]> git.kernelconcepts.de Git - karo-tx-linux.git/blob - mm/madvise.c
Merge tag 'upstream-4.13-rc1' of git://git.infradead.org/linux-ubifs
[karo-tx-linux.git] / mm / madvise.c
1 /*
2  *      linux/mm/madvise.c
3  *
4  * Copyright (C) 1999  Linus Torvalds
5  * Copyright (C) 2002  Christoph Hellwig
6  */
7
8 #include <linux/mman.h>
9 #include <linux/pagemap.h>
10 #include <linux/syscalls.h>
11 #include <linux/mempolicy.h>
12 #include <linux/page-isolation.h>
13 #include <linux/userfaultfd_k.h>
14 #include <linux/hugetlb.h>
15 #include <linux/falloc.h>
16 #include <linux/sched.h>
17 #include <linux/ksm.h>
18 #include <linux/fs.h>
19 #include <linux/file.h>
20 #include <linux/blkdev.h>
21 #include <linux/backing-dev.h>
22 #include <linux/swap.h>
23 #include <linux/swapops.h>
24 #include <linux/shmem_fs.h>
25 #include <linux/mmu_notifier.h>
26
27 #include <asm/tlb.h>
28
29 #include "internal.h"
30
31 /*
32  * Any behaviour which results in changes to the vma->vm_flags needs to
33  * take mmap_sem for writing. Others, which simply traverse vmas, need
34  * to only take it for reading.
35  */
36 static int madvise_need_mmap_write(int behavior)
37 {
38         switch (behavior) {
39         case MADV_REMOVE:
40         case MADV_WILLNEED:
41         case MADV_DONTNEED:
42         case MADV_FREE:
43                 return 0;
44         default:
45                 /* be safe, default to 1. list exceptions explicitly */
46                 return 1;
47         }
48 }
49
50 /*
51  * We can potentially split a vm area into separate
52  * areas, each area with its own behavior.
53  */
54 static long madvise_behavior(struct vm_area_struct *vma,
55                      struct vm_area_struct **prev,
56                      unsigned long start, unsigned long end, int behavior)
57 {
58         struct mm_struct *mm = vma->vm_mm;
59         int error = 0;
60         pgoff_t pgoff;
61         unsigned long new_flags = vma->vm_flags;
62
63         switch (behavior) {
64         case MADV_NORMAL:
65                 new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
66                 break;
67         case MADV_SEQUENTIAL:
68                 new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
69                 break;
70         case MADV_RANDOM:
71                 new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
72                 break;
73         case MADV_DONTFORK:
74                 new_flags |= VM_DONTCOPY;
75                 break;
76         case MADV_DOFORK:
77                 if (vma->vm_flags & VM_IO) {
78                         error = -EINVAL;
79                         goto out;
80                 }
81                 new_flags &= ~VM_DONTCOPY;
82                 break;
83         case MADV_DONTDUMP:
84                 new_flags |= VM_DONTDUMP;
85                 break;
86         case MADV_DODUMP:
87                 if (new_flags & VM_SPECIAL) {
88                         error = -EINVAL;
89                         goto out;
90                 }
91                 new_flags &= ~VM_DONTDUMP;
92                 break;
93         case MADV_MERGEABLE:
94         case MADV_UNMERGEABLE:
95                 error = ksm_madvise(vma, start, end, behavior, &new_flags);
96                 if (error) {
97                         /*
98                          * madvise() returns EAGAIN if kernel resources, such as
99                          * slab, are temporarily unavailable.
100                          */
101                         if (error == -ENOMEM)
102                                 error = -EAGAIN;
103                         goto out;
104                 }
105                 break;
106         case MADV_HUGEPAGE:
107         case MADV_NOHUGEPAGE:
108                 error = hugepage_madvise(vma, &new_flags, behavior);
109                 if (error) {
110                         /*
111                          * madvise() returns EAGAIN if kernel resources, such as
112                          * slab, are temporarily unavailable.
