vmdk: Fix next_cluster_sector for compressed write

This fixes the bug introduced by commit c6ac36e1 (vmdk: Optimize cluster
allocation).

Sometimes, write_len could be larger than cluster size, because it
contains both data and marker.  We must advance next_cluster_sector in
this case, otherwise the image gets corrupted.

Cc: qemu-stable@nongnu.org
Reported-by: NAntoni Villalonga <qemu-list@friki.cat>
Signed-off-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
(cherry picked from commit 5e82a31e)
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>

block/vmdk.c

@@ -1302,6 +1302,8 @@ static int vmdk_write_extent(VmdkExtent *extent, int64_t cluster_offset,
     uLongf buf_len;
     const uint8_t *write_buf = buf;
     int write_len = nb_sectors * 512;
+    int64_t write_offset;
+    int64_t write_end_sector;
 
     if (extent->compressed) {
         if (!extent->has_marker) {
@@ -1320,10 +1322,14 @@ static int vmdk_write_extent(VmdkExtent *extent, int64_t cluster_offset,
         write_buf = (uint8_t *)data;
         write_len = buf_len + sizeof(VmdkGrainMarker);
     }
-    ret = bdrv_pwrite(extent->file,
-                        cluster_offset + offset_in_cluster,
-                        write_buf,
-                        write_len);
+    write_offset = cluster_offset + offset_in_cluster,
+    ret = bdrv_pwrite(extent->file, write_offset, write_buf, write_len);
+
+    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 (ret != write_len) {
         ret = ret < 0 ? ret : -EIO;
         goto out;