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/sched.h>
  18 #include <linux/ksm.h>
  19 #include <linux/fs.h>
  20 #include <linux/file.h>
  21 #include <linux/blkdev.h>
  22 #include <linux/backing-dev.h>
  23 #include <linux/swap.h>
  24 #include <linux/swapops.h>
  25 #include <linux/shmem_fs.h>
  26 #include <linux/mmu_notifier.h>
  27
  28 #include <asm/tlb.h>
  29
  30 #include "internal.h"
  31
  32 /*
  33  * Any behaviour which results in changes to the vma->vm_flags needs to
  34  * take mmap_sem for writing. Others, which simply traverse vmas, need
  35  * to only take it for reading.
  36  */
  37 static int madvise_need_mmap_write(int behavior)
  38 {
  39         switch (behavior) {
  40         case MADV_REMOVE:
  41         case MADV_WILLNEED:
  42         case MADV_DONTNEED:
  43         case MADV_FREE:
  44                 return 0;
  45         default:
  46                 /* be safe, default to 1. list exceptions explicitly */
  47                 return 1;
  48         }
  49 }
  50
  51 /*
  52  * We can potentially split a vm area into separate
  53  * areas, each area with its own behavior.
  54  */
  55 static long madvise_behavior(struct vm_area_struct *vma,
  56                      struct vm_area_struct **prev,
  57                      unsigned long start, unsigned long end, int behavior)
  58 {
  59         struct mm_struct *mm = vma->vm_mm;
  60         int error = 0;
  61         pgoff_t pgoff;
  62         unsigned long new_flags = vma->vm_flags;
  63
  64         switch (behavior) {
  65         case MADV_NORMAL:
  66                 new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
  67                 break;
  68         case MADV_SEQUENTIAL:
  69                 new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
  70                 break;
  71         case MADV_RANDOM:
  72                 new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
  73                 break;
  74         case MADV_DONTFORK:
  75                 new_flags |= VM_DONTCOPY;
  76                 break;
  77         case MADV_DOFORK:
  78                 if (vma->vm_flags & VM_IO) {
  79                         error = -EINVAL;
  80                         goto out;
  81                 }
  82                 new_flags &= ~VM_DONTCOPY;
  83                 break;
  84         case MADV_WIPEONFORK:
  85                 /* MADV_WIPEONFORK is only supported on anonymous memory. */
  86                 if (vma->vm_file || vma->vm_flags & VM_SHARED) {
  87                         error = -EINVAL;
  88                         goto out;
  89                 }
  90                 new_flags |= VM_WIPEONFORK;
  91                 break;
  92         case MADV_KEEPONFORK:
  93                 new_flags &= ~VM_WIPEONFORK;
  94                 break;
  95         case MADV_DONTDUMP:
  96                 new_flags |= VM_DONTDUMP;
  97                 break;
  98         case MADV_DODUMP:
  99                 if (!is_vm_hugetlb_page(vma) && new_flags & VM_SPECIAL) {
 100                         error = -EINVAL;
 101                         goto out;
 102                 }
 103                 new_flags &= ~VM_DONTDUMP;
 104                 break;
 105         case MADV_MERGEABLE:
 106         case MADV_UNMERGEABLE:
 107                 error = ksm_madvise(vma, start, end, behavior, &new_flags);
 108                 if (error) {
 109                         /*
 110                          * madvise() returns EAGAIN if kernel resources, such as
 111                          * slab, are temporarily unavailable.
 112                          */
 113                         if (error == -ENOMEM)
 114                                 error = -EAGAIN;
 115                         goto out;
 116                 }
 117                 break;
 118         case MADV_HUGEPAGE:
 119         case MADV_NOHUGEPAGE:
 120                 error = hugepage_madvise(vma, &new_flags, behavior);
 121                 if (error) {
 122                         /*
 123                          * madvise() returns EAGAIN if kernel resources, such as
 124                          * slab, are temporarily unavailable.
