Comment 2 for bug 1056729

Patch from Wang Xingchao[1], I backported to Ubuntu-3.2.0-31.50. Tested and it works fine. The patch has been merged into mainline 3.7[2][3].

[1] https://patchwork.kernel.org/patch/1450051/
[2] http://repo.or.cz/w/linux-2.6.git/commit/36a21fe6399cafc440163890035ccd9b891de00f
[3] http://lwn.net/Articles/517380/