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/userfaultfd_k.h>
  15 #include <linux/hugetlb.h>
  16 #include <linux/falloc.h>
  17 #include <linux/fadvise.h>
  18 #include <linux/sched.h>
  19 #include <linux/ksm.h>
  20 #include <linux/fs.h>
  21 #include <linux/file.h>
  22 #include <linux/blkdev.h>
  23 #include <linux/backing-dev.h>
  24 #include <linux/pagewalk.h>
  25 #include <linux/swap.h>
  26 #include <linux/swapops.h>
  27 #include <linux/shmem_fs.h>
  28 #include <linux/mmu_notifier.h>
  29
  30 #include <asm/tlb.h>
  31
  32 #include "internal.h"
  33
  34 /*
  35  * Any behaviour which results in changes to the vma->vm_flags needs to
  36  * take mmap_sem for writing. Others, which simply traverse vmas, need
  37  * to only take it for reading.
  38  */
  39 static int madvise_need_mmap_write(int behavior)
  40 {
  41         switch (behavior) {
  42         case MADV_REMOVE:
  43         case MADV_WILLNEED:
  44         case MADV_DONTNEED:
  45         case MADV_FREE:
  46                 return 0;
  47         default:
  48                 /* be safe, default to 1. list exceptions explicitly */
  49                 return 1;
  50         }
  51 }
  52
  53 /*
  54  * We can potentially split a vm area into separate
  55  * areas, each area with its own behavior.
  56  */
  57 static long madvise_behavior(struct vm_area_struct *vma,
  58                      struct vm_area_struct **prev,
  59                      unsigned long start, unsigned long end, int behavior)
  60 {
  61         struct mm_struct *mm = vma->vm_mm;
  62         int error = 0;
  63         pgoff_t pgoff;
  64         unsigned long new_flags = vma->vm_flags;
  65
  66         switch (behavior) {
  67         case MADV_NORMAL:
  68                 new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
  69                 break;
  70         case MADV_SEQUENTIAL:
  71                 new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
  72                 break;
  73         case MADV_RANDOM:
  74                 new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
  75                 break;
  76         case MADV_DONTFORK:
  77                 new_flags |= VM_DONTCOPY;
  78                 break;
  79         case MADV_DOFORK:
  80                 if (vma->vm_flags & VM_IO) {
  81                         error = -EINVAL;
  82                         goto out;
  83                 }
  84                 new_flags &= ~VM_DONTCOPY;
  85                 break;
  86         case MADV_WIPEONFORK:
  87                 /* MADV_WIPEONFORK is only supported on anonymous memory. */
  88                 if (vma->vm_file || vma->vm_flags & VM_SHARED) {
  89                         error = -EINVAL;
  90                         goto out;
  91                 }
  92                 new_flags |= VM_WIPEONFORK;
  93                 break;
  94         case MADV_KEEPONFORK:
  95                 new_flags &= ~VM_WIPEONFORK;
  96                 break;
  97         case MADV_DONTDUMP:
  98                 new_flags |= VM_DONTDUMP;
  99                 break;
 100         case MADV_DODUMP:
 101                 if (!is_vm_hugetlb_page(vma) && new_flags & VM_SPECIAL) {
 102                         error = -EINVAL;
 103                         goto out;
 104                 }
 105                 new_flags &= ~VM_DONTDUMP;
 106                 break;
 107         case MADV_MERGEABLE:
 108         case MADV_UNMERGEABLE:
 109                 error = ksm_madvise(vma, start, end, behavior, &new_flags);
 110                 if (error) {
 111                         /*
 112                          * madvise() returns EAGAIN if kernel resources, such as
 113                          * slab, are temporarily unavailable.
 114                          */
 115                         if (error == -ENOMEM)
 116                                 error = -EAGAIN;
 117                         goto out;
 118                 }
 119                 break;
 120         case MADV_HUGEPAGE:
 121         case MADV_NOHUGEPAGE:
 122                 error = hugepage_madvise(vma, &new_flags, behavior);
 123                 if (error) {
 124                         /*
 125                          * madvise() returns EAGAIN if kernel resources, such as
 126                          * slab, are temporarily unavailable.