 125                          */
 126                         if (error == -ENOMEM)
 127                                 error = -EAGAIN;
 128                         goto out;
 129                 }
 130                 break;
 131         }
 132
 133         if (new_flags == vma->vm_flags) {
 134                 *prev = vma;
 135                 goto out;
 136         }
 137
 138         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 139         *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
 140                           vma->vm_file, pgoff, vma_policy(vma),
 141                           vma->vm_userfaultfd_ctx);
 142         if (*prev) {
 143                 vma = *prev;
 144                 goto success;
 145         }
 146
 147         *prev = vma;
 148
 149         if (start != vma->vm_start) {
 150                 if (unlikely(mm->map_count >= sysctl_max_map_count)) {
 151                         error = -ENOMEM;
 152                         goto out;
 153                 }
 154                 error = __split_vma(mm, vma, start, 1);
 155                 if (error) {
 156                         /*
 157                          * madvise() returns EAGAIN if kernel resources, such as
 158                          * slab, are temporarily unavailable.
 159                          */
 160                         if (error == -ENOMEM)
 161                                 error = -EAGAIN;
 162                         goto out;
 163                 }
 164         }
 165
 166         if (end != vma->vm_end) {
 167                 if (unlikely(mm->map_count >= sysctl_max_map_count)) {
 168                         error = -ENOMEM;
 169                         goto out;
 170                 }
 171                 error = __split_vma(mm, vma, end, 0);
 172                 if (error) {
 173                         /*
 174                          * madvise() returns EAGAIN if kernel resources, such as
 175                          * slab, are temporarily unavailable.
 176                          */
 177                         if (error == -ENOMEM)
 178                                 error = -EAGAIN;
 179                         goto out;
 180                 }
 181         }
 182
 183 success:
 184         /*
 185          * vm_flags is protected by the mmap_sem held in write mode.
 186          */
 187         vma->vm_flags = new_flags;
 188 out:
 189         return error;
 190 }
 191
 192 #ifdef CONFIG_SWAP
 193 static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
 194         unsigned long end, struct mm_walk *walk)
 195 {
 196         pte_t *orig_pte;
 197         struct vm_area_struct *vma = walk->private;
 198         unsigned long index;
 199
 200         if (pmd_none_or_trans_huge_or_clear_bad(pmd))
 201                 return 0;
 202
 203         for (index = start; index != end; index += PAGE_SIZE) {
 204                 pte_t pte;
 205                 swp_entry_t entry;
 206                 struct page *page;
 207                 spinlock_t *ptl;
 208
 209                 orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
 210                 pte = *(orig_pte + ((index - start) / PAGE_SIZE));
 211                 pte_unmap_unlock(orig_pte, ptl);
 212
 213                 if (pte_present(pte) || pte_none(pte))
 214                         continue;
 215                 entry = pte_to_swp_entry(pte);
 216                 if (unlikely(non_swap_entry(entry)))
 217                         continue;
 218
 219                 page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
 220                                                         vma, index, false);
 221                 if (page)
 222                         put_page(page);
 223         }
 224
 225         return 0;
 226 }
 227
 228 static void force_swapin_readahead(struct vm_area_struct *vma,
 229                 unsigned long start, unsigned long end)
 230 {
 231         struct mm_walk walk = {
 232                 .mm = vma->vm_mm,
 233                 .pmd_entry = swapin_walk_pmd_entry,
 234                 .private = vma,
 235         };
 236
 237         walk_page_range(start, end, &walk);
 238
 239         lru_add_drain();        /* Push any new pages onto the LRU now */
 240 }
 241
 242 static void force_shm_swapin_readahead(struct vm_area_struct *vma,
 243                 unsigned long start, unsigned long end,
 244                 struct address_space *mapping)
 245 {
 246         pgoff_t index;
 247         struct page *page;
 248         swp_entry_t swap;
 249
 250         for (; start < end; start += PAGE_SIZE) {
 251                 index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 252
 253                 page = find_get_entry(mapping, index);
 254                 if (!xa_is_value(page)) {
 255                         if (page)
 256                                 put_page(page);
 257                         continue;
 258                 }
 259                 swap = radix_to_swp_entry(page);
 260                 page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
 261                                                         NULL, 0, false);
 262                 if (page)
 263                         put_page(page);
 264         }
 265
 266         lru_add_drain();        /* Push any new pages onto the LRU now */
 267 }
 268 #endif          /* CONFIG_SWAP */
 269
 270 /*
 271  * Schedule all required I/O operations.  Do not wait for completion.
