diff options
Diffstat (limited to 'block/qcow2-cluster.c')
| -rw-r--r-- | block/qcow2-cluster.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 558c23957f..e2c5759d94 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -1601,6 +1601,7 @@ static int zero_single_l2(BlockDriverState *bs, uint64_t offset, int l2_index; int ret; int i; + bool unmap = !!(flags & BDRV_REQ_MAY_UNMAP); ret = get_cluster_table(bs, offset, &l2_table, &l2_index); if (ret < 0) { @@ -1613,12 +1614,22 @@ static int zero_single_l2(BlockDriverState *bs, uint64_t offset, for (i = 0; i < nb_clusters; i++) { uint64_t old_offset; + QCow2ClusterType cluster_type; old_offset = be64_to_cpu(l2_table[l2_index + i]); - /* Update L2 entries */ + /* + * Minimize L2 changes if the cluster already reads back as + * zeroes with correct allocation. + */ + cluster_type = qcow2_get_cluster_type(old_offset); + if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN || + (cluster_type == QCOW2_CLUSTER_ZERO_ALLOC && !unmap)) { + continue; + } + qcow2_cache_entry_mark_dirty(bs, s->l2_table_cache, l2_table); - if (old_offset & QCOW_OFLAG_COMPRESSED || flags & BDRV_REQ_MAY_UNMAP) { + if (cluster_type == QCOW2_CLUSTER_COMPRESSED || unmap) { l2_table[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO); qcow2_free_any_clusters(bs, old_offset, 1, QCOW2_DISCARD_REQUEST); } else { |