[Qemu-devel] [PATCH v4 07/10] qemu-ga: Add Windows VSS requester to quiesce applications and filesystems

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

Add VSS requester functions for to qemu-ga.
This provides facility to request VSS service in Windows guest to quiesce
applications and filesystems. This function is only supported in Windows
2003 or later. In older guests, this function does nothing.

In several versions of Windows which don't support attribute
VSS_VOLSNAP_ATTR_NO_AUTORECOVERY, DoSnapshotSet fails with error
VSS_E_OBJECT_NOT_FOUND. In this patch, we just ignore this error.
To solve this fundamentally, we need a framework to handle mount writable
snapshot on guests, which is required by VSS auto-recovery feature
(a cleanup phase after snapshot is taken).

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
---
 qga/Makefile.objs           |    3 
 qga/vss-win32-requester.cpp |  419 +++++++++++++++++++++++++++++++++++++++++++
 qga/vss-win32-requester.h   |   31 +++
 3 files changed, 452 insertions(+), 1 deletion(-)
 create mode 100644 qga/vss-win32-requester.cpp
 create mode 100644 qga/vss-win32-requester.h

diff --git a/qga/Makefile.objs b/qga/Makefile.objs
index 8d93866..f17a380 100644
--- a/qga/Makefile.objs
+++ b/qga/Makefile.objs
@@ -6,6 +6,7 @@ qga-obj-y += qapi-generated/qga-qmp-marshal.o
 
 ifeq ($(CONFIG_QGA_VSS),y)
 QEMU_CFLAGS += -DHAS_VSS_SDK
-qga-obj-y += vss-win32-provider/
+qga-obj-y += vss-win32-provider/ vss-win32-requester.o
 qga-prv-obj-y += vss-win32-provider/
+$(obj)/vss-win32-requester.o: QEMU_CXXFLAGS += -Wno-unknown-pragmas
 endif
diff --git a/qga/vss-win32-requester.cpp b/qga/vss-win32-requester.cpp
new file mode 100644
index 0000000..7784926
--- /dev/null
+++ b/qga/vss-win32-requester.cpp
@@ -0,0 +1,419 @@
+/*
+ * QEMU Guest Agent win32 VSS Requester implementations
+ *
+ * Copyright Hitachi Data Systems Corp. 2013
+ *
+ * Authors:
+ *  Tomoki Sekiyama   <tomoki.sekiyama@hds.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include <stdio.h>
+#include <assert.h>
+extern "C" {
+#include "guest-agent-core.h"
+}
+#include "vss-win32-requester.h"
+#include "vss-win32-provider.h"
+#include "vss-win32.h"
+#include "inc/win2003/vswriter.h"
+#include "inc/win2003/vsbackup.h"
+
+/* Functions in VSSAPI.DLL */
+typedef HRESULT(STDAPICALLTYPE * t_CreateVssBackupComponents)(
+    OUT IVssBackupComponents**);
+typedef void(APIENTRY * t_VssFreeSnapshotProperties)(IN VSS_SNAPSHOT_PROP*);
+
+static t_CreateVssBackupComponents _CreateVssBackupComponents;
+static t_VssFreeSnapshotProperties _VssFreeSnapshotProperties;
+static IVssBackupComponents *pVssbc;
+static IVssAsync *pAsyncSnapshot;
+static HMODULE hLib;
+static HANDLE hEvent = INVALID_HANDLE_VALUE, hEvent2 = INVALID_HANDLE_VALUE;
+static int cFrozenVols;
+
+GCC_FMT_ATTR(1, 2)
+static void errmsg(const char *fmt, ...)
