4 * Copyright (C) 1994-1999 Linus Torvalds
8 * The msync() system call.
12 #include <linux/mman.h>
13 #include <linux/file.h>
14 #include <linux/syscalls.h>
15 #include <linux/sched.h>
18 * MS_SYNC syncs the entire file - including mappings.
20 * MS_ASYNC does not start I/O (it used to, up to 2.5.67).
21 * Nor does it marks the relevant pages dirty (it used to up to 2.6.17).
22 * Now it doesn't do anything, since dirty pages are properly tracked.
24 * The application may now run fsync() to
25 * write out the dirty pages and wait on the writeout and check the result.
26 * Or the application may run fadvise(FADV_DONTNEED) against the fd to start
27 * async writeout immediately.
28 * So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to
31 SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
34 struct mm_struct *mm = current->mm;
35 struct vm_area_struct *vma;
36 int unmapped_error = 0;
39 if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
41 if (start & ~PAGE_MASK)
43 if ((flags & MS_ASYNC) && (flags & MS_SYNC))
46 len = (len + ~PAGE_MASK) & PAGE_MASK;
54 * If the interval [start,end) covers some unmapped address ranges,
55 * just ignore them, but return -ENOMEM at the end.
57 down_read(&mm->mmap_sem);
58 vma = find_vma(mm, start);
62 /* Still start < end. */
66 /* Here start < vma->vm_end. */
67 if (start < vma->vm_start) {
68 start = vma->vm_start;
71 unmapped_error = -ENOMEM;
73 /* Here vma->vm_start <= start < vma->vm_end. */
74 if ((flags & MS_INVALIDATE) &&
75 (vma->vm_flags & VM_LOCKED)) {
81 if ((flags & MS_SYNC) && file &&
82 (vma->vm_flags & VM_SHARED)) {
84 up_read(&mm->mmap_sem);
85 error = vfs_fsync(file, 0);
87 if (error || start >= end)
89 down_read(&mm->mmap_sem);
90 vma = find_vma(mm, start);
100 up_read(&mm->mmap_sem);
102 return error ? : unmapped_error;