SUNRPC: discard sv_refcnt, and svc_get/svc_put

sv_refcnt is no longer useful.
lockd and nfs-cb only ever have the svc active when there are a non-zero
number of threads, so sv_refcnt mirrors sv_nrthreads.

nfsd also keeps the svc active between when a socket is added and when
the first thread is started, but we don't really need a refcount for
that.  We can simply not destroy the svc while there are any permanent
sockets attached.

So remove sv_refcnt and the get/put functions.
Instead of a final call to svc_put(), call svc_destroy() instead.
This is changed to also store NULL in the passed-in pointer to make it
easier to avoid use-after-free situations.

Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

1 files changed, 4 insertions, 6 deletions

diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
index 81be07c1d3d1..0d6cb3fdc0e1 100644
--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -345,10 +345,10 @@ static int lockd_get(void)
 
 	serv->sv_maxconn = nlm_max_connections;
 	error = svc_set_num_threads(serv, NULL, 1);
-	/* The thread now holds the only reference */
-	svc_put(serv);
-	if (error < 0)
+	if (error < 0) {
+		svc_destroy(&serv);
 		return error;
+	}
 
 	nlmsvc_serv = serv;
 	register_inetaddr_notifier(&lockd_inetaddr_notifier);
@@ -372,11 +372,9 @@ static void lockd_put(void)
 	unregister_inet6addr_notifier(&lockd_inet6addr_notifier);
 #endif
 
-	svc_get(nlmsvc_serv);
 	svc_set_num_threads(nlmsvc_serv, NULL, 0);
-	svc_put(nlmsvc_serv);
 	timer_delete_sync(&nlmsvc_retry);
-	nlmsvc_serv = NULL;
+	svc_destroy(&nlmsvc_serv);
 	dprintk("lockd_down: service destroyed\n");
 }