From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f178.google.com (mail-wi0-f178.google.com [209.85.212.178]) by kanga.kvack.org (Postfix) with ESMTP id 7F1286B0253 for ; Mon, 12 Oct 2015 07:22:57 -0400 (EDT) Received: by wieq12 with SMTP id q12so15332525wie.1 for ; Mon, 12 Oct 2015 04:22:57 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id r4si15287672wif.54.2015.10.12.04.22.56 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 12 Oct 2015 04:22:56 -0700 (PDT) Subject: Re: [RFC] mm: fix a BUG, the page is allocated 2 times 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> From: Vlastimil Babka Message-ID: <561B980C.6060809@suse.cz> Date: Mon, 12 Oct 2015 13:22:52 +0200 MIME-Version: 1.0 In-Reply-To: <20151012100514.GA2544@node> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" , yalin wang 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 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 anywaya?| >> 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? -- 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