[PATCH] sunrpc: Fix trace events to store data in the struct

[James Hogan <james.hogan@imgtec.com>]

Commit 83a712e0afef ("sunrpc: add some tracepoints around enqueue and
dequeue of svc_xprt") merged in v3.19-rc1 added some new trace events,
however a couple of them printed data from dereferenced pointers rather
than storing the data in the struct. In general this isn't safe as the
print may not happen until later when the data may have changed or been
freed, and nor is it portable as userland won't have access to that
other data in order to interpret the trace data itself.

Fix by copying the data into the struct and printing from there.

Fixes: 83a712e0afef ("sunrpc: add some tracepoints around enqueue ...")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Jeff Layton <jlayton@primarydata.com>
Cc: J. Bruce Fields <bfields@redhat.com>
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: <stable@vger.kernel.org> # v3.19+
---
Build tested only. Perhaps somebody familiar with the code could give it
a spin to sanity check the trace output.
---
 include/trace/events/sunrpc.h | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
index b9c1dc6c825a..47dfcaebfaaf 100644
--- a/include/trace/events/sunrpc.h
+++ b/include/trace/events/sunrpc.h
@@ -503,18 +503,22 @@ TRACE_EVENT(svc_xprt_do_enqueue,
 
 	TP_STRUCT__entry(
 		__field(struct svc_xprt *, xprt)
-		__field(struct svc_rqst *, rqst)
+		__field_struct(struct sockaddr_storage, ss)
+		__field(unsigned long, flags);
+		__field(int, pid)
 	),
 
 	TP_fast_assign(
 		__entry->xprt = xprt;
-		__entry->rqst = rqst;
+		xprt ? memcpy(&__entry->ss, &xprt->xpt_remote, sizeof(__entry->ss)) : memset(&__entry->ss, 0, sizeof(__entry->ss));
+		__entry->flags = xprt ? xprt->xpt_flags : 0;
+		__entry->pid = rqst ? rqst->rq_task->pid : 0;
 	),
 
 	TP_printk("xprt=0x%p addr=%pIScp pid=%d flags=%s", __entry->xprt,
-		(struct sockaddr *)&__entry->xprt->xpt_remote,
-		__entry->rqst ? __entry->rqst->rq_task->pid : 0,
-		show_svc_xprt_flags(__entry->xprt->xpt_flags))
+		(struct sockaddr *)&__entry->ss,
+		__entry->pid,
+		show_svc_xprt_flags(__entry->flags))
 );
 
 TRACE_EVENT(svc_xprt_dequeue,
@@ -562,17 +566,21 @@ TRACE_EVENT(svc_handle_xprt,
 
 	TP_STRUCT__entry(
 		__field(struct svc_xprt *, xprt)
+		__field_struct(struct sockaddr_storage, ss)
+		__field(unsigned long, flags);
 		__field(int, len)
 	),
 
 	TP_fast_assign(
 		__entry->xprt = xprt;
+		xprt ? memcpy(&__entry->ss, &xprt->xpt_remote, sizeof(__entry->ss)) : memset(&__entry->ss, 0, sizeof(__entry->ss));
+		__entry->flags = xprt ? xprt->xpt_flags : 0;
 		__entry->len = len;
 	),
 
 	TP_printk("xprt=0x%p addr=%pIScp len=%d flags=%s", __entry->xprt,
-		(struct sockaddr *)&__entry->xprt->xpt_remote, __entry->len,
-		show_svc_xprt_flags(__entry->xprt->xpt_flags))
+		(struct sockaddr *)&__entry->ss, __entry->len,
+		show_svc_xprt_flags(__entry->flags))
 );
 #endif /* _TRACE_SUNRPC_H */
 
-- 
2.0.5