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 qcow_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 qcow_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(s->hd, 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(s->hd, 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(s->hd, 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     qcow_free_snapshots(bs);
 115     return -1;
 116 }
 117
 118 /* add at the end of the file a new list of snapshots */
 119 static int qcow_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 = alloc_clusters(bs, snapshots_size);
 141     offset = snapshots_offset;
 142
 143     for(i = 0; i < s->nb_snapshots; i++) {
 144         sn = s->snapshots + i;
 145         memset(&h, 0, sizeof(h));
 146         h.l1_table_offset = cpu_to_be64(sn->l1_table_offset);
 147         h.l1_size = cpu_to_be32(sn->l1_size);
 148         h.vm_state_size = cpu_to_be32(sn->vm_state_size);
 149         h.date_sec = cpu_to_be32(sn->date_sec);
 150         h.date_nsec = cpu_to_be32(sn->date_nsec);
 151         h.vm_clock_nsec = cpu_to_be64(sn->vm_clock_nsec);
 152
 153         id_str_size = strlen(sn->id_str);
 154         name_size = strlen(sn->name);
 155         h.id_str_size = cpu_to_be16(id_str_size);
 156         h.name_size = cpu_to_be16(name_size);
 157         offset = align_offset(offset, 8);
 158         if (bdrv_pwrite(s->hd, offset, &h, sizeof(h)) != sizeof(h))
 159             goto fail;
 160         offset += sizeof(h);
 161         if (bdrv_pwrite(s->hd, offset, sn->id_str, id_str_size) != id_str_size)
 162             goto fail;
 163         offset += id_str_size;
 164         if (bdrv_pwrite(s->hd, offset, sn->name, name_size) != name_size)
 165             goto fail;
 166         offset += name_size;
 167     }
 168
 169     /* update the various header fields */
 170     data64 = cpu_to_be64(snapshots_offset);
 171     if (bdrv_pwrite(s->hd, offsetof(QCowHeader, snapshots_offset),
 172                     &data64, sizeof(data64)) != sizeof(data64))
 173         goto fail;
 174     data32 = cpu_to_be32(s->nb_snapshots);
 175     if (bdrv_pwrite(s->hd, offsetof(QCowHeader, nb_snapshots),
 176                     &data32, sizeof(data32)) != sizeof(data32))
 177         goto fail;
 178
 179     /* free the old snapshot table */
 180     free_clusters(bs, s->snapshots_offset, s->snapshots_size);
 181     s->snapshots_offset = snapshots_offset;
 182     s->snapshots_size = snapshots_size;
 183     return 0;
 184  fail:
 185     return -1;
 186 }
 187
 188 static void find_new_snapshot_id(BlockDriverState *bs,
 189                                  char *id_str, int id_str_size)
 190 {
 191     BDRVQcowState *s = bs->opaque;
 192     QCowSnapshot *sn;
 193     int i, id, id_max = 0;
 194
 195     for(i = 0; i < s->nb_snapshots; i++) {
 196         sn = s->snapshots + i;
 197         id = strtoul(sn->id_str, NULL, 10);
 198         if (id > id_max)
 199             id_max = id;
 200     }
 201     snprintf(id_str, id_str_size, "%d", id_max + 1);
 202 }
 203
 204 static int find_snapshot_by_id(BlockDriverState *bs, const char *id_str)
 205 {
 206     BDRVQcowState *s = bs->opaque;
 207     int i;
 208
 209     for(i = 0; i < s->nb_snapshots; i++) {
 210         if (!strcmp(s->snapshots[i].id_str, id_str))
 211             return i;
 212     }
 213     return -1;
 214 }
 215
 216 static int find_snapshot_by_id_or_name(BlockDriverState *bs, const char *name)
 217 {
 218     BDRVQcowState *s = bs->opaque;
 219     int i, ret;
 220
 221     ret = find_snapshot_by_id(bs, name);
 222     if (ret >= 0)
 223         return ret;
 224     for(i = 0; i < s->nb_snapshots; i++) {
 225         if (!strcmp(s->snapshots[i].name, name))
 226             return i;
 227     }
 228     return -1;
 229 }
 230
 231 /* if no id is provided, a new one is constructed */
 232 int qcow_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
 233 {
 234     BDRVQcowState *s = bs->opaque;
 235     QCowSnapshot *snapshots1, sn1, *sn = &sn1;
 236     int i, ret;
 237     uint64_t *l1_table = NULL;
 238
 239     memset(sn, 0, sizeof(*sn));
 240
 241     if (sn_info->id_str[0] == '\0') {
 242         /* compute a new id */
 243         find_new_snapshot_id(bs, sn_info->id_str, sizeof(sn_info->id_str));
 244     }
 245
 246     /* check that the ID is unique */
 247     if (find_snapshot_by_id(bs, sn_info->id_str) >= 0)
 248         return -ENOENT;
 249
 250     sn->id_str = qemu_strdup(sn_info->id_str);
 251     if (!sn->id_str)
 252         goto fail;
 253     sn->name = qemu_strdup(sn_info->name);
 254     if (!sn->name)
 255         goto fail;
 256     sn->vm_state_size = sn_info->vm_state_size;
 257     sn->date_sec = sn_info->date_sec;
 258     sn->date_nsec = sn_info->date_nsec;
 259     sn->vm_clock_nsec = sn_info->vm_clock_nsec;
 260
 261     ret = update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1);
