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TOMOYO Linux Cross Reference
Linux/mm/madvise.c

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  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_remove_check_page_size_change(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         unsigned long start, end;
462         struct mm_struct *mm = vma->vm_mm;
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         start = max(vma->vm_start, start_addr);
470         if (start >= vma->vm_end)
471                 return -EINVAL;
472         end = min(vma->vm_end, end_addr);
473         if (end <= vma->vm_start)
474                 return -EINVAL;
475 
476         lru_add_drain();
477         tlb_gather_mmu(&tlb, mm, start, end);
478         update_hiwater_rss(mm);
479 
480         mmu_notifier_invalidate_range_start(mm, start, end);
481         madvise_free_page_range(&tlb, vma, start, end);
482         mmu_notifier_invalidate_range_end(mm, start, end);
483         tlb_finish_mmu(&tlb, start, end);
484 
485         return 0;
486 }
487 
488 /*
489  * Application no longer needs these pages.  If the pages are dirty,
490  * it's OK to just throw them away.  The app will be more careful about
491  * data it wants to keep.  Be sure to free swap resources too.  The
492  * zap_page_range call sets things up for shrink_active_list to actually free
493  * these pages later if no one else has touched them in the meantime,
494  * although we could add these pages to a global reuse list for
495  * shrink_active_list to pick up before reclaiming other pages.
496  *
497  * NB: This interface discards data rather than pushes it out to swap,
498  * as some implementations do.  This has performance implications for
499  * applications like large transactional databases which want to discard
500  * pages in anonymous maps after committing to backing store the data
501  * that was kept in them.  There is no reason to write this data out to
502  * the swap area if the application is discarding it.
503  *
504  * An interface that causes the system to free clean pages and flush
505  * dirty pages is already available as msync(MS_INVALIDATE).
506  */
507 static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
508                                         unsigned long start, unsigned long end)
509 {
510         zap_page_range(vma, start, end - start);
511         return 0;
512 }
513 
514 static long madvise_dontneed_free(struct vm_area_struct *vma,
515                                   struct vm_area_struct **prev,
516                                   unsigned long start, unsigned long end,
517                                   int behavior)
518 {
519         *prev = vma;
520         if (!can_madv_dontneed_vma(vma))
521                 return -EINVAL;
522 
523         if (!userfaultfd_remove(vma, start, end)) {
524                 *prev = NULL; /* mmap_sem has been dropped, prev is stale */
525 
526                 down_read(&current->mm->mmap_sem);
527                 vma = find_vma(current->mm, start);
528                 if (!vma)
529                         return -ENOMEM;
530                 if (start < vma->vm_start) {
531                         /*
532                          * This "vma" under revalidation is the one
533                          * with the lowest vma->vm_start where start
534                          * is also < vma->vm_end. If start <
535                          * vma->vm_start it means an hole materialized
536                          * in the user address space within the
537                          * virtual range passed to MADV_DONTNEED
538                          * or MADV_FREE.
539                          */
540                         return -ENOMEM;
541                 }
542                 if (!can_madv_dontneed_vma(vma))
543                         return -EINVAL;
544                 if (end > vma->vm_end) {
545                         /*
546                          * Don't fail if end > vma->vm_end. If the old
547                          * vma was splitted while the mmap_sem was
548                          * released the effect of the concurrent
549                          * operation may not cause madvise() to
550                          * have an undefined result. There may be an
551                          * adjacent next vma that we'll walk
552                          * next. userfaultfd_remove() will generate an
553                          * UFFD_EVENT_REMOVE repetition on the
554                          * end-vma->vm_end range, but the manager can
555                          * handle a repetition fine.
556                          */
557                         end = vma->vm_end;
558                 }
559                 VM_WARN_ON(start >= end);
560         }
561 
562         if (behavior == MADV_DONTNEED)
563                 return madvise_dontneed_single_vma(vma, start, end);
564         else if (behavior == MADV_FREE)
565                 return madvise_free_single_vma(vma, start, end);
566         else
567                 return -EINVAL;
568 }
569 
570 /*
571  * Application wants to free up the pages and associated backing store.
572  * This is effectively punching a hole into the middle of a file.
573  */
574 static long madvise_remove(struct vm_area_struct *vma,
575                                 struct vm_area_struct **prev,
576                                 unsigned long start, unsigned long end)
577 {
578         loff_t offset;
579         int error;
580         struct file *f;
581 
582         *prev = NULL;   /* tell sys_madvise we drop mmap_sem */
583 
584         if (vma->vm_flags & VM_LOCKED)
585                 return -EINVAL;
586 
587         f = vma->vm_file;
588 
589         if (!f || !f->f_mapping || !f->f_mapping->host) {
590                         return -EINVAL;
591         }
592 
593         if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
594                 return -EACCES;
595 
596         offset = (loff_t)(start - vma->vm_start)
597                         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
598 
599         /*
600          * Filesystem's fallocate may need to take i_mutex.  We need to
601          * explicitly grab a reference because the vma (and hence the
602          * vma's reference to the file) can go away as soon as we drop
603          * mmap_sem.
