mm/madvise.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      linux/mm/madvise.c
   4  *
   5  * Copyright (C) 1999  Linus Torvalds
   6  * Copyright (C) 2002  Christoph Hellwig
   7  */
   8
   9 #include <linux/mman.h>
  10 #include <linux/pagemap.h>
  11 #include <linux/syscalls.h>
  12 #include <linux/mempolicy.h>
  13 #include <linux/page-isolation.h>
  14 #include <linux/page_idle.h>
  15 #include <linux/userfaultfd_k.h>
  16 #include <linux/hugetlb.h>
  17 #include <linux/falloc.h>
  18 #include <linux/fadvise.h>
  19 #include <linux/sched.h>
  20 #include <linux/sched/mm.h>
  21 #include <linux/mm_inline.h>
  22 #include <linux/string.h>
  23 #include <linux/uio.h>
  24 #include <linux/ksm.h>
  25 #include <linux/fs.h>
  26 #include <linux/file.h>
  27 #include <linux/blkdev.h>
  28 #include <linux/backing-dev.h>
  29 #include <linux/pagewalk.h>
  30 #include <linux/swap.h>
  31 #include <linux/swapops.h>
  32 #include <linux/shmem_fs.h>
  33 #include <linux/mmu_notifier.h>
  34
  35 #include <asm/tlb.h>
  36
  37 #include "internal.h"
  38 #include "swap.h"
  39
  40 struct madvise_walk_private {
  41         struct mmu_gather *tlb;
  42         bool pageout;
  43 };
  44
  45 /*
  46  * Any behaviour which results in changes to the vma->vm_flags needs to
  47  * take mmap_lock for writing. Others, which simply traverse vmas, need
  48  * to only take it for reading.
  49  */
  50 static int madvise_need_mmap_write(int behavior)
  51 {
  52         switch (behavior) {
  53         case MADV_REMOVE:
  54         case MADV_WILLNEED:
  55         case MADV_DONTNEED:
  56         case MADV_DONTNEED_LOCKED:
  57         case MADV_COLD:
  58         case MADV_PAGEOUT:
  59         case MADV_FREE:
  60         case MADV_POPULATE_READ:
  61         case MADV_POPULATE_WRITE:
  62         case MADV_COLLAPSE:
  63                 return 0;
  64         default:
  65                 /* be safe, default to 1. list exceptions explicitly */
  66                 return 1;
  67         }
  68 }
  69
  70 #ifdef CONFIG_ANON_VMA_NAME
  71 struct anon_vma_name *anon_vma_name_alloc(const char *name)
  72 {
  73         struct anon_vma_name *anon_name;
  74         size_t count;
  75
  76         /* Add 1 for NUL terminator at the end of the anon_name->name */
  77         count = strlen(name) + 1;
  78         anon_name = kmalloc(struct_size(anon_name, name, count), GFP_KERNEL);
  79         if (anon_name) {
  80                 kref_init(&anon_name->kref);
  81                 memcpy(anon_name->name, name, count);
  82         }
  83
  84         return anon_name;
  85 }
  86
  87 void anon_vma_name_free(struct kref *kref)
  88 {
  89         struct anon_vma_name *anon_name =
  90                         container_of(kref, struct anon_vma_name, kref);
  91         kfree(anon_name);
  92 }
  93
  94 struct anon_vma_name *anon_vma_name(struct vm_area_struct *vma)
  95 {
  96         mmap_assert_locked(vma->vm_mm);
  97
  98         if (vma->vm_file)
  99                 return NULL;
 100
 101         return vma->anon_name;
 102 }
 103
 104 /* mmap_lock should be write-locked */
 105 static int replace_anon_vma_name(struct vm_area_struct *vma,
 106                                  struct anon_vma_name *anon_name)
 107 {
 108         struct anon_vma_name *orig_name = anon_vma_name(vma);
 109
 110         if (!anon_name) {
 111                 vma->anon_name = NULL;
 112                 anon_vma_name_put(orig_name);
 113                 return 0;
 114         }
 115
 116         if (anon_vma_name_eq(orig_name, anon_name))
 117                 return 0;
 118
 119         vma->anon_name = anon_vma_name_reuse(anon_name);
 120         anon_vma_name_put(orig_name);
 121
 122         return 0;
 123 }
 124 #else /* CONFIG_ANON_VMA_NAME */
 125 static int replace_anon_vma_name(struct vm_area_struct *vma,
 126                                  struct anon_vma_name *anon_name)
 127 {
 128         if (anon_name)
 129                 return -EINVAL;
 130
 131         return 0;
 132 }
 133 #endif /* CONFIG_ANON_VMA_NAME */
 134 /*
 135  * Update the vm_flags on region of a vma, splitting it or merging it as
 136  * necessary.  Must be called with mmap_sem held for writing;
 137  * Caller should ensure anon_name stability by raising its refcount even when
 138  * anon_name belongs to a valid vma because this function might free that vma.
 139  */
 140 static int madvise_update_vma(struct vm_area_struct *vma,
 141                               struct vm_area_struct **prev, unsigned long start,
 142                               unsigned long end, unsigned long new_flags,
 143                               struct anon_vma_name *anon_name)
 144 {
 145         struct mm_struct *mm = vma->vm_mm;
 146         int error;
 147         pgoff_t pgoff;
 148
 149         if (new_flags == vma->vm_flags && anon_vma_name_eq(anon_vma_name(vma), anon_name)) {
 150                 *prev = vma;
 151                 return 0;
 152         }
 153
 154         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 155         *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
 156                           vma->vm_file, pgoff, vma_policy(vma),
 157                           vma->vm_userfaultfd_ctx, anon_name);
 158         if (*prev) {
 159                 vma = *prev;
 160                 goto success;
 161         }
 162
 163         *prev = vma;
 164
 165         if (start != vma->vm_start) {
 166                 if (unlikely(mm->map_count >= sysctl_max_map_count))
 167                         return -ENOMEM;
 168                 error = __split_vma(mm, vma, start, 1);
 169                 if (error)
 170                         return error;
 171         }
 172
 173         if (end != vma->vm_end) {
 174                 if (unlikely(mm->map_count >= sysctl_max_map_count))
 175                         return -ENOMEM;
 176                 error = __split_vma(mm, vma, end, 0);
 177                 if (error)
 178                         return error;
 179         }
 180
 181 success:
 182         /*
 183          * vm_flags is protected by the mmap_lock held in write mode.
