From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1162479Ab3DESmT (ORCPT ); Fri, 5 Apr 2013 14:42:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:4053 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1162434Ab3DESmS (ORCPT ); Fri, 5 Apr 2013 14:42:18 -0400 Date: Fri, 05 Apr 2013 14:40:35 -0400 From: Naoya Horiguchi To: KOSAKI Motohiro Cc: Andrew Morton , Mel Gorman , Hugh Dickins , Rik van Riel , KOSAKI Motohiro , Konstantin Khlebnikov , Michal Hocko , HATAYAMA Daisuke , linux-mm@kvack.org, linux-kernel@vger.kernel.org Message-ID: <1365187235-chwg4d0m-mutt-n-horiguchi@ah.jp.nec.com> In-Reply-To: <515F18A8.7030102@gmail.com> References: <1365014138-19589-1-git-send-email-n-horiguchi@ah.jp.nec.com> <1365014138-19589-2-git-send-email-n-horiguchi@ah.jp.nec.com> <515F18A8.7030102@gmail.com> Subject: Re: [PATCH v3 1/3] hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB) Mime-Version: 1.0 Content-Type: text/plain; charset=iso-2022-jp Content-Transfer-Encoding: 7bit Content-Disposition: inline X-Mutt-References: <515F18A8.7030102@gmail.com> X-Mutt-Fcc: ~/Maildir/sent/ User-Agent: Mutt 1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 05, 2013 at 02:32:08PM -0400, KOSAKI Motohiro wrote: > (4/3/13 2:35 PM), Naoya Horiguchi wrote: > > Currently we fail to include any data on hugepages into coredump, > > because VM_DONTDUMP is set on hugetlbfs's vma. This behavior was recently > > introduced by commit 314e51b98 "mm: kill vma flag VM_RESERVED and > > mm->reserved_vm counter". This looks to me a serious regression, > > so let's fix it. > > I don't think this is enough explanations. Let's explain the code meaning > time to time order. > > First, we had no madvice(DONTDUMP) nor coredump_filter(HUGETLB). then hugetlb > pages were never dumped. > > Second, I added coredump_filter(HUGETLB). and then vm_dump_size became.. > > vm_dump_size() > { > /* Hugetlb memory check */ > if (vma->vm_flags & VM_HUGETLB) { > .. > goto whole; > } > if (vma->vm_flags & VM_RESERVED) > return 0; > > The point is, hugetlb was checked before VM_RESERVED. i.e. hugetlb core dump ignored > VM_RESERVED. At this time, "if (vma->vm_flags & VM_HUGETLB)" statement don't need > return 0 because VM_RESERVED prevented to go into the subsequent flag checks. > > Third, Jason added madvise(DONTDUMP). then vm_dump_size became... > > vm_dump_size() > { > if (vma->vm_flags & VM_NODUMP) > return 0; > > /* Hugetlb memory check */ > if (vma->vm_flags & VM_HUGETLB) { > .. > goto whole; > } > if (vma->vm_flags & VM_RESERVED) > return 0; > > Look, VM_NODUMP and VM_RESERVED had similar and different meanings at this time. > > Finally, Konstantin removed VM_RESERVED and hugetlb coredump behavior > has been changed. Things were/are quite complicated, and this is a wonderful step-by-step explanation. Thank you very much. Naoya > Thus, patch [1/3] and [2/3] should be marked [stable for v3.6 or later]. > > Anyway, this patch is correct. Thank you! > > Acked-by: KOSAKI Motohiro