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 "qemu/osdep.h"
  14 #include "vss-common.h"
  15 #include "requester.h"
  16 #include <inc/win2003/vswriter.h>
  17 #include <inc/win2003/vsbackup.h>
  18
  19 /* Max wait time for frozen event (VSS can only hold writes for 10 seconds) */
  20 #define VSS_TIMEOUT_FREEZE_MSEC 10000
  21
  22 /* Call QueryStatus every 10 ms while waiting for frozen event */
  23 #define VSS_TIMEOUT_EVENT_MSEC 10
  24
  25 #define err_set(e, err, fmt, ...)                                           \
  26     ((e)->error_setg_win32_wrapper((e)->errp, __FILE__, __LINE__, __func__, \
  27                                    err, fmt, ## __VA_ARGS__))
  28 /* Bad idea, works only when (e)->errp != NULL: */
  29 #define err_is_set(e) ((e)->errp && *(e)->errp)
  30 /* To lift this restriction, error_propagate(), like we do in QEMU code */
  31
  32 /* Handle to VSSAPI.DLL */
  33 static HMODULE hLib;
  34
  35 /* Functions in VSSAPI.DLL */
  36 typedef HRESULT(STDAPICALLTYPE * t_CreateVssBackupComponents)(
  37     OUT IVssBackupComponents**);
  38 typedef void(APIENTRY * t_VssFreeSnapshotProperties)(IN VSS_SNAPSHOT_PROP*);
  39 static t_CreateVssBackupComponents pCreateVssBackupComponents;
  40 static t_VssFreeSnapshotProperties pVssFreeSnapshotProperties;
  41
  42 /* Variables used while applications and filesystes are frozen by VSS */
  43 static struct QGAVSSContext {
  44     IVssBackupComponents *pVssbc;  /* VSS requester interface */
  45     IVssAsync *pAsyncSnapshot;     /* async info of VSS snapshot operation */
  46     HANDLE hEventFrozen;           /* notify fs/writer freeze from provider */
  47     HANDLE hEventThaw;             /* request provider to thaw */
  48     HANDLE hEventTimeout;          /* notify timeout in provider */
  49     int cFrozenVols;               /* number of frozen volumes */
  50 } vss_ctx;
  51
  52 STDAPI requester_init(void)
  53 {
  54     COMInitializer initializer; /* to call CoInitializeSecurity */
  55     HRESULT hr = CoInitializeSecurity(
  56         NULL, -1, NULL, NULL, RPC_C_AUTHN_LEVEL_PKT_PRIVACY,
  57         RPC_C_IMP_LEVEL_IDENTIFY, NULL, EOAC_NONE, NULL);
  58     if (FAILED(hr)) {
  59         fprintf(stderr, "failed to CoInitializeSecurity (error %lx)\n", hr);
  60         return hr;
  61     }
  62
  63     hLib = LoadLibraryA("VSSAPI.DLL");
  64     if (!hLib) {
  65         fprintf(stderr, "failed to load VSSAPI.DLL\n");
  66         return HRESULT_FROM_WIN32(GetLastError());
  67     }
  68
  69     pCreateVssBackupComponents = (t_CreateVssBackupComponents)
  70         GetProcAddress(hLib,
  71 #ifdef _WIN64 /* 64bit environment */
  72         "?CreateVssBackupComponents@@YAJPEAPEAVIVssBackupComponents@@@Z"
  73 #else /* 32bit environment */
  74         "?CreateVssBackupComponents@@YGJPAPAVIVssBackupComponents@@@Z"
  75 #endif
  76         );
  77     if (!pCreateVssBackupComponents) {
  78         fprintf(stderr, "failed to get proc address from VSSAPI.DLL\n");
  79         return HRESULT_FROM_WIN32(GetLastError());
  80     }
  81
  82     pVssFreeSnapshotProperties = (t_VssFreeSnapshotProperties)
  83         GetProcAddress(hLib, "VssFreeSnapshotProperties");
  84     if (!pVssFreeSnapshotProperties) {
  85         fprintf(stderr, "failed to get proc address from VSSAPI.DLL\n");
  86         return HRESULT_FROM_WIN32(GetLastError());
  87     }
  88
  89     return S_OK;
  90 }
  91
  92 static void requester_cleanup(void)
  93 {
  94     if (vss_ctx.hEventFrozen) {
  95         CloseHandle(vss_ctx.hEventFrozen);
  96         vss_ctx.hEventFrozen = NULL;
  97     }