113                          */
114                         if (error == -ENOMEM)
115                                 error = -EAGAIN;
116                         goto out;
117                 }
118                 break;
119         }
120
121         if (new_flags == vma->vm_flags) {
122                 *prev = vma;
123                 goto out;
124         }
125
126         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
127         *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
128                           vma->vm_file, pgoff, vma_policy(vma),
129                           vma->vm_userfaultfd_ctx);
130         if (*prev) {
131                 vma = *prev;
132                 goto success;
133         }
134
135         *prev = vma;
136
137         if (start != vma->vm_start) {
138                 if (unlikely(mm->map_count >= sysctl_max_map_count)) {
139                         error = -ENOMEM;
140                         goto out;
141                 }
142                 error = __split_vma(mm, vma, start, 1);
143                 if (error) {
144                         /*
145                          * madvise() returns EAGAIN if kernel resources, such as
146                          * slab, are temporarily unavailable.
147                          */
148                         if (error == -ENOMEM)
149                                 error = -EAGAIN;
150                         goto out;
151                 }
152         }
153
154         if (end != vma->vm_end) {
155                 if (unlikely(mm->map_count >= sysctl_max_map_count)) {
156                         error = -ENOMEM;
157                         goto out;
158                 }
159                 error = __split_vma(mm, vma, end, 0);
160                 if (error) {
161                         /*
162                          * madvise() returns EAGAIN if kernel resources, such as
163                          * slab, are temporarily unavailable.
164                          */
165                         if (error == -ENOMEM)
166                                 error = -EAGAIN;
167                         goto out;
168                 }
169         }
170
171 success:
172         /*
173          * vm_flags is protected by the mmap_sem held in write mode.
174          */
175         vma->vm_flags = new_flags;
176 out:
177         return error;
178 }
179
180 #ifdef CONFIG_SWAP
181 static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
182         unsigned long end, struct mm_walk *walk)
183 {
184         pte_t *orig_pte;
185         struct vm_area_struct *vma = walk->private;
186         unsigned long index;
187
188         if (pmd_none_or_trans_huge_or_clear_bad(pmd))
189                 return 0;
190
191         for (index = start; index != end; index += PAGE_SIZE) {
192                 pte_t pte;
193                 swp_entry_t entry;
194                 struct page *page;
195                 spinlock_t *ptl;
196
197                 orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
198                 pte = *(orig_pte + ((index - start) / PAGE_SIZE));
199                 pte_unmap_unlock(orig_pte, ptl);
200
201                 if (pte_present(pte) || pte_none(pte))
202                         continue;
203                 entry = pte_to_swp_entry(pte);
204                 if (unlikely(non_swap_entry(entry)))
205                         continue;
206
207                 page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
208                                                         vma, index, false);
209                 if (page)
210                         put_page(page);
211         }
212
213         return 0;
214 }
215
216 static void force_swapin_readahead(struct vm_area_struct *vma,
217                 unsigned long start, unsigned long end)
218 {
219         struct mm_walk walk = {
220                 .mm = vma->vm_mm,
221                 .pmd_entry = swapin_walk_pmd_entry,
222                 .private = vma,
223         };
224
225         walk_page_range(start, end, &walk);
226
227         lru_add_drain();        /* Push any new pages onto the LRU now */
228 }
229
230 static void force_shm_swapin_readahead(struct vm_area_struct *vma,
231                 unsigned long start, unsigned long end,
232                 struct address_space *mapping)
233 {
234         pgoff_t index;
235         struct page *page;
236         swp_entry_t swap;
237
238         for (; start < end; start += PAGE_SIZE) {
239                 index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
240
241                 page = find_get_entry(mapping, index);
242                 if (!radix_tree_exceptional_entry(page)) {
243                         if (page)
244                                 put_page(page);
245                         continue;
246                 }
247                 swap = radix_to_swp_entry(page);
248                 page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
249                                                         NULL, 0, false);
250                 if (page)
251                         put_page(page);
252         }
253
254         lru_add_drain();        /* Push any new pages onto the LRU now */
255 }
256 #endif          /* CONFIG_SWAP */
257
258 /*
259  * Schedule all required I/O operations.  Do not wait for completion.