 184          */
 185         vma->vm_flags = new_flags;
 186         if (!vma->vm_file) {
 187                 error = replace_anon_vma_name(vma, anon_name);
 188                 if (error)
 189                         return error;
 190         }
 191
 192         return 0;
 193 }
 194
 195 #ifdef CONFIG_SWAP
 196 static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
 197         unsigned long end, struct mm_walk *walk)
 198 {
 199         struct vm_area_struct *vma = walk->private;
 200         unsigned long index;
 201         struct swap_iocb *splug = NULL;
 202
 203         if (pmd_none_or_trans_huge_or_clear_bad(pmd))
 204                 return 0;
 205
 206         for (index = start; index != end; index += PAGE_SIZE) {
 207                 pte_t pte;
 208                 swp_entry_t entry;
 209                 struct page *page;
 210                 spinlock_t *ptl;
 211                 pte_t *ptep;
 212
 213                 ptep = pte_offset_map_lock(vma->vm_mm, pmd, index, &ptl);
 214                 pte = *ptep;
 215                 pte_unmap_unlock(ptep, ptl);
 216
 217                 if (!is_swap_pte(pte))
 218                         continue;
 219                 entry = pte_to_swp_entry(pte);
 220                 if (unlikely(non_swap_entry(entry)))
 221                         continue;
 222
 223                 page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
 224                                              vma, index, false, &splug);
 225                 if (page)
 226                         put_page(page);
 227         }
 228         swap_read_unplug(splug);
 229
 230         return 0;
 231 }
 232
 233 static const struct mm_walk_ops swapin_walk_ops = {
 234         .pmd_entry              = swapin_walk_pmd_entry,
 235 };
 236
 237 static void force_shm_swapin_readahead(struct vm_area_struct *vma,
 238                 unsigned long start, unsigned long end,
 239                 struct address_space *mapping)
 240 {
 241         XA_STATE(xas, &mapping->i_pages, linear_page_index(vma, start));
 242         pgoff_t end_index = linear_page_index(vma, end + PAGE_SIZE - 1);
 243         struct page *page;
 244         struct swap_iocb *splug = NULL;
 245
 246         rcu_read_lock();
 247         xas_for_each(&xas, page, end_index) {
 248                 swp_entry_t swap;
 249
 250                 if (!xa_is_value(page))
 251                         continue;
 252                 swap = radix_to_swp_entry(page);
 253                 /* There might be swapin error entries in shmem mapping. */
 254                 if (non_swap_entry(swap))
 255                         continue;
 256                 xas_pause(&xas);
 257                 rcu_read_unlock();
 258
 259                 page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
 260                                              NULL, 0, false, &splug);
 261                 if (page)
 262                         put_page(page);
 263
 264                 rcu_read_lock();
 265         }
 266         rcu_read_unlock();
 267         swap_read_unplug(splug);
 268
 269         lru_add_drain();        /* Push any new pages onto the LRU now */
 270 }
 271 #endif          /* CONFIG_SWAP */
 272
 273 /*
 274  * Schedule all required I/O operations.  Do not wait for completion.
 275  */
 276 static long madvise_willneed(struct vm_area_struct *vma,
 277                              struct vm_area_struct **prev,
 278                              unsigned long start, unsigned long end)
 279 {
 280         struct mm_struct *mm = vma->vm_mm;
 281         struct file *file = vma->vm_file;
 282         loff_t offset;
 283
 284         *prev = vma;
 285 #ifdef CONFIG_SWAP
 286         if (!file) {
 287                 walk_page_range(vma->vm_mm, start, end, &swapin_walk_ops, vma);
 288                 lru_add_drain(); /* Push any new pages onto the LRU now */
 289                 return 0;
 290         }
 291
 292         if (shmem_mapping(file->f_mapping)) {
 293                 force_shm_swapin_readahead(vma, start, end,
 294                                         file->f_mapping);
 295                 return 0;
 296         }
 297 #else
 298         if (!file)
 299                 return -EBADF;
 300 #endif
 301
 302         if (IS_DAX(file_inode(file))) {
 303                 /* no bad return value, but ignore advice */
 304                 return 0;
 305         }
 306
 307         /*
 308          * Filesystem's fadvise may need to take various locks.  We need to
 309          * explicitly grab a reference because the vma (and hence the
 310          * vma's reference to the file) can go away as soon as we drop
 311          * mmap_lock.
 312          */
 313         *prev = NULL;   /* tell sys_madvise we drop mmap_lock */
 314         get_file(file);
 315         offset = (loff_t)(start - vma->vm_start)
 316                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 317         mmap_read_unlock(mm);
 318         vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED);
 319         fput(file);
 320         mmap_read_lock(mm);
 321         return 0;
 322 }
 323
 324 static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
 325                                 unsigned long addr, unsigned long end,
 326                                 struct mm_walk *walk)
 327 {
 328         struct madvise_walk_private *private = walk->private;
 329         struct mmu_gather *tlb = private->tlb;
 330         bool pageout = private->pageout;
 331         struct mm_struct *mm = tlb->mm;
 332         struct vm_area_struct *vma = walk->vma;
 333         pte_t *orig_pte, *pte, ptent;
 334         spinlock_t *ptl;
 335         struct page *page = NULL;
 336         LIST_HEAD(page_list);
 337
 338         if (fatal_signal_pending(current))
 339                 return -EINTR;
 340
 341 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 342         if (pmd_trans_huge(*pmd)) {
 343                 pmd_t orig_pmd;
 344                 unsigned long next = pmd_addr_end(addr, end);
 345
 346                 tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
 347                 ptl = pmd_trans_huge_lock(pmd, vma);
 348                 if (!ptl)
 349                         return 0;
 350
 351                 orig_pmd = *pmd;
 352                 if (is_huge_zero_pmd(orig_pmd))
 353                         goto huge_unlock;
 354
 355                 if (unlikely(!pmd_present(orig_pmd))) {
 356                         VM_BUG_ON(thp_migration_supported() &&
 357                                         !is_pmd_migration_entry(orig_pmd));
 358                         goto huge_unlock;
 359                 }
 360
 361                 page = pmd_page(orig_pmd);
 362
 363                 /* Do not interfere with other mappings of this page */
 364                 if (page_mapcount(page) != 1)
 365                         goto huge_unlock;
 366
 367                 if (next - addr != HPAGE_PMD_SIZE) {
 368                         int err;
 369
 370                         get_page(page);
 371                         spin_unlock(ptl);
 372                         lock_page(page);
 373                         err = split_huge_page(page);
 374                         unlock_page(page);
 375                         put_page(page);
 376                         if (!err)
 377                                 goto regular_page;
 378                         return 0;
 379                 }
 380
 381                 if (pmd_young(orig_pmd)) {
 382                         pmdp_invalidate(vma, addr, pmd);
 383                         orig_pmd = pmd_mkold(orig_pmd);
 384
 385                         set_pmd_at(mm, addr, pmd, orig_pmd);
 386                         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
 387                 }
 388
 389                 ClearPageReferenced(page);
 390                 test_and_clear_page_young(page);
 391                 if (pageout) {
 392                         if (!isolate_lru_page(page)) {
 393                                 if (PageUnevictable(page))
 394                                         putback_lru_page(page);
 395                                 else
 396                                         list_add(&page->lru, &page_list);
 397                         }
 398                 } else
 399                         deactivate_page(page);
 400 huge_unlock:
 401                 spin_unlock(ptl);
 402                 if (pageout)
 403                         reclaim_pages(&page_list);
 404                 return 0;
 405         }
 406
 407 regular_page:
 408         if (pmd_trans_unstable(pmd))
 409                 return 0;
 410 #endif
 411         tlb_change_page_size(tlb, PAGE_SIZE);
 412         orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 413         flush_tlb_batched_pending(mm);
 414         arch_enter_lazy_mmu_mode();
 415         for (; addr < end; pte++, addr += PAGE_SIZE) {
 416                 ptent = *pte;
 417
 418                 if (pte_none(ptent))
 419                         continue;
 420
 421                 if (!pte_present(ptent))
 422                         continue;
 423
 424                 page = vm_normal_page(vma, addr, ptent);
 425                 if (!page || is_zone_device_page(page))
 426                         continue;
 427
 428                 /*
 429                  * Creating a THP page is expensive so split it only if we
 430                  * are sure it's worth. Split it if we are only owner.
