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>
13 #include <linux/sched.h>
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.
20 static int madvise_need_mmap_write(int behavior
)
28 /* be safe, default to 1. list exceptions explicitly */
34 * We can potentially split a vm area into separate
35 * areas, each area with its own behavior.
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
)
41 struct mm_struct
* mm
= vma
->vm_mm
;
44 int new_flags
= vma
->vm_flags
;
48 new_flags
= new_flags
& ~VM_RAND_READ
& ~VM_SEQ_READ
;
51 new_flags
= (new_flags
& ~VM_RAND_READ
) | VM_SEQ_READ
;
54 new_flags
= (new_flags
& ~VM_SEQ_READ
) | VM_RAND_READ
;
57 new_flags
|= VM_DONTCOPY
;
60 new_flags
&= ~VM_DONTCOPY
;
64 if (new_flags
== vma
->vm_flags
) {
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
));
79 if (start
!= vma
->vm_start
) {
80 error
= split_vma(mm
, vma
, start
, 1);
85 if (end
!= vma
->vm_end
) {
86 error
= split_vma(mm
, vma
, end
, 0);
93 * vm_flags is protected by the mmap_sem held in write mode.
95 vma
->vm_flags
= new_flags
;
104 * Schedule all required I/O operations. Do not wait for completion.
106 static long madvise_willneed(struct vm_area_struct
* vma
,
107 struct vm_area_struct
** prev
,
108 unsigned long start
, unsigned long end
)
110 struct file
*file
= vma
->vm_file
;
115 if (file
->f_mapping
->a_ops
->get_xip_mem
) {
116 /* no bad return value, but ignore advice */
121 start
= ((start
- vma
->vm_start
) >> PAGE_SHIFT
) + vma
->vm_pgoff
;
122 if (end
> vma
->vm_end
)
124 end
= ((end
- vma
->vm_start
) >> PAGE_SHIFT
) + vma
->vm_pgoff
;
126 force_page_cache_readahead(file
->f_mapping
,
127 file
, start
, max_sane_readahead(end
- start
));
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.
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.
147 * An interface that causes the system to free clean pages and flush
148 * dirty pages is already available as msync(MS_INVALIDATE).
150 static long madvise_dontneed(struct vm_area_struct
* vma
,
151 struct vm_area_struct
** prev
,
152 unsigned long start
, unsigned long end
)
155 if (vma
->vm_flags
& (VM_LOCKED
|VM_HUGETLB
|VM_PFNMAP
))
158 if (unlikely(vma
->vm_flags
& VM_NONLINEAR
)) {
159 struct zap_details details
= {
160 .nonlinear_vma
= vma
,
161 .last_index
= ULONG_MAX
,
163 zap_page_range(vma
, start
, end
- start
, &details
);
165 zap_page_range(vma
, start
, end
- start
, NULL
);
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.
173 * NOTE: Currently, only shmfs/tmpfs is supported for this operation.
174 * Other filesystems return -ENOSYS.
176 static long madvise_remove(struct vm_area_struct
*vma
,
177 struct vm_area_struct
**prev
,
178 unsigned long start
, unsigned long end
)
180 struct address_space
*mapping
;
181 loff_t offset
, endoff
;
184 *prev
= NULL
; /* tell sys_madvise we drop mmap_sem */
186 if (vma
->vm_flags
& (VM_LOCKED
|VM_NONLINEAR
|VM_HUGETLB
))
189 if (!vma
->vm_file
|| !vma
->vm_file
->f_mapping
190 || !vma
->vm_file
->f_mapping
->host
) {
194 if ((vma
->vm_flags
& (VM_SHARED
|VM_WRITE
)) != (VM_SHARED
|VM_WRITE
))
197 mapping
= vma
->vm_file
->f_mapping
;
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
);
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
);
212 madvise_vma(struct vm_area_struct
*vma
, struct vm_area_struct
**prev
,
213 unsigned long start
, unsigned long end
, int behavior
)
219 if (vma
->vm_flags
& VM_IO
) {
225 case MADV_SEQUENTIAL
:
227 error
= madvise_behavior(vma
, prev
, start
, end
, behavior
);
230 error
= madvise_remove(vma
, prev
, start
, end
);
234 error
= madvise_willneed(vma
, prev
, start
, end
);
238 error
= madvise_dontneed(vma
, prev
, start
, end
);
249 * The madvise(2) system call.
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.
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
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.
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.
284 asmlinkage
long sys_madvise(unsigned long start
, size_t len_in
, int behavior
)
286 unsigned long end
, tmp
;
287 struct vm_area_struct
* vma
, *prev
;
288 int unmapped_error
= 0;
293 write
= madvise_need_mmap_write(behavior
);
295 down_write(¤t
->mm
->mmap_sem
);
297 down_read(¤t
->mm
->mmap_sem
);
299 if (start
& ~PAGE_MASK
)
301 len
= (len_in
+ ~PAGE_MASK
) & PAGE_MASK
;
303 /* Check to see whether len was rounded up from small -ve to zero */
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.
320 vma
= find_vma_prev(current
->mm
, start
, &prev
);
321 if (vma
&& start
> vma
->vm_start
)
325 /* Still start < end. */
330 /* Here start < (end|vma->vm_end). */
331 if (start
< vma
->vm_start
) {
332 unmapped_error
= -ENOMEM
;
333 start
= vma
->vm_start
;
338 /* Here vma->vm_start <= start < (end|vma->vm_end) */
343 /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
344 error
= madvise_vma(vma
, &prev
, start
, tmp
, behavior
);
348 if (prev
&& start
< prev
->vm_end
)
349 start
= prev
->vm_end
;
350 error
= unmapped_error
;
355 else /* madvise_remove dropped mmap_sem */
356 vma
= find_vma(current
->mm
, start
);
360 up_write(¤t
->mm
->mmap_sem
);
362 up_read(¤t
->mm
->mmap_sem
);
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