260  */
261 static long madvise_willneed(struct vm_area_struct *vma,
262                              struct vm_area_struct **prev,
263                              unsigned long start, unsigned long end)
264 {
265         struct file *file = vma->vm_file;
266
267 #ifdef CONFIG_SWAP
268         if (!file) {
269                 *prev = vma;
270                 force_swapin_readahead(vma, start, end);
271                 return 0;
272         }
273
274         if (shmem_mapping(file->f_mapping)) {
275                 *prev = vma;
276                 force_shm_swapin_readahead(vma, start, end,
277                                         file->f_mapping);
278                 return 0;
279         }
280 #else
281         if (!file)
282                 return -EBADF;
283 #endif
284
285         if (IS_DAX(file_inode(file))) {
286                 /* no bad return value, but ignore advice */
287                 return 0;
288         }
289
290         *prev = vma;
291         start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
292         if (end > vma->vm_end)
293                 end = vma->vm_end;
294         end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
295
296         force_page_cache_readahead(file->f_mapping, file, start, end - start);
297         return 0;
298 }
299
300 static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
301                                 unsigned long end, struct mm_walk *walk)
302
303 {
304         struct mmu_gather *tlb = walk->private;
305         struct mm_struct *mm = tlb->mm;
306         struct vm_area_struct *vma = walk->vma;
307         spinlock_t *ptl;
308         pte_t *orig_pte, *pte, ptent;
309         struct page *page;
310         int nr_swap = 0;
311         unsigned long next;
312
313         next = pmd_addr_end(addr, end);
314         if (pmd_trans_huge(*pmd))
315                 if (madvise_free_huge_pmd(tlb, vma, pmd, addr, next))
316                         goto next;
317
318         if (pmd_trans_unstable(pmd))
319                 return 0;
320
321         tlb_remove_check_page_size_change(tlb, PAGE_SIZE);
322         orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
323         arch_enter_lazy_mmu_mode();
324         for (; addr != end; pte++, addr += PAGE_SIZE) {
325                 ptent = *pte;
326
327                 if (pte_none(ptent))
328                         continue;
329                 /*
330                  * If the pte has swp_entry, just clear page table to
331                  * prevent swap-in which is more expensive rather than
332                  * (page allocation + zeroing).
333                  */
334                 if (!pte_present(ptent)) {
335                         swp_entry_t entry;
336
337                         entry = pte_to_swp_entry(ptent);
338                         if (non_swap_entry(entry))
339                                 continue;
340                         nr_swap--;
341                         free_swap_and_cache(entry);
342                         pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
343                         continue;
344                 }
345
346                 page = vm_normal_page(vma, addr, ptent);
347                 if (!page)
348                         continue;
349
350                 /*
351                  * If pmd isn't transhuge but the page is THP and
352                  * is owned by only this process, split it and
353                  * deactivate all pages.
354                  */
355                 if (PageTransCompound(page)) {
356                         if (page_mapcount(page) != 1)
357                                 goto out;
358                         get_page(page);
359                         if (!trylock_page(page)) {
360                                 put_page(page);
361                                 goto out;
362                         }
363                         pte_unmap_unlock(orig_pte, ptl);
364                         if (split_huge_page(page)) {
365                                 unlock_page(page);
366                                 put_page(page);
367                                 pte_offset_map_lock(mm, pmd, addr, &ptl);
368                                 goto out;
369                         }
370                         put_page(page);
371                         unlock_page(page);
372                         pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
373                         pte--;
374                         addr -= PAGE_SIZE;
375                         continue;
376                 }
377
378                 VM_BUG_ON_PAGE(PageTransCompound(page), page);
379
380                 if (PageSwapCache(page) || PageDirty(page)) {
381                         if (!trylock_page(page))
382                                 continue;
383                         /*
384                          * If page is shared with others, we couldn't clear
385                          * PG_dirty of the page.