 431                  */
 432                 if (PageTransCompound(page)) {
 433                         if (page_mapcount(page) != 1)
 434                                 break;
 435                         get_page(page);
 436                         if (!trylock_page(page)) {
 437                                 put_page(page);
 438                                 break;
 439                         }
 440                         pte_unmap_unlock(orig_pte, ptl);
 441                         if (split_huge_page(page)) {
 442                                 unlock_page(page);
 443                                 put_page(page);
 444                                 orig_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 445                                 break;
 446                         }
 447                         unlock_page(page);
 448                         put_page(page);
 449                         orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 450                         pte--;
 451                         addr -= PAGE_SIZE;
 452                         continue;
 453                 }
 454
 455                 /*
 456                  * Do not interfere with other mappings of this page and
 457                  * non-LRU page.
 458                  */
 459                 if (!PageLRU(page) || page_mapcount(page) != 1)
 460                         continue;
 461
 462                 VM_BUG_ON_PAGE(PageTransCompound(page), page);
 463
 464                 if (pte_young(ptent)) {
 465                         ptent = ptep_get_and_clear_full(mm, addr, pte,
 466                                                         tlb->fullmm);
 467                         ptent = pte_mkold(ptent);
 468                         set_pte_at(mm, addr, pte, ptent);
 469                         tlb_remove_tlb_entry(tlb, pte, addr);
 470                 }
 471
 472                 /*
 473                  * We are deactivating a page for accelerating reclaiming.
 474                  * VM couldn't reclaim the page unless we clear PG_young.
 475                  * As a side effect, it makes confuse idle-page tracking
 476                  * because they will miss recent referenced history.
 477                  */
 478                 ClearPageReferenced(page);
 479                 test_and_clear_page_young(page);
 480                 if (pageout) {
 481                         if (!isolate_lru_page(page)) {
 482                                 if (PageUnevictable(page))
 483                                         putback_lru_page(page);
 484                                 else
 485                                         list_add(&page->lru, &page_list);
 486                         }
 487                 } else
 488                         deactivate_page(page);
 489         }
 490
 491         arch_leave_lazy_mmu_mode();
 492         pte_unmap_unlock(orig_pte, ptl);
 493         if (pageout)
 494                 reclaim_pages(&page_list);
 495         cond_resched();
 496
 497         return 0;
 498 }
 499
 500 static const struct mm_walk_ops cold_walk_ops = {
 501         .pmd_entry = madvise_cold_or_pageout_pte_range,
 502 };
 503
 504 static void madvise_cold_page_range(struct mmu_gather *tlb,
 505                              struct vm_area_struct *vma,
 506                              unsigned long addr, unsigned long end)
 507 {
 508         struct madvise_walk_private walk_private = {
 509                 .pageout = false,
 510                 .tlb = tlb,
 511         };
 512
 513         tlb_start_vma(tlb, vma);
 514         walk_page_range(vma->vm_mm, addr, end, &cold_walk_ops, &walk_private);
 515         tlb_end_vma(tlb, vma);
 516 }
 517
 518 static inline bool can_madv_lru_vma(struct vm_area_struct *vma)
 519 {
 520         return !(vma->vm_flags & (VM_LOCKED|VM_PFNMAP|VM_HUGETLB));
 521 }
 522
 523 static long madvise_cold(struct vm_area_struct *vma,
 524                         struct vm_area_struct **prev,
 525                         unsigned long start_addr, unsigned long end_addr)
 526 {
 527         struct mm_struct *mm = vma->vm_mm;
 528         struct mmu_gather tlb;
 529
 530         *prev = vma;
 531         if (!can_madv_lru_vma(vma))
 532                 return -EINVAL;
 533
 534         lru_add_drain();
 535         tlb_gather_mmu(&tlb, mm);
 536         madvise_cold_page_range(&tlb, vma, start_addr, end_addr);
 537         tlb_finish_mmu(&tlb);
 538
 539         return 0;
 540 }
 541
 542 static void madvise_pageout_page_range(struct mmu_gather *tlb,
 543                              struct vm_area_struct *vma,
 544                              unsigned long addr, unsigned long end)
 545 {
 546         struct madvise_walk_private walk_private = {
 547                 .pageout = true,
 548                 .tlb = tlb,
 549         };
 550
 551         tlb_start_vma(tlb, vma);
 552         walk_page_range(vma->vm_mm, addr, end, &cold_walk_ops, &walk_private);
 553         tlb_end_vma(tlb, vma);
 554 }
 555
 556 static inline bool can_do_pageout(struct vm_area_struct *vma)
 557 {
 558         if (vma_is_anonymous(vma))
 559                 return true;
 560         if (!vma->vm_file)
 561                 return false;
 562         /*
 563          * paging out pagecache only for non-anonymous mappings that correspond
 564          * to the files the calling process could (if tried) open for writing;
 565          * otherwise we'd be including shared non-exclusive mappings, which
 566          * opens a side channel.
