linux-kernel - Re: [PATCH] Added CONFIG_VFAT_FS

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Date:	Wed, 01 Jul 2009 10:44:47 -0500
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Boaz Harrosh <bharrosh@...asas.com>
Cc:	tridge@...ba.org, Pavel Machek <pavel@....cz>,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	john.lanza@...ux.com, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>,
	Steve French <sfrench@...ibm.com>,
	Mingming Cao <cmm@...ibm.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH] Added CONFIG_VFAT_FS_DUALNAMES option

On Wed, 2009-07-01 at 14:48 +0300, Boaz Harrosh wrote:
> On 07/01/2009 01:50 PM, tridge@...ba.org wrote:
> > Hi Pavel,
> > 
> > We did of course consider that, and the changes to the patch to
> > implement collision avoidance are relatively simple. We didn't do it
> > as it would weaken the legal basis behind the patch. I'll leave it to
> > John Lanza (the LF patent attorney) to expand on that if you want more
> > information.
> > 
> 
> You completely lost me here. And I thought I did understand the patent
> and the fix.
> 
> what is the difference between.
> 
> short_name = rand(sid);
> and
> short_name = sid++;
> 
> Now if you would do
> short_name = MD5(long_name);
> 
> That I understand since short_name is some function of long_name
> but if I'm just inventing the short_name out of my hat. In what legal
> system does it matter what is my random function I use?

We're sort of arguing moot technicalities here.  If you look at the way
the filename is constructed, given the constraints of a leading space
and a NULL, the need for a NULL padded leading slash extension and the
need to put control characters in the remaining bytes, we've only got 30
bits to play with, we're never going to avoid collisions in a space of
up to 31 bits.  Technically, a random function is at least as good at
collision avoidance as any deterministic solution ... and it's a lot
easier to code.

James


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