linux-ext4 - Re: [PATCH] jbd: abort instead of waiting for nonexistent transactions

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Message-Id: <1217951437.3886.36.camel@sisko.scot.localnet>
Date:	Tue, 05 Aug 2008 16:50:37 +0100
From:	"Stephen C. Tweedie" <sct@...hat.com>
To:	Duane Griffin <duaneg@...da.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-ext4@...r.kernel.org, Sami Liedes <sliedes@...hut.fi>,
	Stephen Tweedie <sct@...hat.com>
Subject: Re: [PATCH] jbd: abort instead of waiting for nonexistent
	transactions

Hi,

On Tue, 2008-08-05 at 00:51 +0100, Duane Griffin wrote:
> The __log_wait_for_space function sits in a loop checkpointing transactions
> until there is sufficient space free in the journal. However, if there are
> no transactions to be processed (e.g. because the free space calculation is
> wrong due to a corrupted filesystem) it will never progress.
> 
> Check for space being required when no transactions are outstanding and
> abort the journal instead of endlessly looping.

I'm not sure this is the right fix --- it seems like we're fixing the
symptoms, not the problem.

The journal free space fields are reset in journal_reset() when we load
the journal, so we can't get this situation of j_free being insufficient
on an idle filesystem unless the main journal start/end pointers are
corrupt.

Surely we'd be better off detecting this in the first place at mount
time, not later on during checkpoint?

Cheers,
 Stephen


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