SUNRPC: create RPC pipefs superblock per network namespace context

This is the initial step of RPC pipefs virtualization. It changes nothing to
current pipefs behaviour except that mount of pipefs in other than init_net
network namespace context will provide only root tree. No other dentries will
be visible.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

net/sunrpc/rpc_pipe.c

@@ -993,6 +993,7 @@ rpc_fill_super(struct super_block *sb, void *data, int silent)
 {
 	struct inode *inode;
 	struct dentry *root;
+	struct net *net = data;
 
 	sb->s_blocksize = PAGE_CACHE_SIZE;
 	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
@@ -1017,7 +1018,7 @@ static struct dentry *
 rpc_mount(struct file_system_type *fs_type,
 		int flags, const char *dev_name, void *data)
 {
-	return mount_single(fs_type, flags, data, rpc_fill_super);
+	return mount_ns(fs_type, flags, current->nsproxy->net_ns, rpc_fill_super);
 }
 
 static struct file_system_type rpc_pipe_fs_type = {