vfs, freeze: use ACCESS_ONCE() to guard access to ->mnt_flags

The compiler may optimize the while loop and make the check just be done once,
so we should use ACCESS_ONCE() to guard access to ->mnt_flags

Signed-off-by: Miao Xie <[email protected]>
Signed-off-by: Al Viro <[email protected]>
1 file changed