From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH v2 2/5] remus: don't write xenstore data if
 it fails
Date: Tue, 5 Jan 2016 09:27:34 +0000
Message-ID: <568B8C86.9020105@citrix.com>
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To: Wen Congyang <wency@cn.fujitsu.com>, xen devel <xen-devel@lists.xen.org>
Cc: Changlong Xie <xiecl.fnst@cn.fujitsu.com>, Wei Liu <wei.liu2@citrix.com>, Ian Campbell <ian.campbell@citrix.com>, Ian Jackson <ian.jackson@eu.citrix.com>, Shriram Rajagopalan <rshriram@cs.ubc.ca>, Yang Hongyang <hongyang.yang@easystack.cn>
List-Id: xen-devel@lists.xenproject.org

On 05/01/2016 02:06, Wen Congyang wrote:

"if it fails" is ambiguous.  What I think you mean is "remus: resume
immediately if libxl__xc_domain_save_done() completes"

> For example: if the secondary host is down, and we fail to send the data to
> the secondary host. xc_domain_save() returns 0. So in the function
> libxl__xc_domain_save_done(), rc is 0(the helper program exits normally),
> and retval is 0(it is xc_domain_save()'s return value). In such case, we
> just need to complete the stream.
>
> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
> ---
>  tools/libxl/libxl_stream_write.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/tools/libxl/libxl_stream_write.c b/tools/libxl/libxl_stream_write.c
> index 80d9208..ee9c53a 100644
> --- a/tools/libxl/libxl_stream_write.c
> +++ b/tools/libxl/libxl_stream_write.c
> @@ -354,8 +354,12 @@ void libxl__xc_domain_save_done(libxl__egc *egc, void *dss_void,
>       * alive, and check_all_finished() may have torn it down around us.
>       * If the stream is not still alive, we must not continue any work.
>       */
> -    if (libxl__stream_write_inuse(stream))
> -        write_emulator_xenstore_record(egc, stream);
> +    if (libxl__stream_write_inuse(stream)) {
> +        if (dss->remus)

Please put a small comment here as well.  Perhaps

"For remus, if libxl__xc_domain_save_done() completes, there was an
error sending data to the secondary.  Resume the primary ASAP."

~Andrew

> +            stream_complete(egc, stream, 0);
> +        else
> +            write_emulator_xenstore_record(egc, stream);
> +    }
>  }
>  
>  static void write_emulator_xenstore_record(libxl__egc *egc,