[PATCH v2 05/18] svcrdma: Factor out WR chain linking into helper

[Chuck Lever <cel@kernel.org>]

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

svc_rdma_prepare_write_chunk() and svc_rdma_prepare_reply_chunk()
contain identical code for linking RDMA R/W work requests onto a
Send context's WR chain. This duplication increases maintenance
burden and risks divergent bug fixes.

Introduce svc_rdma_cc_link_wrs() to consolidate the WR chain
linking logic. The helper walks the chunk context's rwctxts list,
chains each WR via rdma_rw_ctx_wrs(), and updates the Send
context's chain head and SQE count. Completion signaling is
requested only for the tail WR (posted first).

No functional change.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/sunrpc/xprtrdma/svc_rdma_rw.c | 67 +++++++++++++------------------
 1 file changed, 28 insertions(+), 39 deletions(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
index c5d65164eae2..b1237d81075b 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
@@ -619,15 +619,32 @@ static int svc_rdma_xb_write(const struct xdr_buf *xdr, void *data)
 	return xdr->len;
 }
 
-/*
- * svc_rdma_prepare_write_chunk - Link Write WRs for @chunk onto @sctxt's chain
- *
- * Write WRs are prepended to the Send WR chain so that a single
- * ib_post_send() posts both RDMA Writes and the final Send. Only
- * the first WR in each chunk gets a CQE for error detection;
- * subsequent WRs complete without individual completion events.
- * The Send WR's signaled completion indicates all chained
- * operations have finished.
+/* Link chunk WRs onto @sctxt's WR chain. Completion is requested
+ * for the tail WR, which is posted first.
+ */
+static void svc_rdma_cc_link_wrs(struct svcxprt_rdma *rdma,
+				 struct svc_rdma_send_ctxt *sctxt,
+				 struct svc_rdma_chunk_ctxt *cc)
+{
+	struct ib_send_wr *first_wr;
+	struct list_head *pos;
+	struct ib_cqe *cqe;
+
+	first_wr = sctxt->sc_wr_chain;
+	cqe = &cc->cc_cqe;
+	list_for_each(pos, &cc->cc_rwctxts) {
+		struct svc_rdma_rw_ctxt *rwc;
+
+		rwc = list_entry(pos, struct svc_rdma_rw_ctxt, rw_list);
+		first_wr = rdma_rw_ctx_wrs(&rwc->rw_ctx, rdma->sc_qp,
+					   rdma->sc_port_num, cqe, first_wr);
+		cqe = NULL;
+	}
+	sctxt->sc_wr_chain = first_wr;
+	sctxt->sc_sqecount += cc->cc_sqecount;
+}
+
+/* Link Write WRs for @chunk onto @sctxt's WR chain.
  */
 static int svc_rdma_prepare_write_chunk(struct svcxprt_rdma *rdma,
 					struct svc_rdma_send_ctxt *sctxt,
@@ -636,10 +653,7 @@ static int svc_rdma_prepare_write_chunk(struct svcxprt_rdma *rdma,
 {
 	struct svc_rdma_write_info *info;
 	struct svc_rdma_chunk_ctxt *cc;
-	struct ib_send_wr *first_wr;
 	struct xdr_buf payload;
-	struct list_head *pos;
-	struct ib_cqe *cqe;
 	int ret;
 
 	if (xdr_buf_subsegment(xdr, &payload, chunk->ch_position,
@@ -659,18 +673,7 @@ static int svc_rdma_prepare_write_chunk(struct svcxprt_rdma *rdma,
 	if (unlikely(sctxt->sc_sqecount + cc->cc_sqecount > rdma->sc_sq_depth))
 		goto out_err;
 
-	first_wr = sctxt->sc_wr_chain;
-	cqe = &cc->cc_cqe;
-	list_for_each(pos, &cc->cc_rwctxts) {
-		struct svc_rdma_rw_ctxt *rwc;
-
-		rwc = list_entry(pos, struct svc_rdma_rw_ctxt, rw_list);
-		first_wr = rdma_rw_ctx_wrs(&rwc->rw_ctx, rdma->sc_qp,
-					   rdma->sc_port_num, cqe, first_wr);
-		cqe = NULL;
-	}
-	sctxt->sc_wr_chain = first_wr;
-	sctxt->sc_sqecount += cc->cc_sqecount;
+	svc_rdma_cc_link_wrs(rdma, sctxt, cc);
 	list_add(&info->wi_list, &sctxt->sc_write_info_list);
 
 	trace_svcrdma_post_write_chunk(&cc->cc_cid, cc->cc_sqecount);
@@ -732,9 +735,6 @@ int svc_rdma_prepare_reply_chunk(struct svcxprt_rdma *rdma,
 {
 	struct svc_rdma_write_info *info = &sctxt->sc_reply_info;
 	struct svc_rdma_chunk_ctxt *cc = &info->wi_cc;
-	struct ib_send_wr *first_wr;
-	struct list_head *pos;
-	struct ib_cqe *cqe;
 	int ret;
 
 	info->wi_rdma = rdma;
@@ -748,18 +748,7 @@ int svc_rdma_prepare_reply_chunk(struct svcxprt_rdma *rdma,
 	if (ret < 0)
 		return ret;
 
-	first_wr = sctxt->sc_wr_chain;
-	cqe = &cc->cc_cqe;
-	list_for_each(pos, &cc->cc_rwctxts) {
-		struct svc_rdma_rw_ctxt *rwc;
-
-		rwc = list_entry(pos, struct svc_rdma_rw_ctxt, rw_list);
-		first_wr = rdma_rw_ctx_wrs(&rwc->rw_ctx, rdma->sc_qp,
-					   rdma->sc_port_num, cqe, first_wr);
-		cqe = NULL;
-	}
-	sctxt->sc_wr_chain = first_wr;
-	sctxt->sc_sqecount += cc->cc_sqecount;
+	svc_rdma_cc_link_wrs(rdma, sctxt, cc);
 
 	trace_svcrdma_post_reply_chunk(&cc->cc_cid, cc->cc_sqecount);
 	return xdr->len;
-- 
2.53.0