qemu

1
/*
2
 * Block layer snapshot related functions
3
 *
4
 * Copyright (c) 2003-2008 Fabrice Bellard
5
 *
6
 * Permission is hereby granted, free of charge, to any person obtaining a copy
7
 * of this software and associated documentation files (the "Software"), to deal
8
 * in the Software without restriction, including without limitation the rights
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 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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 * copies of the Software, and to permit persons to whom the Software is
11
 * furnished to do so, subject to the following conditions:
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 *
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 * The above copyright notice and this permission notice shall be included in
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 * all copies or substantial portions of the Software.
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 *
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 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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 * THE SOFTWARE.
23
 */
24

25
#include "qemu/osdep.h"
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#include "block/snapshot.h"
27
#include "block/block_int.h"
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#include "block/qdict.h"
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#include "qapi/error.h"
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#include "qapi/qmp/qdict.h"
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#include "qapi/qmp/qstring.h"
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#include "qemu/option.h"
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#include "sysemu/block-backend.h"
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QemuOptsList internal_snapshot_opts = {
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    .name = "snapshot",
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    .head = QTAILQ_HEAD_INITIALIZER(internal_snapshot_opts.head),
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    .desc = {
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        {
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            .name = SNAPSHOT_OPT_ID,
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            .type = QEMU_OPT_STRING,
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            .help = "snapshot id"
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        },{
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            .name = SNAPSHOT_OPT_NAME,
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            .type = QEMU_OPT_STRING,
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            .help = "snapshot name"
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        },{
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            /* end of list */
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        }
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    },
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};
52

53
int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
54
                       const char *name)
55
{
56
    QEMUSnapshotInfo *sn_tab, *sn;
57
    int nb_sns, i, ret;
58

59
    GLOBAL_STATE_CODE();
60

61
    ret = -ENOENT;
62
    nb_sns = bdrv_snapshot_list(bs, &sn_tab);
63
    if (nb_sns < 0) {
64
        return ret;
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    }
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    for (i = 0; i < nb_sns; i++) {
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        sn = &sn_tab[i];
68
        if (!strcmp(sn->name, name)) {
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            *sn_info = *sn;
70
            ret = 0;
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            break;
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        }
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    }
74
    g_free(sn_tab);
75
    return ret;
76
}
77

78
/**
79
 * Look up an internal snapshot by @id and @name.
80
 * @bs: block device to search
81
 * @id: unique snapshot ID, or NULL
82
 * @name: snapshot name, or NULL
83
 * @sn_info: location to store information on the snapshot found
84
 * @errp: location to store error, will be set only for exception
85
 *
86
 * This function will traverse snapshot list in @bs to search the matching
87
 * one, @id and @name are the matching condition:
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 * If both @id and @name are specified, find the first one with id @id and
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 * name @name.
90
 * If only @id is specified, find the first one with id @id.
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 * If only @name is specified, find the first one with name @name.
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 * if none is specified, abort().
93
 *
94
 * Returns: true when a snapshot is found and @sn_info will be filled, false
95
 * when error or not found. If all operation succeed but no matching one is
96
 * found, @errp will NOT be set.
97
 */
98
bool bdrv_snapshot_find_by_id_and_name(BlockDriverState *bs,
99
                                       const char *id,
100
                                       const char *name,
101
                                       QEMUSnapshotInfo *sn_info,
102
                                       Error **errp)
103
{
104
    QEMUSnapshotInfo *sn_tab, *sn;
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    int nb_sns, i;
106
    bool ret = false;
107

108
    assert(id || name);
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    GLOBAL_STATE_CODE();
110

111
    nb_sns = bdrv_snapshot_list(bs, &sn_tab);
112
    if (nb_sns < 0) {
113
        error_setg_errno(errp, -nb_sns, "Failed to get a snapshot list");
114
        return false;
115
    } else if (nb_sns == 0) {
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        return false;
117
    }
118

119
    if (id && name) {
120
        for (i = 0; i < nb_sns; i++) {
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            sn = &sn_tab[i];
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            if (!strcmp(sn->id_str, id) && !strcmp(sn->name, name)) {
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                *sn_info = *sn;
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                ret = true;
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                break;
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            }
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        }
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    } else if (id) {
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        for (i = 0; i < nb_sns; i++) {
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            sn = &sn_tab[i];
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            if (!strcmp(sn->id_str, id)) {
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                *sn_info = *sn;
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                ret = true;
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                break;
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            }
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        }
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    } else if (name) {
138
        for (i = 0; i < nb_sns; i++) {
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            sn = &sn_tab[i];
140
            if (!strcmp(sn->name, name)) {
141
                *sn_info = *sn;
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                ret = true;
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                break;
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            }
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        }
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    }
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148
    g_free(sn_tab);
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    return ret;
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}
151

