linux/mm/huge_memory.c
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   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 */
  49unsigned 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
  60static struct shrinker deferred_split_shrinker;
  61
  62static atomic_t huge_zero_refcount;
  63struct page *huge_zero_page __read_mostly;
  64
  65static struct page *get_huge_zero_page(void)
  66{
  67        struct page *zero_page;
  68retry:
  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
  92static 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
 101struct 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
 115void 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
 121static 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
 128static 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
 141static 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
 148static 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
 159static 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}
 187static struct kobj_attribute enabled_attr =
 188        __ATTR(enabled, 0644, enabled_show, enabled_store);
 189
 190ssize_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
 198ssize_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
 220static 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
 234static 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}
 273static struct kobj_attribute defrag_attr =
 274        __ATTR(defrag, 0644, defrag_show, defrag_store);
 275
 276static 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}
 282static 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}
 288static struct kobj_attribute use_zero_page_attr =
 289        __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 290
 291static 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}
 296static struct kobj_attribute hpage_pmd_size_attr =
 297        __ATTR_RO(hpage_pmd_size);
 298
 299#ifdef CONFIG_DEBUG_VM
 300static 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}
 306static 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}
 313static struct kobj_attribute debug_cow_attr =
 314        __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 315#endif /* CONFIG_DEBUG_VM */
 316
 317static 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
 331static const struct attribute_group hugepage_attr_group = {
 332        .attrs = hugepage_attr,
 333};
 334
 335static 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
 359remove_hp_group:
 360        sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 361delete_obj:
 362        kobject_put(*hugepage_kobj);
 363        return err;
 364}
 365
 366static 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
 373static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 374{
 375        return 0;
 376}
 377
 378static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 379{
 380}
 381#endif /* CONFIG_SYSFS */
 382
 383static 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;
 433err_khugepaged:
 434        unregister_shrinker(&deferred_split_shrinker);
 435err_split_shrinker:
 436        unregister_shrinker(&huge_zero_page_shrinker);
 437err_hzp_shrinker:
 438        khugepaged_destroy();
 439err_slab:
 440        hugepage_exit_sysfs(hugepage_kobj);
 441err_sysfs:
 442        return err;
 443}
 444subsys_initcall(hugepage_init);
 445
 446static 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        }
 470out:
 471        if (!ret)
 472                pr_warn("transparent_hugepage= cannot parse, ignored\n");
 473        return ret;
 474}
 475__setup("transparent_hugepage=", setup_transparent_hugepage);
 476
 477pmd_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
 484static inline struct list_head *page_deferred_list(struct page *page)
 485{
 486        /* ->lru in the tail pages is occupied by compound_head. */
 487        return &page[2].deferred_list;
 488}
 489
 490void prep_transhuge_page(struct page *page)
 491{
 492        /*
 493         * we use page->mapping and page->indexlru in second tail page
 494         * as list_head: assuming THP order >= 2
 495         */
 496
 497        INIT_LIST_HEAD(page_deferred_list(page));
 498        set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 499}
 500
 501unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
 502                loff_t off, unsigned long flags, unsigned long size)
 503{
 504        unsigned long addr;
 505        loff_t off_end = off + len;
 506        loff_t off_align = round_up(off, size);
 507        unsigned long len_pad;
 508
 509        if (off_end <= off_align || (off_end - off_align) < size)
 510                return 0;
 511
 512        len_pad = len + size;
 513        if (len_pad < len || (off + len_pad) < off)
 514                return 0;
 515
 516        addr = current->mm->get_unmapped_area(filp, 0, len_pad,
 517                                              off >> PAGE_SHIFT, flags);
 518        if (IS_ERR_VALUE(addr))
 519                return 0;
 520
 521        addr += (off - addr) & (size - 1);
 522        return addr;
 523}
 524
 525unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 526                unsigned long len, unsigned long pgoff, unsigned long flags)
 527{
 528        loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 529
 530        if (addr)
 531                goto out;
 532        if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
 533                goto out;
 534
 535        addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
 536        if (addr)
 537                return addr;
 538
 539 out:
 540        return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 541}
 542EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 543
 544static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
 545                        struct page *page, gfp_t gfp)
 546{
 547        struct vm_area_struct *vma = vmf->vma;
 548        struct mem_cgroup *memcg;
 549        pgtable_t pgtable;
 550        unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 551        vm_fault_t ret = 0;
 552
 553        VM_BUG_ON_PAGE(!PageCompound(page), page);
 554
 555        if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
 556                put_page(page);
 557                count_vm_event(THP_FAULT_FALLBACK);
 558                return VM_FAULT_FALLBACK;
 559        }
 560
 561        pgtable = pte_alloc_one(vma->vm_mm, haddr);
 562        if (unlikely(!pgtable)) {
 563                ret = VM_FAULT_OOM;
 564                goto release;
 565        }
 566
 567        clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
 568        /*
 569         * The memory barrier inside __SetPageUptodate makes sure that
 570         * clear_huge_page writes become visible before the set_pmd_at()
 571         * write.
 572         */
 573        __SetPageUptodate(page);
 574
 575        vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 576        if (unlikely(!pmd_none(*vmf->pmd))) {
 577                goto unlock_release;
 578        } else {
 579                pmd_t entry;
 580
 581                ret = check_stable_address_space(vma->vm_mm);
 582                if (ret)
 583                        goto unlock_release;
 584
 585                /* Deliver the page fault to userland */
 586                if (userfaultfd_missing(vma)) {
 587                        vm_fault_t ret2;
 588
 589                        spin_unlock(vmf->ptl);
 590                        mem_cgroup_cancel_charge(page, memcg, true);
 591                        put_page(page);
 592                        pte_free(vma->vm_mm, pgtable);
 593                        ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
 594                        VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
 595                        return ret2;
 596                }
 597
 598                entry = mk_huge_pmd(page, vma->vm_page_prot);
 599                entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 600                page_add_new_anon_rmap(page, vma, haddr, true);
 601                mem_cgroup_commit_charge(page, memcg, false, true);
 602                lru_cache_add_active_or_unevictable(page, vma);
 603                pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 604                set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 605                add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 606                mm_inc_nr_ptes(vma->vm_mm);
 607                spin_unlock(vmf->ptl);
 608                count_vm_event(THP_FAULT_ALLOC);
 609        }
 610
 611        return 0;
 612unlock_release:
 613        spin_unlock(vmf->ptl);
 614release:
 615        if (pgtable)
 616                pte_free(vma->vm_mm, pgtable);
 617        mem_cgroup_cancel_charge(page, memcg, true);
 618        put_page(page);
 619        return ret;
 620
 621}
 622
 623/*
 624 * always: directly stall for all thp allocations
 625 * defer: wake kswapd and fail if not immediately available
 626 * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
 627 *                fail if not immediately available
 628 * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
 629 *          available
 630 * never: never stall for any thp allocation
 631 */
 632static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
 633{
 634        const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
 635
 636        /* Always do synchronous compaction */
 637        if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 638                return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
 639
 640        /* Kick kcompactd and fail quickly */
 641        if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 642                return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
 643
 644        /* Synchronous compaction if madvised, otherwise kick kcompactd */
 645        if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 646                return GFP_TRANSHUGE_LIGHT |
 647                        (vma_madvised ? __GFP_DIRECT_RECLAIM :
 648                                        __GFP_KSWAPD_RECLAIM);
 649
 650        /* Only do synchronous compaction if madvised */
 651        if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 652                return GFP_TRANSHUGE_LIGHT |
 653                       (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
 654
 655        return GFP_TRANSHUGE_LIGHT;
 656}
 657
 658/* Caller must hold page table lock. */
 659static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 660                struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 661                struct page *zero_page)
 662{
 663        pmd_t entry;
 664        if (!pmd_none(*pmd))
 665                return false;
 666        entry = mk_pmd(zero_page, vma->vm_page_prot);
 667        entry = pmd_mkhuge(entry);
 668        if (pgtable)
 669                pgtable_trans_huge_deposit(mm, pmd, pgtable);
 670        set_pmd_at(mm, haddr, pmd, entry);
 671        mm_inc_nr_ptes(mm);
 672        return true;
 673}
 674
 675vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 676{
 677        struct vm_area_struct *vma = vmf->vma;
 678        gfp_t gfp;
 679        struct page *page;
 680        unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 681
 682        if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
 683                return VM_FAULT_FALLBACK;
 684        if (unlikely(anon_vma_prepare(vma)))
 685                return VM_FAULT_OOM;
 686        if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 687                return VM_FAULT_OOM;
 688        if (!(vmf->flags & FAULT_FLAG_WRITE) &&
 689                        !mm_forbids_zeropage(vma->vm_mm) &&
 690                        transparent_hugepage_use_zero_page()) {
 691                pgtable_t pgtable;
 692                struct page *zero_page;
 693                bool set;
 694                vm_fault_t ret;
 695                pgtable = pte_alloc_one(vma->vm_mm, haddr);
 696                if (unlikely(!pgtable))
 697                        return VM_FAULT_OOM;
 698                zero_page = mm_get_huge_zero_page(vma->vm_mm);
 699                if (unlikely(!zero_page)) {
 700                        pte_free(vma->vm_mm, pgtable);
 701                        count_vm_event(THP_FAULT_FALLBACK);
 702                        return VM_FAULT_FALLBACK;
 703                }
 704                vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 705                ret = 0;
 706                set = false;
 707                if (pmd_none(*vmf->pmd)) {
 708                        ret = check_stable_address_space(vma->vm_mm);
 709                        if (ret) {
 710                                spin_unlock(vmf->ptl);
 711                        } else if (userfaultfd_missing(vma)) {
 712                                spin_unlock(vmf->ptl);
 713                                ret = handle_userfault(vmf, VM_UFFD_MISSING);
 714                                VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 715                        } else {
 716                                set_huge_zero_page(pgtable, vma->vm_mm, vma,
 717                                                   haddr, vmf->pmd, zero_page);
 718                                spin_unlock(vmf->ptl);
 719                                set = true;
 720                        }
 721                } else
 722                        spin_unlock(vmf->ptl);
 723                if (!set)
 724                        pte_free(vma->vm_mm, pgtable);
 725                return ret;
 726        }
 727        gfp = alloc_hugepage_direct_gfpmask(vma);
 728        page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 729        if (unlikely(!page)) {
 730                count_vm_event(THP_FAULT_FALLBACK);
 731                return VM_FAULT_FALLBACK;
 732        }
 733        prep_transhuge_page(page);
 734        return __do_huge_pmd_anonymous_page(vmf, page, gfp);
 735}
 736
 737static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 738                pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
 739                pgtable_t pgtable)
 740{
 741        struct mm_struct *mm = vma->vm_mm;
 742        pmd_t entry;
 743        spinlock_t *ptl;
 744
 745        ptl = pmd_lock(mm, pmd);
 746        entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 747        if (pfn_t_devmap(pfn))
 748                entry = pmd_mkdevmap(entry);
 749        if (write) {
 750                entry = pmd_mkyoung(pmd_mkdirty(entry));
 751                entry = maybe_pmd_mkwrite(entry, vma);
 752        }
 753
 754        if (pgtable) {
 755                pgtable_trans_huge_deposit(mm, pmd, pgtable);
 756                mm_inc_nr_ptes(mm);
 757        }
 758
 759        set_pmd_at(mm, addr, pmd, entry);
 760        update_mmu_cache_pmd(vma, addr, pmd);
 761        spin_unlock(ptl);
 762}
 763
 764vm_fault_t vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 765                        pmd_t *pmd, pfn_t pfn, bool write)
 766{
 767        pgprot_t pgprot = vma->vm_page_prot;
 768        pgtable_t pgtable = NULL;
 769        /*
 770         * If we had pmd_special, we could avoid all these restrictions,
 771         * but we need to be consistent with PTEs and architectures that
 772         * can't support a 'special' bit.
