Re: [PATCH v4 3/3] ring-buffer: Skip invalid sub-buffers when validating persistent ring buffer

[Google]

On Tue, 24 Feb 2026 15:52:57 +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 discarding the entire ring buffer. Also, mark there are
> missed events on the discarded 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. Only discard the
> subbuffersa that ar found to be corrupted.
> 
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
> ---
>   Changes in v3:
>   - Record missed data event on commit.
> ---
>  kernel/trace/ring_buffer.c |   21 +++++++++++----------
>  1 file changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 67bc652ba02a..72f82e2e6740 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -2058,17 +2058,18 @@ 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);

This pr_info() should be removed too, because multiple pages
can be discarded.

Thanks,

> -			goto invalid;
> -		}
> -
> -		/* If the buffer has content, update pages_touched */
> -		if (ret)
> -			local_inc(&cpu_buffer->pages_touched);
> -
> -		entries += ret;
> -		entry_bytes += rb_page_size(head_page);
> -		local_set(&cpu_buffer->head_page->entries, ret);
> +			/* Instead of discard whole ring buffer, discard only this sub-buffer. */
> +			local_set(&head_page->entries, 0);
> +			local_set(&head_page->page->commit, RB_MISSED_EVENTS);
> +		} else {
> +			/* If the buffer has content, update pages_touched */
> +			if (ret)
> +				local_inc(&cpu_buffer->pages_touched);
>  
> +			entries += ret;
> +			entry_bytes += rb_page_size(head_page);
> +			local_set(&cpu_buffer->head_page->entries, ret);
> +		}
>  		if (head_page == cpu_buffer->commit_page)
>  			break;
>  	}
> 


-- 
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>