From owner-freebsd-hackers@FreeBSD.ORG  Mon Jun 13 18:58:23 2005
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Date: Mon, 13 Jun 2005 12:55:40 -0600
From: Scott Long <scottl@samsco.org>
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To: Christoph Hellwig <hch@infradead.org>
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Cc: Daniel Eischen <deischen@freebsd.org>, freebsd-hackers@freebsd.org,
	Julian Elischer <julian@elischer.org>, Apache Xie <apachexm@hotmail.com>
Subject: Re: contigmalloc() and mmap()
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Christoph Hellwig wrote:

> On Mon, Jun 13, 2005 at 12:37:07PM -0600, Scott Long wrote:
> 
>>How does linux handle the implications of fork(2) in this scenario?
> 
> 
> it's still counted as the same instance.  Similar for dup or passing
> descriptors over AF_UNIX sockets. The data is explictly not per-process
> but per instance.
> 
> There's not a lot of users actually using this feature, only the tty
> subsystem and multi-channel sound drivers for the old oss API that
> allowed multiple opens of /dev/dsp that way come to mind.
> 
> Lot's of driver use file->private to get at per-device data easily,
> but that's just a shortcut.

Ok, I thought that you were talking about per-process data being in the
file descriptor.

Scott