 272  */
 273 static long madvise_willneed(struct vm_area_struct *vma,
 274                              struct vm_area_struct **prev,
 275                              unsigned long start, unsigned long end)
 276 {
 277         struct file *file = vma->vm_file;
 278
 279         *prev = vma;
 280 #ifdef CONFIG_SWAP
 281         if (!file) {
 282                 force_swapin_readahead(vma, start, end);
 283                 return 0;
 284         }
 285
 286         if (shmem_mapping(file->f_mapping)) {
 287                 force_shm_swapin_readahead(vma, start, end,
 288                                         file->f_mapping);
 289                 return 0;
 290         }
 291 #else
 292         if (!file)
 293                 return -EBADF;
 294 #endif
 295
 296         if (IS_DAX(file_inode(file))) {
 297                 /* no bad return value, but ignore advice */
 298                 return 0;
 299         }
 300
 301         start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 302         if (end > vma->vm_end)
 303                 end = vma->vm_end;
 304         end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
 305
 306         force_page_cache_readahead(file->f_mapping, file, start, end - start);
 307         return 0;
 308 }
 309
 310 static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 311                                 unsigned long end, struct mm_walk *walk)
 312
 313 {
 314         struct mmu_gather *tlb = walk->private;
 315         struct mm_struct *mm = tlb->mm;
 316         struct vm_area_struct *vma = walk->vma;
 317         spinlock_t *ptl;
 318         pte_t *orig_pte, *pte, ptent;
 319         struct page *page;
 320         int nr_swap = 0;
 321         unsigned long next;
 322
 323         next = pmd_addr_end(addr, end);
 324         if (pmd_trans_huge(*pmd))
 325                 if (madvise_free_huge_pmd(tlb, vma, pmd, addr, next))
 326                         goto next;
 327
 328         if (pmd_trans_unstable(pmd))
 329                 return 0;
 330
 331         tlb_change_page_size(tlb, PAGE_SIZE);
 332         orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 333         flush_tlb_batched_pending(mm);
 334         arch_enter_lazy_mmu_mode();
 335         for (; addr != end; pte++, addr += PAGE_SIZE) {
 336                 ptent = *pte;
 337
 338                 if (pte_none(ptent))
 339                         continue;
 340                 /*
 341                  * If the pte has swp_entry, just clear page table to
 342                  * prevent swap-in which is more expensive rather than
 343                  * (page allocation + zeroing).
 344                  */
 345                 if (!pte_present(ptent)) {
 346                         swp_entry_t entry;
 347
 348                         entry = pte_to_swp_entry(ptent);
 349                         if (non_swap_entry(entry))
 350                                 continue;
 351                         nr_swap--;
 352                         free_swap_and_cache(entry);
 353                         pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
 354                         continue;
 355                 }
 356
 357                 page = vm_normal_page(vma, addr, ptent);
 358                 if (!page)
 359                         continue;
 360
 361                 /*
 362                  * If pmd isn't transhuge but the page is THP and
 363                  * is owned by only this process, split it and
 364                  * deactivate all pages.
