On Thu, 2011-06-02 at 18:55 +0100, Ian Jackson wrote:
> libxl callers should not be required to specify the backend if they
> don't want to. So LIBXL_DISK_BACKEND_UNKNOWN should instruct libxl to
> choose the backend for itself.
>
> For now, we do this by simply treating it the same as BACKEND_TAP,
> which itself falls back to other methods.
>
> More thorough fixes for the disk handling will follow.
>
> Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> ---
> tools/libxl/libxl.c | 17 ++++++++++++++++-
> 1 files changed, 16 insertions(+), 1 deletions(-)
>
> diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> index c21cfe7..58df99c 100644
> --- a/tools/libxl/libxl.c
> +++ b/tools/libxl/libxl.c
> @@ -991,6 +991,21 @@ int libxl_device_disk_add(libxl_ctx *ctx, uint32_t
> domid, libxl_device_disk *dis
> device.domid = domid;
> device.kind = DEVICE_VBD;
>
> +
> + /*
> + * Fixing the incoming backend type to try to decide on which
> + * backend to use. Unfortunately at the moment this code is
> + * utterly broken, but it more or less works.
> + */
> +
> + /*
> + * Backend type UNKNOWN should mean "caller does not want to specify",
> + * not "break pointlessely". (Callers should not be required to
^ no e here.
> + * specify the backend if they don't want to.)
> + */
> + if (disk->backend == LIBXL_DISK_BACKEND_UNKNOWN)
> + disk->backend = LIBXL_DISK_BACKEND_TAP;
> +
> /* If blktap is not available then fallback to qdisk */
> if (disk->backend == LIBXL_DISK_BACKEND_TAP &&
> !libxl__blktap_enabled(&gc))
> disk->backend = LIBXL_DISK_BACKEND_QDISK;
> @@ -1138,6 +1153,7 @@ char * libxl_device_disk_local_attach(libxl_ctx *ctx,
> libxl_device_disk *disk)
> dev = disk->pdev_path;
> break;
> case LIBXL_DISK_BACKEND_TAP:
> + case LIBXL_DISK_BACKEND_UNKNOWN:
I think this should be treated the same as you did above, by adding an
explicit fallback before the switch statement, for clarity.
Ian.
> if (disk->format == LIBXL_DISK_FORMAT_VHD ||
> disk->format == LIBXL_DISK_FORMAT_RAW)
> {
> @@ -1175,7 +1191,6 @@ char * libxl_device_disk_local_attach(libxl_ctx *ctx,
> libxl_device_disk *disk)
> disk->pdev_path);
> dev = disk->pdev_path;
> break;
> - case LIBXL_DISK_BACKEND_UNKNOWN:
> default:
> LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "unrecognized disk backend "
> "type: %d", disk->backend);
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