604          */
605         get_file(f);
606         if (userfaultfd_remove(vma, start, end)) {
607                 /* mmap_sem was not released by userfaultfd_remove() */
608                 up_read(&current->mm->mmap_sem);
609         }
610         error = vfs_fallocate(f,
611                                 FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
612                                 offset, end - start);
613         fput(f);
614         down_read(&current->mm->mmap_sem);
615         return error;
616 }
617 
618 #ifdef CONFIG_MEMORY_FAILURE
619 /*
620  * Error injection support for memory error handling.
621  */
622 static int madvise_inject_error(int behavior,
623                 unsigned long start, unsigned long end)
624 {
625         struct page *page;
626         struct zone *zone;
627         unsigned int order;
628 
629         if (!capable(CAP_SYS_ADMIN))
630                 return -EPERM;
631 
632 
633         for (; start < end; start += PAGE_SIZE << order) {
634                 unsigned long pfn;
635                 int ret;
636 
637                 ret = get_user_pages_fast(start, 1, 0, &page);
638                 if (ret != 1)
639                         return ret;
640                 pfn = page_to_pfn(page);
641 
642                 /*
643                  * When soft offlining hugepages, after migrating the page
644                  * we dissolve it, therefore in the second loop "page" will
645                  * no longer be a compound page, and order will be 0.
646                  */
647                 order = compound_order(compound_head(page));
648 
649                 if (PageHWPoison(page)) {
650                         put_page(page);
651                         continue;
652                 }
653 
654                 if (behavior == MADV_SOFT_OFFLINE) {
655                         pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
656                                         pfn, start);
657 
658                         ret = soft_offline_page(page, MF_COUNT_INCREASED);
659                         if (ret)
660                                 return ret;
661                         continue;
662                 }
663 
664                 pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
665                                 pfn, start);
666 
667                 /*
668                  * Drop the page reference taken by get_user_pages_fast(). In
669                  * the absence of MF_COUNT_INCREASED the memory_failure()
670                  * routine is responsible for pinning the page to prevent it
671                  * from being released back to the page allocator.
672                  */
673                 put_page(page);
674                 ret = memory_failure(pfn, 0);
675                 if (ret)
676                         return ret;
677         }
678 
679         /* Ensure that all poisoned pages are removed from per-cpu lists */
680         for_each_populated_zone(zone)
681                 drain_all_pages(zone);
682 
683         return 0;
684 }
685 #endif
686 
687 static long
688 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
689                 unsigned long start, unsigned long end, int behavior)
690 {
691         switch (behavior) {
692         case MADV_REMOVE:
693                 return madvise_remove(vma, prev, start, end);
694         case MADV_WILLNEED:
695                 return madvise_willneed(vma, prev, start, end);
696         case MADV_FREE:
697         case MADV_DONTNEED:
698                 return madvise_dontneed_free(vma, prev, start, end, behavior);
699         default:
700                 return madvise_behavior(vma, prev, start, end, behavior);
701         }
702 }
703 
704 static bool
705 madvise_behavior_valid(int behavior)
706 {
707         switch (behavior) {
708         case MADV_DOFORK:
709         case MADV_DONTFORK:
710         case MADV_NORMAL:
711         case MADV_SEQUENTIAL:
712         case MADV_RANDOM:
713         case MADV_REMOVE:
714         case MADV_WILLNEED:
715         case MADV_DONTNEED:
716         case MADV_FREE:
717 #ifdef CONFIG_KSM
718         case MADV_MERGEABLE:
719         case MADV_UNMERGEABLE:
720 #endif
721 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
722         case MADV_HUGEPAGE:
723         case MADV_NOHUGEPAGE:
724 #endif
725         case MADV_DONTDUMP:
726         case MADV_DODUMP:
727         case MADV_WIPEONFORK:
728         case MADV_KEEPONFORK:
729 #ifdef CONFIG_MEMORY_FAILURE
730         case MADV_SOFT_OFFLINE:
731         case MADV_HWPOISON:
732 #endif
733                 return true;
734 
735         default:
736                 return false;
737         }
738 }
739 
740 /*
741  * The madvise(2) system call.
742  *
743  * Applications can use madvise() to advise the kernel how it should
744  * handle paging I/O in this VM area.  The idea is to help the kernel
745  * use appropriate read-ahead and caching techniques.  The information
746  * provided is advisory only, and can be safely disregarded by the
747  * kernel without affecting the correct operation of the application.
748  *
749  * behavior values:
750  *  MADV_NORMAL - the default behavior is to read clusters.  This
751  *              results in some read-ahead and read-behind.
752  *  MADV_RANDOM - the system should read the minimum amount of data
753  *              on any access, since it is unlikely that the appli-
754  *              cation will need more than what it asks for.
755  *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
756  *              once, so they can be aggressively read ahead, and
757  *              can be freed soon after they are accessed.
758  *  MADV_WILLNEED - the application is notifying the system to read
759  *              some pages ahead.
