[libvirt] [PATCH] [RFC] libxl: add discard support to libxl_device_disk
Daniel P. Berrange
berrange at redhat.com
Thu Jan 30 20:47:21 UTC 2014
On Thu, Jan 30, 2014 at 09:35:13PM +0100, Olaf Hering wrote:
> Translate libvirt discard settings into libxl-4.5 discard settings.
> It makes use of upcoming changes for xen-4.5:
> http://lists.xenproject.org/archives/html/xen-devel/2014-01/msg02632.html
>
> This patch is not compile tested. How is a config file supposed to look
> like to make use of a discard=on|off flag for a given disk image?
Here's two examples:
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2' discard='unmap'/>
<source file='/var/lib/libvirt/images/f14.img'/>
<target dev='vda' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
</disk>
<disk type='file' device='cdrom'>
<driver name='qemu' type='raw' discard='ignore'/>
<source file='/var/lib/libvirt/Fedora-14-x86_64-Live-KDE.iso'/>
<target dev='hdc' bus='ide'/>
<readonly/>
<address type='drive' controller='0' bus='1' target='0' unit='0'/>
</disk>
>
> Signed-off-by: Olaf Hering <olaf at aepfle.de>
> Cc: Jim Fehlig <jfehlig at suse.com>
> ---
> src/libxl/libxl_conf.c | 21 +++++++++++++++++++++
> 1 file changed, 21 insertions(+)
>
> diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c
> index 4cefadf..8fc5e75 100644
> --- a/src/libxl/libxl_conf.c
> +++ b/src/libxl/libxl_conf.c
> @@ -707,6 +707,26 @@ error:
> return -1;
> }
>
> +static void
> +libxlDiskSetDiscard(libxl_device_disk *x_disk, int discard)
> +{
> + if (!x_disk->readwrite)
> + return;
> +#if defined(LIBXL_HAVE_LIBXL_DEVICE_DISK_DISCARD_ENABLE)
> + /* libxl 4.5 */
> + switch (discard) {
> + case VIR_DOMAIN_DISK_DISCARD_DEFAULT:
> + case VIR_DOMAIN_DISK_DISCARD_UNMAP:
> + x_disk->discard_enable = 1;
> + break;
> + default:
> + case VIR_DOMAIN_DISK_DISCARD_IGNORE:
> + x_disk->discard_enable = 0;
> + break;
> + }
> +#endif
In the case where LIBXL_HAVE_LIBXL_DEVICE_DISK_DISCARD_ENABLE is
not defined, then you should call virReportError with the code
VIR_ERR_CONFIG_UNSUPPORTED, if discard != VIR_DOMAIN_DISK_DISCARD_DEFAULT
This ensures apps get an error if they had requested discard instead
of being silently ignored.
Regards,
Daniel
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