Re: [9fans] rio snarf

["Fco. J. Ballesteros" <nemo@lsub.org>]

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Well, having a /dev/snarf created by, say,
binding /tmp/blah to /dev/snarf
does not seem to work, because rio ends up
leaving the biggest thing that was in there
(because it does not truncate the file).

I think it assumes that the behaviour of /dev/snarf is that
of rio's, and not that of a regular file.

Regarding the question, I think you answered it. I understand it
provides a snarf if you have different per-rio snarf files.

thanks

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From: Russ Cox <russcox@gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu>
Subject: Re: [9fans] rio snarf
Date: Wed, 27 Oct 2004 13:51:10 -0400
Message-ID: <ee9e417a04102710516945fe9e@mail.gmail.com>

> Well. We just found that removing snarf from rio fsys makes things
> work great wrt sharing the snarf buffer across machines.

If that's all you want to do, just create a /dev/snarf 
before rio runs -- if it sees one already there, it won't
provide one.

> At first, we thought that if was enough to call open(OTRUNC) while
> copying to the snarf buffer, then we noticed the deadlock with the
> open("/dev/snarf") in rio, then we tried removing snarf from rio, and,
> voila.

This I still don't fully understand.  The reason the snarf buffer doesn't
change until close is probably lost to history, but one nice effect
is that updating the snarf buffer is atomic -- you'll never see a 
partially written one.

> Either I'm crazy because of the lots of coffee I have been drinking, or
> there is something I'm missing regarding why rio has snarf builtin instead
> of using a regular file for that.

Rio used to provide a separate snarf buffer for each instance of rio.
It's only recently that there has been this push toward having one
snarf buffer for the whole system.

Russ