[libvirt] [PATCH] Allow shrinking of file based volumes

Peter Krempa pkrempa at redhat.com
Fri Jan 16 08:52:27 UTC 2015

On Thu, Jan 15, 2015 at 16:42:32 +0000, Daniel Berrange wrote:
> While the main storage driver code allows the flag
> VIR_STORAGE_VOL_RESIZE_SHRINK to be set, none of the backend
> drivers are supporting it. At the very least this can work
> for plain file based volumes since we just ftruncate() them
> to the new size. It does not work with qcow2 volumes, but we
> can arguably delegate to qemu-img for error reporting for that
> instead of second guessing this for ourselves:
> $ virsh vol-resize --shrink /home/berrange/VirtualMachines/demo.qcow2 2G
> error: Failed to change size of volume 'demo.qcow2' to 2G
> error: internal error: Child process (/usr/bin/qemu-img resize /home/berrange/VirtualMachines/demo.qcow2 2147483648) unexpected exit status 1: qemu-img: qcow2 doesn't support shrinking images yet
> qemu-img: This image does not support resize
> See also https://bugzilla.redhat.com/show_bug.cgi?id=1021802
> ---
>  src/storage/storage_backend_fs.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)


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