From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f50.google.com ([74.125.82.50]:37339 "EHLO mail-wm0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753971AbcATUin (ORCPT ); Wed, 20 Jan 2016 15:38:43 -0500 Subject: Re: Kernel 4.4.0 KVM guest on Btrfs locks up on snapshotting To: Roman Mamedov References: <20160120030223.22cc3ae0@natsu> <569EB653.9080700@redhat.com> <20160120040302.308f054e@natsu> <1185704624.11958670.1453278484410.JavaMail.zimbra@redhat.com> <20160120185810.2c566f98@natsu> <569FC3C1.2000804@redhat.com> <20160120234638.39695c15@natsu> Cc: linux-btrfs@vger.kernel.org, kvm@vger.kernel.org From: Paolo Bonzini Message-ID: <569FF04F.7080507@redhat.com> Date: Wed, 20 Jan 2016 21:38:39 +0100 MIME-Version: 1.0 In-Reply-To: <20160120234638.39695c15@natsu> Content-Type: text/plain; charset=windows-1252 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 20/01/2016 19:46, Roman Mamedov wrote: > On Wed, 20 Jan 2016 18:28:33 +0100 Paolo Bonzini > wrote: > >>>> Also, can you find the value of the "FUA" file in sysfs >>>> (e.g. with "cat /sys/block/sda/device/scsi_disk/*/FUA")? >>> >>> It is 0 both in IDE and SCSI modes. >> >> And in the host? > > On the host the backing block device for the host filesystem is an > MD RAID6, it does not have the FUA setting. For the actual sdX > disks, it's all 0 as well. > > As I said this might be not KVM-specific, but rather a Btrfs-only > related issue. That KVM with IDE doesn't show the problem, might be > a coincidence since as you mentioned it doesn't load the disks as > heavily. > > If you're interested in my reproducer outside of KVM, I started a > new thread: > http://permalink.gmane.org/gmane.comp.file-systems.btrfs/52369 Oh that's great. Indeed the "info status" output would have pointed at an ENOSPC. It's definitely not KVM specific. Paolo