[Qemu-devel] [PATCH V4 3/6] qcow2: do not free clusters when fail in header update in qcow2_write_snapshots

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
---
 block/qcow2-snapshot.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 4bd494b..c933b7f 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -304,6 +304,13 @@ static int qcow2_write_snapshots(BlockDriverState *bs, Error **errp)
                    PRIi64 " with size %" PRIu64 ":%d (%s)",
                    offsetof(QCowHeader, nb_snapshots), sizeof(header_data),
                    ret, strerror(-ret));
+        /*
+         * If the snapshot data part have been updated on disk, Then the
+         * clusters at snapshot_offset may be used in next snapshot operation.
+         * If we free those clusters in fail path, they may be allocated and
+         * made dirty causing damage, so skip cluster free for safe.
+         */
+        snapshots_offset = 0;
         goto fail;
     }
 
-- 
1.7.1