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Subject: Re: [PATCH rdma-next] RDMA/core: Use pr_warn_ratelimited
To:     Parav Pandit <parav@mellanox.com>,
        "dledford@redhat.com" <dledford@redhat.com>,
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On 2019/11/5 12:09, Parav Pandit wrote:
> Hi Yixian Liu,
> 
>> -----Original Message-----
>> From: linux-rdma-owner@vger.kernel.org <linux-rdma-
>> owner@vger.kernel.org> On Behalf Of Yixian Liu
>> Sent: Monday, November 4, 2019 9:48 PM
>> To: dledford@redhat.com; jgg@ziepe.ca
>> Cc: Parav Pandit <parav@mellanox.com>; leon@kernel.org; linux-
>> rdma@vger.kernel.org; linuxarm@huawei.com
>> Subject: [PATCH rdma-next] RDMA/core: Use pr_warn_ratelimited
>>
>> This warning can be triggered easily when adding a large number of VLANs
>> while the capacity of GID table is small.
>>
>> Fixes: 598ff6bae689 ("IB/core: Refactor GID modify code for RoCE")
>> Signed-off-by: Yixian Liu <liuyixian@huawei.com>
>> ---
>>  drivers/infiniband/core/cache.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
> Thanks for the patch. However, vlan netdevice addition is an administrative operation allowed to process which has CAP_NET_ADMIN privilege.
> So large number of VLAN addition by a user for a RoCE device whose GID capacity is small is constrained operation.

How can we constrain this operation from an administrator?

> Therefore, we shouldn't be rate limiting it.
> By rate limiting we miss the information about any bugs in GID cache management.

pr_warn_ratelimited only prevent from printing **the same messages** frequently, why information will be lost?

> At best we can convert it to dev_dbg() so that we still get the necessary debug information when needed.
> I wanted to convert them trace functions which will allow us to more debug level prints such as netdev name, vlan etc.
> I think I remember comment from Leon too while working on it, but it was long haul that time.
> 
> Its base infrastructure is just got ready with Chuck Lever's patch.
> So around 5.5, I should convert to trace calls.

Okay, whatever, the situation described in commit message may be occurred, please consider it.

> 
>> diff --git a/drivers/infiniband/core/cache.c b/drivers/infiniband/core/cache.c
>> index 00fb3ea..2990075 100644
>> --- a/drivers/infiniband/core/cache.c
>> +++ b/drivers/infiniband/core/cache.c
>> @@ -579,8 +579,8 @@ static int __ib_cache_gid_add(struct ib_device
>> *ib_dev, u8 port,
>>  out_unlock:
>>  	mutex_unlock(&table->lock);
>>  	if (ret)
>> -		pr_warn("%s: unable to add gid %pI6 error=%d\n",
>> -			__func__, gid->raw, ret);
>> +		pr_warn_ratelimited("%s: unable to add gid %pI6
>> error=%d\n",
>> +				    __func__, gid->raw, ret);
>>  	return ret;
>>  }
>>
>> --
>> 2.7.4
> 
> 
>