4 * Copyright (C) 1999 Linus Torvalds
5 * Copyright (C) 2002 Christoph Hellwig
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>
15 * We can potentially split a vm area into separate
16 * areas, each area with its own behavior.
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
)
22 struct mm_struct
* mm
= vma
->vm_mm
;
25 int new_flags
= vma
->vm_flags
;
29 new_flags
= new_flags
& ~VM_RAND_READ
& ~VM_SEQ_READ
;
32 new_flags
= (new_flags
& ~VM_RAND_READ
) | VM_SEQ_READ
;
35 new_flags
= (new_flags
& ~VM_SEQ_READ
) | VM_RAND_READ
;
38 new_flags
|= VM_DONTCOPY
;
41 new_flags
&= ~VM_DONTCOPY
;
45 if (new_flags
== vma
->vm_flags
) {
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
));
60 if (start
!= vma
->vm_start
) {
61 error
= split_vma(mm
, vma
, start
, 1);
66 if (end
!= vma
->vm_end
) {
67 error
= split_vma(mm
, vma
, end
, 0);
74 * vm_flags is protected by the mmap_sem held in write mode.
76 vma
->vm_flags
= new_flags
;
85 * Schedule all required I/O operations. Do not wait for completion.
87 static long madvise_willneed(struct vm_area_struct
* vma
,
88 struct vm_area_struct
** prev
,
89 unsigned long start
, unsigned long end
)
91 struct file
*file
= vma
->vm_file
;
96 if (file
->f_mapping
->a_ops
->get_xip_page
) {
97 /* no bad return value, but ignore advice */
102 start
= ((start
- vma
->vm_start
) >> PAGE_SHIFT
) + vma
->vm_pgoff
;
103 if (end
> vma
->vm_end
)
105 end
= ((end
- vma
->vm_start
) >> PAGE_SHIFT
) + vma
->vm_pgoff
;
107 force_page_cache_readahead(file
->f_mapping
,
108 file
, start
, max_sane_readahead(end
- start
));
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.
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.
128 * An interface that causes the system to free clean pages and flush
129 * dirty pages is already available as msync(MS_INVALIDATE).
131 static long madvise_dontneed(struct vm_area_struct
* vma
,
132 struct vm_area_struct
** prev
,
133 unsigned long start
, unsigned long end
)
136 if (vma
->vm_flags
& (VM_LOCKED
|VM_HUGETLB
|VM_PFNMAP
))
139 if (unlikely(vma
->vm_flags
& VM_NONLINEAR
)) {
140 struct zap_details details
= {
141 .nonlinear_vma
= vma
,
142 .last_index
= ULONG_MAX
,
144 zap_page_range(vma
, start
, end
- start
, &details
);
146 zap_page_range(vma
, start
, end
- start
, NULL
);
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.
154 * NOTE: Currently, only shmfs/tmpfs is supported for this operation.
155 * Other filesystems return -ENOSYS.
157 static long madvise_remove(struct vm_area_struct
*vma
,
158 unsigned long start
, unsigned long end
)
160 struct address_space
*mapping
;
161 loff_t offset
, endoff
;
163 if (vma
->vm_flags
& (VM_LOCKED
|VM_NONLINEAR
|VM_HUGETLB
))
166 if (!vma
->vm_file
|| !vma
->vm_file
->f_mapping
167 || !vma
->vm_file
->f_mapping
->host
) {
171 if ((vma
->vm_flags
& (VM_SHARED
|VM_WRITE
)) != (VM_SHARED
|VM_WRITE
))
174 mapping
= vma
->vm_file
->f_mapping
;
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
);
184 madvise_vma(struct vm_area_struct
*vma
, struct vm_area_struct
**prev
,
185 unsigned long start
, unsigned long end
, int behavior
)
191 if (vma
->vm_flags
& VM_IO
) {
197 case MADV_SEQUENTIAL
:
199 error
= madvise_behavior(vma
, prev
, start
, end
, behavior
);
202 error
= madvise_remove(vma
, start
, end
);
206 error
= madvise_willneed(vma
, prev
, start
, end
);
210 error
= madvise_dontneed(vma
, prev
, start
, end
);
221 * The madvise(2) system call.
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.
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
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.
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.
256 asmlinkage
long sys_madvise(unsigned long start
, size_t len_in
, int behavior
)
258 unsigned long end
, tmp
;
259 struct vm_area_struct
* vma
, *prev
;
260 int unmapped_error
= 0;
264 down_write(¤t
->mm
->mmap_sem
);
266 if (start
& ~PAGE_MASK
)
268 len
= (len_in
+ ~PAGE_MASK
) & PAGE_MASK
;
270 /* Check to see whether len was rounded up from small -ve to zero */
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.
287 vma
= find_vma_prev(current
->mm
, start
, &prev
);
288 if (vma
&& start
> vma
->vm_start
)
292 /* Still start < end. */
297 /* Here start < (end|vma->vm_end). */
298 if (start
< vma
->vm_start
) {
299 unmapped_error
= -ENOMEM
;
300 start
= vma
->vm_start
;
305 /* Here vma->vm_start <= start < (end|vma->vm_end) */
310 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
311 error
= madvise_vma(vma
, &prev
, start
, tmp
, behavior
);
315 if (start
< prev
->vm_end
)
316 start
= prev
->vm_end
;
317 error
= unmapped_error
;
323 up_write(¤t
->mm
->mmap_sem
);
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