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Date:   Fri, 4 Nov 2022 00:30:51 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     David Howells <dhowells@redhat.com>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Matthew Wilcox <willy@infradead.org>,
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        "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>,
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        "Darrick J . Wong" <djwong@kernel.org>,
        Aravinda Herle <araherle@in.ibm.com>
Subject: Re: [RFC 2/2] iomap: Support subpage size dirty tracking to improve
 write performance
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On Thu, Nov 03, 2022 at 02:51:10PM +0000, David Howells wrote:
> > > filesystems right now.  Dave Howells' netfs infrastructure is trying
> > > to solve the problem for everyone (and he's been looking at iomap as
> > > inspiration for what he's doing).
> > 
> > Btw, I never understod why the network file systems don't just use
> > iomap.  There is nothing block specific in the core iomap code.
> 
> It calls creates and submits bio structs all over the place.  This seems to
> require a blockdev.

The core iomap code (fs/iomap/iter.c) does not.  Most users of it
are block device centric right now, but for example the dax.c uses
iomap for byte level DAX accesses without ever looking at a bdev,
and seek.c and fiemap.c do not make any assumptions on the backend
implementation.