386                          */
387                         if (page_mapcount(page) != 1) {
388                                 unlock_page(page);
389                                 continue;
390                         }
391
392                         if (PageSwapCache(page) && !try_to_free_swap(page)) {
393                                 unlock_page(page);
394                                 continue;
395                         }
396
397                         ClearPageDirty(page);
398                         unlock_page(page);
399                 }
400
401                 if (pte_young(ptent) || pte_dirty(ptent)) {
402                         /*
403                          * Some of architecture(ex, PPC) don't update TLB
404                          * with set_pte_at and tlb_remove_tlb_entry so for
405                          * the portability, remap the pte with old|clean
406                          * after pte clearing.
407                          */
408                         ptent = ptep_get_and_clear_full(mm, addr, pte,
409                                                         tlb->fullmm);
410
411                         ptent = pte_mkold(ptent);
412                         ptent = pte_mkclean(ptent);
413                         set_pte_at(mm, addr, pte, ptent);
414                         tlb_remove_tlb_entry(tlb, pte, addr);
415                 }
416                 mark_page_lazyfree(page);
417         }
418 out:
419         if (nr_swap) {
420                 if (current->mm == mm)
421                         sync_mm_rss(mm);
422
423                 add_mm_counter(mm, MM_SWAPENTS, nr_swap);
424         }
425         arch_leave_lazy_mmu_mode();
426         pte_unmap_unlock(orig_pte, ptl);
427         cond_resched();
428 next:
429         return 0;
430 }
431
432 static void madvise_free_page_range(struct mmu_gather *tlb,
433                              struct vm_area_struct *vma,
434                              unsigned long addr, unsigned long end)
435 {
436         struct mm_walk free_walk = {
437                 .pmd_entry = madvise_free_pte_range,
438                 .mm = vma->vm_mm,
439                 .private = tlb,
440         };
441
442         tlb_start_vma(tlb, vma);
443         walk_page_range(addr, end, &free_walk);
444         tlb_end_vma(tlb, vma);
445 }
446
447 static int madvise_free_single_vma(struct vm_area_struct *vma,
448                         unsigned long start_addr, unsigned long end_addr)
449 {
450         unsigned long start, end;
451         struct mm_struct *mm = vma->vm_mm;
452         struct mmu_gather tlb;
453
454         /* MADV_FREE works for only anon vma at the moment */
455         if (!vma_is_anonymous(vma))
456                 return -EINVAL;
457
458         start = max(vma->vm_start, start_addr);
459         if (start >= vma->vm_end)
460                 return -EINVAL;
461         end = min(vma->vm_end, end_addr);
462         if (end <= vma->vm_start)
463                 return -EINVAL;
464
465         lru_add_drain();
466         tlb_gather_mmu(&tlb, mm, start, end);
467         update_hiwater_rss(mm);
468
469         mmu_notifier_invalidate_range_start(mm, start, end);
470         madvise_free_page_range(&tlb, vma, start, end);
471         mmu_notifier_invalidate_range_end(mm, start, end);
472         tlb_finish_mmu(&tlb, start, end);
473
474         return 0;
475 }
476
477 /*
478  * Application no longer needs these pages.  If the pages are dirty,
479  * it's OK to just throw them away.  The app will be more careful about
480  * data it wants to keep.  Be sure to free swap resources too.  The
481  * zap_page_range call sets things up for shrink_active_list to actually free
482  * these pages later if no one else has touched them in the meantime,
483  * although we could add these pages to a global reuse list for
484  * shrink_active_list to pick up before reclaiming other pages.
485  *
486  * NB: This interface discards data rather than pushes it out to swap,
487  * as some implementations do.  This has performance implications for
488  * applications like large transactional databases which want to discard
489  * pages in anonymous maps after committing to backing store the data
490  * that was kept in them.  There is no reason to write this data out to
491  * the swap area if the application is discarding it.
492  *
493  * An interface that causes the system to free clean pages and flush
494  * dirty pages is already available as msync(MS_INVALIDATE).