 127                          */
 128                         if (error == -ENOMEM)
 129                                 error = -EAGAIN;
 130                         goto out;
 131                 }
 132                 break;
 133         }
 134
 135         if (new_flags == vma->vm_flags) {
 136                 *prev = vma;
 137                 goto out;
 138         }
 139
 140         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 141         *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
 142                           vma->vm_file, pgoff, vma_policy(vma),
 143                           vma->vm_userfaultfd_ctx);
 144         if (*prev) {
 145                 vma = *prev;
 146                 goto success;
 147         }
 148
 149         *prev = vma;
 150
 151         if (start != vma->vm_start) {
 152                 if (unlikely(mm->map_count >= sysctl_max_map_count)) {
 153                         error = -ENOMEM;
 154                         goto out;
 155                 }
 156                 error = __split_vma(mm, vma, start, 1);
 157                 if (error) {
 158                         /*
 159                          * madvise() returns EAGAIN if kernel resources, such as
 160                          * slab, are temporarily unavailable.
 161                          */
 162                         if (error == -ENOMEM)
 163                                 error = -EAGAIN;
 164                         goto out;
 165                 }
 166         }
 167
 168         if (end != vma->vm_end) {
 169                 if (unlikely(mm->map_count >= sysctl_max_map_count)) {
 170                         error = -ENOMEM;
 171                         goto out;
 172                 }
 173                 error = __split_vma(mm, vma, end, 0);
 174                 if (error) {
 175                         /*
 176                          * madvise() returns EAGAIN if kernel resources, such as
 177                          * slab, are temporarily unavailable.
 178                          */
 179                         if (error == -ENOMEM)
 180                                 error = -EAGAIN;
 181                         goto out;
 182                 }
 183         }
 184
 185 success:
 186         /*
 187          * vm_flags is protected by the mmap_sem held in write mode.
 188          */
 189         vma->vm_flags = new_flags;
 190 out:
 191         return error;
 192 }
 193
 194 #ifdef CONFIG_SWAP
 195 static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
 196         unsigned long end, struct mm_walk *walk)
 197 {
 198         pte_t *orig_pte;
 199         struct vm_area_struct *vma = walk->private;
 200         unsigned long index;
 201
 202         if (pmd_none_or_trans_huge_or_clear_bad(pmd))
 203                 return 0;
 204
 205         for (index = start; index != end; index += PAGE_SIZE) {
 206                 pte_t pte;
 207                 swp_entry_t entry;
 208                 struct page *page;
 209                 spinlock_t *ptl;
 210
 211                 orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
 212                 pte = *(orig_pte + ((index - start) / PAGE_SIZE));
 213                 pte_unmap_unlock(orig_pte, ptl);
 214
 215                 if (pte_present(pte) || pte_none(pte))
 216                         continue;
 217                 entry = pte_to_swp_entry(pte);
 218                 if (unlikely(non_swap_entry(entry)))
 219                         continue;
 220
 221                 page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
 222                                                         vma, index, false);
 223                 if (page)
 224                         put_page(page);
 225         }
 226
 227         return 0;
 228 }
 229
 230 static const struct mm_walk_ops swapin_walk_ops = {
 231         .pmd_entry              = swapin_walk_pmd_entry,
 232 };
 233
 234 static void force_shm_swapin_readahead(struct vm_area_struct *vma,
 235                 unsigned long start, unsigned long end,
 236                 struct address_space *mapping)
 237 {
 238         pgoff_t index;
 239         struct page *page;
 240         swp_entry_t swap;
 241
 242         for (; start < end; start += PAGE_SIZE) {
 243                 index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 244
 245                 page = find_get_entry(mapping, index);
 246                 if (!xa_is_value(page)) {
 247                         if (page)
 248                                 put_page(page);
 249                         continue;
 250                 }
 251                 swap = radix_to_swp_entry(page);
 252                 page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
 253                                                         NULL, 0, false);
 254                 if (page)
 255                         put_page(page);
 256         }
 257
 258         lru_add_drain();        /* Push any new pages onto the LRU now */
 259 }
 260 #endif          /* CONFIG_SWAP */
 261
 262 /*
 263  * Schedule all required I/O operations.  Do not wait for completion.
