From b0b6862e5e1a1394e0ab3d5da94ba8b0da8664e2 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 15 Mar 2012 17:20:11 +0100 Subject: [PATCH] qcow2: Fail write_compressed when overwriting data qcow2_alloc_compressed_cluster_offset() already fails if the copied flag is set, because qcow2_write_compressed() doesn't perform COW as it would have to do to allow this. However, what we really want to check here is whether the cluster is allocated or not. With internal snapshots the copied flag may not be set on allocated clusters. Check the cluster offset instead. Signed-off-by: Kevin Wolf --- block/qcow2-cluster.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 7b059908a0..dff782fc21 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -571,15 +571,14 @@ uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs, return 0; } + /* Compression can't overwrite anything. Fail if the cluster was already + * allocated. */ cluster_offset = be64_to_cpu(l2_table[l2_index]); - if (cluster_offset & QCOW_OFLAG_COPIED) { + if (cluster_offset & L2E_OFFSET_MASK) { qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); return 0; } - if (cluster_offset) - qcow2_free_any_clusters(bs, cluster_offset, 1); - cluster_offset = qcow2_alloc_bytes(bs, compressed_size); if (cluster_offset < 0) { qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table); -- 2.11.0