 773         */
 774        BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 775                        !pfn_t_devmap(pfn));
 776        BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 777                                                (VM_PFNMAP|VM_MIXEDMAP));
 778        BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 779
 780        if (addr < vma->vm_start || addr >= vma->vm_end)
 781                return VM_FAULT_SIGBUS;
 782
 783        if (arch_needs_pgtable_deposit()) {
 784                pgtable = pte_alloc_one(vma->vm_mm, addr);
 785                if (!pgtable)
 786                        return VM_FAULT_OOM;
 787        }
 788
 789        track_pfn_insert(vma, &pgprot, pfn);
 790
 791        insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable);
 792        return VM_FAULT_NOPAGE;
 793}
 794EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
 795
 796#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 797static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 798{
 799        if (likely(vma->vm_flags & VM_WRITE))
 800                pud = pud_mkwrite(pud);
 801        return pud;
 802}
 803
 804static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 805                pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 806{
 807        struct mm_struct *mm = vma->vm_mm;
 808        pud_t entry;
 809        spinlock_t *ptl;
 810
 811        ptl = pud_lock(mm, pud);
 812        entry = pud_mkhuge(pfn_t_pud(pfn, prot));
 813        if (pfn_t_devmap(pfn))
 814                entry = pud_mkdevmap(entry);
 815        if (write) {
 816                entry = pud_mkyoung(pud_mkdirty(entry));
 817                entry = maybe_pud_mkwrite(entry, vma);
 818        }
 819        set_pud_at(mm, addr, pud, entry);
 820        update_mmu_cache_pud(vma, addr, pud);
 821        spin_unlock(ptl);
 822}
 823
 824vm_fault_t vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 825                        pud_t *pud, pfn_t pfn, bool write)
 826{
 827        pgprot_t pgprot = vma->vm_page_prot;
 828        /*
 829         * If we had pud_special, we could avoid all these restrictions,
 830         * but we need to be consistent with PTEs and architectures that
 831         * can't support a 'special' bit.
 832         */
 833        BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 834                        !pfn_t_devmap(pfn));
 835        BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 836                                                (VM_PFNMAP|VM_MIXEDMAP));
 837        BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 838
 839        if (addr < vma->vm_start || addr >= vma->vm_end)
 840                return VM_FAULT_SIGBUS;
 841
 842        track_pfn_insert(vma, &pgprot, pfn);
 843
 844        insert_pfn_pud(vma, addr, pud, pfn, pgprot, write);
 845        return VM_FAULT_NOPAGE;
 846}
 847EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
 848#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 849
 850static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
 851                pmd_t *pmd, int flags)
 852{
 853        pmd_t _pmd;
 854
 855        _pmd = pmd_mkyoung(*pmd);
 856        if (flags & FOLL_WRITE)
 857                _pmd = pmd_mkdirty(_pmd);
 858        if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 859                                pmd, _pmd, flags & FOLL_WRITE))
 860                update_mmu_cache_pmd(vma, addr, pmd);
 861}
 862
 863struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 864                pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
 865{
 866        unsigned long pfn = pmd_pfn(*pmd);
 867        struct mm_struct *mm = vma->vm_mm;
 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, flags);
 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, *pgmap);
 898        if (!*pgmap)
 899                return ERR_PTR(-EFAULT);
 900        page = pfn_to_page(pfn);
 901        get_page(page);
 902
 903        return page;
 904}
 905
 906int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 907                  pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 908                  struct vm_area_struct *vma)
 909{
 910        spinlock_t *dst_ptl, *src_ptl;
 911        struct page *src_page;
 912        pmd_t pmd;
 913        pgtable_t pgtable = NULL;
 914        int ret = -ENOMEM;
 915
 916        /* Skip if can be re-fill on fault */
 917        if (!vma_is_anonymous(vma))
 918                return 0;
 919
 920        pgtable = pte_alloc_one(dst_mm, addr);
 921        if (unlikely(!pgtable))
 922                goto out;
 923
 924        dst_ptl = pmd_lock(dst_mm, dst_pmd);
 925        src_ptl = pmd_lockptr(src_mm, src_pmd);
 926        spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 927
 928        ret = -EAGAIN;
 929        pmd = *src_pmd;
 930
 931#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
 932        if (unlikely(is_swap_pmd(pmd))) {
 933                swp_entry_t entry = pmd_to_swp_entry(pmd);
 934
 935                VM_BUG_ON(!is_pmd_migration_entry(pmd));
 936                if (is_write_migration_entry(entry)) {
 937                        make_migration_entry_read(&entry);
 938                        pmd = swp_entry_to_pmd(entry);
 939                        if (pmd_swp_soft_dirty(*src_pmd))
 940                                pmd = pmd_swp_mksoft_dirty(pmd);
 941                        set_pmd_at(src_mm, addr, src_pmd, pmd);
 942                }
 943                add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 944                mm_inc_nr_ptes(dst_mm);
 945                pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 946                set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 947                ret = 0;
 948                goto out_unlock;
 949        }
 950#endif
 951
 952        if (unlikely(!pmd_trans_huge(pmd))) {
 953                pte_free(dst_mm, pgtable);
 954                goto out_unlock;
 955        }
 956        /*
 957         * When page table lock is held, the huge zero pmd should not be
 958         * under splitting since we don't split the page itself, only pmd to
 959         * a page table.
 960         */
 961        if (is_huge_zero_pmd(pmd)) {
 962                struct page *zero_page;
 963                /*
 964                 * get_huge_zero_page() will never allocate a new page here,
 965                 * since we already have a zero page to copy. It just takes a
 966                 * reference.
 967                 */
 968                zero_page = mm_get_huge_zero_page(dst_mm);
 969                set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
 970                                zero_page);
 971                ret = 0;
 972                goto out_unlock;
 973        }
 974
 975        src_page = pmd_page(pmd);
 976        VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
 977        get_page(src_page);
 978        page_dup_rmap(src_page, true);
 979        add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 980        mm_inc_nr_ptes(dst_mm);
 981        pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 982
 983        pmdp_set_wrprotect(src_mm, addr, src_pmd);
 984        pmd = pmd_mkold(pmd_wrprotect(pmd));
 985        set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 986
 987        ret = 0;
 988out_unlock:
 989        spin_unlock(src_ptl);
 990        spin_unlock(dst_ptl);
 991out:
 992        return ret;
 993}
 994
 995#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 996static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
 997                pud_t *pud, int flags)
 998{
 999        pud_t _pud;
1000
1001        _pud = pud_mkyoung(*pud);
1002        if (flags & FOLL_WRITE)
1003                _pud = pud_mkdirty(_pud);
1004        if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1005                                pud, _pud, flags & FOLL_WRITE))
1006                update_mmu_cache_pud(vma, addr, pud);
1007}
1008
1009struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1010                pud_t *pud, int flags, struct dev_pagemap **pgmap)
1011{
1012        unsigned long pfn = pud_pfn(*pud);
1013        struct mm_struct *mm = vma->vm_mm;
1014        struct page *page;
1015
1016        assert_spin_locked(pud_lockptr(mm, pud));
1017
1018        if (flags & FOLL_WRITE && !pud_write(*pud))
1019                return NULL;
1020
1021        if (pud_present(*pud) && pud_devmap(*pud))
1022                /* pass */;
1023        else
1024                return NULL;
1025
1026        if (flags & FOLL_TOUCH)
1027                touch_pud(vma, addr, pud, flags);
1028
1029        /*
1030         * device mapped pages can only be returned if the
1031         * caller will manage the page reference count.