 365                  */
 366                 if (PageTransCompound(page)) {
 367                         if (page_mapcount(page) != 1)
 368                                 goto out;
 369                         get_page(page);
 370                         if (!trylock_page(page)) {
 371                                 put_page(page);
 372                                 goto out;
 373                         }
 374                         pte_unmap_unlock(orig_pte, ptl);
 375                         if (split_huge_page(page)) {
 376                                 unlock_page(page);
 377                                 put_page(page);
 378                                 pte_offset_map_lock(mm, pmd, addr, &ptl);
 379                                 goto out;
 380                         }
 381                         unlock_page(page);
 382                         put_page(page);
 383                         pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
 384                         pte--;
 385                         addr -= PAGE_SIZE;
 386                         continue;
 387                 }
 388
 389                 VM_BUG_ON_PAGE(PageTransCompound(page), page);
 390
 391                 if (PageSwapCache(page) || PageDirty(page)) {
 392                         if (!trylock_page(page))
 393                                 continue;
 394                         /*
 395                          * If page is shared with others, we couldn't clear
 396                          * PG_dirty of the page.
 397                          */
 398                         if (page_mapcount(page) != 1) {
 399                                 unlock_page(page);
 400                                 continue;
 401                         }
 402
 403                         if (PageSwapCache(page) && !try_to_free_swap(page)) {
 404                                 unlock_page(page);
 405                                 continue;
 406                         }
 407
 408                         ClearPageDirty(page);
 409                         unlock_page(page);
 410                 }
 411
 412                 if (pte_young(ptent) || pte_dirty(ptent)) {
 413                         /*
 414                          * Some of architecture(ex, PPC) don't update TLB
 415                          * with set_pte_at and tlb_remove_tlb_entry so for
 416                          * the portability, remap the pte with old|clean
 417                          * after pte clearing.
 418                          */
 419                         ptent = ptep_get_and_clear_full(mm, addr, pte,
 420                                                         tlb->fullmm);
 421
 422                         ptent = pte_mkold(ptent);
 423                         ptent = pte_mkclean(ptent);
 424                         set_pte_at(mm, addr, pte, ptent);
 425                         tlb_remove_tlb_entry(tlb, pte, addr);
 426                 }
 427                 mark_page_lazyfree(page);
 428         }
 429 out:
 430         if (nr_swap) {
 431                 if (current->mm == mm)
 432                         sync_mm_rss(mm);
 433
 434                 add_mm_counter(mm, MM_SWAPENTS, nr_swap);
 435         }
 436         arch_leave_lazy_mmu_mode();
 437         pte_unmap_unlock(orig_pte, ptl);
 438         cond_resched();
 439 next:
 440         return 0;
 441 }
 442
 443 static void madvise_free_page_range(struct mmu_gather *tlb,
 444                              struct vm_area_struct *vma,
 445                              unsigned long addr, unsigned long end)
 446 {
 447         struct mm_walk free_walk = {
 448                 .pmd_entry = madvise_free_pte_range,
 449                 .mm = vma->vm_mm,
 450                 .private = tlb,
 451         };
 452
 453         tlb_start_vma(tlb, vma);
 454         walk_page_range(addr, end, &free_walk);
 455         tlb_end_vma(tlb, vma);
 456 }
 457
 458 static int madvise_free_single_vma(struct vm_area_struct *vma,
 459                         unsigned long start_addr, unsigned long end_addr)
 460 {
 461         struct mm_struct *mm = vma->vm_mm;
 462         struct mmu_notifier_range range;
 463         struct mmu_gather tlb;
 464
 465         /* MADV_FREE works for only anon vma at the moment */
 466         if (!vma_is_anonymous(vma))
 467                 return -EINVAL;
 468
 469         range.start = max(vma->vm_start, start_addr);
 470         if (range.start >= vma->vm_end)
 471                 return -EINVAL;
 472         range.end = min(vma->vm_end, end_addr);
 473         if (range.end <= vma->vm_start)
 474                 return -EINVAL;
 475         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm,
 476                                 range.start, range.end);
 477
 478         lru_add_drain();
 479         tlb_gather_mmu(&tlb, mm, range.start, range.end);
 480         update_hiwater_rss(mm);
 481
 482         mmu_notifier_invalidate_range_start(&range);
 483         madvise_free_page_range(&tlb, vma, range.start, range.end);
 484         mmu_notifier_invalidate_range_end(&range);
 485         tlb_finish_mmu(&tlb, range.start, range.end);
 486
 487         return 0;
 488 }
 489
 490 /*
 491  * Application no longer needs these pages.  If the pages are dirty,
 492  * it's OK to just throw them away.  The app will be more careful about
 493  * data it wants to keep.  Be sure to free swap resources too.  The
 494  * zap_page_range call sets things up for shrink_active_list to actually free
 495  * these pages later if no one else has touched them in the meantime,
 496  * although we could add these pages to a global reuse list for
 497  * shrink_active_list to pick up before reclaiming other pages.
