[Qemu-devel] [PATCH V3 3/7] qcow2: cancel the modification on fail in qcow2_snapshot_create()

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
---
 block/qcow2-snapshot.c |   20 ++++++++++++++++----
 1 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 9e2d695..e0b7a5a 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -378,13 +378,13 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
     ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_DEFAULT,
             sn->l1_table_offset, s->l1_size * sizeof(uint64_t));
     if (ret < 0) {
-        goto fail;
+        goto dealloc_cluster;
     }
 
     ret = bdrv_pwrite(bs->file, sn->l1_table_offset, l1_table,
                       s->l1_size * sizeof(uint64_t));
     if (ret < 0) {
-        goto fail;
+        goto dealloc_cluster;
     }
 
     g_free(l1_table);
@@ -397,7 +397,7 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
      */
     ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1);
     if (ret < 0) {
-        goto fail;
+        goto dealloc_cluster;
     }
 
     /* Append the new snapshot to the snapshot list */
@@ -416,7 +416,7 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
         g_free(s->snapshots);
         s->snapshots = old_snapshot_list;
         s->nb_snapshots = old_snapshot_num;
-        goto fail;
+        goto restore_refcount;
     }
 
     g_free(old_snapshot_list);
@@ -429,6 +429,18 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
 #endif
     return 0;
 
+restore_refcount:
+    if (qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, -1)
+        < 0) {
+        /* Nothing can be done none now, need image check later */
+        error_report("qcow2: Error in restoring refcount in snapshot");
+    }
+
+dealloc_cluster:
+    qcow2_free_clusters(bs, sn->l1_table_offset,
+                        sn->l1_size * sizeof(uint64_t),
+                        QCOW2_DISCARD_ALWAYS);
+
 fail:
     g_free(sn->id_str);
     g_free(sn->name);
-- 
1.7.1