From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from meiko.romanrm.net ([195.154.92.155]:52090 "EHLO meiko.romanrm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932261AbcATN6Q (ORCPT ); Wed, 20 Jan 2016 08:58:16 -0500 Date: Wed, 20 Jan 2016 18:58:10 +0500 From: Roman Mamedov To: Paolo Bonzini Cc: linux-btrfs@vger.kernel.org, kvm@vger.kernel.org Subject: Re: Kernel 4.4.0 KVM guest on Btrfs locks up on snapshotting Message-ID: <20160120185810.2c566f98@natsu> In-Reply-To: <1185704624.11958670.1453278484410.JavaMail.zimbra@redhat.com> References: <20160120030223.22cc3ae0@natsu> <569EB653.9080700@redhat.com> <20160120040302.308f054e@natsu> <1185704624.11958670.1453278484410.JavaMail.zimbra@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/FV.UX2Fq6t49rfNqAZuBWSo"; protocol="application/pgp-signature" Sender: linux-btrfs-owner@vger.kernel.org List-ID: --Sig_/FV.UX2Fq6t49rfNqAZuBWSo Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Wed, 20 Jan 2016 03:28:04 -0500 (EST) Paolo Bonzini wrote: > Can you reproduce it on the host without QEMU in the middle? I did not try to stress-test this on purpose yet, but this is an actively u= sed system which is snapshotting its /home, VMs and root subvolumes every hour,= so far no lock-ups of any other application than KVM, and with KVM it's trivia= lly easy to hit, in fact first two lockups occured in the first two hours of us= ing the kernel 4.4.0 at the hourly snapshots... > 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. Since you mentioned queue depth, I tried setting this on SCSI: echo 1 > /sys/block/sda/device/queue_depth (was 128 by default). Does not solve the issue and doesn't seem to make it = any harder to hit. Couple more details about the locked-up state: - 0.0% "wa" state in 'top', so there's doesn't seem to be any disk activity - I can disconnect and then successfully reconnect to the VNC port of the locked-up QEMU/KVM process (!), so it looks like it's not entirely dead, = but just the virtualization part(?) --=20 With respect, Roman --Sig_/FV.UX2Fq6t49rfNqAZuBWSo Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlafknIACgkQTLKSvz+PZwjJyACaAvZpAe6luaXRR/bxeEvEXaIZ DV4AniyvqgZDj5vL9BvqJ8x8qFDkft4K =wiFi -----END PGP SIGNATURE----- --Sig_/FV.UX2Fq6t49rfNqAZuBWSo--