xref: /linux/mm/madvise.c (revision 8b8eed05a1c650c27e78bc47d07f7d6c9ba779e8)
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/page_idle.h>
15 #include <linux/userfaultfd_k.h>
16 #include <linux/hugetlb.h>
17 #include <linux/falloc.h>
18 #include <linux/fadvise.h>
19 #include <linux/sched.h>
20 #include <linux/sched/mm.h>
21 #include <linux/mm_inline.h>
22 #include <linux/string.h>
23 #include <linux/uio.h>
24 #include <linux/ksm.h>
25 #include <linux/fs.h>
26 #include <linux/file.h>
27 #include <linux/blkdev.h>
28 #include <linux/backing-dev.h>
29 #include <linux/pagewalk.h>
30 #include <linux/swap.h>
31 #include <linux/swapops.h>
32 #include <linux/shmem_fs.h>
33 #include <linux/mmu_notifier.h>
34 
35 #include <asm/tlb.h>
36 
37 #include "internal.h"
38 #include "swap.h"
39 
40 struct madvise_walk_private {
41 	struct mmu_gather *tlb;
42 	bool pageout;
43 };
44 
45 /*
46  * Any behaviour which results in changes to the vma->vm_flags needs to
47  * take mmap_lock for writing. Others, which simply traverse vmas, need
48  * to only take it for reading.
49  */
50 static int madvise_need_mmap_write(int behavior)
51 {
52 	switch (behavior) {
53 	case MADV_REMOVE:
54 	case MADV_WILLNEED:
55 	case MADV_DONTNEED:
56 	case MADV_DONTNEED_LOCKED:
57 	case MADV_COLD:
58 	case MADV_PAGEOUT:
59 	case MADV_FREE:
60 	case MADV_POPULATE_READ:
61 	case MADV_POPULATE_WRITE:
62 	case MADV_COLLAPSE:
63 		return 0;
64 	default:
65 		/* be safe, default to 1. list exceptions explicitly */
66 		return 1;
67 	}
68 }
69 
70 #ifdef CONFIG_ANON_VMA_NAME
71 struct anon_vma_name *anon_vma_name_alloc(const char *name)
72 {
73 	struct anon_vma_name *anon_name;
74 	size_t count;
75 
76 	/* Add 1 for NUL terminator at the end of the anon_name->name */
77 	count = strlen(name) + 1;
78 	anon_name = kmalloc(struct_size(anon_name, name, count), GFP_KERNEL);
79 	if (anon_name) {
80 		kref_init(&anon_name->kref);
81 		memcpy(anon_name->name, name, count);
82 	}
83 
84 	return anon_name;
85 }
86 
87 void anon_vma_name_free(struct kref *kref)
88 {
89 	struct anon_vma_name *anon_name =
90 			container_of(kref, struct anon_vma_name, kref);
91 	kfree(anon_name);
92 }
93 
94 struct anon_vma_name *anon_vma_name(struct vm_area_struct *vma)
95 {
96 	mmap_assert_locked(vma->vm_mm);
97 
98 	return vma->anon_name;
99 }
100 
101 /* mmap_lock should be write-locked */
102 static int replace_anon_vma_name(struct vm_area_struct *vma,
103 				 struct anon_vma_name *anon_name)
104 {
105 	struct anon_vma_name *orig_name = anon_vma_name(vma);
106 
107 	if (!anon_name) {
108 		vma->anon_name = NULL;
109 		anon_vma_name_put(orig_name);
110 		return 0;
111 	}
112 
113 	if (anon_vma_name_eq(orig_name, anon_name))
114 		return 0;
115 
116 	vma->anon_name = anon_vma_name_reuse(anon_name);
117 	anon_vma_name_put(orig_name);
118 
119 	return 0;
120 }
121 #else /* CONFIG_ANON_VMA_NAME */
122 static int replace_anon_vma_name(struct vm_area_struct *vma,
123 				 struct anon_vma_name *anon_name)
124 {
125 	if (anon_name)
126 		return -EINVAL;
127 
128 	return 0;
129 }
130 #endif /* CONFIG_ANON_VMA_NAME */
131 /*
132  * Update the vm_flags on region of a vma, splitting it or merging it as
133  * necessary.  Must be called with mmap_lock held for writing;
134  * Caller should ensure anon_name stability by raising its refcount even when
135  * anon_name belongs to a valid vma because this function might free that vma.
136  */
137 static int madvise_update_vma(struct vm_area_struct *vma,
138 			      struct vm_area_struct **prev, unsigned long start,
139 			      unsigned long end, unsigned long new_flags,
140 			      struct anon_vma_name *anon_name)
141 {
142 	struct mm_struct *mm = vma->vm_mm;
143 	int error;
144 	VMA_ITERATOR(vmi, mm, start);
145 
146 	if (new_flags == vma->vm_flags && anon_vma_name_eq(anon_vma_name(vma), anon_name)) {
147 		*prev = vma;
148 		return 0;
149 	}
150 
151 	vma = vma_modify_flags_name(&vmi, *prev, vma, start, end, new_flags,
152 				    anon_name);
153 	if (IS_ERR(vma))
154 		return PTR_ERR(vma);
155 
156 	*prev = vma;
157 
158 	/* vm_flags is protected by the mmap_lock held in write mode. */
159 	vma_start_write(vma);
160 	vm_flags_reset(vma, new_flags);
161 	if (!vma->vm_file || vma_is_anon_shmem(vma)) {
162 		error = replace_anon_vma_name(vma, anon_name);
163 		if (error)
164 			return error;
165 	}
166 
167 	return 0;
168 }
169 
170 #ifdef CONFIG_SWAP
171 static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
172 		unsigned long end, struct mm_walk *walk)
173 {
174 	struct vm_area_struct *vma = walk->private;
175 	struct swap_iocb *splug = NULL;
176 	pte_t *ptep = NULL;
177 	spinlock_t *ptl;
178 	unsigned long addr;
179 
180 	for (addr = start; addr < end; addr += PAGE_SIZE) {
181 		pte_t pte;
182 		swp_entry_t entry;
183 		struct page *page;
184 
185 		if (!ptep++) {
186 			ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
187 			if (!ptep)
188 				break;
189 		}
190 
191 		pte = ptep_get(ptep);
192 		if (!is_swap_pte(pte))
193 			continue;
194 		entry = pte_to_swp_entry(pte);
195 		if (unlikely(non_swap_entry(entry)))
196 			continue;
197 
198 		pte_unmap_unlock(ptep, ptl);
199 		ptep = NULL;
200 
201 		page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
202 					     vma, addr, &splug);
203 		if (page)
204 			put_page(page);
205 	}
206 
207 	if (ptep)
208 		pte_unmap_unlock(ptep, ptl);
209 	swap_read_unplug(splug);
210 	cond_resched();
211 
212 	return 0;
213 }
214 
215 static const struct mm_walk_ops swapin_walk_ops = {
216 	.pmd_entry		= swapin_walk_pmd_entry,
217 	.walk_lock		= PGWALK_RDLOCK,
218 };
219 
220 static void shmem_swapin_range(struct vm_area_struct *vma,
221 		unsigned long start, unsigned long end,
222 		struct address_space *mapping)
223 {
224 	XA_STATE(xas, &mapping->i_pages, linear_page_index(vma, start));
225 	pgoff_t end_index = linear_page_index(vma, end) - 1;
226 	struct page *page;
