Re: [PATCH -mm] mm, swap: Fix swap space leak in error path of swap_free_entries()

From: Andrew Morton
Date: Tue Apr 25 2017 - 17:37:28 EST


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

> From: Huang Ying <ying.huang@xxxxxxxxx>
>
> 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)