152
/**
153
 * Return a pointer to child of given BDS to which we can fall
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 * back if the given BDS does not support snapshots.
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 * Return NULL if there is no BDS to (safely) fall back to.
156
 */
157
static BdrvChild * GRAPH_RDLOCK
158
bdrv_snapshot_fallback_child(BlockDriverState *bs)
159
{
160
    BdrvChild *fallback = bdrv_primary_child(bs);
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    BdrvChild *child;
162

163
    GLOBAL_STATE_CODE();
164
    assert_bdrv_graph_readable();
165

166
    /* We allow fallback only to primary child */
167
    if (!fallback) {
168
        return NULL;
169
    }
170

171
    /*
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     * Check that there are no other children that would need to be
173
     * snapshotted.  If there are, it is not safe to fall back to
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     * fallback.
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     */
176
    QLIST_FOREACH(child, &bs->children, next) {
177
        if (child->role & (BDRV_CHILD_DATA | BDRV_CHILD_METADATA |
178
                           BDRV_CHILD_FILTERED) &&
179
            child != fallback)
180
        {
181
            return NULL;
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        }
183
    }
184

185
    return fallback;
186
}
187

188
static BlockDriverState * GRAPH_RDLOCK
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bdrv_snapshot_fallback(BlockDriverState *bs)
190
{
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    GLOBAL_STATE_CODE();
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    return child_bs(bdrv_snapshot_fallback_child(bs));
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}
194

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int bdrv_can_snapshot(BlockDriverState *bs)
196
{
197
    BlockDriver *drv = bs->drv;
198

199
    GLOBAL_STATE_CODE();
200

201
    if (!drv || !bdrv_is_inserted(bs) || !bdrv_is_writable(bs)) {
202
        return 0;
203
    }
204

205
    if (!drv->bdrv_snapshot_create) {
206
        BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
207
        if (fallback_bs) {
208
            return bdrv_can_snapshot(fallback_bs);
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        }
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        return 0;
211
    }
212

213
    return 1;
214
}
215

216
int bdrv_snapshot_create(BlockDriverState *bs,
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                         QEMUSnapshotInfo *sn_info)
218
{
219
    BlockDriver *drv = bs->drv;
220
    BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
221

222
    GLOBAL_STATE_CODE();
223

224
    if (!drv) {
225
        return -ENOMEDIUM;
226
    }
227
    if (drv->bdrv_snapshot_create) {
228
        return drv->bdrv_snapshot_create(bs, sn_info);
229
    }
230
    if (fallback_bs) {
231
        return bdrv_snapshot_create(fallback_bs, sn_info);
232
    }
233
    return -ENOTSUP;
234
}
235

236
int bdrv_snapshot_goto(BlockDriverState *bs,
237
                       const char *snapshot_id,
238
                       Error **errp)
239
{
240
    BlockDriver *drv = bs->drv;
241
    BdrvChild *fallback;
242
    int ret, open_ret;
243

244
    GLOBAL_STATE_CODE();
245

246
    if (!drv) {
247
        error_setg(errp, "Block driver is closed");
248
        return -ENOMEDIUM;
249
    }
250

251
    if (!QLIST_EMPTY(&bs->dirty_bitmaps)) {
252
        error_setg(errp, "Device has active dirty bitmaps");
253
        return -EBUSY;
254
    }
255

256
    if (drv->bdrv_snapshot_goto) {
257
        ret = drv->bdrv_snapshot_goto(bs, snapshot_id);
258
        if (ret < 0) {
259
            error_setg_errno(errp, -ret, "Failed to load snapshot");
260
        }
261
        return ret;
262
    }
263

264
    bdrv_graph_rdlock_main_loop();
265
    fallback = bdrv_snapshot_fallback_child(bs);
266
    bdrv_graph_rdunlock_main_loop();
267

268
    if (fallback) {
269
        QDict *options;
270
        QDict *file_options;
271
        Error *local_err = NULL;
272
        BlockDriverState *fallback_bs = fallback->bs;
273
        char *subqdict_prefix = g_strdup_printf("%s.", fallback->name);
274

275
        options = qdict_clone_shallow(bs->options);
276

277
        /* Prevent it from getting deleted when detached from bs */
278
        bdrv_ref(fallback_bs);
279

