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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/hugetlb.h> | |
14 | #include <linux/falloc.h> | |
15 | #include <linux/sched.h> | |
16 | #include <linux/ksm.h> | |
17 | #include <linux/fs.h> | |
18 | #include <linux/file.h> | |
19 | #include <linux/blkdev.h> | |
20 | #include <linux/backing-dev.h> | |
21 | #include <linux/swap.h> | |
22 | #include <linux/swapops.h> | |
23 | ||
24 | /* | |
25 | * Any behaviour which results in changes to the vma->vm_flags needs to | |
26 | * take mmap_sem for writing. Others, which simply traverse vmas, need | |
27 | * to only take it for reading. | |
28 | */ | |
29 | static int madvise_need_mmap_write(int behavior) | |
30 | { | |
31 | switch (behavior) { | |
32 | case MADV_REMOVE: | |
33 | case MADV_WILLNEED: | |
34 | case MADV_DONTNEED: | |
35 | return 0; | |
36 | default: | |
37 | /* be safe, default to 1. list exceptions explicitly */ | |
38 | return 1; | |
39 | } | |
40 | } | |
41 | ||
42 | /* | |
43 | * We can potentially split a vm area into separate | |
44 | * areas, each area with its own behavior. | |
45 | */ | |
46 | static long madvise_behavior(struct vm_area_struct *vma, | |
47 | struct vm_area_struct **prev, | |
48 | unsigned long start, unsigned long end, int behavior) | |
49 | { | |
50 | struct mm_struct *mm = vma->vm_mm; | |
51 | int error = 0; | |
52 | pgoff_t pgoff; | |
53 | unsigned long new_flags = vma->vm_flags; | |
54 | ||
55 | switch (behavior) { | |
56 | case MADV_NORMAL: | |
57 | new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ; | |
58 | break; | |
59 | case MADV_SEQUENTIAL: | |
60 | new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ; | |
61 | break; | |
62 | case MADV_RANDOM: | |
63 | new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ; | |
64 | break; | |
65 | case MADV_DONTFORK: | |
66 | new_flags |= VM_DONTCOPY; | |
67 | break; | |
68 | case MADV_DOFORK: | |
69 | if (vma->vm_flags & VM_IO) { | |
70 | error = -EINVAL; | |
71 | goto out; | |
72 | } | |
73 | new_flags &= ~VM_DONTCOPY; | |
74 | break; | |
75 | case MADV_DONTDUMP: | |
76 | new_flags |= VM_DONTDUMP; | |
77 | break; | |
78 | case MADV_DODUMP: | |
79 | if (new_flags & VM_SPECIAL) { | |
80 | error = -EINVAL; | |
81 | goto out; | |
82 | } | |
83 | new_flags &= ~VM_DONTDUMP; | |
84 | break; | |
85 | case MADV_MERGEABLE: | |
86 | case MADV_UNMERGEABLE: | |
87 | error = ksm_madvise(vma, start, end, behavior, &new_flags); | |
88 | if (error) | |
89 | goto out; | |
90 | break; | |
91 | case MADV_HUGEPAGE: | |
92 | case MADV_NOHUGEPAGE: | |
93 | error = hugepage_madvise(vma, &new_flags, behavior); | |
94 | if (error) | |
95 | goto out; | |
96 | break; | |
97 | } | |
98 | ||
99 | if (new_flags == vma->vm_flags) { | |
100 | *prev = vma; | |
101 | goto out; | |
102 | } | |
103 | ||
104 | pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); | |
105 | *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma, | |
106 | vma->vm_file, pgoff, vma_policy(vma), | |
107 | vma->vm_userfaultfd_ctx); | |
108 | if (*prev) { | |
109 | vma = *prev; | |
110 | goto success; | |
111 | } | |
112 | ||
113 | *prev = vma; | |
114 | ||
115 | if (start != vma->vm_start) { | |
116 | error = split_vma(mm, vma, start, 1); | |
117 | if (error) | |
118 | goto out; | |
119 | } | |
120 | ||
121 | if (end != vma->vm_end) { | |
122 | error = split_vma(mm, vma, end, 0); | |
123 | if (error) | |
124 | goto out; | |
125 | } | |
126 | ||
127 | success: | |
128 | /* | |
129 | * vm_flags is protected by the mmap_sem held in write mode. | |
130 | */ | |
131 | vma->vm_flags = new_flags; | |
132 | ||
133 | out: | |
134 | if (error == -ENOMEM) | |
135 | error = -EAGAIN; | |
