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/swap.h>
21 #include <linux/swapops.h>
22
23 /*
24 * Any behaviour which results in changes to the vma->vm_flags needs to
25 * take mmap_sem for writing. Others, which simply traverse vmas, need
26 * to only take it for reading.
27 */
madvise_need_mmap_write(int behavior)28 static int madvise_need_mmap_write(int behavior)
29 {
30 switch (behavior) {
31 case MADV_REMOVE:
32 case MADV_WILLNEED:
33 case MADV_DONTNEED:
34 return 0;
35 default:
36 /* be safe, default to 1. list exceptions explicitly */
37 return 1;
38 }
39 }
40
41 /*
42 * We can potentially split a vm area into separate
43 * areas, each area with its own behavior.
44 */
madvise_behavior(struct vm_area_struct * vma,struct vm_area_struct ** prev,unsigned long start,unsigned long end,int behavior)45 static long madvise_behavior(struct vm_area_struct *vma,
46 struct vm_area_struct **prev,
47 unsigned long start, unsigned long end, int behavior)
48 {
49 struct mm_struct *mm = vma->vm_mm;
50 int error = 0;
51 pgoff_t pgoff;
52 unsigned long new_flags = vma->vm_flags;
53
54 switch (behavior) {
55 case MADV_NORMAL:
56 new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
57 break;
58 case MADV_SEQUENTIAL:
59 new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
60 break;
61 case MADV_RANDOM:
62 new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
63 break;
64 case MADV_DONTFORK:
65 new_flags |= VM_DONTCOPY;
66 break;
67 case MADV_DOFORK:
68 if (vma->vm_flags & VM_IO) {
69 error = -EINVAL;
70 goto out;
71 }
72 new_flags &= ~VM_DONTCOPY;
73 break;
74 case MADV_DONTDUMP:
75 new_flags |= VM_DONTDUMP;
76 break;
77 case MADV_DODUMP:
78 if (new_flags & VM_SPECIAL) {
79 error = -EINVAL;
80 goto out;
81 }
82 new_flags &= ~VM_DONTDUMP;
83 break;
84 case MADV_MERGEABLE:
85 case MADV_UNMERGEABLE:
86 error = ksm_madvise(vma, start, end, behavior, &new_flags);
87 if (error)
88 goto out;
89 break;
90 case MADV_HUGEPAGE:
91 case MADV_NOHUGEPAGE:
92 error = hugepage_madvise(vma, &new_flags, behavior);
93 if (error)
94 goto out;
95 break;
96 }
97
98 if (new_flags == vma->vm_flags) {
99 *prev = vma;
100 goto out;
101 }
102
103 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
104 *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
105 vma->vm_file, pgoff, vma_policy(vma),
106 vma_get_anon_name(vma));
107 if (*prev) {
108 vma = *prev;
109 goto success;
110 }
111
112 *prev = vma;
113
114 if (start != vma->vm_start) {
115 error = split_vma(mm, vma, start, 1);
116 if (error)
117 goto out;
118 }
119
120 if (end != vma->vm_end) {
121 error = split_vma(mm, vma, end, 0);
122 if (error)
123 goto out;
124 }
125
126 success:
127 /*
128 * vm_flags is protected by the mmap_sem held in write mode.
