check pol->cpd_free_fn() instead of pol->cpd_alloc_fn() when free cpd.
Reviewed-by: NJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Nweiping zhang <zhangweiping@didichuxing.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>