Re: [PATCH v3 1/2] mm/list_lru.c: fix list_lru_count_node() to be race free

From: Vladimir Davydov <vdavydov.dev@gmail.com>
To: Sahitya Tummala <stummala@codeaurora.org>
Cc: Alexander Polakov <apolyakov@beget.ru>,
	Andrew Morton <akpm@linux-foundation.org>,
	Jan Kara <jack@suse.cz>,
	viro@zeniv.linux.org.uk, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v3 1/2] mm/list_lru.c: fix list_lru_count_node() to be race free
Date: Wed, 28 Jun 2017 20:18:54 +0300	[thread overview]
Message-ID: <20170628171854.t4sjyjv55j673qzv@esperanza> (raw)
In-Reply-To: <1498630044-26724-1-git-send-email-stummala@codeaurora.org>

On Wed, Jun 28, 2017 at 11:37:23AM +0530, Sahitya Tummala wrote:
> list_lru_count_node() iterates over all memcgs to get
> the total number of entries on the node but it can race with
> memcg_drain_all_list_lrus(), which migrates the entries from
> a dead cgroup to another. This can return incorrect number of
> entries from list_lru_count_node().
> 
> Fix this by keeping track of entries per node and simply return
> it in list_lru_count_node().
> 
> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
> ---
>  include/linux/list_lru.h |  1 +
>  mm/list_lru.c            | 14 ++++++--------
>  2 files changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
> index cb0ba9f..eff61bc 100644
> --- a/include/linux/list_lru.h
> +++ b/include/linux/list_lru.h
> @@ -44,6 +44,7 @@ struct list_lru_node {
>  	/* for cgroup aware lrus points to per cgroup lists, otherwise NULL */
>  	struct list_lru_memcg	*memcg_lrus;
>  #endif
> +	long nr_count;

'nr_count' sounds awkward. I think it should be called 'nr_items'.

Other than that, looks good to me.