mm/huge_memory.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  Copyright (C) 2009  Red Hat, Inc.
   4  */
   5
   6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   7
   8 #include <linux/mm.h>
   9 #include <linux/sched.h>
  10 #include <linux/sched/mm.h>
  11 #include <linux/sched/coredump.h>
  12 #include <linux/sched/numa_balancing.h>
  13 #include <linux/highmem.h>
  14 #include <linux/hugetlb.h>
  15 #include <linux/mmu_notifier.h>
  16 #include <linux/rmap.h>
  17 #include <linux/swap.h>
  18 #include <linux/shrinker.h>
  19 #include <linux/mm_inline.h>
  20 #include <linux/swapops.h>
  21 #include <linux/backing-dev.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 #include <linux/numa.h>
  37 #include <linux/page_owner.h>
  38 #include <linux/sched/sysctl.h>
  39 #include <linux/memory-tiers.h>
  40
  41 #include <asm/tlb.h>
  42 #include <asm/pgalloc.h>
  43 #include "internal.h"
  44 #include "swap.h"
  45
  46 #define CREATE_TRACE_POINTS
  47 #include <trace/events/thp.h>
  48
  49 /*
  50  * By default, transparent hugepage support is disabled in order to avoid
  51  * risking an increased memory footprint for applications that are not
  52  * guaranteed to benefit from it. When transparent hugepage support is
  53  * enabled, it is for all mappings, and khugepaged scans all mappings.
  54  * Defrag is invoked by khugepaged hugepage allocations and by page faults
  55  * for all hugepage allocations.
  56  */
  57 unsigned long transparent_hugepage_flags __read_mostly =
  58 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  59         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  60 #endif
  61 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  62         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  63 #endif
  64         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
  65         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
  66         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
  67
  68 static struct shrinker deferred_split_shrinker;
  69
  70 static atomic_t huge_zero_refcount;
  71 struct page *huge_zero_page __read_mostly;
  72 unsigned long huge_zero_pfn __read_mostly = ~0UL;
  73
  74 bool hugepage_vma_check(struct vm_area_struct *vma, unsigned long vm_flags,
  75                         bool smaps, bool in_pf, bool enforce_sysfs)
  76 {
  77         if (!vma->vm_mm)                /* vdso */
  78                 return false;
  79
  80         /*
  81          * Explicitly disabled through madvise or prctl, or some
  82          * architectures may disable THP for some mappings, for
  83          * example, s390 kvm.
  84          * */
  85         if ((vm_flags & VM_NOHUGEPAGE) ||
  86             test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
  87                 return false;
  88         /*
  89          * If the hardware/firmware marked hugepage support disabled.
  90          */
  91         if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_NEVER_DAX))
  92                 return false;
  93
  94         /* khugepaged doesn't collapse DAX vma, but page fault is fine. */
  95         if (vma_is_dax(vma))
  96                 return in_pf;
  97
  98         /*
  99          * Special VMA and hugetlb VMA.
 100          * Must be checked after dax since some dax mappings may have
 101          * VM_MIXEDMAP set.
 102          */
 103         if (vm_flags & VM_NO_KHUGEPAGED)
 104                 return false;
 105
 106         /*
 107          * Check alignment for file vma and size for both file and anon vma.
 108          *
 109          * Skip the check for page fault. Huge fault does the check in fault
 110          * handlers. And this check is not suitable for huge PUD fault.
 111          */
 112         if (!in_pf &&
 113             !transhuge_vma_suitable(vma, (vma->vm_end - HPAGE_PMD_SIZE)))
 114                 return false;
 115
 116         /*
 117          * Enabled via shmem mount options or sysfs settings.
 118          * Must be done before hugepage flags check since shmem has its
 119          * own flags.
 120          */
 121         if (!in_pf && shmem_file(vma->vm_file))
 122                 return shmem_huge_enabled(vma, !enforce_sysfs);
 123
 124         /* Enforce sysfs THP requirements as necessary */
 125         if (enforce_sysfs &&
 126             (!hugepage_flags_enabled() || (!(vm_flags & VM_HUGEPAGE) &&
 127                                            !hugepage_flags_always())))
 128                 return false;
 129
 130         /* Only regular file is valid */
 131         if (!in_pf && file_thp_enabled(vma))
 132                 return true;
 133
 134         if (!vma_is_anonymous(vma))
 135                 return false;
 136
 137         if (vma_is_temporary_stack(vma))
 138                 return false;
 139
 140         /*
 141          * THPeligible bit of smaps should show 1 for proper VMAs even
 142          * though anon_vma is not initialized yet.
 143          *
 144          * Allow page fault since anon_vma may be not initialized until
 145          * the first page fault.
 146          */
 147         if (!vma->anon_vma)
 148                 return (smaps || in_pf);
 149
 150         return true;
 151 }
 152
 153 static bool get_huge_zero_page(void)
 154 {
 155         struct page *zero_page;
 156 retry:
 157         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
 158                 return true;
 159
 160         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
 161                         HPAGE_PMD_ORDER);
 162         if (!zero_page) {
 163                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
 164                 return false;
 165         }
 166         preempt_disable();
 167         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
 168                 preempt_enable();
 169                 __free_pages(zero_page, compound_order(zero_page));
 170                 goto retry;
 171         }
 172         WRITE_ONCE(huge_zero_pfn, page_to_pfn(zero_page));
 173
 174         /* We take additional reference here. It will be put back by shrinker */
 175         atomic_set(&huge_zero_refcount, 2);
 176         preempt_enable();
 177         count_vm_event(THP_ZERO_PAGE_ALLOC);
 178         return true;
 179 }
 180
 181 static void put_huge_zero_page(void)
 182 {
 183         /*
 184          * Counter should never go to zero here. Only shrinker can put
 185          * last reference.
 186          */
 187         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
 188 }
 189
 190 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
 191 {
 192         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 193                 return READ_ONCE(huge_zero_page);
 194
 195         if (!get_huge_zero_page())
 196                 return NULL;
 197
 198         if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 199                 put_huge_zero_page();
 200
 201         return READ_ONCE(huge_zero_page);
 202 }
 203
 204 void mm_put_huge_zero_page(struct mm_struct *mm)
 205 {
 206         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 207                 put_huge_zero_page();
 208 }
 209
 210 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
 211                                         struct shrink_control *sc)
 212 {
 213         /* we can free zero page only if last reference remains */
 214         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 215 }
 216
 217 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 218                                        struct shrink_control *sc)
 219 {
 220         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 221                 struct page *zero_page = xchg(&huge_zero_page, NULL);
 222                 BUG_ON(zero_page == NULL);
 223                 WRITE_ONCE(huge_zero_pfn, ~0UL);
 224                 __free_pages(zero_page, compound_order(zero_page));
 225                 return HPAGE_PMD_NR;
 226         }
 227
 228         return 0;
 229 }
 230
 231 static struct shrinker huge_zero_page_shrinker = {
 232         .count_objects = shrink_huge_zero_page_count,
 233         .scan_objects = shrink_huge_zero_page_scan,
 234         .seeks = DEFAULT_SEEKS,
 235 };
 236
 237 #ifdef CONFIG_SYSFS
 238 static ssize_t enabled_show(struct kobject *kobj,
 239                             struct kobj_attribute *attr, char *buf)
 240 {
 241         const char *output;
 242
 243         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
 244                 output = "[always] madvise never";
 245         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 246                           &transparent_hugepage_flags))
 247                 output = "always [madvise] never";
 248         else
 249                 output = "always madvise [never]";
 250
 251         return sysfs_emit(buf, "%s\n", output);
 252 }
 253
 254 static ssize_t enabled_store(struct kobject *kobj,
 255                              struct kobj_attribute *attr,
 256                              const char *buf, size_t count)
 257 {
 258         ssize_t ret = count;
 259
 260         if (sysfs_streq(buf, "always")) {
 261                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 262                 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 263         } else if (sysfs_streq(buf, "madvise")) {
 264                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 265                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 266         } else if (sysfs_streq(buf, "never")) {
 267                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 268                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 269         } else
 270                 ret = -EINVAL;
 271
 272         if (ret > 0) {
 273                 int err = start_stop_khugepaged();
 274                 if (err)
 275                         ret = err;
 276         }
 277         return ret;
 278 }
 279
 280 static struct kobj_attribute enabled_attr = __ATTR_RW(enabled);
 281
 282 ssize_t single_hugepage_flag_show(struct kobject *kobj,
 283                                   struct kobj_attribute *attr, char *buf,
 284                                   enum transparent_hugepage_flag flag)
 285 {
 286         return sysfs_emit(buf, "%d\n",
 287                           !!test_bit(flag, &transparent_hugepage_flags));
 288 }
 289
 290 ssize_t single_hugepage_flag_store(struct kobject *kobj,
 291                                  struct kobj_attribute *attr,
 292                                  const char *buf, size_t count,
 293                                  enum transparent_hugepage_flag flag)
 294 {
 295         unsigned long value;
 296         int ret;
 297
 298         ret = kstrtoul(buf, 10, &value);
 299         if (ret < 0)
 300                 return ret;
 301         if (value > 1)
 302                 return -EINVAL;
 303
 304         if (value)
 305                 set_bit(flag, &transparent_hugepage_flags);
 306         else
 307                 clear_bit(flag, &transparent_hugepage_flags);
 308
 309         return count;
 310 }
 311
 312 static ssize_t defrag_show(struct kobject *kobj,
 313                            struct kobj_attribute *attr, char *buf)
 314 {
 315         const char *output;
 316
 317         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
 318                      &transparent_hugepage_flags))
 319                 output = "[always] defer defer+madvise madvise never";
 320         else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
 321                           &transparent_hugepage_flags))
 322                 output = "always [defer] defer+madvise madvise never";
 323         else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG,
 324                           &transparent_hugepage_flags))
 325                 output = "always defer [defer+madvise] madvise never";
 326         else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
 327                           &transparent_hugepage_flags))
 328                 output = "always defer defer+madvise [madvise] never";
 329         else
 330                 output = "always defer defer+madvise madvise [never]";
 331
 332         return sysfs_emit(buf, "%s\n", output);
 333 }
 334
 335 static ssize_t defrag_store(struct kobject *kobj,
 336                             struct kobj_attribute *attr,
 337                             const char *buf, size_t count)
 338 {
 339         if (sysfs_streq(buf, "always")) {
 340                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 341                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 342                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 343                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 344         } else if (sysfs_streq(buf, "defer+madvise")) {
 345                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 346                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 347                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 348                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 349         } else if (sysfs_streq(buf, "defer")) {
 350                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 351                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 352                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 353                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 354         } else if (sysfs_streq(buf, "madvise")) {
 355                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 356                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 357                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 358                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 359         } else if (sysfs_streq(buf, "never")) {
 360                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 361                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 362                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 363                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 364         } else
 365                 return -EINVAL;
 366
 367         return count;
 368 }
 369 static struct kobj_attribute defrag_attr = __ATTR_RW(defrag);
 370
 371 static ssize_t use_zero_page_show(struct kobject *kobj,
 372                                   struct kobj_attribute *attr, char *buf)
 373 {
 374         return single_hugepage_flag_show(kobj, attr, buf,
 375                                          TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 376 }
 377 static ssize_t use_zero_page_store(struct kobject *kobj,
 378                 struct kobj_attribute *attr, const char *buf, size_t count)
 379 {
 380         return single_hugepage_flag_store(kobj, attr, buf, count,
 381                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 382 }
 383 static struct kobj_attribute use_zero_page_attr = __ATTR_RW(use_zero_page);
 384
 385 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
 386                                    struct kobj_attribute *attr, char *buf)
 387 {
 388         return sysfs_emit(buf, "%lu\n", HPAGE_PMD_SIZE);
 389 }
 390 static struct kobj_attribute hpage_pmd_size_attr =
 391         __ATTR_RO(hpage_pmd_size);
 392
 393 static struct attribute *hugepage_attr[] = {
 394         &enabled_attr.attr,
 395         &defrag_attr.attr,
 396         &use_zero_page_attr.attr,
 397         &hpage_pmd_size_attr.attr,
 398 #ifdef CONFIG_SHMEM
 399         &shmem_enabled_attr.attr,
 400 #endif
 401         NULL,
 402 };
 403
 404 static const struct attribute_group hugepage_attr_group = {
 405         .attrs = hugepage_attr,
 406 };
 407
 408 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 409 {
 410         int err;
 411
 412         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 413         if (unlikely(!*hugepage_kobj)) {
 414                 pr_err("failed to create transparent hugepage kobject\n");
 415                 return -ENOMEM;
 416         }
 417
 418         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 419         if (err) {
 420                 pr_err("failed to register transparent hugepage group\n");
 421                 goto delete_obj;
 422         }
 423
 424         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 425         if (err) {
 426                 pr_err("failed to register transparent hugepage group\n");
 427                 goto remove_hp_group;
 428         }
 429
 430         return 0;
 431
 432 remove_hp_group:
 433         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 434 delete_obj:
 435         kobject_put(*hugepage_kobj);
 436         return err;
 437 }
 438
 439 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 440 {
 441         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 442         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 443         kobject_put(hugepage_kobj);
 444 }
 445 #else
 446 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 447 {
 448         return 0;
 449 }
 450
 451 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 452 {
 453 }
 454 #endif /* CONFIG_SYSFS */
 455
 456 static int __init hugepage_init(void)
 457 {
 458         int err;
 459         struct kobject *hugepage_kobj;
 460
 461         if (!has_transparent_hugepage()) {
 462                 /*
 463                  * Hardware doesn't support hugepages, hence disable
 464                  * DAX PMD support.
