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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/hugetlb.h> | |
13 | #include <linux/sched.h> | |
14 | ||
15 | /* | |
16 | * Any behaviour which results in changes to the vma->vm_flags needs to | |
17 | * take mmap_sem for writing. Others, which simply traverse vmas, need | |
18 | * to only take it for reading. | |
19 | */ | |
20 | static int madvise_need_mmap_write(int behavior) | |
21 | { | |
22 | switch (behavior) { | |
23 | case MADV_REMOVE: | |
24 | case MADV_WILLNEED: | |
25 | case MADV_DONTNEED: | |
26 | return 0; | |
27 | default: | |
28 | /* be safe, default to 1. list exceptions explicitly */ | |
29 | return 1; | |
30 | } | |
31 | } | |
32 | ||
33 | /* | |
34 | * We can potentially split a vm area into separate | |
35 | * areas, each area with its own behavior. | |
36 | */ | |
37 | static long madvise_behavior(struct vm_area_struct * vma, | |
38 | struct vm_area_struct **prev, | |
39 | unsigned long start, unsigned long end, int behavior) | |
40 | { | |
41 | struct mm_struct * mm = vma->vm_mm; | |
42 | int error = 0; | |
43 | pgoff_t pgoff; | |
44 | int new_flags = vma->vm_flags; | |
45 | ||
46 | switch (behavior) { | |
47 | case MADV_NORMAL: | |
48 | new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ; | |
49 | break; | |
50 | case MADV_SEQUENTIAL: | |
51 | new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ; | |
52 | break; | |
53 | case MADV_RANDOM: | |
54 | new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ; | |
55 | break; | |
56 | case MADV_DONTFORK: | |
57 | new_flags |= VM_DONTCOPY; | |
58 | break; | |
59 | case MADV_DOFORK: | |
60 | new_flags &= ~VM_DONTCOPY; | |
61 | break; | |
62 | } | |
63 | ||
64 | if (new_flags == vma->vm_flags) { | |
65 | *prev = vma; | |
66 | goto out; | |
67 | } | |
68 | ||
69 | pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); | |
70 | *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma, | |
71 | vma->vm_file, pgoff, vma_policy(vma)); | |
72 | if (*prev) { | |
73 | vma = *prev; | |
74 | goto success; | |
75 | } | |
76 | ||
77 | *prev = vma; | |
78 | ||
79 | if (start != vma->vm_start) { | |
80 | error = split_vma(mm, vma, start, 1); | |
81 | if (error) | |
82 | goto out; | |
83 | } | |
84 | ||
85 | if (end != vma->vm_end) { | |
86 | error = split_vma(mm, vma, end, 0); | |
87 | if (error) | |
88 | goto out; | |
89 | } | |
90 | ||
91 | success: | |
92 | /* | |
93 | * vm_flags is protected by the mmap_sem held in write mode. | |
94 | */ | |
95 | vma->vm_flags = new_flags; | |
96 | ||
97 | out: | |
98 | if (error == -ENOMEM) | |
99 | error = -EAGAIN; | |
100 | return error; | |
101 | } | |
102 | ||
103 | /* | |
104 | * Schedule all required I/O operations. Do not wait for completion. | |
105 | */ | |
106 | static long madvise_willneed(struct vm_area_struct * vma, | |
107 | struct vm_area_struct ** prev, | |
108 | unsigned long start, unsigned long end) | |
109 | { | |
110 | struct file *file = vma->vm_file; | |
111 | ||
112 | if (!file) | |
113 | return -EBADF; | |
114 | ||
115 | if (file->f_mapping->a_ops->get_xip_page) { | |
116 | /* no bad return value, but ignore advice */ | |
117 | return 0; | |
118 | } | |
119 | ||
120 | *prev = vma; | |
121 | start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; | |
122 | if (end > vma->vm_end) | |
123 | end = vma->vm_end; | |
124 | end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; | |
125 | ||
126 | force_page_cache_readahead(file->f_mapping, | |
127 | file, start, max_sane_readahead(end - start)); | |
128 | return 0; | |
129 | } | |
130 | ||
131 | /* | |
132 | * Application no longer needs these pages. If the pages are dirty, | |
133 | * it's OK to just throw them away. The app will be more careful about | |
134 | * data it wants to keep. Be sure to free swap resources too. The | |
135 | * zap_page_range call sets things up for refill_inactive to actually free | |
136 | * these pages later if no one else has touched them in the meantime, | |
137 | * although we could add these pages to a global reuse list for | |
138 | * refill_inactive to pick up before reclaiming other pages. | |
139 | * | |
