Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/mm/madvise.c
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
File MIME type: text/plain
File size: 6505 byte(s)
Tag kernel26-2.6.12-alx-r9
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/hugetlb.h> |
12 | |
13 | /* |
14 | * We can potentially split a vm area into separate |
15 | * areas, each area with its own behavior. |
16 | */ |
17 | static long madvise_behavior(struct vm_area_struct * vma, unsigned long start, |
18 | unsigned long end, int behavior) |
19 | { |
20 | struct mm_struct * mm = vma->vm_mm; |
21 | int error = 0; |
22 | |
23 | if (start != vma->vm_start) { |
24 | error = split_vma(mm, vma, start, 1); |
25 | if (error) |
26 | goto out; |
27 | } |
28 | |
29 | if (end != vma->vm_end) { |
30 | error = split_vma(mm, vma, end, 0); |
31 | if (error) |
32 | goto out; |
33 | } |
34 | |
35 | /* |
36 | * vm_flags is protected by the mmap_sem held in write mode. |
37 | */ |
38 | VM_ClearReadHint(vma); |
39 | |
40 | switch (behavior) { |
41 | case MADV_SEQUENTIAL: |
42 | vma->vm_flags |= VM_SEQ_READ; |
43 | break; |
44 | case MADV_RANDOM: |
45 | vma->vm_flags |= VM_RAND_READ; |
46 | break; |
47 | default: |
48 | break; |
49 | } |
50 | |
51 | out: |
52 | if (error == -ENOMEM) |
53 | error = -EAGAIN; |
54 | return error; |
55 | } |
56 | |
57 | /* |
58 | * Schedule all required I/O operations. Do not wait for completion. |
59 | */ |
60 | static long madvise_willneed(struct vm_area_struct * vma, |
61 | unsigned long start, unsigned long end) |
62 | { |
63 | struct file *file = vma->vm_file; |
64 | |
65 | if (!file) |
66 | return -EBADF; |
67 | |
68 | start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; |
69 | if (end > vma->vm_end) |
70 | end = vma->vm_end; |
71 | end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; |
72 | |
73 | force_page_cache_readahead(file->f_mapping, |
74 | file, start, max_sane_readahead(end - start)); |
75 | return 0; |
76 | } |
77 | |
78 | /* |
79 | * Application no longer needs these pages. If the pages are dirty, |
80 | * it's OK to just throw them away. The app will be more careful about |
81 | * data it wants to keep. Be sure to free swap resources too. The |
82 | * zap_page_range call sets things up for refill_inactive to actually free |
83 | * these pages later if no one else has touched them in the meantime, |
84 | * although we could add these pages to a global reuse list for |
85 | * refill_inactive to pick up before reclaiming other pages. |
86 | * |
87 | * NB: This interface discards data rather than pushes it out to swap, |
88 | * as some implementations do. This has performance implications for |
89 | * applications like large transactional databases which want to discard |
90 | * pages in anonymous maps after committing to backing store the data |
91 | * that was kept in them. There is no reason to write this data out to |
92 | * the swap area if the application is discarding it. |
93 | * |
94 | * An interface that causes the system to free clean pages and flush |
95 | * dirty pages is already available as msync(MS_INVALIDATE). |
96 | */ |
97 | static long madvise_dontneed(struct vm_area_struct * vma, |
98 | unsigned long start, unsigned long end) |
99 | { |
100 | if ((vma->vm_flags & VM_LOCKED) || is_vm_hugetlb_page(vma)) |
101 | return -EINVAL; |
102 | |
103 | if (unlikely(vma->vm_flags & VM_NONLINEAR)) { |
104 | struct zap_details details = { |
105 | .nonlinear_vma = vma, |
106 | .last_index = ULONG_MAX, |
107 | }; |
108 | zap_page_range(vma, start, end - start, &details); |
109 | } else |
110 | zap_page_range(vma, start, end - start, NULL); |
111 | return 0; |
112 | } |
113 | |
114 | static long madvise_vma(struct vm_area_struct * vma, unsigned long start, |
115 | unsigned long end, int behavior) |
116 | { |
117 | long error = -EBADF; |
118 | |
119 | switch (behavior) { |
120 | case MADV_NORMAL: |
121 | case MADV_SEQUENTIAL: |
122 | case MADV_RANDOM: |
