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