495  */
496 static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
497                                         unsigned long start, unsigned long end)
498 {
499         zap_page_range(vma, start, end - start);
500         return 0;
501 }
502
503 static long madvise_dontneed_free(struct vm_area_struct *vma,
504                                   struct vm_area_struct **prev,
505                                   unsigned long start, unsigned long end,
506                                   int behavior)
507 {
508         *prev = vma;
509         if (!can_madv_dontneed_vma(vma))
510                 return -EINVAL;
511
512         if (!userfaultfd_remove(vma, start, end)) {
513                 *prev = NULL; /* mmap_sem has been dropped, prev is stale */
514
515                 down_read(&current->mm->mmap_sem);
516                 vma = find_vma(current->mm, start);
517                 if (!vma)
518                         return -ENOMEM;
519                 if (start < vma->vm_start) {
520                         /*
521                          * This "vma" under revalidation is the one
522                          * with the lowest vma->vm_start where start
523                          * is also < vma->vm_end. If start <
524                          * vma->vm_start it means an hole materialized
525                          * in the user address space within the
526                          * virtual range passed to MADV_DONTNEED
527                          * or MADV_FREE.
528                          */
529                         return -ENOMEM;
530                 }
531                 if (!can_madv_dontneed_vma(vma))
532                         return -EINVAL;
533                 if (end > vma->vm_end) {
534                         /*
535                          * Don't fail if end > vma->vm_end. If the old
536                          * vma was splitted while the mmap_sem was
537                          * released the effect of the concurrent
538                          * operation may not cause madvise() to
539                          * have an undefined result. There may be an
540                          * adjacent next vma that we'll walk
541                          * next. userfaultfd_remove() will generate an
542                          * UFFD_EVENT_REMOVE repetition on the
543                          * end-vma->vm_end range, but the manager can
544                          * handle a repetition fine.
545                          */
546                         end = vma->vm_end;
547                 }
548                 VM_WARN_ON(start >= end);
549         }
550
551         if (behavior == MADV_DONTNEED)
552                 return madvise_dontneed_single_vma(vma, start, end);
553         else if (behavior == MADV_FREE)
554                 return madvise_free_single_vma(vma, start, end);
555         else
556                 return -EINVAL;
557 }
558
559 /*
560  * Application wants to free up the pages and associated backing store.
561  * This is effectively punching a hole into the middle of a file.
562  */
563 static long madvise_remove(struct vm_area_struct *vma,
564                                 struct vm_area_struct **prev,
565                                 unsigned long start, unsigned long end)
566 {
567         loff_t offset;
568         int error;
569         struct file *f;
570
571         *prev = NULL;   /* tell sys_madvise we drop mmap_sem */
572
573         if (vma->vm_flags & VM_LOCKED)
574                 return -EINVAL;
575
576         f = vma->vm_file;
577
578         if (!f || !f->f_mapping || !f->f_mapping->host) {
579                         return -EINVAL;
580         }
581
582         if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
583                 return -EACCES;
584
585         offset = (loff_t)(start - vma->vm_start)
586                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
587
588         /*
589          * Filesystem's fallocate may need to take i_mutex.  We need to
590          * explicitly grab a reference because the vma (and hence the
591          * vma's reference to the file) can go away as soon as we drop
592          * mmap_sem.
593          */
594         get_file(f);
595         if (userfaultfd_remove(vma, start, end)) {
596                 /* mmap_sem was not released by userfaultfd_remove() */
597                 up_read(&current->mm->mmap_sem);
598         }
599         error = vfs_fallocate(f,
600                                 FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
601                                 offset, end - start);
602         fput(f);
603         down_read(&current->mm->mmap_sem);
604         return error;
605 }
606
607 #ifdef CONFIG_MEMORY_FAILURE
608 /*
609  * Error injection support for memory error handling.
