rpc_pipefs.c: get rid of f_dentry

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/nfs/blocklayout/rpc_pipefs.c

@@ -109,7 +109,7 @@ out:
 static ssize_t bl_pipe_downcall(struct file *filp, const char __user *src,
 			 size_t mlen)
 {
-	struct nfs_net *nn = net_generic(filp->f_dentry->d_sb->s_fs_info,
+	struct nfs_net *nn = net_generic(file_inode(filp)->i_sb->s_fs_info,
 					 nfs_net_id);
 
 	if (mlen != sizeof (struct bl_dev_msg))