Re: [PATCH v2 13/29] migration: fixed-ram: Add URI compatibility check

[Peter Xu]

On Mon, Oct 23, 2023 at 05:35:52PM -0300, Fabiano Rosas wrote:
> The fixed-ram migration format needs a channel that supports seeking
> to be able to write each page to an arbitrary offset in the migration
> stream.
> 
> Signed-off-by: Fabiano Rosas <farosas@suse.de>
> ---
>  migration/migration.c | 22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index 692fbc5ad6..cabb3ad3a5 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -106,22 +106,40 @@ static bool migration_needs_multiple_sockets(void)
>      return migrate_multifd() || migrate_postcopy_preempt();
>  }
>  
> +static bool migration_needs_seekable_channel(void)
> +{
> +    return migrate_fixed_ram();
> +}
> +
>  static bool uri_supports_multi_channels(const char *uri)
>  {
>      return strstart(uri, "tcp:", NULL) || strstart(uri, "unix:", NULL) ||
>             strstart(uri, "vsock:", NULL);
>  }
>  
> +static bool uri_supports_seeking(const char *uri)
> +{
> +    return strstart(uri, "file:", NULL);
> +}
> +
>  static bool
>  migration_channels_and_uri_compatible(const char *uri, Error **errp)
>  {
> +    bool compatible = true;
> +
> +    if (migration_needs_seekable_channel() &&
> +        !uri_supports_seeking(uri)) {
> +        error_setg(errp, "Migration requires seekable transport (e.g. 
> file)");
> +        compatible = false;

We may want to return directly after setting errp once, as error_setg() can
trigger assertion over "*errp==NULL" if below check will fail too.

> +    }
> +
>      if (migration_needs_multiple_sockets() &&
>          !uri_supports_multi_channels(uri)) {
>          error_setg(errp, "Migration requires multi-channel URIs (e.g. tcp)");
> -        return false;
> +        compatible = false;
>      }
>  
> -    return true;
> +    return compatible;
>  }
>  
>  static bool migration_should_pause(const char *uri)
> -- 
> 2.35.3
> 

-- 
Peter Xu