 498  *
 499  * NB: This interface discards data rather than pushes it out to swap,
 500  * as some implementations do.  This has performance implications for
 501  * applications like large transactional databases which want to discard
 502  * pages in anonymous maps after committing to backing store the data
 503  * that was kept in them.  There is no reason to write this data out to
 504  * the swap area if the application is discarding it.
 505  *
 506  * An interface that causes the system to free clean pages and flush
 507  * dirty pages is already available as msync(MS_INVALIDATE).
 508  */
 509 static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
 510                                         unsigned long start, unsigned long end)
 511 {
 512         zap_page_range(vma, start, end - start);
 513         return 0;
 514 }
 515
 516 static long madvise_dontneed_free(struct vm_area_struct *vma,
 517                                   struct vm_area_struct **prev,
 518                                   unsigned long start, unsigned long end,
 519                                   int behavior)
 520 {
 521         *prev = vma;
 522         if (!can_madv_dontneed_vma(vma))
 523                 return -EINVAL;
 524
 525         if (!userfaultfd_remove(vma, start, end)) {
 526                 *prev = NULL; /* mmap_sem has been dropped, prev is stale */
 527
 528                 down_read(&current->mm->mmap_sem);
 529                 vma = find_vma(current->mm, start);
 530                 if (!vma)
 531                         return -ENOMEM;
 532                 if (start < vma->vm_start) {
 533                         /*
 534                          * This "vma" under revalidation is the one
 535                          * with the lowest vma->vm_start where start
 536                          * is also < vma->vm_end. If start <
 537                          * vma->vm_start it means an hole materialized
 538                          * in the user address space within the
 539                          * virtual range passed to MADV_DONTNEED
 540                          * or MADV_FREE.
 541                          */
 542                         return -ENOMEM;
 543                 }
 544                 if (!can_madv_dontneed_vma(vma))
 545                         return -EINVAL;
 546                 if (end > vma->vm_end) {
 547                         /*
 548                          * Don't fail if end > vma->vm_end. If the old
 549                          * vma was splitted while the mmap_sem was
 550                          * released the effect of the concurrent
 551                          * operation may not cause madvise() to
 552                          * have an undefined result. There may be an
 553                          * adjacent next vma that we'll walk
 554                          * next. userfaultfd_remove() will generate an
 555                          * UFFD_EVENT_REMOVE repetition on the
 556                          * end-vma->vm_end range, but the manager can
 557                          * handle a repetition fine.
 558                          */
 559                         end = vma->vm_end;
 560                 }
 561                 VM_WARN_ON(start >= end);
 562         }
 563
 564         if (behavior == MADV_DONTNEED)
 565                 return madvise_dontneed_single_vma(vma, start, end);
 566         else if (behavior == MADV_FREE)
 567                 return madvise_free_single_vma(vma, start, end);
 568         else
 569                 return -EINVAL;
 570 }
 571
 572 /*
 573  * Application wants to free up the pages and associated backing store.
 574  * This is effectively punching a hole into the middle of a file.