129 */
130 vma->vm_flags = new_flags;
131
132 out:
133 if (error == -ENOMEM)
134 error = -EAGAIN;
135 return error;
136 }
137
138 #ifdef CONFIG_SWAP
swapin_walk_pmd_entry(pmd_t * pmd,unsigned long start,unsigned long end,struct mm_walk * walk)139 static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
140 unsigned long end, struct mm_walk *walk)
141 {
142 pte_t *orig_pte;
143 struct vm_area_struct *vma = walk->private;
144 unsigned long index;
145
146 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
147 return 0;
148
149 for (index = start; index != end; index += PAGE_SIZE) {
150 pte_t pte;
151 swp_entry_t entry;
152 struct page *page;
153 spinlock_t *ptl;
154
155 orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
156 pte = *(orig_pte + ((index - start) / PAGE_SIZE));
157 pte_unmap_unlock(orig_pte, ptl);
158
159 if (pte_present(pte) || pte_none(pte) || pte_file(pte))
160 continue;
161 entry = pte_to_swp_entry(pte);
162 if (unlikely(non_swap_entry(entry)))
163 continue;
164
165 page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
166 vma, index);
167 if (page)
168 page_cache_release(page);
169 }
170
171 return 0;
172 }
173
force_swapin_readahead(struct vm_area_struct * vma,unsigned long start,unsigned long end)174 static void force_swapin_readahead(struct vm_area_struct *vma,
175 unsigned long start, unsigned long end)
176 {
177 struct mm_walk walk = {
178 .mm = vma->vm_mm,
179 .pmd_entry = swapin_walk_pmd_entry,
180 .private = vma,
181 };
182
183 walk_page_range(start, end, &walk);
184
185 lru_add_drain(); /* Push any new pages onto the LRU now */
186 }
187
force_shm_swapin_readahead(struct vm_area_struct * vma,unsigned long start,unsigned long end,struct address_space * mapping)188 static void force_shm_swapin_readahead(struct vm_area_struct *vma,
189 unsigned long start, unsigned long end,
190 struct address_space *mapping)
191 {
192 pgoff_t index;
193 struct page *page;
194 swp_entry_t swap;
195
196 for (; start < end; start += PAGE_SIZE) {
197 index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
198
199 page = find_get_entry(mapping, index);
200 if (!radix_tree_exceptional_entry(page)) {
201 if (page)
202 page_cache_release(page);
203 continue;
204 }
205 swap = radix_to_swp_entry(page);
206 page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
207 NULL, 0);
208 if (page)
209 page_cache_release(page);
210 }
211
212 lru_add_drain(); /* Push any new pages onto the LRU now */
213 }
214 #endif /* CONFIG_SWAP */
215
216 /*
217 * Schedule all required I/O operations. Do not wait for completion.
218 */
madvise_willneed(struct vm_area_struct * vma,struct vm_area_struct ** prev,unsigned long start,unsigned long end)219 static long madvise_willneed(struct vm_area_struct *vma,
220 struct vm_area_struct **prev,
221 unsigned long start, unsigned long end)
222 {
223 struct file *file = vma->vm_file;
224
225 *prev = vma;
226 #ifdef CONFIG_SWAP
227 if (!file || mapping_cap_swap_backed(file->f_mapping)) {
228 if (!file)
229 force_swapin_readahead(vma, start, end);
230 else
231 force_shm_swapin_readahead(vma, start, end,
232 file->f_mapping);
233 return 0;
234 }
235 #endif
236
237 if (!file)
238 return -EBADF;
239
240 if (file->f_mapping->a_ops->get_xip_mem) {
241 /* no bad return value, but ignore advice */
242 return 0;
243 }
244
245 start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
246 if (end > vma->vm_end)
247 end = vma->vm_end;
248 end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
249
250 force_page_cache_readahead(file->f_mapping, file, start, end - start);
251 return 0;
252 }
253
254 /*
255 * Application no longer needs these pages. If the pages are dirty,
256 * it's OK to just throw them away. The app will be more careful about
257 * data it wants to keep. Be sure to free swap resources too. The
258 * zap_page_range call sets things up for shrink_active_list to actually free
259 * these pages later if no one else has touched them in the meantime,
260 * although we could add these pages to a global reuse list for
261 * shrink_active_list to pick up before reclaiming other pages.
262 *
263 * NB: This interface discards data rather than pushes it out to swap,
264 * as some implementations do. This has performance implications for
265 * applications like large transactional databases which want to discard
266 * pages in anonymous maps after committing to backing store the data
267 * that was kept in them. There is no reason to write this data out to
268 * the swap area if the application is discarding it.
269 *
270 * An interface that causes the system to free clean pages and flush
271 * dirty pages is already available as msync(MS_INVALIDATE).
272 */
madvise_dontneed(struct vm_area_struct * vma,struct vm_area_struct ** prev,unsigned long start,unsigned long end)273 static long madvise_dontneed(struct vm_area_struct *vma,
274 struct vm_area_struct **prev,
275 unsigned long start, unsigned long end)
276 {
277 *prev = vma;
278 if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
279 return -EINVAL;
280
281 if (unlikely(vma->vm_flags & VM_NONLINEAR)) {
282 struct zap_details details = {
283 .nonlinear_vma = vma,
284 .last_index = ULONG_MAX,
285 };
286 zap_page_range(vma, start, end - start, &details);
287 } else
288 zap_page_range(vma, start, end - start, NULL);
289 return 0;
290 }
291
292 /*
293 * Application wants to free up the pages and associated backing store.
