blockdev: Clean up automatic drive deletion

We automatically delete blockdev host parts on unplug of the guest
device.  Too much magic, but we can't change that now.

The delete happens early in the guest device teardown, before the
connection to the host part is severed.  Thus, the guest part's
pointer to the host part dangles for a brief time.  No actual harm
comes from this, but we'll catch such dangling pointers a few commits
down the road.  Clean up the dangling pointers by delaying the
automatic deletion until the guest part's pointer is gone.

Device usb-storage deliberately makes two qdev properties refer to the
same drive, because it automatically creates a second device.  Again,
too much magic we can't change now.  Multiple references worked okay
before, but now free_drive() dies for the second one.  Zap the extra
reference.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 16 insertions, 4 deletions

diff --git a/hw/usb-msd.c b/hw/usb-msd.c
index 8e9718c..3dbfcab 100644
--- a/hw/usb-msd.c
+++ b/hw/usb-msd.c
@@ -522,24 +522,36 @@ static void usb_msd_password_cb(void *opaque, int err)
 static int usb_msd_initfn(USBDevice *dev)
 {
     MSDState *s = DO_UPCAST(MSDState, dev, dev);
+    DriveInfo *dinfo = s->conf.dinfo;
 
-    if (!s->conf.dinfo || !s->conf.dinfo->bdrv) {
+    if (!dinfo || !dinfo->bdrv) {
         error_report("usb-msd: drive property not set");
         return -1;
     }
 
+    /*
+     * Hack alert: this pretends to be a block device, but it's really
+     * a SCSI bus that can serve only a single device, which it
+     * creates automatically.  Two drive properties pointing to the
+     * same drive is not good: free_drive() dies for the second one.
+     * Zap the one we're not going to use.
+     *
+     * The hack is probably a bad idea.
+     */
+    s->conf.dinfo = NULL;
+
     s->dev.speed = USB_SPEED_FULL;
     scsi_bus_new(&s->bus, &s->dev.qdev, 0, 1, usb_msd_command_complete);
-    s->scsi_dev = scsi_bus_legacy_add_drive(&s->bus, s->conf.dinfo, 0);
+    s->scsi_dev = scsi_bus_legacy_add_drive(&s->bus, dinfo, 0);
     if (!s->scsi_dev) {
         return -1;
     }
     s->bus.qbus.allow_hotplug = 0;
     usb_msd_handle_reset(dev);
 
-    if (bdrv_key_required(s->conf.dinfo->bdrv)) {
+    if (bdrv_key_required(dinfo->bdrv)) {
         if (cur_mon) {
-            monitor_read_bdrv_key_start(cur_mon, s->conf.dinfo->bdrv,
+            monitor_read_bdrv_key_start(cur_mon, dinfo->bdrv,
                                         usb_msd_password_cb, s);
             s->dev.auto_attach = 0;
         } else {