VMDK: move 'static' cid_update flag to bs field

Cid_update is the flag for updating CID on first write after opening the
image. This should be per image open rather than per program life cycle,
so change it from static var of vmdk_write to a field in BDRVVmdkState.
Signed-off-by: NFam Zheng <famcool@gmail.com>
Reviewed-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/vmdk.c

@@ -82,6 +82,7 @@ typedef struct VmdkExtent {
 
 typedef struct BDRVVmdkState {
     int desc_offset;
+    bool cid_updated;
     uint32_t parent_cid;
     int num_extents;
     /* Extent array with num_extents entries, ascend ordered by address */
@@ -853,7 +854,6 @@ static int vmdk_write(BlockDriverState *bs, int64_t sector_num,
     int n;
     int64_t index_in_cluster;
     uint64_t cluster_offset;
-    static int cid_update = 0;
     VmdkMetaData m_data;
 
     if (sector_num > bs->total_sectors) {
@@ -900,9 +900,9 @@ static int vmdk_write(BlockDriverState *bs, int64_t sector_num,
         buf += n * 512;
 
         // update CID on the first write every time the virtual disk is opened
-        if (!cid_update) {
+        if (!s->cid_updated) {
             vmdk_write_cid(bs, time(NULL));
-            cid_update++;
+            s->cid_updated = true;
         }
     }
     return 0;