123 | error = madvise_behavior(vma, start, end, behavior); |
124 | break; |
125 | |
126 | case MADV_WILLNEED: |
127 | error = madvise_willneed(vma, start, end); |
128 | break; |
129 | |
130 | case MADV_DONTNEED: |
131 | error = madvise_dontneed(vma, start, end); |
132 | break; |
133 | |
134 | default: |
135 | error = -EINVAL; |
136 | break; |
137 | } |
138 | |
139 | return error; |
140 | } |
141 | |
142 | /* |
143 | * The madvise(2) system call. |
144 | * |
145 | * Applications can use madvise() to advise the kernel how it should |
146 | * handle paging I/O in this VM area. The idea is to help the kernel |
147 | * use appropriate read-ahead and caching techniques. The information |
148 | * provided is advisory only, and can be safely disregarded by the |
149 | * kernel without affecting the correct operation of the application. |
150 | * |
151 | * behavior values: |
152 | * MADV_NORMAL - the default behavior is to read clusters. This |
153 | * results in some read-ahead and read-behind. |
154 | * MADV_RANDOM - the system should read the minimum amount of data |
155 | * on any access, since it is unlikely that the appli- |
156 | * cation will need more than what it asks for. |
157 | * MADV_SEQUENTIAL - pages in the given range will probably be accessed |
158 | * once, so they can be aggressively read ahead, and |
159 | * can be freed soon after they are accessed. |
160 | * MADV_WILLNEED - the application is notifying the system to read |
161 | * some pages ahead. |
162 | * MADV_DONTNEED - the application is finished with the given range, |
163 | * so the kernel can free resources associated with it. |
164 | * |
165 | * return values: |
166 | * zero - success |
167 | * -EINVAL - start + len < 0, start is not page-aligned, |
168 | * "behavior" is not a valid value, or application |
169 | * is attempting to release locked or shared pages. |
170 | * -ENOMEM - addresses in the specified range are not currently |
171 | * mapped, or are outside the AS of the process. |
172 | * -EIO - an I/O error occurred while paging in data. |
173 | * -EBADF - map exists, but area maps something that isn't a file. |
174 | * -EAGAIN - a kernel resource was temporarily unavailable. |
175 | */ |
176 | asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior) |
177 | { |
178 | unsigned long end; |
179 | struct vm_area_struct * vma; |
180 | int unmapped_error = 0; |
181 | int error = -EINVAL; |
182 | size_t len; |
183 | |
184 | down_write(¤t->mm->mmap_sem); |
185 | |
186 | if (start & ~PAGE_MASK) |
187 | goto out; |
188 | len = (len_in + ~PAGE_MASK) & PAGE_MASK; |
189 | |
190 | /* Check to see whether len was rounded up from small -ve to zero */ |
191 | if (len_in && !len) |
192 | goto out; |
193 | |
194 | end = start + len; |
195 | if (end < start) |
196 | goto out; |
197 | |
198 | error = 0; |
199 | if (end == start) |
200 | goto out; |
201 | |
202 | /* |
203 | * If the interval [start,end) covers some unmapped address |
204 | * ranges, just ignore them, but return -ENOMEM at the end. |
205 | */ |
206 | vma = find_vma(current->mm, start); |
207 | for (;;) { |
208 | /* Still start < end. */ |
209 | error = -ENOMEM; |
210 | if (!vma) |
211 | goto out; |
212 | |
213 | /* Here start < vma->vm_end. */ |
214 | if (start < vma->vm_start) { |
215 | unmapped_error = -ENOMEM; |
216 | start = vma->vm_start; |
217 | } |
218 | |
219 | /* Here vma->vm_start <= start < vma->vm_end. */ |
220 | if (end <= vma->vm_end) { |
221 | if (start < end) { |
222 | error = madvise_vma(vma, start, end, |
223 | behavior); |
224 | if (error) |
225 | goto out; |
226 | } |
227 | error = unmapped_error; |
228 | goto out; |
229 | } |
230 | |
231 | /* Here vma->vm_start <= start < vma->vm_end < end. */ |
232 | error = madvise_vma(vma, start, vma->vm_end, behavior); |
233 | if (error) |
234 | goto out; |
235 | start = vma->vm_end; |
236 | vma = vma->vm_next; |
237 | } |
238 | |
239 | out: |
240 | up_write(¤t->mm->mmap_sem); |
241 | return error; |
242 | } |