From owner-freebsd-hackers@FreeBSD.ORG  Mon Jun 13 18:39:43 2005
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Date: Mon, 13 Jun 2005 12:37:07 -0600
From: Scott Long <scottl@samsco.org>
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To: Christoph Hellwig <hch@infradead.org>
References: <Pine.GSO.4.43.0506131332380.23852-100000@sea.ntplx.net>	<42ADC762.6010801@elischer.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 10:50:26AM -0700, Julian Elischer wrote:
> 
>>Several times in the past we've seen people complainign that Linux 
>>allows a device driver to know
>>who called it and somehow it seems to store somewhere some information 
>>about who
>>openned the device.. thos somehow allows linux to store an arbitrary 
>>structure
>>for each openning process.  I thin from the sond of it that he wants to 
>>do something
>>similar. From the sond of it he wants to have a different buffer be used 
>>depending on
>>who is calling. This would partly work but would not work when processes 
>>fork etc.
>>
>>I think Linux must do some extra housekeeping in this case.
> 
> 
> What Linux does is pretty simple.  The driver has access to the file
> structure, and this structure has a field for driver private data.
> It can store private data in open and free it again in the release
> callback.
> 

How does linux handle the implications of fork(2) in this scenario?

Scott