lockd: remove SIGKILL handling

lockd allows SIGKILL and responds by dropping all locks and restarting
the grace period.  This functionality has been present since 2.1.32 when
lockd was added to Linux.

This functionality is undocumented and most likely added as a useful
debug aid.  When there is a need to drop locks, the better approach is
to use /proc/fs/nfsd/unlock_*.

This patch removes SIGKILL handling as part of preparation for removing
all signal handling from sunrpc service threads.
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/lockd/svc.c

@@ -45,7 +45,6 @@
 
 #define NLMDBG_FACILITY		NLMDBG_SVC
 #define LOCKD_BUFSIZE		(1024 + NLMSVC_XDRSIZE)
-#define ALLOWED_SIGS		(sigmask(SIGKILL))
 
 static struct svc_program	nlmsvc_program;
 
@@ -111,19 +110,6 @@ static void set_grace_period(struct net *net)
 	schedule_delayed_work(&ln->grace_period_end, grace_period);
 }
 
-static void restart_grace(void)
-{
-	if (nlmsvc_ops) {
-		struct net *net = &init_net;
-		struct lockd_net *ln = net_generic(net, lockd_net_id);
-
-		cancel_delayed_work_sync(&ln->grace_period_end);
-		locks_end_grace(&ln->lockd_manager);
-		nlmsvc_invalidate_all();
-		set_grace_period(net);
-	}
-}
-
 /*
  * This is the lockd kernel thread
  */
@@ -138,9 +124,6 @@ lockd(void *vrqstp)
 	/* try_to_freeze() is called from svc_recv() */
 	set_freezable();
 
-	/* Allow SIGKILL to tell lockd to drop all of its locks */
-	allow_signal(SIGKILL);
-
 	dprintk("NFS locking service started (ver " LOCKD_VERSION ").\n");
 
 	/*
@@ -154,12 +137,6 @@ lockd(void *vrqstp)
 		/* update sv_maxconn if it has changed */
 		rqstp->rq_server->sv_maxconn = nlm_max_connections;
 
-		if (signalled()) {
-			flush_signals(current);
-			restart_grace();
-			continue;
-		}
-
 		timeout = nlmsvc_retry_blocked();
 
 		/*
@@ -174,7 +151,6 @@ lockd(void *vrqstp)
 
 		svc_process(rqstp);
 	}
-	flush_signals(current);
 	if (nlmsvc_ops)
 		nlmsvc_invalidate_all();
 	nlm_shutdown_hosts();