 575  */
 576 static long madvise_remove(struct vm_area_struct *vma,
 577                                 struct vm_area_struct **prev,
 578                                 unsigned long start, unsigned long end)
 579 {
 580         loff_t offset;
 581         int error;
 582         struct file *f;
 583
 584         *prev = NULL;   /* tell sys_madvise we drop mmap_sem */
 585
 586         if (vma->vm_flags & VM_LOCKED)
 587                 return -EINVAL;
 588
 589         f = vma->vm_file;
 590
 591         if (!f || !f->f_mapping || !f->f_mapping->host) {
 592                         return -EINVAL;
 593         }
 594
 595         if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
 596                 return -EACCES;
 597
 598         offset = (loff_t)(start - vma->vm_start)
 599                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 600
 601         /*
 602          * Filesystem's fallocate may need to take i_mutex.  We need to
 603          * explicitly grab a reference because the vma (and hence the
 604          * vma's reference to the file) can go away as soon as we drop
 605          * mmap_sem.
 606          */
 607         get_file(f);
 608         if (userfaultfd_remove(vma, start, end)) {
 609                 /* mmap_sem was not released by userfaultfd_remove() */
 610                 up_read(&current->mm->mmap_sem);
 611         }
 612         error = vfs_fallocate(f,
 613                                 FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
 614                                 offset, end - start);
 615         fput(f);
 616         down_read(&current->mm->mmap_sem);
 617         return error;
 618 }
 619
 620 #ifdef CONFIG_MEMORY_FAILURE
 621 /*
 622  * Error injection support for memory error handling.
 623  */
 624 static int madvise_inject_error(int behavior,
 625                 unsigned long start, unsigned long end)
 626 {
 627         struct page *page;
 628         struct zone *zone;
 629         unsigned int order;
 630
 631         if (!capable(CAP_SYS_ADMIN))
 632                 return -EPERM;
 633
 634
 635         for (; start < end; start += PAGE_SIZE << order) {
 636                 unsigned long pfn;
 637                 int ret;
 638
 639                 ret = get_user_pages_fast(start, 1, 0, &page);
 640                 if (ret != 1)
 641                         return ret;
 642                 pfn = page_to_pfn(page);
 643
 644                 /*
 645                  * When soft offlining hugepages, after migrating the page
 646                  * we dissolve it, therefore in the second loop "page" will
 647                  * no longer be a compound page, and order will be 0.
 648                  */
 649                 order = compound_order(compound_head(page));
 650
 651                 if (PageHWPoison(page)) {
 652                         put_page(page);
 653                         continue;
 654                 }
 655
 656                 if (behavior == MADV_SOFT_OFFLINE) {
 657                         pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
 658                                         pfn, start);
 659
 660                         ret = soft_offline_page(page, MF_COUNT_INCREASED);
 661                         if (ret)
 662                                 return ret;
 663                         continue;
 664                 }
 665
 666                 pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
 667                                 pfn, start);
 668
 669                 /*
 670                  * Drop the page reference taken by get_user_pages_fast(). In
 671                  * the absence of MF_COUNT_INCREASED the memory_failure()
 672                  * routine is responsible for pinning the page to prevent it
 673                  * from being released back to the page allocator.