 567          */
 568         return inode_owner_or_capable(&init_user_ns,
 569                                       file_inode(vma->vm_file)) ||
 570                file_permission(vma->vm_file, MAY_WRITE) == 0;
 571 }
 572
 573 static long madvise_pageout(struct vm_area_struct *vma,
 574                         struct vm_area_struct **prev,
 575                         unsigned long start_addr, unsigned long end_addr)
 576 {
 577         struct mm_struct *mm = vma->vm_mm;
 578         struct mmu_gather tlb;
 579
 580         *prev = vma;
 581         if (!can_madv_lru_vma(vma))
 582                 return -EINVAL;
 583
 584         if (!can_do_pageout(vma))
 585                 return 0;
 586
 587         lru_add_drain();
 588         tlb_gather_mmu(&tlb, mm);
 589         madvise_pageout_page_range(&tlb, vma, start_addr, end_addr);
 590         tlb_finish_mmu(&tlb);
 591
 592         return 0;
 593 }
 594
 595 static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 596                                 unsigned long end, struct mm_walk *walk)
 597
 598 {
 599         struct mmu_gather *tlb = walk->private;
 600         struct mm_struct *mm = tlb->mm;
 601         struct vm_area_struct *vma = walk->vma;
 602         spinlock_t *ptl;
 603         pte_t *orig_pte, *pte, ptent;
 604         struct folio *folio;
 605         struct page *page;
 606         int nr_swap = 0;
 607         unsigned long next;
 608
 609         next = pmd_addr_end(addr, end);
 610         if (pmd_trans_huge(*pmd))
 611                 if (madvise_free_huge_pmd(tlb, vma, pmd, addr, next))
 612                         goto next;
 613
 614         if (pmd_trans_unstable(pmd))
 615                 return 0;
 616
 617         tlb_change_page_size(tlb, PAGE_SIZE);
 618         orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 619         flush_tlb_batched_pending(mm);
 620         arch_enter_lazy_mmu_mode();
 621         for (; addr != end; pte++, addr += PAGE_SIZE) {
 622                 ptent = *pte;
 623
 624                 if (pte_none(ptent))
 625                         continue;
 626                 /*
 627                  * If the pte has swp_entry, just clear page table to
 628                  * prevent swap-in which is more expensive rather than
 629                  * (page allocation + zeroing).
 630                  */
 631                 if (!pte_present(ptent)) {
 632                         swp_entry_t entry;
 633
 634                         entry = pte_to_swp_entry(ptent);
 635                         if (!non_swap_entry(entry)) {
 636                                 nr_swap--;
 637                                 free_swap_and_cache(entry);
 638                                 pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
 639                         } else if (is_hwpoison_entry(entry) ||
 640                                    is_swapin_error_entry(entry)) {
 641                                 pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
 642                         }
 643                         continue;
 644                 }
 645
 646                 page = vm_normal_page(vma, addr, ptent);
 647                 if (!page || is_zone_device_page(page))
 648                         continue;
 649                 folio = page_folio(page);
 650
 651                 /*
 652                  * If pmd isn't transhuge but the folio is large and
 653                  * is owned by only this process, split it and
 654                  * deactivate all pages.
 655                  */
 656                 if (folio_test_large(folio)) {
 657                         if (folio_mapcount(folio) != 1)
 658                                 goto out;
 659                         folio_get(folio);
 660                         if (!folio_trylock(folio)) {
 661                                 folio_put(folio);
 662                                 goto out;
 663                         }
 664                         pte_unmap_unlock(orig_pte, ptl);
 665                         if (split_folio(folio)) {
 666                                 folio_unlock(folio);
 667                                 folio_put(folio);
 668                                 orig_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 669                                 goto out;
 670                         }
 671                         folio_unlock(folio);
 672                         folio_put(folio);
 673                         orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 674                         pte--;
 675                         addr -= PAGE_SIZE;
 676                         continue;
 677                 }
 678
 679                 if (folio_test_swapcache(folio) || folio_test_dirty(folio)) {
 680                         if (!folio_trylock(folio))
 681                                 continue;
 682                         /*
 683                          * If folio is shared with others, we mustn't clear
 684                          * the folio's dirty flag.
 685                          */
 686                         if (folio_mapcount(folio) != 1) {
 687                                 folio_unlock(folio);
 688                                 continue;
 689                         }
 690
 691                         if (folio_test_swapcache(folio) &&
 692                             !folio_free_swap(folio)) {
 693                                 folio_unlock(folio);
 694                                 continue;
 695                         }
 696
 697                         folio_clear_dirty(folio);
 698                         folio_unlock(folio);
 699                 }
 700
 701                 if (pte_young(ptent) || pte_dirty(ptent)) {
 702                         /*
 703                          * Some of architecture(ex, PPC) don't update TLB
 704                          * with set_pte_at and tlb_remove_tlb_entry so for
 705                          * the portability, remap the pte with old|clean
 706                          * after pte clearing.
 707                          */
 708                         ptent = ptep_get_and_clear_full(mm, addr, pte,
 709                                                         tlb->fullmm);
 710
 711                         ptent = pte_mkold(ptent);
 712                         ptent = pte_mkclean(ptent);
 713                         set_pte_at(mm, addr, pte, ptent);
 714                         tlb_remove_tlb_entry(tlb, pte, addr);
 715                 }
 716                 mark_page_lazyfree(&folio->page);
 717         }
 718 out:
 719         if (nr_swap) {
 720                 if (current->mm == mm)
 721                         sync_mm_rss(mm);
 722
 723                 add_mm_counter(mm, MM_SWAPENTS, nr_swap);
 724         }
 725         arch_leave_lazy_mmu_mode();
 726         pte_unmap_unlock(orig_pte, ptl);
 727         cond_resched();
 728 next:
 729         return 0;
 730 }
 731
 732 static const struct mm_walk_ops madvise_free_walk_ops = {
 733         .pmd_entry              = madvise_free_pte_range,
 734 };
 735
 736 static int madvise_free_single_vma(struct vm_area_struct *vma,
 737                         unsigned long start_addr, unsigned long end_addr)
 738 {
 739         struct mm_struct *mm = vma->vm_mm;
 740         struct mmu_notifier_range range;
 741         struct mmu_gather tlb;
 742
 743         /* MADV_FREE works for only anon vma at the moment */
 744         if (!vma_is_anonymous(vma))
 745                 return -EINVAL;
 746
 747         range.start = max(vma->vm_start, start_addr);
 748         if (range.start >= vma->vm_end)
 749                 return -EINVAL;
 750         range.end = min(vma->vm_end, end_addr);
 751         if (range.end <= vma->vm_start)
 752                 return -EINVAL;
 753         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm,
 754                                 range.start, range.end);
 755
 756         lru_add_drain();
 757         tlb_gather_mmu(&tlb, mm);
 758         update_hiwater_rss(mm);
 759
 760         mmu_notifier_invalidate_range_start(&range);
 761         tlb_start_vma(&tlb, vma);
 762         walk_page_range(vma->vm_mm, range.start, range.end,
 763                         &madvise_free_walk_ops, &tlb);
 764         tlb_end_vma(&tlb, vma);
 765         mmu_notifier_invalidate_range_end(&range);
 766         tlb_finish_mmu(&tlb);
 767
 768         return 0;
 769 }
 770
 771 /*
 772  * Application no longer needs these pages.  If the pages are dirty,
 773  * it's OK to just throw them away.  The app will be more careful about
 774  * data it wants to keep.  Be sure to free swap resources too.  The
 775  * zap_page_range call sets things up for shrink_active_list to actually free
 776  * these pages later if no one else has touched them in the meantime,
 777  * although we could add these pages to a global reuse list for
 778  * shrink_active_list to pick up before reclaiming other pages.