  98     if (vss_ctx.hEventThaw) {
  99         CloseHandle(vss_ctx.hEventThaw);
 100         vss_ctx.hEventThaw = NULL;
 101     }
 102     if (vss_ctx.hEventTimeout) {
 103         CloseHandle(vss_ctx.hEventTimeout);
 104         vss_ctx.hEventTimeout = NULL;
 105     }
 106     if (vss_ctx.pAsyncSnapshot) {
 107         vss_ctx.pAsyncSnapshot->Release();
 108         vss_ctx.pAsyncSnapshot = NULL;
 109     }
 110     if (vss_ctx.pVssbc) {
 111         vss_ctx.pVssbc->Release();
 112         vss_ctx.pVssbc = NULL;
 113     }
 114     vss_ctx.cFrozenVols = 0;
 115 }
 116
 117 STDAPI requester_deinit(void)
 118 {
 119     requester_cleanup();
 120
 121     pCreateVssBackupComponents = NULL;
 122     pVssFreeSnapshotProperties = NULL;
 123     if (hLib) {
 124         FreeLibrary(hLib);
 125         hLib = NULL;
 126     }
 127
 128     return S_OK;
 129 }
 130
 131 static HRESULT WaitForAsync(IVssAsync *pAsync)
 132 {
 133     HRESULT ret, hr;
 134
 135     do {
 136         hr = pAsync->Wait();
 137         if (FAILED(hr)) {
 138             ret = hr;
 139             break;
 140         }
 141         hr = pAsync->QueryStatus(&ret, NULL);
 142         if (FAILED(hr)) {
 143             ret = hr;
 144             break;
 145         }
 146     } while (ret == VSS_S_ASYNC_PENDING);
 147
 148     return ret;
 149 }
 150
 151 static void AddComponents(ErrorSet *errset)
 152 {
 153     unsigned int cWriters, i;
 154     VSS_ID id, idInstance, idWriter;
 155     BSTR bstrWriterName = NULL;
 156     VSS_USAGE_TYPE usage;
 157     VSS_SOURCE_TYPE source;
 158     unsigned int cComponents, c1, c2, j;
 159     COMPointer<IVssExamineWriterMetadata> pMetadata;
 160     COMPointer<IVssWMComponent> pComponent;
 161     PVSSCOMPONENTINFO info;
 162     HRESULT hr;
 163
 164     hr = vss_ctx.pVssbc->GetWriterMetadataCount(&cWriters);
 165     if (FAILED(hr)) {
 166         err_set(errset, hr, "failed to get writer metadata count");
 167         goto out;
 168     }
 169
 170     for (i = 0; i < cWriters; i++) {
 171         hr = vss_ctx.pVssbc->GetWriterMetadata(i, &id, pMetadata.replace());
 172         if (FAILED(hr)) {
 173             err_set(errset, hr, "failed to get writer metadata of %d/%d",
 174                              i, cWriters);
 175             goto out;
 176         }
 177
 178         hr = pMetadata->GetIdentity(&idInstance, &idWriter,
 179                                     &bstrWriterName, &usage, &source);
 180         if (FAILED(hr)) {
 181             err_set(errset, hr, "failed to get identity of writer %d/%d",
 182                              i, cWriters);
 183             goto out;
 184         }
 185
 186         hr = pMetadata->GetFileCounts(&c1, &c2, &cComponents);
 187         if (FAILED(hr)) {
 188             err_set(errset, hr, "failed to get file counts of %S",
 189                              bstrWriterName);
 190             goto out;
 191         }
 192
 193         for (j = 0; j < cComponents; j++) {
 194             hr = pMetadata->GetComponent(j, pComponent.replace());
 195             if (FAILED(hr)) {
 196                 err_set(errset, hr,
 197                                  "failed to get component %d/%d of %S",
 198                                  j, cComponents, bstrWriterName);
 199                 goto out;
 200             }
 201
 202             hr = pComponent->GetComponentInfo(&info);
 203             if (FAILED(hr)) {
 204                 err_set(errset, hr,
 205                                  "failed to get component info %d/%d of %S",
 206                                  j, cComponents, bstrWriterName);
 207                 goto out;
