qga/vss-win32/requester.cpp

   1 /*
   2  * QEMU Guest Agent win32 VSS Requester implementations
   3  *
   4  * Copyright Hitachi Data Systems Corp. 2013
   5  *
   6  * Authors:
   7  *  Tomoki Sekiyama   <tomoki.sekiyama@hds.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  10  * See the COPYING file in the top-level directory.
  11  */
  12
  13 #include <stdio.h>
  14 #include "vss-common.h"
  15 #include "requester.h"
  16 #include "assert.h"
  17 #include "inc/win2003/vswriter.h"
  18 #include "inc/win2003/vsbackup.h"
  19
  20 /* Max wait time for frozen event (VSS can only hold writes for 10 seconds) */
  21 #define VSS_TIMEOUT_FREEZE_MSEC 10000
  22
  23 /* Call QueryStatus every 10 ms while waiting for frozen event */
  24 #define VSS_TIMEOUT_EVENT_MSEC 10
  25
  26 #define err_set(e, err, fmt, ...) \
  27     ((e)->error_set((e)->errp, err, (e)->err_class, fmt, ## __VA_ARGS__))
  28 #define err_is_set(e) ((e)->errp && *(e)->errp)
  29
  30
  31 /* Handle to VSSAPI.DLL */
  32 static HMODULE hLib;
  33
  34 /* Functions in VSSAPI.DLL */
  35 typedef HRESULT(STDAPICALLTYPE * t_CreateVssBackupComponents)(
  36     OUT IVssBackupComponents**);
  37 typedef void(APIENTRY * t_VssFreeSnapshotProperties)(IN VSS_SNAPSHOT_PROP*);
  38 static t_CreateVssBackupComponents pCreateVssBackupComponents;
  39 static t_VssFreeSnapshotProperties pVssFreeSnapshotProperties;
  40
  41 /* Variables used while applications and filesystes are frozen by VSS */
  42 static struct QGAVSSContext {
  43     IVssBackupComponents *pVssbc;  /* VSS requester interface */
  44     IVssAsync *pAsyncSnapshot;     /* async info of VSS snapshot operation */
  45     HANDLE hEventFrozen;           /* notify fs/writer freeze from provider */
  46     HANDLE hEventThaw;             /* request provider to thaw */
  47     HANDLE hEventTimeout;          /* notify timeout in provider */
  48     int cFrozenVols;               /* number of frozen volumes */
  49 } vss_ctx;
  50
  51 STDAPI requester_init(void)
  52 {
  53     vss_ctx.hEventFrozen =  INVALID_HANDLE_VALUE;
  54     vss_ctx.hEventThaw = INVALID_HANDLE_VALUE;
  55     vss_ctx.hEventTimeout = INVALID_HANDLE_VALUE;
  56
  57     COMInitializer initializer; /* to call CoInitializeSecurity */
  58     HRESULT hr = CoInitializeSecurity(
  59         NULL, -1, NULL, NULL, RPC_C_AUTHN_LEVEL_PKT_PRIVACY,
  60         RPC_C_IMP_LEVEL_IDENTIFY, NULL, EOAC_NONE, NULL);
  61     if (FAILED(hr)) {
  62         fprintf(stderr, "failed to CoInitializeSecurity (error %lx)\n", hr);
  63         return hr;
  64     }
  65
  66     hLib = LoadLibraryA("VSSAPI.DLL");
  67     if (!hLib) {
  68         fprintf(stderr, "failed to load VSSAPI.DLL\n");
  69         return HRESULT_FROM_WIN32(GetLastError());
  70     }
  71
  72     pCreateVssBackupComponents = (t_CreateVssBackupComponents)
  73         GetProcAddress(hLib,
  74 #ifdef _WIN64 /* 64bit environment */
  75         "?CreateVssBackupComponents@@YAJPEAPEAVIVssBackupComponents@@@Z"
  76 #else /* 32bit environment */
  77         "?CreateVssBackupComponents@@YGJPAPAVIVssBackupComponents@@@Z"
  78 #endif
  79         );
  80     if (!pCreateVssBackupComponents) {
  81         fprintf(stderr, "failed to get proc address from VSSAPI.DLL\n");
  82         return HRESULT_FROM_WIN32(GetLastError());
  83     }
  84
  85     pVssFreeSnapshotProperties = (t_VssFreeSnapshotProperties)