 262     if (ret < 0)
 263         goto fail;
 264
 265     /* create the L1 table of the snapshot */
 266     sn->l1_table_offset = alloc_clusters(bs, s->l1_size * sizeof(uint64_t));
 267     sn->l1_size = s->l1_size;
 268
 269     l1_table = qemu_malloc(s->l1_size * sizeof(uint64_t));
 270     for(i = 0; i < s->l1_size; i++) {
 271         l1_table[i] = cpu_to_be64(s->l1_table[i]);
 272     }
 273     if (bdrv_pwrite(s->hd, sn->l1_table_offset,
 274                     l1_table, s->l1_size * sizeof(uint64_t)) !=
 275         (s->l1_size * sizeof(uint64_t)))
 276         goto fail;
 277     qemu_free(l1_table);
 278     l1_table = NULL;
 279
 280     snapshots1 = qemu_malloc((s->nb_snapshots + 1) * sizeof(QCowSnapshot));
 281     if (s->snapshots) {
 282         memcpy(snapshots1, s->snapshots, s->nb_snapshots * sizeof(QCowSnapshot));
 283         qemu_free(s->snapshots);
 284     }
 285     s->snapshots = snapshots1;
 286     s->snapshots[s->nb_snapshots++] = *sn;
 287
 288     if (qcow_write_snapshots(bs) < 0)
 289         goto fail;
 290 #ifdef DEBUG_ALLOC
 291     check_refcounts(bs);
 292 #endif
 293     return 0;
 294  fail:
 295     qemu_free(sn->name);
 296     qemu_free(l1_table);
 297     return -1;
 298 }
 299
 300 /* copy the snapshot 'snapshot_name' into the current disk image */
 301 int qcow_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
 302 {
 303     BDRVQcowState *s = bs->opaque;
 304     QCowSnapshot *sn;
 305     int i, snapshot_index, l1_size2;
 306
 307     snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
 308     if (snapshot_index < 0)
 309         return -ENOENT;
 310     sn = &s->snapshots[snapshot_index];
 311
 312     if (update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, -1) < 0)
 313         goto fail;
 314
 315     if (grow_l1_table(bs, sn->l1_size) < 0)
 316         goto fail;
 317
 318     s->l1_size = sn->l1_size;
 319     l1_size2 = s->l1_size * sizeof(uint64_t);
 320     /* copy the snapshot l1 table to the current l1 table */
 321     if (bdrv_pread(s->hd, sn->l1_table_offset,
 322                    s->l1_table, l1_size2) != l1_size2)
 323         goto fail;
 324     if (bdrv_pwrite(s->hd, s->l1_table_offset,
 325                     s->l1_table, l1_size2) != l1_size2)
 326         goto fail;
 327     for(i = 0;i < s->l1_size; i++) {
 328         be64_to_cpus(&s->l1_table[i]);
 329     }
 330
 331     if (update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1) < 0)
 332         goto fail;
 333
 334 #ifdef DEBUG_ALLOC
 335     check_refcounts(bs);
 336 #endif
 337     return 0;
 338  fail:
 339     return -EIO;
 340 }
 341
 342 int qcow_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)
 343 {
 344     BDRVQcowState *s = bs->opaque;
 345     QCowSnapshot *sn;
 346     int snapshot_index, ret;
 347
 348     snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
 349     if (snapshot_index < 0)
 350         return -ENOENT;
 351     sn = &s->snapshots[snapshot_index];
 352
 353     ret = update_snapshot_refcount(bs, sn->l1_table_offset, sn->l1_size, -1);
 354     if (ret < 0)
 355         return ret;
 356     /* must update the copied flag on the current cluster offsets */
 357     ret = update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0);
 358     if (ret < 0)
 359         return ret;
 360     free_clusters(bs, sn->l1_table_offset, sn->l1_size * sizeof(uint64_t));
 361
 362     qemu_free(sn->id_str);
 363     qemu_free(sn->name);
 364     memmove(sn, sn + 1, (s->nb_snapshots - snapshot_index - 1) * sizeof(*sn));
 365     s->nb_snapshots--;
 366     ret = qcow_write_snapshots(bs);
 367     if (ret < 0) {
 368         /* XXX: restore snapshot if error ? */
 369         return ret;
 370     }
 371 #ifdef DEBUG_ALLOC
 372     check_refcounts(bs);
 373 #endif
 374     return 0;
 375 }
 376
 377 int qcow_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab)
 378 {
 379     BDRVQcowState *s = bs->opaque;
 380     QEMUSnapshotInfo *sn_tab, *sn_info;
 381     QCowSnapshot *sn;
 382     int i;
 383
 384     if (!s->nb_snapshots) {
 385         *psn_tab = NULL;
 386         return s->nb_snapshots;
 387     }
 388
 389     sn_tab = qemu_mallocz(s->nb_snapshots * sizeof(QEMUSnapshotInfo));
 390     for(i = 0; i < s->nb_snapshots; i++) {
 391         sn_info = sn_tab + i;
 392         sn = s->snapshots + i;
 393         pstrcpy(sn_info->id_str, sizeof(sn_info->id_str),
 394                 sn->id_str);
 395         pstrcpy(sn_info->name, sizeof(sn_info->name),
 396                 sn->name);
 397         sn_info->vm_state_size = sn->vm_state_size;
 398         sn_info->date_sec = sn->date_sec;
 399         sn_info->date_nsec = sn->date_nsec;
 400         sn_info->vm_clock_nsec = sn->vm_clock_nsec;
 401     }
 402     *psn_tab = sn_tab;
 403     return s->nb_snapshots;
 404 }
 405