block/qcow2-snapshot.c

   1 /*
   2  * Block driver for the QCOW version 2 format
   3  *
   4  * Copyright (c) 2004-2006 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
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24
  25 #include "qemu-common.h"
  26 #include "block_int.h"
  27 #include "block/qcow2.h"
  28
  29 typedef struct __attribute__((packed)) QCowSnapshotHeader {
  30     /* header is 8 byte aligned */
  31     uint64_t l1_table_offset;
  32
  33     uint32_t l1_size;
  34     uint16_t id_str_size;
  35     uint16_t name_size;
  36
  37     uint32_t date_sec;
  38     uint32_t date_nsec;
  39
  40     uint64_t vm_clock_nsec;
  41
  42     uint32_t vm_state_size;
  43     uint32_t extra_data_size; /* for extension */
  44     /* extra data follows */
  45     /* id_str follows */
  46     /* name follows  */
  47 } QCowSnapshotHeader;
  48
  49 void qcow2_free_snapshots(BlockDriverState *bs)
  50 {
  51     BDRVQcowState *s = bs->opaque;
  52     int i;
  53
  54     for(i = 0; i < s->nb_snapshots; i++) {
  55         qemu_free(s->snapshots[i].name);
  56         qemu_free(s->snapshots[i].id_str);
  57     }
  58     qemu_free(s->snapshots);
  59     s->snapshots = NULL;
  60     s->nb_snapshots = 0;
  61 }
  62
  63 int qcow2_read_snapshots(BlockDriverState *bs)
  64 {
  65     BDRVQcowState *s = bs->opaque;
  66     QCowSnapshotHeader h;
  67     QCowSnapshot *sn;
  68     int i, id_str_size, name_size;
  69     int64_t offset;
  70     uint32_t extra_data_size;
  71
  72     if (!s->nb_snapshots) {
  73         s->snapshots = NULL;
  74         s->snapshots_size = 0;
  75         return 0;
  76     }
  77
  78     offset = s->snapshots_offset;
  79     s->snapshots = qemu_mallocz(s->nb_snapshots * sizeof(QCowSnapshot));
  80     for(i = 0; i < s->nb_snapshots; i++) {
  81         offset = align_offset(offset, 8);
  82         if (bdrv_pread(bs->file, offset, &h, sizeof(h)) != sizeof(h))
  83             goto fail;
  84         offset += sizeof(h);
  85         sn = s->snapshots + i;
  86         sn->l1_table_offset = be64_to_cpu(h.l1_table_offset);
  87         sn->l1_size = be32_to_cpu(h.l1_size);
  88         sn->vm_state_size = be32_to_cpu(h.vm_state_size);
  89         sn->date_sec = be32_to_cpu(h.date_sec);
  90         sn->date_nsec = be32_to_cpu(h.date_nsec);
  91         sn->vm_clock_nsec = be64_to_cpu(h.vm_clock_nsec);
  92         extra_data_size = be32_to_cpu(h.extra_data_size);
  93
  94         id_str_size = be16_to_cpu(h.id_str_size);
  95         name_size = be16_to_cpu(h.name_size);
  96
  97         offset += extra_data_size;
  98
  99         sn->id_str = qemu_malloc(id_str_size + 1);
 100         if (bdrv_pread(bs->file, offset, sn->id_str, id_str_size) != id_str_size)
 101             goto fail;
 102         offset += id_str_size;
 103         sn->id_str[id_str_size] = '\0';
 104
 105         sn->name = qemu_malloc(name_size + 1);
 106         if (bdrv_pread(bs->file, offset, sn->name, name_size) != name_size)
 107             goto fail;
 108         offset += name_size;
 109         sn->name[name_size] = '\0';
 110     }
 111     s->snapshots_size = offset - s->snapshots_offset;
 112     return 0;
 113  fail:
 114     qcow2_free_snapshots(bs);
 115     return -1;
 116 }
 117
 118 /* add at the end of the file a new list of snapshots */
 119 static int qcow2_write_snapshots(BlockDriverState *bs)
 120 {
 121     BDRVQcowState *s = bs->opaque;
 122     QCowSnapshot *sn;
 123     QCowSnapshotHeader h;
 124     int i, name_size, id_str_size, snapshots_size;
 125     uint64_t data64;
 126     uint32_t data32;
 127     int64_t offset, snapshots_offset;
 128
 129     /* compute the size of the snapshots */
