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

[wangyunjian <wangyunjian@huawei.com>]

> -----Original Message-----
> From: Ferruh Yigit [mailto:ferruh.yigit@intel.com]
> Sent: Thursday, August 6, 2020 9:04 PM
> To: wangyunjian <wangyunjian@huawei.com>; dev@dpdk.org
> Cc: keith.wiles@intel.com; ophirmu@mellanox.com; Lilijun (Jerry)
> <jerry.lilijun@huawei.com>; xudingke <xudingke@huawei.com>;
> stable@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] net/tap: free mempool when closing
> 
> On 8/6/2020 1:45 PM, wangyunjian wrote:
> >
> >
> >> -----Original Message-----
> >> From: Ferruh Yigit [mailto:ferruh.yigit@intel.com]
> >> Sent: Thursday, August 6, 2020 12:36 AM
> >> To: wangyunjian <wangyunjian@huawei.com>; dev@dpdk.org
> >> Cc: keith.wiles@intel.com; ophirmu@mellanox.com; Lilijun (Jerry)
> >> <jerry.lilijun@huawei.com>; xudingke <xudingke@huawei.com>;
> >> stable@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@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@dpdk.org
> >>>
> >>> Signed-off-by: Yunjian Wang <wangyunjian@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.

Thanks for your suggestion, will include them in next version.

> 
> >
> > Do I need to split into two patches?
> 
> I think OK to have the change in this patch.

OK

> 
> >
> > Thanks,
> > Yunjian
> >