 208             }
 209
 210             if (info->bSelectable) {
 211                 hr = vss_ctx.pVssbc->AddComponent(idInstance, idWriter,
 212                                                   info->type,
 213                                                   info->bstrLogicalPath,
 214                                                   info->bstrComponentName);
 215                 if (FAILED(hr)) {
 216                     err_set(errset, hr, "failed to add component %S(%S)",
 217                                      info->bstrComponentName, bstrWriterName);
 218                     goto out;
 219                 }
 220             }
 221             SysFreeString(bstrWriterName);
 222             bstrWriterName = NULL;
 223             pComponent->FreeComponentInfo(info);
 224             info = NULL;
 225         }
 226     }
 227 out:
 228     if (bstrWriterName) {
 229         SysFreeString(bstrWriterName);
 230     }
 231     if (pComponent && info) {
 232         pComponent->FreeComponentInfo(info);
 233     }
 234 }
 235
 236 void requester_freeze(int *num_vols, ErrorSet *errset)
 237 {
 238     COMPointer<IVssAsync> pAsync;
 239     HANDLE volume;
 240     HRESULT hr;
 241     LONG ctx;
 242     GUID guidSnapshotSet = GUID_NULL;
 243     SECURITY_DESCRIPTOR sd;
 244     SECURITY_ATTRIBUTES sa;
 245     WCHAR short_volume_name[64], *display_name = short_volume_name;
 246     DWORD wait_status;
 247     int num_fixed_drives = 0, i;
 248
 249     if (vss_ctx.pVssbc) { /* already frozen */
 250         *num_vols = 0;
 251         return;
 252     }
 253
 254     CoInitialize(NULL);
 255
 256     /* Allow unrestricted access to events */
 257     InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION);
 258     SetSecurityDescriptorDacl(&sd, TRUE, NULL, FALSE);
 259     sa.nLength = sizeof(sa);
 260     sa.lpSecurityDescriptor = &sd;
 261     sa.bInheritHandle = FALSE;
 262
 263     vss_ctx.hEventFrozen = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_FROZEN);
 264     if (!vss_ctx.hEventFrozen) {
 265         err_set(errset, GetLastError(), "failed to create event %s",
 266                 EVENT_NAME_FROZEN);
 267         goto out;
 268     }
 269     vss_ctx.hEventThaw = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_THAW);
 270     if (!vss_ctx.hEventThaw) {
 271         err_set(errset, GetLastError(), "failed to create event %s",
 272                 EVENT_NAME_THAW);
 273         goto out;
 274     }
 275     vss_ctx.hEventTimeout = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_TIMEOUT);
 276     if (!vss_ctx.hEventTimeout) {
 277         err_set(errset, GetLastError(), "failed to create event %s",
 278                 EVENT_NAME_TIMEOUT);
 279         goto out;
 280     }
 281
 282     assert(pCreateVssBackupComponents != NULL);
 283     hr = pCreateVssBackupComponents(&vss_ctx.pVssbc);
 284     if (FAILED(hr)) {
 285         err_set(errset, hr, "failed to create VSS backup components");
 286         goto out;
 287     }
 288
 289     hr = vss_ctx.pVssbc->InitializeForBackup();
 290     if (FAILED(hr)) {
 291         err_set(errset, hr, "failed to initialize for backup");
 292         goto out;
 293     }
 294
 295     hr = vss_ctx.pVssbc->SetBackupState(true, true, VSS_BT_FULL, false);
 296     if (FAILED(hr)) {
 297         err_set(errset, hr, "failed to set backup state");
 298         goto out;
 299     }
 300
 301     /*
 302      * Currently writable snapshots are not supported.
 303      * To prevent the final commit (which requires to write to snapshots),
 304      * ATTR_NO_AUTORECOVERY and ATTR_TRANSPORTABLE are specified here.