 465                  */
 466                 transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_NEVER_DAX;
 467                 return -EINVAL;
 468         }
 469
 470         /*
 471          * hugepages can't be allocated by the buddy allocator
 472          */
 473         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
 474         /*
 475          * we use page->mapping and page->index in second tail page
 476          * as list_head: assuming THP order >= 2
 477          */
 478         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
 479
 480         err = hugepage_init_sysfs(&hugepage_kobj);
 481         if (err)
 482                 goto err_sysfs;
 483
 484         err = khugepaged_init();
 485         if (err)
 486                 goto err_slab;
 487
 488         err = register_shrinker(&huge_zero_page_shrinker, "thp-zero");
 489         if (err)
 490                 goto err_hzp_shrinker;
 491         err = register_shrinker(&deferred_split_shrinker, "thp-deferred_split");
 492         if (err)
 493                 goto err_split_shrinker;
 494
 495         /*
 496          * By default disable transparent hugepages on smaller systems,
 497          * where the extra memory used could hurt more than TLB overhead
 498          * is likely to save.  The admin can still enable it through /sys.
 499          */
 500         if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
 501                 transparent_hugepage_flags = 0;
 502                 return 0;
 503         }
 504
 505         err = start_stop_khugepaged();
 506         if (err)
 507                 goto err_khugepaged;
 508
 509         return 0;
 510 err_khugepaged:
 511         unregister_shrinker(&deferred_split_shrinker);
 512 err_split_shrinker:
 513         unregister_shrinker(&huge_zero_page_shrinker);
 514 err_hzp_shrinker:
 515         khugepaged_destroy();
 516 err_slab:
 517         hugepage_exit_sysfs(hugepage_kobj);
 518 err_sysfs:
 519         return err;
 520 }
 521 subsys_initcall(hugepage_init);
 522
 523 static int __init setup_transparent_hugepage(char *str)
 524 {
 525         int ret = 0;
 526         if (!str)
 527                 goto out;
 528         if (!strcmp(str, "always")) {
 529                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 530                         &transparent_hugepage_flags);
 531                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 532                           &transparent_hugepage_flags);
 533                 ret = 1;
 534         } else if (!strcmp(str, "madvise")) {
 535                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 536                           &transparent_hugepage_flags);
 537                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 538                         &transparent_hugepage_flags);
 539                 ret = 1;
 540         } else if (!strcmp(str, "never")) {
 541                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 542                           &transparent_hugepage_flags);
 543                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 544                           &transparent_hugepage_flags);
 545                 ret = 1;
 546         }
 547 out:
 548         if (!ret)
 549                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
 550         return ret;
 551 }
 552 __setup("transparent_hugepage=", setup_transparent_hugepage);
 553
 554 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 555 {
 556         if (likely(vma->vm_flags & VM_WRITE))
 557                 pmd = pmd_mkwrite(pmd);
 558         return pmd;
 559 }
 560
 561 #ifdef CONFIG_MEMCG
 562 static inline struct deferred_split *get_deferred_split_queue(struct page *page)
 563 {
 564         struct mem_cgroup *memcg = page_memcg(compound_head(page));
 565         struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
 566
 567         if (memcg)
 568                 return &memcg->deferred_split_queue;
 569         else
 570                 return &pgdat->deferred_split_queue;
 571 }
 572 #else
 573 static inline struct deferred_split *get_deferred_split_queue(struct page *page)
 574 {
 575         struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
 576
 577         return &pgdat->deferred_split_queue;
 578 }
 579 #endif
 580
 581 void prep_transhuge_page(struct page *page)
 582 {
 583         /*
 584          * we use page->mapping and page->index in second tail page
 585          * as list_head: assuming THP order >= 2
 586          */
 587
 588         INIT_LIST_HEAD(page_deferred_list(page));
 589         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 590 }
 591
 592 static inline bool is_transparent_hugepage(struct page *page)
 593 {
 594         if (!PageCompound(page))
 595                 return false;
 596
 597         page = compound_head(page);
 598         return is_huge_zero_page(page) ||
 599                page[1].compound_dtor == TRANSHUGE_PAGE_DTOR;
 600 }
 601
 602 static unsigned long __thp_get_unmapped_area(struct file *filp,
 603                 unsigned long addr, unsigned long len,
 604                 loff_t off, unsigned long flags, unsigned long size)
 605 {
 606         loff_t off_end = off + len;
 607         loff_t off_align = round_up(off, size);
 608         unsigned long len_pad, ret;
 609
 610         if (off_end <= off_align || (off_end - off_align) < size)
 611                 return 0;
 612
 613         len_pad = len + size;
 614         if (len_pad < len || (off + len_pad) < off)
 615                 return 0;
 616
 617         ret = current->mm->get_unmapped_area(filp, addr, len_pad,
 618                                               off >> PAGE_SHIFT, flags);
 619
 620         /*
 621          * The failure might be due to length padding. The caller will retry
 622          * without the padding.
 623          */
 624         if (IS_ERR_VALUE(ret))
 625                 return 0;
 626
 627         /*
 628          * Do not try to align to THP boundary if allocation at the address
 629          * hint succeeds.
 630          */
 631         if (ret == addr)
 632                 return addr;
 633
 634         ret += (off - ret) & (size - 1);
 635         return ret;
 636 }
 637
 638 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 639                 unsigned long len, unsigned long pgoff, unsigned long flags)
 640 {
 641         unsigned long ret;
 642         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 643
 644         ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE);
 645         if (ret)
 646                 return ret;
 647
 648         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 649 }
 650 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 651
 652 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
 653                         struct page *page, gfp_t gfp)
 654 {
 655         struct vm_area_struct *vma = vmf->vma;
 656         pgtable_t pgtable;
 657         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 658         vm_fault_t ret = 0;
 659
 660         VM_BUG_ON_PAGE(!PageCompound(page), page);
 661
 662         if (mem_cgroup_charge(page_folio(page), vma->vm_mm, gfp)) {
 663                 put_page(page);
 664                 count_vm_event(THP_FAULT_FALLBACK);
 665                 count_vm_event(THP_FAULT_FALLBACK_CHARGE);
 666                 return VM_FAULT_FALLBACK;
 667         }
 668         cgroup_throttle_swaprate(page, gfp);
 669
 670         pgtable = pte_alloc_one(vma->vm_mm);
 671         if (unlikely(!pgtable)) {
 672                 ret = VM_FAULT_OOM;
 673                 goto release;
 674         }
 675
 676         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
 677         /*
 678          * The memory barrier inside __SetPageUptodate makes sure that
 679          * clear_huge_page writes become visible before the set_pmd_at()
 680          * write.
 681          */
 682         __SetPageUptodate(page);
 683
 684         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 685         if (unlikely(!pmd_none(*vmf->pmd))) {
 686                 goto unlock_release;
 687         } else {
 688                 pmd_t entry;
 689
 690                 ret = check_stable_address_space(vma->vm_mm);
 691                 if (ret)
 692                         goto unlock_release;
 693
 694                 /* Deliver the page fault to userland */
 695                 if (userfaultfd_missing(vma)) {
 696                         spin_unlock(vmf->ptl);
 697                         put_page(page);
 698                         pte_free(vma->vm_mm, pgtable);
 699                         ret = handle_userfault(vmf, VM_UFFD_MISSING);
 700                         VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 701                         return ret;
 702                 }
 703
 704                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 705                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 706                 page_add_new_anon_rmap(page, vma, haddr);
 707                 lru_cache_add_inactive_or_unevictable(page, vma);
 708                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 709                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 710                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
 711                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 712                 mm_inc_nr_ptes(vma->vm_mm);
 713                 spin_unlock(vmf->ptl);
 714                 count_vm_event(THP_FAULT_ALLOC);
 715                 count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC);
 716         }
 717
 718         return 0;
 719 unlock_release:
 720         spin_unlock(vmf->ptl);
 721 release:
 722         if (pgtable)
 723                 pte_free(vma->vm_mm, pgtable);
 724         put_page(page);
 725         return ret;
 726
 727 }
 728
 729 /*
 730  * always: directly stall for all thp allocations
 731  * defer: wake kswapd and fail if not immediately available
 732  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
 733  *                fail if not immediately available
 734  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
 735  *          available
 736  * never: never stall for any thp allocation
 737  */
 738 gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma)
 739 {
 740         const bool vma_madvised = vma && (vma->vm_flags & VM_HUGEPAGE);
 741
 742         /* Always do synchronous compaction */
 743         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 744                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
 745
 746         /* Kick kcompactd and fail quickly */
 747         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 748                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
 749
 750         /* Synchronous compaction if madvised, otherwise kick kcompactd */
 751         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 752                 return GFP_TRANSHUGE_LIGHT |
 753                         (vma_madvised ? __GFP_DIRECT_RECLAIM :
 754                                         __GFP_KSWAPD_RECLAIM);
 755
 756         /* Only do synchronous compaction if madvised */
 757         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 758                 return GFP_TRANSHUGE_LIGHT |
 759                        (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
 760
 761         return GFP_TRANSHUGE_LIGHT;
 762 }
 763
 764 /* Caller must hold page table lock. */
 765 static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 766                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 767                 struct page *zero_page)
 768 {
 769         pmd_t entry;
 770         if (!pmd_none(*pmd))
 771                 return;
 772         entry = mk_pmd(zero_page, vma->vm_page_prot);
 773         entry = pmd_mkhuge(entry);
 774         pgtable_trans_huge_deposit(mm, pmd, pgtable);
 775         set_pmd_at(mm, haddr, pmd, entry);
 776         mm_inc_nr_ptes(mm);
 777 }
 778
 779 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 780 {
 781         struct vm_area_struct *vma = vmf->vma;
 782         gfp_t gfp;
 783         struct folio *folio;
 784         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 785
 786         if (!transhuge_vma_suitable(vma, haddr))
 787                 return VM_FAULT_FALLBACK;
 788         if (unlikely(anon_vma_prepare(vma)))
 789                 return VM_FAULT_OOM;
 790         khugepaged_enter_vma(vma, vma->vm_flags);
 791
 792         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
 793                         !mm_forbids_zeropage(vma->vm_mm) &&
 794                         transparent_hugepage_use_zero_page()) {
 795                 pgtable_t pgtable;
 796                 struct page *zero_page;
 797                 vm_fault_t ret;
 798                 pgtable = pte_alloc_one(vma->vm_mm);
 799                 if (unlikely(!pgtable))
 800                         return VM_FAULT_OOM;
 801                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
 802                 if (unlikely(!zero_page)) {
 803                         pte_free(vma->vm_mm, pgtable);
 804                         count_vm_event(THP_FAULT_FALLBACK);
 805                         return VM_FAULT_FALLBACK;
 806                 }
 807                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 808                 ret = 0;
 809                 if (pmd_none(*vmf->pmd)) {
 810                         ret = check_stable_address_space(vma->vm_mm);
 811                         if (ret) {
 812                                 spin_unlock(vmf->ptl);
 813                                 pte_free(vma->vm_mm, pgtable);
 814                         } else if (userfaultfd_missing(vma)) {
 815                                 spin_unlock(vmf->ptl);
 816                                 pte_free(vma->vm_mm, pgtable);
 817                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
 818                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 819                         } else {
 820                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
 821                                                    haddr, vmf->pmd, zero_page);
 822                                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
 823                                 spin_unlock(vmf->ptl);
 824                         }
 825                 } else {
 826                         spin_unlock(vmf->ptl);
 827                         pte_free(vma->vm_mm, pgtable);
 828                 }
 829                 return ret;
 830         }
 831         gfp = vma_thp_gfp_mask(vma);
 832         folio = vma_alloc_folio(gfp, HPAGE_PMD_ORDER, vma, haddr, true);
 833         if (unlikely(!folio)) {
 834                 count_vm_event(THP_FAULT_FALLBACK);
 835                 return VM_FAULT_FALLBACK;
 836         }
 837         return __do_huge_pmd_anonymous_page(vmf, &folio->page, gfp);
 838 }
 839
 840 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 841                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
 842                 pgtable_t pgtable)
 843 {
 844         struct mm_struct *mm = vma->vm_mm;
 845         pmd_t entry;
 846         spinlock_t *ptl;
 847
 848         ptl = pmd_lock(mm, pmd);
 849         if (!pmd_none(*pmd)) {
 850                 if (write) {
 851                         if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
 852                                 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
 853                                 goto out_unlock;
 854                         }
 855                         entry = pmd_mkyoung(*pmd);
 856                         entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 857                         if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
 858                                 update_mmu_cache_pmd(vma, addr, pmd);
 859                 }
 860
 861                 goto out_unlock;
 862         }
 863
 864         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 865         if (pfn_t_devmap(pfn))
 866                 entry = pmd_mkdevmap(entry);
 867         if (write) {
 868                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 869                 entry = maybe_pmd_mkwrite(entry, vma);
 870         }
 871
 872         if (pgtable) {
 873                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 874                 mm_inc_nr_ptes(mm);
 875                 pgtable = NULL;
 876         }
 877
 878         set_pmd_at(mm, addr, pmd, entry);
 879         update_mmu_cache_pmd(vma, addr, pmd);
 880
 881 out_unlock:
 882         spin_unlock(ptl);
 883         if (pgtable)
 884                 pte_free(mm, pgtable);
 885 }
 886
 887 /**
 888  * vmf_insert_pfn_pmd_prot - insert a pmd size pfn
 889  * @vmf: Structure describing the fault
 890  * @pfn: pfn to insert
 891  * @pgprot: page protection to use
 892  * @write: whether it's a write fault
 893  *
 894  * Insert a pmd size pfn. See vmf_insert_pfn() for additional info and
 895  * also consult the vmf_insert_mixed_prot() documentation when
 896  * @pgprot != @vmf->vma->vm_page_prot.