 674                  */
 675                 put_page(page);
 676                 ret = memory_failure(pfn, 0);
 677                 if (ret)
 678                         return ret;
 679         }
 680
 681         /* Ensure that all poisoned pages are removed from per-cpu lists */
 682         for_each_populated_zone(zone)
 683                 drain_all_pages(zone);
 684
 685         return 0;
 686 }
 687 #endif
 688
 689 static long
 690 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 691                 unsigned long start, unsigned long end, int behavior)
 692 {
 693         switch (behavior) {
 694         case MADV_REMOVE:
 695                 return madvise_remove(vma, prev, start, end);
 696         case MADV_WILLNEED:
 697                 return madvise_willneed(vma, prev, start, end);
 698         case MADV_FREE:
 699         case MADV_DONTNEED:
 700                 return madvise_dontneed_free(vma, prev, start, end, behavior);
 701         default:
 702                 return madvise_behavior(vma, prev, start, end, behavior);
 703         }
 704 }
 705
 706 static bool
 707 madvise_behavior_valid(int behavior)
 708 {
 709         switch (behavior) {
 710         case MADV_DOFORK:
 711         case MADV_DONTFORK:
 712         case MADV_NORMAL:
 713         case MADV_SEQUENTIAL:
 714         case MADV_RANDOM:
 715         case MADV_REMOVE:
 716         case MADV_WILLNEED:
 717         case MADV_DONTNEED:
 718         case MADV_FREE:
 719 #ifdef CONFIG_KSM
 720         case MADV_MERGEABLE:
 721         case MADV_UNMERGEABLE:
 722 #endif
 723 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 724         case MADV_HUGEPAGE:
 725         case MADV_NOHUGEPAGE:
 726 #endif
 727         case MADV_DONTDUMP:
 728         case MADV_DODUMP:
 729         case MADV_WIPEONFORK:
 730         case MADV_KEEPONFORK:
 731 #ifdef CONFIG_MEMORY_FAILURE
 732         case MADV_SOFT_OFFLINE:
 733         case MADV_HWPOISON:
 734 #endif
 735                 return true;
 736
 737         default:
 738                 return false;
 739         }
 740 }
 741
 742 /*
 743  * The madvise(2) system call.
 744  *
 745  * Applications can use madvise() to advise the kernel how it should
 746  * handle paging I/O in this VM area.  The idea is to help the kernel
 747  * use appropriate read-ahead and caching techniques.  The information
 748  * provided is advisory only, and can be safely disregarded by the
 749  * kernel without affecting the correct operation of the application.
 750  *
 751  * behavior values:
 752  *  MADV_NORMAL - the default behavior is to read clusters.  This
 753  *              results in some read-ahead and read-behind.
 754  *  MADV_RANDOM - the system should read the minimum amount of data
 755  *              on any access, since it is unlikely that the appli-
 756  *              cation will need more than what it asks for.
 757  *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
 758  *              once, so they can be aggressively read ahead, and
 759  *              can be freed soon after they are accessed.
 760  *  MADV_WILLNEED - the application is notifying the system to read
 761  *              some pages ahead.
 762  *  MADV_DONTNEED - the application is finished with the given range,
 763  *              so the kernel can free resources associated with it.
 764  *  MADV_FREE - the application marks pages in the given range as lazy free,
 765  *              where actual purges are postponed until memory pressure happens.
 766  *  MADV_REMOVE - the application wants to free up the given range of
 767  *              pages and associated backing store.
 768  *  MADV_DONTFORK - omit this area from child's address space when forking:
 769  *              typically, to avoid COWing pages pinned by get_user_pages().
 770  *  MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
 771  *  MADV_WIPEONFORK - present the child process with zero-filled memory in this
 772  *              range after a fork.
 773  *  MADV_KEEPONFORK - undo the effect of MADV_WIPEONFORK
 774  *  MADV_HWPOISON - trigger memory error handler as if the given memory range
 775  *              were corrupted by unrecoverable hardware memory failure.
 776  *  MADV_SOFT_OFFLINE - try to soft-offline the given range of memory.
 777  *  MADV_MERGEABLE - the application recommends that KSM try to merge pages in
 778  *              this area with pages of identical content from other such areas.
 779  *  MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
 780  *  MADV_HUGEPAGE - the application wants to back the given range by transparent
 781  *              huge pages in the future. Existing pages might be coalesced and
 782  *              new pages might be allocated as THP.
 783  *  MADV_NOHUGEPAGE - mark the given range as not worth being backed by
 784  *              transparent huge pages so the existing pages will not be
 785  *              coalesced into THP and new pages will not be allocated as THP.
