anon_vma_lock_write(anon_vma);
2643         } else {
2644                 mapping = head->mapping;
2645
2646                 /* Truncated ? */
2647                 if (!mapping) {
2648                         ret = -EBUSY;
2649                         goto out;
2650                 }
2651
2652                 anon_vma = NULL;
2653                 i_mmap_lock_read(mapping);
2654         }
2655
2656         /*
2657          * Racy check if we can split the page, before freeze_page() will
2658          * split PMDs
2659          */
2660         if (!can_split_huge_page(head, &extra_pins)) {
2661                 ret = -EBUSY;
2662                 goto out_unlock;
2663         }
2664
2665         mlocked = PageMlocked(page);
2666         freeze_page(head);
2667         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2668
2669         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2670         if (mlocked)
2671                 lru_add_drain();
2672
2673         /* prevent PageLRU to go away from under us, and freeze lru stats */
2674         spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2675
2676         if (mapping) {
2677                 void **pslot;
2678
2679                 spin_lock(&mapping->tree_lock);
2680                 pslot = radix_tree_lookup_slot(&mapping->page_tree,
2681                                 page_index(head));
2682                 /*
2683                  * Check if the head page is present in radix tree.
2684                  * We assume all tail are present too, if head is there.
2685                  */
2686                 if (radix_tree_deref_slot_protected(pslot,
2687                                         &mapping->tree_lock) != head)
2688                         goto fail;
2689         }
2690
2691         /* Prevent deferred_split_scan() touching ->_refcount */
2692         spin_lock(&pgdata->split_queue_lock);
2693         count = page_count(head);
2694         mapcount = total_mapcount(head);
2695         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2696                 if (!list_empty(page_deferred_list(head))) {
2697                         pgdata->split_queue_len--;
2698                         list_del(page_deferred_list(head));
2699                 }
2700                 if (mapping)
2701                         __dec_node_page_state(page, NR_SHMEM_THPS);
2702                 spin_unlock(&pgdata->split_queue_lock);
2703                 __split_huge_page(page, list, flags);
2704                 if (PageSwapCache(head)) {
2705                         swp_entry_t entry = { .val = page_private(head) };
2706
2707                         ret = split_swap_cluster(entry);
2708                 } else
2709                         ret = 0;
2710         } else {
2711                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2712                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2713                                         mapcount, count);
2714                         if (PageTail(page))
2715                                 dump_page(head, NULL);
2716                         dump_page(page, "total_mapcount(head) > 0");
2717                         BUG();
2718                 }
2719                 spin_unlock(&pgdata->split_queue_lock);
2720 fail:           if (mapping)
2721                         spin_unlock(&mapping->tree_lock);
2722                 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2723                 unfreeze_page(head);
2724                 ret = -EBUSY;
2725         }
2726
2727 out_unlock:
2728         if (anon_vma) {
2729                 anon_vma_unlock_write(anon_vma);
2730                 put_anon_vma(anon_vma);
2731         }
2732         if (mapping)
2733                 i_mmap_unlock_read(mapping);
2734 out:
2735         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2736         return ret;
2737 }
2738
2739 void free_transhuge_page(struct page *page)
2740 {
2741         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2742         unsigned long flags;
2743
2744         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2745         if (!list_empty(page_deferred_list(page))) {
2746                 pgdata->split_queue_len--;
2747                 list_del(page_deferred_list(page));
2748         }
2749         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2750         free_compound_page(page);
2751 }
2752
2753 void deferred_split_huge_page(struct page *page)
2754 {
2755         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2756         unsigned long flags;
2757
2758         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2759
2760         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2761         if (list_empty(page_deferred_list(page))) {
2762                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2763                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2764                 pgdata->split_queue_len++;
2765         }
2766         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2767 }
2768
2769 static unsigned long deferred_split_count(struct shrinker *shrink,
2770                 struct shrink_control *sc)
2771 {
2772         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2773         return READ_ONCE(pgdata->split_queue_len);
2774 }
2775
2776 static unsigned long deferred_split_scan(struct shrinker *shrink,
2777                 struct shrink_control *sc)
2778 {
2779         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2780         unsigned long flags;
2781         LIST_HEAD(list), *pos, *next;
2782         struct page *page;
2783         int split = 0;
2784
2785         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2786         /* Take pin on all head pages to avoid freeing them under us */
2787         list_for_each_safe(pos, next, &pgdata->split_queue) {
2788                 page = list_entry((void *)pos, struct page, mapping);
2789                 page = compound_head(page);
2790                 if (get_page_unless_zero(page)) {
2791                         list_move(page_deferred_list(page), &list);
2792                 } else {
2793                         /* We lost race with put_compound_page() */
2794                         list_del_init(page_deferred_list(page));
2795                         pgdata->split_queue_len--;
2796                 }
2797                 if (!--sc->nr_to_scan)
2798                         break;
2799         }
2800         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2801
2802         list_for_each_safe(pos, next, &list) {
2803                 page = list_entry((void *)pos, struct page, mapping);
2804                 lock_page(page);
2805                 /* split_huge_page() removes page from list on success */
2806                 if (!split_huge_page(page))
2807                         split++;
2808                 unlock_page(page);
2809                 put_page(page);
2810         }
2811
2812         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2813         list_splice_tail(&list, &pgdata->split_queue);
2814         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2815
2816         /*
2817          * Stop shrinker if we didn't split any page, but the queue is empty.
2818          * This can happen if pages were freed under us.
2819          */
2820         if (!split && list_empty(&pgdata->split_queue))
2821                 return SHRINK_STOP;
2822         return split;
2823 }
2824
2825 static struct shrinker deferred_split_shrinker = {
2826         .count_objects = deferred_split_count,
2827         .scan_objects = deferred_split_scan,
2828         .seeks = DEFAULT_SEEKS,
2829         .flags = SHRINKER_NUMA_AWARE,
2830 };
2831
2832 #ifdef CONFIG_DEBUG_FS
2833 static int split_huge_pages_set(void *data, u64 val)
2834 {
2835         struct zone *zone;
2836         struct page *page;
2837         unsigned long pfn, max_zone_pfn;
2838         unsigned long total = 0, split = 0;
2839
2840         if (val != 1)
2841                 return -EINVAL;
2842
2843         for_each_populated_zone(zone) {
2844                 max_zone_pfn = zone_end_pfn(zone);
2845                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2846                         if (!pfn_valid(pfn))
2847                                 continue;
2848
2849                         page = pfn_to_page(pfn);
2850                         if (!get_page_unless_zero(page))
2851                                 continue;
2852
2853                         if (zone != page_zone(page))
2854                                 goto next;
2855
2856                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2857                                 goto next;
2858
2859                         total++;
2860                         lock_page(page);
2861                         if (!split_huge_page(page))
2862                                 split++;
2863                         unlock_page(page);
2864 next:
2865                         put_page(page);
2866                 }
2867         }
2868
2869         pr_info("%lu of %lu THP split\n", split, total);
2870
2871         return 0;
2872 }
2873 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2874                 "%llu\n");
2875
2876 static int __init split_huge_pages_debugfs(void)
2877 {
2878         void *ret;
2879
2880         ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2881                         &split_huge_pages_fops);
2882         if (!ret)
2883                 pr_warn("Failed to create split_huge_pages in debugfs");
2884         return 0;
2885 }
2886 late_initcall(split_huge_pages_debugfs);
2887 #endif
2888
2889 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2890 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2891                 struct page *page)
2892 {
2893         struct vm_area_struct *vma = pvmw->vma;
2894         struct mm_struct *mm = vma->vm_mm;
2895         unsigned long address = pvmw->address;
2896         pmd_t pmdval;
2897         swp_entry_t entry;
2898         pmd_t pmdswp;
2899
2900         if (!(pvmw->pmd && !pvmw->pte))
2901                 return;
2902
2903         mmu_notifier_invalidate_range_start(mm, address,
2904                         address + HPAGE_PMD_SIZE);
2905
2906         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2907         pmdval = *pvmw->pmd;
2908         pmdp_invalidate(vma, address, pvmw->pmd);
2909         if (pmd_dirty(pmdval))
2910                 set_page_dirty(page);
2911         entry = make_migration_entry(page, pmd_write(pmdval));
2912         pmdswp = swp_entry_to_pmd(entry);
2913         if (pmd_soft_dirty(pmdval))
2914                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2915         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2916         page_remove_rmap(page, true);
2917         put_page(page);
2918
2919         mmu_notifier_invalidate_range_end(mm, address,
2920                         address + HPAGE_PMD_SIZE);
2921 }
2922
2923 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2924 {
2925         struct vm_area_struct *vma = pvmw->vma;
2926         struct mm_struct *mm = vma->vm_mm;
2927         unsigned long address = pvmw->address;
2928         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2929         pmd_t pmde;
2930         swp_entry_t entry;
2931
2932         if (!(pvmw->pmd && !pvmw->pte))
2933                 return;
2934
2935         entry = pmd_to_swp_entry(*pvmw->pmd);
2936         get_page(new);
2937         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2938         if (pmd_swp_soft_dirty(*pvmw->pmd))
2939                 pmde = pmd_mksoft_dirty(pmde);
2940         if (is_write_migration_entry(entry))
2941                 pmde = maybe_pmd_mkwrite(pmde, vma);
2942
2943         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2944         page_add_anon_rmap(new, vma, mmun_start, true);
2945         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
2946         if (vma->vm_flags & VM_LOCKED)
2947                 mlock_vma_page(new);
2948         update_mmu_cache_pmd(vma, address, pvmw->pmd);
2949 }
2950 #endif