From patchwork Wed Dec 12 15:17:42 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: jbd2: Fix assertion failure in jbd2_journal_flush() Date: Wed, 12 Dec 2012 05:17:42 -0000 From: Jan Kara X-Patchwork-Id: 205562 Message-Id: <1355325462-26757-1-git-send-email-jack@suse.cz> To: Ted Tso Cc: linux-ext4@vger.kernel.org, Jan Kara , stable@vger.kernel.org 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 --- fs/jbd2/transaction.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index a74ba46..6873d24 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -209,7 +209,8 @@ repeat: if (!new_transaction) goto alloc_transaction; write_lock(&journal->j_state_lock); - if (!journal->j_running_transaction) { + if (!journal->j_running_transaction && + !journal->j_barrier_count) { jbd2_get_transaction(journal, new_transaction); new_transaction = NULL; }