[PATCH v1 4/4] xprtrdma: Plant XID in on-the-wire RDMA offset (FRWR)

[Chuck Lever <chuck.lever@xxxxxxxxxx>]

Place the associated RPC transaction's XID in the upper 32 bits of
each RDMA segment's rdma_offset field. These bits are currently
always zero.

There are two reasons to do this:

- The R_key only has 8 bits that are different from registration to
  registration. The XID adds more uniqueness to each RDMA segment to
  reduce the likelihood of a software bug on the server reading from
  or writing into memory it's not supposed to.

- On-the-wire RDMA Read and Write operations do not otherwise carry
  any identifier that matches them up to an RPC. The XID in the
  upper 32 bits will act as an eye-catcher in network captures.

Suggested-by: Tom Talpey <ttalpey@xxxxxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
 net/sunrpc/xprtrdma/frwr_ops.c  |    3 ++-
 net/sunrpc/xprtrdma/rpc_rdma.c  |    6 +++---
 net/sunrpc/xprtrdma/xprt_rdma.h |    2 +-
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index 49b314d..3b260d2 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -344,7 +344,7 @@
  */
 static struct rpcrdma_mr_seg *
 frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
-	    int nsegs, bool writing, struct rpcrdma_mr **out)
+	    int nsegs, bool writing, u32 xid, struct rpcrdma_mr **out)
 {
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
 	bool holes_ok = ia->ri_mrtype == IB_MR_TYPE_SG_GAPS;
@@ -398,6 +398,7 @@
 	if (unlikely(n != mr->mr_nents))
 		goto out_mapmr_err;
 
+	ibmr->iova |= ((u64)cpu_to_be32(xid)) << 32;
 	key = (u8)(ibmr->rkey & 0x000000FF);
 	ib_update_fast_reg_key(ibmr, ++key);
 
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 9f53e02..89a2db2 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -357,7 +357,7 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
 
 	do {
 		seg = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
-						   false, &mr);
+						   false, rqst->rq_xid, &mr);
 		if (IS_ERR(seg))
 			return PTR_ERR(seg);
 		rpcrdma_mr_push(mr, &req->rl_registered);
@@ -415,7 +415,7 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
 	nchunks = 0;
 	do {
 		seg = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
-						   true, &mr);
+						   true, rqst->rq_xid, &mr);
 		if (IS_ERR(seg))
 			return PTR_ERR(seg);
 		rpcrdma_mr_push(mr, &req->rl_registered);
@@ -473,7 +473,7 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
 	nchunks = 0;
 	do {
 		seg = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
-						   true, &mr);
+						   true, rqst->rq_xid, &mr);
 		if (IS_ERR(seg))
 			return PTR_ERR(seg);
 		rpcrdma_mr_push(mr, &req->rl_registered);
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index a13ccb6..2ae1ee2 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -472,7 +472,7 @@ struct rpcrdma_memreg_ops {
 	struct rpcrdma_mr_seg *
 			(*ro_map)(struct rpcrdma_xprt *,
 				  struct rpcrdma_mr_seg *, int, bool,
-				  struct rpcrdma_mr **);
+				  u32, struct rpcrdma_mr **);
 	int		(*ro_send)(struct rpcrdma_ia *ia,
 				   struct rpcrdma_req *req);
 	void		(*ro_reminv)(struct rpcrdma_rep *rep,