nfs: add a refcount tracker for struct net as held by the nfs_client

These are long-held references to the netns, so make sure the refcount
tracker is aware of them.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

Author: jtlayton

fs/nfs/client.c

@@ -180,7 +180,7 @@ struct nfs_client *nfs_alloc_client(const struct nfs_client_initdata *cl_init)
 	clp->cl_proto = cl_init->proto;
 	clp->cl_nconnect = cl_init->nconnect;
 	clp->cl_max_connect = cl_init->max_connect ? cl_init->max_connect : 1;
-	clp->cl_net = get_net(cl_init->net);
+	clp->cl_net = get_net_track(cl_init->net, &clp->cl_ns_tracker, GFP_KERNEL);
 
 #if IS_ENABLED(CONFIG_NFS_LOCALIO)
 	seqlock_init(&clp->cl_boot_lock);
@@ -250,7 +250,7 @@ void nfs_free_client(struct nfs_client *clp)
 	if (!IS_ERR(clp->cl_rpcclient))
 		rpc_shutdown_client(clp->cl_rpcclient);
 
-	put_net(clp->cl_net);
+	put_net_track(clp->cl_net, &clp->cl_ns_tracker);
 	put_nfs_version(clp->cl_nfs_mod);
 	kfree(clp->cl_hostname);
 	kfree(clp->cl_acceptor);

include/linux/nfs_fs_sb.h

@@ -125,6 +125,7 @@ struct nfs_client {
 	 */
 	char			cl_ipaddr[48];
 	struct net		*cl_net;
+	netns_tracker		cl_ns_tracker;
 	struct list_head	pending_cb_stateids;
 	struct rcu_head		rcu;