treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 110
[sfrench/cifs-2.6.git] / 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, 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(&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 }