+{
+    va_list ap;
+    va_start(ap, fmt);
+    char *msg = g_strdup_vprintf(fmt, ap);
+    va_end(ap);
+    MessageBox(NULL, msg, "Error in QEMU guest agent", MB_OK | MB_ICONWARNING);
+    g_free(msg);
+}
+
+static void error_set_win32(Error **errp, DWORD err,
+                            ErrorClass eclass, const char *text)
+{
+    char *msg = NULL, *nul = strchr(text, '(');
+    int len = nul ? nul - text : -1;
+
+    /* print error message in native encoding */
+    FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
+                  FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+                  NULL, err, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                  (char *)&msg, 0, NULL);
+    printf("%.*s. (Error: %lx) %s\n", len, text, err, msg);
+    LocalFree(msg);
+
+    /* set error message in UTF-8 encoding */
+    msg = g_win32_error_message(err);
+    error_set(errp, eclass, "%.*s. (Error: %lx) %s", len, text, err, msg);
+    g_free(msg);
+}
+#define error_setg_win32(errp, err, text) \
+    error_set_win32(errp, err, ERROR_CLASS_GENERIC_ERROR, text)
+
+#define __chk(status, text, errp, err_label)    \
+    do {                                        \
+        HRESULT __hr = (status);                \
+        if (FAILED(__hr)) {                     \
+            error_setg_win32(errp, __hr, text); \
+            goto err_label;                     \
+        }                                       \
+    } while (0)
+
+#define _chk(status, msg) __chk(status, "Failed to " msg, err, out)
+#define chk(status)  __chk(status, "Failed to " #status, err, out)
+
+
+HRESULT WaitForAsync(IVssAsync *pAsync)
+{
+    HRESULT ret, hr;
+
+    do {
+        hr = pAsync->Wait();
+        if (FAILED(hr)) {
+            ret = hr;
+            break;
+        }
+        hr = pAsync->QueryStatus(&ret, NULL);
+        if (FAILED(hr)) {
+            ret = hr;
+            break;
+        }
+    } while (ret == VSS_S_ASYNC_PENDING);
+
+    return ret;
+}
+
+HRESULT vss_init(void)
+{
+    HRESULT hr;
+
+    hr = VSSCheckOSVersion();
+    if (hr == S_FALSE) {
+        return hr;
+    }
+
+    hr = CoInitialize(NULL);
+    if (FAILED(hr)) {
+        errmsg("CoInitialize failed [%lx]", hr);
+        goto out;
+    };
+    hr = CoInitializeSecurity(
+        NULL, -1, NULL, NULL, RPC_C_AUTHN_LEVEL_PKT_PRIVACY,
+        RPC_C_IMP_LEVEL_IDENTIFY, NULL, EOAC_NONE, NULL);
+    if (FAILED(hr)) {
+        errmsg("CoInitializeSecurity failed [%lx]", hr);
+        goto out;
+    }
+
+    hLib = LoadLibraryA("VSSAPI.DLL");
+    if (!hLib) {
+        errmsg("LoadLibrary VSSAPI.DLL failed");
+        hr = E_FAIL;
+        goto out;
+    }
+
+    _CreateVssBackupComponents = (t_CreateVssBackupComponents)
+        GetProcAddress(hLib,
+#ifdef _WIN64 /* 64bit environment */
+        "?CreateVssBackupComponents@@YAJPEAPEAVIVssBackupComponents@@@Z"
+#else /* 32bit environment */
+        "?CreateVssBackupComponents@@YGJPAPAVIVssBackupComponents@@@Z"
+#endif
+        );
+    _VssFreeSnapshotProperties = (t_VssFreeSnapshotProperties)
+        GetProcAddress(hLib, "VssFreeSnapshotProperties");
+    if (!_CreateVssBackupComponents || !_VssFreeSnapshotProperties) {
+        errmsg("GetProcAddress failed");
+        hr = E_FAIL;
+        goto out;
+    }
+
+    return S_OK;
+out:
+    vss_deinit();
+    return hr;
+}
+
+static void vss_cleanup(void)
+{
+    if (hEvent != INVALID_HANDLE_VALUE) {
+        CloseHandle(hEvent);
+        hEvent = INVALID_HANDLE_VALUE;
+    }
+    if (hEvent2 != INVALID_HANDLE_VALUE) {
+        CloseHandle(hEvent2);
+        hEvent2 = INVALID_HANDLE_VALUE;
+    }
+    if (pVssbc) {
+        pVssbc->Release();
+        pVssbc = NULL;
+    }
+}
+
+void vss_deinit(void)
+{
+    if (VSSCheckOSVersion() == S_FALSE) {
+        return;
+    }
+
+    vss_cleanup();
+
+    CoUninitialize();
+
+    _CreateVssBackupComponents = NULL;
