u-codalist-z149_at_aetey.se writes:

>> Moving to FUSE would be a much better approach if you want to get rid of
>> kernel complexity. Patches are welcome.
>
> That would be more portable, sure, but I expect that we'd lose performance.
> I appreciate that the current implementation offers very high efficiency
> for read()/write()/seek().

Well, it's very efficient on Linux and NetBSD, and it has zero
efficiency on many other platforms!!

But seriously, in 2010+ all other serious distributed filesystems except
NFS seem to be "FUSE first".   A particular case in point is GlusterFS.
Someone in NetBSD has been getting Gluster ported to NetBSD, and has
reported file read rates over the network (GbE) from remote servers at a
substantial fraction (60%?  more?) of the GbE rate, on a
normal-but-fairly-high-end amd64 box.

So I don't think the performance issues are really that big a deal any
more.