Re: [PATCH v2 7/7] migration: Provide explicit error message for file shutdowns

[Fabiano Rosas <farosas@suse.de>]

Peter Xu <peterx@redhat.com> writes:

> Provide an explicit reason for qemu_file_shutdown()s, which can be
> displayed in query-migrate when used.
>

Can we consider this to cover the TODO:

 * TODO: convert to propagate Error objects instead of squashing
 * to a fixed errno value

or would that need something fancier?

> This will make e.g. migrate-pause to display explicit error descriptions,
> from:
>
> "error-desc": "Channel error: Input/output error"
>
> To:
>
> "error-desc": "Channel is explicitly shutdown by the user"
>
> in query-migrate.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  migration/qemu-file.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/migration/qemu-file.c b/migration/qemu-file.c
> index 419b4092e7..ff605027de 100644
> --- a/migration/qemu-file.c
> +++ b/migration/qemu-file.c
> @@ -87,7 +87,10 @@ int qemu_file_shutdown(QEMUFile *f)
>       *      --> guest crash!
>       */
>      if (!f->last_error) {
> -        qemu_file_set_error(f, -EIO);
> +        Error *err = NULL;
> +
> +        error_setg(&err, "Channel is explicitly shutdown by the user");

It is good that we can grep this message. However, I'm confused about
who the "user" is meant to be here and how are they implicated in this
error.

> +        qemu_file_set_error_obj(f, -EIO, err);
>      }
>  
>      if (!qio_channel_has_feature(f->ioc,