external_snapshot_action() reports bdrv_flush() failure to its caller
as

    An IO error has occurred

The errno code returned by bdrv_flush() is lost.

Improve this to

    Write to node '<device or node name>' failed: <description of errno>

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 blockdev.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 08eccc9052..528db3452f 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1406,8 +1406,10 @@ static void external_snapshot_action(TransactionAction *action,
     }
 
     if (!bdrv_is_read_only(state->old_bs)) {
-        if (bdrv_flush(state->old_bs)) {
-            error_setg(errp, QERR_IO_ERROR);
+        ret = bdrv_flush(state->old_bs);
+        if (ret < 0) {
+            error_setg_errno(errp, -ret, "Write to node '%s' failed",
+                             bdrv_get_device_or_node_name(state->old_bs));
             return;
         }
     }
-- 
2.45.0

On 13/5/24 16:16, Markus Armbruster wrote:
> external_snapshot_action() reports bdrv_flush() failure to its caller
> as
> 
>      An IO error has occurred
> 
> The errno code returned by bdrv_flush() is lost.
> 
> Improve this to
> 
>      Write to node '<device or node name>' failed: <description of errno>
> 
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
>   blockdev.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>