  86         GetProcAddress(hLib, "VssFreeSnapshotProperties");
  87     if (!pVssFreeSnapshotProperties) {
  88         fprintf(stderr, "failed to get proc address from VSSAPI.DLL\n");
  89         return HRESULT_FROM_WIN32(GetLastError());
  90     }
  91
  92     return S_OK;
  93 }
  94
  95 static void requester_cleanup(void)
  96 {
  97     if (vss_ctx.hEventFrozen != INVALID_HANDLE_VALUE) {
  98         CloseHandle(vss_ctx.hEventFrozen);
  99         vss_ctx.hEventFrozen = INVALID_HANDLE_VALUE;
 100     }
 101     if (vss_ctx.hEventThaw != INVALID_HANDLE_VALUE) {
 102         CloseHandle(vss_ctx.hEventThaw);
 103         vss_ctx.hEventThaw = INVALID_HANDLE_VALUE;
 104     }
 105     if (vss_ctx.hEventTimeout != INVALID_HANDLE_VALUE) {
 106         CloseHandle(vss_ctx.hEventTimeout);
 107         vss_ctx.hEventTimeout = INVALID_HANDLE_VALUE;
 108     }
 109     if (vss_ctx.pAsyncSnapshot) {
 110         vss_ctx.pAsyncSnapshot->Release();
 111         vss_ctx.pAsyncSnapshot = NULL;
 112     }
 113     if (vss_ctx.pVssbc) {
 114         vss_ctx.pVssbc->Release();
 115         vss_ctx.pVssbc = NULL;
 116     }
 117     vss_ctx.cFrozenVols = 0;
 118 }
 119
 120 STDAPI requester_deinit(void)
 121 {
 122     requester_cleanup();
 123
 124     pCreateVssBackupComponents = NULL;
 125     pVssFreeSnapshotProperties = NULL;
 126     if (hLib) {
 127         FreeLibrary(hLib);
 128         hLib = NULL;
 129     }
 130
 131     return S_OK;
 132 }
 133
 134 static HRESULT WaitForAsync(IVssAsync *pAsync)
 135 {
 136     HRESULT ret, hr;
 137
 138     do {
 139         hr = pAsync->Wait();
 140         if (FAILED(hr)) {
 141             ret = hr;
 142             break;
 143         }
 144         hr = pAsync->QueryStatus(&ret, NULL);
 145         if (FAILED(hr)) {
 146             ret = hr;
 147             break;
 148         }
 149     } while (ret == VSS_S_ASYNC_PENDING);
 150
 151     return ret;
 152 }
 153
 154 static void AddComponents(ErrorSet *errset)
 155 {
 156     unsigned int cWriters, i;
 157     VSS_ID id, idInstance, idWriter;
 158     BSTR bstrWriterName = NULL;
 159     VSS_USAGE_TYPE usage;
 160     VSS_SOURCE_TYPE source;
 161     unsigned int cComponents, c1, c2, j;
 162     COMPointer<IVssExamineWriterMetadata> pMetadata;
 163     COMPointer<IVssWMComponent> pComponent;
 164     PVSSCOMPONENTINFO info;
 165     HRESULT hr;
 166
 167     hr = vss_ctx.pVssbc->GetWriterMetadataCount(&cWriters);
 168     if (FAILED(hr)) {
 169         err_set(errset, hr, "failed to get writer metadata count");
 170         goto out;
 171     }
 172
 173     for (i = 0; i < cWriters; i++) {
 174         hr = vss_ctx.pVssbc->GetWriterMetadata(i, &id, pMetadata.replace());
 175         if (FAILED(hr)) {
 176             err_set(errset, hr, "failed to get writer metadata of %d/%d",
 177                              i, cWriters);
 178             goto out;
 179         }
 180
 181         hr = pMetadata->GetIdentity(&idInstance, &idWriter,
 182                                     &bstrWriterName, &usage, &source);
 183         if (FAILED(hr)) {
 184             err_set(errset, hr, "failed to get identity of writer %d/%d",
 185                              i, cWriters);
 186             goto out;
 187         }
 188
 189         hr = pMetadata->GetFileCounts(&c1, &c2, &cComponents);
 190         if (FAILED(hr)) {
