Subject: Re: [Linux-cluster] Re: GFS, what's remaining
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Andrew Morton <akpm@osdl.org>
Cc: Daniel Phillips <phillips@istop.com>, Joel.Becker@oracle.com,
       linux-cluster@redhat.com, wim.coekaerts@oracle.com,
       linux-fsdevel@vger.kernel.org, ak@suse.de, linux-kernel@vger.kernel.org
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Date: Sun, 04 Sep 2005 09:37:15 +0100
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On Sad, 2005-09-03 at 21:46 -0700, Andrew Morton wrote:
> Actually I think it's rather sick.  Taking O_NONBLOCK and making it a
> lock-manager trylock because they're kinda-sorta-similar-sounding?  Spare
> me.  O_NONBLOCK means "open this file in nonblocking mode", not "attempt to
> acquire a clustered filesystem lock".  Not even close.

The semantics of O_NONBLOCK on many other devices are "trylock"
semantics. OSS audio has those semantics for example, as do regular
files in the presence of SYS5 mandatory locks. While the latter is "try
lock , do operation and then drop lock" the drivers using O_NDELAY are
very definitely providing trylock semantics.

I am curious why a lock manager uses open to implement its locking
semantics rather than using the locking API (POSIX locks etc) however.

Alan

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