block: Catch attempt to attach multiple devices to a blockdev

For instance, -device scsi-disk,drive=foo -device scsi-disk,drive=foo
happily creates two SCSI disks connected to the same block device.
It's all downhill from there.

Device usb-storage deliberately attaches twice to the same blockdev,
which fails with the fix in place.  Detach before the second attach
there.

Also catch attempt to delete while a guest device model is attached.

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

block.c

@@ -665,6 +665,8 @@ void bdrv_close_all(void)
 
 void bdrv_delete(BlockDriverState *bs)
 {
+    assert(!bs->peer);
+
     /* remove from list, if necessary */
     if (bs->device_name[0] != '\0') {
         QTAILQ_REMOVE(&bdrv_states, bs, list);
@@ -678,6 +680,26 @@ void bdrv_delete(BlockDriverState *bs)
     qemu_free(bs);
 }
 
+int bdrv_attach(BlockDriverState *bs, DeviceState *qdev)
+{
+    if (bs->peer) {
+        return -EBUSY;
+    }
+    bs->peer = qdev;
+    return 0;
+}
+
+void bdrv_detach(BlockDriverState *bs, DeviceState *qdev)
+{
+    assert(bs->peer == qdev);
+    bs->peer = NULL;
+}
+
+DeviceState *bdrv_get_attached(BlockDriverState *bs)
+{
+    return bs->peer;
+}
+
 /*
  * Run consistency checks on an image
  *

block.h

@@ -71,6 +71,9 @@ int bdrv_file_open(BlockDriverState **pbs, const char *filename, int flags);
 int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
               BlockDriver *drv);
 void bdrv_close(BlockDriverState *bs);
+int bdrv_attach(BlockDriverState *bs, DeviceState *qdev);
+void bdrv_detach(BlockDriverState *bs, DeviceState *qdev);
+DeviceState *bdrv_get_attached(BlockDriverState *bs);
 int bdrv_check(BlockDriverState *bs);
 int bdrv_read(BlockDriverState *bs, int64_t sector_num,
               uint8_t *buf, int nb_sectors);

block_int.h

@@ -148,6 +148,8 @@ struct BlockDriverState {
     BlockDriver *drv; /* NULL means no media */
     void *opaque;
 
+    DeviceState *peer;
+
     char filename[1024];
     char backing_file[1024]; /* if non zero, the image is a diff of
                                 this file image */

hw/fdc.c

@@ -1860,10 +1860,10 @@ FDCtrl *fdctrl_init_isa(DriveInfo **fds)
 
     dev = isa_create("isa-fdc");
     if (fds[0]) {
-        qdev_prop_set_drive(&dev->qdev, "driveA", fds[0]->bdrv);
+        qdev_prop_set_drive_nofail(&dev->qdev, "driveA", fds[0]->bdrv);
     }
     if (fds[1]) {
-        qdev_prop_set_drive(&dev->qdev, "driveB", fds[1]->bdrv);
+        qdev_prop_set_drive_nofail(&dev->qdev, "driveB", fds[1]->bdrv);
     }
     if (qdev_init(&dev->qdev) < 0)
         return NULL;
@@ -1882,10 +1882,10 @@ FDCtrl *fdctrl_init_sysbus(qemu_irq irq, int dma_chann,
     fdctrl = &sys->state;
     fdctrl->dma_chann = dma_chann; /* FIXME */
     if (fds[0]) {
-        qdev_prop_set_drive(dev, "driveA", fds[0]->bdrv);
+        qdev_prop_set_drive_nofail(dev, "driveA", fds[0]->bdrv);
     }
     if (fds[1]) {
-        qdev_prop_set_drive(dev, "driveB", fds[1]->bdrv);
+        qdev_prop_set_drive_nofail(dev, "driveB", fds[1]->bdrv);
     }
     qdev_init_nofail(dev);
     sysbus_connect_irq(&sys->busdev, 0, irq);
@@ -1903,7 +1903,7 @@ FDCtrl *sun4m_fdctrl_init(qemu_irq irq, target_phys_addr_t io_base,
 
     dev = qdev_create(NULL, "SUNW,fdtwo");
     if (fds[0]) {
-        qdev_prop_set_drive(dev, "drive", fds[0]->bdrv);
+        qdev_prop_set_drive_nofail(dev, "drive", fds[0]->bdrv);
     }
     qdev_init_nofail(dev);
     sys = DO_UPCAST(FDCtrlSysBus, busdev.qdev, dev);

hw/ide/qdev.c

@@ -83,7 +83,7 @@ IDEDevice *ide_create_drive(IDEBus *bus, int unit, DriveInfo *drive)
 
     dev = qdev_create(&bus->qbus, "ide-drive");
     qdev_prop_set_uint32(dev, "unit", unit);
-    qdev_prop_set_drive(dev, "drive", drive->bdrv);
+    qdev_prop_set_drive_nofail(dev, "drive", drive->bdrv);
     qdev_init_nofail(dev);
     return DO_UPCAST(IDEDevice, qdev, dev);
 }

hw/pci-hotplug.c

@@ -214,7 +214,11 @@ static PCIDevice *qemu_pci_hot_add_storage(Monitor *mon,
             return NULL;
         }
         dev = pci_create(bus, devfn, "virtio-blk-pci");
-        qdev_prop_set_drive(&dev->qdev, "drive", dinfo->bdrv);
+        if (qdev_prop_set_drive(&dev->qdev, "drive", dinfo->bdrv) < 0) {
+            qdev_free(&dev->qdev);
+            dev = NULL;
+            break;
+        }
         if (qdev_init(&dev->qdev) < 0)
             dev = NULL;
         break;