 191             err_set(errset, hr, "failed to get file counts of %S",
 192                              bstrWriterName);
 193             goto out;
 194         }
 195
 196         for (j = 0; j < cComponents; j++) {
 197             hr = pMetadata->GetComponent(j, pComponent.replace());
 198             if (FAILED(hr)) {
 199                 err_set(errset, hr,
 200                                  "failed to get component %d/%d of %S",
 201                                  j, cComponents, bstrWriterName);
 202                 goto out;
 203             }
 204
 205             hr = pComponent->GetComponentInfo(&info);
 206             if (FAILED(hr)) {
 207                 err_set(errset, hr,
 208                                  "failed to get component info %d/%d of %S",
 209                                  j, cComponents, bstrWriterName);
 210                 goto out;
 211             }
 212
 213             if (info->bSelectable) {
 214                 hr = vss_ctx.pVssbc->AddComponent(idInstance, idWriter,
 215                                                   info->type,
 216                                                   info->bstrLogicalPath,
 217                                                   info->bstrComponentName);
 218                 if (FAILED(hr)) {
 219                     err_set(errset, hr, "failed to add component %S(%S)",
 220                                      info->bstrComponentName, bstrWriterName);
 221                     goto out;
 222                 }
 223             }
 224             SysFreeString(bstrWriterName);
 225             bstrWriterName = NULL;
 226             pComponent->FreeComponentInfo(info);
 227             info = NULL;
 228         }
 229     }
 230 out:
 231     if (bstrWriterName) {
 232         SysFreeString(bstrWriterName);
 233     }
 234     if (pComponent && info) {
 235         pComponent->FreeComponentInfo(info);
 236     }
 237 }
 238
 239 void requester_freeze(int *num_vols, ErrorSet *errset)
 240 {
 241     COMPointer<IVssAsync> pAsync;
 242     HANDLE volume;
 243     HRESULT hr;
 244     LONG ctx;
 245     GUID guidSnapshotSet = GUID_NULL;
 246     SECURITY_DESCRIPTOR sd;
 247     SECURITY_ATTRIBUTES sa;
 248     WCHAR short_volume_name[64], *display_name = short_volume_name;
 249     DWORD wait_status;
 250     int num_fixed_drives = 0, i;
 251
 252     if (vss_ctx.pVssbc) { /* already frozen */
 253         *num_vols = 0;
 254         return;
 255     }
 256
 257     CoInitialize(NULL);
 258
 259     assert(pCreateVssBackupComponents != NULL);
 260     hr = pCreateVssBackupComponents(&vss_ctx.pVssbc);
 261     if (FAILED(hr)) {
 262         err_set(errset, hr, "failed to create VSS backup components");
 263         goto out;
 264     }
 265
 266     hr = vss_ctx.pVssbc->InitializeForBackup();
 267     if (FAILED(hr)) {
 268         err_set(errset, hr, "failed to initialize for backup");
 269         goto out;
 270     }
 271
 272     hr = vss_ctx.pVssbc->SetBackupState(true, true, VSS_BT_FULL, false);
 273     if (FAILED(hr)) {
 274         err_set(errset, hr, "failed to set backup state");
 275         goto out;
 276     }
 277
 278     /*
 279      * Currently writable snapshots are not supported.
 280      * To prevent the final commit (which requires to write to snapshots),
 281      * ATTR_NO_AUTORECOVERY and ATTR_TRANSPORTABLE are specified here.
 282      */
 283     ctx = VSS_CTX_APP_ROLLBACK | VSS_VOLSNAP_ATTR_TRANSPORTABLE |
 284         VSS_VOLSNAP_ATTR_NO_AUTORECOVERY | VSS_VOLSNAP_ATTR_TXF_RECOVERY;
 285     hr = vss_ctx.pVssbc->SetContext(ctx);
 286     if (hr == (HRESULT)VSS_E_UNSUPPORTED_CONTEXT) {
 287         /* Non-server version of Windows doesn't support ATTR_TRANSPORTABLE */
 288         ctx &= ~VSS_VOLSNAP_ATTR_TRANSPORTABLE;
 289         hr = vss_ctx.pVssbc->SetContext(ctx);
 290     }
 291     if (FAILED(hr)) {
 292         err_set(errset, hr, "failed to set backup context");
 293         goto out;
 294     }
 295
 296     hr = vss_ctx.pVssbc->GatherWriterMetadata(pAsync.replace());
 297     if (SUCCEEDED(hr)) {
 298         hr = WaitForAsync(pAsync);
 299     }
 300     if (FAILED(hr)) {
 301         err_set(errset, hr, "failed to gather writer metadata");
 302         goto out;
 303     }
 304
 305     AddComponents(errset);
 306     if (err_is_set(errset)) {
 307         goto out;
 308     }
 309
 310     hr = vss_ctx.pVssbc->StartSnapshotSet(&guidSnapshotSet);
 311     if (FAILED(hr)) {
 312         err_set(errset, hr, "failed to start snapshot set");
 313         goto out;
 314     }
 315
 316     volume = FindFirstVolumeW(short_volume_name, sizeof(short_volume_name));
 317     if (volume == INVALID_HANDLE_VALUE) {
 318         err_set(errset, hr, "failed to find first volume");
 319         goto out;
 320     }
 321     for (;;) {
 322         if (GetDriveTypeW(short_volume_name) == DRIVE_FIXED) {
 323             VSS_ID pid;
 324             hr = vss_ctx.pVssbc->AddToSnapshotSet(short_volume_name,
 325                                                   g_gProviderId, &pid);
 326             if (FAILED(hr)) {
 327                 WCHAR volume_path_name[PATH_MAX];
 328                 if (GetVolumePathNamesForVolumeNameW(
 329                         short_volume_name, volume_path_name,
 330                         sizeof(volume_path_name), NULL) && *volume_path_name) {
 331                     display_name = volume_path_name;
 332                 }
 333                 err_set(errset, hr, "failed to add %S to snapshot set",
 334                                  display_name);
 335                 FindVolumeClose(volume);
 336                 goto out;
 337             }
 338             num_fixed_drives++;
 339         }
 340         if (!FindNextVolumeW(volume, short_volume_name,
 341                              sizeof(short_volume_name))) {
 342             FindVolumeClose(volume);
 343             break;
 344         }
 345     }
 346
 347     if (num_fixed_drives == 0) {
 348         goto out; /* If there is no fixed drive, just exit. */
 349     }
 350
 351     hr = vss_ctx.pVssbc->PrepareForBackup(pAsync.replace());
 352     if (SUCCEEDED(hr)) {
 353         hr = WaitForAsync(pAsync);
 354     }
 355     if (FAILED(hr)) {
 356         err_set(errset, hr, "failed to prepare for backup");
 357         goto out;
 358     }
 359
 360     hr = vss_ctx.pVssbc->GatherWriterStatus(pAsync.replace());
 361     if (SUCCEEDED(hr)) {
 362         hr = WaitForAsync(pAsync);
 363     }
 364     if (FAILED(hr)) {
 365         err_set(errset, hr, "failed to gather writer status");
 366         goto out;
 367     }
 368
 369     /* Allow unrestricted access to events */
 370     InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION);
 371     SetSecurityDescriptorDacl(&sd, TRUE, NULL, FALSE);
 372     sa.nLength = sizeof(sa);
 373     sa.lpSecurityDescriptor = &sd;
 374     sa.bInheritHandle = FALSE;
 375
 376     vss_ctx.hEventFrozen = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_FROZEN);
 377     if (vss_ctx.hEventFrozen == INVALID_HANDLE_VALUE) {
 378         err_set(errset, GetLastError(), "failed to create event %s",
 379                 EVENT_NAME_FROZEN);
 380         goto out;
 381     }
 382     vss_ctx.hEventThaw = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_THAW);
 383     if (vss_ctx.hEventThaw == INVALID_HANDLE_VALUE) {
 384         err_set(errset, GetLastError(), "failed to create event %s",
 385                 EVENT_NAME_THAW);
 386         goto out;
 387     }
 388     vss_ctx.hEventTimeout = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_TIMEOUT);
 389     if (vss_ctx.hEventTimeout == INVALID_HANDLE_VALUE) {
 390         err_set(errset, GetLastError(), "failed to create event %s",
 391                 EVENT_NAME_TIMEOUT);
 392         goto out;
 393     }
 394
 395     /*
 396      * Start VSS quiescing operations.
 397      * CQGAVssProvider::CommitSnapshots will kick vss_ctx.hEventFrozen
 398      * after the applications and filesystems are frozen.
