Root/mm/madvise.c

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/page-isolation.h>
13#include <linux/hugetlb.h>
14#include <linux/falloc.h>
15#include <linux/sched.h>
16#include <linux/ksm.h>
17#include <linux/fs.h>
18#include <linux/file.h>
19
20/*
21 * Any behaviour which results in changes to the vma->vm_flags needs to
22 * take mmap_sem for writing. Others, which simply traverse vmas, need
23 * to only take it for reading.
24 */
25static int madvise_need_mmap_write(int behavior)
26{
27    switch (behavior) {
28    case MADV_REMOVE:
29    case MADV_WILLNEED:
30    case MADV_DONTNEED:
31        return 0;
32    default:
33        /* be safe, default to 1. list exceptions explicitly */
34        return 1;
35    }
36}
37
38/*
39 * We can potentially split a vm area into separate
40 * areas, each area with its own behavior.
41 */
42static long madvise_behavior(struct vm_area_struct * vma,
43             struct vm_area_struct **prev,
44             unsigned long start, unsigned long end, int behavior)
45{
46    struct mm_struct * mm = vma->vm_mm;
47    int error = 0;
48    pgoff_t pgoff;
49    unsigned long new_flags = vma->vm_flags;
50
51    switch (behavior) {
52    case MADV_NORMAL:
53        new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
54        break;
55    case MADV_SEQUENTIAL:
56        new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
57        break;
58    case MADV_RANDOM:
59        new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
60        break;
61    case MADV_DONTFORK:
62        new_flags |= VM_DONTCOPY;
63        break;
64    case MADV_DOFORK:
65        if (vma->vm_flags & VM_IO) {
66            error = -EINVAL;
67            goto out;
68        }
69        new_flags &= ~VM_DONTCOPY;
70        break;
71    case MADV_DONTDUMP:
72        new_flags |= VM_NODUMP;
73        break;
74    case MADV_DODUMP:
75        new_flags &= ~VM_NODUMP;
76        break;
77    case MADV_MERGEABLE:
78    case MADV_UNMERGEABLE:
79        error = ksm_madvise(vma, start, end, behavior, &new_flags);
80        if (error)
81            goto out;
82        break;
83    case MADV_HUGEPAGE:
84    case MADV_NOHUGEPAGE:
85        error = hugepage_madvise(vma, &new_flags, behavior);
86        if (error)
87            goto out;
88        break;
89    }
90
91    if (new_flags == vma->vm_flags) {
92        *prev = vma;
93        goto out;
94    }
95
96    pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
97    *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
98                vma->vm_file, pgoff, vma_policy(vma));
99    if (*prev) {
100        vma = *prev;
101        goto success;
102    }
103
104    *prev = vma;
105
106    if (start != vma->vm_start) {
107        error = split_vma(mm, vma, start, 1);
108        if (error)
109            goto out;
110    }
111
112    if (end != vma->vm_end) {
113        error = split_vma(mm, vma, end, 0);
114        if (error)
115            goto out;
116    }
117
118success:
119    /*
120     * vm_flags is protected by the mmap_sem held in write mode.
121     */
122    vma->vm_flags = new_flags;
123
124out:
125    if (error == -ENOMEM)
126        error = -EAGAIN;
127    return error;
128}
129
130/*
131 * Schedule all required I/O operations. Do not wait for completion.
132 */
133static long madvise_willneed(struct vm_area_struct * vma,
134                 struct vm_area_struct ** prev,
135                 unsigned long start, unsigned long end)
136{
137    struct file *file = vma->vm_file;
138
139    if (!file)
140        return -EBADF;
141
142    if (file->f_mapping->a_ops->get_xip_mem) {
143        /* no bad return value, but ignore advice */
144        return 0;
145    }
146
147    *prev = vma;
148    start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
149    if (end > vma->vm_end)
150        end = vma->vm_end;
151    end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
152
153    force_page_cache_readahead(file->f_mapping, file, start, end - start);
154    return 0;
155}
156
157/*
158 * Application no longer needs these pages. If the pages are dirty,
159 * it's OK to just throw them away. The app will be more careful about
160 * data it wants to keep. Be sure to free swap resources too. The
161 * zap_page_range call sets things up for shrink_active_list to actually free
162 * these pages later if no one else has touched them in the meantime,
163 * although we could add these pages to a global reuse list for
164 * shrink_active_list to pick up before reclaiming other pages.
165 *
166 * NB: This interface discards data rather than pushes it out to swap,
167 * as some implementations do. This has performance implications for
168 * applications like large transactional databases which want to discard
169 * pages in anonymous maps after committing to backing store the data
170 * that was kept in them. There is no reason to write this data out to
171 * the swap area if the application is discarding it.
