From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f174.google.com (mail-ig0-f174.google.com [209.85.213.174]) by kanga.kvack.org (Postfix) with ESMTP id 1ABBC6B00DF for ; Wed, 12 Nov 2014 20:46:36 -0500 (EST) Received: by mail-ig0-f174.google.com with SMTP id hn18so4162886igb.1 for ; Wed, 12 Nov 2014 17:46:35 -0800 (PST) Received: from mail-ie0-x235.google.com (mail-ie0-x235.google.com. [2607:f8b0:4001:c03::235]) by mx.google.com with ESMTPS id x10si38543114ich.34.2014.11.12.17.46.34 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 12 Nov 2014 17:46:35 -0800 (PST) Received: by mail-ie0-f181.google.com with SMTP id rp18so14894929iec.12 for ; Wed, 12 Nov 2014 17:46:34 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20141112193450.GA18936@dhcp22.suse.cz> References: <000001cff998$ee0b31d0$ca219570$%yang@samsung.com> <20141112193450.GA18936@dhcp22.suse.cz> Date: Thu, 13 Nov 2014 09:46:34 +0800 Message-ID: Subject: Re: [PATCH 1/2] mm: page_isolation: check pfn validity before access From: Weijie Yang Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Weijie Yang , kamezawa.hiroyu@jp.fujitsu.com, Minchan Kim , Andrew Morton , mgorman@suse.de, mina86@mina86.com, linux-kernel , Linux-MM On Thu, Nov 13, 2014 at 3:34 AM, Michal Hocko wrote: > On Thu 06-11-14 16:08:02, Weijie Yang wrote: >> In the undo path of start_isolate_page_range(), we need to check >> the pfn validity before access its page, or it will trigger an >> addressing exception if there is hole in the zone. > > This looks a bit fishy to me. I am not familiar with the code much but > at least __offline_pages zone = page_zone(pfn_to_page(start_pfn)) so it > would blow up before we got here. Same applies to the other caller > alloc_contig_range. So either both need a fix and then > start_isolate_page_range doesn't need more checks or this is all > unnecessary. Thanks for your suggestion. If start_isolate_page_range()'s user can ensure there isn't hole in the [start_pfn, end_pfn) range, we can remove the checks. But if we cann't, I think it's better reserve these "unnecessary" code. That's really obfuscated : ( > Please do not make this code more obfuscated than it is already... > >> Signed-off-by: Weijie Yang >> --- >> mm/page_isolation.c | 7 +++++-- >> 1 files changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/mm/page_isolation.c b/mm/page_isolation.c >> index d1473b2..3ddc8b3 100644 >> --- a/mm/page_isolation.c >> +++ b/mm/page_isolation.c >> @@ -137,8 +137,11 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, >> undo: >> for (pfn = start_pfn; >> pfn < undo_pfn; >> - pfn += pageblock_nr_pages) >> - unset_migratetype_isolate(pfn_to_page(pfn), migratetype); >> + pfn += pageblock_nr_pages) { >> + page = __first_valid_page(pfn, pageblock_nr_pages); >> + if (page) >> + unset_migratetype_isolate(page, migratetype); >> + } >> >> return -EBUSY; >> } >> -- >> 1.7.0.4 >> >> >> -- >> 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 > > -- > Michal Hocko > SUSE Labs -- 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