 786  *  MADV_DONTDUMP - the application wants to prevent pages in the given range
 787  *              from being included in its core dump.
 788  *  MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
 789  *
 790  * return values:
 791  *  zero    - success
 792  *  -EINVAL - start + len < 0, start is not page-aligned,
 793  *              "behavior" is not a valid value, or application
 794  *              is attempting to release locked or shared pages,
 795  *              or the specified address range includes file, Huge TLB,
 796  *              MAP_SHARED or VMPFNMAP range.
 797  *  -ENOMEM - addresses in the specified range are not currently
 798  *              mapped, or are outside the AS of the process.
 799  *  -EIO    - an I/O error occurred while paging in data.
 800  *  -EBADF  - map exists, but area maps something that isn't a file.
 801  *  -EAGAIN - a kernel resource was temporarily unavailable.
 802  */
 803 SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
 804 {
 805         unsigned long end, tmp;
 806         struct vm_area_struct *vma, *prev;
 807         int unmapped_error = 0;
 808         int error = -EINVAL;
 809         int write;
 810         size_t len;
 811         struct blk_plug plug;
 812
 813         if (!madvise_behavior_valid(behavior))
 814                 return error;
 815
 816         if (start & ~PAGE_MASK)
 817                 return error;
 818         len = (len_in + ~PAGE_MASK) & PAGE_MASK;
 819
 820         /* Check to see whether len was rounded up from small -ve to zero */
 821         if (len_in && !len)
 822                 return error;
 823
 824         end = start + len;
 825         if (end < start)
 826                 return error;
 827
 828         error = 0;
 829         if (end == start)
 830                 return error;
 831
 832 #ifdef CONFIG_MEMORY_FAILURE
 833         if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
 834                 return madvise_inject_error(behavior, start, start + len_in);
 835 #endif
 836
 837         write = madvise_need_mmap_write(behavior);
 838         if (write) {
 839                 if (down_write_killable(&current->mm->mmap_sem))
 840                         return -EINTR;
 841         } else {
 842                 down_read(&current->mm->mmap_sem);
 843         }
 844
 845         /*
 846          * If the interval [start,end) covers some unmapped address
 847          * ranges, just ignore them, but return -ENOMEM at the end.
 848          * - different from the way of handling in mlock etc.
 849          */
 850         vma = find_vma_prev(current->mm, start, &prev);
 851         if (vma && start > vma->vm_start)
 852                 prev = vma;
 853
 854         blk_start_plug(&plug);
 855         for (;;) {
 856                 /* Still start < end. */
 857                 error = -ENOMEM;
 858                 if (!vma)
 859                         goto out;
 860
 861                 /* Here start < (end|vma->vm_end). */
 862                 if (start < vma->vm_start) {
 863                         unmapped_error = -ENOMEM;
 864                         start = vma->vm_start;
 865                         if (start >= end)
 866                                 goto out;
 867                 }
 868
 869                 /* Here vma->vm_start <= start < (end|vma->vm_end) */
 870                 tmp = vma->vm_end;
 871                 if (end < tmp)
 872                         tmp = end;
 873
 874                 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
 875                 error = madvise_vma(vma, &prev, start, tmp, behavior);
 876                 if (error)
 877                         goto out;
 878                 start = tmp;
 879                 if (prev && start < prev->vm_end)
 880                         start = prev->vm_end;
 881                 error = unmapped_error;
 882                 if (start >= end)
 883                         goto out;
 884                 if (prev)
 885                         vma = prev->vm_next;
 886                 else    /* madvise_remove dropped mmap_sem */
 887                         vma = find_vma(current->mm, start);
 888         }
 889 out:
 890         blk_finish_plug(&plug);
 891         if (write)
 892                 up_write(&current->mm->mmap_sem);
 893         else
 894                 up_read(&current->mm->mmap_sem);
 895
 896         return error;
 897 }