Re: [PATCH v14 5/5] ring-buffer: Add persistent ring buffer selftest

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Mon, 30 Mar 2026 16:24:19 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Mon, 30 Mar 2026 21:50:27 +0900
> "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:
> 
> > @@ -2558,12 +2577,64 @@ static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
> >  	kfree(cpu_buffer);
> >  }
> >  
> > +#ifdef CONFIG_RING_BUFFER_PERSISTENT_INJECT
> > +static void rb_test_inject_invalid_pages(struct trace_buffer *buffer)
> > +{
> > +	struct ring_buffer_per_cpu *cpu_buffer;
> > +	struct ring_buffer_cpu_meta *meta;
> > +	struct buffer_data_page *dpage;
> > +	u32 entry_bytes = 0;
> > +	unsigned long ptr;
> > +	int subbuf_size;
> > +	int invalid = 0;
> > +	int cpu;
> > +	int i;
> > +
> > +	if (!(buffer->flags & RB_FL_TESTING))
> > +		return;
> > +
> > +	guard(preempt)();
> > +	cpu = smp_processor_id();
> > +
> > +	cpu_buffer = buffer->buffers[cpu];
> > +	meta = cpu_buffer->ring_meta;
> > +	ptr = (unsigned long)rb_subbufs_from_meta(meta);
> > +	subbuf_size = meta->subbuf_size;
> > +
> > +	for (i = 0; i < meta->nr_subbufs; i++) {
> > +		int idx = meta->buffers[i];
> > +
> > +		dpage = (void *)(ptr + idx * subbuf_size);
> > +		/* Skip unused pages */
> > +		if (!local_read(&dpage->commit))
> > +			continue;
> > +
> > +		/* Invalidate even pages. */
> > +		if (!(i & 0x1)) {
> > +			local_add(subbuf_size + 1, &dpage->commit);
> > +			invalid++;
> > +		} else {
> > +			/* Count total commit bytes. */
> > +			entry_bytes += local_read(&dpage->commit);
> > +		}
> > +	}
> > +
> > +	pr_info("Inject invalidated %d pages on CPU%d, total size: %ld\n",
> > +		invalid, cpu, (long)entry_bytes);
> 
> This is only enabled when testing. Let's make that a pr_warn() as we really
> do want to be able to see it. And it should warn that it is invalidating pages!
> (warn as in pr_warn, it doesn't need a warn as in WARN()).

OK. Let me update it.

Thanks!

> 
> -- Steve
> 
> 
> > +	meta->nr_invalid = invalid;
> > +	meta->entry_bytes = entry_bytes;
> > +}
> > +#else /* !CONFIG_RING_BUFFER_PERSISTENT_INJECT */
> > +#define rb_test_inject_invalid_pages(buffer)	do { } while (0)
> > +#endif
> > +
> >  /* Stop recording on a persistent buffer and flush cache if needed. */
> >  static int rb_flush_buffer_cb(struct notifier_block *nb, unsigned long event, void *data)
> >  {
> >  	struct trace_buffer *buffer = container_of(nb, struct trace_buffer, flush_nb);
> >  
> >  	ring_buffer_record_off(buffer);
> > +	rb_test_inject_invalid_pages(buffer);
> >  	arch_ring_buffer_flush_range(buffer->range_addr_start, buffer->range_addr_end);
> >  	return NOTIFY_DONE;
> >  }


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