linux-kernel - Re: [PATCH 4.2 25/54] memcg: convert threshold to bytes

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Date:	Sat, 24 Oct 2015 14:46:58 +0900
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org
Cc:	stable@...r.kernel.org, Shaohua Li <shli@...com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 4.2 25/54] memcg: convert threshold to bytes

On Fri, 2015-10-23 at 10:45 -0700, Greg Kroah-Hartman wrote:
> 4.2-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Shaohua Li <shli@...com>
> 
> commit 424cdc14138088ada1b0e407a2195b2783c6e5ef upstream.
> 
> page_counter_memparse() returns pages for the threshold, while
> mem_cgroup_usage() returns bytes for memory usage.  Convert the
> threshold to bytes.
> 
> Fixes: 3e32cb2e0a12b6915 ("memcg: rename cgroup_event to mem_cgroup_event").
> Signed-off-by: Shaohua Li <shli@...com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Acked-by: Michal Hocko <mhocko@...e.com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> ---
>  mm/memcontrol.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3687,6 +3687,7 @@ static int __mem_cgroup_usage_register_e
>  > 	> ret = page_counter_memparse(args, "-1", &threshold);
>  > 	> if (ret)
>  > 	> 	> return ret;
> +> 	> threshold <<= PAGE_SHIFT;
>  
>  > 	> mutex_lock(&memcg->thresholds_lock);
>  

mem_cgroup_usage() returns a u64 and I think that the types of
threshold and mem_cgroup_threshold::threshold also need be changed to
u64 to avoid overflow on large 32-bit systems.

Ben.

-- 
Ben Hutchings
Beware of bugs in the above code;
I have only proved it correct, not tried it. - Donald Knuth
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