linux-phytec-fsl

f2fs: handle errors from get_node_page calls

Add check for error pointers returned from get_node_page in order to
avoid dereferencing a bad address on the next use.

Signed-off-by: Jason Hrycay <jason.hrycay@motorola.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>