From: Theodore Ts'o <tytso@mit.edu>
To: Jan Kara <jack@suse.cz>
Cc: linux-ext4@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] jbd2: Fix assertion failure in jbd2_journal_flush()
Date: Fri, 21 Dec 2012 00:16:39 -0500 [thread overview]
Message-ID: <20121221051639.GA16958@thunk.org> (raw)
In-Reply-To: <1355325462-26757-1-git-send-email-jack@suse.cz>
On Wed, Dec 12, 2012 at 04:17:42PM +0100, Jan Kara wrote:
> The following race is possible between start_this_handle() and someone
> calling jbd2_journal_flush().
>
> Process A Process B
> start_this_handle().
> if (journal->j_barrier_count) # false
> if (!journal->j_running_transaction) { #true
> read_unlock(&journal->j_state_lock);
> jbd2_journal_lock_updates()
> jbd2_journal_flush()
> write_lock(&journal->j_state_lock);
> if (journal->j_running_transaction) {
> # false
> ... wait for committing trans ...
> write_unlock(&journal->j_state_lock);
> ...
> write_lock(&journal->j_state_lock);
> if (!journal->j_running_transaction) { # true
> jbd2_get_transaction(journal, new_transaction);
> write_unlock(&journal->j_state_lock);
> goto repeat; # eventually blocks on j_barrier_count > 0
> ...
> J_ASSERT(!journal->j_running_transaction);
> # fails
>
> We fix the race by rechecking j_barrier_count after reacquiring j_state_lock
> in exclusive mode.
>
> CC: stable@vger.kernel.org
> Reported-by:yjwsignal@empal.com
> Signed-off-by: Jan Kara <jack@suse.cz>
Thanks, applied.
- Ted
prev parent reply other threads:[~2012-12-21 5:16 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-12 15:17 [PATCH] jbd2: Fix assertion failure in jbd2_journal_flush() Jan Kara
2012-12-21 5:16 ` Theodore Ts'o [this message]
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