 897  *
 898  * Return: vm_fault_t value.
 899  */
 900 vm_fault_t vmf_insert_pfn_pmd_prot(struct vm_fault *vmf, pfn_t pfn,
 901                                    pgprot_t pgprot, bool write)
 902 {
 903         unsigned long addr = vmf->address & PMD_MASK;
 904         struct vm_area_struct *vma = vmf->vma;
 905         pgtable_t pgtable = NULL;
 906
 907         /*
 908          * If we had pmd_special, we could avoid all these restrictions,
 909          * but we need to be consistent with PTEs and architectures that
 910          * can't support a 'special' bit.
 911          */
 912         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 913                         !pfn_t_devmap(pfn));
 914         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 915                                                 (VM_PFNMAP|VM_MIXEDMAP));
 916         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 917
 918         if (addr < vma->vm_start || addr >= vma->vm_end)
 919                 return VM_FAULT_SIGBUS;
 920
 921         if (arch_needs_pgtable_deposit()) {
 922                 pgtable = pte_alloc_one(vma->vm_mm);
 923                 if (!pgtable)
 924                         return VM_FAULT_OOM;
 925         }
 926
 927         track_pfn_insert(vma, &pgprot, pfn);
 928
 929         insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
 930         return VM_FAULT_NOPAGE;
 931 }
 932 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd_prot);
 933
 934 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 935 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 936 {
 937         if (likely(vma->vm_flags & VM_WRITE))
 938                 pud = pud_mkwrite(pud);
 939         return pud;
 940 }
 941
 942 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 943                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 944 {
 945         struct mm_struct *mm = vma->vm_mm;
 946         pud_t entry;
 947         spinlock_t *ptl;
 948
 949         ptl = pud_lock(mm, pud);
 950         if (!pud_none(*pud)) {
 951                 if (write) {
 952                         if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
 953                                 WARN_ON_ONCE(!is_huge_zero_pud(*pud));
 954                                 goto out_unlock;
 955                         }
 956                         entry = pud_mkyoung(*pud);
 957                         entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
 958                         if (pudp_set_access_flags(vma, addr, pud, entry, 1))
 959                                 update_mmu_cache_pud(vma, addr, pud);
 960                 }
 961                 goto out_unlock;
 962         }
 963
 964         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
 965         if (pfn_t_devmap(pfn))
 966                 entry = pud_mkdevmap(entry);
 967         if (write) {
 968                 entry = pud_mkyoung(pud_mkdirty(entry));
 969                 entry = maybe_pud_mkwrite(entry, vma);
 970         }
 971         set_pud_at(mm, addr, pud, entry);
 972         update_mmu_cache_pud(vma, addr, pud);
 973
 974 out_unlock:
 975         spin_unlock(ptl);
 976 }
 977
 978 /**
 979  * vmf_insert_pfn_pud_prot - insert a pud size pfn
 980  * @vmf: Structure describing the fault
 981  * @pfn: pfn to insert
 982  * @pgprot: page protection to use
 983  * @write: whether it's a write fault
 984  *
 985  * Insert a pud size pfn. See vmf_insert_pfn() for additional info and
 986  * also consult the vmf_insert_mixed_prot() documentation when
 987  * @pgprot != @vmf->vma->vm_page_prot.
 988  *
 989  * Return: vm_fault_t value.
 990  */
 991 vm_fault_t vmf_insert_pfn_pud_prot(struct vm_fault *vmf, pfn_t pfn,
 992                                    pgprot_t pgprot, bool write)
 993 {
 994         unsigned long addr = vmf->address & PUD_MASK;
 995         struct vm_area_struct *vma = vmf->vma;
 996
 997         /*
 998          * If we had pud_special, we could avoid all these restrictions,
 999          * but we need to be consistent with PTEs and architectures that
1000          * can't support a 'special' bit.
1001          */
1002         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
1003                         !pfn_t_devmap(pfn));
1004         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1005                                                 (VM_PFNMAP|VM_MIXEDMAP));
1006         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1007
1008         if (addr < vma->vm_start || addr >= vma->vm_end)
1009                 return VM_FAULT_SIGBUS;
1010
1011         track_pfn_insert(vma, &pgprot, pfn);
1012
1013         insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
1014         return VM_FAULT_NOPAGE;
1015 }
1016 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud_prot);
1017 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1018
1019 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
1020                       pmd_t *pmd, bool write)
1021 {
1022         pmd_t _pmd;
1023
1024         _pmd = pmd_mkyoung(*pmd);
1025         if (write)
1026                 _pmd = pmd_mkdirty(_pmd);
1027         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1028                                   pmd, _pmd, write))
1029                 update_mmu_cache_pmd(vma, addr, pmd);
1030 }
1031
1032 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
1033                 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
1034 {
1035         unsigned long pfn = pmd_pfn(*pmd);
1036         struct mm_struct *mm = vma->vm_mm;
1037         struct page *page;
1038         int ret;
1039
1040         assert_spin_locked(pmd_lockptr(mm, pmd));
1041
1042         /* FOLL_GET and FOLL_PIN are mutually exclusive. */
1043         if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
1044                          (FOLL_PIN | FOLL_GET)))
1045                 return NULL;
1046
1047         if (flags & FOLL_WRITE && !pmd_write(*pmd))
1048                 return NULL;
1049
1050         if (pmd_present(*pmd) && pmd_devmap(*pmd))
1051                 /* pass */;
1052         else
1053                 return NULL;
1054
1055         if (flags & FOLL_TOUCH)
1056                 touch_pmd(vma, addr, pmd, flags & FOLL_WRITE);
1057
1058         /*
1059          * device mapped pages can only be returned if the
1060          * caller will manage the page reference count.
1061          */
1062         if (!(flags & (FOLL_GET | FOLL_PIN)))
1063                 return ERR_PTR(-EEXIST);
1064
1065         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1066         *pgmap = get_dev_pagemap(pfn, *pgmap);
1067         if (!*pgmap)
1068                 return ERR_PTR(-EFAULT);
1069         page = pfn_to_page(pfn);
1070         ret = try_grab_page(page, flags);
1071         if (ret)
1072                 page = ERR_PTR(ret);
1073
1074         return page;
1075 }
1076
1077 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1078                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1079                   struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma)
1080 {
1081         spinlock_t *dst_ptl, *src_ptl;
1082         struct page *src_page;
1083         pmd_t pmd;
1084         pgtable_t pgtable = NULL;
1085         int ret = -ENOMEM;
1086
1087         /* Skip if can be re-fill on fault */
1088         if (!vma_is_anonymous(dst_vma))
1089                 return 0;
1090
1091         pgtable = pte_alloc_one(dst_mm);
1092         if (unlikely(!pgtable))
1093                 goto out;
1094
1095         dst_ptl = pmd_lock(dst_mm, dst_pmd);
1096         src_ptl = pmd_lockptr(src_mm, src_pmd);
1097         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1098
1099         ret = -EAGAIN;
1100         pmd = *src_pmd;
1101
1102 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1103         if (unlikely(is_swap_pmd(pmd))) {
1104                 swp_entry_t entry = pmd_to_swp_entry(pmd);
1105
1106                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
1107                 if (!is_readable_migration_entry(entry)) {
1108                         entry = make_readable_migration_entry(
1109                                                         swp_offset(entry));
1110                         pmd = swp_entry_to_pmd(entry);
1111                         if (pmd_swp_soft_dirty(*src_pmd))
1112                                 pmd = pmd_swp_mksoft_dirty(pmd);
1113                         if (pmd_swp_uffd_wp(*src_pmd))
1114                                 pmd = pmd_swp_mkuffd_wp(pmd);
1115                         set_pmd_at(src_mm, addr, src_pmd, pmd);
1116                 }
1117                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1118                 mm_inc_nr_ptes(dst_mm);
1119                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1120                 if (!userfaultfd_wp(dst_vma))
1121                         pmd = pmd_swp_clear_uffd_wp(pmd);
1122                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1123                 ret = 0;
1124                 goto out_unlock;
1125         }
1126 #endif
1127
1128         if (unlikely(!pmd_trans_huge(pmd))) {
1129                 pte_free(dst_mm, pgtable);
1130                 goto out_unlock;
1131         }
1132         /*
1133          * When page table lock is held, the huge zero pmd should not be
1134          * under splitting since we don't split the page itself, only pmd to
1135          * a page table.
1136          */
1137         if (is_huge_zero_pmd(pmd)) {
1138                 /*
1139                  * get_huge_zero_page() will never allocate a new page here,
1140                  * since we already have a zero page to copy. It just takes a
1141                  * reference.
1142                  */
1143                 mm_get_huge_zero_page(dst_mm);
1144                 goto out_zero_page;
1145         }
1146
1147         src_page = pmd_page(pmd);
1148         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1149
1150         get_page(src_page);
1151         if (unlikely(page_try_dup_anon_rmap(src_page, true, src_vma))) {
1152                 /* Page maybe pinned: split and retry the fault on PTEs. */
1153                 put_page(src_page);
1154                 pte_free(dst_mm, pgtable);
1155                 spin_unlock(src_ptl);
1156                 spin_unlock(dst_ptl);
1157                 __split_huge_pmd(src_vma, src_pmd, addr, false, NULL);
1158                 return -EAGAIN;
1159         }
1160         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1161 out_zero_page:
1162         mm_inc_nr_ptes(dst_mm);
1163         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1164         pmdp_set_wrprotect(src_mm, addr, src_pmd);
1165         if (!userfaultfd_wp(dst_vma))
1166                 pmd = pmd_clear_uffd_wp(pmd);
1167         pmd = pmd_mkold(pmd_wrprotect(pmd));
1168         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1169
1170         ret = 0;
1171 out_unlock:
1172         spin_unlock(src_ptl);
1173         spin_unlock(dst_ptl);
1174 out:
1175         return ret;
1176 }
1177
1178 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1179 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1180                       pud_t *pud, bool write)
1181 {
1182         pud_t _pud;
1183
1184         _pud = pud_mkyoung(*pud);
1185         if (write)
1186                 _pud = pud_mkdirty(_pud);
1187         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1188                                   pud, _pud, write))
1189                 update_mmu_cache_pud(vma, addr, pud);
1190 }
1191
1192 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1193                 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1194 {
1195         unsigned long pfn = pud_pfn(*pud);
1196         struct mm_struct *mm = vma->vm_mm;
1197         struct page *page;
1198         int ret;
1199
1200         assert_spin_locked(pud_lockptr(mm, pud));
1201
1202         if (flags & FOLL_WRITE && !pud_write(*pud))
1203                 return NULL;
1204
1205         /* FOLL_GET and FOLL_PIN are mutually exclusive. */
1206         if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
1207                          (FOLL_PIN | FOLL_GET)))
1208                 return NULL;
1209
1210         if (pud_present(*pud) && pud_devmap(*pud))
1211                 /* pass */;
1212         else
1213                 return NULL;
1214
1215         if (flags & FOLL_TOUCH)
1216                 touch_pud(vma, addr, pud, flags & FOLL_WRITE);
1217
1218         /*
1219          * device mapped pages can only be returned if the
1220          * caller will manage the page reference count.
1221          *
1222          * At least one of FOLL_GET | FOLL_PIN must be set, so assert that here:
1223          */
1224         if (!(flags & (FOLL_GET | FOLL_PIN)))
1225                 return ERR_PTR(-EEXIST);
1226
1227         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1228         *pgmap = get_dev_pagemap(pfn, *pgmap);
1229         if (!*pgmap)
1230                 return ERR_PTR(-EFAULT);
1231         page = pfn_to_page(pfn);
1232
1233         ret = try_grab_page(page, flags);
1234         if (ret)
1235                 page = ERR_PTR(ret);
1236
1237         return page;
1238 }
1239
1240 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1241                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1242                   struct vm_area_struct *vma)
1243 {
1244         spinlock_t *dst_ptl, *src_ptl;
1245         pud_t pud;
1246         int ret;
1247
1248         dst_ptl = pud_lock(dst_mm, dst_pud);
1249         src_ptl = pud_lockptr(src_mm, src_pud);
1250         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1251
1252         ret = -EAGAIN;
1253         pud = *src_pud;
1254         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1255                 goto out_unlock;
1256
1257         /*
1258          * When page table lock is held, the huge zero pud should not be
1259          * under splitting since we don't split the page itself, only pud to
1260          * a page table.
1261          */
1262         if (is_huge_zero_pud(pud)) {
1263                 /* No huge zero pud yet */
1264         }
1265
1266         /*
1267          * TODO: once we support anonymous pages, use page_try_dup_anon_rmap()
1268          * and split if duplicating fails.
