> -----Original Message----- > From: linux-rdma-owner@xxxxxxxxxxxxxxx [mailto:linux-rdma- > owner@xxxxxxxxxxxxxxx] On Behalf Of Jason Gunthorpe > Sent: Monday, March 12, 2018 4:37 PM > To: Ruhl, Michael J <michael.j.ruhl@xxxxxxxxx> > Cc: Doug Ledford <dledford@xxxxxxxxxx>; Leon Romanovsky > <leonro@xxxxxxxxxxxx>; RDMA mailing list <linux-rdma@xxxxxxxxxxxxxxx>; > Matan Barak <matanb@xxxxxxxxxxxx> > Subject: Re: [PATCH rdma-next 05/12] IB/uverbs: Safely extend existing > attributes > > On Mon, Mar 12, 2018 at 08:34:11PM +0000, Ruhl, Michael J wrote: > > > I still think that this flag should be split into two pieces, so I can avoid the > > ib_is_buffer_cleared() if I don't need it. > > You always need it. > > It is part of ABI compatability, if you declare that a struct can be > extended then you have to check that someone isn't using a new > extension with an old kernel. Ok, I think I misunderstood what this is being used for. I was thinking that it was just part of testing the size of the data structure being used. >From what you are saying this is for specific instances of variably sized (extended) data structures? > Globally we define that as meaning the unknown part of the struct is > 0. So this will effectively force the caller to understand that the core doesn't understand any of the "extra" info? I think I understand the difference between uverbs_copy_from_or_zero() and uverbs_copy_from() as well. The or _zero() will only copy the minimum size only (spec vs. user size). So this will require extra code in the handler to make sure that it understands that the user size may be smaller than the "expected" (spec) data size? > If this is a problem for your API then you are probably not designing > it properly for extension.. Since I am not fully understanding the use of this feature, I doubt it is a problem for my API. :) > I actually don't expect MIN_SZ to be used very often. I hope not. :) Thanks Mike > Jason > -- > To unsubscribe from this list: send the line "unsubscribe linux-rdma" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
