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From: Kent Overstreet <kent.overstreet@linux.dev>
To: Dave Chinner <david@fromorbit.com>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>,
	Matthew Wilcox <willy@infradead.org>,
	Christoph Hellwig <hch@infradead.org>, ksummit@lists.linux.dev,
	linux-fsdevel@vger.kernel.org
Subject: Re: [MAINTAINERS/KERNEL SUMMIT] Trust and maintenance of file systems
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On Mon, Sep 11, 2023 at 11:05:09AM +1000, Dave Chinner wrote:
> On Sat, Sep 09, 2023 at 06:42:30PM -0400, Kent Overstreet wrote:
> > On Sat, Sep 09, 2023 at 08:50:39AM -0400, James Bottomley wrote:
> > > So why can't we figure out that easier way? What's wrong with trying to
> > > figure out if we can do some sort of helper or library set that assists
> > > supporting and porting older filesystems. If we can do that it will not
> > > only make the job of an old fs maintainer a lot easier, but it might
> > > just provide the stepping stones we need to encourage more people climb
> > > up into the modern VFS world.
> > 
> > What if we could run our existing filesystem code in userspace?
> 
> You mean like lklfuse already enables?

I'm not seeing that it does?

I just had a look at the code, and I don't see anything there related to
the VFS - AFAIK, a VFS -> fuse layer doesn't exist yet.

And that looks a lot heavier than what we'd ideally want, i.e. a _lot_
more kernel code would be getting pulled in. The entire block layer,
probably the scheduler as well.

What I've got in bcachefs-tools is a much thinner mapping from e.g.
kthreads -> pthreads, block layer -> aio, etc.