[PATCH] xfs: remove incorrect log write optimization

[Alex Elder]

On Mon, 2010-06-28 at 10:34 -0400, Christoph Hellwig wrote:
> We do need a barrier for the first buffer of a split log write.  Otherwise
> we might incorrectly stamp the tail LSN into transactions in the first
> block, or not flush data I/O before updating the inode size.

I'm not sure whether "first block" means the one at the beginning
of the log, or the one at the beginning of a split log write.  In
any case recovery handles the situation correctly if the write at
the end of the log didn't make it to disk before the start of the
log.  I think you're right about ordering with respect to data I/O
though.

This looks good to me.

Reviewed-by: Alex Elder <aelder at sgi.com>

> Signed-off-by: Christoph Hellwig <hch at lst.de>
> 
> Index: xfs-dev/fs/xfs/xfs_log.c
> ===================================================================
> --- xfs-dev.orig/fs/xfs/xfs_log.c	2010-06-28 11:51:30.423004228 +0200
> +++ xfs-dev/fs/xfs/xfs_log.c	2010-06-28 11:52:52.559255519 +0200
> @@ -1423,11 +1423,8 @@ xlog_sync(xlog_t		*log,
>  	XFS_BUF_BUSY(bp);
>  	XFS_BUF_ASYNC(bp);
>  	bp->b_flags |= XBF_LOG_BUFFER;
> -	/*
> -	 * Do an ordered write for the log block.
> -	 * Its unnecessary to flush the first split block in the log wrap case.
> -	 */
> -	if (!split && (log->l_mp->m_flags & XFS_MOUNT_BARRIER))
> +
> +	if (log->l_mp->m_flags & XFS_MOUNT_BARRIER)
>  		XFS_BUF_ORDERED(bp);
>  
>  	ASSERT(XFS_BUF_ADDR(bp) <= log->l_logBBsize-1);
> 
> _______________________________________________
> xfs mailing list
> xfs at oss.sgi.com
> http://oss.sgi.com/mailman/listinfo/xfs