From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751191AbdALLgg (ORCPT ); Thu, 12 Jan 2017 06:36:36 -0500 Received: from mail-oi0-f65.google.com ([209.85.218.65]:33767 "EHLO mail-oi0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750777AbdALLgf (ORCPT ); Thu, 12 Jan 2017 06:36:35 -0500 Subject: Re: [Ocfs2-devel] [PATCH 2/2] ocfs2: fix deadlocks when taking inode lock at vfs entry points To: Eric Ren References: <1483630262-22227-1-git-send-email-zren@suse.com> <1483630262-22227-3-git-send-email-zren@suse.com> <2bfda278-6d7f-87c1-a053-8cbb9fb2463e@suse.com> <6450d035-1eec-88a0-57c2-cc3dcc115a46@gmail.com> <1dbd531e-39c3-d352-1052-bdbcb771a2c0@suse.com> <2cc2b35f-9c93-0093-2365-e3fb02d46078@suse.com> <5c114d4b-8d6b-a26c-be05-ea2604f0b37c@gmail.com> <8789b9ff-b951-2569-8e80-2aabd503215d@suse.com> <340218da-57ae-dcdb-2ad3-b934632b0ab9@suse.com> Cc: ocfs2-devel@oss.oracle.com, linux-kernel@vger.kernel.org, Andrew Morton , Joel Becker , Gang He , Junxiao Bi , mfasheh@versity.com From: Joseph Qi Message-ID: <836cc2c3-f00e-adf2-922e-d4d7a8b3286d@gmail.com> Date: Thu, 12 Jan 2017 19:36:27 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0) Gecko/20100101 Thunderbird/45.6.0 MIME-Version: 1.0 In-Reply-To: <340218da-57ae-dcdb-2ad3-b934632b0ab9@suse.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/1/12 19:24, Eric Ren wrote: > Hi Joseph, > > On 01/09/2017 10:13 AM, Eric Ren wrote: >>>>> So you are trying to fix it by making phase3 finish without really >>>>> doing >>>> Phase3 can go ahead because this node is already under protection >>>> of cluster lock. >>> You said it was blocked... >> Oh, sorry, I meant phase3 can go ahead if this patch set is applied;-) >> >>> "Another hand, the recursive cluster lock (the second one) will be >>> blocked in >>> __ocfs2_cluster_lock() because of OCFS2_LOCK_BLOCKED." >>>>> __ocfs2_cluster_lock, then Process B can continue either. >>>>> Let us bear in mind that phase1 and phase3 are in the same context >>>>> and >>>>> executed in order. That's why I think there is no need to check if >>>>> locked >>>>> by myself in phase1. >> Sorry, I still cannot see it. Without keeping track of the first >> cluster lock, how can we >> know if >> we are under a context that has already been in the protecting of >> cluster lock? How can we >> handle >> the recursive locking (the second cluster lock) if we don't have this >> information? >>>>> If phase1 finds it is already locked by myself, that means the holder >>>>> is left by last operation without dec holder. That's why I think >>>>> it is a bug >>>>> instead of a recursive lock case. >> I think I got your point here. Do you mean that we should just add >> the lock holder at the >> first locking position >> without checking before that? Unfortunately, it's tricky here to know >> exactly which ocfs2 >> routine will be the first vfs >> entry point, such as ocfs2_get_acl() which can be both the first vfs >> entry point and the >> second vfs entry point after >> ocfs2_permission(), right? >> >> It will be a coding bug if the problem you concern about happens. I >> think we don't need to >> worry about this much because >> the code logic here is quite simple;-) > Ping... > > Did I clear your doubts by the last email? I really want to get your > point, if not. > > If there's any problem, I will fix them in the next version;-) Yes, but I still worry about the code bug case will be hidden behind recursive lock... Anyway, It depends on others... Thanks, Joseph > > Thanks, > Eric > >> >> Thanks for your patience! >> Eric >> >>>> D >