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Re: [Qemu-discuss] Is locking option available now?

From: Fam Zheng
Subject: Re: [Qemu-discuss] Is locking option available now?
Date: Wed, 25 Oct 2017 09:13:01 -0400 (EDT)

----- Original Message -----
> I create backing file with 'locking=off', but it seems the locking is
> enabled:
> On *qemu-2.10*
> # qemu-img create -b 'json:{"file": {"driver": "file", "filename":
> "/var/lib/libvirt/images/V.qcow2", "*locking*": "*off*"}}'
> /var/lib/libvirt/images/a.qcow2 -f qcow2
> Formatting '/var/lib/libvirt/images/a.qcow2', fmt=qcow2 size=8589934592
> backing_file=json:{"file": {"driver": "file",, "filename":
> "/var/lib/libvirt/images/V.qcow2",, "locking": "off"}} cluster_size=65536
> lazy_refcounts=off refcount_bits=16
> Then checking if locking works:
> # qemu-kvm /var/lib/libvirt/images/a.qcow2
> VNC server running on ::1:5900
> # qemu-img info /var/lib/libvirt/images/a.qcow2
> qemu-img: Could not open '/var/lib/libvirt/images/a.qcow2': Failed to get
> shared "write" lock
> Is another process using the image?
> It looks "*locking=off*" not worked. So is this option available now? In
> which version this feature will be supported?

This is a run time option, not creation time. So if you don't want locking, 
always provide locking=off when invoking qemu, qemu-img, etc., not just when 

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