Date: Wed, 22 Jan 2014 00:24:14 -0800
From: Christoph Hellwig <hch@infradead.org>
To: Jeff Layton <jlayton@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>, Trond.Myklebust@netapp.com,
        linux-nfs@vger.kernel.org
Subject: Re: [PATCH 7/7] nfs: page cache invalidation for dio
Message-ID: <20140122082414.GA12530@infradead.org>
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 <20131115095241.2c5e1cfb@tlielax.poochiereds.net>
 <20131115150204.GA8105@infradead.org>
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On Tue, Jan 21, 2014 at 02:21:59PM -0500, Jeff Layton wrote:
> In any case, this helps but it's a little odd. With this patch, you add
> an invalidate_inode_pages2 call prior to doing the DIO. But, you've
> also left in the call to nfs_zap_mapping in the completion codepath.
> 
> So now, we shoot down the mapping prior to doing a DIO write, and then
> mark the mapping for invalidation again when the write completes. Was
> that intentional?
> 
> It seems a little excessive and might hurt performance in some cases.
> OTOH, if you mix buffered and DIO you're asking for trouble anyway and
> this approach seems to give better cache coherency.

Thile follows the model implemented and documented in
generic_file_direct_write().