linux-kernel - Re: [PATCH v2 2/9] ext2: tell DAX the size of allocation holes

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Message-ID: <20160829125741.cdnbb2uaditcmnw2@thunk.org>
Date:   Mon, 29 Aug 2016 08:57:41 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Ross Zwisler <ross.zwisler@...ux.intel.com>,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-nvdimm@...1.01.org, Matthew Wilcox <mawilcox@...rosoft.com>,
        Dave Chinner <david@...morbit.com>, linux-mm@...ck.org,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Jan Kara <jack@...e.com>, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org
Subject: Re: [PATCH v2 2/9] ext2: tell DAX the size of allocation holes

On Mon, Aug 29, 2016 at 12:41:16AM -0700, Christoph Hellwig wrote:
> 
> We're going to move forward killing buffer_heads in XFS.  I think ext4
> would dramatically benefit from this a well, as would ext2 (although I
> think all that DAX work in ext2 is a horrible idea to start with).

It's been on my todo list.  The only reason why I haven't done it yet
is because I knew you were working on a solution, and I didn't want to
do things one way for buffered I/O, and a different way for Direct
I/O, and disentangling the DIO code and the different assumptions of
how different file systems interact with the DIO code is a *mess*.

It may have gotten better more recently, but a few years ago I took a
look at it and backed slowly away.....

						- Ted