136 | return error; | |
137 | } | |
138 | ||
139 | #ifdef CONFIG_SWAP | |
140 | static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start, | |
141 | unsigned long end, struct mm_walk *walk) | |
142 | { | |
143 | pte_t *orig_pte; | |
144 | struct vm_area_struct *vma = walk->private; | |
145 | unsigned long index; | |
146 | ||
147 | if (pmd_none_or_trans_huge_or_clear_bad(pmd)) | |
148 | return 0; | |
149 | ||
150 | for (index = start; index != end; index += PAGE_SIZE) { | |
151 | pte_t pte; | |
152 | swp_entry_t entry; | |
153 | struct page *page; | |
154 | spinlock_t *ptl; | |
155 | ||
156 | orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl); | |
157 | pte = *(orig_pte + ((index - start) / PAGE_SIZE)); | |
158 | pte_unmap_unlock(orig_pte, ptl); | |
159 | ||
160 | if (pte_present(pte) || pte_none(pte)) | |
161 | continue; | |
162 | entry = pte_to_swp_entry(pte); | |
163 | if (unlikely(non_swap_entry(entry))) | |
164 | continue; | |
165 | ||
166 | page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE, | |
167 | vma, index); | |
168 | if (page) | |
169 | page_cache_release(page); | |
170 | } | |
171 | ||
172 | return 0; | |
173 | } | |
174 | ||
175 | static void force_swapin_readahead(struct vm_area_struct *vma, | |
176 | unsigned long start, unsigned long end) | |
177 | { | |
178 | struct mm_walk walk = { | |
179 | .mm = vma->vm_mm, | |
180 | .pmd_entry = swapin_walk_pmd_entry, | |
181 | .private = vma, | |
182 | }; | |
183 | ||
184 | walk_page_range(start, end, &walk); | |
185 | ||
186 | lru_add_drain(); /* Push any new pages onto the LRU now */ | |
187 | } | |
188 | ||
189 | static void force_shm_swapin_readahead(struct vm_area_struct *vma, | |
190 | unsigned long start, unsigned long end, | |
191 | struct address_space *mapping) | |
192 | { | |
193 | pgoff_t index; | |
194 | struct page *page; | |
195 | swp_entry_t swap; | |
196 | ||
197 | for (; start < end; start += PAGE_SIZE) { | |
198 | index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; | |
199 | ||
200 | page = find_get_entry(mapping, index); | |
201 | if (!radix_tree_exceptional_entry(page)) { | |
202 | if (page) | |
203 | page_cache_release(page); | |
204 | continue; | |
205 | } | |
206 | swap = radix_to_swp_entry(page); | |
207 | page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE, | |
208 | NULL, 0); | |
209 | if (page) | |
210 | page_cache_release(page); | |
211 | } | |
212 | ||
213 | lru_add_drain(); /* Push any new pages onto the LRU now */ | |
214 | } | |
215 | #endif /* CONFIG_SWAP */ | |
216 | ||
217 | /* | |
218 | * Schedule all required I/O operations. Do not wait for completion. | |
219 | */ | |
220 | static long madvise_willneed(struct vm_area_struct *vma, | |
221 | struct vm_area_struct **prev, | |
222 | unsigned long start, unsigned long end) | |
223 | { | |
224 | struct file *file = vma->vm_file; | |
225 | ||
226 | #ifdef CONFIG_SWAP | |
227 | if (!file) { | |
228 | *prev = vma; | |
229 | force_swapin_readahead(vma, start, end); | |
230 | return 0; | |
231 | } | |
232 | ||
233 | if (shmem_mapping(file->f_mapping)) { | |
234 | *prev = vma; | |
235 | force_shm_swapin_readahead(vma, start, end, | |
236 | file->f_mapping); | |
237 | return 0; | |
238 | } | |
239 | #else | |
240 | if (!file) | |
241 | return -EBADF; | |
242 | #endif | |
243 | ||
244 | if (IS_DAX(file_inode(file))) { | |
245 | /* no bad return value, but ignore advice */ | |
246 | return 0; | |
247 | } | |
248 | ||
249 | *prev = vma; | |
250 | start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; | |
251 | if (end > vma->vm_end) | |
252 | end = vma->vm_end; | |
253 | end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; | |