 264  */
 265 static long madvise_willneed(struct vm_area_struct *vma,
 266                              struct vm_area_struct **prev,
 267                              unsigned long start, unsigned long end)
 268 {
 269         struct file *file = vma->vm_file;
 270         loff_t offset;
 271
 272         *prev = vma;
 273 #ifdef CONFIG_SWAP
 274         if (!file) {
 275                 walk_page_range(vma->vm_mm, start, end, &swapin_walk_ops, vma);
 276                 lru_add_drain(); /* Push any new pages onto the LRU now */
 277                 return 0;
 278         }
 279
 280         if (shmem_mapping(file->f_mapping)) {
 281                 force_shm_swapin_readahead(vma, start, end,
 282                                         file->f_mapping);
 283                 return 0;
 284         }
 285 #else
 286         if (!file)
 287                 return -EBADF;
 288 #endif
 289
 290         if (IS_DAX(file_inode(file))) {
 291                 /* no bad return value, but ignore advice */
 292                 return 0;
 293         }
 294
 295         /*
 296          * Filesystem's fadvise may need to take various locks.  We need to
 297          * explicitly grab a reference because the vma (and hence the
 298          * vma's reference to the file) can go away as soon as we drop
 299          * mmap_sem.
 300          */
 301         *prev = NULL;   /* tell sys_madvise we drop mmap_sem */
 302         get_file(file);
 303         up_read(&current->mm->mmap_sem);
 304         offset = (loff_t)(start - vma->vm_start)
 305                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 306         vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED);
 307         fput(file);
 308         down_read(&current->mm->mmap_sem);
 309         return 0;
 310 }
 311
 312 static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 313                                 unsigned long end, struct mm_walk *walk)
 314
 315 {
 316         struct mmu_gather *tlb = walk->private;
 317         struct mm_struct *mm = tlb->mm;
 318         struct vm_area_struct *vma = walk->vma;
 319         spinlock_t *ptl;
 320         pte_t *orig_pte, *pte, ptent;
 321         struct page *page;
 322         int nr_swap = 0;
 323         unsigned long next;
 324
 325         next = pmd_addr_end(addr, end);
 326         if (pmd_trans_huge(*pmd))
 327                 if (madvise_free_huge_pmd(tlb, vma, pmd, addr, next))
 328                         goto next;
 329
 330         if (pmd_trans_unstable(pmd))
 331                 return 0;
 332
 333         tlb_change_page_size(tlb, PAGE_SIZE);
 334         orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 335         flush_tlb_batched_pending(mm);
 336         arch_enter_lazy_mmu_mode();
 337         for (; addr != end; pte++, addr += PAGE_SIZE) {
 338                 ptent = *pte;
 339
 340                 if (pte_none(ptent))
 341                         continue;
 342                 /*
 343                  * If the pte has swp_entry, just clear page table to
 344                  * prevent swap-in which is more expensive rather than
 345                  * (page allocation + zeroing).
 346                  */
 347                 if (!pte_present(ptent)) {
 348                         swp_entry_t entry;
 349
 350                         entry = pte_to_swp_entry(ptent);
 351                         if (non_swap_entry(entry))
 352                                 continue;
 353                         nr_swap--;
 354                         free_swap_and_cache(entry);
 355                         pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
 356                         continue;
 357                 }
 358
 359                 page = vm_normal_page(vma, addr, ptent);
 360                 if (!page)
 361                         continue;
 362
 363                 /*
 364                  * If pmd isn't transhuge but the page is THP and
 365                  * is owned by only this process, split it and
 366                  * deactivate all pages.
