linux-kernel - Re: [PATCH 1/4] zswap bugfix: memory leaks when re-swapon

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Date:	Fri, 23 Aug 2013 10:28:59 -0500
From:	Seth Jennings <sjenning@...ux.vnet.ibm.com>
To:	Weijie Yang <weijie.yang.kh@...il.com>
Cc:	Minchan Kim <minchan@...nel.org>, Bob Liu <bob.liu@...cle.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	weijie.yang@...sung.com
Subject: Re: [PATCH 1/4] zswap bugfix: memory leaks when re-swapon

On Fri, Aug 23, 2013 at 07:03:37PM +0800, Weijie Yang wrote:
> zswap_tree is not freed when swapoff, and it got re-kzalloc in swapon,
> memory leak occurs.
> Add check statement in zswap_frontswap_init so that zswap_tree is
> inited only once.
> 
> ---
>  mm/zswap.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/zswap.c b/mm/zswap.c
> index deda2b6..1cf1c07 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -826,6 +826,11 @@ static void zswap_frontswap_init(unsigned type)
>  {
>  	struct zswap_tree *tree;
> 
> +	if (zswap_trees[type]) {
> +		BUG_ON(zswap_trees[type]->rbroot != RB_ROOT);  /* invalidate_area set it */

Lets leave this BUG_ON() out.  If we want to make sure that the rbtree has
been properly emptied out, we should do it in
zswap_frontswap_invalidate_area() after the while loop and make it a
WARN_ON() since the problem is not fatal.

Seth

> +		return;
> +	}
> +
>  	tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
>  	if (!tree)
>  		goto err;
> -- 
> 1.7.0.4
> 

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