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Date:   Mon, 14 Jan 2019 17:50:23 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Carlos Maiolino <cmaiolino@redhat.com>
Cc:     Andreas =?iso-8859-1?Q?Gr=FCnbacher?= 
        <andreas.gruenbacher@gmail.com>, Christoph Hellwig <hch@lst.de>,
        Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
        Andreas Dilger <adilger@dilger.ca>, sandeen@redhat.com,
        Dave Chinner <david@fromorbit.com>
Subject: Re: [PATCH 00/10 V2] New ->fiemap infrastructure and ->bmap removal
Message-ID: <20190114165023.GB7187@lst.de>
References: <20181205091728.29903-1-cmaiolino@redhat.com> <CAHpGcM+9ZwsDBRgJYpqwg3_aw5o71T3ARF6JqJG0ziRWQKA-_A@mail.gmail.com> <20181207093429.t3zzkxmfc4wlt5ny@hades.usersys.redhat.com>
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On Fri, Dec 07, 2018 at 10:34:29AM +0100, Carlos Maiolino wrote:
> On Thu, Dec 06, 2018 at 07:56:02PM +0100, Andreas Grünbacher wrote:
> > Hi,
> > 
> > Am Mi., 5. Dez. 2018 um 10:18 Uhr schrieb Carlos Maiolino
> > <cmaiolino@redhat.com>:
> > > This is the second version of the complete series with the goal to remove ->bmap
> > > interface completely, in lieu of FIEMAP.
> > 
> > I'm not thrilled by this approach. How about exposing the iomap
> > operations at the vfs layer (for example, in the super block) and
> > implementing bmap on top of that instead?
> > 
> 
> Well, the idea is exactly to get rid of bmap, not reimplement it. We can use the
> same operation for both cases (fiemap+fibmap), so I honestly don't see which
> advantages would be by reimplementing it.

Exactly.  iomap really is a possibly implementation.  Everytime we
exposed implementation details at the ops level that created horrible
abuses.  The most important still relevant example is
write_begin/write_end, which require fs specific locking but are
exposed in a way where we can't easily enforce that.