227 	struct swap_iocb *splug = NULL;
228 
229 	rcu_read_lock();
230 	xas_for_each(&xas, page, end_index) {
231 		unsigned long addr;
232 		swp_entry_t entry;
233 
234 		if (!xa_is_value(page))
235 			continue;
236 		entry = radix_to_swp_entry(page);
237 		/* There might be swapin error entries in shmem mapping. */
238 		if (non_swap_entry(entry))
239 			continue;
240 
241 		addr = vma->vm_start +
242 			((xas.xa_index - vma->vm_pgoff) << PAGE_SHIFT);
243 		xas_pause(&xas);
244 		rcu_read_unlock();
245 
246 		page = read_swap_cache_async(entry, mapping_gfp_mask(mapping),
247 					     vma, addr, &splug);
248 		if (page)
249 			put_page(page);
250 
251 		rcu_read_lock();
252 	}
253 	rcu_read_unlock();
254 	swap_read_unplug(splug);
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 mm_struct *mm = vma->vm_mm;
266 	struct file *file = vma->vm_file;
267 	loff_t offset;
268 
269 	*prev = vma;
270 #ifdef CONFIG_SWAP
271 	if (!file) {
272 		walk_page_range(vma->vm_mm, start, end, &swapin_walk_ops, vma);
273 		lru_add_drain(); /* Push any new pages onto the LRU now */
274 		return 0;
275 	}
276 
277 	if (shmem_mapping(file->f_mapping)) {
278 		shmem_swapin_range(vma, start, end, file->f_mapping);
279 		lru_add_drain(); /* Push any new pages onto the LRU now */
280 		return 0;
281 	}
282 #else
283 	if (!file)
284 		return -EBADF;
285 #endif
286 
287 	if (IS_DAX(file_inode(file))) {
288 		/* no bad return value, but ignore advice */
289 		return 0;
290 	}
291 
292 	/*
293 	 * Filesystem's fadvise may need to take various locks.  We need to
294 	 * explicitly grab a reference because the vma (and hence the
295 	 * vma's reference to the file) can go away as soon as we drop
296 	 * mmap_lock.
297 	 */
298 	*prev = NULL;	/* tell sys_madvise we drop mmap_lock */
299 	get_file(file);
300 	offset = (loff_t)(start - vma->vm_start)
301 			+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
302 	mmap_read_unlock(mm);
303 	vfs_fadvise(file, offset, end - start, POSIX_FADV_WILLNEED);
304 	fput(file);
305 	mmap_read_lock(mm);
306 	return 0;
307 }
308 
309 static inline bool can_do_file_pageout(struct vm_area_struct *vma)
310 {
311 	if (!vma->vm_file)
312 		return false;
313 	/*
314 	 * paging out pagecache only for non-anonymous mappings that correspond
315 	 * to the files the calling process could (if tried) open for writing;
316 	 * otherwise we'd be including shared non-exclusive mappings, which
317 	 * opens a side channel.
318 	 */
319 	return inode_owner_or_capable(&nop_mnt_idmap,
320 				      file_inode(vma->vm_file)) ||
321 	       file_permission(vma->vm_file, MAY_WRITE) == 0;
322 }
323 
324 static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
325 				unsigned long addr, unsigned long end,
326 				struct mm_walk *walk)
327 {
328 	struct madvise_walk_private *private = walk->private;
329 	struct mmu_gather *tlb = private->tlb;
330 	bool pageout = private->pageout;
331 	struct mm_struct *mm = tlb->mm;
332 	struct vm_area_struct *vma = walk->vma;
333 	pte_t *start_pte, *pte, ptent;
334 	spinlock_t *ptl;
335 	struct folio *folio = NULL;
336 	LIST_HEAD(folio_list);
337 	bool pageout_anon_only_filter;
338 
339 	if (fatal_signal_pending(current))
340 		return -EINTR;
341 
342 	pageout_anon_only_filter = pageout && !vma_is_anonymous(vma) &&
343 					!can_do_file_pageout(vma);
344 
345 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
346 	if (pmd_trans_huge(*pmd)) {
347 		pmd_t orig_pmd;
348 		unsigned long next = pmd_addr_end(addr, end);
349 
350 		tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
351 		ptl = pmd_trans_huge_lock(pmd, vma);
352 		if (!ptl)
353 			return 0;
354 
355 		orig_pmd = *pmd;
356 		if (is_huge_zero_pmd(orig_pmd))
357 			goto huge_unlock;
358 
359 		if (unlikely(!pmd_present(orig_pmd))) {
360 			VM_BUG_ON(thp_migration_supported() &&
361 					!is_pmd_migration_entry(orig_pmd));
362 			goto huge_unlock;
363 		}
364 
365 		folio = pfn_folio(pmd_pfn(orig_pmd));
366 
367 		/* Do not interfere with other mappings of this folio */
368 		if (folio_estimated_sharers(folio) != 1)
369 			goto huge_unlock;
370 
371 		if (pageout_anon_only_filter && !folio_test_anon(folio))
372 			goto huge_unlock;
373 
374 		if (next - addr != HPAGE_PMD_SIZE) {
375 			int err;
376 
377 			folio_get(folio);
378 			spin_unlock(ptl);
379 			folio_lock(folio);
380 			err = split_folio(folio);
381 			folio_unlock(folio);
382 			folio_put(folio);
383 			if (!err)
384 				goto regular_folio;
385 			return 0;
386 		}
387 
388 		if (pmd_young(orig_pmd)) {
389 			pmdp_invalidate(vma, addr, pmd);
390 			orig_pmd = pmd_mkold(orig_pmd);
391 
392 			set_pmd_at(mm, addr, pmd, orig_pmd);
393 			tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
394 		}
395 
396 		folio_clear_referenced(folio);
397 		folio_test_clear_young(folio);
398 		if (folio_test_active(folio))
399 			folio_set_workingset(folio);
400 		if (pageout) {
401 			if (folio_isolate_lru(folio)) {
402 				if (folio_test_unevictable(folio))
403 					folio_putback_lru(folio);
404 				else
405 					list_add(&folio->lru, &folio_list);
406 			}
407 		} else
408 			folio_deactivate(folio);
409 huge_unlock:
410 		spin_unlock(ptl);
411 		if (pageout)
412 			reclaim_pages(&folio_list);
413 		return 0;
414 	}
415 
416 regular_folio:
417 #endif
418 	tlb_change_page_size(tlb, PAGE_SIZE);
419 	start_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
420 	if (!start_pte)
421 		return 0;
422 	flush_tlb_batched_pending(mm);
423 	arch_enter_lazy_mmu_mode();
424 	for (; addr < end; pte++, addr += PAGE_SIZE) {
425 		ptent = ptep_get(pte);
426 
427 		if (pte_none(ptent))
428 			continue;
429 
430 		if (!pte_present(ptent))
431 			continue;
432 
433 		folio = vm_normal_folio(vma, addr, ptent);
434 		if (!folio || folio_is_zone_device(folio))
435 			continue;
436 
437 		/*
438 		 * Creating a THP page is expensive so split it only if we
439 		 * are sure it's worth. Split it if we are only owner.
