[PATCH v2] Do not enter setup_callback_client when finding backchannel failed

[Kinglong Mee <kinglongmee@gmail.com>]

Finding backchannel failed, nfsd should not enter setup_callback_client.

v2. drop ses checking in setup_callback_client and make code more clearer.

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
---
 fs/nfsd/nfs4callback.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index 7f05cd1..44d33ce 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -975,11 +975,15 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
 	clear_bit(NFSD4_CLIENT_CB_UPDATE, &clp->cl_flags);
 	memcpy(&conn, &cb->cb_clp->cl_cb_conn, sizeof(struct nfs4_cb_conn));
 	c = __nfsd4_find_backchannel(clp);
-	if (c) {
-		svc_xprt_get(c->cn_xprt);
-		conn.cb_xprt = c->cn_xprt;
-		ses = c->cn_session;
+	if (!c) {
+		spin_unlock(&clp->cl_lock);
+		nfsd4_mark_cb_down(clp, -ENOTCONN);
+		return;
 	}
+
+	svc_xprt_get(c->cn_xprt);
+	conn.cb_xprt = c->cn_xprt;
+	ses = c->cn_session;
 	spin_unlock(&clp->cl_lock);
 
 	err = setup_callback_client(clp, &conn, ses);
-- 
1.8.4.2