If the 'kmalloc' fails, we must go through the existing error handling
path.
Signed-off-by: NChristophe JAILLET <christophe.jaillet@wanadoo.fr>
Fixes: 52ebea74 ("writeback: make backing_dev_info host cgroup-specific bdi_writebacks")
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@kernel.dk>