440 		 */
441 		if (folio_test_large(folio)) {
442 			int err;
443 
444 			if (folio_estimated_sharers(folio) != 1)
445 				break;
446 			if (pageout_anon_only_filter && !folio_test_anon(folio))
447 				break;
448 			if (!folio_trylock(folio))
449 				break;
450 			folio_get(folio);
451 			arch_leave_lazy_mmu_mode();
452 			pte_unmap_unlock(start_pte, ptl);
453 			start_pte = NULL;
454 			err = split_folio(folio);
455 			folio_unlock(folio);
456 			folio_put(folio);
457 			if (err)
458 				break;
459 			start_pte = pte =
460 				pte_offset_map_lock(mm, pmd, addr, &ptl);
461 			if (!start_pte)
462 				break;
463 			arch_enter_lazy_mmu_mode();
464 			pte--;
465 			addr -= PAGE_SIZE;
466 			continue;
467 		}
468 
469 		/*
470 		 * Do not interfere with other mappings of this folio and
471 		 * non-LRU folio.
472 		 */
473 		if (!folio_test_lru(folio) || folio_mapcount(folio) != 1)
474 			continue;
475 
476 		if (pageout_anon_only_filter && !folio_test_anon(folio))
477 			continue;
478 
479 		VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
480 
481 		if (pte_young(ptent)) {
482 			ptent = ptep_get_and_clear_full(mm, addr, pte,
483 							tlb->fullmm);
484 			ptent = pte_mkold(ptent);
485 			set_pte_at(mm, addr, pte, ptent);
486 			tlb_remove_tlb_entry(tlb, pte, addr);
487 		}
488 
489 		/*
490 		 * We are deactivating a folio for accelerating reclaiming.
491 		 * VM couldn't reclaim the folio unless we clear PG_young.
492 		 * As a side effect, it makes confuse idle-page tracking
493 		 * because they will miss recent referenced history.
494 		 */
495 		folio_clear_referenced(folio);
496 		folio_test_clear_young(folio);
497 		if (folio_test_active(folio))
498 			folio_set_workingset(folio);
499 		if (pageout) {
500 			if (folio_isolate_lru(folio)) {
501 				if (folio_test_unevictable(folio))
502 					folio_putback_lru(folio);
503 				else
504 					list_add(&folio->lru, &folio_list);
505 			}
506 		} else
507 			folio_deactivate(folio);
508 	}
509 
510 	if (start_pte) {
511 		arch_leave_lazy_mmu_mode();
512 		pte_unmap_unlock(start_pte, ptl);
513 	}
514 	if (pageout)
515 		reclaim_pages(&folio_list);
516 	cond_resched();
517 
518 	return 0;
519 }
520 
521 static const struct mm_walk_ops cold_walk_ops = {
522 	.pmd_entry = madvise_cold_or_pageout_pte_range,
523 	.walk_lock = PGWALK_RDLOCK,
524 };
525 
526 static void madvise_cold_page_range(struct mmu_gather *tlb,
527 			     struct vm_area_struct *vma,
528 			     unsigned long addr, unsigned long end)
529 {
530 	struct madvise_walk_private walk_private = {
531 		.pageout = false,
532 		.tlb = tlb,
533 	};
534 
535 	tlb_start_vma(tlb, vma);
536 	walk_page_range(vma->vm_mm, addr, end, &cold_walk_ops, &walk_private);
537 	tlb_end_vma(tlb, vma);
538 }
539 
540 static inline bool can_madv_lru_vma(struct vm_area_struct *vma)
541 {
542 	return !(vma->vm_flags & (VM_LOCKED|VM_PFNMAP|VM_HUGETLB));
543 }
544 
545 static long madvise_cold(struct vm_area_struct *vma,
546 			struct vm_area_struct **prev,
547 			unsigned long start_addr, unsigned long end_addr)
548 {
549 	struct mm_struct *mm = vma->vm_mm;
550 	struct mmu_gather tlb;
551 
552 	*prev = vma;
553 	if (!can_madv_lru_vma(vma))
554 		return -EINVAL;
555 
556 	lru_add_drain();
557 	tlb_gather_mmu(&tlb, mm);
558 	madvise_cold_page_range(&tlb, vma, start_addr, end_addr);
559 	tlb_finish_mmu(&tlb);
560 
561 	return 0;
562 }
563 
564 static void madvise_pageout_page_range(struct mmu_gather *tlb,
565 			     struct vm_area_struct *vma,
566 			     unsigned long addr, unsigned long end)
567 {
568 	struct madvise_walk_private walk_private = {
569 		.pageout = true,
570 		.tlb = tlb,
571 	};
572 
573 	tlb_start_vma(tlb, vma);
574 	walk_page_range(vma->vm_mm, addr, end, &cold_walk_ops, &walk_private);
575 	tlb_end_vma(tlb, vma);
576 }
577 
578 static long madvise_pageout(struct vm_area_struct *vma,
579 			struct vm_area_struct **prev,
580 			unsigned long start_addr, unsigned long end_addr)
581 {
582 	struct mm_struct *mm = vma->vm_mm;
583 	struct mmu_gather tlb;
584 
585 	*prev = vma;
586 	if (!can_madv_lru_vma(vma))
587 		return -EINVAL;
588 
589 	/*
590 	 * If the VMA belongs to a private file mapping, there can be private
591 	 * dirty pages which can be paged out if even this process is neither
592 	 * owner nor write capable of the file. We allow private file mappings
593 	 * further to pageout dirty anon pages.
