From: Kevin Wolf <kwolf@redhat.com>
Date: Tue, 29 Jan 2019 12:47:24 +0000 (+0100)
Subject: qcow2: Prepare qcow2_get_cluster_type() for external data file
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=a4ea184d8af936cdc4bea4afdb5c30ffaed0c4f7;p=qemu.git

qcow2: Prepare qcow2_get_cluster_type() for external data file

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---

diff --git a/block/qcow2.h b/block/qcow2.h
index 7a34bd0c53..8fe2d55005 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -521,7 +521,15 @@ static inline QCow2ClusterType qcow2_get_cluster_type(BlockDriverState *bs,
         }
         return QCOW2_CLUSTER_ZERO_PLAIN;
     } else if (!(l2_entry & L2E_OFFSET_MASK)) {
-        return QCOW2_CLUSTER_UNALLOCATED;
+        /* Offset 0 generally means unallocated, but it is ambiguous with
+         * external data files because 0 is a valid offset there. However, all
+         * clusters in external data files always have refcount 1, so we can
+         * rely on QCOW_OFLAG_COPIED to disambiguate. */
+        if (has_data_file(bs) && (l2_entry & QCOW_OFLAG_COPIED)) {
+            return QCOW2_CLUSTER_NORMAL;
+        } else {
+            return QCOW2_CLUSTER_UNALLOCATED;
+        }
     } else {
         return QCOW2_CLUSTER_NORMAL;
     }