1269          */
1270         pudp_set_wrprotect(src_mm, addr, src_pud);
1271         pud = pud_mkold(pud_wrprotect(pud));
1272         set_pud_at(dst_mm, addr, dst_pud, pud);
1273
1274         ret = 0;
1275 out_unlock:
1276         spin_unlock(src_ptl);
1277         spin_unlock(dst_ptl);
1278         return ret;
1279 }
1280
1281 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1282 {
1283         bool write = vmf->flags & FAULT_FLAG_WRITE;
1284
1285         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1286         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1287                 goto unlock;
1288
1289         touch_pud(vmf->vma, vmf->address, vmf->pud, write);
1290 unlock:
1291         spin_unlock(vmf->ptl);
1292 }
1293 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1294
1295 void huge_pmd_set_accessed(struct vm_fault *vmf)
1296 {
1297         bool write = vmf->flags & FAULT_FLAG_WRITE;
1298
1299         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1300         if (unlikely(!pmd_same(*vmf->pmd, vmf->orig_pmd)))
1301                 goto unlock;
1302
1303         touch_pmd(vmf->vma, vmf->address, vmf->pmd, write);
1304
1305 unlock:
1306         spin_unlock(vmf->ptl);
1307 }
1308
1309 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
1310 {
1311         const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
1312         struct vm_area_struct *vma = vmf->vma;
1313         struct folio *folio;
1314         struct page *page;
1315         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1316         pmd_t orig_pmd = vmf->orig_pmd;
1317
1318         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1319         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1320
1321         if (is_huge_zero_pmd(orig_pmd))
1322                 goto fallback;
1323
1324         spin_lock(vmf->ptl);
1325
1326         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1327                 spin_unlock(vmf->ptl);
1328                 return 0;
1329         }
1330
1331         page = pmd_page(orig_pmd);
1332         folio = page_folio(page);
1333         VM_BUG_ON_PAGE(!PageHead(page), page);
1334
1335         /* Early check when only holding the PT lock. */
1336         if (PageAnonExclusive(page))
1337                 goto reuse;
1338
1339         if (!folio_trylock(folio)) {
1340                 folio_get(folio);
1341                 spin_unlock(vmf->ptl);
1342                 folio_lock(folio);
1343                 spin_lock(vmf->ptl);
1344                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1345                         spin_unlock(vmf->ptl);
1346                         folio_unlock(folio);
1347                         folio_put(folio);
1348                         return 0;
1349                 }
1350                 folio_put(folio);
1351         }
1352
1353         /* Recheck after temporarily dropping the PT lock. */
1354         if (PageAnonExclusive(page)) {
1355                 folio_unlock(folio);
1356                 goto reuse;
1357         }
1358
1359         /*
1360          * See do_wp_page(): we can only reuse the folio exclusively if
1361          * there are no additional references. Note that we always drain
1362          * the LRU pagevecs immediately after adding a THP.
1363          */
1364         if (folio_ref_count(folio) >
1365                         1 + folio_test_swapcache(folio) * folio_nr_pages(folio))
1366                 goto unlock_fallback;
1367         if (folio_test_swapcache(folio))
1368                 folio_free_swap(folio);
1369         if (folio_ref_count(folio) == 1) {
1370                 pmd_t entry;
1371
1372                 page_move_anon_rmap(page, vma);
1373                 folio_unlock(folio);
1374 reuse:
1375                 if (unlikely(unshare)) {
1376                         spin_unlock(vmf->ptl);
1377                         return 0;
1378                 }
1379                 entry = pmd_mkyoung(orig_pmd);
1380                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1381                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1))
1382                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1383                 spin_unlock(vmf->ptl);
1384                 return 0;
1385         }
1386
1387 unlock_fallback:
1388         folio_unlock(folio);
1389         spin_unlock(vmf->ptl);
1390 fallback:
1391         __split_huge_pmd(vma, vmf->pmd, vmf->address, false, NULL);
1392         return VM_FAULT_FALLBACK;
1393 }
1394
1395 static inline bool can_change_pmd_writable(struct vm_area_struct *vma,
1396                                            unsigned long addr, pmd_t pmd)
1397 {
1398         struct page *page;
1399
1400         if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE)))
1401                 return false;
1402
1403         /* Don't touch entries that are not even readable (NUMA hinting). */
1404         if (pmd_protnone(pmd))
1405                 return false;
1406
1407         /* Do we need write faults for softdirty tracking? */
1408         if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd))
1409                 return false;
1410
1411         /* Do we need write faults for uffd-wp tracking? */
1412         if (userfaultfd_huge_pmd_wp(vma, pmd))
1413                 return false;
1414
1415         if (!(vma->vm_flags & VM_SHARED)) {
1416                 /* See can_change_pte_writable(). */
1417                 page = vm_normal_page_pmd(vma, addr, pmd);
1418                 return page && PageAnon(page) && PageAnonExclusive(page);
1419         }
1420
1421         /* See can_change_pte_writable(). */
1422         return pmd_dirty(pmd);
1423 }
1424
1425 /* FOLL_FORCE can write to even unwritable PMDs in COW mappings. */
1426 static inline bool can_follow_write_pmd(pmd_t pmd, struct page *page,
1427                                         struct vm_area_struct *vma,
1428                                         unsigned int flags)
1429 {
1430         /* If the pmd is writable, we can write to the page. */
1431         if (pmd_write(pmd))
1432                 return true;
1433
1434         /* Maybe FOLL_FORCE is set to override it? */
1435         if (!(flags & FOLL_FORCE))
1436                 return false;
1437
1438         /* But FOLL_FORCE has no effect on shared mappings */
1439         if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
1440                 return false;
1441
1442         /* ... or read-only private ones */
1443         if (!(vma->vm_flags & VM_MAYWRITE))
1444                 return false;
1445
1446         /* ... or already writable ones that just need to take a write fault */
1447         if (vma->vm_flags & VM_WRITE)
1448                 return false;
1449
1450         /*
1451          * See can_change_pte_writable(): we broke COW and could map the page
1452          * writable if we have an exclusive anonymous page ...
1453          */
1454         if (!page || !PageAnon(page) || !PageAnonExclusive(page))
1455                 return false;
1456
1457         /* ... and a write-fault isn't required for other reasons. */
1458         if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd))
1459                 return false;
1460         return !userfaultfd_huge_pmd_wp(vma, pmd);
1461 }
1462
1463 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1464                                    unsigned long addr,
1465                                    pmd_t *pmd,
1466                                    unsigned int flags)
1467 {
1468         struct mm_struct *mm = vma->vm_mm;
1469         struct page *page;
1470         int ret;
1471
1472         assert_spin_locked(pmd_lockptr(mm, pmd));
1473
1474         page = pmd_page(*pmd);
1475         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1476
1477         if ((flags & FOLL_WRITE) &&
1478             !can_follow_write_pmd(*pmd, page, vma, flags))
1479                 return NULL;
1480
1481         /* Avoid dumping huge zero page */
1482         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1483                 return ERR_PTR(-EFAULT);
1484
1485         /* Full NUMA hinting faults to serialise migration in fault paths */
1486         if (pmd_protnone(*pmd) && !gup_can_follow_protnone(flags))
1487                 return NULL;
1488
1489         if (!pmd_write(*pmd) && gup_must_unshare(vma, flags, page))
1490                 return ERR_PTR(-EMLINK);
1491
1492         VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
1493                         !PageAnonExclusive(page), page);
1494
1495         ret = try_grab_page(page, flags);
1496         if (ret)
1497                 return ERR_PTR(ret);
1498
1499         if (flags & FOLL_TOUCH)
1500                 touch_pmd(vma, addr, pmd, flags & FOLL_WRITE);
1501
1502         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1503         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1504
1505         return page;
1506 }
1507
1508 /* NUMA hinting page fault entry point for trans huge pmds */
1509 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
1510 {
1511         struct vm_area_struct *vma = vmf->vma;
1512         pmd_t oldpmd = vmf->orig_pmd;
1513         pmd_t pmd;
1514         struct page *page;
1515         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1516         int page_nid = NUMA_NO_NODE;
1517         int target_nid, last_cpupid = (-1 & LAST_CPUPID_MASK);
1518         bool migrated = false, writable = false;
1519         int flags = 0;
1520
1521         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1522         if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) {
1523                 spin_unlock(vmf->ptl);
1524                 goto out;
1525         }
1526
1527         pmd = pmd_modify(oldpmd, vma->vm_page_prot);
1528
1529         /*
1530          * Detect now whether the PMD could be writable; this information
1531          * is only valid while holding the PT lock.
1532          */
1533         writable = pmd_write(pmd);
1534         if (!writable && vma_wants_manual_pte_write_upgrade(vma) &&
1535             can_change_pmd_writable(vma, vmf->address, pmd))
1536                 writable = true;
1537
1538         page = vm_normal_page_pmd(vma, haddr, pmd);
1539         if (!page)
1540                 goto out_map;
1541
1542         /* See similar comment in do_numa_page for explanation */
1543         if (!writable)
1544                 flags |= TNF_NO_GROUP;
1545
1546         page_nid = page_to_nid(page);
1547         /*
1548          * For memory tiering mode, cpupid of slow memory page is used
1549          * to record page access time.  So use default value.
1550          */
1551         if (node_is_toptier(page_nid))
1552                 last_cpupid = page_cpupid_last(page);
1553         target_nid = numa_migrate_prep(page, vma, haddr, page_nid,
1554                                        &flags);
1555
1556         if (target_nid == NUMA_NO_NODE) {
1557                 put_page(page);
1558                 goto out_map;
1559         }
1560
1561         spin_unlock(vmf->ptl);
1562         writable = false;
1563
1564         migrated = migrate_misplaced_page(page, vma, target_nid);
1565         if (migrated) {
1566                 flags |= TNF_MIGRATED;
1567                 page_nid = target_nid;
1568         } else {
1569                 flags |= TNF_MIGRATE_FAIL;
1570                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1571                 if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) {
1572                         spin_unlock(vmf->ptl);
1573                         goto out;
1574                 }
1575                 goto out_map;
1576         }
1577
1578 out:
1579         if (page_nid != NUMA_NO_NODE)
1580                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1581                                 flags);
1582
1583         return 0;
1584
1585 out_map:
1586         /* Restore the PMD */
1587         pmd = pmd_modify(oldpmd, vma->vm_page_prot);
1588         pmd = pmd_mkyoung(pmd);
1589         if (writable)
1590                 pmd = pmd_mkwrite(pmd);
1591         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1592         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1593         spin_unlock(vmf->ptl);
1594         goto out;
1595 }
1596
1597 /*
1598  * Return true if we do MADV_FREE successfully on entire pmd page.
1599  * Otherwise, return false.
1600  */
1601 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1602                 pmd_t *pmd, unsigned long addr, unsigned long next)
1603 {
1604         spinlock_t *ptl;
1605         pmd_t orig_pmd;
1606         struct page *page;
1607         struct mm_struct *mm = tlb->mm;
1608         bool ret = false;
1609
1610         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1611
1612         ptl = pmd_trans_huge_lock(pmd, vma);
1613         if (!ptl)
1614                 goto out_unlocked;
1615
1616         orig_pmd = *pmd;
1617         if (is_huge_zero_pmd(orig_pmd))
1618                 goto out;
1619
1620         if (unlikely(!pmd_present(orig_pmd))) {
1621                 VM_BUG_ON(thp_migration_supported() &&
1622                                   !is_pmd_migration_entry(orig_pmd));
1623                 goto out;
1624         }
1625
1626         page = pmd_page(orig_pmd);
1627         /*
1628          * If other processes are mapping this page, we couldn't discard
1629          * the page unless they all do MADV_FREE so let's skip the page.
1630          */
1631         if (total_mapcount(page) != 1)
1632                 goto out;
1633
1634         if (!trylock_page(page))
1635                 goto out;
1636
1637         /*
1638          * If user want to discard part-pages of THP, split it so MADV_FREE
1639          * will deactivate only them.
1640          */
1641         if (next - addr != HPAGE_PMD_SIZE) {
1642                 get_page(page);
1643                 spin_unlock(ptl);
1644                 split_huge_page(page);
1645                 unlock_page(page);
1646                 put_page(page);
1647                 goto out_unlocked;
1648         }
1649
1650         if (PageDirty(page))
1651                 ClearPageDirty(page);
1652         unlock_page(page);
1653
1654         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1655                 pmdp_invalidate(vma, addr, pmd);
1656                 orig_pmd = pmd_mkold(orig_pmd);
1657                 orig_pmd = pmd_mkclean(orig_pmd);
1658
1659                 set_pmd_at(mm, addr, pmd, orig_pmd);
1660                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1661         }
1662
1663         mark_page_lazyfree(page);
1664         ret = true;
1665 out:
1666         spin_unlock(ptl);
1667 out_unlocked:
1668         return ret;
1669 }
1670
1671 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1672 {
1673         pgtable_t pgtable;
1674
1675         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1676         pte_free(mm, pgtable);
1677         mm_dec_nr_ptes(mm);
1678 }
1679
1680 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1681                  pmd_t *pmd, unsigned long addr)
1682 {
1683         pmd_t orig_pmd;
1684         spinlock_t *ptl;
1685
1686         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1687
1688         ptl = __pmd_trans_huge_lock(pmd, vma);
1689         if (!ptl)
1690                 return 0;
1691         /*
1692          * For architectures like ppc64 we look at deposited pgtable
1693          * when calling pmdp_huge_get_and_clear. So do the
1694          * pgtable_trans_huge_withdraw after finishing pmdp related
1695          * operations.
1696          */
1697         orig_pmd = pmdp_huge_get_and_clear_full(vma, addr, pmd,
1698                                                 tlb->fullmm);
1699         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1700         if (vma_is_special_huge(vma)) {
1701                 if (arch_needs_pgtable_deposit())
1702                         zap_deposited_table(tlb->mm, pmd);
1703                 spin_unlock(ptl);
1704         } else if (is_huge_zero_pmd(orig_pmd)) {
1705                 zap_deposited_table(tlb->mm, pmd);
1706                 spin_unlock(ptl);
1707         } else {
1708                 struct page *page = NULL;
1709                 int flush_needed = 1;
1710
1711                 if (pmd_present(orig_pmd)) {
1712                         page = pmd_page(orig_pmd);
1713                         page_remove_rmap(page, vma, true);
1714                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1715                         VM_BUG_ON_PAGE(!PageHead(page), page);
1716                 } else if (thp_migration_supported()) {
1717                         swp_entry_t entry;
1718
1719                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1720                         entry = pmd_to_swp_entry(orig_pmd);
1721                         page = pfn_swap_entry_to_page(entry);
1722                         flush_needed = 0;
1723                 } else
1724                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1725
1726                 if (PageAnon(page)) {
1727                         zap_deposited_table(tlb->mm, pmd);
1728                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1729                 } else {
1730                         if (arch_needs_pgtable_deposit())
1731                                 zap_deposited_table(tlb->mm, pmd);
1732                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1733                 }
1734
1735                 spin_unlock(ptl);
1736                 if (flush_needed)
1737                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1738         }
1739         return 1;
1740 }
1741
1742 #ifndef pmd_move_must_withdraw
1743 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1744                                          spinlock_t *old_pmd_ptl,
1745                                          struct vm_area_struct *vma)
1746 {
1747         /*
1748          * With split pmd lock we also need to move preallocated
1749          * PTE page table if new_pmd is on different PMD page table.
