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