Re: [PATCH 2/2] blk-ioprio: remove per-disk structure

[Yu Kuai]

Hi,

在 2024/07/12 9:10, Yu Kuai 写道:
> Hi,
>
> 在 2024/07/12 2:03, Bart Van Assche 写道:
> > On 7/11/24 2:00 AM, Yu Kuai wrote:
> > > ioprio works on the blk-cgroup level, all disks in the same cgroup
> > > are the same, and the struct ioprio_blkg doesn't have anything in it.
> > > Hence register the policy is enough, because cpd_alloc/free_fn will
> > > be handled for each blk-cgroup, and there is no need to activate the
> > > policy for disk.
> >
> > As one can see in the output of git grep -nHEB1 '>pd_(alloc|free)_fn\(',
> > none of the pd_alloc_fn / pd_free_fn callers checks whether or not these
> > pointers are NULL. Hence my question why this patch does not trigger any
> > NULL pointer dereferences?
>
> Because the blkcg_deactivate_policy() is removed as well, there are no

Sorry about the typo, blkcg_activate_policy() is removed, all the places
of pd_(alloc|free)_fn can't be reached.

Thanks,
Kuai

> callers now... blkcg_policy_register() is still called to make sure
> cpd_(alloc|free)_fn will still be called.
>
> Thanks,
> Kuai
>
> > Thanks,
> >
> > Bart.
> > .
>
> .