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qcow2: Prepare qcow2_get_cluster_type() for external data file

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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf
2019-03-08 12:26:45 +01:00
parent 808c2bb4c4
commit a4ea184d8a
1 changed files with 9 additions and 1 deletions
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block/qcow2.h
+9 -1
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@@ -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;
}