netdev - Re: [PATCH net-next 01/10] net/smc: add missing dev

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Message-Id: <7961df23-1603-7853-5f3e-f31095aebba0@linux.vnet.ibm.com>
Date:   Thu, 5 Oct 2017 09:54:08 +0200
From:   Ursula Braun <ubraun@...ux.vnet.ibm.com>
To:     Parav Pandit <parav@...lanox.com>
Cc:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "jwi@...ux.vnet.ibm.com" <jwi@...ux.vnet.ibm.com>,
        "schwidefsky@...ibm.com" <schwidefsky@...ibm.com>,
        "heiko.carstens@...ibm.com" <heiko.carstens@...ibm.com>,
        "raspl@...ux.vnet.ibm.com" <raspl@...ux.vnet.ibm.com>
Subject: Re: [PATCH net-next 01/10] net/smc: add missing dev_put



On 10/02/2017 10:36 PM, Parav Pandit wrote:
> Hi Ursula, Dave, Hans,
> 
>> -----Original Message-----
>> From: linux-rdma-owner@...r.kernel.org [mailto:linux-rdma-
>> owner@...r.kernel.org] On Behalf Of Ursula Braun
>> Sent: Wednesday, September 20, 2017 6:58 AM
>> To: davem@...emloft.net
>> Cc: netdev@...r.kernel.org; linux-rdma@...r.kernel.org; linux-
>> s390@...r.kernel.org; jwi@...ux.vnet.ibm.com; schwidefsky@...ibm.com;
>> heiko.carstens@...ibm.com; raspl@...ux.vnet.ibm.com;
>> ubraun@...ux.vnet.ibm.com
>> Subject: [PATCH net-next 01/10] net/smc: add missing dev_put
>>
>> From: Hans Wippel <hwippel@...ux.vnet.ibm.com>
>>
>> In the infiniband part, SMC currently uses get_netdev which calls dev_hold on
>> the returned net device. However, the SMC code never calls dev_put on that net
>> device resulting in a wrong reference count.
>>
>> This patch adds a dev_put after the usage of the net device to fix the issue.
>>
>> Signed-off-by: Hans Wippel <hwippel@...ux.vnet.ibm.com>
>> Signed-off-by: Ursula Braun <ubraun@...ux.vnet.ibm.com>
>> ---
>>  net/smc/smc_ib.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/net/smc/smc_ib.c b/net/smc/smc_ib.c index
>> 547e0e113b17..0b5852299158 100644
>> --- a/net/smc/smc_ib.c
>> +++ b/net/smc/smc_ib.c
>> @@ -380,6 +380,7 @@ static int smc_ib_fill_gid_and_mac(struct smc_ib_device
>> *smcibdev, u8 ibport)
>>  	ndev = smcibdev->ibdev->get_netdev(smcibdev->ibdev, ibport);
>>  	if (ndev) {
>>  		memcpy(&smcibdev->mac, ndev->dev_addr, ETH_ALEN);
>> +		dev_put(ndev);
> 
> I am sorry for providing late comments. smc_ib_fill_gid_and_mac() is not coded correctly.
> Few fixes are needed.
> 1. ULP such as SMC should not open code/deference any function pointer like get_netdev() of the IB device.
> 2. Replace ib_query_gid(..., NULL)
> With
> ib_query_gid(..., gid_attr);
> 
> Use gid_attr.ndev to get the MAC address.
> Do dev_put(gid_attr.ndev);
> 
> Code should look like below,
> 
> struct ib_gid_attr gid_attr;
> 
> rc = ib_query_gid(..., &gid_attr);
> if (rc || !gid_addr.ndev)
> 	return -ENODEV;
> else
> 	memcpy(smcibdev->mac, ndev->dev_addr, ETH_ALEN);
> dev_put(gid_addr.ndev);
> 

Thanks, Parav!
Following your fix ideas I plan to change the function into this one:

static int smc_ib_fill_gid_and_mac(struct smc_ib_device *smcibdev, u8 ibport)
{
        struct ib_gid_attr gattr;
        int rc;

        rc = ib_query_gid(smcibdev->ibdev, ibport, 0,
                          &smcibdev->gid[ibport - 1], &gattr);
        /* the SMC protocol requires specification of the roce MAC address;
         * if net_device cannot be determined, it can be derived from gid 0
         */
        if (rc)
                return rc;

        if (gattr.ndev) {
                memcpy(&smcibdev->mac, gattr.ndev->dev_addr, ETH_ALEN);
                dev_put(gattr.ndev);
        } else {
                memcpy(&smcibdev->mac[ibport - 1][0],
                       &smcibdev->gid[ibport - 1].raw[8], 3);
                memcpy(&smcibdev->mac[ibport - 1][3],
                       &smcibdev->gid[ibport - 1].raw[13], 3);
                smcibdev->mac[ibport - 1][0] &= ~0x02;
        }
        return 0;
}

If you agree, I will submit the corresponding patch including a
	Suggested-by: Parav Pandit <parav@...lanox.com>

Regards, Ursula