Re: [PATCH] perf/core: don't WARN for impossible rb sizes

[Jin, Yao]

On 2/12/2019 9:07 PM, Peter Zijlstra wrote:
> On Tue, Feb 12, 2019 at 10:42:38AM +0800, Jin, Yao wrote:
> > > diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
> > > index 4a9937076331..309ef5a64af5 100644
> > > --- a/kernel/events/ring_buffer.c
> > > +++ b/kernel/events/ring_buffer.c
> > > @@ -734,6 +734,9 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
> > >    	size = sizeof(struct ring_buffer);
> > >    	size += nr_pages * sizeof(void *);
> > > +	if (order_base_2(size) >= MAX_ORDER)
> > > +		goto fail;
> > > +
> > >    	rb = kzalloc(size, GFP_KERNEL);
>
> Yes, Boris also send the entire morning bisecting this.
>
> The problem is that @size is in bytes and MAX_ORDER is in pages.
>
> That should be:
>
>    if (order_base_2(size) >= PAGE_SHIFT+MAX_ORDER)

Thanks Peter! This fix works!

Thanks
Jin Yao