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>
d3073779f8