594 	 */
595 	if (!vma_is_anonymous(vma) && (!can_do_file_pageout(vma) &&
596 				(vma->vm_flags & VM_MAYSHARE)))
597 		return 0;
598 
599 	lru_add_drain();
600 	tlb_gather_mmu(&tlb, mm);
601 	madvise_pageout_page_range(&tlb, vma, start_addr, end_addr);
602 	tlb_finish_mmu(&tlb);
603 
604 	return 0;
605 }
606 
607 static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
608 				unsigned long end, struct mm_walk *walk)
609 
610 {
611 	struct mmu_gather *tlb = walk->private;
612 	struct mm_struct *mm = tlb->mm;
613 	struct vm_area_struct *vma = walk->vma;
614 	spinlock_t *ptl;
615 	pte_t *start_pte, *pte, ptent;
616 	struct folio *folio;
617 	int nr_swap = 0;
618 	unsigned long next;
619 
620 	next = pmd_addr_end(addr, end);
621 	if (pmd_trans_huge(*pmd))
622 		if (madvise_free_huge_pmd(tlb, vma, pmd, addr, next))
623 			return 0;
624 
625 	tlb_change_page_size(tlb, PAGE_SIZE);
626 	start_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
627 	if (!start_pte)
628 		return 0;
629 	flush_tlb_batched_pending(mm);
630 	arch_enter_lazy_mmu_mode();
631 	for (; addr != end; pte++, addr += PAGE_SIZE) {
632 		ptent = ptep_get(pte);
633 
634 		if (pte_none(ptent))
635 			continue;
636 		/*
637 		 * If the pte has swp_entry, just clear page table to
638 		 * prevent swap-in which is more expensive rather than
639 		 * (page allocation + zeroing).
640 		 */
641 		if (!pte_present(ptent)) {
642 			swp_entry_t entry;
643 
644 			entry = pte_to_swp_entry(ptent);
645 			if (!non_swap_entry(entry)) {
646 				nr_swap--;
647 				free_swap_and_cache(entry);
648 				pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
649 			} else if (is_hwpoison_entry(entry) ||
650 				   is_poisoned_swp_entry(entry)) {
651 				pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
652 			}
653 			continue;
654 		}
655 
656 		folio = vm_normal_folio(vma, addr, ptent);
657 		if (!folio || folio_is_zone_device(folio))
658 			continue;
659 
660 		/*
661 		 * If pmd isn't transhuge but the folio is large and
662 		 * is owned by only this process, split it and
663 		 * deactivate all pages.
664 		 */
665 		if (folio_test_large(folio)) {
666 			int err;
667 
668 			if (folio_estimated_sharers(folio) != 1)
669 				break;
670 			if (!folio_trylock(folio))
671 				break;
672 			folio_get(folio);
673 			arch_leave_lazy_mmu_mode();
674 			pte_unmap_unlock(start_pte, ptl);
675 			start_pte = NULL;
676 			err = split_folio(folio);
677 			folio_unlock(folio);
678 			folio_put(folio);
679 			if (err)
680 				break;
681 			start_pte = pte =
682 				pte_offset_map_lock(mm, pmd, addr, &ptl);
683 			if (!start_pte)
684 				break;
685 			arch_enter_lazy_mmu_mode();
686 			pte--;
687 			addr -= PAGE_SIZE;
688 			continue;
689 		}
690 
691 		if (folio_test_swapcache(folio) || folio_test_dirty(folio)) {
692 			if (!folio_trylock(folio))
693 				continue;
694 			/*
695 			 * If folio is shared with others, we mustn't clear
696 			 * the folio's dirty flag.
697 			 */
698 			if (folio_mapcount(folio) != 1) {
699 				folio_unlock(folio);
700 				continue;
701 			}
702 
703 			if (folio_test_swapcache(folio) &&
704 			    !folio_free_swap(folio)) {
705 				folio_unlock(folio);
706 				continue;
707 			}
708 
709 			folio_clear_dirty(folio);
710 			folio_unlock(folio);
711 		}
712 
713 		if (pte_young(ptent) || pte_dirty(ptent)) {
714 			/*
715 			 * Some of architecture(ex, PPC) don't update TLB
716 			 * with set_pte_at and tlb_remove_tlb_entry so for
717 			 * the portability, remap the pte with old|clean
718 			 * after pte clearing.
719 			 */
720 			ptent = ptep_get_and_clear_full(mm, addr, pte,
721 							tlb->fullmm);
722 
723 			ptent = pte_mkold(ptent);
724 			ptent = pte_mkclean(ptent);
725 			set_pte_at(mm, addr, pte, ptent);
726 			tlb_remove_tlb_entry(tlb, pte, addr);
727 		}
728 		folio_mark_lazyfree(folio);
729 	}
730 
731 	if (nr_swap)
732 		add_mm_counter(mm, MM_SWAPENTS, nr_swap);
733 	if (start_pte) {
734 		arch_leave_lazy_mmu_mode();
735 		pte_unmap_unlock(start_pte, ptl);
736 	}
737 	cond_resched();
738 
739 	return 0;
740 }
741 
742 static const struct mm_walk_ops madvise_free_walk_ops = {
743 	.pmd_entry		= madvise_free_pte_range,
744 	.walk_lock		= PGWALK_RDLOCK,
745 };
746 
747 static int madvise_free_single_vma(struct vm_area_struct *vma,
748 			unsigned long start_addr, unsigned long end_addr)
749 {
750 	struct mm_struct *mm = vma->vm_mm;
751 	struct mmu_notifier_range range;
752 	struct mmu_gather tlb;
753 
754 	/* MADV_FREE works for only anon vma at the moment */
755 	if (!vma_is_anonymous(vma))
756 		return -EINVAL;
757 
758 	range.start = max(vma->vm_start, start_addr);
759 	if (range.start >= vma->vm_end)
760 		return -EINVAL;
761 	range.end = min(vma->vm_end, end_addr);
762 	if (range.end <= vma->vm_start)
763 		return -EINVAL;
764 	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm,
765 				range.start, range.end);
766 
767 	lru_add_drain();
768 	tlb_gather_mmu(&tlb, mm);
769 	update_hiwater_rss(mm);
770 
771 	mmu_notifier_invalidate_range_start(&range);
772 	tlb_start_vma(&tlb, vma);
773 	walk_page_range(vma->vm_mm, range.start, range.end,
774 			&madvise_free_walk_ops, &tlb);
775 	tlb_end_vma(&tlb, vma);
776 	mmu_notifier_invalidate_range_end(&range);
777 	tlb_finish_mmu(&tlb);
778 
779 	return 0;
780 }
781 
782 /*
783  * Application no longer needs these pages.  If the pages are dirty,
784  * it's OK to just throw them away.  The app will be more careful about
785  * data it wants to keep.  Be sure to free swap resources too.  The
786  * zap_page_range_single call sets things up for shrink_active_list to actually
787  * free these pages later if no one else has touched them in the meantime,
788  * although we could add these pages to a global reuse list for
789  * shrink_active_list to pick up before reclaiming other pages.