760  *  MADV_DONTNEED - the application is finished with the given range,
761  *              so the kernel can free resources associated with it.
762  *  MADV_FREE - the application marks pages in the given range as lazy free,
763  *              where actual purges are postponed until memory pressure happens.
764  *  MADV_REMOVE - the application wants to free up the given range of
765  *              pages and associated backing store.
766  *  MADV_DONTFORK - omit this area from child's address space when forking:
767  *              typically, to avoid COWing pages pinned by get_user_pages().
768  *  MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
769  *  MADV_WIPEONFORK - present the child process with zero-filled memory in this
770  *              range after a fork.
771  *  MADV_KEEPONFORK - undo the effect of MADV_WIPEONFORK
772  *  MADV_HWPOISON - trigger memory error handler as if the given memory range
773  *              were corrupted by unrecoverable hardware memory failure.
774  *  MADV_SOFT_OFFLINE - try to soft-offline the given range of memory.
775  *  MADV_MERGEABLE - the application recommends that KSM try to merge pages in
776  *              this area with pages of identical content from other such areas.
777  *  MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
778  *  MADV_HUGEPAGE - the application wants to back the given range by transparent
779  *              huge pages in the future. Existing pages might be coalesced and
780  *              new pages might be allocated as THP.
781  *  MADV_NOHUGEPAGE - mark the given range as not worth being backed by
782  *              transparent huge pages so the existing pages will not be
783  *              coalesced into THP and new pages will not be allocated as THP.
784  *  MADV_DONTDUMP - the application wants to prevent pages in the given range
785  *              from being included in its core dump.
786  *  MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
787  *
788  * return values:
789  *  zero    - success
790  *  -EINVAL - start + len < 0, start is not page-aligned,
791  *              "behavior" is not a valid value, or application
792  *              is attempting to release locked or shared pages,
793  *              or the specified address range includes file, Huge TLB,
794  *              MAP_SHARED or VMPFNMAP range.
795  *  -ENOMEM - addresses in the specified range are not currently
796  *              mapped, or are outside the AS of the process.
797  *  -EIO    - an I/O error occurred while paging in data.
798  *  -EBADF  - map exists, but area maps something that isn't a file.
799  *  -EAGAIN - a kernel resource was temporarily unavailable.
800  */
801 SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
802 {
803         unsigned long end, tmp;
804         struct vm_area_struct *vma, *prev;
805         int unmapped_error = 0;
806         int error = -EINVAL;
807         int write;
808         size_t len;
809         struct blk_plug plug;
810 
811         if (!madvise_behavior_valid(behavior))
812                 return error;
813 
814         if (start & ~PAGE_MASK)
815                 return error;
816         len = (len_in + ~PAGE_MASK) & PAGE_MASK;
817 
818         /* Check to see whether len was rounded up from small -ve to zero */
819         if (len_in && !len)
820                 return error;
821 
822         end = start + len;
823         if (end < start)
824                 return error;
825 
826         error = 0;
827         if (end == start)
828                 return error;
829 
830 #ifdef CONFIG_MEMORY_FAILURE
831         if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
832                 return madvise_inject_error(behavior, start, start + len_in);
833 #endif
834 
835         write = madvise_need_mmap_write(behavior);
836         if (write) {
837                 if (down_write_killable(&current->mm->mmap_sem))
838                         return -EINTR;
839         } else {
840                 down_read(&current->mm->mmap_sem);
841         }
842 
843         /*
844          * If the interval [start,end) covers some unmapped address
845          * ranges, just ignore them, but return -ENOMEM at the end.
846          * - different from the way of handling in mlock etc.
847          */
848         vma = find_vma_prev(current->mm, start, &prev);
849         if (vma && start > vma->vm_start)
850                 prev = vma;
851 
852         blk_start_plug(&plug);
853         for (;;) {
854                 /* Still start < end. */
855                 error = -ENOMEM;
856                 if (!vma)
857                         goto out;
858 
859                 /* Here start < (end|vma->vm_end). */
860                 if (start < vma->vm_start) {
861                         unmapped_error = -ENOMEM;
862                         start = vma->vm_start;
863                         if (start >= end)
864                                 goto out;
865                 }
866 
867                 /* Here vma->vm_start <= start < (end|vma->vm_end) */
868                 tmp = vma->vm_end;
869                 if (end < tmp)
870                         tmp = end;
871 
872                 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
873                 error = madvise_vma(vma, &prev, start, tmp, behavior);
874                 if (error)
875                         goto out;
876                 start = tmp;
877                 if (prev && start < prev->vm_end)
878                         start = prev->vm_end;
879                 error = unmapped_error;
880                 if (start >= end)
881                         goto out;
882                 if (prev)
883                         vma = prev->vm_next;
884                 else    /* madvise_remove dropped mmap_sem */
885                         vma = find_vma(current->mm, start);
886         }
887 out:
888         blk_finish_plug(&plug);
889         if (write)
890                 up_write(&current->mm->mmap_sem);
891         else
892                 up_read(&current->mm->mmap_sem);
893 
894         return error;
895 }
896 

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