Re: [dpdk-stable] [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 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).

Do I need to split into two patches?

Thanks,
Yunjian