790  *
791  * NB: This interface discards data rather than pushes it out to swap,
792  * as some implementations do.  This has performance implications for
793  * applications like large transactional databases which want to discard
794  * pages in anonymous maps after committing to backing store the data
795  * that was kept in them.  There is no reason to write this data out to
796  * the swap area if the application is discarding it.
797  *
798  * An interface that causes the system to free clean pages and flush
799  * dirty pages is already available as msync(MS_INVALIDATE).
800  */
801 static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
802 					unsigned long start, unsigned long end)
803 {
804 	zap_page_range_single(vma, start, end - start, NULL);
805 	return 0;
806 }
807 
808 static bool madvise_dontneed_free_valid_vma(struct vm_area_struct *vma,
809 					    unsigned long start,
810 					    unsigned long *end,
811 					    int behavior)
812 {
813 	if (!is_vm_hugetlb_page(vma)) {
814 		unsigned int forbidden = VM_PFNMAP;
815 
816 		if (behavior != MADV_DONTNEED_LOCKED)
817 			forbidden |= VM_LOCKED;
818 
819 		return !(vma->vm_flags & forbidden);
820 	}
821 
822 	if (behavior != MADV_DONTNEED && behavior != MADV_DONTNEED_LOCKED)
823 		return false;
824 	if (start & ~huge_page_mask(hstate_vma(vma)))
825 		return false;
826 
827 	/*
828 	 * Madvise callers expect the length to be rounded up to PAGE_SIZE
829 	 * boundaries, and may be unaware that this VMA uses huge pages.
830 	 * Avoid unexpected data loss by rounding down the number of
831 	 * huge pages freed.
832 	 */
833 	*end = ALIGN_DOWN(*end, huge_page_size(hstate_vma(vma)));
834 
835 	return true;
836 }
837 
838 static long madvise_dontneed_free(struct vm_area_struct *vma,
839 				  struct vm_area_struct **prev,
840 				  unsigned long start, unsigned long end,
841 				  int behavior)
842 {
843 	struct mm_struct *mm = vma->vm_mm;
844 
845 	*prev = vma;
846 	if (!madvise_dontneed_free_valid_vma(vma, start, &end, behavior))
847 		return -EINVAL;
848 
849 	if (start == end)
850 		return 0;
851 
852 	if (!userfaultfd_remove(vma, start, end)) {
853 		*prev = NULL; /* mmap_lock has been dropped, prev is stale */
854 
855 		mmap_read_lock(mm);
856 		vma = vma_lookup(mm, start);
857 		if (!vma)
858 			return -ENOMEM;
859 		/*
860 		 * Potential end adjustment for hugetlb vma is OK as
861 		 * the check below keeps end within vma.
862 		 */
863 		if (!madvise_dontneed_free_valid_vma(vma, start, &end,
864 						     behavior))
865 			return -EINVAL;
866 		if (end > vma->vm_end) {
867 			/*
868 			 * Don't fail if end > vma->vm_end. If the old
869 			 * vma was split while the mmap_lock was
870 			 * released the effect of the concurrent
871 			 * operation may not cause madvise() to
872 			 * have an undefined result. There may be an
873 			 * adjacent next vma that we'll walk
874 			 * next. userfaultfd_remove() will generate an
875 			 * UFFD_EVENT_REMOVE repetition on the
876 			 * end-vma->vm_end range, but the manager can
877 			 * handle a repetition fine.
878 			 */
879 			end = vma->vm_end;
880 		}
881 		VM_WARN_ON(start >= end);
882 	}
883 
884 	if (behavior == MADV_DONTNEED || behavior == MADV_DONTNEED_LOCKED)
885 		return madvise_dontneed_single_vma(vma, start, end);
886 	else if (behavior == MADV_FREE)
887 		return madvise_free_single_vma(vma, start, end);
888 	else
889 		return -EINVAL;
890 }
891 
892 static long madvise_populate(struct vm_area_struct *vma,
893 			     struct vm_area_struct **prev,
894 			     unsigned long start, unsigned long end,
895 			     int behavior)
896 {
897 	const bool write = behavior == MADV_POPULATE_WRITE;
898 	struct mm_struct *mm = vma->vm_mm;
899 	unsigned long tmp_end;
900 	int locked = 1;
901 	long pages;
902 
903 	*prev = vma;
904 
905 	while (start < end) {
906 		/*
907 		 * We might have temporarily dropped the lock. For example,
908 		 * our VMA might have been split.
909 		 */
910 		if (!vma || start >= vma->vm_end) {
911 			vma = vma_lookup(mm, start);
912 			if (!vma)
913 				return -ENOMEM;
914 		}
915 
916 		tmp_end = min_t(unsigned long, end, vma->vm_end);
917 		/* Populate (prefault) page tables readable/writable. */
918 		pages = faultin_vma_page_range(vma, start, tmp_end, write,
919 					       &locked);
920 		if (!locked) {
921 			mmap_read_lock(mm);
922 			locked = 1;
923 			*prev = NULL;
924 			vma = NULL;
925 		}
926 		if (pages < 0) {
927 			switch (pages) {
928 			case -EINTR:
929 				return -EINTR;
930 			case -EINVAL: /* Incompatible mappings / permissions. */
931 				return -EINVAL;
932 			case -EHWPOISON:
933 				return -EHWPOISON;
934 			case -EFAULT: /* VM_FAULT_SIGBUS or VM_FAULT_SIGSEGV */
935 				return -EFAULT;
936 			default:
937 				pr_warn_once("%s: unhandled return value: %ld\n",
938 					     __func__, pages);
939 				fallthrough;
940 			case -ENOMEM:
941 				return -ENOMEM;
942 			}
943 		}
944 		start += pages * PAGE_SIZE;
945 	}
946 	return 0;
947 }
948 
949 /*
950  * Application wants to free up the pages and associated backing store.
951  * This is effectively punching a hole into the middle of a file.
952  */
953 static long madvise_remove(struct vm_area_struct *vma,
954 				struct vm_area_struct **prev,
955 				unsigned long start, unsigned long end)
956 {
957 	loff_t offset;
958 	int error;
959 	struct file *f;
960 	struct mm_struct *mm = vma->vm_mm;
961 
962 	*prev = NULL;	/* tell sys_madvise we drop mmap_lock */
963 
964 	if (vma->vm_flags & VM_LOCKED)
965 		return -EINVAL;
966 
967 	f = vma->vm_file;
968 
969 	if (!f || !f->f_mapping || !f->f_mapping->host) {
970 			return -EINVAL;
971 	}
972 
973 	if (!vma_is_shared_maywrite(vma))
974 		return -EACCES;
975 
976 	offset = (loff_t)(start - vma->vm_start)
977 			+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
978 
979 	/*
980 	 * Filesystem's fallocate may need to take i_rwsem.  We need to
981 	 * explicitly grab a reference because the vma (and hence the
982 	 * vma's reference to the file) can go away as soon as we drop
983 	 * mmap_lock.
984 	 */
985 	get_file(f);
986 	if (userfaultfd_remove(vma, start, end)) {
987 		/* mmap_lock was not released by userfaultfd_remove() */
988 		mmap_read_unlock(mm);
989 	}
990 	error = vfs_fallocate(f,
991 				FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
992 				offset, end - start);
993 	fput(f);
994 	mmap_read_lock(mm);
995 	return error;
996 }
997 
998 /*
999  * Apply an madvise behavior to a region of a vma.  madvise_update_vma
1000  * will handle splitting a vm area into separate areas, each area with its own
1001  * behavior.
1002  */
1003 static int madvise_vma_behavior(struct vm_area_struct *vma,
1004 				struct vm_area_struct **prev,
1005 				unsigned long start, unsigned long end,
1006 				unsigned long behavior)
1007 {
1008 	int error;
1009 	struct anon_vma_name *anon_name;
1010 	unsigned long new_flags = vma->vm_flags;
1011 
1012 	switch (behavior) {
1013 	case MADV_REMOVE:
1014 		return madvise_remove(vma, prev, start, end);
1015 	case MADV_WILLNEED:
1016 		return madvise_willneed(vma, prev, start, end);
1017 	case MADV_COLD:
1018 		return madvise_cold(vma, prev, start, end);
1019 	case MADV_PAGEOUT:
1020 		return madvise_pageout(vma, prev, start, end);
1021 	case MADV_FREE:
1022 	case MADV_DONTNEED:
1023 	case MADV_DONTNEED_LOCKED:
1024 		return madvise_dontneed_free(vma, prev, start, end, behavior);
1025 	case MADV_POPULATE_READ:
1026 	case MADV_POPULATE_WRITE:
1027 		return madvise_populate(vma, prev, start, end, behavior);
1028 	case MADV_NORMAL:
1029 		new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
1030 		break;
1031 	case MADV_SEQUENTIAL:
1032 		new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
1033 		break;
1034 	case MADV_RANDOM:
1035 		new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
1036 		break;
1037 	case MADV_DONTFORK:
1038 		new_flags |= VM_DONTCOPY;
1039 		break;
1040 	case MADV_DOFORK:
1041 		if (vma->vm_flags & VM_IO)
1042 			return -EINVAL;
1043 		new_flags &= ~VM_DONTCOPY;
1044 		break;
1045 	case MADV_WIPEONFORK:
1046 		/* MADV_WIPEONFORK is only supported on anonymous memory. */
1047 		if (vma->vm_file || vma->vm_flags & VM_SHARED)
1048 			return -EINVAL;
1049 		new_flags |= VM_WIPEONFORK;
1050 		break;
1051 	case MADV_KEEPONFORK:
1052 		new_flags &= ~VM_WIPEONFORK;
1053 		break;
1054 	case MADV_DONTDUMP:
1055 		new_flags |= VM_DONTDUMP;
1056 		break;
1057 	case MADV_DODUMP:
1058 		if (!is_vm_hugetlb_page(vma) && new_flags & VM_SPECIAL)
1059 			return -EINVAL;
1060 		new_flags &= ~VM_DONTDUMP;
1061 		break;
1062 	case MADV_MERGEABLE:
1063 	case MADV_UNMERGEABLE:
1064 		error = ksm_madvise(vma, start, end, behavior, &new_flags);
1065 		if (error)
1066 			goto out;
1067 		break;
1068 	case MADV_HUGEPAGE:
1069 	case MADV_NOHUGEPAGE:
1070 		error = hugepage_madvise(vma, &new_flags, behavior);
1071 		if (error)
1072 			goto out;
1073 		break;
1074 	case MADV_COLLAPSE:
1075 		return madvise_collapse(vma, prev, start, end);
1076 	}
1077 
1078 	anon_name = anon_vma_name(vma);
1079 	anon_vma_name_get(anon_name);
1080 	error = madvise_update_vma(vma, prev, start, end, new_flags,
1081 				   anon_name);
1082 	anon_vma_name_put(anon_name);
1083 
1084 out:
1085 	/*
1086 	 * madvise() returns EAGAIN if kernel resources, such as
1087 	 * slab, are temporarily unavailable.
1088 	 */
1089 	if (error == -ENOMEM)
1090 		error = -EAGAIN;
1091 	return error;
1092 }
1093 
1094 #ifdef CONFIG_MEMORY_FAILURE
1095 /*
1096  * Error injection support for memory error handling.
1097  */
1098 static int madvise_inject_error(int behavior,
1099 		unsigned long start, unsigned long end)
1100 {
1101 	unsigned long size;
1102 
1103 	if (!capable(CAP_SYS_ADMIN))
1104 		return -EPERM;
1105 
1106 
1107 	for (; start < end; start += size) {
1108 		unsigned long pfn;
1109 		struct page *page;
1110 		int ret;
1111 
1112 		ret = get_user_pages_fast(start, 1, 0, &page);
1113 		if (ret != 1)
1114 			return ret;
1115 		pfn = page_to_pfn(page);
1116 
1117 		/*
1118 		 * When soft offlining hugepages, after migrating the page
1119 		 * we dissolve it, therefore in the second loop "page" will
1120 		 * no longer be a compound page.
