linux-kernel - Re: [PATCH] Display 0 in meminfo for Committed

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Date:	Mon, 27 Apr 2009 09:15:14 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Eric B Munson <ebmunson@...ibm.com>
Cc:	akpm@...ux-foundation.org, kosaki.motohiro@...fujitsu.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, mel@....ul.ie,
	cl@...ux-foundation.org
Subject: Re: [PATCH] Display 0 in meminfo for Committed_AS when value
	underflows

On Mon, 2009-04-27 at 17:10 +0100, Eric B Munson wrote:
> Splitting this patch from the chunk that addresses the cause of the underflow
> because the solution still requires some discussion.
> 
> Dave Hansen reported that under certain cirumstances the Committed_AS value
> can underflow which causes extremely large numbers to be displayed in
> meminfo.  This patch adds an underflow check to meminfo_proc_show() for the
> Committed_AS value.  Most fields in /proc/meminfo already have an underflow
> check, this brings Committed_AS into line.

Yeah, this is the right fix for now until we can iron out the base
issues.  Eric, I think this may also be a candidate for -stable.

Signed-off-by: Dave Hansen <dave@...ux.vnet.ibm.com>

> From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Signed-off-by: Eric B Munson <ebmunson@...ibm.com>
> ---
>  fs/proc/meminfo.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
> index 74ea974..facb9fb 100644
> --- a/fs/proc/meminfo.c
> +++ b/fs/proc/meminfo.c
> @@ -22,7 +22,7 @@ void __attribute__((weak)) arch_report_meminfo(struct seq_file *m)
>  static int meminfo_proc_show(struct seq_file *m, void *v)
>  {
>  	struct sysinfo i;
> -	unsigned long committed;
> +	long committed;
>  	unsigned long allowed;
>  	struct vmalloc_info vmi;
>  	long cached;
> @@ -36,6 +36,8 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>  	si_meminfo(&i);
>  	si_swapinfo(&i);
>  	committed = atomic_long_read(&vm_committed_space);
> +	if (committed < 0)
> +		committed = 0;
>  	allowed = ((totalram_pages - hugetlb_total_pages())
>  		* sysctl_overcommit_ratio / 100) + total_swap_pages;
> 
-- Dave

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