610  */
611 static int madvise_inject_error(int behavior,
612                 unsigned long start, unsigned long end)
613 {
614         struct page *page;
615
616         if (!capable(CAP_SYS_ADMIN))
617                 return -EPERM;
618
619         for (; start < end; start += PAGE_SIZE <<
620                                 compound_order(compound_head(page))) {
621                 int ret;
622
623                 ret = get_user_pages_fast(start, 1, 0, &page);
624                 if (ret != 1)
625                         return ret;
626
627                 if (PageHWPoison(page)) {
628                         put_page(page);
629                         continue;
630                 }
631
632                 if (behavior == MADV_SOFT_OFFLINE) {
633                         pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
634                                                 page_to_pfn(page), start);
635
636                         ret = soft_offline_page(page, MF_COUNT_INCREASED);
637                         if (ret)
638                                 return ret;
639                         continue;
640                 }
641                 pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
642                                                 page_to_pfn(page), start);
643
644                 ret = memory_failure(page_to_pfn(page), 0, MF_COUNT_INCREASED);
645                 if (ret)
646                         return ret;
647         }
648         return 0;
649 }
650 #endif
651
652 static long
653 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
654                 unsigned long start, unsigned long end, int behavior)
655 {
656         switch (behavior) {
657         case MADV_REMOVE:
658                 return madvise_remove(vma, prev, start, end);
659         case MADV_WILLNEED:
660                 return madvise_willneed(vma, prev, start, end);
661         case MADV_FREE:
662         case MADV_DONTNEED:
663                 return madvise_dontneed_free(vma, prev, start, end, behavior);
664         default:
665                 return madvise_behavior(vma, prev, start, end, behavior);
666         }
667 }
668
669 static bool
670 madvise_behavior_valid(int behavior)
671 {
672         switch (behavior) {
673         case MADV_DOFORK:
674         case MADV_DONTFORK:
675         case MADV_NORMAL:
676         case MADV_SEQUENTIAL:
677         case MADV_RANDOM:
678         case MADV_REMOVE:
679         case MADV_WILLNEED:
680         case MADV_DONTNEED:
681         case MADV_FREE:
682 #ifdef CONFIG_KSM
683         case MADV_MERGEABLE:
684         case MADV_UNMERGEABLE:
685 #endif
686 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
687         case MADV_HUGEPAGE:
688         case MADV_NOHUGEPAGE:
689 #endif
690         case MADV_DONTDUMP:
691         case MADV_DODUMP:
692 #ifdef CONFIG_MEMORY_FAILURE
693         case MADV_SOFT_OFFLINE:
694         case MADV_HWPOISON:
695 #endif
696                 return true;
697
698         default:
699                 return false;
700         }
701 }
702
703 /*
704  * The madvise(2) system call.
705  *
706  * Applications can use madvise() to advise the kernel how it should
707  * handle paging I/O in this VM area.  The idea is to help the kernel
708  * use appropriate read-ahead and caching techniques.  The information
709  * provided is advisory only, and can be safely disregarded by the
710  * kernel without affecting the correct operation of the application.
711  *
712  * behavior values:
713  *  MADV_NORMAL - the default behavior is to read clusters.  This
714  *              results in some read-ahead and read-behind.
715  *  MADV_RANDOM - the system should read the minimum amount of data
716  *              on any access, since it is unlikely that the appli-
717  *              cation will need more than what it asks for.
718  *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
719  *              once, so they can be aggressively read ahead, and
720  *              can be freed soon after they are accessed.
721  *  MADV_WILLNEED - the application is notifying the system to read
722  *              some pages ahead.
723  *  MADV_DONTNEED - the application is finished with the given range,
724  *              so the kernel can free resources associated with it.
725  *  MADV_FREE - the application marks pages in the given range as lazy free,
726  *              where actual purges are postponed until memory pressure happens.
727  *  MADV_REMOVE - the application wants to free up the given range of
728  *              pages and associated backing store.
729  *  MADV_DONTFORK - omit this area from child's address space when forking:
730  *              typically, to avoid COWing pages pinned by get_user_pages().
731  *  MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
732  *  MADV_HWPOISON - trigger memory error handler as if the given memory range
733  *              were corrupted by unrecoverable hardware memory failure.
734  *  MADV_SOFT_OFFLINE - try to soft-offline the given range of memory.
