Commit efda760f authored Mar 28, 2017 by J. Bruce Fields

lockd: fix lockd shutdown race

As reported by David Jeffery: "a signal was sent to lockd while lockd
was shutting down from a request to stop nfs. The signal causes lockd
to call restart_grace() which puts the lockd_net structure on the grace
list. If this signal is received at the wrong time, it will occur after
lockd_down_net() has called locks_end_grace() but before
lockd_down_net() stops the lockd thread. This leads to lockd putting
the lockd_net structure back on the grace list, then exiting without
anything removing it from the list."

So, perform the final locks_end_grace() from the the lockd thread; this
ensures it's serialized with respect to restart_grace().

Reported-by: David Jeffery <djeffery@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

parent ed6473dd

fs/lockd/svc.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -132,6 +132,8 @@ lockd(void *vrqstp)
		{
		int err = 0;
		struct svc_rqst *rqstp = vrqstp;
		struct net *net = &init_net;
		struct lockd_net *ln = net_generic(net, lockd_net_id);

		/* try_to_freeze() is called from svc_recv() */
		set_freezable();
		@@ -176,6 +178,8 @@ lockd(void *vrqstp)
		if (nlmsvc_ops)
		nlmsvc_invalidate_all();
		nlm_shutdown_hosts();
		cancel_delayed_work_sync(&ln->grace_period_end);
		locks_end_grace(&ln->lockd_manager);
		return 0;
		}

		@@ -270,8 +274,6 @@ static void lockd_down_net(struct svc_serv serv, struct net net)
		if (ln->nlmsvc_users) {
		if (--ln->nlmsvc_users == 0) {
		nlm_shutdown_hosts_net(net);
		cancel_delayed_work_sync(&ln->grace_period_end);
		locks_end_grace(&ln->lockd_manager);
		svc_shutdown_net(serv, net);
		dprintk("lockd_down_net: per-net data destroyed; net=%p\n", net);
		}