[PATCH v4 11/30] 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. 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 requests 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  |    5 ++++-
 net/sunrpc/xprtrdma/rpc_rdma.c  |    6 +++---
 net/sunrpc/xprtrdma/xprt_rdma.h |    2 +-
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index fb0944d..97f88bb 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -379,6 +379,7 @@ size_t frwr_maxpages(struct rpcrdma_xprt *r_xprt)
  * @seg: memory region co-ordinates
  * @nsegs: number of segments remaining
  * @writing: true when RDMA Write will be used
+ * @xid: XID of RPC using the registered memory
  * @out: initialized MR
  *
  * Prepare a REG_MR Work Request to register a memory region
@@ -389,7 +390,7 @@ size_t frwr_maxpages(struct rpcrdma_xprt *r_xprt)
  */
 struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
 				struct rpcrdma_mr_seg *seg,
-				int nsegs, bool writing,
+				int nsegs, bool writing, u32 xid,
 				struct rpcrdma_mr **out)
 {
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
@@ -444,6 +445,8 @@ struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
 	if (unlikely(n != mr->mr_nents))
 		goto out_mapmr_err;
 
+	ibmr->iova &= 0x00000000ffffffff;
+	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 2a2023d..3804fb3 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -356,7 +356,7 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
 		return nsegs;
 
 	do {
-		seg = frwr_map(r_xprt, seg, nsegs, false, &mr);
+		seg = frwr_map(r_xprt, seg, nsegs, false, rqst->rq_xid, &mr);
 		if (IS_ERR(seg))
 			return PTR_ERR(seg);
 		rpcrdma_mr_push(mr, &req->rl_registered);
@@ -413,7 +413,7 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
 
 	nchunks = 0;
 	do {
-		seg = frwr_map(r_xprt, seg, nsegs, true, &mr);
+		seg = frwr_map(r_xprt, seg, nsegs, true, rqst->rq_xid, &mr);
 		if (IS_ERR(seg))
 			return PTR_ERR(seg);
 		rpcrdma_mr_push(mr, &req->rl_registered);
@@ -470,7 +470,7 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
 
 	nchunks = 0;
 	do {
-		seg = frwr_map(r_xprt, seg, nsegs, true, &mr);
+		seg = frwr_map(r_xprt, seg, nsegs, 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 eccb930..56b299f 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -580,7 +580,7 @@ int frwr_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
 size_t frwr_maxpages(struct rpcrdma_xprt *r_xprt);
 struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
 				struct rpcrdma_mr_seg *seg,
-				int nsegs, bool writing,
+				int nsegs, bool writing, u32 xid,
 				struct rpcrdma_mr **mr);
 int frwr_send(struct rpcrdma_ia *ia, struct rpcrdma_req *req);
 void frwr_reminv(struct rpcrdma_rep *rep, struct list_head *mrs);