Re: [RFC PATCH] rxe: Fix structure layouts for 32/64 bit compat

[Jason Gunthorpe <jgg-uk2M96/98Pc@public.gmane.org>]

On Wed, Feb 07, 2018 at 11:54:25PM +0000, Bart Van Assche wrote:
> On Wed, 2018-02-07 at 16:41 -0700, Jason Gunthorpe wrote:
> > diff --git a/include/uapi/rdma/rdma_user_rxe.h b/include/uapi/rdma/rdma_user_rxe.h
> > index e3e6852b58eb45..b501deb18d8184 100644
> > +++ b/include/uapi/rdma/rdma_user_rxe.h
> > @@ -58,6 +58,8 @@ struct rxe_global_route {
> >  struct rxe_av {
> >  	__u8			port_num;
> >  	__u8			network_type;
> > +	__u16			reserved1;
> > +	__u32			reserved2;
> 
> Hello Jason,
> 
> Seeing two consecutive reserved members is a bit weird. Have you considered
> to use something like __u8 reserved[6] instead?

Ah, I had that originally but changed it to make pahole work properly..
Can switch it back.

Although, this does really firmly say what the alighment is, eg
down the road someone might be tempted to do:

- __u8 reserved[6];
+ __u32 new_value;
+ __u16 reserved;

Which would be quite wrong..

Jason
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