 779  *
 780  * NB: This interface discards data rather than pushes it out to swap,
 781  * as some implementations do.  This has performance implications for
 782  * applications like large transactional databases which want to discard
 783  * pages in anonymous maps after committing to backing store the data
 784  * that was kept in them.  There is no reason to write this data out to
 785  * the swap area if the application is discarding it.
 786  *
 787  * An interface that causes the system to free clean pages and flush
 788  * dirty pages is already available as msync(MS_INVALIDATE).
 789  */
 790 static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
 791                                         unsigned long start, unsigned long end)
 792 {
 793         zap_page_range(vma, start, end - start);
 794         return 0;
 795 }
 796
 797 static bool madvise_dontneed_free_valid_vma(struct vm_area_struct *vma,
 798                                             unsigned long start,
 799                                             unsigned long *end,
 800                                             int behavior)
 801 {
 802         if (!is_vm_hugetlb_page(vma)) {
 803                 unsigned int forbidden = VM_PFNMAP;
 804
 805                 if (behavior != MADV_DONTNEED_LOCKED)
 806                         forbidden |= VM_LOCKED;
 807
 808                 return !(vma->vm_flags & forbidden);
 809         }
 810
 811         if (behavior != MADV_DONTNEED && behavior != MADV_DONTNEED_LOCKED)
 812                 return false;
 813         if (start & ~huge_page_mask(hstate_vma(vma)))
 814                 return false;
 815
 816         *end = ALIGN(*end, huge_page_size(hstate_vma(vma)));
 817         return true;
 818 }
 819
 820 static long madvise_dontneed_free(struct vm_area_struct *vma,
 821                                   struct vm_area_struct **prev,
 822                                   unsigned long start, unsigned long end,
 823                                   int behavior)
 824 {
 825         struct mm_struct *mm = vma->vm_mm;
 826
 827         *prev = vma;
 828         if (!madvise_dontneed_free_valid_vma(vma, start, &end, behavior))
 829                 return -EINVAL;
 830
 831         if (!userfaultfd_remove(vma, start, end)) {
 832                 *prev = NULL; /* mmap_lock has been dropped, prev is stale */
 833
 834                 mmap_read_lock(mm);
 835                 vma = find_vma(mm, start);
 836                 if (!vma)
 837                         return -ENOMEM;
 838                 if (start < vma->vm_start) {
 839                         /*
 840                          * This "vma" under revalidation is the one
 841                          * with the lowest vma->vm_start where start
 842                          * is also < vma->vm_end. If start <
 843                          * vma->vm_start it means an hole materialized
 844                          * in the user address space within the
 845                          * virtual range passed to MADV_DONTNEED
 846                          * or MADV_FREE.
 847                          */
 848                         return -ENOMEM;
 849                 }
 850                 /*
 851                  * Potential end adjustment for hugetlb vma is OK as
 852                  * the check below keeps end within vma.
 853                  */
 854                 if (!madvise_dontneed_free_valid_vma(vma, start, &end,
 855                                                      behavior))
 856                         return -EINVAL;
 857                 if (end > vma->vm_end) {
 858                         /*
 859                          * Don't fail if end > vma->vm_end. If the old
 860                          * vma was split while the mmap_lock was
 861                          * released the effect of the concurrent
 862                          * operation may not cause madvise() to
 863                          * have an undefined result. There may be an
 864                          * adjacent next vma that we'll walk
 865                          * next. userfaultfd_remove() will generate an
 866                          * UFFD_EVENT_REMOVE repetition on the
 867                          * end-vma->vm_end range, but the manager can
 868                          * handle a repetition fine.
 869                          */
 870                         end = vma->vm_end;
 871                 }
 872                 VM_WARN_ON(start >= end);
 873         }
 874
 875         if (behavior == MADV_DONTNEED || behavior == MADV_DONTNEED_LOCKED)
 876                 return madvise_dontneed_single_vma(vma, start, end);
 877         else if (behavior == MADV_FREE)
 878                 return madvise_free_single_vma(vma, start, end);
 879         else
 880                 return -EINVAL;
 881 }
 882
 883 static long madvise_populate(struct vm_area_struct *vma,
 884                              struct vm_area_struct **prev,
 885                              unsigned long start, unsigned long end,
 886                              int behavior)
 887 {
 888         const bool write = behavior == MADV_POPULATE_WRITE;
 889         struct mm_struct *mm = vma->vm_mm;
 890         unsigned long tmp_end;
 891         int locked = 1;
 892         long pages;
 893
 894         *prev = vma;
 895
 896         while (start < end) {
 897                 /*
 898                  * We might have temporarily dropped the lock. For example,
 899                  * our VMA might have been split.
 900                  */
 901                 if (!vma || start >= vma->vm_end) {
 902                         vma = vma_lookup(mm, start);
 903                         if (!vma)
 904                                 return -ENOMEM;
 905                 }
 906
 907                 tmp_end = min_t(unsigned long, end, vma->vm_end);
 908                 /* Populate (prefault) page tables readable/writable. */
 909                 pages = faultin_vma_page_range(vma, start, tmp_end, write,
 910                                                &locked);
 911                 if (!locked) {
 912                         mmap_read_lock(mm);
 913                         locked = 1;
 914                         *prev = NULL;
 915                         vma = NULL;
 916                 }
 917                 if (pages < 0) {
 918                         switch (pages) {
 919                         case -EINTR:
 920                                 return -EINTR;
 921                         case -EINVAL: /* Incompatible mappings / permissions. */
 922                                 return -EINVAL;
 923                         case -EHWPOISON:
 924                                 return -EHWPOISON;
 925                         case -EFAULT: /* VM_FAULT_SIGBUS or VM_FAULT_SIGSEGV */
 926                                 return -EFAULT;
 927                         default:
 928                                 pr_warn_once("%s: unhandled return value: %ld\n",
 929                                              __func__, pages);
 930                                 fallthrough;
 931                         case -ENOMEM:
 932                                 return -ENOMEM;
 933                         }
 934                 }
 935                 start += pages * PAGE_SIZE;
 936         }
 937         return 0;
 938 }
 939
 940 /*
 941  * Application wants to free up the pages and associated backing store.
 942  * This is effectively punching a hole into the middle of a file.
