[dpdk-stable] [dpdk-dev] [PATCH] net/tap: free mempool when closing

[Ferruh Yigit]

On 8/6/2020 1:45 PM, wangyunjian wrote:
> 
> 
>> -----Original Message-----
>> From: Ferruh Yigit [mailto:ferruh.yigit at intel.com]
>> Sent: Thursday, August 6, 2020 12:36 AM
>> To: wangyunjian <wangyunjian at huawei.com>; dev at dpdk.org
>> Cc: keith.wiles at intel.com; ophirmu at mellanox.com; Lilijun (Jerry)
>> <jerry.lilijun at huawei.com>; xudingke <xudingke at huawei.com>;
>> stable at dpdk.org
>> Subject: Re: [dpdk-dev] [PATCH] net/tap: free mempool when closing
>>
>> On 7/29/2020 12:35 PM, wangyunjian wrote:
>>> From: Yunjian Wang <wangyunjian at huawei.com>
>>>
>>> When setup tx queues, we will create a mempool for the 'gso_ctx'.
>>> The mempool is not freed when closing tap device. If free the tap
>>> device and create it with different name, it will create a new
>>> mempool. This maybe cause an OOM.
>>>
>>> Fixes: 050316a88313 ("net/tap: support TSO (TCP Segment Offload)")
>>> Cc: stable at dpdk.org
>>>
>>> Signed-off-by: Yunjian Wang <wangyunjian at huawei.com>
>>
>> <...>
>>
>>> @@ -1317,26 +1320,31 @@ tap_gso_ctx_setup(struct rte_gso_ctx *gso_ctx,
>> struct rte_eth_dev *dev)
>>>  {
>>>  	uint32_t gso_types;
>>>  	char pool_name[64];
>>> -
>>> -	/*
>>> -	 * Create private mbuf pool with TAP_GSO_MBUF_SEG_SIZE bytes
>>> -	 * size per mbuf use this pool for both direct and indirect mbufs
>>> -	 */
>>> -
>>> -	struct rte_mempool *mp;      /* Mempool for GSO packets */
>>> +	struct pmd_internals *pmd = dev->data->dev_private;
>>> +	int ret;
>>>
>>>  	/* initialize GSO context */
>>>  	gso_types = DEV_TX_OFFLOAD_TCP_TSO;
>>> -	snprintf(pool_name, sizeof(pool_name), "mp_%s", dev->device->name);
>>> -	mp = rte_mempool_lookup((const char *)pool_name);
>>> -	if (!mp) {
>>> -		mp = rte_pktmbuf_pool_create(pool_name, TAP_GSO_MBUFS_NUM,
>>> -			TAP_GSO_MBUF_CACHE_SIZE, 0,
>>> +	if (!pmd->gso_ctx_mp) {
>>> +		/*
>>> +		 * Create private mbuf pool with TAP_GSO_MBUF_SEG_SIZE
>>> +		 * bytes size per mbuf use this pool for both direct and
>>> +		 * indirect mbufs
>>> +		 */
>>> +		ret = snprintf(pool_name, sizeof(pool_name), "mp_%s",
>>> +				dev->device->name);
>>> +		if (ret < 0 || ret >= (int)sizeof(pool_name)) {
>>> +			TAP_LOG(ERR,
>>> +				"%s: failed to create mbuf pool "
>>> +				"name for device %s\n",
>>> +				pmd->name, dev->device->name);
>>
>> Overall looks good. Only above error doesn't say why it failed, informing the
>> user that device name is too long may help her to overcome the error.
> 
> I found that the return value of functions snprintf was not checked
> when modifying the code, so fixed it.
> I think it maybe fail, because the max device name length is
> RTE_DEV_NAME_MAX_LEN(64).

+1 to the check.
My comment was on the log message, which says "failed to create mbuf pool", but
it doesn't say it is failed because of long device name.
If user knows the reason of the failure, can prevent it by providing shorter
device name.
My suggestion is update the error log message to have the reason of failure.

> 
> Do I need to split into two patches?

I think OK to have the change in this patch.

> 
> Thanks,
> Yunjian
>