254 | ||
255 | force_page_cache_readahead(file->f_mapping, file, start, end - start); | |
256 | return 0; | |
257 | } | |
258 | ||
259 | /* | |
260 | * Application no longer needs these pages. If the pages are dirty, | |
261 | * it's OK to just throw them away. The app will be more careful about | |
262 | * data it wants to keep. Be sure to free swap resources too. The | |
263 | * zap_page_range call sets things up for shrink_active_list to actually free | |
264 | * these pages later if no one else has touched them in the meantime, | |
265 | * although we could add these pages to a global reuse list for | |
266 | * shrink_active_list to pick up before reclaiming other pages. | |
267 | * | |
268 | * NB: This interface discards data rather than pushes it out to swap, | |
269 | * as some implementations do. This has performance implications for | |
270 | * applications like large transactional databases which want to discard | |
271 | * pages in anonymous maps after committing to backing store the data | |
272 | * that was kept in them. There is no reason to write this data out to | |
273 | * the swap area if the application is discarding it. | |
274 | * | |
275 | * An interface that causes the system to free clean pages and flush | |
276 | * dirty pages is already available as msync(MS_INVALIDATE). | |
277 | */ | |
278 | static long madvise_dontneed(struct vm_area_struct *vma, | |
279 | struct vm_area_struct **prev, | |
280 | unsigned long start, unsigned long end) | |
281 | { | |
282 | *prev = vma; | |
283 | if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP)) | |
284 | return -EINVAL; | |
285 | ||
286 | zap_page_range(vma, start, end - start, NULL); | |
287 | return 0; | |
288 | } | |
289 | ||
290 | /* | |
291 | * Application wants to free up the pages and associated backing store. | |
292 | * This is effectively punching a hole into the middle of a file. | |
293 | */ | |
294 | static long madvise_remove(struct vm_area_struct *vma, | |
295 | struct vm_area_struct **prev, | |
296 | unsigned long start, unsigned long end) | |
297 | { | |
298 | loff_t offset; | |
299 | int error; | |
300 | struct file *f; | |
301 | ||
302 | *prev = NULL; /* tell sys_madvise we drop mmap_sem */ | |
303 | ||
304 | if (vma->vm_flags & VM_LOCKED) | |
305 | return -EINVAL; | |
306 | ||
307 | f = vma->vm_file; | |
308 | ||
309 | if (!f || !f->f_mapping || !f->f_mapping->host) { | |
310 | return -EINVAL; | |
311 | } | |
312 | ||
313 | if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE)) | |
314 | return -EACCES; | |
315 | ||
316 | offset = (loff_t)(start - vma->vm_start) | |
317 | + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); | |
318 | ||
319 | /* | |
320 | * Filesystem's fallocate may need to take i_mutex. We need to | |
321 | * explicitly grab a reference because the vma (and hence the | |
322 | * vma's reference to the file) can go away as soon as we drop | |
323 | * mmap_sem. | |
324 | */ | |
325 | get_file(f); | |
326 | up_read(¤t->mm->mmap_sem); | |
327 | error = vfs_fallocate(f, | |
328 | FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, | |
329 | offset, end - start); | |
330 | fput(f); | |
331 | down_read(¤t->mm->mmap_sem); | |
332 | return error; | |
333 | } | |
334 | ||
335 | #ifdef CONFIG_MEMORY_FAILURE | |
336 | /* | |
337 | * Error injection support for memory error handling. | |
338 | */ | |
339 | static int madvise_hwpoison(int bhv, unsigned long start, unsigned long end) | |
340 | { | |
341 | struct page *p; | |
342 | if (!capable(CAP_SYS_ADMIN)) | |
343 | return -EPERM; | |
344 | for (; start < end; start += PAGE_SIZE << | |
345 | compound_order(compound_head(p))) { | |
346 | int ret; | |
