From: Trond Myklebust <trond.myklebust@hammerspace.com>
Date: Tue, 16 Jul 2019 07:07:28 -0400
Subject: [PATCH] SUNRPC: Skip zero-refcount transports
Git-commit: 163f88211c147d96b46e376337190a02203ace02
Patch-mainline: v5.3
References: bnc#1192729

When looking for the next transport to use for an RPC call, skip those
that are in the process of being destroyed and that have a zero refcount.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 net/sunrpc/xprtmultipath.c |   20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

--- a/net/sunrpc/xprtmultipath.c
+++ b/net/sunrpc/xprtmultipath.c
@@ -193,9 +193,21 @@ void xprt_iter_default_rewind(struct rpc
 }
 
 static
+bool xprt_is_active(const struct rpc_xprt *xprt)
+{
+	return kref_read(&xprt->kref) != 0;
+}
+
+static
 struct rpc_xprt *xprt_switch_find_first_entry(struct list_head *head)
 {
-	return list_first_or_null_rcu(head, struct rpc_xprt, xprt_switch);
+	struct rpc_xprt *pos;
+
+	list_for_each_entry_rcu(pos, head, xprt_switch) {
+		if (xprt_is_active(pos))
+			return pos;
+	}
+	return NULL;
 }
 
 static
@@ -213,9 +225,12 @@ struct rpc_xprt *xprt_switch_find_curren
 		const struct rpc_xprt *cur)
 {
 	struct rpc_xprt *pos;
+	bool found = false;
 
 	list_for_each_entry_rcu(pos, head, xprt_switch) {
 		if (cur == pos)
+			found = true;
+		if (found && xprt_is_active(pos))
 			return pos;
 	}
 	return NULL;
@@ -260,9 +275,12 @@ struct rpc_xprt *xprt_switch_find_next_e
 		const struct rpc_xprt *cur)
 {
 	struct rpc_xprt *pos, *prev = NULL;
+	bool found = false;
 
 	list_for_each_entry_rcu(pos, head, xprt_switch) {
 		if (cur == prev)
+			found = true;
+		if (found && xprt_is_active(pos))
 			return pos;
 		prev = pos;
 	}