280
        qdict_extract_subqdict(options, &file_options, subqdict_prefix);
281
        qobject_unref(file_options);
282
        g_free(subqdict_prefix);
283

284
        /* Force .bdrv_open() below to re-attach fallback_bs on fallback */
285
        qdict_put_str(options, fallback->name,
286
                      bdrv_get_node_name(fallback_bs));
287

288
        /* Now close bs, apply the snapshot on fallback_bs, and re-open bs */
289
        if (drv->bdrv_close) {
290
            drv->bdrv_close(bs);
291
        }
292

293
        /* .bdrv_open() will re-attach it */
294
        bdrv_graph_wrlock();
295
        bdrv_unref_child(bs, fallback);
296
        bdrv_graph_wrunlock();
297

298
        ret = bdrv_snapshot_goto(fallback_bs, snapshot_id, errp);
299
        open_ret = drv->bdrv_open(bs, options, bs->open_flags, &local_err);
300
        qobject_unref(options);
301
        if (open_ret < 0) {
302
            bdrv_unref(fallback_bs);
303
            bs->drv = NULL;
304
            /* A bdrv_snapshot_goto() error takes precedence */
305
            error_propagate(errp, local_err);
306
            return ret < 0 ? ret : open_ret;
307
        }
308

309
        /*
310
         * fallback was a primary child. It was closed above and set to NULL,
311
         * but the .bdrv_open() call has opened it again, because we set the
312
         * respective option (with the qdict_put_str() call above).
313
         * Assert that .bdrv_open() has attached the right BDS as primary child.
314
         */
315
        bdrv_graph_rdlock_main_loop();
316
        assert(bdrv_primary_bs(bs) == fallback_bs);
317
        bdrv_graph_rdunlock_main_loop();
318

319
        bdrv_unref(fallback_bs);
320
        return ret;
321
    }
322

323
    error_setg(errp, "Block driver does not support snapshots");
324
    return -ENOTSUP;
325
}
326

327
/**
328
 * Delete an internal snapshot by @snapshot_id and @name.
329
 * @bs: block device used in the operation
330
 * @snapshot_id: unique snapshot ID, or NULL
331
 * @name: snapshot name, or NULL
332
 * @errp: location to store error
333
 *
334
 * If both @snapshot_id and @name are specified, delete the first one with
335
 * id @snapshot_id and name @name.
336
 * If only @snapshot_id is specified, delete the first one with id
337
 * @snapshot_id.
338
 * If only @name is specified, delete the first one with name @name.
339
 * if none is specified, return -EINVAL.
340
 *
341
 * Returns: 0 on success, -errno on failure. If @bs is not inserted, return
342
 * -ENOMEDIUM. If @snapshot_id and @name are both NULL, return -EINVAL. If @bs
343
 * does not support internal snapshot deletion, return -ENOTSUP. If @bs does
344
 * not support parameter @snapshot_id or @name, or one of them is not correctly
345
 * specified, return -EINVAL. If @bs can't find one matching @id and @name,
346
 * return -ENOENT. If @errp != NULL, it will always be filled with error
347
 * message on failure.
348
 */
349
int bdrv_snapshot_delete(BlockDriverState *bs,
350
                         const char *snapshot_id,
351
                         const char *name,
352
                         Error **errp)
353
{
354
    BlockDriver *drv = bs->drv;
355
    BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
356
    int ret;
357

358
    GLOBAL_STATE_CODE();
359

360
    if (!drv) {
361
        error_setg(errp, "Device '%s' has no medium",
362
                   bdrv_get_device_name(bs));
363
        return -ENOMEDIUM;
364
    }
365
    if (!snapshot_id && !name) {
366
        error_setg(errp, "snapshot_id and name are both NULL");
367
        return -EINVAL;
368
    }
369

370
    /* drain all pending i/o before deleting snapshot */
371
    bdrv_drained_begin(bs);
372

373
    if (drv->bdrv_snapshot_delete) {
374
        ret = drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp);
375
    } else if (fallback_bs) {
376
        ret = bdrv_snapshot_delete(fallback_bs, snapshot_id, name, errp);
377
    } else {
378
        error_setg(errp, "Block format '%s' used by device '%s' "
379
                   "does not support internal snapshot deletion",
380
                   drv->format_name, bdrv_get_device_name(bs));
381
        ret = -ENOTSUP;
382
    }
383