 943  */
 944 static long madvise_remove(struct vm_area_struct *vma,
 945                                 struct vm_area_struct **prev,
 946                                 unsigned long start, unsigned long end)
 947 {
 948         loff_t offset;
 949         int error;
 950         struct file *f;
 951         struct mm_struct *mm = vma->vm_mm;
 952
 953         *prev = NULL;   /* tell sys_madvise we drop mmap_lock */
 954
 955         if (vma->vm_flags & VM_LOCKED)
 956                 return -EINVAL;
 957
 958         f = vma->vm_file;
 959
 960         if (!f || !f->f_mapping || !f->f_mapping->host) {
 961                         return -EINVAL;
 962         }
 963
 964         if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
 965                 return -EACCES;
 966
 967         offset = (loff_t)(start - vma->vm_start)
 968                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 969
 970         /*
 971          * Filesystem's fallocate may need to take i_rwsem.  We need to
 972          * explicitly grab a reference because the vma (and hence the
 973          * vma's reference to the file) can go away as soon as we drop
 974          * mmap_lock.
 975          */
 976         get_file(f);
 977         if (userfaultfd_remove(vma, start, end)) {
 978                 /* mmap_lock was not released by userfaultfd_remove() */
 979                 mmap_read_unlock(mm);
 980         }
 981         error = vfs_fallocate(f,
 982                                 FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
 983                                 offset, end - start);
 984         fput(f);
 985         mmap_read_lock(mm);
 986         return error;
 987 }
 988
 989 /*
 990  * Apply an madvise behavior to a region of a vma.  madvise_update_vma
 991  * will handle splitting a vm area into separate areas, each area with its own
 992  * behavior.
 993  */
 994 static int madvise_vma_behavior(struct vm_area_struct *vma,
 995                                 struct vm_area_struct **prev,
 996                                 unsigned long start, unsigned long end,
 997                                 unsigned long behavior)
 998 {
 999         int error;
1000         struct anon_vma_name *anon_name;
1001         unsigned long new_flags = vma->vm_flags;
1002
1003         switch (behavior) {
1004         case MADV_REMOVE:
1005                 return madvise_remove(vma, prev, start, end);
1006         case MADV_WILLNEED:
1007                 return madvise_willneed(vma, prev, start, end);
1008         case MADV_COLD:
1009                 return madvise_cold(vma, prev, start, end);
1010         case MADV_PAGEOUT:
1011                 return madvise_pageout(vma, prev, start, end);
1012         case MADV_FREE:
1013         case MADV_DONTNEED:
1014         case MADV_DONTNEED_LOCKED:
1015                 return madvise_dontneed_free(vma, prev, start, end, behavior);
1016         case MADV_POPULATE_READ:
1017         case MADV_POPULATE_WRITE:
1018                 return madvise_populate(vma, prev, start, end, behavior);
1019         case MADV_NORMAL:
1020                 new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
1021                 break;
1022         case MADV_SEQUENTIAL:
1023                 new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
1024                 break;
1025         case MADV_RANDOM:
1026                 new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
1027                 break;
1028         case MADV_DONTFORK:
1029                 new_flags |= VM_DONTCOPY;
1030                 break;
1031         case MADV_DOFORK:
1032                 if (vma->vm_flags & VM_IO)
1033                         return -EINVAL;
1034                 new_flags &= ~VM_DONTCOPY;
1035                 break;
1036         case MADV_WIPEONFORK:
1037                 /* MADV_WIPEONFORK is only supported on anonymous memory. */
1038                 if (vma->vm_file || vma->vm_flags & VM_SHARED)
1039                         return -EINVAL;
1040                 new_flags |= VM_WIPEONFORK;
1041                 break;
1042         case MADV_KEEPONFORK:
1043                 new_flags &= ~VM_WIPEONFORK;
1044                 break;
1045         case MADV_DONTDUMP:
1046                 new_flags |= VM_DONTDUMP;
1047                 break;
1048         case MADV_DODUMP:
1049                 if (!is_vm_hugetlb_page(vma) && new_flags & VM_SPECIAL)
1050                         return -EINVAL;
1051                 new_flags &= ~VM_DONTDUMP;
1052                 break;
1053         case MADV_MERGEABLE:
1054         case MADV_UNMERGEABLE:
1055                 error = ksm_madvise(vma, start, end, behavior, &new_flags);
1056                 if (error)
1057                         goto out;
1058                 break;
1059         case MADV_HUGEPAGE:
1060         case MADV_NOHUGEPAGE:
1061                 error = hugepage_madvise(vma, &new_flags, behavior);
1062                 if (error)
1063                         goto out;
1064                 break;
1065         case MADV_COLLAPSE:
1066                 return madvise_collapse(vma, prev, start, end);
1067         }
1068
1069         anon_name = anon_vma_name(vma);
1070         anon_vma_name_get(anon_name);
1071         error = madvise_update_vma(vma, prev, start, end, new_flags,
1072                                    anon_name);
1073         anon_vma_name_put(anon_name);
1074
1075 out:
1076         /*
1077          * madvise() returns EAGAIN if kernel resources, such as
1078          * slab, are temporarily unavailable.
1079          */
1080         if (error == -ENOMEM)
1081                 error = -EAGAIN;
1082         return error;
1083 }
1084
1085 #ifdef CONFIG_MEMORY_FAILURE
1086 /*
1087  * Error injection support for memory error handling.
1088  */
1089 static int madvise_inject_error(int behavior,
1090                 unsigned long start, unsigned long end)
1091 {
1092         unsigned long size;
1093
1094         if (!capable(CAP_SYS_ADMIN))
1095                 return -EPERM;
1096
1097
1098         for (; start < end; start += size) {
1099                 unsigned long pfn;
1100                 struct page *page;
1101                 int ret;
1102
1103                 ret = get_user_pages_fast(start, 1, 0, &page);
1104                 if (ret != 1)
1105                         return ret;
1106                 pfn = page_to_pfn(page);
1107
1108                 /*
1109                  * When soft offlining hugepages, after migrating the page
1110                  * we dissolve it, therefore in the second loop "page" will
1111                  * no longer be a compound page.