347 | ||
348 | ret = get_user_pages_fast(start, 1, 0, &p); | |
349 | if (ret != 1) | |
350 | return ret; | |
351 | ||
352 | if (PageHWPoison(p)) { | |
353 | put_page(p); | |
354 | continue; | |
355 | } | |
356 | if (bhv == MADV_SOFT_OFFLINE) { | |
357 | pr_info("Soft offlining page %#lx at %#lx\n", | |
358 | page_to_pfn(p), start); | |
359 | ret = soft_offline_page(p, MF_COUNT_INCREASED); | |
360 | if (ret) | |
361 | return ret; | |
362 | continue; | |
363 | } | |
364 | pr_info("Injecting memory failure for page %#lx at %#lx\n", | |
365 | page_to_pfn(p), start); | |
366 | /* Ignore return value for now */ | |
367 | memory_failure(page_to_pfn(p), 0, MF_COUNT_INCREASED); | |
368 | } | |
369 | return 0; | |
370 | } | |
371 | #endif | |
372 | ||
373 | static long | |
374 | madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev, | |
375 | unsigned long start, unsigned long end, int behavior) | |
376 | { | |
377 | switch (behavior) { | |
378 | case MADV_REMOVE: | |
379 | return madvise_remove(vma, prev, start, end); | |
380 | case MADV_WILLNEED: | |
381 | return madvise_willneed(vma, prev, start, end); | |
382 | case MADV_DONTNEED: | |
383 | return madvise_dontneed(vma, prev, start, end); | |
384 | default: | |
385 | return madvise_behavior(vma, prev, start, end, behavior); | |
386 | } | |
387 | } | |
388 | ||
389 | static bool | |
390 | madvise_behavior_valid(int behavior) | |
391 | { | |
392 | switch (behavior) { | |
393 | case MADV_DOFORK: | |
394 | case MADV_DONTFORK: | |
395 | case MADV_NORMAL: | |
396 | case MADV_SEQUENTIAL: | |
397 | case MADV_RANDOM: | |
398 | case MADV_REMOVE: | |
399 | case MADV_WILLNEED: | |
400 | case MADV_DONTNEED: | |
401 | #ifdef CONFIG_KSM | |
402 | case MADV_MERGEABLE: | |
403 | case MADV_UNMERGEABLE: | |
404 | #endif | |
405 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE | |
406 | case MADV_HUGEPAGE: | |
407 | case MADV_NOHUGEPAGE: | |
408 | #endif | |
409 | case MADV_DONTDUMP: | |
410 | case MADV_DODUMP: | |
411 | return true; | |
412 | ||
413 | default: | |
414 | return false; | |
415 | } | |
416 | } | |
417 | ||
418 | /* | |
419 | * The madvise(2) system call. | |
420 | * | |
421 | * Applications can use madvise() to advise the kernel how it should | |
422 | * handle paging I/O in this VM area. The idea is to help the kernel | |
423 | * use appropriate read-ahead and caching techniques. The information | |
424 | * provided is advisory only, and can be safely disregarded by the | |
425 | * kernel without affecting the correct operation of the application. | |
426 | * | |
427 | * behavior values: | |
428 | * MADV_NORMAL - the default behavior is to read clusters. This | |
429 | * results in some read-ahead and read-behind. | |
430 | * MADV_RANDOM - the system should read the minimum amount of data | |
431 | * on any access, since it is unlikely that the appli- | |
432 | * cation will need more than what it asks for. | |
433 | * MADV_SEQUENTIAL - pages in the given range will probably be accessed | |
434 | * once, so they can be aggressively read ahead, and | |
435 | * can be freed soon after they are accessed. | |
436 | * MADV_WILLNEED - the application is notifying the system to read | |
437 | * some pages ahead. | |
438 | * MADV_DONTNEED - the application is finished with the given range, | |
439 | * so the kernel can free resources associated with it. | |
440 | * MADV_REMOVE - the application wants to free up the given range of | |
441 | * pages and associated backing store. | |
442 | * MADV_DONTFORK - omit this area from child's address space when forking: | |
443 | * typically, to avoid COWing pages pinned by get_user_pages(). | |
444 | * MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking. | |
