Thanks for your review. I have saw this review just after the send of
patch v2
在 2022/7/19 下午2:53, Muchun Song 写道:
On Mon, Jul 18, 2022 at 4:37 PM Jinke Han <hanjinke.666@xxxxxxxxxxxxx> wrote:
From: hanjinke <hanjinke.666@xxxxxxxxxxxxx>
In our test of iocost, we encounttered some list add/del corrutions of
inner_walk list in ioc_timer_fn.
The resean can be descripted as follow:
cpu 0 cpu 1
ioc_qos_write ioc_qos_write
ioc = q_to_ioc(bdev_get_queue(bdev));
if (!ioc) {
ioc = kzalloc(); ioc = q_to_ioc(bdev_get_queue(bdev));
if (!ioc) {
ioc = kzalloc();
...
rq_qos_add(q, rqos);
}
...
rq_qos_add(q, rqos);
...
}
When the io.cost.qos file is written by two cpu concurrently, rq_qos may
be added to one disk twice. In that case, there will be two iocs enabled
and running on one disk. They own different iocgs on their active list.
In the ioc_timer_fn function, because of the iocgs from two ioc have the
same root iocg, the root iocg's walk_list may be overwritten by each
other and this lead to list add/del corrutions in building or destorying
the inner_walk list.
And so far, the blk-rq-qos framework works in case that one instance for
one type rq_qos per queue by default. This patch make this explicit and
also fix the crash above.
Signed-off-by: hanjinke <hanjinke.666@xxxxxxxxxxxxx>
The change LGTM. Maybe it is better to add a Fixes tag here so that
others can easily know what Linux versions should be backported.
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Thanks.