 305      */
 306     ctx = VSS_CTX_APP_ROLLBACK | VSS_VOLSNAP_ATTR_TRANSPORTABLE |
 307         VSS_VOLSNAP_ATTR_NO_AUTORECOVERY | VSS_VOLSNAP_ATTR_TXF_RECOVERY;
 308     hr = vss_ctx.pVssbc->SetContext(ctx);
 309     if (hr == (HRESULT)VSS_E_UNSUPPORTED_CONTEXT) {
 310         /* Non-server version of Windows doesn't support ATTR_TRANSPORTABLE */
 311         ctx &= ~VSS_VOLSNAP_ATTR_TRANSPORTABLE;
 312         hr = vss_ctx.pVssbc->SetContext(ctx);
 313     }
 314     if (FAILED(hr)) {
 315         err_set(errset, hr, "failed to set backup context");
 316         goto out;
 317     }
 318
 319     hr = vss_ctx.pVssbc->GatherWriterMetadata(pAsync.replace());
 320     if (SUCCEEDED(hr)) {
 321         hr = WaitForAsync(pAsync);
 322     }
 323     if (FAILED(hr)) {
 324         err_set(errset, hr, "failed to gather writer metadata");
 325         goto out;
 326     }
 327
 328     AddComponents(errset);
 329     if (err_is_set(errset)) {
 330         goto out;
 331     }
 332
 333     hr = vss_ctx.pVssbc->StartSnapshotSet(&guidSnapshotSet);
 334     if (FAILED(hr)) {
 335         err_set(errset, hr, "failed to start snapshot set");
 336         goto out;
 337     }
 338
 339     volume = FindFirstVolumeW(short_volume_name, sizeof(short_volume_name));
 340     if (volume == INVALID_HANDLE_VALUE) {
 341         err_set(errset, hr, "failed to find first volume");
 342         goto out;
 343     }
 344     for (;;) {
 345         if (GetDriveTypeW(short_volume_name) == DRIVE_FIXED) {
 346             VSS_ID pid;
 347             hr = vss_ctx.pVssbc->AddToSnapshotSet(short_volume_name,
 348                                                   g_gProviderId, &pid);
 349             if (FAILED(hr)) {
 350                 WCHAR volume_path_name[PATH_MAX];
 351                 if (GetVolumePathNamesForVolumeNameW(
 352                         short_volume_name, volume_path_name,
 353                         sizeof(volume_path_name), NULL) && *volume_path_name) {
 354                     display_name = volume_path_name;
 355                 }
 356                 err_set(errset, hr, "failed to add %S to snapshot set",
 357                                  display_name);
 358                 FindVolumeClose(volume);
 359                 goto out;
 360             }
 361             num_fixed_drives++;
 362         }
 363         if (!FindNextVolumeW(volume, short_volume_name,
 364                              sizeof(short_volume_name))) {
 365             FindVolumeClose(volume);
 366             break;
 367         }
 368     }
 369
 370     if (num_fixed_drives == 0) {
 371         goto out; /* If there is no fixed drive, just exit. */
 372     }
 373
 374     hr = vss_ctx.pVssbc->PrepareForBackup(pAsync.replace());
 375     if (SUCCEEDED(hr)) {
 376         hr = WaitForAsync(pAsync);
 377     }
 378     if (FAILED(hr)) {
 379         err_set(errset, hr, "failed to prepare for backup");
 380         goto out;
 381     }
 382
 383     hr = vss_ctx.pVssbc->GatherWriterStatus(pAsync.replace());
 384     if (SUCCEEDED(hr)) {
 385         hr = WaitForAsync(pAsync);
 386     }
 387     if (FAILED(hr)) {
 388         err_set(errset, hr, "failed to gather writer status");
 389         goto out;
 390     }
 391
 392     /*
 393      * Start VSS quiescing operations.
 394      * CQGAVssProvider::CommitSnapshots will kick vss_ctx.hEventFrozen
 395      * after the applications and filesystems are frozen.
