From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f51.google.com (mail-pb0-f51.google.com [209.85.160.51]) by kanga.kvack.org (Postfix) with ESMTP id AB7446B0031 for ; Thu, 10 Oct 2013 13:52:50 -0400 (EDT) Received: by mail-pb0-f51.google.com with SMTP id jt11so2948141pbb.10 for ; Thu, 10 Oct 2013 10:52:50 -0700 (PDT) Message-ID: <5256E931.5010403@redhat.com> Date: Thu, 10 Oct 2013 13:51:45 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH] mm: hugetlb: initialize PG_reserved for tail pages of gigantig compound pages References: <1381421561-10203-1-git-send-email-aarcange@redhat.com> <1381421561-10203-2-git-send-email-aarcange@redhat.com> In-Reply-To: <1381421561-10203-2-git-send-email-aarcange@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: Andrew Morton , qemu-devel@nongnu.org, kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Gleb Natapov , Mel Gorman , Hugh Dickins On 10/10/2013 12:12 PM, Andrea Arcangeli wrote: > 11feeb498086a3a5907b8148bdf1786a9b18fc55 introduced a memory leak when > KVM is run on gigantic compound pages. > > 11feeb498086a3a5907b8148bdf1786a9b18fc55 depends on the assumption > that PG_reserved is identical for all head and tail pages of a > compound page. So that if get_user_pages returns a tail page, we don't > need to check the head page in order to know if we deal with a > reserved page that requires different refcounting. > > The assumption that PG_reserved is the same for head and tail pages is > certainly correct for THP and regular hugepages, but gigantic > hugepages allocated through bootmem don't clear the PG_reserved on the > tail pages (the clearing of PG_reserved is done later only if the > gigantic hugepage is freed). > > This patch corrects the gigantic compound page initialization so that > we can retain the optimization in > 11feeb498086a3a5907b8148bdf1786a9b18fc55. The cacheline was already > modified in order to set PG_tail so this won't affect the boot time of > large memory systems. > > Reported-by: andy123 > Signed-off-by: Andrea Arcangeli Acked-by: Rik van Riel -- 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