[Qemu-devel] [PATCH 1/2] monitor: allow device to be ejected if no disk is inserted

[Eduardo Habkost <ehabkost@redhat.com>]

This changes the monitor eject_device() function to not check for
bdrv_is_inserted().

Example run where the bug manifests itself:

(output of 'info block' is stripped to include only the CD-ROM device)

  QEMU 0.11.50 monitor - type 'help' for more information
  (qemu) info block
  ide1-cd0: type=cdrom removable=1 locked=0 [not inserted]
  (qemu) change ide1-cd0 /mnt/common/images/smalldisk1.img
  (qemu) info block
  ide1-cd0: type=cdrom removable=1 locked=0 file=/mnt/common/images/smalldisk1.img ro=0 drv=raw encrypted=0
  (qemu) eject ide1-cd0
  (qemu) info block
  ide1-cd0: type=cdrom removable=1 locked=0 [not inserted]

When using a file, eject works as expected. But when using a host cdrom device:

  (qemu) change ide1-cd0 /dev/cdrom
  (qemu) info block
  ide1-cd0: type=cdrom removable=1 locked=0 file=/dev/cdrom ro=0 drv=host_cdrom encrypted=0
  (qemu) eject ide1-cd0
  (qemu) info block
  ide1-cd0: type=cdrom removable=1 locked=0 file=/dev/cdrom ro=0 drv=host_cdrom encrypted=0

Eject didn't work because the is_inserted() check fails.

I have no clue why the code had the is_inserted() check, as it doesn't matter
if there is a disk present at the host drive, when the user wants the virtual
device to be disconnected from the host device.

The is_inserted() has another side effect: a memory leak if the "change"
command is used multiple times, as do_change() calls eject_device() before
re-opening the block device, but bdrv_close() is never called.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
 monitor.c |   20 +++++++++-----------
 1 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/monitor.c b/monitor.c
index 5bf32f0..d882c51 100644
--- a/monitor.c
+++ b/monitor.c
@@ -741,19 +741,17 @@ static void do_quit(Monitor *mon, const QDict *qdict, QObject **ret_data)
 
 static int eject_device(Monitor *mon, BlockDriverState *bs, int force)
 {
-    if (bdrv_is_inserted(bs)) {
-        if (!force) {
-            if (!bdrv_is_removable(bs)) {
-                monitor_printf(mon, "device is not removable\n");
-                return -1;
-            }
-            if (bdrv_is_locked(bs)) {
-                monitor_printf(mon, "device is locked\n");
-                return -1;
-            }
+    if (!force) {
+        if (!bdrv_is_removable(bs)) {
+            monitor_printf(mon, "device is not removable\n");
+            return -1;
+        }
+        if (bdrv_is_locked(bs)) {
+            monitor_printf(mon, "device is locked\n");
+            return -1;
         }
-        bdrv_close(bs);
     }
+    bdrv_close(bs);
     return 0;
 }
 
-- 
1.6.3.rc4.29.g8146