ncpfs: rcu-delay unload_nls() and freeing ncp_server

makes ->d_hash() and ->d_compare() safety in RCU mode independent
from vfsmount_lock.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ncpfs/inode.c

@@ -782,6 +782,17 @@ static int ncp_fill_super(struct super_block *sb, void *raw_data, int silent)
 	return error;
 }
 
+static void delayed_free(struct rcu_head *p)
+{
+	struct ncp_server *server = container_of(p, struct ncp_server, rcu);
+#ifdef CONFIG_NCPFS_NLS
+	/* unload the NLS charsets */
+	unload_nls(server->nls_vol);
+	unload_nls(server->nls_io);
+#endif /* CONFIG_NCPFS_NLS */
+	kfree(server);
+}
+
 static void ncp_put_super(struct super_block *sb)
 {
 	struct ncp_server *server = NCP_SBP(sb);
@@ -792,11 +803,6 @@ static void ncp_put_super(struct super_block *sb)
 
 	ncp_stop_tasks(server);
 
-#ifdef CONFIG_NCPFS_NLS
-	/* unload the NLS charsets */
-	unload_nls(server->nls_vol);
-	unload_nls(server->nls_io);
-#endif /* CONFIG_NCPFS_NLS */
 	mutex_destroy(&server->rcv.creq_mutex);
 	mutex_destroy(&server->root_setup_lock);
 	mutex_destroy(&server->mutex);
@@ -813,8 +819,7 @@ static void ncp_put_super(struct super_block *sb)
 	vfree(server->rxbuf);
 	vfree(server->txbuf);
 	vfree(server->packet);
-	sb->s_fs_info = NULL;
-	kfree(server);
+	call_rcu(&server->rcu, delayed_free);
 }
 
 static int ncp_statfs(struct dentry *dentry, struct kstatfs *buf)

fs/ncpfs/ncp_fs_sb.h

@@ -38,7 +38,7 @@ struct ncp_mount_data_kernel {
 };
 
 struct ncp_server {
-
+	struct rcu_head rcu;
 	struct ncp_mount_data_kernel m;	/* Nearly all of the mount data is of
 					   interest for us later, so we store
 					   it completely. */