Re: [PATCH] mm: memcontrol-v1: use nofail allocations for soft limit trees

[Michal Hocko]

On Mon 08-06-26 14:36:44, Ruoyu Wang wrote:
> memcg1_init() allocates one soft-limit tree node per NUMA node and
> then initializes the returned object. If kzalloc_node() fails, the rb_root
> and lock initialization dereference NULL.
> 
> The per-node soft-limit tree is required by memcg v1. Use nofail
> GFP_KERNEL allocations for these init-time objects so the init path does
> not continue without the required tree nodes.

This is an early init code executing in during boot. Have you really
seen this allocation failing?

> Signed-off-by: Ruoyu Wang <ruoyuw560@xxxxxxxxx>
> ---
>  mm/memcontrol-v1.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
> index 433bba9dfe715..3f41a15d8a8cf 100644
> --- a/mm/memcontrol-v1.c
> +++ b/mm/memcontrol-v1.c
> @@ -2246,7 +2246,8 @@ static int __init memcg1_init(void)
>  	for_each_node(node) {
>  		struct mem_cgroup_tree_per_node *rtpn;
>  
> -		rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, node);
> +		rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL | __GFP_NOFAIL,
> +				    node);
>  
>  		rtpn->rb_root = RB_ROOT;
>  		rtpn->rb_rightmost = NULL;
> -- 
> 2.51.0

-- 
Michal Hocko
SUSE Labs