[Qemu-devel] [PATCH v2 13/16] qcow2: Repair snapshot table with too many entries

[Max Reitz <mreitz@redhat.com>]

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block/qcow2-snapshot.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 366d9f574c..dac8a778e4 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -444,6 +444,14 @@ int coroutine_fn qcow2_check_read_snapshot_table(BlockDriverState *bs,
     s->snapshots_offset = be64_to_cpu(snapshot_table_pointer.snapshots_offset);
     s->nb_snapshots = be32_to_cpu(snapshot_table_pointer.nb_snapshots);
 
+    if (s->nb_snapshots > QCOW_MAX_SNAPSHOTS && (fix & BDRV_FIX_ERRORS)) {
+        fprintf(stderr, "Discarding %u overhanging snapshots\n",
+                s->nb_snapshots - QCOW_MAX_SNAPSHOTS);
+
+        nb_clusters_reduced += s->nb_snapshots - QCOW_MAX_SNAPSHOTS;
+        s->nb_snapshots = QCOW_MAX_SNAPSHOTS;
+    }
+
     ret = qcow2_validate_table(bs, s->snapshots_offset, s->nb_snapshots,
                                sizeof(QCowSnapshotHeader),
                                sizeof(QCowSnapshotHeader) * QCOW_MAX_SNAPSHOTS,
@@ -452,6 +460,12 @@ int coroutine_fn qcow2_check_read_snapshot_table(BlockDriverState *bs,
         result->check_errors++;
         error_reportf_err(local_err, "ERROR ");
 
+        if (s->nb_snapshots > QCOW_MAX_SNAPSHOTS) {
+            fprintf(stderr, "You can force-remove all %u overhanging snapshots "
+                    "with qemu-img check -r all\n",
+                    s->nb_snapshots - QCOW_MAX_SNAPSHOTS);
+        }
+
         /* We did not read the snapshot table, so invalidate this information */
         s->snapshots_offset = 0;
         s->nb_snapshots = 0;
-- 
2.21.0