linux-ext4 - Re: [PATCH] ext4: avoid lockdep warning when inheriting encryption context

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Date:   Wed, 16 Nov 2016 09:41:10 -0800
From:   Eric Biggers <ebiggers@...gle.com>
To:     Theodore Ts'o <tytso@....edu>
Cc:     linux-ext4@...r.kernel.org,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jaegeuk Kim <jaegeuk@...nel.org>, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH] ext4: avoid lockdep warning when inheriting encryption
 context

On Wed, Nov 16, 2016 at 10:47:38AM -0500, Theodore Ts'o wrote:
> 
> So this is a false positive introduced by
> 
>    1eaa566d368b: jbd2: track more dependencies on transaction commit
> 
> Instead of working around the problem here, perhaps it would be better
> to fix __jbd2_journal_force_commit() so that it calls a newly created
> __jbd2_log_wait_commit() which skips the jbd2_might_wait_for_commit()
> (and then have jbd2_log_wait_commit call __jbd2_log_wait_commit with
> the might_wait_for_commit check)?
> 
> This isn't the only place where jbd2_journal_force_commit() is called
> so if the problem is with the lockdep check, maybe we should just fix
> the logic in the jbd2 layer, hmm?
> 
> 					- Ted

The lockdep warning still seems helpful because it will show places that try to
force-commit the journal while holding an open handle.  Callers probably won't
expect that this will be a no-op, and it may indicate that the attempt to
force-commit the journal is in the wrong place, as it was here.

You and Jan know more about this than I do, though; I could be wrong.

Eric
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