xprtrdma: No direct data placement with krb5i and krb5p

Direct data placement is not allowed when using flavors that
guarantee integrity or privacy. When such security flavors are in
effect, don't allow the use of Read and Write chunks for moving
individual data items. All messages larger than the inline threshold
are sent via Long Call or Long Reply.

On my systems (CX-3 Pro on FDR), for small I/O operations, the use
of Long messages adds only around 5 usecs of latency in each
direction.

Note that when integrity or encryption is used, the host CPU touches
every byte in these messages. Even if it could be used, data
movement offload doesn't buy much in this case.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index dac2990ae2f7..a47f170b20ef 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -570,6 +570,7 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
         struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
         enum rpcrdma_chunktype rtype, wtype;
         struct rpcrdma_msg *headerp;
+        bool ddp_allowed;
         ssize_t hdrlen;
         size_t rpclen;
         __be32 *iptr;
@@ -586,6 +587,13 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
         headerp->rm_credit = cpu_to_be32(r_xprt->rx_buf.rb_max_requests);
         headerp->rm_type = rdma_msg;
 
+        /* When the ULP employs a GSS flavor that guarantees integrity
+         * or privacy, direct data placement of individual data items
+         * is not allowed.
+         */
+        ddp_allowed = !(rqst->rq_cred->cr_auth->au_flags &
+                                                RPCAUTH_AUTH_DATATOUCH);
+
         /*
          * Chunks needed for results?
          *
@@ -597,7 +605,7 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
          */
         if (rpcrdma_results_inline(r_xprt, rqst))
                 wtype = rpcrdma_noch;
-        else if (rqst->rq_rcv_buf.flags & XDRBUF_READ)
+        else if (ddp_allowed && rqst->rq_rcv_buf.flags & XDRBUF_READ)
                 wtype = rpcrdma_writech;
         else
                 wtype = rpcrdma_replych;
@@ -620,7 +628,7 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
                 rtype = rpcrdma_noch;
                 rpcrdma_inline_pullup(rqst);
                 rpclen = rqst->rq_svec[0].iov_len;
-        } else if (rqst->rq_snd_buf.flags & XDRBUF_WRITE) {
+        } else if (ddp_allowed && rqst->rq_snd_buf.flags & XDRBUF_WRITE) {
                 rtype = rpcrdma_readch;
                 rpclen = rqst->rq_svec[0].iov_len;
                 rpclen += rpcrdma_tail_pullup(&rqst->rq_snd_buf);