From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:33052 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728957AbeHORLm (ORCPT ); Wed, 15 Aug 2018 13:11:42 -0400 Message-ID: <8acb99be800a1842278f754986a17d6fc93af409.camel@kernel.org> Subject: Re: [BUG][BISECT] NFSv4 root failures after "fs/locks: allow a lock request to block other requests." From: Jeff Layton To: Krzysztof Kozlowski , NeilBrown Cc: Alexander Viro , "J. Bruce Fields" , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, "linux-samsung-soc@vger.kernel.org" Date: Wed, 15 Aug 2018 10:19:18 -0400 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, 2018-08-15 at 14:28 +0200, Krzysztof Kozlowski wrote: > Hi, > > Bisect pointed commit ce3147990450a68b3f549088b30f087742a08b5d > ("fs/locks: allow a lock request to block other requests.") to failure > boot of NFSv4 with root on several boards. > > Log is here: > https://krzk.eu/#/builders/21/builds/836/steps/12/logs/serial0 > > With several errors: > kernel BUG at ../fs/locks.c:336! > Unable to handle kernel NULL pointer dereference at virtual address 00000004 > > Configuration: > 1. exynos_defconfig > 2. Arch ARM Linux > 3. Boards: > a. Odroid family (ARMv7, octa-core (Cortex-A7+A15), Exynos5422 SoC) > b. Toradex Colibri VF50 (ARMv7, UP, Cortex-A5) > 4. Systemd: v236, 238 > 5. All boards boot from TFTP with NFS root (NFSv4) > > On Colibri VF50 I got slightly different errors: > [ 11.663204] Internal error: Oops - undefined instruction: 0 [#1] ARM > [ 12.455273] Unable to handle kernel NULL pointer dereference at > virtual address 00000004 > and only with some specific GCC (v6.3) or with other conditions which > I did not bisect yet. Maybe Colibri's failure is unrelated to that > commit. > > Best regards, > Krzysztof The BUG is due to a lock being freed when the fl_blocked list wasn't empty (implying that there were still blocked locks waiting on it). There are a number of calls to locks_delete_lock_ctx in posix_lock_inode and I don't think the fl_blocked list is being handled properly with all of them. It only transplants the blocked locks to a new lock when there are surviving locks on the list, and that may not be the case when the whole file is being unlocked. -- Jeff Layton