From owner-freebsd-stable@FreeBSD.ORG Mon May 30 11:41:09 2011 Return-Path: Delivered-To: stable@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 86B011065672; Mon, 30 May 2011 11:41:09 +0000 (UTC) (envelope-from borjam@sarenet.es) Received: from proxypop02.sare.net (proxypop02.sare.net [194.30.18.43]) by mx1.freebsd.org (Postfix) with ESMTP id 42C208FC15; Mon, 30 May 2011 11:41:08 +0000 (UTC) Received: from [172.16.1.55] (izaro.sarenet.es [192.148.167.11]) by proxypop02.sare.net (Postfix) with ESMTPSA id EDB09124E467; Mon, 30 May 2011 13:41:43 +0200 (CEST) Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: text/plain; charset=us-ascii From: Borja Marcos In-Reply-To: <1305876839.13971.5.camel@pow> Date: Mon, 30 May 2011 13:41:03 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <867340A1-B7F4-452C-BB7E-93CAF7E4ABA8@sarenet.es> References: <20110517073029.GA44359@icarus.home.lan> <4DD25264.8040305@FreeBSD.org> <20110517112952.GA48610@icarus.home.lan> <1305876839.13971.5.camel@pow> To: luke@hybrid-logic.co.uk X-Mailer: Apple Mail (2.1084) Cc: Charles Sprickman , stable@FreeBSD.org, Jeremy Chadwick , Andriy Gapon Subject: Re: 8.1R possible zfs snapshot livelock? X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 30 May 2011 11:41:09 -0000 On May 20, 2011, at 9:33 AM, Luke Marsden wrote: >> If you wish to reproduce it, try creating a dataset for /usr/obj, >> running make buildworld on it, replicating at, say, 30 or 60 second >> intervals, and keep several scripts (or rsync) reading the target >> dataset files and just copying them to another place in the usual, >> "classic" way. (example: tar cf - . | ( cd /destination && tar xf -) >>=20 >=20 > Is there a PR for this? I'd like to see it addressed, since read-only > I/O on a dataset which is being updated by `zfs recv` is an important > part of what we plan to do with ZFS on FreeBSD. Hello, Sorry for the delay to anwer. I think I added some information about = this issue to a related PR but I'm unable to find it right now. I had a discussion about this issue as well, you can read the relevant = threads here: http://osdir.com/ml/freebsd-fs/2010-03/msg00062.html http://kerneltrap.org/mailarchive/freebsd-fs/2009/10/31/6535463/thread In hindsight, however, unless you are working in very clearly defined = conditions, it doesn't make much sense to keep even reading activity on = the target dataset. What happens if you keep a file open for reading while the "zfs recv" = operation is done? What happens if you are traversing a directory, which = means that you keep the directory open, and the destination dataset is = "replaced" by a new one by a recv? For read-only operations I would rely on clones instead.=20 Borja.