[RFC,20/23] qcow2: Update L2 bitmap in qcow2_alloc_cluster_link_l2()

Commit Message

Alberto Garcia Oct. 15, 2019, 3:23 p.m. UTC

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 <[e-mail]>
---
 block/qcow2-cluster.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

Patch

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 75579c1470..9a4bf672b3 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);
+        }
      }