1750          *
1751          * We also don't deposit and withdraw tables for file pages.
1752          */
1753         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1754 }
1755 #endif
1756
1757 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1758 {
1759 #ifdef CONFIG_MEM_SOFT_DIRTY
1760         if (unlikely(is_pmd_migration_entry(pmd)))
1761                 pmd = pmd_swp_mksoft_dirty(pmd);
1762         else if (pmd_present(pmd))
1763                 pmd = pmd_mksoft_dirty(pmd);
1764 #endif
1765         return pmd;
1766 }
1767
1768 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1769                   unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
1770 {
1771         spinlock_t *old_ptl, *new_ptl;
1772         pmd_t pmd;
1773         struct mm_struct *mm = vma->vm_mm;
1774         bool force_flush = false;
1775
1776         /*
1777          * The destination pmd shouldn't be established, free_pgtables()
1778          * should have release it.
1779          */
1780         if (WARN_ON(!pmd_none(*new_pmd))) {
1781                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1782                 return false;
1783         }
1784
1785         /*
1786          * We don't have to worry about the ordering of src and dst
1787          * ptlocks because exclusive mmap_lock prevents deadlock.
1788          */
1789         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1790         if (old_ptl) {
1791                 new_ptl = pmd_lockptr(mm, new_pmd);
1792                 if (new_ptl != old_ptl)
1793                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1794                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1795                 if (pmd_present(pmd))
1796                         force_flush = true;
1797                 VM_BUG_ON(!pmd_none(*new_pmd));
1798
1799                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1800                         pgtable_t pgtable;
1801                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1802                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1803                 }
1804                 pmd = move_soft_dirty_pmd(pmd);
1805                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1806                 if (force_flush)
1807                         flush_pmd_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1808                 if (new_ptl != old_ptl)
1809                         spin_unlock(new_ptl);
1810                 spin_unlock(old_ptl);
1811                 return true;
1812         }
1813         return false;
1814 }
1815
1816 /*
1817  * Returns
1818  *  - 0 if PMD could not be locked
1819  *  - 1 if PMD was locked but protections unchanged and TLB flush unnecessary
1820  *      or if prot_numa but THP migration is not supported
1821  *  - HPAGE_PMD_NR if protections changed and TLB flush necessary
1822  */
1823 int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1824                     pmd_t *pmd, unsigned long addr, pgprot_t newprot,
1825                     unsigned long cp_flags)
1826 {
1827         struct mm_struct *mm = vma->vm_mm;
1828         spinlock_t *ptl;
1829         pmd_t oldpmd, entry;
1830         bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
1831         bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
1832         bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
1833         int ret = 1;
1834
1835         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1836
1837         if (prot_numa && !thp_migration_supported())
1838                 return 1;
1839
1840         ptl = __pmd_trans_huge_lock(pmd, vma);
1841         if (!ptl)
1842                 return 0;
1843
1844 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1845         if (is_swap_pmd(*pmd)) {
1846                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1847                 struct page *page = pfn_swap_entry_to_page(entry);
1848
1849                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1850                 if (is_writable_migration_entry(entry)) {
1851                         pmd_t newpmd;
1852                         /*
1853                          * A protection check is difficult so
1854                          * just be safe and disable write
1855                          */
1856                         if (PageAnon(page))
1857                                 entry = make_readable_exclusive_migration_entry(swp_offset(entry));
1858                         else
1859                                 entry = make_readable_migration_entry(swp_offset(entry));
1860                         newpmd = swp_entry_to_pmd(entry);
1861                         if (pmd_swp_soft_dirty(*pmd))
1862                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1863                         if (pmd_swp_uffd_wp(*pmd))
1864                                 newpmd = pmd_swp_mkuffd_wp(newpmd);
1865                         set_pmd_at(mm, addr, pmd, newpmd);
1866                 }
1867                 goto unlock;
1868         }
1869 #endif
1870
1871         if (prot_numa) {
1872                 struct page *page;
1873                 bool toptier;
1874                 /*
1875                  * Avoid trapping faults against the zero page. The read-only
1876                  * data is likely to be read-cached on the local CPU and
1877                  * local/remote hits to the zero page are not interesting.
1878                  */
1879                 if (is_huge_zero_pmd(*pmd))
1880                         goto unlock;
1881
1882                 if (pmd_protnone(*pmd))
1883                         goto unlock;
1884
1885                 page = pmd_page(*pmd);
1886                 toptier = node_is_toptier(page_to_nid(page));
1887                 /*
1888                  * Skip scanning top tier node if normal numa
1889                  * balancing is disabled
1890                  */
1891                 if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) &&
1892                     toptier)
1893                         goto unlock;
1894
1895                 if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
1896                     !toptier)
1897                         xchg_page_access_time(page, jiffies_to_msecs(jiffies));
1898         }
1899         /*
1900          * In case prot_numa, we are under mmap_read_lock(mm). It's critical
1901          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1902          * which is also under mmap_read_lock(mm):
1903          *
1904          *      CPU0:                           CPU1:
1905          *                              change_huge_pmd(prot_numa=1)
1906          *                               pmdp_huge_get_and_clear_notify()
1907          * madvise_dontneed()
1908          *  zap_pmd_range()
1909          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1910          *   // skip the pmd
1911          *                               set_pmd_at();
1912          *                               // pmd is re-established
1913          *
1914          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1915          * which may break userspace.
1916          *
1917          * pmdp_invalidate_ad() is required to make sure we don't miss
1918          * dirty/young flags set by hardware.
1919          */
1920         oldpmd = pmdp_invalidate_ad(vma, addr, pmd);
1921
1922         entry = pmd_modify(oldpmd, newprot);
1923         if (uffd_wp) {
1924                 entry = pmd_wrprotect(entry);
1925                 entry = pmd_mkuffd_wp(entry);
1926         } else if (uffd_wp_resolve) {
1927                 /*
1928                  * Leave the write bit to be handled by PF interrupt
1929                  * handler, then things like COW could be properly
1930                  * handled.
1931                  */
1932                 entry = pmd_clear_uffd_wp(entry);
1933         }
1934
1935         /* See change_pte_range(). */
1936         if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && !pmd_write(entry) &&
1937             can_change_pmd_writable(vma, addr, entry))
1938                 entry = pmd_mkwrite(entry);
1939
1940         ret = HPAGE_PMD_NR;
1941         set_pmd_at(mm, addr, pmd, entry);
1942
1943         if (huge_pmd_needs_flush(oldpmd, entry))
1944                 tlb_flush_pmd_range(tlb, addr, HPAGE_PMD_SIZE);
1945 unlock:
1946         spin_unlock(ptl);
1947         return ret;
1948 }
1949
1950 /*
1951  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1952  *
1953  * Note that if it returns page table lock pointer, this routine returns without
1954  * unlocking page table lock. So callers must unlock it.
1955  */
1956 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1957 {
1958         spinlock_t *ptl;
1959         ptl = pmd_lock(vma->vm_mm, pmd);
1960         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1961                         pmd_devmap(*pmd)))
1962                 return ptl;
1963         spin_unlock(ptl);
1964         return NULL;
1965 }
1966
1967 /*
1968  * Returns page table lock pointer if a given pud maps a thp, NULL otherwise.
1969  *
1970  * Note that if it returns page table lock pointer, this routine returns without
1971  * unlocking page table lock. So callers must unlock it.
1972  */
1973 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1974 {
1975         spinlock_t *ptl;
1976
1977         ptl = pud_lock(vma->vm_mm, pud);
1978         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1979                 return ptl;
1980         spin_unlock(ptl);
1981         return NULL;
1982 }
1983
1984 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1985 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1986                  pud_t *pud, unsigned long addr)
1987 {
1988         spinlock_t *ptl;
1989
1990         ptl = __pud_trans_huge_lock(pud, vma);
1991         if (!ptl)
1992                 return 0;
1993
1994         pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
1995         tlb_remove_pud_tlb_entry(tlb, pud, addr);
1996         if (vma_is_special_huge(vma)) {
1997                 spin_unlock(ptl);
1998                 /* No zero page support yet */
1999         } else {
2000                 /* No support for anonymous PUD pages yet */
2001                 BUG();
2002         }
2003         return 1;
2004 }
2005
2006 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2007                 unsigned long haddr)
2008 {
2009         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2010         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2011         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2012         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2013
2014         count_vm_event(THP_SPLIT_PUD);
2015
2016         pudp_huge_clear_flush_notify(vma, haddr, pud);
2017 }
2018
2019 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2020                 unsigned long address)
2021 {
2022         spinlock_t *ptl;
2023         struct mmu_notifier_range range;
2024
2025         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2026                                 address & HPAGE_PUD_MASK,
2027                                 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
2028         mmu_notifier_invalidate_range_start(&range);
2029         ptl = pud_lock(vma->vm_mm, pud);
2030         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2031                 goto out;
2032         __split_huge_pud_locked(vma, pud, range.start);
2033
2034 out:
2035         spin_unlock(ptl);
2036         /*
2037          * No need to double call mmu_notifier->invalidate_range() callback as
2038          * the above pudp_huge_clear_flush_notify() did already call it.
2039          */
2040         mmu_notifier_invalidate_range_only_end(&range);
2041 }
2042 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2043
2044 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2045                 unsigned long haddr, pmd_t *pmd)
2046 {
2047         struct mm_struct *mm = vma->vm_mm;
2048         pgtable_t pgtable;
2049         pmd_t _pmd;
2050         int i;
2051
2052         /*
2053          * Leave pmd empty until pte is filled note that it is fine to delay
2054          * notification until mmu_notifier_invalidate_range_end() as we are
2055          * replacing a zero pmd write protected page with a zero pte write
2056          * protected page.
2057          *
2058          * See Documentation/mm/mmu_notifier.rst
2059          */
2060         pmdp_huge_clear_flush(vma, haddr, pmd);
2061
2062         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2063         pmd_populate(mm, &_pmd, pgtable);
2064
2065         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2066                 pte_t *pte, entry;
2067                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2068                 entry = pte_mkspecial(entry);
2069                 pte = pte_offset_map(&_pmd, haddr);
2070                 VM_BUG_ON(!pte_none(*pte));
2071                 set_pte_at(mm, haddr, pte, entry);
2072                 pte_unmap(pte);
2073         }
2074         smp_wmb(); /* make pte visible before pmd */
2075         pmd_populate(mm, pmd, pgtable);
2076 }
2077
2078 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2079                 unsigned long haddr, bool freeze)
2080 {
2081         struct mm_struct *mm = vma->vm_mm;
2082         struct page *page;
2083         pgtable_t pgtable;
2084         pmd_t old_pmd, _pmd;
2085         bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false;
2086         bool anon_exclusive = false, dirty = false;
2087         unsigned long addr;
2088         int i;
2089
2090         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2091         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2092         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2093         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2094                                 && !pmd_devmap(*pmd));
2095
2096         count_vm_event(THP_SPLIT_PMD);
2097
2098         if (!vma_is_anonymous(vma)) {
2099                 old_pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2100                 /*
2101                  * We are going to unmap this huge page. So
2102                  * just go ahead and zap it
2103                  */
2104                 if (arch_needs_pgtable_deposit())
2105                         zap_deposited_table(mm, pmd);
2106                 if (vma_is_special_huge(vma))
2107                         return;
2108                 if (unlikely(is_pmd_migration_entry(old_pmd))) {
2109                         swp_entry_t entry;
2110
2111                         entry = pmd_to_swp_entry(old_pmd);
2112                         page = pfn_swap_entry_to_page(entry);
2113                 } else {
2114                         page = pmd_page(old_pmd);
2115                         if (!PageDirty(page) && pmd_dirty(old_pmd))
2116                                 set_page_dirty(page);
2117                         if (!PageReferenced(page) && pmd_young(old_pmd))
2118                                 SetPageReferenced(page);
2119                         page_remove_rmap(page, vma, true);
2120                         put_page(page);
2121                 }
2122                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2123                 return;
2124         }
2125
2126         if (is_huge_zero_pmd(*pmd)) {
2127                 /*
2128                  * FIXME: Do we want to invalidate secondary mmu by calling
2129                  * mmu_notifier_invalidate_range() see comments below inside
2130                  * __split_huge_pmd() ?
2131                  *
2132                  * We are going from a zero huge page write protected to zero
2133                  * small page also write protected so it does not seems useful
2134                  * to invalidate secondary mmu at this time.
2135                  */
2136                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2137         }
2138
2139         /*
2140          * Up to this point the pmd is present and huge and userland has the
2141          * whole access to the hugepage during the split (which happens in
2142          * place). If we overwrite the pmd with the not-huge version pointing
2143          * to the pte here (which of course we could if all CPUs were bug
2144          * free), userland could trigger a small page size TLB miss on the
2145          * small sized TLB while the hugepage TLB entry is still established in
2146          * the huge TLB. Some CPU doesn't like that.