294 * This is effectively punching a hole into the middle of a file.
295 */
madvise_remove(struct vm_area_struct * vma,struct vm_area_struct ** prev,unsigned long start,unsigned long end)296 static long madvise_remove(struct vm_area_struct *vma,
297 struct vm_area_struct **prev,
298 unsigned long start, unsigned long end)
299 {
300 loff_t offset;
301 int error;
302 struct file *f;
303
304 *prev = NULL; /* tell sys_madvise we drop mmap_sem */
305
306 if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB))
307 return -EINVAL;
308
309 f = vma->vm_file;
310
311 if (!f || !f->f_mapping || !f->f_mapping->host) {
312 return -EINVAL;
313 }
314
315 if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
316 return -EACCES;
317
318 offset = (loff_t)(start - vma->vm_start)
319 + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
320
321 /*
322 * Filesystem's fallocate may need to take i_mutex. We need to
323 * explicitly grab a reference because the vma (and hence the
324 * vma's reference to the file) can go away as soon as we drop
325 * mmap_sem.
326 */
327 get_file(f);
328 up_read(¤t->mm->mmap_sem);
329 error = do_fallocate(f,
330 FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
331 offset, end - start);
332 fput(f);
333 down_read(¤t->mm->mmap_sem);
334 return error;
335 }
336
337 #ifdef CONFIG_MEMORY_FAILURE
338 /*
339 * Error injection support for memory error handling.
340 */
madvise_hwpoison(int bhv,unsigned long start,unsigned long end)341 static int madvise_hwpoison(int bhv, unsigned long start, unsigned long end)
342 {
343 struct page *p;
344 if (!capable(CAP_SYS_ADMIN))
345 return -EPERM;
346 for (; start < end; start += PAGE_SIZE <<
347 compound_order(compound_head(p))) {
348 int ret;
349
350 ret = get_user_pages_fast(start, 1, 0, &p);
351 if (ret != 1)
352 return ret;
353
354 if (PageHWPoison(p)) {
355 put_page(p);
356 continue;
357 }
358 if (bhv == MADV_SOFT_OFFLINE) {
359 pr_info("Soft offlining page %#lx at %#lx\n",
360 page_to_pfn(p), start);
361 ret = soft_offline_page(p, MF_COUNT_INCREASED);
362 if (ret)
363 return ret;
364 continue;
365 }
366 pr_info("Injecting memory failure for page %#lx at %#lx\n",
367 page_to_pfn(p), start);
368 /* Ignore return value for now */
369 memory_failure(page_to_pfn(p), 0, MF_COUNT_INCREASED);
370 }
371 return 0;
372 }
373 #endif
374
375 static long
madvise_vma(struct vm_area_struct * vma,struct vm_area_struct ** prev,unsigned long start,unsigned long end,int behavior)376 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
377 unsigned long start, unsigned long end, int behavior)
378 {
379 switch (behavior) {
380 case MADV_REMOVE:
381 return madvise_remove(vma, prev, start, end);
382 case MADV_WILLNEED:
383 return madvise_willneed(vma, prev, start, end);
384 case MADV_DONTNEED:
385 return madvise_dontneed(vma, prev, start, end);
386 default:
387 return madvise_behavior(vma, prev, start, end, behavior);
388 }
389 }
390
391 static int
madvise_behavior_valid(int behavior)392 madvise_behavior_valid(int behavior)
393 {
394 switch (behavior) {
395 case MADV_DOFORK:
396 case MADV_DONTFORK:
397 case MADV_NORMAL:
398 case MADV_SEQUENTIAL:
399 case MADV_RANDOM:
400 case MADV_REMOVE:
401 case MADV_WILLNEED:
402 case MADV_DONTNEED:
403 #ifdef CONFIG_KSM
404 case MADV_MERGEABLE:
405 case MADV_UNMERGEABLE:
406 #endif
407 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
408 case MADV_HUGEPAGE:
409 case MADV_NOHUGEPAGE:
410 #endif
411 case MADV_DONTDUMP:
412 case MADV_DODUMP:
413 return 1;
414
415 default:
416 return 0;
417 }
418 }
419
420 /*
421 * The madvise(2) system call.
422 *
423 * Applications can use madvise() to advise the kernel how it should
424 * handle paging I/O in this VM area. The idea is to help the kernel
425 * use appropriate read-ahead and caching techniques. The information
426 * provided is advisory only, and can be safely disregarded by the
427 * kernel without affecting the correct operation of the application.
