[RFC PATCH v2 20/26] 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 | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index fb6cf8df17..acb7226e03 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -980,6 +980,22 @@ 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)) {
+            uint64_t written_from = m->cow_start.offset;
+            uint64_t written_to = m->cow_end.offset + m->cow_end.nb_bytes;
+            uint64_t l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index + i);
+            int sc;
+            for (sc = 0; sc < s->subclusters_per_cluster; sc++) {
+                uint64_t 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