2147          * See http://support.amd.com/TechDocs/41322_10h_Rev_Gd.pdf, Erratum
2148          * 383 on page 105. Intel should be safe but is also warns that it's
2149          * only safe if the permission and cache attributes of the two entries
2150          * loaded in the two TLB is identical (which should be the case here).
2151          * But it is generally safer to never allow small and huge TLB entries
2152          * for the same virtual address to be loaded simultaneously. So instead
2153          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2154          * current pmd notpresent (atomically because here the pmd_trans_huge
2155          * must remain set at all times on the pmd until the split is complete
2156          * for this pmd), then we flush the SMP TLB and finally we write the
2157          * non-huge version of the pmd entry with pmd_populate.
2158          */
2159         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2160
2161         pmd_migration = is_pmd_migration_entry(old_pmd);
2162         if (unlikely(pmd_migration)) {
2163                 swp_entry_t entry;
2164
2165                 entry = pmd_to_swp_entry(old_pmd);
2166                 page = pfn_swap_entry_to_page(entry);
2167                 write = is_writable_migration_entry(entry);
2168                 if (PageAnon(page))
2169                         anon_exclusive = is_readable_exclusive_migration_entry(entry);
2170                 young = is_migration_entry_young(entry);
2171                 dirty = is_migration_entry_dirty(entry);
2172                 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2173                 uffd_wp = pmd_swp_uffd_wp(old_pmd);
2174         } else {
2175                 page = pmd_page(old_pmd);
2176                 if (pmd_dirty(old_pmd)) {
2177                         dirty = true;
2178                         SetPageDirty(page);
2179                 }
2180                 write = pmd_write(old_pmd);
2181                 young = pmd_young(old_pmd);
2182                 soft_dirty = pmd_soft_dirty(old_pmd);
2183                 uffd_wp = pmd_uffd_wp(old_pmd);
2184
2185                 VM_BUG_ON_PAGE(!page_count(page), page);
2186
2187                 /*
2188                  * Without "freeze", we'll simply split the PMD, propagating the
2189                  * PageAnonExclusive() flag for each PTE by setting it for
2190                  * each subpage -- no need to (temporarily) clear.
2191                  *
2192                  * With "freeze" we want to replace mapped pages by
2193                  * migration entries right away. This is only possible if we
2194                  * managed to clear PageAnonExclusive() -- see
2195                  * set_pmd_migration_entry().
2196                  *
2197                  * In case we cannot clear PageAnonExclusive(), split the PMD
2198                  * only and let try_to_migrate_one() fail later.
2199                  *
2200                  * See page_try_share_anon_rmap(): invalidate PMD first.
2201                  */
2202                 anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
2203                 if (freeze && anon_exclusive && page_try_share_anon_rmap(page))
2204                         freeze = false;
2205                 if (!freeze)
2206                         page_ref_add(page, HPAGE_PMD_NR - 1);
2207         }
2208
2209         /*
2210          * Withdraw the table only after we mark the pmd entry invalid.
2211          * This's critical for some architectures (Power).
2212          */
2213         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2214         pmd_populate(mm, &_pmd, pgtable);
2215
2216         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2217                 pte_t entry, *pte;
2218                 /*
2219                  * Note that NUMA hinting access restrictions are not
2220                  * transferred to avoid any possibility of altering
2221                  * permissions across VMAs.
2222                  */
2223                 if (freeze || pmd_migration) {
2224                         swp_entry_t swp_entry;
2225                         if (write)
2226                                 swp_entry = make_writable_migration_entry(
2227                                                         page_to_pfn(page + i));
2228                         else if (anon_exclusive)
2229                                 swp_entry = make_readable_exclusive_migration_entry(
2230                                                         page_to_pfn(page + i));
2231                         else
2232                                 swp_entry = make_readable_migration_entry(
2233                                                         page_to_pfn(page + i));
2234                         if (young)
2235                                 swp_entry = make_migration_entry_young(swp_entry);
2236                         if (dirty)
2237                                 swp_entry = make_migration_entry_dirty(swp_entry);
2238                         entry = swp_entry_to_pte(swp_entry);
2239                         if (soft_dirty)
2240                                 entry = pte_swp_mksoft_dirty(entry);
2241                         if (uffd_wp)
2242                                 entry = pte_swp_mkuffd_wp(entry);
2243                 } else {
2244                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2245                         entry = maybe_mkwrite(entry, vma);
2246                         if (anon_exclusive)
2247                                 SetPageAnonExclusive(page + i);
2248                         if (!young)
2249                                 entry = pte_mkold(entry);
2250                         /* NOTE: this may set soft-dirty too on some archs */
2251                         if (dirty)
2252                                 entry = pte_mkdirty(entry);
2253                         /*
2254                          * NOTE: this needs to happen after pte_mkdirty,
2255                          * because some archs (sparc64, loongarch) could
2256                          * set hw write bit when mkdirty.
2257                          */
2258                         if (!write)
2259                                 entry = pte_wrprotect(entry);
2260                         if (soft_dirty)
2261                                 entry = pte_mksoft_dirty(entry);
2262                         if (uffd_wp)
2263                                 entry = pte_mkuffd_wp(entry);
2264                         page_add_anon_rmap(page + i, vma, addr, false);
2265                 }
2266                 pte = pte_offset_map(&_pmd, addr);
2267                 BUG_ON(!pte_none(*pte));
2268                 set_pte_at(mm, addr, pte, entry);
2269                 pte_unmap(pte);
2270         }
2271
2272         if (!pmd_migration)
2273                 page_remove_rmap(page, vma, true);
2274         if (freeze)
2275                 put_page(page);
2276
2277         smp_wmb(); /* make pte visible before pmd */
2278         pmd_populate(mm, pmd, pgtable);
2279 }
2280
2281 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2282                 unsigned long address, bool freeze, struct folio *folio)
2283 {
2284         spinlock_t *ptl;
2285         struct mmu_notifier_range range;
2286
2287         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2288                                 address & HPAGE_PMD_MASK,
2289                                 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2290         mmu_notifier_invalidate_range_start(&range);
2291         ptl = pmd_lock(vma->vm_mm, pmd);
2292
2293         /*
2294          * If caller asks to setup a migration entry, we need a folio to check
2295          * pmd against. Otherwise we can end up replacing wrong folio.
2296          */
2297         VM_BUG_ON(freeze && !folio);
2298         VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
2299
2300         if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
2301             is_pmd_migration_entry(*pmd)) {
2302                 /*
2303                  * It's safe to call pmd_page when folio is set because it's
2304                  * guaranteed that pmd is present.
2305                  */
2306                 if (folio && folio != page_folio(pmd_page(*pmd)))
2307                         goto out;
2308                 __split_huge_pmd_locked(vma, pmd, range.start, freeze);
2309         }
2310
2311 out:
2312         spin_unlock(ptl);
2313         /*
2314          * No need to double call mmu_notifier->invalidate_range() callback.
2315          * They are 3 cases to consider inside __split_huge_pmd_locked():
2316          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2317          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2318          *    fault will trigger a flush_notify before pointing to a new page
2319          *    (it is fine if the secondary mmu keeps pointing to the old zero
2320          *    page in the meantime)
2321          *  3) Split a huge pmd into pte pointing to the same page. No need
2322          *     to invalidate secondary tlb entry they are all still valid.
2323          *     any further changes to individual pte will notify. So no need
2324          *     to call mmu_notifier->invalidate_range()
2325          */
2326         mmu_notifier_invalidate_range_only_end(&range);
2327 }
2328
2329 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2330                 bool freeze, struct folio *folio)
2331 {
2332         pmd_t *pmd = mm_find_pmd(vma->vm_mm, address);
2333
2334         if (!pmd)
2335                 return;
2336
2337         __split_huge_pmd(vma, pmd, address, freeze, folio);
2338 }
2339
2340 static inline void split_huge_pmd_if_needed(struct vm_area_struct *vma, unsigned long address)
2341 {
2342         /*
2343          * If the new address isn't hpage aligned and it could previously
2344          * contain an hugepage: check if we need to split an huge pmd.
2345          */
2346         if (!IS_ALIGNED(address, HPAGE_PMD_SIZE) &&
2347             range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PMD_SIZE),
2348                          ALIGN(address, HPAGE_PMD_SIZE)))
2349                 split_huge_pmd_address(vma, address, false, NULL);
2350 }
2351
2352 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2353                              unsigned long start,
2354                              unsigned long end,
2355                              long adjust_next)
2356 {
2357         /* Check if we need to split start first. */
2358         split_huge_pmd_if_needed(vma, start);
2359
2360         /* Check if we need to split end next. */
2361         split_huge_pmd_if_needed(vma, end);
2362
2363         /*
2364          * If we're also updating the next vma vm_start,
2365          * check if we need to split it.
2366          */
2367         if (adjust_next > 0) {
2368                 struct vm_area_struct *next = find_vma(vma->vm_mm, vma->vm_end);
2369                 unsigned long nstart = next->vm_start;
2370                 nstart += adjust_next;
2371                 split_huge_pmd_if_needed(next, nstart);
2372         }
2373 }
2374
2375 static void unmap_folio(struct folio *folio)
2376 {
2377         enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD |
2378                 TTU_SYNC;
2379
2380         VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
2381
2382         /*
2383          * Anon pages need migration entries to preserve them, but file
2384          * pages can simply be left unmapped, then faulted back on demand.
2385          * If that is ever changed (perhaps for mlock), update remap_page().
2386          */
2387         if (folio_test_anon(folio))
2388                 try_to_migrate(folio, ttu_flags);
2389         else
2390                 try_to_unmap(folio, ttu_flags | TTU_IGNORE_MLOCK);
2391 }
2392
2393 static void remap_page(struct folio *folio, unsigned long nr)
2394 {
2395         int i = 0;
2396
2397         /* If unmap_folio() uses try_to_migrate() on file, remove this check */
2398         if (!folio_test_anon(folio))
2399                 return;
2400         for (;;) {
2401                 remove_migration_ptes(folio, folio, true);
2402                 i += folio_nr_pages(folio);
2403                 if (i >= nr)
2404                         break;
2405                 folio = folio_next(folio);
2406         }
2407 }
2408
2409 static void lru_add_page_tail(struct page *head, struct page *tail,
2410                 struct lruvec *lruvec, struct list_head *list)
2411 {
2412         VM_BUG_ON_PAGE(!PageHead(head), head);
2413         VM_BUG_ON_PAGE(PageCompound(tail), head);
2414         VM_BUG_ON_PAGE(PageLRU(tail), head);
2415         lockdep_assert_held(&lruvec->lru_lock);
2416
2417         if (list) {
2418                 /* page reclaim is reclaiming a huge page */
2419                 VM_WARN_ON(PageLRU(head));
2420                 get_page(tail);
2421                 list_add_tail(&tail->lru, list);
2422         } else {
2423                 /* head is still on lru (and we have it frozen) */
2424                 VM_WARN_ON(!PageLRU(head));
2425                 if (PageUnevictable(tail))
2426                         tail->mlock_count = 0;
2427                 else
2428                         list_add_tail(&tail->lru, &head->lru);
2429                 SetPageLRU(tail);
2430         }
2431 }
2432
2433 static void __split_huge_page_tail(struct page *head, int tail,
2434                 struct lruvec *lruvec, struct list_head *list)
2435 {
2436         struct page *page_tail = head + tail;
2437
2438         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2439
2440         /*
2441          * Clone page flags before unfreezing refcount.
2442          *
2443          * After successful get_page_unless_zero() might follow flags change,
2444          * for example lock_page() which set PG_waiters.
2445          *
2446          * Note that for mapped sub-pages of an anonymous THP,
2447          * PG_anon_exclusive has been cleared in unmap_folio() and is stored in
2448          * the migration entry instead from where remap_page() will restore it.
2449          * We can still have PG_anon_exclusive set on effectively unmapped and
2450          * unreferenced sub-pages of an anonymous THP: we can simply drop
2451          * PG_anon_exclusive (-> PG_mappedtodisk) for these here.
2452          */
2453         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2454         page_tail->flags |= (head->flags &
2455                         ((1L << PG_referenced) |
2456                          (1L << PG_swapbacked) |
2457                          (1L << PG_swapcache) |
2458                          (1L << PG_mlocked) |
2459                          (1L << PG_uptodate) |
2460                          (1L << PG_active) |
2461                          (1L << PG_workingset) |
2462                          (1L << PG_locked) |
2463                          (1L << PG_unevictable) |
2464 #ifdef CONFIG_ARCH_USES_PG_ARCH_X
2465                          (1L << PG_arch_2) |
2466                          (1L << PG_arch_3) |
2467 #endif
2468                          (1L << PG_dirty) |
2469                          LRU_GEN_MASK | LRU_REFS_MASK));
2470
2471         /* ->mapping in first and second tail page is replaced by other uses */
2472         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2473                         page_tail);
2474         page_tail->mapping = head->mapping;
2475         page_tail->index = head->index + tail;
2476
2477         /*
2478          * page->private should not be set in tail pages with the exception
2479          * of swap cache pages that store the swp_entry_t in tail pages.
2480          * Fix up and warn once if private is unexpectedly set.
2481          *
2482          * What of 32-bit systems, on which head[1].compound_pincount overlays
2483          * head[1].private?  No problem: THP_SWAP is not enabled on 32-bit, and
2484          * compound_pincount must be 0 for folio_ref_freeze() to have succeeded.
2485          */
2486         if (!folio_test_swapcache(page_folio(head))) {
2487                 VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, page_tail);
2488                 page_tail->private = 0;
2489         }
2490
2491         /* Page flags must be visible before we make the page non-compound. */
2492         smp_wmb();
2493
2494         /*
2495          * Clear PageTail before unfreezing page refcount.
2496          *
2497          * After successful get_page_unless_zero() might follow put_page()
2498          * which needs correct compound_head().
