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, true); 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(¤t->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(¤t->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(¤t->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(¤t->mm->mmap_sem)) 840 return -EINTR; 841 } else { 842 down_read(¤t->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(¤t->mm->mmap_sem); 893 else 894 up_read(¤t->mm->mmap_sem); 895 896 return error; 897 } 898