384
    bdrv_drained_end(bs);
385
    return ret;
386
}
387

388
int bdrv_snapshot_list(BlockDriverState *bs,
389
                       QEMUSnapshotInfo **psn_info)
390
{
391
    GLOBAL_STATE_CODE();
392
    GRAPH_RDLOCK_GUARD_MAINLOOP();
393

394
    BlockDriver *drv = bs->drv;
395
    BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
396

397
    if (!drv) {
398
        return -ENOMEDIUM;
399
    }
400
    if (drv->bdrv_snapshot_list) {
401
        return drv->bdrv_snapshot_list(bs, psn_info);
402
    }
403
    if (fallback_bs) {
404
        return bdrv_snapshot_list(fallback_bs, psn_info);
405
    }
406
    return -ENOTSUP;
407
}
408

409
/**
410
 * Temporarily load an internal snapshot by @snapshot_id and @name.
411
 * @bs: block device used in the operation
412
 * @snapshot_id: unique snapshot ID, or NULL
413
 * @name: snapshot name, or NULL
414
 * @errp: location to store error
415
 *
416
 * If both @snapshot_id and @name are specified, load the first one with
417
 * id @snapshot_id and name @name.
418
 * If only @snapshot_id is specified, load the first one with id
419
 * @snapshot_id.
420
 * If only @name is specified, load the first one with name @name.
421
 * if none is specified, return -EINVAL.
422
 *
423
 * Returns: 0 on success, -errno on fail. If @bs is not inserted, return
424
 * -ENOMEDIUM. If @bs is not readonly, return -EINVAL. If @bs did not support
425
 * internal snapshot, return -ENOTSUP. If qemu can't find a matching @id and
426
 * @name, return -ENOENT. If @errp != NULL, it will always be filled on
427
 * failure.
428
 */
429
int bdrv_snapshot_load_tmp(BlockDriverState *bs,
430
                           const char *snapshot_id,
431
                           const char *name,
432
                           Error **errp)
433
{
434
    BlockDriver *drv = bs->drv;
435

436
    GLOBAL_STATE_CODE();
437
    GRAPH_RDLOCK_GUARD_MAINLOOP();
438

439
    if (!drv) {
440
        error_setg(errp, "Device '%s' has no medium",
441
                   bdrv_get_device_name(bs));
442
        return -ENOMEDIUM;
443
    }
444
    if (!snapshot_id && !name) {
445
        error_setg(errp, "snapshot_id and name are both NULL");
446
        return -EINVAL;
447
    }
448
    if (!bdrv_is_read_only(bs)) {
449
        error_setg(errp, "Device is not readonly");
450
        return -EINVAL;
451
    }
452
    if (drv->bdrv_snapshot_load_tmp) {
453
        return drv->bdrv_snapshot_load_tmp(bs, snapshot_id, name, errp);
454
    }
455
    error_setg(errp, "Block format '%s' used by device '%s' "
456
               "does not support temporarily loading internal snapshots",
457
               drv->format_name, bdrv_get_device_name(bs));
458
    return -ENOTSUP;
459
}
460

461
int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs,
462
                                         const char *id_or_name,
463
                                         Error **errp)
464
{
465
    int ret;
466
    Error *local_err = NULL;
467

468
    GLOBAL_STATE_CODE();
469

470
    ret = bdrv_snapshot_load_tmp(bs, id_or_name, NULL, &local_err);
471
    if (ret == -ENOENT || ret == -EINVAL) {
472
        error_free(local_err);
473
        local_err = NULL;
474
        ret = bdrv_snapshot_load_tmp(bs, NULL, id_or_name, &local_err);
475
    }
476

477
    error_propagate(errp, local_err);
478

479
    return ret;
480
}
481

482

483
static int GRAPH_RDLOCK
484
bdrv_all_get_snapshot_devices(bool has_devices, strList *devices,
485
                              GList **all_bdrvs, Error **errp)
486
{
487
    g_autoptr(GList) bdrvs = NULL;
488

489
    if (has_devices) {
490
        if (!devices) {
491
            error_setg(errp, "At least one device is required for snapshot");
492
            return -1;
493
        }
494

495
        while (devices) {
496
            BlockDriverState *bs = bdrv_find_node(devices->value);
497
            if (!bs) {
498
                error_setg(errp, "No block device node '%s'", devices->value);
499
                return -1;
500
            }
501
            bdrvs = g_list_append(bdrvs, bs);
502
            devices = devices->next;
503
        }
504
    } else {
505
        BlockDriverState *bs;
506
        BdrvNextIterator it;
507
        for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
508
            bdrvs = g_list_append(bdrvs, bs);
509
        }
510
    }
511

