[libvirt] [PATCH] libxl: fix disk detach when <driver> not specified

[Michal Privoznik]

On 02/06/2017 11:08 PM, Jim Fehlig wrote:
> When a user does not explicitly set a <driver> in the disk config,
> libvirt defers selection of a default to libxl. This approach works
> fine when starting a domain with such configuration or attaching a
> disk to a running domain. But when detaching such a disk, libxl
> will fail with "unrecognized disk backend type: 0". libxl makes no
> attempt to recalculate a default backend (driver) on detach and
> simply fails when uninitialized.
> 
> This patch updates the libvirt disk config with the backend selected
> by libxl when starting a domain or attaching a disk to a running
> domain. Another benefit of this approach is that the live XML is
> also updated with the backend driver selected by libxl.
> 
> Signed-off-by: Jim Fehlig <jfehlig at suse.com>
> ---
>  src/libxl/libxl_conf.c   | 33 +++++++++++++++++++++++++++++++++
>  src/libxl/libxl_conf.h   |  4 ++++
>  src/libxl/libxl_domain.c | 25 +++++++++++++++++++++++++
>  src/libxl/libxl_driver.c |  2 +-
>  4 files changed, 63 insertions(+), 1 deletion(-)
> 
> diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c
> index b5186f2..6ef7570 100644
> --- a/src/libxl/libxl_conf.c
> +++ b/src/libxl/libxl_conf.c
> @@ -851,6 +851,7 @@ libxlMakeDisk(virDomainDiskDefPtr l_disk, libxl_device_disk *x_disk)
>           * xl-disk-configuration.txt in the xen documentation and let
>           * libxl pick a suitable backend.
>           */
> +        virDomainDiskSetFormat(l_disk, VIR_STORAGE_FILE_RAW);
>          x_disk->format = LIBXL_DISK_FORMAT_RAW;
>          x_disk->backend = LIBXL_DISK_BACKEND_UNKNOWN;

This doesn't feel right. I know what do you want it here for, but this
function is meant to take 'const' disk definition and translate it to
libxl definition. Although, I don't have a better suggestion where to
put it.

>      }
> @@ -913,6 +914,38 @@ libxlMakeDiskList(virDomainDefPtr def, libxl_domain_config *d_config)
>      return -1;
>  }
>  

The rest looks okay. ACK.

Michal