On Jan 13, 2014, at 7:25 PM, Tomoki Sekiyama <tomoki.sekiy...@hds.com> wrote:
> 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 <tomoki.sekiy...@hds.com> > --- > qga/vss-win32/provider.cpp | 11 ++++++++- > qga/vss-win32/requester.cpp | 52 ++++++++++++++++++++++--------------------- > 2 files changed, 36 insertions(+), 27 deletions(-) > > diff --git a/qga/vss-win32/provider.cpp b/qga/vss-win32/provider.cpp > index c3030d8..b233646 100644 > --- a/qga/vss-win32/provider.cpp > +++ b/qga/vss-win32/provider.cpp > @@ -291,8 +291,17 @@ STDMETHODIMP CQGAVssProvider::BeginPrepareSnapshot( > STDMETHODIMP CQGAVssProvider::IsVolumeSupported( > VSS_PWSZ pwszVolumeName, BOOL *pbSupportedByThisProvider) > { > - *pbSupportedByThisProvider = TRUE; > + HANDLE hEventFrozen; > + > + /* Check if a requester is qemu-ga by whether an event is created */ > + hEventFrozen = OpenEvent(EVENT_ALL_ACCESS, FALSE, EVENT_NAME_FROZEN); > + if (!hEventFrozen) { > + *pbSupportedByThisProvider = FALSE; > + return S_OK; > + } > + CloseHandle(hEventFrozen); > > + *pbSupportedByThisProvider = TRUE; > return S_OK; > } > > diff --git a/qga/vss-win32/requester.cpp b/qga/vss-win32/requester.cpp > index 0a55447..922e74d 100644 > --- a/qga/vss-win32/requester.cpp > +++ b/qga/vss-win32/requester.cpp > @@ -252,6 +252,32 @@ void requester_freeze(int *num_vols, ErrorSet *errset) > > CoInitialize(NULL); > > + /* Allow unrestricted access to events */ > + InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION); > + SetSecurityDescriptorDacl(&sd, TRUE, NULL, FALSE); > + sa.nLength = sizeof(sa); > + sa.lpSecurityDescriptor = &sd; > + sa.bInheritHandle = FALSE; > + > + vss_ctx.hEventFrozen = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_FROZEN); > + if (!vss_ctx.hEventFrozen) { > + err_set(errset, GetLastError(), "failed to create event %s", > + EVENT_NAME_FROZEN); > + goto out; > + } > + vss_ctx.hEventThaw = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_THAW); > + if (!vss_ctx.hEventThaw) { > + err_set(errset, GetLastError(), "failed to create event %s", > + EVENT_NAME_THAW); > + goto out; > + } > + vss_ctx.hEventTimeout = CreateEvent(&sa, TRUE, FALSE, > EVENT_NAME_TIMEOUT); > + if (!vss_ctx.hEventTimeout) { > + err_set(errset, GetLastError(), "failed to create event %s", > + EVENT_NAME_TIMEOUT); > + goto out; > + } > + > assert(pCreateVssBackupComponents != NULL); > hr = pCreateVssBackupComponents(&vss_ctx.pVssbc); > if (FAILED(hr)) { > @@ -362,32 +388,6 @@ void requester_freeze(int *num_vols, ErrorSet *errset) > goto out; > } > > - /* Allow unrestricted access to events */ > - InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION); > - SetSecurityDescriptorDacl(&sd, TRUE, NULL, FALSE); > - sa.nLength = sizeof(sa); > - sa.lpSecurityDescriptor = &sd; > - sa.bInheritHandle = FALSE; > - > - vss_ctx.hEventFrozen = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_FROZEN); > - if (!vss_ctx.hEventFrozen) { > - err_set(errset, GetLastError(), "failed to create event %s", > - EVENT_NAME_FROZEN); > - goto out; > - } > - vss_ctx.hEventThaw = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_THAW); > - if (!vss_ctx.hEventThaw) { > - err_set(errset, GetLastError(), "failed to create event %s", > - EVENT_NAME_THAW); > - goto out; > - } > - vss_ctx.hEventTimeout = CreateEvent(&sa, TRUE, FALSE, > EVENT_NAME_TIMEOUT); > - if (!vss_ctx.hEventTimeout) { > - err_set(errset, GetLastError(), "failed to create event %s", > - EVENT_NAME_TIMEOUT); > - goto out; > - } > - > /* > * Start VSS quiescing operations. > * CQGAVssProvider::CommitSnapshots will kick vss_ctx.hEventFrozen > > Reviewed-by: Yan Vugenfirer <yvuge...@redhat.com>