Re: [PATCH 6/7] xfs: propagate issue-flush error code

Dave Chinner
2009-03-31T23:42:24Z

On Mon, Mar 30, 2009 at 09:33:14PM +0900, Fernando Luis Vázquez Cao wrote:
> blkdev_issue_flush() may fail (i.e. due to media error on FLUSH CACHE
> command execution) so its users should check for the return value.
>
> (This issues was first spotted Bartlomiej Zolnierkiewicz)
>
> Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
> Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>

I think this patch is unnecessary as well as being broken.

> diff -urNp linux-2.6.29-orig/fs/xfs/xfs_vnodeops.c linux-2.6.29/fs/xfs/xfs_vnodeops.c
> --- linux-2.6.29-orig/fs/xfs/xfs_vnodeops.c 2009-03-24 08:12:14.000000000 +0900
> +++ linux-2.6.29/fs/xfs/xfs_vnodeops.c 2009-03-30 15:08:21.000000000 +0900
> @@ -678,20 +678,20 @@ xfs_fsync(
> xfs_iunlock(ip, XFS_ILOCK_EXCL);
> }
>
> - if ((ip->i_mount->m_flags & XFS_MOUNT_BARRIER) && changed) {
> + if (!error && (ip->i_mount->m_flags & XFS_MOUNT_BARRIER) && changed) {

That is wrong. Even if there was a error, we still need to
flush the device if it hasn't already been done.

> /*
> * If the log write didn't issue an ordered tag we need
> * to flush the disk cache for the data device now.
> */
> if (!log_flushed)
> - xfs_blkdev_issue_flush(ip->i_mount->m_ddev_targp);
> + error = xfs_blkdev_issue_flush(ip->i_mount->m_ddev_targp);

What happens if we get an EOPNOTSUPP here?
That is a meaningless error to return to fsync()....

> /*
> * If this inode is on the RT dev we need to flush that
> * cache as well.
> */
> - if (XFS_IS_REALTIME_INODE(ip))
> - xfs_blkdev_issue_flush(ip->i_mount->m_rtdev_targp);
> + if (!error && XFS_IS_REALTIME_INODE(ip))
> + error = xfs_blkdev_issue_flush(ip->i_mount->m_rtdev_targp);

That is broken, too. The realtime device is a different device,
so always should be flushed regardless of the return from the
log device.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com