commit 19125283 upstream.

Write may be called from interrupt context so make sure to use
GFP_ATOMIC for all allocations in write.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Johan Hovold <johan@kernel.org>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@huawei.com>