140 | * NB: This interface discards data rather than pushes it out to swap, | |
141 | * as some implementations do. This has performance implications for | |
142 | * applications like large transactional databases which want to discard | |
143 | * pages in anonymous maps after committing to backing store the data | |
144 | * that was kept in them. There is no reason to write this data out to | |
145 | * the swap area if the application is discarding it. | |
146 | * | |
147 | * An interface that causes the system to free clean pages and flush | |
148 | * dirty pages is already available as msync(MS_INVALIDATE). | |
149 | */ | |
150 | static long madvise_dontneed(struct vm_area_struct * vma, | |
151 | struct vm_area_struct ** prev, | |
152 | unsigned long start, unsigned long end) | |
153 | { | |
154 | *prev = vma; | |
155 | if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP)) | |
156 | return -EINVAL; | |
157 | ||
158 | if (unlikely(vma->vm_flags & VM_NONLINEAR)) { | |
159 | struct zap_details details = { | |
160 | .nonlinear_vma = vma, | |
161 | .last_index = ULONG_MAX, | |
162 | }; | |
163 | zap_page_range(vma, start, end - start, &details); | |
164 | } else | |
165 | zap_page_range(vma, start, end - start, NULL); | |
166 | return 0; | |
167 | } | |
168 | ||
169 | /* | |
170 | * Application wants to free up the pages and associated backing store. | |
171 | * This is effectively punching a hole into the middle of a file. | |
172 | * | |
173 | * NOTE: Currently, only shmfs/tmpfs is supported for this operation. | |
174 | * Other filesystems return -ENOSYS. | |
175 | */ | |
176 | static long madvise_remove(struct vm_area_struct *vma, | |
177 | struct vm_area_struct **prev, | |
178 | unsigned long start, unsigned long end) | |
179 | { | |
180 | struct address_space *mapping; | |
181 | loff_t offset, endoff; | |
182 | int error; | |
183 | ||
184 | *prev = NULL; /* tell sys_madvise we drop mmap_sem */ | |
185 | ||
186 | if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB)) | |
187 | return -EINVAL; | |
188 | ||
189 | if (!vma->vm_file || !vma->vm_file->f_mapping | |
190 | || !vma->vm_file->f_mapping->host) { | |
191 | return -EINVAL; | |
192 | } | |
193 | ||
194 | if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE)) | |
195 | return -EACCES; | |
196 | ||
197 | mapping = vma->vm_file->f_mapping; | |
198 | ||
199 | offset = (loff_t)(start - vma->vm_start) | |
200 | + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); | |
201 | endoff = (loff_t)(end - vma->vm_start - 1) | |
202 | + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); | |
203 | ||
204 | /* vmtruncate_range needs to take i_mutex and i_alloc_sem */ | |
205 | up_read(¤t->mm->mmap_sem); | |
206 | error = vmtruncate_range(mapping->host, offset, endoff); | |
207 | down_read(¤t->mm->mmap_sem); | |
208 | return error; | |
209 | } | |
210 | ||
211 | static long | |
212 | madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev, | |
213 | unsigned long start, unsigned long end, int behavior) | |
214 | { | |
215 | long error; | |
216 | ||
217 | switch (behavior) { | |
218 | case MADV_DOFORK: | |
219 | if (vma->vm_flags & VM_IO) { | |
220 | error = -EINVAL; | |
221 | break; | |
222 | } | |
223 | case MADV_DONTFORK: | |
224 | case MADV_NORMAL: | |
225 | case MADV_SEQUENTIAL: | |
226 | case MADV_RANDOM: | |
227 | error = madvise_behavior(vma, prev, start, end, behavior); | |
228 | break; | |
229 | case MADV_REMOVE: | |
230 | error = madvise_remove(vma, prev, start, end); | |
231 | break; | |
232 | ||
233 | case MADV_WILLNEED: | |
234 | error = madvise_willneed(vma, prev, start, end); | |
235 | break; | |
236 | ||
237 | case MADV_DONTNEED: | |
238 | error = madvise_dontneed(vma, prev, start, end); | |
239 | break; | |
240 | ||
241 | default: | |
242 | error = -EINVAL; | |
243 | break; | |
244 | } | |
245 | return error; | |
246 | } | |
247 | ||
248 | /* | |
249 | * The madvise(2) system call. | |
250 | * | |
251 | * Applications can use madvise() to advise the kernel how it should | |
252 | * handle paging I/O in this VM area. The idea is to help the kernel | |
