Re: [PATCH RFC] driver core: ensure a device has valid node id in device_add()

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Sep 05, 2019 at 09:33:50AM +0800, Yunsheng Lin wrote:
> Currently a device does not belong to any of the numa nodes
> (dev->numa_node is NUMA_NO_NODE) when the FW does not provide
> the node id and the device has not no parent device.
> 
> According to discussion in [1]:
> Even if a device's numa node is not set by fw, the device
> really does belong to a node.
> 
> This patch sets the device node to node 0 in device_add() if
> the fw has not specified the node id and it either has no
> parent device, or the parent device also does not have a valid
> node id.
> 
> There may be explicit handling out there relying on NUMA_NO_NODE,
> like in nvme_probe().
> 
> [1] https://lkml.org/lkml/2019/9/2/466
> 
> Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
> ---
>  drivers/base/core.c  | 17 ++++++++++++++---
>  include/linux/numa.h |  2 ++
>  2 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 1669d41..466b8ff 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -2107,9 +2107,20 @@ int device_add(struct device *dev)
>  	if (kobj)
>  		dev->kobj.parent = kobj;
>  
> -	/* use parent numa_node */
> -	if (parent && (dev_to_node(dev) == NUMA_NO_NODE))
> -		set_dev_node(dev, dev_to_node(parent));
> +	/* use parent numa_node or default node 0 */
> +	if (!numa_node_valid(dev_to_node(dev))) {
> +		int nid = parent ? dev_to_node(parent) : NUMA_NO_NODE;

Can you expand this to be a "real" if statement please?

> +
> +		if (numa_node_valid(nid)) {
> +			set_dev_node(dev, nid);
> +		} else {
> +			if (nr_node_ids > 1U)
> +				pr_err("device: '%s': has invalid NUMA node(%d)\n",
> +				       dev_name(dev), dev_to_node(dev));

dev_err() will show you the exact device properly, instead of having to
rely on dev_name().

And what is a user to do if this message happens?  How do they fix this?
If they can not, what good is this error message?

thanks,

greg k-h