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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/sched.h> |
15 | #include <linux/ksm.h> |
16 | |
17 | /* |
18 | * Any behaviour which results in changes to the vma->vm_flags needs to |
19 | * take mmap_sem for writing. Others, which simply traverse vmas, need |
20 | * to only take it for reading. |
21 | */ |
22 | static int madvise_need_mmap_write(int behavior) |
23 | { |
24 | switch (behavior) { |
25 | case MADV_REMOVE: |
26 | case MADV_WILLNEED: |
27 | case MADV_DONTNEED: |
28 | return 0; |
29 | default: |
30 | /* be safe, default to 1. list exceptions explicitly */ |
31 | return 1; |
32 | } |
33 | } |
34 | |
35 | /* |
36 | * We can potentially split a vm area into separate |
37 | * areas, each area with its own behavior. |
38 | */ |
39 | static long madvise_behavior(struct vm_area_struct * vma, |
40 | struct vm_area_struct **prev, |
41 | unsigned long start, unsigned long end, int behavior) |
42 | { |
43 | struct mm_struct * mm = vma->vm_mm; |
44 | int error = 0; |
45 | pgoff_t pgoff; |
46 | unsigned long new_flags = vma->vm_flags; |
47 | |
48 | switch (behavior) { |
49 | case MADV_NORMAL: |
50 | new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ; |
51 | break; |
52 | case MADV_SEQUENTIAL: |
53 | new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ; |
54 | break; |
55 | case MADV_RANDOM: |
56 | new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ; |
57 | break; |
58 | case MADV_DONTFORK: |
59 | new_flags |= VM_DONTCOPY; |
60 | break; |
61 | case MADV_DOFORK: |
62 | if (vma->vm_flags & VM_IO) { |
63 | error = -EINVAL; |
64 | goto out; |
65 | } |
66 | new_flags &= ~VM_DONTCOPY; |
67 | break; |
68 | case MADV_MERGEABLE: |
69 | case MADV_UNMERGEABLE: |
70 | error = ksm_madvise(vma, start, end, behavior, &new_flags); |
71 | if (error) |
72 | goto out; |
73 | break; |
74 | case MADV_HUGEPAGE: |
75 | case MADV_NOHUGEPAGE: |
76 | error = hugepage_madvise(vma, &new_flags, behavior); |
77 | if (error) |
78 | goto out; |
79 | break; |
80 | } |
81 | |
82 | if (new_flags == vma->vm_flags) { |
83 | *prev = vma; |
84 | goto out; |
85 | } |
86 | |
87 | pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); |
88 | *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma, |
89 | vma->vm_file, pgoff, vma_policy(vma)); |
90 | if (*prev) { |
91 | vma = *prev; |
92 | goto success; |
93 | } |
94 | |
95 | *prev = vma; |
96 | |
97 | if (start != vma->vm_start) { |
98 | error = split_vma(mm, vma, start, 1); |
99 | if (error) |
100 | goto out; |
101 | } |
102 | |
103 | if (end != vma->vm_end) { |
104 | error = split_vma(mm, vma, end, 0); |
105 | if (error) |
106 | goto out; |
107 | } |
108 | |
109 | success: |
110 | /* |
111 | * vm_flags is protected by the mmap_sem held in write mode. |
112 | */ |
113 | vma->vm_flags = new_flags; |
114 | |
115 | out: |
116 | if (error == -ENOMEM) |
117 | error = -EAGAIN; |
118 | return error; |
119 | } |
120 | |
121 | /* |
122 | * Schedule all required I/O operations. Do not wait for completion. |
123 | */ |
124 | static long madvise_willneed(struct vm_area_struct * vma, |
125 | struct vm_area_struct ** prev, |
126 | unsigned long start, unsigned long end) |
127 | { |
128 | struct file *file = vma->vm_file; |
129 | |
130 | if (!file) |
131 | return -EBADF; |
132 | |
133 | if (file->f_mapping->a_ops->get_xip_mem) { |
134 | /* no bad return value, but ignore advice */ |
135 | return 0; |
136 | } |
137 | |
138 | *prev = vma; |
139 | start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; |