1112                  */
1113                 size = page_size(compound_head(page));
1114
1115                 if (behavior == MADV_SOFT_OFFLINE) {
1116                         pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
1117                                  pfn, start);
1118                         ret = soft_offline_page(pfn, MF_COUNT_INCREASED);
1119                 } else {
1120                         pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
1121                                  pfn, start);
1122                         ret = memory_failure(pfn, MF_COUNT_INCREASED | MF_SW_SIMULATED);
1123                         if (ret == -EOPNOTSUPP)
1124                                 ret = 0;
1125                 }
1126
1127                 if (ret)
1128                         return ret;
1129         }
1130
1131         return 0;
1132 }
1133 #endif
1134
1135 static bool
1136 madvise_behavior_valid(int behavior)
1137 {
1138         switch (behavior) {
1139         case MADV_DOFORK:
1140         case MADV_DONTFORK:
1141         case MADV_NORMAL:
1142         case MADV_SEQUENTIAL:
1143         case MADV_RANDOM:
1144         case MADV_REMOVE:
1145         case MADV_WILLNEED:
1146         case MADV_DONTNEED:
1147         case MADV_DONTNEED_LOCKED:
1148         case MADV_FREE:
1149         case MADV_COLD:
1150         case MADV_PAGEOUT:
1151         case MADV_POPULATE_READ:
1152         case MADV_POPULATE_WRITE:
1153 #ifdef CONFIG_KSM
1154         case MADV_MERGEABLE:
1155         case MADV_UNMERGEABLE:
1156 #endif
1157 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
1158         case MADV_HUGEPAGE:
1159         case MADV_NOHUGEPAGE:
1160         case MADV_COLLAPSE:
1161 #endif
1162         case MADV_DONTDUMP:
1163         case MADV_DODUMP:
1164         case MADV_WIPEONFORK:
1165         case MADV_KEEPONFORK:
1166 #ifdef CONFIG_MEMORY_FAILURE
1167         case MADV_SOFT_OFFLINE:
1168         case MADV_HWPOISON:
1169 #endif
1170                 return true;
1171
1172         default:
1173                 return false;
1174         }
1175 }
1176
1177 static bool process_madvise_behavior_valid(int behavior)
1178 {
1179         switch (behavior) {
1180         case MADV_COLD:
1181         case MADV_PAGEOUT:
1182         case MADV_WILLNEED:
1183         case MADV_COLLAPSE:
1184                 return true;
1185         default:
1186                 return false;
1187         }
1188 }
1189
1190 /*
1191  * Walk the vmas in range [start,end), and call the visit function on each one.
1192  * The visit function will get start and end parameters that cover the overlap
1193  * between the current vma and the original range.  Any unmapped regions in the
1194  * original range will result in this function returning -ENOMEM while still
1195  * calling the visit function on all of the existing vmas in the range.
1196  * Must be called with the mmap_lock held for reading or writing.
1197  */
1198 static
1199 int madvise_walk_vmas(struct mm_struct *mm, unsigned long start,
1200                       unsigned long end, unsigned long arg,
1201                       int (*visit)(struct vm_area_struct *vma,
1202                                    struct vm_area_struct **prev, unsigned long start,
1203                                    unsigned long end, unsigned long arg))
1204 {
1205         struct vm_area_struct *vma;
1206         struct vm_area_struct *prev;
1207         unsigned long tmp;
1208         int unmapped_error = 0;
1209
1210         /*
1211          * If the interval [start,end) covers some unmapped address
1212          * ranges, just ignore them, but return -ENOMEM at the end.
1213          * - different from the way of handling in mlock etc.
1214          */
1215         vma = find_vma_prev(mm, start, &prev);
1216         if (vma && start > vma->vm_start)
1217                 prev = vma;
1218
1219         for (;;) {
1220                 int error;
1221
1222                 /* Still start < end. */
1223                 if (!vma)
1224                         return -ENOMEM;
1225
1226                 /* Here start < (end|vma->vm_end). */
1227                 if (start < vma->vm_start) {
1228                         unmapped_error = -ENOMEM;
1229                         start = vma->vm_start;
1230                         if (start >= end)
1231                                 break;
1232                 }
1233
1234                 /* Here vma->vm_start <= start < (end|vma->vm_end) */
1235                 tmp = vma->vm_end;
1236                 if (end < tmp)
1237                         tmp = end;
1238
1239                 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
1240                 error = visit(vma, &prev, start, tmp, arg);
1241                 if (error)
1242                         return error;
1243                 start = tmp;
1244                 if (prev && start < prev->vm_end)
1245                         start = prev->vm_end;
1246                 if (start >= end)
1247                         break;
1248                 if (prev)
1249                         vma = find_vma(mm, prev->vm_end);
1250                 else    /* madvise_remove dropped mmap_lock */
1251                         vma = find_vma(mm, start);
1252         }
1253
1254         return unmapped_error;
1255 }
1256
1257 #ifdef CONFIG_ANON_VMA_NAME
1258 static int madvise_vma_anon_name(struct vm_area_struct *vma,
1259                                  struct vm_area_struct **prev,
1260                                  unsigned long start, unsigned long end,
1261                                  unsigned long anon_name)
1262 {
1263         int error;
1264
1265         /* Only anonymous mappings can be named */
1266         if (vma->vm_file)
1267                 return -EBADF;
1268
1269         error = madvise_update_vma(vma, prev, start, end, vma->vm_flags,
1270                                    (struct anon_vma_name *)anon_name);
1271
1272         /*
1273          * madvise() returns EAGAIN if kernel resources, such as
1274          * slab, are temporarily unavailable.
1275          */
1276         if (error == -ENOMEM)
1277                 error = -EAGAIN;
1278         return error;
1279 }
1280
1281 int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
1282                           unsigned long len_in, struct anon_vma_name *anon_name)
1283 {
1284         unsigned long end;
1285         unsigned long len;
1286
1287         if (start & ~PAGE_MASK)
1288                 return -EINVAL;
1289         len = (len_in + ~PAGE_MASK) & PAGE_MASK;
1290
1291         /* Check to see whether len was rounded up from small -ve to zero */
1292         if (len_in && !len)
1293                 return -EINVAL;
1294
1295         end = start + len;
1296         if (end < start)
1297                 return -EINVAL;
1298
1299         if (end == start)
1300                 return 0;
1301
1302         return madvise_walk_vmas(mm, start, end, (unsigned long)anon_name,
1303                                  madvise_vma_anon_name);
1304 }
1305 #endif /* CONFIG_ANON_VMA_NAME */
1306 /*
1307  * The madvise(2) system call.
1308  *
1309  * Applications can use madvise() to advise the kernel how it should
1310  * handle paging I/O in this VM area.  The idea is to help the kernel
1311  * use appropriate read-ahead and caching techniques.  The information
1312  * provided is advisory only, and can be safely disregarded by the
1313  * kernel without affecting the correct operation of the application.
1314  *
1315  * behavior values:
1316  *  MADV_NORMAL - the default behavior is to read clusters.  This
1317  *              results in some read-ahead and read-behind.
1318  *  MADV_RANDOM - the system should read the minimum amount of data
1319  *              on any access, since it is unlikely that the appli-
1320  *              cation will need more than what it asks for.
1321  *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
1322  *              once, so they can be aggressively read ahead, and
1323  *              can be freed soon after they are accessed.
1324  *  MADV_WILLNEED - the application is notifying the system to read
1325  *              some pages ahead.
