Re: [dpdk-dev] [PATCH v4] net/tap: fix device removal when no queues exist

["Wiles, Keith" <keith.wiles@intel.com>]

> On May 22, 2018, at 11:50 PM, Varghese, Vipin <vipin.varghese@intel.com> wrote:
> 
> Hi Ophir,
> 
> One suggestion shared inline to email
> 
> <Snipped>
> 
>> 
>> diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c index
>> c006d07..52ef799 100644
>> --- a/drivers/net/tap/rte_eth_tap.c
>> +++ b/drivers/net/tap/rte_eth_tap.c
>> @@ -929,6 +929,15 @@ tap_dev_close(struct rte_eth_dev *dev)
>> 		ioctl(internals->ioctl_sock, SIOCSIFFLAGS,
>> 				&internals->remote_initial_flags);
>> 	}
>> +
>> +	if (internals->ka_fd != -1) {
>> +		close(internals->ka_fd);
> 
> Do we need to notify the user which fd is been closed via LOG DEBUG?

Why would we want to have a LOG DEBUG here, it would make the debug output a bit chatty IMO. I mean you could have one, but it seems ok as it is to me.

> 
>> +		internals->ka_fd = -1;
>> +	}
>> +	/*
>> +	 * Since TUN device has no more opened file descriptors
>> +	 * it will be removed from kernel
>> +	 */
>> }
>> 
>> static void
>> @@ -1549,6 +1558,7 @@ eth_dev_tap_create(struct rte_vdev_device *vdev,
>> char *tap_name,
>> 	dev->intr_handle = &pmd->intr_handle;
>> 
>> 	/* Presetup the fds to -1 as being not valid */
>> +	pmd->ka_fd = -1;
>> 	for (i = 0; i < RTE_PMD_TAP_MAX_QUEUES; i++) {
>> 		pmd->rxq[i].fd = -1;
>> 		pmd->txq[i].fd = -1;
>> @@ -1561,13 +1571,17 @@ eth_dev_tap_create(struct rte_vdev_device *vdev,
>> char *tap_name,
>> 			rte_memcpy(&pmd->eth_addr, mac_addr,
>> sizeof(*mac_addr));
>> 	}
>> 
>> -	/* Immediately create the netdevice (this will create the 1st queue). */
>> -	/* rx queue */
>> -	if (tap_setup_queue(dev, pmd, 0, 1) == -1)
>> -		goto error_exit;
>> -	/* tx queue */
>> -	if (tap_setup_queue(dev, pmd, 0, 0) == -1)
>> +	/*
>> +	 * Allocate a TUN device keep-alive file descriptor that will only be
>> +	 * closed when the TUN device itself is closed or removed.
>> +	 * This keep-alive file descriptor will guarantee that the TUN device
>> +	 * exists even when all of its queues are closed
>> +	 */
>> +	pmd->ka_fd = tun_alloc(pmd);
>> +	if (pmd->ka_fd == -1) {
>> +		TAP_LOG(ERR, "Unable to create %s interface", tuntap_name);
>> 		goto error_exit;
>> +	}
>> 
>> 	ifr.ifr_mtu = dev->data->mtu;
>> 	if (tap_ioctl(pmd, SIOCSIFMTU, &ifr, 1, LOCAL_AND_REMOTE) < 0) @@
>> -1961,9 +1975,12 @@ rte_pmd_tap_remove(struct rte_vdev_device *dev)
>> 
>> 	close(internals->ioctl_sock);
>> 	rte_free(eth_dev->data->dev_private);
>> -
>> 	rte_eth_dev_release_port(eth_dev);
>> 
>> +	if (internals->ka_fd != -1) {
>> +		close(internals->ka_fd);
>> +		internals->ka_fd = -1;
>> +	}
>> 	return 0;
>> }
>> 
>> diff --git a/drivers/net/tap/rte_eth_tap.h b/drivers/net/tap/rte_eth_tap.h index
>> babe42d..575dce4 100644
>> --- a/drivers/net/tap/rte_eth_tap.h
>> +++ b/drivers/net/tap/rte_eth_tap.h
>> @@ -81,6 +81,7 @@ struct pmd_internals {
>> 	struct rx_queue rxq[RTE_PMD_TAP_MAX_QUEUES]; /* List of RX
>> queues */
>> 	struct tx_queue txq[RTE_PMD_TAP_MAX_QUEUES]; /* List of TX queues
>> */
>> 	struct rte_intr_handle intr_handle;          /* LSC interrupt handle. */
>> +	int ka_fd;                        /* keep-alive file descriptor */
>> };
>> 
>> /* tap_intr.c */
>> --
>> 2.7.4
> 

Regards,
Keith