 130     offset = 0;
 131     for(i = 0; i < s->nb_snapshots; i++) {
 132         sn = s->snapshots + i;
 133         offset = align_offset(offset, 8);
 134         offset += sizeof(h);
 135         offset += strlen(sn->id_str);
 136         offset += strlen(sn->name);
 137     }
 138     snapshots_size = offset;
 139
 140     snapshots_offset = qcow2_alloc_clusters(bs, snapshots_size);
 141     bdrv_flush(bs->file);
 142     offset = snapshots_offset;
 143     if (offset < 0) {
 144         return offset;
 145     }
 146
 147     for(i = 0; i < s->nb_snapshots; i++) {
 148         sn = s->snapshots + i;
 149         memset(&h, 0, sizeof(h));
 150         h.l1_table_offset = cpu_to_be64(sn->l1_table_offset);
 151         h.l1_size = cpu_to_be32(sn->l1_size);
 152         h.vm_state_size = cpu_to_be32(sn->vm_state_size);
 153         h.date_sec = cpu_to_be32(sn->date_sec);
 154         h.date_nsec = cpu_to_be32(sn->date_nsec);
 155         h.vm_clock_nsec = cpu_to_be64(sn->vm_clock_nsec);
 156
 157         id_str_size = strlen(sn->id_str);
 158         name_size = strlen(sn->name);
 159         h.id_str_size = cpu_to_be16(id_str_size);
 160         h.name_size = cpu_to_be16(name_size);
 161         offset = align_offset(offset, 8);
 162         if (bdrv_pwrite_sync(bs->file, offset, &h, sizeof(h)) < 0)
 163             goto fail;
 164         offset += sizeof(h);
 165         if (bdrv_pwrite_sync(bs->file, offset, sn->id_str, id_str_size) < 0)
 166             goto fail;
 167         offset += id_str_size;
 168         if (bdrv_pwrite_sync(bs->file, offset, sn->name, name_size) < 0)
 169             goto fail;
 170         offset += name_size;
 171     }
 172
 173     /* update the various header fields */
 174     data64 = cpu_to_be64(snapshots_offset);
 175     if (bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, snapshots_offset),
 176                     &data64, sizeof(data64)) < 0)
 177         goto fail;
 178     data32 = cpu_to_be32(s->nb_snapshots);
 179     if (bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, nb_snapshots),
 180                     &data32, sizeof(data32)) < 0)
 181         goto fail;
 182
 183     /* free the old snapshot table */
 184     qcow2_free_clusters(bs, s->snapshots_offset, s->snapshots_size);
 185     s->snapshots_offset = snapshots_offset;
 186     s->snapshots_size = snapshots_size;
 187     return 0;
 188  fail:
 189     return -1;
 190 }
 191
 192 static void find_new_snapshot_id(BlockDriverState *bs,
 193                                  char *id_str, int id_str_size)
 194 {
 195     BDRVQcowState *s = bs->opaque;
 196     QCowSnapshot *sn;
 197     int i, id, id_max = 0;
 198
 199     for(i = 0; i < s->nb_snapshots; i++) {
 200         sn = s->snapshots + i;
 201         id = strtoul(sn->id_str, NULL, 10);
 202         if (id > id_max)
 203             id_max = id;
 204     }
 205     snprintf(id_str, id_str_size, "%d", id_max + 1);
 206 }
 207
 208 static int find_snapshot_by_id(BlockDriverState *bs, const char *id_str)
 209 {
 210     BDRVQcowState *s = bs->opaque;
 211     int i;
 212
 213     for(i = 0; i < s->nb_snapshots; i++) {
 214         if (!strcmp(s->snapshots[i].id_str, id_str))
 215             return i;
 216     }
 217     return -1;
 218 }
 219
 220 static int find_snapshot_by_id_or_name(BlockDriverState *bs, const char *name)
 221 {
 222     BDRVQcowState *s = bs->opaque;
 223     int i, ret;
 224
 225     ret = find_snapshot_by_id(bs, name);
 226     if (ret >= 0)
 227         return ret;
 228     for(i = 0; i < s->nb_snapshots; i++) {
 229         if (!strcmp(s->snapshots[i].name, name))
 230             return i;
 231     }
 232     return -1;