+    _VssFreeSnapshotProperties = NULL;
+    if (hLib) {
+        FreeLibrary(hLib);
+        hLib = NULL;
+    }
+}
+
+int vss_initialized(void)
+{
+    return hLib != NULL;
+}
+
+static void vss_add_components(Error **err)
+{
+    unsigned int cWriters, i;
+    VSS_ID id, idInstance, idWriter;
+    BSTR bstrWriterName;
+    VSS_USAGE_TYPE usage;
+    VSS_SOURCE_TYPE source;
+    unsigned int cComponents, c1, c2, j;
+    IVssExamineWriterMetadata *pMetadata;
+    IVssWMComponent *pComponent;
+    PVSSCOMPONENTINFO pInfo = NULL;
+
+    chk(pVssbc->GetWriterMetadataCount(&cWriters));
+
+    for (i = 0; i < cWriters; i++) {
+        chk(pVssbc->GetWriterMetadata(i, &id, &pMetadata));
+        chk(pMetadata->GetIdentity(&idInstance, &idWriter,
+                                    &bstrWriterName, &usage, &source));
+        chk(pMetadata->GetFileCounts(&c1, &c2, &cComponents));
+
+        for (j = 0; j < cComponents; j++) {
+            chk(pMetadata->GetComponent(j, &pComponent));
+            chk(pComponent->GetComponentInfo(&pInfo));
+            if (pInfo->bSelectable) {
+                chk(pVssbc->AddComponent(idInstance, idWriter, pInfo->type,
+                                         pInfo->bstrLogicalPath,
+                                         pInfo->bstrComponentName));
+            }
+            pComponent->FreeComponentInfo(pInfo);
+            pInfo = NULL;
+            pComponent->Release();
+            pComponent = NULL;
+        }
+
+        pMetadata->Release();
+        pMetadata = NULL;
+    }
+out:
+    if (pComponent) {
+        if (pInfo) {
+            pComponent->FreeComponentInfo(pInfo);
+        }
+        pComponent->Release();
+    }
+    if (pMetadata) {
+        pMetadata->Release();
+    }
+}
+
+void qga_vss_fsfreeze_freeze(int *num_vols, Error **err)
+{
+    IVssAsync *pAsync;
+    HANDLE h;
+    HRESULT hr;
+    LONG ctx;
+    GUID guidSnapshotSet = GUID_NULL;
+    SECURITY_DESCRIPTOR sd;
+    SECURITY_ATTRIBUTES sa;
+    WCHAR buf[64], *b = buf;
+    int n = 0;
+
+    if (pVssbc) { /* already frozen */
+        *num_vols = 0;
+        return;
+    }
+
+    assert(_CreateVssBackupComponents != NULL);
+    chk(_CreateVssBackupComponents(&pVssbc));
+    chk(pVssbc->InitializeForBackup());
+    chk(pVssbc->SetBackupState(true, true, VSS_BT_FULL, false));
+    /*
+     * Currently writable snapshots are not supported.
+     * To prevent the final commit (which requires to write to snapshots),
+     * ATTR_NO_AUTORECOVERY and ATTR_TRANSPORTABLE are specified here.
+     */
+    ctx = VSS_CTX_APP_ROLLBACK | VSS_VOLSNAP_ATTR_TRANSPORTABLE |
+        VSS_VOLSNAP_ATTR_NO_AUTORECOVERY | VSS_VOLSNAP_ATTR_TXF_RECOVERY;
+    hr = pVssbc->SetContext(ctx);
+    if (hr == (HRESULT)VSS_E_UNSUPPORTED_CONTEXT) {
+        /* Non-server version of Windows doesn't support ATTR_TRANSPORTABLE */
+        ctx &= ~VSS_VOLSNAP_ATTR_TRANSPORTABLE;
+        chk(pVssbc->SetContext(ctx));
+    } else {
+        _chk(hr, "SetContext");
+    }
+
+    chk(pVssbc->GatherWriterMetadata(&pAsync));
+    _chk(WaitForAsync(pAsync), "GatherWriterMetadata");
+    pAsync->Release();
+
+    vss_add_components(err);
+    if (error_is_set(err)) {
+        goto out;
+    }
+
+    chk(pVssbc->StartSnapshotSet(&guidSnapshotSet));
+
+    h = FindFirstVolumeW(buf, sizeof(buf));
+    while (h != INVALID_HANDLE_VALUE) {
+        if (GetDriveTypeW(buf) == DRIVE_FIXED) {
+            VSS_ID pid;
+            hr = pVssbc->AddToSnapshotSet(buf, g_gProviderId, &pid);
+            if (FAILED(hr)) {
+                WCHAR name[PATH_MAX];
+                char msg[PATH_MAX+32];
+                if (GetVolumePathNamesForVolumeNameW(
+                        buf, name, sizeof(name), NULL) && *name) {
+                    b = name;
+                }
+                snprintf(msg, sizeof(msg), "add %S to snapshot set", b);
