From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay2.corp.sgi.com [137.38.102.29]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id q6KDM1xb118787 for ; Fri, 20 Jul 2012 08:22:01 -0500 Message-ID: <50095B77.7090203@sgi.com> Date: Fri, 20 Jul 2012 08:21:59 -0500 From: Mark Tinguely MIME-Version: 1.0 Subject: Re: [RFC] xfs: wait for the write of the superblock on unmount References: <20120717215957.855744999@tinguelysgi.com> <20120718220003.396849822@tinguelysgi.com> <20120719015809.GC23387@dastard> In-Reply-To: <20120719015809.GC23387@dastard> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Dave Chinner Cc: xfs@oss.sgi.com On 07/18/12 20:58, Dave Chinner wrote: > On Wed, Jul 18, 2012 at 12:33:58PM -0500, tinguely@sgi.com wrote: >> Sorry, I have been distracted away from this regression. This was previously >> titled "xfs: synchronously write the superblock on unmount". >> >> xfs_wait_buftarg() does not wait for the completion of the write of the >> uncached superblock. This write can race with the shutdown of the log and >> causes a panic if the write does not win the race. >> >> The log write of the superblock is important for possible recovery, but a >> second syncronous write of the same superblock seems redundant. Would just >> waiting for the iodone() of the log write before tearing down the log be >> enough? > > Yes. i.e. something like: > > /* > * The superblock buffer is uncached, so xfs_wait_buftarg() > * will not wait for it. Hence we need to explicitly wait > * for IO completion on the superblock to occur here. > */ > error = xfs_buf_iowait(mp->m_sb_bp); > if (error) > AAAAIEEEE! > > This fix is also needed in xfs_quiesce_attr() for the freeze and > ro,remount cases as well. > > Cheers, > > Dave. > Thanks for the feedback. I chose the ugly lock to block on the superblock buffer because it has XBF_ASYNC set at that point and won't go through the complete() patch. I will look at turning the XBF_ASYNC flag off and wait on a xfs_buf_iowait(). --Mark. _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs