Re: [PATCH v3 2/6] nbd: disallow NBD_SET_SOCK on an active device

Hi,

在 2026/7/13 14:56, Yang Erkun 写道:
> We cannot add a socket to an already running nbd device, the reconfigure
> for netlink can only active dead socket. But for ioctl path, we can call
> NBD_SET_SOCK after NBD_DO_IT, reject this using nbd->pid which has been
> setted when NBD_DO_IT. Besides, it is the root cause for commit
> b98e762e3d71 ("nbd: freeze the queue while we're adding connections").
>
> Signed-off-by: Yang Erkun <[email protected]>
> ---
>   drivers/block/nbd.c | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index b1a5acd57426..a15553ab4b97 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -1302,6 +1302,13 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
>   		goto put_socket;
>   	}
>   
> +	if (nbd->pid) {
> +		dev_err(disk_to_dev(nbd->disk),
> +			"Cannot add socket to a running device\n");
> +		err = -EBUSY;
> +		goto put_socket;
> +	}

I think the checking if fine, but I'd like to add the checking before nbd_get_socket() and
return -EBUSY directly.

> +
>   	nsock = kzalloc_obj(*nsock);
>   	if (!nsock) {
>   		err = -ENOMEM;

-- 
Thanks,
Kuai