linux-kernel - Re: [patch 2/4] mm: memcontrol: don't pass a NULL memcg to mem_cgroup_end

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20141022065217.GS16496@esperanza>
Date:	Wed, 22 Oct 2014 10:52:17 +0400
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	Johannes Weiner <hannes@...xchg.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>, <linux-mm@...ck.org>,
	<cgroups@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [patch 2/4] mm: memcontrol: don't pass a NULL memcg to
 mem_cgroup_end_move()

On Tue, Oct 21, 2014 at 04:21:34PM -0400, Johannes Weiner wrote:
> mem_cgroup_end_move() checks if the passed memcg is NULL, along with a
> lengthy comment to explain why this seemingly non-sensical situation
> is even possible.
> 
> Check in cancel_attach() itself whether can_attach() set up the move
> context or not, it's a lot more obvious from there.  Then remove the
> check and comment in mem_cgroup_end_move().
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Acked-by: Vladimir Davydov <vdavydov@...allels.com>

> ---
>  mm/memcontrol.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 1ff125d2a427..c1fe774d712a 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1452,14 +1452,8 @@ static void mem_cgroup_start_move(struct mem_cgroup *memcg)
>  
>  static void mem_cgroup_end_move(struct mem_cgroup *memcg)
>  {
> -	/*
> -	 * Now, mem_cgroup_clear_mc() may call this function with NULL.
> -	 * We check NULL in callee rather than caller.
> -	 */
> -	if (memcg) {
> -		atomic_dec(&memcg_moving);
> -		atomic_dec(&memcg->moving_account);
> -	}
> +	atomic_dec(&memcg_moving);
> +	atomic_dec(&memcg->moving_account);
>  }
>  
>  /*
> @@ -5383,7 +5377,8 @@ static int mem_cgroup_can_attach(struct cgroup_subsys_state *css,
>  static void mem_cgroup_cancel_attach(struct cgroup_subsys_state *css,
>  				     struct cgroup_taskset *tset)
>  {
> -	mem_cgroup_clear_mc();
> +	if (mc.to)
> +		mem_cgroup_clear_mc();
>  }
>  
>  static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
> -- 
> 2.1.2
> 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/