linux-kernel - Re: [PATCH] memcg: use do_div to divide s64 in 32 bit machine.

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Date:	Fri, 05 Nov 2010 09:34:33 -0700
From:	Greg Thelen <gthelen@...gle.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Young <hidave.darkstar@...il.com>,
	Andrea Righi <arighi@...eler.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH] memcg: use do_div to divide s64 in 32 bit machine.

Minchan Kim <minchan.kim@...il.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@...il.com>
> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
Tested-by: Greg Thelen <gthelen@...gle.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);
--
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