1326  *  MADV_DONTNEED - the application is finished with the given range,
1327  *              so the kernel can free resources associated with it.
1328  *  MADV_FREE - the application marks pages in the given range as lazy free,
1329  *              where actual purges are postponed until memory pressure happens.
1330  *  MADV_REMOVE - the application wants to free up the given range of
1331  *              pages and associated backing store.
1332  *  MADV_DONTFORK - omit this area from child's address space when forking:
1333  *              typically, to avoid COWing pages pinned by get_user_pages().
1334  *  MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
1335  *  MADV_WIPEONFORK - present the child process with zero-filled memory in this
1336  *              range after a fork.
1337  *  MADV_KEEPONFORK - undo the effect of MADV_WIPEONFORK
1338  *  MADV_HWPOISON - trigger memory error handler as if the given memory range
1339  *              were corrupted by unrecoverable hardware memory failure.
1340  *  MADV_SOFT_OFFLINE - try to soft-offline the given range of memory.
1341  *  MADV_MERGEABLE - the application recommends that KSM try to merge pages in
1342  *              this area with pages of identical content from other such areas.
1343  *  MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
1344  *  MADV_HUGEPAGE - the application wants to back the given range by transparent
1345  *              huge pages in the future. Existing pages might be coalesced and
1346  *              new pages might be allocated as THP.
1347  *  MADV_NOHUGEPAGE - mark the given range as not worth being backed by
1348  *              transparent huge pages so the existing pages will not be
1349  *              coalesced into THP and new pages will not be allocated as THP.
1350  *  MADV_COLLAPSE - synchronously coalesce pages into new THP.
1351  *  MADV_DONTDUMP - the application wants to prevent pages in the given range
1352  *              from being included in its core dump.
1353  *  MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
1354  *  MADV_COLD - the application is not expected to use this memory soon,
1355  *              deactivate pages in this range so that they can be reclaimed
1356  *              easily if memory pressure happens.
1357  *  MADV_PAGEOUT - the application is not expected to use this memory soon,
1358  *              page out the pages in this range immediately.
1359  *  MADV_POPULATE_READ - populate (prefault) page tables readable by
1360  *              triggering read faults if required
1361  *  MADV_POPULATE_WRITE - populate (prefault) page tables writable by
1362  *              triggering write faults if required
1363  *
1364  * return values:
1365  *  zero    - success
1366  *  -EINVAL - start + len < 0, start is not page-aligned,
1367  *              "behavior" is not a valid value, or application
1368  *              is attempting to release locked or shared pages,
1369  *              or the specified address range includes file, Huge TLB,
1370  *              MAP_SHARED or VMPFNMAP range.
1371  *  -ENOMEM - addresses in the specified range are not currently
1372  *              mapped, or are outside the AS of the process.
1373  *  -EIO    - an I/O error occurred while paging in data.
1374  *  -EBADF  - map exists, but area maps something that isn't a file.
1375  *  -EAGAIN - a kernel resource was temporarily unavailable.
1376  */
1377 int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int behavior)
1378 {
1379         unsigned long end;
1380         int error;
1381         int write;
1382         size_t len;
1383         struct blk_plug plug;
1384
1385         start = untagged_addr(start);
1386
1387         if (!madvise_behavior_valid(behavior))
1388                 return -EINVAL;
1389
1390         if (!PAGE_ALIGNED(start))
1391                 return -EINVAL;
1392         len = PAGE_ALIGN(len_in);
1393
1394         /* Check to see whether len was rounded up from small -ve to zero */
1395         if (len_in && !len)
1396                 return -EINVAL;
1397
1398         end = start + len;
1399         if (end < start)
1400                 return -EINVAL;
1401
1402         if (end == start)
1403                 return 0;
1404
1405 #ifdef CONFIG_MEMORY_FAILURE
1406         if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
1407                 return madvise_inject_error(behavior, start, start + len_in);
1408 #endif
1409
1410         write = madvise_need_mmap_write(behavior);
1411         if (write) {
1412                 if (mmap_write_lock_killable(mm))
1413                         return -EINTR;
1414         } else {
1415                 mmap_read_lock(mm);
1416         }
1417
1418         blk_start_plug(&plug);
1419         error = madvise_walk_vmas(mm, start, end, behavior,
1420                         madvise_vma_behavior);
1421         blk_finish_plug(&plug);
1422         if (write)
1423                 mmap_write_unlock(mm);
1424         else
1425                 mmap_read_unlock(mm);
1426
1427         return error;
1428 }
1429
1430 SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
1431 {
1432         return do_madvise(current->mm, start, len_in, behavior);
1433 }
1434
1435 SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
1436                 size_t, vlen, int, behavior, unsigned int, flags)
1437 {
1438         ssize_t ret;
1439         struct iovec iovstack[UIO_FASTIOV], iovec;
1440         struct iovec *iov = iovstack;
1441         struct iov_iter iter;
1442         struct task_struct *task;
1443         struct mm_struct *mm;
1444         size_t total_len;
1445         unsigned int f_flags;
1446
1447         if (flags != 0) {
1448                 ret = -EINVAL;
1449                 goto out;
1450         }
1451
1452         ret = import_iovec(READ, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);
1453         if (ret < 0)
1454                 goto out;
1455
1456         task = pidfd_get_task(pidfd, &f_flags);
1457         if (IS_ERR(task)) {
1458                 ret = PTR_ERR(task);
1459                 goto free_iov;
1460         }
1461
1462         if (!process_madvise_behavior_valid(behavior)) {
1463                 ret = -EINVAL;
1464                 goto release_task;
1465         }
1466
1467         /* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */
1468         mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
1469         if (IS_ERR_OR_NULL(mm)) {
1470                 ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
1471                 goto release_task;
1472         }
1473
1474         /*
1475          * Require CAP_SYS_NICE for influencing process performance. Note that
1476          * only non-destructive hints are currently supported.
1477          */
1478         if (!capable(CAP_SYS_NICE)) {
1479                 ret = -EPERM;
1480                 goto release_mm;
1481         }
1482
1483         total_len = iov_iter_count(&iter);
1484
1485         while (iov_iter_count(&iter)) {
1486                 iovec = iov_iter_iovec(&iter);
1487                 ret = do_madvise(mm, (unsigned long)iovec.iov_base,
1488                                         iovec.iov_len, behavior);
1489                 if (ret < 0)
1490                         break;
1491                 iov_iter_advance(&iter, iovec.iov_len);
1492         }
1493
1494         ret = (total_len - iov_iter_count(&iter)) ? : ret;
1495
1496 release_mm:
1497         mmput(mm);
1498 release_task:
1499         put_task_struct(task);
1500 free_iov:
1501         kfree(iov);
1502 out:
1503         return ret;
1504 }