From mboxrd@z Thu Jan  1 00:00:00 1970
To: 9fans@cse.psu.edu
Subject: Re: [9fans] ide fs patch for the current plan9 version
From: geoff@collyer.net
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Date: Wed, 16 May 2001 15:31:35 -0400
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> To apply the patch, I suggest you create two directories
> ./idefs/port and ./idefs/plan9pc, then run rc idefs.rc on ./idefs and
> bind -bc ./idefs/port /sys/src/fs/port 
> bind -bc ./idefs/plan9pc /sys/src/fs/plan9pc
> 
> after that you can mk in /sys/src/fs/plan9pc.  

You probably ought to "mk clean" before you "mk" in
/sys/src/fs/plan9pc.  We tried this sort of overlaid source tree and
found a couple of hazards: existing object (.8) files in the
underlying tree (/sys/src/fs in this case) can cause trouble if they
are unwritable (e.g., due to lack of permission) or if they are newer
than source files in the overlaying tree (./idefs in this case).

Russ and I didn't quite finish a program called stitch to perform this
sort of overlay dynamically (it worked under light load).  Stitch
changed the semantics of creation slightly so that new files in the
served tree were always created in the uppermost layer, though that
could be easily adjusted.  I also made a small tweak to mk to
understand enough about overlays that it would ignore targets (e.g.,
newer object files) in lower layers for the purpose of computing work
to be done.