1032         */
1033        if (!(flags & FOLL_GET))
1034                return ERR_PTR(-EEXIST);
1035
1036        pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1037        *pgmap = get_dev_pagemap(pfn, *pgmap);
1038        if (!*pgmap)
1039                return ERR_PTR(-EFAULT);
1040        page = pfn_to_page(pfn);
1041        get_page(page);
1042
1043        return page;
1044}
1045
1046int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1047                  pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1048                  struct vm_area_struct *vma)
1049{
1050        spinlock_t *dst_ptl, *src_ptl;
1051        pud_t pud;
1052        int ret;
1053
1054        dst_ptl = pud_lock(dst_mm, dst_pud);
1055        src_ptl = pud_lockptr(src_mm, src_pud);
1056        spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1057
1058        ret = -EAGAIN;
1059        pud = *src_pud;
1060        if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1061                goto out_unlock;
1062
1063        /*
1064         * When page table lock is held, the huge zero pud should not be
1065         * under splitting since we don't split the page itself, only pud to
1066         * a page table.
1067         */
1068        if (is_huge_zero_pud(pud)) {
1069                /* No huge zero pud yet */
1070        }
1071
1072        pudp_set_wrprotect(src_mm, addr, src_pud);
1073        pud = pud_mkold(pud_wrprotect(pud));
1074        set_pud_at(dst_mm, addr, dst_pud, pud);
1075
1076        ret = 0;
1077out_unlock:
1078        spin_unlock(src_ptl);
1079        spin_unlock(dst_ptl);
1080        return ret;
1081}
1082
1083void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1084{
1085        pud_t entry;
1086        unsigned long haddr;
1087        bool write = vmf->flags & FAULT_FLAG_WRITE;
1088
1089        vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1090        if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1091                goto unlock;
1092
1093        entry = pud_mkyoung(orig_pud);
1094        if (write)
1095                entry = pud_mkdirty(entry);
1096        haddr = vmf->address & HPAGE_PUD_MASK;
1097        if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1098                update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1099
1100unlock:
1101        spin_unlock(vmf->ptl);
1102}
1103#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1104
1105void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1106{
1107        pmd_t entry;
1108        unsigned long haddr;
1109        bool write = vmf->flags & FAULT_FLAG_WRITE;
1110
1111        vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1112        if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1113                goto unlock;
1114
1115        entry = pmd_mkyoung(orig_pmd);
1116        if (write)
1117                entry = pmd_mkdirty(entry);
1118        haddr = vmf->address & HPAGE_PMD_MASK;
1119        if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1120                update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1121
1122unlock:
1123        spin_unlock(vmf->ptl);
1124}
1125
1126static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1127                        pmd_t orig_pmd, struct page *page)
1128{
1129        struct vm_area_struct *vma = vmf->vma;
1130        unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1131        struct mem_cgroup *memcg;
1132        pgtable_t pgtable;
1133        pmd_t _pmd;
1134        int i;
1135        vm_fault_t ret = 0;
1136        struct page **pages;
1137        unsigned long mmun_start;       /* For mmu_notifiers */
1138        unsigned long mmun_end;         /* For mmu_notifiers */
1139
1140        pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1141                              GFP_KERNEL);
1142        if (unlikely(!pages)) {
1143                ret |= VM_FAULT_OOM;
1144                goto out;
1145        }
1146
1147        for (i = 0; i < HPAGE_PMD_NR; i++) {
1148                pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1149                                               vmf->address, page_to_nid(page));
1150                if (unlikely(!pages[i] ||
1151                             mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1152                                     GFP_KERNEL, &memcg, false))) {
1153                        if (pages[i])
1154                                put_page(pages[i]);
1155                        while (--i >= 0) {
1156                                memcg = (void *)page_private(pages[i]);
1157                                set_page_private(pages[i], 0);
1158                                mem_cgroup_cancel_charge(pages[i], memcg,
1159                                                false);
1160                                put_page(pages[i]);
1161                        }
1162                        kfree(pages);
1163                        ret |= VM_FAULT_OOM;
1164                        goto out;
1165                }
1166                set_page_private(pages[i], (unsigned long)memcg);
1167        }
1168
1169        for (i = 0; i < HPAGE_PMD_NR; i++) {
1170                copy_user_highpage(pages[i], page + i,
1171                                   haddr + PAGE_SIZE * i, vma);
1172                __SetPageUptodate(pages[i]);
1173                cond_resched();
1174        }
1175
1176        mmun_start = haddr;
1177        mmun_end   = haddr + HPAGE_PMD_SIZE;
1178        mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1179
1180        vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1181        if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1182                goto out_free_pages;
1183        VM_BUG_ON_PAGE(!PageHead(page), page);
1184
1185        /*
1186         * Leave pmd empty until pte is filled note we must notify here as
1187         * concurrent CPU thread might write to new page before the call to
1188         * mmu_notifier_invalidate_range_end() happens which can lead to a
1189         * device seeing memory write in different order than CPU.
1190         *
1191         * See Documentation/vm/mmu_notifier.rst
1192         */
1193        pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1194
1195        pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1196        pmd_populate(vma->vm_mm, &_pmd, pgtable);
1197
1198        for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1199                pte_t entry;
1200                entry = mk_pte(pages[i], vma->vm_page_prot);
1201                entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1202                memcg = (void *)page_private(pages[i]);
1203                set_page_private(pages[i], 0);
1204                page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1205                mem_cgroup_commit_charge(pages[i], memcg, false, false);
1206                lru_cache_add_active_or_unevictable(pages[i], vma);
1207                vmf->pte = pte_offset_map(&_pmd, haddr);
1208                VM_BUG_ON(!pte_none(*vmf->pte));
1209                set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1210                pte_unmap(vmf->pte);
1211        }
1212        kfree(pages);
1213
1214        smp_wmb(); /* make pte visible before pmd */
1215        pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1216        page_remove_rmap(page, true);
1217        spin_unlock(vmf->ptl);
1218
1219        /*
1220         * No need to double call mmu_notifier->invalidate_range() callback as
1221         * the above pmdp_huge_clear_flush_notify() did already call it.
1222         */
1223        mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1224                                                mmun_end);
1225
1226        ret |= VM_FAULT_WRITE;
1227        put_page(page);
1228
1229out:
1230        return ret;
1231
1232out_free_pages:
1233        spin_unlock(vmf->ptl);
1234        mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1235        for (i = 0; i < HPAGE_PMD_NR; i++) {
1236                memcg = (void *)page_private(pages[i]);
1237                set_page_private(pages[i], 0);
1238                mem_cgroup_cancel_charge(pages[i], memcg, false);
1239                put_page(pages[i]);
1240        }
1241        kfree(pages);
1242        goto out;
1243}
1244
1245vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1246{
1247        struct vm_area_struct *vma = vmf->vma;
1248        struct page *page = NULL, *new_page;
1249        struct mem_cgroup *memcg;
1250        unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1251        unsigned long mmun_start;       /* For mmu_notifiers */
1252        unsigned long mmun_end;         /* For mmu_notifiers */
1253        gfp_t huge_gfp;                 /* for allocation and charge */
1254        vm_fault_t ret = 0;
1255
1256        vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1257        VM_BUG_ON_VMA(!vma->anon_vma, vma);
1258        if (is_huge_zero_pmd(orig_pmd))
1259                goto alloc;
1260        spin_lock(vmf->ptl);
1261        if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1262                goto out_unlock;
1263
1264        page = pmd_page(orig_pmd);
1265        VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1266        /*
1267         * We can only reuse the page if nobody else maps the huge page or it's
1268         * part.
1269         */
1270        if (!trylock_page(page)) {
1271                get_page(page);
1272                spin_unlock(vmf->ptl);
1273                lock_page(page);
1274                spin_lock(vmf->ptl);
1275                if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1276                        unlock_page(page);
1277                        put_page(page);
1278                        goto out_unlock;
1279                }
1280                put_page(page);
1281        }
1282        if (reuse_swap_page(page, NULL)) {
1283                pmd_t entry;
1284                entry = pmd_mkyoung(orig_pmd);
1285                entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1286                if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1287                        update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1288                ret |= VM_FAULT_WRITE;
1289                unlock_page(page);
1290                goto out_unlock;
1291        }
1292        unlock_page(page);
1293        get_page(page);
1294        spin_unlock(vmf->ptl);
1295alloc:
1296        if (transparent_hugepage_enabled(vma) &&
1297            !transparent_hugepage_debug_cow()) {
1298                huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1299                new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1300        } else
1301                new_page = NULL;
1302
1303        if (likely(new_page)) {
1304                prep_transhuge_page(new_page);
1305        } else {
1306                if (!page) {
1307                        split_huge_pmd(vma, vmf->pmd, vmf->address);
1308                        ret |= VM_FAULT_FALLBACK;
1309                } else {
1310                        ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1311                        if (ret & VM_FAULT_OOM) {
1312                                split_huge_pmd(vma, vmf->pmd, vmf->address);
1313                                ret |= VM_FAULT_FALLBACK;
1314                        }
1315                        put_page(page);
1316                }
1317                count_vm_event(THP_FAULT_FALLBACK);
1318                goto out;
1319        }
1320
1321        if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1322                                        huge_gfp, &memcg, true))) {
1323                put_page(new_page);
1324                split_huge_pmd(vma, vmf->pmd, vmf->address);
1325                if (page)
1326                        put_page(page);
1327                ret |= VM_FAULT_FALLBACK;
1328                count_vm_event(THP_FAULT_FALLBACK);
1329                goto out;
1330        }
1331
1332        count_vm_event(THP_FAULT_ALLOC);
1333
1334        if (!page)
1335                clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1336        else
1337                copy_user_huge_page(new_page, page, vmf->address,
1338                                    vma, HPAGE_PMD_NR);
1339        __SetPageUptodate(new_page);
1340
1341        mmun_start = haddr;
1342        mmun_end   = haddr + HPAGE_PMD_SIZE;
1343        mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1344
1345        spin_lock(vmf->ptl);
1346        if (page)
1347                put_page(page);
1348        if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1349                spin_unlock(vmf->ptl);
1350                mem_cgroup_cancel_charge(new_page, memcg, true);
1351                put_page(new_page);
1352                goto out_mn;
1353        } else {
1354                pmd_t entry;
1355                entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1356                entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1357                pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1358                page_add_new_anon_rmap(new_page, vma, haddr, true);
1359                mem_cgroup_commit_charge(new_page, memcg, false, true);
1360                lru_cache_add_active_or_unevictable(new_page, vma);
1361                set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1362                update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1363                if (!page) {
1364                        add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1365                } else {
1366                        VM_BUG_ON_PAGE(!PageHead(page), page);
1367                        page_remove_rmap(page, true);
1368                        put_page(page);
1369                }
1370                ret |= VM_FAULT_WRITE;
1371        }
1372        spin_unlock(vmf->ptl);
1373out_mn:
1374        /*
1375         * No need to double call mmu_notifier->invalidate_range() callback as
1376         * the above pmdp_huge_clear_flush_notify() did already call it.
