[RFC PATCH v3 21/27] qcow2: Update L2 bitmap in qcow2_alloc_cluster_link_l2()

[Alberto Garcia]

The L2 bitmap needs to be updated after each write to indicate what
new subclusters are now allocated.

This needs to happen even if the cluster was already allocated and the
L2 entry was otherwise valid.

Signed-off-by: Alberto Garcia <address@hidden>
---
 block/qcow2-cluster.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 0a40944667..ed291a4042 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -986,6 +986,23 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, 
QCowL2Meta *m)
 
         set_l2_entry(s, l2_slice, l2_index + i, QCOW_OFLAG_COPIED |
                      (cluster_offset + (i << s->cluster_bits)));
+
+        /* Update bitmap with the subclusters that were just written */
+        if (has_subclusters(s)) {
+            unsigned written_from = m->cow_start.offset;
+            unsigned written_to = m->cow_end.offset + m->cow_end.nb_bytes ?:
+                m->nb_clusters << s->cluster_bits;
+            uint64_t l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index + i);
+            int sc;
+            for (sc = 0; sc < s->subclusters_per_cluster; sc++) {
+                int sc_off = i * s->cluster_size + sc * s->subcluster_size;
+                if (sc_off >= written_from && sc_off < written_to) {
+                    l2_bitmap |= QCOW_OFLAG_SUB_ALLOC(sc);
+                    l2_bitmap &= ~QCOW_OFLAG_SUB_ZERO(sc);
+                }
+            }
+            set_l2_bitmap(s, l2_slice, l2_index + i, l2_bitmap);
+        }
      }
 
 
-- 
2.20.1