qcow2: Helper function for refcount modification

Since refcounts do not always have to be a uint16_t, all refcount blocks
and arrays in memory should not have a specific type (thus they become
pointers to void) and for accessing them, two helper functions are used
(a getter and a setter). Those functions are called indirectly through
function pointers in the BDRVQcowState so they may later be exchanged
for different refcount orders.

With the check and repair functions using this function, the refcount
array they are creating will be in big endian byte order; additionally,
using realloc_refcount_array() makes the size of this refcount array
always cluster-aligned. Both combined allow rebuild_refcount_structure()
to drop the bounce buffer which was used to convert parts of the
refcount array to big endian byte order and store them on disk. Instead,
those parts can now be written directly.

[ kwolf: Fixed a build failure on 32 bit and another with old glib ]

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/block/qcow2.h b/block/qcow2.h
index a9108f55ca..aa6d367818 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -213,6 +213,11 @@ typedef struct Qcow2DiscardRegion {
     QTAILQ_ENTRY(Qcow2DiscardRegion) next;
 } Qcow2DiscardRegion;
 
+typedef uint64_t Qcow2GetRefcountFunc(const void *refcount_array,
+                                      uint64_t index);
+typedef void Qcow2SetRefcountFunc(void *refcount_array,
+                                  uint64_t index, uint64_t value);
+
 typedef struct BDRVQcowState {
     int cluster_bits;
     int cluster_size;
@@ -261,6 +266,9 @@ typedef struct BDRVQcowState {
     int refcount_bits;
     uint64_t refcount_max;
 
+    Qcow2GetRefcountFunc *get_refcount;
+    Qcow2SetRefcountFunc *set_refcount;
+
     bool discard_passthrough[QCOW2_DISCARD_MAX];
 
     int overlap_check; /* bitmask of Qcow2MetadataOverlap values */