1377         */
1378        mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1379                                               mmun_end);
1380out:
1381        return ret;
1382out_unlock:
1383        spin_unlock(vmf->ptl);
1384        return ret;
1385}
1386
1387/*
1388 * FOLL_FORCE can write to even unwritable pmd's, but only
1389 * after we've gone through a COW cycle and they are dirty.
1390 */
1391static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1392{
1393        return pmd_write(pmd) ||
1394               ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1395}
1396
1397struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1398                                   unsigned long addr,
1399                                   pmd_t *pmd,
1400                                   unsigned int flags)
1401{
1402        struct mm_struct *mm = vma->vm_mm;
1403        struct page *page = NULL;
1404
1405        assert_spin_locked(pmd_lockptr(mm, pmd));
1406
1407        if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1408                goto out;
1409
1410        /* Avoid dumping huge zero page */
1411        if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1412                return ERR_PTR(-EFAULT);
1413
1414        /* Full NUMA hinting faults to serialise migration in fault paths */
1415        if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1416                goto out;
1417
1418        page = pmd_page(*pmd);
1419        VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1420        if (flags & FOLL_TOUCH)
1421                touch_pmd(vma, addr, pmd, flags);
1422        if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1423                /*
1424                 * We don't mlock() pte-mapped THPs. This way we can avoid
1425                 * leaking mlocked pages into non-VM_LOCKED VMAs.
1426                 *
1427                 * For anon THP:
1428                 *
1429                 * In most cases the pmd is the only mapping of the page as we
1430                 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1431                 * writable private mappings in populate_vma_page_range().
1432                 *
1433                 * The only scenario when we have the page shared here is if we
1434                 * mlocking read-only mapping shared over fork(). We skip
1435                 * mlocking such pages.
1436                 *
1437                 * For file THP:
1438                 *
1439                 * We can expect PageDoubleMap() to be stable under page lock:
1440                 * for file pages we set it in page_add_file_rmap(), which
1441                 * requires page to be locked.
1442                 */
1443
1444                if (PageAnon(page) && compound_mapcount(page) != 1)
1445                        goto skip_mlock;
1446                if (PageDoubleMap(page) || !page->mapping)
1447                        goto skip_mlock;
1448                if (!trylock_page(page))
1449                        goto skip_mlock;
1450                lru_add_drain();
1451                if (page->mapping && !PageDoubleMap(page))
1452                        mlock_vma_page(page);
1453                unlock_page(page);
1454        }
1455skip_mlock:
1456        page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1457        VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1458        if (flags & FOLL_GET)
1459                get_page(page);
1460
1461out:
1462        return page;
1463}
1464
1465/* NUMA hinting page fault entry point for trans huge pmds */
1466vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1467{
1468        struct vm_area_struct *vma = vmf->vma;
1469        struct anon_vma *anon_vma = NULL;
1470        struct page *page;
1471        unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1472        int page_nid = -1, this_nid = numa_node_id();
1473        int target_nid, last_cpupid = -1;
1474        bool page_locked;
1475        bool migrated = false;
1476        bool was_writable;
1477        int flags = 0;
1478
1479        vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1480        if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1481                goto out_unlock;
1482
1483        /*
1484         * If there are potential migrations, wait for completion and retry
1485         * without disrupting NUMA hinting information. Do not relock and
1486         * check_same as the page may no longer be mapped.
1487         */
1488        if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1489                page = pmd_page(*vmf->pmd);
1490                if (!get_page_unless_zero(page))
1491                        goto out_unlock;
1492                spin_unlock(vmf->ptl);
1493                wait_on_page_locked(page);
1494                put_page(page);
1495                goto out;
1496        }
1497
1498        page = pmd_page(pmd);
1499        BUG_ON(is_huge_zero_page(page));
1500        page_nid = page_to_nid(page);
1501        last_cpupid = page_cpupid_last(page);
1502        count_vm_numa_event(NUMA_HINT_FAULTS);
1503        if (page_nid == this_nid) {
1504                count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1505                flags |= TNF_FAULT_LOCAL;
1506        }
1507
1508        /* See similar comment in do_numa_page for explanation */
1509        if (!pmd_savedwrite(pmd))
1510                flags |= TNF_NO_GROUP;
1511
1512        /*
1513         * Acquire the page lock to serialise THP migrations but avoid dropping
1514         * page_table_lock if at all possible
1515         */
1516        page_locked = trylock_page(page);
1517        target_nid = mpol_misplaced(page, vma, haddr);
1518        if (target_nid == -1) {
1519                /* If the page was locked, there are no parallel migrations */
1520                if (page_locked)
1521                        goto clear_pmdnuma;
1522        }
1523
1524        /* Migration could have started since the pmd_trans_migrating check */
1525        if (!page_locked) {
1526                page_nid = -1;
1527                if (!get_page_unless_zero(page))
1528                        goto out_unlock;
1529                spin_unlock(vmf->ptl);
1530                wait_on_page_locked(page);
1531                put_page(page);
1532                goto out;
1533        }
1534
1535        /*
1536         * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1537         * to serialises splits
1538         */
1539        get_page(page);
1540        spin_unlock(vmf->ptl);
1541        anon_vma = page_lock_anon_vma_read(page);
1542
1543        /* Confirm the PMD did not change while page_table_lock was released */
1544        spin_lock(vmf->ptl);
1545        if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1546                unlock_page(page);
1547                put_page(page);
1548                page_nid = -1;
1549                goto out_unlock;
1550        }
1551
1552        /* Bail if we fail to protect against THP splits for any reason */
1553        if (unlikely(!anon_vma)) {
1554                put_page(page);
1555                page_nid = -1;
1556                goto clear_pmdnuma;
1557        }
1558
1559        /*
1560         * Since we took the NUMA fault, we must have observed the !accessible
1561         * bit. Make sure all other CPUs agree with that, to avoid them
1562         * modifying the page we're about to migrate.
1563         *
1564         * Must be done under PTL such that we'll observe the relevant
1565         * inc_tlb_flush_pending().
1566         *
1567         * We are not sure a pending tlb flush here is for a huge page
1568         * mapping or not. Hence use the tlb range variant
1569         */
1570        if (mm_tlb_flush_pending(vma->vm_mm)) {
1571                flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1572                /*
1573                 * change_huge_pmd() released the pmd lock before
1574                 * invalidating the secondary MMUs sharing the primary
1575                 * MMU pagetables (with ->invalidate_range()). The
1576                 * mmu_notifier_invalidate_range_end() (which
1577                 * internally calls ->invalidate_range()) in
1578                 * change_pmd_range() will run after us, so we can't
1579                 * rely on it here and we need an explicit invalidate.
1580                 */
1581                mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1582                                              haddr + HPAGE_PMD_SIZE);
1583        }
1584
1585        /*
1586         * Migrate the THP to the requested node, returns with page unlocked
1587         * and access rights restored.
1588         */
1589        spin_unlock(vmf->ptl);
1590
1591        migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1592                                vmf->pmd, pmd, vmf->address, page, target_nid);
1593        if (migrated) {
1594                flags |= TNF_MIGRATED;
1595                page_nid = target_nid;
1596        } else
1597                flags |= TNF_MIGRATE_FAIL;
1598
1599        goto out;
1600clear_pmdnuma:
1601        BUG_ON(!PageLocked(page));
1602        was_writable = pmd_savedwrite(pmd);
1603        pmd = pmd_modify(pmd, vma->vm_page_prot);
1604        pmd = pmd_mkyoung(pmd);
1605        if (was_writable)
1606                pmd = pmd_mkwrite(pmd);
1607        set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1608        update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1609        unlock_page(page);
1610out_unlock:
1611        spin_unlock(vmf->ptl);
1612
1613out:
1614        if (anon_vma)
1615                page_unlock_anon_vma_read(anon_vma);
1616
1617        if (page_nid != -1)
1618                task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1619                                flags);
1620
1621        return 0;
1622}
1623
1624/*
1625 * Return true if we do MADV_FREE successfully on entire pmd page.
1626 * Otherwise, return false.
