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Subject: Re: [ckrm-tech] [PATCH 0/5] Allow more than PAGESIZE data read in
	configfs
From: Matt Helsley <matthltc@us.ibm.com>
To: Greg KH <greg@kroah.com>
Cc: Chandra Seetharaman <sekharan@us.ibm.com>, Paul Menage <menage@google.com>,
       linux-kernel@vger.kernel.org, ckrm-tech@lists.sourceforge.net
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Organization: IBM Linux Technology Center
Date: Fri, 13 Oct 2006 16:40:08 -0700
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On Thu, 2006-10-12 at 16:51 -0700, Greg KH wrote:

<snip>

> > BTW, it it not just CKRM/RG, Paul Menage as recently extracted the
> > processes aggregation from cpuset to have an independent infrastructure
> > (http://marc.theaimsgroup.com/?l=ckrm-tech&m=116006307018720&w=2), which
> > has its own file system. I was advocating him to use configfs. But, he
> > also has this issue/limitation. 
> 
> That's one reason it is so easy to just write your own filesystem then.
> What is it these days, less than 200 lines of code?  I bet you can even

For my_school_project_fs perhaps 200 lines is sufficient.

Paul Menage's patch which Chandra was referring to:

http://lkml.org/lkml/2006/9/28/104

is 1700 insertions. RCFS was around 1500 lines -- similar to Paul's
patch -- before we moved to configfs and reduced that to about 300-400
lines. This suggests we'd need around 1500 lines of filesystem code --
7.5 times your estimate.

> condence more things to make it 100 lines if you really try.  That seems
> much more sane than trying to bend configfs into something different.

	I don't agree. I think it's insane not to use configfs just because we
need a list of pids for each group of tasks.

> Why are people so opposed to creating their own filesystems?

	There are lots of reasons not to create your own filesystem. When
you're not already a kernel maintainer it's no small task to create and
get a non-trivial filesystem accepted into the kernel. Getting people to
review whole new filesystems has its own problems:

http://www.ussg.iu.edu/hypermail/linux/kernel/0610.1/1928.html

Cheers,
	-Matt Helsley


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