linux-kernel - Re: [PATCH 1/1 linux-next] jbd2: Fix sparse context imbalance warning

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Date:	Sat, 20 Sep 2014 09:14:11 +0200 (CEST)
From:	Fabian Frederick <fabf@...net.be>
To:	Theodore Ts'o <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1 linux-next] jbd2: Fix sparse context imbalance
 warning



> On 18 September 2014 at 22:44 Theodore Ts'o <tytso@....edu> wrote:
>
>
> On Thu, Sep 18, 2014 at 08:29:34PM +0200, Fabian Frederick wrote:
> > spin_unlock after spin_lock only.
> >
> > This fixes the following sparse warning:
> > fs/jbd2/transaction.c:1102:20: warning: context imbalance
> > in 'jbd2_journal_get_create_access' - different lock contexts for basic
> > block
> >
> > Signed-off-by: Fabian Frederick <fabf@...net.be>
>
> NAK, this is a case where I think it's better to make the static
> analyzers better.  In any case sparse gives a lot of false positives
> for this particular warning, so adding lines of code to try to shut up
> sparse for every single false positive seems to be a losing
> proposition.
>
> I'll note that these sorts of bugs are much more easily picked up
> using lockdep in any case, so we're probably better of just ignoring
> these sorts of warnings.  Better to let the 0day kernel tester warn
> for new sparse warnings, instead of trying to drive sparse warnings
> down to zero.
>
> Cheers,
>
>                                       - Ted

Thanks a lot for explanation Ted. I didn't see J_ASSERT_JH above which BUG_ON
if b_transaction is not ok.


Regards,
Fabian
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