Access to journal->j_running_transaction is not protected by appropriate
lock and thus is racy. We are well aware of that and the code handles
the race properly. Just add a comment and data_race() annotation.
Reported-by: syzbot+30774a6acf6a2cf6d535@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/jbd2/transaction.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 9396666b7314..398d1d9209e2 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -349,7 +349,12 @@ static int start_this_handle(journal_t *journal, handle_t *handle,
}
alloc_transaction:
- if (!journal->j_running_transaction) {
+ /*
+ * This check is racy but it is just an optimization of allocating new
+ * transaction early if there are high chances we'll need it. If we
+ * guess wrong, we'll retry or free unused transaction.
+ */
+ if (!data_race(journal->j_running_transaction)) {
/*
* If __GFP_FS is not present, then we may be being called from
* inside the fs writeback layer, so we MUST NOT fail.
--
2.26.2
