| 1 | |
| 2 | |
| 3 | * linux/mm/msync.c
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| 4 | *
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| 5 | * Copyright (C) 1994-1999 Linus Torvalds
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| 6 |
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| 7 |
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| 8 | |
| 9 | * The msync() system call.
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| 10 |
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| 11 | #include <linux/fs.h>
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| 12 | #include <linux/mm.h>
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| 13 | #include <linux/mman.h>
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| 14 | #include <linux/file.h>
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| 15 | #include <linux/syscalls.h>
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| 16 | #include <linux/sched.h>
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| 17 |
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| 18 | |
| 19 | * MS_SYNC syncs the entire file - including mappings.
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| 20 | *
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| 21 | * MS_ASYNC does not start I/O (it used to, up to 2.5.67).
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| 22 | * Nor does it marks the relevant pages dirty (it used to up to 2.6.17).
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| 23 | * Now it doesn't do anything, since dirty pages are properly tracked.
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| 24 | *
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| 25 | * The application may now run fsync() to
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| 26 | * write out the dirty pages and wait on the writeout and check the result.
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| 27 | * Or the application may run fadvise(FADV_DONTNEED) against the fd to start
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| 28 | * async writeout immediately.
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| 29 | * So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to
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| 30 | * applications.
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| 31 |
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| 32 | SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
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| 33 | {
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| 34 | unsigned long end;
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| 35 | struct mm_struct *mm = current->mm;
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| 36 | struct vm_area_struct *vma;
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| 37 | int unmapped_error = 0;
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| 38 | int error = -EINVAL;
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| 39 |
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| 40 | start = untagged_addr(start);
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| 41 |
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| 42 | if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
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| 43 | goto out;
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| 44 | if (offset_in_page(start))
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| 45 | goto out;
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| 46 | if ((flags & MS_ASYNC) && (flags & MS_SYNC))
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| 47 | goto out;
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| 48 | error = -ENOMEM;
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| 49 | len = (len + ~PAGE_MASK) & PAGE_MASK;
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| 50 | end = start + len;
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| 51 | if (end < start)
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| 52 | goto out;
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| 53 | error = 0;
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| 54 | if (end == start)
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| 55 | goto out;
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| 56 | |
| 57 | * If the interval [start,end) covers some unmapped address ranges,
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| 58 | * just ignore them, but return -ENOMEM at the end. Besides, if the
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| 59 | * flag is MS_ASYNC (w/o MS_INVALIDATE) the result would be -ENOMEM
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| 60 | * anyway and there is nothing left to do, so return immediately.
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| 61 |
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| 62 | mmap_read_lock(mm);
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| 63 | vma = find_vma(mm, start);
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| 64 | for (;;) {
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| 65 | struct file *file;
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| 66 | loff_t fstart, fend;
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| 67 |
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| 68 |
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| 69 | error = -ENOMEM;
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| 70 | if (!vma)
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| 71 | goto out_unlock;
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| 72 |
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| 73 | if (start < vma->vm_start) {
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| 74 | if (flags == MS_ASYNC)
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| 75 | goto out_unlock;
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| 76 | start = vma->vm_start;
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| 77 | if (start >= end)
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| 78 | goto out_unlock;
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| 79 | unmapped_error = -ENOMEM;
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| 80 | }
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| 81 |
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| 82 | if ((flags & MS_INVALIDATE) &&
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| 83 | (vma->vm_flags & VM_LOCKED)) {
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| 84 | error = -EBUSY;
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| 85 | goto out_unlock;
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| 86 | }
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| 87 | file = vma->vm_file;
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| 88 | fstart = (start - vma->vm_start) +
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| 89 | ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
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| 90 | fend = fstart + (min(end, vma->vm_end) - start) - 1;
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| 91 | start = vma->vm_end;
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| 92 | if ((flags & MS_SYNC) && file &&
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| 93 | (vma->vm_flags & VM_SHARED)) {
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| 94 | get_file(file);
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| 95 | mmap_read_unlock(mm);
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| 96 | error = vfs_fsync_range(file, fstart, fend, 1);
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| 97 | fput(file);
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| 98 | if (error || start >= end)
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| 99 | goto out;
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| 100 | mmap_read_lock(mm);
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| 101 | vma = find_vma(mm, start);
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| 102 | } else {
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| 103 | if (start >= end) {
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| 104 | error = 0;
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| 105 | goto out_unlock;
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| 106 | }
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| 107 | vma = find_vma(mm, vma->vm_end);
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| 108 | }
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| 109 | }
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| 110 | out_unlock:
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| 111 | mmap_read_unlock(mm);
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| 112 | out:
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| 113 | return error ? : unmapped_error;
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| 114 | }
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