172 *
173 * An interface that causes the system to free clean pages and flush
174 * dirty pages is already available as msync(MS_INVALIDATE).
175 */
176static long madvise_dontneed(struct vm_area_struct * vma,
177                 struct vm_area_struct ** prev,
178                 unsigned long start, unsigned long end)
179{
180    *prev = vma;
181    if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
182        return -EINVAL;
183
184    if (unlikely(vma->vm_flags & VM_NONLINEAR)) {
185        struct zap_details details = {
186            .nonlinear_vma = vma,
187            .last_index = ULONG_MAX,
188        };
189        zap_page_range(vma, start, end - start, &details);
190    } else
191        zap_page_range(vma, start, end - start, NULL);
192    return 0;
193}
194
195/*
196 * Application wants to free up the pages and associated backing store.
197 * This is effectively punching a hole into the middle of a file.
198 *
199 * NOTE: Currently, only shmfs/tmpfs is supported for this operation.
200 * Other filesystems return -ENOSYS.
201 */
202static long madvise_remove(struct vm_area_struct *vma,
203                struct vm_area_struct **prev,
204                unsigned long start, unsigned long end)
205{
206    loff_t offset;
207    int error;
208    struct file *f;
209
210    *prev = NULL; /* tell sys_madvise we drop mmap_sem */
211
212    if (vma->vm_flags & (VM_LOCKED|VM_NONLINEAR|VM_HUGETLB))
213        return -EINVAL;
214
215    f = vma->vm_file;
216
217    if (!f || !f->f_mapping || !f->f_mapping->host) {
218            return -EINVAL;
219    }
220
221    if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
222        return -EACCES;
223
224    offset = (loff_t)(start - vma->vm_start)
225            + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
226
227    /*
228     * Filesystem's fallocate may need to take i_mutex. We need to
229     * explicitly grab a reference because the vma (and hence the
230     * vma's reference to the file) can go away as soon as we drop
231     * mmap_sem.
232     */
233    get_file(f);
234    up_read(&current->mm->mmap_sem);
235    error = do_fallocate(f,
236                FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
237                offset, end - start);
238    fput(f);
239    down_read(&current->mm->mmap_sem);
240    return error;
241}
242
243#ifdef CONFIG_MEMORY_FAILURE
244/*
245 * Error injection support for memory error handling.
246 */
247static int madvise_hwpoison(int bhv, unsigned long start, unsigned long end)
248{
249    int ret = 0;
250
251    if (!capable(CAP_SYS_ADMIN))
252        return -EPERM;
253    for (; start < end; start += PAGE_SIZE) {
254        struct page *p;
255        int ret = get_user_pages_fast(start, 1, 0, &p);
256        if (ret != 1)
257            return ret;
258        if (bhv == MADV_SOFT_OFFLINE) {
259            printk(KERN_INFO "Soft offlining page %lx at %lx\n",
260                page_to_pfn(p), start);
261            ret = soft_offline_page(p, MF_COUNT_INCREASED);
262            if (ret)
263                break;
264            continue;
265        }
266        printk(KERN_INFO "Injecting memory failure for page %lx at %lx\n",
267               page_to_pfn(p), start);
268        /* Ignore return value for now */
269        memory_failure(page_to_pfn(p), 0, MF_COUNT_INCREASED);
270    }
271    return ret;
272}
273#endif
274
275static long
276madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
277        unsigned long start, unsigned long end, int behavior)
278{
279    switch (behavior) {
280    case MADV_REMOVE:
281        return madvise_remove(vma, prev, start, end);
282    case MADV_WILLNEED:
283        return madvise_willneed(vma, prev, start, end);
284    case MADV_DONTNEED:
285        return madvise_dontneed(vma, prev, start, end);
286    default:
287        return madvise_behavior(vma, prev, start, end, behavior);
288    }
289}
290
291static int
292madvise_behavior_valid(int behavior)
293{
294    switch (behavior) {
295    case MADV_DOFORK:
296    case MADV_DONTFORK:
297    case MADV_NORMAL:
298    case MADV_SEQUENTIAL:
299    case MADV_RANDOM:
300    case MADV_REMOVE:
301    case MADV_WILLNEED:
302    case MADV_DONTNEED:
303#ifdef CONFIG_KSM
304    case MADV_MERGEABLE:
305    case MADV_UNMERGEABLE:
306#endif
307#ifdef CONFIG_TRANSPARENT_HUGEPAGE
308    case MADV_HUGEPAGE:
309    case MADV_NOHUGEPAGE:
310#endif
311    case MADV_DONTDUMP:
312    case MADV_DODUMP:
313        return 1;
314
315    default:
316        return 0;
317    }
318}
319
320/*
321 * The madvise(2) system call.
