From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751740AbbJLKFS (ORCPT ); Mon, 12 Oct 2015 06:05:18 -0400 Received: from mail-wi0-f177.google.com ([209.85.212.177]:36569 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751235AbbJLKFQ (ORCPT ); Mon, 12 Oct 2015 06:05:16 -0400 Date: Mon, 12 Oct 2015 13:05:14 +0300 From: "Kirill A. Shutemov" To: yalin wang Cc: Vlastimil Babka , 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 Subject: Re: [RFC] mm: fix a BUG, the page is allocated 2 times Message-ID: <20151012100514.GA2544@node> References: <1444617606-8685-1-git-send-email-yalin.wang2010@gmail.com> <561B6379.2070407@suse.cz> <4D925B19-2187-4892-A99A-E59D575C2147@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4D925B19-2187-4892-A99A-E59D575C2147@gmail.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 ? Looks like a two patches to me: memory leak and removing always-true part of condifition. -- Kirill A. Shutemov