linux-kernel - Re: [PATCH] mm: memcg: fix unit conversion for K() macro in OOM log

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Message-ID: <aUJ4dsVxsUj52hnz@tiehlicka>
Date: Wed, 17 Dec 2025 10:31:34 +0100
From: Michal Hocko <mhocko@...e.com>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Muchun Song <muchun.song@...ux.dev>,
	Vlastimil Babka <vbabka@...e.cz>,
	Meta kernel team <kernel-team@...a.com>, cgroups@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Chris Mason <clm@...com>
Subject: Re: [PATCH] mm: memcg: fix unit conversion for K() macro in OOM log

On Tue 16-12-25 13:20:54, Shakeel Butt wrote:
> The commit bc8e51c05ad5 ("mm: memcg: dump memcg protection info on oom
> or alloc failures") added functionality to dump memcg protections on OOM
> or allocation failures. It uses K() macro to dump the information and
> passes bytes to the macro. However the macro take number of pages
> instead of bytes. It is defined as:
> 
>  #define K(x) ((x) << (PAGE_SHIFT-10))
> 
> Let's fix this.
> 
> Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
> Reported-by: Chris Mason <clm@...com>
> Fixes: bc8e51c05ad5 ("mm: memcg: dump memcg protection info on oom or alloc failures")

Acked-by: Michal Hocko <mhocko@...e.com>

Thanks!
> ---
>  mm/memcontrol.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index e2e49f4ec9e0..6f000f0e76d2 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5638,6 +5638,6 @@ void mem_cgroup_show_protected_memory(struct mem_cgroup *memcg)
>  		memcg = root_mem_cgroup;
>  
>  	pr_warn("Memory cgroup min protection %lukB -- low protection %lukB",
> -		K(atomic_long_read(&memcg->memory.children_min_usage)*PAGE_SIZE),
> -		K(atomic_long_read(&memcg->memory.children_low_usage)*PAGE_SIZE));
> +		K(atomic_long_read(&memcg->memory.children_min_usage)),
> +		K(atomic_long_read(&memcg->memory.children_low_usage)));
>  }
> -- 
> 2.47.3
> 

-- 
Michal Hocko
SUSE Labs