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authorKevin Wolf <kwolf@redhat.com>2011-11-16 17:22:10 +0100
committerKevin Wolf <kwolf@redhat.com>2011-12-05 14:51:36 +0100
commit9a4767809fe9ac184806bef38be2e2a84e451a65 (patch)
treea36e9f0c88f6dcd7d4f2643b5455204ee2855396
parent43a0cac4658bbee9c9e84554712a94daa092c1cd (diff)
downloadqemu-arm-9a4767809fe9ac184806bef38be2e2a84e451a65.tar.gz
qcow2: Fix order in qcow2_snapshot_delete
First the snapshot must be deleted and only then the refcounts can be decreased. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
-rw-r--r--block/qcow2-snapshot.c48
1 files changed, 33 insertions, 15 deletions
diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 9fb3ff0253..e959ef263e 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -489,32 +489,50 @@ fail:
int qcow2_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)
{
BDRVQcowState *s = bs->opaque;
- QCowSnapshot *sn;
+ QCowSnapshot sn;
int snapshot_index, ret;
+ /* Search the snapshot */
snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
- if (snapshot_index < 0)
+ if (snapshot_index < 0) {
return -ENOENT;
- sn = &s->snapshots[snapshot_index];
+ }
+ sn = s->snapshots[snapshot_index];
- ret = qcow2_update_snapshot_refcount(bs, sn->l1_table_offset, sn->l1_size, -1);
- if (ret < 0)
+ /* Remove it from the snapshot list */
+ memmove(s->snapshots + snapshot_index,
+ s->snapshots + snapshot_index + 1,
+ (s->nb_snapshots - snapshot_index - 1) * sizeof(sn));
+ s->nb_snapshots--;
+ ret = qcow2_write_snapshots(bs);
+ if (ret < 0) {
return ret;
- /* must update the copied flag on the current cluster offsets */
- ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0);
- if (ret < 0)
+ }
+
+ /*
+ * The snapshot is now unused, clean up. If we fail after this point, we
+ * won't recover but just leak clusters.
+ */
+ g_free(sn.id_str);
+ g_free(sn.name);
+
+ /*
+ * Now decrease the refcounts of clusters referenced by the snapshot and
+ * free the L1 table.
+ */
+ ret = qcow2_update_snapshot_refcount(bs, sn.l1_table_offset,
+ sn.l1_size, -1);
+ if (ret < 0) {
return ret;
- qcow2_free_clusters(bs, sn->l1_table_offset, sn->l1_size * sizeof(uint64_t));
+ }
+ qcow2_free_clusters(bs, sn.l1_table_offset, sn.l1_size * sizeof(uint64_t));
- g_free(sn->id_str);
- g_free(sn->name);
- memmove(sn, sn + 1, (s->nb_snapshots - snapshot_index - 1) * sizeof(*sn));
- s->nb_snapshots--;
- ret = qcow2_write_snapshots(bs);
+ /* must update the copied flag on the current cluster offsets */
+ ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0);
if (ret < 0) {
- /* XXX: restore snapshot if error ? */
return ret;
}
+
#ifdef DEBUG_ALLOC
{
BdrvCheckResult result = {0};