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