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

On Fri, 20 Feb 2026 14:56:56 -0500
Steven Rostedt [off-list ref] wrote:

On Wed, 18 Feb 2026 19:14:35 +0900
"Masami Hiramatsu (Google)" [off-list ref] wrote:

quoted

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Skip invalid sub-buffers when validating the persistent ring buffer
instead of invalidate all ring buffers.

  instead of discarding the entire ring buffer.

quoted

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.

quoted

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 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);

Ah, that's a nice flag!

Thanks!

-- Steve

quoted

+		} 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;
 	}

-- 
Masami Hiramatsu (Google) [off-list ref]