qcow2: Enable dirty flag in qcow2_alloc_cluster_link_l2

This is closer to where the dirty flag is really needed, and it avoids
having checks for special cases related to cluster allocation directly
in the writev loop.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/qcow2-cluster.c

@@ -668,11 +668,14 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
     }
 
     /* Update L2 table. */
-
+    if (s->compatible_features & QCOW2_COMPAT_LAZY_REFCOUNTS) {
+        qcow2_mark_dirty(bs);
+    }
     if (qcow2_need_accurate_refcounts(s)) {
         qcow2_cache_set_dependency(bs, s->l2_table_cache,
                                    s->refcount_block_cache);
     }
+
     ret = get_cluster_table(bs, m->offset, &l2_table, &l2_index);
     if (ret < 0) {
         goto err;

block/qcow2.c

@@ -222,7 +222,7 @@ static void report_unsupported_feature(BlockDriverState *bs,
  * updated successfully.  Therefore it is not required to check the return
  * value of this function.
  */
-static int qcow2_mark_dirty(BlockDriverState *bs)
+int qcow2_mark_dirty(BlockDriverState *bs)
 {
     BDRVQcowState *s = bs->opaque;
     uint64_t val;
@@ -803,11 +803,6 @@ static coroutine_fn int qcow2_co_writev(BlockDriverState *bs,
             goto fail;
         }
 
-        if (l2meta->nb_clusters > 0 &&
-            (s->compatible_features & QCOW2_COMPAT_LAZY_REFCOUNTS)) {
-            qcow2_mark_dirty(bs);
-        }
-
         assert((cluster_offset & 511) == 0);
 
         qemu_iovec_reset(&hd_qiov);

block/qcow2.h

@@ -303,6 +303,8 @@ static inline bool qcow2_need_accurate_refcounts(BDRVQcowState *s)
 /* qcow2.c functions */
 int qcow2_backing_read1(BlockDriverState *bs, QEMUIOVector *qiov,
                   int64_t sector_num, int nb_sectors);
+
+int qcow2_mark_dirty(BlockDriverState *bs);
 int qcow2_update_header(BlockDriverState *bs);
 
 /* qcow2-refcount.c functions */