vmdk: Fix next_cluster_sector for compressed write

When the VMDK is streamOptimized (or compressed), the
next_cluster_sector must not be incremented by a fixed number of
sectors. Instead of this, it must be rounded up to the next consecutive
sector. Fixing this results in much smaller compressed images.

Signed-off-by: Radoslav Gerganov <rgerganov@vmware.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/vmdk.c

diff --git a/block/vmdk.c b/block/vmdk.c
index 7bdc3d0..be0d640 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1324,8 +1324,12 @@
 
     write_end_sector = DIV_ROUND_UP(write_offset + write_len, BDRV_SECTOR_SIZE);
 
-    extent->next_cluster_sector = MAX(extent->next_cluster_sector,
-                                      write_end_sector);
+    if (extent->compressed) {
+        extent->next_cluster_sector = write_end_sector;
+    } else {
+        extent->next_cluster_sector = MAX(extent->next_cluster_sector,
+                                          write_end_sector);
+    }
 
     if (ret != write_len) {
         ret = ret < 0 ? ret : -EIO;