Re: NFS over RDMA crashing

[Steve Wise <swise@opengridcomputing.com>]

> I removed your change and started debugging original crash that 
> happens on top-o-tree.   Seems like rq_next_pages is screwed up.  It 
> should always be >= rq_respages, yes?  I added a BUG_ON() to assert 
> this in rdma_read_xdr() we hit the BUG_ON(). Look
>
> crash> svc_rqst.rq_next_page 0xffff8800b84e6000
>   rq_next_page = 0xffff8800b84e6228
> crash> svc_rqst.rq_respages 0xffff8800b84e6000
>   rq_respages = 0xffff8800b84e62a8
>
> Any ideas Bruce/Tom?
>

Guys, the patch below seems to fix the problem.  Dunno if it is correct 
though.  What do you think?

diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c 
b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index 0ce7552..6d62411 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -90,6 +90,7 @@ static void rdma_build_arg_xdr(struct svc_rqst *rqstp,
                 sge_no++;
         }
         rqstp->rq_respages = &rqstp->rq_pages[sge_no];
+       rqstp->rq_next_page = rqstp->rq_respages;

         /* We should never run out of SGE because the limit is defined to
          * support the max allowed RPC data length
@@ -276,6 +277,7 @@ static int fast_reg_read_chunks(struct svcxprt_rdma 
*xprt,

         /* rq_respages points one past arg pages */
         rqstp->rq_respages = &rqstp->rq_arg.pages[page_no];
+       rqstp->rq_next_page = rqstp->rq_respages;

         /* Create the reply and chunk maps */
         offset = 0;