428 *
429 * behavior values:
430 * MADV_NORMAL - the default behavior is to read clusters. This
431 * results in some read-ahead and read-behind.
432 * MADV_RANDOM - the system should read the minimum amount of data
433 * on any access, since it is unlikely that the appli-
434 * cation will need more than what it asks for.
435 * MADV_SEQUENTIAL - pages in the given range will probably be accessed
436 * once, so they can be aggressively read ahead, and
437 * can be freed soon after they are accessed.
438 * MADV_WILLNEED - the application is notifying the system to read
439 * some pages ahead.
440 * MADV_DONTNEED - the application is finished with the given range,
441 * so the kernel can free resources associated with it.
442 * MADV_REMOVE - the application wants to free up the given range of
443 * pages and associated backing store.
444 * MADV_DONTFORK - omit this area from child's address space when forking:
445 * typically, to avoid COWing pages pinned by get_user_pages().
446 * MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
447 * MADV_MERGEABLE - the application recommends that KSM try to merge pages in
448 * this area with pages of identical content from other such areas.
449 * MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
450 *
451 * return values:
452 * zero - success
453 * -EINVAL - start + len < 0, start is not page-aligned,
454 * "behavior" is not a valid value, or application
455 * is attempting to release locked or shared pages.
456 * -ENOMEM - addresses in the specified range are not currently
457 * mapped, or are outside the AS of the process.
458 * -EIO - an I/O error occurred while paging in data.
459 * -EBADF - map exists, but area maps something that isn't a file.
460 * -EAGAIN - a kernel resource was temporarily unavailable.
461 */
SYSCALL_DEFINE3(madvise,unsigned long,start,size_t,len_in,int,behavior)462 SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
463 {
464 unsigned long end, tmp;
465 struct vm_area_struct *vma, *prev;
466 int unmapped_error = 0;
467 int error = -EINVAL;
468 int write;
469 size_t len;
470 struct blk_plug plug;
471
472 #ifdef CONFIG_MEMORY_FAILURE
473 if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
474 return madvise_hwpoison(behavior, start, start+len_in);
475 #endif
476 if (!madvise_behavior_valid(behavior))
477 return error;
478
479 if (start & ~PAGE_MASK)
480 return error;
481 len = (len_in + ~PAGE_MASK) & PAGE_MASK;
482
483 /* Check to see whether len was rounded up from small -ve to zero */
484 if (len_in && !len)
485 return error;
486
487 end = start + len;
488 if (end < start)
489 return error;
490
491 error = 0;
492 if (end == start)
493 return error;
494
495 write = madvise_need_mmap_write(behavior);
496 if (write)
497 down_write(¤t->mm->mmap_sem);
498 else
499 down_read(¤t->mm->mmap_sem);
500
501 /*
502 * If the interval [start,end) covers some unmapped address
503 * ranges, just ignore them, but return -ENOMEM at the end.
504 * - different from the way of handling in mlock etc.
505 */
506 vma = find_vma_prev(current->mm, start, &prev);
507 if (vma && start > vma->vm_start)
508 prev = vma;
509
510 blk_start_plug(&plug);
511 for (;;) {
512 /* Still start < end. */
513 error = -ENOMEM;
514 if (!vma)
515 goto out;
516
517 /* Here start < (end|vma->vm_end). */
518 if (start < vma->vm_start) {
519 unmapped_error = -ENOMEM;
520 start = vma->vm_start;
521 if (start >= end)
522 goto out;
523 }
524
525 /* Here vma->vm_start <= start < (end|vma->vm_end) */
526 tmp = vma->vm_end;
527 if (end < tmp)
528 tmp = end;
529
530 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
531 error = madvise_vma(vma, &prev, start, tmp, behavior);
532 if (error)
533 goto out;
534 start = tmp;
535 if (prev && start < prev->vm_end)
536 start = prev->vm_end;
537 error = unmapped_error;
538 if (start >= end)
539 goto out;
540 if (prev)
541 vma = prev->vm_next;
542 else /* madvise_remove dropped mmap_sem */
543 vma = find_vma(current->mm, start);
544 }
545 out:
546 blk_finish_plug(&plug);
547 if (write)
548 up_write(¤t->mm->mmap_sem);
549 else
550 up_read(¤t->mm->mmap_sem);
551
552 return error;
553 }
554