Re: [PATCH 3/3] zsmalloc: do not take class lock in zs_pages_to_compact()

Sergey Senozhatsky
2015-07-15T04:06:43Z

On (07/11/15 18:45), Sergey Senozhatsky wrote:
[..]
> We re-do this calculations during compaction on a per class basis
> anyway.
>
> zs_unregister_shrinker() will not return until we have an active
> shrinker, so classes won't unexpectedly disappear while
> zs_pages_to_compact(), invoked by zs_shrinker_count(), iterates
> them.
>
> When called from zram, we are protected by zram's ->init_lock,
> so, again, classes will be there until zs_pages_to_compact()
> iterates them.
>
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> ---
> mm/zsmalloc.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index b10a228..824c182 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -1811,9 +1811,7 @@ unsigned long zs_pages_to_compact(struct zs_pool *pool)
> if (class->index != i)
> continue;
>
> - spin_lock(&class->lock);
> pages_to_free += zs_can_compact(class);
> - spin_unlock(&class->lock);
> }
>
> return pages_to_free;

This patch still makes sense. Agree?

-ss