 233 }
 234
 235 /* if no id is provided, a new one is constructed */
 236 int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
 237 {
 238     BDRVQcowState *s = bs->opaque;
 239     QCowSnapshot *snapshots1, sn1, *sn = &sn1;
 240     int i, ret;
 241     uint64_t *l1_table = NULL;
 242     int64_t l1_table_offset;
 243
 244     memset(sn, 0, sizeof(*sn));
 245
 246     if (sn_info->id_str[0] == '\0') {
 247         /* compute a new id */
 248         find_new_snapshot_id(bs, sn_info->id_str, sizeof(sn_info->id_str));
 249     }
 250
 251     /* check that the ID is unique */
 252     if (find_snapshot_by_id(bs, sn_info->id_str) >= 0)
 253         return -ENOENT;
 254
 255     sn->id_str = qemu_strdup(sn_info->id_str);
 256     if (!sn->id_str)
 257         goto fail;
 258     sn->name = qemu_strdup(sn_info->name);
 259     if (!sn->name)
 260         goto fail;
 261     sn->vm_state_size = sn_info->vm_state_size;
 262     sn->date_sec = sn_info->date_sec;
 263     sn->date_nsec = sn_info->date_nsec;
 264     sn->vm_clock_nsec = sn_info->vm_clock_nsec;
 265
 266     ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1);
 267     if (ret < 0)
 268         goto fail;
 269
 270     /* create the L1 table of the snapshot */
 271     l1_table_offset = qcow2_alloc_clusters(bs, s->l1_size * sizeof(uint64_t));
 272     if (l1_table_offset < 0) {
 273         goto fail;
 274     }
 275     bdrv_flush(bs->file);
 276
 277     sn->l1_table_offset = l1_table_offset;
 278     sn->l1_size = s->l1_size;
 279
 280     if (s->l1_size != 0) {
 281         l1_table = qemu_malloc(s->l1_size * sizeof(uint64_t));
 282     } else {
 283         l1_table = NULL;
 284     }
 285
 286     for(i = 0; i < s->l1_size; i++) {
 287         l1_table[i] = cpu_to_be64(s->l1_table[i]);
 288     }
 289     if (bdrv_pwrite_sync(bs->file, sn->l1_table_offset,
 290                     l1_table, s->l1_size * sizeof(uint64_t)) < 0)
 291         goto fail;
 292     qemu_free(l1_table);
 293     l1_table = NULL;
 294
 295     snapshots1 = qemu_malloc((s->nb_snapshots + 1) * sizeof(QCowSnapshot));
 296     if (s->snapshots) {
 297         memcpy(snapshots1, s->snapshots, s->nb_snapshots * sizeof(QCowSnapshot));
 298         qemu_free(s->snapshots);
 299     }
 300     s->snapshots = snapshots1;
 301     s->snapshots[s->nb_snapshots++] = *sn;
 302
 303     if (qcow2_write_snapshots(bs) < 0)
 304         goto fail;
 305 #ifdef DEBUG_ALLOC
 306     qcow2_check_refcounts(bs);
 307 #endif
 308     return 0;
 309  fail:
 310     qemu_free(sn->name);
 311     qemu_free(l1_table);
 312     return -1;
 313 }
 314
 315 /* copy the snapshot 'snapshot_name' into the current disk image */
 316 int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
 317 {
 318     BDRVQcowState *s = bs->opaque;
 319     QCowSnapshot *sn;
 320     int i, snapshot_index;
 321     int cur_l1_bytes, sn_l1_bytes;
 322
 323     snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
 324     if (snapshot_index < 0)
 325         return -ENOENT;
 326     sn = &s->snapshots[snapshot_index];
 327
 328     if (qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, -1) < 0)
 329         goto fail;
 330
 331     if (qcow2_grow_l1_table(bs, sn->l1_size, true) < 0)
 332         goto fail;
 333
 334     cur_l1_bytes = s->l1_size * sizeof(uint64_t);
 335     sn_l1_bytes = sn->l1_size * sizeof(uint64_t);
 336
 337     if (cur_l1_bytes > sn_l1_bytes) {
 338         memset(s->l1_table + sn->l1_size, 0, cur_l1_bytes - sn_l1_bytes);
 339     }
 340
 341     /* copy the snapshot l1 table to the current l1 table */
 342     if (bdrv_pread(bs->file, sn->l1_table_offset,
 343                    s->l1_table, sn_l1_bytes) < 0)