253 | * use appropriate read-ahead and caching techniques. The information | |
254 | * provided is advisory only, and can be safely disregarded by the | |
255 | * kernel without affecting the correct operation of the application. | |
256 | * | |
257 | * behavior values: | |
258 | * MADV_NORMAL - the default behavior is to read clusters. This | |
259 | * results in some read-ahead and read-behind. | |
260 | * MADV_RANDOM - the system should read the minimum amount of data | |
261 | * on any access, since it is unlikely that the appli- | |
262 | * cation will need more than what it asks for. | |
263 | * MADV_SEQUENTIAL - pages in the given range will probably be accessed | |
264 | * once, so they can be aggressively read ahead, and | |
265 | * can be freed soon after they are accessed. | |
266 | * MADV_WILLNEED - the application is notifying the system to read | |
267 | * some pages ahead. | |
268 | * MADV_DONTNEED - the application is finished with the given range, | |
269 | * so the kernel can free resources associated with it. | |
270 | * MADV_REMOVE - the application wants to free up the given range of | |
271 | * pages and associated backing store. | |
272 | * | |
273 | * return values: | |
274 | * zero - success | |
275 | * -EINVAL - start + len < 0, start is not page-aligned, | |
276 | * "behavior" is not a valid value, or application | |
277 | * is attempting to release locked or shared pages. | |
278 | * -ENOMEM - addresses in the specified range are not currently | |
279 | * mapped, or are outside the AS of the process. | |
280 | * -EIO - an I/O error occurred while paging in data. | |
281 | * -EBADF - map exists, but area maps something that isn't a file. | |
282 | * -EAGAIN - a kernel resource was temporarily unavailable. | |
283 | */ | |
284 | asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior) | |
285 | { | |
286 | unsigned long end, tmp; | |
287 | struct vm_area_struct * vma, *prev; | |
288 | int unmapped_error = 0; | |
289 | int error = -EINVAL; | |
290 | size_t len; | |
291 | ||
292 | if (madvise_need_mmap_write(behavior)) | |
293 | down_write(¤t->mm->mmap_sem); | |
294 | else | |
295 | down_read(¤t->mm->mmap_sem); | |
296 | ||
297 | if (start & ~PAGE_MASK) | |
298 | goto out; | |
299 | len = (len_in + ~PAGE_MASK) & PAGE_MASK; | |
300 | ||
301 | /* Check to see whether len was rounded up from small -ve to zero */ | |
302 | if (len_in && !len) | |
303 | goto out; | |
304 | ||
305 | end = start + len; | |
306 | if (end < start) | |
307 | goto out; | |
308 | ||
309 | error = 0; | |
310 | if (end == start) | |
311 | goto out; | |
312 | ||
313 | /* | |
314 | * If the interval [start,end) covers some unmapped address | |
315 | * ranges, just ignore them, but return -ENOMEM at the end. | |
316 | * - different from the way of handling in mlock etc. | |
317 | */ | |
318 | vma = find_vma_prev(current->mm, start, &prev); | |
319 | if (vma && start > vma->vm_start) | |
320 | prev = vma; | |
321 | ||
322 | for (;;) { | |
323 | /* Still start < end. */ | |
324 | error = -ENOMEM; | |
325 | if (!vma) | |
326 | goto out; | |
327 | ||
328 | /* Here start < (end|vma->vm_end). */ | |
329 | if (start < vma->vm_start) { | |
330 | unmapped_error = -ENOMEM; | |
331 | start = vma->vm_start; | |
332 | if (start >= end) | |
333 | goto out; | |
334 | } | |
335 | ||
336 | /* Here vma->vm_start <= start < (end|vma->vm_end) */ | |
337 | tmp = vma->vm_end; | |
338 | if (end < tmp) | |
339 | tmp = end; | |
340 | ||
341 | /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */ | |
342 | error = madvise_vma(vma, &prev, start, tmp, behavior); | |
343 | if (error) | |
344 | goto out; | |
345 | start = tmp; | |
346 | if (prev && start < prev->vm_end) | |
347 | start = prev->vm_end; | |
348 | error = unmapped_error; | |
349 | if (start >= end) | |
350 | goto out; | |
351 | if (prev) | |
352 | vma = prev->vm_next; | |
353 | else /* madvise_remove dropped mmap_sem */ | |
354 | vma = find_vma(current->mm, start); | |
355 | } | |
356 | out: | |
357 | if (madvise_need_mmap_write(behavior)) | |
358 | up_write(¤t->mm->mmap_sem); | |
359 | else | |
360 | up_read(¤t->mm->mmap_sem); | |
361 | ||
362 | return error; | |
363 | } |