From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751296AbdKUHxQ (ORCPT ); Tue, 21 Nov 2017 02:53:16 -0500 Received: from mx2.suse.de ([195.135.220.15]:36597 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751151AbdKUHxO (ORCPT ); Tue, 21 Nov 2017 02:53:14 -0500 Subject: Re: [PATCH 1/1] mm/cma: fix alloc_contig_range ret code/potential leak To: Mike Kravetz , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Joonsoo Kim , Michal Nazarewicz , Michal Hocko , Mel Gorman , Johannes Weiner , Andrew Morton , stable@vger.kernel.org References: <20171120193930.23428-1-mike.kravetz@oracle.com> <20171120193930.23428-2-mike.kravetz@oracle.com> From: Vlastimil Babka Message-ID: Date: Tue, 21 Nov 2017 08:53:11 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <20171120193930.23428-2-mike.kravetz@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/20/2017 08:39 PM, Mike Kravetz wrote: > If the call __alloc_contig_migrate_range() in alloc_contig_range > returns -EBUSY, processing continues so that test_pages_isolated() > is called where there is a tracepoint to identify the busy pages. > However, it is possible for busy pages to become available between > the calls to these two routines. In this case, the range of pages > may be allocated. Unfortunately, the original return code (ret > == -EBUSY) is still set and returned to the caller. Therefore, > the caller believes the pages were not allocated and they are leaked. > > Update the return code with the value from test_pages_isolated(). Good catch and seems ok for a stable fix. But it's another indication that this area needs some larger rewrite. For example, it seems that the tracepoints in test_pages_isolated() will report not only pages which were busy during migration attempt, but also pages that were not at all attempted, because __alloc_contig_migrate_range() gave up? > Fixes: 8ef5849fa8a2 ("mm/cma: always check which page caused allocation failure") > Cc: > Signed-off-by: Mike Kravetz Acked-by: Vlastimil Babka > --- > mm/page_alloc.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 77e4d3c5c57b..3605ca82fd29 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7632,10 +7632,10 @@ int alloc_contig_range(unsigned long start, unsigned long end, > } > > /* Make sure the range is really isolated. */ > - if (test_pages_isolated(outer_start, end, false)) { > + ret = test_pages_isolated(outer_start, end, false); > + if (ret) { > pr_info_ratelimited("%s: [%lx, %lx) PFNs busy\n", > __func__, outer_start, end); > - ret = -EBUSY; > goto done; > } > >