| 1 | |
| 2 | * linux/mm/msync.c
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| 3 | *
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| 4 | * Copyright (C) 1994-1999 Linus Torvalds
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| 5 |
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| 6 |
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| 7 | |
| 8 | * The msync() system call.
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| 9 |
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| 10 | #include <linux/fs.h>
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| 11 | #include <linux/mm.h>
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| 12 | #include <linux/mman.h>
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| 13 | #include <linux/file.h>
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| 14 | #include <linux/syscalls.h>
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| 15 | #include <linux/sched.h>
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| 16 |
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| 17 | |
| 18 | * MS_SYNC syncs the entire file - including mappings.
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| 19 | *
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| 20 | * MS_ASYNC does not start I/O (it used to, up to 2.5.67).
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| 21 | * Nor does it marks the relevant pages dirty (it used to up to 2.6.17).
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| 22 | * Now it doesn't do anything, since dirty pages are properly tracked.
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| 23 | *
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| 24 | * The application may now run fsync() to
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| 25 | * write out the dirty pages and wait on the writeout and check the result.
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| 26 | * Or the application may run fadvise(FADV_DONTNEED) against the fd to start
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| 27 | * async writeout immediately.
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| 28 | * So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to
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| 29 | * applications.
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| 30 |
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| 31 | SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
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| 32 | {
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| 33 | unsigned long end;
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| 34 | struct mm_struct *mm = current->mm;
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| 35 | struct vm_area_struct *vma;
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| 36 | int unmapped_error = 0;
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| 37 | int error = -EINVAL;
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| 38 |
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| 39 | if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
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| 40 | goto out;
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| 41 | if (offset_in_page(start))
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| 42 | goto out;
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| 43 | if ((flags & MS_ASYNC) && (flags & MS_SYNC))
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| 44 | goto out;
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| 45 | error = -ENOMEM;
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| 46 | len = (len + ~PAGE_MASK) & PAGE_MASK;
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| 47 | end = start + len;
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| 48 | if (end < start)
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| 49 | goto out;
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| 50 | error = 0;
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| 51 | if (end == start)
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| 52 | goto out;
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| 53 | |
| 54 | * If the interval [start,end) covers some unmapped address ranges,
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| 55 | * just ignore them, but return -ENOMEM at the end.
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| 56 |
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| 57 | down_read(&mm->mmap_sem);
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| 58 | vma = find_vma(mm, start);
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| 59 | for (;;) {
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| 60 | struct file *file;
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| 61 | loff_t fstart, fend;
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| 62 |
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| 63 |
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| 64 | error = -ENOMEM;
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| 65 | if (!vma)
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| 66 | goto out_unlock;
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| 67 |
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| 68 | if (start < vma->vm_start) {
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| 69 | start = vma->vm_start;
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| 70 | if (start >= end)
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| 71 | goto out_unlock;
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| 72 | unmapped_error = -ENOMEM;
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| 73 | }
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| 74 |
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| 75 | if ((flags & MS_INVALIDATE) &&
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| 76 | (vma->vm_flags & VM_LOCKED)) {
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| 77 | error = -EBUSY;
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| 78 | goto out_unlock;
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| 79 | }
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| 80 | file = vma->vm_file;
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| 81 | fstart = (start - vma->vm_start) +
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| 82 | ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
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| 83 | fend = fstart + (min(end, vma->vm_end) - start) - 1;
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| 84 | start = vma->vm_end;
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| 85 | if ((flags & MS_SYNC) && file &&
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| 86 | (vma->vm_flags & VM_SHARED)) {
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| 87 | get_file(file);
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| 88 | up_read(&mm->mmap_sem);
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| 89 | error = vfs_fsync_range(file, fstart, fend, 1);
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| 90 | fput(file);
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| 91 | if (error || start >= end)
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| 92 | goto out;
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| 93 | down_read(&mm->mmap_sem);
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| 94 | vma = find_vma(mm, start);
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| 95 | } else {
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| 96 | if (start >= end) {
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| 97 | error = 0;
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| 98 | goto out_unlock;
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| 99 | }
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| 100 | vma = vma->vm_next;
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| 101 | }
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| 102 | }
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| 103 | out_unlock:
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| 104 | up_read(&mm->mmap_sem);
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| 105 | out:
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| 106 | return error ? : unmapped_error;
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| 107 | }
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