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

[Andreas Dilger]

On Mar 2, 2026, at 17:55, Milos Nikic <nikic.milos@xxxxxxxxx> wrote:
> 
> 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@xxxxxxxxx>
> Reviewed-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
> Reviewed-by: Jan Kara <jack@xxxxxxx>

Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx <mailto:adilger@xxxxxxxxx>>

> ---
> 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
> 
>