From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Goran Subject: Re: [PATCH] bcache: fix uninterruptible sleep in writeback thread Date: Sat, 17 May 2014 05:47:21 +0000 (UTC) Message-ID: References: <1398981150-27765-1-git-send-email-sp@daterainc.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from plane.gmane.org ([80.91.229.3]:44174 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756293AbaEQFuG (ORCPT ); Sat, 17 May 2014 01:50:06 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1WlXVU-0000jN-6f for linux-bcache@vger.kernel.org; Sat, 17 May 2014 07:50:04 +0200 Received: from l37-193-243-154.novotelecom.ru ([37.193.243.154]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sat, 17 May 2014 07:50:04 +0200 Received: from via-bcache by l37-193-243-154.novotelecom.ru with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sat, 17 May 2014 07:50:04 +0200 Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: linux-bcache@vger.kernel.org Slava Pestov datera.io> writes: > There were two issues here: > > - writeback thread did not start until the device first became dirty > - writeback thread used uninterruptible sleep once running > > Without this patch I see kernel warnings printed and a load average of > 1.52 after booting my test VM. With this patch the warnings are gone and > the load average is near 0.00 as expected. Uninterruptible sleep is indeed fixed (as well as the annoying "blocked for more than 120 seconds" message), but with this patch, I have the following problem. If I run a bcache device with no cache attached, the kernel hangs when I try to reboot. It prints a long stack trace that takes all screen space and I can't see what is above it. If a cache is attached to the bcache device, rebooting works fine. Without the patch, rebooting works both with and without attached cache.