140 | if (end > vma->vm_end) |
141 | end = vma->vm_end; |
142 | end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; |
143 | |
144 | force_page_cache_readahead(file->f_mapping, file, start, end - start); |
145 | return 0; |
146 | } |
147 | |
148 | /* |
149 | * Application no longer needs these pages. If the pages are dirty, |
150 | * it's OK to just throw them away. The app will be more careful about |
151 | * data it wants to keep. Be sure to free swap resources too. The |
152 | * zap_page_range call sets things up for shrink_active_list to actually free |
153 | * these pages later if no one else has touched them in the meantime, |
154 | * although we could add these pages to a global reuse list for |
155 | * shrink_active_list to pick up before reclaiming other pages. |
156 | * |
157 | * NB: This interface discards data rather than pushes it out to swap, |
158 | * as some implementations do. This has performance implications for |
159 | * applications like large transactional databases which want to discard |
160 | * pages in anonymous maps after committing to backing store the data |
161 | * that was kept in them. There is no reason to write this data out to |
162 | * the swap area if the application is discarding it. |
163 | * |
164 | * An interface that causes the system to free clean pages and flush |
165 | * dirty pages is already available as msync(MS_INVALIDATE). |
166 | */ |
167 | static long madvise_dontneed(struct vm_area_struct * vma, |
168 | struct vm_area_struct ** prev, |
169 | unsigned long start, unsigned long end) |
170 | { |
171 | *prev = vma; |
172 | if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP)) |
173 | return -EINVAL; |
174 | |
175 | if (unlikely(vma->vm_flags & VM_NONLINEAR)) { |
176 | struct zap_details details = { |
177 | .nonlinear_vma = vma, |
178 | .last_index = ULONG_MAX, |
179 | }; |
180 | zap_page_range(vma, start, end - start, &details); |
181 | } else |
182 | zap_page_range(vma, start, end - start, NULL); |
183 | return 0; |
184 | } |
185 | |
186 | /* |
187 | * Application wants to free up the pages and associated backing store. |
188 | * This is effectively punching a hole into the middle of a file. |
189 | * |
190 | * NOTE: Currently, only shmfs/tmpfs is supported for this operation. |
191 | * Other filesystems return -ENOSYS. |
192 | */ |
193 | static long madvise_remove(struct vm_area_struct *vma, |
194 | struct vm_area_struct **prev, |
195 | unsigned long start, unsigned long end) |
196 | { |
197 | struct address_space *mapping; |
198 | loff_t offset, endoff; |
199 | int error; |
200 | |
201 | *prev = NULL; /* tell sys_madvise we drop mmap_sem */ |
202 | |
203 | if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB)) |
204 | return -EINVAL; |
205 | |
206 | if (!vma->vm_file || !vma->vm_file->f_mapping |
207 | || !vma->vm_file->f_mapping->host) { |
208 | return -EINVAL; |
209 | } |
210 | |
211 | if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE)) |
212 | return -EACCES; |
213 | |
214 | mapping = vma->vm_file->f_mapping; |
215 | |
216 | offset = (loff_t)(start - vma->vm_start) |
217 | + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); |
218 | endoff = (loff_t)(end - vma->vm_start - 1) |
219 | + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); |
220 | |
221 | /* vmtruncate_range needs to take i_mutex */ |
222 | up_read(¤t->mm->mmap_sem); |
223 | error = vmtruncate_range(mapping->host, offset, endoff); |
224 | down_read(¤t->mm->mmap_sem); |
225 | return error; |
226 | } |
227 | |
228 | #ifdef CONFIG_MEMORY_FAILURE |
229 | /* |
