NFS: Shut down the nfs_client only after all the superblocks

The nfs_client manages state for all the superblocks in the
"cl_superblocks" list, so it must not be shut down until all of them are
gone.

Fixes: 7d3e26a ("NFS: Cancel all existing RPC tasks when shutdown")
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Author: Trond Myklebust

fs/nfs/sysfs.c

@@ -14,6 +14,7 @@
 #include <linux/rcupdate.h>
 #include <linux/lockd/lockd.h>
 
+#include "internal.h"
 #include "nfs4_fs.h"
 #include "netns.h"
 #include "sysfs.h"
@@ -228,6 +229,25 @@ static void shutdown_client(struct rpc_clnt *clnt)
 	rpc_cancel_tasks(clnt, -EIO, shutdown_match_client, NULL);
 }
 
+/*
+ * Shut down the nfs_client only once all the superblocks
+ * have been shut down.
+ */
+static void shutdown_nfs_client(struct nfs_client *clp)
+{
+	struct nfs_server *server;
+	rcu_read_lock();
+	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
+		if (!(server->flags & NFS_MOUNT_SHUTDOWN)) {
+			rcu_read_unlock();
+			return;
+		}
+	}
+	rcu_read_unlock();
+	nfs_mark_client_ready(clp, -EIO);
+	shutdown_client(clp->cl_rpcclient);
+}
+
 static ssize_t
 shutdown_show(struct kobject *kobj, struct kobj_attribute *attr,
 				char *buf)
@@ -259,14 +279,14 @@ shutdown_store(struct kobject *kobj, struct kobj_attribute *attr,
 
 	server->flags |= NFS_MOUNT_SHUTDOWN;
 	shutdown_client(server->client);
-	shutdown_client(server->nfs_client->cl_rpcclient);
 
 	if (!IS_ERR(server->client_acl))
 		shutdown_client(server->client_acl);
 
 	if (server->nlm_host)
 		shutdown_client(server->nlm_host->h_rpcclnt);
 out:
+	shutdown_nfs_client(server->nfs_client);
 	return count;
 }