block/qcow2: Add qcow2_refcount_area()

This function creates a collection of self-describing refcount
structures (including a new refcount table) at the end of a qcow2 image
file. Optionally, these structures can also describe a number of
additional clusters beyond themselves; this will be important for
preallocated truncation, which will place the data clusters and L2
tables there.

For now, we can use this function to replace the part of
alloc_refcount_block() that grows the refcount table (from which it is
actually derived).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170613202107.10125-13-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/block/qcow2.h b/block/qcow2.h
index 2df05ac8dd..3854080725 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -525,6 +525,10 @@ static inline uint64_t refcount_diff(uint64_t r1, uint64_t r2)
 int qcow2_backing_read1(BlockDriverState *bs, QEMUIOVector *qiov,
                   int64_t sector_num, int nb_sectors);
 
+int64_t qcow2_refcount_metadata_size(int64_t clusters, size_t cluster_size,
+                                     int refcount_order, bool generous_increase,
+                                     uint64_t *refblock_count);
+
 int qcow2_mark_dirty(BlockDriverState *bs);
 int qcow2_mark_corrupt(BlockDriverState *bs);
 int qcow2_mark_consistent(BlockDriverState *bs);