At 03:32 PM 4/27/2009, Steve Wise wrote: >Trond Myklebust wrote: >> On Mon, 2009-04-27 at 14:05 -0400, Trond Myklebust wrote: >> >>> It looks looks as though the bug is really that the IB code is using a >>> u64 to store dma handles. As an external user of the IB api, we really >>> shouldn't have to perform this sort of transformation. If it is >>> absolutely necessary, then it should be done by means of specialised >>> accessor functions to initialise/read iova_start value when given a >>> dma_addr_t. >>> >>> I'd therefore prefer the no-cast version (with eventual compiler >>> warnings), in the hope that eventually the IB folks will fix their >>> interface. >>> >> >> Translation: It looks to me as if the interface that we're using is a >> bit too corrupted with IB low level implementation grime. In the future, >> I'd like to see someone come up with a more high level interface for use >> by external code such as the sunrpc module. >> >> > >Clarification: The iova_start isn't used to store dma handles. The Agreed, it's more of a hardware register, that ends up on the wire as well. I think the net of this is that the mr_dma should have a more sensible up-cast that yields the right bits in the iova_start. Maybe a nice machine-dependent macro, defined in the RDMA layer, would be a good approach. Surely the other upper layers need it too. While I have the floor, why doesn't the server have this issue? Looking at the code, it has the same (unsigned long) cast as the client when initializing its iova_start. Tom. >iova_start is the "address" base value that is advertised to a peer to >describe the base address of a memory region. The contents of that can >be more than just a dma handle...its up to the application. For >instance, you could advertise a iova_start of zero or a kernel VA as the >rdma server does. Also, the type is u64 because that is the size used >on the wire as part of the rdma (IB and iWARP) protocols. > > >Steve. > -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
