From: Roman Mamedov <rm@romanrm.net>
To: linux-btrfs@vger.kernel.org, kvm@vger.kernel.org
Subject: Kernel 4.4.0 KVM guest on Btrfs locks up on snapshotting
Date: Wed, 20 Jan 2016 03:02:23 +0500 [thread overview]
Message-ID: <20160120030223.22cc3ae0@natsu> (raw)
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Hello,
I'm facing a strange issue:
Starting with the kernel 4.4.0, a KVM guest stored on a Btrfs filesystem,
if it's using the "virtio-scsi" disk backend, will hard lock-up instantly,
as soon as the Btrfs subvolume which contains its backing file is snapshotted.
There's nothing in dmesg neither on the guest, nor on the host;
the KVM process can be killed from the host just fine and then restarted,
so it doesn't seem to be a kernel-side deadlock of any sort.
KVM disk controller which exhibits the problem:
-device virtio-scsi-pci,id=scsi -device scsi-hd,drive=hd \
The alternative which works fine:
-device ide-hd,drive=hd,bus=ide.0 \
The disk device line is common to both cases:
-drive if=none,id=hd,cache=writeback,aio=threads,format=raw,file=$NAME.img,discard=unmap,detect-zeroes=unmap \
Also tried aio=native with the problematic variant, no change.
Both variants work fine and unaffected by snapshotting on kernel 3.18.25.
Any ideas?
--
With respect,
Roman
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next reply other threads:[~2016-01-19 22:02 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-19 22:02 Roman Mamedov [this message]
2016-01-19 22:18 ` Kernel 4.4.0 KVM guest on Btrfs locks up on snapshotting Paolo Bonzini
2016-01-19 23:03 ` Roman Mamedov
2016-01-20 8:28 ` Paolo Bonzini
2016-01-20 13:58 ` Roman Mamedov
2016-01-20 17:28 ` Paolo Bonzini
2016-01-20 18:46 ` Roman Mamedov
2016-01-20 20:38 ` Paolo Bonzini
2016-01-20 0:19 ` Liu Bo
2016-01-20 5:08 ` Roman Mamedov
2016-01-20 11:34 ` Paolo Bonzini
2016-01-20 15:08 ` Roman Mamedov
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