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Date: Fri, 9 Jun 2023 20:50:07 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, pabeni@...hat.com,
dsahern@...il.com
Subject: Re: [PATCH net-next 1/2] net: create device lookup API with reference tracking
On Fri, Jun 9, 2023 at 8:32 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> New users of dev_get_by_index() and dev_get_by_name() keep
> getting added and it would be nice to steer them towards
> the APIs with reference tracking.
>
> Add variants of those calls which allocate the reference
> tracker and use them in a couple of places.
>
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
> include/linux/netdevice.h | 4 +++
> net/core/dev.c | 75 ++++++++++++++++++++++++++-------------
> net/ethtool/netlink.c | 8 ++---
> net/ipv6/route.c | 12 +++----
> 4 files changed, 65 insertions(+), 34 deletions(-)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index c2f0c6002a84..732d7a226e93 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -3124,6 +3124,10 @@ struct net_device *netdev_sk_get_lowest_dev(struct net_device *dev,
> struct sock *sk);
> struct net_device *dev_get_by_index(struct net *net, int ifindex);
> struct net_device *__dev_get_by_index(struct net *net, int ifindex);
> +struct net_device *netdev_get_by_index(struct net *net, int ifindex,
> + netdevice_tracker *tracker, gfp_t gfp);
> +struct net_device *netdev_get_by_name(struct net *net, const char *name,
> + netdevice_tracker *tracker, gfp_t gfp);
> struct net_device *dev_get_by_index_rcu(struct net *net, int ifindex);
> struct net_device *dev_get_by_napi_id(unsigned int napi_id);
> int dev_restart(struct net_device *dev);
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 6d6f8a7fe6b4..0e9419d220bf 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -758,18 +758,7 @@ struct net_device *dev_get_by_name_rcu(struct net *net, const char *name)
> }
> EXPORT_SYMBOL(dev_get_by_name_rcu);
>
> -/**
> - * dev_get_by_name - find a device by its name
> - * @net: the applicable net namespace
> - * @name: name to find
> - *
> - * Find an interface by name. This can be called from any
> - * context and does its own locking. The returned handle has
> - * the usage count incremented and the caller must use dev_put() to
> - * release it when it is no longer needed. %NULL is returned if no
> - * matching device is found.
> - */
> -
> +/* Deprecated for new users, call netdev_get_by_name() instead */
> struct net_device *dev_get_by_name(struct net *net, const char *name)
> {
> struct net_device *dev;
> @@ -782,6 +771,31 @@ struct net_device *dev_get_by_name(struct net *net, const char *name)
> }
> EXPORT_SYMBOL(dev_get_by_name);
>
> +/**
> + * netdev_get_by_name() - find a device by its name
> + * @net: the applicable net namespace
> + * @name: name to find
> + * @tracker: tracking object for the acquired reference
> + * @gfp: allocation flags for the tracker
> + *
> + * Find an interface by name. This can be called from any
> + * context and does its own locking. The returned handle has
> + * the usage count incremented and the caller must use netdev_put() to
> + * release it when it is no longer needed. %NULL is returned if no
> + * matching device is found.
> + */
> +struct net_device *netdev_get_by_name(struct net *net, const char *name,
> + netdevice_tracker *tracker, gfp_t gfp)
> +{
> + struct net_device *dev;
> +
> + dev = dev_get_by_name(net, name);
> + if (dev)
> + netdev_tracker_alloc(dev, tracker, gfp);
> + return dev;
> +}
> +EXPORT_SYMBOL(netdev_get_by_name);
> +
> /**
> * __dev_get_by_index - find a device by its ifindex
> * @net: the applicable net namespace
> @@ -831,18 +845,7 @@ struct net_device *dev_get_by_index_rcu(struct net *net, int ifindex)
> }
> EXPORT_SYMBOL(dev_get_by_index_rcu);
>
> -
> -/**
> - * dev_get_by_index - find a device by its ifindex
> - * @net: the applicable net namespace
> - * @ifindex: index of device
> - *
> - * Search for an interface by index. Returns NULL if the device
> - * is not found or a pointer to the device. The device returned has
> - * had a reference added and the pointer is safe until the user calls
> - * dev_put to indicate they have finished with it.
> - */
> -
> +/* Deprecated for new users, call netdev_get_by_index() instead */
> struct net_device *dev_get_by_index(struct net *net, int ifindex)
> {
> struct net_device *dev;
> @@ -855,6 +858,30 @@ struct net_device *dev_get_by_index(struct net *net, int ifindex)
> }
> EXPORT_SYMBOL(dev_get_by_index);
>
> +/**
> + * netdev_get_by_index() - find a device by its ifindex
> + * @net: the applicable net namespace
> + * @ifindex: index of device
> + * @tracker: tracking object for the acquired reference
> + * @gfp: allocation flags for the tracker
> + *
> + * Search for an interface by index. Returns NULL if the device
> + * is not found or a pointer to the device. The device returned has
> + * had a reference added and the pointer is safe until the user calls
> + * netdev_put() to indicate they have finished with it.
> + */
> +struct net_device *netdev_get_by_index(struct net *net, int ifindex,
> + netdevice_tracker *tracker, gfp_t gfp)
> +{
> + struct net_device *dev;
> +
> + dev = dev_get_by_index(net, ifindex);
> + if (dev)
> + netdev_tracker_alloc(dev, tracker, gfp);
> + return dev;
> +}
> +EXPORT_SYMBOL(netdev_get_by_index);
> +
> /**
> * dev_get_by_napi_id - find a device by napi_id
> * @napi_id: ID of the NAPI struct
> diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
> index 08120095cc68..107ef80e48e1 100644
> --- a/net/ethtool/netlink.c
> +++ b/net/ethtool/netlink.c
> @@ -113,7 +113,8 @@ int ethnl_parse_header_dev_get(struct ethnl_req_info *req_info,
> if (tb[ETHTOOL_A_HEADER_DEV_INDEX]) {
> u32 ifindex = nla_get_u32(tb[ETHTOOL_A_HEADER_DEV_INDEX]);
>
> - dev = dev_get_by_index(net, ifindex);
> + dev = netdev_get_by_index(net, ifindex, &req_info->dev_tracker,
> + GFP_KERNEL);
> if (!dev) {
> NL_SET_ERR_MSG_ATTR(extack,
> tb[ETHTOOL_A_HEADER_DEV_INDEX],
You forgot to change dev_put(dev) at line 126
> @@ -129,7 +130,8 @@ int ethnl_parse_header_dev_get(struct ethnl_req_info *req_info,
> return -ENODEV;
> }
> } else if (devname_attr) {
> - dev = dev_get_by_name(net, nla_data(devname_attr));
> + dev = netdev_get_by_name(net, nla_data(devname_attr),
> + &req_info->dev_tracker, GFP_KERNEL);
> if (!dev) {
> NL_SET_ERR_MSG_ATTR(extack, devname_attr,
> "no device matches name");
> @@ -142,8 +144,6 @@ int ethnl_parse_header_dev_get(struct ethnl_req_info *req_info,
> }
>
> req_info->dev = dev;
> - if (dev)
> - netdev_tracker_alloc(dev, &req_info->dev_tracker, GFP_KERNEL);
> req_info->flags = flags;
> return 0;
> }
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