commit f9092b108f7b35e463e58bd3dd348ff002ba9e63
author Markus Armbruster <armbru@redhat.com> Fri Jun 25 10:33:39 2010 +0200
committer Kevin Wolf <kwolf@redhat.com> Fri Jul 02 13:18:02 2010 +0200
tree f2407ad08c49e3d15297af524e41b4c645d3d662
parent 8db520cee89bb84f21d107cea2d786894901bc54

savevm: Survive hot-unplug of snapshot device

savevm.c keeps a pointer to the snapshot block device.  If you manage
to get that device deleted, the pointer dangles, and the next snapshot
operation will crash & burn.  Unplugging a guest device that uses it
does the trick:

    $ MALLOC_PERTURB_=234 qemu-system-x86_64 [...]
    QEMU 0.12.50 monitor - type 'help' for more information
    (qemu) info snapshots
    No available block device supports snapshots
    (qemu) drive_add auto if=none,file=tmp.qcow2
    OK
    (qemu) device_add usb-storage,id=foo,drive=none1
    (qemu) info snapshots
    Snapshot devices: none1
    Snapshot list (from none1):
    ID        TAG                 VM SIZE                DATE       VM CLOCK
    (qemu) device_del foo
    (qemu) info snapshots
    Snapshot devices:
    Segmentation fault (core dumped)

Move management of that pointer to block.c, and zap it when the device
it points becomes unusable.

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