+                error_setg_win32(err, hr, msg);
+                goto out;
+            }
+            n++;
+        }
+        if (!FindNextVolumeW(h, buf, sizeof(buf))) {
+            FindVolumeClose(h);
+            break;
+        }
+    }
+
+    chk(pVssbc->PrepareForBackup(&pAsync));
+    _chk(WaitForAsync(pAsync), "PrepareForBackup");
+    pAsync->Release();
+
+    chk(pVssbc->GatherWriterStatus(&pAsync));
+    _chk(WaitForAsync(pAsync), "GatherWriterStatus");
+    pAsync->Release();
+
+    /* 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;
+
+    hEvent = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_FROZEN);
+    if (hEvent == INVALID_HANDLE_VALUE) {
+        error_setg_win32(err, GetLastError(), "CreateEvenet");
+        goto out;
+    }
+    hEvent2 = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_THAW);
+    if (hEvent2 == INVALID_HANDLE_VALUE) {
+        error_setg_win32(err, GetLastError(), "CreateEvenet");
+        goto out;
+    }
+
+    chk(pVssbc->DoSnapshotSet(&pAsyncSnapshot));
+
+    /* Need to call QueryStatus several times to make VSS provider progress */
+    for (int i = 0; i < 1000; i++) {
+        HRESULT hr = S_OK;
+        chk(pAsyncSnapshot->QueryStatus(&hr, NULL));
+        if (hr != VSS_S_ASYNC_PENDING) {
+            error_setg(err, "DoSnapshotSet exited without freeze event");
+            goto out;
+        }
+        DWORD ret = WaitForSingleObject(hEvent, 10);
+        if (ret == WAIT_OBJECT_0) {
+            break;
+        }
+    }
+
+    *num_vols = cFrozenVols = n;
+    return;
+
+out:
+    if (pVssbc) {
+        pVssbc->AbortBackup();
+    }
+    vss_cleanup();
+}
+
+
+void qga_vss_fsfreeze_thaw(int *num_vols, Error **err)
+{
+    IVssAsync *pAsync;
+
+    if (hEvent2 == INVALID_HANDLE_VALUE) {
+        /*
+         * In this case, DoSnapshotSet is aborted or not started,
+         * and no volumes must be frozen. We return without an error.
+         */
+        *num_vols = 0;
+        return;
+    }
+    SetEvent(hEvent2);
+
+    assert(pVssbc);
+    assert(pAsyncSnapshot);
+
+    HRESULT hr = WaitForAsync(pAsyncSnapshot);
+    if (hr == (HRESULT)VSS_E_OBJECT_NOT_FOUND) {
+        /*
+         * On Windows earlier than 2008 SP2 which does not support
+         * VSS_VOLSNAP_ATTR_NO_AUTORECOVERY context, the final commit is not
+         * skipped and VSS is aborted by VSS_E_OBJECT_NOT_FOUND. Still, as the
+         * applications and file systems are frozen, we just ignore the error.
+         */
+        pAsyncSnapshot->Release();
+        pAsyncSnapshot = NULL;
+        goto final;
+    }
+    if (hr == (HRESULT)VSS_E_HOLD_WRITES_TIMEOUT) {
+        _chk(hr, "DoSnapshotSet: Couldn't hold writes. "
+             "Fsfreeze is limited up to 10 seconds");
+    }
+    _chk(hr, "DoSnapshotSet");
+    pAsyncSnapshot->Release();
+    pAsyncSnapshot = NULL;
+
+    chk(pVssbc->BackupComplete(&pAsync));
+    _chk(WaitForAsync(pAsync), "BackupComplete");
+    pAsync->Release();
+
+final:
+    *num_vols = cFrozenVols;
+    cFrozenVols = 0;
+    goto done;
+
+out:
+    if (pVssbc) {
+        pVssbc->AbortBackup();
+    }
+done:
+    vss_cleanup();
+}
diff --git a/qga/vss-win32-requester.h b/qga/vss-win32-requester.h
new file mode 100644
index 0000000..f180f56
--- /dev/null
+++ b/qga/vss-win32-requester.h
@@ -0,0 +1,31 @@
+/*
+ * QEMU Guest Agent VSS Requester declarations
+ *
+ * Copyright Hitachi Data Systems Corp. 2013
+ *
+ * Authors:
+ *  Tomoki Sekiyama   <tomoki.sekiyama@hds.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef VSS_WIN32_REQUESTER_H
+#define VSS_WIN32_REQUESTER_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+HRESULT vss_init(void);
+void vss_deinit(void);
+int vss_initialized(void);
+
+void qga_vss_fsfreeze_freeze(int *nr_volume, struct Error **err);
+void qga_vss_fsfreeze_thaw(int *nr_volume, struct Error **err);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif