qcow2: Tighten cluster_offset alignment assertions

qcow2_alloc_cluster_offset() and qcow2_get_cluster_offset() always
return offsets that are cluster-aligned so don't just check that they
are sector-aligned.

The check in qcow2_co_preadv_task() is also replaced by an assertion
for the same reason.
Signed-off-by: NAlberto Garcia <berto@igalia.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Message-id: 558ba339965f858bede4c73ce3f50f0c0493597d.1579374329.git.berto@igalia.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>

block/qcow2.c

@@ -2167,10 +2167,7 @@ static coroutine_fn int qcow2_co_preadv_task(BlockDriverState *bs,
                                           offset, bytes, qiov, qiov_offset);
 
     case QCOW2_CLUSTER_NORMAL:
-        if ((file_cluster_offset & 511) != 0) {
-            return -EIO;
-        }
-
+        assert(offset_into_cluster(s, file_cluster_offset) == 0);
         if (bs->encrypted) {
             return qcow2_co_preadv_encrypted(bs, file_cluster_offset,
                                              offset, bytes, qiov, qiov_offset);
@@ -2506,7 +2503,7 @@ static coroutine_fn int qcow2_co_pwritev_part(
             goto out_locked;
         }
 
-        assert((cluster_offset & 511) == 0);
+        assert(offset_into_cluster(s, cluster_offset) == 0);
 
         ret = qcow2_pre_write_overlap_check(bs, 0,
                                             cluster_offset + offset_in_cluster,
@@ -3896,7 +3893,7 @@ qcow2_co_copy_range_to(BlockDriverState *bs,
             goto fail;
         }
 
-        assert((cluster_offset & 511) == 0);
+        assert(offset_into_cluster(s, cluster_offset) == 0);
 
         ret = qcow2_pre_write_overlap_check(bs, 0,
                 cluster_offset + offset_in_cluster, cur_bytes, true);