From mboxrd@z Thu Jan 1 00:00:00 1970 From: Fernando Luis Vazquez Cao Subject: Re: [RFC 0/9 v3] fsfreeze: miscellaneous fixes and cleanups Date: Fri, 14 Sep 2012 11:20:41 +0900 Message-ID: <50529479.1040503@lab.ntt.co.jp> References: <1347533862.5646.2.camel@nexus.lab.ntt.co.jp> <20120914005700.GP11511@dastard> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Al Viro , Josef Bacik , Eric Sandeen , Dave Chinner , Christoph Hellwig , Jan Kara , linux-fsdevel@vger.kernel.org To: Dave Chinner Return-path: Received: from tama500.ecl.ntt.co.jp ([129.60.39.148]:39302 "EHLO tama500.ecl.ntt.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752977Ab2INCU6 (ORCPT ); Thu, 13 Sep 2012 22:20:58 -0400 In-Reply-To: <20120914005700.GP11511@dastard> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 2012/09/14 09:57, Dave Chinner wrote: > On Thu, Sep 13, 2012 at 07:57:42PM +0900, Fernando Luis V=E1zquez Cao= wrote: >> This patch set is to address long standing issues in the filesytem f= reeze code >> and to fill some functionality gaps in the API. Some minor code rear= rangements >> are included too. >> >> The following patches are included: >> >> --- >> [1/9] vfs: add __iterate_supers() helper >> [2/9] fsfreeze: add unlocked version of thaw_super >> >> Preparatory patches to fix s_umount lockup of emergency thaw code. >> >> [3/9] fsfreeze: Prevent emergency thaw from looping infinitely >> >> Fix thaw_bdev so that it propagates the error code properly to the c= aller. >> This bug caused emergency thaw to loop infinitely. This is a forward= port of >> a previous patch by Dave Chinner. >> >> [4/9] fsfreeze: emergency thaw will deadlock on s_umount >> >> Avoid emergency thaw deadlock on s_umount by using unlocked version = of >> thaw_super() and __iterate_supers()i (introduced in patches 2 and 1 >> respectively). > Given the problems with emergency thaw, this interface has never > really worked. In the absence of any obvious need for the > functionality (i.e. nobody has reported that it is broken since it > was introduced), why don't we simply remove it? > > IIRC, the emergency thaw code was only added to alleviate > fear-mongering about systems getting stuck with unfreezable ext4 > filesystems (after the "freeze w/ timeout" extensions were knocked > back), and time has indicated those fears were unfounded. > > So, rather than trying to fix the emergency thaw mess, I say we > nuke it from orbit.... As I commented to Eric, In virtualization environments it comes in handy sometimes. For example, in an emergency case where a guest agent dies leaving one or more filesystems frozen emergency thaw is useful. Hopefully my fix is correct and we can keep this feature. Thanks, =46ernando -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel= " in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html