qcow2: Flushing the caches in qcow2_close may fail

qcow2_cache_flush() may fail; if one of the caches failed to be flushed
successfully to disk in qcow2_close() the image should not be marked
clean, and we should emit a warning.

This breaks the (qcow2-specific) iotests 026, 071 and 089; change their
output accordingly.

Cc: qemu-stable@nongnu.org
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/qcow2.c

@@ -1428,10 +1428,23 @@ static void qcow2_close(BlockDriverState *bs)
     s->l1_table = NULL;
 
     if (!(bs->open_flags & BDRV_O_INCOMING)) {
-        qcow2_cache_flush(bs, s->l2_table_cache);
-        qcow2_cache_flush(bs, s->refcount_block_cache);
+        int ret1, ret2;
 
-        qcow2_mark_clean(bs);
+        ret1 = qcow2_cache_flush(bs, s->l2_table_cache);
+        ret2 = qcow2_cache_flush(bs, s->refcount_block_cache);
+
+        if (ret1) {
+            error_report("Failed to flush the L2 table cache: %s",
+                         strerror(-ret1));
+        }
+        if (ret2) {
+            error_report("Failed to flush the refcount block cache: %s",
+                         strerror(-ret2));
+        }
+
+        if (!ret1 && !ret2) {
+            qcow2_mark_clean(bs);
+        }
     }
 
     qcow2_cache_destroy(bs, s->l2_table_cache);