hw/qdev-properties.c

@@ -311,6 +311,8 @@ static int parse_drive(DeviceState *dev, Property *prop, const char *str)
     bs = bdrv_find(str);
     if (bs == NULL)
         return -ENOENT;
+    if (bdrv_attach(bs, dev) < 0)
+        return -EEXIST;
     *ptr = bs;
     return 0;
 }
@@ -320,6 +322,7 @@ static void free_drive(DeviceState *dev, Property *prop)
     BlockDriverState **ptr = qdev_get_prop_ptr(dev, prop);
 
     if (*ptr) {
+        bdrv_detach(*ptr, dev);
         blockdev_auto_del(*ptr);
     }
 }
@@ -660,11 +663,28 @@ void qdev_prop_set_string(DeviceState *dev, const char *name, char *value)
     qdev_prop_set(dev, name, &value, PROP_TYPE_STRING);
 }
 
-void qdev_prop_set_drive(DeviceState *dev, const char *name, BlockDriverState *value)
+int qdev_prop_set_drive(DeviceState *dev, const char *name, BlockDriverState *value)
 {
+    int res;
+
+    res = bdrv_attach(value, dev);
+    if (res < 0) {
+        error_report("Can't attach drive %s to %s.%s: %s",
+                     bdrv_get_device_name(value),
+                     dev->id ? dev->id : dev->info->name,
+                     name, strerror(-res));
+        return -1;
+    }
     qdev_prop_set(dev, name, &value, PROP_TYPE_DRIVE);
+    return 0;
 }
 
+void qdev_prop_set_drive_nofail(DeviceState *dev, const char *name, BlockDriverState *value)
+{
+    if (qdev_prop_set_drive(dev, name, value) < 0) {
+        exit(1);
+    }
+}
 void qdev_prop_set_chr(DeviceState *dev, const char *name, CharDriverState *value)
 {
     qdev_prop_set(dev, name, &value, PROP_TYPE_CHR);

hw/qdev.h

@@ -275,7 +275,8 @@ void qdev_prop_set_string(DeviceState *dev, const char *name, char *value);
 void qdev_prop_set_chr(DeviceState *dev, const char *name, CharDriverState *value);
 void qdev_prop_set_netdev(DeviceState *dev, const char *name, VLANClientState *value);
 void qdev_prop_set_vlan(DeviceState *dev, const char *name, VLANState *value);
-void qdev_prop_set_drive(DeviceState *dev, const char *name, BlockDriverState *value);
+int qdev_prop_set_drive(DeviceState *dev, const char *name, BlockDriverState *value) QEMU_WARN_UNUSED_RESULT;
+void qdev_prop_set_drive_nofail(DeviceState *dev, const char *name, BlockDriverState *value);
 void qdev_prop_set_macaddr(DeviceState *dev, const char *name, uint8_t *value);
 /* FIXME: Remove opaque pointer properties.  */
 void qdev_prop_set_ptr(DeviceState *dev, const char *name, void *value);

hw/s390-virtio.c

@@ -262,7 +262,7 @@ static void s390_init(ram_addr_t ram_size,
         }
 
         dev = qdev_create((BusState *)s390_bus, "virtio-blk-s390");
-        qdev_prop_set_drive(dev, "drive", dinfo->bdrv);
+        qdev_prop_set_drive_nofail(dev, "drive", dinfo->bdrv);
         qdev_init_nofail(dev);
     }
 }

hw/scsi-bus.c

@@ -91,7 +91,10 @@ SCSIDevice *scsi_bus_legacy_add_drive(SCSIBus *bus, BlockDriverState *bdrv, int
     driver = bdrv_is_sg(bdrv) ? "scsi-generic" : "scsi-disk";
     dev = qdev_create(&bus->qbus, driver);
     qdev_prop_set_uint32(dev, "scsi-id", unit);
-    qdev_prop_set_drive(dev, "drive", bdrv);
+    if (qdev_prop_set_drive(dev, "drive", bdrv) < 0) {
+        qdev_free(dev);
+        return NULL;
+    }
     if (qdev_init(dev) < 0)
         return NULL;
     return DO_UPCAST(SCSIDevice, qdev, dev);

hw/usb-msd.c

@@ -532,12 +532,13 @@ static int usb_msd_initfn(USBDevice *dev)
     /*
      * 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.
+     * creates automatically.  But first it needs to detach from its
+     * blockdev, or else scsi_bus_legacy_add_drive() dies when it
+     * attaches again.
      *
      * The hack is probably a bad idea.
      */
+    bdrv_detach(bs, &s->dev.qdev);
     s->conf.bs = NULL;
 
     s->dev.speed = USB_SPEED_FULL;
@@ -609,7 +610,10 @@ static USBDevice *usb_msd_init(const char *filename)
     if (!dev) {
         return NULL;
     }
-    qdev_prop_set_drive(&dev->qdev, "drive", dinfo->bdrv);
+    if (qdev_prop_set_drive(&dev->qdev, "drive", dinfo->bdrv) < 0) {
+        qdev_free(&dev->qdev);
+        return NULL;
+    }
     if (qdev_init(&dev->qdev) < 0)
         return NULL;