From owner-freebsd-fs@FreeBSD.ORG Sun Jul 21 09:37:50 2013 Return-Path: Delivered-To: freebsd-fs@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 6B4EA607 for ; Sun, 21 Jul 2013 09:37:50 +0000 (UTC) (envelope-from avg@FreeBSD.org) Received: from citadel.icyb.net.ua (citadel.icyb.net.ua [212.40.38.140]) by mx1.freebsd.org (Postfix) with ESMTP id B2FBAE96 for ; Sun, 21 Jul 2013 09:37:49 +0000 (UTC) Received: from porto.starpoint.kiev.ua (porto-e.starpoint.kiev.ua [212.40.38.100]) by citadel.icyb.net.ua (8.8.8p3/ICyb-2.3exp) with ESMTP id MAA28755; Sun, 21 Jul 2013 12:37:39 +0300 (EEST) (envelope-from avg@FreeBSD.org) Received: from localhost ([127.0.0.1]) by porto.starpoint.kiev.ua with esmtp (Exim 4.34 (FreeBSD)) id 1V0q5D-000Jif-MD; Sun, 21 Jul 2013 12:37:39 +0300 Message-ID: <51EBABAB.5040808@FreeBSD.org> Date: Sun, 21 Jul 2013 12:36:43 +0300 From: Andriy Gapon User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:17.0) Gecko/20130708 Thunderbird/17.0.7 MIME-Version: 1.0 To: Konstantin Belousov Subject: Re: Deadlock in nullfs/zfs somewhere References: <51E7B686.4090509@FreeBSD.org> <20130718112814.GA5991@kib.kiev.ua> <51E7F05A.5020609@FreeBSD.org> <20130718185215.GE5991@kib.kiev.ua> <51E91277.3070309@FreeBSD.org> <20130719103025.GJ5991@kib.kiev.ua> <51E95CDD.7030702@FreeBSD.org> <20130719184243.GM5991@kib.kiev.ua> <51E99477.1030308@FreeBSD.org> <20130721071124.GY5991@kib.kiev.ua> In-Reply-To: <20130721071124.GY5991@kib.kiev.ua> X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: freebsd-fs@FreeBSD.org X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 21 Jul 2013 09:37:50 -0000 on 21/07/2013 10:11 Konstantin Belousov said the following: > On Fri, Jul 19, 2013 at 10:33:11PM +0300, Andriy Gapon wrote: >> on 19/07/2013 21:42 Konstantin Belousov said the following: >>> Then, you cannot use VFS suspension. Or, in other words, you are >>> directed to abuse the VFS interface. I assure you that any changes to >>> the interface would not take into account such abuse and probably break >>> your hack. >> >> So what would be your recommendation about this problem? Should we add >> another flavor of VFS suspension? The one that would mean "all external >> accesses to this fs must be put on hold", but would not imply "this fs is >> frozen". > > Suspension is very complicated as it is. Adding another flavour would > multiply the current mess^H^H^H^H collection of subtleties. IMO, the best > route is to use the KPI properly, i.e. adding the vn_start_write() braces > around the top-level entries in the mutating code paths. > So how will this help with doing a rollback in the thread that does the following? vfs_write_suspend zfs rollback vfs_write_resume -- Andriy Gapon