Re: [PATCH] blk-cgroup: validate alloc/free function pairs at the start of blkcg_policy_register()

[Michal Koutný]

Hello Linxuan.

On Mon, Feb 10, 2025 at 11:18:27AM +0800, Chen Linxuan <chenlinxuan@xxxxxxxxxxxxx> wrote:
> Move the validation check for cpd/pd_alloc_fn and cpd/pd_free_fn function
> pairs to the start of blkcg_policy_register(). This ensures we immediately
> return -EINVAL if the function pairs are not correctly provided, rather
> than returning -ENOSPC after locking and unlocking mutexes unnecessarily.
> 
> Co-authored-by: Wen Tao <wentao@xxxxxxxxxxxxx>
> Signed-off-by: Wen Tao <wentao@xxxxxxxxxxxxx>
> Signed-off-by: Chen Linxuan <chenlinxuan@xxxxxxxxxxxxx>

If you consider those locks contention a problem (policy registrations
are "only" boot time, possibly module load time), then it's good to refer

Fixes: e84010732225c ("blkcg: add sanity check for blkcg policy operations")

> ---
>  block/blk-cgroup.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)

But it's correct,
Reviewed-by: Michal Koutný <mkoutny@xxxxxxxx>

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