qcow2: Save refcount order in BDRVQcowState

Save the image refcount order in BDRVQcowState. This will be relevant
for future code supporting different refcount orders than four and also
for code that needs to verify a certain refcount order for an opened
image.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/qcow2.c

@@ -455,6 +455,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags)
         ret = -ENOTSUP;
         goto fail;
     }
+    s->refcount_order = header.refcount_order;
 
     if (header.cluster_bits < MIN_CLUSTER_BITS ||
         header.cluster_bits > MAX_CLUSTER_BITS) {
@@ -1143,7 +1144,7 @@ int qcow2_update_header(BlockDriverState *bs)
         .incompatible_features  = cpu_to_be64(s->incompatible_features),
         .compatible_features    = cpu_to_be64(s->compatible_features),
         .autoclear_features     = cpu_to_be64(s->autoclear_features),
-        .refcount_order         = cpu_to_be32(3 + REFCOUNT_SHIFT),
+        .refcount_order         = cpu_to_be32(s->refcount_order),
         .header_length          = cpu_to_be32(header_length),
     };
 

block/qcow2.h

@@ -199,6 +199,7 @@ typedef struct BDRVQcowState {
     int flags;
     int qcow_version;
     bool use_lazy_refcounts;
+    int refcount_order;
 
     bool discard_passthrough[QCOW2_DISCARD_MAX];