From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756218Ab3AMR5u (ORCPT ); Sun, 13 Jan 2013 12:57:50 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:34936 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754928Ab3AMRpW (ORCPT ); Sun, 13 Jan 2013 12:45:22 -0500 Message-Id: <20130113174256.696932018@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Sun, 13 Jan 2013 17:42:59 +0000 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Jan Kara , "Theodore Tso" Subject: [ 04/49] jbd2: fix assertion failure in jbd2_journal_flush() In-Reply-To: <20130113174255.736888844@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jan Kara commit d7961c7fa4d2e3c3f12be67e21ba8799b5a7238a upstream. 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. Reported-by: yjwsignal@empal.com Signed-off-by: Jan Kara Signed-off-by: "Theodore Ts'o" Signed-off-by: Ben Hutchings --- fs/jbd2/transaction.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index deffd94..cd4485d 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; }