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Linux/mm/msync.c

  1 /*
  2  *      linux/mm/msync.c
  3  *
  4  * Copyright (C) 1994-1999  Linus Torvalds
  5  */
  6 
  7 /*
  8  * The msync() system call.
  9  */
 10 #include <linux/fs.h>
 11 #include <linux/mm.h>
 12 #include <linux/mman.h>
 13 #include <linux/file.h>
 14 #include <linux/syscalls.h>
 15 #include <linux/sched.h>
 16 
 17 /*
 18  * MS_SYNC syncs the entire file - including mappings.
 19  *
 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.
 23  *
 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
 29  * applications.
 30  */
 31 SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
 32 {
 33         unsigned long end;
 34         struct mm_struct *mm = current->mm;
 35         struct vm_area_struct *vma;
 36         int unmapped_error = 0;
 37         int error = -EINVAL;
 38 
 39         if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
 40                 goto out;
 41         if (offset_in_page(start))
 42                 goto out;
 43         if ((flags & MS_ASYNC) && (flags & MS_SYNC))
 44                 goto out;
 45         error = -ENOMEM;
 46         len = (len + ~PAGE_MASK) & PAGE_MASK;
 47         end = start + len;
 48         if (end < start)
 49                 goto out;
 50         error = 0;
 51         if (end == start)
 52                 goto out;
 53         /*
 54          * If the interval [start,end) covers some unmapped address ranges,
 55          * just ignore them, but return -ENOMEM at the end.
 56          */
 57         down_read(&mm->mmap_sem);
 58         vma = find_vma(mm, start);
 59         for (;;) {
 60                 struct file *file;
 61                 loff_t fstart, fend;
 62 
 63                 /* Still start < end. */
 64                 error = -ENOMEM;
 65                 if (!vma)
 66                         goto out_unlock;
 67                 /* Here start < vma->vm_end. */
 68                 if (start < vma->vm_start) {
 69                         start = vma->vm_start;
 70                         if (start >= end)
 71                                 goto out_unlock;
 72                         unmapped_error = -ENOMEM;
 73                 }
 74                 /* Here vma->vm_start <= start < vma->vm_end. */
 75                 if ((flags & MS_INVALIDATE) &&
 76                                 (vma->vm_flags & VM_LOCKED)) {
 77                         error = -EBUSY;
 78                         goto out_unlock;
 79                 }
 80                 file = vma->vm_file;
 81                 fstart = (start - vma->vm_start) +
 82                          ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
 83                 fend = fstart + (min(end, vma->vm_end) - start) - 1;
 84                 start = vma->vm_end;
 85                 if ((flags & MS_SYNC) && file &&
 86                                 (vma->vm_flags & VM_SHARED)) {
 87                         get_file(file);
 88                         up_read(&mm->mmap_sem);
 89                         error = vfs_fsync_range(file, fstart, fend, 1);
 90                         fput(file);
 91                         if (error || start >= end)
 92                                 goto out;
 93                         down_read(&mm->mmap_sem);
 94                         vma = find_vma(mm, start);
 95                 } else {
 96                         if (start >= end) {
 97                                 error = 0;
 98                                 goto out_unlock;
 99                         }
100                         vma = vma->vm_next;
101                 }
102         }
103 out_unlock:
104         up_read(&mm->mmap_sem);
105 out:
106         return error ? : unmapped_error;
107 }
108 

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