From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from szxga05-in.huawei.com ([45.249.212.191]:11525 "EHLO szxga05-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750811AbdLHEEU (ORCPT ); Thu, 7 Dec 2017 23:04:20 -0500 Message-ID: <5A2A0F11.2090908@huawei.com> Date: Fri, 8 Dec 2017 12:03:29 +0800 From: alex chen MIME-Version: 1.0 To: Ben Hutchings CC: Greg Kroah-Hartman , piaojun , Joseph Qi , "stable@vger.kernel.org" , Changwei Ge , Mark Fasheh , Joel Becker , Junxiao Bi , Andrew Morton , Linus Torvalds , LKML Subject: Re: [PATCH 4.4 13/16] ocfs2: should wait dio before inode lock in ocfs2_setattr() References: <20171122101110.784746358@linuxfoundation.org> <20171122101111.411869812@linuxfoundation.org> <1512488994.18523.173.camel@codethink.co.uk> <5A2741B2.4040509@huawei.com> <1512671158.18523.187.camel@codethink.co.uk> <5A29DF39.9080305@huawei.com> <1512699985.18523.219.camel@codethink.co.uk> In-Reply-To: <1512699985.18523.219.camel@codethink.co.uk> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org List-ID: On 2017/12/8 10:26, Ben Hutchings wrote: > On Fri, 2017-12-08 at 08:39 +0800, alex chen wrote: >> >> On 2017/12/8 2:25, Ben Hutchings wrote: >>> On Wed, 2017-12-06 at 09:02 +0800, alex chen wrote: >>>> Hi Ben, >>>> >>>> Thanks for your reply. >>>> >>>> On 2017/12/5 23:49, Ben Hutchings wrote: >>>>> On Wed, 2017-11-22 at 11:12 +0100, Greg Kroah-Hartman wrote: >>>>>> 4.4-stable review patch. If anyone has any objections, >>>>>> please let me know. >>>>>> >>>>>> ------------------ >>>>>> >>>>>> From: alex chen >>>>>> >>>>>> commit 28f5a8a7c033cbf3e32277f4cc9c6afd74f05300 upstream. >>>>>> >>>>>> we should wait dio requests to finish before inode lock in >>>>>> ocfs2_setattr(), otherwise the following deadlock will >>>>>> happen: >>>>> >>>>> [...] >>>>> >>>>> I looked at the kernel-doc for inode_dio_wait(): >>>>> >>>>> /** >>>>> * inode_dio_wait - wait for outstanding DIO requests to finish >>>>> * @inode: inode to wait for >>>>> * >>>>> * Waits for all pending direct I/O requests to finish so that we can >>>>> * proceed with a truncate or equivalent operation. >>>>> * >>>>> * Must be called under a lock that serializes taking new references >>>>> * to i_dio_count, usually by inode->i_mutex. >>>>> */ >>>>> >>>>> Now that ocfs2_setattr() calls this outside of the inode locked region, >>>>> what prevents another task adding a new dio request immediately >>>>> afterward? >>>>> >>>> >>>> In the kernel 4.6, firstly, we use the inode_lock() in do_truncate() to >>>> prevent another bio to be issued from this node. >>> >>> [...] >>> >>> Yes but there seems to be a race condition - after the call to >>> inode_dio_wait() and before the call to inode_lock(), another dio >>> request can be added. > > Sorry, I've been mixing up inode_lock() and ocfs2_inode_lock(). > However: > >> In the truncating file situation, the lock order is as follow: >> do_truncate() >> inode_lock() >> notify_change() >> ocfs2_setattr() >> inode_dio_wait() >> --here it is under the protect of inode_lock(), so another dio requests >> from another process will not be added. > > only DIO reads seem to take the inode lock. > I do not clearly understand what you mean. The inode_lock() will be called in ocfs2_file_write_iter(). You mean only DIO writes seem to take the inode_lock()? BTW, in this patch, I just adjusted the inode_dio_wait() to the front of the ocfs2_rw_lock() and didn't adjust the order of inode_lock() and inode_dio_wait(). Thanks, Alex > Ben. > >> ocfs2_rw_lock() >> ocfs2_inode_lock_tracker() >> this function is used to prevent the inode from being modified by another >> nodes in the cluster >> inode_unlock() >> >>> >>> Ben. >>> >> >>