230 | * Error injection support for memory error handling. |
231 | */ |
232 | static int madvise_hwpoison(int bhv, unsigned long start, unsigned long end) |
233 | { |
234 | int ret = 0; |
235 | |
236 | if (!capable(CAP_SYS_ADMIN)) |
237 | return -EPERM; |
238 | for (; start < end; start += PAGE_SIZE) { |
239 | struct page *p; |
240 | int ret = get_user_pages_fast(start, 1, 0, &p); |
241 | if (ret != 1) |
242 | return ret; |
243 | if (bhv == MADV_SOFT_OFFLINE) { |
244 | printk(KERN_INFO "Soft offlining page %lx at %lx\n", |
245 | page_to_pfn(p), start); |
246 | ret = soft_offline_page(p, MF_COUNT_INCREASED); |
247 | if (ret) |
248 | break; |
249 | continue; |
250 | } |
251 | printk(KERN_INFO "Injecting memory failure for page %lx at %lx\n", |
252 | page_to_pfn(p), start); |
253 | /* Ignore return value for now */ |
254 | __memory_failure(page_to_pfn(p), 0, MF_COUNT_INCREASED); |
255 | } |
256 | return ret; |
257 | } |
258 | #endif |
259 | |
260 | static long |
261 | madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev, |
262 | unsigned long start, unsigned long end, int behavior) |
263 | { |
264 | switch (behavior) { |
265 | case MADV_REMOVE: |
266 | return madvise_remove(vma, prev, start, end); |
267 | case MADV_WILLNEED: |
268 | return madvise_willneed(vma, prev, start, end); |
269 | case MADV_DONTNEED: |
270 | return madvise_dontneed(vma, prev, start, end); |
271 | default: |
272 | return madvise_behavior(vma, prev, start, end, behavior); |
273 | } |
274 | } |
275 | |
276 | static int |
277 | madvise_behavior_valid(int behavior) |
278 | { |
279 | switch (behavior) { |
280 | case MADV_DOFORK: |
281 | case MADV_DONTFORK: |
282 | case MADV_NORMAL: |
283 | case MADV_SEQUENTIAL: |
284 | case MADV_RANDOM: |
285 | case MADV_REMOVE: |
286 | case MADV_WILLNEED: |
287 | case MADV_DONTNEED: |
288 | #ifdef CONFIG_KSM |
289 | case MADV_MERGEABLE: |
290 | case MADV_UNMERGEABLE: |
291 | #endif |
292 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
293 | case MADV_HUGEPAGE: |
294 | case MADV_NOHUGEPAGE: |
295 | #endif |
296 | return 1; |
297 | |
298 | default: |
299 | return 0; |
300 | } |
301 | } |
302 | |
303 | /* |
304 | * The madvise(2) system call. |
305 | * |
306 | * Applications can use madvise() to advise the kernel how it should |
307 | * handle paging I/O in this VM area. The idea is to help the kernel |
308 | * use appropriate read-ahead and caching techniques. The information |
309 | * provided is advisory only, and can be safely disregarded by the |
310 | * kernel without affecting the correct operation of the application. |
311 | * |
312 | * behavior values: |
313 | * MADV_NORMAL - the default behavior is to read clusters. This |
314 | * results in some read-ahead and read-behind. |
315 | * MADV_RANDOM - the system should read the minimum amount of data |
316 | * on any access, since it is unlikely that the appli- |
317 | * cation will need more than what it asks for. |
318 | * MADV_SEQUENTIAL - pages in the given range will probably be accessed |
319 | * once, so they can be aggressively read ahead, and |
320 | * can be freed soon after they are accessed. |
321 | * MADV_WILLNEED - the application is notifying the system to read |
322 | * some pages ahead. |
323 | * MADV_DONTNEED - the application is finished with the given range, |
324 | * so the kernel can free resources associated with it. |
325 | * MADV_REMOVE - the application wants to free up the given range of |
326 | * pages and associated backing store. |
327 | * MADV_DONTFORK - omit this area from child's address space when forking: |
