This patch adds the following new fields to BDRVQcow2State: - subclusters_per_cluster: Number of subclusters in a cluster - subcluster_size: The size of each subcluster, in bytes - subcluster_bits: No. of bits so 1 << subcluster_bits = subcluster_size
Images without subclusters are treated as if they had exactly one subcluster per cluster (i.e. subcluster_size = cluster_size). Signed-off-by: Alberto Garcia <be...@igalia.com> Reviewed-by: Max Reitz <mre...@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> --- block/qcow2.h | 5 +++++ block/qcow2.c | 5 +++++ 2 files changed, 10 insertions(+) diff --git a/block/qcow2.h b/block/qcow2.h index 2064dd3d85..eee4c8de9c 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -78,6 +78,8 @@ /* The cluster reads as all zeros */ #define QCOW_OFLAG_ZERO (1ULL << 0) +#define QCOW_EXTL2_SUBCLUSTERS_PER_CLUSTER 32 + #define MIN_CLUSTER_BITS 9 #define MAX_CLUSTER_BITS 21 @@ -295,6 +297,9 @@ typedef struct BDRVQcow2State { int cluster_bits; int cluster_size; int l2_slice_size; + int subcluster_bits; + int subcluster_size; + int subclusters_per_cluster; int l2_bits; int l2_size; int l1_size; diff --git a/block/qcow2.c b/block/qcow2.c index 47f8032f89..e0349e6800 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1444,6 +1444,11 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options, } } + s->subclusters_per_cluster = + has_subclusters(s) ? QCOW_EXTL2_SUBCLUSTERS_PER_CLUSTER : 1; + s->subcluster_size = s->cluster_size / s->subclusters_per_cluster; + s->subcluster_bits = ctz32(s->subcluster_size); + /* Check support for various header values */ if (header.refcount_order > 6) { error_setg(errp, "Reference count entry width too large; may not " -- 2.20.1