 367                  */
 368                 if (PageTransCompound(page)) {
 369                         if (page_mapcount(page) != 1)
 370                                 goto out;
 371                         get_page(page);
 372                         if (!trylock_page(page)) {
 373                                 put_page(page);
 374                                 goto out;
 375                         }
 376                         pte_unmap_unlock(orig_pte, ptl);
 377                         if (split_huge_page(page)) {
 378                                 unlock_page(page);
 379                                 put_page(page);
 380                                 pte_offset_map_lock(mm, pmd, addr, &ptl);
 381                                 goto out;
 382                         }
 383                         unlock_page(page);
 384                         put_page(page);
 385                         pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 386                         pte--;
 387                         addr -= PAGE_SIZE;
 388                         continue;
 389                 }
 390
 391                 VM_BUG_ON_PAGE(PageTransCompound(page), page);
 392
 393                 if (PageSwapCache(page) || PageDirty(page)) {
 394                         if (!trylock_page(page))
 395                                 continue;
 396                         /*
 397                          * If page is shared with others, we couldn't clear
 398                          * PG_dirty of the page.
 399                          */
 400                         if (page_mapcount(page) != 1) {
 401                                 unlock_page(page);
 402                                 continue;
 403                         }
 404
 405                         if (PageSwapCache(page) && !try_to_free_swap(page)) {
 406                                 unlock_page(page);
 407                                 continue;
 408                         }
 409
 410                         ClearPageDirty(page);
 411                         unlock_page(page);
 412                 }
 413
 414                 if (pte_young(ptent) || pte_dirty(ptent)) {
 415                         /*
 416                          * Some of architecture(ex, PPC) don't update TLB
 417                          * with set_pte_at and tlb_remove_tlb_entry so for
 418                          * the portability, remap the pte with old|clean
 419                          * after pte clearing.
 420                          */
 421                         ptent = ptep_get_and_clear_full(mm, addr, pte,
 422                                                         tlb->fullmm);
 423
 424                         ptent = pte_mkold(ptent);
 425                         ptent = pte_mkclean(ptent);
 426                         set_pte_at(mm, addr, pte, ptent);
 427                         tlb_remove_tlb_entry(tlb, pte, addr);
 428                 }
 429                 mark_page_lazyfree(page);
 430         }
 431 out:
 432         if (nr_swap) {
 433                 if (current->mm == mm)
 434                         sync_mm_rss(mm);
 435
 436                 add_mm_counter(mm, MM_SWAPENTS, nr_swap);
 437         }
 438         arch_leave_lazy_mmu_mode();
 439         pte_unmap_unlock(orig_pte, ptl);
 440         cond_resched();
 441 next:
 442         return 0;
 443 }
 444
 445 static const struct mm_walk_ops madvise_free_walk_ops = {
 446         .pmd_entry              = madvise_free_pte_range,
 447 };
 448
 449 static int madvise_free_single_vma(struct vm_area_struct *vma,
 450                         unsigned long start_addr, unsigned long end_addr)
 451 {
 452         struct mm_struct *mm = vma->vm_mm;
 453         struct mmu_notifier_range range;
 454         struct mmu_gather tlb;
 455
 456         /* MADV_FREE works for only anon vma at the moment */
 457         if (!vma_is_anonymous(vma))
 458                 return -EINVAL;
 459
 460         range.start = max(vma->vm_start, start_addr);
 461         if (range.start >= vma->vm_end)
 462                 return -EINVAL;
 463         range.end = min(vma->vm_end, end_addr);
 464         if (range.end <= vma->vm_start)
 465                 return -EINVAL;
 466         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm,
 467                                 range.start, range.end);
 468
 469         lru_add_drain();
 470         tlb_gather_mmu(&tlb, mm, range.start, range.end);
 471         update_hiwater_rss(mm);
 472
 473         mmu_notifier_invalidate_range_start(&range);
 474         tlb_start_vma(&tlb, vma);
 475         walk_page_range(vma->vm_mm, range.start, range.end,
 476                         &madvise_free_walk_ops, &tlb);
 477         tlb_end_vma(&tlb, vma);
 478         mmu_notifier_invalidate_range_end(&range);
 479         tlb_finish_mmu(&tlb, range.start, range.end);
 480
 481         return 0;
 482 }
 483
 484 /*
 485  * Application no longer needs these pages.  If the pages are dirty,
 486  * it's OK to just throw them away.  The app will be more careful about
 487  * data it wants to keep.  Be sure to free swap resources too.  The
 488  * zap_page_range call sets things up for shrink_active_list to actually free
 489  * these pages later if no one else has touched them in the meantime,
 490  * although we could add these pages to a global reuse list for
 491  * shrink_active_list to pick up before reclaiming other pages.
