linux-kernel - RE: [RFC PATCH 0/5] locks: implement "filp-private" (aka UNPOSIX) locks

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Message-ID: <024101cec776$8f004130$ad00c390$@mindspring.com>
Date:	Sat, 12 Oct 2013 11:12:03 -0700
From:	"Frank Filz" <ffilzlnx@...dspring.com>
To:	"'Jeff Layton'" <jlayton@...hat.com>,
	"'Scott Lovenberg'" <scott.lovenberg@...il.com>
Cc:	"'Jeremy Allison'" <jra@...ba.org>,
	"'Andreas Dilger'" <adilger@...ger.ca>,
	<linux-fsdevel@...r.kernel.org>,
	"'Ganesha NFS List'" <nfs-ganesha-devel@...ts.sourceforge.net>,
	<samba-technical@...ts.samba.org>,
	"'Linux Kernel Mailing List'" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH 0/5] locks: implement "filp-private" (aka UNPOSIX) locks

> This blog post of Jeremy's explains some of the history:
> 
> 
> http://www.samba.org/samba/news/articles/low_point/tale_two_stds_os2
> .html
> 
> See the section entitled "First Implementation Past the Post".

Interesting that Jeremy actually suggested the implementation should have
had an arbitrary lock owner as part of the flock structure:

"This is an example of a POSIX interface not being future-proofed against
modern techniques such as threading. A simple amendment to the original
primitive allowing a user-defined "locking context" (like a process id) to
be entered in the struct flock structure used to define the lock would have
fixed this problem, along with extra flags allowing the number of locks per
context to be recorded if needed."

But I'm happy with the lock context per kernel struct file as a solution,
especially since that will allow locks to be sensibly passed to a forked
process.

Another next step would be an asynchronous blocking lock...

Frank

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