From: Lachlan McIlroy Date: Wed, 24 Dec 2008 03:07:32 +0000 (+1100) Subject: [XFS] Fix race in xfs_write() between direct and buffered I/O with DMAPI X-Git-Tag: v2.6.29-rc1~552^2~1 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=25051158bbed127e8672b43396c71c5eb610e5f1;p=linux-2.6-omap-h63xx.git [XFS] Fix race in xfs_write() between direct and buffered I/O with DMAPI 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. Reviewed-by: Christoph Hellwig Signed-off-by: Lachlan McIlroy --- diff --git a/fs/xfs/linux-2.6/xfs_lrw.c b/fs/xfs/linux-2.6/xfs_lrw.c index 92ce34b3787..7e90daa0d1d 100644 --- a/fs/xfs/linux-2.6/xfs_lrw.c +++ b/fs/xfs/linux-2.6/xfs_lrw.c @@ -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;