1121 		 */
1122 		size = page_size(compound_head(page));
1123 
1124 		if (behavior == MADV_SOFT_OFFLINE) {
1125 			pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
1126 				 pfn, start);
1127 			ret = soft_offline_page(pfn, MF_COUNT_INCREASED);
1128 		} else {
1129 			pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
1130 				 pfn, start);
1131 			ret = memory_failure(pfn, MF_COUNT_INCREASED | MF_SW_SIMULATED);
1132 			if (ret == -EOPNOTSUPP)
1133 				ret = 0;
1134 		}
1135 
1136 		if (ret)
1137 			return ret;
1138 	}
1139 
1140 	return 0;
1141 }
1142 #endif
1143 
1144 static bool
1145 madvise_behavior_valid(int behavior)
1146 {
1147 	switch (behavior) {
1148 	case MADV_DOFORK:
1149 	case MADV_DONTFORK:
1150 	case MADV_NORMAL:
1151 	case MADV_SEQUENTIAL:
1152 	case MADV_RANDOM:
1153 	case MADV_REMOVE:
1154 	case MADV_WILLNEED:
1155 	case MADV_DONTNEED:
1156 	case MADV_DONTNEED_LOCKED:
1157 	case MADV_FREE:
1158 	case MADV_COLD:
1159 	case MADV_PAGEOUT:
1160 	case MADV_POPULATE_READ:
1161 	case MADV_POPULATE_WRITE:
1162 #ifdef CONFIG_KSM
1163 	case MADV_MERGEABLE:
1164 	case MADV_UNMERGEABLE:
1165 #endif
1166 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
1167 	case MADV_HUGEPAGE:
1168 	case MADV_NOHUGEPAGE:
1169 	case MADV_COLLAPSE:
1170 #endif
1171 	case MADV_DONTDUMP:
1172 	case MADV_DODUMP:
1173 	case MADV_WIPEONFORK:
1174 	case MADV_KEEPONFORK:
1175 #ifdef CONFIG_MEMORY_FAILURE
1176 	case MADV_SOFT_OFFLINE:
1177 	case MADV_HWPOISON:
1178 #endif
1179 		return true;
1180 
1181 	default:
1182 		return false;
1183 	}
1184 }
1185 
1186 static bool process_madvise_behavior_valid(int behavior)
1187 {
1188 	switch (behavior) {
1189 	case MADV_COLD:
1190 	case MADV_PAGEOUT:
1191 	case MADV_WILLNEED:
1192 	case MADV_COLLAPSE:
1193 		return true;
1194 	default:
1195 		return false;
1196 	}
1197 }
1198 
1199 /*
1200  * Walk the vmas in range [start,end), and call the visit function on each one.
1201  * The visit function will get start and end parameters that cover the overlap
1202  * between the current vma and the original range.  Any unmapped regions in the
1203  * original range will result in this function returning -ENOMEM while still
1204  * calling the visit function on all of the existing vmas in the range.
1205  * Must be called with the mmap_lock held for reading or writing.
1206  */
1207 static
1208 int madvise_walk_vmas(struct mm_struct *mm, unsigned long start,
1209 		      unsigned long end, unsigned long arg,
1210 		      int (*visit)(struct vm_area_struct *vma,
1211 				   struct vm_area_struct **prev, unsigned long start,
1212 				   unsigned long end, unsigned long arg))
1213 {
1214 	struct vm_area_struct *vma;
1215 	struct vm_area_struct *prev;
1216 	unsigned long tmp;
1217 	int unmapped_error = 0;
1218 
1219 	/*
1220 	 * If the interval [start,end) covers some unmapped address
1221 	 * ranges, just ignore them, but return -ENOMEM at the end.
1222 	 * - different from the way of handling in mlock etc.
1223 	 */
1224 	vma = find_vma_prev(mm, start, &prev);
1225 	if (vma && start > vma->vm_start)
1226 		prev = vma;
1227 
1228 	for (;;) {
1229 		int error;
1230 
1231 		/* Still start < end. */
1232 		if (!vma)
1233 			return -ENOMEM;
1234 
1235 		/* Here start < (end|vma->vm_end). */
1236 		if (start < vma->vm_start) {
1237 			unmapped_error = -ENOMEM;
1238 			start = vma->vm_start;
1239 			if (start >= end)
1240 				break;
1241 		}
1242 
1243 		/* Here vma->vm_start <= start < (end|vma->vm_end) */
1244 		tmp = vma->vm_end;
1245 		if (end < tmp)
1246 			tmp = end;
1247 
1248 		/* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
1249 		error = visit(vma, &prev, start, tmp, arg);
1250 		if (error)
1251 			return error;
1252 		start = tmp;
1253 		if (prev && start < prev->vm_end)
1254 			start = prev->vm_end;
1255 		if (start >= end)
1256 			break;
1257 		if (prev)
1258 			vma = find_vma(mm, prev->vm_end);
1259 		else	/* madvise_remove dropped mmap_lock */
1260 			vma = find_vma(mm, start);
1261 	}
1262 
1263 	return unmapped_error;
1264 }
1265 
1266 #ifdef CONFIG_ANON_VMA_NAME
1267 static int madvise_vma_anon_name(struct vm_area_struct *vma,
1268 				 struct vm_area_struct **prev,
1269 				 unsigned long start, unsigned long end,
1270 				 unsigned long anon_name)
1271 {
1272 	int error;
1273 
1274 	/* Only anonymous mappings can be named */
1275 	if (vma->vm_file && !vma_is_anon_shmem(vma))
1276 		return -EBADF;
1277 
1278 	error = madvise_update_vma(vma, prev, start, end, vma->vm_flags,
1279 				   (struct anon_vma_name *)anon_name);
1280 
1281 	/*
1282 	 * madvise() returns EAGAIN if kernel resources, such as
1283 	 * slab, are temporarily unavailable.
1284 	 */
1285 	if (error == -ENOMEM)
1286 		error = -EAGAIN;
1287 	return error;
1288 }
1289 
1290 int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
1291 			  unsigned long len_in, struct anon_vma_name *anon_name)
1292 {
1293 	unsigned long end;
1294 	unsigned long len;
1295 
1296 	if (start & ~PAGE_MASK)
1297 		return -EINVAL;
1298 	len = (len_in + ~PAGE_MASK) & PAGE_MASK;
1299 
1300 	/* Check to see whether len was rounded up from small -ve to zero */
1301 	if (len_in && !len)
1302 		return -EINVAL;
1303 
1304 	end = start + len;
1305 	if (end < start)
1306 		return -EINVAL;
1307 
1308 	if (end == start)
1309 		return 0;
1310 
1311 	return madvise_walk_vmas(mm, start, end, (unsigned long)anon_name,
1312 				 madvise_vma_anon_name);
1313 }
1314 #endif /* CONFIG_ANON_VMA_NAME */
1315 /*
1316  * The madvise(2) system call.
1317  *
1318  * Applications can use madvise() to advise the kernel how it should
1319  * handle paging I/O in this VM area.  The idea is to help the kernel
1320  * use appropriate read-ahead and caching techniques.  The information
1321  * provided is advisory only, and can be safely disregarded by the
1322  * kernel without affecting the correct operation of the application.
1323  *
1324  * behavior values:
1325  *  MADV_NORMAL - the default behavior is to read clusters.  This
1326  *		results in some read-ahead and read-behind.
1327  *  MADV_RANDOM - the system should read the minimum amount of data
1328  *		on any access, since it is unlikely that the appli-
1329  *		cation will need more than what it asks for.
1330  *  MADV_SEQUENTIAL - pages in the given range will probably be accessed
1331  *		once, so they can be aggressively read ahead, and
1332  *		can be freed soon after they are accessed.
1333  *  MADV_WILLNEED - the application is notifying the system to read
1334  *		some pages ahead.
1335  *  MADV_DONTNEED - the application is finished with the given range,
1336  *		so the kernel can free resources associated with it.
1337  *  MADV_FREE - the application marks pages in the given range as lazy free,
1338  *		where actual purges are postponed until memory pressure happens.
