From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6982C43140 for ; Fri, 6 Sep 2019 20:47:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AE93120838 for ; Fri, 6 Sep 2019 20:47:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403861AbfIFUrc (ORCPT ); Fri, 6 Sep 2019 16:47:32 -0400 Received: from mx2.math.uh.edu ([129.7.128.33]:47092 "EHLO mx2.math.uh.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725872AbfIFUrc (ORCPT ); Fri, 6 Sep 2019 16:47:32 -0400 Received: from epithumia.math.uh.edu ([129.7.128.2]) by mx2.math.uh.edu with esmtp (Exim 4.92) (envelope-from ) id 1i6L8e-0007bV-Em; Fri, 06 Sep 2019 15:47:26 -0500 Received: by epithumia.math.uh.edu (Postfix, from userid 7225) id 619B08014CF; Fri, 6 Sep 2019 15:47:24 -0500 (CDT) From: Jason L Tibbitts III To: "J. Bruce Fields" Cc: Wolfgang Walter , linux-nfs@vger.kernel.org, km@cm4all.com, linux-kernel@vger.kernel.org Subject: Re: Regression in 5.1.20: Reading long directory fails References: <4418877.15LTP4gqqJ@stwm.de> <4198657.JbNDGbLXiX@h2o.as.studentenwerk.mhn.de> <20190906144837.GD17204@fieldses.org> Date: Fri, 06 Sep 2019 15:47:24 -0500 In-Reply-To: <20190906144837.GD17204@fieldses.org> (J. Bruce Fields's message of "Fri, 6 Sep 2019 10:48:37 -0400") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>>>> "JBF" == J Bruce Fields writes: JBF> Those readdir changes were client-side, right? Based on that I'd JBF> been assuming a client bug, but maybe it'd be worth getting a full JBF> packet capture of the readdir reply to make sure it's legit. I have been working with bcodding on IRC for the past couple of days on this. Fortunately I was able to come up with way to fill up a directory in such a way that it will fail with certainty and as a bonus doesn't include any user data so I can feel OK about sharing packet captures. I have a capture alongside a kernel trace of the problematic operation in https://www.math.uh.edu/~tibbs/nfs/. Not that I can particularly tell anything useful from that, but bcodding says that it seems to point to some issue in sunrpc. And because I can easily reproduce this and I was able to do a bisect: 2c94b8eca1a26cd46010d6e73a23da5f2e93a19d is the first bad commit commit 2c94b8eca1a26cd46010d6e73a23da5f2e93a19d Author: Chuck Lever Date: Mon Feb 11 11:25:41 2019 -0500 SUNRPC: Use au_rslack when computing reply buffer size au_rslack is significantly smaller than (au_cslack << 2). Using that value results in smaller receive buffers. In some cases this eliminates an extra segment in Reply chunks (RPC/RDMA). Signed-off-by: Chuck Lever Signed-off-by: Anna Schumaker :040000 040000 d4d1ce2fbe0035c5bd9df976b8c448df85dcb505 7011a792dfe72ff9cd70d66e45d353f3d7817e3e M net But of course, I can't say whether this is the actual bad commit or whether it just introduced a behavior change which alters the conditions under which the problem appears. And just to make sure that the blame doesn't lie with the old RHEL7 kernel, I rsynced over the problematic directory to a machine running something slightly more modern (5.1.11, which I know I need to update, but it's already set up to do kerberised NFS) and the same problem exists, though the directory listing does fail at a different place. - J<