From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc MERLIN Subject: Re: BUG: drivers/md/bcache/writeback.c:237 Date: Wed, 2 Mar 2016 20:25:58 -0800 Message-ID: <20160303042558.GP13143@merlins.org> References: <20160226024633.GF29543@merlins.org> <20160226031921.GG29543@merlins.org> <20160226162705.GA18927@merlins.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from magic.merlins.org ([209.81.13.136]:38475 "EHLO mail1.merlins.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756565AbcCCE0F (ORCPT ); Wed, 2 Mar 2016 23:26:05 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: Eric Wheeler Cc: Zhu Yanhai , Kent Overstreet , Christoph Nelles , linux-bcache@vger.kernel.org On Thu, Mar 03, 2016 at 04:17:24AM +0000, Eric Wheeler wrote: > On Fri, 26 Feb 2016, Eric Wheeler wrote: > > On Fri, 26 Feb 2016, Marc MERLIN wrote: > > > > > On Fri, Feb 26, 2016 at 04:55:02AM +0000, Eric Wheeler wrote: > > > > According to Documentation/bcache.txt: > > > > "" If you're booting up and your cache device is gone and never > > > > coming back, you can force run the backing device: > > > > echo 1 > /sys/block/sdb/bcache/running > > > > [...] > > > > The backing device will still use that cache set if it shows up > > > > in the future, but all the cached data will be invalidated. "" > > > > > > > > So it seems that you are safe. (It would be interesting to know how it > > > > invalidates the cache. Maybe bumps the Set UUID? Not sure.) > > > > > > Yeah, that was my understanding too, but I wanted to make sure. > > > Strangely (worringly so?) the cache was replayed at boot, and this time > > > nothing crashed, or any traceback. > > > Now I'm wondering if it pushed garbage onto my filesystem :-/ > > > > I'm not convinced that journal replay will writeback, especially because > > of the documentation stating that forcing a bdev into a running state > > invalidates its cache. I think it just keeps the datastructures in good > > shape on the cachedev, even though the cachedev was invalidated by forcing > > a 'running' state. > > Hi Marc, > > Thank you for your help investigating. The two patches resulting from our > testing are on their way into 4.5. I saw that, thank you. > How has it been running since? Any new backtraces to investigate? No crashes since then, although my last one started when I was shutting the laptop down, and I don't shut down very often (actually virtually never unless I upgrade kernels :) ). But that's another way ot say so far so good :) Thanks for your work looking into this. Marc -- "A mouse is a device used to point at the xterm you want to type in" - A.S.R. Microsoft is to operating systems .... .... what McDonalds is to gourmet cooking Home page: http://marc.merlins.org/ | PGP 1024R/763BE901