2499          */
2500         clear_compound_head(page_tail);
2501
2502         /* Finally unfreeze refcount. Additional reference from page cache. */
2503         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2504                                           PageSwapCache(head)));
2505
2506         if (page_is_young(head))
2507                 set_page_young(page_tail);
2508         if (page_is_idle(head))
2509                 set_page_idle(page_tail);
2510
2511         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2512
2513         /*
2514          * always add to the tail because some iterators expect new
2515          * pages to show after the currently processed elements - e.g.
2516          * migrate_pages
2517          */
2518         lru_add_page_tail(head, page_tail, lruvec, list);
2519 }
2520
2521 static void __split_huge_page(struct page *page, struct list_head *list,
2522                 pgoff_t end)
2523 {
2524         struct folio *folio = page_folio(page);
2525         struct page *head = &folio->page;
2526         struct lruvec *lruvec;
2527         struct address_space *swap_cache = NULL;
2528         unsigned long offset = 0;
2529         unsigned int nr = thp_nr_pages(head);
2530         int i;
2531
2532         /* complete memcg works before add pages to LRU */
2533         split_page_memcg(head, nr);
2534
2535         if (PageAnon(head) && PageSwapCache(head)) {
2536                 swp_entry_t entry = { .val = page_private(head) };
2537
2538                 offset = swp_offset(entry);
2539                 swap_cache = swap_address_space(entry);
2540                 xa_lock(&swap_cache->i_pages);
2541         }
2542
2543         /* lock lru list/PageCompound, ref frozen by page_ref_freeze */
2544         lruvec = folio_lruvec_lock(folio);
2545
2546         ClearPageHasHWPoisoned(head);
2547
2548         for (i = nr - 1; i >= 1; i--) {
2549                 __split_huge_page_tail(head, i, lruvec, list);
2550                 /* Some pages can be beyond EOF: drop them from page cache */
2551                 if (head[i].index >= end) {
2552                         struct folio *tail = page_folio(head + i);
2553
2554                         if (shmem_mapping(head->mapping))
2555                                 shmem_uncharge(head->mapping->host, 1);
2556                         else if (folio_test_clear_dirty(tail))
2557                                 folio_account_cleaned(tail,
2558                                         inode_to_wb(folio->mapping->host));
2559                         __filemap_remove_folio(tail, NULL);
2560                         folio_put(tail);
2561                 } else if (!PageAnon(page)) {
2562                         __xa_store(&head->mapping->i_pages, head[i].index,
2563                                         head + i, 0);
2564                 } else if (swap_cache) {
2565                         __xa_store(&swap_cache->i_pages, offset + i,
2566                                         head + i, 0);
2567                 }
2568         }
2569
2570         ClearPageCompound(head);
2571         unlock_page_lruvec(lruvec);
2572         /* Caller disabled irqs, so they are still disabled here */
2573
2574         split_page_owner(head, nr);
2575
2576         /* See comment in __split_huge_page_tail() */
2577         if (PageAnon(head)) {
2578                 /* Additional pin to swap cache */
2579                 if (PageSwapCache(head)) {
2580                         page_ref_add(head, 2);
2581                         xa_unlock(&swap_cache->i_pages);
2582                 } else {
2583                         page_ref_inc(head);
2584                 }
2585         } else {
2586                 /* Additional pin to page cache */
2587                 page_ref_add(head, 2);
2588                 xa_unlock(&head->mapping->i_pages);
2589         }
2590         local_irq_enable();
2591
2592         remap_page(folio, nr);
2593
2594         if (PageSwapCache(head)) {
2595                 swp_entry_t entry = { .val = page_private(head) };
2596
2597                 split_swap_cluster(entry);
2598         }
2599
2600         for (i = 0; i < nr; i++) {
2601                 struct page *subpage = head + i;
2602                 if (subpage == page)
2603                         continue;
2604                 unlock_page(subpage);
2605
2606                 /*
2607                  * Subpages may be freed if there wasn't any mapping
2608                  * like if add_to_swap() is running on a lru page that
2609                  * had its mapping zapped. And freeing these pages
2610                  * requires taking the lru_lock so we do the put_page
2611                  * of the tail pages after the split is complete.
2612                  */
2613                 free_page_and_swap_cache(subpage);
2614         }
2615 }
2616
2617 /* Racy check whether the huge page can be split */
2618 bool can_split_folio(struct folio *folio, int *pextra_pins)
2619 {
2620         int extra_pins;
2621
2622         /* Additional pins from page cache */
2623         if (folio_test_anon(folio))
2624                 extra_pins = folio_test_swapcache(folio) ?
2625                                 folio_nr_pages(folio) : 0;
2626         else
2627                 extra_pins = folio_nr_pages(folio);
2628         if (pextra_pins)
2629                 *pextra_pins = extra_pins;
2630         return folio_mapcount(folio) == folio_ref_count(folio) - extra_pins - 1;
2631 }
2632
2633 /*
2634  * This function splits huge page into normal pages. @page can point to any
2635  * subpage of huge page to split. Split doesn't change the position of @page.
2636  *
2637  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2638  * The huge page must be locked.
2639  *
2640  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2641  *
2642  * Both head page and tail pages will inherit mapping, flags, and so on from
2643  * the hugepage.
2644  *
2645  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2646  * they are not mapped.
2647  *
2648  * Returns 0 if the hugepage is split successfully.
2649  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2650  * us.
2651  */
2652 int split_huge_page_to_list(struct page *page, struct list_head *list)
2653 {
2654         struct folio *folio = page_folio(page);
2655         struct deferred_split *ds_queue = get_deferred_split_queue(&folio->page);
2656         XA_STATE(xas, &folio->mapping->i_pages, folio->index);
2657         struct anon_vma *anon_vma = NULL;
2658         struct address_space *mapping = NULL;
2659         int extra_pins, ret;
2660         pgoff_t end;
2661         bool is_hzp;
2662
2663         VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
2664         VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
2665
2666         is_hzp = is_huge_zero_page(&folio->page);
2667         VM_WARN_ON_ONCE_FOLIO(is_hzp, folio);
2668         if (is_hzp)
2669                 return -EBUSY;
2670
2671         if (folio_test_writeback(folio))
2672                 return -EBUSY;
2673
2674         if (folio_test_anon(folio)) {
2675                 /*
2676                  * The caller does not necessarily hold an mmap_lock that would
2677                  * prevent the anon_vma disappearing so we first we take a
2678                  * reference to it and then lock the anon_vma for write. This
2679                  * is similar to folio_lock_anon_vma_read except the write lock
2680                  * is taken to serialise against parallel split or collapse
2681                  * operations.
2682                  */
2683                 anon_vma = folio_get_anon_vma(folio);
2684                 if (!anon_vma) {
2685                         ret = -EBUSY;
2686                         goto out;
2687                 }
2688                 end = -1;
2689                 mapping = NULL;
2690                 anon_vma_lock_write(anon_vma);
2691         } else {
2692                 gfp_t gfp;
2693
2694                 mapping = folio->mapping;
2695
2696                 /* Truncated ? */
2697                 if (!mapping) {
2698                         ret = -EBUSY;
2699                         goto out;
2700                 }
2701
2702                 gfp = current_gfp_context(mapping_gfp_mask(mapping) &
2703                                                         GFP_RECLAIM_MASK);
2704
2705                 if (folio_test_private(folio) &&
2706                                 !filemap_release_folio(folio, gfp)) {
2707                         ret = -EBUSY;
2708                         goto out;
2709                 }
2710
2711                 xas_split_alloc(&xas, folio, folio_order(folio), gfp);
2712                 if (xas_error(&xas)) {
2713                         ret = xas_error(&xas);
2714                         goto out;
2715                 }
2716
2717                 anon_vma = NULL;
2718                 i_mmap_lock_read(mapping);
2719
2720                 /*
2721                  *__split_huge_page() may need to trim off pages beyond EOF:
2722                  * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2723                  * which cannot be nested inside the page tree lock. So note
2724                  * end now: i_size itself may be changed at any moment, but
2725                  * folio lock is good enough to serialize the trimming.
2726                  */
2727                 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2728                 if (shmem_mapping(mapping))
2729                         end = shmem_fallocend(mapping->host, end);
2730         }
2731
2732         /*
2733          * Racy check if we can split the page, before unmap_folio() will
2734          * split PMDs
2735          */
2736         if (!can_split_folio(folio, &extra_pins)) {
2737                 ret = -EAGAIN;
2738                 goto out_unlock;
2739         }
2740
2741         unmap_folio(folio);
2742
2743         /* block interrupt reentry in xa_lock and spinlock */
2744         local_irq_disable();
2745         if (mapping) {
2746                 /*
2747                  * Check if the folio is present in page cache.
2748                  * We assume all tail are present too, if folio is there.
2749                  */
2750                 xas_lock(&xas);
2751                 xas_reset(&xas);
2752                 if (xas_load(&xas) != folio)
2753                         goto fail;
2754         }
2755
2756         /* Prevent deferred_split_scan() touching ->_refcount */
2757         spin_lock(&ds_queue->split_queue_lock);
2758         if (folio_ref_freeze(folio, 1 + extra_pins)) {
2759                 if (!list_empty(page_deferred_list(&folio->page))) {
2760                         ds_queue->split_queue_len--;
2761                         list_del(page_deferred_list(&folio->page));
2762                 }
2763                 spin_unlock(&ds_queue->split_queue_lock);
2764                 if (mapping) {
2765                         int nr = folio_nr_pages(folio);
2766
2767                         xas_split(&xas, folio, folio_order(folio));
2768                         if (folio_test_swapbacked(folio)) {
2769                                 __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS,
2770                                                         -nr);
2771                         } else {
2772                                 __lruvec_stat_mod_folio(folio, NR_FILE_THPS,
2773                                                         -nr);
2774                                 filemap_nr_thps_dec(mapping);
2775                         }
2776                 }
2777
2778                 __split_huge_page(page, list, end);
2779                 ret = 0;
2780         } else {
2781                 spin_unlock(&ds_queue->split_queue_lock);
2782 fail:
2783                 if (mapping)
2784                         xas_unlock(&xas);
2785                 local_irq_enable();
2786                 remap_page(folio, folio_nr_pages(folio));
2787                 ret = -EAGAIN;
2788         }
2789
2790 out_unlock:
2791         if (anon_vma) {
2792                 anon_vma_unlock_write(anon_vma);
2793                 put_anon_vma(anon_vma);
2794         }
2795         if (mapping)
2796                 i_mmap_unlock_read(mapping);
2797 out:
2798         xas_destroy(&xas);
2799         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2800         return ret;
2801 }
2802
2803 void free_transhuge_page(struct page *page)
2804 {
2805         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2806         unsigned long flags;
2807
2808         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2809         if (!list_empty(page_deferred_list(page))) {
2810                 ds_queue->split_queue_len--;
2811                 list_del(page_deferred_list(page));
2812         }
2813         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2814         free_compound_page(page);
2815 }
2816
2817 void deferred_split_huge_page(struct page *page)
2818 {
2819         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2820 #ifdef CONFIG_MEMCG
2821         struct mem_cgroup *memcg = page_memcg(compound_head(page));
2822 #endif
2823         unsigned long flags;
2824
2825         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2826
2827         /*
2828          * The try_to_unmap() in page reclaim path might reach here too,
2829          * this may cause a race condition to corrupt deferred split queue.
2830          * And, if page reclaim is already handling the same page, it is
2831          * unnecessary to handle it again in shrinker.
2832          *
2833          * Check PageSwapCache to determine if the page is being
2834          * handled by page reclaim since THP swap would add the page into
2835          * swap cache before calling try_to_unmap().
2836          */
2837         if (PageSwapCache(page))
2838                 return;
2839
2840         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2841         if (list_empty(page_deferred_list(page))) {
2842                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2843                 list_add_tail(page_deferred_list(page), &ds_queue->split_queue);
2844                 ds_queue->split_queue_len++;
2845 #ifdef CONFIG_MEMCG
2846                 if (memcg)
2847                         set_shrinker_bit(memcg, page_to_nid(page),
2848                                          deferred_split_shrinker.id);
2849 #endif
2850         }
2851         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2852 }
2853
2854 static unsigned long deferred_split_count(struct shrinker *shrink,
2855                 struct shrink_control *sc)
2856 {
2857         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2858         struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2859
2860 #ifdef CONFIG_MEMCG
2861         if (sc->memcg)
2862                 ds_queue = &sc->memcg->deferred_split_queue;
2863 #endif
2864         return READ_ONCE(ds_queue->split_queue_len);
2865 }
2866
2867 static unsigned long deferred_split_scan(struct shrinker *shrink,
2868                 struct shrink_control *sc)
2869 {
2870         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2871         struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2872         unsigned long flags;
2873         LIST_HEAD(list), *pos, *next;
2874         struct page *page;
2875         int split = 0;
2876
2877 #ifdef CONFIG_MEMCG
2878         if (sc->memcg)
2879                 ds_queue = &sc->memcg->deferred_split_queue;
2880 #endif
2881
2882         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2883         /* Take pin on all head pages to avoid freeing them under us */
2884         list_for_each_safe(pos, next, &ds_queue->split_queue) {
2885                 page = list_entry((void *)pos, struct page, deferred_list);
2886                 page = compound_head(page);
2887                 if (get_page_unless_zero(page)) {
2888                         list_move(page_deferred_list(page), &list);
2889                 } else {
2890                         /* We lost race with put_compound_page() */
2891                         list_del_init(page_deferred_list(page));
2892                         ds_queue->split_queue_len--;
2893                 }
2894                 if (!--sc->nr_to_scan)
2895                         break;
2896         }
2897         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2898
2899         list_for_each_safe(pos, next, &list) {
2900                 page = list_entry((void *)pos, struct page, deferred_list);
2901                 if (!trylock_page(page))
2902                         goto next;
2903                 /* split_huge_page() removes page from list on success */
2904                 if (!split_huge_page(page))
2905                         split++;
2906                 unlock_page(page);
2907 next:
2908                 put_page(page);
2909         }
2910
2911         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2912         list_splice_tail(&list, &ds_queue->split_queue);
2913         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2914
2915         /*
2916          * Stop shrinker if we didn't split any page, but the queue is empty.
