Re: [PATCH 1/2] make sure data is on disk before calling ->write_inode

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 11 Jan 2010 18:30:47 +0100
Christoph Hellwig <hch@lst.de> wrote:

> --- linux-2.6.orig/fs/fs-writeback.c	2010-01-11 15:53:15.462272627 +0100
> +++ linux-2.6/fs/fs-writeback.c	2010-01-11 15:54:09.662006283 +0100
> @@ -461,15 +461,20 @@ writeback_single_inode(struct inode *ino
>  
>  	ret = do_writepages(mapping, wbc);
>  
> -	/* Don't write the inode if only I_DIRTY_PAGES was set */
> -	if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
> -		int err = write_inode(inode, wait);
> +	/*
> +	 * Make sure to wait on the data before writing out the metadata.
> +	 * This is important for filesystems that modify metadata on data
> +	 * I/O completion.
> +	 */
> +	if (wait) {
> +		int err = filemap_fdatawait(mapping);
>  		if (ret == 0)
>  			ret = err;
>  	}
>  
> -	if (wait) {
> -		int err = filemap_fdatawait(mapping);
> +	/* Don't write the inode if only I_DIRTY_PAGES was set */
> +	if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
> +		int err = write_inode(inode, wait);
>  		if (ret == 0)
>  			ret = err;
>  	}

hm, yeah, it's hard to see how this reordering can harm throughput much.

nfs_write_inode() has vanished in linux-enxt so I just dropped all the
nfs parts of these two patches.  You might want to check that.