512
    *all_bdrvs = g_steal_pointer(&bdrvs);
513
    return 0;
514
}
515

516

517
static bool GRAPH_RDLOCK bdrv_all_snapshots_includes_bs(BlockDriverState *bs)
518
{
519
    GLOBAL_STATE_CODE();
520
    assert_bdrv_graph_readable();
521

522
    if (!bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
523
        return false;
524
    }
525

526
    /* Include all nodes that are either in use by a BlockBackend, or that
527
     * aren't attached to any node, but owned by the monitor. */
528
    return bdrv_has_blk(bs) || QLIST_EMPTY(&bs->parents);
529
}
530

531
/* Group operations. All block drivers are involved. */
532

533
bool bdrv_all_can_snapshot(bool has_devices, strList *devices,
534
                           Error **errp)
535
{
536
    g_autoptr(GList) bdrvs = NULL;
537
    GList *iterbdrvs;
538

539
    GLOBAL_STATE_CODE();
540
    GRAPH_RDLOCK_GUARD_MAINLOOP();
541

542
    if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
543
        return false;
544
    }
545

546
    iterbdrvs = bdrvs;
547
    while (iterbdrvs) {
548
        BlockDriverState *bs = iterbdrvs->data;
549
        bool ok = true;
550

551
        if (devices || bdrv_all_snapshots_includes_bs(bs)) {
552
            ok = bdrv_can_snapshot(bs);
553
        }
554
        if (!ok) {
555
            error_setg(errp, "Device '%s' is writable but does not support "
556
                       "snapshots", bdrv_get_device_or_node_name(bs));
557
            return false;
558
        }
559

560
        iterbdrvs = iterbdrvs->next;
561
    }
562

563
    return true;
564
}
565

566
int bdrv_all_delete_snapshot(const char *name,
567
                             bool has_devices, strList *devices,
568
                             Error **errp)
569
{
570
    ERRP_GUARD();
571
    g_autoptr(GList) bdrvs = NULL;
572
    GList *iterbdrvs;
573

574
    GLOBAL_STATE_CODE();
575
    GRAPH_RDLOCK_GUARD_MAINLOOP();
576

577
    if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
578
        return -1;
579
    }
580

581
    iterbdrvs = bdrvs;
582
    while (iterbdrvs) {
583
        BlockDriverState *bs = iterbdrvs->data;
584
        QEMUSnapshotInfo sn1, *snapshot = &sn1;
585
        int ret = 0;
586

587
        if ((devices || bdrv_all_snapshots_includes_bs(bs)) &&
588
            bdrv_snapshot_find(bs, snapshot, name) >= 0)
589
        {
590
            ret = bdrv_snapshot_delete(bs, snapshot->id_str,
591
                                       snapshot->name, errp);
592
        }
593
        if (ret < 0) {
594
            error_prepend(errp, "Could not delete snapshot '%s' on '%s': ",
595
                          name, bdrv_get_device_or_node_name(bs));
596
            return -1;
597
        }
598

599
        iterbdrvs = iterbdrvs->next;
600
    }
601

602
    return 0;
603
}
604

605

606
int bdrv_all_goto_snapshot(const char *name,
607
                           bool has_devices, strList *devices,
608
                           Error **errp)
609
{
610
    ERRP_GUARD();
611
    g_autoptr(GList) bdrvs = NULL;
612
    GList *iterbdrvs;
613
    int ret;
614

615
    GLOBAL_STATE_CODE();
616

617
    bdrv_graph_rdlock_main_loop();
618
    ret = bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp);
619
    bdrv_graph_rdunlock_main_loop();
620

621
    if (ret < 0) {
622
        return -1;
623
    }
624

625
    iterbdrvs = bdrvs;
626
    while (iterbdrvs) {
627
        BlockDriverState *bs = iterbdrvs->data;
628
        bool all_snapshots_includes_bs;
629

630
        bdrv_graph_rdlock_main_loop();
631
        all_snapshots_includes_bs = bdrv_all_snapshots_includes_bs(bs);
632
        bdrv_graph_rdunlock_main_loop();
633

634
        ret = (devices || all_snapshots_includes_bs) ?
635
              bdrv_snapshot_goto(bs, name, errp) : 0;
636
        if (ret < 0) {
637
            bdrv_graph_rdlock_main_loop();
638
            error_prepend(errp, "Could not load snapshot '%s' on '%s': ",
639
                          name, bdrv_get_device_or_node_name(bs));
640
            bdrv_graph_rdunlock_main_loop();
641
            return -1;
642
        }
643