2917          * This can happen if pages were freed under us.
2918          */
2919         if (!split && list_empty(&ds_queue->split_queue))
2920                 return SHRINK_STOP;
2921         return split;
2922 }
2923
2924 static struct shrinker deferred_split_shrinker = {
2925         .count_objects = deferred_split_count,
2926         .scan_objects = deferred_split_scan,
2927         .seeks = DEFAULT_SEEKS,
2928         .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |
2929                  SHRINKER_NONSLAB,
2930 };
2931
2932 #ifdef CONFIG_DEBUG_FS
2933 static void split_huge_pages_all(void)
2934 {
2935         struct zone *zone;
2936         struct page *page;
2937         unsigned long pfn, max_zone_pfn;
2938         unsigned long total = 0, split = 0;
2939
2940         pr_debug("Split all THPs\n");
2941         for_each_zone(zone) {
2942                 if (!managed_zone(zone))
2943                         continue;
2944                 max_zone_pfn = zone_end_pfn(zone);
2945                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2946                         int nr_pages;
2947
2948                         page = pfn_to_online_page(pfn);
2949                         if (!page || !get_page_unless_zero(page))
2950                                 continue;
2951
2952                         if (zone != page_zone(page))
2953                                 goto next;
2954
2955                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2956                                 goto next;
2957
2958                         total++;
2959                         lock_page(page);
2960                         nr_pages = thp_nr_pages(page);
2961                         if (!split_huge_page(page))
2962                                 split++;
2963                         pfn += nr_pages - 1;
2964                         unlock_page(page);
2965 next:
2966                         put_page(page);
2967                         cond_resched();
2968                 }
2969         }
2970
2971         pr_debug("%lu of %lu THP split\n", split, total);
2972 }
2973
2974 static inline bool vma_not_suitable_for_thp_split(struct vm_area_struct *vma)
2975 {
2976         return vma_is_special_huge(vma) || (vma->vm_flags & VM_IO) ||
2977                     is_vm_hugetlb_page(vma);
2978 }
2979
2980 static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
2981                                 unsigned long vaddr_end)
2982 {
2983         int ret = 0;
2984         struct task_struct *task;
2985         struct mm_struct *mm;
2986         unsigned long total = 0, split = 0;
2987         unsigned long addr;
2988
2989         vaddr_start &= PAGE_MASK;
2990         vaddr_end &= PAGE_MASK;
2991
2992         /* Find the task_struct from pid */
2993         rcu_read_lock();
2994         task = find_task_by_vpid(pid);
2995         if (!task) {
2996                 rcu_read_unlock();
2997                 ret = -ESRCH;
2998                 goto out;
2999         }
3000         get_task_struct(task);
3001         rcu_read_unlock();
3002
3003         /* Find the mm_struct */
3004         mm = get_task_mm(task);
3005         put_task_struct(task);
3006
3007         if (!mm) {
3008                 ret = -EINVAL;
3009                 goto out;
3010         }
3011
3012         pr_debug("Split huge pages in pid: %d, vaddr: [0x%lx - 0x%lx]\n",
3013                  pid, vaddr_start, vaddr_end);
3014
3015         mmap_read_lock(mm);
3016         /*
3017          * always increase addr by PAGE_SIZE, since we could have a PTE page
3018          * table filled with PTE-mapped THPs, each of which is distinct.
3019          */
3020         for (addr = vaddr_start; addr < vaddr_end; addr += PAGE_SIZE) {
3021                 struct vm_area_struct *vma = vma_lookup(mm, addr);
3022                 struct page *page;
3023
3024                 if (!vma)
3025                         break;
3026
3027                 /* skip special VMA and hugetlb VMA */
3028                 if (vma_not_suitable_for_thp_split(vma)) {
3029                         addr = vma->vm_end;
3030                         continue;
3031                 }
3032
3033                 /* FOLL_DUMP to ignore special (like zero) pages */
3034                 page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
3035
3036                 if (IS_ERR_OR_NULL(page))
3037                         continue;
3038
3039                 if (!is_transparent_hugepage(page))
3040                         goto next;
3041
3042                 total++;
3043                 if (!can_split_folio(page_folio(page), NULL))
3044                         goto next;
3045
3046                 if (!trylock_page(page))
3047                         goto next;
3048
3049                 if (!split_huge_page(page))
3050                         split++;
3051
3052                 unlock_page(page);
3053 next:
3054                 put_page(page);
3055                 cond_resched();
3056         }
3057         mmap_read_unlock(mm);
3058         mmput(mm);
3059
3060         pr_debug("%lu of %lu THP split\n", split, total);
3061
3062 out:
3063         return ret;
3064 }
3065
3066 static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
3067                                 pgoff_t off_end)
3068 {
3069         struct filename *file;
3070         struct file *candidate;
3071         struct address_space *mapping;
3072         int ret = -EINVAL;
3073         pgoff_t index;
3074         int nr_pages = 1;
3075         unsigned long total = 0, split = 0;
3076
3077         file = getname_kernel(file_path);
3078         if (IS_ERR(file))
3079                 return ret;
3080
3081         candidate = file_open_name(file, O_RDONLY, 0);
3082         if (IS_ERR(candidate))
3083                 goto out;
3084
3085         pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx]\n",
3086                  file_path, off_start, off_end);
3087
3088         mapping = candidate->f_mapping;
3089
3090         for (index = off_start; index < off_end; index += nr_pages) {
3091                 struct folio *folio = __filemap_get_folio(mapping, index,
3092                                                 FGP_ENTRY, 0);
3093
3094                 nr_pages = 1;
3095                 if (xa_is_value(folio) || !folio)
3096                         continue;
3097
3098                 if (!folio_test_large(folio))
3099                         goto next;
3100
3101                 total++;
3102                 nr_pages = folio_nr_pages(folio);
3103
3104                 if (!folio_trylock(folio))
3105                         goto next;
3106
3107                 if (!split_folio(folio))
3108                         split++;
3109
3110                 folio_unlock(folio);
3111 next:
3112                 folio_put(folio);
3113                 cond_resched();
3114         }
3115
3116         filp_close(candidate, NULL);
3117         ret = 0;
3118
3119         pr_debug("%lu of %lu file-backed THP split\n", split, total);
3120 out:
3121         putname(file);
3122         return ret;
3123 }
3124
3125 #define MAX_INPUT_BUF_SZ 255
3126
3127 static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
3128                                 size_t count, loff_t *ppops)
3129 {
3130         static DEFINE_MUTEX(split_debug_mutex);
3131         ssize_t ret;
3132         /* hold pid, start_vaddr, end_vaddr or file_path, off_start, off_end */
3133         char input_buf[MAX_INPUT_BUF_SZ];
3134         int pid;
3135         unsigned long vaddr_start, vaddr_end;
3136
3137         ret = mutex_lock_interruptible(&split_debug_mutex);
3138         if (ret)
3139                 return ret;
3140
3141         ret = -EFAULT;
3142
3143         memset(input_buf, 0, MAX_INPUT_BUF_SZ);
3144         if (copy_from_user(input_buf, buf, min_t(size_t, count, MAX_INPUT_BUF_SZ)))
3145                 goto out;
3146
3147         input_buf[MAX_INPUT_BUF_SZ - 1] = '\0';
3148
3149         if (input_buf[0] == '/') {
3150                 char *tok;
3151                 char *buf = input_buf;
3152                 char file_path[MAX_INPUT_BUF_SZ];
3153                 pgoff_t off_start = 0, off_end = 0;
3154                 size_t input_len = strlen(input_buf);
3155
3156                 tok = strsep(&buf, ",");
3157                 if (tok) {
3158                         strcpy(file_path, tok);
3159                 } else {
3160                         ret = -EINVAL;
3161                         goto out;
3162                 }
3163
3164                 ret = sscanf(buf, "0x%lx,0x%lx", &off_start, &off_end);
3165                 if (ret != 2) {
3166                         ret = -EINVAL;
3167                         goto out;
3168                 }
3169                 ret = split_huge_pages_in_file(file_path, off_start, off_end);
3170                 if (!ret)
3171                         ret = input_len;
3172
3173                 goto out;
3174         }
3175
3176         ret = sscanf(input_buf, "%d,0x%lx,0x%lx", &pid, &vaddr_start, &vaddr_end);
3177         if (ret == 1 && pid == 1) {
3178                 split_huge_pages_all();
3179                 ret = strlen(input_buf);
3180                 goto out;
3181         } else if (ret != 3) {
3182                 ret = -EINVAL;
3183                 goto out;
3184         }
3185
3186         ret = split_huge_pages_pid(pid, vaddr_start, vaddr_end);
3187         if (!ret)
3188                 ret = strlen(input_buf);
3189 out:
3190         mutex_unlock(&split_debug_mutex);
3191         return ret;
3192
3193 }
3194
3195 static const struct file_operations split_huge_pages_fops = {
3196         .owner   = THIS_MODULE,
3197         .write   = split_huge_pages_write,
3198         .llseek  = no_llseek,
3199 };
3200
3201 static int __init split_huge_pages_debugfs(void)
3202 {
3203         debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
3204                             &split_huge_pages_fops);
3205         return 0;
3206 }
3207 late_initcall(split_huge_pages_debugfs);
3208 #endif
3209
3210 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
3211 int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
3212                 struct page *page)
3213 {
3214         struct vm_area_struct *vma = pvmw->vma;
3215         struct mm_struct *mm = vma->vm_mm;
3216         unsigned long address = pvmw->address;
3217         bool anon_exclusive;
3218         pmd_t pmdval;
3219         swp_entry_t entry;
3220         pmd_t pmdswp;
3221
3222         if (!(pvmw->pmd && !pvmw->pte))
3223                 return 0;
3224
3225         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
3226         pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
3227
3228         /* See page_try_share_anon_rmap(): invalidate PMD first. */
3229         anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
3230         if (anon_exclusive && page_try_share_anon_rmap(page)) {
3231                 set_pmd_at(mm, address, pvmw->pmd, pmdval);
3232                 return -EBUSY;
3233         }
3234
3235         if (pmd_dirty(pmdval))
3236                 set_page_dirty(page);
3237         if (pmd_write(pmdval))
3238                 entry = make_writable_migration_entry(page_to_pfn(page));
3239         else if (anon_exclusive)
3240                 entry = make_readable_exclusive_migration_entry(page_to_pfn(page));
3241         else
3242                 entry = make_readable_migration_entry(page_to_pfn(page));
3243         if (pmd_young(pmdval))
3244                 entry = make_migration_entry_young(entry);
3245         if (pmd_dirty(pmdval))
3246                 entry = make_migration_entry_dirty(entry);
3247         pmdswp = swp_entry_to_pmd(entry);
3248         if (pmd_soft_dirty(pmdval))
3249                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
3250         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
3251         page_remove_rmap(page, vma, true);
3252         put_page(page);
3253         trace_set_migration_pmd(address, pmd_val(pmdswp));
3254
3255         return 0;
3256 }
3257
3258 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
3259 {
3260         struct vm_area_struct *vma = pvmw->vma;
3261         struct mm_struct *mm = vma->vm_mm;
3262         unsigned long address = pvmw->address;
3263         unsigned long haddr = address & HPAGE_PMD_MASK;
3264         pmd_t pmde;
3265         swp_entry_t entry;
3266
3267         if (!(pvmw->pmd && !pvmw->pte))
3268                 return;
3269
3270         entry = pmd_to_swp_entry(*pvmw->pmd);
3271         get_page(new);
3272         pmde = mk_huge_pmd(new, READ_ONCE(vma->vm_page_prot));
3273         if (pmd_swp_soft_dirty(*pvmw->pmd))
3274                 pmde = pmd_mksoft_dirty(pmde);
3275         if (is_writable_migration_entry(entry))
3276                 pmde = maybe_pmd_mkwrite(pmde, vma);
3277         if (pmd_swp_uffd_wp(*pvmw->pmd))
3278                 pmde = pmd_wrprotect(pmd_mkuffd_wp(pmde));
3279         if (!is_migration_entry_young(entry))
3280                 pmde = pmd_mkold(pmde);
3281         /* NOTE: this may contain setting soft-dirty on some archs */
3282         if (PageDirty(new) && is_migration_entry_dirty(entry))
3283                 pmde = pmd_mkdirty(pmde);
3284
3285         if (PageAnon(new)) {
3286                 rmap_t rmap_flags = RMAP_COMPOUND;
3287
3288                 if (!is_readable_migration_entry(entry))
3289                         rmap_flags |= RMAP_EXCLUSIVE;
3290
3291                 page_add_anon_rmap(new, vma, haddr, rmap_flags);
3292         } else {
3293                 page_add_file_rmap(new, vma, true);
3294         }
3295         VM_BUG_ON(pmd_write(pmde) && PageAnon(new) && !PageAnonExclusive(new));
3296         set_pmd_at(mm, haddr, pvmw->pmd, pmde);
3297
3298         /* No need to invalidate - it was non-present before */
3299         update_mmu_cache_pmd(vma, address, pvmw->pmd);
3300         trace_remove_migration_pmd(address, pmd_val(pmde));
3301 }
3302 #endif