 492  *
 493  * NB: This interface discards data rather than pushes it out to swap,
 494  * as some implementations do.  This has performance implications for
 495  * applications like large transactional databases which want to discard
 496  * pages in anonymous maps after committing to backing store the data
 497  * that was kept in them.  There is no reason to write this data out to
 498  * the swap area if the application is discarding it.
 499  *
 500  * An interface that causes the system to free clean pages and flush
 501  * dirty pages is already available as msync(MS_INVALIDATE).
 502  */
 503 static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
 504                                         unsigned long start, unsigned long end)
 505 {
 506         zap_page_range(vma, start, end - start);
 507         return 0;
 508 }
 509
 510 static long madvise_dontneed_free(struct vm_area_struct *vma,
 511                                   struct vm_area_struct **prev,
 512                                   unsigned long start, unsigned long end,
 513                                   int behavior)
 514 {
 515         *prev = vma;
 516         if (!can_madv_dontneed_vma(vma))
 517                 return -EINVAL;
 518
 519         if (!userfaultfd_remove(vma, start, end)) {
 520                 *prev = NULL; /* mmap_sem has been dropped, prev is stale */
 521
 522                 down_read(&current->mm->mmap_sem);
 523                 vma = find_vma(current->mm, start);
 524                 if (!vma)
 525                         return -ENOMEM;
 526                 if (start < vma->vm_start) {
 527                         /*
 528                          * This "vma" under revalidation is the one
 529                          * with the lowest vma->vm_start where start
 530                          * is also < vma->vm_end. If start <
 531                          * vma->vm_start it means an hole materialized
 532                          * in the user address space within the
 533                          * virtual range passed to MADV_DONTNEED
 534                          * or MADV_FREE.
 535                          */
 536                         return -ENOMEM;
 537                 }
 538                 if (!can_madv_dontneed_vma(vma))
 539                         return -EINVAL;
 540                 if (end > vma->vm_end) {
 541                         /*
 542                          * Don't fail if end > vma->vm_end. If the old
 543                          * vma was splitted while the mmap_sem was
 544                          * released the effect of the concurrent
 545                          * operation may not cause madvise() to
 546                          * have an undefined result. There may be an
 547                          * adjacent next vma that we'll walk
 548                          * next. userfaultfd_remove() will generate an
 549                          * UFFD_EVENT_REMOVE repetition on the
 550                          * end-vma->vm_end range, but the manager can
 551                          * handle a repetition fine.
 552                          */
 553                         end = vma->vm_end;
 554                 }
 555                 VM_WARN_ON(start >= end);
 556         }
 557
 558         if (behavior == MADV_DONTNEED)
 559                 return madvise_dontneed_single_vma(vma, start, end);
 560         else if (behavior == MADV_FREE)
 561                 return madvise_free_single_vma(vma, start, end);
 562         else
 563                 return -EINVAL;
 564 }
 565
 566 /*
 567  * Application wants to free up the pages and associated backing store.
