Re: [PATCH rdma-next v1 02/15] RDMA/core: Replace the ib_port_data hw_stats pointers with a ib_port pointer

[Greg KH]

On Mon, Jun 07, 2021 at 11:17:27AM +0300, Leon Romanovsky wrote:
> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> 
> It is much saner to store a pointer to the kobject structure that contains
> the cannonical stats pointer than to copy the stats pointers into a public
> structure.
> 
> Future patches will require the sysfs pointer for other purposes.
> 
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
> ---
>  drivers/infiniband/core/core_priv.h |  1 +
>  drivers/infiniband/core/nldev.c     |  8 ++------
>  drivers/infiniband/core/sysfs.c     | 14 +++++++++++---
>  include/rdma/ib_verbs.h             |  3 ++-
>  4 files changed, 16 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/infiniband/core/core_priv.h b/drivers/infiniband/core/core_priv.h
> index 29809dd30041..ec5c2c3db423 100644
> --- a/drivers/infiniband/core/core_priv.h
> +++ b/drivers/infiniband/core/core_priv.h
> @@ -378,6 +378,7 @@ struct net_device *rdma_read_gid_attr_ndev_rcu(const struct ib_gid_attr *attr);
>  
>  void ib_free_port_attrs(struct ib_core_device *coredev);
>  int ib_setup_port_attrs(struct ib_core_device *coredev);
> +struct rdma_hw_stats *ib_get_hw_stats_port(struct ib_device *ibdev, u32 port_num);
>  
>  int rdma_compatdev_set(u8 enable);
>  
> diff --git a/drivers/infiniband/core/nldev.c b/drivers/infiniband/core/nldev.c
> index 01316926cef6..e9b4b2cccaa0 100644
> --- a/drivers/infiniband/core/nldev.c
> +++ b/drivers/infiniband/core/nldev.c
> @@ -2066,7 +2066,8 @@ static int stat_get_doit_default_counter(struct sk_buff *skb,
>  	}
>  
>  	port = nla_get_u32(tb[RDMA_NLDEV_ATTR_PORT_INDEX]);
> -	if (!rdma_is_port_valid(device, port)) {
> +	stats = ib_get_hw_stats_port(device, port);
> +	if (!stats) {
>  		ret = -EINVAL;
>  		goto err;
>  	}
> @@ -2088,11 +2089,6 @@ static int stat_get_doit_default_counter(struct sk_buff *skb,
>  		goto err_msg;
>  	}
>  
> -	stats = device->port_data ? device->port_data[port].hw_stats : NULL;
> -	if (stats == NULL) {
> -		ret = -EINVAL;
> -		goto err_msg;
> -	}
>  	mutex_lock(&stats->lock);
>  
>  	num_cnts = device->ops.get_hw_stats(device, stats, port, 0);
> diff --git a/drivers/infiniband/core/sysfs.c b/drivers/infiniband/core/sysfs.c
> index d11ceff2b4e4..b153dee1e0fa 100644
> --- a/drivers/infiniband/core/sysfs.c
> +++ b/drivers/infiniband/core/sysfs.c
> @@ -1031,8 +1031,6 @@ static void setup_hw_stats(struct ib_device *device, struct ib_port *port,
>  			goto err;
>  		port->hw_stats_ag = hsag;
>  		port->hw_stats = stats;
> -		if (device->port_data)
> -			device->port_data[port_num].hw_stats = stats;
>  	} else {
>  		struct kobject *kobj = &device->dev.kobj;
>  		ret = sysfs_create_group(kobj, hsag);
> @@ -1053,6 +1051,14 @@ static void setup_hw_stats(struct ib_device *device, struct ib_port *port,
>  	kfree(stats);
>  }
>  
> +struct rdma_hw_stats *ib_get_hw_stats_port(struct ib_device *ibdev,
> +					   u32 port_num)
> +{
> +	if (!ibdev->port_data || !rdma_is_port_valid(ibdev, port_num))
> +		return NULL;
> +	return ibdev->port_data[port_num].sysfs->hw_stats;
> +}
> +
>  static int add_port(struct ib_core_device *coredev, int port_num)
>  {
>  	struct ib_device *device = rdma_device_to_ibdev(&coredev->dev);
> @@ -1171,6 +1177,8 @@ static int add_port(struct ib_core_device *coredev, int port_num)
>  		setup_hw_stats(device, p, port_num);
>  
>  	list_add_tail(&p->kobj.entry, &coredev->port_list);
> +	if (device->port_data && is_full_dev)
> +		device->port_data[port_num].sysfs = p;

You are saving off a pointer to a reference counted structure without
incrementing the reference count on it?  That's brave, and really wrong.
Properly increment/decrement it when using and when done with it.

thnaks,

greg k-h