Re: [PATCH 08/10] tools/xenstored: Extend restore code to handle multiple input buffer

[Juergen Gross <jgross@xxxxxxxx>]

On 16.06.21 16:43, Julien Grall wrote:
> From: Julien Grall <jgrall@xxxxxxxxxx>
>
> Currently, the restore code is considering the stream will contain at
> most one in-flight request per connection. In a follow-up changes, we
> will want to transfer multiple in-flight requests.
>
> The function read_state_buffered() is now extended to restore multiple
> in-flight request. Complete requests will be queued as delayed
> requests, if there a partial request (only the last one can) then it
> will used as the current in-flight request.
>
> Note that we want to bypass the quota check for delayed requests as
> the new Xenstore may have a lower limit.
>
> Lastly, there is no need to change the specification as there was
> no restriction on the number of in-flight requests preserved.
>
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
> ---
>   tools/xenstore/xenstored_core.c | 56 ++++++++++++++++++++++++++++-----
>   1 file changed, 48 insertions(+), 8 deletions(-)
>
> diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
> index a5084a5b173d..5b7ab7f74013 100644
> --- a/tools/xenstore/xenstored_core.c
> +++ b/tools/xenstore/xenstored_core.c
> @@ -1486,6 +1486,10 @@ static void process_message(struct connection *conn, 
> struct buffered_data *in)
>         enum xsd_sockmsg_type type = in->hdr.msg.type;
>         int ret;
>   
> +	/* At least send_error() and send_reply() expects conn->in == in */
> +       assert(conn->in == in);
> +       trace_io(conn, in, 0);
> +
>   	if ((unsigned int)type >= XS_TYPE_COUNT || !wire_funcs[type].func) 
{
>                 eprintf("Client unknown operation %i", type);
>                 send_error(conn, ENOSYS);
> @@ -1515,6 +1519,23 @@ static void process_message(struct connection *conn, 
> struct buffered_data *in)
>         conn->transaction = NULL;
>   }
>   
> +static bool process_delayed_message(struct delayed_request *req)
> +{
> +       struct connection *conn = req->data;
> +       struct buffered_data *saved_in = conn->in;
> +
> +       /*
> +        * Part of process_message() expects conn->in to contains the
> +        * processed response. So save the current conn->in and restore it
> +        * afterwards.
> +        */
> +       conn->in = req->in;
> +       process_message(req->data, req->in);
> +       conn->in = saved_in;
This pattern was added to do_lu_start() already, and it will be needed
for each other function being called via call_delayed().

Maybe it would be better to add conn explicitly to struct
delayed_request (or even better: replace data with conn) and to do the
conn->in saving/setting/restoring in call_delayed() instead?

Other than that:

Reviewed-by: Juergen Gross <jgross@xxxxxxxx>


Juergen

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