Ian Campbell writes ("Re: [Xen-devel] [PATCH 1/9] libxl: disks: Make
LIBXL_DISK_BACKEND_UNKNOWN work"):
> I think this should be treated the same as you did above, by adding an
> explicit fallback before the switch statement, for clarity.
OK. This results in two copies of the same comment. Really we should
have a common function for figuring out the correct backend, but this
at least makes things no worse.
Ian.
commit ee4720b0f9b15be152b10656b9b3e13b83be6c55
Author: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Date: Fri May 6 09:02:02 2011 +0100
libxl: disks: Make LIBXL_DISK_BACKEND_UNKNOWN work
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>
diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index c21cfe7..a36de58 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
+ * 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;
@@ -1126,6 +1141,20 @@ char * libxl_device_disk_local_attach(libxl_ctx *ctx,
libxl_device_disk *disk)
char *dev = NULL;
char *ret = NULL;
+ /*
+ * 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
+ * specify the backend if they don't want to.)
+ */
+ if (disk->backend == LIBXL_DISK_BACKEND_UNKNOWN)
+ disk->backend = LIBXL_DISK_BACKEND_TAP;
+
switch (disk->backend) {
case LIBXL_DISK_BACKEND_PHY:
if (disk->format != LIBXL_DISK_FORMAT_RAW) {
@@ -1175,7 +1204,6 @@ 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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