322 *
323 * Applications can use madvise() to advise the kernel how it should
324 * handle paging I/O in this VM area. The idea is to help the kernel
325 * use appropriate read-ahead and caching techniques. The information
326 * provided is advisory only, and can be safely disregarded by the
327 * kernel without affecting the correct operation of the application.
328 *
329 * behavior values:
330 * MADV_NORMAL - the default behavior is to read clusters. This
331 * results in some read-ahead and read-behind.
332 * MADV_RANDOM - the system should read the minimum amount of data
333 * on any access, since it is unlikely that the appli-
334 * cation will need more than what it asks for.
335 * MADV_SEQUENTIAL - pages in the given range will probably be accessed
336 * once, so they can be aggressively read ahead, and
337 * can be freed soon after they are accessed.
338 * MADV_WILLNEED - the application is notifying the system to read
339 * some pages ahead.
340 * MADV_DONTNEED - the application is finished with the given range,
341 * so the kernel can free resources associated with it.
342 * MADV_REMOVE - the application wants to free up the given range of
343 * pages and associated backing store.
344 * MADV_DONTFORK - omit this area from child's address space when forking:
345 * typically, to avoid COWing pages pinned by get_user_pages().
346 * MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
347 * MADV_MERGEABLE - the application recommends that KSM try to merge pages in
348 * this area with pages of identical content from other such areas.
349 * MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
350 *
351 * return values:
352 * zero - success
353 * -EINVAL - start + len < 0, start is not page-aligned,
354 * "behavior" is not a valid value, or application
355 * is attempting to release locked or shared pages.
356 * -ENOMEM - addresses in the specified range are not currently
357 * mapped, or are outside the AS of the process.
358 * -EIO - an I/O error occurred while paging in data.
359 * -EBADF - map exists, but area maps something that isn't a file.
360 * -EAGAIN - a kernel resource was temporarily unavailable.
361 */
362SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
363{
364    unsigned long end, tmp;
365    struct vm_area_struct * vma, *prev;
366    int unmapped_error = 0;
367    int error = -EINVAL;
368    int write;
369    size_t len;
370
371#ifdef CONFIG_MEMORY_FAILURE
372    if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
373        return madvise_hwpoison(behavior, start, start+len_in);
374#endif
375    if (!madvise_behavior_valid(behavior))
376        return error;
377
378    write = madvise_need_mmap_write(behavior);
379    if (write)
380        down_write(&current->mm->mmap_sem);
381    else
382        down_read(&current->mm->mmap_sem);
383
384    if (start & ~PAGE_MASK)
385        goto out;
386    len = (len_in + ~PAGE_MASK) & PAGE_MASK;
387
388    /* Check to see whether len was rounded up from small -ve to zero */
389    if (len_in && !len)
390        goto out;
391
392    end = start + len;
393    if (end < start)
394        goto out;
395
396    error = 0;
397    if (end == start)
398        goto out;
399
400    /*
401     * If the interval [start,end) covers some unmapped address
402     * ranges, just ignore them, but return -ENOMEM at the end.
403     * - different from the way of handling in mlock etc.
404     */
405    vma = find_vma_prev(current->mm, start, &prev);
406    if (vma && start > vma->vm_start)
407        prev = vma;
408
409    for (;;) {
410        /* Still start < end. */
411        error = -ENOMEM;
412        if (!vma)
413            goto out;
414
415        /* Here start < (end|vma->vm_end). */
416        if (start < vma->vm_start) {
417            unmapped_error = -ENOMEM;
418            start = vma->vm_start;
419            if (start >= end)
420                goto out;
421        }
422
423        /* Here vma->vm_start <= start < (end|vma->vm_end) */
424        tmp = vma->vm_end;
425        if (end < tmp)
426            tmp = end;
427
428        /* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
429        error = madvise_vma(vma, &prev, start, tmp, behavior);
430        if (error)
431            goto out;
432        start = tmp;
433        if (prev && start < prev->vm_end)
434            start = prev->vm_end;
435        error = unmapped_error;
436        if (start >= end)
437            goto out;
438        if (prev)
439            vma = prev->vm_next;
440        else /* madvise_remove dropped mmap_sem */
441            vma = find_vma(current->mm, start);
442    }
443out:
444    if (write)
445        up_write(&current->mm->mmap_sem);
446    else
447        up_read(&current->mm->mmap_sem);
448
449    return error;
450}
451

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