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

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Message-ID: <e9e943910808061747x57dc2ed0s614785d9d0a087a8@mail.gmail.com>
Date:	Thu, 7 Aug 2008 01:47:17 +0100
From:	"Duane Griffin" <duaneg@...da.com>
To:	"Stephen C. Tweedie" <sct@...hat.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>
Subject: Re: [PATCH] jbd: abort instead of waiting for nonexistent transactions

2008/8/5 Stephen C. Tweedie <sct@...hat.com>:
> 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?

Sounds sensible. In fact I've got another patch, waiting for feedback
from the reporter, that adds some very basic validation there (i.e.
first > 0 && last >= first). Not enough, I suspect. I guess we could
do much better?

> Cheers,
>  Stephen

Cheers,
Duane.

-- 
"I never could learn to drink that blood and call it wine" - Bob Dylan
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