From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f71.google.com (mail-oi0-f71.google.com [209.85.218.71]) by kanga.kvack.org (Postfix) with ESMTP id 789476B0038 for ; Tue, 25 Apr 2017 18:05:32 -0400 (EDT) Received: by mail-oi0-f71.google.com with SMTP id g184so130887150oif.6 for ; Tue, 25 Apr 2017 15:05:32 -0700 (PDT) Received: from mga02.intel.com (mga02.intel.com. [134.134.136.20]) by mx.google.com with ESMTPS id s12si13548507ots.35.2017.04.25.15.05.30 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 25 Apr 2017 15:05:31 -0700 (PDT) Message-ID: <1493157929.3209.113.camel@linux.intel.com> Subject: Re: [PATCH -mm] mm, swap: Fix swap space leak in error path of swap_free_entries() From: Tim Chen Date: Tue, 25 Apr 2017 15:05:29 -0700 In-Reply-To: <20170425143718.d05d4f5020b266dfdd61ed9c@linux-foundation.org> References: <20170421124739.24534-1-ying.huang@intel.com> <20170425143718.d05d4f5020b266dfdd61ed9c@linux-foundation.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , "Huang, Ying" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Tim Chen , Rik van Riel , Hugh Dickins , Shaohua Li , Minchan Kim On Tue, 2017-04-25 at 14:37 -0700, Andrew Morton wrote: > On Fri, 21 Apr 2017 20:47:39 +0800 "Huang, Ying" wrote: > > > > > From: Huang Ying > > > > In swapcache_free_entries(), if swap_info_get_cont() return NULL, > > something wrong occurs for the swap entry.A A But we should still > > continue to free the following swap entries in the array instead of > > skip them to avoid swap space leak.A A 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) > > A p = swap_info_get_cont(entries[i], prev); > > A if (p) > > A swap_entry_free(p, entries[i]); > > - else > > - break; > > A prev = p; > So now prev==NULL.A A Will this code get the locking correct in > swap_info_get_cont()?A A I think so, but please double-check. > There are 4 possible cases, and I checked that the logic in swap_info_get_cont do the expected: entries[i] valid? prev A Expected swap_info_get_cont behavior --------------------------------------------------------------------- NO NULL Return NULL p, Do nothing on lock/unlock NO NON-NULL Return NULL p, Unlock prevA YES NULL Return non-NULL p, lock p YES NON-NULL Return non-NULL p, (p != prev) unlock prev and lock pA A A (p == prev) do nothing on lock/unlock Thanks. Tim > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org