735  *  MADV_MERGEABLE - the application recommends that KSM try to merge pages in
736  *              this area with pages of identical content from other such areas.
737  *  MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
738  *  MADV_HUGEPAGE - the application wants to back the given range by transparent
739  *              huge pages in the future. Existing pages might be coalesced and
740  *              new pages might be allocated as THP.
741  *  MADV_NOHUGEPAGE - mark the given range as not worth being backed by
742  *              transparent huge pages so the existing pages will not be
743  *              coalesced into THP and new pages will not be allocated as THP.
744  *  MADV_DONTDUMP - the application wants to prevent pages in the given range
745  *              from being included in its core dump.
746  *  MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
747  *
748  * return values:
749  *  zero    - success
750  *  -EINVAL - start + len < 0, start is not page-aligned,
751  *              "behavior" is not a valid value, or application
752  *              is attempting to release locked or shared pages.
753  *  -ENOMEM - addresses in the specified range are not currently
754  *              mapped, or are outside the AS of the process.
755  *  -EIO    - an I/O error occurred while paging in data.
756  *  -EBADF  - map exists, but area maps something that isn't a file.
757  *  -EAGAIN - a kernel resource was temporarily unavailable.
758  */
759 SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
760 {
761         unsigned long end, tmp;
762         struct vm_area_struct *vma, *prev;
763         int unmapped_error = 0;
764         int error = -EINVAL;
765         int write;
766         size_t len;
767         struct blk_plug plug;
768
769         if (!madvise_behavior_valid(behavior))
770                 return error;
771
772         if (start & ~PAGE_MASK)
773                 return error;
774         len = (len_in + ~PAGE_MASK) & PAGE_MASK;
775
776         /* Check to see whether len was rounded up from small -ve to zero */
777         if (len_in && !len)
778                 return error;
779
780         end = start + len;
781         if (end < start)
782                 return error;
783
784         error = 0;
785         if (end == start)
786                 return error;
787
788 #ifdef CONFIG_MEMORY_FAILURE
789         if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
790                 return madvise_inject_error(behavior, start, start + len_in);
791 #endif
792
793         write = madvise_need_mmap_write(behavior);
794         if (write) {
795                 if (down_write_killable(&current->mm->mmap_sem))
796                         return -EINTR;
797         } else {
798                 down_read(&current->mm->mmap_sem);
799         }
800
801         /*
802          * If the interval [start,end) covers some unmapped address
803          * ranges, just ignore them, but return -ENOMEM at the end.
804          * - different from the way of handling in mlock etc.
805          */
806         vma = find_vma_prev(current->mm, start, &prev);
807         if (vma && start > vma->vm_start)
808                 prev = vma;
809
810         blk_start_plug(&plug);
811         for (;;) {
812                 /* Still start < end. */
813                 error = -ENOMEM;
814                 if (!vma)
815                         goto out;
816
817                 /* Here start < (end|vma->vm_end). */
818                 if (start < vma->vm_start) {
819                         unmapped_error = -ENOMEM;
820                         start = vma->vm_start;
821                         if (start >= end)
822                                 goto out;
823                 }
824
825                 /* Here vma->vm_start <= start < (end|vma->vm_end) */
826                 tmp = vma->vm_end;
827                 if (end < tmp)
828                         tmp = end;
829
830                 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
831                 error = madvise_vma(vma, &prev, start, tmp, behavior);
832                 if (error)
833                         goto out;
834                 start = tmp;
835                 if (prev && start < prev->vm_end)
836                         start = prev->vm_end;
837                 error = unmapped_error;
838                 if (start >= end)
839                         goto out;
840                 if (prev)
841                         vma = prev->vm_next;
842                 else    /* madvise_remove dropped mmap_sem */
843                         vma = find_vma(current->mm, start);
844         }
845 out:
846         blk_finish_plug(&plug);
847         if (write)
848                 up_write(&current->mm->mmap_sem);
849         else
850                 up_read(&current->mm->mmap_sem);
851
852         return error;
853 }