 396      */
 397     hr = vss_ctx.pVssbc->DoSnapshotSet(&vss_ctx.pAsyncSnapshot);
 398     if (FAILED(hr)) {
 399         err_set(errset, hr, "failed to do snapshot set");
 400         goto out;
 401     }
 402
 403     /* Need to call QueryStatus several times to make VSS provider progress */
 404     for (i = 0; i < VSS_TIMEOUT_FREEZE_MSEC/VSS_TIMEOUT_EVENT_MSEC; i++) {
 405         HRESULT hr2 = vss_ctx.pAsyncSnapshot->QueryStatus(&hr, NULL);
 406         if (FAILED(hr2)) {
 407             err_set(errset, hr, "failed to do snapshot set");
 408             goto out;
 409         }
 410         if (hr != VSS_S_ASYNC_PENDING) {
 411             err_set(errset, E_FAIL,
 412                     "DoSnapshotSet exited without Frozen event");
 413             goto out;
 414         }
 415         wait_status = WaitForSingleObject(vss_ctx.hEventFrozen,
 416                                           VSS_TIMEOUT_EVENT_MSEC);
 417         if (wait_status != WAIT_TIMEOUT) {
 418             break;
 419         }
 420     }
 421     if (wait_status != WAIT_OBJECT_0) {
 422         err_set(errset, E_FAIL,
 423                 "couldn't receive Frozen event from VSS provider");
 424         goto out;
 425     }
 426
 427     *num_vols = vss_ctx.cFrozenVols = num_fixed_drives;
 428     return;
 429
 430 out:
 431     if (vss_ctx.pVssbc) {
 432         vss_ctx.pVssbc->AbortBackup();
 433     }
 434     requester_cleanup();
 435     CoUninitialize();
 436 }
 437
 438
 439 void requester_thaw(int *num_vols, ErrorSet *errset)
 440 {
 441     COMPointer<IVssAsync> pAsync;
 442
 443     if (!vss_ctx.hEventThaw) {
 444         /*
 445          * In this case, DoSnapshotSet is aborted or not started,
 446          * and no volumes must be frozen. We return without an error.
 447          */
 448         *num_vols = 0;
 449         return;
 450     }
 451
 452     /* Tell the provider that the snapshot is finished. */
 453     SetEvent(vss_ctx.hEventThaw);
 454
 455     assert(vss_ctx.pVssbc);
 456     assert(vss_ctx.pAsyncSnapshot);
 457
 458     HRESULT hr = WaitForAsync(vss_ctx.pAsyncSnapshot);
 459     switch (hr) {
 460     case VSS_S_ASYNC_FINISHED:
 461         hr = vss_ctx.pVssbc->BackupComplete(pAsync.replace());
 462         if (SUCCEEDED(hr)) {
 463             hr = WaitForAsync(pAsync);
 464         }
 465         if (FAILED(hr)) {
 466             err_set(errset, hr, "failed to complete backup");
 467         }
 468         break;
 469
 470     case (HRESULT)VSS_E_OBJECT_NOT_FOUND:
 471         /*
 472          * On Windows earlier than 2008 SP2 which does not support
 473          * VSS_VOLSNAP_ATTR_NO_AUTORECOVERY context, the final commit is not
 474          * skipped and VSS is aborted by VSS_E_OBJECT_NOT_FOUND. However, as
 475          * the system had been frozen until fsfreeze-thaw command was issued,
 476          * we ignore this error.
 477          */
 478         vss_ctx.pVssbc->AbortBackup();
 479         break;
 480
 481     case VSS_E_UNEXPECTED_PROVIDER_ERROR:
 482         if (WaitForSingleObject(vss_ctx.hEventTimeout, 0) != WAIT_OBJECT_0) {
 483             err_set(errset, hr, "unexpected error in VSS provider");
 484             break;
 485         }
 486         /* fall through if hEventTimeout is signaled */
 487
 488     case (HRESULT)VSS_E_HOLD_WRITES_TIMEOUT:
 489         err_set(errset, hr, "couldn't hold writes: "
 490                 "fsfreeze is limited up to 10 seconds");
 491         break;
 492
 493     default:
 494         err_set(errset, hr, "failed to do snapshot set");
 495     }
 496
 497     if (err_is_set(errset)) {
 498         vss_ctx.pVssbc->AbortBackup();
 499     }
 500     *num_vols = vss_ctx.cFrozenVols;
 501     requester_cleanup();
 502
 503     CoUninitialize();
 504 }