1627 */
1628bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1629                pmd_t *pmd, unsigned long addr, unsigned long next)
1630{
1631        spinlock_t *ptl;
1632        pmd_t orig_pmd;
1633        struct page *page;
1634        struct mm_struct *mm = tlb->mm;
1635        bool ret = false;
1636
1637        tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1638
1639        ptl = pmd_trans_huge_lock(pmd, vma);
1640        if (!ptl)
1641                goto out_unlocked;
1642
1643        orig_pmd = *pmd;
1644        if (is_huge_zero_pmd(orig_pmd))
1645                goto out;
1646
1647        if (unlikely(!pmd_present(orig_pmd))) {
1648                VM_BUG_ON(thp_migration_supported() &&
1649                                  !is_pmd_migration_entry(orig_pmd));
1650                goto out;
1651        }
1652
1653        page = pmd_page(orig_pmd);
1654        /*
1655         * If other processes are mapping this page, we couldn't discard
1656         * the page unless they all do MADV_FREE so let's skip the page.
1657         */
1658        if (page_mapcount(page) != 1)
1659                goto out;
1660
1661        if (!trylock_page(page))
1662                goto out;
1663
1664        /*
1665         * If user want to discard part-pages of THP, split it so MADV_FREE
1666         * will deactivate only them.
1667         */
1668        if (next - addr != HPAGE_PMD_SIZE) {
1669                get_page(page);
1670                spin_unlock(ptl);
1671                split_huge_page(page);
1672                unlock_page(page);
1673                put_page(page);
1674                goto out_unlocked;
1675        }
1676
1677        if (PageDirty(page))
1678                ClearPageDirty(page);
1679        unlock_page(page);
1680
1681        if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1682                pmdp_invalidate(vma, addr, pmd);
1683                orig_pmd = pmd_mkold(orig_pmd);
1684                orig_pmd = pmd_mkclean(orig_pmd);
1685
1686                set_pmd_at(mm, addr, pmd, orig_pmd);
1687                tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1688        }
1689
1690        mark_page_lazyfree(page);
1691        ret = true;
1692out:
1693        spin_unlock(ptl);
1694out_unlocked:
1695        return ret;
1696}
1697
1698static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1699{
1700        pgtable_t pgtable;
1701
1702        pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1703        pte_free(mm, pgtable);
1704        mm_dec_nr_ptes(mm);
1705}
1706
1707int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1708                 pmd_t *pmd, unsigned long addr)
1709{
1710        pmd_t orig_pmd;
1711        spinlock_t *ptl;
1712
1713        tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1714
1715        ptl = __pmd_trans_huge_lock(pmd, vma);
1716        if (!ptl)
1717                return 0;
1718        /*
1719         * For architectures like ppc64 we look at deposited pgtable
1720         * when calling pmdp_huge_get_and_clear. So do the
1721         * pgtable_trans_huge_withdraw after finishing pmdp related
1722         * operations.
1723         */
1724        orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1725                        tlb->fullmm);
1726        tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1727        if (vma_is_dax(vma)) {
1728                if (arch_needs_pgtable_deposit())
1729                        zap_deposited_table(tlb->mm, pmd);
1730                spin_unlock(ptl);
1731                if (is_huge_zero_pmd(orig_pmd))
1732                        tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1733        } else if (is_huge_zero_pmd(orig_pmd)) {
1734                zap_deposited_table(tlb->mm, pmd);
1735                spin_unlock(ptl);
1736                tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1737        } else {
1738                struct page *page = NULL;
1739                int flush_needed = 1;
1740
1741                if (pmd_present(orig_pmd)) {
1742                        page = pmd_page(orig_pmd);
1743                        page_remove_rmap(page, true);
1744                        VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1745                        VM_BUG_ON_PAGE(!PageHead(page), page);
1746                } else if (thp_migration_supported()) {
1747                        swp_entry_t entry;
1748
1749                        VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1750                        entry = pmd_to_swp_entry(orig_pmd);
1751                        page = pfn_to_page(swp_offset(entry));
1752                        flush_needed = 0;
1753                } else
1754                        WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1755
1756                if (PageAnon(page)) {
1757                        zap_deposited_table(tlb->mm, pmd);
1758                        add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1759                } else {
1760                        if (arch_needs_pgtable_deposit())
1761                                zap_deposited_table(tlb->mm, pmd);
1762                        add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1763                }
1764
1765                spin_unlock(ptl);
1766                if (flush_needed)
1767                        tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1768        }
1769        return 1;
1770}
1771
1772#ifndef pmd_move_must_withdraw
1773static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1774                                         spinlock_t *old_pmd_ptl,
1775                                         struct vm_area_struct *vma)
1776{
1777        /*
1778         * With split pmd lock we also need to move preallocated
1779         * PTE page table if new_pmd is on different PMD page table.
1780         *
1781         * We also don't deposit and withdraw tables for file pages.
1782         */
1783        return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1784}
1785#endif
1786
1787static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1788{
1789#ifdef CONFIG_MEM_SOFT_DIRTY
1790        if (unlikely(is_pmd_migration_entry(pmd)))
1791                pmd = pmd_swp_mksoft_dirty(pmd);
1792        else if (pmd_present(pmd))
1793                pmd = pmd_mksoft_dirty(pmd);
1794#endif
1795        return pmd;
1796}
1797
1798bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1799                  unsigned long new_addr, unsigned long old_end,
1800                  pmd_t *old_pmd, pmd_t *new_pmd)
1801{
1802        spinlock_t *old_ptl, *new_ptl;
1803        pmd_t pmd;
1804        struct mm_struct *mm = vma->vm_mm;
1805        bool force_flush = false;
1806
1807        if ((old_addr & ~HPAGE_PMD_MASK) ||
1808            (new_addr & ~HPAGE_PMD_MASK) ||
1809            old_end - old_addr < HPAGE_PMD_SIZE)
1810                return false;
1811
1812        /*
1813         * The destination pmd shouldn't be established, free_pgtables()
1814         * should have release it.
1815         */
1816        if (WARN_ON(!pmd_none(*new_pmd))) {
1817                VM_BUG_ON(pmd_trans_huge(*new_pmd));
1818                return false;
1819        }
1820
1821        /*
1822         * We don't have to worry about the ordering of src and dst
1823         * ptlocks because exclusive mmap_sem prevents deadlock.
1824         */
1825        old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1826        if (old_ptl) {
1827                new_ptl = pmd_lockptr(mm, new_pmd);
1828                if (new_ptl != old_ptl)
1829                        spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1830                pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1831                if (pmd_present(pmd))
1832                        force_flush = true;
1833                VM_BUG_ON(!pmd_none(*new_pmd));
1834
1835                if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1836                        pgtable_t pgtable;
1837                        pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1838                        pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1839                }
1840                pmd = move_soft_dirty_pmd(pmd);
1841                set_pmd_at(mm, new_addr, new_pmd, pmd);
1842                if (force_flush)
1843                        flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1844                if (new_ptl != old_ptl)
1845                        spin_unlock(new_ptl);
1846                spin_unlock(old_ptl);
1847                return true;
1848        }
1849        return false;
1850}
1851
1852/*
1853 * Returns
1854 *  - 0 if PMD could not be locked
1855 *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1856 *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1857 */
1858int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1859                unsigned long addr, pgprot_t newprot, int prot_numa)
1860{
1861        struct mm_struct *mm = vma->vm_mm;
1862        spinlock_t *ptl;
1863        pmd_t entry;
1864        bool preserve_write;
1865        int ret;
1866
1867        ptl = __pmd_trans_huge_lock(pmd, vma);
1868        if (!ptl)
1869                return 0;
1870
1871        preserve_write = prot_numa && pmd_write(*pmd);
1872        ret = 1;
1873
1874#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1875        if (is_swap_pmd(*pmd)) {
1876                swp_entry_t entry = pmd_to_swp_entry(*pmd);
1877
1878                VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1879                if (is_write_migration_entry(entry)) {
1880                        pmd_t newpmd;
1881                        /*
1882                         * A protection check is difficult so
1883                         * just be safe and disable write
1884                         */
1885                        make_migration_entry_read(&entry);
1886                        newpmd = swp_entry_to_pmd(entry);
1887                        if (pmd_swp_soft_dirty(*pmd))
1888                                newpmd = pmd_swp_mksoft_dirty(newpmd);
1889                        set_pmd_at(mm, addr, pmd, newpmd);
1890                }
1891                goto unlock;
1892        }
1893#endif
1894
1895        /*
1896         * Avoid trapping faults against the zero page. The read-only
1897         * data is likely to be read-cached on the local CPU and
1898         * local/remote hits to the zero page are not interesting.
1899         */
1900        if (prot_numa && is_huge_zero_pmd(*pmd))
1901                goto unlock;
1902
1903        if (prot_numa && pmd_protnone(*pmd))
1904                goto unlock;
1905
1906        /*
1907         * In case prot_numa, we are under down_read(mmap_sem). It's critical
1908         * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1909         * which is also under down_read(mmap_sem):
1910         *
1911         *      CPU0:                           CPU1:
1912         *                              change_huge_pmd(prot_numa=1)
1913         *                               pmdp_huge_get_and_clear_notify()
1914         * madvise_dontneed()
1915         *  zap_pmd_range()
1916         *   pmd_trans_huge(*pmd) == 0 (without ptl)
1917         *   // skip the pmd
1918         *                               set_pmd_at();
1919         *                               // pmd is re-established
1920         *
1921         * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1922         * which may break userspace.
1923         *
1924         * pmdp_invalidate() is required to make sure we don't miss
1925         * dirty/young flags set by hardware.
1926         */
1927        entry = pmdp_invalidate(vma, addr, pmd);
1928
1929        entry = pmd_modify(entry, newprot);
1930        if (preserve_write)
1931                entry = pmd_mk_savedwrite(entry);
1932        ret = HPAGE_PMD_NR;
1933        set_pmd_at(mm, addr, pmd, entry);
1934        BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1935unlock:
1936        spin_unlock(ptl);
1937        return ret;
1938}
1939
1940/*
1941 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1942 *
1943 * Note that if it returns page table lock pointer, this routine returns without
1944 * unlocking page table lock. So callers must unlock it.
