linux/net/sunrpc
Roland Dreier d3073779f8 SVCRDMA: Use only 1 RDMA read scatter entry for iWARP adapters
The iWARP protocol limits RDMA read requests to a single scatter
entry.  NFS/RDMA has code in rdma_read_max_sge() that is supposed to
limit the sge_count for RDMA read requests to 1, but the code to do
that is inside an #ifdef RDMA_TRANSPORT_IWARP block.  In the mainline
kernel at least, RDMA_TRANSPORT_IWARP is an enum and not a
preprocessor #define, so the #ifdef'ed code is never compiled.

In my test of a kernel build with -j8 on an NFS/RDMA mount, this
problem eventually leads to trouble starting with:

    svcrdma: Error posting send = -22
    svcrdma : RDMA_READ error = -22

and things go downhill from there.

The trivial fix is to delete the #ifdef guard.  The check seems to be
a remnant of when the NFS/RDMA code was not merged and needed to
compile against multiple kernel versions, although I don't think it
ever worked as intended.  In any case now that the code is upstream
there's no need to test whether the RDMA_TRANSPORT_IWARP constant is
defined or not.

Without this patch, my kernel build on an NFS/RDMA mount using NetEffect
adapters quickly and 100% reproducibly failed with an error like:

    ld: final link failed: Software caused connection abort

With the patch applied I was able to complete a kernel build on the
same setup.

(Tom Tucker says this is "actually an _ancient_ remnant when it had to
compile against iWARP vs. non-iWARP enabled OFA trees.")

Signed-off-by: Roland Dreier <rolandd@cisco.com>
Acked-by: Tom Tucker <tom@opengridcomputing.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-03-24 11:25:25 -07:00
..
auth_gss [SUNRPC]: net/* NULL noise 2008-03-17 22:48:03 -07:00
xprtrdma SVCRDMA: Use only 1 RDMA read scatter entry for iWARP adapters 2008-03-24 11:25:25 -07:00
auth.c
auth_null.c
auth_unix.c
cache.c
clnt.c
Makefile
rpc_pipe.c
rpcb_clnt.c
sched.c
socklib.c
stats.c
sunrpc_syms.c
svc.c
svc_xprt.c [NET] endianness noise: INADDR_ANY 2008-03-17 22:44:53 -07:00
svcauth.c
svcauth_unix.c
svcsock.c
sysctl.c
timer.c
xdr.c
xprt.c
xprtsock.c