Re: [PATCH] mm,vmscan: Make unregister_shrinker() no-op if register_shrinker() failed.

[Michal Hocko <mhocko@kernel.org>]

On Tue 21-11-17 21:04:13, Tetsuo Handa wrote:
> There are users calling unregister_shrinker() when register_shrinker()
> failed. Add sanity check to unregister_shrinker().
> 
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> ---
>  mm/vmscan.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index c02c850..9e100cc 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -297,6 +297,8 @@ int register_shrinker(struct shrinker *shrinker)
>   */
>  void unregister_shrinker(struct shrinker *shrinker)
>  {
> +	if (!shrinker->nr_deferred)
> +		return;

make it WARN_ON(), we really want to know about those, because something
is clearly wrong with them.

>  	down_write(&shrinker_rwsem);
>  	list_del(&shrinker->list);
>  	up_write(&shrinker_rwsem);
> -- 
> 1.8.3.1
> 
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-- 
Michal Hocko
SUSE Labs

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