Merge remote-tracking branch 'kwolf/for-anthony' into staging

* kwolf/for-anthony:
  fdc: simplify media change handling
  qcow2: lock on prealloc
  block: make bdrv_create adopt coroutine
  qcow2: Limit COW to where it's needed
  sheepdog: switch to writethrough mode if cluster doesn't support flush

1 files changed, 9 insertions, 5 deletions

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 353889d41b..10c22fe12b 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -883,15 +883,19 @@ again:
         assert(keep_clusters <= nb_clusters);
         nb_clusters -= keep_clusters;
     } else {
+        keep_clusters = 0;
+        cluster_offset = 0;
+    }
+
+    if (nb_clusters > 0) {
         /* For the moment, overwrite compressed clusters one by one */
-        if (cluster_offset & QCOW_OFLAG_COMPRESSED) {
+        uint64_t entry = be64_to_cpu(l2_table[l2_index + keep_clusters]);
+        if (entry & QCOW_OFLAG_COMPRESSED) {
             nb_clusters = 1;
         } else {
-            nb_clusters = count_cow_clusters(s, nb_clusters, l2_table, l2_index);
+            nb_clusters = count_cow_clusters(s, nb_clusters, l2_table,
+                                             l2_index + keep_clusters);
         }
-
-        keep_clusters = 0;
-        cluster_offset = 0;
     }
 
     cluster_offset &= L2E_OFFSET_MASK;