[PATCH] block/qcow2-cluster: Add missing "fallthrough" annotation

[Thomas Huth <thuth@redhat.com>]

When compiling with -Werror=implicit-fallthrough, the compiler currently
complains:

../../devel/qemu/block/qcow2-cluster.c: In function ‘cluster_needs_new_alloc’:
../../devel/qemu/block/qcow2-cluster.c:1320:12: error: this statement may fall
 through [-Werror=implicit-fallthrough=]
         if (l2_entry & QCOW_OFLAG_COPIED) {
            ^
../../devel/qemu/block/qcow2-cluster.c:1323:5: note: here
     case QCOW2_CLUSTER_UNALLOCATED:
     ^~~~

It's quite obvious that the fallthrough is intended here, so let's add
a comment to silence the compiler warning.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 block/qcow2-cluster.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 996b3314f4..fcdf7af8e6 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1320,6 +1320,7 @@ static bool cluster_needs_new_alloc(BlockDriverState *bs, uint64_t l2_entry)
         if (l2_entry & QCOW_OFLAG_COPIED) {
             return false;
         }
+        /* fallthrough */
     case QCOW2_CLUSTER_UNALLOCATED:
     case QCOW2_CLUSTER_COMPRESSED:
     case QCOW2_CLUSTER_ZERO_PLAIN:
-- 
2.18.2