 344         goto fail;
 345     if (bdrv_pwrite_sync(bs->file, s->l1_table_offset,
 346                     s->l1_table, cur_l1_bytes) < 0)
 347         goto fail;
 348     for(i = 0;i < s->l1_size; i++) {
 349         be64_to_cpus(&s->l1_table[i]);
 350     }
 351
 352     if (qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1) < 0)
 353         goto fail;
 354
 355 #ifdef DEBUG_ALLOC
 356     qcow2_check_refcounts(bs);
 357 #endif
 358     return 0;
 359  fail:
 360     return -EIO;
 361 }
 362
 363 int qcow2_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)
 364 {
 365     BDRVQcowState *s = bs->opaque;
 366     QCowSnapshot *sn;
 367     int snapshot_index, ret;
 368
 369     snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
 370     if (snapshot_index < 0)
 371         return -ENOENT;
 372     sn = &s->snapshots[snapshot_index];
 373
 374     ret = qcow2_update_snapshot_refcount(bs, sn->l1_table_offset, sn->l1_size, -1);
 375     if (ret < 0)
 376         return ret;
 377     /* must update the copied flag on the current cluster offsets */
 378     ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0);
 379     if (ret < 0)
 380         return ret;
 381     qcow2_free_clusters(bs, sn->l1_table_offset, sn->l1_size * sizeof(uint64_t));
 382
 383     qemu_free(sn->id_str);
 384     qemu_free(sn->name);
 385     memmove(sn, sn + 1, (s->nb_snapshots - snapshot_index - 1) * sizeof(*sn));
 386     s->nb_snapshots--;
 387     ret = qcow2_write_snapshots(bs);
 388     if (ret < 0) {
 389         /* XXX: restore snapshot if error ? */
 390         return ret;
 391     }
 392 #ifdef DEBUG_ALLOC
 393     qcow2_check_refcounts(bs);
 394 #endif
 395     return 0;
 396 }
 397
 398 int qcow2_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab)
 399 {
 400     BDRVQcowState *s = bs->opaque;
 401     QEMUSnapshotInfo *sn_tab, *sn_info;
 402     QCowSnapshot *sn;
 403     int i;
 404
 405     if (!s->nb_snapshots) {
 406         *psn_tab = NULL;
 407         return s->nb_snapshots;
 408     }
 409
 410     sn_tab = qemu_mallocz(s->nb_snapshots * sizeof(QEMUSnapshotInfo));
 411     for(i = 0; i < s->nb_snapshots; i++) {
 412         sn_info = sn_tab + i;
 413         sn = s->snapshots + i;
 414         pstrcpy(sn_info->id_str, sizeof(sn_info->id_str),
 415                 sn->id_str);
 416         pstrcpy(sn_info->name, sizeof(sn_info->name),
 417                 sn->name);
 418         sn_info->vm_state_size = sn->vm_state_size;
 419         sn_info->date_sec = sn->date_sec;
 420         sn_info->date_nsec = sn->date_nsec;
 421         sn_info->vm_clock_nsec = sn->vm_clock_nsec;
 422     }
 423     *psn_tab = sn_tab;
 424     return s->nb_snapshots;
 425 }
 426
 427 int qcow2_snapshot_load_tmp(BlockDriverState *bs, const char *snapshot_name)
 428 {
 429     int i, snapshot_index, l1_size2;
 430     BDRVQcowState *s = bs->opaque;
 431     QCowSnapshot *sn;
 432
 433     snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_name);
 434     if (snapshot_index < 0) {
 435         return -ENOENT;
 436     }
 437
 438     sn = &s->snapshots[snapshot_index];
 439     s->l1_size = sn->l1_size;
 440     l1_size2 = s->l1_size * sizeof(uint64_t);
 441     if (s->l1_table != NULL) {
 442         qemu_free(s->l1_table);
 443     }
 444
 445     s->l1_table_offset = sn->l1_table_offset;
 446     s->l1_table = qemu_mallocz(align_offset(l1_size2, 512));
 447
 448     if (bdrv_pread(bs->file, sn->l1_table_offset,
 449                    s->l1_table, l1_size2) != l1_size2) {
 450         return -1;
 451     }
 452
 453     for(i = 0;i < s->l1_size; i++) {
 454         be64_to_cpus(&s->l1_table[i]);
 455     }
 456     return 0;
 457 }