[PATCH v3 1/2] jbd2: gracefully abort instead of panicking on unlocked buffer

[Milos Nikic <nikic.milos@gmail.com>]

In jbd2_journal_get_create_access(), if the caller passes an unlocked
buffer, the code currently triggers a fatal J_ASSERT.

While an unlocked buffer here is a clear API violation and a bug in the
caller, crashing the entire system is an overly severe response. It brings
down the whole machine for a localized filesystem inconsistency.

Replace the J_ASSERT with a WARN_ON_ONCE to capture the offending caller's
stack trace, and return an error (-EINVAL). This allows the journal to
gracefully abort the transaction, protecting data integrity without
causing a kernel panic.

Signed-off-by: Milos Nikic <nikic.milos@gmail.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 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 dca4b5d8aaaa..04d17a5f2a82 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1302,7 +1302,12 @@ int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh)
 		goto out;
 	}
 
-	J_ASSERT_JH(jh, buffer_locked(jh2bh(jh)));
+	if (WARN_ON_ONCE(!buffer_locked(jh2bh(jh)))) {
+		err = -EINVAL;
+		spin_unlock(&jh->b_state_lock);
+		jbd2_journal_abort(journal, err);
+		goto out;
+	}
 
 	if (jh->b_transaction == NULL) {
 		/*
-- 
2.53.0