Re: [PATCH 03/17] Drivers: hv: kvp: Cleanup error handling in KVP

Ben Hutchings
2012-07-25T01:11:03Z

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On Tue, 2012-07-24 at 09:01 -0700, K. Y. Srinivasan wrote:
> In preparation to implementing IP injection, cleanup the way we propagate
> and handle errors both in the driver as well as in the user level daemon.
>
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
> ---
> drivers/hv/hv_kvp.c | 112 +++++++++++++++++++++++++++++++++++++---------
> include/linux/hyperv.h | 17 +++++---
> tools/hv/hv_kvp_daemon.c | 70 +++++++++++++++-------------
> 3 files changed, 138 insertions(+), 61 deletions(-)
>
> diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
> index 0012eed..9b7fc4a 100644
> --- a/drivers/hv/hv_kvp.c
> +++ b/drivers/hv/hv_kvp.c
[...]
> @@ -109,27 +154,52 @@ kvp_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
> {
> struct hv_kvp_msg *message;
> struct hv_kvp_msg_enumerate *data;
> + int error = 0;
>
> message = (struct hv_kvp_msg *)msg->data;
> - switch (message->kvp_hdr.operation) {
> +
> + /*
> + * If we are negotiating the version information
> + * with the daemon; handle that first.
> + */
> +
> + if (in_hand_shake) {
> + if (kvp_handle_handshake(message))
> + in_hand_shake = false;
> + return;
> + }
> +
> + /*
> + * Based on the version of the daemon, we propagate errors from the
> + * daemon differently.
> + */
> +
> + data = &message->body.kvp_enum_data;
> +
> + switch (dm_reg_value) {
> case KVP_OP_REGISTER:
> - pr_info("KVP: user-mode registering done.\n");
> - kvp_register();
> - kvp_transaction.active = false;
> - hv_kvp_onchannelcallback(kvp_transaction.kvp_context);
> + /*
> + * Null string is used to pass back error condition.
> + */
> + if (!strlen(data->data.key))

Do we know that the key is null-terminated here? Shouldn't we just
check whether data->data.key[0] == 0?

> + error = HV_S_CONT;
> break;
>
> - default:
> - data = &message->body.kvp_enum_data;
> + case KVP_OP_REGISTER1:
> /*
> - * Complete the transaction by forwarding the key value
> - * to the host. But first, cancel the timeout.
> + * We use the message header information from
> + * the user level daemon to transmit errors.
> */
> - if (cancel_delayed_work_sync(&kvp_work))
> - kvp_respond_to_host(data->data.key,
> - data->data.value,
> - !strlen(data->data.key));
> + error = *((int *)(&message->kvp_hdr.operation));
[...]

What's with the casting (repeated in many other places)? Wouldn't it be
better to redefine struct hv_kvp_msg to start with something like:

union {
struct hv_kvp_hdr request;
int error;
} kvp_hdr;

Ben.

--
Ben Hutchings
If more than one person is responsible for a bug, no one is at fault.

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