 568  * This is effectively punching a hole into the middle of a file.
 569  */
 570 static long madvise_remove(struct vm_area_struct *vma,
 571                                 struct vm_area_struct **prev,
 572                                 unsigned long start, unsigned long end)
 573 {
 574         loff_t offset;
 575         int error;
 576         struct file *f;
 577
 578         *prev = NULL;   /* tell sys_madvise we drop mmap_sem */
 579
 580         if (vma->vm_flags & VM_LOCKED)
 581                 return -EINVAL;
 582
 583         f = vma->vm_file;
 584
 585         if (!f || !f->f_mapping || !f->f_mapping->host) {
 586                         return -EINVAL;
 587         }
 588
 589         if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
 590                 return -EACCES;
 591
 592         offset = (loff_t)(start - vma->vm_start)
 593                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 594
 595         /*
 596          * Filesystem's fallocate may need to take i_mutex.  We need to
 597          * explicitly grab a reference because the vma (and hence the
 598          * vma's reference to the file) can go away as soon as we drop
 599          * mmap_sem.
 600          */
 601         get_file(f);
 602         if (userfaultfd_remove(vma, start, end)) {
 603                 /* mmap_sem was not released by userfaultfd_remove() */
 604                 up_read(&current->mm->mmap_sem);
 605         }
 606         error = vfs_fallocate(f,
 607                                 FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
 608                                 offset, end - start);
 609         fput(f);
 610         down_read(&current->mm->mmap_sem);
 611         return error;
 612 }
 613
 614 #ifdef CONFIG_MEMORY_FAILURE
 615 /*
 616  * Error injection support for memory error handling.
 617  */
 618 static int madvise_inject_error(int behavior,
 619                 unsigned long start, unsigned long end)
 620 {
 621         struct page *page;
 622         struct zone *zone;
 623         unsigned int order;
 624
 625         if (!capable(CAP_SYS_ADMIN))
 626                 return -EPERM;
 627
 628
 629         for (; start < end; start += PAGE_SIZE << order) {
 630                 unsigned long pfn;
 631                 int ret;
 632
 633                 ret = get_user_pages_fast(start, 1, 0, &page);
 634                 if (ret != 1)
 635                         return ret;
 636                 pfn = page_to_pfn(page);
 637
 638                 /*
 639                  * When soft offlining hugepages, after migrating the page
 640                  * we dissolve it, therefore in the second loop "page" will
 641                  * no longer be a compound page, and order will be 0.
 642                  */
 643                 order = compound_order(compound_head(page));
 644
 645                 if (PageHWPoison(page)) {
 646                         put_page(page);
 647                         continue;
 648                 }
 649
 650                 if (behavior == MADV_SOFT_OFFLINE) {
 651                         pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
 652                                         pfn, start);
 653
 654                         ret = soft_offline_page(page, MF_COUNT_INCREASED);
 655                         if (ret)
 656                                 return ret;
 657                         continue;
 658                 }
 659
 660                 pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
 661                                 pfn, start);
 662
 663                 /*
 664                  * Drop the page reference taken by get_user_pages_fast(). In
 665                  * the absence of MF_COUNT_INCREASED the memory_failure()
 666                  * routine is responsible for pinning the page to prevent it
 667                  * from being released back to the page allocator.
