sb_read may return NULL, let's explicitly check it.
Signed-off-by: NDmitriy Monakhov <dmonakhov@openvz.org>
Cc: Jan Kara <jack@ucw.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>