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Date: Wed, 19 Sep 2018 14:09:09 -0400
From: Johannes Weiner <hannes@cmpxchg.org>
To: Omar Sandoval <osandov@osandov.com>
Cc: linux-btrfs@vger.kernel.org, kernel-team@fb.com, linux-mm@kvack.org
Subject: Re: [PATCH v7 2/6] mm: export add_swap_extent()
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On Tue, Sep 11, 2018 at 03:34:45PM -0700, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> Btrfs will need this for swap file support.
> 
> Signed-off-by: Omar Sandoval <osandov@fb.com>

That looks reasonable. After reading the last patch, it's somewhat
understandable why you cannot simply implemnet ->bmap and use the
generic activation code. But it would be good to explain the reason(s)
for why you can't here briefly to justify this patch.