 668                  */
 669                 put_page(page);
 670                 ret = memory_failure(pfn, 0);
 671                 if (ret)
 672                         return ret;
 673         }
 674
 675         /* Ensure that all poisoned pages are removed from per-cpu lists */
 676         for_each_populated_zone(zone)
 677                 drain_all_pages(zone);
 678
 679         return 0;
 680 }
 681 #endif
 682
 683 static long
 684 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 685                 unsigned long start, unsigned long end, int behavior)
 686 {
 687         switch (behavior) {
 688         case MADV_REMOVE:
 689                 return madvise_remove(vma, prev, start, end);
 690         case MADV_WILLNEED:
 691                 return madvise_willneed(vma, prev, start, end);
 692         case MADV_FREE:
 693         case MADV_DONTNEED:
 694                 return madvise_dontneed_free(vma, prev, start, end, behavior);
 695         default:
 696                 return madvise_behavior(vma, prev, start, end, behavior);
 697         }
 698 }
 699
 700 static bool
 701 madvise_behavior_valid(int behavior)
 702 {
 703         switch (behavior) {
 704         case MADV_DOFORK:
 705         case MADV_DONTFORK:
 706         case MADV_NORMAL:
 707         case MADV_SEQUENTIAL:
 708         case MADV_RANDOM:
 709         case MADV_REMOVE:
 710         case MADV_WILLNEED:
 711         case MADV_DONTNEED:
 712         case MADV_FREE:
 713 #ifdef CONFIG_KSM
 714         case MADV_MERGEABLE:
 715         case MADV_UNMERGEABLE:
 716 #endif
 717 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 718         case MADV_HUGEPAGE:
 719         case MADV_NOHUGEPAGE:
 720 #endif
 721         case MADV_DONTDUMP:
 722         case MADV_DODUMP:
 723         case MADV_WIPEONFORK:
 724         case MADV_KEEPONFORK:
 725 #ifdef CONFIG_MEMORY_FAILURE
 726         case MADV_SOFT_OFFLINE:
 727         case MADV_HWPOISON:
 728 #endif
 729                 return true;
 730
 731         default:
 732                 return false;
 733         }
 734 }
 735
 736 /*
 737  * The madvise(2) system call.
 738  *
 739  * Applications can use madvise() to advise the kernel how it should
 740  * handle paging I/O in this VM area.  The idea is to help the kernel
 741  * use appropriate read-ahead and caching techniques.  The information
 742  * provided is advisory only, and can be safely disregarded by the
 743  * kernel without affecting the correct operation of the application.
 744  *
 745  * behavior values:
 746  *  MADV_NORMAL - the default behavior is to read clusters.  This
 747  *              results in some read-ahead and read-behind.
 748  *  MADV_RANDOM - the system should read the minimum amount of data
 749  *              on any access, since it is unlikely that the appli-
 750  *              cation will need more than what it asks for.
 751  *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
 752  *              once, so they can be aggressively read ahead, and
 753  *              can be freed soon after they are accessed.
 754  *  MADV_WILLNEED - the application is notifying the system to read
 755  *              some pages ahead.
 756  *  MADV_DONTNEED - the application is finished with the given range,
 757  *              so the kernel can free resources associated with it.
 758  *  MADV_FREE - the application marks pages in the given range as lazy free,
 759  *              where actual purges are postponed until memory pressure happens.
 760  *  MADV_REMOVE - the application wants to free up the given range of
 761  *              pages and associated backing store.
 762  *  MADV_DONTFORK - omit this area from child's address space when forking:
 763  *              typically, to avoid COWing pages pinned by get_user_pages().
 764  *  MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
 765  *  MADV_WIPEONFORK - present the child process with zero-filled memory in this
 766  *              range after a fork.
 767  *  MADV_KEEPONFORK - undo the effect of MADV_WIPEONFORK
 768  *  MADV_HWPOISON - trigger memory error handler as if the given memory range
 769  *              were corrupted by unrecoverable hardware memory failure.
 770  *  MADV_SOFT_OFFLINE - try to soft-offline the given range of memory.
 771  *  MADV_MERGEABLE - the application recommends that KSM try to merge pages in
 772  *              this area with pages of identical content from other such areas.
 773  *  MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
 774  *  MADV_HUGEPAGE - the application wants to back the given range by transparent
 775  *              huge pages in the future. Existing pages might be coalesced and
 776  *              new pages might be allocated as THP.
 777  *  MADV_NOHUGEPAGE - mark the given range as not worth being backed by
 778  *              transparent huge pages so the existing pages will not be
 779  *              coalesced into THP and new pages will not be allocated as THP.
