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Date: Tue, 26 Sep 2017 08:32:34 +0200
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 3/7] xfs: protect S_DAX transitions in XFS read path
Message-ID: <20170926063234.GA6870@lst.de>
References: <20170925231404.32723-1-ross.zwisler@linux.intel.com> <20170925231404.32723-4-ross.zwisler@linux.intel.com>
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To: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org, "Darrick J. Wong" <darrick.wong@oracle.com>, "J. Bruce Fields" <bfields@fieldses.org>, Christoph Hellwig <hch@lst.de>, Dan Williams <dan.j.williams@intel.com>, Dave Chinner <david@fromorbit.com>, Jan Kara <jack@suse.cz>, Jeff Layton <jlayton@poochiereds.net>, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org, linux-xfs@vger.kernel.org

We can't just take locking one level up, as we need differnet locking
for different kinds of I/O.

I think you probably want an IOCB_DAX flag to check IS_DAX once and
then stick to it, similar to what we do for direct I/O.