[PATCH v18 4/8] ring-buffer: Skip invalid sub-buffers when rewinding persistent ring buffer

[Steven Rostedt]

On Fri, 24 Apr 2026 15:52:35 +0900
"Masami Hiramatsu (Google)" <mhiramat at kernel.org> wrote:

> @@ -1892,9 +1895,19 @@ static int rb_validate_buffer(struct buffer_data_page *dpage, int cpu,
>  	 * subbuf_size is considered invalid.
>  	 */
>  	tail = local_read(&dpage->commit) & ~RB_MISSED_MASK;
> -	if (tail > meta->subbuf_size - BUF_PAGE_HDR_SIZE)
> -		return -1;
> -	return rb_read_data_buffer(dpage, tail, cpu, &ts, &delta);
> +	if (tail <= meta->subbuf_size - BUF_PAGE_HDR_SIZE)
> +		ret = rb_read_data_buffer(dpage, tail, cpu, &ts, &delta);
> +

This code seriously needs comments.

-- Steve

> +	if (ret < 0 || (prev_ts && prev_ts > ts) || (next_ts && ts > next_ts)) {
> +		local_set(&bpage->entries, 0);
> +		local_set(&bpage->page->commit, 0);
> +		bpage->page->time_stamp = prev_ts ? prev_ts : next_ts;
> +		ret = -1;
> +	} else {
> +		local_set(&bpage->entries, ret);
> +	}
> +
> +	return ret;
>  }
>