From: Eric Sandeen Subject: Re: [PATCH v2 1/7] Adding support to freeze and unfreeze a journal Date: Tue, 10 Jan 2012 21:08:27 -0600 Message-ID: <4F0CFD2B.7010404@redhat.com> References: <1323367477-21685-1-git-send-email-kamal@canonical.com> <1323367477-21685-2-git-send-email-kamal@canonical.com> <4F0C9D87.8010006@sandeen.net> <20120110213104.GI4516@quack.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Eric Sandeen , Kamal Mostafa , Alexander Viro , Andreas Dilger , Matthew Wilcox , Randy Dunlap , Theodore Tso , linux-doc@vger.kernel.org, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Surbhi Palande , Valerie Aurora , Christopher Chaltain , "Peter M. Petrakis" , Mikulas Patocka , Surbhi Palande To: Jan Kara Return-path: Received: from mx1.redhat.com ([209.132.183.28]:65207 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753299Ab2AKDJD (ORCPT ); Tue, 10 Jan 2012 22:09:03 -0500 In-Reply-To: <20120110213104.GI4516@quack.suse.cz> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 1/10/12 3:31 PM, Jan Kara wrote: > On Tue 10-01-12 14:20:23, Eric Sandeen wrote: >> Hrm let me think through this a little more; we actually do: >> >> t16) ext4_journal_start() >> t17) ext4_journal_start_sb() >> t18) handle = ext4_journal_current_handle(); >> t19) if (!handle) vfs_check_frozen() >> t20) ... jbd2_journal_start() > Ah, right. I forgot. > >> So actually we *do* block new handles, but let *existing* ones >> continue (see commits 6b0310fbf087ad6e9e3b8392adca97cd77184084 >> and be4f27d324e8ddd57cc0d4d604fe85ee0425cba9) >> >> So your assertion that a new handle is started is incorrect >> in general, isn't it? So then does the fix seem necessary? >> Or, at least, in the fashion below - maybe we need to just make >> sure all started handles complete before the unlock_updates? >> Or am I missing something...? > Well, the problem with running operations and freezing is more > fundamental I believe. See my email > http://marc.info/?l=linux-fsdevel&m=132585911925796&w=2 > > So I believe we'll need some better exclusion mechanism already in VFS. > > Honza > Yep, saw it, just wasn't sure if this patchset was still under active consideration. Thanks, -Eric