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 int write;
291 size_t len;
292
293 write = madvise_need_mmap_write(behavior);
294 if (write)
295 down_write(¤t->mm->mmap_sem);
296 else
297 down_read(¤t->mm->mmap_sem);
298
299 if (start & ~PAGE_MASK)
300 goto out;
301 len = (len_in + ~PAGE_MASK) & PAGE_MASK;
302
303 /* Check to see whether len was rounded up from small -ve to zero */
304 if (len_in && !len)
305 goto out;
306
307 end = start + len;
308 if (end < start)
309 goto out;
310
311 error = 0;
312 if (end == start)
313 goto out;
314
315 /*
316 * If the interval [start,end) covers some unmapped address
317 * ranges, just ignore them, but return -ENOMEM at the end.
318 * - different from the way of handling in mlock etc.
319 */
320 vma = find_vma_prev(current->mm, start, &prev);
321 if (vma && start > vma->vm_start)
322 prev = vma;
323
324 for (;;) {
325 /* Still start < end. */
326 error = -ENOMEM;
327 if (!vma)
328 goto out;
329
330 /* Here start < (end|vma->vm_end). */
331 if (start < vma->vm_start) {
332 unmapped_error = -ENOMEM;
333 start = vma->vm_start;
334 if (start >= end)
335 goto out;
336 }
337
338 /* Here vma->vm_start <= start < (end|vma->vm_end) */
339 tmp = vma->vm_end;
340 if (end < tmp)
341 tmp = end;
342
343 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
344 error = madvise_vma(vma, &prev, start, tmp, behavior);
345 if (error)
346 goto out;
347 start = tmp;
348 if (prev && start < prev->vm_end)
349 start = prev->vm_end;
350 error = unmapped_error;
351 if (start >= end)
352 goto out;
353 if (prev)
354 vma = prev->vm_next;
355 else /* madvise_remove dropped mmap_sem */
356 vma = find_vma(current->mm, start);
357 }
358 out:
359 if (write)
360 up_write(¤t->mm->mmap_sem);
361 else
362 up_read(¤t->mm->mmap_sem);
363
364 return error;
365 }
366
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