 399      */
 400     hr = vss_ctx.pVssbc->DoSnapshotSet(&vss_ctx.pAsyncSnapshot);
 401     if (FAILED(hr)) {
 402         err_set(errset, hr, "failed to do snapshot set");
 403         goto out;
 404     }
 405
 406     /* Need to call QueryStatus several times to make VSS provider progress */
 407     for (i = 0; i < VSS_TIMEOUT_FREEZE_MSEC/VSS_TIMEOUT_EVENT_MSEC; i++) {
 408         HRESULT hr2 = vss_ctx.pAsyncSnapshot->QueryStatus(&hr, NULL);
 409         if (FAILED(hr2)) {
 410             err_set(errset, hr, "failed to do snapshot set");
 411             goto out;
 412         }
 413         if (hr != VSS_S_ASYNC_PENDING) {
 414             err_set(errset, E_FAIL,
 415                     "DoSnapshotSet exited without Frozen event");
 416             goto out;
 417         }
 418         wait_status = WaitForSingleObject(vss_ctx.hEventFrozen,
 419                                           VSS_TIMEOUT_EVENT_MSEC);
 420         if (wait_status != WAIT_TIMEOUT) {
 421             break;
 422         }
 423     }
 424     if (wait_status != WAIT_OBJECT_0) {
 425         err_set(errset, E_FAIL,
 426                 "couldn't receive Frozen event from VSS provider");
 427         goto out;
 428     }
 429
 430     *num_vols = vss_ctx.cFrozenVols = num_fixed_drives;
 431     return;
 432
 433 out:
 434     if (vss_ctx.pVssbc) {
 435         vss_ctx.pVssbc->AbortBackup();
 436     }
 437     requester_cleanup();
 438     CoUninitialize();
 439 }
 440
 441
 442 void requester_thaw(int *num_vols, ErrorSet *errset)
 443 {
 444     COMPointer<IVssAsync> pAsync;
 445
 446     if (vss_ctx.hEventThaw == INVALID_HANDLE_VALUE) {
 447         /*
 448          * In this case, DoSnapshotSet is aborted or not started,
 449          * and no volumes must be frozen. We return without an error.
 450          */
 451         *num_vols = 0;
 452         return;
 453     }
 454
 455     /* Tell the provider that the snapshot is finished. */
 456     SetEvent(vss_ctx.hEventThaw);
 457
 458     assert(vss_ctx.pVssbc);
 459     assert(vss_ctx.pAsyncSnapshot);
 460
 461     HRESULT hr = WaitForAsync(vss_ctx.pAsyncSnapshot);
 462     switch (hr) {
 463     case VSS_S_ASYNC_FINISHED:
 464         hr = vss_ctx.pVssbc->BackupComplete(pAsync.replace());
 465         if (SUCCEEDED(hr)) {
 466             hr = WaitForAsync(pAsync);
 467         }
 468         if (FAILED(hr)) {
 469             err_set(errset, hr, "failed to complete backup");
 470         }
 471         break;
 472
 473     case (HRESULT)VSS_E_OBJECT_NOT_FOUND:
 474         /*
 475          * On Windows earlier than 2008 SP2 which does not support
 476          * VSS_VOLSNAP_ATTR_NO_AUTORECOVERY context, the final commit is not
 477          * skipped and VSS is aborted by VSS_E_OBJECT_NOT_FOUND. However, as
 478          * the system had been frozen until fsfreeze-thaw command was issued,
 479          * we ignore this error.
 480          */
 481         vss_ctx.pVssbc->AbortBackup();
 482         break;
 483
 484     case VSS_E_UNEXPECTED_PROVIDER_ERROR:
 485         if (WaitForSingleObject(vss_ctx.hEventTimeout, 0) != WAIT_OBJECT_0) {
 486             err_set(errset, hr, "unexpected error in VSS provider");
 487             break;
 488         }
 489         /* fall through if hEventTimeout is signaled */
 490
 491     case (HRESULT)VSS_E_HOLD_WRITES_TIMEOUT:
 492         err_set(errset, hr, "couldn't hold writes: "
 493                 "fsfreeze is limited up to 10 seconds");
 494         break;
 495
 496     default:
 497         err_set(errset, hr, "failed to do snapshot set");
 498     }
 499
 500     if (err_is_set(errset)) {
 501         vss_ctx.pVssbc->AbortBackup();
 502     }
 503     *num_vols = vss_ctx.cFrozenVols;
 504     requester_cleanup();
 505
 506     CoUninitialize();
 507 }