1945 */
1946spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1947{
1948        spinlock_t *ptl;
1949        ptl = pmd_lock(vma->vm_mm, pmd);
1950        if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1951                        pmd_devmap(*pmd)))
1952                return ptl;
1953        spin_unlock(ptl);
1954        return NULL;
1955}
1956
1957/*
1958 * Returns true if a given pud maps a thp, false otherwise.
1959 *
1960 * Note that if it returns true, this routine returns without unlocking page
1961 * table lock. So callers must unlock it.
1962 */
1963spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1964{
1965        spinlock_t *ptl;
1966
1967        ptl = pud_lock(vma->vm_mm, pud);
1968        if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1969                return ptl;
1970        spin_unlock(ptl);
1971        return NULL;
1972}
1973
1974#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1975int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1976                 pud_t *pud, unsigned long addr)
1977{
1978        pud_t orig_pud;
1979        spinlock_t *ptl;
1980
1981        ptl = __pud_trans_huge_lock(pud, vma);
1982        if (!ptl)
1983                return 0;
1984        /*
1985         * For architectures like ppc64 we look at deposited pgtable
1986         * when calling pudp_huge_get_and_clear. So do the
1987         * pgtable_trans_huge_withdraw after finishing pudp related
1988         * operations.
1989         */
1990        orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1991                        tlb->fullmm);
1992        tlb_remove_pud_tlb_entry(tlb, pud, addr);
1993        if (vma_is_dax(vma)) {
1994                spin_unlock(ptl);
1995                /* No zero page support yet */
1996        } else {
1997                /* No support for anonymous PUD pages yet */
1998                BUG();
1999        }
2000        return 1;
2001}
2002
2003static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2004                unsigned long haddr)
2005{
2006        VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2007        VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2008        VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2009        VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2010
2011        count_vm_event(THP_SPLIT_PUD);
2012
2013        pudp_huge_clear_flush_notify(vma, haddr, pud);
2014}
2015
2016void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2017                unsigned long address)
2018{
2019        spinlock_t *ptl;
2020        struct mm_struct *mm = vma->vm_mm;
2021        unsigned long haddr = address & HPAGE_PUD_MASK;
2022
2023        mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
2024        ptl = pud_lock(mm, pud);
2025        if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2026                goto out;
2027        __split_huge_pud_locked(vma, pud, haddr);
2028
2029out:
2030        spin_unlock(ptl);
2031        /*
2032         * No need to double call mmu_notifier->invalidate_range() callback as
2033         * the above pudp_huge_clear_flush_notify() did already call it.
2034         */
2035        mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2036                                               HPAGE_PUD_SIZE);
2037}
2038#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2039
2040static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2041                unsigned long haddr, pmd_t *pmd)
2042{
2043        struct mm_struct *mm = vma->vm_mm;
2044        pgtable_t pgtable;
2045        pmd_t _pmd;
2046        int i;
2047
2048        /*
2049         * Leave pmd empty until pte is filled note that it is fine to delay
2050         * notification until mmu_notifier_invalidate_range_end() as we are
2051         * replacing a zero pmd write protected page with a zero pte write
2052         * protected page.
2053         *
2054         * See Documentation/vm/mmu_notifier.rst
2055         */
2056        pmdp_huge_clear_flush(vma, haddr, pmd);
2057
2058        pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2059        pmd_populate(mm, &_pmd, pgtable);
2060
2061        for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2062                pte_t *pte, entry;
2063                entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2064                entry = pte_mkspecial(entry);
2065                pte = pte_offset_map(&_pmd, haddr);
2066                VM_BUG_ON(!pte_none(*pte));
2067                set_pte_at(mm, haddr, pte, entry);
2068                pte_unmap(pte);
2069        }
2070        smp_wmb(); /* make pte visible before pmd */
2071        pmd_populate(mm, pmd, pgtable);
2072}
2073
2074static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2075                unsigned long haddr, bool freeze)
2076{
2077        struct mm_struct *mm = vma->vm_mm;
2078        struct page *page;
2079        pgtable_t pgtable;
2080        pmd_t old_pmd, _pmd;
2081        bool young, write, soft_dirty, pmd_migration = false;
2082        unsigned long addr;
2083        int i;
2084
2085        VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2086        VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2087        VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2088        VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2089                                && !pmd_devmap(*pmd));
2090
2091        count_vm_event(THP_SPLIT_PMD);
2092
2093        if (!vma_is_anonymous(vma)) {
2094                _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2095                /*
2096                 * We are going to unmap this huge page. So
2097                 * just go ahead and zap it
2098                 */
2099                if (arch_needs_pgtable_deposit())
2100                        zap_deposited_table(mm, pmd);
2101                if (vma_is_dax(vma))
2102                        return;
2103                page = pmd_page(_pmd);
2104                if (!PageDirty(page) && pmd_dirty(_pmd))
2105                        set_page_dirty(page);
2106                if (!PageReferenced(page) && pmd_young(_pmd))
2107                        SetPageReferenced(page);
2108                page_remove_rmap(page, true);
2109                put_page(page);
2110                add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2111                return;
2112        } else if (is_huge_zero_pmd(*pmd)) {
2113                /*
2114                 * FIXME: Do we want to invalidate secondary mmu by calling
2115                 * mmu_notifier_invalidate_range() see comments below inside
2116                 * __split_huge_pmd() ?
2117                 *
2118                 * We are going from a zero huge page write protected to zero
2119                 * small page also write protected so it does not seems useful
2120                 * to invalidate secondary mmu at this time.
2121                 */
2122                return __split_huge_zero_page_pmd(vma, haddr, pmd);
2123        }
2124
2125        /*
2126         * Up to this point the pmd is present and huge and userland has the
2127         * whole access to the hugepage during the split (which happens in
2128         * place). If we overwrite the pmd with the not-huge version pointing
2129         * to the pte here (which of course we could if all CPUs were bug
2130         * free), userland could trigger a small page size TLB miss on the
2131         * small sized TLB while the hugepage TLB entry is still established in
2132         * the huge TLB. Some CPU doesn't like that.
2133         * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2134         * 383 on page 93. Intel should be safe but is also warns that it's
2135         * only safe if the permission and cache attributes of the two entries
2136         * loaded in the two TLB is identical (which should be the case here).
2137         * But it is generally safer to never allow small and huge TLB entries
2138         * for the same virtual address to be loaded simultaneously. So instead
2139         * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2140         * current pmd notpresent (atomically because here the pmd_trans_huge
2141         * must remain set at all times on the pmd until the split is complete
2142         * for this pmd), then we flush the SMP TLB and finally we write the
2143         * non-huge version of the pmd entry with pmd_populate.
2144         */
2145        old_pmd = pmdp_invalidate(vma, haddr, pmd);
2146
2147        pmd_migration = is_pmd_migration_entry(old_pmd);
2148        if (unlikely(pmd_migration)) {
2149                swp_entry_t entry;
2150
2151                entry = pmd_to_swp_entry(old_pmd);
2152                page = pfn_to_page(swp_offset(entry));
2153                write = is_write_migration_entry(entry);
2154                young = false;
2155                soft_dirty = pmd_swp_soft_dirty(old_pmd);
2156        } else {
2157                page = pmd_page(old_pmd);
2158                if (pmd_dirty(old_pmd))
2159                        SetPageDirty(page);
2160                write = pmd_write(old_pmd);
2161                young = pmd_young(old_pmd);
2162                soft_dirty = pmd_soft_dirty(old_pmd);
2163        }
2164        VM_BUG_ON_PAGE(!page_count(page), page);
2165        page_ref_add(page, HPAGE_PMD_NR - 1);
2166
2167        /*
2168         * Withdraw the table only after we mark the pmd entry invalid.
2169         * This's critical for some architectures (Power).
2170         */
2171        pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2172        pmd_populate(mm, &_pmd, pgtable);
2173
2174        for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2175                pte_t entry, *pte;
2176                /*
2177                 * Note that NUMA hinting access restrictions are not
2178                 * transferred to avoid any possibility of altering
2179                 * permissions across VMAs.
2180                 */
2181                if (freeze || pmd_migration) {
2182                        swp_entry_t swp_entry;
2183                        swp_entry = make_migration_entry(page + i, write);
2184                        entry = swp_entry_to_pte(swp_entry);
2185                        if (soft_dirty)
2186                                entry = pte_swp_mksoft_dirty(entry);
2187                } else {
2188                        entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2189                        entry = maybe_mkwrite(entry, vma);
2190                        if (!write)
2191                                entry = pte_wrprotect(entry);
2192                        if (!young)
2193                                entry = pte_mkold(entry);
2194                        if (soft_dirty)
2195                                entry = pte_mksoft_dirty(entry);
2196                }
2197                pte = pte_offset_map(&_pmd, addr);
2198                BUG_ON(!pte_none(*pte));
2199                set_pte_at(mm, addr, pte, entry);
2200                atomic_inc(&page[i]._mapcount);
2201                pte_unmap(pte);
2202        }
2203
2204        /*
2205         * Set PG_double_map before dropping compound_mapcount to avoid
2206         * false-negative page_mapped().
2207         */
2208        if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2209                for (i = 0; i < HPAGE_PMD_NR; i++)
2210                        atomic_inc(&page[i]._mapcount);
2211        }
2212
2213        if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2214                /* Last compound_mapcount is gone. */
2215                __dec_node_page_state(page, NR_ANON_THPS);
2216                if (TestClearPageDoubleMap(page)) {
2217                        /* No need in mapcount reference anymore */
2218                        for (i = 0; i < HPAGE_PMD_NR; i++)
2219                                atomic_dec(&page[i]._mapcount);
2220                }
2221        }
2222
2223        smp_wmb(); /* make pte visible before 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
2234void __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);
2259out:
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
2278void 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
2303void 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
2344static void unmap_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
2359static void remap_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
2370static 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
2377        /*
2378         * Clone page flags before unfreezing refcount.
2379         *
2380         * After successful get_page_unless_zero() might follow flags change,
2381         * for exmaple lock_page() which set PG_waiters.
2382         */
2383        page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2384        page_tail->flags |= (head->flags &
2385                        ((1L << PG_referenced) |
2386                         (1L << PG_swapbacked) |
2387                         (1L << PG_swapcache) |
2388                         (1L << PG_mlocked) |
2389                         (1L << PG_uptodate) |
2390                         (1L << PG_active) |
2391                         (1L << PG_workingset) |
2392                         (1L << PG_locked) |
2393                         (1L << PG_unevictable) |
2394                         (1L << PG_dirty)));
2395
2396        /* ->mapping in first tail page is compound_mapcount */
2397        VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2398                        page_tail);
2399        page_tail->mapping = head->mapping;
2400        page_tail->index = head->index + tail;
2401
2402        /* Page flags must be visible before we make the page non-compound. */
2403        smp_wmb();
2404
2405        /*
2406         * Clear PageTail before unfreezing page refcount.
2407         *
2408         * After successful get_page_unless_zero() might follow put_page()
2409         * which needs correct compound_head().
2410         */
2411        clear_compound_head(page_tail);
2412
2413        /* Finally unfreeze refcount. Additional reference from page cache. */
2414        page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2415                                          PageSwapCache(head)));
2416
2417        if (page_is_young(head))
2418                set_page_young(page_tail);
2419        if (page_is_idle(head))
2420                set_page_idle(page_tail);
2421
2422        page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2423
2424        /*
2425         * always add to the tail because some iterators expect new
2426         * pages to show after the currently processed elements - e.g.
2427         * migrate_pages
2428         */
2429        lru_add_page_tail(head, page_tail, lruvec, list);
2430}
2431
2432static void __split_huge_page(struct page *page, struct list_head *list,
2433                pgoff_t end, unsigned long flags)
2434{
2435        struct page *head = compound_head(page);
2436        struct zone *zone = page_zone(head);
2437        struct lruvec *lruvec;
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        for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2446                __split_huge_page_tail(head, i, lruvec, list);
2447                /* Some pages can be beyond i_size: drop them from page cache */
2448                if (head[i].index >= end) {
2449                        ClearPageDirty(head + i);
2450                        __delete_from_page_cache(head + i, NULL);
2451                        if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2452                                shmem_uncharge(head->mapping->host, 1);
2453                        put_page(head + i);
2454                }
2455        }
2456
2457        ClearPageCompound(head);
2458        /* See comment in __split_huge_page_tail() */
2459        if (PageAnon(head)) {
2460                /* Additional pin to swap cache */
2461                if (PageSwapCache(head))
2462                        page_ref_add(head, 2);
2463                else
2464                        page_ref_inc(head);
2465        } else {
2466                /* Additional pin to page cache */
2467                page_ref_add(head, 2);
2468                xa_unlock(&head->mapping->i_pages);
2469        }
2470
2471        spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2472
2473        remap_page(head);
2474
2475        for (i = 0; i < HPAGE_PMD_NR; i++) {
2476                struct page *subpage = head + i;
2477                if (subpage == page)
2478                        continue;
2479                unlock_page(subpage);
2480
2481                /*
2482                 * Subpages may be freed if there wasn't any mapping
2483                 * like if add_to_swap() is running on a lru page that
2484                 * had its mapping zapped. And freeing these pages
2485                 * requires taking the lru_lock so we do the put_page
2486                 * of the tail pages after the split is complete.
2487                 */
2488                put_page(subpage);
2489        }
2490}
2491
2492int total_mapcount(struct page *page)
2493{
2494        int i, compound, ret;
2495
2496        VM_BUG_ON_PAGE(PageTail(page), page);
2497
2498        if (likely(!PageCompound(page)))
2499                return atomic_read(&page->_mapcount) + 1;
2500
2501        compound = compound_mapcount(page);
2502        if (PageHuge(page))
2503                return compound;
2504        ret = compound;
2505        for (i = 0; i < HPAGE_PMD_NR; i++)
2506                ret += atomic_read(&page[i]._mapcount) + 1;
2507        /* File pages has compound_mapcount included in _mapcount */
2508        if (!PageAnon(page))
2509                return ret - compound * HPAGE_PMD_NR;
2510        if (PageDoubleMap(page))
2511                ret -= HPAGE_PMD_NR;
2512        return ret;
2513}
2514
2515/*
2516 * This calculates accurately how many mappings a transparent hugepage
2517 * has (unlike page_mapcount() which isn't fully accurate). This full
2518 * accuracy is primarily needed to know if copy-on-write faults can
2519 * reuse the page and change the mapping to read-write instead of
2520 * copying them. At the same time this returns the total_mapcount too.
2521 *
2522 * The function returns the highest mapcount any one of the subpages
2523 * has. If the return value is one, even if different processes are
2524 * mapping different subpages of the transparent hugepage, they can
2525 * all reuse it, because each process is reusing a different subpage.
2526 *
2527 * The total_mapcount is instead counting all virtual mappings of the
2528 * subpages. If the total_mapcount is equal to "one", it tells the
2529 * caller all mappings belong to the same "mm" and in turn the
2530 * anon_vma of the transparent hugepage can become the vma->anon_vma
2531 * local one as no other process may be mapping any of the subpages.
2532 *
2533 * It would be more accurate to replace page_mapcount() with
2534 * page_trans_huge_mapcount(), however we only use
2535 * page_trans_huge_mapcount() in the copy-on-write faults where we
2536 * need full accuracy to avoid breaking page pinning, because
2537 * page_trans_huge_mapcount() is slower than page_mapcount().
2538 */
2539int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2540{
2541        int i, ret, _total_mapcount, mapcount;
2542
2543        /* hugetlbfs shouldn't call it */
2544        VM_BUG_ON_PAGE(PageHuge(page), page);
2545
2546        if (likely(!PageTransCompound(page))) {
2547                mapcount = atomic_read(&page->_mapcount) + 1;
2548                if (total_mapcount)
2549                        *total_mapcount = mapcount;
2550                return mapcount;
2551        }
2552
2553        page = compound_head(page);
2554
2555        _total_mapcount = ret = 0;
2556        for (i = 0; i < HPAGE_PMD_NR; i++) {
2557                mapcount = atomic_read(&page[i]._mapcount) + 1;
2558                ret = max(ret, mapcount);
2559                _total_mapcount += mapcount;
2560        }
2561        if (PageDoubleMap(page)) {
2562                ret -= 1;
2563                _total_mapcount -= HPAGE_PMD_NR;
2564        }
2565        mapcount = compound_mapcount(page);
2566        ret += mapcount;
2567        _total_mapcount += mapcount;
2568        if (total_mapcount)
2569                *total_mapcount = _total_mapcount;
2570        return ret;
2571}
2572
2573/* Racy check whether the huge page can be split */
2574bool can_split_huge_page(struct page *page, int *pextra_pins)
2575{
2576        int extra_pins;
2577
2578        /* Additional pins from page cache */
2579        if (PageAnon(page))
2580                extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2581        else
2582                extra_pins = HPAGE_PMD_NR;
2583        if (pextra_pins)
2584                *pextra_pins = extra_pins;
2585        return total_mapcount(page) == page_count(page) - extra_pins - 1;
2586}
2587
2588/*
2589 * This function splits huge page into normal pages. @page can point to any
2590 * subpage of huge page to split. Split doesn't change the position of @page.
2591 *
2592 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2593 * The huge page must be locked.
2594 *
2595 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2596 *
2597 * Both head page and tail pages will inherit mapping, flags, and so on from
2598 * the hugepage.
2599 *
2600 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2601 * they are not mapped.
2602 *
2603 * Returns 0 if the hugepage is split successfully.
2604 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2605 * us.
2606 */
2607int split_huge_page_to_list(struct page *page, struct list_head *list)
2608{
2609        struct page *head = compound_head(page);
2610        struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2611        struct anon_vma *anon_vma = NULL;
2612        struct address_space *mapping = NULL;
2613        int count, mapcount, extra_pins, ret;
2614        bool mlocked;
2615        unsigned long flags;
2616        pgoff_t end;
2617
2618        VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2619        VM_BUG_ON_PAGE(!PageLocked(page), page);
2620        VM_BUG_ON_PAGE(!PageCompound(page), page);
2621
2622        if (PageWriteback(page))
2623                return -EBUSY;
2624
2625        if (PageAnon(head)) {
2626                /*
2627                 * The caller does not necessarily hold an mmap_sem that would
2628                 * prevent the anon_vma disappearing so we first we take a
2629                 * reference to it and then lock the anon_vma for write. This
2630                 * is similar to page_lock_anon_vma_read except the write lock
2631                 * is taken to serialise against parallel split or collapse
2632                 * operations.
