From: Roland Dreier Date: Mon, 24 Mar 2008 16:03:03 +0000 (-0400) Subject: SVCRDMA: Use only 1 RDMA read scatter entry for iWARP adapters X-Git-Tag: v2.6.25-rc7~26 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d3073779f8362d64b804882f5f41c208c4a5e11e;p=linux-2.6 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 Acked-by: Tom Tucker Signed-off-by: J. Bruce Fields Signed-off-by: Linus Torvalds --- diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c index ab54a73648..971271602d 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c @@ -237,14 +237,12 @@ static void rdma_set_ctxt_sge(struct svc_rdma_op_ctxt *ctxt, static int rdma_read_max_sge(struct svcxprt_rdma *xprt, int sge_count) { -#ifdef RDMA_TRANSPORT_IWARP if ((RDMA_TRANSPORT_IWARP == rdma_node_get_transport(xprt->sc_cm_id-> device->node_type)) && sge_count > 1) return 1; else -#endif return min_t(int, sge_count, xprt->sc_max_sge); }