VMDK: bugfix, opening vSphere 4 exported image

The vSphere 4 exported image is streamOptimized extent, which is not
quite correctly handled. Ignore rdgOffset when RGD flag bit not set.
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

@@ -31,6 +31,7 @@
 #define VMDK3_MAGIC (('C' << 24) | ('O' << 16) | ('W' << 8) | 'D')
 #define VMDK4_MAGIC (('K' << 24) | ('D' << 16) | ('M' << 8) | 'V')
 #define VMDK4_COMPRESSION_DEFLATE 1
+#define VMDK4_FLAG_RGD (1 << 1)
 #define VMDK4_FLAG_COMPRESS (1 << 16)
 #define VMDK4_FLAG_MARKER (1 << 17)
 
@@ -55,8 +56,8 @@ typedef struct {
     int64_t desc_offset;
     int64_t desc_size;
     int32_t num_gtes_per_gte;
-    int64_t rgd_offset;
     int64_t gd_offset;
+    int64_t rgd_offset;
     int64_t grain_offset;
     char filler[1];
     char check_bytes[4];
@@ -420,6 +421,7 @@ static int vmdk_open_vmdk4(BlockDriverState *bs,
     uint32_t l1_size, l1_entry_sectors;
     VMDK4Header header;
     VmdkExtent *extent;
+    int64_t l1_backup_offset = 0;
 
     ret = bdrv_pread(file, sizeof(magic), &header, sizeof(header));
     if (ret < 0) {
@@ -435,10 +437,13 @@ static int vmdk_open_vmdk4(BlockDriverState *bs,
     }
     l1_size = (le64_to_cpu(header.capacity) + l1_entry_sectors - 1)
                 / l1_entry_sectors;
+    if (le32_to_cpu(header.flags) & VMDK4_FLAG_RGD) {
+        l1_backup_offset = le64_to_cpu(header.rgd_offset) << 9;
+    }
     extent = vmdk_add_extent(bs, file, false,
                           le64_to_cpu(header.capacity),
                           le64_to_cpu(header.gd_offset) << 9,
-                          le64_to_cpu(header.rgd_offset) << 9,
+                          l1_backup_offset,
                           l1_size,
                           le32_to_cpu(header.num_gtes_per_gte),
                           le64_to_cpu(header.granularity));