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qcow2: Rework qcow2_snapshot_create error handling 

Increase refcounts only after allocating a new L1 table has succeeded in
order to make leaks less likely. If writing the snapshot table fails,
revert in-memory state to be consistent with that on disk.

While at it, make it return the real error codes instead of -1.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
This commit is contained in:
Kevin Wolf 2011-11-16 12:43:59 +01:00
parent 03343166f7
commit d1ea98d56d
1 changed files with 42 additions and 15 deletions
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57
block/qcow2-snapshot.c
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@ -277,7 +277,9 @@ static int find_snapshot_by_id_or_name(BlockDriverState *bs, const char *name)
int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
{
BDRVQcowState *s = bs->opaque;
QCowSnapshot *snapshots1, sn1, *sn = &sn1;
QCowSnapshot *new_snapshot_list = NULL;
QCowSnapshot *old_snapshot_list = NULL;
QCowSnapshot sn1, *sn = &sn1;
int i, ret;
uint64_t *l1_table = NULL;
int64_t l1_table_offset;
@ -303,16 +305,12 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
sn->date_nsec = sn_info->date_nsec;
sn->vm_clock_nsec = sn_info->vm_clock_nsec;
ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1);
if (ret < 0)
goto fail;
/* Allocate the L1 table of the snapshot and copy the current one there. */
l1_table_offset = qcow2_alloc_clusters(bs, s->l1_size * sizeof(uint64_t));
if (l1_table_offset < 0) {
ret = l1_table_offset;
goto fail;
}
bdrv_flush(bs->file);
sn->l1_table_offset = l1_table_offset;
sn->l1_size = s->l1_size;
@ -321,22 +319,50 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
for(i = 0; i < s->l1_size; i++) {
l1_table[i] = cpu_to_be64(s->l1_table[i]);
}
if (bdrv_pwrite_sync(bs->file, sn->l1_table_offset,
l1_table, s->l1_size * sizeof(uint64_t)) < 0)
ret = bdrv_pwrite(bs->file, sn->l1_table_offset, l1_table,
s->l1_size * sizeof(uint64_t));
if (ret < 0) {
goto fail;
}
g_free(l1_table);
l1_table = NULL;
snapshots1 = g_malloc((s->nb_snapshots + 1) * sizeof(QCowSnapshot));
if (s->snapshots) {
memcpy(snapshots1, s->snapshots, s->nb_snapshots * sizeof(QCowSnapshot));
g_free(s->snapshots);
/*
* Increase the refcounts of all clusters and make sure everything is
* stable on disk before updating the snapshot table to contain a pointer
* to the new L1 table.
*/
ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1);
if (ret < 0) {
goto fail;
}
s->snapshots = snapshots1;
ret = bdrv_flush(bs);
if (ret < 0) {
goto fail;
}
/* Append the new snapshot to the snapshot list */
new_snapshot_list = g_malloc((s->nb_snapshots + 1) * sizeof(QCowSnapshot));
if (s->snapshots) {
memcpy(new_snapshot_list, s->snapshots,
s->nb_snapshots * sizeof(QCowSnapshot));
old_snapshot_list = s->snapshots;
}
s->snapshots = new_snapshot_list;
s->snapshots[s->nb_snapshots++] = *sn;
if (qcow2_write_snapshots(bs) < 0)
ret = qcow2_write_snapshots(bs);
if (ret < 0) {
g_free(s->snapshots);
s->snapshots = old_snapshot_list;
goto fail;
}
g_free(old_snapshot_list);
#ifdef DEBUG_ALLOC
{
BdrvCheckResult result = {0};
@ -349,7 +375,8 @@ fail:
g_free(sn->id_str);
g_free(sn->name);
g_free(l1_table);
return -1;
return ret;
}
/* copy the snapshot 'snapshot_name' into the current disk image */