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Message-ID: <725ad89a-038a-45bb-b710-24c2798f0dba@davidwei.uk>
Date: Tue, 9 Jan 2024 08:57:59 -0800
From: David Wei <dw@...idwei.uk>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Jiri Pirko <jiri@...nulli.us>, Sabrina Dubroca <sd@...asysnail.net>,
netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next v5 2/5] netdevsim: allow two netdevsim ports to
be connected
On 2024-01-03 17:39, Jakub Kicinski wrote:
> On Wed, 27 Dec 2023 17:46:30 -0800 David Wei wrote:
>> +static ssize_t nsim_dev_peer_write(struct file *file,
>> + const char __user *data,
>> + size_t count, loff_t *ppos)
>> +{
>> + struct nsim_dev_port *nsim_dev_port, *peer_dev_port;
>> + struct nsim_dev *peer_dev;
>> + unsigned int id, port;
>> + char buf[22];
>> + ssize_t ret;
>> +
>> + if (count >= sizeof(buf))
>> + return -ENOSPC;
>> +
>> + ret = copy_from_user(buf, data, count);
>> + if (ret)
>> + return -EFAULT;
>> + buf[count] = '\0';
>> +
>> + ret = sscanf(buf, "%u %u", &id, &port);
>> + if (ret != 2) {
>> + pr_err("Format is peer netdevsim \"id port\" (uint uint)\n");
>
> netif_err() or dev_err() ? Granted the rest of the file seems to use
> pr_err(), but I'm not sure why...
I can change it to use one of these two in this patchset, then I can
chnage the others separately in another patch. How does that sound?
>
>> + return -EINVAL;
>> + }
>
> Could you put a sleep() here and test removing the device while some
> thread is stuck here? I don't recall exactly but I thought debugfs
> remove waits for concurrent reads and writes which could be problematic
> given we take all the locks under the sun here..
Yep, I'll test this.
>
>> + ret = -EINVAL;
>> + mutex_lock(&nsim_dev_list_lock);
>> + peer_dev = nsim_dev_find_by_id(id);
>> + if (!peer_dev) {
>> + pr_err("Peer netdevsim %u does not exist\n", id);
>> + goto out_mutex;
>> + }
>> +
>> + devl_lock(priv_to_devlink(peer_dev));
>> + rtnl_lock();
>> + nsim_dev_port = file->private_data;
>> + peer_dev_port = __nsim_dev_port_lookup(peer_dev, NSIM_DEV_PORT_TYPE_PF,
>> + port);
>> + if (!peer_dev_port) {
>> + pr_err("Peer netdevsim %u port %u does not exist\n", id, port);
>> + goto out_devl;
>> + }
>> +
>> + if (nsim_dev_port == peer_dev_port) {
>> + pr_err("Cannot link netdevsim to itself\n");
>> + goto out_devl;
>> + }
>> +
>> + rcu_assign_pointer(nsim_dev_port->ns->peer, peer_dev_port->ns);
>> + rcu_assign_pointer(peer_dev_port->ns->peer, nsim_dev_port->ns);
>> + ret = count;
>> +
>> +out_devl:
>
> out_unlock_rtnl
>
>> + rtnl_unlock();
>> + devl_unlock(priv_to_devlink(peer_dev));
>> +out_mutex:
>
> out_unlock_dev_list
>
>> + mutex_unlock(&nsim_dev_list_lock);
>> +
>> + return ret;
>> +}
>> +
>> +static const struct file_operations nsim_dev_peer_fops = {
>> + .open = simple_open,
>> + .read = nsim_dev_peer_read,
>> + .write = nsim_dev_peer_write,
>> + .llseek = generic_file_llseek,
>
> You don't support seek, you want some form of no_seek here.
>
>> + .owner = THIS_MODULE,
>> +};
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