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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Wed, 11 Mar 2020 10:07:38 -0700
Message-ID: <CAPcyv4jk5i0hPpqbZNPhUH8wKPS66pd48xNoPnQpy6vt72+i=w@mail.gmail.com>
Subject: Re: [PATCH V5 00/12] Enable per-file/per-directory DAX operations V5
To:     Christoph Hellwig <hch@lst.de>
Cc:     Dave Chinner <david@fromorbit.com>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        "Theodore Y. Ts'o" <tytso@mit.edu>, Jan Kara <jack@suse.cz>,
        linux-ext4 <linux-ext4@vger.kernel.org>,
        linux-xfs <linux-xfs@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
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On Tue, Mar 10, 2020 at 11:44 PM Christoph Hellwig <hch@lst.de> wrote:
>
> On Wed, Mar 11, 2020 at 05:39:42PM +1100, Dave Chinner wrote:
> > IOWs, the dax_associate_page() related functionality probably needs
> > to be a filesystem callout - part of the aops vector, I think, so
> > that device dax can still use it. That way XFS can go it's own way,
> > while ext4 and device dax can continue to use the existing mechanism
> > mechanisn that is currently implemented....
>
> s/XFS/XFS with rmap/, as most XFS file systems currently don't have
> that enabled we'll also need to keep the legacy path around.

Agree, it needs to be an opt-in capability as ext4 and xfs w/o rmap
will stay on the legacy path for the foreseeable future.