From d7961c7fa4d2e3c3f12be67e21ba8799b5a7238a Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Fri, 21 Dec 2012 00:15:51 -0500 Subject: [PATCH] jbd2: fix assertion failure in jbd2_journal_flush() 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" Cc: stable@vger.kernel.org --- 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 deffd945c8e2..cd4485db42b3 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; }