linux-kernel - Re: [PATCH -mm] mm, swap: Fix swap space leak in error path of swap_free

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Date:   Tue, 25 Apr 2017 14:37:18 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Tim Chen <tim.c.chen@...el.com>,
        Rik van Riel <riel@...hat.com>,
        Hugh Dickins <hughd@...gle.com>, Shaohua Li <shli@...nel.org>,
        Minchan Kim <minchan@...nel.org>
Subject: Re: [PATCH -mm] mm, swap: Fix swap space leak in error path of
 swap_free_entries()

On Fri, 21 Apr 2017 20:47:39 +0800 "Huang, Ying" <ying.huang@...el.com> wrote:

> From: Huang Ying <ying.huang@...el.com>
> 
> In swapcache_free_entries(), if swap_info_get_cont() return NULL,
> something wrong occurs for the swap entry.  But we should still
> continue to free the following swap entries in the array instead of
> skip them to avoid swap space leak.  This is just problem in error
> path, where system may be in an inconsistent state, but it is still
> good to fix it.
> 
> ...
>
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1079,8 +1079,6 @@ void swapcache_free_entries(swp_entry_t *entries, int n)
>  		p = swap_info_get_cont(entries[i], prev);
>  		if (p)
>  			swap_entry_free(p, entries[i]);
> -		else
> -			break;
>  		prev = p;

So now prev==NULL.  Will this code get the locking correct in
swap_info_get_cont()?  I think so, but please double-check.

>  	}
>  	if (p)