[Xen-changelog] [xen-unstable] libxl: convert an empty tap disk into a qdisk

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Ian Campbell <ian.campbell@xxxxxxxxxx>
# Date 1302277139 -3600
# Node ID d9d8e0ceaf46a43bf149d50295c51ad40a58ce7e
# Parent  67b8c2a99f4cce523905cea52cd48ae02421fa27
libxl: convert an empty tap disk into a qdisk

I'm not sure that empty disks which are is_cdrom are especially valid,
or that a cdrom can ever be handled by tapdisk anyway but try to do
something sane since it seems that xl's parse_disk_config() routine
could potentially generate such a configuration (although whether from
a valid input string or not I'm not sure).

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Committed-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
---


diff -r 67b8c2a99f4c -r d9d8e0ceaf46 tools/libxl/libxl.c
--- a/tools/libxl/libxl.c       Fri Apr 08 16:38:36 2011 +0100
+++ b/tools/libxl/libxl.c       Fri Apr 08 16:38:59 2011 +0100
@@ -983,6 +983,14 @@
     if (disk->backend == DISK_BACKEND_TAP && !libxl__blktap_enabled(&gc))
         disk->backend = DISK_BACKEND_QDISK;
 
+    /*
+     * blktap cannot handle empty disks (aka cdroms). Fall back to
+     * qdisk because qemu-xen creates the disk based on the xenstore
+     * entries.
+     */
+    if (disk->backend == DISK_BACKEND_TAP && disk->format == DISK_FORMAT_EMPTY)
+        disk->backend == DISK_BACKEND_QDISK;
+
     switch (disk->backend) {
         case DISK_BACKEND_PHY: 
             libxl__device_physdisk_major_minor(disk->pdev_path, &major, 
&minor);
@@ -995,7 +1003,7 @@
             device.backend_kind = DEVICE_VBD;
             break;
         case DISK_BACKEND_TAP:
-            if (disk->format != DISK_FORMAT_EMPTY) {
+            {
                 const char *dev = libxl__blktap_devpath(&gc,
                                                disk->pdev_path, disk->format);
                 if (!dev) {
@@ -1003,8 +1011,8 @@
                     goto out_free;
                 }
                 flexarray_append(back, "tapdisk-params");
-                flexarray_append(back, libxl__sprintf(&gc, "%s:%s", 
-                    libxl__device_disk_string_of_format(disk->format), 
+                flexarray_append(back, libxl__sprintf(&gc, "%s:%s",
+                    libxl__device_disk_string_of_format(disk->format),
                     disk->pdev_path));
                 flexarray_append(back, "params");
                 flexarray_append(back, libxl__strdup(&gc, dev));
@@ -1013,8 +1021,6 @@
                 flexarray_append(back, "physical-device");
                 flexarray_append(back, libxl__sprintf(&gc, "%x:%x", major, 
minor));
                 device.backend_kind = DEVICE_VBD;
-
-                break;
             }
             break;
         case DISK_BACKEND_QDISK:

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