Re: [PATCH] mm, memcg: fix mem_cgroup_swapout() for THPs

[Huang\, Ying]

Shakeel Butt <shakeelb@xxxxxxxxxx> writes:

> The commit d6810d730022 ("memcg, THP, swap: make mem_cgroup_swapout()
> support THP") changed mem_cgroup_swapout() to support transparent huge
> page (THP). However the patch missed one location which should be
> changed for correctly handling THPs. The resulting bug will cause the
> memory cgroups whose THPs were swapped out to become zombies on
> deletion.

Good catch!  Thanks a lot for fixing!

Best Regards,
Huang, Ying

> Fixes: d6810d730022 ("memcg, THP, swap: make mem_cgroup_swapout() support THP")
> Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
>  mm/memcontrol.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 50e6906314f8..ac2ffd5e02b9 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -6044,7 +6044,7 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
>  	memcg_check_events(memcg, page);
>  
>  	if (!mem_cgroup_is_root(memcg))
> -		css_put(&memcg->css);
> +		css_put_many(&memcg->css, nr_entries);
>  }
>  
>  /**