/* copy the snapshot 'snapshot_name' into the current disk image */
int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
{
BDRVQcowState *s = bs->opaque;
QCowSnapshot *sn;
int i, snapshot_index;
int cur_l1_bytes, sn_l1_bytes;
snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
if (snapshot_index < 0)
return -ENOENT;
sn = &s->snapshots[snapshot_index];
if (qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, -1) < 0)
goto fail;
if (qcow2_grow_l1_table(bs, sn->l1_size, true) < 0)
goto fail;
cur_l1_bytes = s->l1_size * sizeof(uint64_t);
sn_l1_bytes = sn->l1_size * sizeof(uint64_t);
if (cur_l1_bytes > sn_l1_bytes) {
memset(s->l1_table + sn->l1_size, 0, cur_l1_bytes - sn_l1_bytes);
}
/* copy the snapshot l1 table to the current l1 table */
if (bdrv_pread(bs->file, sn->l1_table_offset,
s->l1_table, sn_l1_bytes) < 0)
goto fail;
if (bdrv_pwrite_sync(bs->file, s->l1_table_offset,
s->l1_table, cur_l1_bytes) < 0)
goto fail;
for(i = 0; i < s->l1_size; i++) {
be64_to_cpus(&s->l1_table[i]);
}
if (qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1) < 0)
goto fail;
#ifdef DEBUG_ALLOC
qcow2_check_refcounts(bs);
#endif
return 0;
fail:
return -EIO;
}
/* copy the snapshot 'snapshot_name' into the current disk image */
int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
{
BDRVQcowState *s = bs->opaque;
QCowSnapshot *sn;
int i, snapshot_index, l1_size2;
snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
if (snapshot_index < 0)
return -ENOENT;
sn = &s->snapshots[snapshot_index];
if (!bs->read_only &&
qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, -1) < 0)
goto fail;
if (qcow2_grow_l1_table(bs, sn->l1_size) < 0)
goto fail;
s->l1_size = sn->l1_size;
l1_size2 = s->l1_size * sizeof(uint64_t);
/* copy the snapshot l1 table to the current l1 table */
if (bdrv_pread(s->hd, sn->l1_table_offset,
s->l1_table, l1_size2) != l1_size2)
goto fail;
if (bs->read_only)
s->l1_table_offset = sn->l1_table_offset;
else if (bdrv_pwrite(s->hd, s->l1_table_offset,
s->l1_table, l1_size2) != l1_size2)
goto fail;
for(i = 0;i < s->l1_size; i++) {
be64_to_cpus(&s->l1_table[i]);
}
if (!bs->read_only &&
qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1) < 0)
goto fail;
#ifdef DEBUG_ALLOC
qcow2_check_refcounts(bs);
#endif
return 0;
fail:
return -EIO;
}
/* copy the snapshot 'snapshot_name' into the current disk image */
int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
{
BDRVQcowState *s = bs->opaque;
QCowSnapshot *sn;
int i, snapshot_index;
int cur_l1_bytes, sn_l1_bytes;
int ret;
uint64_t *sn_l1_table = NULL;
/* Search the snapshot */
snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
if (snapshot_index < 0) {
return -ENOENT;
}
sn = &s->snapshots[snapshot_index];
if (sn->disk_size != bs->total_sectors * BDRV_SECTOR_SIZE) {
error_report("qcow2: Loading snapshots with different disk "
"size is not implemented");
ret = -ENOTSUP;
goto fail;
}
/*
* Make sure that the current L1 table is big enough to contain the whole
* L1 table of the snapshot. If the snapshot L1 table is smaller, the
* current one must be padded with zeros.
*/
ret = qcow2_grow_l1_table(bs, sn->l1_size, true);
if (ret < 0) {
goto fail;
}
cur_l1_bytes = s->l1_size * sizeof(uint64_t);
sn_l1_bytes = sn->l1_size * sizeof(uint64_t);
/*
* Copy the snapshot L1 table to the current L1 table.
*
* Before overwriting the old current L1 table on disk, make sure to
* increase all refcounts for the clusters referenced by the new one.
* Decrease the refcount referenced by the old one only when the L1
* table is overwritten.
*/
sn_l1_table = g_malloc0(cur_l1_bytes);
ret = bdrv_pread(bs->file, sn->l1_table_offset, sn_l1_table, sn_l1_bytes);
if (ret < 0) {
goto fail;
}
ret = qcow2_update_snapshot_refcount(bs, sn->l1_table_offset,
sn->l1_size, 1);
if (ret < 0) {
goto fail;
}
ret = qcow2_pre_write_overlap_check(bs,
QCOW2_OL_DEFAULT & ~QCOW2_OL_ACTIVE_L1,
s->l1_table_offset, cur_l1_bytes);
if (ret < 0) {
goto fail;
}
ret = bdrv_pwrite_sync(bs->file, s->l1_table_offset, sn_l1_table,
cur_l1_bytes);
if (ret < 0) {
goto fail;
}
/*
* Decrease refcount of clusters of current L1 table.
*
* At this point, the in-memory s->l1_table points to the old L1 table,
* whereas on disk we already have the new one.
*
* qcow2_update_snapshot_refcount special cases the current L1 table to use
* the in-memory data instead of really using the offset to load a new one,
* which is why this works.
*/
ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset,
s->l1_size, -1);
/*
* Now update the in-memory L1 table to be in sync with the on-disk one. We
* need to do this even if updating refcounts failed.
*/
for(i = 0; i < s->l1_size; i++) {
s->l1_table[i] = be64_to_cpu(sn_l1_table[i]);
}
if (ret < 0) {
goto fail;
}
g_free(sn_l1_table);
sn_l1_table = NULL;
/*
* Update QCOW_OFLAG_COPIED in the active L1 table (it may have changed
* when we decreased the refcount of the old snapshot.
*/
ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0);
if (ret < 0) {
goto fail;
}
#ifdef DEBUG_ALLOC
{
BdrvCheckResult result = {0};
qcow2_check_refcounts(bs, &result, 0);
}
#endif
return 0;
fail:
g_free(sn_l1_table);
return ret;
}
