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_page(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 #ifdef CONFIG_SWAP
226 if (!file || mapping_cap_swap_backed(file->f_mapping)) {
227 *prev = vma;
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 *prev = vma;
246 start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
247 if (end > vma->vm_end)
248 end = vma->vm_end;
249 end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
250
251 force_page_cache_readahead(file->f_mapping, file, start, end - start);
252 return 0;
253 }
254
255 /*
256 * Application no longer needs these pages. If the pages are dirty,
257 * it's OK to just throw them away. The app will be more careful about
258 * data it wants to keep. Be sure to free swap resources too. The
259 * zap_page_range call sets things up for shrink_active_list to actually free
260 * these pages later if no one else has touched them in the meantime,
261 * although we could add these pages to a global reuse list for
262 * shrink_active_list to pick up before reclaiming other pages.
263 *
264 * NB: This interface discards data rather than pushes it out to swap,
265 * as some implementations do. This has performance implications for
266 * applications like large transactional databases which want to discard
267 * pages in anonymous maps after committing to backing store the data
268 * that was kept in them. There is no reason to write this data out to
269 * the swap area if the application is discarding it.
270 *
271 * An interface that causes the system to free clean pages and flush
272 * dirty pages is already available as msync(MS_INVALIDATE).
273 */
madvise_dontneed(struct vm_area_struct * vma,struct vm_area_struct ** prev,unsigned long start,unsigned long end)274 static long madvise_dontneed(struct vm_area_struct * vma,
275 struct vm_area_struct ** prev,
276 unsigned long start, unsigned long end)
277 {
278 *prev = vma;
279 if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
280 return -EINVAL;
281
282 if (unlikely(vma->vm_flags & VM_NONLINEAR)) {
283 struct zap_details details = {
284 .nonlinear_vma = vma,
285 .last_index = ULONG_MAX,
286 };
287 zap_page_range(vma, start, end - start, &details);
288 } else
289 zap_page_range(vma, start, end - start, NULL);
290 return 0;
291 }
292
293 /*
294 * Application wants to free up the pages and associated backing store.
295 * This is effectively punching a hole into the middle of a file.
296 *
297 * NOTE: Currently, only shmfs/tmpfs is supported for this operation.
298 * Other filesystems return -ENOSYS.
299 */
madvise_remove(struct vm_area_struct * vma,struct vm_area_struct ** prev,unsigned long start,unsigned long end)300 static long madvise_remove(struct vm_area_struct *vma,
301 struct vm_area_struct **prev,
302 unsigned long start, unsigned long end)
303 {
304 loff_t offset;
305 int error;
306 struct file *f;
307
308 *prev = NULL; /* tell sys_madvise we drop mmap_sem */
309
310 if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB))
311 return -EINVAL;
312
313 f = vma->vm_file;
314
315 if (!f || !f->f_mapping || !f->f_mapping->host) {
316 return -EINVAL;
317 }
318
319 if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
320 return -EACCES;
321
322 offset = (loff_t)(start - vma->vm_start)
323 + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
324
325 /*
326 * Filesystem's fallocate may need to take i_mutex. We need to
327 * explicitly grab a reference because the vma (and hence the
328 * vma's reference to the file) can go away as soon as we drop
329 * mmap_sem.
330 */
331 get_file(f);
332 up_read(¤t->mm->mmap_sem);
333 error = do_fallocate(f,
334 FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
335 offset, end - start);
336 fput(f);
337 down_read(¤t->mm->mmap_sem);
338 return error;
339 }
340
341 #ifdef CONFIG_MEMORY_FAILURE
342 /*
343 * Error injection support for memory error handling.
344 */
madvise_hwpoison(int bhv,unsigned long start,unsigned long end)345 static int madvise_hwpoison(int bhv, unsigned long start, unsigned long end)
346 {
347 int ret = 0;
348
349 if (!capable(CAP_SYS_ADMIN))
350 return -EPERM;
351 for (; start < end; start += PAGE_SIZE) {
352 struct page *p;
353 int ret = get_user_pages_fast(start, 1, 0, &p);
354 if (ret != 1)
355 return ret;
356 if (bhv == MADV_SOFT_OFFLINE) {
357 printk(KERN_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 break;
362 continue;
363 }
364 printk(KERN_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 ret;
370 }
371 #endif
372
373 static long
madvise_vma(struct vm_area_struct * vma,struct vm_area_struct ** prev,unsigned long start,unsigned long end,int behavior)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 int
madvise_behavior_valid(int behavior)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 1;
412
413 default:
414 return 0;
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 */
SYSCALL_DEFINE3(madvise,unsigned long,start,size_t,len_in,int,behavior)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 }
552