328 | * typically, to avoid COWing pages pinned by get_user_pages(). |
329 | * MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking. |
330 | * MADV_MERGEABLE - the application recommends that KSM try to merge pages in |
331 | * this area with pages of identical content from other such areas. |
332 | * MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others. |
333 | * |
334 | * return values: |
335 | * zero - success |
336 | * -EINVAL - start + len < 0, start is not page-aligned, |
337 | * "behavior" is not a valid value, or application |
338 | * is attempting to release locked or shared pages. |
339 | * -ENOMEM - addresses in the specified range are not currently |
340 | * mapped, or are outside the AS of the process. |
341 | * -EIO - an I/O error occurred while paging in data. |
342 | * -EBADF - map exists, but area maps something that isn't a file. |
343 | * -EAGAIN - a kernel resource was temporarily unavailable. |
344 | */ |
345 | SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior) |
346 | { |
347 | unsigned long end, tmp; |
348 | struct vm_area_struct * vma, *prev; |
349 | int unmapped_error = 0; |
350 | int error = -EINVAL; |
351 | int write; |
352 | size_t len; |
353 | |
354 | #ifdef CONFIG_MEMORY_FAILURE |
355 | if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE) |
356 | return madvise_hwpoison(behavior, start, start+len_in); |
357 | #endif |
358 | if (!madvise_behavior_valid(behavior)) |
359 | return error; |
360 | |
361 | write = madvise_need_mmap_write(behavior); |
362 | if (write) |
363 | down_write(¤t->mm->mmap_sem); |
364 | else |
365 | down_read(¤t->mm->mmap_sem); |
366 | |
367 | if (start & ~PAGE_MASK) |
368 | goto out; |
369 | len = (len_in + ~PAGE_MASK) & PAGE_MASK; |
370 | |
371 | /* Check to see whether len was rounded up from small -ve to zero */ |
372 | if (len_in && !len) |
373 | goto out; |
374 | |
375 | end = start + len; |
376 | if (end < start) |
377 | goto out; |
378 | |
379 | error = 0; |
380 | if (end == start) |
381 | goto out; |
382 | |
383 | /* |
384 | * If the interval [start,end) covers some unmapped address |
385 | * ranges, just ignore them, but return -ENOMEM at the end. |
386 | * - different from the way of handling in mlock etc. |
387 | */ |
388 | vma = find_vma_prev(current->mm, start, &prev); |
389 | if (vma && start > vma->vm_start) |
390 | prev = vma; |
391 | |
392 | for (;;) { |
393 | /* Still start < end. */ |
394 | error = -ENOMEM; |
395 | if (!vma) |
396 | goto out; |
397 | |
398 | /* Here start < (end|vma->vm_end). */ |
399 | if (start < vma->vm_start) { |
400 | unmapped_error = -ENOMEM; |
401 | start = vma->vm_start; |
402 | if (start >= end) |
403 | goto out; |
404 | } |
405 | |
406 | /* Here vma->vm_start <= start < (end|vma->vm_end) */ |
407 | tmp = vma->vm_end; |
408 | if (end < tmp) |
409 | tmp = end; |
410 | |
411 | /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */ |
412 | error = madvise_vma(vma, &prev, start, tmp, behavior); |
413 | if (error) |
414 | goto out; |
415 | start = tmp; |
416 | if (prev && start < prev->vm_end) |
417 | start = prev->vm_end; |
418 | error = unmapped_error; |
419 | if (start >= end) |
420 | goto out; |
421 | if (prev) |
422 | vma = prev->vm_next; |
423 | else /* madvise_remove dropped mmap_sem */ |
424 | vma = find_vma(current->mm, start); |
425 | } |
426 | out: |
427 | if (write) |
428 | up_write(¤t->mm->mmap_sem); |
429 | else |
430 | up_read(¤t->mm->mmap_sem); |
431 | |
432 | return error; |
433 | } |
434 |
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