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From: Greg Thelen <gthelen@google.com>
To: Minchan Kim <minchan.kim@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Dave Young <hidave.darkstar@gmail.com>,
        Andrea Righi <arighi@develer.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>,
        Balbir Singh <balbir@linux.vnet.ibm.com>,
        Wu Fengguang <fengguang.wu@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH] memcg: use do_div to divide s64 in 32 bit machine.
References: <1288973333-7891-1-git-send-email-minchan.kim@gmail.com>
Date: Fri, 05 Nov 2010 09:34:33 -0700
In-Reply-To: <1288973333-7891-1-git-send-email-minchan.kim@gmail.com> (Minchan
	Kim's message of "Sat, 6 Nov 2010 01:08:53 +0900")
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Minchan Kim <minchan.kim@gmail.com> writes:

> Use do_div to divide s64 value. Otherwise, build would be failed
> like Dave Young reported.
>
> mm/built-in.o: In function `mem_cgroup_dirty_info':
> /home/dave/vdb/build/mm/linux-2.6.36/mm/memcontrol.c:1251: undefined
> reference to `__divdi3'
> /home/dave/vdb/build/mm/linux-2.6.36/mm/memcontrol.c:1259: undefined
> reference to `__divdi3'
> make: *** [.tmp_vmlinux1] Error 1
>
> Tested-by: Dave Young <hidave.darkstar@gmail.com>
> Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Tested-by: Greg Thelen <gthelen@google.com>

Thanks for report and the patch.

> ---
>  mm/memcontrol.c |   16 +++++++++-------
>  1 files changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 76386f4..a15d95e 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1247,18 +1247,20 @@ bool mem_cgroup_dirty_info(unsigned long sys_available_mem,
>  	if (dirty_param.dirty_bytes)
>  		info->dirty_thresh =
>  			DIV_ROUND_UP(dirty_param.dirty_bytes, PAGE_SIZE);
> -	else
> -		info->dirty_thresh =
> -			(dirty_param.dirty_ratio * available_mem) / 100;
> +	else {
> +		info->dirty_thresh = dirty_param.dirty_ratio * available_mem;
> +		do_div(info->dirty_thresh, 100);
> +	}
>  
>  	if (dirty_param.dirty_background_bytes)
>  		info->background_thresh =
>  			DIV_ROUND_UP(dirty_param.dirty_background_bytes,
>  				     PAGE_SIZE);
> -	else
> -		info->background_thresh =
> -			(dirty_param.dirty_background_ratio *
> -			       available_mem) / 100;
> +	else {
> +		info->background_thresh = dirty_param.dirty_background_ratio *
> +			available_mem;
> +		do_div(info->background_thresh, 100);
> +	}
>  
>  	info->nr_reclaimable =
>  		mem_cgroup_page_stat(MEMCG_NR_RECLAIM_PAGES);