[PATCH v2 1/3] xprtrdma: Use sendctx DMA state for Send signaling

[Chuck Lever <cel@kernel.org>]

From: Chuck Lever <chuck.lever@oracle.com>

Send signaling matters only when the prepared Send has page
mappings to unmap. Today that test is expressed indirectly with
rl_kref, because the Send-side reference is taken only for Sends
with mapped SGEs.

Split the SGE DMA unmap loop into its own helper and use
sc_unmap_count directly for the signaling decision. This keeps the
current behavior but removes one dependency on the old rl_kref
semantics before the request lifetime rules are changed.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/sunrpc/xprtrdma/frwr_ops.c |  2 +-
 net/sunrpc/xprtrdma/rpc_rdma.c | 22 +++++++++++++---------
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index 7f79a0a2601e..e5c71cf705a3 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -474,7 +474,7 @@ int frwr_send(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
 		++num_wrs;
 	}
 
-	if ((kref_read(&req->rl_kref) > 1) || num_wrs > ep->re_send_count) {
+	if (req->rl_sendctx->sc_unmap_count || num_wrs > ep->re_send_count) {
 		send_wr->send_flags |= IB_SEND_SIGNALED;
 		ep->re_send_count = min_t(unsigned int, ep->re_send_batch,
 					  num_wrs - ep->re_send_count);
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 0e0f21974710..16b9987858d6 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -477,19 +477,11 @@ static void rpcrdma_sendctx_done(struct kref *kref)
 	rep->rr_rxprt->rx_stats.reply_waits_for_send++;
 }
 
-/**
- * rpcrdma_sendctx_unmap - DMA-unmap Send buffer
- * @sc: sendctx containing SGEs to unmap
- *
- */
-void rpcrdma_sendctx_unmap(struct rpcrdma_sendctx *sc)
+static void rpcrdma_sendctx_dma_unmap(struct rpcrdma_sendctx *sc)
 {
 	struct rpcrdma_regbuf *rb = sc->sc_req->rl_sendbuf;
 	struct ib_sge *sge;
 
-	if (!sc->sc_unmap_count)
-		return;
-
 	/* The first two SGEs contain the transport header and
 	 * the inline buffer. These are always left mapped so
 	 * they can be cheaply re-used.
@@ -498,7 +490,19 @@ void rpcrdma_sendctx_unmap(struct rpcrdma_sendctx *sc)
 	     ++sge, --sc->sc_unmap_count)
 		ib_dma_unmap_page(rdmab_device(rb), sge->addr, sge->length,
 				  DMA_TO_DEVICE);
+}
 
+/**
+ * rpcrdma_sendctx_unmap - DMA-unmap Send buffer
+ * @sc: sendctx containing SGEs to unmap
+ *
+ */
+void rpcrdma_sendctx_unmap(struct rpcrdma_sendctx *sc)
+{
+	if (!sc->sc_unmap_count)
+		return;
+
+	rpcrdma_sendctx_dma_unmap(sc);
 	kref_put(&sc->sc_req->rl_kref, rpcrdma_sendctx_done);
 }
 
-- 
2.54.0