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Revision ff8adbcf

IDff8adbcfdbbd9c0f2b01ff8a32bc75082fdd9844

Added by Tomoki Sekiyama about 10 years ago

qga: vss-win32: Fix interference with snapshot creation by other VSS requesters

When a VSS requester such as vshadow.exe or diskshadow.exe requests to
create disk snapshots, Windows may choose qemu-ga VSS provider if it is
only provider registered on the system. However, because it provides only a
function to freeze the filesystem, the snapshotting fails.

This patch adds a check into CQGAVssProvider::IsVolumeSupported() to reject
the request from other VSS requesters, so that the other provider is chosen.

The check of requester is done by confirming event channels between
qemu-ga's requester and provider established. To ensure that the events are
initialized when CQGAVssProvider::IsVolumeSupported() is called, it moves
the initialization earlier.

Signed-off-by: Tomoki Sekiyama <>
Reviewed-by: Gal Hammer <>
Reviewed-by: Yan Vugenfirer <>
Signed-off-by: Michael Roth <>

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