644
        iterbdrvs = iterbdrvs->next;
645
    }
646

647
    return 0;
648
}
649

650
int bdrv_all_has_snapshot(const char *name,
651
                          bool has_devices, strList *devices,
652
                          Error **errp)
653
{
654
    g_autoptr(GList) bdrvs = NULL;
655
    GList *iterbdrvs;
656

657
    GLOBAL_STATE_CODE();
658
    GRAPH_RDLOCK_GUARD_MAINLOOP();
659

660
    if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
661
        return -1;
662
    }
663

664
    iterbdrvs = bdrvs;
665
    while (iterbdrvs) {
666
        BlockDriverState *bs = iterbdrvs->data;
667
        QEMUSnapshotInfo sn;
668
        int ret = 0;
669

670
        if (devices || bdrv_all_snapshots_includes_bs(bs)) {
671
            ret = bdrv_snapshot_find(bs, &sn, name);
672
        }
673
        if (ret < 0) {
674
            if (ret == -ENOENT) {
675
                return 0;
676
            } else {
677
                error_setg_errno(errp, errno,
678
                                 "Could not check snapshot '%s' on '%s'",
679
                                 name, bdrv_get_device_or_node_name(bs));
680
                return -1;
681
            }
682
        }
683

684
        iterbdrvs = iterbdrvs->next;
685
    }
686

687
    return 1;
688
}
689

690
int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
691
                             BlockDriverState *vm_state_bs,
692
                             uint64_t vm_state_size,
693
                             bool has_devices, strList *devices,
694
                             Error **errp)
695
{
696
    g_autoptr(GList) bdrvs = NULL;
697
    GList *iterbdrvs;
698

699
    GLOBAL_STATE_CODE();
700
    GRAPH_RDLOCK_GUARD_MAINLOOP();
701

702
    if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
703
        return -1;
704
    }
705

706
    iterbdrvs = bdrvs;
707
    while (iterbdrvs) {
708
        BlockDriverState *bs = iterbdrvs->data;
709
        int ret = 0;
710

711
        if (bs == vm_state_bs) {
712
            sn->vm_state_size = vm_state_size;
713
            ret = bdrv_snapshot_create(bs, sn);
714
        } else if (devices || bdrv_all_snapshots_includes_bs(bs)) {
715
            sn->vm_state_size = 0;
716
            ret = bdrv_snapshot_create(bs, sn);
717
        }
718
        if (ret < 0) {
719
            error_setg(errp, "Could not create snapshot '%s' on '%s'",
720
                       sn->name, bdrv_get_device_or_node_name(bs));
721
            return -1;
722
        }
723

724
        iterbdrvs = iterbdrvs->next;
725
    }
726

727
    return 0;
728
}
729

730

731
BlockDriverState *bdrv_all_find_vmstate_bs(const char *vmstate_bs,
732
                                           bool has_devices, strList *devices,
733
                                           Error **errp)
734
{
735
    g_autoptr(GList) bdrvs = NULL;
736
    GList *iterbdrvs;
737

738
    GLOBAL_STATE_CODE();
739
    GRAPH_RDLOCK_GUARD_MAINLOOP();
740

741
    if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
742
        return NULL;
743
    }
744

745
    iterbdrvs = bdrvs;
746
    while (iterbdrvs) {
747
        BlockDriverState *bs = iterbdrvs->data;
748
        bool found = false;
749

750
        found = (devices || bdrv_all_snapshots_includes_bs(bs)) &&
751
            bdrv_can_snapshot(bs);
752

753
        if (vmstate_bs) {
754
            if (g_str_equal(vmstate_bs,
755
                            bdrv_get_node_name(bs))) {
756
                if (found) {
757
                    return bs;
758
                } else {
759
                    error_setg(errp,
760
                               "vmstate block device '%s' does not support snapshots",
761
                               vmstate_bs);
762
                    return NULL;
763
                }
764
            }
765
        } else if (found) {
766
            return bs;
767
        }
768

769
        iterbdrvs = iterbdrvs->next;
770
    }
771

772
    if (vmstate_bs) {
773
        error_setg(errp,
774
                   "vmstate block device '%s' does not exist", vmstate_bs);
775
    } else {
776
        error_setg(errp,
777
                   "no block device can store vmstate for snapshot");
778
    }
779
    return NULL;
780
}
781