[PATCH v1 1/5] SUNRPC: fire svc_xprt_free tracepoint before dropping the netns

[Chuck Lever <cel@kernel.org>]

svc_xprt_free() releases the transport's network namespace
reference and then fires trace_svc_xprt_free(), which reads
xpt_net->ns.inum through SVC_XPRT_ENDPOINT_ASSIGNMENTS. When the
transport holds the last reference, the namespace is already on
the cleanup list by the time the tracepoint reads it. The window
is narrow, since cleanup_net() runs from a workqueue, but nothing
holds the namespace alive across it.

Fire the tracepoint before any of the teardown steps, while every
field it records is still valid.

Fixes: 11bbb0f76e99 ("SUNRPC: Trace a few more generic svc_xprt events")
Signed-off-by: Chuck Lever <cel@kernel.org>
---
 net/sunrpc/svc_xprt.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index 77e28dcc4d2a..908569035e57 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -170,6 +170,8 @@ static void svc_xprt_free(struct kref *kref)
 	struct svc_xprt *xprt =
 		container_of(kref, struct svc_xprt, xpt_ref);
 	struct module *owner = xprt->xpt_class->xcl_owner;
+
+	trace_svc_xprt_free(xprt);
 	if (test_bit(XPT_CACHE_AUTH, &xprt->xpt_flags))
 		svcauth_unix_info_release(xprt);
 	put_cred(xprt->xpt_cred);
@@ -179,7 +181,6 @@ static void svc_xprt_free(struct kref *kref)
 		xprt_put(xprt->xpt_bc_xprt);
 	if (xprt->xpt_bc_xps)
 		xprt_switch_put(xprt->xpt_bc_xps);
-	trace_svc_xprt_free(xprt);
 	xprt->xpt_ops->xpo_free(xprt);
 	module_put(owner);
 }
-- 
2.55.0