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

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Message-ID: <20090331233718.GT26138@disturbed>
Date:	Wed, 1 Apr 2009 10:37:18 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Fernando Luis Vázquez Cao 
	<fernando@....ntt.co.jp>
Cc:	Jeff Garzik <jeff@...zik.org>,
	Christoph Hellwig <hch@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Theodore Tso <tytso@....edu>, Ingo Molnar <mingo@...e.hu>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arjan van de Ven <arjan@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Nick Piggin <npiggin@...e.de>, David Rees <drees76@...il.com>,
	Jesper Krogh <jesper@...gh.cc>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	chris.mason@...cle.com, tj@...nel.org, bzolnier@...il.com
Subject: Re: [PATCH 6/7] xfs: propagate issue-flush error code

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@...il.com>
> Signed-off-by: Fernando Luis Vazquez Cao <fernando@....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@...morbit.com
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