linux-ext4 - Re: [PATCH 2/2] ext4: Handle nested ext4_journal

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Message-id: <20090918055010.GN2537@webber.adilger.int>
Date:	Thu, 17 Sep 2009 23:50:10 -0600
From:	Andreas Dilger <adilger@....com>
To:	Curt Wohlgemuth <curtw@...gle.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 2/2] ext4: Handle nested ext4_journal_start/stop calls
	without a journal

On Sep 17, 2009  14:55 -0700, Curt Wohlgemuth wrote:
> This patch fixes a problem with handling nested calls to
> ext4_journal_start/ext4_journal_stop, when there is no journal present.
> 
> 	Signed-off-by: Curt Wohlgemuth <curtw@...gle.com>
> ---
> 
> Instead of using the special value of
> 
>         (handle_t *)0x1
> 
> to represent a handle when there is no journal present, we now use a real
> handle_t, so we can use its ref counting.  The h_transaction field now
> determines if there is a journal present or not.

You _could_ just use the "handle" value as a refcount, and anything less
than, say, 4096 is considered a "special" handle.  I can't imagine the
refcount being more than 3 or 4 even in extreme cases.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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