From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754583AbaEONqQ (ORCPT ); Thu, 15 May 2014 09:46:16 -0400 Received: from cantor2.suse.de ([195.135.220.15]:48611 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754226AbaEONqN (ORCPT ); Thu, 15 May 2014 09:46:13 -0400 Date: Thu, 15 May 2014 15:46:10 +0200 From: Jan Kara To: "Theodore Ts'o" Cc: Jan Kara , Mateusz Guzik , Dave Chinner , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Josef Bacik , Al Viro , Eric Sandeen Subject: Re: [PATCH 2/2] fs: print a message when freezing/unfreezing filesystems Message-ID: <20140515134610.GB660@quack.suse.cz> References: <1400005862-3751-1-git-send-email-mguzik@redhat.com> <1400005862-3751-2-git-send-email-mguzik@redhat.com> <20140514215457.GC5421@dastard> <20140515094236.GE10637@mguzik.redhat.com> <20140515100157.GB27289@quack.suse.cz> <20140515124725.GA8194@thunk.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140515124725.GA8194@thunk.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 15-05-14 08:47:25, Ted Tso wrote: > On Thu, May 15, 2014 at 12:01:57PM +0200, Jan Kara wrote: > > I was tracking down a couple of times what the hell is freezing the > > filesystem (and not unfreezing it) and I agree with Mateusz it would be > > nice if we could tell after the fact who froze the fs. Maybe we could store > > that information in superblock and dump it during emergency thaw? > > Saving it in the superblock would require changing a bunch of file > systems. What if we store this information in memory, and print it > out under certain conditions (i.e., after a soft lockup detection, or > upon request of some magic sysrq request)? By 'superblock' I meant 'struct super_block' ;) So we are in agreement I believe. > Or we could create a tunable threshold and print a message after a > file system has been frozen more than a particular specified duration, > with that duration set conservatively to something like 60 or 120 > seconds by default. I was thinking about this as well but all these "warn after X seconds" warnings tend to have quite a few false positives in practice so dumping this in emergency-thaw sysrq handler or exposing the information somewhere in proc (e.g. mountinfo) would look like a better option to me. Honza -- Jan Kara SUSE Labs, CR