[Ocfs2-devel] [PATCH 2/2] Ocfs2: Handle O_DIRECT writes with coherency option.

[Joel Becker]

On Sat, Oct 09, 2010 at 07:26:42PM +0800, Tristan Ye wrote:
> -	/* concurrent O_DIRECT writes are allowed */
> -	rw_level = !direct_io;
> +	/* 
> +	 * concurrent O_DIRECT writes are allowed with
> +	 * mount_option "coherency=buffered".
> +	 */
> +	if (direct_io) {
> +		rw_level = !(osb->s_mount_opt & OCFS2_MOUNT_COHERENCY_BUFFERED);
> +	} else
> +		rw_level = !direct_io;
> +

	I think I'd like:

	if (direct_io && (osb->s_mount_opt & OCFS2_MOUNT_COHERENCY_BUFFERED))
		rw_level = 0;
	else
		rw_level = 1;

It actually matches your comment much better.  But since we're going to
be using it again later, perhaps you should set 'int full_coherency =
(osb->s_mount_opt & OCFS2_MOUNT_COHERENCY_BUFFERED)' up at the top of
the function and then do:

	rw_level = (!direct_io || full_coherency)

>  	ret = ocfs2_rw_lock(inode, rw_level);
>  	if (ret < 0) {
>  		mlog_errno(ret);
>  		goto out_sems;
>  	}
>  
> +	/*
> +	 * O_DIRECT writes with "coherency=full" need to take EX cluster
> +	 * inode_lock to guarantee coherency.
> +	 */
> +	if ((direct_io) &&
> +	    !(osb->s_mount_opt & OCFS2_MOUNT_COHERENCY_BUFFERED)) {

	Then this check can be:

	if (direct_io && full_coherency) {
		/*
		 * We need to take and drop the inode lock to force
		 * other nodes to drop their caches.  Buffered I/O
		 * already does this in write_begin().
		 */

> +		ret = ocfs2_inode_lock(inode, NULL, 1);
> +		if (ret < 0) {
> +			mlog_errno(ret);
> +			goto out_sems;
> +		}
> +		
> +		/*
> +		 * Safe to drop the inode_lock immediately since we're just
> +		 * telling other nodes to flush their cache.
> +		 */

	And you don't need this comment.

> +		ocfs2_inode_unlock(inode, 1);
> +	}

-- 

"The lawgiver, of all beings, most owes the law allegiance.  He of all
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Joel Becker
Consulting Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127