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Subject: Re: [PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused by
 incorrect clean-up
To:     Greg KH <gregkh@linuxfoundation.org>, kys@microsoft.com
Cc:     linux-kernel@vger.kernel.org, devel@linuxdriverproject.org,
        olaf@aepfle.de, apw@canonical.com, jasowang@redhat.com,
        sthemmin@microsoft.com, Michael.H.Kelley@microsoft.com,
        vkuznets@redhat.com, Haiyang Zhang <haiyangz@microsoft.com>,
        Stable@vger.kernel.org
References: <20181017031241.669-1-kys@linuxonhyperv.com>
 <20181017031406.773-1-kys@linuxonhyperv.com>
 <20181017031406.773-3-kys@linuxonhyperv.com>
 <20181017050705.GE22447@kroah.com>
From:   "Gustavo A. R. Silva" <gustavo@embeddedor.com>
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Message-ID: <79b91529-7c20-a0ad-7dc9-9b7ca89f4792@embeddedor.com>
Date:   Wed, 17 Oct 2018 07:11:49 +0200
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On 10/17/18 7:07 AM, Greg KH wrote:
> On Wed, Oct 17, 2018 at 03:14:04AM +0000, kys@linuxonhyperv.com wrote:
>> From: Dexuan Cui <decui@microsoft.com>
>>
>> In kvp_send_key(), we do need call process_ib_ipinfo() if
>> message->kvp_hdr.operation is KVP_OP_GET_IP_INFO, because it turns out
>> the userland hv_kvp_daemon needs the info of operation, adapter_id and
>> addr_family. With the incorrect fc62c3b1977d, the host can't get the
>> VM's IP via KVP.
>>
>> And, fc62c3b1977d added a "break;", but actually forgot to initialize
>> the key_size/value in the case of KVP_OP_SET, so the default key_size of
>> 0 is passed to the kvp daemon, and the pool files
>> /var/lib/hyperv/.kvp_pool_* can't be updated.
>>
>> This patch effectively rolls back the previous fc62c3b1977d, and
>> correctly fixes the "this statement may fall through" warnings.
>>
>> This patch is tested on WS 2012 R2 and 2016.
>>
>> Fixes: fc62c3b1977d ("Drivers: hv: kvp: Fix two "this statement may fall through" warnings")
>> Signed-off-by: Dexuan Cui <decui@microsoft.com>
>> Cc: K. Y. Srinivasan <kys@microsoft.com>
>> Cc: Haiyang Zhang <haiyangz@microsoft.com>
>> Cc: Stephen Hemminger <sthemmin@microsoft.com>
>> Cc: <Stable@vger.kernel.org>
>> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
>> ---
>>  drivers/hv/hv_kvp.c | 26 ++++++++++++++++++++++----
>>  1 file changed, 22 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
>> index a7513a8a8e37..9fbb15c62c6c 100644
>> --- a/drivers/hv/hv_kvp.c
>> +++ b/drivers/hv/hv_kvp.c
>> @@ -353,6 +353,9 @@ static void process_ib_ipinfo(void *in_msg, void *out_msg, int op)
>>  
>>  		out->body.kvp_ip_val.dhcp_enabled = in->kvp_ip_val.dhcp_enabled;
>>  
>> +		__attribute__ ((fallthrough));
> 
> The comment should be sufficient for this, right?  I haven't seen many
> uses of this attribute before, how common is it?
> 

It's not common at all.

Dexuan, please use a comment instead: /* fall through */

Thanks
--
Gustavo

> 
>> +
>> +	case KVP_OP_GET_IP_INFO:
>>  		utf16s_to_utf8s((wchar_t *)in->kvp_ip_val.adapter_id,
>>  				MAX_ADAPTER_ID_SIZE,
>>  				UTF16_LITTLE_ENDIAN,
>> @@ -405,7 +408,11 @@ kvp_send_key(struct work_struct *dummy)
>>  		process_ib_ipinfo(in_msg, message, KVP_OP_SET_IP_INFO);
>>  		break;
>>  	case KVP_OP_GET_IP_INFO:
>> -		/* We only need to pass on message->kvp_hdr.operation.  */
>> +		/*
>> +		 * We only need to pass on the info of operation, adapter_id
>> +		 * and addr_family to the userland kvp daemon.
>> +		 */
>> +		process_ib_ipinfo(in_msg, message, KVP_OP_GET_IP_INFO);
>>  		break;
>>  	case KVP_OP_SET:
>>  		switch (in_msg->body.kvp_set.data.value_type) {
>> @@ -446,9 +453,9 @@ kvp_send_key(struct work_struct *dummy)
>>  
>>  		}
>>  
>> -		break;
>> -
>> -	case KVP_OP_GET:
>> +		/*
>> +		 * The key is always a string - utf16 encoding.
>> +		 */
>>  		message->body.kvp_set.data.key_size =
>>  			utf16s_to_utf8s(
>>  			(wchar_t *)in_msg->body.kvp_set.data.key,
>> @@ -456,6 +463,17 @@ kvp_send_key(struct work_struct *dummy)
>>  			UTF16_LITTLE_ENDIAN,
>>  			message->body.kvp_set.data.key,
>>  			HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1) + 1;
>> +
>> +		break;
>> +
>> +	case KVP_OP_GET:
>> +		message->body.kvp_get.data.key_size =
>> +			utf16s_to_utf8s(
>> +			(wchar_t *)in_msg->body.kvp_get.data.key,
>> +			in_msg->body.kvp_get.data.key_size,
>> +			UTF16_LITTLE_ENDIAN,
>> +			message->body.kvp_get.data.key,
>> +			HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1) + 1;
> 
> Worst indentation ever :(
> 
> Yeah, I know it follows the others above it, but you should reconsider
> it in the future...
> 
> thanks,
> 
> greg k-h
>