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Date: Wed, 2 Nov 2016 07:30:06 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Jan Kara <jack@suse.cz>
Cc: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        Dave Chinner <david@fromorbit.com>, Ted Tso <tytso@mit.edu>,
        linux-nvdimm@ml01.01.org
Subject: Re: [PATCH 08/11] ext4: Convert DAX faults to iomap infrastructure
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On Tue, Nov 01, 2016 at 10:06:18PM +0100, Jan Kara wrote:
> Convert DAX faults to use iomap infrastructure. We would not have to start
> transaction in ext4_dax_fault() anymore since ext4_iomap_begin takes
> care of that but so far we do that to avoid lock inversion of
> transaction start with DAX entry lock which gets acquired in
> dax_iomap_fault() before calling ->iomap_begin handler.

So far I've tried to avoid the need to avoid having multiple iomap_ops
for the same fs.  Would you be fine with a new IOMAP_FAULT flag for write
faults?