[Qemu-devel] [PATCH v4 08/10] qemu-ga: call Windows VSS requester in fsfreeze command handler

[Tomoki Sekiyama <tomoki.sekiyama@hds.com>]

Support guest-fsfreeze-freeze and guest-fsfreeze-thaw commands for Windows
guests. When fsfreeze command is issued, it calls the VSS requester to
freeze filesystems and applications. On thaw command, it again tells the VSS
requester to thaw them.

This also adds calling of initialize functions for the VSS requester.

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
---
 qga/commands-win32.c |   74 ++++++++++++++++++++++++++++++++++++++++++++++----
 qga/main.c           |   33 ++++++++++++++++++++++
 2 files changed, 100 insertions(+), 7 deletions(-)

diff --git a/qga/commands-win32.c b/qga/commands-win32.c
index 24e4ad0..67dca60 100644
--- a/qga/commands-win32.c
+++ b/qga/commands-win32.c
@@ -15,6 +15,7 @@
 #include <wtypes.h>
 #include <powrprof.h>
 #include "qga/guest-agent-core.h"
+#include "qga/vss-win32-requester.h"
 #include "qga-qmp-commands.h"
 #include "qapi/qmp/qerror.h"
 
@@ -151,34 +152,95 @@ void qmp_guest_file_flush(int64_t handle, Error **err)
     error_set(err, QERR_UNSUPPORTED);
 }
 
+#ifdef HAS_VSS_SDK
+
 /*
  * Return status of freeze/thaw
  */
 GuestFsfreezeStatus qmp_guest_fsfreeze_status(Error **err)
 {
-    error_set(err, QERR_UNSUPPORTED);
-    return 0;
+    if (!vss_initialized()) {
+        error_set(err, QERR_UNSUPPORTED);
+        return 0;
+    }
+
+    if (ga_is_frozen(ga_state)) {
+        return GUEST_FSFREEZE_STATUS_FROZEN;
+    }
+
+    return GUEST_FSFREEZE_STATUS_THAWED;
 }
 
 /*
- * Walk list of mounted file systems in the guest, and freeze the ones which
- * are real local file systems.
+ * Freeze local file systems using Volume Shadow-copy Service.
+ * The frozen state is limited for up to 10 seconds by VSS.
  */
 int64_t qmp_guest_fsfreeze_freeze(Error **err)
 {
-    error_set(err, QERR_UNSUPPORTED);
+    int i;
+
+    slog("guest-fsfreeze called");
+
+    if (!vss_initialized()) {
+        error_set(err, QERR_UNSUPPORTED);
+        return 0;
+    }
+
+    /* cannot risk guest agent blocking itself on a write in this state */
+    ga_set_frozen(ga_state);
+
+    qga_vss_fsfreeze_freeze(&i, err);
+    if (error_is_set(err)) {
+        goto error;
+    }
+
+    return i;
+
+error:
+    qmp_guest_fsfreeze_thaw(NULL);
     return 0;
 }
 
 /*
- * Walk list of frozen file systems in the guest, and thaw them.
+ * Thaw local file systems using Volume Shadow-copy Service.
  */
 int64_t qmp_guest_fsfreeze_thaw(Error **err)
 {
+    int i;
+
+    if (!vss_initialized()) {
+        error_set(err, QERR_UNSUPPORTED);
+        return 0;
+    }
+
+    qga_vss_fsfreeze_thaw(&i, err);
+
+    ga_unset_frozen(ga_state);
+    return i;
+}
+
+#else
+
+GuestFsfreezeStatus qmp_guest_fsfreeze_status(Error **err)
+{
+    error_set(err, QERR_UNSUPPORTED);
+    return 0;
+}
+
+int64_t qmp_guest_fsfreeze_freeze(Error **err)
+{
+    error_set(err, QERR_UNSUPPORTED);
+    return 0;
+}
+
+int64_t qmp_guest_fsfreeze_thaw(Error **err)
+{
     error_set(err, QERR_UNSUPPORTED);
     return 0;
 }
 
+#endif
+
 /*
  * Walk list of mounted file systems in the guest, and discard unused
  * areas.
diff --git a/qga/main.c b/qga/main.c
index 0e04e73..8bcedaf 100644
--- a/qga/main.c
+++ b/qga/main.c
@@ -34,6 +34,10 @@
 #include "qemu/bswap.h"
 #ifdef _WIN32
 #include "qga/service-win32.h"
+#ifdef HAS_VSS_SDK
+#include "qga/vss-win32-provider.h"
+#include "qga/vss-win32-requester.h"
+#endif
 #include <windows.h>
 #endif
 #ifdef __linux__
@@ -701,6 +705,25 @@ static gboolean channel_init(GAState *s, const gchar *method, const gchar *path)
 }
 
 #ifdef _WIN32
+
+static gboolean vss_win32_init(void)
+{
+#ifdef HAS_VSS_SDK
+    if (FAILED(vss_init())) {
+        g_critical("failed to initialize VSS");
+        return false;
+    }
+#endif
+    return true;
+}
+
+static void vss_win32_deinit(void)
+{
+#ifdef HAS_VSS_SDK
+    vss_deinit();
+#endif
+}
+
 DWORD WINAPI service_ctrl_handler(DWORD ctrl, DWORD type, LPVOID data,
                                   LPVOID ctx)
 {
@@ -743,8 +766,12 @@ VOID WINAPI service_main(DWORD argc, TCHAR *argv[])
     service->status.dwWaitHint = 0;
     SetServiceStatus(service->status_handle, &service->status);
 
+    if (!vss_win32_init()) {
+        goto out_bad;
+    }
     g_main_loop_run(ga_state->main_loop);
-
+    vss_win32_deinit();
+out_bad:
     service->status.dwCurrentState = SERVICE_STOPPED;
     SetServiceStatus(service->status_handle, &service->status);
 }
@@ -1175,7 +1202,11 @@ int main(int argc, char **argv)
             { (char *)QGA_SERVICE_NAME, service_main }, { NULL, NULL } };
         StartServiceCtrlDispatcher(service_table);
     } else {
+        if (!vss_win32_init()) {
+            goto out_bad;
+        }
         g_main_loop_run(ga_state->main_loop);
+        vss_win32_deinit();
     }
 #endif