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Date:      Sat, 30 May 1998 13:11:29 +0800
From:      Peter Wemm <peter@netplex.com.au>
To:        "Jordan K. Hubbard" <jkh@time.cdrom.com>
Cc:        Eivind Eklund <eivind@yes.no>, current@FreeBSD.ORG
Subject:   Re: I see one major problem with DEVFS... 
Message-ID:  <199805300511.NAA20017@spinner.netplex.com.au>
In-Reply-To: Your message of "Fri, 29 May 1998 20:52:01 MST." <17374.896500321@time.cdrom.com> 

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"Jordan K. Hubbard" wrote:
> > > E.g. I can shoot my foot off, but I can't sew it back on. :-)
> > 
> > Yes, you can.  You can mount another devfs and 'mv' a device from it
> > (or at least that's the way the specs read - I don't have devfs
> > enabled right now, so I can't test).
> 
> That's utterly rude. :-)
> 
> I hope you're not implying that this is going to be the accepted way
> for doing this in the future as well.  Non-persistence is a big enough
> violation of POLA as it is, and not even being able to do mknod(2)
> operations on a devfs to replace missing entries would be a POLA
> catastrophe.

Remember this is merely step 1.  The Plan is to eventually replace minor/
major devices completely so that the filesystem interface will probably be 
through a 32 bit vnode pointer or something along those lines.  Doing a 
mknod will be practically impossible.  (This has some major benefits but 
will be a major change in the driver/kernel/fs interface.  Drivers won't 
have a major/minor number anymore, they'll just have a unit number..  
specfs will either be gone or won't resemble anything like it does now, 
and will probably hang off devfs instead.

For the problem at hand though, I once suggested to Julian that we use
undelete(2) to make files come back.  "rm -W bpf4" could almost work as is,
except that it wants to stat the file and look for whiteout flags first and
'rm' doesn't create a whiteout in devfs.  (This might be an interesting 
approach to the problem if all unlinks caused a whiteout instead of the 
node disappearing entirely.)

> - Jordan
> 
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> 

Cheers,
-Peter
--
Peter Wemm <peter@netplex.com.au>   Netplex Consulting



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