From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Sun, 21 Sep 2008 23:56:11 -0700 (PDT) Received: from relay.sgi.com (netops-testserver-3.corp.sgi.com [192.26.57.72]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id m8M6u886022296 for ; Sun, 21 Sep 2008 23:56:08 -0700 Message-ID: <48D743F0.1090101@sgi.com> Date: Mon, 22 Sep 2008 17:06:24 +1000 From: Lachlan McIlroy Reply-To: lachlan@sgi.com MIME-Version: 1.0 Subject: [PATCH] Fix race in xfs_write() between direct and buffered I/O with DMAPI Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: xfs-dev , xfs-oss The iolock is dropped and re-acquired around the call to XFS_SEND_NAMESP(). While the iolock is released the file can become cached. We then 'goto retry' and - if we are doing direct I/O - mapping->nrpages may now be non zero but need_i_mutex will be zero and we will hit the WARN_ON(). Since we have dropped the I/O lock then the file size may have also changed so what we need to do here is 'goto start' like we do for the XFS_SEND_DATA() DMAPI event. We also need to update the filesize before releasing the iolock so that needs to be done before the XFS_SEND_NAMESP event. If we drop the iolock before setting the filesize we could race with a truncate. --- a/fs/xfs/linux-2.6/xfs_lrw.c 2008-09-22 15:47:38.000000000 +1000 +++ b/fs/xfs/linux-2.6/xfs_lrw.c 2008-09-22 15:50:56.000000000 +1000 @@ -707,7 +707,6 @@ start: } } -retry: /* We can write back this queue in page reclaim */ current->backing_dev_info = mapping->backing_dev_info; @@ -763,6 +762,17 @@ retry: if (ret == -EIOCBQUEUED && !(ioflags & IO_ISAIO)) ret = wait_on_sync_kiocb(iocb); + isize = i_size_read(inode); + if (unlikely(ret < 0 && ret != -EFAULT && *offset > isize)) + *offset = isize; + + if (*offset > xip->i_size) { + xfs_ilock(xip, XFS_ILOCK_EXCL); + if (*offset > xip->i_size) + xip->i_size = *offset; + xfs_iunlock(xip, XFS_ILOCK_EXCL); + } + if (ret == -ENOSPC && DM_EVENT_ENABLED(xip, DM_EVENT_NOSPACE) && !(ioflags & IO_INVIS)) { xfs_iunlock(xip, iolock); @@ -776,20 +786,7 @@ retry: xfs_ilock(xip, iolock); if (error) goto out_unlock_internal; - pos = xip->i_size; - ret = 0; - goto retry; - } - - isize = i_size_read(inode); - if (unlikely(ret < 0 && ret != -EFAULT && *offset > isize)) - *offset = isize; - - if (*offset > xip->i_size) { - xfs_ilock(xip, XFS_ILOCK_EXCL); - if (*offset > xip->i_size) - xip->i_size = *offset; - xfs_iunlock(xip, XFS_ILOCK_EXCL); + goto start; } error = -ret;