linux-ext4 - Re: [PATCH -v2 1/3] jbd2: Use atomic variables to avoid taking t_handle_lock in jbd2_journal

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Message-ID: <20100810163046.GM3635@thunk.org>
Date:	Tue, 10 Aug 2010 12:30:46 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	ocfs2-devel@....oracle.com, John Stultz <johnstul@...ibm.com>,
	Keith Maanthey <kmannth@...ibm.com>,
	Eric Whitney <eric.whitney@...com>
Subject: Re: [PATCH -v2 1/3] jbd2: Use atomic variables to avoid taking
 t_handle_lock in jbd2_journal_stop

On Mon, Aug 09, 2010 at 09:45:55PM +0200, Jan Kara wrote:
>   Ah, OK. You're right. I just thought we eventually want to remove the
> lock but you're right that currently the code is fine. Sorry for the noise.

I would love to get rid of the j_state_lock, but looking through the
code, I couldn't figure out how to do this safely.  Hence my
conversion of the j_state_lock to a rwlock_t, with the downside of
this causing more cache line bounces.  If someone can suggest a way to
drop needing a global spinlock (whether it is an exclusive or rwlock)
in start_this_handle(), I'd love to hear them.

   			    	    	 - Ted
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