qcow2: Calculate refcount block entry count
The size of a refblock entry is (in theory) variable; calculate
therefore the number of entries per refblock and the according bit shift
(1 << x == entry count) when opening an image.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block/qcow2.c b/block/qcow2.c
index 156a219..3c8b881 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -698,6 +698,9 @@
s->l2_bits = s->cluster_bits - 3; /* L2 is always one cluster */
s->l2_size = 1 << s->l2_bits;
+ /* 2^(s->refcount_order - 3) is the refcount width in bytes */
+ s->refcount_block_bits = s->cluster_bits - (s->refcount_order - 3);
+ s->refcount_block_size = 1 << s->refcount_block_bits;
bs->total_sectors = header.size / 512;
s->csize_shift = (62 - (s->cluster_bits - 8));
s->csize_mask = (1 << (s->cluster_bits - 8)) - 1;
