sb_getblk does not guarantee the buffer head is uptodate. If bh is not
uptodate, the data (may be used as boot code) in area before
F2FS_SUPER_OFFSET may get corrupted when super block is committed.
Signed-off-by: Sheng Yong <shengyong1@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>