statfs() gives ESTALE error

Hi,

An NFS client executes a statfs("file", &buff) call.
"file" exists / existed, the client has read / written it,
but it has already closed it.

user_path(pathname, &path) looks up "file" successfully in the
directory-cache  and restarts the aging timer of the directory-entry.
Even if "file" has already been removed from the server, because the
lookupcache=positive option I use, keeps the entries valid for a while.

nfs_statfs() returns ESTALE if "file" has already been removed from the
server.

If the user application repeats the statfs("file", &buff) call, we
are stuck: "file" remains young forever in the directory-cache.
Signed-off-by: NZoltan Menyhart  <Zoltan.Menyhart@bull.net>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org

fs/nfs/super.c

@@ -431,7 +431,15 @@ static int nfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 		goto out_err;
 
 	error = server->nfs_client->rpc_ops->statfs(server, fh, &res);
+	if (unlikely(error == -ESTALE)) {
+		struct dentry *pd_dentry;
 
+		pd_dentry = dget_parent(dentry);
+		if (pd_dentry != NULL) {
+			nfs_zap_caches(pd_dentry->d_inode);
+			dput(pd_dentry);
+		}
+	}
 	nfs_free_fattr(res.fattr);
 	if (error < 0)
 		goto out_err;