1339  *  MADV_REMOVE - the application wants to free up the given range of
1340  *		pages and associated backing store.
1341  *  MADV_DONTFORK - omit this area from child's address space when forking:
1342  *		typically, to avoid COWing pages pinned by get_user_pages().
1343  *  MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
1344  *  MADV_WIPEONFORK - present the child process with zero-filled memory in this
1345  *              range after a fork.
1346  *  MADV_KEEPONFORK - undo the effect of MADV_WIPEONFORK
1347  *  MADV_HWPOISON - trigger memory error handler as if the given memory range
1348  *		were corrupted by unrecoverable hardware memory failure.
1349  *  MADV_SOFT_OFFLINE - try to soft-offline the given range of memory.
1350  *  MADV_MERGEABLE - the application recommends that KSM try to merge pages in
1351  *		this area with pages of identical content from other such areas.
1352  *  MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
1353  *  MADV_HUGEPAGE - the application wants to back the given range by transparent
1354  *		huge pages in the future. Existing pages might be coalesced and
1355  *		new pages might be allocated as THP.
1356  *  MADV_NOHUGEPAGE - mark the given range as not worth being backed by
1357  *		transparent huge pages so the existing pages will not be
1358  *		coalesced into THP and new pages will not be allocated as THP.
1359  *  MADV_COLLAPSE - synchronously coalesce pages into new THP.
1360  *  MADV_DONTDUMP - the application wants to prevent pages in the given range
1361  *		from being included in its core dump.
1362  *  MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
1363  *  MADV_COLD - the application is not expected to use this memory soon,
1364  *		deactivate pages in this range so that they can be reclaimed
1365  *		easily if memory pressure happens.
1366  *  MADV_PAGEOUT - the application is not expected to use this memory soon,
1367  *		page out the pages in this range immediately.
1368  *  MADV_POPULATE_READ - populate (prefault) page tables readable by
1369  *		triggering read faults if required
1370  *  MADV_POPULATE_WRITE - populate (prefault) page tables writable by
1371  *		triggering write faults if required
1372  *
1373  * return values:
1374  *  zero    - success
1375  *  -EINVAL - start + len < 0, start is not page-aligned,
1376  *		"behavior" is not a valid value, or application
1377  *		is attempting to release locked or shared pages,
1378  *		or the specified address range includes file, Huge TLB,
1379  *		MAP_SHARED or VMPFNMAP range.
1380  *  -ENOMEM - addresses in the specified range are not currently
1381  *		mapped, or are outside the AS of the process.
1382  *  -EIO    - an I/O error occurred while paging in data.
1383  *  -EBADF  - map exists, but area maps something that isn't a file.
1384  *  -EAGAIN - a kernel resource was temporarily unavailable.
1385  */
1386 int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int behavior)
1387 {
1388 	unsigned long end;
1389 	int error;
1390 	int write;
1391 	size_t len;
1392 	struct blk_plug plug;
1393 
1394 	if (!madvise_behavior_valid(behavior))
1395 		return -EINVAL;
1396 
1397 	if (!PAGE_ALIGNED(start))
1398 		return -EINVAL;
1399 	len = PAGE_ALIGN(len_in);
1400 
1401 	/* Check to see whether len was rounded up from small -ve to zero */
1402 	if (len_in && !len)
1403 		return -EINVAL;
1404 
1405 	end = start + len;
1406 	if (end < start)
1407 		return -EINVAL;
1408 
1409 	if (end == start)
1410 		return 0;
1411 
1412 #ifdef CONFIG_MEMORY_FAILURE
1413 	if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
1414 		return madvise_inject_error(behavior, start, start + len_in);
1415 #endif
1416 
1417 	write = madvise_need_mmap_write(behavior);
1418 	if (write) {
1419 		if (mmap_write_lock_killable(mm))
1420 			return -EINTR;
1421 	} else {
1422 		mmap_read_lock(mm);
1423 	}
1424 
1425 	start = untagged_addr_remote(mm, start);
1426 	end = start + len;
1427 
1428 	blk_start_plug(&plug);
1429 	error = madvise_walk_vmas(mm, start, end, behavior,
1430 			madvise_vma_behavior);
1431 	blk_finish_plug(&plug);
1432 	if (write)
1433 		mmap_write_unlock(mm);
1434 	else
1435 		mmap_read_unlock(mm);
1436 
1437 	return error;
1438 }
1439 
1440 SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
1441 {
1442 	return do_madvise(current->mm, start, len_in, behavior);
1443 }
1444 
1445 SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
1446 		size_t, vlen, int, behavior, unsigned int, flags)
1447 {
1448 	ssize_t ret;
1449 	struct iovec iovstack[UIO_FASTIOV];
1450 	struct iovec *iov = iovstack;
1451 	struct iov_iter iter;
1452 	struct task_struct *task;
1453 	struct mm_struct *mm;
1454 	size_t total_len;
1455 	unsigned int f_flags;
1456 
1457 	if (flags != 0) {
1458 		ret = -EINVAL;
1459 		goto out;
1460 	}
1461 
1462 	ret = import_iovec(ITER_DEST, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);
1463 	if (ret < 0)
1464 		goto out;
1465 
1466 	task = pidfd_get_task(pidfd, &f_flags);
1467 	if (IS_ERR(task)) {
1468 		ret = PTR_ERR(task);
1469 		goto free_iov;
1470 	}
1471 
1472 	if (!process_madvise_behavior_valid(behavior)) {
1473 		ret = -EINVAL;
1474 		goto release_task;
1475 	}
1476 
1477 	/* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */
1478 	mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
1479 	if (IS_ERR_OR_NULL(mm)) {
1480 		ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
1481 		goto release_task;
1482 	}
1483 
1484 	/*
1485 	 * Require CAP_SYS_NICE for influencing process performance. Note that
1486 	 * only non-destructive hints are currently supported.
1487 	 */
1488 	if (!capable(CAP_SYS_NICE)) {
1489 		ret = -EPERM;
1490 		goto release_mm;
1491 	}
1492 
1493 	total_len = iov_iter_count(&iter);
1494 
1495 	while (iov_iter_count(&iter)) {
1496 		ret = do_madvise(mm, (unsigned long)iter_iov_addr(&iter),
1497 					iter_iov_len(&iter), behavior);
1498 		if (ret < 0)
1499 			break;
1500 		iov_iter_advance(&iter, iter_iov_len(&iter));
1501 	}
1502 
1503 	ret = (total_len - iov_iter_count(&iter)) ? : ret;
1504 
1505 release_mm:
1506 	mmput(mm);
1507 release_task:
1508 	put_task_struct(task);
1509 free_iov:
1510 	kfree(iov);
1511 out:
1512 	return ret;
1513 }
1514