From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751753AbbJLLW6 (ORCPT ); Mon, 12 Oct 2015 07:22:58 -0400 Received: from mx2.suse.de ([195.135.220.15]:59166 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751286AbbJLLW5 (ORCPT ); Mon, 12 Oct 2015 07:22:57 -0400 Subject: Re: [RFC] mm: fix a BUG, the page is allocated 2 times To: "Kirill A. Shutemov" , yalin wang References: <1444617606-8685-1-git-send-email-yalin.wang2010@gmail.com> <561B6379.2070407@suse.cz> <4D925B19-2187-4892-A99A-E59D575C2147@gmail.com> <20151012100514.GA2544@node> Cc: Andrew Morton , mgorman@techsingularity.net, mhocko@suse.com, David Rientjes , js1304@gmail.com, "Kirill A. Shutemov" , hannes@cmpxchg.org, alexander.h.duyck@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org From: Vlastimil Babka Message-ID: <561B980C.6060809@suse.cz> Date: Mon, 12 Oct 2015 13:22:52 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20151012100514.GA2544@node> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/12/2015 12:05 PM, Kirill A. Shutemov wrote: > On Mon, Oct 12, 2015 at 03:58:51PM +0800, yalin wang wrote: >> >>> On Oct 12, 2015, at 15:38, Vlastimil Babka wrote: >>> >>> On 10/12/2015 04:40 AM, yalin wang wrote: >>>> Remove unlikely(order), because we are sure order is not zero if >>>> code reach here, also add if (page == NULL), only allocate page again if >>>> __rmqueue_smallest() failed or alloc_flags & ALLOC_HARDER == 0 >>> >>> The second mentioned change is actually more important as it removes a memory leak! Thanks for catching this. The problem is in patch mm-page_alloc-reserve-pageblocks-for-high-order-atomic-allocations-on-demand.patch and seems to have been due to a change in the last submitted version to make sure the tracepoint is called. >>> >>>> Signed-off-by: yalin wang >>>> --- >>>> mm/page_alloc.c | 6 +++--- >>>> 1 file changed, 3 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>> index 0d6f540..de82e2c 100644 >>>> --- a/mm/page_alloc.c >>>> +++ b/mm/page_alloc.c >>>> @@ -2241,13 +2241,13 @@ struct page *buffered_rmqueue(struct zone *preferred_zone, >>>> spin_lock_irqsave(&zone->lock, flags); >>>> >>>> page = NULL; >>>> - if (unlikely(order) && (alloc_flags & ALLOC_HARDER)) { >>>> + if (alloc_flags & ALLOC_HARDER) { >>>> page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); >>>> if (page) >>>> trace_mm_page_alloc_zone_locked(page, order, migratetype); >>>> } >>>> - >>>> - page = __rmqueue(zone, order, migratetype, gfp_flags); >>>> + if (page == NULL) >>> >>> "if (!page)" is more common and already used below. >>> We could skip the check for !page in case we don't go through the ALLOC_HARDER branch, but I guess it's not worth the goto, and hopefully the compiler is smart enough anyway… >> agree with your comments, >> do i need send a new patch for this ? I'd guess no need to, Andrew can edit the patch? > > Looks like a two patches to me: memory leak and removing always-true part > of condifition. Yeah but I'd expect both would be in the end folded into the buggy patch in -mm?