Re: [PATCH v2 3/4] ring-buffer: Skip invalid sub-buffers when validating persistent ring buffer

[Steven Rostedt]

On Wed, 18 Feb 2026 19:14:35 +0900
"Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx> wrote:

> From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
> 
> Skip invalid sub-buffers when validating the persistent ring buffer
> instead of invalidate all ring buffers.

  instead of discarding the entire ring buffer.


> 
> If the cache data in memory fails to be synchronized during a reboot,
> the persistent ring buffer may become partially corrupted, but other
> sub-buffers may still contain readable event data, allowing usersto
> recover data from the corrupted ring buffer.

                  ... contain readable event data. Only discard the
                  subbuffers that are found to be corrupted.

> 
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
> ---
>  kernel/trace/ring_buffer.c |   22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index d2b69221a94c..0ae2a5ad8c3e 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -2045,17 +2045,19 @@ static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer)
>  		if (ret < 0) {
>  			pr_info("Ring buffer meta [%d] invalid buffer page\n",
>  				cpu_buffer->cpu);
> -			goto invalid;
> -		}
> -
> -		/* If the buffer has content, update pages_touched */
> -		if (ret)
> -			local_inc(&cpu_buffer->pages_touched);
> -
> -		entries += ret;
> -		entry_bytes += local_read(&head_page->page->commit);
> -		local_set(&cpu_buffer->head_page->entries, ret);
> +			/* Instead of invalidate whole ring buffer, just clear this subbuffer. */
> +			local_set(&head_page->entries, 0);
> +			local_set(&head_page->page->commit, 0);
> +			/* TODO: commit an event to mark this is broken. */

Here's how to fix the TODO:

			local_set(&head_page->page->commit, RB_MISSED_EVENTS);

-- Steve


> +		} else {
> +			/* If the buffer has content, update pages_touched */
> +			if (ret)
> +				local_inc(&cpu_buffer->pages_touched);
>  
> +			entries += ret;
> +			entry_bytes += local_read(&head_page->page->commit);
> +			local_set(&cpu_buffer->head_page->entries, ret);
> +		}
>  		if (head_page == cpu_buffer->commit_page)
>  			break;
>  	}