445 | * MADV_MERGEABLE - the application recommends that KSM try to merge pages in | |
446 | * this area with pages of identical content from other such areas. | |
447 | * MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others. | |
448 | * | |
449 | * return values: | |
450 | * zero - success | |
451 | * -EINVAL - start + len < 0, start is not page-aligned, | |
452 | * "behavior" is not a valid value, or application | |
453 | * is attempting to release locked or shared pages. | |
454 | * -ENOMEM - addresses in the specified range are not currently | |
455 | * mapped, or are outside the AS of the process. | |
456 | * -EIO - an I/O error occurred while paging in data. | |
457 | * -EBADF - map exists, but area maps something that isn't a file. | |
458 | * -EAGAIN - a kernel resource was temporarily unavailable. | |
459 | */ | |
460 | SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior) | |
461 | { | |
462 | unsigned long end, tmp; | |
463 | struct vm_area_struct *vma, *prev; | |
464 | int unmapped_error = 0; | |
465 | int error = -EINVAL; | |
466 | int write; | |
467 | size_t len; | |
468 | struct blk_plug plug; | |
469 | ||
470 | #ifdef CONFIG_MEMORY_FAILURE | |
471 | if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE) | |
472 | return madvise_hwpoison(behavior, start, start+len_in); | |
473 | #endif | |
474 | if (!madvise_behavior_valid(behavior)) | |
475 | return error; | |
476 | ||
477 | if (start & ~PAGE_MASK) | |
478 | return error; | |
479 | len = (len_in + ~PAGE_MASK) & PAGE_MASK; | |
480 | ||
481 | /* Check to see whether len was rounded up from small -ve to zero */ | |
482 | if (len_in && !len) | |
483 | return error; | |
484 | ||
485 | end = start + len; | |
486 | if (end < start) | |
487 | return error; | |
488 | ||
489 | error = 0; | |
490 | if (end == start) | |
491 | return error; | |
492 | ||
493 | write = madvise_need_mmap_write(behavior); | |
494 | if (write) | |
495 | down_write(¤t->mm->mmap_sem); | |
496 | else | |
497 | down_read(¤t->mm->mmap_sem); | |
498 | ||
499 | /* | |
500 | * If the interval [start,end) covers some unmapped address | |
501 | * ranges, just ignore them, but return -ENOMEM at the end. | |
502 | * - different from the way of handling in mlock etc. | |
503 | */ | |
504 | vma = find_vma_prev(current->mm, start, &prev); | |
505 | if (vma && start > vma->vm_start) | |
506 | prev = vma; | |
507 | ||
508 | blk_start_plug(&plug); | |
509 | for (;;) { | |
510 | /* Still start < end. */ | |
511 | error = -ENOMEM; | |
512 | if (!vma) | |
513 | goto out; | |
514 | ||
515 | /* Here start < (end|vma->vm_end). */ | |
516 | if (start < vma->vm_start) { | |
517 | unmapped_error = -ENOMEM; | |
518 | start = vma->vm_start; | |
519 | if (start >= end) | |
520 | goto out; | |
521 | } | |
522 | ||
523 | /* Here vma->vm_start <= start < (end|vma->vm_end) */ | |
524 | tmp = vma->vm_end; | |
525 | if (end < tmp) | |
526 | tmp = end; | |
527 | ||
528 | /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */ | |
529 | error = madvise_vma(vma, &prev, start, tmp, behavior); | |
530 | if (error) | |
531 | goto out; | |
532 | start = tmp; | |
533 | if (prev && start < prev->vm_end) | |
534 | start = prev->vm_end; | |
535 | error = unmapped_error; | |
536 | if (start >= end) | |
537 | goto out; | |
538 | if (prev) | |
539 | vma = prev->vm_next; | |
540 | else /* madvise_remove dropped mmap_sem */ | |
541 | vma = find_vma(current->mm, start); | |
542 | } | |
543 | out: | |
544 | blk_finish_plug(&plug); | |
545 | if (write) | |
546 | up_write(¤t->mm->mmap_sem); | |
547 | else | |
548 | up_read(¤t->mm->mmap_sem); | |
549 | ||
550 | return error; | |
551 | } |