2633                 */
2634                anon_vma = page_get_anon_vma(head);
2635                if (!anon_vma) {
2636                        ret = -EBUSY;
2637                        goto out;
2638                }
2639                end = -1;
2640                mapping = NULL;
2641                anon_vma_lock_write(anon_vma);
2642        } else {
2643                mapping = head->mapping;
2644
2645                /* Truncated ? */
2646                if (!mapping) {
2647                        ret = -EBUSY;
2648                        goto out;
2649                }
2650
2651                anon_vma = NULL;
2652                i_mmap_lock_read(mapping);
2653
2654                /*
2655                 *__split_huge_page() may need to trim off pages beyond EOF:
2656                 * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2657                 * which cannot be nested inside the page tree lock. So note
2658                 * end now: i_size itself may be changed at any moment, but
2659                 * head page lock is good enough to serialize the trimming.
2660                 */
2661                end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2662        }
2663
2664        /*
2665         * Racy check if we can split the page, before unmap_page() will
2666         * split PMDs
2667         */
2668        if (!can_split_huge_page(head, &extra_pins)) {
2669                ret = -EBUSY;
2670                goto out_unlock;
2671        }
2672
2673        mlocked = PageMlocked(page);
2674        unmap_page(head);
2675        VM_BUG_ON_PAGE(compound_mapcount(head), head);
2676
2677        /* Make sure the page is not on per-CPU pagevec as it takes pin */
2678        if (mlocked)
2679                lru_add_drain();
2680
2681        /* prevent PageLRU to go away from under us, and freeze lru stats */
2682        spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2683
2684        if (mapping) {
2685                XA_STATE(xas, &mapping->i_pages, page_index(head));
2686
2687                /*
2688                 * Check if the head page is present in page cache.
2689                 * We assume all tail are present too, if head is there.
2690                 */
2691                xa_lock(&mapping->i_pages);
2692                if (xas_load(&xas) != head)
2693                        goto fail;
2694        }
2695
2696        /* Prevent deferred_split_scan() touching ->_refcount */
2697        spin_lock(&pgdata->split_queue_lock);
2698        count = page_count(head);
2699        mapcount = total_mapcount(head);
2700        if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2701                if (!list_empty(page_deferred_list(head))) {
2702                        pgdata->split_queue_len--;
2703                        list_del(page_deferred_list(head));
2704                }
2705                if (mapping)
2706                        __dec_node_page_state(page, NR_SHMEM_THPS);
2707                spin_unlock(&pgdata->split_queue_lock);
2708                __split_huge_page(page, list, end, flags);
2709                if (PageSwapCache(head)) {
2710                        swp_entry_t entry = { .val = page_private(head) };
2711
2712                        ret = split_swap_cluster(entry);
2713                } else
2714                        ret = 0;
2715        } else {
2716                if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2717                        pr_alert("total_mapcount: %u, page_count(): %u\n",
2718                                        mapcount, count);
2719                        if (PageTail(page))
2720                                dump_page(head, NULL);
2721                        dump_page(page, "total_mapcount(head) > 0");
2722                        BUG();
2723                }
2724                spin_unlock(&pgdata->split_queue_lock);
2725fail:           if (mapping)
2726                        xa_unlock(&mapping->i_pages);
2727                spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2728                remap_page(head);
2729                ret = -EBUSY;
2730        }
2731
2732out_unlock:
2733        if (anon_vma) {
2734                anon_vma_unlock_write(anon_vma);
2735                put_anon_vma(anon_vma);
2736        }
2737        if (mapping)
2738                i_mmap_unlock_read(mapping);
2739out:
2740        count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2741        return ret;
2742}
2743
2744void free_transhuge_page(struct page *page)
2745{
2746        struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2747        unsigned long flags;
2748
2749        spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2750        if (!list_empty(page_deferred_list(page))) {
2751                pgdata->split_queue_len--;
2752                list_del(page_deferred_list(page));
2753        }
2754        spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2755        free_compound_page(page);
2756}
2757
2758void deferred_split_huge_page(struct page *page)
2759{
2760        struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2761        unsigned long flags;
2762
2763        VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2764
2765        spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2766        if (list_empty(page_deferred_list(page))) {
2767                count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2768                list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2769                pgdata->split_queue_len++;
2770        }
2771        spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2772}
2773
2774static unsigned long deferred_split_count(struct shrinker *shrink,
2775                struct shrink_control *sc)
2776{
2777        struct pglist_data *pgdata = NODE_DATA(sc->nid);
2778        return READ_ONCE(pgdata->split_queue_len);
2779}
2780
2781static unsigned long deferred_split_scan(struct shrinker *shrink,
2782                struct shrink_control *sc)
2783{
2784        struct pglist_data *pgdata = NODE_DATA(sc->nid);
2785        unsigned long flags;
2786        LIST_HEAD(list), *pos, *next;
2787        struct page *page;
2788        int split = 0;
2789
2790        spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2791        /* Take pin on all head pages to avoid freeing them under us */
2792        list_for_each_safe(pos, next, &pgdata->split_queue) {
2793                page = list_entry((void *)pos, struct page, mapping);
2794                page = compound_head(page);
2795                if (get_page_unless_zero(page)) {
2796                        list_move(page_deferred_list(page), &list);
2797                } else {
2798                        /* We lost race with put_compound_page() */
2799                        list_del_init(page_deferred_list(page));
2800                        pgdata->split_queue_len--;
2801                }
2802                if (!--sc->nr_to_scan)
2803                        break;
2804        }
2805        spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2806
2807        list_for_each_safe(pos, next, &list) {
2808                page = list_entry((void *)pos, struct page, mapping);
2809                if (!trylock_page(page))
2810                        goto next;
2811                /* split_huge_page() removes page from list on success */
2812                if (!split_huge_page(page))
2813                        split++;
2814                unlock_page(page);
2815next:
2816                put_page(page);
2817        }
2818
2819        spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2820        list_splice_tail(&list, &pgdata->split_queue);
2821        spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2822
2823        /*
2824         * Stop shrinker if we didn't split any page, but the queue is empty.
2825         * This can happen if pages were freed under us.
2826         */
2827        if (!split && list_empty(&pgdata->split_queue))
2828                return SHRINK_STOP;
2829        return split;
2830}
2831
2832static struct shrinker deferred_split_shrinker = {
2833        .count_objects = deferred_split_count,
2834        .scan_objects = deferred_split_scan,
2835        .seeks = DEFAULT_SEEKS,
2836        .flags = SHRINKER_NUMA_AWARE,
2837};
2838
2839#ifdef CONFIG_DEBUG_FS
2840static int split_huge_pages_set(void *data, u64 val)
2841{
2842        struct zone *zone;
2843        struct page *page;
2844        unsigned long pfn, max_zone_pfn;
2845        unsigned long total = 0, split = 0;
2846
2847        if (val != 1)
2848                return -EINVAL;
2849
2850        for_each_populated_zone(zone) {
2851                max_zone_pfn = zone_end_pfn(zone);
2852                for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2853                        if (!pfn_valid(pfn))
2854                                continue;
2855
2856                        page = pfn_to_page(pfn);
2857                        if (!get_page_unless_zero(page))
2858                                continue;
2859
2860                        if (zone != page_zone(page))
2861                                goto next;
2862
2863                        if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2864                                goto next;
2865
2866                        total++;
2867                        lock_page(page);
2868                        if (!split_huge_page(page))
2869                                split++;
2870                        unlock_page(page);
2871next:
2872                        put_page(page);
2873                }
2874        }
2875
2876        pr_info("%lu of %lu THP split\n", split, total);
2877
2878        return 0;
2879}
2880DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2881                "%llu\n");
2882
2883static int __init split_huge_pages_debugfs(void)
2884{
2885        void *ret;
2886
2887        ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2888                        &split_huge_pages_fops);
2889        if (!ret)
2890                pr_warn("Failed to create split_huge_pages in debugfs");
2891        return 0;
2892}
2893late_initcall(split_huge_pages_debugfs);
2894#endif
2895
2896#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2897void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2898                struct page *page)
2899{
2900        struct vm_area_struct *vma = pvmw->vma;
2901        struct mm_struct *mm = vma->vm_mm;
2902        unsigned long address = pvmw->address;
2903        pmd_t pmdval;
2904        swp_entry_t entry;
2905        pmd_t pmdswp;
2906
2907        if (!(pvmw->pmd && !pvmw->pte))
2908                return;
2909
2910        flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2911        pmdval = *pvmw->pmd;
2912        pmdp_invalidate(vma, address, pvmw->pmd);
2913        if (pmd_dirty(pmdval))
2914                set_page_dirty(page);
2915        entry = make_migration_entry(page, pmd_write(pmdval));
2916        pmdswp = swp_entry_to_pmd(entry);
2917        if (pmd_soft_dirty(pmdval))
2918                pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2919        set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2920        page_remove_rmap(page, true);
2921        put_page(page);
2922}
2923
2924void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2925{
2926        struct vm_area_struct *vma = pvmw->vma;
2927        struct mm_struct *mm = vma->vm_mm;
2928        unsigned long address = pvmw->address;
2929        unsigned long mmun_start = address & HPAGE_PMD_MASK;
2930        pmd_t pmde;
2931        swp_entry_t entry;
2932
2933        if (!(pvmw->pmd && !pvmw->pte))
2934                return;
2935
2936        entry = pmd_to_swp_entry(*pvmw->pmd);
2937        get_page(new);
2938        pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2939        if (pmd_swp_soft_dirty(*pvmw->pmd))
2940                pmde = pmd_mksoft_dirty(pmde);
2941        if (is_write_migration_entry(entry))
2942                pmde = maybe_pmd_mkwrite(pmde, vma);
2943
2944        flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2945        if (PageAnon(new))
2946                page_add_anon_rmap(new, vma, mmun_start, true);
2947        else
2948                page_add_file_rmap(new, true);
2949        set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
2950        if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
2951                mlock_vma_page(new);
2952        update_mmu_cache_pmd(vma, address, pvmw->pmd);
2953}
2954#endif
2955