Re: [PATCH] jbd2: gracefully abort on checkpointing state corruptions

[Baokun Li]

On 3/10/26 7:08 AM, Milos Nikic wrote:
> This patch targets two internal state machine invariants in checkpoint.c
> residing inside functions that natively return integer error codes.
>
> - In jbd2_cleanup_journal_tail(): A blocknr of 0 indicates a severely
> corrupted journal superblock. Replaced the J_ASSERT with a WARN_ON_ONCE
> and a graceful journal abort, returning -EUCLEAN.
>
> - In jbd2_log_do_checkpoint(): Replaced the J_ASSERT_BH checking for
> an unexpected buffer_jwrite state. If the warning triggers, we
> explicitly drop the just-taken get_bh() reference and call __flush_batch()
> to safely clean up any previously queued buffers in the j_chkpt_bhs array,
> preventing a memory leak before returning -EUCLEAN.
>
> Signed-off-by: Milos Nikic <nikic.milos@xxxxxxxxx>

Looks good to me, just two minor nits:

 * Replacing EUCLEAN with EFSCORRUPTED would make more sense.
 * Putting jbd2_journal_abort after __flush_batch reads more naturally.

Otherwise, feel free to add:

Reviewed-by: Baokun Li <libaokun@xxxxxxxxxxxxxxxxx>

> ---
>  fs/jbd2/checkpoint.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
> index de89c5bef607..cdfbfd27afae 100644
> --- a/fs/jbd2/checkpoint.c
> +++ b/fs/jbd2/checkpoint.c
> @@ -267,7 +267,17 @@ int jbd2_log_do_checkpoint(journal_t *journal)
>  			 */
>  			BUFFER_TRACE(bh, "queue");
>  			get_bh(bh);
> -			J_ASSERT_BH(bh, !buffer_jwrite(bh));
> +			if (WARN_ON_ONCE(buffer_jwrite(bh))) {
> +				put_bh(bh); /* drop the ref we just took */
> +				spin_unlock(&journal->j_list_lock);
> +				jbd2_journal_abort(journal, -EUCLEAN);
> +
> +				/* Clean up any previously batched buffers */
> +				if (batch_count)
> +					__flush_batch(journal, &batch_count);
> +
> +				return -EUCLEAN;
> +			}
>  			journal->j_chkpt_bhs[batch_count++] = bh;
>  			transaction->t_chp_stats.cs_written++;
>  			transaction->t_checkpoint_list = jh->b_cpnext;
> @@ -325,7 +335,10 @@ int jbd2_cleanup_journal_tail(journal_t *journal)
>  
>  	if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
>  		return 1;
> -	J_ASSERT(blocknr != 0);
> +	if (WARN_ON_ONCE(blocknr == 0)) {
> +		jbd2_journal_abort(journal, -EUCLEAN);
> +		return -EUCLEAN;
> +	}
>  
>  	/*
>  	 * We need to make sure that any blocks that were recently written out