[PATCH v1 1/6] xprtrdma: Add unique trace points for posting Local Invalidate WRs

[Chuck Lever <chuck.lever@xxxxxxxxxx>]

When adding frwr_unmap_async way back when, I re-used the existing
trace_xprtrdma_post_send() trace point to record the return code
of ib_post_send.

Unfortunately there are some cases where re-using that trace point
causes a crash. Instead, construct a trace point specific to posting
Local Invalidate WRs that will always be safe to use in that context,
and will act as a trace log eye-catcher for Local Invalidation.

Fixes: 847568942f93 ("xprtrdma: Remove fr_state")
Fixes: d8099feda483 ("xprtrdma: Reduce context switching due ... ")
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Tested-by: Bill Baker <bill.baker@xxxxxxxxxx>
---
 include/trace/events/rpcrdma.h |   25 +++++++++++++++++++++++++
 net/sunrpc/xprtrdma/frwr_ops.c |    4 ++--
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/rpcrdma.h b/include/trace/events/rpcrdma.h
index 9dd7680..31681cb 100644
--- a/include/trace/events/rpcrdma.h
+++ b/include/trace/events/rpcrdma.h
@@ -735,6 +735,31 @@
 	)
 );
 
+TRACE_EVENT(xprtrdma_post_linv,
+	TP_PROTO(
+		const struct rpcrdma_req *req,
+		int status
+	),
+
+	TP_ARGS(req, status),
+
+	TP_STRUCT__entry(
+		__field(const void *, req)
+		__field(int, status)
+		__field(u32, xid)
+	),
+
+	TP_fast_assign(
+		__entry->req = req;
+		__entry->status = status;
+		__entry->xid = be32_to_cpu(req->rl_slot.rq_xid);
+	),
+
+	TP_printk("req=%p xid=0x%08x status=%d",
+		__entry->req, __entry->xid, __entry->status
+	)
+);
+
 /**
  ** Completion events
  **/
diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index 30065a2..9901a81 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -570,7 +570,6 @@ void frwr_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
 	 */
 	bad_wr = NULL;
 	rc = ib_post_send(r_xprt->rx_ia.ri_id->qp, first, &bad_wr);
-	trace_xprtrdma_post_send(req, rc);
 
 	/* The final LOCAL_INV WR in the chain is supposed to
 	 * do the wake. If it was never posted, the wake will
@@ -583,6 +582,7 @@ void frwr_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
 
 	/* Recycle MRs in the LOCAL_INV chain that did not get posted.
 	 */
+	trace_xprtrdma_post_linv(req, rc);
 	while (bad_wr) {
 		frwr = container_of(bad_wr, struct rpcrdma_frwr,
 				    fr_invwr);
@@ -673,12 +673,12 @@ void frwr_unmap_async(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
 	 */
 	bad_wr = NULL;
 	rc = ib_post_send(r_xprt->rx_ia.ri_id->qp, first, &bad_wr);
-	trace_xprtrdma_post_send(req, rc);
 	if (!rc)
 		return;
 
 	/* Recycle MRs in the LOCAL_INV chain that did not get posted.
 	 */
+	trace_xprtrdma_post_linv(req, rc);
 	while (bad_wr) {
 		frwr = container_of(bad_wr, struct rpcrdma_frwr, fr_invwr);
 		mr = container_of(frwr, struct rpcrdma_mr, frwr);