 780  *  MADV_DONTDUMP - the application wants to prevent pages in the given range
 781  *              from being included in its core dump.
 782  *  MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
 783  *
 784  * return values:
 785  *  zero    - success
 786  *  -EINVAL - start + len < 0, start is not page-aligned,
 787  *              "behavior" is not a valid value, or application
 788  *              is attempting to release locked or shared pages,
 789  *              or the specified address range includes file, Huge TLB,
 790  *              MAP_SHARED or VMPFNMAP range.
 791  *  -ENOMEM - addresses in the specified range are not currently
 792  *              mapped, or are outside the AS of the process.
 793  *  -EIO    - an I/O error occurred while paging in data.
 794  *  -EBADF  - map exists, but area maps something that isn't a file.
 795  *  -EAGAIN - a kernel resource was temporarily unavailable.
 796  */
 797 SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
 798 {
 799         unsigned long end, tmp;
 800         struct vm_area_struct *vma, *prev;
 801         int unmapped_error = 0;
 802         int error = -EINVAL;
 803         int write;
 804         size_t len;
 805         struct blk_plug plug;
 806
 807         if (!madvise_behavior_valid(behavior))
 808                 return error;
 809
 810         if (start & ~PAGE_MASK)
 811                 return error;
 812         len = (len_in + ~PAGE_MASK) & PAGE_MASK;
 813
 814         /* Check to see whether len was rounded up from small -ve to zero */
 815         if (len_in && !len)
 816                 return error;
 817
 818         end = start + len;
 819         if (end < start)
 820                 return error;
 821
 822         error = 0;
 823         if (end == start)
 824                 return error;
 825
 826 #ifdef CONFIG_MEMORY_FAILURE
 827         if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
 828                 return madvise_inject_error(behavior, start, start + len_in);
 829 #endif
 830
 831         write = madvise_need_mmap_write(behavior);
 832         if (write) {
 833                 if (down_write_killable(&current->mm->mmap_sem))
 834                         return -EINTR;
 835         } else {
 836                 down_read(&current->mm->mmap_sem);
 837         }
 838
 839         /*
 840          * If the interval [start,end) covers some unmapped address
 841          * ranges, just ignore them, but return -ENOMEM at the end.
 842          * - different from the way of handling in mlock etc.
 843          */
 844         vma = find_vma_prev(current->mm, start, &prev);
 845         if (vma && start > vma->vm_start)
 846                 prev = vma;
 847
 848         blk_start_plug(&plug);
 849         for (;;) {
 850                 /* Still start < end. */
 851                 error = -ENOMEM;
 852                 if (!vma)
 853                         goto out;
 854
 855                 /* Here start < (end|vma->vm_end). */
 856                 if (start < vma->vm_start) {
 857                         unmapped_error = -ENOMEM;
 858                         start = vma->vm_start;
 859                         if (start >= end)
 860                                 goto out;
 861                 }
 862
 863                 /* Here vma->vm_start <= start < (end|vma->vm_end) */
 864                 tmp = vma->vm_end;
 865                 if (end < tmp)
 866                         tmp = end;
 867
 868                 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
 869                 error = madvise_vma(vma, &prev, start, tmp, behavior);
 870                 if (error)
 871                         goto out;
 872                 start = tmp;
 873                 if (prev && start < prev->vm_end)
 874                         start = prev->vm_end;
 875                 error = unmapped_error;
 876                 if (start >= end)
 877                         goto out;
 878                 if (prev)
 879                         vma = prev->vm_next;
 880                 else    /* madvise_remove dropped mmap_sem */
 881                         vma = find_vma(current->mm, start);
 882         }
 883 out:
 884         blk_finish_plug(&plug);
 885         if (write)
 886                 up_write(&current->mm->mmap_sem);
 887         else
 888                 up_read(&current->mm->mmap_sem);
 889
 890         return error;
 891 }