From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
To: Greg Thelen <gthelen@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Balbir Singh <balbir@linux.vnet.ibm.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Wu Fengguang <fengguang.wu@intel.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Subject: Re: [PATCH] memcg: avoid overflow in memcg_hierarchical_free_pages()
Date: Tue, 9 Nov 2010 12:44:26 +0900 [thread overview]
Message-ID: <20101109124426.312f9979.nishimura@mxp.nes.nec.co.jp> (raw)
In-Reply-To: <1289265320-7025-1-git-send-email-gthelen@google.com>
On Mon, 8 Nov 2010 17:15:20 -0800
Greg Thelen <gthelen@google.com> wrote:
> Use page counts rather than byte counts to avoid overflowing
> unsigned long local variables.
>
> Signed-off-by: Greg Thelen <gthelen@google.com>
> ---
> mm/memcontrol.c | 10 +++++-----
> 1 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 6c7115d..b287afd 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1345,17 +1345,17 @@ memcg_hierarchical_free_pages(struct mem_cgroup *mem)
> {
> unsigned long free, min_free;
>
hmm, the default value of RES_LIMIT is LLONG_MAX, so I think we must declare
"free" as unsinged long long to avoid overflow.
Thanks,
Daisuke Nishimura.
> - min_free = global_page_state(NR_FREE_PAGES) << PAGE_SHIFT;
> + min_free = global_page_state(NR_FREE_PAGES);
>
> while (mem) {
> - free = res_counter_read_u64(&mem->res, RES_LIMIT) -
> - res_counter_read_u64(&mem->res, RES_USAGE);
> + free = (res_counter_read_u64(&mem->res, RES_LIMIT) -
> + res_counter_read_u64(&mem->res, RES_USAGE)) >>
> + PAGE_SHIFT;
> min_free = min(min_free, free);
> mem = parent_mem_cgroup(mem);
> }
>
> - /* Translate free memory in pages */
> - return min_free >> PAGE_SHIFT;
> + return min_free;
> }
>
> /*
> --
> 1.7.3.1
>
next prev parent reply other threads:[~2010-11-09 3:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-09 1:15 [PATCH] memcg: avoid overflow in memcg_hierarchical_free_pages() Greg Thelen
2010-11-09 1:28 ` Minchan Kim
2010-11-09 1:47 ` Johannes Weiner
2010-11-09 3:44 ` Daisuke Nishimura [this message]
2010-11-09 3:52 ` Greg Thelen
2010-11-16 3:45 ` KAMEZAWA Hiroyuki
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